Experimental Neurology 224 (2010) 74–84

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Experimental Neurology

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Review

The endocannabinoid system in gp120-mediated insults andHIV-associated dementia

Monica Bari a,b, Cinzia Rapino b,c, Pamela Mozetic a,b, Mauro Maccarrone b,c,⁎a Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Rome, Italyb European Center for Brain Research (CERC)/Santa Lucia Foundation, Rome, Italyc Department of Biomedical Sciences, University of Teramo, Teramo, Italy

⁎ Corresponding author. Department of Biomedical SPiazza A. Moro 45, I-64100 Teramo, Italy. Fax: +39 086

E-mail address: mmaccarrone@unite.it (M. Maccarro

0014-4886/$ – see front matter © 2010 Elsevier Inc. Adoi:10.1016/j.expneurol.2010.03.025

a b s t r a c t

a r t i c l e i n f o

Available online 29 March 2010

Keywords:CytokinesEndocannabinoidsGliagp120HADHIV-1Immune surveillanceNeuroinflammationNeuroprotectionSignal transduction

Endocannabinoids (eCBs) include a group of lipidmediators that act as endogenous agonists at cannabinoid (CB1,CB2) and vanilloid (TRPV1) receptors. In the last two decades a number of eCBs-metabolizing enzymes have beendiscovered that, together with eCBs and congeners, target receptors and proteins responsible for their transportand intracellular trafficking form the so-called “endocannabinoid system” (ECS). Within the central nervoussystemECSelements participate inneuroprotection against neuroinflammatory/neurodegenerative diseases likeAlzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and multiplesclerosis. More recently, a role for eCBs has been documented also in human immunodeficiency virus-1 (HIV-1)envelope glycoprotein gp120-mediated insults, and inHIV-associateddementia (HAD). Themodulation of ECS inthe latter disease conditions is the subject of this review, that will also address the molecular mechanismsunderlying the neuroprotective effects of eCBs. In particular, the interactions between neurons and glia duringneuroinflammation, and the alterations of ECS in these cells upon gp120 insults and HADwill be discussed, alongwith the potential therapeutic exploitation of ECS-oriented drugs for the treatment of HAD and related disorders.

ciences, University of Teramo,1 266877.ne).

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© 2010 Elsevier Inc. All rights reserved.

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74The endocannabinoid system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Toxicity of the HIV-1 coat glycoprotein gp120 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75HAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Interactions between neurons and glia during neuroinflammation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78ECS in microglial cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Alteration of ECS in vivo and in vitro upon gp120 insults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Introduction

The discovery of endocannabinoids (eCBs) allowed the identifica-tion of a biochemical system (termed “endocannabinoid system,”ECS) of central importance for its pathophysiological roles in healthand disease conditions (McPartland, 1999; Croxford, 2003; Di Marzo,2009; Maccarrone, 2009). In particular, within the central nervous

system (CNS) eCBs have been shown to participate in neuroprotectionagainst neuroinflammatory/neurodegenerative pathologies like Alz-heimer's disease, Parkinson's disease, Huntington's disease, amyo-trophic lateral sclerosis, and multiple sclerosis (Centonze et al., 2007;Hillard, 2008; Basavarajappa et al., 2009; Fernández-Ruiz, 2009; Rossiet al., in press). More recently, a role for (endo)cannabinoids inhuman immunodeficiency virus-1 (HIV-1) envelope glycoproteingp120-mediated insults, and in HIV-associated dementia (HAD) hasbeen documented (Maccarrone et al., 2004; Lu et al., 2008). Theneuroprotective effect of the ECS is due to different mechanisms,including inhibition of glutamate transmission, reduction of Ca2+

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influx and subsequent inhibition of noxious cascades, such asproduction of tumor necrosis factor-α (TNFα), and oxidative stress(Marsicano et al., 2002, 2003; Van der Stelt et al., 2002a). In addition,the neuroprotective activity of eCBs could occur through the control ofglial cell activity. In this context, perivascular macrophages andmicroglia represent the main infected cells in the brain of patientssuffering from HAD, therefore microglial ECS may contribute toneuroinflammatory processes involved in this disease. In this review,we shall briefly describe the main elements of the ECS, the relevanceof neurons-glia interactions in neuroinflammation, and the mainfeatures of gp120-mediated neurotoxicity and HAD. Against thisbackground, we shall summarize gp120-induced alterations of ECSmembers, both in vitro and in vivo, in order to put in a betterperspective how targeting the ECS could reduce the symptomsassociated to gp120 insults and HAD. On the other hand, theinvolvement of ECS in other neuroinflammatory/neurodegenerativediseases has been the subject of comprehensive reviews (Maccarroneet al., 2007; Centonze et al., 2007, 2008; Basavarajappa et al., 2009;Fernandez-Ruiz et al., 2009).

The endocannabinoid system

Endocannabinoids (eCBs) include a group of lipid mediators, ofwhich the best characterized members are N-arachidonoylethanola-mine (anandamide, AEA) and 2-arachidonoylglycerol (2-AG) (Devaneet al., 1992; Stella et al., 1997; Sugiura et al., 2002; see Hanuš andMechoulam, 2010 for a recent review). They bind to classical type-1(CB1) and type-2 (CB2) cannabinoid receptors, and to a purported type-3 (CB3) cannabinoid receptor that is the orphan G protein-coupledreceptor 55 (GPR55) (Matsuda et al., 1990; Munro et al., 1993; Begg etal., 2005; Lauckner et al., 2008). The latter proteins are all seven trans-membrane spanning, G protein-coupled receptors (GPCR). CB1 arefound predominantly within the CNS, although they are expressed alsoin several non-neuronal cells and tissues like liver, adipocytes, immunecells, and reproductive tissues (Howlett et al., 2010). In the CNS, eCBs actas retrograde messengers on presynaptic CB1, transiently suppressingtransmitter release, and therefore theyhavebeen involved in a variety ofsynaptic plasticity-related phenomena (Chevaleyre et al., 2006; Vighand von Gersdorff, 2007; Edwards et al., 2008; Maccarrone, 2009). CB2are expressed mainly on immune cells, but are also present in the brainstem(VanSickle et al., 2005), in central neuronsupon exogenous insults(Viscomi et al., 2009), and in several other peripheral cells (Patel et al.,2010). In particular, CB2 receptors are expressed in microglia, that isimplicated in the control of nociceptive transmission in the spinal cord(Franklin and Stella, 2003; Núñez et al., 2004), and in the retinalganglion cell, a specialised class of neurons (Lu et al., 2000). The eCBsAEA and 2-AG are not stored in intracellular compartments like classicalneurotrasmitters, but are synthesized on-demand in response topathological or physiological stimuli. The biological activity of AEAand 2-AG at their receptors depends on their concentration in theextracellular space, which is controlled by: i) Ca2+-dependent biosyn-thesis throughN-acylphosphatidylethanolamine-specific phospholipaseD (NAPE-PLD) (Di Marzo et al., 1994; Okamoto et al., 2004) (Fig. 1A), orthrough an alternative pathway that involves glycerophospho-N-arachidonoylethanolamine (GP-NArE) as a lipid precursor (Simon andCravatt, 2008), for AEA; and a specific phospholipase C that generatesdiacylglycerol (DAG), then converted to 2-AG by a sn-1-DAG lipase, for2-AG (Bisogno et al., 2003) (Fig. 1B); ii) cellular uptake through a yet-purported AEA membrane transporter (AMT) that is likely to take upalso 2-AG; iii) intracellular degradation by fatty acid amide hydrolase(FAAH), for AEA (Fig. 1A), and/or by a specific monoacylglycerol lipase(MAGL), for 2-AG (Cravatt et al., 1996; McKinney and Cravatt, 2005; DiMarzo, 2008; Fezza et al., 2008) (Fig. 1B). FAAH is a membrane-associated serine hydrolase that belongs to the amidase signature familyof enzymes (Patricelli et al., 1999; Ueda et al., 2000; McKinney andCravatt, 2005; Fezza et al., 2008), and genetic depletion of the faah gene

or pharmacological inhibition of intracellular FAAH activity result inelevated CNS levels of AEA (Cravatt et al., 2001; Fegley et al., 2005;Kathuria et al., 2003). More recently, it has been documented thatFAAH can receive AEA through intracellular storage organelles called“adiposomes” (Oddi et al., 2008), and that constitutive AEA-bindingproteins like albumin and heat shock protein 70.2 can drive transportand trafficking of this eCB from the plasmamembrane to its intracellulartargets (Oddi et al., 2009). Overall, there is a general consensus thatFAAH is a key-controller of the endogenous tone (and hence of thebiological activity) of AEA, a concept that has attracted growinginterest for the development of FAAH inhibitors as potential tools fortherapeutic exploitation, also in the context of neuroinflammatory/neurodegenerative diseases (Centonze et al., 2007, 2008; Ligresti et al.,2009). Additional degradative pathways of AEA and2-AGare depicted inFig. 1, where it is shown that lipoxygenases (LOX) and cyclooxygenase-2(COX-2), the enzymes responsible for the classical “arachidonatecascade” leading to the biosynthesis of leukotrienes, lipoxins andprostanoids (Funk, 2001), can generate hydroxy-derivatives or prosta-mides of AEA and 2-AG, respectively (Van der Stelt et al., 2002b; Rouzerand Marnett, 2008).

The binding of eCBs to cannabinoid receptors triggers varioussignaling pathways, such as the inhibition of adenylyl cyclase, theregulation of ionic currents (inhibition of voltage-gated L, N and P/Q-type Ca2+ channels, activation of K+ channels), the activation of focaladhesion kinase (FAK), of mitogen-activated protein kinase (MAPK),and of cytosolic phospholipase A2, and the activation (through CB1) orthe inhibition (through CB2) of nitric oxide synthetase (Pertwee, 2010).In addition, AEA but not 2-AG behaves as a week ligand to type-1vanilloid receptor (transient receptor potential vanilloid 1, TRPV1), anon-selective cationic channel that is activated by capsaicin, the activeingredient of hot chilli pepper, and by noxious stimuli like heat andprotons (Jung et al., 1999; Jordt and Julius, 2002). More recently, anumber of other TRP channels have been added to the list of eCBstargets, as well as nuclear receptors like the peroxisome proliferator-activated receptors. These new comers have been the subject ofextensive reviews (Di Marzo and De Petrocellis, 2010; Pistis andMelis, 2010). Taken together, eCBs and congeners, their target receptorsand metabolic enzymes, along with the proteins responsible for theirtransport and intracellular trafficking, form the ECS. The latter systemhas been found in many regions of the brain including cortex,hippocampus, basal ganglia, cerebellum, striatum, amygdala, andnucleus accumbens (Maccarrone, 2009). In these areas it seemsinvolved in neuromodulation, motor functions, cognition, emotionalresponses, homeostasis and reward behaviours. The main elements ofthe ECS detected in neurons and glial cells are summarized in Table 1.

