Publications by authors named "Sandra Grès"

33 Publications

Shear Stress-Induced Alteration of Epithelial Organization in Human Renal Tubular Cells.

PLoS One 2015 6;10(7):e0131416. Epub 2015 Jul 6.

Institut National de la Santé et de la Recherche Médicale (INSERM), U1048, Toulouse, France; Université Toulouse III Paul Sabatier, Institute of Metabolic and Cardiovascular Diseases - I2MC, Toulouse, France.

Tubular epithelial cells in the kidney are continuously exposed to urinary fluid shear stress (FSS) generated by urine movement and recent in vitro studies suggest that changes of FSS could contribute to kidney injury. However it is unclear whether FSS alters the epithelial characteristics of the renal tubule. Here, we evaluated in vitro and in vivo the influence of FSS on epithelial characteristics of renal proximal tubular cells taking the organization of junctional complexes and the presence of the primary cilium as markers of epithelial phenotype. Human tubular cells (HK-2) were subjected to FSS (0.5 Pa) for 48 h. Control cells were maintained under static conditions. Markers of tight junctions (Claudin-2, ZO-1), Par polarity complex (Pard6), adherens junctions (E-Cadherin, β-Catenin) and the primary cilium (α-acetylated Tubulin) were analysed by quantitative PCR, Western blot or immunocytochemistry. In response to FSS, Claudin-2 disappeared and ZO-1 displayed punctuated and discontinuous staining in the plasma membrane. Expression of Pard6 was also decreased. Moreover, E-Cadherin abundance was decreased, while its major repressors Snail1 and Snail2 were overexpressed, and β-Catenin staining was disrupted along the cell periphery. Finally, FSS subjected-cells exhibited disappeared primary cilium. Results were confirmed in vivo in a uninephrectomy (8 months) mouse model where increased FSS induced by adaptive hyperfiltration in remnant kidney was accompanied by both decreased epithelial gene expression including ZO-1, E-cadherin and β-Catenin and disappearance of tubular cilia. In conclusion, these results show that proximal tubular cells lose an important number of their epithelial characteristics after long term exposure to FSS both in vitro and in vivo. Thus, the changes in urinary FSS associated with nephropathies should be considered as potential insults for tubular cells leading to disorganization of the tubular epithelium.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131416PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4493045PMC
April 2016

Glitazones inhibit human monoamine oxidase but their anti-inflammatory actions are not mediated by VAP-1/semicarbazide-sensitive amine oxidase inhibition.

J Physiol Biochem 2015 Sep 9;71(3):487-96. Epub 2015 Jan 9.

Institut des Maladies Métaboliques et Cardiovasculaires, Institut National de la Santé et de la Recherche Médicale (INSERM U1048), Toulouse, France,

Glitazones are peroxisome proliferator-activated receptor gamma (PPARγ) agonists widely used as antidiabetic drugs also known as thiazolidinediones. Most of them exert other effects such as anti-inflammatory actions via mechanisms supposed to be independent from PPARγ activation (e.g., decreased plasma monocyte chemoattractant protein-1 (MCP-1) levels). Recently, pioglitazone has been shown to inhibit the B form of monoamine oxidase (MAO) in mouse, while rosiglitazone and troglitazone were described as non-covalent inhibitors of both human MAO A and MAO B. Since molecules interacting with MAO might also inhibit semicarbazide-sensitive amine oxidase (SSAO), known as vascular adhesion protein-1 (VAP-1), and since VAP-1/SSAO inhibitors exhibit anti-inflammatory activity, our aim was to elucidate whether VAP-1/SSAO inhibition could be a mechanism involved in the anti-inflammatory behaviour of glitazones. To this aim, MAO and SSAO activities were measured in human subcutaneous adipose tissue biopsies obtained from overweight women undergoing plastic surgery. The production of hydrogen peroxide, an end-product of amine oxidase activity, was determined in tissue homogenates using a fluorometric method. The oxidation of 1 mM tyramine was inhibited by pargyline and almost resistant to semicarbazide, therefore predominantly MAO-dependent. Rosiglitazone was more potent than pioglitazone in inhibiting tyramine oxidation. By contrast, benzylamine oxidation was only abolished by semicarbazide: hence SSAO-mediated. Pioglitazone hampered SSAO activity only when tested at 1 mM while rosiglitazone was inefficient. However, rosiglitazone exhibited anti-inflammatory activity in human adipocytes by limiting MCP-1 expression. Our observations rule out any involvement of VAP-1/SSAO inhibition and subsequent limitation of leukocyte extravasation in the anti-inflammatory action of glitazones.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s13105-014-0379-3DOI Listing
September 2015

Autotaxin downregulates LPS-induced microglia activation and pro-inflammatory cytokines production.

J Cell Biochem 2014 Dec;115(12):2123-32

Groupe d'Etude sur l'Inflammation Chronique et l'Obésité (GEICO) EA 4516, Université de La Réunion, 15 avenue R. Cassin, CS 92003, 97715, Saint Denis Cedex and Plateforme CYROI, 2 Rue Maxime Rivière, BP 80 005, Sainte Clotilde Cedex, Reunion Island, France.

Inflammation is essential in defense against infection or injury. It is tightly regulated, as over-response can be detrimental, especially in immune-privileged organs such as the central nervous system (CNS). Microglia constitutes the major source of inflammatory factors, but are also involved in the regulation of the inflammation and in the reparation. Autotaxin (ATX), a phospholipase D, converts lysophosphatidylcholine (LPC) into lysophosphatidic acid (LPA) and is upregulated in several CNS injuries. LPA, a pleiotropic immunomodulatory factor, can induce multiple cellular processes including morphological changes, proliferation, death, and survival. We investigated ATX effects on microglia inflammatory response to lipopolysaccharide (LPS), mimicking gram-negative infection. Murine BV-2 microglia and stable transfected, overexpressing ATX-BV-2 (A +) microglia were treated with LPS. Tumor necrosis factor α (TNFα), interleukin (IL)-6, and IL-10 mRNA and proteins levels were examined by qRT-PCR and ELISA, respectively. Secreted LPA was quantified by a radioenzymatic assay and microglial activation markers (CD11b, CD14, B7.1, and B7.2) were determined by flow cytometry. ATX expression and LPA production were significantly enhanced in LPS treated BV-2 cells. LPS induction of mRNA and protein level for TNFα and IL-6 were inhibited in A+ cells, while IL-10 was increased. CD11b, CD14, and B7.1, and B7.2 expressions were reduced in A+ cells. Our results strongly suggest deactivation of microglia and an IL-10 inhibitory of ATX with LPS induced microglia activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jcb.24889DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4275303PMC
December 2014

Pro-fibrotic activity of lysophosphatidic acid in adipose tissue: in vivo and in vitro evidence.

Biochim Biophys Acta 2014 Jan 11;1841(1):88-96. Epub 2013 Oct 11.

Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1048, Toulouse Cedex 4, France; Université de Toulouse, Université Paul Sabatier, Institut des Maladies Métaboliques et Cardiovasculaires, BP84225, 31432 Toulouse Cedex 4, France.

