Late Phase Allergic Reactions

Editor Walter Dorsch, M.D., Ph.D.

Johannes Gutenberg University Children's Hospital Mainz, West Germany

C R C Press Boca Raton A n n A r b o r Boston

T A B L E OF CONTENTS

PART I . INTRODUCTION

Chapter 1 History and Introduction: Late Phase Allergic Reactions 1 J . Pepys

Chapter 2 Definitions and Clinical Symptoms 9 W. Dorsch

PART I I . PATHOGENESIS O F L C R PART I L A . T R I G G E R MECHANISMS

Chapter 3 IgE Antibodies 19 G . O. Solley

Chapter 4 IgE-Independent Mechanisms 25 O. Zetterström

Chapter 5 Exudate from Human Weal and Flare Reactions 31 W. Dorsch and J . Ring

PART I I . B . T H E R O L E O F MEDIATORS

Chapter 6 Mast Cell-Derived Mediators 35 R. F . Lemanske, Jr .

Chapter 7 Histamine 43 J . Ring and W. Dorsch

Chapter 8 Prostaglandins 53 W. Dorsch

Chapter 9 Leukotrienes 59 W. Dorsch and Th. Strasser

Chapter 10 Thromboxanes 65 W. Dorsch

Chapter 11 Platelet-Activating Factor 71 C . P. Page and A. J . Coyle

Chapter 12 Act ivat ion of the Clotting System and Fibrin Deposition in Human LCR 83 Η. F . Dvorak and R. de Shazo

Chapter 13 Kal l ikre in -Kin in System 93 D. Vervloet, P. Dor, and D. Charpin

PART I L C . R O L E O F I N F L A M M A T O R Y C E L L S

Chapter 14 The Role of Inflammatory Cells in LPR 101

K . Leiferman and G . Gleich

PART ΙΠ. PATHOGENESIS O F LNR

Chapter 15

Late Nasal Response—Its Clinical Characteristics, Features, and Possible Mechanisms I l l Z. Pelikan PART IV. PATHOGENESIS O F L B R

Chapter 16 IgE-Dependent Mechanisms in the Induction of L B R 159 W. J . Metzger

Chapter 17 Exercise-Induced Asthma and L B R 169 C . W. Bierman

Chapter 18 Chemotactic Factors and Allergen-Induced L B R 185 S. Durham, K . Few, and A. B. Kay

Chapter 19 The Use of Bronchoalveolar Lavage ( B A L ) to Study Late Phase Allergic Asthma 196 W. J . Metzger

Chapter 20 Platelets and Asthma 211 C . P. Page and A. J . Coyle

Chapter 21 On the Central Role of the Vascular Endothelium in Allergic Reactions 221 B. S. Bochner, A. M. Lamas, S. Benenati, and R. P. Schleimer

PART V. P H A R M A C O L O G I C MODULATION O F L P R O F T H E SKIN, NOSE, AND B R O N C H I A L S Y S T E M

Chapter 22 Corticosteroids 239 H . F . Kauffman, J . G . R. de Monchy, H . Meurs, G . H . Koeter, and K . de Vries

Chapter 23 The Influence of Sodium Cromoglycate and Nedocromil Sodium on LPR 257 J . G . R. de Monchy, H . F . Kauffman, and K . de Vries

Chapter 24 Beta-Adrenergic Agonists 269 D. W. Cockroft

Chapter 25 Muscarinic Cholinergic Antagonists 277 D. W. Cockroft

Chapter 26 Histamine Receptor Antagonists 283 W. Dorsch

Chapter 27 Ketotifen 289 R. Grönneberg

Chapter 28 Xanthines 293 R. Pauwels

Chapter 29 Nonsteroidal Anti- Inf lammatory Drugs 299 A. J . Fairfax

Chapter 30 Thromboxane Synthetase Inhibitors 313 I . Iwamoto, H. Tomioka, and S. Yoshida

Chapter 31 Tranexamic A c i d 321 R. Grönneberg

Chapter 32 Onion Extracts 325 W. Dorsch

Chapter 33 5,8,11,14-Eicosatetraynoic A c i d 333 W. Dorsch

P A R T V I . ANIMAL M O D E L S O F L P R

Chapter 34 Rat Skin Tests 339 R. F . Lemanske, Jr .