Toxicity of the HIV-1 coat glycoprotein gp120

There are several proteins of HIV-1 that have been identified asneurotoxins, including the structural proteins gp120 and gp41, andthe non-structural proteins Tat, Nef, Vpr and Rev (Bergonzini et al.,2009; Sharma and Bhattacharya, 2009; Fellin, 2009). The target cellsfor HIV-1 infection are perivascular macrophages, microglia andastrocytes (Kaul et al., 2001; Anderson et al., 2002) that, once infected,release cytotoxic HIV-1 proteins able to induce cell death in thesurrounding neurons. In particular, gp120 acts as an agonist atchemokine receptor 4 (CXCR4), both in microglia and actrocytes,determining an over-activation of glutamate receptors (particularlythose of the N-methyl-D-aspartate (NMDA) type), as well as calciuminflux, oxidative stress and release of toxic lipids from membranes,such as 4-hydroxynonenal and ceramides (Haughey et al., 2004).These events may trigger the intrinsic pathway of apoptosis that leadsto mitochondrial membrane permeabilization, release of cytocrome cand activation of caspases and endonucleases, which all commitneurons to death. Several studies have confirmed the toxic effect ofgp120 on the neuronal population (Dreyer et al., 1990; Kaul and

Fig. 1.Metabolic pathways of AEA and 2-AG in neurons. A) N-acyltransacylase (NAT) transfers arachidonic acid from the sn-1 position of 1,2-sn-di-arachidonoylphosphatidylcholine(PC) to phosphatidylethanolamine (PE), generating N-arachidonoylphosphatidylethanolamine (NArPE). NArPE is cleaved by an N-acylphosphatidylethanolamine (NAPE)-specificphospholipase D (NAPE-PLD), thus releasing AEA. NArPE can be also hydrolyzed by a secretory phospholipase 2 (sPLA2), which generates N-arachidonoyl-lyso-phosphatidylethanolamine (lyso-NArPE), further hydrolyzed to AEA by a lyso-phospholipase D (lyso-PLD). AEA is mainly degraded by fatty acid amide hydrolase (FAAH), whichbreaks the amide bond and releases arachidonic acid (AA) and ethanolamine (EtNH2). Alternatively, AEA can be oxygenated by lipoxygenases like 12-lipoxygenase (12-LOX), and bycyclooxygenase-2 (COX-2), to generate hydroxy-derivatives (12-HAEA) or prostamides (PGE2-EA), respectively. B) Diacylglycerol (DAG), generated by phosphatidic acid (PA)phosphohydrolase, is converted to 2-AG by a sn-1-DAG lipase (DAGL); alternatively, phospholipase A1 (PLA1) converts phosphatidyl-inositol (PI) into lyso-PI, which is thenconverted into 2-AG by phospholipase C (PLC). 2-AG is cleaved into AA and glycerol mainly by a cytosolic monoacylglycerol lipase (MAGL), and to a minor extent by FAAH. Finally, 2-AG can be oxygenated by COX-2 or 12-LOX, to generate PGE2G and 12-HETE-G, respectively.

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Lipton, 1999). Neonatal rats treated systemically with gp120 showretardation in behavioral development; in addition, reduced volumeand even atrophy of hippocampus have been reported in the sameanimals after injection of gp120, alone or in association with NMDArespectively (Glowa et al., 1992, Hill et al., 1993; Barks et al., 1997).

Furthermore, gp120 induces apoptosis in the brain neocortex of adultrats treated with a dose of 100 ng of viral protein for sevenconsecutive days (Corasaniti et al., 2001). It has also been shownthat bilateral injection of gp120 (10–100 nM) into the intermediatemedial mesopallium of the chick forebrain causes amnesia, while

Table 1Elements of the ECS that have been detected in neurons and glial cells.

Member Description Function

AEA Prototype member offatty acid amides

Bioactive lipid that acts at cannabinoid andvanilloid receptors

2-AG Prototype member ofmonoacylglycerols

Bioactive lipid that acts at cannabinoidreceptors

NAPE-PLD Biosynthetic enzyme Main responsible for the biosynthesis of AEAFAAH Hydrolytic enzyme Main responsible for the degradation of AEADAGL Biosynthetic enzyme Main responsible for the biosynthesis of 2-AGMAGL Hydrolytic enzyme Main responsible for the degradation of 2-AGCB1R, CB2R Cannabinoid receptors Main targets of AEA and 2-AGTRPV1 Vanilloid receptor Target of AEAAMT Anandamide

membrane transporterSo far putative entity responsible for thetransport of AEA, and possibly of 2-AG

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several other studies have shown that gp120 impairs memoryretention in rodents (Glowa et al., 1992; Pugh et al., 2000; Sánchez-Alavez et al., 2000).

Themechanisms of gp120-induced neurotoxicity seem to combinemultiple elements, spanning from apoptosis (Kaul and Lipton, 1999;Perfettini et al., 2005), oxidative damage (Price et al., 2005, 2006) andinterruption of the glutamate–glutamine cycle (Fernandes et al.,2007), to activation of various receptors (NMDA receptor (NMDAR),CXCR4, and chemokine receptor 5 (CCR5)). (Catani et al., 2000;Toggas et al., 1996). A simplified scheme of these events is depicted inFig. 2. In this context, the ability of macrophages to produce pro-inflammatory cytokines like TNFα and interleukin-1 (IL-1) mayfurther increase neuronal cell death (Mattson et al., 2005). It hasalso been shown that gp120 causes necrotic death in human CHP100neuroblastoma cells and, by activating the COX-2 and 5-LOX path-

Fig. 2. Mechanism of HIV-1 infection. The virus enters into glial cells through the envelope gdependent signaling. As a consequence, various cytokines and glutamate are released from gdetails.

ways, it provokes enhanced reactive oxygen species (ROS) formationand membrane lipid peroxidation (Floyd, 1999; Maccarrone et al.,1998). An additional mechanism at the basis of the toxicity of gp120involves the enhancement of IL-1β production, that increases theexpression of COX-2 (localized in neuronal cells), and then theconversion of arachidonic acid into prostaglandin E2 (PGE2). The lattersubstance stimulates a Ca2+-dependent release of glutamate fromastrocytes, responsible for apoptosis of neocortical neurons (Corasa-niti et al., 2001). A further explanation of the neurotoxic effect ofgp120may reside in its ability to trigger the release of TNFα and otherinflammatory cytokines from non-neuronal cells (Bezzi et al., 2001).TNFα, in turn, may cause apoptotic cell death, and as a consequence itmay lead to decreased production of the brain-derived neurotrophicfactor (BDNF) in neurons (Fig. 2). On the other hand, an up-regulationof BDNF levels has been found in HIV-1 patients, where it was mainlyconfined in microglia (Nosheny et al., 2005). The latter evidence maybe a typical inflammatory response evoked by neuronal injury, ratherthan a cause of neurotoxicity. In this context, it should be recalled thatastrocyte infection with HIV-1 has been long considered a rare event,so astrocytes have been thought to play a secondary role in HIV-1neuropathogenesis. However, recently by combining double immu-nohistochemistry, laser capture microdissection, and highly sensitivemultiplexed polymerase chain reaction to detect HIV-1 DNA in singlecells in vivo, extensive infection has been shown in astrocytes fromsubjects with HIV-associated dementia (HAD) (Churchill et al., 2009).In addition, the frequency of astrocyte infection correlated with theseverity of neuropathological changes and proximity to perivascularmacrophages. Taken together, these data indicate that astrocytes canbe extensively infected with HIV-1, and suggest an important role forthem in HAD. Themain features of this neuroinflammatory disease aredescribed in the next section.

lycoprotein gp120, which binds to CXCR4/CCR5 co-receptors and stimulates receptor-lial cells, thus leading to excitotoxic insult, neuronal damage and apoptosis. See text for

Table 2Molecules involved in gp120 toxicity and HAD (see text for details).

Cellular source Signaling molecule Site of action

Monocytes/macrophages eCBsRANTESIL-1βIL-6TNFα

Glia/astrocytes eCBs CCR5INFγ CXCR4TNFα NMDARGlutamate TNFR1D-serine Ca2+ channelsSubstance P CB1

ATP CB2

Ca2+ MAPKNO MKP-1BDNF

Neurons eCBsGlutamateNOSubstance PFractalkine

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HAD

HIV-associated dementia (HAD) is a neurological syndromecharacterized by cognitive impairment, postural disorders andtremor, that affects ∼25% of AIDS patients. HIV-1 is the causativeagent, implicated in the development of HAD and responsible formultiple symptoms. HIV-1 enters the brain soon after infection,causing neuronal damage and microglia/astrocyte dysfunctions thatlead to neuropsychological impairment. In humans, a subset of HIV-infected patients with dementia exhibit neuropathological changes,termed HIVE (HIV-induced encephalitis), in which microglial andastroglial cells play a pivotal role (Kolson and González-Scarano,2000; Kaul et al., 2001; Williams et al., 2009). HIVE is caused by aviral infection of the brain that targets perivascular macrophages(Dhillon et al., 2008). Histopathology includes activated brainmacrophages and astrocytes, inflammatory cuffs of monocyte/macrophages (some of which are infected), activated astrocytes,and inflammatory CD8 T-lymphocytes. Since neurons themselves arenot infected directly, neuronal injury is thought to occur via indirectmechanisms that engage factors released from activated macro-phages and astrocytes. The latter cells are critical for maintainingessential brain functions and their dysfunction contributes to HIV-1neuropathogenesis (González-Scarano and Martín-García, 2005).Astrocytes are latently infected and do not produce new virusparticles, and in HAD they have an impaired glutamate catabolismthat leads to neuronal death.

