[Effects of electroacupuncture on learning-memory function and synaptic plasticity in rats with cerebral ischemia-reperfusion injury based on the BDNF/TrkB pathway].

OBJECTIVE: To observe the effects of electroacupuncture (EA) at "Baihui" (GV 20) and "Sishencong" (EX-HN 1) on the expression of brain-derived neurotrophic factor (BDNF)/tyrosine kinase receptor B (TrkB) pathway, synaptophysin (SYN), and the levels of interleukin-1ß (IL-1ß) and interleukin-18 (IL-18) in the hippocampus of the ischemic side in rats with cerebral ischemia-reperfusion injury (CIRI), and to explore the effects and action mechanism of EA on post-CIRI learning-memory function. METHODS: Forty-eight SPF-grade male SD rats were randomly divided into a sham operation group, a model group, an EA group, and a non-acupoint group, with 12 rats in each group. The CIRI model was established in the model group, the EA group, and the non-acupoint group using the modified ZeaLonga suture method. The rats in the EA group were treated with EA at "Sishencong" (EX-HN 1) and "Baihui" (GV 20), with disperse-dense wave at frequency of 2 Hz/10 Hz and intensity of 1 mA. The rats in the non-acupoint group were treated with EA at non-meridian and non-acupoint points under the ribs bilaterally with the same parameters as the EA group. EA were conducted for 30 min each session, once daily, for 7 days. During the intervention, body weight was measured daily at a fixed time, and neurological deficits were assessed on the 1st, 3rd, and 7th days into intervention. Brain infarct volume was measured using small animal magnetic resonance imaging before and after the intervention. After the intervention, learning-memory function were evaluated using the Morris water maze. Hippocampal morphology was observed with HE staining. The positive expression of SYN in the hippocampus of the ischemic side was detected by immunohistochemistry. BDNF, TrkB, and SYN protein expressions in the hippocampus of the ischemic side were detected by Western blot. IL-1ß and IL-18 levels in the hippocampus of the ischemic side were measured by ELISA. RESULTS: From the 2nd to the 7th day into intervention, compared with the sham operation group, the body weight of rats in the model group was decreased (P<0.01); compared with the model group and the non-acupoint group, the body weight of rats in the EA group was increased (P<0.01). On the 1st day into intervention, compared with the sham operation group, neurological function scores of rats in the model group, the EA group, and the non-acupoint group were increased (P<0.01); on the 3rd and 7th days into intervention, neurological function scores of rats in the model group were higher than those in the sham operation group (P<0.01); on the 7th day, neurological function scores of rats in the EA group were lower than those in the model group and the non-acupoint group (P<0.05). Compared with the sham operation group, escape latency was prolonged (P<0.05), and the number of platform crossings was decreased (P<0.01) in the model group; compared with the model group and the non-acupoint group, escape latency was shortened (P<0.05), and the number of platform crossings was increased (P<0.01) in the EA group. Before intervention, the high signal infarcts were observed in the left ventricles of rats in the model group, the EA group, and the non-acupoint group; after intervention compared with the model group and the non-acupoint group, infarct volume in the EA group was decreased (P<0.01). Neuronal cells in the model group and the non-acupoint group were sparsely and disorderedly arranged, with deep-stained cytoplasm and shrunken nuclei; the number and arrangement of neuronal cells in the EA group were similar to the sham operation group, with less deep-stained cytoplasm and shrunken nuclei compared to the model group. Compared with the sham operation group, the positive expression of SYN, and BDNF TrkB, and SYN protein expressions in the hippocampus of the ischemic side were decreased (P<0.01, P<0.05), while levels of IL-1ß and IL-18 were increased (P<0.01) in the model group; compared with the model group and the non-acupoint group, the positive expression of SYN, and BDNF, TrkB and SYN protein expressions in the hippocampus of the ischemic side were increased (P<0.01, P<0.05), while levels of IL-1ß and IL-18 were decreased (P<0.01) in the EA group. CONCLUSION: EA at "Baihui" (GV 20) and "Sishencong" (EX-HN 1) may improve learning-memory function in rats with CIRI by activating the BDNF/TrkB signaling pathway, reducing neuroinflammatory response, and promoting the recovery of synaptic plasticity.

A Combined Computational and Experimental Approach to Studying Tropomyosin Kinase Receptor B Binders for Potential Treatment of Neurodegenerative Diseases.

