Genetic toxicology and toxicokinetics of arecoline and related areca nut compounds: an updated review.

Areca nut (AN) is consumed by more than 600 million of individuals, particularly in some regions of South Asia, East Africa, and tropical Pacific, being classified as carcinogenic to humans. The most popular way of exposure consists of chewing a mixture of AN with betel leaf, slaked lime, and other ingredients that may also contain tobacco named betel quid (BQ). Arecoline is the principal active compound of AN, and, therefore, has been systematically studied over the years in several in vitro and in vivo genotoxicity endpoints. However, much of this information is dispersed, justifying the interest of an updated and comprehensive review article on this topic. In this sense, it is thus pertinent to describe and integrate the genetic toxicology data available as well as to address key toxicokinetics aspects of arecoline. This review also provides information on the effects induced by arecoline metabolites and related compounds, including other major AN alkaloids and nitrosation derivatives. The complexity of the chemicals involved renders this issue a challenge in genetic toxicology. Overall, positive results in several endpoints have been reported, some of them suggesting a key role for arecoline metabolites. Nevertheless, some negative genotoxicity findings for this alkaloid in short-term assays have also been reported in the literature. Finally, this article also collates information on the potential mechanisms of arecoline-induced genotoxicity, and suggests further approaches to tackle this important toxicological issue.

Aberrant expression of DUSP4 is a specific phenomenon in betel quid-related oral cancer.

Oral cancer due to betel quid chewing habit is very common in South Asian countries. We attempted to detect the presence of a novel gene in epithelial cells stimulated with arecoline, a main component of betel quid. Human gingival epithelial progenitors were cultured and treated with a 3-day alternating regimen with/without 50 µg/ml arecoline for 1 month. DNA microarray and methylation arrays were analyzed to identify the candidate genes. Immunohistochemical staining was performed in the tissue samples. Genome-wide analyses, quantitative reverse transcription PCR and quantitative methylation-specific PCR revealed DUSP4 as the most significant and promising gene. The methylation levels of DUSP4 were significantly higher in the betel quid-related oral squamous cell carcinoma (OSCC) than those in the non-related OSCC and controls (Mann-Whitney U test, p < 0.05). The number of DUSP4 immunopositive cells in betel quid-related OSCC was significantly higher than those from the non-chewing patients and the controls (p < 0.05). Hypermethylation of DUSP4 may be considered as a specific event in betel quid-related oral cancer.

Arecoline induces epithelial mesenchymal transition in HK2 cells by upregulating the ERK-mediated signaling pathway.

Arecoline, a component of betel nuts, is a known carcinogen that causes oral cancers among those who chew betel nuts. Betel nut chewing is also associated with an increased risk of chronic kidney disease (CKD), but the role of arecoline in this association is unclear. This in vitro study investigates the effects of arecoline on cultured human kidney (HK2) cells. We observed that arecoline had no effect on cell viability but increased cell migration in a dose-dependent manner. Western blot analysis showed that arecoline treatment caused a dose-dependent decrease in E-cadherin expression and dose-dependent increases in N-cadherin, vimentin, α-SMA, and collagen expression; reverse transcriptase-polymerase chain reaction analysis revealed dose-dependent increases in α-SMA and collagen mRNA. Arecoline treatment upregulated the expression of phosphorylated extracellular signal-regulated kinase through epithelial mesenchymal transition and renal fibrosis in HK2 cells. These findings demonstrate that arecoline plays a role in inducing the epithelial mesenchymal transition and fibrogenesis in renal tubule cells and suggest that arecoline promotes the progression of CKD.

How Each Component of Betel Quid Is Involved in Oral Carcinogenesis: Mutual Interactions and Synergistic Effects with Other Carcinogens-a Review Article.

