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Mechanisms of thrombin-induced early growth response-1 expression in human buccal mucosal fibroblast
|Publication Year :||2013|
|Abstract:||口腔黏膜下纖維化症(Oral submucous fibrosis，OSF)是一種慢性發炎的口腔黏膜病變，臨床症狀為對刺激性食物耐受性低、口腔黏膜僵硬、張口困難、甚至影響吞嚥以及講話。近年來的研究普遍認為檳榔萃取物是口腔黏膜下纖維化症的主要致病因子，檳榔子的成分使得纖維母細胞增生以及使得過多的膠原蛋白堆積，而嚼食檳榔時檳榔的粗纖維在口腔中反覆摩擦造成微創傷，使得檳榔子內的成分直接接觸口腔組織，使組織呈現慢性發炎的狀態，而在先前的研究發現在BMFs(human buccal mucosal fibroblasts，BMFs)中thrombin可以誘導CTGF表現，但微創傷所引發的thrombin釋出所扮演的角色仍尚未清楚。許多研究指出Egr-1和纖維化疾病有關，在人類正常皮膚和肺纖維母細胞中，Egr-1可以調控col-1A2的啟動子表現，因此進一步想了解thrombin所誘導Egr-1表現在BMFs中的訊息傳遞路徑以及對於膠原蛋白的合成的影響為何。
本研究發現thrombin在BMFs中能誘發Egr-1蛋白質的表現，利用不同PARs促進劑確認thrombin是透過哪個受器誘發下游反應，結果顯示PAR1促進劑可以刺激BMFs誘導Egr-1表現，前處理抗氧化劑抑制劑NAC、ERK抑制劑PD98059、JNK抑制劑SP600125、Smad2/3抑制劑SIS3後，可以抑制thrombin所誘導的Egr-1表現，進一步利用Smad2/3 siRNA處理BMFs後，發現抑制thrombin誘導的Egr-1表現，因此可以推論Smad3在BMFs中可能參與thrombin誘導的Egr-1表現，亦發現前處理綠茶酚EGCG可抑制thrombin誘導的Egr-1表現，另外，thrombin可以促使col1A2基因的表現，Egr-1 siRNA會抑制thrombin所誘導col1A2基因表現，而經由Egr-1 siRNA和EGCG前處理BMFs會抑制由thrombin所誘導膠原蛋白的生成，可以推論Egr-1在纖維化疾病扮演重要角色，而EGCG有治療纖維化疾病的潛力，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 is an insidious, chronic inflammtory disease. Its clinical sign and symptoms include intolerance to spicy food, oral mucosa stiffness, inability to open the mouth, difficulty in swallowing and speech. Recent studies provide an evidence that areca nut is the major etiological factor. Areca alkaloids cause fibroblast proliferation and excessive and abnormal deposition of extracellular matrix in oral mucosa connective tissue. Microtrauma produced by the friction of fibers of areca nuts facilitate direct contact of that areca alkaloids to the oral mucosa result in chronic inflammation. Previous study showed that thrombin induced CTGF expression in human buccal mucosal fibroblasts (BMFs , but the role of thrombin released by microtrauma in oral mucosa is unclear. Recent studies indicated that Early-growth response-1(Egr-1) correlated with fibrogenic response. In human skin fibroblast and lung fibroblast, Egr-1 could cause up-regulation of Col-1A2 gene activity. Therefore, we want to further understand the signaling pathway of thrombin-induced Egr-1 and the role of Egr-1 on collagen synthesis in BMFs.
This study showed that thrombin increased Egr-1 synthesis. To identify which PARs involved in the signaling of thrombin-induced Egr-1, BMFs were treated with PARs agonist. This result showed PAR1 agonist could increase Egr-1 expression in BMFs. Pretreatment with different inhibitors in BMFs, ROS inhibitor NAC, ERK inhibitor PD98059, JNK inhibitor SP600125, Smad2/3 inhibitor SIS3 significantly reduced thrombin-induced Egr-1 expression. To confirm whether Smad2/3 participated in thrombin-induced Egr-1 pathway, Smad2/3 siRNA was used to knockdown Smad2/3. The results confirm that Smad2/3 may participate in thrombin-induced Egr-1 signaling. Furthermore, epigallocatechin-3-gallate (EGCG) dose-dependently reduced thrombin-induced Egr-1 expression. Thrombin increased Col1A2 gene expression, Egr-1 siRNA significantly reduced Col1A2 gene expression. Moreover, the effects of EGCG and Egr-1 siRNA on thrombin-stimulated collagen synthesis were directly evaluated by Sircol collagen assay. The result indicated that collagen expression was reduced in both treatments. In conclusion, our results indicate that thrombin-induced Egr-1 expression is mediated by ROS, ERK, JNK and Smad2/3 pathways in BMFs. The important role of Egr-1 in thrombin-induced collagen synthesis in BMFs is proved. EGCG may be provide a novel therapeutic agent for the prevention or treatment of OSF.
|Appears in Collections:||口腔生物科學研究所|
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