Association of β-catenin with P-Smad3 but not LEF-1 dissociates in vitro profibrotic from anti-inflammatory effects of TGF-β1

Therapeutic potential of melatonin in targeting molecular pathways of organ fibrosis

Fibrosis, the excessive deposition of fibrous connective tissue in an organ in response to injury, is a pathological condition affecting many individuals worldwide. Fibrosis causes the failure of tissue function and is largely irreversible as the disease progresses. Pharmacologic treatment options for organ fibrosis are limited, but studies suggest that antioxidants, particularly melatonin, can aid in preventing and controlling fibrotic damage to the organs. Melatonin, an indole nocturnally released from the pineal gland, is commonly used to regulate circadian and seasonal biological rhythms and is indicated for treating sleep disorders. While it is often effective in treating sleep disorders, melatonin's anti-inflammatory and antioxidant properties also make it a promising molecule for treating other disorders such as organ fibrosis. Melatonin ameliorates the necrotic and apoptotic changes that lead to fibrosis in various organs including the heart, liver, lung, and kidney. Moreover, melatonin reduces the infiltration of inflammatory cells during fibrosis development. This article outlines the protective effects of melatonin against fibrosis, including its safety and potential therapeutic effects. The goal of this article is to provide a summary of data accumulated to date and to encourage further experimentation with melatonin and increase its use as an anti-fibrotic agent in clinical settings.

Ischemia-reperfusion injury: molecular mechanisms and therapeutic targets

Ischemia-reperfusion (I/R) injury paradoxically occurs during reperfusion following ischemia, exacerbating the initial tissue damage. The limited understanding of the intricate mechanisms underlying I/R injury hinders the development of effective therapeutic interventions. The Wnt signaling pathway exhibits extensive crosstalk with various other pathways, forming a network system of signaling pathways involved in I/R injury. This review article elucidates the underlying mechanisms involved in Wnt signaling, as well as the complex interplay between Wnt and other pathways, including Notch, phosphatidylinositol 3-kinase/protein kinase B, transforming growth factor-β, nuclear factor kappa, bone morphogenetic protein, N-methyl-D-aspartic acid receptor-Ca2+-Activin A, Hippo-Yes-associated protein, toll-like receptor 4/toll-interleukine-1 receptor domain-containing adapter-inducing interferon-β, and hepatocyte growth factor/mesenchymal-epithelial transition factor. In particular, we delve into their respective contributions to key pathological processes, including apoptosis, the inflammatory response, oxidative stress, extracellular matrix remodeling, angiogenesis, cell hypertrophy, fibrosis, ferroptosis, neurogenesis, and blood-brain barrier damage during I/R injury. Our comprehensive analysis of the mechanisms involved in Wnt signaling during I/R reveals that activation of the canonical Wnt pathway promotes organ recovery, while activation of the non-canonical Wnt pathways exacerbates injury. Moreover, we explore novel therapeutic approaches based on these mechanistic findings, incorporating evidence from animal experiments, current standards, and clinical trials. The objective of this review is to provide deeper insights into the roles of Wnt and its crosstalk signaling pathways in I/R-mediated processes and organ dysfunction, to facilitate the development of innovative therapeutic agents for I/R injury.

PSmad3+/Olig2- expression defines a subpopulation of gfap-GFP+/Sox9+ neural progenitors and radial glia-like cells in mouse dentate gyrus through embryonic and postnatal development

In mouse dentate gyrus, radial glia-like cells (RGLs) persist throughout life and play a critical role in the generation of granule neurons. A large body of evidence has shown that the combinatorial expression of transcription factors (TFs) defines cell types in the developing central nervous system (CNS). As yet, the identification of specific TFs that exclusively define RGLs in the developing mouse dentate gyrus (DG) remains elusive. Here we show that phospho-Smad3 (PSmad3) is expressed in a subpopulation of neural progenitors in the DG. During embryonic stage (E14-15), PSmad3 was predominantly expressed in gfap-GFP-positive (GFP+)/Sox2+ progenitors located at the lower dentate notch (LDN). As the development proceeds (E16-17), the vast majority of PSmad3+ cells were GFP+/Sox2+/Prox1low+/Ki67+ proliferative progenitors that eventually differentiated into granule neurons. During postnatal stage (P1-P6) PSmad3 expression was observed in GFP+ progenitors and astrocytes. Subsequently, at P14-P60, PSmad3 expression was found both in GFP+ RGLs in the subgranular zone (SGZ) and astrocytes in the molecular layer (ML) and hilus. Notably, PSmad3+ SGZ cells did not express proliferation markers such as PCNA and phospho-vimentin, suggesting that they are predominantly quiescent from P14 onwards. Significantly PSmad3+/GFP+ astrocytes, but not SGZ cells, co-expressed Olig2 and S100β. Together, PSmad3+/Olig2- expression serves as an exclusive marker for a specific subpopulation of GFP+ neural progenitors and RGLs in the mouse DG during both embryonic and postnatal period.

Molecular pathogenesis of subretinal fibrosis in neovascular AMD focusing on epithelial-mesenchymal transformation of retinal pigment epithelium

Age-related macular degeneration (AMD) is a leading cause of vision loss among elderly people in developed countries. Neovascular AMD (nAMD) accounts for more than 90% of AMD-related vision loss. At present, intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) is widely used as the first-line therapy to decrease the choroidal and retinal neovascularizations, and thus to improve or maintain the visual acuity of the patients with nAMD. However, about 1/3 patients still progress to irreversible visual impairment due to subretinal fibrosis even with adequate anti-VEGF treatment. Extensive literatures support the critical role of epithelial-mesenchymal transformation (EMT) of retinal pigment epithelium (RPE) in the pathogenesis of subretinal fibrosis in nAMD, but the underlying mechanisms still remain largely unknown. This review summarized the molecular pathogenesis of subretinal fibrosis in nAMD, especially focusing on the transforming growth factor-β (TGF-β)-induced EMT pathways. It was also discussed how these pathways crosstalk and respond to signals from the microenvironment to mediate EMT and contribute to the progression of nAMD-related subretinal fibrosis. Targeting EMT signaling pathways might provide a promising and effective therapeutic strategy to treat subretinal fibrosis secondary to nAMD.

Identification of novel proteins involved in P2X7-mediated signaling cascades

High concentration of extracellular ATP acts as a danger signal that is sensed by the P2X7 receptor (P2X7R). This ATP-gated ion channel has been shown to induce multiple metabotropic events such as changes in plasma membrane composition and morphology, ectodomain shedding, activation of lipases, kinases, and transcription factors as well as cytokine release. The specific signaling pathways and molecular mechanisms remain largely obscure. Using an unbiased genome-scale CRISPR/Cas9 screening approach in a murine T cell line, Ryoden et al. (2022, 2020) identified three proteins involved in P2X7 regulation and signaling: Essential for Reactive Oxygen Species (EROS) is essential for P2X7 folding and maturation, and Xk and Vsp13a are required for P2X7-mediated phosphatidyl serine exposure and cell lysis. They further provide evidence for an interaction of Xk and Vsp13a at the plasma membrane and confirm the role of Xk in ATP-induced cytolysis in primary CD25⁺CD4⁺ T cells from Xk^-/- mice.

Taking the road less traveled - the therapeutic potential of CBP/β-catenin antagonists

AREAS COVERED

This perspective discusses the challenges of targeting the Wnt signaling cascade, the safety, efficacy, and therapeutic potential of specific CBP/β-catenin antagonists and a rationale for the pleiotropic effects of CBP/β-catenin antagonists beyond Wnt signaling.