PURPOSE OF REVIEW: The roles of the components of betel quid in oral carcinogenesis remain unclear. The purpose of the present review is to highlight the effect of each component of betel quid and to discuss the synergistic effects of other carcinogens along with betel quid in the development of oral cancer in habitual betel quid chewers. RECENT FINDINGS: Betel quid may synergistically participate in carcinogenesis by disrupting the compositions of oral microbiota, accompanied by endotoxins secretion and reactive oxygen species (ROS) production. Microbiome dysbiosis mediated by synergistic effects of betel quid chewing, smoking, and alcohol drinking is possibly linked to oral carcinogenesis, which is firstly discussed in this report. Betel quid and other carcinogenic components, mainly contribute to downregulate the antioxidant proteins and lead to the induction of ROS. The elimination of ROS may prove most effective chemoprevention for betel quid-mediated oral carcinogenesis.

[Systematic evaluation for safety of traditional Chinese medicine Areca catechu and its preparations].

The authors systemically evaluated and analyzed the safety of Areca catechu from domestic and foreign literatures about the herbal origin, toxicity recorded in ancient/current documents, safety case reports of clinical A. catechu, experimental studies on toxicity in recent years, and differences of safety risk between edible and medicinal A. catechu. Subsequently, they proposed a preliminary summary about the clinical characteristics and potential risk factors of safety related cases of A. catechu and its preparations. According to the authors, although clinical adverse events of A. catechu were fewer and controllable, clinicians shall stillstrictly standardize its application, and rationally combine it with other herbs, while strengthening fundamental and clinical studies related to safety, so as to give better guidance to safety application of A. catechu in clinic.

Proteomics Analysis Reveals Involvement of Krt17 in Areca Nut-Induced Oral Carcinogenesis.

The areca nut is a known carcinogen that causes oral cancer in individuals in Southeast Asia, but the molecular mechanism that leads to this malignancy is still unclear. To mimic the habit of areca nut chewing, our laboratory has established four oral cancer cell sublines (SAS, OECM1, K2, C9), which have been chronically exposed to areca nut extract (ANE). To elucidate the molecular basis of areca nut-induced oral carcinogenesis, the differential proteomes between oral cancer cells and the ANE-treated sublines were determined using isobaric mass tag (iTRAQ) labeling and multidimensional liquid chromatography-mass spectrometry (LC-MS/MS). Over 1000 proteins were identified in four sublines, and 196 proteins were found to be differentially expressed in at least two ANE-treated sublines. A bioinformatic analysis revealed that these proteins participate in several pathways, and one of the most prominent pathways was the regulation of epithelial to mesenchymal transition (EMT). In all, 24 proteins including Krt17 were confirmed to be differentially expressed in the ANE-treated sublines. To reveal additional information on the mechanism of ANE-induced carcinogenesis, Krt17 was further investigated. Krt17 knockdown significantly suppressed ANE-induced cell migration and invasion and modulated the EMT process. Furthermore, in a murine model of carcinogen-induced (arecoline cocktail, an active compound of ANE) oral cancer, Krt17 was significantly up-regulated in all hyperplastic tissues and in carcinoma tissues (p < 0.001). In conclusion, we have identified a proteome of oral cancer cells that is associated with chronic areca nut exposure. Krt17 was demonstrated to contribute to areca nut-induced oral malignancy. The results of this study contribute to risk assessment, disease prevention and other clinical applications associated with areca nut-induced oral cancer.

Induction of chromosome instability and stomach cancer by altering the expression pattern of mitotic checkpoint genes in mice exposed to areca-nut.

