Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells
Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells
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DOI：
10.1007/s00125-014-3266-0
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发表时间：
2014-08-01
期刊：
影响因子：
8.2
通讯作者：
Rutter, Guy A.
中科院分区：
文献类型：
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作者：
Gerber, Philipp A.;Bellomo, Elisa A.;Rutter, Guy A.
缺氧性损伤使胰岛分离移植复杂化，并可能导致2型糖尿病患者的胰岛细胞衰竭。编码分泌颗粒锌转运蛋白8的SLC30A8基因的多态可能通过调节胞内锌离子水平来影响2型糖尿病的风险。因此，我们探讨了细胞内锌离子和锌离子在胰岛细胞对低氧反应中的作用。用腺病毒表达的重组靶向性锌探针eCALWY4测定细胞内游离锌。用定量(Q)RT-PCR、免疫印迹或免疫细胞化学方法检测基因表达。在小鼠和人胰岛细胞中，O-2(1%vs5%或21%)作用24 h后，细胞内游离锌离子浓度分别降低40%(p<；0.05)和30%(p<；0.05)。低氧同样降低了胰岛SLC30A8mRNA的表达和β细胞的免疫反应性。基因消融小鼠胰岛SLC30A8可使细胞内锌离子水平降低约40%(p<；0.05)，并减少金属硫蛋白(MT1，MT2)基因的诱导，这暗示了低氧导致细胞内锌离子水平下降。与对照组相比，年龄较大(>；12周)的SLC30A8缺失小鼠的小胰岛在低氧条件下的细胞存活率得到提高，但年轻小鼠没有。胰腺β细胞对低氧的反应特征是SLC30A8表达减少和胞内锌离子浓度降低。低氧诱导的细胞存活变化对ZnT8的依赖可能有助于SLC30A8变体对人类糖尿病风险的作用。
Hypoxic damage complicates islet isolation for transplantation and may contribute to beta cell failure in type 2 diabetes. Polymorphisms in the SLC30A8 gene, encoding the secretory granule zinc transporter 8 (ZnT8), influence type 2 diabetes risk, conceivably by modulating cytosolic Zn2+ levels. We have therefore explored the role of ZnT8 and cytosolic Zn2+ in the response to hypoxia of pancreatic islet cells.Human, mouse or rat islets were isolated and exposed to varying O-2 tensions. Cytosolic free zinc was measured using the adenovirally expressed recombinant targeted zinc probe eCALWY4. Gene expression was measured using quantitative (q)RT-PCR, western (immuno-) blotting or immunocytochemistry. Beta cells were identified by insulin immunoreactivity.Deprivation of O-2 (1% vs 5% or 21%) for 24 h lowered free cytosolic Zn2+ concentrations by 40% (p < 0.05) and similar to 30% (p < 0.05) in mouse and human islet cells, respectively. Hypoxia similarly decreased SLC30A8 mRNA expression in islets, and immunoreactivity in beta cells. Implicating lowered ZnT8 levels in the hypoxia-induced fall in cytosolic Zn2+, genetic ablation of Slc30a8 from mouse islets lowered cytosolic Zn2+ by similar to 40% (p < 0.05) and decreased the induction of metallothionein (Mt1, Mt2) genes. Cell survival in the face of hypoxia was enhanced in small islets of older (> 12 weeks) Slc30a8 null mice vs controls, but not younger animals.The response of pancreatic beta cells to hypoxia is characterised by decreased SLC30A8 expression and lowered cytosolic Zn2+ concentrations. The dependence on ZnT8 of hypoxia-induced changes in cell survival may contribute to the actions of SLC30A8 variants on diabetes risk in humans.