Neurotrophin-evoked rapid excitation through TrkB receptors

Distinct roles of Bdnf I and Bdnf IV transcript variant expression in hippocampal neurons

Brain-derived neurotrophic factor (Bdnf) plays a critical role in brain development, dendritic growth, synaptic plasticity, as well as learning and memory. The rodent Bdnf gene contains nine 5' non-coding exons (I-IXa), which are spliced to a common 3' coding exon (IX). Transcription of individual Bdnf variants, which all encode the same BDNF protein, is initiated at unique promoters upstream of each non-coding exon, enabling precise spatiotemporal and activity-dependent regulation of Bdnf expression. Although prior evidence suggests that Bdnf transcripts containing exon I (Bdnf I) or exon IV (Bdnf IV) are uniquely regulated by neuronal activity, the functional significance of different Bdnf transcript variants remains unclear. To investigate functional roles of activity-dependent Bdnf I and IV transcripts, we used a CRISPR activation system in which catalytically dead Cas9 fused to a transcriptional activator (VPR) is targeted to individual Bdnf promoters with single guide RNAs, resulting in transcript-specific Bdnf upregulation. Bdnf I upregulation is associated with gene expression changes linked to dendritic growth, while Bdnf IV upregulation is associated with genes that regulate protein catabolism. Upregulation of Bdnf I, but not Bdnf IV, increased mushroom spine density, volume, length, and head diameter, and also produced more complex dendritic arbors in cultured rat hippocampal neurons. In contrast, upregulation of Bdnf IV, but not Bdnf I, in the rat hippocampus attenuated contextual fear expression. Our data suggest that while Bdnf I and IV are both activity-dependent, BDNF produced from these promoters may serve unique cellular, synaptic, and behavioral functions.

Skeletal interoception in osteoarthritis

The interoception maintains proper physiological conditions and metabolic homeostasis by releasing regulatory signals after perceving changes in the internal state of the organism. Among its various forms, skeletal interoception specifically regulates the metabolic homeostasis of bones. Osteoarthritis (OA) is a complex joint disorder involving cartilage, subchondral bone, and synovium. The subchondral bone undergoes continuous remodeling to adapt to dynamic joint loads. Recent findings highlight that skeletal interoception mediated by aberrant mechanical loads contributes to pathological remodeling of the subchondral bone, resulting in subchondral bone sclerosis in OA. The skeletal interoception is also a potential mechanism for chronic synovial inflammation in OA. In this review, we offer a general overview of interoception, specifically skeletal interoception, subchondral bone microenviroment and the aberrant subchondral remedeling. We also discuss the role of skeletal interoception in abnormal subchondral bone remodeling and synovial inflammation in OA, as well as the potential prospects and challenges in exploring novel OA therapies that target skeletal interoception.

Plasma and Platelet Brain-Derived Neurotrophic Factor (BDNF) Levels in Bipolar Disorder Patients with Post-Traumatic Stress Disorder (PTSD) or in a Major Depressive Episode Compared to Healthy Controls

Post-traumatic stress disorder (PTSD) is a highly disabling mental disorder arising after traumatism exposure, often revealing critical and complex courses when comorbidity with bipolar disorder (BD) occurs. To search for PTSD or depression biomarkers that would help clinicians define BD presentations, this study aimed at preliminarily evaluating circulating brain-derived-neurotrophic factor (BDNF) levels in BD subjects with PTSD or experiencing a major depressive episode versus controls. Two bloodstream BDNF components were specifically investigated, the storage (intraplatelet) and the released (plasma) ones, both as adaptogenic/repair signals during neuroendocrine stress response dynamics. Bipolar patients with PTSD (n = 20) or in a major depressive episode (n = 20) were rigorously recruited together with unrelated healthy controls (n = 24) and subsequently examined by psychiatric questionnaires and blood samplings. Platelet-poor plasma (PPP) and intraplatelet (PLT) BDNF were measured by ELISA assays. The results showed markedly higher intraplatelet vs. plasma BDNF, confirming platelets' role in neurotrophin transport/storage. No between-group PPP-BDNF difference was reported, whereas PLT-BDNF was significantly reduced in depressed BD patients. PLT-BDNF negatively correlated with mood scores but not with PTSD items like PPP-BDNF, which instead displayed opposite correlation trends with depression and manic severity. Present findings highlight PLT-BDNF as more reliable at detecting depression than PTSD in BD, encouraging further study into BDNF variability contextually with immune-inflammatory parameters in wider cohorts of differentially symptomatic bipolar patients.

Neuropeptides and Their Roles in the Cerebellum

Although more than 30 different types of neuropeptides have been identified in various cell types and circuits of the cerebellum, their unique functions in the cerebellum remain poorly understood. Given the nature of their diffuse distribution, peptidergic systems are generally assumed to exert a modulatory effect on the cerebellum via adaptively tuning neuronal excitability, synaptic transmission, and synaptic plasticity within cerebellar circuits. Moreover, cerebellar neuropeptides have also been revealed to be involved in the neurogenetic and developmental regulation of the developing cerebellum, including survival, migration, differentiation, and maturation of the Purkinje cells and granule cells in the cerebellar cortex. On the other hand, cerebellar neuropeptides hold a critical position in the pathophysiology and pathogenesis of many cerebellar-related motor and psychiatric disorders, such as cerebellar ataxias and autism. Over the past two decades, a growing body of evidence has indicated neuropeptides as potential therapeutic targets to ameliorate these diseases effectively. Therefore, this review focuses on eight cerebellar neuropeptides that have attracted more attention in recent years and have significant potential for clinical application associated with neurodegenerative and/or neuropsychiatric disorders, including brain-derived neurotrophic factor, corticotropin-releasing factor, angiotensin II, neuropeptide Y, orexin, thyrotropin-releasing hormone, oxytocin, and secretin, which may provide novel insights and a framework for our understanding of cerebellar-related disorders and have implications for novel treatments targeting neuropeptide systems.

Ni and Al mixture amplifies cerebellar oxido-inflammatory responses, down regulates AChE and BDNF/NGF levels in motor impairment in male albino rats

BACKGROUND

Aluminum and nickel are potent neurotoxicants to which humans are constantly exposed. Previous studies have demonstrated that these two metals can affect the motor system, but their effects on the cerebellum, a central nervous system region with the highest number of neurons, have remained largely unexplored. Therefore, we conducted a study to investigate the adverse effects of Al, Ni, and Al+Ni in vivo.

METHODS

In our study, seven male Sprague Dawley rats per group were orally exposed to deionized water, 0.2 mg/kg of Ni, 1 mg/kg of Al, and 0.2 mg/kg of Ni + 1 mg/kg of Al (as a binary heavy metals mixture; HMM), respectively.

RESULTS

Ni, Al, and HMM exposed rats accumulated higher levels of Al and Ni compared to controls, and HMM treated animals had higher levels of Ca and Fe in the cerebellum (p < 0.05). Malondialdehyde (MDA) levels were significantly (p < 0.05) higher in the HMM, Ni, and Al treated groups compared to the control group that received deionized water. Superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (GPx) activities were significantly (p < 0.05) reduced in the HMM, Ni, and Al treated groups compared to the control group that received deionized water. Ni, Al, and HMM significantly (p < 0.05) shortened the length of time of the grip in comparison to the control. Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) levels were significantly decreased in the nickel, Al, and heavy metal mixture groups compared with the control group. Moreover, there was a significant decrease in the activity of acetylcholinesterase (AChE) and a increase in cyclooxygenase-2 (COX-2) activity in the Ni, Al, and HMM treated groups compared to the control group.

CONCLUSION

HMM exposed animals had significantly poorer performance in the Rotarod test (p < 0.05) than controls. Al and Ni induced impairment of cerebellar function at various levels.

BDNF and Lactate as Modulators of Hippocampal CA3 Network Physiology

Growing evidence supports the notion that brain-derived neurotrophic factor (BDNF) and lactate are potent modulators of mammalian brain function. The modulatory actions of those biomolecules influence a wide range of neuronal responses, from the shaping of neuronal excitability to the induction and expression of structural and synaptic plasticity. The biological actions of BDNF and lactate are mediated by their cognate receptors and specific transporters located in the neuronal membrane. Canonical functions of BDNF occur via the tropomyosin-related kinase B receptor (TrkB), whereas lactate acts via monocarboxylate transporters or the hydroxycarboxylic acid receptor 1 (HCAR1). Both receptors are highly expressed in the central nervous system, and some of their physiological actions are particularly well characterized in the hippocampus, a brain structure involved in the neurophysiology of learning and memory. The multifarious neuronal circuitry between the axons of the dentate gyrus granule cells, mossy fibers (MF), and pyramidal neurons of area CA3 is of great interest given its role in specific mnemonic processes and involvement in a growing number of brain disorders. Whereas the modulation exerted by BDNF via TrkB has been extensively studied, the influence of lactate via HCAR1 on the properties of the MF-CA3 circuit is an emerging field. In this review, we discuss the role of both systems in the modulation of brain physiology, with emphasis on the hippocampal CA3 network. We complement this review with original data that suggest cross-modulation is exerted by these two independent neuromodulatory systems.