Chapter 35

Late Phase Asthma in an Allergic Rabbit Model 347 W. J . Metzger

Chapter 36 Late Phase Bronchial Reaction in Sheep 363 E . W. Russi

Chapter 37 Late Bronchial Responses in the Guinea Pig 373 P. A. Hutson, S. T. Holgate, and Μ. K . Church

Chapter 38 Skin Test on Monkeys 385 W. Dorsch

PART V I I . L P R AND CHRONIC A L L E R G I C DISEASES

Chapter 39 Lung Function Parameters in Late Bronchial Reactions and Chronic Bronchial Asthma 391 C . K . W. Lai and S. T . Holgate

Chapter 40 Bronchial Hyperreactivity and the Late Phase Reaction in Bronchial Asthma 401 R. Beasley, O. P. Twentyman, and S. T . Holgate

Chapter 41 The Role of Leukotrienes in Chronic Lung Diseases 407 W. Schönfeld, J . Knöller, and W. König

Chapter 42 PAF, Platelets, and Bronchial Hyperreactivity 439 A. J . Coyle and C . P. Page

Chapter 43 Eosinophils in Chronic Bronchopulmonary Disorders 445 P. F . Weiler and S. J . Ackerman

Chapter 44 Alveolar Macrophages and Bronchial Asthma 461 Ph. Godard, M. Damon, J . Bousquet, and F . B. Michel

Chapter 45 Chronic Urticaria and Late Phase Reactions 471 B. Czarnetzki

Chapter 46 The Tangled Web: Cooperation and Interdependency of Mediator Systems in Inflammation 481 M. Jochum and H. Fritz

Chapter 47 Regulatory Mechanisms 493 W. Dorsch, P. O'Byrne, and J . Dolovich

Chapter 48 Pathogenesis and Possible Mechanisms Underlying the Late Phase Reactions 499 Z. Pelikan

PART V I I I . C L I N I C A L CONSEQUENCES

Chapter 49 Differential Diagnosis of the Late Phase Reactions 521 Z. Pelikan

Chapter 50 Drug Therapy: The Effect of Continuous Treatment on Late Phase Reactions 527 O. P. Twentyman and S. T . Holgate

Chapter 51 The Effects of Immunotherapy on Late Phase Reactions 535 R. F . Lemanske, Jr .

Chapter 52 Summary and Conclusions 539 G . Gleich and W. Dorsch

INDEX 545

481

Chapter 46

T H E TANGLED WEB: COOPERATION AND INTERDEPENDENCY OF MEDIATOR SYSTEMS IN

INFLAMMATION

M. Jochum and H. Fritz

T A B L E OF CONTENTS

I . Introduction: Redundancy of Mediator Systems 482

I I . General Pathomechanisms 482

I I I . Cellular Systems and Their Mediators 484

I V . Proteinase Inhibitors 486

V. Diagnostic Approaches to Inflammatory Processes 488

V I . Medicinal Therapy Concepts 489

Suggested References 490

482 Late Phase Allergic Reactions

I . INTRODUCTION: REDUNDANCY O F MEDIATOR SYSTEMS

In previous Chapters of this book, the involvement of various mediator systems i n allergic inflammation has been described. This Chapter focuses on the interdependence o f cell and mediator systems induced either by mechanical in jury, infectious diseases, noxious agents or, last but not least, allergic reactions. I n dependency on the intensity of the noxious event, a series of complex cellular and biochemical events, the so-called inflammatory response, w i l l occur in tissues.

The inflammatory response constitutes a defense mechanism of the organism by which the stimulating agent or irritant is simultaneously eliminated and the healing process started to re-establish its integrity. The accompanying clinical symptoms of redness (rubor), swelling (tumor), heat (calor) and pain (dolor) have not lost any of their importance since their first presentation by the Roman physician Celsus (1st century A . D . ) .

Our perception and knowledge of the biochemical and cellular reactions underlying inflammatory processes are changing continuously as a result o f ever improving techniques of investigations. The importance of known inflammatory mediators becomes relative as new factors are discovered, defined, and to date unknown interactions postulated.

A n almost indefinite number of stimulators, mediators, effectors and inhibitors deter­mines the efficiency or the failure of the inflammatory response. Taking a closer look at the pathomechanisms of inflammation, a redundancy becomes evident: Many cellular and humoral mediators cause the same or similar symptoms, and different cell types, e .g. , the phagocytes, are at least partially able to replace each other in function. Obviously, the inflammatory reaction is too important a protective mechanism to be seriously impaired by the loss of a single cell type or mediator.

I I . G E N E R A L PATHOMECHANISMS

Injuries caused by direct force or microtrauma due to muscular and skeletal strain lead to bleeding and a subsequent f ibr in deposit. The primary stimulus for the activation o f thrombocytes and the plasma enzyme cascade systems (coagulation, f ibrinolysis , comple­ment, kal l ikrein-kinin system) is the exposure of surfaces normally inaccessible to the bloodstream (e.g. , subendothelial layer) to plasma constituents including cells (Figure 1) as well as the release of cellular factors including proteases. This initiates the inflammatory process.

