Development of a method to determine cytochrome P450 1A2, 2C9, 2D6 and 3A4 activity sheep hepatic microsomes.

INTRODUCTION: Ex vivo studies of human fetal hepatic drug metabolism are uncommon as it requires access to functional liver tissue and therefore raises practical and ethical concerns. Large animal models provide an alternative opportunity to study changes in cytochrome P450 (CYP) activity in the mother and fetus during pregnancy. We aimed to develop methods to determine the activity of CYP1A2, CYP2C9, CYP2D6 and CYP3A4 in sheep hepatic microsomes. METHODS: We identified optimal conditions to determine the activity of CYP1A2 (using the probe drug phenacetin), CYP2C9 (diclofenac), CYP2D6 (dextromethorphan) and CYP3A4 (midazolam) by varying techniques for microsome extraction, probe drug concentration, incubation time and microsome concentration. The specificity of each probe drug was assessed by determining the rate of metabolism when specific CYP enzyme inhibitors were included in the reaction. RESULTS: The optimum incubation time and probe drug concentration was six hours with 5 µM phenacetin (CYP1A2), four hours with 10 µM diclofenac (CYP2C9), 30 min with 1 µM of midazolam (CYP3A4) and 10 min with 1 µM dextromethorphan (CYP2D6). For both CYP2D6 and CYP3A4 reactions required 20 µg of microsomal protein, whereas for CYP1A2 and CYP2C9, reactions required 40 µg of microsomal protein. Metabolism of phenacetin, dextromethorphan and midazolam was reduced by specific enzyme inhibitors, but the specific CYP2C9 inhibitor sulfaphenazole did not substantially inhibit diclofenac metabolism. DISCUSSION: This study identifies the optimal conditions for determining CYP activity in maternal sheep hepatic microsomes. In doing so, we have developed a standardised protocol for assessment of microsomal activity of CYP3A4, CYP1A2 and CYP2D6, but we were unable to optimise conditions for assessment of CYP2C9. This approach can be applied to investigate the impact of pregnancy complications on maternal and fetal hepatic drug metabolism.

HepG2-1A2 C2 and C7: Lentivirus vector-mediated stable and functional overexpression of cytochrome P450 1A2 in human hepatoblastoma cells.

Novel HepG2 cell clones 1A2 C2 and 1A2 C7 were independently generated by lentiviral transduction to functionally overexpress cytochrome P450 1A2 (CYP1A2). We found similar and stable CYP1A2 transcript and protein levels in both cell clones leading to specific enzyme activities of about 370 pmol paracetamol x min-1 x mg-1 protein analyzed by phenacetin conversion. Both clones showed dramatically increased sensitivity to the hepatotoxic compound aflatoxin B1 (EC50 < 100 nM) when compared to parental HepG2 cells (EC50∼5 µM). Thus, newly established cell lines are an appropriate tool to study metabolism and toxicity of substances depending on conversion by CYP1A2.

Arylacetamide Deacetylase Enzyme: Presence and Interindividual Variability in Human Lungs.

Human arylacetamide deacetylase (AADAC) is a single microsomal serine esterase involved in the hydrolysis of many acetyl-containing drugs. To date, the presence and activity of the AADAC enzyme in human lungs has been scarcely examined. We investigated its gene and protein expression as well as interindividual variations in AADAC activities in a large number of human lungs (n = 25) using phenacetin as a selective substrate. The kinetic parameters K m and V max were determined. Our findings highlighted a high interindividual variability in both AADAC mRNA levels and hydrolysis activities. Furthermore, for the first time we demonstrated the presence of the AADAC protein in various lung samples by means of immunoblot analysis. As a comparison, phenacetin hydrolysis was detected in pooled human liver microsomes. Lung activities were much lower than those found in the liver. However, similar K m values were found, which suggests that this hydrolysis could be due to the same enzyme. Pulmonary phenacetin hydrolysis proved to be positively correlated with AADAC mRNA (*P < 0.05) and protein (*P < 0.05) levels. Moreover, the average values of AADAC activity in smokers was significantly higher than in nonsmoker subjects (*P < 0.05), and this might have an important role in the administration of some drugs. These findings add more information to our knowledge of pulmonary enzymes and could be particularly useful in the design and preclinical development of inhaled drugs. SIGNIFICANCE STATEMENT: This study investigated the presence and activity of the AADAC enzyme in several human lungs. Our results highlight high interindividual variability in both AADAC gene and protein expression as well as in phenacetin hydrolysis activity. These findings add more information to our knowledge of pulmonary enzymes and could be particularly useful in the design and preclinical development of inhaled drugs.

