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

CYP26B1 is a novel candidate gene for betel quid-related oral squamous cell carcinoma

Substantial epidemiological data suggest a role for environmental factors (for example, the use of alcohol, betel quid (BQ), and cigarettes) in the occurrence of oral squamous cell carcinoma (OSCC), but the evidence for the genes involved has been inconsistent. This study was to investigate the role of CYP26B1, together with the use of alcohol, BQ, and cigarettes, on BQ-related OSCC. The association study (247 OSCC cases and 338 controls) was conducted to examine the possible interplay between CYP26B1 polymorphisms and alcohol, BQ, and cigarettes use. Additional gene expression was evaluated between OSCC tissue and adjacent normal tissue. The genetic polymorphism AA of CYP26B1 appeared to correlate with the risk of OSCC (OR=2.26; 95% CI, 1.35-3.80). Chewing BQ multiplicatively interacted with CYP26B1 AA to increase the OSCC risk (aOR=70.04; 95% CI, 13.62-360.11). The independent risk of OSCC was observed among BQ chewers with CYP26B1 AA, and compared with chewers with the CYP26B1 CC genotype (stratified aOR=2.88; 95% CI, 1.07-7.74). Increased expression of CYP26B1 was observed in tumor tissue compared with adjacent normal tissue. The CYP26B1 gene plays a novel role in the BQ dependent pathogenesis of OSCC.

Bronchial epithelium-derived IL-8 and RANTES increased bronchial smooth muscle cell migration and proliferation by Krüppel-like factor 5 in areca nut-mediated airway remodeling

This study is first to analyze the inflammatory cytokines, produced by the bronchial epithelium after exposure to areca nut extract (ANE), which contribute to airway remodeling by increasing human bronchial smooth muscle cells (BSMC) migration and proliferation. We treated human bronchial epithelial cell lines BEAS-2B and HBE135-E6E7 (HBE) with ANE, saliva-reacted ANE (sANE), and the areca alkaloids arecoline and then harvested the conditioned medium (CM) that was added to BSMC. Exposure of BEAS-2B and HBE to ANE, sANE, and arecoline increased interleukin 8 (IL-8) and Regulated upon Activation, Normal T-cell Expressed, and Secreted (RANTES) production. Cultures of BSMC with ANE-, sANE-, and arecoline-BEAS-2B-CM and -HBE-CM increased BSMC proliferation and migration. Induction of BSMC proliferation and migration by sANE-BEAS-2B-CM and -HBE-CM was associated with increased phosphorylation of Raf, MEK1/2, and extracellular signal regulated kinase (ERK)1/2 and the upregulation of krüppel-like factor 5 (KLF5), cyclin D, and integrin-linked kinase. Blocking ERK1/2 by a specific inhibitor significantly decreased BSMC proliferation and migration by inhibiting KLF5 enhancement. KLF5 knockdown also decreased sANE-BEAS-2B-CM, sANE-HBE-CM, and recombinant human interleukin 8/recombinant human RANTES-mediated BSMC proliferation and migration, suggesting that KLF5 was involved in the regulation of BSMC proliferation and migration. Our study suggests that inhibition of IL-8 and RANTES or IL-8/RANTES-mediated mitogen-activated protein kinase/KLF5 signaling is an attractive therapeutic target for areca nut-induced asthma.

Cytotoxic effects produced by arecoline correlated to epigenetic regulation in human K-562 cells

Epigenetic effects are considered heritable but may also be modified by environmental factors. Arecoline (ARC), a major component of areca nut alkaloids, is an important environmental risk factor for oral cancer and hepatocellular carcinomain Taiwan. The aim of this study was to determine the influence of ARC on the epigenome. The mRNA expression of histone methyltransferases, acetyltransferases, and demethylases were assessed in K-562 cells following exposure to ARC. Results demonstrated that ARC produced changes in the expressions of several genes catalyzing histone methylation (Mll, Setdb1, and Suv39h2), acetylation (Atf2), and demethylation (JMJD6). Since H3K9 methylation is involved in maintaining the stability of heterochromatin structures and inactivating euchromatic gene expressions, data suggest that the ARC-induced epigenetic changes play a role in the mechanisms underlying chemical-mediated cytotoxicity and genotoxicity.

