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David R Brigstock - One of the best experts on this subject based on the ideXlab platform.

  • connective tissue growth factor CTGF inactivation leads to defects in islet cell lineage allocation and β cell proliferation during embryogenesis
    Molecular Endocrinology, 2009
    Co-Authors: Laura A Crawford, David R Brigstock, Karen M. Lyons, Michelle A Guney, Young Ah Oh, Andrea R Deyoung, David M Valenzuela, Andrew J Murphy, George D Yancopoulos, Aris Apartment E Economides
    Abstract:

    The factors necessary for normal pancreatic islet morphogenesis have not been well characterized. Here we report that connective tissue growth factor (CTGF) is involved in the establishment of normal islet endocrine cell ratio and architecture. CTGF is a secreted protein known to modulate several growth factor-signaling pathways including TGF-β, BMP, and Wnt. Although its role in pancreatic diseases such as pancreatitis and pancreatic cancer are well documented, a role for CTGF in normal pancreas development and function has heretofore not been examined. Using a lacZ-tagged CTGF allele, we describe for the first time the expression pattern of CTGF in the developing pancreas and the requirement of CTGF for normal islet morphogenesis and embryonic β-cell proliferation. CTGF is highly expressed in pancreatic ductal epithelium and vascular endothelium, as well as at lower levels in developing insulin+ cells, but becomes down-regulated in β-cells soon after birth. Pancreata from CTGF null embryos have an increase in glucagon+ cells with a concomitant decrease in insulin+ cells, and show defects in islet morphogenesis. Loss of CTGF also results in a dramatic decrease in β-cell proliferation at late gestation. Unlike CTGF null embryos, CTGF heterozygotes survive past birth and exhibit a range of islet phenotypes, including an intermingling of islet cell types, increased number of glucagon+ cells, and β-cell hypertrophy.

  • low density lipoprotein receptor related protein lrp is a heparin dependent adhesion receptor for connective tissue growth factor CTGF in rat activated hepatic stellate cells
    Hepatology Research, 2003
    Co-Authors: David R Brigstock
    Abstract:

    Connective tissue growth factor (CTGF) is a cysteine-rich, extracellular matrix-associated heparin-binding protein implicated in a variety of fibrotic disorders. CTGF is initially synthesized as a mosaic protein containing four discrete structural modules (CTGF1–4) but this is susceptible to proteolytic cleavage yielding isoforms comprising modules 3 and 4 (CTGF3–4) or module 4 alone (CTGF4). In this study, we show that cultured rat hepatic stellate cells (HSCs) produce CTGF1–4 and CTGF3–4 following treatment with transforming growth factor-β and that CTGF is a cell adhesion factor for activated HSCs. Low density lipoprotein receptor-associated protein (LRP) is a receptor for CTGF1–4 or CTGF3–4, but not CTGF4, whereas cell surface heparan sulfate proteoglycans (HSPGs) are binding sites for all CTGF isoforms. Prior occupancy of LRP with other LRP ligands, receptor associated protein, anti-LRP, or a thrombospondin type I peptide (TEWSACSKTCG) resulted in a 50% decrease in the adhesion of activated HSCs to CTGF1–4 or CTGF3–4 whereas there was no effect on CTGF4-mediated adhesion. Co-incubation of CTGF with heparin or perturbation of cell surface HSPGs with heparinase or sodium chlorate completely blocked adhesion of activated HSCs to all CTGF isoforms. Freshly isolated HSCs demonstrated only weak binding to CTGF but strong binding to fibronectin. Thus HSC adhesion is at least partially promoted by CTGF through its binding to LRP, a process that is heparin-dependent. CTGF–LRP interactions are likely mediated by module 3 and CTGF–heparin interactions occur principally in module 4, although additional motifs may account for the heparin-dependency of LRP binding. These data show that LRP and HSPGs are utilized by HSCs for binding to CTGF and suggest that these cell surface molecules may be involved in mediating CTGF activity or adhesive signaling during the activation process.

