Expression and function of β-site amyloid precursor protein-cleaving enzyme 2 in vascular endothelium.

The physiological function of β-site amyloid precursor protein-cleaving enzyme 2 (BACE2) in vascular endothelium of systemic arteries is unknown. In the present study, we generated conditional tamoxifen-inducible endothelial BACE2-deficient mice (eBACE2(-/-) mice). Electron microscopic and Western blot analyses revealed that BACE2 protein is mainly present in endothelial cells of aorta. Genetic deletion of BACE2 in endothelial cells significantly impaired endothelium-dependent relaxations to Ca(2+)-ionophore A23187 in eBACE2(-/-) aortas as compared with tamoxifen-treated control mice, irrespective of sex. Blockade of nitric oxide synthase (NOS) with N(ω)-nitro-l-arginine methyl ester abolished relaxations to A23187. In contrast, endothelium-independent relaxations to nitric oxide donor diethylamine-NONOate were unchanged. Expression of endothelial NOS protein and levels of cyclic nucleotides were also unaffected in eBACE2(-/-) mice. Further analysis of the mechanisms underlying impaired endothelial function demonstrated that treatment with thromboxane A(2) receptor antagonist SQ29548 ameliorated relaxations to A23187 in the aorta of male and female eBACE2(-/-) mice. Furthermore, mRNA and protein expressions of cyclooxygenase-2 as well as production of thromboxane A(2) and prostaglandin F(2α) were significantly increased in the aorta of eBACE2(-/-) mice. In contrast, production of 6-keto prostaglandin F(1α) and prostaglandin E(2) was not affected. In addition, ex vivo treatment of wild-type aortas with proinflammatory cytokines decreased protein expression of BACE2. The results of our study suggest that increased production of vasoconstrictor prostanoids is responsible for impairment of endothelium-dependent relaxations to A23187 in the aorta of eBACE2(-/-) mice. We report a previously unrecognized role of BACE2 in the control of endothelial arachidonic acid metabolism and vasomotor function.NEW & NOTEWORTHY The exact physiological role of BACE2 in endothelial function of systemic arteries is unknown. Our study shows that thromboxane A(2) and prostaglandin F(2α) are responsible for impairment of endothelium-dependent relaxations in endothelium-specific BACE2-deficient mice. The data support an important role of BACE2 in the control of endothelial arachidonic acid metabolism and vasomotor function.