J Ripoche

University of Bordeaux, Burdeos, Aquitaine, France

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Publications (76)280.83 Total impact

  • Journal des Maladies Vasculaires 03/2013; 38(2):113. · 0.24 Impact Factor
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    ABSTRACT: Shear stress is one of mechanical constraints which are exerted by blood flow on endothelial cells (ECs). To adapt to shear stress, ECs align in the direction of flow through adherens junction (AJ) remodeling. However, mechanisms regulating ECs alignment under shear stress are poorly understood. The scaffold protein IQ domain GTPase activating protein 1 (IQGAP1) is a scaffold protein which couples cell signaling to the actin and microtubule cytoskeletons and is involved in cell migration and adhesion. IQGAP1 also plays a role in AJ organization in epithelial cells. In this study, we investigated the potential IQGAP1 involvement in the endothelial cells alignment under shear stress. Progenitor-derived endothelial cells (PDECs), transfected (or not) with IQGAP1 small interfering RNA, were exposed to a laminar shear stress (1.2 N/m(2)) and AJ proteins (VE-cadherin and β-catenin) and IQGAP1 were labeled by immunofluorescence. We show that IQGAP1 is essential for ECs alignment under shear stress. We studied the role of IQGAP1 in AJs remodeling of PDECs exposed to shear stress by studying cell localization and IQGAP1 interactions with VE-cadherin and β-catenin by immunofluorescence and Proximity Ligation Assays. In static conditions, IQGAP1 interacts with VE-cadherin but not with β-catenin at the cell membrane. Under shear stress, IQGAP1 lost its interaction from VE-cadherin to β-catenin. This "switch" was concomitant with the loss of β-catenin/VE-cadherin interaction at the cell membrane. This work shows that IQGAP1 is essential to ECs alignment under shear stress and that AJ remodeling represents one of the mechanisms involved. These results provide a new approach to understand ECs alignment under to shear stress.
    PLoS ONE 01/2013; 8(11):e79919. · 3.73 Impact Factor
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    ABSTRACT: INTRODUCTION: Renal resistive index (RI), determined by Doppler ultrasonography, directly reveals and quantifies modifications in renal vascular resistance. The aim of this study was to evaluate if mean arterial pressure (MAP) is determinant of renal RI in septic, critically ill patients suffering or not from acute kidney injury (AKI). METHODS: This prospective observational study included 96 patients. AKI was defined according to RIFLE criteria and transient or persistent AKI according to renal recovery within 3 days. RESULTS: Median renal RI was 0.72 (0.68-0.75) in patients without AKI and 0.76 (0.72-0.80) in patients with AKI (P=0.001). RI was 0.75 (0.72-0.79) in transient AKI and 0.77 (0.70-0.80) in persistent AKI (P=0.84). RI did not differ in patients given norepinephrine infusion and was not correlated with norepinephrine dose. RI was correlated with MAP (rho= -0.47; P=0.002), PaO2/FiO2 ratio (rho= -0.33; P=0.04) and age (rho=0.35; P=0.015) only in patients without AKI. CONCLUSIONS: A poor correlation between renal RI and MAP, age, or PaO2/FiO2 ratio was found in septic and critically ill patients without AKI compared to patients with AKI. These findings suggest that determinants of RI are multiple. Renal circulatory response to sepsis estimated by Doppler ultrasonography cannot reliably be predicted simply from changes in systemic hemodynamic. As many factors influence its value, the interest in a single RI measurement at ICU admission to determine optimal MAP remains uncertain.
