Cytochrome P-450 Content Research Articles

Population Pharmacokinetic Analysis of Tacrolimus in Adult Chinese Patients with Myasthenia Gravis: A Prospective Study.

Tacrolimus isa widelyused immunosuppressive agent with narrow therapeutic window. Nowadays, tacrolimushasgainedacceptance as atherapeutic option in myasthenia gravis (MG) treament,however, little is known aboutits pharmacokineticcharacteristicsin MGpopulation. In this study, we aimed to investigate the population pharmacokinetic(PopPK) of tacrolimus in patients with MGand to develop model-informed dosing regimens. Trough concentrations of tacrolimus (267 measurements) and cytochrome P450 (CYP) genotypes were determined in 97 Chinese adults. The non-linear mixed-effects model was used for PopPK modeling. Monte Carlo simulations based on the established model were employed to design dosing regimens. The PopPK model was described using a one-compartment model with first-order absorption and elimination. The mean apparent clearance (CL/F) of tacrolimus was 17.1L/h, with a between-subject variability of 20.1%. Covariate screening of demographic characteristics, blood test results, co-medications, and CYP3A5*3 or CYP3A4*1G polymorphisms showed that the CYP3A5*3 genotype and co-administration of a Wuzhi capsule significantly affected tacrolimus CL/F. For patients with the CYP3A5*3*3 allele, the required tacrolimus dose for 75% of subjects to achieve target trough concentrations of 4.8-15ng/mL was 2mg every 12h (q12h). For patients with the CYP3A5*1*1 allele, the required dose was 2mg tacrolimus q12h with a Wuzhi capsule, and for patients with the CYP3A5*1*3 allele, the required dose was 3mg of tacrolimus q12h or 4mg q24h co-administered with a Wuzhi capsule. This model could be employed to optimize individualized therapies for patients with MG.

The Synergistic Antitumor Effect of Tanshinone IIA Plus Adriamycin on Human Hepatocellular Carcinoma Xenograft in BALB/C Nude Mice and Their Influences on Cytochrome P450 CYP3A4 In Vivo.

Objective Hepatocellular carcinoma is one of the most common diseases that seriously threaten human life and health. In this study, we evaluated the inhibitory effect of tanshinone IIA (Tan IIA) combined with adriamycin (ADM) on human hepatocellular carcinoma and developed a platform to assess the function if Chinese herbal ingredients combined with chemotherapy drugs have synergistic antitumor effects in vivo. Methods Established animal model of human hepatocarcinoma HepG2 cell in nude mice. Mice were divided into model control group, Tan IIA group, ADM group, and Tan IIA + ADM group. The changes from general condition, weight, tumor volume, and inhibition rate were observed. The data were gathered from serum AST level and histopathological changes. The content and activity of cytochrome P450 were determined by spectrophotometric analysis. CYP3A4 protein expression was analyzed by western blotting. The binding model crystal structure of Tan IIA and ADM with pregnane X receptor (PXR) was evaluated by Discovery Studio 2.1. Results A combination of Tan IIA with ADM could improve life quality by relieving ADM toxicity, decreasing tumor volume, declining serum AST level, and improving liner pathological section in tumor-bearing mice. The inhibitory rates of Tan IIA, ADM, and cotreatment were 32.77%, 60.96%, and 73.18%, respectively. The Tan IIA group significantly enhanced the content of cytochrome b5, P450, and erythromycin-N-demethylase activity. CYP3A4 protein expression was enhanced obviously by the Tan IIA + ADM group. Virtual molecular docking showed that both Tan IIA and ADM could be stably docked with the same binding site of PXR but different interactions. Conclusions Tan IIA in combination with ADM could improve the life quality in tumor-bearing mice and enhance the antitumor effect. The Tan IIA group increased the concentration of cytochrome P450 enzymes and activity. Combined Tan IIA with ADM could upregulate the CYP3A4 protein expression and make relevant interaction with protein PXR by virtual docking.

Effects of several organophosphates on hepatic cytochrome P450 activities in rats.