Tropomyosin kinase receptor B (TrkB) has been explored as a therapeutic target for neurological and psychiatric disorders. However, the development of TrkB agonists was hindered by our poor understanding of the TrkB agonist binding location and affinity (both affect the regulation of disorder types). This motivated us to develop a combined computational and experimental approach to study TrkB binders. First, we developed a docking method to simulate the binding affinity of TrkB and binders identified by our magnetic drug screening platform from Gotu kola extracts. The Fred Docking scores from the docking computation showed strong agreement with the experimental results. Subsequently, using this screening platform, we identified a list of compounds from the NIH clinical collection library and applied the same docking studies. From the Fred Docking scores, we selected two compounds for TrkB activation tests. Interestingly, the ability of the compounds to increase dendritic arborization in hippocampal neurons matched well with the computational results. Finally, we performed a detailed binding analysis of the top candidates and compared them with the best-characterized TrkB agonist, 7,8-dyhydroxyflavon. The screening platform directly identifies TrkB binders, and the computational approach allows for the quick selection of top candidates with potential biological activities based on the docking scores.

Long-Term Tumor Stability After First-Line Treatment With Larotrectinib in an Infant With NTRK2 Fusion-Positive High-Grade Glioma.

Tissue-agnostic, molecularly targeted therapies are becoming increasingly common in cancer treatment. The molecular drivers of some classes and subclasses of tumors are rapidly being uncovered in an era of deep tumor sequencing occurring at the time of diagnosis. When and how targeted therapies should fit within up-front cytotoxic chemotherapy and radiation paradigms is yet to be determined, because many of them have been studied in single-arm studies in patients with relapsed or refractory cancer. Infant high-grade gliomas (HGGs) are biologically and clinically distinct from older child and adult HGGs, and are divided into 3 molecular subgroups. Group 1 infant HGGs are driven by receptor tyrosine kinase fusions, most commonly harboring an ALK, ROS1, NTRK, or MET fusion. Both larotrectinib and entrectinib are tropomyosin receptor kinase inhibitors with tissue-agnostic approvals for the treatment of patients with solid tumors harboring an NTRK fusion. This report discusses an 11-month-old female who presented with infantile spasms, found to have an unresectable, NTRK fusion-positive infant HGG. Larotrectinib was prescribed when the NTRK fusion was identified at diagnosis, and without additional intervention to date, the patient has continued with stable disease for >3 years. The only adverse event experienced was grade 1 aspartate transaminase and alanine transaminase elevations. The patient has a normal neurologic examination, is developing age-appropriately in all domains (gross motor, fine motor, cognitive, language, and social-emotional). She is no longer on antiseizure medications. To our knowledge, this is the first report of a patient with an infantile HGG receiving targeted therapy as first-line treatment with prolonged stable disease. A prospective study of larotrectinib in patients with newly diagnosed infant HGG is ongoing, and will hopefully help answer questions about durability of response, the need for additional therapies, and long-term toxicities seen with TRK inhibitors.

Psychedelic LSD activates neurotrophic signal but fails to stimulate neural stem cells.

Accumulating evidence has shown that some hallucinogens, such as LSD, have fast and persistent effects on anxiety and depression. According to a proposed mechanism, LSD activates the TrkB and HTR2A signaling pathways, which enhance the density of neuronal dendritic spines and synaptic function, and thus promote brain function. Moreover, TrkB signaling is also known to be crucial for neural stem cell (NSC)-mediated neuroregeneration to repair dysfunctional neurons. However, the impact of LSD on neural stem cells remains to be elucidated. In this study, we observed that LSD and BDNF activated the TrkB pathway in human NSCs similarly to neurons. However, unlike BDNF, LSD did not promote NSC proliferation. These results suggest that LSD may activate an alternative mechanism to counteract the effects of BDNF-TrkB signaling on NSCs. Our findings shed light on the previously unrecognized cell type-specificity of LSD. This could be crucial for deepening our understanding of the mechanisms underlying the effects of LSD.

Ameliorating Effect of Standardized Rice Bran Supplement on Depressive-Like Behaviors in Ovariectomized Mice.