EXPERT OPINION

CBP/β-catenin antagonists can correct lineage infidelity, enhance wound healing, both normal and aberrant (e.g. fibrosis) and force the differentiation and lineage commitment of stem cells and cancer stem cells by regulating enhancer and super-enhancer coactivator occupancy. Small molecule CBP/β-catenin antagonists rebalance the equilibrium between CBP/β-catenin versus p300/β-catenin dependent transcription and may be able to treat or prevent many diseases of aging, via maintenance of our somatic stem cell pool, and regulating mitochondrial function and metabolism involved in differentiation and immune cell function.

Signaling Pathways Involved in Diabetic Renal Fibrosis

Diabetic kidney disease (DKD), as the most common complication of diabetes mellitus (DM), is the major cause of end-stage renal disease (ESRD). Renal interstitial fibrosis is a crucial metabolic change in the late stage of DKD, which is always considered to be complex and irreversible. In this review, we discuss the pathological mechanisms of diabetic renal fibrosis and discussed some signaling pathways that are closely related to it, such as the TGF-β, MAPK, Wnt/β-catenin, PI3K/Akt, JAK/STAT, and Notch pathways. The cross-talks among these pathways were then discussed to elucidate the complicated cascade behind the tubulointerstitial fibrosis. Finally, we summarized the new drugs with potential therapeutic effects on renal fibrosis and listed related clinical trials. The purpose of this review is to elucidate the mechanisms and related pathways of renal fibrosis in DKD and to provide novel therapeutic intervention insights for clinical research to delay the progression of renal fibrosis.

Colorectal Cancer-Associated Smad4 R361 Hotspot Mutations Boost Wnt/β-Catenin Signaling through Enhanced Smad4-LEF1 Binding

About 10% to 30% of patients with colorectal cancer harbor either loss of or missense mutations in SMAD4, a critical component of the TGFβ signaling pathway. The pathophysiologic function of missense mutations in Smad4 is not fully understood. They usually map to the MH2 domain, specifically to residues that are involved in heterodimeric complex formation with regulatory Smads (such as Smad2/3) and ensuing transcriptional activation. These detrimental effects suggest that SMAD4 missense mutations can be categorized as loss-of-function. However, they tend to cluster in a few hotspots, which is more consistent with them acting by a gain-of-function mechanism. In this study, we investigated the functional role of Smad4 R361 mutants by re-expressing two R361 Smad4 variants in several Smad4-null colorectal cancer cell lines. As predicted, R361 mutations disrupted Smad2/3-Smad4 heteromeric complex formation and abolished canonical TGFβ signaling. In that, they were similar to SMAD4 loss. However, RNA sequencing and subsequent RT-PCR assays revealed that Smad4mut cells acquired a gene signature associated with enhanced Lef1 protein function and increased Wnt signaling. Mechanistically, Smad4 mutant proteins retained binding to Lef1 protein and drove a commensurate increase in downstream Wnt signaling as measured by TOP/FOP luciferase assay and Wnt-dependent cell motility. Consistent with these findings, human colorectal cancers with SMAD4 missense mutations were less likely to acquire activating mutations in the key Wnt pathway gene CTNNB1 (encoding β-catenin) than colorectal cancers with truncating SMAD4 nonsense mutations. IMPLICATIONS: Our studies suggest that in colorectal cancer hotspot mutations in Smad4 confer enhanced Wnt signaling and possibly heightened sensitivity to Wnt pathway inhibitors. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/19/5/823/F1.large.jpg.

Promotion of β-Catenin/Forkhead Box Protein O Signaling Mediates Epithelial Repair in Kidney Injury

Fibrosis is characterized by progressively excessive deposition of matrix components and may lead to organ failure. Transforming growth factor-β (TGF-β) is a key cytokine involved in tissue repair and fibrosis. TGF-β's profibrotic signaling pathways converge at activation of β-catenin. β-Catenin is an important transcription cofactor whose function depends on its binding partner. Promoting β-catenin binding to forkhead box protein O (Foxo) via inhibition of its binding to T-cell factor (TCF) reduces kidney fibrosis in experimental murine models. Herein, we investigated whether β-catenin/Foxo diverts TGF-β signaling from profibrotic to physiological epithelial healing. In an in vitro model of wound healing (scratch assay), and in an in vivo model of kidney injury, unilateral renal ischemia reperfusion, TGF-β treatment in combination with either ICG-001 or iCRT3 (β-catenin/TCF inhibitors) increased β-catenin/Foxo interaction, increased scratch closure by increased cell proliferation and migration, reduced the TGF-β-induced mesenchymal differentiation, and healed the ischemia reperfusion injury with less fibrosis. In addition, administration of ICG-001 or iCRT3 reduced the contractile activity induced by TGF-β in C1.1 cells. Together, our results indicate that redirection of β-catenin binding from TCF to Foxo promotes β-catenin/Foxo-mediated epithelial repair. Targeting β-catenin/Foxo may rebuild normal structure of injured kidney.

Protective role of kallistatin in renal fibrosis via modulation of Wnt/β-catenin signaling

Kallistatin is a multiple functional serine protease inhibitor that protects against vascular injury, organ damage and tumor progression. Kallistatin treatment reduces inflammation and fibrosis in the progression of chronic kidney disease (CKD), but the molecular mechanisms underlying this protective process and whether kallistatin plays an endogenous role are incompletely understood. In the present study, we observed that renal kallistatin levels were significantly lower in patients with CKD. It was also positively correlated with estimated glomerular filtration rate (eGFR) and negatively correlated with serum creatinine level. Unilateral ureteral obstruction (UUO) in animals also led to down-regulation of kallistatin protein in the kidney, and depletion of endogenous kallistatin by antibody injection resulted in aggravated renal fibrosis, which was accompanied by enhanced Wnt/β-catenin activation. Conversely, overexpression of kallistatin attenuated renal inflammation, interstitial fibroblast activation and tubular injury in UUO mice. The protective effect of kallistatin was due to the suppression of TGF-β and β-catenin signaling pathways and subsequent inhibition of epithelial-to-mesenchymal transition (EMT) in cultured tubular cells. In addition, kallistatin could inhibit TGF-β-mediated fibroblast activation via modulation of Wnt4/β-catenin signaling pathway. Therefore, endogenous kallistatin protects against renal fibrosis by modulating Wnt/β-catenin-mediated EMT and fibroblast activation. Down-regulation of kallistatin in the progression of renal fibrosis underlies its potential as a valuable clinical biomarker and therapeutic target in CKD.

Targeted inhibition of β-catenin alleviates airway inflammation and remodeling in asthma via modulating the profibrotic and anti-inflammatory actions of transforming growth factor-β1

Background:

TGF-β₁ is a key cytokine involved in both airway inflammation and airway remodeling in asthma because of its anti-inflammatory and profibrotic effect. In our previous study, we found that knockdown of cytosolic β-catenin alleviated the profibrogenic effect of TGF-β₁ without influencing its anti-inflammatory effect. However, the exact role of targeting β-catenin in asthma is not yet fully demonstrated. In the present study, we investigated the effect and mechanism of targeting β-catenin in OVA-challenged asthmatic rats with airway inflammation and remodeling features.

Methods:

We integrated experimental asthma model and asthma related cell model to explore the effect of targeting β-catenin on airway inflammation and remodeling of asthma.

Results:

Blocking β-catenin with ICG001, a small molecule inhibitor of β-catenin/TCF via binding to cAMP-response elementbinding protein, attenuated airway inflammation by increasing levels of anti-inflammation cytokines IL-10, IL-35 and decreasing levels of T helper (Th)2 cells and Th17 cytokine. Suppressing β-catenin by ICG001 inhibited airway remodeling via reducing the level of TGF-β₁ and the expressions of Snail, MMP-7, MMP-9 and, up-regulating expression of E-cadherin, down-regulating expressions of α-SMA and Fn. Inhibition of β-catenin with ICG001 suppressed TGF-β₁ induced proliferation and activation of CCC-REPF-1, blocked TGF-β₁ induced epithelial–mesenchymal transition (EMT) of RLE-6TN.

