NOS3 and Alzheimer disease: In that regard, three BBB endothelial proteins, vascular endothelial growth factor (VEGF), type 2 VEGF receptor (VEGFR2), and endothelial nitric oxide synthase (eNOS), have been proposed to underlie the onset and progression of the pathological hallmarks in AD as well as affect the response of the brain to vascular disease10–12.