Development of Epigallocatechin 3-gallate-Loaded Hydrogel Nanocomposites for Oral Submucous Fibrosis

Oral submucous fibrosis (OSF) is a chronic progressive disease associated with increased collagen deposition and TGF-β1 release. The current therapy and management have been a limited success due to low efficacy and adverse drug reactions. This study aimed to evaluate epigallocatechin 3-gallate (EGCG) encapsulated nanoparticles loaded mucoadhesive hydrogel nanocomposite (HNC) for OSF. Developed HNC formulations were evaluated for their permeation behaviour using in vitro as well as ex vivo studies, followed by evaluation of efficacy and safety by in vivo studies using areca nut extract-induced OSF in rats. The disease condition in OSF-induced rats was assessed by mouth-opening and biochemical markers. The optimized polymeric nanoparticles exhibited the required particle size (162.93 ± 13.81 nm), positive zeta potential (22.50 ± 2.94 mV) with better mucoadhesive strength (0.40 ± 0.002 N), and faster permeation due to interactions of the positively charged surface with the negatively charged buccal mucosal membrane. HNC significantly improved disease conditions by reducing TGF-β1 and collagen concentration without showing toxicity and reverting the fibroid buccal mucosa to normal. Hence, the optimized formulation can be further tested to develop a clinically alternate therapeutic strategy for OSF.

PDE12 disrupts mitochondrial oxidative phosphorylation and mediates mitochondrial dysfunction to induce oral mucosal epithelial barrier damage in oral submucous fibrosis

Oral submucous fibrosis (OSF) is a chronic oral mucosal disease. The pathological changes of OSF include epithelial damage and subepithelial matrix fibrosis. This study aimed to reveal the epithelial injury mechanism of OSF. A histopathological method was used to analyze oral mucosal tissue from OSF patients and OSF rats. The expression of PDE12 in the oral epithelium was analyzed by immunohistochemistry. The epithelial-mesenchymal transition (EMT) and tight junction proteins in arecoline-treated HOKs were explored by western blotting. Epithelial leakage was assessed by transepithelial electrical resistance and lucifer yellow permeability. The expression of PDE12 and the mitochondrial morphology, mitochondrial permeability transition pore opening, mitochondrial membrane potential, and mitochondrial reactive oxygen species (mtROS) were evaluated in arecoline-induced HOKs. Oxidative phosphorylation (OXPHOS) complexes and ATP content were also explored in HOKs. The results showed significant overexpression of PDE12 in oral mucosal tissue from OSF patients and rats. PDE12 was also overexpressed and aggregated in mitochondria in arecoline-induced HOKs, resulting in dysfunction of OXPHOS and impaired mitochondrial function. An EMT, disruption of tight junctions with epithelial leakage, and extracellular matrix remodeling were also observed. PDE12 overexpression induced by PDE12 plasmid transfection enhanced the mtROS level and interfered with occludin protein localization in HOKs. Interestingly, knockdown of PDE12 clearly ameliorated arecoline-induced mitochondrial dysfunction and epithelial barrier dysfunction in HOKs. Therefore, we concluded that overexpression of PDE12 impaired mitochondrial OXPHOS and mitochondrial function and subsequently impaired epithelial barrier function, ultimately leading to OSF. We suggest that PDE12 may be a new potential target against OSF.

Antifibrotic effect of silymarin on arecoline-induced fibrosis in primary human buccal fibroblasts: an in silico and in vitro analysis

BACKGROUND

This study aimed to assess silymarin's anticancer and antifibrotic potential through in silico analysis and investigate its impact on in vitro arecoline-induced fibrosis in primary human buccal fibroblasts (HBF).

METHODS & RESULTS

The study utilized iGEMDOCK for molecular docking, evaluating nine bioflavonoids, and identified silymarin and baicalein as the top two compounds with the highest target affinity, followed by subsequent validation through a 100ns Molecular Dynamic Simulation demonstrating silymarin's stable behavior with Transforming Growth Factor Beta. HBF cell lines were developed from tissue samples obtained from patients undergoing third molar extraction. Arecoline, a known etiological factor in oral submucous fibrosis (OSMF), was employed to induce fibrogenesis in these HBFs. The inhibitory concentration (IC50) of arecoline was determined using the MTT assay, revealing dose-dependent cytotoxicity of HBFs to arecoline, with notable cytotoxicity observed at concentrations exceeding 50µM. Subsequently, the cytotoxicity of silymarin was assessed at 24 and 72 h, spanning concentrations from 5µM to 200µM, and an IC50 value of 143µM was determined. Real-time polymerase chain reaction (qPCR) was used to analyze the significant downregulation of key markers including collagen, epithelial-mesenchymal transition (EMT), stem cell, hypoxia, angiogenesis and stress markers in silymarin-treated arecoline-induced primary buccal fibroblast cells.

