胰淀素对人胰岛β细胞凋亡的影响及其分子机制的初步研究

目的：初步探讨胰淀素（amylin）对人胰岛β细胞凋亡的影响及其分子机制。方法： 分离培养人胰岛细胞，免疫组化鉴定β细胞后分为对照组（培养液中含56 mmol/L葡萄糖）、胰淀素组（培养液中含10μmol/L胰淀素+56 mmol/L葡萄糖）及氨基胍组（培养液中含10 μmol/L胰淀素+05 mmol/L氨基胍+56 mmol/L葡萄糖），于37 ℃、5%CO2 培养24 h后做胰岛素释放实验，测定培养液上清胰岛素、一氧化氮（NO2-/NO3-）、还原型谷胱甘肽(GSH)水平。原位末端核苷酸标记法（TUNEL）和胰岛素免疫组化双染色法及ELISA检测胰岛β细胞凋亡， RT-PCR检测胰岛细胞p53和bcl-2 mRNA表达水平。结果：胰淀素组胰岛β细胞凋亡小体富计系数（217±021）、β细胞凋亡百分数（13%）、NO2-/NO3-（2013±173）μmol/L和p53 mRNA表达水平（034±004）显著高于氨基胍组和对照组(P<001)，而胰岛素（334±131）mU·L-1/1×106 cells、GSH［（56±08） mg/L］和bcl-2 mRNA（007±001）表达水平则显著低于氨基胍组和对照组(P<005)。结论： 胰淀素可诱导人胰岛β细胞凋亡，其机制可能与胰岛β细胞抗氧化能力降低引起p53高表达有关。

Influence of amylin on apoptosis of human pancreatic islet β-cells and its molecular mechanism

AIM: To investigate the molecular mechanism of amylin in inducing apoptosis of human pancreatic islet β-cells. METHODS: Human pancreatic islet cells were isolated and cultured. The cells were treated with amylin or amylin and aminoguanidine (AG group) for 24 h, respectively. Apoptosis of pancreatic islet β-cells was studied by in situ TUNEL method combined with double staining for insulin and ELISA. The levels of insulin, NO2-/NO3- and glutathione (GSH), p53 mRNA and bcl-2 mRNA were also detected. RESULTS: (1) The enrichment factor and the apoptosis rate of pancreatic islet β-cells in amylin group were markedly higher than that in control group and AG group (P<001). (2) The insulin level in amylin group was significantly lower than that in control group and AG group (P<005). (3) The levels of NO2-/NO3- and p53 mRNA in amylin group were significantly higher than that in control group and AG group (P<001), while the levels of GSH and bcl-2 mRNA were markedly decreased as compared with control group and AG group. CONCLUSIONS: Amylin increases apoptosis of human pancreatic islets β cells, resulting in decrease in insulin secretion. This may be due to increased expression of p53 and decreased expression of bcl-2 during the of oxidative stress induced by amylin.