Specific evidence that schizandrins induce a phenobarbital-like cytochrome P-450 form separated from rat liver

Pharmacokinetics of Schizandrin and Its Pharmaceutical Products Assessed Using a Validated LC-MS/MS Method

Schisandra chinensis has been used as an important component in various prescriptions in traditional Chinese medicine and, more recently, in Western-based medicine for its anti-hepatotoxic effect. The aim of this study was to develop a selective, rapid, and sensitive ultra-performance liquid chromatography-tandem mass spectrometry method for pharmacokinetic studies of schizandrin in rats. Liquid-liquid extraction was used for plasma sample preparation. A UHPLC reverse-phase C18e column (100 mm × 2.1 mm, 2 μm) coupled with a mobile phase of methanol-0.1% formic acid (85:15, v/v) was used for sample separation. A triple quadrupole tandem mass spectrometer was used to detect the analytes in the selected reaction monitoring mode. The linear range of schizandrin in rat plasma was 5.0–1000 ng/mL (r² > 0.999), with a lower limit of quantification of 5 ng/mL. The method was validated with regard to accuracy, intra-day and inter-day precision, linearity, stability, recovery, and matrix effects in rat plasma, which were acceptable according to the biological method validation guidelines developed by the FDA. This method was successfully applied to a pharmacokinetic study after oral administration of 3 g/kg and 10 g/kg of Schisandra chinensis products, which yielded a maximum concentration of schizandrin of 0.08 ± 0.07 and 0.15 ± 0.09 μg/mL, respectively. A parallel study design was used to investigate the oral bioavailability of single compound of schizandrin and the herbal extract, the single compound of pure schizandrin (10 mg/kg, i.v.), pure schizandrin (10 mg/kg, p.o.), and the herbal extract of Schisandra chinensis (3 g/kg and 10 g/kg, p.o.) were given individually. The dose of Schisandra chinensis (3 g/kg) equivalent to schizandrin (5.2 mg/kg); the dose of Schisandra chinensis (10 g/kg) equivalent to schizandrin (17.3 mg/kg). The result demonstrated that the oral bioavailability of schizandrin was approximately 15.56 ± 10.47% in rats, however the oral bioavailability of herbal extract was higher than single compound. The method was successfully applied to the pharmacokinetic study of pure schizandrin after oral administration of its pharmaceutical industry products in rats.

Pharmacokinetic interaction between oltipraz and dimethyl-4,4‘-dimethoxy-5,6,5′,6’-dimethylene dioxybiphenyl-2,2′-dicarboxylate (DDB) after single intravenous and oral administration to rats

The aim of this study was to report the pharmacokinetic interaction between oltipraz (50 mg kg−1) and dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate (DDB, 10 mg kg−1) after single intravenous and oral administration to rats. After intravenous administration of oltipraz plus DDB, the area under the plasma concentration–time curve from time zero to time infinity (AUC) of oltipraz was significantly greater (1440 vs 1740 μg min mL−1) than that after oltipraz alone. This was not due to slower clearances of oltipraz after oltipraz plus DDB since the total body, renal and nonrenal clearances were comparable between the two groups of rats. It could be due to a decrease in tissue binding of oltipraz by DDB. The apparent volume of distribution at steady state (Vdss) of DDB was significantly smaller (7060 vs 4650 mL kg−1) than after oltipraz alone. After oral administration of oltipraz plus DDB, the AUC of olitpraz was also significantly greater (479 vs 583 μg min mL−1) than that after oltipraz alone. This was not due to increased absorption of oltipraz from the rat gastrointestinal tract after oltipraz plus DDB but again could be due to a decrease in Vdss of oltipraz by DDB. However, after both intravenous and oral administration, the pharmacokinetic parameters of DDB were comparable between DDB alone and DDB plus oltipraz, indicating that oltipraz did not greatly affect the pharmacokinetics of DDB in rats.

Pharmacokinetic interaction between liquiritigenin (LQ) and DDB: increased glucuronidation of LQ in the liver possibly due to increased hepatic blood flow rate by DDB

It has been reported that both liquiritigenin (LQ) and dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (DDB) have a hepatoprotective effect, and administration of both drugs together shows additive protective effect against acute liver injuries. Therefore, the pharmacokinetic interaction between LQ and DDB in rats was studied. LQ (20 and 50mg/kg for the i.v. and p.o. administration, respectively), DDB (10mg/kg for both i.v. and p.o. administration), and both drugs together were once administered intravenously or orally to rats. After the i.v. administration of both drugs together, the Cl(nr) and AUC of LQ were significantly faster (by 30.5%) and smaller (by 22.5%), respectively, than those of without DDB due to the faster hepatic blood flow rate by DDB. After the p.o. administration of both drugs together, the AUC of LQ was comparable to that of without DDB due to negligible effect of DDB on intestinal metabolism of LQ. The pharmacokinetic parameters of DDB after both i.v. and p.o. administration were not altered by LQ, indicating that LQ did not considerably affect the pharmacokinetics of DDB in rats.

