Airway smooth muscle hypercontractility in asthma

Downregulation of protein phosphatase 2Aα in asthmatic airway smooth muscle

Airway smooth muscle cell (ASM) is renowned for its involvement in airway hyperresponsiveness through impaired ASM relaxation and bronchoconstriction in asthma, which poses a significant challenge in the field. Recent studies have explored different targets in ASM to alleviate airway hyperresponsiveness, however, a sizeable portion of patients with asthma still experience poor control. In our study, we explored protein phosphatase 2 A (PP2A) in ASM as it has been reported to regulate cellular contractility by controlling intracellular calcium ([Ca2+]i), ion channels, and respective regulatory proteins. We obtained human ASM cells and lung tissues from healthy and patients with asthma and evaluated PP2A expression using RNA-Seq data, immunofluorescence, and immunoblotting. We further investigated the functional importance of PP2A by determining its role in bronchoconstriction using mouse bronchus and human ASM cell [Ca2+]i regulation. We found robust expression of PP2A isoforms in human ASM cells with PP2Aα being highly expressed. Interestingly, PP2Aα was significantly downregulated in asthmatic tissue and human ASM cells exposed to proinflammatory cytokines. Functionally, FTY720 (PP2A agonist) inhibited acetylcholine- or methacholine-induced bronchial contraction in mouse bronchus and further potentiated isoproterenol-induced bronchial relaxation. Mechanistically, FTY720 inhibited histamine-evoked [Ca2+]i response and myosin light chain (MLC) phosphorylation in the presence of interleukin-13 (IL-13) in human ASM cells. To conclude, we for the first time established PP2A signaling in ASM, which can be further explored to develop novel therapeutics to alleviate airway hyperresponsiveness in asthma.NEW & NOTEWORTHY This novel study deciphered the expression and function of protein phosphatase 2Aα (PP2Aα) in airway smooth muscle (ASM) during asthma and/or inflammation. We showed robust expression of PP2Aα in human ASM while its downregulation in asthmatic ASM. Similarly, we demonstrated reduced PP2Aα expression in ASM exposed to proinflammatory cytokines. PP2Aα activation inhibited bronchoconstriction of isolated mouse bronchi. In addition, we unveiled that PP2Aα activation inhibits the intracellular calcium release and myosin light chain phosphorylation in human ASM.

Percent Recovery Index Predicts Poor Asthma Control and Exacerbation in Adults

Background

Previous studies indicate that the percent recovery index (PRI: the percentage increase from the maximally reduced FEV1 after bronchodilator inhalation), one of the indexes of methacholine bronchial provocation, may predict acute asthma exacerbations in childhood and elderly asthmatics. It is known that childhood (<12) and elder (>60) asthmatics may be different to adult patients in many aspect including prognosis. However, in adults, a research for predicting value of PRI to exacerbation is still absence. Besides exacerbation, predicting value of PRI to poor asthma control is also unknown. We try to detect whether PRI can predict poor asthma control and exacerbation in adults in this research. Meanwhile, we try to detect whether treatment can influence PRI.

Methods

In 61 adults with asthma, baseline PRI was measured during enrollment. And then baseline PRI was evaluated as a predictor of exacerbation or poor asthma control at an upcoming 3-month follow-up. The covariates included age, sex, BMI, previous exacerbation, smoking status and baseline lung function. After treatment for 3 months, PRI was measured again and compared with baseline PRI.

Results

After the 3-month follow-up, we found that baseline PRI was significantly related to asthma exacerbation (P = 0.023), poor asthma control (ACT at 3 months, P = 0.014), decreased quality of life (decrease of MiniAQLQ, P = 0.010) and cumulative number of EDHO at 3 months (P = 0.039). Meanwhile, no significant correlation was observed between baseline PRI and inflammation factors (FENO, CaNO, and EOS). Finally, PRI was dramatically reduced after standard treatment for 3 months.

