Genetic or pharmacological ablation of ASIC1a is not neuroprotective in a mouse model of spinal cord injury.

Acid sensing ion channel 1a (ASIC1a) is a proton-activated channel that is expressed ubiquitously throughout the central nervous system and in various types of immune cells. Its role in spinal cord injury (SCI) is controversial; inhibition of ASIC1a has been reported to improve SCI pathology on two accounts in vivo but conversely, gene ablation increased kainite-mediated excitotoxic cell death in vitro. Here, we re-examined the role of ASIC1a in a mouse model of SCI. First, we observed functional outcomes up to 42 days post-operation (DPO) in SCI mice with a selective genetic ablation of ASIC1a. Mice lacking ASIC1a had significantly worsened locomotor ability and increased lesion compared to mice possessing the ASIC1a gene. Next, we explored pharmacological antagonism of this ion channel by administering the potent ASIC1a inhibitor, Hi1a. Consistent with a role for ASIC1a to attenuate excitotoxicity, accelerated neuronal cell loss was found at the lesion site in SCI mice treated with Hi1a but there were no differences in locomotor recovery. Moreover, ASIC1a inhibition did not cause significant alterations to neutrophil migration, microglial density, or blood-spinal cord barrier integrity. Thus, we conclude from our genetic data that presence of the ASIC1a gene aids recovery after SCI. We also suggest with our pharmacological data that ASIC1a is not a viable therapeutic target for SCI.