The TLR4-TRIF pathway can protect against the development of experimental allergic asthma.

The Toll-like receptor (TLR) adaptor proteins myeloid differentiating factor 88 (MyD88) and Toll, interleukin-1 receptor and resistance protein (TIR) domain-containing adaptor inducing interferon-ß (TRIF) comprise the two principal limbs of the TLR signalling network. We studied the role of these adaptors in the TLR4-dependent inhibition of allergic airway disease and induction of CD4+ ICOS+ T cells by nasal application of Protollin™, a mucosal adjuvant composed of TLR2 and TLR4 agonists. Wild-type (WT), Trif-/- or Myd88-/- mice were sensitized to birch pollen extract (BPEx), then received intranasal Protollin followed by consecutive BPEx challenges. Protollin's protection against allergic airway disease was TRIF-dependent and MyD88-independent. TRIF deficiency diminished the CD4+ ICOS+ T-cell subsets in the lymph nodes draining the nasal mucosa, as well as their recruitment to the lungs. Overall, TRIF deficiency reduced the proportion of cervical lymph node and lung CD4+ ICOS+ Foxp3- cells, in particular. Adoptive transfer of cervical lymph node cells supported a role for Protollin-induced CD4+ ICOS+ cells in the TRIF-dependent inhibition of airway hyper-responsiveness. Hence, our data demonstrate that stimulation of the TLR4-TRIF pathway can protect against the development of allergic airway disease and that a TRIF-dependent adjuvant effect on CD4+ ICOS+ T-cell responses may be a contributing mechanism.

Factors influencing stomatal conductance in response to water availability in grapevine: a meta-analysis.

The main factors regulating grapevine response to decreasing water availability were assessed under statistical support using published data related to leaf water relations in an extensive range of scion and rootstock genotypes. Matching leaf water potential (Ψleaf ) and stomatal conductance (gs ) data were collected from peer-reviewed literature with associated information. The resulting database contained 718 data points from 26 different Vitis vinifera varieties investigated as scions, 15 non-V. vinifera rootstock genotypes and 11 own-rooted V. vinifera varieties. Linearised data were analysed using the univariate general linear model (GLM) with factorial design including biological (scion and rootstock genotypes), methodological and environmental (soil) fixed factors. The first GLM performed on the whole database explained 82.4% of the variability in data distribution having the rootstock genotype the greatest contribution to variability (19.1%) followed by the scion genotype (16.2%). A classification of scions and rootstocks according to their mean predicted gs in response to moderate water stress was generated. This model also revealed that gs data obtained using a porometer were in average 2.1 times higher than using an infra-red gas analyser. The effect of soil water-holding properties was evaluated in a second analysis on a restricted database and showed a scion-dependant effect, which was dominant over rootstock effect, in predicting gs values. Overall the results suggest that a continuum exists in the range of stomatal sensitivities to water stress in V. vinifera, rather than an isohydric-anisohydric dichotomy, that is further enriched by the diversity of scion-rootstock combinations and their interaction with different soils.

Nanotubes connect CD4+ T cells to airway smooth muscle cells: novel mechanism of T cell survival.

Contact between airway smooth muscle (ASM) cells and activated CD4(+) T cells, a key interaction in diseases such as asthma, triggers ASM cell proliferation and enhances T cell survival. We hypothesized that direct contact between ASM and CD4(+) T cells facilitated the transfer of anti-apoptotic proteins via nanotubes, resulting in increased survival of activated CD4(+) T cells. CD4(+) T cells, isolated from PBMCs of healthy subjects, when activated and cocultured with ASM cells for 24 h, formed nanotubes that were visualized by immunofluorescence and atomic force microscopy. Cell-to-cell transfer of the fluorescent dye calcein-AM confirmed cytoplasmic communication via nanotubes. Immunoreactive B cell lymphoma 2 (Bcl-2) and induced myeloid leukemia cell differentiation protein (Mcl-1), two major anti-apoptotic proteins, were present within the nanotubes. Downregulation of Mcl-1 by small interfering RNA in ASM cells significantly increased T cell apoptosis, whereas downregulation of Bcl-2 had no effect. Transfer of GFP-tagged Mcl-1 from ASM cells to CD4(+) T cells via the nanotubes confirmed directionality of transfer. In conclusion, activated T cells communicate with ASM cells via nanotube formation. Direct transfer of Mcl-1 from ASM to CD(+) T cells via nanotubes is involved in T cell survival. This study provides a novel mechanism of survival of CD4(+) T cells that is dependent on interaction with a structural cell.

