Disrupting nNOS-PSD95 Interaction Improves Neurological and Cognitive Recoveries after Traumatic Brain Injury

Deciphering the dual role of N-methyl-D-Aspartate receptor in postoperative cognitive dysfunction: A comprehensive review

Postoperative cognitive dysfunction (POCD) is a common complication following surgery, adversely impacting patients' recovery, increasing the risk of negative outcomes, prolonged hospitalization, and higher mortality rates. The N-methyl-D-aspartate (NMDA) receptor, crucial for learning, memory, and synaptic plasticity, plays a significant role in the development of POCD. Various perioperative factors, including age and anesthetic use, can reduce NMDA receptor function, while surgical stress, inflammation, and pain may lead to its excessive activation. This review consolidates preclinical and clinical research to explore the intricate relationship between perioperative factors affecting NMDA receptor functionality and the onset of POCD. It discusses the influence of aging, anesthetic administration, perioperative injury, pain, and inflammation on the NMDA receptor-related pathophysiology of POCD. The comprehensive analysis presented aims to identify effective treatment targets for POCD, contributing to the improvement of patient outcomes post-surgery.

Exploring the role of parthanatos in CNS injury: Molecular insights and therapeutic approaches

BACKGROUND

Central nervous system (CNS) injury causes severe organ damage due to both damage resulting from the injury and subsequent cell death. However, there are currently no effective treatments for countering the irreversible loss of cell function. Parthanatos is a poly (ADP-ribose) polymerase 1 (PARP-1)-dependent form of programmed cell death that is partly responsible for neural cell death. Consequently, the mechanism by which parthanatos promotes CNS injury has attracted significant scientific interest.

AIM OF REVIEW

Our review aims to summarize the potential role of parthanatos in CNS injury and its molecular and pathophysiological mechanisms. Understanding the role of parthanatos and related molecules in CNS injury is crucial for developing effective treatment strategies and identifying important directions for future in-depth research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Parthanatos (from Thanatos, the personification of death according to Greek mythology) is a type of programmed cell death that is initiated by the overactivation of PARP-1. This process triggers a cascade of reactions, including the accumulation of poly(ADP-ribose) (PAR), the nuclear translocation of apoptosis-inducing factor (AIF) after its release from mitochondria, and subsequent massive DNA fragmentation caused by migration inhibitory factor (MIF) forming a complex with AIF. Secondary molecular mechanisms, such as excitotoxicity and oxidative stress-induced overactivation of PARP-1, significantly exacerbate neuronal damage following initial mechanical injury to the CNS. Furthermore, parthanatos is not only associated with neuronal damage but also interacts with various other types of cell death. This review focuses on the latest research concerning the parthanatos cell death pathway, particularly considering its regulatory mechanisms and functions in CNS damage. We highlight the associations between parthanatos and different cell types involved in CNS damage and discuss potential therapeutic agents targeting the parthanatos pathway.

Cerebral glucagon-like peptide-1 receptor activation alleviates traumatic brain injury by glymphatic system regulation in mice

AIM

We aimed to assess the effects of cerebral glucagon-like peptide-1 receptor (GLP-1R) activation on the glymphatic system and whether this effect was therapeutic for traumatic brain injury (TBI).

METHODS

Immunofluorescence was employed to evaluate glymphatic system function. The blood-brain barrier (BBB) permeability, microvascular basement membrane, and tight junction expression were assessed using Evans blue extravasation, immunofluorescence, and western blot. Immunohistochemistry was performed to assess axonal damage. Neuronal apoptosis was evaluated using Nissl staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, and western blot. Cognitive function was assessed using behavioral tests.

RESULTS

Cerebral GLP-1R activation restored glymphatic transport following TBI, alleviating BBB disruption and neuronal apoptosis, thereby improving cognitive function following TBI. Glymphatic function suppression by treatment using aquaporin 4 inhibitor TGN-020 abolished the protective effect of the GLP-1R agonist against cognitive impairment.

CONCLUSION

Cerebral GLP-1R activation can effectively ameliorate neuropathological changes and cognitive impairment following TBI; the underlying mechanism could involve the repair of the glymphatic system damaged by TBI.

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.

