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RESUME C’est le but que s’etait fixe le groupe de travail de l’Academie nationale de medecine compose de sept membres sous la direction de Rene Mornex pour essayer d’obtenir une medecine sobre qui dans une approche humaniste soigne mieux au moindre cout. Vingt-six auditions de diverses personnalites essentiellement medicales (soit internes soit externes a l’Academie), mais aussi administratives, ministerielles, ou institutionnelles sont venues nourrir, critiquer, ou renforcer nos propres reflexions, qui s’appuyaient aussi sur les 7 rapports ou communiques precedemment produits et diffuses par notre Academie. La premiere partie a consiste a faire un etat des lieux qui a permis de constater que si la connaissance des recommandations des bonnes pratiques edictees par l’HAS etait bonne, leur application ne l’etaient pas, raisons de nombreuses derives, pour les bilans de sante, pour les depistages de masse (exemple PSA), pour les examens biologiques trop souvent reclames « en bloc », ou d’imagerie legere (comme l’echographie) ou lourde (Scanner, IRM) trop souvent utilisee en premiere ligne devant une pauvrete voire une absence de l’examen clinique. Ces derives pouvaient s’etendre aux prescriptions medicamenteuses, voire aux actes chirurgicaux a la mode souvent permis par l’acces direct au chirurgien sans intermediaire medical ou paramedical. L’etude des responsabilites retrouve la modification des conditions d’exercice avec la presence de plus en plus frequente de l’ecran d’ordinateur s’interposant entre praticien et patient qui ne favorise ni l’interrogatoire ni l’examen clinique. Mais aussi l’activite medicale est sensibilisee de plus en plus par le principe de precaution et le risque de judiciarisation, facteurs declenchant les prescriptions larges « pour se couvrir », temoin en realite d’une attitude defensive deletere, illusoire et inefficace, comme l’ont montre nos auditions assurancielles ou juridiques. Bien sur enfin l’environnement societal par la voix envahissante des medias souvent irresponsables vis-a-vis du patient mais favorisantes pour le consumerisme medical et l’exigence de rapidite exigee par le malade aussi bien pour le diagnostic ou la therapeutique. Les pistes d’ameliorations devront 1 : d’abord se tourner vers l’enseignement de la medecine avec en particulier une reforme serieuse et complete du 2e cycle de la formation initiale du medecin. La segmentation extreme cree par la succession des « certificats de specialites » n’aboutit qu’a une succession d’assimilationregurgitation qui gene non seulement la prise en compte globale du malade mais aussi la memorisation de la semiologie de base et son integration dans l’ensemble du malade ne favorisant pas du tout les choix strategiques des examens complementaires biologiques ou d’imagerie, pas plus que les orientations therapeutiques. L’enseignement clinique doit se faire sur une duree plus longue que les 3 mois actuels avec des enseignements transversaux y compris la pharmaco therapeutique quasiment inexistante. Surtout une evaluation a intervalles reguliers devrait permettre ou non de se presenter au fameux Examen Classant National qui actuellement est le seul but des etudiants en Medecine qu’ils preparent en « bachotant », qui est rempli de lacunes (pas de points negatifs, pas de question sur la strategie diagnostique, pas plus que de questions sur avantages/inconvenients de telle ou telle therapeutique, etc.) D’ou une refonte complete de cet examen classant s’impose. La formation medicale continue, avancee considerable, doit etre revue pour la rendre encore plus efficace en la sortant si possible de plus en plus independante ou controlee vis-a-vis des marketings commerciaux. 2 : Le developpement des recommandations de bonne pratique clinique, souvent coordonnee par l’HAS, est une bonne chose et sont consultes mais souvent avec des textes trop longs de sorte qu’ils sont peu appliques. Ils ne devraient pas depasser 2 pages et donner surtout des indications de cadrage de la pathologie rapportee. 3 : L‘organisation des soins doit tourner de plus en plus vers le parcours de soins et le regroupement des competences aussi bien publiques que privees, avec le developpement des reseaux regionaux, bases sur l’auto adhesion, la reconnaissance par le praticien lui-meme de ses limites de competence medicale et de plateaux techniques. Ceci realise vraiment la strategie pertinente pour chaque pathologie et chaque patient. Les Reunions de Concertation Pluridisciplinaires (RCP) obligatoires pour les pathologies du Cancer en sont aussi un bon exemple si elles gardent un caractere impartial et humain en y incluant fortement le medecin traitant. L’imagerie medicale meriterait une telle reorganisation ou le choix de l’imagerie pertinente reviendrait a l’imageur lui-meme. De meme a l’exemple de plusieurs pays d’Europe, les centres charges des pathologies lourdes devraient etre en nombre limite repartis sur tout le territoire national en accord inter-regional avec les diverses ARS. Les exemples des Instituts de cancerologie dans certains pays ou des « traumas centers » dans d’autres meriteraient d’etre examines. Le mode de financement « dit a l’activite » (T2A) facteur de glissements nefastes et dans les indications et dans les actes, doit etre revu pour valoriser la pertinence et la qualite. Par ailleurs la remuneration des activites medicales devraient valoriser l’acte intellectuel par rapport a l’acte technique ce qui est l’inverse de l’etat actuel, avec les 3 leviers dont pourrait disposer la CNAM : Nomenclature, Entente prealable, Controles avec pour ces derniers l’utilisation d’interlocuteurs adaptes, plus âges, plus experimentes, plus specialises. La pertinence des strategies medicales est une caracteristique essentielle du bon exercice de la medecine. Sous la responsabilite totale des medecins, etat d’esprit, synonyme de qualite et de securite, s’enseigne par compagnonnage, evolue constamment, n’entrave pas les innovations, tout en realisant une efficience economique en ameliorant la qualite des soins respectant les droits fondamentaux du patient.

RESUME En depit des efforts deployes pour favoriser le don d’organes, la penurie persistante est prejudiciable aux malades en attente de transplantation. Depuis 1968 et jusqu’a present, le prelevement a ete limite aux donneurs a coeur battant en etat de mort cerebrale. Dans le sillage des experiences etrangeres, la loi francaise a ouvert depuis aout 2005 une voie nouvelle, celle des « decedes presentant un arret cardiaque et respiratoire persistant » autorisant le prelevement « des reins et du foie ». Dans cet esprit, l’Agence de la biomedecine a soumis a notre groupe de travail un protocole de prelevement dont l’expertise est ici proposee. Les donneurs potentiels sont des victimes d’accidents, de suicides, d’anoxies ou d’hemorragies cerebrales en arret cardiaque irreversible, rebelle a toutes les tentatives de reanimation. Ils repondent a trois des quatre groupes de la classification de Maastricht (la categorie III, celle de l’arret programme des soins, est exclue du protocole). Le prelevement obeit aux memes regles juridiques : consultation du registre des refus, entretien avec les familles confirmant la non-opposition du defunt. Dans le cas contraire, la loi indique qu’ « il est mis fin aux mesures prises pour assurer la conservation des organes » (Ces mesures doivent avoir ete mises en route en urgence pour parer a la souffrance des organes soumis a une ischemie chaude). Dans une premiere etape, l’Agence de la biomedecine a prevu de se limiter a la transplantation renale. Neuf centres francais ont souscrit au protocole et ont ete agrees. Il s’agit donc d’une experience pilote concue avec prudence comme un gage de securite dans la perspective d’une extension ulterieure. Les publications des equipes etrangeres font etat de resultats comparables a ceux des transplantations effectuees a partir des donneurs classiques. En conclusion, le groupe de travail considere que cette initiative merite d’etre encouragee car elle est susceptible de diminuer la regrettable penurie d’organes qui penalise les nombreux patients qui demeurent en attente de transplantation.

