Changes of expression of mitochondrial cytochrome oxidase subunits I and IV in the hippocampus of pilocarpine-treated rats

Objective To investigate the effects of epilepsy on expression of cytochrome oxidase(COX)subnuitsⅠ(COXⅠ)and Ⅳ(COX Ⅳ)encoded by mtDNA and nDNA respectively in rat hippocampus.Methods Male Wistar rats were divided randomly into saline control,acute period(3 h),silent period(7 d),chronic period groups(45 d)after status epilepticus(SE)and group which received pilocarpine(PILO)but did not develop SE.The expressions of COXⅠ and COX Ⅳ in rat hippocampus were detected respectively by immunohistochemical staining and real time quantitative PCR.Results An significant increase in COXⅠ staining was observed in neuronal cell bodies distributed throughout the hippocampus(CA1,CA2,CA3,dentate gyrus)of rats killed 3 h after SE,when compared to the saline-treated group on day 7 after SE,the immunoreactivity was slowly reduced and the immunoreactivity of cell bodies was restricted predominantly to the dentate gyrus,and CA3 regions of the hippocampus.The chronic period(45 d)showed decreased staining with the findings indicating neuronal degeneration such as condensation of cell bodies,vacuolization and rearrangement of pyramidal cell layers in the CA3 of the hippocampus.COXⅠ mRNA showed significantly increased expression in the group at 3 h after SE(P0.001)when compared with the control group.The silent group presented similar levels of expression of COXⅠ,but the chronic group showed significantly decreased level in respect to the control group(P0.001).Slightly increased,but not significant expression of COXⅣ was found in acute(3 h)group,then decreased slightly and remained constant during the following days of epilepsy compared with saline-treated animals.Animals that did not respond to PILO in this study showed similar results with that of control group.Conclusions Dysfunction of COX in the hippocampus are associated with prolonged seizure during experimental temporal lobe epilepsy and mitochondria are more vulnerable to epilepsy.