LPS-induced ENO-1 cell-surface expression results in increased plasmin generation at the cell surface of U937 cells and human blood monocytes. (A) U937 cells (■) or human blood monocytes (□) exposed to 5 μg/mL LPS for 6 hours, as well as unstimulated cells, were preincubated with 15 μM Lys-PLG for 1 hour at 37°C followed by addition of 3 nM t-PA, as indicated. Plasmin proteolytic activity was followed as the conversion of the chromogenic substrate S-2251 (0.5 mM) at 405 nm. Data represent mean values ± SD from 4 independent experiments, each performed in quintuplicate, **P < .01; ***P < .001. (B) U937 cells (■) or human blood monocytes (□) exposed to 5 μg/mL LPS for 6 hours as well as unstimulated cells were preincubated with 15 μM Lys-PLG in the absence (−) or presence of an anti–ENO-1 neutralizing antibody (10 μg/mL), IgG control (10 μg/mL), tranexamic acid (TXA; 10 mM), or α2PI (30 μM). Afterward, 3 nM t-PA and 0.5 mM chromogenic substrate S-2251 were added. Plasmin proteolytic activity was followed as the conversion of the S-2251 substrate at 405 nm. Data represent mean values ± SD from 4 independent experiments, each performed in quintuplicate; *P < .05; **P < .01; ***P < .001.
