Institute of Biology, National Centre for Scientific Research "Demokritos", Athens, Attiki, Greece.
Cell Signal. 2010 May;22(5):791-800. doi: 10.1016/j.cellsig.2010.01.003. Epub 2010 Jan 11.
Chronic hyperglycemia and inflammatory cytokines disrupt and/or attenuate signal transduction pathways that promote normal beta-cell survival, leading to the destruction of endocrine pancreas in type 2 diabetes. There is convincing evidence that autocrine insulin signalling exerts protective anti-apoptotic effects on beta cells. Suppressors of cytokine signalling (SOCS) were induced by several cytokines and inhibit insulin-initiated signal transduction. The aim of this study was to investigate whether high glucose can influence endogenous interleukin-1beta (IL-1beta) and SOCS expression thus affecting insulin signalling and survival in insulin-producing mouse pancreatic beta cells (betaTC-6). Results showed that prolonged exposure of betaTC-6 cells to increased glucose concentrations resulted in significant inhibition of insulin-induced tyrosine phosphorylation of the insulin receptor (IR), and insulin receptor substrate-2 (IRS-2) as well as PI3-kinase activation. These changes were accompanied by impaired activation of the anti-apoptotic signalling protein Akt and annulment of Akt-mediated suppression of the Forkhead family of transcription factors (FoxO) activation. Glucose-induced attenuation of IRS-2/Akt-mediated signalling was associated with increased IL-1beta expression. Enhanced endogenous IL-1beta specifically induced mRNA and protein expression of SOCS-1 in betaTC-6 cells. Inhibition of SOCS-1 expression by SOCS-1-specific small interfering RNA restored IRS-2/PI3K-mediated Akt phosphorylation suppressed by high glucose. The upregulation of endogenous cytokine signalling and FoxO activation were accompanied by enhanced caspase-3 activation and increased susceptibility of cells to apoptosis. These results indicated that glucose-induced endogenous IL-1beta expression increased betaTC-6 cells apoptosis by inhibiting, at least in part, IRS-2/Akt-mediated signalling through SOCS-1 upregulation.
慢性高血糖和炎性细胞因子破坏和/或减弱了促进正常β细胞存活的信号转导途径,导致 2 型糖尿病中内分胰腺的破坏。有确凿的证据表明,胰岛素的自分泌信号对β细胞发挥了保护抗凋亡作用。细胞因子信号转导抑制剂(SOCS)被几种细胞因子诱导,并抑制胰岛素起始的信号转导。本研究的目的是研究高葡萄糖是否能影响内源性白细胞介素-1β(IL-1β)和 SOCS 的表达,从而影响胰岛素产生的小鼠胰岛β细胞(betaTC-6)中的胰岛素信号和存活。结果表明,betaTC-6 细胞长期暴露于高葡萄糖浓度会导致胰岛素诱导的胰岛素受体(IR)和胰岛素受体底物-2(IRS-2)酪氨酸磷酸化以及 PI3-激酶活性显著抑制。这些变化伴随着抗凋亡信号蛋白 Akt 的激活受损和 Akt 介导的 Forkhead 转录因子家族(FoxO)激活的抑制作用丧失。葡萄糖诱导的 IRS-2/Akt 介导的信号转导减弱与 IL-1β表达增加有关。增强的内源性 IL-1β特异性诱导 betaTC-6 细胞中 SOCS-1 的 mRNA 和蛋白表达。SOCS-1 特异性小干扰 RNA 抑制 SOCS-1 表达可恢复高葡萄糖抑制的 IRS-2/PI3K 介导的 Akt 磷酸化。内源性细胞因子信号的上调和 FoxO 的激活伴随着 caspase-3 激活的增加和细胞对凋亡的敏感性增加。这些结果表明,葡萄糖诱导的内源性 IL-1β表达通过 SOCS-1 的上调抑制 IRS-2/Akt 介导的信号转导,至少部分增加了 betaTC-6 细胞的凋亡。