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

CTNNAL1 promotes the structural integrity of bronchial epithelial cells through the RhoA/ROCK1 pathway

Adhesion molecules play critical roles in maintaining the structural integrity of the airway epithelium in airways under stress. Previously, we reported that catenin alpha-like 1 (CTNNAL1) is downregulated in an asthma animal model and upregulated at the edge of human bronchial epithelial cells (HBECs) after ozone stress. In this work, we explore the potential role of CTNNAL1 in the structural adhesion of HBECs and its possible mechanism. We construct a CTNNAL1 ‒/‒ mouse model with CTNNAL1-RNAi recombinant adeno-associated virus (AAV) in the lung and a CTNNAL1-silencing cell line stably transfected with CTNNAL1-siRNA recombinant plasmids. Hematoxylin and eosin (HE) staining reveals that CTNNAL1 ‒/‒ mice have denuded epithelial cells and structural damage to the airway. Silencing of CTNNAL1 in HBECs inhibits cell proliferation and weakens extracellular matrix adhesion and intercellular adhesion, possibly through the action of the cytoskeleton. We also find that the expressions of the structural adhesion-related molecules E-cadherin, integrin β1, and integrin β4 are significantly decreased in ozone-treated cells than in vector control cells. In addition, our results show that the expression levels of RhoA/ROCK1 are decreased after CTNNAL1 silencing. Treatment with Y27632, a ROCK inhibitor, abolished the expressions of adhesion molecules induced by ozone in CTNNAL1-overexpressing HBECs. Overall, the findings of the present study suggest that CTNNAL1 plays a critical role in maintaining the structural integrity of the airway epithelium under ozone challenge, and is associated with epithelial cytoskeleton dynamics and the expressions of adhesion-related molecules via the RhoA/ROCK1 pathway.

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 β4 (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 β4ccsp.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-GSK3β and SOX2 levels, and the correspondingly contrary consequence was detected after treatment with GSK3β agonist (wortmannin). Airway branching defect of β4ccsp.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/GSK3β/SOX2 signal pathway.

Novel role for integrin β4 in asthmatic children infected with Mycoplasma pneumoniae

Objectives: The regulatory role of integrin β4 (ITGB4) in asthmatic children infected with Mycoplasma pneumoniae (MP) was analyzed, and its potential molecular mechanisms and function were studied.Methods: We collected epidemiological data from 70,455 asthmatic children. The immunofluorescence assay was used to test 9 index IgMs against respiratory tract pathogens for 736 serum samples. Then, 98 children with severe asthma were treated via fiberoptic bronchoscope examination. During the surgery, the patients' lavage fluid was collected. Additionally, differences in transforming growth factor-beta (TGF-β) expression between the MP-infected and noninfected groups were examined. Experiments were performed using white blood cell counting methods and flow cytometry for 98 asthmatic children.Results: We tested 736 specimens, and the percentages of MP, RSV, and ADV infections were 50.27%, 11.68%, and 10.05%, respectively. The percentage of eosinophils was increased significantly in the AS-I-MP group, and their TGF-β expression levels were increased, which was related to tissue fibrosis. Furthermore, MP infection exacerbated the decreasing trend of ITGB4 expression in patients' blood compared with the noninfected group.Conclusions: There might be a chain reaction from MP infection to an increase in ITGB4, a decrease in TGF-β, a large accumulation of eosinophils and the development of asthma in children.

Deficiency of Integrin β4 Results in Increased Lung Tissue Stiffness and Responds to Substrate Stiffness via Modulating RhoA Activity

The interaction between extracellular matrix (ECM) and epithelial cells plays a key role in lung development. Our studies found that mice with conditional integrin β4 (ITGB4) knockout presented lung dysplasia and increased stiffness of lung tissues. In accordance with our previous studies regarding the functions of ITGB4 in bronchial epithelial cells (BECs), we hypothesize that the decreased ITGB4 expression during embryonic stage leads to abnormal ECM remodeling and increased tissue stiffness, thus impairing BECs motility and compromising lung development. In this study, we examined lung tissue stiffness in normal and ITGB4 deficiency mice using Atomic Force Microscopy (AFM), and demonstrated that ITGB4 deficiency resulted in increased lung tissue stiffness. The examination of ECM components collagen, elastin, and lysyl oxidase (LOX) family showed that the expression of type VI collagen, elastin and LOXL4 were significantly elevated in the ITGB4-deficiency mice, compared with those in normal groups. Airway epithelial cell migration and proliferation capacities on normal and stiff substrates were evaluated through video-microscopy and flow cytometry. The morphology of the cytoskeleton was detected by laser confocal microscopy, and RhoA activities were determined by fluorescence resonance energy transfer (FRET) microscopy. The results showed that migration and proliferation of ITGB4 deficiency cells were noticeably inhibited, along decreased cytoskeleton stabilization, and hampered RhoA activity, especially for cells cultured on the stiff substrate. These results suggest that decreased ITGB4 expression results in increased lung tissue stiffness and impairs the adaptation of bronchial epithelial cells to substrate stiffness, which may be related to the occurrence of broncho pulmonary dysplasia.

