Suppression of the c-Jun N-terminal kinase pathway by 17β-estradiol can preserve human islet functional mass from proinflammatory cytokine-induced destruction

Background. The c-Jun N-terminal kinase (JNK) activation occurs after islet isolation, oxidative stress, and proinflammatory cytokine (PIC) exposure to beta-cells. Previous studies demonstrated that 17beta-estradiol modulates the activity of JNK; therefore we assessed the effects of 17beta-estradiol on JNK activation on islet survival and function after transplantation. Methods. Isolated human pancreatic islets were incubated with PIC and 17beta-estradiol. Viability was analyzed by a colorimetric assay, islet mass by DNA content, JNK activity by Western. blots, AP-1 nuclear activity with a promoter-Luciferase AP-1 responsive construct, and c-Fos, Jun-D, and ATF-2 nuclear activities by an enzyme-linked immunosorbent assay. Islet functionality was evaluated after transplantation in, streptozotocin-induced diabetic NOD-SCID mice. Results. The 17beta-estradiol enhanced islet viability and islet mass after exposure to PIC. A significant reduction in JNK activation occurred in islets treated with 17beta-estradiol, compared with controls, an effect partially dependent on estrogen receptors. The 17beta-estradiol induced a significant reduction in nuclear AP-1, c-fos, Jun-D, and ATF-2 activities. Animals that received 17beta-estradiol-treated islets had better islet functionality compared with saline solution-treated controls. Conclusions. The 17beta-estradiol improved isolated human pancreatic islets survival after PIC exposure by inhibition, of JNK. These effects were associated with reduction in JNK targets, including the nuclear activities of transcription factors AP-1, c-Jun, c-Fos, Jun-D and ATF-2, involved in apoptosis in beta-cells. The 17beta-estradiol therapy may improve the results in clinical transplantation.