Multivariate approaches for the development of quality control in-situ fiber optics dissolution methods for fixed-dose combination tablets.

The purpose of this research was to develop a fiber optic (FO) dissolution method for quantification of multiple actives in combination pharmaceutical tablets. FO dissolution allows direct API quantification in the vessel, obviating the need for error-prone facets of traditional dissolution methods. However, FO dissolution is potentially challenged by overlapping UV spectra, matrix effects, UV-active excipients, API interactions with excipients and media, and undissolved components attenuating the UV signal. These obstacles might render FO dissolution method development more complex than LC-end dissolution. The case study in this manuscript has the added complexity of a triple combination product (Midol), where acetaminophen, caffeine, and pyrilamine maleate exhibit similar release kinetics, share largely overlapping UV spectra and span an order of magnitude difference in concentration. Single-wavelength quantification required unique features for the actives of interest, which were not available for the formulation of interest without preprocessing. The methods employed for the quantification of actives were a partial least squares multivariate calibration and a peak area calibration, both using prepared mixtures as reference data. The selected combination tablet demonstrated collinear API release; therefore, individual quantification required a design of experiments for mixture design. The advantages of FO dissolution will be discussed in the context of the formulation under investigation. Additionally, some general guidelines will be suggested for the development of other FO methods.

Modulation of Rat Hepatic CYP1A and 2C Activity by Honokiol and Magnolol: Differential Effects on Phenacetin and Diclofenac Pharmacokinetics In Vivo.

Honokiol (2-(4-hydroxy-3-prop-2-enyl-phenyl)-4-prop-2-enyl-phenol) and magnolol (4-Allyl-2-(5-allyl-2-hydroxy-phenyl)phenol) are the major active polyphenol constituents of Magnolia officinalis (Magnoliaceae) bark, which has been widely used in traditional Chinese medicine (Houpu Tang) for the treatment of various diseases, including anxiety, stress, gastrointestinal disorders, infection, and asthma. The aim of this study was to investigate the direct effects of honokiol and magnolol on hepatic CYP1A and 2C-mediated metabolism in vitro using rat liver microsomes and in vivo using the Sprague-Dawley rat model. Honokiol and magnolol inhibited in vitro CYP1A activity (probe substrate: phenacetin) more potently than CYP2C activity (probe substrate: diclofenac): The mean IC50 values of honokiol for the metabolism of phenacetin and diclofenac were 8.59 µM and 44.7 µM, while those of magnolol were 19.0 µM and 47.3 µM, respectively. Notably, the systemic exposure (AUC and Cmax) of phenacetin, but not of diclofenac, was markedly enhanced by the concurrent administration of intravenous honokiol or magnolol. The differential effects of the two phytochemicals on phenacetin and diclofenac in vivo pharmacokinetics could at least be partly attributed to their lower IC50 values for the inhibition of phenacetin metabolism than for diclofenac metabolism. In addition, the systemic exposure, CL, and Vss of honokiol and magnolol tended to be similar between the rat groups receiving phenacetin and diclofenac. These findings improve our understanding of CYP-mediated drug interactions with M. officinalis and its active constituents.

Effect of Gambogenic Acid on Cytochrome P450 1A2, 2B1 and 2E1, and Constitutive Androstane Receptor in Rats.

