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Neurosteroid effects on intracellular calcium and excitotoxicity
Naimová, Žaneta ; Smejkalová, Terézia (advisor) ; Adámek, Pavel (referee)
NMDA receptors belong to the family of ionotropic glutamate receptors, and are involved in synaptic plasticity, learning and memory. However, overactivation by the agonist glutamate can lead to neuronal death - excitotoxicity. Exitotoxicity is a result of excessive calcium influx into the cell through NMDA receptors, and is associated with many cental nervous system (CNS) diseases. Neurosteroids are endogenous compounds capable of NMDA receptor modulation, thus they may have pharmacological potential in the treatment of CNS disorders. The aim of this work was to investigate how pregnanolone sulfate (PA-S) and pregnanolone hemipimelate (PA-hPim) influence somatic calcium and excitotoxicity. We used fluorescence microscopy for recording changes in somatic calcium concentration. We observed that PA-S had no influence on relative somatic calcium concentration. Synthetic analog PA-hPim increased somatic calcium levels slightly. Next, we used oxygen-glucose deprivation (OGD) in vitro to study the influence of neurosteroids on excitotoxicity. Both PA-S and PA-hPim were neuroprotective in the model of acute OGD in vitro. Moreover, PA-S or PA-hPim pretreatment induced ischemic tolerance to a subsequent OGD episode. Our results suggest that neurosteroids PA-S and PA-hPim are potential candidates for the development...
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Effects of NMDA receptor modulators on cell death in models of excitotoxicity in vitro.
Strnadová, Lenka ; Smejkalová, Tereza (advisor) ; Skřenková, Kristýna (referee)
NMDA receptors are ionotropic glutamate receptors (iGluR) activated by the amino acid glutamate and mediating signal transmission in the central nervous system. Their proper activity is essential for synaptogenesis, neuronal plasticity and synaptic transmission. However, excessive activation of NMDAR causes strong influx of calcium ions into neurons which triggers several destructive effects, eventually ending with cell death. This so-called excitotoxicity is present not only in many neurodegenerative diseases, such as Alzheimer's disease or Parkinson's disease, but also in acute pathophysiological conditions, such as stroke or traumatic brain injury. General NMDAR inhibitors that could potentially prevent neuronal excitotoxicity have shown severe negative side effects in models in vivo. On the other hand, selective inhibitors of NMDA receptors with the ability to block the unwanted excessive activity while preserving NMDAR physiological function have shown to be therapeutically useful. This work is going to briefly summarize the knowledge of structure, activation and localization of NMDA receptors, then it is going to describe their rule in mediating neuronal toxicity and a few methods we can use to study excitotoxicity in vitro. Finally, this work will compare the effects of several known NMDAR...
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Steroid - NMDA receptor interaction: Structure-activity study and effect on mutant forms of human NMDA receptors
Krausová, Barbora ; Vyklický, Ladislav (advisor) ; Anděrová, Miroslava (referee) ; Tureček, Rostislav (referee)
N-methyl-D-aspartate (NMDA) receptors are glutamate-gated calcium permeable ion channels that play a key role in excitatory synaptic transmission and plasticity, and their dysfunction underlies several neuropsychiatric disorders. The overactivation of NMDA receptors by tonically increased ambient glutamate can lead to excitotoxicity, associated with various acute and chronic neurological disorders, such as ischemia, Alzheimer and Parkinson's disease, epilepsy or depression. On the opposite, NMDA receptor hypofunction is thought to be implicated in autism, schizophrenia, or intellectual disability. Recent DNA screening for neurological and psychiatric patients revealed numerous mutations in genes encoding for NMDA receptor subunits. The activity of NMDA receptors is influenced by a wide variety of allosteric modulators, including neurosteroids that could both inhibit and potentiate the activity of NMDA receptors, which makes them promising therapeutic targets. In this thesis, we describe new classes of neurosteroid analogues which possess structural modifications at carbons C3 and C17 of the steroidal core, and analogues without D-ring region (perhydrophenanthrenes). We evaluated the structure-activity relationship (SAR) for their modulatory effect on recombinant GluN1/GluN2B receptors. Our results...
