Induction of the AP-1 members c-Jun and JunB by TGF-beta/Smad suppresses early Smad-driven gene activation

H9N2 Avian Influenza Virus Downregulates FcRY Expression in Chicken Macrophage Cell Line HD11 by Activating the JNK MAPK Pathway

The H9N2 avian influenza virus causes reduced production performance and immunosuppression in chickens. The chicken yolk sac immunoglobulins (IgY) receptor (FcRY) transports from the yolk into the embryo, providing offspring with passive immunity to infection against common poultry pathogens. FcRY is expressed in many tissues/organs of the chicken; however, there are no reports investigating FcRY expression in chicken macrophage cells, and how H9N2-infected HD11 cells (a chicken macrophage-like cell line) regulate FcRY expression remains uninvestigated. This study used the H9N2 virus as a model pathogen to explore the regulation of FcRY expression in avian macrophages. FcRY was highly expressed in HD11 cells, as shown by reverse transcription polymerase chain reactions, and indirect immunofluorescence indicated that FcRY was widely expressed in HD11 cells. HD11 cells infected with live H9N2 virus exhibited downregulated FcRY expression. Transfection of eukaryotic expression plasmids encoding each viral protein of H9N2 into HD11 cells revealed that nonstructural protein (NS1) and matrix protein (M1) downregulated FcRY expression. In addition, the use of a c-jun N-terminal kinase (JNK) activator inhibited the expression of FcRY, while a JNK inhibitor antagonized the downregulation of FcRY expression by live H9N2 virus, NS1 and M1 proteins. Finally, a dual luciferase reporter system showed that both the M1 protein and the transcription factor c-jun inhibited FcRY expression at the transcriptional level. Taken together, the transcription factor c-jun was a negative regulator of FcRY, while the live H9N2 virus, NS1, and M1 proteins downregulated the FcRY expression through activating the JNK signaling pathway. This provides an experimental basis for a novel mechanism of immunosuppression in the H9N2 avian influenza virus.

TGF-beta signal transduction: biology, function and therapy for diseases

The transforming growth factor beta (TGF-β) is a crucial cytokine that get increasing concern in recent years to treat human diseases. This signal controls multiple cellular responses during embryonic development and tissue homeostasis through canonical and/or noncanonical signaling pathways. Dysregulated TGF-β signal plays an essential role in contributing to fibrosis via promoting the extracellular matrix deposition, and tumor progression via inducing the epithelial-to-mesenchymal transition, immunosuppression, and neovascularization at the advanced stage of cancer. Besides, the dysregulation of TGF-beta signal also involves in other human diseases including anemia, inflammatory disease, wound healing and cardiovascular disease et al. Therefore, this signal is proposed to be a promising therapeutic target in these diseases. Recently, multiple strategies targeting TGF-β signals including neutralizing antibodies, ligand traps, small-molecule receptor kinase inhibitors targeting ligand-receptor signaling pathways, antisense oligonucleotides to disrupt the production of TGF-β at the transcriptional level, and vaccine are under evaluation of safety and efficacy for the forementioned diseases in clinical trials. Here, in this review, we firstly summarized the biology and function of TGF-β in physiological and pathological conditions, elaborated TGF-β associated signal transduction. And then, we analyzed the current advances in preclinical studies and clinical strategies targeting TGF-β signal transduction to treat diseases.

Lipocalin-2 inhibits pancreatic cancer stemness via the AKT/c-Jun pathway

Cancer stem cells (CSCs) are involved in cancer recurrence and metastasis owing to their self-renewal properties and drug-resistance capacity. Lipocalin-2 (Lcn2) of the lipocalin superfamily is highly expressed in pancreatic cancer. Nevertheless, reports on the involvement of Lcn2 in the regulation of pancreatic CSC properties are scant. This study is purposed to investigate whether Lcn2 plays a crucial role in CSC renewal and stemness maintenance in pancreatic carcinoma. Immunohistochemistry results of tumor tissue chips together with Gene Expression Omnibus sequencing files confirmed that Lcn2 is highly expressed in pancreatic carcinoma compared with that in normal tissues. The exogenous expression of Lcn2 attenuated CSC-associated SOX2, CD44, and EpCAM expression and suppressed sarcosphere formation and tumorigenesis in the pancreatic carcinoma cell line PANC-1, which showed low expression of Lcn2. However, Lcn2 knockout in BxPC-3 cell line, which presented high Lcn2 expression, promoted CSC stemness, further enhancing sarcosphere formation and tumorigenesis. Moreover, Lcn2 was found to regulate stemness in pancreatic cancer depending on the activation of AKT and c-Jun. Lcn2 suppresses stemness properties in pancreatic carcinoma by activating the AKT-c-Jun pathway, and thus, it may be a novel candidate to suppress the stemness of pancreatic cancer. This study provides a new insight into disease progression.

KLF11 deficiency enhances chemokine generation and fibrosis in murine unilateral ureteral obstruction

Progression of virtually all forms of chronic kidney disease (CKD) is associated with activation of pro-inflammatory and pro-fibrotic signaling pathways. Despite extensive research, progress in identifying therapeutic targets to arrest or slow progression of CKD has been limited by incomplete understanding of basic mechanisms underlying renal inflammation and fibrosis in CKD. Recent studies have identified Kruppel-like transcription factors that have been shown to play critical roles in renal development, homeostasis, and response to injury. Although KLF11 deficiency has been shown to increase collagen production in vitro and tissue fibrosis in other organs, no previous study has linked KLF11 to the development of CKD. We sought to test the hypothesis that KLF11 deficiency promotes CKD through upregulation of pro-inflammatory and pro-fibrogenic signaling pathways in murine unilateral ureteral obstruction (UUO), a well-established model of renal fibrosis. We found that KLF11-deficiency exacerbates renal injury in the UUO model through activation of the TGF-β/SMAD signaling pathway and through activation of several pro-inflammatory chemokine signaling pathways. Based on these considerations, we conclude that agents increase KLF11 expression may provide novel therapeutic targets to slow the progression of CKD.

Adult Human Vascular Smooth Muscle Cells on 3D Silk Fibroin Nonwovens Release Exosomes Enriched in Angiogenic and Growth-Promoting Factors

Background. Our earlier works showed the quick vascularization of mouse skin grafted Bombyx mori 3D silk fibroin nonwoven scaffolds (3D-SFnws) and the release of exosomes enriched in angiogenic/growth factors (AGFs) from in vitro 3D-SFnws-stuck human dermal fibroblasts (HDFs). Here, we explored whether coronary artery adult human smooth muscle cells (AHSMCs) also release AGFs-enriched exosomes when cultured on 3D-SFnws in vitro. Methods. Media with exosome-depleted FBS served for AHSMCs and human endothelial cells (HECs) cultures on 3D-SFnws or polystyrene. Biochemical methods and double-antibody arrays assessed cell growth, metabolism, and intracellular TGF-β and NF-κB signalling pathways activation. AGFs conveyed by CD9⁺/CD81⁺ exosomes released from AHSMCs were double-antibody array analysed and their angiogenic power evaluated on HECs in vitro. Results. AHSMCs grew and consumed D-glucose more intensely and showed a stronger phosphorylation/activation of TAK-1, SMAD-1/-2/-4/-5, ATF-2, c-JUN, ATM, CREB, and an IκBα phosphorylation/inactivation on SFnws vs. polystyrene, consistent overall with a proliferative/secretory phenotype. SFnws-stuck AHSMCs also released exosomes richer in IL-1α/-2/-4/-6/-8; bFGF; GM-CSF; and GRO-α/-β/-γ, which strongly stimulated HECs’ growth, migration, and tubes/nodes assembly in vitro. Conclusions. Altogether, the intensified AGFs exosomal release from 3D-SFnws-attached AHSMCs and HDFs could advance grafts’ colonization, vascularization, and take in vivo—noteworthy assets for prospective clinical applications.