BACKGROUND AND OBJECTIVES: Gambogenic acid (GNA), which possesses diverse antitumor activities both in vitro and in vivo, is regarded as a potential anticancer compound. Cytochrome P450 (CYP) enzymes play an important role in the metabolism of most xenobiotics; constitutive androstane receptor (CAR), a nuclear receptor that might be activated by xenobiotics and associated with the expression of some CYPs. In this study, we determined the effect of GNA on multiple rat liver CYP isoforms (CYP1A2, 2B1, and 2E1) and CAR as well as the potential of GNA to interact with co-administered drugs. METHODS: Male SD rats were randomly divided into the control, and the low (5 mg/kg)-, medium (25 mg/kg)-, and high- (100 mg/kg) dose GNA groups. After the intragastric administration of GNA for 14 consecutive days, a cocktail method was adopted to evaluate the activities of CYP1A2, 2B1, and 2E1. The liver expression of CYP1A2, 2B1, and 2E1 and CAR was analyzed by Western blotting (WB) and quantitative real-time reverse-transcription polymerase chain reaction (RT-qPCR). RESULTS: The 14-day administration of GNA significantly increased both the mRNA and protein expressions and the activity of CYP2E1. Additionally, the mRNA and protein expressions of CYP1A2 were clearly induced, while only the high GNA dose increased the activity of liver CYP1A2. Moreover, the mRNA expression levels of CYP2B1 and CAR were increased, but their protein levels and the activity parameters of CYP2B1 did not show significant changes. CONCLUSIONS: The obtained results suggest that the CYP1A2 and CYP2E1 enzymes could be induced in rats after treatment with GNA. Therefore, when GNA is administrated with other drugs, potential drug-drug interactions (DDI) mediated by CYP1A2 and CYP2E1 induction should be taken into consideration.

In vivo pharmacokinetic interaction by ethanolic extract of Gymnema sylvestre with CYP2C9 (Tolbutamide), CYP3A4 (Amlodipine) and CYP1A2 (Phenacetin) in rats.

Gymnema sylvestre (GS) is a medicinal herb used for diabetes mellitus (DM). Herbs are gaining popularity as medicines in DM for its safety purpose. The aim of the present study was to evaluate in vivo pharmacokinetic (PK) interaction between allopathic drugs tolbutamide (TOLBU), amlodipine (AMLO), and phenacetin (PHENA) at low (L) and high (H) doses with ethanolic extract (EL) from GS. EL was extracted and subjected to TLC, total triterpenoid content (19.76 ± 0.02 W/W) and sterol content (0.1837 ± 0.0046 W/W) estimation followed by identification of phytoconstituents using HRLC-MS and GC-MS. PK interaction study with CYP2C9, CYP3A4 and CYP1A2 enzymes were assessed using TOLBU, AMLO and PHENA respectively to index cytochrome (CYP) mediated interaction in rats after concomitant administration of EL extract (400 mg/kg) from GS for 7 days. The rats were divided into four groups for each PK study where, group I and II were positive control for low and high dose of test drugs (CYP substrates) while group II and IV were orally administered EL. The PK study result of PHENA indicated that area under the plasma concentration-time curve (AUC0-24) was significantly (P < 0.0001) increased by 1.4 (L) and 1.3-fold (H), plasma concentration (Cmax) was significantly (P < 0.001) increased by 1.6 (L) and 1.4-fold (H). Whereas for TOLBU; clearance rate (CL) was significantly (P < 0.0001) decreased by 2.4 (L) and 2.3-fold (H), Cmax, was significantly (P < 0.001) decreased by 26.5% (L) and 50.4% (H) and AUC0-24 was significantly (P < 0.0001) decreased by 59.8% (L) and 57.5% (H). Thus, EL is seen to be interacting with CYP1A2 by inhibiting its metabolic activity. HRLC-MS and GC-MS helped identify the presence of gymnemic acid (GA), triterpenoids and steroids in EL which could be the reason for PK interaction of CYP1A2 and CYP2C9. Also, in silico structure based site of metabolism study showed Fe accessibility and intrinsic activity for GA-IV, GA-VI, GA-VII and GA-X with CYP2C9. PK parameters of AMLO were not significantly affected by pre-treatment of EL. Thereby our findings indicate that co-administration of GS with drugs that are metabolized by CYP2C9 and CYP1A2 could lead to potential HDI.

Enzyme-inducing effects of berberine on cytochrome P450 1A2 in vitro and in vivo.

