Pharmacological fMRI; a clinical exploration

Dit proefschrift beschrijft de resultaten van een verkennend onderzoek naar een nieuwe techniek die gebruikt kan worden om de effecten van geneesmiddelen op hersenaktiviteit af te beelden: pharmacologische functionele magnetic resonance imaging (farmacologische fMRI of phMRI). Met behulp van deze techniek werden de effecten onderzocht van drie verschillende medicijnen (de bètablokker propranolol, de selectieve oestrogeen-receptor modulator (SERM) raloxifene en de cholinesteraseremmer galantamine) op hersenaktiviteit van respectievelijk gezonde jongere en oudere controles, en patiënten met geheugenklachten. Aan de hand van de resultaten van dit onderzoek werd nagegaan in hoeverre phMRI toepasbaar zou kunnen zijn in een klinische context. De MRI scanner is al bijna 30 jaar een vast onderdeel van het instrumentarium van radiologen. MRI is een volledig non-invasieve scantechniek die artsen in staat stelt om haarscherpe, driedimensionale afbeeldingen te maken van de verschillende organen van levende patiënten en de eventuele ziekteprocessen die zich daarin afspelen. fMRI is een meer recente toepassing van MRI, waarbij de wisselende magnetische eigenschappen van de rode bloedkleurstof ‘hemoglobine’ worden benut om zwart-wit contrast te geven aan MR plaatjes (Jezzard et al., 2001). Afhankelijk van de mate waarin hersengebieden aktief zijn wordt een sterker of minder sterk bloed-oxygenatie afhankelijk (BOLD) MR signaal gemeten. De meeste fMRI studies vergelijken de gemiddelde signaalintensiteiten van hersengebieden tussen actieve en een minder actieve condities van een bepaalde taak, die tijdens het scannen wordt uitgevoerd. Dit levert driedimensionaal plaatjes op van het hele brein, waarin de gemiddelde intensiteitsverschillen tussen twee taak-condities zijn af te lezen (“contrast plaatjes”). phMRI is een verdere nuancering van fMRI, waarbij contrastplaatjes worden onderzocht op toenames of afnames van intensiteitsverschillen als gevolg van blootstelling aan een bepaalde farmacologische stof. Aangezien de meeste psychotrope geneesmiddelen aangrijpen in specifieke neurotransmittersystemen zou phMRI gebruikt kunnen worden om de toestand van deze systemen te onderzoeken in de gezonde en de zieke situatie. phMRI zou dus eventueel als klinisch-diagnostisch instrument kunnen worden gebruikt. Er is echter nog maar weinig onderzoek gedaan naar de klinische waarde van phMRI (Honey and Bullmore, 2004). Dit proefschrift had tot doel dit terrein verder te verkennen. Patiënten en proefpersonen werden gescand met behulp van fMRI tijdens het uitvoeren van speciaal voor dit onderzoek ontwikkelde geheugentestjes (paradigmata). Hierdoor waren we in staat om hersengebieden zichtbaar te maken die betrokken zijn bij verschillende aspecten van geheugenfunctie. De effecten van geneesmiddelen werden onderzocht op hersenfunctie zoals die werd opgeroepen door bovengenoemde taken. We gebruikten achtereenvolgens een ‘face-encoding’ taak (onthouden van onbekende menselijke gezichten (Small et al., 1999)), een ‘face-recognition’ taak (herkennen van eerder getoonde gezichten), en een n-letter back werkgeheugen taak (tijdelijke opslag van nieuwe informatie (Owen et al., 2005)). Verder werd in samenwerking met Dr. A.H. van Stegeren and Prof. Dr. W.TA.M. Everaerd van de afdeling Klinische en Experimentele Psychologie van de Universiteit van Amsterdam het International Affective Picture System (IAPS) (Lang and Bradley, 1997), aangepast voor gebruik in de MR scanner. Deze taak had tot doel hersengebieden te aktiveren die betrokken zijn bij de opslag van emotioneel negatief geladen (onprettige) informatie. fMRI analyses werden gedaan met de fMRI expert analysis tool (FEAT) uit het data-analyse pakket fMRIB software library (FSL) (Smith et al., 2004). Ons onderzoek leverde de volgende bevindingen op: 1. Effecten van verschillende geneesmiddelen op hersenfunctie bij mensen kunnen worden gemeten met behulp van fMRI, maar zijn vrij klein. 2. Onze bevindingen sluiten aan bij die van ander fMRI onderzoek waaruit blijkt dat de effecten van geneesmiddelen op hersenfunctie regio-specifiek en proces-specifiek kunnen zijn (Honey and Bullmore, 2004). 