Four commonly used organophosphates (fenitrothion, dichlorvos, chlorpyrifos, and trichlorfon) were orally administered to male Sprague-Dawley rats for five days in order to explore their effects on the activities of liver cytochrome P450 (CYP). In addition, Michaelis-Menten kinetics of the metabolic reactions catalyzed by liver CYPs were analyzed following the addition of these compounds to the assay system to examine their potential inhibitory effects on liver CYPs activities. These reactions included ethoxyresorufin O-deethylation, midazolam 4-hydroxylation, tolbutamide hydroxylation, and bufuralol 1’-hydroxylation for CYP1A, 3A, 2C, and 2D activities, respectively. Total CYP content was also examined after oral administration of each organophosphate. Results revealed that oral giving of fenitrothion inhibited significantly CYP1A and 3A activities while elevated activity of CYP2C. Fenitrothion is a potent inhibitor for CYP1A and 2C with Ki values of 0.42 and 36.1 µM, respectively but had a weak inhibitory effect on CYP2D and 3A with Ki values of 290 and 226 µM, respectively. Chlorpyrifos is a potent inhibitor of CYP1A with Ki 0.24 µM and moderately inhibited CYP2C or 3A with Ki values of 84.8 and 77.7 µM, respectively. On the other hand, dichlorvos and trichlorfon caused extremely low or negligible inhibition of different CYP activities. From these results, it is concluded that both fenitrothion and chlorpyrifos may increase the toxicity of chemicals in environmental living organisms through their potent inhibitory effects on these CYP activities, but dichlorvos and trichlorfon may not.

Topically injected adrenocorticotropic hormone induces mechanical hypersensitivity on a full-thickness cutaneous wound model in rats.

Cutaneous wound pain causes physical and psychological stress for patients with wounds. Previous studies reported that stress induces hyperalgesia and deteriorates wound healing. However, the effect of the stress response such as in hypothalamic-pituitary-adrenal (HPA) axis on local wound area is unclear. We aimed to investigate the effects of a stress response on the mechanical withdrawal threshold in the local wound area and describe the identification of a wound pain exacerbation. We topically injected adrenocorticotropic hormone (ACTH) into the granulation tissue of full-thickness cutaneous wound model rats on the fifth day postwounding and measured the mechanical withdrawal thresholds, cytochrome P450 2Bs levels and concentration of 5,6-epoxyeicosatrienoic acid in wound exudate. We found that ACTH induced mechanical hypersensitivity at 4 and 6hours after injection (P=.004 and .021, respectively), and increased gene expression of cytochrome P450 2B12 expression (P=.046). Concentration of 5,6-EET in the wound exudate was moderately correlated with the mechanical withdrawal threshold (r=-.630). Finally, the mechanical withdrawal threshold in the 5,6-EET group was significantly lower than that in the control group at 2hours after the injection (P=.015). We propose that 5,6-EET is one of the most promising contributors to the wound pain exacerbation. These findings could guide clinical wound and pain management.

Metazachlor: Mode of action analysis for rat liver tumour formation and human relevance

