Potentiation of genotoxicity by concurrent application of compounds found in betel quid: arecoline, eugenol, quercetin, chlorogenic acid and Mn2+

Inhibition of cortical synaptic transmission, behavioral nociceptive, and anxiodepressive-like responses by arecoline in adult mice

Areca nut, the seed of Areca catechu L., is one of the most widely consumed addictive substances in the world after nicotine, ethanol, and caffeine. The major effective constituent of A. catechu, arecoline, has been reported to affect the central nervous system. Less is known if it may affect pain and its related emotional responses. In this study, we found that oral application of arecoline alleviated the inflammatory pain and its induced anxiolytic and anti-depressive-like behavior. Arecoline also increased the mechanical nociceptive threshold and alleviated depression-like behavior in naïve mice. In the anterior cingulate cortex (ACC), which acts as a hinge of nociception and its related anxiety and depression, by using the multi-electrode field potential recording and whole-cell patch-clamp recording, we found that the evoked postsynaptic transmission in the ACC of adult mice has been inhibited by the application of arecoline. The muscarinic receptor is the major receptor of the arecoline in the ACC. Our results suggest that arecoline alleviates pain, anxiety, and depression-like behavior in both physiological and pathological conditions, and this new mechanism may help to treat patients with chronic pain and its related anxiety and disorder in the future.

Pharmacodynamic, pharmacokinetic, toxicity, and recent advances in Eugenol's potential benefits against natural and chemical noxious agents: A mechanistic review

The active biological phytochemicals, crucial compounds employed in creating hundreds of medications, are derived from valuable and medicinally significant plants. These phytochemicals offer excellent protection from various illnesses, including inflammatory disorders and chronic conditions caused by oxidative stress. A phenolic monoterpenoid known as eugenol (EUG), it is typically found in the essential oils of many plant species from the Myristicaceae, Myrtaceae, Lamiaceae, and Lauraceae families. One of the main ingredients of clove oil (Syzygium aromaticum (L.), Myrtaceae), it has several applications in industry, including flavoring food, pharmaceutics, dentistry, agriculture, and cosmeceuticals. Due to its excellent potential for avoiding many chronic illnesses, it has lately attracted attention. EUG has been classified as a nonmutant, generally acknowledged as a safe (GRAS) chemical by the World Health Organization (WHO). According to the existing research, EUG possesses notable anti-inflammatory, antioxidant, analgesic, antibacterial, antispasmodic, and apoptosis-promoting properties, which have lately gained attention for its ability to control chronic inflammation, oxidative stress, and mitochondrial malfunction and dramatically impact human wellness. The purpose of this review is to evaluate the scientific evidence from the most significant research studies that have been published regarding the protective role and detoxifying effects of EUG against a wide range of toxins, including biological and chemical toxins, as well as different drugs and pesticides that produce a variety of toxicities, throughout view of the possible advantages of EUG.

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.

Areca nut extract (ANE) inhibits the progression of hepatocellular carcinoma cells via activation of ROS production and activation of autophagy

Hepatocellular carcinoma (HCC) is a worldwide health problem. Currently, there is no effective therapeutic strategy for HCC patients. Chewing areca nut is closely associated with oral cancer and liver cirrhosis. The therapeutic effect of areca nut extract (ANE) on HCC is unknown. Our results revealed that ANE treatment caused a reduction in cell viability and an increase in cell apoptosis and suppressed tumor progression in xenograft models. ANE-treated didn't induce liver tumor in nude mice. For mechanism dissection, ANE treatment caused ROS-mediated autophagy and lysosome formation. Pretreatment with an ROS inhibitor, aminoguanidine hemisulfate (AGH), abolished ANE-induced ROS production. ANE treated cells caused an increase in light chain 3 (LC3)-I to -II conversion, anti-thymocyte globulin 5+12 (ATG5+12), and beclin levels, and apoptosis related-protein changes (an increases in BAX, cleaved poly(ADP-ribose) polymerase (c-PARP), and a decrease in the Bcl-2 level). In conclusion, our study demonstrated that the ANE may be a new potential compound for HCC therapy.

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.

Genotoxicity Assessment of Three Nutraceuticals Containing Natural Antioxidants Extracted from Agri-Food Waste Biomasses

Grapes and apples are the most cultivated fruits in the Mediterranean basin and their agricultural processing is responsible for the production of a large amount of bio-waste. The reuse of this food biomass would increase the volume of recyclable/renewable biomaterial and lower the environmental impact due to the increasing demand for these biological products. To this purpose, agri-food waste from grape and apple processing have become an important source of phytochemicals, and many pharmaceutical industries are using it as starting material to produce dietary supplements, functional foods, and food additives for human consumption. In virtue of the chemical diversity and complexity of agri-food biowaste, developers and producers of nutraceuticals are advised to assess the safety of their final nutraceutical products, in compliance with European Food Safety Authority regulation. Here, we use the Ames test to assess the mutagenicity of three nutraceuticals obtained from agri-food waste biomasses: Taurisolo® from grape pomace of Vitis vinifera L. cv 'Aglianico', AnnurComplex® from Malus pumila M. cv 'Annurca' and Limoncella Apple Extract from Malus domestica B. cv 'Limoncella'. The results showed that all three nutraceuticals were non-mutagenic.

Downregulation of the DNA Repair Gene DDB2 by Arecoline Is through p53's DNA-Binding Domain and Is Correlated with Poor Outcome of Head and Neck Cancer Patients with Betel Quid Consumption

Arecoline is the principal alkaloid in the areca nut, a component of betel quids (BQs), which are carcinogenic to humans. Epidemiological studies indicate that BQ-chewing contributes to the occurrence of head and neck cancer (HNC). Previously, we have reported that arecoline (0.3 mM) is able to inhibit DNA repair in a p53-dependent pathway, but the underlying mechanism is unclear. Here we demonstrated that arecoline suppressed the expression of DDB2, which is transcriptionally regulated by p53 and is required for nucleotide excision repair (NER). Ectopic expression of DDB2 restored NER activity in arecoline-treated cells, suggesting that DDB2 downregulation was critical for arecoline-mediated NER inhibition. Mechanistically, arecoline inhibited p53-induced DDB2 promoter activity through the DNA-binding but not the transactivation domain of p53. Both NER and DDB2 promoter activities declined in the chronic arecoline-exposed cells, which were consistent with the downregulated DDB2 mRNA in BQ-associated HNC specimens, but not in those of The Cancer Genome Atlas (TCGA) cohort (no BQ exposure). Lower DDB2 mRNA expression was correlated with a poor outcome in HNC patients. These data uncover one of mechanisms underlying arecoline-mediated carcinogenicity through inhibiting p53-regulated DDB2 expression and DNA repair.

