Molecular non-genetic biomarkers related to Fenarimol cocarcinogenesis: organ- and sex-specific CYP induction in rat

Effects of Buyang Huanwu Decoction on antioxidant and drug-metabolizing enzymes in rat liver

AIM

To study the effect of Buyang Huanwu Decoction (BYHWD) on the antioxidant enzymes and drug-metabolizing enzymes in rat liver.

METHOD

Following treatment of rats with BYHWD at 6.42, 12.83, or 25.66 g·kg(-1) per day for 15 days, microsomes and cytosols isolated from the liver tissues were prepared by differential centrifugation according to standard procedures. The activities of the antioxidant enzymes and cytochrome b5, NADPH-cytochrome P450 reductase, CYP3A, CYP2E1, UGT, and GST of the rat livers were determined by UV-Vis spectrophotometer.

RESULTS

The activities of ALT, AST, antioxidant enzymes, and the Hepatosomatic Index in serum were not significantly affected. In cytosols, the activity of CAT was significantly increased at the dosage of 12.83 g·kg(-1), and all the other antioxidant activities and MDA levels were not affected by this treatment. BYHWD had no effect on cytochrome b5, NADPH-cytochrome P450 reductase, CYP3A, and UGT. At the highest dose (25.66 g·kg(-1)), the activity of CYP2E1 was significantly inhibited, and the activities of GST and the level of GSH were increased.

CONCLUSION

BYHWD is safe for the liver, and has the functions of detoxification and antioxidant. Patients should be cautioned about the herb-drug interaction of BYHWD and CYP2E1 substrates.

Gender differences in acute pesticide-related illnesses and injuries among farmworkers in the United States, 1998-2007

BACKGROUND

Farmworkers have a high risk for acute pesticide-related illness and injury, and the rate among female farmworkers is approximately twice as high as that among males. Surveillance data were used to identify reasons for this gender difference.

METHODS

We identified acute pesticide-related illness and injury cases among farmworkers from the Sentinel Event Notification System for Occupational Risks (SENSOR)-Pesticides Program and the California Department of Pesticide Regulation. Gender-specific associations with acute pesticide-related illness and injury were assessed using chi-square tests. National Agricultural Workers Survey data were also examined.

RESULTS

The over-representation of females among farmworker illness and injury cases was confined to females who did not handle pesticides (non-handlers). Female non-handler farmworkers who were affected were more likely to be working on fruit and nut crops, to be exposed to off-target pesticide drift, and to be exposed to fungicides and fumigants compared to males.

CONCLUSIONS

Although there is an increased risk for acute pesticide-related illness and injury among female farmworkers, the absolute number of farmworkers with acute pesticide-related illness and injury is far higher among males than females. Furthermore, farmworkers have little or no control over many of the identified contributing factors that led to illness and injury. Stringent enforcement of existing regulations and enhanced regulatory efforts to protect against off-target drift exposures may have the highest impact in reducing acute pesticide-related illness and injury among farmworkers.

Chromosomal aberrations in ovine lymphocytes exposed in vitro to tolylfluanid

Chromosomal aberrations have been used as important cytogenetic biomarkers to study the mutagenic effects of different chemicals in vivo and in vitro. Chromosomal aberrations were evaluated in cultures of sheep lymphocytes in vitro exposed to the fungicide tolylfluanid. Lymphocyte cultures from three donors were exposed to four different concentrations of fungicide (1.10(-4) M(.)L; 1.10(-5) M(.)L; 1.10(-6) M(.)L; 1 × 10(-7) M(.)L). Chromosomal analysis showed a significant (P = 0.018 and 0.038 respectively, Anova test, P < 0.05, Tukey test) increase in the frequency of aberrant cells (ABC) in cultures treated with the highest negative experimental concentrations of tolylfluanid (1.10(-4) M(.)L; 1.10(-5) M(.)L) compared to control. Significantly increased numbers of chromatid breaks (7.67 ± 0.58% against 1.67 ± 2.08%, P = 0.009, Anova test, P < 0.05, Tukey test) and chromatid gaps (7.67 ± 1.15% against 2.67 ± 0.58%, P = 0.003, Anova test, P < 0.05, Tukey test) were observed in ovine cultures treated with the highest experimental concentration of tolylfluanid (1.10(-4) M(.)L). Tolylfluanid induced also chromosomal exchanges (P = 0.038, and 0.016 respectively, Anova test, P < 0.05, Tukey test) in ovine cultures treated with the highest experimental concentrations of tolylfluanid (1.10(-4) M(.)L; 1.10(-5) M(.)L). The mitotic index has not shown any statistical differences between the various treatments and control groups. Our results suggest a significant genotoxic effect of tolylfluanid only at the highest concentration in sheep peripheral lymphocytes in vitro.

