'Characteristics of RNA-Activated Protein Kinase (PKR) in Human and Rodent Ethanol Exposure'

Alcohol misuse negatively impacts the brain; however the root causes underlying the neuropathology of alcohol use disorders are unclear. The overall objective of this study was to examine the hypotheses that 1) ethanol exposure increases RNA-activated protein kinase (PKR/p-PKR) expression resulting in increased neurotoxicity by monoamine oxidase B (MAO-B) mediated oxidative stress and cell death and 2) PKR inhibitors are neuroprotective and can prevent (or reduce) the ethanol-induced expression of monoamine oxidase B. This study examined the effects of binge ethanol exposure and monoamine oxidase inhibition on PKR protein expression in the rat prefrontal cortex by Western Blot analysis. The effects of PKR on cell death and MAO-B (an indicator of oxidative stress) promoter activity were assessed using cell viability and luciferase assays, respectively. Lastly, the subcellular localization of PKR/p-PKR was assessed in the prefrontal cortex of rats following chronic ethanol exposure compared to controls. PKR protein expression was indeed increased in the prefrontal cortex of rats exposed to binge alcohol and this increase was attenuated by MAO inhibitors. Overexpression of PKR in glioblastoma and neuroblastoma cells resulted in cell death in both cell types and viability was restored in glial cells with the administration of a PKR inhibitor. Overexpression of PKR also increased MAO-B promoter activity in glial cells. Immunohistochemical evaluation of PKR and p-PKR in the rat brains exposed to chronic ethanol showed increased glial cell densities with increased PKR and p-PKR expression. The results of this study identified a strong association between PKR levels and both binge and chronic alcohol consumption in the prefrontal cortex of rodents and implicated PKR as a factor in cell death mediated by oxidative stress in in vitro models particularly in glial cells. In an effort to define the signaling pathways linked with alcohol-induced neuropathology, this study suggests that PKR is a prominent element underlying alcohol-induced neurotoxicity. Therefore, PKR and p-PKR may be potential drug targets for the development of new pharmacological therapeutics for the treatment of alcohol-induced neurotoxicity and its associated pathology.