ALK5 inhibition blocks TGFβ-induced CCN1 expression in human foreskin fibroblasts

Involvement of Transforming Growth Factor-β-Associated Kinase 1 in Fixed Airway Obstruction in Asthmatic Patients with Longer Disease Duration Independent on Airway Eosinophilia

Objective

Transforming growth factor-β-associated kinase 1 (TAK1) mediates non-canonical TGF-β signalling by promoting adhesive, migratory, proliferative and contractile responses of fibroblasts to TGF-β₁. However, TAK1 expression status in asthmatic patients with or without fixed airway obstruction (FAO) is unknown.

Patients and Methods

A total of 60 adult asthmatics with FAO were recruited and compared to 43 those without FAO (nFAO). TGF-β₁ concentrations, and total TAK1 and phosphorylated TAK1 (p-TAK1) levels were determined in sputum supernatants, cytospin, and whole cell lysate by ELISA, immunocytochemistry, and Western blot analysis, respectively, in asthmatics with and without FAO.

Results

Asthmatic patients with FAO had much greater sputum TGF-β₁ concentrations than those without FAO. This was independent of airway eosinophilia as there was no significant difference in TGF-β₁ levels between high and low eosinophil counts within FAO and nFAO groups. In contrast, patients with FAO in the presence of sputum eosinophilia had greater expression of TAK1 and p-TAK1 than those without sputum eosinophilia (P=0.0032 and P=0.0061, respectively). The Western Blot data of total TAK1 and p-TAK1 were consistent with the immunocytochemistry, showing upregulation in all sputum cell types (neutrophils, eosinophils, macrophages, lymphocytes and airway epithelial cells). In addition, total TAK1 expression negatively correlated with pre- and post-bronchodilator FEV₁/FVC ratio.

Conclusion

TAK1 may play a key role in asthmatic patients with fixed airway obstruction, which was independent of eosinophilic airway inflammation. The interruption of TAK1 might have favourable clinical impact.

Using the Bleomycin-Induced Model of Fibrosis to Study the Contribution of CCN Proteins to Scleroderma Fibrosis

Approximately 45% of the deaths in the developed world result from conditions with a fibrotic component. Although no specific, focused anti-fibrotic therapies have been approved for clinical use, a long-standing concept is that targeting CCN proteins may be useful to treat fibrosis. Herein, we summarize current data supporting the concept that targeting CCN2 may be a viable anti-fibrotic approach to treat scleroderma. Testing this hypothesis has been made possible by using a mouse model of inflammation-driven skin and lung fibrosis.

Conjunction junction, what's the function? CCN proteins as targets in fibrosis and cancers

Cellular communication network (CCN) proteins are matricellular proteins that coordinate signaling among extracellular matrix, secreted proteins, and cell surface receptors. Their specific in vivo function is context-dependent, but they play profound roles in pathological conditions, such as fibrosis and cancers. Anti-CCN therapies are in clinical consideration. Only recently, however, has the function of these complex molecules begun to emerge. This review summarizes and interprets our current knowledge regarding these fascinating molecules and provides experimental evidence for their utility as therapeutic targets.

CCN1 expression by fibroblasts is required for bleomycin-induced skin fibrosis

The microenvironment contributes to the excessive connective tissue deposition that characterizes fibrosis. Members of the CCN family of matricellular proteins are secreted by fibroblasts into the fibrotic microenvironment; however, the role of endogenous CCN1 in skin fibrosis is unknown. Mice harboring a fibroblast-specific deletion for CCN1 were used to assess if CCN1 contributes to dermal homeostasis, wound healing, and skin fibrosis. Mice with a fibroblast-specific CCN1 deletion showed progressive skin thinning and reduced accumulation of type I collagen; however, the overall mechanical property of skin (Young's modulus) was not significantly reduced. Real time-polymerase chain reaction analysis revealed that CCN1-deficient skin displayed reduced expression of mRNAs encoding enzymes that promote collagen stability (including prolyl-4-hydroxylase and PLOD2), although expression of COL1A1 mRNA was unaltered. CCN1-deficent skin showed reduced hydroxyproline levels. Electron microscopy revealed that collagen fibers were disorganized in CCN1-deficient skin. CCN1-deficient mice were resistant to bleomycin-induced skin fibrosis, as visualized by reduced collagen accumulation and skin thickness suggesting that deposition/accumulation of collagen is impaired in the absence of CCN1. Conversely, CCN1-deficient mice showed unaltered wound closure kinetics, suggesting de novo collagen production in response to injury did not require CCN1. In response to either wounding or bleomycin, induction of α-smooth muscle actin-positive myofibroblasts was unaffected by loss of CCN1. CCN1 protein was overexpressed by dermal fibroblasts isolated from lesional (i.e., fibrotic) areas of patients with early onset diffuse scleroderma. Thus, CCN1 expression by fibroblasts, being essential for skin fibrosis, is a viable anti-fibrotic target.

