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Cytokine-induced metabolic dysfunction of MIN6 beta cells is nitric oxide independent
1Department of Surgery, Division of Tansplantation, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Background:
An important obstacle to islet transplantation is graft injury due to local production of cytokines generated by host nonspecific inflammatory responses. The detrimental effects that cytokines impart on metabolic function have been associated with nitric oxide (NO) production and apoptosis. We tested the in vitro effects of interleukin (IL)-1 beta, tumor necrosis factor (TNF)alpha, and interferon (IFN)gamma on glucose-stimulated insulin release in the MIN6 beta-cell line and correlated metabolic dysfunction with NO production and rates of apoptosis.
Materials And Methods:
MIN6 cells were cultured in the presence of IL-1 beta, TNFalpha, and/or IFN gamma. Insulin release was determined by radioimmunoassay. NO production was determined by the Griess reaction. Apoptosis was determined by measuring the sub-G(1) phase of DNA content of MIN6 cells by flow cytometry.
Results:
Cytokine-induced suppression of glucose-stimulated insulin release was enhanced in a time-dependent manner. NO production was stimulated by IL-1 beta and augmented by TNFalpha and IFN gamma. N(G)-Monomethyl-l-arginine (l-NMMA) blocked cytokine-induced NO production but only partially attenuated suppression of glucose-stimulated insulin release. Apoptosis increased in the presence of cytokines and was slightly reduced when NO production was specifically inhibited.
Conclusions:
Proinflammatory cytokines suppressed glucose-stimulated insulin release in MIN6 cells. The dominant mechanisms involved NO-independent pathways.