Transforming Growth Factor-β1 Decreases β2-Agonist-induced Relaxation in Human Airway Smooth Muscle

Dopamine Receptor D1 Is Exempt from Transforming Growth Factor β-Mediated Antifibrotic G Protein-Coupled Receptor Landscape Tampering in Lung Fibroblasts

Pulmonary fibroblasts are the primary producers of extracellular matrix (ECM) in the lungs, and their pathogenic activation drives scarring and loss of lung function in idiopathic pulmonary fibrosis (IPF). This uncontrolled production of ECM is stimulated by mechanosignaling and transforming growth factor beta 1 (TGF-β1) signaling that together promote transcriptional programs including Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). G protein-coupled receptors (GPCRs) that couple to G α s have emerged as pharmacological targets to inactivate YAP/TAZ signaling and promote lung fibrosis resolution. Previous studies have shown a loss of expression of "antifibrotic GPCRs"-receptors that couple to G α s, in IPF patient-derived fibroblasts compared with non-IPF samples. Of the 14 G α s GPCRs we found to be expressed in lung fibroblasts, the dopamine receptor D1 (DRD1) was one of only two not repressed by TGF-β1 signaling, with the β2-adrenergic receptor being the most repressed. We compared the potency and efficacy of multiple D1 and β2 receptor agonists +/- TGF-β1 treatment in vitro for their ability to elevate cAMP, inhibit nuclear localization of YAP/TAZ, regulate expression of profibrotic and antifibrotic genes, and inhibit cellular proliferation and collagen deposition. Consistently, the activity of β2 receptor agonists was lost, whereas D1 receptor agonists was maintained, after stimulating cultured lung fibroblasts with TGF-β1. These data further support the therapeutic potential of the dopamine receptor D1 and highlight an orchestrated and pervasive loss of antifibrotic GPCRs mediated by TGF-β1 signaling. SIGNIFICANCE STATEMENT: Idiopathic pulmonary fibrosis (IPF) is a deadly lung disease with limited therapies. GPCRs have emerged as a primary target for the development of novel antifibrotic drugs; however, a challenge to this approach is the dramatic changes in GPCR expression in response to profibrotic stimuli. Here, we investigate the impact of TGF-β1 on the expression of antifibrotic GPCRs and show the D1 dopamine receptor expression is uniquely maintained in response to TGF-β1, further implicating it as a compelling target to treat IPF.

Cell-contact-mediated assembly of contractile airway smooth muscle rings

Microtissues in the shape of toroidal rings provide an ideal geometry to better represent the structure and function of the airway smooth muscle present in the small airways, and to better understand diseases such as asthma. Here, polydimethylsiloxane devices consisting of a series of circular channels surrounding central mandrels are used to form microtissues in the shape of toroidal rings by way of the self-aggregation and -assembly of airway smooth muscle cell (ASMC) suspensions. Over time, the ASMCs present in the rings become spindle-shaped and axially align along the ring circumference. Ring strength and elastic modulus increase over 14 d in culture, without significant changes in ring size. Gene expression analysis indicates stable expression of mRNA for extracellular matrix-associated proteins, including collagen I and lamininsα1 andα4 over 21 d in culture. Cells within the rings respond to TGF-β1 treatment, leading to dramatic decreases in ring circumference, with increases in mRNA and protein levels for extracellular matrix and contraction-associated markers. These data demonstrate the utility of ASMC rings as a platform for modeling diseases of the small airways such as asthma.

A potential host and virus targeting tool against COVID-19: Chemical characterization, antiviral, cytoprotective, antioxidant, respiratory smooth muscle relaxant effects of Paulownia tomentosa Steud

COronaVIrus Disease 2019 (COVID-19) is a newly emerging infectious disease that spread across the world, caused by the novel coronavirus Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2). Despite the advancements in science that led to the creation of the vaccine, there is still an urgent need for new antiviral drugs effective against SARS-CoV-2. This study aimed to investigate the antiviral effect of Paulownia tomentosa Steud extract against SARS-CoV-2 and to evaluate its antioxidant properties, including respiratory smooth muscle relaxant effects. Our results showed that P. tomentosa extract can inhibit viral replication by directly interacting with both the 3-chymotrypsin-like protease and spike protein. In addition, the phyto complex does not reduce lung epithelial cell viability and exerts a protective action in those cells damaged by tert-butyl hydroperoxide , a toxic agent able to alter cells' functions via increased oxidative stress. These data suggest the potential role of P. tomentosa extract in COVID-19 treatment, since this extract is able to act both as an antiviral and a cytoprotective agent in vitro.

