Preventive effect of erythromycin on experimental bleomycin-induced acute lung injury in rats

Background--Erythromycin has been reported to have an inhibitory effect on chronic inflammatory airway disease and chronic infiltration of neutrophils into the airway. Bleomycin (BLM) often induces interstitial lung fibrosis following acute lung injury. A study was undertaken to investigate the effects of erythromycin (EM) on experimental bleomycin-induced acute lung injury in rats. Methods--Bleomycin-induced lung injury was assessed by light microscopic examination, measurement of neutrophil elastase activity and of the interleukin 8 (IL-8) content in bronchoalveolar lavage (BAL) fluid. The potential inhibitory effect of erythromycin was assessed by overall comparison of erythromycin untreated (BLM alone), concurrently treated (BLM + EM), and pretreated (BLM + pre-EM) groups. Results--The neutrophil count and concentration of neutrophil-derived elastase in BAL fluid were significantly different in the three groups. The morphological changes of lung injury were also less extensive in rats pretreated with erythromycin. However, these protective effects were not marked in the group concurrently treated with erythromycin. Moreover, the concentration of IL-8 in the BAL fluid tended to be less in the erythromycin treated groups; however, there were no significant differences between the bleomycin-treated groups. Conclusion--Erythromycin exhibits a prophylactic effect on acute lung injury induced by intratracheal administration of bleomycin, which is possibly associated with a downregulation of neutrophil-derived elastase.