Wnt signaling and pulmonary fibrosis

Unravelling the Road to Recovery: Mechanisms of Wnt Signalling in Spinal Cord Injury

Spinal cord injury (SCI) is a complex neurodegenerative pathology that consistently harbours a poor prognostic outcome. At present, there are few therapeutic strategies that can halt neuronal cell death and facilitate functional motor recovery. However, recent studies have highlighted the Wnt pathway as a key promoter of axon regeneration following central nervous system (CNS) injuries. Emerging evidence also suggests that the temporal dysregulation of Wnt may drive cell death post-SCI. A major challenge in SCI treatment resides in developing therapeutics that can effectively target inflammation and facilitate glial scar repair. Before Wnt signalling is exploited for SCI therapy, further research is needed to clarify the implications of Wnt on neuroinflammation during chronic stages of injury. In this review, an attempt is made to dissect the impact of canonical and non-canonical Wnt pathways in relation to individual aspects of glial and fibrotic scar formation. Furthermore, it is also highlighted how modulating Wnt activity at chronic time points may aid in limiting lesion expansion and promoting axonal repair.

Hypoxia Induces Alterations in the Circadian Rhythm in Patients with Chronic Respiratory Diseases

The function of the circadian cycle is to determine the natural 24 h biological rhythm, which includes physiological, metabolic, and hormonal changes that occur daily in the body. This cycle is controlled by an internal biological clock that is present in the body's tissues and helps regulate various processes such as sleeping, eating, and others. Interestingly, animal models have provided enough evidence to assume that the alteration in the circadian system leads to the appearance of numerous diseases. Alterations in breathing patterns in lung diseases can modify oxygenation and the circadian cycles; however, the response mechanisms to hypoxia and their relationship with the clock genes are not fully understood. Hypoxia is a condition in which the lack of adequate oxygenation promotes adaptation mechanisms and is related to several genes that regulate the circadian cycles, the latter because hypoxia alters the production of melatonin and brain physiology. Additionally, the lack of oxygen alters the expression of clock genes, leading to an alteration in the regularity and precision of the circadian cycle. In this sense, hypoxia is a hallmark of a wide variety of lung diseases. In the present work, we intended to review the functional repercussions of hypoxia in the presence of asthma, chronic obstructive sleep apnea, lung cancer, idiopathic pulmonary fibrosis, obstructive sleep apnea, influenza, and COVID-19 and its repercussions on the circadian cycles.

Induced pluripotent stem cells modulate the Wnt pathway in the bleomycin-induced model of idiopathic pulmonary fibrosis

BACKGROUND

The Wnt signaling pathway has been implicated in the pathogenesis of fibrotic disorders and malignancies. Hence, we aimed to assess the potential of the induced pluripotent stem cells (IPS) in modulating the expression of the cardinal genes of the Wnt pathway in a mouse model of idiopathic pulmonary fibrosis (IPF).

METHODS

C57Bl/6 mice were randomly divided into three groups of Control, Bleomycin (BLM), and BLM + IPS; the BLM mice received intratracheal instillation of bleomycin, BLM + IPS mice received tail vein injection of IPS cells 48 h post instillation of the BLM; The Control group received Phosphate-buffered saline instead. After 3 weeks, the mice were sacrificed and Histologic assessments including hydroxy proline assay, Hematoxylin and Eosin, and Masson-trichrome staining were performed. The expression of the genes for Wnt, β-Catenin, Lef, Dkk1, and Bmp4 was assessed utilizing specific primers and SYBR green master mix.

RESULTS

Histologic assessments revealed that the fibrotic lesions and inflammation were significantly alleviated in the BLM + IPS group. Besides, the gene expression analyses demonstrated the upregulation of Wnt, β-Catenin, and LEF along with the significant downregulation of the Bmp4 and DKK1 in response to bleomycin treatment; subsequently, it was found that the treatment of the IPF mice with IPS cells results in the downregulation of the Wnt, β-Catenin, and Lef, as well as upregulation of the Dkk1, but not the Bmp4 gene (P values < 0.05).

CONCLUSION

The current study highlights the therapeutic potential of the IPS cells on the IPF mouse model in terms of regulating the aberrant expression of the factors contributing to the Wnt signaling pathway.

Epithelial Yap/Taz are required for functional alveolar regeneration following acute lung injury

A hallmark of idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases is dysregulated repair of the alveolar epithelium. The Hippo pathway effector transcription factors YAP and TAZ are implicated as essential for type 1 and type 2 alveolar epithelial cell (AT1 and AT2) differentiation in the developing lung, yet aberrant activation of YAP/TAZ is a prominent feature of the dysregulated alveolar epithelium in IPF. In these studies, we sought to define the functional role of YAP/TAZ activity during alveolar regeneration. We demonstrated that Yap and Taz were normally activated in AT2 cells shortly after injury, and deletion of Yap/Taz in AT2 cells led to pathologic alveolar remodeling, failure of AT2-to-AT1 cell differentiation, increased collagen deposition, exaggerated neutrophilic inflammation, and increased mortality following injury induced by a single dose of bleomycin. Loss of Yap/Taz activity prior to an LPS injury prevented AT1 cell regeneration, led to intraalveolar collagen deposition, and resulted in persistent innate inflammation. These findings establish that AT2 cell Yap/Taz activity is essential for functional alveolar epithelial repair and prevention of fibrotic remodeling.

RNA Sequencing of Idiopathic Subglottic Stenosis Tissues Uncovers Putative Profibrotic Mechanisms and Identifies a Prognostic Biomarker

Idiopathic subglottic stenosis (iSGS) is a localized airway disease that almost exclusively affects females. Understanding the molecular mechanisms involved may provide insights leading to therapeutic interventions. Next-generation sequencing was performed on tissue sections from patients with iSGS (n = 22), antineutrophil cytoplasmic antibody-associated vasculitis (AAV; n = 5), and matched controls (n = 9) to explore candidate genes and mechanisms of disease. Gene expression changes were validated, and selected markers were identified by immunofluorescence staining. Epithelial-mesenchymal transition (EMT) and leukocyte extravasation pathways were the biological mechanisms most relevant to iSGS pathogenesis. Alternatively activated macrophages (M2) were abundant in the subepithelium and perisubmucosal glands of the airway in iSGS and AAV. Increased expression of the mesenchymal marker S100A4 and decreased expression of the epithelial marker epithelial cell adhesion molecule (EPCAM) further supported a role for EMT, but to different extents, in iSGS and antineutrophil cytoplasmic antibody-associated subglottic stenosis. In patients with iSGS, high expression of prostate transmembrane protein, androgen induced 1 (PMEPA1), an EMT regulator, was associated with a shorter recurrence interval (25 versus 116 months: hazard ratio = 4.16; P = 0.041; 95% CI, 1.056-15.60). Thus, EMT is a key pathogenetic mechanism of subglottic stenosis in iSGS and AAV. M2 macrophages contribute to the pathogenesis of both diseases, suggesting a shared profibrotic mechanism, and PMEPA1 may be a biomarker for predicting disease recurrence in iSGS.

Plasticity towards Rigidity: A Macrophage Conundrum in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, and ultimately fatal diffuse parenchymal lung disease. The molecular mechanisms of fibrosis in IPF patients are not fully understood and there is a lack of effective treatments. For decades, different types of drugs such as immunosuppressants and antioxidants have been tested, usually with unsuccessful results. Although two antifibrotic drugs (Nintedanib and Pirfenidone) are approved and used for the treatment of IPF, side effects are common, and they only slow down disease progression without improving patients’ survival. Macrophages are central to lung homeostasis, wound healing, and injury. Depending on the stimulus in the microenvironment, macrophages may contribute to fibrosis, but also, they may play a role in the amelioration of fibrosis. In this review, we explore the role of macrophages in IPF in relation to the fibrotic processes, epithelial–mesenchymal transition (EMT), and their crosstalk with resident and recruited cells and we emphasized the importance of macrophages in finding new treatments.

