Abstract MP06: Kinin B1 Receptor Mediates Orexin System Hyperactivity In Salt-sensitive Hypertension

Abstract

Hyperactivity of the orexin system contributes to several animal models of hypertension and enhances arginine vasopressin (AVP) release. We previously reported higher neuronal kinin B1 receptor (B1R) expression and brain AVP levels in hypertensive mice. However, the role of B1R and its interaction with orexin system in neurogenic hypertension have not been studied. In the present study, we tested the hypothesis that kinin B1R contributes to hypertension by upregulation of orexin-AVP signaling in the brain. Deoxycorticosterone acetate (DOCA)-salt treatment (1 mg/g body weight DOCA, 1% saline in drinking water, 3 weeks) of wild-type (WT) male mice produced a significant increase in mean arterial pressure (MAP; radio-telemetry) (138 ±3 mmHg, n=8, p<0.01) that was blunted in B1R knockout mice (121±2 mmHg, P <0.05 vs. WT+DOCA). In WT mice, DOCA-salt, compared to vehicle, increased mRNA levels of orexin receptor 1 (2.5 fold, n=9, p<0.001), orexin receptor 2 (3 fold, n=9, p<0.001) and AVP (3 fold, n=9, p<0.01) in the hypothalamic paraventricular nucleus (PVN), and these DOCA-salt evoked effects were attenuated in B1RKO mice. Similarly, DOCA-salt evoked increases in protein expression of orexin receptor 1 and 2 in the hypothalamic PVN of WT mice were attenuated by 25±5% and 33±5% (p<0.05), respectively, in B1RKO vs WT+DOCA mice. Furthermore, DOCA-salt treatment increased plasma AVP levels in WT mice compared to vehicle treated mice (13.69±1.1 vs. 47.86±8.7 pg/ml, p<0.05), but not in B1RKO mice. Together, these data provide novel evidence that kinin B1R plays an important role in mediating DOCA-salt induced hypertension possibly via upregulating the orexin-AVP signaling in the brain.