AIMS: Berberine (BER) is an important anti-bacterial drug from Chinese herbal medicine and a novel drug candidate for preclinical development in recent years. Here we provide evidence that the effects of berberine on cytochrome P450 (CYP) 1A2 in vitro and in vivo. MAIN METHODS: Real-time polymerase chain reaction and western blotting analysis were employed to evaluate the CYP1A2 mRNA levels and protein expression. The enzyme activity was assessed by the metabolic rate of phenacetin to acetaminophen by LC-MS/MS method. KEY FINDINGS: The results indicated that the CYP1A2 mRNA expression and enzyme activity in HepG2 cells after treated with BER (4.5µg/ml) exhibited a significant induction (16.11-fold and 5.0-fold, respectively), which was consistent with those on rat liver microsomes (4.5-fold and 1.98-fold, respectively) by BER induction (10mg/kg/day, i.p.) ex vivo. Beside, BER induced CYP1A2 activity with increases in AUC0-t and Cmax of acetaminophen and the Ke and t1/2 of phenacetin after oral administration of phenacetin (p<0.05) in vivo. SIGNIFICANCE: This study firstly reported the induction effect of BER on rats CYP1A2 by intraperitoneal route. But, BER didn't show significant induction effect on CYP1A2 by high-dose orally administrating to rats for 6 consecutive days due to the extremely low bioavailability. The potential drug-drug interactions were supposed to happen when the liver exposed to high dose of BER in vivo by changing administration route.

Effects of MicroRNA-34a on the Pharmacokinetics of Cytochrome P450 Probe Drugs in Mice.

MicroRNAs (miRNAs or miRs), including miR-34a, have been shown to regulate nuclear receptor, drug-metabolizing enzyme, and transporter gene expression in various cell model systems. However, to what degree miRNAs affect pharmacokinetics (PK) at the systemic level remains unknown. In addition, miR-34a replacement therapy represents a new cancer treatment strategy, although it is unknown whether miR-34a therapeutic agents could elicit any drug-drug interactions. To address this question, we refined a practical single-mouse PK approach and investigated the effects of a bioengineered miR-34a agent on the PK of several cytochrome P450 probe drugs (midazolam, dextromethorphan, phenacetin, diclofenac, and chlorzoxazone) administered as a cocktail. This approach involves manual serial blood microsampling from a single mouse and requires a sensitive liquid chromatography-tandem mass spectrometry assay, which was able to illustrate the sharp changes in midazolam PK by ketoconazole and pregnenolone 16α-carbonitrile as well as phenacetin PK by α-naphthoflavone and 3-methylcholanthrene. Surprisingly, 3-methylcholanthrene also decreased systemic exposure to midazolam, whereas both pregnenolone 16α-carbonitrile and 3-methylcholanthrene largely reduced the exposure to dextromethorphan, diclofenac, and chlorzoxazone. Finally, the biologic miR-34a agent had no significant effects on the PK of cocktail drugs but caused a marginal (45%-48%) increase in systemic exposure to midazolam, phenacetin, and dextromethorphan in mice. In vitro validation of these data suggested that miR-34a slightly attenuated intrinsic clearance of dextromethorphan. These findings from single-mouse PK and corresponding mouse liver microsome models suggest that miR-34a might have minor or no effects on the PK of coadministered cytochrome P450-metabolized drugs.

Effects of Caffeic Acid and Quercetin on In Vitro Permeability, Metabolism and In Vivo Pharmacokinetics of Melatonin in Rats: Potential for Herb-Drug Interaction.

BACKGROUND AND OBJECTIVES: Melatonin is a popular dietary supplement and also considered as pharmaceutical product for sleep disorders. Caffeic acid and quercetin are widely distributed in leafy vegetables, fruits, tea extract, and both are used as natural antioxidant. There is an immense concern for health researchers to study the herb/food-drug interactions of melatonin. It is mainly metabolized by CYP1A2 in human so that herbs/foods containing cytochrome P450 (CYP) inhibitors can affect pharmacokinetics of melatonin. By considering pharmacokinetic aspects, the present study was undertaken to evaluate the effects of caffeic acid and quercetin on Caco-2 cells permeability, metabolism, CYP1A inhibition in vitro assay systems and a single dose pharmacokinetics of melatonin in vivo rats. METHODS: The effects of caffeic acid and quercetin on melatonin permeability were tested in Caco-2 cells. Metabolic stability and CYP1A activity were investigated in rat liver microsomes (RLMs) using probe substrates (melatonin/phenacetin in vitro). Melatonin and phenacetin were incubated in RLMs with or without caffeic acid and quercetin, and the IC50 values were determined. The pharmacokinetics of melatonin conducted in rats after a single dose (15 mg/kg) pre-treatment with caffeic acid, quercetin and caffeic acid plus quercetin followed by oral dose of melatonin at 5 mg/kg. Analysis of all samples was with LC-MS/MS. RESULTS: Caffeic acid and quercetin did not alter Caco-2 permeability of melatonin in apical to basolateral direction and vice versa. Melatonin was metabolized in rat liver microsomes, which was inhibited by both caffeic acid and quercetin through CYP1A. The concomitant oral administration of melatonin along with 15 mg/kg of caffeic acid or quercetin or caffeic acid plus quercetin significantly (p < 0.05) increased the AUC0-t of melatonin by 30.0, 66.7 and 114.0%, respectively. The apparent oral rat plasma clearance (CL/F) of melatonin also decreased significantly (p < 0.05) by 28.78, 47.87 and 50% in presence of caffeic acid, quercetin and caffeic acid plus quercetin, respectively. CONCLUSION: These findings suggest that caffeic acid and quercetin improved oral exposure of melatonin via CYP1A inhibition pathway.

