title: Steroids inhibit vascular endothelial growth factor expression via TLR4/Akt/NF-κB pathway in chronic rhinosinusitis with nasal polyp.
abstract: Vascular endothelial growth factor (VEGF) is elevated in chronic rhinosinusitis with nasal polyps. Steroids have anti-inflammatory properties and are ideal candidates for treating chronic inflammatory airways. The aims of this study were to identify the inhibitory effects and mechanisms of steroids on lipopolysaccharide (LPS)-induced VEGF expression in nasal polyps. Nasal polyp-derived fibroblasts (NPDFs) were stimulated with LPS alone or with both LPS and steroids were used to determine the expression levels of toll-like receptor (TLR)-4, myeloid differentiation primary response gene 88 (MyD88), and VEGF by using reverse transcription-polymerase chain reaction (RT-PCR). VEGF protein level was analyzed by immunocytochemical staining and enzyme-linked immunosorbent assay (ELISA). Small interfering RNA (siRNA) for TLR4 was transfected to down-regulate TLR4 expression. Activation of Akt and nuclear factor κB (NF-κB) pathway on VEGF expression was determined by Western blot analysis, immunocytochemical staining, and ELISA. Nasal polyp organ cultures were stimulated with LPS alone or in conjunction with steroids or LPS-RS (TLR4 inhibitor) and accessed the expression of VEGF. Steroids decreased the expressions of TLR4, MyD88, and VEGF mRNA and VEGF protein in LPS-stimulated NPDFs. Steroids inhibited LPS-induced VEGF expression levels in dose-dependent manner. The suppression of TLR4 transcription by siRNA treatment reduced LPS-induced expression of both TLR4 and VEGF in NPDFs. Furthermore, steroids inhibited the production of VEGF by blocking Akt and NF-κB activation and preventing with NF-κB translocation. Also, steroid and TLR4 inhibitor decreased VEGF expression in nasal polyp organ cultures. These results indicate that steroids inhibit LPS-induced VEGF expression through the TLR4/Akt/NF-κB signaling pathway in chronic rhinosinusitis with nasal polyp.
authors.affiliation: Biomedical Science, Guro Hospital, Korea University College of Medicine, Seoul 152-703, Korea Institute for Medical Devices Clinical Trial Center, Guro Hospital, Korea University College of Medicine, Seoul 152-703, Korea.
authors.forename: Jung-Sun
authors.initials: JS
authors.lastname: Cho
authors.affiliation: Biomedical Science, Guro Hospital, Korea University College of Medicine, Seoul 152-703, Korea.
authors.forename: Ju-Hyung
authors.initials: JH
authors.lastname: Kang
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Korea University College of Medicine, Seoul 152-703, Korea.
authors.forename: Il-Ho
authors.initials: IH
authors.lastname: Park
authors.affiliation: Biomedical Science, Guro Hospital, Korea University College of Medicine, Seoul 152-703, Korea Institute for Medical Devices Clinical Trial Center, Guro Hospital, Korea University College of Medicine, Seoul 152-703, Korea Department of Otorhinolaryngology-Head and Neck Surgery, Korea University College of Medicine, Seoul 152-703, Korea lhman@korea.ac.kr.
authors.forename: Heung-Man
authors.initials: HM
authors.lastname: Lee
keywords: Chronic rhinosinusitis; Toll-like receptor 4; lipopolysaccharide; nasal polyposis; steroid; vascular endothelial growth factor