Bipolar disorder (BD) is a severe psychiatric illness with a consistent genetic influence, involving complex interactions between numerous genes and environmental factors. Immediate early genes (IEGs) are activated in the brain in response to environmental stimuli, such as stress. The potential to translate environmental stimuli into long-term changes in brain has led to increased interest in a potential role for these genes influencing risk for psychiatric disorders. Our recent finding using network-based approach has shown that the regulatory unit of early growth response gene 3 (EGR3) of IEGs family was robustly repressed in postmortem prefrontal cortex of BD patients. As a central transcription factor, EGR3 regulates an array of target genes that mediate critical neurobiological processes such as synaptic plasticity, memory and cognition. Considering that EGR3 expression is induced by brain-derived neurotrophic factor (BDNF) that has been consistently related to BD pathophysiology, we suggest a link between BDNF and EGR3 and their potential role in BD. A growing body of data from our group and others has shown that peripheral BDNF levels are reduced during mood episodes and also with illness progression. In this same vein, BDNF has been proposed as an important growth factor in the impaired cellular resilience related to BD. Taken together with the fact that EGR3 regulates the expression of the neurotrophin receptor p75NTR and may also indirectly induce BDNF expression, here we propose a feed-forward gene regulatory network involving EGR3 and BDNF and its potential role in BD.

Abstract Psychotic disorders usually become evident during adolescence and early adulthood and are commonly preceded by psychosis risk states. Young people at risk for developing psychosis may already have cognitive deficits. This research examined factors associated with psychosis risk and adverse cognitive performance, particularly in those at risk for developing psychosis. We aimed to characterise genetic risk factors for psychosis risk and adverse cognitive performance. Additionally, early and later biological risk markers for adverse cognitive performance and psychosis risk were explored. Two longitudinal birth cohorts, the Northern Finland Birth Cohort 1986 (NFBC 1986, n=6,985 at 16 years) and Avon Longitudinal Study of Parents and Children (ALSPAC, n=5,217 at 17 years), two NFBC 1986 sub-studies, the Oulu Brain and Mind 1 (n=182 for these analyses) and Oulu Brain and Mind 2 (n=471 for these analyses) studies, and two Irish case control studies, the Adolescent Brain Development (n=212) and Challenging Times (n=211) studies, were utilised. Predictors of interest were selected Single Nucleotide Polymorphisms (SNPs at COMT, BDNF and DRD2), prenatal exposure to maternal cigarette smoking (PEMCS) and adolescent metabolic measures. Though not directly associated with psychotic experiences, the COMT-Val158Met Val-Val genotype interacted with experience of childhood trauma to predict more psychotic experiences. Two DRD2 SNPs were associated with poorer cognitive performance, though only in those with risk for psychotic disorders. PEMCS was associated with adult vocabulary and matrix reasoning performance in males, though not in males with adolescent psychotic experiences. Adolescent academic performance, but not psychotic experiences, were associated with metabolic measures, especially with ratios of omega-3 to total fatty acids. These findings impact on prevention strategies for long-term adverse outcomes. Some risk factors differ for those with psychotic experiences compared to the general population, while others do not. SNPs at COMT and DRD2 may be more relevant in those with psychotic experiences. Interventions targeting these groups may be particularly beneficial. Smoking in pregnancy, however, is harmful to male cognitive performance across the population, suggesting elimination of this risk is more broadly relevant. Fatty acid-related metabolic measures may mark risk for cognitive deficits or may represent a developmental feature that is potentially open to intervention. / Tiivistelmä Psykoottiset häiriöt puhkeavat tavallisesti nuoruusiässä tai varhaisessa aikuisiässä. Varsinaista psykoosijaksoa edeltää usein psykoosialttiusvaihe. Nuoruusiän psykoosialttiusvaiheeseen liittyy kognitiivisia puutoksia. Tässä tutkimuksessa selvitettiin tekijöitä, jotka liittyvät psykoosialttiuteen ja heikkoon kognitiiviseen suoriutumiseen, etenkin nuorilla, jotka olivat psykoosiriskissä. Tutkimuksessa tarkasteltiin