Downregulation of BDNF-TrkB signaling may contribute to the colonic motility disorders in mice with streptozocin-induced diabetes

BACKGROUND

Brain-derived neurotrophic factor (BDNF) acts as a neuromodulator to regulate gut motility, but the role of BDNF in diabetes-related dysmotility is uncertain. The aim of this study was to investigate the possible involvement of BDNF and its receptor TrkB in the colonic hypomotility of mice with streptozotocin (STZ)-induced diabetes.

METHODS

A single intraperitoneal injection of STZ was used to establish a type 1 diabetes model. An organ bath system was applied to observe the contractile activities of colonic muscle strips. Immunofluorescence and western blotting were performed to evaluate the expression of BDNF and TrkB in the colon. ELISA was used to detect BDNF and SP levels in the serum and colon. The patch-clamp technique was applied to record the currents of L-type calcium channels and large conductance Ca2+ -activated K+ channels on smooth muscle cells.

KEY RESULTS

Compared with healthy controls, diabetic mice showed attenuated colonic muscle contraction (p < 0.001), which was partly reversed by BDNF supplementation. TrkB protein expression was significantly reduced in diabetic mice (p < 0.05). In addition, both BDNF and substance P (SP) levels were decreased, and exogenous administration of BDNF increased SP levels in diabetic mice (p < 0.05). Both the TrkB antagonist and the TrkB antibody inhibited the spontaneous contraction of colonic muscle strips (p < 0.01). Moreover, the BDNF-TrkB signaling system enhanced SP-induced muscle contraction.

CONCLUSIONS

Downregulation of BDNF/TrkB signaling and reduced SP release from the colon may contribute to the colonic hypomotility associated with type 1 diabetes. Brain-derived neurotrophic factor supplementation may have therapeutic potential for diabetes-related constipation.

Neutralizing antibodies with neurotropic factor treatment maintain neurodevelopmental gene expression upon exposure to human cytomegalovirus

IMPORTANCE

Human cytomegalovirus (HCMV) infection is the leading cause of non-heritable birth defects worldwide. HCMV readily infects the early progenitor cell population of the developing brain, and we have found that infection leads to significantly downregulated expression of key neurodevelopmental transcripts. Currently, there are no approved therapies to prevent or mitigate the effects of congenital HCMV infection. Therefore, we used human-induced pluripotent stem cell-derived organoids and neural progenitor cells to elucidate the glycoproteins and receptors used in the viral entry process and whether antibody neutralization was sufficient to block viral entry and prevent disruption of neurodevelopmental gene expression. We found that blocking viral entry alone was insufficient to maintain the expression of key neurodevelopmental genes, but neutralization combined with neurotrophic factor treatment provided robust protection. Together, these studies offer novel insight into mechanisms of HCMV infection in neural tissues, which may aid future therapeutic development.

14-3-3ζ Plays a key role in the modulation of neuroplasticity underlying the antidepressant-like effects of Zhi-Zi-Chi-Tang

BACKGROUND

Zhi-Zi-Chi-Tang (ZZCT) is an effective traditional Chinese medicinal formula. ZZCT has been used for the treatment of depression for centuries. Its clinical efficacy in relieving depression has been confirmed. However, the molecular mechanisms of ZZCT regarding neuroplasticity in the pathogenesis of depression have not yet been elucidated.

PURPOSE

The present study aimed to examine the effects of ZZCT on neuroplasticity in mice exposed to chronic unpredictable mild stress (CUMS), and to explore the underlying molecular mechanisms.

METHODS

For this purpose, a murine model of depression was established using the CUMS procedure. Following the intragastric administration of ZZCT or fluoxetine, classic behavioral experiments were performed to observe the efficacy of ZZCT as an antidepressant. Immunofluorescence was used to label and quantify microtubule-associated protein (MAP2) and postsynaptic density protein (PSD95) in the hippocampus. Golgi staining was applied to visualize the dendritic spine density of neurons in the hippocampi. Isolated hippocampal slices were prepared to induce long-term potentiation (LTP) in the CA1 area. The hippocampal protein expression levels of glycogen synthase kinase-3β (GSK-3β), p-GSK-3β (Ser9), cAMP response element binding protein (CREB), p-CREB (Ser133), brain-derived neurotrophic factor (BDNF) and 14-3-3ζ were detected using western blot analysis. The interaction of 14-3-3ζ and p-GSK-3β (Ser9) was examined using co-immunoprecipitation. LV-shRNA was used to knockdown 14-3-3ζ by an intracerebroventricular injection.

RESULTS

ZZCT (6 g/kg) and fluoxetine (20 mg/kg) alleviated depressive-like behavior, restored hippocampal MAP2⁺ PSD95⁺ intensity, and reversed the dendritic spine density of hippocampal neurons and LTP in the CA1 region of mice exposed to CUMS. Both low and high doses of ZZCT (3 and 6 g/kg) significantly promoted the binding of 14-3-3ζ to p-GSK-3β (Ser9) in the hippocampus, and ZZCT (6 g/kg) significantly promoted the phosphorylation of GSK-3β Ser9 and CREB Ser133 in the hippocampus. ZZCT (3 and 6 g/kg) upregulated hippocampal BDNF expression in mice exposed to CUMS. LV-sh14-3-3ξ reduced the antidepressant effects of ZZCT.

CONCLUSION

ZZCT exerted antidepressant effects against CUMS-stimulated depressive-like behavior mice. The knockdown of 14-3-3ζ using lentivirus confirmed that 14-3-3ζ was involved in the ZZCT-mediated antidepressant effects through GSK-3β/CREB/BDNF signaling. On the whole, these results suggest that the antidepressant effects of ZZCT are attributed to restoring damage by neuroplasticity enhancement via the 14-3-3ζ/GSK-3β/CREB/BDNF signaling pathway.

Distinct roles of Bdnf I and Bdnf IV transcript variant expression in hippocampal neurons

Brain-derived neurotrophic factor (Bdnf) plays a critical role in brain development, dendritic growth, synaptic plasticity, as well as learning and memory. The rodent Bdnf gene contains nine 5' non-coding exons (I-IXa), which are spliced to a common 3' coding exon (IX). Transcription of individual Bdnf variants, which all encode the same BDNF protein, is initiated at unique promoters upstream of each non-coding exon, enabling precise spatiotemporal and activity-dependent regulation of Bdnf expression. Although prior evidence suggests that Bdnf transcripts containing exon I (Bdnf I) or exon IV (Bdnf IV) are uniquely regulated by neuronal activity, the functional significance of different Bdnf transcript variants remains unclear. To investigate functional roles of activity-dependent Bdnf I and IV transcripts, we used a CRISPR activation (CRISPRa) system in which catalytically-dead Cas9 (dCas9) fused to a transcriptional activator (VPR) is targeted to individual Bdnf promoters with single guide RNAs (sgRNAs), resulting in transcript-specific Bdnf upregulation. Bdnf I upregulation is associated with gene expression changes linked to dendritic growth, while Bdnf IV upregulation is associated with genes that regulate protein catabolism. Upregulation of Bdnf I, but not Bdnf IV, increased mushroom spine density, volume, length, and head diameter, and also produced more complex dendritic arbors in cultured rat hippocampal neurons. In contrast, upregulation of Bdnf IV, but not Bdnf I, in the rat hippocampus attenuated contextual fear expression. Our data suggest that while Bdnf I and IV are both activity-dependent, BDNF produced from these promoters may serve unique cellular, synaptic, and behavioral functions.

