Biomedical subjects

Lian-Sheng Wang

Publications and source records attributed to Lian-Sheng Wang.

18 recordsLinked to original sources

PubMed2006

Sensitive bioassay for the simultaneous determination of pseudoephedrine and cetirizine in human plasma by liquid-chromatography-ion trap spectrometry.

A liquid chromatography-ion trap mass spectrometry coupled with electrospray ionization (HPLC-ESI-ion trap mass spectrometry) method for simultaneous determination of cetirizine and pseudoephedrine in human plasma is presented. Chromatographic separation was performed on a Hypurity C18 column (Thermo Hypersil-Keystone 2.1 mm x 150 mm, 5 microm, USA), The mobile phase was composed of 65% methanol and 35% water (contained 0.1% formic acid, 10 mM ammonium formate), which was run with a flow-rate of 0.2 ml/min at 40 degrees C. Quantitation was achieved by monitoring the product ions at m/z 166-->m/z 148 (pseudoephedrine), m/z 389.9-->m/z 201.1 (cetirizine), m/z 264-->m/z 246 (tramadol, IS). The calibration curve of pseudoephedrine and cetirizine was established with standard solutions. The limit of detection for pseudoephedrine and cetirizine each was 5 ng/ml. This simplified analytical method is sensitive, specific and accurate enough for simultaneous determination of pseudoephedrine and cetirizine in human plasma and is successfully applied to the pharmacokinetic study of pseudoephedrine and cetirizine.

Adult↗

PubMed2006

Arg-gly-asp-mannose-6-phosphate inhibits activation and proliferation of hepatic stellate cells in vitro.

AIM: To investigate the effect of arg-gly-asp-mannose-6 phosphate (RGD-M6P) on the activation and proliferation of primary hepatic stellate cells in vitro. METHODS: Hepatic stellate cells (HSCs) were isolated from rats by in situ collagenase perfusion of liver and 18% Nycodenz gradient centrifugation and cultured on uncoated plastic plates for 24 h with DMEM containing 10% fetal bovine serum (FBS/DMEM) before the culture medium was substituted with 2% FBS/DMEM for another 24 h. Then, HSCs were cultured in 2% FBS/DMEM with transforming growth factor beta1, M6P, RGD, or RGD-M6P, respectively. Cell morphology was observed under inverted microscope, smooth muscle alpha-actin (alpha-SMA) was detected by immunocytochemistry, type III procollagen (PC III) in supernatant was determined by radioimmunoassay, and the proliferation rate of HSCs was assessed by flow cytometry. RESULTS: RGD-M6P significantly inhibited the morphological transformation and the alpha-SMA and PC III expressions of HSCs in vitro and also dramatically prevented the proliferation of HSCs in vitro. Such effects were remarkably different from those of RGD or M6P. CONCLUSION: The new compound, RGD-M6P, which has a dramatic effect on primary cultured HSCs in vitro, can inhibit the transformation of HSCs in culture caused by TGFbeta1, suppresses the expression of PC III and decreases proliferation rate of HSC. RGD-M6P can be applied as a selective drug carrier targeting at HSCs, which may be a new approach to the prevention and treatment of liver fibrosis.

Actins↗

PubMed2006

Relationship between true fasting plasma insulin level and angiographic characteristics of coronary atherosclerosis.

