Synergistic effects of peroxynitrite on arecoline-induced cytotoxicity in human buccal mucosal fibroblasts

Comprehensive Assessment of Albumin and Uric Acid Levels in Oral Submucous Fibrosis: A Comparative Case-Control Study Involving Different Risk Groups

Background Oral submucous fibrosis (OSMF) is a premalignant disorder that impacts the oral cavity and pharynx. Major risk factors for OSMF are attributed to the consumption of betel nuts or tobacco. These substances harbor various carcinogens that trigger the production of free radicals and reactive oxygen species. Antioxidants are pivotal in preserving cellular integrity and impeding the oncogenic transformation of body cells. In this context, albumin and uric acid, being primary antioxidants present in body fluids, bestow a defensive effect against this condition. Thus, the present study is designed to elucidate the differential concentration of albumin and uric acid between patient cases and healthy cohorts. Methodology This case-control study was conducted to evaluate the albumin and uric acid levels in individuals diagnosed with OSMF (cases) and compare them with healthy controls for a period of six months. A cohort of 100 individuals was partitioned into four groups, with each group comprising 25 individuals: Group I was made up of healthy individuals; Group II consisted of individuals who chew tobacco and areca nuts but are not affected by OSMF; Group III included individuals who only use tobacco without areca nuts and are afflicted with OSMF; and Group IV comprised individuals who consume a combination of areca nuts and tobacco and are diagnosed with OSMF. Biochemical evaluation was carried out using the BS-380 chemistry autoanalyzer (Mindray, Shenzhen, China), and the quantification of serum albumin and uric acid was performed by the uricase-peroxidase (POD) method with dihydroxybenzene sulfonic acid (DHBS). Results The study cohort of 100 individuals was made up of 70 males and 30 females, with an average age of 42.51 (11.62) years. The comparison of the mean concentration of serum albumin across all groups revealed that healthy controls exhibited the highest serum albumin concentration of 4.284 (0.618), with a statistically significant p-value (0.001) across all groups. A comparison of the mean value of serum uric acid among all groups showed that healthy controls had the highest value of serum uric acid (5.26±1.161), with a considerable p-value (0.001) between all groups. Conclusion The present study concluded that serum biomarkers assessed were high in healthy individuals and consumption of areca nuts, tobacco, and their products was significantly associated with low levels of albumin and uric acid. Therefore, both albumin and uric acid can be used as important biomarkers for uncovering oral premalignant lesions and conditions ahead of time and can also be used in mass screening.

Worldwide Prevalence and Clinical Characteristics of RAS Mutations in Head and Neck Cancer: A Systematic Review and Meta-Analysis

In light of the development of RAS inhibitors, a reliable assessment of the prevalence of RAS mutations and their correlation with the clinical features of patients with HNC is crucially needed. This meta-analysis compiles the findings of 149 studies with over 8500 HNC patients and assesses the global prevalence of mutations in the HRAS, KRAS and NRAS genes. The available data were stratified according to geographical region, clinical features, and tumor characteristics, including human papillomavirus (HPV) infection status and tumor stage. In addition, the distribution of codon substitutions in each RAS gene was assessed. The estimated mutation rate is highest for HRAS (7%), followed by KRAS (2.89%) and NRAS (2.20%). HRAS prevalence in South Asia (15.28%) is twice as high as the global estimate. HRAS mutations are more prevalent in oral cavity and salivary gland tumors. In contrast, KRAS mutations are found more frequently in sinonasal tumors, and NRAS mutations are found chiefly in tumors of the nasopharynx. OR analyses show a significant association between HRAS mutations and a high tumor stage (OR=3.63). In addition, there is a significant association between HPV-positive status and KRAS mutations (OR=2.09). This study highlights RAS as a potential therapeutic target in certain subsets of HNC patients.

