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.     

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.     

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.

     

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.     

口腔黏膜下纤维性变中MMP-2基因的表达及意义

目的：检测口腔黏膜下纤维性变中基质金属蛋白酶-2（MMP-2）的表达并探讨其病理意义.方法：抽提11例口腔黏膜下纤维化组织和10例正常口腔黏膜组织的总RNA,通过逆转录聚合酶链反应（PF-PCR）检测MMP-2mRNA在口腔黏膜下纤维性变患者颊黏膜中的表达并与正常口腔黏膜进行比较.结果：口腔黏膜下纤维性变患者颊黏膜组织中MMP-2 mRNA表达高于正常颊黏膜（p＜0.05）.结论：MMP-2基因的表达与口腔黏膜下纤维性变组织重塑过程密切相关.     

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.     

Physiotherapeutic treatment improves oral opening in oral submucous fibrosis

Background:  In oral submucous fibrosis (OSF) fibrous bands and burning mucosal pain restrict oral opening to limit speech and eating. The pathogenesis of OSF remains unclear, while surgical and pharmacological treatments have limited success, and are often inaccessible in communities using areca nut where OSF is prevalent. Improved outcomes are reported for surgical treatment when followed by physiotherapy. We tested the hypothesis that physiotherapy alone can modify tissue remodelling in OSF to increase oral opening.
Materials and methods:  Fifty-four Nepali OSF patients were managed for 4 months in three randomly assigned groups receiving either: five times daily physiotherapy by inter-positioning tongue spatulas between teeth and adding a new spatula every 5–10 days; local injection of hyaluronidase with steroids; or no active treatment.
Results:  More males presented with OSF than females ( p  < 0.05). All patients reported reduced opening and 47% had mucosal pain. Progressive mucosal involvement was always in the same order, starting with the soft palate, and then progressing to the fauces, unilateral buccal mucosa, bilateral buccal mucosa, floor of mouth and finally lip mucosa ( p  < 0.006). Physiotherapy improved oral opening ( p  < 0.0005), but not oral pain, while no clear improvement was seen in untreated patients as well as patients managed by injection.
Conclusions:  We conclude OSF in the Nepali population progresses in a predictable pattern, and that physiotherapy is effective for increasing the oral opening. We further suggest physiotherapy can be readily used to improve OSF in communities with otherwise limited health resources.     

Growth of oral and skin fibroblasts from patients with oral submucous fibrosis

The purpose of the investigation was to evaluate and compare the proliferation (growth) of mouth fibroblasts and skin fibroblasts from patients with oral submucous fibrosis (OSF). Material comprised fibroblasts from fibrous bands situated in the buccal mucosa and from the inner aspect of the forearm of 8 patients with classic features of OSF as well as fibroblasts from 6 buccal mucosa and 8 skin biopsy specimens from healthy non-areca nut chewing individuals. Cells were cultured for 8 days according to standard techniques. Their growth was monitored daily, under optimal conditions as well as exposure to concentrations of arecoline. The data were analyzed using regression analysis, analysis of variance and the Kruskal-Wallis test. We found no statistically significant differences between the proliferation patterns of oral and skin fibroblasts from patients or between those from patients and controls. The reaction of the cells exposed to concentrations of arecoline was similar; at low concentrations (0.1–10 μg/ml) normal growth was maintained, while 100 μg/ml inhibited growth. It is concluded that fibroblasts from mouths affected by OSF have proliferation patterns which fall within normal parameters, that the excessive collagen formation in established OSF is not due to increased fibroblast proliferation and that arecoline does not stimulate fibroblast proliferation.     

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.     

The role of basic fibroblast growth factor in oral submucous fibrosis pathogenesis

Background:  Oral submucous fibrosis (OSF) is a chronic fibrotic disease of oral mucosa and oropharynx, induced by betel quid chewing often resulting in restricted mouth opening. The principal cells implicated as a source of extracellular matrix in areas of fibrosis are fibroblasts. Accumulation of connective tissue matrix is secondary to factors such as cytokines and growth factors. The contribution of basic fibroblast growth factor (bFGF) in disease progression and the consequent stromal changes with increase in the severity of OSF was studied.
Methods:  A case series analysis of 30 cases of OSF was carried out for bFGF expression using immunohistochemistry. Connective tissue changes in these cases were corroborated using aldehyde fuchsin and Verhoeff's hematoxylin special stains.
Results:  bFGF immunoreactivity was found to be increased in fibroblasts and in endothelial cells in early OSF cases, while the expression of bFGF in stroma increased notably in advanced fibrosis.
Conclusion:  Increased bFGF expression in early stages of the disease was explainable to an initial injury phase because of areca consumption, followed by cellular activation by chemotactic cytokines and other growth factors with eventual fibrosis occurring as a result of molecular alteration at the cellular level.     

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。     

Differential induction of heme oxygenase-1 against nicotine-induced cytotoxicity via the PI3K, MAPK, and NF-kappa B pathways in immortalized and malignant human oral keratinocytes

BACKGROUND:  Heme oxygenase-1 (HO-1) exhibits cytoprotective effects in many different cell types and is induced by nicotine exposure in human gingival fibroblasts. However, the role of HO-1 in cancer cells exposed to nicotine has not previously been described.
METHODS:  We investigated the effects of nicotine on HO-1 protein expression and cell viability in immortalized (IHOK) and malignant (HN12) human oral keratinocyte cells using the 3,4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide assay and Western blotting. We also examined the involvement of the phosphoinositide-3-kinase (PI3K), mitogen-activated protein kinase (MAPK), and nuclear factor-κB (NF-κB) signaling pathways in nicotine-induced cytotoxicity and HO-1 levels in IHOK and HN12 cells.
RESULTS:  Nicotine-induced HO-1 production and had cytotoxic effects on cells in both a concentration- and time-dependent manner. Nicotine-induced cytotoxicity and accumulation of HO-1 were greater in IHOK cells than in HN12 cells. Molecular inhibitors of the ERK, p38 MAP kinase, PI3 K, and NF-κB signaling pathways blocked the cytotoxic effects and induction of HO-1 expression by nicotine. Treatment with antioxidants (bilirubin, N -acetylcysteine) protected cells against nicotine-induced cytotoxicity and blocked the upregulation of HO-1, the effects of which were more pronounced in IHOK cells than in HN12 cells.
CONCLUSIONS:  Collectively, these results suggest that HO-1 plays a principal role in the protective response to nicotine in oral cancer and immortalized keratinocytes. Moreover, the addition of exogenous antioxidants may help to protect oral epithelial cells as chemopreventive agents against nicotine-induced oxidative stress.     

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。