Regulation of TGF-beta 1-induced connective tissue growth factor expression in airway smooth muscle cells

Molecular mechanisms of uterine incision healing and scar formation

Wound healing is a tandem process involving inflammation, proliferation, and remodeling, through which damage is repaired and ultimately scar tissue is formed. This process mainly relies on the complex and extensive interaction of growth factors and cytokines, which coordinate the synthesis of various cell types. The loss of normal regulation in any part of this process can lead to excessive scarring or unhealed wounds. Recent studies have shown that it is possible to improve wound healing and even achieve scar-free wound healing through proper regulation of cytokines and molecules in this process. In recent years, many studies have focused on accelerating wound healing and reducing scar size by regulating the molecular mechanisms related to wound healing and scar formation. We summarized the role of these factors in wound healing and scar formation, to provide a new idea for clinical scar-free healing treatment of uterine incisions.

Long non coding RNAs reveal important pathways in childhood asthma: a future perspective

Asthma is a long-term inflammatory disease of the airways of the lungs refers changes that occur in conjunction with, or as a result of, chronic airway inflammation. Airway remodeling the subsequent of inflammation constitutes cellular and extracellular matrix changes in the wall airways, epithelial-to-mesenchymal-transition and airway smooth muscle cell proliferation. Diseases often begin in childhood and despite extensive research, causative pathogenic mechanisms still remain unclear. Transcriptome analysis of childhood asthma reveals distinct gene expression profiles of Long noncoding RNAs which have been reported to play a central regulatory role in various aspects of pathogenesis, clinical course and treatment of asthma. We briefly review current understanding of lnc-RNA dysregulation in children with asthma, focusing on their complex role in the inflammation, cell proliferation and remodeling of airway to guide future researches. We found that the lnc-RNAs increases activity of several oncogenes such c-Myc, Akt, and ERK and various signaling pathways such as MAPK (PI3K, Ras, JNK and p38), NF-κB and Wnt and crosstalk between these pathways by TGFβ, β-catenin, ERK and SKP2. Moreover, two different signal transduction pathways, Wnt and Notch1, can be activated by two lnc-RNAs through sponging the same miRNA for exacerbation cell proliferation.

Targeted Inhibition of Select Extracellular Signal-regulated Kinases 1 and 2 Functions Mitigates Pathological Features of Asthma in Mice

ERK1/2 (extracellular signal-regulated kinases 1 and 2) regulate the activity of various transcription factors that contribute to asthma pathogenesis. Although an attractive drug target, broadly inhibiting ERK1/2 is challenging because of unwanted cellular toxicities. We have identified small molecule inhibitors with a benzenesulfonate scaffold that selectively inhibit ERK1/2-mediated activation of AP-1 (activator protein-1). Herein, we describe the findings of targeting ERK1/2-mediated substrate-specific signaling with the small molecule inhibitor SF-3-030 in a murine model of house dust mite (HDM)-induced asthma. In 8- to 10-week-old BALB/c mice, allergic asthma was established by repeated intranasal HDM (25 μg/mouse) instillation for 3 weeks (5 days/week). A subgroup of mice was prophylactically dosed with 10 mg/kg SF-3-030/DMSO intranasally 30 minutes before the HDM challenge. Following the dosing schedule, mice were evaluated for alterations in airway mechanics, inflammation, and markers of airway remodeling. SF-3-030 treatment significantly attenuated HDM-induced elevation of distinct inflammatory cell types and cytokine concentrations in BAL and IgE concentrations in the lungs. Histopathological analysis of lung tissue sections revealed diminished HDM-induced pleocellular peribronchial inflammation, mucus cell metaplasia, collagen accumulation, thickening of airway smooth muscle mass, and expression of markers of cell proliferation (Ki-67 and cyclin D1) in mice treated with SF-3-030. Furthermore, SF-3-030 treatment attenuated HDM-induced airway hyperresponsiveness in mice. Finally, mechanistic studies using transcriptome and proteome analyses suggest inhibition of HDM-induced genes involved in inflammation, cell proliferation, and tissue remodeling by SF-3-030. These preclinical findings demonstrate that function-selective inhibition of ERK1/2 signaling mitigates multiple features of asthma in a murine model.

trans-Chalcone inhibits transforming growth factor-β1 and connective tissue growth factor-dependent collagen expression in the heart of high-fat diet-fed rats

Objective: Non-alcoholic fatty liver disease (NAFLD) is one of the main risk factors for cardiovascular mortality and morbidity. This study, for the first time, explored the effects of trans-chalcone on cardiac expressions of myocardial fibrosis-related genes, including transforming growth factor -β1 (TGF-β1), connective tissue growth factor (CTGF/CCN2), and collagen type I.Materials and methods: Twenty-eight rats were randomly divided into four groups: control, received 10% tween 80; chalcone, received trans-chalcone; HFD, received high-fat diet (HFD) and 10% tween 80; HFD + chalcone, received HFD and trans-chalcone, by once-daily gavage for 6 weeks. Finally, cardiac expression levels of TGF-β1, CTGF, and collagen type I were determined.Results: HFD feeding increased mRNA levels of collagen type I, TGF-β1, and CTGF in the heart of rats. However, trans-chalcone inhibited HFD-induced changes.Conclusions: trans-Chalcone can act as a cardioprotective compound by inhibiting TGF-β1 and CTGF-dependent stimulation of collagen type I synthesis in the heart of HFD-fed rats.

IL-1 Mediates Tissue-Specific Inflammation and Severe Respiratory Failure in COVID-19

Acute respiratory distress syndrome (ARDS) in COVID-19 has been associated with catastrophic inflammation. We present measurements in humans and a new animal model implicating a role in danger-associated molecular patterns. Calprotectin (S100A8/A9) and high-mobility group box 1 (HMGB1) were measured in patients without/with ARDS, and admission calprotectin was associated with soluble urokinase plasminogen activator receptor (suPAR). An animal model was developed by intravenous injection of plasma from healthy or patients with COVID-19 ARDS into C57/BL6 mice once daily for 3 consecutive days. Mice were treated with one anti-S100A8/A9 antibody, the IL-1 receptor antagonist anakinra or vehicle, and Flo1-2a anti-murine anti-IL-1α monoclonal antibody or the specific antihuman IL-1α antibody XB2001 or isotype controls. Cytokines and myeloperoxidase (MPO) were measured in tissues. Calprotectin, but not HMGB1, was elevated in ARDS. Higher suPAR indicated higher calprotectin. Animal challenge with COVID-19 plasma led to inflammatory reactions in murine lung and intestines as evidenced by increased levels of TNFα, IL-6, IFNγ, and MPO. Lung inflammation was attenuated with anti-S100A8/A9 pre-treatment. Anakinra treatment restored these levels. Similar decrease was found in mice treated with Flo1-2a but not with XB2001. Circulating alarmins, specifically calprotectin, of critically ill COVID-19 patients induces tissue-specific inflammatory responses through an IL-1-mediated mechanism. This could be attenuated through inhibition of IL-1 receptor or of IL-1α.

Exosomes Containing LINC00636 Inhibit MAPK1 through the miR-450a-2-3p Overexpression in Human Pericardial Fluid and Improve Cardiac Fibrosis in Patients with Atrial Fibrillation

The purpose of this study was to investigate the regulatory mechanism of miR-450a-2-3p in myocardial fibrosis in patients with atrial fibrillation. For this purpose, the expression profile of GSE55296 was extracted from the GEO database, and differentially expressed lncRNAs were identified. Gene ontology analysis of the target genes of mir-450a-2-3p indicated that there was a regulatory relationship between LINC00636 and miR-450a-2-3p. Further, the expression levels of the analyzed RNAs were confirmed by RT-qPCR. TGF-β1-induced cardiac fibroblasts (CFs) and human umbilical vein endothelial cells (HUVECs) were used to establish a myocardial fibrosis model and endothelium-mesenchymal transformation (EMT) model in vivo. We hypothesized that exosomes containing LINC00636 regulate the expression of miR-450a-2-3p. LINC00636 was positively correlated with the expression of miR-450a-2-3p. The overexpression of miR-450a-2-3p suppressed the MAPK1 expression in CFs, thereby inhibiting the expression of α-SMA, COL1, and COL3 and preventing CF proliferation. In HUVECs, the miR-450a-2-3p overexpression upregulated the expression of VE-Cadherin (VE-Cad) and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) by inhibiting the mitogen-activated protein kinase 1 (MAPK1) expression, whereas the expression levels of vimentin, COL1, and COL3 decreased. These results indicate that LINC00636, which is present in human pericardial fluid, is an antifibrotic molecule that inhibits MAPK1 through the miR-450a-2-3p overexpression and improves cardiac fibrosis in patients with atrial fibrillation.

MicroRNA-21 inhibition attenuates airway inflammation and remodelling by modulating the transforming growth factor β-Smad7 pathway

BACKGROUND/AIMS

Current asthma therapies remain unsatisfactory for controlling airway remodelling in asthma. MicroRNA-21 is a key player in asthma pathogenesis, but the molecular mechanisms underlying its effects on airway remodelling are not completely understood. We investigated the effects of inhibition of microRNA-21 on allergic airway inflammation and remodelling.

METHODS

Female BALB/c mice were divided into four groups: control, ovalbumin-sensitized and -challenged for 3 months, microRNA-negative control-treated ovalbumin-treated, and microRNA-21 inhibitor-treated ovalbumin-treated groups. Parameters related to airway remodelling, cytokine production, airway inflammation, and airway hyperresponsiveness were compared between groups. Human bronchial smooth muscle cells were used in a mechanism study.

