Benefits of aged garlic extract in modulating toxicity biomarkers against p-dimethylaminoazobenzene and phenobarbital induced liver damage in Rattus norvegicus.

Garlic (Allium sativum L.), a popular spice, has been used for decades in treating several medical conditions. Although Allicin, an active ingredient of garlic has been extensively studied on carcinogen-induced hepatotoxicity and oxidative stress in rats (Rattus norvegicus), no systematic study on the beneficial effects of generic aged garlic and specific aged garlic extract-Kyolic has been done. The present study involves rats fed chronically with two liver carcinogens, p-dimethylaminoazobenzene and phenobarbital, to produce hepatotoxicity. The aged garlic extract was characterized by UV-spectra, FTIR, HPLC and GC-MS. Biochemical and pathophysiological tests were performed by keeping suitable controls at four fixation intervals, namely, 30, 60, 90, and 120 days, utilizing several widely accepted toxicity biomarkers. Compared to the controls, remarkable elevation in the activities of lactate dehydrogenase, gamma glutamyl transferase and decline in catalase and glucose-6-phosphate dehydrogenase were observed in the carcinogen fed rats. Daily administration of aged garlic extract, could favorably modulate the elevated levels of various toxicity biomarkers including serum triglyceride, creatinine, urea, bilirubin, blood urea nitrogen except total cholesterol. It also altered the levels of blood glucose, HDL-cholesterol, albumin, AST, ALT, and hemoglobin contents in carcinogen intoxicated rats, indicating its protective potential against hepatotoxicity and oxidative stress in the experimental rats. Down-regulation of Bcl-2 and p53 proteins caused cell cycle arrest and apoptosis in garlic fed group. Kyolic exhibited additional benefits by arresting cell viability of cancer cells. This study would thus validate the use of aged garlic extract in the treatment of diseases causing liver toxicity including hepatocarcinoma.

Effect of bromide on the transformation and genotoxicity of octyl-dimethyl-p-aminobenzoic acid during chlorination.

Octyl-dimethyl-p-aminobenzoic acid (ODPABA), one of the most commonly used organic UV filters, can undergo considerable transformation in water when entering into the disinfection process. The impacts of bromide on degradation kinetics, formation and speciation of transformation products, regulated disinfection by-products (DBPs) as well as genotoxicity changes during ODPABA chlorination were investigated in this study. Results indicated that the reaction of ODPABA with chlorine followed pseudo-first-order and second-order kinetics. Adding bromide noticeably enhanced the degradation rate of ODPABA, but reduced the impact of chlorine dose. Four halogenated transformation products (Cl-ODPABA, Br-ODPABA, Cl-Br-ODPABA and Br2-ODPABA) were detected by LC-MS/MS. Mono-halogenated products were stable during 24-h chlorination, while di-halogenated products constantly increased. The total yields of trihalomethanes (THMs) and haloacetic acids (HAAs) were both low, but predominated by bromine substitution at high levels of bromide. In addition, SOS/umu tests showed that genotoxicity was generated after ODPABA chlorination, which was increased at least 1.5 times in the presence of bromine. Whereas, no significant genotoxicity variation was observed following bromide concentration change.

Evaluation of the repeated-dose liver micronucleus assay with p-dimethylaminoazobenzene.

The micronucleus induction by p-dimethylaminoazobenzene (DAB), a genotoxic rat liver carcinogen, was assessed in the liver and bone marrow of young adult rats after the repeated administration of DAB for 14 (Lab. 1) and 28 (Lab. 2) days. Three dose levels, 25, 50 and 100mg/kg/day, were used for the investigations in both labs. The frequency of micronucleated hepatocytes was significantly increased in a dose-dependent manner after the repeated administration of DAB at 50mg/kg/day or more for 14 and 28 days. Similarly, the frequency of micronucleated immature erythrocytes in the bone marrow was increased after the repeated administration of DAB at 100mg/kg/day for 14 and 28 days. These results indicate that the repeated-dose liver micronucleus assay allowed for the detection of micronucleus induction by DAB, and that the lowest detectable dose for micronucleus induction in the liver was lower than in the bone marrow. Thus, the repeated-dose liver micronucleus assay using young adult rats is considered suitable for the detection of micronucleus induction by liver carcinogens, such as DAB.