Chemical fate and biological effects of several endocrine disrupters compounds in two echinoderm species

Two echinoderm species, the sea urchin Paracentrotus lividus and the feather star Antedon mediterranea, were exposed for 28 days to several EDCs: three putative androgenic compounds, triphenyltin (TPT), fenarimol (FEN), methyltestosterone (MET), and two putative antiandrogenic compounds, p,p'-DDE (DDE) and cyproterone acetate (CPA). The exposure nominal concentrations were from 10 to 3000 ng L(-1), depending on the compound. This paper is an attempt to join three different aspects coming from our ecotoxicological tests: (1) the chemical behaviour inside the experimental system; (2) the measured toxicological endpoints; (3) the biochemical responses, to which the measured endpoints may depend. The chemical fate of the different compounds was enquired by a modelling approach throughout the application of the 'Aquarium model'. An estimation of the day-to-day concentration levels in water and biota were obtained together with the amount assumed each day by each animal (uptake in microg animal(-1) d(-1) or ng g-wet weight(-1) d(-1)). The toxicological endpoints investigated deal with the reproductive potential (gonad maturation stage, gonad index and oocyte diameter) and with the regenerative potential (growth and histology). Almost all the compounds exerted some kind of effect at the tested concentrations, however TPT was the most effective in altering both reproductive and regenerative parameters (also at the concentration of few ng L(-1)). The biochemical analyses of testosterone (T) and 17beta-estradiol (E(2)) also showed the ability of the selected compounds to significantly alter endogenous steroid concentrations.

Perturbation of murine liver cyp-superfamily of isoforms by different combinations of pesticide mixtures

It was previously found that fenarimol, vinclozolin or acephate, three of the most used pesticides worldwide, provoked a marked perturbation of murine cytochrome P450 (CYP)-linked monooxygenases. Here, to more closely mimic human exposure, it was investigated whether different pesticide combinations administered i.p. in male Swiss Albino CD1 mice in single or repeated fashion (daily, for three consecutive days), affect CYP-dependent oxidations. The four simulated mixtures showed a complex pattern of CYP induction and suppression, especially after repeated injection. For example, while fenarimol alone was the most inducing agent--reaching a 79-fold increase over control in testosterone 2alpha-hydroxylase--followed by vinclozolin and acephate, coadministration with the former markedly reduced induction. Coadministration with vinclozolin, determined various positive and negative modulations. An increase of CYP2B1/2 and CYP3A1/2-associated oxidases and a decrease of ethoxycoumarin metabolism was observed in the acephate and vinclozolin mixture. An equivalent or reduced CYP expression, if compared to double combinations, was seen using the complete mixture. Taken as a whole, the unpredictability of the recorded effects with simple mixtures, shrinks the misleading extrapolation performed on a single pesticide. If reproduced in human, such changes, altering either endogenous metabolism or biotransformation of ubiquitous toxins, might have public health implications.