3. De effecten van geneesmiddelen op hersenfunctie zijn tevens geslachts- en ziekte-(stadium)-specifiek. 4. Deze effecten zijn afhankelijk van de duur van blootstelling aan het farmacologische agens. 5. In het geval van cholinerge stimulatie leidde een éénmalige stootdosis galantamine al tot regio- proces- en ziektespecifieke effecten. 6. We hebben een methode ontwikkeld om de effecten van geneesmiddelen op hersenfunctie tijdens geheugenfunctie te onderzoeken in relatie tot gedragsveranderingen en specifieke hersenprocessen. 7. Indien grote groepen patiënten geïncludeerd worden zijn uitgebreide studies naar de klinische (vroegdiagnostische en predictieve) waarde van de gemeten effecten zeer goed mogelijk. phMRI is voorlopig nog een onderzoeksinstrument. Vanuit klinisch oogpunt kunnen de bevindingen van phMRI studies echter erg interessant zijn. Studies van de regio- en proces-specificiteit van geneesmiddelen kunnen helpen bij het ontwikkelen van geneesmiddelen die meer gericht inwerken op specifieke hersenprocessen. Dit zou mogelijk de effectiviteit van geneesmiddelen kunnen verhogen en het aantal bijwerkingen kunnen verminderen. phMRI kan verder worden ingezet om het werkingsmechanisme van psychotrope geneesmiddelen te onderzoeken. phMRI provokatietests laten bovendien zien dat de onmiddellijke effecten van geneesmiddelen een vroeg-diagnostische waarde kunnen hebben, en misschien zelfs het succes van farmacotherapie kunnen voorspellen (Fu et al., 2004). Toekomstig onderzoek zal moeten uitwijzen in hoeverre phMRI in staat is om klinisch relevante functionele biomarkers aan te tonen in individuele patiënten. Ondertussen kunnen groepsstudies al resultaten leveren die van klinisch belang zouden kunnen zijn voor individuele patiënten. Met phMRI provokatietests kunnen relaties worden gelegd tussen bepaalde klinische verschijnselen en een afwijkende reactiviteit van centrale neurotransmittersystemen. Zijn zulke relaties eenmaal gelegd, dan kunnen patiënten die zich presenteren met de bewuste symptomen of afwijkingen worden behandeld met een gerichte farmacotherapie. De ontwikkelingen in de methodologie van fMRI staan ondertussen niet stil. Er is inmiddels een arsenaal aan nieuwe analysemethoden beschikbaar gekomen, die van belang zouden kunnen zijn voor toekomstig phMRI onderzoek. Ook al staat farmacologische fMRI nog in de kinderschoenen, er wordt met grote stappen vooruitgang geboekt. Het is dus waarschijnlijk dat phMRI, in combinatie met andere technieken, een belangrijk bijdrage zal gaan leveren aan de zoektocht naar biologische markers met een bruikbare klinische waarde. Reference List Fu CHY, Williams SCR, Cleare AJ, Brammer MJ, Walsh ND, Kim J, Andrew CM, Pich EM, Williams PM, Reed LJ, Mitterschiffthaler MT, Suckling J, Bullmore ET. Attenuation of the neural response to sad faces in major depression by antidepressant treatment - A prospective, event-related functional magnetic resonance imaging study. Archives of General Psychiatry 2004; 61:877-889. Honey G, Bullmore E. Human pharmacological MRI. Trends in Pharmacological Sciences 2004; 25:366-374. Jezzard P, Matthews PM, Smith SM. Functional MRI - An introduction to methods. New York: Oxford University Press, 2001. Lang PJ, Bradley MM. International affective picture system (IAPS); Technical manual and affective ratings. NIMH Center for the study of emotion and attention 1997. Owen AM, McMillan KM, Laird AR, Bullmore E. N-back working memory paradigm: A meta-analysis of normative functional neuroimaging. Hum.Brain Mapp. 2005; 25:46-59. Small SA, Perera GM, DeLaPaz R, Mayeux R, Stern Y. Differential regional dysfunction of the hippocampal formation among elderly with memory decline and Alzheimer's disease. Annals of Neurology 1999; 45:466-472. Smith SM, Jenkinson M, Woolrich MW, Beckmann CF, Behrens TEJ, Johansen-Berg H, Bannister PR, De Luca M, Drobnjak I, Flitney DE, Niazy RK, Saunders J, Vickers J, Zhang YY, De Stefano N, Brady JM, Matthews PM. Advances in functional and structural MR image analysis and implementation as FSL. Neuroimage 2004; 23:S208-S219.Barkhof, F. [Promotor]Scheltens, P. [Promotor]Rombouts, S.A.R.B. [Copromotor

