Tetrodecadazinone, a novel tetrodecamycin-pyridazinone hybrid with anti-liver fibrosis activity from Streptomyces sp. HU051.

Tetrodecadazinone (1), a novel tetrodecamycin-pyridazinone hybrid possessing a new 1,2-dimethyl-1-(2-methylnonyl)decahydronaphthalene skeleton, and 4-hydroxydihydrotetrodecamycin (2) were separated from a culture of Streptomyces sp. HU051, together with a known compound, dihydrotetrodecamycin (3). Diverse spectroscopic approaches were applied to assign the structures of 1-3, and the structure of 1 was further confirmed by single crystal X-ray diffraction analysis. Compound 1 is the first example of a pyridazinone-containing natural product. Biosynthetically, 1 is proposed to be derived from a Michael addition reaction of a PKS-derived tetrodecamycin and a piperazic-acid-derived pyridazinone. Biological evaluation revealed 1 could reduce the expressions of extracellular matrix proteins (fibronectin and collagen I) and α-smooth muscle actin (α-SMA) in transforming growth factor-ß (TGF-ß1)-activated LX-2 cells. Preliminary mechanism study showed 1 exerted its anti-liver fibrosis effect by regulating TGF-ß1/Smad2/3 signaling pathway.

TGFB1/INHBA Homodimer/Nodal-SMAD2/3 Signaling Network: A Pivotal Molecular Target in PDAC Treatment.

Pancreatic cancer remains a grueling disease that is projected to become the second-deadliest cancer in the next decade. Standard treatment of pancreatic cancer is chemotherapy, which mainly targets the differentiated population of tumor cells; however, it paradoxically sets the roots of tumor relapse by the selective enrichment of intrinsically chemoresistant pancreatic cancer stem cells that are equipped with an indefinite capacity for self-renewal and differentiation, resulting in tumor regeneration and an overall anemic response to chemotherapy. Crosstalk between pancreatic tumor cells and the surrounding stromal microenvironment is also involved in the development of chemoresistance by creating a supportive niche, which enhances the stemness features and tumorigenicity of pancreatic cancer cells. In addition, the desmoplastic nature of the tumor-associated stroma acts as a physical barrier, which limits the intratumoral delivery of chemotherapeutics. In this review, we mainly focus on the transforming growth factor beta 1 (TGFB1)/inhibin subunit beta A (INHBA) homodimer/Nodal-SMAD2/3 signaling network in pancreatic cancer as a pivotal central node that regulates multiple key mechanisms involved in the development of chemoresistance, including enhancement of the stem cell-like properties and tumorigenicity of pancreatic cancer cells, mediating cooperative interactions between pancreatic cancer cells and the surrounding stroma, as well as regulating the deposition of extracellular matrix proteins within the tumor microenvironment.

TGF-ß Upregulated Mitochondria Mass through the SMAD2/3→C/EBPß→PRMT1 Signal Pathway in Primary Human Lung Fibroblasts.

Tissue remodeling of subepithelial mesenchymal cells is a major pathologic condition of chronic obstructive pulmonary disease and asthma. Fibroblasts contribute to fibrotic events and inflammation in both airway diseases. Recent mechanistic studies established a link between mitochondrial dysfunction or aberrant biogenesis leading to tissue remodeling of the airway wall in asthma. Protein arginine methyltransferase-1 (PRMT1) participated in airway wall remodeling in pulmonary inflammation. This study investigated the mechanism by which PRMT1 regulates mitochondrial mass in primary human airway wall fibroblasts. Fibroblasts from control or asthma patients were stimulated with TGF-ß for up to 48 h, and the signaling pathways controlling PRMT1 expression and mitochondrial mass were analyzed. PRMT1 activity was suppressed by the pan-PRMT inhibitor AMI-1. The SMAD2/3 pathway was blocked by SB203580 and C/EBPß by small interference RNA treatment. The data obtained from unstimulated cells showed a significantly higher basal expression of PRMT1 and mitochondrial markers in asthmatic compared with control fibroblasts. In all cells, TGF-ß significantly increased the expression of PRMT1 through SMAD2/3 and C/EBPß. Subsequently, PRMT1 upregulated the expression of the mitochondria regulators PGC-1α and heat shock protein 60. Both the inhibition of the SAMD2/3 pathway or PRMT1 attenuated TGF-ß-induced mitochondrial mass and C/EBPß and α-SMA expression. These findings suggest that the signaling sequence controlling mitochondria in primary human lung fibroblasts is as follows: TGF-ß→SMAD2/3→C/EBPß→PRMT1→PGC-1α. Therefore, PRMT1 and C/EBPß present a novel therapeutic and diagnostic target for airway wall remodeling in chronic lung diseases.