Neurodevelopmental effects of perinatal fenarimol exposure on rats

Knowledge about the potential toxic effects of fenarimol, a widely used fungicide, is still limited. Fenarimol is an aromatase inhibitor and therefore can affect estrogen/androgen levels in vivo in rodents. In view of these facts, the aim of the present work was to study the effects of fenarimol maternal exposure during different critical phases in the development of central nervous system in rat pups, on early physical and neurobehavioral endpoints essential to their development. For that, the effects of the fungicide fenarimol (150 and 300 mg/kg) were examined at three different developmental stages in the rat: during the first 6 days of gestation, prenatal (15-21 days), or first 6 days of lactation. Three categories of the impact of fenarimol on neonatal growth and neurobehavioral development of offspring were assessed: (1) physical, (2) reflex and strength, and (3) motor coordination. Findings on the pups' physical development did not indicate any significant alterations of the postnatal age at which specific developmental milestones were observed (pinna detachment, development of the fur, eruption of the incisor teeth, opening of the ears and eyes and testes descent). However, there was a reduced rate of weight gain in pups of mothers treated during lactation related to the earlier testing time periods (1-23 days of life). The study of the functional state of the rat pup nervous systems at different stages of postnatal development revealed some neurodevelopmental delays in righting reflex, climbing and grip response and locomotion (20-90 days of life) in the treated groups. Taken together, findings of this study emphasize that, as a result of fenarimol maternal exposure, some neuromuscular and behavioral deficits in nursing pups may occur principally during the last gestational period and lactation. These results could be the basis for further studies on molecular actions of fenarimol in order to predict better the biological consequences of this fungicide.

Steroid levels in crinoid echinoderms are altered by exposure to model endocrine disruptors

Sexual steroids (testosterone and estradiol) were measured in the whole body of wild specimens of the crinoid Antedon mediterranea collected from the Tyrrhenian Sea (Italy). Testosterone levels (274-1,488 pg/g wet weight (w.w.)) were higher than those of estradiol (60-442 pg/g w.w.) and no significant differences between males and females were observed. No clear seasonal trend was either detected - individuals from February, June and October 2004 analyzed - apart from a peak of estradiol in males in autumn. Nonetheless, dramatic changes on tissue steroid levels were observed when individuals were exposed to model androgenic and anti-androgenic compounds for 2 and 4 weeks. The selected compounds were 17 alpha-methyltestosterone (17 alpha-MT), triphenyltin (TPT), fenarimol (FEN), cyproterone acetate (CPA), and p,p'-DDE. Endogenous testosterone levels were significantly increased after exposure to 17 alpha-MT, TPT and FEN, while different responses were observed for estradiol; 17 alpha-MT and FEN increased endogenous estradiol (up to seven-fold), and TPT lead to a significant decrease. Concerning the anti-androgenic compounds, CPA significantly reduced testosterone in a dose-dependent manner without altering estradiol levels, whereas specimens exposed to p,p'-DDE at a low dose (24 ng/L) for 4 weeks showed a four-fold increase in T levels. Overall, the data show the ability of the selected compounds to alter endogenous steroid concentrations in A. mediterranea, and suggest the existence in this echinoderm species of vertebrate-like mechanisms that can be affected by exposure to androgenic and anti-androgenic chemicals.

Identification of New Human Pregnane X Receptor Ligands among Pesticides Using a Stable Reporter Cell System

Pregnane X receptor (PXR, NR1I2) is activated by various chemically unrelated compounds, including environmental pollutants and drugs. We proceeded here to in vitro screening of 28 pesticides with a new reporter system that detects human pregnane X receptor (hPXR) activators. The cell line was obtained by a two-step stable transfection of cervical cancer HeLa cells. The first transfected cell line, HG5LN, contained an integrated luciferase reporter gene under the control of a GAL4 yeast transcription factor-binding site. The second cell line HGPXR was derived from HG5LN and stably expressed hPXR ligand-binding domain fused to GAL4 DNA-binding domain (DBD). The HG5LN cells were used as a control to detect nonspecific activities. Pesticides from various chemical classes were demonstrated, for the first time, to be hPXR activators: (1) herbicides: pretilachlor, metolachlor, and alachlor chloracetanilides, oxadiazon oxiconazole, and isoproturon urea; (2) fungicides: bupirimate and fenarimol pyrimidines, propiconazole, fenbuconazole, prochloraz conazoles, and imazalil triazole; and (3) insecticides: toxaphene organochlorine, permethrin pyrethroid, fipronil pyrazole, and diflubenzuron urea. Pretilachlor, metolachlor, bupirimate, and oxadiazon had an affinity for hPXR equal to or greater than the positive control rifampicin. Some of the newly identified hPXR activators were also checked for their ability to induce cytochrome P450 3A4 expression in a primary culture of human hepatocytes. HGPXR, with HG5LN as a reference, was grafted onto nude mice to assess compound bioavailability through in vivo quantification of hPXR activation. Altogether, our data indicate that HGPXR cells are an efficient tool for identifying hPXR ligands and establishing pesticides as hPXR activators.

