Le système nerveux est responsable de l’interconnexion interne des animaux multicellulaires. Il leur permet en effet d’intégrer les activités physiologiques de leurs différentes composantes en une seule entité fonctionnelle, capable d’interagir avec son environnement. L’évolution et le développement des systèmes nerveux complexes comptent parmi les questions les plus fascinantes de la recherche en biologie. Afin de mettre en place une diversité de types de cellules neurales et de connexions neurales, les animaux métazoaires ne déploient qu’un nombre étonnamment réduit de signaux développementaux. C’est l’intermodulation dynamique de ces signaux qui va pouvoir induire un patron spatial d’identités et de comportements cellulaires distincts. L’acide rétinoïque (AR) est une petite molécule diffusible dérivée de la vitamine A qui contribue à la mise en place des axes du système nerveux central des vertébrés et est un régulateur crucial de la différentiation neuronale. D’autre part, il a été montré que les signaux à l’AR affectaient le phénotype de neurotransmetteurs exhibé par des sous-populations neuronales et jouent des rôles divers dans la morphogenèse du système nerveux périphérique issu des placodes crâniennes et des cellules des crêtes neurales. Néanmoins, bien que le rôle de l’AR dans la régionalisation du système nerveux central ait été étudié de manière extensive, nous en savons beaucoup moins au sujet de l’action de l’AR sur le développement du système nerveux périphérique, sur l’établissement des différentes identités de neurotransmetteurs, ou quant à comment ces fonctions ont évolué. Bien qu’initialement considéré comme spécifique aux vertébrés, un volume croissant de données indique désormais que l’AR serait impliqué dans le développement du système nerveux de divers taxons, tels que les cnidaires, les mollusques gastropodes ainsi que les cordés invertébrés. En particulier, l’amphioxus, céphalocordé dont l’évolution est lente, est connu pour posséder un système de signalisation à l’AR semblable à celui des vertébrés. Le génome de l’amphioxus présente un haut degré de conservation de sa synténie par rapport à celui des vertébrés et exhibe relativement peu de pertes ou de duplications indépendantes de ses gènes développementaux. Par conséquent, l’embryogenèse ainsi que la morphologie de l’amphioxus ressemble par bien des points à celles des vertébrés, ce qui facilite l’identification des traits ancestraux et dérivés et en fait donc un modèle approprié à la recherche comparative. Cette étude vise à fournir une description détaillée de différentes populations neurales au sein du système nerveux périphérique de l’amphioxus et d’explorer les rôles joués par l’AR dans ce processus. À cette fin, des analyses d’expression de gènes et d’immunohistochimie ont été utilisées, en vue d’identifier les différentes sous-populations de progéniteurs et les différents types de cellules neurales. De plus, les niveaux de signaux à l’AR ont été altérés pharmacologiquement à différents stades de développement de l’amphioxus, pour déterminer leurs effets sur la formation des populations neurales identifiées, ainsi que sur les patrons de prolifération et d’apoptose. Les résultats inclus dans ce travail révèlent la présence de différentes populations de cellules neurales chez l’amphioxus et mettent en lumière leur vraisemblable relation phylogénétique avec les structures leur correspondant chez les vertébrés. Par ailleurs, différents rôles contexte-dépendants de la signalisation à l’AR on été documentés, incluant la mise en place de frontières discrètes dans le système nerveux central et l’ectoderme de l’embryon d’amphioxus, et la régulation du développement des progéniteurs neuraux tardifs dans le système nerveux périphérique de manière spécifique à leur type cellulaire. / The nervous system provides internal interconnection to multi-cellular animals. It enables them to integrate the physiological activities of their different components into one functional entity that can successfully interact with its environment. The evolution and development of complex nervous systems is one of the most fascinating questions of biological research. In order to generate a diversity of neural cell types and neural connections, metazoan animals deploy a surprisingly small number of instructive developmental signals, which crosstalk in a dynamic manner to induce a spatial pattern of cell identities and behaviors.Retinoic acid (RA) is a small diffusible signaling molecule derived from