Abstract 621: The G Protein-Coupled Estrogen Receptor GPER is Required for Induction of Nox Activity in Mice
The Nox family of NADPH oxidases is a major source of reactive oxygen species (ROS) such as superoxide (O2-) and hydrogen peroxide (H2O2), which importantly influence cardiovascular function. Vasoactive agonists such as angiotensin II can stimulate Nox-dependent ROS production, whereas endogenous estrogens act as antioxidants under certain conditions. We hypothesized that the intracellular transmembrane G protein-coupled estrogen receptor GPER is involved in the regulation of Nox activity. Using GPER-/- and WT mice, we determined the effect of angiotensin II on O2- production in isolated vascular smooth muscle cells (VSMC) by lucigenin-enhanced chemiluminescence, and on contractile responses in renal arteries prepared for recording of isometric tension. The contribution of NADPH oxidases was assessed using its specific inhibitor gp91ds-tat (3 μmol/L). Angiotensin II (100 nmol/L) acutely increased O2- production in WT VSMC, an effect blocked by gp91ds-tat (6.6±2.1 AU vs. -0.8±2.2 AU after 20 min, n=4-5, p<0.05). Surprisingly, angiotensin II was unable to induce O2- formation in GPER-/- VSMC (-0.2±1.0 AU vs. 6.6±2.1 AU, n=5, p<0.05 vs. WT). Following administration of NADPH (100 μmol/L), maximal NADPH oxidase activity in GPER-/- VSMC was also reduced by 73% (442±185 AU vs. 1617±468 AU, n=5, p<0.05 vs. WT), indicating that the induction of Nox activity is largely impaired by GPER deficiency. In line with these findings, contraction to angiotensin II was 1.9-fold less potent in GPER-/- renal arteries (35±4% vs. 66±11% of contraction to 60 mmol/L KCl, n=5, p<0.05 vs. WT); this difference was abolished by gp91ds-tat, which decreased the contractile response in WT by 47% (p<0.05), but had no effect in GPER-/- arteries. In conclusion, these data indicate that GPER is required for induction of vascular Nox activity in mice, and suggest that estrogen-dependent regulation of ROS production may not be limited to antioxidative effects.
- © 2012 by American Heart Association, Inc.