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The analysis of structural details of the NMDA receptor
Radilová, Kateřina ; Balík, Aleš (advisor) ; Jakubík, Jan (referee)
NMDA receptor is necessary for excitatory transmission in the central nervous system. Altered funtion of the NMDA receptors is associated with many neurodegenerative and neuropsychiatric diseases. All available crystal structures of the NMDAR meant great shift towards our understanding of details of the receptor and its function. Unfortunately, these up- to-date available structures present only certain functional states of receptors and also a few structural data are still missing. For complete comprehension of the process of activation and deactivation of NMDA receptors, we need to supplement the current information with more data. The aim of this thesis was to employ a combination of different approaches (computational modelling, cloning, biochemistry, protein expression and purification and mass spectrometry) to obtain new structural data, by which we would be able to fill in the gaps in current receptor models, especially at various functional states of the receptor. Key words: NMDA receptor, glutamate receptor, computational modelling, structure, cloning, protein expression
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Genetic changes in the regulatory regions of NMDA receptors and their association possible connection the development of schizophrenia
Hrychová, Šárka ; Balík, Aleš (advisor) ; Moravcová, Radka (referee)
Schizophrenia is a serious neuropsychiatric disorder with a severe impact on patients' lives. Based on the experiments in animal models and also from the observations of the influence of the drug in humans it was concluded that the decreased activity of N-methyl-D- aspartate (NMDA) receptor gives rise to behaviour that is associated with the clinical manifestation of schizophrenia. Therefore, it is hypothesized that genetically determined variations in NMDA receptor activity contributes to the emergence and development of schizophrenia. The aim of this bachelor thesis is to summarize current knowledge on genetic alternations particularly in the regulatory regions of NMDA receptors in schizophrenia. Key words: schizophrenia, NMDA receptor, genetic changes
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Structural determinants of regulation of surface delivery of NMDA receptors in mammalian cells
Danačíková, Šárka ; Horák, Martin (advisor) ; Bendová, Zdeňka (referee)
N-methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels activated by agonist glutamate and co-agonist glycine. They play a key role in mediating the fast excitatory synaptic neurotransmission in the mammalian central nervous system. To create a functional heterotetrameric receptor, the presence of two GluN1 subunits combined with GluN2 or GluN3 subunits is necessary. Previous studies confirmed the importance of M3 transmembrane helix and extracellularly localized cysteines in regulation of surface expression of functional NMDA receptors. The aim of my thesis is to elucidate an influence of clinically relevant mutations in M3 transmembrane helix and the role of all known cysteines that form disulphide bonds on surface delivery of NMDA receptor expressed in heterologous monkey kidney fibroblasts cell culture (COS-7). Using molecular biology methods, immunocytochemistry and microscopy I found that the clinically relevant mutations M641I and Y647S in GluN1 subunit and also the mutations of particular cysteines forming disulphide bonds caused substantial decrease of surface expression of NMDA receptors. Furthermore, I discovered that the effect of mutated GluN1 subunits on decrease of surface expression depends on the subunit composition. The contribution of my results lies in elucidating the...
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Effects of sulfated neurosteroids on proteins involved in excitatory synaptic transmission
Naimová, Žaneta ; Smejkalová, Terézia (advisor) ; Mrózková, Petra (referee)
The discovery of steroid compounds capable of synthesize or accumulation in CNS and PNS led to a question about their function. Neurosteroid compounds are capable of modulating synaptic transmission. Effect is direct and fast mediated through nongenomic mechanisms. They are known to affect wide array of channels and receptors - both excitatory and inhibitory. This thesis summarizes findings about effect of sulfated neurosteroid on proteins involved in excitatory synaptic transmission. Thesis covers findings about ionotropic glutamate receptors, TRP channels, metabotropic receptors, sodium and potassium channels. Excessive or insufficient activity of these proteins involved in synaptic transmission can lead to a pathological condition. The purpose of this thesis is to summarize findings about effect of these compounds, point out structural and function characteristic probably responsible for their action and to outline possible pharmacological usage.