Two homeopathic remedies used intermittently provide additional protective effects against hepatotoxicity induced by carcinogens in mice.

The purpose of the study was to evaluate whether potentized cholesterinum (Chol) intermittently used with another homeopathic remedy, Natrum Sulphuricum (Nat Sulph) can provide additional benefits in combating hepatotoxicity generated by chronic feeding of carcinogens, p-dimethylaminoazobenzene (p-DAB), and phenobarbital (PB). Mice were categorized into subgroups: normal untreated (Gr-1); normal + alcohol "vehicle" (Alc) (Gr-2), 0.06% p-DAB +0.05% PB (Gr-3), p-DAB+PB+Alc (Gr-4), p-DAB+PB+Nat Sulph-30 (Gr-5), p-DAB+PB+Chol-200 (Gr-6), p-DAB+PB+Nat Sulph-30+Chol-200 (Gr-7), p-DAB+PB+Nat Sulph-200 (Gr-8), and DAB+PB+Nat Sulph-200+Chol-200 (Gr-9). Hepatotoxicity was assessed through biomarkers like aspartate and alanine aminotransferases (AST and ALT), acid and alkaline phosphatases (AcP and AlkP), reduced glutathione content (GSH), glucose 6-phosphate dehydrogenase (G6PD), gamma glutamyl transferase (GGT), lactate dehydrogenase (LDH), and analysis of lipid peroxidation (LPO) at 30, 60, 90, and 120 days and antioxidant biomarkers like superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) were assayed. Electron microscopic studies (scanning and transmission) and gelatin zymography for matrix metalloproteinases were conducted in liver. The feeding of the homeopathic drugs showed intervention in regard to the increased activities of AST, ALT, AcP, AlkP, GGT, LDH, and LPO and decreased activities of G6PD, SOD, CAT, GR, and GSH noted in the intoxicated mice, more appreciable in Groups 7 and 9. Thus, combined therapy provided additional antihepatotoxic and anticancer effects.

Role of ErbB2 mediated AKT and MAPK pathway in gall bladder cell proliferation induced by argemone oil and butter yellow. Argemone oil and butter yellow induced gall bladder cell proliferation.

The effect of noncytotoxic doses of argemone oil (AO) and butter yellow (BY), the common adulterants in edible oil, on free radical generation and signaling pathway for cell proliferation in primary cells of gall bladder (GB) was undertaken. AO and BY showed no cytotoxicity at 0.1 µl/ml and 0.1 µg/ml concentration, respectively. AO caused significant increase in ROS after 30 min and RNS after 24 h in GB cells while no change was observed following BY treatment. Enhanced level of COX-2 was observed following AO (0.1 µl/ml) and BY (0.1 µg/ml) treatment to cells for 24 h. AO treatment caused phosphorylation of ErbB2, AKT, ERK, and JNK along with increased thymidine uptake indicating cell proliferation ability in GB cells. BY treatment also showed significant expression of these proteins with the exception of phosphorylated JNK. These results suggest that AO and BY have cell proliferative potential in GB cells following up-regulation of COX-2 and ErbB2; however, their downstream signaling molecules and free radical generation have differential response, indicating that the mechanism of proliferation is different for both compounds and may have relevance in gall bladder cancer.

Edible oil adulterants, argemone oil and butter yellow, as aetiological factors for gall bladder cancer.

