Genetic polymorphisms in hMTH1, hOGG1 and hMYH and risk of chronic benzene poisoning in a Chinese occupational population

Oxidative damage to DNA induced by benzene is an important mechanism of its genotoxicity, which leads to chronic benzene poisoning (CBP). Therefore, genetic variation in DNA repair genes may contribute to susceptibility to CBP in the exposed population. We hypothesized that single nucleotide polymorphisms (SNPs) in hMTH1, hOGG1 and hMYH genes are associated with risk of CBP. We genotyped SNPs at codon 83 of hMTH1, codon 326 of hOGG1, and codon 324 of hMYH in 152 CBP patients and 152 healthy workers occupationally exposed to benzene without poisoning manifestations. The genotypes were determined by polymerase chain reaction-restrained fragment length polymorphism (PCR-RFLP) technique. There were 2.51-fold [adjusted odds ratio (OR_adj), 2.51; 95% CI, 1.14-5.49; P = 0.02] and 2.49-fold (OR_adj, 2.49; 95% CI: 1.52-4.07; P < 0.01) increased risk of CBP for individuals carrying genotypes of hMTH1 83Val/Met + Met/Met and hOGG1 326Cys/Cys, respectively. Compared with individuals carrying genotypes of hOGG1 326Cys/Cys and hMYH 324His/His at the same time, there was a 0.33-fold (OR_adj, 0.33; 95% CI: 0.15-0.72; P < 0.05) decreased risk of CBP for those with genotypes of hOGG1 326Ser/Cys + Ser/Ser and hMYH 324His/Gln + Gln/Gln. In the smoking group, there was a 0.15-fold (OR_adj, 0.15; 95% CI, 0.03-0.68; P = 0.01) decreased risk of CBP for subjects carrying genotypes of hMYH 324His/Gln + Gln/Gln compared with those of genotype of hMYH 324His/His. Therefore, our results suggested that polymorphisms at codons 83 of hMTH1 and codon 326 of hOGG1 might contribute to CBP in a Chinese occupational population.     

Genetic variations of CYP2B6 gene were associated with plasma BPDE-Alb adducts and DNA damage levels in coke oven workers

Polycyclic aromatic hydrocarbons (PAHs), the main components of coke oven emissions, can induce activation of cytochrome P450 (CYP) enzymes, which metabolize PAHs and result in DNA damage by forming adducts. This study was designed to know whether genetic variants of CYP genes are associated with plasma benzo[a]pyrene-7,8-diol-9,10-epoxide-albumin (BPDE-Alb) adducts and DNA damage in coke oven workers. In this study, 298 workers were divided into four groups according to the environmental PAHs exposure levels. The concentrations of plasma BPDE-Alb adducts were detected by reverse-phase high-performance liquid chromatography and the DNA damage levels were measured using comet assay. Twelve tag single nucleotide polymorphisms (tagSNPs) of 4 CYP genes were selected and genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In the top group, workers with CYP2B6 rs3760657GA genotype have lower BPDE-Alb adducts and DNA damage levels than those with rs3760657GG genotype (P < 0.05). In the control group, the DNA damage levels of subjects with CYP1A1 rs4646421AA or GA + AA genotypes were lower than those with GG genotype (P < 0.05). However, no such effects were shown for the other tagSNPs. These results suggested that genetic variations of CYP2B6 might be associated with low BPDE-Alb adducts and DNA damage levels in worker with high exposure to PAHs.     

Association of CYP2E1, GST and mEH genetic polymorphisms with urinary acrylamide metabolites in workers exposed to acrylamide