    Critical care (London, England) 09/2012; 16(5):R165. · 4.72 Impact Factor
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    02/2012; , ISBN: 978-953-307-869-4
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    ABSTRACT: IQGAP1 is a scaffold protein that interacts with proteins of the cytoskeleton and the intercellular adhesion complex. In podocytes, IQGAP1 is associated with nephrin in the glomerular slit diaphragm (SD) complex, but its role remains ill-defined. In this work, we investigated the interaction of IQGAP1 with the cytoskeleton and SD proteins in podocytes in culture, and its role in podocyte migration and permeability. Expression, localization, and interactions between IQGAP1 and SD or cytoskeletal proteins were determined in cultured human podocytes by Western blot (WB), immunocytolocalization (IC), immunoprecipitation (IP), and In situ Proximity Ligation assay (IsPL). Involvement of IQGAP1 in migration and permeability was also assessed. IQGAP1 expression in normal kidney biopsies was studied by immunohistochemistry. IQGAP1 expression by podocytes increased during their in vitro differentiation. IC, IP, and IsPL experiments showed colocalizations and/or interactions between IQGAP1 and SD proteins (nephrin, MAGI-1, CD2AP, NCK 1/2, podocin), podocalyxin, and cytoskeletal proteins (α-actinin-4). IQGAP1 silencing decreased podocyte migration and increased the permeability of a podocyte layer. Immunohistochemistry on normal human kidney confirmed IQGAP1 expression in podocytes and distal tubular epithelial cells and also showed an expression in glomerular parietal epithelial cells. In summary, our results suggest that IQGAP1, through its interaction with components of SD and cytoskeletal proteins, is involved in podocyte barrier properties.
    PLoS ONE 01/2012; 7(5):e37695. · 3.73 Impact Factor
  • J Ripoche
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    ABSTRACT: An expansion of knowledge from basic and clinical research has highlighted the critical role of platelets in inflammation and tissue repair in addition to their established contribution to hemostasis. Activated platelets are a rich source of mediators participating to inflammation and tissue regeneration. Platelet-derived microparticles recapitulate essential platelet functions and their contribution to the pathogenesis of inflammatory diseases has been emphasized. Recent findings suggest that platelets are both friends and foes for the liver. Platelets are essential to liver regeneration, platelet-derived serotonin being critical. However platelets can also exacerbate liver damage, as in immune-mediated injury. The dual role of platelets has recently been exemplified in animal models of liver fibrosis. Platelets release profibrogenic mediators, such as CXC Chemokine Ligand 4, that is instrumental in the progression of liver fibrosis. On the other hand, thrombocytopenia aggravates liver fibrosis, an outcome linked to the downregulation of hepatic stellate cell collagen production by platelet derived hepatocyte growth factor. CD154, a key molecule in inflammation, is expressed by platelets and is a pathogenic mediator in inflammatory bowel disease. Here, we summarize some of the mechanisms linking platelets with inflammation and comment few recent articles indicating why platelets may prove to be important pathogenic mediators in liver and gastrointestinal diseases.
    Gastroentérologie Clinique et Biologique 05/2011; 35(5):353-7. · 0.80 Impact Factor
  • Nephrologie & Therapeutique - NEPHROL THER. 01/2011; 7(5):361-362.
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    ABSTRACT: Elastic fibers are composed of microfibrils containing fibrillin-1 and an elastic component, elastin. Microfibrils may not be associated with elastin. In the adult liver, fibrillin-1 and elastin are coexpressed within the stroma and portal tracts vessel walls. Fibrillin-1 is expressed alone around the bile ducts and within the Disse space. There is little work that has studied the elastic fiber organization during the fœtal liver development. Here, we studied the expression of fibrillin-1 and elastin by immunohistochemistry on 20 cases of fœtal liver. During the development of the portal tract, the two components are coexpressed on interstitial elastic fibers and within vessel walls. Fibrillin-1 is expressed alone around the bile structures during their maturation. Unlike adult liver, fibrillin-1 is expressed on thin and very irregular microfibrils within the Disse space. Our study shows that the elastic matrix development in the portal tract follows the development of the different structures, notably biliary structures. In the Disse space, microfibrils are not continuous. Their maturation may be in relation with the change of the hepatic blood flow after birth.
    Morphologie 09/2010; 94(307):87-92.