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The role of endogenous CCN1 in skin biology is largely unknown

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Fibroblast-specific deletion CCN1 causes thinner skin and misaligned collagen

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CCN1-deficient mice were resistant to bleomycin-induced skin fibrosis

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Wound healing closure kinetics was unaffected by loss of CCN1

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CCN1 may be as a target for anti-fibrotic therapy

Yin/Yang expression of CCN family members: Transforming growth factor beta 1, via ALK5/FAK/MEK, induces CCN1 and CCN2, yet suppresses CCN3, expression in human dermal fibroblasts

The role of the microenvironment in driving connective tissue disease is being increasingly appreciated. Matricellular proteins of the CCN family are signaling modifiers that are secreted by cells into the extracellular matrix microenvironment where they have profound, context-dependent effects on organ development, homeostasis and disease. Indeed, CCN proteins are emergent targets for therapeutic intervention. Recent evidence suggests that, in vivo, CCN3 has effects opposing CCN2. Moreover, when CCN3 expression is high, CCN2 expression is low. That is, they appear to be regulated in a yin/yang fashion, leading to the hypothesis that the CCN2:CCN3 ratio is important to control tissue homeostasis. To begin to test the hypothesis that alterations in CCN2:CCN3 expression might be important in skin biology in vivo, we evaluated the relative ex vivo effects of the profibrotic protein TGFbeta1 on dermal fibroblasts on protein and RNA expression of CCN3 and CCN2, as well as the related protein CCN1. We also used signal transduction inhibitors to begin to identify the signal transduction pathways controlling the ability of fibroblasts to respond to TGFbeta1. As anticipated, CCN1 and CCN2 protein and mRNA were induced by TGFbeta1 in human dermal fibroblasts. This induction was blocked by TAK1, FAK, YAP1 and MEK inhibition. Conversely, TGFbeta1 suppressed CCN3 mRNA expression in a fashion insensitive to FAK, MEK, TAK1 or YAP1 inhibition. Unexpectedly, CCN3 protein was not detected in human dermal fibroblasts basally. These data suggest that, in dermal fibroblasts, the profibrotic protein TGFbeta1 has a divergent effect on CCN3 relative to CCN2 and CCN1, both at the mRNA and protein level. Given that the major source in skin in vivo of CCN proteins are fibroblasts, our data are consistent that alterations in CCN2/CCN1: CCN3 ratios in response to profibrotic agents such as TGFbeta1 may play a role in connective tissue pathologies including fibrosis.

Molecular signatures for CCN1, p21 and p27 in progressive mantle cell lymphoma

Mantle cell lymphoma (MCL) is a comparatively rare non-Hodgkin's lymphoma characterised by overexpression of cyclin D1. Many patients present with or progress to advanced stage disease within 3 years. MCL is considered an incurable disease with median survival between 3 and 4 years. We have investigated the role(s) of CCN1 (CYR61) and cell cycle regulators in progressive MCL. We have used the human MCL cell lines REC1 < G519 < JVM2 as a model for disease aggression. The magnitude of CCN1 expression in human MCL cells is REC1 > G519 > JVM2 cells by RQ-PCR, depicting a decrease in CCN1 expression with disease progression. Investigation of CCN1 isoform expression by western blotting showed that whilst expression of full-length CCN1 was barely altered in the cell lines, expression of truncated forms (18-20 and 28-30 kDa) decreased with disease progression. We have then demonstrated that cyclin D1 and cyclin dependent kinase inhibitors (p21^CIP1and p27^KIP1) are also involved in disease progression. Cyclin D1 was highly expressed in REC1 cells (OD: 1.0), reduced to one fifth in G519 cells (OD: 0.2) and not detected by western blotting in JVM2 cells. p27^KIP1 followed a similar profile of expression as cyclin D1. Conversely, p21^CIP1 was absent in the REC1 cells and showed increasing expression in G519 and JVM2 cells. Subcellular localization detected p21^CIP1/ p27^KIP1 primarily within the cytoplasm and absent from the nucleus, consistent with altered roles in treatment resistance. Dysregulation of the CCN1 truncated forms are associated with MCL progression. In conjunction with reduced expression of cyclin D1 and increased expression of p21, this molecular signature may depict aggressive disease and treatment resistance.

