Differential expression of synaptic proteins after chronic restraint stress in rat prefrontal cortex and hippocampus

Potential Role of Bmal1 in Lipopolysaccharide-Induced Depression-Like Behavior and its Associated "Inflammatory Storm"

Inflammation plays an important role in the pathogenesis of depression; however, the underlying mechanisms remain unclear. Apart from the disordered circadian rhythm in animal models and patients with depression, dysfunction of clock genes has been reported to be involved with the progress of inflammation. This study aimed to investigate the role of circadian clock genes, especially brain and muscle ARNT-like 1 (Bmal1), in the linkage between inflammation and depression. Lipopolysaccharide (LPS)-challenged rats and BV2 cells were used in the present study. Four intraperitoneal LPS injections of 0.5 mg/kg were administered once every other day to the rats, and BV2 cells were challenged with LPS for 24 h at the working concentration of 1 mg/L, with or without the suppression of Bmal1 via small interfering RNA. The results showed that LPS could successfully induce depression-like behaviors and an "inflammatory storm" in rats, as indicated by the increased immobility time in the forced swimming test and the decreased saccharin preference index in the saccharin preference test, together with hyperactivity of the hypothalamic-pituitary-adrenal axis, hyperactivation of astrocyte and microglia, and increased peripheral and central abundance of tumor necrosis factor-α, interleukin 6, and C-reactive protein. Moreover, the protein expression levels of brain-derived neurotrophic factor, triggering receptor expressed on myeloid cells 1, Copine6, and Synaptotagmin1 (Syt-1) decreased in the hippocampus and hypothalamus, whereas the expression of triggering receptor expressed on myeloid cells 2 increased. Interestingly, the fluctuation of temperature and serum concentration of melatonin and corticosterone was significantly different between the groups. Furthermore, protein expression levels of the circadian locomotor output cycles kaput, cryptochrome 2, and period 2 was significantly reduced in the hippocampus of LPS-challenged rats, whereas Bmal1 expression was significantly increased in the hippocampus but decreased in the hypothalamus, where it was co-located with neurons, microglia, and astrocytes. Consistently, apart from the reduced cell viability and increased phagocytic ability, LPS-challenged BV2 cells presented a similar trend with the changed protein expression in the hippocampus of the LPS model rats. However, the pathological changes in BV2 cells induced by LPS were reversed after the suppression of Bmal1. These results indicated that LPS could induce depression-like pathological changes, and the underlying mechanism might be partly associated with the imbalanced expression of Bmal1 and its regulated dysfunction of the circadian rhythm.

Potential value of Interleukin-6 as a diagnostic biomarker in human MDD and the antidepressant effect of its receptor antagonist tocilizumab in lipopolysaccharide-challenged rats

Depression is a common mental disease with disastrous effect on the health and wealth globally. Focusing on the role for inflammation and immune activation in the pathogenesis of depression, many tries have been taken into effect targeting at the blockage of inflammatory cytokines, among which interleukin- 6 (IL-6) and its receptor antagonist tocilizumab attracts more attention, with inconsistent findings. Moderate to severe depressive disorder (MSDD) patients were enrolled and the serum concentrations of IL-6 and tumor necrosis factor-α (TNF-α) measured, their correlation with the Hamilton Depression Rating Scale-24 (HAMD-24) scores was analyzed, and their role in discriminating MSDD patients from the health controls were evaluated. Meanwhile, a depression rat model was established by intraperitoneal injection of LPS, and tocilizumab was administrated doing 50 mg/kg via intravenous injection. The behavioral performance was observed, the serum concentration of IL-6, TNF-α, and C-reactive protein (CRP) was measured, and the protein expression of IL-6 and TNF-α in the hippocampus were also detected. The activity of the Hypothalamic-pituitary-adrenal (HPA) axis was observed, and the protein expression levels in the hippocampus were detected via western blot. Moreover, the immunofluorescence staining (IF) technique was used to investigate the co-location of IL-6 and neuron (MAP2), astrocyte (GFAP), or microglial (IBA-1). The results showed that the serum IL-6 level was significantly increased in the MSDD patients and lipopolysaccharide (LPS)-challenged rats, with a significant correlation with the HAMD-24 scores or struggling time in the FST and corticosterone (CORT) abundance. Results of ROC analysis showed a significant diagnosis value of IL-6 in discriminating MSDD patients or depression rats from the controls in the present study. Tocilizumab could relieve the depression-like behaviors induced by LPS, together with a normal abundance of serum CORT and hypothalamic CRH expression. Moreover, tocilizumab could alleviate the "inflammatory storm" and impaired hippocampal synaptic plasticity in LPS-challenged depression rats, inhibiting the hyperactivation of astrocyte and microglia, decreasing the peripheral and central abundance of IL-6, CRP, and TNF-α, and balancing the hippocampal expression levels of synaptic plasticity-associated proteins and key molecular in Wnt/β-catenin signaling pathway. These results indicated a predictive role of IL-6 in discriminating depression from controls, and demonstrated an antidepressant effect of tocilizumab in LPS-challenged rats, targeting at the inflammatory storm and the subsequent impairments of hippocampal synaptic plasticity.

Sex-Dependent Effects of Chronic Restraint Stress on Mood-Related Behaviours and Neurochemistry in Mice

Anxiety and depressive disorders are closely associated; however, the pathophysiology of these disorders remains poorly understood. Further exploration of the mechanisms involved in anxiety and depression such as the stress response may provide new knowledge that will contribute to our understanding of these disorders. Fifty-eight 8-12-week-old C57BL6 mice were separated into experimental groups by sex as follows: male controls (n = 14), male restraint stress (n = 14), female controls (n = 15) and female restraint stress (n = 15). These mice were taken through a 4-week randomised chronic restraint stress protocol, and their behaviour, as well as tryptophan metabolism and synaptic proteins, were measured in the prefrontal cortex and hippocampus. Adrenal catecholamine regulation was also measured. The female mice showed greater anxiety-like behaviour than their male counterparts. Tryptophan metabolism was unaffected by stress, but some basal sex characteristics were noted. Synaptic proteins were reduced in the hippocampus in stressed females but increased in the prefrontal cortex of all female mice. These changes were not found in any males. Finally, the stressed female mice showed increased catecholamine biosynthesis capability, but this effect was not found in males. Future studies in animal models should consider these sex differences when evaluating mechanisms related to chronic stress and depression.

Single dose S-ketamine rescues transcriptional dysregulation of Mtor and Nrp2 in the prefrontal cortex of FSL rats 1 hour but not 14 days post dosing

There is a pressing need to identify biological indicators of major depression to help guide proper diagnosis and optimize treatment. Animal models mimicking aspects of depression constitute essential tools for early-stage exploration of relevant pathways. In this study, we used the Flinders Sensitive and Resistant Line (FSL/FRL) to explore central and peripheral transcriptional changes in vascular endothelial growth factor (VEGF) pathway genes and their temporal regulation after a single dose of S-ketamine (15 mg/kg). We found that S-ketamine induced both rapid (1 hour) and sustained (2 and 14 days) antidepressant-like effects in the FSL rats. Analysis of mRNA expression revealed significant strain effects of Vegf, Vegf164, Vegfr-1, Nrp1, Nrp2, Rictor, and Raptor in the prefrontal cortex (PFC) and of Vegf164, GbetaL, and Tsc1 in the hippocampus (HIP), which indicates suppression of VEGF signaling in the FSL rats compared to FRL rats. This notion was further substantiated by reduced expression of Vegf and Mtor in plasma from FSL rats. In the brain, S-ketamine induced transcriptional changes in the acute phase, not the sustained phase. There were significant treatment effects of S-ketamine on Vegfr-2 in both PFC and HIP and on Vegf and Vegfr-1 in HIP. Moreover, we found that S-ketamine specifically restored reduced levels of Nrp2 and Mtor in the PFC of the FSL rats. In conclusion, this study substantiates the use of the FRL/FSL rats to explore the depressive-like behavior at the transcriptional level of the VEGF pathway genes and study their regulation in response to various treatment paradigms.

