Pro-region of neurotrophins: role in synaptic modulation

The role of BDNF transcription in the antidepressant-like effects of 18β-glycyrrhetinic acid in a chronic social defeat stress model

BACKGROUND

Xiaoyaosan (XYS), a traditional Chinese medicine formulation, has been used in the treatment of depression. However, no studies have yet identified the active compounds responsible for its antidepressant effects in the brain.

STUDY DESIGN

We investigated the antidepressants effects of XYS and identified 18β-glycyrrhetinic acid (18β-GA) as the primary compound present in the brain following XYS injection. Furthermore, we explored the molecular mechanisms underlying the antidepressant-like effects of both XYS and 18β-GA.

METHODS

To investigate the antidepressant-like effects of XYS and elucidate the associated molecular mechanisms, we employed various methodologies, including cell cultures, the chronic social defeat stress (CSDS) model, behavioral tests, immunoprecipitation, quantitative PCR (qPCR) assays, Western blotting assays, luciferase assays, chromatin immunoprecipitation (ChIP) assays, immunofluorescence staining, and dendritic spine analysis.

RESULTS

We identified 18β-GA as the primary compound in the brain following XYS injection. In vitro, 18β-GA was found to bind with ERK (extracellular signal-regulated kinase), subsequently activating ERK kinase activity toward both c-Jun and cAMP response element binding protein (CREB). Moreover, 18β-GA activated brain-derived neurotrophic factor (BDNF) transcription by stimulating nuclear factor-erythroid factor 2-related factor 2 (Nrf2), c-Jun, and CREB, while also inhibiting methyl CpG binding protein 2 (MeCP2) both in vitro and in vivo. Chronic intraperitoneal (i.p.) administration of 18β-GA exhibited prophylactic antidepressant-like effects in a CSDS model, primarily by activating BDNF transcription in the medial prefrontal cortex (mPFC). Interestingly, a single i.p. injection of 18β-GA produced rapid and sustained antidepressant-like effects in CSDS-susceptible mice by engaging the BDNF-tropomyosin receptor kinase B (TrkB) signaling pathway in the mPFC.

CONCLUSION

These findings suggest that the activation of BDNF transcription in the mPFC underlies the antidepressant-like effects of 18β-GA, a key component of XYS in the brain.

BDNF-TrkB Signaling in Mitochondria: Implications for Neurodegenerative Diseases

Brain-derived neurotrophic factor (BDNF) plays a pivotal role in neuronal development, synaptic plasticity, and overall neuronal health by binding to its receptor, tyrosine receptor kinase B (TrkB). This review delves into the intricate mechanisms through which BDNF-TrkB signaling influences mitochondrial function and potentially influences pathology in neurodegenerative diseases. This review highlights the BDNF-TrkB signaling pathway which regulates mitochondrial bioenergetics, biogenesis, and dynamics, mitochondrial processes vital for synaptic transmission and plasticity. Furthermore, we explore how the BDNF-TrkB-PKA signaling in the cytosol and in mitochondria affects mitochondrial transport and distribution and mitochondrial content, which is crucial for supporting the energy demands of synapses. The dysregulation of this signaling pathway is linked to various neurodegenerative diseases, including Alzheimer's and Parkinson's disease, which are characterized by mitochondrial dysfunction and reduced BDNF expression. By examining seminal studies that have characterized this signaling pathway in health and disease, the present review underscores the potential of enhancing BDNF-TrkB signaling to mitigate mitochondrial dysfunction in neurodegenerative diseases, offering insights into therapeutic strategies to enhance neuronal resilience and function.

An insight into crosstalk among multiple signalling pathways contributing to the pathophysiology of PTSD and depressive disorders

Post-traumatic stress disorder (PTSD) and depressive disorders represent two significant mental health challenges with substantial global prevalence. These are debilitating conditions characterized by persistent, often comorbid, symptoms that severely impact an individual's quality of life. Both PTSD and depressive disorders are often precipitated by exposure to traumatic events or chronic stress. The profound impact of PTSD and depressive disorders on individuals and society necessitates a comprehensive exploration of their shared and distinct pathophysiological features. Although the activation of the stress system is essential for maintaining homeostasis, the ability to recover from it after diminishing the threat stimulus is also equally important. However, little is known about the main reasons for individuals' differential susceptibility to external stressful stimuli. The solution to this question can be found by delving into the interplay of stress with the cognitive and emotional processing of traumatic incidents at the molecular level. Evidence suggests that dysregulation in these signalling cascades may contribute to the persistence and severity of PTSD and depressive symptoms. The treatment strategies available for this disorder are antidepressants, which have shown good efficiency in normalizing symptom severity; however, their efficacy is limited in most individuals. This calls for the exploration and development of innovative medications to address the treatment of PTSD. This review delves into the intricate crosstalk among multiple signalling pathways implicated in the development and manifestation of these mental health conditions. By unravelling the complexities of crosstalk among multiple signalling pathways, this review aims to contribute to the broader knowledge base, providing insights that could inform the development of targeted interventions for individuals grappling with the challenges of PTSD and depressive disorders.

Physical Exercise Promotes Beneficial Changes on Neurotrophic Factors in Mesolimbic Brain Areas After AMPH Relapse: Involvement of the Endogenous Opioid System

Addiction is a serious public health problem, and the current pharmacotherapy is unable to prevent drug use reinstatement. Studies have focused on physical exercise as a promising coadjuvant treatment. Our research group recently showed beneficial neuroadaptations in the dopaminergic system related to amphetamine-relapse prevention involving physical exercise-induced endogenous opioid system activation (EXE-OS activation). In this context, additional mechanisms were explored to understand the exercise benefits on drug addiction. Male rats previously exposed to amphetamine (AMPH, 4.0 mg/kg) for 8 days were submitted to physical exercise for 5 weeks. EXE-OS activation was blocked by naloxone administration (0.3 mg/kg) 5 min before each physical exercise session. After the exercise protocol, the rats were re-exposed to AMPH for 3 days, and in sequence, euthanasia was performed and the VTA and NAc were dissected. In the VTA, our findings showed increased immunocontent of proBDNF, BDNF, and GDNF and decreased levels of AMPH-induced TrkB; therefore, EXE-OS activation increased all these markers and naloxone administration prevented this exercise-induced effect. In the NAc, the same molecular markers were also increased by AMPH and decreased by EXE-OS activation. In this study, we propose a close relation between EXE-OS activation beneficial influence and a consequent neuroadaptation on neurotrophins and dopaminergic system levels in the mesolimbic brain area, preventing the observed AMPH-relapse behavior. Our outcomes bring additional knowledge concerning addiction neurobiology understanding and show that EXE-OS activation may be a potential adjuvant tool in drug addiction therapy.

Brain-Heart Axis: Brain-Derived Neurotrophic Factor and Cardiovascular Disease-A Review of Systematic Reviews

BACKGROUND

The brain-heart axis is an intra- and bidirectional complex that links central nervous system dysfunction and cardiac dysfunction. In recent decades, brain-derived neurotrophic factor (BDNF) has emerged as a strategic molecule involved in both brain and cardiovascular disease (CVD). This systematic review of systematic reviews aimed to (1) identify and summarize the evidence for the BDNF genotype and BDNF concentration in CVD risk assessment, (2) evaluate the evidence for the use of BDNF as a biomarker of CVD recovery, and (3) evaluate rehabilitation approaches that can restore BDNF concentration.

METHODS

A comprehensive search strategy was developed using PRISMA. The risk of bias was assessed via ROBIS.

RESULTS

Seven studies were identified, most of which aimed to evaluate the role of BDNF in stroke patients. Only two systematic reviews examined the association of BDNF concentration and polymorphism in CVDs other than stroke.

CONCLUSIONS

The overall evidence showed that BDNF plays a fundamental role in assessing the risk of CVD occurrence, because lower BDNF concentrations and rs6265 polymorphism are often associated with CVD. Nevertheless, much work remains to be carried out in current research to investigate how BDNF is modulated in different cardiovascular diseases and in different populations.