The potential neuroprotective effects of stingless bee honey

Tropical Meliponini bees produce stingless bee honey (SBH). Studies have shown beneficial properties, including antibacterial, bacteriostatic, anti-inflammatory, neurotherapeutic, neuroprotective, wound, and sunburn healing capabilities. High phenolic acid and flavonoid concentrations offer SBH its benefits. SBH can include flavonoids, phenolic acids, ascorbic acid, tocopherol, organic acids, amino acids, and protein, depending on its botanical and geographic origins. Ursolic acid, p-coumaric acid, and gallic acid may diminish apoptotic signals in neuronal cells, such as nuclear morphological alterations and DNA fragmentation. Antioxidant activity minimizes reactive oxygen species (ROS) formation and lowers oxidative stress, inhibiting inflammation by decreasing enzymes generated during inflammation. Flavonoids in honey reduce neuroinflammation by decreasing proinflammatory cytokine and free radical production. Phytochemical components in honey, such as luteolin and phenylalanine, may aid neurological problems. A dietary amino acid, phenylalanine, may improve memory by functioning on brain-derived neurotrophic factor (BDNF) pathways. Neurotrophin BDNF binds to its major receptor, TrkB, and stimulates downstream signaling cascades, which are crucial for neurogenesis and synaptic plasticity. Through BDNF, SBH can stimulate synaptic plasticity and synaptogenesis, promoting learning and memory. Moreover, BDNF contributes to the adult brain's lasting structural and functional changes during limbic epileptogenesis by acting through the cognate receptor tyrosine receptor kinase B (TrkB). Given the higher antioxidants activity of SBH than the Apis sp. honey, it may be more therapeutically helpful. There is minimal research on SBH's neuroprotective effects, and the related pathways contribute to it is unclear. More research is needed to elucidate the underlying molecular process of SBH on BDNF/TrkB pathways in producing neuroprotective effects.

Multicomponent exercise program effects on fitness and cognitive function of elderlies with mild cognitive impairment: Involvement of oxidative stress and BDNF

Regular exercise has been shown to be one of the most important lifestyle influences on improving functional performance, and decreasing morbidity and all-cause mortality among older people. However, although there is some evidence on the effects of aerobic training on oxidative stress, there is little information regarding the effects of multicomponent exercise (dual-task training) and combination of exercise with cognitive stimulation on oxidative stress. In this context, the aim of this study was to verify the effects of a multicomponent exercise program on physical fitness and cognitive function in the elderly with mild cognitive impairment and determine the role of oxidative stress and brain-derived neurotrophic factor (BDNF). At baseline, 37 elderly nursing home residents with mild cognitive impairment were divided into two groups: the control group (CG, n = 12, 81.8 years) and the experimental group (EG, n = 25, 83.2 years). These elderlies followed multicomponent exercise training for 24 weeks, with two sessions per week and 45–50 min per session. The exercises included both aerobic and strength exercises, considering functional movements and light to moderate intensity. Cognitive stimulation comprehended exercises based on word games, puzzles, mathematical calculations, forward and backward counting, computer exercises, exergames, and games on a balanced platform. Physical assessments (weight, height, and body mass index), health and functional parameters (fitness tests: chair stand, arm curls, chair sit-and-reach, eight feet up-and-go, back scratch, 6-min walking, feet together, semi-tandem, and full tandem), lipid profile (total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglycerides), measures of lipid peroxidation damage, thiobarbituric acid reactive substances (TBARS), total antioxidant capacity (TAC), and BDNF were measured in plasma, based on which analyses were performed before and after the 24 weeks of the multicomponent exercise intervention. The results showed an overall improvement in physical and functional performance. Regarding biochemical measures, multicomponent exercises lead to a significant decrease in oxidative damage. The results indicate that multicomponent exercise training induces benefits in functional capacity and reduces damage due to oxidative stress.

BDNF Therapeutic Mechanisms in Neuropsychiatric Disorders

Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain and functions as both a primary neurotrophic signal and a neuromodulator. It serves essential roles in neuronal development, maintenance, transmission, and plasticity, thereby influencing aging, cognition, and behavior. Accumulating evidence associates reduced central and peripheral BDNF levels with various neuropsychiatric disorders, supporting its potential utilization as a biomarker of central pathologies. Subsequently, extensive research has been conducted to evaluate restoring, or otherwise augmenting, BDNF transmission as a potential therapeutic approach. Promising results were indeed observed for genetic BDNF upregulation or exogenous administration using a multitude of murine models of neurological and psychiatric diseases. However, varying mechanisms have been proposed to underlie the observed therapeutic effects, and many findings indicate the engagement of disease-specific and other non-specific mechanisms. This is because BDNF essentially affects all aspects of neuronal cellular function through tropomyosin receptor kinase B (TrkB) receptor signaling, the disruptions of which vary between brain regions across different pathologies leading to diversified consequences on cognition and behavior. Herein, we review the neurophysiology of BDNF transmission and signaling and classify the converging and diverging molecular mechanisms underlying its therapeutic potentials in neuropsychiatric disorders. These include neuroprotection, synaptic maintenance, immunomodulation, plasticity facilitation, secondary neuromodulation, and preservation of neurovascular unit integrity and cellular viability. Lastly, we discuss several findings suggesting BDNF as a common mediator of the therapeutic actions of centrally acting pharmacological agents used in the treatment of neurological and psychiatric illness.

A Brief Overview on BDNF-Trk Pathway in the Nervous System: A Potential Biomarker or Possible Target in Treatment of Multiple Sclerosis?

The growing incidence of neurodegenerative disorders in our populations is leading the research to identify potential biomarkers and targets for facilitating their early management and treatments. Biomarkers represent the crucial indicators of both physiological and pathological processes. Specific changes in molecular and cellular mechanisms of physiological processes result in biochemical alterations at systemic level, which can give us comprehensive information regarding the nature of any disease. In addition, any disease biomarker should be specific and reliable, able to consent of distinguishing the physiological condition of a tissue, organ, or system from disease, and be diverse among the various diseases, or subgroups or phenotypes of them. Accordingly, biomarkers can predict chances for diseases, facilitate their early diagnosis, and set guidelines for the development of new therapies for treating diseases and disease-making process. Here, we focus our attention on brain neurotrophic factor (BDNF)–tropomyosin receptor kinase (Trk) pathway, describing its multiple roles in the maintenance of central nervous system (CNS) health, as well as its implication in the pathogenesis of multiple sclerosis (MS). In addition, we also evidence the features of such pathway, which make of it a potential MS biomarker and therapeutic target.

Treadmill Training for Common Marmoset to Strengthen Corticospinal Connections After Thoracic Contusion Spinal Cord Injury

Spinal cord injury (SCI) leads to locomotor dysfunction. Locomotor rehabilitation promotes the recovery of stepping ability in lower mammals, but it has limited efficacy in humans with a severe SCI. To explain this discrepancy between different species, a nonhuman primate rehabilitation model with a severe SCI would be useful. In this study, we developed a rehabilitation model of paraplegia caused by a severe traumatic SCI in a nonhuman primate, common marmoset (Callithrix jacchus). The locomotor rating scale for marmosets was developed to accurately assess the recovery of locomotor functions in marmosets. All animals showed flaccid paralysis of the hindlimb after a thoracic contusive SCI, but the trained group showed significant locomotor recovery. Kinematic analysis revealed significantly improved hindlimb stepping patterns in trained marmosets. Furthermore, intracortical microstimulation (ICMS) of the motor cortex evoked the hindlimb muscles in the trained group, suggesting the reconnection between supraspinal input and the lumbosacral network. Because rehabilitation may be combined with regenerative interventions such as medicine or cell therapy, this primate model can be used as a preclinical test of therapies that can be used in human clinical trials.

Pleiotropic effects of BDNF on the cerebellum and hippocampus: Implications for neurodevelopmental disorders

Brain-derived neurotrophic factor (BDNF) is one of the most studied neurotrophins in the mammalian brain, essential not only to the development of the central nervous system but also to synaptic plasticity. BDNF is present in various brain areas, but highest levels of expression are seen in the cerebellum and hippocampus. After birth, BDNF acts in the cerebellum as a mitogenic and chemotactic factor, stimulating the cerebellar granule cell precursors to proliferate, migrate and maturate, while in the hippocampus BDNF plays a fundamental role in synaptic transmission and plasticity, representing a key regulator for the long-term potentiation, learning and memory. Furthermore, the expression of BDNF is highly regulated and changes of its expression are associated with both physiological and pathological conditions. The purpose of this review is to provide an overview of the current state of knowledge on the BDNF biology and its neurotrophic role in the proper development and functioning of neurons and synapses in two important brain areas of postnatal neurogenesis, the cerebellum and hippocampus. Dysregulation of BDNF expression and signaling, resulting in alterations in neuronal maturation and plasticity in both systems, is a common hallmark of several neurodevelopmental diseases, such as autism spectrum disorder, suggesting that neuronal malfunction present in these disorders is the result of excessive or reduced of BDNF support. We believe that the more the relevance of the pathophysiological actions of BDNF, and its downstream signals, in early postnatal development will be highlighted, the more likely it is that new neuroprotective therapeutic strategies will be identified in the treatment of various neurodevelopmental disorders.

