Hippocampus-specific deletion of tissue plasminogen activator "tPA" in adult mice impairs depression- and anxiety-like behaviors

The changes of tPA/PAI-1 system are associated with the ratio of BDNF/proBDNF in major depressive disorder and SSRIs antidepressant treatment

Increasing evidence demonstrates that brain-derived neurotrophic factor (BDNF) can be regarded as a biomarker for major depression. Our previous work found that the ratio of mature BDNF (mBDNF) to precursor-BDNF (proBDNF) was a pivotal factor in the pathogenesis of major depressive disorder (MDD). But the mechanism behind the ratio is still obscure. Tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) both play essential roles in depression by regulating the ratio of BDNF/proBDNF. In present study, we analyzed BDNF, proBDNF, tPA and PAI-1 in the peripheral blood in 57 MDD patients pre- and post-treatment and in 57 healthy controls. We verified that BDNF and tPA levels were significantly decreased, whereas proBDNF and PAI-1 levels elevated obviously in MDD group pre-treatment. And after 4 weeks SSRIs treatment, the BDNF and tPA levels increased while the proBDNF and PAI-1 levels reduced. The MDD pre-treatment group had the lowest ratio of BDNF to proBDNF compared to MDD post-treatment group and control group. Though the ratio of tPA/PAI-1 in MDD pre-treatment had not reached the significance, it was still the lowest one among the three groups. The combination of tPA + PAI + BDNF showed the best diagnostic value for MDD. In summary, our data suggested that the interaction between tPA and PAI-1 implicated to the MDD and the antidepressant treatment which might through regulating the BDNF/proBDNF ratio. The combination of tPA, PAI-1 and BDNF might offer a helpful way for MDD diagnosis.

Nigrostriatal Inflammation Is Associated with Nonmotor Symptoms in an Experimental Model of Prodromal Parkinson's Disease

Recent evidence has supported a pathogenic role for neuroinflammation in Parkinson's disease (PD). Inflammatory response has been associated with symptoms and subtypes of PD. However, it is unclear whether immune changes are involved in the initial pathogenesis of PD, leading to the non-motor symptoms (NMS) observed in its prodromal stage. The current study aimed to characterize the behavioral and cognitive changes in a toxin-induced model of prodromal PD-like syndrome. We also sought to investigate the role of neuroinflammation in prodromal PD-related NMS. Male mice were subjected to bilateral intranasal infusion with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or saline (control group), followed by comprehensive behavioral, pathological and neurochemical analysis. Intranasal MPTP infusion was able to cause the loss of dopaminergic neurons in the substantia nigra (SN). In parallel, it induced impairment in olfactory discrimination and social memory consolidation, compulsive and anxiety-like behaviors, but did not influence motor performance. Iba-1 and GFAP expressions were increased in the SN, suggesting an activated state of microglia and astrocytes. Consistent with this, MPTP mice had increased levels of IL-10 and IL-17A, and decreased levels of BDNF and TrkA mRNA in the SN. The striatum showed increased IL-17A, BDNF, and NFG levels compared to control mice. In conclusion, neuroinflammation may play an important role in the early stage of experimental PD-like syndrome, leading to cognitive and behavioral changes. Our results also indicate that intranasal administration of MPTP may represent a valuable mouse model for prodromal PD.

Serotonin transporter knockdown relieves depression-like behavior and ethanol-induced CPP in mice after chronic social defeat stress

Patients with stress-triggered major depression disorders (MDD) can often seek comfort or temporary relief through alcohol consumption, as they may turn to it as a means of self-medication or coping with overwhelming emotions. The use of alcohol as a coping mechanism for stressful events can escalate, fostering a cycle where the temporary relief it provides from depression can deepen into alcohol dependence, exacerbating both conditions. Although, the specific mechanisms involved in stress-triggered alcohol dependence and MDD comorbidities are not well understood, a large body of literature suggests that the serotonin transporter (SERT) plays a critical role in these abnormalities. To further investigate this hypothesis, we used a lentiviral-mediated knockdown approach to examine the role of hippocampal SERT knockdown in social defeat stress-elicited depression like behavior and ethanol-induced place preference (CPP). The results showed that social defeat stress-pro depressant effects were reversed following SERT knockdown demonstrated by increased sucrose preference, shorter latency to feed in the novelty suppressed feeding test, and decreased immobility time in the tail suspension and forced swim tests. Moreover, and most importantly, social stress-induced ethanol-CPP acquisition and reinstatement were significantly reduced following hippocampal SERT knockdown using short hairpin RNA shRNA-expressing lentiviral vectors. Finally, we confirmed that SERT hippocampal mRNA expression correlated with measures of depression- and ethanol-related behaviors by Pearson's correlation analysis. Taken together, our data suggest that hippocampal serotoninergic system is involved in social stress-triggered mood disorders as well as in the acquisition and retrieval of ethanol contextual memory and that blockade of this transporter can decrease ethanol rewarding properties.

Reduced Levels of Brain-Derived Neurotrophic Factor Affect Body Weight, Brain Weight and Behavior

Neurotrophins, which belong to the family of growth factors, not only play crucial roles during development but are also involved in many processes in the postnatal brain. One representative of neurotrophins is brain-derived neurotrophic factor (BDNF). BDNF plays a role in the regulation of body weight and neuronal plasticity and is, therefore, also involved in processes associated with learning and memory formation. Many of the studies on BDNF have been carried out using BDNF-deficient mice. Unfortunately, homozygous deletion of BDNF is lethal in the early postnatal stage, so heterozygous BDNF-deficient mice are often studied. Another possibility is the use of conditional BDNF-deficient mice in which the expression of BDNF is strongly downregulated in some brain cells, for example, in the neurons of the central nervous system, but the expression of BDNF in other cells in the brain is unchanged. To further reduce BDNF expression, we crossed heterozygous BDNF-deficient mice with mice carrying a deletion of BDNF in neurofilament L-positive neurons. These offspring are viable, and the animals with a strong reduction in BDNF in the brain show a strongly increased body weight, which is accompanied by a reduction in brain weight. In addition, these animals show behavioral abnormalities, particularly with regard to locomotion.

Gestational environmental enrichment prevents chronic social stress induced anxiety- and ethanol-related behaviors in offspring

Epidemiological surveys have shown a strong relationship between maternal stress and offspring's mood disorders. Growing evidence suggested that environmental enrichment (EE) improves cognitive function in models of psychiatric and neurological disorders. However, the potential protective effects of gestational EE on social stress-elicited mood disorders in offspring have not been studied. Knowing that the undeveloped brain is more sensitive to gestational environmental stimuli, we hypothesized that initiating cognitive stimulation, during gestation, would protect against social stress-induced behavioral alterations in adulthood. Therefore, the present study aimed to investigate the effects of gestational EE on social stress-elicited anxiety- and ethanol-related behaviors in adult offspring. EE consisted of free access, of dams, to tubular devices of different shapes, colors, and sizes that were changed regularly. After birth and weaning, young adult offspring were exposed to 19 days of social stress and anxiety-like behavior was evaluated by elevated plus maze, open field, and marbles burying tests. The two-bottle choice (TBC) drinking paradigm was used to assess stress-induced ethanol intake. Results showed that gestational EE prevented social stress-elicited anxiogenic-like effects with no differences in spontaneous locomotor activity. Moreover, in the TBC paradigm, mice pre-exposed to EE consistently showed a significantly decreased consumption and preference for ethanol with no effects on tastants' intakes. Interestingly, gestational EE increased serum BDNF levels, which showed a correlation with measures of anxiety- and ethanol-related behaviors. These findings indicate that some neurodevelopmental changes associated with prenatal EE may counteract adult social stress-induced behavioral alterations through a BDNF mechanism. Therefore, we propose that gestational EE has significant protective and beneficial effects on social stress-induced cognitive impairment. It can also alleviate anxiety-like behavior and subsequent excessive alcohol consumption.

