Aniline Hydroxylase Activity Research Articles

Metabolism of β-naphthoflavone by cytochrome P450 isoforms in three air breathing fish, Channa punctatus, Heteropneustes fossilis and Clarias batrachus

The crucial phase I xenobiotic metabolising enzyme cytochrome P450 (CYP 450) has a variety of isoforms and a wide range of substrate specificities. While the roles of mammalian CYP 450 are well established, those of non-mammalian species are much less defined. These roles are frequently extrapolated from mammalian data and assumed to be similar across vertebrate species. In the present study, three air breathing fish species, Channa punctatus, Heteropneustes fossilis and Clarias batrachus were injected intraperitoneally (IP) with 50 mg/kg β-naphthoflavone (β-NF) and its effects on hepatic CYP 450 system were evaluated. β-NF treatment resulted in significant increase (p<0.01) in CYP 450 content and CYP1A mediated EROD (Ethoxyresorufin O-deethylase) activity in all three treated fish groups compared to control. CYP2B mediated N,N-dimethylaniline demethylase activity and CYP2E1 mediated aniline hydroxylase activity showed no response suggesting insensitivity to β-NF treatment. All three fish species showed an increase in CYP3A4 mediated erythromycin N-demethylase activity, but only H. fossilis displayed a significant difference (p<0.05). Of all the activities investigated, EROD activity mediated by CYP1A responded towards β-NF treatment the best and could serve as a sensitive biomarker to gauge the effects of chemical pollutants in the aquatic environment.

Exogenous toluene gas removal improvement in recombinant rabbit cytochrome P450 2E1 (CYP2E1)-transgenic Ardisia pusilla DC

The cytochrome P450 2E1 (CYP2E1) enzyme encoded by CYP2E1 plays an important role in the metabolism of organic compounds in mammalian liver cells. In this study, the plasmid pCAMBIA2300 harboring the rabbit CYP2E1 was transferred into Agrobacterium tumefaciens; this was then transferred into internodes of Ardisia pusilla. Shoot primordia, whose appearance resembles that of the in vitro protocorm-like body of orchids, regenerated from 121 of 332 internodes that were cultured in selection medium supplemented with 5 mg·L−1 kanamycin. PCR analysis confirmed that 25 of 89 putative transgenic plants (28.0%) stably harbored the CYP2E1 and NPTII genes, and Southern blot analysis revealed the presence of one to three copies of CYP2E1 within the genome of the 25 transgenic plants. The mRNA expression of the transgene was confirmed in 12 of 25 CYP2E1-transgenic plants by Northern blot analysis. Western blot analysis indicated the presence of a 53-kDa recombinant rabbit CYP2E1 protein in the 12 CYP2E1-transgenic A. pusilla plants. The aniline 4-hydroxylase activity of rabbit CYP2E1 in nine CYP2E1-transgenic A. pusilla plants was higher than that in non-transgenic A. pusilla plants. There was a statistically significant increase (5.1–6.1-fold) in the toluene removal ability of the transgenic line CYP2E1-2–2 compared to that observed in wild-type Ardisia plants at different times after exogenous toluene exposure.

The effect of co-administration of berberine, resveratrol, and glibenclamide on xenobiotic metabolizing enzyme activities in diabetic rat liver

It is possible to use plant-derived antioxidant molecules in the form of dietary supplements. However, dietary supplement–drug interaction pattern has not been well defined for most of these products. The aim of this study was to determine the effects of berberine, resveratrol, and glibenclamide on xenobiotic metabolizing enzyme activities in diabetic rats. Streptozotocin was administered to create experimental diabetes. Resveratrol (5 mg/kg) (R), glibenclamide (5 mg/kg) (G), and berberine (10 mg/kg) (B) were administered individually or in combinations in DMSO by intraperitoneal administration route to the diabetic rats. DMSO was also given to non-diabetic control (C) and diabetic control (D) groups. Livers of rats were taken under anesthesia at the end of the treatment period (12 days). Ethoxyresorufin O-deethylase (EROD), pentoxyresorufin O-depentylase (PROD), aniline 4-hydroxylase (A4H), erythromycin N-demethylase (ERND), glutathione S-transferase (GST), catalase (CAT), and glutathione reductase (GR) activities were measured in microsomes and cytosols. In addition, histomorphological studies were also performed in the liver tissues. EROD activity of D+R was significantly higher than C and D+R+B. PROD activity of D+R was significantly higher than C, D, D+R+G, D+R+B, and D+R+B+ G. PROD activity of D+B was significantly higher than C and D+R+B. ERND activity of D+R was significantly higher than D+R+G and D+R+B. GST activity of D+R was significantly higher than D+R+G. CAT activity of D+B was significantly lower than C. It is clear that co-administration of resveratrol, berberine, and glibenclamide modifies some of the important xenobiotic metabolizing enzyme activities. Resveratrol and berberine have the potential to cause dietary supplement–drug interaction.