Enhancement of the liver's neuroprotective role ameliorates traumatic brain injury pathology

Traumatic brain injury (TBI) is a pervasive problem worldwide for which no effective treatment is currently available. Although most studies have focused on the pathology of the injured brain, we have noted that the liver plays an important role in TBI. Using two mouse models of TBI, we found that the enzymatic activity of hepatic soluble epoxide hydrolase (sEH) was rapidly decreased and then returned to normal levels following TBI, whereas such changes were not observed in the kidney, heart, spleen, or lung. Interestingly, genetic downregulation of hepatic Ephx2 (which encodes sEH) ameliorates TBI-induced neurological deficits and promotes neurological function recovery, whereas overexpression of hepatic sEH exacerbates TBI-associated neurological impairments. Furthermore, hepatic sEH ablation was found to promote the generation of A2 phenotype astrocytes and facilitate the production of various neuroprotective factors associated with astrocytes following TBI. We also observed an inverted V-shaped alteration in the plasma levels of four EET (epoxyeicosatrienoic acid) isoforms (5,6-, 8,9-,11,12-, and 14,15-EET) following TBI which were negatively correlated with hepatic sEH activity. However, hepatic sEH manipulation bidirectionally regulates the plasma levels of 14,15-EET, which rapidly crosses the blood-brain barrier. Additionally, we found that the application of 14,15-EET mimicked the neuroprotective effect of hepatic sEH ablation, while 14,15-epoxyeicosa-5(Z)-enoic acid blocked this effect, indicating that the increased plasma levels of 14,15-EET mediated the neuroprotective effect observed after hepatic sEH ablation. These results highlight the neuroprotective role of the liver in TBI and suggest that targeting hepatic EET signaling could represent a promising therapeutic strategy for treating TBI.

GluN2B-containing NMDARs in the mammalian brain: pharmacology, physiology, and pathology

Glutamate N-methyl-D-aspartate receptor (NMDAR) is critical for promoting physiological synaptic plasticity and neuronal viability. As a major subpopulation of the NMDAR, the GluN2B subunit-containing NMDARs have distinct pharmacological properties, physiological functions, and pathological relevance to neurological diseases compared with other NMDAR subtypes. In mature neurons, GluN2B-containing NMDARs are likely expressed as both diheteromeric and triheteromeric receptors, though the functional importance of each subpopulation has yet to be disentangled. Moreover, the C-terminal region of the GluN2B subunit forms structural complexes with multiple intracellular signaling proteins. These protein complexes play critical roles in both activity-dependent synaptic plasticity and neuronal survival and death signaling, thus serving as the molecular substrates underlying multiple physiological functions. Accordingly, dysregulation of GluN2B-containing NMDARs and/or their downstream signaling pathways has been implicated in neurological diseases, and various strategies to reverse these deficits have been investigated. In this article, we provide an overview of GluN2B-containing NMDAR pharmacology and its key physiological functions, highlighting the importance of this receptor subtype during both health and disease states.

Gamma frequency entrainment rescues cognitive impairment by decreasing postsynaptic transmission after traumatic brain injury

INTRODUCTION

The relationship between oscillatory activity in hippocampus and cognitive impairment in traumatic brain injury (TBI) remains unclear. Although TBI decreases gamma oscillations and 40 Hz light flicker improves TBI prognosis, the effects and mechanism of rhythmic flicker on TBI remain unclear.

AIMS

In this study, we aimed to explore whether light flicker could reverse cognitive deficits, and further explore its potential mechanisms in TBI mouse model.

METHODS

The Morris water maze test (MWM), step-down test (SDT), and novel object recognition test (NOR) were applied to evaluate the cognitive ability. The local field potential (LFP) recording was applied to measure low gamma reduction of CA1 in hippocampus after TBI. And electrophysiological experiments were applied to explore effects of the gamma frequency entrainment on long-term potentiation (LTP), postsynaptic transmission, and intrinsic excitability of CA1 pyramidal cells (PCs) in TBI mice. Immunofluorescence staining and western blotting were applied to explore the effects of 40 Hz light flicker on the expression of PSD95 in hippocampus of TBI mice.

