Cytotoxicity and arecoline mechanisms in human gingival fibroblasts in vitro

Bioactive Components of Areca Nut: An Overview of Their Positive Impacts Targeting Different Organs

Areca catechu L. is a widely cultivated tropical crop in Southeast Asia, and its fruit, areca nut, has been consumed as a traditional Chinese medicinal material for more than 10,000 years, although it has recently attracted widespread attention due to potential hazards. Areca nut holds a significant position in traditional medicine in many areas and ranks first among the four southern medicines in China. Numerous bioactive compounds have been identified in areca nuts, including alkaloids, polyphenols, polysaccharides, and fatty acids, which exhibit diverse bioactive functions, such as anti-bacterial, deworming, anti-viral, anti-oxidant, anti-inflammatory, and anti-tumor effects. Furthermore, they also display beneficial impacts targeting the nervous, digestive, and endocrine systems. This review summarizes the pharmacological functions and underlying mechanisms of the bioactive ingredients in areca nut. This helps to ascertain the beneficial components of areca nut, discover its medicinal potential, and guide the utilization of the areca nut.

Areca nut and smokeless tobacco exposure induces micronucleus, other nuclear abnormalities and cytotoxicity in early chick embryo

Areca nut (AN) and smokeless tobacco (SLT) are indiscriminately consumed among the populations of Southeast and South Asian countries, even by women during the gestational period. This study aimed to investigate the genotoxic and cytotoxic potentials of AN and Sadagura (SG), a unique homemade SLT preparation, alone and in combination in early chick embryos. Fertile white leghorn chicken eggs were randomly divided into five treatment groups: vehicle control, positive control (Mitomycin C, 20 μg/egg), AN, SG, and AN+SG. AN, SG, and AN+SG were given at dosages of 0.125, 0.25, and 0.5 mg/egg. The hen's egg test for micronucleus induction (HET-MN) was performed in chick embryos to evaluate the genotoxic potential of the test agents. Furthermore, the cytotoxic potential was assessed by studying erythroblast cell populations and the polychromatic erythrocytes (PCEs) to normochromatic erythrocytes (NCEs) ratio. Our results indicated a significant increase (p < .001) in MN frequency and other nuclear abnormalities, suggesting the potential of AN and SG to cause genotoxicity. Also, AN and SG exposure alone and in combination considerably altered the erythroblast cell population (%) and the PCE to NCE ratio in all the treatment periods. Our findings established the genotoxic and cytotoxic potential of both AN and SG alone and in combination during early embryonic development in the chick embryo.

Carcinogenic Effects of Areca Nut and Its Metabolites: A Review of the Experimental Evidence

Oral cancers (OC) are among the most frequent malignancies encountered in Southeast Asia, primarily due to the prevalent habit of betel quid (BQ) and smokeless tobacco use in this region. Areca nut (AN), the primary ingredient in BQ, contains several alkaloids, including arecoline, arecaidine, guvacoline, and guvacine. These have been associated with both the AN abuse liability and carcinogenicity. Additionally, variations in AN alkaloid levels could lead to differences in the addictiveness and carcinogenic potential across various AN-containing products. Recent studies based on animal models and in vitro experiments show cellular and molecular effects induced by AN. These comprise promoting epithelial-mesenchymal transition, autophagy initiation, tissue hypoxia, genotoxicity, cytotoxicity, and cell death. Further, clinical research endorses these undesired harmful effects in humans. Oral submucosal fibrosis, a potentially malignant disease of the oral cavity, is predominantly reported from the geographical areas of the globe where AN is habitually chewed. OC in chronic AN users presents a more aggressive phenotype, such as resistance to anti-cancer drugs. The available evidence on the carcinogenicity of AN based on the findings reported in the recently published experimental studies is discussed in the present review.

Metabolism of the areca alkaloids - toxic and psychoactive constituents of the areca (betel) nut

Areca nut (AN) is consumed by millions of people for its therapeutic and psychoactive effects, making it one of the most widely self-administered psychoactive substances in the world. Even so, AN use/abuse is associated with myriad oral and systemic side effects, affecting most organ systems in the body. Alkaloids abundant in the nut (e.g. arecoline, arecaidine, guvacoline, and guvacine), collectively called the areca alkaloids, are presumably responsible for the major pharmacological effects experienced by users, with arecoline being the most abundant alkaloid with notable toxicological properties. However, the mechanisms of arecoline and other areca alkaloid elimination in humans remain poorly documented. Therefore, the purpose of this review is to provide an in-depth review of areca alkaloid pharmacokinetics (PK) in biological systems, and discuss mechanisms of metabolism by presenting information found in the literature. Also, the toxicological relevance of the known and purported metabolic steps will be reviewed. In brief, several areca alkaloids contain a labile methyl ester group and are susceptible to hydrolysis, although the human esterase responsible remains presumptive. Other notable mechanisms include N-oxidation, glutathionylation, nitrosamine conversion, and carbon-carbon double-bond reduction. These metabolic conversions result in toxic and sometimes less-toxic derivatives. Arecoline and arecaidine undergo extensive metabolism while far less is known about guvacine and guvacoline. Metabolism information may help predict drug interactions with human pharmaceuticals with overlapping elimination pathways. Altogether, this review provides a first-of-its-kind comprehensive analysis of AN alkaloid metabolism, adds perspective on new mechanisms of metabolism, and highlights the need for future metabolism work in the field.