Prediction of inter-individual variability on the pharmacokinetics of CYP1A2 substrates in non-smoking healthy volunteers.

The activity of CYP1A2, a major drug-metabolizing enzyme, is known to be affected by various environmental factors. Our study aimed to predict inter-individual variability of AUC/Dose of CYP1A2 substrates in non-smoking healthy volunteers using the Monte Carlo simulation. Inter-individual variability in hepatic intrinsic clearance of CYP1A2 substrates (CLint,h,1A2) was estimated using dispersion model based on the inter-individual variability (N = 96) of the AUC of caffeine, a major CYP1A2 substrate. The estimated coefficient of variation (CV) of CLint,h,1A2 was 55%, similar to previously reported CLint,h,2D6 (60%) but larger than CLint,h,3A4 (33%). Then, this estimated CV was validated by predicting the CVs of AUC/Dose of tizanidine and phenacetin, which are mainly metabolized by CYP1A2 and have negligible renal clearance. As a result, reported CVs were successfully predicted within 2.5-97.5 percentile range of predicted values. Moreover, CVs for AUC/Dose of the CYP1A2 substrates theophylline and lidocaine, which are affected by other CYPs and renal clearance, were also successfully predicted. The inter-individual variability of AUC/Dose of CYP1A2 substrates was successfully predicted using 55% CV for CLint,h,1A2, and the results, along with those reported by our group for other CYPs, support the prediction of inter-individual variability of pharmacokinetics in the clinical setting.

Effect of Evodiamine on CYP Enzymes in Rats by a Cocktail Method.

The aim of this study was to assess the influence of evodiamine on the activities of the drug-metabolizing enzymes cytochrome P450 (CYP) 1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 in rats. The activities of CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 were measured using specific probe drugs. After pretreatment for 1 week with evodiamine or physiological saline (control group) by oral administration, probe drugs phenacetin (5.0 mg/kg; CYP1A2 activity), tolbutamide (1.0 mg/kg; CYP2C9 activity), omeprazole (10 mg/kg; CYP2C19 activity), metoprolol (20 mg/kg; CYP2D6 activity) and midazolam (10 mg/kg; CYP3A4 activity) were administered to rats by oral administration. The blood was then collected at different times for ultra-performance liquid chromatography-tandem mass spectrometry analysis. The data showed that evodiamine exhibits an inhibitory effect on CYP1A2, CYP2C9 and CYP2D6 by increasing t(1/2), Cmax and AUC(0-∞), and decreasing CL/F compared with those of the control group. However, no significant changes in CYP2C19 and CYP3A4 activities were observed. In conclusion, the results indicated that evodiamine could inhibit CYP1A2, CYP2C9 and CYP2D6, which may affect the disposition of medicines primarily dependent on these pathways. Our work may be the basis of related herb-drug interactions in the clinic.

THE EFFECT OF METHANOL USED AS VEHICULUM ON SERUM PHENACETIN CONCENTRATION IN THE RAT.