psykoosialttiuteen ja heikkoon kognitiiviseen suoriutumiseen liittyviä geneettisiä tekijöitä. Lisäksi tutkittiin biologisia varhaisia ja myöhempiä psykoosialttiutta ja heikkoa kognitiivista suoriutumista ennustavia tekijöitä. Tutkimusaineisto käsitti kaksi pitkittäistä syntymäkohorttia: Pohjois-Suomen syntymäkohortti 1986 (n=6,985 16-vuotiaana) ja englantilainen Avon Longitudinal Study of Parents and Children (ALSPAC, n=5,217 17-vuotiaana) -tutkimukset. Pohjois-Suomen syntymäkohortti 1986:sta analysoitiin kahta ala-otosta eli Aivot ja Mieli I (n=182) ja Aivot ja Mieli II (n=471) tutkimusta. Lisäksi tutkimusaineistoon kuului kaksi irlantilaista tapaus-verrokki tutkimusta: Adolescent Brain Development (n=212) ja Challenging Times (n=211) tutkimukset. Ennustavina tekijöinä tarkasteltiin yhden nukleotidin polymorfismia (Single Nucleotide Polymorphisms, SNP; COMT, BDNF ja DRD2 -geeneissä), äidin raskaudenaikaista tupakointia, lapsuuden traumaattisia kokemuksia ja nuoruusiän metabolisia arvoja. COMT-Val158Met geenin Val-Val genotyyppi ei ollut suoraan yhteydessä psykoottisiin kokemuksiin, mutta yhdessä lapsuuden traumaattisten kokemusten kanssa ennusti suurempaa psykoosioireiden määrää. Kaksi DRD2 SNP-varianttia assosioituivat heikompaan kognitiiviseen suoriutumiseen, vaikkakin vain tutkittavilla jotka olivat psykoosialttiita. Äidin raskaudenaikainen tupakointi ennusti huonompaa kognitiivista suoriutumista pojilla, tosin ei pojilla joilla oli nuoruusiässä psykoosioireita. Metaboliset tekijät, erityisesti omega-3 rasvahapon suhde kokonaisrasvahapon määrään oli yhteydessä koulumenestykseen. Tutkimuksen tulosten perusteella voidaan mahdollisesti suunnitella ennaltaehkäiseviä toimia myöhempien haittojen ehkäisemiseksi. Jotkut tutkituista riskitekijöistä assosioituivat eri tavalla kognitioon psykoosialttiilla kuin yleisväestössä. COMT ja DRD2 geenien variantit psykoosialttiilla saattavat olla keskeisiä. Interventiot nuorille, joilla on nämä variantit ja psykoosioireita, voisivat olla erityisesti hyödyllisiä. Äidin raskauden aikaisen tupakointi ennusti poikien kognitiivista suoriutumista. Äidin raskaudenaikaisen tupakoinnin vähentämisellä olisi suotuinen vaikutus tässäkin suhteessa. Rasvahappoihin liittyvät metaboliset suureet voivat olla riski kognitiivisille puutoksille tai ne voivat merkitä kehityksellistä piirrettä, joka voisi mahdollistaa varhaisen ennaltaehkäisyn.

Depression occurs in about one third of patients with stroke and cardiac arrest. Hyperactivity of the stress system is the most commonly observed neuroendocrine change in major depressive disorder (MDD), which involves elevated levels in the cerebrospinal fluid of corticotropin-releasing hormone (CRH), a key stress neurohormone. Substantial evidence suggests that normalization of the stress system may be a requirement for successful treatment of MDD through region-specific changes in the mesocorticolimbic circuitry. Thus, alteration in the stress system may underlie the emotional and functional impairments observed following brain ischemic events. In addition, recent findings suggest that ischemic brain injury triggers a restorative process, creating a cerebral environment similar to that of early brain development, a period characterized by rapid neuronal growth and neuroplasticity, critical to optimize functional recovery of individuals post stroke. In particular brain-derived neurotrophic factor (BDNF), has been shown to play an important role in the pathophysiology of major depression and cerebral ischemia. However, whether CRH can mediate the expression of BDNF in the reparative process triggered by ischemic injury remains to be characterized. Therefore, the purpose of the current thesis is to characterize the effect of pharmacological blockade of CRH signaling at the onset of a global ischemic stroke, on emotional and cognitive behaviors, alteration in the neuroendocrine stress system, and markers of neuroplasticity including BDNF. To do this, an animal model of global cerebral ischemia with subsequent behavioral testing and postmortem brain analysis was used to determine underlying biochemical and behavioral changes modulated by CRH signaling following brain ischemia. This doctoral work will help elucidate the relationship between CRH and BDNF in the context of cerebral ischemia, and may provide insights for therapies targeting the stress system. These studies address considerations such as: the interplay between stress, neuroplasticity and emotionality, and whether global ischemia can affect mood via changes in the HPA axis response.

