The Neuroprotective Effect And Potential Mechanisms Induced By Ethyl Pyruvate Treatment After Traumatic Brain Injury In Rats

Purpose:Traumatic brain injury (TBI) is a leading cause of death and neurological disability in young adults, for which a clinically effective neuroprotective strategy is currently unavailable. TBI triggers a cascade of events such as oxidative stress and inflammation, leading to secondary brain injury and long-term neurological deficits. Recent studies suggest that ethyl pyruvate (EP), a stable lipophilic ester derivative of pyruvate, is remarkably effective in protecting brain against traumatic and ischemic injury. Since the neuroprotective effects of EP involve ROS scavenging and inflammation suppression, the present study was performed to test the potential beneficial effect of EP treatment and underlying mechanisms following TBI in rats.Methods:Male adult SD rats were subjected to unilateral cortical contusion injury (CCI) and then randomly assigned to sham, vehicle or EP treatment groups. EP was injected intraperitoneally immediately after CCI and again at12,24,36,48, and60h post-CCI. For the first set of experiments, a series of neurobehavioral assessments including foot fault tests and Morris water maze, were performed3-28days after CCI. In the second set of experiments, integrity of blood-brain-barrier (BBB) was determined by evans blue and transmission electron microscopy48h after CCI, activation of microglia was assessed by immunohistochemical staining, and mRNA level of pro-inflammatory cytokines including TNF-α, IL-lα, IL-1β, iNOS and COX-2was detected using quantitative real-time PCR. Moreover, protein expression and enzymatic activity of matrix metalloproteinases (MMPs) including MMP-9and MMP-2were evaluated by western blots and gelatin zymography. In the third part, rat brains were assessed for white matter injury at1-28days after CCI using immunohistochemical staining and transmission electron microscopy in vivo; and the survival and differentiation of oligodendrocyte precursor cells (OPCs) were determined post glutamate or TNF-a injury in vitro.Results:Firstly, EP treatment at30mg/kg significantly improved the foot fault scores on day3-28after CCI, and markedly enhanced the cognitive performance in Morris water maze. Secondly, EP treatment significantly attenuated overexpression of microglia, decreased release of pro-inflammatory cytokines including TNF-a, iNOS, COX-2, IL-1α, IL-1β, and suppressed CCI-induced elevation of MMP-9and MMP-2. Finally, EP treatment also significantly attenuated the remarkable loss of myelin and axon at1-28days after CCI, and improved survival and differentiation of OPCs in vivo and in vitro settings.Conclusion:Our results demonstrate that post-injury administration of EP was effective in improving long-term neurological disability after TBI and decreasing CCI-induced tissue loss28days post injury. And the neuroprotection afforded by EP is likely achieved through improving integrity of BBB and attenuating white matter injury following TBI.