Study of the colonic epithelial-mesenchymal dialogue through establishment of two activated or not mesenchymal cell lines: Activated and resting ones differentially modulate colonocytes in co-culture

Continuous and rapid renewal of the colonic epithelium is crucial to resist the plethora of luminal deleterious agents. Subepithelial fibroblasts contribute to this turnover by regulating epithelial proliferation and differentiation. However, when intestinal homeostasis is disturbed, fibroblasts can acquire an activated phenotype and play a major role in the progression of intestinal pathologies. To evaluate the involvement of fibroblasts in the regulation of colonocytes under homeostatic or pathological conditions, we established resting and activated conditionally immortalized fibroblast cell lines (nF and mF) from mouse colonic mucosa. We then studied the epithelial-mesenchymal interactions between activated or resting fibroblasts and the normal mouse colonocytes (Co) using a co-culture model. Both fibroblastic cell lines were characterized by RT-qPCR, western blot and immunofluorescence assay. Our results showed that nF and mF cells were positive for fibroblastic markers such as vimentin and collagen 1, and negative for cytokeratin 18 and E-cadherin, attesting to their fibroblastic type. They also expressed proteins characteristic of the epithelial stem cell niche such as Grem1, CD90 or Wnt5a. Only rare nF fibroblasts were positive for α-SMA, whereas all mF fibroblasts strongly expressed this marker, supporting that mF cells were activated fibroblasts/myofibroblasts. In coculture, nF fibroblasts and Co cells strongly interacted via paracrine exchanges resulting in BMP4 production in nF fibroblasts, activation of BMP signaling in Co colonocytes, and decreased growth of colonocytes. Activated-type mF fibroblasts did not exert the same effects on Co cells, allowing colonocytes free to proliferate. In conclusion, these two colonic fibroblast lines, associated with Co cells in coculture, should allow to better understand the role of mesenchymal cells in the preservation of homeostasis and the development of intestinal pathologies.

TRAF6 Suppresses the Development of Pulmonary Fibrosis by Attenuating the Activation of Fibroblasts

Pulmonary fibrosis (PF) has a high mortality rate, and its pathogenesis is unknown. TNF receptor-associated factor 6 (TRAF6), a signal transducer for inflammatory signaling, plays crucial roles in the pathogenesis of immune diseases. However, its function in PF remains unknown. Herein, we demonstrated that lungs from mice with bleomycin (BLM)-induced PF were characterized by decreased expression of TRAF6 in lung fibroblasts. Enhancing TRAF6 expression protected mice from BLM-induced PF coupled with a significant reduction in fibroblast differentiation. Furthermore, we demonstrated that overexpression of TRAF6 reversed the activation of myofibroblasts from PF mice by reducing the expression of Wnt3a and subsequently suppressing Wnt/β-catenin signaling. Additionally, the abundance of Tribbles pseudokinase 3 (TRIB3), a stress sensor, was negatively correlated with the abundance of TRAF6 in lung fibroblasts. TRIB3 overexpression decreased TRAF6 abundance by reducing TRAF6 stability in lung fibroblasts during PF. Mechanistic studies revealed that TRIB3 bound to TRAF6 and accelerated basal TRAF6 ubiquitination and degradation. Collectively, our data indicate that reduced TRAF6 expression in fibroblasts is essential for the progression of PF, and therefore, genetically increasing TRAF6 expression or disrupting the TRIB3-TRAF6 interaction could be potential therapeutic strategies for fibroproliferative lung diseases in clinical settings.

Galectin 1-A Key Player between Tissue Repair and Fibrosis

Galectins are ten family members of carbohydrate-binding proteins with a high affinity for β galactose-containing oligosaccharides. Galectin-1 (Gal-1) is the first protein discovered in the family, expressed in many sites under normal and pathological conditions. In the first part of the review article, we described recent advances in the Gal-1 modulatory role on wound healing, by focusing on the different phases triggered by Gal-1, such as inflammation, proliferation, tissue repair and re-epithelialization. On the contrary, Gal-1 persistent over-expression enhances angiogenesis and extracellular matrix (ECM) production via PI3K/Akt pathway activation and leads to keloid tissue. Therefore, the targeted Gal-1 modulation should be considered a method of choice to treat wound healing and avoid keloid formation. In the second part of the review article, we discuss studies clarifying the role of Gal-1 in the pathogenesis of proliferative diabetic retinopathy, liver, renal, pancreatic and pulmonary fibrosis. This evidence suggests that Gal-1 may become a biomarker for the diagnosis and prognosis of tissue fibrosis and a promising molecular target for the development of new and original therapeutic tools to treat fibrosis in different chronic diseases.

Wnt/β-catenin signaling regulates lipopolysaccharide-altered polarizations of RAW264.7 cells and alveolar macrophages in mouse lungs

Introduction

Macrophages are capable of exerting both proinflammatory and anti-inflammatory functions in response to distinct environmental stimuli, by polarizing into classically inflammatory state (M1) and anti-inflammatory phenotype (M2), respectively. The Wnt/β-catenin signaling plays an important role in the tissue homeostasis and immune regulations, including the macrophage polarizations. However, the molecular mechanism of Wnt/β-catenin signaling in regulating alveolar macrophage polarization in an inflammatory state remains unclear.

Methods

The Wnt/β-catenin signaling-altered phenotypes of murine macrophage-like RAW264.7 cells in vitro and alveolar macrophage in vivo in both of naïve and lipopolysaccharide-induced inflammation states were accessed by immunoblotting and immunostaining assays.

Results

The activation of Wnt/β-catenin signaling inhibited macrophage M1 polarization, but promoted alternative M2 polarization in murine RAW264.7 cells under a naïve state. Interestingly, in an LPS-induced inflammation condition, the enhanced Wnt/β-catenin activity suppressed both M1 and M2 polarizations in RAW264.7 cells in vitro, and primary alveolar macrophages of LPS-challenged mice in vivo. Molecular analysis further demonstrated an involvement of Stat signing in regulating Wnt/β-catenin signaling-altered polarizations in mouse alveolar macrophages.

Conclusion

These results suggest a mechanism by which Wnt/β-catenin signaling modulates macrophage polarization in an inflammation state by regulating the Stat signaling pathway.

Adenoviral Transduction of Dickkopf-1 Alleviates Silica-Induced Silicosis Development in Lungs of Mice

Silicosis is an occupational disease caused by inhalation of silica dust, which is hallmarked by progressive pulmonary fibrosis associated with poor prognosis. Wnt/β-catenin signaling is implicated in the development of fibrosis and is a therapeutic target for fibrotic diseases. Previous clinical studies of patients with pneumoconiosis, including silicosis, revealed an increased concentration of circulating WNT3A and DKK1 proteins and inflammatory cells in bronchoalveolar lavage compared with healthy subjects. The present study evaluated the effects of adenovirus-mediated transduction of Dickkopf-1 (Dkk1), a Wnt/β-catenin signaling inhibitor, on the development of pulmonary silicosis in mice. Consistent with previous human clinical studies, our experimental studies in mice demonstrated an aberrant Wnt/β-catenin signaling activity coinciding with increased Wnt3a and Dkk1 proteins and inflammation in lungs of silica-induced silicosis mice compared with controls. Intratracheal delivery of adenovirus expressing murine Dkk1 (AdDkk1) inhibited Wnt/β-catenin activity in mouse lungs. The adenovirus-mediated Dkk1 gene transduction demonstrated the potential to prevent silicosis development and ameliorate silica-induced lung fibrogenesis in mice, accompanied by the reduced expression of epithelia--mesenchymal transition markers and deposition of extracellular matrix proteins compared with mice treated with "null" adenoviral vector. Mechanistically, AdDkk1 is able to attenuate the lung silicosis by inhibiting a silica-induced spike in TGF-β/Smad signaling. In addition, the forced expression of Dkk1 suppressed silica-induced epithelial cell proliferation in polarized human bronchial epithelial cells. This study provides insight into the underlying role of Wnt/β-catenin signaling in promoting the pathogenesis of silicosis and is proof-of-concept that targeting Wnt/β-catenin signaling by Dkk1 gene transduction may be an alternative approach in the prevention and treatment of silicosis lung disease.

ADAM 17 and Epithelial-to-Mesenchymal Transition: The Evolving Story and Its Link to Fibrosis and Cancer

For decades, metalloproteinase 17 (ADAM17) has been the goal of wide investigation. Since its discovery as the tumour necrosis factor-α convertase, it has been studied as the main drug target, especially in the context of inflammatory conditions and tumour. In fact, evidence is mounting to support a key role of ADAM17 in the induction of the proliferation, migration and progression of tumour cells and the trigger of the pro-fibrotic process during chronic inflammatory conditions; this occurs, probably, through the activation of epithelial-to-mesenchymal transition (EMT). EMT is a central morphologic conversion that occurs in adults during wound healing, tumour progression and organ fibrosis. EMT is characterised by the disassembly of cell–cell contacts, remodelling of the actin cytoskeleton and separation of cells, and generates fibroblast-like cells that express mesenchymal markers and have migratory properties. This transition is characterised by loss of epithelial proteins such as E-cadherin and the acquisition of new mesenchymal markers, including vimentin and a-smooth muscle actin. The present review discusses the current understanding of molecular mechanisms involved in ADAM17-dependent EMT in order to individuate innovative therapeutic strategies using ADAM17-related pathways.

