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Intimate partner violence (IPV) is a significant public health concern whose neurological/behavioral sequelae remain to be mechanistically explained. Using a mouse model recapitulating an IPV scenario, we evaluated the female brain neuroendocrine alterations produced by a reiterated male-to-female violent interaction (RMFVI). RMFVI prompted anxiety-like behavior in female mice whose hippocampus displayed a marked neuronal loss and hampered neurogenesis, namely reduced BrdU-DCX-positive nuclei and diminished dendritic arborization in the dentate gyrus (DG): effects paralleled by a substantial downregulation of the estrogen receptor β (ERβ). After RMFVI, the DG harbored reduced brain-derived neurotrophic factor (BDNF) pools and tyrosine kinase receptor B (TrkB) phosphorylation. Accordingly, ERβ knockout (KO) mice had heightened anxiety and curtailed BDNF levels at baseline while dying prematurely during the RMFVI procedure. Strikingly, injecting an ERβ antagonist or agonist into the wild-type (WT) female hippocampus enhanced or reduced anxiety, respectively. Thus, reiterated male-to-female violence jeopardizes hippocampal homeostasis, perturbing the ERβ/BDNF axis and ultimately instigating anxiety and chronic stress., Competing Interests: The authors declare no conflicts of interests., (© 2024 Published by Elsevier Inc.)

The Frontiers in Neurophotonics Symposium is a biennial event that brings together neurobiologists and physicists/engineers who share interest in the development of leading-edge photonics-based approaches to understand and manipulate the nervous system, from its individual molecular components to complex networks in the intact brain. In this Community paper, we highlight several topics that have been featured at the symposium that took place in October 2022 in Québec City, Canada., (© 2024 The Authors.)

In Neurodevelopmental Disorders, alterations of synaptic plasticity may trigger structural changes in neuronal circuits involved in cognitive functions. This hypothesis was tested in mice carrying the human R451C mutation of Nlgn3 gene (NLG3 R451C KI), found in some families with autistic children. To this aim, the spike time dependent plasticity (STDP) protocol was applied to immature GABAergic Mossy Fibers (MF)-CA3 connections in hippocampal slices from NLG3 R451C KI mice. These animals failed to exhibit STD-LTP, an effect that persisted in adulthood when these synapses became glutamatergic. Similar results were obtained in mice lacking the Nlgn3 gene (NLG3 KO mice), suggesting a loss of function. The loss of STD-LTP was associated with a premature shift of GABA from the depolarizing to the hyperpolarizing direction, a reduced BDNF availability and TrkB phosphorylation at potentiated synapses. These effects may constitute a general mechanism underlying cognitive deficits in those forms of Autism caused by synaptic dysfunctions., Competing Interests: The authors declare no competing interests., (© 2022 The Authors.)

Neurons release and respond to brain-derived neurotrophic factor (BDNF) with bursts of brain activity. BDNF action is known to extend to peri-synaptic astrocytes, contributing to synaptic strengthening. This implies that astrocytes have a set of dynamic responses, some of which might be secondary to activation of the tropomyosin tyrosine kinase B (TrkB) receptor. Here, we assessed the contribution of BDNF to long-term synaptic potentiation (LTP), by specifically deleting TrkB in cortical astrocytes. TrkB deletion had no effect on LTP induction, stabilization and maintenance, indicating that TrkB signaling in astrocytes is extraneous to transducing BDNF activity for synaptic strengthening.