CONCLUSION

Silymarin effectively inhibited fibroblast proliferation and downregulated genes associated with cancer progression and EMT pathway, both of which are implicated in malignant transformation. To our knowledge, this study represents the first exploration of silymarin's potential as a novel therapeutic agent in an in vitro model of OSMF.

Polyphenol-based targeted therapy for oral submucous fibrosis

Oral submucous fibrosis (OSF) is a chronic, progressive, and precancerous condition mainly caused by chewing areca nut. Currently, OSF therapy includes intralesional injection of corticosteroids with limited therapeutic success in disease management. Therefore, a combined approach of in silico, in vitro and in vivo drug development can be helpful. Polyphenols are relatively safer than other synthetic counterparts. We used selected polyphenols to shortlist the most suitable compound by in silico tools. Based on the in silico results, epigallocatechin-3-gallate (EGCG), quercetin (QUR), resveratrol, and curcumin had higher affinity and stability with the selected protein targets, transforming growth factor beta-1 (TGF-β1), and lysyl oxidase (LOX). The efficacy of selected polyphenols was studied in primary buccal mucosal fibroblasts followed by in vivo areca nut extract induced rat OSF model. In in vitro studies, the induced fibroblast cells were treated with EGCG and QUR. EGCG was safer at higher concentrations and more efficient in reducing TGF-β1, collagen type-1A2 and type-3A1 mRNA expression than QUR. In vivo studies confirmed that the EGCG hydrogel was efficient in improving the disease conditions compared to the standard treatment betamethasone injection with significant reduction in TGF-β1 and collagen concentrations with increase in mouth opening. EGCG can be considered as a potential, safer and efficient phytomolecule for OSF therapy and its mucoadhesive topical formulation help in the improvement of patient compliance without any side effects. Highlights Potential polyphenols were shortlisted to treat oral submucous fibrosis (OSF) using in silico tools Epigallocatechin 3-gallate (EGCG) significantly reduced TGF-β1 and collagen both in vitro and in vivo EGCG hydrogel enhanced antioxidant defense, modulated inflammation by reducing TGF-β1 and improved mouth opening in OSF rat model.

Inhibition of miR-497 Attenuates Oral Submucous Fibrosis by Inhibiting Myofibroblast Transdifferentiation in Buccal Mucosal Fibroblasts

PURPOSE

Oral submucous fibrosis (OSF) is a common chronic condition with poor prognosis, and existing therapies for OSF are limited in effectiveness. This study was designed to explore the role of miR-497 in arecoline (AR)-induced OSF.

MATERIALS AND METHODS

After miR-497 was silenced or overexpressed in buccal mucosa fibroblasts (BMFs), different concentrations of AR (5-200 μg/ml) were applied to incubate BMFs, and 50 μg/ml of AR was chosen for subsequent experiments. Thereafter, collagen gel contraction assay was used to detect the contractile capacity of BMFs. Transwell assay and wound healing assay were applied to detect migration and invasiveness of the cells. In addition, immunofluorescence staining, qRT-PCR and western blot were conducted to measure the expression of miR-497, collagen I and α-SMA, as well as the phosphorylation of Smad2 and Smad3.

RESULTS

After successful inhibition or overexpression of miR-497 in AR-induced BMFs, the results showed that miR- 497 inhibition suppressed the contractility, migration and invasiveness of AR-induced BMFs, whereas overexpression of miR-497 produced the opposite. In addition, miR-497 inhibition down-regulated the expression level of collagen I and α-SMA in AR-exposed BMFs. Furthermore, TGF-β1 expression, Smad2 and Smad3 phosphorylation were also repressed in AR-induced BMFs after miR-497 inhibition. Correspondingly, overexpression of miR-497 reversed the expression of the aforementioned proteins.

CONCLUSION

miR-497 inhibition may attenuate OSF by inhibiting myofibroblast transdifferentiation in BMFs via the TGF-β1/Smads signaling pathway, indicating that miR-497 might represent an underlying target for treating OSF.

