Hyperhomocysteinémie Homocystinurie maladie métabolique maladie conjonctive

  • Upload
    alyssa

  • View
    67

  • Download
    2

Embed Size (px)

DESCRIPTION

Hyperhomocysteinémie Homocystinurie maladie métabolique maladie conjonctive. Erreur innée Macromolécule conjonctive. Erreur innée Métabolisme. Remodelage tissulaire. dégradation. synthèse. Hyperhomocystéinémies. hyperhomocystéinémie. modérée. intermédiaire. sévère. homocystinurie. - PowerPoint PPT Presentation

Citation preview

  • Hyperhomocysteinmie Homocystinurie

    maladie mtabolique

    maladie conjonctive

  • Erreur inne

    MacromolculeconjonctiveErreur inne

    MtabolismeRemodelage tissulaire

    synthsedgradation

  • Hyperhomocystinmies80mol/L30015204060modresvrehomocystinurieAsymptomatiqueFacteur de risque vasculaireSymptomatologie svreComplicationsintermdiairehyperhomocystinmie100

  • EtiologiesHyperhomocystinmies Dficits enzymatiques

  • EtiologiesDficit en CBSHomozygote: trs svre B6-sensibleB6-rsistantHtrozygote: modre, discrteDficit en MTHFRHomozygote: svre Htrozygote: modre

    Dficit mthylation B12intermdiaireHyperhomocystinmies Dficits enzymatiques5,10-methyleneTHFMTHFRHcyMetSAMSAHcystathionineCysCBSSerHserTHF5-MeTHFXMe-XMSSerGlyB6B12B6proteinesXXX

  • EtiologiesHyperhomocystinmies Dficits vitaminiquesFolates, B6, B12,

    Insuffisance Rnale Chronique

    Facteurs iatrognes- Antifoliques Mthotrexate, anticonvulsivants, Sulfasalazine- Anti B6Isoniazide, Procarbazine, Cyclosrine, Azauridine- Inhibiteur MS protoxyde dazote- Oestroprogestatifs

    Excs dapport en mthionine ?

  • Modles animauxHyperhomocystinmies CBS -/-survie limite+/-avec rgime riche en Met

    MTHFR +/- Modles gntiques Modles dittiquesRgimes riches en Metpoulet pendant la croissancerat adulteporc adulte

  • SymptomatologieHomocystinurie Lsions oculairesEctopie du cristallin : infrieureMyopieLuxation du cristallin

    Diagnostic diffrentielMaladie de Marfan : ectopie suprieure ou externe

  • Lsions squelettiques et musculairesAspect marfanodeTaille leveExtrmits longues et finesArachnodactylieGenu valgumDformation du sternumOstoporoseScolioseHypotonie musculaireSymptomatologieHomocystinurie

  • Lsions vasculairesArtriosclroseAthrothrombose Atteintes neurologiquesRetard mental Autres Lsions cutanes, peau fine, pores largiesDpigmentationPneumothorax

    SymptomatologieHomocystinurie

  • maladie mtabolique

    maladie conjonctiveRemodelages de la paroi artrielleCliniqueHistologique ?Biochimique ?

  • Homocystinurie Remodelage matricielHistological examination showed spectacular alteration of elastic structure in arteries from homocystinuric human extracellular matrix deposition, elastica degeneration, smooth muscle cell hyperplasia, and fibrosis. (Gibson. 1964).

