Effect of inducible nitric oxide synthase on pancreas islet apoptosis in rats

Objective: To investigate the effect and mechanism of cytokine and inducible nitric oxide synthase on apoptosis and function of rat pancreas islets cultured in vitro.

Methods: Islets from Wistar rats were cultured in vitro and divided randomly into four groups: blank control group, cytokine group of islets cultured with TNF-alpha+IL-1beta, aminoguanidine (AG) group of islets cultured with aminoguanidine, and AG + cytokine group of islets cultured with TNF-alpha+IL-1beta and aminoguanidine. The nutrient fluid nitric oxide level and islets cNOS/iNOS activity were detected by test kit and the expressions of iNOS mRNA and apoptosis related gene (Bax, Bcl-2) were evaluated by RT-PCR. The viability of the islets was examined by AO/EB staining and the function of the islets was detected by insulin secretion index assay.

Results: After co-cultured with cytokines IL-1beta and TNF-alpha, the expression and activity of iNOS in islet tissues enhanced (38.93+/-4.72) U/mL and the concentration of NO in medium increased remarkably(313.0+/-35.4) mol/L.The survival rate of cells and the insulin secretion index decreased with the up-regulation of proapoptosis gene and down-regulation of anti-apoptosis gene. But the activity of cNOS remained unchanged. Aminoguanidine reduced the cell apoptosis and increased the survival rate and insulin secretion index, and the activity of iNOS was inhibited.

Conclusions: iNOS plays an important role in the apoptosis of islets cultured by cytokines TNF-alpha and IL1-beta. Aminoguanidine prevents the islets from the damage of iNOS, alleviates the impairment of cytokines to islets, lessens the cell apoptosis and ameliorates the survival and function of islets.