Browsing by study line "Farmakologia"

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.

Multiple sclerosis is a progressive inflammatory disease of the central nervous system that affects young adults. The pathological hallmark of MS is the degradation and loss of oligodendrocytes resulting in demyelination. Damage to axons caused by demyelination severely impairs physical function. Currently there is no cure for MS, but current drugs aim to modify the course of the disease and relieve symptoms. However, they are unable to promote the repair of damaged myelin sheaths, and thus new therapies are needed. In this study, the effect of V-MANF on remyelination was investigated in two commonly used experimental toxin models. V-MANF is a modification of the endoplasmic reticulum located protein MANF, which has been found to have neuroprotective and regenerative properties. Additionally, MANF can regulate ER stress, which contributes to demyelination in MS. The effect of V-MANF on lysolecithin-induced demyelination was examined in organotypic cerebellar brain sections from C57B/6 mice. The study was conducted exceptionally using the brains of adult mice because they are a better model for neurodegenerative diseases. However, when analyzing the results, it was found that there was no demyelination in the tissue cultures, so the effect of V-MANF could not be analyzed. In the other study, C57B/6 mice were given dietary cuprizone for six weeks, followed by daily intranasal administration of either V-MANF or vehicle for seven days. Mice were subjected to behavioral experiments, in which a light/dark box test showed that V-MANFs had a potential anxiolytic effect in mice receiving cuprizone. No significant demyelination was observed by immunohistochemical analysis and therefore the effect of V-MANF on remyelination could not be assessed. However, the results of the study can be utilized in the design of further studies.

Since the discovery of ketamine’s antidepressant response, numerous of studies have been observed it to alleviate depressive symptoms rapidly and effectively within hours. This is a significant advantage compared to traditional antidepressants, which take weeks to show treatment efficacy. Ketamine is a N- methyl-D-aspartate receptor (NMDA) antagonist and its underlying mechanism of is proposed to be in its ability to increase synaptic plasticity and this is ultimately believed to improve mood. On a molecular level, the antidepressant effects have been observed to be dependent on the activation of tropomyosin receptor kinase B (TrkB) signalling pathway. However, the antidepressant mechanism of ketamine remains still poorly understood as no new NMDA-antagonist or other rapid-acting antidepressants have been successfully developed for clinical use despite many years of effort. Therefore, some have proposed that the missing pieces of understanding its antidepressant effects might be linked to ketamine’s ability to modify sleep patterns and circadian-related molecules. Ketamine has especially been demonstrated to increase slow-wave activity during the following night of treatment and these changes have been shown to predict the clinical outcome in patients with major depressive disorder (MDD). Slow-wave activity is a low-frequency and high-amplitude wave seen in electroencephalography, which is highly expressed during the deepest stage of sleep, and this has been prominently found to be reduced in MDD patients. Even more intriguing, there are indications that ketamine might increase slow-wave activity also immediately after its administration. During this time, TrkB signalling is observed to became active. Following these molecular findings, we sought to investigate the link between the TrkB signalling pathway and two prominent processes occurring during slow-wave sleep. During slow-wave sleep processes such as (1) reduction of brain’s energy expenditure and (2) the activation of glymphatic system is known to occur. The glymphatic system is as lymphatic-perivascular network, which is responsible for clearing the brain from the metabolic waste. Thus, in this study, our objective was to investigate whether by causing an acute decline in adenosine-triphosphate (ATP) production or by stimulating the glymphatic network, we could activate the same plasticity-related pathways as ketamine is capable of activating in mice prefrontal cortex. The results of this study suggest that acute metabolic reduction can trigger pathways regarding synaptic plasticity. The metabolic inhibitor, 2-deoxy-D-glucose and mercaptoacetate (2DG+MA), was found to phosphorylate the TrkB receptor and its downstream signalling molecules GSK3β and p70S6K, while MAPK was dephosphorylated. These results correlate with the previous findings of ketamine’s effect after its administration. We also found a plasticity-related marker, MAP2, to be heavily phosphorylated by 2DG+MA, indicating 2DG+MA having a surprising role on neuroplasticity. These results are promising indication of understanding the rapid effects of ketamine and might even give important insight to developing novel antidepressants. However, these findings are only preliminary, and more research is needed to directly link antidepressant effects and energy metabolic inhibition together, as our study did not directly investigate antidepressants and depression-like behaviour in mice.

