DNA methylation down-regulates integrin β4 expression in asthmatic airway epithelial cells

Airway epithelial-derived exosomes induce acute asthma exacerbation after respiratory syncytial virus infection

Acute asthma exacerbation refers to the progressive deterioration of asthma symptoms that is always triggered by virus infection represented by respiratory syncytial virus (RSV). After RSV infection, exaggerated Th2-mediated pulmonary inflammation is the critical pathological response of asthmatic patients with acute exacerbation. Significantly, airway epithelial cells, being the primary targets of RSV infection, play a crucial role in controlling the pulmonary inflammatory response by releasing airway epithelial cell-derived exosomes (AEC-Exos), which potentially influence the development of asthma. However, the specific role of AEC-Exos in acute asthma exacerbation after RSV infection remains obscure. The purpose of this study was to determine the distinct function of AEC-Exos in exacerbating acute asthma following RSV infection. Blockade of exosomes by GW reduce the enhanced pulmonary inflammation significantly. Specifically, the enhanced Th2 inflammation was induced by AEC-Exos thorough transportation of hsa-miR-155-5p-Sirtuin 1 (SIRT1) pathway during acute asthma exacerbation. Targeted inhibition of hsa-miR-155-5p blocks the exaggerated Th2 inflammation effectively in mice with acute asthma exacerbation. In summary, our study showed that during acute asthma exacerbation after RSV infection, AEC-Exos promote the enhanced Th2 inflammation through transportation of increased hsa-miR-155-5p, which was mediated partly through SIRT1-mediated pathway. hsa-miR-155-5p is a potential biomarker for early prediction of acute asthma exacerbation.

Airway epithelial overexpressed cathepsin K induces airway remodelling through epithelial-mesenchymal trophic unit activation in asthma

BACKGROUND AND PURPOSE

Airway epithelial cells (AECs) regulate the activation of epithelial-mesenchymal trophic units (EMTUs) during airway remodelling through secretion of signalling mediators. However, the major trigger and the intrinsic pathogenesis of airway remodelling is still obscure.

EXPERIMENTAL APPROACH

The differing expressed genes in airway epithelia related to airway remodelling were screened and verified by RNA-sequencing and signalling pathway analysis. Then, the effects of increased cathepsin K (CTSK) in airway epithelia on airway remodelling and EMTU activation were identified both in vitro and in vivo, and the molecular mechanism was elucidated in the EMTU model. The potential of CTSK as an an effective biomarker of airway remodelling was analysed in an asthma cohort of differing severity. Finally, an inhibitor of CTSK was administered for potential therapeutic intervention for airway remodelling in asthma.

KEY RESULTS

The expression of CTSK in airway epithelia increased significantly along with the development of airway remodelling in a house dust mite (HDM)-stressed asthma model. Increased secretion of CTSK from airway epithelia induced the activation of EMTUs by activation of the PAR2-mediated pathway. Blockade of CTSK inhibited EMTU activation and alleviated airway remodelling as an effective intervention target of airway remodelling.

CONCLUSION AND IMPLICATIONS

Increased expression of CTSK in airway epithelia is involved in the development of airway remodelling in asthma through EMTU activation, mediated partly through the PAR2-mediated signalling pathway. CTSK is a potential biomarker for airway remodelling, and may also be a useful intervention target for airway remodelling in asthma patients.

Airway epithelial ITGB4 deficiency induces airway remodeling in a mouse model

BACKGROUND

Airway epithelial cells (AECs) with impaired barrier function contribute to airway remodeling through the activation of epithelial-mesenchymal trophic units (EMTUs). Although the decreased expression of ITGB4 in AECs is implicated in the pathogenesis of asthma, how ITGB4 deficiency impacts airway remodeling remains obscure.

OBJECTIVE

This study aims to determine the effect of epithelial ITGB4 deficiency on the barrier function of AECs, asthma susceptibility, airway remodeling, and EMTU activation.

METHODS

AEC-specific ITGB4 conditional knockout mice (ITGB4^-/-) were generated and an asthma model was employed by the sensitization and challenge of house dust mite (HDM). EMTU activation-related growth factors were examined in ITGB4-silenced primary human bronchial epithelial cells of healthy subjects after HDM stimulation. Dexamethasone, the inhibitors of JNK phosphorylation or FGF2 were administered for the identification of the molecular mechanisms of airway remodeling in HDM-exposed ITGB4^-/- mice.

RESULTS

ITGB4 deficiency in AECs enhanced asthma susceptibility and airway remodeling by disrupting airway epithelial barrier function. Aggravated airway remodeling in HDM-exposed ITGB4^-/- mice was induced through the enhanced activation of EMTU mediated by Src homology domain 2-containing protein tyrosine phosphatase 2/c-Jun N-terminal kinase/Jun N-terminal kinase-dependent transcription factor/FGF2 (SHP2/JNK/c-Jun/FGF2) signaling pathway, which was partially independent of airway inflammation. Both JNK and FGF2 inhibitors significantly inhibited the aggravated airway remodeling and EMTU activation in HDM-exposed ITGB4^-/- mice.

