Abeta peptides are thought to be centrally involved in Alzheimer's disease (AD) pathogenesis, although Abeta's pathophysiological mechanisms remain to be elucidated. We previously showed that soluble beta-amyloid1-40 (Abeta) and Abeta1-42 exhibit vasoactive properties, and are able to promote vasoconstriction in rat aortae induced by an endogenous vasoconstrictor, endothelin-1. It is well established that the APOE epsilon4 allele confers risk for both familial and sporadic AD, as well as for hypertension. We now report that physiologic amounts (10 nM) of specific human recombinant apoE isoforms are vasoactive (E4 > E3, and not E2) in isolated rat aortae. In order to investigate if various apoE isoforms could modulate Abeta vasoactivity, we co-incubated Abeta1-40 with various isoforms of apoE in our tissue bath system. Our results show that, while none of the APOE isoforms are able to affect the maximum constriction induced by Abeta; the apoE E4 isoform synergistically enhances the rate of vasoconstriction induced by Abeta. Our data suggest that apoE may promote hypertension and contribute to AD pathogenesis via enhancement of vasoconstriction, and support a link between hypertension, cerebral amyloid angiopathy and AD.