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

Abstract

Somatostatin (SST) has been proven to have cardioprotective effects, but its effects on endothelial cells has not yet well studied. 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)-α-induced endothelial nuclear factor (NF)-κB activation with subsequent interleukin (IL)-6 and IL-8 release. 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-κB activation. The effects of pretreatment with octreotide, an SST analog, and/or N -acetyl-cysteine (NAC) were tested. TNF-α stimulated IL-6 and IL-8 production from HUVECs. SST PC using octreotide at concentrations >10 −8 M attenuated TNF-α-induced IL-6 and IL-8 release, but NAC did not inhibit SST-treated endothelial cells stimulated by TNF-α. EMSA revealed that TNF-α treatment was associated with activation of NF-κB, which could be inhibited by SST PC. By contrast, wortmannin and AG-490 reversed the inhibitory effects of octreotide on TNF-α-induced NF-κB activation, but neither had any definite effects on TNF-α-induced NF-κB activation in the absence of octreotide. Western blots confirmed that octreotide modulated Iκκ at 10 −8 M. SST PC modulates Iκκ in a PI3K- and JAK-2-dependent pathway, which in turn attenuates activation of NF-κB induced by TNF-α in HUVECs.