This study elucidates the association of acrylamide metabolites, N-acetyl-S-(2-carbamoylethyl)-cysteine (AAMA), N-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-cysteine (GAMA2), and N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-cysteine (GAMA3) in urine with genetic polymorphisms of the metabolic enzymes cytochrome P450 2E1 (CYP2E1), microsomal epoxide hydrolase (mEH) in exon 3 and exon 4, glutathione transferase theta (GSTT1) and mu (GSTM1), involved in the activation and detoxification of acrylamide (AA) in humans. Eighty-five workers were recruited, including 51 AA-exposed workers and 34 administrative staffs serve as controls. Personal air sampling was performed for the exposed workers. Each subject provided pre- and post-shift urine samples and blood samples. Urinary AAMA, GAMA2 and GAMA3 levels were simultaneously quantified using liquid chromatography-electronspray ionization/tandem mass spectrometry (LC-ESI-MS/MS). CYP2E1, mEH (in exon 3 and exon 4), GSTT1, and GSTM1 were analyzed using polymerase chain reaction (PCR). Our results reveal that AA personal exposures ranged from 4.37 × 10⁻³ to 113.61 μg/m³ with a mean at 15.36 μg/m³. The AAMA, GAMA2, and GAMA3 levels in the exposed group significantly exceeded those in controls. The GAMAs (the sum of GAMA2 and GAMA3)/AAMA ratios, potentially reflecting the proportion of AA metabolized to glycidamide (GA), varied from 0.003 to 0.456, and indicate high inter-individual variability in the metabolism of AA to GA in this study population. Multivariate regression analysis demonstrates that GSTM1 genotypes significantly modify the excretion of urinary AAMA and the GAMAs/AAMA ratio, exon 4 of mEH was significantly associated with the urinary GAMAs levels after adjustment for AA exposures. These results suggest that mEH and/or GSTM1 may be associated with the formation of urinary AAMA and GAMAs. Further study may be needed to shed light on the role of both enzymes in AA metabolism.     

Genetic association of aromatic hydrocarbon receptor (AHR) and cytochrome P450, family 1, subfamily A,polypeptide 1 (CYP1A1) polymorphisms with dioxin blood concentrations among pregnant Japanese women

Dioxins are metabolized by cytochrome P450, family 1 (CYP1) via the aromatic hydrocarbon receptor (AHR). We determined whether different blood dioxin concentrations are associated with polymorphisms in AHR (dbSNP ID: rs2066853), AHR repressor (AHRR; rs2292596), CYP1 subfamily A polypeptide 1 (CYP1A1; rs4646903 and rs1048963), CYP1 subfamily A polypeptide 2 (CYP1A2; rs762551), and CYP1 subfamily B polypeptide 1 (CYP1B1; rs1056836) in pregnant Japanese women. These six polymorphisms were detected in 421 healthy pregnant Japanese women. Differences in dioxin exposure concentrations in maternal blood among the genotypes were investigated. Comparisons among the GG, GA, and AA genotypes of AHR showed a significant difference (genotype model: P = 0.016 for the mono-ortho polychlorinated biphenyl concentrations and toxicity equivalence quantities [TEQs]). Second, we found a significant association with the dominant genotype model ([TT + TC] vs. CC: P = 0.048 for the polychlorinated dibenzo-p-dioxin TEQs; P = 0.035 for polychlorinated dibenzofuran TEQs) of CYP1A1 (rs4646903). No significant differences were found among blood dioxin concentrations and polymorphisms in AHRR, CYP1A1 (rs1048963), CYP1A2, and CYP1B1. Thus, polymorphisms in AHR and CYP1A1 (rs4646903) were associated with maternal dioxin concentrations. However, differences in blood dioxin concentrations were relatively low.     

Mutagenic and genotoxic effects of carbosulfan in freshwater fish Channa punctatus (Bloch) using micronucleus assay and alkaline single-cell gel electrophoresis

Carbosulfan insecticide is widely used in agriculture and was recently proposed for treatment against pyrethroid-resistant mosquitoes. The mutagenic and genotoxic effect of carbosulfan was carried out in fish Channa punctatus using micronucleus (MN) test and comet assay. The 96 h LC₅₀, estimated by probit analysis in a semi-static bioassay experiment, was 0.268 mg l⁻¹. Based on the LC₅₀ value, three sub-lethal concentrations of carbosulfan (1/4th LC₅₀ = ∼67 μg l⁻¹, 1/2nd LC₅₀ = ∼134 μg l⁻¹ and 3/4th LC₅₀ = ∼201 μg l⁻¹) were selected and fishes were exposed to the said concentrations for 96 h and the samplings were done at regular intervals of 24 h for assessment of the MN frequencies and DNA damage. In general, significant effects (P < 0.01) from both concentrations and time of exposure were observed in exposed fishes. The MN induction was highest on 96 h at all the concentrations in the peripheral blood. Similar trend was observed for the DNA damage measured in terms of the percentage of tail DNA in the erythrocyte and gill cells. This study confirmed that the comet and micronucleus assays are useful tools in determining potential genotoxicity of water pollutants and might be appropriate as a part of monitoring program.     