Gut Microbiota Taxon-Dependent Transformation of Microglial M1/M2 Phenotypes Underlying Mechanisms of Spatial Learning and Memory Impairment after Chronic Methamphetamine Exposure

Methamphetamine (METH) exposure may lead to cognitive impairment. Currently, evidence suggests that METH exposure alters the configuration of the gut microbiota. However, the role and mechanism of the gut microbiota in cognitive impairment after METH exposure are still largely unknown. Here, we investigated the impact of the gut microbiota on the phenotype status of microglia (microglial phenotypes M1 and microglial M2) and their secreting factors, the subsequent hippocampal neural processes, and the resulting influence on spatial learning and memory of chronically METH-exposed mice. We determined that gut microbiota perturbation triggered the transformation of microglial M2 to M1 and a subsequent change of pro-brain-derived neurotrophic factor (proBDNF)-p75NTR-mature BDNF (mBDNF)-TrkB signaling, which caused reduction of hippocampal neurogenesis and synaptic plasticity-related proteins (SYN, PSD95, and MAP2) and, consequently, deteriorated spatial learning and memory. More specifically, we found that Clostridia, Bacteroides, Lactobacillus, and Muribaculaceae might dramatically affect the homeostasis of microglial M1/M2 phenotypes and eventually contribute to spatial learning and memory decline after chronic METH exposure. Finally, we found that fecal microbial transplantation could protect against spatial learning and memory decline by restoring the microglial M1/M2 phenotype status and the subsequent proBDNF-p75NTR/mBDNF-TrkB signaling in the hippocampi of chronically METH-exposed mice. IMPORTANCE Our study indicated that the gut microbiota contributes to spatial learning and memory dysfunction after chronic METH exposure, in which microglial phenotype status plays an intermediary role. The elucidated "specific microbiota taxa-microglial M1/M2 phenotypes-spatial learning and memory impairment" pathway would provide a novel mechanism and elucidate potential gut microbiota taxon targets for the no-drug treatment of cognitive deterioration after chronic METH exposure.

Sarcopenia and Cognitive Decline in Older Adults: Targeting the Muscle-Brain Axis

Declines in physical performance and cognition are commonly observed in older adults. The geroscience paradigm posits that a set of processes and pathways shared among age-associated conditions may also serve as a molecular explanation for the complex pathophysiology of physical frailty, sarcopenia, and cognitive decline. Mitochondrial dysfunction, inflammation, metabolic alterations, declines in cellular stemness, and altered intracellular signaling have been observed in muscle aging. Neurological factors have also been included among the determinants of sarcopenia. Neuromuscular junctions (NMJs) are synapses bridging nervous and skeletal muscle systems with a relevant role in age-related musculoskeletal derangement. Patterns of circulating metabolic and neurotrophic factors have been associated with physical frailty and sarcopenia. These factors are mostly related to disarrangements in protein-to-energy conversion as well as reduced calorie and protein intake to sustain muscle mass. A link between sarcopenia and cognitive decline in older adults has also been described with a possible role for muscle-derived mediators (i.e., myokines) in mediating muscle-brain crosstalk. Herein, we discuss the main molecular mechanisms and factors involved in the muscle-brain axis and their possible implication in cognitive decline in older adults. An overview of current behavioral strategies that allegedly act on the muscle-brain axis is also provided.

Propofol-Induced Developmental Neurotoxicity: From Mechanisms to Therapeutic Strategies

Propofol is the most commonly used intravenous general anesthetic in clinical anesthesia, and it is also widely used in general anesthesia for pregnant women and infants. Some clinical and preclinical studies have found that propofol causes damage to the immature nervous system, which may lead to neurodevelopmental disorders and cognitive dysfunction in infants and children. However, its potential molecular mechanism has not been fully elucidated. Recent in vivo and in vitro studies have found that some exogenous drugs and interventions can effectively alleviate propofol-induced neurotoxicity. In this review, we focus on the relevant preclinical studies and summarize the latest findings on the potential mechanisms and therapeutic strategies of propofol-induced developmental neurotoxicity.

The Molecular Effects of Environmental Enrichment on Alzheimer's Disease

Environmental enrichment (EE) is an environmental paradigm encompassing sensory, cognitive, and physical stimulation at a heightened level. Previous studies have reported the beneficial effects of EE in the brain, particularly in the hippocampus. EE improves cognitive function as well as ameliorates depressive and anxiety-like behaviors, making it a potentially effective neuroprotective strategy against neurodegenerative diseases such as Alzheimer's disease (AD). Here, we summarize the current evidence for EE as a neuroprotective strategy as well as the potential molecular pathways that can explain the effects of EE from a biochemical perspective using animal models. The effectiveness of EE in enhancing brain activity against neurodegeneration is explored with a view to differences present in early and late life EE exposure, with its potential application in human being discussed. We discuss EE as one of the non pharmacological approaches in preventing or delaying the onset of AD for future research.

Ginsenoside-Rg1 mitigates cardiac arrest-induced cognitive damage by modulating neuroinflammation and hippocampal plasticity

Ginsenoside-Rg1 can effectively ameliorate mental disorders, but whether ginsenoside-Rg1 plays a neuroprotective role in cardiac arrest and cardiopulmonary resuscitation (CA/CPR)-induced cognitive impairment remains unclear. In this study, a 5-min asphyxia-based CA/CPR rat model was established to explore the mechanisms underlying the effects of ginsenoside-Rg1 (40 mg·kg-1·d-1, ip, 14 days) on its cognitive alterations. These CA/CPR rats displayed spatial learning and memory impairment in the Morris water maze, as reflected in the compromised basal synaptic transmission and long-term potentiation (LTP) at the Schaffer collateral of hippocampal CA1 area in vivo electrophysiology, whereas the ginsenoside-Rg1 remarkably mitigated these alterations. Next, we found that ginsenoside-Rg1 inhibited hippocampal neuroinflammation by alleviating the CA/CPR-induced hippocampal activation of microglia and astrocytes and the overexpression of related proinflammatory cytokines interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α). In addition, ginsenoside-Rg1 improved CA/CPR-induced hippocampal neuronal apoptosis, dendritic spines and synaptic ultrastructure defects as associated with the upregulation of the key synaptic regulatory proteins. Furthermore, ginsenoside-Rg1 could ameliorate CA/CPR-induced aberrant expression of the key regulators of hippocampal glutamate signaling pathways, excitatory amino acid transporter 2 (EAAT2), excitatory amino acid transporter 1 (EAAT1), Glutamine Synthetase (GS), GluN2B, and glutamate. In conclusion, ginsenoside-Rg1 exerts its neuroprotective effects by ameliorating hippocampus-dependent neuroglia activation-mediated neuroinflammation and neuroplasticity deficits, shedding new light on the therapeutic intervention of CA/CPR-related cognitive disorders.

BDNF Spinal Overexpression after Spinal Cord Injury Partially Protects Soleus Neuromuscular Junction from Disintegration, Increasing VAChT and AChE Transcripts in Soleus but Not Tibialis Anterior Motoneurons

After spinal cord transection (SCT) the interaction between motoneurons (MNs) and muscle is impaired, due to reorganization of the spinal network after a loss of supraspinal inputs. Rats subjected to SCT, treated with intraspinal injection of a AAV-BDNF (brain-derived neurotrophic factor) construct, partially regained the ability to walk. The central effects of this treatment have been identified, but its impact at the neuromuscular junction (NMJ) has not been characterized. Here, we compared the ability of NMJ pre- and postsynaptic machinery in the ankle extensor (Sol) and flexor (TA) muscles to respond to intraspinal AAV-BDNF after SCT. The gene expression of cholinergic molecules (VAChT, ChAT, AChE, nAChR, mAChR) was investigated in tracer-identified, microdissected MN perikarya, and in muscle fibers with the use of qPCR. In the NMJs, a distribution of VAChT, nAChR and Schwann cells was studied by immunofluorescence, and of synaptic vesicles and membrane active zones by electron microscopy. We showed partial protection of the Sol NMJs from disintegration, and upregulation of the VAChT and AChE transcripts in the Sol, but not the TA MNs after spinal enrichment with BDNF. We propose that the observed discrepancy in response to BDNF treatment is an effect of difference in the TrkB expression setting BDNF responsiveness, and of BDNF demands in Sol and TA muscles.

