Browsing by Subject "Parkinson’s disease"
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(2019)Parkinson’s disease is a progressive neurodegenerative disease, in which dopamine neurons are dying in the nigrostriatal dopaminergic pathway. This causes motor symptoms such as slowness of movement, tremor, and rigidity. In addition, various non-motor symptoms appear. All currently used medicines are symptomatic, and there are no disease modifying treatment available for Parkinson’s disease. Several neurotrophic factors have shown promise in animal models of Parkinson’s disease. One of those is cerebral dopamine neurotrophic factor (CDNF) which has been studied in different animal models, including rodents and non-human primates. CDNF is a secreted protein but it is also localized in endoplasmic reticulum (ER). CDNF has two domains, N-terminal and C-terminal, which may have distinct functions. CDNF can be retained in the ER by the ER retention sequence at the end of the C-terminal domain. The C-terminal domain also has an evolutionarily conserved disulfide bridge which is crucial for the biological activity of CDNF. The exact mechanism of CDNF is still unknown. However, it has been shown that CDNF affects the unfolded protein response (UPR) in the presence of ER stress. Neurotrophic factors do not penetrate blood-brain barrier (BBB), for this reason, they need to be injected directly to the brain. Penetration of the BBB is also a problem in the treatment of many other diseases. Various methods for enhancing the BBB penetration of drugs have been studied. For example, permeability of the BBB can be temporarily increased by focused ultrasound combined with microbubbles. Another possibility is the use of a carrier molecule, which can be transported through BBB via specific transport mechanisms. Furthermore, molecule modification offers many applications to achieve enhanced BBB penetration. In view of peripheral administration, a next generation variant of CDNF (ngCDNF) has been developed. The efficacy of this novel variant after intrastriatal injection is equal to that of CDNF in a 6-hydroxydopamine (6-OHDA) rat model of Parkinson’s disease. Systemic administration could also enable treatment of non-motor symptoms of Parkinson’s disease. The aim of this experiment was to study the effects of subcutaneously injected ngCDNF on rotation behaviour, and nigrostriatal TH-positive cells in rats with 6-OHDA lesions. 6-OHDA was injected unilaterally to three different sites in the striatum. Two weeks later, the lesion size was estimated, via amphetamine- induced rotation test. ngCDNF, at two dose levels, was injected twice weekly for three weeks. Amphetamine-induced rotation test was assessed every other week, until week 12. At the end, optical density of tyrosine hydroxylase (TH) was measured from sections of the striatum, and TH positive cells in the substantia nigra were counted. In addition, the effect of ngCDNF on anxiety and depression like behaviour, learning, and locomotor activity were studied at three different levels in naïve mice. Behaviour was analyzed by open field test, forced swim test, and fear conditioning test. The ngCDNF did not seem to have clear effect on rats’ behaviour or TH positive cells and fibers compared to the control group, but positive tendency was found in the group with lower dose. The reduced efficacy of ngCDNF,via subcutaneous administration, is likely due to rapid metabolism and insufficient entry of the active form to the brain. In naïve mice, ngCDNF did not reduce anxiety-like behaviour and did not affect locomotor activity after subcutaneous injections. This result supports previous findings, which suggest that the effects of CDNF are specific to the toxin treated cells and CDNF has no effect in naïve animals.
