The Voltage–gated Proton Channel, Hv1, Enhances Brain Damage from Ischemic Stroke

Howard Hughes Medical Institute, Department of Cardiology, Children's Hospital Boston and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.
Nature Neuroscience (Impact Factor: 16.1). 03/2012; 15(4):565-73. DOI: 10.1038/nn.3059
Source: PubMed


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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    • "Whole cell patch-clamp recordings were made from dorsal horn microglia located in laminar layers I–III of freshly excised spinal cord slices. GFP-labelled microglia were studied in voltage-clamp mode (Wu et al., 2012). After establishing the whole-cell configuration , microglia were held at either À60 mV or À20 mV. "
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    ABSTRACT: Microglial cells are critical in the pathogenesis of neuropathic pain and several microglial receptors have been proposed to mediate this process. Of these receptors, the P2Y12 receptor is a unique purinergic receptor that is exclusively expressed by microglia in the central nervous system (CNS). In this study, we set forth to investigate the role of P2Y12 receptors in microglial electrophysiological and morphological (static and dynamic) activation during spinal nerve transection (SNT)-induced neuropathic pain in mice. First, we found that a genetic deficiency of the P2Y12 receptor (P2Y12(-/-) mice) ameliorated pain hypersensitivities during the initiation phase of neuropathic pain. Next, we characterized both the electrophysiological and morphological properties of microglia in the superficial spinal cord dorsal horn following SNT injury. We show dramatic alterations including a peak at 3 days post injury in microglial electrophysiology while high resolution two-photon imaging revealed significant changes of both static and dynamic microglial morphological properties by 7 days post injury. Finally, in P2Y12(-/-) mice, these electrophysiological and morphological changes were ameliorated suggesting roles for P2Y12 receptors in SNT-induced microglial activation. Our results therefore indicate that P2Y12 receptors regulate microglial electrophysiological as well as static and dynamic microglial properties after peripheral nerve injury, suggesting that the microglial P2Y12 receptor could be a potential therapeutic target for the treatment of neuropathic pain.
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    • "Proton channel activity has been associated with invasive and metastatic phenotypes of different tumors such as gliomas, breast, and colorectal cancer [39] [40] [41] [42]. Additionally, H v 1 channels have been implicated in the enhancement of brain damage after an ischemic stroke [43]. Given the relevance of H v 1 in physiology and pathology, it has become a focus of active research as a potential pharmacological target [44]. "
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    ABSTRACT: The main role of voltage-gated proton channels (Hv1) is to extrude protons from the intracellular milieu when, mediated by different cellular processes, the H(+) concentration increases. Hv1 are exquisitely selective for protons and their structure is homologous to the voltage sensing domain (VSD) of other voltage-gated ion channels like sodium, potassium, and calcium channels. In clear contrast to the classical voltage-dependent channels, Hv1 lacks a pore domain and thus permeation necessarily occurs through the voltage sensing domain. Hv1 channels are activated by depolarizing voltages and increases in internal proton concentration. It has been proposed that local conformational changes of the transmembrane segment S4, driven by depolarization, trigger the molecular rearrangements that open Hv1. However, it is still unclear how the electromechanical coupling is achieved between the VSD and the potential pore, allowing the proton from the intracellular to the extracellular side. Here we provide a revised view of voltage activation in Hv1 channels, offering a comparative scenario with other voltage sensing channels domains. Copyright © 2015. Published by Elsevier B.V.
    Full-text · Article · Aug 2015 · FEBS letters
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    • "Animals and cuprizone treatment Wild-type (WT) C57BL/6 mice, CX3CR1 GFP/+ mice, Hv1 À/À mice, and Hv1 À/À -CX3CR1 GFP/+ mice were used in the present study. All mice were purchased from Jax laboratory except Hv1 À/À mice (Wu et al. 2012; Eyo et al. 2015). Mice were used in accordance with institutional guidelines as approved by the animal care and use committee at Rutgers University. "
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