Role of Janus-associated kinases in somatostatin analog preconditioning of human umbilical-vein endothelial cells

Background: Somatostatin (SST) has been proven to have cardioprotective effects, but its effects on endothelial cells has not yet well studied. Aim: To confirm the phenomenon of SST-induced preconditioning (PC) and the cellular mechanisms involved, we designed an in vitro study to investigate the effects of SST analogs on tumor necrosis factor (TNF)-alpha-induced endothelial nuclear factor (NF)-kappa B activation with subsequent interleukin (IL)-6 and IL-8 release. Methods: Experiments were performed on primary human umbilical-vein endothelial cells (HUVECs). IL-6 and IL-8 were measured using commercial enzyme-linked immunosorbent assay kits. An electrophoretic mobility shift assay (EMSA) was used to demonstrate NF-kappa B activation. The effects of pretreatment with octreotide, an SST analog, and/or N-acetyl-cysteine (NAC) were tested. Results: TNF-alpha stimulated IL-6 and IL-8 production from HUVECs. SST PC using octreotide at concentrations >10(-8) M attenuated TNF-alpha-induced IL-6 and IL-8 release, but NAC did not inhibit SST-treated endothelial cells stimulated by TNF-alpha. EMSA revealed that TNF-alpha treatment was associated with activation of NF-kappa B, which could be inhibited by SST PC. By contrast, wortmannin and AG-490 reversed the inhibitory effects of octreotide on TNF-alpha-induced NF-kappa B activation, but neither had any definite effects on TNF-a-induced NF-kB activation in the absence of octreotide. Western blots confirmed that octreotide modulated I kappa kappa at 10(-8) M. Conclusion: SST PC modulates Ikk in a PI3K-and JAK-2-dependent pathway, which in turn attenuates activation of NF-kappa B induced by TNF-alpha in HUVECs. Copyright (C) 2011, Taiwan Society of Emergency Medicine. Published by Elsevier Taiwan LLC. All rights reserved.