In a 2-year study the herbicide metazachlor (BAS 479H) was shown to significantly increase the incidence of liver tumours in female Wistar rats at a dietary level of 8000 ppm. As metazachlor is not a genotoxic agent, a series of in vivo and in vitro investigative studies were undertaken to elucidate the mode of action (MOA) for metazachlor-induced female rat liver tumour formation. Male and female Wistar rats were given diets containing 0 (control), 200 and 8000 ppm metazachlor for 3, 7, 14 and 28 days. The treatment of male rats with 200 and 8000 ppm metazachlor and female rats with 8000 ppm metazachlor resulted in significant increases in relative liver weight, which was associated with a centrilobular hepatocyte hypertrophy. Hepatocyte replicative DNA synthesis (RDS) was significantly increased in male rats given 8000 ppm metazachlor for 3 and 7 days and in female rats given 200 ppm metazachlor for 7–28 days and 8000 ppm metazachlor for 3–28 days. Significant increases in relative liver weight, centrilobular hepatocyte hypertrophy and hepatocyte RDS were also observed in male and female Wistar rats given and 500 ppm sodium phenobarbital (NaPB) for 3–28 days. The treatment of female Wistar rats with either 8000 ppm metazachlor for 7 days or with 500 ppm NaPB for 3 and 7 days resulted in the nuclear translocation of the hepatic constitutive androstane receptor (CAR). Treatment of male and female Wistar rats with 8000 ppm metazachlor for 14 days resulted in significant increases in hepatic microsomal total cytochrome P450 (CYP) content, CYP2B subfamily-dependent enzyme activities and mRNA levels, together with some increases in CYP3A enzyme activity and mRNA levels. The treatment of male Wistar rat hepatocytes with metazachlor (concentration range 0.5–50 μM) and NaPB (500 μM) for 4 days resulted in increased CYP2B enzyme activities and mRNA levels; with metazachlor and NaPB also producing significant increases in hepatocyte RDS levels. Studies were also performed with hepatocytes from male Sprague-Dawley wild type (WT) rats and CAR knockout (CAR KO) rats. While both treatment with metazachlor and NaPB for 4 days increased CYP2B enzyme activities and mRNA levels in WT rat hepatocytes, only minor effects were observed in CAR KO rat hepatocytes. Treatment with both metazachlor and NaPB only increased RDS in WT but not in CAR KO rat hepatocytes. The treatment of hepatocytes from two male human donors with 0.5–25 μM metazachlor or 500 μM NaPB for 4 days resulted in increases in CYP2B6 and CYP3A4 mRNA levels but had no effect on hepatocyte RDS. EGF as concurrently used positive control demonstrated the expected RDS response in all rat and human hepatocyte cultures. In conclusion, a series of in vivo and in vitro investigative studies have demonstrated that metazachlor is a CAR activator in rat liver, with similar properties to the prototypical CAR activator phenobarbital. A robust MOA for metazachlor-induced female rat liver tumour formation has been established. Based on the lack of effect of metazachlor on RDS in human hepatocytes, it is considered that the MOA for metazachlor-induced rat liver tumour formation is qualitatively not plausible for humans.

Status of insecticide resistance and its biochemical and molecular mechanisms in Anopheles stephensi (Diptera: Culicidae) from Afghanistan

BackgroundInsecticide resistance of Anopheles stephensi, the main malaria vector in eastern Afghanistan, has been reported previously. This study describes the biochemical and molecular mechanisms of resistance to facilitate effective vector control and insecticide resistance management.MethodsMosquito larvae were collected from the provinces of Kunar, Laghman and Nangarhar from 2014 to 2017. The susceptibility of the reared 3–4 days old adults was tested with deltamethrin 0.05%, bendiocarb 0.1%, malathion 5%, permethrin 0.75% and DDT 4%. Cytochrome P450 content and general esterase, glutathione S-transferase (GST) and acetylcholinesterase (AChE) activities were measured in the three field populations and the results were compared with those of the laboratory susceptible An. stephensi Beech strain. Two separate allele-specific PCR assays were used to identify L1014, L1014F and L1014S mutations in the voltage gated sodium channel gene of An. stephensi. Probit analysis, ANOVA and Hardy–Weinberg equilibrium were used to analyse bioassay, biochemical assay and gene frequency data respectively.ResultsThe population of An. stephensi from Kunar was susceptible to bendiocarb, apart from this, all populations were resistant to all the other insecticides tested. The differences between all values for cytochrome P450s, general esterases, GSTs and AChE inhibition rates in the Kunar, Laghman and Nangarhar populations were statistically significant when compared to the Beech strain, excluding GST activities between Kunar and Beech due to the high standard deviation in Kunar. The three different sodium channel alleles [L1014 (wild type), L1014F (kdr west) and L1014S (kdr east)] were all segregated in the Afghan populations. The frequencies of kdr east mutation were 22.9%, 32.7% and 35% in Kunar, Laghman and Nangarhar populations respectively. Kdr west was at the lowest frequency of 4.44%.ConclusionsResistance to different groups of insecticides in the field populations of An. stephensi from Kunar, Laghman and Nangarhar Provinces of Afghanistan is caused by a range of metabolic and site insensitivity mechanisms, including esterases, cytochrome P450s and GSTs combined with AChE and sodium channel target site insensitivity. The intensity and frequency of these mechanisms are increasing in these populations, calling for urgent reorientation of vector control programmes and implementation of insecticide resistance management strategies.

