Urinary Elimination of Coproporphyrins Is Dependent on ABCC2 Polymorphisms and Represents a Potential Biomarker of MRP2 Activity in Humans

MRP2 encoded by ABCC2 gene is involved in the secretion of numerous drugs and endogenous substrates. Patients with Dubin-Johnson syndrome due to mutation in ABCC2 gene have elevated urinary coproporphyrin ratio (UCP I/(I + III)). Here we investigated whether this ratio could serve as a biomarker of MRP2 function. Phenotype-genotype relationships were studied in 74 healthy subjects by measuring individual UCP I/(I + III) ratio obtained on 24-hour urine and by analyzing five common SNPs in ABCC2 gene. The UCP I/(I + III) ratio varied from 14.7% to 46.0% in our population. Subjects with 3972TT genotype had a higher ratio (P = .04) than those carrying the C allele. This higher UCP I/(I + III) ratio was correlated with a higher level of isomer I excretion. This study provides a proof of concept that UCP I/(I + III) ratio can be used as a biomarker of MRP2 function in clinical studies as it provides quantitative information about the in vivo activity of MRP2 in a given patient

Population pharmacokinetics of ciprofloxacin in neonates and young infants less than 3 months age

Ciprofloxacin is used in neonates with suspected or documented Gram-negative serious infections. Currently, its use is off-label partly because of lack of pharmacokinetic studies. Within the FP7 EU project TINN (Treat Infection in NeoNates), our aim was to evaluate the population pharmacokinetics of ciprofloxacin in neonates and young infants \u3c3 months of age and define the appropriate dose in order to optimize ciprofloxacin treatment in this vulnerable population. Blood samples were collected from neonates treated with ciprofloxacin and concentrations were quantified by high-pressure liquid chromatography-mass spectrometry. Population pharmacokinetic analysis was performed using NONMEM software. The data from 60 newborn infants (postmenstrual age [PMA] range, 24.9 to 47.9 weeks) were available for population pharmacokinetic analysis. A two-compartment model with first-order elimination showed the best fit with the data. A covariate analysis identified that gestational age, postnatal age, current weight, serum creatinine concentration, and use of inotropes had a significant impact on ciprofloxacin pharmacokinetics. Monte Carlo simulation demonstrated that 90% of hypothetical newborns with a PMA of \u3c34 weeks treated with 7.5 mg/kg twice daily and 84% of newborns with a PMA ≥34 weeks and young infants receiving 12.5 mg/kg twice daily would reach the AUC/MIC target of 125, using the standard EUCAST MIC susceptibility breakpoint of 0.5 mg/liter. The associated risks of overdose for the proposed dosing regimen were \u3c8%. The population pharmacokinetics of ciprofloxacin was evaluated in neonates and young infants \u3c3 months old, and a dosing regimen was established based on simulation

Insights into the structure and function of the human organic anion transporter 1 in lipid bilayer membranes

The human SLC22A6/OAT1 plays an important role in the elimination of a broad range of endogenous substances and xenobiotics thus attracting attention from the pharmacological community. Furthermore, OAT1 is also involved in key physiological events such as the remote inter-organ communication. Despite its significance, the knowledge about hOAT1 structure and the transport mechanism at the atomic level remains fragmented owing to the lack of resolved structures. By means of protein-threading modeling refined by μs-scaled Molecular Dynamics simulations, the present study provides the first robust model of hOAT1 in outward-facing conformation. Taking advantage of the AlphaFold 2 predicted structure of hOAT1 in inward-facing conformation, we here provide the essential structural and functional features comparing both states. The intracellular motifs conserved among Major Facilitator Superfamily members create a so-called “charge-relay system” that works as molecular switches modulating the conformation. The principal element of the event points at interactions of charged residues that appear crucial for the transporter dynamics and function. Moreover, hOAT1 model was embedded in different lipid bilayer membranes highlighting the crucial structural dependence on lipid-protein interactions. MD simulations supported the pivotal role of phosphatidylethanolamine components to the protein conformation stability. The present model is made available to decipher the impact of any observed polymorphism and mutation on drug transport as well as to understand substrate binding modes

