Smad7: not only a regulator, but also a cross-talk mediator of TGF-β signalling

Status and role of the ubiquitin-proteasome system in renal fibrosis

The ubiquitin-proteasome system (UPS) is a basic regulatory mechanism in cells that is essential for maintaining cell homeostasis, stimulating signal transduction, and determining cell fate. These biological processes require coordinated signaling cascades across members of the UPS to achieve substrate ubiquitination and deubiquitination. The role of the UPS in fibrotic diseases has attracted widespread attention, and the aberrant expression of UPS members affects the fibrosis process. In this review, we provide an overview of the UPS and its relevance for fibrotic diseases. Moreover, for the first time, we explore in detail how the UPS promotes or inhibits renal fibrosis by regulating biological processes such as signaling pathways, inflammation, oxidative stress, and the cell cycle, emphasizing the status and role of the UPS in renal fibrosis. Further research on this system may reveal new strategies for preventing renal fibrosis.

Biomaterials-Based Technologies in Skeletal Muscle Tissue Engineering

For many clinically prevalent severe injuries, the inherent regenerative capacity of skeletal muscle remains inadequate. Skeletal muscle tissue engineering (SMTE) seeks to meet this clinical demand. With continuous progress in biomedicine and related technologies including micro/nanotechnology and 3D printing, numerous studies have uncovered various intrinsic mechanisms regulating skeletal muscle regeneration and developed tailored biomaterial systems based on these understandings. Here, the skeletal muscle structure and regeneration process are discussed and the diverse biomaterial systems derived from various technologies are explored in detail. Biomaterials serve not merely as local niches for cell growth, but also as scaffolds endowed with structural or physicochemical properties that provide tissue regenerative cues such as topographical, electrical, and mechanical signals. They can also act as delivery systems for stem cells and bioactive molecules that have been shown as key participants in endogenous repair cascades. To achieve bench-to-bedside translation, the typical effect enabled by biomaterial systems and the potential underlying molecular mechanisms are also summarized. Insights into the roles of biomaterials in SMTE from cellular and molecular perspectives are provided. Finally, perspectives on the advancement of SMTE are provided, for which gene therapy, exosomes, and hybrid biomaterials may hold promise to make important contributions.

Microvesicles-delivering Smad7 have advantages over microvesicles in suppressing fibroblast differentiation in a model of Peyronie's disease

BACKGROUND

This study compared the differences of microvesicles (MVs) and microvesicles-delivering Smad7 (Smad7-MVs) on macrophage M1 polarization and fibroblast differentiation in a model of Peyronie's disease (PD).

METHODS

Overexpression of Smad7 in rat BMSCs was obtained by pCMV5-Smad7 transfection. MVs were collected from rat BMSCs using ultracentrifugation. In cells, 100 µg/mL of MVs or Smad7-MVs were used to treat the 100 ng/mL of lipopolysaccharide (LPS)-induced RAW264.7 cells or 10 ng/mL of recombinant transforming growth factor-β1 (TGF-β1)-induced fibroblasts. The pro-inflammatory cytokines and markers of M1 macrophages were measured in RAW264.7 cells, and the migration and markers of fibroblast differentiation were measured in fibroblasts. In rats, 50 µg of MVs or Smad7-MVs were used to treat the TGF-β1-induced animals. The pathology of tunica albuginea (TA), the markers of M1 macrophages and fibroblast differentiation in the TA were measured.

RESULTS

The MVs or Smad7-MVs treatment suppressed the LPS-induced macrophage M1 polarization and TGF-β1-induced fibroblast differentiation. Moreover, the Smad7-MVs treatment decreased the fibroblast differentiation compared with the MVs treatment. In the TGF-β1-induced TA of rats, MVs or Smad7-MVs treatment ameliorated the TA fibrosis by suppressing the macrophage M1 polarization and fibroblast differentiation. There was no significance on the M1-polarized macrophages between the MVs treatment and the Smad7-MVs treatment. Meanwhile, the Smad7-MVs treatment had an edge in terms of suppressing the fibroblast differentiation in the TGF-β1-induced PD model compared with the MVs treatment.

CONCLUSIONS

This study demonstrated that Smad7-MVs treatment had advantages over MVs treatment in suppressing of fibroblast differentiation in a model of PD.

Renoprotective mechanisms of exercise training against acute and chronic renal diseases - A perspective based on experimental studies

Regular exercise training can lead to several health benefits, reduce mortality risk, and increase life expectancy. On the other hand, a sedentary lifestyle is a known risk factor for chronic diseases and increased mortality. Acute kidney injury (AKI) and chronic kidney disease (CKD) represent a significant global health problem, affecting millions of people worldwide. The progression from AKI to CKD is well-recognized in the literature, and exercise training has emerged as a potential renoprotective strategy. Thus, this article aims to review the main molecular mechanisms underlying the renoprotective actions of exercise training in the context of AKI and CKD, focusing on its antioxidative, anti-inflammatory, anti-apoptotic, anti-fibrotic, and autophagy regulatory effects. For that, bibliographical research was carried out in Medline/PubMed and Scielo databases. Although the pathophysiological mechanisms involved in renal diseases are not fully understood, experimental studies demonstrate that oxidative stress, inflammation, apoptosis, and dysregulation of fibrotic and autophagic processes play central roles in the development of tissue damage. Increasing evidence has suggested that exercise can beneficially modulate these mechanisms, potentially becoming a safe and effective non-pharmacological strategy for kidney health protection and promotion. Thus, the evidence base discussed in this review suggests that an adequate training program emerges as a valuable tool for preserving renal function in experimental animals, mainly through the production of antioxidant enzymes, nitric oxide (NO), irisin, IL-10, and IL-11. Future research can continue to explore these mechanisms to develop specific guidelines for the prescription of exercise training in different populations of patients with kidney diseases.

Characterization of cell cycle, inflammation, and oxidative stress signaling role in non-communicable diseases: Insights into genetic variants, microRNAs and pathways

Non-Communicable Diseases (NCDs) significantly impact global health, contributing to over 70% of premature deaths, as reported by the World Health Organization (WHO). These diseases have complex and multifactorial origins, involving genetic, epigenetic, environmental and lifestyle factors. While Genome-Wide Association Study (GWAS) is widely recognized as a valuable tool for identifying variants associated with complex phenotypes; the multifactorial nature of NCDs necessitates a more comprehensive exploration, encompassing not only the genetic but also the epigenetic aspect. For this purpose, we employed a bioinformatics-multiomics approach to examine the genetic and epigenetic characteristics of NCDs (i.e. colorectal cancer, coronary atherosclerosis, squamous cell lung cancer, psoriasis, type 2 diabetes, and multiple sclerosis), aiming to identify novel biomarkers for diagnosis and prognosis. Leveraging GWAS summary statistics, we pinpointed Single Nucleotide Polymorphisms (SNPs) independently associated with each NCD. Subsequently, we identified genes linked to cell cycle, inflammation and oxidative stress mechanisms, revealing shared genes across multiple diseases, suggesting common functional pathways. From an epigenetic perspective, we identified microRNAs (miRNAs) with regulatory functions targeting these genes of interest. Our findings underscore critical genetic pathways implicated in these diseases. In colorectal cancer, the dysregulation of the "Cytokine Signaling in Immune System" pathway, involving LAMA5 and SMAD7, regulated by Hsa-miR-21-5p, Hsa-miR-103a-3p, and Hsa-miR-195-5p, emerged as pivotal. In coronary atherosclerosis, the pathway associated with "binding of TCF/LEF:CTNNB1 to target gene promoters" displayed noteworthy implications, with the MYC factor controlled by Hsa-miR-16-5p as a potential regulatory factor. Squamous cell lung carcinoma analysis revealed significant pathways such as "PTK6 promotes HIF1A stabilization," regulated by Hsa-let-7b-5p. In psoriasis, the "Endosomal/Vacuolar pathway," involving HLA-C and Hsa-miR-148a-3p and Hsa-miR-148b-3p, was identified as crucial. Type 2 Diabetes implicated the "Regulation of TP53 Expression" pathway, controlled by Hsa-miR-106a-5p and Hsa-miR-106b-5p. In conclusion, our study elucidates the genetic framework and molecular mechanisms underlying NCDs, offering crucial insights into potential genetic/epigenetic biomarkers for diagnosis and prognosis. The specificity of pathways and related miRNAs in different pathologies highlights promising candidates for further clinical validation, with the potential to advance personalized treatments and alleviate the global burden of NCDs.