The xenobiotic absorption process is dependent on many factors, related both to the substance and form of its administration. During administration of small amounts of drugs, the effect of vehiculum on drug fate in the body becomes also evident. The intensity of absorption depends on numerous factors not necessarily related to the substance and its formulation, and also on biotransformation and active transport processes. Additional problem is the fact that many medicines are lipophilic compounds and insoluble in the water (e.g. phenacetin). Methanol and its aqueous solutions facilitate administration to the experimental animals, in the dissolved form of a number of medicines practically insoluble in water. Taking into consideration that methanol is particularly for rats, of low toxicity, it is quite frequently applied as vehiculum. The aim of this study was to investigate the potential interactions that may occur during the use of methanol as vehiculum and compare changes when were used solution 1% of carboxymethylcellulose. The study was performed on male Wistar rats. The tests were performed using phenacetin, which is recognized as biomarker of CYP 2E 1 isoform activity. Phenacetin was given per os in a single dose of 100 mg/kg b. w. Various procedures of phenacetin administration were tested, including solubilization in methanol or suspension in 1% water solution of carboxymethylcellulose. The results of this study show that methanol influences the phenacetin bioavailability and kinetics. Comparing the administration of this drug in methanol solutions against 1% of carboxymethylcellulose, it is in the case of phenacetin triple increase in AUC0-4 h. The presence of methanol affects the shape of kinetic curves of phenacetin causing higher their course until 4 hours after administration.

Effects of Ziziphus jujuba fruit extracts on cytochrome P450 (CYP1A2) activity in rats.

Drug-drug interactions have become a serious problem in the clinic, since plant-based medicines are extensively used. The present study investigated the effects of Ziziphus jujuba fruit (ZJ) extract on the pharmacokinetics of phenacetin, a typical substrate of a cytochrome P450 enzyme CYP 1A2, in rats. The rats were pretreated with the water extract (1.0 g · kg(-1)) or the ethanolic extract (3.6 g · kg(-1)) of ZJ for 10 days, and the pharmacokinetics of phenacetin was investigated after intravenous administration. In an in vitro assay, acetaminophen formation in the hepatic microsomes of ZJ-treated rats was investigated to assess CYP1A2 activity. Our results demonstrated that the treatment with the water and ethanolic extracts of ZJ decreased the plasma concentration of phenacetin and increased the plasma concentration of acetaminophen, resulting in a 43.2% and 15.5% reduction in the AUC0-120 of phenacetin, respectively, and a 53.2% and 64.9% increase in the AUC0-120 of acetaminophen, respectively after intravenous administration. The water or ethanolic extract of ZJ significantly increased the clearance of phenacetin and acetaminophen formation in hepatic microsomes. In conclusion, ZJ extracts displayed effects on the pharmacokinetics of phenacetin and increased the CYP1A2 activity in rats. Therefore, precaution on drug-drug interactions should be taken when ZJ is co-administered with drugs metabolized by CYP1A2, which may result in decreased concentrations of these drugs.

Effects of suberoylanilide hydroxamic acid on rat cytochrome P450 enzyme activities.

Vorinostat (suberoylanilide hydroxamic acid, SAHA) is the first approved histone deacetylase (HDAC) inhibitor for the treatment of cutaneous T-cell lymphoma after progressive disease following two systemic therapies. The rats were randomly divided into SAHA groups (low, medium and high dosage) and control group. The SAHA group rats were given 12.3, 24.5, and 49 mg/kg SAHA, respectively, by continuous intragastric administration for 7 days. The influence of SAHA on the activities of CYP450 isoforms CYP2B6, CYP1A2, CYP2C19, CYP2D6 and CYP2C9 were evaluated by cocktail method, they were responsed by the changes of pharmacokinetic parameters of bupropion, phenacetin, tolbutamide, metroprolol and omeprazole. The five probe drugs were given to rats through intragastric administration, and the plasma concentration were determined by UPLC-MS/MS. The result of SAHA group compared to control group, there were statistical pharmacokinetics difference for bupropion, phenacetin, tolbutamide and metroprolol. Continuous intragastric administration for 7 days may induce the activities of CYP2C19 of rats, inhibit CYP1A2 and slightly inhibit CYP2B6 and CYP2D6 of rats. This may give advising for reasonable drug use after co-used with SAHA. The results indicated that drug co-administrated with SAHA may need dose adjustment. Furthermore, continuous intragastric administration of SAHA for 7 days, liver cell damaged, causing liver cell edema, in liver metabolism process.

Effect of Dimethoate on the Activity of Hepatic CYP450 Based on Pharmacokinetics of Probe Drugs.