Airway arginase expression and Nω-hydroxy-nor-arginine effect on methacholine-induced bronchoconstriction differentiate Lewis and Fischer rat strains.

Innate airway hyperresponsiveness (AHR) is well modeled by two strains of rat, the hyperresponsive Fischer 344 rat and the normoresponsive Lewis rat. Arginase has been implicated in AHR associated with allergic asthma models. We addressed the role of arginase in innate AHR using the Fischer-Lewis model. In vivo arginase inhibition with N(ω)-hydroxy-nor-arginine (nor-NOHA) was evaluated on methacholine-induced bronchoconstriction in the Fischer and the Lewis rats. Arginase activity and mRNA expression were quantified in structural and resident cells of the proximal airway tree. The effect of nor-NOHA was evaluated on cultured tracheal smooth muscle proliferation. Fischer rats exhibited significantly greater changes in respiratory resistance and elastance in response to methacholine compared with Lewis rats. nor-NOHA reduced the methacholine-induced bronchoconstriction in the central airways of Lewis rats, while it did not change the innate AHR of Fischer rats. Lewis rats exhibited greater arginase activity in tracheal smooth muscle but a lower proliferation rate compared with Fischer rats. Smooth muscle proliferation was not affected by nor-NOHA in either strain of rats. The strain-specific arginase expression in the smooth muscle may contribute to the differences in sensitivity of the methacholine challenged airways of Lewis and Fischer rats to inhibition of arginase.

IL-22 contributes to TGF-ß1-mediated epithelial-mesenchymal transition in asthmatic bronchial epithelial cells.

BACKGROUND: Allergic asthma is characterized by airway inflammation in response to antigen exposure, leading to airway remodeling and lung dysfunction. Epithelial-mesenchymal transition (EMT) may play a role in airway remodeling through the acquisition of a mesenchymal phenotype in airway epithelial cells. TGF-ß1 is known to promote EMT; however, other cytokines expressed in severe asthma with extensive remodeling, such as IL-22, may also contribute to this process. In this study, we evaluated the contribution of IL-22 to EMT in primary bronchial epithelial cells from healthy and asthmatic subjects. METHODS: Primary bronchial epithelial cells were isolated from healthy subjects, mild asthmatics and severe asthmatics (n=5 patients per group). The mRNA and protein expression of epithelial and mesenchymal cell markers and EMT-associated transcription factors was evaluated following stimulation with TGF-ß1, IL-22 and TGF-ß1+IL-22. RESULTS: Primary bronchial epithelial cells stimulated with TGF-ß1 underwent EMT, demonstrated by decreased expression of epithelial markers (E-cadherin and MUC5AC) and increased expression of mesenchymal markers (N-cadherin and vimentin) and EMT-associated transcription factors. IL-22 alone had no effect on epithelial or mesenchymal gene expression. However, IL-22+TGF-ß1 promoted the expression of some EMT transcription factors (Snail1 and Zeb1) and led to a more profound cadherin shift, but only in cells obtained from severe asthmatics. CONCLUSION: The impact of IL-22 on airway epithelial cells depends on the cytokine milieu and the clinical phenotype of the patient. Further studies are required to determine the molecular mechanism of IL-22 and TGF-ß1 cooperativity in driving EMT in primary human bronchial epithelial cells.

Roflumilast inhibits lipopolysaccharide-induced tumor necrosis factor-α and chemokine production by human lung parenchyma.

