NOS3 and Cerebral ischemia: It was reported that exogenous rhEPO could enhance the EPO level in the brain, increase the vascular endothelial growth factor (VEGF), and its receptor vascular endothelial growth factor receptor-2 expression and regulate HIF-1α and the endothelial nitric oxide synthase (eNOS) expression through activating AMPK-KLF2 signaling, eventually promoting angiogenesis at 7 days after cerebral ischemia (Chen GH.