    The arteriosclerotic plaques occuring in homocystinuria, whether caused by CBS deficiency, methyl transferase deficiency, or MTHFR deficiency, are typical fibrous plaques, characterized by smooth muscle cell hyperplasia, deposition of extracellular matrix and collagen, and degeneration and destruction of elastic fibers. (McCully, 1983)

  • Porcs adultesHyperhomocysteinemieCoronaireOrcein stained 6 m transverse sectionControlehyperhomocysteinemie (x 2) AtheroscleroseEvnement prcoce (4 mois)majeur (~50 %)Rgime riche en MetHyperhomocystinmie modre Dgradation des structures lastiques artrielles

  • Dfaut des structures lastiques artrielles - consquences tissulairesSouris KO elastine (-/-)

    proliferation et migration SMCs

    formation neointimastenose(DY. Li, 2002)Fenestration

    SMCs migration

    Hyperhomocysteinemie

    proliferation SMCs

    paississement intimal

  • Dfaut dassemblageDgradation des structures lastiques?Lhyperhomocysteinemie induit une dgradation majeure des structures lastiquesqui peut acclrer le dveloppement de lathrosclrose

  • Composantamorphe:lastinemicrofibrillesfibrilline-1, -2MAGPfibuline-1, -2Fibre lastiqueStructures elastiques

  • FibrillinesIn vivo : embryon de pouletFib sans dfaut des structures lastiques (Boot. 2004)poulet en croissance :Fib dfaut structures lastiques (Hill. 2002)In vitro : Fib-1 : dfaut de repliement domaines EGF (2005) Fib-1 : dysfonction ( calcium binding, Hubmacher. 2005) Proteoglycansaggregation perturbation interactions (McCully. 1993) Synthse et rticulation lastine : observations contradictoiresFibres lastiques anormalesHyperhomocysteinemie et lastogense

  • Porcs + rgime riche en Met : fenestration des lames lastiques contenu en lastine aorte abdominale et coronaire (Charpiot. 1998) Souris ApoE -/- mice + rgime riche en Met (Hoffman. 2001) elastolyse dans aorteDegradation structures lastiques artriellesIn vivo, animal adulte Rats + rgime riche en Met (Zulli. 1995) disparition des lames lastiques aorteHyperhomocysteinemie dgradation des structures lastiques

  • Hyperhomocysteinemia induces a major degradation of the elastic structure in full grown arteries

    Proteolytic breakdown ?

  • Porc + rgime riche en Met Elastin content (Vv, %) 12ControlHyperhcy048*CH10 M100 MHcy50 m04810100M Hcy*72 hHyperhomocysteinemiemodre4 moisIn vivoEx vivoCulture dexplants artriels + Hcy Aorte abdominaleProcessus ElastolytiqueAorte abdominale

  • *040Specific elastolytic activity (AU / mg protein)10100M Hcy+Phe101001002000*CHCH+Phe+Phe (phenanthroline)Inhibiteur de metalloproteinasesProcessus ElastolytiquePorc + rgime riche en Met 72 hHyperhomocysteinemiemodre4 moisIn vivoEx vivoCulture dexplants artriels + Hcy Aorte abdominaleAorte abdominale

  • Elastin content (Vv, %) 1210 M100 MHcy04810100M Hcy*100 M + GM6001100 + GM6001GM6001, inhibiteur large spectre des MMPs previent la degradation structurale induite par HcyProcessus Elastolytique MMP-dpendant

  • MMP-9MMP-2Gelatin-zymographie72 kDa -68 kDa -92 kDa -TIMPs26 kDa -22 kDa -TIMP-1TIMP-2Reverse zymographie- 92 kDa- 72 kDa- 68 kDaWestern BlotSpecific activity (AU / mg protein)Balance MMP/TIMP10 50 100 M Hcy MMP-2 et MMP-9 lastolytiques

    Inhibiteurs tissulaires inchangs

  • In vivo, the degradation of the arterial elastic structures induced by hyperhomocysteinemia is more marked in the inner part of the media.- In vivo in human(Mc Cully. 1983) ...disruption of the elastic laminae, usually more marked toward the innermost elastic membrane,

    - In vivo in animal(Charpiot. 1998)Haemodynamic strains ?Endothelium ?Hyperhomocysteinemie dgradation des structures lastiques

