Inflammation and atherosclerosis
Dr Khamis Al hashmi MD PhD.
Assistant professor
Department of Physiology and Clinical Physiology
COM&HS, SQU
IAS-OSLA Course “Lipid Metabolism and Cardiovascular Risk” Muscat, Oman, 8-10 February 2015
Outlines
• Process of Atherosclerosis
• Role of lipoproteins (LDL & VLDL) in inflammation
• Inflammatory marker as risk factors for CVD
• Inflammatory markers as target for therapy
Atherosclerosis
• Disease of cardiovascular system affecting vessel wall.
• It leads to the narrowing of arteries or complete blockage.
• Its main components are endothelial disfunction, lipid deposition, inflammatory reaction in the vascular wall.
• Remodeling of vessel wall.
Atherosclerosis
• Intense cross-talk between EC, VSMC, plasma-derived inflammatory cells, lymphocytes (involves array of chemokines, cytokines, growth factors).
• Attraction of cells to the sites of atherosclerotic lesion.
• Migration, proliferation, apoptosis, excess production of extracellular matrix.
Arterial wall: structure and function
The development of atherosclerosis
• The key event – damage to the endothelium caused by excess of lipoproteins, hypertension, diabetes, components of cigarette smoke.
• Endothelium becomes more permeable to lipoproteins.
• Lipoproteins move below the endothelial layer (to intima).
• Endothelium loses its cell-repelent quality.
• Inflammatory cells move itno the vascular wall.
The development of atherosclerosis • Disfunctional endothelium express adhesion molecules –
selectins, mediated the „rolling“ interaction of cells. • The key molecule - vascular cell addhesion molecule-1
(VCAM-1) promotes monocytes adhesion (precursors of macrophages).
• Addhering cells are stimulated by monocyte chemoattractant protein-1 (MCP-1).
• Monocytes cross the endothelium, settle down in the intima.
Inflammation in atherosclerosis (mononuclear cells)
Fom the review article: Libby P.: Inflammation in atherosclerosis. Nature 420, 2002: 868-874
Endothelial cells undergo inflammatory activation, produce different leukocyte adhesion molecules (VCAM-1). Monocytes penetrate into tunica intima. Their receptor CCR2 interact with MCP-1
Inflammation in atherosclerosis (T-lymhocytes)
Fom the review article: Libby P.: Inflammation in atherosclerosis. Nature 420, 2002: 868-874
T-lymphocytes enter the intima facilitated by VCAM-1 and trio chemokines- IP-10 (inducible protein-1), Mig (monokine induced by interferon-g) and I-TAC (interferon-inducible T-cells a-chemoattractant). Trio chemokines bind to CXCR3 chemokine receptor expressed by T-cells in the atherogenic lesion.
Inflammation in atherosclerosis (mast cells)
Fom the review article: Libby P.: Inflammation in atherosclerosis. Nature 420, 2002: 868-874
Mast cells infiltrate to the intima. Chemoattractant eotaxin mediate migration of mast cells and interacts with the chemokine receptor CCR3. Resident mast cells in the intima degranulate, release TNF-a, heparin, and enzymes activating proMMPs.
The process of atherogenesis – an overview
The process of atherogenesis
• Lipid entry into the arterial wall is a key process in atherogenesis.
• Hypercholesterolemia – factor for VCAM-1 and MCP-1 induction.
• LDL and VLDL are most atherogenic, enter vascular wall more easily.
• LDL – in plasma are protected against oxidation by vit. E, ubiquinon, plasma antioxidants (b-carotene, vit. C).
• Out of plasma, LDL phospholipides and fatty acids oxidize.
The process of atherogenesis
• Activated macrophages produce enzymes – lipoxygenases, myeloperoxidase, NADPH oxidase ROS
• Oxidized LDL are cytotoxic to endothelial cells, mitogenic for macrophages.
• Oxidized LDL apolipoprotein apoB100 bind to the scavenger receptor.
• Scavenger receptors are not subjected to regulation by intracellular cholesterol level.
• Macrophages take up oxidized LDL, overload with lipids.
The process of atherogenesis
• Foam cells ruptured (apoptosis).
• Lipid release to intima and their acumulation becomes centre of atherosclerotic plaques.