Cytotoxic Effects of Betel Quid and Areca Nut Aqueous Extracts on Mouse Fibroblast, Human Mouth-Ordinary-Epithelium 1 and Human Oral Squamous Cell Carcinoma Cell Lines

Background:

Betel quid chewing is more common among the older generation in rural areas of Malaysia. Oral cancer in Asia has been associated with the habit of chewing betel quid and areca nut.

Objective:

This study aims to investigate the cytotoxic effects of betel quid and areca nut extracts on the fibroblast (L929), mouth-ordinary-epithelium 1 (MOE1) and oral squamous cell carcinoma (HSC-2) cell lines.

Methods:

L929, MOE1 and HSC-2 cells were treated with 0.1, 0.2 and 0.4 g/ml of betel quid and areca nut extracts for 24, 48 and 72 h. MTT assay was performed to assess the cell viability.

Results:

Both extracts, regardless of concentration, significantly reduced the cell viability of L929 compared with the control (P<0.05). Cell viability of MOE1 was significantly enhanced by all betel quid concentrations compared with the control (P<0.05). By contrast, 0.4 g/ml of areca nut extract significantly reduced the cell viability of MOE1 at 48 and 72 h of incubation. Cell viability of HSC-2 was significantly lowered by all areca nut extracts, but 0.4 g/ml of betel quid significantly increased the cell viability of HSC-2 (P<0.05).

Conclusion:

Areca nut extract is cytotoxic to L929 and HSC-2, whereas the lower concentrations of areca nut extract significantly increased the cell viability of MOE1 compared to the higher concentration and control group. Although betel quid extract is cytotoxic to L929, the same effect is not observed in MOE1 and HSC-2 cell lines. Further investigations are needed to clarify the mechanism of action.

Study of salivary arecoline in areca nut chewers

Aims:

Arecoline, a predominant alkaloid present in arecanut, has been implicated in the pathogenesis of several oral diseases because of its mutagenic and carcinogenic potential. The response of cultured cells to arecoline is highly dependent on its concentration; arecoline stimulates cultured cells above 0.1 μg/ml and is cytotoxic above 10 μg/ ml. Although this alkaloid seems important for areca nut induced oral diseases and carcinogenesis, little is known of the levels achieved before, during and after chewing. Also, it is prudent to understand its effects in arecanut chewers for a comprehensive understanding of its pathogenesis. Accordingly, the present study quantified the salivary arecoline levels in arecanut chewers.

Materials and Methods:

The study participants were divided into Study Group A & B and Control Group C; unstimulated whole saliva was collected by spitting method for a period of 5 min. Then, participants in Group A and C chewed 0.5 g of areca nut without any other additives while in Group B were asked to chew 0.5 g of inert rubber base impression material. Stimulated whole saliva from all three groups was collected into graduated tubes during chewing at time intervals of 1, 3, 5, 10, 15, 20 and 25 min. Then, all participants were asked to remove nut particles or inert rubber base material from the mouth, and saliva samples were collected further up to 20 min, changing tubes at 5 min interval. Salivary arecoline was quantitated by HPLC-MS. The tabulation and descriptive statistics of the study were carried out.

Results:

In the present study, baseline levels of arecoline were zero in all three groups, whereas mean salivary arecoline levels during chewing were 76.93 ng/ml, 129.83 ng/ml and 64.83 ng/ml and after chewing were 196.17 ng/ml, 321.12 ng/ml and 43.75 ng/ml in Groups A, B and Control respectively, which were significantly higher than reported threshold levels.

Conclusions:

The data from this study reveals that a significant amount of arecoline would be trapped in oral cavity, or being re-circulated between blood and saliva might have resulted in surprisingly high levels of arecoline even 10 mins after chewing in both groups after which the levels started declining. The higher levels of salivary arecoline achieved during and after chewing are enough to cause cytotoxic and genotoxic effects on oral tissues over a period of time in chronic chewers. The great differences in salivary arecoline levels achieved during chewing, may contribute to the variable response to areca nut seen in communities where this habit is widespread. Areca nut users have persistent background salivary arecoline levels long after chewing, whereas concentrations achieved are highly variable and consistent with a role in oral pre-malignancy and malignancy..