Menopausal depression, often associated with hormonal fluctuations such as decreased estrogen levels, imposes significant mental health burdens. Despite the antidepressant biological properties of standardized rice bran supplement (RBS), its impact on menopausal depression and underlying mechanisms remains largely unexplored. In this study, we investigated the antidepressant effects of RBS in a mouse model of estrogen deficiency-induced depression. Ovariectomized (OVX) mice received oral doses of RBS (250 and 1000 mg/kg) and 17ß estradiol over a 20-week period. RBS administration resulted in decreased immobility time in the tail suspension and forced swim tests, along with increased locomotor activity in the open field test. Furthermore, RBS enhanced nitric oxide production and neuronal nitric oxide synthase (nNOS) expression in the hippocampi of OVX mice. Additionally, RBS administration phosphorylated extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), and tropomyosin receptor kinase B and increased the protein expression of brain-derived neurotrophic factor (BDNF) in the hippocampus. These findings suggest that RBS alleviated depressive behaviors in OVX mice by augmenting hippocampal nNOS expression and activating the ERK-CREB-BDNF signaling pathway. Therefore, based on these results, we propose that RBS is a promising agent to treat menopausal depression, a challenging condition.

Early protein restriction in rats induces anhedonia in adult offspring: A key role of BDNF-TrkB signaling in the nucleus accumbens shell.

Clinical evidence suggests that early malnutrition promotes symptoms related to psychiatric disorders later in life. Nevertheless, the molecular mechanisms underpinning nutritional injury induce depression remains unknown. The purpose of the present study was to evaluate whether perinatal protein restriction increases vulnerability to developing depressive-like behavior in adulthood by focusing on anhedonia, a core symptom of depression. To this, male adult Wistar rats submitted to a protein restriction schedule at perinatal age (PR-rats), were subjected to the sucrose preference test (SPT), the novel object recognition test (NORT), the forced swim test (FST), and the elevated plus maze (EPM), and compared to animals fed with a normoprotein diet. To investigate neurobiological substrates linked to early protein undernutrition-facilitated depressive-like behavior, we assessed the levels of brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the nucleus accumbens (NAc), and evaluated the reversal of anhedonic-like behavior by infusing ANA-12. We found that early malnutrition decreased sucrose preference, impaired performance in the NORT and increased immobility time in the FST. Furthermore, perinatal protein-restriction-induced anhedonia correlated with increased BDNF and p-TrkB protein levels in the NAc, a core structure in the reward circuit linked with anhedonia. Finally, bilateral infusion of the TrkB antagonist ANA-12 into the NAc shell ameliorated a reduced sucrose preference in the PR-rats. Altogether, these findings revealed that protein restriction during pregnancy and lactation facilitates depressive-like behavior later in life and may increase the risk of developing anhedonia by altering BDNF-TrkB in the NAc shell.

Examination of Akt and GSK3ß in BDNF-mediated reductions in BACE1 activity in neuronal cells.

Brain-derived neurotrophic factor (BDNF) content and signaling has been identified as one potential regulator of amyloid precursor protein (APP) processing. Recently published work has demonstrated that BDNF reduces BACE1 activity while also elevating the inhibition of GSK3ß in the prefrontal cortex of male C57BL/6J mice. These results provide evidence that BDNF alters APP processing by reducing BACE1 activity, which may act through GSK3ß inhibition. The purpose of this study was to further explore the role of GSK3ß in BDNF-induced regulation on BACE1 activity. We utilized a cell culture and an in vitro activity assay model to pharmacologically target BDNF and GSK3ß signaling to confirm its involvement in the BDNF response. Treatment of differentiated SH-SY5Y neuronal cells with 75 ng/mL BDNF resulted in elevated pTrkB content, pAkt content, pGSK3ß content, and reduced BACE1 activity. An in vitro BACE1 activity assay utilizing mouse prefrontal cortex (n = 6/group) supplemented with BDNF, BDNF + ANA12 (Trkb antagonist), or BDNF + wortmannin (Akt inhibitor) demonstrated that BDNF reduced BACE1 activity; however, in the presence of TrkB or Akt inhibition, this effect was abolished. An in vitro ADAM10 activity assay utilizing mouse prefrontal cortex (n = 6/group) supplemented with BDNF, BDNF + ANA12 (Trkb antagonist), or BDNF + wortmannin (Akt inhibitor) demonstrated that BDNF did not alter ADAM10 activity. However, inhibiting BDNF signaling reduced ADAM10 activity. Collectively these studies suggest that GSK3ß inhibition may be necessary for BDNF-induced reductions in BACE1 activity. These findings will allow for the optimization of future therapeutic strategies by selectively targeting TrkB activation and GSK3ß inhibition.