RESULTS

In this asthma model, ovalbumin-sensitized and -challenged mice exhibited allergic airway inf lammation and airway remodelling. MicroRNA-21 inhibitor-treated mice had fewer inflammatory cells, lower TH2 cytokine production, and suppressed parameters related to remodelling such as goblet cell hyperplasia, collagen deposition, hydroxyproline content, and expression of smooth muscle actin. Inhibition of microRNA-21 decreased transforming growth factor β1 expression and induced Smad7 expression in lung tissue. In human bronchial smooth muscle cells stimulated with transforming growth factor β1, microRNA-21 inhibition upregulated Smad7 expression and decreased markers of airway remodelling.

CONCLUSION

Inhibition of microRNA-21 had both anti-inflammatory and anti-remodelling effects in this model of ovalbumin-induced chronic asthma. Our data suggest that the microRNA-21-transforming growth factor β1-Smad7 axis modulates the pathogenesis of ovalbumin-induced chronic asthma and in human bronchial smooth muscle cells. MicroRNA-21 inhibitors may be a novel therapeutic target in patients with allergic asthma, especially those with airway remodelling.

Identification of microRNAs enriched in exosomes in human pericardial fluid of patients with atrial fibrillation based on bioinformatic analysis

Background

Atrial fibrillation (AF) is related to structural and electrical atria remodeling. Atrial fibrosis development and progression is characteristic of structural remodeling and is taken as the AF perpetuation substrate. Increasing evidence has confirmed that microRNAs (miRNAs) are associated with AF, including cardiac fibrosis.

Methods

Pericardial fluid (PF) samples were collected from nine adult patients who had congenital heart disease with persistent AF or sinus rhythm (SR) undergoing surgery. Abnormally expressed miRNAs were acquired, and P<0.05 and fold change >2 were taken as the thresholds of differentially expressed miRNAs (DE-miRNAs). The predicted target genes were obtained by miRTarBase. The Database for Annotation, Visualization and Integrated Discovery was used to annotate functions and analyze pathway abundance for latent targets of DE-miRNAs. STRING database was applied to construct a protein–protein interplay (PPI) network, and Cytoscape software was used to visualize the miRNA-hub gene-Kyoto Encyclopedia of Genes and Genomes (KEGG) network. DE-miRNA expressions were evaluated by quantitative polymerase chain reaction (qPCR).

Results

Fifty-five exosomal DE-miRNAs were found between the AF and SR samples; these included 24 miRNAs that were upregulated and 31 that were downregulated. For the top 3 downregulated miRNAs (miR-382-3p, miR-3126-5p, and miR-450a-2-3p) 283 predicted target genes were identified, and were implicated in cardiac fibrosis-related pathways, including the hypoxia-inducible factor-1 (HIF1), mitogen-activated protein kinase (MAPK), and adrenergic and insulin pathways. The top 10 hub genes in the PPI network, including mitogen-activated protein kinase 1 (MAPK1) and AKT serine/threonine kinase 1 (AKT1), were identified as hub genes. By establishing the miRNA-hub gene-KEGG network, we observed that these hub genes, which were regulated by miR-382-3p, miR-3126-5p, and miR-450a-2-3p, were involved in many KEGG pathways associated with cardiac fibrosis, such as the AKT1/glycogen synthase kinsase-3β (GSK-3β) and transforming growth factor-β (TGF-β)/MAPK1 pathways.

Conclusions

The findings of the present study suggest that miR-382-3p, miR-450a-2-3p, and miR-3126-5p contained in exosomes in human PF are pivotal in the progression of AF. The results of qPCR showed that miR-382-3p was consistent with our sequencing data, which indicates its potential value as a therapeutic target for AF.

Quantitative proteomics analysis of the treatment of asthma rats with total flavonoid extract from chamomile

OBJECTIVE

Asthma is a chronic immune disease that has become a serious public health problem. The currently available medications are not ideal because of their limitations and side effects; hence, new target proteins and signaling cascades for precise and safe therapy treatment are needed. This work established an ovalbumin-induced asthma rat model and treated it with total flavonoid extract from the Xinjiang chamomile. The proteins that were differentially expressed in the chamomile extract-treated asthmatic rats and the asthma and healthy rat groups were identified using isobaric tagging followed by LC-MS/MS. Kyoto encyclopedia of genes and genomes pathway analysis of the differentially expressed proteins was performed.

RESULTS

Pathways involved in purine metabolism, herpes simplex infection, and JNK phosphorylation and activation mediated by activated human TAK1 were enriched, indicating the intrinsic links between the mechanism of asthma development and treatment effects. Furthermore, we constructed a protein-protein interaction network and identified KIF3A as a potential target protein of chamomile extract that affected the Hedgehog signaling pathway.

CONCLUSIONS

This study may provide new insights into the pathogenesis of asthma and reveal several proteins and pathways that could be exploited to develop novel treatment approaches.

Immunolocalization of transforming growth factor-beta1, connective tissue growth factor, phosphorylated-SMAD2/3, and phosphorylated-ERK1/2 during mouse incisor development

BACKGROUND/AIMS

Connective tissue growth factor (CTGF) is a downstream mediator of transforming growth factor-beta 1 (TGF-β₁) and TGF-β₁-induced CTGF expression is regulated through SMAD and mitogen-activated protein kinase (MAPK) signaling pathways. However, little is known about the localization of CTGF and TGF-β₁ signaling cascades during incisor development. Therefore, we aimed to investigate the distribution pattern of TGF-β₁, CTGF, phosphorylated-SMAD2/3 (p-SMAD2/3), and phosphorylated-ERK1/2 (p-ERK1/2) in the developing mouse incisors.

MATERIALS AND METHODS

ICR mice heads of embryonic (E) day 16.5, postnatal (PN) day 0.5 and PN3.5 were processed for immunohistochemistry.

RESULTS

From E16.5 to PN3.5, moderate to strong staining for TGF-β₁ and CTGF was localized in stellate reticulum (SR), transit amplifying (TA) cells, outer enamel epithelium (OEE), preameloblasts (PA), preodontoblasts (PO), and dental papilla (DP). p-SMAD2/3 was weakly positive in SR and OEE at E16.5 and PN0.5 but was strongly positive in SR and OEE at PN3.5. Particularly, in the stem cell niche, p-SMAD2/3 was only localized in SR cells adjacent to OEE. There was no staining for p-SMAD2/3 in TA cells, PA and PO, although weak to moderate staining for p-SMAD2/3 was seen in DP. From E16.5 to PN3.5, p-ERK1/2 was negative in TA cells, OEE, PA and PO, whereas weak to moderate staining for p-ERK1/2 was observed in SR. DP was moderately stained for p-ERK1/2.

CONCLUSIONS

TGF-β₁ and CTGF show a similar expression, while p-SMAD2/3 and p-ERK1/2 exhibit differential distribution pattern, which indicates that CTGF and TGF-β₁ signaling cascades might play a regulatory role in incisor development.

Simvastatin and the Rho-kinase inhibitor Y-27632 prevent myofibroblast transformation in Peyronie's disease-derived fibroblasts via inhibition of YAP/TAZ nuclear translocation

OBJECTIVES

To uncover the anti-myofibroblast (MFB) properties of Rho-kinase inhibitor (compound Y-27632) and simvastatin in an in vitro model of Peyronie's disease (PD), a sexually debilitating disease caused by an irreversible fibrotic plaque in the penile tunica albuginea (TA).

MATERIALS AND METHODS

Primary human fibroblasts (FBs) were isolated from surgically obtained TA tissue from patients with PD. To induce MFB status, cells were stimulated with 3 ng/mL transforming growth factor-β1 (TGF-β1). Increasing doses of Y-27632 and simvastatin were added. Real-time quantitative PCR was used to assess mRNA expression of α-smooth muscle actin (α-SMA), collagen III, elastin and connective tissue growth factor (CTGF) after 72 h. Western blot analysis was used to quantify α-SMA protein contents, and immunofluorescence (IF) was used to visualize MFB differentiation by staining for α-SMA after 72 h. A resazurin-based assay was used to assess cell viability to ensure the anti-MFB effect of the drugs. A mechanistic study was performed using IF staining for YAP/TAZ nuclear translocation.

RESULTS

After 72 h of stimulation with TGF-β1, a six- to 10-fold upregulation of α-SMA could be observed. When treated with Y-27632 or simvastatin, the α-SMA, collagen III, elastin and CTGF mRNA expression was impeded. Additionally, TGF-β1 stimulation showed a twofold increase in α-SMA protein expression, which was reversed to non-stimulated levels after treatment with Y-27632 and simvastatin. Using IF, stimulated cells were identified as MFB (α-SMA+, Vim+) as opposed to the non-stimulated, Y-27632- and simvastatin-treated cells (α-SMA-, Vim+). The resazurin-based assay confirmed that the cell viability was not compromised by the administered drugs. On stimulation with TGF-β1, nuclear translocation of YAP/TAZ could be observed, which was prevented by adding the aforementioned compounds.

CONCLUSION

Transformation of FBs into the contractile and extracellular matrix-producing MFBs occurs after TGF-β1 stimulation. In our experiments, Rho-kinase inhibition and simvastatin treatment were shown to prevent this in TGF-β1-stimulated cells on an RNA and protein level through the inhibition of YAP/TAZ nuclear translocation. Y-27632 and simvastatin could become a novel treatment option in the early treatment of PD.

