N‐terminal valine adduct from the anti‐HIV drug abacavir in rat haemoglobin as evidence for abacavir metabolism to a reactive aldehyde in vivo

Abstract

BACKGROUND AND PURPOSEThe aim of this study was to obtain evidence for the activation of the nucleoside reverse transcriptase inhibitor abacavir to reactive aldehyde metabolites in vivo. Protein haptenation by these reactive metabolites may be a factor in abacavir-induced toxic events. EXPERIMENTAL APPROACHThe formation of N-terminal valine adducts from the abacavir-derived aldehydes was investigated in the haemoglobin of Wistar rats treated with eight daily doses (120 mg·kg -1 ) of abacavir. The analyses were conducted by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry upon comparison with synthetic standards. KEY RESULTSAn N-terminal valine haemoglobin adduct derived from an a,b-unsaturated aldehyde metabolite of abacavir was identified in vivo for the first time. CONCLUSIONS AND IMPLICATIONSThis preliminary work on abacavir metabolism provides the first unequivocal evidence for the formation of an a,b-unsaturated aldehyde metabolite in vivo and of its ability to form haptens with proteins. The methodology described herein can be used to assess the formation of this metabolite in human samples and has the potential to become a valuable pharmacological tool for mechanistic studies of abacavir toxicity. In fact, the simplicity of the method suggests that the abacavir adduct with the N-terminal valine of haemoglobin could be used to investigate abacavir-induced toxicity for accurate risk/benefit estimations.

The importance of hapten–protein complex formation in the development of drug allergy

“…Formation of the carboxylate has been shown to proceed through a two-step oxidation process, via a reactive aldehyde intermediate. Hapten-protein complex formation has been studied using HSA, GSTP and haemoglobin, and abacavir-protein complexes have been identified in patients [59][60][61]. However, the role of these complexes in the development of drug allergy is unclear.…”

Quo vadis blood protein adductomics?

“… APCI=atmospheric pressure chemical ionization, FITC = fluorescein isothiocyanate, FLD=fluorescence detection, HBFA = heptafluorobutyric anhydride, HRMS=high resolution mass spectrometry, hydr = hydrolysis, NCI=negative chemical ionization, PFPITC = pentafluorophenyl isothiocyanate, PITC = phenylisothiocyanate a Hb b globin c (Gries and Leng 2013 ) CAS:264285-90-7 d (Sachse et al 2017 ) CAS:1531625-56-5 e (Hielscher et al 2017 ) CAS:133278-70-3; e1) (Müller 2013 ) f (von Stedingk et al 2010 ) CAS:252663-74-4; f1) (Yang et al 2018 ); f2) (Schettgen et al 2016 ) g (Yang et al 2018 ) CAS:21768-51-4 h CAS:51078-53-6 i CAS:51078-49-0 j (Carlsson et al 2015 ), only the FITC derivative has a CAS number k (Lewalter et al 2012 ) CAS:15363-84-5 l (Bader et al 2013 ) CAS:223443-77-4 m (von Stedingk et al 2014 ), N -[2-(2-oxo-3-oxazolidinyl)ethyl]-L-valine CAS:173962-82-8 n (CDC-NHANES 2020 ) N-terminal peptide (VHLTPEEK) of the ß-Hb-chain: N-(Hydroxymethyl)-VHLTPEEK (CAS:1307263-38-2), also the terminal amino acids of the α-Hb-chain was reported but not quantified in the CDC-NHANES studies, N-(hydroxymethyl)-VLSPADK, CAS:1307263-39-3; n1) (Yang et al 2017 ) o (Charneira et al 2012 ) CAS:1350434-49-9 p (Käfferlein et al 2016 ) CAS:74310-99-9 q CAS:848640-59-5 r (Mráz et al 2006 ) CAS:84860-36-6 s (Xu et al 2014 ) HETE-Val, CAS:190187-17-8 t (Boysen et al 2019 ) CAS:2416700-26-8, main product u (Wheelock et al 2018 ) v (Schutze et al 1995 ) w (Padros and Pelletier 2001 ); * were validated in the German Working Group “Analyses in Biological Materials of the permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work” and the standard operation values are available online ( https://onlinelibrary.wiley.com/doi/book/10.1002/3527600418 ) ** the compounds are commercially available, SciFinder search 23.7.21 …”

Mass Spectrometry-Based Methodologies for Targeted and Untargeted Identification of Protein Covalent Adducts (Adductomics): Current Status and Challenges

“…The identification and quantification of adducts formed with N -terminal Val of Hb for biomonitoring proposes are based on a modified Edman procedure in which adducted N -terminal Val are specifically detached as hydantoins, upon reaction with an isothiocyanate. The demonstration of the in vivo bioactivation of the anti-HIV drugs nevirapine and abacavir to reactive metabolites [36,37,38] and the studies on the occupational and environmental exposures to ethylene oxide, acrylamide and acrylonitrile [39,40,41,42], are among the most significative applications of the targeted version of this methodology. Törnqvist’s group led the development of this approach and the shift to untargeted adductomics was possible with the use of fluorescein isothiocyanate (FITC), as the derivatizing agent [43].…”