The biochemical and molecular cascades that result in neuronaldeath upon HAD are complex, involving not only the virus andneurons but also glial cells, macrophages and lymphocytes, as detailedin the next section. In fact, infiltration of lymphocytes and macro-phages, activation of microglia and astrocytes, and production of pro-inflammatory cytokines are brain hallmarks of HAD. Several studiesdemonstrated that the neurological manifestations in HAD werecaused by the participation of chemokines and excitotoxic moleculessecreted by infected cells, in particular macrophages. It is believedthat these cells facilitate virus entry into the brain, and thatneurotropic viruses adapt to grow in these cells leading to neuronalinjury. Chemokines are low molecular weight substances which areexpressed by the resident cells of the CNS. The chemokine RANTES(regulated on activation, normal t cell expressed and secreted) andother members of the IL-8 superfamily are the natural ligands forCCR5 and CXCR4 receptors, that are exploited by HIV-1 for enteringinto the cell. In other words, CCR5 and CXCR4 are co-receptors of HIV-1.It seems noteworthy that high expression of RANTES has been observedin the cerebrospinal fluid (CSF) of patients suffering from HAD (Kelderet al., 1998). Cytokines such as TNFα, interferon-γ (IFN-γ), IL-1 and IL-4,and messengers like nitric oxide (NO) are also involved in HIV-1neuropathogenesis, causing a gliotic response in both microglia andastrocytes in vitro (Koka et al., 1995). In particular, it seems that viralgp120 and gp41 glycoproteins can regulate the induction of IL-1 andIFN-γ, as well as the expression of the inducible form of NO synthase(iNOS) (Koka et al., 1995).Moreover,molecules thatmodulate neuronalsignaling play a key role in maintenance of normal physiology of manycompartments of the CNS. For example arachidonic acid (AA), that is acomponent of cell membranes, is responsible for the interactionbetweenmacrophages and astrocytes, and is released under the controlof RANTES (Vanzani et al., 2006). Another important mediator ofneurotoxicity in the so-called “AIDS dementia complex” (ADC) isglutamate. It should be recalled that ADC is defined as a constellation ofcognitive, motor, and behavioral dysfunctions frequently observed inpersons with AIDS. ADC may occur at any stage of AIDS, but is usuallyassociated with later stages of the disease. Its severity varies amongpatients and often, but not always, is progressive. Various pathogenicmechanisms have been proposed for ADC, including effects of HIV-1-mediated cytokine production and direct neural cell damage by HIV-1(Portegies, 1994). However, glutamate has been widely recognized as a

key toxic factor, that can be detected also in the medium of HIV-1-infected macrophages (Jiang et al., 2001; Xing et al., 2009).

Some of the signaling molecules involved in the development ofHAD are summarized in Table 2. Among these, the elucidation of theindispensable substances would be much helpful for developingpotential therapeutic strategies against HAD. At present, blockers ofNMDAR, of Ca2+ channels, of MAPK, or of different GPCRs (includingCB1 and CB2) could be relevant for therapeutic exploitation. Also,some chemokines can serve as potential therapeutic agents for HAD,as they can compete with the virus for the binding sites on the cellsurface. It should be noted that the mechanisms by which neuronsbecome dysfunctional and die in HAD are similar to those that occur inAlzheimer's disease. Here, the β-amyloid protein may initiate noxiouscascades, whereas in HAD the likely initiating factors are HIV-1proteins gp120 and Tat, that trigger excitotoxicity, inflammation andultimately apoptosis. Moreover, the evidence that astrocytes areinvolved in HIV-1 infection, and in particular in the resulting HIVE andHAD, further highlights the importance of modulating the astrocytereservoir in all strategies aimed at treating these diseases (Watt et al.,2009). Recently, it was demonstrated that curcumin, a substancederived from the roots of Curcuma plants, may provide an effectivetherapeutic strategy against HAD (Tang et al., 2009). In fact, curcuminsupplementation seems to be effective to counteract the toxic effectsof gp120, and hence it might be beneficial for the treatment of HAD(Tang et al., 2009). Several studies in the last few years havedemonstrated the involvement of this compound in differentinflammatory diseases (Aggarwald and Sung, 2009), as well as inneuroprotection (Yang et al., 2008). In addition, the role of curcuminas a therapeutic for immune disorders has been recently documented(Jagetia and Aggarwal, 2007), and is most likely due to thesuppression of HIV replication through inhibition of HIV integraseand protease (Barthelemy et al., 1998). Therefore, non-toxic curcumincould be used as a lead compound in combinatorial drug developmentagainst HIV infections (Balasubramanyam et al., 2004). At any rate,future experiments are deemed necessary to further investigate themechanism(s) of action of curcumin, and the reasons for itstherapeutic efficacy in HAD, and possibly in other neuroinflammatorydisorders.

Interactions between neurons and glia during neuroinflammation

Within the CNS microglia and macroglia together with astrocytes,oligodendrocytes and ependymal cells form the glia. For a long time,

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glial cells have been considered as supportive cells that providestructural and metabolic aid to neurons. Only recently they have beenidentified as signaling cells, that can be excited by increasedintracellular concentrations of Ca2+ ions. It has been demonstratedthat neuronal activity can trigger Ca2+ elevations in astrocytes by theGABAA receptor antagonist bicuculline (Hirase et al., 2004), bypicrotoxin (Göbel et al., 2007), or by inducers of epileptic-likedischarges (Seifert et al., 2009). Excitation of astrocytes determinesthe activation of metabotropic glutamate receptors (mGluRs) withrelease of glutamate that acts at pre- and/or post-synaptic levels, tomodulate synaptic transmission and neuronal excitability at bothexcitatory and inhibitory synapses. Astrocytes, through a processnamed “gliotransmission,” release several active molecules such asglutamate, ATP, D-serine and TNFα (Parpura et al., 1994; Cotrina et al.,1998; Mothet et al., 2000; Stellwagen and Malenka, 2006). Inparticular, TNFα modulates neuronal excitability by activatingpurinergic ionotropic receptors. In addition, using mixed culturesfrom wild-type and TNFα knockout mice it was demonstrated thatastrocytes are the primary source of this pro-inflammatory cytokine(Stellwagen and Malenka, 2006). Therefore astrocytes, by releasingchemical transmitters, modulate synaptic transmission and neuronalfunction. The role of glia in neurotransmission has gained so muchattention, that a novel concept of “tripartite synapses” has beenrecently proposed (Perea et al., 2009). The term “tripartite synapse”refers to the existence of a bidirectional communication betweenastrocytes and neurons. Consistent with this concept, in addition tothe classic “bipartite” information flow between the pre- and post-synaptic neurons, astrocytes exchange information with the synapticneuronal elements, responding to synaptic activity and, in turn,regulating synaptic transmission. Consequently, in contrast to theclassically accepted paradigm that brain function results exclusivelyfrom neuronal activity mediated by neurotransmitters, there is anemerging view, in which brain function actually arises from thecoordinated activity of a network comprising also glia-derived signalstermed “gliotransmitters”. Recent in vitro studies suggest that thechemokine ligand 12 (CXCL-12), much alike glutamate and ATP,determines Ca2+-dependent release of glutamate by astrocytes (Bezziet al., 2001; Calì et al., 2008). CXCL-12 activates its CXCR4 receptorwith production of TNFα that, once released by astrocytes, acts inautocrine and paracrine manners on its type-1 TNF receptor (TNFR1).In turn, the activation of TNFR1 triggers a signal transduction thatinvolves PGE2 production, Ca2+ increase and glutamate release(Fig. 2).

CXCR4 is also expressed in microglia and its activation causes astrong release of TNFα. It is noteworthy that in hippocampal culturesof neurons, astrocytes and microglia, an increase of TNFα-mediatedglutamate release by astrocytes-microglia is excitotoxic, and triggersneuronal apoptosis. Moreover, CXCL-12 may contribute to neuronalapoptosis in the brain upon HIV-1 infection. In fact, microglial cells,considered as the resident immune sentinels of CNS, exist in twofunctional states called “resting microglia” and “activated microglia”(Stella, 2009). The resting microglial cells have a small cell body and ahighly ramified morphology, that allows them to preserve the CNSenvironment. The activation of microglia occurs under pathologicalconditions, when the neural cells are damaged. Neurons releasechemoattractants that increase motility (i.e., chemokinesis) andrecruitment (i.e., chemotaxis) of microglia in the damaged area. Inthe chemotactic process, the interaction between activated glial cellsand chemoattractants initiates different cellular events, that includechanges in ion fluxes, alterations in integrin avidity, production ofsuperoxide anions and secretion of lysosomal enzymes (Murdoch andFinn, 2000). Under the activated state, microglia act as cells ofimmunological surveillance and transform themselves into phago-cytic cells able to protect central neurons by removing toxins andpathogens from the surroundings (Garden and Möller, 2006). To thisend, activated microglia express membrane receptors that recognize

toxins, pathogens and molecules released by damaged cells, includingfractalkine, ATP, glutamate and eCBs. In particular, activation of CBreceptors expressed by activated microglia seems to control theirimmune-related functions (Stella, 2009). Microglia can have a pro-inflammatory (M1) or anti-inflammatory (M2) phenotype (Gardenand Möller, 2006; Gordon, 2003), to exacerbate or remove neuronaldamage respectively, depending on the receptors activated and onenhanced expression of specific genes.

Finally, alterations in Ca2+-dependent glutamate release by astro-cytes are shown in many inflammatory diseases, thus determining asignificant neuronal damage like that observed in HAD. Moreover,mature astrocytes can bind, internalize and degrade the β-amyloidprotein, that is central in the pathogenesis of Alzheimer's disease(Wyss-Coray et al., 2003). This protective action of astrocytes could bedecreased in Alzheimer's disease, where the astrocytes that surroundthe plaques become unable to remove the β-amyloid protein (Wyss-Coray et al., 2003). Overall, microglia could be an important defenceagainst neuroinflammatory diseases, such as Alzheimer's disease,multiple sclerosis, amyotrophic lateral sclerosis and HAD. The role ofECS in this neuroprotective activity is discussed in the next section.