Lysophosphatidic acid (LPA) is a pro-fibrotic mediator acting via specific receptors (LPARs) and is synthesized by autotaxin, that increases with obesity. We tested whether LPA could play a role in adipose tissue (AT)-fibrosis associated with obesity. Fibrosis [type I, III, and IV collagens (COL), fibronectin (FN), TGFβ, CTGF and αSMA] and inflammation (MCP1 and F4/80) markers were quantified: (i) in vivo in inguinal (IAT) and perigonadic (PGAT) AT from obese-diabetic db/db mice treated with the LPAR antagonist Ki16425 (5mg/kg/day ip for 7 weeks); and (ii) in vitro in human AT explants in primary culture for 72h in the presence of oleoyl-LPA (10μM) and/or Ki16425 (10μM) and/or the HIF-1α inhibitor YC-1 (100μM). Treatment of db/db mice with Ki16425 reduced Col I and IV mRNAs in IAT and PGAT while Col III mRNAs were only reduced in IAT. This was associated with reduction of COL protein staining in both IAT and PGAT. AT explants showed a spontaneous and time-dependent increase in ATX expression and production of LPA in the culture medium, along with increased levels of Col I and III, TGFβ and αSMA mRNAs and of COL protein staining. In vitro fibrosis was blocked by Ki16425 and was further amplified by oleoyl-LPA. LPA-dependent in vitro fibrosis was blocked by co-treatment with YC1. Our results show that endogenous and exogenous LPA exert a pro-fibrotic activity in AT in vivo and in vitro. This activity could be mediated by an LPA1R-dependent pathway and could involve HIF-1α.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbalip.2013.10.003DOI Listing
January 2014

Involvement of autotaxin/lysophosphatidic acid signaling in obesity and impaired glucose homeostasis.

Biochimie 2014 Jan 29;96:140-3. Epub 2013 Apr 29.

Institut des maladies métaboliques et cardiovasculaires (I2MC), Inserm U1048. Université Paul Sabatier, Toulouse, France.

Autotaxin (ATX) is a secreted lysophospholipase D involved in synthesis of lysophosphatidic acid (LPA), a phospholipid growth factor acting via specific receptors (LPA1R to LPA6R) and involved in several pathologies including obesity. ATX is secreted by adipocytes and contributes to circulating LPA. ATX expression is up-regulated in obese patients and mice in relationship with insulin resistance and impaired glucose tolerance. LPA1R is the most abundant subtype in adipose tissue. Its expression is higher in non-adipocyte cells than in adipocytes and is not altered in obesity. ATX increases and LPA1R decreases while preadipocytes differentiate into adipocytes (adipogenesis). LPA inhibits adipogenesis through down-regulation of the pro-adipogenic transcription factor PPARγ2. Adipocyte-specific knockout (FATX-KO) mice or mice treated with the LPAR antagonist Ki16425 gain more weight and accumulate more adipose tissue than wild type or control mice fed a high fat diet (HFD). These observations suggest that LPA (via LPA1R) exerts a tonic inhibitory effect on adipose tissue expansion that could, at least in part, result from the anti-adipogenic activity of LPA. A possible negative impact of LPA on insulin-sensitivity might also be considered. Despite being more sensitive to nutritional obesity, FATX-KO and Ki16425-treated mice fed a HFD show improved glucose tolerance when compared to wild type mice. Moreover, exogenously injected LPA acutely impairs glucose tolerance and insulin secretion. These observations show that LPA exerts a tonic deleterious impact on glucose homeostasis. In conclusion, ATX and LPA1R represent potential interesting pharmacological targets for the treatment of obesity-associated metabolic diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biochi.2013.04.010DOI Listing
January 2014

Oxidation of high doses of serotonin favors lipid accumulation in mouse and human fat cells.

Mol Nutr Food Res 2013 Jun 6;57(6):1089-99. Epub 2013 Feb 6.

Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Université de Toulouse, UPS, Toulouse, France.

Scope: The ingestion of serotonin-rich food (bananas, chocolate) increases 5-hydroxytryptamine (5-HT) in blood and its corresponding oxidation products in urines but without direct central consequences since the neurotransmitter does not easily cross the blood-brain barrier. However, there are numerous peripheral effects of serotonin, and recently, 5-HT aldehydic oxidation products have been demonstrated to behave as ligands of peroxisome proliferator-activated receptor γ (PPAR-γ). Since this nuclear factor manages lipid handling by adipose tissue, the response of fat cells to 5-HT exposure needed further investigation.

Methods And Results: Serotonin oxidation was studied on human adipose tissue homogenates and mouse 3T3F442A preadipocytes by fluorometric and radiometric methods. Gene expression was assessed by real-time RT-PCR in human adipocytes and in 3T3F442A after mid- and long-term exposure to 5-HT while triacylglycerols and proteins were assessed by spectrophotometry. Six-hour exposure of human adipocytes to 250 μM 5-HT increased gene expression of lipid-binding proteins, glucose carriers, and enzymes of triacylglycerol synthesis (FABP4, CD36, GLUT1, and phosphoenolpyruvate carboxykinase), as did rosiglitazone treatment. Long-term serotoninergic stimulation of cultured 3T3F442A preadipocytes by 100-250 μM 5-HT enhanced fat storage and upregulation of PPAR-γ-responsive genes, in a manner sensitive to MAO- or PPAR-γ inhibition. Our observations suggest an unpredicted peripheral effect of serotonin on adipose tissue that depends on its amine oxidation.

Conclusion: Besides being centrally active on eating behavior, 5-HT may promote PPAR-γ activation and subsequent lipogenic effects in fat cells, raising the interest to consider its level in future diet formulations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mnfr.201200681DOI Listing
June 2013

Influence of secreted factors from human adipose tissue on glucose utilization and proinflammatory reaction.

J Physiol Biochem 2013 Sep 27;69(3):625-32. Epub 2013 Jan 27.

Institut National de la Santé et de la Recherche Médicale (INSERM), U1048 Toulouse, France.

The objective of the present study was to characterize the nature of the autocrine/paracrine signal within human adipose tissue that may alter glucose metabolism and the inflammatory status in adipocytes. We prepared a conditioned medium from abdominal dermolipectomies in the absence (CM) or the presence (CMBSA) of bovine serum albumin (BSA), and we tested the influence of CM and CMBSA on glucose transport, maximal insulin response, and the expression of inflammation marker genes in differentiated human SGBS adipocytes. We found that CMBSA increased basal and reduced insulin-stimulated glucose incorporation along with a reduced mRNA level of the glucose transport GLUT4, and an increased expression of GLUT1. These effects were associated with a potent upregulation in the mRNA level of the proinflammatory cytokines IL-6 and MCP-1. These regulations were strongly attenuated in the absence of BSA during the preparation of CM, or after BSA depletion of CM, and were attributed to water-soluble molecules rather than lipids. Finally, fractionation of CMBSA by isoelectric focusing showed that part of its bioactivity could be reproduced with proteins with pHi ranging from 6.6 to 7.6. In conclusion, our results demonstrate that the production by human adipose tissue of autocrine/paracrine neutral proteins is able to increase the inflammatory status of the adipocytes and to deteriorate their glucose metabolism and maximal insulin response, and their release is greatly amplified by the presence of albumin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s13105-013-0238-7DOI Listing
September 2013

5-hydroxytryptamine actions in adipocytes: involvement of monoamine oxidase-dependent oxidation and subsequent PPARγ activation.