Introdução: A fibromialgia (FM) é uma síndrome de dor crônica musculoesquelética difusa, cuja etiologia não está totalmente conhecida. A síndrome cursa com dor, alterações do humor e sintomas de ruptura do ritmo circadiano. Sabe-se que seu processo fisiopatogênico envolve um desbalanço entre os sistemas de modulação excitatório e inibitório da dor. A capacidade do sistema modulatório inibitório está enfraquecida, com hiperativação de neurônios e da neuroglia, constituindo um quadro de sensibilização central. Portanto, estudos adicionais são necessários para compreender a relação entre possíveis marcadores séricos da hiperativação neuronal, tais como o Brain Derived Neurotrophic Factor (BDNF) e a proteína S100 beta (S100B). Além disso, estudos que busquem opções terapêuticas com efeito em vias neurobiológicas alternativas, tais como a melatonina, uma indolamina com efeitos ressincronizador, analgésico, anti-inflamatório e em sistemas moduladores da dor, como o gabaérgico, opioidérgico e glutamatérgico. Objetivos: 1) Primário: Avaliar se os níveis séricos de BDNF e S100B teriam associação com a FM e se ambos os mediadores sorológicos poderiam ser associados com o limiar de dor à pressão. 2) Secundário: Testar o tratamento com melatonina isolada ou em combinação com amitriptilina é melhor que amitriptilina isolada para modificar o sistema modulatório da dor. Assim, para provar tais hipóteses, neste estudo foram quantificados a modulação condicionada da dor e níveis de BDNF sérico em pacientes que receberam tratamento com melatonina isolada ou associada com amitriptilina. Foi também testado se melatonina melhoraria os sintomas clínicos como dor, limiar de dor à pressão e qualidade do sono relacionado à FM. Métodos: Foram selecionadas pacientes com diagnóstico de FM de acordo com o American College of Rheumatology (ACR) 2010. No primeiro estudo, de desenho transversal, foram incluídas 56 mulheres com FM, com idades entre 18 e 65 anos. Foram avaliados o limiar de dor à pressão e dosagem sérica de BDNF e S100B. No segundo estudo, foram incluídas 63 pacientes com os mesmos critérios de inclusão descritos no estudo transversal. As pacientes foram randomizadas e receberam, ao deitar, amitriptilina (25mg) (n=21), melatonina (10mg) (n=21) ou melatonina (10 mg) + amitriptilina (25mg) (n=21), durante seis semanas. O sistema modulatório descendente da dor foi acessado pela modulação condicionada da dor, através da mensuração da escala numérica de dor (NPS(0-10)) durante aferição do limiar de dor ao calor. Resultados: O resultado do estudo transversal mostrou que BDNF e S100B séricos foram correlacionados. BDNF e S100B foram inversamente correlacionados com limiar de dor à pressão. BDNF sérico foi associado com limiar de dor à pressão, idade e transtorno obsessivo compulsivo, enquanto que S100B sérica foi apenas associada com limiar de dor à pressão. O ensaio clínico randomizado demonstrou que a melatonina aumentou a potência do sistema modulatório da dor inibitório e que a modulação condicionada da dor foi negativamente correlacionada com BDNF sérico. Conclusões: Os estudos desta tese demonstram que S100B e BDNF, ambos mediadores chave no processo de sensibilização central, foram inversamente correlacionados com o limiar de dor à pressão. BDNF sérico foi, ainda, inversamente correlacionado com a redução da dor. Portanto, a avaliação sérica de BDNF e S100B merece estudos adicionais para determinar seu potencial papel sinalizador no espectro da sensibilização central nessa doença. / Introduction: Fibromyalgia (FM) is a syndrome of chronic diffuse musculoskeletal pain whose etiology is not fully known. This syndrome causes pain, mood swings and symptoms of rupture of the circadian rhythm. Its pathophysiological process involves an imbalance between excitatory and inhibitory pain modulatory systems. The ability of inhibitory systems is weakened, providing a framework of central sensitization, with dysfunction in the descending pain modulatory system, hyper-activation of neurons and neuroglia. Therefore, additional studies are needed to understand the possible relationship between serum markers of neuronal hyperactivity, such as Brain Derived Neurotrophic Factor (BDNF) and S100B. Particularly, studies seeking therapeutic options with effect in neurobiological alternative pathways such as melatonin, a indolamine with resynchronization, analgesic, and anti-inflammatory effects and actions on the modulatory pain systems such as GABAergic, opiodergic and glutamatergic. Objectives: 1) Primary: Evaluate whether the serum levels of BDNF and S100B have association with FM and if both serological mediators could be associated with pressure pain threshold. 