Ellagic Acid Attenuates BLM-Induced Pulmonary Fibrosis via Inhibiting Wnt Signaling Pathway

Idiopathic pulmonary fibrosis is a progressive lung disease with high mortality and limited therapy that is characterized by epithelial cell damage and fibroblast activation. Ellagic acid is a natural polyphenol compound widely found in fruits and nuts that has multiple pharmacological activities. In this study, we explored the potential effects and mechanisms of Ellagic acid on pulmonary fibrosis in vivo and in vitro. In vivo studies showed that Ellagic acid significantly alleviated bleomycin (BLM)-induced pulmonary fibrosis in mice. In vitro experiments indicated that Ellagic acid could suppress Wnt signaling and attenuate Wnt3a-induced myofibroblast activation and the phosphorylation of Erk2 and Akt. Further studies showed that Ellagic acid could induce autophagy formation in myofibroblasts mainly by suppressing mTOR signaling and promoting apoptosis of myofibroblasts. In vivo experiments revealed that Ellagic acid significantly inhibited myofibroblast activation and promoted autophagy formation. Taken together, our results show that Ellagic acid effectively attenuates BLM-induced pulmonary fibrosis in mice by suppressing myofibroblast activation and promoting autophagy and apoptosis of myofibroblasts by inhibiting the Wnt signaling pathway.

Cigarette Smoke and Nicotine-Containing Electronic-Cigarette Vapor Downregulate Lung WWOX Expression, Which Is Associated with Increased Severity of Murine Acute Respiratory Distress Syndrome

A history of chronic cigarette smoking is known to increase risk for acute respiratory distress syndrome (ARDS), but the corresponding risks associated with chronic e-cigarette use are largely unknown. The chromosomal fragile site gene, WWOX, is highly susceptible to genotoxic stress from environmental exposures and thus an interesting candidate gene for the study of exposure-related lung disease. Lungs harvested from current versus former/never-smokers exhibited a 47% decrease in WWOX mRNA levels. Exposure to nicotine-containing e-cigarette vapor resulted in an average 57% decrease in WWOX mRNA levels relative to vehicle-treated controls. In separate studies, endothelial (EC)-specific WWOX knockout (KO) versus WWOX flox control mice were examined under ARDS-producing conditions. EC WWOX KO mice exhibited significantly greater levels of vascular leak and histologic lung injury. ECs were isolated from digested lungs of untreated EC WWOX KO mice using sorting by flow cytometry for CD31+ CD45-cells. These were grown in culture, confirmed to be WWOX deficient by RT-PCR and Western blotting, and analyzed by electric cell impedance sensing as well as an FITC dextran transwell assay for their barrier properties during methicillin-resistant Staphylococcus aureus or LPS exposure. WWOX KO ECs demonstrated significantly greater declines in barrier function relative to cells from WWOX flox controls during either methicillin-resistant S. aureus or LPS treatment as measured by both electric cell impedance sensing and the transwell assay. The increased risk for ARDS observed in chronic smokers may be mechanistically linked, at least in part, to lung WWOX downregulation, and this phenomenon may also manifest in the near future in chronic users of e-cigarettes.

A Positive Feed Forward Loop between Wnt/β-Catenin and NOX4 Promotes Silicon Dioxide-Induced Epithelial-Mesenchymal Transition of Lung Epithelial Cells

Silicosis is a chronic fibrotic lung disease caused by the accumulation of silica dust in the distal lung. Canonical Wnt signaling and NADPH oxidase 4 (NOX4) have been demonstrated to play a crucial role in the pathogenesis of pulmonary fibrosis including silicosis. However, the underlying mechanisms of crosstalk between these two signalings are not fully understood. In the present study, we aimed to explore the interaction of Wnt/β-catenin and NOX4 of human epithelial cells in response to an exposure of silica dust. Results demonstrated an elevated expression of key components of Wnt/β-catenin signaling and NOX4 in the lungs of silicon dioxide- (SiO₂-) induced silicosis mice. Furthermore, the activated Wnt/β-catenin and NOX4 signaling are accompanied by an inhibition of cell proliferation, an increase of ROS production and cell apoptosis, and an upregulation of profibrogenic factors in BEAS-2B human lung epithelial cells exposed to SiO₂. A mechanistic study further demonstrated that the Wnt3a-mediated activation of canonical Wnt signaling could augment the SiO₂-induced NOX4 expression and reactive oxygen species (ROS) production but reduced glutathione (GSH), while Wnt inhibitor DKK1 exhibited an opposite effect to Wnt3a. Vice versa, an overexpression of NOX4 further activated SiO₂-induced Wnt/β-catenin signaling and NFE2-related factor 2 (Nrf2) antioxidant response along with a reduction of GSH, whereas the shRNA-mediated knockdown of NOX4 showed an opposite effect to NOX4 overexpression. These results imply a positive feed forward loop between Wnt/β-catenin and NOX4 signaling that may promote epithelial-mesenchymal transition (EMT) of lung epithelial cells in response to an exposure of silica dust, which may thus provide an insight into the profibrogenic role of Wnt/β-catenin and NOX4 crosstalk in lung epithelial cell injury and pathogenesis of silicosis.

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.

Growth Hormone-Releasing Hormone in Lung Physiology and Pulmonary Disease

Growth hormone-releasing hormone (GHRH) is secreted primarily from the hypothalamus, but other tissues, including the lungs, produce it locally. GHRH stimulates the release and secretion of growth hormone (GH) by the pituitary and regulates the production of GH and hepatic insulin-like growth factor-1 (IGF-1). Pituitary-type GHRH-receptors (GHRH-R) are expressed in human lungs, indicating that GHRH or GH could participate in lung development, growth, and repair. GHRH-R antagonists (i.e., synthetic peptides), which we have tested in various models, exert growth-inhibitory effects in lung cancer cells in vitro and in vivo in addition to having anti-inflammatory, anti-oxidative, and pro-apoptotic effects. One antagonist of the GHRH-R used in recent studies reviewed here, MIA-602, lessens both inflammation and fibrosis in a mouse model of bleomycin lung injury. GHRH and its peptide agonists regulate the proliferation of fibroblasts through the modulation of extracellular signal-regulated kinase (ERK) and Akt pathways. In addition to downregulating GH and IGF-1, GHRH-R antagonist MIA-602 inhibits signaling pathways relevant to inflammation, including p21-activated kinase 1-signal transducer and activator of transcription 3/nuclear factor-kappa B (PAK1-STAT3/NF-κB and ERK). MIA-602 induces fibroblast apoptosis in a dose-dependent manner, which is an effect that is likely important in antifibrotic actions. Taken together, the novel data reviewed here show that GHRH is an important peptide that participates in lung homeostasis, inflammation, wound healing, and cancer; and GHRH-R antagonists may have therapeutic potential in lung diseases.

Pulmonary Aptamer Signatures in Children's Interstitial and Diffuse Lung Disease

Rationale: Biomarker signatures are needed in children with children's interstitial and diffuse lung disease (chILD) to improve diagnostic approaches, increase our understanding of disease pathogenesis, monitor disease progression, and develop new treatment strategies. Proteomic technology using SOMAmer (Slow Off-rate Modified Aptamer) nucleic acid-based protein-binding reagents allows for biomarker discovery.Objectives: We hypothesized that proteins and protein pathways in BAL fluid (BALF) would distinguish children with neuroendocrine cell hyperplasia of infancy (NEHI), surfactant dysfunction mutations, and other chILD diagnoses and control subjects.Methods: BALF was collected for clinical indications and banked in patients with chILD and disease control subjects using standardized protocols over 10 years. BALF supernatant was analyzed using an aptamer assay to measure 1,129 protein levels. Protein levels were compared between groups using an ANOVA and adjusted for multiple comparisons using false discovery rate. Proteins were classified into pathways. Hierarchical clustering was used to define endotypes in the group of children with NEHI.Measurements and Main Results: After correcting for multiple testing, children with NEHI (n = 22) had 202 aptamers that were significantly different (P < 0.05) in BALF compared with control subjects (n = 9). Children with surfactant mutation (n = 8) had 51 aptamers significantly different (P < 0.05) in BALF compared with control subjects (n = 9). Proteins associated with pulmonary fibrosis and inflammation were associated with the surfactant dysfunction group but not the NEHI group. Using hierarchical clustering analysis, two distinct NEHI endotypes were identified.Conclusions: Distinct proteins and protein pathways can be determined from BALF of children with chILD, and these hold promise to further our understanding of chILD.

