Activity of MMP-12 secreted by ASMC and stimulation by IL-1β. (A) Gelatin zymography detection of activity of MMPs released into the conditioned media by ASMC treated for 48 hours (lane 1, protein markers; lane 2, control; lane 3, 10 ng/ml IL-1β; lane 4, 10 ng/ml TGF-β; lane 5, TGF-β plus IL-1β; lane 6, 10 ng/ml TNF-α; lane 7, TNF-α plus IL-1β; lane 8, 10 ng/ml IL-13). (B) Time-dependent stimulation of MMP-12 activity by 10 ng/ml IL-1β. Lane s, human MMP-12 standard protein used as a positive control. Lane n, negative control. (C) Concentration-dependent stimulation of MMP-12 activity by IL-1β for 48 hours. Relevant band intensities were quantified by scanning densitometric analysis and normalized to 5 × 105 cells. Results are the mean ± SEM from three ASMC donors. *P < 0.05, **P < 0.01 compared with control.