2) Secondary: To test the hypothesis that treatment with melatonin alone or in combination with amitriptyline is better than amitriptyline alone to modify the endogenous pain modulatory system. Thus, to prove these hypothesis, it was quantified the conditioned pain modulation and serum BDNF levels in FM patients receiving treatment with melatonin alone or in combination with amitriptyline. Also, it was tested whether melatonin would improve clinical symptoms such as pain, pressure pain threshold and quality of sleep related to FM. Methods: Patients with FM according to the American College of Rheumatology (ACR) 2010 were selected. In the first study, a cross-sectional design, 56 women aging 18-65 years old, with FM were included. It was evaluated the pressure pain threshold, and serum levels of BDNF and S100B. In the second study, 63 patients were included with the same inclusion criteria described in the cross-sectional study. Patients were randomized and received at bedtime amitriptyline (25 mg) (n = 21), melatonin (10 mg) (n = 21) or melatonin (10 mg) + amitriptyline (25 mg) (n = 21) for six weeks. The descending pain modulatory system was accessed by the conditioned pain modulation, measuring the numerical pain scale [NPS (0-10)] during the heat pain threshold. Results: On the cross-sectional study serum BDNF and S100B were correlated. Serum BDNF and S100B were correlated with the pressure pain threshold. Serum BDNF was associated with pressure pain threshold, age and obsessive compulsive disorder, while serum S100B was associated with pressure pain threshold, only. The randomized clinical trial showed that melatonin increased the efficacy of inhibitory pain modulatory system and the conditioned pain modulation was negatively correlated with serum BDNF. Conclusions: The studies of this thesis show that both key mediators of the central sensitization process, BDNF and S100B, were inversely correlated with the pressure pain threshold. They also showed that melatonin increased the inhibitory pain modutalory system. Furthermore, it emphasizes that serum BDNF was inversely correlated with pain reduction. Therefore, assessment of serum BDNF and S100B deserve further studies to determine their potential as a proxy for the central sensitization spectrum in FM.

A exposição a eventos traumáticos durante a infância está associada a um prejuízo na cognição, neurobiologia e morfologia cerebral. No entanto, não se sabe se o trauma está relacionado a essas mudanças em amostras que não apresentam potenciais fatores de confusão como idade avançada, cronicidade do transtorno psiquiátrico e múltiplos episódios de humor. O impacto do trauma na infância foi avaliado em duas amostras diferentes nesta tese: 1) crianças com e sem história de trauma; 2) pacientes com diagnóstico de THB logo após a recuperação do primeiro episódio de mania com e sem história de trauma na infância e controles saudáveis com e sem história de trauma na infância. Os resultados sugerem que o trauma está associado a mudanças na neurobiologia, cognição e morfologia cerebral. Crianças com trauma apresentaram aumento nos níveis de BDNF, TNF-α, IL-6 e IL-10 comparadas com crianças sem trauma. No entanto, após a exclusão de crianças com história de doença inflamatória, apenas os níveis de BDNF e TNF-α permaneceram aumentados em crianças com trauma. Na população com transtorno bipolar, a história de trauma na infância foi associada a uma diminuição no QI, atenção auditiva e memória verbal e memória de trabalho enquanto um padrão diferente foi observado nos controles saudáveis com história de abuso infantil. Pacientes com THB e trauma também apresentaram menor volume total do CC em comparação aos pacientes com THB e sem trauma, com diferenças significativas também na região anterior do CC. Por outro lado, não encontramos diferenças significativas entre o volume do CC nos pacientes com ou sem trauma em comparação aos controles saudáveis. Estes achados reforçam a extensão e gravidade do impacto negativo do trauma na infância, em diferentes etapas do desenvolvimento, afetando tanto aspectos cognitivos, como neurobiológicos e de morfologia cerebral. / Exposure to traumatic events during childhood is associated with