Regulation of hypoxia-inducible factor-1α in human buccal mucosal fibroblasts stimulated with arecoline

Hypoxia-inducible factor (HIF)-1α is consistently and dramatically upregulated in a variety of fibrotic diseases. The aim of this study was to compare HIF-1α expression from fibroblasts derived from human normal buccal mucosa and oral submucous fibrosis (OSF) specimens and further to explore the potential mechanisms that may lead to induce HIF-1α expression. OSF buccal mucosal fibroblasts (BMFs) demonstrated significantly higher HIF-1α mRNA expression than normal BMFs (p<0.005). Arecoline, the major areca nut alkaloid, was also found to elevate HIF-1α mRNA expression in a dose-dependent manner (p<0.05). Moreover, arecoline-induced HIF-1α expression was downregulated by mitogen-activated protein kinase inhibitor U0126, phosphatidylinositol 3-kinase inhibitor LY294002, p38 inhibitor SB203580, cyclooxygenase-2 inhibitor NS-398, and glutathione precursor N-acetyl-L-cysteine (p<0.05). Taken together, hypoxia plays an important role in the pathogenesis of areca quid chewing-associated OSF. These pharmacological agents may be further used as chemoprevention agents for OSF.

Antifibrotic effect of Centella asiatica Linn and asiatic acid on arecoline-induced fibrosis in human buccal fibroblasts

AIM

The aim of the present study was to investigate the in vitro antifibrogenic effects of Centella asiatica Linn (CA) and its bioactive triterpene aglycone asiatic acid (AA) on arecoline-induced fibrosis in primary human buccal fibroblasts (HBF).

METHODS

An ethanolic extract of CA was prepared, and AA was purchased commercially. High-performance thin-layer chromatography (HPTLC) was performed to quantify AA in the CA extract; colorimetric assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) was performed to determine an half-maximal inhibitory concentration. HBF were cultured and stimulated with arecoline. The inhibitory effects of CA and AA at different concentrations were assessed using gene-expression studies on fibrosis-related markers: transforming growth factor-β1, collagen 1 type 2, and collagen 3 type 1. The stimulatory effect of arecoline and the inhibitory effect of AA on fibroblast morphology and extracellular matrix were assessed qualitatively using Masson trichrome stain.

RESULTS

The HPTLC analysis determined 1.2% AA per 100 g of CA extract. Arecoline produced a concentration-dependent increase in the fibrotic markers, treatment with CA significantly downregulated fibrotic markers at higher concentrations, and AA downregulated at lower concentrations. Arecoline altered fibroblast morphology and stained strongly positive for collagen, and AA treatment regained fibroblast morphology with faint collagen staining.

CONCLUSION

CA and AA can be used as antifibrotic agents.

Oral submucous fibrosis: an update

Oral submucous fibrosis (OSF) is a premalignant condition caused by betel chewing. It is very common in Southeast Asia but has started to spread to Europe and North America. OSF can lead to squamous cell carcinoma, a risk that is further increased by concomitant tobacco consumption. OSF is a diagnosis based on clinical symptoms and confirmation by histopathology. Hypovascularity leading to blanching of the oral mucosa, staining of teeth and gingiva, and trismus are major symptoms. Major constituents of betel quid are arecoline from betel nuts and copper, which are responsible for fibroblast dysfunction and fibrosis. A variety of extracellular and intracellular signaling pathways might be involved. Treatment of OSF is difficult, as not many large, randomized controlled trials have been conducted. The principal actions of drug therapy include antifibrotic, anti-inflammatory, and antioxygen radical mechanisms. Potential new drugs are on the horizon. Surgery may be necessary in advanced cases of trismus. Prevention is most important, as no healing can be achieved with available treatments.

Regulation of protease-activated receptor-1 expression in human buccal fibroblasts stimulated with arecoline

BACKGROUND

The purpose of this study was to compare the major thrombin receptor protease-activated receptor-1 (PAR-1) expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanisms that may lead to induce PAR-1 expression.

METHODS

Thirty OSF and 10 normal buccal mucosa specimens were examined by immunohistochemistry. Buccal mucosal fibroblasts (BMFs) were challenged with arecoline by using Western blot analysis. N-acetyl-L-cysteine (NAC), LY294002, herbimycin A, NS-398, and PD98059 were added to find the possible regulatory mechanisms.