Conclusion

PRI is efficient in the prediction of poor asthma control and exacerbation in adults. The predictive value of PRI may rely on the inherent property of asthmatic airway smooth muscle (ASM) independent of inflammation factors. Effective treatment can alleviate PRI dramatically and that indicate PRI may also be valuable in evaluation of curative effect.

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.

Anti-asthmatic fraction screening and mechanisms prediction of Schisandrae Sphenantherae Fructus based on a combined approach

Objective: Schisandrae Sphenantherae Fructus (SSF) is a traditional Chinese medicine used to treat coughs and pulmonary inflammatory diseases. However, the pharmacodynamic material basis and mechanisms for SSF in asthma treatment remain unclear. This study aims to screen the anti-asthmatic fraction and verify the pharmacodynamic material basis, predict the potential mechanism, and verify the interaction ability between compounds and core targets.

Methods: First, three fractions from SSF were compared in terms of composition, comparison, and anti-asthmatic effects. Then, the ultra-performance liquid chromatography-quadrupole/time-of-flight-mass spectrometry/mass spectrometry (UPLC-Q/TOF-MS/MS) strategy was used to identify the compounds from the active fraction, and the anti-asthmatic efficacy of the active fraction was further studied by the ovalbumin (OVA)-induced asthma murine model. Finally, network pharmacology and molecular methods were used to study the relationships between active compounds, core targets, and key pathways of PEF in asthma treatments.

Results: The petroleum ether fraction (PEF) of SSF showed better effects and could significantly diminish lung inflammation and mitigate the level of serum immunoglobulin E (IgE), interleukin (IL)-4, IL-5, IL-6, IL-13, and IL-17 in mice. A total of 26 compounds from the PEF were identified, among which the main compounds are lignans and triterpenes. Moreover, 21 active compounds, 129 overlap-ping targets, and 10 pathways were screened by network pharmacology tools. The top five core targets may play a great role in asthma treatment. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that the PEF can treat asthma by acting on multiple asthma pathological processes, including the IL-17 signaling pathway, T helper (Th) 17 cell differentiation, and the calcium signaling pathway. Molecular docking was performed to evaluate the interactions of the protein–ligand binding, and most docked complexes had a good binding ability.

Conclusion: The present results might contribute to exploring the active compounds with anti-asthmatic activity.

Metal-Stimulated Interleukin-6 Production Through a Proton-Sensing Receptor, Ovarian Cancer G Protein-Coupled Receptor 1, in Human Bronchial Smooth Muscle Cells: A Response Inhibited by Dexamethasone

Purpose

Human bronchial smooth muscle cells (BSMCs) contribute to airway obstruction and hyperresponsiveness in patients with bronchial asthma. BSMCs also generate cytokines and matricellular proteins in response to extracellular acidification through the ovarian cancer G protein-coupled receptor 1 (OGR1). Cobalt (Co) and nickel (Ni) are occupational agents, which cause occupational asthma. We examined the effects of Co and Ni on interleukin-6 (IL-6) secretion by human BSMCs because these metals may act as ligands of OGR1.

Methods

Human BSMCs were incubated in Dulbecco's Modified Eagle Medium (DMEM) containing 0.1% bovine serum albumin (BSA) (0.1% BSA-DMEM) for 16 hours and stimulated for the indicated time by exchanging the medium with 0.1% BSA-DMEM containing any of the metals or pH-adjusted 0.1% BSA-DMEM. IL-6 mRNA expression was quantified via reverse transcription polymerase chain reaction (RT-PCR) using the real-time TaqMan technology. IL-6 was measured using an enzyme-linked immunosorbent assay. Dexamethasone (DEX) was added 30 minutes before each stimulation. To knock down the expression of OGR1 in BSMCs, small interfering RNA (siRNA) targeting OGR1 (OGR1-siRNA) was transfected to the cells and non-targeting siRNA (NT-siRNA) was used as a control.