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(2023)Parkinson’s disease (PD) is a progressive neurodegenerative disease characterized by the death of nigrostriatal dopaminergic neurons and formation of intraneuronal protein aggregates called Lewy bodies and Lewy neurites. These inclusions consist of a protein called α-synuclein (aSyn) but also of other proteins, lipids and cell organelles. Progressive cell death leads to nonmotor and motor symptoms. Current therapies for PD are symptomatic and do not modify the disease progression. Therefore, there is a need for the development of therapies attenuating the neurodegeneration. The pre-formed fibrils (PFF) model enables studying of aSyn aggregation and mechanisms behind inclusion formation. The PFF model is based on the exogenous aSyn fibrils’ tendency to result in formation of Lewy body -like inclusions when added in cell culture or in animals. Primary neuronal cultures of mice and rats have typically been used to model aSyn aggregation in vitro with the PFF model. Primary neuronal cultures provide practicality and are able to depict relevant features of dopaminergic neurons. To gain insight about the composition of E13.5 primary embryonic mouse midbrain culture and to enable adaptation of an existing protocol to study other cell types, this study identified and quantified several relevant cellular phenotypes in the micro island culture. The cells were fixed on day in vitro (DIV) 8 or DIV 22 and analysis was conducted using fluorescent immunocytochemistry combined with automated image analysis software, CellProfiler. On DIV 8, tyrosine hydroxylase -positive dopaminergic neurons represented 5 % of the total cells in the culture. Neuronal nuclear antigen -positive neurons resulted representing 30 % of the total cells. Gabaergic neurons were identified to be abundant in the culture and certain dopaminergic neurons were identified as immunoreactive for GABA. Choline acetyltransferase -positive cholinergic neurons were also identified to be present in the culture. The number of oligodendrocyte precursors (OPCs) was observed to be significantly smaller than the number of dopaminergic neurons. OPCs represented around 1 % of the culture on DIV 8. Glutaminergic neurons, parvalbumin-positive interneurons, microglia or astrocytes were not identified in the culture on DIV 8. The number of astrocytes was observed to increase as the incubation time was prolonged to DIV 22. Overall these findings provide valuable insights of the composition of cell phenotypes in E13.5 mouse midbrain culture. The results also provide additional validation for suitability of the original protocol to robustly produce midbrain dopaminergic cultures with minimal number of glial cells. Understanding more about the relevance and interplay of different cell phenotypes in PD pathophysiology can provide valuable insight for the development of potential therapeutic strategies.
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(2018)MicroRNAs are ~22 nucleotide long RNA strands which regulate gene expression by binding to the 3’UTRs of messenger RNAs. MicroRNAs are predicted to regulate about a half of all protein-coding genes in the human genome thus affecting many cellular processes. One crucial part of microRNA biogenesis is the cleaving of pre-miRNA strands into mature microRNAs by the type III RNase enzyme, Dicer. Dicer has been shown to be downregulated due to aging and in many disease states. Particularly central nervous system disorders are linked to dysregulated microRNA processing. According to the latest studies, Dicer is crucial to the survival of dopaminergic neurons and conditional Dicer knockout mice show severe nigrostriatal dopaminergic cell loss, which is a hallmark of Parkinson’s disease. By activating Dicer with a small-molecule drug, enoxacin, the survival of dopaminergic cells exposed to stress is significantly improved. However, enoxacin, which is a fluoroquinolone antibiotic, activates Dicer only at high concentrations (10-100 μM) and is polypharmacological, which may cause detrimental side effects. Therefore, enoxacin is not a suitable drug candidate for Dicer deficiencies and better Dicer-activating drug candidates are needed. The aim of this work was to develop a cell-based fluorescent assay to screen for Dicer-activating compounds. Assays which measure Dicer activity have already been developed, but they have some pitfalls which don’t make them optimal to use for high-throughput screening of Dicer-activating compounds. Some are cell-free enzyme-based assays and thus neglect Dicer in its native context. The RNA to be processed by Dicer does not represent a common mammalian RNA type. Most assays do not have internal normalizing factors, such as a second reporter protein to account for e.g. cell death, or the analysis method is not feasible for high-throughput screening data. Considering these disadvantages, the study started by designing a reporter plasmid in silico. The plasmid expresses two fluorescent proteins, mCherry (red) and EGFP (green), and a mCherry transcripttargeting siRNA implemented into a pre-miR155 backbone which is processed by Dicer. Thus, measuring the ratios of red and green fluorescence intensities will give an indication on Dicer activity. The plasmid also has additional regulatory elements for stabilizing expression levels. The plasmid was then produced by molecular cloning methods and its functionality was tested with Dicer-modulating compounds. The assay was optimised by testing it in different cell lines and varying assay parameters, and stable cell lines were created to make large-scale screening more convenient. Finally, a small-scale screen was done with ten pharmacologically active compounds. Transiently transfected, in Chinese hamster ovarian cells, mCherry silencing was too efficient for reliable detection of improvement in silencing efficiency due to floor effect. With an inducible, Tet-On, system in FLP-IN 293 T-Rex cells, the expression could be controlled by administering doxycycline and the improvement in silencing was quantifiable. The assay seemed to be functional after 72 hours and 120 hours of incubation using enoxacin (100 μM) as a positive control. However, the screening found no compounds to significantly reduce mCherry/EGFP fluorescence ratio and, additionally, the effect of enoxacin was abolished. Therefore, a more thorough analysis on the effects of enoxacin was done and, although statistically significant, enoxacin was only marginally effective in reducing mCherry/EGFP fluorescence ratio after 72 hours of treatment. It should be noted from the small-scale screening that metformin and BDNF, compounds previously shown to elevate Dicer levels, showed similar effects to enoxacin. The quality of the assay in terms of high-throughput screening was determined by calculating Zfactors and coefficients of variations for the experiments, which showed that the variability of the assay was acceptable, but the differences between controls was not large enough for reliable screening. In conclusion, the effects of metformin and BDNF should be further studied and regarding the assay, more optimisation is needed for large-scale, high-throughput, screening to be done with minimal resources.