Influence of BDNF Val66Met polymorphism on excitatory-inhibitory balance and plasticity in human motor cortex

OBJECTIVE

While previous studies showed that the single nucleotide polymorphism (Val66Met) of brain-derived neurotrophic factor (BDNF) can impact neuroplasticity, the influence of BDNF genotype on cortical circuitry and relationship to neuroplasticity remain relatively unexplored in human.

METHODS

Using individualised transcranial magnetic stimulation (TMS) parameters, we explored the influence of the BDNF Val66Met polymorphism on excitatory and inhibitory neural circuitry, its relation to I-wave TMS (ITMS) plasticity and effect on the excitatory/inhibitory (E/I) balance in 18 healthy individuals.

RESULTS

Excitatory and inhibitory indexes of neurotransmission were reduced in Met allele carriers. An E/I balance was evident, which was influenced by BDNF with higher E/I ratios in Val/Val homozygotes. Both long-term potentiation (LTP-) and depression (LTD-) like ITMS plasticity were greater in Val/Val homozygotes. LTP- but not LTD-like effects were restored in Met allele carriers by increasing stimulus intensity to compensate for reduced excitatory transmission.

CONCLUSIONS

The influence of BDNF genotype may extend beyond neuroplasticity to neurotransmission. The E/I balance was evident in human motor cortex, modulated by BDNF and measurable using TMS. Given the limited sample, these preliminary findings warrant further investigation.

SIGNIFICANCE

These novel findings suggest a broader role of BDNF genotype on neurocircuitry in human motor cortex.

Neuroplasticity: A Key Player in the Antidepressant Action of Chinese Herbal Medicine

Traditional Chinese medicine (TCM) is a systematic medicine. It provides alternative strategies for the treatment of depression with its clinical experience, comprehensive diagnosis, and treatment theory. Chinese herbal medicine (CHM) is the major form of TCM prescription, and numerous CHMs have been demonstrated to possess remarkable antidepressant-like properties. A diversity of mechanisms have been implicated in CHM-associated antidepressant property. This paper reviewed the neuroplastic mechanisms underlying the antidepressant actions of CHM, finding that CHM repairs neuroplasticity by improving neurogenesis, neurotrophic factors, synaptic spine morphology, cell signaling, glutamatergic system, monoamine neurotransmitters, and neural apoptosis. CHM thereby exerts an antidepressant effect, attempting to offer a better understanding of the mechanisms implicated in TCM-related antidepressant-like efficacy and laying a foundation for the scientific evaluation and development of TCM in treating depression.

Anredera cordifolia extract enhances learning and memory in senescence-accelerated mouse-prone 8 (SAMP8) mice

Learning and memory impairment may result from age-related decline in synaptic plasticity-related proteins in the hippocampus. Therefore, exploration of functional foods capable of ameliorating memory and cognition decline is an interesting endeavor in neuroscience research. We report the effects of Anredera cordifolia (AC) extract on learning and memory deficits in a senescence-accelerated mouse-prone 8 (SAMP8) mouse model, which demonstrate age-related memory deficits and related pathological changes in the brain. After 8 weeks of oral administration of AC extract, the mice were trained in the Novel Object Recognition (NOR) task, and after 7 more weeks, in the Morris Water Maze (MWM) task. Following the completion of behavioral testing, the blood biochemistry parameters, the hippocampal levels of brain-derived neurotropic factor (BDNF), PSD95, and NR2A, and the p-cAMP-response element binding (p-CREB)/CREB ratio were measured. The AC-treated group spent more time exploring the novel objects in the NOR task, and showed faster acquisition and better retention in the MWM task than the negative control (CN) group. In addition, AC enhanced the levels of the aforementioned neuronal plasticity-related proteins, and did not affect the blood biochemistry parameters. Therefore, our data suggest that the AC extract may improve learning and memory without causing any noticeable side effects in the body.

Dysregulation of Multiple Signaling Neurodevelopmental Pathways during Embryogenesis: A Possible Cause of Autism Spectrum Disorder

Understanding the autistic brain and the involvement of genetic, non-genetic, and numerous signaling pathways in the etiology and pathophysiology of autism spectrum disorder (ASD) is complex, as is evident from various studies. Apart from multiple developmental disorders of the brain, autistic subjects show a few characteristics like impairment in social communications related to repetitive, restricted, or stereotypical behavior, which suggests alterations in neuronal circuits caused by defects in various signaling pathways during embryogenesis. Most of the research studies on ASD subjects and genetic models revealed the involvement of mutated genes with alterations of numerous signaling pathways like Wnt, hedgehog, and Retinoic Acid (RA). Despite significant improvement in understanding the pathogenesis and etiology of ASD, there is an increasing awareness related to it as well as a need for more in-depth research because no effective therapy has been developed to address ASD symptoms. Therefore, identifying better therapeutic interventions like "novel drugs for ASD" and biomarkers for early detection and disease condition determination are required. This review article investigated various etiological factors as well as the signaling mechanisms and their alterations to understand ASD pathophysiology. It summarizes the mechanism of signaling pathways, their significance, and implications for ASD.

Therapeutic Potential of AAV1-Rheb(S16H) Transduction against Neurodegenerative Diseases

Neurotrophic factors (NTFs) are essential for cell growth, survival, synaptic plasticity, and maintenance of specific neuronal population in the central nervous system. Multiple studies have demonstrated that alterations in the levels and activities of NTFs are related to the pathology and symptoms of neurodegenerative disorders, such as Parkinson’s disease (PD), Alzheimer’s disease (AD), and Huntington’s disease. Hence, the key molecule that can regulate the expression of NTFs is an important target for gene therapy coupling adeno-associated virus vector (AAV) gene. We have previously reported that the Ras homolog protein enriched in brain (Rheb)–mammalian target of rapamycin complex 1 (mTORC1) axis plays a vital role in preventing neuronal death in the brain of AD and PD patients. AAV transduction using a constitutively active form of Rheb exerts a neuroprotective effect through the upregulation of NTFs, thereby promoting the neurotrophic interaction between astrocytes and neurons in AD conditions. These findings suggest the role of Rheb as an important regulator of the regulatory system of NTFs to treat neurodegenerative diseases. In this review, we present an overview of the role of Rheb in neurodegenerative diseases and summarize the therapeutic potential of AAV serotype 1 (AAV1)-Rheb(S16H) transduction in the treatment of neurodegenerative disorders, focusing on diseases, such as AD and PD.

Robustly High Hippocampal BDNF levels under Acute Stress in Mice Lacking the Full-length p75 Neurotrophin Receptor

BACKGROUND

Brain-derived neurotrophic factor (BDNF) exerts its effects on neural plasticity via 2 distinct receptor types, the tyrosine kinase TrkB and the p75 neurotrophin receptor (p75NTR). The latter can promote inflammation and cell death while TrkB is critically involved in plasticity and memory, particularly in the hippocampus. Acute and chronic stress have been associated with suppression of hippocampal BDNF expression and impaired hippocampal plasticity. We hypothesized that p75NTR might be involved in the hippocampal stress response, in particular in stress-induced BDNF suppression, which might be accompanied by increased neuroinflammation.

METHOD

We assessed hippocampal BDNF protein concentrations in wild-type mice compared that in mice lacking the long form of the p75NTR (p75NTR^ExIII-/-) with or without prior exposure to a 1-hour restraint stress challenge. Hippocampal BDNF concentrations were measured using an optimized ELISA. Furthermore, whole-brain mRNA expression of pro-inflammatory interleukin-6 (Il6) was assessed with RT-PCR.

RESULTS

Deletion of full-length p75NTR was associated with higher hippocampal BDNF protein concentration in the stress condition, suggesting persistently high hippocampal BDNF levels in p75NTR-deficient mice, even under stress. Stress elicited increased whole-brain Il6 mRNA expression irrespective of genotype; however, p75NTR^ExIII-/- mice showed elevated baseline Il6 expression and thus a lower relative increase.

CONCLUSIONS

Our results provide evidence for a role of p75NTR signaling in the regulation of hippocampal BDNF levels, particularly under stress. Furthermore, p75NTR signaling modulates baseline but not stress-related Il6 gene expression in mice. Our findings implicate p75NTR signaling as a potential pathomechanism in BDNF-dependent modulation of risk for neuropsychiatric disorders.

