Academic literature on the topic 'Crigler-Najjar'

Crigler-Najjar syndrome type 2 in an autosomal recessive congenital non-hemolytic hyperbilirubinemia caused by UDP-glucuronosyltransferase deficiency. Only a few hundred cases have been described in the literature so far. We are reporting Crigler-Najjar syndrome type 2 in an 18 year old female born out of consanguineous marriage. Keyword: Crigler-Najjar syndrome; UDP-glucuronosyltransferase; Bangladesh DOI: 10.3329/jom.v12i1.6359J Medicine 2011; 12 : 81-85

Crigler-Najjar syndromes are rare, autosomal recessive disorders caused by mutations in the genes of bilirubin metabolism. The management of these pregnancies is controversial due to paucity of literature. We discuss here a successfully managed case of pregnancy with Crigler-Najjar Syndrome.International Journal of Human and Health Sciences Vol. 04 No. 01 January’20 Page : 60-62

Inherited disorders of bilirubin metabolism involve four autosomal recessive syndromes: Gilbert, Crigler- Najjar, Dubin-Johnson and Rotor, among which the first two are characterized by unconjugated and the second two by conjugated hyperbilirubinemia. Gilbert syndrome occurs in 2%-10% of general population, while others are rare. Except for Crigler-Najjar syndrome, hereditary hyperbilirubinemias belong to benign disorders and thus no treatment is required.

The Crigler-Najjar disease is a rare disorder originally described in 1952 and characterized by a severe unconjugated hyperbilirubinemia appearing in the first days of life and persisting throughout life. In 1969, Arias et al proposed to subdivide such patients into two groups. The first group (Crigler-Najjar disease type 1) consisted of the most severely jaundiced infants in whom bilirubin encephalopathy developed resulting in death, usually within the first year of life, and whose plasma bilirubin level did not decrease during treatment with phenobarbital. Their bile was described as virtually colorless and appeared to contain only a trace amount of bilirubin, all in the unconjugated form. In the second group (Crigler-Najjar disease type 2), bilirubin conjugates were detected in normally yellow bile. In these patients, the unconjugated hyperbilirubinemia was less severe and encephalopathy was absent.

To the Editor.— Rubaltelli et al1 recently described the use of tin-protoporphyrin (SnPp) to block bilirubin formation in a child with the potentially fatal Crigler-Najjar Type II disease, a genetic disorder characterized by an inability to conjugate and excrete bilirubin in the normal way. Although repeated administration of SnPp failed to suppress the plasma bilirubin concentration significantly in their patient, perhaps because of the buffering effect of a relatively large extravascular pool of bilirubin, it did appear to diminish the need for phototherapy, suggesting that SnPp might be a useful adjuvant to phototherapy in the treatment of Crigler-Najjar disease.

La maladie de Crigler-Najjar est une affection rare du métabolisme hépatique liée à un déficit partiel ou total de l'activité de l'enzyme UGT1A1 conjuguant la bilirubine. La maladie se manifeste dans les premières heures suivant la naissance par un ictère intense et persistant à bilirubine non conjuguée. Sur le plan clinique, les enfants atteints sont à risque élevé de lésions cérébrales irréversibles liées à des dépôts de bilirubine non-conjuguée dans les noyaux gris centraux (ictère nucléaire). Depuis la description de cette pathologie par Crigler et Najjar en 1952, des études moléculaires ont permis d'identifier le gène responsable. UGT1A1 est situé à l'extrémité du bras long du chromosome 2 et comporte 5 exons. Il existe deux formes de maladie de Crigler-Najjar : le type I dans lequel le déficit d'activité est complet et l’enzyme non inductible et le type II dans lequel le déficit est partiel et l’enzyme inductible. Au cours de ce travail, nous avons décrit plusieurs nouvelles anomalies de séquences responsables de maladie de Crigler-Najjar de type I ou de type II, tout en les resituant dans un contexte d’analyse de relations génotype-phénotype. Dans un deuxième temps, nous avons étudié plus particulièrement deux familles de malades ayant une présentation moléculaire particulière (premier cas d’isodisomie uniparentale paternelle du chromosome 2, caractérisation d'une large délétion dans le gène UGT1A1), soulignant ainsi l’importance de l’enquête familiale dans cette pathologie. Dans une dernière partie, nous avons caractérisé sur le plan moléculaire un effet fondateur pour la mutation c. 1070A>G dans la population tunisienne au sein de laquelle la maladie de Crigler-Najjar est particulièrement fréquente