Effect of Seabuckthorn leaves on Antioxidant and Microsomal Enzymes in poultry birds

In vivo studies on broiler birds were carried out to evaluate effect of aflatoxin and seabuckthorn leaves on microsomal enzyme system, antioxidant enzymes and biochemical parameters i.e. serum triglyceride, total plasma protein, aminopyrine demethylase, aniline hydroxylase, NADPH cytochrome P450 reductase, catalase, LPO, superoxide dismutase, GSH, blood urea nitrogen (BUN) and creatinine levels in poultry. The poultry birds were divided into six groups containing six birds each. Aflatoxin (400 ppb) and seabuckthorn leaves (10000ppm) was administered continuously in poultry feed. Aflatoxin increased serum triglyceride, blood urea nitrogen and creatinine levels where as seabuckthorn leaves supplementation at 10000ppm significantly decreased triglyceride (P<0.05), blood urea nitrogen (P<0.05) and creatinine levels in birds. Toxin decreased liver, kidney and blood superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) activity, whereas, seabuckthorn leaves (SBTL) increased the activity of these enzymes as compared to control group. The level of lipid peroxidation was significantly increased in the toxin exposed group and decreased in case of SBTL. The activity of Aminopyrine demethylase and Aniline hydroxylase increased, while the activity of NADPH cytochrome P450 reductase is decreased in case of toxin group whereas in case of seabuckthorn leaves exposed group showed no significant change in case of aminopyrine demethylase and NADPH cytochrome P450 reductase, however, the activity of Aniline hydroxylase decreased. On the basis of present study, it could be concluded that the seabuckthorn leaves reduced the effect of Aflatoxin which produced oxidative stress by altering the levels of antioxidant enzymes of liver and kidney in adult poultry birds.

Abstract A007: Methyl jasmonate and finasteride synergistically reduce testosterone-induced benign prostatic hyperplasia through regulation of inflammatory and apoptotic processes in rats

Abstract Background: Phytotherapy is becoming a treatment option in management of diseases, including benign prostatic hyperplasia (BPH). We have shown previously that methyl jasmonate (MeJA) ameliorated BPH; however, the underlying mechanism of action remains unknown. This study was designed to investigate in mechanistic terms the protective role of MeJA in BPH. Methods: BPH was induced by daily injections of testosterone propionate (TP) (3 mg/kg) for 28 days. Results: The weight and organo-somatic weight of prostate in BPH rats were 6.8 and 5.1 times higher than castrated-control group, respectively. Inflammatory markers, prostatic myeloperoxidase,and total nitric oxide were significantly increased in BPH group. The activity of aniline hydroxylase (Phase I drug metabolizing enzyme) was significantly increased in BPH rats by 22%. In BPH group, immunohistochemistry revealed strong expression of prostatic inducible nitric oxide synthase, cyclooxygenase-2 and Bcl2, while mild expression of p53 and Bax WAS seen. Serum triglyceride and total cholesterol were significantly increased, while HDL-c was decreased in BPH. Interestingly, MeJA and finasteride (singly or combination) attenuated inflammatory and apoptotic indices in BPH rats. Conclusion: MeJA and finasteride synergistically protect against TP-induced BPH via mechanisms that involve antiinflammation, induction of apoptosis, and inhibition of phase I drug metabolizing enzyme. Citation Format: Oluwatosin A. Adaramoye, Solomon E. Owumi, Olubukola Akanni, Oluwabunmi E. Olapade-Olaopa, Olusoji J. Abiola, Oluyemi Akinloye. Methyl jasmonate and finasteride synergistically reduce testosterone-induced benign prostatic hyperplasia through regulation of inflammatory and apoptotic processes in rats [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A007.