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    ABSTRACT: Inflammation and lipid metabolism pathways are linked, and deregulation of this interface may be critical in hepatic steatosis. The importance of the dialog between inflammatory signaling pathways and the unfolded protein response (UPR) in metabolism has been underlined. Herein, we studied the role of CD154, a key mediator of inflammation, in hepatic steatosis. To this end, Balb/c mice, wild-type or deficient in CD154 (CD154KO), were fed a diet rich in olive oil. In vitro, the effect of CD154 was studied on primary hepatocyte cultures and hepatocyte-derived cell lines. Results showed that CD154KO mice fed a diet rich in olive oil developed hepatic steatosis associated with reduced apolipoprotein B100 (apoB100) expression and decreased secretion of very low-density lipoproteins. This phenotype correlated with an altered UPR as assessed by reduced X-Box binding protein-1 (XBP1) messenger RNA (mRNA) splicing and reduced phosphorylation of eukaryotic initiation factor 2α. Altered UPR signaling in livers of CD154KO mice was confirmed in tunicamycin (TM) challenge experiments. Treatment of primary hepatocyte cultures and hepatocyte-derived cell lines with soluble CD154 increased XBP1 mRNA splicing in cells subjected to either oleic acid (OA) or TM treatment. Moreover, CD154 reduced the inhibition of apoB100 secretion by HepG2 cells grown in the presence of high concentrations of OA, an effect suppressed by XBP1 mRNA silencing and in HepG2 cells expressing a dominant negative form of inositol requiring ER-to-nucleus signaling protein-1. The control of the UPR by CD154 may represent one of the mechanisms involved in the pathophysiology of hepatic steatosis. Conclusion: Our study identifies CD154 as a new mediator of hepatic steatosis.
    Hepatology 08/2010; 52(6):1968-79. · 12.00 Impact Factor
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    British Journal of Haematology 01/2010; 149(2):302 - 306. · 4.94 Impact Factor
  • Journal Des Maladies Vasculaires - J MAL VASCUL. 01/2010; 35(2):111-112.
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    ABSTRACT: Altered angiogenesis is a characteristic feature in SSc and remains ill-understood. VEGF is believed to play a central role. Serum VEGF is elevated in SSc patients but questions remain concerning the source of circulating VEGF. Here we investigated platelet activation and the role of platelets as a source of VEGF and other angiogenic mediators in this disease. A cohort of 40 patients with SSc was included. Age- and sex-matched healthy subjects and subjects presenting a primary RP were included as controls. Platelets were isolated, activated with thrombin and the secretion of VEGF, platelet derived growth factor, homodimeric form BB (PDGF-BB), TGF-beta1 and angiopoietins-1 and -2 measured. Plasma concentrations of these mediators and the functionality of platelet-derived VEGF were also studied. Platelet activation was assayed by measuring plasma beta-thromboglobulin and expression of P-selectin on platelets. The effect of iloprost on VEGF secretion by platelets was studied. Platelets from SSc patients, in contrast to controls, secreted large amounts of VEGF when activated, but not PDGF-BB, TGF-beta1 or angiopoietins. Increased expression of membrane P-selectin confirmed platelet activation in the patients. Iloprost inhibited VEGF secretion by platelets both in vivo and in vitro, through inhibition of platelet activation. Platelets transport high levels of VEGF in SSc. They may contribute to circulating VEGF because of ongoing activation in the course of the disease. If activated at the contact of injured endothelium, platelets may be important in the altered angiogenesis associated with the disease through the secretion of high levels of VEGF.
    Rheumatology (Oxford, England) 07/2009; 48(9):1036-44. · 4.24 Impact Factor
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    ABSTRACT: Expression of tissue inhibitors of matrix metalloproteinases (TIMPs) is one way that activated platelets intervene in tissue remodeling and angiogenesis. Our study was designed to investigate their synthesis in megakaryocytes (MKs) and their storage in platelets. TIMP expression in MKs derived from blood CD34(+) progenitor cells of normal donors and a megakaryocytic cell line (CHRF-288-11) grown in serum-free conditions and platelets from normal donors or two patients with gray platelet syndrome was studied by immunofluorescence labeling, reverse transcription-polymerase chain reaction, and western blotting. Biosynthesis of TIMPs 1-4 in MKs was indicated by presence of their messenger RNAs as shown by polymerase chain reaction and of their proteins. Immunofluorescence labeling suggested a primarily granular localization of TIMPs in MKs and platelets. But when colocalization with von Willebrand factor, fibrinogen, P-selectin, and other alpha-granule proteins was assessed in platelets by confocal microscopy, TIMP-1, -2, and -4 were localized as distinct fluorescent patches apart from the established alpha-granule markers and largely independent of platelet metalloproteinases. TIMP-3 differed for it also had an alpha-granule location. Western blotting confirmed the presence of TIMPs 1-4 in platelets and thrombin activation resulted in their extensive release to the medium. Platelets from two patients with gray platelet syndrome, congenitally deficient in alpha-granules, showed sparse labeling of von Willebrand factor and fibrinogen confined to vestigial alpha-granules; however, localization of the TIMPs was unchanged. TIMPs are synthesized and organized in MKs and platelets independently of other secreted proteins present in alpha-granule pools.
