Insulin-like growth factor binding proteins and IGFBP proteases: A dynamic system regulating the ovarian folliculogenesis

International audienceThe aim of the present article is to update our understanding of the expression of the insulin-like growth factor binding proteins (IGFBPs), IGFBP proteases and their implication in the different processes of ovarian folliculogenesis in mammals. In the studied species, IGFs and several small-molecular weight IGFBPs (in particular IGFBP-2 and IGFBP-4) are considered, respectively, as stimulators and inhibitors of follicular growth and maturation. IGFs play a key role in sensitizing ovarian granulosa cells to FSH action during terminal follicular growth. Concentrations of IGFBP-2 and IGFBP-4 in follicular fluid strongly decrease during follicular growth, leading to an increase in IGF bioavailability. Inversely, atresia is characterized by an increase of IGFBP-2 and IGFBP-4 levels, leading to a decrease in IGF bioavailability. Changes in intrafollicular IGFBPs content are due to variations in mRNA expression and/or proteolytic degradation by the pregnancy-associated plasma protein-A (PAPP-A), and likely participates in the selection of dominant follicles. The identification of PAPP-A2, as an IGFBP-3 and -5 protease, and stanniocalcins (STCs) as inhibitors of PAPP-A activity extends the IGF system. Studies on their implication in folliculogenesis in mammals are still in the early stages

LA PROTEOLYSE DE L'INSULIN-LIKE GROWTH FACTOR BINDING PROTEIN-4 (IGFBP-4) DANS LES FOLLICULES OVARIENS CHEZ LES MAMMIFERES DOMESTIQUES (IDENTIFICATION DE LA PROTEASE, ETUDE DE SA REGULATION, CONSEQUENCES SUR LA MATURATION FOLLICULAIRE)

LES IGFS (INSULIN-LIKE GROWTH FACTORS) JOUENT UN ROLE CRUCIAL DANS LE DEVELOPPEMENT FOLLICULAIRE EN AMPLIFIANT L'ACTION DES HORMONES GONADOTROPES HYPOPHYSAIRES, FSH ET LH. LEUR ACTION STIMULANTE EST MODULEE PAR LA PRESENCE DE PROTEINES DE LIAISON, LES IGF-BINDING PROTEINS (IGFBPS), DANS LE LIQUIDE FOLLICULAIRE. CHEZ LA BREBIS, LA VACHE, LA TRUIE, LA JUMENT ET LA FEMME, LA CROISSANCE ET L'ATRESIE FOLLICULAIRE SONT ASSOCIEES RESPECTIVEMENT A UNE DIMINUTION ET A UNE AUGMENTATION DES TENEURS EN IGFBP-4 DANS LE LIQUIDE FOLLICULAIRE. CES VARIATIONS SONT ESSENTIELLEMENT DUES A DES VARIATIONS DE L'ACTIVITE PROTEOLYTIQUE CAPABLE DE LA DEGRADER. LES OBJECTIFS DE NOTRE TRAVAIL ONT ETE 1) D'IDENTIFIER LA PROTEASE RESPONSABLE DE LA DEGRADATION PROTEOLYTIQUE DE L'IGFBP-4 DANS LES FOLLICULES PREOVULATOIRES ; 2) DE DETERMINER LES MECANISMES LOCAUX DE REGULATION DE L'ACTIVITE PROTEOLYTIQUE ; 3) DE RECHERCHER LE ROLE BIOLOGIQUE DES FRAGMENTS DE PROTEOLYSE DE L'IGFBP-4 DANS LA MATURATION FOLLICULAIRE. NOUS AVONS MONTRE QUE LA PREGNANCY-ASSOCIATED PLASMA PROTEIN-A (PAPP-A) EST LA METALLOPROTEASE IMPLIQUEE DANS LA DEGRADATION DE L'IGFBP-4 DANS LES FOLLICULES PREOVULATOIRES DE BREBIS, DE VACHE, DE TRUIE ET DE JUMENT. CHEZ LA TRUIE ET LA VACHE, L'EXPRESSION DES ARNMS DE LA PAPP-A DANS LES CELLULES DE GRANULOSA EST ETROITEMENT CORRELEE A CELLE DE L'AROMATASE ET DES RECEPTEURS A LH. ELLE EST MAXIMALE DANS LES FOLLICULES PREOVULATOIRES ET FAIBLE, MAIS NON NULLE, DANS LES FOLLICULES ATRETIQUES ET DANS LES FOLLICULES IMMATURES. AU NIVEAU POST-TRADUCTIONNEL, L'IGF-I POTENTIALISE LA PROTEOLYSE DE L'IGFBP-4 PAR LA PAPP-A. A L'INVERSE, LES IGFBP-2 ET -3 AINSI QUE DES PEPTIDES DE LIAISON A L'HEPARINE DERIVES DU DOMAINE CARBOXY-TERMINAL DE L'IGFBP-3 OU -5 OU DU CTGF (CONNECTIVE TISSUE GROWTH FACTOR), DU HIP (HEPARAN/HEPARIN INTERACTING PEPTIDE) ET DE LA VITRONECTINE INHIBENT LA DEGRADATION DE L'IGFBP-4 PAR LE LIQUIDE FOLLICULAIRE DE FOLLICULES PREOVULATOIRES. CES EFFETS PASSENT PAR UNE REDUCTION DE LA BIODISPONIBILITE INTRAFOLLICULAIRE DES IGFS ET/OU PAR UNE INTERACTION DIRECTE AVEC LA PAPP-A PAR L'INTERMEDIAIRE DU DOMAINE DE LIAISON A L'HEPARINE. ENFIN, IN VITRO, DES RESULTATS PRELIMINAIRES MONTRENT UN EFFET POTENTIALISATEUR DES FRAGMENTS CARBOXY-TERMINAUX DE L'IGFBP-4 SUR LA PRODUCTION DE PROGESTERONE PAR LES CELLULES DE GRANULOSA OVINES CULTIVEES EN PRESENCE D'IGF-I, SUGGERANT QUE LA DEGRADATION PROTEOLYTIQUE DE L'IGFBP-4 ABOUTIT A UNE AMPLIFICATION DE L'ACTION DE L'IGF-I EN PARTICIPANT A L'AUGMENTATION DE SA BIODISPONIBILITE ET EN POTENTIALISANT SON ACTION AU NIVEAU CELLULAIRE.PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Identification of BMP9 and BMP10 as functional activators of the orphan activin receptor-like kinase 1 (ALK1) in endothelial cells.