BACKGROUND: Dimethoate (DM), one of the most widely used systemic organophosphate insecticide, has been reported to exert toxic effects after long-time subchronic exposure. This study aims at investigating the toxic effect of DM on liver after repeated administration of low doses of DM in rats. METHODS: Twenty Sprague-Dawley rats were randomly divided into the control group (n = 10) and the DM group (n = 10). After 2 weeks' exposure to DM at low dosage (5 mg/kg), biochemical parameters of hepatic functions were measured, histology and CYP450 expressed in liver was detected. The activities of CYP1A2, CYP2C11, CYP2D1, and CYP3A2 were evaluated by the Cocktail method. RESULTS: The level of AChE (acetylcholinesterase) was significantly decreased, hepatic functions were damaged and the mRNA level of CYP2D1 was significantly increased in the DM group (p < 0.05). The pharmacokinetics of probe drug revealed AUC(0-t), AUC(0-∞), t1/2 and Cmax of metoprolol was shorten in the DM group (p < 0.05). However, there were no statistical differences in MRT, t1/2, CL and Tmax for phenacetin, tolbutamide and midazolam. CONCLUSIONS: A low dosage of DM could induce the activity of CYP2D1 in liver and increase the metabolism of metoprolol when exposed for 2 weeks.

Investigation of omeprazole and phenacetin first-pass metabolism in humans using a microscale bioreactor and pharmacokinetic models.

A new in vitro microfluidic platform (integrated insert dynamic microfluidic platform, IIDMP) allowing the co-culture of intestinal Caco-2 TC7 cells and of human primary hepatocytes was used to test the absorption and first-pass metabolism of two drugs: phenacetin and omeprazole. The metabolism of these drugs by CYP1A2, CYP2C19 and CYP3A4 was evaluated by the calculation of bioavailabilities and of intrinsic clearances using a pharmacokinetic (PK) model. To demonstrate the usefulness of the device and of the PK model, predictions were compared with in vitro and in vivo results from the literature. Based on the IIDMP experiments, hepatic in vivo clearances of phenacetin and omeprazole in the IIDMP were predicted to be 3.10 ± 0.36 and 1.46 ± 0.25 ml/min/kg body weight, respectively. This appeared lower than the in vivo observed data with values ranging between 11.9-19.6 and 5.8-7.5 ml/min/kg body weight, respectively. Then the calculated hepatic and intestinal clearances led to predicting an oral bioavailability of 0.85 and 0.77 for phenacetin and omeprazole versus 0.92 and 0.78 using separate data from the simple monoculture of Caco-2 TC7 cells and hepatocytes in Petri dishes. When compared with the in vivo data, the results of oral bioavailability were overestimated (0.37 and 0.71, respectively). The feasibility of co-culture in a device allowing the integration of intestinal absorption, intestinal metabolism and hepatic metabolism in a single model was demonstrated. Nevertheless, further experiments with other drugs are needed to extend knowledge of the device to predict oral bioavailability and intestinal first-pass metabolism.

Effects of vitexin on the pharmacokinetics and mRNA expression of CYP isozymes in rats.

In traditional therapy with Chinese medicine, vitexin has several pharmacological properties, including antinociceptive, antispasmodic, antioxidant, antimyeloperoxidase, and α-glucosidase inhibitory activities. Recently, vitexin was shown to protect the heart against ischemia/reperfusion injury in an in vitro model by inhibiting apoptosis. The purpose of this study was to find out whether vitexin influences the effect on rat cytochrome P450 (CYP) enzymes (CYP1A2, CYP2C11, and CYP3A1) by using cocktail probe drugs in vivo; the influence on the levels of CYP mRNA was also studied. A cocktail solution at a dose of 5 mL/kg, which contained phenacetin (10 mg/kg), tolbutamide (1 mg/kg), and midazolam (5 mg/kg), was given as oral administration to rats treated with short or long period of intravenous vitexin via the caudal vein. Blood samples were collected at a series of time points, and the concentrations of probe drugs in plasma were determined by HPLC-mass spectrometry (MS)/MS. The corresponding pharmacokinetic parameters were calculated by the software of DAS 2.0. In addition, real-time reverse transcription-polymerase chain reaction was performed to determine the effects of vitexin on the mRNA expression of CYP1A2, CYP2C11, and CYP3A1 in rat liver. Treatment with short or long period of vitexin had no effects on rat CYP1A2. However, CYP3A1 enzyme activity was inhibited by vitexin in a concentration-dependent and time-dependent manner. Furthermore, CYP2C11 enzyme activity was induced after short period treatment but inhibited after long period of vitexin treatment. The mRNA expression results were in accordance with the pharmacokinetic results. In conclusion, vitexin can either inhibit or induce activities of CYP2C11 and CYP3A1. Therefore, caution is needed when vitexin is co-administered with some CYP2C11 or CYP3A1 substrates in clinic, which may result in treatment failure and herb-drug interactions.