ProBDNF and Brain-Derived Neurotrophic Factor Prodomain Differently Modulate Acetylcholine Release in Regenerating and Mature Mouse Motor Synapses

The effects of brain-derived neurotrophic factor (BDNF) processing by-products (proBDNF and BDNF prodomain) on the activity of mouse neuromuscular junctions (NMJs) were studied in synapses formed during the reinnervation of extensor digitorum longus muscle (m. EDL) and mature synapses of the diaphragm. The parameters of spontaneous miniature endplate potentials (MEPPs) and evoked endplate potentials (EPPs) were analyzed in presence of each of the BDNF maturation products (both – 1 nM). In newly formed NMJs, proBDNF caused an increase in the resting membrane potential of muscle fibers and a decrease in the frequency of MEPPs, which was prevented by tertiapin-Q, a G-protein-coupled inwardly rectifying potassium channels (GIRK) blocker but not by p75 receptor signaling inhibitor TAT-Pep5. proBDNF had no effect on the parameters of EPPs. BDNF prodomain in newly formed synapses had effects different from those of proBDNF: it increased the amplitude of MEPPs, which was prevented by vesamicol, an inhibitor of vesicular acetylcholine (ACh) transporter; and reduced the quantal content of EPPs. In mature NMJs, proBDNF did not influence MEPPs parameters, but BDNF prodomain suppressed both spontaneous and evoked ACh release: decreased the frequency and amplitude of MEPPs, and the amplitude and quantal content of EPPs. This effect of the BDNF prodomain was prevented by blocking GIRK channels, by TAT-Pep5 or by Rho-associated protein kinase (ROCK) inhibitor Y-27632. At the same time, the BDNF prodomain did not show any inhibitory effects in diaphragm motor synapses of pannexin 1 knockout mice, which have impaired purinergic regulation of neuromuscular transmission. The data obtained suggest that there is a previously unknown mechanism for the acute suppression of spontaneous and evoked ACh release in mature motor synapses, which involves the activation of p75 receptors, ROCK and GIRK channels by BDNF prodomain and requires interaction with metabotropic purinoreceptors. In general, our results show that both the precursor of BDNF and the product of its maturation have predominantly inhibitory effects on spontaneous and evoked ACh release in newly formed or functionally mature neuromuscular junctions, which are mainly opposite to the effects of BDNF. The inhibitory influences of both proteins related to brain neurotrophin are mediated via GIRK channels of mouse NMJs.

IL-33 in the basolateral amygdala integrates neuroinflammation into anxiogenic circuits via modulating BDNF expression

Hyper-inflammatory reaction plays a crucial role in the pathophysiology of depression and anxiety disorders. However, the mechanisms underlying inflammation-induced anxiety changes remain poorly understood. Here, we showed that in the lipopolysaccharide (LPS)-induced anxiety model, Interleukin (IL)-33, a member of the IL-1 family, was up-regulated in the basolateral amygdala, and IL-33 deficiency prevent anxiety-like behavior. Overexpression of IL-33 in amygdalar astrocytes led to anxiety-like response via repressing brain-derived neurotrophic factor (BDNF) expression. Mechanically, IL-33 suppressed BDNF expression through NF-κB pathway to impair GABAergic transmission in the amygdala and NF-κB inhibitor abolished the effect of IL-33 on anxiety. Administration of an inverse GABAA receptor agonist increased the anxiety of IL-33- deficient mice. These results reveal that inflammatory response can activate anxiogenic circuits by suppressing BDNF and GABAergic neurons transmission, suggesting that IL-33 in basolateral amygdalar is a linker between inflammation and anxiety.

Remembering how to run: a descriptive wheel run analysis in CF1 males and females mice

Physical exercise is known to have beneficial effects on general health and wellbeing in humans and it is also related to neuronal plasticity, increasing neurogenesis and consequently leading to improvements in processes such as learning and memory. In this sense, wheel running performance in mice appears as an extensively used behavioral approach for neurobiological studies. Here, we explored the running patterns in CF1 male and female mice allowing voluntary wheel running for 20 min along three consecutive days. We analyzed differences in the accumulated distance traveled, instant velocity, and latency to run and breaks taken in both males and females, comparing performance between days. Results revealed that after a first experience with the wheel, animals that had learnt how to run on day 1 quickly look forward to stepping into the wheel in subsequent training days, reflected by a significant increase in daily running distance and velocity. Further, no differences were found in the running performance between males and females. In summary, in a first experience with the wheel, animals get familiarized with the wheel and grow accustomed to it.

Agonistic analog of growth hormone-releasing hormone promotes neurofunctional recovery and neural regeneration in ischemic stroke

Ischemic stroke can induce neurogenesis. However, most stroke-generated newborn neurons cannot survive. It has been shown that MR-409, a potent synthetic agonistic analog of growth hormone-releasing hormone (GHRH), can protect against some life-threatening pathological conditions by promoting cell proliferation and survival. The present study shows that long-term treatment with MR-409 (5 or 10 μg/mouse/d) by subcutaneous (s.c.) injection significantly reduces the mortality, ischemic insult, and hippocampal atrophy, and improves neurological functional recovery in mice operated on for transient middle cerebral artery occlusion (tMCAO). Besides, MR-409 can stimulate endogenous neurogenesis and improve the tMCAO-induced loss of neuroplasticity. MR-409 also enhances the proliferation and inhibits apoptosis of neural stem cells treated with oxygen and glucose deprivation-reperfusion. The neuroprotective effects of MR-409 are closely related to the activation of AKT/CREB and BDNF/TrkB pathways. In conclusion, the present study demonstrates that GHRH agonist MR-409 has remarkable neuroprotective effects through enhancing endogenous neurogenesis in cerebral ischemic mice.

Dynamics of biomarkers across the stages of traumatic spinal cord injury - implications for neural plasticity and repair

BACKGROUND

Traumatic spinal cord injury (SCI) is a complex medical condition causing significant physical disability and psychological distress. While the adult spinal cord is characterized by poor regenerative potential, some recovery of neurological function is still possible through activation of neural plasticity mechanisms. We still have limited knowledge about the activation of these mechanisms in the different stages after human SCI.

OBJECTIVE

In this review, we discuss the potential role of biomarkers of SCI as indicators of the plasticity mechanisms at work during the different phases of SCI.

METHODS

An extensive review of literature related to SCI pathophysiology, neural plasticity and humoral biomarkers was conducted by consulting the PubMed database. Research and review articles from SCI animal models and SCI clinical trials published in English until January 2021 were reviewed. The selection of candidates for humoral biomarkers of plasticity after SCI was based on the following criteria: 1) strong evidence supporting involvement in neural plasticity (mandatory); 2) evidence supporting altered expression after SCI (optional).

RESULTS

Based on selected findings, we identified two main groups of potential humoral biomarkers of neural plasticity after SCI: 1) neurotrophic factors including: Brain derived neurotrophic factor (BDNF), Nerve growth factor (NGF), Neurotrofin-3 (NT-3), and Insulin-like growth factor 1 (IGF-1); 2) other factors including: Tumor necrosis factor-alpha (TNF-α), Matrix Metalloproteinases (MMPs), and MicroRNAs (miRNAs). Plasticity changes associated with these biomarkers often can be both adaptive (promoting functional improvement) and maladaptive. This dual role seems to be influenced by their concentrations and time-window during SCI.

CONCLUSIONS

Further studies of dynamics of biomarkers across the stages of SCI are necessary to elucidate the way in which they reflect the remodeling of neural pathways. A better knowledge about the mechanisms underlying plasticity could guide the selection of more appropriate therapeutic strategies to enhance positive spinal network reorganization.

Increased plasma brain-derived neurotrophic factor (BDNF) as a potential biomarker for and compensatory mechanism in mild cognitive impairment: a case-control study

Background: Previous meta-analyses examining the continuum of Alzheimer’s disease (AD) concluded significantly decreased peripheral brain-derived neurotrophic factor (BDNF) in AD. However, across different meta-analyses, there remain inconsistent findings on peripheral BDNF levels in individuals with mild cognitive impairment (MCI). This issue has been attributed to the highly heterogenous clinical and laboratory factors. Thus, BDNF’s level, discriminative accuracy for identifying all-cause MCI and its subtypes, and its associations with other biomarkers and neurocognitive domains, remain largely unknown.