RESULTS

PAR-1 expression was significantly higher in OSF specimens (p < .05). Arecoline was found to elevate PAR-1 expression in a dose-dependent and time-dependent manner (p < .05). The addition of NAC, LY294002, herbimycin A, NS398, and PD98059 markedly inhibited the arecoline-induced PAR-1 expression (p < .05).

CONCLUSION

PAR-1 expression is significantly upregulated in areca quid chewing-associated OSF. Arecoline-induced PAR-1 expression was downregulated by NAC, LY294002, herbimycin A, NS398, and PD98059.

Heat shock protein 27 expression in areca quid chewing-associated oral squamous cell carcinomas

OBJECTIVES

Heat shock protein (HSP) 27 is a low-molecular-weight protein that functions as a molecular chaperone and plays a cytoprotective role through its antioxidant activity during cell stress. Areca quid chewing is associated with the high incidence of oral squamous cell carcinomas (OSCCs) in Taiwan. The aim of this study was to compare heat shock protein 27 (HSP27) expression in OSCCs and the normal oral tissues.

METHODS

Forty-eight OSCCs from areca quid chewers and ten normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry for HSP27. The normal human oral keratinocytes (HOKs) were challenged with arecoline, the major alkaloid of areca nut, by Western blot for HSP27. Furthermore, epigallocatechin-3 gallate (EGCG), glutathione precursor N-acetyl-L-cysteine (NAC), cyclooxygenase-2 inhibitor NS-398, HSP inhibitor quercetin, extracellular signal-regulated protein kinase (ERK) inhibitor PD98059, and p38 inhibitor SB203580 were added to find the possible regulatory mechanisms.

RESULTS

Heat shock protein 27 exhibited higher expression in OSCCs than normal specimens (P < 0.05). Arecoline was found to elevate HSP27 expression in a dose- and time-dependent manner (P < 0.05). The additions of pharmacological agents were found to inhibit arecoline-induced HSP27 expression (P < 0.05).

CONCLUSIONS

Heat shock protein 27 expression is significantly elevated in areca quid chewing-associated OSCCs. Arecoline-induced HSP27 expression was downregulated by EGCG, NS398, NAC, quercetin, PD98059, and SB203580.

β-catenin expression in areca quid chewing-associated oral squamous cell carcinomas and upregulated by arecoline in human oral epithelial cells

BACKGROUND/PURPOSE

Nuclear localization of β-catenin is known to associate with malignant transformation of many squamous cell carcinomas. The aim of this study was to compare β-catenin expression in normal human oral epithelium and areca quid chewing associated oral squamous cell carcinomas (OSCCs) and further to explore the potential mechanisms that may lead to induce β-catenin expression.

METHODS

A total of 40 areca quid chewing-associated OSCCs and 10 normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The oral epithelial cell line GNM cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, extracellular signal-regulated protein kinase inhibitor PD98059, glutathione precursor N-acetyl-l-cysteine (NAC), tyrosine kinase inhibitor herbimycin-A, p38 inhibitor SB203580, and phosphatidylinositaol 3-kinase inhibitor LY294002 were added to find the possible regulatory mechanisms.

RESULTS

β-catenin expression was significantly higher in OSCC specimens than that in normal oral epithelial specimens (p < 0.05). It was demonstrated that normal oral epithelium showed only membranous staining for β-catenin, and membranous staining was lost or reduced with an increase in cytoplasmic/nuclear staining in OSCCs. Arecoline was found to elevate β-catenin expression in a dose-dependent manner (p < 0.05). The addition of PD98059, NAC, herbimycin-A, SB203580, and LY294002 markedly inhibited the arecoline-induced β-catenin expression (p < 0.05).

CONCLUSION

β-catenin expression is significantly upregulated in areca quid chewing-associated OSCC. The localization of β-catenin expression is correlated with the tumor size and clinical stage. In addition, β-catenin expression induced by arecoline is downregulated by PD98059, NAC, herbimycin-A, SB203580, and LY294002.

