Corticosterone antagonist or TrkB agonist attenuates schizophrenia-like behavior in a mouse model combining Bdnf-e6 deficiency and developmental stress

Targeting TrkB-PSD-95 coupling to mitigate neurological disorders

Tropomyosin receptor kinase B (TrkB) signaling plays a pivotal role in dendritic growth and dendritic spine formation to promote learning and memory. The activity-dependent release of brain-derived neurotrophic factor at synapses binds to pre- or postsynaptic TrkB resulting in the strengthening of synapses, reflected by long-term potentiation. Postsynaptically, the association of postsynaptic density protein-95 with TrkB enhances phospholipase Cγ-Ca2+/calmodulin-dependent protein kinase II and phosphatidylinositol 3-kinase-mechanistic target of rapamycin signaling required for long-term potentiation. In this review, we discuss TrkB-postsynaptic density protein-95 coupling as a promising strategy to magnify brain-derived neurotrophic factor signaling towards the development of novel therapeutics for specific neurological disorders. A reduction of TrkB signaling has been observed in neurodegenerative disorders, such as Alzheimer's disease and Huntington's disease, and enhancement of postsynaptic density protein-95 association with TrkB signaling could mitigate the observed deficiency of neuronal connectivity in schizophrenia and depression. Treatment with brain-derived neurotrophic factor is problematic, due to poor pharmacokinetics, low brain penetration, and side effects resulting from activation of the p75 neurotrophin receptor or the truncated TrkB.T1 isoform. Although TrkB agonists and antibodies that activate TrkB are being intensively investigated, they cannot distinguish the multiple human TrkB splicing isoforms or cell type-specific functions. Targeting TrkB-postsynaptic density protein-95 coupling provides an alternative approach to specifically boost TrkB signaling at localized synaptic sites versus global stimulation that risks many adverse side effects.

Maternal Resveratrol Supplementation Attenuates Prenatal Stress Impacts on Anxiety- and Depressive-like Behaviors by Regulating Bdnf Transcripts Expression in the Brains of Adult Male Offspring Rats

BACKGROUND

Prenatal stress has been reported to harm the physiological and biochemical functions of the brain of the offspring, potentially resulting in anxiety- and depression-like behaviors later in life. Trans-Resveratrol (RESV) is known for its anti-inflammatory, anxiolytic, and antidepressant properties. However, whether administering RESV during pregnancy can counteract the anxiety- and depression-like behaviors induced by maternal stress is unknown.

OBJECTIVE

This study aimed to assess the protective potential of RESV against molecular and behavioral changes induced by prenatal stress.

METHODS

During pregnancy, the dams received 50 mg/kg BW/day of RESV orally. They underwent a movement restriction for forty-five minutes, three times a day, in addition to being exposed to artificial light 24 h before delivery. The male offspring were left undisturbed until early adulthood, at which point they underwent behavioral assessments, including the open field test, elevated plus maze, and forced swim test. Subsequently, they were euthanized, and the hippocampus and prefrontal cortex were extracted for RT-qPCR analysis to measure Bdnf mRNA expression.

RESULTS

By weaning, results showed that prenatal stress led to reduced weight gain and, in adulthood, increased anxiety- and depression-like behaviors and changes in Bdnf mRNA expression. However, these effects were attenuated by maternal RESV supplementation.

CONCLUSIONS

The findings suggest that RESV can prevent anxiety- and depression-like behaviors induced by prenatal stress by modulating Bdnf mRNA expression.

The Role of Brain-Derived Neurotrophic Factor as an Essential Mediator in Neuronal Functions and the Therapeutic Potential of Its Mimetics for Neuroprotection in Neurologic and Psychiatric Disorders

Among neurotrophins, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4/5), BDNF has been extensively studied for its physiological role in cell survival and synaptic regulation in the central nervous system's (CNS's) neurons. BDNF binds to TrkB (a tyrosine kinase) with high affinity, and the resulting downstream intracellular signaling cascades play crucial roles in determining cell fate, including neuronal differentiation and maturation of the CNS neurons. It has been well demonstrated that the downregulation/dysregulation of the BDNF/TrkB system is implicated in the pathogenesis of neurologic and psychiatric disorders, such as Alzheimer's disease (AD) and depression. Interestingly, the effects of BDNF mimetic compounds including flavonoids, small molecules which can activate TrkB-mediated signaling, have been extensively investigated as potential therapeutic strategies for brain diseases, given that p75NTR, a common neurotrophin receptor, also contributes to cell death under a variety of pathological conditions such as neurodegeneration. Since the downregulation of the BDNF/TrkB system is associated with the pathophysiology of neurodegenerative diseases and psychiatric disorders, understanding how alterations in the BDNF/TrkB system contribute to disease progression could provide valuable insight for the prevention of these brain diseases. The present review shows recent advances in the molecular mechanisms underlying the BDNF/TrkB system in neuronal survival and plasticity, providing critical insights into the potential therapeutic impact of BDNF mimetics in the pathophysiology of brain diseases.

