Figure 5.

TGF-β1 activation of PI3K/AKT is dependent on p38 MAPK and protects fibroblasts from apoptosis induced by FasL and cycloheximide. (A) Primary normal adult lung fibroblasts (left panel) and IPF fibroblasts (right panel) were treated with TGF-β1 (2 ng/ml) in the presence/absence of inhibitors of p38 MAPK (SB203580, 6 μM) or ALK5 (SB431542, 1 μM) for 16 hours. AKT phosphorylation was assessed by Western immunoblotting. Membranes were stripped and probed for total AKT. Data shown represent three normal and three IPF fibroblast cell lines. (B) IMR-90 fibroblasts were treated with the combination of FasL (250 ng/ml) and cycloheximide (500 ng/ml) with/without TGF-β1 (2 ng/ml) alone or with an inhibitor of PI3K (LY294002, 10 μM) for 16 hours. Apoptosis was assessed by ELISA for ssDNA, and is normalized to the untreated control.