Demethyleneberberine promotes apoptosis and suppresses TGF-ß/Smads induced EMT in the colon cancer cells HCT-116.

Colorectal cancer (CRC) is one of the most common malignant tumours in the world. Recent reports have revealed natural products displayed inhibition on colon cancer potential by suppressing transforming growth factor-ß/Smads induced epidermal-mesenchymal transition (EMT). In this article, 12 kinds of natural berberine analogues were screened for their effects on the inhibition of the colon cancer cells, the results showed that demethyleneberberine (DM-BBR) exhibited an interesting and potential effect on inducing the apoptosis of HCT-116 cells with drug concentrations of 6, 12 and 18 µM. Particularly, DM-BBR reversed the EMT process by inhibiting the expression of p-Smad2 and p-Smad3 in the transforming growth factor-ß/Smads signal pathway, up-regulated pro-apoptotic protein cleaved caspase-9, and blocked cell cycle at the S phase and increasing the expression of cyclin proteins P27 and P21. Taken together, these findings suggested that DM-BBR could promote apoptosis and suppress TGF-ß/Smads induced EMT in the colon cancer cells HCT-116.

The regulatory protein SnoN antagonizes activin/Smad2 protein signaling and thereby promotes adipocyte differentiation and obesity in mice.

Ski-related oncogene SnoN (SnoN or SKIL) regulates multiple signaling pathways in a tissue- and developmental stage-dependent manner and has broad functions in embryonic angiogenesis, mammary gland alveologenesis, cancer, and aging. Here, we report that SnoN also plays a critical role in white adipose tissue (WAT) development by regulating mesenchymal stem cell (MSC) self-renewal and differentiation. We found that SnoN promotes MSC differentiation in the adipocyte lineage by antagonizing activin A/Smad2, but not TGFß/Smad3 signaling. Mice lacking SnoN or expressing a mutant SnoN defective in binding to the Smads were protected from high-fat diet-induced obesity and insulin resistance, and MSCs lacking a functional SnoN exhibited defective differentiation. We further demonstrated that activin, via Smad2, appears to be the major regulator of WAT development in vivo We also noted that activin A is abundantly expressed in WAT and adipocytes through an autocrine mechanism and promotes MSC self-renewal and inhibits adipogenic differentiation by inducing expression of the gene encoding the homeobox transcription factor Nanog. Of note, SnoN repressed activin/Smad2 signaling and activin A expression, enabling expression of adipocyte-specific transcription factors and promoting adipogenic differentiation. In conclusion, our study has revealed that SnoN plays an important in vivo role in adipocyte differentiation and WAT development in vivo by decreasing activity in the activin/Smad2 signaling pathway.

LEM domain-containing protein 3 antagonizes TGFß-SMAD2/3 signaling in a stiffness-dependent manner in both the nucleus and cytosol.

Transforming growth factor-ß (TGFß) signaling through SMAD2/3 is an important driver of pathological fibrosis in multiple organ systems. TGFß signaling and extracellular matrix (ECM) stiffness form an unvirtuous pathological circuit in which matrix stiffness drives activation of latent TGFß, and TGFß signaling then drives cellular stress and ECM synthesis. Moreover, ECM stiffness also appears to sensitize cells to exogenously activated TGFß through unknown mechanisms. Here, using human fibroblasts, we explored the effect of ECM stiffness on a putative inner nuclear membrane protein, LEM domain-containing protein 3 (LEMD3), which is physically connected to the cell's actin cytoskeleton and inhibits TGFß signaling. We showed that LEMD3-SMAD2/3 interactions are inversely correlated with ECM stiffness and TGFß-driven luciferase activity and that LEMD3 expression is correlated with the mechanical response of the TGFß-driven luciferase reporter. We found that actin polymerization but not cellular stress or LEMD3-nuclear-cytoplasmic couplings were necessary for LEMD3-SMAD2/3 interactions. Intriguingly, LEMD3 and SMAD2/3 frequently interacted in the cytosol, and we discovered LEMD3 was proteolytically cleaved into protein fragments. We confirmed that a consensus C-terminal LEMD3 fragment binds SMAD2/3 in a stiffness-dependent manner throughout the cell and is sufficient for antagonizing SMAD2/3 signaling. Using human lung biopsies, we observed that these nuclear and cytosolic interactions are also present in tissue and found that fibrotic tissues exhibit locally diminished and cytoplasmically shifted LEMD3-SMAD2/3 interactions, as noted in vitro Our work reveals novel LEMD3 biology and stiffness-dependent regulation of TGFß by LEMD3, providing a novel target to antagonize pathological TGFß signaling.