  • connective tissue growth factor CTGF ccn2 in hepatic fibrosis
    Hepatology Research, 2003
    Co-Authors: Amy W Rachfal, David R Brigstock
    Abstract:

    Connective tissue growth factor (CTGF/CCN2) is a highly profibrogenic molecule which is overexpressed in many fibrotic lesions, including those of the liver. CTGF/CCN2 is transcriptionally activated by transforming growth factor-beta (TGF-β) and appears to mediate some of the extracellular matrix (ECM)-inducing properties that have been previously attributed to TGF-β. CTGF/CCN2 and TGF-β stimulate connective tissue cell proliferation and ECM synthesis in vitro and exhibit shared fibrogenic and angiogenic properties in vivo. In fibrotic liver, CTGF/CCN2 mRNA and protein are produced by fibroblasts, myofibroblasts, hepatic stellate cells (HSCs), endothelial cells, and bile duct epithelial cells. CTGF/CCN2 is also produced at high levels in hepatocytes during cytochrome P-4502E1-mediated ethanol oxidation. CTGF/CCN2 expression in cultured HSCs is enhanced following their activation or stimulation by TGF-β while exogenous CTGF/CCN2 is able to promote HSC adhesion, proliferation, locomotion, and collagen production. Collectively, these data suggest that during initiating or downstream fibrogenic events in the liver, production of CTGF/CCN2 is regulated primarily by TGF-β in one or more cell types and that CTGF/CCN2 plays important roles in HSC activation and progression of fibrosis. This article reviews the data that support the importance of CTGF/CCN2 in hepatic fibrosis and highlights the concept that CTGF/CCN2 may represent a new therapeutic target in this disease.

  • Connective tissue growth factor (CTGF/CCN2) in hepatic fibrosis.
    Hepatology Research, 2003
    Co-Authors: Amy W Rachfal, David R Brigstock
    Abstract:

    Connective tissue growth factor (CTGF/CCN2) is a highly profibrogenic molecule which is overexpressed in many fibrotic lesions, including those of the liver. CTGF/CCN2 is transcriptionally activated by transforming growth factor-beta (TGF-β) and appears to mediate some of the extracellular matrix (ECM)-inducing properties that have been previously attributed to TGF-β. CTGF/CCN2 and TGF-β stimulate connective tissue cell proliferation and ECM synthesis in vitro and exhibit shared fibrogenic and angiogenic properties in vivo. In fibrotic liver, CTGF/CCN2 mRNA and protein are produced by fibroblasts, myofibroblasts, hepatic stellate cells (HSCs), endothelial cells, and bile duct epithelial cells. CTGF/CCN2 is also produced at high levels in hepatocytes during cytochrome P-4502E1-mediated ethanol oxidation. CTGF/CCN2 expression in cultured HSCs is enhanced following their activation or stimulation by TGF-β while exogenous CTGF/CCN2 is able to promote HSC adhesion, proliferation, locomotion, and collagen production. Collectively, these data suggest that during initiating or downstream fibrogenic events in the liver, production of CTGF/CCN2 is regulated primarily by TGF-β in one or more cell types and that CTGF/CCN2 plays important roles in HSC activation and progression of fibrosis. This article reviews the data that support the importance of CTGF/CCN2 in hepatic fibrosis and highlights the concept that CTGF/CCN2 may represent a new therapeutic target in this disease.

  • Establishment of a recombinant expression system for connective tissue growth factor (CTGF) that models CTGF processing in utero.
    Reproduction, 2003
    Co-Authors: D. K. Ball, E. E-d. A. Moussad, M. A. E. Rageh, S. A. Kemper, David R Brigstock
    Abstract:

    Connective tissue growth factor (CTGF) stimulates cell proliferation, migration, adhesion and extracellular matrix production, and functions in processes such as development, differentiation, angiogenesis, implantation, wound healing and fibrosis. CTGF is a 38 kDa protein that comprises four discrete structural modules (modules 1‐4) but is susceptible to limited proteolysis in utero yielding bioactive isoforms that comprise either modules 3 and 4( 16‐20kDa) or module 4 (10kDa). Here we report the development of a stable cell line, termed DB1, that was generated by transfecting cDNA encoding full-length human CTGF into Chinese hamster ovary cells that were mutant for heparin sulphate and chondroitin sulphate. DB1 cells produced 38kDa CTGF and low molecular mass CTGFs that had N-termini between modules 2 and 3a t Ala 181 (20kDa), Leu 184 (18kDa) or Ala 197 (16kDa) or between modules 3 and 4 at Gly 253 (10kDa). CTGF was exported from DB1 cells as early as 5min after synthesis and all isoforms were readily purified from conditioned medium by sequential steps of heparin affinity, cation exchange, and reverse-phase chromatography. The 38kDa CTGF was faithfully glycosylated and underwent limited proteolysis in the presence of thrombin, kallikrein or uterine fluids, the last of which was antagonized by anti-thrombin III. All CTGF isoforms promoted cell adhesion, mitosis and epithelial transdifferentiation in vitro as well as subcutaneous fibrosis invivo .T he establishment of this recombinant expression system allows for massscale production of all previously reported uterine CTGF isoforms, demonstrates that module 4 contains functional domains involved in a broad range of biological activities, and will facilitate studies of CTGF processing in vitro.