Fibroblast-to-myofibroblast transition in bronchial asthma

Bronchial asthma is a chronic inflammatory disease in which bronchial wall remodelling plays a significant role. This phenomenon is related to enhanced proliferation of airway smooth muscle cells, elevated extracellular matrix protein secretion and an increased number of myofibroblasts. Phenotypic fibroblast-to-myofibroblast transition represents one of the primary mechanisms by which myofibroblasts arise in fibrotic lung tissue. Fibroblast-to-myofibroblast transition requires a combination of several types of factors, the most important of which are divided into humoural and mechanical factors, as well as certain extracellular matrix proteins. Despite intensive research on the nature of this process, its underlying mechanisms during bronchial airway wall remodelling in asthma are not yet fully clarified. This review focuses on what is known about the nature of fibroblast-to-myofibroblast transition in asthma. We aim to consider possible mechanisms and conditions that may play an important role in fibroblast-to-myofibroblast transition but have not yet been discussed in this context. Recent studies have shown that some inherent and previously undescribed features of fibroblasts can also play a significant role in fibroblast-to-myofibroblast transition. Differences observed between asthmatic and non-asthmatic bronchial fibroblasts (e.g., response to transforming growth factor β, cell shape, elasticity, and protein expression profile) may have a crucial influence on this phenomenon. An accurate understanding and recognition of all factors affecting fibroblast-to-myofibroblast transition might provide an opportunity to discover efficient methods of counteracting this phenomenon.

Rhynchophylline attenuates allergic bronchial asthma by inhibiting transforming growth factor-β1-mediated Smad and mitogen-activated protein kinase signaling transductions in vivo and in vitro

Rhynchophylline (Rhy) is a major active component of Uncaria rhynchophylla and exhibits the potential to inhibit the proliferation of airway smooth muscle cells (ASMCs). In the current study, it was hypothesized that Rhy serves a key role in the anti-asthma effect of Uncaria rhynchophylla by inhibiting transforming growth factor-β1 (TGF-β1)-mediated activation of Smad and mitogen-activated protein kinase (MAPK) signaling. Allergic asthma was induced in mice using ovalbumin (OVA), and the effect of Rhy treatment on inflammatory and allergic responses in the bronchoalveolar lavage fluid (BALF) and serum of mice was determined. Subsequently, the changes in TGF-β1-induced Smad and MAPK signaling following Rhy administration were detected to determine the mechanism associated with this treatment. In addition, TGF-β1 was employed to induce hyperplasia of ASMCs, and the effect of Rhy on proliferation of ASMCs, and Smad and MAPK signaling in vitro was also assessed. The administration of Rhy attenuated the recruitment of eosinophils in BALF induced by OVA, which was associated with the suppressed production of immunoglobulin E, interleukin (IL)-13, IL-4 and IL-5. At the molecular level, the administration of Rhy suppressed the expression levels of TGF-β1, Smad4, p-Smad2 and p-Smad3, while it induced the expression of Smad7, indicating the inhibitory effect of Rhy on TGF-β1-mediated Smad and MAPK signaling. Furthermore, Rhy inhibited the proliferation of ASMCs and, similar to the results of the in vivo assay, it blocked the pro-hyperplasia signaling transduction in vitro. In conclusion, the current study demonstrated the anti-asthma effect of Rhy, which depended on the inhibition of TGF-β1-mediated Smad and MAPK signaling.

Transforming growth factor-β1 increases C-C chemokine ligand 11 production in interleukin 4-stimulated human periodontal ligament cells

Transforming growth factor (TGF)-β1 is a multifunctional cytokine, which can control certain functions of various kinds of cells. However, it is unclear whether TGF-β1 affects T-cell migration in periodontal lesions. The aim of this study was to examine the effects of TGF-β1 on the production of C-C chemokine ligand (CCL)11, which is a T-helper 2-type chemokine, in human periodontal ligament cells (HPDLC). Interleukin (IL)-4 induced CCL11 production, but TGF-β1 did not, in HPDLC. However, TGF-β1 enhanced CCL11 production in IL-4-stimulated HPDLC. Western blot analysis showed that the signal transducer and activator of transcription 6 (STAT6) pathway was highly activated in HPDLC that had been stimulated with both IL-4 and TGF-β1. Mitogen-activated protein kinase activation did not differ between the HPDLC treated with a combination of IL-4 and TGF-β1 and those treated with IL-4 or TGF-β1 alone. Moreover, a STAT6 inhibitor significantly inhibited CCL11 production in HPDLC that had been stimulated with IL-4 and TGF-β1. The current study clearly demonstrated that TGF-β1 enhanced IL-4-induced CCL11 production in HPDLC. The STAT6 pathway is important for CCL11 production in IL-4- and TGF-β1-treated HPDLC.

Unique mechanisms of connective tissue growth factor regulation in airway smooth muscle in asthma: Relationship with airway remodelling

Neovascularization, increased basal membrane thickness and increased airway smooth muscle (ASM) bulk are hallmarks of airway remodelling in asthma. In this study, we examined connective tissue growth factor (CTGF) dysregulation in human lung tissue and animal models of allergic airway disease. Immunohistochemistry revealed that ASM cells from patients with severe asthma (A) exhibited high expression of CTGF, compared to mild and non‐asthmatic (NA) tissues. This finding was replicated in a sheep model of allergic airways disease. In vitro, transforming growth factor (TGF)‐β increased CTGF expression both in NA‐ and A‐ASM cells but the expression was higher in A‐ASM at both the mRNA and protein level as assessed by PCR and Western blot. Transfection of CTGF promoter‐luciferase reporter constructs into NA‐ and A‐ASM cells indicated that no region of the CTGF promoter (−1500 to +200 bp) displayed enhanced activity in the presence of TGF‐β. However, in silico analysis of the CTGF promoter suggested that distant transcription factor binding sites may influence CTGF promoter activation by TGF‐β in ASM cells. The discord between promoter activity and mRNA expression was also explained, in part, by differential post‐transcriptional regulation in A‐ASM cells due to enhanced mRNA stability for CTGF. In patients, higher CTGF gene expression in bronchial biopsies was correlated with increased basement membrane thickness indicating that the enhanced CTGF expression in A‐ASM may contribute to airway remodelling in asthma.

Betaglycan (TGFBR3) up-regulation correlates with increased TGF-β signaling in Marfan patient fibroblasts in vitro

BACKGROUND

Marfan syndrome (MFS), a congenital connective tissue disorder leading to aortic aneurysm development, is caused by fibrillin-1 (FBN1) gene mutations. Transforming growth factor beta (TGF-β) might play a role in the pathogenesis. It is still a matter of discussion if and how TGF-β up-regulates the intracellular downstream pathway, although TGF-β receptor 3 (TGFBR3 or Betaglycan) is thought to be involved. We aimed to elucidate the role of TGFBR3 protein in TGF-β signaling in Marfan patients.

METHODS

Dermal fibroblasts of MFS patients with haploinsufficient (HI; n=9) or dominant negative (DN; n=4) FBN1 gene mutations, leading to insufficient or malfunctioning fibrillin-1, respectively, were used. Control cells (n=10) were from healthy volunteers. We quantified TGFBR3 protein expression by immunofluorescence microscopy and gene expression of FBN1, TGFB1, its receptors, and downstream transcriptional target genes by quantitative polymerase chain reaction.

RESULTS

Betaglycan protein expression in FBN1 mutants pooled was higher than in controls (P=.004) and in DN higher than in HI (P=.015). In DN, significantly higher mRNA expression of FBN1 (P=.014), SMAD7 (P=.019), HSP47 (P=.023), and SERPINE1 (P=.008), but a lower HSPA5 expression (P=.029), was observed than in HI. A pattern of higher expression was noted for TGFB1 (P=.059), FN1 (P=.089), and COL1A1 (P=.089) in DN as compared to HI. TGFBR3 protein expression in cells, both presence in the endoplasmic reticulum and amount of vesicles per cell, correlated positively with TGFB1 mRNA expression (Rs=0.60, P=.017; Rs=0.55, P=.029; respectively). TGFBR3 gene expression did not differ between groups.

CONCLUSION

We demonstrated that activation of TGF-β signaling is higher in patients with a DN than an HI FBN1 gene mutation. Also, TGFBR3 protein expression is increased in the DN group and correlates positively with TGFB1 expression in groups pooled. We suggest that TGFBR3 protein expression is involved in up-regulated TGF-β signaling in MFS patients with a DN FBN1 gene mutation.

The leukotriene receptor antagonist pranlukast attenuates airway remodeling by suppressing TGF-β signaling

BACKGROUND/OBJECTIVE

Asthma is a chronic airway disease characterized by airway eosinophilic inflammation and remodeling, which are associated with a loss in lung function. Although both contribute significantly to asthma pathogenesis, mechanistic studies and drug discovery have focused on inflammatory targets. In this study, we investigated the effect of the leukotriene receptor antagonist pranlukast on allergic airway inflammation and remodeling in vivo and in vitro.

METHOD

Four groups of female BALB/c mice (control; ovalbumin [OVA]-sensitized and -challenged; dimethyl sulfoxide [DMSO]-treated OVA; and pranlukast-treated OVA) were examined. Lung pathology, cytokine production, and airway hyperresponsiveness (AHR) measurements were compared among these groups. A human fetal lung fibroblast HFL-1 cell line was used in the peribranchial fibrosis analysis.

RESULTS

OVA-sensitized and -challenged mice exhibited allergic airway inflammation and significant increases in Th2 cytokines. Pranlukast-treated mice showed significant attenuation of allergic airway inflammation. The pranlukast treatment decreased AHR and attenuated airway remodeling to goblet cell hyperplasia, collagen deposition, α-smooth muscle actin expression, and pro-fibrotic gene expression. We further demonstrated that pranlukast not only inhibited transforming growth factor-beta 1 (TGF-β1)-induced Smad signaling in human fetal lung fibroblast cells but also simultaneously reduced collagen synthesis and pro-fibrotic gene expression.

