Androgens have been implicated in the development of hypertension and castration minimizes the pressor effect of angiotensin (Ang) II. Previously we showed that Ang II-induced hypertension and associated pathophysiological changes are diminished in male cytochrome P450 (CYP) 1B1 gene disrupted mice. Since CYP1B1 metabolizes testosterone to 6β-hydroxytestosterone (6β-OHT); this study was conducted to determine its contribution in modulation of Ang II-induced hypertension. Eight weeks old male Cyp1b1+/+ and Cyp1b1-/- mice were either castrated or injected with 6β-OHT (15 μg/g, i.p. every 3rd day) or vehicle (DMSO, 50 μl), infused with Ang II (700 ng/kg/min) or vehicle for 2 weeks, and systolic blood pressure (SBP) was measured by tail cuff. Castration attenuated Ang II-induced increase in SBP in both Cyp1b1+/+ (184 ± 6 vs. 129 ± 4 mmHg, P < 0.05) and Cyp1b1-/- mice (150 ± 6 vs. 129 ± 4 mmHg, P < 0.05). In Cyp1b1+/+ mice, 6β-OHT did not alter Ang II-induced increase in SBP (184 ± 6 vs. 180 ± 8 mmHg, P < 0.05), but enhanced it in Cyp1b1-/- mice (150 ± 6 vs. 172 ± 8 mmHg, P < 0.05). Castration improved endothelial dysfunction associated with Ang II-induced hypertension in Cyp1b1+/+ mice, as demonstrated by increased relaxation of the aorta to acetylcholine. No endothelial dysfunction was observed in Cyp1b1-/- mice given Ang II with or without castration. In Cyp1b1+/+ mice, 6β-OHT did not alter Ang II-induced endothelial dysfunction, however, in Cyp1b1-/- mice infused with Ang II, 6β-OHT caused endothelial dysfunction. We have shown that Ang II-induced hypertension is associated with increased vascular production of reactive oxygen species (ROS) in Cyp1b1+/+ mice, and this increase is attenuated in Cyp1b1-/- mice, as measured by dihydroethidium fluorescence. In both Cyp1b1+/+ and Cyp1b1-/- mice given Ang II, castration abolished the increased ROS production. In Cyp1b1+/+ mice, 6β-OHT did not alter levels of ROS produced by Ang II, however, 6β-OHT further increased ROS production in Cyp1b1-/- mice given Ang II. These data suggest that 6β-OHT, a CYP1B1 metabolite of testosterone, contributes to the hypertensive effect of Ang II in male mice. Moreover, CYP1B1 could serve as a novel target for the development of agents for the treatment of androgen-mediated hypertension.
Effect of RIP Overexpression on Abiotic Stress Tolerance and Development of Rice