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(2020)Parkinson’s disease (PD) is a neurodegenerative disease in which dopaminergic neurons that form the nigrostriatal pathway gradually die. This causes the main motor symptoms of Parkinson’s disease: tremor, rigidity and bradykinesia. While PD affects 1-2% of total population, all currently used medicines are symptomatic, and there is no disease modifying therapy available at present. Although several different animal models for Parkinson’s disease exist, the lack of adequate animal models is often cited as a major obstacle for predicting the clinical success of potential drug candidates. Lewy bodies (LBs) are abnormal aggregates that develop and spread inside nerve cells of human PD patients, their main structural component being α-synuclein. Because α-synuclein is thought to play a major role in the pathology of PD, much research has been focused on it. Different α-synuclein-based animal models of PD exist today, of which the most recent are based on using direct injections of preformed α-synuclein fibrils (PFFs). These new α-synuclein based disease models have helped to understand the disease process in PD better, but cell death in these models takes longer to achieve and is often less pronounced compared to traditional neurotoxin based animal models of PD. The aim of this study was to participate in the development and characterization of a novel mouse model of PD. This new model combines PFF-injections with the commonly used neurotoxin 6-OHDA, which should result in more robust dopamine pathway degeneration than what is seen with the current PFF-based models. The main hypothesis of this study was that the combination of intrastriatal injections of PFFs and a low dose of 6-OHDA would cause gradual spreading of the α-synuclein aggregation pathology in the nigrostriatal dopamine pathway and progressive dopamine neuron loss leading to motor deficits. C57BL/6 mice were stereotactically injected unilaterally with both PFF and 6-OHDA, and their performance was assessed every other week with different behavioral tests until week 12. At the end, brains were collected and optical density of tyrosine hydroxylase (TH) and dopamine transporter (DAT) was measured from striatal sections, and TH and DAT positive cells in the substantia nigra were counted. The amount of Lewy bodies present in the brain slices was also counted from the cortex and substantia nigra areas of the brain. In the histological assays, statistically significant reductions of both TH and DAT were found in the brain sections of the PFF + 6-OHDA combination group and the amount of TH and DAT positive cells were lower in this group compared to the group receiving vehicle treatment only. However, the results of behavioral tests were non-significant, although a non-statistical positive trend in the amphethamine-induced rotations test was observed where mice receiving PFF + 6-OHDA rotated the most. Taken together, combination model that utilizes both PFF and 6-OHDA injections seems like a promising candidate in modelling PD in mice, but much more research and further development of the model is required before this combination model is ready and robust for use in drug development.
