Targeting TGFβ superfamily ligand accessory proteins as novel therapeutics for chronic lung disorders

Perfluorooctanoic acid induced lung toxicity via TGF-β1/Smad pathway, crosstalk between airway hyperresponsiveness and fibrosis: withdrawal impact

Perfluorooctanoic acid (PFOA) is an environmental persistent agent to which humans are exposed daily through food and water. This study investigated the lung toxic effects induced by ingested PFOA (30 mg/kg/day) for 8 weeks in adult male rats and the impact following 8 weeks of its withdrawal. PFOA increased MDA and reduced TAC inducing oxidative stress. It induced airway hyperresponsiveness (AHR) via increased bronchoalveolar lavage fluid (BALF) IL-4, IL-5, IL-13, IL-9, eosinophil count, TNF-α, and IL-1ß; reduced IL-12; increased serum IgE; and increased urocortin expression in lung tissues. Moreover, it induced pulmonary fibrosis via increased serum KL-6, and SFTP-D, altered pulmonary structure, and increased deposition of collagen fibers in lung tissues. Furthermore, it increased TGF-β1, Smad2, and Smad3 and reduced Smad7 gene expression in lung tissues. These gene alterations were positively correlated with AHR and fibrosis-related factors. The recovered lung upon PFOA withdrawal showed complete resolution of oxidative stress and slight amelioration of other studying parameters. Exposure to PFOA induced lung toxicity by disrupting the TGF-β1/Smad signaling pathway, which acts as a crosstalk between AHR and fibrosis. Additionally, PFOA altered pulmonary architecture, triggered inflammation, and caused oxidative stress. The lung exhibited partial alleviation upon recovery.

Transforming growth factor beta 1 induced endothelin-1 release is peroxisome proliferator-activated receptor gamma dependent in A549 cells

Background

Endothelin-1 (ET-1) is involved in pulmonary vascular remodeling. The aim of this study was to investigate the biochemical interactions between PPAR-γ, TGF-β1 and ET-1 in vitro.

Methods

A549 cells were pre-treated with S2505 (10 μM), S2871 (10 μM) with/without SB203580 (10 μM) for 60 min following 2 h treatment with 10 ng/mL TGF-β1. A549 cells were also transfected with positive or negative PPAR-γ plasmids for comparison. RT-PCR, ELISA, western blotting and confocal laser scanning microscopy (CLSM) were used to measure the relevant expression of mRNA, protein, mediators of pathways and nuclear factor translocation.

Results

SB203580 inhibited TGF-β1 induced ET-1 expression in A549 cells. S2871 decreased PPAR-γ mRNA and increase TGF-β1-induced ET-1 expression. S2871 increased phosphorylation of p38 MAPK and Smad2. Cells transfected with PPAR-γ negative plasmid increased TGF-β1 induced ET-1 expression, and increased the expression of phospho-p38 MAPK and phospho-Smad2. S2505 increased PPAR-γ mRNA expression, suppressed the increased TGF-β1-induced expression of ET-1. S2505 inhibited TGF-β1 induced phosphorylation of p38 MAPK and Smad2, also the nuclear translocation of Smad2. Cells transfected with PPAR-γ positive plasmid reduced TGF-β1-induced ET-1 expression, and inhibited the expression of phospho-p38 MAPK and phospho-Smad2.

Conclusions

TGF-β1 induced release of endothelin-1 is PPAR-γ dependent in cultured A549 cells.

Altered Expression of Bone Morphogenetic Protein Accessory Proteins in Murine and Human Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a chronic, progressive fibrotic disease with a poor prognosis. The balance between transforming growth factor β1 and bone morphogenetic protein (BMP) signaling plays an important role in tissue homeostasis, and alterations can result in pulmonary fibrosis. We hypothesized that multiple BMP accessory proteins may be responsible for maintaining this balance in the lung. Using the bleomycin mouse model for fibrosis, we examined an array of BMP accessory proteins for changes in mRNA expression. We report significant increases in mRNA expression of gremlin 1, noggin, follistatin, and follistatin-like 1 (Fstl1), and significant decreases in mRNA expression of chordin, kielin/chordin-like protein, nephroblastoma overexpressed gene, and BMP and activin membrane-bound inhibitor (BAMBI). Protein expression studies demonstrated increased levels of noggin, BAMBI, and FSTL1 in the lungs of bleomycin-treated mice and in the lungs of idiopathic pulmonary fibrosis patients. Furthermore, we demonstrated that transforming growth factor β stimulation resulted in increased expression of noggin, BAMBI, and FSTL1 in human small airway epithelial cells. These results provide the first evidence that multiple BMP accessory proteins are altered in fibrosis and may play a role in promoting fibrotic injury.