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Pharmacological animal model of Alzheimer's disease (rat model Samaritan) and mediator system of N-methyl-D-aspartate receptor and nitric oxide
Matušková, Hana ; Krištofíková, Zdena (advisor) ; Soukup, Ondřej (referee)
Alzheimer's disease is a neurodegenerative disorder with the highest prevalence in the population and for which we do not have a cure so far. The aim of this thesis was to test the mediator system of the N-methyl-D-aspartate receptor and nitric oxide in an animal model of sporadic form of Alzheimer's disease (Samaritan Alzheimer's Rat Model; Taconic Pharmaceuticals, USA). Then compare these results with changes in hippocampal cholinergic system and cognitive tests. The Samaritan rat model is based on the unilateral in vivo application of β-amyloid42 and the pro-oxidative substances (ferrous sulfate heptahydrate and L-buthionine-(S,R)-sulfoximine). Neurochemical methods included testing of the NR1/NR2A/NR2B subunits of the N-methyl-D-aspartate receptor and activity of nitric oxide synthases (neuronal, endothelial, inducible) in the cortex, in both cases in the right and left hemisphere separately. Our results show that Samaritan rats exhibited significant changes in expression of NR2A/NR2B subunits of the N-methyl-D-aspartate receptor and activity of inducible nitric oxide synthase in cortex compared to control rats. The results of glutamatergic system are consistent with changes in activity of cholinergic transporter and cognitive tests (Morris water maze and active allothetic place avoidance)....
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Synthesis and Properties of Neuroactive Steroids
Kapras, Vojtěch ; Chodounská, Hana (advisor) ; Pour, Milan (referee) ; Drašar, Pavel (referee)
Herein is reported the synthesis of molecular probes for action of neuroactive steroids in vitro and in living organisms. In the first part, preparation of enantiomeric pregnane steroids is investigated, ultimately resulting into the total synthesis of ent-progesterone. The chirality of the target molecule is introduced by a highly effective organocatalytic asymmetric Robinson annulation. A new method for the sequential construction of five-membered carbocyclic ring is introduced as the key step. This is composed of substrate-controlled copper-catalyzed conjugate addition followed by radical oxygenation and subsequent thermal cyclization employing the persistent radical effect. The synthesis of truncated neurosteroid analogs is described and their biological activity at the NMDA receptor is compared with the native hormone. In the second part, methodology for specific deuterium labeling of both angular methyls of the 5β-pregnane steroid core is explored. Special attention was paid to the Barton-McCombie deoxygenation as the tool for introduction of the last deuterium atom into the methyl group. Both positions were labelled with total of three deuterium atoms in high isotopic purity.
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Synthesis and Properties of Neuroactive Steroids
Kapras, Vojtěch
Herein is reported the synthesis of molecular probes for action of neuroactive steroids in vitro and in living organisms. In the first part, preparation of enantiomeric pregnane steroids is investigated, ultimately resulting into the total synthesis of ent-progesterone. The chirality of the target molecule is introduced by a highly effective organocatalytic asymmetric Robinson annulation. A new method for the sequential construction of five-membered carbocyclic ring is introduced as the key step. This is composed of substrate-controlled copper-catalyzed conjugate addition followed by radical oxygenation and subsequent thermal cyclization employing the persistent radical effect. The synthesis of truncated neurosteroid analogs is described and their biological activity at the NMDA receptor is compared with the native hormone. In the second part, methodology for specific deuterium labeling of both angular methyls of the 5β-pregnane steroid core is explored. Special attention was paid to the Barton-McCombie deoxygenation as the tool for introduction of the last deuterium atom into the methyl group. Both positions were labelled with total of three deuterium atoms in high isotopic purity.
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