Fluconazole, a Fungal Cytochrome P450 Enzyme Inhibitor: The Potential Role in Augmenting Hepatotoxicity and Hyperinsulinemia Induced by Dexamethasone in Rats

Insulin resistance (IR) is a widespread health problem characterized by failure of cell responses to insulin. IR increases the risk of fungal infections. Long-term administration of dexamethasone is a therapeutic need accompanied IR and fungal infections. Fluconazole is the first-line antifungal therapy that inhibit fungal cytochrome P450 (CYP450) enzyme. It has a hepatotoxic effect and moderate inhibitory effect on multiple CYP450 enzymes that could affect the pharmacokinetics of drugs used to treat insulin resistance such as metformin. This study aims to evaluate the effect of administration of fluconazole on liver function, CYP450 concentration and level of insulin resistance induced by dexamethasone and high fat diet. Insulin resistance in rats was induced by dexamethasone (0.1mg/kg/day s.c) (DEX) for 2 weeks, after eight weeks of high fat diet (HFD) until the end of the experiment. Oral administration of fluconazole (20, 40 mg/kg) (FLU20, 40) was started concomitantly with DEX for 2 weeks. Metformin (400mg/kg) (MET) was used as a reference treatment for IR and administered orally for 2 weeks with DEX and FLU (20, 40). Concomitant administration of FLU either 20mg/kg or 40 mg/kg with DEX showed significant increase in IR, AST and ALT compared by that caused by DEX alone or with MET. FLU showed a significant decrease in serum CYP450 that elevated by DEX. Massive fibrosis was noticed in histological assessments of liver tissues of HFD+DEX+FLU (20, 40) groups. In conclusion administration of FLU in case of IR induced by HFD+DEX resulted in deterioration of liver functions and decrease in the therapeutic efficacy of MET.

Non‐Additive Effects of Changing the Composition of the Cytochrome P450 Ensemble in Human Liver Microsomes: the Focus on CYP2E1 and Alcohol‐Drug Interactions

Recent studies on a large selection of human liver microsomes (HLM) demonstrated the lack of a straight correlation between the composition of human cytochrome P450 ensemble and the profile of drug metabolism. At the same time, there is an emerging recognition of the functional importance of physical interactions between multiple P450 species co‐localized in the microsomal membrane. Due to complex effects of these interactions any change in the content of a particular P450 enzyme may affect drug metabolism in a complex, hard‐to‐predict manner. Of particular practical importance are the functional effects of the changes in the composition of P450 ensemble induced by alcohol consumption. Although the multi‐fold increase in the content of cytochrome P450 2E1 (CYP2E1) in liver observed in both alcoholics and moderate alcohol consumers is well documented, the role of CYP2E1 in the instances of alcohol‐drug interactions is commonly considered insignificant due to a minor role of this enzyme in drug metabolism. However, the involvement of CYP2E1 in alcohol‐drug interactions may stretch far beyond its immediate effects on the metabolism of its substrates.The aim of this study is to probe the effect of increasing concentrations of CYP2E1 in HLM on the metabolism of drug substrates of other P450 species. In a search for a model system suitable for these studies we introduced a method based on incorporation of purified cytochromes P450 into HLM that allows creating the microsomal preparations with altered composition of the P450 ensemble. Incorporation of CYP2E1 into HLM results in an increase in the rate of CYP2E1‐dependent metabolism of chlorzoxazone, which is proportional to the amount of the incorporated enzyme up to its content of 0.3 nmol per mg protein (or ~50% of CYP2E1 in the total P450 content). Studies with a series of substrates of drug‐metabolizing P450 species showed that CYP2E1 incorporation also results in pronounced alterations in the metabolism of substrates of several other P450 enzymes. The most important effect is observed on CYP2C19. The changes in the effective KM and Vmax values with such probe substrates as 7‐etoxy‐4‐cyanocoumarin (CEC, the substrate of CYP2C19 and CYP1A2), 7‐dimethylamino‐4‐trifluoromethylcoumarin (coumarin‐152, the substrate of CYP2B6, CYP2C19 and CYP2C9) and N‐butyl 7‐methoxy‐4‐(aminomethyl)‐coumarin (BMAMC, the substrate of CYP1A2, CYP2C19 and CYP2D6) reveal a substantial decrease in the involvement of CYP2C19 in their metabolism. Furthermore, increase in CYP2E1 content causes an important changes in the function of CYP3A enzymes, which is revealed in a compromised homotropic cooperativity, decreased affinity and increased Vmax observed with 7‐benzyloxyquinoline, a selective substrate of CYP3A4 and CYP3A5. These observations suggest that ethanol‐dependent induction CYP2E1 may be involved in pronounced pharmacokinetic interactions of alcohol with such drug substrates of CYP2C19 and CYP3A enzymes as benzodiazepines (diazepam), tricyclic antidepressants (amitriptylline, imipramine) and anticonvulsants (phenytoin, carbamazepine).Support or Funding InformationThis research was supported by grant R21‐AA024548 from NIH.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Serum Metabolomic Profiling Identifies Key Metabolic Signatures Associated With Pathogenesis of Alcoholic Liver Disease in Humans.