Leech extract alleviates idiopathic pulmonary fibrosis by TGF-β1/Smad3 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Leech, as a traditional Chinese medicine for the treatment of blood circulation and blood stasis, was also widely used to cure pulmonary fibrosis in China. In clinical practice, some traditional Chinese medicine preparation such as Shui Zhi Xuan Bi Hua Xian Tang and Shui Zhi Tong Luo Capsule composed of leech, could improve the clinical symptoms and pulmonary function in patients with idiopathic pulmonary fibrosis (IPF). However, the material basis of the leech in the treatment of IPF were not yet clear.

AIM OF THE STUDY

Screen out the components of leech that have the anti-pulmonary fibrosis effects, and further explore the therapeutic mechanism of the active components.

MATERIALS AND METHODS

In this study, the different molecular weight components of leech extract samples were prepared using the semi-permeable membranes with different pore sizes. The therapeutic effects of the leech extract groups with molecular weight greater than 10 KDa (>10 KDa group), between 3 KDa and 10 KDa (3-10 KDa group), and less than 3 KDa (<3 KDa group) on pulmonary fibrosis were firstly investigated by cell proliferation and cytotoxicity assay (MTT), cell wound healing assay, immunofluorescence staining (IF) and Western blot (WB) assay through the TGF-β1-induced fibroblast cell model. Then bleomycin-induced pulmonary fibrosis (BML-induced PF) mouse model was constructed to investigate the pharmacological activities of the active component group of leech extract in vivo. Pathological changes of the mouse lung were observed by hematoxylin-eosin staining (H&E) and Masson's trichrome staining (Masson). The hydroxyproline (HYP) content of lung tissues was quantified by HYP detection kit. The levels of extracellular matrix-related fibronectin (FN) and collagen type Ⅰ (Collagen Ⅰ), pyruvate kinase M2 (PKM2) monomer and Smad7 protein were determined via WB method. PKM2 and Smad7 protein were further characterized by IF assays.

RESULTS

Using TGF-β1-induced HFL1 cell line as a PF cell model, the in vitro results demonstrated that the >10 KDa group could significantly inhibited the cell proliferation and migration, downregulated the expression level of cytoskeletal protein vimentin and α-smooth muscle actin (α-SMA), and reduced the deposition of FN and Collagen Ⅰ. In the BML-induced PF mouse model, the >10 KDa group significantly reduced the content of HYP, downregulated the expression levels of FN and Collagen Ⅰ in lung tissues, and delayed the pathological changes of lung tissue structure. The results of WB and IF assays further indicated that the >10 KDa group could up-regulate the expression level of PKM2 monomer and Smad7 protein in the cellular level, thereby delaying the progression of pulmonary fibrosis.

CONCLUSIONS

Our study revealed that the >10 KDa group was the main material basis of the leech extract that inhibited pulmonary fibrosis through TGF-β1/Smad3 signaling pathway.

Nicotinamide phosphoribose transferase facilitates macrophage-mediated pulmonary fibrosis through the Sirt1-Smad7 pathway in mice

Pulmonary fibrosis is a challenging lung disease characterized by a bleak prognosis. A pivotal element in the progression of this disease is the dysregulated recruitment of macrophages. Nicotinamide phosphoribose transferase (NAMPT), secreted by alveolar epithelial cells and inflammatory cells, has been previously identified to influence macrophage inflammation in acute lung injury through the nicotinamide adenine dinucleotide (NAD) rescue synthesis pathway. Nonetheless, the exact role of NAMPT in the regulation of lung fibrosis is yet to be elucidated. In our research, we employed bleomycin (BLM) to induce pulmonary fibrosis in Namptflox/flox;Cx3cr1CreER mice, using Namptflox/flox mice as controls. Our findings revealed an augmented expression of NAMPT concurrent with a marked increase in the secretion of NAD and inflammatory cytokines such as IL-6, TNF-α, and TGF-β1 post-BLM treatment. Furthermore, an upsurge in NAMPT-positive macrophages was observed in the lungs of BLM-treated Namptflox/flox mice. Notably, a conditional knockout of NAMPT (NAMPT cKO) in lung macrophages curtailed the BLM-induced inflammatory responses and significantly mitigated pulmonary fibrosis. This was associated with diminished phospho-Sirt1 (p-Sirt1) expression levels and a concomitant rise in mothers against decapentaplegic homolog 7 (Smad7) expression in BLM-treated mouse lungs and murine RAW 264.7 macrophage cells. Collectively, our data suggests that NAMPT exacerbates macrophage-driven inflammation and pulmonary fibrosis via the Sirt1-Smad7 pathway, positioning NAMPT as a promising therapeutic target for pulmonary fibrosis intervention.

SMAD7 expression in CAR-T cells improves persistence and safety for solid tumors

Despite the tremendous progress of chimeric antigen receptor T (CAR-T) cell therapy in hematological malignancies, their application in solid tumors has been limited largely due to T-cell exhaustion in the tumor microenvironment (TME) and systemic toxicity caused by excessive cytokine release. As a key regulator of the immunosuppressive TME, TGF-β promotes cytokine synthesis via the NF-κB pathway. Here, we coexpressed SMAD7, a suppressor of TGF-β signaling, with a HER2-targeted CAR in engineered T cells. These novel CAR-T cells displayed high cytolytic efficacy and were resistant to TGF-β-triggered exhaustion, which enabled sustained tumoricidal capacity after continuous antigen exposure. Moreover, SMAD7 substantially reduced the production of inflammatory cytokines by antigen-primed CAR-T cells. Mechanistically, SMAD7 downregulated TGF-β receptor I and abrogated the interplay between the TGF-β and NF-κB pathways in CAR-T cells. As a result, these CAR-T cells persistently inhibited tumor growth and promoted the survival of tumor-challenged mice regardless of the hostile tumor microenvironment caused by a high concentration of TGF-β. SMAD7 coexpression also enhanced CAR-T-cell infiltration and persistent activation in patient-derived tumor organoids. Therefore, our study demonstrated the feasibility of SMAD7 coexpression as a novel approach to improve the efficacy and safety of CAR-T-cell therapy for solid tumors.

The role of transforming growth factor beta in myopia development

Myopia is widely recognized as an epidemic. Studies have found a link between Transforming Growth Factor-beta (TGF-β) and myopia, but the specific molecular mechanisms are not fully understood. In this study, a monocular model in tree shrews (Tupaia belangeri) was established to verify the molecular mechanism of TGF-β in myopia. The results indicated that there were significant changes in TGF-βs during the treatment of myopia, which could enhance the refractive ability and axial length of the eye. Immunohistochemical staining, real-time fluorescent quantitative PCR, and immunoblotting results showed a significant upregulation of MMP2 and NF-κB levels, and a significant downregulation of COL-I expression in the TGF-β treated eyes, suggesting that NF-κB and MMP2 are involved in the signaling pathways of TGF-βs induced myopia and axial elongation. Moreover, the expression levels of IL-6, IL-8, MCP-1, IL-1β, TNF-α, TAK1, and NF-κB in the retina were all significantly elevated. This indicates that TGF-β stimulates the inflammatory response of retinal pigment epithelial cells through the TAK1-NF-κB signaling pathway. In conclusion, this study suggests that TGF-β promotes the progression of myopia by enhancing intraocular inflammation.

Multifaceted TGF-β signaling, a master regulator: From bench-to-bedside, intricacies, and complexities

Physiological embryogenesis and adult tissue homeostasis are regulated by transforming growth factor-β (TGF-β), an evolutionarily conserved family of secreted polypeptide factors, acting in an autocrine and paracrine manner. The role of TGF-β in inflammation, fibrosis, and cancer is complex and sometimes even contradictory, exhibiting either inhibitory or promoting effects depending on the stage of the disease. Under pathological conditions, especially fibrosis and cancer, overexpressed TGF-β causes extracellular matrix deposition, epithelial-mesenchymal transition, cancer-associated fibroblast formation, and/or angiogenesis. In this review article, we have tried to dive deep into the mechanism of action of TGF-β in inflammation, fibrosis, and carcinogenesis. As TGF-β and its downstream signaling mechanism are implicated in fibrosis and carcinogenesis blocking this signaling mechanism appears to be a promising avenue. However, targeting TGF-β carries substantial risk as this pathway is implicated in multiple homeostatic processes and is also known to have tumor-suppressor functions. There is a need for careful dosing of TGF-β drugs for therapeutic use and patient selection.