impairment in cognition, neurobiology and brain morphology. However, it is unknown if trauma is related to these changes in samples that do not show the potential confounds of advancing age, chronicity of psychiatry disorder and multiple mood episodes. We evaluated the impact of childhood trauma in two different samples: 1) children with and without childhood trauma; 2) pacients with a BD diagnosis recently recovered from a first manic episode with and without childhood trauma and healthy controls with and without childhood trauma. The results suggest that childhood trauma is associated to changes in neurobiology, cognition and brain morphology. Children with trauma showed higher levels of BDNF, TNF-α, IL-6 e IL-10 compared to children without trauma. However, after excluding children with history of inflammatory disease, only BDNF and TNF-α levels remained increased in children with trauma. In BD patients, the childhood trauma was associated to a decreased IQ, auditory attention, verbal memory, and working memory and a different pattern was observed in healthy subjects with a history of childhood abuse. The total CC volume was found to be smaller in BD patients with trauma compared to BD patients without trauma and differences were more pronounced also in the anterior region of the CC. On the other hand, we did not find significant differences in the CC volume of patients with/without trauma compared to the healthy subjects. These findings reinforce the extent and severity of the negative impact of childhood trauma in different stages of development, affecting cognitive aspects, as well as neurobiological and brain morphology.

Le déclin cognitif associé au vieillissement chez l’Homme, impacte fortement la vie quotidienne des personnes âgées. Si la pratique musicale apparait comme une activité de loisir prometteuse pour le maintien d’un bon fonctionnement cognitif au cours du vieillissement, les mécanismes neurobiologiques sous-jacents sont à l’heure actuelle, mal connus. L’objectif de ce travail a donc été d’étudier les effets d’une exposition tardive et chronique à la musique sur les performances comportementales et certains processus neurobiologiques au cours du vieillissement chez le rat Wistar. Si quelques études rapportent qu’une exposition à la musique améliore les performances d’apprentissage et de mémoire, associé à une augmentation de la neurogenèse hippocampique et du BDNF chez le Rongeur jeune adulte, il n’en existe aucune qui se soit intéressée à ces effets chez le Rongeur âgé. Des rats d’âge médian ont été répartis dans 2 groupes, l’un exposé à de la musique et l’autre à du bruit blanc, puis inclus dans une étude longitudinale, au cours de laquelle les performances comportementales ont été évaluées jusqu’à l’âge de 24 mois, suivi d’analyses biologiques. Ainsi, nous avons pu montrer qu’une exposition chronique à la musique démarrant à un âge médian, réduit le déclin cognitif associé au vieillissement. En revanche, la neurogenèse hippocampique et le BDNF n’apparaissent pas comme des mécanismes neurobiologiques potentiels impactés par la musique chez le rat âgé. / Cognitive decline associated to aging impacts daily life of elderly. While the music practice appears as promising leisure activity to prevent cognitive decline in elder, little is known about the neurobiological mechanisms involved. The aim of this work was to study the effects of music exposure on behavioral performances and some neurobiological processes across aging in rats. Indeed, improved behavioral performances together with an increased hippocampal neurogenesis and a higher BDNF expression were reported after music exposure in both young and adult animals. Yet, no study has so far investigated these effects in aged rats. After a fine appraisal of the cognitive state in middle-aged Wistar rats (15 months), they were divided in two groups, exposed either to classic music or to white noise. Thereafter, a longitudinal follow up of 9 months was performed. We observed for the first time that chronic music exposure alleviated age-related cognitive decline. However, contrary to what was observed in adult animals, we did not reported any differences in age-related changes of hippocampal neurogenesis and BDNF expression. These promising results of a beneficial effect of music exposure in the field of aging still lay open the question about the underlying mechanisms in the context of aging of the beneficial effect of music exposure.

