Meng Z X, Sun J X, Ling J J, Lv J H, Zhu D Y, Chen Q, Sun Y J, Han X
Key Laboratory of Human Functional Genomics of Jiangsu Province, School of Basic Medical Science, Nanjing Medical University, Nanjing, PR China.
Diabetologia. 2006 Dec;49(12):2959-68. doi: 10.1007/s00125-006-0447-5. Epub 2006 Oct 11.
AIMS/HYPOTHESIS: Prostaglandin E(2) (PGE(2)) is a well-recognised inhibitor of glucose-stimulated insulin secretion (GSIS). The aim of this study was to investigate the signalling pathway of PGE(2) in beta cell function regulation in HIT-T15 cells and isolated rat islets.
mRNA levels of the prostaglandin E receptor 3 (Ptger3) were measured by real-time PCR. Western blot analysis was used to detect changes in the levels of PTGER3, phosphorylated and total Akt, phosphorylated and total forkhead box 'Other' (Foxo). Transient transfection and reporter assays were used to measure Foxo transcriptional activity. The biological significance of PGE(2) in beta cell function was analysed using MTT, flow cytometry and GSIS assays.
We found that treating HIT-T15 cells with exogenous PGE(2) stimulated Ptger3 gene expression specifically, and diminished cAMP generation. These were accompanied by the downregulation of Akt and Foxo phosphorylation in HIT-T15 cells and isolated rat islets. Moreover, PGE(2) upregulated basal and partially reversed constitutively active Akt-inactivated Foxo transcriptional activity. Furthermore, GSIS was impaired in PGE(2)-treated HIT-T15 cells and isolated islets. However, the dosage used in the above experiments did not affect beta cell viability and apoptosis. In addition, insulin-like growth factor 1 (IGF-1) pretreatment reversed the effects of PGE(2), and wortmannin treatment abolished the preventive effects of IGF-1.
CONCLUSIONS/INTERPRETATION: Our observations strongly suggest that PGE(2) can induce pancreatic beta cell dysfunction through the induction of Ptger3 gene expression and inhibition of Akt/Foxo phosphorylation without impacting beta cell viability. These results shed light on the mechanisms of PGE(2) actions in pancreatic beta cell dysfunction.
目的/假设：前列腺素E₂（PGE₂）是一种公认的葡萄糖刺激胰岛素分泌（GSIS）抑制剂。本研究旨在探讨PGE₂在HIT-T15细胞和分离的大鼠胰岛β细胞功能调节中的信号通路。
通过实时PCR检测前列腺素E受体3（Ptger3）的mRNA水平。采用蛋白质免疫印迹分析检测PTGER3、磷酸化和总Akt、磷酸化和总叉头框“其他”（Foxo）水平的变化。采用瞬时转染和报告基因检测来测量Foxo转录活性。使用MTT、流式细胞术和GSIS检测分析PGE₂在β细胞功能中的生物学意义。
我们发现用外源性PGE₂处理HIT-T15细胞可特异性刺激Ptger3基因表达，并减少cAMP生成。这些变化伴随着HIT-T15细胞和分离的大鼠胰岛中Akt和Foxo磷酸化的下调。此外，PGE₂上调基础水平并部分逆转组成型活性Akt失活的Foxo转录活性。此外，PGE₂处理的HIT-T15细胞和分离的胰岛中GSIS受损。然而，上述实验中使用的剂量不影响β细胞活力和凋亡。此外，胰岛素样生长因子1（IGF-1）预处理可逆转PGE₂的作用，渥曼青霉素处理可消除IGF-1的预防作用。
结论/解读：我们的观察结果强烈表明，PGE₂可通过诱导Ptger3基因表达和抑制Akt/Foxo磷酸化来诱导胰腺β细胞功能障碍，而不影响β细胞活力。这些结果揭示了PGE₂在胰腺β细胞功能障碍中的作用机制。