BACKGROUND: Reports about the relationships between specific insulin concentration and coronary heart disease risk are controversial. HYPOTHESIS: The objective of this study was to examine the association between insulin level and the severity of coronary atherosclerosis. METHODS: The study population consisted of 507 consecutive patients (376 men and 131 women) who underwent coronary angiography for suspected or known coronary atherosclerosis. The patients' habits of smoking and drinking were investigated, and anthropometric measurements including body mass index, systolic and diastolic blood pressures, as well as plasma measurements including lipids and blood glucose were taken. The true insulin level was measured using a highly sensitive two-site sandwich ELISA. The severity of coronary atherosclerosis was defined by the Gensini score system. The statistical methods including Kruskal-Wallis test, chi-square analysis, Spearman correlation analysis, and multivariate stepwise linear regression analysis were employed to explore the relationship between specific insulin level and coronary atherosclerosis. RESULTS: When the Gensini score was examined as a categorical variable classified by tertile values, subjects with a high Gensini score had significantly higher values of fasting plasma specific insulin level (p = 0.022). The Spearman correlation analysis suggest that the Gensini score correlated significantly with true insulin (mIU/l) (r = 0.095, p = 0.033). However, the results from the multivariate stepwise linear regression analysis show that the association between specific insulin level and severity of coronary atherosclerosis lost its significance. CONCLUSIONS: The level of plasma fasting specific insulin was associated significantly with the severity of coronary atherosclerosis, as measured by Gensini score, but hyperinsulinemia showed no association with the severity of coronary atherosclerosis in multivariate analyses.

Aged↗

PubMed2006

Prediction of chromatographic relative retention time of polychlorinated biphenyls from the molecular electronegativity distance vector.

Using the molecular electronegativity distance vector (MEDV) descriptors derived directly from the molecular topological structures, the gas chromatographic relative retention times (RRTs) of 209 polychlorinated biphenyls (PCBs) on the SE-54 stationary phase were predicted. A five-variable regression equation with the correlation coefficient of 0.9964 and the root mean square errors of 0.0152 was developed. The descriptors included in the equation represent degree of chlorination (nCl), nonortho index (Ino), and interactions between three pairs of atom types, i.e., atom groups -C= and -C=, -C= and >C=, -C= and -Cl. It has been proved that the retention times of all 209 PCB congeners can be accurately predicted as long as there are more than 50 calibration compounds. In the same way, the MEDV descriptors are also used to develop the five- or six-variable models of RRTs of PCBs on other 18 stationary phases and the correlation coefficients in both modeling stage and LOO cross-validation step are not lower than 0.99 except two models.

Chromatography, Gas↗

PubMed2006

Induction of collateral artery growth and improvement of post-infarct heart function by hepatocyte growth factor gene transfer.

AIM: To study the effect of adenovirus5-mediated human hepatocyte growth factor (Ad(5)-HGF) transfer on post-infarct heart failure in a swine model. METHODS: Twelve young Suzhong swine were randomly divided into 2 groups: the Ad(5)-HGF group (n=6) and the null-Ad(5) group (n=6). Four weeks after left anterior descending coronary artery (LAD) ligation, Ad5-HGF was transferred into the myocardium via the right coronary artery. Coronary angiography and gated cardiac perfusion imaging were performed at the end of 4 and 7 weeks after LAD ligation, respectively, to evaluate collateral artery growth and cardiac perfusion. Then all animals were killed, the expression of HGF and alpha-smooth muscle actin (alpha-SMA) were evaluated by enzyme-linked immunosorbent assay and immunohistochemistry. RESULTS: Compared with the null-Ad(5) group, higher expression of human HGF was observed in the myocardium in the Ad(5)-HGF group (109.3+/-7.8 vs 6.2+/-2.6, t=30.685, P<0.01). The left ventricular ejection fraction was higher in the Ad(5)-HGF group than in the null-Ad(5) group (43.9+/-4.3 vs 30.4+/-2.8, t=6.514, P<0.01). From the 4th week to the 7th week after operation, left ventricular end systolic volume (42.1+/-3.0 vs 31.0+/-4.9, t=12.800, P<0.01) and left ventricular end diastolic volume (62.2+/-4.2 vs 55.0+/-4.8 t=13.207, P<0.01) were improved in the Ad(5)-HGF group. Cardiac perfusion was significantly improved in the Ad(5)-HGF group. In the Ad(5)-HGF group, growth of collateral arteries was obviously greater (average rank sum 9.17 vs 3.83, n=6, u=-2.687, P<0.01), and the number of alpha-SMA(+) vessels/mm(2) was significantly greater (56.1+/-4.2 vs 16.4+/-3.5, t=17.731, P<0.01) than in the null-Ad(5) group. CONCLUSION: High expression levels of human HGF were observed in the myocardium because of non-infarct-related vessel transfer. HGF can increase the number of functional arterioles and improve collateral artery growth. HGF can improve cardiac perfusion and heart function.

