Methylene blue protects mitochondrial respiration from ethanol withdrawal stress

Methylene blue (MB), a tricyclic phenothiazine drug, has been reported to enhance mitochondrial functions including mitochondrial respiration. By comparison, stress associated with abrupt ethanol withdrawal (EW) impedes mitochondrial functions. We investigated whether MB protects mitochondrial respiration and cell survival from EW stress through a key mitochondrial enzyme, cytochrome c oxidase (COX). We also investigated whether the MB’s protection involves the inhibition of an excitatory neurotransmitter, glutamate. Male rats were exposed to and withdrawn from ethanol-diet (7.5%, 5 weeks). MB (0.5 mg/kg, intraperitoneal) was injected for the last 5 days of ethanol-diet and on the first day of EW. Cerebellum was then harvested to measure mitochondrial respiration and COX expression using real-time XF respirometer and immunohistochemistry, respectively. Separately, HT22 cells (a murine hippocampal cell line) were exposed to and abruptly withdrawn for 4 hours from chronic ethanol (100 mM, 3 days). MB was administered during EW with or without a COX inhibitor (NaN3) or glutamate. Mitochondrial respiration, COX content, and cell viability were then assessed using real-time XF respirometer, an immunoblot method, and Calcein assay, respectively. MB attenuated the suppressing effects of EW on mitochondrial respiration, COX content, and cell survival. This protection was reduced after NaN3 or glutamate cotreatment. These results suggest that MB treatment help maintain mitochondrial respiratory and cellular integrity through COX-upregulation and glutamateinhibition upon EW stress. MB treatment may help identify mitochondrial mechanisms underlying hyperexcitatory CNS disorders.