ITGB4 deficiency induces mucus hypersecretion by upregulating MUC5AC in RSV-infected airway epithelial cells

Respiratory syncytial virus (RSV) infection is the main cause of bronchiolitis in children. Excessive mucus secretion is one of the primary symbols in RSV related lower respiratory tract infections (RSV-related LRTI), which is closely associated with the occurrence and development of asthma in later life. Integrin β4 (ITGB4) is down-regulated in the airway epithelial cells (AECs) of asthma patients which plays a critical role in the pathogenesis of asthma. However, whether ITGB4 is involved in the pathological processes of RSV infection remains unclear. In this study, we found that decreased expression of ITGB4 was negatively correlated with the level of MUC5AC in childhood AECs following RSV infection. Moreover, ITGB4 deficiency led to mucus hypersecretion and MUC5AC overexpression in the small airway of RSV-infected mice. MUC5AC expression was upregulated by ITGB4 in HBE cells through EGFR, ERK and c-Jun pathways. EGFR inhibitors treatment inhibited mucus hypersecretion and MUC5AC overexpression in ITGB4-deficient mice after RSV infection. Together, these results demonstrated that epithelial ITGB4 deficiency induces mucus hypersecretion by upregulating the expression of MUC5AC through EGFR/ERK/c-Jun pathway, which further associated with RSV-related LRTI.

Airway epithelial integrin β4 suppresses allergic inflammation by decreasing CCL17 production

Airway epithelial cells (AECs) play a key role in asthma susceptibility and severity. Integrin β4 (ITGB4) is a structural adhesion molecule that is down-regulated in the airway epithelium of asthma patients. Although a few studies hint toward the role of ITGB4 in asthmatic inflammation pathogenesis, their specific resultant effects remain unexplored. In the present study, we determined the role of ITGB4 of AECs in the regulation of Th2 response and identified the underpinning molecular mechanisms. We found that ITGB4 deficiency led to exaggerated lung inflammation and AHR with higher production of CCL17 in house dust mite (HDM)-treated mice. ITGB4 regulated CCL17 production in AECs through EGFR, ERK and NF-κB pathways. EFGR-antagonist treatment or the neutralization of CCL17 both inhibited exaggerated pathological marks in HDM-challenged ITGB4-deficient mice. Together, these results demonstrated the involvement of ITGB4 deficiency in the development of Th2 responses of allergic asthma by down-regulation of EGFR and CCL17 pathway in AECs.

Airway epithelial ITGB4 deficiency in early life mediates pulmonary spontaneous inflammation and enhanced allergic immune response

Lung immune responses to respiratory pathogens and allergens are initiated in early life which will further influence the later onset of asthma. The airway epithelia form the first mechanical physical barrier to allergic stimuli and environmental pollutants, which is also the key regulator in the initiation and development of lung immune response. However, the epithelial regulation mechanisms of early-life lung immune responses are far from clear. Our previous study found that integrin β4 (ITGB4) is decreased in the airway epithelium of asthma patients with specific variant site. ITGB4 deficiency in adult mice aggravated the lung Th2 immune responses and enhanced airway hyper-responsiveness (AHR) with a house dust mite (HDM)-induced asthma model. However, the contribution of ITGB4 to the postnatal lung immune response is still obscure. Here, we further demonstrated that ITGB4 deficiency following birth mediates spontaneous lung inflammation with ILC2 activation and increased infiltration of eosinophils and lymphocytes. Moreover, ITGB4 deficiency regulated thymic stromal lymphopoietin (TSLP) production in airway epithelial cells through EGFR pathways. Neutralization of TSLP inhibited the spontaneous inflammation significantly in ITGB4-deficient mice. Furthermore, we also found that ITGB4 deficiency led to exaggerated lung allergic inflammation response to HDM stress. In all, these findings indicate that ITGB4 deficiency in early life causes spontaneous lung inflammation and induces exaggerated lung inflammation response to HDM aeroallergen.

ITGB4 deficiency in bronchial epithelial cells directs airway inflammation and bipolar disorder-related behavior

BACKGROUND

Chronic persistent airway inflammation has been associated with the comorbidity of asthma and bipolar disorder (BD). However, the direct relevance between airway inflammation and BD-like psychiatric comorbidity is almost unknown. Integrin β4 (ITGB4) is downregulated on the airway epithelial of asthma patients, which might play a critical role in the parthenogenesis of airway inflammation. So this study aimed to examine the role of ITGB4 deficiency in mediating airway inflammation and further leading to the BD-like behaviors.