Eriocheir sinensis vesicle-associated membrane protein can enhance host cell phagocytosis to resist Spiroplasma eriocheiris infection

Vesicle-associated membrane protein (VAMP) belongs to the receptor protein on the membrane of the secretory transport vesicle and involves in host immune function. The intracellular pathogen Spiroplasma eriocheiris could cause Eriocheir sinensis tremor disease. In a previous study, it was found E. sinensis VAMP (EsVAMP) was differently expressed in S. eriocheiris infection by proteomics analysis. This study mainly aims at the function of EsVAMP in the process of the S. eriocheiris infection. The length of EsVAMP gene was 1681 bp, which contained a 395 bp open reading frame, 90 bp 5'-non-coding region (UTR) and 1277 bp 3'-UTR. The results of qPCR showed that EsVAMP was expressed highly in hemocytes and nerves, followed by gills, intestines and hepatopancreas, and lowly expressed in heart and muscles. EsVAMP in hemocytes was up-regulated after S. eriocheiris infection. After EsVAMP over-expression and S. eriocheiris infection, the RAW264.7 cell morphology and cell viability of the experiment group were significantly better than the control group. Meanwhile, the copy number of S. eriocheiris in the experiment group was significantly lower than that in the control group. After EsVAMP and pCMV-Cre-mCherry were ligated and transfected into RAW264.7 cells, it was found that EsVAMP and lysosome co-localized. Meanwhile, the phagocytosed inactivated S. eriocheiris number and phagocytosed efficiency in RAW264.7 cells were increased significantly. The interference experiment was carried out by synthesizing EsVAMP dsRNA to verify that the EsVAMP transcriptions were successfully suppressed. The S. eriocheiris copy number and the mortality of crab increased significantly after EsVAMP RNAi and S. eriocheiris infection. Meanwhile, the phagocytosed inactivated S. eriocheiris number and phagocytosed efficiency in hemocytes decreased significantly after EsVAMP RNAi and S. eriocheiris infection. These results showed that VAMP was involved in the cell phagocytosis to resist pathogen infection.

Central and cardiac stress resiliences consistently linked to integrated immuno-neuroendocrine responses across stress models in male mice

Stress resilience, and behavioural and cardiovascular impacts of chronic stress, are theorised to involve integrated neuro-endocrine/inflammatory/transmitter/trophin signalling. We tested for this integration, and whether behaviour/emotionality, together with myocardial ischaemic tolerance, are consistently linked to these pathways across diverse conditions in male C57Bl/6 mice. This included: Restraint Stress (RS), 1 hr restraint/day for 14 days; Chronic Unpredictable Mild Stress (CUMS), 7 stressors randomised over 21 days; Social Stress (SS), 35 days social isolation with brief social encounters in final 13 days; and Control conditions (CTRL; un-stressed mice). Behaviour was assessed via open field (OFT) and sucrose preference (SPT) tests, and neurobiology from frontal cortex (FC) and hippocampal transcripts. Endocrine factors, and function and ischaemic tolerance in isolated hearts, were also measured. Model characteristics ranged from no behavioural or myocardial changes with homotypic RS, to increased emotionality and cardiac ischaemic injury (with apparently distinct endocrine/neurobiological profiles) in CUMS and SS models. Highly integrated expression of HPA axis, neuro-inflammatory, BDNF, monoamine, GABA, cannabinoid and opioid signalling genes was confirmed across conditions, and consistent/potentially causal correlations identified for: i) Locomotor activity (noradrenaline, ghrelin; FC Crhr1, Tnfrsf1b, Il33, Nfkb1, Maoa, Gabra1; hippocampal Il33); ii) Thigmotaxis (adrenaline, leptin); iii) Anxiety-like behaviour (adrenaline, leptin; FC Tnfrsf1a; hippocampal Il33); iv) Depressive-like behaviour (ghrelin; FC/hippocampal s100a8); and v) Cardiac stress-resistance (noradrenaline, leptin; FC Il33, Tnfrsf1b, Htr1a, Gabra1, Gabrg2; hippocampal Il33, Tnfrsf1a, Maoa, Drd2). Data support highly integrated pathway responses to stress, and consistent adipokine, sympatho-adrenergic, inflammatory and monoamine involvement in mood and myocardial disturbances across diverse conditions.

Investigation of Synaptic Vesicle Proteins in Rat Brain Tissue Using Real-Time qPCR

For many years real-time quantitative polymerase chain reaction (qPCR) has been the golden standard to measure gene expression levels in brain tissue. However, today it is generally accepted that many factors may affect the outcome of the study and more consensus is required to perform and interpret real-time qPCR experiments in a comparable way. Here we describe the basic techniques used for more than a decade in our laboratory to extract RNA and protein from the same piece of frozen brain tissue and to quantify relative mRNA levels with real-time qPCR and SYBR Green.

A Guide to Analysis of Relative Synaptic Protein Abundance by Quantitative Fluorescent Western Blotting

The introduction of fluorescent detection systems has revolutionized the applicability of Western blotting for quantitative protein expression analyses. The fundamental premise behind fluorescent Western blotting is the combination of distinct fluorescent dye-conjugated secondary antibodies and high performance digital imaging solutions in which the fluorescence signal is directly proportional to the amount of protein enabling quantitative measurements and simultaneous detection of several target proteins. This aspect of Western blotting is now widely used, especially in preclinical research, to detect quantitative changes in protein levels and phosphorylation status between experimental groups. This chapter provides a detailed step-by-step guide for best practice procedures during the entire process from sample preparation, SDS polyacrylamide gel electrophoresis to electrotransfer of proteins and highlights approaches that can be applied to increase data output.

Cross-fostering alleviates depression-like behavior mediated by EAAT2 and SNARE complex in prenatal stress offspring rat

Previous studies have shown that prenatal stress (PS) can potentially contribute to depression-like behavior in offspring and that this effect may be moderated by cross-fostering. However, the underlying mechanism of this effect remains to be determined. This study aimed to determine the effect of cross-fostering on the expression of EAAT2 and the SNARE complex in the hippocampus and the prefrontal cortex of PS offspring rats and to demonstrate functional effects on depression-like behavior. The impacts of cross-fostering were functionally assessed using the sucrose preference test (SPT), the forced swimming test (FST) and the elevated plus maze (EPM). Quantitative real-time PCR was used to determine changes in the expression of EAAT2 and SNAREs mRNA in the hippocampus and the prefrontal cortex of offspring rats. PS offspring rats showed significantly decreased sucrose preference and prolonged immobility time, while cross-fostering effectively increased sucrose preference and shorten the time of immobility. The expression of EAAT2 mRNA in PS offspring rats was markedly reduced, whilst the core mRNA expression of the SNARE complex increased. Our results provide strong evidence demonstrating that cross-fostering can alleviate depression-like behavior and regulate the abnormal expression levels of EAAT2 mRNA and SNARE complex in the hippocampus and the prefrontal cortex of PS offspring rats. Our findings contribute to further understanding of the pathogenesis of PS-induced depression and may help to inform the future development of novel treatment approaches.

Human-Relevant Sensitivity of iPSC-Derived Human Motor Neurons to BoNT/A1 and B1

The application of botulinum neurotoxins (BoNTs) for medical treatments necessitates a potency quantification of these lethal bacterial toxins, resulting in the use of a large number of test animals. Available alternative methods are limited in their relevance, as they are based on rodent cells or neuroblastoma cell lines or applicable for single toxin serotypes only. Here, human motor neurons (MNs), which are the physiological target of BoNTs, were generated from induced pluripotent stem cells (iPSCs) and compared to the neuroblastoma cell line SiMa, which is often used in cell-based assays for BoNT potency determination. In comparison with the mouse bioassay, human MNs exhibit a superior sensitivity to the BoNT serotypes A1 and B1 at levels that are reflective of human sensitivity. SiMa cells were able to detect BoNT/A1, but with much lower sensitivity than human MNs and appear unsuitable to detect any BoNT/B1 activity. The MNs used for these experiments were generated according to three differentiation protocols, which resulted in distinct sensitivity levels. Molecular parameters such as receptor protein concentration and electrical activity of the MNs were analyzed, but are not predictive for BoNT sensitivity. These results show that human MNs from several sources should be considered in BoNT testing and that human MNs are a physiologically relevant model, which could be used to optimize current BoNT potency testing.

