Enhanced tumor necrosis factor suppression and cyclic adenosine monophosphate accumulation by combination of phosphodiesterase inhibitors and prostanoids

摘要

AbstractWe investigated cooperative effects of phosphodiesterase (PDE) inhibitors and prostanoids on cyclic adenosine monophosphate (cAMP) accumulation and tumor necrosis factor (TNF)‐α synthesis in human peripheral blood mononuclear cells (PBMC). PDE inhibitors alone induced only a small increase in cAMP levels in lipopolysaccharide (LPS)‐stimulated PBMC. Cicaprost (a stable analogue of prostacyclin) and pentoxifylline added simultaneously to LPS‐stimulated PBMC (2.0 × 106/ml) induced a rapid increase of cAMP to a level of 100 nM that peaked within 10 min and remained at a plateau for up to 4 h. Thus combined prostanoids and PDE inhibitors enhanced cAMP accumulation. TNF‐α suppression in the presence of pentoxifylline and prostanoids exceeded that of either drug alone. The potency of different PDE inhibitors (theophylline, pentoxifylline, penthy‐droxifylline, albifylline, torbafylline, A 802715, amrinone and rolipram) to increase cAMP levels in combination with cicaprost was evaluated after 1 h of incubation. The dose‐dependent increase of cAMP for all PDE inhibitors tested in this combined stimulation provided a useful tool for evaluating the potency of PDE inhibitors on cAMP accumulation. The effective concentration of PDE inhibitors, which raised cAMP levels to 300 of control, (EC300), correlated with the IC50for TNF‐α suppression (r= 0.930,p= 0.007, with theophylline excluded from the analysis). Interestingly, by contrast, the specific type IV PDE inhibitor rolipram caused only a moderate rise of accumulated cAMP in the same cells. Our data support cAMP as an essential mediator for TNF‐α suppression by PDE inhibitors. Furthermore, an enhanced inhibiting effect on TNF‐α production may prove therapeutically advantageous. It may occur in inflammatory and infectious diseasesin vivo, since high levels of endogenous prostaglandins are libera