Nitric oxides mediates a shift from early necrosis to late apoptosis in cytokine-treated β-cells that is associated with irreversible DNA damage

Abstract

Hughes KJ, Chambers KT, Meares GP, Corbett JA. Nitric oxides mediates a shift from early necrosis to late apoptosis in cytokine-treated ␤-cells that is associated with irreversible DNA damage. Am J Physiol Endocrinol Metab 297: E1187-E1196, 2009. First published September 8, 2009 doi:10.1152/ajpendo.00214.2009.-For many cell types, including pancreatic ␤-cells, nitric oxide is a mediator of cell death; however, it is paradoxical that for a given cell type nitric oxide can induce both necrosis and apoptosis. This report tests the hypothesis that cell death mediated by nitric oxide shifts from an early necrotic to a late apoptotic event. Central to this transition is the ability of ␤-cells to respond and repair nitric oxide-mediated damage. ␤-Cells have the ability to repair DNA that is damaged following 24-h incubation with IL-1; however, cytokine-induced DNA damage becomes irreversible following 36-h incubation. This irreversible DNA damage following 36-h incubation with IL-1 correlates with the activation of caspase-3 (cleavage and activity). The increase in caspase activity correlates with reductions in endogenous nitric oxide production, as nitric oxide is an inhibitor of caspase activity. In contrast, caspase cleavage or activation is not observed under conditions in which ␤-cells are capable of repairing damaged DNA (24-h incubation with cytokines). These findings provide evidence that ␤-cell death in response to cytokines shifts from an early necrotic process to apoptosis and that this shift is associated with irreversible DNA damage and caspase-3 activation.islet; insulin; death INSULIN-DEPENDENT DIABETES MELLITUS is an autoimmune disease characterized by the selective destruction of pancreatic ␤-cells found in islets of Langerhans (20). Cytokines, released by invading leukocytes during insulitis, are believed to play a role in ␤-cell destruction (32, 41). In rodent islets, the macrophagederived cytokine interleukin (IL)-1 is sufficient to impair insulin secretion and induce islet damage (10). The destructive actions of IL-1 are augmented by IFN␥ and TNF (50). In islets isolated from most mouse strains and humans, IL-1 and IFN␥ are the minimal combination of cytokines required to induce damage, and this damage is enhanced by TNF (2,13,23,33).Nitric oxide plays a central role in regulating the response(s) of ␤-cells to cytokines. Cytokines stimulate the expression of the inducible isoform of nitric oxide synthase (iNOS) and the production of micromolar levels of nitric oxide by ␤-cells (9,11,15,17,48). Nitric oxide reduces ␤-cell viability, as determined by the neutral red assay as well as 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay (49). In addition, nitric oxide inhibits insulin secretion by attenuating the oxidation of glucose to CO 2 by inhibiting the activity of mitochondrial iron-sulfur center-containing enzymes such as aconitase and complexes of the electron transport system (15). This results in a fourfold decrease in cellular ATP levels (18, 30). Since glucose-sti...

FoxO1 and SIRT1 Regulate β-Cell Responses to Nitric Oxide

“…Following short exposures to cytokines, under conditions in which nitric oxide-mediated damage is reversible, biochemical assays indicate that cell death is necrotic in nature. At points in which ␤-cells no longer have the capacity to recover from this damage, cytokine-mediated ␤-cell death shifts to an apoptotic process that is associated with irreversible DNA damage and caspase activation (14). Similar to what has been observed in ␤-cells, nitric oxide has been implicated in the induction of both necrosis and apoptosis of multiple cell types (27)(28)(29).…”

“…The addition of a NOS inhibitor to islets pretreated for 24 h with IL-1 (without removing IL-1) results in a time-dependent recovery of insulin secretion and mitochondrial function (3) and the repair of damaged DNA (14,15). This recovery response requires new gene expression, the activation of JNK, and can be stimulated by nitric oxide (16,17).…”

“…The ability of ␤-cells to recover from cytokine-and nitric oxide-induced damage is temporally limited. Following a 36-h exposure to IL-1, ␤-cells are no longer capable of recovering metabolic and secretory function, and the islets are committed to death (14,18). Studies have shown that cytokines can kill ␤-cells by nitric oxide-dependent and -independent necrotic and apoptotic mechanisms (19 -26).…”

Deoxyhypusine synthase haploinsufficiency attenuates acute cytokine signaling

“…Pro-inflammatory cytokines (e.g., IL-1β, IFNγ) trigger mitogenactivated protein kinase and NFκB pathways, promoting β-cell necrosis via production of nitric oxide in the short term, and triggering apoptosis via endoplasmic reticulum (ER) and oxidative stress pathways in the longer term. 8,9 Similarly, lipotoxicity arising from high fat diets triggers impairments in insulin release and eventual apoptosis. 10 Despite its central importance in metabolic physiology, the β cell in general has a poor capacity to withstand stresses, a feature that is compounded by its limited numbers and low inherent replication rate.…”

Involvement of the RNA-binding protein ARE/poly(U)-binding factor 1 (AUF1) in the cytotoxic effects of proinflammatory cytokines on pancreatic beta cells

“…However, even if present, in MIN6 cells the effect on mRNA stability appears to have less impact on iNOS levels than the attenuation of the NFκB signalling. NO production plays a pivotal role in the deleterious action exerted by proinflammatory cytokines on beta cells [44]. Therefore, at least part of the protective effect of AUF1 silencing can probably be attributed to the smaller induction of iNOS.…”