vitamin A that contributes to the axial patterning of the vertebrate central nervous system and functions as a crucial regulator of neuronal differentiation. Moreover, RA signals have been shown to affect the neurotransmitter phenotype of specific neuronal subsets and play distinct roles during the morphogenesis of the peripheral nervous system from cranial placodes and neural crest. However, while the role of RA signaling in the regionalization of the central nervous system has been extensively studied, much less is known about its actions in cranial placodes and neural crest derivatives, in the establishment of different neurotransmitter identities, or how these functions might have evolved.Albeit initially believed to be vertebrate-specific, a growing body of evidence now implicates RA signaling in the nervous system development of various distant taxa, such as cnidarians, gastropod mollusks and invertebrate chordates. In particular, the slow evolving cephalochordates, commonly called amphioxus, are known to possess a vertebrate-like RA signaling system. The amphioxus genome has retained a high degree of synteny with vertebrate genomes and exhibits relatively little losses or independent duplications of developmental genes. Accordingly, amphioxus embryogenesis and morphology also display remarkable similarity with vertebrates, which allows the identification of ancestral as well as newly derived traits and makes these animals attractive models for comparative research.This study aims at providing a detailed description of the development of different neural cell populations in the central and peripheral nervous system of amphioxus and explores the roles played by RA signaling during this process. To this end, gene expression analyses and immunohistochemistry were used, in order to identify distinct subsets of neural progenitors and neural cell types. Furthermore, RA signaling levels were manipulated pharmacologically at different stages of amphioxus development, to assess their effects on the formation of identified neural cell populations as well as on proliferation and apoptosis patterns. The results presented in this work reveal the presence of distinct neural cell populations in amphioxus and highlight their likely phylogenetic relationships with corresponding structures in other chordates. In addition, several context-dependent functions of RA signaling were documented, which include the generation of discrete boundaries in the central nervous system and ectoderm of amphioxus embryos as well as the cell type-specific regulation of late neural progenitor development in the peripheral nervous system. The observed roles of RA signaling in the amphioxus neural tube and peripheral nervous system correspond well to those reported for the vertebrate hindbrain and cranial placodes, supporting the current hypothesis of a close evolutionary relationship between these structures and suggesting that the involvement of RA signals in their development is a conserved feature of chordates.

For decades the opioid receptors have been an attractive therapeutic target for the treatment of pain. Since the first discovery of enkephalin, approximately a dozen endogenous opioid peptides have been known to produce opioid activity and analgesia, but their therapeutics have been limited mainly due to low blood brain barrier penetration and poor resistance to proteolytic degradation. One versatile approach to overcome these drawbacks is the cyclization of linear peptides to cyclic peptides with constrained topographical structure. Compared to their linear parents, cyclic analogs exhibit better metabolic stability, lower offtarget toxicity, and improved bioavailability. Extensive structure-activity relationship studies have uncovered promising compounds for the treatment of pain as well as further elucidate structural elements required for selective opioid receptor activity. The benefits that come with employing cyclization can be further enhanced through the generation of polycyclic derivatives. Opioid ligands generally have a short peptide chain and thus the realm of polycyclic peptides has yet to be explored. In this review, a brief history of designing ligands for the opioid receptors, including classic linear and cyclic ligands, is discussed along with recent approaches and successes of cyclic peptide ligands for the receptors. Various scaffolds and approaches to improve bioavailability are elaborated and concluded with a discourse towards polycyclic peptides.

