Reduced adaptation of glutamatergic stress response is associated with pessimistic expectations in depression.
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ABSTRACT:
SUBMITTER: Cooper JA
PROVIDER: S-EPMC8155144 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The mechanisms underlying chronic stress-induced dysfunction of glutamatergic transmission that contribute to helplessness-associated depressive disorder are unknown. We investigated the relationship of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and stress, and the neuroplastic changes of stress-induced depression-like behavior in the ventrolateral periaqueductal gray (vlPAG). We conducted whole-cell patch-clamp electrophysiological recordings in the vlPAG neurons. Depression-like behavior was assayed using tail suspension test and sucrose preference test. Surface and cytosolic glutamate receptor 1 (GluR1) AMPA receptor expression was analyzed using western blotting. Phosphorylated GluR1 expression was quantified using western blotting and immunohistochemical analysis. Unpredictable inescapable foot shock stress caused reduction in glutamatergic transmission originating from both presynaptic and postsynaptic loci in the vlPAG that was associated with behavioral despair and anhedonia in chronic stress-induced depression. Pharmacological inhibition of GluR1 function in the vlPAG caused depression-like behavior. Diminished glutamatergic transmission was due to reduced glutamate release presynaptically and enhanced GluR1-endocytosis from the cell surface postsynaptically. Chronic stress-induced neuroplastic changes and maladaptive behavior were reversed and mimicked by administration of glucocorticoid receptor (GR) antagonist and agonist, respectively. However, chronic stress did not affect γ-aminobutyric acid (GABA)-mediated inhibitory synaptic transmission in the vlPAG. These results demonstrate that depression-like behavior is associated with remarkable reduction in glutamatergic, but not GABAergic, transmission in the vlPAG. These neuroplastic changes and maladaptive behavior are attributed to GR-dependent mechanisms. As reduced GluR1-associated responses in the vlPAG contribute to chronic stress-induced neuroplastic changes, this cellular mechanism may be a critical component in the pathogenesis of stress-associated neuropsychiatric disorders.
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Project description:Learning objectiveAfter participating in this activity, learners should be better able to evaluate the evidence supporting the antidepressant effects of glutamatergic modulators.Both preclinical and clinical studies have implicated glutamatergic system dysfunction in the pathophysiology of mood disorders such as bipolar depression and major depressive disorder. In particular, rapid reductions in depressive symptoms have been noted in response to subanesthetic doses of the glutamatergic modulator ketamine in subjects with major depressive disorder or bipolar depression. These results have prompted the repurposing or development of other glutamatergic modulators, both as monotherapy or adjunctive to other therapies. Here, we highlight the evidence supporting the antidepressant effects of various glutamatergic modulators, including (1) broad glutamatergic modulators (ketamine, esketamine, dextromethorphan, dextromethorphan-quinidine [Nuedexta], AVP-786, nitrous oxide [N2O], AZD6765), (2) subunit (NR2B)-specific N-methyl-D-aspartate (NMDA) receptor antagonists (CP-101,606/traxoprodil, MK-0657 [CERC-301]), (3) glycine-site partial agonists (D-cycloserine, GLYX-13, sarcosine, AV-101), and (4) metabotropic glutamate receptor modulators (AZD2066, RO4917523/basimglurant, JNJ40411813/ADX71149, R04995819 [RG1578]).
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Project description:We estimate a monthly interacted-VAR model for euro area macroeconomic aggregates allowing for the impact of uncertainty shocks to depend on the state of the average outlook for the economy measured by survey data. We find that, in response to an uncertainty shock, the peak decrease in industrial production and inflation is around three and a half times larger during pessimistic times. We build an assessment of the role of uncertainty for a path of innovations consistent with the increase in the observed VSTOXX measure of uncertainty since the outset of the COVID-19 epidemics in February and March 2020. Industrial production is predicted to experience a year-over-year peak loss of around 9.2% in the fourth quarter of 2020, and subsequently to recover with a rebound to pre-crisis levels roughly in June 2021. The large impact is the result of an extreme shock to uncertainty occurring at a time of very negative expectations for the economic outlook. We conduct simulations that quantify the potential benefit of recovered confidence in reducing the uncertainty-induced losses associated with a possible third wave of the pandemic.
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Project description:Exposure to stress throughout life can cumulatively influence later health, even among young adults. The negative effects of high cumulative stress exposure are well-known, and a shift from episodic to stimulus-response memory has been proposed to underlie forms of psychopathology that are related to high lifetime stress. At the other extreme, effects of very low stress exposure are mixed, with some studies reporting that low stress leads to better outcomes, while others demonstrate that low stress is associated with diminished resilience and negative outcomes. However, the influence of very low lifetime stress exposure on episodic and stimulus-response memory is unknown. Here we use a lifetime stress assessment system (STRAIN) to assess cumulative lifetime stress exposure and measure memory performance in young adults reporting very low and moderate levels of lifetime stress exposure. Relative to moderate levels of stress, very low levels of lifetime stress were associated with reduced use and retention (24 h later) of stimulus-response (SR) associations, and a higher likelihood of using context memory. Further, computational modeling revealed that participants with low levels of stress exhibited worse expression of memory for SR associations than those with moderate stress. These results demonstrate that very low levels of stress exposure can have negative effects on cognition.
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Project description:Accumulating evidence indicates that dysfunction of the glutamatergic neurotransmission has been widely involved in the pathophysiology and treatment of depression. Photobiomodulation therapy (PBMT) has been demonstrated to regulate neuronal function both in vitro and in vivo. Herein, we aim to investigate whether the antidepressant phenotype of PBMT is associated with the improvement of glutamatergic dysfunction and to explore the mechanisms involved. Results showed that PBMT decreased extracellular glutamate levels via upregulation of glutamate transporter-1 (GLT-1) and rescued astrocyte loss in the cerebral cortex and hippocampus, which also alleviated dendritic atrophy and upregulated the expression of AMPA receptors on the postsynaptic membrane, ultimately exhibiting behaviorally significant antidepressant effects in mice exposed to chronic unpredictable mild stress (CUMS). Notably, PBMT also obtained similar antidepressant effects in a depressive mouse model subcutaneously injected with corticosterone (CORT). Evidence from in vitro mechanistic experiments demonstrated that PBMT treatment significantly increased both the GLT-1 mRNA and protein levels via the Akt/NF-κB signaling pathway. NF-κB-regulated transcription was in an Akt-dependent manner, while inhibition of Akt attenuated the DNA-binding efficiency of NF-κB to the GLT-1 promoter. Importantly, in vitro, we further found that PKA activation was responsible for phosphorylation and surface levels of AMPA receptors induced by PBMT, which is likely to rescue excitatory synaptic transmission. Taken together, our research suggests that PBMT as a feasible therapeutic approach has great potential value to control the progression of depression.
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Project description:Major depressive disorder is a common and devastating psychiatric disease, and the prevalence and burden are substantially increasing worldwide. Multiple studies of depression patients have implicated glucose metabolic dysfunction in the pathophysiology of depression. However, the molecular mechanisms by which glucose and related metabolic pathways modulate depressive-like behaviors are largely uncharacterized. Uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) is a glucose metabolite with pivotal functions as a donor molecule for O-GlcNAcylation. O-GlcNAc transferase (OGT), a key enzyme in protein O-GlcNAcylation, catalyzes protein posttranslational modification by O-GlcNAc and acts as a stress sensor. Here, we show that Ogt mRNA was increased in depression patients and that astroglial OGT expression was specifically upregulated in the medial prefrontal cortex (mPFC) of susceptible mice after chronic social-defeat stress. The selective deletion of astrocytic OGT resulted in antidepressant-like effects, and moreover, astrocytic OGT in the mPFC bidirectionally regulated vulnerability to social stress. Furthermore, OGT modulated glutamatergic synaptic transmission through O-GlcNAcylation of glutamate transporter-1 (GLT-1) in astrocytes. OGT astrocyte-specific knockout preserved the neuronal morphology atrophy and Ca2+ activity deficits caused by chronic stress and resulted in antidepressant effects. Our study reveals that astrocytic OGT in the mPFC regulates depressive-like behaviors through the O-GlcNAcylation of GLT-1 and could be a potential target for antidepressants.