Local inflammation can be induced by physical means (e .g. , impaired tissue through straining, heat, cold, radiation, chemical substances), auto-immune processes and invasive microorganisms (bacteria, f u n g i , viruses). In response to the inflammatory s t imul i , the defense and eliminating mechanisms are primari ly cellular in nature wi th the phagocytes playing a major role. Vasoactive and permeability enhancing factors are released provoking the extravasation of f l u i d f rom the vasculature. This results in edema formation and thus swelling of the interstitial tissue. The impaired microcirculation leads to ischemia and hy­poxia.

During both injury and inflammation the biochemical, cellular, and immunological reactions all take the same course but with different emphasis being placed on each event according to the triggering st imuli .

Attracted by chemotactic substances f rom the wounded or inflamed area, mobile leu­kocytes adhere to the endothelium of capillary vessels and migrate into the altered tissue fo l lowing the concentration gradient o f the attracting substances. The polymorphonuclear granulocytes, which are the first to migrate (within hours after damage), are fol lowed by monocytes and macrophages (within 24 h) and somewhat later by eosinophils and lympho­cytes (after a few days). It is the main task of these cells to eliminate degenerated and

483

injury — - Inflammation Infection

Activation -

Humoral Systems & Mediators

Τ Coagulation Cascade (SFMC)

Fibrinolysis Cascade (FDP)

Complement Cascade (C3a.C5a)

Kallikrein-Kinin- System (Kinins)

Cascade Proteinases

Peptide Mediators (see f )

Mutual Activation

Cellular Systems & Mediators

τ Thrombocytes. Endothelial Cells

Phagocytes (Granulocytes.

Monocytes. Macrophages)

Fibroblasts, Mast Cells, etc.

Cellular Proteinases & Components

Altered Structural Components

FIGURE 1. Relationships between mediator systems, the plasma protease cascades and inflammatory cells, in inflammation, cf. Figure 2 and text. SFMC: soluble fibrin monomer complexes; FDP: fibrin or fibrinogen degradation products; C3a & C5a: complement-derived anaphylatoxins; Kinins, bradykinin, etc.

impaired or destroyed tissue as wel l as foreign bodies and invasive microorganisms. I n order to be recognized and incorporated by the phagocytes the tissue particles or microbes have to be labeled ( 4 'opsonized") as being " f o r e i g n or degenerated" by humoral factors, the so-called opsonins (e .g . , f ibronectin, immunoglobulins). After incorporation into phagosomes which fuse w i t h lysosomes to digestive vacuoles, the phagolysosomes, degradation of the intracellularly deposited material by hydrolytic and oxidative processes takes place.

The immune system normally reacts more slowly than the non-specific defense mech­anisms. Therefore, the specific recognition of foreign substances and invasive microorga­nisms via antibodies or via cytotoxic T-lymphocytes usually takes place only days after the injury. Repair mechanisms responsible for the healing process start relatively early w i t h the proliferation of tissue-specific cells l ike histiocytes and fibroblasts. The stimulation of these cells by inflammatory mediators leads to the enhanced synthesis of tissue-specific substances such as collagen, elastin, and proteoglycans.

The most important aspect of the inflammatory reaction is the close cooperation between the humoral and cellular systems (Figure 1). Thereby a decisive role is played by proteolytic enzymes (proteases or proteinases) and the products of system-specific proteolysis in the humoral enzyme cascade systems on the one hand and of non-specific proteolysis caused by liberated lysosomal enzymes on the other hand. Both the proteases themselves and products of their actions, the biologically highly active polypeptides, are potent inflammatory mediators. Their pathogenetic potential becomes relevant when the extent o f their production exceeds the requirement for the healing process.

The system-specific proteases of the plasma enzyme cascades are generated f rom their inactive precursors (proenzymes) after direct (Hageman factor) or cofactor-transmitted con­tact (high molecular weight kininogen for plasma prokall ikrein and factor X I ) w i t h wounded surfaces as wel l as by cellular proteases, e .g. , thrombokinases and plasminogen activators, that are released from altered or stimulated cells in the injured region. Their primary tasks are prevention of bleeding and induction of wound healing. Thrombin provokes f ibr in production and aggregation of thrombocytes. Plasmin digests the f ibr in during assembly of the repair tissue substances newly synthesized by fibroblasts. These cells are stimulated to produce repair tissue substances such as collagens, elastin, proteoglycans etc. by the f i b r i n -stabilizing factor X I I I , which itself is activated by thrombin. Addit ional ly , several system-

484 Late Phase Allergic Reactions

Injury Inflammation

rC Thrombokinase

Plasminogen Activators

Surfaces PL

Specific Activation of Cascade Systems &

Mediotor Production

Coagulation Fibrinolysis Complement Kallikrein

— SFMC

— C3a.C5a - i Kinin

r~

Activation

1—

j a.]-Proteinase Inhibitor

o t 2 " M a c r o 9 l o b u l ' n e t c _j - » - Lysosomal Proteinases

and

r;

L .