Adenoviridae↗

PubMed2005

Determination of sinomenine in human plasma by HPLC/ESI/ion trap mass spectrum.

BACKGROUND: Sinomenine is a pure alkaloid with a variety of pharmacological actions including anti-inflammation, immuno-suppression, analgesia, antihypertension, and antiarrhythmia. Methods have been developed to measure sinomenine in rats and rabbits through high-performance liquid chromatography (HPLC). But only one report described a method for determination of sinomenine in humans. METHOD: We developed a method to quantitate sinomenine in human plasma based on liquid chromatography-ion trap mass spectrometry coupled with electrospray ionization (HPLC/ESI/ion trap mass spectrum). RESULTS: The calibration curve (r2=0.9993) of sinomenine was established with standard solutions. The mean inter-day and intra-day CVs<15%. The limit of detection for sinomenine was 0.5 ng/ml. The relative recovery of high, middle and low concentration was 99%, 103%, and 118%, respectively. CONCLUSION: The method is simple, rapid, sensitive, specific, and accurate enough for determination of sinomenine in human plasma and may be used to investigate the metabolism and pharmacokinetics of sinomenine.

Chromatography, High Pressure Liquid↗

PubMed2005

Ile118Val genetic polymorphism of CYP3A4 and its effects on lipid-lowering efficacy of simvastatin in Chinese hyperlipidemic patients.

OBJECTIVES: To determine the frequencies of CYP3A4 alleles (CYP3A4*4,*5 and *6) in Chinese hyperlipidemic patients and to observe the impact of CYP3A4*4 (Ile118Val) genetic polymorphism on the lipid-lowering effects of simvastatin and on the activity of CYP3A4. METHODS: From hospitalized and non-hospitalized patients, 211 unrelated hyperlipidemic patients were recruited for genotyping. CYP3A4 genotypes were determined by means of polymerase chain reaction and restriction fragment length polymorphism analysis. Of the non-hospitalized hyperlipidemic patients, 8 with CYP3A4*1/*1 and 8 with CYP3A4*1/*4 genotypes were selected to be treated with 20 mg simvastatin daily for 4 weeks. Serum triglycerides (TG), cholesterol (CHO) and low-density lipoprotein (LDL) levels were determined using an automated analyzer (Hitachi 747, Boehringer Mannheim, Mannheim, Germany). CYP3A4 activity was determined by the ratio of 6-hydroxycortisol to free cortisol (6-OHC/FC) in the morning spot urine with a high-throughput liquid chromatography-tandem mass spectrometry method. RESULTS: Of 211 subjects, 14 (allele frequency 3.32%) were heterozygous for CYP3A4*4 (Ile118Val). Nevertheless, no subjects with a CYP3A4*5 or CYP3A4*6 allele or homozygous for CYP3A4*4 were identified. The ratio of 6beta-OHC/FC was 9.9 +/- 13.7 and 56.6 +/- 35.7 in subjects with the Ile118Val variant (n = 8) and in CYP3A4 wild-type subjects (n = 8), respectively (P = 0.0039). After oral intake of simvastatin 20 mg daily for 4 weeks, the change of serum lipids in CYP3A4*1/*1 and CYP3A4*1/*4 groups showed a significant difference, with a mean decrease in triglycerides and total cholesterol of 38.1 +/- 7.6% versus 25.1 +/- 8.3% (P = 0.034) and of 35.8 +/- 9.6% versus 22.0 +/-20.4% (P = 0.0015) (means +/- SD), respectively. We found no statistically significant difference in the reductions of LDL between subjects carrying the *1 and *4 genotypes (29.0 +/- 7.4% versus 36.8 +/- 8.8%, P = 0.0721). CONCLUSIONS: The allele frequency of CYP3A4*4 was 3.32% among the hyperlipidemic patients from the Chinese mainland. CYP3A4*4 was an allelic variant related to a functional decrease of CYP3A4 activity, and *4 expression seemed to increase the lipid-lowering effects of simvastatin.