Morphological and behavioral analysis of Slc35f1-deficient mice revealed no neurodevelopmental phenotype

SLC35F1 is a member of the sugar-like carrier (SLC) superfamily that is expressed in the mammalian brain. Malfunction of SLC35F1 in humans is associated with neurodevelopmental disorders. To get insight into the possible roles of Slc35f1 in the brain, we generated Slc35f1-deficient mice. The Slc35f1-deficient mice are viable and survive into adulthood, which allowed examining adult Slc35f1-deficient mice on the anatomical as well as behavioral level. In humans, mutation in the SLC35F1 gene can induce a Rett syndrome-like phenotype accompanied by intellectual disability (Fede et al. Am J Med Genet A 185:2238-2240, 2021). The Slc35f1-deficient mice, however, display only a very mild phenotype and no obvious deficits in learning and memory as, e.g., monitored with the novel object recognition test or the Morris water maze test. Moreover, neuroanatomical parameters of neuronal plasticity (as dendritic spines and adult hippocampal neurogenesis) are also unaltered. Thus, Slc35f1-deficient mice display no major alterations that resemble a neurodevelopmental phenotype.

The Novel Pimavanserin Derivative ST-2300 with Histamine H3 Receptor Affinity Shows Reduced 5-HT2A Binding, but Maintains Antidepressant- and Anxiolytic-like Properties in Mice

The therapy of depression is challenging and still unsatisfactory despite the presence of many antidepressant drugs on the market. Consequently, there is a continuous need to search for new, safer, and more effective antidepressant therapeutics. Previous studies have suggested a potential association of brain histaminergic/serotoninergic signaling and antidepressant- and anxiolytic-like effects. Here, we evaluated the in vivo antidepressant- and anxiolytic-like effects of the newly developed multiple-active ligand ST-2300. ST-2300 was developed from 5-HT_2A/2C inverse agonist pimavanserin (PIM, ACP-103) and incorporates a histamine H₃ receptor (H₃R) antagonist pharmacophore. Despite its parent compound, ST-2300 showed only moderate serotonin 5-HT_2A antagonist/inverse agonist affinity (K_i value of 1302 nM), but excellent H₃R affinity (K_i value of 14 nM). In vivo effects were examined using forced swim test (FST), tail suspension test (TST), and the open field test (OFT) in C57BL/6 mice. Unlike PIM, ST-2300 significantly increased the anxiolytic-like effects in OFT without altering general motor activity. In FST and TST, ST-2300 was able to reduce immobility time similar to fluoxetine (FLX), a recognized antidepressant drug. Importantly, pretreatment with the CNS-penetrant H₃R agonist (R)-α-methylhistamine reversed the antidepressant-like effects of ST-2300 in FST and TST, but failed to reverse the ST-2300-provided anxiolytic effects in OFT. Present findings reveal critical structural features that are useful in a rational multiple-pharmacological approach to target H₃R/5-HT_2A/5-HT_2C.

Mechanisms affecting brain remodeling in depression: do all roads lead to impaired fibrinolysis?

Fibrinolysis occurs when plasminogen activators, such as tissue plasminogen activator (tPA), convert plasminogen to plasmin, which dissolves the fibrin clot. The proteolytic activity of tPA and plasmin is not restricted to fibrin degradation. In the extravascular space, these two proteases modify a variety of substrates other than fibrin, playing a crucial role in physiological and pathological tissue remodeling. In the brain, for example, tPA and plasmin mediate the conversion of brain-derived neurotrophic factor precursor (proBDNF) to mature brain-derived neurotrophic factor precursor (BDNF). Thus, the fibrinolytic system influences processes reported to be dysfunctional in depression, including neurogenesis, synaptic plasticity, and reward processing. The hypothesis that decreased fibrinolytic activity is an important element in the pathogenesis of depression is supported by the association between depression and increased levels of plasminogen activator inhibitor (PAI)-1, the main inhibitor of tPA. Also, various biochemical markers of depression induce PAI-1 synthesis, including hypercortisolism, hyperinsulinemia, hyperleptinemia, increased levels of cytokines, and hyperhomocysteinemia. Moreover, hypofibrinolysis provides a link between depression and emotional eating, binge eating, vegetarianism, and veganism. This paper discusses the role of reduced fibrinolytic activity in the bidirectional interplay between depression and its somatic manifestations and complications. It also reviews evidence that abnormal fibrinolysis links heterogeneous conditions associated with treatment-resistant depression. Understanding the role of hypofibrinolysis in depression may open new avenues for its treatment.

Participation of Central Muscarinic Receptors on the Nervous Form of Chagas Disease in Mice Infected via Intracerebroventricular with Colombian Trypanosoma cruzi Strain

Acute chagasic encephalitis is a clinically severe central nervous system (CNS) manifestation. However, the knowledge of the nervous form of Chagas disease is incomplete. The role of the muscarinic acetylcholine receptor (mAChR) on mice behavior and brain lesions induced by Trypanosoma cruzi (Colombian strain) was herein investigated in mice treated with the mAChR agonist and antagonist (carbachol and atropine), respectively. Immunosuppressed or non-immunosuppressed mice were intracerebroventricularly (icv) or intraperitoneally (ip) infected. All groups were evaluated 15 d.p.i. (days post infection). Intraperitoneally infected animals had subpatent parasitemia. Patent parasitemia occurred only in icv infected mice. The blockade of mAChR increased the parasitemia, parasitism and lesions compared to its activation. Infected not treated (INT ip) mice did not present meningitis and encephalitis, regardless of immunosuppression. INT icv brains presented higher cellularity, discrete signs of cellular degeneration, frequent presence of parasites and focal meningitis. The immunosuppressed atropine + icv mice presented increased intracellular parasitism associated with degenerative parenchymal changes, while carbachol + icv mice presented discrete meningitis, preservation of the cortex and absence of relevant parasitism. Cholinergic receptor blockage increased impairment of coordination vs. receptor activation. Muscarinic cholinergic pathway seems to be involved in immune mediated cell invasion events while its blockade favored infection evolution, brain lesions, and behavioral alterations.

Proteolytic cleavage of proBDNF to mBDNF in neuropsychiatric and neurodegenerative diseases

Brain-derived neurotrophic factor (BDNF) is involved in pathophysiological mechanisms in neuropsychiatric diseases, including depression, anxiety, and schizophrenia (SZ), as well as neurodegenerative diseases like Parkinson's disease (PD) and Alzheimer's disease (AD). An imbalance or insufficient pro-brain-derived neurotrophic factor (proBDNF) transformation into mature BDNF (mBDNF) is potentially critical to the disease pathogenesis by impairing neuronal plasticity as suggested by results from many studies. Thus, promoting proBDNF transformation into mBDNF is therefore hypothesized as beneficial for the treatment of neuropsychiatric and neurodegenerative diseases. ProBDNF is proteolytically cleaved into the mBDNF by intracellular furin/proprotein convertases and extracellular proteases (plasmin/matrix metallopeptidases). This article reviews the mechanisms of the conversion of proBDNF to mBDNF and the research status of intracellular/extracellular proteolytic proteases for neuropsychiatric and neurodegenerative disorders.

Simultaneous Blockade of Histamine H3 Receptors and Inhibition of Acetylcholine Esterase Alleviate Autistic-Like Behaviors in BTBR T+ tf/J Mouse Model of Autism

Autism spectrum disorder (ASD) is a heterogenous neurodevelopmental disorder defined by persistent deficits in social interaction and the presence of patterns of repetitive and restricted behaviors. The central neurotransmitters histamine (HA) and acetylcholine (ACh) play pleiotropic roles in physiological brain functions that include the maintenance of wakefulness, depression, schizophrenia, epilepsy, anxiety and narcolepsy, all of which are found to be comorbid with ASD. Therefore, the palliative effects of subchronic systemic treatment using the multiple-active test compound E100 with high H₃R antagonist affinity and AChE inhibitory effect on ASD-like behaviors in male BTBR T+tf/J (BTBR) mice as an idiopathic ASD model were assessed. E100 (5, 10 and 15 mg/kg, i.p.) dose-dependently palliated social deficits of BTBR mice and significantly alleviated the repetitive/compulsive behaviors of tested animals. Moreover, E100 modulated disturbed anxiety levels, but failed to modulate hyperactivity parameters, whereas the reference AChE inhibitor donepezil (DOZ, one milligram per kilogram) significantly obliterated the increased hyperactivity measures of tested mice. Furthermore, E100 mitigated the increased levels of AChE activity in BTBR mice with observed effects comparable to that of DOZ and significantly reduced the number of activated microglial cells compared to the saline-treated BTBR mice. In addition, the E100-provided effects on ASD-like parameters, AChE activity, and activated microglial cells were entirely reversed by co-administration of the H₃R agonist (R)-α-methylhistamine (RAM). These initial overall results observed in an idiopathic ASD mice model show that E100 (5 mg/kg) alleviated the assessed behavioral deficits and demonstrate that simultaneous targeting of brain histaminergic and cholinergic neurotransmissions is crucial for palliation of ASD-like features, albeit further in vivo assessments on its effects on brain levels of ACh as well as HA are still needed.

