Developing a novel neutralizing monoclonal antibody against TrkB.

The TrkB receptor, which is highly expressed in various human cancers and considered a pro-oncogene, was targeted to develop neutralizing monoclonal antibodies against its immunoglobulin-like (Ig-like) domains. Recombinant TrkB-IgL peptide, including the Ig-like C2 type 1 (Ig-C2-type 1) and Ig-like C2 type 2 (Ig-C2-type 2) domains, was expressed and purified from E. coli. Mice were immunized with this peptide, and hybridoma clones producing anti-TrkB-IgL antibodies were generated. Among 23 ELISA-positive TrkB-IgL hybridoma clones, four (TrkB-IgL 5.11, 4.11, 4.6, 4.3) showed anti-proliferative effects compared to the control on human breast cancer (MCF-7) and human colon cancer (HCT116) cells, as assessed using the xCELLigence system. Western blot analysis revealed that TrkB-IgL 5.11 and 4.11 significantly suppressed TrkB-mediated signaling pathways compared to the control. Purified TrkB-IgL monoclonal antibodies (mAbs) exhibited anti-proliferative effects compared to both positive and negative controls using the xCELLigence system. The TrkB-IgL 5.11 mAb notably suppressed phosphorylation of TrkB, Akt, and ERK and induced Caspase-3 and Caspase-9 activities in a dose-dependent manner, as determined by Western blotting. Additionally, immunostaining confirmed the localization of these mAbs on the SH-SY5Y cell membrane, which is known for high TrkB expression. In conclusion, the TrkB-IgL 5.11 antibody effectively inhibits cancer cell proliferation and induces apoptosis by suppressing key signaling pathways. These findings demonstrate the potential of this antibody as a therapeutic agent for cancers that overexpress TrkB. Additionally, it is considered a promising candidate for humanization, which would facilitate its application in cancer treatment. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-024-04063-x.

Phenylpropanoid-rich maize root extract serves as a natural antidepressant.

BACKGROUND: Depression is a serious and complex mental disease that has attracted worldwide attention because of its high incidence rate, high disability rate and high mortality. Excitotoxicity is one of the most important mechanisms involved in the pathophysiological process of depression. In our previous studies, n-butanol extract from maize roots was found to have good neuroprotective effects due to its antioxidative activity. However, the antidepressive effective constituents, efficacy in vivo and mechanism of action of maize root extracts have not been determined. PURPOSE: This study aimed to determine the main active neuroprotective compound in maize root extract and investigate its antidepressant effects and possible underlying mechanism in vitro and in vivo. METHODS: Sixteen extracts were isolated and purified from maize roots. The active components of the most active extracts of maize roots (hereafter referred to as EM 2) were identified using UF-HPLC-QTOF/MS. In vitro cell models of NMDA-induced excitotoxicity in SH-SY5Y cells were used to analyze the anti-excitatory activity of the extracts. The MTT assay and Annexin V-FITC/PI Apoptosis Detection were used to evaluate cell viability. Several network pharmacological strategies have been employed to investigate the potential mechanism of action of EM 2. The effects of EM 2 on depressive-like behaviors were evaluated in CUMS mice. Changes in the levels of related proteins were detected via western blotting. RESULTS: Among the 16 extracts extracted by n-butanol, EM 2 was determined to be the most active extract against NMDA-induced excitotoxicity by n-butanol extraction. Meanwhile, seventeen compounds were further identified as the main active components of EM 2. Mechanistically, EM 2 inhibited NMDA-induced excitatory injury in SH-SY5Y cells and alleviated the depressive-like behaviors of CUMS mice by suppressing NR2B and subsequently mediating the downstream CREB/TRKB/BDNF, PI3K/Akt and MAPK pathways, as well as the Nrf2/HO-1 antioxidant signaling pathway. CONCLUSION: The study indicated that EM 2 could potentially be developed as a potential therapeutic candidate to cure depression in NMDA-induced excitatory damage.

Unveiling the protective potential of mirabegron against thioacetamide-induced hepatic encephalopathy in rats: Insights into cAMP/PPAR-γ/p-ERK1/2/p S536 NF-κB p 65 and p-CREB/BDNF/TrkB in parallel with oxidative and apoptotic trajectories.