Conclusion:

Blockade of β-catenin/TCF not only prevents TGF-β₁ induced EMT and profibrogenic effects involved in pathological remodeling of airway, but also alleviates airway inflammation in asthma by balancing pro-inflammatory and anti-inflammatory cytokine. In conclusion, targeting β-catenin specifically via inhibition of β-catenin/TCF might be a new therapeutic strategy for asthma.

The reviews of this paper are available via the supplemental material section.

LncRNA Gm12840 mediates WISP1 to regulate ischemia-reperfusion-induced renal fibrosis by sponging miR-677-5p

Aim: We aimed to identify that long noncoding RNAs (lncRNAs) are involved in ischemia-reperfusion (IR)-induced late fibrosis of kidney and may constitute novel therapeutic strategies for acute kidney injury-induced chronic kidney disease. Materials & methods: We performed the mouse model of IR later induced renal fibrosis and analyzed lncRNA profiles using second-generation sequencing during the pathogenesis. Results: The expression levels of 43 lncRNAs and 141 lncRNAs were respectively changed significantly 7 days and 2 weeks after IR treatment. Based on the correlation analysis of the differentially expressed genes, the interaction networks of lncRNAs, miRNAs and mRNA were structured. Conclusion: LncRNA (Gm12840) could act as a sponge for miR-677-5p to mediate fibroblast activation induced by TGF-β1 via the WISP1/PKB (Akt) signaling pathway.

Involvement of TGF-β and Autophagy Pathways in Pathogenesis of Diabetes: A Comprehensive Review on Biological and Pharmacological Insights

Despite recent advancements in clinical drugs, diabetes treatment still needs further progress. As such, ongoing research has attempted to determine the precise molecular mechanisms of the disorder. Specifically, evidence supports that several signaling pathways play pivotal roles in the development of diabetes. However, the exact molecular mechanisms of diabetes still need to be explored. This study examines exciting new hallmarks for the strict involvement of autophagy and TGF-β signaling pathways in the pathogenesis of diabetes and the design of novel therapeutic strategies. Dysregulated autophagy in pancreatic β cells due to hyperglycemia, oxidative stress, and inflammation is associated with diabetes and accompanied by dysregulated autophagy in insulin target tissues and the progression of diabetic complications. Consequently, several therapeutic agents such as adiponectin, ezetimibe, GABA tea, geniposide, liraglutide, guava extract, and vitamin D were shown to inhibit diabetes and its complications through modulation of the autophagy pathway. Another pathway, TGF-β signaling pathway, appears to play a part in the progression of diabetes, insulin resistance, and autoimmunity in both type 1 and 2 diabetes and complications in diabetes. Subsequently, drugs that target TGF-β signaling, especially naturally derived ones such as resveratrol, puerarin, curcumin, hesperidin, and silymarin, as well as Propolis, Lycopus lucidus, and Momordica charantia extracts, may become promising alternatives to current drugs in diabetes treatment. This review provides keen insights into novel therapeutic strategies for the medical care of diabetes.

Wnt signaling pathway in aging-related tissue fibrosis and therapies

Fibrosis is the final hallmark of pathological remodeling, which is a major contributor to the pathogenesis of various chronic diseases and aging-related organ failure to fully control chronic wound-healing and restoring tissue function. The process of fibrosis is involved in the pathogenesis of the kidney, lung, liver, heart and other tissue disorders. Wnt is a highly conserved signaling in the aberrant wound repair and fibrogenesis, and sustained Wnt activation is correlated with the pathogenesis of fibrosis. In particular, mounting evidence has revealed that Wnt signaling played important roles in cell fate determination, proliferation and cell polarity establishment. The expression and distribution of Wnt signaling in different tissues vary with age, and these changes have key effects on maintaining tissue homeostasis. In this review, we first describe the major constituents of the Wnt signaling and their regulation functions. Subsequently, we summarize the dysregulation of Wnt signaling in aging-related fibrotic tissues such as kidney, liver, lung and cardiac fibrosis, followed by a detailed discussion of its involvement in organ fibrosis. In addition, the crosstalk between Wnt signaling and other pathways has the potential to profoundly add to the complexity of organ fibrosis. Increasing studies have demonstrated that a number of Wnt inhibitors had the potential role against tissue fibrosis, specifically in kidney fibrosis and the implications of Wnt signaling in aging-related diseases. Therefore, targeting Wnt signaling might be a novel and promising therapeutic strategy against aging-related tissue fibrosis.

An integrated metabolism in vivo analysis and network pharmacology in UC rats reveal anti-ulcerative colitis effects from Sophora flavescens EtOAc extract

Ulcerative colitis (UC), an immune system disease, is characterized by long duration and easy relapse. Sophora flavescens (S. flavescens), also named "Kushen", is a traditional Chinese medicine, widely used to treat UC in clinics. Alkaloids and flavonoids are the main constituents of S. flavescens. Previous studies indicated that the effects of S. flavescens against UC mainly attribute to its alkaloids. In view of the clinical applications of its flavonoids and our preliminary experiments on the effects of S. flavescens treatment, we speculated that flavonoids also could exert an anti-UC effect, but its efficacy and mechanism are still not yet to be revealed. Herein, we examined the pharmacodynamic effects of the ethyl acetate (EtOAc) extract of S. flavescens EtOAc (SFE) against dextran sodium sulfate-induced UC rats for the first time. Pharmacodynamic effects indicated that SFE could significantly alleviate the loss in the body weight and shortening of the colon length, reduce colon bleeding and improve colon tissue damage of UC rats. A total of 28 prototypes and 41 metabolites were unambiguously or tentatively detected in rat's plasma and urine. Among them, 28 prototypes and 3 phase I metabolites shared 40 UC targets, the targets contributed to 51 metabolic pathways in 5 modules. Additionally, genistein, formononetin, isokurarinone, kurarinone, maackiain, kushenol N, trifolirnizin, kuraridin and norkurarinone were suggested to be potential active compounds in SFE for treating UC by comprehensively investigating the results of network pharmacology analysis, metabolic analysis in vivo, and previous researches. Finally, a combination of metabolic analysis in vivo with network pharmacology can elucidate the material basis and pharmacodynamic effect of traditional Chinese medicines, and lay the foundation for further clarify the anti-UC mechanism of SFE.

Dependence and Guidance Receptors-DCC and Neogenin-In Partial EMT and the Actions of Serine Proteases

The Epithelial-Mesenchymal Transition (EMT) is an important concept in understanding the processes of oncogenesis, especially with respect to the relationship between cell proliferation and metastatic properties such as spontaneous cell motility, chemotaxic migration and tissue invasion. EMT is now recognized as a more complex phenomenon than an all-or-nothing event, in which different components of the EMT may have distinct roles in the physio-pathological regulation of cell function and which may in turn depend on differential interactions with cell constituents and metabolic products. This mini-review summarizes recent work on the induction of cancer properties in parallel with the presence of EMT activities in the presence of serine proteases, with the focus on those tumor suppressors known as "dependence" receptors such as neogenin and Deleted in Colorectal Cancer (DCC). It is concluded that various forms of partial EMT should be given more detailed investigation and consideration as the results could have valuable implications for the development of disease-specific and patient-specific therapies.

