Browsing by study line "Neurovetenskap"

Tiivistelmä – Referat – Abstract Mental disorders are among the leading causes of global disease burden and years lived with disability. Their pathogenesis is poorly understood and there are enormous challenges in the development of biomarkers to aid in diagnosis and more effective therapeutic options. It has been documented that the microbiota-gut-brain axis shows alterations in mental disorders such as anxiety, depression, autism spectrum disorders, bipolar disorder and schizophrenia. Here we study the gut microbiota of individuals with axis I mental disorders and their unaffected siblings by 16S RNA gene amplicon sequencing. In the Central Valley of Costa Rica, a total of 37 participants were recruited and diagnosed using a Best Estimate Diagnosis protocol. For each of the individuals diagnosed with a mental disorder a healthy sibling was selected after matching by age and gender. A total of 13 pairs of 26 siblings, affected and unaffected, was used for the analysis. In a subsequent analysis, individuals were also divided into the three categories of “unaffected” (UA), “affected without psychosis” (AA) and “affected with psychosis” (AP). They underwent clinical assessments about their habits and diet and about resilience (Connor-Davidson Resilience Scale), current status (SADS-C) and disability (WHODAS 2.0). Their fecal samples were collected freshly and stored at -80°C. DNA was extracted, libraries constructed by PCR and subjected for Illumina MiSeq 300 paired-end 16S RNA amplicon sequencing for analysis of the gut microbiota. The sequencing data were analyzed using the R packages mare and vegan for gut microbiota composition, diversity and richness, taking into account the identified confounders. All participants were of Hispanic ethnicity, residents of the San José Greater Metropolitan Area, adults and 69% of them were women. Affected individuals had major depression, bipolar affective disorder, psychosis non-otherwise specified or schizoaffective disorder. Based on beta-diversity analysis as a measure of the community-level microbiota variation, it was found that the use of levothyroxine (R2=0.08, p=0.005) and of irbesartan (R2=0.068 ,p=0.001) had a significant impact on the microbiota composition and hence the use of these drugs was included as confounder in further analyses. Several statistically significant differences in the relative abundance of intestinal bacteria were identified: Differences were found in the relative abundance of bacterial families Peptostreptococcaceae, Ruminococcaceae, Porphyromonadaceae, and in bacterial genera Pseudomonas, Barnesiella, Odoribacter, Paludibacter, Lactococcus, Clostridium, Acidaminococcus and Haemophilus. Our results indicate that affected individuals have more pro-inflammatory Proteobacteria (Pseudomonas) and less bacteria associated to healthy phenotype, such as Barnesiella and Ruminococcaceae, the former being dose-dependently depleted in AP and AA compared to UA. Furthermore, we documented decreased bacterial richness among affected participants while no significant differences were detected in alpha diversity. Our study identified significant differences in the microbiota of individuals affected by mental illness when comparing to their healthy siblings. The results may have important implications for the holistic understanding of mental health and its diagnosis and therapeutics. Larger studies to confirm these findings would be justified.

Pain is a subjective feeling often difficult to interpret or study and thus, pain of those unable to communicate their pain is difficult to recognize. According to the new definition of pain by IASP (Raja et al 2020), verbal description is only one of the many behaviours that can be used to express pain, and the inability to communicate pain does not negate the possibility of experiencing it. This addition to the definition points out that non-human animals, too, even if they cannot express it in words, are capable of both experiencing and communicating pain. Can we as humans interpret a state of pain in an animal in a trustworthy way – and in a manner that would be respectful and non-invasive to the animal? Infrared thermography (IRT) is a technology based on using infrared radiation instead of normal light to form images. These images can be used to quantify the surface temperature of an object with high resolution. The intensity of the radiation emitted by the object being imaged depends on the surface temperature and for this reason thermal imaging enables detecting and measuring changes of surface temperature. Pain and stress might manifest physiologically as activation of the autonomic nervous system, which in turn might result in changes in surface temperatures of the body. These changes might be detectable with a thermal camera. If we could establish a link between certain intricate temperature changes of the head area to certain type of activation of the sympathetic nervous system resulting from pain, thermal imaging could have the potential to detect this. In this study I investigated if there were detectable temperature changes in animal patients before and after a standard examination conducted to each patient admitted to the Wildlife Hospital of Helsinki Zoo, where my data was gathered. Another question was whether the patients that had pain differed in their temperature changes as compared to other patients. The question at the heart of my research was whether there would be a change in peripheral facial temperatures of patients before and after the examination. Another question was whether thermal patterns would be different for pain- and non-pain patients. I found that for some parameters, the temperature differences between pain- and non-pain patients were indeed different, for example the crown temperature of birds seemed to change with examination for patients without pain but not for patients with pain. A more prominent finding was that temperatures decrease across many parameters after an examination as compared to prior to it, across all or many patient groups. My research does not univocally show that thermal imaging could be used to detect pain; rather it affirms the thought that the measurement of changes in peripheral temperatures could be a potential window to non-invasively detect some changes of activation of the sympathetic nervous system in animals.

