Reaction of nitroso derivatives of dinitropyrenes with sulfhydryl groups of peptides and hemoglobin in vitro and in rats

Abstract

Diesel engine emissions have been classified as a potential human carcinogen and may cause a variety of other health effects. Human exposure to diesel engine emissions is highly variable within the population. Therefore, specific methods for the biomonitoring of human exposure to diesel engine emissions are required for exposure assessment within epidemiological studies. Haemoglobin adducts of dinitropyrenes may serve as biomarkers for human exposures to diesel engine emissions.

To characterize structures of dinitropyrene reaction products with sulfhydryl groups, glutathione was used to trap electrophilic nitroso intermediates formed from dinitropyrenes and glutathione S-conjugates were identified and characterized by Qtrap techniques using (HPLC-MS/MS) high-performance liquid chromatography coupled to triple quadrupole mass spectrometry. Nitrosonitropyrene-derived sulfinamides, sulfenamides and glutathione thioethers bound to carbon atoms in the aromatic ring, presumably formed by a rearrangement of intermediate sulfenamide cations, were formed in low yields.

In haemoglobin from rats orally administered dinitropyrenes, mild alkaline hydrolysis of haemoglobin released aminonitropyrenes, which were identified by HPLC-MS/MS.

The results demonstrate that dinitropyrenes undergo nitroreduction in rats and that the intermediate nitrosonitropyrenes bind to heamoglobin. The haemoglobin adducts formed from dinitropyrenes seem, in contrast to previous studies, to be hydrolysable and thus represent sulfen- and sulfinamides derived from the intermediate nitrosonitropyrenes.

The developed Qtrap methods to detect and characterize glutathione S-conjugates rapidly may have wide applications in attempts to characterize reactive intermediates formed in complex mixtures in low concentrations.

Kewords: :

• Diesel engine emissions
• haemoglobin binding
• nitroarenes
• glutathione S-conjugates
• reactive metabolites

Acknowledgements

The authors thank Dr Axel Pähler (F. Hoffmann-La Roche, Basel, Switzerland) for the use of the API 4000 Qtrap system. Work was supported financially by the Forschungsvereinigung Automobiltechnik e.V. (FAT), the Fonds der Chemischen Industrie and the German Scholarship Foundation (Studienstiftung des deutschen Volkes e.V.)