Effects of tebuconazole on cytochrome P450 enzymes, oxidative stress, and endocrine disruption in male rats.

The major objective of the present study was to determine the ability of a triazole fungicide tebuconazole to induce cytochrome P450-dependent monooxygenases, oxidative stress, and endocrine-disrupting activity using male rats treated with tebuconazole at 10, 25, and 50 mg/kg p.o. once daily for 28 days. In liver, tebuconazole dose-dependently increased microsomal contents of cytochrome P450 and cytochrome b5 and the activities of NADPH-cytochrome P450 reductase, 7-ethoxyresorufin O-deethylase, methoxyresorufin O-demethylase, pentoxyresorufin O-dealkylase, 7-ethoxycoumarin O-deethylase, aniline hydroxylase, and erythromycin N-demethylase. In kidney, tebuconazole increased 7-ethoxycoumarin O-deethylase activity without affecting other monooxygenase activities. In marked contrast to liver and kidney, tebuconazole decreased testicular 7-ethoxyresorufin O-deethylase, methoxyresorufin O-demethylase, 7-ethoxycoumarin O-deethylase, aniline hydroxylase, and erythromycin N-demethylase activities. The results of immunoblot analysis of liver microsomes of controls and tebuconazole-treated rats revealed that tebuconazole induced CYP1A1/2, CYP2B1/2, CYP2E1, and CYP3A proteins in liver. Additions of tebuconazole to liver microsomes inhibited microsomal 7-ethoxycoumarin O-deethylase activity in vitro (IC50 = 1.50-1.69 µM). Treatment of rats with tebuconazole decreased glutathione content and increased glutathione S-transferase, superoxide dismutase, catalase, and glutathione peroxidase activities in liver; increased superoxide dismutase activities in kidney and testis; but decreased glutathione S-transferase activity in testis. Treatments with tebuconazole decreased serum testosterone concentration and cauda epididymal sperm count. The present study demonstrates that tebuconazole induces a multiplicity of CYPs and oxidative stress in liver; inhibits testicular P450 and glutathione S-transferase activities; and produces anti-androgenic effects in male rats.

Methyl jasmonate reduces testosterone-induced benign prostatic hyperplasia through regulation of inflammatory and apoptotic processes in rats

BackgroundPhytotherapy is becoming a treatment option in management of diseases including benign prostatic hyperplasia (BPH). We have shown previously that methyl jasmonate (MeJA) ameliorated BPH, however the underlying mechanism of action remains unknown. This study was designed to investigate in mechanistic terms the protective role of MeJA in BPH. MethodsBPH was induced by daily injections of testosterone propionate (TP) (3mg/kg) for 28 days. ResultsThe weight and organo-somatic weight of prostate in BPH rats were 6.8 and 5.1 times higher than castrated-control group, respectively. Inflammatory markers; prostatic myeloperoxidase and total nitric oxide were significantly increased in BPH group. The activity of aniline hydroxylase (Phase I drug metabolizing enzyme) was significantly increased in BPH rats by 22%. In BPH group, immuno-histochemistry revealed strong expression of prostatic inducible nitric oxide synthase, cyclooxygenase-2 and Bcl2, while mild expression of p53 and Bax were seen. Serum triglyceride and total cholesterol were significantly increased, while HDL-c was decreased in BPH. Interestingly, MeJA and finasteride (singly or combination) attenuated inflammatory indices and induced apoptotic parameters in BPH rats. ConclusionMeJA protects against TP-induced BPH via mechanisms that involve anti-inflammation, induction of apoptosis and inhibition of phase I drug metabolizing enzyme.

