Effects of phosphodiesterase inhibition by pentoxifylline on MAPK P38 and cAMP/PKA intracellular signaling pathways

Abstract

Phosphodiesterase inhibition attenuates neutrophil oxidative burst and TNF-α production. We postulated that pentoxifylline (PTX), a non-specific phosphodiesterase inhibitor, decreases whole blood TNF-α production by p38 MAPK- and cAMP-response element binding protein (CREB)-dependent mechanisms. In addition, PTX may attenuate neutrophil oxidative burst by decreasing p38 MAPK activation. Human whole blood and isolated neutrophils (1 × 10 6 cells/ml) were stimulated with fMLP (1 μM), PTX (2 mM), and fMLP + PTX concomitantly. Proteins were separated by SDS-PAGE, transferred to membranes, and immunoblotted with phosphorylated and whole p38 and CREB antibodies. TNF-α (ELISA) and neutrophil oxidative burst (flow cytometry) were measured in whole blood. PTX significantly decreased both fMLP-induced TNF-α (65%) in whole blood and neutrophil oxidative burst (75%). p38 MAPK phosphorylation was significantly attenuated by PTX treatment of fMLP-stimulated neutrophils, whereas CREB phosphorylation was significantly increased. In conclusion, PTX regulates proinflammatory cytokine synthesis likely by activating the cAMP/PKA signaling pathway and attenuating p38 MAPK activation. In addition, attenuation of neutrophil oxidative burst by PTX occurs, at least in part, by its down regulatory effects on the p38 signaling pathway.