Project description:Recent studies implicate microglia alterations in the pathogenesis and pathophysiology of depression. For example, chronic unpredictable stress (CUS) in mice can cause degeneration of microglia and depressive-like symptoms, which can be reversed by microglia stimulating drugs. To further test the causal role of microglia in CUS-induced depression and its reversal by an anti-depressive procedure, we examined the effects of microglia depletion with the CSF-1 antagonist PLX5622 or pharmacological blockade of microglial activation with minocycline on normal mood-related behavior, CUS-induced depressive-like symptoms, and the amelioration of these symptoms by electroconvulsive treatment (ECT). We report that microglia-depleted mice showed no depression, anxiety or spatial memory disturbances. Microglia depletion had no effect on the development of CUS-induced depressive-like symptoms and suppressed neurogenesis, but it completely abrogated the beneficial effects of ECT on depression and neurogenesis, as well as on the all ECT-induced transcriptomic changes. ECT induced several morphological changes in microglia, suggestive of increased activation status, and blockade of this activation by minocycline attenuated the anti-depressive and pro-neurogenesis effect of ECT and reduced the number of contacts between microglia and neurogenic cells. The immune checkpoint gene Lag3, whose expression by microglia was increased following CUS, was the only microglial transcript significantly reduced by ECT. Furthermore, treatment of depressed-like mice with a LAG3 monoclonal antibody was further tested.
Project description:Background: Major depressive disorder (MDD) is a recurring affective disorder that is two times more prevalent in females than males. Evidence supports immune system dysfunction as a major contributing factor to MDD, notably in a sexually dimorphic manner. Nuclear factor erythroid 2-related factor 2 (Nrf2), a regulator of antioxidant signaling during inflammation, is dysregulated in many chronic inflammatory disorders, however its role in depression and the associated sex differences have yet to be explored. Here we investigated the sex-specific antidepressant and immunomodulatory effects of the potent Nrf2 activator dimethyl fumarate (DMF), as well as the associated gene expression profiles. Methods: Male and female rats were treated with vehicle or DMF (25 mg/kg) while subjected to 8 weeks of chronic unpredictable stress. The effect of DMF treatment on stress-induced depression- and anxiety-like behaviours, as well as deficits in recognition and spatial learning and memory were then assessed. Hippocampal (HIP) microglial activation and alterations in gene transcripts were also evaluated. Results: DMF treatment during stress exposure had antidepressant effects in male but not female rats, with no anxiolytic effects in either sex. Recognition learning and memory and spatial learning and memory were impaired in chronically stressed males and females, respectively, however DMF treatment rescued these deficits. DMF treatment also prevented stress-induced HIP microglial activation in males. Conversely, females displayed no HIP microglial activation associated with stress exposure. Lastly, chronic stress elicited sex-specific alterations in HIP gene expression, many of which were normalized in animals treated with DMF. Of note, several differentially expressed genes in males were related to inflammatory or immune responses. Conclusions: Collectively, these findings support a greater role of immune processes in males than females in a rodent model of depression. This suggests that pharmacotherapies that target Nrf2 have the potential to be an effective sex-specific treatment for depression. Major depressive disorder is two times more prevalent in females than males. Further, immune system dysfunction has been shown to contribute to the development of depression, with previous studies consistently reporting chronic low-grade inflammation in depressed individuals. Not surprisingly, the immune system dysfunction associated with depression appears to be sex specific. As such, while anti-inflammatory drugs have shown antidepressant effects in preclinical studies, the sex differences in these effects are seldomly investigated. Thus, this study sought to determine the sex-specific antidepressant and immune modulatory effects of dimethyl fumarate (DMF) treatment. DMF is a drug that activates the protein nuclear factor erythroid 2-related factor 2 to initiate anti-inflammatory signaling pathways. Here, male and female rats were exposed to 8 weeks of chronic stress while receiving daily DMF treatment. Subsequently, their expression of depression- and anxiety-like behaviours, as well as learning and memory deficits were assessed. Changes in the levels of an inflammatory marker in the brain and alterations in gene expression were also evaluated. DMF treatment had antidepressant effects in male rats only but did not have anti-anxiety effects in either sex. The learning and memory deficits in both sexes were rescued with DMF treatment. Notably, chronic stress only increased inflammatory marker levels in male rats, which was prevented by DMF treatment. Additionally, DMF normalized several of the sex-specific gene alterations induced by chronic stress, with many of the male-specific genes relating to inflammatory processes. These data suggest that anti-inflammatory drugs may be an effective antidepressant treatment in males.
Project description:Depression is one of the most common neuropsychiatric disorders. Although the pathogenesis of depression is still unknown, environmental risk factors and genetics are implicated. Copper (Cu), a cofactor of multiple enzymes, is involved in regulating depression-related processes. Depressed patients carrying the apolipoprotein ε4 allele display more severe depressive symptoms, indicating that ApoE4 is closely associated with an increased risk of depression. The study explored the effect of low-dose Cu (0.13 ppm) exposure and ApoE4 on depression-like behavior of mice and further investigate the possible mechanisms. The 4-month-old ApoE4 mice and wild-type (WT) mice were treated with 0.13 ppm CuCl2 for 4 months. After the treatment, ApoE4 mice displayed obvious depression-like behavior compared with the WT mice, and Cu exposure further exacerbated the depression-like behavior of ApoE4 mice. There was no significant difference in anxiety behavior (Open field test) and memory behavior (Morris water maze). Proteomic analysis revealed that the differentially expressed proteins between Cu-exposed and non-exposed ApoE4 mice were mainly involved in Ras signaling pathway, protein export, axon guidance, serotonergic synapse, GABAergic synapse, dopaminergic synapse. Among these differentially expressed proteins, immune response and synaptic function are highly correlated. Representative protein expression changes are quantified by Western blot, showing consistent results as determined by proteomic analysis. Hippocampal astrocytes and microglia were increased in Cu-exposed ApoE4 mice, suggesting that neuroglial cells played an important role in the pathogenesis of depression. Taken together, our study demonstrated that Cu exposure exacerbates depression-like behavior of ApoE4 mice and the mechanisms may involve the dysregulation of synaptic function and immune response, and overactivation of neuroinflammation.