RESULTS

We found that 40 Hz light flicker restored low gamma reduction of CA1 in hippocampus after TBI. And 40 Hz, but not random or 80 Hz light flicker, reversed cognitive impairment after TBI in behavioral tests. Moreover, 40 Hz light flicker improved N-methyl-D-aspartate (NMDA) receptor-dependent LTP (LTP_NMDAR ) and L-type voltage-gated calcium channel-dependent LTP (LTP_L-VGCC ) after TBI treatment. And gamma frequency entrainment decreased excitatory postsynaptic currents (EPSCs) of CA1 PCs in TBI mice. Our results have illustrated that 40 Hz light flicker could decrease intrinsic excitability of PCs after TBI treatment in mice. Furthermore, 40 Hz light flicker decreased the expression of PSD95 in hippocampus of TBI mice.

CONCLUSION

These results demonstrated that 40 Hz light flicker rescues cognitive impairment by decreasing postsynaptic transmission in PCs after TBI treatment in mice.

Effect of seabuckthorn seed protein and its arginine-enriched peptides on combating memory impairment in mice

The current study characterized the combating memory impairment effect of seabuckthorn seed protein (SSP) and the arginine (Arg)-enriched peptides (SSPP) on d-galactose-induced brain aging in mice. The Arg content in SSP and SSPP were 10.11 and 17.82 g/100 g, respectively. Seven Arg peptides (Ile/Leu-Arg, Arg-Glu, Asp-Arg-Pro, Arg-Try-Ala, Glu-Arg-Ser, Val-Gly-Arg-Pro, and Lys-Thr-Glu-Arg) were identified from SSPP. The animal experiments of the Morris water maze and the step-down test indicated that the oral administration of SSP (0.25, 0.5, 1.0 mg/g·d) and SSPP (0.25, 0.5, 1.0 mg/g·d) significantly (p < 0.05) reversed the learning and memory impairment symptoms. The activation of endothelial nitric oxide (NO) synthase and neuronal NO synthase were increased, and inducible NO synthase decreased after SSP and SSPP in the hippocampus compared to the model group, with the SSPP being quite effective. Moreover, the treatment significantly exhibited the ability to normalize the serum inflammatory cytokine levels (NF-ĸB, TNF-α, IL-6) and suppress the Arg-inducible nitric oxide (Arg-iNO) pathway. Therefore, SSP and SSPP ingestion reversed the behavioral learning and memory impairment symptoms possibly associated with the anti-inflammation and Arg-iNO pathway. Consumption of SSP and SSPP diets can be beneficial to memory impairment.

Development of a Potent Cyclic Peptide Inhibitor of the nNOS/PSD-95 Interaction

The complex between the N-methyl-d-aspartate receptor (NMDAR), neuronal nitric oxide synthase (nNOS), and the postsynaptic density protein-95 (PSD-95) is an attractive therapeutic target for the treatment of acute ischemic stroke. The complex is formed via the PDZ protein domains of PSD-95, and efforts to disrupt the complex have generally been based on C-terminal peptides derived from the NMDAR. However, nNOS binds PSD-95 through a β-hairpin motif, providing an alternative starting point for developing PSD-95 inhibitors. Here, we designed a cyclic nNOS β-hairpin mimetic peptide and generated cyclic nNOS β-hairpin peptide arrays with natural and unnatural amino acids (AAs), which provided molecular insights into this interaction. We then optimized cyclic peptides and identified a potent inhibitor of the nNOS/PSD-95 interaction, with the highest affinity reported thus far for a peptide macrocycle inhibitor of PDZ domains, which serves as a template for the development of treatment for acute ischemic stroke.