Dihydroartemisinin up-regulates VE-cadherin expression in human renal glomerular endothelial cells.

The antimalarial agent dihydroartemisinin (DHA) has been shown to be anti-inflammatory. In this study, we found that DHA increased the expression of the junctional protein vascular endothelial (VE)-cadherin in human renal glomerular endothelial cells. In addition, DHA inhibited TGF-ß RI-Smad2/3 signalling and its downstream effectors SNAIL and SLUG, which repress VE-cadherin gene transcription. Correspondingly, DHA decreased the binding of SNAIL and SLUG to the VE-cadherin promoter. Together, our results suggest an effect of DHA in regulating glomerular permeability by elevation of VE-cadherin expression.

TGF-ß1 Promotes Hepatocellular Carcinoma Invasion and Metastasis via ERK Pathway-Mediated FGFR4 Expression.

BACKGROUND/AIMS: TGF-ß1 is beneficial during early liver disease but is tumor-progressive during late stages especially for hepatocellular carcinoma (HCC). Thus, exploring the underlying mechanisms may provide information about a potentially therapeutic role of TGF-ß1 in HCC. METHODS: Western blot and real-time quantitative PCR were used to quantify FGFR4 expression in HCC cell lines and a normal liver cell line. After constructing the best silencing FGFR4 expression vector, migration and invasiveness of TGF-ß1 in HCC was studied in vitro and in vivo. Western blot was used to study the mechanism of TGF-ß1 induction on FGFR4 expression with various inhibitors. RESULTS: HepG2 cell lines had the most FGFR4 expression, and data show that silencing FGFR4 suppressed cell proliferation, invasion and migration in HCC induced by TGF-ß1 in vitro and in vivo. Moreover, TGF-ß1 induced FGFR4 expression through the ERK pathway. CONCLUSION: Promoting FGFR4 expression via the ERK pathway, TGF-ß1 contributes to HCC invasion and metastasis.

Inhibition of mTOR ameliorates bleomycin-induced pulmonary fibrosis by regulating epithelial-mesenchymal transition.

Epithelial-mesenchymal transition (EMT) plays a pivotal role in idiopathic pulmonary fibrosis (IPF). In bleomycin-induced pulmonary fibrosis mice, we observed that inhibition of mTOR (mammalia target of rapamycin) attenuated IPF. Rapamycin suppressed the down-regulation of E-cadherin and up-regulation of fibronectin in bleomycin-induced pulmonary fibrosis mice. In addition, dual immunofluorescence staining for E-cadherin and fibronectin demonstrated that rapamycin pretreatment decreased the proportions of AECs undergoing EMT in bleomycin-induced pulmonary fibrosis, indicating that mTOR inhibition suppressed EMT in vivo. In the setting of transforming growth factor (TGF)-ß1-induced EMT in AECs, we found that mTOR inhibitor attenuated TGF-ß1-induced EMT in AECs. This EMT was characterized by morphology and cell skeleton changes and the expression of EMT phenotype markers. Finally, mTOR blockade decreased S6k and TGF-ß1-induced Smad2/3 phosphorylation. Bleomycin induced pulmonary fibrosis and EMT in mice, while mTOR repression inhibited bleomycin-induced pulmonary fibrosis and attenuated EMT in vivo. Hence, our study provided evidence of a novel mechanism by which mTOR inhibitor ameliorates pulmonary fibrosis. Suppression of mTOR and EMT may be a target for treatment of pulmonary fibrosis.

In vitro and ex vivo anti-fibrotic effects of LY2109761, a small molecule inhibitor against TGF-ß.

