Atherosclerosis

Atheroma are not merely filled with lipid, but contain cells whose functions critically influence atherogenesis: Intrinsic Vascular Wall Cells: Endothelium Smooth Muscle Cells Inflammatory Cells: Macrophages T Lymphocytes Mast Cells

Cell Types in the Human Atheroma Monocyte/ Macrophage T-lymphocytes Tunica Media Intima Smooth muscle cells Endothelium

No symptoms + Symptoms Schematic Time Course of Human Atherogenesis Time (y) Symptoms Lesion initiation Ischemic Heart Disease Cerebrovascular Disease Peripheral Vascular Disease

Macrophage Functions in Atherogenesis Attachment

Leukocyte–Endothelial Adhesion Molecules Mono T B PMN

Vascular Cell Adhesion Molecule 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 VCAM-1, a cytokine-regulatable mononuclear leukocyte adhesion molecule, in rabbit aortic endothelium Li H et al. Arterioscler Thromb 1993;13:

VCAM-1 Expression in Rabbit Aorta Li H et al. Arterioscler Thromb 1993;13: weeks on atherogenic diet

Penetration Macrophage Functions in Atherogenesis

Monocyte Chemoattractant Protein 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 protein-1 reduces atherosclerosis in low-density lipoprotein receptor– deficient mice Gu L et al. Mol Cell 1998;2:

Reduced Lipid Deposition in MCP-1– Deficient Atherosclerotic Mice Gu L et al. Mol Cell 1998;2: LDL-R –/– MCP-1 +/+ LDL-R –/– MCP-1 –/–

Gu L et al. Mol Cell 1998;2: Reduced Lipid Deposition in MCP-1– Deficient Atherosclerotic Mice Oil Red Staining % Aortic Surface Stained Time on Diet:12 – 14 weeks +/+-/- ** * +/+-/- 20 – 25 weeks *P = compared to +/+ **p = compared to +/+

Macrophage Functions in Atherogenesis Activation

Macrophage Functions in Atherogenesis Division

Macrophage Colony-Stimulating Factor (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 human and experimental atherogenesis Rosenfeld ME et al. Am J Pathol 1992;140: Clinton SK et al. Am J Pathol 1992;140:

M-CSF Expression in Atheroma Intimal M-CSF in Atheroma

M-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: Qiao JH et al. Role of macrophage colony-stimulating factor in atherosclerosis: studies of osteopetrotic mice. Am J Pathol 1997;150: Rajavashisth T et al. Heterozygous osteopetrotic (op) mutation reduces atherosclerosis in LDL receptor– deficient mice. J Clin Invest 1998;101:

M-CSF Deficiency (op mutation) Reduces Atheroma in LDL Receptor–Knockout Mice Rajavashisth T et al. J Clin Invest 1998;101: /+op/+op/op

M-CSF Gene Dosage Relates to Atheroma Size in LDLR –/– Mice Rajavashisth T et al. J Clin Invest 1998;101: Fatty Lesions in Aortic Root (m 2 /section) (10) * (4) * (12) Genotype op/++/+op/op

Molecular Mediators of Atherogenesis M-CSF MCP-1 VCAM-1

Anatomy of the Atherosclerotic Plaque Lumen Lipid Core Fibrous cap Shoulder Intima Media Elastic laminæ Internal External

Schematic Time Course of Human Atherogenesis Transition from chronic to acute atheroma Ischemic Heart Disease Cerebrovascular Disease Peripheral Vascular Disease

Thrombosis of a Disrupted Atheroma, the Cause of Most Acute Coronary Syndromes, Results from: Weakening of the fibrous cap Weakening of the fibrous cap Thrombogenicity of the lipid core Illustration courtesy of Michael J. Davies, M.D.

Matrix Metabolism and Integrity of the Plaque’s Fibrous Cap Libby P. Circulation 1995;91: – Synthesis Breakdown Lipid core IL-1 TNF- MCP-1 M-CSF Fibrous cap IFN-  CD-40L Collagen-degradingProteinases Tissue Factor Procoagulant

Increased Expression of Interstitial Collagenase (CL) by Smooth Muscle Cells (SMC) and Macrophages (M) in Human Atheroma Galis ZS et al. J Clin Invest 1994;94:

Plaque Rupture with Thrombosis Thrombus Fibrous cap 1 mm Lipid core Illustration courtesy of Frederick J. Schoen, M.D., Ph.D.

Thrombosis of a Disrupted Atheroma, the Cause of Most Acute Coronary Syndromes, Results from: Weakening of the fibrous cap Thrombogenicity of the lipid core Thrombogenicity of the lipid core Illustration courtesy of Michael J. Davies, M.D.

CD40 and Tissue Factor in Atheroma CD40 Mach F et al. Circulation 1997;96: Tissue Factor

CD40 Ligation Induces Tissue Factor Expression in Human Monocyte-Derived Macrophages Log Fluorescence Cell Numbers rCD40L/-CD40L rCD40L T cell/membranes/ -CD40L T cell/ membranes Mach F et al. Circulation 1997;96:

CD40 ligand on activated platelets triggers an inflammatory reaction of endothelial cells Henn V et al. Nature 1998;391:

Inflammation Can Promote Thrombosis Platelet Tissue Factor Fibrinogen Via gp llb/llla Fibrin CD40L Platelet- Fibrin Thrombus Fibrinopeptides Platelet

Inflammation Participates in All Phases of Atherothrombotic Disease Lesion initiation Lesion progression Thrombotic complications

Slide Source: Lipids Online Thanks