Reducing sugars trigger oxidative modification and apoptosis in pancreatic β-cells by provoking oxidative stress through the glycation reaction

Abstract

Several reducing sugars brought about apoptosis in isolated rat pancreatic islet cells and in the pancreatic beta-cell-derived cell line HIT. This apoptosis was characterized biochemically by inter-nucleosomal DNA cleavage and morphologically by nuclear shrinkage, chromatin condensation and apoptotic body formation. N-Acetyl-L-cysteine, an antioxidant, and aminoguanidine, an inhibitor of the glycation reaction, inhibited this apoptosis. We also showed directly that proteins in beta-cells were actually glycated by using an antibody which can specifically recognize proteins glycated by fructose, but not by glucose. Furthermore, fluorescence-activated cell sorting analysis using dichlorofluorescein diacetate showed that reducing sugars increased intracellular peroxide levels prior to the induction of apoptosis. Levels of carbonyl, an index of oxidative modification, and of malondialdehyde, a lipid peroxidation product, were also increased. Taken together, these results suggest that reducing sugars trigger oxidative modification and apoptosis in pancreatic beta-cells by provoking oxidative stress mainly through the glycation reaction, which may explain the deterioration of beta-cells under conditions of diabetes.

The different apoptotic potential of the p53 codon 72 alleles increases with age and modulates in vivo ischaemia-induced cell death

“…[1][2][3] In vivo, at the systemic level, these same agents play a major role in the basic mechanisms of ageing and agerelated patho-physiologic processes, such as atherosclerosis. [4][5][6][7] At the genetic levels, the data recently obtained on p66Shc null mice confirmed the existence of profound ties among the mechanisms involved in cell death, ageing, and age-related diseases. Indeed, this mouse strain is characterised by a 30% extension of lifespan, 8 a decrease in the levels of in vivo systemic and tissue oxidative stress and vascular apoptosis, 9 and by an abrogation of oxidative stress-induced, p53-dependent apoptosis.…”

“…47 Western blot assay and co-immunoprecipitation assay Whole-cell lysates for Western blot were obtained from DFs cultured in the presence or absence of 20 mM dRib for 48 h, from LCLs cultured in the presence or absence of 10 mM dRib for 24 h, and from SaOs2 transfected cells. Cells were lysed in RIPA Buffer (1% Triton x-100, 50 mM Tris-HCl (pH 8.0), 10 mM Tris-HCl (pH 7.5), 150 mM NaCl, 5 mM EDTA (pH 8.0), added of protease inhibitor cocktail (Sigma) and 1 mM NaVO 4 . To obtain whole-cell lysate for co-immunoprecipitation assay, DFs and SaOs2 were lysed in CO-IP Buffer (0.5% NP-40, 50 mM Tris-HCl (pH 8.0), 10 mM TrisHCl (pH 7.5), 150 mM NaCl, 5 mM EDTA (pH 8.0), with addition of protease inhibitor cocktail (Sigma), and 1 mM NaVO 4 .…”

Pancreatic beta cell senescence contributes to the pathogenesis of type 2 diabetes in high-fat diet-induced diabetic mice

“…To adapt to hyperglycaemia during the pathogenesis of type 2 diabetes, augmented beta cell proliferation causes a compensatory increase in beta cell mass. The disruption of an adequate increase in beta cell mass leads to type 2 diabetes [6][7][8][9][10][11][12]. After a long-term, high-fat diet, the beta cell proliferation markedly decreased and islet cellular senescence was observed.…”

“…Decreased beta cell mass occurs in humans with type 2 diabetes and animal models of type 2 diabetes [6][7][8][9][10][11][12]. Chronic hyperglycaemia leads to progressive loss of beta cell mass with a prolonged increase in the rate of beta cell apoptosis without a compensatory increase in beta cell growth.…”

“…In addition to necrosis, markedly increased beta cell apoptosis is regarded as one of the major factors in the pathogenesis of diabetes. The cellular mechanisms of increased beta cell apoptosis, which include hyperglycaemia-induced oxidative stress [8,12], are being intensively studied [13][14][15][16][17][18].…”