CONCLUSIONS

The leukotriene receptor antagonist pranlukast can reduce airway inflammation and remodeling by inhibiting TGF-β/Smad signaling in an OVA-sensitized and -challenged asthma mouse model, thus suppressing AHR.

Microvesicle-mediated delivery of miR-1343: impact on markers of fibrosis

Tissue fibrosis, the development of fibrous connective tissue as a result of injury or damage, is associated with many common diseases and cannot be treated effectively. The complex biological processes accompanying fibrosis often involve aberrant signaling through the transforming growth factor beta (TGF-β) pathway. In the search for mechanisms to repress this signaling, microRNAs have emerged as a novel class of molecules capable of targeting single members of the TGF-β pathway, or the pathway as a whole. We previously identified miR-1343 as a potent repressor of TGF-β signaling and fibrosis through the direct attenuation of both canonical TGF-β receptors. Here, we build upon our previous findings to better characterize the function of endogenous miR-1343 in normal biology and examine the potential role of exogenous miR-1343 as a repressor of TGF-β signaling. CRISPR/Cas9-mediated deletion of miR-1343 from A549 lung epithelial cells impacts several processes and genes implicated in fibrosis and known to be TGF-β pathway effectors. Moreover, the responses are opposite to those we observed previously when miR-1343 was overexpressed in the same cell type. We also show that miR-1343 can be shuttled into exosomes, a type of extracellular vesicle that are exported by cells into the surrounding medium and can be absorbed by distant target cells. miR-1343 delivered into primary lung fibroblasts by exosomes has a measurable function in reducing TGF-β signaling and markers of fibrosis. These results highlight a role for miR-1343 in fine-tuning the TGF-β pathway and suggest its use as a therapeutic in fibrotic disease.

Knockdown of FSTL1 inhibits PDGF‑BB‑induced human airway smooth muscle cell proliferation and migration

Abnormal proliferation and migration of airway smooth muscle (ASM) cells serve roles in airway remodeling, and contribute to airway hyper‑responsiveness. Follistatin‑like protein 1 (FSTL1) is a secreted glycoprotein that belongs to the follistatin family of proteins. It was reported that in the lungs of patients suffering from severe asthma, FSTL1 is highly expressed by macrophages. However, the role of FSTL1 in ASM cell proliferation and migration remains unknown. The present study aimed to investigate the role of FSTL1 in cell proliferation and migration mediated by platelet‑derived growth factor subunit B (PDGF‑BB) in human ASM cells. The results of the present study demonstrated that PDGF‑BB stimulation upregulated FSTL1 expression levels in ASM cells in vitro. Knockdown of FSTL1 inhibited cell proliferation and arrested the cell cycle in the G2/M phase in PDGF‑BB‑stimulated ASM cells. Additionally, knockdown of FSTL1 inhibited PDGF‑BB‑induced ASM cell migration. Furthermore, FSTL1 knockdown caused the downregulation of phosphorylated (p)‑extracellular signal‑regulated kinase (ERK) and p‑protein kinase B (AKT) expression levels induced by PDGF‑BB in ASM cells. In conclusion, the present study demonstrated that knockdown of FSTL1 inhibited ASM cell proliferation and migration induced by PDGF‑BB, at least partially via inhibiting the activation of ERK and AKT. FSTL1 may therefore represent a novel therapeutic target for airway remodeling in childhood asthma.

TGF-β Targets the Hippo Pathway Scaffold RASSF1A to Facilitate YAP/SMAD2 Nuclear Translocation

Epigenetic inactivation of the Hippo pathway scaffold RASSF1A is associated with poor prognosis in a wide range of sporadic human cancers. Loss of expression reduces tumor suppressor activity and promotes genomic instability, but how this pleiotropic biomarker is regulated at the protein level is unknown. Here we show that TGF-β is the physiological signal that stimulates RASSF1A degradation by the ubiquitin-proteasome pathway. In response to TGF-β, RASSF1A is recruited to TGF-β receptor I and targeted for degradation by the co-recruited E3 ubiquitin ligase ITCH. RASSF1A degradation is necessary to permit Hippo pathway effector YAP1 association with SMADs and subsequent nuclear translocation of receptor-activated SMAD2. We find that RASSF1A expression regulates TGF-β-induced YAP1/SMAD2 interaction and leads to SMAD2 cytoplasmic retention and inefficient transcription of TGF-β targets genes. Moreover, RASSF1A limits TGF-β induced invasion, offering a new framework on how RASSF1A affects YAP1 transcriptional output and elicits its tumor-suppressive function.

A paracrine network regulates the cross-talk between human lung stem cells and the stroma

The signals that regulate stem cell self-renewal and differentiation in the lung remain elusive. Lung stem cells undergo self-renewal or lineage commitment to replenish tissue, depending on cross-talk with their environment. This environment, also known as the niche, includes mesenchymal and endothelial tissues. Here we define molecular mechanisms involved in the interaction between human lung Lgr6+ stem cells (LSCs) and fibroblasts in a functional microenvironment. We reveal a central role for p38α MAPK in establishing and maintaining such cross-talk, acting in both cell types. In LSCs, p38α induces the expression of SDF-1, which activates the stroma. p38α is essential for fibroblast activation and induction of cytokine expression, in particular TNFα. This paracrine network induces a hierarchical activation leading to the recruitment of endothelium, establishing a functional microenvironment. Disruption of this cross-talk abrogates proper LSC differentiation in vivo and may lead to lung dysfunction and disease.

The human lung contains Lgr6-positive progenitor cells, which have the potential to generate multiple epithelial lineages in cell explant studies. Here, the authors present a role of p38a MAPK signalling in regulating the cross-talk between this lung progenitor cell population and the stromal and endothelial cells comprising their niche microenvironment.

Smad4 Deficiency in Smooth Muscle Cells Initiates the Formation of Aortic Aneurysm

RATIONALE

Aortic aneurysm is a life-threatening cardiovascular disorder caused by the predisposition for dissection and rupture. Genetic studies have proved the involvement of the transforming growth factor-β (TGF-β) pathway in aortic aneurysm. Smad4 is the central mediator of the canonical TGF-β signaling pathway. However, the exact role of Smad4 in smooth muscle cells (SMCs) leading to the pathogenesis of aortic aneurysms is largely unknown.

OBJECTIVE

To determine the role of smooth muscle Smad4 in the pathogenesis of aortic aneurysms.

METHODS AND RESULTS

Conditional gene knockout strategy combined with histology and expression analysis showed that Smad4 or TGF-β receptor type II deficiency in SMCs led to the occurrence of aortic aneurysms along with an upregulation of cathepsin S and matrix metallopeptidase-12, which are proteases essential for elastin degradation. We further demonstrated a previously unknown downregulation of matrix metallopeptidase-12 by TGF-β in the aortic SMCs, which is largely abrogated in the absence of Smad4. Chemotactic assay and pharmacologic treatment demonstrated that Smad4-deficient SMCs directly triggered aortic wall inflammation via the excessive production of chemokines to recruit macrophages. Monocyte/macrophage depletion or blocking selective chemokine axis largely abrogated the progression of aortic aneurysm caused by Smad4 deficiency in SMCs.

CONCLUSIONS

The findings reveal that Smad4-dependent TGF-β signaling in SMCs protects against aortic aneurysm formation and dissection. The data also suggest important implications for novel therapeutic strategies to limit the progression of the aneurysm resulting from TGF-β signaling loss-of-function mutations.

AFAP1 Is a Novel Downstream Mediator of TGF-β1 for CCN2 Induction in Osteoblasts

Background

CCN2 acts as an anabolic growth factor to regulate osteoblast differentiation and function. CCN2 is induced by TGF-β1 and acts as a mediator of TGF-β1 induced matrix production in osteoblasts and Src is required for CCN2 induction by TGF-β1; however, the molecular mechanisms that control CCN2 induction in osteoblasts are poorly understood. AFAP1 binds activated forms of Src and can direct the activation of Src in certain cell types, however a role for AFAP1 downstream of TGF-β1 or in osteoblats is undefined. In this study, we investigated the role of AFAP1 for CCN2 induction by TGF-β1 in primary osteoblasts.

Results

We demonstrated that AFAP1 expression in osteoblasts occurs in a biphasic pattern with maximal expression levels occurring during osteoblast proliferation (~day 3), reduced expression during matrix production/maturation (~day 14–21), an a further increase in expression during mineralization (~day 21). AFAP1 expression is induced by TGF-β1 treatment in osteoblasts during days 7, 14 and 21. In osteoblasts, AFAP1 binds to Src and is required for Src activation by TGF-β1 and CCN2 promoter activity and protein induction by TGF-β1 treatment was impaired using AFAP1 siRNA, indicating the requirement of AFAP1 for CCN2 induction by TGF-β1. We also demonstrated that TGF-β1 induction of extracellular matrix protein collagen XIIa occurs in an AFAP1 dependent fashion.

Conclusions

This study demonstrates that AFAP1 is an essential downstream signaling component of TGF-β1 for Src activation, CCN2 induction and collagen XIIa in osteoblasts.

SP600125 promotes resolution of allergic airway inflammation via TLR9 in an OVA-induced murine acute asthma model

BACKGROUND

c-Jun N-terminal kinase (JNK) relays extracellular stimuli through phosphorylation cascades that lead to various cell responses. In the present study, we aimed to investigate the effect of the JNK inhibitor SP600125 on the resolution of airway inflammation, and the underlying mechanism using a murine acute asthma model.