J Neural Transm (Vienna) 2013 Jun 28;120(6):919-26. Epub 2012 Dec 28.

Université de Toulouse, UPS, Institut de Médecine Moléculaire de Rangueil (I2MC), Toulouse, France.

Serotonin (5-HT) is a brain neurotransmitter instrumental for the antidepressant action of selective inhibitors of serotonin reuptake (SSRIs) while it also plays important roles in peripheral organs. Recently, the 5-HT oxidation products, 5-hydroxyindoleacetate and 5-methoxy-indoleacetate, have been shown to bind to peroxisome proliferator-activated receptor γ (PPARγ) and to enhance lipid accumulation in preadipocytes. Since we already reported that adipocytes exhibit elevated monoamine oxidase (MAO) and primary amine oxidase activities, we verified how adipocytes readily oxidize 5-HT, with the objective to determine whether such oxidation promotes PPARγ activation and lipid storage. To this aim, serotonin was tested on cultured 3T3 F442A preadipocytes and on human adipocytes. Results showed that 5-HT was oxidized by MAO in both models. Daily treatment of 3T3 F442A preadipocytes for 8 days with 100-500 μM 5-HT promoted triglyceride accumulation and emergence of adipogenesis markers. At 250 μM, 5-HT alone reproduced half of 50 nM insulin-induced adipogenesis, and exhibited an additive differentiating effect when combined with insulin. Moreover, the 5-HT-induced expression of PPARγ-responsive genes (PEPCK, aP2/FABP4) was blocked by GW 9662, a PPARγ-inhibitor, or by pargyline, a MAO-inhibitor. In human fat cells, 6-h exposure to 100 μM 5-HT increased PEPCK expression as did the PPARγ-agonist rosiglitazone. Since hydrogen peroxide, another amine oxidation product, did not reproduce such enhancement, we propose that serotonin can promote PPARγ activation in fat cells, via the indoleacetate produced during MAO-dependent oxidation. Such pathway could be involved in the adverse effects of several antidepressant SSRIs on body weight gain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00702-012-0959-8DOI Listing
June 2013

The amine oxidase inhibitor phenelzine limits lipogenesis in adipocytes without inhibiting insulin action on glucose uptake.

J Neural Transm (Vienna) 2013 Jun 16;120(6):997-1003. Epub 2012 Dec 16.

Institut National de la Santé et de la Recherche Médicale, U 1048 Bat L4, team 3, CHU Rangueil, Toulouse, France.

The antidepressant phenelzine is a monoamine oxidase inhibitor known to inhibit various other enzymes, among them semicarbazide-sensitive amine oxidase (currently named primary amine oxidase: SSAO/PrAO), absent from neurones but abundant in adipocytes. It has been reported that phenelzine inhibits adipocyte differentiation of cultured preadipocytes. To further explore the involved mechanisms, our aim was to study in vitro the acute effects of phenelzine on de novo lipogenesis in mature fat cells. Therefore, glucose uptake and incorporation into lipid were measured in mouse adipocytes in response to phenelzine, other hydrazine-based SSAO/PrAO-inhibitors, and reference agents. None of the inhibitors was able to impair the sevenfold activation of 2-deoxyglucose uptake induced by insulin. Phenelzine did not hamper the effect of lower doses of insulin. However, insulin-stimulated glucose incorporation into lipids was dose-dependently inhibited by phenelzine and pentamidine, but not by semicarbazide or BTT2052. In contrast, all these SSAO/PrAO inhibitors abolished the transport and lipogenesis stimulation induced by benzylamine. These data indicate that phenelzine does not inhibit glucose transport, the first step of lipogenesis, but inhibits at 100 μM the intracellular triacylglycerol assembly, consistently with its long-term anti-adipogenic effect and such rapid action was not found with all the hydrazine derivatives tested. Therefore, the alterations of body weight control consecutive to the use of this antidepressant drug might be not only related to central effects on food intake/energy expenditure, but could also depend on its direct action in adipocytes. Nonetheless, phenelzine antilipogenic action is not merely dependent on SSAO/PrAO inhibition.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00702-012-0951-3DOI Listing
June 2013

Cell autonomous lipin 1 function is essential for development and maintenance of white and brown adipose tissue.

Mol Cell Biol 2012 Dec 1;32(23):4794-810. Epub 2012 Oct 1.

Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland.

Through analysis of mice with spatially and temporally restricted inactivation of Lpin1, we characterized its cell autonomous function in both white (WAT) and brown (BAT) adipocyte development and maintenance. We observed that the lipin 1 inactivation in adipocytes of aP2(Cre/+)/Lp(fEx2)(-)(3/fEx2)(-)(3) mice resulted in lipodystrophy and the presence of adipocytes with multilocular lipid droplets. We further showed that time-specific loss of lipin 1 in mature adipocytes in aP2(Cre-ERT2/+)/Lp(fEx2)(-)(3/fEx2)(-)(3) mice led to their replacement by newly formed Lpin1-positive adipocytes, thus establishing a role for lipin 1 in mature adipocyte maintenance. Importantly, we observed that the presence of newly formed Lpin1-positive adipocytes in aP2(Cre-ERT2/+)/Lp(fEx2)(-)(3/fEx2)(-)(3) mice protected these animals against WAT inflammation and hepatic steatosis induced by a high-fat diet. Loss of lipin 1 also affected BAT development and function, as revealed by histological changes, defects in the expression of peroxisome proliferator-activated receptor alpha (PPARα), PGC-1α, and UCP1, and functionally by altered cold sensitivity. Finally, our data indicate that phosphatidic acid, which accumulates in WAT of animals lacking lipin 1 function, specifically inhibits differentiation of preadipocytes. Together, these observations firmly demonstrate a cell autonomous role of lipin 1 in WAT and BAT biology and indicate its potential as a therapeutical target for the treatment of obesity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/MCB.00512-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497595PMC
December 2012

Depot-specific regulation of autotaxin with obesity in human adipose tissue.

J Physiol Biochem 2012 Dec 27;68(4):635-44. Epub 2012 May 27.

Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Inserm U1048, Université Paul Sabatier, Equipe n°3 (Bat L4), 1 Avenue Jean Poulhès, BP 84225, 31432 Toulouse Cedex 4, France.