RESUME Le diagnostic permet de reconnaitre une maladie pour en assurer une prise en charge appropriee. Le diagnostic, element essentiel de la decision medicale, releve de la responsabilite du medecin. Le concept remonte aux origines de la medecine, la rationalite de la demarche diagnostique s’est enrichie au cours des deux derniers siecles des apports de la science. Le schema selon lequel le diagnostic est issu du recueil et de la hierarchisation des symptomes et des signes cliniques, confirme et precise par les examens complementaires doit etre garde en memoire comme un principe fondamental. L’elaboration du diagnostic beneficie de nombreuses innovations. Elles concernent les moyens techniques disponibles (biologie, imagerie) et les nouvelles methodes pour tirer partie des donnees (statistiques, algorithme). Le developpement des moyens de diagnostic impose de nouvelles responsabilites aux medecins : renouvellement des connaissances exigeant une formation continue efficace, bon usage des moyens disponibles imposant l’evaluation des pratiques professionnelles. La mise en oeuvre du diagnostic doit tenir compte de l’evolution de la societe : le malade et son entourage demandent a etre consideres comme des partenaires. L’information du malade, meme si elle doit etre nuancee en fonction des circonstances, est une obligation. Le public n’admet pas l’erreur diagnostique, le developpement des plaintes en resulte. Il faut que les medecins soient avertis et prepares a cette situation. On doit considerer a part le role du diagnostic dans la decision medicale en situation d’urgence. Si on s’aventure a prevoir l’evolution, on retient : la recherche d’investigations non traumatisantes, le role de l’informatique dans la diffusion des connaissances, l’influence de la telemedecine dans l’organisation sanitaire, l’influence des associations de malades notamment dans la prise en charge des maladies rares.

Background: In membranous nephropathy, the development of glomerular lesions is related to the formation of immune complexes at subepithelial sites. These deposits are associated with modifications in the fibrinolytic activity of glomerular cells leading to the appearance of fibrin degradation products in the deposits and the urine. A previous study has shown that immune complexes interact with glomerular epithelial cells (GEC) through the neonatal Fc receptor (FcRn). We therefore determined whether this binding could be responsible for a modification in the fibrinolytic activity of GEC. Methods: Endocytosis of heat-aggregated immunoglobulins (AgIgG) in cultured human GEC was studied by immunofluorescence and confocal microscopy. The release of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor 1 (PAI) by GEC or whole glomeruli was assessed by ELISA, fibrin zymography and Northern blot. Results: Human GEC in culture bound AgIgG that possess characteristics similar to soluble immune complexes and internalized them by 10 min. This process was mediated by FcRn since chicken aggregated IgG (AgIgY), that do not bind FcRn, did not colocalize with AgIgG in GEC. AgIgG but not AgIgY induced a decrease of FcRn expression at the membrane and within the cells. The binding of AgIgG to GEC elicited a dose- and time-dependent increase in the release of uPA activity, as in the uPA protein and mRNA expression without modification in the release of PAI. This process was not abrogated by agents inhibiting endocytosis and/or transcytosis such as cytochalasin B, suggesting an endocytosis-independent uPA regulation. Conclusion: GEC response to AgIgG overload comprises at least two sequential steps: (1) a FcRn-mediated endocytosis; (2) an endocytosis-independent fibrinolytic imbalance leading to plasmin generation which could favor in vivo AgIgG clearance and matrix remodeling.

Regulation of growth-hormone-receptor gene expression by growth hormone and pegvisomant in human mesangial cells.BackgroundMice transgenic for growth hormone develop mesangial proliferation, glomerular hypertrophy, and progressive glomerular sclerosis suggesting that the growth hormone–insulin-like growth factor I (IGF-I) pathway plays an important role. Therefore, we studied the impact of variable concentrations of 22 kD, 20 kD growth hormone, as well as of the growth hormone receptor antagonist pegvisomant (B2036-PEG), on both the growth hormone receptor (GHR/GHBP) gene expression and growth hormone binding protein (GHBP) formation in a human glomerular mesangial cell line. Further, the impact on collagen, IGF-I and IGF binding protein-1 (IGFBP-1) formation was studied.MethodsIn order to assess transcription, quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used.ResultsPhysiologic doses of 22 kD or 20 kD growth hormone caused a dose-dependent and significant (P < 0.01) up-regulation of GHR/GHBP gene transcription, whereas supraphysiologic doses (50 and 500ng/mL) resulted in down-regulation (P < 0.001). Whenever pegvisomant was used, there was no increase in GHR/GHBP expression. These data were confirmed using run-on experiments. Further, the assessment of GHBP presented a constant, dose-dependent increase, which was completely abolished in the experiments where pegvisomant was used.ConclusionWe present data showing that growth hormone has a direct impact on GHR/GHPB gene transcription and that pegvisomant is a potent growth hormone receptor antagonist in human mesangial cells. In addition, although the GHR/GHBP gene transcription is down-regulated by supraphysiologic growth hormone concentrations, this effect was not found when GHBP levels were measured. This finding may reflect a self-inhibitory effect of growth hormone on the level of GHR/GHBP gene transcription, which does not involve the regulation of the shedding of GHBP and may, therefore, be of physiologic interest.

The renin-angiotensin system plays a major role in the control of blood pressure and of salt balance, but it is also involved in physiological and pathological processes, development, inflammation and cardiac hypertrophy. A concept has emerged suggesting that these effects are due to a local activation of the renin-angiotensin system. The search for a receptor of renin was based on the idea that tissue (pro)renin is taken up from the circulation and on data suggesting that renin has cellular effects independent of angiotensin II.Endothelial cells and cardiac myocytes bind (pro)renin via the mannose-6-phosphate receptor, mainly a clearance receptor as no cellular effect has been specifically attributed to prorenin binding. A functional receptor was cloned recently. It mediates intracellular signalling by activating the mitogen activated protein kinases, extracellular signal regulated kinases 1 and 2, and acts as a co-factor by increasing the efficiency of angiotensinogen cleavage by receptor-bound (pro)renin. The receptor is abundantly expressed in heart, brain, placenta and eye, compared with a lower expression in liver and kidney. In normal human kidney and heart, it is localized in the mesangium and in the coronary and kidney artery, associated with smooth-muscle cells and co-localized with renin.This receptor provides a functional role for prorenin and may help to understand the physiological and pathological role of elevated levels of prorenin and of local activation of the renin-angiotensin system. From a practical point of view, it questions the need for a pharmacological compound blocking (pro)renin binding and activity as an alternative to the classical inhibitors of the renin-angiotensin system.

Background. Haemolytic uraemic syndrome (HUS) is a rare and severe disease of various aetiologies in adults. The effect of fresh frozen plasma (FFP) infusion in adults suffering from HUS is not well defined. The aim of this retrospective study was to analyse the causes of HUS in adults admitted in a single renal intensive care unit (ICU) and to determine the life and renal prognosis factors, while most patients (78%) received FFP infusion. Methods. We recorded clinical, biological, and histological data of 55 adults admitted in our renal ICU for HUS between 1990 and 1998. 49 of them having had a renal biopsy. By stepwise logistic regression analysis, we examined the parameters that were associated with the in-hospital mortality and renal function at discharge. Results. HUS complicated different diseases in 40 patients (HIV infection n = 18, nephropathies n = 10, allotransplantation n = 7, malignant diseases n = 5) and appeared as a primary in 15 patients. Factors influencing the in-hospital mortality were positive HIV serology (odds ratio (OR) >20, P=0.0002) and requirement for haemodialysis (OR >35, P = 0.004). A pre-existing nephropathy was a bad prognosis factor for renal function (OR >99, P = 0.02), while fever was associated with better renal prognosis (OR = 1 10, P = 0.033). Conclusions. HUS in adults remains a severe disease, with a high mortality rate in HIV patients and in those who required haemodialysis. However. as compared with previous studies, we observed an improvement in renal outcome, particularly in patients with primary HUS, suggesting a beneficial effect of FFP infusion, at least in these forms.

