Roflumilast inhibits leukocyte-endothelial cell interactions, expression of adhesion molecules and microvascular permeability

Background and purpose: The present study addressed the effects of the investigational PDE4 inhibitor roflumilast on leukocyte- endothelial cell interactions and endothelial permeability in vivo and in vitro. Experimental approach: In vivo, intravital video- microscopy was used to determine effects of roflumilast p.o. on leukocyte-endothelial cell interactions and microvascular permeability in rat mesenteric venules. In vitro, the effects of roflumilast N-oxide, the active metabolite of roflumilast in humans, and other PDE4 inhibitors on neutrophil adhesion to tumour necrosis factor alpha (TNF alpha)- activated human umbilical vein endothelial cells ( HUVEC), E- selectin expression and thrombin- induced endothelial permeability was evaluated. Flow cytometry was used to determine the effect of roflumilast on N- formyl-methionyl-leucyl- phenylalanine ( fMLP)- induced CD11b upregulation on human neutrophils. Key results: In vivo, roflumilast, given 1 h before lipopolysaccharide ( LPS), dose- dependently reduced leukocyte- endothelial cell interactions in rat mesenteric postcapillary venules. It also diminished histamine- induced microvascular permeability. Immunohistochemical analyses revealed that roflumilast prevented LPS- induced endothelial P- and E- selectin expression. In vitro, roflumilast N- oxide concentration- dependently suppressed neutrophil adhesion to TNF alpha-activated HUVEC and CD11b expression on fMLP- stimulated neutrophils. It also reduced TNF alpha-induced E- selectin expression on HUVEC, when PDE3 activity was blocked. HUVEC permeability elicited by thrombin was concentration- dependently suppressed by roflumilast N- oxide. While roflumilast N- oxide was as potent as roflumilast at inhibiting stimulated endothelial cell and neutrophil functions, both compounds were significantly more potent than the structurally unrelated PDE4 inhibitors, rolipram or cilomilast. Conclusions and implications: These findings further support earlier observations on the inhibition of inflammatory cell influx and protein extravasation by roflumilast in vivo.