CAPON-nNOS coupling can serve as a target for developing new anxiolytics

The role of nitric oxide and hormone signaling in chronic stress, anxiety, depression and post-traumatic stress disorder

This paper provides a summary of the role of nitric oxide (NO) and hormones in the development of chronic stress, anxiety, depression, and post-traumatic stress disorder (PTSD). These mental health conditions are prevalent globally and involve complex molecular interactions. Although there is a significant amount of research and therapeutic options available, the underlying mechanisms of these disorders are still not fully understood. The primary pathophysiologic processes involved in chronic stress, anxiety, depression, and PTSD include dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, the intracellular influence of neuronal nitric oxide synthase (nNOS) on transcription factors, an inflammatory response with the formation of nitrergic oxidative species, and reduced serotonergic transmission in the dorsal raphe nucleus. Despite the extensive literature on this topic, there is a great need for further research to clarify the complexities inherent in these pathways, with the primary aim of improving psychiatric care.

Recessive variants in the intergenic NOS1AP-C1orf226 locus cause monogenic kidney disease responsive to anti-proteinuric treatment

In genetic disease, an accurate expression landscape of disease genes and faithful animal models will enable precise genetic diagnoses and therapeutic discoveries, respectively. We previously discovered that variants in NOS1AP , encoding nitric oxide synthase 1 (NOS1) adaptor protein, cause monogenic nephrotic syndrome (NS). Here, we determined that an intergenic splice product of N OS1AP / Nos1ap and neighboring C1orf226/Gm7694 , which precludes NOS1 binding, is the predominant isoform in mammalian kidney transcriptional and proteomic data. Gm7694 -/- mice, whose allele exclusively disrupts the intergenic product, developed NS phenotypes. In two human NS subjects, we identified causative NOS1AP splice variants, including one predicted to abrogate intergenic splicing but initially misclassified as benign based on the canonical transcript. Finally, by modifying genetic background, we generated a faithful mouse model of NOS1AP -associated NS, which responded to anti-proteinuric treatment. This study highlights the importance of intergenic splicing and a potential treatment avenue in a mendelian disorder.

Rasd1 is involved in white matter injury through neuron-oligodendrocyte communication after subarachnoid hemorrhage

AIMS

Rasd1 has been reported to be correlated with neurotoxicity, metabolism, and rhythm, but its effect in case of subarachnoid hemorrhage (SAH) remained unclear. White matter injury (WMI) and ferroptosis participate in the early brain injury (EBI) after SAH. In this work, we have investigated whether Rasd1 can cause ferroptosis and contribute to SAH-induced WMI.

METHODS

Lentivirus for Rasd1 knockdown/overexpression was administrated by intracerebroventricular (i.c.v) injection at 7 days before SAH induction. SAH grade, brain water content, short- and long-term neurobehavior, Western blot, real-time PCR, ELISA, biochemical estimation, immunofluorescence, diffusion tensor imaging (DTI), and transmission electron microscopy (TEM) were systematically performed. Additionally, genipin, a selective uncoupling protein 2(UCP2) inhibitor, was used in primary neuron and oligodendrocyte co-cultures for further in vitro mechanistic studies.

RESULTS

Rasd1 knockdown has improved the neurobehavior, glia polarization, oxidative stress, neuroinflammation, ferroptosis, and demyelination. Conversely, Rasd1 overexpression aggravated these changes by elevating the levels of reactive oxygen species (ROS), inflammatory cytokines, MDA, free iron, and NCOA4, as well as contributing to the decrease of the levels of UCP2, GPX4, ferritin, and GSH mechanistically. According to the in vitro study, Rasd1 can induce oligodendrocyte ferroptosis through inhibiting UCP2, increasing reactive oxygen species (ROS), and activating NCOA4-mediated ferritinophagy.

CONCLUSIONS

It can be concluded that Rasd1 exerts a modulated role in oligodendrocytes ferroptosis in WMI following SAH.

nNOS in Erbb4-positive neurons regulates GABAergic transmission in mouse hippocampus

Neuronal nitric oxide synthase (nNOS, gene name Nos1) orchestrates the synthesis of nitric oxide (NO) within neurons, pivotal for diverse neural processes encompassing synaptic transmission, plasticity, neuronal excitability, learning, memory, and neurogenesis. Despite its significance, the precise regulation of nNOS activity across distinct neuronal types remains incompletely understood. Erb-b2 receptor tyrosine kinase 4 (ErbB4), selectively expressed in GABAergic interneurons and activated by its ligand neuregulin 1 (NRG1), modulates GABA release in the brain. Our investigation reveals the presence of nNOS in a subset of GABAergic interneurons expressing ErbB4. Notably, NRG1 activates nNOS via ErbB4 and its downstream phosphatidylinositol 3-kinase (PI3K), critical for NRG1-induced GABA release. Genetic removal of nNos from Erbb4-positive neurons impairs GABAergic transmission, partially rescued by the NO donor sodium nitroprusside (SNP). Intriguingly, the genetic deletion of nNos from Erbb4-positive neurons induces schizophrenia-relevant behavioral deficits, including hyperactivity, impaired sensorimotor gating, and deficient working memory and social interaction. These deficits are ameliorated by the atypical antipsychotic clozapine. This study underscores the role and regulation of nNOS within a specific subset of GABAergic interneurons, offering insights into the pathophysiological mechanisms of schizophrenia, given the association of Nrg1, Erbb4, Pi3k, and Nos1 genes with this mental disorder.

Preclinical evaluation of ZL006-05, a new antistroke drug with fast-onset antidepressant and anxiolytic effects

BACKGROUND

Poststroke depression and anxiety, independent predictor of poor functional outcomes, are common in the acute phase of stroke. Up to now, there is no fast-onset antidepressive and anxiolytic agents suitable for the management of acute stroke. ZL006-05, a dual-target analgesic we developed, dissociates nitric oxide synthase from postsynaptic density-95 while potentiates α2-containing γ-aminobutyric acid type A receptor. This study aims to determine whether ZL006-05 can be used as an antistroke agent with fast-onset antidepressant and anxiolytic effects.

METHODS

Photothrombotic stroke and transient middle cerebral artery occlusion were induced in rats and mice. Infarct size was measured by TTC(2,3,5-Triphenyltetrazolium chloride) staining or Nissl staining. Neurological defects were assessed by four-point scale neurological score or modified Neurological Severity Scores. Grid-walking, cylinder and modified adhesive removal tasks were conducted to assess sensorimotor functions. Spatial learning was assessed using Morris water maze task. Depression and anxiety were induced by unpredictable chronic mild stress. Depressive behaviours were assessed by tail suspension, forced swim and sucrose preference tests. Anxiety behaviours were assessed by novelty-suppressed feeding and elevated plus maze tests. Pharmacokinetics, toxicokinetics and long-term toxicity studies were performed in rats.

RESULTS

Administration of ZL006-05 in the acute phase of stroke attenuated transient and permanent ischaemic injury and ameliorated long-term functional impairments significantly, with a treatment window of 12 hours after ischemia, and reduced plasminogen activato-induced haemorrhagic transformation. ZL006-05 produced fast-onset antidepressant and anxiolytic effects with onset latency of 1 hour in the normal and CMS mice, had antidepressant and anxiolytic effects in stroke mice. ZL006-05 crossed the blood-brain barrier and distributed into the brain rapidly, and had a high safety profile in toxicokinetics and long-term toxicological studies.

CONCLUSION

ZL006-05 is a new neuroprotectant with fast-onset antidepressant and anxiolytic effects and has translational properties in terms of efficacy, safety and targeting of clinical issues.

"NO" Time in Fear Response: Possible Implication of Nitric-Oxide-Related Mechanisms in PTSD

Post-traumatic stress disorder (PTSD) is a psychiatric condition characterized by persistent fear responses and altered neurotransmitter functioning due to traumatic experiences. Stress predominantly affects glutamate, a neurotransmitter crucial for synaptic plasticity and memory formation. Activation of the N-Methyl-D-Aspartate glutamate receptors (NMDAR) can trigger the formation of a complex comprising postsynaptic density protein-95 (PSD95), the neuronal nitric oxide synthase (nNOS), and its adaptor protein (NOS1AP). This complex is pivotal in activating nNOS and nitric oxide (NO) production, which, in turn, activates downstream pathways that modulate neuronal signaling, including synaptic plasticity/transmission, inflammation, and cell death. The involvement of nNOS and NOS1AP in the susceptibility of PTSD and its comorbidities has been widely shown. Therefore, understanding the interplay between stress, fear, and NO is essential for comprehending the maintenance and progression of PTSD, since NO is involved in fear acquisition and extinction processes. Moreover, NO induces post-translational modifications (PTMs), including S-nitrosylation and nitration, which alter protein function and structure for intracellular signaling. Although evidence suggests that NO influences synaptic plasticity and memory processing, the specific role of PTMs in the pathophysiology of PTSD remains unclear. This review highlights pathways modulated by NO that could be relevant to stress and PTSD.