Adjunctive raloxifene treatment improves attention and memory in men and women with schizophrenia

There is increasing clinical and molecular evidence for the role of hormones and specifically estrogen and its receptor in schizophrenia. A selective estrogen receptor modulator, raloxifene, stimulates estrogen-like activity in brain and can improve cognition in older adults. The present study tested the extent to which adjunctive raloxifene treatment improved cognition and reduced symptoms in young to middle-age men and women with schizophrenia. Ninety-eight patients with a diagnosis of schizophrenia or schizoaffective disorder were recruited into a dual-site, thirteen-week, randomized, double-blind, placebocontrolled, crossover trial of adjunctive raloxifene treatment in addition to their usual antipsychotic medications. Symptom severity and cognition in the domains of working memory, attention/processing speed, language and verbal memory were assessed at baseline, 6 and 13 weeks. Analyses of the initial 6-week phase of the study using a parallel groups design (with 39 patients receiving placebo and 40 receiving raloxifene) revealed that participants receiving adjunctive raloxifene treatment showed significant improvement relative to placebo in memory and attention/processing speed. There was no reduction in symptom severity with treatment compared with placebo. There were significant carryover effects, suggesting some cognitive benefits are sustained even after raloxifene withdrawal. Analysis of the 13-week crossover data revealed significant improvement with raloxifene only in attention/processing speed. This is the first study to show that daily, oral adjunctive raloxifene treatment at 120 mg per day has beneficial effects on attention/processing speed and memory for both men and women with schizophrenia. Thus, raloxifene may be useful as an adjunctive treatment for cognitive deficits associated with schizophrenia.TW Weickert, D Weinberg, R Lenroot, SV Catts, R Wells, A Vercammen, M O, Donnell, C Galletly, D Liu, R Balzan, B Short, D Pellen, J Curtis, VJ Carr, J Kulkarni, PR Schofield and CS Weicker

Role of estrogen and other sex hormones in brain aging: Neuroprotection and DNA repair