Sirt1 attenuates astrocyte activation via modulating Dnajb1 and chaperone-mediated autophagy after closed head injury

Our previous study indicates that Silent information regulator 1 (Sirt1) is involved in macroautophagy by upregulating light chain 3 (LC3) expression in astrocyte to exert a neuroprotective effect. Chaperon-mediated autophagy (CMA), another form of autophagy, is also upregulated after brain injury. However, little is known about the role of Sirt1 in regulation of the CMA. In the present study, an in vivo model of closed head injury (CHI) and an in vitro model of primary cortical astrocyte stimulated with interleukin-1β were employed to mimic the astrocyte activation induced by traumatic brain injury. Lentivirus carrying target complementary DNA (cDNA) or short hairpin RNA (shRNA) sequence was used to overexpress Sirt1 or knockdown DnaJ heat shock protein family member B1 (Dnajb1) (a molecular chaperone). We found that Sirt1 overexpression ameliorated neurological deficits, reduced tissue loss, and attenuated astrocyte activation after CHI, which was reversed by Dnajb1-shRNA administration. The upregulation of CMA activity induced by CHI in vivo and in vitro was inhibited after Dnajb1 knockdown. Sirt1 potently promoted CMA activity via upregulating Dnajb1 expression. Mechanically, Sirt1 could interact with Dnajb1 and modulate the deacetylation and ubiquitination of Dnajb1. These findings collectively suggest that Sirt1 plays a protective role against astrocyte activation, which may be associated with the regulation of the CMA activity via modulating the deacetylation and ubiquitination of Dnajb1 after CHI.

Targeting neuronal nitric oxide synthase and the nitrergic system in post-traumatic stress disorder

RATIONALE

Current pharmacological approaches to treatment of post-traumatic stress disorder (PTSD) lack adequate effectiveness. As a result, identifying new molecular targets for drug development is necessary. Furthermore, fear learning and memory in PTSD can undergo different phases, such as fear acquisition, consolidation, and extinction. Each phase may involve different cellular pathways and brain regions. As a result, effective management of PTSD requires mindfulness of the timing of drug administration. One of the molecular targets currently under intense investigation is the N-methyl-D-aspartate (NMDA)-type glutamate receptor (NMDAR). However, despite the therapeutic efficacy of drugs targeting NMDAR, their translation into clinical use has been challenging due to their various side effects. One possible solution to this problem is to target signaling proteins downstream to NMDAR to improve targeting specificity. One of these proteins is the neuronal nitric oxide synthase (nNOS), which is activated following calcium influx through the NMDAR.

OBJECTIVE

In this paper, we review the literature on the pharmacological modulation of nNOS in animal models of PTSD to evaluate its therapeutic potential. Furthermore, we attempt to decipher the inconsistencies observed between the findings of these studies based on the specific phase of fear learning which they had targeted.

RESULTS

Inhibition of nNOS may inhibit fear acquisition and recall, while not having a significant effect on fear consolidation and extinction. However, it may improve extinction consolidation or reconsolidation blockade.

CONCLUSIONS

Modulation of nNOS has therapeutic potential against PTSD and warrants further development for use in the clinical setting.

Inhibition of PSD95-nNOS protein-protein interactions decreases morphine reward and relapse vulnerability in rats

Glutamate signalling through the N-methyl-d-aspartate receptor (NMDAR) activates the enzyme neuronal nitric oxide synthase (nNOS) to produce the signalling molecule nitric oxide (NO). We hypothesized that disruption of the protein-protein interaction between nNOS and the scaffolding protein postsynaptic density 95 kDa (PSD95) would block NMDAR-dependent NO signalling and represent a viable therapeutic route to decrease opioid reward and relapse-like behaviour without the unwanted side effects of NMDAR antagonists. We used a conditioned place preference (CPP) paradigm to evaluate the impact of two small-molecule PSD95-nNOS inhibitors, IC87201 and ZL006, on the rewarding effects of morphine. Both IC87201 and ZL006 blocked morphine-induced CPP at doses that lacked intrinsic rewarding or aversive properties. Furthermore, in vivo fast-scan cyclic voltammetry (FSCV) was used to ascertain the impact of ZL006 on morphine-induced increases in dopamine (DA) efflux in the nucleus accumbens shell (NAc shell) evoked by electrical stimulation of the medial forebrain bundle (MFB). ZL006 attenuated morphine-induced increases in DA efflux at a dose that did not have intrinsic effects on DA transmission. We also employed multiple intravenous drug self-administration approaches to examine the impact of ZL006 on the reinforcing effects of morphine. Interestingly, ZL006 did not alter acquisition or maintenance of morphine self-administration, but reduced lever pressing in a morphine relapse test after forced abstinence. Our results provide behavioural and neurochemical support for the hypothesis that inhibition of PSD95-nNOS protein-protein interactions decreases morphine reward and relapse-like behaviour, highlighting a previously unreported application for these novel therapeutics in the treatment of opioid addiction.