Advances in nitric oxide regulators for the treatment of ischemic stroke

Ischemic stroke (IS) is a life-threatening disease worldwide. Nitric oxide (NO) derived from l-arginine catalyzed by NO synthase (NOS) is closely associated with IS. Three isomers of NOS (nNOS, eNOS and iNOS) produce different concentrations of NO, resulting in quite unlike effects during IS. Of them, n/iNOSs generate high levels of NO, detrimental to brain by causing nerve cell apoptosis and/or necrosis, whereas eNOS releases small amounts of NO, beneficial to the brain via increasing cerebral blood flow and improving nerve function. As a result, a large variety of NO regulators (NO donors or n/iNOS inhibitors) have been developed for fighting IS. Regrettably, up to now, no review systematically introduces the progresses in this area. This article first outlines dynamic variation rule of NOS/NO in IS, subsequently highlights advances in NO regulators against IS, and finally presents perspectives based on concentration-, site- and timing-effects of NO production to promote this field forward.

Culin5 aggravates hypoxic pulmonary hypertension by activating TRAF6/NF-κB/HIF-1α/VEGF

Hypoxic pulmonary hypertension (HPH) lacks effective pharmacologic treatments. Microarray-based gene expression indicates the crucial role of Cullin 5 (Cul 5) in HPH. This study showed that Cul 5 was upregulated in HPH patients and a murine model of HPH. In vitro, Cul 5 promoted the angiogenesis and adhesion capacity of human pulmonary artery endothelial cells (PAECs), which could be mitigated by Cul 5 inactivation mediated by pevonedistat or NEDD8 silence. In vivo, silencing of Cul 5 in the endothelium and Cul 5 inactivation by pevonedistat could also alleviate hypoxic vascular remodeling. Mechanistic research showed that Cul 5 participated in HPH pathogenesis via the TRAF6/NF-κB/HIF-1α/VEGF pathway. Inhibition of the TRAF6/NF-κB/HIF-1α/VEGF pathway could reverse Cul 5-induced human PAEC dysfunction. These findings demonstrate that Cul 5 is an important mediator of HPH via the TRAF6/NF-κB/HIF-1α/VEGF pathway firstly, and could be considered as a potential therapeutic target in the clinical treatment of HPH.

The Physiological Function of nNOS-Associated CAPON Proteins and the Roles of CAPON in Diseases

In this review, the structure, isoform, and physiological role of the carboxy-terminal PDZ ligand of neuronal nitric oxide synthase (CAPON) are summarized. There are three isoforms of CAPON in humans, including long CAPON protein (CAPON-L), short CAPON protein (CAPON-S), and CAPON-S' protein. CAPON-L includes three functional regions: a C-terminal PDZ-binding motif, carboxypeptidase (CPE)-binding region, and N-terminal phosphotyrosine (PTB) structural domain. Both CAPON-S and CAPON-S' only contain the C-terminal PDZ-binding motif. The C-terminal PDZ-binding motif of CAPON can bind with neuronal nitric oxide synthase (nNOS) and participates in regulating NO production and neuronal development. An overview is given on the relationship between CAPON and heart diseases, diabetes, psychiatric disorders, and tumors. This review will clarify future research directions on the signal pathways related to CAPON, which will be helpful for studying the regulatory mechanism of CAPON. CAPON may be used as a drug target, which will provide new ideas and solutions for treating human diseases.

nNOS and Neurological, Neuropsychiatric Disorders: A 20-Year Story

In the central nervous system, nitric oxide (NO), a free gas with multitudinous bioactivities, is mainly produced from the oxidation of L-arginine by neuronal nitric oxide synthase (nNOS). In the past 20 years, the studies in our group and other laboratories have suggested a significant involvement of nNOS in a variety of neurological and neuropsychiatric disorders. In particular, the interactions between the PDZ domain of nNOS and its adaptor proteins, including post-synaptic density 95, the carboxy-terminal PDZ ligand of nNOS, and the serotonin transporter, significantly influence the subcellular localization and functions of nNOS in the brain. The nNOS-mediated protein-protein interactions provide new attractive targets and guide the discovery of therapeutic drugs for neurological and neuropsychiatric disorders. Here, we summarize the work on the roles of nNOS and its association with multiple adaptor proteins on neurological and neuropsychiatric disorders.

Hippocampus: Molecular, Cellular, and Circuit Features in Anxiety

Anxiety disorders are currently a major psychiatric and social problem, the mechanisms of which have been only partially elucidated. The hippocampus serves as a major target of stress mediators and is closely related to anxiety modulation. Yet so far, its complex anatomy has been a challenge for research on the mechanisms of anxiety regulation. Recent advances in imaging, virus tracking, and optogenetics/chemogenetics have permitted elucidation of the activity, connectivity, and function of specific cell types within the hippocampus and its connected brain regions, providing mechanistic insights into the elaborate organization of the hippocampal circuitry underlying anxiety. Studies of hippocampal neurotransmitter systems, including glutamatergic, GABAergic, cholinergic, dopaminergic, and serotonergic systems, have contributed to the interpretation of the underlying neural mechanisms of anxiety. Neuropeptides and neuroinflammatory factors are also involved in anxiety modulation. This review comprehensively summarizes the hippocampal mechanisms associated with anxiety modulation, based on molecular, cellular, and circuit properties, to provide tailored targets for future anxiety treatment.

Enhanced AMPAR-dependent synaptic transmission by S-nitrosylation in the vmPFC contributes to chronic inflammatory pain-induced persistent anxiety in mice

Chronic pain patients often have anxiety disorders, and some of them suffer from anxiety even after analgesic administration. In this study, we investigated the role of AMPAR-mediated synaptic transmission in the ventromedial prefrontal cortex (vmPFC) in chronic pain-induced persistent anxiety in mice and explored potential drug targets. Chronic inflammatory pain was induced in mice by bilateral injection of complete Freund's adjuvant (CFA) into the planta of the hind paws; anxiety-like behaviours were assessed with behavioural tests; S-nitrosylation and AMPAR-mediated synaptic transmission were examined using biochemical assays and electrophysiological recordings, respectively. We found that CFA induced persistent upregulation of AMPAR membrane expression and function in the vmPFC of anxious mice but not in the vmPFC of non-anxious mice. The anxious mice exhibited higher S-nitrosylation of stargazin (an AMPAR-interacting protein) in the vmPFC. Inhibition of S-nitrosylation by bilaterally infusing an exogenous stargazin (C302S) mutant into the vmPFC rescued the surface expression of GluA1 and AMPAR-mediated synaptic transmission as well as the anxiety-like behaviours in CFA-injected mice, even after ibuprofen treatment. Moreover, administration of ZL006, a small molecular inhibitor disrupting the interaction of nNOS and PSD-95 (20 mg·kg-1·d-1, for 5 days, i.p.), significantly reduced nitric oxide production and S-nitrosylation of AMPAR-interacting proteins in the vmPFC, resulting in anxiolytic-like effects in anxious mice after ibuprofen treatment. We conclude that S-nitrosylation is necessary for AMPAR trafficking and function in the vmPFC under chronic inflammatory pain-induced persistent anxiety conditions, and nNOS-PSD-95 inhibitors could be potential anxiolytics specific for chronic inflammatory pain-induced persistent anxiety after analgesic treatment.

Nos1+ and Nos1- excitatory neurons in the BLA regulate anxiety- and depression-related behaviors oppositely

BACKGROUND

The basolateral amygdala (BLA) neurons are primarily glutamatergic and have been associated with emotion regulation. However, little is known about the roles of BLA neurons expressing neuronal nitric oxide synthase (nNOS, Nos1) in the regulation of emotional behaviors.

METHODS

Using Nos1-cre mice and chemogenetic and optogenetic manipulations, we specifically silenced or activated Nos1⁺ or Nos1^- neurons in the BLA, or silenced their projections to the anterdorsal bed nucleus of the stria terminalis (adBNST) and ventral hippocampus (vHPC). We measured anxiety behaviors in elevated plus maze (EPM) and open-field test (OFT), and measured depression behaviors in forced swimming test (FST) and tail suspension test (TST).

RESULTS

BLA Nos1⁺ neurons were predominantly glutamatergic, and glutamatergic but not GABAergic Nos1⁺ neurons were involved in controlling anxiety- and depression-related behaviors. Interestingly, by selectively manipulating the activities of BLA Nos1⁺ and Nos1^- excitatory neurons, we found that they had opposing effects on anxiety- and depression-related behaviors. BLA Nos1⁺ excitatory neurons projected to the adBNST, this BLA-adBNST circuit controlled the expression of anxiety- and depression-related behaviors, while BLA Nos1^- excitatory neurons projected to vHPC, this BLA-vHPC circuit contributed to the expression of anxiety- and depression-related behaviors. Moreover, excitatory vHPC-adBNST circuit antagonized the role of BLA-adBNST circuit in regulating anxiety- and depression-related behaviors.