The process of atherogenesis
• Plaque growth – periodically accelerated by a cycle of plaque rupture and thrombosis.
• This happens: – Active macrophages and T lymphocytes preferentially
reside at the edge of the plaque. – Macrophages secrete enzymes degrade extracellular
matrix of the cap (MMP – collagenases, gelatinases, and stromelysin)
– T-cells activated by macrophages secrete IFN-g and pro-inflammatory cytokines IL-1, IL-2, and TNF-a.
The process of atherogenesis
• IFN-g induces macrophage MMP expression. • IFN-g inhibits VSMC proliferation and collagen synthesis which
further weakening the cap. • VSMC undergo apoptosis. • After plaque rupture the area is exposed its interior to the
blood. • The interior of the plaque is highly thrombogenic – the small-
molecular-weight glycoprotein (tissue factor) initiates the extrinsic clotting cascade.
• Tissue factor complexes with factor VII/VIIa, factor IX and X are activated.
• Platelets are activated and thrombus forms quickly on the surface of a ruptured plaque.
• Thrombus completely occludes the arterial lumen. It cause tissue necrosis (myocardial infarction or brain stroke).
Role of lipoproteins in Inflammation
Lipoprotein Classes and Inflammation
Doi H, et al. Circulation. 2000;102:670-676; Colome C, et al. Atherosclerosis. 2000;49:295-302; Cockerill GW, et al. Arterioscler Thromb Vasc Biol. 1995;15:1987-1994.
HDL LDL Chylomicrons, VLDL, and
their catabolic remnants
> 30 nm 20–22 nm
Potentially proinflammatory
9–15 nm
Potentially anti- inflammatory
Role of LDL in Inflammation
Steinberg D, et al. N Engl J Med. 1989;320:915-924.
Endothelium
Vessel Lumen
LDL
LDL Readily Enter the Artery Wall Where They May Be Modified
LDL
Intima
Modified LDL
Modified LDL Are Proinflammatory
Hydrolysis of Phosphatidylcholine to Lysophosphatidylcholine
Other Chemical Modifications
Oxidation of Lipids and Apo B
Aggregation
Slide source: www.lipidonline.org
LDL
LDL
Modified LDL Stimulate Expression of MCP-1 in Endothelial Cells
Navab M, et al. J Clin Invest. 1991;88:2039-2046.
Endothelium
Vessel Lumen
Intima
Monocyte
Modified LDL
MCP-1
Slide source: www.lipidonline.org
LDL
LDL
Differentiation of Monocytes into Macrophages
Steinberg D, et al. N Engl J Med. 1989;320:915-924.
Endothelium
Vessel Lumen
Intima
Monocyte
Modified LDL
Modified LDL Promotes Differentiation of Monocytes into Macrophages
MCP-1
Macrophage
Slide source: www.lipidonline.org
LDL
LDL
Modified LDL Induces Macrophages to Release Cytokines That Stimulate Adhesion Molecule Expression in Endothelial
Cells
Nathan CF. J Clin Invest. 1987;79:319-326.
Endothelium
Vessel Lumen Monocyte
Modified LDL
Macrophage
MCP-1
Adhesion Molecules
Cytokines
Intima
Slide source: www.lipidonline.org
LDL
LDL Endothelium
Vessel Lumen Monocyte
Macrophage
MCP-1
Adhesion Molecules
Steinberg D et al. N Engl J Med 1989;320:915-924.
Macrophages Express Receptors That Take up Modified LDL
Foam Cell
Modified LDL Taken Up by Macrophage
Intima
Slide source: www.lipidonline.org
LDL
LDL Endothelium
Vessel Lumen Monocyte
Macrophage
Adhesion Molecules
Macrophages and Foam Cells Express Growth Factors and Proteinases
Foam Cell
Intima Modified
LDL Cytokines
Cell Proliferation Matrix Degradation
Growth Factors Metalloproteinases
Ross R. N Engl J Med. 1999;340:115-126.
MCP-1
Slide source: www.lipidonline.org
Endothelium
Vessel Lumen Monocyte
Macrophage
MCP-1 Adhesion Molecules
The Remnants of VLDL and Chylomicrons Are Also Proinflammatory
Foam Cell
Intima Modified Remnants Cytokines
Cell Proliferation Matrix Degradation
Doi H, et al. Circulation. 2000;102:670-676.