    Experimental hematology 05/2009; 37(7):849-56. · 3.11 Impact Factor
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    ABSTRACT: In adult liver, the mesenchymal cells, portal fibroblasts and vascular smooth muscle cells can transdifferentiate into myofibroblasts, and are involved in portal fibrosis. Differential expression of markers, such as alpha-smooth muscle actin (ASMA), h-caldesmon and cellular retinol-binding protein-1 allows their phenotypic discrimination. The aim of our study was to explore the phenotypic evolution of the mesenchymal cells during fetal development in normal liver and in liver with portal fibrosis secondary to ductal plate malformation in a series of Meckel-Gruber syndrome, autosomal recessive polycystic kidney disease and Ivemark's syndrome. At the early steps of the portal tract maturation, portal mesenchymal cells expressed only ASMA. During the maturation process, these cells were found condensed around the biliary and vascular structures. At the end of maturation process, only cells around vessels expressed ASMA and cells of the artery tunica media also expressed h-caldesmon. In contrast, ASMA positive cells persisted around the abnormal biliary ducts in fibrous livers. As in adult liver, there is a phenotypic heterogeneity of the mesenchymal cells during fetal liver development. During portal tract maturation, myofibroblastic cells disappear in normal development but persist in fibrosis following ductal plate malformation.
    Comparative Hepatology 02/2009; 8:5. · 1.88 Impact Factor
  • Gastroenterologie Clinique Et Biologique - GASTROEN CLIN BIOL. 01/2009; 33(3).
  • Revue De Medecine Interne - REV MED INTERNE. 01/2008; 29.
  • Journal Des Maladies Vasculaires - J MAL VASCUL. 01/2008; 33.
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    ABSTRACT: Constitutive secretion of complement C3 and factor B by the endothelial cell (EC) is lowered by therapeutic concentrations of glucocorticoids such as hydrocortisone or dexamethasone, whereas regulatory protein factor H production is increased by these hormones. In contrast, the pro-inflammatory cytokine IL-1α has a stimulatory effect on C3 and factor B secretion by the endothelium and an inhibitory effect on factor H secretion. In this study, we examined the combined effect of IL-1α and glucocorticoids on C3 and factor B expression by the endothelial cell. When dexamethasone or hydrocortisone were added to IL-1α, significant potentialization of IL-1α-induced stimulation of C3 and factor B production was observed, occurring at various concentrations of either stimuli. Dose-response experiments indicate that, in vitro, optimal concentrations are in the range of 10−7 to 10−5m for dexamethasone and 50–200 U for IL-1α. In contrast, dexamethasone counteracts, in an additive way, the inhibitory effect of IL-1α on regulatory complement protein factor H production by EC. Such a potentialization between glucocorticoids and IL-1α was not observed for another marker of endothelial activation, IL-1α-induced stimulation of coagulation tissue factor expression. The association of glucocorticoids and IL-1α therefore appears to be a specific and major stimulus for the secretion of complement C3 and factor B, two acute-phase proteins, by the endothelium. As a result of the in vitro endothelium stimulation by glucocorticoids and IL-1α, C3a is generated in the vicinity of the endothelial cell. This study further suggests that complement activation, with its deleterious consequences, may result from the stimulation of endothelium in situations where high levels of IL-1α and endogenous glucocorticoids coexist, such as in septic shock.
