Het Brein in Ontwikkeling chemisch blootgesteld

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1 Het Brein in Ontwikkeling chemisch blootgesteld Oorzaak van Autisme? Didima M.G. de Groot

2 Introduction 1 Brain development The brain comprises a whole set of distinct regions ( brain organs ) developing along specific neural processes Each brain region has its own window of development Each brain region has its own cell types and composition Autism Neurodevelopmental disorder Various disease types / degrees >>> autism spectrum disorder (ASD) Incidence is increasing (not only due to modern technologies) Precise etiology unknown, but Large genetic origin Environmental stressors (direct and indirect effects) Triple Hit hypothesis Important role in the etiology of autism is played by Brain development Genetics Environment

3 Autism & Triple Hit Hypothesis Contents of the Presentation 2 [ ] Brain development: Basic Processes Cells Networks Underlying vulnerability Genetics Not here Exogenous stressors Maternal infections Drugs Chemicals Immune system development Example laboratory study Rat model & life-long DOTC exposure

4 Brain development

5 Basic processes of nervous system development Proliferation Cell migration Glia differentiation and Maturation Cells Neuronal Differentiation Apoptosis Synaptogenesis Myelination Neurite Outgrowth and Network Formations Network 3

6 Developing brain more vulnerable than the adult The brain comprises many distinct regions With different structural, functional, molecular composition All basic neural processes may occur simultaneously Over the different brain regions Each with different time span ( window ) Different for distinct cell-types /networks. There are many targets throughout development making the developing brain more vulnerable than the adult brain to potential toxic substances / environmental stressors 4

7 Basic processes of nervous system development Proliferation Cell migration Glia differentiation and Maturation Cells Neuronal Differentiation Apoptosis Synaptogenesis Myelination Neurite Outgrowth and Network Formations Network 3a

8 Repair mechanisms in developing brain larger than in the adult Nervous System Cell Proliferation Different cell-types in large numbers proliferate over extended time Moment / duration of time window differs per brainregion and celltype vulnerable at many more stages / locations than other organs Different cell types in specific cell ratio s communicate cell loss changes in cell ratio s damage 5 Nervous System Cell Proliferation : progenitor cells Progenitor cells symetric division 2 daughter cells (~progenitor cells) With time asymmetric division # neurons ; # progenitor cells In mature brain proliferation limited Possibilities of repairing injuries

9 Basic processes of nervous system development Proliferation Cell migration Glia differentiation and Maturation Cells Neuronal Differentiation Apoptosis Synaptogenesis Myelination Neurite Outgrowth and Network Formations Network 3b

10 Glial cell differentiation and maturation radial glia Microglia *: 10-15%; mesoderm; scavenging CNS; immune defense Radial glia *: stem cell-like neurons and astrocytes Astrocytes **: Development: guidance axons & synapses; cues to neuron development Adult brain: maintain ionic and trophic balance of external milieu; astrocyte propagate intracellular Ca 2+ waves; release gliotransmitters in a Ca 2+ dependent manner Oligodendrocytes **: myelin formation electrical isolation axons oligo s * develop in parallel with neurogenesis (in most regions of the brain) 6 ** develop after initial wave of neurogenesis, often appearing later than neurons in a given region

11 Microglia in the brain Microglia: celltype / function Specialized immune cells Specialized type of macrophage Involved in normal brain development Microglia residence Reside in central nervous system Microglia origin Derived from bone marrow monocytes (mesoderm) (!!! This is unlike other CNS cells (ectoderm)) They enter the CNS after birth [kettenmann et al, 2011;. Svahn et al, 2012] Microglia inextricably link the CNS with the immune system 7

12 Laboratory study Rat study with perinatal lifelong exposure* to DOTC (* Test Guideline OECD 443) Background / Introduction Hypothesis Aim of study

13 Background / Introduction DOTC rat study During early development Interaction exists between the immune system and brain development Neurodevelopmental disorders like autism spectrum disorder (ASD) may originate from disruption of this interaction [Smith et al, 2007] Disruption may be caused by early exposure to drugs / chemicals Organotin compounds Affect the development of an individual At hormonal, immune, nervous systems level; Systems, that are more vulnerable during development than maturity 8 DOTC (dioctyltin chloride) Is an environmental organotin compound Occuring in the food chain Affecting early development Especially immune system; not nervous system [WHO doc. 73, 2006; Kishi et al., 2006] DOTC in rats in a regulatory setting of OECD TG 433 (EOGRTS) Effects on immune system development [Tonk et al., 2011] Effects on maternal immune system during lactation [Menke et al., 2012]