Renin is an aspartyl protease essential for the control of blood pressure and was long suspected to have cellular receptors. We report the expression cloning of the human renin receptor complementary DNA encoding a 350-amino acid protein with a single transmembrane domain and no homology with any known membrane protein. Transfected cells stably expressing the receptor showed renin- and prorenin-specific binding. The binding of renin induced a fourfold increase of the catalytic efficiency of angiotensinogen conversion to angiotensin I and induced an intracellular signal with phosphorylation of serine and tyrosine residues associated to an activation of MAP kinases ERK1 and ERK2. High levels of the receptor mRNA are detected in the heart, brain, placenta, and lower levels in the kidney and liver. By confocal microscopy the receptor is localized in the mesangium of glomeruli and in the subendothelium of coronary and kidney artery, associated to smooth muscle cells and colocalized with renin. The renin receptor is the first described for an aspartyl protease. This discovery emphasizes the role of the cell surface in angiotensin II generation and opens new perspectives on the tissue renin-angiotensin system and on renin effects independent of angiotensin II.

Our previous study demonstrated that the GR is expressed in the human kidney glomerulus. The function of the GR of glomerular cells might be affected by the concentration of intracellular glucocorticoids, which is modulated by 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2). Because the expression of 11betaHSD2 in the glomerular cells remains unclear, we used competitive RT-PCR and immunoblotting to detect the expression of 11betaHSD2 mRNA and protein in isolated human glomeruli, in whole kidney cortex as a positive control, and in a human glomerular visceral epithelial cell line. 11betaHSD2 mRNA was detected in all samples. Specific antihuman 11betaHSD2 antibody recognized a single band at 41 kDa, consistent with the molecular mass of human 11betaHSD2, in the samples of the isolated glomeruli and whole kidney cortex. Furthermore, definite 11betaHSD2 enzymatic activity was also determined with the sample of isolated glomeruli. We also performed immunohistochemistry by light and electron microscopy to determine the cellular and subcellular localization of 11betaHSD2 in the human glomeruli. Immunoreactivity of the enzyme was clearly observed in the glomerular visceral epithelial cells and endothelial cells as well as in the distal convoluted tubules and collecting ducts. The subcellular localization of 11betaHSD2 was shown to be endoplasmic reticulum. These results suggest that 11betaHSD2 might play a crucial role in modulating the intracellular concentration of glucocorticoids in human glomerular cells.

Le role des proteases et des antiproteases dans la progression de l’insuffisance renale chronique a ete bien documente. La plupart des etudes ont concerne la plasmine et les activateurs du plasminogene de la famille des serine-proteases, et les metalloproteases matricielles. Recemment, l’attention s’est portee sur la renine, une aspartyl-protease. La renine est une enzyme essentielle du systeme renine angiotensine et le clivage de l’angiotensinogene en angiotensine I est l’etape limitante de la generation d’angiotensine II (Ang II), puissant peptide vaso-actif egalement implique dans les processus de fibrose renale. Notre groupe vient de cloner un recepteur fonctionnel de la renine. La fixation de la (pro)renine est associee a deux evenements majeurs : d’une part, l’augmentation de l’activite catalytique de la (pro)renine pour son substrat l’angiotensinogene, d’autre part, l’activation des MAP kinases ERK1/2 (Extracellular Regulated Kinases) dont on connait le role dans les processus de differenciation, d’hypertrophie et de proliferation cellulaires. L’analyse immunohistochimique de coupes de cœur et de rein humains normaux montre que le recepteur de la renine est trouve dans les arteres coronaires et renales, ainsi que dans les glomerules, associe aux cellules musculaires lisses vasculaires et aux cellules mesangiales glomerulaires. Dans les cellules musculaires lisses, la conversion de l’angiotensine I en Ang II serait plus efficace du fait de la proximite de l’enzyme de conversion membranaire et les effets biologiques seraient optimises, l’Ang II etant generee au voisinage des ses recepteurs. L’analyse par Northern blot indique que l’ARN messager du recepteur est tres abondamment exprime dans le cœur, le cerveau et le placenta, et a un moindre degre dans le rein, le foie et le pancreas.

The urokinase receptor (uPAR) is a multifunctional molecule involved in pericellular, fibrinolytic, and proteolytic activities, as well as in cell adhesion and chemotaxis and may play a role in the pathogenesis of tissue remodeling occurring during glomerulonephritis. We analyzed sequentially the expression of uPAR by immunohistochemistry and in situ hybridization in an accelerated model of nephrotoxic nephritis in rats. A strong induction of uPAR mRNA expression was observed in glomeruli as soon as 1 h after nephrotoxic serum injection. The intensity of glomerular uPAR mRNA and antigen expression increased and peaked at 24 h. At that time, numerous glomerular fibrin deposits, monocyte/marcrophage infiltration, and heavy proteinuria were observed. Fibrin deposition was detected at 6 h, peaked at 24 h, and progressively declined over the next 3 weeks, while uPAR antigen expression remained elevated until the end of the study (3 weeks). By double labeling, we showed that the expression of uPAR was mediated by both intrinsic glomerular cells and infiltrating macrophages. Severe podocytic lesions developed within 3 days after antiserum injection, and glomerulosclerosis rapidly progressed within 2–3 weeks. These results show that glomerular uPAR expression is induced in nephrotoxic nephritis and suggest that uPAR may promote local proteolysis and also tissue remodeling, leading to the late development of glomerulosclerosis.

BACKGROUND Plasminogen activator inhibitor type 1 (PAI-1) exerts antifibrinolytic and profibrotic activities. Inside the glomerulus, PAI-1 is mainly synthesized by mesangial cells. We hypothesized that thrombin, via its receptor protease activated receptor type 1 (PAR-1), present on the membrane of glomerular cells, is an important mediator of PAI-1 synthesis. METHODS Using the technique of Peten et al., we microdissected the glomeruli of 23 kidney transplanted patients admitted in our department from 1993 to 1997, and we followed-up these patients for up to 5 years, with sometimes iterative renal biopsies. With this technique, we also microdissected the glomeruli of three patients who have had a nephrectomy for cancer (control patients). We investigated mRNA expression of the PAI-1, the thrombin receptor PAR-1, the alpha2 chain of type IV (alpha2 IV) collagen, and of a housekeeping gene (cyclophilin) by reverse transcription-polymerase chain reaction. The results were correlated with the renal function and the histological findings classified into acute rejection (9 biopsies), chronic rejection (22 biopsies), or normal (8 biopsies). RESULTS A significant up-regulation of PAI-1 and alpha2 IV collagen mRNA was observed in acute rejection (P

Tissue-specific expression patterns of the paired type IV collagen genes COL4A5 and COL4A6 form the basis for organ involvement in X-linked Alport syndrome, a disorder in which these genes are mutated. We investigated the proximal promoter region of COL4A5 and COL4A6 using glomerular visceral epithelial cells, in which COL4A5 alone is transcribed; keratinocytes, in which the genes are co-transcribed; and additional model cell lines. By RNase protection assays, the intergenic region is 292 base pairs. Transcription start sites for two 5' splice variants of COL4A6 are 1 kilobase apart. Transient transfections with reporter gene constructs revealed that the minimal promoters for COL4A5 and COL4A6 are within 100 base pairs of their respective transcription start sites and are functionally distinct. In further transfection, gel shift and footprinting assays, we defined a bidirectional positive regulatory element, which functions in several cell types, but not in glomerular visceral epithelial cells selectively transcribing COL4A5. The existence of separate promoters for COL4A5 and COL4A6 permits fine control over their expression. Activation through the bidirectional element can bring about co-expression of the genes, exploiting their paired arrangement. Features of the proximal promoter region frame its roles in a hierarchy regulating type IV collagen gene expression.

