Macrolides reduce the expression of surface Mac-1 molecule on neutrophil

Several reports described a favorable effect of "low-dose and long-term" erythromycin (EM) on chronic obstructive pulmonary diseases including diffuse panbronchiolitis (DPB), although its mechanism still remains obscure. We investigated the effect of some macrolides, erythromycin (EM), rokitamycin (RKM), midecamycin (MDM) on the expression of neutrophil adhesion molecule Mac-1 using LPS-stimulated human whole blood as an experimental vivo model. Samples from six healthy volunteer were treated with various concentrations (0.02 ug/ml-20 ug/ml) of EM, RKM and MDM for 1 to 3 hs. Surface expression of Mac-1 antigen was determined by use of flow-cytometry. When pretreated with EM and MDM for 1 and 3 hs, significant reduction in Mac-1 expression was observed, but with RKM no substantial reduction. These findings indicate that some macrolides such as EM suppress the surface expression of Mac-1 on neutrophil and may alleviate local alveolar injury in chronic pulmonary diseases.