Meningeal lymphatics vessels (mLVs), the recently characterized lymphatics in the central nervous system (CNS), provide a link between the adaptive immune system and the CNS. mLVs could be important for the activation of T cell-mediated adaptive immune response, by draining antigens from the brain to the deep cervical lymph nodes, where they are presented to T cells. In traumatic brain injury (TBI), we hypothesized that the activation of self-reactive T cells (i.e., T cells able to recognize self, brain-derived antigens and promote an immune reaction), possibly underlies the pathogenesis of the disease. In order to test this hypothesis and to decipher the specific role of mLVs in the modulation of T cell-mediated neuro-immune response after TBI, we ablated the existing mLVs in adult male C57BL/6OlaJ mice (with the use of the AAV-mVEGFR3 1-4 Ig vector), induced TBI with controlled cortical impact, and examined the motor function of the mice and the activation of different T cell populations in the brain, as well as in the secondary lymphoid (spleen and lymph nodes – LNs) and non-lymphoid organs (meninges). Our data showed that the T cell-mediated adaptive neuro-immune response in TBI was unaffected by the depletion of mLVs. Our results, however, are preliminary, due to the limited sample size used in this study, which reduces the statistical power and restricts our ability to conclude for the effect of mLV depletion on TBI recovery.

Microglia, the resident macrophage-like glial cells of the central nervous system (CNS), form the first line of defense against pathogens in the brain, and regulate both innate and adaptive immunity. Any abnormalities in their microenvironment lead to microglial activation, characterized by alterations in their gene expression, morphology, and functional behavior. Once activated, microglia respond to CNS injury and inflammation by, e.g., migrating to the site of damage, releasing pro-inflammatory cytokines, as well as phagocyting cell debris and pathogens. Prolonged activation of microglia expressing pro-inflammatory phenotypes can lead to exacerbated CNS damage. Hence, limiting CNS inflammation by stimulating microglial polarization towards their pro-resolving phenotypes would be of great clinical relevance. The research of our laboratory focuses on CNS injury and repair, as well as finding novel therapies for ischemic stroke. Specialized pro-resolving mediators (SPMs) derived from essential fatty acids have been proposed to offer a potential therapeutic approach for ischemic stroke via promoting resolution of post-stroke inflammation. Previous studies have revealed the ability of SPMs to induce a transformation of macrophages, the immune cells strongly resembling microglia, towards their anti-inflammatory phenotypes. The aim of this study was therefore to assess whether SPMs have similar effects on BV2 microglia, specifically on their lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines, tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6). In addition to assessing the cytokine levels, our aim was to determine the optimal conditions for studying the effects of SPMs on microglial migration. In the present study, the levels of TNF-α and IL-6 were determined by specific ELISAs, and the transwell assay was used to measure microglial migration. Resolvins E1 (RvE1) and D1 (RvD1), as well as protectin D1 (PD1) and 15-epimer of lipoxin A4 (15-epi-LXA4) were all associated with decreased levels of TNF-α and IL-6, with RvE1 having the most potential as a resolving agent. In addition, we observed that serum starvation notably decreases the release of IL-6 and affects microglial migration. Overall, our results support the idea that SPMs could provide a novel therapeutic strategy for stroke therapy as they contribute to the resolution of CNS inflammation.