Effects of emodin, a plant-derived anthraquinone, on TGF-β1-induced cardiac fibroblast activation and function

Cardiac fibrosis accompanies a number of pathological conditions and results in altered myocardial structure, biomechanical properties and function. The signaling networks leading to fibrosis are complex, contributing to the general lack of progress in identifying effective therapeutic approaches to prevent or reverse this condition. Several studies have shown protective effects of emodin, a plant-derived anthraquinone, in animal models of fibrosis. A number of questions remain regarding the mechanisms whereby emodin impacts fibrosis. Transforming growth factor beta 1 (TGF-β1) is a potent stimulus of fibrosis and fibroblast activation. In the present study, experiments were performed to evaluate the effects of emodin on activation and function of cardiac fibroblasts following treatment with TGF-β1. We demonstrate that emodin attenuates TGF-β1-induced fibroblast activation and collagen accumulation in vitro. Emodin also inhibits activation of several canonical (SMAD2/3) and noncanonical (Erk1/2) TGF-β signaling pathways, while activating the p38 pathway. These results suggest that emodin may provide an effective therapeutic agent for fibrosis that functions via specific TGF-β signaling pathways.

Melanoma Plasticity: Promoter of Metastasis and Resistance to Therapy

Melanoma is the deadliest form of skin cancer. Although targeted therapies and immunotherapies have revolutionized the treatment of metastatic melanoma, most patients are not cured. Therapy resistance remains a significant clinical challenge. Melanoma comprises phenotypically distinct subpopulations of cells, exhibiting distinct gene signatures leading to tumor heterogeneity and favoring therapeutic resistance. Cellular plasticity in melanoma is referred to as phenotype switching. Regardless of their genomic classification, melanomas switch from a proliferative and differentiated phenotype to an invasive, dedifferentiated and often therapy-resistant state. In this review we discuss potential mechanisms underpinning melanoma phenotype switching, how this cellular plasticity contributes to resistance to both targeted therapies and immunotherapies. Finally, we highlight novel strategies to target plasticity and their potential clinical impact in melanoma.

Intercellular coupling between peripheral circadian oscillators by TGF-β signaling

Coupling between cell-autonomous circadian oscillators is crucial to prevent desynchronization of cellular networks and disruption of circadian tissue functions. While neuronal oscillators within the mammalian central clock, the suprachiasmatic nucleus, couple intercellularly, coupling among peripheral oscillators is controversial and the molecular mechanisms are unknown. Using two- and three-dimensional mammalian culture models in vitro (mainly human U-2 OS cells) and ex vivo, we show that peripheral oscillators couple via paracrine pathways. We identify transforming growth factor-β (TGF-β) as peripheral coupling factor that mediates paracrine phase adjustment of molecular clocks through transcriptional regulation of core-clock genes. Disruption of TGF-β signaling causes desynchronization of oscillator networks resulting in reduced amplitude and increased sensitivity toward external zeitgebers. Our findings reveal an unknown mechanism for peripheral clock synchrony with implications for rhythmic organ functions and circadian health.

TGF-β as a driver of fibrosis: physiological roles and therapeutic opportunities

Many chronic diseases are marked by fibrosis, which is defined by an abundance of activated fibroblasts and excessive deposition of extracellular matrix, resulting in loss of normal function of the affected organs. The initiation and progression of fibrosis are elaborated by pro-fibrotic cytokines, the most critical of which is transforming growth factor-β1 (TGF-β1). This review focuses on the fibrogenic roles of increased TGF-β activities and underlying signaling mechanisms in the activated fibroblast population and other cell types that contribute to progression of fibrosis. Insight into these roles and mechanisms of TGF-β as a universal driver of fibrosis has stimulated the development of therapeutic interventions to attenuate fibrosis progression, based on interference with TGF-β signaling. Their promise in preclinical and clinical settings will be discussed. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

JUN promotes chicken female differentiation by inhibiting Smad2

The sex determination and control of poultry is a key problem in production and scientific research despite few studies on regulatory factors, especially transcription factors in sex determination. In the early stage of this study, high-throughput sequencing was used to screen the differentially expressed gene JUN in male and female embryonic stem cells (ESCs) and primordial germ cells (PGCs). The qRT-PCR discovered that the JUN gene significantly increased from embryonic days (E) 2.5 later in chicken embryo development, and the female gonad expression was much higher than that of the male after E14.5. Lentivirus shRNA-JUN, shRNA-Smad2 interference, and OE-JUN overexpression vectors were successfully constructed. After interfering with JUN in vivo, male characteristics appeared in ZW embryonic gonads at E18.5. Meanwhile, the male-specific genes DMRT1 and Sox9 were upregulated, the female-specific genes FOXL2, ESR1, and CYP19A1 were downregulated, and the estradiol in the gonads was significantly decreased. The situation was reversed after the overexpression of JUN, ZZ chicken embryo developed into female sexual characteristics. The double luciferase report has found that the Smad2 promoter activity was significantly upregulated after interference with JUN, and significantly increased after the deletion of the JUN binding site. After the injection of the Smad2-shRNA vector into the blood vessel in vivo, it was discovered that DMRT1 and Sox9 of ZW embryos at E18.5 were downregulated, FOXL2 and CYP19A1 were significantly upregulated, and the gonads show femininity. In conclusion, this study proves that JUN is a key regulator in the process of chicken female sex differentiation, which can inhibit the transcription of Smad2 and promote the synthesis of estradiol, and participate in the process of chicken sex differentiation. This study lays a foundation for the analysis of the molecular mechanism of chicken sex determination and the development of poultry sex control technology.

Fibroblast contributions to ischemic cardiac remodeling

The heart can respond to increased pathophysiological demand through alterations in tissue structure and function 1 . This process, called cardiac remodeling, is particularly evident following myocardial infarction (MI), where the blockage of a coronary artery leads to widespread death of cardiac muscle. Following MI, necrotic tissue is replaced with extracellular matrix (ECM), and the remaining viable cardiomyocytes (CMs) undergo hypertrophic growth. ECM deposition and cardiac hypertrophy are thought to represent an adaptive response to increase structural integrity and prevent cardiac rupture. However, sustained ECM deposition leads to the formation of a fibrotic scar that impedes cardiac compliance and can induce lethal arrhythmias. Resident cardiac fibroblasts (CFs) are considered the primary source of ECM molecules such as collagens and fibronectin, particularly after becoming activated by pathologic signals. CFs contribute to multiple phases of post-MI heart repair and remodeling, including the initial response to CM death, immune cell (IC) recruitment, and fibrotic scar formation. The goal of this review is to describe how resident fibroblasts contribute to the healing and remodeling that occurs after MI, with an emphasis on how fibroblasts communicate with other cell types in the healing infarct scar 1 –6 .

Induction of LOX by TGF-β1/Smad/AP-1 signaling aggravates rat myocardial fibrosis and heart failure

This study aims to evaluate the efficacy of lysyl oxidase (LOX) inhibition in regulating rat myocardial fibrosis and chronic heart failure (CHF) and to validate the regulation of LOX by TGF-β1/Smad2/3 signaling in this process. A rat model of CHF was established by abdominal aortic coarctation. The renin-angiotensin-aldosterone system (RAAS) indexes (PRA, ACE2, Ang II, and ALD), cardiac function indicators (LVEF, LVFS, SAP, DAP, and LVEDP), ventricular remodeling- and fibrosis-related indicators (hydroxyproline, collagen deposition,and MMP-2/9), and morphological changes of myocardial tissues were examined. Rat cardiac fibroblasts (RCFs) were used in vitro assays. CHF patients showed increased LOX activity, accompanied by activated RAAS and TGF-β1. Furthermore, inhibition of LOX by β-aminopropionitrile (BAPN) mitigated the RAAS activation and attenuated cardiac dysfunction, ventricular remodeling, myocardial fibrosis, and collagen deposition in CHF rats. Moreover, TGF-β1 signaling diminished the LOX inhibition-mediated antiheart failure effect. Further assays showed that TGF-β1/Smad2/3 signaling increased expression of c-jun (AP-1 transcription factor subunit), which transcriptionally induced LOX expression. Additionally, BAPN abrogated the TGF-β1-mediated increase in cell proliferation and levels of MMP-2/9 and collagen I/III in RCFs. In conclusion, LOX can be induced by TGF-β1/Smad/AP-1 signaling and LOX inhibition attenuates rat myocardial fibrosis and CHF.