Fine-particulate matter aggravates cigarette smoke extract-induced airway inflammation via Wnt5a-ERK pathway in COPD

Background

Exposure to environmental particulate matter (PM) ≤2.5 μm in diameter (PM_2.5) and smoking are common contributors to COPD, and pertinent research implicates both factors in pulmonary inflammation. Using in vivo mouse and in vitro human cellular models, we investigated the joint impact of PM_2.5 pollution, and cigarette smoke (CS) in mice or cigarette-smoke extract (CSE) in cells on COPD inflammation, and explored potential mechanisms.

Methods

Tissue changes in lungs of C57BL/6 mice exposed to PM_2.5 and CS were studied by light microscopy, H&E, immunochemistry, and immunofluorescence-stained sections. Levels of inflammatory factors induced by PM_2.5/CS in mice and PM_2.5/CSE in 16HBE cells were also monitored by quantitative reverse-transcription (qRT)-PCR and ELISA. Expression of genes related to the Wnt5a-signaling pathway was assessed at transcriptional and protein levels using immunofluorescence, qRT-PCR, and Western blotting.

Results

Inflammatory response to combined exposure of PM_2.5 and CS or CSE in mouse and 16HBE cells surpassed responses incited separately. Although separate PM_2.5 and CS/CSE exposure upregulated the expression of Wnt5a (a member of the Wnt-secreted glycoprotein family), combined PM_2.5 and CS/CSE exposure produced a steeper rise in Wnt5a levels. Use of a Wnt5a antagonist (BOX5) successfully blocked related inflammatory effects. ERK phosphorylation appeared to mediate the effects of Wnt5a in the COPD model, promoting PM_2.5 aggravation of CS/CSE-induced airway inflammation.

Conclusion

Our findings suggest that combined PM_2.5 and CS/CSE exposure induce airway inflammation and Wnt5a expression in vivo in mice and in vitro in 16HBE cells. Furthermore, PM_2.5 seems to aggravate CS/CSE-induced inflammation via the Wnt5a–ERK pathway in the context of COPD.

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.

Lung Repair and Regeneration in ARDS: Role of PECAM1 and Wnt Signaling

ARDS is an acute inflammatory pulmonary process triggered by severe pulmonary and systemic insults to the alveolar-capillary membrane. This causes increased vascular permeability and the development of interstitial and alveolar protein-rich edema, leading to acute hypoxemic respiratory failure. Supportive treatment includes the use of lung-protective ventilatory strategies that decrease the work of breathing, can improve oxygenation, and minimize ventilator-induced lung injury. Despite substantial advances in supportive measures, there are no specific pharmacologic treatments for ARDS, and the overall hospital mortality rate remains about 40% in most series. The pathophysiology of ARDS involves interactions among multiple mechanisms, including immune cell infiltration, cytokine storm, alveolar-capillary barrier disruption, cell apoptosis, and the development of fibrosis. Here we review some new developments in the molecular basis of lung injury, with a focus on possible novel pharmacologic interventions aimed at improving the outcomes of patients with ARDS. Our focus is on platelet-endothelial cell adhesion molecule-1, which contributes to the maintenance and restoration of vascular integrity following barrier disruption. We also highlight the wingless-related integration site signaling pathway, which appears to be a central mechanism for lung healing as well as for fibrotic development.

Downregulation of WNT11 is associated with bladder tissue fibrosis in patients with interstitial cystitis/bladder pain syndrome without Hunner lesion

This study assessed the functional role of WNT genes and the association between WNT signalling cascades and fibrosis in interstitial cystitis/bladder pain syndrome (IC/BPS) patients. Twenty-five patients (3 males, 22 females; mean age 59.7 ± 10.9 years), included 7 non-Hunner-type IC (NHIC), 18 Hunner-type IC (HIC), and 5 non-IC (control) groups. The expression of sonic hedgehog, WNT gene family, and genes previously reported as biomarkers for IC/BPS were examined using RT-PCR in biopsy specimens from the mucosa and submucosa layer of the bladder. WNT2B, WNT5A, WNT10A, and WNT11 functions in the urothelium were evaluated by silencing in an HBlEpC cell line. Pelvic Pain and Urgency/Frequency Patient Symptom Scale scores, O’Leary-Sant Symptom and Problem Index scores, and Visual Analogue Scores did not differ between the NHIC and HIC groups. However, HIC patients had significantly shorter symptom duration (30.9 vs 70.8 months, p = 0.046), higher daily urinary frequency (16.1 versus 8.5 times, p = 0.006), and smaller bladder capacity (208.6 versus 361.4 ml, p = 0.006) than NHIC patients. Overall WNT gene expression was lower in NHIC than HIC patients. Bladder epithelial tissues from HIC patients were characterised by the downregulation of WNT11. Silencing of WNT11, WNT2B, WNT5A, and WNT10A in HBlEpCs resulted in fibrotic changes, indicated by fibrotic morphology, increased fibrosis-related gene expression, and nuclear localisation of phosphorylated SMAD2, and increased vimentin and fibronectin levels. Downregulation of WNT11 results in fibrotic changes of bladder epithelial cells and is associated with the pathogenesis and differential diagnosis of NHIC. Decreased expression of WNT11 is a potential biomarker for predicting NHIC.

The hedgehog and Wnt/β-catenin system machinery mediate myofibroblast differentiation of LR-MSCs in pulmonary fibrogenesis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal lung disease that is characterized by enhanced changes in stem cell differentiation and fibroblast proliferation. Resident mesenchymal stem cells (LR-MSCs) can undergo phenotype conversion to myofibroblasts to augment extracellular matrix production, impairing function and contributing to pulmonary fibrosis. Hedgehog and Wnt signaling are developmental signal cascades that play an essential role in regulating embryogenesis and tissue homeostasis. Recently, it has been reported that both hedgehog and Wnt signaling play important roles in pulmonary fibrogenesis. Thus, the identification of specific target regulators may yield new strategy for pulmonary fibrosis therapies. In our work, we demonstrated the critical role of Gli1, Wnt7b, Wnt10a and Fzd10 in the process of pulmonary fibrogenesis in vitro and in vivo. Gli1 was induced in LR-MSCs following TGF-β1 treatment and fibrotic lung tissues. Inhibition of Gli1 suppressed myofibroblast differentiation of LR-MSCs and pulmonary fibrosis, and decreased the expression of Wnt7b, Wnt10a and β-catenin. Gli1 bound to and increased promoter activity of the Wnt7b and Wnt10a genes, and Wnt7b and Wnt10a were critical activators of Wnt/β-catenin signaling. It was noteworthy that Fzd10 knockdown reduced Wnt7b and Wnt10a-induced activation of Wnt/β-catenin signaling, which imply that Wnt7b and Wnt10a may be the ligands for Fzd10. Moreover, siRNA-mediated inhibition of Fzd10 prevented TGF-β1-induced myofibroblast differentiation of LR-MSCs in vitro and impaired bleomycin-induced pulmonary fibrosis. We conclude that hedgehog and Wnt/β-catenin signaling play a critical role in promoting myofibroblast differentiation of LR-MSCs and development of pulmonary fibrosis. These findings elucidate a therapeutic approach to attenuate pulmonary fibrosis through targeted inhibition of Gli1 or Fzd10.

The Wnt7b/β-catenin signaling pathway is involved in the protective action of calcitonin gene-related peptide on hyperoxia-induced lung injury in premature rats

Background

Calcitonin gene-related peptide (CGRP) can protect against hyperoxia-induced lung injury, making the upregulation of CGRP a potential therapeutic approach for this type of injury. However, the effects of CGRP on the Wnt7b/β-catenin signaling pathway are unclear. In this study, we investigated the roles of CGRP and the Wnt7b/β-catenin signaling pathway in hyperoxia-induced lung injury.

