PubMed1991
The aim of this study was to characterize the dynamics and functional relevance of interleukin-1 beta (IL-1 beta)-induced nitric oxide production in isolated pancreatic islets. Thus, islets were isolated from adult rats, precultured for 3-5 days in medium RPMI-1640 plus 10% fetal calf serum, and then exposed to IL-1 beta for different time periods, after which islet nitrite production and aconitase activity were determined. IL-1 beta (5 ng/ml) did not increase islet nitrite production during the first hour of incubation. Moreover, the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (Meth-arg; 5 mM) failed to prevent the initial (90 min) IL-1 beta-induced increase in islet insulin release. After 4, 7, and 24 h, however, nitrite production was increased by 50%, 93%, and 139%, respectively. Islet aconitase activity and glucose oxidation rates were decreased by 70% after incubation for 24 h with IL-1 beta. Both Meth-arg and N alpha-p-tosyl-L-lysine chloromethyl ketone (0.1 mM), a protease inhibitor, could completely counteract the IL-1 beta-induced increases in nitrite production and inhibition of aconitase activity and glucose oxidation rates. In a separate series of experiments, islets were incubated for 60 min with or without IL-1 beta and the RNA synthesis inhibitor actinomycin-D (5 micrograms/ml) and subsequently incubated for another 9 h without any additions. The presence of actinomycin-D during the 1-h IL-1 beta incubation period prevented the IL-1 beta-induced rise in nitrite production and the IL-1 beta-induced inhibition of aconitase activity and insulin release. It is concluded that IL-1 beta-induced nitric oxide production is a late event which requires gene transcription and does not mediate the initial stimulatory effects of IL-1 beta on beta-cell function. However, the gradually augmented rate of nitric oxide production may inhibit the enzyme aconitase, leading to a suppressed mitochondrial activity and a defective insulin release in response to nutrient secretagogues.