Early life stress (ELS) has been associated with the development of psychiatric disorders such as anxiety and depression later in life. The central hypothesis is that these disorders are caused by a malfunctioning of the serotonin system and serotonin (5-HT) produced in the dorsal raphe nucleus (DRN). The DRN is anatomically connected to the medial prefrontal cortex (mPFC), especially to the infra- and prelimbic cortex, where 5-HT modulates behaviors such as impulsivity and cognitive flexibility. The DRN and mPFC mediate with low-frequency network oscillations, which are indicative of the state of the network and its funtional connectivity, as disturbances in these network oscillations have been connected to neuropsychiatric disorders. The aim of the thesis is to investigate whether and how ELS can influence the local field potential (LFP) activity of the mPFC and DRN and the functional connectivity of the DRN and mPFC. This is researched by characterizing and comparing the LFP activity recorded in the DRN, where 5-HTergic neurons are located, and in layer 5 of the infralimbic area of the mPFC. To accomplish these aims, a well-established animal model of early-life stress, the limited bedding and nesting model (LBN), was used. The model causes fragmented maternal care due to the stress of the dam, which in turn leads to the stress of the pups. Simultaneous multi-site recordings of LFP and multi-unit activity (MUA) within DRN and mPFC were performed in vivo during postnatal days (PND) 10-11 from control and LBN pups to characterize the network activity of these two brain areas and then investigate possible changes in their functional connectivity. The efficacy of the LBN model was determined by the observed decreased weight gain of LBN animals compared to controls. From the data, the LFP activity of the DRN and mPFC were characterized. The activity was characterized as power spectrum, wavelet spectrum, and MUA with DRN showing discontinuous activity with low signal-to-noise ratio and low frequency theta oscillations (4-12 Hz), while mPFC showed almost continuous activity with higher signal-to-noise ratio and developing gamma oscillations (20-50 Hz). The power of LFP signal of the areas was not found to be affected by ELS. To investigate if the coupling by synchrony between DRN and mPFC networks is altered by ELS, I analyzed wavelet coherence by computing coherence values between LFP signals in DRN and mPFC in a control and ELS for frequencies from 1 to 50Hz. The functional connectivity was affected by ELS. Statistically significant changes were observed in wavelet coherence in the lower frequencies of 1-2.8 Hz between the control and LBN treatment, suggesting impaired synchronization between DRN and mPFC at 1-2.8Hz frequency range immediately after ELS exposure at PND 10-11 mice. Caveats of the study were low signal-to-noise ratio of the recordings, the small group size of LBN animals (n=5) as well as the uneven sex distribution (male n=11, female n=3) which prevented the sex-based comparison of the effects of ELS. The thesis examines postnatal LFP brain activity in the DRN and mPFC and the functional connectivity between these brain areas. The results of the thesis show that ELS exposure is able to influence the functional connectivity of these two brain regions. The results support previous findings, which have found alterations in the functional connectivity of the neural networks underlying neuropsychiatric disorders in adulthood. The findings of this thesis suggest that ELS could affect the functional connectivity of a developing network and thus increase the risk of the development of neuropsychiatric disorders. Further studies are needed with larger group size, even gender balance, and better signal-to-noise ratio of recordings.

In recent years, psychedelics have shown promise in the treatment of conditions like depression and addiction. The therapeutic effects of psychedelics have been linked to their ability to increase plasticity in the brain, an effect that has also been seen for antidepressants. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, which has an important role in the development of the nervous system, as well as promotion of neuronal survival and differentiation during adulthood. BDNF, through its receptor TrkB, has been implicated in antidepressant action, and BDNF-TrkB signalling is involved in many aspects of plasticity. Recently, antidepressants have been reported to bind directly to TrkB, and through this binding mediate their plasticity-enhancing, as well as behavioural effects. Psychedelics have been shown to increase structural and functional plasticity, but the mechanisms behind these effects are not fully understood. For example, the serotonergic receptor 5-HT2A is known to be behind the acute hallucinogenic effects of psychedelics, but its role in plasticity is still debated. The aim of this study was to investigate the mechanisms of LSD-induced plasticity. The dimerization of TrkB was examined after LSD treatment in the protein-fragment complementation assay (PCA). Phosphorylation of TrkB signalling markers mTOR and ERK, which have known effects on plasticity, was assessed in Western blot, and the total expression of BDNF was examined with the enzyme-linked immunosorbent assay (ELISA). The timeline of the effects was investigated, and the involvement of 5-HT2A in TrkB dimerization and the phosphorylation of ERK was assessed by combining LSD treatment with the 5-HT2A antagonist M100907. Dimerization was also assessed in a TrkB mutant (Y433F) that has previously been shown to disrupt antidepressant effects on plasticity. These experiments showed that LSD treatment increased TrkB dimerization as well as phosphorylation of mTOR and ERK. The Y433F mutation interfered with LSD-induced TrkB dimerization, but the effects of LSD on TrkB dimerization or ERK phosphorylation were not blocked by M100907. Together, these data suggest that 5-HT2A is not involved in LSD-induced promotion of TrkB dimerization or ERK phosphorylation. The increases in phosphorylation and dimerization were found to be most robust after a 1 h LSD treatment, however an increase in BDNF expression was seen in cortical neuron cultures only after a 24 h treatment with LSD. The results reported in this study support the view that 5-HT2A might not be needed for the plasticity-inducing effects of psychedelics. If this is true, the development of treatments that target plasticity without hallucinatory effects could be possible. Overall, this research provides insight into the mechanisms of LSD-induced plasticity and offers new and interesting directions for future research in the field.

