TNF-α induces Lnk expression through PI3K-dependent signaling pathway in human umbilical vein endothelial cells

Background. A better understanding of activation process of endothelial cells (ECs) might reveal new ways of controlling inflammation. Adaptor proteins play crucial roles in ECs activation. Lnk is a newly discovered adaptor protein that has been proposed as a negative regulator of cytokine signaling. While limited information is available about Lnk in human ECs. This study was conducted to investigate the effect of TNF-alpha on Lnk expression in ECs and to identify the signal transduction pathway that is associated with Lnk regulation. Materials and methods. Primary human umbilical vein endothelial cells (HUVECs) were cultured with designated doses of TNF-a and harvested at designated time points. Then Lnk mRNA and protein were detected using real-time polymerase chain reaction, immunoprecipitation and Western blot analysis, respectively. Results. The data demonstrated that Lnk mRNA and protein expression are induced significantly (P < 0.05) by TNF-alpha in a dose- and time-dependent manner. This inductive effect was abolished while phosphatidylinositol 3-kinase (PI3K) pathway was blocked by the PI3K inhibitor LY294002 and Wortmannin. Conclusion. These results suggest that TNF-a induces Lnk expression through PI3K-dependent signaling pathway in HUVEC. This may indicate a role for this new adaptor protein in the regulation of TNF-alpha-induced ECs activation. (c) 2006 Elsevier Inc. All rights reserved.