Deficiency of the microglial Hv1 proton channel attenuates neuronal pyroptosis and inhibits inflammatory reaction after spinal cord injury

Abstract

Background: Spinal cord injury (SCI) causes neurological dysfunction with devastating consequences. SCI pathogenesis is accompanied by inflammasome activation and neuronal damage. But the spatial pattern and the time course of neuronal pyroptosis and apoptosis after SCI should be further elucidated. The microglial voltagegated proton channel (Hv1) is implicated in reactive oxygen species (ROS)-induced neuronal damage following ischemic stroke. However, there is a lack of quantification on the neuronal pyroptosis and apoptosis associated with microglial Hv1 after SCI. Methods: We analyzed spatial and temporal characteristics of neuronal pyroptosis and apoptosis following SCI and investigated the effects of Hv1 deficiency on neuronal pyroptosis and the nod-like receptor 3 (NLRP3) inflammasome pathway by using a mouse model of SCI. We tested the effects of Hv1-deficient microglia on ROS production in vivo and examined the relationship between ROS and neuronal pyroptosis in vitro. Results: We observed that apoptosis was detected closer to the injury core than pyroptosis. The incidence of neuronal apoptosis peaked on day 1 after SCI and occurred before pyroptosis. Hv1 deficiency reduced neuronal apoptosis and NLRP3-inflammasome-mediated pyroptosis, improved axonal regeneration, and reduced motor deficits. SCI led to elevated ROS levels, whereas Hv1 deficiency downregulated microglial ROS generation. In vitro, ROS upregulated neuronal pyroptosis and activated the NLRP3 inflammasome pathway, both of which were reversed by addition of a ROS scavenger. Our results suggested that microglial Hv1 regulated neuronal apoptosis and NLRP3-induced neuronal pyroptosis after SCI by mediating ROS production. Conclusion: Following SCI, neuronal pyroptosis lasted longer and occurred farther away from the injury core compared with that of neuronal apoptosis. Microglial Hv1 deficiency downregulated microglial ROS generation and reduced apoptosis and NLRP3-induced neuronal pyroptosis. Our findings may provide novel insights into Hv1associated mechanisms underlying neuronal damage after SCI.

Programmed cell death in spinal cord injury pathogenesis and therapy

“…114 In a recent study, the results showed that microglial voltage-gated proton channel deficiency could reduce NLRP3induced neuronal pyroptosis. 115 Furthermore, the neuroprotection of erythropoetin (EPO) against sevoflurane induced-neuronal pyroptosis is related to Erk1/2-Nrf2/Bach1 signal pathway. 116 A previous study demonstrated that S pneumoniae could induce pyroptosis in murine microglia and that NLRP3 inflammasome is critical for caspase-1 activation during pyroptosis.…”

Nimodipine Promotes Functional Recovery After Spinal Cord Injury in Rats

“…We stabilized the spinal cord in a small animal spinal holder (RWD, Inc., China) by clamping the T8 and T11 vertebrae with stabilizing forceps. Spinal contusion injury was performed with a metal rod (10-g weight) dropped from a height of 25 mm onto the exposed dorsal surface of the spinal cord using a modified NYU impactor ( Li et al, 2020 ). After spinal contusion, the wound was rinsed with normal saline and sutured in layers.…”

Functions and Mechanisms of the Voltage-Gated Proton Channel Hv1 in Brain and Spinal Cord Injury

“…This was confirmed in CD11b + microglia/macrophages isolated from the adult spinal cord at 3 days post-injury. In situ, cells immunoreactive for Hv1 coexpress ionized calcium-binding adaptor molecule 1 (Iba1), a known marker for microglia/macrophages (Li et al, 2020b). Furthermore, a nearly four-fold increase in Hv1 protein expression was observed in spinal cord tissue at 3 days post-injury (Li et al, 2021).…”