Crigler-Najjar syndrome is a rare hepatic disorder due to partial or total deficiency of enzymatic activity of UGT1A1 involved in bilirubin conjugation. The disease manifests itself during the first hours of life by intense and persistent unconjugated hyperbilirubinaemia. Affected children are at high risk to develop brain non-reversible damages (kernicterus) due to bilirubin encephalopathy. Since 1952 and the description of this syndrome by Crigler and Najjar, molecular studies allowed to identify the gene. UGT1A1 gene is located on the terminal part of the chromosome 2 and is composed of 5 exons. Crigler-Najjar syndrome can take two forms: type I with complete and non-inducible enzymatic deficiency and type II with non-complete and inducible enzymatic deficiency. In this work, we have described new mutations responsible for Crigler-Najjar syndrome type I or II and we have analysed them in terms of phenotype-genotype correlations. Secondly we have studied two families with non-canonical presentation (first description of paternal isodisomy for chromosome 2, molecular characterisation of a large deletion in UGT1A1 gene), highlighting the importance of familial investigations in this syndrome. In the last part, we have molecularly characterised a founder effect for the mutation c. 1070A>G in the Tunisian population, in whom Crigler-Najjar syndrome is particularly frequent

Thesis (Ph.D.)--University of Florida, 2005.
Typescript. Title from title page of source document. Document formatted into pages; contains 127 pages. Includes Vita. Includes bibliographical references.

La maladie de Crigler-Najjar de type 1 (CN-1) est une pathologie autosomique récessive très rare due à un déficit complet en Bilirubine UDP-Glucuronosyl Transférase (UGT1A1), une enzyme du métabolisme de la bilirubine. L'accumulation de bilirubine dans le sérum se traduit par un ictère intense pouvant entraîner des troubles neurologiques très graves. Le traitement actuel de CN-1 est la photothérapie. Cependant, le seul traitement curatif reste la transplantation hépatique. CN-1 est un bon modèle pour la thérapie génique car l'histologie du foie est préservée, et il existe un modèle animal, le rat Gunn. Parmi les vecteurs de thérapie génique se trouvent les virus adéno-associés, ou AAV. Ils présentent l'avantage de transduire des cellules en division ou quiescentes, et ne sont pas issus de virus pathogènes, contrairement à d'autres vecteurs. Leur efficacité a été démontrée pour le traitement de nombreuses maladies métaboliques telles que l'hémophilie B. La première partie de ce projet concernait l'utilisation de vecteurs AAV chez le jeune rat Gunn. La correction de l'hyperbilirubinémie fut transitoire, et des phénomènes intégratifs observés. La seconde partie de l'étude s'appliqua ensuite à mesurer les risques potentiels liés à cette intégration grâce à un protocole utilisant un agent promoteur de tumeurs chez le rat, le 2-acétylaminofluorène. Les résultats obtenus n'indiquèrent pas de risque tumorigène particulier. Enfin, dans la dernière partie de cette étude, des AAV dits « self complementary », furent utilisés afin de corriger CN-1 chez le rat Gunn adulte. Le suivi des animaux montra une diminution significative de l'hyperbilirubinémie à long terme. En conclusion, les vecteurs AAVr ne semblent pas adaptés au traitement des maladies métaboliques héréditaires dans le modèle du jeune rat. Les niveaux de transduction à long terme sont très faibles, malgré la persistance du transgène sous forme intégrée au niveau de quelques hépatocytes. Ces phénomènes intégratifs semblent aléatoires, cependant de nouvelles expérimentations sont nécessaires afin de confirmer cette hypothèse. Les vecteurs AAVsc ont par contre permis la correction à long terme de l'hyperbilirubinémie chez le rat Gunn adulte. Cette étude va se poursuivre chez le primate non-humain, et pourrait ainsi constituer une première étape vers le développement d'un essai clinique de CN-1, qui pourrait ensuite être appliqué à d'autres maladies métaboliques héréditaires