Results

Co and Ni both significantly increased IL-6 secretion in human BSMCs at 300 μM. This significant increase in IL-6 mRNA expression was observed 5 hours after stimulation. BSMCs transfected with OGR1-siRNA produced less IL-6 than BSMCs transfected with NT-siRNA in response to either Co or Ni stimulation. DEX inhibited Co- and Ni-stimulated IL-6 secretion by human BSMCs as well as pH 6.3-stimulated IL-6 secretion in a dose-dependent manner. DEX did not decrease phosphorylation of ERK1/2, p38 MAP kinase, and NF-κB p65 induced by either Co or Ni stimulation.

Conclusion

Co and Ni induce secretion of IL-6 in human BSMCs through activation of OGR1. Co- and Ni-stimulated IL-6 secretion is inhibited by DEX.

Mitochondrial ATP-Sensitive K+ Channel Opening Increased the Airway Smooth Muscle Cell Proliferation by Activating the PI3K/AKT Signaling Pathway in a Rat Model of Asthma

Abnormal proliferation of airway smooth muscle cells (ASMCs) leads to airway remodeling and the development of asthma. This study aimed to assess whether mitochondrial ATP-sensitive K+ (mitoK_ATP) channels regulated the proliferation of ASMCs by regulating the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway in asthmatic rats. Forty-eight Sprague Dawley rats were immunized with ovalbumin-containing alum to establish the asthma models. The ASMCs were isolated and identified by phase-contrast microscopic images and immunohistochemical staining for α-smooth muscle actin. The ASMCs were treated with a potent activator of mitoK_ATP, diazoxide, or an inhibitor of mitoK_ATP, 5-hydroxydecanoate (5-HD). Rhodamine-123 (R-123) was used for detecting the mitochondrial membrane potential (Δψm). The proliferation of ASMCs was examined by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. The protein and mRNA expressions of AKT and p-AKT were detected using western blotting and quantitative real-time PCR. The results showed that diazoxide enhanced the mitoK_ATP channel opening in ASMCs in the rat model of asthma, while 5-HD impeded it. Diazoxide also increased ASMC proliferation in the rat model of asthma, whereas 5-HD alleviated it. However, LY294002, a PI3K/AKT pathway inhibitor, reversed the functional roles of diazoxide in the proliferation ability of ASMCs in the rat model of asthma. Furthermore, treatment with diazoxide induced the phosphorylation of AKT, and treatment with 5-HD decreased the phosphorylation of AKT in ASMCs in the rat model of asthma. In conclusion, the mitoK_ATP channel opening increased the proliferation of ASMCs by activating the PI3K/AKT signaling pathway in a rat model of asthma.

The Interplay Between Asthma and Other Diseases: Role of Ca2+/cAMP Signalling

OBJECTIVE

Asthma is correlated with a higher risk of manifesting other diseases, including hypertension, diabetes, obesity, psychiatric and neurological diseases, and cancer. Therefore, revealing this interplay between asthma and these illnesses may provide novel insights into their pathogenesis.

RESULTS

It is highly debated that dysregulation of Ca2+ homeostasis is involved in the pathogenesis of these maladies. Not surprisingly, calcium (Ca2+) channel blockers (CCBs), classically used as antihypertensive medicines, have been demonstrating off-label effects such as alleviating asthma symptoms, in addition to antidiabetic, antiobesity, anticancer and antineurodegenerative effects. Our studies about Ca2+/cAMP signalling may shed some new light on this field.

CONCLUSION

Thus, considering that asthma and associated illnesses such as hypertension, diabetes, obesity, cancer and neurodegenerative diseases have become highly prevalent medical problems in the world, the comprehension of this interplay between asthma and other disorders could improve drug therapy.