CONCLUSIONS

BLA Nos1⁺ and Nos1^- excitatory neuron subpopulations exert different effects on anxiety- and depression-related behaviors through distinct projection circuits, providing a new insight of BLA excitatory neurons in emotional regulation.

LIMITATIONS

We did not perform retrograde labeling from adBNST and vHPC regions.

Disrupting the nNOS/NOS1AP interaction in the medial prefrontal cortex impairs social recognition and spatial working memory in mice

The neuronal isoform of nitric oxide synthase (nNOS) and its interacting protein NOS1AP have been linked to several mental disorders including schizophrenia and depression. An increase in the interaction between nNOS and NOS1AP in the frontal cortex has been suggested to contribute to the emergence of these disorders. Here we aimed to uncover whether disruption of their interactions in the frontal cortex leads to mental disorder endophenotypes. Targeting the medial prefrontal cortex (mPFC), we stereotaxically injected wild-type C57BL/6J mice with recombinant adeno-associated virus (rAAV) expressing either full-length NOS1AP, the nNOS binding region of NOS1AP (i.e. NOS1AP_396-503), or the nNOS amino-terminus (i.e. nNOS_1-133), which was shown to disrupt the interaction of endogenous nNOS with PSD-95. We tested these mice in a comprehensive behavioural battery, assessing different endophenotypes related to mental disorders. We found no differences in anxiety-related and exploratory behaviours. Likewise, social interaction was comparable in all groups. However, social recognition was impaired in NOS1AP and NOS1AP_396-503 mice. These mice, as well as mice overexpressing nNOS_1-133 also displayed impaired spatial working memory (SWM) capacity, while spatial reference memory (SRM) remained intact. Finally, mice overexpressing NOS1AP and nNOS_1-133, but not NOS1AP_396-503, failed to habituate to the startling pulses in an acoustic startle response (ASR) paradigm, though we found no difference in overall startle intensity or prepulse inhibition (PPI) of the ASR. Our findings indicate a distinct role of NOS1AP/nNOS/PSD-95 interactions in the mPFC to contribute to specific endophenotypic changes observed in different mental disorders.

Gene Therapy, A Potential Therapeutic Tool for Neurological and Neuropsychiatric Disorders: Applications, Challenges and Future Perspective

Neurological and neuropsychiatric disorders are the main risks for the health care system, exhibiting a huge socioeconomic load. The available range of pharmacotherapeutics mostly provides palliative consequences and fails to treat such conditions. The molecular etiology of various neurological and neuropsychiatric disorders is mostly associated with a change in genetic background, which can be inherited/triggered by other environmental factors. To address such conditions, gene therapy is considered a potential approach claiming a permanent cure of the disease primarily by deletion, silencing, or edition of faulty genes and by insertion of healthier genes. In gene therapy, vectors (viral/nonvial) play an important role in delivering the desired gene to a specific region of the brain. Targeted gene therapy has unraveled opportunities for the treatment of many neurological and neuropsychiatric disorders. For improved gene delivery, the current techniques mainly focus on designing a precise viral vector, plasmid transfection, nanotechnology, microRNA, and in vivo clustered regulatory interspaced short palindromic repeats (CRISPR)-based therapy. These latest techniques have great benefits in treating predominant neurological and neurodevelopmental disorders, including Parkinson's disease, Alzheimer's disease, and autism spectrum disorder, as well as rarer diseases. Nevertheless, all these delivery methods have their limitations, including immunogenic reactions, off-target effects, and a deficiency of effective biomarkers to appreciate the effectiveness of therapy. In this review, we present a summary of the current methods in targeted gene delivery, followed by the limitations and future direction of gene therapy for the cure of neurological and neuropsychiatric disorders.

Design of fast-onset antidepressant by dissociating SERT from nNOS in the DRN

Major depressive disorder (MDD) is one of the most common mental disorders. We designed a fast-onset antidepressant that works by disrupting the interaction between the serotonin transporter (SERT) and neuronal nitric oxide synthase (nNOS) in the dorsal raphe nucleus (DRN). Chronic unpredictable mild stress (CMS) selectively increased the SERT-nNOS complex in the DRN in mice. Augmentation of SERT-nNOS interactions in the DRN caused a depression-like phenotype and accounted for the CMS-induced depressive behaviors. Disrupting the SERT-nNOS interaction produced a fast-onset antidepressant effect by enhancing serotonin signaling in forebrain circuits. We discovered a small-molecule compound, ZZL-7, that elicited an antidepressant effect 2 hours after treatment without undesirable side effects. This compound, or analogous reagents, may serve as a new, rapidly acting treatment for MDD.

Targeting NMDA Receptors at the Neurovascular Unit: Past and Future Treatments for Central Nervous System Diseases

The excitatory neurotransmission of the central nervous system (CNS) mainly involves glutamate and its receptors, especially N-methyl-D-Aspartate receptors (NMDARs). These receptors have been extensively described on neurons and, more recently, also on other cell types. Nowadays, the study of their differential expression and function is taking a growing place in preclinical and clinical research. The diversity of NMDAR subtypes and their signaling pathways give rise to pleiotropic functions such as brain development, neuronal plasticity, maturation along with excitotoxicity, blood-brain barrier integrity, and inflammation. NMDARs have thus emerged as key targets for the treatment of neurological disorders. By their large extracellular regions and complex intracellular structures, NMDARs are modulated by a variety of endogenous and pharmacological compounds. Here, we will present an overview of NMDAR functions on neurons and other important cell types involved in the pathophysiology of neurodegenerative, neurovascular, mental, autoimmune, and neurodevelopmental diseases. We will then discuss past and future development of NMDAR targeting drugs, including innovative and promising new approaches.

Protein S-Nitrosation: Biochemistry, Identification, Molecular Mechanisms, and Therapeutic Applications

Protein S-nitrosation (SNO), a posttranslational modification (PTM) of cysteine (Cys) residues elicited by nitric oxide (NO), regulates a wide range of protein functions. As a crucial form of redox-based signaling by NO, SNO contributes significantly to the modulation of physiological functions, and SNO imbalance is closely linked to pathophysiological processes. Site-specific identification of the SNO protein is critical for understanding the underlying molecular mechanisms of protein function regulation. Although careful verification is needed, SNO modification data containing numerous functional proteins are a potential research direction for druggable target identification and drug discovery. Undoubtedly, SNO-related research is meaningful not only for the development of NO donor drugs but also for classic target-based drug design. Herein, we provide a comprehensive summary of SNO, including its origin and transport, identification, function, and potential contribution to drug discovery. Importantly, we propose new views to develop novel therapies based on potential protein SNO-sourced targets.

Ion flux-independent NMDA receptor signaling

NMDA receptors play vital roles in a broad array of essential brain functions, from synaptic transmission and plasticity to learning and memory. Historically, the fundamental roles of NMDARs were attributed to their specialized properties of ion flux. More recently, it has become clear that NMDARs also signal in an ion flux-independent manner. Here, we review these non-ionotropic NMDAR signaling mechanisms that have been reported to contribute to a broad array of neuronal functions and dysfunctions including synaptic transmission and plasticity, cell death and survival, and neurological disorders.

Targeting PSD95/nNOS by ZL006 alleviates social isolation-induced heightened attack behavior in mice

RATIONALE

Deregulated attack behaviors have devastating social consequences; however, satisfactory clinical management for the behavior is still an unmet need so far. Social isolation (SI) has been common during the COVID-19 pandemic and may have detrimental effects on mental health, including eliciting heightened attack behavior.

OBJECTIVES

This study aims to explore whether injection of ZL006 can alleviate SI-induced escalation of attack behavior in mice.

METHODS

Pharmacological tools, biochemical methods, and behavioral tests were used to explore the potential therapeutic effects of ZL006 targeting postsynaptic density 95 (PSD95)/neuronal nitric oxide synthase (nNOS) pathway on escalation of attack behavior induced by SI in mice.

RESULTS

ZL006 mitigated SI-induced escalated attack behaviors and elevated nitric oxide (NO) level in the cortex of the SI mice. The beneficial effects of ZL006 lasted for at least 72 h after a single injection of ZL006. Potentiation of NO levels by L-arginine blocked the effects of ZL006. Moreover, a sub-effective dose of 7-NI in combination with a sub-effective dose of ZL006 decreased both SI-induced escalated attack behaviors and NO levels in mice subjected to SI.

CONCLUSIONS

Our study highlights the importance of the PSD95/nNOS pathway in mediating SI-induced escalation of attack behavior. ZL006 may be a promising therapeutic strategy for treating aggressive behaviors.