ECS in microglial cells

In vitro and in vivo studies suggest that eCBs play a relevant role inthe cellular networks betweenmicroglia and neurons in neurotoxicityand neuroinflammation (Galve-Roperh et al., 2008; Massi et al., 2008;Wolf et al., 2008; Stella, 2009). Microglial cells express various ECSproteins, including receptors and enzymes responsible for thesynthesis and degradation of eCBs (Carrier et al., 2004; Massi et al.,2008; Stella, 2009). The CB1 receptor is detected in microglial cells atlow levels, and it is predominantly found in intracellular compart-ments, but its functional role is not yet fully understood (Walter et al.,2003). However, a role for CB1 in NO production has beendocumented during microglial response to neuroinflammation(Waksman et al., 1999). On the other hand, CB2 receptors areexpressed in perivascular microglia of human cerebellum, in “primed”microglia (i.e., microglia exposed to a certain substance like anantigen) from human, rat or mouse tissues, and also in rat neonatalmicroglial cells (Carlisle et al., 2002; Núñez et al., 2004; Ramirez et al.,2005; Rock et al., 2007). These localizations may suggest that CB2 isinvolved in immunomodulatory processes, as well as in microgliamigration (Walter et al., 2003) and proliferation (Carrier et al., 2004).In this context, in vitro studies on activated microglia describesignificant expression of CB2 upon inflammation, while the samereceptor is detected at very low levels in healthy brain (Cabral andGriffin-Thomas, 2008; Pazos et al., 2005). In addition, some pathogensand cytokines can regulate the expression of CB2 (Carayon et al., 1998;Lee et al., 2001), that is reduced by lipopolysaccharide (LPS) in primedmicroglia (Carlisle et al., 2002). In activated microglia of rat spinalcord different brain insults, such as neuropathic pain or chronicinflammation, can up- or down-regulate CB2 expression respectively(Zhang et al., 2003).

On the other hand, activation of CB2 by 2-AG increases theproliferation and recruitment of anti-inflammatory (i.e., M2 pheno-type) microglia at the sites of lesion, as demonstrated by the reducedrelease of detrimental factors like TNFα and free radicals (Carrieret al., 2004; Palazuelos et al., 2009), as well as by the increased releaseof trophic factors like BDNF, and by the improved elimination of celldebris (Stella, 2009).

CB2 receptors are over-expressed in activated microglia inresponse to neuroinflammatory events typical of neurologicaldiseases, most notably in HAD and its equivalent in primates, thesimian immunodeficiency virus-induced encephalitis (SIVE) (Benitoet al., 2005). In this context, it has been reported that the activation ofCB2 protects microglial cells against HIV-1 infection (Benito et al.,2005), an effect that could be due to a CB2-mediated down-regulation

Table 3Neuronal alterations of ECS induced in vivo by gp120.

Member of ECS Effect of gp120

AEA ↓⁎

NAPE-PLD ↔FAAH ↑⁎

AMT ↑2-AG N.D.DAGL N.D.MAGL N.D.CB1, CB2 ↔TRPV1 ↔

N.D., not determined.⁎ Observed also in astrocytes in vitro.

80 M. Bari et al. / Experimental Neurology 224 (2010) 74–84

of CCR5, the chemokine receptor responsible for the docking andentry of HIV-1 into microglial cells (Peterson et al., 2004; Rock et al.,2007). Incidentally, also the β-amyloid plaque-rich regions of thebrain have been shown to be immunopositive for CB2 (and FAAH)proteins (Benito et al., 2007).

The recognition that microglia express CB2, and that activation ofthis receptor regulates the immune surveillance within the CNS (Wolfet al., 2008), indicates that CB2 may serve as an ideal therapeutictarget (Stella, 2009). Also of interest seems the fact that eCBs, beinghighly lipophilic compounds, can readily penetrate the blood–brainbarrier, thus accessing the brain. Furthermore, eCBs analogues can bedesigned to have low toxicity, minimal psychotropic properties, andselectivity towards target cells that express CB2, particularly theimmune sentinels of CNS.

In vitro experiments demonstrated that microglia, when activated,produce high amounts of eCBs, that can be ∼20-fold more abundantthan those detected in neurons and astroytes (Walter et al., 2002,2003). One pivotal action of eCBs in microglia is to generate pro-survival signals throughdifferentmechanisms. For instance, in glial cells(e)CBs enhance the release of the anti-inflammatory cytokine IL-1(Molina-Holgado et al., 2003), or they induce upon activation the ex-pression of themitogen-activated protein kinase phosphatase (MKP-1),with subsequent extracellularly regulated kinase-1/2 (ERK-1/2) kinasedephosphorylation and arrest of NO release (Eljaschewitsch et al.,2006). Therefore, this neuroprotective effect may restrict the inflam-mation to damaged areas, preventing a wider neuronal degeneration.On theother hand,microglial cells are able to inactivate both AEA and 2-AG (Witting et al., 2004). In fact, FAAH activity is increased in gliomatissues and in human U87 glioma cells, and it could influence tumorgrowth through the well-known pro-inflammatory agent arachidonicacid, released from FAAH substrates (Massi et al., 2008). Moreover, ina recent report it was demonstrated that hydrolysis of 2-AG in mouseBV-2microglial cells can be carried out by a novelMAGL (Muccioli et al.,2007), that could also contribute to the control of tumor growth.

Overall, eCBs exert their protective effects in microglial cells bytwo different pathways. On one hand, they promote the biosynthesisand release of pro-survival signals in glial cells, and on the other handthey induce selective death of tumor cells through glia-derivedmolecules. This picture suggests that eCBs production by glial cellsmay constitute an endogenous defence mechanism aimed atpreventing the propagation of neuroinflammation and neuronal celldamage. Therefore, the stimulation of CB2 by specific agonists, as wellas the inhibition of eCBs degradation by specific inhibitors ofhydrolytic enzymes, could be helpful in preventing inflammatoryprocesses associated with neurodegeneration.

Alteration of ECS in vivo and in vitro upon gp120 insults

In the last few years evidence has been accumulated to show thateCBs play a role in HIV-1 infection and HAD. For instance, in vitro itwas demonstrated that eCBs prevent HIV-1 trans-activator protein(Tat)-induced cytotoxicity, using rat C6 glioma cells as a paradigm(Esposito et al., 2002). In these cells the CB1 and CB2 agonist WIN55,212-2 has been shown to inhibit the expression of iNOS, and of NOrelease caused by treatment of C6 cells with Tat in combination withIFN-γ. The effect of WIN 55,212-2 was uniquely due to CB1 receptors,as shown by experiments carried out with selective receptor agonistsand antagonists. Stimulation of CB1 also inhibited Tat+IFN-γ-induced and NO-mediated cell toxicity. Moreover, treatment of C6cells with Tat+IFN-γ induced a significant inhibition of CB1, but notCB2, receptor expression (Esposito et al., 2002). This effect wasmimicked by NO donors, suggesting that the inhibition of CB1

expression was due to Tat+IFN-γ-induced NOS over-expression.Finally, Tat+IFN-γ treatment also induced a significant inhibition ofAEA uptake by C6 cells, without affecting AEA hydrolysis by FAAH.Taken together, these findings demonstrate that the ECS, through the

modulation of NO biosynthesis, reduces HIV-1 cytotoxicity induced byTat, and is itself regulated by Tat (Esposito et al., 2002). Later on, anin vivo study demonstrated that neuronal apoptosis induced by HIV-1coat glycoprotein gp120 in the rat neocortex was paralleled by a time-dependent increase in the activity and immunoreactivity of FAAH (upto ∼300% of controls), by a similar increase in the activity of the AEAmembrane transporter, and by decreased (down to ∼50%) endoge-nous levels of AEA (Maccarrone et al., 2004). On the other hand, theAEA-synthetase NAPE-PLD and the AEA-binding cannabinoid andvanilloid receptors were not affected by gp120 (Table 3). Also, theactivity of 5-LOX, which generates AEA derivatives able to inhibitFAAH (Van der Stelt et al., 2002b), decreased down to ∼25% of thecontrols upon gp120 treatment, due to a reduced protein level (downto ∼45%). Thus, it was proposed that reduction of 5-LOX mightcontribute to the up-regulation of FAAH observed in gp120-injectedrats. In addition, the FAAH inhibitor methyl-arachidonyl fluoropho-sphonate significantly reduced gp120-induced apoptosis in rat brainneocortex, whereas selective blockers of AEA membrane transporteror of AEA-binding receptors were ineffective (Maccarrone et al.,2004). Overall, these results suggest that gp120, by activating FAAH,decreases endogenous levels of AEA, and the latter effect seemsinstrumental in the execution of delayed neuronal apoptosis in thebrain neocortex of rats. A similar reduction of the endogenous tone ofAEA (down to ∼50% of controls), due to enhanced FAAH activity (up to∼200%), has been recently shown also in vitro, using human U373MGastrocytoma cells challenged with gp120 (Spagnuolo et al., 2008).Together with the in vivo data, these findings suggest that gp120might elicit the same alterations of the ECS in both neurons andastrocytes.

Another well-established effect of gp120 is at the level of theblood–brain barrier (BBB), whose integrity is compromised thusenhancing monocyte migration towards the brain (Kanmogne et al.,2007). Human brain microvascular endothelial cells (HBMEC) are anessential component of the BBB. Using cocultures of HBMECs andhuman astrocytes as a model system for human BBB, recently it hasbeen shown for the first time that CB receptors agonists inhibit gp120-induced calcium influx mediated by substance P, and significantlydecrease the permeability of HBMECs. Moreover, in these cells theyprevent down-regulation of tight junction proteins ZO-1, claudin-5and JAM-1, inhibit the transmigration of humanmonocytes across theBBB, and block BBB permeability in vivo (Lu et al., 2008). These resultsdemonstrate that CB receptors agonists are able to restore theintegrity of HBMECs and BBB following insults by gp120, potentiallyleading to better strategies for the treatment of gp120 insults and HADby means of ECS-oriented pharmacotherapies (Lu et al., 2008). In thiscontext, there is growing evidence that also 2-AG could decrease BBBpermeability and inhibit the expression of some pro-inflammatorycytokines such as TNFα, IL-1 and IL-6 (Panikashvili et al., 2006). Infact, many in vitro and in vivo studies in cells of the CNS have shownthat (e)CBs are able to inhibit the release of pro-inflammatory

81M. Bari et al. / Experimental Neurology 224 (2010) 74–84

cytokines (Puffenbarger et al., 2000, Facchinetti et al., 2003, Molina-Holgado et al., 2003, Sheng et al., 2005), and conversely to enhancethe release of anti-inflammatory cytokines such as IL-4 and IL-10(Cabral and Griffin-Thomas, 2008). In keeping with a protective roleof eCBs, preliminary in vitro data have further documented thatpharmacological inhibition of FAAH activity markedly reduces (by∼85%) the release of TNFα from human astrocytoma cells treated withgp120 (Spagnuolo et al., 2008). Remarkably, it has been shown thatthe latter cells express functional CB1 receptors, and that activation ofthese receptors induces intracellular calcium increase and glutamateexocytosis (Spagnuolo et al., 2008). Therefore, also type-1 cannabi-noid receptors seem to be engaged in astrocytes, in order to regulatecytokine release upon neuroinflammatory processes. The overallinvolvement of ECS in gp120-mediated insults is schematicallydepicted in Fig. 3.

