Phagocytic cell NADPH oxidase (NOX) generates reactive oxygen species (ROS) as part of innate immunity. Unfortunately, ischemia can also induce this pathway and inflict damage on native cells. The voltage-gated proton channel Hv1 enables NOX function by compensating cellular loss of electrons with protons. Accordingly, we investigated whether NOX-mediated brain damage in stroke can be inhibited by suppression of Hv1. We found that mouse and human brain microglia, but not neurons or astrocytes, expressed large Hv1-mediated currents. Hv1 was required for NOX-dependent ROS generation in brain microglia in situ and in vivo. Mice lacking Hv1 were protected from NOX-mediated neuronal death and brain damage 24 h after stroke. These results indicate that Hv1-dependent ROS production is responsible for a substantial fraction of brain damage at early time points after ischemic stroke and provide a rationale for Hv1 as a therapeutic target for the treatment of ischemic stroke.
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