6β-Hydroxytestosterone, a Cytochrome P450 1B1 Metabolite of Testosterone, Contributes to Angiotensin II–Induced Hypertension and Its Pathogenesis in Male Mice. Issue 6 (June 2015) - Pingili, Ajeeth K.
Abstract Previously, we showed that Cyp1b1 gene disruption minimizes angiotensin II–induced hypertension and associated pathophysiological changes in male mice. This study was conducted to test the hypothesis that cytochrome P450 1B1-generated metabolites of testosterone, 6β-hydroxytestosterone and 16α-hydroxytestosterone, contribute to angiotensin II–induced hypertension and its pathogenesis. Angiotensin II infusion for 2 weeks increased cardiac cytochrome P450 1B1 activity and plasma levels of 6β-hydroxytestosterone, but not 16α-hydroxytestosterone, in Cyp1b1+/+ mice without altering Cyp1b1 gene expression; these effects of angiotensin II were not observed in Cyp1b1−/− mice. Angiotensin II–induced increase in systolic blood pressure and associated cardiac hypertrophy, and fibrosis, measured by intracardiac accumulation of α-smooth muscle actin, collagen, and transforming growth factor-β, and increased nicotinamide adenine dinucleotide phosphate oxidase activity and production of reactive oxygen species; these changes were minimized in Cyp1b1−/− or castrated Cyp1b1+/+ mice, and restored by treatment with 6β-hydroxytestoterone. In Cyp1b1+/+ mice, 6β-hydroxytestosterone did not alter the angiotensin II–induced increase in systolic blood pressure; the basal systolic blood pressure was also not affected by this agent in either genotype. Angiotensin II or castration did not alter cardiac, angiotensin II type 1 receptor, angiotensin-converting enzyme, Mas receptor, or androgen receptor mRNA levels in Cyp1b1+/+ or in Cyp1b1−/− mice. These data suggest that the testosterone metabolite, 6β-hydroxytestosterone, contributes to angiotensin II–induced hypertension and associated cardiac pathogenesis in male mice, most probably by acting as a permissive factor. Moreover, cytochrome P450 1B1 could serve as a novel target for developing agents for treating renin–angiotensin and testosterone-dependent hypertension and associated pathogenesis in males.