Expression of β1integrin in normal epithelium, oral submucous fibrosis and oral squamous cell carcinoma

INTRODUCTION AND AIMS

The possible reason suggested for epithelial atrophy in oral submucous fibrosis (OSMF) is ischemia. Dysregulation in the epithelial proliferation and maturation is also thought to be a cause. The β1 integrin identifies the oral epithelial stem cells. The changes induced by the arecanut on these cells may result in epithelial alterations. The aim of this study is to evaluate the stem cells distribution and percentage by assessing the β1 integrin expression.

MATERIALS AND METHODS

The study included normal oral mucosa (15 cases) and disease group (97 cases). The disease group was further subdivided into early (29 cases), moderate (34 cases), advanced OSMF (18 cases) and oral squamous cell carcinoma(OSCC) associated with OSMF (16 cases). The tissues were stained for β1 integrin antibodies. The positive cells and staining intensities were analysed to determine the staining index, and statistically evaluated using KW test statistics.

RESULTS

β1 integrin was observed in retepegs region and the percentage of positive cells was 14%- 30% in the control. In OSMF, the β1 integrin positivity was observed in basal and suprabasal layers, and the percentage was ranged from 2%-71%. β1 integrin expression in OSCC was observed both in central and peripheral cells and ranged from 17%-85%. On comparison, the difference in staining index among normal, OSMF and carcinomas was significant at p<0.01. The stem cells percentage was increased both in OSMF and carcinomas. The non-dysplastic epithelium of OSMF with severe atrophy showed lowest percentage. It is inferred that absence of stem cells and proliferation may attribute for the atrophy.

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.

Arecoline is cytotoxic for human endothelial cells

BACKGROUND

Oral submucous fibrosis is a pre-malignant fibrotic condition caused by areca nut use and involves reduced mucosal vascularity. Arecoline is the principal areca nut alkaloid and is cytotoxic for epithelium and fibroblasts. Endothelial cell cycle arrest is reported on exposure to arecoline, as is cytotoxicity for endothelial-lung carcinoma hybrid cells. We here describe cytotoxicity for primary human endothelial cultures from seven separate donors.

MATERIALS AND METHODS

Human umbilical vein endothelial cells were exposed to increasing concentrations of arecoline and examined by: phase-contrast microscopy, haemocytometer counts, transmission electron microscopy, lactate dehydrogenase release and the methyl-thiazol-tetrazolium assay.

RESULTS

Vacuolation and detachment of endothelium were observed at and above arecoline concentrations of 333 μg/ml or more. Ultrastructural features of cellular stress were seen after 24-h treatment with 111 μg/ml arecoline and included reduced ribosomal studding of endoplasmic reticulum, increased autophagolysosomal structures, increased vacuolation and reduced mitochondrial cristae with slight swelling. Similar changes were seen at 4 h with arecoline at 333 μg/ml or above, but with more severe mitochondrial changes including increased electron density of mitochondrial matrix and greater cristal swelling, while by 24 h, these cells were frankly necrotic. Haemocytometer counts were paralleled by both lactate dehydrogenase release and the methyl-thiazol-tetrazolium assays.

CONCLUSIONS

Arecoline is cytotoxic via necrosis for endothelium, while biochemical assays indicate no appreciable cellular leakage before death and detachment, as well as no clear effect on mitochondrial function in viable cells. Arecoline toxicity may thus contribute to reduced vascularity in oral submucous fibrosis.

Cytotoxicity and genotoxicity of chlorhexidine on macrophages in vitro

Chlorhexidine (CHX) is the most widely used antiseptic for wound, skin disinfection, and dental hygiene. The aim of this study is to investigate the possible correlation between CHX-induced cytogenotoxicity and alterations in normal cell cycle on RAW264.7 macrophages. The cytotoxicity, mechanism of cell death, mitotic activity, and reactive oxygen species (ROS) generation were determined by tetrazolium bromide reduction assay, flow cytometry, cytokinesis-block proliferation index, and superoxide dismutase-inhibitable reduction of ferricytochrome c, respectively. The genotoxicity was measured using comet assay and cytokinesis-block micronucleus assay. The cytotoxicity of CHX in RAW264.7 cells presented a dose- and time-dependent manner (p < 0.05). The mode of cell death shifted from apoptosis to necrosis when the dosage of CHX increased. The genotoxicity of CHX in RAW264.7 cells had shown DNA damage in a dose-dependent manner (p < 0.05). Prolongation of cell cycle and the increase of ROS generation also expressed in a dose-dependent manner (p < 0.05). Taken together, the data suggested that CHX-induced cytotoxicity and genotoxicity on macrophages may be via ROS generation.