Autotaxin (ATX) is a lysophospholipase D involved in synthesis of a bioactive mediator: lysophosphatidic. ATX is abundantly produced by adipocytes and exerts a negative action on adipose tissue expansion. In both mice and humans, ATX expression increases with obesity in association with insulin resistance. In the present study, fat depot-specific regulation of ATX was explored in human. ATX mRNA expression was quantified in visceral and subcutaneous adipose tissue in obese (BMI > 40 kg/m(2); n = 27) and non-obese patients (BMI < 25 kg/m(2); n = 10). Whatever the weight status of the patients is, ATX expression was always higher (1.3- to 6-fold) in subcutaneous than in visceral fat. Nevertheless, visceral fat ATX was significantly higher (42 %) in obese than in non-obese patients, whereas subcutaneous fat ATX remained unchanged. In obese patients, visceral fat ATX expression was positively correlated with diastolic arterial blood pressure (r = 0.67; P = 0.001). This correlation was not observed with subcutaneous fat ATX. Visceral fat ATX was mainly correlated with leptin (r = 0.60; P = 0.001), inducible nitric oxide synthase (r = 0.58; P = 0,007), and apelin receptor (r = 0.50; P = 0.007). These correlations were not observed with subcutaneous fat ATX. These results reveal that obesity-associated upregulation of human adipose tissue ATX is specific to the visceral fat depot.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s13105-012-0181-zDOI Listing
December 2012

Benzylamine antihyperglycemic effect is abolished by AOC3 gene invalidation in mice but not rescued by semicarbazide-sensitive amine oxidase expression under the control of aP2 promoter.

J Physiol Biochem 2012 Dec 1;68(4):651-62. Epub 2012 May 1.

Institut National de la Santé et de la Recherche Médicale (INSERM) U1048, I2MC, CHU Rangueil, 31432 Toulouse, France.

Semicarbazide-sensitive amine oxidase (SSAO) is a transmembrane enzyme that metabolizes primary amines from endogenous or dietary origin. SSAO is highly expressed in adipose, smooth muscle and endothelial cells. In each of these cell types, SSAO is implicated in different biological functions, such as glucose transport activation, extracellular matrix maturation and leucocyte extravasation, respectively. However, the physiological functions of SSAO and their involvement in pathogenesis remain uncompletely characterized. To better understand the role of adipose tissue SSAO, we investigated whether it was necessary and/or sufficient to produce the antihyperglycemic effect of the SSAO-substrate benzylamine, already reported in mice. Therefore, we crossed SSAO-deficient mice invalidated for AOC3 gene and transgenic mice expected to express human SSAO in an adipocyte-specific manner, under the control of aP2 promoter. The aP2-human AOC3 construct (aP2-hAOC3) was equally expressed in the adipose tissue of mice expressing or not the native murine form and almost absent in other tissues. However, the corresponding SSAO activity found in adipose tissue represented only 20 % that of control mice. As a consequence, the benzylamine antihyperglycemic effect observed during glucose tolerance test in control was abolished in AOC3-KO mice but not rescued in mice expressing aP2-hAOC3. The capacity of benzylamine or methylamine to activate glucose uptake in adipocytes exhibited parallel variations in the corresponding genotypes. Although the aP2-hAOC3 construct did not allow a total rescue of SSAO activity in adipose tissue, it could be assessed from our observations that adipocyte SSAO plays a pivotal role in the increased glucose tolerance promoted by pharmacological doses of benzylamine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s13105-012-0171-1DOI Listing
December 2012

Autotaxin protects microglial cells against oxidative stress.

Free Radic Biol Med 2012 Jan 8;52(2):516-26. Epub 2011 Dec 8.

Laboratoire de Biochimie et Génétique Moléculaire, Groupe d'Etude sur l'Inflammation Chronique et l'Obésité, Plateforme CYROI, Université de La Réunion, 97715 Saint Denis de La Réunion Cedex 09, France.

Oxidative stress occurs when antioxidant defenses are overwhelmed by oxygen-reactive species and can lead to cellular damage, as seen in several neurodegenerative disorders. Microglia are specialized cells in the central nervous system that act as the first and main form of active immune defense in the response to pathological events. Autotaxin (ATX) plays an important role in the modulation of critical cellular functions, through its enzymatic production of lysophosphatidic acid (LPA). In this study, we investigated the potential role of ATX in the response of microglial cells to oxidative stress. We show that treatment of a microglial BV2 cell line with hydrogen peroxide (H(2)O(2)) stimulates ATX expression and LPA production. Stable overexpression of ATX inhibits microglial activation (CD11b expression) and protects against H(2)O(2)-treatment-induced cellular damage. This protective effect of ATX was partially reduced in the presence of the LPA-receptor antagonist Ki16425. ATX overexpression was also associated with a reduction in intracellular ROS formation, carbonylated protein accumulation, proteasomal activity, and catalase expression. Our results suggest that up-regulation of ATX expression in microglia could be a mechanism for protection against oxidative stress, thereby reducing inflammation in the nervous system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.freeradbiomed.2011.11.014DOI Listing
January 2012

Metabolic adaptation to a high-fat diet is associated with a change in the gut microbiota.

Gut 2012 Apr 22;61(4):543-53. Epub 2011 Nov 22.

Institut National de la Santé et de la Recherche Médicale, Toulouse, France.

Objective: The gut microbiota, which is considered a causal factor in metabolic diseases as shown best in animals, is under the dual influence of the host genome and nutritional environment. This study investigated whether the gut microbiota per se, aside from changes in genetic background and diet, could sign different metabolic phenotypes in mice.

Methods: The unique animal model of metabolic adaptation was used, whereby C57Bl/6 male mice fed a high-fat carbohydrate-free diet (HFD) became either diabetic (HFD diabetic, HFD-D) or resisted diabetes (HFD diabetes-resistant, HFD-DR). Pyrosequencing of the gut microbiota was carried out to profile the gut microbial community of different metabolic phenotypes. Inflammation, gut permeability, features of white adipose tissue, liver and skeletal muscle were studied. Furthermore, to modify the gut microbiota directly, an additional group of mice was given a gluco-oligosaccharide (GOS)-supplemented HFD (HFD+GOS).

Results: Despite the mice having the same genetic background and nutritional status, a gut microbial profile specific to each metabolic phenotype was identified. The HFD-D gut microbial profile was associated with increased gut permeability linked to increased endotoxaemia and to a dramatic increase in cell number in the stroma vascular fraction from visceral white adipose tissue. Most of the physiological characteristics of the HFD-fed mice were modulated when gut microbiota was intentionally modified by GOS dietary fibres.

Conclusions: The gut microbiota is a signature of the metabolic phenotypes independent of differences in host genetic background and diet.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/gutjnl-2011-301012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292714PMC
April 2012

A hypomorphic mutation in Lpin1 induces progressively improving neuropathy and lipodystrophy in the rat.

J Biol Chem 2011 Jul 1;286(30):26781-93. Epub 2011 Jun 1.

Hubrecht Institute-KNAW and University Medical Center Utrecht, 3584 CT Utrecht, The Netherlands.

