The role of phosphodiesterase 4B in IL-8/LTB₄-induced human neutrophil chemotaxis evaluated with a phosphodiesterase 4B inhibitor

PDE4B was previously shown to be a dominant PDE4 subtype of neutrophils. However, its physiological role in the neutrophil function has not been evaluated. In this study, the inhibitory effects of a phosphodiesterase 4B (PDE4B)- selective inhibitor (compound A) and subtype non-selective PDE4 inhibitors (roflumilast and cilomilast) were evaluated in human peripheral blood cells. Compound A, roflumilast and cilomilast in a similar manner inhibited TNF-α production by LPS-stimulated human mononuclear cells. However, the inhibitory effect of compound A on IL-8 or LTB4-induced chemotactic response of neutrophils was modest even at the highest concentration (10 μmol L^-1), whereas roflumilast and cilomilast inhibited IL-8 or LTB₄-induced neutrophil chemotaxis. Our results suggest that PDE4B does not play an important role during the chemotactic response of human neutrophils.