BACKGROUND: Roflumilast is the first phosphodiesterase-4 (PDE4) inhibitor to have been approved for the treatment of COPD. The anti-inflammatory profile of PDE4 inhibitors has not yet been explored in human lung tissues. We investigated the effects of roflumilast and its active metabolite roflumilast-N-oxide on the lipopolysaccharide (LPS)-induced release of tumor necrosis factor-alpha (TNF-α) and chemokines by human lung parenchymal explants. We also investigated roflumilast's interaction with the long-acting ß2-agonist formoterol. METHODS: Explants from 25 patients undergoing surgical lung resection were incubated with Roflumilast, Roflumilast-N-oxide and formoterol and stimulated with LPS. Levels of TNF-α, chemokines (in the culture supernatants) and cyclic adenosine monophosphate (in tissue homogenates) were determined with appropriate immunoassays. RESULTS: Roflumilast and Roflumilast-N-oxide concentration-dependently reduced the release of TNF-α and chemokines CCL2, CCL3, CCL4, CXCL9 and CXCL10 from LPS-stimulated human lung explants, whereas CXCL1, CXCL5 and CXCL8 release was not altered. Formoterol (10 nM) partially decreased the release of the same cytokines and significantly increased the inhibitory effect of roflumilast on the release of the cytokines. CONCLUSIONS: In human lung parenchymal explants, roflumilast and roflumilast-N-oxide reduced the LPS-induced release of TNF-α and chemokines involved in the recruitment of monocytes and T-cells but not those involved in the recruitment of neutrophils. Addition of formoterol to roflumilast provided superior in vitro anti-inflammatory activity, which may translate into greater efficacy in COPD.

T cell-induced airway smooth muscle cell proliferation via the epidermal growth factor receptor.

Allergic asthma is a heterogeneous disease with no curative therapies. T cells infiltrate the airway smooth muscle (ASM) layer and may be implicated in airway remodeling and the increase of ASM mass, a cardinal feature of asthma. The mechanism by which CD4(+) T cells drive airway remodeling remains unknown. This study sought to determine the T cell-mediated mechanism of ASM cell proliferation. We hypothesized that CD4(+) T cells adhere to ASM cells via CD44, and induce ASM cell proliferation through the activation of the epidermal growth factor receptor (EGFR). A coculture model showed that the contact of antigen-stimulated CD4(+) T cells with ASM cells induced high levels of EGFR ligand expression in CD4(+) T cells and the activation of matrix metalloproteinase (MMP)-9, required for the shedding of EGFR ligands. The inhibition of EGFR and MMP-9 prevented the increase of ASM cell proliferation after coculture. The hyaluronan receptor CD44 is the dominant mediator of the tight adherence of T cells to ASM and is colocalized with MMP-9 on the cell surface. Moreover, the neutralization of CD44 prevents ASM cell hyperplasia. These data provide a novel mechanism by which antigen-stimulated CD4(+) T cells induce the remodeling indicative of a direct trophic role for CD4(+) T cells.

Models to study airway smooth muscle contraction in vivo, ex vivo and in vitro: implications in understanding asthma.

Asthma is a chronic obstructive airway disease characterised by airway hyperresponsiveness (AHR) and airway wall remodelling. The effector of airway narrowing is the contraction of airway smooth muscle (ASM), yet the question of whether an inherent or acquired dysfunction in ASM contractile function plays a significant role in the disease pathophysiology remains contentious. The difficulty in determining the role of ASM lies in limitations with the models used to assess contraction. In vivo models provide a fully integrated physiological response but ASM contraction cannot be directly measured. Ex vivo and in vitro models can provide more direct assessment of ASM contraction but the loss of factors that may modulate ASM responsiveness and AHR, including interaction between multiple cell types and disruption of the mechanical environment, precludes a complete understanding of the disease process. In this review we detail key advantages of common in vivo, ex vivo and in vitro models of ASM contraction, as well as emerging tissue engineered models of ASM and whole airways. We also highlight important findings from each model with respect to the pathophysiology of asthma.

Smooth muscle in tissue remodeling and hyper-reactivity: airways and arteries.

Smooth muscle comprises a key functional component of both the airways and their supporting vasculature. Dysfunction of smooth muscle contributes to and exacerbates a host of breathing-associated pathologies such as asthma, chronic obstructive pulmonary disease and pulmonary hypertension. These diseases may be marked by airway and/or vascular smooth muscle hypertrophy, proliferation and hyper-reactivity, and related conditions such as fibrosis and extracellular matrix remodeling. This review will focus on the contribution of airway or vascular smooth dysfunction to common airway diseases.

An airway smooth muscle cell niche under physiological pulsatile flow culture using a tubular dense collagen construct.

