Transcript The HMG-Co-A reductase inhibitor, atorvastatin, promotes a

The HMG-Co-A reductase
inhibitor, atorvastatin, promotes a
Th2 bias and reverses paralysis in
central nervous system
autoimmune disease
Youssef, et. al.
Presented by Andrea Crowell
November 1, 2004
Multiple Sclerosis
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Immune system attacks myelin
Disruption of electrical conductivity results in fatigue and
disturbances of vision, strength, balance, coordination,
sensations, and bladder and bowel function.
Commonly treated with Interferon Beta (injectable)
Geographical distribution of MS in the
United States
Statins and Inflammation
Given to heart transplant recipients who
have high cholesterol levels and need to
be immunosuppressed
 Lower cholesterol AND suppress immune
system, esp. when taken with cyclosporin
 Findings from more later studies suggest
statins might inhibit antigen presentation
to pro-inflammatory Th1 cells
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HMG-CoA Reductase Pathway
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Acetyl-CoA (citric acid cycle) and
acetoacetyl-CoA to 3-hydroxy-3methylglutaryl-CoA (HMG-CoA)
HMG-CoA to mevalonate – by
HMG-CoA reductase (target of
statins)
Mevalonate to IPP by mevalonate
kinase (mutation -> HIDS:
Hyperimmunoglobinemia D –
recurrent fevers)
IPP to geranyl-PP by farnesyl-PP
synthetase
Geranyl-PP to farnesyl-PP by
farnesyl-PP synthetase (target of
bisphosphonates – to treat
osteoporosis)
EAE model
Experimental Autoimmune Encephalomyelitis
 3 types, reflecting different disease phenotypes
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– MOG p35-55
chronic
– PLP p139-151
relapsing-remitting
– MBP Ac1-11 specific TCR transgenic
fulminant
Atorvastatin prevented or reversed chronic
and relapsing paralysis in EAE mice
a, b: MOG p35-55 mice
c, d: PLP p139-151 mice
e: TCR transgenic mice – atorvastatin administered before immunization
f: PLP p139-151 mice – atorvastatin dose response curve 0.01–10 mg/kg
(0.01mg/kg dose did not significantly reduce EAE)
Histological evidence of EAE reduced with
atorvastatin treatment
• Atorvastatin treatment started before EAE induction prevented (10mg/kg) or
decreased the incidence and severity of relapse in SJL/J mice
• Treatment started during acute EAE decreased the incidence and severity of
relapse in SJL/J mice
MHC II expression in CNS white matter –
assessed by histology
Naïve CNS
PBS
1mg/kg
10mg/kg
SJL/J
C57BL/6
• High levels of MHC II expression were observed on microglia within or
adjacent to EAE lesions
• Atorvastatin treatment downregulated MHC II expression on these cells.
MHC II expression in CNS white matter –
assessed by FACS
a) MHC II expression increased when microglia were treated with IFN-gamma,
compared with untreated cells
b) Treating the cells with IFN-gamma + atorvastatin, MHC II expression did
not differ from the untreated cells
c) With IFN-gamma + atorvastatin + L mevalonate treatment, MHC II
expression increased
MHC II expression in CNS white matter –
assessed by immunohistochemistry
e) Untreated microglia (inset shows isotype-matched control IgG staining)
f) Treatment with IFN-gamma
g) Treatment with IFN-gamma + atorvastatin
h) Treatment with IFN-gamma + atorvastatin + L-mevalonate
MHC II expression in CNS white matter –
assessed by FACS
Mean peak fluorescence intensity for MHC II expression
• Atorvastatin reverses the effect of IFN-gamma
• L-mevalonate reversed the effect of atorvastatin
CIITA
MHC class II transactivator (CIITA) is the master regulator of MHC II expression
in antigen presenting cells
CIITA has multiple promoter regions, with pIV being predominant in epithelial
cells and pI predominant in bone marrow derived cells.
A previous study reported that statins suppressed IFN-gamma inducible CIITA
transcription.
CIITA transcription
EOC microglia
B10.PL microglia
• IFN-gamma increases CIITA transcription
• Atorvastatin reverses effect of IFN-gamma
• L-mevalonate reverses effect of atorvastatin
Results suggest that statins inhibit CIITA transcription in general, rather
than by selective activity at a particular promoter region.
Effect of atorvastatin on T cell activation and
Th regulation
Atorvastatin suppresses recall response to EAE-activating antigen in all 3 mouse models.
Splenocyte proliferation (measured by 3H incorporation) was suppressed by
1mg/kg and 10mg/kg atorvastatin.
- C57BL/6 mice were MOG p35-55 immunized
- SJL/J mice were PLP p139-151 immunized
Effect of atorvastatin on T cell activation and
Th regulation
Th1-associated cytokine secretion suppressed by atorvastatin.
Effect of atorvastatin on T cell activation and
Th regulation
Th2-associated cytokine secretion suppressed by atorvastatin.
Results of atorvastatin treatment of naïve Th0 cells from TCR transgenic mouse:
a: Suppressed
proliferation of
splenocytes in
vitro
b-e: Th1-associated
cytokine secretion
was suppressed
f-i: Th2-
associated
cytokine
secretion was
enhanced
Addition of L-mevalonate reversed these effects, indicating that atorvastatin acts via
inhibition of the mevalonate pathway.
In vivo atorvastatin treatment promotes Th2 bias
via STAT4 inhibition and STAT6 induction
• STAT 4 phosphorylation suppressed
• STAT6 phosphorylation is promoted
• STAT4 is required for Th1 lineage
commitment
• STAT6 is required for Th2 lineage
committment
STAT: Signal Transducer and Activator of Transcription
Atorvastatin has immunomodulatory effects
on both APC cells and T cells.
In vivo atorvastatin treatment (A) or
in vitro treatment (B) of only APC cells
or only T cells suppressed proliferation.
Atorvastatin has immunomodulatory effects
on both APC cells and T cells.
Inhibition of proliferation by atorvastatin treatment of either APCs or T cells also
produced a Th2 pattern of cytokine secretion.
Th1
Th2
Atorvastatin has immunomodulatory effects
on both APC cells and T cells.
The expression levels of MHC II on primary macrophages, as well as the
expression of the co-stimulatory molecules CD40, CD80, and CD86 were
measured.
• IFN-gamma induced expression.
• Atorvastatin inhibited IFN-gamma-induced expression.
• L-Mevalonate reversed atorvastatin inhibition.
Adoptive transfer of atorvastatin-treated T
cells prevents induction of EAE.
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Irradiated mice that received T cells from mice TCR transgenic mice
treated with 10mg/kg of atorvastatin were protected against EAE
induction following immunization.
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Atorvastatin-treated T cells were divided into CD4+ and CD8+ cells. The
CD4+ cells protected against EAE while the CD8+ cells did not.
Conclusions
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Oral atorvastatin treatment prevented or reversed
chronic and relapsing EAE paralysis.
Atorvastatin promoted differentiation of Th0 cells to Th2
cells.
Atorvastatin treatment induced a population of
regulatory T cells that suppressed EAE paralysis.
Statins may be a good treatment for Multiple
Sclerosis and other Th1-mediated autoimmune
diseases due to its pleiotropic
immunomodulatory effects.