Synaptamide Modulates Astroglial Activity in Mild Traumatic Brain Injury

At present, the study of the neurotropic activity of polyunsaturated fatty acid ethanolamides (N-acylethanolamines) is becoming increasingly important. N-docosahexaenoylethanolamine (synaptamide, DHEA) is a highly active metabolite of docosahexaenoic acid (DHA) with neuroprotective, synaptogenic, neuritogenic, and anti-inflammatory properties in the nervous system. Synaptamide tested in the present study was obtained using a chemical modification of DHA isolated from squid Berryteuthis magister liver. The results of this study demonstrate the effects of synaptamide on the astroglial response to injury in the acute (1 day) and chronic (7 days) phases of mild traumatic brain injury (mTBI) development. HPLC-MS study revealed several times increase of synaptamide concentration in the cerebral cortex and serum of experimental animals after subcutaneous administration (10 mg/kg/day). Using immunohistochemistry, it was shown that synaptamide regulates the activation of GFAP- and S100β-positive astroglia, reduce nNOS-positive immunostaining, and stimulates the secretion of neurotrophin BDNF. Dynamics of superoxide dismutase production in synaptamide treatment confirm the antioxidant efficacy of the test compound. We found a decrease in TBI biomarkers such as GFAP, S100β, and IL-6 in the blood serum of synaptamide-treated experimental animals using Western blot analysis. The results indicate the high therapeutic potential of synaptamide in reducing the severity of the brain damage consequences.

Fabrication of multifunctional metal-organic frameworks nanoparticles via layer-by-layer self-assembly to efficiently discover PSD95-nNOS uncouplers for stroke treatment

Background

Disruption of the postsynaptic density protein-95 (PSD95)—neuronal nitric oxide synthase (nNOS) coupling is an effective way to treat ischemic stroke, however, it still faces some challenges, especially lack of satisfactory PSD95-nNOS uncouplers and the efficient high throughput screening model to discover them.

Results

Herein, the multifunctional metal–organic framework (MMOF) nanoparticles as a new screening system were innovatively fabricated via layer-by-layer self-assembly in which His-tagged nNOS was selectively immobilized on the surface of magnetic MOF, and then PSD95 with green fluorescent protein (GFP-PSD95) was specifically bound on it. It was found that MMOF nanoparticles not only exhibited the superior performances including the high loading efficiency, reusability, and anti-interference ability, but also possessed the good fluorescent sensitivity to detect the coupled GFP-PSD95. After MMOF nanoparticles interacted with the uncouplers, they would be rapidly separated from uncoupled GFP-PSD95 by magnet, and the fluorescent intensities could be determined to assay the uncoupling efficiency at high throughput level.

Conclusions

In conclusion, MMOF nanoparticles were successfully fabricated and applied to screen the natural actives as potential PSD95-nNOS uncouplers. Taken together, our newly developed method provided a new material as a platform for efficiently discovering PSD95-nNOS uncouplers for stoke treatment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01583-7.

Postsynaptic signaling at glutamatergic synapses as therapeutic targets

Dysregulation of glutamatergic synapses plays an important role in the pathogenesis of neurological diseases. In addition to mediating excitatory synaptic transmission, postsynaptic glutamate receptors interact with various membrane and intracellular proteins. They form structural and/or signaling synaptic protein complexes and thereby play diverse postsynaptic functions. Recently, several postsynaptic protein complexes have been associated with various neurological diseases and hence, have been characterized as important therapeutic targets. Moreover, novel small molecules and therapeutic peptides targeting and modulating the activities of these protein complexes have been discovered, some of which have advanced through preclinical translational research and/or clinical studies. This article describes the recent investigation of eight key protein complexes associated with the postsynaptic ionotropic and metabotropic glutamate receptors as therapeutic targets for central nervous system diseases.