Human BDNF/TrkB variants impair hippocampal synaptogenesis and associate with neurobehavioural abnormalities

Brain-derived neurotrophic factor (BDNF) signals through its high affinity receptor Tropomyosin receptor kinase-B (TrkB) to regulate neuronal development, synapse formation and plasticity. In rodents, genetic disruption of Bdnf and TrkB leads to weight gain and a spectrum of neurobehavioural phenotypes. Here, we functionally characterised a de novo missense variant in BDNF and seven rare variants in TrkB identified in a large cohort of people with severe, childhood-onset obesity. In cells, the E183K BDNF variant resulted in impaired processing and secretion of the mature peptide. Multiple variants in the kinase domain and one variant in the extracellular domain of TrkB led to a loss of function through multiple signalling pathways, impaired neurite outgrowth and dominantly inhibited glutamatergic synaptogenesis in hippocampal neurons. BDNF/TrkB variant carriers exhibited learning difficulties, impaired memory, hyperactivity, stereotyped and sometimes, maladaptive behaviours. In conclusion, human loss of function BDNF/TrkB variants that impair hippocampal synaptogenesis may contribute to a spectrum of neurobehavioural disorders.

The Dual-Active Histamine H3 Receptor Antagonist and Acetylcholine Esterase Inhibitor E100 Alleviates Autistic-Like Behaviors and Oxidative Stress in Valproic Acid Induced Autism in Mice

The histamine H3 receptor (H3R) functions as auto- and hetero-receptors, regulating the release of brain histamine (HA) and acetylcholine (ACh), respectively. The enzyme acetylcholine esterase (AChE) is involved in the metabolism of brain ACh. Both brain HA and ACh are implicated in several cognitive disorders like Alzheimer’s disease, schizophrenia, anxiety, and narcolepsy, all of which are comorbid with autistic spectrum disorder (ASD). Therefore, the novel dual-active ligand E100 with high H3R antagonist affinity (hH3R: K_i = 203 nM) and balanced AChE inhibitory effect (EeAChE: IC₅₀ = 2 µM and EqBuChE: IC₅₀ = 2 µM) was investigated on autistic-like sociability, repetitive/compulsive behaviour, anxiety, and oxidative stress in male C57BL/6 mice model of ASD induced by prenatal exposure to valproic acid (VPA, 500 mg/kg, intraperitoneal (i.p.)). Subchronic systemic administration with E100 (5, 10, and 15 mg/kg, i.p.) significantly and dose-dependently attenuated sociability deficits of autistic (VPA) mice in three-chamber behaviour (TCB) test (all p < 0.05). Moreover, E100 significantly improved repetitive and compulsive behaviors by reducing the increased percentage of marbles buried in marble-burying behaviour (MBB) (all p < 0.05). Furthermore, pre-treatment with E100 (10 and 15 mg/kg, i.p.) corrected decreased anxiety levels (p < 0.05), however, failed to restore hyperactivity observed in elevated plus maze (EPM) test. In addition, E100 (10 mg/kg, i.p.) mitigated oxidative stress status by increasing the levels of decreased glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT), and decreasing the elevated levels of malondialdehyde (MDA) in the cerebellar tissues (all p < 0.05). Additionally, E100 (10 mg/kg, i.p.) significantly reduced the elevated levels of AChE activity in VPA mice (p < 0.05). These results demonstrate the promising effects of E100 on in-vivo VPA-induced ASD-like features in mice, and provide evidence that a potent dual-active H3R antagonist and AChE inhibitor (AChEI) is a potential drug candidate for future therapeutic management of autistic-like behaviours.

Environmental enrichment decreases chronic psychosocial stress-impaired extinction and reinstatement of ethanol conditioned place preference in C57BL/6 male mice

RATIONALE

During the last few decades, alcohol use disorders (AUD) have reached an epidemic prevalence, yet social influences on alcoholism have not been fully addressed. Several factors can modulate alcohol intake. On one hand, stress can reinforce ethanol-induced behaviors and be an important component in AUD and alcoholism. On the other hand, environmental enrichment (EE) has a neuroprotective role and prevents the development of excessive ethanol intake in rodents. However, studies showing the role of EE in chronic psychosocial stress-impaired ethanol-conditioned rewards are nonexistent.

AIM

The purpose of the current study is to explore the potential protective role of EE on extinction and reinstatement of ethanol-conditioned place preference (EtOH-CPP) following chronic psychosocial stress.

METHODS

In the first experiment and after the EtOH-CPP test, the mice were subjected to 15 days of chronic stress, then housed in a standard (SE) or enriched environment (EE) while EtOH-CPP extinction was achieved by repeated exposure to the CPP chambers without ethanol injection. In the second experiment and after the EtOH-CPP test, extinction was achieved as described above. Mice were then exposed to chronic stress for 2 weeks before being housed in a SE or EE. EtOH-CPP reinstatement was induced by a single exposure to the conditioning chambers.

RESULTS

As expected, stress exposure increased anxiety-like behavior and reduced weight gain. More importantly, we found that EE significantly shortened chronic stress-delayed extinction and decreased the reinstatement of EtOH-CPP.

CONCLUSION

These results support the hypothesis that EE reduces the impact of alcohol-associated environmental stimuli, and hence it may be a general intervention for reducing cue-elicited craving and relapse in humans.

Possible Involvement of Tissue Plasminogen Activator/Brain-Derived Neurotrophic Factor Pathway in Anti-Depressant Effects of Electroacupuncture in Chronic Unpredictable Mild Stress-Induced Depression in Rats

OBJECTIVE

Using a rat model of chronic unpredictable mild stress (CUMS), to investigate the effects of electroacupuncture (EA) on the tissue plasminogen activator (tPA)/brain-derived neurotrophic factor (BDNF) pathway.

METHODS

Sixty male Sprague-Dawley rats were randomly divided into four groups: normal, model, fluoxetine (fluox), or EA. Experimental groups were subjected to 28 d of CUMS modeling. One hour after CUMS, the fluox and EA groups were treated with fluox and a 20 min EA intervention, respectively. Depressive-like behaviors were assessed by open field and sucrose preference tests. After the rats were sacrificed, brains were dissected and processed using hematoxylin and eosin (HE) staining to observe changes in the morphology and quantity of neurons in the hippocampal cornu ammonis 3 area. Western blot and real-time polymerase chain reaction (PCR) demonstrated the effects of EA on the tPA/BDNF pathway-related molecules in the hippocampi and raphe nuclei.

RESULTS

Compared to the model group, the number of horizontal and vertical movements and the percentage of sucrose consumption in the EA groups were significantly increased (P < 0.01). Compared to the model group, HE staining showed that the hippocampal neurons in the EA and fluox groups were arranged neatly, with rich layers and complete cell structures. The Western blot and real-time PCR showed that the levels of tPA, BDNF, tropomyosin receptor kinase B, and BDNF micro RNA (mRNA) in the hippocampi of the EA group were higher than in the model group (P < 0.01, P < 0.01, P < 0.05, P < 0.01, respectively). The content of p75NTR, proBDNF, and tPA mRNA in the hippocampi of the EA group displayed no significant differences compared to the model group. The tPA mRNA content in the raphe nuclei of the EA group was higher than in the model group (P < 0.01), and the BDNF content in the raphe nuclei was lower than in the model group (P < 0.05). There were no significant differences in tPA and BDNF mRNA between the EA and model groups.