Dietary administration of cumin-derived cuminaldehyde induce neuroprotective and learning and memory enhancement effects to aging mice

Cuminaldehyde (CA) is one of the major compounds of the essential oil of Cuminum cyminum. The aim of this study was to evaluate the effects of CA on aging, specifically on spatial learning and memory. To achieve our objective, an in vitro study on SH-SY5Y cells was performed to analyze the neuroprotective effect of CA against dexamethasone using the MTT assay. An in vivo study was performed for evaluation of the spatial learning and memory using Morris water maze (MWM). RT-PCR was performed to quantify the expression of specific genes (Bdnf, Icam and ApoE) in the mice brain. The results obtained showed a neuroprotective effect of CA against dexamethasone-induced neuronal toxicity. The escape latency of CA-treated aged mice was significantly decreased as compared to the water-treated aged mice after 4 days of training in MWM. Moreover, CA treatment up-regulated the gene expression of Bdnf, Icam and ApoE, while it down-regulated the gene expression of IL-6. These findings suggest that CA has a neuroprotective effect, as well as a spatial learning and memory enhancement potential through the modulation of genes coding for neurotrophic factors and/or those implicated in the imbalance of neural circuitry and impairment of synaptic plasticity.

Cuminaldehyde (CA) is one of the major compound of the essential oil of Cuminum cyminum. The aim of this study was to evaluate the effects of CA on aging, specifically on spatial learning and memory. To achieve our objective, an in vitro study on SH-SY5Y cells was performed to analyze the neuroprotective effect of CA against dexamethasone using the MTT assay. An in vivo study was performed for evaluation of the spatial learning and memory using Morris water maze (MWM). RT-PCR was performed to quantify the expression of specific genes (Bdnf, Icam and ApoE) in the mice brain. The results obtained showed a neuroprotective effect of CA against dexamethasone-induced neuronal toxicity. The escape latency of CA-treated aged mice was significantly decreased as compared to the water-treated aged mice after 4 days of training in MWM. Moreover, CA treatment up-regulated the gene expression of Bdnf, Icam and ApoE, while it down-regulated the gene expression of IL-6. These findings suggest that CA has a neuroprotective effect, as well as a spatial learning and memory enhancement potential through the modulation of genes coding for neurotrophic factors and/or those implicated in the imbalance of neural circuitry and impairment of synaptic plasticity.

Therapeutic potential of targeting G protein-gated inwardly rectifying potassium (GIRK) channels in the central nervous system

G protein-gated inwardly rectifying potassium channels (Kir3/GirK) are important for maintaining resting membrane potential, cell excitability and inhibitory neurotransmission. Coupled to numerous G protein-coupled receptors (GPCRs), they mediate the effects of many neurotransmitters, neuromodulators and hormones contributing to the general homeostasis and particular synaptic plasticity processes, learning, memory and pain signaling. A growing number of behavioral and genetic studies suggest a critical role for the appropriate functioning of the central nervous system, as well as their involvement in many neurologic and psychiatric conditions, such as neurodegenerative diseases, mood disorders, attention deficit hyperactivity disorder, schizophrenia, epilepsy, alcoholism and drug addiction. Hence, GirK channels emerge as a very promising tool to be targeted in the current scenario where these conditions already are or will become a global public health problem. This review examines recent findings on the physiology, function, dysfunction, and pharmacology of GirK channels in the central nervous system and highlights the relevance of GirK channels as a worthful potential target to improve therapies for related diseases.

The Cerebellum on Cocaine

The traditional cerebellum’s role has been linked to the high computational demands for sensorimotor control. However, several findings have pointed to its involvement in executive and emotional functions in the last decades. First in 2009 and then, in 2016, we raised why we should consider the cerebellum when thinking about drug addiction. A decade later, mounting evidence strongly suggests the cerebellar involvement in this disorder. Nevertheless, direct evidence is still partial and related mainly to drug-induced reward memory, but recent results about cerebellar functions may provide new insights into its role in addiction. The present review does not intend to be a compelling revision on available findings, as we did in the two previous reviews. This minireview focuses on specific findings of the cerebellum’s role in drug-related reward memories and the way ahead for future research. The results discussed here provide grounds for involving the cerebellar cortex’s apical region in regulating behavior driven by drug-cue associations. They also suggest that the cerebellar cortex dysfunction may facilitate drug-induced learning by increasing glutamatergic output from the deep cerebellar nucleus (DCN) to the ventral tegmental area (VTA) and neural activity in its projecting areas.

Antidepressants Promote and Prevent Cancers

The review states that antidepressants (ADs) increase brain-derived neurotrophic factor (BDNF) transmission concomitantly in the brain and the blood: ADs increasing BDNF synthesis in specific areas of the central nervous system (CNS) could presumably affect megakaryocyte's production of platelets. ADs increase BDNF levels in the CNS and improve mood. In the blood, ADs increase BDNF release from platelets. The hypothesis presented here is that the release of BDNF from platelets contributes to the ADs effects on neurogenesis and on tumor growth in the cancer disease. Oncological studies indicate that chemicals ADs exert an aggravating effect on the cancer disease, possibly by promoting proplatelets formation and enhancing BDNF release from platelets in the tumor.

Mechanisms of small nerve fiber pathology

Small fiber pathology is increasingly recognized as a potential contributor to neuropathic pain in different clinical syndromes, however, the underlying mechanisms leading to nociceptor sensitization and degeneration are unclear. With the diversity in clinical pain phenotypes and etiology of small fiber pathology, individual mechanisms are assumed, but are not yet fully understood. The thinly-myelinated Aδ- and unmyelinated C-nerve fibers are mainly affected and clinically require special small fiber test methods to capture functional, morphological, and electrophysiological alterations. Several methods have been established and implemented in clinical practice in the last years. In parallel, experimental and in vitro test systems have been developed allowing important insights into the molecular mechanisms underlying nociceptor sensitization and degeneration as main hallmarks of small fiber pathology. In our narrative review, we focus on these methods and current knowledge, and provide a synopsis of the achievements made so far in this exciting field.

Schwann Cell Autocrine and Paracrine Regulatory Mechanisms, Mediated by Allopregnanolone and BDNF, Modulate PKCε in Peripheral Sensory Neurons

Protein kinase type C-ε (PKCε) plays important roles in the sensitization of primary afferent nociceptors, such as ion channel phosphorylation, that in turn promotes mechanical hyperalgesia and pain chronification. In these neurons, PKCε is modulated through the local release of mediators by the surrounding Schwann cells (SCs). The progesterone metabolite allopregnanolone (ALLO) is endogenously synthesized by SCs, whereas it has proven to be a crucial mediator of neuron-glia interaction in peripheral nerve fibers. Biomolecular and pharmacological studies on rat primary SCs and dorsal root ganglia (DRG) neuronal cultures were aimed at investigating the hypothesis that ALLO modulates neuronal PKCε, playing a role in peripheral nociception. We found that SCs tonically release ALLO, which, in turn, autocrinally upregulated the synthesis of the growth factor brain-derived neurotrophic factor (BDNF). Subsequently, glial BDNF paracrinally activates PKCε via trkB in DRG sensory neurons. Herein, we report a novel mechanism of SCs-neuron cross-talk in the peripheral nervous system, highlighting a key role of ALLO and BDNF in nociceptor sensitization. These findings emphasize promising targets for inhibiting the development and chronification of neuropathic pain.

Pathogenic or protective? Neuropeptide Y in amyotrophic lateral sclerosis

Neuropeptide Y (NPY) is an endogenous peptide of the central and enteric nervous systems which has gained significant interest as a potential neuroprotective agent for treatment of neurodegenerative disease. Amyotrophic lateral sclerosis (ALS) is an aggressive and fatal neurodegenerative disease characterized by motor deficits and motor neuron loss. In ALS, recent evidence from ALS patients and animal models has indicated that NPY may have a role in the disease pathogenesis. Increased NPY levels were found to correlate with disease progression in ALS patients. Similarly, NPY expression is increased in the motor cortex of ALS mice by end stages of the disease. Although the functional consequence of increased NPY levels in ALS is currently unknown, NPY has been shown to exert a diverse range of neuroprotective roles in other neurodegenerative diseases; through modulation of potassium channel activity, increased production of neurotrophins, inhibition of endoplasmic reticulum stress and autophagy, reduction of excitotoxicity, oxidative stress, neuroinflammation and hyperexcitability. Several of these mechanisms and signalling pathways are heavily implicated in the pathogenesis of ALS. Therefore, in this review, we discuss possible effects of NPY and NPY-receptor signalling in the ALS disease context, as determining NPY's contribution to, or impact on, ALS disease mechanisms will be essential for future studies investigating the NPY system as a therapeutic strategy in this devastating disease.