Colorectal Cancer Risk Prediction Using the rs4939827 Polymorphism of the SMAD7 Gene in the Romanian Population

Colorectal cancer (CRC) is globally recognized as a prevalent malignancy known for its significant mortality rate. Recent years have witnessed a rising incidence trend in colorectal cancer, emphasizing the necessity for early diagnosis. Our study focused on examining the impact of the SMAD7 gene variant rs4939827 on the risk of colorectal cancer occurrence. The composition of our study group included 340 individuals, comprising 170 CRC diagnosed patients and 170 healthy controls. We performed genotyping of all biological samples using the TaqMan assay on the ABI 7500 Real-Time PCR System (Applied Biosystems, Waltham, MA, USA). This investigation focused on the rs4939827 gene variant, assessing its association with CRC risk and clinicopathological characteristics. Genotyping results for the SMAD7 gene variant rs4939827 revealed a 42.6% prevalence of the C allele in CRC patients (p = 0.245) and a 22.8% prevalence of the T allele in control subjects (p = 0.109). This study concluded that there was an elevated risk of CRC in the dominant model for CC/CT+TT, with a p-value of 0.113 and an odds ratio (OR) of 2.781, within a 95% confidence interval (CI) of 0.998 to 3.456. The findings of our research indicate a correlation between variants of the SMAD7 gene and the likelihood of developing colorectal cancer in our study population. Consequently, these results could be instrumental in facilitating early diagnosis of colorectal cancer utilizing information on single-nucleotide polymorphism (SNP) and genetic susceptibility to the disease.

Functional Roles of CD133: More than Stemness Associated Factor Regulated by the Microenvironment

CD133 protein has been one of the most used surface markers to select and identify cancer cells with stem-like features. However, its expression is not restricted to tumoral cells; it is also expressed in differentiated cells and stem/progenitor cells in various normal tissues. CD133 participates in several cellular processes, in part orchestrating signal transduction of essential pathways that frequently are dysregulated in cancer, such as PI3K/Akt signaling and the Wnt/β-catenin pathway. CD133 expression correlates with enhanced cell self-renewal, migration, invasion, and survival under stress conditions in cancer. Aside from the intrinsic cell mechanisms that regulate CD133 expression in each cellular type, extrinsic factors from the surrounding niche can also impact CD33 levels. The enhanced CD133 expression in cells can confer adaptive advantages by amplifying the activation of a specific signaling pathway in a context-dependent manner. In this review, we do not only describe the CD133 physiological functions known so far, but importantly, we analyze how the microenvironment changes impact the regulation of CD133 functions emphasizing its value as a marker of cell adaptability beyond a cancer-stem cell marker.

Comprehensive analysis of the relationship between xanthine oxidoreductase activity and chronic kidney disease

Chronic kidney disease (CKD) is a common disease that seriously endangers human health. However, the potential relationship between xanthine oxidoreductase (XOR) activity and CKD remains unclear. In this study, we used clinical data, CKD datasets from the Gene Expression Omnibus database, and untargeted metabolomics to explain the relationship between XOR activity and CKD. First, XOR activity showed high correlation with the biomarkers of CKD, such as serum creatinine, blood urea nitrogen, uric acid, and estimated glomerular filtration rate. Then, we used least absolute shrinkage and selection operator logical regression algorithm and random forest algorithm to screen CKD molecular markers from differentially expressed genes, and the results of qRT-PCR of XDH, KOX-1, and ROMO1 were in accordance with the results of bioinformatics analyses. In addition, untargeted metabolomics analysis revealed that the purine metabolism pathway was significantly enriched in CKD patients in the simulated models of kidney fibrosis.

Involvement of Epithelial-Mesenchymal Transition (EMT) in Autoimmune Diseases

Epithelial-mesenchymal transition (EMT) is a complex reversible biological process characterized by the loss of epithelial features and the acquisition of mesenchymal features. EMT was initially described in developmental processes and was further associated with pathological conditions including metastatic cascade arising in neoplastic progression and organ fibrosis. Fibrosis is delineated by an excessive number of myofibroblasts, resulting in exuberant production of extracellular matrix (ECM) proteins, thereby compromising organ function and ultimately leading to its failure. It is now well acknowledged that a significant number of myofibroblasts result from the conversion of epithelial cells via EMT. Over the past two decades, evidence has accrued linking fibrosis to many chronic autoimmune and inflammatory diseases, including systemic sclerosis (SSc), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), and inflammatory bowel diseases (IBD). In addition, chronic inflammatory states observed in most autoimmune and inflammatory diseases can act as a potent trigger of EMT, leading to the development of a pathological fibrotic state. In the present review, we aim to describe the current state of knowledge regarding the contribution of EMT to the pathophysiological processes of various rheumatic conditions.

Genetic analysis and allele-specific expression of SMAD7 3'UTR variants in human colorectal cancer reveal a novel somatic variant exhibiting allelic imbalance

BACKGROUND

Considering the impact of SMAD7 deregulation in colorectal cancer (CRC) progression and the significance of single nucleotide variant (SNV)-mediated disruptions of microRNA (miRNA)-dependent regulation for cancer susceptibility, our study aimed to analyze genetic variation in the SMAD7 3' untranslated region ( 3'UTR) in CRC, measure differences in allelic mRNA expression, and evaluate its interference with miRNA-mediated post-transcriptional regulation.

PATIENTS AND METHODS

This study included 80 patients with different CRC stages and six human colon cancer cell lines of various histological origins. SMAD7 3'UTR was analyzed by direct sequencing, followed by the relative quantification of differential allelic expression of detected variants by allele-specific qRT-PCR. In silico tools were employed for predictions of regulatory consequences of detected variants.

RESULTS

A total of four different SNVs in one cell line and nine patients were found, among which were a novel somatic point variant and three already known germline variants (rs16950113, rs1050799536, and rs1043778717). All evaluated SNVs exhibited variable extents of allelic imbalance in expression. In silico analysis predicted significant effects of SNVs on miRNA binding efficiency, with each SNV disrupting existing and creating new target sites for one or more miRNAs.

CONCLUSION

Imbalance observed in the expression of SNV alleles altering miRNA binding suggests that all investigated SNVs are potential contributing factors impacting SMAD7 expression regulation in CRC that further studies should investigate.

TGF-β Inhibitors for Therapeutic Management of Kidney Fibrosis

Kidney fibrosis is a common pathophysiological mechanism of chronic kidney disease (CKD) progression caused by several underlying kidney diseases. Among various contributors to kidney fibrosis, transforming growth factor-β1 (TGF-β1) is the major factor driving fibrosis. TGF-β1 exerts its profibrotic attributes via the activation of canonical and non-canonical signaling pathways, which induce proliferation and activation of myofibroblasts and subsequent accumulation of extracellular matrix. Over the past few decades, studies have determined the TGF-β1 signaling pathway inhibitors and evaluated whether they could ameliorate the progression of CKD by hindering kidney fibrosis. However, therapeutic strategies that block TGF-β1 signaling have usually demonstrated unsatisfactory results. Herein, we discuss the therapeutic concepts of the TGF-β1 signaling pathway and its inhibitors and review the current state of the art regarding regarding TGF-β1 inhibitors in CKD management.

Renal fibrosis as a hallmark of diabetic kidney disease: Potential role of targeting transforming growth factor-beta (TGF-β) and related molecules

INTRODUCTION

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease (ESRD) worldwide. Currently, there is no effective treatment to completely prevent DKD progression to ESRD. Renal fibrosis and inflammation are the major pathological features of DKD, being pursued as potential therapeutic targets for DKD.

AREAS COVERED

Inflammation and renal fibrosis are involved in the pathogenesis of DKD. Anti-inflammatory drugs have been developed to combat DKD but without efficacy demonstrated. Thus, we have focused on the mechanisms of TGF-β-induced renal fibrosis in DKD, as well as discussing the important molecules influencing the TGF-β signaling pathway and their potential development into new pharmacotherapies, rather than targeting the ligand TGF-β and/or its receptors, such options include Smads, microRNAs, histone deacetylases, connective tissue growth factor, bone morphogenetic protein 7, hepatocyte growth factor, and cell division autoantigen 1.