There is also accumulated evidence that expression of CB2 is up-regulated in vitro by microglia and other immune cells in response toexternal stimuli (Carlisle et al., 2002), and in vivo during states ofchronic neuroinflammation (Maresz et al., 2005; Beltramo et al., 2006;Fernández-López et al., 2006). The existence of profound changes inthe distribution pattern of CB2 (and also of FAAH) protein was alsodemonstrated in cortical regions of macaque brains affected by SIVE(Benito et al., 2005). Since AEA is able to reduce glutamatergic activity

Fig. 3. Involvement of ECS in gp120 infection. Schematic representation of gp120-induced neHIV-1, and they trigger complex neurotoxic cascades that involve the dysregulation of astrocthat amplifies glutamate release, and eventually induces excitotoxic insult and neuronal apoand release of pro-survival signals (like IL-4 and IL-10), and the simultaneous inhibition of pare able to restore the integrity of the blood–brain barrier (BBB), compromised by gp12transmigration of infected monocytes towards the central nervous system. See text for deta

in the striatum of rats (Gubellini et al., 2002), it can be suggested thatreduction of endogenous AEA upon gp120 exposure might allowelevation of synaptic glutamate and subsequent excitotoxic neuronalcell death.

Conclusions

All available data suggest that during inflammation a large numberof molecules are engaged to induce neuronal damage, and thus theymight be used as potential therapeutic targets to curve a hyperactiveimmune response, thus curing or slowing down the progression ofneuroinflammatory diseases like HAD. Through the use of selectiveagonists or antagonists of CB1, CB2 or TRPV1 receptors (just to mentionthose that are well-characterized to date), or of inhibitors of eCBsmetabolic enzymes (in particular of FAAH), it may be possible to targetspecific cell types, such asmicroglia, that are deeply involved in immunesurveillance and inflammatory processes within the brain. In thiscontext, plant-derived cannabinoids have been already used in thetreatment of patients with AIDS, in order to reduce pain and improvetheir quality of life (Galal et al., 2009; Hanuš and Mechoulam, 2010). In1992 the Food and Drug Administration (FDA) has approved Marinol, aproduct containing dronabinol, as an appetite stimulant for AIDS

uronal apoptosis. Microglia are the only cells in the CNS that are productively infected byytes. When activated by the viral coat protein gp120, these cells massively release TNFα,ptosis. On the other hand, the neuroprotective effect of (e)CBs implies the biosynthesisro-inflammatory cytokines (like TNFα, IL-1 and IL-6). In addition, CB1 and CB2 agonists0 insults, thus preventing the down-regulation of tight junction proteins, and henceils.

82 M. Bari et al. / Experimental Neurology 224 (2010) 74–84

patients. Dronabinol is a synthetic Δ9-tetrahydrocannabinol (thepsychoactive ingredient of Cannabis sativa extracts), and FDA approvalhas further intensified the research interest in these compounds. Thefuture will tell whether eCBs analogues or ECS-oriented drugs willbecome useful therapeutics, and whether HAD and possibly otherneuroinflammatory diseases will benefit from eCBs-containing pills. Ona final note, chances are that distinctive alterations of ECS elementsfound in central immune cells of HAD patients might be reflected bysimilar alterations in peripheral immune cells, like circulating lympho-cytes. This has been the case for a number of neurodegenerative/neuroinflammatory disorders (Centonze et al., 2008), and if found truealso for HAD it could open the avenue to novel diagnostic markers ofdisease stage and progression.

Acknowledgments

Wewish to thank Professor Alessandro Finazzi Agrò (University ofRome Tor Vergata) for his continuing support, and Fondazione Cassadi Risparmio di Teramo (project 2009-2012 to M.M.) for financialsupport.

References

Aggarwald, B.B., Sung, B., 2009. Pharmacological basis for the role of curcumin inchronic diseases: an age-old spice with modern targets. Trends Pharmacol. Sci. 30,85–94.

Anderson, E., Zink, W., Xiong, H., Gendelman, H.E., 2002. HIV-1-associated dementia: ametabolic encephalopathy perpetrated by virus-infected and immune-competentmononuclear phagocytes. J. Acquir. Immune Defic. Syndr. 31, S43–S54.

Balasubramanyam, K., Varier, R.A., Altaf, M., Swaminathan, V., Siddappa, N.B., Ranga, U.,Kundu, T.K., 2004. Curcumin, a novel p300/CREB-binding protein-specific inhibitorof acetyltransferase, represses the acetylation of histone/nonhistone proteins andhistone acetyltransferase-dependent chromatin transcription. J Biol Chem. 279,51163–51171.

Barks, J.D., Liu, X.H., Sun, R., Silverstein, F.S., 1997. gp120, a human immunodeficiencyvirus-1 coat protein, augments excitotoxic hippocampal injury in perinatal rats.Neuroscience 76, 397–409.

Barthelemy, S., Vergnes, L., Moynier, M., Guyot, D., Labidalle, S., Bahraoui, E., 1998.Curcumin and curcumin derivatives inhibit Tat-mediated transactivation of type 1human immunodeficiency virus long terminal repeat. Res. Virol. 149, 43–52.

Basavarajappa, B.S., Nixon, R.A., Arancio, O., 2009. Endocannabinoid system: emergingrole from neurodevelopment to neurodegeneration. Mini Rev. Med. Chem. 9,448–462.

Begg, M., Pacher, P., Bátkai, S., Osei-Hyiaman, D., Offertáler, L., Mo, F.M., Liu, J., Kunos, G.,2005. Evidence for novel cannabinoid receptors. Pharmacol. Ther. 106, 133–145.

Beltramo, M., Bernardini, N., Bertorelli, R., Campanella, M., Nicolussi, E., Fredduzzi, S.,Reggiani, A., 2006. CB2 receptor-mediated antihyperalgesia: possible directinvolvement of neural mechanisms. Eur. J. NeuroSci. 23, 1530–1538.

Benito, C., Kim, W.K., Chavarría, I., Hillard, C.J., Mackie, K., Tolón, R.M., Williams, K.,Romero, J., 2005. A glial endogenous cannabinoid system is upregulated in thebrains of macaques with simian immunodeficiency virus-induced encephalitis.J. Neurosci. 25, 2530–2536.

Benito, C., Núñez, E., Pazos, M.R., Tolón, R.M., Romero, J., 2007. The endocannabinoidsystem and Alzheimer's disease. Mol. Neurobiol. 36, 75–81.

Bergonzini, V., Calistri, A., Salata, C., Del Vecchio, C., Sartori, E., Parolin, C., Palu, G., 2009.Nef and cell signaling transduction: a possible involvement in the pathogenesis ofhuman immunodeficiency virus-associated dementia. J. Neurovirol. 20, 1–11.

Bezzi, P., Domercq, M., Vesce, S., Volterra, A., 2001. Neuron-astrocyte cross-talk duringsynaptic transmission: physiological and neuropathological implications. Prog.Brain Res. 132, 255–265.

Bisogno, T., Howell, F., Williams, G., Minassi, A., Cascio, M.G., Ligresti, A., Matias, I.,Schiano-Moriello, A., Paul, P., Williams, E.J., Gangadharan, U., Hobbs, C., Di Marzo,V., Doherty, P., 2003. Cloning of the first sn1-DAG lipases points to the spatial andtemporal regulation of endocannabinoid signaling in the brain. J. Cell. Biol. 163,463–468.

Cabral, G.A., Griffin-Thomas, L., 2008. Cannabinoids as therapeutic agents for ablatingneuroinflammatory disease. Endocr. Metab. Immune Disord. Drug Targets 8,159–172.

Calì, C., Marchaland, J., Regazzi, R., Bezzi, P., 2008. SDF 1-alpha (CXCL12) triggersglutamate exocytosis from astrocytes on a millisecond time scale: imaging analysisat the single-vesicle level with TIRF microscopy. J. Neuroimmunol. 198, 82–91.

Carayon, P., Marchand, J., Dussossoy, D., Derocq, J.M., Jbilo, O., Bord, A., Bouaboula, M.,Galiègue, S., Mondière, P., Pénarier, G., Fur, G.L., Defrance, T., Casellas, P., 1998.Modulation and functional involvement of CB2 peripheral cannabinoid receptorsduring B-cell differentiation. Blood 92, 3605–3615.

Carlisle, S.J., Marciano-Cabral, F., Staab, A., Ludwick, C., Cabral, G.A., 2002. Differentialexpression of the CB2 cannabinoid receptor by rodent macrophages andmacrophage-like cells in relation to cell activation. Int. Immunopharmacol. 2,69–82.

Carrier, E.J., Kearn, C.S., Barkmeier, A.J., Breese, N.M., Yang, W., Nithipatikom, K., Pfister,S.L., Campbell, W.B., Hillard, C.J., 2004. Cultured rat microglial cells synthesize theendocannabinoid 2-arachidonylglycerol, which increases proliferation via a CB2receptor-dependent mechanism. Mol. Pharmacol. 65, 999–1007.

Catani, M.V., Corasaniti, M.T., Navarra, M., Nisticò, G., Finazzi-Agrò, A., Melino, G., 2000.gp120 induces cell death in human neuroblastoma cells through the CXCR4 andCCR5 chemokine receptors. J. Neurochem. 74, 2373–2379.

Centonze, D., Battistini, L., Maccarrone, M., 2008. The endocannabinoid system inperipheral lymphocytes as a mirror of neuroinflammatory diseases. Curr. Pharm.Des. 14, 2370–2382.

Centonze, D., Finazzi-Agrò, A., Bernardi, G., Maccarrone, M., 2007. The endocannabinoidsystem in targeting inflammatory neurodegenerative diseases. Trends Pharmacol.Sci. 28, 180–187.

Churchill, M.J., Wesselingh, S.L., Cowley, D., Pardo, C.A., McArthur, J.C., Brew, B.J., Gorry,P.R., 2009. Extensive astrocyte infection is prominent in human immunodeficiencyvirus-associated dementia. Ann. Neurol. 66, 253–258.

Chevaleyre, V., Takahashi, K.A., Castillo, P.E., 2006. Endocannabinoid-mediated synapticplasticity in the CNS. Annu. Rev. Neurosci. 29, 37–76.

Corasaniti, M.T., Maccarrone, M., Nistico, R., Malorni, W., Rotiroti, D., Bagetta, G., 2001.Exploitation of the HIV-1 coat glycoprotein, gp120, in neurodegenerative studiesin vivo. J. Neurochem. 79, 1–8.

