Fig. 3

Nicotine Stimulates the Proliferation of Lung Fibroblasts via α7 nAChR-mediated Induction of ERK. a Lung fibroblasts were cultured for up to 72 h after transfection with control (Csi) or α7 nAChR siRNAs (α7si). Silencing of α7 nAChR was confirmed with Western blot (not shown). At the appropriate times, the experiment was halted and live cells counted. Nicotine stimulated cell proliferation at 48 and 72 h, while α7 nAChR siRNA inhibited the nicotine-induced response at 48 and 72 h when compared to nicotine-treated control cells. b Fibroblasts were cultured for up to 72 h with or without nicotine (50 μg/ml) in the presence or absence of PD98059 (MI, 50 μM), an inhibitor of MEK-1. Cell number was determined with the use of a Neubauer hemacytometer along with trypan blue stain. Cell viability was unchanged with treatment (Not Shown). Note that nicotine stimulated fibroblast proliferation at 48 h, but the effect was most noticeable at 72 h. The inhibitor PD98095 alone did not affect the proliferation of cells, but inhibited the stimulatory effect of nicotine. Experiments were repeated at least 3 times. Significance was assessed using p values <0.05 obtained by 2-way ANOVA with Bonferroni posttest