Cigarette smoke extract induces inflammatory cytokine and chemokine production in human bronchial epithelial cells

Chronic obstructive pulmonary disease (COPD) is a common inflammatory lung disease. It has been known that cigarette smoke (CS) is a major cause of COPD and can induce alteration of the expression of many genes, including inflammatory genes. The receptor for advanced glycation end products (RAGE) is a 35 kDa pattern recognition receptor and its signalling pathways are involved in inflammatory responses. Soluble form of RAGE (sRAGE) is recognised as a decoy receptor of RAGE. However, the role of RAGE in mediating CS-induced inflammatory cytokine and chemokine production, contributing to airway inflammation in COPD, is poorly understood. Inhaled corticosteroids are the main anti-inflammatory therapies for COPD, but their effectiveness is controversial. This underlines the needs for new anti-inflammatory drugs. Cordycepin and simvastatin are drugs with potential anti-inflammatory effects, but their effects on CS-induced inflammatory cytokine and chemokine production have not been explored. This study aimed to investigate whether cigarette smoke extract (CSE) could induce inflammatory cytokine and chemokine production in human bronchial epithelial cells, to assess the role of RAGE in this process, and to explore the potential effects of cordycepin and simvastatin on CSE-induced cytokine and chemokine production. Confluent BEAS-2B human bronchial epithelial cells were treated with CSE (1%, 2.5%, and 5%) for 24 hours. The concentration of a group of cytokines and chemokines implicated in COPD, such as CXCL5 (ENA- 78), CCL11 (eotaxin), CXCL1(GRO-α), CXCL10 (IP-10), CXCL8 (interleukin-8, IL-8), and IL-6 in the culture medium was measured by ELISA. sRAGE secretion and RAGE expression were analayzed by ELISA and Western blotting, respectively. The effect of the specific RAGE inhibitor (FPS-ZM1) (0.5 -1.5 mM) on CSE-induced cytokine/chemokine production was explored to assess the role of RAGE. Experiments were also conducted to investigate the effects of cordycepin (5-25 μM) and simvastatin (0.625-5 μM) on CSE-induced cytokine/chemokine production and the possible involvement of RAGE and RAGE ligand high mobility group box 1 (HMGB-1). The cytotoxicity of CSE (1-5%) and FPS-ZM1 (0.5-1.5 mM) was assessed by MTT cell viability assay. We found that CXCL1, CXCL5, CXCL10 and CCL11 could not be detected in both untreated and CSE-treated cells, but the production of IL-8 and IL-6 was markedly increased by CSE. sRAGE secretion was undetectable in both untreated and CSE-treated cells. Interestingly, RAGE was highly expressed in untreated cells and was not further increased by CSE treatment. CSE-induced IL-8 and IL-6 production was partially inhibited by FPS-ZM1, but RAGE expression was not affected. CSE-induced IL-8 production was also partially inhibited by both cordycepin and simvastatin, but CSE-induced IL-6 production was enhanced by cordycepin and was not affected by simvastatin. Furthermore, RAGE and HMGB-1 expression was not affected by cordycepin and simvastatin. Our results suggest cigarette smoke may contribute to the pathogenesis of COPD by promoting IL-6 and IL-8 production from human bronchial epithelial cells. This process may be partially mediated by RAGE. Cordycepin and simvastatin can reduce CSE-induced IL-8 production, unlikely via inhibition of RAGE pathway, and may have therapeutic potential in neutrophil-driven airway inflammation in COPD