Phosphorylation of low density lipoprotein receptor-related protein 6 is involved in receptor for advanced glycation end product-mediated β-catenin stabilization in a toluene diisocyanate-induced asthma model

Bongkrekic acid alleviates airway inflammation via breaking the mPTP/mtDAMPs/RAGE feedback loop in a steroid-insensitive asthma model

Mitochondrial dysfunction is critical in the pathogenesis of asthma. Mitochondrial permeability transition pore (mPTP) regulates the release of mitochondrial damage-associated molecular patterns (mtDAMPs) to maintain mitochondrial homeostasis. Bongkrekic acid (BKA) is a highly selective inhibitor of mPTP opening, participates the progression of various diseases. This research investigated the exact roles of BKA and mPTP in the pathogenesis of asthma and elucidated its underlying mechanisms. In the present study, cytochrome c, one of the mtDAMPs, levels were elevated in asthmatic patients, and associated to airway inflammation and airway obstruction. BKA, the inhibitor of mPTP markedly reversed TDI-induced airway hyperresponsiveness, airway inflammation, and mitochondrial dysfunction. Pretreatment with mitochondrial precipitation, to simulate the release of mtDAMPs, further increased TDI-induced airway inflammation and the expression of RAGE in mice. Administration of the inhibitor of RAGE, FPS-ZM1, alleviated the airway inflammation, the abnormal open of mPTP and mitochondrial dysfunction induced by mtDAMPs and TDI. Furthermore, stimulation with different mtDAMPs activated RAGE signaling in human bronchial epithelial cells. Accordingly, our study indicated that mPTP was important and BKA was efficient in alleviating inflammation in TDI-induced asthma. A positive feedback loop involving mPTP, mtDAMPs and RAGE was present in TDI-induced asthma, indicating that mPTP might serve as a potential therapeutic target for asthma.

Mitoquinone ameliorated airway inflammation by stabilizing β-catenin destruction complex in a steroid-insensitive asthma model

BACKGROUND AND PURPOSE

Mitochondrial dysfunction is an essential part of the pathophysiology of asthma, and potential treatments that target the malfunctioning mitochondria have attracted widespread attention. We have previously demonstrated that aberrant epithelial β-catenin signaling played a crucial role in a toluene diisocyanate (TDI)-induced steroid-insensitive asthma model. The objective of this study was to determine if the mitochondrially targeted antioxidant mitoquinone(MitoQ) regulated the activation of β-catenin in TDI-induced asthma.

METHOD

Mice were sensitized and challenged with TDI to generate a steroid-insensitive asthma model. Human bronchial epithelial cells (16HBE) were exposed to TDI-human serum albumin (HSA) and ethidium bromide(EB) to simulate the TDI-induced asthma model and mitochondrial dysfunction.

RESULTS

MitoQ dramatically attenuated TDI-induced AHR, airway inflammation, airway goblet cell metaplasia, and collagen deposition and markedly protected epithelial mitochondrial functions by preserving mass and diminishing the production of reactive oxygen species (ROS). MitoQ administration stabilized β-catenin destruction complex from disintegration and inhibited the activation of β-catenin. Similarly, YAP1, an important constituent of β-catenin destruction complex, was inhibited by Dasatinib, which alleviated airway inflammation and the activation of β-catenin, and restored mitochondrial mass. In vitro, treating 16HBE cells with EB led to the activation of YAP1 and β-catenin signaling, decreased the expression of glucocorticoid receptors and up-regulated interleukin (IL)-1β, IL6 and IL-8 expression.

CONCLUSION

Our results indicated that mitochondria mediates airway inflammation by regulating the stability of the β-catenin destruction complex and MitoQ might be a promising therapeutic approach to improve airway inflammation and severe asthma.

AVAILABILITY OF DATA AND MATERIALS

The data that support the findings of this study are available from the corresponding author upon reasonable request. Some data may not be made available because of privacy or ethical restrictions.

miR-3934 regulates the apoptosis and secretion of inflammatory cytokines of basophils via targeting RAGE in asthma

Background

Several miRNAs are now known to have clear connections to the pathogenesis of asthma. The present study focused on the potential role of miR-3934 during asthma development.

Methods

miR-3934 was detected as a down-regulated miRNA in basophils by sequencing analysis. Next, the expression levels of miR-3934 in peripheral blood mononuclear cells of 50 asthma patients and 50 healthy volunteers were examined by RT-qPCR methods. The basophils were then treated with AGEs and transfected with miR-3934 mimics. The apoptosis levels were examined by flow cytometry assay; and the expression levels of cytokines were detected using the ELISA kits. Finally, the Western blot was performed to examined the expression of key molecules in the TGF-β/Smad signaling pathway.