Carcinogenic potential of argemone oil (AO) and butter yellow (BY), the adulterants encountered in edible oil, in gall bladder of Swiss albino mice was undertaken to investigate the potential aetiological factors of gall bladder carcinoma (GBC) in the Indo-Gangetic basin. Twice weekly intraperitoneal (ip) administration of AO (5 ml/kg body wt) and BY (25 mg/kg body wt) to Swiss albino male and female mice for 30 and 60 days indicated that females were more vulnerable to these adulterants in terms of responses to inflammatory markers. Subsequent experiments with dietary exposure of AO (1%) and BY (0.06%) for 6 months in female mice showed symptoms related to cachexia, jaundice and anaemia. High levels of total cholesterol, low density lipoprotein (LDL), TG, bilirubin and low level of high density lipoprotein (HDL) as well as gallstone formation was shown by AO exposure only, leading to the development of adenocarcinoma. BY exposure resulted in adenoma and hyperplasia without stone formation. The cyclooxygenase (COX-2) overexpression was found to be related to prostaglandin E2 (PGE2) production in AO treated mice but not in BY exposed animals, thereby indicating a differential pathway specific carcinogenicity. PGE2 stimulates the secretion of secreted mucins (MUC5AC), which is involved in stone formation following AO exposure. Enhanced secretion of membrane bound mucins (MUC4) in BY and AO exposed mice resulted in the activation of ErbB2 and downstream signalling such as p-AKT, p-ERK and p-JNK, which ultimately affects the target proteins, p53 and p21 leading to adenoma and adenocarcinoma, respectively. The study suggests that AO and BY are responsible for producing GBC in mice along with stone formation in the AO exposed animals.

[Parasitic factor and cancer].

There is opinion in the literature as to that liver trematode infections, such as opisthorchiasis, clonorchiasis, fascioliasis, and metorchiasis, can induce cancer of the liver pancreas, intestine - this all is clinically observed. The authors were the first in world practice to show the development of a hepatic blastomatous process in animals (albino rats, cats) with opisthorchiasis in 13%; cancer developed in 28 and 56% with the use of a hepatotropic carcinogen and combined (opisthorchiasis + a carcinogen) exposure, respectively. Throughout his life, a human being can easily catch these trematodes that have carcinogenic activity and these diseases concurrent with household and food carcinogens can give rise to tumors in the liver pancreas and intestine. Timely diagnosis and specific anthelmintic therapy are necessary to prevent parasitic cancer.

Intrinsic apoptosis and NF-κB signaling are potential molecular targets for chemoprevention by black tea polyphenols in HepG2 cells in vitro and in a rat hepatocarcinogenesis model in vivo.

Antiproliferative and apoptosis inducing effects of black tea polyphenols (Polyphenon-B) on HepG2 cells in vitro and in a rat hepatocarcinogenesis model in vivo were investigated. Viability of HepG2 cells was evaluated by the MTT assay, and apoptosis by AO-EB and DAPI staining, cell cycle analysis, and annexin V-PI assay. For the in vivo study, male Sprague-Dawley rats treated with dimethylaminoazobenzene (DAB) (0.06%) were used. The expression of Bcl-2 and NF-κB family members were analyzed by immunoblotting. Administration of Polyphenon-B induced dose-dependent inhibition of growth of HepG2 cells and reduced tumor incidence in DAB administered animals. HepG2 cells also exhibited morphological features characteristic of apoptotic cell death. In addition, administration of Polyphenon-B increased the expression of Bax, tBid, Smac/Diablo, cytochrome C, Apaf-1, caspases, and IκB with PARP cleavage, and decreased the expression of Bcl-2, Bcl-xL, pBad, NF-κB, p-IκB-α, IKKß and Ub in both HepG2 cells and in DAB-treated animals. These results provide evidence that Polyphenon-B effectively inhibits proliferation and induces apoptosis both in vitro and in vivo by inhibiting NF-κB, and inducing intrinsic apoptosis by modulating the expression of a network of interrelated molecules eventually culminating in caspase-mediated cell death.

Anti-carcinogenic potentials of a plant extract (Hydrastis canadensis): I. Evidence from in vivo studies in mice (Mus musculus).