Heat shock protein 47 expression in oral squamous cell carcinomas and upregulated by arecoline in human oral epithelial cells

BACKGROUND

Heat shock protein 47 (HSP47) is a product of CBP2 gene located at chromosome 11q13.5, a region frequently amplified in human cancers. Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). The aim of this study was to compare HSP47 expression in normal human oral epithelium and OSCC and further to explore the potential mechanisms that may lead to induce HSP47 expression.

METHODS

Thirty-two OSCC specimens and ten normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The oral epithelial cell line OC2 cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), extracellular signal-regulated protein kinase (ERK) inhibitor PD98059, phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, cyclooxygenase-2 inhibitor NS-398, and tyrosine kinase inhibitor herbimycin A were added to find the possible regulatory mechanisms.

RESULTS

HSP47 expression was significantly higher in OSCC specimens than normal epithelium (P<0.05). No significant difference in HSP47 expression was observed with respect to age, sex, T category, stage, and differentiation (P>0.05). The lower HSP47 expression was associated with lymph node metastasis (P=0.015). Arecoline was found to elevate HSP47 expression in a dose- and time-dependent manner (P<0.05). The addition of NAC, PD98059, LY294002, NS398, and herbimycin A markedly inhibited the arecoline-induced HSP47 expression (P<0.05).

CONCLUSION

  Our findings demonstrated that HSP47 expression is significantly upregulated in areca quid chewing-associated OSCCs. HSP47 could be used clinically as a marker for lymph node metastasis of oral carcinogenesis. In addition, arecoline-induced HSP47 expression was downregulated by NAC, PD98059, LY294002, NS398, and herbimycin A.

Hypoxia inducible factor-1α expression in areca quid chewing-associated oral squamous cell carcinomas

OBJECTIVES

Hypoxia inducible factor (HIF)-1α gene expression is mainly induced by tissue hypoxia. Overexpression of HIF-1α has been demonstrated in a variety of cancers. The aim of this study was to compare HIF-1α expression in normal human oral epithelium and areca quid chewing-associated oral squamous cell carcinoma (OSCC) and further to explore the potential mechanisms that may lead to induce HIF-1α expression.

METHODS

Twenty-five OSCC from areca quid chewing-associated OSCC and 10 normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The oral epithelial cell line GNM cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), AP-1 inhibitor curcumin, extracellular signal-regulated protein kinase inhibitor PD98059, and protein kinase C inhibitor staurosporine were added to find the possible regulatory mechanisms.

RESULTS

Hypoxia inducible factor-1α expression was significantly higher in OSCC specimens than normal specimen (P<0.05). Arecoline was found to elevate HIF-1α expression in a dose- and time-dependent manner (P<0.05). The addition of NAC, curcumin, PD98059, and staurosporine markedly inhibited the arecoline-induced HIF-1α expression (P<0.05).

CONCLUSIONS

Hypoxia inducible factor-1α expression is significantly upregulated in areca quid chewing-associated OSCC and HIF-1α expression induced by arecoline is downregulated by NAC, curcumin, PD98059, and staurosporine.

Hemeoxygenase-1 expression in response to arecoline-induced oxidative stress in human umbilical vein endothelial cells

BACKGROUND

Arecoline, the most abundant areca alkaloid, has been reported to stimulate reactive oxygen species (ROS) production in several cell types. Overproduction of ROS has been implicated in atherogenesis. Hemeoxygenase-1 (HO-1) has cytoprotective activities in vascular tissues. This study investigated the effect of arecoline on adhesion molecule expression and explored the role of HO-1 in this process.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with arecoline, then ROS levels and the expression of adhesion molecules and HO-1 were analyzed and potential signaling pathways investigated.

RESULTS

After 2h of arecoline treatment, ROS production was stimulated and reached a maximum at 12h. Expression of the adhesion molecules ICAM and VCAM was also induced. Glutathione pretreatment completely blocked arecoline-stimulated ROS production and VCAM expression, but not ICAM expression. Arecoline also induced HO-1 expression and this effect was partly due by ROS stimulation. Inhibition of c-jun N-terminal kinase (JNK) by SP600125, p38 by SB 203580, or tyrosine kinase by genistein reduced arecoline-induced HO-1 expression. In contrast, inhibition of ERK (extracellular signal-related MAP kinase) by PD98059 had no effect. Transfection of HUVECs with the GFP/HO-1 gene, which resulted in a 5-fold increase in HO-1 activity, markedly, but not completely, inhibited the decrease in cell viability caused by arecoline.