Cytotoxicity of ammonium hexafluorosilicate on human gingival fibroblasts

Ammonium hexafluorosilicate (SiF), which is claimed to significantly improve occlusion of dentinal tubules, was proposed as a novel desensitizer for dentine hypersensitivity (DH). However, the cytotoxicity of SiF on oral cells is lacking. The purpose of this study was to investigate the cytotoxicity of SiF on human gingival fibroblasts (hGFs) under different dosages (0.001%, 0.01%, 0.1%, and 1%) and treatment durations (1, 5, 10, and 30min). Cell proliferation, mitochondrial membrane potential (MMP) and cell cycle were tested by MTT assay, JC-1 staining and flow cytometry, respectively. Glutathione (GSH) depletion was analyzed to further investigate the underlying mechanism of SiF-induced cytotoxicity. MTT assay showed that there was significantly lower number of viable cells when the hGFs were treated with 0.01% (10min), 0.1% (10 and 30min) and 1% (5, 10, and 30min) SiF than the control group (p<0.05). MMP decreased and GSH depletion increased dramatically along with higher concentrations (0.1% and 1% SiF) and prolonged times (10 and 30min). DNA synthesis [S (%)] of cells treated with 0.1% and 1% SiF (5, 10, and 30min) was significantly lower than the control group (p<0.05). Our results indicate exposure to up to 0.01% SiF for less than 5min causes low or no cytotoxicity in vitro.

Elevated snail expression mediates tumor progression in areca quid chewing-associated oral squamous cell carcinoma via reactive oxygen species

BACKGROUND

Snail is an important transcription factor implicated in several tumor progression and can be induced by reactive oxygen species (ROS). Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). Therefore, we hypothesize that the major areca nut alkaloid arecoline may induce Snail via ROS and involve in the pathogenesis of areca quid chewing-associated OSCC.

METHODOLOGY/PRINCIPAL FINDING

Thirty-six OSCC and ten normal oral epithelium specimens were examined by immunohistochemistry and analyzed by the clinico-pathological profiles. Cytotoxicity, 2', 7'-dichlorofluorescein diacetate assay, and western blot were used to investigate the effects of arecoline in human oral keratinocytes (HOKs) and oral epithelial cell line OECM-1 cells. In addition, antioxidants N-acetyl-L-cysteine (NAC), curcumin, and epigallocatechin-3 gallate (EGCG) were added to find the possible regulatory mechanisms. Initially, Snail expression was significantly higher in OSCC specimens (p<0.05). Elevated Snail expression was associated with lymph node metastasis (p = 0.031) and poor differentiation (p = 0.017). Arecoline enhanced the generation of intracellular ROS at the concentration higher than 40 µg/ml (p<0.05). Arecoline was also found to induced Snail expression in a dose- and time-dependent manner (p<0.05). Treatment with NAC, curcumin, and EGCG markedly inhibited arecoline induced Snail expression (p<0.05).

CONCLUSION/SIGNIFICANCE

Our results suggest that Snail overexpression in areca quid chewing-associated OSCC is associated with tumors differentiation and lymph node metastasis. Arecoline-upregulated Snail expression may be mediated by ROS generation. In addition, arecoline induced Snail expression was downregulated by NAC, curcumin, and EGCG.

The expression of O(6) -methylguanine-DNA methyltransferase in human oral keratinocytes stimulated with arecoline

BACKGROUND

O(6) -methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that can protect cells from carcinogenic effects of alkylating agents by removing adducts from the O(6) position of guanine. Evidences indicated that areca quid chewing may increase the risk of oral squamous cell carcinoma (OSCC). This study was to investigate the role of MGMT expression in OSCCs and the normal oral tissues.

METHODS

Thirty-two OSCCs from areca quid chewers and ten normal oral tissue biopsy samples without areca quid chewing were analyzed by the immunohistochemistry for MGMT. Primary human oral keratinocytes (HOKs) were challenged with arecoline, the major alkaloid of areca nut, by Western blot. Nicotine, an important component of cigarette smoke, was added to find the possible regulatory mechanisms.

RESULTS

Significant association was observed between low MGMT expression and advanced clinical stage of OSCCs and lymph node metastasis (P = 0.03). MGMT expression was significantly higher in patients only chewing areca quid than patients both chewing areca quid and smoking (P = 0.028). Arecoline was found to elevate MGMT expression in a dose- and time-dependent manner. The addition of nicotine was found to enhance arecoline-induced MGMT expression.

CONCLUSION

Our results indicate that MGMT could be used clinically as a predictive marker for tumor processing, the potential for lymph node metastasis as well as advanced clinical stage. MGMT expression was significantly upregulated by arecoline in HOKs. Nicotine has a synergistic effect of arecoline-induced MGMT expression. The cigarette smoking may act synergistically in the pathogenesis of OSCC in areca quid chewers via the upregulation of MGMT.