Prevention of the return of extinguished fear by disrupting the interaction of neuronal nitric oxide synthase with its carboxy-terminal PDZ ligand

Exposure therapy based on the extinction of fear memory is first-line treatment for post-traumatic stress disorder (PTSD). However, fear extinction is relatively easy to learn but difficult to remember, extinguished fear often relapses under a number of circumstances. Here, we report that extinction learning-induced association of neuronal nitric oxide synthase (nNOS) with its carboxy-terminal PDZ ligand (CAPON) in the infralimbic (IL) subregion of medial prefrontal cortex negatively regulates extinction memory and dissociating nNOS-CAPON can prevent the return of extinguished fear in mice. Extinction training significantly increases nNOS-CAPON association in the IL. Disruptors of nNOS-CAPON increase extracellular signal-regulated kinase (ERK) phosphorylation and facilitate the retention of extinction memory in an ERK2-dependent manner. More importantly, dissociating nNOS-CAPON after extinction training enhances long-term potentiation and excitatory synaptic transmission, increases spine density in the IL, and prevents spontaneous recovery, renewal and reinstatement of remote fear of mice. Moreover, nNOS-CAPON disruptors do not affect other types of learning. Thus, nNOS-CAPON can serve as a new target for treating PTSD.

Therapeutic time windows of compounds against NMDA receptors signaling pathways for ischemic stroke

Much evidence has proved that excitotoxicity induced by excessive release of glutamate contributes largely to damage caused by ischemia. In view of the key role played by NMDA receptors in mediating excitotoxicity, compounds against NMDA receptors signaling pathways have become the most promising type of anti-stroke candidate compounds. However, the limited therapeutic time window for neuroprotection is a key factor preventing NMDA receptor-related compounds from showing efficacy in all clinical trials for ischemic stroke. In this perspective, the determination of therapeutic time windows of these kinds of compounds is useful in ensuring a therapeutic effect and accelerating clinical application. This mini-review discussed the therapeutic time windows of compounds against NMDA receptors signaling pathways, described related influence factors and the status of clinical studies. The purpose of this review is to look for compounds with wide therapeutic time windows and better clinical application prospect.

Hippocampal overexpression of NOS1AP promotes endophenotypes related to mental disorders

BACKGROUND

Nitric oxide synthase 1 adaptor protein (NOS1AP; previously named CAPON) is linked to the glutamatergic postsynaptic density through interaction with neuronal nitric oxide synthase (nNOS). NOS1AP and its interaction with nNOS have been associated with several mental disorders. Despite the high levels of NOS1AP expression in the hippocampus and the relevance of this brain region in glutamatergic signalling as well as mental disorders, a potential role of hippocampal NOS1AP in the pathophysiology of these disorders has not been investigated yet.

METHODS

To uncover the function of NOS1AP in hippocampus, we made use of recombinant adeno-associated viruses to overexpress murine full-length NOS1AP or the NOS1AP carboxyterminus in the hippocampus of mice. We investigated these mice for changes in gene expression, neuronal morphology, and relevant behavioural phenotypes.

FINDINGS

We found that hippocampal overexpression of NOS1AP markedly increased the interaction of nNOS with PSD-95, reduced dendritic spine density, and changed dendritic spine morphology at CA1 synapses. At the behavioural level, we observed an impairment in social memory and decreased spatial working memory capacity.

INTERPRETATION

Our data provide a mechanistic explanation for a highly selective and specific contribution of hippocampal NOS1AP and its interaction with the glutamatergic postsynaptic density to cross-disorder pathophysiology. Our findings allude to therapeutic relevance due to the druggability of this molecule.

FUNDING

This study was funded in part by the DFG, the BMBF, the Academy of Finland, the NIH, the Japanese Society of Clinical Neuropsychopharmacology, the Ministry of Education of the Russian Federation, and the European Community.

Disrupting the Interaction of nNOS with CAPON Prevents the Reinstatement of Morphine Conditioned Place Preference

Drug abuse is a dramatic challenge for the whole society because of high relapse rate. Environmental cues are crucial for the preference memory of drug abuse. Extinction therapy has been developed to inhibit the motivational effect of drug cues to prevent the reinstatement of morphine abuse. However, extinction therapy alone only forms a new kind of unstable inhibitory memory. We found that morphine conditioned place preference (CPP) extinction training increased the association of nitric oxide synthase (nNOS) with its carboxy-terminal PDZ ligand (CAPON) in the dorsal hippocampus (dHPC) significantly and blocking the morphine-induced nNOS-CAPON association using Tat-CAPON-12C during and after extinction training reversed morphine-induced hippocampal neuroplasticity defect and prevented the reinstatement and spontaneous recovery of morphine CPP. Moreover, in the hippocampal selective ERK2 knock-out or nNOS knockout mice, the effect of Tat-CAPON-12C on the reinstatement of morphine CPP and hippocampal neuroplasticity disappeared, suggesting ERK2 is necessary for the effects of Tat-CAPON-12C. Together, our findings suggest that nNOS-CAPON interaction in the dHPC may affect the consolidation of morphine CPP extinction and dissociating nNOS-CAPON prevents the reinstatement and spontaneous recovery of morphine CPP, possibly through ERK2-mediated neuroplasticity and extinction memory consolidation, offering a new target to prevent the reinstatement of drug abuse.

Targeting GluN2B/NO Pathway Ameliorates Social Isolation-Induced Exacerbated Attack Behavior in Mice

Exacerbated attack behavior has a profound socioeconomic impact and devastating social consequences; however, there is no satisfactory clinical management available for an escalated attack behavior. Social isolation (SI) is widespread during this pandemic and may exert detrimental effects on mental health, such as causing heightened attack behavior. To explore the therapeutic approaches that alleviate the SI-induced heightened attack behavior, we utilized pharmacological methods targeting the GluN2B/NO signaling pathway during the attack behavior. Ifenprodil and TAT-9C peptide targeting GluN2B showed that the inhibition of GluN2B mitigated the SI-induced escalated attack behavior and the SI-induced aberrant nitric oxide (NO) level in the brain. Additionally, the potentiation of the NO level by L-arginine reversed the effects of the inhibition of GluN2B. Moreover, we showed that high doses of L-NAME and 7-NI and subeffective doses of L-NAME in combination with ifenprodil or TAT-9C or subeffective doses of 7-NI plus ifenprodil or TAT-9C all decreased the SI-induced escalated attack behavior and reduced the NO level, further supporting the idea that GluN2B/NO signaling is a crucial modulator of the escalated attack behavior.

Involvement of 5-HT1A receptor-mediated histone acetylation in the regulation of depression

Depression is one of the most common and disabling mental disorders. There is growing evidence that 5-HT1A receptor is involved in the regulation of depressive-related behaviors. However, the exact mechanism underlying the role of 5-HT1A receptor in depression remains unknown. Histone acetylation is associated with the pathophysiology and treatment of depression. In the current study, we investigated whether the epigenetic histone deacetylase (HDAC)-induced histone acetylation mediates the regulation of 5-HT1A receptor in depressive behaviors. We showed that 5-HT1A receptor selective agonist (±)-8-hydroxy-2-(dipropylamino) tetralin hydrobromide led to significant increase in acetylation of H3 at lysine 9 (Ac-H3K9) and H4 at lysine 5 (Ac-H4K5) and lysine 12 (Ac-H4K12) with obviously decreasing histone deacetylase 1 (HDAC1), histone deacetylase 2 (HDAC2), histone deacetylase 4 (HDAC4) and histone deacetylase 5 (HDAC5) expression in hippocampus of mice. Conversely, 5-HT1A receptor selective antagonist NAN-190 decreased the level of acetylation of H3 and H4 with increasing the expression of HDAC1, HDAC2, HDAC4 and HDAC5 in the hippocampus. Furthermore, we found that HDAC inhibitors, trichostatin A or suberoylanilide hydroxamic acid infusion to hippocampus prevented the depressive behaviors induced by NAN-190, as well as histone H3 and H4 acetylation in mice. Our results suggested that epigenetic histone acetylation coupled with 5-HT1A receptor may play vital role in the pathophysiology and treatment of depressive disorders.

