BMDMs were pre-treated with MK-801 (1.0 μM) or vehicle for 30 min and then for 3 h with 12 nM enzymatically-active tPA (EA-tPA), EA-tPA and plasminogen (Plg) (200 nM), Plg, or vehicle. Expression of the mRNAs encoding TNFα, IL-1β, IL-6 and CCL2 was determined (mean ± SEM; n = 6; **p<0.01, ***p<0.001, N.S., not statistically significant; one-way ANOVA with Bonferroni’s post hoc test). In separate control experiments (not shown), we demonstrated that the MK-801 blocked the ability of 12 nM EI-tPA to inhibit cytokine expression induced by LPS (0.1 μg/ml).