— --f\ Proteinase Inhibitors |

and j j Antioxidants j j

Oxidative Denaturation and

Non-specific Degradation

Antithrombin III I

j <*-2~plasm'n l n h'bitor j

^C1-Esterase Inhibitor^

I

r _ 1 j Elimination as inactive I Enzyme-Inhibitor Complexes

I Superoxide Dismutose Reactive Oxygen Species j , Catalase.etc I 1 1

Cascade Systems' Factors Proteinase Inhibitors Transport Proteins Connective Tissue Structures

Activation

Thrombocytes. Endothelial Cells. Phagocytes. Mast Cells. Lymphocytes. Fibroblasts

FIGURE 2. Pathomechanisms in inflammation: products of plasma proteinase cascade systems and phag­ocytic processes as inflammatory mediators and their natural antagonists, proteinase inhibitors and antiox­idants. For abbreviations see Figure 1 and text.

specific proteases produce special inflammatory mediators (Figure 2): thrombin the soluble f ibr in monomer complexes (SFMC), plasmin the f ibr in and fibrinogen degradation products (FDP), the complement esterases via the classical ( C I esterases) and/or the alternative pathway (complement factor C3) the anaphylatoxins C3a, C4a, and C5a, and plasma ka l ­l ikrein the kinins. These peptide mediators are pathophysiologically active in several ways, for example, by:

• Inhibit ion of coagulation (SFMC, FDP) • Increase in vasoactivity and reduction of blood pressure (anaphylatoxins and kinins) • Edema formation (FDP, anaphylatoxins and kinins) • Chemotaxis of granulocytes and monocytes (C5a and C3a) • Aggregation of thrombocytes and granulocytes (C5a) • Phagocytosis of granulocytes (C5a) • Degranulation (release of histamine) of mast cells (anaphylatoxins)

I I I . C E L L U L A R SYSTEMS AND T H E I R MEDIATORS

The cellular reactions which are initiated by the peptide mediators are transmitted either directly via mediator-specific receptors on the membranes of the target cells, or indirectly by stimulation of the synthesis of cellular mediators such as prostaglandins, leukotrienes etc. (Table 1). Kinins for instance have specific receptors on certain cells. Additionally they activate the ubiquitously occurring membrane-bound phospholipase A 2 which in turn initiates the synthesis of arachidonic acid metabolites. Depending on the actual k inin concentration and cell type, antagonistic prostaglandins (e.g. PGE 2 and PGF 2 a ) can also be produced during such a process. The diverse arachidonic acid metabolites activate particular functions o f their target cells (Table 1) which may either amplify or suppress the effect of the peptide mediators. These mechanisms operate to enhance or suppress the defense mechanism.

485

T A B L E 1 Arachidonic Acid Metabolism in Inflammation: Stimulation and Metabolites

(Eicosanoids)

Stimuli

ι Cell membrane

I Release of:

Proteinases, peptide mediators, hypoxia, toxins

Phospholipase activation

Arachidonic acid

Enzymes produce: Cyclooxygenase or lipoxygenases etc. Prostaglandins (PG) & thromboxane (TX) or leu-kotrienes & HPETEs & HETEs3

Biological effects: Vasoconstriction: T X A 2 , PGF 2 o , PGD 2 , PGE2; LTC 4 , L T D 6 , LTE 4 ; HPETEs, HETEs vasodilation: PGE2, PGI 2 ; HPETEs, HETEs permeability increase: LTC 4 , L T D 4 , LTE 4

platelet aggregation: T X A 2 , PGE2 platelet aggregation inhibition: PGI 2 , PGD 2 , PGE2

neutrophil aggregation: LTB 4 ; HPETEs, HETEs

Derivatives of hydroxyperoxy- or hydroxyeicosatetraenoic acid.

T A B L E 2 Cellular Mediators in Inflammation and Their Major Sources

Mediator Histamine, Serotonine Platelet activating factor (PAF) Cytokines

Interleukins ( I L 1 , 2, 3) GMCSF 2 b

B-cell stimulating factor (BSF) Interferon-α,7 Tumor necrosis factor (TNF)

Arachidonic acid metabolites Prostaglandin E 2 (PGE2) Prostacyclin (PGI2) Thromboxane (TXA 2 ) Leukotriene B 4 (LTB 4 ) Leukotriene C 4 , D 4 , E 4 (SRSA)C

Lysosomal proteinases (cf. Table 4) Lysosomal Glycosidases (cf. Table 4) Oxidants (reactive oxygen metabolites)

Sourcea

Bas, Mast, Thromb Bas, Mast, PMN

Lympho, Macro Lympho Lympho Lympho, Macro Macro, Mono

Macro, Mono, PMN Eos Macro, Thromb, PMN Bas, Mast, PMN Bas, Eos, PMN Macro, Mast Fibro, Macro, Mono, PMN Fibro, Macro, Mono, PMN Macro, Mono, PMN

a Basophils; Lymphocytes; PMN = Neutrophils; Eosinophils; Macrophages; Mast cells; Fibroblasts; Monocytes; Thrombocytes

b Granulocyte-monocyte colony stimulating factor. c Slow-reacting substances of anaphylaxis.