Alcoholic liver disease (ALD) develops in a subset of heavy drinkers (HDs). The goals of our study were to (1) characterize the global serum metabolomic changes in well‐characterized cohorts of controls (Cs), HDs, and those with alcoholic cirrhosis (AC); (2) identify metabolomic signatures as potential diagnostic markers, and (3) determine the trajectory of serum metabolites in response to alcohol abstinence. Serum metabolic profiling was performed in 22 Cs, 147 HDs, and 33 patients with AC using ultraperformance liquid chromatography–tandem mass spectrometry. Hepatic gene expression was conducted in Cs (n = 16) and those with AC (n = 32). We found progressive changes in the quantities of metabolites from heavy drinking to AC. Taurine‐conjugated bile acids (taurocholic acid [TCA], 127‐fold; taurochenodeoxycholic acid [TCDCA], 131‐fold; and tauroursodeoxycholic acid, 56‐fold) showed more striking elevations than glycine‐conjugated forms (glycocholic acid [GCA], 22‐fold; glycochenodeoxycholic acid [GCDCA], 22‐fold; and glycoursodeoxycholic acid [GUDCA], 11‐fold). This was associated with increased liver cytochrome P450, family 7, subfamily B, member 1 and taurine content (more substrates); the latter was due to dysregulation of homocysteine metabolism. Increased levels of GCDCA, TCDCA, GCA, and TCA positively correlated with disease progression from Child‐Pugh A to C and Model for End‐Stage Liver Disease scores, whereas GCDCA, GCA, and GUDCA were better predictors of alcohol abstinence. The levels of glucagon‐like peptide 1 (GLP‐1) and fibroblast growth factor (FGF) 21 but not FGF19 were increased in HDs, and all three were further increased in those with AC. Conclusion: Serum taurine/glycine‐conjugated bile acids could serve as noninvasive markers to predict the severity of AC, whereas GLP‐1 and FGF21 may indicate a progression from heavy drinking to AC.

The Protection of Selenium Against Cadmium-Induced Mitochondrial Damage via the Cytochrome P450 in the Livers of Chicken.

Cadmium (Cd) is a heavy metal in natural environment and has extreme toxicity. Selenium (Se) has protective effect against heavy metal-induced injury or oxidative stress. Cytochrome P450 (CYP450) enzymes are a family of hemoproteins primarily responsible for detoxification functions. In order to investigate whether CYP450 is related to the damage of livers caused by Cd exposure, we chose forty-eight 28-day-old healthy Hailan cocks for four groups: control group, Se group, Cd group, and Se + Cd group. After 90-day treatment, euthanized for experiment. Based on an established subchronic Cd poisoning model in chicken, this experiment was designed to detect mitochondrial structure, malondialdehyde (MDA), glutathione (GSH), DNA and protein crosslink (DPC) and protein carbonyl (PCO) content, the CYP450 and b5 contents, the aminopyrine-N-demethylase (AND), erythromycin N-demethylase (ERND), aniline 4-hydroxylase (AH) and NADPH-cytochrome C reducatase (CR) activities, and mRNA expression level in the livers. The present results indicated that the MDA content, PCO content, and DPC index in Cd group were higher than those observed in other three groups. Most of the mitochondrial structure is incomplete in Cd group. The contents of CYP450 and b5 were decreased in Cd group. The activities of AND, ERND, AH, and CR got reduced after Cd exposure, as observed in CYP450 gene expression. Our results showed that CYP450 system was involved in the entire process of injury and protection. This research provides a comprehensive evaluation of the oxidative stress effects of Cd related to CYP450 in chicken.

