ABSTRACT
Objective To investigate whether interleukin 18 (IL 18) and IL 1? converting enzyme (ICE, caspase 1) is expressed in islet ? cells and the mechanism of their expression control. Methods Rat insulinoma (RIN) cells, FACS purified rat ? cells, isolated rat islets, and islets isolated from interferon regulatory factor 1 (IRF 1) gene knockout mice were incubated with or without cytokines. Reverse transcription polymerase chain reaction (RT PCR) was used to quantitate IL 18 and caspase 1 mRNA expression. IL 18 protein expression was detected by using Western blot. Results (1)Interferon ? (IFN ?) increased IL 18 mRNA expression in RIN cells, purified rat ? cells, and intact rat islets, and the effect was unchanged in IRF 1 knockout mouse islets. (2) IFN ? highly up regulated caspase 1 mRNA expression in RIN cells and intact rat islets, but the expression was abolished in IRF 1 knockout mouse islets. (3) IL 18 protein was undetectable in lysates and supernatants of RIN cells. Conclusion IFN ? up regulates IL 18 and caspase 1 expression in islet ? cells. IL 18 expression is not dependent on a transcription factor IRF 1, while caspase 1 expression is in an IRF 1 dependent way.