Bioengineered tissue equivalents should provide physiologically relevant biochemical and mechanical cues to support the growth and differentiation of seeded cells. Herein, tubular dense collagen constructs (TDCCs) with collagen content comparable to native extracellular matrix were used to investigate the effect of shear stress alone (i.e. under laminar fluid flow), and shear stress in combination with circumferential strain (i.e. under pulsatile fluid flow) on the proliferation, alignment, and phenotype of three-dimensionally (3D) seeded airway smooth muscle cells (ASMCs). In addition, the effect of ASMC-mediated remodelling on TDCC matrix morphological and mechanical properties was investigated. Compared to static culture, pulsatile flow increased seeded ASMC growth by 70%, improved the homogeneity of cell distribution within the TDCCs and induced differential cellular alignment depending on the primary stimuli. Specifically, within the inner wall, where shear stress is predominant, ASMCs were aligned parallel to fluid flow direction, while within the outer wall ASMCs were aligned parallel to the circumferential strain (perpendicular to fluid flow). In contrast, under laminar flow, ASMCs were aligned parallel to fluid flow direction within both walls. Compared to laminar flow, pulsatile flow resulted in increased positive staining for α-smooth muscle actin, and in up-regulated typical ASMC contractile markers suggesting that circumferential strain modulates ASMC differentiation. Pulsatile flow also caused a 60 and 30% increase in collagen density within both acellular and cellular TDCCs, respectively, which was reflected in an increased apparent modulus. Compared to static culture, pulsatile stimulation of cellular constructs resulted in 70% higher circumferential strength. The TDCCs provide ASMC niche for greater insight into the responses of 3D seeded SMCs to physiologically equivalent in vitro dynamic conditioning.

Th17-associated cytokines promote human airway smooth muscle cell proliferation.

Increased airway smooth muscle (ASM) mass is a hallmark of airway remodeling in severe asthma. Th17-associated cytokines, particularly IL-17A, IL-17F, and IL-22, have been postulated to play a role in the pathogenesis of asthma. To investigate the in vitro effect of Th17 cytokines on the proliferation and survival of airway smooth muscle cells (ASMCs), human ASMCs from asthmatic and nonasthmatic subjects were incubated with IL-17A, IL-17F, or IL-22. The aforementioned cytokines demonstrated an ability to promote proliferation and survival of ASMCs from asthmatic and nonasthmatic subjects, which were mediated by selective activation of their corresponding receptors on ASMCs, including IL-17RA, IL-17RC, or IL-22R1, respectively. IL-17A and IL-17F-induced proliferation of ASMCs was dependent on ERK1/2 MAPK pathway, while IL-22-induced proliferation involved both ERK1/2 MAPK and NF-κB pathways. The involvement of signaling pathways was further confirmed by the inhibition of proliferation by knockdown of ERK1/2 MAPK or NF-κB p65 expression with pathway-specific siRNA. Together, our results show that Th17-associated cytokines promote proliferation and reduce the apoptotic rate of human ASMCs, raising the possibility that Th17 cytokines may contribute to increasing airway smooth muscle mass and airway remodeling in asthma.

Autocrine-regulated airway smooth muscle cell migration is dependent on IL-17-induced growth-related oncogenes.

BACKGROUND: Airway smooth muscle cell (ASMC) migration is one of the proposed mechanisms underlying the increased airway smooth muscle mass seen in airway remodeling of patients with severe asthma. IL-17-related cytokines are a new subgroup of inflammatory mediators that have been suggested to play a role in regulating smooth muscle function. We hypothesized that IL-17-induced chemokine production from smooth muscle cells can contribute to migration of additional smooth muscle cells in the airways of asthmatic patients. OBJECTIVE: We sought to investigate the effect of IL-17 on smooth muscle-derived chemokines and to examine the mechanisms involved in their production and contribution to the increase in airway smooth muscle migration. METHODS: The effect of IL-17-induced supernatants on human ASMC migration was investigated. IL-17-induced growth-related oncogene (GRO) production and mRNA expression was assessed by using ELISA and RT-PCR, respectively. The direct effect of GROs on ASMC migration and the involvement of the CXCR2 receptor were also examined. RESULTS: IL-17-induced supernatants promoted ASMC migration. After IL-17 stimulation, GROs were the most abundant chemokines produced from ASMCs, and blocking their effect by using neutralizing antibodies significantly inhibited ASMC migration. In addition, a combination of recombinant human GRO-α, GRO-ß, and GRO-γ was able to promote significant migration of ASMCs that was mediated through the CXCR2 receptor. CONCLUSION: These findings suggest that IL-17-induced GROs can be an important mediator of ASMC migration and therefore might contribute to the pathogenesis of airway remodeling in asthmatic patients.