Metastatic prostate cancer (mPCa) is one of the leading causes of cancer-related mortality in both the US and Europe. Androgen deprivation is the first-line therapy for mPCa; however, resistance to therapy inevitably occurs and the disease progresses to the castration resistant stage, which is uncurable. A definition of novel targeted therapies is necessary for the establishment of innovative and more effective protocols of personalized oncology. We employed genetically engineered mouse models of PCa and human samples to characterize the expression of the TRPM8 cation channel in both hormone naïve and castration resistant tumors. We show that Trpm8 expression marks both indolent (Pten-null) and aggressive (Pten/Trp53 double-null and TRAMP) mouse prostate adenocarcinomas. Importantly, both mouse and human castration-resistant PCa preserve TRPM8 protein expression. Finally, we tested the effect of TRPM8 agonist D-3263 administration in combination with enzalutamide or docetaxel on the viability of aggressive mouse PCa cell lines. Our data demonstrate that D-3263 substantially enhances the pro-apoptotic activity of enzalutamide and docetaxel in TRAMP-C1 e TRAMP-C2 PCa cell lines. To conclude, this study provides the basis for pre-clinical in vivo testing of TRPM8 targeting as a novel strategy to implement the efficacy of standard-of-care treatments for advanced PCa.

Memory consolidation requires astrocytic microdomains for protein recycling; but whether this lays a mechanistic foundation for long-term information storage remains enigmatic. Here we demonstrate that persistent synaptic strengthening invited astrocytic microdomains to convert initially internalized (pro)-brain-derived neurotrophic factor (proBDNF) into active prodomain (BDNFpro) and mature BDNF (mBDNF) for synaptic re-use. While mBDNF activates TrkB, we uncovered a previously unsuspected function for the cleaved BDNFpro, which increases TrkB/SorCS2 receptor complex at post-synaptic sites. Astrocytic BDNFpro release reinforced TrkB phosphorylation to sustain long-term synaptic potentiation and to retain memory in the novel object recognition behavioral test. Thus, the switch from one inactive state to a multi-functional one of the proBDNF provides post-synaptic changes that survive the initial activation. This molecular asset confines local information storage in astrocytic microdomains to selectively support memory circuits., (© 2021. The Author(s).)

Recent computational advancements in the simulation of biochemical processes allow investigating the mechanisms involved in protein regulation with realistic physics-based models, at an atomistic level of resolution. These techniques allowed us to design a drug discovery approach, named Pharmacological Protein Inactivation by Folding Intermediate Targeting (PPI-FIT), based on the rationale of negatively regulating protein levels by targeting folding intermediates. Here, PPI-FIT was tested for the first time on the cellular prion protein (PrP), a cell surface glycoprotein playing a key role in fatal and transmissible neurodegenerative pathologies known as prion diseases. We predicted the all-atom structure of an intermediate appearing along the folding pathway of PrP and identified four different small molecule ligands for this conformer, all capable of selectively lowering the load of the protein by promoting its degradation. Our data support the notion that the level of target proteins could be modulated by acting on their folding pathways, implying a previously unappreciated role for folding intermediates in the biological regulation of protein expression.

Spinocerebellar ataxia type 35 (SCA35) is a rare autosomal-dominant neurodegenerative disease caused by mutations in the TGM6 gene, which codes for transglutaminase 6 (TG6). Mutations in TG6 induce cerebellar degeneration by an unknown mechanism. We identified seven patients bearing new mutations in TGM6. To gain insights into the molecular basis of mutant TG6-induced neurotoxicity, we analyzed all the seven new TG6 mutants and the five TG6 mutants previously linked to SCA35. We found that the wild-type (TG6-WT) protein mainly localized to the nucleus and perinuclear area, whereas five TG6 mutations showed nuclear depletion, increased accumulation in the perinuclear area, insolubility and loss of enzymatic function. Aberrant accumulation of these TG6 mutants in the perinuclear area led to activation of the unfolded protein response (UPR), suggesting that specific TG6 mutants elicit an endoplasmic reticulum stress response. Mutations associated with activation of the UPR caused death of primary neurons and reduced the survival of novel Drosophila melanogaster models of SCA35. These results indicate that mutations differently impacting on TG6 function cause neuronal dysfunction and death through diverse mechanisms and highlight the UPR as a potential therapeutic target for patient treatment., (© The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

We have recently reported that long-term memory retention requires synaptic glia for proBDNF uptake and recycling. Through the recycling course, glial cells release endocytic BDNF, a mechanism that is activated in response to glutamate via AMPA and mGluRI/II receptors. Cortical astrocytes express receptors for many different transmitters suggesting for a complex signaling controlling endocytic BDNF secretion. Here, we demonstrated that the extracellular nucleotide ATP, activating P2X and P2Y receptors, regulates endocytic BDNF secretion in cultured astrocytes. Our data indicate that distinct glioactive molecules can participate in BDNF glial recycling and suggest that cortical astrocytes contributing to neuronal plasticity can be influenced by neurotransmitters in tune with synaptic needs.