Genetic variants in SMARC genes are associated with DNA damage levels in Chinese population

The switching defective/sucrose nonfermenting (SWI/SNF) related, matrix associated, actin dependent regulators of chromatin (SMARC) are components of human SWI/SNF like chromatin remodeling protein complexes, which are essential in the process of DNA damage repair. In this study, we hypothesized that genetic variants in SMARC genes may modify the capacity of DNA repair to damage. To test this hypothesis, we genotyped a total of 20 polymorphisms in five key SMARC genes (SMARCA5, SMARCC2, SMARCD1, SMARCD2, SMARCD3) to evaluate their associations with DNA damage levels in 307 subjects. The DNA damage levels were measured with comet assay. The multiple linear regression was used to assess the relationship between each polymorphism and DNA damage levels in additive model. We found that the genotypes of rs6857360 (β = 0.23, 95% CI = 0.06–0.40, P = 0.008) in SMARCA5, rs6919 (β = 0.20, 95% CI = 0.05–0.34, P = 0.008) and rs2727280 (β = 0.18, 95% CI = 0.04–0.33, P = 0.013) in SMARCD2, and rs17173769 (β = −0.27, 95% CI = −0.52 to −0.01, P = 0.045) in SMARCD3 were significantly associated with DNA damage levels. After combining these four polymorphisms, we found that the more unfavorable alleles the subjects carried, the heavier DNA damage they suffered, suggesting a locus-dosage effect between combined genotypes and DNA damage levels (P for trend = 0.006). These findings suggest that genetic variants in SMARC genes may contribute the individual variations of DNA damage levels in Chinese population. Further larger and functional studies are warranted to confirm our findings.     

Relation of PON1 and CYP1A1 genetic polymorphisms to clinical findings in a cross-sectional study of a Greek rural population professionally exposed to pesticides

Allelic variants of CYP1A1 and PON1 have been extensively studied as susceptibility factors in toxic response, although little is known about the role of these variants as risk factors for the plethora of diseases appearing in the human population. In this study we investigated the hypothesis of correlation of CYP1A1 and PON1 enzymes with the incidence of various medical examination findings in a Greek rural population professionally exposed to a variety of pesticides. The medical history of 492 individuals, randomly selected for the total population of 42,000, was acquired by interviews and their genotype determined for the CYP1A1*2A, PON1 M/L and PON1 Q/R polymorphisms. The assessment of exposure to pesticides of the population was verified by analytical methods. Analysis of the genetic data revealed that the allele frequencies of PON1 R, M and CYP1A1*2A alleles were 0.243, 0.39 and 0.107 respectively. The CYP1A1*2A polymorphism was found to have significant association with chronic obstructive pneumonopathy (p = 0.045), peripheral circulatory problems (trend p = 0.042), arteritis (p = 0.022), allergies (trend p = 0.046), hemorrhoids (trend p = 0.026), allergic dermatitis (p = 0.0016) and miscarriages (p = 0.012). The PON1 Q/R polymorphism was found to have significant association with hypertension (p = 0.046) and chronic constipation (p = 0.028) whereas, the L/M polymorphism, with diabetes (p = 0.036), arteritis (trend p = 0.022) and hemorrhoids (trend p = 0.027). Our results demonstrated an association between the CYP1A1/PON1 polymorphisms and several medical examination findings, thus indicating the possible involvement of the human detoxification system to health effects in a rural population exposed professionally to pesticides.     