Systems biology reveals how altered TGFβ signalling with age reduces protection against pro-inflammatory stimuli

Osteoarthritis (OA) is a degenerative condition caused by dysregulation of multiple molecular signalling pathways. Such dysregulation results in damage to cartilage, a smooth and protective tissue that enables low friction articulation of synovial joints. Matrix metalloproteinases (MMPs), especially MMP-13, are key enzymes in the cleavage of type II collagen which is a vital component for cartilage integrity. Transforming growth factor beta (TGFβ) can protect against pro-inflammatory cytokine-mediated MMP expression. With age there is a change in the ratio of two TGFβ type I receptors (Alk1/Alk5), a shift that results in TGFβ losing its protective role in cartilage homeostasis. Instead, TGFβ promotes cartilage degradation which correlates with the spontaneous development of OA in murine models. However, the mechanism by which TGFβ protects against pro-inflammatory responses and how this changes with age has not been extensively studied. As TGFβ signalling is complex, we used systems biology to combine experimental and computational outputs to examine how the system changes with age. Experiments showed that the repressive effect of TGFβ on chondrocytes treated with a pro-inflammatory stimulus required Alk5. Computational modelling revealed two independent mechanisms were needed to explain the crosstalk between TGFβ and pro-inflammatory signalling pathways. A novel meta-analysis of microarray data from OA patient tissue was used to create a Cytoscape network representative of human OA and revealed the importance of inflammation. Combining the modelled genes with the microarray network provided a global overview into the crosstalk between the different signalling pathways involved in OA development. Our results provide further insights into the mechanisms that cause TGFβ signalling to change from a protective to a detrimental pathway in cartilage with ageing. Moreover, such a systems biology approach may enable restoration of the protective role of TGFβ as a potential therapy to prevent age-related loss of cartilage and the development of OA.

Collagen peptides promote photoaging skin cell repair by activating the TGF-β/Smad pathway and depressing collagen degradation

Collagen hydrolysate has been widely used as a nutraceutical agent against skin aging and has gained increasing attention.

RhoA, Rac1, and Cdc42 differentially regulate αSMA and collagen I expression in mesenchymal stem cells

Mesenchymal stem cells (MSC) are suggested to be important progenitors of myofibroblasts in fibrosis. To understand the role of Rho GTPase signaling in TGFβ-induced myofibroblast differentiation of MSC, we generated a novel MSC line and its descendants lacking functional Rho GTPases and Rho GTPase signaling components. Unexpectedly, our data revealed that Rho GTPase signaling is required for TGFβ-induced expression of α-smooth muscle actin (αSMA) but not of collagen I α1 (col1a1). Whereas loss of RhoA and Cdc42 reduced αSMA expression, ablation of the Rac1 gene had the opposite effect. Although actin polymerization and MRTFa were crucial for TGFβ-induced αSMA expression, neither Arp2/3-dependent actin polymerization nor cofilin-dependent severing and depolymerization of F-actin were required. Instead, F-actin levels were dependent on cell contraction, and TGFβ-induced actin polymerization correlated with increased cell contraction mediated by RhoA and Cdc42. Finally, we observed impaired collagen I secretion in MSC lacking RhoA or Cdc42. These data give novel molecular insights into the role of Rho GTPases in TGFβ signaling and have implications for our understanding of MSC function in fibrosis.

YAP/TAZ regulates TGF-β/Smad3 signaling by induction of Smad7 via AP-1 in human skin dermal fibroblasts

Background

Transcription factors YAP and TAZ function as the primary mediators of the Hippo pathway. Yet, crosstalk of YAP and TAZ with other signaling pathways remains relatively unexplored. We have explored the impact of YAP and TAZ levels on the TGF-β/Smad signaling pathway in human skin dermal fibroblasts.

Methods

YAP and TAZ levels in dermal fibroblasts were reduced in dermal fibroblasts by siRNA-mediated knockdown. The effects of YAP and TAZ reduction on TGF-β/Smad signaling were examined by quantitative real-time PCR, Western analysis, and immunostaining. Luciferase reporter assays and electrophoretic mobility shift assays were conducted to investigate the transcription factor DNA-binding and transcriptional activities.

Results

Knockdown of both YAP and TAZ (YAP/TAZ), but not either separately, impaired TGF-β1-induced Smad3 phosphorylation and Smad3 transcriptional activity, thereby inhibiting the expression of TGF-β target genes. This reduction by reduced levels of YAP/TAZ results from induction of inhibitory Smad7, which inhibits Smad3 phosphorylation and activity by TGF-β1. Conversely, prevention of Smad7 induction restores Smad3 phosphorylation and Smad3 transcriptional activity in fibroblasts that have reduced YAP/TAZ. In agreement with these findings, inhibition of YAP/TAZ transcriptional activity, similar to the reduction of YAP/TAZ levels, also significantly induced Smad7 and impaired TGF-β/Smad signaling. Further investigations revealed that reduced levels of YAP/TAZ led to induction of activator protein-1 (AP-1) activity, Activated AP-1 bound to DNA sequences in the Smad7 gene promoter, and deletion of these AP-1 binding sequences substantially reduced Smad7 promoter reporter activity.

Conclusion

YAP/TAZ functions in concert with transcription factor AP-1 and Smad7 to regulate TGF-β signaling, in human dermal fibroblasts. Reduction of YAP/TAZ levels leads to activation of AP-1 activity, which induces Smad7. Smad7 suppresses the TGF-β pathway.

Electronic supplementary material

The online version of this article (10.1186/s12964-018-0232-3) contains supplementary material, which is available to authorized users.

Involvement of JunB Proto-Oncogene in Tail Formation During Early Xenopus Embryogenesis

Integration of signaling pathways is important for the establishment of the body plan during embryogenesis. However, little is known about how the multiple signals interact to regulate morphogenesis. Here, we show that junb is expressed in the posterior neural plate and the caudal fin during Xenopus embryogenesis and that overexpression of wild-type JunB induces small head phenotypes and ectopic tail-like structures. A mutant form of JunB that lacked GSK3 and MAPK phosphorylation sites showed stronger tail-like structure-inducing activity than wild-type JunB. Moreover, the mutant JunB induced expression of tailbud and neural marker genes, but not somite and chordoneural hinge (CNH) marker genes in ectopic tail-like structures. In ectodermal explants of Xenopus embryos, overexpression of JunB increased the expression of tailbud and posterior marker genes including fgf3, xbra (t) and wnt8. These results indicate that JunB is capable of inducing the ectopic formation of tissues similar to the tailbud, and that the tailbud-inducing activity of JunB is likely to be regulated by FGF and Wnt pathways. Overall, our results suggest that JunB is a regulator of tail organization possibly through integration of several morphogen signaling pathways.