Airway smooth muscle function in asthma

Known to have affected around 340 million people across the world in 2018, asthma is a prevalent chronic inflammatory disease of the airways. The symptoms such as wheezing, dyspnea, chest tightness, and cough reflect episodes of reversible airway obstruction. Asthma is a heterogeneous disease that varies in clinical presentation, severity, and pathobiology, but consistently features airway hyperresponsiveness (AHR)—excessive airway narrowing due to an exaggerated response of the airways to various stimuli. Airway smooth muscle (ASM) is the major effector of exaggerated airway narrowing and AHR and many factors may contribute to its altered function in asthma. These include genetic predispositions, early life exposure to viruses, pollutants and allergens that lead to chronic exposure to inflammatory cells and mediators, altered innervation, airway structural cell remodeling, and airway mechanical stress. Early studies aiming to address the dysfunctional nature of ASM in the etiology and pathogenesis of asthma have been inconclusive due to the methodological limitations in assessing the intrapulmonary airways, the site of asthma. The study of the trachealis, although convenient, has been misleading as it has shown no alterations in asthma and it is not as exposed to inflammatory cells as intrapulmonary ASM. Furthermore, the cartilage rings offer protection against stress and strain of repeated contractions. More recent strategies that allow for the isolation of viable intrapulmonary ASM tissue reveal significant mechanical differences between asthmatic and non-asthmatic tissues. This review will thus summarize the latest techniques used to study ASM mechanics within its environment and in isolation, identify the potential causes of the discrepancy between the ASM of the extra- and intrapulmonary airways, and address future directions that may lead to an improved understanding of ASM hypercontractility in asthma.

Inhibition of ABCC1 Decreases cAMP Egress and Promotes Human Airway Smooth Muscle Cell Relaxation

In most living cells, the second messenger roles for 3',5'-cyclic adenosine monophosphate (cAMP) are short-lived, confined to the intracellular space, and tightly controlled by the binary switch-like actions of the stimulatory G protein (Gαs)-activated adenylyl cyclase (cAMP production) and cAMP-specific phosphodiesterase (cAMP breakdown). Using human airway smooth muscle (HASM) cells in culture as a model, here we report that activation of the cell surface β2-adrenoceptor (β2AR), a Gs-coupled G protein-coupled receptor (GPCR), evokes cAMP egress to the extracellular space. Increased extracellular cAMP levels ([cAMP]_e) are long-lived in culture and induced by receptor-dependent and receptor-independent mechanisms in such a way as to define a universal response class of increased intracellular cAMP levels ([cAMP]_i). We find that HASM cells express multiple ATP-binding cassette (ABC) membrane transporters, with ABCC1 being the most highly enriched transcript mapped to multidrug resistance associated proteins (MRPs). We show that pharmacological inhibition or downregulation of ABCC1 with small interfering RNA markedly reduces β2AR-evoked cAMP release from HASM cells. Further, inhibition of ABCC1 activity or expression decreases basal tone and increases β-agonist-induced HASM cellular relaxation. These findings identify a previously unrecognized role for ABCC1 in the homeostatic regulation of [cAMP]_i in HASM that may be conserved traits of the Gs-coupled family of GPCRs. Hence, the general features of this activation mechanism may uncover new disease-modifying targets in the treatment of airflow obstruction in asthma. Surprisingly, we find that serum cAMP levels are elevated in a small cohort of patients with asthma as compared with controls that warrants further investigation.

Airway smooth muscle pathophysiology in asthma

The airway smooth muscle (ASM) cell plays a central role in the pathogenesis of asthma and constitutes an important target for treatment. These cells control muscle tone and thus regulate the opening of the airway lumen and air passage. Evidence indicates that ASM cells participate in the airway hyperresponsiveness as well as the inflammatory and remodeling processes observed in asthmatic subjects. Therapeutic approaches require a comprehensive understanding of the structure and function of the ASM in both the normal and disease states. This review updates current knowledge about ASM and its effects on airway narrowing, remodeling, and inflammation in asthma.

