Peroxynitrite Is a Mediator of Cytokine-Induced Destruction of Human Pancreatic Islet β Cells

Abstract

SUMMARY:The proinflammatory cytokines, interleukin-1␤ (IL-1␤), tumor necrosis factor ␣ (TNF␣), and interferon ␥ (IFN␥), are cytotoxic to pancreatic islet ␤ cells, possibly by inducing nitric oxide and/or oxygen radical production in the ␤ cells. Peroxynitrite, the reaction product of nitric oxide and the superoxide radical, is a strong oxidant and cytotoxic mediator; therefore, we hypothesized that peroxynitrite might be a mediator of cytokine-induced islet ␤-cell destruction. To test this hypothesis we incubated islets isolated from human pancreata with the cytokine combination of IL-1␤, TNF␣, and IFN␥. We found that these cytokines induced significant increases in nitrotyrosine, a marker of peroxynitrite, in islet ␤ cells, and the increase in nitrotyrosine preceded islet-cell destruction. Peroxynitrite mimicked the effects of cytokines on nitrotyrosine formation and islet ␤-cell destruction. L-N G -monomethyl arginine, an inhibitor of nitric oxide synthase, prevented cytokine-induced nitric oxide production but not hydrogen peroxide production, nitrotyrosine formation, or islet ␤-cell destruction. In contrast, guanidinoethyldisulphide, an inhibitor of inducible nitric oxide synthase and scavenger of peroxynitrite, prevented cytokine-induced nitric oxide and hydrogen peroxide production, nitrotyrosine formation, and islet ␤-cell destruction. These results suggest that cytokine-induced peroxynitrite formation is dependent upon increased generation of superoxide (measured as hydrogen peroxide) and that peroxynitrite is a mediator of cytokine-induced destruction of human pancreatic islet ␤ cells. (Lab Invest 2001, 81:1683-1692.

Responses of GLP1-secreting L-cells to cytotoxicity resemble pancreatic β-cells but not α-cells

“…Cytokine cocktail increased Nfkb1 transcription in all cell lines, which was accompanied by strong induction of Nos2 expression and a significant increase in nitrite levels in the culture medium as observed previously in cytokine-exposed b-cell models, human islets and FACSpurified rat b-cells (Corbett et al 1993, Lortz et al 2000, Lakey et al 2001, Sigfrid et al 2003, Souza et al 2004, Larsen et al 2007, Zhang et al 2007, Gurzov et al 2008, Moore et al 2011, 2012. Although gene expression data does not reflect activity of NFkB, it should be noted that NFkB autoregulates its own expression.…”

Improvement of the Mitochondrial Antioxidant Defense Status Prevents Cytokine-Induced Nuclear Factor-κB Activation in Insulin-Producing Cells

“…The development of autoimmune diabetes in NOD mice is associated with peroxynitrite formation at the ␤-cell level (32), and the iNOS inhibitor and peroxynitrite scavenger guanidinoethyldisulphide prevents diabetes in these animals (33). Furthermore, human pancreatic islets are sensitive to peroxynitrite-induced cell dysfunction and cell death (34), and this radical mediates some of the deleterious effects of cytokines in human pancreatic ␤-cells (35). Thus, protection against peroxynitrite may be important to prevent ␤-cell death.…”

The novel inosine analogue, INO-2002, protects against diabetes development in multiple low-dose streptozotocin and non-obese diabetic mouse models of type I diabetes

“…Inosine is also metabolized to uric acid, which has been demonstrated to be a scavenger of free radicals, including peroxynitrite (Ames et al 1981, Becker et al 1989. Peroxynitrite formation has been implicated in b-cell death resulting in development of type I diabetes (Lakey et al 2001; administration of peroxynitrite scavenger compounds has proved effective in preventing type I diabetes in a variety of animal models (Szabó et al 2002, Mabley et al 2004. However, based on the structure of INO-2002 and its inability to be metabolized, we can surmise that both these mechanisms are unlikely to mediate the protective effects of INO-2002 in type I diabetes.…”