Substrate binding and lipid-mediated allostery in the human organic anion transporter 1 at the atomic-scale

The Organic Anion Transporter 1 is a membrane transporter known for its central role in drug elimination by the kidney. hOAT1 is an antiporter translocating substrate in exchange for a-ketoglutarate. The understanding of hOAT1 structure and function remains limited due to the absence of resolved structure of hOAT1. Benefiting from conserved structural and functional patterns shared with other Major Facilitator Superfamily transporters, the present study intended to investigate fragments of hOAT1 transport function and modulation of its activity in order to make a step forward the understanding of its transport cycle. μs-long molecular dynamics simulation of hOAT1 were carried out suggesting two plausible binding sites for a typical substrate, adefovir, in line with experimental observations. The well-known B-like motif binding site was observed in line with previous studies. However, we here propose a new inner binding cavity which is expected to be involved in substrate translocation event. Binding modes of hOAT1 co-substrate α-ketoglutarate were also investigated suggesting that it may bind to highly conserved intracellular motifs. We here hypothesise that α-ketoglutarate may disrupt the pseudo-symmetrical intracellular charge-relay system which in turn may participate to the destabilisation of OF conformation. Investigations regarding allosteric communications along hOAT1 also suggest that substrate binding event might modulate the dynamics of intracellular charge relay system, assisted by surrounding lipids as active partners. We here proposed a structural rationalisation of transport impairments observed for two single nucleotide polymorphisms, p.Arg50His and p.Arg454Gln suggesting that the present model may be used to transport dysfunctions arising from hOAT1 mutations

Perfusate Metabolomics Content and Expression of Tubular Transporters During Human Kidney Graft Preservation by Hypothermic Machine Perfusion

Background. Ischemia-related injury during the preimplantation period impacts kidney graft outcome. Evaluating these lesions by a noninvasive approach before transplantation could help us to understand graft injury mechanisms and identify potential biomarkers predictive of graft outcomes. This study aims to determine the metabolomic content of graft perfusion fluids and its dependence on preservation time and to explore whether tubular transporters are possibly involved in metabolomics variations. Methods. Kidneys were stored on hypothermic perfusion machines. We evaluated the metabolomic profiles of perfusion fluids (n=35) using liquid chromatography coupled with tandem mass spectrometry and studied the transcriptional expression of tubular transporters on preimplantation biopsies (n=26), both collected at the end of graft perfusion. We used univariate and multivariate analyses to assess the impact of perfusion time on these parameters and their relationship with graft outcome. Results. Seventy-two metabolites were found in preservation fluids at the end of perfusion, of which 40% were already present in the native conservation solution. We observed an increase of 23 metabolites with a longer perfusion time and a decrease of 8. The predictive model for time-dependent variation of metabolomics content showed good performance (R2=76%, Q2=54%, accuracy=41%, and permutation test significant). Perfusion time did not affect the mRNA expression of transporters. We found no correlation between metabolomics and transporters expression. Neither the metabolomics content nor transporter expression was predictive of graft outcome. Conclusions. Our results call for further studies, focusing on both intra- and extratissue metabolome, to investigate whether transporter alterations can explain the variations observed in the preimplantation period

Utilisation du Lopinavir chez les patients VIH+ [Virus de l'"immunodéficience humaine plus] du CISIH [Centre d'information et de soins de l'immunodéficience humaine] de Tours (évaluation pharmaceutique)

