Mouse Neuroblastoma Neuro2a Cells Research Articles

Antinociceptive effect and anti-inflammatory activity of 1,4-naphthoquinones in mice

Aim: The ability of synthetic 1,4-naphthoquinones (1,4-NQs) to prevent adenosine triphosphate (ATP)-induced and purinergic P2X7 receptor (P2X7R) mediated inflammation in macrophage and neurodegeneration of neuronal cells in vitro was previously established. The aim of the present study was to investigate analgesic-like and anti-inflammatory activity of 1,4-NQs thioglucoside derivatives, compounds U-286 and U-548, in in vivo experiments. Methods: Spectrofluorimetry approach and YO-PRO-1 fluorescent dye uptake determination were applied to study the effect of 1,4-NQs upon ATP-induced P2X7R mediated macropore formation in mouse neuroblastoma Neuro-2a cells and macrophages RAW 264.7 cells. An acetic acid-induced writhing test, hot plate test, and carrageenan-induced paw edema test were used as an in vivo mouse models to study the ability of 1,4-NQs to inhibit pain and inflammation. In the in vivo experiments, compounds were administered to mice intraperitoneally at dosages of 0.1 mg/kg, 1.0 mg/kg and 10.0 mg/kg. A group of animals that received injections of sterile water was used as a control. Each dosage group and the control group consisted of 6 mice. Results: In the present work the analgesic-like and anti-inflammatory activity of 1,4-NQs, U-286 and U-548, was demonstrated. Compound U-548 showed a significant inhibitory effect in antinociceptive tests reducing the number of mouse writhings and eliminating the latent time of mouse hind paw licking, correspondingly. Selected compounds were able to almost completely reduce the size of carrageenan-induced paw edema 24 h after injection and had a potent anti-inflammatory activity. Observed effects were accompanied with aptitude of studied 1,4-NQs to inhibit the formation of purinergic P2X7R macropore associated with inflammation and nociceptive pain. Conclusions: The results obtained allow to consider compounds U-286 and U-548 and as a pharmacological basis for the development of new analgesic-like and anti-inflammatory drugs.

Notoginsenoside R1 attenuates bupivacaine induced neurotoxicity by activating Jak1/Stat3/Mcl1 pathway

Bupivacaine, a common amide local anesthetic, can provide effective analgesia or pain relief but can also cause neurotoxicity, which remains a mounting concern in clinic and animal care. However, the precise underlying mechanisms have not been fully elucidated. A natural compound, notoginsenoside R1 (NG-R1) has been reported to exhibit a neuroprotective role in stress conditions. In this study, we explored the function and mechanism of NG-R1 in alleviating bupivacaine-induced neurotoxicity in mouse hippocampal neuronal (HT-22) and mouse neuroblastoma (Neuro-2a) cell lines. Our results exhibited that NG-R1 treatment can significantly rescue the decline of cell survival induced by bupivacaine. Tunel staining and western blotting showed that NG-R1 could attenuate BPV‑induced cell apoptosis. Besides, we focused on Mcl1 as a potential target as it showed opposite expression tendency in response to NG-R1 and bupivacaine exposure. Mcl1 knockdown blocked the inhibitory effect of NG-R1 on cell apoptosis against bupivacaine treatment. Intriguingly, we found that NG-R1 can upregulate Mcl1 transcription by activating Stat3 and promote its nuclear translocation. In addition, NG-R1 can also promote Jak1 phosphorylation and docking analysis provide a predicted model for interaction between NG-R1 and phosphorylated Jak1. Taken together, our results demonstrated that NG-R1 can attenuate bupivacaine induced neurotoxicity by activating Jak1/Stat3/Mcl1 pathway

Dyngo-4a Induces Neuroblastoma Cell Differentiation Through The AKT and ERK1/2 Pathway.