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(2023)Parkinson’s disease is a progressive neurodegenerative disorder which is commonly treated with Levodopa (L-dopa) and Dopa Decarboxylase (DDC)/ Catechol-O-methyltransferase (COMT) inhibitors. The main problem with this treatment is the intestinal conversion of L-dopa to dopamine despite DDC and COMT inhibition which probably occurs by the Tyrosine Decarboxylase (TyrDC) of intestinal bacteria. This study aims to find new inhibitor molecules that would have dual inhibitory effects towards both DDC and TyrDC enzymes. Currently, available DDC inhibitors cannot inhibit the bacterial TyrDC enzyme. A recently found TyrDC inhibitor (S)-α-Fluoromethyltyrosine (AFMT) is not able to inhibit the human DDC enzyme, respectively. The dual inhibition of both decarboxylases could reduce the dosing frequency and side effects related to L-dopa. In addition, the object of this study is to produce the human DDC enzyme by DNA recombinant technique as well as develop and optimize a biochemical DDC inhibition assay to study the effect of selected small molecule compounds towards inhibition of DDC and L-dopa conversion in E. faecalis model by previously developed cell-based assay. The human DDC was successfully produced in a TB medium with a yield of 1.8 mg/mL. The Km value of DDC for L-dopa was found to be 34 μM which indicates a high affinity for L-dopa. In the optimization of the DDC inhibition assay, the sample volume of 80 μL and incubation time of 3 h with detection reagent was found to give the highest fluorometric signal with sufficient robustness. In the initial screening of test compounds, 14 % of the compounds (n=59) were classified as active towards human DDC, while 31 % of the compounds were active towards L-dopa conversion in the E. faecalis model. Of those compounds, five were having dose-dependent dual inhibitory effects, but the IC50 values of them were higher compared to either carbidopa or AFMT. The most effective compounds were 8009-2501 (IC50 37 μM in E. faecalis model and 19 % inhibition at 1000 μM towards DDC enzyme) and 8012-3386 (IC50 248 μM in E. faecalis model and 37 % inhibition at 1000 μM towards DDC enzyme). However, this study confirms the possibility to find dual decarboxylase inhibitors. By optimizing the structures as well as investigating the mechanism of action, selectivity, and structure-activity relationships of the most active compounds, it is possible to find more effective dual inhibitors in the future.
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(2021)Parkinson’s disease (PD) is a progressive chronic neurodegenerative disorder, which results in the selective loss of dopaminergic neurons in the substantia nigra (SN). The loss of these neurons results in the dysfunction of the nigrostriatal pathway bringing forth the characteristic motor symptoms seen in PD: postural instability, rigidity, slowness of movement and resting tremors. Non-motor symptoms, such as cognitive deficits, depression and impaired olfaction, typically emerge before motor symptoms. Currently available treatments only provide symptomatic relief with diminishing returns over time and no improvements on the overall outcome of the disease. Neurotrophic factors (NTF) have been of particular interest as a possible curative treatment for PD due to their potential for neuroprotection and neurorestoration. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an NTF that has shown promising results in numerous in vitro and in vivo studies of PD. However, therapy with MANF and other NTFs involves surgical intervention for local administration, as NTFs cannot cross the blood-brain barrier (BBB). Therefore, the therapeutic potential of a systemically administered NTF would be tremendous, as it would lead to a significantly more favorable risk-benefit ratio for the patient. The aim of the current investigation is to evaluate the efficacy of a next generation variant of MANF in the 6-hydroxydopamine toxin-induced unilateral lesion rat model of PD. Prior in vivo results suggested that subcutaneously injected MANF variant is able to penetrate the BBB. Amphetamine-induced rotational behavior (AMPH-ROTO) was used to evaluate the severity of the unilateral lesions during the experiment every other week until the end of the experiment at week eight. Animals were divided into treatment groups during week two based on their AMPH-ROTO results. Animals received MANF variant either subcutaneously through an implanted osmotic minipump at two different dosages or as a single dose divided into three separate intrastriatal injections. Tyrosine hydroxylase (TH) immunohistochemical staining was performed on brain sections collected from the striatum and SN for data analysis. In addition to AMPH-ROTO results, the efficacy of treatment was determined via the optical density of TH-positive striatal fibers and the number of TH-positive cells in the SN. Statistically significant differences (defined by p < 0.05 and a non-zero mean difference at a 95 % confidence interval) were observed only in the number of TH-positive cells in the SN favoring intrastriatal MANF variant treatment over both intrastriatal MANF and the vehicle treatment. The main concern regarding the validity of the results was related to the heterogeneous lesion sizes in different treatment groups possibly resulting in unsuccessful randomization due to excessive baseline differences. The inadvertent negative effects of this was further exacerbated by low a priori statistical power, which in the end had likely caused inflated effect sizes. Thus, assessment of the definitions of the used statistical parameters and the limitations of the experimental design suggest that presently, the efficacy of the MANF variant could not be evaluated reliably, in spite of the statistically significant result.
