ASIC‐like currents in freshly isolated cerebral artery smooth muscle cells are inhibited by endogenous oxidase activity

Acid Sensing Ion Channels (ASICs) are a novel class of neuronal cation channels gated by extracellular [H + ]. We recently identified the presence of ASIC‐like channels in cerebral vascular smooth muscle cells (cVSMCs). In most isolated cVSMCs, however, ASIC‐like channels are electrically silent. Since neuronal ASICs are inhibited by oxidizing agents, we considered the hypothesis that cVSMC ASIC currents are inhibited by oxidative stress present in VSMCs. To test this hypothesis, we used whole‐cell patch clamp. We first examined the effect of reducing agents on extracellular [H + ] gated currents in isolated mouse cVSMCs. Pretreatment with 2 mM DTT increased the amplitude of the current evoked by pH 6.0 from 0.4±0.1 to 14.9±3.6 pA/pF. The potentiated currents were inhibited by the ASIC blocker amiloride (100 μM). The effect of reducing agents was reversed by the oxidizing agent DTNB. Moreover, apocynin (50 μM), an NADPH oxidase (NOX) inhibitor, increased current amplitude evoked by pH 6.0 (0.9±0.5 to 7.0±2.6 pA/pF). Treatment with allopurinol, a xanthine oxidase (XO) inhibitor, potentiated the ASIC‐like activity similarly. These findings demonstrate that reducing agents unmask electrically silent VSMC ASIC‐like channels, which may be suppressed by endogenous NOX and XO. The role of VSMC ASIC channels in oxidative stress related vascular dysfunction remains to be determined.