Regulation of interleukin-6 expression by arecoline in human buccal mucosal fibroblasts is related to intracellular glutathione levels

OBJECTIVES: Cytokines play an important role in regulating fibroblast function and is likely to play a key role in regulating the initiation and progression of scarring in any fibrotic disease. Interleukin-6 (IL-6) has been implicated in the development of a variety of fibrotic diseases. The aim of this study was to compare IL-6 expression in fibroblasts cultured from normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induce IL-6 expression. METHODS: mRNA level of IL-6 in fibroblasts from OSF was compared with normal buccal mucosa. The effects of arecoline, the major areca nut alkaloid, on IL-6 expression in normal human buccal mucosa fibroblasts (BMFs) were measured in vitro. mRNA was quantified with AlphaImager 2000. To determine whether glutathione (GSH) levels were important in the induction of IL-6 by arecoline, we pretreated cells with 2-oxothiazolidine-4-carboxylic acid (OTZ) to boost GSH levels or with buthionine sulfoximine (BSO) to deplete GSH. RESULTS: Fibroblasts derived from OSF exhibited higher IL-6 gene expression than BMF in mRNA levels (P < 0.05). The exposure of quiescent BMF to arecoline resulted in the elevation of IL-6 mRNA expression in a dose-dependent manner (P < 0.05). IL-6 gene regulated by arecoline correlated with intracellular GSH levels in BMF. Arecoline at a concentration of 129 muM induced about 2.7-fold IL-6 mRNA levels over the 6-h incubation period. However, BSO enhanced the IL-6 mRNA levels by 3.9-fold (P < 0.05). In addition, OTZ was found to marginally reduce the arecoline-induced IL-6 expression by about 1.7-fold (P < 0.05). CONCLUSIONS: Taken together, these results suggest that IL-6 expression is significantly upregulated in OSF fibroblasts in areca quid chewers and arecoline may be responsible for the enhanced IL-6 expression. In addition, the regulation of IL-6 expression induced by arecoline is critically dependent on the intracellular GSH concentrations.     

槟榔碱对颊黏膜成纤维细胞增殖及迁移的影响

目的通过观察槟榔碱诱发人颊黏膜成纤维细胞增殖、迁移能力以及微丝形态的改变,探讨槟榔碱在口腔黏膜下纤维性变(OSF)的致病途径。方法使用甲噻唑四唑氮(MTT)比色法、划痕法、激光共聚焦扫描显微镜检测不同浓度槟榔碱(5、10、20、40、80μg·mL^-1)对成纤维细胞增殖、迁移、微丝形态的影响。结果5、10、20μg·mL^-1的槟榔碱可轻微提高颊黏膜成纤维细胞增殖迁移能力及微丝聚合(P<0.05);40、80μg·mL^-1的槟榔碱抑制颊黏膜成纤维细胞增殖、迁移能力及微丝解聚(P<0.05)。结论槟榔碱改变颊黏膜成纤维细胞增殖、迁移能力及微丝形态分布,可能在口腔黏膜下纤维性变病理过程中起着重要的作用。     

槟榔碱及机械刺激构建大鼠口腔黏膜下纤维化模型

目的 利用槟榔碱和机械刺激构建Sprague-Dawley（SD）大鼠口腔黏膜下纤维化（OSF）模型。方法 采用两因素析因实验设计将48只大鼠分为8个组,每组6只。分别用不同浓度（0、0.5、2、8 mg·mL ^-1）槟榔碱涂擦及机械刺激 (有或无毛刷涂擦)。处理16周后测量开口度;取局部颊黏膜行苏木精-伊红（HE）染色观察病理变化;并检测组织内Ⅲ型胶原、转化生长因子-β1（TGF-β1）和γ干扰素（IFN-γ）的表达情况。结果 2和8 mg·mL ^-1（中、高）浓度槟榔碱处理16周,颊黏膜出现了典型的OSF病理特征;开口度显著减小并且Ⅲ型胶原、TGF-β1表达显著增加（P<0.05）。机械刺激虽可导致黏膜Ⅲ型胶原、TGF-β1和IFN-γ表达增高（P<0.05）,但无病理学改变,开口度改变不显著。结论 中、高浓度槟榔碱有致OSF作用;机械刺激无法导致大鼠OSF的发生。     

Elevated transglutaminase-2 expression mediates fibrosis in areca quid chewing-associated oral submucocal fibrosis via reactive oxygen species generation

Objectives

Transglutaminase-2 (TGM-2) protein is involved in the cross-linking of matrix proteins resulting in several fibrotic disorders and can be induced by reactive oxygen species (ROS). Little is known about its role in the development of oral submucocal fibrosis (OSF). Hence, we hypothesize that TGM-2 may have a role in the pathogenesis of areca quid chewing-associated OSF and arecoline, a major areca nut alkaloid, could regulate TGM-2 via ROS generation.

