BACE1 and brain ischemia: Studies show that β-secretase (β-site amyloid precursor protein cleaving enzyme 1, BACE1) protein levels and activity are elevated in sporadic AD brains, and that BACE1 levels are upregulated under stress conditions such as oxidative stress, cerebral ischemia, and hypoxia, all of which are associated with increased AD incidence [5,6,7].