Crigler-Najjar type 1 disease (CN-1) is a very rare, recessive inherited disorder due to a total lack in Bilirubin UDP-Glucuronosyl Transferase (UGT1A1), an enzyme of bilirubin metabolism. The accumulation of bilirubin in the serum results in an intense jaundice, and can lead to sever neurological troubles. The current treatment for CN-1 is phototherapy. However, the only curative treatment is still liver transplantation. CN-1 is a good model for gene therapy because liver histology is preserved, and there is an animal model, the Gunn rat. Among all gene therapy vectors are the adeno-associated viruses. They can transduce dividing or quiescent cells, and don’t come from pathogenic viruses, contrarily to other vectors. Their efficiency has been proved for the recovery of metabolic diseases such as hemophilia B. The first part of this project was about the use of AAV vectors in the young Gunn rat. The correction of hyperbilirubinemia was transient, and integrative phenomena were observed. The second part of the study applied to measure the potential risks due to this integration with a protocol using a tumour promoting agent in rat, the 2-acetylaminofluorene. No particular risk of tumorigenesis was seen. In the last part of this study, AAV self complementary were used to correct CN-1 in the adult Gunn rat. The follow-up of animals showed a significant decrease of hyperbilirubinemia in the long-term. In conclusion, AAVr don’t seem to be adapted to the treatment of hereditary metabolic diseases in the young rat model. Transduction levels in the long-term are very weak, in spite of integrated forms in some hepatocytes. These integrative phenomena seem to appear randomly, however new experiments will be necessary to confirm this hypothesis. AAVsc vectors led to the long-term correction of hyperbilirubinemia in the adult Gunn rat. This study will continue in the non-human primate model, and could be the first step towards the development of a clinical trial for CN-1, which could then be applied to other hereditary metabolic diseases

La maladie de Crigler Najjar de type I est une maladie métabolique du foie due à un déficit total en UDP-glucuronosyl transférase A1 (UGT1A1). Chez les patients, Dans cette maladie, une mutation du gène codant l'enzyme UGT1A1 entraîne une hyperbilirubinémie non conjuguée responsable d'un ictère. Le traitement actuel repose sur une photothérapie, voire une transplantation hépatique. Cette maladie représente un paradigme pour la thérapie génique des maladies héréditaires du foie. Une guérison du modèle animal spontané de CNI, le rat Gunn, a été obtenue par thérapie génique daddition avec des vecteurs viraux. Cependant, ces approches présentent notamment le risque potentiel de mutagenèse insertionnelle. Ces inconvénients font apparaître l'intérêt du développement de nouvelles approches de thérapie génique ciblée. Les nucléases à doigts de zinc (ZFNs) et les Transcription Activator-like Effectors Nucleases permettent la modification du génome à façon par correction génique notamment. La première partie de la thèse a consisté à développer un système de vectorisation virale de ZFNs avec des vecteurs lentiviraux et AAV. Dans un second temps, nous avons utilisé les outils développés pour mettre au point une stratégie de réparation génique in vivo de l'UGT1A1 chez le rat Gunn. Cette stratégie a permis une correction subthérapeutique de la bilirubinémie. Ce projet a démontré la faisabilité d'une stratégie de thérapie génique ciblée pour les maladies héréditaires du foie. Cela offre de nouvelles possibilités de thérapie génique avec une meilleure spécificité et une amélioration de la biosécurité