The Lpin1 gene encodes the phosphatidate phosphatase (PAP1) enzyme Lipin 1, which plays a critical role in lipid metabolism. In this study we describe the identification and characterization of a rat model with a mutated Lpin1 gene (Lpin1(1Hubr)), generated by N-ethyl-N-nitrosourea mutagenesis. Lpin1(1Hubr) rats are characterized by hindlimb paralysis and mild lipodystrophy that are detectable from the second postnatal week. Sequencing of Lpin1 identified a point mutation in the 5'-end splice site of intron 18 resulting in mis-splicing, a reading frameshift, and a premature stop codon. As this mutation does not induce nonsense-mediated decay, it allows the production of a truncated Lipin 1 protein lacking PAP1 activity. Lpin1(1Hubr) rats developed hypomyelination and mild lipodystrophy rather than the pronounced demyelination and adipocyte defects characteristic of Lpin1(fld/fld) mice, which carry a null allele for Lpin1. Furthermore, biochemical, histological, and molecular analyses revealed that these lesions improve in older Lpin1(1Hubr) rats as compared with young Lpin1(1Hubr) rats and Lpin1(fld/fld) mice. We observed activation of compensatory biochemical pathways substituting for missing PAP1 activity that, in combination with a possible non-enzymatic Lipin 1 function residing outside of its PAP1 domain, may contribute to the less severe phenotypes observed in Lpin1(1Hubr) rats as compared with Lpin1(fld/fld) mice. Although we are cautious in making a direct parallel between the presented rodent model and human disease, our data may provide new insight into the pathogenicity of recently identified human LPIN1 mutations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M110.197947DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3143639PMC
July 2011

Adipose-specific disruption of autotaxin enhances nutritional fattening and reduces plasma lysophosphatidic acid.

J Lipid Res 2011 Jun 18;52(6):1247-55. Epub 2011 Mar 18.

Institut National de la Santé et de la Recherche Médicale (INSERM), U1048, Toulouse, Cedex 4, France.

Autotaxin (ATX) is a secreted lysophospholipase D that generates the lipid mediator lysophosphatidic acid (LPA). ATX is secreted by adipose tissue and its expression is enhanced in obese/insulin-resistant individuals. Here, we analyzed the specific contribution of adipose-ATX to fat expansion associated with nutritional obesity and its consequences on plasma LPA levels. We established ATX(F/F)/aP2-Cre (FATX-KO) transgenic mice carrying a null ATX allele specifically in adipose tissue. FATX-KO mice and their control littermates were fed either a normal or a high-fat diet (HFD) (45% fat) for 13 weeks. FATX-KO mice showed a strong decrease (up to 90%) in ATX expression in white and brown adipose tissue, but not in other ATX-expressing organs. This was associated with a 38% reduction in plasma LPA levels. When fed an HFD, FATX-KO mice showed a higher fat mass and a higher adipocyte size than control mice although food intake was unchanged. This was associated with increased expression of peroxisome proliferator-activated receptor (PPAR)γ2 and of PPAR-sensitive genes (aP2, adiponectin, leptin, glut-1) in subcutaneous white adipose tissue, as well as in an increased tolerance to glucose. These results show that adipose-ATX is a negative regulator of fat mass expansion in response to an HFD and contributes to plasma LPA levels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1194/jlr.M014985DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3090245PMC
June 2011

Cancer cell expression of autotaxin controls bone metastasis formation in mouse through lysophosphatidic acid-dependent activation of osteoclasts.

PLoS One 2010 Mar 17;5(3):e9741. Epub 2010 Mar 17.

INSERM, U664, Lyon, France.

Background: Bone metastases are highly frequent complications of breast cancers. Current bone metastasis treatments using powerful anti-resorptive agents are only palliative indicating that factors independent of bone resorption control bone metastasis progression. Autotaxin (ATX/NPP2) is a secreted protein with both oncogenic and pro-metastatic properties. Through its lysosphospholipase D (lysoPLD) activity, ATX controls the level of lysophosphatidic acid (LPA) in the blood. Platelet-derived LPA promotes the progression of osteolytic bone metastases of breast cancer cells. We asked whether ATX was involved in the bone metastasis process. We characterized the role of ATX in osteolytic bone metastasis formation by using genetically modified breast cancer cells exploited on different osteolytic bone metastasis mouse models.

Methodology/principal Findings: Intravenous injection of human breast cancer MDA-B02 cells with forced expression of ATX (MDA-B02/ATX) to immunodeficiency BALB/C nude mice enhanced osteolytic bone metastasis formation, as judged by increased bone loss, tumor burden, and a higher number of active osteoclasts at the metastatic site. Mouse breast cancer 4T1 cells induced the formation of osteolytic bone metastases after intracardiac injection in immunocompetent BALB/C mice. These cells expressed active ATX and silencing ATX expression inhibited the extent of osteolytic bone lesions and decreased the number of active osteoclasts at the bone metastatic site. In vitro, osteoclast differentiation was enhanced in presence of MDA-B02/ATX cell conditioned media or recombinant autotaxin that was blocked by the autotaxin inhibitor vpc8a202. In vitro, addition of LPA to active charcoal-treated serum restored the capacity of the serum to support RANK-L/MCSF-induced osteoclastogenesis.

Conclusion/significance: Expression of autotaxin by cancer cells controls osteolytic bone metastasis formation. This work demonstrates a new role for LPA as a factor that stimulates directly cancer growth and metastasis, and osteoclast differentiation. Therefore, targeting the autotaxin/LPA track emerges as a potential new therapeutic approach to improve the outcome of patients with bone metastases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0009741PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2840030PMC
March 2010

Seipin deficiency alters fatty acid Delta9 desaturation and lipid droplet formation in Berardinelli-Seip congenital lipodystrophy.

Biochimie 2009 Jun 6;91(6):796-803. Epub 2009 Feb 6.

INSERM, UMR, CDR Saint-Antoine, Paris, France.

Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare recessive disease characterized by near absence of adipose tissue and severe insulin resistance. In most cases, BSCL is due to loss-of-function mutations in the genes encoding either seipin of unknown function or 1-acyl-glycerol-3-phosphate O-acyltransferase 2 (AGPAT2) which catalyses the formation of phosphatidic acid from lysophosphatidic acid. We studied the lipid profile of lymphoblastoid cell-lines from 20 BSCL patients with null mutations in the genes encoding either seipin (n=12) or AGPAT2 (n=8) in comparison to nine control cell-lines. In seipin deficient cells, we observed alterations in the pattern of lipid droplets which were decreased in size and increased in number as compared to control cells. We also observed alterations in the triglycerides content as well as in the fatty acid composition from triglycerides and phosphatidylethanolamine, with an increased proportion of saturated fatty acids at the expense of the corresponding monounsaturated fatty acids, reflecting a defect in Delta9-desaturase activity. In AGPAT2 deficient cells, no specific alterations in lipid droplet pattern nor in fatty acid composition was observed but the cellular level of lysophosphatidic acid was increased as compared to that of control and seipin deficient cells. These results indicate that seipin like AGPAT2 is involved in lipid metabolism but exerts a different function. Seipin intervenes at a proximal step in triglycerides and phospholipids biosynthesis being involved in the pathway that links fatty acid Delta9 desaturation to lipid droplet formation. These findings provide new insights into how seipin deficiency causes severe lipodystrophy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biochi.2009.01.011DOI Listing
June 2009

Phosphatidic acid mediates demyelination in Lpin1 mutant mice.