Metformin use and respiratory outcomes in asthma-COPD overlap

Background

Metformin is associated with improved respiratory outcomes in asthma; however, metformin in COPD and asthma-COPD overlap (ACO) remains unexplored.

Objective

To determine the association between metformin use and respiratory outcomes in COPD and ACO.

Study design and methods

Participants with COPD (FEV1/FVC < 0.70) in the Genetic Epidemiology of COPD study (COPDGene®) were categorized as ACO (n = 510), defined as concurrent physician-diagnosed asthma before age 40 years, or COPD alone (n = 3459). We estimated the association of baseline metformin use with (1) rate of total and severe respiratory exacerbations during follow-up, (2) cross-sectional St. George’s Respiratory Questionnaire (SGRQ) score, six-minute walk distance (6MWD), and post-bronchodilator FEV1 percent predicted (FEV1pp), and (3) 5-year change in SGRQ, 6MWD, and FEV1pp. We also examined change in SGRQ, 6MWD and FEV1pp among participants who initiated metformin during follow-up (n = 108) compared to persistent metformin non-users (n = 2080). Analyses were adjusted for sociodemographic factors, medications, and comorbidities.

Results

Among participants with ACO, metformin use was associated with lower rate of total (adjusted incidence rate ratio [aIRR] 0.3; 95% confidence interval [95%CI] 0.11, 0.77) and severe exacerbations (aIRR 0.29; 95%CI 0.10, 0.89). Among participants with COPD alone, there was no association between metformin use with total (aIRR 0.98; 95%CI 0.62, 1.5) or severe exacerbations (aIRR 1.3; 95% CI 0.68, 2.4) (p-interaction < 0.05). Metformin use was associated with lower baseline SGRQ score (adjusted mean difference [aMD] − 2.7; 95%CI − 5.3, − 0.2) overall. Metformin initiation was associated with improved SGRQ score (aMD –10.0; 95% CI − 18.7, − 1.2) among participants with ACO but not COPD alone (p-interaction < 0.05). There was no association between metformin use and 6MWD or FEV1pp in any comparison.

Conclusions

Metformin use was associated with fewer respiratory exacerbations and improved quality of life among individuals with ACO but not COPD alone. Results suggest a potential role for metformin in ACO which requires further prospective study.

Trial Registry: NCT00608764

Changes in Type 2 Biomarkers After Anti-IL5 Treatment in Patients With Severe Eosinophilic Asthma

Patients with severe eosinophilic asthma (SEA) suffer from frequent asthma exacerbations, where eosinophils are major effector cells in airway inflammation, and anti-interleukin (IL)-5 becomes an effective treatment modality to control eosinophilic inflammation of SEA. Fifteen patients with SEA who had been treated with anti-IL5 (reslizumab, 100 mg monthly intravenously) for 6 months at Ajou University Hospital (Suwon, Korea) were enrolled in this study. Clinical parameters, including total blood eosinophil count (TEC), FEV1%, fractional exhaled nitric oxide (FeNO) levels, and serum biomarkers such as eosinophil-derived neurotoxin (EDN), periostin (PON), and transforming growth factor-β1 (TGF-β1), were analyzed. EDN levels and TEC decreased significantly after 1 month of treatment (P < 0.05 for both), while no changes were noted in FeNO/PON/TGF-β1 levels. FEV1% increased after 2 months of treatment (P < 0.05). A positive correlation was observed between TEC and EDN levels (r = 0.60, P = 0.02). Significant negative correlations were noted between age and TEC/EDN levels (r = -0.57, P = 0.02 and r = -0.56, P = 0.03, respectively). Baseline TEC was higher in the EDN-responder group (≥75% decrease) than in the non-responder group (P = 0.06) with a positive correlation between %reduction in EDN and TEC (r = 0.67, P = 0.01). The onset age was younger and asthma duration was longer in the FEV1%-non-responder group (<12% increase) than in the FEV1%-responder group (P = 0.07 and P = 0.007, respectively). In conclusion, changes in the serum EDN level may be a potential biomarker for monitoring eosinophilic inflammation after anti-IL5 treatment in SEA, which is affected by onset age and asthma duration.

