Astragaloside IV promotes cerebral angiogenesis and neurological recovery after focal ischemic stroke in mice via activating PI3K/Akt/mTOR signaling pathway

Abstract

Our previous work has shown that activating PI3K/Akt/mTOR signaling pathway is involved in angiogenesis after ischemic stroke, and recent studies have revealed that astragaloside IV (AS-IV) exerts beneficial effects on cerebral protection after ischemic stroke. However, it is unclear whether the beneficial effects of AS-IV against ischemic stroke is related to angiogenesis and PI3K/Akt/mTOR signaling pathway. The aim of this study was to investigate the effects of AS-IV on angiogenesis and long-term neurological recovery after focal ischemic stroke as well as the underlying mechanisms. After mice model of distal middle cerebral artery occlusion (dMCAO), AS-IV was administered with low dose (10 mg/kg), medium dose (20 mg/kg) or high dose (40 mg/kg) once daily for 14 days. We report herein that AS-IV (20 mg/kg) significantly ameliorated long-term neurological recovery and attenuated histological damage, while promoting cerebral blood flow recovery in ischemic mice. Moreover, AS-IV administration enhanced microvessel density as well as astrocyte and pericyte coverage around microvessels in the peri-infarct cortex. In vitro, AS-IV promoted endothelial cells (ECs) proliferation and tube formation after oxygen-glucose deprivation (OGD), which was partially inhibited by the specific PI3K inhibitor LY294002. Finally, AS-IV increased the expression of vascular endothelial growth factor (VEGF) through activating the PI3K/AKT/mTOR signaling pathway in the process of promoting angiogenesis. These results suggested that AS-IV may promote angiogenesis after ischemic stroke through increasing the expression of VEGF via PI3K/Akt/mTOR pathway, which unveils novel therapeutic effects of AS-IV and suggests promising application of AS-IV in ischemic stroke.