INHIBITORY EFFECT OF ERYTHROMYCIN ON INTERLEUKIN-8 PRODUCTION BY 1-ALPHA,25-DIHYDROXYVITAMIN D3-STIMULATED THP-1 CELLS

We have recently reported that long-term administration of erythromyci n at a low dose reduced the number of neutrophils and concentrations o f interleukin 8 (IL-8) in bronchoalveolar lavage fluid in patients wit h chronic lower respiratory tract disease. To investigate the mechanis m of action of erythromycin, we evaluated its effect on IL-8 productio n in the 1 alpha,25-dihydroxyvitamin D3-stimulated human monocytic cel l line THP-1. Erythromycin at a concentration of 10 mu g/ml significan tly reduced IL-8 production by THP-1 cells stimulated with lipopolysac charide (10 ng/ml) and 1% normal human serum compared with the amount produced by untreated cells (untreated cells, 2,448 pg/ml; erythromyci n-treated cells, 872 pg/ml), Our results suggest that erythromycin may impair IL-8 production by alveolar macrophages, ultimately reducing n eutrophil accumulation in the airspace.