Neutrophil-Induced Endothelial Cell Damage: Inhibition By A 14-Membered Ring Macrolide Through The Action Of Nitric Oxide

Macrolide antibiotics have been used worldwide for about 40 years. The clinical effectiveness of oral erythromycin for diffuse panbronchiolitis has been established and erythromycin seems to act not only as an antibacterial but also as an anti-inflammatory agent, We investigated the effect of 14-membered ring macrolides, erythromycin and clarithromycin, on human neutrophil functions and endothelial cell damage induced by neutrophils. The superoxide production of neutrophils and Ca2+ influx into neutrophils induced by N-formyl-methionyl-leucyl-phenylalanine was inhibited by treatment with erythromycin but not by treatment with clarithromycin, When endothelial cells were cocultured with neutrophils, nitric oxide (NO) presumably released from endothelial cells were enhanced by treatment with erythromycin but not by treatment with clarithromycin and endothelial cell injury induced by neutrophils was ameliorated by addition of erythromycin but not by clarithromycin. The reduction of neutrophil-induced endothelial cell injury by erythromycin was abolished by treatment with carboxy-PTIO which traps NO in the medium. Moreover nitrite in the medium in which endothelial cells were incubated with neutrophils was enhanced by treatment with erythromycin and the enhancement of nitrite by erythromycin was partially canceled by addition of H-89, an inhibitor of cyclic AMP-dependent protein kinase (PKA), Erythromycin seems to ameliorate neutrophil-induced endothelial cell injury by affecting not only neutrophil functions but the release of NO from endothelial cells through the action of PKA. The usefulness for the treatment of diseases worsened by the interaction between neutrophils and endothelium might be different among 14-membered ring macrolides.