Cotrina, M.L., Lin, J.H., Nedergaard, M., 1998. Cytoskeletal assembly and ATP releaseregulate astrocytic calcium signaling. J. Neurosci. 18, 8794–8804.

Cravatt, B.F., Demarest, K., Patricelli, M.P., Bracey, M.H., Giang, D.K., Martin, B.R.,Lichtman, A.H., 2001. Supersensitivity to anandamide and enhanced endogenouscannabinoid signaling in mice lacking fatty acid amide hydrolase. Proc. Natl. Acad.Sci. U. S. A. 98, 9371–9376.

Cravatt, B.F., Giang, D.K., Mayfield, S.P., Boger, D.L., Lerner, R.A., Gilula, N.B., 1996.Molecular characterization of an enzyme that degrades neuromodulatory fatty-acid amides. Nature 384, 83–87.

Croxford, J.L., 2003. Therapeutic potential of cannabinoids in CNS disease. CNS Drugs 17,179–202.

Devane, W.A., Hanus, L., Breuer, A., Pertwee, R.G., Stevenson, L.A., Griffin, G., Gibson, D.,Mandelbaum, A., Etinger, A., Mechoulam, R., 1992. Isolation and structure of a brainconstituent that binds to the cannabinoid receptor. Science 258, 1946–1949.

Dhillon, N.K., Williams, R., Callen, S., Zien, C., Narayan, O., Buch, S., 2008. Roles of MCP-1in development of HIV-dementia. Front. Biosci. 13, 3913–3918.

Di Marzo, V., Fontana, A., Cadas, H., Schinelli, S., Cimino, G., Schwartz, J.C., Piomelli, D.,1994. Formation and inactivation of endogenous cannabinoid anandamide incentral neurons. Nature 372, 686–691.

Di Marzo, V., 2008. Endocannabinoids: synthesis and degradation. Rev. Physiol.Biochem. Pharmacol. 160, 1–24.

Di Marzo, V., 2009. The endocannabinoid system: its general strategy of action, tools forits pharmacological manipulation and potential therapeutic exploitation. Pharma-col. Res. 60, 77–84.

Di Marzo, V., De Petrocellis, L., 2010. Endocannabinoids as regulators of transientreceptor potential (TRP) channels: a further opportunity to develop newendocannabinoid-based therapeutic drugs. Curr. Med. Chem. 17, 1430–1449.

Dreyer, E.B., Kaiser, P.K., Offermann, J.T., Lipton, S.A., 1990. HIV-1 coat proteinneurotoxicity prevented by calcium channel antagonists. Science 248, 364–367.

Edwards, D.A., Zhang, L., Alger, B.E., 2008. Metaplastic control of the endocannabinoidsystem at inhibitory synapses in hippocampus. Proc. Natl. Acad. Sci. U. S. A. 105,8142–8147.

Eljaschewitsch, E., Witting, A., Mawrin, C., Lee, T., Schmidt, P.M., Wolf, S., Hoertnagl, H.,Raine, C.S., Schneider-Stock, R., Nitsch, R., Ullrich, O., 2006. The endocannabinoidanandamide protects neurons during CNS inflammation by induction of MKP-1 inmicroglial cells. Neuron 49, 67–79.

Esposito, G., Ligresti, A., Izzo, A.A., Bisogno, T., Ruvo, M., Di Rosa, M., Di Marzo, V., Iuvone,T., 2002. The endocannabinoid system protects rat glioma cells against HIV-1 Tatprotein-induced cytotoxicity. Mechanism and regulation. J. Biol. Chem. 277,50348–50354.

Facchinetti, F., Del Giudice, E., Furegato, S., Passarotto, M., Leon, A., 2003. Cannabinoidsablate release of TNF alpha in rat microglial cells stimulated with lypopolysacchar-ide. Glia 41, 161–168.

Fegley, D., Gaetani, S., Duranti, A., Tontini, A., Mor, M., Tarzia, G., Piomelli, D., 2005.Characterization of the fatty acid amide hydrolase inhibitor cyclohexyl carbamicacid 3'-carbamoyl-biphenyl-3-yl ester (URB597): effects on anandamide andoleoylethanolamide deactivation. J. Pharmacol. Exp. Ther. 313, 352–358.

Fellin, T., 2009. Communication between neurons and astrocytes: relevance to themodulation of synaptic and network activity. J. Neurochem. 108, 533–544.

Fernandes, S.P., Edwards, T.M., Ng, K.T., Robinson, S.R., 2007. HIV-1 protein gp120rapidly impairs memory in chicks by interrupting the glutamate-glutamine cycle.Neurobiol. Learn. Mem. 87, 1–8.

Fernández-López, D., Martínez-Orgado, J., Nuñez, E., Romero, J., Lorenzo, P., Moro, M.A.,Lizasoain, I., 2006. Characterization of the neuroprotective effect of the cannabinoidagonist WIN-55212 in an in vitro model of hypoxic-ischemic brain damage innewborn rats. Pediatr. Res. 60, 169–173.

Fernández-Ruiz, J., 2009. The endocannabinoid system as a target for the treatment ofmotor dysfunction. Br. J. Pharmacol. 156, 1029–1040.

Fezza, F., De Simone, C., Amadio, D., Maccarrone, M., 2008. Fatty acid amide hydrolase: agate-keeper of the endocannabinoid system. Subcell. Biochem. 49, 101–132.

Floyd, R.A., 1999. Antioxidants, oxidative stress, and degenerative neurologicaldisorders. Proc. Soc. Exp. Biol. Med. 222, 236–245.

Franklin, A., Stella, N., 2003. Arachidonylcyclopropylamide increases microglial cellmigration through cannabinoid CB2 and abnormal-cannabidiol-sensitive receptors.Eur. J. Pharmacol. 474, 195–198.

83M. Bari et al. / Experimental Neurology 224 (2010) 74–84

Funk, C.D., 2001. Prostaglandins and leukotrienes: advances in eicosanoid biology.Science 294, 1871–1875.

Galal, A.M., Slade, D., Gul, W., El-Alfy, A.T., Ferreira, D., Elsohly, M.A., 2009. Naturallyoccurring and related synthetic cannabinoids and their potential therapeuticapplications. Recent Pat CNS Drug Discov. 4, 112–136.

Galve-Roperh, I., Aguado, T., Palazuelos, J., Guzmán, M., 2008. Mechanisms of control ofneuron survival by the endocannabinoid system. Curr. Pharm. Des. 14, 2279–2288.

Garden, G.A., Möller, T., 2006. Microglia biology in health and disease. J. NeuroimmunePharmacol. 1, 127–137.

Glowa, J.R., Panlilio, L.V., Brenneman, D.E., Gozes, I., Fridkin, M., Hill, J.M., 1992. Learningimpairment following intracerebral administration of the HIV envelope proteingp120 or a VIP antagonist. Brain Res. 570, 49–53.

Göbel, W., Kampa, B.M., Helmchen, F., 2007. Imaging cellular network dynamics inthree dimensions using fast 3D laser scanning. Nat. Methods 4, 73–79.

González-Scarano, F., Martín-García, J., 2005. The neuropathogenesis of AIDS. Nat RevImmunol. 569–581.

Gordon, S., 2003. Alternative activation of macrophages. Nat. Rev. Immunol. 3, 23–35.Gubellini, P., Picconi, B., Bari, M., Battista, N., Calabresi, P., Centonze, D., Bernardi, G.,

Finazzi-Agrò, A., Maccarrone, M., 2002. Experimental parkinsonism alters endo-cannabinoid degradation: implications for striatal glutamatergic transmission.J. Neurosci. 22, 6900–6907.

Hanuš, , , R., L.O., Mechoulam, R., 2010. Novel natural and synthetic ligands of theendocannabinoid system. Curr. Med. Chem. 17, 1341–1359.

Haughey, N.J., Cutler, R.G., Tamara, A., McArthur, J.C., Vargas, D.L., Pardo, C.A., Turchan, J.,Nath, A., Mattson, M.P., 2004. Perturbation of sphingolipid metabolism andceramide production in HIV-dementia. Ann. Neurol. 55, 257–267.

Hillard, C.J., 2008. Role of cannabinoids and endocannabinoids in cerebral ischemia.Curr. Pharm. Des. 14, 2347–2361.

Hill, J.M., Mervis, R.F., Avidor, R., Moody, T.W., Brenneman, D.E., 1993. HIV envelopeprotein-induced neuronal damage and retardation of behavioral development inrat neonates. Brain Res. 603, 222–233.

Hirase, H., Qian, L., Barthó, P., Buzsáki, G., 2004. Calcium dynamics of cortical astrocyticnetworks in vivo. PLoS Biol. 2, E96.

Howlett, A.C., Blume, L.C., Dalton, G.D., 2010. CB1 cannabinoid receptors and theirassociated proteins. Curr. Med. Chem. 17, 1382–1393.

Jagetia, G.C.., Aggarwal, B.B., 2007. "Spicing up" of the immune system by curcumin.J. Clin. Immunol. 27, 19–35.

Jiang, Z.G., Piggee, C., Heyes, M.P., Murphy, C., Quearry, B., Bauer, M., Zheng, J.,Gendelman, H.E., Markey, S.P., 2001. Glutamate is a mediator of neurotoxicity insecretions of activatedHIV-1-infectedmacrophages. J. Neuroimmunol. 117, 97–107.

Jordt, S.E., Julius, D., 2002. Molecular basis for species-specific sensitivity to "hot" chilipeppers. Cell 108, 421–430.

Jung, J., Hwang, S.W., Kwak, J., Lee, S.Y., Kang, C.J., Kim, W.B., Kim, D., Oh, U., 1999.Capsaicin binds to the intracellular domain of the capsaicin-activated ion channel.J. Neurosci. 19, 529–538.

Kanmogne, G.D., Schall, K., Leibhart, J., Knipe, B., Gendelman, H.E., Persidsky, Y., 2007.HIV-1 gp120 compromises blood–brain barrier integrity and enhances monocytemigration across blood–brain barrier: implication for viral neuropathogenesis.J. Cereb. Blood Flow Metab. 27, 123–134.

Kathuria, S., Gaetani, S., Fegley, D., Valiño, F., Duranti, A., Tontini, A., Mor, M., Tarzia, G.,La Rana, G., Calignano, A., Giustino, A., Tattoli, M., Palmery, M., Cuomo, V., Piomelli,D., 2003. Modulation of anxiety through blockade of anandamide hydrolysis. Nat.Med. 9, 76–81.

