Mitochondrial Respiratory Chain Enzyme Activities, mtDNA Variants and Gene Expression Levels in Idiopathic Parkinson's Disease

Purpose: Mitochondrial dysfunction has been implicated in the development of idiopathic Parkinson's disease. In this study, it was aimed to investigate the relationship between mitochondrial respiratory chain enzyme deficiency and variants in ND2 and ND4 region of Complex I and expressions of these genes. Complex IV activity and glutathione level were also studied. Methods: Activities of Complex I, Complex IV, citrate synthase and glutathione levels were measured from muscle biopsy samples of 19 idiopathic Parkinson's Disease patients. Entire ND2 and ND4 regions of Complex I were screened by sequencing and expression levels of these regions were also examined by using relative quantitative RT-PCR. Results: A significant decrease in Complex I and IV activities was found in Parkinson's Disease patients (19.73 +/- 8.24 U/mg protein, 11.51 +/- 6.45 U/mg protein) compared with the control group (31.48 +/- 8.28 U/mg protein, 30.02 +/- 14.76 U/mg protein), respectively. Although several sequence variants were detected in ND2 and ND4 genes, they didn't account for the decrease in Complex I activity. ND2 (19 % and 21 %) and ND4 (14 % and 13 %) mRNA expressions were reduced in two of 19 patients. Conclusion: Taken together, Complex I and IV dysfunctions and mitochondrial abnormalities might be the result of oxidative stress contributing to the pathogenesis of idiopathic Parkinson's Disease since we found that reduced glutathione levels were decreased 47 % in these patients.