Altered BRCA1 and BRCA2 responses and mutation of BRCA1 gene in mice exposed chronically and transgenerationally to aqueous extract of betel nut (AEBN)

The Brca1 and Brca2 tumor suppressor genes are involved in the maintenance of genomic integrity as they facilitate error free DNA repair. This study was designed to understand the role of Brca1 and Brca2 in betel nut (BN) induced chronic and transgenerational carcinogenesis in mice. Young male and female Swiss Albino mice were chronically as well as transgenerationally exposed to aqueous extract of betel nut (AEBN) in drinking water (2 mg ml(-1)) for up to 24 weeks. In chronically exposed mice, the levels of Brca1 and Brca2 proteins were elevated to approximately 1.4-fold over the age matched controls after 2 weeks of exposure to AEBN, followed by a decline below the controls. In transgenerationally exposed mice, both Brca1 and Brca2 proteins remained below the controls from the onset of AEBN exposure and rapidly declined further, indicating a loss of tumor suppressor protection. Nucleotide sequencing of exon 11 of Brca1 and exon 27 of Brca2 did not reveal mutation in liver nodules of chronically exposed mice, while a G → C mutation Brca1 was observed in liver nodules as well as in solid tumors developing in transgenerationally exposed mice. Thus, the genomic instability arising due to the lowering in the levels of Brca1 and Brca2 proteins and mutation in exon 11 of Brca1 gene contributed to the increased risk of cancer in mice exposed transgenerationally to AEBN.

A characterization of the antioxidant enzyme activity and reproductive toxicity in male rats following sub-chronic exposure to areca nut extracts

In the present study, areca nut extracts (ANE) administered to male rats by gavage at a dose of 100mg/kg/day for a period of 15, 30, or 45 days resulted in signs of reproductive toxicity. ANE administration resulted in a significant decline (30-57% in epididymal sperm count and 27-61% in sperm motility) as well as substantial abnormalities in sperm morphology. Significant variances in activities of antioxidant enzymes were also observed. Malondialdehyde (MDA) levels, which represent the level of lipid peroxidation, increased by 16-188% and levels of sialic acid decreased by 2-46% compared with that in controls. These results indicate that ANE induced spermatogenic damage, as indicated by a decrease in sperm counts and sperm motility as well as the activity of antioxidant enzymes, an increase in sperm abnormalities, and alterations in sialic acid and MDA levels. Such effects reflect that ANE administration resulted in reactive oxygen species (ROS)-induced oxidative stress in the testis, cauda epididymis, and sperm of male rats.

4beta-Hydroxywithanolide E from Physalis peruviana (golden berry) inhibits growth of human lung cancer cells through DNA damage, apoptosis and G2/M arrest

Background

The crude extract of the fruit bearing plant, Physalis peruviana (golden berry), demonstrated anti-hepatoma and anti-inflammatory activities. However, the cellular mechanism involved in this process is still unknown.

Methods

Herein, we isolated the main pure compound, 4β-Hydroxywithanolide (4βHWE) derived from golden berries, and investigated its antiproliferative effect on a human lung cancer cell line (H1299) using survival, cell cycle, and apoptosis analyses. An alkaline comet-nuclear extract (NE) assay was used to evaluate the DNA damage due to the drug.

Results

It was shown that DNA damage was significantly induced by 1, 5, and 10 μg/mL 4βHWE for 2 h in a dose-dependent manner (p < 0.005). A trypan blue exclusion assay showed that the proliferation of cells was inhibited by 4βHWE in both dose- and time-dependent manners (p < 0.05 and 0.001 for 24 and 48 h, respectively). The half maximal inhibitory concentrations (IC₅₀) of 4βHWE in H1299 cells for 24 and 48 h were 0.6 and 0.71 μg/mL, respectively, suggesting it could be a potential therapeutic agent against lung cancer. In a flow cytometric analysis, 4βHWE produced cell cycle perturbation in the form of sub-G₁ accumulation and slight arrest at the G₂/M phase with 1 μg/mL for 12 and 24 h, respectively. Using flow cytometric and annexin V/propidium iodide immunofluorescence double-staining techniques, these phenomena were proven to be apoptosis and complete G₂/M arrest for H1299 cells treated with 5 μg/mL for 24 h.

