Effects of high concentration glucose on the expression of NF-κB, Bax and cytochrome C and apoptosis of islet cells in mice

Abstract

The roles of NF-kappaB (NF-κB) expression, Bax activity and cytochrome C (Cyt C) release, apoptosis of islet cells induced by high concentration glucose were explored in vitro. Pancreatic islet cells, which were isolated from Kunming mice, were cultured with different concentrations of glucose in DMEM, and divided into the following groups: G1, G2, G3, G4, G5, and G6 groups, corresponding to the glucose concentrations of 5.6, 7.8, 11.1, 16.7, 22.5, and 27.6 mmol/L, respectively. After culture for 120 h, insulin secretion was evaluated by radioimmunoassay, and the NF-κB expression was detected by immunocytochemistry. Bax activity and Cyt C release were measured by immunofluorescence, and apoptosis was examined by Hoechst33342 assay. The results showed that in G1, G2 and G3 groups, insulin secretion was enhanced with the increase of glucose concentration, and the NF-κB expression was also increased (P<0.05), but Bax activity, Cyt C release and apoptosis rate showed no significant difference among them. However, in G4, G5, and G6 groups, apoptosis rate of islet cells, NF-κB expression, Bax activity, and Cyt C release were all significantly increased, and insulin secretion was impaired as compared with G1, G2, and G3 groups (P<0.05). It was concluded that the exposure of islet cells to high glucose could induce islet cells apoptosis as well as impaired insulin secretion. The NF-κB signaling pathway and mitochondria pathway in islet cells might play some roles in the progressive loss of islet cells in diabetes. The inhibition of the NF-κB expression could be an effective strategy for protecting pancreatic islet cells.

Keywords

islet cells / apoptosis / high concentration glucose / nuclear factor-κB / cytochrome C / Bax

References

[1] KarinM., LinA.. NF-κB at the crossroads of life and death. Nat Immunol, 2002, 3(3): 221-227

[2] GhoshS., MauryaD.K., KrishnaM.. Role of iNOS in bystander signaling between macrophages and lymphoma cells. Int J Radiat Oncol Biol Phys, 2008, 72(5): 1567-1574

[3] GreenD.R., ReedJ.C.. Mitochondria and apoptosis. Science, 1998, 281(5381): 1309-1312

[4] GuillausseauP.J., MeasT., VirallyM., et al.. Abnormalities in insulin secretion in type 2 diabetes mellitus. Diabetes Metab, 2008, 34(Suppl2): S43-S48

[5] ButlerA.E., JansonJ., Bonner-WeirS., et al.. Cell deficit and increased cell apoptosis in humans with type 2 diabetes. Diabetes, 2003, 52(1): 102-110

[6] KarinM., Ben-NeriahY.. Phosphorylation meets ubiquitination: the control of NF-[kappa]B activity. Annu Rev Immunol, 2000, 18: 621-663

[7] CnopM., WelshN., JonasJ.C., et al.. Mechanisms of pancreatic beta-cell death in type 1 and type 2 diabetes: many differences, few similarities. Diabetes, 2005, 54(Suppl2): S97-S107

[8] BakerM.S., ChenX., CaoX.C., et al.. Expression of a dominant negative inhibitor of NF-kappaB protects MIN6 beta-cells from cytokine-induced apoptosis. J Surg Res, 2001, 97(2): 117-122

[9] MelloulD.. Role of NF-kappaB in beta-cell death. Biochem Soc Trans, 2008, 36(Pt3): 334-339

[10] RakatziI., MuellerH., RitzelerO., et al.. Adiponectin counteracts cytokine- and fatty acid-induced apoptosis in the pancreatic β-cell line INS-1. Diabetologia, 2004, 47(2): 249-258

[11] ElouilH., CardozoA.K., EizirikD.L., et al.. High glucose and hydrogen peroxide increase c-Myc and haeme-oxygenase 1 mRNA levels in rat pancreatic islets without activating NF-kappaB. Diabetologia, 2005, 48(3): 496-505

[12] DarvilleM.I., EizirikD.L.. Regulation by cytokines of the inducible nitric oxide synthase promoter in insulin-producing cells. Diabetologia, 1998, 41(9): 1101-1108

[13] NorlinS., AhlgrenU., EdlundH.. Nuclear factor-κB activity in β-cells is required for glucose-stimulated insulin secretion. Diabetes, 2005, 54(1): 125-132

[14] CardozoA.K., HeimbergH., HeremansY., et al.. A comprehensive analysis of cytokine-induced and nuclear factor-κB-dependent genes in primary rat pancreatic β-cells. J Biol Chem, 2001, 276(52): 48879-48886

[15] HeimbergH., HeremansY., JobinC., et al.. Inhibition of cytokine-induced NF-κB activation by adenovirus-mediated expression of a NF-κB super-repressor prevents β-cell apoptosis. Diabetes, 2001, 50(10): 2219-2224

[16] GiannoukakisN., RudertW.A., TruccoM., et al.. Protection of human islets from the effects of interleukin-1β by adenoviral gene transfer of an IκB repressor. J Biol Chem, 2000, 275(4): 36509-36513