Orientadores: Sergio Tadeu Matins Marba, Helder José Lessa Zambelli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-22T03:05:39Z (GMT). No. of bitstreams: 1 Zomignani_AndreaPeterson_M.pdf: 1128762 bytes, checksum: 59ae9805910c4b220c7bfa8d2e7bcbab (MD5) Previous issue date: 2012 / Resumo: Objetivo: Descrever uma população de recém-nascidos com encefalocele. Método: Estudo restrospectivo, descritivo e analítico por análise dos prontuários de recém-nascidos com diagnóstico de encefalocele, no Hospital da Mulher Prof. Dr. José Aristodemo Pinotti - Centro de Atenção Integral à Saúde da Mulher (CAISM), da Universidade Estadual de Campinas (UNICAMP). Foram incluídos todos os pacientes nascidos com diagnóstico de encefalocele no período de janeiro/1997 a julho/2008. Foram estudados: idade materna, paridade, pré-natal, apresentação fetal, tipo de parto, sexo, idade gestacional, índice de Apgar, peso, tipo de encefalocele, tratamento cirúrgico, ocorrência de óbitos, período de internação e retardo do desenvolvimento neuropsicomotor (RDNPM). Foram calculadas as frequências para cada variável analisada e a associação entre algumas variáveis foi verificada estatisticamente pelos testes qui-quadrado e exato de Fisher, considerando alfa de 5%. Resultados: Foram analisados 43 casos com prevalência de 1,24/1000 nascimentos. A faixa de idade materna de maior ocorrência foi 18 a 32 anos (83%), em mães não primigestas (65%), que fizeram os exames pré-natais (95%). A apresentação fetal mais recorrente foi cefálica (45%) com parto cesáreo (65%). Foram encontrados mais casos em meninas, com idade gestacional _37 semanas, tendo a maioria das crianças com a malformação nascido a termo (79%). No primeiro minuto houve Apgar menor ou igual a 7 em 58% dos casos. Em 67% dos casos o peso foi adequado, 27% foram baixo peso e 4,6% muito baixo peso. O tipo de encefalocele mais prevalente foi occipital e em 67% dos casos houve cirurgia. O óbito ocorreu em 31% dos recém nascidos e 55% tiveram período de internação de 1 a 15 dias. Em 62% dos casos foi descrito retardo do desenvolvimento neuropsicomotor. Conclusões: A prevalência de encefalocele foi de 1,24/1000 nascimentos e esteve associada às mães jovens e não primigestas. A apresentação cefálica foi à apresentação mais comum e o tipo de parto mais frequente foi parto cesáreo. Foi mais comum a presença de encefalocele em meninas, com idade gestacional _37 semanas, em nascidos a termo, com índice de Apgar baixo e com peso adequado. A maioria teve encefalocele occipital e precisou de cirurgia, sendo a taxa de mortalidade alta. Na maioria dos casos houve RDNPM / Abstract: Objective: To describe a serie of newborns with encephalocele. Method: Retrospective, descriptive and analytical study, with medical records analysis of newborns with encephalocele, born at the Hospital da Mulher Prof. Dr. José Aristodemo Pinotti - Center for Integral Assistance to Women's Health at the University of Campinas (UNICAMP). All the patients born with these conditions were selected from January/1997 until July/2008. It was studied: maternal age, parity, prenatal care, fetal presentation, mode of delivery, gender, gestational age, Apgar score, birth weight, type of encephalocele, surgical treatment, occurrence of death, hospitalization period, delayed neuropsychomotor development. Frequencies were calculated for each variable and the association among then were assessed statistically using the chi-square and Fisher exact test, considering a 5% alpha. Results: There were 43 cases with prevalence of 1,24/100 births. Maternal age range most frequent was 18 to 32 years (83%), in not primigravidae (65%), who made the prenatal care (95%). The most recurrent fetal presentation was cephalic (45%) with cesarean sections (65%). More cases were found in girls, with gestational age _37 weeks, with the majority of infants with malformations born at term (79%). First minute Apgar score was less than or equal to 7 in 58% of the cases. In 67% of the cases the weight was appropriate, 27% were low birth weight, and 4,6% were very low birth weight infants. The most prevalent type of encephalocele was occipital; 67% of the cases were underwent the surgery. Death occurred in 31% of the newborns and hospitalization period, in most cases, was 1 to 15 days. Neuropsychomotor development delay was observed in 62% of the cases. Conclusions: The prevalence of encephalocele was 1,24/1000 births and there was associated with young mothers and not primiparous. The cephalic presentation was common and there were more cesarean sections. It was more common the presence of encephalocele in girls, with gestational age _37 weeks in term newborns with low Apgar score and appropriate weight. Most had occipital encephalocele and needed surgery, and there was a high mortality rate. In most cases there were neurological deficit / Mestrado / Saude da Criança e do Adolescente / Mestra em Ciências

