Abstract 070: Superoxide And Hydrogen Peroxide Differentially Modulate Mouse Afferent Arteriolar Myogenic Responses Via Protein Kinase C And Protein Kinase G And Their Coupling To Membrane Potential
Background: Although reactive oxygen species (ROS) mediate normal myogenic responses (MRs) of afferent arterioles (Affs), oxidative stress contribute to impaired MRs in chronic kidney disease (CKD) and thereby to barotrauma. The mechanisms underlying these apparently conflicting reports are unclear. MRs depend on reductions in membrane potential (Em) that activate voltage-operated calcium channels to raise intracellular [Ca2+]. Therefore, we tested the hypothesis that MRs are increased by superoxide (O2.-) and reduced by hydrogen peroxide (H2O2) through differential signaling via protein kinase C (PKC) - and protein kinase G (PKG) - dependent changes in Em.
Methods: MRs were assessed from changes in luminal diameter of mouse individual isolated perfused Affs (n = 5-6 per group) with change in perfusion pressure (PP) from 40 to 80 mmHg. The effects of O2.- and H2O2 on the MR were assessed after incubation with 1 μM paraquat (PQ increases O2.-) or incubation with 10 μM H2O2. O2.- with PP was assessed from PEG-SOD inhibitable ethidium:dihydroethidium fluorescence, and H2O2 from PEG-catalase (CAT) inhibitable H2DCFDA fluorescence and Em from DiBAC4(3) fluorescence.
Results: 1. PQ increased O2.- with PP by 32 ± 4% (P<0.001) and MR by 140 ± 33% (P<0.01) (prevented by PEG-SOD), but H2O2 reduced MR by 50 ± 2% (P<0.0001) (prevented by PEG-CAT). 2. The PP-induced fall in Em was increased by PQ (PQ -19 ± 2% vs vehicle -4 ± 1%, P<0.001), but was reversed by H2O2 (H2O2 +16 ± 1% vs vehicle -4 ± 1%, P<0.001). 3. Inhibition of PKC with 3 μM of Gö6983 blocked the reduction in Em with PQ (PQ -19 ± 2% vs PQ+ Gö6983 -2 ± 2%, P<0.01), while inhibition of PKG with 30 μM of Rp-8-Br-PET-cGMPS blocked the increase in Em with H2O2 (H2O2 +16 ± 2% vs H2O2+Rp-8-Br-PET-cGMPS -2 ± 1%, P<0.05).
Conclusions: O2.- signals via PKC to depolarize the Em and thereby to activate the MR whereas H2O2 signals via PKG to hyperpolarize the Em and thereby to inhibit the MR. Thus, O2.- and H2O2 signaling via specific G-protein-coupled changes in Em may explain the differential effects of ROS on MRs.
Author Disclosures: L. Li: A. Employment; Significant; Faculty member. B. Research Grant (includes principal investigator, collaborator, or consultant and pending grants as well as grants already received); Significant; PPG from NIH, P.I.Christopher S. Wilcox. E. Lai: A. Employment; Significant; Faculty member, P.I. C.S. Wilcox: A. Employment; Significant; P.I.. B. Research Grant (includes principal investigator, collaborator, or consultant and pending grants as well as grants already received); Significant; PPG from NIH.
- © 2014 by American Heart Association, Inc.