Hypertension enhances Aß-induced neurovascular dysfunction, promotes ß-secretase activity, and leads to amyloidogenic processing of APP.

Hypertension (HTN) doubles the risk of Alzheimer's disease (AD), but the mechanisms remain unclear. Amyloid-ß (Aß), a key pathogenic factor in AD, induces cerebrovascular dysfunction. We hypothesized that HTN acts in concert with Aß to amplify its deleterious cerebrovascular effects and to increase Aß production. Infusion of angiotensin II (ANGII; intravenously) elevated blood pressure and attenuated the cerebral blood flow (CBF) response to whisker stimulation or the endothelium-dependent vasodilator acetylcholine (ACh) (P < 0.05). Neocortical application of Aß in mice receiving ANGII worsened the responses to ACh (P < 0.05). The cerebrovascular dysfunction observed in Tg2576 mice, in which Aß is elevated both in blood and in brain due to expression of mutated amyloid precursor protein (APP), was not aggravated by neocortical application of ANGII or by a 2-week administration of 'slow pressor' of ANGII (600 ng/kg per minute; subcutaneously). In contrast, ANGII aggravated the dysfunction in TgSwDI mice, in which Aß is increased only in brain. Slow-pressor ANGII induced microvascular amyloid deposition in Tg2576 mice and enhanced ß-secretase APP cleavage. In Chinese hamster ovary (CHO) cells producing Aß, ANGII increased ß-secretase activity, Aß1-42, and the Aß42/40 ratio. We conclude that HTN enhances amyloidogenic APP processing, effects that may contribute to the pathogenic interaction between HTN and AD.