Materials

Forty OSF specimens from areca quid chewing-associated OSF and ten normal buccal mucosa biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The expression of TGM-2 from fibroblasts cultured from OSF and normal buccal mucosa was evaluated by Western blot. The effect of arecoline on normal buccal mucosa fibroblasts (BMFs) was used to elucidate whether TGM-2 expression could be affected by arecoline by using 2′, 7′-dichlorofluorescein diacetate assay and Western blot. In addition, glutathione precursor N-acetyl-l-cysteine (NAC) and epigallocatechin-3 gallate (EGCG) were added to find the possible regulatory mechanisms.

Results

TGM-2 expression was significantly higher in OSF specimens than normal specimens (p < 0.05). Fibroblasts derived from OSF were found to exhibit higher TGM-2 expression than BMFs in protein levels (p < 0.05). Arecoline significantly upregulated the intracellular ROS generation in a dose-dependent manner (p < 0.05). TGM-2 protein induced by arecoline was found in BMFs in a dose-dependent manner (p < 0.05). Treatment with NAC and EGCG markedly inhibited TGM-2 expression induced by arecoline (p < 0.05).

Conclusions

Our results suggest that TGM-2 expression is significantly upregulated in OSF tissues from areca quid chewers. Arecoline-upregulated TGM-2 expression may be mediated by ROS generation.

Clinical relevance

TGM-2 protein is upregulated in areca quid chewing-associated OSF. Using this in vitro model, antioxidants could inhibit arecoline-upregulated TGM-2 expression. NAC and EGCG may serve as a useful agent in controlling OSF.

     

Increased plasminogen activator inhibitor-1/tissue type plasminogen activator ratio in oral submucous fibrosis

OBJECTIVE: Plasminogen activators and their inhibitors are thought to be key participants in the balance of proteolytic and antiproteolytic activities that regulate extracellular matrix (ECM) turnover. However, little is known about the expression of plasminogen/plasmin system at the site of oral submucous fibrosis (OSF). METHODS: We compared the activities of tissue type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) between fibroblasts derived from normal buccal mucosa and OSF by using an enzyme-linked immunosorbent assay. Furthermore, arecoline, a major areca nut alkaloid, was challenged with normal buccal mucosal fibroblasts (BMFs) to elucidate whether the activities of t-PA and PAI-1 could be affected by arecoline. RESULTS: Both t-PA and PAI-1 were found to be increased in OSF than in BMFs (P < 0.01). In addition, there was a statistically significant difference in PAI-1/t-PA ratio between OSF and BMF (P < 0.01). The addition of arecoline upregulated not only PAI-1, but also t-PA in BMFs (P < 0.05). In addition, the ratio between PAI-1 and t-PA was found to be significantly increased by a linear regression assay (P < 0.01). CONCLUSION: These results suggest that OSF caused by areca quid chewing may be the result of an imbalance in the plasminogen/plasmin system, the net result of which is increased deposition of ECM.     

核受体共激活因子7在槟榔碱诱导的上皮间充质转化中的生物学功能

目的研究核受体共激活因子7(nuclear receptor coactivator 7,NCOA7)在口腔黏膜下纤维性变(OSF)中的表达及意义,并探讨其在人口腔角质细胞株HOKs间充质转化过程中的作用。方法收集OSF组织30例及正常口腔黏膜组织15例,采用免疫印迹法检测NCOA7、上皮间充质转化相关标记物在OSF组织及正常黏膜组织中蛋白水平的表达情况;以Western blot法检测槟榔碱刺激后HOKs中NCOA7、上皮及间充质标记物的蛋白水平变化。结果 NCOA7在30例OSF组织高表达(P<0.05);同时在细胞基底层出现间充质标记物的阳性表达。NCOA7在槟榔碱刺激的HOKs中高表达,且具有槟榔碱浓度依赖性(P=0.004 3);随着槟榔碱浓度的升高,上皮标志物表达逐渐下调,间充质标记物表达逐渐升高。结论口腔黏膜下纤维性变组织中高表达的NCOA7,可能参与调控上皮细胞间充质转化过程,进一步促进纤维化进程。     