JunD Is Required for Proliferation of Prostate Cancer Cells and Plays a Role in Transforming Growth Factor-β (TGF-β)-induced Inhibition of Cell Proliferation

TGF-β inhibits proliferation of prostate epithelial cells. However, prostate cancer cells in advanced stages become resistant to inhibitory effects of TGF-β. The intracellular signaling mechanisms involved in differential effects of TGF-β during different stages are largely unknown. Using cell line models, we have shown that TGF-β inhibits proliferation in normal (RWPE-1) and prostate cancer (DU145) cells but does not have any effect on proliferation of prostate cancer (PC3) cells. We have investigated the role of Jun family proteins (c-Jun, JunB, and JunD) in TGF-β effects on cell proliferation. Jun family members were expressed at different levels and responded differentially to TGF-β treatment. TGF-β effects on JunD protein levels, but not mRNA levels, correlated with its effects on cell proliferation. TGF-β induced significant reduction in JunD protein in RWPE-1 and DU145 cells but not in PC3 cells. Selective knockdown of JunD expression using siRNA in DU145 and PC3 cells resulted in significant reduction in cell proliferation, and forced overexpression of JunD increased the proliferation rate. On the other hand, knockdown of c-Jun or JunB had little, if any, effect on cell proliferation; overexpression of c-Jun and JunB decreased the proliferation rate in DU145 cells. Further studies showed that down-regulation of JunD in response to TGF-β treatment is mediated via the proteasomal degradation pathway. In conclusion, we show that specific Jun family members exert differential effects on proliferation in prostate cancer cells in response to TGF-β, and inhibition of cell proliferation by TGF-β requires degradation of JunD protein.

Protective role for miR-9-5p in the fibrogenic transformation of human dermal fibroblasts

Background

Excessive accumulation of extracellular matrix (ECM) proteins is the hallmark of fibrotic diseases, including skin fibrosis. This response relies on the activation of dermal fibroblasts that evolve into a pro-fibrogenic phenotype. One of the major players in this process is the cytokine transforming growth factor-β (TGF-β). MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate gene expression affecting a wide range of pathophysiological events including fibrogenesis. MicroRNA-9-5p (miR-9-5p) has been shown to exert a protective role in lung and peritoneal fibrosis. This study aimed to evaluate the role of miR-9-5p in skin fibrosis.

Results

miR-9-5p is up-regulated in TGF-β1-treated human dermal fibroblasts (HDFs). In silico identification of miR-9-5p targets spotted the type II TGF-β receptor (TGFBR2) as a potential TGF-β signaling-related effector for this miRNA. Consistently, over-expression of miR-9-5p in HDFs down-regulated TGFBR2 at both the mRNA and protein levels and reduced the phosphorylation of Smad2 and the translocation of Smad2/3 to the nucleus. In keeping, over-expression of miR-9-5p significantly delayed TGF-β1-dependent transformation of dermal fibroblasts, decreasing the expression of ECM protein collagen, type I, alpha 1 (Col1α1), and fibronectin (FN), the amount of secreted collagen proteins, and the expression of the archetypal myofibroblast marker alpha-smooth muscle actin (α-SMA). By contrast, specific inhibition of miR-9-5p resulted in enhanced presence of fibrosis markers. The expression of miR-9-5p was also detected in the skin and plasma in the mouse model of bleomycin-induced dermal fibrosis. Using lentiviral constructs, we demonstrated that miR-9-5p over-expression was also capable of deterring fibrogenesis in this same model.

Conclusions

miR-9-5p significantly prevents fibrogenesis in skin fibrosis. This is mediated by an abrogation of TGF-β-mediated signaling through the down-regulation of TGFBR2 expression in HDFs. These results may pave the way for future diagnostic or therapeutic developments for skin fibrosis based on miR-9-5p.

Electronic supplementary material

The online version of this article (doi:10.1186/s13069-016-0044-2) contains supplementary material, which is available to authorized users.

Failed degradation of JunB contributes to overproduction of type I collagen and development of dermal fibrosis in patients with systemic sclerosis

OBJECTIVE

The excessive deposition of extracellular matrix, including type I collagen, is a key aspect in the pathogenesis of connective tissue diseases such as systemic sclerosis (SSc; scleroderma). To further our understanding of the mechanisms governing the dysregulation of type I collagen production in SSc, we investigated the role of the activator protein 1 (AP-1) family of transcription factors in regulating COL1A2 transcription.

METHODS

The expression and nuclear localization of AP-1 family members (c-Jun, JunB, JunD, Fra-1, Fra-2, and c-Fos) were examined by immunohistochemistry and Western blotting in dermal biopsy specimens and explanted skin fibroblasts from patients with diffuse cutaneous SSc and healthy controls. Gene activation was determined by assessing the interaction of transcription factors with the COL1A2 enhancer using transient transfection of reporter gene constructs, electrophoretic mobility shift assays, chromatin immunoprecipitation analysis, and RNA interference involving knockdown of individual AP-1 family members. Inhibition of fibroblast mammalian target of rapamycin (mTOR), Akt, and glycogen synthase kinase 3β (GSK-3β) signaling pathways was achieved using small-molecule pharmacologic inhibitors.

RESULTS

Binding of JunB to the COL1A2 enhancer was observed, with its coalescence directed by activation of gene transcription through the proximal promoter. Knockdown of JunB reduced enhancer activation and COL1A2 expression in response to transforming growth factor β. In SSc dermal fibroblasts, increased mTOR/Akt signaling was associated with inactivation of GSK-3β, leading to blockade of JunB degradation and, thus, constitutively high expression of JunB.

CONCLUSION

In patients with SSc, the accumulation of JunB resulting from altered mTOR/Akt signaling and a failure of proteolytic degradation underpins the aberrant overexpression of type I collagen. These findings identify JunB as a potential target for antifibrotic therapy in SSc.

C18 ORF1, a novel negative regulator of transforming growth factor-β signaling

Transforming growth factor (TGF)-β signaling is deliberately regulated at multiple steps in its pathway from the extracellular microenvironment to the nucleus. However, how TGF-β signaling is activated or attenuated is not fully understood. We recently identified transmembrane prostate androgen-induced RNA (TMEPAI), which is involved in a negative feedback loop of TGF-β signaling. When we searched for a family molecule(s) for TMEPAI, we found C18ORF1, which, like TMEPAI, possesses two PY motifs and one Smad-interacting motif (SIM) domain. As expected, C18ORF1 could block TGF-β signaling but not bone morphogenetic protein signaling. C18ORF1 bound to Smad2/3 via its SIM and competed with the Smad anchor for receptor activation for Smad2/3 binding to attenuate recruitment of Smad2/3 to the TGF-β type I receptor (also termed activin receptor-like kinase 5 (ALK5)), in a similar fashion to TMEPAI. Knockdown of C18ORF1 prolonged duration of TGF-β-induced Smad2 phosphorylation and concomitantly potentiated the expression of JunB, p21, and TMEPAI mRNAs induced by TGF-β. Consistently, TGF-β-induced cell migration was enhanced by the knockdown of C18ORF1. These results indicate that the inhibitory function of C18ORF1 on TGF-β signaling is similar to that of TMEPAI. However, in contrast to TMEPAI, C18ORF1 was not induced upon TGF-β signaling. Thus, we defined C18ORF1 as a surveillant of steady state TGF-β signaling, whereas TMEPAI might help C18ORF1 to inhibit TGF-β signaling in a coordinated manner when cells are stimulated with high levels of TGF-β.

Transcriptional regulation of haematopoietic stem cells

Haematopoietic stem cells (HSCs) are a rare cell population found in the bone marrow of adult mammals and are responsible for maintaining the entire haematopoietic system. Definitive HSCs are produced from mesoderm during embryonic development, from embryonic day 10 in the mouse. HSCs seed the foetal liver before migrating to the bone marrow around the time of birth. In the adult, HSCs are largely quiescent but have the ability to divide to self-renew and expand, or to proliferate and differentiate into any mature haematopoietic cell type. Both the specification of HSCs during development and their cellular choices once formed are tightly controlled at the level of transcription. Numerous transcriptional regulators of HSC specification, expansion, homeostasis and differentiation have been identified, primarily from analysis of mouse gene knockout experiments and transplantation assays. These include transcription factors, epigenetic modifiers and signalling pathway effectors. This chapter reviews the current knowledge of these HSC transcriptional regulators, predominantly focusing on the transcriptional regulation of mouse HSCs, although transcriptional regulation of human HSCs is also mentioned where relevant. Due to the breadth and maturity of this field, we have prioritised recently identified examples of HSC transcriptional regulators. We go on to highlight additional layers of control that regulate expression and activity of HSC transcriptional regulators and discuss how chromosomal translocations that result in fusion proteins of these HSC transcriptional regulators commonly drive leukaemias through transcriptional dysregulation.