BACKGROUND: There are strong indications for a causal association between areca-nut consumption and cancers. In Meghalaya, India, the variety of areca-nut is used as raw and unprocessed form whose chemical composition and pharmacological actions have been reported. Yet we know little on the initial pathway involved in areca-nut associated carcinogenesis since it is difficult to assess its effects on genetic alterations without interference of other compounding factors. Therefore, present study was undertaken in mice to verify the ability of raw areca-nut (RAN) to induce cancer and to monitor the expression of certain genes involved in carcinogenesis. This study was not intended to isolate any active ingredients from the RAN and to look its action. METHODS: Three groups of mice (n = 25 in each) were taken and used at different time-points for different experimental analysis. The other three groups of mice (n = 15 in each) were considered for tumor induction studies. In each set, two groups were administered RAN-extract ad libitum in drinking water with or without lime. The expression of certain genes was assessed by conventional RT-PCR and immunoblotting. The mice were given the whole RAN-extract with and without lime in order to mimic the human consumption style of RAN. RESULTS: Histological preparation of stomach tissue revealed that RAN induced stomach cancer. A gradual increase in the frequency of precocious anaphase and aneuploid cells was observed in the bone marrow cells with a greater increment following RAN + lime administeration. Levels of p53, Bax, Securin and p65 in esophageal and stomach cells were elevated during early days of RAN exposure while those of different mitotic checkpoint proteins were downregulated. Apoptotic cell death was detected in non-cancerous stomach cells but not in tumor cells which showed overexpression of Bax and absence of PARP. CONCLUSION: Present study suggested (a) RAN induces stomach cancer, however, presence of lime promoted higher cell transformation and thereby developed cancer earlier, (b) perturbations in components of the chromosome segregation machinery could be involved in the initial process of carcinogenicity and (c) the importance of precocious anaphase as a screening marker for identification of mitotic checkpoint defects during early days.

Systematic Review of Roles of Arecoline and Arecoline N-Oxide in Oral Cancer and Strategies to Block Carcinogenesis.

Betel quid and areca nut are complex mixture carcinogens, but little is known about whether their derived single-agent arecoline or arecoline N-oxide (ANO) is carcinogenic, and the underlying mechanisms remain unclear. In this systematic review, we analyzed recent studies on the roles of arecoline and ANO in cancer and strategies to block carcinogenesis. In the oral cavity, flavin-containing monooxygenase 3 oxidizes arecoline to ANO, and both alkaloids conjugate with N-acetylcysteine to form mercapturic acid compounds, which are excreted in urine, reducing arecoline and ANO toxicity. However, detoxification may not be complete. Arecoline and ANO upregulated protein expression in oral cancer tissue from areca nut users compared to expression levels in adjacent normal tissue, suggesting a causal relationship between these compounds and oral cancer. Sublingual fibrosis, hyperplasia, and oral leukoplakia were diagnosed in mice subjected to oral mucosal smearing of ANO. ANO is more cytotoxic and genotoxic than arecoline. During carcinogenesis and metastasis, these compounds increase the expression of epithelial-mesenchymal transition (EMT) inducers such as reactive oxygen species, transforming growth factor-ß1, Notch receptor-1, and inflammatory cytokines, and they activate EMT-related proteins. Arecoline-induced epigenetic markers such as sirtuin-1 hypermethylation, low protein expression of miR-22, and miR-886-3-p accelerate oral cancer progression. Antioxidants and targeted inhibitors of the EMT inducers used reduce the risk of oral cancer development and progression. Our review findings substantiate the association of arecoline and ANO with oral cancer. Both of these single compounds are likely carcinogenic to humans, and their mechanisms and pathways of carcinogenesis are useful indicators for cancer therapy and prognosis.

Reproductive toxic potential of panmasala in male Swiss albino mice.

Some ingredients of panmasala have the ability to penetrate the blood-testis barrier but the reproductive toxic potential of panmasala has not been studied. This study is aimed to assess the possible damage caused by panmasala to male reproductive system in mice. Swiss albino male mice were randomly divided into 7 groups receiving either standard control diet or panmasala-containing diet. Three doses (0.5%, 1.5% and 3%) of panmasala plain (PMP) as well as panmasala with tobacco (PMT)-gutkha were given for a period of 6 months. Assessment of organ weight, sperm count and morphology, spermatid count, sperm production, testicular 17ß-hydroxysteroid dehydrogenase (17ß-HSD) activity and histology were conducted. A nonsignificant decrease in absolute and relative weight of testis and epididymis was observed. Spermatid count, sperm count and production were significantly decreased and 17ß-HSD activity was found considerably declined at 3% of both PMP- and PMT-treated groups as compared to control. The histological observations revealed panmasala induced testicular damage. Abnormal morphology of sperm head shape was significantly elevated in higher doses of both types of panmasala-treated groups than control. The results suggests that panmasala has reproductive toxic potential and more alteration is seen with gutkha as compared to panmasala plain, indicating that similar effects might also be possible in humans.