In vitro inhibitory effects of asiaticoside and madecassoside on human cytochrome P450

The inhibitory effects and types of inhibition of asiaticoside and madecassoside on human CYPs were studied in vitro using recombinant human CYPs. The median inhibitory concentrations (IC₅₀) of asiaticoside and madecassoside were determined for CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4. Asiaticoside inhibited CYP2C19 (IC₅₀ = 412.68 ± 15.44 μM) and CYP3A4 (IC₅₀ = 343.35 ± 29.35 μM). Madecassoside also inhibited CYP2C19 (IC₅₀ = 539.04 ± 14.18 μM) and CYP3A4 (IC₅₀ = 453.32 ± 39.33 μM). Asiaticoside and madecassoside had no effect on the activities of CYP1A2, CYP2C9 and CYP2D6 and CYP2E1. Assessment of mechanism-based inhibition and the type of inhibition were performed for asiaticoside and madecassoside with CYP2C19 and CYP3A4. These results suggested that madecassoside is a mechanism-based inhibitor of CYP2C19 and CYP3A4. Assessment of mechanism-based inhibition by asiaticoside was limited by its low solubility. Asiaticoside exhibited non-competitive inhibition of CYP2C19 (K_i = 385.24 ± 8.75 μM) and CYP3A4 (K_i = 535.93 ± 18.99 μM). Madecassoside also showed non-competitive inhibition of CYP2C19 (K_i = 109.62 ± 6.14 μM) and CYP3A4 (K_i = 456.84 ± 16.43 μM). These results suggest that asiaticoside and madecassoside could cause drug-drug interactions via inhibition of CYP2C19 and CYP3A4. An in vivo study is needed to examine this further.     

OGG1 Ser326Cys polymorphism interacts with cigarette smoking to increase oxidative DNA damage in human sperm and the risk of male infertility

8-Oxoguanine DNA glycosylase 1 (OGG1) plays an important role in repairing oxidative DNA damage induced by chemical agents, such as tobacco. This study examined the effects of OGG1 Ser326Cys polymorphism and cigarette smoking, alone or combined, on sperm oxidative DNA damage and the risk of male infertility. A total of 620 idiopathic infertile subjects and 480 fertile controls were recruited in this study. Sperm 8-hydroxydeoxyguanine (8-OHdG) was measured by immunofluorescent assay using flow cytometry and genotypes were determined by OpenArray platform with a chip-based Taq-Man genotyping technology. Our results demonstrated that both cigarette smoking and OGG1 polymorphism can affect the sperm 8-OHdG levels. Individuals with variant Cys/Cys homozygote showed higher levels of sperm 8-OHdG than wide-type homozygote carriers (Ser/Ser). Stratified analysis found that the association between OGG1 polymorphism and sperm 8-OHdG levels was only observed among smokers with pack-years ≥5 but not among those subjects with pack-years < 5 (pack-years = packs smoked per day × years as a smoker). Further analysis based on the case–control study revealed that variant allele (Cys) of OGG1 was significantly associated with male infertility risk in a dominant model (OR = 1.35, 95% CI: 1.01–1.82; trend P < 0.001). Furthermore, we found a significant gene–environment interaction between OGG1 Ser326Cys polymorphism and cigarette smoking in relation to male infertility risk (P_interation = 0.0003). These findings provided the first evidence about potential interactive effects of OGG1 polymorphism and cigarette smoking on male infertility risk.     

Occupational exposure to low levels of benzene: Biomarkers of exposure and nucleic acid oxidation and their modulation by polymorphic xenobiotic metabolizing enzymes

This study investigated nucleic acid oxidation associated with exposure to benzene at low levels in 239 workers recruited among traffic policemen, taxi drivers and gasoline pump attendants of the city of Parma (Italy). Biomarkers of exposure, namely urinary t,t-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA), urinary cotinine, and urinary biomarkers of nucleic acid oxidation, namely 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo), 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydroguanine (8-oxoGua) were determined by liquid chromatography–tandem mass spectrometry. Relevant polymorphisms of NAD(P)H:quinone oxidoreductase (NQO1), glutathione S-transferases M1-1 (GSTM1), T1-1 (GSTT1), and A1 (GSTA1) were characterized by polymerase chain reaction-based methods in a subgroup of subjects. Biomarkers of nucleic acid oxidation were correlated with each other (r ≥ 0.32, p < 0.0001) and with exposure biomarkers (r ≥ 0.28, p < 0.0001). Multiple linear regression models including age, sex and smoking habits as independent variables demonstrated that benzene exposure is associated with oxidation damage to nucleic acid, particularly to RNA (p < 0.0001) and is modulated by the NQO1 polymorphism. The study confirmed a significant modulating effect of GSTM1 (p = 0.010), GSTT1 (p = 0.023) and GSTA1 (p = 0.048) polymorphisms on S-PMA excretion, with a significant interaction between GSTM1 and both GSTT1 and GSTA1 (p = 0.006 and p = 0.037, respectively).     