Are There Betel Quid Mixtures Less Harmful than Others? A Scoping Review of the Association between Different Betel Quid Ingredients and the Risk of Oral Submucous Fibrosis

Oral submucous fibrosis (OSF) is a potentially malignant condition of the oral cavity characterized by progressive fibrosis of the submucosal tissues. OSF is typically associated with the use of betel quid (BQ), a chewing package made of natural products (e.g., areca nut, betel leaves), with or without smokeless tobacco. BQ ingredients contain pro-carcinogenic bioactive compounds, but also potentially protective biomolecules, and we have shown recently that the chemical properties of different BQ recipes vary, which may explain the unequal prevalence of OSF and oral cancer in BQ users in different geographical regions. Hence, this scoping review was aimed at evaluating the existing literature regarding different BQ compounds and their association with OSF. The repository of the National Library of Medicine (MEDLINE/PubMed), medRxiv databases, Google scholar, Baidu scholar, CNKI, and EBSCO were used to search for publications that investigated the association between BQ chewing and OSF up to November 2021. The search terminology was constructed using the keywords "betel quid" and "oral submucous fibrosis", and their associated terms, with the use of Boolean operators. The search was conducted under Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines, together with clear inclusion and exclusion criteria. The review showed that the risk of developing OSF varied between different BQ recipes, and that chewing BQ mixtures containing betel inflorescence (BI) significantly increased the risk of OSF, as did the addition of tobacco. Conversely, the use of betel leaf in the mixture was likely to be protective, which may be due to the presence of polyphenols. Although further research is needed to determine the effect of individual BQ ingredients in the development of OSF, our pilot results provide the scope and rationale for informing future chemopreventive strategies for OSF and oral cancer in BQ chewers.

Arecoline suppresses epithelial cell viability by upregulating tropomyosin-1 through the transforming growth factor-β/Smad pathway

CONTEXT

Oral submucous fibrosis (OSF) is a chronic and progressive disease. Arecoline, present in betel nuts, has been proposed as a vital aetiological factor. However, the underlying mechanism remains unclear.

OBJECTIVES

This research elucidates the expression of tropomyosin-1 (TPM1) and its regulation mechanism in HaCaT cells treated with arecoline.

MATERIALS AND METHODS

HaCaT cells were assigned into three groups: (1) Control; (2) Treated with arecoline (0.16 mM) for 48 h (3) Treated with arecoline (0.16 mM) and transfected with small interfering RNA (siRNA) for TPM1 (50 nM) for 48 h. CCK8, cell cycle, and apoptosis phenotypic analyses were performed. PCR and western blot analyses were performed to detect the expression level of TPM1 and examine the related signalling pathway.

RESULTS

The IC₅₀ of arecoline was approximately 50 μg/mL (0.21 mM). The arecoline dose (0.16 mM) and time (48 h) markedly increased TPM1 expression at the mRNA and protein levels in HaCaT cells. Arecoline suppressed the cell growth, caused cell cycle arrest at the G1 phase, and induced cell apoptosis in HaCaT cells. siRNA-mediated knockdown of TPM1 attenuated the effect of arecoline on cell proliferation, apoptosis, and cell cycle arrest at the G1 phase. Furthermore, blocking of the transforming growth factor (TGF)-β receptor using SB431542 significantly suppressed TPM1 expression in the cells treated with arecoline.

DISCUSSION AND CONCLUSIONS

Arecoline suppresses HaCaT cell viability by upregulating TPM1 through the TGF-β/Smad signalling pathway. This research provides a scientific basis for further study of arecoline and TPM1 in OSF and can be generalised to broader pharmacological studies. TPM1 may be a promising molecular target for treating OSF.

Oral Submucous Fibrosis: A Review on Biomarkers, Pathogenic Mechanisms, and Treatments

Oral submucous fibrosis (OSF) is a collagen deposition disorder that affects a patient’s oral function and quality of life. It may also potentially transform into malignancy. This review summarizes the risk factors, pathogenic mechanisms, and treatments of OSF based on clinical and bio-molecular evidence. Betel nut chewing is a major risk factor that causes OSF in Asia. However, no direct evidence of arecoline-induced carcinogenesis has been found in animal models. Despite identification of numerous biomarkers of OSF lesions and conducting trials with different drug combinations, clinicians still adopt conservative treatments that primarily focus on relieving the symptoms of OSF. Treatments focus on reducing inflammation and improving mouth opening to improve a patient’s quality of life. In conclusion, high-quality clinical studies are needed to aid clinicians in developing and applying molecular biomarkers as well as standard treatment guidelines.

