Fig. 5.

Effect of a TGFβRI antagonist on TGF-β1- and hypoxia-induced downregulation of PPAR-γ. Quiescent rat PASMCs were pretreated with the ALK5 inhibitor SB431542 (SB, 0.5 μM) for 1 h, then challenged with TGF-β1 (2 ng/ml) for 30 min (A) or 24 h (B). Smad3 phosphorylation (30 min after TGF-β1 treatment) (A) and PPAR-γ protein expression (24 h after TGF-β1 treatment) (B) were detected by Western blot analysis and normalized using α-tubulin as an internal control. C: PASMCs were pretreated with SB431542 (0.5 μM) for 1 h, then exposed to hypoxia (1% O₂) for 24 h. Western blot of PPAR-γ protein was normalized using α-tubulin. Results are means ± SE; n = number of wells. *P < 0.05 compared with vehicle control; #P < 0.05 compared with TGF-β1 alone or hypoxia.