Abstract P103: Anti-hypertensive Mechanisms of Action of G _q/11 Inhibitor Ligands

Abstract

Chronic blockade of individual G protein coupled receptors (GPCRs) has proven to be inadequate strategy for managing hypertension partly because the subcellular heterotrimeric G proteins that propagate intracellular signaling can simultaneously couple to several other vasopressor receptors. Whether blood pressure can better be controlled by directly targeting G proteins has not been thoroughly investigated due to paucity of selective, cell-permeable inhibitors. Here, we tested whether chemical inhibition of Gq/11 proteins in vivo and ex vivo using recently discovered small-molecule inhibitor ligands, YM-254890 (YM), FR-900359 (FR) and WU-07047 (WU) is sufficient to reverse hypertension in mice. Using ex vivo vessel reactivity assay, we found that Gq/11 inhibitors markedly reduced vasoconstriction evoked with phenylephrine (PE), vasopressin, endothelin-1, and the thromboxane analog U-46619. Blockade of PE-induced contractility by the Gq/11 inhibitors showed the following rank-order potency: FR LogIC50 -0.008 ± 0 > YM LogIC50 -0.49 ± 0 > WU LogIC50 -64.95 ± 6.4. YM and WU but not FR inhibited PE-induced vasoconstriction through G protein-dependent and independent pathways by blocking L-type calcium channel-mediated Ca 2+ influx. Acute subcutaneous injection of FR and YM (0.3 mg/kg, s.c.) in normotensive and N ω -Nitro-L-arginine methyl ester (L-NAME) hypertension mice elicited marked hypotension, which was more severe (ΔSBP = -25 ± 2.7 vs. ΔSBP = -21 ± 2.2 mmHg) and long lasting (FR t1/2 ≅ 12 hr vs. YM t1/2 ≅ 4 hr) after the injection of FR relative to YM. In DOCA-salt hypertension mice, chronic injection of FR (0.3 mg/kg, s.c., daily for seven days) reversed hypertension (vehicle SBP: 149 ± 5 vs. FR SBP: 117 ± 7 mmHg) and sustained blood pressure reduction several days after terminating the injection regimen (DOCA SBP: 141 ± 2 vs. SBP 5 days post FR: 128 ± 5 mmHg). Our results together support the hypothesis that increased Gq/11 activity in blood pressure-regulating organs is involved in the pathogenesis of hypertension, and that direct systemic blockade of Gq/11 reverses hypertension. The findings provide clear evidence for targeting Gq/11 in the cardiovascular system as an effective therapy for treating hypertension.