Hinokitiol ablates myofibroblast activation in precancerous oral submucous fibrosis by targeting Snail

Oral submucous fibrosis (OSF) is a precancerous condition with symptoms of limited mouth opening and areca nut chewing habit has been implicated in its pathogenesis. Hinokitiol, a natural tropolone derived from Chamacyparis taiwanensis, has been reported to improve oral lichen planus and inhibit various cancer cells. Here, we showed that hinokitiol reduced the myofibroblast activities in fBMFs and prevented the arecoline-induced transdifferentiation. Treatment of hinokitiol dose-dependently downregulated the myofibroblast markers as well as various EMT transcriptional factors. In particular, we identified that Snail was able to bind to the E-box in the α-SMA promoter. Our data suggested that exposure of fBMFs to hinokitiol mitigated the hallmarks of myofibroblasts, while overexpression of Snail eliminated the effect of hinokitiol. These findings revealed that the inhibitory effect of hinokitiol on myofibroblasts was mediated by repression of α-SMA via regulation of Snail and showed the anti-fibrotic potential of hinokitiol in the treatment of OSF.

Augmentation of oral submucous fibrosis by NSAIDs in the presence of risk factors

Various Risk factors initiate Submucous fibrosis which may be augmented by NSAIDs. A number of animal studies on their mechanism indirectly support it especially regarding alterations in prostaglandin synthesis. This study has been designed to find association of these drugs with Oral Submucous fibrosis in the presence of risk factors. Newly diagnosed patients of Oral Sub mucous fibrosis were recruited for this study who attended Dental Department of Karachi Medical and Dental College from July 1 till Dec 31, 2013.A structured interview and medical record of each patient was used to determine the demographic profile, any addiction, previous and present illnesses and drug (s) used. Through examination of Oral cavity was carried out to access the severity of disease as per modified Khanna & Andrade Classification (1995). Statistical Analysis was done by SPSS 15. Total 102 patients were recruited from dental OPD as per criteria of inclusion. Among these patients 36 (49.31%) were using NSAIDs in which Acetaminophen (30.55%), Acetylsalicylic acid (25.00%) and Diclophenac (19.44%) were 1st, 2nd and 3rd most common drugs. Data shows that 14 patients (28.88%) had mild and 22(61.11%) had sever fibrosis which was significantly high (P<0.05). Mild fibrosis was seen in 05 (45.46%) and Sever fibrosis in 06 (54.54%) out of total 11 patients who were using NSAIDSs since less than or equal to 6 months. Similarly mild fibrosis was seen in 09 (36.00%) and Sever fibrosis in 16 (64.00%) out of total 25 patients who were on NSAIDs since more than 6 months. No statistical significant difference (P>0.05) in severity of fibrosis is seen in patients who were using NSAIDs since less than or equal to 6 months but statistical significant difference (P<0.05) in severity of fibrosis is seen in patients who on these drugs since more than 6 months. Addiction burden was calculated by Average Duration x Average Frequency, which was 92.72 for Pan, 88.88 for Supari and 61.30 for Miscellaneous. No statistically significant difference (P>0.05) was seen in addiction burden of various substances in these patients. An association of NSAIDs with Oral Sub mucous fibrosis exists. The pathology is augmented if these drugs are used in the presence of risk factors. Therefore these drugs should not be prescribed to these patients until a clear benefit is not targeted.

Total, direct, and indirect effects of paan on oral cancer

PURPOSE

Paan (betel leaf and betel nut quid) used with or without tobacco has been positively associated with oral cancer. Oral submucous fibrosis (OSMF), a precancerous condition caused by paan, lies on the causal pathway between paan use and oral cancer. The purpose of this analysis was to estimate the effect of paan consumption on oral cancer risk when it is mediated by OSMF.

METHODS

We used mediation methods proposed by VanderWeele, which are based on causal inference principles, to characterize the total, direct, and indirect effects of paan, consumed with and without tobacco, on oral cancer mediated by OSMF. We reanalyzed case-control data collected from three hospitals in Karachi, Pakistan, between July 1996 and March 1998.

RESULTS

For paan without tobacco, the total effect on oral cancer was OR 7.39, 95 % CI 1.01, 38.11, the natural indirect effect (due to OSMF among paan users) was OR 2.48, 95 % CI 0.99, 10.44, and the natural direct effect (due to paan with OSMF absent) was OR 3.32, 95 % CI 0.68, 10.07. For paan with tobacco, the total direct effect was OR 15.68, 95 % CI 3.00, 54.90, the natural indirect effect was OR 2.18, 95 % CI 0.82, 5.52, and the natural direct effect was OR 7.27, 95 % CI 2.15, 20.43.

CONCLUSIONS

Paan, whether or not it contained tobacco, raised oral cancer risk irrespective of OSMF. Oral cancer risk was higher among those who used paan with tobacco.