Hepatic encephalopathy (HE) is one of the most prevalent and severe hepatic and brain disorders in which escalation of the oxidative, inflammatory and apoptotic trajectories pathologically connects acute liver injury with neurological impairment. Mirabegron (Mira) is a beta3 adrenergic receptor agonist with proven antioxidant and anti-inflammatory activities. The current research pointed to exploring Mira's hepato-and neuroprotective impacts against thioacetamide (TAA)-induced HE in rats. Rats were distributed into three experimental groups: the normal control group, the TAA group, received TAA (200 mg/kg/day for three consecutive days) and the Mira-treated group received Mira (10 mg/kg/day; oral gavage) for 15 consecutive days and intoxicated with TAA from the 13th to the 15th day of the experimental period. Mira counteracted hyperammonemia, enhanced rats' locomotor capability and motor coordination. It attenuated hepatic/neurological injuries by its antioxidant, anti-apoptotic as well as anti-inflammatory potentials. Mira predominantly targeted cyclic adenosine monophosphate (cAMP)/phosphorylated extracellular signal-regulated kinase (p-Erk1/2)/peroxisome proliferator-activated receptor gamma (PPARγ) dependent pathways via downregulation of p S536-nuclear factor kappa B p65 (p S536 NF-κB p 65)/tumor necrosis alpha (TNF-α) axis. Meanwhile, it attenuated nuclear factor erythroid 2-related factor (Nrf2) depletion in parallel with restoring of the neuroprotective defensive pathway by upregulation of cerebral cAMP/PPAR-γ/p-ERK1/2 and p-CREB/BDNF/TrkB besides reduction of GFAP immunoreactivity. Mira showed anti-apoptotic activity through inhibition of Bax immunoreactivity and elevation of Bcl2. To summarize, Mira exhibited a hepato-and neuroprotective effect against TAA-induced HE in rats via shielding antioxidant defense and mitigation of the pathological inflammatory and apoptotic axis besides upregulation of neuroprotective signaling pathways.

BDNF-TrkB Signaling Pathway in Spinal Cord Injury: Insights and Implications.

Spinal cord injury (SCI) is a neurodegenerative disorder that has critical impact on patient's life expectance and life span, and this disorder also leads to negative socioeconomic features. SCI is defined as a firm collision to the spinal cord which leads to the fracture and the dislocation of vertebrae. The current available treatment is surgery. However, it cannot fully treat SCI, and many consequences remain after the surgery. Accordingly, finding new therapeutics is critical. BDNF-TrkB signaling is a vital signaling in neuronal differentiation, survival, overgrowth, synaptic plasticity, etc. Hence, many studies evaluate its impact on various neurodegenerative disorders. There are several studies evaluating this signaling in SCI, and they show promising outcomes. It was shown that various exercises, chemical interventions, etc. had significant positive impact on SCI by affecting BDNF-TrkB signaling pathway. This study aims to accumulate and evaluate these data and inspect whether this signaling is effective or not.

Combining Network Pharmacology and Experimental Verification to Ascertain the Mechanism of Action of Asparagus officinalis Against the Brain Damage Caused by Fluorosis.

Asparagus officinalis (ASP) has antioxidation, anti-inflammatory, antiaging, and immune system-enhancing effects. We explored the preventive and therapeutic consequences of ASP on the brain damage elicited by fluorosis through network pharmacology and in vivo experimental validation. We ascertained the pharmaceutically active ingredients and drug targets of ASP from the Traditional Chinese Medicine Systems Pharmacology database, predicted the disease targets of fluorosis-induced brain injury using GeneCards and Online Mendelian Inheritance in Man databases, obtained target protein-protein interaction networks in the Search Tool for the Retrieval of Interacting Genes/Proteins database, used Cytoscape to obtain key targets and active ingredients, and conducted enrichment analyses of key targets in the Database for Annotation, Visualization and Integrated Discovery. Enrichment analyses showed that "mitogen-activated protein kinase" (MAPK), "phosphoinositide 3-kinase/protein kinase B" (PI3K-Akt), "nuclear factor-kappa B" (NF-κB), and the "neurotrophin signaling pathway" were the most enriched biological processes and signaling pathways. ASP could alleviate fluorosis-based injury, improve brain-tissue damage, increase urinary fluoride content, and improve oxidation levels and inflammatory-factor levels in the body. ASP could also reduce dental fluorosis, bone damage, fluoride concentrations in blood and bone, and accumulation of lipid peroxide. Upon ASP treatment, expression of silent information regulator (SIRT)1, brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB), MAPK, NF-κB, PI3K, Akt, and B-cell lymphoma-2 in rat brain tissue increased gradually, whereas that of Bax, caspase-3, and p53 decreased gradually. We demonstrated that ASP could regulate the brain damage caused by fluorosis through the SIRT1/BDNF/TrkB signaling pathway, and reported the possible part played by ASP in preventing and treating fluorosis.