Crigler Najjar type 1 (CNI) disease is a liver metabolic inherited disease due to UDP-glucuronosyl transferase (UGT1A1) enzyme deficiency. The patients have a mutation into the UGT1A1 gene responsible for an unconjugated hyperbilirubinemia that lead to an icterus. They are treated with phototherapy and liver transplantation. CNI is a paradigm for liver inherited diseases. Gene therapy represents a new hope for the treatment of such diseases. Lifelong cure of the Gunn rat model of CNI has been obtained through gene therapy with viral vectors. However, there are still drawbacks, such as risks of insertional mutagenesis. Thus, it is important to develop strategies of targeted gene therapy. Zinc Finger Nucleases (ZFNs) and Transcription Activator-like Effectors Nucleases (TALENs) allow targeted genome editing, through gene repair for example. They induce a specific DNA double strand break that promotes the insertion of an exogenous custom DNA donor through homologous recombination. The first part of this thesis consisted in the development of lentiviral and AAV vectors to deliver a whole ZFNs pair. The second part consisted in using these tools for in vivo gene repair in the Gunn rat. We showed that the endogenous mutation of UGT1A1 gene in the Gunn rat can be repaired in vivo at a level sufficient to obtain a subtherapeutic effect. Such recent strategies may offer safer therapeutic options to treat inherited monogenic diseases

2006/2007
INTRODUZIONE A basse concentrazioni la bilirubina non coniugata (unconjugated bilirubin, UCB) prodotta dalla degradazione dell’emoglobina, sembra essere un potente anti-ossidante, mentre è estremamente dannosa ad alte concentrazioni, causando encefalopatia nei neonati con severo ittero. Il 70% dei bambini che presentano kernittero muoiono entro sette giorni di vita, mentre il 30% dei sopravvissuti manifesta irreversibili conseguenze come sordità, ritardo mentale e danni cerebrali permanenti. L’encefalopatia dovuta ad alti livelli di bilirubina rappresenta oggi la maggior causa di riammissione ospedaliera nei neonati entro il primo mese di vita. Storicamente gli studi riguardanti le modalità di ingresso della bilirubina nel sistema nervoso centrale si sono concentrati sulla barriera emato-encefalica (blood brain barrier, BBB), costituita dai microvasi e dai capillari del cervello (micro vessels, MV). Tali studi hanno dimostrato come solamente la bilirubina non coniugata e non legata all’albumina del sangue, definita “bilirubina libera” (free bilirubin, Bf) sia capace di attraversare le membrane cellulari e diffondere nel tessuto. Tuttavia i microvasi non sono l’unica interfaccia sangue-tessuto presente nel cervello. Una seconda barriera è costituita dai plessi coroidei (CP). Questi, collocati nei ventricoli del cervello, mediano il passaggio delle molecole dal sangue al liquido cefalorachidiano e viceversa, posseggono una ampia superficie di scambio, il più alto flusso sanguigno del sistema nervoso centrale ed un fenotipo barriera meno restrittivo rispetto ai microvasi del parenchima. L’ingresso della bilirubina nel cervello sembra essere attivamente controllato da due trasportatori appartenenti alla famiglia delle “ATP dependent transporters”, Mrp1 e Pgp. Tali trasportatori potrebbero mantenere bassa la concentrazione della bilirubina limitandone l’ ingresso a livello di barriere o agendo direttamente a livello delle cellule del parenchima. Nonostante l’ impatto di questi trasportatori sulla disponibilità nel sistema nervoso centrale non solo della bilirubina ma egualmente di atre molecole potenzialmente tossiche, così come dei principi attivi, la loro espressione e localizzazione nelle interfacce sangue-cervello non sono del tutto chiare. Per tali motivi il lavoro di questi tre anni di tersi è stato incentrato a: Ia) chiarire il livello di espressione proteica relativa di Mrp1 e Pgp nelle due principali barriere cerebrali, la BBB (blood brain barrier, barriera emano encefalica) e la BCSFB (blood CerebroSpinal Fluid barrier, barriera emato liquorale); Ib) Definire l’andamento della loro espressione nel