Wnt pathway in pulmonary fibrosis in the bleomycin mouse model

Circular RNAs and their roles in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease with limited treatment options. Circular RNAs (circRNAs) have emerged as a novel class of non-coding RNAs with diverse functions in cellular processes. This review paper aims to explore the potential involvement of circRNAs in the pathogenesis of IPF and their diagnostic and therapeutic implications. We begin by providing an overview of the epidemiology and risk factors associated with IPF, followed by a discussion of the pathophysiology underlying this complex disease. Subsequently, we delve into the history, types, biogenesis, and functions of circRNAs and then emphasize their regulatory roles in the pathogenesis of IPF. Furthermore, we examine the current methodologies for detecting circRNAs and explore their diagnostic applications in IPF. Finally, we discuss the potential utility of circRNAs in the treatment of IPF. In conclusion, circRNAs hold great promise as novel biomarkers and therapeutic targets in the management of IPF.

The role of mitochondrial dysfunction in macrophages on SiO2 -induced pulmonary fibrosis: A review

Several epidemiologic and toxicological studies have widely regarded that mitochondrial dysfunction is a popular molecular event in the process of silicosis from different perspectives, but the details have not been systematically summarized yet. Thus, it is necessary to investigate how silica dust leads to pulmonary fibrosis by damaging the mitochondria of macrophages. In this review, we first introduce the molecular mechanisms that silica dust induce mitochondrial morphological and functional abnormalities and then introduce the main molecular mechanisms that silica-damaged mitochondria induce pulmonary fibrosis. Finally, we conclude that the mitochondrial abnormalities of alveolar macrophages caused by silica dust are involved deeply in the pathogenesis of silicosis through these two sequential mechanisms. Therefore, reducing the silica-damaged mitochondria will prevent the potential occurrence and fatality of the disease in the future.

Dehydrozingerone alleviates pulmonary fibrosis via inhibition of inflammation and epithelial-mesenchymal transition by regulating the Wnt/β-catenin pathway

In idiopathic pulmonary fibrosis (IPF), excessive collagen deposition predisposes to irreversible lung function decline, respiratory failure, and ultimately death. Due to the limited therapeutic efficacy of FDA-approved medications, novel drugs are warranted for better treatment outcomes. Dehydrozingerone (DHZ) is an analogue of curcumin that has been investigated against pulmonary fibrosis using a bleomycin-induced pulmonary fibrosis model in rats. In in vitro, TGF-β-induced differentiation models (NHLF, LL29, DHLF and A549 cells) were adopted to assess fibrotic markers expression and explored the mechanism of action. DHZ administration attenuated the bleomycin-induced elevation of lung index, inflammatory cell infiltrations, and hydroxyproline levels in lung tissues. Furthermore, treatment with DHZ mitigated the bleomycin-mediated elevation of extracellular matrix (ECM), epithelial-to-mesenchymal-transition (EMT), and collagen deposition markers and improved lung mechanics. In addition, treatment with DHZ significantly suppressed the BLM-induced apoptosis and rescued the BLM-induced pathological abnormalities in lung tissues. In-vitro assays revealed that DHZ suppressed the expression of TGF-β-elevated collagen deposition, EMT and ECM markers in both mRNA/protein levels. Our findings showed that DHZ has anti-fibrotic effect against pulmonary fibrosis by modulating Wnt/β-catenin signaling, suggesting that DHZ may serve as a potential treatment option for IPF.

Anti-oxidant and anti-inflammatory effects of ellagic and punicic acid in an in vitro model of cardiac fibrosis

Cardiac fibrosis is a pathological process characterized by an excessive deposition of extracellular matrix (ECM) and an increased production of fibrillar collagen in the cardiac interstitium, mainly caused by the activation of cardiac fibroblasts and their transition into myofibroblasts. Oxidative stress is deeply implicated in the pathogenesis of cardiac fibrosis both directly and via its involvement in the tumor growth factor β1 (TGF-β1) signaling. Ellagic acid (EA) and punicic acid (PA) are the main components of the Punica granatum L (pomegranate) fruit and seed oil respectively, whose antioxidant, anti-inflammatory and anti-fibrotic effects have been previously described. Therefore, the aim of this study was to investigate the effects of EA or PA or EA+PA in an in vitro model of cardiac fibrosis. Immortalized Human Cardiac Fibroblasts (IM-HCF) were stimulated with 10 ng/ml of TGF-β1 for 24 h to induce a fibrotic damage. Cells were then treated with EA (1 µM), PA (1 µM) or EA+PA for additional 24 h. Both EA and PA reduced the pro-fibrotic proteins expressions and the intracellular reactive oxygen species (ROS) accumulation. The anti-oxidant activity was also observed by Nrf2 activation with the consequent TGF-β1-Smad2/3-MMP2/9 and Wnt/β-catenin signaling inhibition, thus reducing collagen production. EA and PA significantly inhibit NF-κB pathway and, consequently, TNF-α, IL-1β and IL-6 levels: the greater effect was observed when EA and PA were used in combination. These results suggest that EA, PA and in particular EA+PA might be effective in reducing fibrosis through their antioxidant and anti-inflammatory properties by the modulation of different molecular pathways.

Function and regulation of GPX4 in the development and progression of fibrotic disease

Fibrosis is a common feature of fibrotic diseases that poses a serious threat to global health due to high morbidity and mortality in developing countries. There exist some chemical compounds and biomolecules associated with the development of fibrosis, including cytokines, hormones, and enzymes. Among them, glutathione peroxidase 4 (GPX4), as a selenoprotein antioxidant enzyme, is widely found in the embryo, testis, brain, liver, heart, and photoreceptor cells. Moreover, it is shown that GPX4 elicits diverse biological functions by suppressing phospholipid hydroperoxide at the expense of decreased glutathione (GSH), including loss of neurons, autophagy, cell repair, inflammation, ferroptosis, apoptosis, and oxidative stress. Interestingly, these processes are intimately related to the occurrence of fibrotic disease. Recently, GPX4 has been reported to exhibit a decline in fibrotic disease and inhibit fibrosis, suggesting that alterations of GPX4 can change the course or dictate the outcome of fibrotic disease. In this review, we summarize the role and underlying mechanisms of GPX4 in fibrosis diseases such as lung fibrosis, liver fibrosis, kidney fibrosis, cardiac fibrosis, and myelofibrosis.

Effects of the decrease of β-catenin expression on human vaginal fibroblasts of women with pelvic organ prolapse

BACKGROUND

Pelvic organ prolapse (POP) lowers the quality of life in elderly women, and there have been no studies on its role in the pathogenesis of POP. The purpose of this study is to investigate the effect of β-catenin on proliferation and collagen anabolism in human vaginal fibroblasts (HVFs).