Ethanolic extract of Hydrastis canadensis has been tested for its possible anti-cancer potentials against p-dimethylaminoazobenzene (p-DAB) induced hepatocarcinogenesis in mice. Mice were chronically fed p-dimethylaminoazobenzene (p-DAB) and phenobarbital (PB), two hepato-carcinogens for 1, 2, 3 and 4 months, respectively, and were divided into sub-groups: i) fed normal low protein diet (Gr. I, normal control); ii) fed diet mixed with 0.06% p-DAB at a daily dose of 165 mg/kg b.w. per mouse plus 0.05% PB plus 0.06 ml 90% alcohol (vehicle of the crude extract) (Gr. II, carcinogen treated); iii) fed diet mixed with p-DAB and PB at the same daily dose plus crude extract of Hydrastis canadensis (Gr. III, drug treated). Several biochemical parameters like acid and alkaline phosphatases, alanine amino-, aspartate amino-, and gamma glutamyl-transferases, lipid peroxidation, reduced glutathione content, lactate dehydrogenase, catalase and glucose-6-phosphate dehydrogenase activities and electron microscopy of liver in different groups of treated and control mice were studied. A critical analysis of results of these studies suggested anti-cancer potentials of the drug suitable for use as a supportive complementary medicine in liver cancer.

Effect of antioxidant vitamins A, C, E and their analogues on azo-dye binding protein in liver of rats treated with p-dimethylaminoazobenzene.

p-Dimethylaminoazobenzene (DAB) is an azo-dye and known to cause liver tumour in rats. Azo-dye binding protein is a specific cytosolic protein involved in the translocation of azo-dye carcinogen metabolites from liver cytoplasm into the nucleus. Administration of vitamin A (40,000 and 50,000 IU), L-ascorbic acid (500 and 1000 mg) and vitamin E succinate (200-500 mg) reduced the amount of azo-dye binding protein in liver of rats treated with DAB. Supplementation of high doses of vitamin A acetate, vitamin A palmitate, sodium ascorbate, ascorbyl palmitate and vitamin E acetate had no effect on the quantity of azo-dye binding protein in liver. When the vitamin mixture was given, the level of azo-dye binding protein decreased in the liver at all the studied doses, which may be due to their synergistic effect.

Efficacy of a plant extract (Chelidonium majus L.) in combating induced hepatocarcinogenesis in mice.

Ethanolic whole plant extract of Chelidonium majus, extensively used in traditional systems of medicine against various liver ailments, has been tested for its possible anti-tumor, hepato-protective and anti-genotoxic effects in p-dimethylaminoazobenzene (p-DAB) induced hepatocarcinogenesis in mice through multiple assays: cytogenetical, biochemical, histological and electron microscopical. Different sets of mice, 5 (for 7, 15 and 30 days' treatment) or 10 (for 60, 90 and 120 days) each, were chronically fed a diet suitably mixed with p-DAB and phenobarbital to develop liver tumors. One sub-group of carcinogen fed mice was also fed C. majus extract; 0.1 ml daily (drug-treated) while the other equal amount of dilute ethyl alcohol ("vehicle" of plant extract) (positive control). A separate group of mice was maintained with normal diet without any carcinogen treatment (negative control). Data of several cytogenetical endpoints and biochemical assay of some toxicity marker enzymes at all fixation intervals and histology of liver sections through ordinary, scanning and transmission electron microscopy at 60 and 120 days and that of spleen and kidney at 90 days were critically analyzed in the treated lots vis-a-vis controls. The results suggest anti-tumor, anti-genotoxic and hepato-protective effects of the plant extract, showing potentials for use in cancer therapy.

Dietary supplementation of vitamin A, C and E prevents p-dimethylaminoazobenzene induced hepatic DNA damage in rats.

