Etude des mécanismes de transports impliqués dans le passage du méthotrexate au travers des barrières hémato-encéphalique et hémato-oculaires chez la souris

CHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocSudocFranceF

Problèmes liés à l'utilisation du cisapride chez le nouveau-né (contribution du pharmacien dans la prise en charge du reflux gastro-œsophagien)

PARIS-BIUP (751062107) / SudocSudocFranceF

Transient Receptor Potential Vanilloid in the Brain Gliovascular Unit: Prospective Targets in Therapy

The gliovascular unit (GVU) is composed of the brain microvascular endothelial cells forming blood–brain barrier and the neighboring surrounding “mural” cells (e.g., pericytes) and astrocytes. Modulation of the GVU/BBB features could be observed in a variety of vascular, immunologic, neuro-psychiatric diseases, and cancers, which can disrupt the brain homeostasis. Ca2+ dynamics have been regarded as a major factor in determining BBB/GVU properties, and previous studies have demonstrated the role of transient receptor potential vanilloid (TRPV) channels in modulating Ca2+ and BBB/GVU properties. The physiological role of thermosensitive TRPV channels in the BBB/GVU, as well as their possible therapeutic potential as targets in treating brain diseases via preserving the BBB are reviewed. TRPV2 and TRPV4 are the most abundant isoforms in the human BBB, and TRPV2 was evidenced to play a main role in regulating human BBB integrity. Interspecies differences in TRPV2 and TRPV4 BBB expression complicate further preclinical validation. More studies are still needed to better establish the physiopathological TRPV roles such as in astrocytes, vascular smooth muscle cells, and pericytes. The effect of the chronic TRPV modulation should also deserve further studies to evaluate their benefit and innocuity in vivo

Caractérisations fonctionnelle et moléculaire de transporteurs impliqués dans les échanges de cations organiques au niveau des barrières hémato-encéphalique et hémato-oculaire chez la souris

Les échanges moléculaires localisés au niveau de la barrière hémato-encéphalique (BHE) et au niveau des capillaires rétiniens et de l épithélium pigmentaire formant respectivement les barrières hémato-rétiniennes interne et externe (BHR), dont l association est assimilée aux barrières hémato-oculaires, sont régulés par la présence de transporteurs facilitant l entrée et/ou la sortie du parenchyme cérébral ou rétinien. Nos recherches ont porté, in vivo chez la souris, sur l identification de transporteurs de cations organiques présents au niveau de ces interfaces à l aide de la technique de perfusion carotidienne in situ, de la technique de PCR en temps réel et de la technique d immunofluorescence sur tissu fixé. Nous nous sommes intéressés à l antiport proton/cations organiques d amine tertiaire ou dit de la clonidine et de la famille de transporteurs de cations organiques (Oct). Nous avons démontré l expression fonctionnelle au niveau des interfaces cérébrale et oculaire du transporteur de haute capacité, faible affinité de la clonidine dont l identité moléculaire est inconnue. Sa caractérisation fonctionnelle a été accomplie indiquant l absence de couplage directe avec les ions sodium, potassium et chlorure mais l influence de protons permettant un fonctionnement de type antiport. L identification d autres substrats notamment de type opiacés et de la nicotine a pu être réalisée. En revanche, les transporteurs Oct1, 2 et 3 n ont pu être mis en évidence au niveau de la BHE alors que les expressions du transporteur Oct2, et également d un transporteur de monoamines de type Net, ont pu être objectivées fonctionnellement au niveau des BHRThe molecular exchanges located at the blood-brain barrier (BBB) constituted of the endothelia of brain capillaries and at the retinal capillaries and at the retinal pigmentary epithelium forming respectively the inner and outer blood-retinal barriers (BRB), which could be assimilated to the blood ocular barriers, are regulated by the presence of transporters which facilitate influx in and/or efflux from brain or retinal parenchyma. Our research dealt with the identification, in vivo, in mice, of organic cation transporters present at these interfaces and responsible in particular for the psychotropic permeation, using the in situ carotid perfusion method, the real-time PCR technique and the immunofluorescence technique in fixed tissues. We were interested in the cationic/proton antiporter of tertiary amine or said to be transporter of clonidine and in the organic cation transporter (Oct) family. We demonstrated the expression at the brain and ocular interfaces of the high-capacity, low-affinity transporter said to be of clonidine , not yet molecularly identified. Its functional characterization was accomplished, showing the lack of direct coupling with sodium, potassium and chloride but the proton influence allowing an antiporter functioning. The identification of other substrates notably opiate-type drugs and nicotine could be achieved. However, the expression of Oct1, 2 and 3 could not be shown at the BBB whereas an expression of the Oct2 transporter could be functionally established at the BRB; moreover, at the BRB, the expression of the monoamine Net-like transporter could be functionally characterizedPARIS-BIUP (751062107) / SudocSudocFranceF