SMAD regulatory networks construct a balanced immune system

A balanced immune response requires combating infectious assaults while striving to maintain quiescence towards the self. One of the central players in this process is the pleiotropic cytokine transforming growth factor-β (TGF-β), whose deficiency results in spontaneous systemic autoimmunity in mice. The dominant function of TGF-β is to regulate the peripheral immune homeostasis, particularly in the microbe-rich and antigen-rich environment of the gut. To maintain intestinal integrity, the epithelial cells, myeloid cells and lymphocytes that inhabit the gut secrete TGF-β, which acts in both paracrine and autocrine fashions to activate its signal transducers, the SMAD transcription factors. The SMAD pathway regulates the production of IgA by B cells, maintains the protective mucosal barrier and promotes the balanced differentiation of CD4(+) T cells into inflammatory T helper type 17 cells and suppressive FOXP3(+) T regulatory cells. While encounters with pathogenic microbes activate SMAD proteins to evoke a protective inflammatory immune response, SMAD activation and synergism with immunoregulatory factors such as the vitamin A metabolite retinoic acid enforce immunosuppression toward commensal microbes and innocuous food antigens. Such complementary context-dependent functions of TGF-β are achieved by the co-operation of SMAD proteins with distinct dominant transcription activators and accessory chromatin modifiers. This review highlights recent advances in unravelling the molecular basis for the multi-faceted functions of TGF-β in the gut that are dictacted by fluid orchestrations of SMADs and their myriad partners.

Overlapping activities of TGF-β and Hedgehog signaling in cancer: therapeutic targets for cancer treatment

Recent advances in the field of cancer therapeutics come from the development of drugs that specifically recognize validated oncogenic or pro-metastatic targets. The latter may be mutated proteins with altered function, such as kinases that become constitutively active, or critical components of growth factor signaling pathways, whose deregulation leads to aberrant malignant cell proliferation and dissemination to metastatic sites. We herein focus on the description of the overlapping activities of two important developmental pathways often exacerbated in cancer, namely Transforming Growth Factor-β (TGF-β) and Hedgehog (HH) signaling, with a special emphasis on the unifying oncogenic role played by GLI1/2 transcription factors. The latter are the main effectors of the canonical HH pathway, yet are direct target genes of TGF-β/SMAD signal transduction. While tumor-suppressor in healthy and pre-malignant tissues, TGF-β is often expressed at high levels in tumors and contributes to tumor growth, escape from immune surveillance, invasion and metastasis. HH signaling regulates cell proliferation, differentiation and apoptosis, and aberrant HH signaling is found in a variety of cancers. We discuss the current knowledge on HH and TGF-β implication in cancer including cancer stem cell biology, as well as the current state, both successes and failures, of targeted therapeutics aimed at blocking either of these pathways in the pre-clinical and clinical settings.

JunB contributes to Id2 repression and the epithelial-mesenchymal transition in response to transforming growth factor-β

JunB helps set in motion the transcriptional program necessary for the epithelial–mesenchymal transition and tissue fibrosis in response to TGF-β.

The process of epithelial–mesenchymal transition (EMT) in response to transforming growth factor–β (TGF-β) contributes to tissue fibrosis, wound healing, and cancer via a mechanism that is not fully understood. This study identifies a critical role of JunB in the EMT and profibrotic responses to TGF-β. Depletion of JunB by small interfering ribonucleic acid abrogates TGF-β–induced disruption of cell–cell junctions, formation of actin fibers, focal adhesions, and expression of fibrotic proteins. JunB contributes to Smad-mediated repression of inhibitor of differentiation 2 through interaction with transcription repressor activating transcription factor 3. Importantly, JunB mediates the TGF-β induction of profibrotic response factors, fibronectin, fibulin-2, tropomyosin (Tpm1), and integrin-β3, which play critical roles in matrix deposition, cell–matrix adhesion, and actin stress fibers. In summary, JunB provides important input in setting the transcriptional program of the EMT and profibrotic responses to TGF-β. Thus, JunB represents an important target in diseases associated with EMT, including cancer and fibrosis.

Key signaling nodes in mammary gland development and cancer: Smad signal integration in epithelial cell plasticity

Smad proteins are the key intermediates of transforming growth factor-beta (TGF-β) signaling during development and in tissue homeostasis. Pertubations in TGF-β/Smad signaling have been implicated in cancer and other diseases. In the cell nucleus, Smad complexes trigger cell type- and context-specific transcriptional programs, thereby transmitting and integrating signals from a variety of ligands of the TGF-β superfamily and other stimuli in the cell microenvironment. The actual transcriptional and biological outcome of Smad activation critically depends on the genomic integrity and the modification state of genome and chromatin of the cell. The cytoplasmic and nuclear Smads can also modulate the activity of other signal transducers and enzymes such as microRNA-processing factors. In the case of breast cancer, the role of Smads in epithelial plasticity, tumor-stroma interactions, invasion, and metastasis seems of particular importance.

Ultraviolet irradiation induces CYR61/CCN1, a mediator of collagen homeostasis, through activation of transcription factor AP-1 in human skin fibroblasts

UV irradiation from the sun elevates the production of collagen-degrading matrix metalloproteinases (MMPs) and reduces the production of new collagen. This imbalance of collagen homeostasis impairs the structure and function of the dermal collagenous extracellular matrix (ECM), thereby promoting premature skin aging (photoaging). We report here that aberrant dermal collagen homeostasis in UV-irradiated human skin is mediated in part by a CCN-family member, cysteine-rich protein-61 (CYR61/CCN1). CYR61 is significantly elevated in acutely UV-irradiated human skin in vivo, and UV-irradiated human skin fibroblasts. Knockdown of CYR61 significantly attenuates UV irradiation-induced inhibition of type-I procollagen and upregulation of MMP-1. Determination of CYR61 mRNA and protein indicates that the primary mechanism of CYR61 induction by UV irradiation is transcriptional. Analysis of CYR61 proximal promoter showed that a sequence conforming to the consensus binding site for transcription factor activator protein-1 (AP-1) is required for promoter activity. UV irradiation increased the binding of AP-1-family members c-Jun and c-Fos to this AP-1 site. Furthermore, functional blockade of c-Jun or knockdown of c-Jun significantly reduced the UV irradiation-induced activation of CYR61 promoter and CYR61 gene expression. These data show that CYR61 is transcriptionally regulated by UV irradiation through transcription factor AP-1, and mediates altered collagen homeostasis that occurs in response to UV irradiation in human skin fibroblasts.

Role of Smad3, acting independently of transforming growth factor-beta, in the early induction of Wnt-beta-catenin signaling by parathyroid hormone in mouse osteoblastic cells

Parathyroid hormone (PTH) exerts an anabolic action on bone but the mechanisms are incompletely understood. We showed previously that PTH interacts with the canonical Wnt-beta-catenin signaling pathway via the transforming growth factor (TGF)-beta signaling molecule, Smad3, to modulate osteoblast differentiation and apoptosis. Here, we examined which actions of Smad3 are TGF-beta-independent in stimulating the osteoblast phenotype and PTH-induced Wnt-beta-catenin signaling. For this, the TGF-beta receptor type 1 [activin receptor-like kinase (ALK5)] inhibitor (SB431542), and a Smad3 mutant in which the site normally phosphorylated by ALK5 is mutated from SSVS to AAVA, was used. PTH induced total beta-catenin and reduced phosphorylated beta-catenin levels at 1, 6, and 24 h in mouse osteoblastic MC3T3-E1 cells. Transient transfection of Smad3AAVA inhibited the PTH induction of total beta-catenin and reduction of phosphorylated beta-catenin levels at 6 and 24 h, but not at 1 h, indicating that the early effects occur independently of TGF-beta receptor signaling. On the other hand, MC3T3-E1 cell clones in which Smad3AAVA was stably expressed demonstrated elevated beta-catenin levels, although alkaline phosphatase (ALP) activity and mineralization were unaltered. In contrast, MC3T3-E1 cell clones in which wild-type Smad3 was stably expressed exhibited increased ALP activity and mineralization that were decreased by the ALK5 inhibitor, SB431542, although the beta-catenin levels induced in these cells were not modulated. In conclusion, the present study indicates that PTH induces osteoblast beta-catenin levels via Smad3 independently of, and dependently on, TGF-beta in the early and later induction phases, respectively.