Key regions aberrantly connected within cerebello-thalamo-cortical circuit and their genetic mechanism in schizophrenia: an fMRI meta-analysis and transcriptome study

Recent studies have showed aberrant connectivity of cerebello-thalamo-cortical circuit (CTCC) in schizophrenia (SCZ), which might be a heritable trait. However, these individual studies vary greatly in their methods and findings, and important areas within CTCC and related genetic mechanism are unclear. We searched for consistent regions of circuit dysfunction using a functional magnetic resonance imaging (fMRI) meta-analysis, followed by meta-regression and functional annotation analysis. Gene annotation analysis was performed to identify genes over-expressed in these regions by using the Allen Human Brain Atlas, followed by a set of gene functional feature analyses. 19 studies (1333 patients and 1174 healthy controls) were included in this meta-analysis. SCZ was characterized by hyperconnectivity of the auditory network, visual system, and sensorimotor areas, and hypoconnectivity of the frontal gyrus, cerebellum, thalamus, and caudate nucleus, which were significantly linked to age, sex, duration of illness, and the severity of symptoms and functionally enriched in domains involving self, sensory, action, and social. 2922 genes were significantly over-expressed in these regions, which were enriched for important molecular functions, biological processes, and cellular components of the neurons/cells in the brain as well as SCZ and other mental diseases. These genes were specially expressed in the brain tissue, in the neurons of the cerebellum, subcortex and cortex and during nearly all developmental stages, and constructed a protein-protein interaction network supported by 85 hub genes with functional significance. These findings suggest key regions aberrantly connected within CTCC in SCZ, which may indicate the neural substrate of "cognitive dysmetria" and be a consequence of complex interactions from a wide range of genes with diverse functional features.

Olanzapine Induces Adipogenesis and Glucose Uptake by Activating Glycolysis and Synergizing with the PI3K-AKT Pathway

BACKGROUND

Administration of olanzapine (OLA) is closely associated with obesity and glycolipid abnormalities in patients with schizophrenia (SCZ), although the exact molecular mechanisms remain elusive.

OBJECTIVE

We conducted comprehensive animal and molecular experiments to elucidate the mechanisms underlying OLA-induced weight gain.

METHODS

We investigated the mechanisms of OLA-induced adipogenesis and lipid storage by employing a real-time ATP production rate assay, glucose uptake test, and reactive oxygen species (ROS) detection in 3T3-L1 cells and AMSCs. Rodent models were treated with OLA using various intervention durations, dietary patterns (normal diets/western diets), and drug doses. We assessed body weight, epididymal and liver fat levels, and metabolic markers in both male and female mice.

RESULTS

OLA accelerates adipogenesis by directly activating glycolysis and its downstream PI3K signaling pathway in differentiated adipocytes. OLA promotes glucose uptake in differentiated 3T3-L1 preadipocytes. In mouse models with normal glycolipid metabolism, OLA administration failed to increase food intake and weight gain despite elevated GAPDH expression, a marker related to glycolysis and PI3K-AKT. This supports the notion that glycolysis plays a significant role in OLA-induced metabolic dysfunction.

CONCLUSION

OLA induces glycolysis and activates the downstream PI3K-AKT signaling pathway, thereby promoting adipogenesis.

Effects of chronic empathic stress on synaptic efficacy, as well as short-term and long-term plasticity at the Schaffer collateral/commissural- CA1 synapses in the dorsal hippocampus of rats

Empathy, the ability to comprehend and share others' emotional states, impacts brain functions. This in vivo electrophysiological study explored the influence of chronic empathic stress on synaptic efficacy, as well as short-term and long-term plasticity at the Schaffer collateral/Commissural - CA1 synapses in the dorsal hippocampus of rats, in situations of social equality and inequality. Forty-eight male rats were randomized into six groups: control, pseudo-observer, pseudo-demonstrator, observer, demonstrator, and co-demonstrator (Co, Pse-Ob, Pse-De, Ob, De, Co-De) groups. Stress induction (2h/day, 21 days) was performed in situations of equality and inequality. Serum corticosterone levels, slope, amplitude, and area under the curve (AUC) of field excitatory postsynaptic potentials (fEPSPs) were assessed in the hippocampal CA1 area using input-output (I/O) functions, paired-pulse (PP) responses with different interpulse intervals (IPIs), and long-term potentiation (LTP) after high-frequency stimulation (HFS). The fEPSP slope, amplitude, and AUC significantly decreased in all stress groups, especially in the De and Pse-De groups. These parameters were significantly increased in the Co-De and Ob groups compared to the De group. Notably, the corticosterone levels strongly confirmed the electrophysiological findings. Chronic empathic stress could disrupt synaptic efficacy and plasticity in the CA1 area. Empathic stress, involving the presence of cagemates in situations of social equality and inequality, can modify long-term plasticity and serum corticosterone levels in demonstrators and co-demonstrators. Under empathic stress related to situations of inequality, freely moving observers may influence the demonstrators' stress experience. Therefore, the presence of a conspecific in the social inequality conditions had significant suppressive effects on long-term plasticity, while conversely, under equality conditions, long-term plasticity was favorably improved through social buffering.

