Metabolism of bis(4-fluorobenzyl)trisulfide and its formation of hemoglobin adduct in rat erythrocytes

摘要

Bis(4-fluorobenzyl)trisulfide (BFBTS) is a promising new antitumor agent under investigation. It was metabolized rapidly in vivo in rat, but the metabolic fate and primary site of metabolism have not been clarified. In this study, we investigated the role of blood in the metabolism of BFBTS and compared the BFBTS metabolic potencies in whole blood, plasma, and red blood cells (RBCs) in vitro. Three major metabolites of BFBTS [bis(4-fluorobenzyl) disulfide, para-fluorobenzyl-mercaptan, and para-fluorobenzoic acid] were detected in RBCs and whole blood. Significant metabolism of BFBTS was observed in RBCs that were identified as the primary site of BFBTS metabolism. Thiols, including endogenous thiols and hemoglobin, were proven to be the critical factor in BFBTS metabolism. S-Fluorobenzylmercaptocysteine Hb (hemoglobin) adducts were characterized in vitro at BFBTS concentration of 250 mM and higher, whereas such Hb adducts were not detected in RBCs from Sprague-Dawley rats receiving a single intravenous injection of BFBTS at a high dose of 50 mg/kg. Liquid chromatography-tandem mass spectrometry results revealed that adduction induced by BFBTS was prone to take place at Cys125 of globin b chains. Otherwise, glutathionylation of Hb was also observed that may be attributed to the oxidative effect of BFBTS. In summary, BFBTS was unstable when it met with thiols, and RBCs were the main site of BFBTS metabolism. Hb adducts induced by BFBTS could be detected in vitro at high concentration but not in vivo even at high dose.