CONCLUSION

EA may reverse depressive-like behaviors in CUMS, which may be related to the tPA/BDNF pathway in the hippocampus.

DNA Methylation of the t-PA Gene Differs Between Various Immune Cell Subtypes Isolated From Depressed Patients Receiving Electroconvulsive Therapy

BACKGROUND

Major depressive disorder (MDD) represents a tremendous health threat to the world's population. Electroconvulsive therapy (ECT) is the most effective treatment option for refractory MDD patients. Ample evidence suggests brain-derived neurotrophic factor (BDNF) to play a crucial role in ECT's mode of action. Tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) are involved in BDNF production.

HYPOTHESIS

The DNA methylation of gene regions encoding for t-PA and PAI-1 might be a suitable biomarker for ECT response prediction.

METHODS

We withdrew blood from two cohorts of treatment-resistant MDD patients receiving ECT. In the first cohort (n = 59), blood was collected at baseline only. To evaluate DNA methylation changes throughout the treatment course, we acquired a second group (n = 28) and took blood samples at multiple time points. DNA isolated from whole blood and defined immune cell subtypes (B cells, monocytes, natural killer cells, and T cells) served for epigenetic analyses.

RESULTS

Mixed linear models (corrected for multiple testing by Sidak's post-hoc test) revealed (1) no detectable baseline blood DNA methylation differences between ECT remitters (n = 33) and non-remitters (n = 53) in the regions analyzed, but (2) a significant difference in t-PA's DNA methylation between the investigated immune cell subtypes instead (p < 0.00001). This difference remained stable throughout the treatment course, showed no acute changes after ECT, and was independent of clinical remission.

CONCLUSION

DNA methylation of both proteins seems to play a minor role in ECT's mechanisms. Generally, we recommend using defined immune cell subtypes (instead of whole blood only) for DNA methylation analyses.

Lentiviral-mediated let-7d microRNA overexpression induced anxiolytic- and anti-depressant-like behaviors and impaired dopamine D3 receptor expression

Generalized anxiety and major depression disorders (MDD) are severe debilitating mood disorders whose etiology are not fully understood, but growing evidence indicates that microRNAs (miRNAs) might play a key role in their neuropathophysiological mechanisms. In the current study, we investigate the role of Lethal-7 (let-7d) miRNA, and its direct target dopamine D3 receptor (D3R) gain-of-function, in the hippocampus, in preclinical models of anxiety and depression in mice. For this purpose, we have constructed a lentiviral vector carrying let-7d miRNA and its anxiolytic effect was investigated by employing the open-field (OF) and the elevated plus maze (EPM) tests. The anti-depressant activity was evaluated using the tail suspension and the forced-swim tests (TST & FST). Our results show that let-7d overexpression significantly improved the measures of anxiety in the OF and EPM tests. In addition, let-7d increased the mobility time in the TST and FST. Interestingly, gene expression interaction analysis shows that the D3R mRNA negatively correlates with let-7d expression. In a different set of experiments, we used a tetracycline-inducible (tet-off) lentiviral vector to overexpress D3R to assess its gain-of-function in the hippocampus on anxiety- and depression-like behaviors. In line, we found that in the absence of doxycycline, D3R produced a significant anxiogenic and depressant-like response. Most importantly, these effects were abrogated when mice were fed doxycycline in drinking water. Our results provide the first evidence for an anxiolytic and anti-depressant-like action of let-7d through a potential D3R target-mediated mechanism which might open new avenues for anxiolytic and anti-depressant therapies.

High-Intensity Interval Training on Neuroplasticity, Balance between Brain-Derived Neurotrophic Factor and Precursor Brain-Derived Neurotrophic Factor in Poststroke Depression Rats

BACKGROUND

High-intensity interval training (HIIT) improves functional and mental health in the patients with stroke. To investigate the potential mechanisms of HIIT on poststroke depression (PSD).

METHODS

Wistar rats were randomly divided into control, Sham, PSD, moderate intensity continuous training (MICT), and HIIT groups. After PSD model was successful made, the maximum speed (Smax) and the blood lactate threshold corresponding speed (S_LT) were measured. Different intensity training protocols were performed on the MICT and HIIT groups, respectively. The behavioral tests (open field, forced swimming, and sucrose preference tests) were performed before and after training. Nissl staining was used to observe the changes of neuronal cell morphology in the left hippocampus. The expression of mature brain-derived neurotrophic factor (mBDNF), tropomyosin receptor kinase B (TrkB), precursor BDNF (proBDNF), pan-neurotrophin receptor 75 (p75NTR), NR2A, NR2B proteins, and BDNF, tissue plasminogen activator (tPA) mRNA in the hippocampus were detected by Western blotting, immunohistochemistry or RT-PCR after training.

RESULTS

After 28 days of training, higher center occupancy, immobility time, and level of proBDNF, p75NTR, and NR2B proteins, lower sucrose preference and level of mBDNF, TrkB, NR2A proteins, and BDNF, tPA mRNA were observed in the PSD group. Neuronal cells and Nissl body in the hippocampus were loosely arranged and lightly stained in the PSD group. The ethological findings, Nissl staining especially in the CA1 and dentate gyrus areas, expression of proteins and mRNA above in the MICT and HIIT rats were reversed. And the HIIT group changed more significantly compared with MICT.

CONCLUSIONS

HIIT was superior to MICT in improving depression in the PSD rats might via increasing mBDNF/proBDNF ratio and further improving neural plasticity in the hippocampus.

Dopamine transporter (DAT) knockdown in the nucleus accumbens improves anxiety- and depression-related behaviors in adult mice

Many epidemiological and clinical studies have demonstrated a strong comorbidity between anxiety and depression, and a number of experimental studies indicates that the dopamine transporter (DAT) is involved in the pathophysiology of anxiety and depression. However, studies using laboratory animals have yielded inconclusive results. The aim of the present study was to examine the effects of DAT manipulation on anxiety- and depression-like behaviors in mice. For this purpose, animals were stereotaxically injected with DAT siRNA-expressing lentiviral vectors (siDAT) in the caudate putamen (CPu) or in the nucleus accumbens (Nacc) and the behavioral outcomes were assessed using the open-field (OF), elevated-plus maze (EPM), light-dark box (LDB), sucrose preference (SPT), novelty suppressed feeding (NSF), and forced-swim (FST) tests. The results showed that in the Nacc, but not in the CPu, siDAT increased the time spent at the center of the arena and decreased the number of fecal boli in the OF test. In the EPM and LDB tests, Nacc siDAT injection increased the entries and time spent on open arms, and increased the time spent in the light side of the box, respectively, suggesting an anxiolytic-like activity. In addition, siDAT, in the Nacc, induced significant antidepressant-like effects, evidenced by increased sucrose preference, shorter latency to feed in the NSF test, and decreased immobility time in the FST. Most importantly, Pearson's test clearly showed significant correlations between DAT mRNA in the Nacc with anxiety and depression parameters. Overall, these results suggest that low DAT levels, in the Nacc, might act as protective factors against anxiety and depression. Therefore, targeting DAT activity might be a very attractive approach to tackle affective disorders.

Altered levels of brain-derived neurotrophic factor, proBDNF and tissue plasminogen activator in children with posttraumatic stress disorder

The current study aims to compare the serum brain-derived neurotrophic factor (BDNF), proBDNF and tissue plasminogen activator (tPA) levels in cases that have developed posttraumatic stress disorder (PTSD) in consequence of sexual abuse with those in healthy control subjects. Thirty-one female patients between 8 and 18 years of age who have been diagnosed with PTSD due to sexual abuse and thirty-one healthy female volunteer controls were included in the study. Frequency, intensity and severity of PTSD symptoms were assessed on the basis of Clinician-Administered Post-Traumatic Stress Disorder Scale for Children and Adolescents (CAPS-CA). Serum BDNF, proBDNF and tPA levels were measured by Enzyme-Linked Immunosorbent Assay (ELISA) method. Results of the present study revealed that serum levels of BDNF and proBDNF in PTSD group were significantly lower but tPA level was significantly higher as compared to healthy control subjects. There were no correlations between CAPS-CA scores and BDNF, proBDNF and tPA levels. Decreased levels of BDNF, as suggested to have a role in the etiopathogenesis of PTSD, appear to be a result of the reduction in proBDNF production. The increased tPA levels in such cases, on the other hand, can be a compensatory mechanism serving to increase the BDNF levels.