EXPERT OPINION

TGF-β is a critical driver of renal fibrosis in DKD. Molecules that modulate TGF-β signaling rather than TGF-β itself are potentially superior targets to safely combat DKD. A comprehensive elucidation of the pathogenesis of DKD is important, which requires a better model system and access to clinical samples via collaboration between basic and clinical researchers.

Hepatocyte-specific Prominin-1 protects against liver injury-induced fibrosis by stabilizing SMAD7

Prominin-1 (PROM1), also known as CD133, is expressed in hepatic progenitor cells (HPCs) and cholangiocytes of the fibrotic liver. In this study, we show that PROM1 is upregulated in the plasma membrane of fibrotic hepatocytes. Hepatocellular expression of PROM1 was also demonstrated in mice (Prom1^CreER; R26^TdTom) in which cells expressed TdTom under control of the Prom1 promoter. To understand the role of hepatocellular PROM1 in liver fibrosis, global and liver-specific Prom1-deficient mice were analyzed after bile duct ligation (BDL). BDL-induced liver fibrosis was aggravated with increased phosphorylation of SMAD2/3 and decreased levels of SMAD7 by global or liver-specific Prom1 deficiency but not by cholangiocyte-specific Prom1 deficiency. Indeed, PROM1 prevented SMURF2-induced SMAD7 ubiquitination and degradation by interfering with the molecular association of SMAD7 with SMURF2. We also demonstrated that hepatocyte-specific overexpression of SMAD7 ameliorated BDL-induced liver fibrosis in liver-specific Prom1-deficient mice. Thus, we conclude that PROM1 is necessary for the negative regulation of TGFβ signaling during liver fibrosis.

Targeting fibrosis, mechanisms and cilinical trials

Fibrosis is characterized by the excessive extracellular matrix deposition due to dysregulated wound and connective tissue repair response. Multiple organs can develop fibrosis, including the liver, kidney, heart, and lung. Fibrosis such as liver cirrhosis, idiopathic pulmonary fibrosis, and cystic fibrosis caused substantial disease burden. Persistent abnormal activation of myofibroblasts mediated by various signals, such as transforming growth factor, platelet-derived growth factor, and fibroblast growh factor, has been recongized as a major event in the occurrence and progression of fibrosis. Although the mechanisms driving organ-specific fibrosis have not been fully elucidated, drugs targeting these identified aberrant signals have achieved potent anti-fibrotic efficacy in clinical trials. In this review, we briefly introduce the aetiology and epidemiology of several fibrosis diseases, including liver fibrosis, kidney fibrosis, cardiac fibrosis, and pulmonary fibrosis. Then, we summarise the abnormal cells (epithelial cells, endothelial cells, immune cells, and fibroblasts) and their interactions in fibrosis. In addition, we also focus on the aberrant signaling pathways and therapeutic targets that regulate myofibroblast activation, extracellular matrix cross-linking, metabolism, and inflammation in fibrosis. Finally, we discuss the anti-fibrotic drugs based on their targets and clinical trials. This review provides reference for further research on fibrosis mechanism, drug development, and clinical trials.

Signaling pathways of chronic kidney diseases, implications for therapeutics

Chronic kidney disease (CKD) is a chronic renal dysfunction syndrome that is characterized by nephron loss, inflammation, myofibroblasts activation, and extracellular matrix (ECM) deposition. Lipotoxicity and oxidative stress are the driving force for the loss of nephron including tubules, glomerulus, and endothelium. NLRP3 inflammasome signaling, MAPK signaling, PI3K/Akt signaling, and RAAS signaling involves in lipotoxicity. The upregulated Nox expression and the decreased Nrf2 expression result in oxidative stress directly. The injured renal resident cells release proinflammatory cytokines and chemokines to recruit immune cells such as macrophages from bone marrow. NF-κB signaling, NLRP3 inflammasome signaling, JAK-STAT signaling, Toll-like receptor signaling, and cGAS-STING signaling are major signaling pathways that mediate inflammation in inflammatory cells including immune cells and injured renal resident cells. The inflammatory cells produce and secret a great number of profibrotic cytokines such as TGF-β1, Wnt ligands, and angiotensin II. TGF-β signaling, Wnt signaling, RAAS signaling, and Notch signaling evoke the activation of myofibroblasts and promote the generation of ECM. The potential therapies targeted to these signaling pathways are also introduced here. In this review, we update the key signaling pathways of lipotoxicity, oxidative stress, inflammation, and myofibroblasts activation in kidneys with chronic injury, and the targeted drugs based on the latest studies. Unifying these pathways and the targeted therapies will be instrumental to advance further basic and clinical investigation in CKD.

LncRNA-Dependent Mechanisms of Transforming Growth Factor-β: From Tissue Fibrosis to Cancer Progression

Transforming growth factor-β (TGF-β) is a crucial pathogenic mediator of inflammatory diseases. In tissue fibrosis, TGF-β regulates the pathogenic activity of infiltrated immunocytes and promotes extracellular matrix production via de novo myofibroblast generation and kidney cell activation. In cancer, TGF-β promotes cancer invasion and metastasis by enhancing the stemness and epithelial mesenchymal transition of cancer cells. However, TGF-β is highly pleiotropic in both tissue fibrosis and cancers, and thus, direct targeting of TGF-β may also block its protective anti-inflammatory and tumor-suppressive effects, resulting in undesirable outcomes. Increasing evidence suggests the involvement of long non-coding RNAs (lncRNAs) in TGF-β-driven tissue fibrosis and cancer progression with a high cell-type and disease specificity, serving as an ideal target for therapeutic development. In this review, the mechanism and translational potential of TGF-β-associated lncRNAs in tissue fibrosis and cancer will be discussed.

Epithelial-mesenchymal transition in organ fibrosis development: current understanding and treatment strategies

Organ fibrosis is a process in which cellular homeostasis is disrupted and extracellular matrix is excessively deposited. Fibrosis can lead to vital organ failure and there are no effective treatments yet. Although epithelial–mesenchymal transition (EMT) may be one of the key cellular mechanisms, the underlying mechanisms of fibrosis remain largely unknown. EMT is a cell phenotypic process in which epithelial cells lose their cell-to-cell adhesion and polarization, after which they acquire mesenchymal features such as infiltration and migration ability. Upon injurious stimulation in different organs, EMT can be triggered by multiple signaling pathways and is also regulated by epigenetic mechanisms. This narrative review summarizes the current understanding of the underlying mechanisms of EMT in fibrogenesis and discusses potential strategies for attenuating EMT to prevent and/or inhibit fibrosis. Despite better understanding the role of EMT in fibrosis development, targeting EMT and beyond in developing therapeutics to tackle fibrosis is challenging but likely feasible.

TFPI2 suppresses the interaction of TGF-β2 pathway regulators to promote endothelial-mesenchymal transition in diabetic nephropathy

Endothelial–mesenchymal transition (EndMT) is an important source of myofibroblasts, but also contributes to the progression of diabetic nephropathy (DN). By several differential gene expression analyses from the Gene Expression Omnibus (GEO) database, the tissue factor pathway inhibitor 2 (TFPI2) gene, known as a tumor suppressor, was shown to be dysregulated in DN; however, the potential role and regulatory mechanism of TFPI2 in DN are unclear. Here, we found abnormal upregulation of TFPI2 in the renal cortex of diabetic mice, accompanied by impaired renal function. We also injected a single dose of adeno-associated virus (AAV)2 carrying shRNA targeting TFPI2 intravenously into these mice and found that knockdown of TFPI2 improved renal function and reduced renal fibrosis and cell apoptosis in experimental DN. Furthermore, hyperglycemia-induced EndMT was inhibited in the absence of TFPI2, as evidenced by increased expression of endothelial markers (VE-cadherin and CD31) and decreased expression of mesenchymal markers (α-SMA, desmin, and FSP-1). To further explore the mechanism in vitro, human renal glomerular endothelial cells (hRGECs) were incubated in the presence of high glucose or transforming growth factor beta (TGF-β)2. TFPI2 deficiency inhibited high glucose-induced cell apoptosis and TGF-β2-induced EndMT in hRGECs, while overexpression of TFPI2 had the opposite effects. Importantly, TGF-β2 is a crucial driver of EndMT, and we found that TFPI2 promoted TGF-β2/Smad signaling activation by interferring the interaction of TGF-β pathway regulators (SMURF2 with SMAD7). Our results show that TFPI2 regulates EndMT and the TGF-β2 signaling pathway and is a potential promoter of DN pathogenesis.