MATERIALS AND METHODS

The adherence and differential adherence methods were used to culture and purify HVFs. RNA interference was applied to knockdown β-catenin and lithium chloride was used to activate Wnt/β-catenin signaling pathway. β-catenin nuclear translocation was tested by immunofluorescence, and HVF proliferation was detected by performing MTT assays.

RESULTS

The expression of β-catenin, phosphorylated-β-catenin, phosphorylated-glycogen synthase kinase 3β (p-GSK3β), collagen I, matrix metalloproteinase 2 (MMP2), and tissue-derived inhibitors of metalloproteinases 2 (TIMP2) was assessed by western blot analysis. The expression of β-catenin and collagen I was lower in HVFs of POP group than that of control group. The proliferation rate of HVFs in POP group was lower than that in control group. Knockdown of β-catenin decreased the cell proliferation rate and the expression of collagen I. Lithium chloride can activate the Wnt/β-catenin signaling pathway.

CONCLUSION

β-catenin participates in the proliferation and collagen I synthesis of HVFs. The decrease of β-catenin expression may be closely related to the occurrence, and development of POP. LiCl can activate the Wnt/β-catenin signaling pathway in HVFs and thus increase HVFs proliferation and collagen synthesis.

Targeting of canonical WNT signaling ameliorates experimental sclerodermatous chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a major life-threatening complication of allogeneic hematopoietic stem cell transplantation. The molecular mechanisms underlying cGVHD remain poorly understood, and targeted therapies for clinical use are not well established. Here, we examined the role of the canonical WNT pathway in sclerodermatous cGVHD (sclGVHD). WNT signaling was activated in human sclGVHD with increased nuclear accumulation of the transcription factor β-catenin and a WNT-biased gene expression signature in lesional skin. Treatment with the highly selective tankryase inhibitor G007-LK, the CK1α agonist pyrvinium, or the LRP6 inhibitor salinomycin abrogated the activation of WNT signaling and protected against experimental cGVHD, without a significant impact on graft-versus-leukemia effect (GVL). Treatment with G007-LK, pyrvinium, or salinomycin almost completely prevented the development of clinical and histological features in the B10.D2 (H-2d) → BALB/c (H-2d) and LP/J (H-2b) → C57BL/6 (H-2b) models of sclGVHD. Inhibition of canonical WNT signaling reduced the release of extracellular matrix from fibroblasts and reduced leukocyte influx, suggesting that WNT signaling stimulates fibrotic tissue remodeling by direct effects on fibroblasts and by indirect inflammation-dependent effects in sclGVHD. Our findings may have direct translational potential, because pyrvinium is in clinical use, and tankyrase inhibitors are in clinical trials for other indications.

The self-fulfilling prophecy of pulmonary fibrosis: a selective inspection of pathological signalling loops

Pulmonary fibrosis is a devastating, progressive disease and carries a prognosis worse than most cancers. Despite ongoing research, the mechanisms that underlie disease pathogenesis remain only partially understood. However, the self-perpetuating nature of pulmonary fibrosis has led several researchers to propose the existence of pathological signalling loops. According to this hypothesis, the normal wound-healing process becomes corrupted and results in the progressive accumulation of scar tissue in the lung. In addition, several negative regulators of pulmonary fibrosis are downregulated and, therefore, are no longer capable of inhibiting these feed-forward loops. The combination of pathological signalling loops and loss of a checks and balances system ultimately culminates in a process of unregulated scar formation. This review details specific signalling pathways demonstrated to play a role in the pathogenesis of pulmonary fibrosis. The evidence of detrimental signalling loops is elucidated with regard to epithelial cell injury, cellular senescence and the activation of developmental and ageing pathways. We demonstrate where these loops intersect each other, as well as common mediators that may drive these responses and how the loss of pro-resolving mediators may contribute to the propagation of disease. By focusing on the overlapping signalling mediators among the many pro-fibrotic pathways, it is our hope that the pulmonary fibrosis community will be better equipped to design future trials that incorporate the redundant nature of these pathways as we move towards finding a cure for this unrelenting disease.

Modulation of Wnt/β-catenin signaling in IL-17A-mediated macrophage polarization of RAW264.7 cells

Macrophages play pivotal roles in host defense and immune homeostasis, which have two major functional polarization states, the classically activated M1 and the alternatively activated M2. Interleukin (IL)-17A is an immune modulator able to shape macrophage phenotypes. Wnt/β-catenin is a developmental signaling pathway that plays crucial roles in morphogenesis and tissue homeostasis, which has also been recently demonstrated playing roles in immune regulation. A growing amount of evidence suggests that both Wnt and IL-17A signaling are involved in macrophage polarization. However, their interaction in macrophage polarization remains elusive. The aim of present study was to explore impacts of Wnt/β-catenin on IL-17A-mediated macrophage M1/M2 polarization in murine monocyte/macrophage-like cell line RAW264.7. Results revealed that IL-17A activated Wnt/β-catenin signaling and induced macrophage M1 polarization, but inhibited M2 polarization. In contrast, the activation of Wnt/β-catenin signaling led to the inhibition of M1 macrophage polarization but the promotion of M2 polarization. Importantly, the activation of Wnt/β-catenin also showed abilities to inhibit the IL-17A-induced M1 macrophage polarization while diminishing the IL-17A-inhibited M2 polarization. Molecular analysis further uncovered that the JAK/STAT signaling pathway was involved in the interaction of Wnt/β-catenin and IL-17A in the modulation of macrophage polarization. These results suggested that the Wnt/β-catenin signaling modulated IL-17A-altered macrophage polarization in part by regulating the JAK/STAT signaling pathway. This study thus revealed a novel function of Wnt/β-catenin signaling in regulating IL-17A-altered macrophage polarization.

Schisandrin B attenuates bleomycin-induced pulmonary fibrosis in mice through the wingless/integrase-1 signaling pathway

Purpose/Aim: Pulmonary fibrosis (PF) is characterized by the progressive and ultimately fatal accumulation of fibroblasts and extracellular matrix in the lung that distorts its architecture and compromises its function.Objective: The present study investigated the potential protective effects of schisandrin B (Sch B) on the Wingless/Integrase-1 (Wnt) signaling pathway in attenuating inflammation and oxidative stress in ICR mice.Methods: Sixty healthy ICR mice were randomly divided into the following groups: control group, bleomycin (BLM) group, Sch B low dose (Sch B-L) group, Sch B medium dose (Sch B-M) group, Sch B high dose (Sch B-H) group, and dexamethasone (DXM) group. The expression of transforming growth factor (TGF)-β1 was examined by ELISA. In addition, the levels of superoxide dismutase (SOD), hydroxyproline (HYP), and the total antioxidant capacity (T-AOC) were determined. The protein and mRNA levels of matrix metalloproteinase 7 (MMP7) and β-catenin in mice were analyzed by western blot and quantitative real -quantitative time PCR (qRT-PCR), respectively.Results: Lung tissues from the BLM group exhibited significantly more inflammatory changes and a significantly greater number of collagen fibers than lung tissues from the control group. In addition, the lung tissues from these BLM-treated mice exhibited slightly increased MMP7 and β-catenin protein expression. Lung tissues from the Sch B-H group exhibited fewer inflammatory changes and fewer collagen fibers than lung tissues from the BLM group. Furthermore, the lung tissues from the Sch B-H mice exhibited decreased HYP and TGF-β1 levels, but increased SOD and T-AOC levels.Conclusions: The present study provided evidence that Sch B may be a potential therapeutic agent for the treatment of PF.

