Excitotoxic cell death due to the massive release of glutamate and ATP contributes to the secondary extension of cellular and tissue loss following traumatic spinal cord injury (SCI). Evidence from blockage experiments suggests that overexpression and activation of purinergic receptors, especially P2X7, causes excitotoxicity in neurodegenerative diseases and traumatisms of the central nervous system. We hypothesize that the downregulation of specific miRNAs after the SCI contributes to the overexpression of P2X7 and that restorative strategies can be used to reduce excitotoxic response. In the present study, we have employed bioinformatic analyses to identify microRNAs whose dowregulation following SCI can be responsible for P2X7 overexpression and excitotoxic activity. Additional luciferase assays validated microRNA-135a-5p (miR-135a) as a posttranscriptional modulator of P2X7. Moreover, gene expression analysis in spinal cord samples from a rat SCI model confirmed that the decrease in miR-135a expression correlates with P2X7 overexpression after injury. Transfection of cultures of Neuro-2a neuronal cell line with a miR-135a inhibitory sequences (antagomiR-135a), simulating the reduction of miR-135a observed after SCI, resulted in the increase of P2X7 expression and the subsequent ATP-dependent rise in intracellular calcium concentration. Conversely, a restorative strategy employing miR-135a mimics reduced P2X7expression attenuating the increase in intracellular calcium concentration that depends on this receptor and protecting cells from excitotoxic death. Therefore, we conclude that miR-135a is a potential therapeutic target for SCI and that restoration of its expression may reduce the deleterious effects of ATP-dependent excitotoxicity induced after a traumatic spinal cord injury.
Effect of Ginkgo biloba leaf extract on serum nuclear factor‐κB content and intracellular calcium concentration after traumatic spinal cord injury
