Objective To investigate the metabolism of strychnine(STN)and the metabolic interaction between STN and glycyrrhetic acid(GA)in vitro.Methods Human liver microsomes(HLM)and human recombinant cytochrome P450(CYP)isofor...Objective To investigate the metabolism of strychnine(STN)and the metabolic interaction between STN and glycyrrhetic acid(GA)in vitro.Methods Human liver microsomes(HLM)and human recombinant cytochrome P450(CYP)isoforms were employed to study the metabolism of STN and the metabolic interaction of STN with GA in vitro.Results In HLM,the Km,Vmax,and clearance of STN were 88.50μmol/L,0.88 nmol/(mg·min),and 9.93 mL/(mg·min),respectively.STN was metabolized mainly by CYP3A4.However,STN noncompetitively inhibited CYP3A4-catalyzed testosterone 6β-hydroxylation with IC50 value of 5.9μmol/L and Ki value of 5.5 μmol/L.Moreover,GA competitively inhibited STN metabolism with IC50 value of 10.6μmol/L and Ki value of 17.7μmol/L.Conclusion Although STN is mainly metabolized by CYP3A4 in vitro,STN has noncompetitive inhibition on CYP3A4-catalyzed testosterone 6β-hydroxylation.Moreover,GA could competitively inhibit STN metabolism.The present work is helpful to elucidate the metabolic interaction between STN and GA.展开更多
In the present study, the potential inhibition behaviors of notoginseng total saponins(NS), safflower total flavonoids(SF), and their combination(CNS) towards three major isoforms of UDP-glucuronosyltransferases(UGTs)...In the present study, the potential inhibition behaviors of notoginseng total saponins(NS), safflower total flavonoids(SF), and their combination(CNS) towards three major isoforms of UDP-glucuronosyltransferases(UGTs) in human liver microsomes(HLMs) were investigated to study the mechanism of the synergistic effect of CNS.Etoposide, trifluoperazine and azidothymidine were selected as the probe drugs to elucidate the activities of UGT1A1, 1A4 and 2B7 by UPLC-MS/MS method, respectively.The results showed that CNS, NS and SF significantly inhibited the activities of UGT1A1, 1A4 and 2B7(P<0.05) with the IC_(50) values less than 30 mg/mL.Furthermore, the inhibitory effects of CNS towards UGT1A1, 1A4 and 2B7 were stronger than those of NS and SF(P<0.05).In conclusion, the combination of NS and SF could increase their inhibitory effects on UGT1A1, 1A4 and 2B7 activities in HLMs and might be conducive to reduce the phase II metabolism of the effective constituents in CNS.The potential herb-drug interactions of CNS based on UGT enzymes provided a useful experimental basis for its further research and development.展开更多
Background: T-2 toxin poses a great threat to human health because it has the highest toxicity of the currently known trichothecene mycotoxins. To understand the in vivo toxicity and transformation mechanism of T-2 to...Background: T-2 toxin poses a great threat to human health because it has the highest toxicity of the currently known trichothecene mycotoxins. To understand the in vivo toxicity and transformation mechanism of T-2 toxin, we investigated the role of two principal phase Ⅰ drug-metabolizing enzymes(cytochrome P450 [CYP450] enzymes) on the metabolism of T-2 toxin, which are crucial to the metabolism of endogenous substances and xenobiotics. We also investigated carboxylesterase, which also plays an important role in the metabolism of toxic substances.Methods: A chemical inhibition method and a recombinant method were employed to investigate the metabolism of the T-2 toxin by the CYP450 enzymes, and a chemical inhibition method was used to study carboxylesterase metabolism. Samples incubated with human liver microsomes were analyzed by high performance liquid chromatography-triple quadrupole mass spectrometry(HPLC- Qq Q MS) after a simple pretreatment.Results: In the presence of a carboxylesterase inhibitor, only 20% T-2 toxin was metabolized. When CYP enzyme inhibitors and a carboxylesterase inhibitor were both present, only 3% of the T-2 toxin was metabolized. The contributions of the CYP450 enzyme family to T-2 toxin metabolism followed the descending order CYP3A4, CYP2E1, CYP1A2, CYP2B6 or CYP2D6 or CYP2C19.Conclusions: Carboxylesterase and CYP450 enzymes are of great importance in T-2 toxin metabolism, in which carboxylesterase is predominant and CYP450 has a subordinate role. CYP3A4 is the principal member of the CYP450 enzyme family responsible for T-2 toxin metabolism. The metabolite produced by carboxylesterase is HT-2, and the metabolite produced by CYP 3A4 is 3'-OH T-2. The different metabolites show different toxicities. Our results will provide useful data concerning the toxic mechanism, the safety evaluation, and the health risk assessment of T-2 toxin.展开更多
基金National Natural Science Foundation of China (30630075)
文摘Objective To investigate the metabolism of strychnine(STN)and the metabolic interaction between STN and glycyrrhetic acid(GA)in vitro.Methods Human liver microsomes(HLM)and human recombinant cytochrome P450(CYP)isoforms were employed to study the metabolism of STN and the metabolic interaction of STN with GA in vitro.Results In HLM,the Km,Vmax,and clearance of STN were 88.50μmol/L,0.88 nmol/(mg·min),and 9.93 mL/(mg·min),respectively.STN was metabolized mainly by CYP3A4.However,STN noncompetitively inhibited CYP3A4-catalyzed testosterone 6β-hydroxylation with IC50 value of 5.9μmol/L and Ki value of 5.5 μmol/L.Moreover,GA competitively inhibited STN metabolism with IC50 value of 10.6μmol/L and Ki value of 17.7μmol/L.Conclusion Although STN is mainly metabolized by CYP3A4 in vitro,STN has noncompetitive inhibition on CYP3A4-catalyzed testosterone 6β-hydroxylation.Moreover,GA could competitively inhibit STN metabolism.The present work is helpful to elucidate the metabolic interaction between STN and GA.
