Tumor necrosis factor-alpha induces VCAM-1-mediated inflammation via c-Src-dependent transactivation of EGF receptors in human cardiac fibroblasts

Background: Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine and elevated in the regions of tissue injury and inflammatory diseases. The deleterious effects of TNF-alpha on fibroblasts may aggravate heart inflammation mediated through the up-regulation of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1). However, the mechanisms underlying TNF-alpha-induced VCAM-1 expression in cardiac fibroblasts remain unknown. This study aimed to investigate the roles of TNF-alpha in VCAM-1 expression and its effects on human cardiac fibroblasts (HCFs). Results: The primary culture HCFs were used in this study. The results obtained with Western blotting, real time-quantitative PCR, and promoter activity analyses showed that TNF-alpha-induced VCAM-1 expression was mediated through TNF receptor (TNFR) 1-dependent gene up-regulation. Activation of TNFR1 by TNF-alpha transactivated c-Src-dependent EGF receptor (EGFR) linking to PI3K/Akt cascade, and then led to transcriptional activity of NF-kappa B. Moreover, the results of promoter reporter assay demonstrated that the phosphorylated p65 NF-kappa B turned on VCAM-1 gene expression. Subsequently, up-regulation of VCAM-1 promoted monocytes adhesion to HCFs challenged with TNF-a determined by cell adhesion assay. Conclusions: Taken together, these results indicate that in HCFs, activation of NF-kappa B by c-Src-mediated transactivation of EGFR/PI3K/Akt cascade is required for TNF-alpha-induced VCAM-1 expression. Finally, increased VCAM-1 enhances monocytes adhering to HCFs challenged with TNF-a. Understanding the mechanisms of VCAM-1 up-regulated by TNF-alpha on HCFs may provide rationally therapeutic interventions for heart injury or inflammatory diseases.