The histamine H3R antagonist DL77 attenuates autistic behaviors in a prenatal valproic acid-induced mouse model of autism

Autistic spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairment in social communication and restricted/repetitive behavior patterns or interests. Antagonists targeting histamine H3 receptor (H3R) are considered potential therapeutic agents for the therapeutic management of different brain disorders, e.g., cognitive impairments. Therefore, the effects of subchronic treatment with the potent and selective H3R antagonist DL77 (5, 10, or 15 mg/kg, i.p.) on sociability, social novelty, anxiety, and aggressive/repetitive behavior in male Tuck-Ordinary (TO) mice with ASD-like behaviors induced by prenatal exposure to valproic acid (VPA, 500 mg/kg, i.p.) were evaluated using the three-chamber test (TCT), marble burying test (MBT), nestlet shredding test (NST), and elevated plus maze (EPM) test. The results showed that VPA-exposed mice exhibited significantly lower sociability and social novelty preference compared to VPA-exposed mice that were pretreated with DL77 (10 or 15 mg/kg, i.p.). VPA-exposed mice presented a significantly higher percentage of buried marbles in MBT and shredded nestlet significantly more in NST compared to the control groups. However, VPA-exposed animals pretreated with DL77 (10 or 15 mg/kg, i.p.) buried a reduced percentage of marbles in MBT and presented a significantly lower percentage of shredding behavior in NST. On the other hand, pretreatment with DL77 (5, 10, or 15 mg/kg, i.p.) failed to restore the disturbed anxiety levels and hyperactivity observed in VPA-exposed animals in EPM, whereas the reference drug donepezil (DOZ, 1 mg/kg, i.p.) significantly palliated the anxiety and reduced the hyperactivity measures of VPA-exposed mice. Furthermore, pretreatment with DL77 (10 or 15 mg/kg, i.p.) modulated oxidative stress status by increasing GSH and decreasing MDA, and it attenuated the proinflammatory cytokines IL-1β, IL-6 and TNF-α exacerbated by lipopolysaccharide (LPS) challenge, in VPA-exposed mouse brain tissue. Taken together, these results provide evidence that modulation of brain histaminergic neurotransmission, such as by subchronic administration of the H3R antagonist DL77, may serve as an effective pharmacological therapeutic target to rescue ASD-like behaviors in VPA-exposed animals, although further investigations are necessary to corroborate and expand these initial data.

Stress-induced hippocampus Npas4 mRNA expression relates to specific psychophysiological patterns of stress response

Neuronal Per-Arnt-Sim (PAS) domain protein 4 (Npas4) is a key protein that intervenes in GABA synapse scaling and neurotrophicity enhancing. Since GABA and neurotrophicity are implicated in stress response and Npas4-deficient rodents exhibit behavioral alterations, an investigation was designed in rats to verify whether stress-induced spontaneous hippocampus Npas4 mRNA expression would be associated with specific patterns of stress response. The rats were exposed to one of three stressor levels: no stress (CTL, n = 15), exposure to a footshock apparatus (Sham, S, n = 40) and footshock (F, n = 80). After stress exposure the S and F rats were tested in an activity cage, and subsequently in an elevated plus maze (EPM), just prior to the sacrifice. Using cluster analysis, the animals already assigned to a stress level were also distributed into 2 subgroups depending on their Npas4 mRNA levels. The low (L) and high (H) Npas4 expression subgroups were identified in the S and F groups, the CTL group being independent of the Npas4 levels. The Npas4 effect was studied through the interaction between stress (S and F) and Npas4 level (L and H). The biological stress response was similar in H and L rats, except blood corticosterone that was slightly lower in the H rats. The H rats were more active in the actimetry cage and presented higher levels of exploration in the EPM. They also exhibited higher hippocampus activation, as assessed by the c-fos, Egr1 and Arc mRNA levels. Therefore high Npas4 expression favors stress management.

Role of tissue-type plasminogen activator and plasminogen activator inhibitor-1 in psychological stress and depression

Major depressive disorder is a common illness worldwide, but the pathogenesis of the disorder remains incompletely understood. The tissue-type plasminogen activator-plasminogen proteolytic cascade is highly expressed in the brain regions involved in mood regulation and neuroplasticity. Accumulating evidence from animal and human studies suggests that tissue-type plasminogen activator and its chief inhibitor, plasminogen activator inhibitor-1, are related to stress reaction and depression. Furthermore, the neurotrophic hypothesis of depression postulates that compromised neurotrophin brain-derived neurotrophic factor (BDNF) function is directly involved in the pathophysiology of depression. In the brain, the proteolytic cleavage of proBDNF, a BDNF precursor, to mature BDNF through plasmin represents one mechanism that can change the direction of BDNF action. We also discuss the implications of tissue-type plasminogen activator and plasminogen activator inhibitor-1 alterations as biomarkers for major depressive disorder. Using drugs that increase tissue-type plasminogen activator or decrease plasminogen activator inhibitor-1 levels may open new avenues to develop conceptually novel therapeutic strategies for depression treatment.

Environmental enrichment reduces chronic psychosocial stress-induced anxiety and ethanol-related behaviors in mice

Previous research from our laboratory has shown that exposure to chronic psychosocial stress increased voluntary ethanol consumption and preference as well as acquisition of ethanol-induced conditioned place preference (CPP) in mice. This study was done to determine whether an enriched environment could have "curative" effects on chronic psychosocial stress-induced ethanol intake and CPP. For this purpose, experimental mice "intruders" were exposed to the chronic subordinate colony (CSC) housing for 19 consecutive days in the presence of an aggressive "resident" mouse. At the end of that period, mice were tested for their anxiety-like behavior using the elevated plus maze (EPM) test then housed in a standard or enriched environment (SE or EE respectively). Anxiety and ethanol-related behaviors were investigated using the open field (OF) test, a standard two-bottle choice drinking paradigm, and the CPP procedure. As expected, CSC exposure increased anxiety-like behavior and reduced weight gain as compared to single housed colony (SHC) controls. In addition, CSC exposure increased voluntary ethanol intake and ethanol-CPP. Interestingly, we found that EE significantly and consistently reduced anxiety and ethanol consumption and preference. However, neither tastants' (saccharin and quinine) intake nor blood ethanol metabolism were affected by EE. Finally, and most importantly, EE reduced the acquisition of CPP induced by 1.5g/kg ethanol. Taken together, these results support the hypothesis that EE can reduce voluntary ethanol intake and ethanol-induced conditioned reward and seems to be one of the strategies to reduce the behavioral deficits and the risk of anxiety-induced alcohol abuse.

Peripheral blood mRNA expressions of stress biomarkers in manic episode and subsequent remission

Theoretical models of the neuroprogressive nature of bipolar disorder (BD) are based on the hypothesis that it is an accelerated aging disease, with the allostatic load playing a major role. Glucocorticoids, oxidative stress markers, inflammatory cytokines and neurotrophins play important roles in BD. The messenger ribonucleic acid (mRNA) expressions of brain-derived neurotrophic factor (BDNF), tissue plasminogen activator (tPA), glucocorticoid receptor (GR), heat shock protein 70 (HSP70), tumour necrosis factor-alpha (TNF-α) were examined in the peripheral blood of 20 adult male, drug-free BD patients during manic and remission periods and in 20 adult male, healthy controls. mRNA expression was measured using the quantitative real-time polymerase chain reaction (qRT-PCR). Compared to the controls, the expressions of BDNF and tPA mRNA were down-regulated in mania. In remission, BNDF and tPA mRNA levels increased, but they were still lower than those of the controls. Between mania and remission periods, only the change in mRNA levels of BDNF reached statistical significance. The results suggest that BDNF and tPA may be biomarkers of BD and that proteolytic conversion of BDNF may be important in the pathophysiology of BD. The change in BDNF levels between mania and remission could be adaptive and used to follow the progression of BD.

