Airway epithelial integrin ß4-deficiency exacerbates lipopolysaccharide-induced acute lung injury.

Airway epithelial cells, the first barrier of the respiratory tract, play an indispensable role in innate immunity. Integrin ß4 (ITGB4) is a structural adhesion molecule that is involved in the pathological progression of acute inflammatory diseases and is downregulated in asthmatic patients. Research has shown that endothelial ITGB4 has proinflammatory properties in acute lung injury (ALI). However, the role of epithelial ITGB4 in a murine ALI model is still unknown. This study investigated the role of ITGB4 in lipopolysaccharide (LPS)-induced ALI. We found that ITGB4 in the airway epithelium had remarkably increased after the introduction of LPS in vivo and in vitro. Then, we constructed airway epithelial cell-specific ITGB4 knockout (ITGB4-/- ) mice to study its role in ALI. At a time point of 12 h after the tracheal injection of LPS, ITGB4-/- mice showed increased macrophages (mainly M1-type macrophages) and neutrophil infiltration into the lungs; inflammation-related proteins including interleukin (IL)-6, tumor necrosis factor, and IL-17A were significantly elevated compared to their levels in ITGB4+/+ mice. Furthermore, we investigated the role of ITGB4 in the anti-inflammatory response. Intriguingly, in the ITGB4-/- + LPS group, we found significantly reduced expression of anti-inflammatory factors, including IL-10 messenger RNA (mRNA) and ARG-1 mRNA. We also observed that monocyte chemotactic protein (MCP-1) increased significantly both in vivo and in vitro. Airway epithelium activates macrophages, most likely driven by MCP-1, which we confirmed in the coculture of epithelia and macrophages. These phenomena indicate that ITGB4 in airway epithelial cells plays an important role in the process of inflammation and activation of macrophages in ALI. Overall, these data demonstrated a novel link between airway epithelial ITGB4 and the inflammatory response in LPS-induced ALI.

Modulation of the EMT/MET Process by E-Cadherin in Airway Epithelia Stress Injury.

Persistent injury and the following improper repair in bronchial epithelial cells are involved in the pathogenesis of airway inflammation and airway remodeling of asthma. E-cadherin (ECAD) has been shown to be involved in airway epithelium injury repair, but its underlying mechanisms to this process is poorly understood. Here, we describe a previously undetected function of ECAD in regulating the balance of EMT and MET during injury repair. Injury in mice and human bronchial epithelial cells (HBECs) was induced by successive ozone stress for 4 days at 30 min per day. ECAD overexpression in HBECs was induced by stable transfection. EMT features, transforming growth factor beta1 (TGF-ß1) secretion, transcriptional repressor Snail expression, and ß-catenin expression were assayed. Ozone exposure and then removal successfully induced airway epithelium injury repair during which EMT and MET occurred. The levels of TGF-ß1 secretion and Snail expression increased in EMT process and decreased in MET process. While ECAD overexpression repressed EMT features; enhanced MET features; and decreased TGF-ß1 secretion, Snail mRNA level, and ß-catenin protein expression. Moreover, activating ß-catenin blocked the effects of ECAD on EMT, MET and TGF-ß1 signaling. Our results demonstrate that ECAD regulates the balance between EMT and MET, by preventing ß-catenin to inhibit TGFß1 and its target genes, and finally facilitates airway epithelia repair.

[Progress of epithelial-mesenchymal transition in respiratory system and the modulatory mechanism of cell adhesion].

Epithelial-mesenchymal transition (EMT) plays an important role in the development and pathogenesis of respiratory system. Epithelial cells are characterized by well-developed, intercellular contacts, whereas EMT triggers the sequential destabilization of cell-cell adhesive junctions. The dynamic remodeling of the epithelial cell adhesion molecules is important for maintaining the integrity and normal function of epithelium. This paper reviews the research progress of EMT in lung development, lung injury repair and chronic lung diseases, and summarizes the effect of cell junctions and cell adhesion molecules on EMT molecular events.

Epigenetic regulation of TIMP1 expression by 8-oxoguanine DNA glycosylase-1 binding to DNA:RNA hybrid.

8-Oxoguanine DNA glycosylase-1 (OGG1)-initiated base excision repair pathway is primarily responsible for 7, 8-dihydro-8-oxoguanine (8-oxoG) removal from DNA. Recent studies, however, have shown that 8-oxoG in gene regulatory elements may serve as an epigenetic mark, and OGG1 has distinct functions in modulating gene expression. Genome-wide mapping of oxidative stress-induced OGG1 enrichment within introns was documented, but its significance has not yet been fully characterized. Here, we explored whether OGG1 recruited to intron 1 of tissue inhibitor of metalloproteinase-1 (TIMP1) gene and modulated its expression. Using chromatin and DNA:RNA hybrid immunoprecipitation assays, we report recruitment of OGG1 to the DNA:RNA hybrid in intron 1, where it increases nascent RNA but lowers mRNA levels in O3-exposed human airway epithelial cells and mouse lungs. Decrease in TIMP1 expression is alleviated by antioxidant administration, small interfering RNA depletion, or inhibition of OGG1 binding to its genomic substrate. In vitro studies revealed direct interaction between OGG1 and 8-oxoG containing DNA:RNA hybrid, without excision of its substrate. Inhibition of OGG1 binding to DNA:RNA hybrid translated into an increase in TIMP1 expression and a decrease in oxidant-induced lung inflammatory responses as well as airway remodeling. Data documented here reveal a novel molecular link between OGG1 at damaged sites and transcription dynamics that may contribute to oxidative stress-induced cellular and tissue responses.-Pan, L., Wang, H., Luo, J., Zeng, J., Pi, J., Liu, H., Liu, C., Ba, X., Qu, X., Xiang, Y., Boldogh, I., Qin, X. Epigenetic regulation of TIMP1 expression by 8-oxoguanine DNA glycosylase-1 binding to DNA:RNA hybrid.