Acute Sprint Interval Exercise Increases Both Cognitive Functions and Peripheral Neurotrophic Factors in Humans: The Possible Involvement of Lactate

There is increasing attention to sprint interval exercise (SIE) training as a time-efficient exercise regime. Recent studies, including our own (Kujach et al., 2018), have shown that acute high-intensity intermittent exercise can improve cognitive function; however, the neurobiological mechanisms underlying the effect still remain unknown. We thus examined the effects of acute SIE on cognitive function by monitoring the peripheral levels of growth and neurotrophic factors as well as blood lactate (LA) as potential mechanisms. Thirty-six young males participated in the current study and were divided into two groups: SIE (n = 20; mean age: 21.0 ± 0.9 years) and resting control (CTR) (n = 16; mean age: 21.7 ± 1.3 years). The SIE session consisted of 5 min of warm-up exercise and six sets of 30 s of all-out cycling exercise followed by 4.5 min of rest on a cycling-ergometer. Blood samples to evaluate the changes of serum concentrations of brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and blood LA were obtained at three time points: before, immediately after, and 60 min after each session. A Stroop task (ST) and trail making test (TMT) parts A and B were used to assess cognitive functions. Acute SIE shortened response times for both the ST and TMT A and B. Meanwhile, the peripheral levels of BDNF, IGF-1, and VEGF were significantly increased after an acute bout of SIE compared to those in CTR. In response to acute SIE, blood LA levels significantly increased and correlated with increased levels of BDNF, IGF-1, and VEGF. Furthermore, cognitive function and BDNF are found to be correlated. The current results suggest that SIE could have beneficial effects on cognitive functions with increased neuroprotective factors along with peripheral LA concentration in humans.

The Role of Altered BDNF/TrkB Signaling in Amyotrophic Lateral Sclerosis

Brain derived neurotrophic factor (BDNF) is well recognized for its neuroprotective functions, via activation of its high affinity receptor, tropomysin related kinase B (TrkB). In addition, BDNF/TrkB neuroprotective functions can also be elicited indirectly via activation of adenosine 2A receptors (A_2aRs), which in turn transactivates TrkB. Evidence suggests that alterations in BDNF/TrkB, including TrkB transactivation by A_2aRs, can occur in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Although enhancing BDNF has been a major goal for protection of dying motor neurons (MNs), this has not been successful. Indeed, there is emerging in vitro and in vivo evidence suggesting that an upregulation of BDNF/TrkB can cause detrimental effects on MNs, making them more vulnerable to pathophysiological insults. For example, in ALS, early synaptic hyper-excitability of MNs is thought to enhance BDNF-mediated signaling, thereby causing glutamate excitotoxicity, and ultimately MN death. Moreover, direct inhibition of TrkB and A_2aRs has been shown to protect MNs from these pathophysiological insults, suggesting that modulation of BDNF/TrkB and/or A_2aRs receptors may be important in early disease pathogenesis in ALS. This review highlights the relevance of pathophysiological actions of BDNF/TrkB under certain circumstances, so that manipulation of BDNF/TrkB and A_2aRs may give rise to alternate neuroprotective therapeutic strategies in the treatment of neural diseases such as ALS.

Myricetin attenuates the severity of seizures and neuroapoptosis in pentylenetetrazole kindled mice by regulating the of BDNF-TrkB signaling pathway and modulating matrix metalloproteinase-9 and GABAA

Currently available antiepileptic drugs are effective; however, frequently associated with adverse effects that limit their therapeutic value. Compounds that target the molecular events underlying epilepsy, with minor or no adverse effects, would be of clinical value. Matrix metalloproteinase-9 (MMP-9) and the brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling pathway may be involved in epileptogenesis. The current study investigated the effects of the plant-derived hydroxyflavone, myricetin, in a pentylenetetrazole (PTZ)-induced mouse model of epilepsy. Mice received an intraperitoneal injection of 35 mg/kg body weight PTZ on alternate days (13 injections) and were observed for 30 min following each PTZ injection. Myricetin (100 or 200 mg/kg body weight) was administered orally to the treatment groups (n=18/group) for 26 days, 30 min prior to each PTZ injection. Treatment with myricetin reduced seizure and mortality rates. Increased apoptotic cell count and elevated expression levels of apoptotic proteins caused by PTZ kindling were downregulated following treatment with myricetin. The BDNF-TrkB signaling pathway and MMP-9 expression levels were regulated by myricetin. Expression of γ-aminobutyric acid A (GABA) receptor and glutamic acid decarboxylase 65, as well as the glutamate/GABA balance, were restored following treatment with myricetin. The results of the present study indicated that myricetin may exert protective effects by regulating the molecular events associated with epileptogenesis.

The Paroxysmal Depolarization Shift: Reconsidering Its Role in Epilepsy, Epileptogenesis and Beyond

Paroxysmal depolarization shifts (PDS) have been described by epileptologists for the first time several decades ago, but controversy still exists to date regarding their role in epilepsy. In addition to the initial view of a lack of such a role, seemingly opposing hypotheses on epileptogenic and anti-ictogenic effects of PDS have emerged. Hence, PDS may provide novel targets for epilepsy therapy. Evidence for the roles of PDS has often been obtained from investigations of the multi-unit correlate of PDS, an electrographic spike termed “interictal” because of its occurrence during seizure-free periods of epilepsy patients. Meanwhile, interictal spikes have been found to be associated with neuronal diseases other than epilepsy, e.g., Alzheimer’s disease, which may indicate a broader implication of PDS in neuropathologies. In this article, we give an introduction to PDS and review evidence that links PDS to pro- as well as anti-epileptic mechanisms, and to other types of neuronal dysfunction. The perturbation of neuronal membrane voltage and of intracellular Ca²⁺ that comes with PDS offers many conceivable pathomechanisms of neuronal dysfunction. Out of these, the operation of L-type voltage-gated calcium channels, which play a major role in coupling excitation to long-lasting neuronal changes, is addressed in detail.

Brain Derived Neurotrophic Factor (BDNF) Delays Onset of Pathogenesis in Transgenic Mouse Model of Spinocerebellar Ataxia Type 1 (SCA1)

Spinocerebellar ataxia type 1 (SCA1) is a fatal neurodegenerative disease caused by an abnormal expansion of CAG repeats in the Ataxin-1 (ATXN1) gene and characterized by motor deficits and cerebellar neurodegeneration. Even though mutant ATXN1 is expressed from an early age, disease onset usually occurs in patient’s mid-thirties, indicating the presence of compensatory factors that limit the toxic effects of mutant ATXN1 early in disease. Brain derived neurotrophic factor (BDNF) is a growth factor known to be important for the survival and function of cerebellar neurons. Using gene expression analysis, we observed altered BDNF expression in the cerebella of Purkinje neuron specific transgenic mouse model of SCA1, ATXN1[82Q] mice, with increased expression during the early stage and decreased expression in the late stage of disease. We therefore investigated the potentially protective role of BDNF in early stage SCA1 through intraventricular delivery of BDNF via ALZET osmotic pumps. Extrinsic BDNF delivery delayed onset of motor deficits and Purkinje neuron pathology in ATXN1[82Q] mice supporting its use as a novel therapeutic for SCA1.

Brain-Derived Neurotrophic Factor Is Required for the Neuroprotective Effect of Mifepristone on Immature Purkinje Cells in Cerebellar Slice Culture

Endogenous γ-aminobutyric acid (GABA)-dependent activity induces death of developing Purkinje neurons in mouse organotypic cerebellar cultures and the synthetic steroid mifepristone blocks this effect. Here, using brain-derived neurotrophic factor (BDNF) heterozygous mice, we show that BDNF plays no role in immature Purkinje cell death. However, interestingly, BDNF haploinsufficiency impairs neuronal survival induced by mifepristone and GABA_A-receptors antagonist (bicuculline) treatments, indicating that the underlying neuroprotective mechanism requires the neurotrophin full expression.

Effect of Nobiletin on Experimental Model of Epilepsy

Background

The effects of nobiletin, a plant-derived flavonoid was examined against pentylenetetrazole (PTZ)-induced seizures. The study also aimed to assess whether nobiletin potentiated the effects of antiepileptic drug clonazepam (CZP).

Methods

PTZ (92 mg/kg, subcutaneous) was used to induce seizures in mice. Treatment groups (n = 18/group) received nobiletin (12.5, 25, or 50 mg/kg) via oral gavage for 6 consecutive days and 45 min prior to PTZ injection. CZP (0.015-2.0 mg/kg) was administered 15 min prior to PTZ. Skeletal muscle strength was assessed by measuring grip strength and Chimney test was performed to study the motor performance in animals. TUNEL assay was done to study neuro-apoptosis. RT-PCR and Western blot analysis were performed for assessment of mRNA and protein expressions.

Results

Nobiletin and CZP improved muscle strength and motor coordination and reduced seizure severity significantly. The administration of nobiletin and CZP, individually or in combination, downregulated seizure-induced increases in apoptotic cell count and apoptotic protein expression, modulated the expression of gamma-aminobutyric acid (GABA)A and glutamate decarboxylase 65 and restored the glutamate/GABA balance. Nobiletin and CZP administration significantly upregulated phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling.

Conclusion

Nobiletin exerted protective effect against seizures by regulating signaling pathways associated with epileptogenesis and potentiated the effects of CZP.

Calcium Release Mediated by Redox-Sensitive RyR2 Channels Has a Central Role in Hippocampal Structural Plasticity and Spatial Memory

AIMS

Previous studies indicate that hippocampal synaptic plasticity and spatial memory processes entail calcium release from intracellular stores mediated by ryanodine receptor (RyR) channels. In particular, RyR-mediated Ca²⁺ release is central for the dendritic spine remodeling induced by brain-derived neurotrophic factor (BDNF), a neurotrophin that stimulates complex signaling pathways leading to memory-associated protein synthesis and structural plasticity. To examine if upregulation of ryanodine receptor type-2 (RyR2) channels and the spine remodeling induced by BDNF entail reactive oxygen species (ROS) generation, and to test if RyR2 downregulation affects BDNF-induced spine remodeling and spatial memory.

RESULTS

Downregulation of RyR2 expression (short hairpin RNA [shRNA]) in primary hippocampal neurons, or inhibition of nitric oxide synthase (NOS) or NADPH oxidase, prevented agonist-mediated RyR-mediated Ca²⁺ release, whereas BDNF promoted cytoplasmic ROS generation. RyR2 downregulation or inhibitors of N-methyl-d-aspartate (NMDA) receptors, or NOS or of NADPH oxidase type-2 (NOX2) prevented RyR2 upregulation and the spine remodeling induced by BDNF, as did incubation with the antioxidant agent N-acetyl l-cysteine. In addition, intrahippocampal injection of RyR2-directed antisense oligodeoxynucleotides, which caused significant RyR2 downregulation, caused conspicuous defects in a memorized spatial memory task.

INNOVATION

The present novel results emphasize the key role of redox-sensitive Ca²⁺ release mediated by RyR2 channels for hippocampal structural plasticity and spatial memory.

CONCLUSION

Based on these combined results, we propose (i) that BDNF-induced RyR2-mediated Ca²⁺ release and ROS generation via NOS/NOX2 are strictly required for the dendritic spine remodeling and the RyR2 upregulation induced by BDNF, and (ii) that RyR2 channel expression is crucial for spatial memory processes. Antioxid. Redox Signal. 29, 1125-1146.

Divergent Prelimbic Cortical Pathways Interact with BDNF to Regulate Cocaine-seeking

A single BDNF microinfusion into prelimbic (PrL) cortex immediately after the last cocaine self-administration session decreases relapse to cocaine-seeking. The BDNF effect is blocked by NMDAR antagonists. To determine whether synaptic activity in putative excitatory projection neurons in PrL cortex is sufficient for BDNF's effect on relapse, the PrL cortex of male rats was infused with an inhibitory Designer Receptor Exclusively Activated by Designer Drugs (DREADD) viral vector driven by an αCaMKII promoter. Immediately after the last cocaine self-administration session, rats were injected with clozapine-N-oxide 30 min before an intra-PrL BDNF microinfusion. DREADD-mediated inhibition of the PrL cortex blocked the BDNF-induced decrease in cocaine-seeking after abstinence and cue-induced reinstatement after extinction. Unexpectedly, DREADD inhibition of PrL neurons in PBS-infused rats also reduced cocaine-seeking, suggesting that divergent PrL pathways affect relapse. Next, using a cre-dependent retroviral approach, we tested the ability of DREADD inhibition of PrL projections to the NAc core or the paraventricular thalamic nucleus (PVT) to alter cocaine-seeking in BDNF- and PBS-infused rats. Selective inhibition of the PrL-NAc pathway at the end of cocaine self-administration blocked the BDNF-induced decrease in cocaine-seeking but had no effect in PBS-infused rats. In contrast, selective inhibition of the PrL-PVT pathway in PBS-infused rats decreased cocaine-seeking, and this effect was prevented in BDNF-infused rats. Thus, activity in the PrL-NAc pathway is responsible for the therapeutic effect of BDNF on cocaine-seeking whereas inhibition of activity in the PrL-pPVT pathway elicits a similar therapeutic effect in the absence of BDNF.SIGNIFICANCE STATEMENT The major issue in cocaine addiction is the high rate of relapse. However, the neuronal pathways governing relapse remain unclear. Using a pathway-specific chemogenetic approach, we found that BDNF differentially regulates two key prelimbic pathways to guide long-term relapse. Infusion of BDNF in the prelimbic cortex during early withdrawal from cocaine self-administration decreases relapse that is prevented when neurons projecting from the prelimbic cortex to the nucleus accumbens core are inhibited. In contrast, BDNF restores relapse when neurons projecting from the prelimbic cortex to the posterior paraventricular thalamic nucleus are inhibited. This study demonstrates that two divergent cortical outputs mediate relapse that is regulated in opposite directions by infusing BDNF in the prelimbic cortex during early withdrawal from cocaine.

A brief primer on the mediational role of BDNF in the exercise-memory link

One of the most amazing aspects of the human brain is its ability to learn information and use it to change behaviour. A key neurotrophin that influences memory function is brain-derived neurotrophic factor (BDNF). This review briefly discusses the mechanistic role that BDNF may play in facilitating learning and memory. We also describe the role of exercise on this relationship. As discussed herein, BDNF may influence memory via BDNF-induced alterations in membrane receptor expression and translocation, as well as activating several pathways (PLC-y, PI3K, ERK) that act together to facilitate cellular effects that influence synaptic plasticity. Exercise may help to facilitate BDNF expression and its downstream cellular pathways from both direct and indirect mechanisms.

Baicalin reverses the impairment of synaptogenesis induced by dopamine burden via the stimulation of GABAAR-TrkB interaction in minimal hepatic encephalopathy

BACKGROUND

It has been reported that D1 receptor (D₁R) activation reduces GABA_A receptor (GABA_AR) current, and baicalin (BAI) displays therapeutic efficacy in diseases involving cognitive impairment.

METHODS

We investigated the mechanisms by which BAI could improve DA-induced minimal hepatic encephalopathy (MHE) using immunoblotting, immunofluorescence, and co-immunoprecipitation.

RESULTS

BAI did not induce toxicity on the primary cultured neurons. And no obvious toxicity of BAI to the brain was found in rats. DA activated D₁R/dopamine and adenosine 3'5'-monophosphate-regulated phospho-protein (DARPP32) to reduce the GABA_AR current; BAI treatment did not change the D₁R/DARPP32 levels but blocked DA-induced reduction of GABA_AR levels in primary cultured neurons. DA decreased the interaction of GABA_AR with TrkB and the expression of downstream AKT, which was blocked by BAI treatment. Moreover, BAI reversed the decrease in the expression of GABA_AR/TrkB/AKT and prevented the impairment of synaptogenesis and memory deficits in MHE rats.

CONCLUSIONS

These results suggest that BAI has neuroprotective and synaptoprotective effects on MHE which are not related to upstream D₁R/DARPP32 signaling, but to the targeting of downstream GABA_AR signaling to TrkB.

Mechanisms of nerve growth factor signaling in bone nociceptors and in an animal model of inflammatory bone pain

Sequestration of nerve growth factor has been used successfully in the management of pain in animal models of bone disease and in human osteoarthritis. However, the mechanisms of nerve growth factor-induced bone pain and its role in modulating inflammatory bone pain remain to be determined. In this study, we show that nerve growth factor receptors (TrkA and p75) and some other nerve growth factor-signaling molecules (TRPV1 and Nav1.8, but not Nav1.9) are expressed in substantial proportions of rat bone nociceptors. We demonstrate that nerve growth factor injected directly into rat tibia rapidly activates and sensitizes bone nociceptors and produces acute behavioral responses with a similar time course. The nerve growth factor-induced changes in the activity and sensitivity of bone nociceptors we report are dependent on signaling through the TrkA receptor, but are not affected by mast cell stabilization. We failed to show evidence for longer term changes in expression of TrkA, TRPV1, Nav1.8 or Nav1.9 in the soma of bone nociceptors in a rat model of inflammatory bone pain. Thus, retrograde transport of NGF/TrkA and increased expression of some of the common nerve growth factor signaling molecules do not appear to be important for the maintenance of inflammatory bone pain. The findings are relevant to understand the basis of nerve growth factor sequestration and other therapies directed at nerve growth factor signaling, in managing pain in bone disease.