The presence of LPS in OVA inhalations affects airway inflammation and AHR but not remodeling in a rodent model of asthma.

Ovalbumin (OVA) is the most frequently used allergen in animal models of asthma. Lipopolysaccharide (LPS) contaminating commercial OVA may modulate the evoked airway inflammatory response to OVA. However, the effect of LPS in OVA on airway remodeling, especially airway smooth muscle (ASM) has not been evaluated. We hypothesized that LPS in commercial OVA may enhance allergen-induced airway inflammation and remodeling. Brown Norway rats were sensitized with OVA on day 0. PBS, OVA, or endotoxin-free OVA (Ef-OVA) was instilled intratracheally on days 14, 19, 24. Bronchoalveolar lavage (BAL) fluid, lung, and intrathoracic lymph node tissues were collected 48 h after the last challenge. Immunohistochemistry for α-smooth muscle actin, Periodic-Acid-Schiff staining, and real-time qPCR were performed. Airway hyperresponsiveness (AHR) was also measured. BAL fluid macrophages, eosinophils, neutrophils, and lymphocytes were increased in OVA-challenged animals, and macrophages and neutrophils were significantly lower in Ef-OVA-challenged animals. The ASM area in larger airways was significantly increased in both OVA and Ef-OVA compared with PBS-challenged animals. The mRNA expression of IFN-γ and IL-13 in lung tissues and IL-4 in lymph nodes was significantly increased by both OVA and Ef-OVA compared with PBS and were not significantly different between OVA and Ef-OVA. Monocyte chemoattractant protein (MCP)-1 in BAL fluid and AHR were significantly increased in OVA but not in Ef-OVA. LPS contamination in OVA contributes to the influx of macrophages and MCP-1 increase in the airways and to AHR after OVA challenges but does not affect OVA-induced Th1 and Th2 cytokine expression, goblet cell hyperplasia, and ASM remodeling.

Bcl-2-associated autophagy regulator Naf-1 required for maintenance of skeletal muscle.

Nutrient-deprivation autophagy factor-1 (NAF-1) was identified as an endoplasmic reticulum (ER) BCL-2-interacting protein, which functions to mediate the ability of ER BCL-2 to antagonize Beclin 1-dependent autophagy and depress ER calcium stores. In humans, a point mutation in Naf-1 (synonyms: Cisd2, Eris, Miner1 and Noxp70) is responsible for the neurodegenerative disorder Wolfram Syndrome 2. Here, we describe the generation and characterization of the Naf-1 gene deletion in mice. Naf-1 null mice display discernable clinical signs of degeneration at 2-3 months of age, with early evidence of significant defects in the structure and performance of skeletal muscle. Skeletal muscles from Naf-1 knockout mice demonstrate a significant shift towards slow-twitch (type I) fibers and greater resistance to muscle fatigue. Force-generating capacity is dramatically reduced in Naf-1(-/-) muscle. Consistent with its role in ER BCL-2-mediated regulation of autophagy and calcium flux, these physiological deficiencies were accompanied by augmented autophagy and dysregulated calcium homeostasis. In contrast, this also included adaptive enlargement of mitochondria with extensive cristae structures. Thus, NAF-1, a BCL-2-associated autophagy regulator, is required for homeostatic maintenance of skeletal muscle. Our findings uncover a novel pathway that is required for normal muscle maintenance, which may ultimately provide a novel therapeutic target for treating certain muscle pathologies.

Treatment with a sphingosine-1-phosphate analog inhibits airway remodeling following repeated allergen exposure.

Sphingosine-1-phosphate (S1P) is an immunomodulatory lipid mediator that plays an important role in lymphocyte trafficking. Elevated levels of S1P are found in bronchoalveolar lavage (BAL) fluid of patients with asthma; however, its role in disease is not known. FTY720, a synthetic analog of S1P, has been shown to abrogate allergic inflammation and airway hyperresponsiveness following acute allergen challenge. However, its effects on asthmatic airway remodeling induced by repeated allergen exposure are unknown. Ovalbumin (OVA)-sensitized rats were challenged on days 14, 19, and 24 after sensitization. FTY720 or vehicle (PBS) therapy was administered 1 h prior to each challenge. BAL fluid and quantitative histological analysis were performed 48 h after the last challenge. FTY720 inhibited OVA-induced features of airway remodeling including increased airway smooth muscle mass and bronchial neovascularization, without affecting lymphocyte numbers in secondary lymphoid organs. Furthermore, CD3+ cells adjacent to airway smooth muscle bundles were increased in OVA-challenged rats but the increase was inhibited by FTY720. There was an expansion of bronchus-associated lymphoid tissue following FTY720 treatment of OVA-challenged animals. Real-time quantitative PCR revealed that Th2-associated transcription factors were inhibited following FTY720 therapy. Airway remodeling is a cardinal feature of severe asthma. These results demonstrate that allergen-driven airway remodeling can be inhibited by FTY720, offering potential new therapies for the treatment of severe asthma.