Krüppel-like factor 7 attenuates hippocampal neuronal injury after traumatic brain injury

Our previous study has shown that the transcription factor Krüppel-like factor 7 (KLF7) promotes peripheral nerve regeneration and motor function recovery after spinal cord injury. KLF7 also participates in traumatic brain injury, but its regulatory mechanisms remain poorly understood. In the present study, an HT22 cell model of traumatic brain injury was established by stretch injury and oxygen-glucose deprivation. These cells were then transfected with an adeno-associated virus carrying KLF7 (AAV-KLF7). The results revealed that, after stretch injury and oxygen-glucose deprivation, KLF7 greatly reduced apoptosis, activated caspase-3 and lactate dehydrogenase, downregulated the expression of the apoptotic markers B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) and cleaved caspase-3, and increased the expression of βIII-tubulin and the antiapoptotic marker Bcl-2. Furthermore, KLF7 overexpression upregulated Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) phosphorylation in HT22 cells treated by stretch injury and oxygen-glucose deprivation. Immunoprecipitation assays revealed that KLF7 directly participated in the phosphorylation of STAT3. In addition, treatment with AG490, a selective inhibitor of JAK2/STAT3, weakened the protective effects of KLF7. A mouse controlled cortical impact model of traumatic brain injury was then established. At 30 minutes before modeling, AAV-KLF7 was injected into the ipsilateral lateral ventricle. The protein and mRNA levels of KLF7 in the hippocampus were increased at 1 day after injury and recovered to normal levels at 3 days after injury. KLF7 reduced ipsilateral hippocampal atrophy, decreased the injured cortex volume, downregulated Bax and cleaved caspase-3 expression, and increased the number of 5-bromo-2'-deoxyuridine-positive neurons and Bcl-2 protein expression. Moreover, KLF7 transfection greatly enhanced the phosphorylation of JAK2 and STAT3 in the ipsilateral hippocampus. These results suggest that KLF7 may protect hippocampal neurons after traumatic brain injury through activation of the JAK2/STAT3 signaling pathway. The study was approved by the Institutional Review Board of Mudanjiang Medical University, China (approval No. mdjyxy-2018-0012) on March 6, 2018.

Revisiting Excitotoxicity in Traumatic Brain Injury: From Bench to Bedside

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality. Consequences vary from mild cognitive impairment to death and, no matter the severity of subsequent sequelae, it represents a high burden for affected patients and for the health care system. Brain trauma can cause neuronal death through mechanical forces that disrupt cell architecture, and other secondary consequences through mechanisms such as inflammation, oxidative stress, programmed cell death, and, most importantly, excitotoxicity. This review aims to provide a comprehensive understanding of the many classical and novel pathways implicated in tissue damage following TBI. We summarize the preclinical evidence of potential therapeutic interventions and describe the available clinical evaluation of novel drug targets such as vitamin B12 and ifenprodil, among others.

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.

SerpinA3N attenuates ischemic stroke injury by reducing apoptosis and neuroinflammation

Objective

To assess the effect of serine protein inhibitor A3N (serpinA3N) in ischemic stroke and to explore its mechanism of action.

Methods

Mouse ischemic stroke model was induced by transient middle cerebral artery occlusion followed by reperfusion. The expression pattern of serpinA3N was assessed using immunofluorescence, Western blot analysis, and real‐time quantitative PCR. An adeno‐associated virus (AAV) and recombinant serpinA3N were administered. Additionally, co‐immunoprecipitation‐mass spectrometry and immunofluorescence co‐staining were used to identify protein interactions.

Results

SerpinA3N was upregulated in astrocytes and neurons within the ischemic penumbra after stroke in the acute phase. The expression of serpinA3N gradually increased 6 h after reperfusion, peaked on the day 2–3, and then decreased by day 7. Overexpression of serpinA3N by AAV significantly reduced the infarct size and improved motor function, associated with alleviated inflammation and oxidative stress. SerpinA3N treatment also reduced apoptosis both in vivo and in vitro. Co‐immunoprecipitation‐mass spectrometry and Western blotting revealed that clusterin interacts with serpinA3N, and Akt‐mTOR pathway members were upregulated by serpinA3N both in vivo and in vitro.

Conclusions

SerpinA3N is expressed in astrocytes and penumbra neurons after stroke in mice. It reduces brain damage possibly via interacting with clusterin and inhibiting neuronal apoptosis and neuroinflammation.