A crescente importância do ciclo silvestre da raiva envolvendo morcegos e mamíferos terrestres demonstra a importância do estudo da epidemiologia do vírus da raiva nessas espécies. Foram estudadas amostras provenientes de diversas espécies de animais silvestres terrestres procedentes de uma área de Mata Atlântica nativa no litoral Norte do Estado de São Paulo. Este estudo pesquisou a presença de anticorpos contra o vírus da raiva por meio dos Testes de RFFIT, SFIMT e ELISA em amostras de soro de animais capturados em uma área desmatada, transpostos e monitorados em uma área de soltura. E ainda a pesquisa do vírus da raiva por meio das técnicas de IFD, IC e RT-PCR em amostras de sistema nervoso central dos animais encontrados mortos na região. A positividade observada foi de 10,8% na RFFIT, 34,0% no SFIMT e 1,13% no ELISA. Todos as amostras submetidas as técnicas de IFD, IC e RT-PCR apresentaram resultados negativos. Os resultados observados demonstram circulação do vírus entre as espécies silvestres da área. / The emergent importance of rabies in terrestrial wild animals demonstrates the importance of epidemiological studies regarding rabies virus in those animal species. Samples from several wild species from a native Rainforest area in the North coast of São Paulo State Brazil were studied. The aim of the present study was the research of anti-rabies antibodies in those animals using the RFFIT, SFIMT and ELISA techniques in animals captured and monitorated in a release área. And also by rabies virus detection using FAT, MIT and RT-PCR techniques in central nervous system samples from animals found dead in the same area. The observed positivity was 10,8% on RFFIT, 34,0% on SFIMT e 1,13% on ELISA. All samples tested by the FAT, MIT and RT-PCR techniques presented negative results. The observed results are an evidence of rabies virus circulation between wild animal species in the studied area.

The aim of this Thesis is to investigate the use of hyaluronic acid as a material for the design of scaffolds aimed at CNS regeneration. The motivation comes from the need of searching for new strategies that allow regeneration in the central nervous system. In degenerative diseases, such as Parkinson's disease, where the progressive loss of neuronal subpopulations occurs, a permissive environment able to support regeneration and connectivity of neurons from the host tissue may be a promising therapy to recover lost functionalities. In this Thesis we have focused on the development of structures able to integrate within the brain, supporting neural cells attachment and survival. We hypothesized that hyaluronic acid provides an enabling environment and appropriate for regeneration due to its biocompatibility and diverses physiological applications. Biocompatible hydrogels based on modified hyaluronic acid were synthesized. Covalently crosslinked hyaluronic acid hydrogels, alone or in combination with acrylic polymers, were synthesized and permitted to develop different porous structures which may serve in different applications as cell supply, cell repopulation or tissue regeneration. Highly porous with interconnected spherical pores, hollow tubes or multichanneled scaffolds were developed. The processes allow for a wide range of shapes for different applications within the scope of central nervous system regeneration. Furthermore, in vitro culture of human cell lines together with biomaterials was performed. A human microvascular endothelial cell line (hCMEC/D3) and a human glioma cell line (U373) were chosen for the studies. Experiments were focused on the interaction between hyaluronan based scaffolds and those cell lines composing the blood-brain-barrier (BBB) in the central nervous system. Biocompatibility, viability and phenotype characteristics were assessed. / Baiget Orts, MA. (2012). HYALURONAN BASED BIOMATERIALS FOR CENTRAL NERVOUS TISSUE REGENERATION [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14576 / Palancia