Betulinic acid protects against N-nitrosodimethylamine-induced redox imbalance in testes of rats

ABSTRACTObjectives: N-nitrosodimethylamine (NDMA) is known to elicit carcinogenic activity in the liver and kidney of animals. There is a dearth of information of its effect in testis. This study evaluated the protective role of betulinic acid (BA) against NDMA-induced redox imbalance in testes of rats.Methodology: Twenty-four male rats were assigned into four groups and treated with normal saline, BA, NDMA and [BA+NDMA]. BA (25 mg/kg) was given for 14 days, while NDMA (5 mg/kg) was given on days 7 and 12.Results: Administration of NDMA significantly increased the weight and relative weight of testes by 51 and 71%, respectively, while treatment with BA attenuated the weight-gain. Furthermore, NDMA decreased the sperm count, motility and live–dead ratio by 57, 36 and 37%, respectively, and increased total sperm abnormality by 56%. However, BA attenuated the changes in the spermiogram of NDMA-treated rats. NDMA significantly decreased the activities of antioxidative enzymes, follicle-stimulating and luteinizing hormones, while testicular levels of thiobarbituric acid reactive substances and total cholesterol were increased. Also, NDMA increased the activities of aniline hydroxylase and aminopyrine-N-demethylase. Supplementation with BA attenuated NDMA-induced alteration in these biochemical indices.Conclusion: BA protects against NDMA-induced redox imbalance via activation of antioxidative pathway.

The effects of fenvalerate on hepatic and cerebral xenobiotic metabolizing enzymes in selenium and/or iodine deficient rats.

Particularly in developing countries, selenium and/or iodine deficiencies are encountered and use of pesticides in agriculture are not well-controlled. Fenvalerate is a pyrethroid insectide used in agriculture and has applications against a wide range of pests. This study was designed to evaluate the effects of fenvalerate on hepatic and cerebral xenobiotic metabolizing enzyme activities in the presence of iodine and/or selenium deficiency on a rat model. Iodine and/or selenium deficiency was induced by feeding three-week-old Wistar rats with a diet containing <0.005 mg selenium kg-1, and/or administering 1% sodium perchlorate in drinking water for 7 weeks. Test groups received fenvalerate (100 mg kg-1 BW IP) for the last 7 days. Hepatic and cerebral microsomal aniline hydroxylase (CYP2E1) and cytosolic glutathione S-transferase (GST) activities were determined. Besides, hepatic NADPH-cytochrome P450 reductase (P450R), ethoxyresorufin O-deethylase (EROD, CYP1A1/1A2) and penthoxyresorufin O-depenthylase (PROD, CYP2B1/2B2), activities were also measured. Fenvalerate had a general inductive effect on the hepatic and cerebral xenobiotic metabolizing enzyme activities. Moreover, enzyme activities were also altered by iodine and/or selenium deficiency, but the effects seemed to be enzyme- and tissue-specific. The inductive effect of fenvalerate, particularly in high dose exposures, may change the metabolism of several xenobiotics, including drugs, as well as endogenous substrates. The effects may vary depending on the selenium and/or iodine status of individual.

Hepatoprotective and antioxidant potential of Asphodeline lutea (L.) Rchb. roots extract in experimental models in vitro/in vivo.

The aim of this study was to investigate the effect of Asphodeline lutea (L.) Rchb. dry root extract (ALE) administered alone and against carbon tetrachloride (CCl4)-induced liver injury in vitro/in vivo. The dried roots of A. lutea were extracted with 70% ethanol and was characterized with HPLC-UV. Hepatoprotective potential was investigated by in vivo/in vitro assays in Wistar rats as well as antioxidant properties. At concentrations ranging from 10 to 200μg/mL of ALE significant cytotoxic effects on isolated hepatocytes were found. ALE showed some toxicity in Wistar rats discerned by increased ALT (Alanine transaminase), ALP (Alkaline phosphatase) activities and MDA (malondialdehyde) quantity, decreased GSH (reduced glutathione) levels without affecting the activity of the antioxidant enzymes (GPx (Gluthatione peroxidase), GR (Glutathione reductase) and GST (Glutathione-S-transferase activity)). The antioxidant and hepatoprotective potential of ALE was also observed in vitro/in vivo against CCl4-induced liver injury, where ALE normalizes all the examined parameters perturbated by CCl4 administration. In addition, ALE preserved the decreased cytochrome P450 level and EMND (Ethylmorphine-N-Demethylase) activity without affecting AH (Aniline 4-Hydroxylase) activity. ALE is rich in anthraquinones, naphthalenes and caffeic acid. The pro-oxidant effects of ALE could be due to naphthalene and anthraquinone bioactivation pathways involving toxic metabolites.