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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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(2024)Parkinson’s disease (PD) is a prevalent neurodegenerative disease characterized by movement disorders, such as bradykinesia, akinesia, and tremor. The degeneration of dopaminergic neurons in the central nervous system (CNS) is the most central aspect of the pathophysiology of PD-related movement disorders. The treatment of PD motor symptoms is based on increasing the diminished dopaminergic signalling in the CNS. This can be achieved by using medications such as dopamine agonists and monoamine oxidase B inhibitors. Levodopa, which acts as a precursor of dopamine in the body, is currently considered the most effective treatment for PD motor symptoms. Unlike dopamine, levodopa can cross the blood-brain barrier. Thus, levodopa must reach the CNS before being metabolized into dopamine to achieve the desired therapeutic effect. Dopa decarboxylase (DDC) inhibitors and catechol-O-methyltransferase inhibitors have been co-administered alongside levodopa to reduce its peripheral metabolism. However, when administered orally, levodopa is also metabolized in the gut by tyrosine decarboxylase, an enzyme produced by gut bacteria. Inhibi tion of bacterial tyrosine decarboxylase (TyrDC) could increase the effectiveness of levodopa treatment and reduce the needed levodopa dosage. The aim of this study was to synthesize and assess the biological activity of novel analogues of previously identified hit compounds which are dual inhibitors of TyrDC and DDC. Our goal was also to gain a deeper understanding of the structure-activity relationships of these compounds. Some of the compounds synthesized in this study were able to inhibit both TyrDC and DDC. Unfortunately, they were also either toxic towar ds human cells, and/or lacked efficacy in a bacterial cell-based assay used to determine the inhibition of levodopa metabolism. However, the data generated in this study can be utilized to design and synthesize new analogs to discover more efficacious and safer TyrDC and DDC dual inhibitors.
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(2022)Parkinson’s disease (PD) is a progressive neurodegenerative disorder with the neuropathological hallmark of intraneuronal inclusions called Lewy bodies (LB). Accumulation of α-synuclein (α-syn) and cellular components into LBs coincides with degeneration of dopaminergic neurons in the midbrain, substantia nigra. Degeneration of dopaminergic neurons eventually leads to motor dysfunctions. Currently, the treatments for PD are symptomatic. For this reason, new disease-modifying treatments are needed to slow down or prevent the disease progression. Neurotrophic factors (NTFs) have been an interest of research for a couple of decades because of their neuroprotective properties. The main aim of this study was to investigate if brain-derived neurotrophic factor (BDNF) reduces pre-formed fibril (PFF) induced aggregation of α-syn in dopaminergic neurons. PFF-model was used to mimic the accumulation of LBs in neurons, as PFFs induce aggregation of endogenous α-syn in neurons. Additionally, the dose dependence of BDNF was tested. The secondary objective was to investigate the interaction of tropomyosin receptor kinase B (TrkB) signaling pathway and α-syn aggregation using TrkB agonists and antagonists. The cultured dopaminergic neurons isolated from the midbrain of mouse embryos were treated with PFFs on the day in vitro (DIV) 8. BDNF or control treatments were added either 1 hour after the PFF-treatment or on DIV 12. Neurons were fixed on DIV 15 and fluorescent immunohistochemistry was performed. After the detection of fluorescence with automated, high-content imaging, image analysis was done for quantifying dopaminergic neurons, and dopaminergic neurons positive for LB-like aggregates by using unbiased image analysis CellProfilerTM software. Both BDNF and positive control glial cell line-derived neurotrophic factor (GDNF) significantly reduced LB-like aggregates in dopaminergic neurons at both timepoints. GDNF was more effective at both timepoints than BDNF. Both tested doses of BDNF lowered the number of LB-like aggregates, but a more robust effect was seen with the higher dose. The highest tested dose for the TrkB agonists was toxic to the cultured dopaminergic neurons, whereas the lower doses did not affect either the survival or the number of LB-like aggregates. BDNF promoted the survival of the dopaminergic neurons despite the survival-reducing adverse effect of TrkB antagonist K252a. This study provided new information on the effects of exogenously added BDNF on PFF-model with primary neuronal culture. Research on the underlying mechanisms of α-syn aggregation and the protective effects of NTFs can forward the development of new therapies against PD.
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