7,8-DHF inhibits BMSC oxidative stress via the TRKB/PI3K/AKT/NRF2 pathway to improve symptoms of postmenopausal osteoporosis.

Postmenopausal osteoporosis (PMO) is characterized by bone loss and microstructural damage, and it is most common in older adult women. Currently, there is no cure for PMO. The flavonoid chemical 7,8-dihydroxyflavone (7,8-DHF) specifically activates tropomyosin receptor kinase B (TRKB). Furthermore, 7,8-DHF has various biological characteristics, including anti-inflammatory and antioxidant effects. However, the specific implications and fundamental mechanisms of 7,8-DHF in PMO remain unclear. We used protein imprinting, flow cytometry, tissue staining, and other methods to estimate the preventive mechanisms of 7,8-DHF against hydrogen peroxide (H2O2)-induced apoptosis in primary mouse bone marrow mesenchymal stem cells (BMSCs), osteogenic differentiation ability, and bone mass in ovariectomized (OVX) mice. We found that 7,8-DHF effectively prevented H2O2-induced reductions in the viability and osteogenic differentiation capacity of primary BMSCs. Mechanistically, 7,8-DHF induced the TRKB to activate the PI3K/AKT/NRF2 pathway. In vivo experiments with the OVX mouse model confirmed that 7,8-DHF can inhibit oxidative stress and promote bone formation, indicating that 7,8-DHF improves the viability and osteogenic differentiation ability of BMSCs stimulated via H2O2 by activating the TRKB/PI3K/AKT and NRF2 pathways, thereby improving PMO.

Ginsenoside Re Prevents Depression-like Behaviors via Inhibition of Inflammation, Oxidative Stress, and Activating BDNF/TrkB/ERK/CREB Signaling: An In Vivo and In Vitro Study.

Depression is a widespread disease, with high mortality and recurrence rates. Recent studies have shown that elevated cytokine levels are implicated in the molecular mechanisms of depression. Oxidative stress contributes to the stimulation of cytokine production. Growing evidence suggests that ginsenoside Re (Gs-Re) exerts a neuroprotective effect on the hippocampus by suppressing oxidative stress and inflammation. However, the effect and mechanism of Gs-Re in the treatment of depression remain understudied. This study aimed to evaluate the neuroprotective and antidepressant-like effects of Gs-Re and the possible underlying mechanisms. In this article, the antidepressant-like effect of the Gs-Re was studied both in vitro (H2O2-induced oxidative stress in HT-22 cells) and in vivo (reserpine-induced depressive model mice). Our results indicated that, at the cellular level, Gs-Re effectively enhanced cell survival following H2O2 stimulation, inhibited the mass production of oxidative stress markers (MDA and ROS), and prevented the occurrence of apoptosis. Moreover, Gs-Re significantly reduced the levels of proinflammatory cytokines IL-1ß, IL-6, and TNF-α and restored the abnormal mitochondrial membrane potential. Subsequently, Gs-Re treatment reversed reserpine-induced neuroinflammation and depressive-like behaviors in vivo and inhibited microglia overactivation. Furthermore, the alterations in the BDNF/TrkB/ERK/CREB signaling pathway induced by H2O2 or reserpine in HT-22 cells or in the mouse hippocampus were significantly reversed by Gs-Re. K252a blocked the improvement of Gs-Re on depression-like behavior and eliminated the inhibition of oxidative stress and neuroinflammation in vivo. This study suggested that Gs-Re produces neuroprotective and depressive effects by inhibiting oxidative stress and inflammation and activating the BDNF/TrkB/ERK/CREB pathway.

Rice Protein Peptides Ameliorate DSS-Induced Cognitive Impairment and Depressive Behavior in Mice by Modulating Phenylalanine Metabolism and the BDNF/TRKB/CREB Pathway.

