Inflammation and the Pathogenesis Inflammation and the Pathogenesis

of Atherothrombotic Diseaseof Atherothrombotic Disease

Peter Libby, M.D.Peter Libby, M.D.

Atheroma are not merely filled with lipid, Atheroma are not merely filled with lipid, but contain cells whose functions critically but contain cells whose functions critically influence atherogenesis:influence atherogenesis:

Intrinsic Vascular Wall Cells:

Endothelium

Smooth Muscle Cells

Inflammatory Cells:

Macrophages

T Lymphocytes

Mast Cells

Cell Types in the Human AtheromaCell Types in the Human Atheroma

Monocyte/Monocyte/MacrophageMacrophage

T-lymphocytesT-lymphocytesTunicaMedia

Intima

Smooth musclecells

EndotheliumEndothelium

No No symptomssymptoms ++ Symptoms Symptoms

Schematic Time Course of Human Schematic Time Course of Human AtherogenesisAtherogenesis

Time (y)Time (y)

SymptomsSymptoms

Lesion initiationLesion initiation

Ischemic HeartIschemic HeartDiseaseDisease

CerebrovascularCerebrovascularDiseaseDisease

Peripheral VascularPeripheral VascularDiseaseDisease

Macrophage Functions in AtherogenesisMacrophage Functions in Atherogenesis

AttachmentAttachment

Leukocyte–Endothelial Adhesion MoleculesLeukocyte–Endothelial Adhesion Molecules

MonoMonoTT

BB PMNPMN

Vascular Cell Adhesion Molecule 1Vascular Cell Adhesion Molecule 1(VCAM-1)(VCAM-1)

Binds monocytes and lymphocytes- Cells found in atheroma

Expressed by endothelium over nascent fatty streaks

Expressed by microvessels of the mature atheroma

An atherogenic diet rapidly induces An atherogenic diet rapidly induces

VCAM-1, a cytokine-regulatable VCAM-1, a cytokine-regulatable

mononuclear leukocyte adhesion mononuclear leukocyte adhesion

molecule, in rabbit aortic endotheliummolecule, in rabbit aortic endothelium

Li H et al. Arterioscler Thromb 1993;13:197-204.

VCAM-1 Expression in Rabbit AortaVCAM-1 Expression in Rabbit Aorta

Li H et al. Arterioscler Thromb 1993;13:197-204.

3 weeks on atherogenic diet

PenetrationPenetration

Macrophage Functions in AtherogenesisMacrophage Functions in Atherogenesis

Monocyte Chemoattractant Protein 1Monocyte Chemoattractant Protein 1(MCP-1)(MCP-1)

A potent mononuclear cell chemoattractant

Produced by endothelial and smooth muscle cells

Localizes in human and experimental atheroma

Absence of monocyte chemoattractant Absence of monocyte chemoattractant

protein-1 reduces atherosclerosis in protein-1 reduces atherosclerosis in

low-density lipoprotein receptor–low-density lipoprotein receptor–

deficient micedeficient mice

Gu L et al. Mol Cell 1998;2:275-281.

Reduced Lipid Deposition in MCP-1–Reduced Lipid Deposition in MCP-1–Deficient Atherosclerotic MiceDeficient Atherosclerotic Mice

Gu L et al. Mol Cell 1998;2:275-281.

LDL-R –/–LDL-R –/–

MCP-1 +/+MCP-1 +/+

LDL-R –/–LDL-R –/–

MCP-1 –/–MCP-1 –/–

Gu L et al. Mol Cell 1998;2:275-281.

Reduced Lipid Deposition in MCP-1–Reduced Lipid Deposition in MCP-1–Deficient Atherosclerotic MiceDeficient Atherosclerotic Mice

0

5

10

15

20

25

30

Oil

Red S

tain

ing

% A

ort

ic S

urf

ace

Sta

ined

Time on Diet: 12 – 14 weeks

+/+ -/-

***

+/+ -/-

20 – 25 weeks *P = 0.001 compared to +/+**p = 0.005 compared to +/+

Macrophage Functions in AtherogenesisMacrophage Functions in Atherogenesis

Activation

Macrophage Functions in AtherogenesisMacrophage Functions in Atherogenesis

Division

Macrophage Colony-Stimulating Factor Macrophage Colony-Stimulating Factor (M-CSF)(M-CSF)

A potent monocyte activator and co-mitogen

Produced by endothelial and smooth muscle cells

Localizes in human and experimental atheroma

Augmented M-CSF gene expression in Augmented M-CSF gene expression in

human and experimental atherogenesishuman and experimental atherogenesis

Rosenfeld ME et al. Am J Pathol 1992;140:291-300.Clinton SK et al. Am J Pathol 1992;140:301-316.

M-CSF Expression in AtheromaM-CSF Expression in Atheroma

IntimalM-CSF

inAtheroma

M-CSF Promotes AtherogenesisM-CSF Promotes Atherogenesis

Smith JD et al. Decreased atherosclerosis in mice deficient in both macrophage colony-stimulating factor (op) and apolipoprotein E. Proc Natl Acad Sci U S A 1995;92:8264-8268.