METHODS

Female C57BL/6 mice were sensitized with saline or ovalbumin (OVA) on day 0, and challenged with OVA on day 14-20. Meanwhile, some of the mice were treated with SP600125 (30 mg/kg) intraperitoneally 2 h before each challenge. The airway inflammation was evaluated by counting the numbers of various types of inflammatory cells in bronchoalveolar lavage fluid (BALF), histopathology, cytokines production and mucus secretion in individual mouse. In addition, we analyzed the protein levels of phosphorylated JNK and TLR9 in the lung tissues.

RESULTS

SP600125 markedly reduced the invasion of inflammatory cells into the peribronchial regions, and decreased the numbers of eosinophils, monocytes, neutrophils and lymphocytes in BALF. SP600125 also reduced the level of plasma OVA-specific IgE, lowered the production of pro-inflammatory cytokines in BALF and alleviated mucus secretion. Meanwhile, SP600125 inhibited OVA-induced, increased expression of p-JNK and TLR9 in the lung tissues.

CONCLUSIONS

Collectively, our data demonstrated that SP600125 promoted resolution of allergic airway inflammation via TLR9 in an OVA-induced murine acute asthma model. The JNK-TLR9 pathway may be a new therapeutic target in the treatment for the allergic asthma.

The Three A's in Asthma - Airway Smooth Muscle, Airway Remodeling & Angiogenesis

Asthma affects more than 300 million people worldwide and its prevalence is still rising. Acute asthma attacks are characterized by severe symptoms such as breathlessness, wheezing, tightness of the chest, and coughing, which may lead to hospitalization or death. Besides the acute symptoms, asthma is characterized by persistent airway inflammation and airway wall remodeling. The term airway wall remodeling summarizes the structural changes in the airway wall: epithelial cell shedding, goblet cell hyperplasia, hyperplasia and hypertrophy of the airway smooth muscle (ASM) bundles, basement membrane thickening and increased vascular density. Airway wall remodeling starts early in the pathogenesis of asthma and today it is suggested that remodeling is a prerequisite for other asthma pathologies. The beneficial effect of bronchial thermoplasty in reducing asthma symptoms, together with the increased potential of ASM cells of asthmatics to produce inflammatory and angiogenic factors, indicate that the ASM cell is a major effector cell in the pathology of asthma. In the present review we discuss the ASM cell and its role in airway wall remodeling and angiogenesis.

Anti-CTGF single-chain variable fragment dimers inhibit human airway smooth muscle (ASM) cell proliferation by down-regulating p-Akt and p-mTOR levels

Connective tissue growth factor (CTGF) contributes to airway smooth muscle (ASM) cell hyperplasia in asthma. Humanized single-chain variable fragment antibody (scFv) was well characterized as a CTGF antagonist in the differentiation of fibroblast into myofibroblast and pulmonary fibrosis in our previous studies. To further improve the bioactivity of scFv, we constructed a plasmid to express scFv-linker-matrilin-6×His fusion proteins that could self-assemble into the scFv dimers by disulfide bonds in matrilin under non-reducing conditions. An immunoreactivity assay demonstrated that the scFv dimer could highly bind to CTGF in a concentration-dependent manner. The MTT and EdU assay results revealed that CTGF (≥10 ng/mL) promoted the proliferation of ASM cells, and this effect was inhibited when the cells were treated with anti-CTGF scFv dimer. The western blot analysis results showed that increased phosphorylation of Akt and mTOR induced by CTGF could be suppressed by this scFv dimer. Based on these findings, anti-CTGF scFv dimer may be a potential agent for the prevention of airway remodeling in asthma.

Attenuated development of cardiac fibrosis in left ventricular pressure overload by SM16, an orally active inhibitor of ALK5

Pressure overload-induced TGF-β signaling activates cardiac fibroblasts (CFB) and leads to increased extracellular matrix (ECM) protein synthesis including fibrosis. Excessive ECM accumulation may in turn affect cardiac function contributing to development of heart failure. The aim of this study was to examine the effects of SM16, an orally active small molecular inhibitor of ALK5, on pressure overload-induced cardiac fibrosis. One week after aortic banding (AB), C57Bl/6J mice were randomized to standard chow or chow with SM16. Sham operated animals served as controls. Following 4 weeks AB, mice were characterized by echocardiography and cardiovascular magnetic resonance before sacrifice. SM16 abolished phosphorylation of SMAD2 induced by AB in vivo and by TGF-β in CFB in vitro. Interestingly, Masson Trichrome and Picrosirius Red stained myocardial left ventricular tissue revealed reduced development of fibrosis and collagen cross-linking following AB in the SM16 treated group, which was confirmed by reduced hydroxyproline incorporation. Furthermore, treatment with SM16 attenuated mRNA expression following induction of AB in vivo and stimulation with TGF-β in CFB in vitro of Col1a2, the cross-linking enzyme LOX, and the pro-fibrotic glycoproteins SPARC and osteopontin. Reduced ECM synthesis by CFB and a reduction in myocardial stiffness due to attenuated development of fibrosis and collagen cross-linking might have contributed to the improved diastolic function and cardiac output seen in vivo, in combination with reduced lung weight and ANP expression by treatment with SM16. Despite these beneficial effects on cardiac function and development of heart failure, mice treated with SM16 exhibited increased mortality, increased LV dilatation and inflammatory heart valve lesions that may limit the use of SM16 and possibly also other small molecular inhibitors of ALK5, as future therapeutic drugs.

Regulation of pulmonary inflammation by mesenchymal cells

Pulmonary inflammation and tissue remodelling are common elements of chronic respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and pulmonary hypertension (PH). In disease, pulmonary mesenchymal cells not only contribute to tissue remodelling, but also have an important role in pulmonary inflammation. This review will describe the immunomodulatory functions of pulmonary mesenchymal cells, such as airway smooth muscle (ASM) cells and lung fibroblasts, in chronic respiratory disease. An important theme of the review is that pulmonary mesenchymal cells not only respond to inflammatory mediators, but also produce their own mediators, whether pro-inflammatory or pro-resolving, which influence the quantity and quality of the lung immune response. The notion that defective pro-inflammatory or pro-resolving signalling in these cells potentially contributes to disease progression is also discussed. Finally, the concept of specifically targeting pulmonary mesenchymal cell immunomodulatory function to improve therapeutic control of chronic respiratory disease is considered.

Smooth muscle LDL receptor-related protein-1 deletion induces aortic insufficiency and promotes vascular cardiomyopathy in mice

Valvular disease is common in patients with Marfan syndrome and can lead to cardiomyopathy. However, some patients develop cardiomyopathy in the absence of hemodynamically significant valve dysfunction, suggesting alternative mechanisms of disease progression. Disruption of LDL receptor-related protein-1 (Lrp1) in smooth muscle cells has been shown to cause vascular pathologies similar to Marfan syndrome, with activation of smooth muscle cells, vascular dysfunction and aortic aneurysms. This study used echocardiography and blood pressure monitoring in mouse models to determine whether inactivation of Lrp1 in vascular smooth muscle leads to cardiomyopathy, and if so, whether the mechanism is a consequence of valvular disease. Hemodynamic changes during treatment with captopril were also assessed. Dilation of aortic roots was observed in young Lrp1-knockout mice and progressed as they aged, whereas no significant aortic dilation was detected in wild type littermates. Diastolic blood pressure was lower and pulse pressure higher in Lrp1-knockout mice, which was normalized by treatment with captopril. Aortic dilation was followed by development of aortic insufficiency and subsequent dilated cardiomyopathy due to valvular disease. Thus, smooth muscle cell Lrp1 deficiency results in aortic dilation and insufficiency that causes secondary cardiomyopathy that can be improved by captopril. These findings provide novel insights into mechanisms of cardiomyopathy associated with vascular activation and offer a new model of valvular cardiomyopathy.

Cardiac and respiratory dysfunction in Duchenne muscular dystrophy and the role of second messengers

Duchenne muscular dystrophy (DMD) affects young boys and is characterized by the absence of dystrophin, a large cytoskeletal protein present in skeletal and cardiac muscle cells and neurons. The heart and diaphragm become necrotic in DMD patients and animal models of DMD, resulting in cardiorespiratory failure as the leading cause of death. The major consequences of the absence of dystrophin are high levels of intracellular Ca(2+) and the unbalanced production of NO that can finally trigger protein degradation and cell death. Cytoplasmic increase in Ca(2+) concentration directly and indirectly triggers different processes such as necrosis, fibrosis, and activation of macrophages. The absence of the neuronal isoform of nitric oxide synthase (nNOS) and the overproduction of NO by the inducible isoform (iNOS) further increase the intracellular Ca(2+) via a hypernitrosylation of the ryanodine receptor. NO overproduction, which further induces the expression of iNOS but decreases the expression of the endothelial isoform (eNOS), deregulates the muscle tissue blood flow creating an ischemic situation. The high levels of Ca(2+) in dystrophic muscles and the ischemic state of the muscle tissue would culminate in a positive feedback loop. While efforts continue toward optimizing cardiac and respiratory care of DMD patients, both Ca(2+) and NO in cardiac and respiratory muscle pathways have been shown to be important to the etiology of the disease. Understanding the mechanisms behind the fine regulation of Ca(2+) -NO may be important for a noninterventional and noninvasive supportive approach to treat DMD patients, improving the quality of life and natural history of DMD patients.