Bronchoconstriction and airway biology: potential impact and therapeutic opportunities

Recent work has demonstrated that mechanical forces occurring in the airway as a consequence of bronchoconstriction are sufficient to not only induce symptoms but also influence airway biology. Animal and human in vitro and in vivo work demonstrates that the airways are structurally and functionally altered by mechanical stress induced by bronchoconstriction. Compression of the airway epithelium and mechanosensing by the airway smooth muscle trigger the activation and release of growth factors, causing cell proliferation, extracellular matrix protein accumulation, and goblet cell differentiation. These effects of bronchoconstriction are of major importance to asthma pathophysiology and appear sufficient to induce remodeling independent of the inflammatory response. We review these findings in detail and discuss previous studies in light of this new evidence regarding the influence of mechanical forces in the airways. Furthermore, we highlight potential impacts of therapies influencing mechanical forces on airway structure and function in asthma.

Selective activation of angiotensin AT2 receptors attenuates progression of pulmonary hypertension and inhibits cardiopulmonary fibrosis

BACKGROUND AND PURPOSE

Pulmonary hypertension (PH) is a devastating disease characterized by increased pulmonary arterial pressure, which progressively leads to right-heart failure and death. A dys-regulated renin angiotensin system (RAS) has been implicated in the development and progression of PH. However, the role of the angiotensin AT2 receptor in PH has not been fully elucidated. We have taken advantage of a recently identified non-peptide AT2 receptor agonist, Compound 21 (C21), to investigate its effects on the well-established monocrotaline (MCT) rat model of PH.

EXPERIMENTAL APPROACH

A single s.c. injection of MCT (50 mg·kg(-1) ) was used to induce PH in 8-week-old male Sprague Dawley rats. After 2 weeks of MCT administration, a subset of animals began receiving either 0.03 mg·kg(-1) C21, 3 mg·kg(-1) PD-123319 or 0.5 mg·kg(-1) A779 for an additional 2 weeks, after which right ventricular haemodynamic parameters were measured and tissues were collected for gene expression and histological analyses.

KEY RESULTS

Initiation of C21 treatment significantly attenuated much of the pathophysiology associated with MCT-induced PH. Most notably, C21 reversed pulmonary fibrosis and prevented right ventricular fibrosis. These beneficial effects were associated with improvement in right heart function, decreased pulmonary vessel wall thickness, reduced pro-inflammatory cytokines and favourable modulation of the lung RAS. Conversely, co-administration of the AT2 receptor antagonist, PD-123319, or the Mas antagonist, A779, abolished the protective actions of C21.

CONCLUSIONS AND IMPLICATIONS

Taken together, our results suggest that the AT2 receptor agonist, C21, may hold promise for patients with PH.

Scleroderma pathogenesis: a pivotal role for fibroblasts as effector cells

Scleroderma (systemic sclerosis; SSc) is characterised by fibrosis of the skin and internal organs in the context of autoimmunity and vascular perturbation. Overproduction of extracellular matrix components and loss of specialised epithelial structures are analogous to the process of scar formation after tissue injury. Fibroblasts are the resident cells of connective tissue that become activated at sites of damage and are likely to be important effector cells in SSc. Differentiation into myofibroblasts is a hallmark process, although the mechanisms and cellular origins of this important fibroblastic cell are still unclear. This article reviews fibroblast biology in the context of SSc and highlights the potentially important place of fibroblast effector cells in fibrosis. Moreover, the heterogeneity of fibroblast properties, multiplicity of regulatory pathways and diversity of origin for myofibroblasts may underpin clinical diversity in SSc, and provide novel avenues for targeted therapy.

Transforming growth factor β and severe asthma: a perfect storm

Asthma is a chronic inflammatory airway disease involving complex interplay between resident and infiltrative cells, which in turn are regulated by a wide range of host mediators. Identifying useful biomarkers correlating with clinical symptoms and degree of airway obstruction remain important to effective future asthma treatments. Transforming growth factor β (TGF-β) is a major mediator involved in pro-inflammatory responses and fibrotic tissue remodeling within the asthmatic lung. Its role however, as a therapeutic target remains controversial. The aim of this review is to highlight its role in severe asthma including interactions with adaptive T-helper cells, cytokines and differentiation through regulatory T-cells. Associations between TGF-β and eosinophils will be addressed and the effects of genetic polymorphisms of the TGF-β1 gene explored in the context of asthma. We highlight TGF-β1 as a potential future therapeutic target in severe asthma including its importance in identifying emerging clinical phenotypes in asthmatic subjects who may be suitable for individualized therapy through TGF-β modulation.