Evaluation of cytotoxicity of areca nut and its commercial products on normal human gingival fibroblast and oral squamous cell carcinoma cell lines.

Consumption of areca nut products is the most common cause of oral cancers, particularly in South Asian countries. This study evaluates the cytotoxic and necrotizing effects of areca nut and its formulations on normal human gingival fibroblasts (HGF-1) and oral squamous cell carcinoma (OSCC, CAL-27) cell lines. Identification of various carcinogens and adulterants using LC-HR-ESI-MS/MS analysis was performed in the extracts of areca nut and its products. Apart from alkaloids and flavonoids, a major adulterant, saccharin was found in all the samples of chalia (one of the most common chewing products of areca nut) in the ranges between 1.697-7.170 mg/g of the sample. Cytotoxic studies showed that most of the areca nut products were found cytotoxic to HGF-1 cells while being relatively non-cytotoxic against CAL-27 cells, rather they promote the growth of cancer cells. Our findings revealed that the components of areca nut and its products were injurious to HGF-1 cells and caused necrosis, which may attenuate HGF-1 protection toward oral epithelial cells. Moreover, the non-cytotoxic effect of these products on cancer cell lines suggests further predisposal of the habitual chewers for developing oral carcinomas. This study will give a better understanding of the hazardous effects of areca nut products.

Vildagliptin, a dipeptidyl peptidase-4 inhibitor, reduces betel-nut induced carcinogenesis in female mice.

AIM: Betel-nut, a popular masticatory among Southeast Asian populations is a class I carcinogen, previously associated with dyslipidemia and aberrant lipid metabolism, and is reported to be used more frequently by females, than males. This study investigates the potential of repurposing the anti-diabetic drug, vildagliptin, a dipeptidyl peptidase-4 inhibitor, for alleviating the oncogenic condition in female Swiss Albino mice administered an aqueous extract of betel-nut (AEBN) orally (2 mg ml-1) for 24 weeks. MAIN METHODS: Tissues were investigated by histopathological, immunohistochemical and apoptosis assays. Biochemical analyses of oxidative stress markers and lipid profile were performed using different tissues and sera. The expressions of different proteins involved in lipid metabolism and oncogenic pathways were evaluated by Western blotting. KEY FINDINGS: AEBN induced carcinogenesis primarily in the liver by significantly impairing AMPK signaling, inducing oxidative stress, activating Akt/mTOR signaling, increasing Ki-67 immunoreactivity and cyclin D1 expression, and significantly diminishing apoptosis. Co-administration of AEBN with vildagliptin (10 mg kg-1 body weight) for 8 weeks reduced liver dysplasia, and significantly decreased free palmitic acid, increased free oleic acid, normalized lipid profile, decreased oxidative stress, cyclin D1 expression, Ki-67 immunoreactivity, and Bcl2 expression, and increased the ratio of apoptotic/non-apoptotic cells. Mechanistically, vildagliptin elicited these physiological and molecular alterations by restoring normal AMPK signaling and reducing the cellular expressions of FASN and HMGCR, restoring AMPK-dependent phosphorylation of p53 at Ser-15 and reducing Akt/mTOR signaling. SIGNIFICANCE: These results indicate that vildagliptin may alleviate betel-nut induced carcinogenesis in the liver of female mice.

Is the blood donated by habitual nut quid chewers suitable for use in transfusion?

