Effects of prostaglandin E2 and cAMP elevating drugs on GM-CSF release by cultured human airway smooth muscle cells. Relevance to asthma therapy.

Human airway smooth muscle (HASM) cells release granulocyte macrophage-colony stimulating factor (GM-CSF) and express cyclooxygenase (COX)-2 (resulting in the release of prostaglandin [PG] E2) after stimulation with cytokines. Because COX-2 activity can regulate a number of inflammatory processes, we have assessed its effects, as well as those of agents that modulate cyclic adenosine monophosphate (cAMP), on GM-CSF release by HASM cells. Cells stimulated with a combination of proinflammatory cytokines (interleukin-1beta and tumor necrosis factor-alpha each at 10 ng/ml) for 24 h released significant amounts of PGE2 (measured by radioimmunoassay) and GM-CSF (measured by enzyme-linked immunosorbent assay). Indomethacin and other COX-1/COX-2 inhibitors caused concentration-dependent inhibitions of PGE2 concomitantly with increases in GM-CSF formation. Addition of exogenous PGE2 or the beta2-agonist fenoterol, which increase cAMP, to cytokine-treated HASM cells had no effect on GM-CSF release unless COX activity was first blocked with indomethacin. The type 4 phosphodiesterase inhibitors rolipram and SB 207499 both caused concentration-dependent reductions in GM-CSF production. Thus, when HASM cells are activated with cytokines they release PGE2, which acts as a "braking mechanism" to limit the coproduction of GM-CSF. Moreover, agents that elevate cAMP also reduce GM-CSF formation by these cells.