Annexin A8 regulates Wnt signaling to maintain the phenotypic plasticity of retinal pigment epithelial cells

Wnt signalling mediates complex cell-cellinteractions during development and proliferation. Annexin A8 (AnxA8), a calcium-dependent phospholipid-binding protein, and canonical Wnt signalling mechanisms have both been implicated in retinal pigment epithelial (RPE) cell differentiation. The aim here was to examine the possibility of cross-talk between AnxA8 and Wnt signalling, as both are down-regulated upon fenretinide (FR)-mediated RPE transdifferentiation. AnxA8 suppression in RPE cells via siRNA or administration of FR induced neuronal-like cell transdifferentiation and reduced expression of Wnt-related genes, as measured by real-time PCR and western blotting. AnxA8 gene expression, on the other hand, remained unaltered upon manipulating Wnt signalling, suggesting Wnt-related genes to be downstream effectors of AnxA8. Co-immunoprecipitation revealed an interaction between AnxA8 and β-catenin, which was reduced in the presence of activated TGF-β1. TGF-β1 signalling also reversed the AnxA8 loss-induced cell morphology changes, and induced β-catenin translocation and GSK-3β phosphorylation in the absence of AnxA8. Ectopic over-expression of AnxA8 led to an increase in active β-catenin and GSK-3β phosphorylation. These data demonstrate an important role for AnxA8 as a regulator of Wnt signalling and a determinant of RPE phenotype, with implications for regenerative medicine approaches that utilise stem cell-derived RPE cells to treat conditions such as age-related macular degeneration.

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.

Promotion of β-catenin/Foxo1 signaling ameliorates renal interstitial fibrosis

Transforming growth factor β (TGF-β) is the key cytokine involved in causing fibrosis through cross-talk with major profibrotic pathways. However, inhibition of TGF-β to prevent fibrosis would also abrogate its anti-inflammatory and wound-healing effects. β-catenin is a common co-factor in most TGF-β signaling pathways. β-catenin binds to T-cell factor (TCF) to activate profibrotic genes and binds to Forkhead box O (Foxo) to promote cell survival under oxidative stress. Using a proximity ligation assay in human kidney biopsies, we found that β-catenin/Foxo interactions were higher in kidney with little fibrosis, whereas β-catenin/TCF interactions were upregulated in the kidney of patients with fibrosis. We hypothesised that β-catenin/Foxo is protective against kidney fibrosis. We found that Foxo1 protected against rhTGF-β1-induced profibrotic protein expression using a CRISPR/cas9 knockout of Foxo1 or TCF1 in murine kidney tubular epithelial C1.1 cells. Co-administration of TGF-β with a small molecule inhibitor of β-catenin/TCF (ICG-001), protected against kidney fibrosis in unilateral ureteral obstruction. Collectively, our human, animal and in vitro findings suggest β-catenin/Foxo as a therapeutic target in kidney fibrosis.

Signal flow control of complex signaling networks

Complex disease such as cancer is often caused by genetic mutations that eventually alter the signal flow in the intra-cellular signaling network and result in different cell fate. Therefore, it is crucial to identify control targets that can most effectively block such unwanted signal flow. For this purpose, systems biological analysis provides a useful framework, but mathematical modeling of complicated signaling networks requires massive time-series measurements of signaling protein activity levels for accurate estimation of kinetic parameter values or regulatory logics. Here, we present a novel method, called SFC (Signal Flow Control), for identifying control targets without the information of kinetic parameter values or regulatory logics. Our method requires only the structural information of a signaling network and is based on the topological estimation of signal flow through the network. SFC will be particularly useful for a large-scale signaling network to which parameter estimation or inference of regulatory logics is no longer applicable in practice. The identified control targets have significant implication in drug development as they can be putative drug targets.

Silencing TBX1 Exerts Suppressive Effects on Epithelial-Mesenchymal Transition and Inflammation of Chronic Rhinosinusitis Through Inhibition of the TGF-Smad2/3 Signaling Pathway in Mice

Background

Chronic rhinosinusitis (CRS) is a multifactorial inflammatory disease characterized by high prevalence and morbidity, and little is known about the mechanisms that underlie its pathogenesis.

Objective

This study focuses on the effect of T-box 1 (TBX1) on the epithelial–mesenchymal transition (EMT) and inflammation of CRS via the transforming growth factor (TGF)β-Smad2/3 signaling pathway.

Methods

CRS mice models were established by Merocel nasal packing material, followed by the streptococcus pneumoniae cultivation. The expression levels of TBX1 in the sinus mucosa tissues of mice were measured accordingly. The successfully modeled mice were subsequently injected with TBX1 mimic or TBX1 inhibitor and the TGFβ-Smad2/3 signaling pathway inhibitor (SB-431542) to elucidate the influence of TBX1 on EMT and inflammation in CRS, with the expression of the EMT-related factors (E-cadherin, Vimentin, alpha-smooth muscle actin [α-SMA]), Th1 cytokines (interleukin [IL]-2, interferon-γ), and Th2 cytokines (IL-4, IL-8, total immunoglobulin E) assayed.

Results

TBX1 expression exhibited upregulated levels in the sinus mucosa tissues of the mice. In addition, TBX1 downregulation was found to inhibit the expression of TGFβ as well as the extent of Smad2 and Smad3 phosphorylation. Silencing TBX1 was shown to elevate the expression of Th1 cytokines and E-cadherin, while diminishing expression of Th2 cytokines, Vimentin and α-SMA.

Conclusions

Taken together, the key findings of our study highlight the inhibitory role of TBX1 in the process of EMT and inflammation in CRS mice via the inhibition of the TGFβ-Smad2/3 signaling pathway, underlining the promise of TBX1 as a potential target for CRS therapy.

Combined melatonin and poricoic acid A inhibits renal fibrosis through modulating the interaction of Smad3 and β-catenin pathway in AKI-to-CKD continuum

Background:

Acute kidney injury (AKI) is one of the major risk factors for progression to chronic kidney disease (CKD) and renal fibrosis. However, effective therapies remain poorly understood. Here, we examined the renoprotective effects of melatonin and poricoic acid A (PAA) isolated from the surface layer of Poria cocos, and investigated the effects of combined therapy on the interaction of TGF-β/Smad and Wnt/β-catenin in a rat model of renal ischemia-reperfusion injury (IRI) and hypoxia/reoxygenation (H/R) or TGF-β1-induced HK-2 cells.

Methods:

Western blot and immunohistochemical staining were used to examine protein expression, while qRT-PCR was used to examine mRNA expression. Coimmunoprecipitation, chromatin immunoprecipitation, RNA interference, and luciferase reporter gene analysis were employed to explore the mechanisms of PAA and melatonin’s renoprotective effects.

Results:

PAA and combined therapy exhibited renoprotective and antifibrotic effects, but the underlying mechanisms were different during AKI-to-CKD continuum. Melatonin suppressed Smad-dependent and Smad-independent pathways, while PAA selectively inhibited Smad3 phosphorylation through distrupting the interactions of Smad3 with TGFβRI and SARA. Further studies demonstrated that the inhibitory effects of melatonin and PAA were partially depended on Smad3, especially PAA. Melatonin and PAA also inhibited the Wnt/β-catenin pathway and its profibrotic downstream targets, and PAA performed better. We further determined that IRI induced a nuclear Smad3/β-catenin complex, while melatonin and PAA disturbed the interaction of Smad3 and β-catenin, and supplementing with PAA could enhance the inhibitory effects of melatonin on the TGF-β/Smad and Wnt/β-catenin pathways.

Conclusions:

Combined melatonin and PAA provides a promising therapeutic strategy to treat renal fibrosis during the AKI-to-CKD continuum.