Subanesthetic-dose ketamine, an N-methyl-D-aspartate receptor (NMDAR) blocker, exerts rapid antidepressant effects that sustain long after its elimination from the body. The precise mechanism remains unknown, but regulation of TrkB (tropomyosin receptor kinase B), ERK (extracellular-regulated kinase 1 and 2), GSK3β (glycogen synthase kinase 3β) and mTOR (mammalian target of rapamycin) signaling within the prefrontal cortex (PFC) have been deemed important for its antidepressant-like effects in rodents. In addition, activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is thought to be an important step in its mechanism. Nitrous oxide (N2O), another NMDAR antagonist and a putative rapid-acting antidepressant, regulates the same molecular pathways as ketamine in the rodent PFC. The fast pharmacokinetics of N2O have been exploited to show that markers of neuronal excitation, including phosphorylation of ERK, are upregulated in the PFC during its acute pharmacological effects (NMDAR blockade), while regulation of TrkB, GSK3β and P70S6K emerges only upon N2O withdrawal. In the first part of this study, we investigated the N2O-induced biochemical changes associated with neuronal excitation and BDNF-TrkB signaling in the PFC and further, the requirement for AMPAR activation in inducing them. We focused on the effects seen after the acute pharmacological effects of N2O. N2O (65% for 20 min) was administered to adult male C57BL/6 mice with or without pretreatment with AMPAR antagonist (NBQX, 10 mg/kg) and PFC samples were collected 15 minutes after stopping N2O delivery. Within this time N2O is expected to be completely eliminated. The brain samples were analyzed using western blot, enzyme-linked immunosorbent assay and quantitative reverse transcription PCR. We observed that N2O increased levels of phosphorylated TrkB, GSK3β and P70S6K, and these effects were not attenuated by NBQX pretreatment. At the same time, we observed a decrease in the levels of phosphorylated ERK, which was attenuated in mice that received NBQX prior to N2O. Tissue levels of BDNF protein or messenger RNA (exon IV) were not different between control and experimental groups. These results indicate that the mechanism of N2O is associated with TrkB and ERK signaling that are regulated independently of each other. It appears that AMPAR activation is not required for TrkB signaling, although it might play a role in ERK signaling. Further, N2O-induced TrkB phosphorylation in the PFC is not associated with changes in total levels of BDNF. In the second part of the study, we aimed to search for new ketamine-like NMDAR blockers with antidepressant potential. Ketamine was used as a query compound for in silico substructure search to find commercial ketamine analogs. The retrieved ketamine analogs were filtered by their computed ADMET properties and then further screened virtually by docking them to the pore region of NMDAR complex (protein data bank code: 4TLM), around the predicted binding site of ketamine. Finally, we sought to study if selected ketamine analogs could elicit ketamine-like effects on TrkB and ERK signaling in mouse primary cortical neurons. However, we did not proceed to test the analogs since ketamine (positive control) did not show any effects on TrkB or ERK phosphorylation in our culture. Overall, this study advances the understanding of the mechanism of N2O, possibly giving new insight of the antidepressant mechanisms of NMDAR-blocking agents more generally. Additionally, we found promising ketamine analogs that await experimental testing.

Rodent studies indicate that the effects of pharmacological antidepressant treatments depend on the TrkB (tropomyosin-related kinase B) receptor of the neurotrophic factor BDNF (brain-derived neurotrophic factor). However, the mechanism by which TrkB signaling becomes active remains disputed. Our group proposes that the activation of TrkB signaling is a result of an indirect physiological adaptation to the drug treatment, which is supported by observations made with rapid-acting antidepressants ketamine and nitrous oxide. Previous studies indicate that the immediate effects of the drugs are followed by a sedative state resembling deep sleep, during which TrkB signaling becomes active. The sedative state is accompanied with a drop in core body temperature, and preliminary findings indicate that preventing the drug-induced hypothermia blocks TrkB signaling in the cortex.    The purpose of this study was to investigate the effect of ambient temperature on TrkB signaling in the hippocampus following nitrous oxide administration. Nitrous oxide (65 % ad 100 % O2) was administered to adult male mice for 20 minutes. After the drug treatment the animals were kept in different recovery conditions: room temperature or a heightened ambient temperature of approximately 36 °C for 15 minutes. Following the recovery, the animals were euthanised, and hippocampus samples were collected from the animals. Levels of BDNF and TrkB signaling were analysed with ELISA and western blot, respectively.    Nitrous oxide caused a significant drop in core body temperature, but this was not accompanied with increased BDNF levels or TrkB signaling. Evidence suggests that hippocampal atrophy contributes to depression, but the acute effects of antidepressant treatments on TrkB signaling in this brain area appear to be less pronounced than those seen in the prefrontal cortex. The findings indicate that nitrous oxide has a replicable hypothermic effect, but this is not associated with increased TrkB signaling in the hippocampus.