Results

miR-3934 was down-regulated in the basophils of asthmatic patients. The expression of the pro-inflammatory cytokines IL-6, IL-8 and IL-33 was enhanced in basophils from asthmatic patients, and this effect was partially reversed by transfection of miR-3934 mimics. Furthermore, receiver operating characteristics analysis showed that miR-3934 levels can be used to distinguish asthma patients from healthy individuals. miR-3934 partially inhibited advanced glycation end products-induced increases in basophil apoptosis by suppressing expression of RAGE.

Conclusion

Our results indicate that miR-3934 acts to mitigate the pathogenesis of asthma by targeting RAGE and suppressing TGF-β/Smad signaling.

RAGE mediates airway inflammation via the HDAC1 pathway in a toluene diisocyanate-induced murine asthma model

BACKGROUND

Exposure to toluene diisocyanate (TDI) is a significant pathogenic factor for asthma. We previously reported that the receptor for advanced glycation end products (RAGE) plays a key role in TDI-induced asthma. Histone deacetylase (HDAC) has been reported to be important in asthmatic pathogenesis. However, its effect on TDI-induced asthma is not known. The aim of this study was to determine the role of RAGE and HDAC in regulating airway inflammation using a TDI-induced murine asthma model.

METHODS

BALB/c mice were sensitized and challenged with TDI to establish an asthma model. FPS-ZM1 (RAGE inhibitor), JNJ-26482585 and romidepsin (HDAC inhibitors) were administered intraperitoneally before each challenge. In vitro, the human bronchial epithelial cell line 16HBE was stimulated with TDI-human serum albumin (TDI-HSA). RAGE knockdown cells were constructed and evaluated, and MK2006 (AKT inhibitor) was also used in the experiments.

RESULTS

In TDI-induced asthmatic mice, the expression of RAGE, HDAC1, and p-AKT/t-AKT was upregulated, and these expressions were attenuated by FPS-ZM1. Airway reactivity, Th2 cytokine levels in lymph supernatant, IgE, airway inflammation, and goblet cell metaplasia were significantly increased in the TDI-induced asthmatic mice. These increases were suppressed by JNJ-26482585 and romidepsin. In addition, JNJ-26482585 and romidepsin ameliorated the redistribution of E-cadherin and β-catenin in TDI-induced asthma. In TDI-HSA-stimulated 16HBE cells, knockdown of RAGE attenuated the upregulation of HDAC1 and phospho-AKT (p-AKT). Treatment with the AKT inhibitor MK2006 suppressed TDI-induced HDAC1 expression.

CONCLUSIONS

These findings indicate that RAGE modulates HDAC1 expression via the PI3K/AKT pathway, and that inhibition of HDAC prevents TDI-induced airway inflammation.

The axis of the receptor for advanced glycation endproducts in asthma and allergic airway disease

Asthma is a generalized term that describes a scope of distinct pathologic phenotypes of variable severity, which share a common complication of reversible airflow obstruction. Asthma is estimated to affect almost 400 million people worldwide, and nearly ten percent of asthmatics have what is considered "severe" disease. The majority of moderate to severe asthmatics present with a "type 2-high" (T2-hi) phenotypic signature, which pathologically is driven by the type 2 cytokines Interleukin-(IL)-4, IL-5, and IL-13. However, "type 2-low" (T2-lo) phenotypic signatures are often associated with more severe, steroid-refractory neutrophilic asthma. A wide range of clinical and experimental studies have found that the receptor for advanced glycation endproducts (RAGE) plays a significant role in the pathogenesis of asthma and allergic airway disease (AAD). Current experimental data indicates that RAGE is a critical mediator of the type 2 inflammatory reactions which drive the development of T2-hi AAD. However, clinical studies demonstrate that increased RAGE ligands and signaling strongly correlate with asthma severity, especially in severe neutrophilic asthma. This review presents an overview of the current understandings of RAGE in asthma pathogenesis, its role as a biomarker of disease, and future implications for mechanistic studies, and potential therapeutic intervention strategies.

JNK modulates RAGE/β-catenin signaling and is essential for allergic airway inflammation in asthma

As a leading cause of occupational asthma, toluene diisocyanate (TDI)-induced asthma is an inflammatory disease of the airways with one of the most significant characteristics involving inflammation, in which the receptor of advanced glycation end products (RAGE) plays an extremely important role. However, the mechanism underlying the upregulation of RAGE is still unknown. The aim of the present study was to examine whether JNK mediates β-catenin stabilization via activation of RAGE in asthma. Herein from the results by analyzing the blood from healthy donors and patients with asthma, it was found that the expression of RAGE and p-JNK is highly correlated and elevated concomitantly with the severity of bronchial asthma. Additionally, upon sensitizing and challenging the mice with TDI, we found that RAGE inhibitor (FPS-ZM1) and JNK inhibitor (SP600125) significantly reduced the TDI-induced asthma inflammation in vivo. Furthermore, SP600125 also considerably restored RAGE and p-JNK expression. Besides, the in vitro results from TDI-HSA treatment of 16HBE cells reveal that therapeutic inhibition of JNK reduced TDI driving RAGE expression and β-catenin translocation, while treatment with Anisomycin, a JNK agonist, showed the opposite effect. Moreover, genetic knockdown of RAGE does not contribute to JNK phosphorylation, indicating that JNK functions upstream of RAGE. Collectively, these findings highlight a role for JNK signaling in RAGE/β-catenin regulation and have important therapeutic implications for the treatment of TDI induced asthma.