Catastrophic childhood epilepsies are characterized by persistent seizures and are frequently associated with cognitive and developmental impairments. Many, approximately 30%, of these epilepsies are rare genetic disorders that do not have effective therapeutic options. The bench to drug process is lengthy and expensive, and thus it is critical to find more affordable drug screening options. Zebrafish are an ideal model organism for screening studies as they share considerable (70%) genetic similarities with humans and are cheap to maintain with efficient breeding capabilities. In the present study, 37 zebrafish lines were screened for epileptic brain activity to identify high priority genes for future pharmacology studies. Each zebrafish line, generated by CRISPR-Cas9 represents a single gene loss of function mutation associated with 3 epilepsy based on genome wide association studies. Larval zebrafish were screened for spontaneous seizure activity using electrophysiological assays. The following 8 genes were significantly associated with spontaneous seizure activity in zebrafish: EEF1A, ARX, GRIN1, GABRB3, PNPO, STRADA, SCN1A, and STXBP1. There is now an open-source database for all 37 zebrafish lines, which contains sequencing information, survival curves, behavioral profiles, and electrophysiological data. The findings reveal novel target genes for future drug development and discovery. Future work is needed to explore whether zebrafish also model co-morbidities commonly seen in human patients with epilepsy.

Epigenetics is the study of changes in gene function without affecting the DNA sequence. Epigenetics studies the effects of the environment and behavior on the genome. Researchers have been able to detect several epigenetic modifications such as –DNA methylation, histone acetylation, and microRNA-associated gene silencing. Changes in the epigenome are essential for proper cell function and normal development and can also be induced by environmental factors. Stress is defined as a biological response to physiological and psychological demands which can affect cellular homeostasis. Factors such as prenatal life stress can affect gene function without directly altering the DNA nucleotide sequence. Elevated levels of stress can immobilize with the ability to impair cognitive function. There is evidence that suggests the involvement of epigenetic regulation in disorders such as addiction, depression, schizophrenia, and cognitive dysfunction. Therefore, this systematic review discusses recent findings of the role of epigenetics in prenatal exposure to stress. To achieve this, the thesis will cover different subtopics from genetics, neurobiology, and diseases, neuroscience, biological psychiatry, life sciences, medicine, behavioral brain research, biochemistry & molecular biology, as well as neuroendocrinology. Research questions are 1) Is there an association between epigenetics and prenatal stress? 2) What kind of mechanisms have been found? 3) What kind of techniques have been used in the identification of potential epigenetic mechanisms? What genes are associated with these epigenetic changes?. This study followed the "The Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) guideline checklist. Eligibility criteria and search terms where be selected and documented to offer the widest range of articles covering the subjects of this study. A literature search was done using PubMed/Medline, Google scholar, and gray literature. The last sample comprised 59 articles. Data were extracted so that the participants, intervention, comparisons, and outcomes were included. The literature search conducted in this systematic review identified a few findings. First is that the majority of animal and human studies found a significant or moderate association between epigenetics and prenatal stress. Second, DNA methylation is the most studied epigenetic mechanism in maternal exposure to stress Third, genome-wide studies were more common in human studies than in animals and the most widely used method used is Infinium HumanMethylation450 Bead Chip. However, the common methods used in human and animal studies are most likely because of the small sample size and causation cannot be determined. Finally, NR3C1 and FKBP5 genes were the most studied in human studies where they showed the strongest association between prenatal stress and epigenetic modifications. While in animal studies, the most studied genes were Bdnf and Dnmt1 as they showed a significant methylation level after maternal prenatal stress exposure. In conclusion, maternal prenatal stress could trigger epigenetic alterations in neonates in both animals and humans. This holistic review detailed and evaluated locus-specific and studies exploring current knowledge about associations between maternal prenatal stress and epigenetic changes.

