Contreras Juan L, Smyth Cheryl A, Bilbao Guadalupe, Young Carlton J, Thompson J Anthony, Eckhoff Devin E
Transplant Center, Division of Transplantation, University of Alabama at Birmingham, 748 Lyons-Harrison Research Building, 701 19th Street South, Birmingham, AL 35294, USA.
Transplantation. 2002 Oct 27;74(8):1063-9. doi: 10.1097/00007890-200210270-00001.
Pancreatic islets are susceptible to myriad insults that occur during islet isolation and transplantation. Studies demonstrated the role of Akt in regulating pancreatic beta-cell growth and survival. Activation of Akt maintains Bad phosphorylation and prevents its binding to mitochondrial targets, decreases caspase-9 activity, and prevents the translocation of forkhead transcription factors (FKHR). Simvastatin activates Akt in mammalian cells; therefore, we investigated the role of simvastatin on human pancreatic islets (HPI) survival.
HPI were treated with simvastatin, with and without LY294002, an inhibitor of phosphoinositide 3-kinase. PI viability was examined with ethidium bromide-acridine orange, and apoptosis was examined using a quantitative assay. Akt, Bad, FKHR phosphorylation, and mitochondrial cytochrome release were analyzed by Western blots. Caspase-9 activity was assessed by a fluorometric assay. A limited number of HPI were transplanted after simvastatin treatment in diabetic NOD-SCID mice.
Low levels of Akt phosphorylation (activation) were demonstrated early after islet isolation. Akt activation; increase in islet viability; and decrease in Bad phosphorylation, cytochrome release, caspase-9 activation, and translocation of FKHR were observed after simvastatin treatment, effects reversed by LY294002. Among recipients of islets without simvastatin, none demonstrated reversal of diabetes after the transplant. In contrast, 58% of the recipients given islets treated with simvastatin remained euglycemic 30 days after the transplant.
Targeting the survival pathway with simvastatin exerts a cytoprotective effect on isolated PI. Activation of the Akt pathway is a potential new therapeutic approach to reduce loss of functional islet mass to bolster success in clinical islet transplantation.
胰岛在分离和移植过程中易受多种损伤。研究表明Akt在调节胰腺β细胞生长和存活中起作用。Akt的激活可维持Bad的磷酸化并阻止其与线粒体靶点结合，降低caspase-9活性，并阻止叉头转录因子（FKHR）的易位。辛伐他汀可在哺乳动物细胞中激活Akt；因此，我们研究了辛伐他汀对人胰岛（HPI）存活的作用。
用辛伐他汀处理HPI，同时使用和不使用磷酸肌醇3激酶抑制剂LY294002。用溴化乙锭-吖啶橙检测PI活力，并用定量分析检测细胞凋亡。通过蛋白质免疫印迹分析Akt、Bad、FKHR的磷酸化以及线粒体细胞色素释放。通过荧光分析评估caspase-9活性。在糖尿病NOD-SCID小鼠中，对经辛伐他汀处理后的少量HPI进行移植。
胰岛分离后早期显示Akt磷酸化（激活）水平较低。辛伐他汀处理后观察到Akt激活、胰岛活力增加、Bad磷酸化、细胞色素释放、caspase-9激活和FKHR易位减少，LY294002可逆转这些作用。在未用辛伐他汀处理的胰岛受体中，移植后无一只糖尿病得到逆转。相比之下，接受经辛伐他汀处理的胰岛的受体中，58%在移植后30天仍维持血糖正常。
用辛伐他汀靶向存活途径对分离的PI发挥细胞保护作用。激活Akt途径是一种潜在的新治疗方法，可减少功能性胰岛数量的损失，以提高临床胰岛移植的成功率。