Chihhsin Tang - One of the best experts on this subject based on the ideXlab platform.

  • CTGF increases vascular endothelial growth factor dependent angiogenesis in human synovial fibroblasts by increasing mir 210 expression
    Cell Death and Disease, 2014
    Co-Authors: Showmei Chuang, Chihhsin Tang, Chunhao Tsai, Shihwei Wang
    Abstract:

    Connective tissue growth factor (CTGF, a.k.a. CCN2) is inflammatory mediator and abundantly expressed in osteoarthritis (OA). Angiogenesis is essential for OA progression. Here, we investigated the role of CTGF in vascular endothelial growth factor (VEGF) production and angiogenesis in OA synovial fibroblasts (OASFs). We showed that expression of CTGF and VEGF in synovial fluid were higher in OA patients than in controls. Directly applying CTGF to OASFs increased VEGF production then promoted endothelial progenitor cells tube formation and migration. CTGF induced VEGF by raising miR-210 expression via PI3K, AKT, ERK, and nuclear factor-κB (NF-κB)/ELK1 pathways. CTGF-mediating miR-210 upregulation repressed glycerol-3-phosphate dehydrogenase 1-like (GPD1L) expression and PHD activity and subsequently promoted hypoxia-inducible factor (HIF)-1α-dependent VEGF expression. Knockdown of CTGF decreased VEGF expression and abolished OASF-conditional medium-mediated angiogenesis in vitro as well as angiogenesis in chick chorioallantoic membrane and Matrigel-plug nude mice model in vivo. Taken together, our results suggest CTGF activates PI3K, AKT, ERK, and NF-κB/ELK1 pathway, leading to the upregulation of miR-210, contributing to inhibit GPD1L expression and prolyl hydroxylases 2 activity, promoting HIF-1α-dependent VEGF expression and angiogenesis in human synovial fibroblasts.

  • CTGF increases matrix metalloproteinases expression and subsequently promotes tumor metastasis in human osteosarcoma through down regulating mir 519d
    Oncotarget, 2014
    Co-Authors: Hsiaochi Tsai, Honglin Su, Chunyin Huang, Yichin Fong, Chihhsin Tang
    Abstract:

    // Hsiao-Chi Tsai 1 , Hong-Lin Su 1 , Chun-Yin Huang 2,3 , Yi-Chin Fong 4,5 , Chin-Jung Hsu 4,5 and Chih-Hsin Tang 6,7,8 1 Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan 2 Department of Orthopaedic Surgery, China Medical University Beigang Hospital, Yun-Lin County, Taiwan 3 Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan 4 School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan 5 Department of Orthopedic Surgery, China Medical University Hospital, Taichung, Taiwan 6 Graduate Institute of Basic Medical Science, China Medical University, Taichung, Taiwan 7 Department of Pharmacology, School of Medicine, China Medical University, Taichung, Taiwan 8 Department of Biotechnology, College of Health Science, Asia University, Taichung, Taiwan Correspondence: Chih-Hsin, Tang , email: // Keywords : Osteosarcoma; MicroRNA; MMP; CTGF; Metastasis Received : April 13, 2014 Accepted : May 19, 2014 Published : May 21, 2014 Abstract Osteosarcoma, the most common primary malignant bone tumor, shows potent capacity for local invasion and distant metastasis. Connective tissue growth factor (CTGF/CCN2), a secreted protein, binds to integrins, modulates invasive behavior of certain human cancer cells. Effect of CTGF in metastasis of human osteosarcoma is unknown. We found overexpression of CTGF increasing matrix metalloproteinases (MMPs)-2 and MMP-3 expression as well as promoting cell migration. MicroRNA (miRNA) analysis of CTGF-overexpressed osteosarcoma versus control cells probed mechanisms of CTGF-mediated promotion of migration. Among miRNAs regulated by CTGF, miR-519d was most downregulated after CTGF treatment. Co-transfection with miR-519d mimic reversed CTGF-mediated MMPs expression and cell migration. Also, MEK and ERK inhibitors or mutants reduced CTGF-increased cell migration and miR-519d suppression. By contrast, knockdown of CTGF diminished lung metastasis in vivo . Clinical samples indicate CTGF expression as linked with clinical stage and tumor metastasis. Taken together, data show CTGF elevating MMPs expression and subsequently promoting tumor metastasis in human osteosarcoma, down-regulating miR-519d via MEK and ERK pathways, making CTGF a new molecular therapeutic target in osteosarcoma metastasis.

