Thelephoric acid is an antioxidant produced by the hydrolysis of polyozellin, which is isolated from Polyozellus multiplex. In the present study, the inhibitory effects of polyozellin and thelephoric acid on 9 cytochrome P450 (CYP) family members (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) were examined in pooled human liver microsomes (HLMs) using a cocktail probe assay. Polyozellin exhibited weak inhibitory effects on the activities of all 9 CYPs examined, whereas thelephoric acid exhibited dose- and time-dependent inhibition of all 9 CYP isoforms (IC50 values, 3.2-33.7 muM). Dixon plots of CYP inhibition indicated that thelephoric acid was a competitive inhibitor of CYP1A2 and CYP3A4. In contrast, thelephoric acid was a noncompetitive inhibitor of CYP2D6. Our findings indicate that thelephoric acid may be a novel, non-specific CYP inhibitor, suggesting that it could replace SKF-525A in inhibitory studies designed to investigate the effects of CYP enzymes on the metabolism of given compounds.
Cytochrome P-450 CYP1A2 ; Cytochrome P-450 CYP2D6 ; Cytochrome P-450 CYP2E1 ; Cytochrome P-450 Enzyme System* ; Humans ; Hydrolysis ; Metabolism ; Microsomes, Liver ; Proadifen* ; Protein Isoforms

Gukang Capsules are often used in combination with drugs to treat fractures, osteoarthritis, and osteoporosis. Cytochrome P450(CYP450) mainly exists in the liver and participates in the oxidative metabolism of a variety of endogenous and exogenous substances and serves as an important cause of drug-metabolic interactions and adverse reactions. Therefore, it is of great significance to study the effect of Gukang Capsules on the activity and expression of CYP450 for increasing its clinical rational medication and improving the safety of drug combination. In this study, the Cocktail probe method was used to detect the changes in the activities of CYP1A2, CYP3A2, CYP2C11, CYP2C19, CYP2D4, and CYP2E1 in rat liver after treatment with high-, medium-and low-dose Gukang Capsules. The rat liver microsomes were extracted by the calcium chloride method, and protein expression of the above six CYP isoform enzymes was detected by Western blot. The results showed that the low-dose Gukang Capsules could induce CYP3A2 and CYP2D4 in rats, medium-dose Gukang Capsules had no effect on them, and high-dose Gukang Capsules could inhibit them in rats. The high-dose Gukang Capsules did not affect CYP2C11 in rats, but low-and medium-dose Gukang Capsules could induce CYP2C11 in rats. Gukang Capsules could inhibit CYP2C19 in rats and induce CYP1A2 in a dose-independent manner, but did not affect CYP2E1. If Gukang Capsules were co-administered with CYP1A2, CYP2C19, CYP3A2, CYP2C11, and CYP2D4 substrates, the dose should be adjusted to avoid drug interactions.
Rats ; Animals ; Cytochrome P-450 CYP1A2/metabolism* ; Cytochrome P-450 CYP2C19 ; Cytochrome P-450 CYP2E1/pharmacology* ; Rats, Sprague-Dawley ; Cytochrome P-450 Enzyme System/metabolism* ; Microsomes, Liver ; Liver ; Cytochrome P-450 CYP3A/metabolism*

Animals ; Cytochrome P-450 CYP1A2 ; Cytochrome P-450 CYP2C19 ; metabolism ; Cytochrome P-450 Enzyme System ; metabolism ; Cytochromes ; metabolism ; Liver Cirrhosis ; enzymology ; Rats

<p>AIMTo identify the cytochrome P450 (CYP) isoform (s) involved in daidzein mono-hydroxylated metabolites using human liver microsomes.p><p>METHODSKinetic analysis of the rates of formation of mono-hydroxylated metabolites of daidzein, including 7,8,4'-trihydroxyisoflavone (7,8,4'-THI), 7,3',4'-trihydroxyisoflavone (7,3',4'-THI) and 6,7,4'-trihydroxyisoflavone (6,7,4'-THI), was performed using human liver microsomes (HLM) and recombinant enzymes at substrate concentrations ranging from 0.5 to 400 micromol x L(-1). Nine selective inhibitors or substrate probes specific for different CYP isoforms were applied for screening the isoform(s) responsible for mono-hydroxylated metabolism of daidzein.p><p>RESULTSMichaelis-Menten kinetic parameters were best fitted to one-component enzyme kinetic model. The mean Km (micromol x L(-1) ) and V(max) (micromol x g(-1) x min(-1)) values were 27 +/- 10 and 4. 8 +/- 2.1, 54 +/- 22 and 2.3 +/- 1.0, 51 +/- 29 and 2.2 +/- 0.8, for the formation rates of 7,8,4'-THI, 7,3',4'-THI, and 6,7,4'-THI, respectively. Furafylline, the CYP1A2 specific inhibitor, estrogen, and monoclonal antibody raised against human CYP1A2 (MAB-1A2) apparently inhibited the formation of mono-hydroxylated metabolites, The IC50 of Fur for the formation of 7,3',4'-THI, 6,7,4'-THI and 7,8,4'-THI was 1.0, 0.9 and 0. 8 mol x L(-1), respectively. The IC50 of estrogen for the formation of 7,3',4'-THI, 6,7,4'-THI and 7,8,4'-THI were 51, 60 and 64 mol x L(-1) respectively. The IC50 of MAB-1A2 for the formation of the mono-hydroxylated products was 1 mol x L(-1), but neither other selective inhibitor nor substrate probes, including coumarin (CYP2D6), sulphaphenzole ( CYP2C9/10), omeprazole ( CYP2C19), quinidine (CYP2D6), diethyldithiocarbamate (CYP2E1), troleandomycin (CYP3A4) and keteconazole (CYP3A4), did so with human liver microsomes.p><p>CONCLUSIONThe in vitro studies indicated that daidzein mono-hydroxylated products were principally metabolized by CYP1A2 in human.p>
Cytochrome P-450 CYP1A2 ; metabolism ; Cytochrome P-450 CYP1A2 Inhibitors ; Estrogens ; pharmacology ; Humans ; Hydroxylation ; Isoflavones ; metabolism ; Microsomes, Liver ; metabolism ; Theophylline ; analogs & derivatives ; pharmacology