Growth Factors Metalloproteinases
Remnant Lipoproteins
Remnants
Slide source: www.lipidonline.org
LDL
LDL
Miyazaki A, et al. Biochim Biophys Acta. 1992;1126:73-80.
Endothelium
Vessel Lumen Monocyte
Modified LDL
Macrophage
MCP-1 Adhesion Molecules
Cytokines
HDL Prevents Formation of Foam Cells
Intima HDL Promote Cholesterol Efflux
Foam Cell
Slide source: www.lipidonline.org
LDL
LDL
Mackness MI, et al. Biochem J. 1993;294:829-834.
Endothelium
Vessel Lumen Monocyte
Modified LDL
Macrophage
MCP-1 Adhesion Molecules
Cytokines
HDL Inhibits the Oxidative Modification of LDL
Foam Cell
HDL Promotes Cholesterol Efflux Intima
HDL Inhibits
Oxidation of LDL
Slide source: www.lipidonline.org
LDL
LDL
Cockerill GW, et al. Arterioscler Thromb Vasc Biol. 1995;15: 1987-1994.
Endothelium
Vessel Lumen
Monocyte
Modified LDL
Macrophage
MCP-1 Adhesion Molecules
Cytokines
Inhibition of Adhesion Molecules
Intima
HDL Inhibit Oxidation
of LDL
HDL Inhibits Adhesion Molecule Expression
Foam Cell
HDL Promotes Cholesterol Efflux
Slide source: www.lipidonline.org
Inflammatory markers as risk for Cardiovascular diseases and target
for therapy
Risk Factors for Future Cardiovascular Events: WHS
Relative Risk of Future Cardiovascular Events
0
Ridker PM et al. N Engl J Med 2000;342:836-843.
Lipoprotein(a) Homocysteine IL-6 TC LDL-C sICAM-1 SAA Apo B TC:HDL-C hs-CRP hs-CRP + TC:HDL-C
1.0 2.0 4.0 6.0
hs-CRP as a Risk Factor for Future CVD
Relative Risk (upper vs lower quartile)
CHD Death
MI
Stroke
CHD
PVD
CVD
CHD
CHD
CHD
CHD
0
MRFIT (Kuller 1996)
PHS (Ridker 1997)
PHS (Ridker 1997)
CHS/RHPP (Tracy 1997)
PHS (Ridker 1998)
WHS (Ridker 1998, 2000)
MONICA (Koenig 1999)
Helsinki (Roivainen 2000)
Caerphilly(Mendall 2000)
Britain (Danesh 2000)
1.0 2.0 3.0 4.0 5.0 6.0
Relative Risks of Future MI among Apparently Healthy Middle-Aged Men: Physician’s Health Study
Relative Risk for Future MI
0 1.0 2.0 4.0 6.0
Lipoprotein(a)
Homocysteine
Fibrinogen
tPA Antigen
hs-CRP
hs-CRP + TC/HDL-C
Total Cholesterol
TC:HDL-C
Ridker PM. Ann Intern Med 1999;130:933-937. 1999 ACP-ASIM.
0.0
0.5
1.0
1.5
2.0
hs-CRP and Relative Risk of Recurrent Coronary Events: CARE
Ridker PM et al. Circulation 1998;98:839-844. 1998 Lippincott Williams & Wilkins.
1 <0.12
Rela
tive R
isk
Quintile of hs-CRP (range, mg/dL)
P=0.02
2 0.12-0.20
3 0.21-0.37
4 0.38-0.66
5 >0.66
P Trend = 0.044
0
1
2
3
Inflammation, Pravastatin, and Relative Risk of Recurrent Coronary Events: CARE
Ridker PM et al. Circulation 1998;98:839-844. 1998 Lippincott Williams & Wilkins.
Pravastatin
Rela
tive R
isk
Inflammation Absent
P Trend = 0.005
Placebo Pravastatin Placebo
Inflammation Present
Mean B
aseline (
mg/d
L)
Inflammation absent
Inflammation present
250
200
150
100
50
0 TC LDL-C HDL-C TG
Baseline Lipid Levels in Patients with and without Inflammation: CARE
Ridker PM et al. Circulation 1998;98:839-844.
