TGF-β 誘導頰黏膜纖維母細胞 CTGF 表現機轉及以Curcumin 治療口腔黏膜下纖維化症之研究

Abstract

口腔黏膜下纖維化症 (Oral submucous fibrosis, 或簡稱OSF)，是一種慢性隱伏性的口腔黏膜纖維性病變。臨床上，本症的主要特徵是口腔黏膜變白、變僵硬。導致不能張口，說話、咀嚼及吞嚥發生困難。流行病學研究指出，嚼檳榔是口腔黏膜下纖維化症的最主要致病因子。除了檳榔萃取物本身以外，嚼檳榔不論是由於檳榔萃取物產生的細胞毒性或是由於檳榔的粗纖維造成的微小外傷都足以使結締組織中出現不等程度的慢性發炎細胞浸潤，釋放細胞激素，刺激纖維母細胞合成膠原蛋白。細胞激素中以轉型生長因子β (TGF-β) 及結締組織生長因子(CTGF)在OSF病變過程中扮演一個最重要角色。 CTGF是TGF-β的下游基因產物。 但是關於口腔黏膜中TGF-β1誘導CTGF表現的訊息傳遞路徑仍不清楚。 本研究發現在正常成人頰黏膜纖維母細胞中，TGF-β1 亦可以誘導CTGF的表現。且濃度愈高，誘導效應就愈明顯。 前處理 TGF-β1 receptor ALK5抑制劑 ( SB431542 )、ras-related small GTPase Rac1抑制劑 ( NSC23766 )、JNK抑制劑 ( SP600125 ) 可以幾乎完全阻斷TGF-β1誘導的CTGF表現。進一步研究確認， TGF-β 可促進Rac1 及 JNK的活化， 但抑制Rac1的活性不會對smad3的磷酸化造成影響。 因此，Rac-1並非透過smad3參與TGF-β1誘導CTGF 之表現。 TGF-β1可能透過 ALK5，Rac1及 JNK路徑誘導CTGF的表現。 另外我們亦發現薑黃素 (curcumin)可抑制口腔黏膜中TGF-β1誘導CTGF的表現 。冀望未來可以藉由抑制這些訊息傳遞路徑成員來達到抑制或治療口腔黏膜下纖維化症。

Oral submucous fibrosis (OSF) is a chronic oral mucosal disease characterized by epithelial atrophy and progressive accumulation of collagen fibers in the lamina propria and the underlying submucosal layer. It has been shown that TGF-β is the main trigger for both the increased collagen production and decreased degradation pathways in OSF. However, the pathogenesis of OSF is still not well understood. In fibroblasts, connective tissue growth factor (CTGF) is a downstream target of TGF-β and synergizes with TGF-β to promote a sustained fibrotic response in vivo. Neutralizing antibody to human CTGF inhibited TGF-β-induced fibrosis, suggesting that CTGF is essential for the fibrotic response to TGF-β. Suppression of CTGF might prevent a progressive fibrotic response to stimulation by TGF-β. Previously, we have showed the presence of CTGF in fibroblasts, epithelial and endothelial cells of OSF tissues. In this study, we showed that TGF-β stimulated CTGF synthesis in a dose- and time- dependent manner in buccal mucosal fibroblasts. Pretreatment with TGF-β1 receptor ALK5 inhibitor SB431542, ras-related small GTPase Rac1 inhibitor NSC23766, JNK inhibitor SP600125 and antioxidant N-acetyl-L-cysteine (NAC), but not ERK inhibitor PD98059, p38 MAPK inhibitor SB203580, significantly reduced TGF-β induced CTGF synthesis. Furthermore, curcumin almost completely inhibited TGF-β-induced CTGF synthesis and the inhibition is dose-dependent. These results indicated that arecoline induced CTGF synthesis was mediated by Rac 1, ROS, JNK pathways and curcumin could be a useful agent in controlling OSF.