Suppressive effects of a selective inducible nitric oxide synthase (iNOS) inhibitor on pancreatic beta-cell dysfunction.

AIMS/HYPOTHESIS: Type 1 diabetes mellitus is an autoimmune disease characterized by dysfunction and destruction of the pancreatic beta cells. Interleukin-1beta (IL-1beta) has been reported to cause suppression of insulin secretion from pancreatic islets via induction of inducible nitric oxide synthase (iNOS) followed by nitric oxide (NO) production. In this study, we investigated the effects of inhibition of iNOS on pancreatic beta-cell dysfunction in non-obese diabetic (NOD) mice and IL-1beta-treated isolated rat pancreatic islets using a novel specific inhibitor, ONO-1714.
METHODS: Female NOD mice which received subcutaneous infusion of ONO-1714 (4 microg/kg/day or 40 microg/kg/day) from 10 to 14 weeks after birth were compared with untreated NOD mice. In addition, pancreatic islets were isolated from Sprague-Dawley rats and cultured for 24 h with IL-1beta (100 U/mL) with or without ONO-1714 or the non-selective NOS inhibitor NG-monomethyl-L-arginine (L-NMMA). We measured insulin secretion and insulin content of the islets by ELISA, iNOS mRNA expression by reverse transcription-polymerase chain reaction, and NO generation by Griess Reagent System.
RESULTS: Hyperglycaemia was observed in NOD mice. ONO-1714 treatment blunted this increase and tended to preserve insulin secretion, although body weight increase did not differ between the groups. Insulitis was also attenuated in the ONO-1714-administered group compared to the control group. Furthermore, in isolated rat pancreatic islets ONO-1714 prevented IL-1beta-induced inhibition of insulin secretion, this protection being evident in much lower concentrations than with L-NMMA. While ONO-1714 completely inhibited IL-1beta-induced NO production, it did not reduce expression of islet iNOS mRNA. CONCLUSION/
INTERPRETATION: These findings indicate that ONO-1714 is promising as a therapeutic agent for autoimmune diabetes.