Pasteurella multocida toxin (PMT) upregulates CTGF which leads to mTORC1 activation in Swiss 3T3 cells

Pasteurella multocida toxin (PMT) is a mitogenic protein that hijacks cellular signal transduction pathways via deamidation of heterotrimeric G proteins. We previously showed that rPMT activates mTOR signaling via a Gαq/11/PLCβ/PKC mediated pathway, leading in part to cell proliferation and migration. Herein, we show that mTOR and MAPK, but not membrane-associated tyrosine kinases, are activated in serum-starved 3T3 cells by an autocrine/paracrine substance(s) secreted into the conditioned medium following rPMT treatment. Surprisingly, this diffusible factor(s) is capable of activating mTOR and MAPK pathways even in MEF Gαq/11 double knockout cells. Microarray analysis identified connective tissue growth factor (CTGF) mRNA as the most upregulated gene in rPMT-treated serum-starved 3T3 cells relative to untreated cells. These results were further confirmed using RT-PCR and Western blot analyses. In accord with rPMT-induced mTOR activation, upregulation of CTGF protein was observed in WT MEF, but not in Gαq/11 double knockout MEF cells. Although CTGF expression is regulated by TGFβ, rPMT did not activate TGFβ pathway. In addition, MEK inhibitors U0126 or PD98059, but not mTOR specific inhibitors, rapamycin and Torin 1, inhibited rPMT-induced upregulation of CTGF. Importantly, CTGF overexpression in serum-starved 3T3 cells using adenovirus led to phosphorylation of ribosomal protein S6, a downstream target of mTOR. However, despite the ability of CTGF to activate the mTOR pathway, upregulation of CTGF alone could not induce morphological changes as those observed in rPMT-treated cells. Our findings reveal that CTGF plays an important role, but there are additional factors involved in the mitogenic action of PMT.

IFN-γ and TNF-α synergize to inhibit CTGF expression in human lung endothelial cells

Connective tissue growth factor (CTGF/CCN2) is an angiogenetic and profibrotic factor, acting downstream of TGF-β, involved in both airway- and vascular remodeling. While the T-helper 1 (Th1) cytokine interferon-gamma (IFN-γ) is well characterized as immune-modulatory and anti-fibrotic cytokine, the role of IFN-γ in lung endothelial cells (LEC) is less defined. Tumour necrosis factor alpha (TNF-α) is another mediator that drives vascular remodeling in inflammation by influencing CTGF expression. In the present study we investigated the influence of IFN-γ and TNF-α on CTGF expression in human LEC (HPMEC-ST1.6R) and the effect of CTGF knock down on human LEC. IFN-γ and TNF-α down-regulated CTGF in human LEC at the promoter-, transcriptional- and translational-level in a dose- and time-dependent manner. The inhibitory effect of IFN-γ on CTGF-expression could be almost completely compensated by the Jak inhibitor AG-490, showing the involvement of the Jak-Stat signaling pathway. Besides the inhibitory effect of IFN-γ and TNF-α alone on CTGF expression and LEC proliferation, these cytokines had an additive inhibitory effect on proliferation as well as on CTGF expression when administered together. To study the functional role of CTGF in LEC, endogenous CTGF expression was down-regulated by a lentiviral system. CTGF silencing in LEC by transduction of CTGF shRNA reduced cell proliferation, but did not influence the anti-proliferative effect of IFN-γ and TNF-α. In conclusion, our data demonstrated that CTGF was negatively regulated by IFN-γ in LEC in a Jak/Stat signaling pathway-dependent manner. In addition, an additive effect of IFN-γ and TNF-α on inhibition of CTGF expression and cell proliferation could be found. The inverse correlation between IFN-γ and CTGF expression in LEC could mean that screwing the Th2 response to a Th1 response with an additional IFN-γ production might be beneficial to avoid airway remodeling in asthma.

Ets-1 is essential for connective tissue growth factor (CTGF/CCN2) induction by TGF-β1 in osteoblasts

Background

Ets-1 controls osteoblast differentiation and bone development; however, its downstream mechanism of action in osteoblasts remains largely undetermined. CCN2 acts as an anabolic growth factor to regulate osteoblast differentiation and function. CCN2 is induced by TGF-β1 and acts as a mediator of TGF-β1 induced matrix production in osteoblasts; however, the molecular mechanisms that control CCN2 induction are poorly understood. In this study, we investigated the role of Ets-1 for CCN2 induction by TGF-β1 in primary osteoblasts.

Results

We demonstrated that Ets-1 is expressed and induced by TGF-β1 treatment in osteoblasts, and that Ets-1 over-expression induces CCN2 protein expression and promoter activity at a level similar to TGF-β1 treatment alone. Additionally, we found that simultaneous Ets-1 over-expression and TGF-β1 treatment synergize to enhance CCN2 induction, and that CCN2 induction by TGF-β1 treatment was impaired using Ets-1 siRNA, demonstrating the requirement of Ets-1 for CCN2 induction by TGF-β1. Site-directed mutagenesis of eight putative Ets-1 motifs (EBE) in the CCN2 promoter demonstrated that specific EBE sites are required for CCN2 induction, and that mutation of EBE sites in closer proximity to TRE or SBE (two sites previously shown to regulate CCN2 induction by TGF-β1) had a greater effect on CCN2 induction, suggesting potential synergetic interaction among these sites for CCN2 induction. In addition, mutation of EBE sites prevented protein complex binding, and this protein complex formation was also inhibited by addition of Ets-1 antibody or Smad 3 antibody, demonstrating that protein binding to EBE motifs as a result of TGF-β1 treatment require synergy between Ets-1 and Smad 3.

Conclusions

This study demonstrates that Ets-1 is an essential downstream signaling component for CCN2 induction by TGF-β1 in osteoblasts, and that specific EBE sites in the CCN2 promoter are required for CCN2 promoter transactivation in osteoblasts.

A crosstalk between the Smad and JNK signaling in the TGF-β-induced epithelial-mesenchymal transition in rat peritoneal mesothelial cells

Transforming growth factor β (TGF-β) induces the process of epithelial-mesenchymal transition (EMT) through the Smad and JNK signaling. However, it is unclear how these pathways interact in the TGF-β1-induced EMT in rat peritoneal mesothelial cells (RPMCs). Here, we show that inhibition of JNK activation by introducing the dominant-negative JNK1 gene attenuates the TGF-β1-down-regulated E-cadherin expression, and TGF-β1-up-regulated α-SMA, Collagen I, and PAI-1 expression, leading to the inhibition of EMT in primarily cultured RPMCs. Furthermore, TGF-β1 induces a bimodal JNK activation with peaks at 10 minutes and 12 hours post treatment in RPMCs. In addition, the inhibition of Smad3 activation by introducing a Smad3 mutant mitigates the TGF-β1-induced second wave, but not the first wave, of JNK1 activation in RPMCs. Moreover, the inhibition of JNK1 activation prevents the TGF-β1-induced Smad3 activation and nuclear translocation, and inhibition of the TGF-β1-induced second wave of JNK activation greatly reduced TGF-β1-induced EMT in RPMCs. These data indicate a crosstalk between the JNK1 and Samd3 pathways during the TGF-β1-induced EMT and fibrotic process in RPMCs. Therefore, our findings may provide new insights into understanding the regulation of the TGF-β1-related JNK and Smad signaling in the development of fibrosis.

Activation of JNK signaling mediates connective tissue growth factor expression and scar formation in corneal wound healing

Connective Tissue Growth Factor (CTGF) and Transforming growth factor-β1 (TGF-β1) are key growth factors in regulating corneal scarring. Although CTGF was induced by TGF-β1 and mediated many of fibroproliferative effects of TGF-β1, the signaling pathway for CTGF production in corneal scarring remains to be clarified. In the present study, we firstly investigated the effects of c-Jun N-terminal kinase (JNK) on CTGF expression induce by TGF-β1 in Telomerase-immortalized human cornea stroma fibroblasts (THSF). Then, we created penetrating corneal wound model and determined the effect of JNK in the pathogenesis of corneal scarring. TGF-β1 activated MAPK pathways in THSF cells. JNK inhibitor significantly inhibited CTGF, fibronectin and collagen I expression induced by TGF-β1 in THSF. In corneal wound healing, the JNK inhibitor significantly inhibited CTGF expression, markedly improved the architecture of corneal stroma and reduced corneal scar formation, but did not have a measurable impact on corneal wound healing in vivo. Our results indicate that JNK mediates the expression of CTGF and corneal scarring in corneal wound healing, and might be considered as specific targets of drug therapy for corneal scarring.

A potential role of the JNK pathway in hyperoxia-induced cell death, myofibroblast transdifferentiation and TGF-β1-mediated injury in the developing murine lung

Background

Transforming growth factor-beta 1 (TGF-β1) has been implicated in hyperoxia-induced cell death and impaired alveolarization in the developing lung. In addition, the c-JunNH2-terminal kinase (JNK) pathway has been shown to have a role for TGF-β1-mediated effects. We hypothesized that the JNK pathway is an important regulator of hyperoxia-induced pulmonary responses in the developing murine lung.

Results

We used cultured human lung epithelial cells, fetal rat lung fibroblasts and a neonatal TGF-β1 transgenic mouse model. We demonstrate that hyperoxia inhibits cell proliferation, activates cell death mediators and causes cell death, and promotes myofibroblast transdifferentiation, in a dose-dependent manner. Except for fibroblast proliferation, the effects were mediated via the JNK pathway. In addition, since we observed increased expression of TGF-β1 by epithelial cells on exposure to hyperoxia, we used a TGF-β1 transgenic mouse model to determine the role of JNK activation in TGF-β1 induced effects on lung development and on exposure to hyperoxia. We noted that, in this model, inhibition of JNK signaling significantly improved the spontaneously impaired alveolarization in room air and decreased mortality on exposure to hyperoxia.