Plasminogen Activator Inhibitor-1 in depression: Results from Animal and Clinical Studies

Evidence suggests that plasminogen activator inhibitor-1 (PAI-1) is a stress-related factor, and serum PAI-1 levels are increased in patients with major depressive disorders (MDD). Herein, we analysed PAI-1 protein levels in the brain, cerebrospinal fluid (CSF) and serum of rodents exposed to chronic unpredictable mild stress or treated with escitalopram. In addition, we examined PAI-1 concentrations in serum obtained from 17 drug-free depressed patients before and after escitalopram treatment. We found that PAI-1 expression was increased in area 1 of the cingulate cortex and prelimbic cortex of the medial prefrontal cortex as well as in the hippocampal cornu ammonis 3 and dentate gyrus in stressed rats. A downregulation of PAI-1 following chronic escitalopram treatment was also found. PAI-1 levels were higher in the CSF and serum in stressed rats than in controls, although the difference did not reach statistical significance in the serum. Escitalopram treatment significantly decreased PAI-1 levels in the serum, but not in the CSF. MDD patients had significantly greater serum PAI-1 concentrations than controls. Our results suggest that PAI-1 is implicated in the pathophysiology of depression.

Nucleus accumbens lentiviral-mediated gain of function of the oxytocin receptor regulates anxiety- and ethanol-related behaviors in adult mice

Anxiety is believed to influence ethanol use human in alcoholics. Studies using laboratory animals suggested an interaction between oxytocin and the behavioral effects of ethanol. Our previous study implicated a potential role for the oxytocin receptor (OxtR) in regulating ethanol-conditioned place preference. Here, we examined anxiety and the behavioral responses to ethanol in C57BL/6 mice stereotaxically injected in the nucleus accumbens (NAcc) with lentiviral vectors expressing an empty vector (Mock) or the OxtR cDNA. For anxiety we used the elevated-plus maze, the open-field and the marble-burying tests and for ethanol we used the two-bottle choice paradigm, the wire-hanging and ethanol-induced loss-of-righting-reflex tests. We found that, compared to Mock, OxtR overexpression led to anxiolytic-like behavior without altering spontaneous locomotor activity. Most importantly, we found that, relative to Mock controls, increased expression of the OxtR in the NAcc led to decreased ethanol consumption and preference in the two-bottle choice protocol and increased resistance to ethanol-induced sedation. We also compared the consequence of OxtR modulation on the consumption and preference of saccharin and quinine and found that the two experimental groups did not differ for any tastant. These results provide further evidence that the oxytocin system contributes to the regulation of ethanol drinking and sensitivity and position OxtR as a central molecular mediator of ethanol's effects within the mesolimbic system. Taken together, the current findings suggest that OxtR manipulation may be a relevant strategy to address ethanol use disorders.

Morphological and behavioral characterization of adult mice deficient for SrGAP3

SrGAP3 belongs to the family of Rho GTPase proteins. These proteins are thought to play essential roles in development and in the plasticity of the nervous system. SrGAP3-deficient mice have recently been created and approximately 10 % of these mice developed a hydrocephalus and died shortly after birth. The others survived into adulthood, but displayed neuroanatomical alteration, including increased ventricular size. We now show that SrGAP3-deficient mice display increased brain weight together with increased hippocampal volume. This increase was accompanied by an increase of the thickness of the stratum oriens of area CA1 as well as of the thickness of the molecular layer of the dentate gyrus (DG). Concerning hippocampal adult neurogenesis, we observed no significant change in the number of proliferating cells. The density of doublecortin-positive cells also did not vary between SrGAP3-deficient mice and controls. By analyzing Golgi-impregnated material, we found that, in SrGAP3-deficient mice, the morphology and number of dendritic spines was not altered in the DG. Likewise, a Sholl-analysis revealed no significant changes concerning dendritic complexity as compared to controls. Despite the distinct morphological alterations in the hippocampus, SrGAP3-deficient mice were relatively inconspicuous in their behavior, not only in the open-field, nest building but also in the Morris water-maze. However, the SrGAP3-deficient mice showed little to no interest in burying marbles; a behavior that is seen in some animal models related to autism, supporting the view that SrGAP3 plays a role in neurodevelopmental disorders.

Sustained lentiviral-mediated overexpression of microRNA124a in the dentate gyrus exacerbates anxiety- and autism-like behaviors associated with neonatal isolation in rats

Autism spectrum disorders (ASD) are highly disabling psychiatric disorders. Despite a strong genetic etiology, there are no efficient therapeutic interventions that target the core symptoms of ASD. Emerging evidence suggests that dysfunction of microRNA (miR) machinery may contribute to the underlying molecular mechanisms involved in ASD. Here, we report a stress model demonstrating that neonatal isolation-induced long-lasting hippocampal elevation of miR124a was associated with reduced expression of its target BDNF mRNA. In addition, we investigated the impact of lentiviral-mediated overexpression of miR124a into the dentate gyrus (DG) on social interaction, repetitive- and anxiety-like behaviors in the neonatal isolation (Iso) model of autism. Rats isolated from the dams on PND 1 to PND 11 were assessed for their social interaction, marble burying test (MBT) and repetitive self-grooming behaviors as adults following miR124a overexpression. Also, anxiety-like behavior and locomotion were evaluated in the elevated plus maze (EPM) and open-field (OF) tests. Results show that, consistent with previously published reports, Iso rats displayed decreased social interaction contacts but increased repetitive- and anxiety-like behaviors. Interestingly, across both autism- and anxiety-like behavioral assays, miR124a overexpression in the DG significantly exacerbated repetitive behaviors, social impairments and anxiety with no effect on locomotor activity. Our novel findings attribute neonatal isolation-inducible cognitive impairments to induction of miR124a and consequently suppressed BDNF mRNA, opening venues for intercepting these miR124a-mediated damages. They also highlight the importance of studying microRNAs in the context of ASD and identify miR124a as a novel potential therapeutic target for improving mood disorders.

Mice with Sort1 deficiency display normal cognition but elevated anxiety-like behavior

Exposure to stressful life events plays a central role in the development of mood disorders in vulnerable individuals. However, the mechanisms that link mood disorders to stress are poorly understood. Brain-derived neurotrophic factor (BDNF) has long been implicated in positive regulation of depression and anxiety, while its precursor (proBDNF) recently showed an opposing effect on such mental illnesses. P75(NTR) and sortilin are co-receptors of proBDNF, however, the role of these receptors in mood regulation is not established. Here, we aimed to investigate the role of sortilin in regulating mood-related behaviors and its role in the proBDNF-mediated mood abnormality in mice. We found that sortilin was up-regulated in neocortex (by 78.3%) and hippocampus (by 111%) of chronically stressed mice as assessed by western blot analysis. These changes were associated with decreased mobility in the open field test and increased depression-like behavior in the forced swimming test. We also found that sortilin deficiency in mice resulted in hyperlocomotion in the open field test and increased anxiety-like behavior in both the open field and elevated plus maze tests. No depression-like behavior in the forced swimming test and no deficit in spatial cognition in the Morris water maze test were found in the Sort1-deficient mice. Moreover, the intracellular and extracellular levels of mature BDNF and proBDNF were not changed when sortilin was absent in vivo and in vitro. Finally, we found that both WT and Sort1-deficient mice injected with proBDNF in lateral ventricle displayed increased depression-like behavior in the forced swimming test but not anxiety-like behaviors in the open field and elevated plus maze tests. The present study suggests that sortilin functions as a negative regulator of mood performance and can be a therapeutic target for the treatment of mental illness.

