Effects of betel quid ingredients on human oral mucosal fibrosis and carcinogenesis

• Main Authors: Dean-Hwa Shieh, 謝典華
• Other Authors: Tien-Yu Shieh
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/9ths52

博士 === 高雄醫學大學 === 牙醫學研究所 === 91 === Oral submucous fibrosis (OSF) is a chronic inflammatory disease characterized by excessive deposition of fibrous contents in submucous layer of oral connective tissues that leads to limitation of mouth opening and increasing difficulty in speaking, chewing and swallowing. It results from an increased collagen synthesis, and a decreased collagenase activity. Collagen degradation is demonstrated via the intracellular phagocytosis route and by the extracellular collagenase-dependent route. The extracellular regulation involves the balance of matrix metalloproteinases and tissue inhibitor of metalloproteinases (TIMPs). Elevated TIMP-1 protein has been thought to be associated with oral fibrosis, however whether TIMP-1 expression in OSF is modulated at the transcriptional level is still unknown. OSF is an oral precancerous condition, and is associated with betel quid (BQ) chewing habits. The present study used arecoline, arecaidine and safrole, which were thought to be major toxic ingredients in BQ, as candidates to explore the role of TIMP-1 expression in OSF pathogenesis. The results indicated that TIMP-1 protein secretion by OSF fibroblasts was more than normal fibroblasts from the same patients, and the mRNA expression of TIMP-1 in OSF fibroblasts was higher than normal fibroblasts of the same patients. Arecoline and safrole significantly elevated TIMP-1 protein and mRNA expression. In Taiwan, 86% of betel quid chewers are also smokers. This study also used arecoline, safrole and nicotine, which are released in saliva during BQ chewing plus cigarette smoking, to evaluate the collagen phagocytosis by fibroblasts. The results demonstrated that collagen phagocytosis by fibroblasts from the normal region was higher than from the OSF region of the same patients. Collagen phagocytosis by fibroblasts exhibited a dose-dependent inhibition as the concentration of arecoline, safrole and nicotine increased. Besides, nicotine had a synergistic effect on arecoline- or safrole-inhibited collagen phagocytosis. Our results concluded that heterogeneity of fibroblasts existed in the same patients and increased mRNA expression of TIMP-1 in buccal mucosal fibroblasts by arecoline and safrole as a possible mechanism for oral submucous fibrosis. In addition, deficiency in collagen phagocytosis of fibroblasts might participate in the pathogenesis of oral submucous fibrosis. Arecoline, safrole and nicotine inhibit collagen phagocytosis by fibroblasts may induce OSF formation in Taiwan's patients. On the other hand, oral submucous fibrosis could progress to oral cancer, but the mechanism of malignant change was still unknown. The research would explore this oral carcinogenesis mechanism. Added different concentrations of arecoline and safrole to the cultured oral epithelial cells and fibroblasts, and detected the telomerase activity and DNA aneuploidy. Besides, this study also quantified the cytokeratin 19 levels of oral epithelial cells. The results depicted that arecoline and safrole inhibited the proliferation of oral epithelial cells and fibroblasts. There were significant differences in cytokeratin 19 levels between normal and OSF epithelial cells of the same patients, and the cytokeratin 19 levels augmented as arecoline and safrole concentrations increased. Telomerase activity was significant difference between normal and OSF fibroblasts of the same patients, and was significant difference between normal and OSF epithelial cells of the same patients. Arecoline and safrole showed to elevate telomerase activity. No significant difference of DNA aneuploidy was observed between normal and OSF cells of the same patients. Our results concluded that arecoline and safrole could induce tumor marker expression, and there might be individual variations. The possible carcinogenesis mechanism of OSF to oral cancer was that the oral epithelial cells and fibroblasts were stimulated by the betel quid contents at the same time, and oral fibroblasts secreted some substances to promote the malignant change of the oral epithelial cells. The present study also observed the expression of oncogenes and tumor supressor genes in oral carcinogensis. We collected the tissue specimens from normal oral mucosa, oral submucous fibrosis lesion and oral squamous cell carcinoma lesion of the same patients, and measured oncogene or tumor supressor gene expression by using DNA microarray. The results indicated that changes in gene expression of c-fos, c-myc and E-cadherin were the early events in oral carcinogenesis and followed by the changes in gene expression of EGFR, erbB-2, c-myc and p53. These findings need further issues to clarify the correlation between the changes of these genes and oral carcinogenesis.