Binding of 3‐hydroxybenzo[a]pyrene to bovine hemoglobin and albumin

Abstract

Previous studies examined the bioavailability and first-pass biotransformation of 3-hydroxy[(3)H]benzo[a]pyrene ([(3)H]-3-OHBaP) in an isolated perfused catfish intestinal model. This work showed that 3-OHBaP, or a metabolite formed in intestine, bound covalently to blood protein. In this study, the blood adducts were characterized in vitro by incubating bovine ferric hemoglobin or albumin with [(3)H]-3OHBaP under various conditions. Incubation of 2 microM [(3)H]-3-OHBaP with hemoglobin for 1 h resulted in 7.49 pmol bound/mg protein, while albumin binding was 1.37 pmol/mg protein. Mild acid hydrolysis released only 5% of the radioactivity from 3-OHBaP-hemoglobin adducts. After gel filtration, the 3-OHBaP-hemoglobin adducts were examined by HPLC analysis. A single peak of radioactivity was detected at the same retention time as the heme component of hemoglobin. Unbound 3-OHBaP was oxidized to BaP-3,6-dione during incubation with ferric hemoglobin. Treatment of hemoglobin with ascorbic acid decreased the formation of hemoglobin adducts by 33%, while hydrogen peroxide treatment increased adduct formation by 44%. Incubation of [(3)H]-BaP-3-beta-D-glucuronide (BaP-3G) with hemoglobin and beta-glucuronidase resulted in greater binding to hemoglobin than incubation with [(3)H]-3-OHBaP alone. The hemoglobin adduct obtained from [(3)H]-BaP-3G also co-migrated with heme. These results indicate that an oxidative process is involved in formation of the heme adduct and that 3-OHBaP or BaP-3G might be a precursor of the bound metabolite.

Evaluation of 3-hydroxy-benzo[a]pyrene levels in Nile tilapia (Oreochromis niloticus) after waterborne exposure to Benzo[a]pyrene

“…Some studies evaluated the in vitro 3-OH-BaP effects and showed that low concentrations of 3-OH-BaP (from 8 to 67 ng mL À1 ) may exert estrogenic activity (van Lipzig et al 2005) and form covalent bonds with macromolecules (Moorthy et al 2003;Sugihara and James 2003), leading to adverse consequences at the organism level. Although adverse effects were not assessed and the levels of free 3-OH-BaP measured in plasma (0.4 ng mL À1 ) were lower than concentrations capable of producing toxic effects, as it was quantified in one pooled sample, the levels obtained in our study may have been diluted.…”

Proteomics as a route to identification of toxicity targets in environmental toxicology

“…Pollutant chemicals can react with proteins in a variety of ways including formation of adducts (e.g. benzo [a] pyrene [10]), alteration of phosphorylation status (e.g. phorbol esters and akadoic acid [11]), alteration of thiols (e.g.…”

Olive oil prevents benzo(a)pyrene [B(a)P]-induced colon carcinogenesis through altered B(a)P metabolism and decreased oxidative damage in ApcMin mouse model

“…Pathological changes in target tissues induced by toxicants were associated with production of highly reactive free radicals that ultimately lead to oxidative damage [76]. Studies have explored how B(a)P metabolites bind to DNA and proteins and cause damage as a result of the B(a)P hydroxylase enzymes [77-79]. The antioxidant properties of dietary lipids have proven to be effective in ameliorating the effects of carcinogens by protecting against lipid peroxidation and scavenge oxygen derived free radicals [80].…”