MMP enzyme activities are elevated in AMs and BAL fluid from Op/Op mice.

BAL fluid and cells were obtained from Op/Op and control mice at 2 months of age and evaluated by zymography. (A) Gelatin zymogram done by using BAL fluid from Op/Op (lanes 1-4) or control (lanes 5-8) mice. Proteolytic activity was elevated in BAL fluid of Op/Op mice at positions corresponding to molecular weights of 92 kd, 72 kd, and 22 kd, which correspond in size to MMP-9, MMP-2, and MMP-12, respectively. All proteolytic activity was inhibited completely by EDTA treatment of gels (not shown). (B) Casein zymogram done by using BAL cell lysates pooled from 4 Op/Op mice (lane 9) or 4 control mice (lane 10) mice. As in the experiment described above, proteolytic activity was inhibited completely by EDTA treatment of gels (not shown). (C) Gelatin zymogram done by using BAL fluid from control mice that received IL-3 or PBS 48 hours before collection. The analyses were done as described above for panel A. Increased proteolytic activity at 92 kd and 72 kd occurred in mice exposed to IL-3 but not in those exposed to PBS. (D) IL-3 stimulation of MMP mRNA transcript levels in murine RAW264.7 macrophages in vitro. Cells were cultured in the absence (lane 15) or presence of IL-3 (100 ng/mL; lane 16) or in the presence of IL-3 and cycloheximide (lane 17) for 3 hours, after which total RNA was isolated and evaluated by RT-PCR using MMP-sequence–specific primers.