槟榔碱及机械刺激构建大鼠口腔黏膜下纤维化模型

目的 利用槟榔碱和机械刺激构建Sprague-Dawley（SD）大鼠口腔黏膜下纤维化（OSF）模型。方法 采用两因素析因实验设计将48只大鼠分为8个组,每组6只。分别用不同浓度（0、0.5、2、8 mg·mL ^-1）槟榔碱涂擦及机械刺激 (有或无毛刷涂擦)。处理16周后测量开口度;取局部颊黏膜行苏木精-伊红（HE）染色观察病理变化;并检测组织内Ⅲ型胶原、转化生长因子-β1（TGF-β1）和γ干扰素（IFN-γ）的表达情况。结果 2和8 mg·mL ^-1（中、高）浓度槟榔碱处理16周,颊黏膜出现了典型的OSF病理特征;开口度显著减小并且Ⅲ型胶原、TGF-β1表达显著增加（P<0.05）。机械刺激虽可导致黏膜Ⅲ型胶原、TGF-β1和IFN-γ表达增高（P<0.05）,但无病理学改变,开口度改变不显著。结论 中、高浓度槟榔碱有致OSF作用;机械刺激无法导致大鼠OSF的发生。     

Arecoline and oral keratinocytes may affect the collagen metabolism of fibroblasts

Background:  The characteristic of oral submucous fibrosis (OSF) is related with the disturbance of synthesis and degradation of extracellular matrix. Arecoline, the areca nut (betel nut) component of betel quid, plays a major role in pathogenesis of OSF. But the exact mechanism how arecoline influences the collagen metabolism is unclear.
Methods:  Oral keratinocytes and fibroblasts were cocultured and keratinocytes were pre-treated by arecoline. Fibroblasts alone, fibroblasts stimulated by arecoline, fibroblasts cocultured with keratinocytes and fibroblasts cocultured with keratinocyte pre-treated by arecoline were included as the four groups in the present study. The concentration of collagen, the content and activity of matrix metalloproteinase (MMP) and the concentration of tissue inhibitor of metalloproteinase (TIMP) were assessed.
Results:  The collagen production of fibroblasts decreased when cocultured with keratinocytes; when cocultured with keratinocytes pre-treated by arecoline, fibroblasts produced more soluble collagen than non-pretreated coculture group. MMP-9 was produced only in coculture groups. There was no significant difference in the two coculture groups. The activation ratio of pro-MMP-2 in arecoline pre-treated keratinocytes-fibroblasts coculture group was significantly higher than that of non-coculture groups, but no significant difference existed in the two coculture groups. TIMP-1 produced by arecoline pre-treated keratinocytes-fibroblasts coculture group was significantly higher than those by the other three groups.
Conclusion:  TIMP-1 and the interaction of oral keratinocytes and fibroblasts play important role in pathogenesis of OSF.     

Effects of arecoline, safrole, and nicotine on collagen phagocytosis by human buccal mucosal fibroblasts as a possible mechanism for oral submucous fibrosis in Taiwan

BACKGROUND: Oral submucous fibrosis (OSF) is associated with the betel quid chewing habit, and 86% of betel quid chewers in Taiwan are also smokers. Arecoline and safrole are major principles in the composition of betel quid, and nicotine is the main toxic ingredient of cigarettes. METHODS: To explore the pathogenesis of OSF, flow cytometry was used to compare collagen phagocytosis by fibroblasts from the normal and the OSF region of the same 15 OSF patients. RESULTS: The results indicated that heterogeneity of fibroblasts existed because collagen phagocytosis by fibroblasts from the normal region was higher than from the OSF region in the same patient. The percentage of phagocytic cells was significantly inhibited by 10, 25 and 50 microg/ml arecoline, safrole and nicotine in normal fibroblast cultures, respectively, and the percentage of phagocytic cells was significantly reduced by 25, 25 and 50 microg/ml arecoline, safrole and nicotine in OSF fibroblast cultures, respectively. Collagen phagocytosis by fibroblasts exhibited prominent 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. CONCLUSIONS: The present study concludes that even in the same person, the collagen phagocytosis by fibroblasts is different between normal and OSF region. The deficiency in collagen phagocytosis by fibroblasts of the lesion might participate in the pathogenesis of OSF. Arecoline, safrole and nicotine, which are released in saliva during BQ chewing plus cigarette smoking, inhibit collagen phagocytosis by fibroblasts in a dose-dependent manner and may induce OSF formation in Taiwan's patients.     