Association of SMAD7 genetic markers and haplotypes with colorectal cancer risk

Purpose

Colorectal cancer (CRC) is one of the common cancers with a high mortality rate worldwide. In Iran, there has been a trend of increased incidence of colorectal cancer in the last three decades that necessitates the early diagnosis. Genetic factors have an influential role in its etiology along with the conventional risk factors such as age, diet, and lifestyle. Results from GWAS have shown significant associations between SMAD7 gene variants and risk of CRC. This study aimed to assess the association of certain polymorphisms as well as haplotypes of this gene and risk of colorectal cancer.

Methods and materials

This study was designed as a case–control association study. After obtaining ethical approval and informed consent, blood samples from 209 patients with colorectal cancer were collected and DNA was extracted. Four variants: rs4939827, rs34007497, rs8085824 and rs8088297 were genotyped using ARMS-PCR method.

Results

SMAD7 rs4939827 in the recessive and co-dominant models was associated with colorectal cancer risk [TT/CT + CC: OR = 2.90, 95%CI (1.38–6.09), p = 0.005; CC + TT/CT: OR = 1.66, 95%CI (1.00–2.75), p = 0.01]. Haplotype analysis indicated that some SNP combinations including two for-SNPs haplotypes of T-T-C-C and T-C-C-A were significantly associated with CRC risk.

Conclusion

Based on the identified association of SMAD7 gene variations and haplotypes with colorectal cancer risk in our population, genetic variations in this gene region may have a role in CRC development. This data may shed light on the genetic predisposition of CRC which involves different pathways including TGF-β.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01150-3.

Genome-Wide Analysis of Smad7-Mediated Transcription in Mouse Embryonic Stem Cells

Smad7 has been identified as a negative regulator of the transforming growth factor TGF-β pathway by direct interaction with the TGF-β type I receptor (TβR-I). Although Smad7 has also been shown to play TGF-β unrelated functions in the cytoplasm and in the nucleus, a comprehensive analysis of its nuclear function has not yet been performed. Here, we show that in ESCs Smad7 is mainly nuclear and acts as a general transcription factor regulating several genes unrelated to the TGF-β pathway. Loss of Smad7 results in the downregulation of several key stemness master regulators, including Pou5f1 and Zfp42, and in the upregulation of developmental genes, with consequent loss of the stem phenotype. Integrative analysis of genome-wide mapping data for Smad7 and ESC self-renewal and pluripotency transcriptional regulators revealed that Smad7 co-occupies promoters of highly expressed key stemness regulators genes, by binding to a specific consensus response element NCGGAAMM. Altogether, our data establishes Smad7 as a new, integral component of the regulatory circuitry that controls ESC identity.

SMAD7 and SMAD4 expression in colorectal cancer progression and therapy response

Inhibitory SMAD7 and common mediator SMAD4 play crucial roles in SMAD-dependent TGF-β signaling that is often disrupted in colorectal cancer (CRC). This study aimed to profile the expression of SMAD7 and SMAD4 in primary and metastatic CRC and to evaluate their significance in disease progression and therapy response. The expression of SMAD7 and SMAD4 genes was analyzed by quantitative real-time PCR in tissues from 35 primary and metastatic CRC patients and in vitro in 7 human cell lines originating from colon tissue. Expression levels of SMAD7 and SMAD4, as well as their ratio, were determined and their association with tumor characteristics and response to therapy were evaluated. SMAD4 level was significantly lower in tumors compared to non-tumor tissues in both primary (p = 0.001) and metastatic (p = 0.001) CRC patients, while tumor expression of SMAD7 was significantly lower from non-tumor tissue only in metastatic patients (p = 0.017). SMAD7/SMAD4 ratio was elevated in CRC primary tumor tissues and cell lines compared to corresponding non-tumor tissues and cell line, respectively (p = 0.003). SMAD7 expression was significantly elevated in primary tumor tissues obtained from responders to neoadjuvant chemoradiotherapy (nCRT) compared to non-responders (p = 0.014). Alterations of expression and ratio of SMAD7 and SMAD4 in CRC cell lines, primary rectal cancer, and liver metastasis emphasize the importance of these genes in different stages of disease progression. Differential expression of SMAD7 in responders versus non-responders to nCRT should be further investigated for its potential predictive value.

Tril dampens Nodal signaling through Pellino2- and Traf6-mediated activation of Nedd4l

Toll-like receptor 4 (Tlr) interactor with leucine-rich repeats (Tril) functions as a Tlr coreceptor to mediate innate immunity in adults. In Xenopus embryos, Tril triggers degradation of the transforming growth factor β (Tgf-ß) family inhibitor, Smad7. This enhances bone morphogenetic protein (Bmp) signaling to enable ventral mesoderm to commit to a blood fate. Here, we show that Tril simultaneously dampens Nodal signaling by catalytically activating the ubiquitin ligase NEDD4 Like (Nedd4l). Nedd4l then targets Nodal receptors for degradation. How Tril signals are transduced in a nonimmune context is unknown. We identify the ubiquitin ligase Pellino2 as a protein that binds to the cytoplasmic tail of Tril and subsequently forms a complex with Nedd4l and another E3 ligase, TNF-receptor associated factor 6 (Traf6). Pellino2 and Traf6 are essential for catalytic activation of Nedd4l, both in Xenopus and in mammalian cells. Traf6 ubiquitinates Nedd4l, which is then recruited to membrane compartments where activation occurs. Collectively, our findings reveal that Tril initiates a noncanonical Tlr-like signaling cascade to activate Nedd4l, thereby coordinately regulating the Bmp and Nodal arms of the Tgf-ß superfamily during vertebrate development.

Cyclophilins A and B oppositely regulate renal tubular epithelial cell phenotype

Restoration of kidney tubular epithelium following sublethal injury sequentially involves partial epithelial–mesenchymal transition (pEMT), proliferation, and further redifferentiation into specialized tubule epithelial cells (TECs). Because the immunosuppressant cyclosporine-A produces pEMT in TECs and inhibits the peptidyl-prolyl isomerase (PPIase) activity of cyclophilin (Cyp) proteins, we hypothesized that cyclophilins could regulate TEC phenotype. Here we demonstrate that in cultured TECs, CypA silencing triggers loss of epithelial features and enhances transforming growth factor β (TGFβ)-induced EMT in association with upregulation of epithelial repressors Slug and Snail. This pro-epithelial action of CypA relies on its PPIase activity. By contrast, CypB emerges as an epithelial repressor, because CypB silencing promotes epithelial differentiation, prevents TGFβ-induced EMT, and induces tubular structures in 3D cultures. In addition, in the kidneys of CypB knockout mice subjected to unilateral ureteral obstruction, inflammatory and pro-fibrotic events were attenuated. CypB silencing/knockout leads to Slug, but not Snail, downregulation. CypB support of Slug expression depends on its endoplasmic reticulum location, where it interacts with calreticulin, a calcium-buffering chaperone related to Slug expression. As CypB silencing reduces ionomycin-induced calcium release and Slug upregulation, we suggest that Slug expression may rely on CypB modulation of calreticulin-dependent calcium signaling. In conclusion, this work uncovers new roles for CypA and CypB in modulating TEC plasticity and identifies CypB as a druggable target potentially relevant in promoting kidney repair.

Protective effect of hydrogen sulfide on the kidney (Review)

Hydrogen sulfide (H₂S) is a physiologically important gas transmitter that serves various biological functions in the body, in a manner similar to that of carbon monoxide and nitric oxide. Cystathionine-β-synthase, cystathionine-γ-lyase and cysteine transaminase/3-mercaptopyruvate sulphotransferase are important enzymes involved H₂S production in vivo, and the mitochondria are the primary sites of metabolism. It has been reported that H₂S serves an important physiological role in the kidney. Under disease conditions, such as ischemia-reperfusion injury, drug nephrotoxicity and diabetic nephropathy, H₂S serves an important role in both the occurrence and development of the disease. The present review aimed to summarize the production, metabolism and physiological functions of H₂S, and the progress in research with regards to its role in renal injury and renal fibrosis in recent years.