The preventive effect of antioxidant vitamins A, C, E and their analogues against DNA damage induced by a hepatocarcinogen p-dimethylaminoazobenzene (DAB) was assessed by comet assay. For genotoxicity (DNA damage) study, male albino rats were divided into 11 groups, consisting of four rats each. Group I served as control. Group II to VII received 1, 10, 100, 200, 300 and 400 mg per kg body wt of DAB respectively; group VIII to XI received 500 mg/kg body wt of DAB. They were sacrificed by cervical decapitation 3, 6, 12 and 24 h after treatment; livers were excised immediately and subjected to comet assay to measure DNA damage. To study the effect of vitamins, experiments were conducted on a group of 275 rats divided into 3 sets of 25 rats each. First set served as control; second set received 0.06% DAB and third set received 0.06% DAB, along with analogues of vitamins A, C and E. Rats fed with 0.06% DAB were provided water ad libitum for a period of 4 months, followed by a normal (basal) diet for further 2 months. Vitamins A (10,000-50,000 IU), C (75-1000 mg) and E (50-500 mg) and their analogues were given (per kg body wt) to the third set of rats by gavage route once in a week for a period of 6 months. The DAB induced DNA damage only at the highest tested dose of 500 mg/kg body wt. Administration of high doses of vitamin A acid, L-ascorbic acid and vit. E succinate individually prevented the DNA damage. However, administration of a mixture of these vitamins at low doses prevented the DAB-induced DNA damage, which may be due to their synergistic effect. The results indicate that there is a significant advantage in mixed vitamins therapy at low dose over the treatment with individual vitamins.

Supportive evidence for the anticancerous potential of alternative medicine against hepatocarcinogenesis in mice.

INTRODUCTION: The present study examines if Lycopodium 200 (Lyco-200) has demonstrable anti-cancer activities in mice which are chronically fed carcinogens, p-dimethylaminoazobenzene (p-DAB) and phenobarbital (PB) to induce liver cancer. MATERIALS AND METHODS: Mice in 5 different groups were chronically fed for varying periods of time: group I: normal diet; group II: normal diet + alcohol 200); group III: p-DAB + PB; group IV: p-DAB + PB + alcohol 200 (vehicle of Lyco-200 being ethyl alcohol); group V: p-DAB + PB + Lyco-200. They were sacrificed at day 7, 15, 30, 60, 90 or 120, and the following parameters were assessed: cytogenetic endpoints like chromosome aberrations, micronuclei, mitotic index and sperm-head anomaly; toxicity biomarkers like acid and alkaline phosphatases, alanine and aspartate amino transferase, glutathione reductase, succinate dehydrogenase and catalase activities, lipid peroxidation and reduced glutathione content. Additionally, scanning and transmission electron microscopic analyses of liver tissues were made at day 90 and 120, and immunodetection of p53 protein as well as gelatin zymography for matrix metalloproteinases in liver tissue were performed. Furthermore, studies were conducted on blood glucose, hemoglobin and cholesterol, estradiol, testosterone and cortisol, and lymphocyte and hepatic cell viabilities. Physical properties of Lyco-200 and potentized alcohol 200 were analyzed by using methods such as UV, Fourier Transform Infrared Spectroscopy (FTIR), Fluorescence Spectroscopy, 1H-NMR and 13C-NMR (Nuclear Magnetic Resonance Spectroscopy). RESULTS: Lyco-200 reduced cytogenetic damages yielding positive modulations of all biochemical, pathological and other risk factors, cell viability and expression of p53 protein and matrix metalloproteinases as compared to controls. CONCLUSION: Studies on other mammals are recommended to further investigate the potential of Lyco-200 in liver cancer.

Homeostatic response under carcinogen withdrawal, heme oxygenase 1 expression and cell cycle association.

