Cross-talk between TLR3 and TNF-α or IFN-γ Signaling in Induction of CXCL8/IL-8 and CXCL10/IP-10 Expression in Airway Epithelial Cells

CXCL8/IL-8 is a chemoattractant for neutrophils and mast cells, and regulates inflammatory cell recruitment in allergy, infection, and other neutrophil-related diseases. Interferon (IFN) -γ-inducible protein 10 (CXCL10/IP-10) is a chemokine that attracts mononuclear cells, Th1 cells, and natural killer cells. We investigated the levels of CXCL8/IL-8 and CXCL10/IP-10 expression by airway epithelial cells after exposure to the inflammatory cytokines tumor necrosis factor (TNF) -α and IFN-γ, and to poly I:C, a synthetic analog of double-stranded RNA that is a ligand of Toll-like receptor 3 (TLR3). Poly I:C, TNF-α, IFN-γ, and combinations of poly I:C with TNF-α or IFN-γ were used to stimulate the airway epithelial cell line BEAS-2B. Following stimulation, we determined CXCL8/IL-8 and CXCL10/IP-10 mRNA levels by real-time PCR and protein levels by ELISA. Poly I:C treatment upregulated mRNA and protein expression for both CXCL8/IL-8 and CXCL10/IP-10. The addition of TNF-α, but not IFN-γ, to poly I:C further increased the expression of CXCL8/IL-8 mRNA and protein. The addition of either TNF-α or IFN-γ to the poly I:C treatment further increased CXCL10/IP-10 mRNA and protein expression. Cross-talk between TLR3 signaling and inflammatory cytokines regulates the expression of CXCL8/IL-8 and CXCL10/IP-10 in airway epithelial cells. From our results, TNF-α and IFN-γ produce different effects on TLR3 signaling

Effects of Corticosteroids on Osteopontin Expression in a Murine Model of Allergic Asthma

BACKGROUND: Osteopontin (OPN) contributes to the development of T helper 1 (Th1)-mediated immunity and Th1-associated diseases. However, the role of OPN in bronchial asthma is unclear. Corticosteroids reduce airway inflammation, as reflected by the low eosinophil and T-cell counts, and the low level of cytokine expression. We investigated OPN production and the inhibitory effects of corticosteroids on OPN production in a murine model of allergic asthma. METHODS: BALB/c mice were sensitized by intraperitoneal injections of ovalbumin (OVA) with alum. Some mice received daily injections of dexamethasone (DEX) or phosphate-buffered saline for 1 week. All OVA-challenged mice were exposed to aerosolized 1% OVA for 30 min an hour after these injections. After the OVA challenge, the mice were killed, and bronchoalveolar lavage (BAL) fluid and lung tissue were examined. RESULTS: The levels of OPN protein in BAL fluid and OPN mRNA in lung tissue increased after OVA challenge. Most OPN-expressing cells were CD11c+ cells and some were T cells. DEX decreased the levels of OPN protein in the BAL fluid, and those of OPN mRNA and OPN protein in lung tissue. CONCLUSIONS: OPN may play an important role in allergic bronchial asthma. Corticosteroids inhibit OPN production in mice with allergic asthma. The beneficial effect of corticosteroids in bronchial asthma is partly due to their inhibitory effects on OPN production