Seasonal variations of DNA-adduct patterns in open field farmers handling pesticides

Seasonal variations of DNA-adduct levels in peripheral blood cells were evaluated in open field farmers (n=26) by use of the 32P-postlabelling assay. Samples were collected before (sample S0) and during (sample S4) the period of intensive pesticide use. A similar sampling procedure was applied to a referent group (n=29). Exposure to pesticides was estimated via a detailed questionnaire. For the group of farmers, an increase in mean adduct level was observed during the season (mean RALS0=3.9+/-3.4 x 10(-10), mean RALS4=13.3+/-15.7 x 10(-10); p=0.008; RAL=relative adduct level). The mean adduct levels were significantly different between farmers and referents only in the S4 samples, with higher levels for farmers (p=0.02). The number of different adducts per individual was higher for farmers at S4 when compared with S0 (p=0.02) and compared with the referents at S4 (p=0.03). However, the increase of the adduct level in farmers did not seem to be attributable to the occurrence of specific new adducts in S4 as compared with S0, but was supposedly due to intensification of pre-existing spots and/or appearance of new unspecific ones. This would be in agreement with indirect genotoxic (epigenetic) effects known for several pesticides, even though a direct mechanism cannot be ruled out definitively. The implication of the pesticides used by the farmers in the modulation of DNA-adduct patterns was explored by analysis of exposure data obtained from the questionnaire.

Prenatal and perinatal fenarimol-induced genotoxicity in leukocytes of in vivo treated rats

The identification of environmental compounds that have adverse effects on reproductive health and animal development is particularly challenging. Fenarimol, a systemic fungicide, is considered non or weakly genotoxic. However, its available toxicological data are controversial and incomplete. This study was conducted in rat in vivo to determine whether this compound (150 and 300 mg/kg) had adverse effects on DNA integrity in dams and pups after maternal subcutaneous exposure. The animals were exposed during early gestation (1-6 days), late gestation (last 6 days), or first 6 days of lactation. Findings on fenarimol genotoxicity showed an adverse effect when detected by the Comet assay, both in dams and pup, and state that animal sensitivity to fenarimol is higher during postnatal period. Since the DNA damage increases during the time of exposure (2 h to 6 days after the birth), our data on pups suggest that fenarimol can mainly act on cell DNA through direct exposure of litter via milk.

Antiandrogenic effects in short-term in vivo studies of the fungicide fenarimol

The fungicide fenarimol has estrogenic and antiandrogenic activity and inhibits aromatase activity in vitro. We tested, whether fenarimol had antiandrogenic effects in vivo. In a Hershberger assay, fenarimol given orally to castrated testosterone-treated male rats caused markedly reduced weights of ventral prostate, seminal vesicles, musc. levator ani/bulbocavernosus, and bulbourethral glands. Qualitatively similar, but weaker, effects were also evident in intact fenarimol-exposed young adult males, except that prostates were not significantly affected. Changes in androgen-regulated gene expression were determined by real-time RT-PCR in ventral prostates and fenarimol caused a pronounced decrease of prostate binding protein C3 (PBP C3), ornithin decarboxylase (ODC), and insulin-like-growth factor 1 (IGF-1) mRNA levels. The antiandogenic drug flutamide, included as a positive control, caused down-regulation of PBP C3 mRNA and up-regulation of TRPM-2 mRNA levels. Serum T4 levels were reduced after fenarimol treatment and a tendency towards increased LH levels was seen. However, no effects on testosterone levels or testosterone production ex vivo could be revealed. Taken together these results indicate that fenarimol acts as an antiandrogen in vivo having effects qualitatively comparable to those of flutamide on organ level, whereas differential effects on gene expression were observed. In an additional Hershberger test, the effects of fenarimol were compared to those of estradiol benzoate, prochloraz and the aromatase inhibitor fadrozole. The data indicate a similar mode of action of fenarimol and prochloraz in the males, whereas no indications were found that the estrogenic or aromatase inhibitory properties had important impact on the effects observed in the males. Thus, it is suggested that fenarimol mediates its antiandrogenic effects at least partly via antagonism of androgen receptors.