Transforming growth factor-beta signaling in skin: stromal to epithelial cross-talk

In this issue, Denton et al., describe a mouse model of postnatal deletion of the transforming growth factor (TGF)-beta receptor type II (TbetaRII) in skin fibroblasts. Using a tamoxifen-dependent inducible Cre-lox strategy, the authors demonstrate the pivotal role played by TGF-beta signaling in fibroblasts during wound healing. Healing of full-thickness wounds after fibroblast-specific deletion of TbetaRII in the skin was severely impaired and exhibited delayed re-epithelialization. This study emphasizes the importance of fibroblasts in mesenchymal-epithelial interaction in the skin during wound repair.

Signaling cross-talk between TGF-beta/BMP and other pathways

Transforming growth factor-beta (TGF-beta)/bone morphogenic protein (BMP) signaling is involved in the vast majority of cellular processes and is fundamentally important during the entire life of all metazoans. Deregulation of TGF-beta/BMP activity almost invariably leads to developmental defects and/or diseases, including cancer. The proper functioning of the TGF-beta/BMP pathway depends on its constitutive and extensive communication with other signaling pathways, leading to synergistic or antagonistic effects and eventually desirable biological outcomes. The nature of such signaling cross-talk is overwhelmingly complex and highly context-dependent. Here we review the different modes of cross-talk between TGF-beta/BMP and the signaling pathways of Mitogen-activated protein kinase, phosphatidylinositol-3 kinase/Akt, Wnt, Hedgehog, Notch, and the interleukin/interferon-gamma/tumor necrosis factor-alpha cytokines, with an emphasis on the underlying molecular mechanisms.

Transforming growth factor-beta in cutaneous melanoma

Transforming growth factor-beta (TGF-beta) plays a complex role during carcinogenesis. It may either act as a tumor suppressor through its broad antiproliferative potential or as a tumor promoter either via direct effects on tumor cell aggressiveness or indirectly by modulating stromal responses, angiogenesis and immune surveillance. Increased production of TGF-beta by cancer cells is often associated with tumor grade. Melanoma cells largely escape cell cycle arrest normally induced by TGF-beta in normal melanocytes, yet produce active TGF-beta and are capable of efficient transcriptional responses to the growth factor. In this review, we summarize the current knowledge about the role played by TGF-beta in melanoma progression and hypothesize about the appropriateness of targeting TGF-beta signaling for therapeutic intervention.

Bovine dialyzable leukocyte extract modulates AP-1 DNA-binding activity and nuclear transcription factor expression in MCF-7 breast cancer cells

BACKGROUND

We have previously demonstrated that bovine dialyzable leukocyte extract (bDLE) induces death through an apoptosis mechanism in MCF-7 breast cancer cells. Depending on the cell type and stimulus, activating protein-1 (AP-1) has been shown to regulate cell proliferation and differentiation, the stress response, apoptosis and survival. It remains unknown whether AP-1 and other transcription factors are mechanisms by which bDLE induces cell death.

METHODS

To determine whether bDLE modulates the AP-1 DNA binding and gene expression, MCF-7 breast cancer cells were treated with bDLE (0, 1, 5, 10 U) for 72 h and evaluated by electrophoretic mobility shift assay, reverse transcriptase-polymerase chain reaction and Western blot assays.

RESULTS

bDLE induced inhibition of cell growth, suppressed the AP-1 DNA-binding activity, decreased c-Jun protein expression and modulated NFATx, NFATc, NFkappaB, c-Jun and c-Fos transcription factor gene expression in MCF-7 breast cancer cells.

DISCUSSION

The present data indicate that bDLE can block the AP-1 DNA-binding activity and expression of several transcriptions factors in breast cancer cells, which will have great potential in improving cancer therapy.

Jun N-terminal kinase 1 regulates epithelial-to-mesenchymal transition induced by TGF-beta1

Transforming growth factor beta1 (TGF-beta1) is a cardinal cytokine in the pathogenesis of airway remodeling, and promotes epithelial-to-mesenchymal transition (EMT). As a molecular interaction between TGF-beta1 and Jun N-terminal kinase (JNK) has been demonstrated, the goal of this study was to elucidate whether JNK plays a role in TGF-beta1-induced EMT. Primary cultures of mouse tracheal epithelial cells (MTEC) from wild-type, JNK1-/- or JNK2-/- mice were comparatively evaluated for their ability to undergo EMT in response to TGF-beta1. Wild-type MTEC exposed to TGF-beta1 demonstrated a prominent induction of mesenchymal mediators and a loss of epithelial markers, in conjunction with a loss of trans-epithelial resistance (TER). Significantly, TGF-beta1-mediated EMT was markedly blunted in epithelial cells lacking JNK1, while JNK2-/- MTEC underwent EMT in response to TGF-beta1 in a similar way to wild-type cells. Although Smad2/3 phosphorylation and nuclear localization of Smad4 were similar in JNK1-/- MTEC in response to TGF-beta1, Smad DNA-binding activity was diminished. Gene expression profiling demonstrated a global suppression of TGF-beta1-modulated genes, including regulators of EMT in JNK1-/- MTEC, in comparison with wild-type cells. In aggregate, these results illuminate the novel role of airway epithelial-dependent JNK1 activation in EMT.

TGF-beta suppresses POEM expression through ERK1/2 and JNK in osteoblasts

POEM, also called nephronectin, is an extracellular matrix protein that is considered to play a critical role as an adhesion molecule in the development and functioning of various tissues, such as kidneys and bones. In the present study, we examined the molecular mechanism of POEM gene expression, and found that transforming growth factor-beta (TGF-beta) strongly inhibited POEM expression in the mouse osteoblastic cell line, MC3T3-E1. TGF-beta-induced decrease of POEM expression occurred in both time- and dose-dependent manners through the activation of TGF-beta receptor I and extracellular signal-regulated kinase/c-Jun N-terminal kinase pathways.

Transforming growth factor-β and fibrosis

Transforming growth factor-β (TGF-β), a prototype of multifunctional cytokine, is a key regulator of extracellular matrix (ECM) assembly and remodeling. Specifically, TGF-β isoforms have the ability to induce the expression of ECM proteins in mesenchymal cells, and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the ECM. Elevated TGF-β expression in affected organs, and subsequent deregulation of TGF-β functions, correlates with the abnormal connective tissue deposition observed during the onset of fibrotic diseases. During the last few years, tremendous progress has been made in the understanding of the molecular aspects of intracellular signaling downstream of the TGF-β receptors. In particular, Smad proteins, TGF-β receptor kinase substrates that translocate into the cell nucleus to act as transcription factors, have been studied extensively. The role of Smad3 in the transcriptional regulation of typeIcollagen gene expression and in the development of fibrosis, demonstrated both in vitro and in animal models with a targeted deletion of Smad3, is of critical importance because it may lead to novel therapeutic strategies against these diseases. This review focuses on the mechanisms underlying Smad modulation of fibrillar collagen expression and how it relates to fibrotic processes.