Effect of Acetone on Reactive Oxygen Species to Mice Skin

Acetone is one of the organic solvents that causes skin barrier disruption such as eczema and dermatitis, ichthyosis and xerosis, and ROS (reactive oxygen species) paly a role of skin toxicity. This study is focused on investigating the effect of ROS of applied acetone. Acetone was applied to mice skin (0.25ml/㎠) four times (6h, 12h, 18h, 24h) every day for two or four days. Increased activity of acid phosphatase (ACP) and increased content of lipid peroxide (LPO) in acetone was determined in the applied group for four days(4ACE) compared with the acetone applied group for two days (2ACE). As for the ROS generating enzymes, one of them, xanthine oxidase (XO) showed no differences between control and 2ACE despite the significantly different 4ACE. There were some differences between 2ACE and 4ACE on the activities of cytochrome P450 dependent aniline hydroxylase (CYPdAH), which seemed to be the increased rates of acetone metabolites. There were more decreased rates of the activities of ROS scavenging enzymes, glutathione peroxidase (GPx), catalase (CAT), superoxide dismutae (SOD), glutathione S-transferase (GST), and glutathione (GSH) contents in 4ACE compared with 2ACE. The results indicate that the damaged skin tissue could cause unbalance of the ROS generating system and scavenging system by the frequent exposure of acetone application.

Antidiabetic and antioxidant effects of saponarin from Gypsophila trichotoma on streptozotocin-induced diabetic normotensive and hypertensive rats

BackgroundDiabetes and hypertension are diseases that often coexist, which increases the risk of chronic organ damages and cardiovascular complications. PurposeTo evaluate the effects of saponarin, isolated from Gypsophila trichotoma Wend, on blood pressure, glycemia, body weight, and liver biochemical parameters related to oxidative stress in diabetic normotensive Wistar Kyoto rats (NTR) and spontaneously hypertensive rats (SHR). MethodsDiabetes was induced by administration of streptozotocin (40mg/kg, i.p.). The following biochemical parameters: reduced glutathione (GSH), malondialdehyde (MDA), total cytochrome P450, aniline hydroxylase (AH) activity, as well as the activities of antioxidant enzymes such as glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) were measured in the livers of euthanized rats. ResultsSaponarin exerted slight antihypertensive activity in non-diabetic SHR, judged by 19% (p<0.05) decrease of the initial blood pressure. However, such effect was not observed in streptozotocin-induced diabetic SHR (SHR-D). Streptozotocin-induced diabetes was evidenced by 78% (p<0.05) and by 171% (p<0.05) increase in blood glucose level in NTR and SHR, respectively. In non-diabetic SHR the initial MDA quantity was by 36% (p<0.05) higher and the initial GSH levels were by 28% (p<0.05) lower in comparison to non-diabetic NTR. Significant decrease in the activities of GPx, GR, and GST was measured in the livers of all diabetic rats. Treatment with saponarin ameliorated the above mentioned liver parameters in both diabetic strains, however its effects were less pronounced in the diabetic SHR group. ConclusionTaken together our data indicate that diabetes and hypertension in combination are more difficult to be modulated by saponarin.

Alteration in the expression of cytochrome P450s (CYP1A1, CYP2E1, and CYP3A11) in the liver of mouse induced by microcystin-LR.