Identification of influential proteins in the classical retinoic acid signaling pathway

BackgroundIn the classical pathway of retinoic acid (RA) mediated gene transcription, RA binds to a nuclear hormone receptor dimer composed of retinoic acid receptor (RAR) and retinoid X receptor (RXR), to induce the expression of its downstream target genes. In addition to nuclear receptors, there are other intracellular RA binding proteins such as cellular retinoic acid binding proteins (CRABP1 and CRABP2) and cytochrome P450 (CYP) enzymes, whose contributions to the RA signaling pathway have not been fully understood. The objective of this study was to compare the significance of various RA binding receptors, i.e. CRABP1, CRABP2, CYP and RAR in the RA signaling pathway. In this regard, we developed a mathematical model of the RA pathway, which is one of the few models, if not the only one, that includes all main intracellular RA binding receptors. We then performed a global sensitivity analysis (GSA) to investigate the contribution of the RA receptors to RA-induced mRNA production, when the cells were treated with a wide range of RA levels, from physiological to pharmacological concentrations.ResultsOur results show that CRABP2 and RAR are the most and the least important proteins, respectively, in controlling the model performance at physiological concentrations of RA (1–10 nM). However, at higher concentrations of RA, CYP and RAR are the most sensitive parameters of the system. Furthermore, we found that depending on the concentrations of all RA binding proteins, the rate of metabolism of RA can either change or remain constant following RA therapy. The cellular levels of CRABP1 are more important than that of CRABP2 in controlling RA metabolite formation at pharmacological conditions (RA = 0.1–1 μM). Finally, our results indicate a significant negative correlation between total mRNA production and total RA metabolite formation at pharmacological levels of RA.ConclusionsOur simulations indicate that the significance of the RA binding proteins in the RA pathway of gene expression strongly depends on intracellular concentration of RA. This study not only can explain why various cell types respond to RA therapy differently, but also can potentially help develop pharmacological methods to increase the efficacy of the drug.

Combined toxicity of organophosphate flame retardants and cadmium to Corbicula fluminea in aquatic sediments

Organophosphate flame retardants (OPFRs), as alternatives to polybrominated biphenyl ethers (PBDEs), are frequently detected in various environmental matrices. Owing to urbanization and industrial pollution, co-contamination of OPFRs and heavy metals is ubiquitous in the environment. The toxicity of OPFRs in aqueous phase is a significant concern, but uncertainty still exists regarding the co-toxicity to benthic organisms of OPFRs and metals in sediments. Hence, we explored the physiological response of Corbicula fluminea to OPFRs and Cd in sediments. The results indicated that the antioxidant system in the clams was stimulated in the presence of OPFRs and Cd, and the oxidative stress increased with increasing concentrations of OPFRs. In contrast, the cytochrome P450 (CYP450) content and acetylcholinesterase (AChE) activity were reduced by exposure to both OPFRs and Cd. The cytochrome P450 4 family (CYP4) mRNA expression and OPFR toxicity were lower than those in previously reported experiments conducted in the water phase. Moreover, the expression levels of metallothionein (MT) and AChE mRNA decreased when OPFRs and Cd were present together. The highest integrated biomarker response (IBR) index (IBR = 15.41) was observed in the presence of 45 mg kg−1 Cd + 200 mg kg−1 OPFRs, rather than the 45 mg kg−1 Cd + 400 mg kg−1 OPFRs treatment (IBR = 9.48). In addition, CYP450 and AChE in the digestive glands of C. fluminea exhibited significant correlations with the concentration of the OPFR/Cd mixture (p < 0.01) and could be effective biomarkers for OPFR and Cd co-contamination. The results potentially contribute to more realistic predictions and evaluations of the environmental risks posed by OPFRs in aquatic sediments contaminated with heavy metals, particularly with respect to the risk to benthic organisms.

