Inhibition of PAF-induced expression of CD11b and shedding of L-selectin on human neutrophils and eosinophils by the type IV selective PDE inhibitor, rolipram

Abstract

We quantitatively determined whether the selective phosphodiesterase (PDE) inhibitor, rolipram, inhibits changes in the adhesion molecules CD11b and L-selectin on platelet-activating factor (PAF)-stimulated human neutrophils and eosinophils in vitro.Incubations were performed in human whole blood obtained from healthy volunteers, to restrict activation by purification procedures and to simulate in vivo conditions, in which different cell types may interact, more closely. Receptor expression was measured after fixation of cells, using monoclonal antibodies and flow cytometry.Concentration-dependent inhibition of the PAF-induced CD11b expression and L-selectin shedding for neutrophils and eosinophils was observed with rolipram, dibutyryl cyclic adenosine monophosphate (cAMP), prostaglandin E 2 (PGE 2 ), and isoproterenol. However, these inhibitions did not exceed 50%. Preincubation with rolipram (10 -8 M) and subsequent incubation with isoproterenol (0.5×10 -8 M) or PGE 2 (10 -8 M) induced a cumulative, but not synergistic, effect. Using the combination of rolipram with isoproterenol or PGE 2 , inhibition of PAF-induced Lselectin shedding from eosinophils was as high as 71±28 and 67±21%, respectively. Other inhibitions were below 50%.In conclusion, rolipram inhibits CD11b expression and L-selectin shedding of platelet-activating factor-stimulated neutrophils and eosinophils in whole blood in a concentration-dependent fashion. Inhibitions did not exceed 50%, even at high concentrations. The inhibition of platelet-activating factor induced shedding of Lselectin from eosinophils with a combination of rolipram and prostaglandin E 2 or isoproterenol, however, was found to be approximately 70%. Inhibition of rolling adhesion of eosinophils may, therefore, be a mode of action of type IV phosphodiesterase inhibitors.

Rolipram inhibits leukocyte‐endothelial cell interactions in vivo through P‐ and E‐selectin downregulation

“…Indeed, b 2 -integrins can interact with endothelial cell ligand(s) other than ICAM-1 (Staunton et al, 1989;Lo et al, 1989;Stacker & Springer, 1991). Therefore, the ®ndings in the present study suggest that the decrease in leukocyte adhesion and emigration induced by rolipram under subacute in¯ammatory conditions can be partly explained by its ability to downregulate both P-and E-selectin expression on the endothelial cell surface together with decreased b 2 -integrin expression on leukocytes as found in other studies (Derian et al, 1995;Teixeira et al, 1996;Berends et al, 1997;Santamaria et al, 1997).…”

“…Although rolipram administration had no eect on ICAM-1 expression, its ability to decrease b 2 -integrin expression on leukocyte cell surface (Derian et al, 1995;Teixeira et al, 1996;Berends et al, 1997;Santamaria et al, 1997), may account for the further reduction observed in leukocyte adhesion. Indeed, b 2 -integrins can interact with endothelial cell ligand(s) other than ICAM-1 (Staunton et al, 1989;Lo et al, 1989;Stacker & Springer, 1991).…”

“…The eects observed seemed to be mediated through endothelial P-selectin downregulation, since angiotensin-II-induced leukocyte recruitment is primarily dependent on increased endothelial P-selectin expression (Piqueras et al, 2000). Nevertheless, although the inhibition of P-selectin expression may delay the onset of leukocyte adhesion and emigration, a direct eect of rolipram on leukocyte surface adhesion molecule expression cannot be excluded, since downregulation of b 2 -integrins by this PDE-4 inhibitor has been extensively demonstrated in several in vitro studies (Derian et al, 1995;Teixeira et al, 1996;Berends et al, 1997;Santamaria et al, 1997).…”

Prostaglandin D2 is a potent chemoattractant for human eosinophils that acts via a novel DP receptor

“…41 The ability of PGD 2 to activate eosinophils while at the same time stimulating adenylyl cyclase is intriguing, as increased cAMP levels would be expected to attenuate eosinophil responses. The phosphodiesterase-4 inhibitor rolipram has been shown to inhibit eosinophil migration and CD11b expression in response to eotaxin, 42 PAF, 18,43,44 and C5a. Stimulation of adenylyl cyclase with forskolin 44 or isoproterenol 43 or addition of dibutyryl cAMP 43 had similar effects.…”

“…The phosphodiesterase-4 inhibitor rolipram has been shown to inhibit eosinophil migration and CD11b expression in response to eotaxin, 42 PAF, 18,43,44 and C5a. Stimulation of adenylyl cyclase with forskolin 44 or isoproterenol 43 or addition of dibutyryl cAMP 43 had similar effects. This raised the possibility that PGD 2 could have opposing actions on eosinophils and that its stimulatory effect could be blunted by concomitant stimulation of adenylyl cyclase, especially at higher concentrations of PGD 2 .…”