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How does inflammation
contribute to pathogenesis of
atherosclerosis
Petri Kovanen MD PhD
Wihuri Research Institute
Helsinki, Finland
Joint EAS-ESC Session:
(14:00 - 14:22) in Belgrade room
ESC STOCKHOLM 30.8.2010
Inflammation and atherosclerosis
- an early start
Rudolf Virchow 1821-1902
Endarteritis deformans
“The development of an
atheroma is a consequence of
an inflammatory process in
the arterial intima, and a local
reactive fibrotic thickening
ensues when the inflammatory
process stimulates the
connective tissue cells in the
intima to proliferate”
Infection and atherosclerosis
Sir William Osler 1908 
Bacteria: Chl. pneumoniae, H. pylori, oral pathogens
(the ”bacterial burden”)
Viruses: CMV, HSV1, HSV2, adeno, coxsackie, influenza A,
hepatitis type A
•
•
•
•
Epidemiological studies
Demonstration of microbes in the atheromas
Experiments with animals
Prospective studies in patient populations
• Studies with antibiotics: negative
• Development of vaccines! Against what?
Exogenous antigen ?
or
Endogenous antigen = auto-antigen?
Immunity and atherosclerosis
20 years ago : T cells
Original Conclusions:
HLA-DR staining
DR-inducing cytokine must be
present in plaque
IFN-ɣ known to induce DR
DR+ Endothelium
IFN-ɣ is produced by activated T cells
DR+ Macrophages
Thus, immune activation in plaques
- autoantigen presentation
- inflammatory cytokines produced
•Athero-Antigen?
•Auto-Antigen?
= oxLDL
DR+ Smooth
Muscle Cells
HLA-DR in human plaque
Jonasson & Hansson 1985
Fatty streak formation in human fetal aortas is
enchanced by maternal hypercholesterolemia:
evidence for early oxidation of LDL
Apo-B (+)
MDA-lysine (+)
4HNE-lysine (+)
MDA-lysine (-)
Normocholesterolemic mother
Napoli C et al. JCI 1997
Adhesion of
monocytes
to activated
endothelium
Response
to
Retention
Transmigration of monocytes
Human coronary fatty streak:
scavenging modified LDL
Endothel
Monocyte
Macrophage
Scavenger Rec
Foam cell
Herbert Stary
Scavenger receptors - members of
a bigger family
Molecular components of the innate immune system
(it is all about the ancient PATTERNS)
RECEPTORS
Pattern Recognition Receptors (PRRs)
- Scavenger receptors SR-A and CD36 (cargo uptake)
- Toll-like receptors (TLRs) (signaling)
- Receptors for Avanced Glycosylation Products (RAGEs)
LIGANDS
Pathogen-Associated Molecular Patterns (PAMPs)
Scavenger receptors recognize PathogenAssociated Molecular Patterns (PAMPS)
"Recent danger"
"Ancient danger"
Binder et al JLR 2005
The TLRs are there for the
lipoproteins of pathogens
Lipoproteins take their toll on the host. Janeway CA Jr, Medzhitov R.
Curr Biol. 1999 Dec 2;9(23):R879-82
TLR signaling
pathway and its
relevance to
atherogenesis
Endogen
1
TLR4 both endogenous
ligands (autoantigens)
and exogenous ligands
(eg. LPS)
2
TLR4 signaling most
relevant in atherosclerosis
3
Michelsen et al. J Immunol 2004;173:5901-5907
Exogen
Exogen
TLR expression in
human
atherosclerotic
plaques
Internal mammary
arteries
Carotid arteries
Edfeldt, K. et al. Circulation 2002;105:1158-1161
What is the fate of cholesterol
crystals in atherosclerosis?
The Internet Pathology
Laboratory, University of Utah
- Cholesterol crystals and immune cells abundant in the lesions
- IL-1β protein ↑ during lesion progression
- Knocking out IL-1β or IL-1β receptor1 > atherosclerosis ↓
Macrophages phagocytose
cholesterol crystals (CHC)
CHC
Bright field:
Arrows indicate chol.crystals
Confocal:
Reflection (chol.crystals)
Nucleus (Hoechst)
Cell membrane (CTXb-647)
Optical thickness 0.7 μm
CHC + cytD
Cholesterol crystals induce IL-1β
secretion in the presence of a TLR
ligand
Monocytes
Macrophages
The NLRP3 inflammasome
IL-1β
macrophage
IL-1β
Hit #1
LPS
TLR
proIL-1β
caspase-1
ASC
NLRP3 receptor
NF-κβ
IL1B
stress signals
cholesterol
crystals
Hit #2
Novel pathways of
inflammation:
cholesterol crystals
NLRP3 inflammasomes are required for atherogenesis
and activated by cholesterol crystals.
Duewell P, Kono H, Rayner KJ, Sirois CM, Vladimer G,
Bauernfeind FG, Abela GS, Franchi L, Nuñez G, Schnurr M,
Espevik T, Lien E, Fitzgerald KA, Rock KL, Moore KJ, Wright
SD, Hornung V, Latz E.
Nature. 2010 Apr 29;464(7293):1357-61
Fig. 1 Cholesterol crystals
appear in early atherosclerotic
lesions
Heterogeneity of human
macrophages (CD68): GM and M
+ GM-CSF
+ M-CSF
GM-Mac phenotype (CD14 -)
M-Mac phenotype (CD14 +)
Waldo et al. Am J Pathol 2008;172:1112-6
Heterogeneity of human
macrophages (all CD68+)
Human coronary artery atherosclerotic lesion
CD14 (+) elongated
CD14 (-) rounded
M
GM
Waldo et al. Am J Pathol 2008;172:1112-6
Heterogeneity of human
macrophages:
The GM and M colony stimulating factors (CSFs)
The GM-Mac phenotype that predominates
in normal intima expresses genes known to mediate reverse
cholesterol transport and macrophage emigration from
the vessel wall.
The M-Mac phenotype that predominates
in diseased intima is deficient in the same
atheroprotective genes but expresses proinflammatory genes.
Waldo et al. Am J Pathol 2008;172:1112-6
From M-Mac to M1 and M2 another level of complexity
Macrophage
Monocyte
Th1
M-CSF
IFN-g + LPS
IL-4
M1 pro-athero
M2 anti-athero
Th2
Martinez et al. J Immunol 2006
Resolution of inflammation: Th2-driven
Infl. Cytokine
production
Efferocytosis
M2
M1
Macrophage death and defective inflammation resolution in atherosclerosis.
Tabas I. Nat Rev Immunol. 2010 Jan;10(1):36-46
The switch from early to
advanced atherosclerosis
M2
M1
Macrophage death and defective inflammation resolution in atherosclerosis.
Tabas I. Nat Rev Immunol. 2010 Jan;10(1):36-46
Formation of a vulnerable plaque:
defective clearance of apoptotic foam cells
Macrophage death and defective inflammation resolution in atherosclerosis.
Tabas I. Nat Rev Immunol. 2010 Jan;10(1):36-46
Rupture-prone plaque: high-risk plaque
The ”thin-cap fibroatheroma”
inflammation
fibrosis
thin cap
lipid-rich
core
What is the physiological level of LDLcholesterol? Leads to regression
of plaque = curative treatment
mmol/l
18
8
3.5
3.0
2.5
2.0
1 mM
=40mg/dL
Nobel Prize-winners Brown ja Goldstein, Dallas Texas