Chronic hypoxia limits H2O2-induced inhibition of ASIC 1-dependent store-operated calcium entry in pulmonary arterial smooth muscle

摘要

Our laboratory shows that acid-sensing ion channel 1 (ASIC1) contributes to the development of hypoxic pulmonary hypertension by augmenting store-operated Ca^+ entry (SOCE) that is associated with enhanced agonist-induced vaso-constriction and arterial remodeling. However, this enhanced Ca2+ influx following chronic hypoxia (CH) is not dependent on an increased ASIC1 protein expression in pulmonary arterial smooth muscle cells (PASMC). It is well documented that hypoxic pulmonary hypertension is associated with changes in redox potential and reactive oxygen species homeostasis. ASIC1 is a redox-sensitive channel showing increased activity in response to reducing agents, representing an alternative mechanism of regulation. We hypothesize that the enhanced SOCE following CH results from removal of an inhibitory effect of hydrogen peroxide (H2O2) on ASIC1. We found that CH increased PASMC superoxide (O2'~) and decreased rat pulmonary arterial H2O2 levels. This decrease in H2O2 is a result of decreased Cu/Zn superoxide dismutase expression and activity, as well as increased glutathione peroxidase (GPx) expression and activity following CH. Whereas H2O2 inhibited ASIC 1-dependent SOCE in PASMC from control and CH animals, addition of catalase augmented ASIC 1-mediated SOCE in PASMC from control rats but had no further effect in PASMC from CH rats. These data suggest that, under control conditions, H2O2 inhibits ASIC 1-dependent SOCE. Furthermore, H2O2 levels are decreased following CH as a result of diminished dismutation of Oi~ and increased H2O2 catalysis through GPx-1, leading to augmented ASIC 1-dependent SOCE.