Elevation of S100A4 expression in buccal mucosal fibroblasts by arecoline: involvement in the pathogenesis of oral submucous fibrosis

Background

S100A4, a member of the calcium-binding proteins, is dramatically elevated in a variety of fibrotic diseases. Areca quid chewing is the most important etiological factor in the pathogenesis of oral submucous fibrosis (OSF). OSF has been considered as a pre-cancerous condition of oral mucosa. The aim of this study was to determine the critical role of S100A4 expression in the pathogenesis of OSF both in vitro and in vivo.

Methodology/Principal Finding

Thirty OSF tissues from areca quid chewers and ten normal buccal mucosa samples without areca quid chewing were analyzed by using immunohistochemistry for S100A4 expression in vivo. Collagen gel contraction capability and expression of tissue inhibitor of metalloproteinases 1 (TIMP1)/MMP9 in arecoline-stimulated BMFs with S100A4 knockdown was presented in vitro. Initially, S100A4 expression was higher in areca quid chewing-associated OSF specimens than normal buccal mucosa specimens (p = 0.001). Arecoline, a major areca nut alkaloid, led to dose- and time-dependent elevation of S100A4 expression in normal buccal mucosa fibroblasts BMFs (p<0.05). The additions of pharmacological agents rapamycin (mTOR inhibitor), PD98059 (ERK inhibitor), and Bay117082 (NF-κB inhibitor) were found to inhibit arecoline-induced S100A4 expression (p<0.05) in BMFs. Down-regulation of S100A4 by lentiviral infection significantly reversed arecoline-induced collagen gel contraction and TIMP1/MMP9 expression.

Conclusion/Significance

These results suggest that S100A4 expression is significantly up-regulated in OSF specimens. Arecoline-induced S100A4 expression was down-regulated by rapamycin, PD98059, and Bay117082. Targeting S100A4 might be a potential therapeutic target for OSF through TIMP1/MMP9 down-regulation.

[Epidemiological study of betel nut chewing among elementary and middle school students in Loudi city, Hunan province]

OBJECTIVE

To investigate the prevalence of betel nut chewing and oral submucous fibrosis (OSF) among elementary and middle school students in Loudi city, Hunan province.

METHODS

According to the standard of the third national oral health epidemiological investigation, the subjects were selected through a two-stage random sampling procedure. A face to face questionnaire survey was conducted among students by random sampling from 6 schools, and oral examination was performed to find the prevalence of OSF.

RESULTS

Of the 4087 eligible students, 4019 students participated in the survey(98.3%). Among the 4019 students, there were 498 betel nut chewers, the prevalence of betel nut chewing was 12.4%, which was much higher in male than in female students (437/2073, 21.1% vs 61/1946, 3.1%, P < 0.05). The proportion of students who were chewing areca nuts increased with increasing grades (P < 0.05). The prevalence was highest in senior schools (229/1077, 21.3%)and lowest in elementary schools (126/1983, 6.4%). Most students who were chewing areca nuts in elementary school obtained betel nuts from their parents (61/126, 48.4%), but most middle school betel nut chewers obtained betel nuts from their friends (88/143, 61.5% and 165/229, 72.1%). Five OSF cases (0.12%) were diagnosed among the 4019 students, all of them were male senior school students.

CONCLUSIONS

Betel nut chewing was common and OSF cases were found among elementary and middle school students in Loudi city. There were more male than female students who were chewing betel nut.

Development of an in vivo mouse model to study oral submucous fibrosis

BACKGROUND

Epidemiological data have shown an association of areca nut chewing with oral submucous fibrosis (OSF). Experimental evidence to confirm this has been limited. Fibrosis-promoting activity of areca nut was tested in an animal model.

METHOD

Buccal mucosa of a group of 20 female BALB/c strain mice, 10-12 weeks of age, was treated twice daily 6 days per week with topical application of aqueous areca nut extracts for 300-600 days. A control group (n = 20) was treated with 50 mM NaCl. The influence of areca nut on the oral epithelium and connective tissue was recorded semiquantitatively by light microscopy.

RESULTS

The areca nut-treated oral epithelium showed progressive changes in epithelial thickness leading to atrophy, increased cellularity of fibroblasts, fibrosis of connective tissue, focal infiltration of inflammatory cells and muscle atrophy. On killing after 600 days of treatment, the scores on cellularity, inflammation and muscle atrophy were significantly different to the control group (P = 0.03).

CONCLUSION

The study provides further evidence that areca nut contributes to the development of OSF in treated animals. The model has the potential to test synergism of areca nut with other carcinogens and any therapeutic interventions.