  • CTGF increases il 6 expression in human synovial fibroblasts through integrin dependent signaling pathway
    PLOS ONE, 2012
    Co-Authors: Hsiente Chen, Hsikai Tsou, Showmei Chuang, Chihhsin Tang
    Abstract:

    Background Connective tissue growth factor (CTGF; also known as CCN2) is an inflammatory mediator, and shows elevated levels in regions of severe injury and inflammatory diseases. CTGF is abundantly expressed in osteoarthritis (OA). However, the relationship between CTGF and IL-6 in OA synovial fibroblasts (OASFs) is mostly unknown. Methodology/Principal Findings OASFs showed significant expression of CTGF, and expression was higher than in normal SFs. OASFs stimulation with CTGF induced concentration-dependent increases in IL-6 expression. CTGF mediated IL-6 production was attenuated by αvβ5 integrin neutralized antibody and apoptosis signal-regulating kinase 1 (ASK1) shRNA. Pretreatment with p38 inhibitor (SB203580), JNK inhibitor (SP600125), AP-1 inhibitors (Curcumin and Tanshinone IIA), and NF-κB inhibitors (PDTC and TPCK) also inhibited the potentiating action of CTGF. CTGF-mediated increase of NF-κB and AP-1 luciferase activity was inhibited by SB203580 and SP600125 or ASK1 shRNA or p38 and JNK mutant. Conclusions/Significance Our results suggest that CTGF increased IL-6 production in OASFs via the αvβ5 integrin, ASK1, p38/JNK, and AP-1/NF-κB signaling pathways.

  • CTGF enhances migration and mmp 13 up regulation via αvβ3 integrin fak erk and nf κb dependent pathway in human chondrosarcoma cells
    Journal of Cellular Biochemistry, 2009
    Co-Authors: Chunyiu Huang, Hsiente Chen, Yichin Fong, Weihung Yang, Chihhsin Tang
    Abstract:

    : Tumor malignancy is associated with several features such as proliferation ability and frequency of metastasis. Connective tissue growth factor (CTGF), a secreted protein that binds to integrins, modulates the invasive behavior of certain human cancer cells. However, the effect of CTGF on migration activity in human chondrosarcoma cells is mostly unknown. Here we found that CTGF increased the migration and expression of matrix metalloproteinase (MMP)-13 in human chondrosarcoma cells (JJ012 cells). RGD peptide, alphavbeta3 monoclonal antibody (mAb) and MAPK kinase (MEK) inhibitors (PD98059 and U0126) but not RAD peptide inhibited the CTGF-induced increase of the migration and MMP-13 up-regulation of chondrosarcoma cells. CTGF stimulation increased the phosphorylation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). In addition, treatment of JJ012 cells with NF-kappaB inhibitor (PDTC) or IkappaB protease inhibitor (TPCK) inhibited CTGF-induced cell migration and MMP-13 up-regulation. Stimulation of JJ012 cells with CTGF also induced IkappaB kinase alpha/beta (IKK alpha/beta) phosphorylation, IkappaBalpha phosphorylation, p65 Ser(536) phosphorylation, and kappaB-luciferase activity. The CTGF-mediated increases in kappaB-luciferase activities were inhibited by RGD, PD98059, U0126 or FAK, and ERK2 mutant. Taken together, our results indicated that CTGF enhances the migration of chondrosarcoma cells by increasing MMP-13 expression through the alphavbeta3 integrin, FAK, ERK, and NF-kappaB signal transduction pathway.