  • 10 M100 MHcy50 m6 m transverse section. (+) catechine- stained elastic structureEx vivo, explants arteriels en culture + homocysteine

    mediaHyperhomocysteinemie dgradation des structures lastiques

  • Hyperhomocysteinemia induces a major degradation of the elastic structure in full grown arteries

    Localization ?

    mediated by MMPs/TIMPs imbalancein favour of elastinolytic MMP-2 and MMP-9

  • MMP -2MMP-9Hcy6 m transverse sections expression MMP-2 et MMP-9 dans la partie interne de la mdiaMMPs Expression tissulaire mediaHyperhomocysteinemie dgradation des structures lastiquesImmunohistochimie

  • HcyTIMPs Expression tissulaire Hyperhomocysteinemie dgradation des structures lastiquesTIMP -1TIMP-2expression et distributionTIMP-1 et TIMP-2 inchanges 6 m transverse sectionsImmunohistochimie

  • contribution of endothelium?mediated by MMPs/TIMPs imbalance, in favour of elastinolytic MMP-2 and MMP-9,more marked in the inner part of the media, even ex vivoHyperhomocysteinemia induces a major degradation of the elastic structure in full grown arteries

  • Gelatin Zymography72 kDa -MMP-2***1002000***100200092 kDa -Activity (%)Activity (%)MMP-9(Lamy. 2004)Potentiel protolytique des cellules endothliales

  • -Casein Zymography1050100M Homocysteine25027 kDa -Potentiel protolytique des cellules endothliales

  • HyperhomocysteinemieProblme mtaboliqueActivation de systmes protolytiques- dsquilibre MMPs/TIMPs : MMP-2, MMP-9- serine protease(s?) activatrice de MMPsDgradation des structures lastiques artriellesArtriosclrose, athrosclrosemtabolismeremodelageclinique

  • Hyperhomocysteinemie induit une dgradation majeure induces a major elastic structure degradation,facilitating the development of atherosclerosis,mediated by MMPs/TIMPs imbalance, in favour of elastinolytic MMP-2 and MMP-9,more marked in the inner part of the media.Endothelial cells may participate through- elastinolytic MMPs : MMP-2 and MMP-9- MMPs activating serine proteases : hK1

  • Atteinte structures lastiques artre, cristallin (?), peau (?)

    Elastolyse vs dfaut dlastogense dans:- hyperhomocysteinemies acquises- hyperhomocysteinemies innes

    dfaut dassemblage des fibres lastiques sensibilit la dgradation protolytique ? expression/activit des MMPs ?

    Et les collagnes ?os, artre, peau (?)

    Hyperhomocystinmie Remodelage matriciel

  • Laboratoire de Physiopathologie des Tissus non Minraliss Facult de Chirurgie Dentaire Universit Ren Descartes MontrougeLaboratoire de Biochimie UMRs-608. Facult de Pharmacie Universit de la Mditerrane. Marseille.Thierry AugierAndr BarlatierAlexandrine BertaudRaymond CalafClaire CeriniCorinne ChareyreEdouard LamyCcile GenovesioPhilippe CharpiotGaston GodeauSylvie Igondjo-TchenKarim Senni

    First, a few word on homocysteine which is a thiol containing amino acid formed during the metabolism of methionine and is not constitutive of the structural backbone of proteins. Physiological, homocysteine (it) is found in plasma at concentration lower than 15 M. Over 15 M, we speak of mild hyperhomocysteinemia between 15 and 40 M, highhyperhomocysteinemia between 40 and 80 M and severe hyperhomocysteinemia often found in homocystinuria wich is the major form of hyperhomocysteinemia.A possible relation between homocysteine and atherosclerosis has emerged with the earliest descriptions in the 60s of homocystinuria. Indeed, homocystinuric children who were mentally retarded and displayed marphanod syndrome with abnormalities of the connective tissues, had severe and premature (atherothrombotic disease) vascular accident that often lead to death before adulthood.Following these observations, many epidemiological and clinical studies were conduced and evidenced that even moderate hyperhomocysteinemia is as a risk factor for atherosclerosis.The physiopathological processes by which homocysteine could promote atherosclerosis are not fully elucidated. Several mechanisms are currently investigated. One of these mechanism is the destruction of the elastic laminae that was first described by Mc Cully in arteries from homocystinuric patients. he described very early the alteration of extracellular matrix in arteries from homocystinuric child.The former observations reported fibrosisdeposition of collagen, proteoglycanesdegradation of the elastic structuresConsidering the whole matrix is a too large topic for this talk, I would like to foccus mainly on the last point : the degradation of elastic structure which was observed in many different models of hyperhomocysteinemia