WNK3 Promotes Neuronal Survival after Traumatic Brain Injury in Rats

With-no-lysine kinase 3 (WNK3) is a key regulator of chloride ion transport and neuronal survival in diverse cell types. WNK3 was previously found to regulate the activity of Na⁺-K⁺-2Cl^- cotransporter-1 (NKCC1) in ischemia-associated brain damage. However, the role of WNK3 in traumatic brain injury (TBI) has not yet been studied. A weight-drop TBI model was established in Sprague-Dawley rats. Overexpression and specific inhibition were used to investigate the role of WNK3 in TBI via Western blot, immunofluorescence, neuronal apoptosis, brain water content, and neurological score analyses. We found pronounced TBI-induced downregulation of WNK3 expression and upregulation of NKCC1 expression in neurons, especially at 48 h. Overexpression of WNK3 significantly ameliorated neuronal apoptosis, blood-brain barrier (BBB) disruption, brain edema and neurological deficits at 48 h after TBI. These effects were concomitant with reductions in p-NKCC1 and phosphorylated extracellular signal-regulated kinase (p-ERK1/2) expression. Furthermore, bumetanide administration enhanced the neuroprotective effects of WNK3 overexpression against brain injury. Thus, WNK3 plays a neuroprotective role in TBI, and overexpression of WNK3 may increase cell resistance to apoptotic insults and brain edema, thereby alleviating secondary brain injury.

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.

PSD-95 protects the pancreas against pathological damage through p38 MAPK signaling pathway in acute pancreatitis

Acute pancreatitis is one of the leading causes of gastrointestinal disorder-related hospitalizations, yet its pathogenesis remains to be fully elucidated. Postsynaptic density protein-95 (PSD-95) is closely associated with tissue inflammation and injury. We aimed to investigate the expression of PSD-95 in pancreatic acinar cells, and its function in regulating the inflammatory response and pancreatic pathological damage in acute pancreatitis. A mouse model of edematous acute pancreatitis was induced with caerulein and lipopolysaccharide in C57BL/6 mice. Tat-N-dimer was injected to inhibit the PSD-95 activity separately, or simultaneously with SB203580, inhibitor of p38 MAPK phosphorylation. Rat pancreatic acinar cells AR42J were cultured with 1 μM caerulein to build a cell model of acute pancreatitis. PSD-95-knockdown and negative control cell lines were constructed by lentiviral transfection of AR42J cells. Paraffin-embedded pancreatic tissue samples were processed for routine HE staining to evaluate the pathological changes of human and mouse pancreatic tissues. Serum amylase and inflammatory cytokine levels were detected with specific ELISA kits. Immunofluorescence, immunohistochemical, Western-blot, and qRT-PCR were used to detect the expression levels of PSD-95, p38, and phosphorylated p38. Our findings showed that PSD-95 is expressed in the pancreatic tissues of humans, C57BL/6 mice, and AR42J cells, primarily in the cytoplasm. PSD-95 expression increased at 2 h, reaching the peak at 6 h in mice and 12 h in AR42J cells. IL-6, IL-8, and TNF-α increased within 2 h of disease induction. The pancreatic histopathologic score was greater in the PSD-95 inhibition group compared with the control (P < 0.05), while it was lesser when phosphorylation of p38 MAPK was inhibited compared with the PSD-95 inhibition group (P < 0.05). Moreover, phosphorylation of p38 MAPK increased statistically after PSD-95 knocked-down. In conclusion, PSD-95 effectively influences the pathological damage of the pancreas in acute pancreatitis by affecting the phosphorylation of p38 MAPK.

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.