Neuropeptide Y administration reverses tricyclic antidepressant treatment-resistant depression induced by ACTH in mice

Depression is one of the most common mental disorders and a primary cause of disability. To better treat patients suffering this illness, elucidation of the underlying psychopathological and neurobiological mechanisms is urgently needed. Based on the above-mentioned evidence, we sought to investigate the effects of neuropeptide Y (NPY) treatment in tricyclic antidepressant treatment-resistant depression induced by adrenocorticotropic hormone (ACTH) administration. Mice were treated with NPY (5.84, 11.7 or 23.4mmol/μl) intracerebroventricularly (i.c.v.) for one or five days. The levels of serum corticosterone, tryptophan (TRP), kynurenine (KYN), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) and indoleamine 2,3-dioxygenase (IDO) activity in the hippocampus were analyzed. The behavioral parameters (depressive-like and locomotor activity) were also verified. This study demonstrated that ACTH administration increased serum corticosterone levels, KYN, 5-HIAA levels, IDO activity (hippocampus), immobility in the forced swimming test (FST) and the latency to feed in the novelty suppressed feeding test (NSFT). In addition, ACTH administration decreased the BDNF and NGF levels in the hippocampus of mice. NPY treatment was effective in preventing these hormonal, neurochemical and behavioral alterations. It is suggested that the main target of NPY is the modulation of corticosterone and neuronal plasticity protein levels, which may be closely linked with pharmacological action in a model of tricyclic antidepressant treatment-resistant depression. Thus, this study demonstrated a protective effect of NPY on the alterations induced by ACTH administration in mice, indicating that it could be useful as a therapy for the treatment of tricyclic antidepressant treatment-resistant depression.

Selective lentiviral-mediated suppression of microRNA124a in the hippocampus evokes antidepressants-like effects in rats

Several lines of evidences suggest that the brain-derived neutrophic factor (BDNF) is implicated in the pathophysiology of depression. However, the molecular mechanisms are not fully understood. In the current study we aimed to investigate how genetic modulation of BDNF in the hippocampus using microRNa124a (miR124a)-expressing lentiviral vectors (LV) might affect depression-like behavior in adult rats. For this purpose, we assessed the expression level of miR124a and its direct target BDNF in the hippocampus and the cortex after 21-days exposure to social defeat stress. Results demonstrated that miR124a was up-regulated in the hippocampus but not in the cortex. In contrast, and as expected, BDNF transcripts were down-regulated. In a different set of experiments, male Wistar rats received bilateral intra-hippocampal or intra-cortical infusions of BDNF- and miR124a-expressing lentiviral vectors and depression-like behavior was assessed after 21-days social defeat stress using the novelty suppressed feeding, the sucrose preference and the forced swim tests. The results indicated that miR124a overexpression exacerbated depression-like behavior. However, an anti-depressant like effect was observed when BDNF or miR124a-silencers (siR124a) were injected into the hippocampus. Importantly, when expressed into the cortex, LV-miR124a, LV-siR124a and LV-BDNF had no effect on depression. Our findings indicate that hippocampal miR124a and its direct target BDNF play an important role in depression-like behavior. Taken together, the current results reveal, for the first time, a potential molecular regulation of miR124a on BDNF, and the pronounced behavioral consequences of this regulation shed light on the mechanisms underlying BDNF anti-depressant potential.

β-Caryophyllene, a CB2 receptor agonist produces multiple behavioral changes relevant to anxiety and depression in mice

Recent evidence suggests that the cannabinoid receptor subtype 2 (CB2) is implicated in anxiety and depression disorders, although few systematic studies in laboratory animals have been reported. The aim of the current experiments was to test the effects of the CB2 receptor potent-selective agonist β-caryophyllene (BCP) in animals subjected to models of anxiolytic- and antidepressant-like effects. Therefore effects of BCP (50mg/kg) on anxiety were assessed using the elevated plus maze (EPM), open field (OF), and marble burying test (MBT). However for depression, the novelty-suppressed feeding (NSF), tail suspension test (TST), and forced swim tests (FST) were used. Results indicated that adult mice receiving BCP showed amelioration of all the parameters observed in the EPM test. Also, BCP significantly increased the time spent in the center of the arena without altering the general motor activity in the OF test. This dose was also able to decrease the number of buried marbles and time spent digging in the MBT, suggesting an anti-compulsive-like effect. In addition, the systemic administration of BCP reduced immobility time in the TST and the FST. Finally, BCP treatment decreased feeding latency in the NSF test. Most importantly, pre-administration of the CB2 receptor antagonist AM630, fully abrogated the anxiolytic and the anti-depressant effects of BCP. Taken together, these preclinical results suggest that CB2 receptors may provide alternative therapeutic targets for the treatment of anxiety and depression. The possibility that BCP may ameliorate the symptoms of these mood disorders offers exciting prospects for future studies.

Altered behavior in mice with deletion of the alpha2-antiplasmin gene

Background

The α2-antiplasmin (α2AP) protein is known to be a principal physiological inhibitor of plasmin, and is expressed in various part of the brain, including the hippocampus, cortex, hypothalamus and cerebellum, thus suggesting a potential role for α2AP in brain functions. However, the involvement of α2AP in brain functions is currently unclear.

Objectives

The goal of this study was to investigate the effects of the deletion of the α2AP gene on the behavior of mice.

Methods

The motor function was examined by the wire hang test and rotarod test. To evaluate the cognitive function, a repeated rotarod test, Y-maze test, Morris water maze test, passive or shuttle avoidance test and fear conditioning test were performed. An open field test, dark/light transition test or tail suspension test was performed to determine the involvement of α2AP in anxiety or depression-like behavior.

Results and Conclusions

The α2AP knockout (α2AP^−/−) mice exhibited impaired motor function compared with α2AP^+/+ mice. The α2AP^−/− mice also exhibited impairments in motor learning, working memory, spatial memory and fear conditioning memory. Furthermore, the deletion of α2AP induced anxiety-like behavior, and caused an anti-depression-like effect in tail suspension. Therefore, our findings suggest that α2AP is a crucial mediator of motor function, cognitive function, anxiety-like behavior and depression-like behavior, providing new insights into the role of α2AP in the brain functions.

Anxiolytic and antidepressant-like activities of the novel and potent non-imidazole histamine H₃ receptor antagonist ST-1283

Previous studies have suggested a potential link between histamine H₃ receptors (H₃R) signaling and anxiolytic-like and antidepressant-like effects. The aim of this study was to investigate the acute effects of ST-1283, a novel H₃R antagonist, on anxiety-related and depression-related behaviors in comparison with those of diazepam and fluoxetine. The effects of ST-1283 were evaluated using the elevated plus maze test, open field test, marbles burying test, tail suspension test, novelty suppressed feeding test, and forced swim test in male C57BL/6 mice. The results showed that, like diazepam, ST-1283 (7.5 mg/kg) significantly modified all the parameters observed in the elevated plus maze test. In addition, ST-1283 significantly increased the amount of time spent in the center of the arena without altering general motor activity in the open field test. In the same vein, ST-1283 reduced the number of buried marbles as well as time spent digging in the marbles burying test. The tail suspension test and forced swim test showed that ST-1283 was able to reduce immobility time, like the recognized antidepressant drug fluoxetine. In the novelty suppressed feeding test, treatment with ST-1283 decreased latency to feed with no effect on food intake in the home cage. Importantly, pretreatment with the H₃R agonist R-α-methylhistamine abrogated the anxiolytic and antidepressant effects of ST-1283. Taken together, the present series of studies demonstrates the novel effects of this newly synthesized H₃R antagonist in a number of preclinical models of psychiatric disorders and highlights the histaminergic system as a potential therapeutic target for the treatment of anxiety-related and depression-related disorders.