Matrix metalloproteinase 2 (MMP2) has been reported to be secreted by collagen-stimulated platelets, and active MMP2 has been shown to play a role in platelet aggregation. It has been demonstrated that MMP2 activation is dependent on the complex (membrane type 1 [MT1]-MMP/tissue inhibitor of MMP2 [TIMP2]) receptor and MMP2. We have investigated human platelets as a possible source of MT1-MMP, and we have studied its role in MMP2 activation and in platelet aggregation. Gelatin zymograms showed the existence of MMP2 at proforms (68 kd) and activated-enzyme forms (62-59 kd) in supernatants of resting and activated platelets, respectively. No gelatinolytic activity was associated with the platelet pellet after aggregation, suggesting a total release of MMP2 during cell activation. By Western blot analysis in nonreduced conditions, MT1-MMP was found on resting platelet membranes in 2 forms–the inactive 45-kd form and an apparent 89-kd form, which totally disappeared under reduced conditions. After platelet degranulation, only the 45-kd form was detected. Reverse transcription–polymerase chain reaction experiments showed the expression in platelets of messenger RNA encoding for MMP2, MT1-MMP, and TIMP2. Flow cytometry analysis showed that MT1-MMP, MMP2, and TIMP2 expressions were enhanced at the activated platelet surface. MMP inhibitors, recombinant TIMP2, and synthetic BB94 inhibited collagen-induced platelet aggregation in a concentration-dependent manner, indicating the role of activated MT1-MMP in the modulation of platelet function. In conclusion, our results demonstrate the expression of the trimolecular complex components (MT1-MMP/TIMP2/MMP2) by blood platelets as well as the ability of MMP inhibitors to modulate the aggregating response.

Background. Hemolytic uremic syndrome (HUS) is a rare complication in solid organ transplantation. It can be associated with severe hypertension. Several risk factors have been identified including immunosuppressive drugs such as cyclosporin A and, more recently, tacrolimus. Methods. Here we report a case of tacrolimus-induced HUS in a 61-yr-old woman after liver transplantation. Hypertension, microangiopathic anemia and end-stage renal failure occurred 2 yr after liver transplantation. Results. At admission, she had malignant hypertension with a severe hypertensive retinopathy, renal failure (creatininemia: 800 μmol/L) and microangiopathic anemia (Hb: 7.3 g/dL, a low platelet count and elevated lactate dehydrogenase). At renal biopsy, histologic findings were ischemic and sclerotic glomeruli with hyaline thrombi, severe mesangiolysis and interstitial fibrosis. Conclusion. Despite steroid treatment, antihypertensive agents and fresh frozen plasma therapy, end-stage renal failure was observed and chronic hemodialysis treatment was required.

Objective: To determine the epidemiological trends, spectrum of etiologies, morbidity and mortality of acute renal failure (ARF) in patients over 80 years old.¶Design: Historical cohort analysis.¶Setting: Intensive care unit (ICU) of nephrology, Tenon Hospital, Paris.¶Patients and participants: The criteria of inclusion was ARF, defined on the basis of a creatinine value over 120 μmol/l, in patients over 80 years of age admitted between October 1971 and September 1996. When moderate chronic nephropathy was pre-existing, ARF was defined by the increase of at least 50 % over the basal creatininemia.¶Measurements and results: Three hundred and eighty-one patients over 80 years of age were included. The etiology and mechanism of ARF are detailed. 29 % of the patients received dialysis. Global mortality at the hospital was 40 %. Factors significantly associated with a poor prognosis are identified. Mean survival after hospitalization was 19 months.¶Conclusion: The frequency of admission to ICUs for ARF in patients older than 80 years seems to be on the increase. Mortality is less severe than expected. These patients could benefit from the renal replacement therapy of modern intensive care medicine.

Hemolytic uremic syndrome (HUS) is an uncommon cause of end-stage renal failure in adults, and few data are available concerning the outcome of renal transplantation in these patients. We conducted this retrospective multicentric study to appreciate the outcome of adult renal transplant recipients whose primary disease was HUS. Sixteen patients, transplanted between 1975 and 1995, were included in the study. In each case, initial diagnosis of HUS was documented by a kidney biopsy. These 16 patients received a total of 25 allografts: 1 graft for 9 patients, 2 grafts for 5 patients, and 3 grafts for 2 patients. Nine patients (56%) developed definite clinical and pathologic evidence of recurrence on at least 1 graft. Four additional patients (25%) demonstrated only some clinical or pathologic evidence of recurrence which could not be distinguished from acute vascular rejection. Three patients had no sign of recurrence of the initial disease. The 1-year graft survival rate was 63% and the 5-year graft survival rate was 18.5%. In the group of patients with proven or possible recurrence (n = 13), the 1-year and 5-year graft survival rates were 49% and less than 10%, respectively. The recurrence was an early event, occurring before the end of the first month after transplantation in half the cases. The recurrence rate was 92% in non-nephrectomized patients and 50% in patients with bilateral nephrectomy. In the literature, 71 adult patients with primary HUS had received a total of 90 kidney grafts. Among them, 54% had a recurrence on their graft, which was diagnosed in 52% of the kidney transplants. It is note-worthy that when data from the literature are pooled with our results, the rate of recurrence appears to be significantly lower in binephrectomized patients than in patients with their native kidneys at the time of transplantation (5 of 14 versus 27 of 35 patients, respectively, p = 0.0155). By univariate analysis, no other risk factor for recurrence could be identified. Treatment with cyclosporine A did not influence the recurrence rate. We conclude that recurrence of HUS after renal transplantation is a frequent, early, and severe complication, leading rapidly to graft loss. Prospective studies are needed to confirm that bilateral nephrectomy prior to transplantation decreases the rate of recurrence.

Background. The outcome of 60 renal transplantations in 53 patients with end-stage renal disease (ESRD) because of lupus nephritis was studied retrospectively and compared with 106 controls matched for age, sex, maximum panel-reactive antibody (PRA) level, and date of transplantation. Methods. The patients received their transplants over a 260-month period (21.5 years) between October 1971 and August 1993. The population was predominantly women (90%), and the mean age at the time of the transplantation was 33.2 years (range: 21-54 years). Fifty-six transplants (93%) were from cadaveric donors, and 4 (7%) were from living-related donors; 46 patients (86%) had primary allografts, and 7 (14%) received a second allograft. The duration of disease before transplantation was 93.6±6.2 months, and the duration of dialysis before transplantation was 48±6 months. Results. No patient had clinically active systemic lupus erythematosus (SLE) at the time of transplantation. The 1-year graft and patient survival rates were 83% and 98%, and the 5-year graft and patient survival rates were 69% and 96%. Actuarial graft and patient survival rates in SLE patients were not significantly different from those of the matched control group. Chronic rejection was the major risk factor for graft loss. Lupus nephritis recurred in the graft of one patient 3 months after transplantation, and there were extrarenal manifestations of SLE in four others. Conclusions. The present study confirms that patients with SLE can receive transplants with excellent graft and patient survival rates and a low rate of clinical recurrent lupus nephritis.

Hyperfiltration, associated with kidney hypertrophy and hyperplasia, are early markers of diabetic nephropathy [1, 2]. Procedures for the identification of renal molecules potentially involved in this early process are of particular interest. In order to detect hyperexpression of major renal proteins in early diabetic nephropathy, we used the well-known model of streptozotocin (STZ)induced diabetes in rats [3] and a robust technique of subtracted hybridization between normal and diabetic kidneys [4 ‐ 6]. Two subtracted probes were elaborated after hydridization of diabetic rat kidney cDNA with control rat kidney mRNA. These probes were used to screen a diabetic rat kidney cDNA library. Two clones were overexpressed in diabetic rat kidneys and corresponded to the multi-drug resistance 1 (mdr 1) cDNA and to the b-amyloid protein precursor (bPP), respectively. This study describes the results of subtractive hybridization cloning in rats, as well as some data obtained in human kidney sections originating from diabetic patients.