Soyasapogenol B and Genistein Attenuate Lipopolysaccharide-Induced Memory Impairment in Mice by the Modulation of NF-κB-Mediated BDNF Expression

Lactobacillus plantarum C29-fermented defatted soybean (FDS), which contains soyasaponins such as soyasaponin I (SI) and soyasapogenol B (SB) and isoflavones such as genistin (GE) and genistein (GT), attenuated memory impairment in mice. Moreover, in the preliminary study, FDS and its soyasaponins and isoflavones significantly inhibited NF-κB activation in LPS-stimulated microglial BV2 cells. Therefore, we examined the effects of FDS and its constituents SI, SB, GT, and GE on LPS-induced memory impairment in mice. Oral administration of FDS (80 mg/kg), which has higher concentrations of SB and GE than DS, recovered LPS-impaired cognitive function in Y-maze (55.1 ± 3.5%) and passive avoidance tasks (50.9 ± 19.2 s) to 129.2% (74.1 ± 3.5%) and 114.2% (290.0 ± 22.4 s) of normal mice, respectively (P < 0.05). SB and GE (10 μM) also more potently attenuated LPS-impaired cognitive behavior than SI and GT, respectively. SB (10 mg/kg) was the most effective: treatment recovered LPS-impaired spontaneous alternation and latency time to 105.7% and 126.8% of normal control mice, respectively (P < 0.05). SB and GE significantly increased BDNF expression and CREB phosphorylation in LPS-treated mice and corticosterone-stimulated SH-SY5Y cells. Furthermore, SB and GE (10 μM) also significantly inhibited NF-κB activation in LPS-treated mice. These findings suggested that FDS and its constituent soyasaponins and isoflavones may attenuate memory impairment by the regulation of NF-κB-mediated BDNF expression.

Treadmill exercise with bone marrow stromal cells transplantation potentiates recovery of locomotor function after spinal cord injury in rats

Transplantation of bone marrow stromal cells (BMSCs) is regarded as a promising candidate for the spinal cord injury (SCI). In the present study, we investigated whether treadmill exercise potentiate the effect of BM-SCs transplantation on the functional recovery in the SCI rats. The spinal cord contusion injury applied at the T9–T10 level using the impactor. Cultured BMSCs were transplanted into the lesion at 1 week after SCI induction. Treadmill exercise was conducted for 6 weeks. Basso-Beattie-Bresnahan (BBB) scale for locomotor function was determined. Sprouting axons in the lesion cavity were detected by immunofluorescence staining for neurofilament-200. Brain-derived neurotrophic factor (BDNF) and synapsin-I expressions were analyzed using western blotting. BMSCs transplantation improved BBB score and increased expressions of neurofilament-200, BDNF, and synapsin-I in the SCI rats. Treadmill exercise potentiated the improving effect of BMSCs transplantation on BBB score in the SCI rats. This potentiating effect of treadmill exercise could be ascribed to the enhancement of BDNF expression in the SCI rats.

Neuroprotection by plumbagin involves BDNF-TrkB-PI3K/Akt and ERK1/2/JNK pathways in isoflurane-induced neonatal rats

OBJECTIVES

This study was designed to assess the effects of plumbagin on isoflurane-induced neurotoxicity.

METHODS

Neonatal Sprague Dawley rat pups were treated with plumbagin (50, 100 or 150 mg/kg body weight, orally) from postnatal day 2. The pups on postnatal day 7 were subjected to isoflurane (0.75%) exposure for 6 h. Neuronal apoptosis in the hippocampal tissues was detected by TUNEL assay and FluroJade B staining following isoflurane exposure. Protein expressions were analysed by immunoblotting. RT-PCR was performed to assess mRNA levels of brain-derived neurotrophic factor (BDNF) and TrkB.

KEY FINDINGS

We observed reduced apoptosis in hippocampal CA1, CA3 and dentate gyrus regions along with severely reduced pro-apoptotic factors (Bad, Bax and cleaved caspase-3) expression and raised levels of Bcl-2, Bcl-xL, survivin, xIAP and cIAPs (cell survival proteins) in plumbagin supplemented rats. Decrease in the levels of JNK, phospho-JNK, c-Jun and phospho-c-Jun with enhanced ERK1/2 levels was observed on plumbagin pretreatment. Down-regulated PI3K/Akt signalling following isoflurane was activated by plumbagin as evidenced by raised PI3K/Akt pathway proteins - mTORc1, Akt, phospho-Akt, GSK-3β, phospho-GSK-3β, PTEN and NF-κBp65 in the hippocampal tissues as detected by Western blotting. The mRNA levels were enhanced on plumbagin supplementation.

CONCLUSIONS

Plumbagin exerted its neuroprotective effects by effectively suppressing isoflurane-induced neuronal apoptosis via regulating BDNF-TrkB-PI3/Akt and ERK/JNK signalling.

Therapeutic Potentials of Synapses after Traumatic Brain Injury: A Comprehensive Review

Massive studies have focused on the understanding of the pathobiology of cellular and molecular changes and injury mechanisms after traumatic brain injury (TBI), but very few studies have specially discussed the role of synapses in the context of TBI. This paper specifically highlights the role and therapeutic potentials of synapses after TBI. First, we review and conclude how synapses interact with constant structural, metabolic, neuroendocrine, and inflammatory mechanisms after TBI. Second, we briefly describe several key synaptic proteins involved in neuroplasticity, which may be novel neuronal targets for specific intervention. Third, we address therapeutic interventions in association with synapses after TBI. Finally, we concisely discuss the study gaps in the synapses after TBI, in hopes that this would provide more insights for future studies. Synapses play an important role in TBI; while the understandings on the synaptic participation in the treatments and prognosis of TBI are lacking, more studies in this area are warranted.

Neurotrophins and Proneurotrophins: Focus on Synaptic Activity and Plasticity in the Brain

Neurotrophins have been intensively studied and have multiple roles in the brain. Neurotrophins are first synthetized as proneurotrophins and then cleaved intracellularly and extracellularly. Increasing evidences demonstrate that proneurotrophins and mature neurotrophins exerts opposing role in the central nervous system. In the present review, we explore the role of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4) and their respective proform in cellular processes related to learning and memory. We focused on their roles in synaptic activity and plasticity in the brain with an emphasis on long-term potentiation, long-term depression, and basal synaptic transmission in the hippocampus and the temporal lobe area. We also discuss new findings on the role of the Val66Met polymorphism on the BDNF propeptide on synaptic activity.

Neurobiology of local and intercellular BDNF signaling

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family of secreted proteins. Signaling cascades induced by BDNF and its receptor, the receptor tyrosine kinase TrkB, link neuronal growth and differentiation with synaptic plasticity. For this reason, interference with BDNF signaling has emerged as a promising strategy for potential treatments in psychiatric and neurological disorders. In many brain circuits, synaptically released BDNF is essential for structural and functional long-term potentiation, two prototypical cellular models of learning and memory formation. Recent studies have revealed an unexpected complexity in the synaptic communication of mature BDNF and its precursor proBDNF, not only between local pre- and postsynaptic neuronal targets but also with participation of glial cells. Here, we consider recent findings on local actions of the BDNF family of ligands at the synapse and discuss converging lines of evidence which emerge from per se conflicting results.

Brain-derived neurotrophic factor plasma levels and premature cognitive impairment/dementia in type 2 diabetes

AIM

To assess the relationship of brain-derived neurotrophic factor (BDNF) with cognitive impairment in patients with type 2 diabetes.

METHODS

The study included 40 patients with diabetes mellitus type 2 (DM2), 37 patients with chronic kidney disease in hem dialysis hemodialysis therapy (HD) and 40 healthy subjects. BDNF in serum was quantified by ELISA. The Folstein Mini-Mental State Examination was used to evaluate cognitive impairment.

RESULTS

The patients with DM2 and the patients in HD were categorized into two groups, with cognitive impairment and without cognitive impairment. The levels of BDNF showed significant differences between patients with DM2 (43.78 ± 9.05 vs 31.55 ± 10.24, P = 0.005). There were no differences between patients in HD (11.39 ± 8.87 vs 11.11 ± 10.64 P = 0.77); interestingly, ferritin levels were higher in patients with cognitive impairment (1564 ± 1335 vs 664 ± 484 P = 0.001). The comparison of BDNF values, using a Kruskal Wallis test, between patients with DM2, in HD and healthy controls showed statistical differences (P < 0.001).

CONCLUSION

Low levels of BDNF are associated with cognitive impairment in patients with DM2. The decrease of BDNF occurs early and progressively in patients in HD.