Fibrosis is a pathophysiological state characterized by the excessive formation/deposition of fibrous extracellular matrix. Transforming growth factor-beta (TGF-ß) is a central profibrotic mediator, and targeting TGF-ß is a promising strategy in the development of drugs for the treatment of fibrosis. Therefore, the effect of LY2109761, a small molecule inhibitor against TGF-ß with targets beyond TGF-ß signaling, on fibrogenesis was elucidated in vitro (HepG2 cells and LX-2 cells) and ex vivo (human and rat precision-cut liver slices). Our results displayed an anti-fibrotic effect of LY2109761, as it markedly down-regulated gene and protein expression of collagen type 1, as well as gene expression of the inhibitor of metalloproteinases 1. This effect on fibrosis markers was partially mediated by targeting TGF-ß signaling, seeing that LY2109761 inhibited TGF-ß1 gene expression and SMAD2 protein phosphorylation. Interestingly, particularly at a high concentration, LY2109761 decreased SMAD1 protein phosphorylation and gene expression of the inhibitor of DNA binding 1, which appeared to be TGF-ß-independent effects. In conclusion, LY2109761 exhibited preclinical anti-fibrotic effects via both TGF-ß-dependent and -independent pathways. These results illustrate that small molecule inhibitors directed against TGF-ß could possibly influence numerous signaling pathways and thereby mitigate fibrogenesis.

Curcumin inhibits TGF-ß1-induced connective tissue growth factor expression through the interruption of Smad2 signaling in human gingival fibroblasts.

BACKGROUND/PURPOSE: Many fibrotic processes are associated with an increased level of transforming growth factor-ß1 (TGF-ß1). TGF-ß1 can increase synthesis of matrix proteins and enhance secretion of protease inhibitors, resulting in matrix accumulation. Connective tissue growth factor (CTGF) is a downstream profibrotic effector of TGF-ß1 and is associated with the fibrosis in several human organs. Curcumin has been applied to reduce matrix accumulation in fibrotic diseases. This study was aimed to evaluate whether curcumin could suppress TGF-ß1-induced CTGF expression and its related signaling pathway involving in this inhibitory action in primary human gingival fibroblasts. METHODS: The differences in CTGF expression among three types of gingival overgrowth and normal gingival tissues were assessed by immunohistochemistry. Gingival fibroblast viability in cultured media with different concentrations of curcumin was studied by MTT assay. The effect of curcumin on TGF-ß1-induced CTGF expression in primary human gingival fibroblasts was examined by immunoblotting. Moreover, the proteins involved in TGF-ß1 signaling pathways including TGF-ß1 receptors and Smad2 were also analyzed by immunoblotting. RESULTS: CTGF was highly expressed in fibroblasts, epithelial cells and some of endothelial cells, smooth muscle cells, and inflammatory cells in phenytoin-induced gingival overgrowth tissues rather than in those of hereditary and inflammatory gingival overgrowth tissues. Moreover, CTGF expression in the epithelial and connective tissue layers was higher in phenytoin-induced gingival overgrowth tissues than in normal gingival tissues. Curcumin was nontoxic and could reduce TGF-ß1-induced CTGF expression by attenuating the phosphorylation and nuclear translocation of Smad2. CONCLUSION: Curcumin can suppress TGF-ß1-induced CTGF expression through the interruption of Smad2 signaling.

Transforming Growth Factor-ß1 Modulates the Expression of Syndecan-4 in Cultured Vascular Endothelial Cells in a Biphasic Manner.

Proteoglycans are macromolecules that consist of a core protein and one or more glycosaminoglycan side chains. Previously, we reported that transforming growth factor-ß1 (TGF-ß1 ) regulates the synthesis of a large heparan sulfate proteoglycan, perlecan, and a small leucine-rich dermatan sulfate proteoglycan, biglycan, in vascular endothelial cells depending on cell density. Recently, we found that TGF-ß1 first upregulates and then downregulates the expression of syndecan-4, a transmembrane heparan sulfate proteoglycan, via the TGF-ß receptor ALK5 in the cells. In order to identify the intracellular signal transduction pathway that mediates this modulation, bovine aortic endothelial cells were cultured and treated with TGF-ß1 . Involvement of the downstream signaling pathways of ALK5-the Smad and MAPK pathways-in syndecan-4 expression was examined using specific siRNAs and inhibitors. The data indicate that the Smad3-p38 MAPK pathway mediates the early upregulation of syndecan-4 by TGF-ß1 , whereas the late downregulation is mediated by the Smad2/3 pathway. Multiple modulations of proteoglycan synthesis may be involved in the regulation of vascular endothelial cell functions by TGF-ß1 . J. Cell. Biochem. 118: 2009-2017,2017. © 2016 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc.