Development and validation of a rapid LC-MS/MS method for simultaneous quantification of arecoline and its two active metabolites in rat plasma and its application to a pharmacokinetic study

Arecoline is the primary active and toxic constituent of areca nut. Arecaidine and arecoline N-oxide are two major active metabolites of arecoline. In this work, an accurate and simple high performance liquid chromatography tandem mass spectrometry method for simultaneous quantification of arecoline, arecaidine and arecoline N-oxide in rat plasma was developed and fully validated to study their pharmacokinetic behaviors in rats. After extracted from rat plasma by protein precipitation with methanol and then concentrated, the analytes were chromatographic separated on a Sepax Sapphire C₁₈ analytical column. The mobile phase consisted of methanol and 2 mM ammonium acetate buffer solution containing 0.2% (v/v) formic acid (8:92, v/v) under isocratic elution. The analytes were detected by multiple reaction monitoring (MRM) with an electrospray ionization source in the positive ion mode. The transitions of m/z 156.2 → 53.2, m/z 142.2 → 44.2 and m/z 172.2 → 60.2 were selected for arecoline, arecaidine and arecoline N-oxide, respectively. The method was linear over the concentration range of 0.5-100 ng/mL for arecoline, 5-5000 ng/mL for arecaidine and arecoline N-oxide with no carry-over effect. The accuracies and intra- and inter-batch precisions were all within the acceptance limits. No matrix effect and potential interconversion between the analytes and other metabolites were observed in this method. The validated method was further employed to a preclinical pharmacokinetic study of arecoline, arecaidine and arecoline N-oxide after oral treatment with 20 mg/kg arecoline to rats.

The Dual Antioxidant/Prooxidant Effect of Eugenol and Its Action in Cancer Development and Treatment

The formation of reactive oxygen species (ROS) during metabolism is a normal process usually compensated for by the antioxidant defense system of an organism. However, ROS can cause oxidative damage and have been proposed to be the main cause of age-related clinical complications and diseases such as cancer. In recent decades, the relationship between diet and cancer has been more studied, especially with foods containing antioxidant compounds. Eugenol is a natural compound widely found in many aromatic plant species, spices and foods and is used in cosmetics and pharmaceutical products. Eugenol has a dual effect on oxidative stress, which can action as an antioxidant or prooxidant agent. In addition, it has anti-carcinogenic, cytotoxic and antitumor properties. Considering the importance of eugenol in the area of food and human health, in this review, we discuss the role of eugenol on redox status and its potential use in the treatment and prevention of cancer.

RIFM fragrance ingredient safety assessment, Eugenol, CAS Registry Number 97-53-0

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Reproductive toxicity was determined to have the most conservative systemic exposure derived NO[A]EL of 230 mg/kg/day. A gavage multigenerational continuous breeding study conducted in rats on a suitable read across analog resulted in a MOE of 12,105 while considering 22.6% absorption from skin contact and 100% from inhalation. A MOE of >100 is deemed acceptable.

The hepatotoxicity and testicular toxicity induced by arecoline in mice and protective effects of vitamins C and e

Arecoline is a major alkaloid of areca nuts which are widely chewed by southeast Asian and it manifests various toxic effects in different organs of human and animals. In this work, mature mice were treated by vitamins C plus E, arecoline, or both daily for four weeks. The results showed that arecoline significantly increased the levels of serum alkaline phosphatase (ALP), glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT) and significantly decreased the levels of reduced glutathione (GSH), glutathione-S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) in the liver tissues. Additionally, the body weight, testis weight, sperm counts, motility and normal sperms also were significantly decreased. The supplement of vitamins C and E can bring the activities of ALP and GPT to normal levels and partially restore the sperm counts compared to the arecoline-treated group but have no other positive effects. In conclusion, the vitamins C and E partially attenuated the arecoline-induced hepatotoxiciy but basically had on protective effects against the arecoline-induced testicular toxicity.

Arecoline inhibits epithelial cell viability by upregulating the apoptosis pathway: implication for oral submucous fibrosis

Oral submucous fibrosis (OSF) is a chronic inflammatory disease characterized by the accumulation of excess collagen, and areca nut chewing has been proposed as a significant etiological factor for disease manifestation. However, the underlying molecular mechanisms regarding areca nut chewing-induced OSF are only partially understood. Herein, we reported that arecoline markedly induced morphologic change in HaCaT epithelial cells, but had no obvious effect on Hel fibroblast cells. MTS assay revealed that arecoline significantly suppressed HaCaT cell viability. Moreover, flow cytometric analysis indicated that arecoline substantially promoted HaCaT cell, but not Hel cell apoptosis in a dose-dependent manner. Furthermore, arecoline-induced HaCaT cell apoptosis was found to be associated with increased expression and activation of cleaved-Bid, cleaved-PARA and cleaved-caspase-3. Collectively, our results suggest that HaCaT epithelial cells are more sensitive than Hel fibroblast cells to arecoline-induced cytotoxicity, which may be involved in the pathogenesis of OSF.

Eugenol triggers apoptosis in breast cancer cells through E2F1/survivin down-regulation

Background

Breast cancer is a major health problem that threatens the lives of millions of women worldwide each year. Most of the chemotherapeutic agents that are currently used to treat this complex disease are highly toxic with long-term side effects. Therefore, novel generation of anti-cancer drugs with higher efficiency and specificity are urgently needed.

Methods

Breast cancer cell lines were treated with eugenol and cytotoxicity was measured using the WST-1 reagent, while propidium iodide/annexinV associated with flow cytometry was utilized in order to determine the induced cell death pathway. The effect of eugenol on apoptotic and pro-carcinogenic proteins, both in vitro and in tumor xenografts was assessed by immunoblotting. While RT-PCR was used to determine eugenol effect on the E2F1 and survivin mRNA levels. In addition, we tested the effect of eugenol on cell proliferation using the real-time cell electronic sensing system.