Lentiviral delivery of a vesicular glutamate transporter 1 (VGLUT1)-targeting short hairpin RNA vector into the mouse hippocampus impairs cognition

Glutamate is the principle excitatory neurotransmitter in the mammalian brain, and dysregulation of glutamatergic neurotransmission is implicated in the pathophysiology of several psychiatric and neurological diseases. This study utilized novel lentiviral short hairpin RNA (shRNA) vectors to target expression of the vesicular glutamate transporter 1 (VGLUT1) following injection into the dorsal hippocampus of adult mice, as partial reductions in VGLUT1 expression should attenuate glutamatergic signaling and similar reductions have been reported in schizophrenia. The VGLUT1-targeting vector attenuated tonic glutamate release in the dorsal hippocampus without affecting GABA, and selectively impaired novel object discrimination (NOD) and retention (but not acquisition) in the Morris water maze, without influencing contextual fear-motivated learning or causing any adverse locomotor or central immune effects. This pattern of cognitive impairment is consistent with the accumulating evidence for functional differentiation along the dorsoventral axis of the hippocampus, and supports the involvement of dorsal hippocampal glutamatergic neurotransmission in both spatial and nonspatial memory. Future use of this nonpharmacological VGLUT1 knockdown mouse model could improve our understanding of glutamatergic neurobiology and aid assessment of novel therapies for cognitive deficits such as those seen in schizophrenia.

Chronic psychosocial stress causes delayed extinction and exacerbates reinstatement of ethanol-induced conditioned place preference in mice

RATIONALE

We have shown previously, using an animal model of voluntary ethanol intake and ethanol-conditioned place preference (EtOH-CPP), that exposure to chronic psychosocial stress induces increased ethanol intake and EtOH-CPP acquisition in mice.

OBJECTIVE

Here, we examined the impact of chronic subordinate colony (CSC) exposure on EtOH-CPP extinction, as well as ethanol-induced reinstatement of CPP.

METHODS

Mice were conditioned with saline or 1.5 g/kg ethanol and were tested in the EtOH-CPP model. In the first experiment, the mice were subjected to 19 days of chronic stress, and EtOH-CPP extinction was assessed during seven daily trials without ethanol injection. In the second experiment and after the EtOH-CPP test, the mice were subjected to 7 days of extinction trials before the 19 days of chronic stress. Drug-induced EtOH-CPP reinstatement was induced by a priming injection of 0.5 g/kg ethanol.

RESULTS

Compared to the single-housed colony mice, CSC mice exhibited increased anxiety-like behavior in the elevated plus maze (EPM) and the open field tests. Interestingly, the CSC mice showed delayed EtOH-CPP extinction. More importantly, CSC mice showed increased alcohol-induced reinstatement of the EtOH-CPP behavior.

CONCLUSION

Taken together, this study indicates that chronic psychosocial stress can have long-term effects on EtOH-CPP extinction as well as drug-induced reinstatement behavior and may provide a suitable model to study the latent effects of chronic psychosocial stress on extinction and relapse to drug abuse.

Stress and trauma: BDNF control of dendritic-spine formation and regression

Chronic restraint stress leads to increases in brain derived neurotrophic factor (BDNF) mRNA and protein in some regions of the brain, e.g. the basal lateral amygdala (BLA) but decreases in other regions such as the CA3 region of the hippocampus and dendritic spine density increases or decreases in line with these changes in BDNF. Given the powerful influence that BDNF has on dendritic spine growth, these observations suggest that the fundamental reason for the direction and extent of changes in dendritic spine density in a particular region of the brain under stress is due to the changes in BDNF there. The most likely cause of these changes is provided by the stress initiated release of steroids, which readily enter neurons and alter gene expression, for example that of BDNF. Of particular interest is how glucocorticoids and mineralocorticoids tend to have opposite effects on BDNF gene expression offering the possibility that differences in the distribution of their receptors and of their downstream effects might provide a basis for the differential transcription of the BDNF genes. Alternatively, differences in the extent of methylation and acetylation in the epigenetic control of BDNF transcription are possible in different parts of the brain following stress. Although present evidence points to changes in BDNF transcription being the major causal agent for the changes in spine density in different parts of the brain following stress, steroids have significant effects on downstream pathways from the TrkB receptor once it is acted upon by BDNF, including those that modulate the density of dendritic spines. Finally, although glucocorticoids play a canonical role in determining BDNF modulation of dendritic spines, recent studies have shown a role for corticotrophin releasing factor (CRF) in this regard. There is considerable improvement in the extent of changes in spine size and density in rodents with forebrain specific knockout of CRF receptor 1 (CRFR1) even when the glucocorticoid pathways are left intact. It seems then that CRF does have a role to play in determining BDNF control of dendritic spines.

Impaired learning resulting from respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the major cause of respiratory illness in infants worldwide. Neurologic alterations, such as seizures and ataxia, have been associated with RSV infection. We demonstrate the presence of RSV proteins and RNA in zones of the brain--such as the hippocampus, ventromedial hypothalamic nucleus, and brainstem--of infected mice. One month after disease resolution, rodents showed behavioral and cognitive impairment in marble burying (MB) and Morris water maze (MWM) tests. Our data indicate that the learning impairment caused by RSV is a result of a deficient induction of long-term potentiation in the hippocampus of infected animals. In addition, immunization with recombinant bacillus Calmette-Guérin (BCG) expressing RSV nucleoprotein prevented behavioral disorders, corroborating the specific effect of RSV infection over the central nervous system. Our findings provide evidence that RSV can spread from the airways to the central nervous system and cause functional alterations to the brain, both of which can be prevented by proper immunization against RSV.

Individual differences in elevated plus-maze exploration predicted higher ethanol consumption and preference in outbred mice

Psychiatric illnesses, such as anxiety, are highly comorbid with drug use disorders in general and alcohol abuse in particular. Unfortunately, the causal role of anxiety in ethanol addiction is still unclear. We asked the question whether high anxiety predicts predilection of mice to voluntarily consume more alcohol than water. In the current study, we used the voluntary alcohol intake in two bottle choice drinking paradigm to explore whether high anxiety predicts higher alcohol preference and intake in outbred Tuck-Ordinary "TO" mice. To this end, mice were tested for their anxiety-like behavior using the elevated plus maze, open field and the marble burying test prior to voluntary continuous access to increasing concentrations of alcohol solutions. To assess their taste discrimination, mice had access to saccharin and quinine solutions. Results showed that compared to low-anxious mice (LAM), high-anxious mice (HAM) showed greater consumption and preference for ethanol but not for saccharin and quinine suggesting alterations in the rewarding effects of alcohol. Taken together, these findings suggest a correlative link between trait anxiety and the behavioral responses to ethanol.

Trypanosoma cruzi-induced depressive-like behavior is independent of meningoencephalitis but responsive to parasiticide and TNF-targeted therapeutic interventions

Inflammatory cytokines and microbe-borne immunostimulators have emerged as triggers of depressive behavior. Behavioral alterations affect patients chronically infected by the parasite Trypanosoma cruzi. We have previously shown that C3H/He mice present acute phase-restricted meningoencephalitis with persistent central nervous system (CNS) parasitism, whereas C57BL/6 mice are resistant to T. cruzi-induced CNS inflammation. In the present study, we investigated whether depression is a long-term consequence of acute CNS inflammation and a contribution of the parasite strain that infects the host. C3H/He and C57BL/6 mice were infected with the Colombian (type I) and Y (type II) T. cruzi strains. Forced-swim and tail-suspension tests were used to assess depressive-like behavior. Independent of the mouse lineage, the Colombian-infected mice showed significant increases in immobility times during the acute and chronic phases of infection. Therefore, T. cruzi-induced depression is independent of active or prior CNS inflammation. Furthermore, chronic depressive-like behavior was triggered only by the type I Colombian T. cruzi strain. Acute and chronic T. cruzi infection increased indoleamine 2,3-dioxygenase (IDO) expression in the CNS. Treatment with the selective serotonin reuptake inhibitor (SSRI) fluoxetine abrogated the T. cruzi-induced depressive-like behavior. Moreover, treatment with the parasiticide drug benznidazole abrogated depression. Chronic T. cruzi infection of C57BL/6 mice increased tumor necrosis factor (TNF) expression systemically but not in the CNS. Importantly, TNF modulators (anti-TNF and pentoxifylline) reduced immobility. Therefore, direct or indirect parasite-induced immune dysregulation may contribute to chronic depressive disorder in T. cruzi infection, which opens a new therapeutic pathway to be explored.