Endothelium-specific endothelin-1 overexpression induces superoxide production and angiogenesis after middle cerebral artery occlusion

Abstract

Endothelin-1 (ET-1) has been implicated in ischemic stroke, and acts as a mediator of superoxide production after cerebral ischemic challenge. Using transgenic mouse approach, we specifically targeted the ET-1 gene to endothelial cell using the Tie-1 promoter (TET-1). TET-1 mice showed more severe neurological score and higher percentage of infarct volume after middle cerebral artery occlusion (MCAO). To understand the mechanistic basis behind the detrimental role of endothelium ET-1, we hypothesized that ET-1 potentiates the reactive oxygen species (ROS) production, subsequently leads to the lipids peroxidation and edema formation. TET-1 mice displayed higher level of superoxide production in ipsilateral hemisphere when compared to Ntg counterparts after MCAO. Higher serum nitric oxide (NO) level as well as ischemic penumbra nitrotyrosine expression were found in TET-1 mice after MCAO, suggesting that excessive NO release in TET-1 mice accompanied by ROS production might, presumably, play a role in rendering neuronal cell death. MCAO induced the expression of GFAP and Heat shock protein 70 (HSP70) on the ischemic hemisphere in TET-1 mice, this pinpoints the role of endothelium ET-1 on glial inflammatory and stress response under ischemic condition. Moreover, hypoxic inducing factor-1 (HIF-1), VEGF and vWF have been found to be highly induced in TET-1 mice after 2hr ischemia/22hr reperfusion. Taken together, these results suggest that endothelium ET-1 mediates the ROS formation accompanied by NO release, thereafter, renders neuronal cell death. In addition, it induces post-ischemic angiogenesis at least in part via HIF-1 pathway.