ERYTHROCYTE ENZYMES CATALYZE 1-NITROPYRENE AND 3-NITROFLUORANTHENE NITROREDUCTION

Nitroarenes are environmental contaminants produced during incomplete combustion processes. Nitroreduction, the most important pathway of ni troarene toxification, occurs mainly in the liver and intestine. In th e present study, we show that human red cells may also possess the met abolic competence to reduce I-nitropyrene (NP) and 3-nitrofluoranthene (NF), the nitroarenes chosen as model compounds, to their correspondi ng amino derivatives, 1-aminopyrene (AP) and 3-aminofluoranthene (AF). The requirement of the cofactor couple NADH/FMN suggests that erythro cyte nitroreductase activity occurs via one electron transfer. The pre sence of oxygen strongly inhibited the haemolysate-catalyzed nitroaren e reduction, whether measured as amine formation or nitroarene disappe arance. Intermediate reactive species, that bind covalently to haemogl obin and/or other erythrocyte proteins, are formed during nitroreducti on catalyzed by human haemolysate. In fact, the reduced metabolites AP and AF were released after mild acid hydrolysis of red cell proteins exposed to NP and NF, thus suggesting that sulphinamide adducts have b een formed.