Flavin-containing monooxygenase 3 (FMO3) role in busulphan metabolic pathway

• Published in: PloS one Vol. 12; no. 11; p. e0187294
• Main Authors: El-Serafi, Ibrahim, Terelius, Ylva, Abedi-Valugerdi, Manuchehr, Naughton, Seán, Saghafian, Maryam, Moshfegh, Ali, Mattsson, Jonas, Potácová, Zuzana, Hassan, Moustapha
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 09.11.2017; Public Library of Science (PLoS)
• Subjects: Adolescent; Adult; Alkylation; Analysis; Animals; Antifungal agents; Biocompatibility; Biology and Life Sciences; Bone marrow; Busulfan; Busulfan - metabolism; Cancer therapies; Cell metabolism; Child; Child, Preschool; Conditioning; Cytochrome; Cytochrome P450; Dimethylaniline monooxygenase (N-oxide-forming); Dosage and administration; Drug dosages; Drugs; Enzyme kinetics; Enzymes; Flavin; Flavin adenine dinucleotide; Gene expression; Gene Expression Regulation - drug effects; Glutathione; Glutathione Transferase - genetics; Glutathione Transferase - metabolism; Hematopoietic Stem Cell Transplantation; Humans; Hypotheses; Immunosuppressive agents; In vivo methods and tests; Kinetics; Laboratories; Liver; Male; Medicin och hälsovetenskap; Medicine; Medicine and Health Sciences; Metabolic Networks and Pathways - drug effects; Metabolism; Metabolites; Metabolome - drug effects; Mice; Mice, Inbred C57BL; Microsomes; Microsomes - enzymology; Middle Aged; Oxidation; Oxygenases - antagonists & inhibitors; Oxygenases - genetics; Oxygenases - metabolism; Phenylthiourea; Potassium; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rodents; Stem cell transplantation; Stem cells; Studies; Substrate Specificity - drug effects; Sulfolane; Thiophenes - metabolism; Time Factors; Toxicity; Transplantation; Transplantation Conditioning; Transplants & implants; Treatment outcome; Urine; Voriconazole; Voriconazole - pharmacology; Sweden
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0187294

Busulphan (Bu) is an alkylating agent used in the conditioning regimen prior to hematopoietic stem cell transplantation (HSCT). Bu is extensively metabolized in the liver via conjugations with glutathione to form the intermediate metabolite (sulfonium ion) which subsequently is degraded to tetrahydrothiophene (THT). THT was reported to be oxidized forming THT-1-oxide that is further oxidized to sulfolane and finally 3-hydroxysulfolane. However, the underlying mechanisms for the formation of these metabolites remain poorly understood. In the present study, we performed in vitro and in vivo investigations to elucidate the involvement of flavin-containing monooxygenase-3 (FMO3) and cytochrome P450 enzymes (CYPs) in Bu metabolic pathway. Rapid clearance of THT was observed when incubated with human liver microsomes. Furthermore, among different recombinant microsomal enzymes, the highest intrinsic clearance for THT was obtained via FMO3 followed by several CYPs including 2B6, 2C8, 2C9, 2C19, 2E1 and 3A4. In Bu- or THT-treated mice, inhibition of FMO3 by phenylthiourea significantly suppressed the clearance of both Bu and THT. Moreover, the simultaneous administration of a high dose of THT (200μmol/kg) to Bu-treated mice reduced the clearance of Bu. Consistently, in patients undergoing HSCT, repeated administration of Bu resulted in a significant up-regulation of FMO3 and glutathione-S-transfrase -1 (GSTA1) genes. Finally, in a Bu-treated patient, additional treatment with voriconazole (an antimycotic drug known as an FMO3-substrate) significantly altered the Bu clearance. In conclusion, we demonstrate for the first time that FMO3 along with CYPs contribute a major part in busulphan metabolic pathway and certainly can affect its kinetics. The present results have high clinical impact. Furthermore, these findings might be important for reducing the treatment-related toxicity of Bu, through avoiding interaction with other concomitant used drugs during conditioning and hence improving the clinical outcomes of HSCT.