Methods: To address this heterogeneity, we compared a healthy control cohort (n=56, 45 female) to an MCI cohort (n=40, 28 female), to determine whether plasma BDNF, hs-CRP, and DHEA-S can differentiate healthy from MCI individuals, including two MCI subtypes (amnestic [aMCI] and non-amnestic [non-aMCI]). The associations between BDNF with other biomarkers and neurocognitive tests were examined. Adults with cerebral palsy were included as sensitivity analyses.

Results: Compared to healthy controls, BDNF was significantly higher in all-cause MCI, aMCI, and non-aMCI. Furthermore, BDNF had good (AUC=0.84, 95% CI=0.74 to 0.95, p<0.001) and excellent discriminative accuracies (AUC=0.92, 95% CI=0.84 to 1.00, p<0.001) for all-cause MCI and non-amnestic MCI, respectively. BDNF was significantly and positively associated with plasma hs-CRP (β=0.26, 95% CI=0.02 to 0.50, p=0.038), despite attenuated association upon controlling for BMI (β=0.15, 95% CI=-0.08 to 0.38, p=0.186). Multiple inverse associations between BDNF and detailed neurocognitive tests were also detected.

Conclusions: These findings suggest BDNF is increased as a compensatory mechanism in preclinical dementia, supporting the neurotrophic and partially the inflammatory hypotheses of cognitive impairment.

Met carriers of the BDNF Val66Met polymorphism show reduced Glx/NAA in the pregenual ACC in two independent cohorts

The Met allele of the Val66Met SNP of the BDNF gene (rs6265) is associated with impaired activity-dependent release of brain-derived neurotrophic factor (BDNF), resulting in reduced synaptic plasticity, impaired glutamatergic neurotransmission, and morphological changes. While previous work has demonstrated Val66Met effects on magnetic resonance spectroscopy (MRS) markers of either glutamatergic metabolism (Glx) or neuronal integrity (NAA), no study has investigated Val66Met effects on these related processes simultaneously. As these metabolites share a metabolic pathway, the Glx/NAA ratio may be a more sensitive marker of changes associated with the Val66Met SNP. This ratio is increased in psychiatric disorders linked to decreased functioning in the anterior cingulate cortex (ACC). In this study, we investigated the correlation of the Val66Met polymorphism of the BDNF gene with Glx/NAA in the pregenual anterior cingulate cortex (pgACC) using MRS at 3 Tesla (T) (n = 30, all males) and 7 T (n = 98, 40 females). In both cohorts, Met carriers had lower Glx/NAA compared to Val homozygotes. Follow-up analyses using absolute quantification revealed that the Met carriers do not show decreased pgACC glutamate or glutamine levels, but instead show increased NAA compared to the Val homozygotes. This finding may in part explain conflicting evidence for Val66Met as a risk factor for developing psychiatric illnesses.

rTMS induces analgesia and modulates neuroinflammation and neuroplasticity in neuropathic pain model rats

Neuropathic pain (NP) is related to the presence of hyperalgesia, allodynia, and spontaneous pain, affecting 7%-10% of the general population. Repetitive transcranial magnetic stimulation (rTMS) is applied for NP relief, especially in patients with refractory pain. As NP response to existing treatments is often insufficient, we aimed to evaluate rTMS treatment on the nociceptive response of rats submitted to an NP model and its effect on pro-and anti-neuroinflammatory cytokine and neurotrophin levels. A total of 106 adult male Wistar rats (60 days old) were divided into nine experimental groups: control, control + sham rTMS, control + rTMS, sham NP, sham neuropathic pain + sham rTMS, sham neuropathic pain + rTMS, NP, neuropathic pain + sham rTMS, and neuropathic pain + rTMS. NP establishment was achieved 14 days after the surgery to establish chronic constriction injury (CCI) of the sciatic nerve. Rats were treated with 5 min daily sessions of rTMS for eight consecutive days. Nociceptive behavior was assessed using von Frey and hot plate tests at baseline, after NP establishment, and post-treatment. Biochemical assays to assess the levels of brain-derived neurotrophic factor (BDNF), tumor necrosis factor-alpha (TNF-α), and interleukin (IL)-10, were performed in the prefrontal cortex (PFC) and spinal cord tissue homogenates. rTMS treatment promoted a partial reversal of mechanical allodynia and total reversal of thermal hyperalgesia induced by CCI. Moreover, rTMS increased the levels of BDNF, TNF-α, and IL-10 in the PFC. rTMS may be a promising tool for the treatment of NP. The alterations induced by rTMS on neurochemical parameters may have contributed to the analgesic effect presented.

Genetic Factors That Could Affect Concussion Risk in Elite Rugby

Elite rugby league and union have some of the highest reported rates of concussion (mild traumatic brain injury) in professional sport due in part to their full-contact high-velocity collision-based nature. Currently, concussions are the most commonly reported match injury during the tackle for both the ball carrier and the tackler (8-28 concussions per 1000 player match hours) and reports exist of reduced cognitive function and long-term health consequences that can end a playing career and produce continued ill health. Concussion is a complex phenotype, influenced by environmental factors and an individual's genetic predisposition. This article reviews concussion incidence within elite rugby and addresses the biomechanics and pathophysiology of concussion and how genetic predisposition may influence incidence, severity and outcome. Associations have been reported between a variety of genetic variants and traumatic brain injury. However, little effort has been devoted to the study of genetic associations with concussion within elite rugby players. Due to a growing understanding of the molecular characteristics underpinning the pathophysiology of concussion, investigating genetic variation within elite rugby is a viable and worthy proposition. Therefore, we propose from this review that several genetic variants within or near candidate genes of interest, namely APOE, MAPT, IL6R, COMT, SLC6A4, 5-HTTLPR, DRD2, DRD4, ANKK1, BDNF and GRIN2A, warrant further study within elite rugby and other sports involving high-velocity collisions.

Social and Biological Parameters Involved in Suicide Ideation During the COVID-19 Pandemic: A Narrative Review

Fear is an indispensable characteristic of any infectious disease, and the alarm will be further amplified when the infection spreads uncontrollable, unpredictable, and global. The novel corona virus (SARS CoV-2) lead Covid-19, has been declared as a global emergency by WHO as it has affected millions of people with a high mortality rate. The non-availability of medicine for Covid-19 and the various control measures such as social distancing, self-isolation, house quarantine, and the new normal implementation by different nations across the world to control the spread of Covid-19 made people vulnerable to fear and anxiety. As a result, considerable number of Covid-19-related suicidal deaths has been reported across the world during this pandemic. There have been several studies which describe the psychosocial aspects of suicidal ideation. However, the research on the biological aspects of suicidal ideation/suicidal risk factors that are related to pandemic are unreported. Hence this review article is intended to provide a comprehensive analysis of suicidal deaths during Covid-19 and also aimed to addresses the possible link between suicidal ideation and different factors, including psycho-social, behavioral, neurobiological factors (proximal, distal, and inflammatory) and immunity. The alterations in glutamatergic and GABAergic neurotransmitters had upregulated the GABARB3, GABARA4, GABARA3, GABARR1, GABARG2, and GAD2 gene expressions in suicidal victims. The changes in the Kynurenine (KYN) pathway, Hypothalamus-Pituitary-Adrenal axis (HPA axis) hyperactivation, and dysregulation of serotonin biosynthesis would significantly alter the brain chemistry in people with suicide ideation.

