Genomewide Association Study Identifies Novel Genetic Loci That Modify Antiplatelet Effects and Pharmacokinetics of Clopidogrel.

Genetic variants in the pharmacokinetic (PK) mechanism are the main underlying factors affecting the antiplatelet response to clopidogrel. Using a genomewide association study (GWAS) to identify new genetic loci that modify antiplatelet effects in Chinese patients with coronary heart disease, we identified novel variants in two transporter genes (SLC14A2 rs12456693, ATP-binding cassette [ABC]A1 rs2487032) and in N6AMT1 (rs2254638) associated with P2Y12 reaction unit (PRU) and plasma active metabolite (H4) concentration. These new variants dramatically improved the predictability of PRU variability to 37.7%. The associations between these loci and PK parameters of clopidogrel and H4 were observed in additional patients, and its function on the activation of clopidogrel was validated in liver S9 fractions (P < 0.05). Rs2254638 was further identified to exert a marginal risk effect for major adverse cardiac events in an independent cohort. In conclusion, new genetic variants were systematically identified as risk factors for the reduced efficacy of clopidogrel treatment.

Effect of St. John's wort supplementation on the pharmacokinetics of bupropion in healthy male Chinese volunteers.

The objective of this study was to investigate the effects of continuous St. John's wort administration on single-dose pharmacokinetics of bupropion, a substrate of cytochrome P450 (CYP) 2B6, in healthy Chinese volunteers. Eighteen unrelated healthy male subjects participated in this study. The single-dose pharmacokinetics of bupropion and hydroxybupropion were determined before (control) and after a long-term period of St. John's wort intake (325 mg, three times a day for 14 days). Plasma concentrations of bupropion and hydroxybupropion were determined before and at 0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12, 24, 36, 48, 60 and 72 h after dosing. St. John's wort treatment decreased the area under the concentration versus time curve extrapolated to infinity of bupropion in healthy volunteers from 1.4 microg.h ml(-1) (95% confidence interval [CI] = 1.2-1.6 microg.h ml(-1)) after bupropion alone to 1.2 microg.h ml(-1) (95% CI = 1.1-1.3 microg.h ml(-1)) during St. John's wort treatment. St. John's wort treatment increased the oral clearance of bupropion from 108.3 l h(-1) (95% CI = 95.4-123.0 l h(-1)) to 130.0 l h(-1) (95% CI = 118.4-142.7 l h(-1)). No change in the time to peak concentration (t(max)) and the blood elimination half-life (t(1/2)) of bupropion was observed between the control and St. John's wort-treated phases. However, the half-life of hydroxybupropion between two phases had a significant difference by a Student's t test after logarithmic transformation. St. John's wort treatment decreased the half-life of hydroxybupropion from 26.7 h (95% CI = 23.8-29.9 h) to 24.4 h (95% CI = 21.9-27.3 h). St. John's wort decreased, to a statistically significant extent, the plasma concentrations of bupropion, probably mainly by increasing the clearance of bupropion.

Effect of Schisandra chinensis extract and Ginkgo biloba extract on the pharmacokinetics of talinolol in healthy volunteers.

The authors investigated the effect of herbal medicine Schisandra chinensis extract (SchE) and Ginkgo biloba extract (GBE) on the oral pharmacokinetics of P-glycoprotein substrate talinolol in humans. Twelve healthy male volunteers took a single 100-mg oral dose of talinolol either alone or after pretreatment with 300 mg SchE twice daily or with 120 mg GBE three times daily for 14 days. On day 14, a single 100-mg oral dose of talinolol was administered. Plasma concentrations of talinolol from zero to 24 h were measured by high-performance liquid chromatography. SchE increased the area under the curve (AUC)(0-24) of talinolol by 47% (90% confidence interval (CI), 18-84%; p = 0.010), and GBE by 21% (90% CI = 11-32%; p = 0.002). The C(max) of talinolol increased by 51% (90% CI = 21-89%; p = 0.007) with SchE treatment and by 33% (90% CI = 18-51%; p = 0.002) with GBE treatment, respectively. The t(1/2) of talinolol increased by 7% (90% CI = -4% to 19%; p = 0.320) with SchE treatment and by 11% (90% CI = -12% to 38%; p = 0.436) with GBE treatment, respectively. The results suggest that both SchE and GBE significantly inhibited P-glycoprotein in humans. Patients receiving either SchE or GBE may require dose adjustments when treated with drugs primarily transported by P-glycoprotein.

[Studies on anti-implantation and hormone activity of yuehchukene, an alkaloid isolated from the root of Murraya paniculata].

Oral or subcutaneous administration of yuehchukene to female mice at the dosage of 2 or 4 mg/kg.d on day 1-3 of gestation resulted in 100% anti-implantation effect. However, yuehchukene at 4 mg/kg.d was found to have no anti-implantation effect in hamsters. Allen-Doisy test showed that yuehchukene had obvious estrogenic activity. Treatment of immature mice with yuehchukene at the dosage of 2 or 4 mg/kg.d for 3 days caused an increase of uterine weight. Combined use of yuehchukene with estradiol was shown to have synergistic effect on promoting uterine growth. Experiments showed that the estrogenic activity of yuehchukene was weaker than that of estriol. The affinity of this compound for estrogen receptor was also found to be weaker than that of estriol.