Opioids and the Blood-Brain Barrier: A Dynamic Interaction with Consequences on Drug Disposition in Brain

International audienceBackground: Opioids are widely used in pain management, acting via opioid receptors and/or Toll-like receptors (TLR) present at the central nervous system (CNS). At the blood-brain barrier (BBB), several influx and efflux transporters, such as the ATP-binding cassette (ABC) P-glycoprotein (P-gp, ABCB1), Breast Cancer Resistance Protein (BCRP, ABCG2) and multidrug resistance-associated proteins (MRP, ABCC) transporters, and solute carrier transporters (SLC), are responsible for the transport of xenobiotics from the brain into the bloodstream or vice versa.Objective: ABC transporters export several clinically employed opioids, altering their neuropharmacokinetics and CNS effects. In this review, we explore the interactions between opioids and ABC transporters, and decipher the molecular mechanisms by which opioids can modify their expression at the BBB.Results: P-gp is largely implicated in the brain-to-blood efflux of opioids, namely morphine and oxycodone. Long-term exposure to morphine and oxycodone has proven to up-regulate the expression of ABC transporters, such as P-gp, BCRP and MRPs, at the BBB, which may lead to increased tolerance to the antinociceptive effects of such drugs. Recent studies uncover two mechanisms by which morphine may up-regulate P-gp and BCRP at the BBB: 1) via a glutamate, NMDA-receptor and COX-2 signaling cascade, and 2) via TLR4 activation, subsequent development of neuroinflammation, and activation of NF-kB, presumably via glial cells.Conclusion: The BBB-opioid interaction can culminate in bilateral consequences, since ABC transporters condition the brain disposition of opioids, while opioids also affect the expression of ABC transporters at the BBB, which may result in increased CNS drug pharmacoresistance

Imaging probes and modalities for the study of Solute Carrier O (SLCO)-transport function in vivo

International audienceTransporters of the Solute Carrier O (SLCO) family, former organic anion-transportingpolypeptides (OATP), are now recognized as key players in pharmacokinetics. Imagingis increasingly regarded as a relevant method to elucidate and decipher the intrinsicrole of SLCO in controlling drug disposition in plasma and tissues. Current research inthis representative field of translational research is based on different imagingmodalities including nuclear imaging, such as Single Photon Emission ComputedTomography (SPECT) or Positron Emission Tomography (PET), as well as MagneticResonance Imaging (MRI). Imaging modalities can be compared in terms of sensitivity,quantitative properties, spatial resolution, variety of ligands and radiation exposure. Allof these approaches rely on the use of SLCO-substrates that are detected usingcorresponding modalities. The present review aims at reporting and comparing theimaging probes that have been proposed to study SLCO-transport function, in termsof $in\ vitro$ specificity, $in\ vivo$ behavior and clinical validation

Spinal cord ischaemia following surgery of the abdominal aorta. Report of three cases and review of the literature

Three cases of spinal cord ischaemia following abdominal aortic surgery are presented. Aortoiliac reconstruction for occlusive disease (2 cases) and aortorenal by-pass (1 case) were the operative procedures which gave origin to the lethal complication. Anatomy and physiopathology related to the ischaemic damage are discussed and world literature is reviewed

Mechanistic insights into P-glycoprotein ligand transport and inhibition revealed by enhanced molecular dynamics simulations

P-glycoprotein (P-gp) plays a crucial role in cellular detoxification and drug efflux processes, transitioning between inward-facing (IF) open, occluded, and outward-facing (OF) states to facilitate substrate transport. Its role is critical in cancer therapy, where P-gp contributes to the multidrug resistance phenotype. In our study, classical and enhanced molecular dynamics (MD) simulations were conducted to dissect the structural and functional features of the P-gp conformational states. Our advanced MD simulations, including kinetically excited targeted MD (ketMD) and adiabatic biasing MD (ABMD), provided deeper insights into state transition and translocation mechanisms. Our findings suggest that the unkinking of TM4 and TM10 helices is a prerequisite for correctly achieving the outward conformation. Simulations of the IF-occluded conformations, characterized by kinked TM4 and TM10 helices, consistently demonstrated altered communication between the transmembrane domains (TMDs) and nucleotide binding domain 2 (NBD2), suggesting the implication of this interface in inhibiting P-gp's efflux function. A particular emphasis was placed on the unstructured linker segment connecting the NBD1 to TMD2 and its role in the transporter's dynamics. With the linker present, we specifically noticed a potential entrance of cholesterol (CHOL) through the TM4-TM6 portal, shedding light on crucial residues involved in accommodating CHOL. We therefore suggest that this entry mechanism could be employed for some P-gp substrates or inhibitors. Our results provide critical data for understanding P-gp functioning and developing new P-gp inhibitors for establishing more effective strategies against multidrug resistance