A link among schizophrenia, diabetes, and asthma: Role of Ca2+/cAMP signaling

Asthma has been associated with an increased risk for developing schizophrenia. In addition, schizophrenia has been associated with an increased risk for developing type 2 diabetes mellitus, resulting in an elevated cardiovascular risk and in a limited life expectancy. It is well discussed that dysregulations related to Ca²⁺ signaling could link these diseases, in addition to cAMP signaling pathways. Thus, revealing this interplay among schizophrenia, diabetes, and asthma may provide novel insights into the pathogenesis of these diseases. Publications involving Ca²⁺ and cAMP signaling pathways, schizophrenia, diabetes, and asthma (alone or combined) were collected by searching PubMed and EMBASE. Both Ca²⁺ and cAMP signaling pathways (Ca²⁺/cAMP signaling) control the release of neurotransmitters and hormones, in addition to airway smooth muscle contractility, then dysregulations of these cellular processes may be involved in these diseases. Taking into consideration, the experience of our group in this field, this narrative review debated the involvement of Ca²⁺/cAMP signaling in this link among schizophrenia, diabetes, and asthma, including its pharmacological implications.

Extracellular acidification-induced CXCL8 production through a proton-sensing receptor OGR1 in human airway smooth muscle cells: a response inhibited by dexamethasone

Background

Human airway smooth muscle cells (ASMCs) contribute to bronchial contraction and airway hyperresponsiveness in patients with bronchial asthma. They also generate cytokines, chemokines, and matricellular proteins. Ovarian cancer G protein-coupled receptor 1 (OGR1) senses extracellular protons and mediates the production of interleukin-6 (IL-6) and connective tissue growth factor (CTGF) in ASMCs.

Methods

ASMCs were stimulated for the indicated time by pH 6.3 or pH 7.4-adjusted Dulbecco’s Modified Eagle Medium (DMEM) containing 0.1% bovine serum albumin (BSA) (0.1% BSA-DMEM). As a control stimulant, pH 7.4-adjusted 0.1% BSA-DMEM containing 10 ng/mL tumor necrosis factor-α (TNF-α) was used. Interleukin-8/C-X-C motif chemokine ligand 8 (CXCL8) mRNA expression in ASMCs was quantified by RT-PCR using real-time TaqMan technology. CXCL8 secreted from ASMCs was measured by enzyme-linked immunosorbent assay (ELISA). Phosphorylation at serine 536 of NF-κB p65 and binding of p65 to oligonucleotide containing an NF-κB consensus binding site were analyzed by Western blotting and an ELISA-based kit.

Results

Acidic pH induced a significant increase of CXCL8 mRNA expression and CXCL8 protein secretion in ASMCs. ASMCs transfected with small interfering RNA (siRNA) targeted for OGR1 produced less CXCL8 compared with those transfected with non-targeting siRNA. Protein kinase C (PKC) inhibitor, MEK1/2 inhibitor, and the inhibitor of IκB phosphorylation reduced acidic pH-stimulated CXCL8 production in ASMCs. Dexamethasone also inhibited acidic pH-stimulated CXCL8 production of ASMCs in a dose-dependent manner. Dexamethasone did not affect either phosphorylation or binding to the consensus DNA site of NF-κB p65.

Conclusions

CXCL8 released from ASMCs by extracellular acidification may play a pivotal role in airway accumulation of neutrophils. Glucocorticoids inhibit acidic pH-stimulated CXCL8 production independent of serine 536 phosphorylation and the binding to DNA of NF-κB p65, although NF-κB activity is essential for CXCL8 production in ASMCs.

Attenuation of murine and human airway contraction by a peptide fragment of the cytoskeleton regulatory protein gelsolin