Allometric scaling of hepatic biotransformation in rainbow trout

Biotransformation may substantially impact the toxicity and accumulation of xenobiotic chemicals in fish. However, this activity can vary substantially within and among species. In this study, liver S9 fractions from rainbow trout (4–400 g) were used to evaluate relationships between fish body mass and the activities of phase I and phase II metabolic enzymes. An analysis of log-transformed data, expressed per gram of liver (g liver−1), showed that total cytochrome P450 (CYP) concentration, UDP-glucuronosyltransferase (UGT) activity, and glutathione S-transferase (GST) activity exhibited small but significant inverse relationships with fish body weight. In contrast, in vitro intrinsic clearance rates (CLIN VITRO,INT) for three polycyclic aromatic hydrocarbons (PAHs) increased with increasing body weight. Weight normalized liver mass also decreased inversely with body weight, suggesting a need to express hepatic metabolism data per gram of body weight (g BW−1) in order to reflect the metabolic capabilities of the whole animal. When the data were recalculated in this manner, negative allometric relationships for CYP concentration, UGT activity, and GST activity became more pronounced, while CLIN VITRO,INT rates for the three PAHs showed no significant differences across fish sizes. Ethoxyresorufin O-deethylase (EROD) activity normalized to tissue weight (g liver−1) or body weight (g BW−1) exhibited a non-monotonic pattern with respect to body weight. The results of this study may have important implications for chemical modeling efforts with fish.

Complex effects of pollution on fish in major rivers in the Czech Republic

Monitoring the contamination level in aquatic environments and assessing the impact on aquatic life occurs throughout the world. In the present study, an approach based on a combination of biomarkers and the distribution of various industrial and municipal pollutants was used to investigate the effect of aquatic environmental contamination on fish. Monitoring was performed in ten rivers in the Czech Republic (Berounka, Dyje, Elbe, Lužnice, Odra, Ohře, Otava, Sázava, Svratka, and Vltava rivers, with one or two locations in each river) at the same sites that were regularly monitored within the Czech National Monitoring Program in 2007–2011. Health status, hepatic ethoxyresorufin-O-deethylase (EROD) activity, total cytochrome P450 content, and the plasma vitellogenin concentration were assessed in wild chub (Squalius cephalus) males caught at the monitored sites. The contamination level was the highest in the Svratka River downstream of Brno. Among all measured persistent organic pollutants (POPs), polychlorinated biphenyls and dichlorodiphenyltrichloroethane and its metabolites were the major contributors of POPs in fish muscle. Elbe, Odra, and Svratka rivers were identified as the most polluted. Fish from these locations showed reduced gonad size, increased vitellogenin concentration in male plasma, EROD, and total cytochrome P450 content. These biomarkers can be used for future environmental monitoring assessments. Overall, this study improves our understanding of the relationship between human activities and pollutant loads and further contributes to the decision to support local watershed managers to protect water quality in this region.

Di (2-ethylhexyl) phthalate (DEHP)-induced hepatotoxicity in quails (Coturnix japonica) via triggering nuclear xenobiotic receptors and modulating cytochrome P450 systems

Di (2-ethylhexyl) phthalate (DEHP) is a widely distributed pollutant that is of great concern due to its negative health effects. However, whether DEHP exposure causes liver toxicity in birds remains unclear. To clarify the potential hepatotoxicity of DEHP, quails were exposed to 0, 250, 500 and 1000 mg/kg BW/day DEHP by gavage treatment for 45 days. The livers of DEHP-exposed quails showed histomorphological changes. DEHP exposure induced a significant increase in cytochrome P450 enzyme system (CYP450s) activity (including aniline-4-hydroxylase (AH), aminopyrine N-demethylase (APND), erythromycin N-demethylase (ERND) and NADPH-cytochrome C reductase (NCR)) and in the contents of total cytochrome P450 (CYP450) and cytochrome b5 (Cyt b5) in quail liver. DEHP exposure also influenced the expression of nuclear xenobiotic receptors (NXRs) and CYP450 isoforms in the liver. The results suggested that DEHP-induced hepatotoxicity in quail liver is associated with activation of the NXRs pathway responses and disruption of CYP450s homeostasis. This study will help to further elucidate DEHP exposure-induced liver toxicity in quails.

The Resveratrol Alleviates the Hepatic Toxicity of CuSO4 in the Rat.