Results

Eugenol at low dose (2 μM) has specific toxicity against different breast cancer cells. This killing effect was mediated mainly through inducing the internal apoptotic pathway and strong down-regulation of E2F1 and its downstream antiapoptosis target survivin, independently of the status of p53 and ERα. Eugenol inhibited also several other breast cancer related oncogenes, such as NF-κB and cyclin D1. Moreover, eugenol up-regulated the versatile cyclin-dependent kinase inhibitor p21^WAF1 protein, and inhibited the proliferation of breast cancer cells in a p53-independent manner. Importantly, these anti-proliferative and pro-apoptotic effects were also observed in vivo in xenografted human breast tumors.

Conclusion

Eugenol exhibits anti-breast cancer properties both in vitro and in vivo, indicating that it could be used to consolidate the adjuvant treatment of breast cancer through targeting the E2F1/survivin pathway, especially for the less responsive triple-negative subtype of the disease.

Arecoline, a major alkaloid of the areca nut, causes neurotoxicity through enhancement of oxidative stress and suppression of the antioxidant protective system

Arecoline, an areca nut alkaloid, has been noted for its potential cognition-enhancing effects in patients with Alzheimer dementia. However, it has been confirmed that areca nut use is associated with oral and pharyngeal cancers. In addition, arecoline is genotoxic and cytotoxic both in vitro and in vivo through oxidative stress-dependent mechanisms. The aim of this study was to investigate whether arecoline would interfere with the antioxidant defense system and induce cytotoxicity in rat primary cortical neurons. Results indicate that arecoline (50-200 μM) induces neuronal cell death, and catalase, NADPH oxidase inhibitors (diphenyleneiodonium chloride and apocynin), and a caspase inhibitor (z-VAD-fmk) can prevent arecoline-induced cell death. Furthermore, arecoline increased reactive oxygen species production and upregulated protein expression and mRNA levels of NADPH oxidase 2, which could be attenuated by catalase and NADPH oxidase inhibitors. Arecoline also attenuated neuronal antioxidant defense by decreasing glutathione (GSH) level and superoxide dismutase activity. In addition, arecoline enhanced the expression of proapoptotic proteins (cytochrome c, Bax, caspase-9, and caspase-3) and attenuated the expression of the antiapoptotic protein Bcl-2. Moreover, NADPH oxidase inhibitors could attenuate the arecoline-induced GSH depletion and reverse arecoline-induced changes in proapoptotic and antiapoptotic proteins. In conclusion, the results indicate that arecoline could induce neuronal apoptotic death by attenuating antioxidant defense and enhancing oxidative stress.

Arecoline arrests cells at prometaphase by deregulating mitotic spindle assembly and spindle assembly checkpoint: implication for carcinogenesis

One apparent feature of cancerous cells is genomic instability, which may include various types of chromosomal aberrations, such as translocation, aneuploidy, and the presence of micronuclei inside the cells. Mutagenic factors that promote the emergence of genomic instability are recognized as risk factors for the development of human malignancies. In Asia, betel quid (BQ) chewing is one of such risk factors for oral cancer. Areca nut is an essential constitute of BQ and is declared as a group I carcinogen by the International Agency for Research on Cancer. However, the molecular and cellular mechanisms regarding the carcinogenicity of areca nut are not fully explored. Here we reported that arecoline, a major alkaloid of areca nut, could arrest cells at prometaphase with large amounts of misaligned chromosomes. This prometaphase arrest was evidenced by condensed chromosome pattern, increased histone H3 phosphorylation, and accumulation of mitotic proteins, including aurora A and cyclin B(1). To investigate the molecular mechanisms accounting for arecoline-induced prometaphase arrest, we found that arecoline could stabilize mitotic spindle assembly, which led to distorted organization of mitotic spindles, misalignment of chromosomes, and up-regulation of spindle assembly checkpoint (SAC) genes. The SAC proteins BubR1 and Mps1 were differentially modified between the cells treated with arecoline and nocodazole. This together with aurora A overexpression suggested that SAC might be partly suppressed by arecoline. As a result, the arecoline-exposed cells might produce progeny that contained various chromosomal aberrations and exhibited genomic instability.

Prediction of rodent carcinogenic potential of naturally occurring chemicals in the human diet using high-throughput QSAR predictive modeling

Consistent with the U.S. Food and Drug Administration (FDA) Critical Path Initiative, predictive toxicology software programs employing quantitative structure-activity relationship (QSAR) models are currently under evaluation for regulatory risk assessment and scientific decision support for highly sensitive endpoints such as carcinogenicity, mutagenicity and reproductive toxicity. At the FDA's Center for Food Safety and Applied Nutrition's Office of Food Additive Safety and the Center for Drug Evaluation and Research's Informatics and Computational Safety Analysis Staff (ICSAS), the use of computational SAR tools for both qualitative and quantitative risk assessment applications are being developed and evaluated. One tool of current interest is MDL-QSAR predictive discriminant analysis modeling of rodent carcinogenicity, which has been previously evaluated for pharmaceutical applications by the FDA ICSAS. The study described in this paper aims to evaluate the utility of this software to estimate the carcinogenic potential of small, organic, naturally occurring chemicals found in the human diet. In addition, a group of 19 known synthetic dietary constituents that were positive in rodent carcinogenicity studies served as a control group. In the test group of naturally occurring chemicals, 101 were found to be suitable for predictive modeling using this software's discriminant analysis modeling approach. Predictions performed on these compounds were compared to published experimental evidence of each compound's carcinogenic potential. Experimental evidence included relevant toxicological studies such as rodent cancer bioassays, rodent anti-carcinogenicity studies, genotoxic studies, and the presence of chemical structural alerts. Statistical indices of predictive performance were calculated to assess the utility of the predictive modeling method. Results revealed good predictive performance using this software's rodent carcinogenicity module of over 1200 chemicals, comprised primarily of pharmaceutical, industrial and some natural products developed under an FDA-MDL cooperative research and development agreement (CRADA). The predictive performance for this group of dietary natural products and the control group was 97% sensitivity and 80% concordance. Specificity was marginal at 53%. This study finds that the in silico QSAR analysis employing this software's rodent carcinogenicity database is capable of identifying the rodent carcinogenic potential of naturally occurring organic molecules found in the human diet with a high degree of sensitivity. It is the first study to demonstrate successful QSAR predictive modeling of naturally occurring carcinogens found in the human diet using an external validation test. Further test validation of this software and expansion of the training data set for dietary chemicals will help to support the future use of such QSAR methods for screening and prioritizing the risk of dietary chemicals when actual animal data are inadequate, equivocal, or absent.