Conclusions

When viewed in combination, these studies demonstrate that hyperoxia-induced cell death, myofibroblast transdifferentiation, TGF-β1- and hyperoxia-mediated pulmonary responses are mediated, at least in part, via signaling through the JNK pathway.

Transforming growth factor-β and nuclear factor E2–related factor 2 regulate antioxidant responses in airway smooth muscle cells: role in asthma

RATIONALE

Aberrant airway smooth muscle cell (ASMC) function and overexpression of transforming growth factor (TGF)-β, which modulates ASMC proliferative and inflammatory function and induces oxidant release, are features of asthma. Nuclear factor E2-related factor 2 (Nrf2) activates antioxidant genes conferring protection against oxidative stress.

OBJECTIVES

To determine the role of Nrf2 in ASMCs and its modulation by TGF-β, and compare Nrf2 activity in ASMCs from subjects with severe and nonsevere asthma and healthy subjects.

METHODS

ASMCs were cultured from airways of subjects without asthma, and from airway biopsies from patients with severe and nonsevere asthma. We studied Nrf2 activation on antioxidant gene expression and proliferation, the effect of TGF-β on Nrf2 transcriptional activity, and the impact of Nrf2 activation on TGF-β–mediated proliferation and IL-6 release. Nrf2–antioxidant response elements binding and Nrf2-dependent antioxidant gene expression was determined in asthmatic ASMCs.

MEASUREMENTS AND MAIN RESULTS

Activation of Nrf2 led to up-regulation of the antioxidant genes heme oxygenase (HO)-1, NAD(P)H:quinone oxidoreductase, and manganese superoxide dismutase, and a reduction in proliferation. TGF-β reduced Nrf2-mediated antioxidant gene transcription through induction of activating transcription factor-3 expression. Nrf2 activation attenuated TGF-β–mediated reduction in HO-1,ASMC proliferation, and IL-6 release. Nrf2–antioxidant response elements binding was reduced in ASMCs from patients with severe asthma compared with ASMCs from patients with nonsevere asthma and normal subjects. HO-1 expression was reduced in ASMCs from patients with both nonsevere and severe asthma compared with healthy subjects.

CONCLUSIONS

Nrf2 regulates antioxidant responses and proliferation in ASMCs and is inactivated by TGF-β. Nrf2 reduction may underlie compromised antioxidant protection and aberrant ASM function in asthma.

Interleukin(IL)-4 promotion of CXCL-8 gene transcription is mediated by ERK1/2 pathway in human pulmonary artery endothelial cells

Interleukin-4 is central to allergic pulmonary inflammatory responses, but its contribution to airway neutrophilia remains controversial. The endothelium plays a critical role in regulating leukocyte recruitment and migration during inflammation. However, its response to IL-4 is reported to either increase or decrease the production of neutrophil chemotactic factors. We hypothesized that these conflicting findings may be due to the tissue and the size of the vessels from which endothelial cells have been derived. The expression of CXCL-8 by human primary culture umbilical veins endothelial cells (HUVECs), human pulmonary artery endothelial cells (HPAECs), and human pulmonary microvascular endothelial cells (HPMECs) when stimulated with recombinant human IL-4 (rhIL-4) was studied. The chemoattractant property of the cells' supernatants for neutrophils was evaluated using Boyden chambers. The role of the nuclear factor-κB (NF-κB), and mitogen-activated protein kinases (MAPK) in IL-4-induced HPAECs was studied using Western blotting and electrophoretic mobility shift assay (EMSA). We demonstrated that IL-4 increased the mRNA expression and the protein production of CXCL-8 in HPAECs, but not in HUVECs and HPMECs. The supernatants of HAPECs stimulated by IL-4 significantly promoted neutrophils migration in a dose-dependent manner, and was significantly attenuated by an inhibitor of CXCL-8. We also found that extracellular-regulated protein kinase1/2 (ERK1/2) is activated by IL-4 in HPAECs, but not JUN-N-terminal protein kinase (JNK) or p38 MAPK pathway. Furthermore, NF-κB-DNA binding activity, phosphorylation of IκBα and p65 levels were not affected by rhIL-4 in HAPECs. These findings indicate marked functional differences in the response of micro and macro-ECs to IL-4. ERK1/2, rather than NF-κB, JNK and p38 MAPK signaling, plays a role in IL-4 induced chemokine activation. Our results suggest that inhibition of ERK1/2 may be a possible target for airway neutrophilia in allergic lung diseases.

TGF-β regulates Nox4, MnSOD and catalase expression, and IL-6 release in airway smooth muscle cells

Reactive oxygen species (ROS) are generated as a result of normal cellular metabolism, mainly through the mitochondria and peroxisomes, but their release is enhanced by the activation of oxidant enzymes such as NADPH oxidases or downregulation of endogenous antioxidant enzymes such as manganese-superoxide dismutase (MnSOD) and catalase. Transforming growth factor-β (TGF-β), found to be overexpressed in airway smooth muscle (ASM) from asthmatic and chronic obstructive pulmonary disease patients, may be a pivotal regulator of abnormal ASM cell (ASMC) function in these diseases. An important effect of TGF-β on ASMC inflammatory responses is the induction of IL-6 release. TGF-β also triggers intracellular ROS release in ASMCs by upregulation of NADPH oxidase 4 (Nox4). However, the effect of TGF-β on the expression of key antioxidant enzymes and subsequently on oxidant/antioxidant balance is unknown. Moreover, the role of redox-dependent pathways in the mediation of the proinflammatory effects of TGF-β in ASMCs is unclear. In this study, we show that TGF-β induced the expression of Nox4 while at the same time inhibiting the expression of MnSOD and catalase. This change in oxidant/antioxidant enzymes was accompanied by elevated ROS levels and IL-6 release. Further studies revealed a role for Smad3 and phosphatidyl-inositol kinase-mediated pathways in the induction of oxidant/antioxidant imbalance and IL-6 release. The changes in oxidant/antioxidant enzymes and IL-6 release were reversed by the antioxidants N-acetyl-cysteine (NAC) and ebselen through inhibition of Smad3 phosphorylation, indicating redox-dependent activation of Smad3 by TGF-β. Moreover, these findings suggest a potential role for NAC in preventing TGF-β-mediated pro-oxidant and proinflammatory responses in ASMCs. Knockdown of Nox4 using small interfering RNA partially prevented the inhibition of MnSOD but had no effect on catalase and IL-6 expression. These findings provide novel insights into redox regulation of ASM function by TGF-β.

Src is a major signaling component for CTGF induction by TGF-beta1 in osteoblasts

Connective tissue growth factor (CTGF/CCN2) is induced by transforming growth factor beta1 (TGF-beta1) where it acts as a downstream mediator of TGF-beta1 induced matrix production in osteoblasts. We have shown the requirement of Src, Erk, and Smad signaling for CTGF induction by TGF-beta1 in osteoblasts; however, the potential interaction among these signaling pathways remains undetermined. In this study we demonstrate that TGF-beta1 activates Src kinase in ROS17/2.8 cells and that treatment with the Src family kinase inhibitor PP2 prevents Src activation and CTGF induction by TGF-beta1. Additionally, inhibiting Src activation prevented Erk activation, Smads 2 and 3 activation and nuclear translocation by TGF-beta1, demonstrating that Src is an essential upstream signaling partner of both Erk and Smads in osteoblasts. MAPKs such as Erk can modulate the Smad pathway directly by mediating the phosphorylation of Smads or indirectly through activation/inactivation of required nuclear co-activators that mediate Smad DNA binding. When we treated cells with the Erk inhibitor, PD98059, it inhibited TGF-beta1-induced CTGF protein expression but had no effect on Src activation, Smad activation or Smad nuclear translocation. However PD98059 impaired transcriptional complex formation on the Smad binding element (SBE) of the CTGF promoter, demonstrating that Erk activation was required for SBE transactivation. These data demonstrate that Src is an essential upstream signaling transducer of Erk and Smad signaling with respect to TGF-beta1 in osteoblasts and that Smads and Erk function independently but are both essential for forming a transcriptionally active complex on the CTGF promoter in osteoblasts.

Involvement of IL-13 in tobacco smoke-induced changes in the structure and function of rat intrapulmonary airways

Chronic obstructive pulmonary disease (COPD) involves disease of small airways with an increase in airway smooth muscle sensitivity to spasmogens and with structural changes described as airway remodeling. We investigated the effect of tobacco smoke (TS) exposure on the structure and function of small airways in rats and the role of IL-13 in this response. Precision-cut lung slices (230-280 microm) were prepared from male Sprague-Dawley rats after acute (3 d) or chronic (8 or 16 wk) daily exposure to TS or air. Carbachol (CCh) and 5-hydroxytryptamine (5HT) concentration responses were performed on airways (50-400 microm diameter). The effect of IL-13 in vitro on small airway sensitivity to CCh and 5HT was also determined. Acute exposure to TS did not affect the sensitivity of the intrapulmonary airways to either spasmogen. After 8 weeks of TS exposure, airway hyperresponsiveness (AHR) to CCh was evident (log EC(50) CCh: air = 0.22 microM; TS = -0.12 microM; P = 0.019); AHR to 5HT was also observed after the 16-week exposure to TS (air = -0.85 microM; TS = -1.06 microM; P = 0.038). Chronic TS exposure increased airway wall SMA content, which correlated with increased expression of IL-13 and transforming growth factor (TGF)-beta(1) in the lung tissues. In vitro incubation with IL-13, but not TGF-beta(1), induced changes in small airway sensitivity to CCh and 5HT. Chronic TS exposure induces increased responsiveness in intrapulmonary airways of rats that may be mediated in part by an increase in IL-13.

