SUN-248 Estradiol Changes Angiotensin II-Induced ERK1/2 Phosphorylation by Different Pathways in the Hypothalamus and Lamina Terminalis

Female gonadal hormones, especially 17β-estradiol (E2), are known to mediate hydromineral homeostasis and blood pressure mainly by attenuating renin-angiotensin system (RAS) actions. The RAS plays an essential role in the maintenance of hydromineral and cardiovascular homeostasis via angiotensin II (ANGII), a key component of the RAS. However, the cellular mechanisms of the interaction between E2 and ANGII and its physiological role are not fully elucidated. Recently, our group showed that ERK1/2 is involved in sodium intake and vasopressin release induced by ANGII in female rats. In addition, E2 decreases ERK1/2 phosphorylation induced by ANGII in the hypothalamus and in structures of the lamina terminalis (LT). Thus, the goal of the present study was evaluated some mechanisms that could be involved in ERK1/2 dephosphorylation induced by E2 in response to ANGII, such as MAPK phosphatase 1 (MKP-1) and GRK5. For this, Wistar female rats (~250g) were submitted to ovariectomy and on the following day they were treated with estradiol cypionate (10µg/rat, sc) or vehicle (corn oil, 0.1mL/rat, sc) for eight days. On the eighth day, the rats received an intracerebroventricular (icv, lateral ventricle) injection of angiotensin II (25ng/2μL/rat) or vehicle (0.9% saline, 2μL/rat). After five min of ANGII injection the animals were decapitated for brain collection for MKP-1 and GRK5 expression analysis by western blot. Data were analyzed using ANOVA two or three-way, followed by Newman-Keuls post-test and the level of significance was set at 5%. It was observed that E2 increased MKP-1 expression only in hypothalamus (F(1,18)=24.3, p<0.001) in ovariectomized rats, independent of ANGII stimulus. Because the inhibitory effect of E2 on vasopressin release induced by ANGII was reversed by PKC inhibition, it was analyzed the role of PKC on MKP-1 expression and it was observed that PKC inhibition (Chelerythrine, 100µM/2µL/rat) reversed the positive effect of E2 on MKP-1 expression (F(1,30)=4.7, p<0.05) in the hypothalamus. In addition, E2 decreased GRK5 expression only in the LT (F(1,21)=12.7, p<0.01) in response to ANGII. Taken together, these results suggest that E2 requires PKC/MKP-1 pathway to decrease ERK1/2 phosphorylation in the hypothalamus and consequent vasopressin release induced by ANGII. While in the LT, the inhibitory effect of E2 involves decreasing GRK5 expression compromising ERK1/2 phosphorylation and sodium intake induced by ANGII. A significant contribution of this work is the identification of some steps of ANGII signaling modulated by E2, which can explain, at least in part, its regulation on the central ANGII effects.