A tale of two proteins: differential roles and regulation of Smad2 and Smad3 in TGF-beta signaling

Transforming growth factor-beta (TGF-beta) is an important growth inhibitor of epithelial cells, and insensitivity to this cytokine results in uncontrolled cell proliferation and can contribute to tumorigenesis. Smad2 and Smad3 are direct mediators of TGF-beta signaling, however little is known about the selective activation of Smad2 versus Smad3. The Smad2 and Smad3 knockout mouse phenotypes and studies comparing Smad2 and Smad3 activation of TGF-beta target genes, suggest that Smad2 and Smad3 have distinct roles in TGF-beta signaling. The observation that TGF-beta inhibits proliferation of Smad3-null mammary gland epithelial cells, whereas Smad3 deficient fibroblasts are only partially growth inhibited, suggests that Smad3 has a different role in epithelial cells and fibroblasts. Herein, the current understanding of Smad2 and Smad3-mediated TGF-beta signaling and their relative roles are discussed, in addition to potential mechanisms for the selective activation of Smad2 versus Smad3. Since alterations in the TGF-beta signaling pathway play an important role in promoting tumorigenesis and cancer progression, methods for therapeutic targeting of the TGF-beta signaling pathway are being pursued. Determining how Smad2 or Smad3 differentially regulate the TGF-beta response may translate into developing more effective strategies for cancer therapy.

Transforming Growth Factor β Signaling via Ras in Mesenchymal Cells Requires p21-Activated Kinase 2 for Extracellular Signal-Regulated Kinase-Dependent Transcriptional Responses

Transforming growth factor beta (TGF-beta) signaling via Smad proteins occurs in various cell types. However, whereas the biological response to TGF-beta can be as distinct as growth promoting (i.e., mesenchymal cells) versus growth inhibiting (i.e., epithelial cells), few discernible differences in TGF-beta signaling have been reported. In the current study, we examined the role of Ras in the proliferative response to TGF-beta and how it might interface with Smad-dependent and Smad-independent TGF-beta signaling targets. TGF-beta stimulated Ras activity in a subset of mesenchymal, but not epithelial, cultures and was required for extracellular signal-regulated kinase (ERK)-dependent transcriptional responses. Although dominant negative Ras had no effect on TGF-beta internalization or Smad-dependent signaling (i.e., phosphorylation, nuclear translocation, or SBE-luciferase activity), it did prevent the hyperphosphorylation of the Smad transcriptional corepressor TG-interacting factor (TGIF). This was not sufficient, however, to overcome the mitogenic response stimulated by TGF-beta, which was dependent on signals downstream of p21-activated kinase 2 (PAK2). Moreover, although the initial activation of Ras and PAK2 are distinctly regulated, TGF-beta-stimulated PAK2 activity is required for Ras-dependent ERK phosphorylation and Elk-1 transcription. These findings show the requirement for crosstalk between two Smad-independent pathways in regulating TGF-beta proliferation and indicate that the mechanism(s) by which TGF-beta stimulates growth is not simply the opposite of its growth inhibitory actions.

Physical and functional cooperation between AP-1 and beta-catenin for the regulation of TCF-dependent genes

Stabilization of cytoplasmic beta-catenin is a hallmark of a variety of cancers. The stabilized beta-catenin is able to translocate to the nucleus, where it acts as a transcriptional activator of T-cell factor (TCF)-regulated genes. beta-Catenin may cross-talk with many signalling cascades to activate target genes. Whether beta-catenin cooperates with AP-1, another transcriptional complex activated during tumorigenesis is not fully clarified. We show that beta-catenin co-immunoprecipitates with c-Jun and c-Fos. GST pull-down experiments indicate a physical association of the armadillo repeat domain of beta-catenin with the DNA-binding domain of c-Jun and of the C-terminal domain of beta-catenin with the N-terminal domain of c-Fos. Promoter studies indicate that overexpression of AP-1 activates the transcription of two beta-catenin target genes, cyclin D1 and c-myc, by a mechanism independent of the AP-1 site, and fully dependent on the TCF-binding site. We further demonstrate that AP-1/beta-catenin synergism is involved during serum-induced cyclin D1 transcriptional activation. We identify a TCF-binding site on the cyclin D1 promoter which binds in vivo a complex induced by serum, containing beta-catenin, TCF4, c-Fos, c-Jun, JunB and JunD. This novel mechanism of interaction between two signalling cascades might contribute to the potentiation of malignancy.

Transcriptional regulation of mouse mast cell protease-7 by TGF-β

Mouse mast cell protease-7 (mmcp-7) is a tryptase predominantly expressed in differentiated connective tissue-type mast cells. Previous study revealed that transforming growth factor-beta (TGF-beta) increases gene transcript of mmcp-7 in mast cells. The present study explored molecular mechanism of the up-regulation of mmcp-7 by TGF-beta. Luciferase-based reporter assays using deletion and point mutations of mmcp-7 promoter showed a critical region spanning nt -126 to -122 relative to the transcriptional start site, a Smad-binding element, for transcriptional activation by the TGF-beta pathway. In addition, a region from nt -104 to -98, a TPA-responsive element, was also necessary for the transactivation. Consistent with the current model for the TGF-beta signaling, Smad4 was required for the transcription of mmcp-7 by Smad3, a signal mediator of TGF-beta. Treatment with TGF-beta in mast cells resulted in the differential gene induction of the AP-1 components, i.e., transient induction of c-fos but not of c-jun and junB. Expression of c-fos further enhanced Smad3 and Smad4-induced transcription of mmcp-7, whereas c-jun expression inhibited the transcription. Our results suggest that TGF-beta stimulates mmcp-7 transcription through the Smad3-Smad4 pathway as well as c-fos induction, and that the AP-1 components distinctly related with the TGF-beta pathway.

Role of astrocytes in reproduction and neuroprotection

Hypothalamic astrocytes secrete TGF-beta and 3 alpha,5 alpha-tetrahydro progesterone (3 alpha,5 alpha-THP) in culture. When the astrocyte-conditioned medium (ACM) was incubated with the hypothalamic cell line GT1-7, it resulted in the secretion of GnRH. Immunoneutralization with TGF-beta antibody or ultra-filteration with a 10 kDa cut off filter resulted in attenuation of the GnRH releasing ability of ACM, indicating that TGF-beta was a major factor involved with GnRH release. Treatment with estrogens increases TGF-beta secretion. These observations indicate a significant role of astrocytes in GnRH secretion. Serum-deprivation results in the death of GT1-7 neurons in culture and addition of ACM or TGF-beta to the culture, attenuates cell death. The mechanism of protection from cell death appears to involve phosphorylation of MKK4, JNK, c-Jun(Ser63), and enhancement of AP-1 binding. Co-administration of JNK inhibitors, but not MEK inhibitors attenuated ACM or TGF-beta-induced c-Jun(Ser63) phosphorylation and their neuroprotective effects. These studies suggest that astrocytes can protect neurons, at least in part, by the release of TGF-beta and activation of a c-Jun/AP-1 protective pathway.

Curcumin blocks fibrosis in anti-Thy 1 glomerulonephritis through up-regulation of heme oxygenase 1

BACKGROUND

Induction of heme oxygenase 1 (HO-1) has been shown to be beneficial in a variety of pathologic settings. Curcumin, a polyphenolic compound, has antifibrotic effects in lung models of fibrosis, and is known to induce HO-1 in renal tubular cells. In this study, we determined whether curcumin has antifibrotic properties in glomerular fibrosis and if these effects are mediated by induction of HO-1.

METHODS

Curcumin effects on HO-1 expression in cultured mesangial cells and in glomeruli in vivo were analyzed by Northern and Western blotting. The dose-dependent effect of curcumin on glomerular fibrosis was tested in the anti-Thy 1 glomerulonephritis model. Curcumin was applied at doses of 10 to 200 mg/kg body weight by intraperitoneal injection from days 3 to 5 after induction of disease. On day 6, glomeruli were harvested and markers of fibrosis [plasminogen activator inhibitor-1 (PAI-1), transforming growth factor-beta (TGF-beta), fibronectin, periodic acid-Schiff (PAS) staining] were analyzed. The effect of HO-1 inhibition was tested in a second experiment were nephritic rats were treated with curcumin (100 mg/kg body weight) or the combination of curcumin and the HO-1 inhibitor zinc protoporphyrin (100 microg/kg).