METHODS

ITGB4^-/- mice were generated by mating ITGB4^fl/fl mice with CCSP-rtTA^tg/-/TetO-Cretg/tg mice. Mania-like behavior tests were performed, including hyperlocomotion, D-amphetamine-induced hyperactivity, open-field test, and elevated plus-maze test. Depressive-like behavior tests were carried out, including sucrose preference, forced swimming, and learned helplessness. Inflammatory cells (Th17, Th1, Th2) in the lung were examined by flow cytometry. Futhermore, inflammatory cytokines (IL-4, IL-13) in bronchoalveolar lavage fluid and sera were detected by ELISA. Protein expression of the IL-4Rα on choroid plexus, microglial marker (IBA1), and synapse-associated proteins (synaptophysin, SYP) in the hippocampus and prefrontal cortex were examined by western blotting. Additionally, proinflammatory cytokines (IL-1β, IL-6, and TNF-α) in the hippocampus and prefrontal cortex were detected by immunohistochemistry. Inflammatory disorder in the lung, hippocampus, and prefrontal cortex was tested by hematoxylin and eosin (H&E) staining. And cell apoptosis in the hippocampus and prefrontal cortex was measured by TUNEL test.

RESULTS

ITGB4^-/- mice exhibited mania-like behavior, including hyperlocomotion, D-amphetamine-induced hyperactivity, and reduced anxiety-like behavior. While under stressful conditions, ITGB4^-/- mice manifested depressive-like behavior, including anhedonia, behavioral despair, and enhanced learned helplessness. At the same time, ITGB4^-/- mice mainly exerted Th2-type inflammation in periphery, like the number and major cytokines IL-4 and IL-13 of Th2-type inflammation. ITGB4^-/- mice also showed a significant increase of microglia and pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α in the hippocampus and prefrontal cortex. Additionally, neuron damage, increased neuron apoptosis, and the decrease of SYP were found in ITGB4^-/- mice.

CONCLUSIONS

These findings confirmed that airway inflammatory induced by ITGB4 deficiency is the important incentive for the BD-like behavior during asthma pathogenesis. The ITGB4-deficient mice provide a validated animal model for us to study the possible mechanism of BD-like psychiatric comorbidity of asthma patients.

ITGB4 is essential for containing HDM-induced airway inflammation and airway hyperresponsiveness

Airway epithelial cells play a significant role in the pathogenesis of asthma. Although the structural and functional defects of airway epithelial cells have been postulated to increase asthma susceptibility and exacerbate asthma severity, the mechanism and implication of these defects remain uncertain. Integrin β4 (ITGB4) is a structural adhesion molecule that is downregulated in the airway epithelium of asthma patients. In this study, we demonstrated that ITGB4 deficiency leads to severe allergy-induced airway inflammation and airway hyper-responsiveness (AHR) in mice. After house dust mite (HDM) challenge, epithelial cell-specific ITGB4-deleted mice showed increased lymphocyte, eosinophil, and neutrophil infiltration into lung compared with that of the wild-type mice. ITGB4 deficiency also resulted in increased expression of the Th2 cytokine IL-4, IL-13, and the Th17 cytokine IL-17A in the lung tissue and in the T cells after HDM challenge. The aggravated inflammation in ITGB4 defect mice was partly caused by enhanced disrupted epithelial barrier integrity after HDM stress, which induced the increased thymic stromal lymphopoietin secretion from airway epithelial cells. This study therefore demonstrates that ITGB4 plays a pivotal role in containing allergen-mediated lung inflammation and airway hyper-responsiveness in allergic asthma.

Nitric Oxide Synthase Activity Correlates with OGG1 in Ozone-Induced Lung Injury Animal Models

Background: NO is an important cellular signaling molecule which is derived from L-arginine by nitric oxide synthase (NOS) and the effects of NOS signaling in lung injury is conflicting. The present study was designed to observe the effect of NOS and Arginase signaling in the occurrence and development of lung injury and its mechanism. Methods: An ozone-stressed lung injury animal model was established by exposure to 2.0 ppm O₃ for 30 min every day for consecutive 12 day with or without the administration of NO precursor L-arginine or non-selective NOS inhibitor N-nitro-L-arginine methyl ester (L-NAME). Then, the lung histopathology, the releases of inflammatory mediators and the production of ROS were assayed by immunohistochemistry, ELISA and flow cytometry respectively. The activities and expression of NOS and Arginase were assayed by biochemical methods and western blot. Correspondingly, the release of 8-oxoguanine glycosylase 1(8-OxoG) and 8-oxoguanine glycosylase 1 (OGG1) were assayed by ELISA and western blot. The correlation between NOS/Arginase signaling with 8-OxoG/ OGG1 was also analyzed by Pearson correlation coefficients and immunofluorescence in NOS deficient bronchial epithelial cells. Results: In ozone-induced rat lung injury models, lung inflammation as well as lung architecture was disrupted in a time dependent manner. Ozone treatment with L-arginine showed a substantial attenuation of adverse lung histopathological changes and treatment with L-NAME promoted the inflammation and remodeling. Importantly, the expression of NOS was promoted by L-arginine and inhibited by L-NAME and the expression of Arginase was promoted by L-NAME treatment. Further, we observed significantly higher levels of 8-OxoG and lower levels of OGG1 in ozone group which was reversed by L-arginine and promoted by L-NAME. The expression of NOS is closely related with 8-OxoG /OCG1. Conclusion: These findings give further evidence that the NOS signaling is related with base excise repair.