corso dello sviluppo post-natale in situazione fisiologica. II) Valutare l’effetto di elevati livelli serici di bilirubina sull’espressione di Mrp1 e Pgp nelle barriere emato encefaliche, come prima linea di difesa verso la bilirubina nel kernittero. Per raggiungere questo secondo obiettivo abbiamo utilizzato il ratto Gunn, considerato il modello in vivo per la sindrome di Crigler-Najjar e il kernittero. I ratti Gunn presentano elevati livelli di bilirubina serica ed un quadro clinico simile a quanto si riscontra nell’uomo. L’iperbilirubinemia, nel ratto, è dovuta ad una mutazione nell’enzima responsabile della coniugazione del pigmento, passaggio fondamentale per la sua successiva eliminazione. Nell’omozigote (jj) la bilirubina totale nel sangue (TBS) è molte volte più alta che nell’eterozigote (Jj) in cui l’allele non mutato codifica per l’enzima nella sua forma attiva, sufficiente a mantenere livelli di bilirubina normali. RISULTATI Ia) Attraverso una quantificazione relativa dell’ espressione proteica, ottenuta tramite Western blot, abbiamo dimostrato una espressione speculare dei due trasportatori nelle interacce sangue cervello. Mentre i microvasi sono caratterizzati dalla forte espressione di Pgp, ed i livelli di Mrp1 sono 15-20 volte inferiori rispetto ai plessi, questi ultimi presentano una elevata espressione di Mrp1 ed una quasi completa assenza di Pgp. Per quanto riguarda l’espressione di Mrp1 nei plessi coroidei (CP), abbiamo potuto evidenziare una differenza, con la massima espressione nel plesso del 4° ventricolo rispetto ai ventricoli laterali. Tramite immunofluorescenza abbiamo poi evidenziato per entrambe i trasportatori una localizzazione lato sangue, con Pgp luminale nei vasi e Mrp1 baso-laterale nel plessi coroidei. Ib) Anche l’andamento dell’espressione durane lo sviluppo post-natale differisce. Mentre Mrp1 è sin dalla nascita (2 giorni di vita) altamente espresso in entrambe le barriere, Pgp è inizialmente espresso a livelli più bassi (4,6 volte meno) rispetto all’ adulto (60 giorni). Contemporaneamente anche la densità dei vasi nel parenchima aumenta. II) Nel modello iperbilirubinemico rappresentato dal ratto Gunn, la TBS (jj) e molte volte più alta che nell’ eterozigote (Jj) e tale differenza permane per tutto l’arco di tempo esaminato (0-60 giorni dalla nascita). Al contrario la bilirubina libera (calcolata) è elevata solo nelle prime due settimane di vita, quando il rapporto bilirubina-albumina nel sangue è superiore all’unità. Poi, il rapido aumento della concentrazione ematica di albumina determina un significativo calo della Bf. Mentre l’analisi degli effetti (macroscopici) dell’iperbilirubinemia sullo sviluppo degli emisferi cerebrali non evidenzia differenze tra Jj e jj; in questi ultimi la crescita del cervelletto è severamente inibita. Già a 17 giorni di vita l’ipoplasia del cervelletto si manifesta con una differenza nel peso del 50% nei jj rispetto agli animali normo bilirubinemici di pari età. Durante tale periodo anche l’espressione dei due trasportatori nelle barriere è modificata. L’espressione proteica di Pgp nella BBB degli animali iperbilirubinemici è aumentata ad ogni età presa in esame. Tuttavia tale incremento non modifica in maniera importante la quantità del trasportatore nei MV durante lo sviluppo post natale, rimanendo quindi poco espresso (5 volte meno rispetto all’adulto) almeno fino ai 17 giorni di vita. Contemporaneamente la presenza Mrp1 nella BCSFB è inibita. Già a 9 giorni nel plesso del 4° ventricolo Mrp1 è il 50% rispetto al controllo (pari età, Jj). Anche se nei plessi dei ventricoli laterali l’inibizione dell’espressione è inferiore, nell’insieme la quantità di Mrp1 è fortemente ridotta negli animali iperbilirubinemici. Contrariamente, nei ratti Jj, Mrp1 ha un andamento simile a quello descritto nella sezione (Ib). CONCLUSIONI I risultati da noi ottenuti sottolineano importanti differenze tra le due barriere. La barriera emato-encefalica si sviluppa durante il primo periodo post-natale, in un ambiente caratterizzato dalla forte presenza di membrane cellulari. Similarmente l’espressione di Pgp è