The aim of the study is to check whether dyngo-4a can inhibit neuroblastoma (NB) proliferation and induce NB cell differentiation Background: Dynamin plays a role in regulating neurotransmission, signaling pathways, nutrient uptake, and pathogen infection, enhancing cell proliferation, tumor invasion, and metastasis. Studies have reported that dyngo-4a, a dynamin inhibitor, can be used to identify potential biomarkers and promising novel therapeutic targets for cancer treatment. To our knowledge, no published reports are showing that dynamin inhibitors can reduce NB cell proliferation and induce differentiation. In this study, we report that dyngo-4a can inhibit NB proliferation and induce NB cell differentiation. In this study, mouse neuroblastoma (Neuro-2a) cells were cultured in the presence or absence of dyngo-4a or retinoic acid (RA), or in the presence of both dyngo-4a and RA, or in the presence of sequential administration of dyngo-4a and RA to compare the effects on the inhibition of cell proliferation and effects on neuroblastoma cell differentiation induction. The neural cell markers, Nestin and Tuj 1 (Neuron-specific class III beta-tubulin), were used to demonstrate that the differentiated cells have neuronal cell features. The phosphorylation of Protein Kinase B (AKT), extracellular signalregulated kinases1/2 (ERK1/2), and epidermal growth factor receptor (EGFR) were determined to examine the potential mechanisms of induced differentiation. Dyngo-4a or RA or dyngo-4a with subsequent RA administration induced Neuro-2a cell differentiation. However, RA with subsequent dyngo-4a administration results in almost total death of the Neuro-2a cells. The differentiation rate induced by dyngo-4a was significantly higher than the rate by RA treatment (72.5 ± 1.4% vs. 52.9 ± 3.1% with neuron features, P<0.05; 39.0 ± 0.8% vs. 29.9 ± 1.8% for axons under light microscopy, p<0.05). The differentiation rate of cells treated with dyngo-4a first, followed by RA, was greater than when they were added together (74.8 ± 3.8% vs. 10.6 ± 3.6%; 45.5 ± 1.6% vs. 12.4 ± 0.6%, p<0.01). Co-administration of dyngo-4a and RA at the same time diminished differentiation efficacy significantly. Dyngo-4a induced Neuro-2a cell differentiation and increased Tuj-1 positive staining by the 6th day post- treatment. Dyngo-4a also inhibited Neuro-2a cell proliferation in a dose-dependent manner. Regarding the mechanism, dyngo-4a treatment showed a significant increase in p-AKT and p-ERK1/2 but not in p-EGFR. At a level comparable to RA, dynamin inhibition with dyngo-4a lowers proliferation and causes differentiation of Neuro-2a mouse NB cells in vitro. The AKT pathway is activated by dynago- 4a, which results in differentiation. The combination of RA with dynago-4a reduces the efficiency of differentiation. The application of dynago-4a followed by RA, on the other hand, enhances the differentiating effect, implying alternative mechanistic roles in the process.

Cdk1 protects against oxygen-glucose deprivation and reperfusion-induced Golgi fragmentation and apoptosis through mediating GM130 phosphorylation.

Increasing evidence has indicated that the Golgi apparatus (GA) is involved in the development of cerebral ischemia-reperfusion (IR) injury. Finding effective neuroprotective agents targeting GA has become a priority in the treatment of ischemic stroke. GM130, a key structural protein present on the cis-face of the GA, maintains its structure through its phosphorylation and dephosphorylation. However, the molecular mechanisms by which GM130 regulates IR-induced neuronal apoptosis are not well elucidated. Mouse neuroblastoma Neuro2a (N2A) cells were subjected to oxygen-glucose deprivation and reperfusion (OGDR) insult. Cell proliferation and apoptosis were determined using MTT assay, TUNEL staining, and flow cytometry. GA morphology was detected by immunocytochemical staining and immunofluorescence microscopy. GA-related protein and mRNA levels were detected by WB and qPCR, respectively. Treatment with Purvalanol A, an effective Cdk1 inhibitor, and transfection of Cdk1-shRNA were carried out to inhibit OGDR-induced Cdk1 elevation. The results demonstrated that OGDR induced Golgi fragmentation, neuronal apoptosis, GM130 phosphorylation, and p115 cleavage in N2A cells. Cdk1 elevation after OGDR was closely correlated with GM130 phosphorylation, not p115. Inhibition of Cdk1 significantly attenuated OGDR-induced Golgi fragmentation and cell apoptosis. Cdk1 interacted with GM130 and decreased its phosphorylation on the serine 25 site in N2A cells exposed to OGDR. The present findings reveal that Cdk1 protects against IR-induced GA fragmentation and apoptosis, likely through the mediation of GM130 phosphorylation. This neuroprotective potential of Cdk1 against IR insult and the underlying mechanism will pave the way for potential clinical applications targeting the GA organelle for cerebral IR-related disorders.

Tyrosine hydroxylase phosphorylation is under the control of serine 40.

Tyrosine hydroxylase catalyzes the initial and rate-limiting step in the biosynthesis of the neurotransmitter dopamine. The phosphorylation state of Ser40 and Ser31 is believed to exert a direct effect on the enzymatic activity of tyrosine hydroxylase. Interestingly, some studies report that Ser31 phosphorylation affects Ser40 phosphorylation, while Ser40 phosphorylation has no effect on Ser31 phosphorylation, a process named hierarchical phosphorylation. Here, we provide a detailed investigation into the signal transduction mechanisms regulating Ser40 and Ser31 phosphorylation in dopaminergic mouse MN9D and Neuro2A cells. We find that cyclic nucleotide signaling drives Ser40 phosphorylation, and that Ser31 phosphorylation is strongly regulated by ERK signaling. Inhibition of ERK1/2 with UO126 or PD98059 reduced Ser31 phosphorylation, but surprisingly had no effect on Ser40 phosphorylation, contradicting a role for Ser31 in the regulation of Ser40. Moreover, to elucidate a possible hierarchical mechanism controlling tyrosine hydroxylase phosphorylation, we introduced tyrosine hydroxylase variants in Neuro2A mouse neuroblastoma cells that mimic either phosphorylated or unphosphorylated serine residues. When we introduced a Ser40Ala tyrosine hydroxylase variant, Ser31 phosphorylation was completely absent. Additionally, neither the tyrosine hydroxylase variant Ser31Asp, nor the variant Ser31Ala had any significant effect on basal Ser40 phosphorylation levels. These results suggest that tyrosine hydroxylase is not controlled by hierarchical phosphorylation in the sense that first Ser31 has to be phosphorylated and subsequently Ser40, but, conversely, that Ser40 phosphorylation is essential for Ser31 phosphorylation. Overall our study suggests that Ser40 is the crucial residue to target so as to modulate tyrosine hydroxylase activity.

Neuroprotection by Polyherbal Medicine Divya-Medha-Vati Against Scopolamine-Induced Cognitive Impairment Through Modulation of Oxidative Stress, Acetylcholine Activity, and Cell Signaling.

Alzheimer disease is associated with cognitive impairments and neuronal damages. In this study, Scopolamine, a model drug used for the generation of Alzheimer-like symptoms induced cognitive dysfunction in C57BL/6 mice. It also elevated acetylcholine esterase (AcHE) activity, and reduced antioxidant (superoxide dismutase and catalase) activity in cortex tissue. Scop reduced neuronal density and increased pyknotic neurons in hippocampus tissue. In mouse neuroblastoma (Neuro2a) cells, Scop triggered a dose-dependent loss of cell viability and neurite outgrowth reduction. Scop-treated Neuro2a cells showed oxidative stress and reduction in mRNA expression for brain-derived neurotrophic factor (BDNF), nerve growth factor-1 (NGF-1), and Synapsin-1 (SYN-1) genes. Mice treated with Divya-Medha-Vati (DMV), an Ayurvedic polyherbal medicine showed protection against Scop-induced cognitive impairment (Morris Water Maze Escape Latency, and Elevated Plus Maze Transfer Latency). DMV protected against Scop-induced AcHE activity, and loss of antioxidant activities in the mice brain cortex while sustaining neuronal density in the hippocampus region. In the Neuro2a cells, DMV reduced Scop-induced loss of cell viability and neurite outgrowth loss. DMV protected the cells against induction of oxidative stress and promoted mRNA expression of BDNF, NGF-1, and SYN-1 genes. Phytochemical profiling of DMV showed the presence of Withanolide A, Withanolide B, Bacopaside II, Jujubogenin, Apigenin, Gallic acid, Caffeic acid, and Quercetin that are associated with antioxidant and neurostimulatory activities. In conclusion, the study showed that Divya-Medha-Vati was capable of promoting neuronal health and inhibiting Alzheimer-like cognitive dysfunction through enhanced antioxidant activities and modulation of neuronal activities.

