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。     

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。     

Stimulation of human buccal mucosa fibroblasts in vitro by betel-nut alkaloids

Oral submucous fibrosis (OSF) is characterized by excessive collagen production by mucosal fibroblasts and is associated with the habitual chewing of betel-nuts (Areca catechu); nut extracts stimulate fibroblast activity in vitro. The metabolism of arecoline, the major alkaloid in the nut, by human buccal mucosa fibroblasts in vitro was investigated; alkaloid metabolites extracted from culture media were analysed by gas chromatography and thin-layer chromatography. [3H]-arecoline was metabolized predominantly to [3H]-arecaidine and this was accompanied by a concentration-dependent stimulation of collagen synthesis and cell proliferation. Arecaidine was a more potent stimulator than arecoline. The rate of hydrolysis of a series of synthetic arecaidine esters (methyl, ethyl, butyl, propyl and pentyl) by fibroblasts was closely correlated with the extent of stimulation of collagen synthesis. Thus fibroblasts are responsive to the major metabolite of arecoline and hydrolysis of the ester group may be necessary for this action. Exposure of buccal mucosa fibroblasts to these alkaloids in vivo may contribute to the accumulation of collagen in OSF.     

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。     

Observations on the effect of areca nut extracts on oral fibroblast proliferation

The effects of aqueous extracts of raw, baked and boiled areca nuts were tested on cultured human buccal mucosa fibroblasts. Cells were exposed to extract concentrations of 0, 50, 100, 150, 300 and 500 μg/ml. The arecoline and arecaidine content was determined in the extracts with HPLC and raw nut contained 5.5% in m. baked nut 6.6% mm and boiled nut 7.1% m/m. Extract concentrations of 50 to 150 μg/ml inhibited cell growth in a concentration-dependent manner but did not lead to total cell death during a 7 day period. However, total cell death did occur with concentrations of 300 and 500 μg/ml. It is concluded that areca nut extract is toxic to cultured fibroblasts and inhibits their proliferation in a concentration-dependent manner.     

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.     

槟榔提取物抑制人类口腔黏膜成纤维细胞生长的实验研究

目的通过比较正常口腔黏膜和口腔黏膜下纤维性变(OSF)组织中成纤维细胞(FB)增殖差异、检测槟榔提取物(ANE)对成纤维细胞增殖的影响,来探讨OSF的发病机理.方法对人类口腔黏膜成纤维细胞进行分离培养,然后用四唑盐(MTT)比色试验法检测OSF患者和正常人口腔黏膜FB增殖状况,并且观察ANE对FB增殖的影响.结果表示增殖水平的OD值在OSF-FB为0.254±0.045,高于NM-FB的OD值0.236±0.012(P<0.05),ANE以浓度-效应依赖关系抑制FB增殖.结论 OSF-FB细胞增殖率较NM-FB高;ANE对口腔黏膜FB有细胞毒作用,提示槟榔及其有效成分不完全是通过直接刺激FB增殖而诱发OSF.     

Deficiency in collagen and fibronectin phagocytosis by human buccal mucosa fibroblasts in vitro as a possible mechanism for oral submucous fibrosis

Oral submucous fibrosis (OSF), a chronic oral mucosal condition commonly found in south Asians, is a disorder characterized by a quantitative as well as a qualitative alteration of collagen deposition within the subepithelial layer of the oral mucosa. Since degradation of collagen by fibroblast phagocytosis is an important pathway for physiological remodelling of soft connective tissues, we have investigated phagocytosis of collagen- and fibronectin-coated latex beads by fibroblast cultures with an in vitro model system. Coated fluorescent latex beads were incubated with human oral mucosa fibroblasts and the fluorescence associated with internalized beads was measured by flow cytometry. Cells from normal tissues that had been incubated with beads for 16 h contained a mean of 75% collagen phagocytic cells and 70% fibronectin phagocytic cells; however, about 15% and 10% of phagocytic cells individually contained more than twice the mean number of beads per cell. In contrast, cells from OSF tissues exhibited a 40% reduction of the proportions of collagen phagocytic cells (mean=35%) and a 48% decrease of the proportions of fibronectin phagocytic cells (mean=22%), none of the cells having a high number of beads as compared to normal fibroblasts. OSF lesions appear to contain fibroblasts with marked deficiencies in collagen and fibronectin phagocytosis. To investigate if inhibition of phagocytosis could be demonstrated in vitro, normal fibroblast cultures were incubated with areca nut alkaloids (arecoline, arecaidine). The cultures had a dose-dependent reduction in the proportions of phagocytic cells. On the other hand, corticosteroid used in the treatment of OSF exhibited a dose-dependent enhancement in the proportion of phagocytic cells. Therefore, our hypothesis for OSF, although over-simplified, is that betel nut alkaloids (arecoline, arecaidine) inhibit fibroblast phagocytosis and this provides a mechanism for the development of OSF. The benefit of a local intralesional injection of corticosteroid is also possibly, at least in part, through an enhancement of fibroblast collagen phagocytosis.     

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.     

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.     