BDNF/TrkB signalling, in cooperation with muscarinic signalling, retrogradely regulates PKA pathway to phosphorylate SNAP-25 and Synapsin-1 at the neuromuscular junction.

BACKGROUND: Protein kinase A (PKA) enhances neurotransmission at the neuromuscular junction (NMJ), which is retrogradely regulated by nerve-induced muscle contraction to promote Acetylcholine (ACh) release through the phosphorylation of molecules involved in synaptic vesicle exocytosis (SNAP-25 and Synapsin-1). However, the molecular mechanism of the retrograde regulation of PKA subunits and its targets by BDNF/TrkB pathway and muscarinic signalling has not been demonstrated until now. At the NMJ, retrograde control is mainly associated with BDNF/TrkB signalling as muscle contraction enhances BDNF levels and controls specific kinases involved in the neurotransmission. Neurotransmission at the NMJ is also highly modulated by muscarinic receptors M1 and M2 (mAChRs), which are related to PKA and TrkB signallings. Here, we investigated the hypothesis that TrkB, in cooperation with mAChRs, regulates the activity-dependent dynamics of PKA subunits to phosphorylate SNAP-25 and Synapsin-1. METHODS: To explore this, we stimulated the rat phrenic nerve at 1Hz (30 minutes), with or without subsequent contraction (abolished by µ-conotoxin GIIIB). Pharmacological treatments were conducted with the anti-TrkB antibody clone 47/TrkB for TrkB inhibition and exogenous h-BDNF; muscarinic inhibition with Pirenzepine-dihydrochloride and Methoctramine-tetrahydrochloride for M1 and M2 mAChRs, respectively. Diaphragm protein levels and phosphorylation' changes were detected by Western blotting. Location of the target proteins was demonstrated using immunohistochemistry. RESULTS: While TrkB does not directly impact the levels of PKA catalytic subunits Cα and Cß, it regulates PKA regulatory subunits RIα and RIIß, facilitating the phosphorylation of critical exocytotic targets such as SNAP-25 and Synapsin-1. Furthermore, the muscarinic receptors pathway maintains a delicate balance in this regulatory process. These findings explain the dynamic interplay of PKA subunits influenced by BDNF/TrkB signalling, M1 and M2 mAChRs pathways, that are differently regulated by pre- and postsynaptic activity, demonstrating the specific roles of the BDNF/TrkB and muscarinic receptors pathway in retrograde regulation. CONCLUSION: This complex molecular interplay has the relevance of interrelating two fundamental pathways in PKA-synaptic modulation: one retrograde (neurotrophic) and the other autocrine (muscarinic). This deepens the fundamental understanding of neuromuscular physiology of neurotransmission that gives plasticity to synapses and holds the potential for identifying therapeutic strategies in conditions characterized by impaired neuromuscular communication.

Plasma-derived exosome miR-10a-5p promotes premature ovarian failure by target BDNF via the TrkB/Akt/mTOR signaling pathway.

Premature ovarian failure (POF) is characterized by a significant decline in the ovarian follicle pool and oocyte reserve, alongside an increase in the number of low-quality oocytes and apoptosis of granulosa cells (GCs). Exosome-derived miRNA plays a regulatory role in crucial cellular activities and contributes to the onset and progression of POF. In this study, we successfully established a rabbit model of POF and conducted in vitro and in vivo experiments that confirmed DiI-labeled Pla-Exos (exosomes derived from plasma) could enter the follicle through blood circulation, with GCs capable of uptaking these exosomes. Our RNA-seq analysis revealed elevated expression of miR-10a-5p in Pla-Exos from POF rabbits. Moreover, our findings demonstrate that exosomal miR-10a-5p suppresses GCs proliferation and induces apoptosis via the mitochondrial pathway. Additionally, exosomal miR-10a-5p inhibits the TrkB/Akt/mTOR signaling pathway by downregulating BDNF expression, thereby modulating the expression levels of proteins and genes associated with the cell cycle, follicle development, and GCs senescence. In conclusion, our study highlights the role of Pla-Exos miR-10a-5p in promoting rabbit POF through the TrkB/Akt/mTOR signaling pathway by targeting BDNF. These findings provide new insights into potential therapeutic targets for POF, offering valuable references for addressing concerns related to female reproductive function.

Administration of low dose intranasal ketamine exerts a neuroprotective effect on whole brain irradiation injury model in wistar rats.

