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

We quantitatively determined whether the selective phosphodiesterase ( PDE) inhibitor, rolipram, inhibits changes in the adhesion molecules C D11b and L-selectin on platelet-activating factor (PAF)-stimulated hum an neutrophils and eosinophils in vitro. Incubations were performed in human whole blood obtained from healthy volunteers, to restrict activ ation by purification procedures and to simulate in vivo conditions, i n which different cell types may interact, more closely. Receptor expr ession was measured after fixation of cells, using monoclonal antibodi es and flow cytometry. Concentration-dependent inhibition of the PAF-i nduced CD11b expression and L-selectin shedding for neutrophils and eo sinophils was observed with rolipram, dibutyryl cyclic adenosine monop hosphate (cAMP), prostaglandin E-2 (PGE(2)), and isoproterenol. Howeve r, these inhibitions did not exceed 50%. Preincubation with rolipram ( 10(-8) M) and subsequent incubation with isoproterenol (0.5x10(-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), inhi bition of PAF-induced L-selectin shedding from eosinophils was as high as 71+/-28 and 67+/-21%, respectively. Other inhibitions were below 5 0%. In conclusion, rolipram inhibits CD11b expression and L-selectin s hedding of platelet-activating factor-stimulated neutrophils and eosin ophils in whole blood in a concentration-dependent fashion. Inhibition s did not exceed 50%, even at high concentrations. The inhibition of p latelet-activating factor induced shedding of L-selectin from eosinoph ils with a combination of rolipram and prostaglandin E-2 or isoprotere nol, however, was found to be approximately 70%. Inhibition of rolling adhesion of eosinophils may, therefore, be a mode of action of type I V phosphodiesterase inhibitors.