Screening for protein adducts of naphthalene and chrysene in plasma of exposed Atlantic cod (Gadus morhua)

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are well known contaminants, ubiquitously present in the habitat and spawning areas for Atlantic cod (Gadus morhua). The Atlantic cod is a key species and a globally important food source, thus continuous monitoring of PAHs is considered highly valuable to ensure ecosystem sustainability and human food safety. PAH adducts to plasma proteins are applied as sensitive biomarkers of PAH exposure in humans and other species, thus the presence of PAH protein adducts in Atlantic cod plasma was investigated to identify PAH protein adduct biomarker candidates of exposure to PAHs. Blood plasma samples were collected from Atlantic cod (n = 66) one week after exposure by intramuscular injection of single PAHs (i.e. naphthalene and chrysene), and their corresponding dihydrodiol metabolites (i.e. (-)-(1R,2R)-1,2-dihydronaphthalene-1,2-diol and (-)-(1R,2R)-1,2-dihydrochrysene-1,2-diol). The samples were analyzed by shotgun tandem mass spectrometry (MS) and the resulting MS data were analyzed in Byonic™ to screen for proteins susceptible to adduct formation with naphthalene and chrysene. Furthermore, a wildcard modification search was performed to obtain additional information regarding potential modifications other than the targeted metabolites. The amino acid adductation sites and the metabolites involved in PAH adductation are reported. Forty-four proteins were found to bind PAHs. Alpha-2-macroglobulin-like proteins, apolipoproteins B-100-like proteins and an alpha-2-HS-glycoprotein were detected with the highest number of bound PAHs. This first insight into PAH protein adducts of Atlantic cod plasma generates valuable knowledge for the development of highly sensitive biomarkers of PAH exposure.

Keywords: Atlantic cod; Biomarker; Fish toxicology; Polycyclic aromatic hydrocarbons; Protein adduct; Proteomics.