Exposure to ionizing radiation leads to oxidative stress and neuroinflammation, resulting in neurocognitive impairments. Adverse effects are also associated with glutamate-induced excitotoxicity due to alterations in the composition of glutamate receptors. Ketamine, which is a noncompetitive NMDA glutamate receptor antagonist, has been stated to exert an impact on glutamatergic receptors. This study aims to reveal the possible alleviating or preventive effects of ketamine, which maintains glutamate homeostasis and decreases neurodegeneration, in a radiation-induced neurotoxicity model. Twenty-one female Wistar Queryrats were included in the study and 14 of these underwent whole brain irradiation (IR) with a 20 Gray single dose. Animals were allocated into three groups. Group 1: Normal control; Group 2: Placebo / IR + Saline; Group 3: IR + Ketamine. Ketamine was administered in addition to IR to rats in Group 3. The one-way ANOVA statistical test was used to compare groups. The value of p < 0.05 was considered statistically significant. When administered in addition to irradiation, ketamine treatment significantly increased scores in the three-chamber sociability test, open field test, and passive avoidance learning test. It also raised neuron counts in the hippocampal CA1 and CA3 regions as well as in Purkinje cells, and enhanced levels of brain-derived neurotrophic factor and tyrosine receptor kinase-B. Furthermore, ketamine administration resulted in decreased levels of glial fibrillary acidic protein, malondialdehyde, and tumor necrosis factor-alpha, indicating a reduction in neuroinflammation and oxidative stress. Ketamine exerted a significant protective impact on radiation-induced neurocognitive impairments and enhanced social-memory capacity by reducing neuronal loss, oxidative stress, and neuroinflammation. Our findings suggest that ketamine is beneficial in the treatment or prevention of neurodegeneration via the regulation of the BDNF/TrkB signaling pathway besides decreasing neuroinflammation and blocking NMDA receptors.

A rare olive compound oleacein functions as a TrkB agonist and mitigates neuroinflammation both in vitro and in vivo.

BACKGROUND: Neuroinflammation is widely acknowledged as a characteristic feature of almost all neurological disorders and specifically in depression- and anxiety-like disorders. In recent years, there has been significant attention on natural compounds with potent anti-inflammatory effects due to their potential in mitigating neuroinflammation and neuroplasticity. METHODS: In the present study, we aimed to evaluate the neuroprotective effects of oleacein (OC), a rare secoiridoid derivative found in extra virgin olive oil. Our goal was to explore the BDNF/TrkB neurotrophic activity of OC and subsequently assess its potential for modulating neuroinflammatory response using human neuroblastoma cells (SH-SY5Y cells) and an in vivo model of depression induced by lipopolysaccharide (LPS)-mediated inflammation. RESULTS: In SH-SY5Y cells, OC exhibited a significant dose-dependent increase in BDNF expression. This enhancement was absent when cells were co-treated with inhibitors of BDNF's receptor TrkB, as well as downstream molecules PI3K and MEK. Whole-transcriptomics analysis revealed that OC upregulated cell cycle-related genes under normal conditions, while downregulating inflammation-associated genes in LPS-induced conditions. Furthermore, surface plasmon resonance (SPR) assays demonstrated that OC exhibited a stronger and more stable binding affinity to TrkB compared to the positive control, 7,8-dihydroxyflavone. Importantly, bioluminescence imaging revealed that a single oral dose of OC significantly increased BDNF expression in the brains of Bdnf-IRES-AkaLuc mice. Furthermore, oral administration of OC at a dosage of 10 mg/kg body weight for 10 days significantly reduced immobility time in the tail suspension test compared to the LPS-treated group. RT-qPCR analysis revealed that OC significantly decreased the expression of pro-inflammatory cytokines Tnfα, Il6, and Il1ß, while simultaneously enhancing Bdnf expression, as well as both pro and mature BDNF protein levels in mice hippocampus. These changes were comparable to those induced by the positive control antidepressant drug fluoxetine. Additionally, microarray analysis of mouse brains confirmed that OC could counteract LPS-induced inflammatory biological events. CONCLUSION: Altogether, our study represents the first report on the potential antineuroinflammatory and antidepressant properties of OC via modulation of BDNF/TrkB neurotrophic activity. This finding underscores the potential of OC as a natural therapeutic agent for depression- and anxiety-related disorders.

Astragaloside IV mediates radiation-induced neuronal damage through activation of BDNF-TrkB signaling.

BACKGROUND: Electromagnetic radiation is relevant to human life, and radiation can trigger neurodegenerative diseases by altering the function of the central nervous system through oxidative stress, mitochondrial dysfunction, and protein degradation. Astragaloside IV (AS-IV) is anti-oxidative, anti-apoptotic, activates the BDNF-TrkB pathway and enhances synaptic plasticity in radiated mice, which can exert its neuroprotection. However, the exact molecular mechanisms are still unclear. PURPOSE: This study investigated whether AS-IV could play a neuroprotective role by regulating BDNF-TrkB pathway in radiation damage and its underlying molecular mechanisms. METHODS: Transgenic mice (Thy1-YFP line H) were injected with AS-IV (40 mg/kg/day body weight) by intraperitoneal injection daily for 4 weeks, followed by X-rays. PC12 cells and primary cortical neurons were also exposed to UVA after 24 h of AS-IV treatment (25 µg/ml and 50 µg/ml) in vitro. The impact of radiation on learning and cognitive functions was visualized in the Morris water maze assay. Subsequently, Immunofluorescence and Golgi-Cox staining analyses were utilized to investigate the structural damage of neuronal dendrites and the density of dendritic spines. Transmission electron microscopy was performed to examine how the radiation affected the ultrastructure of neurons. Finally, western blotting analysis and Quantitative RT-PCR were used to evaluate the expression levels and locations of proteins in vitro and in vivo. RESULTS: Radiation induced BDNF-TrkB signaling dysregulation and decreased the levels of neuron-related functional genes (Ngf, Bdnf, Gap-43, Ras, Psd-95, Arc, Creb, c-Fos), PSD-95 and F-actin, which subsequently led to damage of neuronal ultrastructure and dendrites, loss of dendritic spines, and decreased dendritic complexity index, contributing to spatial learning and memory deficits. These abnormalities were prevented by AS-IV treatment. In addition, TrkB receptor antagonists antagonized these neuroprotective actions of AS-IV. 7,8-dihydroxyflavone and AS-IV had neuroprotective effects after radiation. CONCLUSION: AS-IV inhibits morphological damage of neurons and cognitive dysfunction in mice after radiation exposure, resulting in a neuroprotective effect, which were mediated by activating the BDNF-TrkB pathway.

Retrograde adenosine/A2A receptor signaling facilitates excitatory synaptic transmission and seizures.

Retrograde signaling at the synapse is a fundamental way by which neurons communicate and neuronal circuit function is fine-tuned upon activity. While long-term changes in neurotransmitter release commonly rely on retrograde signaling, the mechanisms remain poorly understood. Here, we identified adenosine/A2A receptor (A2AR) as a retrograde signaling pathway underlying presynaptic long-term potentiation (LTP) at a hippocampal excitatory circuit critically involved in memory and epilepsy. Transient burst activity of a single dentate granule cell induced LTP of mossy cell synaptic inputs, a BDNF/TrkB-dependent form of plasticity that facilitates seizures. Postsynaptic TrkB activation released adenosine from granule cells, uncovering a non-conventional BDNF/TrkB signaling mechanism. Moreover, presynaptic A2ARs were necessary and sufficient for LTP. Lastly, seizure induction released adenosine in a TrkB-dependent manner, while removing A2ARs or TrkB from the dentate gyrus had anti-convulsant effects. By mediating presynaptic LTP, adenosine/A2AR retrograde signaling may modulate dentate gyrus-dependent learning and promote epileptic activity.

Multi-frequency electromagnetic radiation induces anxiety in mice via inflammation in the cerebral cortex.

Modern life is filled with radiofrequency electromagnetic radiation (RF-EMR) in various frequency bands, while the health risks are not clear. In this study, mice were whole-body exposed to 0.9/1.5/2.65 GHz radiofrequency radiation at 4 W/kg for 2 h per day for 4 weeks to investigate the emotional effects. It was found that the mice showed anxiety but no severe depression. The ELISA results showed a significant decrease in amino acid neurotransmitters (GABA, DA, 5-HT), although acetylcholine (ACH) levels were not significantly altered. Furthermore, Western blot results showed that BDNF, TrkB, and CREB levels were increased in the cerebral cortex, while NF-κB levels were decreased. In addition, pro-inflammatory factors (IL-6, IL-1ß, TNF-α) were significantly elevated, and anti-inflammatory factors (IL-4, IL-10) tended to decrease. In conclusion, multi-frequency electromagnetic radiation induces an inflammatory response through the CREB-BDNF-TrkB and NF-κB pathways in the cerebral cortex and causes a decrease in excitatory neurotransmitters, which ultimately causes anxiety in mice.

Type II & III inhibitors of tropomyosin receptor kinase (Trk): a 2020-2022 patent update.