Steven N Popoff - One of the best experts on this subject based on the ideXlab platform.

  • The role of connective tissue growth factor (CTGF/CCN2) in skeletogenesis.
    Critical Reviews in Eukaryotic Gene Expression, 2020
    Co-Authors: John A. Arnott, Fayez F Safadi, Thomas A Owen, Alex G Lambi, Christina Mundy, Honey Hendesi, Robin A Pixley, Steven N Popoff
    Abstract:

    Connective tissue growth factor (CTGF) is a 38kDa, cysteine rich, extracellular matrix protein composed of four domains or modules. CTGF has been shown to regulate a diverse array of cellular functions and has been implicated in more complex biological processes such as angiogenesis, chondrogenesis, and osteogenesis. A role for CTGF in the development and maintenance of skeletal tissues first came to light in studies demonstrating its expression in cartilage and bone cells which was dramatically increased during skeletal repair or regeneration. The physiological significance of CTGF in skeletogenesis was confirmed in CTGF-null mice, which exhibited multiple skeletal dysmorphisms as a result of impaired growth plate chondrogenesis, angiogenesis, and bone formation/mineralization. Given the emerging importance of CTGF in osteogenesis and chondrogenesis, this review will focus on its expression in skeletal tissues, its effects on osteoblast and chondrocyte differentiation and function, and the skeletal implications of ablation or over-expression of CTGF in knockout or transgenic mouse models, respectively. In addition, this review will examine the role of integrin-mediated signaling and the regulation of CTGF expression as it relates to skeletogenesis. We will emphasize CTGF studies in bone or bone cells, and will identify opportunities for future investigations concerning CTGF and chondrogenesis/osteogenesis.

  • the role of connective tissue growth factor CTGF ccn2 in skeletogenesis
    Critical Reviews in Eukaryotic Gene Expression, 2011
    Co-Authors: John A. Arnott, Fayez F Safadi, Thomas A Owen, Alex G Lambi, Christina Mundy, Honey Hendesi, Robin A Pixley, Steven N Popoff
    Abstract:

    Connective tissue growth factor (CTGF) is a 38kDa, cysteine rich, extracellular matrix protein composed of four domains or modules. CTGF has been shown to regulate a diverse array of cellular functions and has been implicated in more complex biological processes such as angiogenesis, chondrogenesis, and osteogenesis. A role for CTGF in the development and maintenance of skeletal tissues first came to light in studies demonstrating its expression in cartilage and bone cells which was dramatically increased during skeletal repair or regeneration. The physiological significance of CTGF in skeletogenesis was confirmed in CTGF-null mice, which exhibited multiple skeletal dysmorphisms as a result of impaired growth plate chondrogenesis, angiogenesis, and bone formation/mineralization. Given the emerging importance of CTGF in osteogenesis and chondrogenesis, this review will focus on its expression in skeletal tissues, its effects on osteoblast and chondrocyte differentiation and function, and the skeletal implications of ablation or over-expression of CTGF in knockout or transgenic mouse models, respectively. In addition, this review will examine the role of integrin-mediated signaling and the regulation of CTGF expression as it relates to skeletogenesis. We will emphasize CTGF studies in bone or bone cells, and will identify opportunities for future investigations concerning CTGF and chondrogenesis/osteogenesis.

  • connective tissue growth factor CTGF acts as a downstream mediator of tgf β1 to induce mesenchymal cell condensation
    Journal of Cellular Physiology, 2007
    Co-Authors: Jason J Song, Fayez F Safadi, Reem A Kanaan, Thomas A Owen, Rulla Aswad, Mario C Rico, Mary F Barbe, Steven N Popoff
    Abstract:

    Mesenchymal cell (MC) condensation or the aggregation of MCs precedes chondrocyte differentiation and is required for subsequent cartilage formation during endochondral ossification. In this study, we used micromass cultures of C3H10T1/2 cells as an in vitro model system for studying MC condensation and the events important for this process. Transforming growth factor β1 (TGF-β1) served as the initiator of MC condensation in our model system and we were interested in determining whether CTGF functions as a downstream mediator of TGF-β1. CTGF is a matricellular protein that has been found to be expressed in MC condensations and in the perichondrium. Micromass cultures of C3H10T1/2 cells condensed under TGF-β1 stimulation concomitant with dramatic up-regulation of CTGF mRNA and protein levels. CTGF silencing by either CTGF siRNA or CTGF antisense oligonucleotide approaches showed that TGF-β1-induced condensation was CTGF dependent. Furthermore, silencing of CTGF expression resulted in significant reductions in cell proliferation and migration, events that are crucial during MC condensation. In addition, up-regulation of Fibronectin (FN) and suppression of Sox9 expression by TGF-β1 was also found to be mediated by CTGF. Immunofluorescence of developing mouse vertebrae showed that CTGF, TGF-β1 and FN were co-expressed in condensations of MCs, while Sox9 expression was low at this stage. During subsequent chondrogenesis, Sox9 expression was high in chondrocytes while CTGF expression was limited to the perichondrium. Thus, CTGF is an essential downstream mediator of TGF-β1-induced MC condensation through its effects on cell proliferation and migration. CTGF is also involved in up-regulating FN and suppressing Sox9 expression during TGF-β1 induced MC condensation. J. Cell. Physiol. 210: 398–410, 2007. © 2006 Wiley-Liss, Inc.

  • expression of connective tissue growth factor in bone its role in osteoblast proliferation and differentiation in vitro and bone formation in vivo
    Journal of Cellular Physiology, 2003
    Co-Authors: Fayez F Safadi, Jie Xu, Steven L Smock, Reem A Kanaan, Abdulhafez Selim, Paul R Odgren, Sandy C Marks, Thomas A Owen, Steven N Popoff
    Abstract:

    Connective tissue growth factor (CTGF) is a secreted, extracellular matrix-associated signaling protein that regulates diverse cellular functions. In vivo, CTGF is expressed in many tissues with highest levels in the kidney and brain. The purpose of this study was twofold; first, to localize CTGF in normal bone in vivo during growth and repair, and second, to examine CTGF expression and function in primary osteoblast cultures in vitro and test its effect on bone formation in vivo. Northern and Western blot analyses confirmed that CTGF is expressed in normal long bones during the period of growth or modeling. In situ hybridization and immunohistochemical analysis demonstrated intense staining for CTGF mRNA and protein in osteoblasts lining metaphyseal trabeculae. Examination of CTGF expression in the fracture callus demonstrated that it was primarily localized in osteoblasts lining active, osteogenic surfaces. In primary osteoblast cultures, CTGF mRNA levels demonstrated a bimodal pattern of expression, being high during the peak of the proliferative period, abating as the cells became confluent, and increasing to peak levels and remaining high during mineralization. This pattern suggests that CTGF may play a role in osteoblast proliferation and differentiation as previously demonstrated for fibroblasts and chondrocytes. Treatment of primary osteoblast cultures with anti-CTGF neutralizing antibody caused a dose-dependent inhibition of nodule formation and mineralization. Treatment of primary osteoblast cultures with recombinant CTGF (rCTGF) caused an increase in cell proliferation, alkaline phosphatase activity, and calcium deposition, thereby establishing a functional connection between CTGF and osteoblast differentiation. In vivo delivery of rCTGF into the femoral marrow cavity induced osteogenesis that was associated with increased angiogenesis. This study clearly shows that CTGF is important for osteoblast development and function both in vitro and in vivo.

Oscar A Carretero - One of the best experts on this subject based on the ideXlab platform.

