Download and apoE-/- mice - Science Mission

Inflammation and atherosclerosis
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Immune cells dominate early lesions
Immune effector molecules accelerate lesion
progression
Activation of inflammation elicits acute coronary
syndromes
Atherosclerosis is an inflammatory disease in which
immune mechanisms interact with metabolic risk
factors to initiate, propagate and activate lesions
in the arterial wall
The numbers
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CAD causes 38% of all deaths in North America
Most common cause of death in men under 65 y.o.
and second most common cause of women
Dispite advances in control of
hypercholesterolemia (statins),CVD expected to be
the main cause of death globally over the next 15
years due to rapidly increasing prevalence of
obesity and diabetes
Pathogenesis of coronary artery thrombosis
Cellular players in atherogenesis and plaque rupture
The early lesion: modified lipoproteins and foam cell formation
Role of macrophages
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MCSF induces monocytes entering lesion to
differentiate into macrophages
Macrophage differentiation associated with TLRs
and scavenger receptors
MCSF/apoE KO shows reduced atherosclerosis
Scavenger receptors bind bacterial endotoxins,
apoptotic cells and oxLDL
SR/apoE KOs show reduced atherosclerosis
The macrophage as an inflammatory mediator
TNF-R
IL-1R
IFN-gR
Toll-like
NFkB
MAP
KINASE
JAK/STAT
IRF
GENES
Inflammation, Anti-Microbial
Response, Apoptosis, …
TLR receptors and atherosclerosis
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10 family members
Recognize pathogen associated molecular patterns
(e.g. LPS, dsRNA) as well as oxLDL, HSP60 etc.
Initiate signaling cascades leading to production of
inflammatory cytokines, proteases, reactive oxygen
species
In addition to macrophages, expressed by dendritic
cells, mast cells, endothelial cells
Macrophage-T cell interactions in atherosclerosis
T cells and atherosclerosis
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Immune cells patrol tissues in search of antigen
T cell infiltrate is common feature of atherosclerotic
lesions
• Predominantly CD4+ cells, recognize antigen/MHC II
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CD4+ T cells reactive to oxLDL, HSP60, bacterial
products detected in human lesions
NK cells present in early lesions, recognize lipid
antigens
NK activation increases athero in apoE KO mice
T cell responses
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Th1 response activates macrophages and functions in the
defense against intracellular pathogens
Th2 response elicits allergic inflammation
Atherosclerotic lesions contains cytokines that promote Th1
responses
Activated Th1 effector cells in lesions produce macrophage
activating cytokine IFNg
IFNg improves efficiency of ag presentation and augments
synthesis of TNFa and IL-1
IFNg, TNFa and IL-1 in turn stimulate production of many other
inflammatory mediators
apoE mice lacking IFNg or downstream mediators such as IL-18
or T-bet show reduced athero
Anti-inflammatory factors and atherosclerosis
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Anti-inflammatory factors such as TGFb and IL-10
are protective
IL-10 KO increases athero in mice and exacerbates
thrombosis
Abrogation of TGF signaling in T cells leads to
large unstable atherosclerotic lesions
Immune cells and plaque rupture
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Preferentially occurs where fibrous cap is thin
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Active immune cells are abundant at site of rupture
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Immune cells produce inflammatory molecules and
proteolytic enzymes that weaken cap, activate cells
in the core and transform stable plaque into
vulnerable, leading to plaque rupture
MMPs likely to play important roles
Systemic inflammatory markers in atherosclerosis
Systemic indicators of inflammation
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Inflammatory process in lesions may lead to
increased plasma levels of cytokines and acute
phase proteins
CRP and IL-6 are elevated in patients with unstable
angina and MI
Levels correlate with prognosis
TLR-3/4
MyD88
“Independent”
MyD88
“Dependent”
TANK
NEMO
TBK-1
IKKi
IKK-1
IKK-2
IkB
IRF-3
NF-kB
Antiviral
Response
Inflammatory
Response
MyD88/apoE KO mice show reduced athero
MyD88/apoE Ko mice show reduced chemokine expression
MyD88/apoE KO macs show reduced chemokine expression
and recruitment in response to inflammatory cytokines
Links between infection and atherosclerosis
• Unlikely to be caused by single organism
• Diverse pathogens have been detected within lesions
• Bacteria and viruses accelerate athero in murine
models
Potential mechanisms
• Stimulation of inflammatory cytokines
• Alteration of adhesion molecule expression
? Lipid metabolism ?