Effect of in vitro estrogenic pesticides on human oestrogen receptor α and β mRNA levels

Nine widely distributed pesticides were recently demonstrated to possess potential estrogenic properties in oestrogen receptor (ER) transactivation and/or E-screen assays. We tested the effect of these nine pesticides on the human ERalpha and ERbeta mRNA steady state levels in the mamma cancer fibroblast MCF-7BUS cells using on-line RT-PCR. Like 17beta-oestradiol (E2), fenarimol significantly decreased the ERalpha and increased the ERbeta mRNA level. Endosulfan and pirimicarb alone decreased the ERalpha mRNA level weakly. After co-exposure with E2, all the tested pesticides counteracted the E2-induced decrease of the ERalpha mRNA level, but only significantly for prochloraz, dieldrin, and tolchlofos-methyl. Alone no pesticides affected the ERbeta mRNA level significantly, but chlorpyrifos increased the mRNA level weakly. Co-exposure with E2 elicited a significant increased ERbeta mRNA level by prochloraz, fenarimol, endosulfan, dieldrin, and tolchlofos-methyl, whereas no significant effect of the carbamate pesticides on the ERbeta mRNA level was observed. This study demonstrated that organochlor and organophosphorous pesticides possess the ability to interfere with the ERalpha and ERbeta mRNA steady state levels.

The investigation of the genotoxic effects of fenarimol and propamocarb in mouse bone marrow in vivo

In this study, we aimed to evaluate the genotoxic effects of fungicides fenarimol and propamocarb which are used to protect crops from fungi. For this reason, bone-marrow micronucleus and chromosome aberration tests were carried out in Swiss albino mice. Mice were injected with four different doses of fenarimol and propamocarb intraperitoneally; 50, 100, 200 and 400 mg/kg b.w. Fenarimol did not induce any significant increase in micronucleated erythrocytes after 24, 36, and 48 h treatment but it decreased the ratio of polychromatic/normochromatic erythrocytes at all dose groups and sampling intervals. Fenarimol did not increase the number of chromosome aberrations significantly, but it reduced the mitotic index at the higher doses (P < 0.05). Propamocarb did not increase the frequency of micronucleated erythrocytes, but decreased the polychromatic/normochromatic erythrocytes ratio at all sampling intervals. Propamocarb increased only gaps in total chromosome aberrations, but when gaps were excluded, there were no significant differences in total aberrations between the control and dose groups (P > 0.05). Propamocarb also reduced the mitotic index compared with the negative control group (P < 0.001). Contributing these results, we can suggest that fenarimol and propamocarb are non-genotoxic in mouse bone marrow in vivo but have cytotoxic effects.

Evaluation of the genotoxicity induced by the fungicide fenarimol in mammalian and plant cells by use of the single-cell gel electrophoresis assay

Fenarimol, a systemic pyrimidine carbinol fungicide, is considered to be not genotoxic or weakly genotoxic, although the available toxicological data are controversial and incomplete. Our results obtained in vitro with leukocytes of two different rodent species (rat and mouse) show that fenarimol affects DNA, as detected by the single-cell gel electrophoresis (SCGE, Comet) assay. This fungicide is able to induce DNA damage in a dose-related manner, with significant effectiveness at 36 nM, but without significant interspecies differences. Simultaneous exposure of rat leukocytes to fenarimol (36-290 nM) and a model genotoxic compound (50 microg/ml bleomycin) produced a supra-additive cytotoxic and genotoxic effect. This supports previous findings suggesting possible co-toxic, co-mutagenic, cancer-promoting and co-carcinogenic potential of fenarimol, and modification of the effects of other xenobiotics found to be influenced by this agrotoxic chemical, with consequent different toxicological events. The potential for DNA strand breaks to act as a biomarker of genetic toxicity in plants in vivo was also considered, in view of the fact that higher plants represent reliable sensors in an ecosystem. Significant DNA breakage was observed in the nuclei of Impatiens balsamina leaves after in vivo treatment with fenarimol (145 nM, 1h). More than 50% of the cells showed such DNA damage.