Glial cells respond to neuronal activation and release neuroactive molecules (termed "gliotransmitters") that can affect synaptic activity and modulate plasticity. In this study, we used molecular genetic tools, ultra-structural microscopy, and electrophysiology to assess the role of brain-derived neurotrophic factor (BDNF) on cortical gliotransmission in vivo. We find that glial cells recycle BDNF that was previously secreted by neurons as pro-neurotrophin following long-term potentiation (LTP)-inducing electrical stimulation. Upon BDNF glial recycling, we observed tight, temporal, highly localized TrkB phosphorylation on adjacent neurons, a process required to sustain LTP. Engagement of BDNF recycling by astrocytes represents a novel mechanism by which cortical synapses can expand BDNF action and provide synaptic changes that are relevant for the acquisition of new memories. Accordingly, mice deficient in BDNF glial recycling fail to recognize familiar from novel objects, indicating a physiological requirement for this process in memory consolidation., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Video Abstract: Newly generated neurons initiate polarizing signals that specify a single axon and multiple dendrites, a process critical for patterning neuronal circuits in vivo. Here, we report that the pan-neurotrophin receptor p75(NTR) is a polarity regulator that localizes asymmetrically in differentiating neurons in response to neurotrophins and is required for specification of the future axon. In cultured hippocampal neurons, local exposure to neurotrophins causes early accumulation of p75(NTR) into one undifferentiated neurite to specify axon fate. Moreover, knockout or knockdown of p75(NTR) results in failure to initiate an axon in newborn neurons upon cell-cycle exit in vitro and in the developing cortex, as well as during adult hippocampal neurogenesis in vivo. Hence, p75(NTR) governs neuronal polarity, determining pattern and assembly of neuronal circuits in adult hippocampus and cortical development., (Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.)

Immunoglobulin (Ig) isotype diversification by class switch recombination (CSR) is an essential process for mounting a protective humoral immune response. Ig CSR deficiencies in humans can result from an intrinsic B cell defect; however, most of these deficiencies are still molecularly undefined and diagnosed as common variable immunodeficiency (CVID). Here, we show that extracellular adenosine critically contributes to CSR in human naive and IgM memory B cells. In these cells, coordinate stimulation of B cell receptor and toll-like receptors results in the release of ATP stored in Ca(2+)-sensitive secretory vesicles. Plasma membrane ectonucleoside triphosphate diphosphohydrolase 1 CD39 and ecto-5'-nucleotidase CD73 hydrolyze ATP to adenosine, which induces CSR in B cells in an autonomous fashion. Notably, CVID patients with impaired class-switched antibody responses are selectively deficient in CD73 expression in B cells, suggesting that CD73-dependent adenosine generation contributes to the pathogenesis of this disease., (Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.)

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, which has been reported to regulate neurogenesis in the dentate gyrus, but the molecular control over this process remains unclear. We demonstrated that by activating TrkB receptor tyrosine kinase, BDNF controls the size of the surviving pool of newborn neurons at the time of connectivity. The TrkB-dependent decision regarding survival in these newborn neurons takes place at approximately four to six weeks of age. Before newborn neurons start to die they exhibit a drastic reduction in dendritic complexity and spine density, which may reflect a failure of these cells to integrate appropriately. Both the failure to become integrated, and subsequent dying, leads to impaired neurogenesisdependent plasticity and increased anxiety-like behavior in mice lacking a functional TrkB receptor in newborn neurons. Thus, our data demonstrate the importance of BDNF/TrkB signaling for the survival and integration of newborn neurons in the adult hippocampus and suggest a critical function of these neurons in regulating the anxiety state of the animal.

