In addition, data from both biopsies of patients with AD and mouse AD models have provided some insights into the mechanisms underlying capillary constriction and reduced blood flow; in this regard, amyloid-beta enhanced oxidative stress in pericytes via NADPH oxidase-4, leading to endothelin-1-mediated effects of endothelin A receptors on capillary-related pericytes [26]. This evidence concerns the gene NOX4 and Alzheimer disease.