Association of betel nut with carcinogenesis: revisit with a clinical perspective

Betel nut (BN), betel quid (BQ) and products derived from them are widely used as a socially endorsed masticatory product. The addictive nature of BN/BQ has resulted in its widespread usage making it the fourth most abused substance by humans. Progressively, several additives, including chewing tobacco, got added to simple BN preparations. This addictive practice has been shown to have strong etiological correlation with human susceptibility to cancer, particularly oral and oropharyngeal cancers.

The PUBMED database was searched to retrieve all relevant published studies in English on BN and BQ, and its association with oral and oropharyngeal cancers. Only complete studies directly dealing with BN/BQ induced carcinogenesis using statistically valid and acceptable sample size were analyzed. Additional relevant information available from other sources was also considered.

This systematic review attempts to put in perspective the consequences of this widespread habit of BN/BQ mastication, practiced by approximately 10% of the world population, on oral cancer with a clinical perspective. BN/BQ mastication seems to be significantly associated with susceptibility to oral and oropharyngeal cancers. Addition of tobacco to BN has been found to only marginally increase the cancer risk. Despite the widespread usage of BN/BQ and its strong association with human susceptibility to cancer, no serious strategy seems to exist to control this habit. The review, therefore, also looks at various preventive efforts being made by governments and highlights the multifaceted intervention strategies required to mitigate and/or control the habit of BN/BQ mastication.

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.

Cell proliferative effect of polyxyloses extracted from the rhizomes of wild turmeric, Curcuma aromatica

Hot water-soluble crude polysaccharides were extracted from the rhizomes of wild turmeric, Curcuma aromatica Salisb. (Zingiberaceae), using dry grinding, boiling water extraction, and then ethanol precipitation. The crude polysaccharide extract was then fractionated by DEAE-cellulose ion exchange column chromatography, and subsequently further purified by Superdex G-200 gel filtration column chromatography, giving two relatively abundant polysaccharide fractions, called P11 and P21, and a much less common fraction P22 obtained in insufficient amounts for further analysis. The two main polysaccharide fractions were evaluated for monosaccharide composition by acid hydrolysis and high performance liquid chromatography (HPLC), whilst the molecular weight and functional groups were determined by gel permeable chromatography (GPC) and FT-IR, respectively. Fractions P11 and P21 were found to be polyxyloses with molecular weight-averages of 469,171 and 157,665 Da, respectively. P11 (100 microg/mL) could significantly induce human gingival fibroblast cells proliferation by 30%, while P21 (100 microg/mL) could significantly inhibit gingival fibroblast cells proliferation by 92%. The in vitro human primary gingival fibroblast cell proliferation in cell culture at a concentration of 100 microg/mL.

A new matrix for analyzing low molecular mass compounds and its application for determination of carcinogenic areca alkaloids by matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Arecoline is the main alkaloid present in the areca nut (or betel nut) and it has central nervous system effects. Its pharmacological activities induce the constriction of the bronchial smooth muscles, and stimulation of the lacrimal and intestinal glands. Chewing areca nut is harmful to health because this habit may increase the risk of the development of oral cancer. In this study, a fast method was provided for the determination of areca alkaloids by matrix-assisted laser desorption ionization (MALDI) mass spectrometer with a time-of-flight (TOF) analyzer. Traditionally the MALDI-TOF method was not suitable for the analysis of small molecular weight (m/z<600) compounds because of the high background of the matrix. In this study, a new matrix was utilized to decrease the background interference effectively. After simple sample preparation, 1 microL sample supernatant was mixed with 1 microL matrix and then deposited on the target plate. This new matrix was also used to test the MALDI imaging experiment. Application of this MALDI-TOF method for trace analysis of arecoline by this new matrix in human plasma at sub microM level proved workable.

Protective effects of antioxidants on micronuclei induced by camphorquinone/N,N-dimethyl-p-toluidine employing in vitro mammalian test system

Camphorquinone (CQ) is widely used as an initiator in modern visible-light (VL) cured resin systems. CQ is also characterized as a potential allergenic compound. To date, there is growing concern that CQ may produce genetic damage by inducing mutation. In this study, CQ in the presence of reducing agent N,N-dimethyl-p-toluidine (DMT) with or without VL irradiation was analyzed for the induction of chromosomal aberrations indicated by micronuclei (MN) induced in CHO cells. Our data demonstrated that an increase in the numbers of MN was observed with CQ/DMT with or without VL irradiation (p < 0.05). Significant prolongation of cell cycles was observed by the treatment with CQ/DMT with or without VL irradiation (p < 0.05). In addition, VL irradiated CQ/DMT was found to exhibit significantly genotoxic and cytotoxic effects as compared with CQ/DMT alone (p < 0.05). Furthermore, to determine whether oxidative stress could modulate the MN induced by CQ/DMT with or without VL irradiation in CHO cells, cells were pre-treated with various antioxidants 10 mM N-acetyl-L-cysteine (NAC), 2 mM ascorbic acid, and 2 mM alpha-tocopherol. The pre-treatment with antioxidants could antagonize not only the increased MN cells but also the prolonged cell cycle induced by CQ/DMT with or without VL irradiation in CHO cells (p < 0.05). Our findings provide the evidences for the induction of MN by CQ/DMT employing mammalian test system, indicating clastogenic activity of CQ/DMT with or without VL irradiation in vitro. In addition, VL irradiated CQ/DMT exhibits higher genotoxic and cytotoxic effects than CQ/DMT alone. Moreover, NAC, ascorbic acid, and alpha-tocopherol act as the antagonists against the genotoxicity and cytotoxicity of CQ/DMT with or without VL irradiation.