The upregulation of insulin-like growth factor-1 in oral submucous fibrosis

Insulin-like growth factor-1 (IGF-1) is a member of a family of two interacting polypeptide hormone ligands with close homology to proinsulin. IGF-1 can influence mesenchymal cell migration, proliferation, and extracellular matrix deposition, thus implicating it in the progression of fibrotic disorders. Currently, there is limited information about the regulation of IGF-1 expression in areca quid-associated oral submucous fibrosis (OSF). The aim of this study was to compare IGF-1 expression in normal human buccal mucosa and OSF specimens and further explore the potential mechanism that may lead to induce IGF-1 expression. Twenty OSF specimens and 10 normal buccal mucosa were examined by immunohistochemistry. The activity of IGF-1 from cells cultured from OSF and normal buccal mucosa were by using reverse-transcriptase polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Furthermore, the effect of arecoline, the major areca nut alkaloid, was added to explore the potential mechanism that may lead to induce IGF-1 expression. IGF-1 expression was significantly higher in OSF specimens (p<0.05) and expressed mainly by fibroblasts, endothelial cells, and inflammatory cells. OSF demonstrated significantly higher IGF-1 protein expression than normal buccal mucosa fibroblast (BMF) both in mRNA and protein levels (p<0.05). In addition, arecoline was also found to elevate IGF-1 mRNA and protein expression in a dose-dependent manner (p<0.05). Taken together, the data presented here demonstrated that IGF-1 expression is significantly upregulated in OSF from areca quid chewers and arecoline may be responsible for the enhanced IGF-1 expression in vivo.

Raised keratinocyte growth factor-1 expression in oral submucous fibrosis in vivo and upregulated by arecoline in human buccal mucosal fibroblasts in vitro

BACKGROUND

Keratinocyte growth factor-1 (KGF-1) is the seventh member of the fibroblast growth factor family. KGF-1 is produced by mesenchymal cells such as fibroblasts and upregulated in a variety of hyperplastic tissues. Currently, there is limited information about the regulation of KGF-1 expression in areca quid-associated oral submucous fibrosis (OSF). The aim of the study was to compare KGF-1 expression in normal human buccal mucosa and OSF specimens and further to explore the potential mechanism that may lead to induce KGF-1 expression.

METHODS

The expression of KGF-1 from fibroblasts cultured from OSF and normal buccal mucosa were using reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, arecoline, a major areca nut alkaloid, was challenged to normal buccal mucosa fibroblasts (BMFs) to elucidate whether KGF-1 expression could affect by arecoline. Furthermore, 25 OSF specimens and six normal buccal mucosa specimens were examined by immunohistochemistry.

RESULTS

Fibroblasts derived from OSF were found to exhibit higher KGF-1 expression than BMFs both in mRNA and protein levels (P < 0.05). In addition, upregulation of KGF-1 mRNA gene and protein expression were found in BMFs stimulated by arecoline (P < 0.05). From the results of immunohistochemistry, KGF-1 expression was significantly higher in OSF specimens and expressed mainly by fibroblasts, endothelial cells, inflammatory cells, and epithelial cells.

CONCLUSIONS

Taken together, these results suggest that KGF-1 expression is significantly upregulated in OSF tissues from areca quid chewers and arecoline may be responsible for the enhanced KGF-1 expression in vivo.

The upregulation of type I plasminogen activator inhibitor in oral submucous fibrosis

Type I plasminogen activator inhibitor (PAI-1) is a 50 kDa glycoprotein belonging to the serine protease superfamily. PAI-1 is consistently and dramatically upregulated in a variety of fibrotic diseases. The aim of this study was to compare PAI-1 expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induced PAI-1 expression. Twenty-five OSF specimens and six normal buccal mucosa were examined by immunohistochemistry. The activity of PAI-1 from cells cultured from OSF and normal buccal mucosa were assayed using reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blots. PAI-1 expression was significantly higher in OSF specimens and expressed mainly by fibroblasts, endothelial cells, and inflammatory cells. In addition, OSF exhibited higher PAI-1 expression than normal buccal mucosa fibroblast (BMF) both in mRNA and protein levels. To verify whether arecoline, a major areca nut alkaloid, could affect PAI-1 expression by human BMFs, RT-PCR and Western blots were used. The results demonstrated highly elevated PAI-1 mRNA and protein expression in normal human BMFs stimulated by arecoline. Taken together, these results suggest that PAI-1 expression is significantly upregulated in OSF tissues from areca quid chewers, and arecoline may be responsible for the enhanced PAI-1 expression in vivo.