The Role of TGF-β Signaling Pathways in Cancer and Its Potential as a Therapeutic Target

The transforming growth factor-β (TGF-β) signaling pathway mediates various biological functions, and its dysregulation is closely related to the occurrence of malignant tumors. However, the role of TGF-β signaling in tumorigenesis and development is complex and contradictory. On the one hand, TGF-β signaling can exert antitumor effects by inhibiting proliferation or inducing apoptosis of cancer cells. On the other hand, TGF-β signaling may mediate oncogene effects by promoting metastasis, angiogenesis, and immune escape. This review summarizes the recent findings on molecular mechanisms of TGF-β signaling. Specifically, this review evaluates TGF-β's therapeutic potential as a target by the following perspectives: ligands, receptors, and downstream signaling. We hope this review can trigger new ideas to improve the current clinical strategies to treat tumors related to the TGF-β signaling pathway.

miR-195-5p Regulates the Phenotype Switch of CCSM Cells by Targeting Smad7

INTRODUCTION

Phenotype switch refers to the process in which smooth muscle cells change from contractile type to synthetic type and acquire the ability of proliferation. Phenotypic transformation involves many changes of cell function, such as collagen deposition and fibrosis, which affect the normal erectile function of penis.

AIM

To investigate the role of miR-195-5p in regulating the Phenotype switch of the corpus cavernosum smooth muscle (CCSM) cells.

METHODS

A small mother against decapentaplegic 7(Smad7) virus vector and a miR-195-5p mimics or an si-Smad7 viral vector and a miR-195-5p inhibitor were transfected into CCSM cells. The cells were obtained by primary culture of rat corpus cavernosum smooth muscle tissue. Real-time polymerase chain reaction (PCR) experiments, Western blotting, hematoxylin-eosin (HE) staining, transwell experiments, MTT assays, and flow cytometry were used to detect miR-195-5p, Smad7, phenotype switch markers of CCSM cells and related protein expression, as well as changes in cell morphology, migration, proliferation and apoptosis.

MAIN OUTCOME MEASURE

To study the regulation of miR-195-5p in CCSM cells by overexpression and silencing strategies.

RESULTS

Overexpressed miR-195-5p promoted the transformation of CCSM cells from a contractile type to a synthetic type. Meanwhile, the migration ability and proliferation ability of CCSM cells increased, and the apoptosis rate decreased. The expression-silencing of miR-195-5p gave rise to the opposite effect. The results of the rescue experiment demonstrated that overexpressed Smad7 rescued the inhibitory of the switch of the CCSM cell phenotype from the contractile type to the synthesis type caused by overexpression of miR-195-5p alone. Moreover, the enhancement effect of the migration ability and proliferation ability of CCSM cells was also eliminated, and the apoptosis rate was increased. Silencing miR-195-5p and Smad7 at the same time resulted in the opposite effect.

CONCLUSION

miR-195-5p may regulate the phenotype switch of CCSM cells by targeting Smad7. Zhang J, Zhang X, Zhang J, et al. miR-195-5p Regulates the Phenotype Switch of CCSM Cells by Targeting Smad7. Sex Med 2021;9:100349.

Expression and function of Smad7 in autoimmune and inflammatory diseases

Transforming growth factor-β (TGF-β) plays a critical role in the pathological processes of various diseases. However, the signaling mechanism of TGF-β in the pathological response remains largely unclear. In this review, we discuss advances in research of Smad7, a member of the I-Smads family and a negative regulator of TGF-β signaling, and mainly review the expression and its function in diseases. Smad7 inhibits the activation of the NF-κB and TGF-β signaling pathways and plays a pivotal role in the prevention and treatment of various diseases. Specifically, Smad7 can not only attenuate growth inhibition, fibrosis, apoptosis, inflammation, and inflammatory T cell differentiation, but also promotes epithelial cells migration or disease development. In this review, we aim to summarize the various biological functions of Smad7 in autoimmune diseases, inflammatory diseases, cancers, and kidney diseases, focusing on the molecular mechanisms of the transcriptional and posttranscriptional regulation of Smad7.

Role of sialidase Neu3 and ganglioside GM3 in cardiac fibroblasts activation

Cardiac fibrosis is a key physiological response to cardiac tissue injury to protect the heart from wall rupture. However, its progression increases heart stiffness, eventually causing a decrease in heart contractility. Unfortunately, to date, no efficient antifibrotic therapies are available to the clinic. This is primarily due to the complexity of the process, which involves several cell types and signaling pathways. For instance, the transforming growth factor beta (TGF-β) signaling pathway has been recognized to be vital for myofibroblasts activation and fibrosis progression. In this context, complex sphingolipids, such as ganglioside GM3, have been shown to be directly involved in TGF-β receptor 1 (TGF-R1) activation. In this work, we report that an induced up-regulation of sialidase Neu3, a glycohydrolytic enzyme involved in ganglioside cell homeostasis, can significantly reduce cardiac fibrosis in primary cultures of human cardiac fibroblasts by inhibiting the TGF-β signaling pathway, ultimately decreasing collagen I deposition. These results support the notion that modulating ganglioside GM3 cell content could represent a novel therapeutic approach for cardiac fibrosis, warranting for further investigations.

Transforming Growth Factor-β Signaling in Fibrotic Diseases and Cancer-Associated Fibroblasts

Transforming growth factor-β (TGF-β) signaling is essential in embryo development and maintaining normal homeostasis. Extensive evidence shows that TGF-β activation acts on several cell types, including epithelial cells, fibroblasts, and immune cells, to form a pro-fibrotic environment, ultimately leading to fibrotic diseases. TGF-β is stored in the matrix in a latent form; once activated, it promotes a fibroblast to myofibroblast transition and regulates extracellular matrix (ECM) formation and remodeling in fibrosis. TGF-β signaling can also promote cancer progression through its effects on the tumor microenvironment. In cancer, TGF-β contributes to the generation of cancer-associated fibroblasts (CAFs) that have different molecular and cellular properties from activated or fibrotic fibroblasts. CAFs promote tumor progression and chronic tumor fibrosis via TGF-β signaling. Fibrosis and CAF-mediated cancer progression share several common traits and are closely related. In this review, we consider how TGF-β promotes fibrosis and CAF-mediated cancer progression. We also discuss recent evidence suggesting TGF-β inhibition as a defense against fibrotic disorders or CAF-mediated cancer progression to highlight the potential implications of TGF-β-targeted therapies for fibrosis and cancer.

Overexpression of Smad7 in hypothalamic POMC neurons disrupts glucose balance by attenuating central insulin signaling

OBJECTIVE

Although the hypothalamus is crucial for peripheral metabolism control, the signals in specific neurons involved remain poorly understood. The aim of our current study was to explore the role of the hypothalamic gene mothers against decapentaplegic homolog 7 (Smad7) in peripheral glucose disorders.

METHODS

We studied glucose metabolism in high-fat diet (HFD)-fed mice and middle-aged mice with Cre-mediated recombination causing 1) overexpression of Smad7 in hypothalamic proopiomelanocortin (POMC) neurons, 2) deletion of Smad7 in POMC neurons, and 3) overexpression of protein kinase B (AKT) in arcuate nucleus (ARC) in Smad7 overexpressed mice. Intracerebroventricular (ICV) cannulation of insulin was used to test the hypothalamic insulin sensitivity in the mice. Hypothalamic primary neurons were used to investigate the mechanism of Smad7 regulating hypothalamic insulin signaling.

RESULTS

We found that Smad7 expression was increased in POMC neurons in the hypothalamic ARC of HFD-fed or middle-aged mice. Furthermore, overexpression of Smad7 in POMC neurons disrupted the glucose balance, and deletion of Smad7 in POMC neurons prevented diet- or age-induced glucose disorders, which was likely to be independent of changes in body weight or food intake. Moreover, the effect of Smad7 was reversed by overexpression of AKT in the ARC. Finally, Smad7 decreased AKT phosphorylation by activating protein phosphatase 1c in hypothalamic primary neurons.

CONCLUSIONS

Our results demonstrated that an excess of central Smad7 in POMC neurons disrupts glucose balance by attenuating hypothalamic insulin signaling. In addition, we found that this regulation was mediated by the activity of protein phosphatase 1c.