Characterization of Arecoline-Induced Effects on Cytotoxicity in Normal Human Gingival Fibroblasts by Global Gene Expression Profiling

Areca nut is the most widely used psychoactive substance and an important environmental risk factor for development of oral premalignant lesions and cancer. Arecoline, the major alkaloid of areca nut, has been known to cause cytotoxicity and genotoxicity in mammalian cells in vivo and in vitro and even contributes to carcinogenicity. However, the susceptible genes accounting for arecoline-induced damage in normal human oral cells are still lacking, which possibly involves in initial molecular damage via alternation of gene expression level on biological pathways. The present study was undertaken to characterize the toxic effects of arecoline in gene expression profiling on normal human gingival fibroblasts (HGF) using cDNA microarray and quantitative real-time reverse transcription PCR. The cytotoxicity of arecoline on HGF-1 cell line was elevated in a dose-dependent manner (p < 0.05) accompanied with distinct morphological change and formation of intracellular vacuoles were observed. At optimum concentration of arecoline determined from dose-response curve of the cytotoxicity, a large number of genes were significantly repressed than induced by arecoline in global gene expression profiling. Five induced- and seven repressed genes including glutathione synthetase were further validated, and their gene expression changes were increased in a dose-dependent manner in a concentration range of 50-150 microg/ml. In conclusion, we proposed a tentative model to explain arecoline-induced effects on contribution of oral pathogenesis. The findings identified that 12 susceptible genes can potentially serve as biomarkers of arecoline-induced damage in betel chewers.

Areca nut extracts reduce the intracellular reactive oxygen species and release of myeloperoxidase by human polymorphonuclear leukocytes

BACKGROUND AND OBJECTIVE

Polymorphonuclear leukocytes (PMN) represent the first line of host defense. Areca nut extract inhibits the bactericidal activity of, and the release of superoxide anion (O2- ) by, PMN. This study investigated the effects of areca nut extract on the intracellular production of reactive oxygen species (ROS) and on the extracellular release of lysosomal enzyme, myeloperoxidase (MPO), by PMN. The effects of arecoline, a principal component of areca nut, were also examined.

MATERIAL AND METHODS

Human PMN were treated with various concentrations of areca nut extract or arecoline followed by treatment with Hanks' balanced salt solution, with or without cytochalasin B and fMet-Leu-Phe (CB/fMLP). The viability of PMN was determined using propidium iodide staining and flow cytometry. The presence of intracellular ROS was determined using 2',7'-dichlorofluorescin diacetate and fluorometry. MPO release was determined using a substrate assay.

RESULTS

Areca nut extract (25 and 50 microg/ml) significantly decreased the viability of PMN. The intracellular levels of ROS and the extracellular release of MPO were induced in PMN by CB/fMLP. Exposure of PMN to areca nut extract (up to 25 microg/ml) or to arecoline (up to 2 mg/ml) did not directly affect the levels of ROS and MPO activity. However, under conditions that did not affect the viability of PMN, the ability of CB/fMLP to trigger production of intracellular ROS and release of MPO in human PMN was significantly suppressed by areca nut extract and arecoline.

CONCLUSION

Areca nut impaired the activation of PMN by CB/fMLP that might decrease the effectiveness of PMN in the host defense. Alternatively, exposure of PMN to areca nut extract could decrease the capacity of PMN to damage tissues.

A metabolomic approach to the metabolism of the areca nut alkaloids arecoline and arecaidine in the mouse

