Role of Histone Deacetylase SIRT1 in Arecoline-Induced Cytotoxicity in Clone-9 cells
| Autor: | Chi-Yao Huang, 黃紀堯 |
|---|---|
| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 Betel quid chewing not only led to oral, pharyngeal and esophageal cancers, but also closely associated with liver cirrhosis and hepatocellular carcinoma (HCC). Arecoline is the most abundant alkaloid in betel quid and is cytotoxic, genotoxic, mutagenic and tumorigenic to various kind of cells. Previous studies show that upregulate of Sirtuin1 (SIRT1) is essential for tumor cell growth in HCC cell line. SIRT1 belongs to the class III histone deacetylase that utilizes NAD+ as a cofactor for their function, it deacetylates histone proteins to silence gene expression, and also deacetylates nonhistone proteins to change their function. SIRT1 plays a critical role in regulating cell growth and apoptosis. Previous studies in our laboratory indicated that arecoline inhibited cell growth and induced apoptosis through different signaling pathway in the normal rat liver cell line (Clone-9). Therefore, we studied the role of SIRT1 in arecoline-inhibited cell growth and -induced apoptosis in Clone-9 cells. In addition, we studied whether arecoline led to other cytotoxicity in Clone-9 cells. We found that arecoline upregulated SIRT1 protein and mRNA expression. Arecoline also enhanced SIRT1 promoter activity. SIRT1 inhibitor nicotinamide (NAM) attenuated arecoline-induced anti-proliferation of Clone-9 cells. The promoter of Cyclin D1 is occupied by the corepressor complex such as HDAC and histone methyltransferase (HMT) Suv39H1 to inhibited Cyclin D1 transcription. We found that arecoline decreased both Cyclin D1 and Suv39H1 protein level, and NAM attenuated arecoline-induced Cyclin D1 down-regulation. However, Suv39H1 inhibitor chaetocin (CHN) increased SIRT1 protein expression rather than inhibited Cyclin D1 protein expression. Thus, arecoline increased SIRT1 via decreased Suv39H1, resulted in inhibition of Cyclin D1, and cell growth inhibition. Previous studies in our laboratory indicated that arecoline-induced apoptosis through ATM/ATR-p53 pathway. In this study, we found that NAM did not affect arecoline-induced acetyl-p53 but attenuated arecoline-induced TGF-β. Thus, SIRT1 mediated arecoline-induced apoptosis through TGF-β instead of p53. Finally, we also found that the inflammation marker cyclooxygenase-2 (Cox-2) protein expression was upregulated and E-cadherin protein was downregulated after arecoline treatment. In conclusion, arecoline inhibits cell growth and induces apoptosis via increases SIRT1 protein expression. In addition, arecoline lead to hepatocyte inflammation and epithelial-mesenchymal transition (EMT). |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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