NAD(P)H Oxidase-derived H₂O₂ Signals Chloride Channel Activation in Cell Volume Regulation and Cell Proliferation

Cellular swelling triggers the activation of Cl^- channels (volume-sensitive outwardly rectifying (VSOR) Cl^- channels) in many cell types. Ensuing regulatory volume decrease has been considered the primary function of these channels. However, Cl^- channels, which share functional properties with volume-sensitive Cl^- channels, have been shown to be involved in other physiological processes, including cell proliferation and apoptosis, raising the question of their physiological roles and the signal transduction pathways involved in their activation. Here we report that exogenously applied H₂O₂ elicited VSOR Cl ^- channel activation. Furthermore, activation of these channels was found to be coupled to NAD(P)H oxidase activity. Also, epidermal growth factor, known to increase H₂O₂ production, activated Cl ^- channels with properties identical to swelling-sensitive Cl ^- channels. It is concluded that NAD(P)H oxidase-derived H ₂O₂ is the common signal transducing molecule that mediates the activation of these ubiquitously expressed anion channels under a variety of physiological conditions.