A comparison of the effect of five phenothiazines on hepatic CYP isoenzymes in rats

We examined the influence of five phenothiazine derivatives on the activity and the expression of hepatic cytochrome P450 (CYP) 1A, 2B, 2C6, 2C11, 2E1 and 3A2 in male Sprague-Dawley rats. Twenty mg/kg of phenothiazine, chlorpromazine, and thioridazine, or 1 mg/kg of trifluoperazine and perphenazine was administered intraperitoneally for 4 consecutive days. Phenothiazine increased the total CYP content and induced CYP1A, CYP2B, and CYP3A. Western blot analysis showed marked induction of CYP1A1 by phenothiazine. Chlorpromazine induced CYP2B, and CYP3A without a significant increase in the CYP content. Thioridazine decreased the total CYP content and reduced CYP2C11, CYP2E1, and CYP3A. Neither trifluoperazine nor perphenazine significantly altered the catalytic activity or the protein level of any enzyme examined. These results suggest that the antipsychotic phenothiazine derivatives examined here hardly affect CYP1A at the pharmacological doses, while phenothiazine does induce it. Although a relatively short period and small dose of administration might counteract the influence, trifluoperazine and perphenazine have less effect on CYP subfamilies than chlorpromazine or thioridazine.

Effect of liquorice and glycyrrhizin on rat liver carcinogen metabolizing enzymes

We investigated the effect of single or repeated intake of conspicuous amounts of licorice root extract (LE, 3138 or 6276 mg/kg body weight (bw) per os) or its natural constituent glycyrrhizin (G, 240 or 480 mg/kg bw per os) on Sprague-Dawley rat liver monooxygenases. Whereas a single LE or G dose was unable to affect CYP superfamily, four daily doses induced CYP3A, CYP1A2 and to varying extents CYP2B1-linked monooxygenases. A boosting effect on testosterone 6beta- (CYP3A1/2, CYP1A1/2), 7alpha- (CYP1A1/2, CYP2A1), 16alpha- (CYP2B1, CYP2C11), 2alpha- (CYP2C11) and 2beta- (CYP3A1, CYP1A1) -dependent oxidases as well as on androst-4-ene-3,17-dione- (CYP3A1/2) -supported monooxygenases were also achieved. Harmful outcomes associated to CYP changes (e.g. cotoxicity, cocarcinogenicity and promotion) may be of concern.

Evaluation of rat hepatic 2E1 activity in function of age, sex and inducers: choice of an experimental model capable of testing the hepatotoxicity of low molecular weight compounds

The aim of this work on rat hepatic P450 2E1 activity was to seek the most suitable experimental model to study the role of cytochrome P450 2E1 in the metabolism of industrial chemicals. Two sets of experiments were devoted to selecting the age and sex of animals and to estimating the response of male and female rats to different inducers. In the first set, the effect of three inducers (fasting; ethanol; acetone) was studied in male rats aged 5, 7 and 9 weeks. In the second set, the effect of different inducers, namely beta-naphthoflavone (BNF), phenobarbital (PB), ethanol, acetone and pyridine, on PNP and chlorzoxazone (CLZO) hydroxylase activities was studied in 7 week old male and female rats. The results demonstrate firstly that microsomal p-nitrophenol (PNP) hydroxylase activity significantly decreases in control male rats in inverse function of age, and secondly that induction by ethanol decreases with age. The PNP hydroxylase activity level of controls and the significant increases in PNP hydroxylase activity observed in 7 week old male rats show that this is the most suitable age for the second set of experiments. In this second set, it was shown that P450 1A (induced by BNF) is involved in CLZO hydroxylase activity only. PB increased the hydroxylase activities in male and female rats by about 1.5 and 1.7 times those of the controls, respectively. The effects of P450 2E1 inducers in function of sex show that male rats exhibited more significant increases in PNP and CLZO hydroxylase activities than female. The specificity of these two substrates is discussed. Neither of these two reactions was specifically catalysed by P450 2E1, but PNP may be considered as the most specific and the least sensitive substrate. In addition, the linear relationship observed between the two substrates (PNP and CLZO) showed a good correlation between their activities (r = 0.90, P < 0.001). In conclusion, these results suggest the use of the 7 week old male rat as the experimental model to study the role of cytochrome P450 2E1 in the hepatotoxicity of low molecular weight industrial chemicals.

