17,18-Epoxyeicosatetraenoic Acid Inhibits TNF-α-Induced Inflammation in Cultured Human Airway Epithelium and LPS-Induced Murine Airway Inflammation

17,18-Epoxyeicosatetraenoic acid (17,18-EpETE), an eicosapentaenoic acid metabolite, is generated from dietary oil in the gut, and antiinflammatory activity of 17,18-EpETE was recently reported.To evaluate the inhibitory effects of 17,18-EpETE in airway inflammation, we examined in vitro and in vivo effects on mucus production, neutrophil infiltration, and cytokine/chemokine production in airway epithelium.Nasal tissue localization of G protein-coupled receptor 40 (GPR40), a receptor of 17,18-EpETE, was determined by immunohistochemical staining. Expression of GPR40 mRNA in nasal mucosa of chronic rhinosinusitis (CRS) patients and control subjects was determined by reverse transcription-polymerase chain reaction (RT-PCR). The in vitro effects on airway epithelial cells were examined using normal human bronchial epithelial cells and NCI-H292 cells. To examine the in vivo effects of 17,18-EpETE on airway inflammation, we induced goblet cell metaplasia, mucus production, and neutrophil infiltration in mouse nasal epithelium by intranasal lipopolysaccharide (LPS) instillation.GPR40 is mainly expressed in human nasal epithelial cells and submucosal gland cells. RT-PCR analysis revealed that the expression of GPR40 mRNA was increased in nasal tissues from CRS patients compared with those from control subjects. 17,18-EpETE significantly inhibited tumor necrosis factor (TNF)-α-induced production of interleukin (IL)-6 , IL-8, and mucin from cultured human airway epithelial cells dose dependently, and these antiinflammatory effects on cytokine production were abolished by GW1100, a selective GPR40 antagonist. Intraperitoneal injection or intranasal instillation of 17,18-EpETE significantly attenuated LPS-induced mucus production and neutrophil infiltration in mouse nasal epithelium. Inflammatory cytokine/chemokine production in lung tissues and bronchoalveolar lavage fluids was also inhibited.These results indicate that 17,18-EpETE plays a regulatory role in mucus hypersecretion and neutrophil infiltration in nasal inflammation. Local or systemic administration may provide a new therapeutic approach for the treatment of intractable airway disease such as CRS.