Se pretende obtener un material semibiodegradable basado en ácido hialurónico químicamente enlazado a cadenas de polímeros acrílicos. Los hidrogeles de ácido hialurónico presentan en general buenas características para su utilización en regeneración del sistema nervioso central: es biodegradable, es un componente importante del tejido neural, sus propiedades mecánicas son semejantes a las del tejido cerebral, promueve la formación de nuevos capilares (angiogénesis), y limita la inflamación. Con este nuevo material se pretende mejorar el excesivo grado de hinchado en medio fisiológico, su rápida degradación, mejorar la adhesión celular, además la matriz permanente de las cadenas acrílicas pueden actuar como un soporte permanente durante el proceso regenerativo sin que se produzca una pérdida brusca de propiedades mecánicas y estructurales. El trabajo consiste en caracterizar este nuevo material así como los productos intermedios necesarios para su obtención final, comparándolo con las propiedades de un hidrogel de ácido hialurónico sin incorporar cadenas acrílicas. Los estudios celulares se llevaran a cabo in vitro, como fase preliminar para futuros implantes en el cortex cerebral, estudiando la capacidad de diferenciación de precursores neurales y de generación de nuevos capilares con el fenotipo típico de la barrera hematoencefálica, mediante el estudio de cocultivos de precursores neurales y células endoteliales. / Perez Garnes, M. (2015). Structures based on semi-degradable biomaterials for neural regeneration in the central nervous system [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48799 / TESIS

Chronic kidney disease (CKD), a reduction in kidney function, has reached pandemic proportions and imposes a major healthcare burden worldwide. A hallmark of CKD is the accumulation of several chemical compounds, called uremic toxins, which inflict systemic and renal-specific damage. Of the known uremic toxins, kynurenine (Kyn) is known to be particularly vasculotoxic and is implicated in several complications of CKD. Indoleamine 2,3-dioxygenase 1 (IDO), which catalyzes the first step in the metabolism of Tryptophan (Trp), regulates immune response to inflammatory cytokines in tissues. IDO plays a role in apoptosis and damage during acute kidney injury (AKI), a transient decrease in kidney function. During metabolism of Trp, IDO generates Kyn, a uremic solute, and therefore IDO may play a role in the brain and kidney damage due to accumulation of Kyn. The objective of the current study was to investigate the role and regulation of IDO in CKD pathology. Studies were performed to determine whether IDO is protective or pathologic and to find how IDO is regulated in the kidney during CKD. IDO in renopathology was examined using murine models of CKD. CKD was induced via a 0.2% adenine-supplemented diet (AD) model for 21 days. IDO regulation was examined using an Indoxyl Sulfate (IS)-specific solute model. Renal function in the IDO+/+ and IDO-/- AD mice was assessed through weekly measurement of blood urea nitrogen (BUN). H&E and Masson’s trichrome stains were used to assess percentages of glomerulosclerosis (GS) and immune infiltration (II), and combined interstitial fibrosis and tubular atrophy (IFTA) score in IDO+/+ and IDO-/- mice with and without CKD. IDO protein concentration in the kidneys of all mice with and without CKD and IDO+/+ IS mice was determined via immunoblotting. Patients with kidney disease suffer from neuropsychological disorders and neurocognitive decline. The effects of uremic solutes on the CNS was examined using immortalized human umbilical endothelial vein cells (HUVEC-TERT), in vitro. Cell proliferation and viability, in the presence of IS, were measured by BrdU and Alamar blue assays, respectively. In both IDO+/+ and IDO-/-, 21 days of AD results in significant deterioration of renal function. The average IFTA score and percentage of II in IDO-/- mice increased with AD compared to ND (p<0.05, p<0.001). IDO expression was seen sporadically in the glomeruli and walls of major vessels in the kidneys of 4d AD IDO+/+ mice, and in the tubules and vessel walls in the kidneys of 14d AD IDO+/+ mice. In IDO+/+ ND mice, endogenous IDO protein expression was undetectable at a signal intensity of 119.86 ± 268.01, whereas IDO+/+ AD mice showed a 370-fold higher level of IDO protein expression compared to IDO+/+ ND (p<0.001). IDO-/- AD IDO protein expression was 9.5-fold higher than in IDO-/- AD (p<0.05). IDO expression was found to be 58-fold higher in IDO+/+ mice with IS treatment (p<0.05). In the IS mice, non-significant trends toward decrease in cellular proliferation and viability with time were also observed (p=ns). IDO is upregulated at the protein level both in a CKD model and directly by the uremic solute, IS. IDO appears to be protective in the kidney during CKD, given the trend toward increased percentage of GS and II in IDO-/- compared to IDO+/+ mice with CKD, though there is little difference seen in total kidney IFTA. IDO upregulation is linked to increased apoptosis. Blocking uremic solute production would therefore prevent IDO protein upregulation and reduce apoptosis, alleviating renal damage during CKD.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第21861号 / 人博第890号 / 新制||人||213(附属図書館) / 2018||人博||890(吉田南総合図書館) / 京都大学大学院人間・環境学研究科共生人間学専攻 / (主査)教授 神﨑 素樹, 教授 石原 昭彦, 教授 久代 恵介 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

N-acetylaspartate (NAA) is one of the most abundant molecules in the mammalian central nervous system (CNS). The current paradigm suggests that NAA is synthesized in neurons by the enzyme N-acetyltransferase 8-like (NAT8L) and hydrolyzed into aspartate and acetate by the enzyme aspartoacylase (ASPA) in oligodendrocytes. Although the function of NAA is not well understood, several hypotheses have been proposed since its discovery several decades ago. Among the most cited theory is the concept of acetate delivery to oligodendrocytes via NAA for the synthesis of fatty acids for myelin lipids and myelination. Another concept suggests that NAA functions as a molecular water pump to remove molecular water from oxidative phosphorylation. In contrast, disruption of NAA metabolism has been associated with oxidative stress contributing to neurodegeneration, as seen in Canavan disease, a monogenic disorder associated with loss-of-function mutations in ASPA. Accumulation of NAA in the CNS and peripheral organs is pathognomonic for Canavan disease (CD) and is used clinically to diagnose this rare disease. Symptoms typically occur within months after birth and primarily manifest in the CNS with spongy degeneration of the white matter. Initially, affected patients present with poor feeding, lack of head control, hydrocephalus; later, they miss developmental milestones and develop seizures. Only supportive treatment is available possibly helping patients to survive past the first couple of years. Gene therapy has been considered early on for the treatment of CD. The first trial in humans demonstrated safety but did not result in symptomatic improvement. In addition to gene therapy for the treatment of CD, NAA has gained increasing interest in neurodegenerative and psychiatric disorders, but also in adipose tissue. Here, we are investigating the function of NAA in the context of ASPA deficiency, aka Canavan disease. We found that impaired NAA metabolism caused by ASPA mutations is characterized by a neurometabolic profile that suggests cellular shift from glucose towards fatty acid metabolism for energy production. Although, we found a similar metabolic signature in asymptomatic mice within days after birth, longitudinal comparison suggest that disease progression leads to fatty acid depletion, which is not present in asymptomatic mice, potentially challenging the concept that NAA-derived acetate is essential for lipid synthesis in the myelinating brain. Using rAAV to determine the reversibility of this metabolic phenotype, we found that early treatment prevents loss of myelin, normalizes the neurometabolic phenotype and keeps Canavan mice asymptomatic; in contrast, later treatment only allows for partial normalization of the neurometabolome, despite adequate ASPA gene delivery by rAAV, independent of ubiquitous or astrocyte-restricted hASPA expression. Furthermore, we found that non-enzymatically active hASPA might play a ubiquitous role in glucose uptake regulation in vivo. Importantly, we identified brain regions with metabolic changes that also correspond to the areas with significant histopathologic alterations. Finally, we confirmed the glycolytic changes in a Canavan disease patient cell line using Seahorse metabolic analyzer, demonstrating the decreased rate of glycolysis for energy production. Overall, our findings reveal a novel metabolic phenomenon in Canavan disease and NAA metabolism that allows to assign a novel function of N-acetylaspartate.