The inhibition activity of 36 flavonoids against CYP1A2 was determined by our previously developed in vitro method. The Comparative Molecular Similarity Indexes Analysis (CoMSJA) approach was used to probe the quantitative relationships between the flavonoids' molecular structural descriptors and their inhibitory activities. A reliable CoMSIA model with the combined electrostatic and hydrophobic fields was derived with the regression coefficient R2 of 0.948 and the cross-validation regression coefficient q2 of 0.630, separately, which is capable of elucidating the quantitative relationship between the 3D structural descriptors of the flavones and their bioactivities. Comparing with flavone, the larger pi-pi conjugated system of alpha-naphthoflavone significantly improved the biologically inhibitory ability. Based on the core structure of the latter, either electropositive substituents or hydrophobic groups at the 6, 3', and 4' ring positions or electronegative counterparts at the 5 ring position, can enhance the inhibitory potency against CYP1 A2 according to the CoMSIA contour maps.
Cytochrome P-450 CYP1A2 ; metabolism ; Cytochrome P-450 CYP1A2 Inhibitors ; Flavonoids ; chemistry ; pharmacology ; Humans ; Microsomes, Liver ; metabolism ; Models, Molecular ; Molecular Structure ; Quantitative Structure-Activity Relationship

CYP1A2 is an important cytochrome P450 enzymes, which is involved in metabolism of many clinical drugs and activation of some precarcinogens. CYP1A2 activity can be influenced by various factors including genetic polymorphism, drugs, food and so on, in which the CYP1A2 genetic polymorphism is the basis of difference on the activity and induction of CYP1A2. Therefore,the genotyping of CYP1A2 plays an important part in individualization of therapy.
Carcinogens ; metabolism ; Cytochrome P-450 CYP1A2 ; genetics ; metabolism ; Genotype ; Humans ; Inactivation, Metabolic ; genetics ; Polymorphism, Genetic ; genetics

P450 1A2 is responsible for the metabolism of clinically important drugs and the metabolic activation of environmental chemicals. Genetic variations of P450 1A2 can influence its ability to perform these functions, and thus, this study aimed to characterize the functional significance of three P450 1A2 allelic variants containing nonsynonymous single nucleotide polymorphisms (P450 1A2*8, R456H; *15, P42R; *16, R377Q). Variants containing these SNPs were constructed and the recombinant enzymes were expressed and purified in Escherichia coli. Only the P42R variant displayed the typical CO-binding spectrum indicating a P450 holoenzyme with an expression level of approximately 170 nmol per liter culture, but no P450 spectra were observed for the two other variants. Western blot analysis revealed that the level of expression for the P42R variant was lower than that of the wild type, however the expression of variants R456H and R377Q was not detected. Enzyme kinetic analyses indicated that the P42R mutation in P450 1A2 resulted in significant changes in catalytic activities. The P42R variant displayed an increased catalytic turnover numbers (k(cat)) in both of methoxyresorufin O-demethylation and phenacetin O-deethylation. In the case of phenacetin O-deethylation analysis, the overall catalytic efficiency (k(cat)/K(m)) increased up to 2.5 fold with a slight increase of its K(m) value. This study indicated that the substitution P42R in the N-terminal proline-rich region of P450 contributed to the improvement of catalytic activity albeit the reduction of P450 structural stability or the decrease of substrate affinity. Characterization of these polymorphisms should be carefully examined in terms of the metabolism of many clinical drugs and environmental chemicals.
Biotransformation ; Blotting, Western ; Cytochrome P-450 CYP1A2* ; Escherichia coli ; Genetic Variation ; Metabolism ; Phenacetin ; Polymorphism, Single Nucleotide

