TGF-β1 stimulates IL-8 release, COX-2 expression, and PGE₂release in human airway smooth muscle cells

We have recently shown that endogenous prostanoids are critical in bradykinin-stimulated interleukin (IL)-8 release from human airway smooth muscle (ASM) cells. In this study, we tested the ability of transforming growth factor (TGF)-beta1 to stimulate IL-8 release, cyclooxygenase (COX)-2 expression and PGE(2) generation in cultured human ASM cells and explored the role of COX products and COX-2 induction on IL-8 release. TGF-beta1 stimulated IL-8 release, COX-2 induction, and PGE(2) generation in a concentration- and time-dependent manner. Maximal IL-8 release was achieved with 10 ng/ml of TGF-beta1 after 16 h of incubation, which was inhibited by the transcription inhibitor actinomycin D and the corticosteroid dexamethasone but was not affected by the nonselective COX inhibitor indomethacin and the selective COX-2 inhibitor NS-398 despite their inhibition on TGF-beta1-induced PGE(2) release. These results show for the first time that TGF-beta1 stimulates IL-8 release, COX-2 induction, and PGE(2) generation in human ASM cells and that PGE(2) generation is not critical for TGF-beta1-induced IL-8 release. These findings suggest that TGF-beta1 may play an important role in the pathophysiology of asthma.