Aging is an inevitable biological process characterized by a progressive decline in physiological function and increased susceptibility to disease. The detrimental effects of aging are observed in all tissues, the brain being the most important one due to its main role in the homeostasis of the organism. As our knowledge about the underlying mechanisms of brain aging increases, potential approaches to preserve brain function rise significantly. Accumulating evidence suggests that loss of genomic maintenance may contribute to aging, especially in the central nervous system (CNS) owing to its low DNA repair capacity. Sex hormones, particularly estrogens, possess potent antioxidant properties and play important roles in maintaining normal reproductive and non-reproductive functions. They exert neuroprotective actions and their loss during aging and natural or surgical menopause is associated with mitochondrial dysfunction, neuroinflammation, synaptic decline, cognitive impairment and increased risk of age-related disorders. Moreover, loss of sex hormones has been suggested to promote an accelerated aging phenotype eventually leading to the development of brain hypometabolism, a feature often observed in menopausal women and prodromal Alzheimer's disease (AD). Although data on the relation between sex hormones and DNA repair mechanisms in the brain is still limited, various investigations have linked sex hormone levels with different DNA repair enzymes. Here, we review estrogen anti-aging and neuroprotective mechanisms, which are currently an area of intense study, together with the effect they may have on the DNA repair capacity in the brain.Fil: Zarate, Sandra Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas; ArgentinaFil: Stevnsner, Tinna. University of Aarhus; DinamarcaFil: Gredilla, Ricardo. Universidad Complutense de Madrid; Españ

Mécanismes de neuroprotection de stéroïdes neuroactifs de la toxicité du MPTP

Tableau d'honneur de la Faculté des études supérieures et postdorales, 2014-2015Les études chez l’humain et les modèles animaux ont montré que les œstrogènes exercent des effets bénéfiques importants sur le risque de développer la maladie de Parkinson. Bien que les œstrogènes soient neuroprotecteurs, leurs actions périphériques limitent actuellement leur utilisation pour le traitement ou la prévention de maladies neurodégénératives, d’où l’importance de trouver des stratégies alternatives qui reproduisent les effets favorables des œstrogènes mais minimisent les effets indésirables. Lors de cette thèse, nous avons montré que l’activation du récepteur membranaire des œstrogènes couplé aux protéines G (GPER1), un récepteur non-féminisant, est aussi puissante que le 17β-estradiol à protéger les neurones dopaminergiques de la toxicité du MPTP chez des souris mâles, un modèle de la maladie de Parkinson. La neuroprotection par le 17β-estradiol est perdue lorsque le GPER1 ou les récepteurs des œstrogènes (ER) α/β sont bloqués, montrant que les ERα/β et le GPER1 sont requis dans la protection des neurones dopaminergiques par le 17β-estradiol. Ces résultats suggèrent une potentielle interaction entre les ERα/β et le GPER1. Utilisant une approche pharmacologique, nos résultats montrent que le ERα interagit avec le GPER1 pour augmenter la signalisation d’Akt ainsi que les niveaux de Bcl-2 et du BDNF, et protéger les neurones dopaminergiques de l’effet toxique du MPTP. L’effet neuroprotecteur du GPER1 se fait indépendamment des ERα/β, quoique le GPER1 requière la collaboration des ERα/β pour augmenter les niveaux du BDNF. L’investigation du mécanisme d’action du raloxifène, un modulateur sélectif des récepteurs des œstrogènes utilisé en clinique, a révélé que le raloxifène agit par le GPER1 pour activer Akt, augmenter les niveaux de Bcl-2 et du BDNF, et protéger les neurones dopaminergiques et les niveaux plasmatiques d’androgènes. La progestérone, un stéroïde non-féminisant, possède également des propriétés neuroprotectrices chez les souris MPTP. De plus, nos résultats montrent que la progestérone, lorsqu’administrée après le MPTP, permet la récupération partielle des neurones dopaminergiques. Lors de cette thèse, nous avons montré l’effet neuroprotecteur de plusieurs composés qui pourraient servir de stratégies alternatives à l’utilisation des œstrogènes. L’investigation des récepteurs oestrogéniques impliqués dans la neuroprotection fournissent d’importantes informations pour le développement de nouvelles thérapies.Studies in humans and animal models have shown that estrogens exert significant beneficial effects on the risk to develop Parkinson's disease. Although estrogens are neuroprotective, their peripheral actions currently limit their use for the treatment or prevention of neurodegenerative diseases, hence the importance of finding alternative strategies that mimic the beneficial effects of estrogen but minimize adverse effects. In this thesis, we have shown that activation of the membrane G protein-coupled estrogen receptor (GPER1), a non-feminizing receptor, is as potent as 17β-estradiol to protect dopaminergic neurons against MPTP toxicity in male mice, a model of Parkinson's disease. Neuroprotection by 17β-estradiol is lost when the GPER1 or estrogen receptors (ER) α/β are blocked, indicating that both ERα/β and GPER1 are required for the protection of dopaminergic neurons by 17β-estradiol. These results suggest a potential interaction between ERα/β and GPER1. Using a pharmacological approach, our results show that ERα interacts with GPER1 to increase Akt signaling, as well as the levels of Bcl-2 and BDNF, and protect dopaminergic neurons from the toxic effect of MPTP. However, the neuroprotective effect of GPER1 is independent of ERα/β, while GPER1 requires collaboration with ERα/β to increase BDNF levels. Investigation of the mechanism of action of raloxifene, a selective estrogen receptor modulator used in the clinic, has revealed that raloxifene acts through GPER1 to activate Akt, increasing the levels of Bcl-2 and BDNF, and protects dopaminergic neurons and plasma androgen levels. Progesterone, a non-feminizing steroid, has neuroprotective properties in MPTP mice. In addition, our results show that progesterone, when administered after MPTP, has rescued effects on dopaminergic neurons. In this thesis, we have shown the neuroprotective capacity of several compounds that could serve as alternative strategies to the use of estrogen. Investigation of estrogen receptors involved in neuroprotection provides important information for the development of new therapies