The dichotomous role of TGF-β in controlling liver cancer cell survival and proliferation

Hepatocellular carcinoma (HCC) is the major form of primary liver cancer and one of the most prevalent and life-threatening malignancies globally. One of the hallmarks in HCC is the sustained cell survival and proliferative signals, which are determined by the balance between oncogenes and tumor suppressors. Transforming growth factor beta (TGF-β) is an effective growth inhibitor of epithelial cells including hepatocytes, through induction of cell cycle arrest, apoptosis, cellular senescence, or autophagy. The antitumorigenic effects of TGF-β are bypassed during liver tumorigenesis via multiple mechanisms. Furthermore, along with malignant progression, TGF-β switches to promote cancer cell survival and proliferation. This dichotomous nature of TGF-β is one of the barriers to therapeutic targeting in liver cancer. Thereafter, understanding the underlying molecular mechanisms is a prerequisite for discovering novel antitumor drugs that may specifically disable the growth-promoting branch of TGF-β signaling or restore its tumor-suppressive arm. This review summarizes how TGF-β inhibits or promotes liver cancer cell survival and proliferation, highlighting the functional switch mechanisms during the process.

Identification of Putative Non-Substrate-Based XT-I Inhibitors by Natural Product Library Screening

Fibroproliferative diseases are characterized by excessive accumulation of extracellular matrix (ECM) components leading to organ dysfunction. This process is characterized by an increase in myofibroblast content and enzyme activity of xylosyltransferase-I (XT-I), the initial enzyme in proteoglycan (PG) biosynthesis. Therefore, the inhibition of XT-I could be a promising treatment for fibrosis. We used a natural product-inspired compound library to identify non-substrate-based inhibitors of human XT-I by UPLC-MS/MS. We combined this cell-free approach with virtual and molecular biological analyses to confirm and prioritize the inhibitory potential of the compounds identified. The characterization for compound potency in TGF-β1-driven XYLT1 transcription regulation in primary dermal human fibroblasts (key cells in ECM remodeling) was addressed by gene expression analysis. Consequently, we identified amphotericin B and celastrol as new non-substrate-based XT-I protein inhibitors. Their XT-I inhibitory effects were mediated by an uncompetitive or a competitive inhibition mode, respectively. Both compounds reduced the cellular XYLT1 expression level and XT-I activity. We showed that these cellular inhibitor-mediated changes involve the TGF-β and microRNA-21 signaling pathway. The results of our study provide a strong rationale for the further optimization and future usage of the XT-I inhibitors identified as promising therapeutic agents of fibroproliferative diseases.

Antiphotoaging Effect of 3,5-Dicaffeoyl-epi-quinic Acid against UVA-Induced Skin Damage by Protecting Human Dermal Fibroblasts In Vitro

Cutaneous aging is divided into intrinsic and exogenous aging correspondingly contributing to the complex biological phenomenon in skin. Intrinsic aging is also termed chronological aging, which is the accumulation of inevitable changes over time and is largely genetically determined. Superimposed on this intrinsic process, exogenous aging is associated with environmental exposure, mainly to ultraviolet (UV) radiation and more commonly termed as photoaging. UV-induced skin aging induces increased expression of matrix metalloproteinases (MMPs) which in turn causes the collagen degradation. Therefore, MMP inhibitors of natural origin are regarded as a primary approach to prevent or treat photoaging. This study investigated the effects of 3,5-dicaffeoyl-epi-quinic acid (DEQA) on photoaging and elucidated its molecular mechanisms in UVA-irradiated human dermal fibroblasts (HDFs). The results show that treatment with DEQA decreases MMP-1 production and increases type I collagen production in UVA-damaged HDFs. In addition, treatment of UVA-irradiated HDFs with DEQA downregulates MMP-1, MMP-3 and MMP-9 expression via blocking MAPK-cascade-regulated AP-1 transcriptional activity in UVA-irradiated HDFs. Furthermore, DEQA relieves the UVA-mediated suppression of type I procollagen and collagen expression through stimulating TGF-β/Smad signaling, leading to activation of the Smad 2/3 and Smad 4 nuclear translocation. These results suggest that DEQA could be a potential cosmetic agent for prevention and treatment of skin photoaging.

The role of Smad7 in cutaneous wound healing

Chronic refractory wounds are generally caused by local tissue defects and necrosis, and they are characterized by delayed wound healing as well as high recurrence, which seriously affects life quality. However, effective therapeutics to treat wounds are currently unavailable. Therapy primarily aims to accelerate generation of granulation tissue and decrease recurrence. The pathogenesis of chronic refractory wounds is closely related to multiple complex signaling pathways and a series of cytokines. Among these signaling pathways, TGF-β/Smad7 axis plays a critical role. Specifically, Smad7 is an antagonist of TGF-β that inhibits activation of TGF-β. Moreover, Smad7 promotes wound healing by regulating cytokines and controlling growth, differentiation and apoptosis of cells, which may be exploited to cure the disease. This review aims to reveal the exact functions and mechanisms of Smad7 in regulation of wound healing.

CXCR4 Inhibition Enhances Efficacy of FLT3 Inhibitors in FLT3-Mutated AML Augmented by Suppressed TGF-b Signaling

Given the proven importance of the CXCL12/CXCR4 axis in the stroma–acute myeloid leukemia (AML) interactions and the rapid emergence of resistance to FLT3 inhibitors, we investigated the efficacy and safety of a novel CXCR4 inhibitor, LY2510924, in combination with FLT3 inhibitors in preclinical models of AML with FLT3-ITD mutations (FLT3-ITD-AML). Quizartinib, a potent FLT3 inhibitor, induced apoptosis in FLT3-ITD-AML, while LY2510924 blocked surface CXCR4 without inducing apoptosis. LY2510924 significantly reversed stroma-mediated resistance against quizartinib mainly through the MAPK pathway. In mice with established FLT3-ITD-AML, LY2510924 induced durable mobilization and differentiation of leukemia cells, resulting in enhanced anti-leukemia effects when combined with quizartinib, whereas transient effects were seen on non-leukemic blood cells in immune-competent mice. Sequencing of the transcriptome of the leukemic cells surviving in vivo treatment with quizartinib and LY2510924 revealed that genes related to TGF-β signaling may confer resistance against the drug combination. In co-culture experiments of FLT3-ITD-AML and stromal cells, both silencing of TGF-β in stromal cells or TGF-β-receptor kinase inhibitor enhanced apoptosis by combined treatment. Disruption of the CXCL12/CXCR4 axis in FLT3-ITD-AML by LY2510924 and its negligible effects on normal immunocytes could safely enhance the potency of quizartinib, which may be further improved by blockade of TGF-β signaling.

HDAC inhibitors promote pancreatic stellate cell apoptosis and relieve pancreatic fibrosis by upregulating miR-15/16 in chronic pancreatitis

In chronic pancreatitis, PSCs are activated by proinflammatory cytokines to induce pancreatic fibrogenesis. HDAC inhibition protected against the pancreatic fibrosis and the apoptosis of PSCs through induced apoptosis and depressed inflammation. In our study, we found that miR-15 and miR-16 decreased significantly in chronic pancreatitis and HDAC inhibition could recover the levels of these two miRNAs. HDAC regulated the transcription of miR-15 and miR-16, which then modulate the apoptosis and fibrosis of PSCs. And we proved that Bcl-2 and Smad5 were the target genes of miR-15 and miR-16, which illustrated how HDAC inhibition alleviated the apoptosis and fibrogenesis of PSCs in chronic pancreatitis. These results suggested that HDAC inhibition protects against CP by promoting apoptosis and TGF-β/Smads signaling pathways, and indicated that HDAC inhibition is a potential therapy to alleviate CP patients in clinic, and these need to be explored further.

KLF2 inhibits TGF-β-mediated cancer cell motility in hepatocellular carcinoma

Feedback regulation plays a pivotal role in determining the intensity and duration of TGF-β signaling and subsequently affecting the pathophysiological roles of TGF-β, including those in liver malignancy. KLF2, a member of the Krüppel-like factor (KLF) family transcription factors, has been implicated in impeding hepatocellular carcinoma (HCC) development. However, the underlying molecular mechanisms are not fully understood. In the present study, we found that TGF-β stimulates the expression of KLF2 gene in several HCC cell lines. KLF2 protein is able to inhibit TGF-β/Smad signaling in HCC cells as assessed by luciferase reporter assay. Further studies indicated that KLF2 inhibits the transcriptional activity of Smad2/3 and Smad4 and ameliorates TGF-β-induced target gene expression, therefore creating a novel negative feedback loop in TGF-β signaling. Functionally, stably expression of KLF2 in HCCLM3 cells attenuated TGF-β-induced cancer cell motility in wound-healing and transwell assays by interfering with TGF-β-mediated upregulation of MMP2. Together, our results revealed that KLF2 protein has a tumor-suppressive function in HCC through a negative feedback loop over TGF-β signaling.