Role of Isocitrate Dehydrogenase 2 on DNA Hydroxymethylation in Human Airway Smooth Muscle Cells

Global DNA hydroxymethylation mediated by the TET (ten-eleven translocation) enzyme was induced in allergen-induced airway hyperresponsiveness in mouse lung tissues and specifically in isolated airway smooth muscle (ASM) cells. TET is an α-ketoglutarate (α-KG)-dependent enzyme, and the production of α-KG is catalyzed by IDH (isocitrate dehydrogenase). However, the role of IDH in the regulation of DNA hydroxymethylation in ASM cells is unknown. In comparison with nonasthmatic cells, asthmatic ASM cells exhibited higher TET activity and IDH2 (but not IDH-1 or IDH-3) gene expression levels. We modified the expression of IDH2 in ASM cells from humans with asthma by siRNA and examined the α-KG levels, TET activity, global DNA hydroxymethylation, cell proliferation, and expression of ASM phenotypic genes. Inhibition of IDH2 in asthmatic ASM cells decreased the α-KG levels, TET activity, and global DNA hydroxymethylation, and reversed the aberrant ASM phenotypes (including decreased cell proliferation and ASM phenotypic gene expression). Specifically, asthmatic cells transfected with siRNA against IDH2 showed decreased 5hmC (5-hydroxymethylcytosine) levels at the TGFB2 (transforming growth factor-β2) promoter determined by oxidative bisulfite sequencing. Taken together, our findings reveal that IDH2 plays an important role in the epigenetic regulation of ASM phenotypic changes in asthmatic ASM cells, suggesting that IDH2 is a potential therapeutic target for reversing the abnormal phenotypes seen in asthma.

Dexamethasone rescues TGF-β1-mediated β2-adrenergic receptor dysfunction and attenuates phosphodiesterase 4D expression in human airway smooth muscle cells

Glucocorticoids (GCs) and β2-adrenergic receptor (β2AR) agonists improve asthma outcomes in most patients. GCs also modulate gene expression in human airway smooth muscle (HASM), thereby attenuating airway inflammation and airway hyperresponsiveness that define asthma. Our previous studies showed that the pro-fibrotic cytokine, transforming growth factor- β1 (TGF-β1) increases phosphodiesterase 4D (PDE4D) expression that attenuates agonist-induced levels of intracellular cAMP. Decreased cAMP levels then diminishes β2 agonist-induced airway relaxation. In the current study, we investigated whether glucocorticoids reverse TGF-β1-effects on β2-agonist-induced bronchodilation and modulate pde4d gene expression in HASM. Dexamethasone (DEX) reversed TGF-β1 effects on cAMP levels induced by isoproterenol (ISO). TGF-β1 also attenuated G protein-dependent responses to cholera toxin (CTX), a Gαs stimulator downstream from the β2AR receptor. Previously, we demonstrated that TGF-β1 treatment increased β2AR phosphorylation to induce hyporesponsiveness to a β2 agonist. Our current data shows that expression of grk2/3, kinases associated with attenuation of β2AR function, are not altered with TGF-β1 stimulation. Interestingly, DEX also attenuated TGF-β1-induced pde4d gene expression. These data suggest that steroids may be an effective therapy for treatment of asthma patients whose disease is primarily driven by elevated TGF-β1 levels.

Analyzing kinetic signaling data for G-protein-coupled receptors

In classical pharmacology, bioassay data are fit to general equations (e.g. the dose response equation) to determine empirical drug parameters (e.g. EC50 and Emax), which are then used to calculate chemical parameters such as affinity and efficacy. Here we used a similar approach for kinetic, time course signaling data, to allow empirical and chemical definition of signaling by G-protein-coupled receptors in kinetic terms. Experimental data are analyzed using general time course equations (model-free approach) and mechanistic model equations (mechanistic approach) in the commonly-used curve-fitting program, GraphPad Prism. A literature survey indicated signaling time course data usually conform to one of four curve shapes: the straight line, association exponential curve, rise-and-fall to zero curve, and rise-and-fall to steady-state curve. In the model-free approach, the initial rate of signaling is quantified and this is done by curve-fitting to the whole time course, avoiding the need to select the linear part of the curve. It is shown that the four shapes are consistent with a mechanistic model of signaling, based on enzyme kinetics, with the shape defined by the regulation of signaling mechanisms (e.g. receptor desensitization, signal degradation). Signaling efficacy is the initial rate of signaling by agonist-occupied receptor (kτ), simply the rate of signal generation before it becomes affected by regulation mechanisms, measurable using the model-free analysis. Regulation of signaling parameters such as the receptor desensitization rate constant can be estimated if the mechanism is known. This study extends the empirical and mechanistic approach used in classical pharmacology to kinetic signaling data, facilitating optimization of new therapeutics in kinetic terms.

