Noninvasive detection of hydroxyl radical generation in lung by diesel exhaust particles

Diesel exhaust particles (DEP) induce pulmonary tumors, asthma-like symptom s, and the like in experimental animals. The involvement of reactive oxygen species (ROS) is suggested in the injuries induced by DEP, though the gene ration of ROS has not been proven. The present study provided the first dir ect evidence of (OH)-O-. generation in the lungs of living mice after intra tracheal instillation of DEP, using noninvasive L-band ESR spectroscopy and a membrane-impermeable nitroxyl probe. (OH)-O-. generation is confirmed wi th the enhancement of in vivo ESR signal decay rate of the probe. The decay rate at mid-thorax was significantly enhanced in DEP-treated mice compared to that in vehicle-treated mice. The enhancement was completely suppressed by the administration of either (OH)-O-. scavengers, catalase, or desferri oxamine, while the administration of SOD further increased the rate. The ad ministration of Fenton's reagents into the lung also enhanced the decay rat e of the probe at mid-thorax of mice. These results clearly provided eviden ce that the intratracheal exposure to DEP in mice produced (OH)-O-. in the lung through an iron-catalyzed reaction of superoxide/H2O2. This first dire ct evidence of (OH)-O-. generation in DEP-treated mice lung may be utilized to determine treatments for DEP-induced lung injury. (C) 2001 Elsevier Sci ence Inc.