IMMUNOCHEMICAL IDENTIFICATION AND LOCALIZATION OF CYTOCHROME P-450HSjISOZYME, AN ENZYME RELATED TO NITROSAMINE METABOLISM, IN HUMAN GASTRIC MUCOSA AND GASTRIC CARCINOMA

Monoclonal antibody (MAb) to rat liver cyto-chrome P-450j isozyme, an activating enzyme specific to nitrosamine metabolism, was used coupled with immunoblotting, densitometer scanning of SDS-PAGE gels and immunohistochemical technique. The trace P-450HSj isozyme (Mr. 51.5 Kd) was found in human gastric mucosa. It was similar to P-450j in molecular weight, catalytic and immunochemical properties. The concentrations of P-450HSj in mucosa of lesser curvature were higher than those in greater curvature. This might be one of the important reasons that lesser curvature is the commonest area for gastric carcinoma. But there was possibly less P-450HSj in gastric mucosa with cancer. Im-munohistochemically, P-450HSj was discovered in the cytoplasm of some glandular epithelial cells, especially in the glands with hyperplastic and intestinal metaplastic changes adjacent to carcinoma. It was also found in some normal glands and in tumor cells of high-differentiated adenocarcinoma, but not in those of low-differentiated ones. Following subjects are discussed: (1) the method of detecting trace P-450HSj, (2) the rule of distribution of P-450HSj, and (3) the relationship between the isozyme and the occurrence of gastric cancer caused by nitrosa-mines.

Effects of Tianma(Rhizoma Gastrodiae)and Gouteng(Ramulus Uncariae Rhynchophyllae cum Uncis)on cytochrome P450 enzyme activities in rats

OBJECTIVE:To investigate the efficacy of Tianma(Rhizoma Gastrodiae)and Gouteng(Ramulus Uncariae Rhynchophyllae cum Uncis)on cytochrome P450(CYP450)enzyme activities in rats.METHODS:A cocktail strategy was followed to evaluate the influence of Tianma(Rhizoma Gastrodiae)and Gouteng(Ramulus Uncariae Rhynchophyllae cum Uncis)on the activities of CYP450 isoforms(CYP1A2,CYP3A4,CYP2E1,CYP2C19,CYP2C9,CYP2D6),which were determined by changes in the pharmacokinetic parameters of six probe drugs,theophylline,dapsone,chlorzoxazone,omeprazole,tolbutamide and dextromethorphan.Study groups included,Control group(CG),Tianma(Rhizoma Gastrodiae)group(TM),Gouteng(Ramulus Uncariae Rhynchophyllae cum Uncis)group(GT)and Tianma Gouteng(Gastrodia Uncaria)group(TMGT).RESULTS:No significant differences between Tianma(Rhizoma Gastrodiae)and control groups were found.Compared with the control group,in the Gouteng(Ramulus Uncariae Rhynchophyllae cum Uncis)group both the AUC and t1/2 of dapsone and tolbutamide were reduced,whereas the CL(clearance rate)of dapsone and tolbutamide were increased.Compared with the control group,in the Tianma Gouteng group,the AUC and t1/2 of dapsone and tolbutamide were reduced,the CL of dapsone and tolbutamide were increased,and the AUC and t1/2 of chlorzoxazone were increased and the CL of chlorzoxazone was reduced.CONCLUSION:Tianma(Rhizoma Gastrodiae)has no significant effect on the six CYP450 subtypes.The activities of CYP3A4 and CYP2C9 were increased by Gouteng(Ramulus Uncariae Rhynchophyllae cum Uncis).The activities of CYP3A4 and CYP2C9 were increased,whereas the activity of CYP32E1 was reduced by combined Tianma(Rhizoma Gastrodiae)and Gouteng(Ramulus Uncariae Rhynchophyllae cum Uncis).

Immunohistochemical localization of cytochrome P450 enzymes 2C and 4A in the normal rat brain

Objective To localize cytochrome P450 enzymes 4A and 2C in central nervous cells of normal male rats.Methods Eight drug/alcohol untreated normal male rats (150-200 g of body weight) were treated by the optimized perfusion technique, then brain tissues were postfixed, paraffin-embedded and cut into series sections, which were labeled by the improved strept-avidin-biotin complex DAB-nickel enhancer (SABC-DAB-Ni) immunohistochemistry and hematoxylin & eosin (H & E) stain techniques.Results The immunohistochemical results indicated that P450 2C-11 enzyme was localized in diverse numbers of neurons as well as some neuroglial cells, with focal or defuse distribution in many brain regions such as cerebrum, thalamus, olfactory bulb, hypothalamus, brain-stem, hippocampus, cerebellum, interpositus nucleus, caudate-putamen, and globus pallidus. In contrast, no positive findings of P450 4A-2, 3 and 8 enzymes were obtained in the same animals. With high magnification, 2C-11 protein was able to be roughly observed on the endoplasmic reticulum of the rat neurons.Conclusions P450 2C-11 protein, rather than P450 4A-2, 3 and 8, may be a candidate of brain P450 enzymes in the normal male rats.