Modulation of aggregation and structural polymorphisms of β-amyloid fibrils in cellular environments by pyroglutamate-3 variant cross-seeding

Amyloidogenic deposition of β-amyloid (Aβ) peptides in human brain involves not only the wild-type Aβ (wt-Aβ) sequences, but also posttranslationally modified Aβ (PTM-Aβ) variants. Recent studies hypothesizes that the PTM-Aβ variants may trigger the deposition of wt-Aβ, which underlies the pathology of Sporadic Alzheimer's disease. Among PTM-Aβ variants, the pyroglutamate-3-Aβ (pyroE3-Aβ) has attracted much attention because of their significant abundances and broad distributions in senile plaques and dispersible and soluble oligomers. pyroE3-specific antibodies are being tested as potential anti-Aβ drugs in clinical trials. However, evidence that support the triggering effect of pyroE3-Aβ on wt-Aβ in cells remain lacking, which diminishes its pathological relevance. We show here that cross-seeding with pyroE3-Aβ40 leads to accelerated extracellular and intracellular aggregation of wt-Aβ40 in different neuronal cells. Cytotoxicity levels are elevated through the cross-seeded aggregation, comparing with the self-seeded aggregation of wt-Aβ40 or the static presence of pyroE3-Aβ40 seeds. For the extracellular deposition in mouse neuroblastoma Neuro2a (N2a) cells, the cytotoxicity elevation correlates positively with the seeding efficiency. Besides aggregation rates, cross-seeding with pyroE3-Aβ40 also modulates the molecular level structural polymorphisms of the resultant wt-Aβ40 fibrils. Using solid-state nuclear magnetic resonance (ssNMR) spectroscopy, we identified key structural differences between the parent pyroE3/ΔE3 and wt-Aβ40 fibrils within their fibrillar cores. Structural propagation from seeds to daughter fibrils is demonstrated to be more pronounced in the extracellular seeding in N2a cells by comparing the ssNMR spectra from different seeded wt-Aβ40 fibrils, but less significant in the intracellular seeding process in human neuroblastoma SH-SY5Y cells.

Long non-coding RNA HOXA11-AS regulates ischemic neuronal death by targeting miR-337-3p/YBX1 signaling pathway: protective effect of dexmedetomidine

Cerebral ischemia/reperfusion (I/R) is a common neurological disease. Homeobox A11 antisense RNA (HOXA11-AS), a long non-coding RNA (lncRNA), has been demonstrated as an important regulator in diverse human cancers. However, its function and regulatory mechanism in ischemic stroke remains largely unknown. Dexmedetomidine (Dex) have received wide attraction because of its neuroprotective effects. This study aimed to explore the possible link between Dex and HOXA11-AS in protecting neuronal cells from by ischemia/reperfusion-induced apoptosis. We used oxygen-glucose deprivation and reoxygenation (OGD/R) in mouse neuroblastoma Neuro-2a cells and middle cerebral artery occlusion (MACO) mouse model to test the link. We found that Dex significantly alleviated OGD/R-induced DNA fragmentation, cell viability and apoptosis, and rescued the decreased HOXA11-AS expression after ischemic damage in Neuro-2a cells. Gain-/loss-of-function studies revealed that HOXA11-AS promoted proliferation, inhibited apoptosis in Neuro-2a cells exposed to OGD/R. Knockdown of HOXA11-AS decreased the protective effect of Dex on OGD/R cells. HOXA11-AS was found to transcriptionally regulate microRNA-337-3p (miR-337-3p) expression as evidenced by luciferase reporter assay, while miR-337-3p expression was upregulated following ischemia in vitro and in vivo. Besides, knockdown of miR-337-3p protected OGD/R-induced apoptotic death of Neuro-2a cells. Furthermore, HOXA11-AS functioned as a competing endogenous RNA (ceRNA) and competed with Y box protein 1 (Ybx1) mRNA for directly binding to miR-337-3p, which protected ischemic neuronal death. Dex treatment protected against ischemic damage and improved overall neurological functions in vivo. Our data suggest a novel mechanism of Dex neuroprotection for ischemic stroke through regulating lncRNA HOXA11-AS by targeting the miR-337-3p/Ybx1 signaling pathway, which might help develop new strategies for the therapeutic interventions in cerebral ischemic stroke.