Neuronal Nitric Oxide Synthase in Nucleus Accumbens Specifically Mediates Susceptibility to Social Defeat Stress through Cyclin-Dependent Kinase 5

Stress-induced depression is common worldwide. NAc, a "reward" center, is recently reported to be critical to confer the susceptibility to chronic social defeat stress (CSDS) and the depression-related outcome. However, the underlying molecular mechanisms have not been well characterized. In this study, we induced depression-like behaviors with CSDS and chronic mild stress in male mice to mimic social and environmental factors, respectively, and observed animal behaviors with social interaction test, tail suspension test, and sucrose preference test. To determine the role of neuronal nitric oxide synthase (nNOS) and its product nitric oxide (NO), we used brain region-specifically nNOS overexpression and stereotaxic injection of NO inhibitor or donor. Moreover, the downstream molecular cyclin-dependent kinase 5 (CDK5) was explored by conditional KO and gene mutation. We demonstrate that nNOS-implicated mechanisms in NAc shell (NAcSh), including increased cell number, increased protein expression levels, and increased specific enzyme activity, contribute the susceptibility to social defeat and the following depression-like behaviors. NAcSh nNOS does not directly respond to chronic mild stress but facilitates the depression-like behaviors. The increased NAcSh nNOS expression after CSDS leads to the social avoidance and depression-like behaviors in defeated mice, which is dependent on the nNOS enzyme activity and NO production. Moreover, we identify the downstream signal in NAcSh. S-nitrosylation of CDK5 by NO contributes to enhanced CDK5 activity, leading to depression-related behaviors in susceptible mice. Therefore, NAcSh nNOS mediates susceptibility to social defeat stress and the depression-like behaviors through CDK5.SIGNIFICANCE STATEMENT Stress-induced depression is common worldwide, and chronic exposure to social and psychological stressors is important cause of human depression. Our study conducted with chronic social defeat stress mice models demonstrates that nNOS in NAcSh is crucial to regulate the susceptibility to social defeat stress and the following depression-like behaviors, indicating NAcSh nNOS as the responding molecule to social factors of depression. Moreover, we discover the downstream mechanism of NAcSh nNOS in mediating the susceptibility is NO and S-nitrosylation of CDK5. Thus, NAcSh nNOS mediates susceptibility to social defeat stress through CDK5 is a potential mechanism for depression, which may interpret how the brain transduces social stress exposure into depression.

Dorsal Hippocampus to Infralimbic Cortex Circuit is Essential for the Recall of Extinction Memory

Posttraumatic stress disorder subjects usually show impaired recall of extinction memory, leading to extinguished fear relapses. However, little is known about the neural mechanisms underlying the impaired recall of extinction memory. We show here that the activity of dorsal hippocampus (dHPC) to infralimbic (IL) cortex circuit is essential for the recall of fear extinction memory in male mice. There were functional neural projections from the dHPC to IL. Using optogenetic manipulations, we observed that silencing the activity of dHPC-IL circuit inhibited recall of extinction memory while stimulating the activity of dHPC-IL circuit facilitated recall of extinction memory. "Impairment of extinction consolidation caused by" conditional deletion of extracellular signal-regulated kinase 2 (ERK2) in the IL prevented the dHPC-IL circuit-mediated recall of extinction memory. Moreover, silencing the dHPC-IL circuit abolished the effect of intra-IL microinjection of ERK enhancer on the recall of extinction memory. Together, we identify a dHPC to IL circuit that mediates the recall of extinction memory, and our data suggest that the dysfunction of dHPC-IL circuit and/or impaired extinction consolidation may contribute to extinguished fear relapses.

Environmental enrichment implies GAT-1 as a potential therapeutic target for stroke recovery

Rationale: Stroke is a leading cause of adult disability worldwide, but no drug provides functional recovery during the repair phase. Accumulating evidence demonstrates that environmental enrichment (EE) promotes stroke recovery by enhancing network excitability. However, the complexities of utilizing EE in a clinical setting limit its translation.

Methods: We used multifaceted approaches combining electrophysiology, chemogenetics, optogenetics, and floxed mice in a mouse photothrombotic stroke model to reveal the key target of EE-mediated stroke recovery.

Results: EE reduced tonic gamma-aminobutyric acid (GABA) inhibition and facilitated phasic GABA inhibition in the peri-infarct cortex, thereby promoting network excitability and stroke recovery. These beneficial effects depended on GAT-1, a GABA transporter regulating both tonic and phasic GABA signaling, as EE positively regulated GAT-1 expression, trafficking, and function. Furthermore, GAT-1 was necessary for EE-induced network plasticity, including structural neuroplasticity, input synaptic strengthening in the peri-infarct cortex, output synaptic strengthening in the corticospinal tract, and sprouting of uninjured corticospinal axons across the midline into the territory of denervated spinal cord, and functional recovery from stroke. Moreover, restoration of GAT-1 function in the peri-infarct cortex by its overexpression showed similar beneficial effects on stroke recovery as EE exposure.

Conclusion: GAT-1 is a key molecular substrate of the effects of EE on network excitability and consequent stroke recovery and can serve as a novel therapeutic target for stroke treatment during the repair phase.

Neuroprotective Effect of N-Cyclohexylethyl-[A/G]-[D/E]-X-V Peptides on Ischemic Stroke by Blocking nNOS-CAPON Interaction

The protein-protein interaction between neuronal nitric oxide syntheses (nNOS) and the carboxy-terminal PDZ ligand of nNOS (CAPON) is a potential target for the treatment of ischemic stroke. Our previous study had identified ZLc-002 as a promising lead compound for inhibiting nNOS-CAPON coupling. To find better neuroprotective agents disrupting the ischemia-induced nNOS-CAPON interaction, a series of N-cyclohexylethyl-[A/G]-[D/E]-X-V peptides based on the carboxy-terminal tetrapeptide of CAPON was designed, synthesized, and evaluated in this study. Herein, we reported an affinity-based fluorescence polarization (FP) method using 5-carboxyfluorescein (5-FAM) labeled CAPON (496-506) peptide as the probe for high-throughput screening of the small-molecule inhibitors of the PDZ domain of nNOS. N-Cyclohexylethyl-ADAV displayed the most potent affinity for the nNOS PDZ domain in the FP and isothermal titration calorimetry (ITC) (ΔH = -1670 ± 151.0 cal/mol) assays. To improve bioavailability, lipophilicity, and membrane permeability, the Asp methylation was employed to get N-cyclohexylethyl-AD(OMe)AV, which possesses good blood-brain barrier (BBB) permeability in vitro parallel artificial membrane permeability assay (PAMPA)-BBB (Pe = 6.07 cm/s) and in vivo assays. In addition, N-cyclohexylethyl-AD(OMe)AV (10 mg/kg body weight, i.v., immediately after reperfusion) substantially reduced infarct size in rats, which was measured 24 h after reperfusion and subjected to 120 min of middle cerebral artery occlusion (MCAO).

nNOS-mediated protein-protein interactions: promising targets for treating neurological and neuropsychiatric disorders

Neurological and neuropsychiatric disorders are one of the leading causes of disability worldwide and affect the health of billions of people. Nitric oxide (NO), a free gas with multitudinous bioactivities, is mainly produced from the oxidation of L-arginine by neuronal nitric oxide synthase (nNOS) in the brain. Inhibiting nNOS benefits a variety of neurological and neuropsychiatric disorders, including stroke, depression and anxiety disorders, post-traumatic stress disorder, Parkinson's disease, Alzheimer's disease, chronic pain, and drug addiction. Due to critical roles of nNOS in learning and memory and synaptic plasticity, direct inhibition of nNOS may cause severe side effects. Importantly, interactions of several proteins, including post-synaptic density 95 (PSD-95), carboxy-terminal PDZ ligand of nNOS (CAPON) and serotonin transporter (SERT), with the PSD/Disc-large/ZO-1 homologous (PDZ) domain of nNOS have been demonstrated to influence the subcellular distribution and activity of the enzyme in the brain. Therefore, it will be a preferable means to interfere with nNOS-mediated protein-protein interactions (PPIs), which do not lead to undesirable effects. Herein, we summarize the current literatures on nNOS-mediated PPIs involved in neurological and neuropsychiatric disorders, and the discovery of drugs targeting the PPIs, which is expected to provide potential targets for developing novel drugs and new strategy for the treatment of neurological and neuropsychiatric disorders.

CAPON Is a Critical Protein in Synaptic Molecular Networks in the Prefrontal Cortex of Mood Disorder Patients and Contributes to Depression-Like Behavior in a Mouse Model

Aberrant regulation and activity of synaptic proteins may cause synaptic pathology in the prefrontal cortex (PFC) of mood disorder patients. Carboxy-terminal PDZ ligand of NOS1 (CAPON) is a critical scaffold protein linked to synaptic proteins like nitric oxide synthase 1, synapsins. We hypothesized that CAPON is altered together with its interacting synaptic proteins in the PFC in mood disorder patients and may contribute to depression-like behaviors in mice subjected to chronic unpredictable mild stress (CUMS). Here, we found that CAPON-immunoreactivity (ir) was significantly increased in the dorsolateral PFC (DLPFC) and anterior cingulate cortex in major depressive disorder (MDD), which was accompanied by an upregulation of spinophilin-ir and a downregulation of synapsin-ir. The increases in CAPON and spinophilin and the decrease in synapsin in the DLPFC of MDD patients were also seen in the PFC of CUMS mice. CAPON-ir positively correlated with spinophilin-ir (but not with synapsin-ir) in mood disorder patients. CAPON colocalized with spinophilin in the DLPFC of MDD patients and interacted with spinophilin in human brain. Viral-mediated CAPON downregulation in the medial PFC notably reversed the depression-like behaviors in the CUMS mice. These data suggest that CAPON may contribute to aspects of depressive behavior, possibly as an interacting protein for spinophilin in the PFC.