Effects of monoamine oxidase inhibitor and cytochrome P450 2D6 status on 5-methoxy-N,N-dimethyltryptamine metabolism and pharmacokinetics

5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is a natural psychoactive indolealkylamine drug that has been used for recreational purpose. Our previous study revealed that polymorphic cytochrome P450 2D6 (CYP2D6) catalyzed 5-MeO-DMT O-demethylation to produce active metabolite bufotenine, while 5-MeO-DMT is mainly inactivated through deamination pathway mediated by monoamine oxidase (MAO). This study, therefore, aimed to investigate the impact of CYP2D6 genotype/phenotype status and MAO inhibitor (MAOI) on 5-MeO-DMT metabolism and pharmacokinetics. Enzyme kinetic studies using recombinant CYP2D6 allelic isozymes showed that CYP2D6.2 and CYP2D6.10 exhibited 2.6- and 40-fold lower catalytic efficiency (V_max/K_m), respectively, in producing bufotenine from 5-MeO-DMT, compared with wild-type CYP2D6.1. When co-incubated with MAOI pargyline, 5-MeO-DMT O-demethylation in 10 human liver microsomes showed significantly strong correlation with bufuralol 1′-hydroxylase activities (R² = 0.98; P < 0.0001) and CYP2D6 contents (R² = 0.77; P = 0.0007), whereas no appreciable correlations with enzymatic activities of other P450 enzymes. Furthermore, concurrent MAOI harmaline sharply reduced 5-MeO-DMT depletion and increased bufotenine formation in human CYP2D6 extensive metabolizer hepatocytes. In vivo studies in wild-type and CYP2D6-humanized (Tg-CYP2D6) mouse models showed that Tg-CYP2D6 mice receiving the same dose of 5-MeO-DMT (20 mg/kg, i.p.) had 60% higher systemic exposure to metabolite bufotenine. In addition, pretreatment of harmaline (5 mg/kg, i.p.) led to 3.6- and 4.4-fold higher systemic exposure to 5-MeO-DMT (2 mg/kg, i.p.), and 9.9- and 6.1-fold higher systemic exposure to bufotenine in Tg-CYP2D6 and wild-type mice, respectively. These findings indicate that MAOI largely affects 5-MeO-DMT metabolism and pharmacokinetics, as well as bufotenine formation that is mediated by CYP2D6.     

Anti-hyperglycemic and antigenotoxic potential of Ulva rigida ethanolic extract in the experimental diabetes mellitus

An increased reactive oxygen species (ROS) and insufficient antioxidant activity is known in diabetes mellitus (DM). Antioxidant compounds in the human foods or supplementary diets can be used to counteract several diseases. The analysis of micronuclei (MN) is a cytogenetic technique used to show chromosomal damage caused by clastogenic affects. The present study was designed to evaluate: (i) the effects of diabetes mellitus on bone marrow MN frequency, (ii) the effect of oral administration of Ulva rigida ethanolic extract (URE) on MN frequency produced by DM, and (iii) some hematological values in normal and streptozotocin-induced diabetic rats. Daily fluid and food consumptions, weekly body weights, blood glucose concentrations and serum insulin levels were also examined in the study groups during the two different administration periods. The blood glucose concentration and MN frequency have been significantly increased in diabetic rats compared with the normal rats (p < 0.0001). Especially, URE-30d group treatment in diabetic rats was significantly decreased blood glucose concentrations and MN frequency. This is the first report on the anti-hyperglycemic, anti-oxidative and genotoxic/antigenotoxic capacity of U. rigida in vivo. Our results suggest that URE shows strong anti-hyperglycemic and antigenotoxic effect on the genotoxicity produced by DM in rats.     