Effect of bifendate on the pharmacokinetics of cyclosporine in relation to the CYP3A4*18B genotype in healthy subjects

AIM

To evaluate the potential drug-drug interactions between bifendate and cyclosporine, a substrate of CYP3A4, in relation to different CYP3A4*18B genotype groups.

METHODS

Eighteen unrelated healthy subjects (six CYP3A4*1*1, six CYP3A4*1/*18B, and six CYP3A4*18/*18B) were selected for this study. After repeated oral administration of a placebo or bifendate (three times daily for 14 d), the whole-blood level of cyclosporine was measured using high performance liquid chromatography-electrospray mass spectrometry (HPLC/ESI-MS). This study was carried out in a two-phase randomized crossover manner.

RESULTS

After the treatment with bifendate, the areas under the curve (AUC(0-24) and AUC(0-infinity)) decreased significantly by 9.7%+/-3.7% (P=0.01) and 19.2%+/-16.8% (P=0.001) in CYP3A4*1/*1 subjects, 11.3%+/-9.4% (P=0.03) and 10.5%+/-9.6% (P=0.043) in CYP3A4*1/*18B subjects, and 40.2%+/-14.7% (P=0.02) and 37.5%+/-15.8% (P=0.003) in CYP3A4*18B/*18B subjects. Meanwhile, the decreases in the AUC(0-24) and AUC(0-infinity) values in the three groups were significantly different (using one-way analysis of variance, P=0.001 and P=0.001), and the change in the CYP3A4*18B/*18B group was greater than that in the other two groups. The oral clearance of cyclosporine was altered in all the subjects, with substantial increases by 10.2%+/-4.4% (P=0.004) in CYP3A4*1/*1 subjects, 14.0%+/-12.0% (P=0.048) in CYP3A4*1/*18B subjects, and 32.4%+/-21.7% (P=0.013) in CYP3A4*18B/*18B subjects.

CONCLUSION

These results suggest that bifendate decreases the plasma concentration of cyclosporine in a CYP3A4 genotype-dependent manner.

Effect of biphenyl dimethyl dicarboxylate on the humoral immunosuppression by ketoconazole in mice

The present study was undertaken to investigate the effect of biphenyl dimethyl dicarboxylate (PMC) on the humoral immunosuppression by ketoconazole (KCZ) in ICR mice. PMC at a dose of 6 mg/kg was administered orally to mice daily for 14 consecutive days. KCZ was suspended in RPMI 1640 medium and orally administered at 160 mg/kg/day 2 hrs after the administration of PMC. Mice were immunized and challenged with sheep red blood cells (SRBC). The results of the present study are summarized as follows; a gain of body weight and relative weights of spleen and liver were significantly increased by combination of PMC and KCZ, as compared with those in mice treated with KCZ alone. Splenic plaque forming cells (PFC) and hemagglutination (HA) titers to SRBC were greatly enhanced by the combination of PMC and KCZ, compared with treatment of KCZ alone. The elevation of serum glutamicpyruvic transaminase (S-GPT) and total protein levels caused by KCZ were reduced to normal level by the combination of PMC and KCZ. In addition, lower serum albumin and A/G ratio were also increased to normal level. These findings indicate that PMC has a protective effect against KCZ-induced humoral immunosuppression.

Enhanced effectiveness of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate in combination with garlic oil against experimental hepatic injury in rats and mice

The present study was designed to evaluate the effects of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate (PMC) in combination with garlic oil against chemical-induced hepatic injury in rats and mice. Rats insulted with carbon tetrachloride were concomitantly treated with PMC and/or garlic oil (50 and 100 mg kg-1, respectively) for four weeks. Whereas treatment of animals with garlic oil alone was ineffective in suppressing carbon tetrachloride-induced hepatotoxicity, administration of PMC in combination with garlic oil more effectively protected the liver against the carbon tetrachloride-induced insult than PMC alone, as monitored by serum aminotransferase activity. Hepatoprotective effects of the formulation were further supported by the changes in the numbers of Kupffer cells and dead hepatocytes. Although prior treatment of rats with PMC for three days failed to protect hepatotoxicity elicited by allyl alcohol, the formulation of PMC and garlic oil was capable of blocking allyl alcohol-induced hepatotoxicity by approximately 40%. To further examine the effect of the agents on lipid metabolism in the liver, hepatic triglycerides and cholesterol contents were assessed in mice after a diet containing PMC and/or garlic oil for one week followed by a single dose of carbon tetrachloride. Garlic oil appeared to be more effective in bringing hepatic lipid levels to those of control than PMC alone. Treatment of animals with PMC in combination with garlic oil synergistically improved chemical-induced impairment of hepatic triglycerides and cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanistic study of the inhibition of aflatoxin b1-induced hepatotoxicity by dimethyl 4,4'-dimethoxy-5,6,5',6'-dimethylenedioxy biphenyl-2, 2'-dicarboxylate

The mechanism of DDB (dimethyl 4,4'-dimethoxy-5,6,5',6'-dimethylenedioxy biphenyl-2,2'-dicarboxylate) prevention of aflatoxin B1 (AFB1)-induced hepatotoxicity in rats has been investigated. Pretreatment of DDB (200 mg/kg) daily for 4 days significantly suppressed (P < 0.05) the AFB1-induced hepatic damage as evidenced by the increase of serum marker enzymes. DDB induced rat hepatic cytochrome P450IA1, IIB1 and glutathione S-transferase activities. The hepatic microsomes derived from DDB treated rats increased the mutation frequency of AFB1 and enhanced the binding of AFB1 to DNA. However, the hepatic S9 fraction from DDB treated rats showed a protective effect against AFB1-induced damage. It is concluded that the protective effect of DDB against AFB1-induced damage might be mediated by the induced glutathione S-transferase activity and not from the accelerated hepatic cytochrome P450 detoxification pathway of AFB1 which was previously believed.