Genes Dev 2008 Jun;22(12):1647-61

Department of Medical Genetics, University of Lausanne, 1005 Lausanne, Switzerland.

Lipids play crucial roles in many aspects of glial cell biology, affecting processes ranging from myelin membrane biosynthesis to axo-glial interactions. In order to study the role of lipid metabolism in myelinating glial cells, we specifically deleted in Schwann cells the Lpin1 gene, which encodes the Mg2+-dependent phosphatidate phosphatase (PAP1) enzyme necessary for normal triacylglycerol biosynthesis. The affected animals developed pronounced peripheral neuropathy characterized by myelin degradation, Schwann cell dedifferentiation and proliferation, and a reduction in nerve conduction velocity. The observed demyelination is mediated by endoneurial accumulation of the substrate of the PAP1 enzyme, phosphatidic acid (PA). In addition, we show that PA is a potent activator of the MEK-Erk pathway in Schwann cells, and that this activation is required for PA-induced demyelination. Our results therefore reveal a surprising role for PA in Schwann cell fate determination and provide evidence of a direct link between diseases affecting lipid metabolism and abnormal Schwann cell function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1101/gad.1638008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2428062PMC
June 2008

Lysophosphatidic acid and renal fibrosis.

Biochim Biophys Acta 2008 Sep 11;1781(9):582-7. Epub 2008 Apr 11.

Inserm, U858/I2MR, Department of Metabolism and Obesity, Team #3, 1 Avenue Jean Poulhès, BP 84225, 31432 Toulouse Cedex 4, France.

The development of fibrosis involves a multitude of events and molecules. Until now the majority of these molecules were found to be proteins or peptides. But recent data show significant involvement of the phospholipid lysophosphatidic acid (LPA) in the development of pulmonary, liver and renal fibrosis. The latest data on the role of LPA and the G-protein-coupled LPA1 receptor in the development of renal fibrosis will be discussed. LPA1-receptor activation was found to be associated with increased vascular leakage and increased fibroblast recruitment in pulmonary fibrosis. Furthermore, in renal fibrosis LPA1-receptor activation stimulates macrophage recruitment and connective tissue growth factor expression. The observations make this receptor an interesting alternative and new therapeutic target in fibrotic diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbalip.2008.04.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577601PMC
September 2008

LPA1 receptor activation promotes renal interstitial fibrosis.

J Am Soc Nephrol 2007 Dec 14;18(12):3110-8. Epub 2007 Nov 14.

Inserm, U858/I2MR, Department of Metabolism and Obesity, Team 3, Toulouse, France.

Tubulointerstitial fibrosis in chronic renal disease is strongly associated with progressive loss of renal function. We studied the potential involvement of lysophosphatidic acid (LPA), a growth factor-like phospholipid, and its receptors LPA(1-4) in the development of tubulointerstitial fibrosis (TIF). Renal fibrosis was induced in mice by unilateral ureteral obstruction (UUO) for up to 8 d, and kidney explants were prepared from the distal poles to measure LPA release into conditioned media. After obstruction, the extracellular release of LPA increased approximately 3-fold. Real-time reverse transcription PCR (RT-PCR) analysis demonstrated significant upregulation in the expression of the LPA(1) receptor subtype, downregulation of LPA3, and no change of LPA2 or LPA4. TIF was significantly attenuated in LPA1 (-/-) mice compared to wild-type littermates, as measured by expression of collagen III, alpha-smooth muscle actin (alpha-SMA), and F4/80. Furthermore, treatment of wild-type mice with the LPA1 antagonist Ki16425 similarly reduced fibrosis and significantly attenuated renal expression of the profibrotic cytokines connective tissue growth factor (CTGF) and transforming growth factor beta (TGFbeta). In vitro, LPA induced a rapid, dose-dependent increase in CTGF expression that was inhibited by Ki16425. In conclusion, LPA, likely acting through LPA1, is involved in obstruction-induced TIF. Therefore, the LPA1 receptor might be a pharmaceutical target to treat renal fibrosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1681/ASN.2007020196DOI Listing
December 2007

Adipogenesis-related increase of semicarbazide-sensitive amine oxidase and monoamine oxidase in human adipocytes.

Biochimie 2007 Aug 24;89(8):916-25. Epub 2007 Feb 24.

U858 INSERM, I2MR, IFR 31, CHU Rangueil, BP 84225, 31432 Toulouse Cedex 4, France.

A strong induction of semicarbazide-sensitive amine oxidase (SSAO) has previously been reported during murine preadipocyte lineage differentiation but it remains unknown whether this emergence also occurs during adipogenesis in man. Our aim was to compare SSAO and monoamine oxidase (MAO) expression during in vitro differentiation of human preadipocytes and in adipose and stroma-vascular fractions of human fat depots. A human preadipocyte cell strain from a patient with Simpson-Golabi-Behmel syndrome was first used to follow amine oxidase expression during in vitro differentiation. Then, human preadipocytes isolated from subcutaneous adipose tissues were cultured under conditions promoting ex vivo adipose differentiation and tested for MAO and SSAO expression. Lastly, human adipose tissue was separated into mature adipocyte and stroma-vascular fractions for analyses of MAO and SSAO at mRNA, protein and activity levels. Both SSAO and MAO were increased from undifferentiated preadipocytes to lipid-laden cells in all the models: 3T3-F442A and 3T3-L1 murine lineages, human SGBS cell strain or human preadipocytes in primary culture. In human subcutaneous adipose tissue, the adipocyte-enriched fraction exhibited seven-fold higher amine oxidase activity and contained three- to seven-fold higher levels of mRNAs encoded by MAO-A, MAO-B, AOC3 and AOC2 genes than the stroma-vascular fraction. MAO-A and AOC3 genes accounted for the majority of their respective MAO and SSAO activities in human adipose tissue. Most of the SSAO and MAO found in adipose tissue originated from mature adipocytes. Although the mechanism and role of adipogenesis-related increase in amine oxidase expression remain to be established, the resulting elevated levels of amine oxidase activities found in human adipocytes may be of potential interest for therapeutic intervention in obesity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biochi.2007.02.013DOI Listing
August 2007

Secretion and lysophospholipase D activity of autotaxin by adipocytes are controlled by N-glycosylation and signal peptidase.

Biochim Biophys Acta 2007 Jan 6;1771(1):93-102. Epub 2006 Dec 6.

Inserm, U586, Unité de Recherches sur les Obésités, Toulouse, F-31432, France.