Project description:Emerging evidence has shown that noncoding RNAs, particularly microRNAs (miRNAs), contribute to the pathogenesis of mood and anxiety disorders, although the molecular mechanisms are poorly understood. Here we show altered levels of miR-17-92 in adult hippocampal neural progenitors have a significant impact in neurogenesis and anxiety- and depression-related behaviors in mice. miR-17-92 deletion in adult neural progenitors causes a decrease, while its overexpression an increase of neurogenesis in the dentate gyrus, through regulating genes in the glucocorticoid pathway, especially serum- and glucocorticoid-inducible protein kinase-1 (Sgk1). miR-17-92 knockout mice show anxiety- and depression-like behaviors, whereas miR-17-92 overexpressing mice exhibit anxiolytic and antidepression-like behaviors. Furthermore, we show that miR-17-92 expression in the adult mouse hippocampus responds to chronic stress, and miR-17-92 rescues proliferation defects, induced by corticosterone, in hippocampal neural progenitors. Our study uncovers a crucial role for miR-17-92 in adult neural progenitors to regulate neurogenesis and anxiety- and depression-like behaviors.
Project description:Despite studies providing insight into the neurobiology of chronic stress, depression and anxiety, long noncoding RNA (lncRNA)-mediated mechanisms underlying the common and distinct pathophysiology of these stress-induced disorders remain nonconclusive. In a previous study, we used the chronic mild stress paradigm to separate depression-susceptible, anxiety-susceptible and insusceptible rat subpopulations. In the current study, lncRNA and messenger RNA (mRNA) expression was comparatively profiled in the hippocampus of the three stress groups using microarray technology. Groupwise comparisons identified distinct sets of lncRNAs and mRNAs associated with the three different behavioral phenotypes of the stressed rats. To investigate the regulatory roles of the dysregulated lncRNAs upon mRNA expression, correlations between the differential lncRNAs and mRNAs were first analyzed by combined use of weighted gene coexpression network analysis and ceRNA theory-based methods. Subsequent functional analysis of strongly correlated mRNAs indicated that the dysregulated lncRNAs were involved in various biological pathways and processes to specifically induce rat susceptibility or resiliency to depression or anxiety. Further intersectional analysis of phenotype-associated and drug-associated lncRNA-mRNA networks and subnetworks assisted in identifying 16 hub lncRNAs as potential targets of anti-depression/anxiety drugs. Collectively, our study established the molecular basis for understanding the similarities and differences in pathophysiological mechanisms underlying stress-induced depression or anxiety and stress resiliency, revealing several important lncRNAs that represent potentially new therapeutic drug targets for depression and anxiety disorders.
Project description:Up to 75% of systematic lupus erythematosus (SLE) patients experience neuropsychiatric (NP) symptoms, called neuropsychiatric SLE (NPSLE), yet the underlying mechanisms remain elusive. Microglia control synaptic pruning during early postnatal brain development. The process in NPSLE remains unclear. Here, we show that microglia-coordinated elimination of synaptic terminals participated in NPSLE in MRL/lpr mice, a lupus-prone murine model. We elucidated that lupus mice developed increased depression- and anxiety-like behaviors and persistent phagocytic microglia reactivation before overt peripheral lupus pathology. Microglial engulfment of synapses explained behavioral disorders. To elucidate the mechanism of synaptic pruning by microglia, we sequenced the gene expression in sorted microglia from both lupus (MRL/lpr) mice and the wild-type (MRL/mpj) controls.
Project description:Stress is associated with an increased prevalence of anxiety and depression. Repeated social defeat (RSD) stress in mice increases the release of monocytes from the bone marrow that are recruited to the brain by microglia. These monocytes enhance inflammatory signaling and augment anxiety. Moreover, RSD promotes stress sensitization, in which exposure to acute stress 24 days after cessation of RSD causes anxiety recurrence. The purpose of this study was to determine whether microglia were critical to stress sensitization and exhibited altered gene expression 24 days after RSD.
Project description:Individual differences in human temperament can increase the risk of psychiatric disorders like depression and anxiety. Our laboratory utilized a rat model of temperamental differences to assess neurodevelopmental factors underlying emotional behavior differences. Rats selectively bred for low novelty exploration (Low Responders, LR) display high levels of anxiety- and depression-like behavior compared to High Novelty Responder (HR) rats. Using transcriptome profiling, the present study uncovered vast gene expression differences in the early postnatal HR versus LR limbic brain, including changes in genes involved in cellular metabolism. These data led us to hypothesize that rats prone to high (versus low) anxiety/depression-like behavior exhibit distinct patterns of brain metabolism during the first weeks of life, which may reflect disparate patterns of synaptogenesis and brain circuit development. All samples were generated from Sprague-Dawley male rats selectively bred for high novelty response (HRs) or low novelty response (LRs).