A Selective Increase in Particulate Superoxide Dismutase Activity in Parkinsonian Substantia Nigra

TLDR

In Parkinsonian substantia nigra, increased particulate superoxide dismutase activity may represent a protective response to free radicals or could contribute to cell death via hydrogen peroxide accumulation. The authors quantified total, cytosolic, and particulate SOD activity in postmortem substantia nigra and cerebellum using a spectrophotometric assay that distinguishes isoenzymes by potassium cyanide inhibition. While total and cytosolic SOD activity were unchanged in Parkinson’s disease brains, particulate SOD activity was higher in the substantia nigra and unchanged in cerebellum.

Abstract

Abstract The total activity of superoxide dismutase (SOD) and cytosolic and particulate activity of SOD in human substantia nigra and cerebellum were measured by a spectrophotometric method based on the ability of SOD to inhibit the autoxidation of adrenaline. The cystosolic and particulate isoenzymes of SOD were differentiated by the inclusion of potassium cyanide which selectively inhibits cytosolic copper/zinc‐dependent SOD activity. In autopsied human brains, there was no difference in total SOD) activity, or the activity of SOD in cytosol in substantia nigra jof patients dying with Parkinson's disease compared to age‐matched controls. However, the activity of the particulate form of SOD was higher in the parkinsonian substantia nigra compared to control tissue. In the cerebellum there was no difference in the total, cytosolic, or particulate activity of SOD between parkinsonian patients and age‐matched controls. Increased activity of SOD in particulate fraction may be a protective response to elevated levels of toxic free radicals in the parkinsonian substantia nigra. Alternatively, increased SOD activity may induce cell death through the accumulation of hydrogen peroxide.