We have previously reported that mice genetically deficient in the actin binding protein gelsolin exhibit impaired airway smooth muscle (ASM) relaxation. Primary cultured ASM cells from these mice demonstrate enhanced inositol triphosphate (IP₃) synthesis and increased intracellular calcium in response to G_q-coupled agonists. We hypothesized that this was due to increased intracellular availability of unbound phosphatidylinositol 4,5-bisphosphate (PIP₂), based on the fact that gelsolin contains a short peptide region that binds PIP₂, presumably making it a less available substrate. We now questioned whether a peptide that corresponds to the PIP₂ binding region of gelsolin could modulate ASM signaling and contraction. The 10 amino acid sequence of the gelsolin peptide within the PIP₂-binding region was incubated with primary cultures of human ASM cells, and IP₃ synthesis was measured in response to a G_q-coupled agonist. Gelsolin peptide-treated cells generated less IP₃ under basal and bradykinin or acetylcholine (G_q-coupled) conditions. Acetylcholine-induced contractile force measured in isolated tracheal rings from mice and human tracheal muscle strips in organ baths was attenuated in the presence of the gelsolin peptide. The gelsolin peptide also attenuated methacholine-induced airway constriction in murine precision-cut lung slices. Furthermore, this peptide fragment delivered to the respiratory system of mice via nebulization attenuated subsequent methacholine-induced increases in airway resistance in vivo. The current study demonstrates that introduction of this small gelsolin peptide into the airway may be a novel therapeutic option in bronchoconstrictive diseases.

Echocardiographic Assessment of Ventricular Function in Young Patients with Asthma

Background

Despite significant advances in understanding the pathophysiology and management of asthma, some of systemic effects of asthma are still not well defined.

Objectives

To compare heart function, baseline physical activity level, and functional exercise capacity in young patients with mild-to-moderate asthma and healthy controls.

Methods

Eighteen healthy (12.67 ± 0.39 years) and 20 asthmatics (12.0 ± 0.38 years) patients were enrolled in the study. Echocardiography parameters were evaluated using conventional and tissue Doppler imaging (TDI).

Results

Although pulmonary acceleration time (PAT) and pulmonary artery systolic pressure (PASP) were within normal limits, these parameters differed significantly between the control and asthmatic groups. PAT was lower (p < 0.0001) and PASP (p < 0.0002) was higher in the asthma group (114.3 ± 3.70 ms and 25.40 ± 0.54 mmHg) than the control group (135.30 ± 2.28 ms and 22.22 ± 0.40 mmHg). The asthmatic group had significantly lower early diastolic myocardial velocity (E', p = 0.0047) and lower E' to late (E'/A', p = 0.0017) (13.75 ± 0.53 cm/s and 1.70 ± 0.09, respectively) compared with control group (15.71 ± 0.34 cm/s and 2.12 ± 0.08, respectively) at tricuspid valve. In the lateral mitral valve tissue Doppler, the asthmatic group had lower E' compared with control group (p = 0.0466; 13.27 ± 0.43 cm/s and 14.32 ± 0.25 cm/s, respectively), but there was no statistic difference in the E'/A' ratio (p = 0.1161). Right isovolumetric relaxation time was higher (p = 0.0007) in asthmatic (57.15 ± 0.97 ms) than the control group (52.28 ± 0.87 ms), reflecting global myocardial dysfunction. The right and left myocardial performance indexes were significantly higher in the asthmatic (0.43 ± 0.01 and 0.37 ± 0.01, respectively) compared with control group (0.40 ± 0.01 and 0.34 ± 0.01, respectively) (p = 0.0383 and p = 0.0059, respectively). Physical activity level, and distance travelled on the six-minute walk test were similar in both groups.

Conclusion

Changes in echocardiographic parameters, evaluated by conventional and TDI, were observed in mild-to-moderate asthma patients even with normal functional exercise capacity and baseline physical activity level. Our results suggest that the echocardiogram may be useful for the early detection and evoluation of asthma-induced cardiac changes.

TGF-β1 Evokes Human Airway Smooth Muscle Cell Shortening and Hyperresponsiveness via Smad3