INTRODUCTION: The Trk family proteins are membrane-bound kinases predominantly expressed in neuronal tissues. Activated by neurotrophins, they regulate critical cellular processes through downstream signaling pathways. Dysregulation of Trk signaling can drive a range of diseases, making the design and study of Trk inhibitors a vital area of research. This review explores recent advances in the development of type II and III Trk inhibitors, with implications for various therapeutic applications. AREAS COVERED: Patents covering type II and III inhibitors targeting the Trk family are discussed as a complement of the previous review, Type I inhibitors of tropomyosin receptor kinase (Trk): a 2020-2022 patent update. Relevant patents were identified using the Web of Science database, Google, and Google Patents. EXPERT OPINION: While type II and III Trk inhibitor development has advanced more gradually compared to their type I counterparts, they hold significant promise in overcoming resistance mutations and achieving enhanced subtype selectivity - a critical factor in reducing adverse effects associated with pan-Trk inhibition. Recent interdisciplinary endeavors have marked substantial progress in the design of subtype selective Trk inhibitors, with impressive success heralded by the type III inhibitors. Notably, the emergence of mutant-selective Trk inhibitors introduces an intriguing dimension to the field, offering precise treatment possibilities.

TNF receptor 2 knockout mouse had reduced lung cancer growth and schizophrenia-like behavior through a decrease in TrkB-dependent BDNF level.

The relationship between schizophrenia (SCZ) and cancer development remains controversial. Based on the disease-gene association platform, it has been revealed that tumor necrosis factor receptor (TNFR) could be an important mediatory factor in both cancer and SCZ development. TNF-α also increases the expression of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) in the development of SCZ and tumor, but the role of TNFR in mediating the association between the two diseases remains unclear. We studied the vital roles of TNFR2 in the progression of tumor and SCZ-like behavior using A549 lung cancer cell xenografted TNFR2 knockout mice. TNFR2 knockout mice showed significantly decreased tumor size and weight as well as schizophrenia-like behaviors compared to wild-type mice. Consistent with the reduced tumor growth and SCZ-like behaviors, the levels of TrkB and BDNF expression were significantly decreased in the lung tumor tissues and pre-frontal cortex of TNFR2 knockout mice. However, intravenous injection of BDNF (160 µg/kg) to TNFR2 knockout mice for 4 weeks increased tumor growth and SCZ-like behaviors as well as TrkB expression. In in vitro study, significantly decreased cell growth and expression of TrkB and BDNF by siTNFR2 transfection were found in A549 lung cancer cells. However, the addition of BDNF (100 ng/ml) into TNFR2 siRNA transfected A549 lung cancer cells recovered cell growth and the expression of TrkB. These results suggest that TNFR2 could be an important factor in mediating the comorbidity between lung tumor growth and SCZ development through increased TrkB-dependent BDNF levels.

Study on the role and mechanism of Tan IIA in Alzheimer's disease based on CREB-BDNF-TrkB pathway.

The occurrence and development of Alzheimer's disease (AD) is closely related to neuronal loss, inflammatory response, cholinergic imbalance, and Tau protein hyperphosphorylation. Previous studies have confirmed that Streptozotocin (STZ) can be used to establish a rat model of AD by injecting it into the rat brain via the lateral ventricle. Our previous research showed that Danshentone IIA (Tan IIA) can improve cognitive dysfunction in rats caused by CC chemokine ligand 2, and network pharmacology results show that Tan IIA is very likely to improve AD symptoms through the cyclic adenosine monophosphate response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), and tyrosine kinase receptor protein (TrkB) pathway. The results of the water maze experiment showed that after Tan IIA treatment, the escape latency of AD rats was shortened and the number of platform crossings increased; in the new object recognition experiment, the discrimination index of AD rats significantly increased after treatment; Nissl staining and Tunel staining results showed that Tan IIA increased the number of surviving neurons in the hippocampus of cognitively impaired rats and reduced neuronal apoptosis; Bielschowsky silver staining results showed that Tan IIA reduced neurofibrillary tangles (NFTs) in the AD rats; Tan IIA can reduce the inflammatory response and oxidative stress reaction in the hippocampus of AD rats, and at the same time reduce the activity of acetylcholinesterase. Tan IIA can significantly increase the expression of CREB, BDNF, TrkB in the hippocampal tissue of STZ-injured rats (P < 0.05). These data suggest that Tan IIA may upregulate the expression of the CREB-BDNF-TrkB signaling pathway in the hippocampus of brain tissue, produce anti-neuroinflammatory, antioxidant stress, inhibit neuronal apoptosis effects, and improve cholinergic neurotransmitter disorder induced by STZ, reduce the neuronal damage and learning and memory impairment caused by STZ in rats, and improve the cognitive function of rats.