Sex differences in steroid levels and steroidogenesis in the nervous system : Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions

Hormone Replacement Therapy and Risk for Neurodegenerative Diseases

Over the past two decades, there has been a significant amount of research investigating the risks and benefits of hormone replacement therapy (HRT) with regards to neurodegenerative disease. Here, we review basic science studies, randomized clinical trials, and epidemiological studies, and discuss the putative neuroprotective effects of HRT in the context of Alzheimer's disease, Parkinson's disease, frontotemporal dementia, and HIV-associated neurocognitive disorder. Findings to date suggest a reduced risk of Alzheimer's disease and improved cognitive functioning of postmenopausal women who use 17β-estradiol. With regards to Parkinson's disease, there is consistent evidence from basic science studies for a neuroprotective effect of 17β-estradiol; however, results of clinical and epidemiological studies are inconclusive at this time, and there is a paucity of research examining the association between HRT and Parkinson's-related neurocognitive impairment. Even less understood are the effects of HRT on risk for frontotemporal dementia and HIV-associated neurocognitive disorder. Limits to the existing research are discussed, along with proposed future directions for the investigation of HRT and neurodegenerative diseases

Effects of Bisphenol-A and Other Endocrine Disruptors Compared With Abnormalities of Schizophrenia: An Endocrine-Disruption Theory of Schizophrenia

In recent years, numerous substances have been identified as so-called “endocrine disruptors” because exposure to them results in disruption of normal endocrine function with possible adverse health outcomes. The pathologic and behavioral abnormalities attributed to exposure to endocrine disruptors like bisphenol-A (BPA) have been studied in animals. Mental conditions ranging from cognitive impairment to autism have been linked to BPA exposure by more than one investigation. Concurrent with these developments in BPA research, schizophrenia research has continued to find evidence of possible endocrine or neuroendocrine involvement in the disease. Sufficient information now exists for a comparison of the neurotoxicological and behavioral pathology associated with exposure to BPA and other endocrine disruptors to the abnormalities observed in schizophrenia. This review summarizes these findings and proposes a theory of endocrine disruption, like that observed from BPA exposure, as a pathway of schizophrenia pathogenesis. The review shows similarities exist between the effects of exposure to BPA and other related chemicals with schizophrenia. These similarities can be observed in 11 broad categories of abnormality: physical development, brain anatomy, cellular anatomy, hormone function, neurotransmitters and receptors, proteins and factors, processes and substances, immunology, sexual development, social behaviors or physiological responses, and other behaviors. Some of these similarities are sexually dimorphic and support theories that sexual dimorphisms may be important to schizophrenia pathogenesis. Research recommendations for further elaboration of the theory are proposed