The AKT inhibitor MK2206 suppresses airway inflammation and the pro‑remodeling pathway in a TDI‑induced asthma mouse model

The cellular and molecular mechanisms via which MK2206, an AKT inhibitor, prevents the activation of AKT in toluene diisocyanate (TDI)‑induced asthma remain unclear. Thus, the present study aimed to evaluate the potential effects of MK2206 on airway AKT activation, inflammation and remodeling in a TDI‑induced mouse model of asthma. A total of 24 BALB/c mice were selected and randomly divided into untreated (AOO), asthma (TDI), MK2206 (TDI + MK2206), and dexamethasone (TDI + DEX) groups. Phosphorylated AKT (p‑AKT), total AKT, airway remodeling indices, α‑smooth muscle actin (α‑SMA) and collagen I levels in pulmonary tissue were measured using western blotting. Airway inflammation factors, including interleukin (IL)‑4, ‑5, ‑6, and ‑13 in bronchoalveolar lavage fluid (BALF) and IgE in serum, were determined using ELISA. Additionally, the airway hyperresponsiveness (AHR) and pulmonary pathology of all groups were evaluated. The results of the present study demonstrated that p‑AKT levels in lung protein lysate were upregulated, and neutrophil, eosinophil and lymphocyte counts were increased in the lungs obtained from the asthma group compared with the AOO group. Both MK2206 and DEX treatment in TDI‑induced mice resulted not only in the attenuation of AKT phosphorylation, but also reductions in neutrophil, eosinophil and lymphocyte counts in the lungs of mice in the asthma group. Consistently, increases in the levels of the inflammatory cytokines IL‑4, ‑5, ‑6 and ‑13 analyzed in BALF, and serum IgE in the TDI group were demonstrated to be attenuated in the TDI + MK2206 and TDI + DEX groups. Furthermore, α‑SMA and AHR were significantly attenuated in the TDI + MK2206 group compared with the TDI group. These results revealed that MK2206 not only inhibited AKT activation, but also served a role in downregulating airway inflammation and airway remodeling in chemical‑induced asthma. Therefore, the findings of the present study may provide important insight into further combination therapy.

Association of RAGE gene multiple variants with the risk for COPD and asthma in northern Han Chinese

Clinical and experimental data have shown that the receptor for advanced glycation end products (RAGE) is implicated in the pathogenesis of respiratory disorders. In this study, we genotyped five widely-evaluated variants in RAGE gene, aiming to assess their association with the risk for chronic obstructive pulmonary disease (COPD) and asthma in northern Han Chinese. Genotypes were determined in 105 COPD patients, 242 asthma patients and 527 controls. In single-locus analysis, there was significant difference in the genotype distributions of rs1800624 between COPD patients and controls (p=0.022), and the genotype and allele distributions of rs1800625 differed significantly (p=0.040 and 0.016) between asthma patients and controls. Haplotype analysis revealed that haplotype T-A-G-T (allele order: rs1800625, rs1800624, rs2070600, rs184003) was significantly associated with a reduced COPD risk (OR=0.32, 95% CI: 0.06-0.60), and haplotype T-A-A-G was significantly associated with a reduced asthma risk (OR=0.19, 95% CI: 0.04-0.96). Further haplotype-phenotype analysis showed that high- and low-density lipoprotein cholesterol and blood urea nitrogen were significant mediators for COPD (p_sim=0.041, 0.043 and 0.030, respectively), and total cholesterol was a significant mediator for asthma (p_sim=0.009). Taken together, our findings indicate that RAGE gene is a promising candidate for COPD and asthma, and importantly both disorders are genetically heterogeneous.