Detailed knowledge of the role that particular genes and factors play during the development and in the normal function of the auditory system is necessary to develop successful regenerative inner ear therapies. Islet1 transcription factor and brain derived neurothrophic factor (BDNF) have great potential to play a role in regenerative inner ear therapy as both have been shown to be sufficient for self-repair regeneration in cochlea in animal studies. In this study we looked at the roles these two factors play in the development and function of the auditory system. In the transgenic mice used in the study, overexpression of Isl1 affected cell specification during embryonic development, leading to enlargement of the cochleovestibular ganglion and accelerated nerve fiber extension and branching in mutant embryos. The hearing of young transgenic mice was not affected. However, it started to decline in 1-month-old animals. This early onset of age-related hearing loss was found to be a consequence of the neurodegeneration of the olivocochlear system caused by Pax2-driven Isl1 misexpression in the hindbrain. Our data provide the first evidence that the alternation of the olivocochlear system efferent system accelerates the age-related functional decline of hearing without the loss of OHCs. The functional role of...

The doctoral dissertation: Searching for pathomechanisms of late-life minor depression – a combined MRI, biomarker and meta-analytic study was one of the first studies investigating the underlying pathophysiology of minor depression. The dissertation comprises a systematic review of the prevalence rates of minor depression, two meta-analyses of peripheral BDNF changes in major depressive disorder, as well as two original studies investigating serum BDNF, S100B and NSE levels and gray matter changes in minor depression. The limitations of studies and proposed improvements to the study design are discussed extensively.:1. INTRODUCTION 1.1 Motivation 1.1.1 Minor depression in the spectrum of psychiatric disorders 1.1.2 Minor depression is prevalent but unrecognized. 1.2 Theoretical background 1.2.1 Overview of depression hypotheses 1.2.2 Neurotrophic hypothesis of depressive disorders 1.2.3 Glial hypothesis of depressive disorders 1.2.4 Structural neuroimaging changes in major depression 1.3. Rationale and hypotheses of the empirical studies 1.3.1 Research questions 1.3.2 Research hypotheses 2. EMPIRICAL STUDIES 2.1 The prevalence of minor depression in the late life 2.2 The meta-analysis of BDNF changes in mood disorders 2.3 The meta-analysis of BDNF changes following ECT in depression 2.4 Serum biomarkers in minor depression 2.5 Structural brain imaging in minor depression 3. GENERAL DISCUSSION 3.1 Summary of results 3.2 Implications for research 3.3 Implications for clinical studies SUMMARY REFERENCES APPENDIX A: DECLARATION OF CONTRIBUTION APPENDIX B: STATEMENT OF AUTHORSHIP APPENDIX C: CURRICULUM VITAEAPPENDIX D: ACADEMIC CONTRIBUTIONS APPENDIX E: ACKNOWLEDGMENT

Detailed knowledge of the role that particular genes and factors play during the development and in the normal function of the auditory system is necessary to develop successful regenerative inner ear therapies. Islet1 transcription factor and brain derived neurothrophic factor (BDNF) have great potential to play a role in regenerative inner ear therapy as both have been shown to be sufficient for self-repair regeneration in cochlea in animal studies. In this study we looked at the roles these two factors play in the development and function of the auditory system. In the transgenic mice used in the study, overexpression of Isl1 affected cell specification during embryonic development, leading to enlargement of the cochleovestibular ganglion and accelerated nerve fiber extension and branching in mutant embryos. The hearing of young transgenic mice was not affected. However, it started to decline in 1-month-old animals. This early onset of age-related hearing loss was found to be a consequence of the neurodegeneration of the olivocochlear system caused by Pax2-driven Isl1 misexpression in the hindbrain. Our data provide the first evidence that the alternation of the olivocochlear system efferent system accelerates the age-related functional decline of hearing without the loss of OHCs. The functional role of...