The novel inhibitor PRI-724 for Wnt/β-catenin/CBP signaling ameliorates bleomycin-induced pulmonary fibrosis in mice

Purpose/Aim of the Study: Wnt/β-catenin signaling was reported to be activated in pulmonary fibrosis, and was focused on as a target for antifibrotic therapy. However, the mechanism how the inhibition of Wnt/β-catenin signaling ameliorate pulmonary fibrosis has not been fully elucidated. The purpose of this study is to explore the target cells of Wnt/β-catenin inhibition in pulmonary fibrosis and to examine the antifibrotic effect of the novel inhibitor PRI-724 specifically disrupting the interaction of β-catenin and CBP. Materials and Methods: The effect of C-82, an active metabolite of PRI-724, on the expression of TGF-β1 and α-smooth muscle actin (SMA) was examined on fibroblasts and macrophages. We also examined the effects of PRI-724 in mouse model of bleomycin-induced pulmonary fibrosis. Results: The activation and increased accumulation of β-catenin in the canonical pathway were detected in lung fibroblasts as well as macrophages stimulated by Wnt3a using Western blotting. Treatment with C-82 reduced CBP protein and increased p300 protein binding to β-catenin in the nucleus of lung fibroblasts. In addition, C-82 inhibited the expression of SMA in lung fibroblasts treated with TGF-β, indicating the inhibition of myofibroblast differentiation. In the fibrotic lungs induced by bleomycin, β-catenin was stained strongly in macrophages, but the staining of β-catenin in alveolar epithelial cells and fibroblasts was weak. The administration of PRI-724 ameliorated pulmonary fibrosis induced by bleomycin in mice when administered with a late, but not an early, treatment schedule. Analysis of bronchoalveolar fluid (BALF) showed a decreased number of alveolar macrophages. In addition, the level of TGF-β1 in BALF was decreased in mice treated with PRI-724. C-82 also inhibited the production of TGF-β1 by alveolar macrophages. Conclusions: These results suggest that the β-catenin/CBP inhibitor PRI-724 is a potent antifibrotic agent that acts by modulating the activity of macrophages in the lungs.

β-Catenin/Smad3 Interaction Regulates Transforming Growth Factor-β-Induced Epithelial to Mesenchymal Transition in the Lens

Cataracts are the leading cause of blindness worldwide. Although surgery is a successful method to restore vision loss due to cataracts, post-surgical complications can occur, such as secondary cataracts, also known as posterior capsular opacification (PCO). PCO arises when lens epithelial cells (LEC) are left behind in the capsular bag following surgery and are induced to undergo epithelial to mesenchymal transition (EMT). Following EMT, LEC morphology and phenotype are altered leading to a loss of transparency and vision. Transforming growth factor (TGF)-β-induced signaling through both canonical, TGF-β/Smad, and non-canonical, β-catenin/Wnt and Rho/ROCK/MRTF-A, pathways have been shown to be involved in lens EMT, and thus PCO. However, the interactions between these signaling pathways in the lens have not been thoroughly explored. In the current study we use rat LEC explants as an ex vivo model, to examine the interplay between three TGF-β-mediated pathways using α-smooth muscle actin (α-SMA) as a molecular marker for EMT. We show that Smad3 inhibition via SIS3 prevents nuclear translocation of β-catenin and MRTF-A, and α-SMA expression, suggesting a key role of Smad3 in regulation of MRTF-A and β-catenin nuclear transport in LECs. Further, we demonstrate that inhibition of β-catenin/CBP interaction by ICG-001 decreased the amount of phosphorylated Smad3 upon TGF-β stimulation in addition to significantly decreasing the expression levels of TGF-β receptors, TBRII and TBRI. Overall, our findings demonstrate interdependence between the canonical and non-canonical TGF-β-mediated signaling pathways controlling EMT in the lens.

Opposing Regulation of Cancer Properties via KRT19-Mediated Differential Modulation of Wnt/β-Catenin/Notch Signaling in Breast and Colon Cancers

Although Keratin 19 (KRT19) has been reported as a tumor cell marker and found to interact with other proteins that modulate cancer properties, its role in cancer prognosis remains to be fully elucidated. We found that KRT19 expression was increased in both colon and breast cancer, but that knockdown of KRT19 showed opposing effects on cancer properties. In colon cancer, KRT19 knockdown resulted in suppression of cancer via downregulation of Wnt/Notch signaling without altering NUMB transcription. In breast cancer, KRT19 knockdown led to an increase in cancer properties because of attenuated Wnt and enhanced Notch signaling. In colon cancer, KRT19 interacted with β-catenin but not with RAC1, allowing the LEF/TCF transcription factor to bind primarily to the LEF1 and TCF7 promoter regions, whereas in breast cancer, KRT19 interacted with the β-catenin/RAC1 complex and led to apparent upregulation of NUMB expression and NUMB-mediated suppression of Notch signaling. These results reveal a novel differential role of KRT19 in carcinogenesis, due to differential modulation of Wnt/β-catenin/Notch signaling crosstalk through various interactions of KRT19 with only β-catenin or with the β-catenin/RAC1 complex, which might have implications for clinical cancer research.

Ghrelin attenuates myocardial fibrosis after acute myocardial infarction via inhibiting endothelial-to mesenchymal transition in rat model

Ghrelin, a peptide hormone produced in the gastrointestinal tract, has recently been found to be associated with the onset of myocardial fibrosis (MF). The exact mechanism, however, remains elusive. This study sought to identify the function and mechanism of ghrelin on MF after acute myocardial infarction (AMI). AMI was established in Spraque-Dawley rats by ligation of the left anterior descending (LAD). Ghrelin or saline was intraperitoneally injected two times per day for 8 weeks after ligation. The weight of heart (mg) and the weight ratio of heart to body (mg/g) as well as the fibrotic area were increased, while serum level of ghrelin was decreased after AMI. Ghrelin significantly ameliorated MF and decreased deposition of collagens in perivascular fibrosis area. In addition, ghrelin inhibited Endothelial-to-mesenchymal transition (EndMT), a crucial process for MF, in perivascular fibrosis area and TGF-β1-induced human coronary artery endothelial cells (HCAECs). Mechanistically, ghrelin persistently decreased the phosphorylation of Smad2/3 and enhanced the expression of Smad7 and p-AMPK in vivo and in vitro. After the abolition of Smad7, GHSR-1a and AMPK pathway, the effect of ghrelin on EndMT was significantly inhibited. In conclusion, these results presented a novel finding that ghrelin attenuated MF after AMI via regulation EndMT in a GHSR-1a/AMPK/Smad7- dependent manner.

Serine protease modulation of Dependence Receptors and EMT protein expression

Expression of the tumour suppressor Deleted in Colorectal Cancer (DCC) and the related protein neogenin is reduced by the mammalian serine protease chymotrypsin or the bacterial serine protease subtilisin, with increased cell migration. The present work examines whether these actions are associated with changes in the expression of cadherins, β-catenin and vimentin, established markers of the Epithelial-Mesenchymal Transition (EMT) which has been linked with cell migration and tumour metastasis. The results confirm the depletion of DCC and neogenin and show that chymotrypsin and subtilisin also reduce expression of β-catenin in acutely prepared tissue sections but not in human mammary adenocarcinoma MCF-7 or MDA-MB-231 cells cultured in normal media, or primary normal human breast cells. A loss of β-catenin was also seen in low serum media but transfecting cells with a dcc-containing plasmid induced resistance. E-cadherin was not consistently affected but vimentin was induced by low serum-containing media and was increased by serine proteases in MCF-7 and MDA-MB-231 cells in parallel with increased wound closure. Vimentin might contribute to the promotion of cell migration. The results suggest that changes in EMT proteins depend on the cells or tissues concerned and do not parallel the expression of DCC and neogenin. The increased cell migration induced by serine proteases is not consistently associated with the expression of the EMT proteins implying either that the increased migration may be independent of EMT or supporting the view that EMT is not itself consistently related to migration. (241).