Microcystins (MCs) are cyclic heptapeptide toxins and can accumulate in the liver. Cytochrome P450s (CYPs) play an important role in the biotransformation of endogenous substances and xenobiotics in animals. It is unclear if the CYPs are affected by MCs exposure. The objective of this study was to evaluate the effects of microcystin-LR (MCLR) on cytochrome P450 isozymes (CYP1A1, CYP2E1, and CYP3A11) at mRNA level, protein content, and enzyme activity in the liver of mice the received daily, intraperitoneally, 2, 4, and 8 µg/kg body weight of MCLR for seven days. The result showed that MCLR significantly decreased ethoxyresorufin-O-deethylase (EROD) (CYP1A1) and erythromycin N-demthylase (ERND) (CYP3A11) activities and increased aniline hydroxylase (ANH) activity (CYP2E1) in the liver of mice during the period of exposure. Our findings suggest that MCLR exposure may disrupt the function of CYPs in liver, which may be partly attributed to the toxicity of MCLR in mice.

Medicinal Mushroom Cracked-Cap Polypore, Phellinus rimosus (Higher Basidiomycetes) Attenuates Acute Ethanol-Induced Lipid Peroxidation in Mice

Alcohol abuse and alcoholism remain one of the major health issues worldwide, especially in developing countries. The protective effect of Phellinus rimosus against acute alcohol-induced lipid peroxidation in the liver, kidney, and brain as well as its effect against antioxidant enzyme activity such as superoxide (SOD) and catalase (CAT) in the liver was evaluated in mice. Ethyl acetate extract of Ph. Rimosus (50 mg/kg body wt, p.o.) 1 h before each administration of alcohol (3 mL/kg, p.o.; total 2 doses at 24-h intervals) protected against lipid peroxidation in all organs and attenuated the decline of SOD and CAT activity in the liver. The fold increase in lipid peroxidation, including conjugated diene and thiobarbituric acid reactive substance (TBARS) levels, was highest in the liver. There were 2.6- and 1.5- fold increases in TBARS levels in the liver of the alcohol alone- and alcohol+Ph. Rimosus-treated groups, compared with that of the normal group. Activity of SOD and CAT in the liver of alcohol- and alcohol+Ph. Rimosus- treated animals was 9.05±1.38, 18.76±1.71, and 11.26±1.02, 31.58±3.35 IU/mg protein, respectively. Extract at 1 mg/mL inhibited 50.6% activity of aniline hydroxylase (CYP2E1) in liver homogenate. From these results, we concluded that the extract significantly protected against the lipid peroxidation. Protection in the liver may be due to the inhibitory effect on CYP2E1 as well as the direct radical scavenging effect of Ph. Rimosus, which warrants further research.

Hepatic Cytochrome P450 as Biomarkers of Cypermethrin Toxicity in Freshwater Teleost, Channa punctatus (Bloch)

In this study, Channa punctatus was treated with sub-lethal concentration of cypermethrin (6.6 µg/L) for 5, 10 and 15 days and its effect on total CYP 450 and the activity of hepatic CYP450 isoforms measured. Total CYP450 content and CYP1A mediated EROD activity was significantly induced (p<0.05) in all three treated groups compared to control whereas only 15 days treated group showed significant induction in CYP2B mediated N,Ndimethylaniline demethylase activity. CYP2E1 mediated aniline hydroxylase activity showed only a marginal increase while there was inhibition of CYP3A4 mediated erythromycin demethylase activity. Liver somatic index (LSI) also showed a marginal increase in all the treated groups. Results showed differential induction of CYP1A, CYP2B, CYP2E1 and inhibition of CYP3A4 isoform due to cypermethrin treatment in C. punctatus. The study clearly showed CYP1A isoform as the most responsive and important biomarker for monitoring the aquatic pollution.