In most cases the different defense or inflammatory cells produce several mediators.

Some of the most potent ones, like the cytokines (Table 2) , have been characterized in

greater detail only recently. They represent polypeptides or glycoproteins which can stimulate

diverse functions of different target cells: Interleukins stimulate the growth of various cell

populations ( IL1 and I L 2 of B- and T-lymphocytes and IL3 (like GMCSF) of hemopoetic

stem cells of granulocytes, monocytes and eosinophils) as wel l as the synthesis of acute-

phase proteins ( IL1) . Addit ional ly , BSF promotes the growth of mast cells. The interferons

α and y can activate monocytes and the immune defense when present in higher concen­

tration, whereas lower amounts suppress these functions. According to recent findings the

tumor necrosis factor (TNF) is especially pathogenically effective: Among other effects it

induces fever and activates adipocytes to l ipolysis, fibroblasts to synthesize PGE 2 and mast

486 Late Phase Allergic Reactions

cells to produce or liberate PAF, SRSA, histamine and serotonin (Table 2). Addit ional ly , T N F can stimulate granulocytes to such an extent that they excrete their lysosomal granules into the extracellular lumen which strongly promotes the inflammatory process.

The described inflammatory mediators represent a most complex communication system whose most important function is to bring messages to cells. The messenger substances (mediators) can originate f rom the proteolytic cascade systems (coagulation, complement, kal l ikrein-kinin system etc.) and f rom cells. They can stimulate diverse cell populations and thus at the same time initiate different cell functions and may in some cases also activate the cells which produce them itself. On demand, they stimulate and enhance mediator production and thus an amplification of cell functions. A n important characteristic o f the cellular mediators is their restricted range and short l ifetime: They are rapidly bound and degraded by their target cells. Generally, higher mediator concentrations are found i n the inflamed area and its close surrounding as wel l as occasionally in the inflammatory exudates. Systemically, they can only be demonstrated (e .g . , in blood) for short periods during massive injuries or inflammatory processes. W i t h few exceptions, this also applies to the mediators originating f rom the proteolytic cascade systems like the kinins and anaphylatoxins.

The regeneration capability of the organism relies on the fact that different mediators can initiate the same cell function. The healing process caused by essential cell functions is thus guaranteed even though one mediator is not produced in sufficient amounts.

This communication system of the inflammatory mediators operating essentially for " impairment restr ict ion" and rapid healing implies, therefore, the interaction of agonistic and antagonistic stimulation on a cellular level. The organism can thus appropriately respond to the manifold traumatic and inflammatory st imuli to regain the balance of the disturbed physiological homeostasis. This aim is supported by an increased production of the so-called acute-phase proteins such as f ibrinogen, complement factor C3, C-reactive protein and ceruloplasmin which support the specific as wel l as the non-specific defense reactions.

IV. PROTEINASE INHIBITORS

Regulation of the proteinase activities o f the plasma cascade systems occurs by activation of inactive proenzymes via liberated cellular proteinases (e .g. , by thrombokinase and plas­minogen activators) as wel l as by exposure of proenzymes and assembling factors to " f o r ­e i g n " , e .g. , subendothelial surfaces (intrinsic coagulation cascade). These processes which are essential for wound healing are primarily restricted to the injured area. The system-specific proteinase inhibitors, antithrombin I I I , a 2 -plasmin inhibitor and Cl- inactivator pre­vent excessive, i .e. systemic activation of the proteolytic cascades and thus simultaneously the formation of peptide mediators as wel l as non-specific proteolysis of endogenous proteins for example by plasmin (see Figure 2). In plasma these inhibitors are normally present in high excess over the maximally releasable amounts of their target enzymes. Thus they effectively restrict the activities of their primary target enzymes, thrombin (antithrombin I I I ) , plasmin (a 2 -plasmin inhibi tor) , complement CI-esterase and plasma kall ikrein ( C l -inhibitor) .

The outstanding characteristic of the proteinase inhibitors as protective substances against excessive proteolysis in the organism may be derived also from the fact that they represent the third largest plasma protein fraction besides albumin and the immunoglobulins. The primary target enzymes of most o f these inhibitors (approximately 90% of all of them) are the cellular proteinases and in particular the lysosomal digestive enzymes f rom phagocytes.

It is the central task of the lysosomes containing phagocytes like granulocytes, monocytes and macrophages to l imi t the inflammatory process in the wound or inflamed area by phagocytosis of the inflammatory st imuli ( c f Chapter 52, Section I I ) . During the phagocytic process various aggressive substances which arise f rom the intracellular oxidation/degra-

487

T A B L E 3 Substrates of Lysosomal Proteinases from Phagocytes

Connective tissue: elastin, collagen, proteoglycans, glycosaminoglycans, fibronectin, laminin, etc.

