Figure 5.

Transforming growth factor beta (TGF-β)-stimulated activation of p38, but not of Smad, was inhibited by fluoroquinolones (FQs). Cultured A549 and HepG2 cells were serum-deprived for 24 h before growth factor stimulation. A549 (A–D) and HepG2 (C) cells were incubated in the presence of 20 μM ciprofloxacin (A) or clinafloxacin (B,C) for 30 min before incubation with 200 pM TGF-β for the indicated times. Smad2/3 and p38 phosphorylations were determined by Western blotting. Phosphorylated protein levels of the indicated experimental groups were quantified as a percentage relative to the level of the control experiments. Data are representative of at least three independent experiments (right-hand panel; * p ≤ 0.05, ** p ≤ 0.01). (D) Because the maximal stimulation of p38 activation by TGF-β is approximately 30 min, A549 cells were treated with 200 pM TGF-β in the absence or presence of the indicated concentrations of clinafloxacin for 30 min, and Smad2/3 and p38 phosphorylation were determined by Western blotting as described in (A). Phosphorylated protein levels of the indicated experimental groups were quantified as a percentage relative to the level of TGF-β-treated cells (right-hand graphs; ** p ≤ 0.01).