Transforming growth factor β1 (TGF-β1), a cytokine whose levels are elevated in the airways of patients with asthma, perpetuates airway inflammation and modulates airway structural cell remodeling. However, the role of TGF-β1 in excessive airway narrowing in asthma, or airway hyperresponsiveness (AHR), remains unclear. In this study, we set out to investigate the direct effects of TGF-β1 on human airway smooth muscle (HASM) cell shortening and hyperresponsiveness. The dynamics of AHR and single-cell excitation-contraction coupling were measured in human precision-cut lung slices and in isolated HASM cells using supravital microscopy and magnetic twisting cytometry, respectively. In human precision-cut lung slices, overnight treatment with TGF-β1 significantly augmented basal and carbachol-induced bronchoconstriction. In isolated HASM cells, TGF-β1 increased basal and methacholine-induced cytoskeletal stiffness in a dose- and time-dependent manner. TGF-β1-induced single-cell contraction was corroborated by concomitant increases in myosin light chain and myosin phosphatase target subunit 1 phosphorylation levels, which were attenuated by small interfering RNA-mediated knockdown of Smad3 and pharmacological inhibition of Rho kinase. Strikingly, these physiological effects of TGF-β1 occurred through a RhoA-independent mechanism, with little effect on HASM cell [Ca2+]i levels. Together, our data suggest that TGF-β1 enhances HASM excitation-contraction coupling pathways to induce HASM cell shortening and hyperresponsiveness. These findings reveal a potential link between airway injury-repair responses and bronchial hyperreactivity in asthma, and define TGF-β1 signaling as a potential target to reduce AHR in asthma.

New perspectives on the regulation of type II inflammation in asthma

Asthma is a chronic inflammatory disease of the lungs which has been thought to arise as a result of inappropriately directed T helper type-2 (Th2) immune responses of the lungs to otherwise innocuous inhaled antigens. Current asthma therapeutics are directed towards the amelioration of downstream consequences of type-2 immune responses (i.e. β-agonists) or broad-spectrum immunosuppression (i.e. corticosteroids). However, few approaches to date have been focused on the primary prevention of immune deviation. Advances in molecular phenotyping reveal heterogeneity within the asthmatic population with multiple endotypes whose varying expression depends on the interplay between numerous environmental factors and the inheritance of a broad range of susceptibility genes. The most common endotype is one described as "type-2-high" (i.e. high levels of interleukin [IL]-13, eosinophilia, and periostin). The identification of multiple endotypes has provided a potential explanation for the observations that therapies directed at typical Th2 cytokines (IL-4, IL-5, and IL-13) and their receptors have often fallen short when they were tested in a diverse group of asthmatic patients without first stratifying based on disease endotype or severity. However, despite the incorporation of endotype-dependent stratification schemes into clinical trial designs, variation in drug responses are still apparent, suggesting that additional genetic/environmental factors may be contributing to the diversity in drug efficacy. Herein, we will review recent advances in our understanding of the complex pathways involved in the initiation and regulation of type-2-mediated immune responses and their modulation by host factors (genetics, metabolic status, and the microbiome). Particular consideration will be given to how this knowledge could pave the way for further refinement of disease endotypes and/or the development of novel therapeutic strategies for the treatment of asthma .

A novel role for primary cilia in airway remodeling

Primary cilia (PC) are solitary cellular organelles that play critical roles in development, homeostasis, and disease pathogenesis by modulating key signaling pathways such as Sonic Hedgehog and calcium flux. The antenna-like shape of PC enables them also to facilitate sensing of extracellular and mechanical stimuli into the cell, and a critical role for PC has been described for mesenchymal cells such as chondrocytes. However, nothing is known about the role of PC in airway smooth muscle cells (ASMCs) in the context of airway remodeling. We hypothesized that PC on ASMCs mediate cell contraction and are thus integral in the remodeling process. We found that PC are expressed on ASMCs in asthmatic lungs. Using pharmacological and genetic methods, we demonstrated that PC are necessary for ASMC contraction in a collagen gel three-dimensional model both in the absence of external stimulus and in response to the extracellular component hyaluronan. Mechanistically, we demonstrate that the effect of PC on ASMC contraction is, to a small extent, due to their effect on Sonic Hedgehog signaling and, to a larger extent, due to their effect on calcium influx and membrane depolarization. In conclusion, PC are necessary for the development of airway remodeling by mediating calcium flux and Sonic Hedgehog signaling.