Airway Remodeling in Asthma

Asthma is an inflammatory disease of the airways that may result from exposure to allergens or other environmental irritants, resulting in bronchoconstriction, wheezing, and shortness of breath. The structural changes of the airways associated with asthma, broadly referred to as airway remodeling, is a pathological feature of chronic asthma that contributes to the clinical manifestations of the disease. Airway remodeling in asthma constitutes cellular and extracellular matrix changes in the large and small airways, epithelial cell apoptosis, airway smooth muscle cell proliferation, and fibroblast activation. These pathological changes in the airway are orchestrated by crosstalk of different cell types within the airway wall and submucosa. Environmental exposures to dust, chemicals, and cigarette smoke can initiate the cascade of pro-inflammatory responses that trigger airway remodeling through paracrine signaling and mechanostimulatory cues that drive airway remodeling. In this review, we explore three integrated and dynamic processes in airway remodeling: (1) initiation by epithelial cells; (2) amplification by immune cells; and (3) mesenchymal effector functions. Furthermore, we explore the role of inflammaging in the dysregulated and persistent inflammatory response that perpetuates airway remodeling in elderly asthmatics.

Tetrandrine Ameliorates Airway Remodeling of Chronic Asthma by Interfering TGF-β1/Nrf-2/HO-1 Signaling Pathway-Mediated Oxidative Stress

Background

Imbalanced oxidative stress and antioxidant defense are involved in airway remodeling in asthma. It has been demonstrated that Tetrandrine has a potent role in antioxidant defense in rheumatoid arthritis and hypertension. However, the correlation between Tetrandrine and oxidative stress in asthma is utterly blurry. This study aimed to investigate the role of Tetrandrine on oxidative stress-mediated airway remolding.

Materials and Methods

Chronic asthma was established by ovalbumin (OVA) administration in male Wistar rats. Histopathology was determined by HE staining. Immunofluorescence was employed to detect the expression of α-SMA and Nrf-2. Level of oxidative stress and matrix metalloproteinases were examined by ELISA kits. Cell viability and cell cycle of primary airway smooth muscle cells (ASMCs) were evaluated by CCK8 and flow cytometry, respectively. Signal molecules were detected using western blot.

Results

Tetrandrine effectively impairs OVA-induced airway inflammatory and airway remodeling by inhibiting the expression of CysLT1 and CysLTR1. The increase of oxidative stress and subsequent enhancement of MMP9 and TGF-β1 expression were rescued by the administration of Tetrandrine in the rat model of asthma. In in vitro experiments, Tetrandrine markedly suppressed TGF-β1-evoked cell viability and cell cycle promotion of ASMCs in a dose-dependent manner. Furthermore, Tetrandrine promoted Nrf-2 nuclear transcription and activated its downstream HO-1 in vivo and in vitro.

Conclusion

Tetrandrine attenuates airway inflammatory and airway remodeling in rat model of asthma and TGF-β1-induced cell proliferation of ASMCs by regulating oxidative stress in primary ASMCs, suggesting that Tetrandrine possibly is an effective candidate therapy for asthma.

Regulatory cytokine function in the respiratory tract

The respiratory tract is an important site of immune regulation; required to allow protective immunity against pathogens, while minimizing tissue damage and avoiding aberrant inflammatory responses to inhaled allergens. Several cell types work in concert to control pulmonary immune responses and maintain tolerance in the respiratory tract, including regulatory and effector T cells, airway and interstitial macrophages, dendritic cells and the airway epithelium. The cytokines transforming growth factor β, interleukin (IL-) 10, IL-27, and IL-35 are key coordinators of immune regulation in tissues such as the lung. Here, we discuss the role of these cytokines during respiratory infection and allergic airway disease, highlighting the critical importance of cellular source and immunological context for the effects of these cytokines in vivo.