孕烷X受体介导佐米曲坦对大鼠肝细胞色素P450 CYP 3A的诱导作用

目的:考察佐米曲坦对大鼠肝细胞色素P450 CYP3A1/2的诱导是否由孕烷X受体(PXR)介导。方法:在构建的基于PXR的荧光素酶报告基因上,观察不同浓度佐米曲坦(10、50、100μmol.L-1)对大鼠肝细胞色素P450 CYP3A1/2的诱导作用。以经典的诱导剂16α-氰基孕烯醇酮(PCN)作为阳性对照,空白溶剂(DMSO)作为阴性对照。结果:与阴性对照组相比,阳性对照组、佐米曲坦在100μmol.L-1浓度时,对CYP3A1有明显的诱导作用,活性分别增加了1.93、1.96倍(P<0.05);阳性对照组、佐米曲坦10μmol.L-1、50μmol.L-1浓度组对CYP3A2也有明显的诱导作用,其活性分别增加了2.51、2.10、1.63倍(P<0.01、<0.05)。结论:PXR通路是佐米曲坦诱导大鼠CYP3A1/2的一个重要途径。

异莲心碱对大鼠CYP3A酶活性的影响

目的:探讨异莲心碱对CYP3A酶活性的影响,以了解异莲心碱与CYP3A酶底物合用药时可能产生的相互作用。方法:①建立体外肝微粒体混合酶代谢体系;②以睾酮作为底物探针,用HPLC建立检测CYP3A酶代谢活性的方法,考察体外代谢体系的最佳孵育条件;③将不同浓度异莲心碱分别与睾酮共同孵育于肝微粒体代谢体系中,测定在有或无异莲心碱存在下睾酮的减少量,以评估异莲心碱对CYP3A酶代谢的影响。结果:在肝微粒体孵育体系中,睾酮体外代谢的最佳孵育条件为底物浓度200μmol/L,代谢时间210 min。异莲心碱对CYP3A酶抑制作用较弱,IC50>1 000μmol/L。结论:异莲心碱对CYP3A酶无显著影响,可以与其底物联合用药。

Herb-drug enzyme-mediated interactions and the associated experimental methods： a review

OBJECTIVE: To review the interactions between herbs and widely used drugs and summarize the associated experimental methods.METHODS: Definite herb-drug interactions were obtained by searching Pub Med, other large overseas databases and summarizing new researches from China. We summarize some methods to assess the interaction between herbs and drugs involving microsomal, cell culture and animal experiments, and clinical trials, classifying this method as single ingredient herbs, crude herb extracts, andherbal formulae.RESULTS: Many herbs interact with drugs through a complex cytochrome P450 and/or P-glycoprotein mechanism. Herb-induced enzyme inhibition and/or induction may result in enhanced and / or decreased plasma, tissue, urine and bile drug concentrations, leading to a change in a drug's pharmacokinetic parameters and resulting in the improper treatment of patients and potentially severe side effects. Use of an appropriate method for comprehensively assessing herb-drug interactions can minimize clinical risks. Different methods were used by researchers to assess the pharmacological changes of drugs in vivo and in vitro and the mechanisms of the interactions from microsomal, cell culture and animal experiments, and clinical trials are discussed in this review.CONCLUSION: Co-medication with herbs can result in changes in pharmacological effects of many drugs. This review describes the assessment of single-ingredient herbs, crude herb extracts, and herbal formulae. When choosing a research method to investigate herb-drug interactions, the properties of the drugs and herbs should be considered.

Effect of Yajieshaba,a preparation of Dai indigenous medicine,on enhanced liver detoxification

OBJECTIVE:To explore the mechanistic effects of Yajieshaba(YJSB) on enhanced liver detoxification.METHODS:The effects of YJSB on alanine aminotransferase(ALT) and aspartate aminotransferase(AST) were assayed in five acute chemical liver injury models[carbon tetrachloride(CCU),D-galactosamine(D-Glan),4-acetamidophenol(AAP),thioacetamide(TAA) and 1-naphthyl isothiocyanate(ANIT)].Sleep latency and sleep time of pentobarbital sodium were tested in control mice and CCL model miceafter oral YJSB administration.The effects of YJSB on drug metabolism enzymes of liver microsomes were tested in control rats and CCI_4model rats.The levels of cytochrome P450(CYP450) and Cyt b5 in liver microsomes were assayed using the method by Omura and Sato,and activities of erythromycin N-demethylase(ERD)and aminopyrine N-demethyl(ADM) were evaluated by Nash colorimetry.Probe substrate-based high performance liquid chromatography(HPLC)methods were established for CYP3A4 and CYP1A2.RESULTS:The level of serum ALT was reduced by YJSB at 3.51 g/kg in the five models as follows:CCl_4 > D-Glan,AAP,ANIT > TAA.YJSB treatment did not reduce the level of serum AST.YJSB at 3.51 g/kg prolonged the sleep latency in control mice and shortened the sleep time of control mice and CCl_4 model mice.For control rats,YJSB at 2.43 g/kg increased the levels of CYP450 and Cyt b5 and induced the activities of ERD and ADM;for liver injuries induced by CCI_4 in rats,YJSB at 2.43 g/kg increasedthe levels of CYP450 and Cyt b5.These results suggest that YJSB at 2.43 g/kg induces CYP3A4 and CYP1A2.CONCLUSION:These results suggest that YJSB enhanced liver detoxification and the mechanisms may be partially related to CYP3A4 and CYP1A2 induction.