Stable Acetaldehyde−Protein Adducts as Biomarkers of Alcohol Exposure

Abstract

The consumption of alcoholic beverages has been associated with increased risks of a number of chronic disorders including cancers. It is still not clear whether ethyl alcohol or other components such as metabolites are directly involved in the carcinogenic process or whether the effects are due to the modulation of metabolism of other carcinogens. At present, there is no good biomarker of alcohol intake, particularly at low or moderate levels of consumption. A number of studies have shown the ability of the major metabolite acetaldehyde to react with proteins in vitro to give stable and unstable adducts. The interaction of acetaldehyde with model peptides, which correspond to N-terminal globin sequences, was studied. The major stable adduct was identified by mass spectrometry and NMR as a diastereoisomeric mixture of imidazolidinones. This is believed to be formed by reaction and cyclization of the initial Schiff base adduct with the N-terminal valine. Incubation of human globin with acetaldehyde (0-2 mM) yielded products which were identified as the N-terminal adducts by electrospray ionization mass spectrometry (ESI-MS) of proteolytic digests. The specificity and sensitivity of the analysis was improved by the use of on-line HPLC-ESI-MS. Tryptic digests of the modified globin which contained both the N-terminal acetaldehyde adducts of alpha-globin (heptapeptide) and beta-globin (octapeptide) were resolved. These results suggest that analysis of stable imidazolidinone adducts is a promising approach to estimation of alcohol exposure.

Novel lipid hydroperoxide‐derived hemoglobin histidine adducts as biomarkers of oxidative stress

“…There appears to be a fine balance between internal cyclization of aldehyde‐derived protein adducts,13, 14 intramolecular reactions with adjacent nucleophiles as observed in histone H4,38–40, and intermolecular cross‐linking reactions that are observed with HNE 41, 42. In studies with model peptides derived from hemoglobin, Conduah Birt et al 43 demonstrated that with monofunctional aldehydic electrophiles such as acetaldehyde, the major products arose from Schiff base formation at the N‐terminal valine residue. However, the α,β ‐unsaturated aldehyde that is present in 4‐ONE significantly alters regioselectivity of the reaction with nucleophilic amino acid residues.…”

Hapten–protein binding: from theory to practical application in the in vitro prediction of skin sensitization

“…Since those first attempts, a number of studies have been conducted on the subject of protein haptenation in an effort to detect, characterize and quantify the process. Although not always related to skin sensitization, these studies have nevertheless achieved important milestones in our understanding of protein haptenation mechanisms (22–29). Over recent years, methodology applied to characterize protein–hapten binding has improved substantially, including immunochemistry, nuclear magnetic resonance (NMR) and mass spectrometry.…”

“…Peptides with sequences analogous to a part of human proteins are also used to assess chemical reactivity. DS3 peptide, which has a sequence analogous to the N‐terminal part of the human globin (sequence VLSPADKTNWGHEYRMFCQIG), was used to investigate binding of 4‐chlorobenzenediazonium hexafluorophosphate (27), acetaldehyde (24) and 5‐chloro‐2‐methylisothiazol‐3‐one (44). Glycine apart, this peptide contains 1 residue of each of the commonly occurring amino acids.…”

Evaluation of the Effect of Ethanol’s Toxic Metabolite Acetaldehyde on the Gastrointestinal Oligopeptide Transporter, PEPT1: In Vitro and in Vivo Studies

“…Acetaldehyde is a highly reactive metabolite implicated in causing cytotoxicity by binding tissue macromolecules and disrupting cellular functions (Lieber, 1997) through selective modification of amino acid residues resulting in the formation of stable adducts. At the molecular level, AcH reversibly binds to amino acid residues and N‐terminus of proteins, including hemoglobin and albumin (Brandsch et al., 2004; Conduah Birt et al., 1998; Hecht et al., 2001; Niemela et al., 1991; Wickramasinghe et al., 1994; Zhang et al., 2002). Furthermore, AcH adducts have been shown to increase paracellular permeability in vitro (Rao, 1998) by reversibly disrupting epithelial tight junctions (Atkinson and Rao, 2001), altering cellular differentiation and adhesion (Koivisto and Salaspuro, 1998), and attaching to plasma thrombin protein binding sites, thereby inactivating coagulation factors (Brecher and Adamu, 2002).…”