Interaction between pro-inflammatory and anti-inflammatory cytokines in insulin-producing cells

Pro-inflammatory cytokines cause beta-cell dysfunction and death. The aim of this study was to investigate the interactions between different pro- and anti-inflammatory cytokines and their effects on apoptotic beta-cell death pathways. Insulin-producing RINm5F cells were exposed to different combinations of cytokines. Gene expression analyses of manganese superoxide dismutase (MnSOD) and inducible nitric oxide synthase (iNOS) were performed by real-time RT-PCR. Cell viability was measured by the MTT assay, NF kappa B activation using a SEAP reporter gene assay, protein expression by western blotting and caspase-3 activity using the DEVD cleavage method. IL-1 beta, tumour necrosis factor alpha (TNF alpha) and a combination of all three pro-inflammatory cytokines increased while IFN gamma alone did not affect NF kappa B activity and iNOS gene and protein expression. Interestingly, the anti-inflammatory cytokines IL-4, IL-13 and IL-10 decreased IL-1 beta-stimulated NF kappa B activation and iNOS expression. IL-1 beta, TNF alpha and the pro-inflammatory cytokine combination also increased MnSOD gene and protein expression. But IL-4, IL-13 and IL-10 did not affect MnSOD expression and did not modulate IL-1 beta-stimulated MnSOD expression. Caspase-3 activity was increased by IL-10 and the pro-inflammatory cytokine combination, and to a lesser extent by TNF alpha,. In contrast, IFN gamma had no effect on caspase-3 activity. IL-4, IL-13 and IL-10 decreased caspase-3 activity and increased viability of insulin-producing cells treated with pro-inflannuatory cytokines. The anti-inflammatory cytokines counteracted the cytotoxic effects of proinflammatory cytokines in insulin-producing cells. This was achieved through the reduction of nitrosative stress. Thus, a balance between the anti-inflammatory and the proinflammatory cytokines is of crucial importance for the prevention of pancreatic beta-cell destruction.