FUNCTIONAL ROLE OF ESTROGEN RECEPTORS DURING AGING AND THEIR INVOLVEMENT IN INFLAMMATORY PROCESSESS

Estrogens are female sex hormones, belonging to a group of steroids, and they are responsible for the sexual characteristics of the female. They also have effects on bone, cardiovascular system, brain, and skin. The effects of estrogens are mediated by binding to their cognate receptors, the estrogen receptors (ER\u3b1 and ER\u3b2). ERs are transcription factors that regulate transcription by associating with estrogen-responsive-elements (EREs) located within the promoter of target genes. The aim of my studies was to evaluate the effect of aging and blockade of ovarian functions on estrogen receptor transcriptional activity and ER anti-inflammatory action . In specific aim #1 we proposed to study genes driven by ERE-containing promoters: endogenous as well as surrogate reporters; within specific aim #2 we proposed to provide support to the theory that lack of estrogen anti-inflammatory activity is a major component for the onset of pathologies associated with menopause (osteoporosis, atherosclerosis, metabolic and neurological dysfunctions). In our study we evaluated ER activity during aging in ERE-Luc mice. The analysis showed that ER\u3b1 is still synthesized during while with age, ovariectomy further increases ER\u3b1 content in uterus, aorta and hippocampus, but not in the brain. To evaluate ER transcriptional activity in aging and after ovx we first studied the expression of the reporter luciferase (by measuring luciferase mRNA); next we evaluated the expression of ER endogenous genes such as Prothymosin alpha (PTMA) and Progesteron Receptor (PgR) known to be a direct target of ER. This study showed that the ER present in aged tissues is fully functional from the transcriptional point of view. In ovx animals the trend of ER activity is unclear. We were intrigued by the observation that, in aged female mice, a reduction of circulating levels of estrogens induced by ovariectomy was associated with an increased ER activity in several organs. To further study this phenomenon we gonadectomised male and female mice at the age of 5 months and we measured luciferase activity by in vivo imaging at 6 or 20 months of age. Luciferase activity is higher in females than in males in both groups of age, however gonadectomy does not affect luciferase activity in young males (with the exception of the chest), but clearly decreases photon emission in aged mice. In our study we also tested the hypothesis that with aging the loss of the anti-inflammatory activity of estrogens may explain the increased susceptibility to inflammatory disorders (i.e., osteoporosis, atherosclerosis, diabetes, certain neurodegenerative disorders), reported by epidemiological studies in women. Our analysis focused primarily on TNF\u3b1, IL1\u3b2, MCP1 and MIP2. The mRNA of all these inflammatory mediators was shown to increase progressively with aging. To evaluate the influence of estrogens on the expression of inflammatory genes, we measured the content of mRNA encoding for inflammatory mediators in different tissues of ovariectomized females. Due to the relevance of inflammatory processes in the CNS, we next focused on the effect of ovariectomy in the different brain areas by IHC studies the state of reactivity of microglia and astrocytes, cells known to play a relevant role in neuroinflammation. Our data show morphological differences between astrocytes in ovariectomized compared to sham operated mice in all the brain areas at all months of age. Also microglia presents a morphological activation in all the brain areas, as observed in astrocytes. Finally we investigated the extent to which the susceptibility to an inflammatory stimulus changed during aging and if the ovariectomy was playing a role in this phenomenon. In the hippocampus TNF\u3b1 production increases with aging, MIP2 and MCP1 espression changes at 12 months and is similar at 18 months, whereas mRNA levels of IL1 beta are not affected by aging. Ovariectomy does not seem to influence the inflammatory process