Abstract P045: Central Cytochrome P450 1B1 Generated 17Beta Estradiol Metabolite 2-Methoxyestradiol Minimizes Angiotensin II-induced Hypertension in Female Mice

Abstract

Recently we have shown that 17beta-estradiol (E2)-generated cytochrome P450 1B1 (CYP1B1) metabolite 2-methoxyestradiol (2-ME) protects against angiotensin II (Ang II)-induced hypertension in female mice. The demonstration that central E2 inhibits Ang II-induced hypertension together with the expression of CYP1B1 in various areas in the brain and the production of 2-ME from E2 by microglia cells led us to hypothesize that 2-ME contributes to the inhibitory effect of E2 on the brain on Ang II- induced hypertension in female mice. To test this hypothesis, we examined the effect of intracerebroventricular (ICV) administered E2 in ovariectomized (OVX) wild-type ( Cyp1b1 +/+ ) and OVX Cyp1b1 -/- mice on the action of systemic Ang II (700 ng/kg/min) for 14 days. E2 (1.5 μg/2μL/injection) or its vehicle (20% w/v 2-Hydroxypropyl-β-cyclodextrin dissolved in artificial CSF) was injected (400 nL/min every 2 nd day) via a cannula implanted in the brain. Mean arterial blood pressure (MAP) was measured by radiotelemetry (n=3-4). E2 but not its vehicle attenuated Ang II-induced increase in MAP on Day 12 in OVX Cyp1b1 +/+ (111±2 vs. 154±5, mmHg, P<0.05). ICV injections of 2-ME but not E2 (1.5 μg/2μL/injection every 2 nd day) attenuated the increase in MAP by Ang II in OVX Cyp1b1-/- mice (111±1 vs. 141±6, mmHg, P<0.05). Administration of ganglionic blocker hexamethonium (30 mg/Kg, IP) on day 14 of Ang II infusion resulted in greater reduction in MAP (P<0.05, n=4) in centrally injected E2 in OVX Cyp1b1 -/- , and vehicle-injected OVX Cyp1b1 +/+ mice (Δ90±1 and Δ91±14, mmHg) than in E2 injected OVX Cyp1b1 +/+ (Δ68±5 mmHg), and 2-ME injected OVX Cyp1b1 -/- mice (Δ60±4 mmHg). Furthermore, in intact Cyp1b1 -/- , but not OVX Cyp1b1 -/- mice reconstitution of CYP1B1 in the brain by transduction with adenovirus (AdV)-CYP1B1-cDNA (ICV 2μL of 1.0 X 10 12 particle/mL) reduced systolic blood pressure (SBP) measured by tail-cuff on Day12 (136±2 vs. 166±6 mmHg, P<0.05, n=4-5). ICV injection of AdV-GFP-cDNA in these mice did not alter Ang II-induced increase in SBP (168±8 and 171±2 mmHg, n=4). These data suggest that central effect of E2 to attenuate Ang II-induced hypertension is dependent on brain CYP1B1 and is most likely mediated via generation of 2-ME, which decreases sympathetic outflow in female mice.