Immunocytochemical study of the distribution of the free radical scavenging enzymes CU/ZN superoxide dismutase (SOD1); MN superoxide dismutase (MN SOD) and catalase in the normal human spinal cord and in motor neuron disease

Abstract

Interest in free radical-mediated mechanisms of motor neuron injury has arisen following the discovery of point mutations in the CU/ZN superoxide dismutase (SOD1) gene in a proportion of cases of familial motor neuron disease (MND). Evidence is emerging which indicates that oxidative stress may contribute to the pathophysiology of sporadic MND. Free radical scavenging enzymes form a major component of the anti-oxidant defense system. The aim of this study was to compare the distribution and density of immunoreactivity to CU/ZN SOD, Mn SOD and catalase in the spinal cord of sporadic MND cases ( n = 10) compared to normal controls ( n = 8). There was abundant expression of CU/ZN SOD, Mn SOD and catalase in spinal motor neurons, suggesting important roles for these enzymes in neuroprotective pathways in this cell group. In MND cases, there was no evidence in surviving motor neurons of a consistent alteration in the protein expression of any of these enzymes. There was evidence of increased expression of these enzymes in glial cells present in the ventral and intermediate grey matter and degenerating descending motor pathways of the spinal cord in MND cases. The changes observed were more marked in the cervical compared to lumbar spinal segments. Further investigation is required to determine whether these findings represent a compensatory response to a pathophysiological process involving oxidative stress.