ADENOSINE 3',5'-CYCLIC-MONOPHOSPHATE ATTENUATES NEUTROPHIL-MEDIATED INCREASE IN ENDOTHELIAL PERMEABILITY

We studied the effects of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) and cholera toxin (CT) on I-125-labeled albumin flux across confluent monolayers of bovine pulmonary microvessel endothelial cells (BMVEC) grown on polycarbonate filters (10(5) BMVEC/filter). 8-BrcAMP and CT increased endothelial adenosine 3,5'-cyclic monophosphate (cAMP) concentrations about twofold. Polymorphonuclear leukocytes (PMN) were layered on BMVEC monolayers (ratio of 10:1) and activated with phorbol 12 -myristate 13 acetate (PMA; 5 x 10(-9) M). Transendothelial I-125-labeled albumin clearance rate was measured to determine the endothelial permeability alterations. Activation of PMN in control monolayers resulted in an increase in transendothelial I-125-labeled albumin clearance rate from 0.090 +/- 0.011 to 0.37 +/- 0.06 mul/min (P < 0.01). Treatment of endothelial monolayers with 8-BrcAMP (10(-3) M) significantly attenuated the increase in endothelial permeability after PMN activation (transendothelial I-125-labeled albumin clearance rate increased to 0.19 +/- 0.03 mul/min; P < 0.01). Pretreatment of BMVEC monolayers with CT (10(-8) M) for 3 h before PMN activation prevented the PMN-mediated increase in endothelial permeability (I-125-labeled albumin clearance rate only increased to 0.13 +/- 0.018 mul/min). To simulate the effect of PMN activation, hydrogen peroxide (H2O2) was added directly onto BMVEC; both 8-BrcAMP and CT were shown to reduce the H2O2-mediated increase in endothelial permeability. 8-Br-cAMP and CT pretreatment did not prevent PMN adhesion to BMVEC monolayer and superoxide anion and H2O2 production after PMA activation of PMN. We conclude that increased endothelial cAMP concentration prevents PMN-mediated endothelial injury by an action of the cyclic nucleotide on endothelial cells.