Pathways to Identify Electrophiles In Vivo Using Hemoglobin Adducts: Hydroxypropanoic Acid Valine Adduct and Its Possible Precursors

Abstract

Analytical methods and tools for the characterization of the human exposome by untargeted mass spectrometry approaches are advancing rapidly. Adductomics methods have been developed for untargeted screening of short-lived electrophiles, in the form of adducts to proteins or DNA, in vivo. The identification of an adduct and its precursor electrophile in the blood is more complex than that of stable chemicals. The present work aims to illustrate procedures for the identification of an adduct to N-terminal valine in hemoglobin detected with adductomics, and pathways for the tracing of its precursor and possible exposure sources. Identification of the adduct proceeded via preparation and characterization of standards of adduct analytes. Possible precursor(s) and exposure sources were investigated by measurements in blood of adduct formation by precursors in vitro and adduct levels in vivo. The adduct was identified as hydroxypropanoic acid valine (HPA-Val) by verification with a synthesized reference. The HPA-Val was measured together with other adducts (from acrylamide, glycidamide, glycidol, and acrylic acid) in human blood (n = 51, schoolchildren). The HPA-Val levels ranged between 6 and 76 pmol/g hemoglobin. The analysis of reference samples from humans and rodents showed that the HPA-Val adduct was observed in all studied samples. No correlation of the HPA-Val level with the other studied adducts was observed in humans, nor was an increase in tobacco smokers observed. A small increase was observed in rodents exposed to glycidol. The formation of the HPA-Val adduct upon incubation of blood with glycidic acid (an epoxide) was shown. The relatively high adduct levels observed in vivo in relation to the measured reactivity of the epoxide, and the fact that the epoxide is not described as naturally occurring, suggest that glycidic acid is not the only precursor of the HPA-Val adduct identified in vivo. Another endogenous electrophile is suspected to contribute to the in vivo HPA-Val adduct level.

A comparison of the exposure system of glycidol‐related chemicals on the formation of glycidol‐hemoglobin adducts

“…Other Hb adducts have been identified from substances other than glycidol, including ethylene oxide, glyoxal, methyl vinyl ketone, acrylamide, acrylic acid, methyl glyoxal, ethyl vinyl ketone, glycidamide (Carlsson et al., 2019 ), and furfuryl alcohol (Monien et al., 2021 ). Glycidol administration to mice or rats resulted in the formation of a hydroxypropanoic acid valine adduct ( m/z 577) from glycidic acid, a minor metabolite of glycidol (Vryonidis et al., 2022 ). Furthermore, our previous study showed that acrylamide or glucose can affect the formation of diHOPrVal (Shimamura et al., 2022 ).…”

Mass Spectrometry-Based Strategies for Assessing Human Exposure Using Hemoglobin Adductomics

“…Acrylic acid is used in several industrial applications and can also be produced by the Maillard reaction; it has also been seen to form adducts in hemoglobin . While glycidic acid is not known to be an environmental contaminant, it is believed to be a precursor of a hydroxypropanoic acid adduct observed in human hemoglobin samples …”

“…33 While glycidic acid is not known to be an environmental contaminant, it is believed to be a precursor of a hydroxypropanoic acid adduct observed in human hemoglobin samples. 34 The other electrophiles used in this study were chosen due to their documented status as contact allergens, which can induce allergic contact dermatitis (ACD) with repeated exposure. These contact allergens can act as haptens and trigger an immune response when they combine with a carrier protein which the immune system recognizes as "altered self".…”

“… 33 While glycidic acid is not known to be an environmental contaminant, it is believed to be a precursor of a hydroxypropanoic acid adduct observed in human hemoglobin samples. 34 …”