The contribution of microglial activation to oligodendrocyte precursor cell (OPC) damage in the brain is considered to be a principal pathophysiological feature of periventricular leukomalacia (PVL). Nicotinamide adenine dinucleotide phosphate oxidase (NOX)-dependent reactive oxygen species (ROS) produced in microglia has been shown to be significantly toxic to OPCs. The voltage-gated proton channel Hvl is selectively expressed in microglia and is essential for NOX-dependent ROS production in the central nervous system. This study aimed to investigate the effects of microglial Hvl deficiency on the protection of OPCs from oxygen-glucose deprivation (OGD)-induced injury in vitro. In the present study, the levels of OGD-induced ROS and pro-inflammatory cytokine production were dramatically lower in Hvl-deficient microglia (Hvl(-/-)) than in wild-type (WT) microglia. Following OGD, OPCs co-cultured with WT microglia had increased apoptosis and decreased proliferation and maturation, while those co-cultured with Hvl microglia had attenuated apoptosis and greater proliferation and differentiation. Furthermore, the attenuated damage and enhanced regeneration of OPCs were associated with decreases in extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase phosphorylation. These results indicate that the protective effects of Hvl deficiency on OPCs are due to the suppression of ROS and pro-inflammatory cytokine production in microglia. We thus suggest that the microglial proton channel Hvl may be a potential therapeutic target in PVL. (C) 2017 Elsevier Inc. All rights reserved.