Garvan Institute of Medical Research, Sydney, NSW, Australia.
Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium.
Sci Rep. 2019 Sep 6;9(1):12827. doi: 10.1038/s41598-019-49289-5.
The loss of functional beta cell mass characterises all forms of diabetes. Beta cells are highly susceptible to stress, including cytokine, endoplasmic reticulum (ER) and oxidative stress. This study examined the role of pleckstrin homology-like, domain family A, member 3 (Phlda3) in beta cell survival under stress conditions and the regulatory basis. We found that the mRNA levels of Phlda3 were markedly upregulated in vivo in the islets of diabetic humans and mice. In vitro, exposure of MIN6 cells or islets to cytokines, palmitate, thapsigargin or ribose upregulated Phlda3 mRNA and protein levels, concurrent with the induction of ER stress (Ddit3 and Trb3) and antioxidant (Hmox1) genes. Furthermore, HO treatment markedly increased PHLDA3 immunostaining in human islets. Phlda3 expression was differentially regulated by adaptive (Xbp1) and apoptotic (Ddit3) unfolded protein response (UPR) mediators. siRNA-mediated knockdown of Xbp1 inhibited the induction of Phlda3 by cytokines and palmitate, whereas knockdown of Ddit3 upregulated Phlda3. Moreover, knockdown of Phlda3 potentiated cytokine-induced apoptosis in association with upregulation of inflammatory genes (iNos, IL1β and IκBα) and NFκB phosphorylation and downregulation of antioxidant (Gpx1 and Srxn1) and adaptive UPR (Xbp1, Hspa5 and Fkbp11) genes. Knockdown of Phlda3 also potentiated apoptosis under oxidative stress conditions induced by ribose treatment. These findings suggest that Phlda3 is crucial for beta cell survival under stress conditions. Phlda3 regulates the cytokine, oxidative and ER stress responses in beta cells via the repression of inflammatory gene expression and the maintenance of antioxidant and adaptive UPR gene expression. Phlda3 may promote beta cell survival in diabetes.
功能性β细胞数量的减少是所有类型糖尿病的特征。β细胞对压力(包括细胞因子、内质网(ER)和氧化应激)高度敏感。本研究探讨了 pleckstrin homology-like, domain family A, member 3 (Phlda3) 在β细胞应激条件下的生存作用及其调控基础。我们发现,Phlda3 的 mRNA 水平在糖尿病患者和小鼠的胰岛中明显上调。在体外,MIN6 细胞或胰岛暴露于细胞因子、棕榈酸、他普西龙或核糖时,上调 Phlda3 的 mRNA 和蛋白水平,同时诱导 ER 应激(Ddit3 和 Trb3)和抗氧化(Hmox1)基因。此外,HO 处理显著增加了人胰岛中 PHLDA3 的免疫染色。Phlda3 的表达受适应性(Xbp1)和凋亡(Ddit3)未折叠蛋白反应(UPR)调节剂的差异调节。Xbp1 的 siRNA 介导的敲低抑制了细胞因子和棕榈酸诱导的 Phlda3 诱导,而 Ddit3 的敲低则上调了 Phlda3。此外,Phlda3 的敲低与炎症基因(iNos、IL1β 和 IκBα)和 NFκB 磷酸化的上调以及抗氧化(Gpx1 和 Srxn1)和适应性 UPR(Xbp1、Hspa5 和 Fkbp11)基因的下调相关,增强了细胞因子诱导的凋亡。Phlda3 的敲低还增强了核糖处理诱导的氧化应激条件下的细胞凋亡。这些发现表明 Phlda3 对于应激条件下的β细胞存活至关重要。Phlda3 通过抑制炎症基因的表达和维持抗氧化和适应性 UPR 基因的表达来调节β细胞中的细胞因子、氧化应激和 ER 应激反应。Phlda3 可能在糖尿病中促进β细胞的存活。