Increased Ccl3, Ccl11, and activity of Mmp13 in BAL fluid after instillation with MWCNTs. ELISA analysis was performed in the BAL fluid of vehicle, 1 mg/kg, 2 mg/kg, and 4 mg/kg MWCNT instilled C57BL/6 mice for chemokines (A) Ccl3 and (B) Ccl11. Collagenase activity in the BAL fluid of vehicle control (10% surfactant in saline) and MWCNT instilled mice was measured using SensoLyte® Mmp13 Assay Kit. (C) The relative fluorescence units (RFUs) and (D) the reaction velocity of Mmp13 were dose-dependent increased 30 days post-MWCNT instillation. The mean ± SEM of six mice per group are shown, # p < 0.05 and ## p < 0.01 compared with the vehicle control mice.