oxLDL
CD36
cholesterol
CE
Inflammatory
stimuli
ABCA1
LPS, IL-1b, TNFa
oxysterol
IL-1R
RXR LXR
TOLL4
TNFR
INFLAMMATION
 iNOS  IL-1b
 IL-6 COX2
 MMP9
CHOLESTEROL
EFFLUX
 PLTP  ABCAI
 ApoE/CII  LPL
MACROPHAGE
Synthetic LXR agonist reduces atherosclerosis
inLDLR-/- and apoE-/- mice
LDLR-/- Aortic Sections
ApoE-/- Aortic Sections
300000
p < 0.005
250000
250000
200000
197870
150000
136610
100000
Lesion area (mM2/section)
Lesion area (mM2/section)
p < 0.005
200000
150000
134470
100000
70621
50000
50000
0
0
high fat
Joseph et al. PNAS 2002
+ GW3965
vehicle
GW3965
Loss of bone marrow LXR expression accelerates athero
Aortic Lesion Coverage
(%)
*
C57Bl6
BMT
*
LXRab -/BMT
apoE -/BMT
7.5
5.0
2.5
0.0
Tangirala et al. PNAS 2002
Bacterial or viral infection blocks expression of LXR
target genes in macrophages
ABCA1
ABCA1
apoE
ABCG1
SREBP-1c
FAS
iNOS
36B4
Castrillo et al., Molecular Cell 2003
FAS
MX-1
IFN-b
36B4
Infl A + T
Infl A + GW
Infl A
T1317
GW3965
+/- Influenza A
ctrl
E. Coli + T
E. Coli
T1317
GW3965
ctrl
+/- E. coli
E. Coli + GW
Antonio Castrillo, Sean Joseph
TLR3 and TLR4 ligands inhibit cholesterol efflux
from macrophages
Cholesterol efflux
apoAI-dependent efflux (%)
14
12
Ctrl
LXR ligand
10
8
*
6
**
4
*
2
0
**
Activation of TLR3 inhibits LXR signaling in vivo
Aorta
Spleen
11
ABCA1
7
5
*
5
3
1
mRNA
mRNA
9
ABCA1
vehicle
*
3
1
Poly IC
GW3965
*
Both
3
mRNA
mRNA
4
apoE
3
2
*
1
mRNA
17
*
13
9
5
*
2
1
5
ABCG1
mRNA
19
apoE
ABCG1
*
3
1
1
IFN-b
5
500
mRNA
mRNA
7
3
200
100
0
IP-10
mRNA
mRNA
300
300
100
1
400
IFN-b
50
30
10
IP-10
TLR-LXR crosstalk:
potential implications for atherosclerosis
virus
cholesterol
efflux
bacteri
a
other signals
C
TLR-3/4
?
C
ABCA1
 Foam cell formation
C
C
TANK
C
C
TBK-1IKKi
IRF-3
LXR
RXR
ABCA1, ABCG1,
apoE
Immunization with pneumococus induces
oxLDL-specific IgM
Immunization with pneumococus induces
oxLDL-specific IgM
s. pneumo
s. pneumo + s. pneumo block
s. pneumo + oxLDL block
E06 (ox PL)
Plasma from mice immunized with pneumococus
inhibits macrophage binding of oxLDL
Immunization with pneumococus reduces
atherosclerosis in LDLR-/- mice