Role of Wnt/β-catenin pathway agonist SKL2001 in Caerulein-induced acute pancreatitis

The goal of this study was to clarify the protective role of the Wnt/β-catenin pathway agonist SKL2001 in a rat model of Caerulein-induced acute pancreatitis. AR42J cells and rats were divided into 4 groups: control, Caerulein, SKL2001 + Caerulein, and SKL2001 + control. Cell apoptosis was examined using flow cytometry. Hematoxylin-eosin staining was performed to observe pathological changes in pancreatic and small intestinal tissues. Inflammatory cytokines were detected by enzyme-linked immunosorbent assay (ELISA), while genes related to the Wnt/β-catenin pathway were quantified using quantitative real-time PCR. In vitro results showed that Caerulein promoted cell necrosis, inhibited the Wnt/β-catenin pathway, and increased the level of inflammatory cytokines. However, SKL2001 reduced cell necrosis and inflammatory cytokines and activated the Wnt/β-catenin pathway. Additionally, in vivo results demonstrated the accumulation of fluid (i.e., edema), hemorrhage, inflammation and necrosis of the pancreatic acini occurred 6 h after the final Caerulein induction, with the damage reaching a maximal level 12 h after the final Caerulein induction; meanwhile, the Wnt/β-catenin pathway was evidently inhibited with an enhanced level of inflammatory cytokines. The aforementioned damage was further aggravated 12 h later. Nevertheless, the pancreatic and small intestinal tissue damages were alleviated in Caerulein-induced rats treated with SKL2001. In conclusion, activation of the Wnt/β-catenin pathway could inhibit Caerulein-induced cell apoptosis and inflammatory cytokine release, thus improving pancreatic and intestinal damage in rats with acute pancreatitis.

Snail and kidney fibrosis

Snail family zinc finger 1 (SNAI1) is a transcription factor expressed during renal embryogenesis, and re-expressed in various settings of acute kidney injury (AKI). Subjected to tight regulation, SNAI1 controls major biological processes responsible for renal fibrogenesis, including mesenchymal reprogramming of tubular epithelial cells, shutdown of fatty acid metabolism, cell cycle arrest and inflammation of the microenvironment surrounding tubular epithelial cells. The present review describes in detail the interactions of SNAI1 with AKI-associated signalling pathways. We also discuss how this central factor has been iteratively (and promisingly) targeted in a number of animal models in order to prevent or slow down renal fibrogenesis.

Epigallocatechingallate attenuates myocardial injury in a mouse model of heart failure through TGF‑β1/Smad3 signaling pathway

The present study aimed to assess the protective effect of epigallocatechingallate (EGCG) against myocardial injury in a mouse model of heart failure and to determine the mechanism underlying regulation of the transforming growth factor-β1/mothers against decapentaplegic homolog 3 (TGF-β1/Smad3) signaling pathway. Mouse models of heart failure were established. Alterations in ejection fraction, left ventricular internal diastolic diameter (LVIDd) and left ventricular internal systolic diameter (LVIDs) were measured by echocardiography. Pathological alterations of myocardial tissue were determined by hematoxylin and eosin, and Masson staining. The levels of serum brain natriuretic peptide (BNP), N-terminal-proBNP, interleukin (IL)-1β, IL-6, tumor necrosis factor-α, malondialdehyde, superoxide dismutase and glutathione peroxidase were detected with ELISA. Expression of collagen I, collagen III were detected by western blotting and reverse transcription quantitative polymerase chain reaction. Transforming growth factor-β1 (TGF-β1), Smad3, phosphorylated (p)-Smad3, apoptosis regulator BAX (Bax), caspase-3 and apoptosis regulator Bcl₂ in mouse cardiac tissue were measured by western blotting. P-smad3 and TGF-β1 were measured by immunofluorescence staining. EGCG reversed the alterations in LVIDd and LVIDs induced by establishment of the model of heart failure, increased ejection fraction, inhibited myocardial fibrosis, attenuated the oxidative stress, inflammatory and cardiomyocyte apoptosis and lowered the expression levels of collagen I and collagen III. Following treatment with TGF-β1 inhibitor, the protective effect of EGCG against heart failure was attenuated. The results of the present study demonstrated that EGCG can inhibit the progression and development of heart failure in mice through inhibition of myocardial fibrosis and reduction of ventricular collagen remodeling. This protective effect of EGCG is likely mediated through inhibition of TGF-β1/smad3 signaling pathway.

Matrix metalloproteinase 9 is associated with peritoneal membrane solute transport and induces angiogenesis through β-catenin signaling

Background

For patients using peritoneal dialysis (PD), the peritoneal membrane can develop fibrosis and angiogenesis, leading to ultrafiltration failure, chronic hypervolemia and increased risk of technique failure and mortality. Matrix metalloproteinases (MMPs), and specifically the gelatinases (MMP2 and MMP9), may be involved in peritoneal membrane injury.

Methods

From stable PD patients, mesothelial cells were assayed for MMP gene expression. MMP9 was overexpressed in mouse peritoneum by adenovirus, and MMP9 -/- mice were subjected to transforming growth factor β (TGF-β)-induced peritoneal fibrosis.

Results

MMP9 mRNA expression correlated with peritoneal membrane solute transport properties. Overexpression of MMP9 in the mouse peritoneum induced submesothelial thickening and angiogenesis. MMP9 induced mesothelial cell transition to a myofibroblast phenotype measured by increased alpha smooth muscle actin and decreased E-cadherin expression. Angiogenesis was markedly reduced in MMP9 -/- mice treated with an adenovirus expressing active TGF-β compared with wild-type mice. TGF-β-mediated E-cadherin cleavage was MMP9 dependent, and E-cadherin cleavage led to β-catenin-mediated signaling. A β-catenin inhibitor blocked the angiogenic response induced by AdMMP9.

Conclusions

Our data suggest that MMP9 is involved in peritoneal membrane injury possibly through cleavage of E-cadherin and induction of β-catenin signaling. MMP9 is a potential biomarker for peritoneal membrane injury and is a therapeutic target to protect the peritoneal membrane in PD patients.

β-Catenin/CBP-Dependent Signaling Regulates TGF-β-Induced Epithelial to Mesenchymal Transition of Lens Epithelial Cells

Purpose

Transforming growth factor-β–induced epithelial–mesenchymal transition (EMT) is one of the main causes of posterior capsular opacification (PCO) or secondary cataract; however, the signaling events involved in TGF-β–induced PCO have not been fully characterized. Here, we focus on examining the role of β-catenin/cyclic AMP response element–binding protein (CREB)-binding protein (CBP) and β-catenin/T-cell factor (TCF)-dependent signaling in regulating cytoskeletal dynamics during TGF-β–induced EMT in lens epithelial explants.

Methods

Rat lens epithelial explants were cultured in medium M199 in the absence of serum. Explants were treated with TGF-β2 in the presence or absence of the β-catenin/CBP interaction inhibitor, ICG-001, or the β-catenin/TCF interaction inhibitor, PNU-74654. Western blot and immunofluorescence experiments were carried out and analyzed.

Results

An increase in the expression of fascin, an actin-bundling protein, was observed in the lens explants upon stimulation with TGF-β, and colocalized with F-actin filaments. Inhibition of β-catenin/CBP interactions, but not β-catenin/TCF interactions, led to a decrease in TGF-β–induced fascin and stress fiber formation, as well as a decrease in the expression of known markers of EMT, α-smooth muscle actin (α-SMA) and matrix metalloproteinase 9 (MMP9). In addition, inhibition of β-catenin/CBP–dependent signaling also prevented TGF-β–induced downregulation of epithelial cadherin (E-cadherin) in lens explants.