<div><b>Background:</b> Bupropion, an atypical antidepressant and smoking cessation aid, is associated with wide inter-subject variability in its efficacy and safety. Variability in response to bupropion therapy is thought to be driven by variability in metabolism. Bupropion undergoes complex phase 1 and 2 stereoselective metabolism. Though bupropion`s pharmacology is not fully understood, much of it is thought to be due to its metabolites, specially, S, S-hydroxybupropion. In vitro studies (functional assays measuring IC50 at dopamine transporter-DAT, norepinephrine transporter-NET, various subtypes of nicotinic receptors-nAChR) and mouse models (forced swim test to assess antidepressant effect, antinociceptive models to assess antagonism of nicotine effects) indicate S, S-hydroxybupropion to contribute more towards efficacy as an antidepressant and smoking cessation aid than racemic bupropion and R, R-hydroxybupropion, respectively. Both pharmacokinetics (PK) and pharmacodynamics (PD) of bupropion and its metabolites are complex and reported to be stereoselective. As bupropion is known to act on multiple central nervous system (CNS) targets (DAT, NET nAChR), understanding CNS disposition (target site) is critical to explain variability in bupropion`s therapeutic and toxic effects. </div><div><b>Objective: </b>The objective of our study was to characterize the exposure of bupropion enantiomers and corresponding phase 1 metabolite diastereomers in plasma and brain in a surrogate non-clinical species, and to subsequently develop animal-to-human-translational population-PK and Physiologically Based PK (PBPK) models to predict human brain concentrations of bupropion and its active metabolite S, S-hydroxybupropion. Application of these PK modeling approaches to map the time course of unbound brain concentration can then be compared to in vitro potency measures at DAT, NET and nAChRs to predict target engagement over time (PD). Establishing relationships between plasma PK, target site PK along with PD would elucidate possible cause(s) of inter-patient variability to bupropion therapy. </div><div><b>Methods: </b>The first step towards development of a CNS model was to identify a nonclinical species with phase 1 metabolism closest to humans. To accomplish this, hepatic microsomal incubations of four species-rat, mouse, non-human primates (NHPs) and humans were conducted separately for the R- and S-bupropion enantiomers, and the formation of enantiomer-specific metabolites was determined using LC-MS/MS. Intrinsic formation clearance (CLint) of metabolites across the four species (rats, mice, NHPs, humans) was determined from the formation rate versus substrate concentration relationship. </div><div>Racemic bupropion (10 mg/kg) and preformed S, S-hydroxybupropion (2 mg/kg) were administered subcutaneously to adult male Sprague Dawley rats (n = 24/compound). Brain and plasma were collected from rats (n = 3) at eight time points for 6 hours and analyzed using a chiral LC-MS/MS method. Rat plasma protein and brain homogenate binding studies were conducted for all analytes to correct for unbound fraction using equilibrium dialysis method.</div><div>A plasma-brain compartmental pharmacokinetic approach was used to describe the blood–brain-barrier transport of both bupropion and S, S-hydroxybupropion. Also, a 2-compartment permeability-limited brain model consisting of brain blood, brain mass compartments was developed and incorporated into a whole body physiologically-based pharmacokinetic (PBPK) parent-metabolite model for bupropion and S, S-hydroxybupropion. Both population PK and PBPK modeling approaches were subsequently translated to humans to predict human plasma and brain site exposure and its relationship to DAT and NET IC50 potencies.