Rice protein peptide (RPP) has been reported to alleviate the symptoms of dextran sulfate sodium (DSS)-induced colitis, but its potential protective effect and fundamental neurobiological mechanisms against DSS-induced inflammatory bowel disease (IBD), coupled with depression and cognitive impairment, remain unclear. In this study, RPP treatment in DSS-induced mice inhibited decreases in body weight and colon length and improved intestinal barrier function and behavioral performance. RPP treatment enhanced phenylalanine and tyrosine metabolism in the brains of mice, and it upregulated metabolites such as l-dopa, phenylethylamine, and 3,4-dihydroxyphenylacetate. Additionally, RPP treatment enhanced the brain-derived neurotrophic factor (BDNF) by upregulating the BDNF/TrkB/CREB signaling pathway. Spearman's correlation analysis revealed that the phenylalanine and tyrosine contents in the brain were significantly negatively correlated with the BDNF/TrkB/CREB signaling pathway and behavioral performance. In conclusion, this study suggested that RPP may serve as a unique nutritional strategy for preventing IBD and its associated cognitive impairment and depression symptoms.

Inhibition of 5-HT alleviates PTSD-like behaviors and promotes hippocampal neuroplasticity by modulating hippocampal autophagy in rats.

5-Hydroxytryptamine (5-HT) plays a substantial role in mitigating depression and anxiety. However, the potential effects of 5-HT against posttraumatic stress disorder (PTSD) and its underlying mechanisms remain unclear. Elevated plus maze test evaluates anxiety-related behaviors, and the open field test is used to assess overall activity levels and anxiety. Inflammatory cytokine levels were determined using ELISA. The levels of 5-HT and dopamine were measured using HPLC. mRNA and protein levels were examined by PCR and Western blot, respectively. Rats exposed to single prolonged stress (SPS) exhibited typical PTSD-like phenotypes, with decreased levels of 5-HT in the hippocampus and significant reductions in its downstream targets, brain-derived neurotrophic factor (BDNF) and TrkB. In addition, it was discovered that the autophagy signaling pathway might be involved in regulating hippocampal BDNF in rats exposed to SPS. Subsequent treatment with an intracerebral injection of sh-SERT significantly inhibited anxiety and cognitive dysfunction in rats. Moreover, sh-SERT treatment was observed to substantially reverse the increase in autophagy signaling protein expression and consequently improve the expression of BDNF and TrkB proteins, which had been reduced. The current study demonstrates that sh-SERT exhibits significant anti-PTSD effects, potentially mediated in part through the reduction of cellular autophagy to enhance hippocampal synaptic plasticity.NEW & NOTEWORTHY The study demonstrated that sh-SERT exhibits significant anti-posttraumatic stress disorder (PTSD) effects, potentially mediated in part through the reduction of cellular autophagy to enhance hippocampal synaptic plasticity.

Morphine-responsive neurons that regulate mechanical antinociception.

Opioids are widely used, effective analgesics to manage severe acute and chronic pain, although they have recently come under scrutiny because of epidemic levels of abuse. While these compounds act on numerous central and peripheral pain pathways, the neuroanatomical substrate for opioid analgesia is not fully understood. By means of single-cell transcriptomics and manipulation of morphine-responsive neurons, we have identified an ensemble of neurons in the rostral ventromedial medulla (RVM) that regulates mechanical nociception in mice. Among these, forced activation or silencing of excitatory RVMBDNF projection neurons mimicked or completely reversed morphine-induced mechanical antinociception, respectively, via a brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)-dependent mechanism and activation of inhibitory spinal galanin-positive neurons. Our results reveal a specific RVM-spinal circuit that scales mechanical nociception whose function confers the antinociceptive properties of morphine.

Influence of Genetic Polymorphisms on Cognitive Function According to Dietary Exposure to Bisphenols in a Sample of Spanish Schoolchildren.