    Here are the results in minipig 1. The degradation induced by a dietary induced hyperhomocysteinemia was characterized by a decrease in elastin content andthe opening of gaps,called fenestrae, in the elastic laminae 2. such a defect was also found again all over the atherosclerotic arteries 3. This event is early 4 This is an important event: from a quantitative point of vue, the decrease in elastin content was up to 50% in coronary arteriesMoreover,

    This is also importatnt due to the phenotypic and tissue consequencesThe increased fenestration open pathways through the elastic laminae, such as during aging.This allows SMCs migrationMoreover, the lack of structuration af the arterial wall in elastin deficient mice resulted in proliferation and migration of SMCs, then intimal thickening and stenosisAnd hyperhomocysteinemia is also known to induce SMC hyperplasia and intimal thickening

    All together this is believed to accelerate the developpement of arterio-atherosclerotic lesionsThis lead to the next question

    Is it a defect in the assemblyOr a degradation of the elastic structureRemember that the elastic fiber is composed of a core of elastin associated with mifibrilles, mainly fibrilline-1 and some other glycoproteinsSeveral processes occure in the assembly of the elastic fiber and in the association of fibers to form the laminae You know the former hypothesis about a defect of the crosslinking of elastin. There is some conflicting observationsAnyway may be this occurs during the formation of elastic laminae in growing arteries, but this is not sufficisant in full grown arteries, due to the very low turn over of elastin

    Fibrillins were shown to be a target for homocysteine. A defect in fibrillin, quantitative defect or misfolding or dysfunction could led to abnormal arterial elastic structure (but in a different way than in Marfan syndrom)

    Proteoglycans are also involved in elastic fiber formation an abnormal aggregation of proteoglycans (in culture of fibroblasts from homocystinuric pati ents) could disturbe the elastic fiber formation On another hand, in full-grown arteries the elastin defect was described as a degradation process.This was observed inanimals fed a met-rich diet:apoE deficeint miceas well as ratsas well as pigsTo investigate this point we developped an exvivo model reproducing the alteration observed in vivo in pigsprevent

    The destruction of the elastic structure is more marked in the inner part of the media, even in culture free from haemodynamic strains(the microphotographs represent the inner half of the media)What about MMPs ans TIMPs?The expression of MMP-2 and -9 was increased in the innerpart of the mediawhereas timp expression was nearly unchangedFor this study we cultured arterial explants with physiopathological concentrations of homocysteine. We choose this ex vivo model because :It maintains cell-matrix interaction contrary to cell cultureIt make it possible to control homocysteine concentrations used in experiment which is difficult with in vivo modelAnd lastly its a model free of haemodynamic strainsIn practice, we cultured 5-mm segments of pig abdominal aorta in NCTC medium during 48 hours with physiopathological concentrations of homocysteine going from physiological homocysteinemia with 10 M to severe hyperhomocysteinemia with 100 M. First it is necessary to confirm th key role of MMPs in the arterial elastic degradation in vivo, by using MMPs inhibitors in Hhcy animals

    2nd pointWhat are the respective relevance of on one hand elastolysis and on the other hand elastogenesis defect

    The hcy-induecd misfolding of Fib-1 led to an increased sensitivity of Fib to proteolysis

    Could induce an increased expression or activity of MMPs, as shown in most of the inherited elastopathies.