Voluntary running wheel exercise induces cognitive improvement post traumatic brain injury in mouse model through redressing aberrant excitation regulated by voltage-gated sodium channels 1.1, 1.3, and 1.6.

Traumatic brain injury (TBI) leads to disturbed brain discharge rhythm, elevated excitability, anxiety-like behaviors, and decreased learning and memory capabilities. Cognitive dysfunctions severely affect the quality of life and prognosis of TBI patients, requiring effective rehabilitation treatment. Evidence indicates that moderate exercise after brain injury decreases TBI-induced cognitive decline. However, the underlying mechanism remains unelucidated. Our results demonstrate that TBI causes cognitive impairment behavior abnormalities and overexpression of Nav1.1, Nav1.3 and Nav1.6 proteins inside the hippocampus of mice models. Three weeks of voluntary running wheel (RW) exercise treatments before or/and post-injury effectively redressed the aberrant changes caused by TBI. Additionally, a 10% exercise-conditioned medium helped recover cell viability, neuronal sodium current and expressions of Nav1.1, Nav1.3 and Nav1.6 proteins across cultured neurons after injury. Therefore, the results validate the neuroprotection induced by voluntary RW exercise treatment before or/and post-TBI. The RW exercise-induced improvement in cognitive behaviors and neuronal excitability could be associated with correcting the Nav1.1, Nav1.3, and Nav1.6 expression levels. The current study proves that voluntary exercise is an effective treatment strategy against TBI. The study also highlights novel potential targets for rehabilitating TBI, including the Navs proteins.

Reduced Expression of Voltage-Gated Sodium Channel Beta 2 Restores Neuronal Injury and Improves Cognitive Dysfunction Induced by Aß1-42.

Voltage-gated sodium channel beta 2 (Nav2.2 or Navß2, coded by SCN2B mRNA), a gene involved in maintaining normal physiological functions of the prefrontal cortex and hippocampus, might be associated with prefrontal cortex aging and memory decline. This study investigated the effects of Navß2 in amyloid-ß 1-42- (Aß1-42-) induced neural injury model and the potential underlying molecular mechanism. The results showed that Navß2 knockdown restored neuronal viability of Aß1-42-induced injury in neurons; increased the contents of brain-derived neurotrophic factor (BDNF), enzyme neprilysin (NEP) protein, and NEP enzyme activity; and effectively altered the proportions of the amyloid precursor protein (APP) metabolites including Aß42, sAPPα, and sAPPß, thus ameliorating cognitive dysfunction. This may be achieved through regulating NEP transcription and APP metabolism, accelerating Aß degradation, alleviating neuronal impairment, and regulating BDNF-related signal pathways to repair neuronal synaptic efficiency. This study provides novel evidence indicating that Navß2 plays crucial roles in the repair of neuronal injury induced by Aß1-42 both in vivo and in vitro.

Exercise-Induced Cognitive Improvement Is Associated with Sodium Channel-Mediated Excitability in APP/PS1 Mice.

Elevated brain activation, or hyperexcitability, induces cognitive impairment and confers an increased risk of Alzheimer's disease (AD). Blocking the overexcitation of the neural network may be a promising new strategy to prevent, halt, and even reverse this condition. Physical exercise has been shown to be an effective cognitive enhancer that reduces the risk of AD in elderly individuals, but the underlying mechanisms are far from being fully understood. We explored whether long-term treadmill exercise attenuates amyloid precursor protein (APP)/presenilin-1 (PS1) mutation-induced aberrant network activity and thus improves cognition by altering the numbers and/or distribution of voltage-gated sodium channels (Nav) in transgenic mice. APP/PS1 mice aged 2, 3.5, 5, 6.5, 8, and 9 months underwent treadmill exercise with different durations or at different stages of AD. The alterations in memory, electroencephalogram (EEG) recordings, and expression levels and distributions of Nav functional members (Nav1.1α, Nav1.2, Nav1.6, and Navß2) were evaluated. The results revealed that treadmill exercise with 12- and 24-week durations 1) induced significant improvement in novel object recognition (NOR) memory and Morris water maze (MWM) spatial memory; 2) partially reduced abnormal spike activity; and 3) redressed the disturbed cellular distribution of Nav1.1α, aberrant Navß2 cleavage augmentation, and Nav1.6 upregulation. Additionally, APP/PS1 mice in the 24-week exercise group showed better performance in the NOR task and a large decrease in Nav1.6 expression, which was close to the wild-type level. This study suggests that exercise improves cognition and neural activity by altering the numbers and distribution of hippocampal Nav in APP/PS1 mice. Long-term treadmill exercise, for about 24 weeks, starting in the preclinical stage, is a promising therapeutic strategy for preventing AD and halting its progress.

Metabolites of isocorynoxeine in rats after its oral administration.