Neuroplasticity and the Biological Role of Brain Derived Neurotrophic Factor in the Pathophysiology and Management of Depression

Depression is a mental illness that can have serious implications if left untreated. Studies involving a neurotrophic factor called brain derived neurotrophic factor (BDNF) and its associated signaling pathways have solidified our understanding of the pathophysiology of depression. The objective of this literature review is to gain a better understanding of the mechanism by which reduced levels of BDNF are implicated in depression and how antidepressants facilitate the treatment of depression by increasing BDNF levels. The specific approach is to learn about the key involvements of BDNF and its receptor TrkB (tropomyosin receptor kinase B) and how their interactions and subsequent intracellular signaling cascades bring about enhanced neuroplastic changes. In this literature review, we searched for past review articles focusing on BDNF. We collected data using PubMed and created a summary of our findings. The results showed that stress and depression through the reduction of BDNF levels contribute to neuroplastic changes while antidepressants through enhanced BDNF levels are able to generate positive neuroplastic outcomes and thereby help resolve depressive symptoms. In this paper, we will delve into how a better understanding of the neural circuitry involving BDNF will enable us to both understand how current antidepressants work in the limbic regions of the brain as well as search for novel rapid-acting antidepressants to use in clinical practice.

Effect of Physical Activity on Cognitive Function and Neurogenesis: Roles of BDNF and Oxidative Stress

Context: Cognitive disorders are one of the most common neurological problems that can be caused by lifestyle patterns, especially sedentary lifestyle, poor nutrition, exposure to a variety of toxins or diseases. Evidence Acquisition: There are various strategies recommended for the prevention and treatment of these disorders, including drug therapy, psychological therapy, dietary pattern changes, and physical activity. Results: It seems that physical activity with biological mechanisms can have beneficial effects on the central nervous system and improve cognitive function, including enhanced learning and memory, as well as reduced depression and anxiety. Conclusions: Of the major mechanisms that physical activity can affect cognitive function include increased neurogenic factors, decreased oxidative stress, decreased inflammatory mediators, and mitochondrial biogenesis. Therefore, it is recommended that people with cognitive impairments can use physical activity as an appropriate strategy to prevent and treat cognitive impairment problems.

Developmental exposure to mepanipyrim induces locomotor hyperactivity in zebrafish (Danio rerio) larvae

Mepanipyrim is a widely used fungicide, and residues of mepanipyrim are frequently detected in commodities. However, the neurotoxicity and underlying mechanisms of mepanipyrim are still insufficiently understood. In this study, zebrafish embryos at 0.5-1.0 post-fertilization hours (hpf) were exposed to 0.1, 1, 10 and 100 μg/L mepanipyrim for 7 days. Our results showed that mepanipyrim could cause the locomotor hyperactivity and increase the concentration of γ-amino butyric acid (GABA) and the Na⁺/K⁺- and Ca²⁺-ATPase activities in zebrafish larvae. We have conducted the RNA-sequence and RT-qPCR to analyze the gene expressions. The mRNA expression levels of calcium/sodium ion conduction associated genes were observably up-regulated, demonstrating that mepanipyrim could enhance the cell energy metabolism, the synaptic transmission and skeletal muscle contraction, which were consistent with the locomotor hyperactivity. Meanwhile, exposure to mepanipyrim could significantly change the gene expression levels of gad1, bdnf, nlgn1, and type A and B GABA receptors in zebrafish larvae. This is the first study focusing on the underlying mechanisms of the neurotoxic effects that are induced by mepanipyrim.

The BDNF Val66Met Polymorphism, Regular Exercise, and Cognition: A Systematic Review

The purpose of this study was to synthesize research evidence from studies on the relationships among the BDNF Val66Met polymorphism, regular exercise, and cognition in human subjects. PubMed, CINAHL, and Web of Science were searched systematically. Search limiters applied in these databases included humans, English language, time limits from 2009 to 2019, and peer-reviewed journal articles. Eight studies were included in the current review. While there was some evidence to tentatively suggest that greater levels of exercise were associated with certain forms of memory in Val/Val homozygotes than Met carriers, more research is needed to corroborate these findings. Regarding attention/information processing speed, executive function as well as global cognition, the evidence is either inconsistent or sparse and does not allow for tentative conclusions. Compelling evidence from high-quality clinical trials is needed to re-examine the relationship between the BDNF Val66Met polymorphism, exercise, and cognition.

Pro-BDNF Knockout Causes Abnormal Motor Behaviours and Early Death in Mice

Brain derived neurotrophic factor (BDNF) is a member of the neurotrophin family, best characterized for its survival and differentiative effects in the central nervous system. Pro-BDNF, known as the precursor of BDNF, is believed to have opposite functions to mature BDNF (mBDNF). The opposing effects of Pro-BDNF and mBDNF have led researchers to propose a 'yin' (Pro-BDNF) and 'yang' (mBDNF) model of which, the specific mechanism of its opposing functions is unclear and requires further investigation. In order to elucidate pro-BDNF's explicit role, we established a pro-BDNF knockout (KO) mouse model. This BDNF pro-domain KO mouse model showed significant weight loss, impaired righting reflex, abnormal motor behaviours and short lifespan (less than 22 days), mimicking a Huntington's disease (HD)-like phenotype. ELISA results showed BDNF pro-domain KO not only blocked pro-BDNF, but also significantly affected the level of mBDNF. Abnormal morphologic changes were found in the dentate gyrus (DG) of the hippocampus in pro-BDNF KO mice, and western blot confirmed significant cell apoptosis in pro-BDNF KO mice brains. Furthermore, the expression of glutamic acid decarboxylase 65/67 (GAD65/67) was significantly reduced in pro-BDNF KO mice, indicating impaired inhibitory neurotransmission. Heterozygous (Het) mice showed impaired learning and memory capability and depressive-like behaviours, compared with wild type (WT) mice. Overall, these results support that pro-domain of BDNF is an indispensable part of the BDNF gene; without the proper formation of pro-BDNF, mBDNF cannot be produced successfully and function correctly on its own. Our study also supports the BDNF hypothesis in the pathogenesis of HD.

Increased ratio of mature BDNF to precursor-BDNF in patients with major depressive disorder with severe anhedonia

BACKGROUND

Although studies have shown that severe anhedonia in patients with major depressive disorder (MDD) is associated with poor treatment outcomes, the biological mechanism of this feature is unclear. The aim of this study was to investigate the dysfunction of brain-derived neurotrophic factor (BDNF) metabolism, measured by the ratio of mature BDNF to precursor-BDNF, in MDD patients with severe anhedonia.

METHODS

We measured plasma levels of mature BDNF (mBDNF), precursor-BDNF (proBDNF), tissue plasminogen activator (tPA) and tropomyosin-related kinase B (trkB) in outpatients with MDD with anhedonia (n = 26), outpatients with MDD without anhedonia (n = 29) and age- and sex-matched healthy controls (HCs, n = 38) by enzyme-linked immunosorbent assay kits, and we calculated the ratio of mBDNF to proBDNF (M/P). We compared these biological determinants among the three groups and explored the interrelationships between anhedonia severity and BDNF metabolism.

RESULTS

The levels of mBDNF, proBDNF, and tPA and the ratio of M/P were identified with highly significant differences among the three groups. Compared with MDD patients without anhedonia and healthy controls, MDD patients with anhedonia showed higher level of the ratio of M/P, and it was positively associated with the SHAPS scores in MDD patients. Compared to healthy controls, the plasma tPA concentrations were higher in MDD patients with anhedonia but were not different from those in MDD patients without anhedonia.

CONCLUSION

These results provide novel evidence regarding the relationship between anhedonia and plasma BDNF metabolism. The hypermetabolism of BDNF may be a function of anhedonia rather than other characteristics in MDD.

Intensity-dependent effects of consecutive treadmill exercise on spatial learning and memory through the p-CREB/BDNF/NMDAR signaling in hippocampus

Exercise is the most recommended non-pharmacological intervention to improve neurocognitive functions under physiological and pathological conditions. However, it remains to be elucidated concerning the influence and the underlying neurological molecular mechanism of different exercise intensity on cognitive function. In this study, we aimed to explore the effects of exercise intensity on spatial learning and memory, as well as the regulation of brain-derived neurotrophic factor (BDNF)/p-CREB/NMDAR signal. In the research, low-intensity consecutive treadmill (LICT) and high-intensity consecutive treadmill (HICT) were implied to rats for 8 weeks. We found that the performances in the Morris water maze were improved in the LICT group, while reduced in the HICT group as compared with the sedentary rats. Moreover, the expression of BDNF mRNA, phosphorylation cAMP-response-element binding protein (p-CREB), mature BDNF (mBDNF), tropomyosin receptor kinase B (TrkB), tissue plasminogen activator (t-PA), and NR2B proteins was increased, whereas the expression of precursor BDNF (proBDNF) and pan-neurotrophin receptor 75 (p75NTR) proteins was decreased in the hippocampus of LICT group compared with the sedentary rats. On the contrary, the expression of proteins and mRNA aforementioned in the LICT group showed a reversed tendency in the hippocampus of HICT rats. These findings suggest that the consecutive low-intensity exercise and high-intensity exercise exert different effects on spatial learning and memory by oppositely regulating the mutual stimulation of p-CREB and BDNF mRNA feedback loop, as well as the t-PA/BDNF/NMDAR which is the post-translation cascades of BDNF signaling.