Vortioxetine ameliorates anhedonic-like behaviour and promotes strategic cognitive performance in a rodent touchscreen task

Depression-associated cognitive impairments are among the most prevalent and persistent symptoms during remission from a depressive episode and a major risk factor for relapse. Consequently, development of antidepressant drugs, which also alleviate cognitive impairments, is vital. One such potential antidepressant is vortioxetine that has been postulated to exhibit both antidepressant and pro-cognitive effects. Hence, we tested vortioxetine for combined antidepressant and pro-cognitive effects in male Long-Evans rats exposed to the chronic mild stress (CMS) paradigm. This well-established CMS paradigm evokes cognitive deficits in addition to anhedonia, a core symptom of depression. Learning and memory performance was assessed in the translational touchscreen version of the paired-associates learning task. To identify the mechanistic underpinning of the neurobehavioural results, transcriptional profiling of genes involved in the stress response, neuronal plasticity and genes of broad relevance in neuropsychiatric pathologies were assessed. Vortioxetine substantially relieved the anhedonic-like state in the CMS rats and promoted acquisition of the cognitive test independent of hedonic phenotype, potentially due to an altered cognitive strategy. Minor alterations in gene expression profiling in prefrontal cortex and hippocampus were found. In summary, our findings suggest that vortioxetine exhibits an antidepressant effect as well as behavioural changes in a translational learning task.

Dysfunction of the SNARE complex in neurological and psychiatric disorders

The communication between neurons constitutes the basis of all neural activities, and synaptic vesicle exocytosis is the fundamental biological event that mediates most communication between neurons in the central nervous system. The SNARE complex is the core component of the protein machinery that facilitates the fusion of synaptic vesicles with presynaptic terminals and thereby the release of neurotransmitters. In synapses, each release event is dependent on the assembly of the SNARE complex. In recent years, basic research on the SNARE complex has provided a clearer understanding of the mechanism underlying the formation of the SNARE complex and its role in vesicle formation. Emerging evidence indicates that abnormal expression or dysfunction of the SNARE complex in synapse physiology might contribute to abnormal neurotransmission and ultimately to synaptic dysfunction. Clinical research using postmortem tissues suggests that SNARE complex dysfunction is correlated with various neurological diseases, and some basic research has also confirmed the important role of the SNARE complex in the pathology of these diseases. Genetic and pharmacogenetic studies suggest that the SNARE complex and individual proteins might represent important molecular targets in neurological disease. In this review, we summarize the recent progress toward understanding the SNARE complex in regulating membrane fusion events and provide an update of the recent discoveries from clinical and basic research on the SNARE complex in neurodegenerative, neuropsychiatric, and neurodevelopmental diseases.

Dysregulation of miR-185, miR-193a, and miR-450a in the skin are linked to the depressive phenotype

BACKGROUND

Dysregulated microRNAs (miRNAs) in dermal fibroblasts of depressive subjects, indicate biomarker potential and can possibly aid clinical diagnostics. To overcome methodological challenges related to human experiments and fibroblast cultures, we here validate 38 miRNAs previously observed to be dysregulated in human fibroblasts from depressed subjects, in the skin of four distinct rat models of depression.

METHODS

In the presented study male rats from the adrenocorticotropic hormone (ACTH) model (n = 10/group), the chronic mild stress model (n = 10/group), Wistar Kyoto/Wistar Hannover rats (n = 10/group), and Flinders Resistant/Flinders Sensitive Line rats (n = 8/group) were included. Real-time qPCR was utilized to investigate miRNA alterations in flash-frozen skin-biopsies from the ear and fibroblast cultures.

RESULTS

In the ACTH rat model of depression, we identified nine dysregulated miRNAs in the skin and three in the fibroblasts. As the skin presented three times the amount of dysregulated miRNAs compared to the fibroblasts, skin instead of fibroblasts were continuously used for studies with the other rat models. In the skin from the four rat models of depression, 15 out of 38 miRNAs re-exhibited significant dysregulation in at least one of the rat models of depression and 67% were regulated in the same direction as in the human study. miR-450a and miR-193a presented dysregulation across rat models and miR-193a and miR-185 exhibited very strong dysregulation (30-fold and 50-fold, respectively). Lastly, an Ingenuity Pathway Analysis indicated functional overlap between dysregulated miRNAs, and common regulated pathways.

CONCLUSION

Flash-frozen skin is a valid alternative to fibroblast cultures as the skin appear to retain more of the miRNA dysregulation present in vivo. A sub-population of 15 miRNAs appear to be specific for the depressive phenotype, as they are dysregulated in both human depressed patients and distinct rat models of depression. We propose miR-450a, miR-185, and miR-193a as biomarker candidates of particular interest.

Interaction of chronic intermittent ethanol and repeated stress on structural and functional plasticity in the mouse medial prefrontal cortex

Stress is a risk factor that plays a considerable role in the development and maintenance of alcohol (ethanol) abuse and relapse. Preclinical studies examining ethanol-stress interactions have demonstrated elevated ethanol drinking, cognitive deficits, and negative affective behaviors in mice. However, the neural adaptations in prefrontal cortical regions that drive these aberrant behaviors produced by ethanol-stress interactions are unknown. In this study, male C57BL/6J mice were exposed to chronic intermittent ethanol (CIE) and repeated forced swim stress (FSS). After two cycles of CIE x FSS, brain slices containing the prelimbic (PrL) and infralimbic (IfL) cortex were prepared for analysis of adaptations in dendritic spines and synaptic plasticity. In the PrL cortex, total spine density was increased in mice exposed to CIE. Immediately following induction of long-term potentiation (LTP), the fEPSP slope was increased in the PrL of CIE x FSS treated mice, indicative of a presynaptic adaptation on post-tetanic potentiation (PTP). In the IfL cortex, CIE exposure regardless of FSS experience resulted in an increase in spine density. FSS alone or when combined with CIE exposure increased PTP following LTP induction. Repeated FSS episodes increased IfL cortical paired-pulse facilitation, a second measure of presynaptic plasticity. In summary, CIE exposure resulted in structural adaptations while repeated stress exposure drove metaplastic changes in presynaptic function, demonstrating distinct morphological and functional changes in PrL and IfL cortical neurons. Thus, the structural and functional adaptations may be one mechanism underlying the development of excessive drinking and cognitive deficits associated with ethanol-stress interactions.

Chronic stress induces significant gene expression changes in the prefrontal cortex alongside alterations in adult hippocampal neurogenesis

Adult hippocampal neurogenesis is involved in stress-related disorders such as depression, posttraumatic stress disorders, as well as in the mechanism of antidepressant effects. However, the molecular mechanisms involved in these associations remain to be fully explored. In this study, unpredictable chronic mild stress in mice resulted in a deficit in neuronal dendritic tree development and neuroblast migration in the hippocampal neurogenic niche. To investigate molecular pathways underlying neurogenesis alteration, genome-wide gene expression changes were assessed in the prefrontal cortex, hippocampus and the hypothalamus alongside neurogenesis changes. Cluster analysis showed that the transcriptomic signature of chronic stress is much more prominent in the prefrontal cortex compared to the hippocampus and the hypothalamus. Pathway analyses suggested huntingtin, leptin, myelin regulatory factor, methyl-CpG binding protein and brain-derived neurotrophic factor as the top predicted upstream regulators of transcriptomic changes in the prefrontal cortex. Involvement of the satiety regulating pathways (leptin) was corroborated by behavioural data showing increased food reward motivation in stressed mice. Behavioural and gene expression data also suggested circadian rhythm disruption and activation of circadian clock genes such as Period 2. Interestingly, most of these pathways have been previously shown to be involved in the regulation of adult hippocampal neurogenesis. It is possible that activation of these pathways in the prefrontal cortex by chronic stress indirectly affects neuronal differentiation and migration in the hippocampal neurogenic niche via reciprocal connections between the two brain areas.

Differential serum exosome microRNA profile in a stress-induced depression rat model

BACKGROUND

Increasing evidence has shown the important role of exosomes in the maintenance of brain function and pathogenesis of brain disease, but little is known about their association with depression. The aim of this project was to explore the miRNA profile of exosomes in the serum of rats with depression induced by chronic unpredictable mild stress (CUMS).