Effects of tetrandrine combined with acetylcysteine on exercise tolerance, pulmonary function and serum TNF-β1 and MMP-7 in silicosis patients

The aim of the study was to investigate the effects of tetrandrine combined with acetylcysteine on exercise tolerance, pulmonary function, transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase 7 (MMP-7) in silicosis patients. A retrospective analysis was performed on 149 silicosis patients admitted to the Maternal and Child Health Care Hospital of Zhangqiu District between August, 2015 and September, 2017. Of the 149 patients, 70 patients treated with acetylcysteine comprised the control group, and 79 treated with tetrandrine combined with acetylcysteine constituted the study group. The concentrations of serum TGF-β1 and MMP-7 before and after treatment were detected by enzyme-linked immunosorbent assay (ELISA), and the exercise tolerance and pulmonary function were compared. Chest distress, chest pain, cough, expectoration and dyspnea in the two groups were relieved after treatment, and the improvement rates of chest distress, chest pain and dyspnea in the study group were significantly higher than those in the control group (P<0.05). Before treatment, there was no significant difference in the results of the 6-minute walk test (6MWT) between the two groups (P>0.05). After treatment, the 6MWT in the two groups was significantly increased (P<0.05), and the improvement effect in the study group was more marked than that in the control group (P<0.05). There was no significant difference in the pulmonary function indexes between the two groups before treatment (P>0.05). Before treatment, there was no significant difference in serum TGF-β1 and MMP-7 expression levels between the two groups (P>0.05). By contrast, after treatment, the levels in the two groups were significantly decreased, with the levels in the study group being significantly lower than that the control group (P<0.05). In conclusion, tetrandrine combined with acetylcysteine can improve pulmonary function and exercise tolerance of patients with silicosis by inhibiting the expressions of TGF-β1 and MMP-7, thus improving clinical efficacy.

Lysyl hydroxylase 3 increases collagen deposition and promotes pulmonary fibrosis by activating TGFβ1/Smad3 and Wnt/β-catenin pathways

INTRODUCTION

Lysyl hydroxylase 3 (LH3) is a collagen post-translational modifying enzyme; it is abnormally activated during the formation of collagen cross-links. iCRT3 is an inhibitor of both Wnt and β-catenin responsive transcription. We hypothesized that LH3 is regulated by TGFβ1/Smad3 signaling and Wnt/β-catenin signaling pathways. Some evidence suggested that there is complicated cross-talk between the two signal pathways in the genesis of pulmonary fibrosis.

MATERIAL AND METHODS

The normal culturing human lung cancer cell line A549 was derived from pulmonary epithelial cells. Transforming growth factor-β1 (TGF-β1) was induced A549 cells of pulmonary fibrosis. MTT assays detected cell growth stimulation by TGF-β1; collagen pyridine-crosslinking contents were detected by ELISA kits. Immunofluorescence were used to evaluate expression of key molecules in PLOD3 (LH3), Wnt/β-catenin and TGFβ1/Smad3 pathways.

RESULTS

Our findings suggested that iCRT3 could decrease LH3 protein expression (p < 0.01), Wnt1, β-catenin and p-Smad3 protein expression (p < 0.05). Knock-down PLOD3 could decrease LH3, collagen I gene and protein expression (p < 0.05). These effects were associated with decreasing collagen pyridine-crosslinking production (p < 0.05). However, ovexpression PLOD3 could increase LH3, collagen I gene and protein expression (p < 0.05). The result showed that LH3 plays an important role in collagen post-translational modifications, and it is regulated by Wnt/β-catenin and TGFβ1/Smad3 pathways.

CONCLUSIONS

This study suggests that PLOD3 (LH3) represents a target to prevent pulmonary fibrosis.

TGF-β-driven downregulation of the Wnt/β-Catenin transcription factor TCF7L2/TCF4 in PDGFRα+ fibroblasts

Mesenchymal stromal/stem cells (MSCs) are multipotent progenitors essential for organogenesis, tissue homeostasis, regeneration, and scar formation. Tissue injury upregulates TGF-β signaling, which modulates myofibroblast fate, extracellular matrix remodeling, and fibrosis. However, the molecular determinants of MSCs differentiation and survival remain poorly understood. The canonical Wnt Tcf/Lef transcription factors regulate development and stemness, but the mechanisms by which injury-induced cues modulate their expression remain underexplored. Here, we studied the cell-specific gene expression of Tcf/Lef and, more specifically, we investigated whether damage-induced TGF-β impairs the expression and function of TCF7L2, using several models of MSCs, including skeletal muscle fibro-adipogenic progenitors. We show that Tcf/Lefs are differentially expressed and that TGF-β reduces the expression of TCF7L2 in MSCs but not in myoblasts. We also found that the ubiquitin-proteasome system regulates TCF7L2 proteostasis and participates in TGF-β-mediated TCF7L2 protein downregulation. Finally, we show that TGF-β requires HDACs activity to repress the expression of TCF7L2. Thus, our work found a novel interplay between TGF-β and Wnt canonical signaling cascades in PDGFRα+ fibroblasts and suggests that this mechanism could be targeted in tissue repair and regeneration.

Dynamic decreased expression and hypermethylation of secreted frizzled-related protein 1 and 4 over the course of pulmonary fibrosis in mice

Aberrantly activated Wnt signaling pathway and dysregulation of extracellular antagonists of Wnt signaling have been revealed in pulmonary fibrosis. In this study we evaluated the expression of secreted frizzled-related proteins (SFRPs) and their aberrant promoter methylation to investigate the involvement of epigenetic regulation in pulmonary fibrosis. The pulmonary fibrosis induced by intratracheal injection of bleomycin (BLM) into mice was adopted. The transcription and relative protein expression of SFRPs were detected at Day 7 (D7), D14, and D21. DNA methylation analysis was performed by methylation-specific polymerase chain reaction (MSP). A DNA methyltransferase (DNMT) inhibitor (5-aza-2'-deoxycytidine; 5-aza) was used for demethylation and the relative β-catenin expression levels were measured to assess overactivity of the canonical Wnt signaling pathway. The transcription and protein expression of SFRP1 significantly decreased at D14 and D21, whereas the transcription and protein expression of SFRP4 significantly decreased at D7 and stayed downregulated until D21. The significantly hypermethylated promoters of SFRP1 and SFRP4 resulted in impaired transcription and decreased expression during pulmonary fibrosis in mice. Besides, reactivation of SFRP1 and SFRP4 by 5-aza reduced β-catenin mRNA and protein expression in vivo and in vitro. Animal experiments confirmed that 5-aza could significantly alleviate bleomycin-induced pulmonary fibrosis in mice. Thus, changes of promoter hypermethylation might downregulate SFRP1 and SFRP4 at different stages of pulmonary fibrosis, and the finding supports the usefulness of DNMT inhibitors, which might effectively reverse activation of β-catenin and reduce pulmonary fibrosis in mice. These data provide a possible new direction in the research on pulmonary fibrosis treatments.