SLC1A3 C3590T but not BDNF G196A is a predisposition factor for stress as well as depression, in an adolescent eastern Indian population

Background

Adolescence is a distinctive stage of various changes and is noted as peak age for onset of many psychiatric disorders, especially linked to stress and depression. Several genetic variations are being increasingly known to be linked with stress and depression. The polymorphisms in two such genes, the BDNF and SLC1A3, have been reported to be linked with either depression/stress or with suicidal behaviour. These genes have not been validated in Indian population, and therefore there is a need to investigate these genes in Indian population. The present study was undertaken to test whether the known polymorphisms SLC1A3 C3590T, SLC1A3 C869G and BDNF G196A are associated or not with stress or depression in an eastern Indian population.

Methods

A case-control association study was performed with 108 cases having variable levels of stress and depression and 205 matched controls. Detection of stress and depression was done by using standard instruments as PSS and CES-D, respectively and demographic profile was obtained for each individual on the basis of personal data sheet. Genotyping for the selected polymorphisms was performed by PCR followed by restriction digestion.

Results

The SNP SLC1A3 C3590T was found to be associated with stress and depression (p = 0.0042, OR = 2.072). Therefore, the T allele increases the risk by more than two folds for stress and depression in the present population. The other allele of SLC1A3, G869C, as well as BDNF G196A were not associated with stress or depression in the population studied.

Conclusion

SLC1A3 C3590T is a predisposition factor for stress and depression in an eastern Indian population, whereas SLC1A3 G869C and BDNF G196A were not found to be a risk factor. Therefore, presence of T allele of SLC1A3 C3590T, may predict the development of stress and depression in an individual. This may also help in the understanding of pathophysiology of the disease. However, these findings warrant a wider study in Indian populations and would be of significance in understanding the predisposition of stress and depression in this population.

The Relationships Between Stress, Mental Disorders, and Epigenetic Regulation of BDNF

Brain-derived neurotrophic factor (BDNF), a critical member of the neurotrophic family, plays an important role in multiple stress-related mental disorders. Although alterations in BDNF in multiple brain regions of individuals experiencing stress have been demonstrated in previous studies, it appears that a set of elements are involved in the complex regulation. In this review, we summarize the specific brain regions with altered BDNF expression during stress exposure. How various environmental factors, including both physical and psychological stress, affect the expression of BDNF in specific brain regions are further summarized. Moreover, epigenetic regulation of BDNF, including DNA methylation, histone modification, and noncoding RNA, in response to diverse types of stress, as well as sex differences in the sensitivity of BDNF to the stress response, is also summarized. Clarification of the underlying role of BDNF in the stress process will promote our understanding of the pathology of stress-linked mental disorders and provide a potent target for the future treatment of stress-related illness.

tDCS-Enhanced Consolidation of Writing Skills and Its Associations With Cortical Excitability in Parkinson Disease: A Pilot Study

Background. Learning processes of writing skills involve the re-engagement of previously established motor programs affected by Parkinson disease (PD). To counteract the known problems with consolidation in PD, transcranial direct current stimulation (tDCS) could be imperative to achieve a lasting regeneration of habitual motor skills. Objective. To examine tDCS-enhanced learning of writing and explore alterations in cortical excitability after stimulation in PD compared with healthy controls (HCs). Methods. Ten patients and 10 HCs received 2 training sessions combined with 20 minutes of 1-mA anodal tDCS or sham on the left primary motor cortex in a randomized crossover design. Writing skills on a tablet and paper were assessed at baseline, after training, and after 1 week of follow-up. Before and immediately after the intervention, cortical excitability and inhibition were measured during rest and activity. Results. Writing amplitude and velocity improved when practice was tDCS supplemented compared with sham in PD. Benefits were sustained at retention for trained and untrained tasks on the tablet as well as for writing on paper. No improvements were found for HCs. Reduced resting motor thresholds after tDCS indicated tDCS-enhanced cortical excitability. Additionally, increments in motor-evoked potential amplitudes correlated with improved writing in PD, whereas HCs showed the opposite pattern. Conclusion. Our results endorse the usefulness of tDCS-boosted learning in PD, at least when applied to improving writing capacity. Although further confirmatory studies are needed, these novel findings are striking because tDCS-mediated consolidation was found for learning a motor task directly affected by PD.

Loss of TrkB Signaling in Parvalbumin-Expressing Basket Cells Results in Network Activity Disruption and Abnormal Behavior

The GABAergic system is regulated by the brain-derived neurotrophic factor (BDNF)/Tropomyosin-related kinase B (TrkB) pathway, but the cell-intrinsic role of TrkB signaling in parvalbumin cortical interneuron development and function is unclear. We performed conditional ablation of the TrkB receptor in parvalbumin-expressing (PV) interneurons to study whether postnatal loss of TrkB in parvalbumin cells affects their survival, connectivity, spontaneous and evoked neuronal activity and behavior. Using in vivo recordings of local field potentials, we found reduced gamma oscillations in the sensory cortex of PVcre+; TrkBF/F conditional knockout mice (TrkB cKO), along with increased firing of putative excitatory neurons. There was a significant downregulation in parvalbumin neuron number in cerebral and cerebellar cortices of TrkB cKO mice. In addition, inhibitory synaptic connections between basket cells and pyramidal neurons were profoundly reduced in the neocortex of TrkB cKO mice and there was a loss of cortical volume. TrkB cKO mice also showed profound hyperactivity, stereotypies, motor deficits and learning/memory defects. Our findings demonstrate that the targeting and/or synapse formation of PV-expressing basket cells with principal excitatory neurons require TrkB signaling in parvalbumin cells. Disruption of this signaling has major consequences for parvalbumin interneuron connectivity, network dynamics, cognitive and motor behavior.

From Healthy Aging to Frailty: In Search of the Underlying Mechanisms

Population aging is accelerating rapidly worldwide, from 461 million people older than 65 years in 2004 to an estimated 2 billion people by 2050, leading to critical implications for the planning and delivery of health and social care. The most problematic expression of population aging is the clinical condition of frailty, which is a state of increased vulnerability that develops as a consequence of the accumulation of microscopic damages in many physiological systems that lead to a striking and disproportionate change in health state, even after an apparently small insult. Since little is known about the biology of frailty, an important perspective to understand this phenomenon is to establish how the alterations that physiologically occur during a condition of healthy aging may instead promote cumulative decline with subsequent depletion of homoeostatic reserve and increase the vulnerability also after minor stressor events. In this context, the present review aims to provide a description of the molecular mechanisms that, by having a critical impact on behavior and neuronal function in aging, might be relevant for the development of frailty. Moreover, since these biological systems are also involved in the coping strategies set in motion to respond to environmental challenges, we propose a role for lifestyle stress as an important player to drive frailty in aging.