Antiproliferative and pro-apoptotic activity of eugenol-related biphenyls on malignant melanoma cells

Background

Malignant melanoma is one of the most aggressive skin cancer and chemotherapeutic agents currently in use are still unsatisfactory. Prevention and early diagnosis are the only effective tools against this tumour whose incidence and mortality rates are highly increased during the last decades in fair skin populations. Therefore the search for novel therapeutic approaches is warranted. Aim of this work was to identify and test new compounds with antiproliferative and cytotoxic activity on melanoma cells. We tested eugenol together with six natural and synthetic eugenol-related compounds for their capability to inhibit cell growth on primary melanoma cell lines established from patients' tissue samples.

Results

Eugenol and isoeugenol monomers and their respective O-methylated forms did not show to inhibit melanoma cells proliferation. Conversely, the dimeric forms (biphenyls) showed some antiproliferative activity which was mild for dehydrodieugenol, higher for its O,O'-methylated form (O,O'-dimethyl-dehydrodieugenol), and markedly pronounced for the racemic mixture of the brominated biphenyl (6,6'-dibromo-dehydrodieugenol) (S7), being its enantiomeric form (S) the most effective compared to the other compounds. Such activity resulted to be selective against tumour cells, without affecting cultured normal human skin fibroblasts. Dose and time dependence curves have been obtained for the enantiomeric form S7-(S). Then IC₅₀ and minimal effective doses and times have been established for the melanoma cell lines tested. TUNEL and phosphatidylserine exposure assays demonstrated the occurrence of apoptotic events associated with the antiproliferative activity of S7-(S). Cytotoxic activity and apoptosis induced by treating melanoma cells with eugenol-related biphenyls was partially dependent by caspase activation.

Conclusion

Our findings demonstrate that the eugenol related biphenyl (S)-6,6'-dibromo-dehydrodieugenol elicits specific antiproliferative activity on neuroectodermal tumour cells partially triggering apoptosis and its activity should be further investigated on in vivo melanoma models in order to evaluate the real anticancer effectiveness on such tumour.

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.

Copper-mediated oxidative DNA damage induced by eugenol: possible involvement of O-demethylation

Eugenol used as a flavor has potential carcinogenicity. DNA adduct formation via 2,3-epoxidation pathway has been thought to be a major mechanism of DNA damage by carcinogenic allylbenzene analogs including eugenol. We examined whether eugenol can induce oxidative DNA damage in the presence of cytochrome P450 using [32P]-5'-end-labeled DNA fragments obtained from human genes relevant to cancer. Eugenol induced Cu(II)-mediated DNA damage in the presence of cytochrome P450 (CYP)1A1, 1A2, 2C9, 2D6, or 2E1. CYP2D6 mediated eugenol-dependent DNA damage most efficiently. Piperidine and formamidopyrimidine-DNA glycosylase treatment induced cleavage sites mainly at T and G residues of the 5'-TG-3' sequence, respectively. Interestingly, CYP2D6-treated eugenol strongly damaged C and G of the 5'-ACG-3' sequence complementary to codon 273 of the p53 gene. These results suggest that CYP2D6-treated eugenol can cause double base lesions. DNA damage was inhibited by both catalase and bathocuproine, suggesting that H2O2 and Cu(I) are involved. These results suggest that Cu(I)-hydroperoxo complex is primary reactive species causing DNA damage. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine was significantly increased by CYP2D6-treated eugenol in the presence of Cu(II). Time-of-flight-mass spectrometry demonstrated that CYP2D6 catalyzed O-demethylation of eugenol to produce hydroxychavicol, capable of causing DNA damage. Therefore, it is concluded that eugenol may express carcinogenicity through oxidative DNA damage by its metabolite.

Eugenol Causes Melanoma Growth Suppression through Inhibition of E2F1 Transcriptional Activity

Metastatic malignant melanoma is an extremely aggressive cancer, with no currently viable therapy. 4-Allyl-2-methoxyphenol (eugenol) was tested for its ability to inhibit proliferation of melanoma cells. Eugenol but not its isomer, isoeugenol (2-methoxy-4-propenylphenol), was found to be a potent inhibitor of melanoma cell proliferation. In a B16 xenograft study, eugenol treatment produced a significant tumor growth delay (p = 0.0057), an almost 40% decrease in tumor size, and a 19% increase in the median time to end point. More significantly, 50% of the animals in the control group died from metastatic growth, whereas none in the treatment group showed any signs of invasion or metastasis. Eugenol was well tolerated as determined by measurement of bodyweights. Examination of the mechanism of the antiproliferative action of eugenol in the human malignant melanoma cell line, WM1205Lu, showed that it arrests cells in the S phase of the cell cycle. Flow cytometry coupled with biochemical analyses demonstrated that eugenol induced apoptosis. cDNA array analysis showed that eugenol caused deregulation of the E2F family of transcription factors. Transient transfection assays and electrophoretic mobility shift assays showed that eugenol inhibits the transcriptional activity of E2F1. Overexpression of E2F1 restored about 75% of proliferation ability in cultures. These results indicate that deregulation of E2F1 may be a key factor in eugenol-mediated melanoma growth inhibition both in vitro and in vivo. Since the E2F transcription factors provide growth impetus for the continuous proliferation of melanoma cells, these results suggest that eugenol could be developed as an E2F-targeted agent for melanoma treatment.