CXCR4受体在口腔鳞癌细胞系中的表达及对细胞增殖和迁徙的影响

目的:观察口腔鳞癌细胞系(OSCC)中趋化因子受体CXCR4的表达,检测SDF-1/CXCR4反应轴对OSCC增殖的作用,SDF-1对CXCR4阳性肿瘤细胞的趋化作用,探讨CXCR4受体在OSCC中的功能及活性。方法:细胞涂片免疫荧光法检测CXCR4蛋白在OSCC细胞系的表达,流式细胞仪直接免疫荧光法检测OSCC细胞系中CXCR4蛋白的表达量,MTT法检测细胞的增殖能力,体外迁徙实验检测SDF-1/CXCR4反应轴对OSCC细胞的趋化作用。采用SPSS10.0软件包进行ANOVA方差分析和t检验。结果:CXCR4蛋白在OSCC细胞系呈阳性表达,表达率为68.62%。OSCC细胞在SDF-l作用下,其增殖反应显著增强,CXCR4抗体可显著抑制肿瘤细胞的增殖,SDF-1可显著诱导OSCC细胞的移动。结论:CXCR4受体与OSCC细胞增殖、迁徙功能有一定关系。     

槟榔碱预处理后的Hacat细胞及人口腔黏膜成纤维细胞中AngⅡ及AT1R蛋白的表达研究

目的:通过检测血管紧张素Ⅱ(AngⅡ)及血管紧张素Ⅱ-1型受体(AT1R)在不同浓度槟榔碱预处理后的Hacat细胞及人口腔黏膜成纤维细胞(OMFB)中的表达与分布情况,了解槟榔碱对这两种细胞表达AngⅡ及AT1R的影响,探讨口腔黏膜下纤维性变(OSF)可能的发病机制。方法:采用免疫细胞化学SABC法,分别测定AngⅡ及AT1R兔抗人多克隆抗体在Hacat细胞和OMFB及分别在20μg/mL、40μg/mL、80μg/mL槟榔碱预处理后的这两种细胞中的表达与分布情况。结果:①0～80μg/mL槟榔碱预处理后Hacat细胞中AngⅡ蛋白均有表达,80μg/mL预处理组阳性细胞数高于其余3组,差别有统计学意义(P<0.01)。②对照组及20μg/mL槟榔碱干预组Hacat细胞中未见明显AT1R蛋白表达,40μg/mL槟榔碱干预组细胞中AT1R蛋白弱阳性表达,80μg/mL槟榔碱干预组细胞AT1R蛋白呈阳性表达,表达有显著性差异(P<0.01)。结论:一定浓度的槟榔碱可以诱导Hacat细胞中AngⅡ及AT1R蛋白的表达升高,且二者的表达多位于发生了形态学变化的细胞上,推测AngⅡ及AT1R可能参与了槟榔碱的致OSF进程。     

Therapeutic Interventions in Oral Submucous Fibrosis: An Experimental and Clinical Study

Introduction

Oral submucous fibrosis (OSF) is a chronic debilitating disease and premalignant condition of the oral cavity and is a serious public health issue in India and many parts of the world. The treatment is still elusive and empirical because of poorly understood etiopathogenesis, which is believed to be multifactorial including areca nut chewing, ingestion of chillies, genetic and immunologic processes, nutritional deficiencies, and many others. The present investigations was focused to understand the possible therapeutic interventions of anti-OSF agents in arecoline induced experimental in vitro model of OSF and clinical application of these anti-OSF agents in the restoration of various grade of the disease.

Materials and Methods

The 127 subjects were selected from patients who visited the OPD of Department of Oral and Maxillofacial Surgery, Faculty of Dental Sciences, K.G. Medical University, Lucknow. Further the subjects were divided in two groups on the basis of clinical examination. Group-1 subjects showed presence of fibrosis bands in the labial and/or buccal mucosa, loss of elasticity, difficulty to open the mouth and had a habit chewing areca-nut in some form. Group-2 subjects had no habit of chewing areca-nut, were apparently healthy with no mucosal disorder. The samples were collected and were immediately transported to Indian Institute of Toxicology Research, Lucknow, for isolation and cultivation of primary cultures of mucosal fibroblast cells. Then isolation and cultivation of oral mucosal fibroblast, identification of non-cytotoxic doses of arecoline, real time PCR, immunocytochemistry, cytokine determination in culture cells, western blot analyses, functional activity of collagenase, lysyl oxidase enzyme activity, collagen beads assay, cyclooxygenase (COX-2) expression analysis was done.