inizialmente bassa ed incrementa molto durante lo sviluppo post-natale. Al contrario I plessi coroidei appaiono precocemente in età embrionale, contribuiscono allo sviluppo del cervello e posseggono il più alta espressione di enzimi di fase II, coinvolti nel metabolismo di potenziali sostanze tossiche, del cervello. Un alto livello di Mrp1 sin dalla nascita suggerisce un suo coinvolgimento nel trasporto di qualche sostanza importante nello sviluppo del cervello o in un suo precoce coinvolgimento nel mantenimento dello stato ossido riduttivo, o nell’eliminazione di metabolici dal sistema nervoso centrale. Elevati livelli di bilirubina, come nel modello Gunn, modulano sia l’espressione di Pgp nella BBB, che di Mrp1 nella BCSFB. Tuttavia l’incremento nell’espressione di Pgp nei microvasi non sembra essere sufficiente a contrastare efficacemente l’ingresso della bilirubina libera, molto elevata fino al 17 giorno di vita. La simultanea riduzione di Mrp1 nei plessi coroidei, può facilitare l’ingresso o ridurre l’efflusso della bilirubina nel liquido cefalo rachidiano, consentendo l’accumulo e conseguente danno dei tessuti esposti.
................................................................ ....................... .. .BACKGROUND The unconjugated bilirubin (UCB), a heme degradation product, has been suggested to be a potent antioxidant at low concentration while it seems to be extremely dangerous at higher concentrations, causing encephalopathy in severely jaundiced neonates. Around 70% of children with kernicterus die within seven days, while the 30% survivors usually suffer irreversible sequels, including hearing loss, paralysis of upward gaze, mental retardation, and cerebral palsy with athetosis. Bilirubin encephalopathy is actually the leading cause of hospital readmission of newborns within the first month after birth. Historically the studies concerning the bilirubin entry the central nervous system have focused on the blood brain barrier (BBB), located at the level of the endothelial cells forming the brain micro vessels (MV), leading to the “free bilirubin theory”. It consists in the idea that only the free unconjugated bilirubin, the part of bilirubin exceeding the binding ability of the serum albumin, is able to cross the cell membranes and diffuse in tissue. In brain a second blood brain barrier is present. It is located at the level of the epithelial cells forming the choroids plexuses, between the blood and the cerebrospinal fluid (blood-cerebrospinal fluid barrier, BCSFB). Despite the largest surface area available for the exchanges, the high blood flux, the strategically position between two circulating fluids and the more leaky phenotype, limited studies have been made concerning its role in limiting the bilirubin entry the brain. Two ATP dependent transporters, the Multidrug Resistance-associated Protein 1 (Mrp1) and the MultiDrug resistance Protein (Pgpor MDR1), appear to be actively involved in UCB trafficking. The transporters play an important role in keeping extra cellular bilirubin concentration, such as potentially toxic compounds, below toxic levels by limiting the entry of UCB from blood to brain, or else in controlling intracellular bilirubin levels in parenchyma cells. Despite the importance of Mrp1 and Pgp on BBI their pattern of expression and cellular localization remains still unsettled. Based on these considerations - The first aim of the thesis was clarify the relative protein expression of these transporters at the two major BBI protecting the brain from toxic insults (Ia), and to identify their post-natal developmental profile of expression and cellular localisation (Ib). Similarly, no data about the Mrp1 and Pgp expression on BBI during the bilirubin encephalopathy are available. - The second aim of the thesis was investigate a relation between the high level of blood bilirubin and Mrp1 and Pgp expression in brain barriers in vivo using the Gunn rat (II), in witch the symptoms closely correlate to the human kernicterus and Crigler-Najjar syndrome type I. In this animal model, a mutation in the enzyme responsible for the