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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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Possible influencing the motor performance of developing rats by repeated administration of the NMDA receptor antagonist specific for NR2 subunit
Kozlová, Lucie ; Mareš, Pavel (advisor) ; Valeš, Karel (referee)
Nonspecific NMDA receptor antagonists induce hyperlocomotion in rats. The aim of this work is to determine whether the NMDA receptor antagonist specific for NR2 subunit exhibit similar negative effect as nonspecific antagonists. This subunit is predominant in the brain in the early postnatal period. The introduction summarizes the data on NMDA receptors and the development of rat. The experimental part deals with the action of a specific NMDA receptor antagonist Ro 25-6981 on motor performance of developing rats. Substance was repeatedly administered to rats at postnatal days 7 to 11. Spontaneous locomotion and motor performance of the animals were repeatedly tested up to adulthood by battery of tests appropriate for individual ages. Our research demonstrated that this substance does not have significant effect on motor system of laboratory rat and that it might be further tested as a possible age-bound antiepileptic drug.
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Simulation of the interaction of steroid allosteric modulators of NMDA receptors with membrane
Riedlová, Kamila ; Konopásek, Ivo (advisor) ; Novák, Josef (referee)
Molecular dynamics (MD) method allows the real-time monitoring of the system composed of molecules and atoms, such as phospholipid bilayer or biomolecule. Applications of MD are very common in drug design where the real experimental procedures could be much more financially- and time-consuming or even impossible. The aim of this project is to explain the applications and advantages of MD method in case of studies of lipid membranes, with a special emphasis on a study od neurosteriod behaviour in lipid bilayer. Properly designed and synthesized neurosteroids could be used for the treatment of the serious neurological diseases. This work also included the experimental data obtained by MD simulations for two neurosteroids - pregnanolone glutamate and pregnanolone sulphate. Behaviour of this molecules in model membranes was observed and analyzed by MD simulations. Key words: molecular dynamics simulation, model membrane, lipid bilayer, NMDA receptor, neurosteroids, pregnanolone glutamate, pregnanolone sulfate
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The mechanism of regulation of NMDA receptors transport to the cell surface
Lichnerová, Katarína ; Horák, Martin (advisor) ; Bendová, Zdeňka (referee)
N-methyl-D-aspartate (NMDA) receptors are a class of ionotropic glutamate receptors, involved in excitatory synaptic transmission, synaptic plasticity and excitotoxicity. They form heterotetrameric complexes composed of GluN1, GluN2A-D and/or GluN3A-B subunits that are activated by glutamate and glycine. Previous reports showed that different subunits of NMDA receptors, especially the GluN2 subunits, confer different functional and pharmacological properties on the receptor complexes. However, the subunit-dependent differences in the regulation of intracellular processing and transport of NMDA receptor subtypes has not been clearly elucidated. The aim of this work was to clarify the mechanisms of regulation of the NMDA receptor transport. In our experiments we performed immunocytochemistry of receptors on heterologous COS-7 cells and cultured cerebellar granule cells (CGC), both expressing recombinant NMDA receptors. The results of my work show that the transport of NMDA receptors is regulated by presence of GluN2A and GluN2B subunits. Our results further showed that transport of the GluN1/GluN2C receptors is regulated by three specific areas of the GluN2C subunit: i) the A2 segment within the amino- terminal domain, ii.) the M3 domain, and iii.) the proximal part of the C-terminus containing the...
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The influence of the neuroactive steroids inhibiting NMDA receptors on behaviour
Chvojková, Markéta ; Valeš, Karel (advisor) ; Mareš, Pavel (referee)
The neuroactive steroid pregnanolone glutamate (Pg glu), a synthetic analogue of the naturally occurring pregnanolone sulfate (3alpha5betaS), has neuroprotective properties and a minimum of adverse effects. The subject of my thesis is the influence of selected structural modifications of the molecule Pg glu on biological effects. The first modification involves an increase of lipophilicity, the second involves the attachment of a positively charged group to C3. All these neuroactive steroids are use-dependent inhibitors of NMDA receptors. The first aim of this thesis was to determine the neuroprotective effectiveness of the neuroactive steroids chosen. The second aim was to explore the influence of selected neuroactive steroids on motor coordination, reflexes, anxiety and locomotor activity, as well as the effect of their high doses. The third aim was to create a battery of behavioural tests for screening the biological effects of analogues of Pg glu in laboratory rodents. The neuroprotective effects were evaluated in a model of excitotoxic damage of hippocampus in the rat on the basis of its behavioural consequences. The neuroprotective efficacy of androstane glutamate (And glu) and Pg glu was demonstrated. In the case of positively charged molecules, neuroprotective efficacy was not demonstrated....
