Calcineurin activity as an indicator of oxidative stress in normal islet cells and insulinoma cells

A comparative study was conducted to evaluate calcineurin activity in normal pancreatic beta cells and insulinoma cells in relation to their oxidative state. In comparison to normal islets, insulinoma cells had enhanced oxidative stress as evidenced by increased content of thiobarbituric acid reactive substances. In addition, diminished activity of calcineurin in insulinoma cells was concomitant with decreased content of reduced glutathione and glutathione peroxidase activity signifying diminished antioxidant status in these cells. Culturing insulinoma cells in presence of the calcineurin inhibitor cyclosporin A resulted in further decrease of calcineurin activity with restoration of glutathione peroxidase but without restoration of reduced glutathione levels. These results indicate that an estimate of oxidative stress in pancreatic islets and insulinoma cells can be obtained by assaying calcineurin activity.