Aggregatibacter actinomycetemcomitans outer membrane protein 29 (Omp29) induces TGF-ß-regulated apoptosis signal in human gingival epithelial cells via fibronectin/integrinß1/FAK cascade.

Gingival junctional epithelial cell apoptosis caused by periodontopathic bacteria exacerbates periodontitis. This pathological apoptosis is involved in the activation of transforming growth factor ß (TGF-ß). However, the molecular mechanisms by which microbes induce the activation of TGF-ß remain unclear. We previously reported that Aggregatibacter actinomycetemcomitans (Aa) activated TGF-ß receptor (TGF-ßR)/smad2 signalling to induce epithelial cell apoptosis, even though Aa cannot bind to TGF-ßR. Additionally, outer membrane protein 29 kDa (Omp29), a member of the Aa Omps family, can induce actin rearrangements via focal adhesion kinase (FAK) signalling, which also plays a role in the activation of TGF-ß by cooperating with integrin. Accordingly, we hypothesized that Omp29-induced actin rearrangements via FAK activity would enhance the activation of TGF-ß, leading to gingival epithelial cell apoptosis in vitro. By using human gingival epithelial cell line OBA9, we found that Omp29 activated TGF-ßR/smad2 signalling and decreased active TGF-ß protein levels in the extracellular matrix (ECM) of cell culture, suggesting the transactivation of TGF-ßR. Inhibition of actin rearrangements by cytochalasin D or blebbistatin and knockdown of FAK or integrinß1 expression by siRNA transfection attenuated TGF-ßR/smad2 signalling activity and reduction of TGF-ß levels in the ECM caused by Omp29. Furthermore, Omp29 bound to fibronectin (Fn) to induce its aggregation on integrinß1, which is associated with TGF-ß signalling activity. All the chemical inhibitors and siRNAs tested blocked Omp29-induced OBA9 cells apoptosis. These results suggest that Omp29 binds to Fn in order to facilitate Fn/integrinß1/FAK signalling-dependent TGF-ß release from the ECM, thereby inducing gingival epithelial cell apoptosis via TGF-ßR/smad2 pathway.

Baicalein attenuates hypertrophic scar formation via inhibition of the transforming growth factor-ß/Smad2/3 signalling pathway.

BACKGROUND: Hypertrophic scars (HPSs) are characterized by excessive fibrosis associated with aberrant function of fibroblasts. Currently no satisfactory treatment has been developed. OBJECTIVES: To investigate the effect of baicalein on HPSs and its underlying mechanisms. METHODS: Baicalein was administered intradermally (10 µmol L(-1) in 100 µL sterile saline plus 10% dimethylsulfoxide) to mechanical-load-induced scars in mice once a day for 14 or 28 days. Histological and immunohistochemical studies were performed to evaluate scar hypertrophy and the function of fibroblasts. Human HPS-derived fibroblasts (HSFs) were determined by immunofluorescence study, collagen gel contraction assay and wound-healing assay. Also, protein expression of the transforming growth factor (TGF)-ß signalling pathway was detected using Western blotting. Lastly, a molecular docking study and kinase binding assay were conducted in search of the potential interaction between baicalein and activin receptor-like kinase (ALK)5. RESULTS: Baicalein treatment significantly attenuated HPS formation and collagen deposition in a mechanical-load-induced mouse model. Baicalein also inhibited the proliferation and activation of fibroblasts in vitro and in vivo. Furthermore, baicalein impaired the contractile and migration ability of HSFs. Protein expression investigation revealed that baicalein had an inhibitory effect on TGF-ß/Smad2/3 signalling. Such bioactivity of baicalein may result from its selective binding to the ATP-binding pocket of ALK5, as suggested by the molecular docking study and kinase binding assay. CONCLUSIONS: Baicalein could serve as a promising agent for treatment of HPSs and a selective ALK5 inhibitor.

AMPK Inhibits the Stimulatory Effects of TGF-ß on Smad2/3 Activity, Cell Migration, and Epithelial-to-Mesenchymal Transition.