Niclosamide alleviates pulmonary fibrosis in vitro and in vivo by attenuation of epithelial-to-mesenchymal transition, matrix proteins & Wnt/β-catenin signaling: A drug repurposing study

Drug repurposing off late has been emerging as an inspiring alternative approach to conventional, exhaustive and arduous process of drug discovery. It is a process of identifying new therapeutic values for a drug already established for the treatment of a certain condition. Our current study is aimed at repurposing the old anti-helimenthic drug Niclosamide as an anti-fibrotic drug against pulmonary fibrosis (PF). PF is most common lethal interstitial lung disease hallmarked by deposition of extracelluar matrix and scarring of lung. Heterogenous nature, untimely diagnosis and lack of appropriate treatment options make PF an inexorable lung disorder. Prevailing void in PF treatment and drug repositioning strategy of drugs kindled our interest to demonstrate the anti-fibrotic activity of Niclosamide. Our study is aimed at investigating the anti-fibrotic potential of Niclosamide in TGF-β1 induced in vitro model of PF and 21-day model of Bleomycin induced PF in vivo respectively. Our study results showed that Niclosamide holds the potential to exert anti-fibrotic effect by hampering fibroblast migration, attenuating EMT, inhibiting fibrotic signaling and by regulating WNT/β-catenin signaling as evident from protein expression studies. Our study findings can give new directions to development of Niclosamide as an anti-fibrotic agent for treatment of pulmonary fibrosis.

Wenyang Huazhuo Tongluo formula inhibits fibrosis via suppressing Wnt/β-catenin signaling pathway in a Bleomycin-induced systemic sclerosis mouse model

Background

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. So far, no Western medicine treatment can completely inhibit or reverse the progress of SSc, while at the same time, our previous series of studies have shown that the treatment of SSc by the Wenyang Huazhuo Tongluo formula (WYHZTL), a Chinese herbal decoction, shows a delightful prospect. The aim of this study is to further investigate the mechanism of anti-fibrosis of WYHZTL formula in SSc mouse model.

Methods

The Bleomycin-induced SSc mouse model was treated with saline (BLM), high-dosage of WYHZTL formula (WYHZTL-H), medium-dosage of WYHZTL formula (WYHZTL-M), low-dosage of WYHZTL formula (WYHZTL-L) and XAV-939, a small molecule inhibitor of Wnt/β-catenin signaling pathway, by the intragastric administration and intraperitoneal injection, respectively. The mRNA and protein levels of Wnt/β-catenin signaling pathway associated genes, fibrosis markers and histopathology were detected by reverse transcription-quantitative polymerase chain reaction, Western blotting and hematoxylin/eosin-staining. The levels of Wnt1, CTGF and DKK1 protein in serum were detected by enzyme-linked immunosorbent assay.

Results

Compared with BLM group, the WYHZTL formula and XAV-939 could significantly inhibit the thickness of the skin tissue of the SSc mouse model. The mRNA expression levels of GSK3β and DKK1 in the WYHZTL formula and XAV-939-treated group were significantly higher than those in the BLM group, while Wnt1, β-catenin, TCF4, cyclin D1, survivin, VEGF, CTGF, FN1, collagen I/III were decreased. Compared with BLM group, the protein expression levels of GSK3β and DKK1 in the WYHZTL formula and XAV-939-treated group were upregulated, while Wnt1, β-catenin, cyclin D1, survivin, CTGF, FN1, collagen I/III were downregulated. WYHZTL formula and XAV-939 could inhibit expression of Wnt1 and CTGF, but promoted DKK1 in serum. Furthermore, WYHZTL-H seemed more effective than WYHZTL-M and/or XAV-939 on regulating Wnt1, β-catenin, TCF4, GSK3β, DKK1, cyclin D1, survivin, VEGF, CTGF, FN1 and collagen I/III.

Conclusion

This present study demonstrates that WYHZTL formula has anti-fibrosis effect in Bleomycin-induced SSc mouse model in a dosage-dependent manner, and the molecular mechanism may be related to the inhibition of Wnt/β-catenin signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s13020-018-0175-z) contains supplementary material, which is available to authorized users.

WNT receptor signalling in lung physiology and pathology

The WNT signalling cascades have emerged as critical regulators of a wide variety of biological aspects involved in lung development as well as in physiological and pathophysiological processes in the adult lung. WNTs (secreted glycoproteins) interact with various transmembrane receptors and co-receptors to activate signalling pathways that regulate transcriptional as well as non-transcriptional responses within cells. In physiological conditions, the majority of WNT receptors and co-receptors can be detected in the adult lung. However, dysregulation of WNT signalling pathways contributes to the development and progression of chronic lung pathologies, including idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma and lung cancer. The interaction between a WNT and the (co-)receptor(s) present at the cell surface is the initial step in transducing an extracellular signal into an intracellular response. This proximal event in WNT signal transduction with (cell-specific) ligand-receptor interactions is of great interest as a potential target for pharmacological intervention. In this review we highlight the diverse expression of various WNT receptors and co-receptors in the aforementioned chronic lung diseases and discuss the currently available biologicals and pharmacological tools to modify proximal WNT signalling.