Methods

Premature Sprague Dawley (SD) rats were exposed to 21, 40, 60 and 95% oxygen for 3, 7 and 14 days. The animals’ body weights, survival rates and endogenous CGRP levels were measured. Lung samples were harvested for histological analyses and measurements of malondialdehyde (MDA) concentration and total antioxidant capacity (TAOC). We also assessed the MDA concentration and TAOC in the lung tissues after administration of 200 nmol/kg CGRP_8–37 (a CGRP antagonist). Finally, alveolar epithelial type II (AEC II) cells were isolated from premature rats, exposed to 21 or 95% oxygen for 3, 7 and 14 days, and treated with 10^− 8 mol/l exogenous CGRP. The protein expressions of Wnt7b and β-catenin were assessed using western blotting, and TCF and c-myc mRNA expressions were assessed using qPCR.

Results

Rats exposed to 60 and 95% oxygen had significantly lower body weights and survival rates than the 21 and 40% groups, and the decrease was time dependent. Endogenous CGRP was elevated in the lung tissues of premature rats exposed to 95% oxygen. CGRP_8–37 induced apparent inflammation in the lung tissue and alveolar structural remodeling. In addition, the expression levels of Wnt7b and β-catenin were markedly increased after exposure for 3 days. They peaked at 7 days, then declined at 14 days. The levels of TCF/c-myc in AEC II cells increased significantly after CGRP treatment when compared with cells that had only undergone hyperoxia.

Conclusions

CGRP protected against hyperoxia-induced lung injury in premature rats. This process involves the Wnt7b/β-catenin signaling pathway.

Lrp5/β-Catenin Signaling Controls Lung Macrophage Differentiation and Inhibits Resolution of Fibrosis

Previous studies established that attenuating Wnt/β-catenin signaling limits lung fibrosis in the bleomycin mouse model of this disease, but the contribution of this pathway to distinct lung cell phenotypes relevant to tissue repair and fibrosis remains incompletely understood. Using microarray analysis, we found that bleomycin-injured lungs from mice that lack the Wnt coreceptor low density lipoprotein receptor-related protein 5 (Lrp5) and exhibit reduced fibrosis showed enrichment for pathways related to extracellular matrix processing, immunity, and lymphocyte proliferation, suggesting the contribution of an immune-matrix remodeling axis relevant to fibrosis. Activation of β-catenin signaling was seen in lung macrophages using the β-catenin reporter mouse, Axin2^+/LacZ. Analysis of lung immune cells by flow cytometry after bleomycin administration revealed that Lrp5^-/- lungs contained significantly fewer Siglec F^low alveolar macrophages, a cell type previously implicated as positive effectors of fibrosis. Macrophage-specific deletion of β-catenin in CD11c^cre;β-catenin^flox mice did not prevent development of bleomycin-induced fibrosis but facilitated its resolution by 8 weeks. In a nonresolving model of fibrosis, intratracheal administration of asbestos in Lrp5^-/- mice also did not prevent the development of fibrosis but hindered the progression of fibrosis in asbestos-treated Lrp5^-/- lungs, phenocopying the findings in bleomycin-treated CD11c^cre;β-catenin^flox mice. Activation of β-catenin signaling using lithium chloride resulted in worsened fibrosis in wild-type mice, further supporting that the effects of loss of Lrp5 are directly mediated by Wnt/β-catenin signaling. Together, these data suggest that lung myeloid cells are responsive to Lrp5/β-catenin signaling, leading to differentiation of an alveolar macrophage subtype that antagonizes the resolution of lung fibrosis.

Distinct Roles of Wnt/β-Catenin Signaling in the Pathogenesis of Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis

Wnt signaling pathways are tightly controlled under a physiological condition, under which they play key roles in many biological functions, including cell fate specification and tissue regeneration. Increasing lines of evidence recently demonstrated that a dysregulated activation of Wnt signaling, particularly the Wnt/β-catenin signaling, was involved in the pathogenesis of chronic pulmonary diseases, such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). In this respect, Wnt signaling interacts with other cellular signaling pathways to regulate the initiation and pathogenic procedures of airway inflammation and remodeling, pulmonary myofibroblast proliferation, epithelial-to-mesenchymal transition (EMT), and development of emphysema. Intriguingly, Wnt/β-catenin signaling is activated in IPF; an inhibition of this signaling leads to an alleviation of pulmonary inflammation and fibrosis in experimental models. Conversely, Wnt/β-catenin signaling is inactivated in COPD tissues, and its reactivation results in an amelioration of airspace enlargement with a restored alveolar epithelial structure and function in emphysema models. These studies thus imply distinct mechanisms of Wnt/β-catenin signaling in the pathogenesis of these two chronic pulmonary diseases, indicating potential targets for COPD and IPF treatments. This review article aims to summarize the involvement and pathogenic roles of Wnt signaling pathways in the COPD and IPF, with a focus on the implication of Wnt/β-catenin signaling as underlying mechanisms and therapeutic targets in these two incurable diseases.

Galectin-1 inhibition attenuates profibrotic signaling in hypoxia-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by lung remodeling arising from epithelial injury, aberrant fibroblast growth, and excessive deposition of extracellular matrix. Repeated epithelial injury elicits abnormal wound repair and lung remodeling, often associated with alveolar collapse and edema, leading to focal hypoxia. Here, we demonstrate that hypoxia is a physiological insult that contributes to pulmonary fibrosis (PF) and define its molecular roles in profibrotic activation of lung epithelial cells. Hypoxia increased transcription of profibrotic genes and altered the proteomic signatures of lung epithelial cells. Network analysis of the hypoxic epithelial proteome revealed a crosstalk between transforming growth factor-β1 and FAK1 (focal adhesion kinase-1) signaling, which regulated transcription of galectin-1, a profibrotic molecule. Galectin-1 physically interacted with and activated FAK1 in lung epithelial cells. We developed a novel model of exacerbated PF wherein hypoxia, as a secondary insult, caused PF in mice injured with subclinical levels of bleomycin. Hypoxia elevated expression of phosphorylated FAK1, galectin-1, and α-smooth muscle actin and reduced caspase-3 activation, suggesting aberrant injury repair. Galectin-1 inhibition caused apoptosis in the lung parenchyma and reduced FAK1 activation, preventing the development of hypoxia-induced PF. Galectin-1 inhibition also attenuated fibrosis-associated lung function decline. Further, galectin-1 transcript levels were increased in the lungs of IPF patients. In summary, we have identified a profibrotic role of galectin-1 in hypoxia signaling driving PF.

Selective inhibitor of Wnt/β-catenin/CBP signaling ameliorates hepatitis C virus-induced liver fibrosis in mouse model

Chronic hepatitis C virus (HCV) infection is one of the major causes of serious liver diseases, including liver cirrhosis. There are no anti-fibrotic drugs with efficacy against liver cirrhosis. Wnt/β-catenin signaling has been implicated in the pathogenesis of a variety of tissue fibrosis. In the present study, we investigated the effects of a β-catenin/CBP (cyclic AMP response element binding protein) inhibitor on liver fibrosis. The anti-fibrotic activity of PRI-724, a selective inhibitor of β-catenin/CBP, was assessed in HCV GT1b transgenic mice at 18 months after HCV genome expression. PRI-724 was injected intraperitoneally or subcutaneously in these mice for 6 weeks. PRI-724 reduced liver fibrosis, which was indicated by silver stain, Sirius Red staining, and hepatic hydroxyproline levels, in HCV mice while attenuating αSMA induction. PRI-724 led to increased levels of matrix metalloproteinase (MMP)-8 mRNA in the liver, along with elevated levels of intrahepatic neutrophils and macrophages/monocytes. The induced intrahepatic neutrophils and macrophages/monocytes were identified as the source of MMP-8. In conclusion, PRI-724 ameliorated HCV-induced liver fibrosis in mice. We hypothesize that inhibition of hepatic stellate cells activation and induction of fibrolytic cells expressing MMP-8 contribute to the anti-fibrotic effects of PRI-724. PRI-724 is a drug candidate which possesses anti-fibrotic effect.

Loss of lung WWOX expression causes neutrophilic inflammation

The tumor suppressor WW domain-containing oxidoreductase (WWOX) exhibits regulatory interactions with an array of transcription factors and signaling molecules that are positioned at the well-known crossroads between inflammation and cancer. WWOX is also subject to downregulation by genotoxic environmental exposures, making it of potential interest to the study of lung pathobiology. Knockdown of lung WWOX expression in mice was observed to cause neutrophil influx and was accompanied by a corresponding vascular leak and inflammatory cytokine production. In cultured human alveolar epithelial cells, loss of WWOX expression resulted in increased c-Jun- and IL-8-dependent neutrophil chemotaxis toward cell monolayers. WWOX was observed to directly interact with c-Jun in these cells, and its absence resulted in increased nuclear translocation of c-Jun. Finally, inhibition of the c-Jun-activating kinase JNK abrogated the lung neutrophil influx observed during WWOX knockdown in mice. Altogether, these observations represent a novel mechanism of pulmonary neutrophil influx that is highly relevant to the pathobiology and potential treatment of a number of different lung inflammatory conditions.

