1α, 25-dihydroxyvitamin D3 inhibits transforming growth factor ß1-induced epithelial-mesenchymal transition via ß-catenin pathway.

BACKGROUND: The transforming growth factor ß1 (TGF-ß1)-induced epithelial-mesenchymal transition (EMT) has been proven associated with the pathogenesis of asthmatic airway remodeling, in which the Wnt/ß-catenin pathway plays an important role, notably with regard to TGF-ß1. Recent studies have shown that 1α, 25-dihydroxyvitamin D3(1α, 25(OH)2D3) inhibits TGF-ß1-induced EMT, although the underlying mechanism have not yet been fully elucidated. METHODS: Alveolar epithelial cells were exposed to 1α, 25(OH)2D3, ICG-001, or a combination of both, followed by stimulation with TGF-ß1. The protein expression of E-cadherin, α-smooth muscle actin, fibronectin, and ß-catenin was analyzed by western blotting and immunofluorescence analysis. The mRNA transcript of Snail was analyzed using RT-qPCR, and matrix metalloproteinase 9 (MMP-9) activity was analyzed by gelatin zymogram. The activity of the Wnt/ß-catenin signaling pathway was analyzed using the Top/Fop flash reporters. RESULTS: Both 1α, 25(OH)2D3 and ICG-001 blocked TGF-ß1-induced EMT in alveolar epithelial cells. In addition, the Top/Fop Flash reporters showed that 1α, 25(OH)2D3 suppressed the activity of the Wnt/ß-catenin pathway and reduced the expression of target genes, including MMP-9 and Snail, in synergy with ICG-001. CONCLUSION: 1α, 25(OH)2D3 synergizes with ICG-001 and inhibits TGF-ß1-induced EMT in alveolar epithelial cells by negatively regulating the Wnt/ß-catenin signaling pathway.

Baicalin inhibits PDGF-induced proliferation and migration of airway smooth muscle cells.

Airway smooth muscle (ASM) cell proliferation and migration play important roles in airway remodeling in asthma. In vitro platelet-derived growth factor (PDGF) induced ASM cell proliferation and migration. Baicalin is one of flavonoid extracts from Scutellaria baicalensis, which has an anti-asthma effect. However, little is known about its role in PDGF-induced proliferation and migration in rat ASM (RASM) cells. In this study, we aimed to investigate the effects of baicalin on PDGF-induced RASM cell proliferation and migration. We also identified the signaling pathway by which baicalin influences RASM cell proliferation and migration. In the current study, we demonstrated that baicalin suppressed PDGF-induced RASM cell proliferation, arrested PDGF-induced cell-cycle progression. It also suppressed PDGF-induced RASM cell migration. Furthermore, baicalin suppressed PDGF-induced expression of phosphorylated p38, ERK1/2 and JNK in RASM cells. In summary, our study is the first to show that baicalin pretreatment can significantly inhibit PDGF-induced RASM cell proliferation and migration by suppressing the MAPK signaling pathway, and baicalin may be a useful chemotherapeutic agent for asthma.

Inhibition of allergic airway inflammation by antisense-induced blockade of STAT6 expression.

BACKGROUND: The signal transducer and activator of transcription 6 (STAT6) expression in lung epithelial cells plays a pivotal role in asthma pathogenesis. Activation of STAT6 expression results in T helper cell type 2 (Th2) cell differentiation leading to Th2-mediated IgE production, development of allergic airway inflammation and hyperreactivity. Therefore, antagonizing the expression and/or the function of STAT6 could be used as a mode of therapy for allergic airway inflammation. METHODS: In this study, we synthesized a 20-mer phosphorothioate antisense oligonucleotide (ASODN) overlapping the translation starting site of STAT6 and constructed STAT6 antisense RNA (pANTI-STAT6), then transfected them into murine spleen lymphocytes and analyzed the effects of antagonizing STAT6 function in vitro and in a murine model of asthma. RESULTS: In vitro, we showed suppression of STAT6 expression and interleukin (IL)-4 production of lymphocytes by STAT6 ASODN. This effect was more prominent when cells were cultured with pANTI-STAT6. In a murine model of asthma associated with allergic pulmonary inflammation in ovalbumin (OVA)-sensitized mice, local intranasal administration of fluorescein isothiocyanate (FITC)-labeled STAT6 ASODN to DNA uptake in lung cells was accompanied by a reduction of intracellular STAT6 expression. Such intrapulmonary blockade of STAT6 expression abrogated signs of lung inflammation, infiltration of eosinophils and Th2 cytokine production. CONCLUSION: These data suggest a critical role of STAT6 in the pathogenesis of asthma and the use of local delivery of STAT6 ASODN as a novel approach for the treatment of allergic airway inflammation such as in asthma.