CONCLUSIONS

This study demonstrates that, in HUVECs, arecoline stimulates ROS production and ICAM and VCAM expression. HO-1 expression is also upregulated through the ROS, tyrosine kinase, and MAPK (JNK and p38) signaling pathways.

The upregulation of metallothionein-1 expression in areca quid chewing-associated oral squamous cell carcinomas

Metallothioneins (MTs) are a family of low molecular weight, cysteine-rich, inducible, intracellular proteins that bind heavy metals with high affinity. MT-1 is known as a stress-inducible protein and functions as an antioxidant enzyme. Areca quid chewing is a major risk factor in the development and further progression of oral squamous cell carcinoma (OSCC). The aim of this study was to compare MT-1 expression in normal human oral epithelium and OSCC and further explore the potential mechanism that may lead to induce MT-1 expression. Thirty four OSCC and 10 normal epithelium specimens were examined by immunohistochemistry and analyzed by the clinico-pathological profiles. The oral epithelial cell line GMN cells were challenged with arecoline, a major areca nut alkaloid, by reverse-transcriptase polymerase chain reaction. Furthermore, tobacco smoke carcinogen benzo[a]pyrene (BaP) and glutathione (GSH) precursor N-acetyl-l-cysteine (NAC) were added to find the possible regulatory mechanisms. The results from immunohistochemistry demonstrated that MT-1 expression was significantly higher in OSCC specimens (p<0.05). No significant difference in MT-1 expression was observed with respect to age, sex, T category, and stage (p>0.05). The high MT-1 expression was associated with lymph node metastasis (p=0.012). In addition, arecoline was found to elevate MT-1 mRNA in a dose-dependent manner (p<0.05). Furthermore, the addition of BaP enhanced the arecoline-induced MT-1 expression (p<0.05). The addition of NAC markedly inhibited the arecoline-induced MT-1 expression (p<0.05). These results lead to the conclusion that MT-1 expression is significantly upregulated in areca quid chewing associated-OSCC. The expression profile suggests MT-1 could be used clinically as a marker for tumors possessing the potential for lymph node metastasis. The compounds of tobacco products may act synergistically in the pathogenesis of OSCC in areca quid chewers. The regulation of MT-1 expression induced by arecoline is critically dependent on the intracellular GSH concentration.

The upregulation of heat shock protein 70 expression in areca quid chewing-associated oral squamous cell carcinomas

Heat shock protein 70 (HSP70) is an important stress-induced protein. Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). The aim of this study was to compare HSP70 expression in normal human oral epithelium and OSCC and further to explore the potential mechanisms that may lead to induce HSP70 expression. 41 OSCC and 10 normal epithelium specimens were examined by immunohistochemistry and analyzed by the clinico-pathological profiles. The oral epithelial cell line GNM cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), AP-1 inhibitor curcumin, extracellular signal-regulated protein kinase inhibitor PD98059, and protein kinase C inhibitor staurosporine were added to find the possible regulatory mechanisms. The results from immunohistochemistry demonstrated that HSP70 expression was significantly higher in OSCC specimens (p<0.05). No significant difference in HSP70 expression was observed with respect to age, sex, T category, and stage (p>0.05). The low HSP70 expression was associated with lymph node metastasis (p=0.005). The high HSP70 expression was found in poor differentiated tumor groups (p=0.036). Arecoline was found to elevate HSP70 expression in a dose- and time-dependent manner (p<0.05). The addition of NAC, curcumin, PD98059, and staurosporine markedly inhibited the arecoline-induced HSP70 expression (p<0.05). Taken together, HSP70 expression is significantly upregulated in areca quid chewing-associated OSCC. HSP70 could be used clinically as a marker for tumors possessing the potential for differentiation as well as lymph node metastasis. In addition, arecoline-induced HSP70 expression was downregulated by NAC, curcumin, PD98059, and staurosporine.