AMP-activated protein kinase (AMPK), an important downstream effector of the tumor suppressor liver kinase 1 (LKB1) and pharmacologic target of metformin, is well known to exert a preventive and inhibitory effect on tumorigenesis; however, its role in cancer progression and metastasis has not been well characterized. The present study investigates the potential roles of AMPK in inhibiting cancer-cell migration and epithelial-to-mesenchymal transition (EMT) by regulating the canonical transforming growth factor ß (TGF-ß) signaling pathway, an important promoting factor for cancer progression. Our results showed that activation of AMPK by metformin inhibited TGF-ß-induced Smad2/3 phosphorylation in cancer cells in a dose-dependent manner. The effect of metformin is dependent on the presence of LKB1. A similar effect was obtained by expressing a constitutive active mutant of AMPKα1 subunit, whereas the expression of a dominant negative mutant of AMPKα1 or ablation of AMPKα subunits greatly enhanced TGF-ß stimulation of Smad2/3 phosphorylation. As a consequence, expression of genes downstream of Smad2/3, including plasminogen activator inhibitor-1, fibronectin, and connective tissue growth factor, was suppressed by metformin in a LKB1-dependent fashion. In addition, metformin blocked TGF-ß-induced inteleukin-6 expression through both LKB1-dependent and -independent mechanisms. Our results also indicate that activation of LKB1/AMPK inhibits TGF-ß-stimulated cancer cell migration. Finally, TGF-ß induction of EMT was inhibited by phenformin and enhanced by knockdown of LKB1 expression with shRNA. Together, our data suggest that AMPK could be a drug target for controlling cancer progression and metastasis.

Identification of TGF-ß receptor-1 as a key regulator of carbon nanotube-induced fibrogenesis.

Carbon nanotubes (CNTs) induce rapid interstitial lung fibrosis, but the underlying mechanisms are unclear. Previous studies indicated that the ability of CNTs to penetrate lung epithelium, enter interstitial tissue, and stimulate fibroblasts to produce collagen matrix is important to lung fibrosis. In this study, we investigated the activation of transforming growth factor-ß receptor-1 [TGF-ß R1; i.e., activin receptor-like kinase 5 (ALK5) receptor] and TGF-ß/Smad signaling pathway in CNT-induced collagen production in human lung fibroblasts. Human lung fibroblasts and epithelial cells were exposed to low, physiologically relevant concentrations (0.02-0.6 µg/cm(2)) of single-walled CNTs (SWCNT) and multiwalled CNTs (MWCNT) in culture and analyzed for collagen, TGF-ß1, TGF-ß R1, and SMAD proteins by Western blotting and immunofluorescence. Chemical inhibition of ALK5 and short-hairpin (sh) RNA targeting of TGF-ß R1 and Smad2 were used to probe the fibrogenic mechanism of CNTs. Both SWCNT and MWCNT induced an overexpression of TGF-ß1, TGF-ß R1 and Smad2/3 proteins in lung fibroblasts compared with vehicle or ultrafine carbon black-exposed controls. SWCNT- and MWCNT-induced collagen production was blocked by ALK5 inhibitor or shRNA knockdown of TGF-ß R1 and Smad2. Our results indicate the critical role of TGF-ß R1/Smad2/3 signaling in CNT-induced fibrogenesis by upregulating collagen production in lung fibroblasts. This novel finding may aid in the design of mechanism-based risk assessment and development of rapid screening tests for nanomaterial fibrogenicity.

Hydrogen sulfide alleviates myocardial collagen remodeling in association with inhibition of TGF-ß/Smad signaling pathway in spontaneously hypertensive rats.

The study was designed to explore the role and possible mechanisms of hydrogen sulfide (H2S) in the regulation of myocardial collagen remodeling in spontaneously hypertensive rats (SHRs). We treated nine-week-old male SHRs and age- and sex-matched Wistar-Kyoto rats (WKYs) with NaHS (90 µmol/kg(-1)·day(-1)) for 9 wks. At 18 wks, plasma H2S, tail arterial pressure, morphology of the heart, myocardial ultrastructure and collagen volume fraction (CVF), myocardial expressions of collagen I and III protein and procollagen I and III mRNA, transforming growth factor-ß1 (TGF-ß1), TGF-ß type I receptor (TßR-I), type II receptor (TßR-II), p-Smad2 and 3, matrix metalloproteinase (MMP)-13 and tissue inhibitors of MMP (TIMP)-1 proteins were determined. TGF-ß1-stimulated cultured cardiac fibroblasts (CFs) were used to further study the mechanisms. The results showed that compared with WKYs, SHRs showed a reduced plasma H2S, elevated tail artery pressure and increased myocardial collagen, TGF-ß1, TßR-II, p-Smad2 and p-Smad3 expressions. However, NaHS markedly decreased tail artery pressure and inhibited myocardial collagen, TGF-ß1, TßR-II, p-Smad2 and p-Smad3 protein expressions, but H2S had no effect on the expressions of MMP-13 and TIMP-1. Hydralazine reduced blood pressure but had no effect on myocardial collagen, MMP-13 and TIMP-1 expressions and TGF-ß1/Smad signaling pathway. H2S prevented activation of the TGF-ß1/Smad signaling pathway and abnormal collagen synthesis in CFs. In conclusion, the results suggested that H2S could prevent myocardial collagen remodeling in SHR. The mechanism might be associated with inhibition of collagen synthesis via TGF-ß1/Smad signaling pathway.

