RT Journal Article
SR Electronic
T1 Characterization of Phase I Metabolism of Resibufogenin and Evaluation of the Metabolic Effects on Its Antitumor Activity and Toxicity
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 299
OP 308
DO 10.1124/dmd.114.060996
VO 43
IS 3
A1 Jing Ning
A1 Zhen-Long Yu
A1 Liang-Hai Hu
A1 Chao Wang
A1 Xiao-Kui Huo
A1 Sa Deng
A1 Jie Hou
A1 Jing-Jing Wu
A1 Guang-Bo Ge
A1 Xiao-Chi Ma
A1 Ling Yang
YR 2015
UL http://dmd.aspetjournals.org/content/43/3/299.abstract
AB Resibufogenin (RB), one of the major active compounds of the traditional Chinese medicine Chansu, has displayed great potential as a chemotherapeutic agent in oncology. However, it is a digoxin-like compound that also exhibits extremely cardiotoxic effects. The present study aimed to characterize the metabolic behaviors of RB in humans as well as to evaluate the metabolic effects on its bioactivity and toxicity. The phase I metabolic profile in human liver microsomes was characterized systemically, and the major metabolite was identified as marinobufagenin (5β-hydroxylresibufogenin, 5-HRB) by liquid chromatography–mass spectrometry and nuclear magnetic imaging techniques. Both cytochrome P450 (P450) reaction phenotyping and inhibition assays using P450-selective chemical inhibitors demonstrated that CYP3A4 was mainly involved in RB 5β-hydroxylation with much higher selectivity than CYP3A5. Kinetic characterization demonstrated that RB 5β-hydroxylation in both human liver microsomes and human recombinant CYP3A4 obeyed biphasic kinetics and displayed similar apparent kinetic parameters. Furthermore, 5-HRB could significantly induce cell growth inhibition and apoptosis in A549 and H1299 by facilitating apoptosome assembly and caspase activation. Meanwhile, 5-HRB displayed very weak cytotoxicity of human embryonic lung fibroblasts, and in mice there was a greater tolerance to acute toxicity. In summary, CYP3A4 dominantly mediated 5β-hydroxylation and was found to be a major metabolic pathway of RB in the human liver, whereas its major metabolite (5-HRB) displayed better druglikeness than its parent compound RB. Our findings lay a solid foundation for RB metabolism studies in humans and encourage further research on the bioactive metabolite of RB.