Cthrc1 lowers pulmonary collagen associated with bleomycin-induced fibrosis and protects lung function

Idiopathic pulmonary fibrosis (IPF) involves collagen deposition that results in a progressive decline in lung function. This process involves activation of Smad2/3 by transforming growth factor (TGF)‐β and Wnt signaling pathways. Collagen Triple Helix Repeat‐Containing‐1 (Cthrc1) protein inhibits Smad2/3 activation. To test the hypothesis that Cthrc1 limits collagen deposition and the decline of lung function, Cthrc1 knockout (Cthrc1^−/−) and wild‐type mice (WT) received intratracheal injections of 2.5 U/kg bleomycin or saline. Lungs were harvested after 14 days and Bronchoalveolar lavage (BAL) TGF‐β, IL1‐β, hydroxyproline and lung compliance were assessed. TGF‐β was significantly higher in Cthrc1^−/− compared to WT (53.45 ± 6.15 ng/mL vs. 34.48 ± 11.05) after saline injection. Bleomycin injection increased TGF‐β in both Cthrc1^−/− (66.37 ± 8.54 ng/mL) and WT (63.64 ± 8.09 ng/mL). Hydroxyproline was significantly higher in Cthrc1^−/− compared to WT after bleomycin‐injection (2.676 ± 0.527 μg/mg vs. 1.889 ± 0.520, P = 0.028). Immunohistochemistry of Cthrc1^‐/‐ lung sections showed intracellular localization and activation of β‐catenin Y654 in areas of tissue remodeling that was not evident in WT. Lung compliance was significantly reduced by bleomycin in Cthrc1^−/− but there was no effect in WT animals. These data suggest Cthrc1 reduces fibrotic tissue formation in bleomycin‐induced lung fibrosis and the effect is potent enough to limit the decline in lung function. We conclude that Cthrc1 plays a protective role, limiting collagen deposition and could form the basis of a novel therapy for pulmonary fibrosis.

Decoy Wnt receptor (sLRP6E1E2)-expressing adenovirus induces anti-fibrotic effect via inhibition of Wnt and TGF-β signaling

Aberrant activation of the canonical Wingless type (Wnt) signaling pathway plays a key role in the development of hypertrophic scars and keloids, and this aberrant activation of Wnt pathway can be a potential target for the development of novel anti-fibrotic agents. In this study, we evaluated the anti-fibrotic potential of a soluble Wnt decoy receptor (sLRP6E1E2)-expressing non-replicating adenovirus (Ad; dE1-k35/sLRP6E1E2) on human dermal fibroblasts (HDFs), keloid fibroblasts (KFs), and keloid tissue explants. Higher Wnt3a and β-catenin expression was observed in the keloid region compared to the adjacent normal tissues. The activity of β-catenin and mRNA expression of type-I and -III collagen were significantly decreased following treatment with dE1-k35/sLRP6E1E2 in HDFs and KFs. The expression of LRP6, β-catenin, phosphorylated glycogen synthase kinase 3 beta, Smad 2/3 complex, and TGF-β1 were decreased in Wnt3a- or TGF-β1-activated HDFs, following administration of dE1-k35/sLRP6E1E2. Moreover, dE1-k35/sLRP6E1E2 markedly inhibited nuclear translocation of both β-catenin and Smad 2/3 complex. The expression levels of type-I and -III collagen, fibronectin, and elastin were also significantly reduced in keloid tissue explants after treatment with dE1-k35/sLRP6E1E2. These results indicate that Wnt decoy receptor-expressing Ad can degrade extracellular matrix in HDFs, KFs, and primary keloid tissue explants, and thus it may be beneficial for treatment of keloids.

Therapeutic Potential of Umbilical Cord Mesenchymal Stem Cells for Inhibiting Myofibroblastic Differentiation of Irradiated Human Lung Fibroblasts

Radiation-induced lung injury (RILI) limits the benefits of radiotherapy in patients with lung cancer. Radiation-induced differentiation of lung fibroblasts to myofibroblasts plays a key role in RILI. Recent studies have shown that mesenchymal stem cells (MSCs) can protect against lung fibrosis and that Wnt/β-catenin signaling is involved in fibrotic processes. In the present study, we explored the therapeutic potential of human umbilical cord MSCs (HUMSCs) for preventing radiation-induced differentiation of human lung fibroblasts (HLFs) to myofibroblasts. There are two advantages in the use of HUMSCs; namely, they are easily obtained and have low immunogenicity. Irradiated HLFs were co-cultured with HUMSCs. Expression of α-smooth muscle actin (α-SMA), a myofibroblast marker, was measured by Western blot analysis and immunohistochemistry. Irradiation (X-rays, 5 Gy) induced the differentiation of HLFs into myofibroblasts, which was inhibited by co-culture with HUMSCs. Irradiation also caused activation of the canonical Wnt/β-catenin signaling in HLFs, as judged by increased phosphorylation of glycogen synthase kinase 3β, nuclear accumulation of β-catenin, and elevated levels of Wnt-inducible signaling protein-1 (WISP-1) in the conditioned medium. However, co-culture with HUMSCs attenuated the radiation-induced activation of the Wnt/β-catenin signaling. We also measured the expression of FRAT1 that can enhance the Wnt/β-catenin signaling by stabilizing β-catenin. Co-culture with HUMSCs decreased FRAT1 protein levels in irradiated nHLFs. Thus, co-culture with HUMSCs attenuated the radiation-induced activation of Wnt/β-catenin signaling in HLFs, thereby inhibiting myofibroblastic differentiation of HLFs. Wnt/β-catenin signaling is a potential therapeutic target for limiting RILI in patients receiving radiotherapy for lung cancer.

Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) promotes lung fibroblast proliferation, survival and differentiation to myofibroblasts

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic progressively fatal disease. Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) is a glycosylated transmembrane protein that induces the expression of some matrix metalloproteinase (MMP) in neighboring stromal cells through direct epithelial–stromal interactions. EMMPRIN is highly expressed in type II alveolar epithelial cells at the edges of the fibrotic areas in IPF lung sections. However, the exact role of EMMPRIN in IPF is unknown.

Methods

To determine if EMMPRIN contributes to lung fibroblast proliferation, resistance to apoptosis, and differentiation to myofibroblasts, normal Human lung fibroblasts (NHLF) transiently transfected with either EMMPRIN/GFP or GFP were treated with TGF- β1 from 0 to 10 ng/ml for 48 h and examined for cell proliferation (thymidine incorporation), apoptosis (FACS analysis and Cell Death Detection ELISA assay), cell migration (Modified Boyden chamber) and differentiation to myofibroblasts using Western blot for α–smooth actin of cell lysates. The effect of EMMPRIN inhibition on NHLF proliferation, apoptosis, migration and differentiation to myofibroblasts after TGF- β1 treatment was examined using EMMPRIN blocking antibody. We examined the mechanism by which EMMPRIN induces its effects on fibroblasts by studying the β-catenin/canonical Wnt signaling pathway using Wnt luciferase reporter assays and Western blot for total and phosphorylated β-catenin.

Results

Human lung fibroblasts overexpressing EMMPRIN had a significant increase in cell proliferation and migration compared to control fibroblasts. Furthermore, EMMPRIN promoted lung fibroblasts resistance to apoptosis. Lung fibroblasts overexpressing EMMPRIN showed a significantly increased expression of α- smooth muscle actin, a marker of differentiation to myofibroblasts compared to control cells. TGF-β1 increased the expression of EMMPRIN in lung fibroblasts in a dose-dependent manner. Attenuation of EMMPRIN expression with the use of an EMMPRIN blocking antibody markedly inhibited TGF-β1 induced proliferation, migration, and differentiation of fibroblasts to myofibroblasts. EMMPRIN overexpression in lung fibroblasts was found to induce an increase in TOPFLASH luciferase reporter activity when compared with control fibroblasts.