Specific receptor binding of renin on human mesangial cells in culture increases plasminogen activator inhibitor-1 antigen. Some proteases possess a membrane receptor that focalizes their proteolytic activity on the cell surface and may mediate a proliferative effect, such as urokinase on glomerular epithelial cells. Since some hypertensive states are associated with high concentrations of renin and proliferation of arteriolar smooth muscle cells, we asked whether renin, an aspartyl-protease, would bind to mesangial cells that are smooth-muscle derived cells, which would induce their proliferation. The binding of 125 I labeled recombinant human renin ( 125 I-R) was studied on human primary mesangial cells and mesangial cells immortalized by transfection with SV40-T antigen. At 37°C, the binding of 125 I-R was time dependent and reached a plateau after two hours. 125 I-R was found to bind in a saturable and specific manner with a K d = 0.4nM and 1nM and 8,000 and 2,000 binding sites/cell, for primary and immortalized cells, respectively. When binding experiments were performed in the presence RO 42-5892, a synthetic inhibitor of renin, RO 42-5892 could inhibit the specific binding of labeled renin only at concentrations 1,000 times superior to the IC 50, indicating that the renin-mesangial receptor interaction did not depend on the active site of renin. Analysis by SDS-PAGE and autoradiography of cross-linking experiments of 125 I-R bound to a membrane preparation showed a band of approximately 110 to 120 kDa, suggesting a Mr of 70 to 80kDa for the renin receptor. Incubation of mesangial cells with 100nM renin for 24 hours provoked a 100% increase of 3 H thymidine incorporation that was not accompanied by an increase of the cell number, even after a seven day period of incubation. However, the incubation of mesangial cells with renin for 24 hours induced a significant increase (170% of control, P = 0.04) of plasminogen activator inhibitor-1 (PAI1) antigen in the conditioned medium. In conclusion, we have shown that human mesangial cells in culture express a specific receptor for renin, and that the binding of renin increases 3 H thymidine incorporation independently of renin enzymatic activity. The absence of cell proliferation, the increase of 3 H thymidine incorporation and the increase of PAI1 antigen suggest that the binding of renin can induce mesangial cell activation, which is reflected by a change in the fibrinolytic capacity of the cells. The role of this receptor remains to be determined in nephropathies and hypertensive states associated with high plasma/tissue renin concentrations, hypertrophy of mesangial or smooth muscle cells and extracellular matrix remodeling.

Numerous glomerular and vascular nephritides are associated with fibrin formation and deposition within the kidney. Thrombin, which induces fibrin formation, also exerts numerous cellular effects on both circulating cells and intrinsic glomerular cells through the activation of the functional thrombin receptor. By immunohistochemistry and in situ hybridization, we demonstrated the constitutive expression of the functional thrombin receptor in the normal human kidney. Both glomerular epithelial and mesangial cells in culture also express the functional thrombin receptor, as shown by the binding of a specific monoclonal antibody against this receptor and Northern blot analysis. Thrombin has a potent mitogenic effect on cultured glomerular cells, suggesting that it could be at least, in part, one of the mediators that induces glomerular cell proliferation in glomerular diseases. Furthermore, we demonstrated that thrombin upregulates the synthesis of plasminogen activators and their type 1 inhibitor in these cells. Thrombin induces protein kinase C activation and an increase in intracellular calcium in these cells. Finally, we demonstrated that the functional thrombin receptor is internalized after addition of thrombin and thrombin receptor-activating peptide (homologous internalization) and also after phorbol myristate acetate addition (heterologous internalization).

Human mesangial cells have been used to study the regulation of thrombin receptor protein and mRNA expression during cross-talk between different signal transduction pathways. Persistent activation of thrombin receptor by thrombin led to homologous down-regulation of thrombin receptor protein. However, thrombin receptor mRNA expression was not affected, suggesting that increased receptor degradation is responsible for homologous down-regulation. Chronic activation of protein kinase C by phorbol 12-myristate 13-acetate (PMA) and of adenylylcyclase by prostaglandin E1 (PGE1) resulted in heterologous down-regulation of thrombin receptor protein. In contrast to thrombin, PMA and PGE1 reduced in parallel thrombin receptor mRNA levels to 51% and 24% of control, respectively, indicating that heterologous down-regulation of thrombin receptor protein is, at least in part, due to inhibition of receptor mRNA expression. The mechanisms of heterologous down-regulation of thrombin receptor protein have been studied in detail and compared to homologous down-regulation. PMA-induced down-regulation was completely blocked by GF 109 203 X, an inhibitor of protein kinase C. However, the loss of thrombin receptor induced by thrombin was not prevented by GF 109 203 X, indicating that homologous regulation is not dependent on protein kinase C activation. The heterologous effect of PGE1 was mimicked by 8-bromo-cAMP, isobutylmethylxanthine, and forskolin, suggesting that an increase in intracellular cAMP level is involved in heterologous regulation. Interestingly, heterologous down-regulation induced by PGE1 seems not to require previous internalization of thrombin receptor. These data indicate that thrombin receptor protein and mRNA expression can be regulated in homologous and heterologous ways by different mechanisms.

Receptor binding and degradation of urokinase-type plasminogen activator by human mesangial cells. The binding of [ 125 I] labeled urokinase-type plasminogen activator (u-PA) was studied on human mesangial cells (MC) in culture. The binding of active [ 125 I]u-PA at 37°C reached a plateau after 30 minutes of incubation and remained stable for at least four hours. When the supernatant was analyzed with trichloracetic acid (TCA), TCA soluble radioactive material could be detected after a lag phase of 30 minutes, and then increased linearly for four hours. Analysis by electrophoresis on SDS PAGE and autoradiography of the cell associated radioactivity and of the intracellular content showed that active u-PA and u-PA complexed to plasminogen activator inhibitor type-1 (PAI-1) were bound to the cell surface, but only u-PA/PAI-1 complexes were internalized and degraded. Therefore, the K d and the number of binding sites were determined by competitive inhibition curves at 4°C using diisopropyl-fluorophosphate (DFP) u-PA. Scatchard plots showed a K d = 400 ± 30 pM, and B max = 240,000 ± 25,000 sites/cell. Excess of the amino terminal fragment of u-PA (ATF) completely blocked the specific binding of [ 125 I]u-PA, confirming that the binding of u-PA was independent of the presence of the active site and/or of the formation of complexes with PAI-1. 3 H thymidine incorporation by mesangial cells after stimulation with 100nM active u-PA showed that u-PA had a moderate but significant mitogenic effect, in contrast to inactive u-PA and ATF. However, this mitogenic effect was not accompanied by a proliferative effect. Pretreatment of mesangial cell with a phosphoinositol-specific phospholipase C decreased the binding of [ 125 I]u-PA by 60%, indicating that the majority of the u-PA receptor is anchored in the membrane by a phosphatidylinositol group. These results, together with a positive labeling of MC with monoclonal antibodies to the receptor of U937 cells, and the positive RNA hybridization with the cDNA probe for the human receptor cloned from U937 cells, indicate that the u-PA receptor on mesangial cells is identical to the one of U937 cells. In conclusion, human mesangial cells in culture express a specific receptor for u-PA, which could play a major role in the regulation of u-PA activity by degrading u-PA complexed to PAI-1.

