Resolving Inflammation after Stroke through Modulation of Formyl Peptide Receptor 2/The Lipoxin Receptor
File(s)
Author(s)
Smith, Helen Katherine
Type
Thesis
Abstract
Stroke kills 15 million people a year and causes disabilities in many more millions who survive.
Most strokes are caused by a blood clot, yet only seven percent of patients qualify
for early pharmacological clot removal. Damage is frequently exacerbated even as blood
reperfuses an ischaemic brain region, through a concomitant inflammatory response to the
damaged tissue. Following the continual failure in clinical trials of drugs intended to
tackle both initial excitotoxic cell death and pro-‐inflammatory mechanisms during
ischaemia/reperfusion (I/R), this thesis is premised on enhancing 'pro-‐resolving'
anti-‐inflammatory pathways.
Formyl Peptide Receptor 2/the lipoxin receptor (FPR2/ALX; mouse orthologue Fpr2/3) and two of its
ligands, Lipoxin A4 (LXA4) and Annexin A1 (AnxA1), are part of an
endogenous anti-‐ inflammatory system. They actively resolve inflammation through a
reduction in characteristic leukocyte-‐endothelial (L-‐E) interactions, while promoting
the production of anti-‐inflammatory cytokines and non-‐phlogistic phagocytosis of leukocytes
already within tissue. Chapters 3-‐5 of this thesis describe the development of mouse model of
global cerebral I/R (5 min ischaemia/40 min or
2 h reperfusion) through which L-‐E interactions are assessed using intravital
microscopy. Substantial reductions in L-‐E interactions following treatment with
FPR2/ALX ligands (AnxA1 N-‐ terminal peptide AnxA1Ac2-‐26 and LXA4 analogue
15-‐epi-‐LXA4) are demonstrated along with variations in cytokine levels (MCP-‐1,
IL-‐6 and IL-‐10) after 2 h of reperfusion. The reductions are shown to be variable
with respect to the duration of reperfusion, concentration of 15-‐epi-‐LXA4 and the time of
treatment administration. In addition, the effects are abrogated by co-‐treatment with FPR
antagonists, which independently cause a highly pronounced acute inflammatory response in the
model. Chapters 6 and 7 provide further investigation into the role of FPRs in stroke
and inflammation, through chemotaxis studies on human monocytes (from stroke patients and healthy
controls) and through use of an FPR1-‐target MRI contrast agent in
mice following lipopolysaccaride-‐induced inflammation.
Overall, the data provide evidence that Fpr2/3 ligands are able to reduce inflammation following
cerebral I/R, that an FPR2/ALX-‐targeted drug may therefore be effective in human stroke, and that
its optimal use is likely to be administration time, dose and FPR2/ALX ligand-‐dependent.
Most strokes are caused by a blood clot, yet only seven percent of patients qualify
for early pharmacological clot removal. Damage is frequently exacerbated even as blood
reperfuses an ischaemic brain region, through a concomitant inflammatory response to the
damaged tissue. Following the continual failure in clinical trials of drugs intended to
tackle both initial excitotoxic cell death and pro-‐inflammatory mechanisms during
ischaemia/reperfusion (I/R), this thesis is premised on enhancing 'pro-‐resolving'
anti-‐inflammatory pathways.
Formyl Peptide Receptor 2/the lipoxin receptor (FPR2/ALX; mouse orthologue Fpr2/3) and two of its
ligands, Lipoxin A4 (LXA4) and Annexin A1 (AnxA1), are part of an
endogenous anti-‐ inflammatory system. They actively resolve inflammation through a
reduction in characteristic leukocyte-‐endothelial (L-‐E) interactions, while promoting
the production of anti-‐inflammatory cytokines and non-‐phlogistic phagocytosis of leukocytes
already within tissue. Chapters 3-‐5 of this thesis describe the development of mouse model of
global cerebral I/R (5 min ischaemia/40 min or
2 h reperfusion) through which L-‐E interactions are assessed using intravital
microscopy. Substantial reductions in L-‐E interactions following treatment with
FPR2/ALX ligands (AnxA1 N-‐ terminal peptide AnxA1Ac2-‐26 and LXA4 analogue
15-‐epi-‐LXA4) are demonstrated along with variations in cytokine levels (MCP-‐1,
IL-‐6 and IL-‐10) after 2 h of reperfusion. The reductions are shown to be variable
with respect to the duration of reperfusion, concentration of 15-‐epi-‐LXA4 and the time of
treatment administration. In addition, the effects are abrogated by co-‐treatment with FPR
antagonists, which independently cause a highly pronounced acute inflammatory response in the
model. Chapters 6 and 7 provide further investigation into the role of FPRs in stroke
and inflammation, through chemotaxis studies on human monocytes (from stroke patients and healthy
controls) and through use of an FPR1-‐target MRI contrast agent in
mice following lipopolysaccaride-‐induced inflammation.
Overall, the data provide evidence that Fpr2/3 ligands are able to reduce inflammation following
cerebral I/R, that an FPR2/ALX-‐targeted drug may therefore be effective in human stroke, and that
its optimal use is likely to be administration time, dose and FPR2/ALX ligand-‐dependent.
Version
Open Access
Date Issued
2013-02
Date Awarded
2013-04
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Gavins, Felicity
Publisher Department
Medicine
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)