The induction of prostaglandin E2 production, interleukin-6 production, cell cycle arrest, and cytotoxicity in primary oral keratinocytes and KB cancer cells by areca nut ingredients is differentially regulated by MEK/ERK activation

There are about 200-600 million betel quid (BQ) chewers in the world. BQ chewing is one of the major risk factor of hepatocarcinoma, oropharyngeal, and esophagus cancers in Taiwan, India, and Southeast Asian countries. Thus, the precise molecular mechanisms deserve investigation. We used cultured primary keratinocytes and KB cells, RT-PCR, flow cytometry, Western blotting, and ELISA to evaluate whether alterations in early gene expression is crucial in the carcinogenic processes of BQ. We observed the induction of c-Fos mRNA expression in human gingival keratinocyte (GK) and KB carcinoma cells by areca nut (AN) extract and arecoline. A maximal increment in c-fos gene expression was shown at about 30 min after challenge. AN extract (100-800 microg/ml) and arecoline (0.1-0.8 mM) also stimulated ERK1/ERK2 phosphorylation with a maximal stimulation at 5-10 min of exposure. Pretreatment by U0126 (30 microM), a MEK inhibitor, markedly inhibited the c-Fos, cyclooxygenase-2 (COX-2), and IL-6 mRNA expression of the KB epithelial cells. In addition, U0126 and PD98059 (50 microM) also decreased AN extract- and arecoline-associated PGE2 and IL-6 production in GK and KB cells. However, U0126 by itself arrested the cells in G0/G1 phase, but was not able to prevent AN- and arecoline-induced cell death or apoptosis. In contrast, U0126 enhanced the AN-induced apoptosis of KB cells. AN ingredients thus play a significant role in the pathogenesis of oropharyngeal cancer by activation of MEK1/ERK/c-Fos pathway, which promotes keratinocyte inflammation, cell survival, and affects cell cycle progression.

Lack of modifying effects of eugenol on development of lung proliferative lesions induced by urethane in transgenic mice carrying the human prototype c-Ha-ras gene

To investigate the modifying effects of eugenol (EUG), a component of cigarette smoke, on lung carcinogenesis, male and female transgenic mice carrying the human prototype c-Ha-ras gene (rasH2 mice) were given a single intraperitoneal injection of 250 mg/kg urethane (UR) or saline, followed by a diet containing 6,000 ppm EUG or basal diet for 26 weeks. Their non-transgenic CB6F1 littermates (non-Tg mice) were also treated in the same manner. In both male and female rasH2 mice, alveolar/bronchiolar hyperplasias, adenomas and carcinomas were observed in all UR-treated groups. However, there were no significant intergroup differences in the incidences and multiplicities of these lesions between the UR alone and UR + EUG groups. In non-Tg mice, alveolar/bronchiolar hyperplasias, adenomas or carcinomas were sporadically observed in UR-treated groups of both sexes, with no significant differences in the incidences and multiplicities between the UR alone and UR + EUG groups. There were no intergroup differences between them in the PCNA-positive ratios of adenomas or carcinomas and the areas of adenomas or carcinomas to the whole lung area examined. The present results suggest that the EUG treatment does not exert modifying effects on lung carcinogenesis induced by UR in both male and female rasH2 mice and non-Tg mice.

Eugenol triggers different pathobiological effects on human oral mucosal fibroblasts

Pathobiological effects of eugenol (4-allyl-2-methoxyphenol), a major constituent of betel quid (BQ), were studied on oral mucosal fibroblasts. At a concentration higher than 3 mmol/L, eugenol was cytotoxic to oral mucosal fibroblasts in a concentration- and time-dependent manner. Cell death was associated with intracellular depletion of glutathione (GSH). Most of the GSH was depleted prior to the onset of cell death. At concentrations of 3 mmol/L and 4 mmol/L, eugenol depleted about 45% and 77% of GSH after one-hour incubation. In addition, eugenol decreased cellular ATP level in a concentration- and time-dependent manner. Eugenol also inhibited lipid peroxidation. Inhibition of lipid peroxidation was partially explained by its dose-dependent inhibition of xanthine oxidase activity. The IC50 of eugenol on xanthine oxidase activity was about 0.3 mmol/L. No DNA strand break activity for eugenol was found at concentrations between 0.5 and 3 mmol/L. Taken together, frequent exposure of oral mucosa to a high concentration of eugenol during the chewing of BQ might be involved in the pathogenesis of oral submucous fibrosis and oral cancer via its cytotoxicity. In contrast, eugenol at a concentration less than 1 mmol/L might protect cells from the genetic attack of reactive oxygen species via inhibition of xanthine oxidase activity and lipid peroxidation.

Observations on the effect of areca nut extracts on oral fibroblast proliferation

The effects of aqueous extracts of raw, baked and boiled areca nuts were tested on cultured human buccal mucosa fibroblasts. Cells were exposed to extract concentrations of 0, 50, 100, 150, 300 and 500 micrograms/ml. The arecoline and arecaidine content was determined in the extracts with HPLC and raw nut contained 5.5% m/m, baked nut 6.6% m/m and boiled nut 7.1% m/m. Extract concentrations of 50 to 150 micrograms/ml inhibited cell growth in a concentration-dependent manner but did not lead to total cell death during a 7 day period. However, total cell death did occur with concentrations of 300 and 500 micrograms/ml. It is concluded that areca nut extract is toxic to cultured fibroblasts and inhibits their proliferation in a concentration-dependent manner.

Modulatory effect of Areca nut on the action of mace (Myristica fragrans, Houtt) on the hepatic detoxification system in mice

The present paper reports the modifying potential of areca nut (Areca catechu), an ingredient of the habitual masticatory betel quid, on the induction of the hepatic detoxification system in mice by mace (the aril of nutmeg, Myristica fragrans) a known chemopreventor of chemically induced carcinogenesis. The modulatory effect of areca nut was assessed by determining the levels of enzymes of the hepatic detoxification system, such as glutathione S-transferase (GST), cytochrome b5 and cytochrome P-450, and the content of acid-soluble sulphhydryl (-SH). Mice were fed either control diet or diet containing 0.25, 0.5 or 1% areca nut for 45 days. During the last 10 days the diet was supplemented with 0.5 or 1% mace. At 0.5 and 1% in the diet, areca nut decreased mace-induced increases in hepatic GST and -SH levels and elevated further increases in the levels of cytochrome b5 and cytochrome P-450.