Thrombin is a potent activator of human glomerular epithelial cells (HGEC). Here we compare short-term and long-term effects of thrombin and thrombin receptor agonist peptide (TRAP) which selectively activates the functional thrombin receptor. TRAP, as thrombin, increases intracellular free Ca2+ concentration and acts synergistically with growth factors possessing tyrosine kinase receptors on DNA synthesis. Thrombin induces synthesis of proteins of the fibrinolytic system and cell proliferation if it is present for at least 8 h. TRAP alone does not stimulate protein synthesis and is not mitogenic. However, in the presence of the aminopeptidase inhibitor amastatin all long-term effects of thrombin can be fully mimicked by TRAP. In conclusion, different effects of thrombin and TRAP may be related to the degradation of TRAP by cellular ectoenzymes. The recently cloned thrombin receptor accounts for early intracellular signals and long-term cellular effects that require sustained activation of this receptor.

Role of the renin-angiotensin system on the renal functional reserve in renal transplant recipients. To determine the renal functional reserve in renal transplant recipients, we measured the glomerular filtration rate by inulin clearance and the renal plasma flow by PAH clearance before and during an amino acid infusion (Totamine, 6 to 8 mg/kg/min for 90 to 120 min) in 18 transplanted patients with stable renal function. To test the role of the renin-angiotensin system on the renal functional reserve, we performed a crossover placebo-controlled randomized trial of acute blockade of the renin-angiotensin system by injection of perindoprilat (2 mg i.v.), an inhibitor of angiotensin converting enzyme before amino acid infusion, each patient being studied twice at seven day intervals. Amino acid infusion induced a time-dependent increase in the glomerular filtration rate (P = 0.04), whether or not the renin-angiotensin system was blocked. Maximal increases were from 49.1 ± 4.1 to 58.9 ± 5.4, mean ± SE (18.5%), in control conditions and from 52.4 ± 5.6 to 62.1 ± 5.5 ml/min/1.73 m2 (19.7%) after perindoprilat. The increase in glomerular filtration rate was less pronounced in patients taking cyclosporin A than in patients treated with steroid and azathioprine. Amino acid infusion also induced a significant and time-dependent increase (15.2 to 20.2%) in the renal plasma flow (P < 0.01) whether or not perindoprilat had been given. Furthermore, perindoprilat alone increased renal plasma flow by 13.6%, and this effect seemed additive with that of amino acids. Perindoprilat injection decreased filtration fraction (from 0.20 ± 0.01 to 0.19 ± 0.01). This parameter returned to basal values after amino acid infusion (0.20 ± 0.01). Amino acid infusion decreased renal vascular resistances as did perindoprilat alone. After perindoprilat administration, renal vascular resistances further decreased during amino acid infusion (P = 0.03). These results demonstrate that renal transplant recipients possess a renal functional reserve of which the mobilization is not inhibited in acute experiments by blockade of the renin-angiotensin system.

The mechanisms of glomerular injury can be separated into nonimmunologically mediated glomerulonephritis (GN) such as diabetes, leading to glomerular hypertension and into immunologically mediated GN. The immunologically mediated GN may induce chronic glomerulopathy such as membranous GN or proliferative GN. The final pathway of these two types of GN is proteinuria and renal failure linked to glomerulosclerosis. In inflammatory GN, most of the mediators could be synthesized either by infiltrating cells or by resident glomerular cells. They include cytokines, lymphokines, complement activation, generation of superoxyde anions, arachidonic acid metabolites, and fibrin deposition. (a) We have investigated the interaction between isolated glomeruli and platelets and have demonstrated that lipidic and proteic extracts of glomeruli enhance thromboxane B2 platelet synthesis. This fact is related to the generation by isolated glomeruli of saturated fatty acids and tissue factor. (b) We investigated the interaction between rat isolated glomeruli and peritoneal macrophages. We have demonstrated that 12-HETE synthesized by isolated glomeruli induce macrophage prostaglandin synthesis which, in turn, inhibits the 12-HETE synthesis. (c) We have demonstrated, using human glomerular epithelial cells, that alpha-thrombin, the active form of thrombin, generated before fibrin formation, is able to induce cell proliferation and abolishes the profibrinolytic activity of these cells. In summary, the mechanisms of glomerular injury are complex, certainly acting by multiple pathways. So far, the mediators leading to proteinuria and renal failure after glomerular injury remain under investigation.

Using an immortalized human glomerular epithelial cell line (E71 A1), we studied the effect of endothelin-1 (ET-1), a potent vasoconstrictor peptide, on the synthesis of urokinase type plasminogen activator (u-PA) and its receptor (u-PAR). The results show that ET-1 had no effect on u-PA synthesis but induced an increase in u-PAR number (2.8 +/- 0.6 x 10(4) vs 1.2 +/- 0.5 x 10(4) sites per cell, p less than 0.001) without change in receptor affinity (280 +/- 80 pM vs 250 +/- 50 pM, NS), maximal effect being observed at 10(-7) M. Time course shows that a plateau was reached after a 24 hour incubation. ET-1 induced-increase in binding capacity was abolished by cycloheximide. ET-1 also induced an increase in u-PAR mRNA level, which was completely blocked by alpha-amanitin (5 micrograms/ml). Cycloheximide (1 microgram/ml) alone induced an increase in u-PAR mRNA level and this effect was enhanced when cycloheximide was combined with ET-1. Our data show that ET-1 can induce an increase in membrane expression of u-PAR through activation of the transcription of the u-PAR gene and de novo protein synthesis.

Tumor necrosis factor α increases antifibrinolytic activity of cultured human mesangial cells. Tumor necrosis factorα (TNFα) is likely to exert a major influence in the pathogenesis of glomerulopathies. Besides its proinflammatory properties, TNFα interacts with cell growth and synthesis of components of the fibrinolytic system. In this study, we report the effects of recombinant human TNFα on the synthesis of tissue-type plasminogen activator (t-PA) and its inhibitor (PAI-1) by human mesangial cells in culture. We first demonstrate that TNFα binds specifically to a single class of high affinity receptors (K d 5.10 -11 M; 1500 receptors/cell). TNFα has an antimitogenic effect on human mesangial cells since it decreased DNA synthesis, measured by 3 H-thymidine incorporation, in a dose-dependent manner. Release of cytosolic LDH and incorporated 51 Cr was not increased by 100 ng/ml TNFα as compared with control, indicating that this monokine is not cytotoxic for cultured human mesangial cells. Zymographic analysis and reverse fibrin autography disclosed a 120 kD t-PA-PAI-1 complex and a 50 kD free form of PAI-1 in the supernatants of both unstimulated and TNF-stimulated cells; PAI-1 was released in excess and free t-PA was not observed. TNFα (0 to 100 ng/ml) had no effect on t-PA synthesis, but enhanced PAI-1 release in a time- and dose-dependent manner (97% increase of PAI-1 synthesis after a 24 hour incubation). This effect was abolished by cycloheximide, suggesting that protein synthesis was required. Northern blot analysis showed that TNFα increased the steady-state PAI-1 mRNA levels in a time-dependent manner, with a maximal effect at two hours. Finally, in contrast to what was reported for rat mesangial cells, we failed to demonstrate a production of TNFα in human mesangial cells themselves by immunoradiometric assay, immunocytochemistry and Northern blot analysis using a specific TNFα cDNA probe. We conclude that TNFα has an antimitogenic activity on human mesangial cells in culture and enhances the synthesis of PAI-1. Whether TNFα plays a role in glomerular PAI-1 deposition and persistency of fibrin in vivo remains to be determined.

