Abstract Body: Previously, we reported that 17β-estradiol (E2)- cytochrome P450 (CYP) 1B1-generated metabolite 2-methoxyestradiol (2-ME) in the paraventricular nucleus (PVN) protects from angiotensin (Ang) II-induced hypertension. Recently, we showed that intracerebroventricular (ICV) administration of 12(S)-hydroxyeicosatetraenoic acid (12S-HETE), an arachidonic acid-12/15-lipoxygenase (LO) metabolite produces a greater increase in blood pressure (BP) in ovariectomized (OVX) than intact LO knockout (KO) mice. These observations led to the hypothesis that 2-ME protects from Ang II-induced hypertension by inhibiting the production and action of 12S-HETE in the brain in female mice. ICV 2-ME (1.5 µg/2 µL/ alternate day) but not its vehicle (20% w/v hydroxypropyl-β-cyclodextrin) minimized the effect of Ang II (700 ng/kg/min, subcutaneous, osmotic pump, two weeks) to increase mean arterial blood pressure (MAP: Day 0 vs Day 12; 105±3 to 121±2 vs 105±3 to 153±8, mmHg) measured by radiotelemetry, urinary norepinephrine level (ELISA, 445±27 vs 898±20, ng/mL), lo mRNA expression (RT-PCR, 1.5±0 vs 2.0±1, arbitrary unit), 12S-HETE level (ELISA, 136±26 vs 285±44, pg/mg protein), and GFAP+ (immunostaining, astrocyte marker, 35±3 vs 67±3, number of cells per PVN section) cells in PVN and kidney fibrosis (histochemical-staining, 4.0±0.3 vs 9.8±0.7, arbitrary unit) in OVX-LOKO mice transduced with ICV-adenovirus-LO-DNA (1.28X10¹¹ pfu/ml, 2 µL, single injection) that have 12S-HETE in the brain (PVN) but not in plasma (n=4/group; P<0.05). ICV siRNA (0.4 nM, 2 µL, single injection) against 12S-HETE receptors LTB4 and GPR31 minimized Ang II-induced increased systolic BP measured by tail-cuff in intact CYP1B1 KO mice that have E2 but lacks 2-ME (mmHg, control: 108±3 to 175±6, siRNA-LTB4r2: 110±5 to 141±3, siRNA-GPR31: 114±1 to 145±2; n=8 per group). Moreover, the actions of ICV 12S-HETE (50 ng/2 µL every 3rd day) to enhance the effect of Ang II-induced increase in MAP were also minimized by ICV siRNA-LTB4 and GPR31 respectively in OXV-LOKO mice (mmHg, control: 102±2 to 168±1, siRNA-LTB4r2: 101±2 to 122±6, siRNA-GPR31: 101±3 to 129±3; n=4 per group). These data suggest that E2-CYP1B1 metabolite 2-ME, by inhibiting the production and action of 12S-HETE in the brain via LTB4r2 and GPR31 receptors protect from Ang II-induced hypertension in female mice. Thus, 2-ME and/or 12S-HETE receptor blockers could be useful for treating hypertension and its pathogenesis in females with ovarian failure.