METHODS

A rat model of depression was replicated via CUMS. Behavioral performance was observed, and serum exosomes were isolated and identified. The protein expression levels of brain-derived neurotrophic factor (BDNF), TrkB, and synaptotagmin 1 in the hippocampus, prefrontal cortex (PFC), and serum exosomes were measured. GO and KEGG enrichment analysis of differential genes was carried out using the R package clusterProfiler.

RESULTS

The CUMS rats showed depression-like behaviors, together with decreased expression levels of BDNF, TrkB, and synaptotagmin 1 in the hippocampus, PFC, and serum exosomes. GO and KEGG enrichment analysis indicated that the differential expression of miRNAs might play an important role in the pathogenesis of stress-induced depression through the MAPK pathway, Wnt pathway, and mTOR pathway.

LIMITATIONS

The protein expression levels of BDNF, TrkB, and synaptotagmin 1 were measured only in the hippocampus and PFC. The function of the differentially expressed miRNAs was not verified in the animal model, which should be investigated in detail in future studies.

CONCLUSIONS

The miRNA profile was altered in rats with stress-induced depression, which might be considered a potential biomarker for the early diagnosis of depression.

Preclinical PET Studies of [11C]UCB-J Binding in Minipig Brain

PURPOSE

Loss of neuronal synapse function is associated with a number of brain disorders. The [¹¹C]UCB-J positron emission tomography (PET) tracer allows for in vivo examination of synaptic density, as it binds to synaptic vesicle glycoprotein 2A (SV2A) expressed in presynaptic terminals. Here, we characterise [¹¹C]UCB-J imaging in Göttingen minipigs.

PROCEDURES

Using PET imaging, we examined tracer specificity and compared kinetic models. We explored the use of a standard blood curve and centrum semiovale white matter as a reference region. We compared in vivo [¹¹C]UCB-J PET imaging to in vitro autoradiography, Western blotting and real-time quantitative polymerase chain reaction.

RESULTS

The uptake kinetics of [¹¹C]UCB-J could be described using a 1-tissue compartment model and blocking of SV2A availability with levetiracetam showed dose-dependent specific binding. Population-based blood curves resulted in reliable [¹¹C]UCB-J binding estimates, while it was not possible to use centrum semiovale white matter as a non-specific reference region. Brain [¹¹C]UCB-J PET signals correlated well with [³H]UCB-J autoradiography and SV2A protein levels.

CONCLUSIONS

[¹¹C]UCB-J PET is a valid in vivo marker of synaptic density in the minipig brain, with binding values close to those reported for humans. Minipig models of disease could be valuable for investigating the efficacy of putative neuroprotective agents for preserving synaptic function in future non-invasive, longitudinal studies.

Differential expression of synaptic markers regulated during neurodevelopment in a rat model of schizophrenia-like behavior

Schizophrenia is considered a neurodevelopmental disorder. Recent reports relate synaptic alterations with disease etiology. The inbred Roman High- (RHA-I) and Low- (RLA-I) Avoidance rat strains are a congenital neurobehavioral model, with the RHA-I displaying schizophrenia-related behaviors and serotonin 2A (5-HT2A) and metabotropic glutamate 2 (mGlu2) receptor alterations in the prefrontal cortex (PFC). We performed a comprehensive characterization of the RHA-I/RLA-I rats by real-time qPCR and Western blotting for 5-HT1A, 5-HT2A, mGlu2, dopamine 1 and dopamine 2 receptors (DRD1 and DRD2), AMPA receptor subunits Gria1, Gria2 and NMDA receptor subunits Grin1, Grin2a and Grin2b, as well as pre- and post-synaptic components in PFC and hippocampus (HIP). Besides corroborating decreased mGlu2 (Grm2) expression, we found increased mRNA levels for Snap25, Synaptophysin (Syp), Homer1 and Neuregulin-1 (Nrg1) in the PFC of the RHA-I and decreased expression of Vamp1, and Snapin in the HIP. We also showed alterations in Vamp1, Grin2b, Syp, Snap25 and Nrg1 at protein levels. mRNA levels of Brain Derived Neurotrophic Factor (BDNF) were increased in the PFC of the RHA-I rats, with no differences in the HIP, while BDNF protein levels were decreased in PFC and increased in HIP. To investigate the temporal dynamics of these synaptic markers during neurodevelopment, we made use of the open source BrainCloud™ dataset, and found that SYP, GRIN2B, NRG1, HOMER1, DRD1 and BDNF expression is upregulated in PFC during childhood and adolescence, suggesting a more immature neurobiological endophenotype in the RHA-I strain.

Antidepressant-like effect induced by P2X7 receptor blockade in FSL rats is associated with BDNF signalling activation

BACKGROUND

P2X7 receptors (P2X7R) are ligand-gated ion channels activated by adenosine 5'-triphosphate (ATP), which are involved in processes that are dysfunctional in stress response and depression, such as neurotransmitter release, and neuroimmune response. Genetic and pharmacological inhibition of the P2X7R induce antidepressant-like effects in animals exposed to stress. However, the effect of P2X7R antagonism in an animal model of depression based on selective breeding has not previously been studied, and the mechanism underling the antidepressant-like effect induced by the P2X7R blockade remains unknown.

AIMS

The present study aimed to: (1) determine whether P2X7R blockade induces antidepressant-like effects in the Flinders Sensitive Line (FSL) rats and, (2) investigate whether brain-derived neurotrophic factor (BDNF) signalling in the frontal cortex and hippocampus is involved in this effect.

METHODS

FSL and the control Flinders Resistant Line (FRL) rats were treated with vehicle or the P2X7R antagonist A-804598 (3, 10 or 30 mg/Kg/day) for 1 or 7 days before being exposed to the forced swim test (FST). After the behavioural test, animals were decapitated, their brains were removed and the frontal cortex, ventral and dorsal hippocampus were dissected for BDNF signalling analysis.

RESULTS

We found that repeated treatment with A-804598 (30 mg/Kg) reduced the immobility time in the FST and activated the BDNF signalling in the ventral hippocampus of FSL rats.

CONCLUSIONS

P2X7R blockade induces an antidepressant-like effect associated with increased levels of BDNF-AKT-p70 S6 kinase in the ventral hippocampus, which may be mediated by tropomyosin-related kinase B (TRKB) receptor activation supporting the notion of P2X7R antagonism as a potential new antidepressant strategy.

Hemisphere-dependent endocannabinoid system activity in prefrontal cortex and hippocampus of the Flinders Sensitive Line rodent model of depression

Altered endocannabinoid (eCB) signalling is suggested as an important contributor to the pathophysiology of depression. To further elucidate this, we conducted a study using a genetic rat model of depression, the Flinders Sensitive Line (FSL), and their controls, the Flinders Resistant Line (FRL) rats. Plasma, right and left prefrontal cortex, and hippocampus were isolated from FSL and FRL rats. We analyzed each region for the eCB anandamide (AEA) and 2-arachidonoylglycerol (2-AG) levels by liquid chromatography/multiple reaction monitoring (LC/MRM), mRNA and protein levels of the cannabinoid type 1 receptor (CB₁R), fatty acid amide hydrolase (FAAH) and monoacyl glycerol lipase (MAGL) by real time qPCR and Western blotting. Content of 2-AG was lower in the left side of the hippocampus and prefrontal cortex in FSL rats compared to FRL rats. Inversely, levels of AEA were higher in right hippocampus than in left hippocampus. In plasma, AEA levels were increased and 2-AG decreased. Cannabinoid receptor 1 (Cnr1), Faah and Magl mRNA levels were prominently decreased in right prefrontal cortex of FSL rats as compared to FRL rats. Protein expression of CB₁R and FAAH were decreased in left hippocampus. In summary, our data suggest a decreased eCB signalling in the FSL rats, which could contribute to the depressive-like behaviour. Interestingly, the altered eCB system activity appear to be hemisphere-specific in the limbic regions. Our study support the existing literature and showed altered eCB system activity in this particular animal model of depression.