Elevated vimentin expression in buccal mucosal fibroblasts by arecoline in vitro as a possible pathogenesis for oral submucous fibrosis

Areca quid chewing is strongly correlated with oral submucous fibrosis (OSF) in Taiwan. The cytotoxicity of arecoline, a major areca nut alkaloid, on human oral fibroblasts has been extensively studied. To date, however, there has been little research exploring the possible effects of arecoline on cytoskeleton components. In this study, in addition to conducting a cytotoxicity assay, we examine the effect of arecoline on vimentin, an intermediate filament, and its expression in human buccal mucosal fibroblasts on exposure to various levels of arecoline (0-200 microg/ml) for 48 h. At a concentration above 50 microg/ml, arecoline demonstrated dose-dependent cytotoxicity (P<0.05) for cultured fibroblasts. Using sodium dodecyl sulphate-polyacrylamide gel electrophoresis, we demonstrated dose-dependent elevation of 57 kDa cytoskeletal-protein levels for arecoline. Evidence from immunoblotting assay indicated this 57 kDa cytoskeletal protein was vimentin. The increase in vimentin with arecoline exposure corresponded to that noted for fibroblasts cultured from OSF patients. Immunohistochemical assay also revealed that vimentin expression was much higher for OSF specimens than for normal buccal mucosa. We suggest these results may advance understanding of the possible pathogenesis for submucous fibrosis through the transformation of normal buccal mucosa as a result of areca quid chewing.

Increased tissue inhibitor of metalloproteinase-1 expression and inhibition of gelatinase A activity in buccal mucosal fibroblasts by arecoline as possible mechanisms for oral submucous fibrosis

Oral submucous fibrosis (OSF) is a pre-malignant fibrotic lesion of the mouth in areca quid chewers. It is probably a consequence of disturbances in the hemeostatic equilibrium between synthesis and degradation of extracellular matrix molecules (ECM). To date, there has been little research about the role of tissue inhibitors of metalloproteinase (TIMPs) and matrix metalloproteinases (MMPs) in the pathogenesis of OSF. In the present study, we examined the activity of TIMPs from cells cultured from OSF and normal buccal mucosa. OSF specimens were found to have higher TIMP-1 expression than normal buccal mucosal fibroblasts (BMFs) by Western blots. To verify whether arecoline, a major areca nut alkaloid, could affect TIMP or MMP production by human BMFs, Western blots and gelatine zymography were used. Arecoline was found to elevate TIMP-1 expression at the concentration level under 20 microg/ml in a dose-dependent manner. The amount of TIMP-1 was about 2.7 fold at a concentration level of 10 microg/ml compared with control. From gelatin zymograms, the main gelatinolytic proteinase secreted by the human BMFs was MMP-2, and only minimal amounts of MMP-9 could be detectable from zymogram. In addition, arecoline was found to inhibit MMP-2 secretion and production at the concentration level of 40 microg/ml. The gelatinolytic activity of MMP-2 was about 54% at a concentration level of 80 microg/ml compared with control. Taken together, it was found that arecoline acted not only as an inhibitor on gelatinolytic activity of MMP-2, but also a stimulator for TIMP-1 activity. These synergistic effects may contribute to the ECM components accumulation in the areca quid associated OSF.

Quantitative estimation of PCNA, c-myc, EGFR and TGF-alpha in oral submucous fibrosis--an immunohistochemical study

The objectives of the present study were to evaluate the expression of three proliferation markers, viz., epidermal growth factor receptor (EGFR), transforming growth factor-alpha (TGF-alpha) and proliferating cell nuclear antigen (PCNA) and one genomic marker, c-myc in OSMF. Oral tissues were stained with monoclonal antibodies to PCNA, c-myc, TGF-alpha and EGFR. The results were analyzed with Photoquant image analysis software. The expression of PCNA, c-myc, TGF-alpha and EGFR was higher in oral submucous fibrosis (OSMF) than in normal control oral mucosa. The oral epithelium was divided into a proliferative compartment (stratum germinativum) and a differentiated compartment (stratum spinosum). A differential pattern of expression of PCNA and c-myc was observed in OSMF. While the intensity of staining decreased, the percent area of expression of PCNA and c-myc increased in stratum germinativum in OSMF (P<0.05). This suggests that greater proportions of cells exhibit PCNA and c-myc immunoreactivity and are in the proliferative pool in OSMF. TGF-alpha levels increased in the proliferative layers and EGFR levels increased in the differentiated layers (P<0.05) of the oral epithelium in OSMF. Quantitative measurement of these oncoproteins substantiates the precancerous nature of OSMF and may provide intermediate end-points in prospective chemopreventive trials.

