Background: Low-dose and long-term administration of macrolide antibiotics into patients with chronic airway inflammatory diseases could favorably modify their clinical conditions. However, the therapeutic mode of action of macrolides is not well understood. Free oxygen radicals, including nitric oxide (NO), are well recognized as the important final effector molecules in the development and the maintenance of inflammatory diseases.
Purpose: The influence of macrolide antibiotics on NO generation was examined in vivo.
Methods: Male ICR mice, 5 weeks of age, were orally administered with either roxithromycin, clarithromycin, azithromycin or josamycin once a day for 2-4 weeks. The mice were then injected intraperitoneally with 5.0 mg/kg lipopolysaccharide (LPS) and the plasma NO level was examined 6 h later.
Results: Although pre-treatment of mice with macrolide antibiotics for 2 weeks scarcely affected NO generation by LPS injection, the administration of macrolide antibiotics, except for josamycin, for 4 weeks significantly inhibited LPS-induced NO generation. The data in the present study also showed that pre-treatment of mice with macrolide antibiotics for 4 weeks significantly suppresses not only production of pro-inflammatory cytokines interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha, but also inducible nitric oxide synthase mRNA expressions, which are enhanced by LPS injection.
Conclusion: These results strongly suggest that suppressive activity of macrolide antibiotics on NO generation in response to LPS stimulation in vivo may, in part, account for the clinical efficacy of macrolides on chronic inflammatory diseases.