Dose-dependent genotoxic effect of pan masala and areca nut in the Salmonella typhimurium assay

Aqueous extracts of different brands of pan masala and scented supari were tested for mutagenicity by the Salmonella typhimurium assay using tester strains TA98 and TA100. These extracts were found to be mutagenic to both tester strains. The mutagenic effects of pan masala and scented supari extracts were similar to that produced by areca nut extract. The addition of 500 ppm saccharin to the supari extracts did not alter the mutagenic response.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

In vitro genotoxic effects of areca nut extract and arecoline

The genotoxic potential of the aqueous extract of areca nut as well as arecoline, the major alkaloid of the areca nut, was tested with the help of cytogenetic markers such as sister-chromatid exchanges and chromosome aberrations, utilizing Chinese hamster ovary (CHO) cells. The continuous-treatment and pulse-treatment schedules yielded dose-dependent elevations in the frequencies of sister-chromatid exchange and chromosomal aberration in CHO cells, indicating a genotoxic effect of both the extract and arecoline. The results also imply that, besides arecoline, there may be some other water-extractable substances in the areca nut that make the extract more genotoxic. The chromosome damage was found to be more severe on treating the cells with low concentrations and for longer duration, which mimic the effects of chronic areca nut consumption.

Evaluation of pan masala for toxic effects on liver and other organs

The acute and chronic oral toxicity of pan masala (betel quid without betel leaf) was assessed in gavage studies in rats. Clinical parameters (liver and serum glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase and alkaline phosphatase) and organ weights were measured. The results indicate that chronic feeding of pan masala impaired liver function, as indicated by changes in enzyme activity, and decreased relative weights of the gonads and brain.

Evaluation in a battery of in vivo assays of four in vitro genotoxins proved to be noncarcinogens in rodents

2-Chlorethanol, 8-hydroxyquinoline, 2,6-toluenediamine, and eugenol, previously found to behave as genotoxins in in vitro systems and as noncarcinogens in rodents, were evaluated for their ability to induce genotoxic effects in vivo. Rats were given by gavage a single or two successive doses equal to one-half the corresponding LD50, killed at different times after treatment, and examined for the following end points: the frequency of both micronucleated polychromatic erythrocytes in the bone marrow and micronucleated hepatocytes (after partial hepatectomy); the in vivo-in vitro induction of DNA fragmentation, as measured by the alkaline elution technique, and of unscheduled DNA synthesis, as measured by autoradiography, in hepatocyte primary cultures. The two latter end points were also evaluated after in vitro exposure of hepatocytes to log-spaced subtoxic concentrations. 2-Chloroethanol, 8-hydroxyquinoline, and eugenol never produced effects indicative of genotoxic activity. The same happened with 2,6-toluenediamine, with the exception of a significant increase over controls in the amounts of DNA damage and repair displayed by hepatocyte cultures obtained from rats given two 1/2 LD50 separated by a 24 h interval. Our results, which, apart the above mentioned exception, are in concordance with the rodent carcinogenicity results, contribute to underline the role of in vivo short-term tests for the detection of potential genotoxic carcinogens.

Cytogenetic surveillance of tobacco-areca nut (mava) chewers, including patients with oral cancers and premalignant conditions

Three cytogenetic endpoints were studied in non-chewing healthy controls and 3 groups of tobacco-areca nut chewers, viz. normal chewers, chewers with oral submucous fibrosis and chewers with oral cancer. Frequencies of sister-chromatid exchanges and chromosome aberrations in peripheral blood lymphocytes and of micronucleated cells in exfoliated buccal mucosa were evaluated. All the parameters showed statistically significant elevations in all 3 groups of chewers compared to the controls. The data indicate possible application of the parameters as sensitive endpoints for monitoring tobacco-areca nut chewers, the group of individuals at higher risk of developing oral cancer, the commonest cancer among Indian males.

Effect of 'Pan Masala' on the germ cells of male mice

Cytogenetic analyses of meiotic metaphase I germ cells and abnormalities of head morphology of caudal sperms were conducted in male mice following oral feeding of Pan Masala. The substance was ground to a fine powder, dispersed in polysorbate solution and administered via gavage to the animals at 84, 420 and 840 mg/kg body weight at the rate of 10 ml/kg body weight. Polysorbate and cyclophosphamide served as the vehicle control and positive control respectively. The two higher doses, 420 and 840 mg, gave a significant increase in the frequency of X-Y univalents and breaks over those of the vehicle control. Frequency of sperm head abnormalities were significantly high for all the doses tested. The results indicate that Pan Masala is a potent clastogen, reaches the testes and affects the germinal cells.

The beneficial and hazardous effects of simple phenolic compounds

The current emphasis on screening the environment for man-made genotoxic and carcinogenic compounds detracts from studies on the possible health hazard or beneficial effects of naturally occurring agents to which humans are exposed daily. The simple phenolics, which are ubiquitous among plants, used as food additives, and ingested daily in milligram quantities, belong to this category of compounds. They induce double-strand DNA breaks. DNA adducts, mutations and chromosome aberrations in a great variety of test systems. However, they can suppress the genotoxic activity of numerous carcinogenic compounds in both in vitro and in vivo assays. This dual function of dietary phenolics also becomes evident when their carcinogenic or anticarcinogenic potential is examined. Some, but not all, phenolics induce precancerous lesions, papillomas and cancers, act as cocarcinogens, and exert a promoting effect in various rodent assays. On the other hand, phenolics have proved to be potent inhibitors of carcinogenesis at the initiation and promotion stages induced by carcinogens and promoters of different molecular structures. The extent to which a health hazard or protective activity of complex dietary mixtures is due to their phenolic content remains an unresolved issue. In addition, these multiple, occasionally contradictory functions of simple phenolics make it difficult to propose their use as chemopreventive agents.