BDNF-Related Imbalance of Copine 6 and Synaptic Plasticity Markers Couples With Depression-Like Behavior and Immune Activation in CUMS Rats

Chronic stress is a contributing risk factor in the pathogenesis of depression. Although the mechanisms are multifaceted, the relationship can be ascribed partly to stress-related alterations in immune activation and brain plasticity. Considering the increasing evidence regarding the role of Copine 6 in the regulation of synaptic plasticity, the aim of the present study is to investigate Copine 6 expression in the hippocampus and the prefrontal cortex (PFC) in a stress-induced depression rat model. The behavior of the rats was evaluated via the open field test, saccharin preference test, elevated plus maze test, tail suspension test, Morris water maze, and forced swimming test. The plasma concentrations of C-reactive protein (CRP) and interleukin-6 (IL-6) were measured, and the protein expressions of brain-derived neurotrophic factor (BDNF), Copine 6, and synaptic plasticity markers in the hippocampus and the PFC were also detected. The results showed that chronic unpredictable mild stress (CUMS) induces depression-like behavior in rats, accompanied by increased plasma concentrations of CRP and IL-6. Moreover, the protein expressions of BDNF, Copine 6, and synapsin I were decreased in both the hippocampus and the PFC of CUMS rats, and the protein expression of synaptotagmin I was decreased in the hippocampus. Furthermore, Pearson's test revealed a potential relationship between the depression-like behavior, the plasma CRP concentration, and the protein expressions of BDNF, Copine 6, synapsin I, or synaptotagmin I in the hippocampus or the PFC. Together with our previous results, the current findings suggest that apart from immune activation, the BDNF-related imbalance of Copine 6 expression in the brain might play a crucial role in stress-associated depression-like behaviors and synaptic plasticity changes.

Temporal Dynamics of Acute Stress-Induced Dendritic Remodeling in Medial Prefrontal Cortex and the Protective Effect of Desipramine

Stressful events are associated with increased risk of mood disorders. Volumetric reductions have been reported in brain areas critical for the stress response, such as medial prefrontal cortex (mPFC), and dendritic remodeling has been proposed as an underlying factor. Here, we investigated the time-dependent effects of acute stress on dendritic remodeling within the prelimbic (PL) region of the PFC, and whether treatment with the antidepressant desipramine (DMI) may interfere. Rodents were subjected to foot-shock stress: dendritic length and spine density were analyzed 1 day, 7 days, and 14 days after stress. Acute stress produced increased spine density and decreased cofilin phosphorylation at 1 day, paralleled with dendritic retraction. An overall shift in spine population was observed at 1 day, resulting in a stress-induced increase in small spines. Significant atrophy of apical dendrites was observed at 1 day, which was prevented by chronic DMI, and at 14 days after stress exposure. Chronic DMI resulted in dendritic elaboration at 7 days but did not prevent the effects of FS-stress. Collectively, these data demonstrate that 1) acute stressors may induce rapid and sustained changes of PL neurons; and 2) chronic DMI may protect neurons from rapid stress-induced synaptic changes.

Genome-wide transcriptome analysis of hippocampus in rats indicated that TLR/NLR signaling pathway was involved in the pathogenisis of depressive disorder induced by chronic restraint stress

Data from clinical investigations and laboratory fundings have provided preliminary evidence for the effectiveness and safety of acupuncture therapy in depression. However, the mechanisms underlying the antidepressant response of acupuncture are not fully elucidated. To elucidate the potential effects of acupuncture for depression on the hippocampal genome-wide transcriptome at the molecular level, we evaluated the transcriptomic profile of depression rats under treatment of acupuncture, and fluoxetine. We identified a very significant effect of acupucture intervention, with 107 genes differentially expressed in acupuncture vs. model group; while 41 genes between fluoxetine vs. model group. Notably, the 54 differentially expressed genes between acupuncture and fluoxetine showed the significantly different effect between acupuncture and fluoxetine. Through GO (gene ontology) functional term and KEGG (kyoto encyclopedia of genes and genomes) pathway analysis, we identified that the upregulation of gene sets were related to inflammatory response, innate immunity and immune response. We found that toll-like receptor signalling pathway and NOD like receptor signalling pathway were associated with the function of inflammatory response, innate immunity and immune response. Importantly, acupuncture reversed the upregulation of gene sets that were related to inflammatory response, innate immunity and immune response (including toll-like receptor signalling pathway and NOD like receptor signalling pathway), which might be critical for the pathogenesis of depression and provide evidence for the antidepressive effects of acupuncture by regulating inflammatory response, innate immunity and immune response via toll-like receptor signalling pathway and NOD like receptor signalling pathway.

IGF-II promotes neuroprotection and neuroplasticity recovery in a long-lasting model of oxidative damage induced by glucocorticoids

Insulin-like growth factor-II (IGF-II) is a naturally occurring hormone that exerts neurotrophic and neuroprotective properties in a wide range of neurodegenerative diseases and ageing. Accumulating evidence suggests that the effects of IGF-II in the brain may be explained by its binding to the specific transmembrane receptor, IGFII/M6P receptor (IGF-IIR). However, relatively little is known regarding the role of IGF-II through IGF-IIR in neuroprotection. Here, using adult cortical neuronal cultures, we investigated whether IGF-II exhibits long-term antioxidant effects and neuroprotection at the synaptic level after oxidative damage induced by high and transient levels of corticosterone (CORT). Furthermore, the involvement of the IGF-IIR was also studied to elucidate its role in the neuroprotective actions of IGF-II. We found that neurons treated with IGF-II after CORT incubation showed reduced oxidative stress damage and recovered antioxidant status (normalized total antioxidant status, lipid hydroperoxides and NAD(P) H:quinone oxidoreductase activity). Similar results were obtained when mitochondria function was analysed (cytochrome c oxidase activity, mitochondrial membrane potential and subcellular mitochondrial distribution). Furthermore, neuronal impairment and degeneration were also assessed (synaptophysin and PSD-95 expression, presynaptic function and FluoroJade B® stain). IGF-II was also able to recover the long-lasting neuronal cell damage. Finally, the effects of IGF-II were not blocked by an IGF-IR antagonist, suggesting the involvement of IGF-IIR. Altogether these results suggest that, in or model, IGF-II through IGF-IIR is able to revert the oxidative damage induced by CORT. In accordance with the neuroprotective role of the IGF-II/IGF-IIR reported in our study, pharmacotherapy approaches targeting this pathway may be useful for the treatment of diseases associated with cognitive deficits (i.e., neurodegenerative disorders, depression, etc.).

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First evidence that IGF-II reverts oxidative synaptic damage produced by corticoids.

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IGF-II recovers mitochondrial function in synapses after oxidative damage.

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IGF-II restores mitochondrial distribution in neurons after oxidative damage.

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Evidence of the involvement of IGF-II receptor in the recovery of synaptic function.

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IGF-II reverts neurodegeneration induced by oxidative damage produced by corticoids.

Age- and Sex-Dependent Impact of Repeated Social Stress on Intrinsic and Synaptic Excitability of the Rat Prefrontal Cortex

Stress is implicated in psychiatric illnesses that are characterized by impairments in cognitive functions that are mediated by the medial prefrontal cortex (mPFC). Because sex and age determine stress vulnerability, the effects of repeated social stress occurring during early adolescence, mid-adolescence, or adulthood on the cellular properties of male and female rat mPFC Layer V neurons in vitro were examined. Repeated resident-intruder stress produced age- and sex-specific effects on mPFC intrinsic and synaptic excitability. Mid-adolescents were particularly vulnerable to effects on intrinsic excitability. The maximum number of action potentials (APs) evoked by increasing current intensity was robustly decreased in stressed male and female mid-adolescent rats compared with age-matched controls. These effects were associated with stress-induced changes in AP half-width, amplitude, threshold, and input resistance. Social stress at all ages generally decreased synaptic excitability by decreasing the amplitude of spontaneous excitatory postsynaptic potentials. The results suggest that whereas social stress throughout life can diminish the influence of afferents driving the mPFC, social stress during mid-adolescence additionally affects intrinsic characteristics of mPFC neurons that determine excitability. The depressant effects of social stress on intrinsic and synaptic mPFC neurons may underlie its ability to affect executive functions and emotional responses, particularly during adolescence.