International audienceALK1 is an endothelial-specific type I receptor of the TGFbeta receptor family whose heterozygous mutations cause hereditary hemorrhagic telangiectasia type 2. Although TGFbeta1 and TGFbeta3 have been shown to bind ALK1 under specific experimental conditions, they may not represent the physiological ligands for this receptor. In the present study, we demonstrate that BMP9 induces the phosphorylation of Smad1/5/8 in microvascular endothelial cells, and this phosphorylation lasts over a period of 24 hours. BMP9 also activates the ID1 promoter-derived BMP response element (BRE) in a dose-dependent manner (EC50 = 45 +/- 27 pg/mL), and this activation is abolished by silencing ALK1 expression or addition of ALK1 extracellular domain. Overexpression of endoglin increases the BMP9 response, whereas silencing of both BMPRII and ActRIIA expressions completely abolishes it. BMP10, which is structurally close to BMP9, is also a potent ALK1 ligand. Finally, we demonstrate that BMP9 and BMP10 potently inhibit endothelial cell migration and growth, and stimulate endothelial expression of a panel of genes that was previously reported to be activated by the constitutively active form of ALK1. Taken together, our results suggest that BMP9 and BMP10 are two specific ALK1 ligands that may physiologically trigger the effects of ALK1 on angiogenesis

∆2-Troglitazone and 2-Deoxyglucose inhibit breast cancer cell proliferation: a consequence of the alteration of the cancer cell metabolism?

Présentation PosterNational audienceBackground: Resistance to conventional therapies and the absence of targeted therapy for triple negative mammary tumors are strong arguments for the search for new therapeutic agents. In cancer cells, the dependency on glycolysis for energy generation provides a biochemical basis to preferentially kill the malignant cells by inhibiting glycolysis. Thiazolidinediones display antiproliferative effects in vitro and in vivo which could be the result of mechanisms targeting cell metabolism. Our objective is to characterize the modifications of breast cancer cell metabolism after ∆2-Troglitazone (∆2T) exposure and to compare it with the effects of 2-deoxyglucose (2-DG), a well known inhibitor of glucose metabolism.Methods: The triple-negative breast cancer cell line MDA-MB231 cells were exposed to D2T and 2-DG. Cell numbers were assessed by crystal violet staining assay. Cell proliferation was determined by BrDU incorporation assay. Gene expression was analysed by RT-PCR. Protein expression was analyzed by immunoblotting and immunolocalisation.Results: 48h cell treatment with increasing concentrations of D2T (0-100µM) and 2-DG (0-10mM) inhibited cell proliferation in a dose-dependent manner. Nevertheless, cell viability was not as much affected suggesting that D2T and 2-DG mainly slowed down cell cycle. Concomitantly, both compounds induced endoplasmic reticulum stress. In contrast to 2-DG, the effect of D2T was not reversed by addition of an excess of glucose. At the metabolic level, NAD+/NADH ratio was increased after a 24h treatment with D2T or 2-DG. Under the same conditions, the mRNA levels of two key glycolysis enzymes, hexokinase and phosphofructokinase, were reduced.Conclusion: Our studies show that ∆2T and 2-DG induce changes in triple-negative breast cancer cell metabolism. The importance of the metabolic deregulation in the antitumoral effect of ∆2T has now to be demonstrated