Influence of arecoline on immune system: II. Suppression of thymus-dependent immune responses and parameter of non-specific resistance after short-term exposure

Arecoline, a major alkaloid of arecanut was screened to explore its modulatory influence on cell-mediated immune response in a murine model system. The in vivo and in vitro effects were evaluated at subtoxic concentrations of arecoline. Delayed type hypersensitivity (DTH) reactions to sheep red blood cells (SRBC) were evaluated in male mice. When treated subcutaneously with 20 mg/kg bw (1/5 of LD50) dose of arecoline for 1, 2 or 3 weeks, the DTH reactions were significantly suppressed. At arecoline concentration of 10 mg/kg bw, there was a moderate reduction in DTH response, while no appreciable change was observed at a dosage of 5 mg/kg bw. The effects were not dependent on the duration of treatment. In contrast, treating with arecoline continuously for 4 days following SRBC immunization showed significant suppression in DTH reactions at both 10 and 20 mg/kg bw doses. When treated after 12 h following immunization with 20 mg/kg bw arecoline, significant reduction in DTH reactions were seen. While moderate reduction in response was observed with arecoline dosage of 10 mg/kg bw, there was no alteration in response at the dose level of 5mg/kg bw. Recovery experiments in mice revealed that arecoline mediated effects are of a reversible nature. Arecoline treatment did not appreciably alter the host resistance to endotoxin shock. In vitro experiments revealed both dose-dependent and time-dependent cytotoxic effects of arecoline when spleen cells were incubated with varying concentrations of arecoline. Concomitant exposure of arecoline at concentrations of 10(-6) - 10(-4) M with con A, markedly suppressed both 3H-thymidine incorporation and interleukin-2 production of splenic cells. In contrast, concomitant exposure of arecoline with IL-2 did not alter 3H-thymidine incorporation in the IL-2 dependent cytolytic T-lymphocyte line (CTLL), except at the concentration of 10(-4) M arecoline. From these studies it is concluded that the dose-dependent suppressive effects of arecoline on DTH response to SRBC and on certain in vitro lymphocyte functions are more clear than the host resistance to endotoxin shock.

Evaluation of the mutagenicity of 'pan masala', a chewing substitute widely used in India

Mutagenicity of polar and non-polar extracts of a popular brand of 'pan masala' was examined using the Salmonella/mammalian microsome test (Ames assay) and 2 tester strains of Salmonella typhimurium, TA98 and TA100. These extracts were also subjected to pretreatment with sodium nitrite at acidic pH, to simulate conditions for endogenous nitrosation. The aqueous, aqueous:ethanolic and chloroform extracts as well as their nitrosated mixtures were non-mutagenic in the Ames assay, in the presence and absence of metabolic activation. Only the ethanolic extract elicited a weak mutagenic response in strain TA98 without metabolic activation demonstrating the presence of direct-acting frameshift mutagens in 'pan masala'.

Negative evidence in vivo of DNA-damaging, mutagenic and chromosomal effects of eugenol

The DNA-damaging, mutagenic and chromosomal effects of eugenol were assayed by the DNA alkaline elution technique, the granuloma pouch assay and the bone marrow micronucleus test in rats. With all the techniques used, eugenol did not show any genotoxic activity.

Quantitative methods for assessing a synergistic or potentiated genotoxic response

The problem of assessing chemical interactions in studies of genotoxicity is discussed. Attention is focused on assessing possible synergism or potentiation when the observed genotoxic response is binary (yes-no). Different forms of enhancement are distinguished based upon different assumptions on the genotoxic activity of the experimental treatments. A generalized linear statistical model is considered that links the probability of the binary response to the doses, and data-analytic strategies are described for detecting synergy and potentiation in factorially designed experiments. This approach is illustrated with a series of analyses of various genotoxicity data-sets.

Influence of arecoline on immune system: I. Short term effects on general parameters and on the adrenal and lymphoid organs

Arecoline, a suspected carcinogenic/cocarcinogenic alkaloid was screened to explore in detail its immunomodulatory influence in murine model system. The oral LD50 value for male mice was 371 mg/kg bw whereas it was 309 mg/kg bw for female mice. The subcutaneous LD50 value for both sexes was 97 mg/kg bw. Only a marginal difference was observed in intraperitoneal LD50 values between male (120 mg/kg bw) and female (109 mg/kg bw) mice. Arecoline was administered subcutaneously to male mice at subtoxic dose levels (5, 10, and 20 mg/kg bw) for 1, 2 and 3 weeks on a daily basis. In groups where significant decreases in body weight were present (at 20 mg/kg bw for both sexes), reductions in thymus weight were also noted. Spleen, mesenteric lymph nodes (MLN), liver, and kidney showed moderate reductions in their weights. Histopathological effects at 20 mg/kg bw included lymphocyte depletion of the thymic cortex, and the B and T lymphocyte areas in spleen and MLN. In concordance with the zona fasciculata hypertrophy of adrenals, corticosterone concentration in serum increased depending on the dose with a significant elevation at 20 mg/kg bw. While total protein, albumin, glucose, acid phosphatase and hemoglobin concentrations were not altered, increases in SGOT and SGPT levels were observed at the high dose. The white and red blood cell counts decreased in a dose-dependent manner. Marked reduction in cell number of thymus, and moderate effect on cellularity of spleen and MLN, were observed at 20 mg/kg bw. In vitro exposure of rat thymocytes to arecoline resulted in a biphasic oxygen consumption response with progressive increase in oxygen consumption, reaching a maximum value at 10(-5) M and decreasing sharply at 10(-3) M. Exogenously added substrates such as glucose, pyruvic acid and lactic acid retarded the fall in the oxygen consumption induced at 10(-3) M arecoline. These observations demonstrate the effects of arecoline on lymphoid organs, which may be due to its direct action or through the elevation of corticosterone.

A comparative analysis of data on the clastogenicity of 951 chemical substances tested in mammalian cell cultures

A literature review was conducted using original papers published during 1964-1985 on the in vitro clastogenicity of chemical substances. Results of tests on 951 chemical substances were abstracted from over 240 reports to form the database. The evaluation of these data relied on each author's original conclusion on a positive or negative outcome. Of these 951 substances, 447 (47%) were consistently positive either with or without activation; 417 (44%) were negative in the direct test but not tested with metabolic activation systems; 4 were negative but tested only with activation; and 30 (3%) were clearly negative both with and without activation. The remaining 53 substances gave variable results when tested under different experimental protocols or in different cell types, but were positive in at least one test. Although discrepant results were found associated with some cell types, the addition of metabolic activation systems tended to eliminate such variability. No one cell appeared to be superior in response to all clastogens. For screening purposes, the choice of cell may thus depend more on the general usefulness and reliability of a cell type than on a strong response to a particular chemical. However, the use of a suitable metabolic activation system does appear to be of critical importance. The concentration at which clastogenic effects were detected varied extensively for different test substances, ranging from a minimum of 4.3 X 10(-8) to 6.9 X 10(2) mM. Possible mechanisms of action for substances active at only high levels are discussed, but no satisfactory explanation is available at this time. The relevance of tests conducted at concentrations high enough to alter significantly the osmolarity and other culture conditions is considered, and caution urged in the interpretation of test results obtained under physiologically stressful conditions. The clastogenic potential was compared quantitatively using an index of effective concentration (D20) and one which estimates the number of cells with exchange aberrations expected per mg/ml (TR) for data obtained by using a uniform protocol and cultures of Chinese hamster lung (CHL) cells. Both values were distributed over a wide range, demonstrating the variety of genotoxic potential in chemicals. In general, a substance which was active at only high concentrations produced fewer exchange-type aberrations. In vivo activity, as measured by tumourigenic effect and formation of micronuclei in bone marrow, tended to be greater for substances with a D20 below 10(-2) mg/ml and a TR value over 10(3).(ABSTRACT TRUNCATED AT 400 WORDS)