The expression of plasticity-related genes in an acute model of stress is modulated by chronic desipramine in a time-dependent manner within medial prefrontal cortex

It is well established that stress plays a major role in the pathogenesis of neuropsychiatric diseases. Stress-induced alteration of synaptic plasticity has been hypothesized to underlie the morphological changes observed by neuroimaging in psychiatric patients in key regions such as hippocampus and prefrontal cortex (PFC). We have recently shown that a single acute stress exposure produces significant short-term alterations of structural plasticity within medial PFC. These alterations were partially prevented by previous treatment with chronic desipramine (DMI). In the present study we evaluated the effects of acute Foot-shock (FS)-stress and pre-treatment with the traditional antidepressant DMI on the gene expression of key regulators of synaptic plasticity and structure. Expression of Homer, Shank, Spinophilin, Densin-180, and the small RhoGTPase related gene Rac1 and downstream target genes, Limk1, Cofilin1 and Rock1 were investigated 1 day (1d), 7 d and 14d after FS-stress exposure. We found that DMI specifically increases the short-term expression of Spinophilin, as well as Homer and Shank family genes, and that both acute stress and DMI exert significant long-term effects on mRNA levels of genes involved in spine plasticity. These findings support the knowledge that acute FS stress and antidepressant treatment induce both rapid and sustained time-dependent alterations in structural components of synaptic plasticity in rodent medial PFC.

Protective effects of chronic treatment with a standardized extract of Ginkgo biloba L. in the prefrontal cortex and dorsal hippocampus of middle-aged rats

This study assessed the effects of chronic treatment with a standardized extract of Ginkgo biloba L. (EGb) on short-term and long-term memory as well as on anxiety-like and locomotor activity using the plus-maze discriminative avoidance task (PM-DAT). Additionally, we evaluated the antioxidant and neuroprotective effects of EGb on the prefrontal cortex (PFC) and dorsal hippocampus (DH) of middle-aged rats using the comet assay. Twelve-month-old male Wistar rats were administered vehicle or EGb (0.5mgkg(-1) or 1.0gkg(-1)) for 30days. Behavioural data showed that EGb treatment improved short-term memory. Neither an anti-anxiety effect nor a change in locomotor activity was observed. Twenty-four hours after the behavioural tests, the rats were decapitated, and the PFC and DH were quickly dissected out and prepared for the comet assay. The levels of DNA damage in the PFC were significantly lower in rats that were treated with 1.0gkg(-1) EGb. Both doses of EGb decreased H2O2-induced DNA breakage in cortical cells, whereas the levels of DNA damage in the EGb-treated animals were significantly lower than those in the control animals. No significant differences in the level of DNA damage in hippocampal cells were observed among the experimental groups. EGb treatment was not able to reduce H2O2-induced DNA damage in hippocampal cells. Altogether, our data provide the first demonstration that chronic EGb treatment improved the short-term memory of middle-aged rats, an effect that could be associated with a reduction in free radical production in the PFC. These data suggest that EGb treatment might increase the survival of cortical neurons and corroborate and extend the view that EGb has protective and therapeutic properties.

Chronic stress induces persistent changes in global DNA methylation and gene expression in the medial prefrontal cortex, orbitofrontal cortex, and hippocampus

Chronic stress is associated with a plethora of cognitive symptoms such as emotional dysregulation and impaired executive function that have been attributed to modifications in neuroanatomy in the orbitofrontal cortex (OFC), medial prefrontal cortex (mPFC), and hippocampus (HPC). While many studies have examined stress-induced changes in neuronal morphology, synaptic plasticity, and cellular function, there has been little investigation into persistent changes in gene expression that may be responsible for the maintenance of these changes. This study exposed adult rats to a chronic stressor and then examined changes in mRNA gene expression in the OFC, mPFC and HPC following a two-week withdrawal period. mRNA bio-sequencing results revealed sex- and region-dependent changes. Surprisingly the greatest changes in gene expression were found in the OFC, and similar to anatomical studies, analysis of gene changes with Ingenuity Pathway Analysis software demonstrated that the mPFC and OFC exhibited contrasting activation of canonical pathways and functional networks. The HPC demonstrated the largest degree of sex-dependent change in gene expression. In general, chronic stress induced persistent changes in gene expression in the three brain regions we examined and these changes could be associated with the commonly reported cognitive symptoms. The current study highlights the region- and sex-dependent nature of the brain's response to chronic stress and the difficulty we face when attempting to develop treatment options.

Dendritic Spines in Depression: What We Learned from Animal Models

Depression, a severe psychiatric disorder, has been studied for decades, but the underlying mechanisms still remain largely unknown. Depression is closely associated with alterations in dendritic spine morphology and spine density. Therefore, understanding dendritic spines is vital for uncovering the mechanisms underlying depression. Several chronic stress models, including chronic restraint stress (CRS), chronic unpredictable mild stress (CUMS), and chronic social defeat stress (CSDS), have been used to recapitulate depression-like behaviors in rodents and study the underlying mechanisms. In comparison with CRS, CUMS overcomes the stress habituation and has been widely used to model depression-like behaviors. CSDS is one of the most frequently used models for depression, but it is limited to the study of male mice. Generally, chronic stress causes dendritic atrophy and spine loss in the neurons of the hippocampus and prefrontal cortex. Meanwhile, neurons of the amygdala and nucleus accumbens exhibit an increase in spine density. These alterations induced by chronic stress are often accompanied by depression-like behaviors. However, the underlying mechanisms are poorly understood. This review summarizes our current understanding of the chronic stress-induced remodeling of dendritic spines in the hippocampus, prefrontal cortex, orbitofrontal cortex, amygdala, and nucleus accumbens and also discusses the putative underlying mechanisms.

Moderate swimming suppressed the growth and metastasis of the transplanted liver cancer in mice model: with reference to nervous system

Physical activity has been shown to suppress tumor initiation and progression. The neurotransmitter dopamine (DA) is closely related to movement and exhibits antitumor properties. However, whether the suppressive effects of physical activity on tumors was mediated by the nervous system via increased DA level remains unknowns. Here we show that regular moderate swimming (8 min/day, 9 weeks) raised DA levels in the prefrontal cortex, serum and tumor tissue, suppressed growth, reduced lung metastasis of transplanted liver cancer, and prolonged survival in a C57BL/6 mouse model, while overload swimming (16 and 32 min/day, 9 weeks) had the opposite effect. In nude mice that were orthotopically implanted with human liver cancer cell lines, DA treatment significantly suppressed growth and lung metastasis by acting on the D2 receptor (DR2). Furthermore, DR2 blockade attenuated the suppressive effect of moderate swimming on liver cancer. Both moderate swimming and DA treatment suppressed the transforming growth factor-beta (TGF-β1)-induced epithelial-mesenchymal transition of transplanted liver cancer cells. At the molecular level, DR2 signaling inhibited extracellular signal-regulated kinase phosphorylation and expression of TGF-β1 in vitro. Together, these findings demonstrated a novel mechanism by which the moderate exercise suppressed liver cancer through boosting DR2 activity, while overload exercise had the opposite effect, highlighting the possible importance of the dopaminergic system in tumor growth and metastasis of liver cancer.

Depression-like Behavior Induced by Nesfatin-1 in Rats: Involvement of Increased Immune Activation and Imbalance of Synaptic Vesicle Proteins

Depression is a multicausal disorder and has been associated with metabolism regulation and immuno-inflammatory reaction. The anorectic molecule nesfatin-1 has recently been characterized as a potential mood regulator, but its precise effect on depression and the possible mechanisms remain unknown, especially when given peripherally. In the present study, nesfatin-1 was intraperitoneally injected to the rats and the depression-like behavior and activity of the hypothalamic-pituitary-adrenal (HPA) axis were evaluated. The plasma concentrations of nesfatin-1, interleukin 6 (IL-6), and C-reactive protein (CRP); and the hypothalamic expression levels of nesfatin-1, synapsin I, and synaptotagmin I mRNA were evaluated in nesfatin-1 chronically treated rats. The results showed that both acute and chronic administration of nesfatin-1 increased immobility in the forced swimming test (FST), and resulted in the hyperactivity of HPA axis, as indicated by the increase of plasma corticosterone concentration and hypothalamic expression of corticotropin-releasing hormone (CRH) mRNA. Moreover, after chronic nesfatin-1 administration, the rats exhibited decreased activity and exploratory behavior in the open field test (OFT) and increased mRNA expression of synapsin I and synaptotagmin I in the hypothalamus. Furthermore, chronic administration of nesfatin-1 elevated plasma concentrations of IL-6 and CRP, which were positively correlated with despair behavior, plasma corticosterone level, and the hypothalamic mRNA expression of synapsin I and synaptotagmin I. These results indicated that exogenous nesfatin-1 could induce the immune-inflammatory activation, which might be a central hug linking the depression-like behavior and the imbalanced mRNA expression of synaptic vesicle proteins in the hypothalamus.