BACKGROUND/PURPOSE: Betel quid (BQ) chewing is a popular oral masticatory activity, and there are approximately 600 million BQ chewers worldwide. Although chewing BQ has been linked to the patho-genesis of oral cancer, leukoplakia, and oral submucous fibrosis. The question whether the mixed constituents present in areca nut, which may exert cytotoxic effects on red blood cells (RBCs), has never been addressed. METHODS: Heparinized blood specimens were obtained with informed consent from healthy laboratory personnel. RBCs were separated with the standard procedure and adjusted to 10% hematocrit with PBS. Various concentrations of areca nut extract (ANE; 100-800 microg/mL) were added to these RBC preparations and incubated at 37 degrees C for 4 hours. Two portions (0.4 mL each) of the incubated RBCs were then used for measuring osmotic deformability index and for observing RBC morphology with scanning electron microscopy. The remaining RBCs were used for determining membrane sulfhydryl groups and protein profiles by sodium dodecyl sulfate polyacrylamide gel electrophoresis. RESULTS: Blood incubated with various concentrations of ANE showed concentration-dependent decreases in osmotic deformability index and membrane sulfhydryl groups. Membrane protein profiles revealed a significant loss of the band 3 fraction, with the concomitant appearance of several new protein bands in the electropheretogram. Finally, drastic morphological changes of ANE-treated RBCs were observed. CONCLUSION: We suggest that to assure the quality of transfusion, the blood donated by a habitual BQ chewer should be used with caution because of its possible contamination with areca nut ingredients that may be cytotoxic to RBCs.

Oral cancer: Clinicopathological features and associated risk factors in a high risk population presenting to a major tertiary care center in Pakistan.

Oral squamous cell carcinoma (OSCC) has the highest prevalence in head and neck cancers and is the first and second most common cancer in males and females of Pakistan respectively. Major risk factors include peculiar chewing habits like areca nut, betel quid, and tobacco. The majority of OSCC presents at an advanced stage with poor prognosis. On the face of such a high burden of this preventable cancer, there is a relative lack of recent robust data and its association with known risk factors from Pakistan. The aim of this study was to identify the socioeconomic factors and clinicopathological features that may contribute to the development of OSCC. A total of 186 patients diagnosed and treated at a tertiary care hospital, Karachi Pakistan were recruited. Clinicopathological and socioeconomic information was obtained on a structured questionnaire. Descriptive analysis was done for demographics and socioeconomic status (SES) while regression analysis was performed to evaluate the association between SES and chewing habits, tumor site, and tumor stage. The majority of patients were males and the mean age of OSCC patients was 47.62±12.18 years. Most of the patients belonged to low SES (68.3%) and 77.4% were habitual of chewing. Gender (male) and SES were significantly associated with chewing habits (p<0.05). Odds of developing buccal mucosa tumors in chewers (of any type of substance) and gutka users were 2 and 4 times higher than non-chewers respectively. Middle age, chewing habits, and occupation were significantly associated with late stage presentation of OSCC (p<0.05). In conclusion, male patients belonging to low SES in their forties who had chewing habits for years constituted the bulk of OSCC. Buccal mucosa was the most common site in chewers and the majority presented with late stage tumors.

Betel quid-associated cancer: Prevention strategies and targeted treatment.

Betel quid (BQ) and areca nut use are at risk of cancer. This review includes the latest evidence of carcinogenesis caused by BQ exposure, suggests possible prevention strategies. We conducted a systematic literature search in the PubMed and Web of Science databases to identify relevant articles published in the past 10 years according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria. Arecoline N-oxide, a metabolite of areca nut, is likely an initiator in carcinogenesis and is detoxified by N-acetylcysteine. Oral potentially malignant disorder and reactive oxygen species involved in carcinogenesis pathways may be treatable using antioxidants. Screening programs conducted by trained physicians are useful for identifying patients with early stages of oral cancer in high-risk groups. Anti-inflammatory medications may be used as chemopreventive agents in the disease-free stage after surgery. The association between survival and tumor somatic mutations in patients who chew BQ should be addressed in cancer studies. Current evidence on the natural course from BQ exposure to cancer occurrence and development provides information for developing primary, secondary, and tertiary prevention strategies against BQ-associated cancer at clinical or translational levels.

Arecoline suppresses epithelial cell viability through the Akt/mTOR signaling pathway via upregulation of PHLPP2.