14 Hypothesis DOTC, development of immune system and brain Given the notion of affected maternal immune system, and also developing immune system of the offspring [Menke et al, 2012; Tonk et al, 2011], we hypothesized that DOTC, under the circumstances of life-long exposure (OECD TG 443 *) and the dosages used, might have affected normal brain development in the same offspring * Unique exposure scenario: 2 wk premating to postnatal day 70 of F1-generation 9

15 Aim of this study with DOTC in rats To explore structural and functional brain development upon DOTC exposure, measuring at 2 test-ages -PND 21 and 61 - to provide information on 2 distinct windows of development mating/birth to PND 21 PND 21 to 61 Applying combinations of non-invasive (in vivo imaging; behavior) and invasive measures (brain Weight, brain Specific gravity) To explain and compare the results with findings on autism in man using genome wide gene expression profiling Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with high genetic origin but believed to increase in incidence due to environmental exposure e.g. to certain chemicals. 10

16 Laboratory study Rat study with perinatal lifelong exposure* to DOTC (* Test Guideline OECD 443) Study design

17 Perinatal lifelong exposure to DOTC Guideline OECD TG 433: EOGRTS; Ext.1 gen reprod.tox. study Exposure -2wks premating to PND 70/90 Dose groups: mg/kg BW/day 0, 3, 10, 30 Clinical Testing Endpoints analyses Dev.landmarks PND 21 PND 61 Male Behavior offspring (F1) Neuropathology Doses 0, (3,10), 30mg DOTC Brain Macroscopy structure Auditory Startle Response PND 23 function 11 Parents (F0) PND1 to 70/90 Repro/Dev.-cohort Immune-cohort Neuro-cohort [ Parents (F0) ] Offspring (F1) N=10/sex/group Brain [ 18 F]FDG PET PND 17, 21, 35, 61 Function Brain MR Imaging structure Microarray Gene Expression >Explain results >Translate to man

18 Laboratory study Rat study with perinatal lifelong exposure* to DOTC (* Test Guideline OECD 443) Results summarized Conclusions

19 Rat study with life-long exposure to DOTC (TG OECD 443) Summary of results Effects on maternal & developing immune system [Menke et al, 2012; Tonk et al, 2011] Effects on structural and functional brain development Transient overgrowth of brain region volume (as in autism) derived from MRI was supported by transient hyper-metabolism as demonstrated by [ 18 F]FDG brain PET, which in turn concurred with effects on auditory startle response (hyper-reactivity). Genome wide gene expression profiling supported the transient effects on development of the offspring, and on development of its immune and nervous systems upon DOTC. Exploring the translation of effects to neurodevelopmental disorders in humans, our results in rats show large similarities with alterations in individuals diagnosed with Autism Spectrum Disorders (ASD). Altered expression of genes reported in man were found in our rat study as well. 12

20 Rat study with life-long exposure to DOTC (TG OECD 443) 13 Hypothesis Given the notion of affected maternal immune system, and also developing immune system of the offspring [Menke et al, 2012; Tonk et al, 2011], we hypothesized that DOTC, under the circumstances of life-long exposure (OECD TG 443) and the dosages used, might have affected normal brain development in the same offspring Conclusions Impaired immune system seems basis for the disturbed brain development during very early exposure (unique (life-long) exposure scenario of TG OECD 443) supporting importance of immune system for normal brain development suggesting link to autism in man

21 Acknowledgements TNO Zeist Radboud University Medical Center Nijmegen: MRI Groningen University Medical Center: PET Partly supported by the Dutch Ministeries of Health, Welfare & Sports, Social Affairs Het Brein in Ontwikkeling chemisch blootgesteld Oorzaak van Autisme? Didima M.G. de Groot

FUNCTIONAL EEG ANALYZE IN AUTISM. Dr. Plamen Dimitrov

FUNCTIONAL EEG ANALYZE IN AUTISM Dr. Plamen Dimitrov Preamble Autism or Autistic Spectrum Disorders (ASD) is a mental developmental disorder, manifested in the early childhood and is characterized by qualitative