Smad2 and Smad3 cooperate and antagonize simultaneously in vertebrate neurogenesis.

The transforming growth factor beta (TGF-ß) pathway plays key roles in development and cancer. TGF-ß signaling converges on the Smad2 and Smad3 effectors, which can either cooperate or antagonize to regulate their transcriptional targets. Here we performed in vivo and in silico experiments to study how such cooperativity and antagonism might function during neurogenesis. In vivo electroporation experiments in the chick embryo neural tube show that Smad2 and Smad3 cooperate to promote neurogenesis, as well as the transcription of Smad3-specific targets. Knockdown of Smad2 enhances neurogenesis and the transcription of Smad3-specific targets. A mathematical model of the TGF-ß pathway fits the experimental results and predicts that the proportions of the three different trimeric complexes formed dictates the transcriptional responses of the R-Smad proteins. As such, Smad2 targets are activated solely by the Smad2-Smad2-Smad4 complex, whereas Smad3 targets are activated both by Smad2-Smad3-Smad4 and Smad3-Smad3-Smad4 trimers. We have modeled the Smad responses onto arbitrary genes and propose that this mechanism might be extended to additional activities of TGF-ß in development and disease.

Nuclear SMAD2 restrains proliferation of glioblastoma.

AIMS: Although TGFß receptor signaling has been shown to play a role in regulation of the growth and metastasis of glioblastoma multiforme (GBM), the downstream pathway through either SMAD2 or SMAD3 has not been elucidated. In this study, we investigate whether nuclear SMAD2 can restrain the proliferation of glioblastoma. METHODS: A total of 23 resected specimens from GBM patients were collected for SMAD2 detection. Human GBM cell line A172, U87mg, D341m and Hs683 were maintained in Dulbecco's modified Eagle's medium and transfected with SMAD2 and SMAD3 shRNA plasmids. Gene expression was detected by RT-qPCR and Western and cell growth were detected by MTT assay. RESULTS: Our results showed that the phosphorylated SMAD2 (pSMAD2, the nuclear and functional form of SMAD2) levels in GBM were significantly lower than the paired normal brain tissue in patients. Depletion of SMAD2, but not SMAD3, significantly abolished the inhibitory effects of TGFß1 on the growth of GBM cells, possibly through pSMAD2-mediated increases in cell-cycle inhibitor, p27. CONCLUSION: Our data suggest that TGFß/SMAD2 signaling cascades restrains growth of GBM.

Follistatin-like 1 attenuates differentiation and survival of erythroid cells through Smad2/3 signaling.

Hematopoiesis is a complex process tightly controlled by sets of transcription factors in a context-dependent and stage-specific manner. Smad2/3 transcription factor plays a central role in differentiation and survival of erythroid cells. Here we report that follistatin-like 1 (FSTL1) treatment impairs hemin-induced erythroid differentiation and cell survival. FSTL1 differentially regulates transforming growth factor beta (TGF-ß) and bone morphogenetic protein (BMP) signaling. Blockade of Smad2/3 signaling with the ALK5/type I TGF-ßR kinase inhibitor, SB-525334, was efficacious for rescue of erythroid differentiation blockage and apoptosis. Reversely, activation of Smad1/5/8 signaling with BMP4 cannot rescue FSTL1-mediated erythroid differentiation blockage and apoptosis. Collectively, these data provide mechanistic insight into the regulation of erythropoiesis by FSTL1 signaling and lay a foundation for exploring FSTL1 signaling as a therapeutic target for anemia.