Les plaquettes sont considérées comme l'un des réservoirs les plus importants non seulement des facteurs de croissance, mais aussi des facteurs neurotrophiques qui pourraient contribuer à la réparation des lésions vasculaires et à la prévention de la détérioration neurologique. Parmi ces facteurs, le facteur neurotrophique dérivé du cerveau (Brain-Derived Neurotrophic Factor ou BDNF) – une protéine appartenant à la famille des neurotrophines– est largement exprimée à la fois dans l'hippocampe et au niveau des plaquettes. Les plaquettes constituent un important réservoir de BDNF; cependant, on ne sait que peu de choses sur les facteurs modulant la libération de ce dernier dans la circulation et si les médicaments antiplaquettaires affectent cette sécrétion. Dans le cadre de ce projet, nous avons émis l’hypothèse principale que les différentes voies d’activation plaquettaire peuvent mener à une libération de BDNF, où celle-ci est affectée par les antiplaquettaires. A cette fin, les plaquettes ont été isolées à partir d’échantillons sanguins de volontaires sains (Groupe 1), de patients souffrant de maladies cardiovasculaires stables requérant la prise de médicaments antiplaquettaires [en prévention secondaire et en double thérapie à l’acide acétylsalicylique (ASA ou Aspirine) en association avec un antagoniste du récepteur P2Y12], (Groupe 2) ou en monothérapie à l’ASA (Groupe 3), versus de patients atteints de maladies valvulaires ou de cardiomyopathies ne requérant pas la prise de médicaments antiplaquettaires (Groupe 4). L’agrégation plaquettaire a été étudiée par agrégométrie optique en réponse à des agonistes spécifiques : adénosine diphosphate (ADP), acide arachidonique (AA), épinéphrine, collagène et Thrombin-receptor activated peptide 6 (TRAP-6 amide). Les antiplaquettaires testés sont dirigés contre la cyclo-oxygénase-1 ou COX-1 (ASA), contre le récepteur de P2Y12 de l’ADP (AR-C) et contre le récepteur αIIbβ3 du fibrinogène (Abciximab). La libération du BDNF a été quantifiée par ELISA. La présence du BDNF et de son récepteur Tropomyosin-Related Kinase Receptor type B (TrKB) a été détectée par immunobuvardage. Nous avons montré que l’activation des plaquettes par les différents agonistes testés induit une agrégation plaquettaire de l’ordre de 80% et permet de libérer jusqu’à 5 fois plus de BDNF, passant de 2500 pg / 250 x 106 plaquettes à l’état basal à approximativement 13000 pg / 250 x 106 plaquettes à l’état stimulé. Tous les antiplaquettaires testés réduisent la libération de BDNF par les plaquettes stimulées. Cependant, le niveau d’inhibition et sa significativité dépendent de la nature de l’agoniste; à savoir que l’ASA réduit significativement la sécrétion de BDNF en réponse à l’AA, à l’épinéphrine et au TRAP-6; alors que l’AR-C était plus efficace en réponse à l’ADP, l’AA et l’épinéphrine. L’Abciximab est un antagoniste qui inhibe la sécrétion de BDNF en réponse à tous les agonistes, en inhibant aussi l’agrégation plaquettaire. Notons que la libération de BDNF en réponse au collagène est inhibée par l’ASA et l’AR-C, alors que l’agrégation n’a pas été affectée. Ainsi, aucune corrélation positive et significative entre l’agrégation plaquettaire et la libération de BDNF n’a pu être obtenue. La présence des antiplaquettaires réduits à différents degrés la libération de BDNF chez les différents groupes des patients, malgré que son expression intraplaquettaire était similaire entre les groupes. On remarque que les antiplaquettaires réduisent plus significativement la quantité du BDNF relâchée chez les patients sous mono ou double thérapie antiplaquettaire en comparaison avec les volontaires sains et les patients atteints de maladies valvulaires. Nous avons aussi démontré que le BDNF exogène active les plaquettes isolées et lavées chez les volontaires sains, en induisant une forte agrégation stable et irréversible. Par contre, le BDNF exogène n’arrive pas à agréger les plaquettes en plasma riche en plaquettes. De plus, nos résultats indiquent que la forme tronquée du récepteur BDNF, le TrKB, est exprimée au niveau des plaquettes de volontaires sains. L’inhibition de l’activité kinase du TrKB abolit l’agrégation induite par le BDNF. Ces résultats suggèrent que l’action du BDNF dans les plaquettes lavées pourrait passer par l’intermédiaire du TrKB. Cette étude nous permet de conclure que le BDNF est présent dans les plaquettes et est libéré suite à l’activation plaquettaire et que cette libération est réduite par les antiplaquettaires. Cependant, l’agrégation plaquettaire ne semble pas être associée directement à la sécrétion du BDNF, ce qui suggère que d’autres mécanismes sous-jacents pourraient intervenir dans le contrôle de cette sécrétion. Les antiplaquettaires réduisent la libération de BDNF et il semble que l’action pro-agrégante du BDNF sur les plaquettes lavées passe par l’intermédiaire du TrKB, sans exclure la possibilité