C1-inhibitor protects against brain ischemia/reperfusion injury via inhibition of cell recruitment and inflammation

C1-inhibitor (C1-INH), a major inhibitor of complement and contact-kinin systems, is neuroprotective in cerebral ischemia^{1, 2}. Actually C1-INH induces a reduction of the ischemic volume up to 73% and 90% in CD1 and C57 mice respectively. Furthermore C1-INH is able to prevent neurodegeneration and significantly lowers general and focal neurological deficits. These data showed that C1-INH has a potent neuroprotective effect in ischemia/reperfusion injury. In order to clarify the mechanism of this action we evaluated in the present study the expression of neurodegeneration and inflammation related factors in CD1 mice, treated with C1-INH (15U) or saline and subjected to 2 h of ischemia and 2 or 46 h of reperfusion. mRNA expression was measured by RT-PCR in brain cortex. Ischemia was induced by occlusion of the middle cerebral artery (MCAO) using a nylon monofilament introduced into the internal carotid artery and advanced so as to block the origin of the MCA. At the end of the ischemic period, the filament was removed and reperfusion allowed. C1-INH significantly dampened the mRNA expression of the adhesion molecules P-selectin and ICAM-1 induced by the ischemic insult. These data has been confirmed by immunohistochemistry analysis: C1-INH markedly inhibited the activation and/or recruitment of microglia/macrophage, as well as the infiltration of leukocyte. It significantly decreased the pro-inflammatory cytokine (TNFa, IL-18) and increased the protective cytokine (IL-6, IL-10) gene expression. C1-INH treatment prevented the decrease of NFH gene, a marker of cellular integrity and counteracted the increase of pro-caspase 3, an apoptosis index. In conclusion, C1-INH exerts an anti-inflammatory and anti-apoptotic action on ischemia/reperfusion injury. Our present and past data support a major effect of C1-INH on cell recruitment from the vasculature to the ischemic site.