Highly selective inhibition of myosin motors provides the basis of potential therapeutic application

Direct inhibition of smooth muscle myosin (SMM) is a potential means to treat hypercontractile smooth muscle diseases. The selective inhibitor CK-2018571 prevents strong binding to actin and promotes muscle relaxation in vitro and in vivo. The crystal structure of the SMM/drug complex reveals that CK-2018571 binds to a novel allosteric pocket that opens up during the "recovery stroke" transition necessary to reprime the motor. Trapped in an intermediate of this fast transition, SMM is inhibited with high selectivity compared with skeletal muscle myosin (IC₅₀ = 9 nM and 11,300 nM, respectively), although all of the binding site residues are identical in these motors. This structure provides a starting point from which to design highly specific myosin modulators to treat several human diseases. It further illustrates the potential of targeting transition intermediates of molecular machines to develop exquisitely selective pharmacological agents.

The impact of vitamin D on asthmatic human airway smooth muscle

Asthma is a chronic heterogeneous disorder, which involves airway inflammation, airway hyperresponsiveness (AHR) and airway remodeling. The airway smooth muscle (ASM) bundle regulates the broncho-motor tone and plays a critical role in AHR as well as orchestrating inflammation. Vitamin D deficiency has been linked to increased severity and exacerbations of symptoms in asthmatic patients. It has been shown to modulate both immune and structural cells, including ASM cells, in inflammatory diseases. Given that current asthma therapies have not been successful in reversing airway remodeling, vitamin D supplementation as a potential therapeutic option has gained a great deal of attention. Here, we highlight the potential immunomodulatory properties of vitamin D in regulating ASM function and airway inflammation in bronchial asthma.

Altered Innate Immune Responses in Neutrophils from Patients with Well- and Suboptimally Controlled Asthma

BACKGROUND

Respiratory infections are a major cause of asthma exacerbations where neutrophilic inflammation dominates and is associated with steroid refractory asthma. Structural airway cells in asthma differ from nonasthmatics; however it is unknown if neutrophils differ. We investigated neutrophil immune responses in patients who have good (AGood) and suboptimal (ASubopt) asthma symptom control.

METHODS

Peripheral blood neutrophils from AGood (ACQ < 0.75, n = 11), ASubopt (ACQ > 0.75, n = 7), and healthy controls (HC) (n = 9) were stimulated with bacterial (LPS (1 μg/mL), fMLF (100 nM)), and viral (imiquimod (3 μg/mL), R848 (1.5 μg/mL), and poly I:C (10 μg/mL)) surrogates or live rhinovirus (RV) 16 (MOI1). Cell-free supernatant was collected after 1 h for neutrophil elastase (NE) and matrix metalloproteinase- (MMP-) 9 measurements or after 24 h for CXCL8 release. Results. Constitutive NE was enhanced in AGood neutrophils compared to HC. fMLF stimulated neutrophils from ASubopt but not AGood produced 50% of HC levels. fMLF induced MMP-9 was impaired in ASubopt and AGood compared to HC. fMLF stimulated CXCL8 but not MMP-9 was positively correlated with FEV1 and FEV1/FVC. ASubopt and AGood responded similarly to other stimuli.

CONCLUSIONS

Circulating neutrophils are different in asthma; however, this is likely to be related to airflow limitation rather than asthma control.

Asthma therapy and its effect on airway remodelling

Asthma remains a major health problem with significant morbidity, mortality and economic costs. In asthma, airway remodelling, which refers to all the microscopic structural changes seen in the airway tissue, has been recognised for many decades and remains one of the defining characteristics of the disease; however, it is still poorly understood. The detrimental pathophysiological consequences of some features of remodelling, like increased airway smooth muscle mass and subepithelial fibrosis, are well documented. However, whether targeting these by therapy would be beneficial is unknown. Although the prevailing thinking is that remodelling is an abnormal response to persistent airway inflammation, recent evidence, especially from studies of remodelling in asthmatic children, suggests that the two processes occur in parallel. The effects of asthma therapy on airway remodelling have not been studied extensively due to the challenges of obtaining airway tissue in the context of clinical trials. Corticosteroids remain the cornerstone of asthma therapy, and their effects on remodelling have been better studied than other drugs. Bronchial thermoplasty is the only asthma therapy to primarily target remodelling, although how it results in the apparent clinical benefits seen is not exactly clear. In this article we discuss the mechanisms of airway remodelling in asthma and review the effects of conventional and novel asthma therapies on the process.

