Mitochondrial involvement in transhemispheric diaschisis following hypoxia–ischemia: Clomethiazole-mediated amelioration

Mitochondria play a central role in both the physiological and pathophysiological regulation of cell survival/death. Increasing evidence places mitochondrial dysfunction at the center of many neuropathological conditions. The present study investigates the extent of mitochondrial dysfunction in cortical, hippocampal and cerebellar tissues in a rat model of hypoxia–ischemia (HI). We hypothesized that; mitochondrial dysfunction in situ may be prevented by treatment with clomethiazole (CMZ), a GABAA receptor agonist. Assessment of mitochondrial FAD-linked respiration at both 1- and 3-day post-HI revealed a marked decrease in activity from ipsilateral cortical and hippocampal regions (P<0.001). In addition, small changes were seen in contralateral cortical and hippocampal tissues as well as in the cerebellum at 3-days (P<0.05). Assessment of the mitochondrial electron transport chain (complexes I–V), and mitochondrial markers of integrity (citrate synthase) and oxidative stress (aconitase) confirmed mitochondrial impairment in ipsilateral regions following HI. Complexes I, II–III, V and citrate synthase were also impaired in contralateral regions and cerebellum 3-days post-HI. Treatment with CMZ (414 mg/kg/day via minipumps) provided marked protection to all aspects of neuronal tissue assessed. Circulating cytokine (interleukin [IL]-1α, IL-1β, tumor necrosis factor [TNF]-α, granulocyte macrophage colony-stimulating factor [GM-CSF], IL-4 and IL-10) levels were also assessed in these animals 3-days post-HI. Plasma IL-1α, IL-1β, TNF-α and GM-CSF levels were significantly increased post-HI. Treatment with CMZ ameliorated the increases in IL-1α, IL-1β, TNF-α and GM-CSF levels while increasing plasma IL-4 and IL-10 levels. This study provides evidence of the extent of mitochondrial damage following an HI-insult. In addition, we have shown that protection afforded by CMZ extends to preservation of mitochondrial function and integrity via anti-inflammatory mediated pathways.