Myofibroblast repair mechanisms post-inflammatory response: a fibrotic perspective

INTRODUCTION

Fibrosis is a complex chronic disease characterized by a persistent repair response. Its pathogenesis is poorly understood but it is typically the result of chronic inflammation and maintained with the required activity of transforming growth factor-β (TGFβ) and extracellular matrix (ECM) tension, both of which drive fibroblasts to transition into a myofibroblast phenotype.

FINDINGS

As the effector cells of repair, myofibroblasts migrate to the site of injury to deposit excessive amounts of matrix proteins and stimulate high levels of contraction. Myofibroblast activity is a decisive factor in whether a tissue is properly repaired by controlled wound healing or rendered fibrotic by deregulated repair. Extensive studies have documented the various contributing factors to an abrogated repair response. Though these fibrotic factors are known, very little is understood about the opposing antifibrotic molecules that assist in a successful repair, such as prostaglandin E2 (PGE₂) and ECM retraction. The following review will discuss the general development of fibrosis through the transformation of myofibroblasts, focusing primarily on the prominent profibrotic pathways of TGFβ and ECM tension and antifibrotic pathways of PGE₂ and ECM retraction.

CONCLUSIONS

The idea is to understand the ways in which the cell, after an injury and inflammatory response, normally controls its repair mechanisms through its homeostatic regulators so as to mimic them therapeutically to control abnormal pathways.

Resveratrol attenuates hyperoxia-induced oxidative stress, inflammation and fibrosis and suppresses Wnt/β-catenin signalling in lungs of neonatal rats

Although survival rate of infants born prematurely has been raised by supplemental oxygen treatment, it is followed by high morbidity of hyperoxia-induced bronchopulmonary dysplasia. In this study, the effect of resveratrol on the lung injury was evaluated in hyperoxia-exposed rats of preterm birth. The results demonstrated that hyperoxia led to thickened alveolar wall, simplified alveolar architecture and fibrosis. In addition, elevated methane dicarboxylic aldehyde level, decreased glutathione level and superoxide dismutase activity were also found in hyperoxic lungs, as well as the increased tumor necrosis factor-α, interleukin-1β and interleukin-6 in the bronchoalveolar lavage fluid. Fibrotic-associated proteins transforming growth factor-β1, α-smooth muscle actin, collagen I and fibronectin deposition were also found in interstitial substance of lungs. Furthermore, Wnt/β-catenin signalling was found to be active in hyperoxia-induced lungs. In addition, expression of SP-C was increased and T1α was decreased in hyperoxia-exposed lungs. Resveratrol intraperitoneal administration alleviated hyperoxia-induced histological injury of lungs, regulated redox balance, decreased pro-inflammatory cytokine release, and down-regulated expression of fibrotic-associated proteins. Furthermore, Wnt/β-catenin signalling was also suppressed by resveratrol, as represented by diminished expression of lymphoid enhancer factor-1, Wnt induced signalling protein-1 and cyclin D1. In addition, the increase of SP-C and decrease of T1α expression was prevented as well. The present study showed that resveratrol could protect lungs from hyperoxia-induced injury through its antioxidant, anti-inflammatory and anti-fibrotic effects. The transdifferentiation of alveolar epithelial type II cells to alveolar epithelial type I cells promotion and Wnt/β-catenin signalling suppression are also involved in the protective effect.

Common pathway signature in lung and liver fibrosis

Fibrosis, a progressive accumulation of extracellular matrix components, encompasses a wide spectrum of distinct organs, and accounts for an increasing burden of morbidity and mortality worldwide. Despite the tremendous clinical impact, the mechanisms governing the fibrotic process are not yet understood, and to date, no clinically reliable therapies for fibrosis have been discovered. Here we applied Regeneration Intelligence, a new bioinformatics software suite for qualitative analysis of intracellular signaling pathway activation using transcriptomic data, to assess a network of molecular signaling in lung and liver fibrosis. In both tissues, our analysis detected major conserved signaling pathways strongly associated with fibrosis, suggesting that some of the pathways identified by our algorithm but not yet wet-lab validated as fibrogenesis related, may be attractive targets for future research. While the majority of significantly disrupted pathways were specific to histologically distinct organs, several pathways have been concurrently activated or downregulated among the hepatic and pulmonary fibrosis samples, providing new evidence of evolutionary conserved pathways that may be relevant as possible therapeutic targets. While future confirmatory studies are warranted to validate these observations, our platform proposes a promising new approach for detecting fibrosis-promoting pathways and tailoring the right therapy to prevent fibrogenesis.

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.

The roles of microRNAs and protein components of the microRNA pathway in lung development and diseases

Decades of studies have shown evolutionarily conserved molecular networks consisting of transcriptional factors, diffusing growth factors, and signaling pathways that regulate proper lung development. Recently, microRNAs (miRNAs), small, noncoding regulatory RNAs, have been integrated into these networks. Significant advances have been made in characterizing the developmental stage- or cell type-specific miRNAs during lung development by using approaches such as genome-wide profiling and in situ hybridization. Results from gain- or loss-of-function studies revealed pivotal roles of protein components of the miRNA pathway and individual miRNAs in regulating proliferation, apoptosis, differentiation, and morphogenesis during lung development. Aberrant expression or functions of these components have been associated with pulmonary disorders, suggesting their involvement in pathogenesis of these diseases. Moreover, genetically modified mice generated in these studies have become useful models of human lung diseases. Challenges in this field include characterization of collective function and responsible targets of miRNAs specifically expressed during lung development, and translation of these basic findings into clinically relevant information for better understanding of human diseases. The goal of this review is to discuss the recent progress on the understanding of how the miRNA pathway regulates lung development, how dysregulation of miRNA activities contributes to pathogenesis of related pulmonary diseases, and to identify relevant questions and future directions.

p300/β-Catenin Interactions Regulate Adult Progenitor Cell Differentiation Downstream of WNT5a/Protein Kinase C (PKC)

Maintenance of stem/progenitor cell-progeny relationships is required for tissue homeostasis during normal turnover and repair. Wnt signaling is implicated in both maintenance and differentiation of adult stem/progenitor cells, yet how this pathway serves these dichotomous roles remains enigmatic. We previously proposed a model suggesting that specific interaction of β-catenin with either of the homologous Kat3 co-activators, p300 or CREB-binding protein, differentially regulates maintenance versus differentiation of embryonic stem cells. Limited knowledge of endogenous mechanisms driving differential β-catenin/co-activator interactions and their role in adult somatic stem/progenitor cell maintenance versus differentiation led us to explore this process in defined models of adult progenitor cell differentiation. We focused primarily on alveolar epithelial type II (AT2) cells, progenitors of distal lung epithelium, and identified a novel axis whereby WNT5a/protein kinase C (PKC) signaling regulates specific β-catenin/co-activator interactions to promote adult progenitor cell differentiation. p300/β-catenin but not CBP/β-catenin interaction increases as AT2 cells differentiate to a type I (AT1) cell-like phenotype. Additionally, p300 transcriptionally activates AT1 cell-specific gene Aqp-5. IQ-1, a specific inhibitor of p300/β-catenin interaction, prevents differentiation of not only primary AT2 cells, but also tracheal epithelial cells, and C2C12 myoblasts. p300 phosphorylation at Ser-89 enhances p300/β-catenin interaction, concurrent with alveolar epithelial cell differentiation. WNT5a, a traditionally non-canonical WNT ligand regulates Ser-89 phosphorylation and p300/β-catenin interactions in a PKC-dependent manner, likely involving PKCζ. These studies identify a novel intersection of canonical and non-canonical Wnt signaling in adult progenitor cell differentiation that has important implications for targeting β-catenin to modulate adult progenitor cell behavior in disease.