Results and Conclusions

This study, shows that the reduction of phagocytic cells was strongly related to the arecoline levels in fibroblast culture when we exposed arecoline to normal oral mucosal cells (NOMC) and cells from OSF patient. An enhancement of phagocytic cells was observed following the pre exposure of cells to 1 μM dexamethasone, a glucocorticoids, In this study, histologic evidence is presented which supports the finding that COX-2 expression is upregulated in OSF specimens compared to normal oral submucosal cells. Strong immunostaining for COX-2 was detected in arecoline exposed NOMC and cells from OSF patient. Areca nut extract up-regulates prostaglandin production, cyclooxygenase-2 mRNA and protein expression of human oral keratinocytes. The number of phagocytic cells and phagocytic activity in cultured human oral fibroblasts from OSF site was lower than the fibroblasts from the normal regions of the same person.     

Arecoline induced cell cycle arrest, apoptosis, and cytotoxicity to human endothelial cells

Betel quid (BQ) chewing is a common oral habit in South Asia and Taiwan. BQ consumption may increase the risk of oral squamous cell carcinoma (OSCC), oral submucous fibrosis (OSF), and periodontitis as well as systemic diseases (atherosclerosis, hypertension, etc.). However, little is known about the toxic effect of BQ components on endothelial cells that play important roles for angiogenesis, carcinogenesis, tissue fibrosis, and cardiovascular diseases. EAhy 926 (EAHY) endothelial cells were exposed to arecoline, a major BQ alkaloid, for various time periods. Cytotoxicity was estimated by 3-(4, 5- dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assay. The cell cycle distribution of EAHY cells residing in sub-G0/G1, G0/G1, S-, and G2/M phases was analyzed by propidium iodide staining of cellular DNA content and flow cytometry. Some EAHY cells retracted, became round-shaped in appearance, and even detached from the culture plate after exposure to higher concentrations of arecoline (> 0.4 mM). At concentrations of 0.4 and 0.8 mM, arecoline induced significant cytotoxicity to EAHY cells. At similar concentrations, arecoline induced G2/M cell cycle arrest and increased sub-G0/G1 population, a hallmark of apoptosis. Interestingly, prolonged exposure to arecoline (0.1 mM) for 12 and 21 days significantly suppressed the proliferation of EAHY cells, whereas EAHY cells showed adaptation and survived when exposed to 0.05 mM arecoline. These results suggest that BQ components may contribute to the pathogenesis of OSF and BQ chewing-related cardiovascular diseases via toxicity to oral or systemic endothelial cells, leading to impairment of vascular function. During BQ chewing, endothelial damage may be induced by areca nut components and associate with the pathogenesis of OSF, periodontitis, and cardiovascular diseases.     

槟榔碱对口腔角质形成细胞端粒酶逆转录酶表达的影响

目的：观察槟榔碱对人口腔角质形成细胞（KC）端粒酶逆转录酶（hTERT）mRNA及蛋白表达的影响，进一步探讨hTERT在口腔黏膜下纤维性变（OSF）癌变过程中的作用机制。方法：体外培养正常口腔黏膜的上皮细胞，将实验细胞分为0．03、0．06、0．09g／L槟榔碱组、空白对照组。采用Western印迹法和RT-PCR方法观察槟榔碱对KC hTERT mRNA及蛋白表达的影响。结果：槟榔碱能呈剂量依赖性增加KC hTERT mRNA及蛋白表达，0．03、0．06、0．09g／L槟榔碱组hTERT mRNA及蛋白表达均高于空白对照组（P〈0．05）。结论：槟榔碱对KChTERT mRNA与蛋白表达有明显诱导作用，且在一定范围内呈剂量依赖关系，槟榔碱诱导KChTERT过度表达可能在OSF癌变过程中起重要作用。     

An in-vitro comparison of human fibroblasts from normal and oral submucous fibrosis tissue

Fibroblasts cultured in vitro from normal buccal tissue and from tissue from oral submucous fibrosis (OSF) associated with betel-nut chewing showed no significant difference in their rates of proliferation in culture, nor in the rate at which they hydrolysed the betel nut alkaloid arecoline to arecaidine. Basal rates of collagen synthesis were slightly higher in the OSF cells but, on addition of arecoline, the rate of collagen synthesis in normal and OSF cells was stimulated to the same level.