Comparison of mRNA contents of interleukin-1Β and nitric oxide synthase in pancreatic islets isolated from female and male nonobese diabetic mice
Abstract
Interleukin-1 beta (IL-1 beta) 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-1 beta 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-1 beta 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-1 beta 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-1 beta bioactivity showed differences roughly reflecting the mRNA levels in the NOD mouse islets. In the NMRI mouse islets the IL-1 beta 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-1 beta was produced by macrophages. The levels of IL-1 beta 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-1 beta in vitro, both NOD and NMRI islets responded with a marked increase in nitric oxide production. It is concluded that the presence of IL-1 beta 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.