2 Hypertension June 2015 vascular oxidative stress , and hypertension and that targeting

Hypertension is a multifactorial disorder involving perturbations of the vasculature, the kidney, and the central nervous system. This disease represents a major risk factor for stroke, myocardial infarction, and heart failure. Despite treatment with multiple drugs, 24% of hypertensive patients remain hypertensive, likely because of the mechanisms contributing to blood pressure elevation that are not affected by current treatments. In almost all experimental models of hypertension, production of reactive oxygen species (ROS: O2 .− and H 2 O 2 ) is increased in multiple organs. In the vasculature, ROS promote vasoconstriction and remodeling, thus increasing systemic vascular resistance. Systemic vascular resistance is increased in virtually all cases of adult hypertension, and thus, understanding alterations of vascular function in hypertension remains of utmost importance. The mitochondria are an important source of O2 . − , and we have recently shown that overexpression of mitochondrial superoxide dismutase (SOD2) or scavenging of mitochondrial ROS with mitochondria-targeted antioxidants attenuate hypertension. Regulation of mitochondrial O2 . − and therapeutic potential of targeting the mitochondria, however, is poorly defined. We previously reported that inhibition of mitochondrial cyclophilin D (CypD) in isolated endothelial mitochondria reduces O2 . − production, and recent studies have shown that CypD deficiency reduced O2 . − production in leukocytes. CypD is a regulatory subunit of the mitochondrial permeability transition pore and acts as Ca sensitizer for mitochondrial permeability transition pore opening, which is implicated in the regulation of cell death. CypD has been targeted for reducing ischemic heart injury and transplant rejection using the nonspecific CypD inhibitor cyclosporine A. However, the off-target effects of cyclosporine A paradoxically lead to increased sympathetic outflow, endothelin production, vasoconstriction, and hypertension, which is likely associated with calcineurin inhibition. Indeed, genetic CypD depletion did not alter the basal blood pressure. We therefore hypothesized that CypD contributes to O2 . − overproduction in mitochondria, Abstract—Vascular superoxide (O2 .− ) and inflammation contribute to hypertension. The mitochondria are an important source of O2 . − ; however, the regulation of mitochondrial O2 . − and the antihypertensive potential of targeting the mitochondria remain poorly defined. Angiotensin II and inflammatory cytokines, such as interleukin 17A and tumor necrosis factor-α (TNFα) significantly contribute to hypertension. We hypothesized that angiotensin II and cytokines cooperatively induce cyclophilin D (CypD)–dependent mitochondrial O2 . − production in hypertension. We tested whether CypD inhibition attenuates endothelial oxidative stress and reduces hypertension. CypD depletion in CypD mice prevents overproduction of mitochondrial O2 . − in angiotensin II–infused mice, attenuates hypertension by 20 mm Hg, and improves vascular relaxation compared with wild-type C57Bl/6J mice. Treatment of hypertensive mice with the specific CypD inhibitor Sanglifehrin A reduces blood pressure by 28 mm Hg, inhibits production of mitochondrial O2 . − by 40%, and improves vascular relaxation. Angiotensin II–induced hypertension was associated with CypD redox activation by S-glutathionylation, and expression of the mitochondria-targeted H 2 O 2 scavenger, catalase, abolished CypD S-glutathionylation, prevented stimulation mitochondrial O2 . − , and attenuated hypertension. The functional role of cytokine–angiotensin II interplay was confirmed by co-operative stimulation of mitochondrial O2 . − by 3-fold in cultured endothelial cells and impairment of aortic relaxation incubated with combination of angiotensin II, interleukin 17A, and tumor necrosis factor-α which was prevented by CypD depletion or expression of mitochondria-targeted SOD2 and catalase. These data support a novel role of CypD in hypertension and demonstrate that targeting CypD decreases mitochondrial O2 . − , improves vascular relaxation, and reduces hypertension. (Hypertension. 2016;67:00-00. DOI: 10.1161/HYPERTENSIONAHA.115.07085.)