Aujourd'hui, les antiprotéases, classe thérapeutique majeure dans le traitement antirétroviral, entraînent des effets indésirables pouvant être limitants. La découverte des antiprotéases, notamment du lopinavir est récente et l'évaluation en terme d'efficacité et de tolérance est incomplète. Nous avons réalisé une étude rétrospective de 35 patients du Centre d'Information et de Soins de l'Immunodéficience Humaine de Tours, infectés par le Virus de l'Immunodéficience Humaine, traités par lopinavir. Nous avons analysé les données virologiques, immunologiques et biologiques. L'impact des concentrations de lopinavir sur les paramètres étudiés a également été abordé. L'efficacité virologique a été objectivée pour 17 patients (71 et 43 pourcent des sujets naïfs et non naïfs). L'analyse biologique a été réalisée chez 26 des 35 patients. La triglycéridémie et la cholestérolémie étaient perturbées dans 92 et 80 pourcent des cas, respectivement. Notre étude a confirmé la bonne efficacité de ce médicament et a permis de montrer que les anomalies du bilan lipidique pouvaient en partie être expliquées par des concentrations de lopinavir trop élevées.TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Impact de la prise en compte des déficits en DPD dans le contrôle de la toxicité des chimiothérapies comportant du 5-FU dans le cancer colorectal

TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Place du suivi thérapeutique du 5-fluorouracile dans les différents schémas de traitement des cancers des voies aéreodigestives supérieures

Le 5-fluorouracile (5-FU) est un antinéoplasique cytotoxique de la classe des antimétabolites indiqué dans le traitement de diverses tumeurs solides, notamment des cancers d'origine digestive, du cancer du sein et des cancers des voies aérodigestives supérieures (VADS).Son utilisation est fréquemment associée à la survenue d'une toxicité, en particulier d'origine digestive, cutanéomuqueuese et hématologique. Cependant, il a été montré que cette toxicité pouvait être diminuée par une adaptation de posologie puisqu'il existe une relation concentration-effet concernant les effets indésirables mais aussi la réponse thérapeutique. Le suivi thérapeutique pharmacologique (STP) du 5-FU est actuellement proposé, pour les cancers de la tête et du cou, dans les schémas d'administration à la dose de 1000 mg/mø en perfusion continue, sans radiothérapie concomitante (RT). L'adaptation de posologie est effectuée par rapport à une valeur d'AUC cible d'environ 30 000 æg/L.h. L'expérience acquise par certains centres laisse penser que des concentrations supérieures pourraient être bien tolérées. Par ailleurs, aucune donnée n'est disponible sur les relations concentration-effet pour les autres doses, telles que 750 ou 600 mg/mø en perfusion continue. C'est pourquoi nous avons mis en place une étude prospective qui a concerné 66 patients atteints d'un cancer des VADS, recevant des doses de 5-FU de 1000 ou 750 mg/mø sans RT ou de 600 mg/mø associé à la RT. Les valeurs d'AUC calculées pour chaque cure ont été confrontées aux observations concernant la toxicité et la réponse clinique pour les différents types de traitement. Dans les schémas à 1000 et 750 mg/mø, les AUC des cures concernées par une toxicité étaient supérieures à celles pour lesquelles il n'y avait pas de toxicité. L'effet de l'AUC était significatif pour la dose de 1000 mg/mø et le seuil associé à un risque accru de toxicité était de 50 000 æg/L.h, soit supérieur au seuil actuellement proposé (30 000 æg/L.h). En revanche, pour les schémas à 600 mg/mø avec RT, le niveau d'exposition au 5-FU n'avait aucun impact sur la survenue d'une toxicité. Concernant la réponse clinique, l'influence de l'AUC n'a pas été mise en évidence. La relation concentration-effet n'ayant pas été retrouvée pour les schémas à 600 mg/mø associé à la RT, le STP du 5-FU ne semble donc pas justifié. En revanche, il est indispensable dans les schémas à 1000 mg/mø pour limiter la toxicité et il semble intéressant de poursuivre les études pour la dose de 750 mg/mø, afin d'établir une valeur d'AUC cible spécifique à cette posologie.TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Réévaluation des critères d'utilisation de la carboxypeptidase en cas de surexposition au methotrexate administré à haute dose

TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF