Male A/J mice (10-12 weeks of age; Jackson Laboratories, Bar Harbor, ME) were housed in an environmentally controlled animal facility at the University of Illinois at Chicago (UIC) for the duration of the experiments. All animal procedures follow the guideline of the UIC Animal Care and Use Committee. PM (10 mg/kg, in 50 μl of saline) was delivered via intratracheal aspiration 1 hr after NAC or calpeptin treatment, as previously described [12, 15] . Animals were sacrificed 24 hr after PM treatment, and bronchoalveolar lavage (BAL) and lung tissue were collected [12, 19] . Total BAL cells were counted with a hemocytometer. The BAL fluid was used for protein and cytokine measurement (Bio-Rad, Hercules, CA) according to the user's manual.