Advances in the study of phencyclidine-induced schizophrenia-like animal models and the underlying neural mechanisms

Schizophrenia (SZ) is a chronic, severe mental disorder with heterogeneous clinical manifestations and unknown etiology. Research on SZ has long been limited by the low reliability of and ambiguous pathogenesis in schizophrenia animal models. Phencyclidine (PCP), a noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, rapidly induces both positive and negative symptoms of SZ as well as stable SZ-related cognitive impairment in rodents. However, the neural mechanism underlying PCP-induced SZ-like symptoms is not fully understood. Nondopaminergic pathophysiology, particularly excessive glutamate release induced by NMDAR hypofunction in the prefrontal cortex (PFC), may play a key role in the development of PCP-induced SZ-like symptoms. In this review, we summarize studies on the behavioral and metabolic effects of PCP and the cellular and circuitary targets of PCP in the PFC and hippocampus (HIP). PCP is thought to target the ventral HIP-PFC pathway more strongly than the PFC-VTA pathway and thalamocortical pathway. Systemic PCP administration might preferentially inhibit gamma-aminobutyric acid (GABA) neurons in the vHIP and in turn lead to hippocampal pyramidal cell disinhibition. Excitatory inputs from the HIP may trigger sustained, excessive and pathological PFC pyramidal neuron activation to mediate various SZ-like symptoms. In addition, astrocyte and microglial activation and oxidative stress in the cerebral cortex or hippocampus have been observed in PCP-induced models of SZ. These findings perfect the hypoglutamatergic hypothesis of schizophrenia. However, whether these effects direct the consequences of PCP administration and how about the relationships between these changes induced by PCP remain further elucidation through rigorous, causal and direct experimental evidence.

Changes in BDNF methylation patterns after cognitive remediation therapy in schizophrenia: A randomized and controlled trial

Although cognitive remediation therapy (CRT) produces cognitive benefits in schizophrenia, we do not yet understand whether molecular changes are associated with this cognitive improvement. A gene central to synaptic plasticity, the BDNF, has been proposed as one potential route. This study assesses whether BDNF methylation changes following CRT-produced cognitive improvement are detected. A randomized and controlled trial was performed with two groups (CRT, n = 40; TAU: Treatment as Usual, n = 20) on a sample of participants with schizophrenia. CRT was delivered by trained therapists using a web-based computerized program. Mixed Models, where the interaction of treatment (CRT, TAU) by time (T0: 0 weeks, T1: 16 weeks) was the main effect were used. Then, we tested the association between the treatment and methylation changes in three CpG islands of the BDNF gene. CRT group showed significant improvements in some cognitive domains. Between-groups differential changes in 5 CpG units over time were found, 4 in island 1 (CpG1.2, CpG1.7, CpG1.10, CpG1.17) and 1 in island 3 (CpG3.2). CRT group showed increases in methylation in CpG1.2, CpG1.7 and decreases in pG1.10, CpG1.17, and CpG3.2. Differences in the degree of methylation were associated with changes in Speed of Processing, Working Memory, and Verbal Learning within the CRT group. Those findings provide new data on the relationship between cognitive improvement and changes in peripheral methylation levels of BDNF gene, a key factor involved in neuroplasticity regulation. Trial Registration: NCT04278027.

Recent advances in the crosstalk between the brain-derived neurotrophic factor and glucocorticoids

Brain-derived neurotrophic factor (BDNF), a key neurotrophin within the brain, by selectively activating the TrkB receptor, exerts multimodal effects on neurodevelopment, synaptic plasticity, cellular integrity and neural network dynamics. In parallel, glucocorticoids (GCs), vital steroid hormones, which are secreted by adrenal glands and rapidly diffused across the mammalian body (including the brain), activate two different groups of intracellular receptors, the mineralocorticoid and the glucocorticoid receptors, modulating a wide range of genomic, epigenomic and postgenomic events, also expressed in the neural tissue and implicated in neurodevelopment, synaptic plasticity, cellular homeostasis, cognitive and emotional processing. Recent research evidences indicate that these two major regulatory systems interact at various levels: they share common intracellular downstream pathways, GCs differentially regulate BDNF expression, under certain conditions BDNF antagonises the GC-induced effects on long-term potentiation, neuritic outgrowth and cellular death, while GCs regulate the intraneuronal transportation and the lysosomal degradation of BDNF. Currently, the BDNF-GC crosstalk features have been mainly studied in neurons, although initial findings show that this crosstalk could be equally important for other brain cell types, such as astrocytes. Elucidating the precise neurobiological significance of BDNF-GC interactions in a tempospatial manner, is crucial for understanding the subtleties of brain function and dysfunction, with implications for neurodegenerative and neuroinflammatory diseases, mood disorders and cognitive enhancement strategies.