Quantitative Proteomic Analysis Reveals Molecular Adaptations in the Hippocampal Synaptic Active Zone of Chronic Mild Stress-Unsusceptible Rats

BACKGROUND

While stressful events are recognized as an important cause of major depressive disorder, some individuals exposed to life stressors maintain normal psychological functioning. The molecular mechanism(s) underlying this phenomenon remain unclear. Abnormal transmission and plasticity of hippocampal synapses have been implied to play a key role in the pathoetiology of major depressive disorder.

METHODS

A chronic mild stress protocol was applied to separate susceptible and unsusceptible rat subpopulations. Proteomic analysis using an isobaric tag for relative and absolute quantitation coupled with tandem mass spectrometry was performed to identify differential proteins in enriched hippocampal synaptic junction preparations.

RESULTS

A total of 4318 proteins were quantified, and 89 membrane proteins were present in differential amounts. Of these, SynaptomeDB identified 81 (91%) having a synapse-specific localization. The unbiased profiles identified several candidate proteins within the synaptic junction that may be associated with stress vulnerability or insusceptibility. Subsequent functional categorization revealed that protein systems particularly involved in membrane trafficking at the synaptic active zone exhibited a positive strain as potential molecular adaptations in the unsusceptible rats. Moreover, through STRING and immunoblotting analysis, membrane-associated GTP-bound Rab3a and Munc18-1 appear to coregulate syntaxin-1/SNAP25/VAMP2 assembly at the hippocampal presynaptic active zone of unsusceptible rats, facilitating SNARE-mediated membrane fusion and neurotransmitter release, and may be part of a stress-protection mechanism in actively maintaining an emotional homeostasis.

CONCLUSIONS

The present results support the concept that there is a range of potential protein adaptations in the hippocampal synaptic active zone of unsusceptible rats, revealing new investigative targets that may contribute to a better understanding of stress insusceptibility.

Methylprednisolone attenuates lipopolysaccharide-induced Fractalkine expression in kidney of Lupus-prone MRL/lpr mice through the NF-kappaB pathway

BACKGROUND

Fractalkine (FKN) is involved in the occurrence and development of human lupus nephritis. It is known to be upregulated by lipopolysaccharide (LPS) as a stimulus in vivo. MRL/lpr mice have been used as an in vivo model to study lupus nephritis. Methylprednisolone (MP) is used widely in the clinical treatment of progressive glomerular diseases such as lupus nephritis. The aim of this study is to explore the mechanism of LPS induced FKN expression and to determine whether other molecular mechanisms contribute to the signaling pathway of MP action in MRL/lpr mice.

METHODS

Forty-eight female MRL/lpr mice at 12 weeks of age were randomly distributed into six groups. Each group received various treatments for 8 weeks by receiving twice weekly intraperitoneal injections of (1) MP (MP-treated mice), of (2) SC-514 (SC-514-induced mice), of (3) normal saline and a single injection of LPS (LPS-induced mice), of (4) MP and a single injection of LPS (LPS + MP mice), of (5) SC-514 and a single injection of LPS (LPS + SC mice) and of (6) normal saline (control mice). One-way ANOVA was used for data analysis and P value <0.05 was considered statistically significantly.

RESULTS

The expression of FKN and NF-kappaB p65 mRNA was detected by qPCR. The expression of FKN protein and the activation of NF-kappaB p65 were detected by immunohistochemistry and western blots respectively. The expression of FKN in the kidney of LPS induced mice was significantly increased and this was mediated by increased expression of NF-κB p65 and an increase in NF-kappaB phospho-p65. MP reduced proteinuria and ameliorated the renal damage in MRL/lpr mice. MP as well as the NF-kappaB inhibitor, SC-514, inhibited the LPS-induced increase of expression of FKN and the activation of NF-kappaB.

CONCLUSIONS

The results indicate that MP attenuates LPS-induced FKN expression in kidney of MRL/lpr mice through the NF-kappaB pathway.

Potential roles for Homer1 and Spinophilin in the preventive effect of electroconvulsive seizures on stress-induced CA3c dendritic retraction in the hippocampus

Electroconvulsive therapy (ECT) remains the treatment of choice for patients with severe or drug-resistant depressive disorders, yet the mechanism behind its efficacy remains poorly characterized. In the present study, we used electroconvulsive seizures (ECS), an animal model of ECT, to identify proteins possibly involved in the preventive effect of ECS on stress-induced neuronal atrophy in the hippocampus. Rats were stressed daily using the 21-day 6h daily restraint stress paradigm and subjected to sham seizures, a single ECS on the last day of the restraint period or daily repeated seizures for 10 consecutive days during the end of the restraint period. Consistent with previous findings, dendritic atrophy was observed in the CA3c hippocampal region of chronically stressed rats. In addition, we confirmed our recent findings of increased spine density in the CA1 region following chronic restraint stress. The morphological alterations in the CA3c area were prevented by treatment with ECS. On the molecular level, we showed that the synaptic proteins Homer1 and Spinophilin are targeted by ECS. Repeated ECS blocked stress-induced up-regulation of Spinophilin protein levels and further increased the stress-induced up-regulation of Homer1. Given the roles of Spinophilin in the regulation of AMPA receptors and Homer1 in the regulation of metabotropic glutamate receptors (mGluRs), our data imply the existence of a mechanism where ECS regulate cell excitability by modulating AMPA receptor function and mGluR related calcium homeostasis. These molecular changes could potentially contribute to the mechanism induced by ECS which prevents the stress-induced morphological changes in the CA3c region.

Chronic restraint stress increases the protein expression of VEGF and its receptor VEGFR-2 in the prefrontal cortex

In the present study the central and peripheral regulation of VEGF, its cognate receptors, and regulators were examined after acute and chronic restraint stress in rats. After chronic restraint stress (6 h per day for 21 days) the protein levels of VEGF (175 ± 24%) and its receptor VEGFR-2 (169 ± 17%) increased significantly in the prefrontal cortex (A and B). mRNA levels of VEGFR-2 (132 ± 11%) were also significantly increased (D). In the hippocampus no significant changes were observed at the mRNA or protein levels. In serum there was a tendency towards increased VEGF protein expression after both acute and chronic restraint stress (C).

Differential regulation of the serotonin transporter by vesicle-associated membrane protein 2 in cells of neuronal versus non-neuronal origin

The serotonin transporter (SERT) is a key regulator of serotonergic signalling as it mediates the re-uptake of synaptic serotonin into nerve terminals, thereby terminating or modulating its signal. It is well-known that SERT regulation is a dynamic process orchestrated by a wide array of proteins and mechanisms. However, molecular details on possible coordinated regulation of SERT activity and 5-HT release are incomplete. Here, we report that vesicle-associated membrane protein 2 (VAMP2), a SNARE protein that mediates vesicle fusion with the plasma membrane, interacts with SERT. This was documented in vitro, through GST pull-down assays, by co-immunoprecipitation experiments on heterologous cells and rat hippocampal synaptosomes, and with FRET analysis in live transfected HEK-293 MSR cells. The related isoforms VAMP1 and VAMP3 also physically interact with SERT. However, comparison of the three VAMP isoforms shows that only VAMP2 possesses a functionally distinct role in relation to SERT. VAMP2 influences 5-HT uptake, cell surface expression and the delivery rate of SERT to the plasma membrane differentially in HEK-293 MSR and PC12 cells. Moreover, siRNA-mediated knock-down of endogenous VAMP2 reduces 5-HT uptake in CAD cells stably expressing low levels of heterologous SERT. Deletion and mutant analysis suggest a role for the isoform specific C-terminal domain of VAMP2 in regulating SERT function. Our data identify a novel interaction between SERT and a synaptic vesicle protein and support a link between 5-HT release and re-uptake.