Effect of (-)- and (+)-gossypol on fertility in male rats.

(+)-Gossypol has neither antifertility effect nor toxicity at the dosage of 30 mg/kg orally for 14 days in male rats, but slight damage was found in the germinal epithelium of the testis in animals dosed for 4 weeks. (-)-Gossypol at 30 mg/kg orally for 7 days clearly had an antifertility effect in male rats. It appears that (-)-gossypol is the active stereoisomer of racemic gossypol.

Effect of (+/-)-, (+)- and (-)-gossypol on the lactate dehydrogenase-X activity of rat testis.

The effect of (+/-)-, (+)- and (-)-gossypol on testicular lactate dehydrogenase-X (LDH-X) was studied in vitro and in vivo. It was found that racemic gossypol and the two optical enantiomers had similar inhibitory effects on rat testicular LDH-X in vitro. However, neither racemic gossypol nor the enantiomers exhibited an inhibitory effect on testicular LDH-X in vivo. It is concluded that inhibition of testicular LDH-X is not likely to be the mechanism of the antifertility action of gossypol. The inhibition of testicular LDH-X in vitro by all three preparations of gossypol is probably non-specific.

Hepatotoxicity of gossypol in rats.

Gossypol acetic acid (GAA) at the dosage of 30 mg/kg daily for 2 weeks could prolong the sleeping time of pentobarbital, increase the SGPT level, decrease the liver concentration of cytochrome P-450 and GSH content, inhibit the activity of cytochrome C reductase and aminopyrine-N-demethylase, but was without effect on cytochrome b5 and aniline hydroxylase. At a smaller daily dosage (15 mg/kg for 4 weeks), GAA could induce the rise of SGPT level and GSH content without affecting the liver metabolizing enzymes. GAA at both dosages could induce marked pathological changes of liver cells in treated rats, such as vacuolation of mitochondria, dilation of endoplasmic reticulum and widening of perinuclear space as well as proliferation of collagen fibers in Disse's spaces. GAA could induce the formation of O2 and H2O2 and could inhibit Ca2+ sequestration in rat liver microsomes in vitro. [C14]-gossypol could bind to microsomal protein irreversibly either in the presence or absence of NADPH. It may be concluded that GAA is capable of causing damage to liver cells.

Comparative study on the metabolism of optical gossypol in rats.

The comparative metabolism of (+)- and (-)-gossypol in rats was studied. After oral administration of the drugs to rats, the half-lives of (+)- and (-)-gossypol in the gastrointestinal tract were found to be 18.4 h and 13.5 h, respectively. The tissue distribution of (+)-gossypol was very similar to that of (-)-gossypol. After oral administration, high drug levels were found in the liver while moderate concentrations were present in the spleen, lungs, blood, heart and kidneys. The drug levels in the testes and fat were rather low. The excretion rates of the (+)- and (-)-gossypol were quite similar. Most of the ingested drug was excreted in the feces, while only a small fraction was eliminated in the urine. After i.v. injection of the drugs to rats, the half-lives of free (+)- and (-)-gossypol were found to be 7.80 h and 3.96 h, respectively. The clearance rates of the two optical isomers were 7.81 and 29.36 ml/h, respectively.

Effect of gossypol acetic acid on the epididymis: histochemical and scanning electron microscope studies.

Rats were treated orally with gossypol acetic acid at 30 or 10 mg/kg daily, 6 days a week, for 8, 12, 14 or 16 weeks. At the end of each treatment regimen, treated rats and an equal number of control rats were killed for histological and histochemical studies. From 8 weeks onward, as a result of the treatment, the tubular lumen of the corpus epididymides became narrowed with thickened pseudostratified epithelium and there was a reduction in the amount of spermatozoa. There was an increase in esterase, alkaline phosphatase, acid phosphatase and ATPase activity. These changes increased in intensity with the duration of treatment. Scanning electron microscopic examinations of the corpus epididymides of rats treated for 16 weeks, compared with those of controls, revealed similar changes, namely, narrowing of the tubular lumen, thickening of the pseudostratified epithelium and reduction in the number of spermatozoa.

Effects of gossypol acetic acid on rat luteal cells in vitro.

The action of gossypol acetic acid (GAA) on 125I-hCG binding, gonadotropin-stimulated cAMP accumulation and progesterone production was investigated utilizing rat ovaries. Incubation of luteal cells for 3 h with increasing concentration of GAA caused a significant inhibition of gonadotropin-stimulated steroidogenesis. The inhibitory effect of GAA was concentration dependent. GAA at concentrations of 10-30 micrograms/ml reduced cAMP formation in response to hCG. It was shown that the activity of adenylate cyclase of luteal cells was inhibited by 10 micrograms/ml GAA. GAA at a concentration of 30 micrograms/ml was found to have an inhibitory effect on 8Br-cAMP-stimulated progesterone production. GAA did not affect 125I-hCG binding to LH receptor on the luteal cell surface. These results suggest that in luteal cells GAA inhibits steroidogenesis at the step of gonadotropin-stimulated cAMP formation. Adenylate cyclase of luteal cells was inhibited.