Turpentine oil induced inflammation decreases absorption and increases distribution of phenacetin without altering its elimination process in rats.

Plasma concentrations and pharmacokinetics of phenacetin, a CYP1A2 substrate were determined in normal and experimentally induced inflamed rats by turpentine oil to know the role of inflammation on the pharmacokinetics of phenacetin and formation of its active metabolite (paracetamol) by CYP1A2 in wistar albino rats, weighing about 200-250 g that were randomly divided into two groups consisting six in each group. Rats in group I (control) received phenacetin (150 mg kg(-1), PO) where as group II received phenacetin 12 h after induction of inflammation by turpentine oil (0.4 mL, i.m). Blood samples were collected from retro orbital plexus at pre-determined time intervals prior to and at 0.166, 0.33, 0.67, 1.5, 2, 4, 8 and 12 h post-administration of phenacetin. Plasma was separated and analyzed for phenacetin and its metabolite paracetamol by HPLC assay. Based on plasma concentrations of phenacetin and its metabolite paracetamol, the pharmacokinetic parameters were determined by compartmental methods. C(max) of phenacetin was significantly (p < 0.01) decreased to 19.50 ± 2.74 µg mL(-1) in inflamed conditions compared to 38.13 ± 2.20 µg mL(-1) obtained in normal rats. Except, for significant (p < 0.001) increase in volume of distribution at steady state (V(dss)) from 2.87 ± 0.37 to 8.03 ± 1.26 L kg(-1) and increased the rate of absorption with shorter absorption half-life (t(1/2ka)) for phenacetin in inflammation. None of the pharmacokinetic parameters of either phenacetin or its metabolite paracetamol were affected. It can be concluded that turpentine oil induced inflammation has no role on the activity of CYP1A2 in rats, as the plasma concentrations and pharmacokinetic parameters of paracetamol were found unaltered.

Pharmacokinetic of four probe drugs in adriamycin-induced nephropathy rat.

BACKGROUND AND AIM: Probe drugs have been widely used to assess the activities of various CYP450 (cytochromes P450) isoenzymes in many fields of drug metabolism and pharmacogenetics. The nephrotic syndrome characterized by massive proteinuria and hypoproteinemia, whether that would influence the pharmacokinetics of probe drugs or not is still unclear. The purpose of the study was to investigate the pharmacokinetic of four probe drugs in adriamycin (ADR)-induced nephropathy rat. MATERIALS AND METHODS: The rats were randomly divided into Control-group (n = 10) and ADR-group (n = 10). Nephrotic syndrome was established by weekly injections of ADR for 2 weeks. After dynamic monitoring of 24-h total urinary protein for 4 weeks, we confirmed that nephrotic syndrome had developed. The rats were administered intragastrically with phenacetin, tolbutamide, omeprazole and bupropion (15, 5, 15, and 15 mg/kg, respectively). The blood samples were determined by LC-MS (Liquid Chromatography-Mass Spectrometry) method. RESULTS: The pharmacokinetics parameter of tolbutamide in ADR-group and Control-group were AUC(0-t) 15.371 ± 4.107, 6.901 ± 5.738 (mg/L*h), MRT(0-t) 8.751 ± 0.754, 6.032 ± 0.63 (h), t1/2 3.88 ± 0.423, 3.602 ± 0.693 (h), Tmax 6.2 ± 3.768, 1.95 ± 0.798 (h), CL/F 0.038 ± 0.005, 0.107 ± 0.037 (L/h/kg), V/F 0.212 ± 0.043, 0.567 ± 0.258 (L/kg), Cmax 1.853 ± 0.384, 1.422 ± 1.312 (mg/L). There was statistical difference in AUC, MRT, CL, V and Tmax of tolbutamide between two groups (p < 0.05), but no pharmacokinetics difference for phenacetin, bupropion and omeprazole. CONCLUSIONS: The pharmacokinetics of tolbutamide was changed in ADR-induced nephropathy rat. It is not suitable for tolbutamide to evaluate the activity of CYP450 in nephrotic syndrome.