The Molecular Simulation Study of nNOS Activation Induced by the Interaction Between Its Calmodulin-Binding Domain and SUMO1

Neuronal nitric oxide synthase (nNOS), an enzyme required for learning and memory, catalyzes L-arginine decomposition during nitric oxide production in mammalian neurons. Over-activation of nNOS leads to oxidative/nitrosative stress, which is part of the pathophysiological process of various neuropsychiatric disorders. Previous experimental studies suggest that nNOS is a target for small ubiquitin-like modifier 1 (SUMO1), and that SUMO1-ylation upregulates nNOS catalytic activity in hippocampal neurons. To date, a comprehensive structural model has not been proposed for nNOS SUMO1-ylation. In this study, our aim was to build in silico models to identify the non-bonded interactions between SUMO1 and the calmodulin binding domain (CaMBD) of nNOS. Using molecular docking and molecular dynamics simulation, we found that SUMO1 modification stabilizes the conformation of nNOS CaMBD, and helps maintain a conformation beneficial for nNOS catalysis. Analysis of the polar contacts and hydrogen bonds, and the root mean square derivation results showed that R726 and R727 of CaMBD formed polar contacts or high occupancy hydrogen bonds with SUMO1. Correlation factor analysis and free energy calculations showed that the W716, L734, F740, M745, and F781 residues were also involved in the SUMO1/CaMBD interaction in an orientation-dependent manner. The potential inhibitor binding pocket of SUMO1, aimed at disrupting SUMO1/CaMBD binding, was detected from the virtual screening results. Our in silico studies revealed that interfering with the non-bonded interactions of SUMO1/CaMBD would blocked nNOS SUMO-ylation and subsequent hyperactivation. This work provides novel structural insight into the functional regulation of nNOS by post-translational SUMO1 modification, and provides suggestions for the design of drugs targeting nNOS hyperactivation.

Revisiting Traumatic Brain Injury: From Molecular Mechanisms to Therapeutic Interventions

Studying the complex molecular mechanisms involved in traumatic brain injury (TBI) is crucial for developing new therapies for TBI. Current treatments for TBI are primarily focused on patient stabilization and symptom mitigation. However, the field lacks defined therapies to prevent cell death, oxidative stress, and inflammatory cascades which lead to chronic pathology. Little can be done to treat the mechanical damage that occurs during the primary insult of a TBI; however, secondary injury mechanisms, such as inflammation, blood-brain barrier (BBB) breakdown, edema formation, excitotoxicity, oxidative stress, and cell death, can be targeted by therapeutic interventions. Elucidating the many mechanisms underlying secondary injury and studying targets of neuroprotective therapeutic agents is critical for developing new treatments. Therefore, we present a review on the molecular events following TBI from inflammation to programmed cell death and discuss current research and the latest therapeutic strategies to help understand TBI-mediated secondary injury.

Neuroprotective effects of ZL006 in Aβ1-42-treated neuronal cells

Amyloid beta (Aβ)-induced neurotoxicity and oxidative stress plays an important role in the pathogenesis of Alzheimer’s disease (AD). ZL006 is shown to reduce over-produced nitric oxide and oxidative stress in ischemic stroke by interrupting the interaction of neuronal nitric oxide synthase and postsynaptic density protein 95. However, few studies are reported on the role of ZL006 in AD. To investigate whether ZL006 exerted neuroprotective effects in AD, we used Aβ_1–42 to treat primary cortical neurons and N2a neuroblastoma cells as an in vitro model of AD. Cortical neurons were incubated with ZL006 or dimethyl sulfoxide for 2 hours and treated with Aβ_1–42 or NH₃•H₂O for another 24 hours. The results of cell counting Kit-8 (CCK-8) assay and calcein-acetoxymethylester/propidium iodide staining showed that ZL006 pretreatment rescued the neuronal death induced by Aβ_1–42. Fluorescence and western blot assay were used to detect oxidative stress and apoptosis-related proteins in each group of cells. Results showed that ZL006 pretreatment decreased neuronal apoptosis and oxidative stress induced by Aβ_1–42. The results of CCK8 assay showed that inhibition of Akt or NF-E2-related factor 2 (Nrf2) in cortical neurons abolished the protective effects of ZL006. Moreover, similar results were also observed in N2a neuroblastoma cells. ZL006 inhibited N2a cell death and oxidative stress induced by Aβ_1–42, while inhibition of Akt or Nrf2 abolished the protective effect of ZL006. These results demonstrated that ZL006 reduced Aβ_1–42-induced neuronal damage and oxidative stress, and the mechanisms might be associated with the activation of Akt/Nrf2/heme oxygenase-1 signaling pathways.