que d’autres types de récepteurs plaquettaires soient impliqués dans le signal déclenché par le BDNF. L’implication physiopathologique du BDNF libéré suite à l’activation plaquettaire ou sa biodisponibilité en présence des antiplaquettaires au niveau cardiovasculaire reste à être élucidée afin de révéler son potentiel diagnostique ou thérapeutique. / Platelets are considered one of the most important reservoirs not only of growth factors but also of neurotrophic factors that may contribute to the repair of vascular lesions and prevention of neurological deterioration. Among these factors, the Brain-Derived Neurotrophic Factor (BDNF), a protein belonging to the neurotrophin family, is largely expressed in both the hippocampus and platelets. In fact, platelets constitute an important reservoir of BDNF; however, little is known about the factors controlling its release into the circulation and whether antiplatelet drugs affect this secretion. Henceforth, the main hypothesis of this project is that platelet activation pathways lead to BDNF release which is affected by antiplatelet agents. For this purpose, platelets were isolated from the blood of four groups of human subjects following their consent. Group 1 consisted of healthy volunteers; Group 2 and Group 3 consisted of patients with stable cardiovascular disease on, respectively, dual antiplatelet therapy (aspirin + P2Y12 receptor antagonist) or monotherapy (aspirin) as secondary prevention; and Group 4 consisted of patients with valvular disease or cardiomyopathy who are not on antiplatelet therapy. Platelet aggregation was studied by optical aggregometry in response to the following agonists: adenosine diphosphate (ADP), arachidonic acid (AA), epinephrine, collagen, and thrombin-receptor activated peptide 6 (TRAP-6 amide). The antiplatelet agents that were tested antagonize cyclooxygenase-1 (COX-1) (acetylsalicylic acid (ASA) or aspirin), ADP P2Y12 receptor (AR-C), and fibrinogen receptor αIIbβ3 (Abciximab). BDNF release was quantified by ELISA. BDNF protein and its Tropomyosin-Related Kinase Receptor Type B (TrKB) receptor were detected by immunoblotting. Our results show that platelet activation in response to several agonists tested induced 80% platelet aggregation and augmented BDNF release by 5 folds, from 2500 pg / 250 x 106 platelets at baseline to approximately 13000 pg / 250 x 106 after stimulation. Moreover, all the tested antiplatelet agents reduced the release of BDNF by stimulated platelets. However, the level of reduction varied differentially between platelet antagonists depending on the platelet agonist used. Indeed, ASA significantly reduced BDNF secretion in response to AA, epinephrine, and TRAP-6, whereas AR-C was more effective in response to ADP, AA, and epinephrine. Abciximab inhibited BDNF secretion as well as platelet aggregation in response to all agonists. Noteworthy, the release of BDNF in response to collagen was inhibited by ASA and AR-C, while platelet aggregation was not affected. Accordingly, no significant correlation between platelet aggregation and BDNF release could be obtained. Although intra-platelet expression was similar in the different groups, the presence of antiplatelet agents reduced the release of BDNF to varying degrees between groups. As such, antiplatelet agents reduced BDNF release more significantly in patients on dual or mono antiplatelet therapy (Groups 2 and 3) as compared to healthy volunteers (Group 1) and valvular disease patients (Group 4). We have also shown that exogenous BDNF activated isolated/washed platelets from healthy volunteers, inducing strong, stable, and irreversible aggregation. In contrast, exogenous BDNF could not induce aggregation of platelets in platelet-rich plasma. In addition, our results indicate that the truncated form of the BDNF receptor, TrKB, is expressed in platelets of healthy volunteers. Hence, the inhibition of TrKB kinase activity abolished BDNF-induced aggregation. These results suggest that the action of BDNF in washed platelets might ensue through TrKB. We conclude from this study that BDNF is present in platelets and released following platelet activation, and its release is reduced by antiplatelet agents. However, platelet aggregation does not appear to be directly associated with BDNF secretion, suggesting that other underlying mechanisms may be involved in controlling its secretion. Antiplatelet agents reduce the release of BDNF, and it appears that the pro-aggregating action of BDNF on washed platelets ensues, non-exclusively, through TrKB, which means that other types of platelet receptors may also be involved in BDNF signaling. The pathophysiological implication of BDNF released following platelet activation or its bioavailability in the presence of antiplatelet agents in the cardiovascular system thus remain to be elucidated in order to reveal its diagnostic or therapeutic potential.