Role of genetic polymorphisms of CYP1A1, CYP3A5, CYP2C9, CYP2D6, and PON1 in the modulation of DNA damage in workers occupationally exposed to organophosphate pesticides

Organophosphate pesticides (OPs) are primarily metabolized by several xenobiotic metabolizing enzymes (XMEs). Very few studies have explored genetic polymorphisms of XMEs and their association with DNA damage in pesticide-exposed workers. The present study was designed to determine the role of genetic polymorphisms of CYP1A1, CYP3A5, CYP2C9, CYP2D6, and PON1 in the modulation of DNA damage in workers occupationally exposed to OPs. We examined 284 subjects including 150 workers occupationally exposed to OPs and 134 normal healthy controls. The DNA damage was evaluated using the alkaline comet assay and genotyping was done using PCR-RFLP. The results revealed that the PONase activity toward paraoxonase and AChE activity was found significantly lowered in workers as compared to control subjects (p < 0.001). Workers showed significantly higher DNA damage compared to control subjects (14.37 ± 2.15 vs. 6.24 ± 1.37 tail% DNA, p < 0.001). Further, the workers with CYP2D6*3 PM and PON1 (QQ and MM) genotypes were found to have significantly higher DNA damage when compared to other genotypes (p < 0.05). In addition, significant increase in DNA damage was also observed in workers with concomitant presence of certain CYP2D6 and PON1 (Q192R and L55M) genotypes which need further extensive studies. In conclusion, the results indicate that the PON1 and CYP2D6 genotypes can modulate DNA damage elicited by some OPs possibly through gene-environment interactions.     

Evaluation of anti-oxidative,genotoxic and antigenotoxic potency of Codium tomentosum Stackhouse ethanolic extract in human lymphocytes in vitro

The genome is constantly exposed to agents, both exogenous and endogenous, that damage DNA. Consequently, it is very important that determination of this agents and the protective agents. In this work, we evaluated the antigenotoxic/antimutagenic activity of the crude ethanolic extracts of Codium tomentosum Stackhouse (Chlorophyceae) (CTE), collected from The Coast of South East Marmara Sea, in human lymphocytes culture in vitro against genotoxic/mutagenic agents MMC, EMS and H₂O₂ by using chromosome aberration (CA), sister chromatid exchange (SCE) and micronuclei (MN) assays as experimental endpoints. Also, in the present study, we determined total phenolic content and total antioxidant capacity (in soluble lipid and water). In addition, total protein, total carbohydrate, vitamins (A, C and E) and pigments (chlorophyll a, chlorophyll b and carotene) contents were also determined. Results of CA, SCE and MN tests show that CTEs have not shown genotoxic effect. In CTE plus MMC-, EMS- or H₂O₂- treated cultures, CA, SCE and MN frequency which induced by MMC, EMS or H₂O₂ has been decreased significantly (p < 0.05–0.001). This is the first report on genotoxicity/antigenotoxicity and anti-oxidative capacity of Codium tomentosum. Our results have clearly shown that CTE has strong anti-oxidative and antigenotoxic effect.     

Effects of Thai Musa species on prevention of UVB-induced skin damage in mice

The effects of oral administration of Musa sapientum and Musa suerier on prevention of UVB induced skin damages were investigated in male ICR mice. Animals were orally administered 50 mg/day ascorbic acid, or M. sapientum or M. suerier’s fruit pulps at dose of 0.5, 1 or 1.5 mg/g body weight/day for 12 weeks. Concurrently, the shaved backs of animals were irradiated with UVB for 12 weeks. The intensity of irradiation was progressively increased, from 54 mJ/cm² per exposure at week 1–126 mJ/cm² at week 11. A significant decrease (p < 0.05) in skin elasticity (from 0.82 ± 0.02 to 0.42 ± 0.09) and total glutathione (from (193.6 ± 18.7 to 152.7 ± 7.8 ng/mg protein) as compared with the control group (water-administered UVB-irradiated mice) was observed after 12 weeks of UVB exposure. When l-ascorbic acid (0.72 ± 0.01) or 1 mg/g body weight/day M. suerier (0.84 ± 0.06) were administered to UVB-irradiated mice, the reduction in skin elasticity was significantly inhibited (p < 0.05). Moreover, the significant increase (p < 0.05) in level of total glutathione was found in these groups (220.8 ± 13.3 ng/mg protein for l-ascorbic acid and 224.9 ± 20.1 ng/mg protein for M. suerier). These findings suggest the potential effect of daily consumption of M. suerier on prevention of skin damage from repeated UVB exposure.     

