Abstract
Destruction of pancreatic islet beta-cells in type 1 diabetes appears to result from direct contact with infiltrating T-cells and macrophages and exposure to inflammatory cytokines such as interferon (IFN)-gamma, interleukin (IL)-1 beta, and tumor necrosis factor TNF-alpha that such cells produce. We recently reported on a method for selection of insulinoma cells that are resistant to the cytotoxic effects of inflammatory cytokines (INS-1(res)), involving their growth in progressively increasing concentrations of IL-1 beta plus IFN-gamma, and selection of surviving cells. In the current study, we have investigated the molecular mechanism of cytokine resistance in INS-1(res) cells. By focusing on the known components of the IFN-gamma receptor signaling pathway, we have discovered that expression levels of signal transducer and activator of transcription (STAT)-1 alpha are closely correlated with the cytokine-resistant and -sensitive phenotypes. That STAT-1 alpha is directly involved in development of cytokine resistance is demonstrated by an increase of viability from 10 +/- 2% in control cells to 50 +/- 6% in cells with adenovirus-mediated overexpression of STAT-1 alpha (p < 0.001) after culture of both cell groups in the presence of 100 units/ml IFN-gamma plus 10 ng/ml IL-1 beta for 48 h. The resistance to IL-1 beta plus IFN-gamma in STAT-1 alpha-expressing cells is due in part to interference with IL-1 beta-mediated stimulation of inducible nitric-oxide synthase expression and nitric oxide production. Furthermore, overexpression of STAT-1 alpha does not impair robust glucose-stimulated insulin secretion in the INS-1-derived cell line 832/13. We conclude that expression of STAT-1 alpha may be a means of protecting insulin-producing cell lines from cytokine damage, which, in conjunction with appropriate cell-impermeant macroencapsulation devices, may allow such cells to be used for insulin replacement in type 1 diabetes.
Highlights
Type 1 diabetes is caused by autoimmune destruction of pancreatic islet -cells
We recently reported on a method for selection of insulinoma cells that are resistant to the cytotoxic effects of inflammatory cytokines (INS-1res), involving their growth in progressively increasing concentrations of IL-1 plus IFN-␥, and selection of surviving cells
833/15 and 833/117 cells that are grown in the continual presence of cytokines are IFN-␥- and IFN-␥ plus IL-1-resistant [14], and contain 6.9 and 7.0 times as much signal transducer and activator of transcription (STAT)-1␣ protein, respectively, as the same cell lines that had been grown in the absence of cytokines for 4 weeks or more
Summary
Destruction of -cells appears to result from direct contact with infiltrating T-cells and macrophages and exposure to inflammatory cytokines such as IFN-␥,1 IL-1, enthusiasm for this important finding is tempered by the fact that the number of human pancreata available for islet transplantation in the United States is on the order of several thousand per year [6, 7], which does not approach the number of patients that could benefit from this new form of therapy To deal with this problem, we and others have been attempting to develop a replenishable source of cells that could serve as islet surrogates for cell-based insulin replacement in diabetes (9 –13). Our findings suggest that expression of STAT-1␣ in insulin-secreting cell lines may be a means for enhancing their survival in a transplant setting
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