Browsing by Subject "Huntington’s disease"
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(2021)Huntington’s disease (HD) is a rare but devastating neurodegenerative disease, progressively culminating in severe brain atrophy and death. The disease is caused by an inherited mutation resulting in a CAG trinucleotide repeat expansion in the huntingtin gene, leading to the production of a neurotoxic protein, known as mutant huntingtin, with an abnormally long polyglutamine stretch. Even though the genetic background of HD is known, the cellular pathways affected in the disease are complex and not completely understood. Increasing evidence indicates that endoplasmic reticulum (ER) stress – a condition of disturbances in normal ER activity, leading to accumulation and aggregation of misfolded proteins in the ER lumen – is a central factor in the pathogenesis of HD and other neurodegenerative diseases. In the literature review of this thesis, known pathogenic cellular mechanisms of HD and how these cellular mechanisms are connected to ER stress, are discussed. Unpublished data from previous studies in our laboratory have indicated that the ER luminal protein canopy homolog 2 (CNPY2) could play a role in the regulation of neuronal survival, including the viability of mutant huntingtin expressing neurons. The aim of the experimental part of this study was to gain insight into a possible function of CNPY2 in HD, by examining the levels of the protein in neuronal models of HD under various conditions, such as ER stress, and by searching for potential interacting partners of CNPY2 amongst known ER stress regulators. The obtained results show that the levels of CNPY2 are increased in striatal neurons expressing mutant huntingtin, and that the secretion of CNPY2 is increased by these neurons, compared to control neurons expressing normal huntingtin. Further, we show that CNPY2 interacts with the major ER stress regulator binding immunoglobulin protein (BiP) in human neuroblastoma cells treated with the ER stress inducer tunicamycin, and that the intracellular levels of CNPY2 are altered by tunicamycin treatment. Together, these findings indicate that CNPY2 could be involved in the pathogenesis of HD. However, further research on the functions of CNPY2 and its role in ER stress regulation is required to understand the nature of this involvement.
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(2018)Histamine acts as a neurotransmitter in the central and peripheral nervous system and it has a role in various body functions. Histamine neurons spread widely to most of the central nervous system where histamine has an important role in sleep-wake cycles, regulation of appetite, and motor functions. The effects of histamine are mediated mostly by H1-, H2- and H3-receptors in the central nervous system. The synthesis of histamine and the release of histamine from the presynaptic nerve endings are regulated by H3-receptor via negative feedback. H3-receptors are located also on the presynaptic cell membranes of other neurons where they regulate the release of other neurotransmitters. Several animal experiments have shown that H3-receptor-mediated mechanisms have been observed to have an important role in the regulation of the motor functions together with other neurotransmitter systems especially in the basal ganglia area. The histaminergic system is involved in the patophysiology of diseases such as Parkinson’s disease, Tourette’s syndrome and Huntington’s disease where motor performance is impaired. Functional, physiological and genetical changes in the histaminergic system have been observed in patients with these diseases. There are no clinically used histaminergic compounds for the treatment of these diseases, though recently in animal experiments the histaminergic compounds have proved to be promising. The aim of this Master’s thesis study was to examine the effects of histamine deficiency in the brain on the levodopainduced dyskinesias in histidine decarboxylase knock-out mice (HDC KO) (n=9) and wild-type mice (n=12) in a 6-OHDA mouse model of Parkinson’s disease. The mice were injected with a neurotoxic 6-OHDA solution (3 μg) into the right medial forebrain bundle to cause a unilateral dopaminergic lesion. The success of degeneration of dopaminergic neurons were measured by a rotating rod test and amphetamine-induced (2.5 mg/kg) and apomorphineinduced (0.5 mg/kg) rotameter tests. A daily treatment of levodopa and benserazide (4.5 mg/kg, 1.125 mg/kg) was initiated after the behavioural studies for 10 days. On the last day of the treatment the dyskinesias of the mice were filmed for one minute after 20, 40, 60, 80, 100 and 120 minutes after levodopa dose. After the filming, the mice were killed by decapitation and their middle brains were collected for immunohistochemical studies to measure the extent of the dopaminergic lesion. No statistically significant difference was observed between genotypes in levodopa-induced dyskinesias. In previous studies of our study group more severe levodopa-induced dyskinesias were observed in HDC KO mice when the dopaminergic lesion was caused in the striatum in the 6-OHDA mouse model. The degenerated brain area and thereby the extent of the lesion may have importance in observing the difference between levodopa-induced dyskinesias. In this Master’s thesis study the dopaminergic lesions were equally successful with both genotypes. Therefore differently successful lesions between the genotypes can not be the reason why the difference in genotypes in levodopa-induced dyskinesias was not observed. HDC KO mice were observed to have significantly increased ipsilateral rotational behaviour induced by amphetamine in amphetamine-induced rotametry. Previous studies have shown that HDC KO mice have increased dopamine release and high dopamine metabolite levels which might explain the increased rotational behaviour induced by amphetamine in this study. The observations of earlier studies and this Master’s thesis study verify the relation between histaminergic and dopaminergic systems in motor functions.
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