Conclusion

These findings indicate that TGF-β1 induces the release of EMMPRIN that activates β-catenin/canonical Wnt signaling pathway. EMMPRIN overexpression induces an anti-apoptotic and pro-fibrotic phenotype in lung fibroblasts that may contribute to the persistent fibro-proliferative state seen in IPF.

The Wnt/β-catenin signaling pathway regulates the development of airway remodeling in patients with asthma

Airway remodeling is a key characteristic of chronic asthma, particularly in patients with a fixed airflow limitation. The mechanisms underlying airway remodeling are poorly understood, and no therapeutic option is available. The Wnt/β-catenin signaling pathway is involved in various physiological and pathological processes, including fibrosis and smooth muscle hypertrophy. In this study, we investigated the roles of Wnt/β-catenin signaling in airway remodeling in patients with asthma. Wnt7a mRNA expression was prominent in induced sputum from patients with asthma compared with that from healthy controls. Next, we induced a chronic asthma mouse model with airway remodeling features, including subepithelial fibrosis and airway smooth muscle hyperplasia. Higher expression of Wnt family proteins and β-catenin was detected in the lung tissue of mice with chronic asthma compared to control mice. Blocking β-catenin expression with a specific siRNA attenuated airway inflammation and airway remodeling. Decreased subepithelial fibrosis and collagen accumulation in the β-catenin siRNA-treated mice was accompanied by reduced expression of transforming growth factor-β. We further showed that suppressing β-catenin in the chronic asthma model inhibited smooth muscle hyperplasia by downregulating the tenascin C/platelet-derived growth factor receptor pathway. Taken together, these findings demonstrate that the Wnt/β-catenin signaling pathway is highly expressed and regulates the development of airway remodeling in chronic asthma.

A proteomics approach to identifying key protein targets involved in VEGF inhibitor mediated attenuation of bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a life expectancy of less than 5 years post diagnosis for most patients. Poor molecular characterization of IPF has led to insufficient understanding of the pathogenesis of the disease, resulting in lack of effective therapies. In this study, we have integrated a label-free LC-MS based approach with systems biology to identify signaling pathways and regulatory nodes within protein interaction networks that govern phenotypic changes that may lead to IPF. Ingenuity Pathway Analysis of proteins modulated in response to bleomycin treatment identified PI3K/Akt and Wnt signaling as the most significant profibrotic pathways. Similar analysis of proteins modulated in response to vascular endothelial growth factor (VEGF) inhibitor (CBO-P11) treatment identified natural killer cell signaling and PTEN signaling as the most significant antifibrotic pathways. Mechanistic/mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) were identified to be key mediators of pro- and antifibrotic response, where bleomycin (BLM) treatment resulted in increased expression and VEGF inhibitor treatment attenuated expression of mTOR and ERK. Using a BLM mouse model of pulmonary fibrosis and VEGF inhibitor CBO-P11 as a therapeutic measure, we identified a comprehensive set of signaling pathways and proteins that contribute to the pathogenesis of pulmonary fibrosis that can be targeted for therapy against this fatal disease.

Blocking the Wnt/β-Catenin Pathway by Lentivirus-Mediated Short Hairpin RNA Targeting β-Catenin Gene Suppresses Silica-Induced Lung Fibrosis in Mice

Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. While the pathogenesis of silicosis is not clearly understood, the Wnt/β-catenin signaling pathway is thought to play a major role in lung fibrosis. To explore the role of Wnt/β-catenin pathway in silicosis, we blocked Wnt/β-catenin pathway both in silica-treated MLE-12 cells (a mouse pulmonary epithelial cell line) and in a mouse silicosis model by using a lentiviral vector expressing a short hairpin RNA silencing β-catenin (Lv-shβ-catenin). In vitro, Lv-shβ-catenin significantly decreased the expression of β-catenin, MMP2 and MMP9, and secretion of TGF-β1. In vivo, intratracheal treatment with Lv-shβ-catenin significantly reduced expression of β-catenin in the lung and levels of TGF-β1 in bronchoalveolar lavage fluid, and notably attenuated pulmonary fibrosis as evidenced by hydroxyproline content and collagen I\III synthesis in silica-administered mice. These results indicate that blockade of the Wnt/β-catenin pathway can prevent the development of silica-induced lung fibrosis. Thus Wnt/β-catenin pathway may be a target in prevention and treatment of silicosis.

Epithelial-mesenchymal transition and hepatic fibrosis

Liver fibrosis is a key step of the "hepatitis - liver fibrosis/cirrhosis - liver cancer" sequence, and effective control and even reverse of liver fibrosis are imperative to prevent the development of liver cancer. Epithelial-mesenchymal transition is a hotspot in research of liver fibrosis, and numerous in vivo and in vitro experiments have been done in recent years. This paper reviews the relationship between epithelial-mesenchymal transition and hepatic fibrosis.

Morin ameliorates chemically induced liver fibrosis in vivo and inhibits stellate cell proliferation in vitro by suppressing Wnt/β-catenin signaling

The anti-fibrotic effect of morin was examined in LX-2 cells (culture-activated human hepatic stellate cells) and in diethylnitrosamine induced rat model of liver fibrosis. The in vitro study was designed to determine whether morin affects the survival of cultured LX-2 cells, while the in vivo study was designed to evaluate the antioxidant and anti-fibrotic efficacy of morin on diethylnitrosamine induced liver fibrosis in male albino Wistar rat. The activities of liver function enzymes in serum, liver lipid peroxide levels, activities of serum antioxidant enzymes and liver architecture were monitored to cast light on the antioxidant and hepatoprotective nature of morin. To establish the anti-fibrotic effects of morin, the levels of key Wnt signaling molecules which are strongly associated with the signal transduction pathway of HSC activation were measured. Overall, from the in vitro results, it was observed that morin at 50 μM concentration inhibited the proliferation of cultured LX-2 cells, inhibited Wnt signaling and induced G1 cell cycle arrest. The in vivo results further confirmed that morin by downregulating the expressions of GSK-3β, β-catenin and cyclin D1 ameliorated DEN-induced liver fibrosis. Hence morin could be employed as a promising chemopreventive natural supplement for liver fibrosis.