Vascular and non-vascular contributors to memory reduction during traumatic brain injury

Traumatic brain injury (TBI) is an increasing health problem. It is a complex, progressive disease that consists of many factors affecting memory. Studies have shown that increased blood-brain barrier (BBB) permeability initiates pathological changes in neuro-vascular network but the role of cerebrovascular dysfunction and its mediated mechanisms associated with memory reduction during TBI are still not well understood. Changes in BBB, inflammation, extravasation of blood plasma components, activation of neuroglia lead to neurodegeneration. Extravasated proteins such as amyloid-beta, fibrinogen, and cellular prion protein may form degradation resistant complexes that can lead to neuronal dysfunction and degeneration. They also have the ability to activate astrocytes, and thus, can be involved in memory impairment. Understanding the triggering mechanisms and the places they originate in vasculature or in extravascular tissue may help to identify potential therapeutic targets to ameliorate memory reduction during TBI. The goal of this review is to discuss conceptual mechanisms that lead to short-term memory reduction during non-severe TBI considering distinction between vascular and non-vascular effects on neurons. Some aspects of these mechanisms need to be confirmed further. Therefore, we hope that the discussion presented bellow may lead to experiments that may clarify the triggering mechanisms of memory reduction after head trauma.

MeCP2 Deficiency Disrupts Kainate-Induced Presynaptic Plasticity in the Mossy Fiber Projections in the Hippocampus

Methyl cytosine binding protein 2 (MeCP2) is a structural chromosomal protein involved in the regulation of gene expression. Mutations in the gene encoding MeCP2 result in Rett Syndrome (RTT), a pervasive neurodevelopmental disorder. RTT is one of few autism spectrum disorders whose cause was identified as a single gene mutation. Remarkably, abnormal levels of MeCP2 have been associated to other neurodevelopmental disorders, as well as neuropsychiatric disorders. Therefore, many studies have been oriented to investigate the role of MeCP2 in the nervous system. In the present work, we explore cellular and molecular mechanisms affecting synaptic plasticity events in vivo in the hippocampus of MeCP2 mutant mice. While most studies addressed postsynaptic defects in the absence of MeCP2, we took advantage of an in vivo activity-paradigm (seizures), two models of MeCP2 deficiency, and neurobiological assays to reveal novel defects in presynaptic structural plasticity in the hippocampus in RTT rodent models. These approaches allowed us to determine that MeCP2 mutations alter presynaptic components, i.e., disrupts the plastic response of mossy fibers to synaptic activity and results in reduced axonal growth which is correlated with imbalanced trophic and guidance support, associated with aberrant expression of brain-derived neurotrophic factor and semaphorin 3F. Our results also revealed that adult-born granule cells recapitulate maturational defects that have been only shown at early postnatal ages. As these cells do not mature timely, they may not integrate properly into the adult hippocampal circuitry. Finally, we performed a hippocampal-dependent test that revealed defective spatial memory in these mice. Altogether, our studies establish a model that allows us to evaluate the effect of the manipulation of specific pathways involved in axonal guidance, synaptogenesis, or maturation in specific circuits and correlate it with changes in behavior. Understanding the mechanisms underlying the neuronal compromise caused by mutations in MeCP2 could provide information on the pathogenic mechanism of autistic spectrum disorders and improve our understanding of brain development and molecular basis of behavior.

Oligodendrocytes regulate presynaptic properties and neurotransmission through BDNF signaling in the mouse brainstem

Neuron–glia communication contributes to the fine-tuning of synaptic functions. Oligodendrocytes near synapses detect and respond to neuronal activity, but their role in synapse development and plasticity remains largely unexplored. We show that oligodendrocytes modulate neurotransmitter release at presynaptic terminals through secretion of brain-derived neurotrophic factor (BDNF). Oligodendrocyte-derived BDNF functions via presynaptic tropomyosin receptor kinase B (TrkB) to ensure fast, reliable neurotransmitter release and auditory transmission in the developing brain. In auditory brainstem slices from Bdnf^+/– mice, reduction in endogenous BDNF significantly decreased vesicular glutamate release by reducing the readily releasable pool of glutamate vesicles, without altering presynaptic Ca²⁺ channel activation or release probability. Using conditional knockout mice, cell-specific ablation of BDNF in oligodendrocytes largely recapitulated this effect, which was recovered by BDNF or TrkB agonist application. This study highlights a novel function for oligodendrocytes in synaptic transmission and their potential role in the activity-dependent refinement of presynaptic properties.

Marijuana use among adolescents is associated with deleterious alterations in mature BDNF

Background

With increases in marijuana use and legalization efforts, it is imperative to establish its impact on the developing brain. Therefore, we investigated whether exposure to marijuana alters brain derived neurotropic-factor (BDNF), given its critical role in brain development and plasticity. We then examined whether onset age of cannabis use was associated with more severe changes. A single site, cohort study following 500 urban healthy American adolescents. Changes in plasma m-BDNF levels were longitudinally assessed, and a multi-method approach was implemented to ascertain marijuana use. Multivariate and general linear model (GLM) regression modeling were utilized to test the main hypothesis, controlling for confounders.

Results

Group-based trajectory modeling identified four distinct groups, characterized by naive (60% control), starters (14%), chronic users (20%), and experimenting/quitters (6%). Compared to controls, those initiating marijuana use had similar pre-existent m-BDNF (1939.2 ± 221 vs. 2640.7 ± 1309 ng/ml, p=0.4) After adjusting for confounding factors, GLM analyses revealed that, compared to controls, younger adolescents increased BDNF levels when experimenting and during moderate marijuana use. Older adolescents had a steeper increase in endogenous BDNF levels, particularly when escalating use. Multivariate analyses confirmed marijuana use as a predictor of m-BDNF (p = 0.001).

Conclusions

This is the first study demonstrating BDNF alterations were not a precondition. Rather, BDNF alteration was secondary to marijuana use, serving as cautionary evidence of marijuana's deleterious effects. Findings suggest that when marijuana use escalates, the BDNF pathway becomes more deregulated. Analyses confirm that age of marijuana use onset influences the magnitude of these changes.

Decreased Serum Brain-Derived Neurotrophic Factor (BDNF) Levels in Patients with Alzheimer's Disease (AD): A Systematic Review and Meta-Analysis

Findings from previous studies reporting the levels of serum brain-derived neurotrophic factor (BDNF) in patients with Alzheimer's disease (AD) and individuals with mild cognitive impairment (MCI) have been conflicting. Hence, we performed a meta-analysis to examine the aggregate levels of serum BDNF in patients with AD and individuals with MCI, in comparison with healthy controls. Fifteen studies were included for the comparison between AD and healthy control (HC) (n = 2067). Serum BDNF levels were significantly lower in patients with AD (SMD: -0.282; 95% confidence interval [CI]: -0.535 to -0.028; significant heterogeneity: I² = 83.962). Meta-regression identified age (p < 0.001) and MMSE scores (p < 0.001) to be the significant moderators that could explain the heterogeneity in findings in these studies. Additionally, there were no significant differences in serum BDNF levels between patients with AD and MCI (eight studies, n = 906) and between MCI and HC (nine studies, n = 5090). In all, patients with AD, but not MCI, have significantly lower serum BDNF levels compared to healthy controls. This meta-analysis confirmed the direction of change in serum BDNF levels in dementia. This finding suggests that a significant change in peripheral BDNF levels can only be detected at the late stage of the dementia spectrum. Molecular mechanisms, implications on interventional trials, and future directions for studies examining BDNF in dementia were discussed.

Actions of Brain-Derived Neurotrophin Factor in the Neurogenesis and Neuronal Function, and Its Involvement in the Pathophysiology of Brain Diseases

It is well known that brain-derived neurotrophic factor, BDNF, has an important role in a variety of neuronal aspects, such as differentiation, maturation, and synaptic function in the central nervous system (CNS). BDNF stimulates mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK), phosphoinositide-3kinase (PI3K), and phospholipase C (PLC)-gamma pathways via activation of tropomyosin receptor kinase B (TrkB), a high affinity receptor for BDNF. Evidence has shown significant contributions of these signaling pathways in neurogenesis and synaptic plasticity in in vivo and in vitro experiments. Importantly, it has been demonstrated that dysfunction of the BDNF/TrkB system is involved in the onset of brain diseases, including neurodegenerative and psychiatric disorders. In this review, we discuss actions of BDNF and related signaling molecules on CNS neurons, and their contributions to the pathophysiology of brain diseases.