Multiple cytochrome P-450 subfamilies are co-induced with P-glycoprotein by both phenothiazine and 2-acetylaminofluorene in rats

We studied the effects of two P-glycoprotein (P-gp) inducers, 2-acetylaminofluorene (2-AAF) and phenothiazine (PTZ), administered intraperitoneally, on the activities and content of hepatic cytochrome P-450 (CYP) subfamilies in hepatic microsomes of Sprague-Dawley rats. After 4-day administration of 2-AAF or PTZ, the P-gp content was increased. The total CYP content after PTZ treatment was significantly increased compared with that of controls. The CYP1A, CYP2B and CYP3A2 contents were induced, while the CYP2C6, CYP2C11 and CYP2E1 contents remained unaffected. A marked increase in CYP1A1 was found after administration of each compound. Ethoxyresorufin O-deethylase, pentoxyresorufin O-deethylase, and testosterone 6beta hydroxylation activities showed a significant increase after both 2-AAF and PTZ treatments. In particular, ethoxyresorufin O-deethylase exhibited more than ten times greater activity than that of the controls after the treatments. These results suggest that P-gp inducers affect several CYP subfamilies in addition to CYP3A, which is reported to be up-regulated coordinately with P-gp by a CYP3A inducer.

Carbamazepine induces multiple cytochrome P450 subfamilies in rats

We compared the effect of three different doses (30, 60, and 100 mg/kg) of carbamazepine (CBZ) administered intraperitoneally for 1, 3, and 7 days on the activity and protein content of hepatic cytochrome P450 (CYP) subfamilies in Sprague-Dawley rats. After 3-day- and 7-day administration with CBZ, the total CYP content had increased in a dose-dependent fashion. Among six enzyme activities examined, only aniline hydroxylase activity remained unchanged after 7-day treatment with CBZ. Pentoxyresorufin O-deethylase activity showed the most significant increase and was induced up to 7 days in a time-dependent fashion. Pretreatment of rats with cycloheximide significantly suppressed the pentoxyresorufin O-deethylase induction by one dose of 100 mg/day CBZ. Immunoblot analysis showed a significant correlation between the protein content of each isoenzyme examined and its activity except CYP2E1 after 7-day treatment with CBZ. Similar results were obtained in the mRNA levels of CYP subfamilies. These results suggested that CBZ may induce multiple CYP subfamilies, except CYP2E1, and the activity and the protein content of CYP2B showed the greatest increase with increased CYP2B mRNA.

Induction of hepatic CYP2B in foetal and neonatal rats after maternal administration of phenobarbital

We examined hepatic cytochrome P450 (CYP) induction in rat foetuses and neonates by phenobarbital administered through placenta or breast feeding. In an intraperitoneal study, phenobarbital was administered intraperitoneally to mother rats once a day for 7 consecutive days before delivery. The livers were removed from foetuses, neonates, and mothers just before and 5 and 10 days after delivery. In oral administration study, water containing phenobarbital was given orally ad libitum from day 13 of pregnancy to 3 weeks after delivery (end of lactation). The livers were removed from neonates and mothers just before and one week after delactation. Phenobarbital administered intraperitoneally increased both the activity and the protein expression of CYP2B in 5-day-old neonates, even though the administration ended before delivery. This increase had disappeared in 10-day-old neonates. In mother rats, phenobarbital increased CYP2B just before and 5 days after delivery, while no increase was detected 10 days after delivery. Phenobarbital administered orally also increased both the activity and the protein expression of CYP2B of neonates and mothers during lactation and this increase also disappeared 1 week after delactation. Neither activity nor protein expression of CYP3A were induced in perinates at any age examined in either administration route. In mother rats, increase in CYP3A was found only just before delivery in the peritoneal administration study. Our results suggest that phenobarbital administered through placenta or breast milk transiently induces hepatic CYP2B in newborn rats but that the influence of phenobarbital does not last long.