The areca alkaloids comprise arecoline, arecaidine, guvacoline, and guvacine. Approximately 600 million users of areca nut products, for example, betel quid chewers, are exposed to these alkaloids, principally arecoline and arecaidine. Metabolism of arecoline (20 mg/kg p.o. and i.p.) and arecaidine (20 mg/kg p.o. and i.p.) was investigated in the mouse using a metabolomic approach employing ultra-performance liquid chromatography-time-of-flight mass spectrometric analysis of urines. Eleven metabolites of arecoline were identified, including arecaidine, arecoline N-oxide, arecaidine N-oxide, N-methylnipecotic acid, N-methylnipecotylglycine, arecaidinylglycine, arecaidinylglycerol, arecaidine mercapturic acid, arecoline mercapturic acid, and arecoline N-oxide mercapturic acid, together with nine unidentified metabolites. Arecaidine shared six of these metabolites with arecoline. Unchanged arecoline comprised 0.3-0.4%, arecaidine 7.1-13.1%, arecoline N-oxide 7.4-19.0%, and N-methylnipecotic acid 13.5-30.3% of the dose excreted in 0-12 h urine after arecoline administration. Unchanged arecaidine comprised 15.1-23.0%, and N-methylnipecotic acid 14.8%-37.7% of the dose excreted in 0-12 h urine after arecaidine administration. The major metabolite of both arecoline and arecaidine, N-methylnipecotic acid, is a novel metabolite arising from carbon-carbon double-bond reduction. Another unusual metabolite found was the monoacylglyceride of arecaidine. What role, if any, that is played by these uncommon metabolites in the toxicology of arecoline and arecaidine is not known. However, the enhanced understanding of the metabolic transformation of arecoline and arecaidine should contribute to further research into the clinical toxicology of the areca alkaloids.

Immunosuppression, hepatotoxicity and depression of antioxidant status by arecoline in albino mice

BACKGROUND

There are about 600 million betel quid chewers in the world. Betal quid chewing is one of the major risk factors of hepatocarcinoma, oropharyngeal and esophagus cancers. Arecoline, the main Areca alkaloid of the betel nut is reported to have cytotoxic, genotoxic and mutagenic effects in various cells. It shows strong correlation to the incidence of oral submucosal fibrosis, leukoplakia and oral cancer, and has also been found to impose toxic manifestations in immune, hepatic and other defense systems of the recipient.

AIM

The precise molecular mechanisms underlying the toxic effects of arecoline deserve investigation. To clarify the action of arecoline on defense systems, immune, hepatic and detoxification system were studied in mice.

METHOD

Cell count and cell cycle of the splenocytes were studied for evaluating cell immunity. Liver function test (LFT) was followed by assaying different enzyme systems from serum (SGPT, SGOT and ALP) and liver (GST for detoxication enzyme, SOD and catalase for antioxidant enzymes and GSH for non-enzymatic antioxidant) and by ultrastructural studies of hepatocytes.

RESULTS

Here we report that arecoline arrested splenic lymphocyte cell cycle at lower concentration with induced apoptosis at higher concentration thereby causing immunosuppression in arecoline recipients. Besides, it resulted in hepatotoxicity in arecoline recipient mice by disrupting the hepatocyte ultrastructure, as judged by liver ultrastructural studies that showed decreased nuclear size, RER with profusely inflated cysternae and abundance of lipid droplets, and by up regulating hepatotoxic marker enzymes (SGOT and SGPT) in serum. Arecoline also caused depression of antioxidants, i.e., superoxide dismutase (SOD), catalase, reduced glutathione (GSH) and glutathione-S-transferase (GST) that are known to neutralize reactive oxygen species.

CONCLUSION

All these above-mentioned results led us to conclude that arecoline attacks multiple targets to finally generate systemic toxicity in mice.

In vitro effects of arecoline on sperm motility and cyclooxygenase-2 expression

Semen samples were obtained from 30 volunteers who had never consumed betel quid. Swim-up spermatozoa from the 30 seminal samples of non-betel quid chewers and also non-smokers, usually not exposed to passive smoking, were treated in vitro with arecoline at different concentrations to evaluate the action of these drugs on sperm motility. Highly motile sperms were collected and divided into 5 equal fractions. Four fractions were supplemented with various concentrations of arecoline and one as control. The study was carried out at time 0 and +1, +2, +3 and +4 hr of incubation. Sperm cells were also extracted and blotted with COX-2 antibody after arecoline treatment after 4 hr incubation. The sperm motility parameters, i.e., motility, average path velocity, curvilinear velocity, straight-line velocity and linearity, were significantly decreased after arecoline treatment. In vitro, arecoline induces the COX-2 expression of sperm cells in a dose-dependent manner. This is the first report to demonstrate that arecoline may mediate COX-2 expression in human sperms, resulting in inflammation response. This situation may act on the structure responsible for the flagellar motion and cause the reduction of sperm motility.