BACKGROUND: Neurodevelopmental disorders (NDDs) like intellectual disability (ID) are highly heritable, but the environment plays an important role. For example, endocrine disrupting chemicals (EDCs), including bisphenol A (BPA) and its analogues, have been termed neuroendocrine disruptors. This study aimed to evaluate the influence of different genetic polymorphisms (SNPs) on cognitive function in Spanish schoolchildren according to dietary bisphenol exposure. METHODS: A total of 102 children aged 6-12 years old were included. Ten SNPs in genes involved in brain development, synaptic plasticity, and neurotransmission (BDNF, NTRK2, HTR2A, MTHFR, OXTR, SLC6A2, and SNAP25) were genotyped. Then, dietary exposure to bisphenols (BPA plus BPS) was estimated and cognitive functions were assessed using the WISC-V Spanish form. RESULTS: BDNF rs11030101-T and SNAP25 rs363039-A allele carriers scored better on the fluid reasoning domain, except for those inheriting the BDNF rs6265-A allele, who had lower scores. Secondly, relevant SNP-bisphenol interactions existed in verbal comprehension (NTRK2 rs10868235 (p-int = 0.043)), working memory (HTR2A rs7997012 (p-int = 0.002), MTHFR rs1801133 (p-int = 0.026), and OXTR rs53576 (p-int = 0.030)) and fluid reasoning (SLC6A2 rs998424 (p-int = 0.004)). CONCLUSIONS: Our findings provide the first proof that exploring the synergistic or additive effects between genetic variability and bisphenol exposure on cognitive function could lead to a better understanding of the multifactorial and polygenic aetiology of NDDs.

Pyrazolo[1,5-a]pyrimidine as a Prominent Framework for Tropomyosin Receptor Kinase (Trk) Inhibitors-Synthetic Strategies and SAR Insights.

Tropomyosin receptor kinases (Trks) are transmembrane receptor tyrosine kinases named TrkA, TrkB, and TrkC and encoded by the NTRK1, NTRK2, and NTRK3 genes, respectively. These kinases have attracted significant attention and represent a promising therapeutic target for solid tumor treatment due to their vital role in cellular signaling pathways. First-generation TRK inhibitors, i.e., Larotrectinib sulfate and Entrectinib, received clinical approval in 2018 and 2019, respectively. However, the use of these inhibitors was significantly limited because of the development of resistance due to mutations. Fortunately, the second-generation Trk inhibitor Repotrectinib (TPX-0005) was approved by the FDA in November 2023, while Selitrectinib (Loxo-195) has provided an effective solution to this issue. Another macrocycle-based analog, along with many other TRK inhibitors, is currently in clinical trials. Two of the three marketed drugs for NTRK fusion cancers feature a pyrazolo[1,5-a] pyrimidine nucleus, prompting medicinal chemists to develop numerous novel pyrazolopyrimidine-based molecules to enhance clinical applications. This article focuses on a comprehensive review of chronological synthetic developments and the structure-activity relationships (SAR) of pyrazolo[1,5-a]pyrimidine derivatives as Trk inhibitors. This article will also provide comprehensive knowledge and future directions to the researchers working in the field of medicinal chemistry by facilitating the structural modification of pyrazolo [1,5-a]pyrimidine derivatives to synthesize more effective novel chemotherapeutics as TRK inhibitors.

Molecular Adaptations of BDNF/NT-4 Neurotrophic and Muscarinic Pathways in Ageing Neuromuscular Synapses.

Age-related conditions, such as sarcopenia, cause physical disabilities for an increasing section of society. At the neuromuscular junction, the postsynaptic-derived neurotrophic factors brain-derived neurotrophic factor (BDNF) and neurotrophin 4 (NT-4) have neuroprotective functions and contribute to the correct regulation of the exocytotic machinery. Similarly, presynaptic muscarinic signalling plays a fundamental modulatory function in this synapse. However, whether or not these signalling pathways are compromised in ageing neuromuscular system has not yet been analysed. The present study analyses, through Western blotting, the differences in expression and activation of the main key proteins of the BDNF/NT-4 and muscarinic pathways related to neurotransmission in young versus ageing Extensor digitorum longus (EDL) rat muscles. The main results show an imbalance in several sections of these pathways: (i) a change in the stoichiometry of BDNF/NT-4, (ii) an imbalance of Tropomyosin-related kinase B receptor (TrkB)-FL/TrkB-T1 and neurotrophic receptor p 75 (p75NTR), (iii) no changes in the cytosol/membrane distribution of phosphorylated downstream protein kinase C (PKC)ßI and PKCε, (iv) a reduction in the M2-subtype muscarinic receptor and P/Q-subtype voltage-gated calcium channel, (v) an imbalance of phosphorylated mammalian uncoordinated-18-1 (Munc18-1) (S313) and synaptosomal-associated protein 25 (SNAP-25) (S187), and (vi) normal levels of molecules related to the management of acetylcholine (Ach). Based on this descriptive analysis, we hypothesise that these pathways can be adjusted to ensure neurotransmission rather than undergoing negative alterations caused by ageing. However, further studies are needed to assess this hypothetical suggestion. Our results contribute to the understanding of some previously described neuromuscular functional age-related impairments. Strategies to promote these signalling pathways could improve the neuromuscular physiology and quality of life of older people.

