Mitochondrial Complex I Deficiency in Parkinson's Disease

TLDR

The authors examined mitochondrial respiratory‑chain enzyme proteins in the substantia nigra of nine Parkinson’s disease patients and nine matched controls postmortem. Complex I activity was markedly reduced in Parkinson’s patients, while total protein, mitochondrial mass, and succinate cytochrome c reductase activity were unchanged, indicating a specific Complex I defect analogous to MPTP toxicity.

Abstract

Abstract: The structure and function of mitochondrial respiratory‐chain enzyme proteins were studied postmortem in the substantia nigra of nine patients with Parkinson's disease and nine matched controls. Total protein and mitochondrial mass were similar in the two groups. NADH‐ubiquinone reductase (Complex I) and NADH cytochrome c reductase activities were significantly reduced, whereas succinate cytochrome c reductase activity was normal. These results indicated a specific defect of Complex I activity in the substantia nigra of patients with Parkinson's disease. This biochemical defect is the same as that produced in animal models of parkinsonism by 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) and adds further support to the proposition that Parkinson's disease may be due to an environmental toxin with action(s) similar to those of MPTP.