Mesenchymal stem cells reduce cigarette smoke-induced inflammation and airflow obstruction in rats via TGF-β1 signaling

Cigarette smoke has been shown to cause chronic inflammation of the lungs, eventually leading to chronic obstructive pulmonary disease (COPD). Additionally, recent studies have suggested that mesenchymal stem cells (MSCs) can mediate local inflammatory responses in the lungs. Thus, the aim of the present study was to test the effects of rat MSCs (rMSCs) on inflammation of the lungs and destructive pulmonary function induced by cigarette smoke in rats. Rats were exposed to cigarette smoke for 7 weeks. rMSCs were cultured in vitro and infused intratracheally into cigarette smoke-exposed rats. The total and differential cell counts in the bronchoalveolar lavage fluid (BALF), histological changes, pro-inflammatory cytokines, transforming growth factor-β1 (TGF-β1) expression, and pulmonary function were evaluated. Additionally, human peripheral blood mononuclear cells and human MSCs were cocultured in vitro to detect cytokines and TGF-β1 levels. We found that rMSC administration resulted in downregulation of pro-inflammatory cytokines in the lungs while increasing TGF-β1 expression, reducing total inflammatory cell numbers in the BALF, and improving pulmonary histopathology and airflow obstruction. Coculture revealed that human MSCs mediated an anti-inflammatory effect partly via upregulation of TGF-β1. These findings suggested that MSCs may have therapeutic potential in cigarette smoke-induced inflammation and airflow obstruction, partly via upregulation of TGF-β1.

Fibrosis-related biomarkers and risk of total and cause-specific mortality: the cardiovascular health study

Fibrosis has been implicated in diverse diseases of the liver, kidney, lungs, and heart, but its importance as a risk factor for mortality remains unconfirmed. We determined the prospective associations of 2 complementary biomarkers of fibrosis, transforming growth factor-β (TGF-β) and procollagen type III N-terminal propeptide (PIIINP), with total and cause-specific mortality risks among community-living older adults in the Cardiovascular Health Study (1996-2010). We measured circulating TGF-β and PIIINP levels in plasma samples collected in 1996 and ascertained the number of deaths through 2010. Both TGF-β and PIIINP were associated with elevated risks of total and pulmonary mortality after adjustment for sociodemographic, clinical, and biochemical risk factors. For total mortality, the hazard ratios per doubling of TGF-β and PIIINP were 1.09 (95% confidence interval (CI): 1.01, 1.17; P = 0.02) and 1.14 (CI: 1.03, 1.27; P = 0.01), respectively. The corresponding hazard ratios for pulmonary mortality were 1.27 (CI: 1.01, 1.60; P = 0.04) for TGF-β and 1.52 (CI: 1.11, 2.10; P = 0.01) for PIIINP. Associations of TGF-β and PIIINP with total and pulmonary mortality were strongest among individuals with higher C-reactive protein concentrations (P for interaction < 0.05). Our findings provide some of the first large-scale prospective evidence that circulating biomarkers of fibrosis measured late in life are associated with death.

Epithelial-mesenchymal transition in lung development and disease: does it exist and is it important?

Epithelial-mesenchymal transition (EMT) is a process when epithelial cells gradually transform into mesenchymal-like cells losing their epithelial functionality and characteristics. EMT is thought to be involved in the pathogenesis of numerous lung diseases ranging from developmental disorders, fibrotic tissue remodelling to lung cancer. The most important question--namely what is the importance and contribution of EMT in the pathogenesis of several chronic lung conditions (asthma, COPD, bronchiolitis obliterans syndrome and lung fibrosis)--is currently intensely debated. This review gives a brief insight into the mechanism and assessment methods of EMT in various pulmonary diseases and summarises the recent literature highlighting the controversial experimental data and conclusions.

The interaction of endothelin-1 and TGF-β1 mediates vascular cell remodeling

BACKGROUND

Pulmonary arterial hypertension is characterized by increased thickness of pulmonary vessel walls due to both increased proliferation of pulmonary arterial smooth muscle cell (PASMC) and deposition of extracellular matrix. In patients suffering from pulmonary arterial hypertension, endothelin-1 (ET-1) synthesis is up-regulated and may increase PASMC activity and vessel wall remodeling through transforming growth factor beta-1 (TGF-β1) and connective tissue growth factor.

OBJECTIVE

To assess the signaling pathway leading to ET-1 induced proliferation and extracellular matrix deposition by human PASMC.

METHODS

PASMC were serum starved for 24 hours before stimulation with either ET-1 and/or TGF-β1. ET-1 was inhibited by Bosentan, ERK1/2 mitogen activated protein kinase (MAPK) was inhibited by U0126 and p38 MAPK was inhibited by SB203580.