The fibroblast population in oral submucous fibrosis

The purpose of the investigation was to compare the morphology of fibroblasts cultured from healthy oral mucosa and mucosa of patients with oral submucous fibrosis (OSF) and to collate the occurrence of cell types of similar morphology. Cells cultured from biopsy specimens from the buccal mucosa of six subjects who did not chew the areca nut and six patients with OSF who chewed areca nut were grown according to standard techniques. Ninety cells per cell line were recorded daily for 8 days, classified into types F1, F2 and F3 according to their morphology, and the results statistically analyzed. We found that there was a relative increase of F3 cells in relation to Fl cells in OSF resulting in the ratio of F3 to F1 cells being significantly larger in OSF than the ratio in the controls. As it has been reported that F3 cells m rat connective tissues produce significantly more collagen types I and III than F1 cells, we concluded that a change of fibroblast population has occurred in OSF and that this relative increase of F3 cells in humans, which could be committed to the production of large quantities of collagen, can be an explanation for the excessive collagen formation in OSF.     

Cytotoxic and non-genotoxic effects of arecoline on human buccal fibroblasts in vitro

Chang YC, Tai KW, Cheng MH, Chou LSS, Chou MY: Cytotoxic and non-genotoxic effects of arecoline on human buccal fibroblasts in vitro. J Oral Pathol Med 1998; 27: 68–71. © Munksgaard, 1998.
Betel quid chewing has been linked to oral submucous fibrosis and oral cancer. Cytotoxicity and genotoxicity assays were used to investigate the pathobiologi-cal effects of arecoline on cultured human buccal fibroblasts. Arecoline increased double-stranded polynucleic acid at the concentration of 0.1 to 10 μg/ml in a concentration-dependent manner. At a concentration higher than 50 μg/ml, arecoline was cytotoxic to cultured fibroblasts and the cytotoxicity was dose-dependent. No genotoxicity for arecoline was found even at a concentration of 400 μg/ml. On the other hand, 600 μg/ml glutathione (GSH) and 200 μg/ml glycyrrhizin could prevent the arecoline-induced cytotoxicity. These results indicate that arecoline is a cytotoxic agent and no genotoxicity was found to human buccal fibroblasts. Furthermore, increasing consumption of GSH- and glycyrrhizin-rich foods may reduce the oral diseases associated with betel quid chewing.     

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.     

Cytopathologic effects of arecoline on human gingival fibroblasts in vitro

Arecoline, a major betel nut alkaloid, has been detected in saliva obtained during betel nut chewing in concentrations up to 140 μg/ml, corresponding to 0.9 mM. Arecoline in the millimolar concentration range might participate in the initiation and/or progression of periodontal disease during the long-term effects of betel nut chewing. In this study, cell growth, cell proliferation, assessment of cytoplasmic enzyme lactate dehydrogenase (LDH) and collagen synthesis were used to investigate the effects of human gingival fibroblasts exposed to arecoline levels of 0–200 μg/ml. Control culture exhibited a normal monolayer of long spindle-shaped fibroblast morphology. Arecoline-treated human gingival fibroblasts showed a more rounded appearance and detached at the higher concentrations. At concentrations higher than 75 μg/ml, many cells had detached from the surface of the petri dish and numerous floating cells could be seen under the inverted microscope. At a concentrations higher than 25 μg/ml, arecoline inhibited cell growth, proliferation and collagen synthesis and increased LDH leakage in a dose-dependent manner (P<0.05). These results indicate that arecoline is a cytotoxic agent to human gingival fibroblasts. Repeated and long-term exposure to arecoline could impair gingival fibroblast function. Betel quid chewers might be more susceptible to destruction of the periodontium and less responsive to a regeneration procedures during periodontal therapy. Received: 31 August 1998 / Accepted: 3 November 1998     

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.     

Interferon gamma (IFN-γ) may reverse oral submucous fibrosis

Oral submucous fibrosis (OSF) is a chronic disease of the oral cavity and oropharyngx characterised by fibrosis in the submucosa leading to progressive limitation of the mouth opening. Interferon gamma (IFN-gamma) is a known anti-fibrotic cytokine. In this study we have investigated: a) the effect of IFN-gamma on collagen synthesis by arecoline-stimulated OSF fibroblasts in vitro (n=5), b) the effect of intra-lesional IFN-gamma on the fibrosis of OSF patients (n=29) and c) the immunohistochemical analysis of pre- and post-treatment inflammatory cell infiltrates and cytokine levels in the lesional tissue (n=29). The results show that the increased collagen synthesis in vitro in response to arecoline was inhibited in the presence of IFN-gamma (0.01-10.0 U/ ml) in a dose-related way. In an open uncontrolled study intra-lesional IFN-gamma treatment showed improvement in the patients mouth opening from an inter-incisal distance before treatment of 21 +/- 7 mm, to 30 +/- 7 mm immediately after treatment and 30 +/- 8 mm 6-months later, giving a net gain of 8 +/- 4 mm (42%) (range 4-15 mm). Patients also reported reduced burning dysaesthesia and increased suppleness of the buccal mucosa. The post-treatment immunohistochemistry showed a decreased amount of inflammatory cell infiltrate and an altered level of cytokines compared with the pre-treatment lesional tissue. The effect of IFN-gamma on collagen synthesis appears to be a key to the treatment of these patients, and intra-lesional injections of the cytokine may have a significant therapeutic effect on OSF.