Prostaglandin E-2(PGE(2)) is a well-known mediator of beta-cell dysfunction in both type 1 and type 2 diabetes.We recently reported that down-regulation of the Akt pathway activity is implicated in PGE(2)-induced panc...Prostaglandin E-2(PGE(2)) is a well-known mediator of beta-cell dysfunction in both type 1 and type 2 diabetes.We recently reported that down-regulation of the Akt pathway activity is implicated in PGE(2)-induced pancreatic beta-cell dysfunction.The aim of this study was to further dissect the signaling pathway of this process in pancreatic beta-cell line HIT-T15 cells and primary mouse islets.We found that PGE(2) time-dependently increased the c-Jun N-terminal kinase(JNK) pathway activity.JNK inhibition by the JNK-specific inhibitor SP600125 reversed PGE(2)-inhibited glucose-stimulated insulin secretion(GSIS).PGE(2) induced dephosphorylation of Akt and FOXO1, leading to nuclear localization and transactivation of FOXO1.Activation of FOXO1 induced nuclear exclusion but had no obvious effect on the whole-cell protein level of pancreatic and duodenal homeobox 1(PDX1).However, these effects were all attenuated by JNK inhibition.Furthermore, adenovirus-mediated overexpression of dominant-negative(DN)FOXO1 abolished whereas constitutively active(CA)-FOXO1 mimicked the effects of PGE(2) on GSIS in isolated mouse islets.In addition, we demonstrated that DN-JNK1 but not DN-JNK2 or CA-Akt abolished the PGE(2)-induced AP-1 luciferase reporter activity, whereas DN-JNK1 and CA-Akt but not DN-JNK2 reversed the effect of PGE(2) on FOXO1 transcriptional activity, and overexpression of DN-JNK1 rescued PGE(2)-impaired GSIS in mouse islets.Our results revealed that activation of the JNK is involved in PGE(2)induced beta-cell dysfunction.PGE(2)-mediated JNK1 activation, through dephosphorylation of Akt and FOXO1, leads to nuclear accumulation of FOXO1 and nucleocytoplasmic shuttling of PDX1, finally resulting in defective GSIS in pancreatic beta-cells.展开更多
文摘Prostaglandin E-2(PGE(2)) is a well-known mediator of beta-cell dysfunction in both type 1 and type 2 diabetes.We recently reported that down-regulation of the Akt pathway activity is implicated in PGE(2)-induced pancreatic beta-cell dysfunction.The aim of this study was to further dissect the signaling pathway of this process in pancreatic beta-cell line HIT-T15 cells and primary mouse islets.We found that PGE(2) time-dependently increased the c-Jun N-terminal kinase(JNK) pathway activity.JNK inhibition by the JNK-specific inhibitor SP600125 reversed PGE(2)-inhibited glucose-stimulated insulin secretion(GSIS).PGE(2) induced dephosphorylation of Akt and FOXO1, leading to nuclear localization and transactivation of FOXO1.Activation of FOXO1 induced nuclear exclusion but had no obvious effect on the whole-cell protein level of pancreatic and duodenal homeobox 1(PDX1).However, these effects were all attenuated by JNK inhibition.Furthermore, adenovirus-mediated overexpression of dominant-negative(DN)FOXO1 abolished whereas constitutively active(CA)-FOXO1 mimicked the effects of PGE(2) on GSIS in isolated mouse islets.In addition, we demonstrated that DN-JNK1 but not DN-JNK2 or CA-Akt abolished the PGE(2)-induced AP-1 luciferase reporter activity, whereas DN-JNK1 and CA-Akt but not DN-JNK2 reversed the effect of PGE(2) on FOXO1 transcriptional activity, and overexpression of DN-JNK1 rescued PGE(2)-impaired GSIS in mouse islets.Our results revealed that activation of the JNK is involved in PGE(2)induced beta-cell dysfunction.PGE(2)-mediated JNK1 activation, through dephosphorylation of Akt and FOXO1, leads to nuclear accumulation of FOXO1 and nucleocytoplasmic shuttling of PDX1, finally resulting in defective GSIS in pancreatic beta-cells.