This work presents the metabolites of isocorynoxeine (ICOR), which is one of four bioactive tetracyclic oxindole alkaloids isolated from Uncaria hooks used commonly in the traditional Chinese medicines and Kampo medicines. After oral administration of 40 mg kg(-1) ICOR to rats, bile was drained and analyzed by LC-MS. Two phase I metabolites, namely 11-hydroxyisocorynoxeine (M1) and 10-hydroxyisocorynoxeine (M2), and two phase II metabolites, namely 11-hydroxyisocorynoxeine 11-O-ß-D-glucuronide (M3) and 10-hydroxyisocorynoxeine 10-O-ß-D-glucuronide (M4), were isolated from rat excreta and bile, respectively, whose structures were elucidated on the basis of CD, NMR, and MS.

Navß2 Intracellular Fragments Contribute to Aß1-42-Induced Cognitive Impairment and Synaptic Deficit Through Transcriptional Suppression of BDNF.

A pathological hallmark of Alzheimer's disease (AD) is the region-specific accumulation of the amyloid-beta protein (Aß), which triggers aberrant neuronal excitability, synaptic impairment, and progressive cognitive decline. Previous works have demonstrated that Aß pathology induced aberrant elevation in the levels and excessive enzymatic hydrolysis of voltage-gated sodium channel type 2 beta subunit (Navß2) in the brain of AD models, accompanied by alteration in excitability of hippocampal neurons, synaptic deficits, and subsequently, cognitive dysfunction. However, the mechanism is unclear. In this research, by employing cell models treated with toxic Aß1-42 and AD mice, the possible effects and potential mechanisms induced by Navß2. The results reveal that Aß1-42 induces remarkable increases in Navß2 intracellular domain (Navß2-ICD) and decreases in both BDNF exons and protein levels, as well as phosphorylated tropomyosin-related kinase B (pTrkB) expression in cells and mice, coupled with cognitive impairments, synaptic deficits, and aberrant neuronal excitability. Administration with exogenous Navß2-ICD further enhances these effects induced by Aß1-42, while interfering the generation of Navß2-ICD and/or complementing BDNF neutralize the Navß2-ICD-conducted effects. Luciferase reporter assay verifies that Navß2-ICD regulates BDNF transcription and expression by targeting its promoter. Collectively, our findings partially elucidate that abnormal enzymatic hydrolysis of Navß2 induced by Aß1-42-associated AD pathology leads to intracellular Navß2-ICD overload, which may responsible to abnormal neuronal excitability, synaptic deficit, and cognition dysfunction, through its transcriptional suppression on BDNF. Therefore, this work supplies novel evidences that Navß2 plays crucial roles in the occurrence and progression of cognitive impairment of AD by transcriptional regulatory activity of its cleaved ICD.

MicroRNA­449a regulates the progression of brain aging by targeting SCN2B in SAMP8 mice.

Our previous study demonstrated that the expression of sodium channel voltage­gated beta 2 (SCN2B) increased with aging in senescence­accelerated mouse prone 8 (SAMP8) mice, and was identified to be associated with a decline in learning and memory, while the underlying mechanism is unclear. In the present study, multiple differentially expressed miRNAs, which may be involved in the process of aging by regulating target genes, were identified in the prefrontal cortex and hippocampus of SAMP8 mice though miRNA microarray analysis. Using bioinformatics prediction, SCN2B was identified to be one of the potential target genes of miR­449a, which was downregulated in the hippocampus. Previous studies demonstrated that miR­449a is involved in the occurrence and progression of aging by regulating a variety of target genes. Therefore, it was hypothesized that miR­449a may be involved in the process of brain aging by targeting SCN2B. To verify this hypothesis, the following experiments were conducted: A reverse transcription­quantitative polymerase chain reaction assay revealed that the expression level of miR­449a was significantly decreased in the prefrontal cortex and hippocampus of 12­month old SAMP8 mice; a dual­luciferase reporter assay verified that miR­449a regulated SCN2B expression by binding to the 3'­UTR 'seed region'; an anti­Ago co­immunoprecipitation combined with Affymetrix microarray analyses demonstrated that the target mRNA highly enriched with Ago­miRNPs was confirmed to be SCN2B. Finally, overexpression of miR­449a or inhibition of SCN2B promoted the extension of hippocampal neurons in vitro. The results of the present study suggested that miR­449a was downregulated in the prefrontal cortex and hippocampus of SAMP8 mice and may regulate the process of brain aging by targeting SCN2B.

Notoginsenoside R1-Induced Neuronal Repair in Models of Alzheimer Disease Is Associated With an Alteration in Neuronal Hyperexcitability, Which Is Regulated by Nav.

Alzheimer disease is characterized by a progressive cognitive deficit and may be associated with an aberrant hyperexcitability of the neuronal network. Notoginsenoside R1 (R1), a major activity ingredient from Panax notoginseng, has demonstrated favorable changes in neuronal plasticity and induced neuroprotective effects in brain injuries, resulting from various disorders, however, the underlying mechanisms are still not well understood. In the present study, we aimed to explore the possible neuroprotective effects induced by R1 in a mouse model of AD and the mechanisms underlying these effects. Treatment with R1 significantly improved learning and memory functions and redressed neuronal hyperexcitability in amyloid precursor protein/presenilin-1 mice by altering the numbers and/or distribution of the members of voltage-gated sodium channels (Nav). Moreover, we determined whether R1 contributed to the regulation of neuronal excitability in Aß-42-injured cells. Results of our study demonstrated that treatment with R1 rescued Aß1-42-induced injured neurons by increasing cell viability. R1-induced alleviation in neuronal hyperexcitability might be associated with reduced Navß2 cleavage, which partially reversed the abnormal distribution of Nav1.1α. These results suggested that R1 played a vital role in the recovery of Aß1-42-induced neuronal injury and hyperexcitability, which is regulated by Nav proteins. Therefore, R1 may be a promising candidate in the treatment of AD.