Cytisine-N-methylene-(5,7,4'-trihydroxy)- isoflavone ameliorates ischemic stroke-induced brain injury in mouse by regulating the oxidative stress and BDNF-Trkb/Akt pathway.

BACKGROUND: A novel compound Cytisine-N-methylene-(5,7,4'-trihydroxy)- isoflavone (LY01) found in the Sophora alopecuroides L is a neuroprotective agent. However, the effect and potential mechanism of LY01 treatment for ischemic stroke (IS) have not been fully elucidated. AIM OF THE STUDY: The aim of this study is to demonstrate whether LY01 can rescue ischemic stroke-induced brain injury and oxygen-glucose deprivation/reperfusion (OGD/R). RESULTS: Our results show that intragastric administration of LY01 improves ischemic stroke behaviors in mice, as demonstrated by neurological score, infarct volume, cerebral water content, rotarod test for activity. Compared with the model group, the ginkgo biloba extract (EGb) and LY01 reversed the neurological score, infarct volume, cerebral water content, rotarod test in model mice. Further analysis showed that the LY01 rescued oxidative stress in the model mice, which was reflected in the increased levels of catalase, superoxide dismutase, total antioxidant capacity and decreased levels of malondialdehyde in the serum of the model mice. Moreover, the expression of the brain-derived neurotrophic factor brain-derived neurotrophic factor (BDNF), phosphorylated protein kinase B (p-Akt), Bax, Bcl-2, (p)-tropomysin related kinase B (p-Trkb) was restored and the expression of Bax, glial fibrillary acidic protein (GFAP) in the brains of the model mice was inhibited through LY01 treatment. In the polymerase chain reaction (PCR) data, after giving LY01, the expression in the brains of model mice was that, IL-10 increased and IL-1ß, Bax, Bcl-2 decreased. Furthermore, the results indicated that LY01 improved cell viability, reactive oxygen species content, and mitochondrial membrane potential dissipation induced by OGD/R in primary culture of rat cortical neurons. Bax and caspase-3 activity was upregulated compared to the before after treatment with LY01. CONCLUSIONS: Our study suggests that LY01 reversed ischemic stroke by reducing oxidative stress and activating the BDNF-TrkB/Akt pathway and exerted a neuroprotective action against OGD/R injury via attenuation, a novel approach was suggested to treat ischemic stroke. Our observations justify the traditional use of LY01 for a treatment of IS in nervous system.

BMSC-Derived Exosomes Carrying miR-26a-5p Ameliorate Spinal Cord Injury via Negatively Regulating EZH2 and Activating the BDNF-TrkB-CREB Signaling.

BACKGROUND: Spinal cord injury (SCI) is a destructive neurological and pathological state that causes major motor, sensory and autonomic dysfunctions. Bone marrow mesenchymal stem cells (BMSCs)-derived exosomes show great therapeutic potential for SCI. Exosomes derived from miR-26a-modified MSCs promote axonal regeneration following SCI. Our study aims to uncover the mechanisms by which BMSC-derived exosomes carrying miR-26a-5p regulate SCI. METHODS: BMSCs and BMSC-derived exosomes were isolated and characterized by Oil Red O and alizarin red staining, transmission electron microscopy, flow cytometry, nanoparticle tracking analysis and Western blotting. PC12 cells were treated with lipopolysaccharides (LPS), and SCI was established through laminectomy with contusion injury in rats. Annexin-V staining, CCK-8 and EdU incorporation were applied to determine cell apoptosis, viability, and proliferation. Hematoxylin and Eosin, Nissl and TUNEL staining was used to evaluate SCI injury and apoptosis in the spinal cord. Luciferase and chromatin immunoprecipitation assays were applied to evaluate gene interaction. RESULTS: BMSC-derived exosomes facilitated LPS-treated PC12 cell proliferation and inhibited apoptosis by delivering miR-26a-5p. Moreover, BMSC-derived exosomal miR-26a-5p alleviated SCI. Furthermore, miR-26a-5p inhibited EZH2 expression by directly binding to EZH2, and EZH2 inhibited BDNF expression via promoting H3K27me3. Increased phosphorylated CREB enhanced KCC2 transcription and expression by binding to its promoter. Knockdown of miR-26a-5p abrogated BMSC-derived exosome-mediated protection in LPS-treated PC12 cells, but it was reversed by KCC2 overexpression. CONCLUSION: BMSC-derived exosomes carrying miR-26a-5p repressed EZH2 expression to promote BDNF and TrkB expression and CREB phosphorylation and subsequently increase KCC2 expression, thus protecting PC12 cells and ameliorating SCI.