Highlights of drug metabolism research in China

In the past 30 years, the study of drug metabolism in China has followed a zigzag path, from the initial uprising stage to devastation, and then to regeneration. In the reviving decade of 1976-1985, studies have extended to various aspects of the field of drug metabolism and pharmacokinetics. There are rapid increases both in modern facilities and trained personnel. Therefore, it is expected that in the coming decade drug metabolism research in China will be carried out at much higher levels with more interesting results.

A dual assay for the specific screening of 3-methylcholanthrene- and phenobarbital-like chemical inducers of cytochrome P-450 monooxygenases

We present and evaluate a dual assay, the CYPIA (Cytochrome P-450 induction assay) for the detection and the simultaneous identification of chemicals belonging either to the 3-methylcholanthrene or phenobarbital classes of cytochrome P-450 monooxygenase inducers. These inducers play an important role in the mutagenic activation of chemical compounds as well as in many pharmacological and toxicological events and therefore should be screened by drug and chemical designers. After treatment of male rats or mice by chemicals, the liver preparations (S9) have been used in the Salmonella typhimurium test, to activate either ethidium bromide or cyclophosphamide into mutagenic metabolites. These transformations are specifically catalyzed by cytochrome P-450-dependent monooxygenases induced by 3-methylcholanthrene-like and phenobarbital-like chemical inducers, respectively. The mutagenicity data were strikingly correlated with other methods (production of [3H]benzo[a]pyrene bay-region metabolites, benzphetamine demethylase activity, immunological double-diffusion analysis). Compared to the latter methods, the CYPIA, based on a single and widespread technology, introduces an interesting simplification, and improves the specificity and the sensitivity of the responses.

Study of benzphetamine-N-demethylase in streptozotocin-diabetic mice and rats: evidence for the induction of catalytically and immunologically specific forms of cytochrome P450

Phenobarbital treatment and streptozotocin-diabetes both increase, in mouse and rat microsomes, a benzphetamine-N-demethylase activity which can be inhibited by a specific antibody raised against purified rat phenobarbital-induced cytochrome P-450. However, similar studies performed on cytochrome P-450 A and B fractions separated by DEAE-cellulose chromatography, clearly proved that streptozotocin-diabetes promotes in mice the synthesis of two new species of cytochrome P-450 and that the streptozotocin diabetes-induced forms are different in mouse and rat. No such modifications were observed in the mixed-function oxidase system of congenitally diabetic mice.

Immunological and enzymatic comparison of hepatic cytochrome P-450 fractions from phenobarbital-, 3-methylcholanthrene-, beta-naphthoflavone- and 2,3,7,8- tetrachlorodibenzo-p-dioxin-treated rats

A comparison of the cytochrome P-450 forms induced in rat liver microsomes by phenobarbital on the one hand, and 3-methylcholanthrene, beta-naphthoflavone and 2,3,7,8-tetrachlorodibenzo-p-dioxin on the other hand, was performed using specific antibodies: anti-P-450 B2 PB IG (against the phenobarbital-induced cytochrome P-450) and anti-P-450 B2 BNF IG (against the beta-naphthoflavone-induced cytochrome P-450). On DEAE-cellulose chromatography, four cytochrome P-450 fractions were separated, called P-450 A (non-adsorbed), P-450 Ba, P-450 Bb and P-450 Bc, from control, phenobarbital-, 3-methylcholanthrene, beta-naphthoflavone- and 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated rats. Cytochrome P-450 A fractions appeared to be unmodified by the inducers, whereas the specifically induced cytochrome P-450 forms were always recovered in Bb fractions. The P-450 Bb fractions induced by 3-methylcholanthrene, beta-naphthoflavone and 2,3,7,8-tetrachlorodibenzo-p-dioxin exhibited common antigenic determinants, comparable catalytic activities (benzphetamine N-demethylase, benzo[a]pyrene hydroxylase) and similar mol. wts. Moreover, the inhibition patterns by the two antibodies of benzphetamine N-demethylase and benzo[a]pyrene hydroxylase activities catalysed by 3-methylcholanthrene, beta-naphthoflavone and 2,3,7,8-tetrachlorodibenzo-p-dioxin microsomes or by the corresponding P-450 Bb fractions in a reconstituted system were quite identical. By these different criteria, beta-naphthoflavone, 3-methylcholanthrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin seem to induce a common cytochrome P-450 species in rat liver.