Electro-acupuncture-induced neuroprotection is associated with activation of the IGF-1/PI3K/Akt pathway following adjacent dorsal root ganglionectomies in rats.

The aim of the present study was to investigate the putative role and underlying mechanisms of insulin­like growth factor 1 (IGF­1) in mediating neuroplasticity in rats subjected to partial dorsal root ganglionectomies following electro­acupuncture (EA) treatment. The rats underwent bilateral removal of the L1­L4 and L6 dorsal root ganglia (DRG), sparing the L5 DRG, and were subsequently subjected to 28 days of EA treatment at two paired acupoints, zusanli (ST 36)­xuanzhong (GB 39) and futu (ST 32)­sanyinjiao (SP 6), as the EA Model group. Rats that received partial dorsal root ganglionectomies without EA treatment served as a control (Model group). Subsequently, herpes simplex virus (HSV)­IGF­1, HSV­small interfering (si) RNA­IGF­1 and the associated control vectors were injected into the L5 DRG of rats in the EA Model group. HSV­IGF­1 transfection enhanced EA­induced neuroplasticity, which manifested as partial recovery in locomotor function, remission hyperpathia, growth of DRG­derived spared fibers, increased expression of phosphorylated (p­) phosphatidylinositol 3­kinase (PI3K) and Akt, and increased pPI3K/PI3K and pAkt/Akt expression ratios. By contrast, HSV­siRNA­IGF­1 treatment attenuated these effects induced by HSV­IGF­1 transfection. The results additionally demonstrated that HSV­IGF­1 transfection augmented the outgrowth of neurites in cultured DRG neurons, and interference of the expression of IGF­1 retarded neurite outgrowth. Co­treatment with a PI3K inhibitor or Akt siRNA inhibited the aforementioned effects induced by the overexpression of IGF­1. In conclusion, the results of the present study demonstrated the crucial roles of IGF­1 in EA­induced neuroplasticity following adjacent dorsal root ganglionectomies in rats via the PI3K/Akt signaling pathway.

Neuroprotection induced by Navß2­knockdown in APP/PS1 transgenic neurons is associated with NEP regulation.

Voltage­gated sodium channel ß2 (Navß2), as an unconventional substrate of ß­site amyloid precursor protein cleaving enzyme 1, is involved in regulating the neuronal surface expression of sodium channels. A previous study demonstrated that knockdown of Navß2 protected neurons and induced spatial cognition improvement by partially reducing pathological amyloidogenic processing of amyloid precursor protein (APP) in aged APP/presenilin 1 (PS1) transgenic mice. The present study aimed to investigate whether Navß2 knockdown altered APP metabolism via regulation of the Aß­degrading enzyme neprilysin (NEP). APPswe/PS1ΔE9 mice (APP/PS1 transgenic mice with a C57BL/6J genetic background) carrying a Navß2­knockdown mutation (APP/PS1/Navß2­kd) or without Navß2 knockdown (APP/PS1) were used for cell culture and further analysis. The present results demonstrated that in APP/PS1 mouse­derived neurons, Navß2 knockdown partially reversed the reduction in pathological APP cleavage, and the recovery of neurite extension and neuron area. Additionally, Navß2 knockdown increased NEP activity and levels, and the levels of intracellular domain fragment binding to the NEP promoter. The present findings suggested that knockdown of Navß2 reversed the APP/PS1 mutation­induced deficiency in amyloid ß degradation by regulating NEP.

Navß2 knockdown improves cognition in APP/PS1 mice by partially inhibiting seizures and APP amyloid processing.

Voltage-gated sodium channels beta 2 (Navß2, encoded by SCN2B) is a substrate of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) and regulates cell surface expression of channels in neurons. Previous studies reported enhanced Navß2 processing by BACE1 in Alzheimer's disease (AD) model and patients. We investigated whether changes in Navß2 expression affect neuronal seizure and amyloid precursor protein (APP) processing in an AD mouse model. Our study used eight-month-old APP/presenilin 1 (PS1) mice and transgenic Navß2 knockdown [by 61% vs. wild type (WT)] APP/PS1 mice (APP/PS1/Navß2-kd), with age-matched WT and Navß2 knockdown (Navß2-kd) mice as controls. We found that Navß2 knockdown in APP/PS1 mice partially reversed the abnormal Navß2 cleavage and the changes in intracellular and total Nav1.1α expression. It also restored sodium currents density in hippocampal neurons and neuronal activity, as indicated by EEG tracing; improved Morris water maze performance; and shifted APP amyloidogenic metabolism towards non-amyloidogenic processing. There were no differences in these indicators between WT and Navß2-kd mice. These results suggest Navß2 knockdown may be a promising strategy for treating AD.