    Clinical & Experimental Immunology 01/2008; 101(1):142-149. · 3.41 Impact Factor
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    ABSTRACT: In response to glomerular injury, mesangial cells are activated into myofibroblasts, which contribute to the physiopathology of glomerulosclerosis. We have previously shown that chronic treatment of cultured human mesangial cells with mycophenolic acid (MPA), a specific inhibitor of guanosine nucleotide synthesis, prevents their activation and alters cytoskeleton protein expression and associated functions, such as contractility and migratory capacity. The aim of the present study was to explore the mechanisms underlying MPA-induced mesangial cytoskeleton alterations. We therein show that coincubation with guanosine (100 microM) compensates for the effects of MPA on mesangial cell proliferation and migration, and prevents MPA-induced overexpression of alpha-smooth muscle actin (SMA) and basic calponin (b-calp), indicating that guanylates are involved in mesangial responses to MPA. MPA decreased the GTP-bound (active) form of both RhoA, Rac1 and Cdc42, and specifically altered the expression level of Rac1. Pharmacological inhibition of RhoA activity reduced expression of both SMA and calponin, whereas overexpression of a dominant-negative form of Rac1 increased SMA expression. Conversely, overexpression of constitutively active Rac1 resulted in SMA and b-calp down-regulation, and fully prevented their stimulation by MPA, indicating that Rac inactivation is responsible for MPA effects on mesangial cytoskeletal expression. These results show that in human mesangial cells, RhoA and Rac1 exert opposite effects on the expression of two major cytoskeletal proteins: SMA and basic calponin. Moreover, these data highlight for the first time an integrated mechanism whereby MPA regulates mesangial phenotype, which is mediated by loss of Rac activity.
    Biochemical Pharmacology 06/2007; 73(9):1491-8. · 4.58 Impact Factor
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    ABSTRACT: The ARE (AU-rich element) is a post-transcriptional element controlling both mRNA turnover and translation initiation by primarily inducing poly(A) tail shortening. The mechanisms by which the ARE-associated proteins induce deadenylation are still obscure. One possibility among others would be that an ARE-ARE-BP (ARE-binding protein) complex intervenes in the PABP [poly(A)-binding protein]-poly(A) tail association and facilitates poly(A) tail accessibility to deadenylases. Here, we show by several experimental approaches that AUF1 (AU-rich element RNA-binding protein 1)/hnRNP (heterogeneous nuclear ribonucleoprotein) D, an mRNA-destabilizing ARE-BP, can bind poly(A) sequence in vitro. First, endogenous AUF1 proteins from HeLa cells specifically bound poly(A), independently of PABP. Secondly, using polyadenylated RNA probes, we showed that (i) the four recombinant AUF1 isoforms bind poly(A) as efficiently as PABP, (ii) the AUF1 binding to poly(A) does not change when the polyadenylated probe contains the GM-CSF (granulocyte/macrophage-colony stimulating factor) ARE, suggesting that, in vitro, the AUF1-poly(A) association was independent of the ARE sequence itself. In vitro, the binding of AUF1 isoforms to poly(A) displayed oligomeric and co-operative properties and AUF1 efficiently displaced PABP from the poly(A). Finally, the AUF1 molar concentration in HeLa cytoplasm was only 2-fold lower than that of PABP, whereas in the nucleus, its molar concentration was similar to that of PABP. These in vitro results suggest that, in vivo, AUF1 could compete with PABP for the binding to poly(A). Altogether, our results may suggest a role for AUF1 in controlling PABP-poly(A) tail association.
    Biochemical Journal 01/2007; 400(2):337-47. · 4.65 Impact Factor

Publication Stats

1k Citations
280.83 Total Impact Points

Institutions

  • 1995–2012
    • University of Bordeaux
      Burdeos, Aquitaine, France
  • 1996–2011
    • Université Victor Segalen Bordeaux 2
      Burdeos, Aquitaine, France
  • 1995–2008
    • Centre Hospitalier Universitaire Rouen
      Rouen, Upper Normandy, France
  • 2002–2005
    • Centre Hospitalier Universitaire de Bordeaux
      Burdeos, Aquitaine, France
  • 1988–1993
    • Unité Inserm U1077
      Caen, Lower Normandy, France
  • 1986–1988
    • University of Oxford
      • Department of Biochemistry
      Oxford, ENG, United Kingdom