P.1.g.058 The influence of brain serotonergic system on the expression and activity of cytochrome P450 in the liver

The aldehyde dehydrogenase inhibitor disulfiram (DS) has been used to deter drinking in alcoholics, but it also precipitates pharmacokinetic interactions with coadministered drugs. From previous experiments conducted in vitro, it has been proposed that the ethanol-inducible cytochrome P450 2E1 (CYP2E1) is the major target for inhibition by DS, but the inference from reported drug interactions is that the drug inhibits multiple CYPs. The aim of the present study was to evaluate the inhibition of major constitutive CYPs in rat liver by DS. Thus, the effects of DS on activities mediated by CYPs 2A1/2, 2C11, 2E1, and 3A, which constitute ∼80% of total CYPs in male rat liver, were evaluated. It was found that CYP2E1-mediated aniline 4-hydroxylase activity was weakly inhibited by DS in vitro, but that preincubation of the drug with NADPH-supplemented microsomes to generate metabolites of DS enhanced the extent of inhibition somewhat. In contrast, constitutive testosterone hydroxylases were inhibited effectively at low concentrations of DS (20 μM decreased the activities of all hydroxylation pathways to 40–60% of control), and a preincubation step between DS and NADPH-fortified microsomes enhanced the inhibition of CYP2C11 and 3A2 activities. In vivo studies were undertaken in which a single dose of DS (100 mg/kg, i.p.) was administered to rats; 24 hr later, CYP2E1-mediated aniline 4-hydroxylase activity was decreased to about 50% of the activity in untreated control rats. CYP2E1 apoprotein and mRNA were also decreased to 38% of the respective control, and CYP3A apoprotein and CYP3A2 mRNA responded similarly. In contrast, CYP2C11 apoprotein was decreased to 66% of control after DS administration, and CYP2A1 expression was unchanged. These findings establish that multiple CYPs are targets for inhibition by DS and provide a basis for clinically significant drug interactions involving CYPs other than 2E1. In addition, the in vivo modulation of CYP function by DS administration is not restricted to enzyme inactivation and may also include down-regulatory effects mediated at a pretranslational level.

Effects of Sub Chronic Dermal Exposure of Gasoline Blended with Varying Concentration of Benzene on Hepatic Mixed Function Oxidases in Rats

Interaction of chemicals in a mixture, their biotransformation and adverse impact, if any, on environment and workroom atmosphere needs to be evaluated to identify the nature of potential toxic effects elicited by constituent chemical(s) in a mixture. The nature of chemical interaction(s) through which an individual chemical in a mixture undergoes metabolism and/or biotransformation in the target tissue could be helpful in evaluation of its toxic potential. Gasoline is a unique example of such chemical mixture where interaction of aromatics viz., benzene, toluene, ethyl benzene and xylene (BTEX) traverses through a common metabolic pathway involving cytochrome P-450 dependent mixed function oxidases. Travis et al. [1] has quantitatively evaluated that gasoline vapor has an antagonistic effect on benzene metabolism and its biotransformation products. It was reported that 1000 ppm gasoline vapor had the same inhibitory effect as 500 ppm toluene on the metabolism of 290 ppm benzene, indicating that there may be many confounding factors in gasoline which might affect the metabolism of benzene in turn affecting its toxicity at the molecular level. It has been reported that benzene causes myelotoxicity through its bioactive metabolites. Such biotransformation mechanisms involve cytochrome P-450 dependent Phase-I enzymes and the products are further detoxified through Phase-II enzymes. It was therefore considered pertinent to study the impact of gasoline blended with 1, 3 and 5% benzene concentrations. Female albino rats weighing 200–250 gm were exposed by dermal route to gasoline blended with varying benzene concentrations, @ 2 g/kg body wt., six days a week over a period of 90 days. The activities of hepatic mixed function oxidases, viz., aniline hydroxylase and aminopyrene demethylase as a monitor of Phase-I enzymes and Glutathione-S-Transferase for Phase-II enzyme was estimated along with free glutathione levels. Serum creatine kinase was also estimated to assess the extent of muscular dystrophy. The results of this sub chronic study will be discussed in the context of interaction of gasoline with varying concentration of benzene in experimental animals. Keywords: mixed function oxidases, benzene, toxicology, gasoline

Protective Effects of a Purified Saponin Mixture from Astragalus corniculatus Bieb., in vivo Hepatotoxicity Models