Beneficial role of vitamin D3 in the prevention of certain respiratory diseases

There is evidence of aberrations in the vitamin D-endocrine system in subjects with respiratory diseases. Vitamin D deficiency is highly prevalent in patients with respiratory diseases, and patients who receive vitamin D have significantly larger improvements in inspiratory muscle strength and maximal oxygen uptake. Studies have provided an opportunity to determine which proteins link vitamin D to respiratory pathology, including the major histocompatibility complex class II molecules, vitamin D receptor, vitamin D-binding protein, chromosome P450, Toll-like receptors, poly(ADP-ribose) polymerase-1, and the reduced form of nicotinamide adenine dinucleotide phosphate. Vitamin D also exerts its effect on respiratory diseases through cell signaling mechanisms, including matrix metalloproteinases, mitogen-activated protein kinase pathways, the Wnt/β-catenin signaling pathway, prostaglandins, reactive oxygen species, and nitric oxide synthase. In conclusion, vitamin D plays a significant role in respiratory diseases. The best form of vitamin D for use in the treatment of respiratory diseases is calcitriol because it is the active metabolite of vitamin D3 and modulates inflammatory cytokine expression. Further investigation of calcitriol in respiratory diseases is needed.

Wnt signaling in skeletal muscle dynamics: myogenesis, neuromuscular synapse and fibrosis

The signaling pathways activated by Wnt ligands are related to a wide range of critical cell functions, such as cell division, migration, and synaptogenesis. Here, we summarize compelling evidence on the role of Wnt signaling on several features of skeletal muscle physiology. We briefly review the role of Wnt pathways on the formation of muscle fibers during prenatal and postnatal myogenesis, highlighting its role on the activation of stem cells of the adult muscles. We also discuss how Wnt signaling regulates the precise formation of neuromuscular synapses, by modulating the differentiation of presynaptic and postsynaptic components, particularly regarding the clustering of acetylcholine receptors on the muscle membrane. In addition, based on previous evidence showing that Wnt pathways are linked to several diseases, such as Alzheimer's and cancer, we address recent studies indicating that Wnt signaling plays a key role in skeletal muscle fibrosis, a disease characterized by an increase in the extracellular matrix components leading to failure in muscle regeneration, tissue disorganization and loss of muscle activity. In this context, we also discuss the possible cross-talk between the Wnt/β-catenin pathway with two other critical profibrotic pathways, transforming growth factor β and connective tissue growth factor, which are potent stimulators of the accumulation of connective tissue, an effect characteristic of the fibrotic condition. As it has emerged in other pathological conditions, we suggests that muscle fibrosis may be a consequence of alterations of Wnt signaling activity.

Targeting sphingosine kinase 1 attenuates bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease, wherein transforming growth factor β (TGF-β) and sphingosine-1-phosphate (S1P) contribute to the pathogenesis of fibrosis. However, the in vivo contribution of sphingosine kinase (SphK) in fibrotic processes has not been documented. Microarray analysis of blood mononuclear cells from patients with IPF and SphK1- or SphK2-knockdown mice and SphK inhibitor were used to assess the role of SphKs in fibrogenesis. The expression of SphK1/2 negatively correlated with lung function and survival in patients with IPF. Also, the expression of SphK1 was increased in lung tissues from patients with IPF and bleomycin-challenged mice. Knockdown of SphK1, but not SphK2, increased survival and resistance to pulmonary fibrosis in bleomycin-challenged mice. Administration of SphK inhibitor reduced bleomycin-induced mortality and pulmonary fibrosis in mice. Knockdown of SphK1 or treatment with SphK inhibitor attenuated S1P generation and TGF-β secretion in a bleomycin-induced lung fibrosis mouse model that was accompanied by reduced phosphorylation of Smad2 and MAPKs in lung tissue. In vitro, bleomycin-induced expression of SphK1 in lung fibroblast was found to be TGF-β dependent. Taken together, these data indicate that SphK1 plays a critical role in the pathology of lung fibrosis and is a novel therapeutic target.

Wnt/β-Catenin Signaling: a Promising New Target for Fibrosis Diseases

Wnt/β-catenin signaling is involved in virtually every aspect of embryonic development and also controls homeostatic self-renewal in a number of adult tissues. Recently, emerging evidence from researches of organ fibrosis suggest that sustained Wnt/β-catenin pathway reactivation is linked to the pathogenesis of fibrotic disorders. Here we focus on Wnt/β-catenin-related pathogenic effects in different organs, such as lung fibrosis, liver fibrosis, skin fibrosis and renal fibrosis. Additionally, Wnt/β-catenin signaling works in a combinatorial manner with TGF-β signaling in the process of fibrosis, and TGF-β signaling can induce expression of Wnt/β-catenin superfamily members and vice versa. Moreover, network analysis, based on pathway databases, revealed that key factors in the Wnt pathway were targeted by some differentially expressed microRNAs detected in fibrosis diseases. These findings demonstrated the crosstalks between Wnt/β-catenin pathway and TGF-β signalings, and microRNAs, highlighting the role of Wnts in organ fibrogenesis. Most importantly, nowadays there is a variety of Wnt pathway inhibitors which give us the potential therapeutic feasibility, modulation of the Wnt pathway may, therefore, present as a suitable and promising therapeutic strategy in the future.

Activation of canonical Wnt signalling is required for TGF-β-mediated fibrosis

The transforming growth factor-β (TGF-β) signalling pathway is a key mediator of fibroblast activation that drives the aberrant synthesis of extracellular matrix in fibrotic diseases. Here we demonstrate a novel link between transforming growth factor-β and the canonical Wnt pathway. TGF-β stimulates canonical Wnt signalling in a p38-dependent manner by decreasing the expression of the Wnt antagonist Dickkopf-1. Tissue samples from human fibrotic diseases show enhanced expression of Wnt proteins and decreased expression of Dickkopf-1. Activation of the canonical Wnt pathway stimulates fibroblasts in vitro and induces fibrosis in vivo. Transgenic overexpression of Dickkopf-1 ameliorates skin fibrosis induced by constitutively active TGF-β receptor type I signalling and also prevents fibrosis in other TGF-β-dependent animal models. These findings demonstrate that canonical Wnt signalling is necessary for TGF-β-mediated fibrosis and highlight a key role for the interaction of both pathways in the pathogenesis of fibrotic diseases.

Aberrant activation of the TGF-β pathway leads to fibrotic disease. Distler and colleagues show that TGF-β-mediated fibrosis requires the decrease of Dickkopf-1, an antagonist of canonical Wnt signalling, suggesting that the two pathways interact for the manifestation of this disease.

