Functional Activities and Immunohistochemical Distribution of Superoxide Dismutase in Normal, Dysplastic and Squamous Cell Carcinoma Oral Tissues

摘要

Although reactive oxygen intermediates (ROI) fulfill physiological roles e.g., intracellular signaling and protection against microbes, sustained ROI levels result in oxidative stress and its deleterious sequelae e.g., DNA mutations to include transmissions and translations (Wink, et al., 1998). Consequently, aberrant antioxidant enzyme function has been speculated to be a key contributor in carcinogenesis. Levels of superoxide dismutase (SOD), the antioxidant enzyme responsible for the dismutation of superoxide to hydrogen peroxide and oxygen, can vary greatly depending upon tissue site and donor status. The purpose of this study was to determine the functional SOD activities TOTAL, MITOCHONDRIAL (Mn), and cytosolic (CuZn) in histologically confirmed non- inflamed normal oral mucosal, inflamed normal oral mucosal, and oral squamous cell carcinoma tissues (SCC) and to characterize the in vivo cellular distribution of MnSOD and CuZnSOD in representative sections of the above tissues, as well as, oral epithelial dysplasia. Materials and methods: Total (tot), cytosolic (CuZn), and mitochondrial (Mn) SOD activities were spectrophotometrically determined (25 deg C, 550 nm) by calculating the rate of inhibition of reduction of acetylated cytochrome c. Immunohistochemical studies using standard techniques (avidin-biotin-peroxidase) and commercially available CuZnSOD and MnSOD antibodies were completed. Results of functional SOD assays: (1) all of the samples showed the highest proportion of SOD activity located within the mitochondria, (2) both the inflamed normal and SCC tissues contained a heavy influx of host inflammatory cells, and (3) the overall data trends show a SCC > inflamed normal > non-inflamed normal distribution in SOD activities.