Effect of licorice and glycyrrhizin on murine liver CYP-dependent monooxygenases

This study is aimed to investigate the effect of the prolonged intake of conspicuous amounts of licorice (LE), or its natural constituent glycyrrhizin (G) on murine liver CYP-catalyzed drug metabolism. For this purpose the modulation of the regio- and stereo-selective hydroxylation of testosterone, together with the use of highly specific substrates as probes for different CYP isoforms such as ethoxyresorufin (CYP1A1), methoxyresorufin (1A2), pentoxyresorufin (2B1), p-nitrophenol (2E1) and aminopyrine (3A), were investigated. Daily doses of licorice root extract (3,138 or 6,276 mg/kg b.w. per os), or G (240 or 480 mg/kg b.w. per os), were administered to different groups of Swiss Albino CD1 mice of both sexes for 1, 4 or 10 consecutive days. While a single LE or G dose was unable to affect the multienzymatic CYP-system, using both schedules of repeated treatment, either LE or G were able to significantly induce hepatic CYP3A- and, to a lesser extent, 2B1- and 1A2-dependent microsomal monooxygenase activities, as well as 6beta- (mainly associated to CYP3A), 2alpha-, 6alpha- (CYP2A1, 2B1), 7alpha-, 16alpha- (CYP2B9) and 16beta-testosterone hydroxylase (TH) activities in male and female mice. Data on CYP3A modulation, the major isoform present in human liver, was confirmed by using Western immunoblotting with anti-CYP3A1/2 rabbit polyclonal antibodies raised against purified rat CYP3A. Northern blotting analysis using CYP3A cDNA biotinylated probe showed that the expression of such isozyme is regulated at the mRNA level. These results suggest that the induction of cytochrome P450-dependent activities by the prolonged intake of high LE or G doses, may result in accelerated metabolism of coadministered drugs with important implications for their disposition. The adverse effects associated with CYP changes such as toxicity/cotoxicity and comutagenicity may also have clinical consequences.

Liver damage induced by bile duct ligation affects CYP isoenzymes differently in rats

We examined the influence of liver damage induced by bile duct ligation on the activity and the expression of hepatic cytochrome P450 (CYP) 1A, 2B, 2C6, 2C11, 2E1 and 3A2 in male Sprague-Dawley rats. In the ligation group, testosterone 2 alpha-, 16 alpha-, and 6 beta-hydroxylase activities were severely decreased, whereas ethoxyresorufin O-deethylase and progesterone 21-hydroxylase activities relatively remained. Pentoxyresorufin O-deethylase and chlorzoxazone 6-hydroxylase activities were reduced to approximately one thirds those of control. The protein contents of these isoenzymes expressed in hepatic microsomes of the ligation group were decreased to 45%, 32%, 79%, 13%, 58%, and 23% of control for CYP1A, 2B, 2C6, 2C11, 2E1 and 3A2, respectively. The rank order of magnitude of the influence of bile duct ligation on CYP isoenzymes, assessed by the reduction in the enzyme activity and the protein content, corresponded with each other except CYP1A. The reduction of the enzyme activities significantly correlated with the reduction in the protein contents of different isoenzymes. These results suggested that bile duct ligation affected CYP isoenzyme activities and contents with different extent.

Cytotoxic activity and transformation of BALB/c 3T3 cells in vitro by the insecticide acephate

Cytotoxic and cell transforming activity of the organophosphate insecticide acephate have been studied in an in vitro experimental model which foresees the exposure of BALB/c 3T3 cells to the chemical. The assay was performed in the presence or absence of metabolic activation system derived from phenobarbital and beta-naphthoflavone induced rats (S9-mix). Cytotoxicity of acephate was unaffected by the presence of the metabolizing fraction. Cell-transforming potential, evidenced through the induction of transformation foci, was observed at all tested doses (i.e. 100, 200 and 400 micrograms/ml) with or without exogenous bioactivation. This activity was related with cell proliferation since it was particularly evident in a level-II cell-transformation assay when the cells were allowed to perform active proliferative activity. These findings, obtained in a medium-term (6-8 weeks) test, may contribute to a better understanding of the action of acephate in the multistep carcinogenesis, proving more information on the oncogenic risk to humans.