This article is available online at http://dmd.aspetjournals.org
ABSTRACT:In this study, we investigated the possible involvement of acylCoA, reactive intermediary metabolites of 2-arylpropionic acids (profens), in protein adduct formation in rat liver homogenate and in human serum albumin ( 2-Arylpropionic acids (profens) are a commonly used class of nonsteroidal anti-inflammatory drugs, widely prescribed as analgesic, antipyretic, and anti-inflammatory agents. Conjugation with glucuronic acid is a major route for the biotransformation and elimination of profen drugs, such as ibuprofen, carprofen, fenoprofen, and naproxen (Spahn-Langguth et al., 1997). Studies have shown that these acyl-linked glucuronides are chemically reactive species that undergo hydrolysis to regenerate the pharmacologically active parent drug and that also undergo intramolecular acyl migration to yield -glucuronidase-resistant isomers (Spahn-Langguth and Benet, 1992;Spahn-Langguth et al., 1997;. More importantly, these electrophilic metabolites have been shown to bind covalently to serum albumins in vitro and to plasma and tissue proteins in vivo (Spahn-Langguth and Benet, 1992;; and, therefore, metabolic activation of profen drugs by acyl glucuronidation has been proposed as a metabolic route to mediate the idiosyncratic liver toxicity associated with the use of profen drugs (Boelsterli et al., 1995).Another metabolic route of profen drugs is the acyl-CoA thioester pathway, recently recognized also as yielding reactive metabolites of acidic drugs. Sallustio et al. (2000) demonstrated that covalent binding of nafenopin to human liver proteins is directly associated with formation of a nafenopin acyl-CoA thioester intermediate. A number of studies on protein fatty acylation have shown that endogenous acyl-CoAs, including palmitoyl-CoA and arachidonoyl-CoA, can react nonenzymatically with sulfhydryl groups on proteins and peptides in vitro in a time-and concentration-dependent fashion (Bharadwaj and Bizzozero, 1995;Duncan and Gilman, 1996). Our recent studies with 2-phenylpropionic acid (2-PPA 3 ) demonstrated that 2-phenylpropionyl-S-acyl-CoA (2-PPA-CoA) was able to acylate glutathione sulfhydryl to form 2-PPA-S-acyl-glutathione at a rate that was approximately 70-fold more rapid than the similar reactions with 2-PPA-1-O-acyl glucuronides . The present study was designed to examine the covalent binding of 2-PPA-CoA to human serum albumin and rat liver homogenate in vitro. 2-PPA was chosen because it is the simplest congener of profen drugs and is capable of forming 2-PPA-CoA, as inferred from the unidirectional chiral inversion of 2-PPA in vivo (Fournel and Caldwell, 1986). Results from these in vitro studies strongly suggest that acyl-CoA thioesters of profen drugs are chemically reactive electrophiles and are able to bind covalently to tissue proteins in vitro, which may, therefore, contribute significantly to covalent adduct formation of profen drugs in vivo, in addition to acyl glucuronides.
Materials and Methods
Materials. (R)-(Ϫ)-