Muscle proteins: myosin, tropomyosin, actin, troponin

Opsonins: fibronectin, immunoglobulins, factors of the complement system, C-reactive protein, etc.

Transport proteins: prealbumin, transferrin, haptoglobin, coeruloplasmin, etc.

Proteinase inhibitors: a,-Proteinase inhibitor (α,-antitrypsin), α,-antichymotrypsin, antithrombin I I I , a2-plasmin inhibitor, Cl-inactivator Proteohormones:

insulin, glucagon, substance P, kinins, etc. Receptors:

insulin receptor on cell membranes

T A B L E 4 Lysosomal Digestive Enzymes

Neutral serine proteinases (elastase, cathepsin G) Acid thiol and aspartate proteinases (cathepsins) Neutral metallo proteinases (collagenases) Aminopeptidases and carboxypeptidases Carbohydrate cleaving enzymes such as α-glucosidase, a-N-acetylglucosaminidase, α-glucoronidase, a-galacto-

sidase, α-mannosidase and lysozyme Phosphatases and phosphoprotein-phosphatases Arylsulfatases Phospholipases, lipases, triglyceride lipases Ribonucleases and desoxyribonucleases Myeloperoxidase (oxidizing in the presence of hydrogen peroxide: H 2 0 2 )

dation machinery are released from the cell . However, they are normally rapidly inactived by specific antagonists. Those include α j-proteinase inhibitor, which is present in high concentration in interstitial f l u i d , as wel l as antioxidants such as superoxide dismutase (SOD) and catalase being of cellular or igin. After immigration of the phagocytes into the inflamed area, their overstimulation, for instance by T N F or larger amounts of C3a, can cause degranulation. In this process the lysosomal granules are excreted and their content is thus released extracellularly which may result in a local exhaustion of the endogenous protective antagonists. By this means the most important inhibitor o f the lysosomal proteinase elastase from granulocytes, a r proteinase inhibitor, is inactivated both oxidatively by the myelo-peroxidase/hydrogen peroxide system or oxygen free radicals, and proteolytically by catheptic thiol proteinases and neutral metallo proteinases f rom macrophages. The lysosomal elastase, which is produced in an amount of approximately 300 mg/d has its optimum proteolytic activity in the physiological p H range and can therefore unrestrictedly degrade structural elements such as basal membranes, elastin, collagen, fibronectin, and proteoglycans as wel l as humoral factors including the proteinase inhibitors o f the plasma cascade systems (see Figure 2 and Table 3). This degradation process is strongly enhanced by various other hydrolytic enzymes derived f rom degranulated and disintegrated phagocytes and tissue cells in the inflamed area (see Table 4) . The released lysosomal proteinases exhibit strongest pathogenetic effects (cf. Figure 2 and Table 3). Hence, the tools o f the intracellular protein catabolism become extracellularly potent inflammatory mediators through the fo l lowing mechanisms:

1 the destruction of vital endogenous structural and humoral substances leading among others to

488 Late Phase Allergic Reactions

2. severe alterations of tissues and thus to the exposure of normally coated structures as " f o r e i g n surfaces" which stimulate the immunological defense mechanisms; this may result in chronic inflammation or in an autoimmune disease;

3. the production of other inflammatory mediators in a direct or indirect way. For instance, lysosomal elastase can cleave o f f a C3a-like anaphylatoxin from complement factor C3, but can also provoke an increased production of peptide mediators of the plasma enzyme cascade systems by proteolytic inactivation of relevant proteinase inhibitors (see Figure 2 and Table 3).

In this way an init ial ly local tissue defect or inflammatory process is spread by various transport media (interstitial f l u i d , lymph f l u i d , blood): the body temperature rises, the gran­ulocytes are mobilised, and the synthesis o f non-specific defense proteins, the acute-phase reactants, is stimulated.

Remarkably, the protective or regulatory proteinase inhibitors, α,-proteinase inhibitor, CI - inh ib i tor , and a^antichymotrypsin, are also acute-phase reactants. The latter responds especially quickly (wi th in a few hours) and strongly (increase in concentration up to six times of the normal level in plasma) due to an inflammatory stimulus. I t seems logical that the organism reacts to an increased requirement of protective substances during the inf lam­matory process w i t h an enhanced synthesis especially of a 1 -antichymotrypsin and a t -pro ­teinase inhibitor, the inhibitors of lysosomal digestive proteinases. The importance of such a counter-regulation for the healing process is underlined by the observation that the excessive consumption of proteinase inhibitors such as antithrombin I I I and a 2 -macroglobulin, which are not acute-phase proteins, has a very bad prognosis. a 2 -Macroglobul in very effectively inhibits most of the lysosomal proteinases as wel l as plasmin and plasma kal l ikrein .