Soluble form of the APP fragment, sAPPβ, positively regulates tau secretion

Extracellular tau has been highlighted in the pathogenesis of Alzheimer disease (AD), which is the most common neurodegenerative disease. Pathological analyses as well as model animal studies suggest that amyloid-β peptide (Aβ) deposition facilitates the spreading of tau aggregation pathology via extracellular tau. However, the precise mechanism of tau secretion remains unknown. Here, we show that the overexpression of amyloid precursor protein (APP) enhances the secretion of tau phosphorylated at threonine 181 in mouse neuroblastoma Neuro2a cells. Moreover, we found that soluble amyloid precursor protein β (sAPPβ), which is generated by β-site APP cleaving enzyme 1 (BACE1), mediates tau secretion. Our results demonstrate that BACE1-mediated cleavage of APP plays pathological roles in AD pathogenesis by not only Aβ production, but by the spreading of tau aggregation pathology via sAPPβ in AD patients.

In-cell 31P solid-state NMR measurements of the lipid dynamics and influence of exogeneous β-amyloid peptides on live neuroblastoma neuro-2a cells

Non-specific disruption of cellular membranes induced by aggregation of exogeneous β-amyloid (Aβ) peptides is considered a viable pathological mechanism in Alzheimer's disease (AD). The solid-state nuclear magnetic resonance (ssNMR) spectroscopy has been widely applied in model liposomes to provide important insights on the molecular interactions between membranes and Aβ aggregates. Yet, the feasibility of in-cell ssNMR spectroscopy to probe Aβ-membrane interactions in native cellular environments has rarely been tested. Here we report the application of in-cell31P ssNMR spectroscopy on live mouse neuroblastoma Neuro-2a (N2a) cells under moderate magic angle spinning (MAS) conditions. Both cell viability and cytoplasmic membrane integrity are retained for up to six hours under 5 kHz MAS frequency at 277 K, which allow applications of direct-polarization 31P spectroscopy and 31P spin-spin (T2) relaxation measurements. The 31P T2 relaxation time constant of N2a cells is significantly increased compared with the model liposome prepared with comparable major phospholipid compositions. With the addition of 5 μM 40-residue Aβ (Aβ1–40) peptides, the 31P T2 relaxation is instantly accelerated. This work demonstrates the feasibility of using in-cell31P ssNMR to investigate the Aβ-membrane interactions in the biologically relevant cellular system.

State-Dependent Inhibition of Voltage-Gated Sodium Channels in Neuroblastoma Neuro-2A Cells by Arachidonic Acid from Halichondria okadai.

Voltage-gated sodium channels (Nav) are closely associated with epilepsy, cardiac and skeletal muscle diseases, and neuropathic pain. Several toxic compounds have been isolated from the marine sponge Halichondria okadai; however, toxic substances that modulate Nav are yet to be identified. This study aimed to identify Nav inhibitors from two snake venoms and H. okadai using mouse neuroblastoma Neuro-2A cells (N2A), which primarily express the specific Nav subtype Nav1.7, using whole-cell patch-clamp recordings. We successfully isolated arachidonic acid (AA, 1) from the hexane extract of H. okadai, and then the fatty acid-mediated modulation of Nav in N2A was investigated in detail for the first time. Octanoic acid (2), palmitic acid (3), and oleic acid (4) showed no inhibitory activity at 100 μM, whereas AA (1), dihomo-γ-linolenic acid (DGLA, 5), and eicosapentaenoic acid (EPA, 6) showed IC50 values of 6.1 ± 2.0, 58 ± 19, and 25 ± 4.0 μM, respectively (N = 4, mean ± SEM). Structure and activity relationships were investigated for the first time using two ω-3 polyunsaturated fatty acids (PUFAs), EPA (6) and eicosatetraenoic acid (ETA, 7), and two ω-6 PUFAs, AA (1) and DGLA (5), to determine their effects on a resting state, activated state, and inactivated state. Steady-state analysis showed that the half inactivation potential was largely hyperpolarized by 10 μM AA (1), while 50 μM DGLA (5), 50 μM EPA (6), and 10 μM ETA (7) led to a slight change. The percentages of the resting state block were 24 ± 1, 22 ± 1, 34 ± 4, and 38 ± 9% in the presence of AA (1), DGLA (5), EPA (6), and ETA (7), respectively, with EPA (6) and ETA (7) exhibiting a greater inhibition than both AA (1) and DGLA (5), and their inhibitions did not increase in the following depolarization pulses. None of the compounds exhibited the use-dependent block. The half recovery times from the inactivated state for the control, AA (1), DGLA (5), EPA (6), and ETA (7) were 7.67 ± 0.33, 34.3 ± 1.10, 15.5 ± 1.10, 10.7 ± 0.31, and 3.59 ± 0.18 ms, respectively, with AA (1) exhibiting a distinctively large effect. Overall, distributed binding to the resting and the inactivated states of Nav would be significant for the inhibition of Nav, which presumably depends on the active structure of each PUFA.