Conclusions

We show that β-catenin/CBP–dependent signaling regulates fascin, MMP9, and α-SMA expression during TGF-β–induced EMT. We demonstrate that β-catenin/CBP–dependent signaling is crucial for TGF-β–induced EMT in the lens.

Dact1, a Wnt-Pathway Inhibitor, Mediates Human Mesangial Cell TGF-β1-Induced Apoptosis

Chronic kidney disease (CKD) is a worldwide public health problem that affects millions of men and women of all ages and racial groups. Loss of mesangial cells (MC) represents an early common feature in the pathogenesis of CKD. Transforming growth factor-β1 (TGF-β1) is a key inducer of kidney damage and triggers several pathological changes in renal cells, notably MC apoptosis. However, the mechanism of MC apoptosis induced by TGF-β1 remains elusive. Here, we demonstrate for the first time a novel regulatory pathway in which the disheveled-binding antagonist of β-catenin 1 (Dact1) gene is upregulated by TGF-β1, inducing MC apoptosis. We also show that the inhibitory effect of Dact1 and TGF-β1 on the transcriptional activation of the pro-survival Wnt pathway is the mechanism of death induction. In addition, Dact1 mRNA/protein levels are increased in kidney remnants from 5/6 nephrectomized rats and strongly correlate with TGF-β1 expression. Together, our results point to Dact1 as a novel element controlling MC survival that is causally related to CKD progression. J. Cell. Physiol. 232: 2104-2111, 2017. © 2016 Wiley Periodicals, Inc.

Pigment epithelium-derived factor attenuates myocardial fibrosis via inhibiting Endothelial-to-Mesenchymal Transition in rats with acute myocardial infarction

Endothelial mesenchymal transition (EndMT) plays a critical role in the pathogenesis and progression of interstitial and perivascular fibrosis after acute myocardial infarction (AMI). Pigment epithelium-derived factor (PEDF) is shown to be a new therapeutic target owing to its protective role in cardiovascular disease. In this study, we tested the hypothesis that PEDF is an endogenous inhibitor of EndMT and represented a novel mechanism for its protective effects against overactive cardiac fibrosis after AMI. Masson’s trichrome (MTC) staining and picrosirius red staining revealed decreased interstitial and perivascular fibrosis in rats overexpressing PEDF. The protective effect of PEDF against EndMT was confirmed by co-labeling of cells with the myofibroblast and endothelial cell markers. In the endothelial cells of microvessels in the ischemic myocardium, the inhibitory effect of PEDF against nuclear translocation of β-catenin was observed through confocal microscopic imaging. The correlation between antifibrotic effect of PEDF and inactivation of β-catenin was confirmed by co-transfecting cells with lentivirus carrying PEDF or PEDF RNAi and plasmids harboring β-catenin siRNA(r) or constitutive activation of mutant β-catenin. Taken together, these results establish a novel finding that PEDF could inhibit EndMT related cardiac fibrosis after AMI by a mechanism dependent on disruption of β-catenin activation and translocation.

The WNT-less wonder: WNT-independent β-catenin signaling

β-catenin is known as an Armadillo protein that regulates gene expression following WNT pathway activation. However, WNT-independent pathways also activate β-catenin. During the establishment of the melanocyte lineage, β-catenin plays an important role. In the context of physiopathology, β-catenin is activated genetically or transiently in various cancers, including melanoma, where it can be found in the nucleus of tumors. In this review, we discuss alternative pathways that activate β-catenin independent of WNTs and highlight what is known regarding these pathways in melanoma. We also discuss the role of β-catenin as a transcriptional regulator in various cell types, with emphasis on the different transcription factors it associates with independent of WNT induction. Finally, the role of WNT-independent β-catenin in melanocyte development and melanomagenesis is also discussed.

Epigallocatechin-3-gallate attenuates cadmium-induced chronic renal injury and fibrosis

Cadmium (Cd) pollution is a serious environmental problem. Kidney is a main target organ of Cd toxicity. This study was undertaken to investigate the potential protective effects of epigallocatechin-3-gallate (EGCG) against chronic renal injury and fibrosis induced by CdCl2. Rat model was induced by exposing to 250 mg/L CdCl2 through drinking water. The renal function was evaluated by detecting the levels of blood urea nitrogen (BUN) and serum creatinine (SCR). The oxidative stress was measured by detecting the levels of malondialdehyde (MDA), nitric oxide (NO), reduced glutathione/oxidized glutathione (GSH/GSSG) and renal enzymatic antioxidant status. Additionally, the renal levels of transforming growth factor-β1 (TGF-β1), Smad3, phosphorylation-Smad3 (pp-Smad3), α-smooth muscle actin (α-SMA), vimentin and E-cadherin were measured by western blot assay. Renal levels of microRNA-21 (miR-21), miR-29a/b/c and miR-192 were measured by quantitative RT-PCR. It was found that EGCG ameliorated the CdCl2-induced renal injury, inhibited the level of oxidative stress, normalized renal enzymatic antioxidant status and E-cadherin level, as well as attenuated the over generation of TGF-β1, pp-Smad3, vimentin and α-SMA. EGCG also decreased the production of miR-21 and miR-192, and enhanced the levels of miR-29a/b/c. These results showed that EGCG could attenuate Cd induced chronic renal injury.

Mechanisms of TGFβ-Induced Epithelial-Mesenchymal Transition

Transitory phenotypic changes such as the epithelial–mesenchymal transition (EMT) help embryonic cells to generate migratory descendants that populate new sites and establish the distinct tissues in the developing embryo. The mesenchymal descendants of diverse epithelia also participate in the wound healing response of adult tissues, and facilitate the progression of cancer. EMT can be induced by several extracellular cues in the microenvironment of a given epithelial tissue. One such cue, transforming growth factor β (TGFβ), prominently induces EMT via a group of specific transcription factors. The potency of TGFβ is partly based on its ability to perform two parallel molecular functions, i.e. to induce the expression of growth factors, cytokines and chemokines, which sequentially and in a complementary manner help to establish and maintain the EMT, and to mediate signaling crosstalk with other developmental signaling pathways, thus promoting changes in cell differentiation. The molecules that are activated by TGFβ signaling or act as cooperating partners of this pathway are impossible to exhaust within a single coherent and contemporary report. Here, we present selected examples to illustrate the key principles of the circuits that control EMT under the influence of TGFβ.

Autophagy links β-catenin and Smad signaling to promote epithelial-mesenchymal transition via upregulation of integrin linked kinase

TGF-β1 induces epithelial-mesenchymal transition (EMT) and autophagy in a variety of cells. However, the role of autophagy in TGF-β1-induced EMT has not been clearly elucidated and the underlying mechanisms are unclear. In the present study, we found that TGF-β1 induced both autophagy and EMT in mouse tubular epithelial C1.1 cells. Inhibition of autophagy by 3-methyladenine or siRNA knockdown of Beclin 1 reduced TGF-β1-induced increase of vimentin and decreased E-cadherin expression. In contrast, rapamycin-associated enhancement of TGF-β1-induced autophagy increased EMT of C1.1 cells. Serum rescue inhibited autophagy followed by reversal of EMT. Blocking of autophagosome-lysosomal but not proteosomal degradation reduced the decrease of E-cadherin, demonstrating a role for autophagy in degradation of E-cadherin during EMT. Autophagy promoted the activation of Src and Src-associated phosphorylation of β-catenin at Y-654 leading to pY654-β-catenin/p-Smad2 complex formation. Chromatin immunoprecipitation assay demonstrated binding by the pY654-β-catenin/p-Smad2 complex to ILK promoter thus increasing ILK expression. Taken together, our results demonstrate that TGF-β1-induced autophagy links β-catenin and Smad signaling to promote EMT in C1.1 cells through a novel pY654-β-catenin/p-Smad2/ILK pathway. The pathway delineated links disruption of E-cadherin/β-catenin-mediated cell-cell contact to induction of EMT via upregulation of ILK.