Sex, hormones and neurogenesis in the hippocampus: hormonal modulation of neurogenesis and potential functional implications

The hippocampus is an area of the brain that undergoes dramatic plasticity in response to experience and hormone exposure. The hippocampus retains the ability to produce new neurones in most mammalian species and is a structure that is targeted in a number of neurodegenerative and neuropsychiatric diseases, many of which are influenced by both sex and sex hormone exposure. Intriguingly, gonadal and adrenal hormones affect the structure and function of the hippocampus differently in males and females. Adult neurogenesis in the hippocampus is regulated by both gonadal and adrenal hormones in a sex- and experience-dependent way. Sex differences in the effects of steroid hormones to modulate hippocampal plasticity should not be completely unexpected because the physiology of males and females is different, with the most notable difference being that females gestate and nurse the offspring. Furthermore, reproductive experience (i.e. pregnancy and mothering) results in permanent changes to the maternal brain, including the hippocampus. This review outlines the ability of gonadal and stress hormones to modulate multiple aspects of neurogenesis (cell proliferation and cell survival) in both male and female rodents. The function of adult neurogenesis in the hippocampus is linked to spatial memory and depression, and the present review provides early evidence of the functional links between the hormonal modulation of neurogenesis that may contribute to the regulation of cognition and stress.

Ketamine regulates the presynaptic release machinery in the hippocampus

In the search for new drug targets, that may help point the way to develop fast-acting treatments for mood disorders, we have explored molecular pathways regulated by ketamine, an NMDA receptor antagonist, which has consistently shown antidepressant response within a few hours of administration. Using Sprague-Dawley rats we investigated the effects of ketamine on the presynaptic release machinery responsible for neurotransmitter release at 1, 2 and 4 h as well as 7 days after administration of a single subanesthetic dose of ketamine (15 mg/kg). A large reduction in the accumulation of SNARE complexes was observed in hippocampal synaptic membranes after 1, 2 and 4 h of ketamine administration. In parallel, we found a selective reduction in the expression of the synaptic vesicle protein synaptotagmin I and an increase in the levels of synapsin I in hippocampal synaptosomes suggesting a mechanism by which ketamine reduces SNARE complex formation, in part, by regulating the number of synaptic vesicles in the nerve terminals. Moreover, ketamine reduced Thr(286)-phosphorylated αCaMKII and its interaction with syntaxin 1A, which identifies CaMKII as a potential target for second messenger-mediated actions of ketamine. In addition, despite previous reports of ketamine-induced inhibition of GSK-3, we were unable to detect regulation of its activity after ketamine administration. Our findings demonstrate that ketamine rapidly induces changes in the hippocampal presynaptic machinery similar to those that are obtained only with chronic treatments with traditional antidepressants. This suggests that reduction of neurotransmitter release in the hippocampus has possible relevance for the rapid antidepressant effect of ketamine.

Transient activation of mTOR following forced treadmill exercise in rats

The beneficial effect of exercise on hippocampal plasticity is possibly mediated by increased angiogenesis and neurogenesis. In angiogenesis, insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and hypoxia-inducible factor 1, alpha subunit (HIF1α) are important factors, while the induction of neurogenesis requires signaling through the VEGF receptor, Flk-1 (VEGFR-2). VEGF expression is believed to be regulated by two distinct mTOR (mammalian target of Rapamycin)-containing multiprotein complexes mTORC1 and mTORC2, respectively. This study was initiated to investigate the effect of exercise on the expression of VEGF, cognate receptors, HIF1α, mTORC1, and mTORC2 in hippocampus and frontal cortex. To this end, we measured messenger RNA (mRNA) levels in rat brain using quantitative real-time polymerase chain reaction (real-time qPCR) after forced treadmill exercise for 1 day, 2 weeks, and 8 weeks. Rats were euthanized either immediately (0 h) or 24 h after last exercise session. Here, we show that exercise affected mRNA levels of VEGF, VEGFR2, and the coreceptor neuropilin 2 (NRP2) when the rats were euthanized immediately, whereas at 24 h only the expression of mTOR was regulated after a single bout of exercise. In conclusion, the effect of treadmill exercise on the VEGF system is acute rather than chronic and there is a transient activation of mTOR. More studies are needed to understand whether this could be beneficial in the treatment of neuropsychiatric disorders.

A gene-environment study of cytoglobin in the human and rat hippocampus

BACKGROUND

Cytoglobin (Cygb) was discovered a decade ago as the fourth vertebrate heme-globin. The function of Cygb is still unknown, but accumulating evidence from in vitro studies point to a putative role in scavenging of reactive oxygen species and nitric oxide metabolism and in vivo studies have shown Cygb to be up regulated by hypoxic stress. This study addresses three main questions related to Cygb expression in the hippocampus: 1) Is the rat hippocampus a valid neuroanatomical model for the human hippocampus; 2) What is the degree of co-expression of Cygb and neuronal nitric oxide synthase (nNOS) in the rat hippocampus; 3) The effect of chronic restraint stress (CRS) on Cygb and nNOS expression.

METHODS

Immunohistochemistry was used to compare Cygb expression in the human and rat hippocampi as well as Cygb and nNOS co-expression in the rat hippocampus. Transcription and translation of Cygb and nNOS were investigated using quantitative real-time polymerase chain reaction (real-time qPCR) and Western blotting on hippocampi from Flinders (FSL/FRL) rats exposed to CRS.

PRINCIPAL FINDINGS

Cygb expression pattern in the human and rat hippocampus was found to be similar. A high degree of Cygb and nNOS co-expression was observed in the rat hippocampus. The protein levels of nNOS and Cygb were significantly up-regulated in FSL animals in the dorsal hippocampus. In the ventral hippocampus Cygb protein levels were significantly up-regulated in the FSL compared to the FRL, following CRS.

SIGNIFICANCE

The rodent hippocampus can be used to probe questions related to Cygb protein localization in human hippocampus. The high degree of Cygb and nNOS co-expression gives support for Cygb involvement in nitric oxide metabolism. CRS induced Cygb and nNOS expression indicating that Cygb expression is stress responsive. Cygb and nNOS may be important in physiological response to stress.

The neural plasticity theory of depression: assessing the roles of adult neurogenesis and PSA-NCAM within the hippocampus

Depression is a devastating and prevalent disease, with profound effects on neural structure and function; however the etiology and neuropathology of depression remain poorly understood. Though antidepressant drugs exist, they are not ideal, as only a segment of patients are effectively treated, therapeutic onset is delayed, and the exact mechanism of these drugs remains to be elucidated. Several theories of depression do exist, including modulation of monoaminergic neurotransmission, alterations in neurotrophic factors, and the upregulation of adult hippocampal neurogenesis, and are briefly mentioned in the review. However none of these theories sufficiently explains the pathology and treatment of depression unto itself. Recently, neural plasticity theories of depression have postulated that multiple aspects of brain plasticity, beyond neurogenesis, may bridge the prevailing theories. The term “neural plasticity” encompasses an array of mechanisms, from the birth, survival, migration, and integration of new neurons to neurite outgrowth, synaptogenesis, and the modulation of mature synapses. This review critically assesses the role of adult hippocampal neurogenesis and the cell adhesion molecule, PSA-NCAM (which is known to be involved in many facets of neural plasticity), in depression and antidepressant treatment.

Synapsin II gene expression in the dorsolateral prefrontal cortex of brain specimens from patients with schizophrenia and bipolar disorder: effect of lifetime intake of antipsychotic drugs

Synapsins are neuronal phosphoproteins crucial to regulating the processes required for normal neurotransmitter release. Synapsin II, in particular, has been implied as a candidate gene for schizophrenia. This study investigated synapsin II mRNA expression, using Real Time RT-PCR, in coded dorsolateral prefrontal cortical samples provided by the Stanley Foundation Neuropathology Consortium. Synapsin IIa was decreased in patients with schizophrenia when compared to both healthy subjects and patients with bipolar disorder, whereas the synapsin IIb was only significantly reduced in patients with schizophrenia when compared to healthy subjects, but not patients with bipolar disorder. Furthermore, lifetime antipsychotic drug use was positively associated with synapsin IIa expression in patients with schizophrenia. Results suggest that impairment of synaptic transmission by synapsin II reduction may contribute to dysregulated convergent molecular mechanisms which result in aberrant neural circuits that characterize schizophrenia, while implicating involvement of synapsin II in therapeutic mechanisms of currently prescribed antipsychotic drugs.