Conditional knockout of ITGB4 in bronchial epithelial cells directs bronchopulmonary dysplasia.

Neonatal respiratory system disease is closely associated with embryonic lung development. Our group found that integrin ß4 (ITGB4) is downregulated in the airway epithelium of asthma patients. Asthma is the most common chronic respiratory illness in childhood. Therefore, we suspect whether the deletion of ITGB4 would affect fetal lung development. In this study, we characterized the role of ITGB4 deficiency in bronchopulmonary dysplasia (BPD). ITGB4 was conditionally knocked out in CCSP-rtTA, Tet-O-Cre and ITGB4f/f triple transgenic mice. Lung tissues at different developmental stages were collected for experimental detection and transcriptome sequencing. The effects of ITGB4 deficiency on lung branching morphogenesis were observed by fetal mouse lung explant culture. Deleting ITGB4 from the airway epithelial cells results in enlargement of alveolar airspaces, inhibition of branching, the abnormal structure of epithelium cells and the impairment of cilia growth during lung development. Scanning electron microscopy showed that the airway epithelial cilia of the ß4ccsp.cre group appear to be sparse, shortened and lodging. Lung-development-relevant factors such as SftpC and SOX2 significantly decreased both mRNA and protein levels. KEGG pathway analysis indicated that multiple ontogenesis-regulating-relevant pathways converge to FAK. Accordingly, ITGB4 deletion decreased phospho-FAK, phospho-GSK3ß and SOX2 levels, and the correspondingly contrary consequence was detected after treatment with GSK3ß agonist (wortmannin). Airway branching defect of ß4ccsp.cre mice lung explants was also partly recovered after wortmannin treatment. Airway epithelial-specific deletion of ITGB4 contributes to lung developmental defect, which could be achieved through the FAK/GSK3ß/SOX2 signal pathway.

[Research progress of lung aging in chronic respiratory diseases].

Cell aging is an extremely complex process, which is characterized by mitochondrial structural dysfunction, telomere shortening, inflammatory microenvironment, protein homeostasis imbalance, epigenetic changes, abnormal DNA damage and repair, etc. Aging is usually accompanied by structural and functional damage of tissues and organs which further induces the occurrence and development of aging-related diseases. Aging includes physiological aging caused by increased age and pathological aging induced by a variety of factors. Noteworthy, as a target organ directly contacting with the outside air, lung is more prone to various stimuli, causing pathological premature aging which is lung aging. Studies have found that there is a certain proportion of senescent cells in the lungs of most chronic respiratory diseases. However, the underlying mechanism by which these senescent cells induce lung senescence and their role in chronic respiratory diseases is still obscure. This paper focuses on the causes and classification of lung aging, the internal mechanism of lung aging involved in chronic respiratory diseases, and the application of anti-aging treatments in chronic respiratory diseases. We hope to provide new research ideas and theoretical basis for the clinical prevention and treatment in chronic respiratory diseases.

Integrin-ß4 regulates the dynamic changes of phenotypic characteristics in association with epithelial-mesenchymal transition (EMT) and RhoA activity in airway epithelial cells during injury and repair.

Background: In airway disease such as asthma a hyperactive cellular event of epithelial-mesenchymal transition (EMT) is considered as the mechanism of pathological airway tissue remodeling after injury to the airway epithelium. And the initiation of EMT in the airways depends on the epithelial disruption involving dissolution and/or destabilization of the adhesive structures between the cells and ECM. Previously, we have shown that integrin-ß4, an epithelial adhesion molecule in bronchial epithelium is an important regulator of cell proliferation and wound repair in human airway epithelial cells. Therefore, in this study we aimed to investigate whether integrin-ß4 also regulates EMT phenotypes during injury and repair in airway epithelial cells of both wild type/integrin-ß4-/- mice in vivo and cultured cells treated with integrin-ß4/nonsense siRNA in vitro. Methods: We induced injury to the airway epithelial cells by either repeated exposure to ozone and mechanical scratch wound, and subsequently examined the EMT-related phenotypic features in the airway epithelial cells including biomarkers expression, adhesion and cytoskeleton reorganization and cell stiffness. Results: The results show that in response to injury (ozone exposure/scratch wound) and subsequent spontaneous repair (ozone withdrawal/wound healing) both in vivo and in vitro, the airway epithelial cells underwent dynamic changes in the epithelial and mesenchymal biomarkers expression, adhesion and cytoskeleton structures as well as cell stiffness, all together exhibiting enhanced EMT phenotypic features after injury and reversal of the injury-induced effects during repair. Importantly, these injury/repair-associated EMT phenotypic changes in airway epithelial cells appeared to be dependent on integrin-ß4 expression. More specifically, when integrin-ß4 was deficient in mice (integrin-ß4-/-) the repair of ozone-injured airway epithelium was impaired and the recovery of ozone-enhanced EMT biomarkers expression in the airway epithelium was delayed. Similarly, in the scratch wounded airway epithelial cells with integrin-ß4 knockdown, the cells were impaired in all aspects related to EMT during wound and repair including cell proliferation, wound closure rate, adhesion and cytoskeleton protein expression (vinculin and vimentin), mesenchymal-like F-actin reorganization, cell stiffness and RhoA activation. Conclusion: Taken together, these results suggested that integrin-ß4 may be essential in regulating the effects of injury and repair on EMT in airway epithelial cells via influencing both the cell adhesion to ECM and cells' physical phenotypes through RhoA signaling pathway.

[Research progress of respiratory syncytial virus (RSV) infection and respiratory diseases in infancy].

Lower respiratory tract infection (LRTI) induced by respiratory syncytial virus (RSV) is an important cause of hospitalization for infants. Compared with adults, infants are more likely to cause serious respiratory diseases after RSV infection due to the specific immature airway structure and immune system. The balance of immune resistance and immune tolerance of the host is critical to effective virus clearance and disease control. This paper reviews the relationship between RSV infection and respiratory diseases in infancy, the influence factors of the high pathogenicity of RSV infection in early life, as well as the research progress of anti-RSV therapy, and expands the specific molecular events regulating immune resistance and immune tolerance. We expect to present new ideas for the prevention and treatment of RSV-related respiratory diseases in clinical practice.

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.

Analysis on the relevance of asthma susceptibility with the alteration of integrin ß 4 expression.

Accumulated research has suggested the importance of the adhesion molecules modulation as therapeutic approach for bronchial asthma. Adhesion molecules expression alteration contributes to the pathogenesis of asthma. In order to probe the roles of expression imbalance of adhesion molecules in asthma pathogenesis, expression profiling of adhesion molecules was performed using cDNA microarray assay. The results showed that the expression pattern of adhesion molecules was altered in peripheral blood leucocytes of asthma patients. In this study, we focused on one of the abnormally expressed molecule, integrin ß4, which was down-regulated in all asthma patients, to analyze the relevance of asthma susceptibility with the alteration of integrin ß4 expressions. Real time PCR was used to verify the down-regulation of integrin ß4 in additional 38 asthma patients. Next, the 5'flanking region of integrin ß4 DNA were amplified, sequenced and site-directed mutagenesis technology in correspondent variation sites were carried out. Among 4 variation sites found in 5' flanking region of integrin ß4, 3 were related to asthma susceptibility: -nt1029 G/A, -nt 1051 G/A, and -nt 1164 G/C. A reduction of human integrin ß4 promoter activity was observed at mutants of these sites. This study demonstrates that various adhesion molecules in asthma patients are abnormally expressed. Mutations in 5' flanking region result in reduced integrin ß4 expression, which is related to increased risk of asthma.