Cu is toxic to humans and other animals. Oxidative stress is an important mechanism involved in Cu toxicity. Resveratrol (RSV) is an antioxidative compound, so could counteract Cu toxicity. The aim of this study was to determine whether RSV protects the liver from the effects of CuSO4. Forty male Sprague-Dawley rats (5weeks old, 110-120g) were divided into four groups (n = 10 per group), a control group and groups treated with CuSO4 at a dose of 200mg/kg body weight (BW), RSV at a dose of 15mg/kg BW, and CuSO4 at a dose of 200mg/kg BW and RSV at a dose of 15mg/kg BW. The treatments were orally administered for 30days. The livers were removed from the rats at the end of the study, and the cytochrome P450, cytochrome b5, Cu, Fe, Zn, glutathione peroxidase, superoxide dismutase, reactive oxygen species, aspartate aminotransferase, and alanine aminotransferase concentrations in the livers were determined. CuSO4 decreased the BW, liver weight, and cytochrome P450, cytochrome b5, Fe, Zn, glutathione peroxidase, and superoxide dismutase concentrations but increased the Cu, aspartate aminotransferase, alanine aminotransferase, and reactive oxygen species concentrations relative to the control group. RSV alleviated the toxic effects of CuSO4 on the liver, indicating that RSV attenuates CuSO4-induced liver injury by decreasing the liver transaminase concentration and oxidative stress, promoting antioxidative activity and cytochrome P450 enzymes, and maintaining balance in the trace element concentrations. The results indicate that RSV could be used to treat CuSO4 toxicity.

Effect of Pre-Soaking on Seedling Establishment and Pretilachlor Tolerance in Four Rice Genotypes

This study aimed to investigate the effects of pre-soaking for 2 h before seeding on rice seedling establishment after 15-day spraying with pretilachlor. The cytochrome P-450 content, glutathione S-transferase (GSTs), and root activity were also determined. Seedlings of four rice cultivars with contrasting tolerance of pretilachlor were compared. Seed pre-treatment by pre-soaking increased the survivability and growth under pretilachlor spray and improved seedling establishment by increasing P-450, GSTs and root activities. Tolerant genotypes, super hybrid rice, responded better to pre-soaking in direct-seeded rice treated with pretilachlor. It is important for establishment in direct-seeded rice with pre-soaking seeds before sowing in improving emergence and seedling. The positive effect of pre-soaking was proved in all four rice genotypes. Seed pre-soaking will be effective in direct-seeded rice culture to protect rice treated with pre-emergence herbicide and control weedy rice.

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.

Comparisons of microsomal cytochrome P450 content and enzymatic activity towards selected model substrates and insecticides in different tissues from the migratory locust (Locusta migratoria)

Cytochrome P450 monooxygenases (P450s) are important enzymes for biotransformations of various endogenous and xenobiotic substances in various organisms. In this study, we examined microsomal P450 protein content and enzymatic activity in four major detoxification tissues dissected from fifth-instar nymphs of the migratory locust (Locusta migratoria). The highest microsomal P450 protein content was found in the gastric caeca (a part of the midgut), followed by the midgut, Malpighian tubules and fat bodies. Microsomal P450s showed the highest aromatic hydroxylation, O-dealkylation and O-dearylation activities towards six of the seven model substrates examined in the fat bodies. Although the gastric caeca showed the highest P450 protein content, the enzymatic activities towards six of the seven model substrates were the lowest in this tissue. Further, the midgut, gastric caeca and fat bodies showed significant metabolic activities towards two pyrethroid insecticides (deltamethrin and fluvalinate), but no significant activities towards the other four insecticides (malathion, chlorpyrifos, carbaryl and methoprene). These results support our conclusions: 1) total P450 protein content alone cannot be reliably used to predict its enzymatic activity, and 2) insect P450 enzymatic activity is both tissue and substrate dependent.

Disease-Drug Interactions in Inflammatory States via Effects on CYP-Mediated Drug Clearance.

The human inflammatory response can result in the alteration of drug clearance through effects on drug-metabolizing enzymes or drug transporters. In this article, clinical examples are reviewed of how diseases with moderate to severe inflammation can decrease cytochrome P450 (CYP)-mediated drug clearance and alter plasma protein binding. Also examined is how albumin, α-1-acid glycoprotein, drug fraction unbound in plasma, CYP content, and oral clearance can change dynamically with time in response to inflammation.