Suppression of IL-8 production from airway cells by tiotropium bromide in vitro

Isao Suzaki¹, Kazuhito Asano², Yusuke Shikama³, Taisuke Hamasaki¹, Ayako Kanei¹, Harumi Suzaki^1
1Department of Otorhinolaryngology, School of Medicine, Showa University, Tokyo, Japan; ²Division of Physiology, School of Nursing and Rehabilitation Sciences, Showa University, Yokohama, Japan; ³Department of Respiratory Diseases, Showa University Northern Yokohama Hospital, Yokohama, Japan

Background: COPD is characterized by persistent and progressive airway inflammation. Although neutrophilic airway inflammation is generally accepted to be a major factor in the pathogenesis of COPD, the influence of the agents used for the treatment of COPD on neutrophil functions such as chemotaxis is not fully understood.
Purpose: The present study aimed to examine the influence of tiotropium bromide on the production of interleukin (IL)-8 from human airway epithelial cells and lung fibroblasts (LFs) after lipopolysaccharide (LPS) stimulation in vitro.
Methods: BEAS-2B cells, human bronchial epithelial cell line, and LFs, at a concentration of 5 × 10⁵ cells/mL, were stimulated with LPS in the presence of various concentrations of tiotropium bromide. IL-8 in culture supernatants was examined by enzyme-linked immunosorbent assay (ELISA). IL-8 messenger ribonucleic acid (mRNA) expression was examined by real-time polymerase chain reaction. The influence of tiotropium bromide on LPS-induced signaling pathways was also analyzed by examining nuclear factor-kappa (NF-κ)B activation and signaling protein phosphorylation by ELISA.
Results: Tiotropium bromide at >15 pg/mL inhibited IL-8 production from both BEAS-2B cells and LFs after LPS stimulation. Tiotropium bromide also suppressed IL-8 mRNA expression through the inhibition of NF-κB activation and signaling protein, extracellular-signal-regulated kinase 1/2, and c-Jun N-terminal kinase, phosphorylation.
Conclusion: The present results strongly suggest that tiotropium bromide exerts the inhibitory effect on neutrophilic inflammation through the suppression of IL-8 production from epithelial cells and LFs by interfering with LPS-mediated signaling pathways and thus may contribute to lower cellular inflammation in COPD, which is responsible for favorable modification of the disease.

Keywords: IL-8, suppression, tiotropium bromide, airway cells, in vitro