In this study, the in vivo effects of a purified saponin mixture (PSM), obtained from Astragalus corniculatus Bieb., were investigated using two in vivo hepatotoxicity models based on liver damage caused by paracetamol (PC) and carbon tetrachloride (CCl4 ). The effects of PSM were compared with silymarin. Male Wistar rats were challenged orally with 20% CCl4 or PC (2 g/kg) four days after being pre-treated with PSM (100 mg/kg) or silymarin (200 mg/kg). A significant decrease of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase (LDH) activities and glutathione (GSH) levels and an increase of malondialdehyde (MDA) quantity was observed after CCl4 and PC administration alone. PSM pre-treatment decreased serum transaminases and LDH activities and MDA levels and increased the levels of cell protector GSH. Biotransformation phase I enzymes were also assessed in both models. In the CCl4 hepatotoxicity model, pre-treatment with PSM or silymarin resulted in significantly increased activities of ethylmorphine-N-demethylase and aniline 4-hydroxylase activity and cytochrome P450, compared to the CCl4 only group. Neither silymarin nor PSM influenced PC biotransformation. Our results suggest that PSM, obtained from A. corniculatus, Bieb. showed in vivo hepatoprotective and antioxidant activities against CCl4 and PC-induced liver damage comparable to that of silymarin.

Impact of six fruits—banana, guava, mangosteen, pineapple, ripe mango and ripe papaya—on murine hepatic cytochrome P450 activities

The effects of six Thai fruits, namely banana, guava, mangosteen, pineapple, ripe mango and ripe papaya, on cytochrome P450 (P450) activities were investigated. The median inhibitory concentrations (IC(50) ) of each of the fruit juices on CYP1A1, CYP1A2, CYP2E1 and CYP3A11 activities were determined. Pineapple juice showed the strongest inhibitory effect against all the evaluated P450 isozyme activities in mouse hepatic microsomes, followed by mangosteen, guava, ripe mango, ripe papaya and banana. The study was further performed in male ICR mice given pineapple juice intragastrically at doses of 10, 20 and 40 mg kg(-1) per day for 7 or 28 days. In a concentration-dependent fashion, the pineapple juice raised ethoxyresorufin O-deethylase, aniline hydroxylase and erythromycin N-demethylase activities, which are marker enzymatic reactions responsible for CYP1A1, CYP2E1 and CYP3A11, respectively. The effect of pineapple juice on the expression of CYP1A1, CYP2E1 and CYP3A11 mRNAs corresponded to their enzymatic activities. However, the pineapple juice significantly decreased methoxyresorufin O-demethylase activity. These observations supported that the six Thai fruits were a feasible cause of food-drug interaction or adverse drug effects owing to their potential to modify several essential P450 activities. Individuals consuming large quantities of pineapple for long periods of time should be cautioned of these potential adverse effects.

Diverse action of acrylamide on cytochrome P450 and glutathione S-transferase isozyme activities, mRNA levels and protein levels in human hepatocarcinoma cells

Humans are exposed to acrylamide in their diet and cigarette smoke. Acrylamide is metabolized into glycidamide by CYP2E1. However, very few studies regarding the effects of acrylamide on cytochrome P450 and Glutathione S-Transferase (GST) isozymes have been pursued. The aim of this study is to elucidate the effects of acrylamide on cytochrome P450 and GST isozymes in HepG2 cell line. Treatment with 1.25 and 2.5mM acrylamide caused 9.5- and 3.7-fold increases and 4.0- and 3.3-fold increases in CYP1A-associated ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-demethylase (MROD) activities, respectively. These increases were consistent with increases in mRNA and protein levels of these isozymes. Similarly, CYP2E1-associated aniline 4-hydroxylase (ANH) activity, protein levels, and mRNA levels increased 2.1- and 2.6-fold, 2.4- and 3.2-fold, and 1.4- and 1.9-fold following 1.25 and 2.5mM acrylamide treatments, respectively. In addition, GST-mu activity was increased 2.4- and 5.1-fold by acrylamide. Moreover, GST-mu mRNA and protein levels increased twofold as a result of acrylamide treatment. In contrast, GST-pi protein and mRNA levels decreased significantly. In conclusion, human cell exposure to acrylamide causes an increase in the levels of carcinogenicity and toxicity and a disturbance in drug metabolism, possibly due to complex effects on P450 and GST isozymes.