Proteolytic processes are principally irreversible and often destructive. Therefore, an increased turn-over or metabolization rate of endogenous substances (for instance after tissue injuries) has to be balanced by de novo synthesis o f relevant substances or tissues which proceeds only s lowly. This is in clear contrast to the possibility of an immediate counter-regulation w i t h other inflammatory systems comprising for example the arachidonic acid metabolites (prostaglandins, leukotrienes etc.) and biogenic amines, whereby antagonistically effective mediators can be produced and released most rapidly.

V, DIAGNOSTIC APPROACHES TO INFLAMMATORY PROCESSES

A t present, a clearcut chemical diagnosis of locally restricted inflammatory processes is not possible systemically. The quantities o f inflammatory mediators present outside the inflamed area are minute as they are rapidly metabolized and eliminated. Moreover, they have only a short l ife-time and thus a l imited range of action. However, they may be detected in inflammatory effusions, a fact, that has significantly contributed to the elucidation of locally proceeding pathomechanisms. A more favorable situation exists when characteristic metabolites accumulate and become detectable through sensitive and specific immunological methods. This is true for certain arachidonic acid metabolites and the lysosomal elastase from granulocytes. Elastase normally is present in blood as enzyme-α,-proteinase inhibitor complex, i . e . , i n an enzymatically inactive f o r m . This complex is eliminated f rom the cir­culation via the reticuloendothelial system (RES) with a half-l ife of approximately 1 h (cf. Figure 2).

Cell-specific factors of this type are gaining importance for diagnostic purposes and their release pattern during the inflammatory reaction may give valuable hints for new therapeutic approaches.

489

V I . MEDICINAL T H E R A P Y CONCEPTS

Drug-related therapy concepts for the treatment of inflammatory processes should be orientated primari ly on the extent o f participation and the mode of action of inflammatory mediators and cells and the cascade systems as w e l l . This especially applies to the corti­costeroids which — as we know today — diversely influence the various cellular systems. For example, as membrane 1/2 protecting agents they inhibit the synthesis of prostaglandins and leukotrienes thereby diminishing protein exudation into the interstitial space and thus reducing edema formation. On the other hand, corticosteroids suppress the phagocytic po­tential of inflammatory cells, especially that of the granulocytes. Thereby the capability of these cells to clear damaged tissue, toxic metabolites and invasive microorganisms is sig­nificantly reduced. However, the clearance function is essential for the healing process. In addition, the corticosteroids impair the immune defense thus making the organism sensitive to bacterial and other infections. Even the plasma cascade systems are influenced by cor­ticosteroids, e .g . , by stimulation or inhibit ion of the synthesis of plasminogen activators and their inhibitors. This diversity of actions makes the therapeutic use of corticosteroids in inflammatory diseases rather problematic, especially i f such a therapy is performed w i t h high doses over a longer period. There is danger then that for short-term, positive effects extensive disadvantages have to be put up w i t h regard to long-term wound healing and defense against infections.

Today's attention is directed towards the development of nonsteroidal anti-inflammatory drugs (NSAIDs) . In experimental models and clinical studies, a number of such drugs are being currently tested for their compatability and therapeutic usefulness. NSAIDs are mostly substances which inhibit the synthesis of cellular mediators and certain cell functions (cf. Table 1 and 2). Inhibit ion of cell functions can be achieved by the blockade of mediator-specific receptors by mediator antagonists. The best results so far have been achieved by selectively acting inhibitors and antagonists. Examples are the inhibit ion of leukotriene synthesis or phagocyte stimulation by T N F . In the clinical application of NSAIDs one has to be aware of the fact that a close cooperation of inflammatory mediators and inflammatory cells is essential for the healing process. Drugs should control excessive production and stimulation to such a degree that physiological levels are maintained. Drug treatment should especially avoid impairment of the phagocytic process including the clearance function and the immunological defense reactions.

Compared to the application of N S A I D s , therapeutic approaches to avoid overactivation of proteolytic cascade systems on the one hand and the extracellular oxidative denaturation and proteolytic digestion on the other hand are wel l understood. It is possible to measure endogenous inhibitor levels of lysosomal digestive enzymes quickly and reliably. The dosage and the therapeutically effective concentration of administered proteinase inhibitors are easy to regulate in vivo. When unequivocal indications such as congenital or acquired massive inhibitor deficiency syndromes exist, protein-inhibitors are already applied cl inically. Ex­amples include a,-proteinase inhibitor (as an inhibitor of granulocytic elastase) for treatment of lung emphysema, antithrombin I I I for treatment of life-threatening coagulation defects, and the C1 -esterase inhibitor (C1 -inactivator) for the treatment of angioneurotic edema (see Figure 2). Various laboratories are currently producing proteinase inhibitors by recombinant D N A techniques for therapeutic purposes. Those include the abovementioned inhibitors as well as other human proteinase inhibitors of thrombin (e.g. hirudin) and of the granulocytic elastase (e.g. variants of a r proteinase inhibitor and the miniprotein eglin). I f the application of inhibitors in severe diseases such as sepsis, polytrauma and acute respiratory distress syndrome (ARDS) show the expected positive results, their more general therapeutic use for wound healing and local inflammatory processes should be envisaged.