RESULTS

Curcumin potently induced mesangial cell HO-1 expression in vitro and up-regulated glomerular HO-1 expression in nephritic animals in vivo. Curcumin treatment led to a significant, dose-dependent reduction of markers of fibrosis and proteinuria, with maximal inhibition at doses of 50 to 100 mg/kg. Beneficial effects of curcumin on markers of fibrosis and proteinuria were lost after HO-1 inhibition.

CONCLUSION

Curcumin has antifibrotic effects in glomerular disease, which are mediated through an induction of HO-1.

Revealing transforming growth factor-beta signaling transduction in human kidney by gene expression data mining

Tumor growth factor-beta (TGF-beta) is a key mediator of glomerular and tubulointerstitial pathobiology in chronic kidney disease. Its signaling transduction controls a diverse number of biological processes in a dynamic and context-dependent manner. We applied a data mining strategy to deconvolute gene expression patterns across hundreds of microarray data sets to reveal members of the TGF-beta signaling network in human kidney. This strategy is composed of three major steps: (i) select genes known to be involved and expressionally regulated in TGF-beta signaling as "bait"; (ii) select microarray data sets in which the bait genes are strongly co-regulated; (iii) identify (or "fish") additional TGF-beta signaling genes by a non-parametric statistic-based gene scoring system (NP score). The 40 genes with highest NP scores and significant permutation p values were selected for in silico validation, and used to identify a network, in which 35 of these genes were found to be connected by literature- derived relationships. Transcription factors were found to be enriched in the top list. Among them, activated transcription factor 3 (ATF3) had the highest NP score, and was proposed to play a pivotal role in TGF-beta signaling in human kidney. Finally, we implemented a non-parametric pathway ranking (NPPR) tool (Mootha et al., 2003) to rank pathways and identified canonical biological pathways associated with the down-stream of TGF-beta signaling.

Crosstalk mechanisms between the mitogen-activated protein kinase pathways and Smad signaling downstream of TGF-beta: implications for carcinogenesis

Transforming growth factor-beta (TGF-beta) superfamily members signal via membrane-bound heteromeric serine-threonine kinase receptor complexes. Upon ligand-binding, receptor activation leads to phosphorylation of cytoplasmic protein substrates of the Smad family. Following phosphorylation and oligomerization, the latter move into the nucleus to act as transcription factors to regulate target gene expression. TGF-beta responses are not solely the result of the activation Smad cascade, but are highly cell-type specific and dependent upon interactions of Smad signaling with a variety of other intracellular signaling mechanisms, initiated or not by TGF-beta itself, that may either potentiate, synergize, or antagonize, the rather linear TGF-beta/Smad pathway. These include, (a), regulation of Smad activity by mitogen-activated protein kinases (MAPKs), (b), nuclear interaction of activated Smads with transcriptional cofactors, whether coactivators or corepressors, that may be themselves be regulated by diverse signaling mechanisms, and (c), negative feedback loops exerted by inhibitory Smads, transcriptional targets of the Smad cascade. This review focuses on how MAPKs modulate the outcome of Smad activation by TGF-beta, and how cross-signaling mechanisms between the Smad and MAPK pathways may take place and affect cell fate in the context of carcinogenesis.

TGF-beta and TNF-alpha: antagonistic cytokines controlling type I collagen gene expression

The balance between production and degradation of type I collagen plays a critical role in the development and maintenance of organ and tissue integrity. It also represents the most crucial element governing the process of tissue repair. The synthesis of type I collagen gene is highly regulated by different cytokines at the transcriptional level. Especially, transforming growth factor beta (TGF-beta), a key player in the physiopathology of tissue repair, enhances type I collagen gene expression. In contrast, tumor necrosis factor alpha (TNF-alpha), whose matrix-remodelling function is opposite to that of TGF-beta, reduces type I collagen gene expression. This review focuses on transcriptional regulation of type I collagen by TGF-beta and TNF-alpha and on the molecular mechanisms that control the antagonistic activity of TNF-alpha against TGF-beta-driven type I collagen gene expression.

Increased longevity of hematopoiesis in continuous bone marrow cultures and adipocytogenesis in marrow stromal cells derived from Smad3(-/-) mice

OBJECTIVE

To determine the role of Smad3 in modulating hematopoiesis, continuous bone marrow cultures were established from Smad-/- mice, and the longevity of hematopoiesis and extent of adipogenesis in the supportive hematopoietic microenvironment were compared to those from cultures of control, Smad3+/+ or heterozygous Smad3+/- mice.

MATERIALS AND METHODS

Long-term bone marrow cultures (LTBMCs) were established from Smad3+/+, Smad3+/-, or Smad3-/- mice. On a weekly basis, the number of cobblestone islands, number of nonadherent cells, confluence of the adherent cells, or CFU-GEMM colonies was determined. Bone marrow stromal cell lines were established and cobblestone island production on these cell lines determined in the presence of nonadherent cells from week-42 Smad3-/- or week-4 C57BL/6J LTBMCs.

RESULTS

Initial proliferative capacity of the LTBMCs was similar in all groups through week 20, at which time there was an increase in cobblestone islands and production of nonadherent cells and CFU-GEMM colonies in the Smad3-/- group. By week 28, only the Smad3-/- LTBMCs had significantly maintained increased production of these parameters. Maintenance of cobblestone islands indicative of the most primitive hematopoietic progenitor cells persisted past 45 weeks in Smad3-/- cultures. The Smad3-/- stromal cell line also demonstrated increased support of cobblestone island production when incubated with nonadherent cells from week-42 Smad3-/- or week-4 C57BL/6J LTBMCs. Evaluation of adipocytogenesis in stromal cells showed significantly greater accumulation of adipocytes in lines from Smad3-/- than from Smad3+/+ mice.

CONCLUSIONS

These data provide evidence for a significant effect of deletion of the Smad3 signaling pathway in increased hematopoiesis in LTBMCs and support the negative regulatory influence of TGFbeta signaling on adipocytogenesis and long-term hematopoiesis in vitro.

CHIP Controls the Sensitivity of Transforming Growth Factor-β Signaling by Modulating the Basal Level of Smad3 through Ubiquitin-mediated Degradation

Transforming growth factor-beta (TGF-beta) signaling is critical in a variety of biological processes such as cell proliferation, differentiation, and apoptosis. TGF-beta signaling is mediated by a group of proteins including TGF-beta receptors and Smads. It is known that different cells can exhibit different sensitivities to TGF-beta. Several molecular mechanisms, such as the differential expression of the receptor levels, have been suggested as contributing to these differences. Here, we report evidence for a novel mechanism of regulating TGF-beta sensitivity that depends on the role of CHIP (carboxyl terminus of Hsc70-interacting protein) in regulating the basal level of Smad3 via the ubiquitin-dependent degradation pathway. First, using a luciferase assay we found that overexpression of CHIP inhibited TGF-beta signaling, whereas silencing CHIP expression by small interfering RNAs led to increased TGF-beta signaling sensitivity. Second, based on the results of cell proliferation assays and JunB expression, we found that TGF-beta signaling could be abolished by stably overexpressing CHIP. Third, in those cell lines with stably expressed CHIP, we observed that the Smad3 protein level was dramatically decreased. Finally, we demonstrated that CHIP served as a U-box dependent E3 ligase that can directly mediate ubiquitination and degradation of Smad3 and that this action of CHIP was independent of TGF-beta signaling. Taken together, these findings suggest that CHIP can modulate the sensitivity of the TGF-beta signaling by controlling the basal level of Smad3 through ubiquitin-mediated degradation.