Autotaxin (ATX) is a lysophospholipase D involved in synthesis of lysophosphatidic acid (LPA). ATX is secreted by adipocytes and is associated with adipogenesis and obesity-associated diabetes. Here we have studied the mechanisms involved in biosynthesis and secretion of ATX by mouse 3T3-F442A adipocytes. We found that inhibition of N-glycosylation with tunicamycin or by double point deletion of the amino-acids N53 and N410 of ATX inhibit its secretion. In addition, N-glycosidase treatment and point deletion of the amino-acid N410 inhibits the lysophospholipase D activity of ATX. Analysis of the amino-acid sequence of mouse ATX shows the presence of a N-terminal signal peptide. Treatment with the signal peptidase inhibitor globomycin inhibits ATX secretion by adipocytes. Transfection in Cos-7 cells of site-directed deleted ATX shows that ATX secretion is dependent on the hydrophobic core sequence of the signal peptide, not on the putative signal peptidase cleavage site sequence. Analysis of the amino-acid sequence of mouse ATX also reveals the presence of a putative cleavage site by the protein convertase furin. Treatment of adipocytes with the furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone does not modified secretion or lysophospholipase D activity of ATX. Transfection in Cos-7 cells of site-directed deleted ATX shows that the furin recognition site is not required for secretion or lysophospholipase D activity of ATX. In conclusion, the present work demonstrates the crucial role of N-glycosylation in secretion and activity of ATX. The present work also confirms the crucial role signal peptidase in secretion of ATX by adipocytes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbalip.2006.11.010DOI Listing
January 2007

Short- and long-term insulin-like effects of monoamine oxidases and semicarbazide-sensitive amine oxidase substrates in cultured adipocytes.

Metabolism 2006 Oct;55(10):1397-405

Institut National de la Santé et de la Recherche Médicale, U586 INSERM, IFR 31, CHU Rangueil, 31432 Toulouse cedex 4, France.

Semicarbazide-sensitive amine oxidase (SSAO) is known to increase during in vitro adipogenesis and to be one of the most highly expressed membrane proteins of white adipocytes. Although less well documented, mitochondrial monoamine oxidases (MAOs) are also present in adipocytes and share with SSAO the capacity to generate hydrogen peroxide. This work therefore aimed to compare several biologic effects of MAO and SSAO substrates in 3T3-F442A adipocytes. In differentiated cells, tyramine oxidation was predominantly MAO dependent, whereas benzylamine oxidation was SSAO dependent. Both amines partially mimicked insulin actions, including stimulation of Akt phosphorylation and glucose uptake. In addition, tyramine and benzylamine impaired tumor necrosis factor alpha-dependent nitric oxide formation in a pargyline- and semicarbazide-sensitive manner, respectively. Various biogenic amines were tested in competition for tyramine or benzylamine oxidation and classified as MAO-preferring (methoxytyramine, tryptamine) or SSAO-preferring substrates (methylamine, octopamine). Short-term incubation with 1 mmol/L of all amines except histamine stimulated glucose uptake up to 20% to 50% of maximal insulin activation. One-week treatment with either MAO or SSAO substrates alone allowed postconfluent cells to differentiate into adipocytes, reproducing 60% of insulin-promoted lipid accumulation. All amines also exerted a slight improvement in the adipogenic action of insulin. Therefore, like SSAO, substrate activation of MAO can interact with adipocyte metabolism by mimicking diverse effects of insulin in addition to preventing tumor necrosis factor alpha-dependent responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.metabol.2006.06.011DOI Listing
October 2006

Anionic peptide factor/phosphatidylcholine particles promote the inhibition of vascular cell adhesion molecule-1 in human umbilical vein endothelial cells.

Pathobiology 2005 ;72(4):213-9

UMR 476 INSERM/1260 INRA, Faculté de Médecine, Marseille, France.

Objective: High-density lipoproteins (HDLs) have significant cardiovascular benefits by retarding the progression of atherosclerosis. One of the mechanisms is the inhibition by HDLs of the vascular cell adhesion molecule-1 (VCAM-1) expression in endothelial cells. Our objective was to test the effect on VCAM-1 expression by the human umbilical vein endothelial cells (HUVEC) of a minor HDL2 and HDL3 apolipoprotein, the anionic peptide factor (APF). The peptide has previously been found to develop some beneficial effects against atherosclerosis, i.e. by promoting the cholesterol efflux from endothelial cells.

Methods: We examined the effects of two HDL apolipoproteins A-I and APF, either in presence or absence of phosphatidylcholines (PCs), or free PCs, on the expression of VCAM-1 by HUVEC. The cells were stimulated with either the tumor necrosis factor-alpha (TNFalpha, 500 pg/ml) or the calcium bound to heparin (10 microg Ca2+/ml, 50 microg heparin/ml).

Results: In the presence of TNFalpha, only the free PCs (0.25 and 1 mM) developed an inhibitory effect (up to 50%). In the absence of TNFalpha and in the presence of calcium bound to heparin, either the lipid-free APF (3.5 microM) or the APF/PC complexes (1:57 molar ratio) or the free PCs (0.25 mM) exhibited a substantial inhibitory effect (72, 71 and 42%, respectively).

Conclusion: Our present findings suggest for the first time that one of the mechanisms of the antiatherogenic action of APF involves the inhibition of VCAM-1 expression by HUVEC. The peptide, through its phospholipid-binding and its calcium antagonist abilities, appears to confer on the HDLs a protective effect against the early cellular event of the inflammatory process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1159/000086791DOI Listing
October 2005

Production of lysophosphatidic acid in blister fluid: involvement of a lysophospholipase D activity.

J Invest Dermatol 2005 Sep;125(3):421-7

Service de Dermatologie, Hôpital Rangueil, Toulouse Cedex, France.

Lysophosphatidic acid (LPA) is present in abundance in serum resulting from platelet activation and is also found in other biological fluids. LPA controls numerous cellular responses and plays a role in specific functions such as wound healing, especially in the skin. Nevertheless, its presence in the skin has never been investigated. Since re-epithelialization occurs after blister rupture, we tested the presence of endogenous LPA in blister fluid and investigated a possible mechanism for its biosynthesis and biological functions. Using a radioenzymatic assay, LPA was detected in 33 blister fluids originating from 24 bullous dermatoses, and at higher concentrations than in plasma. In parallel, blister fluids contained a lysophospholipase D (LPLD) activity but no detectable phospholipase A2 activity. The expressions of the LPLD autotaxin (ATX) and of LPA1-receptor (LPA1-R) were greatly increased in blister skin when compared with normal skin. Finally, LPA was found to have a positive effect on the migration of cultured keratinocytes. These results show that LPA is present in blister fluid synthesized by the LPLD ATX. Due to its ability to enhance keratinocyte migration, LPA in blister fluid could, via the LPA1-R, play an important role in re-epithelialization occurring after blister rupture.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.0022-202X.2005.23855.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1885457PMC
September 2005

The endothelial cholesterol efflux is promoted by the high-density lipoprotein anionic peptide factor.

Metabolism 2005 Aug;54(8):1087-94

Department of UMR 476 INSERM/1260 INRA, Faculty of Medicine, 27 bd Jean Moulin, 13385 Marseille, France.