The Effect of Swimming on Anxiety-Like Behaviors and Corticosterone in Stressed and Unstressed Rats

This study assessed the effect of swimming training on anxiety-like behaviors and corticosterone. Thirty adult male Wistar rats were randomly assigned to five study conditions: swimming training (ST); exposure to chronic mild stress (CS); exposure to chronic mild stress followed by swimming training (CS + ST); exposure to chronic mild stress followed by a recovery period (CS + recovery); control. The exercise training consisted of 60 min of swimming exercise per day, for five days a week, and four consecutive weeks. A chronic mild stress program (CMS) was applied for a period of four weeks. Anxiety-like behaviors were measured by open field test (OFT). The number of excrements and blood corticosterone were used as physiological parameters of anxiety. To assess corticosterone, blood samples were taken 48 h after the last session of experiments. Compared to other study conditions, the lowest anxiety-like behaviors and corticosterone concentrations were observed in the ST condition in unstressed rats. In stressed rats, as in the ST + CS group, swimming training probably reduced some anxiety behaviors, but the results showed increased corticosterone compared to control and CS + Recovery. Anxiety parameters and corticosterone concentrations were greatest in the CS condition. In the ST group, anxiety parameters were less than for the ST + CS group. In the CS + Recovery group, anxiety parameters were less than for the CS group. In summary, self-paced swimming training could attenuate some anxiety parameters in both stressed and non-stressed rats. The effect of swimming training in unstressed rats was more prominent than in stressed rats. In stressed rats, a period of recovery was more effective than swimming training in reducing corticosterone. Mechanisms of anxiety reduction other than cortisol should be investigated in future research.

HDAC2 (Histone deacetylase 2): A critical factor in environmental enrichment-mediated stroke recovery

Environmental enrichment (EE) is a generally accepted strategy to promote stroke recovery and its beneficial effect is positively correlated with neuroplasticity. However, the mechanisms underlying it remain elusive. Histone deacetylase 2 (HDAC2), a negative regulator of neuroplasticity, is up-regulated after stroke. Thus, we hypothesized that HDAC2 may participate in EE-mediated stroke recovery. In this study, focal stroke was induced by photothrombosis in male mice exposing to EE or standard housing (SH) conditions. Recombinant virus vectors, including Ad-HDAC2-Flag, AAV-CAG-EGFP-Cre, LV-shHDAC2, or their controls were microinjected into the motor cortex at 3 days before stroke. Grid-walking and cylinder tasks were conducted to assess motor function. Western blot and immunostaining were used to uncover the mechanisms underlying EE-mediated stroke recovery. We found that EE exposure reversed stroke-induced HDAC2 up-regulation, implicating HDAC2 in EE-mediated functional recovery. Importantly, EE-dependent stroke recovery was counteracted by over-expressing HDAC2, and HDAC2 knockdown promoted functional recovery from stroke to the similar extent as EE exposure. Moreover, the knockdown of HDAC2 epigenetically enhanced expressions of neurotrophins and neuroplasticity-related proteins, with similar effects as EE, and consequently, whole brain and corticospinal tract (CST) rewiring. Together, our findings indicate that HDAC2 is critical for EE-dependent functional restoration. Precisely targeting HDAC2 may mimic EE and serve as a novel therapeutic strategy for stroke recovery.

Effects of inosine monophosphate and exercise training on neuronal nitric oxide synthase in the mouse brain

Recently, the purine nucleoside inosine has been demonstrated to have several neuroprotective effects. Similarly, exercise training has well-known beneficial effects on mental health and cognitive function. Neuronal nitric oxide synthase (nNOS) is a key neuronal messenger in several brain regions, and the downregulation of nNOS has been shown to improve brain function. However, whether inosine and exercise training have combined effects on nNOS pathway-related proteins in the brain remains unknown. We found, for the first time, that inosine monophosphate (IMP), which is a precursor of inosine, decreases nNOS levels in the ventral hippocampus (vHp) and the cerebellum (Ce), but not in the dorsal hippocampus (dHp). In the vHp, the phosphorylation of cAMP response element-binding protein (CREB) was also upregulated, which negatively correlated with nNOS protein levels. In the cerebral cortex (Cx), no significant activation of the nNOS pathway was observed. In the dHp, vHp, Cx, and Ce, no interactions between the effects of IMP and exercise on nNOS protein and CREB phosphorylation levels were observed. The phosphorylation of nNOS was regulated by the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. Although IMP induced minor changes in Akt phosphorylation, nNOS phosphorylation was unchanged by either IMP or exercise. In conclusion, in the vHp, which is associated with emotional behavior, IMP decreased nNOS levels and activated CREB, suggesting that IMP can elicit anxiolytic effects.

nNOS-CAPON blockers produce anxiolytic effects by promoting synaptogenesis in chronic stress-induced animal models of anxiety

BACKGROUND AND PURPOSE

Anxiety disorder is a common mental health disorder. However, there are few safe and fast-acting anxiolytic drugs available that can treat anxiety disorder. We previously demonstrated that the interaction of neuronal NOS (nNOS) with its carboxy-terminal PDZ ligand (CAPON) is involved in regulating anxiety-related behaviours. Here, we further investigated the anxiolytic effects of nNOS-CAPON disruptors in chronic stress-induced anxiety in animals.

EXPERIMENTAL APPROACH

Mice were intravenously treated with nNOS-CAPON disruptors, ZLc-002 or Tat-CAPON12C, at the last week of chronic mild stress (CMS) exposure. We also infused corticosterone (CORT) into the hippocampus of mice to model anxiety behaviours and also delivered ZLc-002 or Tat-CAPON12C on the last week of chronic CORT treatment via pre-implanted cannula. Anxiety-related behaviours were examined using elevated plus maze, open field, novelty-suppressed feeding and light-dark (LD) tests. The level of nNOS-CAPON interaction was determined by co-immunoprecipitation (CO-IP) and proximity ligation assay (PLA). The neural mechanisms underlying the behavioural effects of nNOS-CAPON uncoupling in anxiety animal models were assessed by western blot, immunofluorescence and Golgi-Cox staining.

KEY RESULTS

ZLc-002 and Tat-CAPON12C reversed CMS- or CORT-induced anxiety-related behaviours. ZLc-002 and Tat-CAPON12C increased synaptogenesis along with improved dendritic remodelling in CMS mice or CORT-treated cultured neurons. Meanwhile, blocking nNOS-CAPON interaction significantly activated the cAMP response element-binding protein (CREB)-brain-derived neurotrophic factor (BDNF) pathway, which is associated with synaptic plasticity.

CONCLUSION AND IMPLICATIONS

Collectively, these results provide evidence for the anxiolytic effects of nNOS-CAPON uncouplers and their underlying mechanisms in anxiety disorders.

nNOS-expressing neurons in the vmPFC transform pPVT-derived chronic pain signals into anxiety behaviors

Anxiety is common in patients suffering from chronic pain. Here, we report anxiety-like behaviors in mouse models of chronic pain and reveal that nNOS-expressing neurons in ventromedial prefrontal cortex (vmPFC) are essential for pain-induced anxiety but not algesia, using optogenetic and chemogenetic strategies. Additionally, we determined that excitatory projections from the posterior subregion of paraventricular thalamic nucleus (pPVT) provide a neuronal input that drives the activation of vmPFC nNOS-expressing neurons in our chronic pain models. Our results suggest that the pain signal becomes an anxiety signal after activation of vmPFC nNOS-expressing neurons, which causes subsequent release of nitric oxide (NO). Finally, we show that the downstream molecular mechanisms of NO likely involve enhanced glutamate transmission in vmPFC CaMKIIα-expressing neurons through S-nitrosylation-induced AMPAR trafficking. Overall, our data suggest that pPVT excitatory neurons drive chronic pain-induced anxiety through activation of vmPFC nNOS-expressing neurons, resulting in NO-mediated AMPAR trafficking in vmPFC pyramidal neurons.

Chronic pain usually induces anxiety. Here, the authors report that vmPFC nNOS-expressing neurons are activated by excitatory inputs from pPVT during chronic pain and subsequently induce anxiety-like behaviors in mice through promoting AMPAR trafficking.

