Etude du passage cérébral du 99mTc-sestamibi chez la souris (influence de trois protéines ABC (P-glycoprotéine, Mrp1, Bcrp) et du potentiel de membrane)

PARIS-BIUP (751062107) / SudocSudocFranceF

Mécanismes de perméabilité membranaire des cations organiques au travers de la barrière hémato-encéphalique et des barrières hémato-oculaires

Au cours de nos recherches nous avons adapté la technique de perfusion carotidienne in situ chez la souris pour la mesure du transport hémato-oculaire et hémato-cérébral de nutriments et xénobiotiques De plus, nous nous sommes intéressés à l étude du transport du 99mTc-sestamibi. L effet de trois transporteurs d efflux: la P-gp, la Mrp1 et la Bcrp, ainsi que l effet du potentiel de membrane sur son transport au niveau de la BHE ont été évalués. Parmis ces trois transporteurs seule la P-gp modifie le passage cérébral du 99mTc-mibi. De même, nous avons montré l influence in vivo du potentiel de la membrane sur ce transport. Ce travail nous a permis d envisager l hypothèse de la présence de transporteurs de cations organiques, favorisant l entrée cérébrale du 99mTc-sestamibi. Enfin, nous avons exploré l influence de trois transporteurs de cations organiques Oct1, 2 et 3 sur le passage cérébral et oculaire du TEA et du MPP+. Si nos études indiquent l absence de fonctionnalité de ces Octs à la BHE, elles montrent cette influence au niveau oculaire. De plus, nos travaux suggèrent l existence d autres transporteurs de cations au niveau de ces barrières, à caractériserWe have adapted the mouse in situ brain perfusion technique for the study of xenobiotics blood/brain and blood/eye transport characteristics. Moreover, we measured 99mTc-sestamibi brain transport, and the influence of 3 efflux transporters: P-gp, Mrp1 and Bcrp and membrane potential on this transport. At the difference of Mrp1 and Bcrp, only P-gp modifies 99mTc-sestamibi brain distribution. Our results also indicated the ability of the membrane potential to influence its distribution. Our results seem to show the capacity of organic cation transporters to support 99mTc-sestamibi brain transport. Finally, we explored the influence of 3 organic cation transporters Oct1, 2 and 3 on TEA and MPP+ brain and eye influx. If our studies indicate the absence of functionality of these Octs at the blood/brain interface, they showed this influence at the ocular level. Moreover, our work suggested the existence of other our data suggested the influence of other organic cation transporters at the level of the brain and eye blood interface that remain to be identifiedPARIS-BIUP (751062107) / SudocSudocFranceF

Transport of Biogenic Amine Neurotransmitters at the Mouse Blood–Retina and Blood–Brain Barriers by Uptake1 and Uptake2

International audienceUptake1 and uptake2 transporters are involved in the extracellular clearance of biogenic amine neurotransmitters at synaptic clefts. We looked for them at the blood-brain barrier (BBB) and blood-retina barriers (BRB), where they could be involved in regulating the neurotransmitter concentration and modulate/terminate receptor-mediated effects within the neurovascular unit (NVU). Uptake2 (Oct1-3/Slc22a1-3, Pmat/Slc29a4) and Mate1/Slc47a1 transporters are also involved in the transport of xenobiotics. We used in situ carotid perfusion of prototypic substrates like [(3)H]-1-methyl-4-phenylpyridinium ([(3)H]-MPP(+)), [(3)H]-histamine, [(3)H]-serotonin, and [(3)H]-dopamine, changes in ionic composition and genetic deletion of Oct1-3 carriers to detect uptake1 and uptake2 at the BBB and BRB. We showed that uptake1 and uptake2 are involved in the transport of [(3)H]-dopamine and [(3)H]-MPP(+) at the blood luminal BRB, but not at the BBB. These functional studies, together with quantitative RT-PCR and confocal imaging, suggest that the mouse BBB lacks uptake1 (Net/Slc6a2, Dat/Slc6a3, Sert/Slc6a4), uptake2, and Mate1 on both the luminal and abluminal sides. However, we found evidence for functional Net and Oct1 transporters at the luminal BRB. These heterogeneous transport properties of the brain and retina NVUs suggest that the BBB helps protect the brain against biogenic amine neurotransmitters in the plasma while the BRB has more of a metabolic/endocrine role

Blood-brain and retinal barriers show dissimilar ABC transporter impacts and concealed effect of P-glycoprotein on a novel verapamil influx carrier.

BACKGROUND AND PURPOSE: The respective impact and interplay between ABC (P-glycoprotein/P-gp/Abcb1a, BCRP/ABCG2, MRP/ABCC) and SLC transporter functions at the blood-brain barrier (BBB) and blood-retinal barriers (BRB) are incompletely understood. EXPERIMENTAL APPROACH: We measured the initial cerebral and retinal distribution of selected ABC substrates by in situ carotid perfusion using P-gp/Bcrp knockout mice and chemical ABC/SLC modulation strategies. P-gp, Bcrp, Mrp1 and Mrp4 were studied by confocal retina imaging. KEY RESULTS: Chemical or physical disruption of P-gp increased [(3) H]-verapamil transport by ~10-fold at the BBB and ~1.5-fold at the BRB. [(3) H]-Verapamil transport involved influx-mediated by an organic cation clonidine-sensitive/diphenhydramine-sensitive proton antiporter at both barriers; this effect was unmasked when P-gp was partially or fully inhibited/disrupted at the BBB. Studies of [(3) H]-mitoxantrone and [(3) H]-zidovudine transport suggested, respectively, that Bcrp efflux was less involved at the BRB than BBB, whereas Mrps were significantly and similarly involved at both barriers. Confocal imaging showed that P-gp and Bcrp were expressed in intra-retinal vessels (inner BRB/iBRB) but absent from the blood/basal membrane of cells of the retinal pigment epithelium (outer BRB/oBRB/RPE) where, in contrast, Mrp1 and Mrp4 were localized. CONCLUSIONS AND IMPLICATIONS: P-gp, Bcrp, Mrp1 and Mrp4 are differentially expressed at the outer and inner BRB, resulting in an altered ability to limit substrate distribution at the retina as compared with the BBB. [(3) H]-Verapamil distribution is not P-gp-specific and involves a proton antiporter at both the BBB and BRB. However, this transport is concealed by P-gp at the BBB, but not at the BRB, where P-gp activity is reduced