  • connecting tubule glomerular feedback antagonizes tubuloglomerular feedback in vivo
    American Journal of Physiology-renal Physiology, 2010
    Co-Authors: Hong Wang, Martin A Dambrosio, Jeffrey L Garvin, Oscar A Carretero
    Abstract:

    In vitro experiments showed that the connecting tubule (CNT) sends a signal that dilates the afferent arteriole (Af-Art) when Na+ reabsorption in the CNT lumen increases. We call this process CNT glomerular feedback (CTGF) to differentiate it from tubuloglomerular feedback (TGF), which is a cross talk between the macula densa (MD) and the Af-Art. In TGF, the MD signals the Af-Art to constrict when NaCl transport by the MD is enhanced by increased luminal NaCl. CTGF is mediated by CNT Na+ transport via epithelial Na+ channels (ENaC). However, we do not know whether CTGF occurs in vivo or whether it opposes the increase in Af-Art resistance caused by TGF. We hypothesized that CTGF occurs in vivo and opposes TGF. To test our hypothesis, we conducted in vivo micropuncture of individual rat nephrons, measuring stop-flow pressure (PSF) as an index of glomerular filtration pressure. To test whether activation of CTGF opposes TGF, we used benzamil to block CNT Na+ transport and thus CTGF. CTGF inhibition with the ENaC blocker benzamil (1 μM) potentiated the decrease in PSF at 40 and 80 nl/min. Next, we tested whether we could augment CTGF by inhibiting NaCl reabsorption in the distal convoluted tubule with hydrochlorothiazide (HCTZ, 1 mM) to enhance NaCl delivery to the CNT. In the presence of HCTZ, benzamil potentiated the decrease in PSF at 20, 40, and 80 nl/min. We concluded that in vivo CTGF occurs and opposes the vasoconstrictor effect of TGF.

  • possible mediators of connecting tubule glomerular feedback
    Hypertension, 2009
    Co-Authors: Martin A Dambrosio, Jeffrey L Garvin, Hong Wang, Oscar A Carretero
    Abstract:

    In the renal cortex, the connecting tubule (CNT) returns to the glomerular hilum and contacts the afferent arteriole (Af-Art). Increasing Na delivery to the CNT dilates the Af-Art by activating epithelial Na channels, a process that we call connecting tubule glomerular feedback (CTGF). However, the mediator(s) of CTGF are unknown. We tested the hypothesis that Na reabsorption by the CNT induces release of arachidonic acid metabolites that diffuse to and dilate the Af-Art. Microdissected rabbit Af-Arts and adherent CNTs were simultaneously microperfused. CTGF was measured as the increase in diameter of norepinephrine-preconstricted Af-Arts in response to switching NaCl concentration in the lumen of the CNT from 10 to 80 mmol/L. Under control conditions, CTGF was repeatable and completely reversed norepinephrine-induced vasoconstriction. In the presence of 5,8,11,14-eicosatetraynoic acid, an inhibitor of arachidonic acid metabolism, CTGF was completely blocked (−0.7±0.3 versus 7.3±0.5 μm), suggesting that arachidonic acid metabolites mediate CTGF. Because both cyclooxygenase-derived prostaglandins and epoxygenase-derived epoxyeicosatrienoic acids are known vasodilatory arachidonic acid metabolites, we tested whether indomethacin or MS-PPOH (a cyclooxygenase and an epoxygenase inhibitor) could block CTGF. Both indomethacin and MS-PPOH partially blocked CTGF (2.3±0.8 versus 6.5±0.5 μm, and 2.9±0.8 versus 6.6±1.1 μm, respectively). When combined, they completely blocked CTGF (−0.4±0.3 versus 6.6±1.1 μm). We confirmed these findings by using the epoxyeicosatrienoic acid antagonist 14,15-EEZE. The combination of indomethacin plus 14,15-EEZE completely abolished CTGF (−0.3±0.2 versus 8.0±1.0 μm). We conclude that increasing Na concentrations in the CNT stimulate release of prostaglandins and epoxyeicosatrienoic acids, which mediate CTGF.

Philip C Trackman - One of the best experts on this subject based on the ideXlab platform.

  • transforming growth factor β1 tgfβ1 stimulates connective tissue growth factor ccn2 CTGF expression in human gingival fibroblasts through a rhoa independent rac1 cdc42 dependent mechanism statins with forskolin block tgfβ1 induced ccn2 CTGF expressio
    Journal of Biological Chemistry, 2008
    Co-Authors: Samuel A Black, Philip C Trackman
    Abstract:

    Abstract Regulation of connective tissue growth factor (CCN2/CTGF) in gingival fibroblasts is unique and may provide therapeutic opportunities to treat oral fibrotic diseases. RhoA was previously implicated in mediating the expression of CCN2/CTGF. We now present evidence that Rho family GTPases Rac1 and Cdc42 are the principal mediators of the transforming growth factor-β1 (TGFβ1)-stimulated expression of CCN2/CTGF in primary human gingival fibroblasts. TGFβ1 does not stimulate RhoA activation in gingival fibroblasts, and the overexpression of dominant-negative RhoA does not reduce CCN2/CTGF expression in response to TGFβ1. In contrast, the overexpression of dominant-negative forms of Cdc42 or Rac1 results in a dramatic reduction of CCN2/CTGF protein levels. Lovastatin and a geranylgeranyltransferase inhibitor reduce the TGFβ1-stimulated levels of CCN2/CTGF protein by ∼75 and 100%, respectively. We previously demonstrated that JNK1 phosphorylation by TGFβ1 is also critical for TGFβ1-induced CCN2/CTGF expression, and forskolin partially reduces levels of phosphorylated JNK1. Inhibition of geranylgeranyltransferase has no effect on levels of JNK phosphorylation in response to TGFβ1 suggesting Rho-GTPases act independently of JNK1. The combination of lovastatin and forskolin results in a greater inhibitory effect than each agent alone and reduces CCN2/CTGF mRNA and protein expression by greater than 90%. This novel combination has additive inhibitory effects on the TGFβ1-stimulated expression of CCN2/CTGF in human gingival fibroblasts through the simultaneous disruption of Rho- and JNK1-mediated pathways, respectively. This combination of available therapeutic compounds may therefore be useful in designing treatment strategies for oral fibrotic conditions in which gingival CCN2/CTGF is elevated.

  • tissue specific mechanisms for ccn2 CTGF persistence in fibrotic gingiva interactions between camp and mapk signaling pathways and prostaglandin e2 ep3 receptor mediated activation of the c jun n terminal kinase
    Journal of Biological Chemistry, 2007
    Co-Authors: Samuel A Black, Amitha H Palamakumbura, Maria Stan, Philip C Trackman
    Abstract:

    Abstract Prostaglandin E2 blocks transforming growth factor TGF β1-induced CCN2/CTGF expression in lung and kidney fibroblasts. PGE2 levels are high in gingival tissues yet CCN2/CTGF expression is elevated in fibrotic gingival overgrowth. Gingival fibroblast expression of CCN2/CTGF in the presence of PGE2 led us to compare the regulation of CCN2/CTGF expression in fibroblasts cultured from different tissues. Data demonstrate that the TGFβ1-induced expression of CCN2/CTGF in human lung and renal mesangial cells is inhibited by 10 nm PGE2, whereas human gingival fibroblasts are resistant. Ten nm PGE2 increases cAMP accumulation in lung but not gingival fibroblasts, which require 1 μm PGE2 to elevate cAMP. Micromolar PGE2 only slightly reduces the TGFβ1-stimulated CCN2/CTGF levels in gingival cells. EP2 prostaglandin receptor activation with butaprost blocks the TGFβ1-stimulated expression of CCN2/CTGF expression in lung, but not gingival, fibroblasts. In lung fibroblasts, inhibition of the TGFβ1-stimulated CCN2/CTGF by PGE2, butaprost, or forskolin is due to p38, ERK, and JNK MAP kinase inhibition that is cAMP-dependent. Inhibition of any two MAPKs completely blocks CCN2/CTGF expression stimulated by TGFβ1. These data mimic the inhibitory effects of 10 nm PGE2 and forskolin that were dependent on PKA activity. In gingival fibroblasts, the sole MAPK mediating the TGFβ1-stimulated CCN2/CTGF expression is JNK. Whereas forskolin reduces TGFβ1-stimulated expression of CCN2/CTGF by 35% and JNK activation in gingival fibroblasts, micromolar PGE2-stimulated JNK in gingival fibroblasts and opposes the inhibitory effects of cAMP on CCN2/CTGF expression. Stimulation of the EP3 receptor with sulprostone results in a robust increase in JNK activation in these cells. Taken together, data identify two mechanisms by which TGFβ1-stimulated CCN2/CTGF levels in human gingival fibroblasts resist down-regulation by PGE2: (i) cAMP cross-talk with MAPK pathways is limited in gingival fibroblasts; (ii) PGE2 activation of the EP3 prostanoid receptor stimulates the activation of JNK.