H2O2 sensitivity of Kv channels in hypoxic pulmonary vasoconstriction : experimental conditions matter

Abstract

Hypoxic pulmonary vasoconstriction (HPV) optimizes gas exchange but, when impaired, can result in life-threatening hypoxemia. Moreover, under conditions of generalized alveolar hypoxia, HPV can result in pulmonary hypertension. Voltage-gated K+ channels (Kv channels) are key to HPV: a change in the intracellular hydrogen peroxide (H2O2) levels during acute hypoxia is assumed to modulate these channels’ activity to trigger HPV. However, there are longstanding conflicting findings on whether H2O2 inhibits or activates Kv channels. Therefore, we hypothesized that H2O2 affects Kv channels depending on the experimental conditions, i.e., the H2O2 concentration, the channel’s subunit configuration or the experimental clamping potential in electrophysiological recordings. Therefore, cRNAs encoding the Kv1.5 channel and the auxiliary Kvβ subunits (Kvβ1.1, Kvβ1.4) were generated via in vitro transcription before being injected into Xenopus laevis oocytes for heterologous expression. The K+ currents of homomeric (Kv1.5) or heteromeric (Kv1.5/Kvβ1.1 or Kv1.5/Kvβ1.4) channels were assessed by two-electrode voltage clamp. The response of the Kv channels to H2O2 was markedly dependent on (a) the clamping potential, (b) the H2O2 concentration, and (c) the Kv channel’s subunit composition. In conclusion, our data highlight the importance of the choice of experimental conditions when assessing the H2O2 sensitivity of Kv channels in the context of HPV, thus providing an explanation for the long-lasting controversial findings reported in the literature.