Roflumilast inhibits lipopolysaccharide-induced inflammatory mediators via suppression of nuclear factor-κB, p38 mitogen-activated protein kinase, and c-Jun NH2-terminal kinase activation

Roflumilast, a potent and selective phosphodiesterase 4 (PDE4) inhibitor, has been demonstrated to be an effective anti-inflammatory agent in airway inflammatory diseases. In the present study, we investigated the mechanism of anti-inflammatory effects of roflumilast in murine macrophage cell line RAW264.7 cells. Roflumilast inhibited NO, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-1 beta production via suppression of their gene expressions in lipopolysaccharide (LPS)-stimulated macrophages. To elucidate the mechanism by which roflumilast inhibits the production of inflammatory mediators, we examined the effect of roflumilast on the activation of nuclear factor-kappa B (NF-kappa B) in these cells. Roflumilast inhibited the DNA binding activity of NF-kappa B by preventing inhibitor kappa B alpha phosphorylation and degradation. The phosphorylation of mitogen-activated protein ( MAP) kinases, including stress-activated protein kinase/dc-Jun NH2-terminal kinase (JNK) and p38 MAP kinase, was also markedly inhibited by roflumilast. Similar to the effects of roflumilast, treatment of either SB203580 [4-(4-fluorophenyl)2-(4-methylsulfinylphenyl)-5-( 4- pyridyl) imidazole] or SP600125 [anthra(1,9-cd)pyrazol-6(2H)-one 1,9- pyrazoloanthrone], specific inhibitors of p38 MAP kinase and JNK, respectively, suppressed NO, TNF-alpha, and IL-1 beta production. Consistent with in vitro results, administration of roflumilast recovered the survival rate of LPS-treated mice, with concurrent suppression of plasma levels of nitrite/nitrate, TNF-alpha, and IL-1 beta. These results suggest that the inhibitory activity of roflumilast on the production of inflammatory mediators seems to be mediated via inhibition of NF-kappa B, p38 MAP kinase, and JNK activation in macrophages.