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 expression of NF-kappaB in oral submucous fibrosis--evidence for NF-kappaB induction by safrole in human buccal mucosal fibroblasts

Nuclear factor-kappa B (NF-kappaB) is considered to be important in many inflammatory and immune responses. The aim of this study was to compare NF-kappaB expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induction of NF-kappaB expression. Seventeen OSF and six normal buccal mucosa specimens were examined by immunohistochemistry. Primary human buccal mucosal fibroblasts (BMFs) were established and challenged with safrole, a major polyphenolic compound in the influorescence of Piper betel, by cytotoxicity and western blot assays. Furthermore, glutathione precursor N-acetyl-L-cysteine (NAC), extracellular signal-regulated protein kinase (ERK) inhibitor PD98059, cyclooxygenase-2 (COX-2) inhibitor NS-398, dexamethasone, and cyclosporin A were added to find the possible mechanism. NF-kappaB expression was significantly higher in OSF specimens and expressed mainly by fibroblasts, endothelial cells, and inflammatory cells. Safrole was cytotoxic to BMFs in a dose-dependent manner (p<0.05). Western blot demonstrated highly elevated NF-kappaB protein expression in BMFs stimulated by safrole (p<0.05). In addition, pretreatment with pharmacological agents markedly inhibited the safrole induced-NF-kappaB expression (p<0.05). The result suggests that chewing areca quid may activate NF-kappaB expression that may be involved in the pathogenesis of OSF. NF-kappaB expression induced by safrole in fibroblasts may be mediated by ERK activation and COX-2 signal transduction pathway.

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.

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.

Clastogenic effect for cigarette smoking but not areca quid chewing as measured by micronuclei in exfoliated buccal mucosal cells

The objective of this study was to use the micronuclei from exfoliated buccal mucosal cells to investigate the clastogenic effects of areca quid chewing and cigarette smoking, as well as the interaction between the two. The study population was selected from residents of seven villages recruited for a community-cohort study. A total of 141 subjects were recruited based on the regular consumption of cigarettes and betel quid. Salient personal characteristics were collected from interview using a specially designed questionnaire. Micronuclei were scored on Feulgen/fast green-stained smear preparations of exfoliated cells obtained by scraping the surface of the buccal mucosa. There was no significant interaction between the chewing of betel nut and cigarette smoking. Heavy smoking was positively associated with MN frequency, with areca quid chewing negatively associated. A significant positive trend was demonstrated for the relationship between MN frequency and either daily cigarette consumption or cumulative smoking pack-years. By contrast, negative trends were demonstrated for the analogous relationships with areca quid chewing. These results indicate that heavy smoking, but not areca quid chewing, increases MN formation. These findings suggest that the carcinogenesis of the oral cancers induced by areca quid chewing in Taiwan may be through a pathway other than genotoxicity.

Peroxynitrite mediates calcium-dependent mitochondrial dysfunction and cell death via activation of calpains

Chondrocyte cell death is a hallmark of inflammatory and degenerative joint diseases such as rheumatoid arthritis (RA) and osteoarthritis (OA), but the molecular and cellular mechanisms involved have yet to be elucidated. Because 3-nitrotyrosine, a marker for reactive nitrogen species such as peroxynitrite, has been observed in OA and RA cartilage and has been associated with chondrocyte cell death, we investigated the mechanisms by which peroxynitrite induces cell death in human articular chondrocytes. The earliest biochemical event observed, subsequent to treatment with either peroxynitrite or the peroxynitrite generator SIN-1, was a rapid rise in intracellular calcium that lead to mitochondrial dysfunction and cell death. Although, chondrocyte death exhibited several classical hallmarks of apoptosis, including annexin V labeling, increased fraction of cells with subG1 DNA content and DNA condensation, we did not find evidence for caspase involvement either by Western blotting, fluorimetric assays, or caspase inhibition. Additionally, peroxynitrite did not inhibit cellular caspase activity. Furthermore, using other established assays of cell viability, including the MTT assay and release of lactate dehydrogenase, we found that the predominant mode of cell death involved calcium-dependent cysteine proteases, otherwise known as calpains. Our data show, for the first time, that peroxynitrite induces mitochondrial dysfunction in cells via a calcium-dependent process that leads to caspase-independent apoptosis mediated by calpains.

