Nicotine augments LPS-induced pro-MMP-9 release from differentiated HL-60 cells in a dose- and α7nAChR-dependent manner. (A) Gelatin Zymography: A representative gelatin zymogram shows increased pro-MMP-9 (92 kDa) activity in the cell-free media (corresponding to 10,000 cells) of five-day DMSO-differentiated HL-60 cells stimulated with LPS (1.0 μg ml-1) plus nicotine (10-4 M, Lane 2); compared to LPS alone (Lane 1). Nicotine-induced augmentation of LPS-induced MMP-9 activity is abrogated by pre-incubation of DMSO-differentiated HL-60 cells with an α7-type nAChR inhibitor (α-bungarotoxin, 200 ng ml-1, Lane 3). (B) Relative fold increases (mean, s.d.) in MMP-9 gelatinolytic activity were quantified by densitometry (n= 5, * p < 0.05, ¶ p < 0.01). Error bars represent standard deviations of the mean.