Prolonged exposure to arecoline arrested human KB epithelial cell growth: Regulatory mechanisms of cell cycle and apoptosis

Arecoline, the main areca alkaloid in betel quid (BQ), is reported to have cytotoxic, genotoxic, and mutagenic effects in various cells. It shows strong correlation to the incidence of oral submucous fibrosis, leukoplakia, and oral cancer. To clarify the role of arecoline in BQ-induced carcinogenesis, primary human gingival keratinocyes (GK) and human KB epithelial cells were used for studying the molecular mechanisms of arecoline-mediated cell cycle deregulation for comparison. After 24 h of exposure, arecoline (0.2-0.8 mM) inhibited KB cell growth in a dose- and time-dependent manner with a reduction in cell number by 27-37 and 37-58%, respectively, as determined by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and sulforhodamine B (SRB) assays. Incubation of KB cells with arecoline (0.1-0.4 mM) caused late-S and G2/M phases' cell cycle arrest. Western blot analysis revealed that arecoline induced cyclin Bl, Wee 1, and phosphorylated cdc2 protein levels whereas it declined p21 protein expression in KB cancer cells. Nevertheless, arecoline induced p21, but decreased cdc2 and cyclin B1 protein levels in GK. We demonstrated that higher concentrations of arecoline (0.2-1.2 mM) induced both cell necrosis and apoptosis as detected by DNA fragmentation and Annexin V-PI staining after long-term (48 h) treatment. Our results suggest that differential regulation of S and/or G2/M cell cycle-related proteins in the GK and KB cells play a crucial role in different stages of BQ-mediated carcinogenesis.

Induction of vascular endothelial growth factor gene expression by proinflammatory cytokines in human pulp and gingival fibroblasts

Vascular endothelial growth factor (VEGF) enhances the permeability of blood vessels, which is an important vascular change observed during inflammatory processes. The purpose of this in vitro study was to investigate the effect of proinflammatory cytokines on the expression of VEGF mRNA gene in human pulp and gingival fibroblasts. Interlukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) were used to evaluate VEGF mRNA gene expression in human pulp and gingival fibroblasts. The levels of mRNAs were measured by quantitative reverse-transcriptase polymerase chain reaction analysis. Both IL-1alpha and TNF-alpha induced significantly high levels of VEGF mRNA gene expression in human pulp and gingival fibroblasts (p < 0.05). In addition, TNF-alpha was found to be more effective in the induction of VEGF mRNA gene expression in pulp than gingival fibroblasts (p < 0.05). Moreover, IL-1alpha was found to be more effective in the induction of VEGF mRNA gene expression than TNF-alpha in gingival fibroblast cultures (p < 0.05). These results indicate that proinflammatory cytokines can induce VEGF mRNA gene expression, and such an effect may partially contribute to the destruction of pulpal and periapical tissues through promoting expansion of the vascular network coincident to progression of the inflammation.

Developmental toxicity of arecoline, the major alkaloid in betel nuts, in zebrafish embryos

BACKGROUND

The major alkaloid in the betel nut, arecoline, has been reported to be potent in inducing developmentally toxic effects by generally lowering the embryo weight and retarding development of the embryo. This study examined the adverse effects of arecoline and tried to unravel the mechanism through the tools of molecular biology.

METHODS

Arecoline was administered to zebrafish embryos by incubation at concentrations ranging from 0.01-0.04% (wt/vol) and lethality and morphological changes were recorded. The expression of genes was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization. In addition, the protective effects of several antioxidants were tested.

RESULTS

The survival rate of treated embryos during a three-day incubation significantly declined as the arecoline concentration increased. Treated embryos showed general growth retardation and lower rate of heartbeat. When examined at the 24-hr stage, the relative amounts of transcripts of p53, p21, and cyclin D1, and the spatial expression patterns of these genes in treated groups, were comparable to those of the untreated early stages of embryos. Finally, the addition of glutathione (GSH) or its precursor, N-acetyl-L-cysteine (NAC), ameliorated the developmental retardation of embryos by arecoline.

CONCLUSIONS

Arecoline-treated embryos exhibited general developmental retardation in a dose-dependent manner. Our results from RT-PCR, in situ hybridization, and antioxidant-protection experiments indicate that the mechanism underlying growth retardation by arecoline in embryos is predominantly due to a general cytotoxic effect induced by depletion of intracellular thiols.

High-performance liquid chromatographic determination of arecoline in human saliva

Arecoline (methyl-1,2,5,6-tetrahydro-1-methyl nicotinate) is an alkaloid found in the areca catechu nut which is a major component of the 'betel quid' chewed by a large proporation of the population in India, South Asia and the South Pacific islands. It is commonly associated with the development of oral leukoplakia, oral submucous fibrosis and oral cancer. We have developed a new ion-pairing reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of arecoline in saliva, using arecaidine (1,2,5,6-tetrahydro-1-methylnicotinic acid) as an internal standard. The optimal wavelength was established using UV absorbance scans. It was showed that 215 nm is the optimal wavelength to maximise the signal in detecting arecoline in the mobile phase. Arecoline was extracted from saliva with hexane-isoamyl alcohol (1%) and reconstituted with mobile phase for HPLC analysis. The developed method is an easy and reliable method of determining arecoline concentrations in saliva. Sensitivity, specificity, precision, accuracy and reproducibility of the method were demonstrated to be satisfactory for measuring the arecoline level.

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.