Abstract
Covalent protein modifications by electrophilic acyl glucuronide (AG) metabolites are hypothetical causes of hypersensitivity reactions associated with certain carboxylate drugs. The complex rearrangements and reactivities of drug AG have been defined in great detail, and protein adducts of carboxylate drugs, such as diclofenac, have been found in liver and plasma of experimental animals and humans. However, in the absence of definitive molecular characterization, and specifically, identification of signature glycation conjugates retaining the glucuronyl and carboxyl residues, it cannot be assumed any of these adducts is derived uniquely or even fractionally from AG metabolites. We have therefore undertaken targeted mass spectrometric analyses of human serum albumin (HSA) isolated from diclofenac patients to characterize drug-derived structures and, thereby, for the first time, have deconstructed conclusively the pathways of adduct formation from a drug AG and its isomeric rearrangement products in vivo. These analyses were informed by a thorough understanding of the reactions of HSA with diclofenac AG in vitro. HSA from six patients without drug-related hypersensitivities had either a single drug-derived adduct or one of five combinations of 2–8 adducts from among seven diclofenac N-acylations and three AG glycations on seven of the protein’s 59 lysines. Only acylations were found in every patient. We present evidence that HSA modifications by diclofenac in vivo are complicated and variable, that at least a fraction of these modifications are derived from the drug’s AG metabolite, and that albumin adduction is not inevitably a causation of hypersensitivity to carboxylate drugs or a coincidental association.
Footnotes
- Received March 31, 2014.
- Accepted May 29, 2014.
↵1 Current affiliation: Division of Molecular and System Toxicology, Department of Pharmaceutical Sciences, University of Basel, Pharmacenter, Basel, Switzerland.
↵2 Current affiliation: Safety Science Consultant, Macclesfield, United Kingdom.
This work was undertaken principally through a CASE studentship awarded to T.G.H. that was funded by the BBSRC (Integrative Mammalian Biology award) and Safety Assessment U.K., AstraZeneca U.K. Ltd, as part of the Centre for Drug Safety Science supported by the Medical Research Council [Gant G0700654]. X.M. was funded by the NIHR Biomedical Research Centre in Microbial Diseases; S.L.R. by Safety Assessment U.K., AstraZeneca U.K. Ltd; and C.J.E. by the MRC Centre for Drug Safety Science.
Some of the data in this article were published previously in the form of conference abstracts: Hammond T, Regan S, Meng X, Jenkins R, Kenna G, Sathish J, and Williams D (2009) An investigation into the in vitro and in vivo fate of acyl glucuronides. British Pharmacology Society Winter Meeting; 2009 Dec 15–17; London, UK. British Pharmacology Society; http://www.pA2online.org/abstracts/Vol7Issue4abst074P.pdf; Hammond TG, Regan SL, Meng X, Maggs JL, Jenkins RE, Kenna GL, Sathish JG, Williams DP, and Park BK (2010) Protein binding and pharmacokinetics of reactive acyl glucuronide drug metabolites, in Toxicology; 2010 28–31 Mar; Edinburgh, Scotland. Vol 278, pp 357–358, British Toxicology Society Annual Congress; Hammond T, Regan S, Meng X, Berry N, Maggs J, Jenkins R, Kenna G, Sathish J, Williams D, and Park K (2011) In vitro assessment of the interactions between acyl glucuronide drug metabolites and human serum albumin. British Pharmacology Society Winter Meeting; 2010 14–16 Dec; London, UK. British Pharmacology Society; http://www.pA2online.org/abstracts/Vol8Issue1abst019P.pdf; Hammond TG, Regan SL, Meng X, Maggs JL, Jenkins RE, Kenna JG, Sathish JG, Williams DP, and Park BK (2011) In vitro assessment of the interactions between diclofenac and tolmetin acyl glucuronide drug metabolites and human serum albumin, in Toxicology; 2011 27–30 Mar; Durham, UK. Vol 290, pp 40–41. British Toxicology Society Annual Congress.
↵This article has supplemental material available at jpet.aspetjournals.org.
- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics
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