Epileptic brain fluorescent imaging reveals apigenin can relieve the myeloperoxidase-mediated oxidative stress and inhibit ferroptosis

Myeloperoxidase (MPO)-mediated oxidative stress has been suggested to play an important role in the pathological dysfunction of epileptic brains. However, there is currently no robust brain-imaging tool to detect real-time endogenous hypochlorite (HClO) generation by MPO or a fluorescent probe for rapid high-throughput screening of antiepileptic agents that control the MPO-mediated chlorination stress. Herein, we report an efficient two-photon fluorescence probe (named HCP) for the real-time detection of endogenous HClO signals generated by MPO in the brain of kainic acid (KA)-induced epileptic mice, where HClO-dependent chlorination of quinolone fluorophore gives the enhanced fluorescence response. With this probe, we visualized directly the endogenous HClO fluxes generated by the overexpression of MPO activity in vivo and ex vivo in mouse brains with epileptic behaviors. Notably, by using HCP, we have also constructed a high-throughput screening approach to rapidly screen the potential antiepileptic agents to control MPO-mediated oxidative stress. Moreover, from this screen, we identified that the flavonoid compound apigenin can relieve the MPO-mediated oxidative stress and inhibit the ferroptosis of neuronal cells. Overall, this work provides a versatile fluorescence tool for elucidating the role of HClO generation by MPO in the pathology of epileptic seizures and for rapidly discovering additional antiepileptic agents to prevent and treat epilepsy.

Molecular Mechanisms of Non-ionotropic NMDA Receptor Signaling in Dendritic Spine Shrinkage

Structural plasticity of dendritic spines is a key component of the refinement of synaptic connections during learning. Recent studies highlight a novel role for the NMDA receptor (NMDAR), independent of ion flow, in driving spine shrinkage and LTD. Yet little is known about the molecular mechanisms that link conformational changes in the NMDAR to changes in spine size and synaptic strength. Here, using two-photon glutamate uncaging to induce plasticity at individual dendritic spines on hippocampal CA1 neurons from mice and rats of both sexes, we demonstrate that p38 MAPK is generally required downstream of non-ionotropic NMDAR signaling to drive both spine shrinkage and LTD. In a series of pharmacological and molecular genetic experiments, we identify key components of the non-ionotropic NMDAR signaling pathway driving dendritic spine shrinkage, including the interaction between NOS1AP (nitric oxide synthase 1 adaptor protein) and neuronal nitric oxide synthase (nNOS), nNOS enzymatic activity, activation of MK2 (MAPK-activated protein kinase 2) and cofilin, and signaling through CaMKII. Our results represent a large step forward in delineating the molecular mechanisms of non-ionotropic NMDAR signaling that can drive shrinkage and elimination of dendritic spines during synaptic plasticity.SIGNIFICANCE STATEMENT Signaling through the NMDA receptor (NMDAR) is vitally important for the synaptic plasticity that underlies learning. Recent studies highlight a novel role for the NMDAR, independent of ion flow, in driving synaptic weakening and dendritic spine shrinkage during synaptic plasticity. Here, we delineate several key components of the molecular pathway that links conformational signaling through the NMDAR to dendritic spine shrinkage during synaptic plasticity.

Systemic administration of ZLc-002 exerts anxiolytic-like effects by dissociation of nNOS from CAPON in adult mice

Anxiety is recognized as primary clinical phenotype of psychiatric disorders. However, many patients with anxiety have not yet received effective treatment. Our previous study demonstrated that hippocampal nNOS-CAPON interaction is implicated in anxiety-related behaviors, and blocking nNOS-CAPON interaction in the hippocampus produces anxiolytic-like effects. Here, ZLc-002, a small molecule inhibitor of nNOS-CAPON coupling, was evaluated for anxiolytic-like properties after systemic administered using anxiety behavioral tests, including open-field (OF), elevated plus maze (EPM), novelty-suppressed feeding (NSF) and light-dark (LD) tests. We reported that ZLc-002 when administered intraperitoneally at the dose of 40 or 80 mg/kg/d for 14 days produces anxiolytic-like effects. Furthermore, the similar effects of ZLc-002 were observed when administered intravenously at the dose of 10, 20 or 40 mg/kg/d for 7 days. More importantly, the mice dosing with 80 mg/kg/d ZLc-002 intraperitoneally or 40 mg/kg/d ZLc-002 intravenously for 3 days exerted significant behavioral effects. However, intragastric administration with ZLc-002 was devoid of effect on anxiety behaviors, even at high doses. Furthermore, intraperitoneal or intravenous treatment of ZLc-002 significantly disrupted the interaction between nNOS and CAPON in the hippocampus of adult mice, and there was a significant anxiolytic-like effect of ZLc-002 at day 3 after intrahippocampal microinjection. Our results verified that systemic administration of putative small molecule inhibitor of nNOS-CAPON can be used for the treatment of anxiety disorders.

Cannabinoids, TRPV and nitric oxide: the three ring circus of neuronal excitability

Endocannabinoid system is considered a relevant player in the regulation of neuronal excitability, since it contributes to maintaining the balance of the synaptic ionic milieu. Perturbations to bioelectric conductances have been implicated in the pathophysiological processes leading to hyperexcitability and epileptic seizures. Cannabinoid influence on neurosignalling is exerted on classic receptor-mediated mechanisms or on further molecular targets. Among these, transient receptor potential vanilloid (TRPV) are ionic channels modulated by cannabinoids that are involved in the transduction of a plethora of stimuli and trigger fundamental downstream pathways in the post-synaptic site. In this review, we aim at providing a brief summary of the most recent data about the cross-talk between cannabinoid system and TRPV channels, drawing attention on their role on neuronal hyperexcitability. Then, we aim to unveil a plausible point of interaction between these neural signalling systems taking into consideration nitric oxide, a gaseous molecule inducing profound modifications to neural performances. From this novel perspective, we struggle to propose innovative cellular mechanisms in the regulation of hyperexcitability phenomena, with the goal of exploring plausible CB-related mechanisms underpinning epileptic seizures.

Dissociating nNOS (Neuronal NO Synthase)-CAPON (Carboxy-Terminal Postsynaptic Density-95/Discs Large/Zona Occludens-1 Ligand of nNOS) Interaction Promotes Functional Recovery After Stroke via Enhanced Structural Neuroplasticity

Background and Purpose- Stroke is a major public health concern worldwide. Although clinical treatments have improved in the acute period after stroke, long-term therapeutics remain limited to physical rehabilitation in the delayed phase. This study is aimed to determine whether nNOS (neuronal NO synthase)-CAPON (carboxy-terminal postsynaptic density-95/discs large/zona occludens-1 ligand of nNOS) interaction may serve as a new therapeutic target in the delayed phase for stroke recovery. Methods- Photothrombotic stroke and transient middle cerebral artery occlusion were induced in mice. Adeno-associated virus (AAV)-cytomegalovirus (CMV)-CAPON-125C-GFP (green fluorescent protein)-3Flag and the other 2 drugs (Tat-CAPON-12C and ZLc-002) were microinjected into the peri-infarct cortex immediately and 4 to 10 days after photothrombotic stroke, respectively. ZLc-002 was also systemically injected 4 to 10 days after transient middle cerebral artery occlusion. Grid-walking task and cylinder task were conducted to assess motor function. Western blotting, immunohistochemistry, Golgi staining, and electrophysiology recordings were performed to uncover the mechanisms. Results- Stroke increased nNOS-CAPON association in the peri-infarct cortex in the delayed period. Inhibiting the ischemia-induced nNOS-CAPON association substantially decreased the number of foot faults in the grid-walking task and forelimb asymmetry in the cylinder task, suggesting the promotion of functional recovery from stroke. Moreover, dissociating nNOS-CAPON significantly facilitated dendritic remodeling and synaptic transmission, indicated by increased dendritic spine density, dendritic branching, and length and miniature excitatory postsynaptic current frequency but did not affect stroke-elicited neuronal loss, infarct size, or cerebral edema, suggesting that nNOS-CAPON interaction may function via regulating structural neuroplasticity, rather than neuroprotection. Furthermore, ZLc-002 reversed the transient middle cerebral artery occlusion-induced impairment of motor function. Conclusions- Our results reveal that nNOS-CAPON coupling can serve as a novel pharmacological target for functional restoration after stroke.

PKCγ promotes axonal remodeling in the cortico-spinal tract via GSK3β/β-catenin signaling after traumatic brain injury

Traumatic brain injury (TBI) is a common cause of death and disability. Enhancing the midline-crossing of the contralateral corticospinal tract (CST) to the denervated side of spinal cord facilitates functional recovery after TBI. Activation of the gamma isoform of PKC (PKCγ) in contralateral CST implicates its roles in promoting CST remodeling after TBI. In this study, we deployed loss and gain of function strategies in N2a cells and primary cortical neurons in vitro, and demonstrated that PKCγ is not only important but necessary for neuronal differentiation, neurite outgrowth and axonal branching but not for axonal extension. Mechanically, through the phosphorylation of GSK3β, PKCγ stabilizes the expression of cytosolic β-catenin and increase GAP43 expression, thus promoting axonal outgrowth. Further, rAAV2/9-mediated delivery of constitutive PKCγ in the corticospinal tract after unilateral TBI in vivo additionally showed that specifically delivery of active PKCγ mutant to cortical neuron promotes midline crossing of corticospinal fibers from the uninjured side to the denervated cervical spinal cord. This PKCγ-mediated injury response promoted sensorimotor functional recovery. In conclusion, PKCγ mediates stability of β-catenin through the phosphorylation of GSK3β to facilitate neuronal differentiation, neurite outgrowth and axonal branching, and PKCγ maybe a novel therapeutic target for physiological and functional recovery after TBI.