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

Betel quid chewing has been linked to oral submucous fibrosis and oral cancer. Cytotoxicity and genotoxicity assays were used to investigate the pathobiological effects of arecoline on cultured human buccal fibroblasts. Arecoline increased double-stranded polynucleic acid at the concentration of 0.1 to 10 micrograms/ml in a concentration-dependent manner. At a concentration higher than 50 micrograms/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 micrograms/ml. On the other hand, 600 micrograms/ml glutathione (GSH) and 200 micrograms/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.

Betel: consumption and consequences

Betel is a compound of natural substances chewed for its psychostimulating effects. Betel is composed of the nut of the areca palm (Areca catechu), the leaf of the betel pepper (Piper betle), and lime (calcium hydroxide). Approximately 200 million persons chew betel regularly throughout the western Pacific basin and south Asia. Only three drugs (nicotine, ethanol, and caffeine) are consumed more widely than betel. When betel is chewed, it produces mild psychoactive and cholinergic effects. There is copious production of a blood-red saliva that can stain oral structures. After years of chewing, the teeth may become red-brown to nearly black. Betel use is associated with oral leukoplakia, submucous fibrosis, and squamous cell carcinoma. Use of betel is discouraged in Western countries because of its alleged carcinogenic and perceived dysesthetic properties; nevertheless, betel is widely available in the West.

[Experimental study on aqueous areca nut extracts inducing oral submucous fibrosis in rats. I. Observation of histomorphology]

The purpose of this study was to establish the animal model of oral submucous fibrosis (OSF) in buccal mucosa of SD rats by submucosa injecting and surface painting aqueous areca nut extracts (AANE). The animals of all groups were killed randomly in the 12th, 16th, 22nd and 28th week. The buccal mucosae were collected, and were detected by light microscope and transmission electron microscope. The results were obtained: at different stages, the OSF-like lesions appeared in different degrees among some animals of the model groups, including atrophic epithelium with loss or partial loss of rate pegs, inflammation, accumulation and disorder of collagen fibre in juxta-epithelial region, along with concomitant muscle degeneration. The lesions didn't reverse obviously themselves after the authors stopped using AANE. Histomorphologic changes didn't appear in any animal of the control groups. The results indicated that the typical and stable OSF animal model were induced rapidly by submucosa injecting and surface painting AANE.

[Experimental study on aqueous areca nut extracts inducing oral submucous fibrosis in rats. II. Effection of mast cells on collagen metabolism]

The effection of mast cells (MC) on collagen metabolism of oral submucous fibrosis (OSF) induced by aqueous areca nut extracts (AANE) in rats was studied by transmission electron microscope, histochemical and biochemical analyses. The results revealed that there was a close relationship between MC and fibroblats (FB) in the pathogensis of OSF; MC which appeared in the buccal mucosa in the model groups increased significantly and became more active in the function. A great deal of collagen compacted in the buccal mucosa in the model groups. The contents of tissue hydroxyproline (Hyp) in the model groups were obviously higher than those in the control groups. Moreover, the longer the time of irritation continued, the higher the contents were. The number of MC had a higher positive correlation with the contents of tissue Hyp at the same time. Total serum Hyp had no significant difference among all the groups and any stages. The results indicated that some aqueous components of areca nuts might disturb collagen metabolism by accumulation and activation of MC.

Role of areca nut consumption in the cause of oral cancers. A cytogenetic assessment

BACKGROUND

Cytogenetic studies, framed to assess the possible genomic damage caused by areca nut consumption (without tobacco and not as a component of betel quid), were performed among areca nut chewers, which included normal people who chew areca nuts, patients with oral submucous fibrosis, and patients with oral cancer, and healthy nonchewing controls.

RESULTS

The analysis showed statistically significant increases in the frequencies of sister chromatid exchanges and chromosome aberrations in peripheral blood lymphocytes and the percentage of micronucleated cells in exfoliated cells of buccal mucosa among all three groups of chewers when compared with those of the controls.

CONCLUSIONS

The current data, the first of this type among only areca nut chewers, highlight that this popular masticatory is erroneously considered "safe" and that it increases the genomic damage even when chewed without tobacco. The data also signify that, henceforth, in cytogenetic biomonitoring, areca nut consumption also should be considered as one of the confounding factors.

Stabilisation of collagen by betel nut polyphenols as a mechanism in oral submucous fibrosis

Treatment of reconstituted collagen fibrils and pieces of rat dermis with the crude extract, purified tannins or (+)-catechin from betel nut (Areca catechu) increases their resistance to both human and bacterial collagenases in a concentration-dependent manner. These tanning agents may stabilise collagen in vivo following damage to the oral epithelium, and promote the sub-epithelial fibrosis which occurs in betel nut chewers.