Habitual betel quid chewing and risk for hepatocellular carcinoma complicating cirrhosis

This case-control study aimed to assess the independent and interactive role of habitual betel quid chewing and known risk factors for hepatocellular carcinoma (HCC). Subjects enrolled included 210 pairs of sex- and age-matched cirrhotic patients with HCC, patients with cirrhosis alone, and healthy controls. Information on risk factors was obtained through serologic examination of hepatitis B surface antigen (HBsAg) and antibodies to hepatitis C virus (anti-HCV), and a standardized personal interview with a structured questionnaire. Multivariate analysis indicated that betel quid chewing (odds ratio [OR], 5.81; 95% confidence interval [CI], 2.26-14.94); HBsAg (OR, 37.98; 95% CI, 19.65-73.42); and anti-HCV (OR, 47.23; 95% CI, 18.86-118.25) were independent risk factors for HCC when HCC patients were compared with healthy controls. Using patients with cirrhosis alone as a reference group, multivariate analysis indicated that only betel quid chewing (OR, 1.69; 95% CI, 1.04-2.76) and HBsAg (OR, 1.54; 95% CI, l.01-2.37) were independent risk factors for HCC. There was an additive interaction between betel quid chewing and the presence of either HBsAg (synergy index, 5.22) or anti-HCV (synergy index, 1.35). Moreover, a higher risk of HCC was associated with a longer duration of betel quid chewing and a larger amount of betel quid consumed (each p(for trend) < 0.0001). In conclusion, betel quid chewing is an independent risk factor for cirrhotic HCC. There is an additive interaction between betel quid chewing and chronic hepatitis B and/or hepatitis C virus infection.

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.

The up-regulation of cyclooxygenase-2 expression in human buccal mucosal fibroblasts by arecoline: a possible role in the pathogenesis of oral submucous fibrosis

BACKGROUND

Aberrant and persistent tissue inflammation are believed to play an important role on the occurrence of tissue fibrosis. Cyclooxygenase (COX)-2 is an inducible enzyme responsible for prostaglandin synthesis in certain inflammatory diseases. The purpose of this study was to compare COX-2 expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induce COX-2 expression.

METHODS

Fifteen OSF specimens and six normal buccal mucosa were examined by immunohistochemistry. Primary human buccal mucosa fibroblasts (BMFs) were established and challenged with arecoline analyzed by reverse transcriptase polymerase chain reaction. Furthermore, to elucidate whether induction of COX-2 is associated with cytotoxicity, aspirin (a non-selective inhibitor of COX enzyme) and NS-398 (a selective COX-2 inhibitor), were added to test their protective effects.

RESULTS

COX-2 expression was significantly higher in OSF specimens and expressed mainly by epithelial cells, endothelial cells, and cells with fibroblast morphology. In vitro studies indicated that BMFs did not express COX-2 constitutively. However, when the cells were treated with 80 micro g/ml arecoline, COX-2 expression was up-regulated as early as half an hour. This indicates that COX-2 expression is an early cellular response and regulated by arecoline at transcriptional level. In addition, pre-treatment with glutathione (GSH) precursor, 2-oxothiazolidine-4-carboxylic acid (OTZ), led to a decrease in induction of COX-2 mRNA by arecoline. GSH synthesis inhibitor, buthionine sulfoximine (BSO), was found to increase arecoline-induced COX-2 mRNA levels. Moreover, both of aspirin and NS-398 at non-cytotoxic doses are not able to prevent arecoline-induced cytotoxicity. This indicates that arecoline cytotoxicity is not directly via the induction of COX-2 expression.

CONCLUSIONS

Taken together, these results suggest that COX-2 expression is significantly up-regulated in OSF tissues from areca quid chewers and arecoline may among other constituents be responsible for the enhanced COX-2 expression in vivo. The regulation of COX-2 expression induced by arecoline is critically dependent on the cellular GSH concentration.

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.