Pathogenesis of Atherosclerosis

1. Pathogenesis of Atherosclerosis Judith Berliner, Ph.D. Departments of Pathology and Medicine Division of Cardiology David Geffen School of Medicine at UCLA

3. Fatty Streak

4. Early Fibrous Plaque

5. Advanced Plaque

6. Thrombus

7. Ages of Progression Fatty Streak – 0-30 Fibrous Plaque – 30-50 Complicated Plaque – 40+ Thrombosis – 50+

8. Susceptible Sites (SS)

9. Coronary Distribution of lesions

10. Lipid Accumulation at Branches

11. Flow Patterns

12. Less Susceptible

13. More Susceptible

14. Nitric Oxide Function (anti-inflammatory) • Causes smooth muscle cell relaxation (vasodilation) • Suppresses SMC proliferation and matrix synthesis • Reduces the expression of inflammatory genes • Inhibits platelet aggregation

16. E-NOS Low in More Susceptible Areas

17. Antioxidant NrF2 is Activated in Non-Susceptible Areas

18. Inflammatory Molecules are Increased in Susceptible Areas

19. Early Fatty Streak

20. Lipids Rapidly Accumulate

21. Fatty Streak Formation

22. Fatty Streak • Retention of LDL • Entry of monocytes • Foam cell formation

24. Fatty Streaks Form in the Fetus of Hypercholesterolemic Mothers

26. Localization of Macrophages in Fibrous Plaques Human coronary artery lesionImmunoperoxidase with Mab to macrophages (HAM-56)

27. Endothelial Morphology

28. Alterations in Endothelial Cells and Monocytes in Fatty Streak Lesions • Endothelial cells display increased adhesion molecules and chemotactic factors. VCAM-1, MCP-1, IL-8. • In fat feeding there is an increase in the number of monocytes in the blood and a change in the ratio of subtypes. • 3. Monocytes become more adhesive for • endothelium.Only specific monocyte subtypes • enter the vessel wall: GR1/ly6C hi

29. Effects of Leukocyte Trafficking Genes on Atherosclerosis In Knockout Mouse Models Defect Response M-CSF less MCP-1, CCR2 less P, E selectin less VCAM-1 less

30. Macrophage Foam Cells

31. Foam Cell Formation Normal LDL does not cause foam cell formation Aggregated LDL-taken up by the LDL receptor Oxidized LDL-taken up by scavenger receptors CD 36, SRA-1, LOX-1 Sphingomyelinase modified LDL-taken up by scavenger receptors Foam cell formation is inhibited by HDL Foam cells accumulate near the EC

32. Gene CD36 SRA-1 LOX-1 Apo A1 ABC-A1 Effect Less Less Less More More Effect of genes related to foam cell formation on fatty streak formation

33. Atheroma / Fibrous Plaque

35. Fibrous Plaque • Cytokines produced by macrophages lead to SMC migration and proliferation • SMC proteases digest elastic lamina to aid migration of SMC into the intima • SMC synthesize collagen and specific proteoglycans • SMC take up lipid forming foam cells • SMC and monocytes die by apoptosis or necrosis liberating cell contents. • Lymphocytes enter the lesion.

36. Smooth muscle cells migrate into the intima

37. Effect of genes related to SMC migration, proliferation, matrix synthesis and death of foam cells on plaque formation Gene PDGF IL-1beta FGF Effect on atherogenesis Less Less Less

38. Formation of the Necrotic Core

41. Role of Lymphocytes in Atherosclerosis • T cells, mainly of Th-1 subtype,enter the vessel. They produce high levels of gamma interferon.Knockout of gamma in mice decrease atherosclerosis. • 2.B1b cells are increased. B1b are innate • immune cells that make antibodies to oxidized • lipids which also react with bacteria. They may • serve a protective function.

43. Complex plaque

44. Characteristics of the complex plaque • Accelerated cell death and growth of necrotic core • Angiogenesis • Formation of small thrombi on lumenal surface • Hemorrhage from newly formed vessels • Incorporation of thrombi and clots into vessel wall

45. Vasa Vasorum

46. Angiostatin Decreases Lesions

48. Small Thrombi

49. Cell Death in the Intima

50. Genes associated with formation of the complex plaque • VEGF, angiogenesis • Regulators of thrombosis • Regulators of thrombolysis • Regulators of apoptosis