</div><div><b>Results: </b>The total clearance of S-bupropion was higher than that of R-bupropion in monkey and human liver microsomes. The contribution of hydroxybupropion to the total racemic bupropion clearance was 38%, 62%, 17%, and 96% in human, monkey, rat, and mouse, respectively. In the same species order, threohydrobupropion contributed 53%, 23%, 17%, and 3%, and erythrohydrobupropion contributed 9%, 14%, 66%, and 1.3%, respectively, to racemic bupropion clearance. Hepatic microsomal incubation studies indicated non-human primates to be the appropriate species to model CNS disposition. However, the cost and limited pharmacokinetic and pharmacodynamic data in NHPs were insurmountable barriers to conducting in vivo studies in NHPs. After considering multiple factors, such as the formation of reductive metabolites (higher in rats than mice), which are also thought to contribute to bupropion`s therapeutic efficacy, availability of microdialysis data measuring bupropion and dopamine, norepinephrine levels in brain extracellular fluid (ECF) and other in vitro potency evaluations in rats, rat was chosen as the surrogate species to model bupropion`s disposition.</div><div>In rats, unbound plasma and brain exposures and plasma clearances of both R and S-bupropion were similar. The exposure to parent was higher (50 to 100-fold) than to metabolites. The exposure of oxidative metabolites (R, R- and S, S-hydroxybupropion) was 2 to 3-fold higher in brain and plasma than reductive metabolites (R, R- and S, S-threohydrobupropion, S, R- and R, S-erythrohydrobupropion). Hepatic clearances of R- and S-bupropion scaled from in vitro rat hepatic microsomal incubation studies were 3-fold and 25-fold lower than their respective in vivo unbound apparent clearances. This could possibly be due to substantial contribution of metabolic pathways not characterized in this in vivo study and/or possible extrahepatic disposition in the rat. The unbound brain to unbound plasma AUC0-6h ratio (Kp,uu) of R- and S-bupropion were 0.43 and 0.38 respectively. Kp,uu of oxidative metabolites (R, R- and S, S-hydroxybupropion) and reductive metabolites (R, R- and S, S-threohydrobupropion) were close to 1. Kp,uu of S, R-erythrohydrobupropion was 0.43 and that of pre-formed S, S-hydroxybupropion was 5.</div><div>With respect to population PK modeling of both bupropion and S, S-hydroxybupropion, a plasma-brain compartmental model structure with time dependent change in brain influx clearance was required to adequately characterize the BBB transport of parent and this active metabolite. Using a physiologically-based pharmacokinetic model (PBPK) approach too, incorporation of active efflux and carrier mediated uptake terms in addition to passive permeability was necessary to adequately characterize brain disposition of bupropion and S, S-hydroxybupropion. Both modeling approaches (population-PK and PBPK) when translated to humans indicated that the predicted human brain exposures fall below the reported DAT and NET IC50 measures of bupropion and S, S-hydroxybupropion. </div><div><b>Conclusion: </b>Specific to our work in the rat, the discrepancy between in vitro scaled hepatic clearance and in vivo plasma clearance of R and S-bupropion suggests alternative non-CYP mediated clearance pathways and/or extra hepatic disposition of bupropion. Both translational PK models indicate active process such as efflux transporter or carrier mediated uptake could be involved in bupropion`s disposition in the brain. Variability in expression of these speculated active/carrier mediated transporters could possibly cause variability in response. Also, other CNS targets could contribute to bupropion`s therapeutic efficacy, elucidation of which would require further investigation.</div><div><br></div>