Adult↗

PubMed2005

Synthesis of reassortant infectious bursal disease virus in chickens injected directly with infectious clones from different virus strains.

The infectious bursal disease virus (IBDV), a member of the Birnaviridae family, containing a bisegmented double-stranded RNA genome, encodes four structural viral proteins, VP1, VP2, VP3, and VP4, as well as a non-structural protein, VP5. In the present paper, the segment A from two IBDV strains, field isolate ZJ2000 and attenuated strain HZ2, were inserted into one NaeI site by site-directed silent mutagenesis and subcloned into the eukaryotic expression plasmid pCI under the control of the human cytomegalovirus (hCMV) immediate early enhancer and promoter to construct the recombinant plasmids pCI-AKZJ2000 and pCI-AKHZ2, respectively. Each of the two recombinants was combined with another recombinant pCI plasmid containing the marked segment B of strain HZ2 (pCI-mB), and injected intramuscularly into non-immunized chickens. Two chimeric IBDV strains were recovered from the chickens. Two out of eight chickens in each of two groups showed the bursal histopathological change. The reassortant virus derived from pCI-AKZJ2000/pCI-mB can infect chicken embryos and shows relatively low virulence. We have developed a novel virus reverse genetic approach for the study of IBDV. The results also form the basis for investigating the role of VP1 in viral replication and pathogenecity.

Animals↗

PubMed2004

St John's wort induces both cytochrome P450 3A4-catalyzed sulfoxidation and 2C19-dependent hydroxylation of omeprazole.

OBJECTIVE: St John's wort, an extract of the medicinal plant Hypericum perforatum, is widely used as an herbal antidepressant. Although the ability of St John's wort to induce cytochrome P450 (CYP) 3A4-mediated reaction has been well established, the effect on CYP2C19 is still not determined. Thus the objective of this study was to determine the impact of St John's wort on the pharmacokinetic profiles of omeprazole and its metabolites. METHODS: Twelve healthy adult men (6 CYP2C19*1/CYP2C19*1, 4 CYP2C19*2/CYP2C19*2 and 2 CYP2C19*2/CYP2C19*3) were enrolled in a 2-phase randomized crossover design. In each phase the volunteers received placebo or a 300-mg St John's wort tablet 3 times daily for 14 days. Then all subjects took a 20-mg omeprazole capsule orally. Blood samples were collected up to 12 hours after omeprazole administration. Omeprazole and its metabolites were quantified by use of HPLC with ultraviolet detection. RESULTS: Omeprazole and its metabolites all exhibit CYP2C19 genotype-dependent pharmacokinetic profiles. After a 14-day treatment with St John's wort, substantial decreases in plasma concentrations of omeprazole were observed. The peak plasma concentration (C(max)) significantly decreased by 37.5% +/- 13.3% (P =.001) in CYP2C19*2/CYP2C19*2 or *3 and by 49.6% +/- 20.7% (P =.017) in CYP2C19*1/CYP2C19*1; the area under the concentration-time curve extrapolated to infinity [AUC(0- infinity )] decreased by 37.9% +/- 21.3% (P =.014) and 43.9% +/- 23.7% (P =.011) in CYP2C19 mutant and wild genotypes, respectively. Moreover, the C(max) and AUC(0- infinity ) of omeprazole sulfone increased by 160.3% +/- 45.5% (P =.001) and by 136.6% +/- 84.6% (P =.014), 155.5% +/- 58.8% (P =.001), and 158.7% +/- 101.4% (P =.017) in mutant and wild genotypes, respectively. St John's wort increased the C(max) of 5-hydroxyomeprazole by 38.1% +/- 30.5% (P =.028) and the AUC(0- infinity ) by 37.2% +/- 26% (P =.005) in CYP2C19 wild-type subjects, whereas it did not produce any significant alterations to the corresponding pharmacokinetic parameters in subjects with variant genotypes. CONCLUSION: St John's wort induces both CYP3A4-catalyzed sulfoxidation and CYP2C19-dependent hydroxylation of omeprazole and enormously decreases the plasma concentrations of omeprazole. Clinically relevant interactions with other drugs may occur and must be taken into account when St John's wort is being taken.

Adolescent↗

PubMed2004

The influence of St John's Wort on CYP2C19 activity with respect to genotype.

Induction of cytochrome p450 isozymes is the major cause for clinical drug interactions of St. John's wort. The relationships of St. John's wort to cytochrome p450 isoforms have been fully investigated, but its effect on CYP2C19 is lacking. Thus, the aim of the present study was to observe the effect of St. John's wort on CYP2C19 activity using CYP1A2 as a control. Twelve healthy adult men-6 extensive metabolizers of CYP2C19 (2C19(*)1/2C19(*)1) and 6 poor metabolizers (4 2C19(*)2/2C19(*)2 and 2 2C19(*)2/2C19(*)3)-were enrolled in a two-phase, randomized, crossover manner. All subjects took a 300-mg St. John's wort tablet or placebo three times daily for 14 days, and then the activities of CYP2C19 and CYP1A2 were measured using mephenytoin and caffeine. It was found that St. John's wort treatment significantly increased CYP2C19 activity in CYP2C19 wild-genotype subjects, with urinary 4'-hydroxymephenytoin excretion raised by 151.5% +/- 91.9% (p = 0.0156), whereas no significant alteration was observed for CYP2C19 poor metabolizers. Repeated St. John's wort administration did not affect the CYP1A2 phenotypic ratio for both CYP2C19 genotype subjects. In conclusion, St. John's wort is an inducer to the human CYP2C19, and clinicians should pay great attention when St. John's wort is added to or withdrawn from an existing drug regimen containing substrates for such enzymes.

Adult↗

PubMed2003

Relationship between CYP3A activity and breast cancer susceptibility in Chinese Han women.

BACKGROUND: Breast cancer is the most frequent type of tumor in women. The main cause of breast cancer remains unknown. Extensive studies have shown that endogenous steroid hormones, especially estrogens, are important in the development and the progression of breast cancer, and the carcinogenesis of estrogens is related to their major oxidative metabolites, 16alpha-hydroxyestrogens and 4-hydroxyestrogens. CYP3A plays a major role in the 4- and 16alpha-hydroxylation of estrogens. Furthermore, CYP3A is present in human mammary epithelial cells and expressed higher and more frequently in malignant breast cells than in the adjacent normal breast tissue. Hence, it will be significant to perform more work to determine the association between CYP3A activity and breast cancer susceptibility. AIMS: To evaluate the relationship of CYP3A activity to breast cancer susceptibility in Chinese Han women using the plasma 1-hydroxymidazolam (1-OHMDZ) to midazolam (MDZ) ratio as the marker of CYP3A activity. METHODS: One hundred and twenty-nine Chinese Han female breast tumor patients and 121 healthy unrelated female volunteers were enrolled in the current study. After an overnight fast, each subject was administered a single oral dose (7.5 mg) of midazolam. Blood samples (5 ml) were drawn at 1 h after the drug administration. The concentration of parent MDZ and its major metabolite 1-OH-MDZ was measured in all the plasma samples using high-performance liquid chromatography. RESULTS: Complete chromatographic data on plasma ratios of 1-OHMDZ to MDZ for 103 cases of breast cancer and 114 controls were available. The plasma concentration ratios of 1-OHMDZ to MDZ were 0.4520+/-0.2318 and 0.3298+/-0.1610 for the malignant cases and the controls, respectively. A higher CYP3A activity was found in the breast cancer cases than in the controls ( P<0.001), and the CYP3A activity of patients with lymph-node metastasis was higher than that of patients without lymph-node metastasis ( P=0.028). CYP3A activity in estrogen receptor or progesterone receptor positive cases was the same as in estrogen receptor or progesterone receptor negative cases ( P=0.124, 0.175). CONCLUSIONS: Our results indicate that high CYP3A activity may contribute to breast cancer disease genesis and may promote breast cancer to lymph-node metastasis.

Aryl Hydrocarbon Hydroxylases↗

PubMed2003

Gly389Arg polymorphism of beta1-adrenergic receptor is associated with the cardiovascular response to metoprolol.

OBJECTIVES: Our objectives were to determine whether the Gly389 polymorphism of the beta(1)-adrenergic receptor exhibits reduced responsiveness in vivo and to test the hypothesis that the Gly389Arg polymorphism affects the blood pressure and heart rate response to metoprolol. METHODS: beta(1)-Adrenergic receptor genotype was determined by polymerase chain reaction-restriction fragment length polymorphism assay. Exercise-induced heart rate increases were compared to determine the functional significance in vivo in 8 healthy Chinese men homozygous for Gly389 and 8 homozygous for Arg389. All of the subjects were given 25, 50, or 75 mg of metoprolol every 8 hours; the dosages were given in a random order, and each dosage was given for 1 day. The degree of beta-blockade was measured as the reduction in resting and exercise heart rates and blood pressures. Plasma metoprolol concentrations were measured by the use of HPLC-fluorescence detection. RESULTS: Exercise led to a workload-dependent increase in heart rate. There were no differences in exercise-induced heart rate increases between Arg389 and Gly389 homozygotes. Oral metoprolol caused significant dose-dependent decreases in both resting and exercise heart rates in both groups. The reductions in the resting heart rate in 3 dosage levels of metoprolol were 6.3% +/- 0.8% versus 4.1% +/- 0.7%, 10.1% +/- 1.0% versus 6.2% +/- 1.1%, and 14.4% +/- 1.4% versus 10.9% +/- 1.3% in homozygous Arg389 subjects and Gly389 subjects, respectively (P =.008). We also found differences with respect to the exercise heart rate (8.9% +/- 0.5%, 14.0% +/- 0.9%, and 20.1% +/- 1.5% in Arg389 subjects and 6.6% +/- 0.7%, 11.7% +/- 1.0%, and 16.4% +/- 1.3% in Gly389 subjects; P =.017) and systolic pressure (5.9% +/- 0.7%, 9.2% +/- 1.0%, and 11.6% +/- 1.2% in Arg389 subjects and 4.6% +/- 0.5%, 6.0% +/- 0.8%, and 9.9% +/- 0.9% in Gly389 subjects; P =.011). However, the difference in the fall in diastolic pressure was not statistically significant (P =.442). CONCLUSIONS: The Arg389 variant of the beta(1)-adrenergic receptor was associated with a greater response to metoprolol than that of Gly389 in young, male Chinese subjects. These data suggested that the beta(1)-adrenergic receptor Gly389Arg polymorphism is of major functional importance in vivo.

Adult↗

PubMed2003

The distribution and gender difference of CYP3A activity in Chinese subjects.

AIMS: To investigate the distribution of CYP3A activity in the Chinese population, and to test for gender-related differences in CYP3A activity. METHODS: Using midazolam as a probe drug, CYP3A activity in 202 Chinese healthy subjects (104 men) was measured by plasma 1'-hydroxymidazolam:midazolam (1'-OH-MDZ:MDZ) ratio at 1 h after oral administration of 7.5 mg midazolam. The different phases of the menstrual cycle including preovulatory, ovulatory and luteal phases of 66 women phenotyped with midazolam were recorded. The concentrations of 1'-OH-MDZ and MDZ in plasma were measured by HPLC RESULTS: A 13-fold variation of CYP3A activity (log1'-OH-MDZ:MDZ: range -0.949-0.203) was shown. The CYP3A activity was normally distributed as indicated by the frequency distribution histogram, the probit plot and the Kolmogorov-Smirnov test (P > 0.05). The CYP3A activity of women was higher than that of men (median: -0.36 vs -0.43, P < 0.05; 95% CI for difference: -0.127, -0.012). There was a significant difference in CYP3A activity between the three phases of the menstrual cycle. The activity was highest in the preovulatory phase and decreased sequentially in the ovulatory and luteal phases (P < 0.05). CONCLUSIONS: A normal distribution of CYP3A activity was observed in the Chinese population. The CYP3A activity is higher in female subjects than in males. CYP3A activity differed across the phases of the menstrual cycle.

Administration, Oral↗

PubMed2002

Simultaneous determination of fluoxetine and its metabolite p-trifluoromethylphenol in human liver microsomes using a gas chromatographic-electron-capture detection procedure.

An gas chromatography-electron-capture detection method has been developed for simultaneous determination of fluoxetine and p-trifluoromethylphenol (TFMP), an O-dealkylated metabolite of fluoxetine in human liver microsomes. Prior to the analysis, aliquots of alkalinized microsomal mixture were extracted with ethyl acetate solvent containing acetonitrile (10%, v/v) and the derivatizing reagent, pentafluorobenzenesulfonyl chloride (0.1%, v/v). The organ phase was retained and taken to dryness, the residue was reconstituted in methanol, and the aliquot of extracts was injected directly into a gas chromatograph equipped with an electron-capture detector. 2,4-Dichlorophenol was added to the initial incubation mixture and carried through the procedure as the internal standard. The method provided the mean recoveries of up to 103% for fluoxetine and 104% for TFMP. Acceptable relative standard deviations were found for both within-run and day-to-day assays. The practical limit of detection (signal-to-noise ratio=3) was 1.62 ng/ml for TFMP and 6.92 ng/ml for fluoxetine in human liver microsomes, and the limit of quantitation was 8.1 pg for TFMP and 34.6 pg for fluoxetine. The assay is rapid and sensitive and has been applied successfully to simultaneous quantification of fluoxetine and TFMP in human liver microsomes with different CYP2C19 genotypes.

Chromatography, Gas↗

PubMed2002

O-Dealkylation of fluoxetine in relation to CYP2C19 gene dose and involvement of CYP3A4 in human liver microsomes.

This work evaluated the kinetic behavior of fluoxetine O-dealkylation in human liver microsomes from different CYP2C19 genotypes and identified the isoenzymes of cytochrome P450 involved in this metabolic pathway. The kinetics of the rho-trifluoromethylphenol (TFMP) formation from fluoxetine was determined in human liver microsomes from three homozygous (wt/wt) and three heterozygous (wt/m1) extensive metabolizers (EMs) and three poor metabolizers (PMs) with m1 mutation (m1/m1) with respect to CYP2C19. The formation rate of TFMP was determined by gas chromatograph with electron-capture detection. The kinetics of TFMP formation was best described by the two-enzyme and single-enzyme Michaelis-Menten equation for liver microsomes from CYP2C19 EMs and PMs, respectively. The mean intrinsic clearance (V(max)/K(m)) for the high- and low-affinity component was 25.2 microl/min/nmol and 3.8 microl/min/nmol of cytochrome P450 in the homozygous EMs microsomes and 12.8 microl/min/nmol and 2.9 microl/min/nmol of cytochrome P450 in the heterozygous EMs microsomes, respectively. Omeprazole (a CYP2C19 substrate) at a high concentration and triacetyloleandomycin (a selective inhibitor of CYP3A4) substantially inhibited O-dealkylation of fluoxetine. Furthermore, fluoxetine O-dealkylation was correlated significantly with S-mephenytoin 4'-hydroxylation at a low substrate concentration and midazolam 1'-hydroxylation at a high substrate concentration in liver microsomes of 11 Chinese individuals, respectively. Moreover, there were obvious differences in the O-dealkylation of fluoxetine in liver microsomes from different CYP2C19 genotypes and in microsomal fractions of different human-expressed lymphoblast P450s. The results demonstrated that polymorphic CYP2C19 and CYP3A4 enzymes were the major cytochrome P450 isoforms responsible for fluoxetine O-dealkylation, whereas CYP2C19 catalyzed the high-affinity O-dealkylation of fluoxetine, and its contribution to this metabolic reaction was gene dose-dependent.

Algorithms↗

PubMed2002

Quantitative structure retention relationship studies for predicting relative retention times of chlorinated phenols on gas chromatography.