Roxithromycin treatment inhibits TGF-β1-induced activation of ERK and AKT and down-regulation of caveolin-1 in rat airway smooth muscle cells

BACKGROUND

Roxithromycin (RXM) has been widely used in asthma treatment; however, the mechanism has not been fully understood. The aim of our study was to investigate the underlying mechanism of RXM treatment in mediating the effect of transforming growth factor (TGF)-β1 on airway smooth muscle cells (ASMCs) proliferation and caveolinn-1 expression.

METHODS

Firstly, the rat ovalbumin (OVA) model was built according to the previous papers. Rat ASMCs were prepared and cultured, and then TGF-β1 production in ASMCs was measured by enzyme-linked immunosorbent assay (ELISA). Moreover, the proliferation of ASMCs was determined using cell counting kit (CCK-8) assay. Additionally, the expressions of caveolin-1, phosphorylated-ERK1/2 (p-ERK1/2) and phosphorylated-AKT (p-AKT) in ASMCs treated with or without PD98059 (an ERK1/2 inhibitor), wortannin (a PI3K inhibitor), β-cyclodextrin (β-CD) and RXM were measured by Western blot. Finally, data were evaluated using t-test or one-way ANOVA, and then a P value < 0.05 was set as a threshold.

RESULTS

Compared with normal control, TGF-β1 secretion was significantly increased in asthmatic ASMCs; meanwhile, TGF-β1 promoted ASMCs proliferation (P < 0.05). However, ASMCs proliferation was remarkably inhibited by RXM, β-CD, PD98059 and wortmannin (P < 0.05). Moreover, the expressions of p-ERK1/2 and p-AKT were increased and peaked at 20 min after TGF-β1 stimulation, and then suppressed by RXM. Further, caveolin-1 level was down-regulated by TGF-β1 and up-regulated by inhibitors and RXM.

CONCLUSION

Our findings demonstrate that RXM treatment inhibits TGF-β1-induced activation of ERK and AKT and down-regulation of caveolin-1, which may be the potential mechanism of RXM protection from chronic inflammatory diseases, including bronchial asthma.

Human airway smooth muscle maintain in situ cell orientation and phenotype when cultured on aligned electrospun scaffolds

Human airway smooth muscle (HASM) contraction plays a central role in regulating airway resistance in both healthy and asthmatic bronchioles. In vitro studies that investigate the intricate mechanisms that regulate this contractile process are predominantly conducted on tissue culture plastic, a rigid, 2D geometry, unlike the 3D microenvironment smooth muscle cells are exposed to in situ. It is increasingly apparent that cellular characteristics and responses are altered between cells cultured on 2D substrates compared with 3D topographies. Electrospinning is an attractive method to produce 3D topographies for cell culturing as the fibers produced have dimensions within the nanometer range, similar to cells' natural environment. We have developed an electrospun scaffold using the nondegradable, nontoxic, polymer polyethylene terephthalate (PET) composed of uniaxially orientated nanofibers and have evaluated this topography's effect on HASM cell adhesion, alignment, and morphology. The fibers orientation provided contact guidance enabling the formation of fully aligned sheets of smooth muscle. Moreover, smooth muscle cells cultured on the scaffold present an elongated cell phenotype with altered contractile protein levels and distribution. HASM cells cultured on this scaffold responded to the bronchoconstrictor bradykinin. The platform presented provides a novel in vitro model that promotes airway smooth muscle cell development toward a more in vivo-like phenotype while providing topological cues to ensure full cell alignment.