Activity-dependent secretion of brain-derived neurotrophic factor (BDNF) is thought to enhance synaptic plasticity, but the mechanisms controlling extracellular availability and clearance of secreted BDNF are poorly understood. We show that BDNF is secreted in its precursor form (pro-BDNF) and is then cleared from the extracellular space through rapid uptake by nearby astrocytes after theta-burst stimulation in layer II/III of cortical slices, a paradigm resulting in long-term potentiation of synaptic transmission. Internalization of pro-BDNF occurs via the formation of a complex with the pan-neurotrophin receptor p75 and subsequent clathrin-dependent endocytosis. Fluorescence-tagged pro-BDNF and real-time total internal reflection fluorescence microscopy in cultured astrocytes is used to monitor single endocytic vesicles in response to the neurotransmitter glutamate. We find that endocytosed pro-BDNF is routed into a fast recycling pathway for subsequent soluble NSF attachment protein receptor-dependent secretion. Thus, astrocytes contain an endocytic compartment competent for pro-BDNF recycling, suggesting a specialized form of bidirectional communication between neurons and glia.

New neurons in the adult dentate gyrus are widely held to incorporate into hippocampal circuitry via a stereotypical sequence of morphological and physiological transitions, yet the molecular control over this process remains unclear. We studied the role of brain-derived neurotrophic factor (BDNF)/TrkB signaling in adult neurogenesis by deleting the full-length TrkB via Cre expression within adult progenitors in TrkB(lox/lox) mice. By 4 weeks after deletion, the growth of dendrites and spines is reduced in adult-born neurons demonstrating that TrkB is required to create the basic organization of synaptic connections. Later, when new neurons normally display facilitated synaptic plasticity and become preferentially recruited into functional networks, lack of TrkB results in impaired neurogenesis-dependent long-term potentiation and cell survival becomes compromised. Because of the specific lack of TrkB signaling in recently generated neurons a remarkably increased anxiety-like behavior was observed in mice carrying the mutation, emphasizing the contribution of adult neurogenesis in regulating mood-related behavior.

Regulation of brain-derived neurotrophic factor (BDNF) secretion plays a critical role in long-term potentiation (LTP). It is generally thought that the supply for this secretion is newly synthesized BDNF targeted to the synapse. Here we provide evidence that hippocampal neurons additionally recycle BDNF for activity-dependent secretion. Exogenously applied BDNF is internalized by cultured neurons and rapidly becomes available for activity-dependent secretion, which is controlled by the same mechanisms that regulate the secretion of newly synthesized BDNF. Moreover, BDNF recycling replaced the new synthesis pathway in mediating the maintenance of LTP in hippocampal slices: the late phase LTP, which is abolished by protein synthesis inhibition, was rescued in slices preincubated with BDNF. Thus, endocytosed BDNF is fed back to the activity-dependent releasable pool required for LTP maintenance.

Neurotrophins play an important role in modulating activity-dependent neuronal plasticity. In particular, threshold levels of brain-derived neurotrophic factor (BDNF) are required to induce long-term potentiation (LTP) in acute hippocampal slices. Conversely, the administration of exogenous BDNF prevents the induction of long-term depression (LTD) in the visual cortex. A long-standing missing link in the analysis of this modulatory role of BDNF was the determination of the time-course of endogenous BDNF secretion in the same organotypic preparation in which LTP and LTD are elicited. Here, we fulfilled this requirement in slices of perirhinal cortex. Classical theta-burst stimulation patterns evoking LTP lasting >180 min elicited a large increase in BDNF secretion that persisted 5-12 min beyond the stimulation period. Weaker theta-burst stimulation patterns leading only to the initial phase of LTP ( approximately 35 min) were accompanied by a smaller increase in BDNF secretion lasting <1 min. Sequestration of BDNF by TrkB-IgG receptor bodies prevented LTP. Low-frequency stimulations leading to LTD were accompanied by reductions in BDNF secretion that never lasted beyond the duration of the stimulation.

