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 TV-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.
The long-term low-dose administration of erythromycin is effective in treating chronic inflammatory diseases of the lower respiratory tract. The aim of this study was to clarify the mechanism for this therapeutic effect of erythromycin. We measured its effect on the production of superoxide anion (O2-) by polymorphonuclear leukocytes (PMN) that was induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP) or by phorbol myristate acetate (PMA). 25 μM erythromycin inhibited fMLP-induced O2- production by about 50%, but not PMA-induced O2- production. Moreover, this inhibition was overcome by adding an inhibitor of cyclic AMP-dependent protein kinase (PKA), H-89. The fMLP-induced O2- production was also inhibited by isoproterenol, a β-adrenergic agonist, and by dibutyryl cyclic AMP, a cell membrane permeating analogue of cyclic AMP. The inhibition was also overcome by the addition of H-89. Therefore, the effect of erythromycin seemed to be, in part, mediated through the activation of PKA. The inhibition by erythromycin of O2- generation by PMN may contribute to the beneficial effect of this drug in treating chronic respiratory diseases.
Neutrophils are thought to play a key role in tissue injury. We investigated the role of human neutrophil-derived elastase in the induction of injury to human pulmonary artery endothelial cells. Incubation of endothelial cells with neutrophils increased the release of lactate dehydrogenase activity, thrombomodulin, and preloaded fura-2 from endothelial cells, indicating that neutrophils induce endothelial cell injury. Attachment alone of neutrophils to endothelial cells appeared to induce activation because elastase release and N-formyl-mentionyl-leucyl-phenylalanine (fMLP)-induced superoxide (O2––) production from neutrophils incubated with endothelial cells were greater than from neutrophils only. When endothelial cell were incubated with neutrophils stimulated by fMLP or phorbol myristate acetate, the amount of elastase in the medium and endothelial cell damage was further enhanced. However, when neutrophils were blocked from direct attachment to endothelial cells using a membrane filter, endothelial cell damage was ameliorated, while exogenous neutrophil elastase and medium containing neutrophil-released elastase did not induce endothelial cell injury. An inhibitor of neutrophil elastase, ONO-5046 Na, as well as erythromycin, which reduces neutrophil-derived elastase, dramatically inhibited neutrophil-induced endothelial cell injury. Superoxide dismutase (SOD) partially inhibited injury. Injury was completely inhibited by treatment with a combination of ONO-5046 Na and SOD. These results suggest that attachment of neutrophils to endothelial cells is important for endothelial cell damage and that neutrophil-derived elastase plays an important role in endothelial cell injury in combination with O2––. In addition, ONO-5046 Na and erythromycin may be useful in treating diseases worsened by excessive neutrophil activity.
Phosphatidicacrd (PA) dose-dependently induced superoxrde (0;) production of electropermeabilized human neutrophils but not of intact neutrophrls, indrcatmg that PA induces the acttvatron of NADPH oxtdase by actmg on an intracellular target. The 0; production by PA was not inhibited by protein kinase C (PKC) inhibitors, such as staurosporine and calphostin C, and an inhibitor of PA phosphohydrolase, propranolol. These observations suggest that the activation of the oxidase by PA is independent of the activity of PKC and may dominate the activation by dtacylglycerol which is formed from PA via the action of PA phosphohydrolase. Furthermore, the productton by PA, as well as that by phorbol myrtstate acetate, was inhibited by cychc AMP and GDPBS. Therefore, PA seems to act at a site downstream of PKC.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.