Figure 4

Suppression of TGF-β1-induced tubulogenesis by a p38 inhibitor. (A-C) J3B1A cells were grown in collagen gels for 6 days and subsequently treated with 50 pg/ml TGF-β1 alone (A), co-treated with TGF-β1 and U0126, an inhibitor of the ERK activators MEK1 and MEK2 (B), or co-treated with TGF-β1 and PD169316, a p38 inhibitor (C), for 4 days. The inhibitors were added two hours before treatment with TGF-β1. Whereas relatively high concentrations (20 μM) of U0126 only attenuate TGF-β1-induced tubulogenesis, PD169316 has a profound inhibitory effect at a concentration as low as 5 μM. Bars, 200 μm. (D) Quantitative analysis of inhibition of tubulogenesis. Data were expressed as mean number of outgrowths per colony ± s.e.m. from at least three separate experiments, and statistical significance was determined using the Student's unpaired t-test. p < 0.01 and p < 0.0005 for values of 5 μM and 10 μM U0126, respectively, compared with cultures incubated with TGF-β1 alone (Ctrl). p < 0.05 and p < 0.0005 for values of 5 μM and 10 μM SP 600125, respectively, compared with cultures incubated with TGF-β1 alone (Ctrl). p < 0.0005 for values of 2 μM PD169316 compared with cultures incubated with TGF-β1 alone (Ctrl).