UBIAD1 protects against oxygen-glucose deprivation/reoxygenation injury via nNOS/NO pathway.

Cerebral infarction is a subtype of stroke with high incidence and disability rate. Ischemia reperfusion injury (IRI) is the key point of cerebral infarction treatment. UbiA prenyltransferase domain containing 1 (UBIAD1) is a kind of enzyme with various biological functions including electron transport in mitochondrial respiratory chain, lipid metabolism, and oxidative stress which are related to IRI. The purpose of this study aims to determine the neuroprotective effects and the underlying mechanisms of UBIAD1 in cerebral IRI. We employed oxygen-glucose deprivation/reoxygenation (OGD/R) model in mouse neuroblastoma Neuro2a (N2a) cells to mimic cerebral IRI. Lentivirus vector over-expressed UBIAD1 was transfacted into N2a cells to maintain high and stable expression of UBIAD1. In the first part of the experiment, N2a cells were divided into 5 groups: A non-OGD (N2a cells without exposure to OGD) group, groups of reoxygenation 0, 4, 12 and 24 h after 4 h of OGD, respectively. In the second part of the experiment, N2a cells were divided into 6 groups: A Con (normal cell)+non-OGD group, an EV (cell transfected with empty vector)+non-OGD group, an OE (over-expressed UBIAD1)+non-OGD group, a Con+OGD/R group, an EV+OGD/R group, and an OE+OGD/R group. In the third part, the N2a cells were divided into 8 groups: A Con+non-OGD group, an OE+non-OGD group, a Con+non-OGD+nNOS inhibitior 7-nitroindazole (7-NI) group, an OE+non-OGD+7-NI group, a Con+OGD/R group, an OE+OGD/R group, a Con+OGD/R+7-NI group, and an OE+OGD/R+7-NI group. The morphological changes of Golgi apparatus were observed under the confocal laser scanning microscope. The mRNA and protein levels of UBIAD1, secretory pathway Ca2+-ATPase isoform 1 (SPCA1), and NOS were determined by real-time PCR and Western blotting, respectively. Cell apoptosis rate was detected with flow cytometry; cell viability was detected with MTT assay, and NO release was determined with Griess assay. Compared with the non-OGD group, the expression levels of UBIAD1 mRNA and protein in N2a cells in the groups of 0, 4, 12 and 24 h reoxygenation after OGD 4 h decreased significantly (P<0.05 or P<0.01), and the longer the reoxygenation time, the more significant the reduction of UBIAD1 expression. Compared with the Con+OGD/R group and the EV+OGD/R group, mRNA and protein levels of UBIAD1 and SPCA1 were increased (P<0.05 or P<0.01), the apoptosis rate was decreased (all P<0.01), and the cell viability was increased (all P<0.01) in the OE+OGD/R group. The Golgi fragmentation was less in the OE+OGD/R group than that in the Con+ OGD/R group and the EV+OGD/R group. The mRNA and protein levels of endothelial NOS (eNOS) and neuronal NOS (nNOS) were decreased (P<0.05 or P<0.01), and the level of NO was decreased (all P<0.01) in the groups over-expressed UBIAD1 (OE+non-OGD group vs Con+non-OGD group, OE+OGD/R group vs Con+OGD/R group). The level of NO and apoptosis rate of N2a cells were decreased (all P<0.01) in the the groups pretreated with 7-NI (Con+OGD/R+7-NI group vs Con+OGD/R group, OE+OGD/R+7-NI group vs OE+OGD/R group). UBIAD1 may exerts protective effects on OGD/R induced N2a cells by ameliorating Golgi apparatus dysfunction via the nNOS/NO pathway.

