Comparison of mRNA contents of interleukin-1 b and nitric oxide synthase in pancreatic islets isolated from female and male nonobese diabetic mice

Abstract

Interleukin-1Β (IL-1Β) has been suggested to mediate beta-cell destruction in insulin-dependent diabetes mellitus (IDDM) by inducing nitric oxide production. In this study, we assessed the levels of IL-1Β and the inducible form of nitric oxide synthase (iNOS), using a semi-quantitative polymerase chain reaction assay, and performed determinations of nitrite accumulation and IL-1Β bioactivity, on pancreatic islets isolated from 5- and 16-week-old female and male nonobese diabetic (NOD) mice and from nondiabetes prone NMRI mice. NOD mouse islets contained notable amounts of IL-1Β mRNA. At 5 weeks of age, but not at 16 weeks, the values were higher in islets isolated from NOD females compared to males. The IL-1Β bioactivity showed differences roughly reflecting the mRNA levels in the NOD mouse islets. In the NMRI mouse islets the IL-1Β bioactivity was very low. The expression of iNOS mRNA increased in both male and female islets between 5 and 16 weeks of age. Immunocytochemistry of pancreatic sections indicated the presence of macrophages especially in the peri-insular area of the NOD mice which suggests that IL-1Β was produced by macrophages. The levels of IL-1Β activity and mRNA in freshly isolated islets from NOD 5-week-old females did not correlate to the iNOS mRNA content or to the nitrite production. However, after incubation with IL-1Β in vitro, both NOD and NMRI islets responded with a marked increase in nitric oxide production. It is concluded that the presence of IL-1Β in isolated NOD mouse islets, via an induction of iNOS expression and nitric oxide production, cannot explain the gender difference in diabetes incidence in NOD mice.