Non-Canonical Wnt Predominates in Activated Rat Hepatic Stellate Cells, Influencing HSC Survival and Paracrine Stimulation of Kupffer Cells

The Wnt system is highly complex and is comprised of canonical and non-canonical pathways leading to the activation of gene expression. Our aim was to examine changes in the expression of Wnt ligands and regulators during hepatic stellate cell (HSC) transdifferentiation and assess the relative contributions of the canonical and non-canonical Wnt pathways in fibrogenic activated HSC. The expression profile of Wnt ligands and regulators in HSC was not supportive for a major role for β-catenin-dependent canonical Wnt signalling, this verified by inability to induce Topflash reporter activity in HSC even when expressing a constitutive active β-catenin. We detected expression of Wnt5a in activated HSC which can signal via non-canonical mechanisms and showed evidence for non-canonical signalling in these cells involving phosphorylation of Dvl2 and pJNK. Stimulation of HSC or Kupffer cells with Wnt5a regulated HSC apoptosis and expression of TGF-β1 and MCP1 respectively. We were unable to confirm a role for β-catenin-dependent canonical Wnt in HSC and instead propose autocrine and paracrine functions for Wnts expressed by activated HSC via non-canonical pathways. The data warrant detailed investigation of Wnt5a in liver fibrosis.

Paracrine Wnt1 Drives Interstitial Fibrosis without Inflammation by Tubulointerstitial Cross-Talk

AKI with incomplete epithelial repair is a major contributor to CKD characterized by tubulointerstitial fibrosis. Injury-induced epithelial secretion of profibrotic factors is hypothesized to underlie this link, but the identity of these factors and whether epithelial injury is required remain undefined. We previously showed that activation of the canonical Wnt signaling pathway in interstitial pericytes cell autonomously drives myofibroblast activation in vivo. Here, we show that inhibition of canonical Wnt signaling also substantially prevented TGFβ-dependent myofibroblast activation in vitro. To investigate whether Wnt ligand derived from proximal tubule is sufficient for renal fibrogenesis, we generated a novel mouse strain with inducible proximal tubule Wnt1 secretion. Adult mice were treated with vehicle or tamoxifen and euthanized at 12 or 24 weeks postinjection. Compared with vehicle-treated controls, kidneys with tamoxifen-induced Wnt1 expression from proximal tubules displayed interstitial myofibroblast activation and proliferation and increased matrix protein production. PDGF receptor β-positive myofibroblasts isolated from these kidneys exhibited increased canonical Wnt target gene expression compared with controls. Notably, fibrotic kidneys had no evidence of inflammatory cytokine expression, leukocyte infiltration, or epithelial injury, despite the close histologic correlation of each with CKD. These results provide the first example of noninflammatory renal fibrosis. The fact that epithelial-derived Wnt ligand is sufficient to drive interstitial fibrosis provides strong support for the maladaptive repair hypothesis in the AKI to CKD transition.

Ca(2+) and EGF induce the differentiation of human embryo mesenchymal stem cells into epithelial-like cells

The mesenchymal to epithelial transition (MET) occurs in organ development and anti-tumorigenesis. We have investigated the effects of calcium (Ca(2+)) and epidermal growth factor (EGF) on human mesenchymal stem cell (hMSCs) differentiation into epithelial-like cells. hMSCs lost their biological characteristics after EGF transfection, and MET was achieved by adding 0.4 mmol Ca(2+). Western blotting and immunofluorescence showed expression of EGF, keratin, keratin 19 (K19), β1-integrin, E-cadherin and phosphorylated focal adhesion kinase (p-FAK, Ser-910) increased in hMSCs infected with EGF and exposed to Ca(2+), although Smad3 activation was downregulated. hMSCs co-stimulated with EGF transfection and Ca(2+) can therefore differentiate into epithelial-like cells in vitro.

Signaling pathway cooperation in TGF-β-induced epithelial-mesenchymal transition

Transdifferentiation of epithelial cells into cells with mesenchymal properties and appearance, that is, epithelial-mesenchymal transition (EMT), is essential during development, and occurs in pathological contexts, such as in fibrosis and cancer progression. Although EMT can be induced by many extracellular ligands, TGF-β and TGF-β-related proteins have emerged as major inducers of this transdifferentiation process in development and cancer. Additionally, it is increasingly apparent that signaling pathways cooperate in the execution of EMT. This update summarizes the current knowledge of the coordination of TGF-β-induced Smad and non-Smad signaling pathways in EMT, and the remarkable ability of Smads to cooperate with other transcription-directed signaling pathways in the control of gene reprogramming during EMT.

Human bone marrow-derived mesenchymal stem cells display enhanced clonogenicity but impaired differentiation with hypoxic preconditioning

Stem cells are promising candidate cells for regenerative applications because they possess high proliferative capacity and the potential to differentiate into other cell types. Mesenchymal stem cells (MSCs) are easily sourced but do not retain their proliferative and multilineage differentiative capabilities after prolonged ex vivo propagation. We investigated the use of hypoxia as a preconditioning agent and in differentiating cultures to enhance MSC function. Culture in 5% ambient O(2) consistently enhanced clonogenic potential of primary MSCs from all donors tested. We determined that enhanced clonogenicity was attributable to increased proliferation, increased vascular endothelial growth factor secretion, and increased matrix turnover. Hypoxia did not impact the incidence of cell death. Application of hypoxia to osteogenic cultures resulted in enhanced total mineral deposition, although this effect was detected only in MSCs preconditioned in normoxic conditions. Osteogenesis-associated genes were upregulated in hypoxia, and alkaline phosphatase activity was enhanced. Adipogenic differentiation was inhibited by exposure to hypoxia during differentiation. Chondrogenesis in three-dimensional pellet cultures was inhibited by preconditioning with hypoxia. However, in cultures expanded under normoxia, hypoxia applied during subsequent pellet culture enhanced chondrogenesis. Whereas hypoxic preconditioning appears to be an excellent way to expand a highly clonogenic progenitor pool, our findings suggest that it may blunt the differentiation potential of MSCs, compromising their utility for regenerative tissue engineering. Exposure to hypoxia during differentiation (post-normoxic expansion), however, appears to result in a greater quantity of functional osteoblasts and chondrocytes and ultimately a larger quantity of high-quality differentiated tissue.

A glimpse of the pathogenetic mechanisms of Wnt/β-catenin signaling in diabetic nephropathy

The Wnt family of proteins belongs to a group of secreted lipid-modified glycoproteins with highly conserved cysteine residues. Prior results indicate that Wnt/β-catenin signaling plays a prominent role in cell differentiation, adhesion, survival, and apoptosis and is involved in organ development, tumorigenesis, and tissue fibrosis, among other functions. Accumulating evidence has suggested that Wnt/β-catenin exhibits a pivotal function in the progression of diabetic nephropathy (DN). In this review, we focused on discussing the dual role of Wnt/β-catenin in apoptosis and epithelial mesenchymal transition (EMT) formation of mesangial cells. Moreover, we also elucidated the effect of Wnt/β-catenin in podocyte dysfunction, tubular EMT formation, and renal fibrosis under DN conditions. In addition, the molecular mechanisms involved in this process are introduced. This information provides a novel molecular target of Wnt/β-catenin for the protection of kidney damage and in delay of the progression of DN.