Literature review on the safety of Toyocerin,a non-toxigenic and non-pathogenic Bacillus cereus var. toyoi preparation

Bacillus cereus var. toyoi is a naturally occurring, non-toxigenic and non-pathogenic strain of B. cereus. Safety studies were conducted on a B. toyoi preparation (Toyocerin^®), including but not limited to enterotoxicity, eye irritation, genotoxicity, acute, subchronic and chronic toxicity studies and human clinical trials. In rabbits, Toyocerin^® did not exhibit enterotoxicity and was only slightly irritating to the eyes. It was non-mutagenic in an Ames assay at up to 10,000 μg/plate and did not exhibit clastogenic activity in a chromosomal aberration test at up to 450 mg/ml. It was non-toxic in acute and repeated-dose (30 and 60 days and 1 year) toxicity studies in rats and mice at up to 3 × 10¹¹ spores/kg bw/day. In an eight-day human clinical trial, Toyocerin^® did not cause any adverse effects in healthy male and female subjects at 1 × 10⁹ and 1 × 10¹⁰ spores/kg bw/day. In feeding trials, Toyocerin^® did not cause any adverse effects in rabbits, pigs, chickens, turkeys and cattle at doses ranging from 8.5 × 10⁷ to 4 × 10⁹ spores/kg bw/day for durations of 2 weeks to 18 months. Taken together, these studies demonstrate that Toyocerin^® is safe at the doses tested.     

A case-control study of polymorphisms in xenobiotic and arsenic metabolism genes and arsenic-related bladder cancer in New Hampshire

Arsenic is associated with bladder cancer risk even at low exposure levels. Genetic variation in enzymes involved in xenobiotic and arsenic metabolism may modulate individual susceptibility to arsenic-related bladder cancer. Through a population-based case-control study in NH (832 cases and 1191 controls), we investigated gene-environment interactions between arsenic metabolic gene polymorphisms and arsenic exposure in relation to bladder cancer risk. Toenail arsenic concentrations were used to classify subjects into low and high exposure groups. Single nucleotide polymorphisms (SNPs) in GSTP1, GSTO2, GSTZ1, AQP3, AS3MT and the deletion status of GSTM1 and GSTT1 were determined. We found evidence of genotype-arsenic interactions in the high exposure group; GSTP1 Ile105Val homozygous individuals had an odds ratio (OR) of 5.4 [95% confidence interval (CI): 1.5–20.2; P for interaction = 0.03] and AQP3 Phe130Phe carriers had an OR = 2.2 (95% CI: 0.8–6.1; P for interaction = 0.10). Bladder cancer risk overall was associated with GSTO2 Asn142Asp (homozygous; OR = 1.4; 95% CI: 1.0–1.9; P for trend = 0.06) and GSTZ1 Glu32Lys (homozygous; OR = 1.3; 95% CI: 0.9–1.8; P for trend = 0.06). Our findings suggest that susceptibility to bladder cancer may relate to variation in genes involved in arsenic metabolism and oxidative stress response and potential gene-environment interactions requiring confirmation in other populations.     

Chlorophyll a, an active anti-proliferative compound of Ludwigia octovalvis, activates the CD95 (APO-1/CD95) system and AMPK pathway in 3T3-L1 cells