Human mesangial cells in culture synthesize and secrete plasminogen activator inhibitor 1 (PAI-1) and tissue-type plasminogen activator (t-PA). Phorbol myristate acetate (PMA), a known activator of protein kinase C, induces a three to four-fold increase in t-PA and PAI-1 release over a period of 24 h, whereas cell-associated t-PA and PAI-1 levels remain relatively stable. A similar effect is obtained with oleylacetyl glycerol, a more physiologic protein kinase C activator. The effect of PMA is suppressed in the presence of H7, an inhibitor of cellular protein kinases, and by cycloheximide and actinomycin D, indicating a requirement for de novo protein and RNA synthesis, respectively. Northern blot analysis of PMA-treated cells reveals a rapid and transient increase in PAI-1 mRNA reaching a maximum after 4–8 h, whereas increase in t-PA mRNA levels requires 24 h. Activation of protein kinase A by addition of 8-bromocyclic AMP (8-bromo cAMP) has no significant effect on PAI-1 release but inhibits the PMA-mediated increases in PAI-1 antigen and mRNA. Addition of 8-bromo cAMP alone does not affect t-PA release. When added to PMA-stimulated cells, 8-bromo cAMP inhibits t-PA release in a dose-dependent manner, but causes a superinduction of t-PA mRNA. 8-bromo cAMP also induces a decrese in PMA-stimulated intracellular t-PA release. Similar inhibition is observed after stimulation of endogenous adenylate cyclase with prostaglandin E1 or isoproterenol. This indicates that protein kinase A activation may inhibit PMA-stimulated t-PA release via a post-transcriptional effect, e.g. inhibition of protein synthesis or activation of protein degradation. In conclusion, hormones or mediators which activate protein kinase C can stimulate t-PA and PAI-1 synthesis in human mesangial cells. Protein kinase A activation has no effect on the basal release of PAI-1 and t-PA by human mesangial cells, and, in contrast to endothelial cells, it inhibits both PMA-stimulated PAI-1 and t-PA releases. This cell-specific regulation of t-PA and PAI-1 seems to be mediated by differenial transcriptional and post transcriptional mechanisms.

Stable cell line of T-SV40 immortalized human glomerular visceral epithelial cells. Human subcultures (third passage) of glomerular visceral epithelial cells (VEC) isolated from one month old kidney were successfully transfected by two recombinant plasmids containing the cloned oncogenes from the simian virus 40 large T antigen and H-ras gene. One postcrisis cell clone (56/10 A1) was selected, propagated and characterized. One hundred percent of the 56/10 A1 cells (current passage > 100th; doubling time 30 hrs) expressed the nuclear T-SV40 antigen assayed by IF; the cells failed to express H-ras (RNA blot analysis). Immortalized cells were morphologically and phenotypically compared to parental cell type (third passage). Phenotypic characterization of the 56/10 Al cells was achieved using indirect immunofluorescence (IF) and immunogold silver staining coupled to bright field and epipolarization microscopy. Both parental and 56/10 A1 cells displayed positivity for cytokeratin, CALLA and PHM5, whereas von Willebrand factor was not detected in the two cell types. Since we have previously shown that human glomerular epithelial cells in culture synthetize plasminogen activator (PA) related compounds, we investigated the secretion pattern of these products in parental and transfected cells. Zymographic analysis of secreted PA related compounds revealed production of free urokinase (u-PA) and type 1 plasminogen activator inhibitor (PAI-1) complexed to tissular plasminogen activator (t-PA). Finally, in the transfected cells, increased cGMP generation under atrial natriuretic factor (ANF) stimulation agreed with previous work performed on nontransfected human VEC. In conclusion, the establishment of a human permanent cell line which retains most of the phenotypic features of parental glomerular visceral epithelial cells should represent a new tool to study human glomerular cell functions.

Human glomerular epithelial cells (GECs) in culture synthesize single-chain, urokinase-type plasminogen activator (SC-uPA), tissue-type plasminogen activator (t-PA), and plasminogen activator inhibitor 1 (PAI-1) and possess specific membrane-binding sites for u-PA. Using purified 125I-alpha thrombin, we demonstrate here the presence of two populations of specific binding sites for thrombin on GECs (1.Kd = 4.3 +/- 1.0 x 10(-10) M, 5.4 +/- 1.4 x 10(4) M sites per cell, 2. Kd = 1.6 +/- 0.5 x 10(-8) M, 7.9 +/- 1.8 x 10(5) sites per cell). Purified human alpha thrombin promoted the proliferation of GECs and induced a time- and dose-dependent increase of SC-uPA, t-PA, and PAI-1 antigens released by GECs. Thrombin-mediated increase in antigen was paralleled by an increase in the levels of corresponding u-PA and PAI-1 messenger RNA. In contrast, thrombin decreased u-PA activity in conditioned medium. This discrepancy between u-PA antigen and u-PA activity was explained by a limited proteolysis of SC-uPA by thrombin, leading to a two-chain form detected by immunoblotting and that could not be activated by plasmin. Thrombin also decreased the number of u-PA binding sites on GECs (p less than 0.05) without changing receptor affinity. Hirudin inhibited the binding and the cellular effects of thrombin, whereas thrombin inactivated by diisopropylfluorophosphate had no effect, indicating that both membrane binding and catalytic activity of thrombin were required. We conclude that thrombin, through specific membrane receptors, stimulates proliferation of GECs and decreases the fibrinolytic activity of GECs both at the cell surface and in the conditioned medium. These results suggest that thrombin could be involved in the pathogenesis of extracapillary proliferation and persistency of fibrin deposits in crescentic glomerulonephritis.

Protein kinase C (PKC) activation is regulated by Ca2+, phospholipids, diacylglycerol (DAG) and fatty acids. Phorbol myristate acetate (PMA) which mimics the effect of DAG on PKC induces transcriptional activation of the urokinase-type plasminogen activator (u-PA) gene in LLC-PK1 cells. We examined in the present work the relationships between PKC activity, fatty acids, and u-PA synthesis in this cell line. We showed that H7, an inhibitor of PKC, inhibited the PMA-induced u-PA synthesis by LLC-PK1 cells. PMA-induced u-PA synthesis was enhanced by eicosatetraynoic acid (ETYA), a competitive inhibitor of both the lipoxygenase and cyclooxygenase pathways and inhibited by nordihydroguaiaretic acid (NDGA), an inhibitor of the lipoxygenase pathway. Three other unrelated lipoxygenase inhibitors (phenidone 100 microM, BW755 50 microM and diethylcarbamazine 50 microM) had no effect on u-PA biosynthesis. Two polyunsaturated fatty acids other than ETYA, arachidonic acid and linoleic acid, also potentiated the PMA effect and a lipoxygenase derivative, 12 hydroxyeicosatetraenoic acid (12 HETE), did not modify the basal and PMA-stimulated u-PA syntheses. PKC activity purified from cytosol of LLC-PK1 cells was stimulated by addition of 16 nM PMA in vitro and this effect was blunted by simultaneous addition of 5 microM NDGA. By Northern blot analysis using a pig u-PA cDNA probe we found that PMA increased the steady state level of u-PA mRNA after 2 h of incubation and that NDGA inhibited this effect. These data suggest that NDGA inhibits PMA-stimulated PKC activity in intact cells leading to a decrease of u-PA mRNA level and u-PA biosynthesis in PMA-stimulated LLC-PK1 cells. Polyunsaturated fatty acids have opposite effects.

A 24-year-old white woman with a past history of recurrent venous thromboses of the lower extremities was admitted for hypertension and renal failure. She had a chronic cutaneous ulcer on the anterior side of the left leg and oral ulcers of the palatum. Laboratory tests demonstrated rapidly progressive renal failure and the presence of an anticardiolipin antibody (ELISA). Thrombosis of the inferior vena cava was shown by phlebocavography. Renal biopsy revealed typical thrombotic microangiopathy. Tissue-type plasminogen activator (tPA) was visualized by immunofluorescence in endothelial cells of renal arterioles and glomeruli. Normal plasma levels of tPA, urokinase and plasminogen activator inhibitor 1 were found by ELISA, and tPA antigen levels rose after desmopressin acetate infusion. Thus, in this case, the diffuse thrombotic process was not related to defective circulating or renal fibrinolytic systems and could be promoted by the procoagulant effect of antiphospholipid antibodies.

