Abstract

Endoplasmic reticulum (ER) stress plays a critical role in pancreatic β cell destruction which leads to the pathogenesis of type 1 diabetes mellitus (T1DM). Vitamin D (VD) has been reported to reduce the risk of T1DM; however, it remains unknown whether VD affects ER stress in pancreatic β cells. In this study, we investigated the role of the active form of VD, 1,25-dihydroxyvitamin D3 [1,25-(OH)₂D₃], in ER stress-induced β cell apoptosis and explored its potential mechanism in mouse insulinoma cell line mouse insulinoma 6 (MIN6). The results of cell counting kit-8 (CCK8) and flow cytometric analyses showed that 1,25-(OH)₂D₃ caused a significant increase in the viability of MIN6 cells injured by H₂O₂. The protein kinase like ER kinase (PERK) signal pathway, one of the most conserved branches of ER stress, was found to be involved in this process. H₂O₂ activated the phosphorylation of PERK, upregulated the activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP) expression, and subsequently initiated cell apoptosis, which were significantly reversed by 1,25-(OH)₂D₃ pretreatment. In addition, GSK2606414, a specific inhibitor of PERK, suppressed PERK phosphorylation and reduced the expressions of ATF4 and CHOP, leading to a significant decrease in β cell apoptosis induced by H₂O₂. Taken together, the present findings firstly demonstrated that 1,25-(OH)₂D₃ could prevent MIN6 cells against ER stress-associated apoptosis by inhibiting the PERK-ATF4-CHOP pathway. Therefore, our results suggested that 1,25-(OH)₂D₃ might serve as a potential therapeutic target for preventing pancreatic β cell destruction in T1DM.

中文翻译：

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1,25-（OH）2D3通过抑制PERK-ATF4-CHOP途径保护胰腺β细胞免受H2O2诱导的凋亡

摘要

内质网（ER）应激在胰腺β细胞破坏中起关键作用，胰岛β细胞破坏导致1型糖尿病（T1DM）的发病机理。据报道，维生素D（VD）可以降低罹患T1DM的风险；但是，VD是否会影响胰腺β细胞的内质网应激仍是未知的。在这项研究中，我们研究了VD的活性形式1,25-二羟基维生素D3 [1,25-（OH）₂ D ₃ ]在内质网应激诱导的β细胞凋亡中的作用，并探讨了其在小鼠胰岛素瘤中的潜在机制。细胞系小鼠胰岛素瘤6（MIN6）。细胞计数试剂盒8（CCK8）和流式细胞仪分析的结果表明1,25-（OH）₂ D ₃导致受H ₂ O损伤的MIN6细胞的活力显着增加₂。发现蛋白激酶如ER激酶（PERK）信号通路是ER应激最保守的分支之一，它参与了这一过程。H ₂ O ₂激活了PERK的磷酸化，上调了激活转录因子4（ATF4）和C / EBP同源蛋白（CHOP）的表达，随后启动了细胞凋亡，被1,25-（OH）₂ D显着逆转₃预处理。此外，PERK的特异性抑制剂GSK2606414抑制PERK磷酸化并降低ATF4和CHOP的表达，从而导致H ₂ O ₂诱导的β细胞凋亡显着减少。。综上所述，本发明的发现首先证明1，25-（OH）₂ D ₃可以通过抑制PERK-ATF4-CHOP途径来阻止MIN6细胞抵抗ER应激相关的细胞凋亡。因此，我们的结果表明1,25-（OH）₂ D ₃可能作为预防T1DM中胰腺β细胞破坏的潜在治疗靶标。