BACKGROUND: Chronic injury deregulates cellular homeostasis and induces a number of alterations leading to disruption of cellular processes such as cell cycle checkpoints and apoptosis, driving to carcinogenesis. The stress protein heme oxygenase-1 (HO-1) catalyzes heme degradation producing biliverdin, iron and CO. Induction of HO-1 has been suggested to be essential for a controlled cell growth. The aim of this work was to analyze the in vivo homeostatic response (HR) triggered by the withdrawal of a potent carcinogen, p-dimethylaminoazobenzene (DAB), after preneoplastic lesions were observed. We analyzed HO-1 cellular localization and the expression of HO-1, Bcl-2 and cell cycle related proteins under these conditions comparing them to hepatocellular carcinoma (HC). METHODS: The intoxication protocol was designed based on previous studies demonstrating that preneoplastic lesions were evident after 89 days of chemical carcinogen administration. Male CF1 mice (n = 18) were used. HR group received DAB (0.5 % w/w) in the diet for 78 days followed by 11 days of carcinogen deprivation. The HC group received the carcinogen and control animals the standard diet during 89 days. The expression of cell cycle related proteins, of Bcl-2 and of HO-1 were analyzed by western blot. The cellular localization and expression of HO-1 were detected by immnunohistochemistry. RESULTS: Increased expression of cyclin E/CDK2 was observed in HR, thus implicating cyclin E/CDK2 in the liver regenerative process. p21cip1/waf1 and Bcl-2 induction in HC was restituted to basal levels in HR. A similar response profile was found for HO-1 expression levels, showing a lower oxidative status in the carcinogen-deprived liver. The immunohistochemical studies revealed the presence of macrophages surrounding foci of necrosis and nodular lesions in HR indicative of an inflammatory response. Furthermore, regenerative cells displayed changes in type, size and intensity of HO-1 immunostaining. CONCLUSION: These results demonstrate that the regenerative capacity of the liver is still observed in the pre-neoplastic tissue after carcinogen withdrawal suggesting that reversible mechanism/s to compensate necrosis and to restitute homeostasis are involved.

Genotoxicity studies OF p-dimethylaminoazobenzene (DAB).

The potential genotoxicity of the rodent liver carcinogen p-dimethylaminoazobenzene (DAB) was evaluated in compliance with the guidelines for genotoxicity studies of drugs (Notification No. 1604, Nov. 1, 1999, Ministry of Health and Welfare, Japan) and the OECD guidelines for testing chemicals. DAB was clearly positive in both the bacterial reverse mutation test (Ames test) and in vitro chromosomal aberration test in the presence of metabolic activation, whereas it was weakly positive at toxic doses in the rat bone marrow micronucleus test. It has been reported that DAB was clearly positive in in vivo genotoxicity tests, i.e., a mouse alkaline single cell gel electrophoresis (comet) assay and a young rat liver micronucleus test. These results suggest that the test system using the liver is effective for in vivo genotoxicity assessment of chemicals that show mutagenicity in in vitro genotoxicity tests in the presence of metabolic activation.

Species-specific effects of the hepatocarcinogens 3'-methyl-4-dimethyl-aminoazobenzene and ortho-aminoazotoluene in mouse and rat liver.

The effects of rat-specific hepatocarcinogen 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB), mouse-specific hepatocarcinogen ortho-aminoazotoluene (OAT), non-species-specific hepatocarcinogen diethylnitrosamine (DENA), and non-carcinogenic 4'-methyl-4-dimethylaminoazobenzene (4'-MeDAB) on glucocorticoid induction of tyrosine aminotransferase (TAT) and DNA-binding activity of hepatocyte nuclear factor 3 (HNF3) family of transcription factors were investigated with carcinogen-susceptible and -resistant animals. Species-specific hepatocarcinogens 3'-MeDAB and OAT strongly inhibited glucocorticoid induction of TAT in the liver of susceptible but not resistant animals. DENA, which is highly carcinogenic for the liver of both rats and mice inhibited glucocorticoid induction of TAT in both species, while non-carcinogenic 4'-MeDAB was absolutely ineffective both in rats and mice. The inhibition of TAT activity by the carcinogens was due to reduced levels of TAT mRNA, which is most likely to be a result of the reduced rate of transcription initiation of the TAT gene. In all cases, the TAT inhibition was accompanied by significant reduction of DNA-binding activity of the HNF3 transcription factor, which is known to be critical to glucocorticoid regulation of TAT gene. We also demonstrated that the described species-specific effects of OAT and of 3'-MeDAB on HNF3 DNA-binding activity may be initiated not only by administration in vivo, but also by their direct administration to homogenate, intact nuclei or nuclear lysate, but not to nuclear extract fraction, obtained by precipitation with 0.32 g/mL of ammonium sulfate (Fraction I). We showed, that a factor responsible for this effect might be precipitated in 0.32-0.47 g/mL interval of ammonium sulfate concentration. In contrast, non-specific hepatocarcinogen DENA was effective upon being added directly to Fraction I, implying a different mechanism of its action.