基金National Natural Science Foundation of China(Grant No.81573684)National Key Technology R&D Program "New Drug Innovation" of China(Grant No.2018ZX09711001-008-003)Beijing Municipal Science and Technology Project(Grant No.Z181100002218028)
文摘In the present study, the potential inhibition behaviors of notoginseng total saponins(NS), safflower total flavonoids(SF), and their combination(CNS) towards three major isoforms of UDP-glucuronosyltransferases(UGTs) in human liver microsomes(HLMs) were investigated to study the mechanism of the synergistic effect of CNS.Etoposide, trifluoperazine and azidothymidine were selected as the probe drugs to elucidate the activities of UGT1A1, 1A4 and 2B7 by UPLC-MS/MS method, respectively.The results showed that CNS, NS and SF significantly inhibited the activities of UGT1A1, 1A4 and 2B7(P<0.05) with the IC_(50) values less than 30 mg/mL.Furthermore, the inhibitory effects of CNS towards UGT1A1, 1A4 and 2B7 were stronger than those of NS and SF(P<0.05).In conclusion, the combination of NS and SF could increase their inhibitory effects on UGT1A1, 1A4 and 2B7 activities in HLMs and might be conducive to reduce the phase II metabolism of the effective constituents in CNS.The potential herb-drug interactions of CNS based on UGT enzymes provided a useful experimental basis for its further research and development.
基金supported by the Key Projects in the National Science & Technology Pillar Program of China (2011BAK10B07)the National Major Special Projects in the Ministry of Science and Technology of China (2012 2X09301003-001-010)
文摘Background: T-2 toxin poses a great threat to human health because it has the highest toxicity of the currently known trichothecene mycotoxins. To understand the in vivo toxicity and transformation mechanism of T-2 toxin, we investigated the role of two principal phase Ⅰ drug-metabolizing enzymes(cytochrome P450 [CYP450] enzymes) on the metabolism of T-2 toxin, which are crucial to the metabolism of endogenous substances and xenobiotics. We also investigated carboxylesterase, which also plays an important role in the metabolism of toxic substances.Methods: A chemical inhibition method and a recombinant method were employed to investigate the metabolism of the T-2 toxin by the CYP450 enzymes, and a chemical inhibition method was used to study carboxylesterase metabolism. Samples incubated with human liver microsomes were analyzed by high performance liquid chromatography-triple quadrupole mass spectrometry(HPLC- Qq Q MS) after a simple pretreatment.Results: In the presence of a carboxylesterase inhibitor, only 20% T-2 toxin was metabolized. When CYP enzyme inhibitors and a carboxylesterase inhibitor were both present, only 3% of the T-2 toxin was metabolized. The contributions of the CYP450 enzyme family to T-2 toxin metabolism followed the descending order CYP3A4, CYP2E1, CYP1A2, CYP2B6 or CYP2D6 or CYP2C19.Conclusions: Carboxylesterase and CYP450 enzymes are of great importance in T-2 toxin metabolism, in which carboxylesterase is predominant and CYP450 has a subordinate role. CYP3A4 is the principal member of the CYP450 enzyme family responsible for T-2 toxin metabolism. The metabolite produced by carboxylesterase is HT-2, and the metabolite produced by CYP 3A4 is 3'-OH T-2. The different metabolites show different toxicities. Our results will provide useful data concerning the toxic mechanism, the safety evaluation, and the health risk assessment of T-2 toxin.