RESULTS

ET-1 increased PASMC proliferation when combined with serum. This effect involved the mitogen activated protein kinases (MAPK) ERK1/2 MAPK and was abrogated by Bosentan which caused a G1- arrest through activation of p27((Kip)). Regarding the contribution of extracellular matrix deposition in vessel wall remodeling, TGF-β1 increased the deposition of collagen type-I and fibronectin, which was further increased when ET-1 was added mainly through ERK1/2 MAPK. In contrast, collagen type-IV was not affected by ET-1. Bosentan dose-dependently reduced the stimulatory effect of ET-1 on collagen type-I and fibronectin, but had no effect on TGF-β1.

CONCLUSION AND CLINICAL RELEVANCE

ET-1 alone does not induce PASMC proliferation and extracellular matrix deposition. However, ET-1 significantly up-regulates serum induced proliferation and TGF-β1 induced extracellular matrix deposition, specifically of collagen type-I and fibronectin. The synergistic effects of ET-1 on serum and TGF-β1 involve ERK1/2 MAPK and may thus present a novel mode of action in the pathogenesis of pulmonary arterial hypertension.

Qingfei Xiaoyan Wan alleviates asthma through multi-target network regulation

BACKGROUND

Qingfei Xiaoyan Wan (QFXY), a traditional Chinese formula, is widely used for relieving cough, asthma, upper respiratory tract infection, bronchitis, pneumonia, and etc. in clinic. Comparing with other anti-asthma drugs, it is characterised with moderate and persistent efficacy as well as few side effects, however, the underlying action mechanism still remains elusive. This study aimed to identify QFXY multi-target network regulation as an asthma controller.

METHODS

This study established asthma model induced by histamine phosphate and acetylcholine chloride (His&Ach) in guinea pigs, which then were administered orally with QFXY. Hematoxylin-Eosin staining sections were applied for evaluating QFXY effect. In both Model and QFXY groups, customized microarrays and 2D electrophoresis were adopted to detect differentially expressed genes (diff genes) and proteins (diff proteins) respectively, and some diff proteins were identified with MALDI-TOF/MS. The checked diff genes and proteins underwent Cluster, GO and KEGG analysis. Based on GAD and HPRD databases, QFXY-asthma target regulation network was constructed.

RESULTS

His&Ach-induced asthma model of guinea pigs was established. HE sections presented anti-inflammation and anti-remodelling effects of QFXY. Comparing with the Model group, 55 diff genes and 6 diff proteins were identified in QFXY group. Validation by qPCR and Western blot showed the microarray and 2D data reliable. Furthermore, QFXY-asthma target regulation network was achieved.

CONCLUSIONS

A primarily combined genomic and proteomic screening of QFXY targets displayed a series of candidate genes and proteins, which indicated that the effect of QFXY relied on the combined mechanism, anti-inflammation and anti-remodelling, as well as influencing signal transduction in vivo.

Unraveling the signaling pathways promoting fibrosis in Dupuytren's disease reveals TNF as a therapeutic target

Dupuytren's disease is a very common progressive fibrosis of the palm leading to flexion deformities of the digits that impair hand function. The cell responsible for development of the disease is the myofibroblast. There is currently no treatment for early disease or for preventing recurrence following surgical excision of affected tissue in advanced disease. Therefore, we sought to unravel the signaling pathways leading to the development of myofibroblasts in Dupuytren's disease. We characterized the cells present in Dupuytren's tissue and found significant numbers of immune cells, including classically activated macrophages. High levels of proinflammatory cytokines were also detected in tissue from Dupuytren's patients. We compared the effects of these cytokines on contraction and profibrotic signaling pathways in fibroblasts from the palmar and nonpalmar dermis of Dupuytren's patients and palmar fibroblasts from non-Dupuytren's patients. Exogenous addition of TNF, but not other cytokines, including IL-6 and IL-1β, promoted differentiation into specifically of palmar dermal fibroblasts from Dupuytren's patients in to myofibroblasts. We also demonstrated that TNF acts via the Wnt signaling pathway to drive contraction and profibrotic signaling in these cells. Finally, we examined the effects of targeted cytokine inhibition. Neutralizing antibodies to TNF inhibited the contractile activity of myofibroblasts derived from Dupuytren's patients, reduced their expression of α-smooth muscle actin, and mediated disassembly of the contractile apparatus. Therefore, we showed that localized inflammation in Dupuytren's disease contributes to the development and progression of this fibroproliferative disorder and identified TNF as a therapeutic target to down-regulate myofibroblast differentiation and activity.