The prevention of atherosclerosis depends on the high-density lipoprotein (HDL) capacity to stimulate the efflux of unesterified cholesterol (UC). We tested here the effects of 2 HDL apolipoproteins, apo A-I and the 7-kd anionic peptide factor (APF), on the UC efflux by human endothelial ECV 304 cells in culture. Apolipoprotein A-I (10 micromol/L) or APF (3.5 micromol/L) in lipid-free forms or small particles (13 nm with apo A-I or 19 nm with APF) were incubated in the presence of [4-14C]UC. The phosphatidylcholines (PCs) were present either at a low level (0.35 mmol/L with apo A-I or 0.20 mmol/L with APF) or at a high level (1 mmol/L with apo A-I). We also tested either large 53-nm bile lipoprotein complex-like particles (3.5 micromol/L APF [13 microg/500 microL]) with a high PC level (0.65 mmol/L) or a 9-residue synthetic peptide (13 microg/500 microL), derived from the NH2-terminal domain of HDL3-APF, in a lipid-free or low-lipidated (0.20 mmol/L PCs) form. A control was developed in absence of the added compounds. A rapid [4-14C]UC efflux mediated by APF added in free form or in 19-nm complexes was 2.2- to 2.3-fold higher than that mediated by apo A-I in free form or in 13-nm particles (P < .05). The level of this high APF-related efflux was comparable with that obtained with the 12-nm native HDLs (10 micromol/L apo A-I) or free PCs (1 mmol/L). The increase in the UC efflux was much more limited (1.4-fold) in the presence of the 53-nm APF/high-PC particles, but it was higher than that mediated by apo A-I. In addition, the efflux mediated by the synthetic peptide, in lipid-free or low-lipidated form, constituted the major part of that related to the full-length APF. Thus, all these particles are very active HDL components, able to act as cholesterol acceptors. Interestingly, we further showed a new anti-atherogenic property of APF as well as its metabolic importance and clinical relevance. By its involvement in the first step of the reverse cholesterol transport, APF could reduce the risk of cardiovascular disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.metabol.2005.03.013DOI Listing
August 2005

Lysophosphatidic acid inhibits adipocyte differentiation via lysophosphatidic acid 1 receptor-dependent down-regulation of peroxisome proliferator-activated receptor gamma2.

J Biol Chem 2005 Apr 14;280(15):14656-62. Epub 2005 Feb 14.

INSERM U586, Institut Louis Bugnard, Rangueil Hospital, BP84225, 31432 Toulouse, Cedex 4, France.

Lysophosphatidic acid (LPA) is a bioactive phospholipid acting via specific G protein-coupled receptors that is synthesized at the extracellular face of adipocytes by a secreted lysophospholipase D (autotaxin). Preadipocytes mainly express the LPA(1) receptor subtype, and LPA increases their proliferation. In monocytes and CV1 cells LPA was recently reported to bind and activate peroxisome proliferator-activated receptor gamma (PPARgamma), a transcription factor also known to play a pivotal role in adipogenesis. Here we show that, unlike the PPARgamma agonist rosiglitazone, LPA was unable to increase transcription of PPARgamma-sensitive genes (PEPCK and ALBP) in the mouse preadipose cell line 3T3F442A. In contrast, treatment with LPA decreased PPARgamma2 expression, impaired the response of PPARgamma-sensitive genes to rosiglitazone, reduced triglyceride accumulation, and reduced the expression of adipocyte mRNA markers. The anti-adipogenic activity of LPA was also observed in the human SGBS (Simpson-Golabi-Behmel syndrome) preadipocyte cell line, as well as in primary preadipocytes isolated from wild type mice. Conversely, the anti-adipogenic activity of LPA was not observed in primary preadipocytes from LPA(1) receptor knock-out mice, which, in parallel, exhibited a higher adiposity than wild type mice. In conclusion, LPA does not behave as a potent PPARgamma agonist in adipocytes but, conversely, inhibits PPARgamma expression and adipogenesis via LPA(1) receptor activation. The local production of LPA may exert a tonic inhibitory effect on the development of adipose tissue.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M412585200DOI Listing
April 2005

Vascular cell adhesion molecule-1 (VCAM-1) plays a central role in the pathogenesis of severe forms of vasculitis due to hepatitis C-associated mixed cryoglobulinemia.

J Hepatol 2005 Mar;42(3):334-40

INSERM U387, Hôpital Sainte-Marguerite, 270 Boulevard Sainte-Marguerite, 13009 Marseille, France.

Background/aims: To better characterize the molecules involved in leukocyte tissue infiltration during hepatitis C-mixed cryoglobulinemia (HCV-MC)-associated vasculitis.

Methods: The involvement of ELAM, ICAM-1 and VCAM-1 was evaluated in 36 patients with HCV-MC vasculitis using three different approaches: concentrations of soluble forms by specific ELISA, tissue expression by immunohistochemistry on patients nerve biopsies, endothelial expression by FACS analysis, on cells activated in vitro by cryoprecipitates purified from HCV-MC patients.

Results: Concentrations of sVCAM-1 were significantly elevated in the serum of HCV-MC patients compared to HCV patients without MC, the highest concentrations being found in severe vasculitis. VCAM-1 expression was detected on blood vessels from nerve biopsies performed in patients with severe vasculitis. When added to endothelial cells in vitro, HCV-MC patients cryoprecipitate induced VCAM-1 but also ELAM and ICAM-1 expression possibly through a mechanism due to the C1q complement fraction interaction with endothelial cells, since C1q was consistently present in the cryoprecipitates.

Conclusions: VCAM-1 is mainly involved in the pathogenesis of HCV-MC-associated severe vasculitis and may be a potential interesting therapeutic target.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jhep.2004.11.034DOI Listing
March 2005

Platelet-derived lysophosphatidic acid supports the progression of osteolytic bone metastases in breast cancer.

J Clin Invest 2004 Dec;114(12):1714-25

INSERM, U403, 69372 Lyon Cedex 08, France.

The role of lysophosphatidic acid (LPA) in cancer is poorly understood. Here we provide evidence for a role of LPA in the progression of breast cancer bone metastases. LPA receptors LPA(1), LPA(2), and LPA(3) were expressed in human primary breast tumors and a series of human breast cancer cell lines. The inducible overexpression of LPA(1) in MDA-BO2 breast cancer cells specifically sensitized these cells to the mitogenic action of LPA in vitro. In vivo, LPA(1) overexpression in MDA-BO2 cells enhanced the growth of subcutaneous tumor xenografts and promoted bone metastasis formation in mice by increasing both skeletal tumor growth and bone destruction. This suggested that endogenous LPA was produced in the tumor microenvironment. However, MDA-BO2 cells or transfectants did not produce LPA. Instead, they induced the release of LPA from activated platelets which, in turn, promoted tumor cell proliferation and the LPA(1)-dependent secretion of IL-6 and IL-8, 2 potent bone resorption stimulators. Moreover, platelet-derived LPA deprivation in mice, achieved by treatment with the platelet antagonist Integrilin, inhibited the progression of bone metastases caused by parental and LPA(1)-overexpressing MDA-BO2 cells and reduced the progression of osteolytic lesions in mice bearing CHO-beta3wt ovarian cancer cells. Overall, our data suggest that, at the bone metastatic site, tumor cells stimulate the production of LPA from activated platelets, which enhances both tumor growth and cytokine-mediated bone destruction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1172/JCI22123DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC535068PMC
December 2004