Airway smooth muscle and airway hyperresponsiveness in asthma - mechanisms of airway smooth muscle dysfunction

Discovery of zolinium TSG1180 as a novel agonist of transgelin-2 for treating asthma

Asthma is a complex and heterogeneous respiratory disease that causes serious social and economic burdens. Current drugs such as β2-agonists cannot fully control asthma. Our previous study found that Transgelin-2 is a potential target for treating asthmatic pulmonary resistance. Herein, we discovered a zolinium compound, TSG1180, that showed a strong interaction with Transgelin-2. The equilibrium dissociation constants (KD) of TSG1180 to Transgelin-2 were determined to be 5.363 × 10-6 and 9.81 × 10-6 M by surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). Cellular thermal shift assay (CETSA) results showed that the thermal stability of Transgelin-2 increased after coincubation of TSG1180 with lysates of airway smooth muscle cells (ASMCs). Molecular docking showed that Arg39 may be the key residue for the binding. Then, the SPR result showed that the binding affinity of TSG1180 to Transgelin-2 mutant (R39E) was decreased by 1.69-fold. Real time cell analysis (RTCA) showed that TSG1180 treatment could relax ASMCs by 19 % (P < 0.05). Once Transgelin-2 was inhibited, TSG1180 cannot induce a relaxation effect, suggesting that the relaxation effect was specifically mediated by Transgelin-2. In vivo study showed TSG1180 effectively reduced pulmonary resistance by 64 % in methacholine-induced mice model (P < 0.05). Furthermore, the phosphorylation of Ezrin at T567 was increased by 8.06-fold, the phosphorylation of ROCK at Y722 was reduced by 38 % and the phosphorylation of RhoA at S188 was increased by 52 % after TSG1180 treatment. These results suggested that TSG1180 could be a Transgelin-2 agonist for further optimization and development as an anti-asthma drug.

Allyl isothiocyanate mitigates airway inflammation and constriction in a house dust mite-induced allergic asthma model via upregulation of tight junction proteins and the TRPA1 modulation

Asthma is a chronic inflammatory disease that has been associated with insufficient vegetable intake. Allyl Isothiocyanate (AITC) is a natural isothiocyanate found in cruciferous plants with anti-inflammatory and antioxidant abilities. Our study aimed to investigate the potential effect of AITC on tracheal constriction in a house dust mite (HDM)-induced asthma animal model, and explore the underlying mechanisms. To investigate the effects of AITC on HDM-induced allergic asthma model, established by intranasally administering extracts of HDM and AITC or DEX was given orally for four weeks. Flexivent SCIREQ, H&E staining, ELISA were employed to evaluate the lung function and the cytokine secretion. Possible mechanisms were determined by Western blot. Rat tracheae contraction was measured by Labscribe. We utilized lung epithelial cells (BEAS-2B) to assess the adhesion response to the combination of inflammatory factors TNF-α and IL-4. The results of the study showed that AITC significantly reduced tracheal constriction in ex vivo experiments and improved lung function in in vivo experiments compared to HDM-induced mice. Additionally, AITC decreased cytokine secretion, inflammatory cell infiltration in the lung, and constriction-related proteins expression in both lung and tracheae. Moreover, AITC increased tight junction-related protein expression in lung tissues. In vitro experiments showed that AITC had a protective effect through TRPA1 channel without affecting cell viability. Our results demonstrate that AITC has potential anti-asthma effects in HDM-induced asthma models by alleviating airway inflammation and airway constriction through increasing tight junction-related protein expression and suppressing Ca2+ signaling. These findings suggest that AITC may be a beneficial adjuvant therapy in asthma treatment.

Rhinovirus induces airway remodeling: what are the physiological consequences?

BACKGROUND

Rhinovirus infections commonly evoke asthma exacerbations in children and adults. Recurrent asthma exacerbations are associated with injury-repair responses in the airways that collectively contribute to airway remodeling. The physiological consequences of airway remodeling can manifest as irreversible airway obstruction and diminished responsiveness to bronchodilators. Structural cells of the airway, including epithelial cells, smooth muscle, fibroblasts, myofibroblasts, and adjacent lung vascular endothelial cells represent an understudied and emerging source of cellular and extracellular soluble mediators and matrix components that contribute to airway remodeling in a rhinovirus-evoked inflammatory environment.

MAIN BODY

While mechanistic pathways associated with rhinovirus-induced airway remodeling are still not fully characterized, infected airway epithelial cells robustly produce type 2 cytokines and chemokines, as well as pro-angiogenic and fibroblast activating factors that act in a paracrine manner on neighboring airway cells to stimulate remodeling responses. Morphological transformation of structural cells in response to rhinovirus promotes remodeling phenotypes including induction of mucus hypersecretion, epithelial-to-mesenchymal transition, and fibroblast-to-myofibroblast transdifferentiation. Rhinovirus exposure elicits airway hyperresponsiveness contributing to irreversible airway obstruction. This obstruction can occur as a consequence of sub-epithelial thickening mediated by smooth muscle migration and myofibroblast activity, or through independent mechanisms mediated by modulation of the β2 agonist receptor activation and its responsiveness to bronchodilators. Differential cellular responses emerge in response to rhinovirus infection that predispose asthmatic individuals to persistent signatures of airway remodeling, including exaggerated type 2 inflammation, enhanced extracellular matrix deposition, and robust production of pro-angiogenic mediators.

CONCLUSIONS

Few therapies address symptoms of rhinovirus-induced airway remodeling, though understanding the contribution of structural cells to these processes may elucidate future translational targets to alleviate symptoms of rhinovirus-induced exacerbations.

Desert particulate matter from Afghanistan increases airway obstruction in human distal lungs exposed to type 2 cytokine IL-13

Introduction

Deployment related asthma-like symptoms including distal airway obstruction have been described in U.S. military personnel who served in Iraq and Afghanistan. The mechanisms responsible for the development of distal airway obstruction in deployers exposed to desert particulate matter (PM) is not well understood. We sought to determine if respiratory exposure to PM from Afghanistan (PMa) increases human distal airway hyperresponsiveness (AHR) with or without exposures to IL-13, a type 2 cytokine. We further tested whether mitochondrial dysfunction, such as ATP signaling and oxidative stress, may contribute to PMa- mediated AHR.

Methods

Precision-cut lung slices from donors without a history of lung disease, tobacco smoking, or vaping were pre-treated with IL-13 for 24 h. This was followed by exposure to PMa or PM from California (PMc, control for PMa) for up to 72 h. The role of hydrogen peroxide and ATP in AHR was assessed using the antioxidant enzyme catalase or an ATP receptor P2Y13 antagonist MRS2211. AHR in response to methacholine challenges as well as cytokine IL-8 production were measured.

Results

PMa alone, but not PMc alone, trended to increase AHR. Importantly, the combination of PMa and IL-13 significantly amplified AHR compared to control or PMc+IL-13. PMa alone and in combination with IL-13 increased IL-8 as compared to the control. PMa increased H2O2 and ATP. MRS211 and catalase reduced AHR in PCLS exposed to both PMa and IL-13.

Discussion

Our data suggests that PMa in a type 2 inflammation-high lung increased AHR in part through oxidative stress and ATP signaling.