Site of allergic airway narrowing and the influence of exogenous surfactant in the Brown Norway rat.

BACKGROUND: The parameters R(N) (newtonian resistance), G (tissue damping), and H (tissue elastance) of the constant phase model of respiratory mechanics provide information concerning the site of altered mechanical properties of the lung. The aims of this study were to compare the site of allergic airway narrowing implied from respiratory mechanics to a direct assessment by morphometry and to evaluate the effects of exogenous surfactant administration on the site and magnitude of airway narrowing. METHODS: We induced airway narrowing by ovalbumin sensitization and challenge and we tested the effects of a natural surfactant lacking surfactant proteins A and D (Infasurf®) on airway responses. Sensitized, mechanically ventilated Brown Norway rats underwent an aerosol challenge with 5% ovalbumin or vehicle. Other animals received nebulized surfactant prior to challenge. Three or 20 minutes after ovalbumin challenge, airway luminal areas were assessed on snap-frozen lungs by morphometry. RESULTS: At 3 minutes, R(N) and G detected large airway narrowing whereas at 20 minutes G and H detected small airway narrowing. Surfactant inhibited R(N) at the peak of the early allergic response and ovalbumin-induced increase in bronchoalveolar lavage fluid cysteinyl leukotrienes and amphiregulin but not IgE-induced mast cell activation in vitro. CONCLUSION: Allergen challenge triggers the rapid onset of large airway narrowing, detected by R(N) and G, and subsequent peripheral airway narrowing detected by G and H. Surfactant inhibits airway narrowing and reduces mast cell-derived mediators.

Histamine may induce airway remodeling through release of epidermal growth factor receptor ligands from bronchial epithelial cells.

Asthma is a chronic inflammatory disease that is associated with airway remodeling, including hyperplasia of airway epithelial cells and airway smooth muscle cells, and goblet cell differentiation. We wished to address the potential role of histamine, a key biogenic amine involved in allergic reactions, in airway remodeling through the epidermal growth factor receptor (EGFR) pathway. Here, we demonstrate that histamine releases 2 EGFR ligands, amphiregulin and heparin-binding epidermal growth factor-like growth factor (HB-EGF), from airway epithelial cells. Amphiregulin and HB-EGF were expressed in airway epithelium of patients with asthma. Histamine up-regulated their mRNA expression (amphiregulin 3.2-fold, P<0.001; HB-EGF 2.3-fold, P<0.05) and triggered their release (amphiregulin EC(50) 0.50 µM, 31.2 ± 2.7 pg/ml with 10 µM histamine, P<0.01; HB-EGF EC(50) 0.54 µM, 78.5 ± 1.8 pg/ml with 10 µM histamine, P<0.001) compared to vehicle control (amphiregulin 19.3 ± 0.9 pg/ml; HB-EGF 60.2 ± 1.0 pg/ml), in airway epithelial cells. Histamine increased EGFR phosphorylation (2.1-fold by Western blot analysis) and induced goblet cell differentiation (CLCA1 up-regulation by real-time qPCR) in normal human bronchial epithelial (NHBE) cells. Moreover, amphiregulin and HB-EGF caused proliferation and migration of both NHBE cells and human airway smooth muscle cells. These results suggest that histamine may induce airway remodeling via the epithelial-derived EGFR ligands amphiregulin and HB-EGF.

Effects of decorin and biglycan on human airway smooth muscle cell adhesion.