Cytotoxic and genotoxic effects of the azo-dye p-dimethylaminoazobenzene in mice: a time-course study.

The cytotoxic and genotoxic effects of chronic feeding of the azo-dye p-dimethylaminoazobenzene (p-DAB) during 7, 15, 30, 60, 90 and 120 days have been assessed in mice. The endpoints used for genotoxic analysis were chromosome aberrations (CA), micronuclei (MN) and mitotic index (MI) in bone-marrow cells, and sperm-head abnormality (SHA) in male gonads. The activities of marker enzymes for toxicity, such as glutamate oxalo-acetate transaminase (GOT), glutamate pyruvate transaminase (GPT), acid phosphatase (ACP) and alkaline phosphatase (ALKP) were also assayed periodically, as was lipid peroxidation (LPO). Chronic feeding of p-DAB produced increased numbers of chromosome aberrations, nuclear anomalies and sperm-head abnormalities, as compared with normal untreated controls, generally in a time-dependent manner until 60 days, after which the anomalies persisted, but rather erratically. However, although there was some noticeable modulation in enzyme activities in the corresponding p-DAB-fed mice as well, these were not strictly time-dependent.

Evaluation of liver and peripheral blood micronucleus assays with 9 chemicals using young rats. A study by the Collaborative Study Group for the Micronucleus Test (CSGMT)/Japanese Environmental Mutagen Society (JEMS)-Mammalian Mutagenicity Study Group (MMS).

We conducted simultaneous liver and peripheral blood micronucleus assays in young rats with seven rodent hepatocarcinogens-4,4'-methylenedianiline (MDA), quinoline, o-toluidine, 4-chloro-o-phenylenediamine (CPDA), dimethylnitrosamine (DMN), p-dimethylaminoazobenzene (DAB), and di(2-ethylhexyl)phthalate (DEHP)-and two mutagenic chemicals-kojic acid and methylmethanesulfonate (MMS). Quinoline, DMN, and DAB were positive in the liver assay, while o-toluidine, kojic acid, DAB, and MMS were positive in the peripheral blood assay. o-Toluidine, kojic acid, and DAB are reportedly negative in mouse bone marrow micronucleus assays, indicating a species difference. Our results revealed a correlation between micronucleus induction in hepatocytes and hepatocarcinogenicity. This technique can be useful for the detection of micronucleus-inducing chemicals that require metabolic activation, and it enables simultaneous comparison of the micronucleus-inducing potential of chemicals in the liver and peripheral blood in the same individual.

Detection of a smaller, 32-kDa 8-oxoguanine DNA glycosylase 1 in 3'-methyl-4-dimethylamino-azobenzene-treated mouse liver.

We previously reported that 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB) increased the 8-hydroxyguanine (8-OH-Gua) content in nuclear DNA and the base excision repair activity in mouse liver. However, to understand the mechanism of 3'-MeDAB carcinogenesis, a further investigation of the 8-OH-Gua repair systems was necessary. In this report, we examined the expression of the repair enzyme, 8-oxoguanine DNA glycosylase 1 (OGG1), in 3'-MeDAB-treated mouse liver. We prepared four kinds of anti-peptide polyclonal antibodies raised against mouse OGG1 (mOGG1). The sequences used as epitopes were designed from positions located close to the N-terminus, the nuclear localization signal (NLS), and the regions containing Lys(249) and Asp(267), which are involved in the catalytic mechanisms of mOGG1 (glycosylase and lyase, respectively). Immunoblotting, using all four antibodies, revealed a 32-kDa protein (mOGG1-32) in addition to the 38-kDa mOGG1 in the 3'-MeDAB-treated mouse liver. Moreover, immunostaining with mOGG1 antibody yielded strong, positive signals in the 3'-MeDAB-treated mouse liver nuclei. However, we could not detect any difference in the Ogg1 mRNA expression pattern. Although the function of mOGG1-32 remains unclear, these findings suggest that 3'-MeDAB may alter the function of the DNA repair protein, and this action may be related to 3'-MeDAB carcinogenesis.