Expression of WNT5A in Idiopathic Pulmonary Fibrosis and Its Control by TGF-β and WNT7B in Human Lung Fibroblasts

The wingless (Wnt) family of signaling ligands contributes significantly to lung development and is highly expressed in patients with usual interstitial pneumonia (UIP). We sought to define the cellular distribution of Wnt5A in the lung tissue of patients with idiopathic pulmonary fibrosis (IPF) and the signaling ligands that control its expression in human lung fibroblasts and IPF myofibroblasts. Tissue sections from 40 patients diagnosed with IPF or UIP were probed for the immunolocalization of Wnt5A. Further, isolated lung fibroblasts from normal or IPF human lungs, adenovirally transduced for the overexpression or silencing of Wnt7B or treated with TGF-β1 or its inhibitor, were analyzed for Wnt5A protein expression. Wnt5A was expressed in IPF lungs by airway and alveolar epithelium, smooth muscle cells, endothelium, and myofibroblasts of fibroblastic foci and throughout the interstitium. Forced overexpression of Wnt7B with or without TGF-β1 treatment significantly increased Wnt5A protein expression in normal human smooth muscle cells and fibroblasts but not in IPF myofibroblasts where Wnt5A was already highly expressed. The results demonstrate a wide distribution of Wnt5A expression in cells of the IPF lung and reveal that it is significantly increased by Wnt7B and TGF-β1, which, in combination, could represent key signaling pathways that modulate the pathogenesis of IPF.

β-Catenin Signaling and Roles in Liver Homeostasis, Injury, and Tumorigenesis

β-catenin (encoded by CTNNB1) is a subunit of the cell surface cadherin protein complex that acts as an intracellular signal transducer in the WNT signaling pathway; alterations in its activity have been associated with the development of hepatocellular carcinoma and other liver diseases. Other than WNT, additional signaling pathways also can converge at β-catenin. β-catenin also interacts with transcription factors such as T-cell factor, forkhead box protein O, and hypoxia inducible factor 1α to regulate the expression of target genes. We discuss the role of β-catenin in metabolic zonation of the adult liver. β-catenin also regulates the expression of genes that control metabolism of glucose, nutrients, and xenobiotics; alterations in its activity may contribute to the pathogenesis of nonalcoholic steatohepatitis. Alterations in β-catenin signaling may lead to activation of hepatic stellate cells, which is required for fibrosis. Many hepatic tumors such as hepatocellular adenomas, hepatocellular cancers, and hepatoblastomas have mutations in CTNNB1 that result in constitutive activation of β-catenin, so this molecule could be a therapeutic target. We discuss how alterations in β-catenin activity contribute to liver disease and how these might be used in diagnosis and prognosis, as well as in the development of therapeutics.

Expression profile of plasma microRNAs in premature infants with respiratory distress syndrome

As well-known regulators of gene expression, microRNAs (miRNAs) are important not only in cell proliferation and differentiation, but also in tumorigenesis and organ development. It has been estimated that miRNAs may be responsible for regulating the expression of almost one third of the human genome. Simultaneously, with advances in neonatal care in the clinic, an increased number of premature infants are being saved and, thus, respiratory distress syndrome (RDS) has become more common. However, previous non-miRNA studies have suggested their connection with RDS. In the present study, a miRNA microarray, including >1,891 capture probes was used to compared the expression profiles of plasma miRNAs between RDS and control groups. miRNAs, which were observed to have consistent fold-changes (fold-change ≥ 1.3) between the two groups were selected and validated using reverse transcription-quantitative polymerase chain reaction. As a result, 171 differentially expressed miRNAs were identified, including two upregulated and seven downregulated miRNAs. Of these miRNAs, four were selected as having higher fold-changes between the two groups. This is the first time, to the best of our knowledge, that these nine miRNAs have been reported in RDS. It was hypothesized that these novel miRNAs may be important in RDS, and may provide meaningful biomarkers for the diagnosis of RDS.

Early activation of pro-fibrotic WNT5A in sepsis-induced acute lung injury

INTRODUCTION

The mechanisms of lung repair and fibrosis in the acute respiratory distress syndrome (ARDS) are poorly known. Since the role of WNT/β-catenin signaling appears to be central to lung healing and fibrosis, we hypothesized that this pathway is activated very early in the lungs after sepsis.

METHODS

We tested our hypothesis using a three-step experimental design: (1) in vitro lung cell injury model with human bronchial epithelial BEAS-2B and lung fibroblasts (MRC-5) cells exposed to endotoxin for 18 hours; (2) an animal model of sepsis-induced ARDS induced by cecal ligation and perforation, and (3) lung biopsies from patients who died within the first 24 hours of septic ARDS. We examined changes in protein levels of target genes involved in the Wnt pathway, including WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, matrix metalloproteinase-7 (MMP7), cyclin D1, and vascular endothelial growth factor (VEGF) by Western blotting and immunohistochemistry. Finally, we validated the main gene targets of this pathway in experimental animals and human lungs.

RESULTS

Protein levels of WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, total β-catenin, MMP7, cyclin D1, and VEGF increased after endotoxin stimulation in BEAS-2B and MRC-5 cells. Lungs from septic animals and from septic humans demonstrated acute lung inflammation, collagen deposition, and marked increase of WNT5A and MMP7 protein levels.

CONCLUSIONS

Our findings suggest that the WNT/β-catenin signaling pathway is activated very early in sepsis-induced ARDS and could play an important role in lung repair and fibrosis. Modulation of this pathway might represent a potential target for treatment for septic and ARDS patients.

Alveolar epithelium: beyond the barrier

I am deeply honored to have been awarded an American Thoracic Society Recognition Award for Scientific Accomplishment for 2014. Over the last 20 years, it has become clear that the alveolar epithelium, my area of research focus, is not simply a gas exchange surface and barrier to leakage of fluid and protein into the alveoli, but is an active participant in the pathogenesis of a number of lung diseases, including pulmonary fibrosis. Recognition by this Award stimulates a review of the awardee's contributions to the field, as summarized in this perspective.

β-catenin is overexpressed in hepatic fibrosis and blockage of Wnt/β-catenin signaling inhibits hepatic stellate cell activation

β-catenin, a core component of Wnt/β-catenin signaling, has been shown to be an important regulator of cellular proliferation and differentiation. Abnormal activation of Wnt/β-catenin signaling promotes tissue fibrogenesis. In the present study, the role of β-catenin during liver fibrogenesis was analyzed and the functional effects of β-catenin gene silencing in hepatic stellate cells (HSCs) using small interfering (si)RNA were investigated. The expression of β-catenin in human hepatic fibrosis tissues of different grades and normal human hepatic tissues was examined using immunohistochemistry. To inhibit the Wnt/β-catenin signaling pathway, siRNA for β-catenin was developed and transiently transfected into HSC-T6 cells using Lipofectamine 2000. β-catenin expression was evaluated by quantitative polymerase chain reaction (qPCR) and western blot analysis. The expression of collagen types I and III was evaluated by qPCR and immunofluorescent staining. Cellular proliferation and the cell cycle were analyzed using a methyl thiazolyl tetrazolium assay. Apoptosis was assessed by Annexin V staining. A higher expression level of β-catenin was identified in the patients with high-grade hepatic fibrosis in comparison with that of the normal controls. Additionally, β-catenin siRNA molecules were successfully transfected into HSCs and induced inhibition of β-catenin expression in a time-dependent manner. β-catenin siRNA treatment also inhibited synthesis of collagen types I and I in transfected HSCs. Furthermore, compared with those of the control group, siRNA-mediated knockdown of β-catenin in HSC-T6 cells inhibited cell proliferation and resulted in cell apoptosis. This study suggests a significant functional role for β-catenin in the development of liver fibrosis and demonstrates that downregulation of the Wnt/β-catenin signaling pathway inhibits HSC activation. Thus, this study provides a novel strategy for the treatment of hepatic fibrosis.

