| Summary: | 碩士 === 長庚大學 === 生物醫學研究所 === 101 === Several factors have been shown to trigger the mechanisms for the pathogenesis of heart diseases. Although these factors concerning about the increased incidence of inflammatory responses in heart diseases are well known, the intracellular signaling mechanisms regulated by these factors are obscure. Several studies have demonstrated that the recruitment and adhesion of circulating polymorphonuclear cells (PMNs) to cardiac fibroblast (CF) play pivotal roles in the initiation and progression of heart dysfunction. This event is mediated through the up-regulation of adhesive molecules on CF and PMNs and then leads to heart lesion. Adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) is a inducible cell surface glycoprotein on several cell types and regulates several inflammatory and immune responses. Thus, up-regulation of VCAM-1 by pro-inflammatory mediators that govern PMN adhesion to CF may occur and contribute to the damage of these cells seen in inflammatory responses of heart diseases. During these interactions, PMNs and CF may undergo cytokine-specific up-regulation of adhesion molecules. Moreover, elevated levels of pro-inflammatory mediators including TNF- in heart have been detected in patients with heart failure. The relationship between TNF-alpha-induced adhesion molecules and heart failure remain unclear. Therefore, in this study, we investigated the mechanisms underlying the intracellular signal involved in TNF-alpha-induced VCAM-1 expression in human cardiac fibroblast (HCFs). The data obtained with Western blotting, RT-PCR, real time-PCR, and monocyte adhesion analyses showed that TNF-alpha-induced VCAM-1 expression was mediated through a TNF receptor-dependent transcriptional activation. Moreover, TNF-alpha-induced VCAM-1 expression was mediated through c-Src-dependent transactivation of receptor tyrosine kinases (RTKs: EGFR, PI3K/Akt), phosphorylation of PKCs, and phosphorylation of MAPKs (e.g. p38 MAPK, JNK1/2, and p42/p44 MAPK), and then activated transcription factor NF-kB or AP-1 respectively. In addition, we also found the activity of NADPH oxidase and production of ROS would regulate the expression of VCAM-1. the data of VCAM-1 promoter assay demonstrated that TNF-alpha stimulated VCAM-1 promoter activation and gene transcription via activation of NF-kB and AP-1. Eventually, up-regulation of VCAM-1 by TNF-alpha promoted THP-1 monocyte adhesion to HCFs. These results provided a new insight into the mechanisms of TNF-alpha action, supporting the hypothesis that cytokines may contribute to leukocytes/HCFs interaction and promote inflammatory responses involved in the development of heart dysfunction.
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