Retraction Note: Apicidin induces endoplasmic reticulum stress- and mitochondrial dysfunction-associated apoptosis via phospholipase Cγ1- and Ca2+-dependent pathway in mouse Neuro-2a neuroblastoma cells.

Retraction Note: Apicidin induces endoplasmic reticulum stress- and mitochondrial dysfunction-associated apoptosis via phospholipase Cγ1- and Ca2+-dependent pathway in mouse Neuro-2a neuroblastoma cells.

The CX3CL1 intracellular domain exhibits neuroprotection via insulin receptor/insulin-like growth factor receptor signaling

CX3CL1, also known as fractalkine, is best known for its signaling activity through interactions with its cognate receptor CX3CR1. However, its intrinsic function that is independent of interaction with CX3CR1 remains to be fully understood. We demonstrate that the intracellular domain of CX3CL1 (CX3CL1-ICD), generated upon sequential cleavages by α-/β-secretase and γ-secretase, initiates a back signaling activity, which mediates direct signal transmission to gene expression in the nucleus. To study this, we fused a synthetic peptide derived from CX3CL1-ICD, named Tet34, with a 13-amino acid tetanus sequence at the N terminus to facilitate translocation into neuronal cells. We show that treatment of mouse neuroblastoma Neuro-2A cells with Tet34, but not its scrambled control (Tet34s), induced cell proliferation, as manifested by changes in protein levels of transcription factors and progrowth molecules cyclin D1, PCNA, Sox5, and Cdk2. Further biochemical assays reveal elevation of phosphorylated insulin receptor β subunit, insulin-like growth factor-1 receptor β subunit, and insulin receptor substrates as well as activation of proliferation-linked kinase AKT. In addition, transgenic mice overexpressing membrane-anchored C-terminal CX3CL1 also exhibited activation of insulin/insulin-like growth factor-1 receptor signaling. Remarkably, we found that this Tet34 peptide, but not Tet34s, protected against endoplasmic reticulum stress and cellular apoptosis when Neuro-2A cells were challenged with toxic oligomers of β-amyloid peptide or hydrogen peroxide. Taken together, our results suggest that CX3CL1-ICD may have translational potential for neuroprotection in Alzheimer's disease and for disorders resulting from insulin resistance.

Identification of a Novel Small RNA Encoded in the Mouse Urokinase Receptor uPAR Gene (Plaur) and Its Molecular Target Mef2d.

Urokinase receptor (uPAR) is a glycosylphosphatidylinositol (GPI)-anchored receptor of urokinase (uPA), which is involved in brain development, nerve regeneration, wound healing and tissue remodeling. We have recently shown that Plaur, which encodes uPAR, is an early response gene in murine brain. Assumingly, diverse functions of Plaur might be attributed to hypothetical, unidentified microRNAs encoded within introns of the Plaur gene. Using a bioinformatic approach we identified novel small RNAs within the Plaur gene and named them Plaur-miR1-3p and Plaur-miR1-5p. We confirmed Plaur-dependent expression of Plaur-miR1-3p and Plaur-miR1-5p in the mouse brain and mouse neuroblastoma Neuro2a cells. Utilizing an in silico MR-microT algorithm in DianaTools we selected two target genes – Mef2d and Emx2 with the highest binding scores to small RNAs selected from identified Plaur-Pre-miR1. Furthermore, sequencing of mouse brain samples for Plaur-miR1-5p target genes revealed two more genes—Nrip3 and Snrnp200. The expression of Emx2, Mef2d, and Snrnp200 in the mouse brain and Mef2d and Snrnp200 in Neuro2a cells correlated with expression of Plaur and small RNAs—Plaur-miR1-3p and Plaur-miR1-5p. Finally, we demonstrated elevated MEF2D protein expression in the mouse brain after Plaur induction and displayed activating effects of Plaur-miR1-5p on Mef2d expression in Neuro2a cells using Luciferase reporter assay. In conclusion, we have identified Plaur-miR1-3p and Plaur-miR1-5p as novel small RNAs encoded in the Plaur gene. This finding expands the current understanding of Plaur function in brain development and functioning.