Exosomal miR-106a derived from gastric cancer promotes peritoneal metastasis via direct regulation of Smad7

Peritoneal metastasis develops in more than half of patients with gastric cancer but influencing factors are poorly characterized. Exosomes are increasingly recognized as a new mediator in cancer directional metastasis through the transfer of nucleic acids or proteins to neighboring or distant cells. The role of exosomes in peritoneal metastasis and whether it could establish pre-metastatic milieu are largely unknown. Here, we assessed the migration of gastric cancer (GC) cells and identified that PKH26-labeled exosomes from GC cells can be ingested by peritoneal mesothelial cells (MCs). Additionally, miRNA (miR-106a) that highly enriched in GC-derived exosomes (GC-exos) and essential for destroying the mesothelial barrier was demonstrated through the observation of the injury of the MCs including migratory enhancement and imbalance of apoptosis and proliferation. Moreover, either stimulating miR-106a or treatment with GC-exos could inhibit the expression of Smad7, accompanied by the concurrent elevated α-SMA and fibronectin in MCs. Silencing of miR-106a abolished GC-exos-induced gene expression in MCs. The MCs regain the viability, apoptosis reduction and Smad7 expression after rescue experiment conducted in miR-106a-enriched GC-exos. Xenograft model suggested that exosomal miR-106a had a potential to promote tumor growth through targeting Smad7. Collectively, we revealed that the delivery of miR-106a from GC-exos plays a crucial role in gastric cancer peritoneal metastasis.Abbreviations: MiR-106a: microRNA-106a; Smad7: small mothers against decapentaplegic 7; GC: gastric cancer; MCs: mesothelial cells; Exos: exosomes; HG: high-differentiated gastric cancer cells; LG: low-differentiated gastric cancer cells.

Diverse Role of TGF-β in Kidney Disease

Inflammation and fibrosis are two pathological features of chronic kidney disease (CKD). Transforming growth factor-β (TGF-β) has been long considered as a key mediator of renal fibrosis. In addition, TGF-β also acts as a potent anti-inflammatory cytokine that negatively regulates renal inflammation. Thus, blockade of TGF-β inhibits renal fibrosis while promoting inflammation, revealing a diverse role for TGF-β in CKD. It is now well documented that TGF-β1 activates its downstream signaling molecules such as Smad3 and Smad3-dependent non-coding RNAs to transcriptionally and differentially regulate renal inflammation and fibrosis, which is negatively regulated by Smad7. Therefore, treatments by rebalancing Smad3/Smad7 signaling or by specifically targeting Smad3-dependent non-coding RNAs that regulate renal fibrosis or inflammation could be a better therapeutic approach. In this review, the paradoxical functions and underlying mechanisms by which TGF-β1 regulates in renal inflammation and fibrosis are discussed and novel therapeutic strategies for kidney disease by targeting downstream TGF-β/Smad signaling and transcriptomes are highlighted.

Human Skin Keratinocytes on Sustained TGF-β Stimulation Reveal Partial EMT Features and Weaken Growth Arrest Responses

Defects in wound closure can be related to the failure of keratinocytes to re-epithelize. Potential mechanisms driving this impairment comprise unbalanced cytokine signaling, including Transforming Growth Factor-β (TFG-β). Although the etiologies of chronic wound development are known, the relevant molecular events are poorly understood. This lack of insight is a consequence of ethical issues, which limit the available evidence to humans. In this work, we have used an in vitro model validated for the study of epidermal physiology and function, the HaCaT cells to provide a description of the impact of sustained exposure to TGF-β. Long term TGF-β1 treatment led to evident changes, HaCaT cells became spindle-shaped and increased in size. This phenotype change involved conformational re-arrangements for actin filaments and E-Cadherin cell-adhesion structures. Surprisingly, the signs of consolidated epithelial-to-mesenchymal transition were absent. At the molecular level, modified gene expression and altered protein contents were found. Non-canonical TGF-β pathway elements did not show relevant changes. However, R-Smads experienced alterations best characterized by decreased Smad3 levels. Functionally, HaCaT cells exposed to TGF-β1 for long periods showed cell-cycle arrest. Yet, the strength of this restraint weakens the longer the treatment, as revealed when challenged by pro-mitogenic factors. The proposed setting might offer a useful framework for future research on the mechanisms driving wound chronification.

Contextual Regulation of TGF-β Signaling in Liver Cancer

Primary liver cancer is one of the leading causes for cancer-related death worldwide. Transforming growth factor beta (TGF-β) is a pleiotropic cytokine that signals through membrane receptors and intracellular Smad proteins, which enter the nucleus upon receptor activation and act as transcription factors. TGF-β inhibits liver tumorigenesis in the early stage by inducing cytostasis and apoptosis, but promotes malignant progression in more advanced stages by enhancing cancer cell survival, EMT, migration, invasion and finally metastasis. Understanding the molecular mechanisms underpinning the multi-faceted roles of TGF-β in liver cancer has become a persistent pursuit during the last two decades. Contextual regulation fine-tunes the robustness, duration and plasticity of TGF-β signaling, yielding versatile albeit specific responses. This involves multiple feedback and feed-forward regulatory loops and also the interplay between Smad signaling and non-Smad pathways. This review summarizes the known regulatory mechanisms of TGF-β signaling in liver cancer, and how they channel, skew and even switch the actions of TGF-β during cancer progression.

TGF-β/Smad and Renal Fibrosis

Renal fibrosis is characterized by excessive deposition of extracellular matrix (ECM) that disrupts and replaces functional parenchyma, which leads to organ failure. It is known as the major pathological mechanism of chronic kidney disease (CKD). Although CKD has an impact on no less than 10% of the world population, therapeutic options are still limited. Regardless of etiology, elevated TGF-β levels are highly correlated with the activated pro-fibrotic pathways and disease progression. TGF-β, the key driver of renal fibrosis, is involved in a dynamic pathophysiological process that leads to CKD and end-stage renal disease (ESRD). It is becoming clear that epigenetics regulates renal programming, and therefore, the development and progression of renal disease. Indeed, recent evidence shows TGF-β1/Smad signaling regulates renal fibrosis via epigenetic-correlated mechanisms. This review focuses on the function of TGF-β/Smads in renal fibrogenesis, and the role of epigenetics as a regulator of pro-fibrotic gene expression.

The role of FSH and TGF-β superfamily in follicle atresia

Most of the mammalian follicles undergo a degenerative process called “follicle atresia”. Apoptosis of granulosa cells is the main characteristic of follicle atresia. Follicle stimulating hormone (FSH) and the transforming growth factor β (TGF-β) superfamily have important regulatory functions in this process. FSH activates protein kinase A and cooperating with insulin receptor substrates, it promotes the PI3K/Akt pathway which weakens apoptosis. Both Smad or non-Smad signaling of the transforming growth factor β superfamily seem to be related to follicle atresia, and the effect of several important family members on follicle atresia is concluded in this article. FSH and TGF-β are likely to mutually influence each other and what we have already known about the possible underlying molecular mechanism is also discussed below.

Heptachlor-induced epithelial to mesenchymal transition in HK-2 cells mediated via TGF-β1/Smad signalling

This study investigated the effect of heptachlor-induced oxidative stress (OS) on transforming growth factor (TGF)-β1-mediated epithelial to mesenchymal transition (EMT) in human renal proximal tubular epithelial (HK-2) cells. Following treatment of HK-2 cells with an increasing concentration of heptachlor (0.01–10 µM) for 24 h, the intracellular reactive oxygen species and malondialdehyde level increased, whereas the glutathione-s-hydroxylase (GSH) level declined significantly in a dose-dependent manner. Pretreatment with N-acetyl cysteine attenuates the heptachlor-induced OS. In this study, we have shown that heptachlor-induced OS regulates the mRNA expression of TGF-β1-mediated Smad signalling genes accompanied by increased nuclear localization of phosphorylated Smad-2 and phosphorylated Smad-3. Furthermore, the m-RNA and protein level of epithelial marker, that is, E-cadherin decreased while the mesenchymal marker, that is, α-smooth muscle actin increased in heptachlor exposed HK-2 cells. In conclusion, heptachlor-induced OS might be responsible for the activation of TGF-β1/Smad signalling which ultimately leads to renal damage by means of EMT.