sb-290157 and Reperfusion-Injury

The complement anaphylatoxin C3a contributes to injury after cerebral ischemia in mice. This study assesses the effect of C3a receptor antagonist (C3aRA) on leukocyte infiltration into the ischemic zone. Transient or permanent middle cerebral artery occlusion (MCAO) was induced in wild-type C57Bl/6 mice. Intraperitoneal C3aRA or vehicle was administered 45 mins before or 1 h after occlusion. Twenty-four hours after occlusion, we harvested brain tissue and purified inflammatory cells using flow cytometry. Soluble intercellular adhesion molecule (ICAM)-1 protein levels were assessed using enzyme-linked immunosorbent assays, and ICAM-1 and C3a receptor (C3aR) expression was confirmed via immunohistochemistry. In the transient MCAO model, animals receiving C3aRA showed smaller strokes, less upregulation of C3aR-positive granulocytes, and less ICAM-1 protein on endothelial cells than vehicle-treated animals; no significant differences in other inflammatory cell populations were observed. C3a receptor antagonist-treated and vehicle-treated animals showed no differences in stroke volume or inflammatory cell populations after permanent MCAO. These data suggest that blocking the binding of C3a to C3aR modulates tissue injury in reperfused stroke by inhibiting the recruitment of neutrophils to the ischemic zone. It further establishes antagonism of the C3a anaphylatoxin as a promising strategy for ameliorating injury after ischemia/reperfusion.

Topics: Anaphylatoxins; Animals; Arginine; Benzhydryl Compounds; Brain; Brain Ischemia; Complement C3a; Disease Models, Animal; Flow Cytometry; Granulocytes; Infarction, Middle Cerebral Artery; Intercellular Adhesion Molecule-1; Male; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Receptors, Complement; Reperfusion Injury

1. Complement activation is implicated in the pathogenesis of intestinal ischaemia-reperfusion injury (I/R), although the relative importance of individual complement components is unclear. A C3a receptor antagonist N(2)-[(2,2-diphenylethoxy)acetyl]-l-arginine (C3aRA) has been compared with a C5a receptor antagonist (C5aRA), AcF-[OPdChaWR], in a rat model of intestinal I/R. 2. C3aRA (IC(50)=0.15 microm) and C5aRA (IC(50)=0.32 microm) bound selectively to human polymorphonuclear leukocyte (PMN) C3a and C5a receptors, respectively. Effects on circulating neutrophils and blood pressure in the rat were also assessed. 3. Anaesthetised rats, subjected to intestinal ischaemia (30 min) and reperfusion (120 min), were administered intravenously with either (A) the C3aRA (0.1-1.0 mg x kg(-1)); the C5aRA (1.0 mg x kg(-1)); the C3aRA+C5aRA (each 1.0 mg x kg(-1)); or vehicle, 45 min prior, or (B) the C3aRA (1.0 mg x kg(-1)) or vehicle, 120 min prior to reperfusion. 4. The C3aRA and C5aRA, administered 45 min prior to reperfusion, displayed similar efficacies at ameliorating several disease markers (increased oedema, elevated ALT levels and mucosal damage) of rat intestinal I/R. The combination drug treatment did not result in greater injury reduction than either antagonist alone. However, doses of the C3aRA (0.01-10 mg x kg(-1)) caused transient neutropaenia, and the highest dose (10 mg x kg(-1)) also caused a rapid and transient hypertension. 5. The C3aRA (1.0 mg x kg(-1)), delivered 120 min prior to reperfusion to remove the global effect of C3aRA-induced neutrophil sequestration, did not attenuate the markers of intestinal I/R, despite persistent C3aR antagonism at this time. 6. C3aR antagonism does not appear to be responsible for the anti-inflammatory actions of this C3aRA in intestinal I/R in the rat. Instead, C3aRA-mediated global neutrophil tissue sequestration during ischaemia and early reperfusion may account for the protective effects observed.

Topics: Alanine Transaminase; Animals; Anti-Inflammatory Agents; Arginine; Australia; Benzhydryl Compounds; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Combinations; Female; Humans; Injections, Intravenous; Intestinal Mucosa; Membrane Proteins; Neutropenia; Neutrophils; Peptides, Cyclic; Rats; Rats, Wistar; Receptor, Anaphylatoxin C5a; Receptors, Complement; Reperfusion Injury; Time Factors