Qiao JH et al. Role of macrophage colony-stimulating factor in atherosclerosis: studies of osteopetrotic mice. Am J Pathol 1997;150:1687-1699.

Rajavashisth T et al. Heterozygous osteopetrotic (op) mutation reduces atherosclerosis in LDL receptor–deficient mice. J Clin Invest 1998;101:2702-2710.

M-CSF Deficiency (M-CSF Deficiency (opop mutation) Reduces mutation) Reduces Atheroma in LDL Receptor–Knockout MiceAtheroma in LDL Receptor–Knockout Mice

Rajavashisth T et al. J Clin Invest 1998;101:2702-2710.

+/++/+ op/+op/+ op/opop/op

M-CSF Gene Dosage Relates to Atheroma M-CSF Gene Dosage Relates to Atheroma Size in LDLR –/– MiceSize in LDLR –/– Mice

Rajavashisth T et al. J Clin Invest 1998;101:2702-2710.

107

Fatt

y L

esi

ons

in A

ort

ic R

oot

(m

2/s

ect

ion) 106

105

104

103

(10)* (4)

*

(12)

Genotypeop/++/+ op/op

Molecular Mediators of AtherogenesisMolecular Mediators of Atherogenesis

M-CSFMCP-1

VCAM-1

Anatomy of the Atherosclerotic PlaqueAnatomy of the Atherosclerotic Plaque

LumenLipidCore

Fibrous cap

Shoulder

Intima

MediaElasticlaminæ

Internal

External

Schematic Time Course of Human Schematic Time Course of Human AtherogenesisAtherogenesis

Transition from chronic to acute atheromaTransition from chronic to acute atheroma

Ischemic HeartIschemic HeartDiseaseDisease

CerebrovascularCerebrovascularDiseaseDisease

Peripheral VascularPeripheral VascularDiseaseDisease

Thrombosis of a Disrupted Atheroma, the Thrombosis of a Disrupted Atheroma, the Cause of Most Acute Coronary Cause of Most Acute Coronary Syndromes, Results from:Syndromes, Results from:

Weakening of Weakening of the fibrous capthe fibrous cap

Thrombogenicity of the lipid core

Illustration courtesy of Michael J. Davies, M.D.

Matrix Metabolism and Integrity of the Matrix Metabolism and Integrity of the Plaque’s Fibrous CapPlaque’s Fibrous Cap

Libby P. Circulation 1995;91:2844-2850.

+ + + +

++

–

Synthesis Breakdown

Lipid core

IL-1TNF-MCP-1M-CSF

FibrouscapIFN-IFN-

CD-40L

Collagen-degradingCollagen-degradingProteinasesProteinases

Tissue FactorTissue FactorProcoagulantProcoagulant

Increased Expression of Interstitial Increased Expression of Interstitial Collagenase (CL) by Smooth Muscle Cells Collagenase (CL) by Smooth Muscle Cells (SMC) and Macrophages (M(SMC) and Macrophages (M) in Human ) in Human AtheromaAtheroma

Galis ZS et al. J Clin Invest 1994;94:2493-2503.

Plaque Rupture with ThrombosisPlaque Rupture with Thrombosis

Thrombus Fibrous cap

1 mmLipid core

Illustration courtesy of Frederick J. Schoen, M.D., Ph.D.

Thrombosis of a Disrupted Atheroma, the Thrombosis of a Disrupted Atheroma, the Cause of Most Acute Coronary Cause of Most Acute Coronary Syndromes, Results from:Syndromes, Results from:

Weakening of the fibrous cap

Thrombogenicity Thrombogenicity of the lipid coreof the lipid core

Illustration courtesy of Michael J. Davies, M.D.

CD40 and Tissue Factor in AtheromaCD40 and Tissue Factor in Atheroma

CD40

Mach F et al. Circulation 1997;96:396-399.

Tissue Factor

CD40 Ligation Induces Tissue Factor CD40 Ligation Induces Tissue Factor Expression in Human Monocyte-Derived Expression in Human Monocyte-Derived MacrophagesMacrophages

Log Fluorescence

Cell

Nu

mb

ers

160

120

80

40

0

160

120

80

40

0100 101 102 103 100 101 102 103

rCD40L/-CD40L

rCD40L

T cell/membranes/-CD40L

T cell/membranes

Mach F et al. Circulation 1997;96:396-399.

CD40 ligand on activated platelets CD40 ligand on activated platelets

triggers an inflammatory reaction of triggers an inflammatory reaction of

endothelial cellsendothelial cells

Henn V et al. Nature 1998;391:591-594.

Inflammation Can Promote ThrombosisInflammation Can Promote Thrombosis

PlateletPlatelet

TissueTissueFactorFactor

FibrinogenFibrinogen

Via gp llb/lllaVia gp llb/llla

FibrinFibrinCD40LCD40LPlatelet-Platelet-

FibrinFibrinThrombusThrombus

FibrinopeptidesFibrinopeptides

PlateletPlatelet

Inflammation Participates in All Phases of Inflammation Participates in All Phases of Atherothrombotic DiseaseAtherothrombotic Disease

Lesion initiation

Lesion progression

Thrombotic complications