The Circadian Clock is Essential for the Crosstalk of VEGF-Notch-mediated Endothelial Angiogenesis in Ischemic Stroke

Abstract

Ischemic stroke is a major public health problem in China. Angiogenesis plays an essential role in the rehabilitation of ischemic brain injury. Recent studies demonstrated that the circadian clock is involved in the process of ischemic stroke, however, the exact mechanism of the circadian clock in regulating angiogenesis after cerebral infarction remains unclear. In the present study, we determined that environmental circadian disruption (ECD) could increase the stroke severity and impair the ability of angiogenesis in a transient middle cerebral artery occlusion (MCAO) rat model, by detecting the rat’s infarct volume, neurological test, and western blot of angiogenesis-related protein, including vascular endothelial growth factor (VEGF), matrix metalloproteinase-2 (MMP-2). We further report that the core circadian clock, aryl hydrocarbon receptor nuclear translocator-like 1 (BMAL1, also known as ARNTL1), plays an irreplaceable role in angiogenesis. Overexpression of BMAL1 promotes tube forming, migration, and wound healing capacity, and upregulate the VEGF and Notch pathway protein level. While this kind of promoting effect is reversed by the Notch pathway inhibitor, DAPT, according to the results of angiogenesis capacity and VEGF pathway protein level. In conclusion, our study reveals the intervention of ECD in angiogenesis in ischemic stroke and further identifies the exact mechanism by which BMAL1 regulates angiogenesis through the VEGF-Notch1 pathway.