Kaul, M., Lipton, S.A., 1999. Chemokines and activated macrophages in HIV gp120-induced neuronal apoptosis. Proc. Natl. Acad. Sci. U. S. A. 96, 8212–8216.

Kaul, M., Garden, G.A., Lipton, S.A., 2001. Pathways to neuronal injury and apoptosis inHIV-associated dementia. Nature 410, 988–994.

Kelder, W., McArthur, J.C., Nance-Sproson, T., McClernon, D., Griffin, D.E., 1998. Beta-chemokines MCP-1 and RANTES are selectively increased in cerebrospinal fluid ofpatients with human immunodeficiency virus-associated dementia. Ann. Neurol.44, 831–835.

Koka, P., He, K., Zack, J.A., Kitchen, S., Peacock, W., Fried, I., Tran, T., Yashar, S.S., Merrill,J.E., 1995. Human immunodeficiency virus 1 envelope proteins induce interleukin1, tumor necrosis factor alpha, and nitric oxide in glial cultures derived from fetal,neonatal, and adult human brain. J. Exp. Med. 182, 941–952.

Kolson, D.L., González-Scarano, F., 2000. HIV and HIV dementia. J. Clin. Invest. 106,11–13.

Lauckner, J.E., Jensen, J.B., Chen, H.Y., Lu, H.C., Hille, B., Mackie, K., 2008. GPR55 is acannabinoid receptor that increases intracellular calcium and inhibits M current.Proc. Natl. Acad. Sci. U. S. A. 105, 2699–2704.

Lee, S.F., Newton, C., Widen, R., Friedman, H., Klein, T.W., 2001. Differential expressionof cannabinoid CB(2) receptor mRNA in mouse immune cell subpopulations andfollowing B cell stimulation. Eur. J. Pharmacol. 423, 235–241.

Ligresti, A., Petrosino, S., Di Marzo, V., 2009. From endocannabinoid profiling to“endocannabinoid therapeutics”. Curr Opin Chem Biol. 13, 321–331.

Lu, Q., Straiker, A., Lu, Q., Maguire, G., 2000. Expression of CB2 cannabinoid receptormRNA in adult rat retina. Vis. Neurosci. 17, 91–95.

Lu, T.S., Avraham, H.K., Seng, S., Tachado, S.D., Koziel, H., Makriyannis, A., Avraham, S.,2008. Cannabinoids inhibit HIV-1 Gp120-mediated insults in brain microvascularendothelial cells. J Immunol. 181, 6406–6416.

Maccarrone, M., 2009. The endocannabinoid system and its manifold central actions. In:Tettamanti, G., Goracci, G. (Eds.), Handbook of neurochemistry and molecularneurobiology—neural lipids. Springer, pp. 385–405.

Maccarrone, M., Battista, N., Centonze, D., 2007. The endocannabinoid pathway inHuntington's disease: a comparison with other neurodegenerative diseases. Prog.Neurobiol. 81, 349–379.

Maccarrone, M., Navarra, M., Corasaniti, M.T., Nisticò, G., Finazzi Agrò, A., 1998.Cytotoxic effect of HIV-1 coat glycoprotein gp120 on human neuroblastomaCHP100 cells involves activation of the arachidonate cascade. Biochem. J. 333,45–49.

Maccarrone, M., Piccirilli, S., Battista, N., Del Duca, C., Nappi, G., Corasaniti, M.T., Finazzi-Agrò, A., Bagetta, G., 2004. Enhanced anandamide degradation is associated withneuronal apoptosis induced by the HIV-1 coat glycoprotein gp120 in the ratneocortex. J. Neurochem. 89, 1293–1300.

Maresz, K., Carrier, E.J., Ponomarev, E.D., Hillard, C.J., Dittel, B.N., 2005. Modulation ofthe cannabinoid CB2 receptor in microglial cells in response to inflammatorystimuli. J. Neurochem. 95, 437–445.

Marsicano, G., Moosmann, B., Hermann, H., Lutz, B., Behl, C., 2002. Neuroprotectiveproperties of cannabinoids against oxidative stress: role of the cannabinoidreceptor CB1. J, Neurochem. 80, 448–456.

Marsicano, G., Goodenough, S., Monory, K., Hermann, H., Eder, M., Cannich, A., Azad, S.C.,Cascio, M.G., Gutiérrez, S.O., van der Stelt, M., López-Rodriguez, M.L., Casanova, E.,Schütz, G., Zieglgänsberger, W., Di Marzo, V., Behl, C., Lutz, B., 2003. CB1 cannabinoidreceptors and on-demand defense against excitotoxicity. Science 302, 84–88.

Massi, P., Valenti, M., Bolognini, D., Parolaro, D., 2008. Expression and function of theendocannabinoid system in glial cells. Curr. Pharm. Des. 14, 2289–2298.

Matsuda, L.A., Lolait, S.J., Brownstein, M.J., Young, A.C., Bonner, T.I., 1990. Structure of acannabinoid receptor and functional expression of the cloned cDNA. Nature 346,561–564.

Mattson, M.P., Haughey, N.J., Nath, A., 2005. Cell death in HIV dementia. Cell DeathDiffer. 1, 893–904.

McKinney, M.K., Cravatt, B.F., 2005. Structure and function of fatty acid amidehydrolase. Annu. Rev. Biochem. 74, 411–432.

McPartland, J., 1999. Marijuana andmedicine: the endocrine effects of Cannabis. Altern.Ther. Women's Health 1, 41–44.

Molina-Holgado, F., Pinteaux, E., Moore, J.D., Molina-Holgado, E., Guaza, C., Gibson, R.M.,Rothwell, N.J., 2003. Endogenous interleukin-1 receptor antagonist mediates anti-inflammatory and neuroprotective actions of cannabinoids in neurons and glia.J. Neurosci. 23, 6470–6474.

Mothet, J.P., Parent, A.T., Wolosker, H., Brady Jr., R.O., Linden, D.J., Ferris, C.D., Rogawski,M.A., Snyder, S.H., 2000. D-serine is an endogenous ligand for the glycine site of theN-methyl-D-aspartate receptor. Proc. Natl. Acad. Sci. U. S. A. 97, 4926–4931.

Muccioli, G.G., Xu, C., Odah, E., Cudaback, E., Cisneros, J.A., Lambert, D.M., López Rodríguez,M.L., Bajjalieh, S., Stella, N., 2007. Identification of a novel endocannabinoid-hydrolyzing enzyme expressed by microglial cells. J. Neurosci. 27, 2883–2889.

Munro, S., Thomas, K.L., Abu-Shaar, M., 1993. Molecular characterization of a peripheralreceptor for cannabinoids. Nature 365, 61–65.

Murdoch, C., Finn, A., 2000. Chemokine receptors and their role in vascular biology.J. Vasc. Res. 37, 1–7.

Nosheny, R.L., Mocchetti, I., Bachis, A., 2005. Brain-derived neurotrophic factor as aprototype neuroprotective factor against HIV-1-associated neuronal degeneration.Neurotox Res. 8, 187–198.

Núñez, E., Benito, C., Pazos, M.R., Barbachano, A., Fajardo, O., González, S., Tolón, R.M.,Romero, J., 2004. Cannabinoid CB2 receptors are expressed by perivascularmicroglial cells in the human brain: an immunohistochemical study. Synapse 53,208–213.

Oddi, S., Fezza, F., Pasquariello, N., De Simone, C., Rapino, C., Dainese, E., Finazzi-Agrò, A.,Maccarrone, M., 2008. Evidence for the intracellular accumulation of anandamidein adiposomes. Cell. Mol. Life Sci. 65, 840–850.

Oddi, S., Fezza, F., Pasquariello, N., D'Agostino, A., Catanzaro, G., De Simone, C., Rapino,C., Finazzi-Agrò, A., Maccarrone, M., 2009. Molecular identification of albumin andHsp70 as cytosolic anandamide-binding proteins. Chem Biol. 16, 624–632.

Okamoto, Y., Morishita, J., Tsuboi, K., Tonai, T., Ueda, N., 2004. Molecular characteriza-tion of a phospholipase D generating anandamide and its congeners. J. Biol. Chem.279, 5298–5305.

Palazuelos, J., Aguado, T., Pazos, M.R., Julien, B., Carrasco, C., Resel, E., Sagredo, O., Benito,C., Romero, J., Azcoitia, I., Fernández-Ruiz, J., Guzmán, M., Galve-Roperh, I., 2009.Microglial CB2 cannabinoid receptors are neuroprotective in Huntington's diseaseexcitotoxicity. Brain 132, 3152–3164.

Panikashvili, D., Shein, N.A., Mechoulam, R., Trembovler, V., Kohen, R., Alexandrovich,A., Shohami, E., 2006. The endocannabinoid 2-AG protects the blood–brain barrierafter closed head injury and inhibits mRNA expression of proinflammatorycytokines. Neurobiol. Dis. 22, 257–264.

Patel, K.D., Davison, J.S., Quentin, J., Pittman, O.J., Sharkey, K.A., 2010. Cannabinoid CB2

receptors in health and disease. Curr. Med. Chem. 17, 1394–1410.Parpura, V., Basarsky, T.A., Liu, F., Jeftinija, K., Jeftinija, S., Haydon, P.G., 1994. Glutamate-

mediated astrocyte-neuron signalling. Nature 369, 744–777.Patricelli, M.P., Lovato, M.A., Cravatt, B.F., 1999. Chemical and mutagenic investigations

of fatty acid amide hydrolase: evidence for a family of serine hydrolases withdistinct catalytic properties. Biochemistry 38, 9804–9812.

Pazos,M.R., Núñez, E., Benito, C., Tolón, R.M., Romero, J., 2005. Functional neuroanatomyofthe endocannabinoid system. Pharmacol. Biochem. Behav. 81, 239–247.

Pertwee, R.G., 2010. Receptors and channels targeted by synthetic cannabinoid receptoragonists and antagonists. Curr. Med. Chem. 17, 1360–1381.

Perfettini, J.L., Castedo, M., Roumier, T., Andreau, K., Nardacci, R., Piacentini, M.,Kroemer, G., 2005. Mechanisms of apoptosis induction by the HIV-1 envelope. CellDeath Differ. 12, 916–923.

Perea, G., Navarrete, M., Araque, A., 2009. Tripartite synapses: astrocytes process andcontrol synaptic information. Trends Neurosci. 32, 421–431.

Peterson, P.K., Gekker, G., Hu, S., Cabral, G., Lokensgard, J.R., 2004. Cannabinoids andmorphine differentially affect HIV-1 expression in CD4(+) lymphocyte andmicroglial cell cultures. J. Neuroimmunol. 147, 123–126.

