Session: SAT 834-867-Islet Biology
Bench to Bedside
Poster Board SAT-845
Since various cytokines have been shown to stimulate IFN-γ production in immune competent cells, we determined the effects of cytokines on IFN-γ production in MIN6 cells. However, expression of IFN-γ was not influenced in those treated with cytokines (TNFα, IL-1β, IL12+IL18, and IFN-α). Although we also reported the expression of RIG-I and MDA5, intracellular receptors for dsRNA, in pancreatic β-cells in FT1DM patients, treatment of MIN6 cells with poly(I:C) had no stimulatory effect on IFN-γ.
Endoplasmic reticulum (ER) stress is also one of cellular responses followed by virus infection. Therefore, we studied the effects of ER stress inducers on the IFN-γ expression in MIN6 cells. Treatment with 10 μg/ml of tunicamycin and 1 μM of thapsigargin exhibited a dose-dependent increase in IFN-γ mRNA expression up to 5.80±1.27-fold and 47.2±14.3-fold increase, respectively. Treatment with 10 μg/ml brefeldin A and 1 μM of palminate for 24 h also increased IFN-γ mRNA level 2.4±0.2-fold and 3.9±0.8-fold, respectively. In addition, glucose starvation by culturing MIN6 cells with no glucose for 24 h exhibited a 99.8±7.8-fold increase in IFN-γ mRNA expression. These ER stress inducers also increased IFN-γ protein levels analyzed by Western blot analysis. Experiments using kinase inhibitors demonstrated that expression of IFN-γ was mediated by JNK but not by p38 MAPK or MEK1/2. We further investigated the role of ER stress-induced IFN-γ production in pancreatic β-cells. In TUNEL staining, transfection of IFN-γ siRNA significantly suppressed thapsigargin-induced apoptosis in MIN6 cells. This result showed that ER stress-induced IFN-γ was involved in ER stress-induced apoptosis of pancreatic β-cells.
Our present study is the first report showing that ER stress induces IFN-γ expression in pancreatic β-cells. We suggest that ER stress-induced IFN-γ expression might play an important role in the abrupt β-cell apoptosis in FT1DM.
Nothing to Disclose: MI, HS, FF, SI, ST, ST, KA, TE, TK
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