International audience; Long-term use of calcineurine inhibitors (CNIs) may contribute to the development of chronic allograft dysfunction (CAD). We investigate the impact of the introduction of MMF combined with cyclosporine (CsA) 50% dose reduction. An open, randomized, controlled, multicenter, prospective study was conducted in 103 patients, receiving a CsA-based therapy with a serum creatinine between 1.7-3.4 mg/dL, more than 1 year after transplantation. They were randomized to receive MMF with half dose of CsA (MMF group) or to continue their maintenance CsA dose (control group). A total of 96 weeks after randomization, the evolution of renal function assessed by regression line analysis of 1/SeCr improved in the MMF group (positive slope) vs. the control group (negative slope), 4.2 x 10(-4) vs. -3.0 x 10(-4), respectively (p < 0.001). Concurrently, the absolute renal function improved significantly in the MMF group. No episode of biopsy-proven acute rejection occurred. One patient in each group lost his graft because of biopsy-proven chronic allograft nephropathy. There was a significant decrease of triglycerides level in the MMF group. Anemia and diarrhea were statistically more frequent in the MMF group. In CAD, the reduction of CsA in the presence of MMF results in significant improvement in renal function during a 2-year follow-up.

A role for cytomegalovirus (CMV) infection in the etiologies of acute and chronic rejection in renal allograft recipients has been suggested. We previously reported that preemptive treatment of CMV infection with ganciclovir in kidney transplant patients was safe and effective. We now present a retrospective analysis of 169 consecutive renal transplant patients, of whom 87 (51.5%) received preemptive treatment with ganciclovir (CMV(+) group). No patient died of CMV infection. Actuarial graft and patient survival rates were not different between the CMV(+) and the CMV(-) groups (graft survival: 68% and 69%; patient survival: 89% and 88%, respectively). At the end of the study, the mean plasma creatinine levels were not statistically different between the two groups (185+/-13 and 166+/-12 micromol/L for the CMV(+) group and the CMV(-) group, respectively). These results suggest that preemptive treatment of CMV infection with ganciclovir may prevent the CMV-induced renal injury and graft loss.

The renin-angiotensin system (RAS) has become increasingly complex. New components have been identified, and additional roles for angiotensin peptides and their receptors are being uncovered. A functional (pro)renin receptor has been cloned that acts as (pro)renin cofactor on cell surface, enhancing the efficiency of angiotensinogen cleavage by (pro)renin and unmasking prorenin catalytic activity. Binding of (pro)renin to the receptor mediates (pro)renin cellular effects by activating mitogen-activating protein (MAP) kinases, extracellular signal-regulated kinases (ERK)1/2. Immunofluorescence studies have localized the receptor on mesangial and vascular smooth muscle cells in human heart and kidney. This suggests that the renin receptor might represent a means to capture (pro)renin from the circulation and to concentrate (pro)renin at the interface between smooth muscle and endothelial cells. In this article, we review the biochemical characteristics of this receptor and of other renin-binding proteins, and discuss their physiologic significance.

In France, 45,000 patients are treated by hemodialysis and/or transplantation for chronic renal failure. Every year 7,000 new patients need such a therapeutic approach. The estimated cost of this pathology is about 1% of the total amount of the budget of social security, even though the number of patients is limited. Some treatments were shown to be effective in improving the progression of chronic renal failure, as for example the anti-hypertensive therapy and the adequate treatment of diabetes mellitus. Collagen deposition in each segment of the kidney, mainly in the interstitium, plays a pivotal role in the progression of renal deficiency in chronic renal failure. In order to ameliorate the progression renal failure it would be essential to know: 1) the different types of collagen deposit; 2) the proteinase/antiproteinase systems involved in the remodelling of the extracellular matrix (serine-protease, metallo-protease and their inhibitors); 3) the autocrine/paracrine effects of proteases and of growth factors on collagen synthesis. The more precise the knowledge of these factors, the more useful will be new pharmacological-, gene- or cellular therapies for limiting the progression of chronic renal failure.

The role of proteases and of antiproteases in the progression of renal disease is well established. Most studies have focused on the serine-proteases of the plasmin/plasminogen activator system and on matrix metalloproteases. Recently, renin, an aspartyl-protease, has attracted much attention because of the role of angiotensin II in the progression of renal lesions and because of the discovery of a functional renin receptor. This receptor is a 45 kDa membrane-protein that binds specifically renin and prorenin. The binding of renin induces an increase of the catalytic efficiency of angiotensinogen conversion into angiotensin I by receptor-bound renin compared to renin in soluble phase, and a rapid phosphorylation of the receptor on serine and tyrosine residues associated with an activation of MAP kinases ERK1/2. Immunofluorescence and confocal analyses on normal human kidney and cardiac biopsies show that the receptor is localized within the mesangial area of glomeruli and in the sub-endothelium of kidney and coronary arteries, associated to smooth-muscle cells. In summary, this receptor exerts dual effects, mediating renin cellular response and increasing the efficiency of angiotensinogen cleavage by membrane-bound renin. These observations emphasizes the importance of angiotensin II generation at the cell surface and the cellular effects of renin add new dimensions (and complexity) to the classical dogma that angiotensin II is the only effector of the RAS.

Plasminogen activator inhibitor type 1 is a potential target in renal fibrogenesis. The progression of renal lesions to fibrosis involves several mechanisms, among which the inhibition of extracellular matrix (ECM) degradation appears to play an important role. Two interrelated proteolytic systems are involved in matrix degradation: the plasminogen activation system and the matrix metalloproteinase system. The plasminogen activator inhibitor type 1 (PAI-1), as the main inhibitor of plasminogen activation, regulates fibrinolysis and the plasmin-mediated matrix metalloproteinase activation. PAI-1 is also a component of the ECM, where it binds to vitronectin. PAI-1 is not expressed in the normal human kidney but is strongly induced in various forms of kidney diseases, leading to renal fibrosis and terminal renal failure. Thrombin, angiotensin II, and transforming growth factor-beta are potent in vitro and in vivo agonists in increasing PAI-1 synthesis. Several experimental and clinical studies support a role for PAI-1 in the renal fibrogenic process occurring in chronic glomerulonephritis, diabetic nephropathy, focal segmental glomerulosclerosis, and other fibrotic renal diseases. Experimental models of renal diseases in PAI-1-deficient animals are in progress, and preliminary results indicate a role for PAI-1 in renal fibrogenesis. Inhibition of PAI-1 activity or of PAI-1 synthesis by specific antibodies, peptidic antagonists, antisense oligonucleotides, or decoy oligonucleotides has been obtained in vitro, but needs to be evaluated in vivo for the prevention or the treatment of renal fibrosis.

The binding of Fc fragments of Ig on glomerular epithelial cells (GEC) was observed previously, but the receptor could not be identified. In immunofluorescence and immunohistochemical studies using normal adult human kidney sections, the presence of the so-called neonatal Fc receptor (FcRn) was demonstrated on GEC as well as in the brush border of proximal tubular cells. FcRn transcripts were also detected on isolated glomeruli by reverse transcription-PCR. Using an immortalized GEC line, the presence of the FcRn was confirmed by flow cytometry, reverse transcription-PCR, Western blotting, and by the pH dependence of the binding of heat-aggregated IgG. Because it is well established that the FcRn is involved in IgG transcytosis, it is hypothesized that the FcRn in the kidney may play a role in the reabsorption of IgG. Ongoing studies should clarify the role of the FcRn as a potential target for immune complexes on GEC and should assess its relevance in physiology and pathology.