A new method of quantitative structure-retention relationship (QSRR) studies was reported for predicting gas chromatography (GC) relative retention times (RRTs) of chlorinated phenols (CPs) using a DB-5 column. Chemical descriptors were calculated from the molecular structure of CPs and related to their gas chromatographic RRTs by using multiple linear regression analysis. The proposed model had a multiple square correlation coefficient R2 = 0.970, standard error SE = 0.0472, and significant level P = 0.0000. The QSRR model also reveals that the gas chromatographic relative retention times of CPs are associated with physicochemical property interactions with the stationary phase, and influenced by the number of chlorine and oxygen in the CP mOlecules.

Chlorine Compounds↗

PubMedDate not supplied

Combined MEDV-GA-MLR method for QSAR of three panels of steroids, dipeptides, and COX-2 inhibitors.

The MEDV-13, molecular electronegativity distance vector based on 13 atomic types, has at best 91 descriptors. It is impossible to indirectly use multiple linear regression (MLR) to derive a quantitative structure-activity relationship (QSAR) model. Although principal component regression (PCR) or partial least-squares regression (PLSR) can be employed to develop a latent QSAR model, it is still difficult how to determine the principal components (PCs) and depict the physical meaning of the PCs. So, a genetic algorithm (GA) is first employed to select an optimal subset of the descriptors from original MEDV-13 descriptor set. Then MLR is utilized to build a QSAR model between the optimal subset and the biological activities of three sets of compounds. For 31 benchmark steroids, a 5-descriptor QSAR model (M1) between the corticosteroid-binding globulin (CBG) binding affinity of the steroids and 5-descriptor subset is developed. The root-mean-square error of estimations (RMSEE) and the correlation coefficient of estimations (r) between the CBG binding affinity (BA) observed and the BA estimated by M1 are 0.422 and 0.9182, respectively. The root-mean-square error of predictions (RMSEP) and the correlation coefficient of predictions (q) between the BA observed and the BA predicted by leave-one-out cross validations are 0.504 and 0.8818, respectively. For 58 dipeptides inhibiting angiotensin-converting enzyme (ACE), a 5-variable QSAR model (M2) between the pIC(50) of peptides and 5-descriptor subset is derived. The M2 has a high quality with RMSEE = 0.339 and r = 0.9398 and RMSEP = 0.370 and q = 0.9280. For 16 indomethacin amides and esters (ImAE) inhibiting cyclooxygenase-2 (COX-2), a 6-variable QSAR model (M3) with RMSEE = 0.079 and r = 0.9839 and RMSEP = 0.151 and q = 0.9413 is built.

Cyclooxygenase 2↗

PubMedDate not supplied

VSMP: a novel variable selection and modeling method based on the prediction.

The use of numerous descriptors that are indicative of molecular structure and topology is becoming more common in quantitative structure-activity relationship (QSAR). How to choose the adequate descriptors for QSAR studies is important but difficult because there are no absolute rules to govern this choice. A variety of variable selection techniques including stepwise, partial least squares/principal component analysis (PLS/PCA), neural network, and evolutionary algorithm such as genetic algorithm have been applied to this common problem. All-subsets regression (ASR) is capable of finding out the best variable subset from among a large pool. In this paper, a novel variable selection and modeling method based on the prediction, for short VSMP, has been developed. Here two controllable parameters, the interrelation coefficient between the pairs of the independent variables (r(int)) and the correlation coefficient (q(2)) obtained using the leave-one-out (LOO) cross-validation technique, are introduced into the ASR to improve its performances. This technique differs from the other variable selection procedures related to the ASR by two main features: (1) The search of various optimal subset search is controlled by the statistic q(2) or root-mean-square error (RMSEP) in the LOO cross-validation step rather than the correlation coefficient obtained in the modeling step (r(2)). (2) The searching speed of all optimal subsets is expedited by the statistic r(int) together with q(2). A comparison of the results of the VSMP applied to the Selwood data set (n = 31 compounds, m = 53 descriptors) with those obtained from alternative algorithms shows the good performance of the technique.

Journal Article↗