MicroRNA-181a-5p enhances cell proliferation in medullary thymic epithelial cells via regulating TGF-β signaling

The expression profiles of miRNAs in thymus tissues from mice of different age have been demonstrated in our previous study. After an integrated analysis of the miRNA expression profiles, we demonstrated that the expression of miR-181a-5p was significantly decreased in thymic epithelial cells (TECs) from 10- to 19-month-old mice when compared with that in TECs from 1-month-old mice by quantitative reverse transcriptase polymerase chain reaction. We hypothesized that miR-181a-5p in TECs might be associated with the age-related thymus involution through regulating some genes or signaling pathway. To test this hypothesis, the mouse medullary thymic epithelial cells (MTEC1) were used. Transfection with miR-181a-5p mimic promoted the proliferation of MTEC1 cells, but did not affect apoptosis. The effect was reversed when the expression of miR-181a-5p was suppressed in MTEC1 cells. Furthermore, the transforming growth factor beta receptor I (Tgfbr1) was confirmed as a direct target of miR-181a-5p by luciferase assay. Moreover, it was found that overexpression of miR-181a-5p down-regulated the phosphorylation of Smad3 and blocked the activation of the transforming growth factor beta signaling. Nevertheless, an inversely correlation was observed between the expression of Tgfbr1 and miR-181a-5p in TECs derived from mice of different age. Collectively, we provide evidence that miR-181a-5p may be an important endogenous regulator in the proliferation of TECs, and the expression levels of miR-181a-5p in TECs may be associated with the age-related thymus involution.

5Z-7-Oxozeanol Inhibits the Effects of TGFβ1 on Human Gingival Fibroblasts

Transforming growth factor (TGF)β acts on fibroblasts to promote the production and remodeling of extracellular matrix (ECM). In adult humans, excessive action of TGFβ is associated with fibrotic disease and fibroproliferative conditions, including gingival hyperplasia. Understanding how the TGFβ1 signals in fibroblasts is therefore likely to result in valuable insights into the fundamental mechanisms underlying fibroproliferative disorders. Previously, we used the TAK1 inhibitor (5Z)-7-Oxozeaenol to show that, in dermal fibroblasts, the non-canonical TAK1 pathway mediates the ability of TGFβ1 to induce genes promoting tissue remodeling and repair. However, the extent to which TAK1 mediates fibroproliferative responses in fibroblasts in response to TGFβ1 remains unclear. Herein, we show that, in gingival fibroblasts, (5Z)-7-Oxozeaenol blocks the ability of TGFβ1 to induce expression of the pro-fibrotic mediator CCN2 (connective tissue growth factor, CTGF) and type I collagen protein. Moreover, genome-wide expression profiling revealed that, in gingival fibroblasts, (5Z)-7-Oxozeaenol reduces the ability of TGFβ1 to induce mRNA expression of essentially all TGFβ1-responsive genes (139/147), including those involved with a hyperproliferative response. Results from microarray analysis were confirmed using real time polymerase chain reaction analysis and a functional cell proliferation assay. Our results are consistent with the hypothesis that TAK1 inhibitors might be useful in treating fibroproliferative disorders, including that in the oral cavity.

CCN2 requires TGF-β signalling to regulate CCAAT/enhancer binding proteins and inhibit fat cell differentiation

INTRODUCTION

Fat cell differentiation (FCD) potentiates adipose cell characteristics including lipid storage and insulin sensitivity. In vitro, we have demonstrated that CCN2, also known as connective tissue growth factor (CTGF), inhibits FCD in NIH3T3-L1 cells and in adipocytes isolated from mouse epididymal fat pads. The aim of this study was to determine if the CCN2 effect on FCD is dependent on TGF-β and TGF-β downstream pathway signalling.

METHODS

NIH3T3-L1 cells were differentiated using standard methods with IBMX/Dex/Insulin. FCD at day 10 was confirmed by induced gene markers resistin and adiponectin and by lipid accumulation. Cells were treated at d0 with single dose active rhTGF-β1 (2 ng/mL), rhCCN2 (500 ng/mL) and/or TGF-β type 1 receptor blocker (SB431542, 5 μM). Early induction of FCD transcription factors: CCAAT/enhancer binding proteins (C/EBPs) and peroxisome proliferator-activated receptor-γ (PPAR-γ), were also determined.

RESULTS

In an early time course from 2 h, single doses of rhTGF-β1 or rhCCN2 significantly inhibited by ~70 % the induction of C/EBP-β and -δ mRNA, and also nuclear protein levels otherwise seen during FCD, whereas only delayed effects on PPAR-γ, at 48 h, occurred. Furthermore, the CCN2 inhibition of FCD markers adiponectin and resistin and lipid accumulation by Oil red O stain were each prevented by TGF-β receptor blockade. Similar prevention was found using pan-specific anti-TGF-β neutralising antibody. CCN2 and TGF-β treatment each rapidly phosphorylated SMAD-3 signalling in early stages of FCD.

CONCLUSION

This work shows novel findings that CCN2 effects on FCD are both TGF-β and TGF-β pathway dependent and are related to early effects on C/EBPs.