Testosterone Metabolite 6ß-Hydroxytestosterone Contributes to Angiotensin II-Induced Abdominal Aortic Aneurysms in Apoe-/- Male Mice.

Background Sex is a prominent risk factor for abdominal aortic aneurysms (AAAs), and angiotensin II (Ang II) induces AAA formation to a greater degree in male than in female mice. We previously reported that cytochrome P450 1B1 contributes to the development of hypertension, as well as AAAs, in male mice. We also found that a cytochrome P450 1B1-generated metabolite of testosterone, 6ß-hydroxytestosterone (6ß-OHT), contributes to Ang II-induced hypertension and associated cardiovascular and renal pathogenesis in male mice. The current study was conducted to determine the contribution of 6ß-OHT to Ang II-induced AAA development in Apoe-/- male mice. Methods and Results Intact or castrated Apoe-/-/Cyp1b1+/+ and Apoe-/-/Cyp1b1-/- male mice were infused with Ang II or its vehicle for 28 days, and administered 6ß-OHT every third day for the duration of the experiment. Abdominal aortas were then evaluated for development of AAAs. We observed a significant increase in the incidence and severity of AAAs in intact Ang II-infused Apoe-/-/Cyp1b1+/+ mice, compared with vehicle-treated mice, which were minimized in castrated Apoe-/-/Cyp1b1+/+ and intact Apoe-/-/Cyp1b1-/- mice infused with Ang II. Treatment with 6ß-OHT significantly restored the incidence and severity of AAAs in Ang II-infused castrated Apoe-/-/Cyp1b1+/+ and intact Apoe-/-/Cyp1b1-/- mice. However, administration of testosterone failed to increase AAA incidence and severity in Ang II-infused intact Apoe-/-/Cyp1b1-/- mice. Conclusions Our results indicate that the testosterone-cytochrome P450 1B1-generated metabolite 6ß-OHT contributes to Ang II-induced AAA development in Apoe-/- male mice.

Cytochrome P450 1B1 Is Critical for Neointimal Growth in Wire-Injured Carotid Artery of Male Mice.

Background We have reported that cytochrome P450 1B1 ( CYP 1B1), expressed in cardiovascular tissues, contributes to angiotensin II -induced vascular smooth muscle cell ( VSMC ) migration and proliferation and development of hypertension in various experimental animal models via generation of reactive oxygen species. This study was conducted to determine the contribution of CYP 1B1 to platelet-derived growth factor-BB-induced VSMC migration and proliferation in vitro and to neointimal growth in vivo. Methods and Results VSMC s isolated from aortas of male Cyp1b1 +/+ and Cyp1b1 -/- mice were used for in vitro experiments. Moreover, carotid arteries of Cyp1b1 +/+ and Cyp1b1 -/- mice were injured with a metal wire to assess neointimal growth after 14 days. Platelet-derived growth factor- BB -induced migration and proliferation and H2O2 production were found to be attenuated in VSMC s from Cyp1b1 -/- mice and in VSMC s of Cyp1b1 +/+ mice treated with 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, a superoxide dismutase and catalase mimetic. In addition, wire injury resulted in neointimal growth, as indicated by increased intimal area, intima/media ratio, and percentage area of restenosis, as well as elastin disorganization and adventitial collagen deposition in carotid arteries of Cyp1b1 +/+ mice, which were minimized in Cyp1b1 -/- mice. Wire injury also increased infiltration of inflammatory and immune cells, as indicated by expression of CD 68+ macrophages and CD 3+ T cells, respectively, in the injured arteries of Cyp1b1 +/+ mice, but not Cyp1b1 -/- mice. Administration of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl attenuated neointimal growth in wire-injured carotid arteries of Cyp1b1 +/+ mice. Conclusions These data suggest that CYP 1B1-dependent oxidative stress contributes to the neointimal growth caused by wire injury of carotid arteries of male mice.