CONCLUSIONS

Airway epithelial ITGB4 deficiency induces airway remodeling in a mouse model of asthma through enhanced EMTU activation that is regulated by the SHP2/JNK/c-Jun/FGF2 pathway.

ITGB4 deficiency induces DNA damage by downregulating HDAC1 in airway epithelial cells under stress stimulation

BACKGROUND

DNA damage in airway epithelia under exogenous disruptors can trigger various pulmonary diseases. Integrin beta 4 (ITGB4) is a structural adhesion molecule, which is indicated to regulate the process of DNA damage in airway epithelia for its unique long cytoplasmic domain subunit.

METHODS

The expression level of ITGB4 and the degree of DNA damage were observed in the house dust mite (HDM)-stressed model and ozone-challenged model, respectively. Besides, ITGB4 conditional knockout mice and ITGB4-deficient airway epithelial cells were constructed to observe the influence of ITGB4 deficiency on DNA damage. Furthermore, the influence of ITGB4 deficiency on HDAC1 expression in airway epithelia was determined under stress stimulation. Finally, corresponding intervention strategies were carried out to verify the involvement of the ITGB4-mediated HDAC1 pathway in DNA damage of airway epithelial cells.

RESULTS

HDM stress and ozone challenge reduced the expression of ITGB4, which is accompanied by the increased expression of 8-oxoG and γ-H2AX both in vivo and in vitro. Moreover, ITGB4 deficiency in airway epithelia aggravates the degree of DNA damage under HDM stimulation and ozone stress, respectively. Furthermore, ITGB4 deficiency downregulated the expression of HDAC1 during DNA damage, and restoring HDAC1 can reverse the enhanced DNA damage in airway epithelial cells after exogenous stress.

CONCLUSIONS

This study confirmed the involvement of ITGB4 in the regulation of DNA damage through mediating HDAC1 in airway epithelial cells under exogenous stress. These results supply some useful insights into the mechanism of DNA damage in airway epithelial cells, which would provide possible targets for early prediction and intervention of pulmonary diseases.

Developments in the field of allergy in 2020 through the eyes of Clinical and Experimental Allergy

While 2020 will be remembered for the global coronavirus pandemic, there were also important advances in the field of allergy. In this review article, we summarize key findings reported in Clinical and Experimental Allergy during 2020. We hope this provides readers with an accessible snapshot of the work published in our journal during this time.

The DNA methylation of FOXO3 and TP53 as a blood biomarker of late-onset asthma

BACKGROUND

Late-onset asthma (LOA) is beginning to account for an increasing proportion of asthma patients, which is often underdiagnosed in the elderly. Studies on the possible relations between aging-related genes and LOA contribute to the diagnosis and treatment of LOA. Forkhead Box O3 (FOXO3) and TP53 are two classic aging-related genes. DNA methylation varies greatly with age which may play an important role in the pathogenesis of LOA. We supposed that the differentially methylated sites of FOXO3 and TP53 associated with clinical phenotypes of LOA may be useful biomarkers for the early screening of LOA.

METHODS

The mRNA expression and DNA methylation of FOXO3 and TP53 in peripheral blood of 43 LOA patients (15 mild LOA, 15 moderate LOA and 13 severe LOA) and 60 healthy controls (HCs) were determined. The association of methylated sites with age was assessed by Cox regression to control the potential confounders. Then, the correlation between differentially methylated sites (DMSs; p-value < 0.05) and clinical lung function in LOA patients was evaluated. Next, candidate DMSs combining with age were evaluated to predict LOA by receiver operating characteristic (ROC) analysis and principal components analysis (PCA). Finally, HDM-stressed asthma model was constructed, and DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-AZA) were used to determine the regulation of DNA methylation on the expression of FOXO3 and TP53.

RESULTS

Compared with HCs, the mRNA expression and DNA methylation of FOXO3 and TP53 vary significantly in LOA patients. Besides, 8 DMSs from LOA patients were identified. Two of the DMSs, chr6:108882977 (FOXO3) and chr17:7591672 (TP53), were associated with the severity of LOA. The combination of the two DMSs and age could predict LOA with high accuracy (AUC values = 0.924). In HDM-stressed asthma model, DNA demethylation increased the expression of FOXO3 and P53.

CONCLUSIONS

The mRNA expression of FOXO3 and TP53 varies significantly in peripheral blood of LOA patients, which may be due to the regulation of DNA methylation. FOXO3 and TP53 methylation is a suitable blood biomarker to predict LOA, which may be useful targets for the risk diagnosis and clinical management of LOA.