The Antidepressant Action of Fluoxetine Involves the Inhibition of Dlx5/6 in Cortical GABAergic Neurons through a TrkB-Dependent Pathway.

Major depressive disorder (MDD) is a complex and devastating illness that affects people of all ages. Despite the large use of antidepressants in current medical practice, neither their mechanisms of action nor the aetiology of MDD are completely understood. Experimental evidence supports the involvement of Parvalbumin-positive GABAergic neurons (PV-neurons) in the pathogenesis of MDD. DLX5 and DLX6 (DLX5/6) encode two homeodomain transcription factors involved in cortical GABAergic differentiation and function. In the mouse, the level of expression of these genes is correlated with the cortical density of PV-neurons and with anxiety-like behaviours. The same genomic region generates the lncRNA DLX6-AS1, which, in humans, participates in the GABAergic regulatory module downregulated in schizophrenia and ASD. Here, we show that the expression levels of Dlx5/6 in the adult mouse brain are correlated with the immobility time in the forced swim test, which is used to measure depressive-like behaviours. We show that the administration of the antidepressant fluoxetine (Flx) to normal mice induces, within 24 h, a rapid and stable reduction in Dlx5, Dlx6 and Dlx6-AS1 expression in the cerebral cortex through the activation of the TrkB-CREB pathway. Experimental Dlx5 overexpression counteracts the antidepressant effects induced by Flx treatment. Our findings show that one of the short-term effects of Flx administration is the reduction in Dlx5/6 expression in GABAergic neurons, which, in turn, has direct consequences on PV expression and on behavioural profiles. Variants in the DLX5/6 regulatory network could be implicated in the predisposition to depression and in the variability of patients' response to antidepressant treatment.

Neuroprotection by ADAM10 inhibition requires TrkB signaling in the Huntington's disease hippocampus.

Synaptic dysfunction is an early pathogenic event leading to cognitive decline in Huntington's disease (HD). We previously reported that the active ADAM10 level is increased in the HD cortex and striatum, causing excessive proteolysis of the synaptic cell adhesion protein N-Cadherin. Conversely, ADAM10 inhibition is neuroprotective and prevents cognitive decline in HD mice. Although the breakdown of cortico-striatal connection has been historically linked to cognitive deterioration in HD, dendritic spine loss and long-term potentiation (LTP) defects identified in the HD hippocampus are also thought to contribute to the cognitive symptoms of the disease. The aim of this study is to investigate the contribution of ADAM10 to spine pathology and LTP defects of the HD hippocampus. We provide evidence that active ADAM10 is increased in the hippocampus of two mouse models of HD, leading to extensive proteolysis of N-Cadherin, which has a widely recognized role in spine morphology and synaptic plasticity. Importantly, the conditional heterozygous deletion of ADAM10 in the forebrain of HD mice resulted in the recovery of spine loss and ultrastructural synaptic defects in CA1 pyramidal neurons. Meanwhile, normalization of the active ADAM10 level increased the pool of synaptic BDNF protein and activated ERK neuroprotective signaling in the HD hippocampus. We also show that the ADAM10 inhibitor GI254023X restored LTP defects and increased the density of mushroom spines enriched with GluA1-AMPA receptors in HD hippocampal neurons. Notably, we report that administration of the TrkB antagonist ANA12 to HD hippocampal neurons reduced the beneficial effect of GI254023X, indicating that the BDNF receptor TrkB contributes to mediate the neuroprotective activity exerted by ADAM10 inhibition in HD. Collectively, these findings indicate that ADAM10 inhibition coupled with TrkB signaling represents an efficacious strategy to prevent hippocampal synaptic plasticity defects and cognitive dysfunction in HD.

Atypical cellular responses mediated by intracellular constitutive active TrkB (NTRK2) kinase domains and a solely intracellular NTRK2-fusion oncogene.