Mutagenic potential of binary mixtures of nitro-polychlorinated dibenzo-p-dioxins and related compounds

The mutagenic potential of binary mixtures of nitro-polychlorinated dibenzo-p-dioxins and other environmentally related compounds was determined using Salmonella typhimurium strain TA98 in the standard plate incorporation assay. Samples tested included binary mixtures of 4-nitro-4'-chlorobiphenyl with 6-nitro-4,2',3',4',5'-pentachlorobiphenyl, 4-nitrobenzo-p-dioxin with 4-nitro-2,3,8-trichlorodibenzo-p-dioxin, and benzo[a]pyrene with either nitropentachlorobiphenyl or nitrotrichlorodibenzo-p-dioxin. Inhibition was the primary interaction observed for the mixtures of polyhalogenated dioxins or biphenyls with the direct-acting mutagens nitrodibenzo-p-dioxin or nitrochlorobiphenyl. At the highest dose tested, nitrotrichlorodibenzo-p-dioxin inhibited the bacterial mutagenicity of nitrodibenzo-p-dioxin by almost 50%, while pentachlorobiphenyl inhibited the mutagenicity of nitrobiphenyl by 34%. Conversely, synergism was the primary interaction observed for mixtures of halogenated aromatics with the promutagen benzo[a]pyrene. The addition of nitrotrichlorodioxin to benzo[a]pyrene enhanced the mutagenicity of the latter compound by as much as 70%, while the mutagenic potential of a mixture of benzo[a]pyrene and nitropentachlorobiphenyl was approximately 50% greater than the mutagenicity of benzo[a]pyrene alone. In summary, mixtures of nonmutagenic nitropolyhalogenated biphenyls or dibenzo-p-dioxins appear to inhibit the mutagenicity of direct-acting mutagens, while these same compounds seem to enhance the mutagenic potential of the promutagen benzo[a]pyrene.

Factors affecting the mutagenic activity of quercetin for Salmonella typhimurium TA98: metal ions, antioxidants and pH

The mutagenic activity of quercetin for Salmonella typhimurium TA98 was inhibited by addition of metal salts. MnCl2 was a potent inhibitor, followed by CuCl2, FeSO4, and FeCl3, the probable mechanism being facilitated catalytic oxidation of quercetin. With quercetin incorporated at a level of 100 nmoles/plate, approximate doses (nmoles/plate) to give 50% inhibition of mutagenic activity were: MnCl2 less than 10 (-S9), 18 (+S9); CuCl2 65 (-S9), greater than 100 (+S9); FeSO4 190 (-S9), greater than 300 (+S9); or FeCl3 275 (-S9), greater than 300 (+S9). Ascorbate, superoxide dismutase, and, to a lesser extent, NADH and NADPH, all enhanced the mutagenic activity of quercetin in the absence of the mammalian-microsome (S9) system, but had no significant effect in the presence of the S9 mix. The maximum enhancement of activity by ascorbate or superoxide dismutase was approximately 87% of the increase achieved by addition of the S9 mix. Tyrosinase (catechol oxidase) substantially reduced the mutagenic activity of quercetin in the absence of the S9 mix. At lower levels of tyrosinase, activity was restored by incorporation of the S9 mix. It is proposed that the S9 mix enhances the mutagenic activity of quercetin by scavenging superoxide radicals, thus inhibiting the autoxidation of quercetin, and possibly by reducing quinone oxidation products of quercetin. The mutagenic activity of quercetin increased substantially when the pH of the media was decreased. This may be due in part to a decrease in ionization of quercetin at lower pH, thereby increasing its absorption by the tester strain, to a decrease in the rate of autoxidation of quercetin at lower pH, or to a combination of these.

Modifying influences of betel quid ingredients on B(a)P-induced carcinogenesis in the buccal pouch of hamster

The present study evaluates the incidence of tumors in hamster buccal pouches following short-term (10 days) and long-term (6 months) topical exposures to graded doses of benzo(a)pyrene, B(a)P (25 micrograms, 50 micrograms and 100 micrograms per pouch either daily for 10 days or thrice weekly for 6 months) alone or in combination with extract of tobacco (1 mg/pouch, twice daily), betel nut (1 mg/pouch, twice daily) or betel leaf (5 mg/pouch, twice daily). Given alone, the three doses of B(a)P respectively yielded, 6 months after the last treatment, 4%, 8.7% and 16.7% tumors in the short-term study, and 20%, 35% and 61% tumors in the long-term study. Short-term treatments with individual ingredients of betel quid did not produce any tumors while long-term treatments produced tumors only with tobacco (17.6%) and betel nut (10.5%). When B(a)P, and betel quid ingredients were painted concomitantly for 10 days, there was, depending upon the dose of B(a)P, complete or partial suppression of tumor production. But when B(a)P-plus-tobacco or B(a)P-plus-betel nut treatments were given for 6 months, there was a considerable increase in tumor incidence. Betel leaf extract, in both short-term and long-term studies, expressed its inhibitory influence on B(a)P-induced tumorigenesis.

Genotoxicity of garlic, turmeric and asafoetida in mice

The genotoxic effects of orally administered garlic and turmeric were evaluated in bone-marrow cells of mice by performing the micronucleus test. Another spice, asafoetida, was tested for the induction of sister-chromatid exchanges (SCEs) in spermatogonia of mice. Results of the micronucleus test with garlic and turmeric were not significantly different from control values. Orally administered asafoetida, however, showed a weak SCE-inducing effect in spermatogonia.