How alcohol drinking affects our genes: an epigenetic point of view

This work highlights recent studies in epigenetic mechanisms that play a role in alcoholism, which is a complex multifactorial disorder. There is a large body of evidence showing that alcohol can modify gene expression through epigenetic processes, namely DNA methylation and nucleosomal remodeling via histone modifications. In that regard, chronic exposure to ethanol modifies DNA and histone methylation, histone acetylation, and microRNA expression. The alcohol-mediated chromatin remodeling in the brain promotes the transition from use to abuse and addiction. Unravelling the multiplex pattern of molecular modifications induced by ethanol could support the development of new therapies for alcoholism and drug addiction targeting epigenetic processes.

Imaging resilience and recovery in alcohol dependence

BACKGROUND AND AIMS

Resilience and recovery are of increasing importance in the field of alcohol dependence (AD). This paper describes how imaging studies in man can be used to assess the neurobiological correlates of resilience and, if longitudinal, of disease trajectories, progression rates and markers for recovery to inform treatment and prevention options.

METHODS

Original papers on recovery and resilience in alcohol addiction and its neurobiological correlates were identified from PubMed and have been analyzed and condensed within a systematic literature review.

RESULTS

Findings deriving from functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies have identified links between increased resilience and less task-elicited neural activation within the basal ganglia, and benefits of heightened neural pre-frontal cortex (PFC) engagement regarding resilience in a broader sense; namely, resilience against relapse in early abstinence of AD. Furthermore, findings consistently propose at least partial recovery of brain glucose metabolism and executive and general cognitive functioning, as well as structural plasticity effects throughout the brain of alcohol-dependent patients during the course of short-, medium- and long-term abstinence, even when patients only lowered their alcohol consumption to a moderate level. Additionally, specific factors were found that appear to influence these observed brain recovery processes in AD, e.g. genotype-dependent neuronal (re)growth, gender-specific neural recovery effects, critical interfering effects of psychiatric comorbidities, additional smoking or marijuana influences or adolescent alcohol abuse.

CONCLUSIONS

Neuroimaging research has uncovered neurobiological markers that appear to be linked to resilience and improved recovery capacities that are furthermore influenced by various factors such as gender or genetics. Consequently, future system-oriented approaches may help to establish a broad neuroscience-based research framework for alcohol dependence.

Neuroimmunologic and Neurotrophic Interactions in Autism Spectrum Disorders: Relationship to Neuroinflammation

Autism spectrum disorders (ASD) are the most prevalent set of pediatric neurobiological disorders. The etiology of ASD has both genetic and environmental components including possible dysfunction of the immune system. The relationship of the immune system to aberrant neural circuitry output in the form of altered behaviors and communication characterized by ASD is unknown. Dysregulation of neurotrophins such as BDNF and their signaling pathways have been implicated in ASD. While abnormal cortical formation and autistic behaviors in mouse models of immune activation have been described, no one theory has been described to link activation of the immune system to specific brain signaling pathways aberrant in ASD. In this paper we explore the relationship between neurotrophin signaling, the immune system and ASD. To this effect we hypothesize that an interplay of dysregulated immune system, synaptogenic growth factors and their signaling pathways contribute to the development of ASD phenotypes.

Beyond good and evil: A putative continuum-sorting hypothesis for the functional role of proBDNF/BDNF-propeptide/mBDNF in antidepressant treatment

Depression and posttraumatic stress disorder are assumed to be maladaptive responses to stress and antidepressants are thought to counteract such responses by increasing BDNF (brain-derived neurotrophic factor) levels. BDNF acts through TrkB (tropomyosin-related receptor kinase B) and plays a central role in neuroplasticity. In contrast, both precursor proBDNF and BDNF propeptide (another metabolic product from proBDNF cleavage) have a high affinity to p75 receptor (p75R) and usually convey apoptosis and neuronal shrinkage. Although BDNF and proBDNF/propeptide apparently act in opposite ways, neuronal turnover and remodeling might be a final common way that both act to promote more effective neuronal networking, avoiding neuronal redundancy and the misleading effects of environmental contingencies. This review aims to provide a brief overview about the BDNF functional role in antidepressant action and about p75R and TrkB signaling to introduce the "continuum-sorting hypothesis." The resulting hypothesis suggests that both BDNF/proBDNF and BDNF/propeptide act as protagonists to fine-tune antidepressant-dependent neuroplasticity in crucial brain structures to modulate behavioral responses to stress.

Evaluation of plasma brain-derived neurotrophic factor levels and self-perceived cognitive impairment post-chemotherapy: a longitudinal study

Background

Preliminary evidence suggests that changes in plasma brain-derived neurotrophic factor (BDNF) levels may contribute to the occurrence of chemotherapy-associated cognitive impairment (CACI), and a previous study suggested that carriers of the BDNF Met homozygous genotype are protected from CACI.

Methods

This multicenter, prospective cohort study involved chemotherapy-receiving early-stage breast cancer (ESBC) patients. Self-perceived cognitive function was longitudinally assessed using the validated FACT-Cog (ver. 3) across three time points: Prior to chemotherapy (T1), during chemotherapy (T2), and at the end of chemotherapy (T3). Plasma BDNF levels were quantified using enzyme-linked immunosorbent assay. Genotyping was performed using Sanger Sequencing.

Results

A total of 51 chemotherapy-receiving ESBC patients (mean age: 52.6 ± 9.5 years) were recruited, and 11 patients (21.6%) reported subjective cognitive impairment post-chemotherapy. Overall, there was a reduction in median plasma BDNF levels over time (T1: 5423.0 pg/ml; T2: 5313.6 pg/ml; T3: 4050.3 pg/ml; p < 0.01). After adjusting for confounding factors, longitudinal analysis revealed that BDNF levels were associated with self-reported concentration deficit (p = 0.032). Carriers of Val/Val (p = 0.011) and Val/Met (p = 0.003) BDNF genotypes demonstrated a significant reduction in plasma BDNF levels over time; however, plasma BDNF levels were similar across all time points among Met homozygous carriers (p = 0.107).

Conclusion

There was a statistically significant change in BDNF levels post-chemotherapy in ESBC patients, and plasma BDNF levels were associated with self-perceived concentration deficit in patients receiving chemotherapy.

Alleviative effects of fluoxetine on depressive-like behaviors by epigenetic regulation of BDNF gene transcription in mouse model of post-stroke depression

Fluoxetine, one of the selective serotonin reuptake inhibitor (SSRI) antidepressants, has been thought to be effective for treating post-stroke depression (PSD). Recent work has shown that fluoxetine may exert an antidepressive effect through increasing the level of brain-derived neurotrophic factor (BDNF), but the underlying mechanism still remains unclear. In the present study, we successfully established the PSD model using male C57BL/6 J mice by photothrombosis of the left anterior cortex combined with isolatied-housing conditions. In the process, we confirmed that fluoxetine could improve the depression-like behaviors of PSD mice and upregulate the expression of BDNF in the hippocampus. However, depletion of BDNF by transfecting lentivirus-derived shBDNF in hippocampus suppressed the effect of fluoxetine. Furthermore, we demonstrated the epigenetic mechanisms involved in regulation of BDNF expression induced by fluoxetine. We found a statistically significant increase in DNA methylation at specific CpG sites (loci 2) of Bdnf promoter IV in the hippocampus of PSD mice. We also found that fluoxetine treatment could disassociate the MeCP2-CREB-Bdnf promoter IV complex via phosphorylation of MeCP2 at Ser421 by Protein Kinase A (PKA). Our research highlighted the importance of fluoxetine in regulating BDNF expression which could represent a potential strategy for preventing PSD.

Estrogens and the cognitive symptoms of schizophrenia: Possible neuroprotective mechanisms

Schizophrenia is a complex neuropsychiatric illness with marked sex differences. Women have later onset and lesser symptoms, which has led to the hypothesis that estrogens are protective in schizophrenia. Cognitive dysfunction is a hallmark of the disease and the symptom most correlated with functional outcome. Here we describe a number of mechanisms by which estrogens may be therapeutic in schizophrenia, with a focus on cognitive symptoms. We review the relationship between estrogens and brain derived neurotrophic factor, neuroinflammation, NMDA receptors, GABA receptors, and luteinizing hormone. Exploring these pathways may enable novel treatments for schizophrenia and a greater understanding of this devastating disease.