The insular cortex has been implicated in the neurocircuitry underlying alcohol addiction. The role of the insular cortex and its projections in regulating ethanol intake in AA (Alko-Alcohol) rats has been studied using chemogenetic tools. Chemogenetic activation of the anterior agranular insula (aAI) in AA rats through excitatory DREADDs expressed in the aAI has been found to decrease ethanol consumption. The aAI projects to the central nucleus of the amygdala (CeA), another brain region involved in the development of addiction, particularly in the withdrawal/negative affect stage. In the current study, we sought to further investigate the role of the aAI and the CeA in regulating voluntary ethanol consumption in AA rats. First, we characterized the efferent projections of the aAI in AA rats by chemogenetically activating the aAI with DREADDs and then measuring c-Fos expression in various regions of interest throughout the brain. Next, we investigated the role of the aAI --> CeA projection in ethanol intake by chemogenetically activating or inhibiting the aAI --> CeA projection using the dual viral Cre-dependent DREADD approach. We examined the effects of this manipulation on voluntary ethanol consumption in AA rats in a two-bottle choice paradigm. Finally, we examined the roles of CeA D1Rs (dopamine receptors) and 5-HT2ARs (serotonin receptors) in regulating ethanol intake by examining the effects of pharmacological agonism or antagonism of these receptors on voluntary ethanol consumption in AA rats. Our results from the first experiment reveal significant activation of brain regions including the posterior agranular insula, the mediodorsal nucleus of the thalamus, and the posterior piriform cortex following chemogenetic activation of the aAI. The projections from the aAI to these regions are potentially important in the aAI circuitry in AA rats and are therefore of interest in future studies on the role of aAI circuitry in ethanol intake. In the second experiment, we found no significant effects of aAI --> CeA projection activation or inhibition on ethanol consumption in AA rats, indicating that this projection may not be a key component in regulating ethanol intake in these rats. Finally, we found no significant effects of pharmacological D1R antagonism, 5-HT2AR antagonism, or 5-HT2AR agonism in the CeA on ethanol intake in AA rats, although there was a non-significant trend towards a dose-dependent decrease in ethanol consumption with increasing dose of the D1R antagonist. Our results reveal new neural projections that should be investigated in future research on the role of the aAI in regulating ethanol intake. Studies on the neurobiology underlying alcoholism may reveal new pharmacological or anatomical targets for treatments of alcoholism in humans.

White matter (WM) structural connectivity alterations have been linked to depression. This study aimed to identify structural connectivity metrics associated with Major depressive disorder (MDD) and predictive of different symptom phenotypes. The study sample included N=29 control and N=86 subjects with MDD who underwent a clinical interview, Mini-International Neuropsychiatric Interview (MINI), and assessment of depression symptoms severity. Using a 3T MRI scanner, diffusion tensor imaging (DTI) was employed to capture WM connectivity markers at baseline. While no distinct differences between control and MDD groups were observed at the whole-brain network level, significant alterations were evident at the node level. Clinical group demonstrated enhanced connectivity, particularly in the DefaultB and LimbicB subsystems, as evidenced by measures such as eigenvector centrality. Furthermore, notable differences were observed in clustering coefficient and local efficiency, predominantly in DefaultB, LimbicB, and VisPeri networks, with MDD patients showing higher connectivity. Analysis of the association between WM structural connectivity measures, both global (e.g. global efficiency) and local (e.g. clustering coefficient) with MDD symptom scores and related symptoms, revealed no significant correlation at the whole-brain level, both at baseline and post-intervention. Distinct patterns were identified when evaluating node-level metrics averaged across networks, which together with group differences, point to MDD patients exhibiting characteristics consistent with regular networks. Hierarchical clustering based on standardized baseline DTI structural connectivity within the clinical cohort revealed three distinct clusters of MDD patients, with the first cluster exhibiting a higher WHO-5 score, indicating a potential association with better well-being. These findings provide insight into MDD-specific brain regions’ structural alterations and underscore the heterogeneity of depression symptom profiles. Further research is needed, including a higher sample size and control for confounding factors.