Arecoline, the major active ingredient of the betel nut, is involved in the pathogenesis of oral submucous fibrosis. However, the underlying mechanism of this pathogenesis remains unclear. In this study, we found that arecoline suppresses the cell proliferation of the HaCaT epithelial cell and induces cell cycle arrest at the G1/S phase with an IC50 of 50 µg/mL. Furthermore, we found that arecoline reduces the protein level of cyclin D1, but it has no effect on its mRNA level and protein stability, implying that arecoline may modulate the translation of cyclin D1. We also observed the downregulation of the Akt/mTOR signaling pathway after treatment with arecoline, which may be related to the translation of cyclin D1. RNA-seq analysis identified that PHLPP2, the direct upstream target of Akt, is significantly upregulated after arecoline treatment. siRNA-mediated knockdown of PHLPP2 recovered the phosphorylation state of Akt, as well as attenuated the effect of arecoline on cell viability. Thus, our study revealed the crucial role of PHLPP2 in arecoline-induced cell viability suppression.

MDM2 SNP 309 and p53 codon 72 polymorphisms are associated with the outcome of oral carcinoma patients receiving postoperative irradiation.

BACKGROUND AND PURPOSE: The p53 tumor suppression pathway is important in effects associated with radiotherapy. The mouse double minute 2 (MDM2) plays a pivotal role in this pathway by down regulating p53. A functional T-to-G polymorphism at nucleotide 309 in MDM2 promoter intron 1 (SNP309) has been identified which influenced transcription activity. A G-to-C SNP at p53 codon 72 results in an Arg/Pro polymorphism, which is associated with apoptosis induction potential and p53 mutation status. MATERIALS AND METHODS: We sequenced both MDM2 SNP309 and p53 codon 72 SNP in patients with oral squamous cell carcinoma (OSCC, n=189), oral submucosal fibrosis (OSF, n=70), and 116 controls. RESULTS: Neither MDM2 SNP309 nor p53 codon 72 SNP was associated with susceptibility to or the age at onset of OSCC or OSF. p53 codon 72 SNP Arg/Arg polymorphism was associated with the progression of OSCC, and the overall (OS) and disease-free survival (DFS) of irradiated patients. The MDM2 SNP309 G/G polymorphism was associated with poor OS in advanced OSCC, and the OS and DSF of irradiated patients. The combination of MDM2 SNP309 G/G and p53 codon 72 Arg/Arg polymorphism is associated with the worst OS and DFS. CONCLUSIONS: Advanced OSCC has high mortality and recurrence. We identified that both MDM2 SNP309 and p53 codon 72 SNP could be useful factors for evaluating the outcome of advanced OSCC treated with adjuvant radiation.

The effect of maternal betel quid exposure during pregnancy on adverse birth outcomes among aborigines in Taiwan.

In considering documented developmental toxicity and teratogenicity found in earlier research, maternal betel quid chewing may very well be linked to a higher risk of adverse birth outcomes. The aim of this study was to investigate the significance of betel quid chewing, together with the use of cigarettes or alcohol, either independently or combined, on birth-related outcomes. A total of 1264 aboriginal women who had just given birth in 10 hospitals in Southern and Eastern Taiwan were recruited. Information on their maternal and newborn characteristics was obtained from medical charts and by performing personal interviews using a validated questionnaire. Maternal areca nut chewing during pregnancy was found to be significantly associated with both birth weight loss (-89.54 g) and birth length reduction (-0.43 cm). A significantly lower male newborn rate (aOR=0.62) was observed among aboriginal women with a habit of betel quid chewing during pregnancy. The use of this substance conveyed a 2.40- and 3.67-fold independent risk of low birth weight and full-term low birth weight, respectively. An enhanced risk (aOR=3.26-5.99) of low birth weight was observed among women concomitantly using betel quid, cigarette and alcohol during gestation. Our findings suggest that betel quid chewing during pregnancy has a substantial effect on a number of birth outcomes, including sex ratio at birth, lower birth weight and reduced birth length.