Long-Term Effect of Pravastatin on hs-CRP: CARE Placebo and Pravastatin Groups
Adapted from Ridker PM et al. Circulation 1999;100:230-235. 1999 Lippincott Williams & Wilkins.
Pravastatin
Placebo
Media
n h
s-C
RP
Concentr
ation (
mg/d
L)
–21.6%
(P=0.007)
0.25
0.24
0.23
0.22
0.21
0.20
0.19
0.18 Baseline 5 Years
CRP in Combination with LDL-C as a Method to Target Statin Therapy in Primary Prevention:
AFCAPS/TexCAPS
Ridker PM et al. N Engl J Med 2001;344:1959-1965.
Study Group Lovastatin Placebo NNT
Low LDL-C/low CRP 0.025 0.022 _
Low LDL-C/high CRP 0.029 0.051 48
High LDL-C/low CRP 0.020 0.050 33
High LDL-C/high CRP 0.038 0.055 58
Median LDL-C = 149.1 mg/dL; Median CRP = 0.16 mg/dL
Event Rate
CRP in Combination with TC:HDL-C Ratio as a Method to Target Statin Therapy in Primary Prevention:
AFCAPS/TexCAPS
Ridker PM et al. N Engl J Med 2001;344:1959-1965.
Study Group Lovastatin Placebo NNT
Low TC:HDL-C/low CRP 0.024 0.025 983
Low TC:HDL-C/high CRP 0.025 0.050 43
High TC:HDL-C/low CRP 0.021 0.050 35
High TC:HDL-C/high CRP 0.041 0.057 62
Median TC:HDL-C = 5.96; Median CRP = 0.16 mg/dL
Event Rate
0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5
0.0
0
0.0
2
0.0
4
0.0
6
0.0
8
0.1
0
0.0
2
0.0
4
0.0
6
0.0
8
0.1
0
Follow-Up (Years)
LDL > 1.8 mmol/L, CRP > 2 mg/L
LDL < 1.8mmo/L, CRP > 2 mg/L LDL > 1.8 mmol/L, CRP < 2 mg/L
LDL < 1.8mmol/L, CRP < 2 mg/L
Clinical Relevance of Achieved LDL and Achieved hsCRP
After Treatment with Statin Therapy PROVE IT–TIMI 22
Ridker et al NEJM 2005;352:20-28.
Rosuvastatin 20 mg (N=8901)
MI
Stroke
Unstable
Angina
CVD Death
CABG/PTCA
JUPITER Multi-National Randomized Double Blind Placebo Controlled Trial of
Rosuvastatin in the Prevention of Cardiovascular Events Among Individuals With Low LDL and Elevated hsCRP
4-week
run-in
Ridker et al, Circulation 2003;108:2292-2297.
No Prior CVD or DM Men >50, Women >60
LDL <3.4 mmol/L
hsCRP >2 mg/L
JUPITER
Trial Design
Placebo (N=8901)
Argentina, Belgium, Brazil, Bulgaria, Canada, Chile, Colombia, Costa Rica,
Denmark, El Salvador, Estonia, Germany, Israel, Mexico, Netherlands,
Norway, Panama, Poland, Romania, Russia, South Africa, Switzerland,
United Kingdom, Uruguay, United States, Venezuela
JUPITER
Primary Trial Endpoint : MI, Stroke, UA/Revascularization, CV Death
Placebo 251 / 8901
Rosuvastatin 142 / 8901
HR 0.56, 95% CI 0.46-0.69
P < 0.00001
Number Needed to Treat (NNT5) = 25
- 44 %
0 1 2 3 4
0.0
0
0.0
2
0.0
4
0.0
6
0.0
8
Cu
mu
lati
ve I
nci
de
nce
Number at Risk Follow-up (years)
Rosuvastatin
Placebo
8,901 8,631 8,412 6,540 3,893 1,958 1,353 983 544 157
8,901 8,621 8,353 6,508 3,872 1,963 1,333 955 534 174
Summary • Several line of evidence indicate that
atherosclerosis is an inflammatory process
• Modified LDL is a key player in the trigger of inflammation and in progression of atherosclerosis
• Inflammatory markers such as hs-CRP are useful in cardiovascular risk stratification and found to be a useful target for therapeutic intervention.