Background & Aims: The role of autoimmunity underlying paraneoplastic gut dysmotility remains unsettled. Because anti-Hu antibodies may impair enteric neuronal function, we tested whether anti-HuD-positive sera from patients with paraneoplastic gut dysmotility or commercial anti-HuD antibodies activated the apoptotic cascade in a neuroblastoma cell line and cultured myenteric neurons., Methods: Anti-HuD antibodies from patients with severe paraneoplastic gut dysmotility were characterized by immunofluorescence and immunoblot. SH-Sy5Y neuroblasts and cultured myenteric neurons were exposed to sera containing anti-HuD antibodies or 2 commercial anti-HuD antibodies. Cells were processed for terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) technique to evaluate apoptosis. Immunofluorescence was used to identify activated caspase-3 and apaf-1, along with microtubule-associated protein 2., Results: In SH-Sy5Y cells, the percentage of TUNEL-positive nuclei observed after exposure to anti-HuD-positive sera (32% +/- 7%) or anti-HuD antibodies (23% +/- 2%) was significantly greater than that of control sera or fetal calf serum (P < 0.001). The time-course analysis showed a significantly greater number of apoptotic neuroblastoma cells evoked by the 2 commercial anti-HuD antibodies at 24, 48, and 72 hours versus controls. The number of TUNEL-positive myenteric neurons exposed to anti-HuD antibodies (60% +/- 14%) was significantly greater than that of fetal calf serum (7% +/- 2%; P < 0.001). Apaf-1 and caspase-3 immunolabeling showed intense cytoplasmic staining in a significantly greater proportion of cells exposed to anti-HuD-positive sera or to commercial anti-HuD antibodies compared with controls., Conclusions: Anti-HuD antibodies evoked neuronal apoptosis that may contribute to enteric nervous system impairment underlying paraneoplastic gut dysmotility. Apaf-1 activation suggests participation of a mitochondria-dependent apoptotic pathway.

The regulation of neurotrophin (NT) secretion is critical for many aspects of NT-mediated neuronal plasticity. Neurons release NTs by activity-regulated secretion pathways, initiated either by neurotransmitters and/or by existing NTs by a positive-feedback mechanism. This process depends on calcium release from intracellular stores. Little is known, however, about potential pathways that down-regulate NT secretion. Here we demonstrate that nitric oxide (NO) induces a rapid down-regulation of brain-derived neurotrophic factor (BDNF) secretion in cultured hippocampal neurons. Similar effects occur by activating a downstream target of intracellular NO, the soluble guanylyl cyclase, or by increasing the levels of its product, cGMP. Furthermore, down-regulation of BDNF secretion is mediated by cGMP-activated protein kinase G, which prevents calcium release from inositol 1,4,5-trisphosphate-sensitive stores. Our data indicate that the NO/cGMP/protein kinase G pathway represents a signaling mechanism by which neurons can rapidly down-regulate BDNF secretion and suggest that, in hippocampal neurons, NT secretion is finely tuned by both stimulatory and inhibitory signals.

Neurotrophins, secreted in an activity-dependent manner, are thought to be involved in the activity-dependent refinement of synaptic connections. Here we demonstrate that in hippocampal neurons and the rat pheochromocytoma cell line PC12 application of exogenous neurotrophins induces secretion of neurotrophins, an effect that is mediated by the activation of tyrosine kinase neurotrophin receptors (Trks). Like activity-dependent secretion of neurotrophins, neurotrophin-induced neurotrophin secretion requires mobilization of calcium from intracellular stores. Because neurotrophins are likely to be released from both dendrites and axons, neurotrophin-induced neurotrophin release represents a potential positive feedback mechanism, contributing to the reinforcement and stabilization of synaptic connections.