EDN1 and early-onset autosomal dominant Alzheimer disease: Amyloid β causes an increase in the production of neurons that produces endothelin 1 (ET1) by upregulating endothelin-converting enzyme 2 (ECE2) changing ET1 from an inactive precursor to active form; this upregulation of endothelin 1 and endothelin-converting enzyme axis due to amyloid β 1-40 causes chronic reduction of the cerebral blood flow in Alzheimer disease.