Potential therapeutic targets for cardiac fibrosis: TGFbeta, angiotensin, endothelin, CCN2, and PDGF, partners in fibroblast activation

Fibrosis is one of the largest groups of diseases for which there is no therapy but is believed to occur because of a persistent tissue repair program. During connective tissue repair, "activated" fibroblasts migrate into the wound area, where they synthesize and remodel newly created extracellular matrix. The specialized type of fibroblast responsible for this action is the alpha-smooth muscle actin (alpha-SMA)-expressing myofibroblast. Abnormal persistence of the myofibroblast is a hallmark of fibrotic diseases. Proteins such as transforming growth factor (TGF)beta, endothelin-1, angiotensin II (Ang II), connective tissue growth factor (CCN2/CTGF), and platelet-derived growth factor (PDGF) appear to act in a network that contributes to myofibroblast differentiation and persistence. Drugs targeting these proteins are currently under consideration as antifibrotic treatments. This review summarizes recent observations concerning the contribution of TGFbeta, endothelin-1, Ang II, CCN2, and PDGF and to fibroblast activation in tissue repair and fibrosis and the potential utility of agents blocking these proteins in affecting the outcome of cardiac fibrosis.

Should treatments for asthma be aimed at the airway smooth muscle?

The airway smooth muscle (ASM) cell is an important part of the airway wall of asthma patients because of its increased contractile properties, which appear to be enhanced in this condition and which contribute to airflow obstruction and bronchial hyper-responsiveness. ASM cells are also abnormal in asthma with increased expression of certain chemokines, with increased proliferation rate, numbers and size. beta-adrenergic agonists and corticosteroids are the two most important treatments for asthma; other drugs used are leukotriene receptor antagonists and theophylline. Combination therapy of beta-adrenergic agonists and corticosteroids has become the treatment of choice for moderate-to-severe asthma. beta-adrenergic agonists cause relaxation of ASM cells, leading to a decrease in airflow obstruction of asthma and acute relief of symptoms. Corticosteroids also have direct effects on ASM cells. It is postulated that the effect of anti-inflammatory agents on ASM cells is the most important determinant of the therapeutic effects of these agents. Targeting the ASM cell in asthma could be the focus of therapies for asthma. Specific delivery of active agents to ASM cells may also be part of this strategy.

Abrogation of TGF-beta1-induced fibroblast-myofibroblast differentiation by histone deacetylase inhibition

Idiopathic pulmonary fibrosis (IPF) is a devastating disease with no known effective pharmacological therapy. The fibroblastic foci of IPF contain activated myofibroblasts that are the major synthesizers of type I collagen. Transforming growth factor (TGF)-beta1 promotes differentiation of fibroblasts into myofibroblasts in vitro and in vivo. In the current study, we investigated the molecular link between TGF-beta1-mediated myofibroblast differentiation and histone deacetylase (HDAC) activity. Treatment of normal human lung fibroblasts (NHLFs) with the pan-HDAC inhibitor trichostatin A (TSA) inhibited TGF-beta1-mediated alpha-smooth muscle actin (alpha-SMA) and alpha1 type I collagen mRNA induction. TSA also blocked the TGF-beta1-driven contractile response in NHLFs. The inhibition of alpha-SMA expression by TSA was associated with reduced phosphorylation of Akt, and a pharmacological inhibitor of Akt blocked TGF-beta1-mediated alpha-SMA induction in a dose-dependent manner. HDAC4 knockdown was effective in inhibiting TGF-beta1-stimulated alpha-SMA expression as well as the phosphorylation of Akt. Moreover, the inhibitors of protein phosphatase 2A and 1 (PP2A and PP1) rescued the TGF-beta1-mediated alpha-SMA induction from the inhibitory effect of TSA. Together, these data demonstrate that the differentiation of NHLFs to myofibroblasts is HDAC4 dependent and requires phosphorylation of Akt.

Calcitonin induces connective tissue growth factor through ERK1/2 signaling in renal tubular cells

Calcitonin (CT), a polypeptide hormone, plays important roles in a variety of physiological processes. CT has been used clinically to treat osteoporosis and humoral hypercalcemia of malignancy. In order to clarify the pharmacological effects of CT in the kidney, we identified potential downstream genes induced by CT in the renal cells. Using a cDNA subtraction hybridization method, we identified connective tissue growth factor (CTGF) as a CT-induced gene in the porcine renal cell line, LLC-PK1. Furthermore, we found that CT-mediated induction of the gene was not inhibited by cycloheximide, which suggests that CTGF gene was not induced by an increased synthesis of regulating proteins. Therefore, CTGF is an immediate early gene. We further demonstrated that the regulation of CTGF gene expression by CT involved the ERK1/2 pathway, because PD98059, a MEK1 inhibitor, partially inhibited the mRNA expression of CTGF induced by CT. CT-induced CTGF protein expression was also observed in vivo. Our present findings suggest that CT induces the transcription of CTGF through ERK1/2 phosphorylation. We also identified twelve other genes induced by CT that, like CTGF, were related to wound healing. These results suggest that CT may have an effect on renal differentiation and wound healing in the kidney.

PLATELET-DERIVED GROWTH FACTOR, TRANSFORMING GROWTH FACTOR-β, AND CONNECTIVE TISSUE GROWTH FACTOR IN A PORCINE BRONCHIAL MODEL OF OBLITERATIVE BRONCHIOLITIS

The expression of platelet-derived growth factor (PDGF), transforming growth factor (TGF)-beta, and connective tissue growth factor (CTGF) and the effect of imatinib, an agent inhibiting PDGF receptors, were assessed in a porcine bronchial transplantation model of obliterative bronchiolitis (OB). Up-regulation of PDGF-A, PDGF receptors alpha and beta, and TGF-beta expression occurred in allografts, whereas PDGF-B and CTGF expression was similar in allo- and autografts. Imatinib modified the inflammatory responses and expression patterns of PDGF-A and PDGF receptors. This study further confirms PDGF and TGF-beta as mediators of OB and supports the concept of the importance of the pathways signaled through PDGF receptors in post-transplant OB.

Cell type-specific regulation of CCN2 protein expression by PI3K-AKT-FoxO signaling

The biological activity of connective tissue growth factor (CTGF, CCN2) is regulated at the level of intracellular signaling leading to gene expression, and by its extracellular interaction partners which determine the functional outcome of CCN2 action. In this overview, we summarize the data which provide evidence that one of the major signaling pathways, phosphatidylinositol-3 kinase (PI3K)-AKT signaling, shows a remarkable cell type-dependence in terms of regulation of CCN2 expression. In smooth muscle cells, fibroblasts, and epithelial cells, inhibition of this pathway either reduced CCN2 expression or was not involved in CCN2 gene expression depending on the stimulus used. In microvascular endothelial cells by contrast, activation of PI3K-AKT signaling was inversely related to CCN2 expression. Upregulation of CCN2 upon inhibition of PI3K-AKT was also observed in primary cultures of human endothelial cells (HUVEC) exposed to laminar flow in an in vitro flow-through system. In different types of endothelial cells, FoxO transcription factors, which are negatively regulated by AKT, were identified as potent activators of CCN2 gene expression. In HUVEC, we observed a correlation between enhanced nuclear localization of FoxO1 and increased synthesis of CCN2 protein in areas of non-uniform shear stress. These data indicate that FoxO proteins are key regulators of CCN2 gene expression which determine the effect of PI3K-AKT activation in terms of CCN2 regulation. Short summary Phosphatidylinositol-3 kinase (PI3K)-AKT signaling shows a remarkable cell type-dependence in terms of regulation of CCN2 expression. In endothelial cells activation of PI3K - AKT signaling was inversely related to CCN2 expression. FoxO transcription factors, which are negatively regulated by AKT, were identified as potent activators of CCN2 gene expression.

Use of a three-dimensional cell culture model to study airway smooth muscle-mast cell interactions in airway remodeling

Increased airway smooth muscle (ASM) mass and infiltration by mast cells are key features of airway remodeling in asthma. We describe a model to investigate the relationship between ASM, the extracellular matrix, mast cells, and airway remodeling. ASM cells were cultured in a three-dimensional (3-D) collagen I gel (3-D culture) alone or with mast cells. Immunocytochemistry and Western blotting of ASM in 3-D cultures revealed a spindle-shaped morphology and significantly lower alpha-smooth muscle actin and vimentin expression than in ASM cultured in monolayers on collagen type I or plastic (2-D culture). In 3-D cultures, basal ASM proliferation, examined by Ki67 immunocytochemistry, was reduced to 33 +/- 7% (P < 0.05) of that in 2-D cultures. The presence of mast cells in cocultures increased ASM proliferation by 1.8-fold (P < 0.05). Gelatin zymography revealed more active matrix metalloproteinase (MMP)-2 in 3-D than in 2-D culture supernatants over 7 days. Functional MMP activity was examined by gel contraction. The spontaneous gel contraction over 7 days was significantly inhibited by the MMP inhibitor ilomastat. Mast cell coculture enhanced ASM gel contraction by 22 +/- 16% (not significant). Our model shows that ASM has different morphology, with lower contractile protein expression and basal proliferation in 3-D culture. Compared with standard techniques, ASM synthetic function, as shown by MMP production and activity, is sustained over longer periods. The presence of mast cells in the 3-D model enhanced ASM proliferation and MMP production. Airway remodeling in asthma may be more accurately modeled by our system than by standard culture systems.