Conclusions

In this study, we demonstrated that golden berry-derived 4βHWE is a potential DNA-damaging and chemotherapeutic agent against lung cancer.

Co-treating with arecoline and 4-nitroquinoline 1-oxide to establish a mouse model mimicking oral tumorigenesis

The aim of this study was to establish an effective mouse model of oral cancer and to use this model to identify potential markers of oral tumor progression. C57BL/6JNarl mice were treated with arecoline, 4-nitroquinoline 1-oxide (4-NQO), or both arecoline and 4-NQO in high and low doses for 8 weeks to induce oral tumor. The induced oral lesions were observed for 20 weeks to assess the efficiency of cancer induction and survival rate of the mice. In addition, two target proteins that are frequently overexpressed during tongue cancer tumorigenesis, alphaB-crystallin and Hsp27, were examined by immunohistochemical analysis. In mice exposed to 4-NQO (200 microg/mL) and arecoline (500 microg/mL), the tongue lesions showed evidence of hyperplasia, papilloma, dysplasia, and carcinoma, and the lesions were pathologically similar to those lesions in human oral cancer. The tongue tumor incidence rate was 100% in mice exposed to concomitant 4-NQO (200 microg/mL) and arecoline (500 microg/mL) treatment, 57% in mice exposed to 4-NQO only, and 0% in mice exposed to arecoline only. Immunohistochemical analysis demonstrated that, consistent with human studies, alphaB-crystallin and Hsp27 were upregulated in murine oral tumors. In conclusion, we have established a powerful animal model that enables the study of the promoting effects of arecoline on tongue tumorigenesis. Data subsequently attained from this mouse model support a role for alphaB-crystallin and Hsp27 as clinical markers for tumor progression.

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.

Up-regulation of inflammatory signalings by areca nut extract and role of cyclooxygenase-2 -1195G>a polymorphism reveal risk of oral cancer

Because the mRNA expression of cyclooxygenase-2 (COX-2) is up-regulated by arecoline in human gingival fibroblasts, as shown in our previous study, we further investigated the mRNA expression level of COX-2 and its upstream effectors in three oral epithelial carcinoma cell lines (KB, SAS, and Ca9-22) by using areca nut extract (ANE) and saliva-reacted ANE (sANE). A case-control study of 377 oral squamous cell carcinoma (OSCC) patients and 442 controls was conducted to evaluate the gene-environment interaction between COX-2 promoter polymorphisms and substance use of alcohol, betel quid, and cigarettes (ABC) in risk of OSCC. The heterogeneous characteristics of the oral site and the COX-2 -1195G>A polymorphism in these cell lines showed diverse inflammatory response (KB>>Ca9-22>SAS) after 24-hour ANE/sANE treatments, and the COX-2 up-regulation might be mostly elicited from alternative nuclear factor-kappaB activation. In the case-control study, betel chewing [adjusted odds ratios (aOR), 42.2] posed a much higher risk of OSCC than alcohol drinking and cigarette smoking (aORs, 2.4 and 1.8, respectively), whereas the COX-2 -1195A/A homozygote presented a potential genetic risk (OR, 1.55). The strongest joint effect for OSCC was seen in betel chewers with -1195A/A homozygote (aOR, 79.44). In the non-betel chewing group, the -1195A/G and A/A genotypes together with the combined use of alcohol and cigarettes increased risk to 15.1-fold and 32.1-fold, respectively, compared with the G/G genotype without substance use. Taken together, these findings illustrate a valuable insight into the potential role of the COX-2 promoter region in contributing to the development of betel-related OSCC, including ANE/sANE-induced transcriptional effects and enhanced joint effects of COX-2 -1195A allele with substance use of ABC.