PCR-Based Biomolecular Detection

1,3-Butadiene (BD) and trichloroethylene (TCE) are occupational hazards and environmental pollutants that are associated with toxicity and carcinogenicity.

Hydroxymethylvinyl ketone (HMVK) and S-(1,2-dichlorovinyl)-L-cysteine sulfoxide (DCVCS) are Michael acceptor intermediates resulting from bioactivation of BD and TCE, respectively.

Hemoglobin (Hb) adducts were characterized to investigate the presence of these reactive intermediates in the circulation and to help the development of Hb adducts as biomarkers of exposure to BD and TCE.

Hb was also considered a model for how other proteins may interact with these reactive intermediates to gain insights into mechanisms of cellular toxicity.

Initially, we investigated in vitro reactivity of DCVCS and HMVK with nucleophilic amino acids that were used as models for nucleophilic residues of Hb.

HMVK and DCVCS readily formed monoadducts and diadducts that were characterized by nuclear magnetic resonance and mass spectrometry.

A diadduct of N-acetyl-L-cysteine with DCVCS provided evidence for the protein cross-linking potential of DCVCS.

DCVCS exhibited high selectivity towards sulfhydryl groups in comparison with HMVK which also reacted with lysine and N-terminal valine residues.

Potential biomarkers of BD and TCE exposure were identified after both in vitro exposure of rat erythrocytes to HMVK or DCVCS and after in vivo treatment of rats with 3-butene-1,2-diol (BDD) and S-(1,2-dichlorovinyl)-L-cysteine (DCVC), the precursors of HMVK and DCVCS, respectively.

Using trypsin digestion and analysis by liquid chromatography/tandem mass spectrometry, we pinpointed Cys125 of beta chains as the preferred modification site for HMVK after rats were treated with BDD.

After acute and subacute exposure of rats to high and low doses of DCVC for 1-5 days, the presence of DCVCS-derived cross-links rather than monoadducts at different DCVC dosing regimens suggested that cross-links could serve as possible biomarkers of TCE exposure.

Collectively, our results provide evidence that bioactivation pathways that result in HMVK and DCVCS formation occur in vivo after exposure to BDD and DCVC, respectively.

In addition, HMVK and DCVCS formed in the liver may be transported via the circulation to extrahepatic tissues to cause toxicity.