Ludwigia octovalvis is an aquatic plant widely distributed in Taiwan. It is traditionally used as a diuretic and is consumed as health drink. In this study, we evaluated the anti-proliferative activity of extracts and active constituent (chlorophyll a; CHL-a) of L. octovalvis in 3T3-L1 adipocytes; its mode of action on apoptosis was also investigated. Results showed that, among the different extracts and fractions, the ethylacetate layer (EAL) possessed the most potent anti-proliferative activity. Activity guided fractionation of the EAL obtained the bioactive constituent CHL-a (IC₅₀: 24.10 ± 0.83 nM). At concentrations 5–30 nM, CHL-a exhibited a dose-dependent accumulation of the Sub-G1 peak and caused cell cycle arrest at the G0/G1 phase. At 30 nM, it significantly reduced the cell viability, induced the appearance of DNA fragments, and enhanced the activation of caspase-3. Western blot data revealed that CHL-a decreased the level of Bcl-2, and increased the expression of CD95 (APO-1/CD95) and Bax. Furthermore, CHL-a up-regulated the AMPK and p-AMPK levels, and down-regulated the expression of PPAR-γ. These results conclude that CHL-a possesses potent anti-proliferative activity, and its apoptotic effects on 3T3-L1 adipocytes are mediated through the activation of CD95 (APO-1/CD95) system and the AMPK signaling pathway.     

Chemoprotective properties of rooibos (Aspalathus linearis), honeybush (Cyclopia intermedia) herbal and green and black (Camellia sinensis) teas against cancer promotion induced by fumonisin B1 in rat liver

The chemoprotective properties of unfermented and fermented rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia) herbal teas, and green and black teas (Camellia sinensis) were investigated against fumonisin B₁ (FB₁) promotion in rat liver utilizing diethylnitrosamine (DEN) as cancer initiator. The various teas differently affected the clinical chemical parameters associated with liver and kidney damage associated with FB₁ suggesting specific FB₁/iron/polyphenolic interactions. Green tea enhanced (P < 0.05) the FB₁-induced reduction of the oxygen radical absorbance capacity, while fermented herbal teas and unfermented honeybush significantly (P < 0.05) decreased FB₁-induced lipid peroxidation in the liver. The teas exhibited varying effects on FB₁-induced changes in the activities of catalase, glutathione peroxidase (GPx) glutathione reductase (GR) as well as the glutathione (GSH) status. Unfermented rooibos and honeybush significantly (P < 0.05) to marginally (P < 0.1) reduced the total number of foci (>10 μm), respectively, while all the teas reduced the relative amount of the larger foci. Fermentation seems to reduce the protective effect of the herbal teas. Differences in the major polyphenolic components and certain FB₁/polyphenolic/tissue interactions may explain the varying effects of the different teas on the oxidative parameters, hepatotoxic effects and cancer promotion in rat liver.     

Characterization of major phytocannabinoids, cannabidiol and cannabinol, as isoform-selective and potent inhibitors of human CYP1 enzymes

Inhibitory effects of Δ⁹-tetrahydrocannabinol (Δ⁹-THC), cannabidiol (CBD), and cannabinol (CBN), the three major constituents in marijuana, on catalytic activities of human cytochrome P450 (CYP) 1 enzymes were investigated. These cannabinoids inhibited 7-ethoxyresorufin O-deethylase activity of recombinant CYP1A1, CYP1A2, and CYP1B1 in a competitive manner. CBD most potently inhibited the CYP1A1 activity; the apparent K_i value (0.155 μM) was at least one-seventeenth of the values for other CYP1 isoforms. On the other hand, CBN more effectively decreased the activity of CYP1A2 and CYP1B1 (K_i = 0.0790 and 0.148 μM, respectively) compared with CYP1A1 (K_i = 0.541 μM). Δ⁹-THC less potently inhibited the CYP1 activity than CBD and CBN, and showed low selectivity against the CYP1 inhibition (K_i = 2.47-7.54 μM). The preincubation of CBD resulted in a time- and concentration-dependent decrease in catalytic activity of all the recombinant CYP1 enzymes and human liver microsomes. Similarly, the preincubation of Δ⁹-THC or CBN caused a time- and concentration-dependent inhibition of recombinant CYP1A1. The inactivation of CYP1A1 by CBD indicated the highest k_inact/K_I value (540 l/mmol/min) among the CYP1 enzyme sources tested. The inactivation of recombinant CYP1A1 and human liver microsomes by CBD required NADPH, was not influenced by dialysis and by glutathione, N-acetylcysteine, and superoxide dismutase as trapping agents. These results indicated that CBD and CBN showed CYP1 isoform-selective direct inhibition and that CBD was characterized as a potent mechanism-based inhibitor of human CYP1 enzymes, especially CYP1A1.