84 M. Bari et al. / Experimental Neurology 224 (2010) 74–84

Pistis, M., Melis, M., 2010. From surface to nuclear receptors: the endocannabinoidfamily extends its assets. Curr. Med. Chem. 17, 1450–1467.

Price, T.O., Ercal, N., Nakaoke, R., Banks, W.A., 2005. HIV-1 viral proteins gp120 and Tatinduce oxidative stress in brain endothelial cells. Brain Res. 1045, 57–63.

Portegies, P., 1994. AIDS dementia complex: a review. J Acquir Immune Defic Syndr. 7,S38–S48.

Price, T.O., Uras, F., Banks, W.A., Ercal, N., 2006. A novel antioxidant N-acetylcysteineamide prevents gp120- and Tat-induced oxidative stress in brain endothelial cells.Exp. Neurol. 201, 193–202.

Puffenbarger, R.A., Boothe, A.C., Cabral, G.A., 2000. Cannabinoids inhibit LPS-induciblecytokine mRNA expression in rat microglial cells. Glia 29, 58–69.

Pugh, C.R., Johnson, J.D., Martin, D., Rudy, J.W., Maier, S.F., Watkins, L.R., 2000. Humanimmunodeficiency virus-1 coat protein gp120 impairs contextual fear conditioning:a potential role in AIDS related learning and memory impairments. Brain Res. 861,8–15.

Ramírez, B.G., Blázquez, C., Gómez del Pulgar, T., Guzmán, M., Ceballos, T., 2005.Prevention of Alzheimer's disease pathology by cannabinoids: neuroprotectionmediated by blockade of microglial activation. J. Neurosci. 23, 1904–1913.

Rock, R.B., Gekker, G., Hu, S., Sheng, W.S., Cabral, G.A., Martin, B.R., Peterson, P.K., 2007.WIN55, 212–2-mediated inhibition of HIV-1 expression in microglial cells:involvement of cannabinoid receptors. J. Neuroimmune Pharmacol. 2, 178–183.

Rossi, S., Bernardi, G., Centonze, D., The endocannabinoid system in the inflammatoryand neurodegenerative processes of multiple sclerosis and of amyotrophic lateralsclerosis. Exp. Neurol., in press. doi:10.1016/j.expneurol.2010.03.030.

Rouzer, C.A., Marnett, L.J., 2008. Non-redundant functions of cyclooxygenases:oxygenation of endocannabinoids. J. Biol. Chem. 283, 8065–8069.

Sánchez-Alavez, M., Criado, J., Gómez-Chavarín, M., Jiménez-Anguiano, A., Navarro, L.,Díaz-Ruiz, O., Galicia, O., Sánchez-Narváez, F., Murillo-Rodríguez, E., Henriksen, S.J.,Elder, J.H., Prospéro-García, O., 2000. HIV- and FIV-derived gp120 alter spatialmemory, LTP, and sleep in rats. Neurobiol. Dis. 7, 384–394.

Seifert, G., Carmignoto, G., Steinhäuser, C., 2009. Astrocyte dysfunction in epilepsy.Brain Res, Rev. 31.

Sharma, D., Bhattacharya, J., 2009. Cellular & molecular basis of HIV-associatedneuropathogenesis. Indian J. Med. Res. 129, 637–651.

Sheng, W.S., Hu, S., Min, X., Cabral, G.A., Lokensgard, J.R., Peterson, P.K., 2005. Syntheticcannabinoid WIN55, 212–2 inhibits generation of inflammatory mediators by IL-1beta-stimulated human astrocytes. Glia 49, 211–219.

Simon, G.M., Cravatt, B.F., 2008. Anandamide biosynthesis catalyzed by the phospho-diesterase GDE1 and detection of glycerophospho-N-acylethanolamine precursorsin mouse brain. J. Biol. Chem. 283, 9341–9349.

Spagnuolo, P., Calì, C., Marchaland, J., Bari, M., Maccarrone, M., Bezzi, P., Bagetta, G.,2008. (Endo)cannabinoids regulate TNF-alpha and glutamate release fromastrocytes. XI Workshop On Apoptosis in Biology and Medicine. (12-14 September2008, Sendai, Japan).

Stella, N., 2009. Endocannabinoid signaling in microglial cells. Neuropharmacology 56,244–253.

Stella, N., Schweitzer, P., Piomelli, D., 1997. A second endogenous cannabinoid thatmodulates long-term potentiation. Nature 388, 773–778.

Stellwagen, D., Malenka, R.C., 2006. Synaptic scaling mediated by glial TNF-alpha.Nature 440, 1054–1059.

Sugiura, T., Kobayashi, Y., Oka, S., Waku, K., 2002. Biosynthesis and degradation ofanandamide and 2-arachidonoylglycerol and their possible physiological signifi-cance. Prostaglandins Leukot. Essent. Fatty Acids 66, 173–192.

Tang, H., Lu, D., Pan, R., Qin, X., Xiong, H., Dong, J., 2009. Curcumin improves spatialmemory impairment induced by human immunodeficiency virus type 1 glycopro-tein 120 V3 loop peptide in rats. Life Sci. 85, 1–10.

Toggas, S.M., Masliah, E., Mucke, L., 1996. Prevention of HIV-1 gp120-induced neuronaldamage in the central nervous system of transgenic mice by the NMDA receptorantagonist memantine. Brain Res. 706, 303–307.

Ueda, N., Puffenbarger, R.A., Yamamoto, S., Deutsch, D.G., 2000. The fatty acid amidehydrolase (FAAH). Chem. Phys. Lipids 108, 107–121.

Van der Stelt, M., Veldhuis, W.B., Maccarrone, M., Bär, P.R., Nicolay, K., Veldink, G.A., DiMarzo, V., Vliegenthart, J.F., 2002a. Acute neuronal injury, excitotoxicity, and theendocannabinoid system. Mol. Neurobiol. 26, 317–346.

Van der Stelt, M., van Kuik, J.A., Bari, M., van Zadelhoff, G., Leeflang, B.R., Veldink, G.A.,Finazzi-Agrò, A., Vliegenthart, J.F., Maccarrone, M., 2002b. Oxygenated metabolitesof anandamide and 2-arachidonoylglycerol: conformational analysis and interac-tion with cannabinoid receptors, membrane transporter, and fatty acid amidehydrolase. J Med Chem. 45, 3709–3720.

Van Sickle, M.D., Duncan, M., Kingsley, P.J., Mouihate, A., Urbani, P., Mackie, K., Stella, N.,Makriyannis, A., Piomelli, D., Davison, J.S., Marnett, L.J., Di Marzo, V., Pittman, Q.J.,Patel, K.D., Sharkey, K.A., 2005. Identification and functional characterization ofbrainstem cannabinoid CB2 receptors. Science 310, 329–332.

Vanzani, M.C., Iacono, R.F., Caccuri, R.L., Troncoso, A.R., Berria, M.I., 2006. Regional differencesin astrocyte activation in HIV-associated dementia. Medicina (B Aires). 66, 108–112.

Vigh, J., Von Gersdorff, H., 2007. Endocannabinoids mediate synaptic plasticity at mixedsynapses. Neuron 56, 945–946.

Viscomi, M.T., Oddi, S., Latini, L., Pasquariello, N., Florenzano, F., Bernardi, G., Molinari,M., Maccarrone, M., 2009. Selective CB2 receptor agonism protects central neuronsfrom remote axotomy-induced apoptosis through the PI3K/Akt pathway.J. Neurosci. 29, 4564–4570.

Waksman, Y., Olson, J.M., Carlisle, S.J., Cabral, G.A., 1999. The central cannabinoidreceptor (CB1)mediates inhibition of nitric oxide production by rat microglial cells.J. Pharmacol. Exp. Ther. 288, 1357–1366.

Walter, L., Franklin, A.,Witting, A.,Moller, T., Stella, N., 2002. Astrocytes in culture produceanandamide and other acylethanolamides. J. Biol. Chem. 277, 20869–20876.

Walter, L., Franklin, A., Witting, A., Wade, C., Xie, Y., Kunos, G., Mackie, K., Stella, N.,2003. Nonpsychotropic cannabinoid receptors regulate microglial cell migration.J. Neurosci. 23, 1398–1405.

Watt, M.H., Maman, S., Earp, J.A., Eng, E., Setel, P.W., Golin, C.E., Jacobson, M., 2009. “It'sall the time in my mind”: facilitators of adherence to antiretroviral therapy in aTanzanian setting. Soc. Sci. Med. 68, 1793–1800.

Williams, R., Yao, H., Dhillon, N.K., Buch, S.J., 2009. HIV-1 Tat co-operates with IFN-gamma and TNF-alpha to increase CXCL10 in human astrocytes. PLoS ONE 4, 5709.

Witting, A., Walter, L., Wacker, J., Möller, T., Stella, N., 2004. P2X7 receptors control 2-arachidonoylglycerol production by microglial cells. Proc. Natl. Acad. Sci. U. S. A.101, 3214–3219.

Wolf, S.A., Tauber, S., Ullrich, O., 2008. CNS immune surveillance and neuroinflamma-tion: endocannabinoids keep control. Curr. Pharm. Des. 14, 2266–2278.

Wyss-Coray, T., Loike, J.D., Brionne, T.C., Lu, E., Anankov, R., Yan, F., Silverstein, S.C.,Husemann, J., 2003. Adult mouse astrocytes degrade amyloid-beta in vitro and insitu. Nat. Med. 9, 453–457.

Xing, H.Q., Hayakawa, H., Gelpi, E., Kubota, R., Budka, H., Izumo, S., 2009. Reducedexpression of excitatory amino acid transporter 2 and diffuse microglial activationin the cerebral cortex in AIDS cases with or without HIV encephalitis.J. Neuropathol. Exp. Neurol. 68, 199–209.

Yang, S., Zhang, D., Yan, Z., Hu, X., Qian, S., Jie, L., Wilson, B., Bloc, M., Hong, J.S., 2008.Curcumin protects dopaminergic neuron against LPS-induced neurotoxicity inprimary rat neuron/glia culture. Neurochem. Res. 33, 2044–2053.

Zhang, J., Hoffert, C., Vu, H.K., Groblewski, T., Ahmad, S., O'Donnell, D., 2003. Induction ofCB2 receptor expression in the rat spinal cord of neuropathic but not inflammatorychronic pain models. Eur. J. NeuroSci. 17, 2750–2754.