Objectives: The mechanism of the efficacy of long-term low-dose macrolide therapy for chronic sinusitis is not fully understood. The authors studied the inhibitory effect of erythromycin on interleukin-8 (IL-8) secretion from exudative cells in the nasal discharge of patients with chronic sinusitis. Study Design and Methods: Exudative cells in the nasal discharge were isolated from six patients with nonallergic chronic sinusitis. The cells, more than 90% of which were neutrophils, were incubated with or without erythromycin in the presence of 10 μg/mL of lipopolysaccharide. The IL-8 concentrations in the culture supernatants were measured by enzyme- linked immunoassay. Results: The amount of secreted IL-8 in the absence of erythromycin was 682 ± 226 pg/106 cells/24 h. The IL-8 secretion was significantly reduced to 66 ± 15% and 46 ± 13% of the control in the presence of 10-6 and 10-5 M of erythromycin, respectively. Conclusion: Erythromycin may act as a biologic modulator that inhibits IL-8 secretion from exudative cells and thereby blocks the vicious circle of neutrophil recruitment and IL-8 generation in the inflammatory site in chronic sinusitis.
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