Aims/hypothesis: Insulin-producing beta cells are destroyed by oxidative and nitrosative stress during the pathogenesis of Type I (insulin-dependent) diabetes mellitus. These cells are more sensitive than others due to their deficiency of well known antioxidant enzymes like superoxide dismutase, glutathione peroxidase and catalase. However the peroxiredoxins discovered in the past decade form a large family of highly conserved thioredoxin-dependent peroxide reductases, which are present in most tissues. We investigated whether peroxiredoxins I and II are present in pancreatic beta cells and if they are inducible by oxidative and nitrosative stress.
Methods: To detect these enzymes in insulin-producing beta cells we used semiquantitative RT-PCR, western blots and immunohistochemistry. The expression of peroxiredoxins I and II was analysed after treatment with cytokines, hydrogen peroxide, alloxan or streptozotocin in the rat insulinoma cells INS-1 using RT-PCR and western blots.
Results: We show that peroxiredoxins I and II are present in the cytoplasm of pancreatic islet cells as well as in insulinoma cell lines beta TC6-F7 and INS-1. Peroxiredoxins I and II were up-regulated by all stress agents used.
Conclusion/interpretation: Beta cells, undersupplied with well characterized antioxidant enzymes, possess an additional antioxidant system which is inducible by oxidative as well as nitrosative stress.