Aripiprazole combined with nerve growth factor improves cognitive function in mice with schizophrenia model

The pathogenesis and treatment of cognitive dysfunction in patients with schizophrenia (SCZ) remains a challenge. Exploring new effective treatment strategies is relevant for the improvement of cognitive function. Aripiprazole (ARI) is an atypical antipsychotic that improves some cognitive functions. Nerve growth factor (NGF) has been shown to improve cognitive function in certain neurological impairments and partial neurological deficits, but its mechanism of action in cognitive dysfunction in SCZ is unclear. In this study, we established schizophrenia mouse model with dizocilpine (MK-801); treated mice with ARI alone or in combination with NGF; assessed spontaneous activity and cognitive function using open field test and Morris water maze test; and measured brain-derived neurotrophic factor (BDNF) protein and mRNA expression levels using immunohistochemistry and molecular biology assays. The results showed that ARI alone or in combination with NGF can improve increased spontaneous activity and spatial learning memory deficits in model mice by elevating BDNF expression levels in prefrontal cortex (PFC) and hippocampus (HIP). The results suggest that ARI combined with NGF can improve cognitive function in SCZ, which provides new ideas and directions for the clinical treatment of cognitive dysfunction in SCZ.

Diverse Functions of Multiple Bdnf Transcripts Driven by Distinct Bdnf Promoters

The gene encoding brain-derived neurotrophic factor (Bdnf) consists of nine non-coding exons driven by unique promoters, leading to the expression of nine Bdnf transcripts that play different roles in various brain regions and physiological stages. In this manuscript, we present a comprehensive overview of the molecular regulation and structural characteristics of the multiple Bdnf promoters, along with a summary of the current knowledge on the cellular and physiological functions of the distinct Bdnf transcripts produced by these promoters. Specifically, we summarized the role of Bdnf transcripts in psychiatric disorders, including schizophrenia and anxiety, as well as the cognitive functions associated with specific Bdnf promoters. Moreover, we examine the involvement of different Bdnf promoters in various aspects of metabolism. Finally, we propose future research directions that will enhance our understanding of the complex functions of Bdnf and its diverse promoters.

Elucidation of the mechanisms underlying tumor aggravation by the activation of stress-related neurons in the paraventricular nucleus of the hypothalamus

A growing body of evidence suggests that excess stress could aggravate tumor progression. The paraventricular nucleus (PVN) of the hypothalamus plays an important role in the adaptation to stress because the hypothalamic-pituitary-adrenal (HPA) axis can be activated by inducing the release of corticotropin-releasing hormone (CRH) from the PVN. In this study, we used pharmacogenetic techniques to investigate whether concomitant activation of CRH^PVN neurons could directly contribute to tumor progression. Tumor growth was significantly promoted by repeated activation of CRH^PVN neurons, which was followed by an increase in the plasma levels of corticosterone. Consistent with these results, chronic administration of glucocorticoids induced tumor progression. Under the concomitant activation of CRH^PVN neurons, the number of cytotoxic CD8⁺ T cells in the tumor microenvironment was dramatically decreased, and the mRNA expression levels of hypoxia inducible factor 1 subunit α (HIF1α), glucocorticoid receptor (GR) and Tsc22d3 were upregulated in inhibitory lymphocytes, tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs). Furthermore, the mRNA levels of various kinds of driver molecules related to tumor progression and tumor metastasis were prominently elevated in cancer cells by concomitant activation of CRH^PVN neurons. These findings suggest that repeated activation of the PVN-CRHergic system may aggravate tumor growth through a central-peripheral-associated tumor immune system.

A protocol for establishing a male G×E schizophrenia mouse model

Schizophrenia pathogenesis involves both genetic and environmental factors (G×E). Here, we present a protocol to prepare a schizophrenia rodent model with a specific G×E pair. We describe the breeding of Bdnf-e6-/- mice with genetic deficiency in promoter-VI-driven BDNF expression. We then detail the procedure to expose the mice to postnatal environmental stress including hypoxia, social isolation, and corticosterone. This model better represents the etiology of schizophrenia and thus may facilitate basic research and drug development for schizophrenia. For complete details on the use and execution of this protocol, please refer to Chen et al. (2022).¹.