The theoretical basis for the therapeutic application of antioxidants is based on the same

490 Late Phase Allergic Reactions

Stimuli

- I I

Chemoattractants

Reactive Oxygen Metabolites

^ - - - 0 2 . H 2 ° 2 1 1 0 2 , OH

Elastase Myeloperoxidase Lactoferrin

' Eglin Ε - I — Fl

H2O2/ \H2O2, 02

\

—ί-Λ Catalase / | 2 H ? 0 , ^ 0 , · 2 H :,0( \

SOD I 2 0} - P H ' - O . . * Η,Ο,Γ

Unspeclfic Proteolysis

V.il 4 X M e t i-X

Oxidative Denaturation

H-,0- + CI .°Η;Ό •· OCI H . Ü , I OCI - H;;0 f CI ••- Ό ,

Multifunctional: Oxid. Denaturation

Op + Fe-'' ··- Fe?' » 0;. H:.02 · Fe:'! - - F e 3 ' t OH t OH

Iron Transport Complement Inhibition etc

FIGURE 3. Lysosomal factors and products of phagocytic processes released extracellularly due to overstimulation of polymorphonuclear gran­ulocytes (PMN) and suitable antagonists for their elimination.

basic principles and is similarly wel l defined as in the case of the proteinase inhibitors (see Figures 2 and 3). A n optimal substance would be one which rapidly eliminates accumulating oxidants in the extracellular space. Superoxide dismutase (SOD), which is already applied in special clinical situations, converts the relatively short-living superoxide radicals ( 0 2 ~ ) to hydrogen peroxide ( H 2 0 2 ) . However hydrogen peroxide also acts — together w i t h mye­loperoxidase — as a strong oxidant and rapidly inactivates, among others, the α prote inase inhibitor. Thus, the simultanous application of an agent such as catalase which eliminates H 2 0 2 is necessary. On a long-term basis, a better solution is the development of low molecular mass synthetic antioxidants which have a broad scavanger spectrum and can be given orally. Intensive research in this area makes it l ikely that the therapy of inflammatory processes can be much improved by the application of N S A I D as wel l as by proteinase inhibitors and antioxidants in the future.

SUGGESTED R E F E R E N C E S

Oppenheim, J . J . , Rosenstreich, D. L . , Potter, ML, Eds. , Cellular Functions in Immunity and Inflam­mation, Edward Arnold Publishers London, 1981. Brune, Κ., The concept of inflammatory mediators, in Discoveries in Pharmacology, Vol. 2. Haemodyn-amics, Hormones & Inflammation, Parnham, M . J., Bruinvels, J., Eds., Elsevier, Amsterdam, 1984, 487. Fritz, H . , Jochum, M . , Duswald, K . - H . , Dittmer, H . , Kortman, H . , Neumann, S., Lang, H . , Gran­ulocyte proteinases as mediators of unspecific proteolysis in inflammation: a review, in Selected Topics in Clinical Enzymology, Vol. 2. Goldberg, D. M . , Werner M . , Eds., Walter de Gruyter, Berlin, 1984, 305.

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Lang, Η. and Greiling, Η., (Eds.,) Pathobiochemie der Entzündung, Springer-Verlag, Berlin, 1984. Dierich, M . P., Förster, O . , Grunicke, H . , Guder, W. G . , and Lang, H . , Inflammation and phago­cytosis, J. Clin. Chem. Clin. Biochem., 25, 785, 1987. Durrum, S. K . , Interleukins: an overview, in Lipid Mediators in the Immunology of Shock, Panbert-Braquet, M . , Ed., Plenum Press, New York, 1987, 311. Neuhof, H . , Humorale Veränderungen im Schock. Die pathogenetische Bedeutung der Mediatoren, in Schock, Kil l ian, J., Meßmer, K . , and Ahnefeld, F. W. , Eds., Springer-Verlag, Berlin, 1987, 37. Neumann, S. , Lang, H . , Entzündung, in Lehrbuch der Klinischen Chemie und Pathobiochemie, Greiling, H . , and Gressner, Α. M . , Eds., Schattauer-Verlag, Stuttgart, 1987, 1022. Schlag, G . and Redl, H . , Eds. , First Vienna Shock Forum, Part A: Pathophysiological Role of Mediators and Mediator Inhibitors in Shock, Alan R. Liss, New York, 1987.