Downregulation of COX-2 expression and PGE2 by TGF-β1 in A549 cells.

<p>(A) Expression of COX-2 protein was detected by immunoblotting as described in Materials and Methods. Treatment with TGF-β1 (5 ng/mL) suppressed expression of COX-2 but not COX-1 in A549 cells. HMGB1 was measured as a loading control. (B) Dose-dependent downregulation of COX-2 by TGF-β1. Twenty-four hours after TGF-β1 stimulation (1-10 ng/mL), expression of COX-2 and COX-1 was detected. (C) SB431542 (10 µM) or SIS3 (30 µM) blocked TGF-β1-induced COX-2 downregulation. Cells were pretreated for 60 min with the inhibitor, and then incubated with or without TGF-β1 (5 ng/mL) for 24 h. (D) TGF-β1 suppressed COX-2 production in A549 cells. Cells were treated with TGF-β1 (1-10 ng/mL) or NS-398 (50 µM) for 24 h, then the concentration of PGE2 in culture medium was measured by EIA as described in Materials and Methods. Each value represents the mean ± SE (n = 4). Significant differences between the indicated groups and control group are indicated by **(P < 0.01).