Growth on a decorin matrix results in decreased human airway smooth muscle cell (HASMC) number, by decreasing proliferation and increasing apoptosis. We questioned whether these effects were related to abnormal extracellular matrix (ECM)-cell adhesion. HASMCs were seeded on decorin, biglycan, collagen type I or plastic. Actin organization and focal adhesion formation were assessed by staining for filamentous (F) and globular (G) actin, and vinculin, respectively. Gene expression for focal adhesion proteins, ECM molecules and HASMC receptors was measured. Protein levels for fibronectin, α(2), α(5), α(v) and ß(3) integrin subunits and, focal adhesion kinase (FAK) were assessed. F-actin filaments were prominent in cells seeded on collagen I and plastic, less apparent in cells cultured on biglycan and faint in cells on decorin. Vinculin clustering was decreased in cells seeded on decorin and biglycan, as was vinculin gene expression. Compared to cells on plastic, cells on decorin had an increase in fibronectin gene expression. Seeding on decorin caused an increase in α(2) integrin subunit and platelet-derived growth factor receptor A gene expression. There was also an increase in α(2) and α(v) integrin subunit protein. Finally, FAK protein levels in cells seeded on decorin or biglycan were decreased compared to cells seeded on plastic or collagen I. Cells grown on proteoglycan matrices demonstrate evidence of abnormalities during many of the key processes involved in normal cell adhesion. Upregulation of cell surface receptor proteins, such as α(2) integrin subunit, may represent a compensatory mechanism to overcome poor adhesion induced by growth on these matrices.

Interleukin-13 inhibits proliferation and enhances contractility of human airway smooth muscle cells without change in contractile phenotype.

IL-13 is an important mediator of allergen-induced airway hyperresponsiveness. This Th2 cytokine, produced by activated T cells, mast cells, and basophils, has been described to mediate a part of its effects independently of inflammation through a direct modulation of the airway smooth muscle (ASM). Previous studies demonstrated that IL-13 induces hyperresponsiveness in vivo and enhances calcium signaling in response to contractile agonists in vitro. We hypothesized that IL-13 drives human ASM cells (ASMC) to a procontractile phenotype. We evaluated ASM phenotype through the ability of the cell to proliferate, to contract, and to express contractile protein in response to IL-13. We found that IL-13 inhibits human ASMC proliferation (expression of Ki67 and bromodeoxyuridine incorporation) in response to serum, increasing the number of cells in G0/G1 phase and decreasing the number of cells in G2/M phases of the cell cycle. IL-13-induced inhibition of proliferation was not dependent on signal transducer and activator of transcription-6 but was IL-13Rα2 receptor dependent and associated with a decrease of Kruppel-like factor 5 expression. In parallel, IL-13 increased calcium signaling and the stiffening of human ASMC in response to 1 µM histamine, whereas the stiffening response to 30 mM KCl was unchanged. However, Western blot analysis showed unchanged levels of calponin, smooth muscle α-actin, vinculin, and myosin. We conclude that IL-13 inhibits proliferation via the IL-13Rα2 receptor and induces hypercontractility of human ASMC without change of the phenotypic markers of contractility.

Steroid-insensitive ERK1/2 activity drives CXCL8 synthesis and neutrophilia by airway smooth muscle.

Severe or refractory asthma affects 5 to 15% of all patients with asthma, but is responsible for more than half of the health burden associated with the disease. Severe asthma is characterized by a dramatic increase in smooth muscle and airway inflammation. Although glucocorticoids are the mainstay of treatment in asthma, they are unable to fully control the disease in individuals with severe asthma. We found that airway smooth muscle cells (ASMCs) from individuals with severe asthma showed elevated activities of the ERK1/ERK2 and p38 MAPK pathways despite treatment with oral and inhaled glucocorticoids, which increased the expression of DUSP1, a phosphatase shown to limit p38 MAPK activity. In ex vivo ASMCs, TNF-α but not IL-17A induced expression of the neutrophil chemoattractant CXCL8. Moreover, TNF-α led to up-regulation of the ERK1/ERK2 and p38 MAPKs pathways, with only the latter being sensitive to pretreatment with the glucocorticoid dexamethasone. In contrast to epithelial and endothelial cells, TNF-α-stimulated CXCL8 synthesis was dependent on ERK1/ERK2 but not on p38 MAPK. Moreover, suppressing ERK1/ERK2 activation prevented neutrophil recruitment by ASMCs, whereas suppressing p38 MAPK activity had no impact. Taken together, these results highlight the ERK1/ERK2 MAPK cascade as a novel and attractive target in severe asthma because the activation of this pathway is insensitive to the action of glucocorticoids and is involved in neutrophil recruitment, contributing the to inflammation seen in the disease.