Chronic mild stress induced anxiety-like behaviors can Be attenuated by inhibition of NOX2-derived oxidative stress

Chronic stress-induced anxiety disorder is a highly-prevalent, modern social disease in which oxidative stress plays an important role. It is necessary to determine the underlying mechanisms governing this disorder to establish an effective treatment target for anxiety disorders. In this study, we examined the behavioral changes in mice subjected to chronic mild stress (CMS). We found that CMS exposure leads to anxiety-like phenotypes and increased levels of oxidative stress in the ventral hippocampus of mice. Furthermore, CMS increased the excitatory synaptic transmission of pyramidal cells in the ventral CA1 (vCA1). Administration of 4-hydroxy-3-methoxy-acetophenone (apocynin), an inhibitor of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, clearly ameliorated the changes induced by CMS exposure. In addition, our results of behavioral tests and analyses of reactive oxygen species (ROS) using NOX2-deficient mice indicate that CMS-induced enhanced oxidative stress level is primarily caused by the increased expression of NOX2. NOX2-derived oxidative stress can serve as a target for anxiety therapy led by chronic stress.

Disruption of nNOS-NOS1AP protein-protein interactions suppresses neuropathic pain in mice

Elevated N-methyl-D-aspartate receptor (NMDAR) activity is linked to central sensitization and chronic pain. However, NMDAR antagonists display limited therapeutic potential because of their adverse side effects. Novel approaches targeting the NR2B-PSD95-nNOS complex to disrupt signaling pathways downstream of NMDARs show efficacy in preclinical pain models. Here, we evaluated the involvement of interactions between neuronal nitric oxide synthase (nNOS) and the nitric oxide synthase 1 adaptor protein (NOS1AP) in pronociceptive signaling and neuropathic pain. TAT-GESV, a peptide inhibitor of the nNOS-NOS1AP complex, disrupted the in vitro binding between nNOS and its downstream protein partner NOS1AP but not its upstream protein partner postsynaptic density 95 kDa (PSD95). Putative inactive peptides (TAT-cp4GESV and TAT-GESVΔ1) failed to do so. Only the active peptide protected primary cortical neurons from glutamate/glycine-induced excitotoxicity. TAT-GESV, administered intrathecally (i.t.), suppressed mechanical and cold allodynia induced by either the chemotherapeutic agent paclitaxel or a traumatic nerve injury induced by partial sciatic nerve ligation. TAT-GESV also blocked the paclitaxel-induced phosphorylation at Ser15 of p53, a substrate of p38 MAPK. Finally, TAT-GESV (i.t.) did not induce NMDAR-mediated motor ataxia in the rotarod test and did not alter basal nociceptive thresholds in the radiant heat tail-flick test. These observations support the hypothesis that antiallodynic efficacy of an nNOS-NOS1AP disruptor may result, at least in part, from blockade of p38 MAPK-mediated downstream effects. Our studies demonstrate, for the first time, that disrupting nNOS-NOS1AP protein-protein interactions attenuates mechanistically distinct forms of neuropathic pain without unwanted motor ataxic effects of NMDAR antagonists.

Tau binding protein CAPON induces tau aggregation and neurodegeneration

To understand the molecular processes that link Aβ amyloidosis, tauopathy and neurodegeneration, we screened for tau-interacting proteins by immunoprecipitation/LC-MS. We identified the carboxy-terminal PDZ ligand of nNOS (CAPON) as a novel tau-binding protein. CAPON is an adaptor protein of neuronal nitric oxide synthase (nNOS), and activated by the N-methyl-D-aspartate receptor. We observed accumulation of CAPON in the hippocampal pyramidal cell layer in the App^NL-G-F -knock-in (KI) brain. To investigate the effect of CAPON accumulation on Alzheimer’s disease (AD) pathogenesis, CAPON was overexpressed in the brain of App^NL-G-F mice crossbred with MAPT (human tau)-KI mice. This produced significant hippocampal atrophy and caspase3-dependent neuronal cell death in the CAPON-expressing hippocampus, suggesting that CAPON accumulation increases neurodegeneration. CAPON expression also induced significantly higher levels of phosphorylated, oligomerized and insoluble tau. In contrast, CAPON deficiency ameliorated the AD-related pathological phenotypes in tauopathy model. These findings suggest that CAPON could be a druggable AD target.

To understand the molecular processes that link Aβ amyloidosis, tauopathy and neurodegeneration, the authors screened for tau-interacting proteins. They demonstrated that a novel tau binding protein CAPON accelerates tau pathology and neuronal cell death in an Alzheimer’s disease mouse model.

Neuronal nitric oxide synthase and affective disorders

Affective disorders including major depressive disorder (MDD), bipolar disorder (BPD), and general anxiety affect more than 10% of population in the world. Notably, neuronal nitric oxide synthase (nNOS), a downstream signal molecule of N-methyl-D-aspartate receptors (NMDARs) activation, is abundant in many regions of the brain such as the prefrontal cortex (PFC), hippocampus, amygdala, dorsal raphe nucleus (DRN), locus coeruleus (LC), and hypothalamus, which are closely associated with the pathophysiology of affective disorders. Decreased levels of the neurotransmitters including 5-hydroxytryptamine or serotonin (5-HT), noradrenalin (NA), and dopamine (DA) as well as hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis are common pathological changes of MDD, BPD, and anxiety. Increasing data suggests that nNOS in the hippocampus play a crucial role in the etiology of MDD whereas nNOS-related dysregulation of the nitrergic system in the LC is closely associated with the pathogenesis of BPD. Moreover, hippocampal nNOS is implicated in the role of serotonin receptor 1 A (5-HTR1 A) in modulating anxiety behaviors. Augment of nNOS and its carboxy-terminal PDZ ligand (CAPON) complex mediate stress-induced anxiety and disrupting the nNOS-CAPON interaction by small molecular drug generates anxiolytic effect. To date, however, the function of nNOS in affective disorders is not well reviewed. Here, we summarize works about nNOS and its signal mechanisms implicated in the pathophysiology of affective disorders. On the basis of this review, it is suggested that future research should more fully focus on the role of nNOS in the pathomechanism and treatment of affective disorders.

Viral vectors as a novel tool for clinical and neuropsychiatric research applications

Background

A viral vector is a genetically modified vector produced by genetic engineering. As pathogenic genes in the virus are completely or largely eliminated, it is safe to be widely used in multidisciplinary research fields for expressing genes, such as neuroscience, metabolism, oncology and so on. Neuroscience and psychiatry are the most closely related disciplines in either basic research or clinical research, but the application of viral vectors in neuropsychiatry has not received much attention or not been widely accepted.

Objective

This article will focus on the application of viral vectors in basic and clinical neuropsychiatric research.

Methods

By using viral vectors, scientists can perform neurological labelling, gene expression regulation and physiological manipulation for investigating phenomenon from molecular mechanisms to behaviours. At the same time, to treat mental or neurological disorders, viral vectors can be designed for gene therapy, which alter gene expression levels or repair mutated genes in the brains of patients.

Perspective

Viral vectors play an important role in basic research and clinical applications. To further understand brain function and prevent mental and neurological diseases, we hypothesize that viral vectors could be used along with various advanced technologies, such as sequencing and high-throughput expression analysis in the neuroscience research field.

Delivery of Glucosylceramidase Beta Gene Using AAV9 Vector Therapy as a Treatment Strategy in Mouse Models of Gaucher Disease

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder caused by mutations in the GBA gene. Enzyme replacement treatment is the most effective therapy available for type 1 GD patients, but it is very expensive and does not improve neurologic outcomes in type 2 and 3 GD patients. This study evaluated the effectiveness of an adeno-associated virus 9 (AAV9) vector expressing the Gba gene delivered systemically in GD mouse models. To detect the therapeutic effects of the AAV9-mediated Gba transfer on the systemic symptoms of GD, an inducible whole-body Gba knockout mouse was developed in which tamoxifen effectively induced whole-body Gba gene deletion, and the mice displayed systemic symptoms of GD. The AAV9-CMV-Gba vector, with the expression of Gba driven by the universal CMV promoter, restored GCase activity in multiple organs and prolonged the lifespan in tamoxifen-induced GD mice after intravenous injection. Mice with brain-specific Gba deletion were also included in this study as a model of neuropathic GD (nGD) and injected intraperitoneally on postnatal day 5 with the AAV9-SYN-Gba vector; this improved the GCase activity, ameliorated the neuropathological changes and extended the mean lifespan two-fold. This study demonstrates that AAV9-mediated gene transfer is a potentially effective treatment for GD.