conjugation and subsequent elimination of bilirubin, leads to the total absence of the enzymatic activity in the homozygous animals (jj), causing a severe life long hyperbilirubinemia. In the heterozygous Gunn rats (Jj), the enzymatic activity, until if reduced, is present and result in normal serum bilirubin levels. RESULTS Ia) By quantitative Western blot, we have demonstrated a mirroring expression of the two transporters at the blood brain interfaces in the adult rat. On the BBB the Pgp is strongly expressed and the Mrp1 amount is 15-20 times lower than in CPs. At the contrary, the CPs are characterized by the high expression of Mrp1, with a difference between the lateral ventricle (LV) and the 4th ventricle (4thV) CP, the former being a lower Mrp1 expression than in the last. In both LV and 4thV CPs, Pgp is virtually absent. By immunofluorescence we revealed that both ABC transporters are located at the blood side, the Pgp luminal on MV, and Mrp1 basal on CPs. Ib) With respect to the post-natal development, the Mrp1 expression is high since the early post-natal age and do not change significantly from birth to adult life in both barriers. By contrast, Pgp expression is weak a P9 and increase 4.6 fold with maturation on MV. Synchronously the density of Pgp stained MV in parenchyma seems increasing. II) In the homozygous Gunn rat (jj) the total bilirubin in serum is several time higher than in the heterozygous (Jj) animals all life long. By contrast the (calculated) free bilirubin is extremely elevated until the first week of life, when the bilirubin-albumin ratio exceed the unit, then drop due to the developmental increasing albumin concentration in blood. While no differences in Cx weight have been found between Jj and jj rat at every postnatal age, the cerebellum development is strongly impaired by the bilirubin toxic effect, displaying a Summarymarked hypoplasia, with about the 50% of weight loss respect the Jj control at 17 days after the birth. Concerning the ABC transporters, the differential pattern of expression between blood brain interfaces is maintained. But, in jj Gunn rats, the Pgp expression at the BBB is up-regulated at every post natal age analysed, also if this increase do not seems to be sufficient to confer protection at list until P17, when the amount of the transporter in the MV is about 5 times lower than in adult (P60). At the same time the Mrp1 expression on the BCSFB is down regulated. Since P9 the amount of Mrp1 in the 4thV CP of jj rats drops around to the 50% respect the amount in the littermates. In the LV CP the decrease is less marked, but in any case the Mrp1expression in both CPs is strongly impaired. This down regulation seems to be post-transcriptional. In the Jj animals, the Mrp1 relative expression is already high in both plexuses at early postnatal stages. A significant difference was noted only between LV CP (76%) and 4thV CP at P60 (100%). CONCLUSIONS All together these results indicate that the two barriers differ: The BBB develops after the birth and is surrounded by the lipid rich parenchyma environment, in agreement with the transporter preference for the lipid compounds and the strong post-natal developmental increase of the Pgp amount on MV. The CPs develops early in the foetal life, are involved in the guidance of the brain development and posses the highest phase II metabolising enzymes in the brain. The Mrp1 amount in CPs is similar to the adult level since the birth and may be involved in the transport of some compounds important in the brain development, in the detoxification or in the maintenance of the redox state (GS- sulfo- conjugates, LC4, etc.). In Gunn rats, as model for Kernicterus and Crigler-Najjar syndrome type I, the Pgp offered protection is not sufficiently modulate until P17, when the amount of the free bilirubin is elevated and could cross the brain barriers. The simultaneously down regulation of Mrp1 at the BCSFB may facilitate the entry of the bilirubin or strongly impair their clearance in the central nervous system, leading to the accumulation in brain and subsequent damage of tissue.
1974