Trk (NTRK) receptor and NTRK gene fusions are oncogenic drivers of a wide variety of tumors. Although Trk receptors are typically activated at the cell surface, signaling of constitutive active Trk and diverse intracellular NTRK fusion oncogenes is barely investigated. Here, we show that a high intracellular abundance is sufficient for neurotrophin-independent, constitutive activation of TrkB kinase domains. In HEK293 cells, constitutive active TrkB kinase and an intracellular NTRK2-fusion oncogene (SQSTM1-NTRK2) reduced actin filopodia dynamics, phosphorylated FAK, and altered the cell morphology. Atypical cellular responses could be mimicked with the intracellular kinase domain, which did not activate the Trk-associated MAPK/ERK pathway. In glioblastoma-like U87MG cells, expression of TrkB or SQSTM1-NTRK2 reduced cell motility and caused drastic changes in the transcriptome. Clinically approved Trk inhibitors or mutating Y705 in the kinase domain, blocked the cellular effects and transcriptome changes. Atypical signaling was also seen for TrkA and TrkC. Moreover, hallmarks of atypical pTrk kinase were found in biopsies of Nestin-positive glioblastoma. Therefore, we suggest Western blot-like immunoassay screening of NTRK-related (brain) tumor biopsies to identify patients with atypical panTrk or phosphoTrk signals. Such patients could be candidates for treatment with NTRK inhibitors such as Larotrectinhib or Entrectinhib.

Subchronic administration of scopolamine reverses UCMS-induced behavior in mice via eEF2 protein dephosphorylation.

BACKGROUND: The cholinergic system has been increasingly linked to the pathophysiology of mood disorders such as depression, with the potential involvement of nicotinic and/or muscarinic receptors. Conventional antidepressants usually require weeks of daily dosing to achieve a full antidepressant response. In contrast, clinical studies have shown that scopolamine, a nonselective muscarinic acetylcholine receptor antagonist, can induce potent and rapid antidepressant effects, requiring only a few days of treatment. This study aimed to examine the suitability of the unpredictable chronic mild stress (UCMS) model of depression to reproduce the above scopolamine antidepressant activity patterns. METHODS: Rapid and sustained antidepressant-like effects were assessed by using the splash test, sucrose preference test (SPT), tail suspension test (TST), and forced swimming test (FST) in animals undergoing the UCMS procedure and stress-naïve C57BL/6J mice. Western Blotting was used to measure tropomyosin receptor kinase B (TrkB), mammalian target of rapamycin (mTOR), eukaryotic elongation factor (eEF2) and postsynaptic density protein 95 (PSD95) levels. RESULTS: Scopolamine induced antidepressant-like effects in a dose-dependent manner only after subchronic, but not single, administration in the UCMS model of depression in C57BL/6J mice without affecting locomotor activity. Specifically, scopolamine administered at a dose of 0.3 mg/kg for four consecutive days significantly reversed the UCMS-induced depressive-like behavior, such as apathy, anhedonia, and behavioral despair, while scopolamine, given at the same dose but only once, did not relieve the above symptoms. Scopolamine treatment was accompanied by eEF2 protein dephosphorylation and its subsequent reactivation in the prefrontal cortex (PFC). CONCLUSION: Subchronic administration of scopolamine is needed to ameliorate UCMS-induced depressive-like behavior. The suggested mechanism of scopolamine action covers eEF2 protein activity in the PFC.

The tyrosine phosphatases LAR and PTPRδ act as receptors of the nidogen-tetanus toxin complex.

Tetanus neurotoxin (TeNT) causes spastic paralysis by inhibiting neurotransmission in spinal inhibitory interneurons. TeNT binds to the neuromuscular junction, leading to its internalisation into motor neurons and subsequent transcytosis into interneurons. While the extracellular matrix proteins nidogens are essential for TeNT binding, the molecular composition of its receptor complex remains unclear. Here, we show that the receptor-type protein tyrosine phosphatases LAR and PTPRδ interact with the nidogen-TeNT complex, enabling its neuronal uptake. Binding of LAR and PTPRδ to the toxin complex is mediated by their immunoglobulin and fibronectin III domains, which we harnessed to inhibit TeNT entry into motor neurons and protect mice from TeNT-induced paralysis. This function of LAR is independent of its role in regulating TrkB receptor activity, which augments axonal transport of TeNT. These findings reveal a multi-subunit receptor complex for TeNT and demonstrate a novel trafficking route for extracellular matrix proteins. Our study offers potential new avenues for developing therapeutics to prevent tetanus and dissecting the mechanisms controlling the targeting of physiological ligands to long-distance axonal transport in the nervous system.