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Study of neurosteroid effect on the NMDA subtype of glutamate receptor.
Krausová, Barbora ; Vyklický, Ladislav (advisor) ; Bendová, Zdeňka (referee)
N-methyl-D-aspartate (NMDA) receptors are glutamatergic ionotropic receptors involved in excitatory synaptic transmission, synaptic plasticity and excitotoxicity. They are heteromeric complexes of GluN1 combined with GluN2A-D and/or GluN3A-B subunits that are activated by glutamate and glycine. Many allosteric modulators can influence the activity of these receptors including neurosteroids. Pregnanolone sulfáte (3α5βS) is an endogenous neurosteroid that inhibits NMDA receptors in a use-dependent manner and has neuroprotective effect. Binding site for 3α5βS on the NMDA receptor molecule is still not indentified. The aim of my work was to contribute to the identification of the biding site by kinetic analysis of rate of response return from 3α5βS inhibition. Using the point mutation we also attempted to identify the amino acids residues that could be involved in the neurosteroid binding. In order to study the effect of 3α5βS on NMDA receptors the electropfysiological recordings on human embryonic kidney 293T cells expressing recombinant GluN1/GluN2B receptors was performed. We confirm that the effect of 3α5βS on GluN1/GluN2B receptors is voltage-independent. The results of my work indicate that steroids can reach the binding site on the NMDA receptors through the membrane rather than directly from the aqueous...
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The behavioral effects of NMDA receptor antagonists
Chvojková, Markéta ; Valeš, Karel (advisor) ; Horák, Martin (referee)
NMDA (N-methyl-D-aspartate) receptors are glutamate-gated ion channels, which are located in the central nervous system. They permit excitatory neurotransmission and are crucial for synaptic plasticity and other functions, but on the other hand for excitotoxicity. By the administration of NMDA receptor antagonists it would be possible to restrict the consequences of excessive glutamate exposure. However, the use of many of these drugs is made impossible by their serious behavioral side effects. NMDA receptor antagonists can influence cognitive and motor functions in laboratory animals and also in humans, and can cause temporary psychosis. These negative behavioral effects are most pronounced in the case of non-competitive antagonists. Conversely, the behavioral side effects of uncompetitive antagonists, antagonists selective for NMDA receptors containing a NR2B subunit or NMDA receptor glycine binding site antagonists are milder. From a clinical point of view, some other behavioral effects of NMDA receptor antagonists are beneficial. These effects include anxiolytic and antidepressant effects and also an alleviation of cognitive deficit and behavioral aberration in Alzheimer's disease through the administration of memantine. The aim of this thesis is to summarize the main behavioral effects known to us of...
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Preparation of neuroactive steroids for study of NMDA receptors
Vidrna, Lukáš ; Hodek, Petr (advisor) ; Pouzar, Vladimir (referee)
Neurosteroids are an important group of substances that affect communication between neurons. They act as allosteric modulators of membrane receptors for neurotransmitters. One of the most important systems influenced by neurosteroids are NMDA receptors; however, a binding site(s) for their inhibition by steroids have not been found yet. This work is focused on the synthesis of fluorescently labeled photoaffinity probe, which may help explain the structure and location of binding site(s) and simplify the development of new neuroprotectives. A structural analogue of the endogenous neurosteroid, (20S)-20-Azido-5β-pregnan- 3α-yl N-(7-nitrobenz-2-oxa-1,3-diazole-4-yl)-L-glutamyl 1-ester (8), was prepared. The structure of compound 8 includes photolabile azido group, as well as covalently bounded fluorescent NBD group. In addition, a photoaffinity probe with a modified steroid skeleton - pyridinium 17aα-azido-17α-methyl-17a-homo-5β-androstan-3α-yl 3-sulfate (29) - was synthesized. The ability of compound 8 and 29 to inhibit activated NMDA receptor has been verified for recombinant NR1-1a/NR2B receptors expressed in HEK293 cells using a patch-clamp technique. Additionally, the IC50 values of compounds 8 and 29 have been calculated. (In Czech) Key words: neuroactive steroid, NMDA receptor, photoffinity...
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