Blockade of the Wnt/β-catenin pathway attenuates bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease and characterized by abnormal growth of fibroblasts and lung scarring. While the pathogenesis of IPF is not clearly understood, activation of transforming growth factor-β (TGF-β) and disruption of alveolar basement membrane seem to play important roles in leading to excess disruption of the matrix, which is associated with activated matrix metalloproteinase (MMP) and aberrant proliferation of myofibroblasts. The Wnt/β-catenin pathway is an important regulator of cellular proliferation and differentiation and abnormal activation of Wnt/β-catenin signal was observed in IPF. We examined whether inhibition of the Wnt/β-catenin pathway could attenuate pulmonary fibrosis in a bleomycin-induced murine model of pulmonary fibrosis. Pulmonary fibrosis was induced in C57BL/6N mice by intratracheal instillation of bleomycin. To inhibit the Wnt/β-catenin pathway, small interfering RNA (siRNA) for β-catenin was administered into trachea 2 h before bleomycin instillation and every 48 h afterward until sacrifice on day 14. The level of β-catenin expression was increased in the epithelial cells of bleomycin-administered mice. Intratracheal treatment with β-catenin siRNA significantly reduced β-catenin expression, pulmonary fibrosis and collagen synthesis in bleomycin-administered mice compared with controls, with no significant effect on the inflammatory response. The β-catenin-targeted siRNA also significantly decreased the levels of MMP-2 (P<0.01) and TGF-β (P<0.01) expression in the lung tissue. Blockade of the Wnt/β-catenin pathway by β-catenin siRNA decreased bleomycin-induced pulmonary fibrosis in the murine model. These findings suggest that targeting Wnt/β-catenin signaling may be an effective therapeutic approach in the treatment of IPF.

WNT/β-catenin signaling is modulated by mechanical ventilation in an experimental model of acute lung injury

PURPOSE

The mechanisms involved in lung injury progression during acute lung injury (ALI) are still poorly understood. Because WNT/β-catenin signaling has been shown to be involved in epithelial cell injury and hyperplasia during inflammation and sepsis, we hypothesized that it would be modulated by mechanical ventilation (MV) in an experimental model of sepsis-induced ALI.

METHODS

This study was a prospective, randomized, controlled animal study performed using adult male Sprague-Dawley rats. Sepsis was induced by cecal ligation and perforation. At 18 h, surviving animals were randomized to spontaneous breathing or two strategies of MV for 4 h: low tidal volume (V (T)) (6 ml/kg) plus 10 cmH2O of positive end-expiratory pressure (PEEP) versus high (20 ml/kg) tidal volume (V (T)) with zero PEEP. Histological evaluation, measurements of WNT5A, total β-catenin, and matrix metalloproteinase-7 (MMP7) protein levels by Western blot, and their immunohistochemical localization in the lungs were analyzed.

RESULTS

Sepsis and high-V (T) MV caused lung inflammation and perivascular edema with cellular infiltrates and collagen deposition. Protein levels of WNT5A, β-catenin, and MMP7 in the lungs were increased in animals with sepsis-induced ALI. High-V (T) MV was associated with higher levels of WNT5A, β-catenin, and MMP7 protein levels (p < 0.001), compared to healthy control animals. By contrast, low-V (T) MV markedly reduced WNT5A, β-catenin, and MMP7 protein levels (p < 0.001).

CONCLUSIONS

Our findings demonstrate that the WNT/β-catenin signaling pathway is modulated early during sepsis and ventilator-induced lung injury, suggesting that activation of this pathway could play an important role in both lung injury progression and repair.

Nuclear β-catenin is increased in systemic sclerosis pulmonary fibrosis and promotes lung fibroblast migration and proliferation

Pulmonary fibrosis is a disease that results in loss of normal lung architecture, but the signaling events that drive tissue destruction are incompletely understood. Wnt/β-catenin signaling is important in normal lung development, but whether abnormal signaling occurs in lung fibrosis due to systemic sclerosis and the consequences of β-catenin signaling toward the fibrogenic phenotype remain poorly defined. In this study, we show nuclear β-catenin accumulation in fibroblastic foci from lungs of patients with systemic sclerosis-associated advanced pulmonary fibrosis. Forced activation of β-catenin signaling in three independently derived sources of normal human lung fibroblasts promotes proliferation and migratory activities but is not sufficient to activate classic markers of fibroblast activation, such as TGF-β, type 1 collagen, α-smooth muscle actin, and connective tissue growth factor. These findings indicate that activation of β-catenin signaling in pulmonary fibroblasts may be a common feature of lung fibrosis, contributing to fibroproliferative and migratory activities associated with the disease.

Activation of the WNT/β-catenin pathway attenuates experimental emphysema

RATIONALE

Chronic obstructive pulmonary disease (COPD) is a devastating disease, for which no causal therapy is available.

OBJECTIVES

To characterize WNT/β-catenin signaling in COPD in humans and elucidate its potential role as a preventive and therapeutic target in experimental emphysema in mice.

METHODS

The expression, localization, and activity of WNT/β-catenin signaling was assessed in 12 COPD and 12 transplant donor samples using quantitative reverse transcriptase polymerase chain reaction, immunohistochemistry, and Western blotting. The role of WNT/β-catenin signaling was assessed in elastase- and cigarette smoke-induced emphysema and therapeutic modulation thereof in elastase-induced emphysema in TOPGAL reporter and wild-type mice in vivo.

MEASUREMENTS AND MAIN RESULTS

No differences in the mRNA expression profile of the main WNT/β-catenin signaling components were observed comparing COPD and donor lung homogenates. Immunohistochemical analysis revealed reduced numbers of nuclear β-catenin-positive alveolar epithelial cells in COPD. Similarly, WNT/β-catenin signaling was down-regulated in both experimental emphysema models. Preventive and therapeutic, WNT/β-catenin activation by lithium chloride attenuated experimental emphysema, as assessed by decreased airspace enlargement, improved lung function, reduced collagen content, and elevated expression of alveolar epithelial cell markers.

CONCLUSIONS

Decreased WNT/β-catenin signaling is involved in parenchymal tissue destruction and impaired repair capacity in emphysema. These data indicate a crucial role of WNT/β-catenin signaling in lung repair mechanisms in vivo, and highlight WNT/β-catenin activation as a future therapeutic approach for emphysema.

New insights into the mechanism of fibroblast to myofibroblast transformation and associated pathologies

Myofibroblasts are a differentiated cell type essential for wound healing, participating in tissue remodeling following insult. Myofibroblasts are typically activated fibroblasts, although they can also be derived from other cell types, including epithelial cells, endothelial cells, and mononuclear cells. In most organ systems, cell signals initiated following tissue-specific insult or during the metastatic process lead to differentiation of fibroblasts or other precursor cells to the myofibroblast phenotype. In addition to their beneficial and necessary role in wound healing, myofibroblasts also contribute to a number of pathologies, primarily fibrotic processes and tumor invasiveness. This review explores both traditional and nontraditional concepts of myofibroblast differentiation in the cornea, skin, heart, and other tissues, as well as some of the pathologies associated with myofibroblast activities.

The role of pleiotrophin and beta-catenin in fetal lung development

Mammalian lung development is a complex biological process, which is temporally and spatially regulated by growth factors, hormones, and extracellular matrix proteins. Abnormal changes of these molecules often lead to impaired lung development, and thus pulmonary diseases. Epithelial-mesenchymal interactions are crucial for fetal lung development. This paper reviews two interconnected pathways, pleiotrophin and Wnt/β-catenin, which are involved in fibroblast and epithelial cell communication during fetal lung development.