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Project description:In various educational systems, students are sorted into separate secondary schools on the basis of their academic ability. Research suggests that this type of tracking impacts students' educational expectations, as expectations generally align with students' ability track. However, most research is cross-sectional and students with lower expectations are possibly also sorted into lower tracks. Moreover, the extent to which track placement influences expectations may vary across students. In this paper, we address the following research question: how does ability tracking impact the development of student expectations and how does this vary by students' migration background. Based on the literature on the immigrant aspiration-achievement paradox, we expect that students with a migration background are less likely to adapt expectations downwardly, and more likely to adapt expectations upward in response to track placement. Using German panel data, we examine the educational expectations of students with and without a migration background, before and after track placement. Moreover, we use variations in tracking procedures across German states to study how students who get tracked compare with students who do not get tracked in the development of their educational expectations. We show that students are more likely to upwardly adjust their expectations when their track placement exceeds their expectations and to downwardly adjust their expectations when their track placement is below their expectations. We find little support for the hypothesized variations by student migration background. Students whose parent(s) hold (a) Bachelor degree(s) are more likely to upwardly adjust their expectations when their track placement exceeds their expectations than students whose parent(s) maximally hold an upper secondary or vocational degree(s).
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Project description:Major depressive disorder (MDD) affects around 350 million people worldwide; however, the underlying genetic basis remains largely unknown. In this study, we took into account that MDD is a gene-environment disorder, in which stress is a critical component, and used whole-genome screening of functional variants to investigate the 'missing heritability' in MDD. Genome-wide association studies (GWAS) using single- and multi-locus linear mixed-effect models were performed in a Los Angeles Mexican-American cohort (196 controls, 203 MDD) and in a replication European-ancestry cohort (499 controls, 473 MDD). Our analyses took into consideration the stress levels in the control populations. The Mexican-American controls, comprised primarily of recent immigrants, had high levels of stress due to acculturation issues and the European-ancestry controls with high stress levels were given higher weights in our analysis. We identified 44 common and rare functional variants associated with mild to moderate MDD in the Mexican-American cohort (genome-wide false discovery rate, FDR, <0.05), and their pathway analysis revealed that the three top overrepresented Gene Ontology (GO) processes were innate immune response, glutamate receptor signaling and detection of chemical stimulus in smell sensory perception. Rare variant analysis replicated the association of the PHF21B gene in the ethnically unrelated European-ancestry cohort. The TRPM2 gene, previously implicated in mood disorders, may also be considered replicated by our analyses. Whole-genome sequencing analyses of a subset of the cohorts revealed that European-ancestry individuals have a significantly reduced (50%) number of single nucleotide variants compared with Mexican-American individuals, and for this reason the role of rare variants may vary across populations. PHF21b variants contribute significantly to differences in the levels of expression of this gene in several brain areas, including the hippocampus. Furthermore, using an animal model of stress, we found that Phf21b hippocampal gene expression is significantly decreased in animals resilient to chronic restraint stress when compared with non-chronically stressed animals. Together, our results reveal that including stress level data enables the identification of novel rare functional variants associated with MDD.
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Project description:One of the many effects of soft tissues under mechanical solicitation in the cellular damage produced by highly localized strain. Here, we study the response of peripheral stress fibers (SFs) to external stretch in mammalian cells, plated onto deformable micropatterned substrates. A local fluorescence analysis reveals that an adaptation response is observed at the vicinity of the focal adhesion sites (FAs) due to its mechanosensor function. The response depends on the type of mechanical stress, from a Maxwell-type material in compression to a complex scenario in extension, where a mechanotransduction and a self-healing process takes place in order to prevent the induced severing of the SF. A model is proposed to take into account the effect of the applied stretch on the mechanics of the SF, from which relevant parameters of the healing process are obtained. In contrast, the repair of the actin bundle occurs at the weak point of the SF and depends on the amount of applied strain. As a result, the SFs display strain-softening features due to the incorporation of new actin material into the bundle. In contrast, the response under compression shows a reorganization with a constant actin material suggesting a gliding process of the SFs by the myosin II motors.
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