Long-term methylglyoxal intake aggravates murine Th2-mediated airway eosinophil infiltration

Asthma outcomes is aggravated in obese patients. Excess of methylglyoxal (MGO) in obese/diabetic patients has been associated with diverse detrimental effects on cell function. This study aimed to evaluate the effects of long-term oral intake of MGO on ovalbumin-induced eosinophil inflammation. Male C57/Bl6 mice received 0.5% MGO in the drinking water for 12 weeks. Mice were sensitized and challenged with ovalbumin (OVA), and at 48 h thereafter, bronchoalveolar lavage (BAL) fluid and lungs were collected for cell counting, morphological analysis, and ELISA, mRNA expressions and DHE assays. In MGO-treated mice, OVA challenge significantly increased the peribronchiolar infiltrations of inflammatory cells and eosinophils compared with control group. Higher levels of IL-4, IL-5, and eotaxin in BAL fluid were also detected in MGO compared with control group. In addition, lung tissue of MGO-treated mice displayed significant increases in mRNA expressions of NF-κB and iNOS whereas COX-2 expression remained unchanged. The high TNF-α mRNA expression observed in lungs of OVA-challenged control mice was not further increased by MGO treatment. In MGO group, OVA-challenge increased significantly the NOX-2 and NOX-4 mRNA expressions, without affecting the NOX-1 expression. Levels of reactive-oxygen species (ROS) were significantly higher in lungs of MGO-treated mice, and no further increase by OVA-challenge was observed. In conclusion, 12-week intake of MGO exacerbates Th2-mediated airway eosinophil infiltration by activation of NF-kB/iNOS-dependent signaling pathway and positive regulation of NOX-2 and NOX-4 in the lung tissues. Scavengers of MGO could be an option to prevent obesity-related asthma.

Consistent Biomarkers and Related Pathogenesis Underlying Asthma Revealed by Systems Biology Approach

Asthma is a common chronic airway disease worldwide. Due to its clinical and genetic heterogeneity, the cellular and molecular processes in asthma are highly complex and relatively unknown. To discover novel biomarkers and the molecular mechanisms underlying asthma, several studies have been conducted by focusing on gene expression patterns in epithelium through microarray analysis. However, few robust specific biomarkers were identified and some inconsistent results were observed. Therefore, it is imperative to conduct a robust analysis to solve these problems. Herein, an integrated gene expression analysis of ten independent, publicly available microarray data of bronchial epithelial cells from 348 asthmatic patients and 208 healthy controls was performed. As a result, 78 up- and 75 down-regulated genes were identified in bronchial epithelium of asthmatics. Comprehensive functional enrichment and pathway analysis revealed that response to chemical stimulus, extracellular region, pathways in cancer, and arachidonic acid metabolism were the four most significantly enriched terms. In the protein-protein interaction network, three main communities associated with cytoskeleton, response to lipid, and regulation of response to stimulus were established, and the most highly ranked 6 hub genes (up-regulated CD44, KRT6A, CEACAM5, SERPINB2, and down-regulated LTF and MUC5B) were identified and should be considered as new biomarkers. Pathway cross-talk analysis highlights that signaling pathways mediated by IL-4/13 and transcription factor HIF-1α and FOXA1 play crucial roles in the pathogenesis of asthma. Interestingly, three chemicals, polyphenol catechin, antibiotic lomefloxacin, and natural alkaloid boldine, were predicted and may be potential drugs for asthma treatment. Taken together, our findings shed new light on the common molecular pathogenesis mechanisms of asthma and provide theoretical support for further clinical therapeutic studies.

RAGE mediates β-catenin stabilization via activation of the Src/p-Cav-1 axis in a chemical-induced asthma model

We previously demonstrated receptor for advanced glycation end products (RAGE) was required for β-catenin stabilization in a toluene diisocyanate (TDI)-induced asthma model, suggesting it plays an important role in TDI-induced airway inflammation. The aim of this study was to examine whether RAGE mediates β-catenin stabilization via activation of the Src/p-Cav-1 axis in TDI-induced asthma model. To generate a chemical-induced asthma model, male BALB/c mice were sensitized and challenged with TDI. Before each challenge, FPS-ZM1 (RAGE inhibitor) and PP2 (Src inhibitor) was given via intraperitoneal injection. In the TDI-exposed mice, airway reactivity, airway inflammation, goblet cell metaplasia, and the release of Th2 cytokines and IgE increased significantly. The level of membrane β-catenin decreased but was increased in the cytoplasm. Increased expression of RAGE, p-Src, and p-Cav-1 was also detected in TDI-exposed lungs. However, all these changes were inhibited by FPS-ZM1 and PP2. In TDI-HSA stimulated human airway epithelial (16HBE) cells, the expression of p-Src and p-Cav-1, and the abnormal distribution of β-catenin were significantly increased, and then inhibited in RAGE knockdown cells. Similarly, PP2 or non-phosphorylatable Cav-1 mutant (Y14F-Cav-1) treated 16HBE cells had the same effect on the distribution of β-catenin. In addition, blockage of RAGE signaling and phosphorylation of Cav-1 eliminated the translocation of β-catenin from cytomembrane to cytoplasm. Our results showed that RAGE modulates β-catenin aberrant distribution via activation of Src/p-Cav-1 in a chemical-induced asthma model.