Differential expression of TRKB tyrosine kinase in the two histological types of parotid salivary duct carcinoma with cancer aggressiveness.

Parotid salivary duct carcinoma (SDC) is a rare and aggressive parotid gland carcinoma (PGC). SDC has two origins: de novo and ex pleomorphic adenoma (SDC ex PA); however, because of its rarity, the clinical and molecular features of the two types of SDC are not sufficiently understood. Here, we studied the differences in their clinicopathological and molecular features using clinical specimens while comparing them to those of adenoid cystic carcinoma (AdCC), an intermediate-grade PGC. Clinicopathological analysis of tissues from patients with PGC revealed significant associations between histological types and malignant phenotypes, including nodal metastasis, recurrence, vascular invasion, and neural invasion, and revealed more malignant phenotypes of de novo SDC than of SDC ex PA. The de novo SDC showed a significantly higher frequency of intra-neural invasion (intra-NI) and vascular invasion than AdCC and SDC ex PA. PGCs with high intra-NI were significantly correlated with malignant phenotypes and survival rates. Recently, we observed the overexpression of tropomyosin receptor kinase B (TRKB), a receptor tyrosine kinase, in PGC cells. Here, immunohistochemical and clinicopathological analyses showed that TRKB was highly expressed in SDC cells, particularly de novo SDC cells, and was significantly associated with poor survival and highly malignant phenotypes, including intra-NI and vascular invasion. Collectively, these data show that TRKB expression is significantly elevated in PGC, particularly in de novo SDC, and can be one of the biomarkers of their aggressiveness.

Novel CAR-T cells targeting TRKB for the treatment of solid cancer.

Chimeric antigen receptor (CAR) T-cell therapy is highly effective for treating blood cancers such as B-cell malignancies, however, its effectiveness as an approach to treat solid tumors remains to be further explored. Here, we focused on the development of CAR-T cell therapies targeting tropomyosin-related kinase receptor B (TRKB), a highly expressed protein that is significantly associated with tumor progression, malignancy, and drug resistance in multiple forms of aggressive solid tumors. To achieve this, we screened brain-derived neurotrophic factor (BDNF) and neurotrophin 4 (NTF4) ligand-based CAR-T cells for their efficiency in targeting the TRKB receptor in the context of solid tumors, particularly hepatocellular carcinoma and pancreatic cancer. We demonstrated that TRKB is overexpressed not only in hepatocellular carcinoma and pancreatic carcinoma cell lines but also in cancer stem-like cells (CSCs). Notably, BDNF-CAR T and NTF4-CAR T cells could not only effectively target and kill TRKB-expressing pan-cancer cell lines in a dose-dependent manner but also effectively kill CSCs. We also performed in vivo studies to show that NTF4-CAR T cells have a better potential to inhibit the tumor growth of hepatocellular carcinoma xenografts in mice, compared with BDNF-CAR T cells. Taken together, our findings suggest that CAR-T targeting TRKB may be a promising approach for developing novel therapies to treat solid cancers.

Esketamine Prevents Postoperative Emotional and Cognitive Dysfunction by Suppressing Microglial M1 Polarization and Regulating the BDNF-TrkB Pathway in Ageing Rats with Preoperative Sleep Disturbance.

Postoperative depression (POD) and postoperative cognitive dysfunction (POCD) have placed heavy burden on patients' physical and mental health in recent years. Sleep disturbance before surgery is a common phenomenon that has been increasingly believed to affect patients' recovery, especially in aged patients, while little attention has been paid to sleep disruption before surgery and the potential mechanism remains ambiguous. Ketamine has been reported to attenuate POCD after cardiac surgery and elicit rapid-acting and sustained antidepressant actions. The present study aimed to clarify the effect of esketamine's (the S-enantiomer of ketamine) protective effects and possible mechanisms of action in POCD and POD. Our results showed that sleep disturbance before surgery exacerbated microglial M1 polarization and microglial BDNF-TrkB signalling dysfunction induced by surgery, resulting in postoperative emotional changes and cognitive impairments. Notably, treatment with esketamine reversed the behavioural abnormalities through inhibiting the M1 polarization of microglia and the inflammatory response thus improving BDNF-TrkB signalling in vivo and vitro. In addition, esketamine administration also reversed the impaired hippocampal synaptic plasticity which has been perturbed by sleep disturbance and surgery. These findings warrant further investigations into the interplay of esketamine and may provide novel ideas for the implication of preoperative preparations and the prevention of postoperative brain-related complications.