β-catenin is overexpressed in hepatic fibrosis and blockage of Wnt/β-catenin signaling inhibits hepatic stellate cell activation

β-catenin, a core component of Wnt/β-catenin signaling, has been shown to be an important regulator of cellular proliferation and differentiation. Abnormal activation of Wnt/β-catenin signaling promotes tissue fibrogenesis. In the present study, the role of β-catenin during liver fibrogenesis was analyzed and the functional effects of β-catenin gene silencing in hepatic stellate cells (HSCs) using small interfering (si)RNA were investigated. The expression of β-catenin in human hepatic fibrosis tissues of different grades and normal human hepatic tissues was examined using immunohistochemistry. To inhibit the Wnt/β-catenin signaling pathway, siRNA for β-catenin was developed and transiently transfected into HSC-T6 cells using Lipofectamine 2000. β-catenin expression was evaluated by quantitative polymerase chain reaction (qPCR) and western blot analysis. The expression of collagen types Ⅰ and Ⅲ was evaluated by qPCR and immunofluorescent staining. Cellular proliferation and the cell cycle were analyzed using a methyl thiazolyl tetrazolium assay. Apoptosis was assessed by Annexin V staining. A higher expression level of β-catenin was identified in the patients with high-grade hepatic fibrosis in comparison with that of the normal controls. Additionally, β-catenin siRNA molecules were successfully transfected into HSCs and induced inhibition of β-catenin expression in a time-dependent manner. β-catenin siRNA treatment also inhibited synthesis of collagen types Ⅰ and Ⅲ in transfected HSCs. Furthermore, compared with those of the control group, siRNA-mediated knockdown of β-catenin in HSC-T6 cells inhibited cell proliferation and resulted in cell apoptosis. This study suggests a significant functional role for β-catenin in the development of liver fibrosis and demonstrates that downregulation of the Wnt/β-catenin signaling pathway inhibits HSC activation. Thus, this study provides a novel strategy for the treatment of hepatic fibrosis.

Protective effect of the herbal medicine Gan‑fu‑kang against carbon tetrachloride‑induced liver fibrosis in rats

The aim of the present study was to investigate the effect of a herbal medicine formula, Gan-fu-kang (GFK), on the treatment of liver fibrosis in rats and the mechanisms via which it exerts its effect. Liver fibrosis was induced in rats by subcutaneous injection of carbon tetrachloride (CCl4) at 0.5 mg/kg body weight, twice a week for 8 weeks. The rats were randomly selected to receive saline or GFK at 31.25, 312.5 or 3,125 mg/kg body weight/day between weeks 9 and 20. An additional group of rats without CCl4 injection was used as the baseline. In the liver fibrosis model rats, an increase in plasma liver enzymes, fibrotic markers in serum and liver fibrosis, production of α-smooth muscle actin, matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-1, synthesis of collagen and activation of the Wnt/β-catenin signaling pathway were observed. GFK administration was found to significantly reduce these changes. Results of this study demonstrate that GFK has a protective and therapeutic effect on liver fibrosis induced by CCl4, which may be associated with its inhibitory activity on HSC proliferation and collagen synthesis, effectively downregulating Wnt/β-catenin signaling.

Expression of fibroblast growth factor 9 in normal human lung and idiopathic pulmonary fibrosis

The fibroblast growth factor (FGF) family of signaling ligands contributes significantly to lung development and maintenance in the adult. FGF9 is involved in control of epithelial branching and mesenchymal proliferation and expansion in developing lungs. However, its activity and expression in the normal adult lung and by epithelial and interstitial cells in fibroproliferative diseases like idiopathic pulmonary fibrosis (IPF) are unknown. Tissue samples from normal organ donor human lungs and those of a cohort of patients with mild to severe IPF were sectioned and stained for the immunolocalization of FGF9. In normal lungs, FGF9 was confined to smooth muscle surrounding airways, alveolar ducts and sacs, and blood vessels. In addition to these same sites, lungs of IPF patients expressed FGF9 in a population of myofibroblasts within fibroblastic foci, hypertrophic and hyperplastic epithelium of airways and alveoli, and smooth muscle cells surrounding vessels embedded in thickened interstitium. The results demonstrate that FGF9 protein increased in regions of active cellular hyperplasia, metaplasia, and fibrotic expansion of IPF lungs, and in isolated human lung fibroblasts treated with TGF-β1 and/or overexpressing Wnt7B. The cellular distribution and established biologic activity of FGF9 make it a potentially strong candidate for contributing to the progression of IPF.

Inhibition of LRP5/6-mediated Wnt/β-catenin signaling by Mesd attenuates hyperoxia-induced pulmonary hypertension in neonatal rats

BACKGROUND

Hyperoxia-induced neonatal lung injury is associated with activation of Wnt/β-catenin signaling. Low-density lipoprotein receptor-related proteins 5 and 6 (LRP5/6) are Wnt coreceptors that bind to Wnt ligands and mediate canonical Wnt/β-catenin signaling. We hypothesized that inhibition of LRP5/6 by their universal inhibitor, Mesd, would attenuate hyperoxia-induced lung injury.

METHODS

Newborn rat pups were randomly exposed to normoxia or hyperoxia at 90% FiO2 and injected intraperitoneally with placebo or Mesd every other day for 14 d. On day 15, phosphorylation of LRP5/6 (pLRP5/6), expression of Wnt/β-catenin target genes, cyclin D1 and Wnt-induced signaling protein-1 (WISP-1), right-ventricular systolic pressure (RVSP), right-ventricular hypertrophy (RVH), pulmonary vascular remodeling, alveolarization, and vascularization were measured.

RESULTS

Hyperoxia exposure markedly induced pLRP5/6, cyclin D1, and WISP-1 expression in the lungs of placebo animals, but they were significantly attenuated by the administration of Mesd. Mesd also significantly attenuated hyperoxia-induced pulmonary hypertension (PH) and pulmonary vascular remodeling. However, there was no effect on alveolarization or vascularization after Mesd administration.

CONCLUSION

This study demonstrates that LRP5/6 mediates pulmonary vascular remodeling and PH in hyperoxia-induced neonatal lung injury, thereby suggesting a potential therapeutic target to alleviate PH in neonates with severe bronchopulmonary dysplasia.

miR-375 regulates rat alveolar epithelial cell trans-differentiation by inhibiting Wnt/β-catenin pathway

Alveolar epithelial cell (AEC) trans-differentiation is a process where type II alveolar epithelial cells (AEC II) trans-differentiate into type I alveolar epithelial cells (AEC I) during lung recovery after various injuries, in which AEC I are damaged. This process is critical for lung tissue repair. MicroRNAs are a group of small RNAs that regulate gene expression at the post-transcriptional level. They have the potential to regulate almost every aspect of cell physiology. However, whether AEC trans-differentiation is regulated by microRNAs is completely unknown. In this study, we found that miR-375 was downregulated during AEC trans-differentiation. The overexpression of miR-375 with an adenoviral vector inhibited alveolar epithelial trans-differentiation as indicated by an increase in the AEC II marker, surfactant protein C, and decreases in the AEC I markers, T1α and advanced glycosylation end product-specific receptor. miR-375 also inhibited the Wnt/β-catenin pathway. The constitutively activation of Wnt/β-catenin signaling with a stabilized form of β-catenin blocked the miR-375 effects. Frizzled 8 was identified as a target of miR-375. In summary, our results demonstrate that miR-375 regulates AEC trans-differentiation through the Wnt/β-catenin pathway. This discovery may provide new targets for therapeutic intervention to benefit lung recovery from injuries.

Role of β-catenin-regulated CCN matricellular proteins in epithelial repair after inflammatory lung injury

Repair of the lung epithelium after injury is integral to the pathogenesis and outcomes of diverse inflammatory lung diseases. We previously reported that β-catenin signaling promotes epithelial repair after inflammatory injury, but the β-catenin target genes that mediate this effect are unknown. Herein, we examined which β-catenin transcriptional coactivators and target genes promote epithelial repair after inflammatory injury. Transmigration of human neutrophils across cultured monolayers of human lung epithelial cells resulted in a fall in transepithelial resistance and the formation of discrete areas of epithelial denudation ("microinjury"), which repaired via cell spreading by 96 h. In mice treated with intratracheal (i.t.) LPS or keratinocyte chemokine, neutrophil emigration was associated with increased permeability of the lung epithelium, as determined by increased bronchoalveolar lavage (BAL) fluid albumin concentration, which decreased over 3-6 days. Activation of β-catenin/p300-dependent gene expression using the compound ICG-001 accelerated epithelial repair in vitro and in murine models. Neutrophil transmigration induced epithelial expression of the β-catenin/p300 target genes Wnt-induced secreted protein (WISP) 1 and cysteine-rich (Cyr) 61, as determined by real-time PCR (qPCR) and immunostaining. Purified neutrophil elastase induced WISP1 upregulation in lung epithelial cells, as determined by qPCR. WISP1 expression increased in murine lungs after i.t. LPS, as determined by ELISA of the BAL fluid and qPCR of whole lung extracts. Finally, recombinant WISP1 and Cyr61 accelerated repair, and Cyr61-neutralizing antibodies delayed repair of the injured epithelium in vitro. We conclude that β-catenin/p300-dependent expression of WISP1 and Cyr61 is critical for epithelial repair and represents a potential therapeutic target to promote epithelial repair after inflammatory injury.