Rotundine (1 micromol L(-1)) was incubated with a panel of rCYP enzymes (1A2, 2C9, 2C19, 2D6 and 3A4) in vitro. The remained parent drug in incubates was quantitatively analyzed by an Agilent LC-MS. CYP2C19, 3A4 and 2D6 were identified to be the isoenzymes involved in the metabolism of rotundine. The individual contributions of CYP2C19, 3A4 and 2D6 to the rotundine metabolism were assessed using the method of total normalized rate to be 31.46%, 60.37% and 8.17%, respectively. The metabolites of rotundine in incubates were screened with ESI-MS at selected ion mode, and were further identified using MS2 spectra and precise molecular mass obtained from an Agilent LC/Q-TOF-MSMS, as well as MS(n) spectra of LC-iTrap-MS(n). The predominant metabolic pathway of rotundine in rCYP incubates was O-demethylation. A total 5 metabolites were identified including 4 isomerides of mono demethylated rotundine and one di-demethylated metabolite. The results also showed that CYP2C19, 2D6 and 3A4 mediated O-demethylation of methoxyl groups at different positions of rotundine. Furthermore, the ESI-MS cleavage patterns of rotundine and its metabolites were explored by using LC/Q-TOF-MSMS and LC/iTrap-MS(n) techniques.
Analgesics, Non-Narcotic ; metabolism ; Aryl Hydrocarbon Hydroxylases ; metabolism ; Berberine Alkaloids ; metabolism ; Chromatography, Liquid ; Cytochrome P-450 CYP1A2 ; metabolism ; Cytochrome P-450 CYP2C19 ; Cytochrome P-450 CYP2C9 ; Cytochrome P-450 CYP2D6 ; metabolism ; Cytochrome P-450 CYP3A ; metabolism ; Cytochrome P-450 Enzyme System ; metabolism ; Dopamine Antagonists ; metabolism ; Humans ; Isoenzymes ; metabolism ; Methylation ; Recombinant Proteins ; metabolism ; Spectrometry, Mass, Electrospray Ionization

<p>OBJECTIVETo observe the effect of ketoconazole on the activity of cytochrome P450 (CYP) 1A2 and 3A4 in hepatic microsomes of healthy adults.p><p>METHODSHuman hepatic microsomes obtained from healthy adults were randomly divided into control group and ketoconazole-treatment groups at different concentrations. After 15 min of culture, the substrates (testosterone for CYP3A4 and phenacetin for CYP1A2) were added and incubated for another 20 min. The metabolites (6-testosterone and acetaminophen) were then measured with high-performance liquid chromatography (HPLC) to assess the activities of CYP3A4 and 1A2.p><p>RESULTSSignificant difference was found between the groups in the quantity of 6-testosterone and the relative activity of CYP3A4 (P<0.05). The IC(50) of ketoconazole for CYP3A4 was 0. 16 mg/L. Both the quantity of 6-testosterone and the relative activity of CYP3A4 were reduced gradually with the increment of ketoconazole concentration. Significant differences were found between the ketoconazole groups and the control group in both the quantity of acetaminophen and the relative activity of CYP1A2 (P<0.05). Ketoconazole at low doses reduced CYP1A2 activity and but increased the activities at high doses (P<0.05).p><p>CONCLUSIONIn the range of maximum clinical blood concentration, ketoconazole can inhibit the activity of CYP3A4, but not that of CYP1A2, in the hepatic microsomes in healthy adults.p>
Adult ; Antifungal Agents ; pharmacology ; Cytochrome P-450 CYP1A2 ; metabolism ; Cytochrome P-450 CYP3A ; metabolism ; Dose-Response Relationship, Drug ; Female ; Humans ; Ketoconazole ; pharmacology ; Male ; Microsomes, Liver ; drug effects ; enzymology

<p>OBJECTIVETo investigate the changes in hepatic functions and activities of CYP1A2 and CYP3A4 in rats after acute exposure to high altitude.p><p>METHODSTwelve healthy male Wistar rats were randomly divided into control group and exposure group for acute exposure to normal and high altitude (4010 m) environment. Blood samples were collected from the vena orbitalis posterior for detection of the hepatic function. Hepatic pathologies of the rats were examined microscopically with HE staining. Liver microsomes were extracted by differential centrifugation to assess the activities of CYP1A2 and 3A4 using P450-GloTM kit.p><p>RESULTSIn rats with acute exposure to high altitude, AST, ALT, and ALP all increased significantly by 48.50%, 47.90%, and 103.02%, respectively, and TP decreased significantly by 17.80% as compared with those in rats maintained in normal altitude environment (P<0.05). Pathological examination of the liver revealed edema of the central vein of the liver and hepatocyte karyopyknosis in rats after acute exposure to high altitude, which also resulted in significantly lowered activities of CYP1A2 and 3A4 in the liver (by 96.56% and 43.53%, respectively).p><p>CONCLUSIONAcute exposure to high altitude can cause obvious liver injuries and lowered activities of CYP1A2 and 3A4 in rats to severely affect drug metabolism in the liver and result in increased concentration, prolonged half-life and reduced clearance of drugs.p>
Altitude ; Animals ; Cytochrome P-450 CYP1A2 ; Cytochrome P-450 CYP3A ; metabolism ; Cytochromes ; metabolism ; Liver ; pathology ; Male ; Microsomes, Liver ; enzymology ; Rats ; Rats, Wistar