Delta2-Troglitazone alters energetic metabolism in triple-negative breast cancer cells: a mechanism to sensitize cancer cells to chemotherapy?

National audienc

Up date on IGFBP-4: regulation of IGFBP-4 levels and functions, in vitro and in vivo.

Of the six known high affinity insulin-like growth factor binding-proteins (IGFBPs), IGFBP-4 appears to be unique in that it is the only IGFBP that functions mostly like a traditional binding protein. In this regard, none of the IGF independent effects that have been ascribed for other IGFBPs have been described for IGFBP-4. However, recent in vitro and in vivo studies, in particular the recent identification of pregnancy-associated plasma protein-A as a major IGFBP-4 protease, are consistent with the idea that IGFBP-4 is an extremely important component of IGF system in several tissues including gonads and bone. In this review, we have provided an update on IGFBP-4 research and we have summarized our current understanding of the regulation of levels and actions of IGFBP-4 and proteolytic fragments both in vitro and in vivo

Delta-2-Troglitazone targets mitochondria in triple-negative breast cancer cells: a metabolic change contributing to sensitization of cancer cells to chemotherapy?

Présentation PosterNational audienceBackground: Resistance to conventional therapies for triple-negative mammary tumors are strong arguments for the search for new therapeutic agents. A strategy is to develop drugs targeting energetic metabolism to sensitize cancer cells to chemotherapy. Thiazolidinediones display antiproliferative effects which could be the result of mechanisms altering cell metabolism. Our objectives are to characterize the modifications of the triple-negative breast cancer cell line MDA-MB231 metabolism after Delta-2-Troglitazone (D2T) exposure and to define whether D2T could potentiate the action of chemotherapeutic agents.Methods: Cell numbers were assessed by crystal violet staining. NAD+ and NADH concentrations were determined by chemiluminescence. Lactate and glucose concentrations were measured with an YSI 2950 Biochemistry Analyzer. Mitochondrial activity was assessed by oxygraphy. Results: 48h cell treatment with D2T (75 µM) inhibited cell proliferation. At the metabolic level, NAD+/NADH ratio was increased after a 24h treatment, suggesting that glycolysis and/or mitochondrial respiration could be altered. Oxygen consumption was diminished after a 24h exposure to D2T, associated with a decreased mitochondrial efficiency and a mitochondrial decoupling. At the glycolytic level, lactate production and glucose consumption were increased in D2T-treated cells. Finally, D2T at a lower dose (15 µM) potentiated the effects of 2-DG (2-Deoxyglucose, a glycolytic inhibitor) and doxorubicin on cell viability. Conclusion: D2T induces metabolic changes in cancer cells MDA-MB231. D2T targets mitochondrial activity likely leading to the stimulation of glycolysis. Besides, a low dose of D2T potentiates the action of 2-DG and doxorubicin on cell viability. The impact of the D2T/doxorubicin combination on proliferation and apoptosis has to be characterized. Overall, the link between the metabolic alteration observed with D2T and its antiproliferative effect has to be demonstrated

Energy restriction mimetic agents to target cancer cells: Comparison between 2-deoxyglucose and thiazolidinediones.

International audienceThe use of energy restriction mimetic agents (ERMAs) to selectively target cancer cells addicted to glycolysis could be a promising therapeutic approach. Thiazolidinediones (TZDs) are synthetic agonists of the nuclear receptor peroxisome proliferator-activated receptor (PPAR)γ that were developed to treat type II diabetes. These compounds also display anticancer effects which appear mainly to be independent of their PPARγ agonist activity but the molecular mechanisms involved in the anticancer action are not yet well understood. Results obtained on ciglitazone derivatives, mainly in prostate cancer cell models, suggest that these compounds could act as ERMAs. In the present paper, we introduce how compounds like 2-deoxyglucose target the Warburg effect and then we discuss the possibility that the PPARγ-independent effects of various TZD could result from their action as ERMAs