Construction of Self-Assembling Lipopeptide-Based Benign Nanovesicles to Prevent Amyloid Fibril Formation and Reduce Cytotoxicity of GxxxGxxxGxxxG Motif.

Alzheimer's disease, a progressive severe neurodegenerative disorder, has been until now incurable, in spite of serious efforts worldwide. We have designed self-assembled myristoyl-KPGPK lipopeptide-based biocompatible nanovesicles, which can inhibit amyloid fibrillation made by the transmembrane GxxxGxxxGxxxG motif of Aβ-protein and human myelin protein zero as well as reduce their neurotoxicity. Various spectroscopic and microscopic investigations illuminate that the lipopeptide-based nanovesicles dramatically inhibit random coil-to-β-sheet transformation of Aβ25-37 and human myelin protein zero protein precursor, which is the prerequisite of GxxxGxxxGxxxG motif-mediated fibril formation. Förster resonance energy transfer (FRET) assay using synthesized Cy-3 (FRET donor) and Cy-5 (FRET acceptor)-conjugated Aβ25-37 also exhibits that nanovesicles strongly inhibit the fibril formation of Aβ25-37. The mouse neuro-2a neuroblastoma cell line is used, which revealed the GxxxGxxxGxxxG-mediated cytotoxicity. However, the neurotoxicity has been diminished by co-incubating the GxxxGxxxGxxxG motif with the nanovesicles.

Chemical Proteomics Reveals Off-Targets of the Anandamide Reuptake Inhibitor WOBE437.

Anandamide or N-arachidonoylethanolamine (AEA) is a signaling lipid that modulates neurotransmitter release via activation of the type 1 cannabinoid receptor (CB1R) in the brain. Termination of anandamide signaling is thought to be mediated via a facilitated cellular reuptake process that utilizes a purported transporter protein. Recently, WOBE437 has been reported as a novel, natural product-based inhibitor of AEA reuptake that is active in cellular and in vivo models. To profile its target interaction landscape, we synthesized pac-WOBE, a photoactivatable probe derivative of WOBE437, and performed chemical proteomics in mouse neuroblastoma Neuro-2a cells. Surprisingly WOBE437, unlike the widely used selective inhibitor of AEA uptake OMDM-1, was found to increase AEA uptake in Neuro-2a cells. In line with this, WOBE437 reduced the cellular levels of AEA and related N-acylethanolamines (NAEs). Using pac-WOBE, we identified saccharopine dehydrogenase-like oxidoreductase (SCCPDH), vesicle amine transport 1 (VAT1), and ferrochelatase (FECH) as WOBE437-interacting proteins in Neuro-2a cells. Further genetic studies indicated that SCCPDH and VAT1 were not responsible for the WOBE437-induced reduction in NAE levels. Regardless of the precise mechanism of action of WOB437 in AEA transport, we have identified SSCPHD, VAT1, and FECH as unprecedented off-targets of this molecule which should be taken into account when interpreting its cellular and in vivo effects.

Loss of RNA binding protein HuD facilitates the production of the senescence-associated secretory phenotype

HuD, an RNA binding protein, plays a role in the regulation of gene expression in certain types of cells, including neuronal cells and pancreatic β-cells, via RNA metabolism. Its aberrant expression is associated with the pathogenesis of several human diseases. To explore HuD-mediated gene regulation, stable cells expressing short hairpin RNA against HuD were established using mouse neuroblastoma Neuro2a (N2a) cells, which displayed enhanced phenotypic characteristics of cellular senescence. Two approaches, RNA immunoprecipitation (RNA IP)-NanoString profiling and cytokine array, were used to subsequently identify a subset of putative HuD targets that act as senescence-associated secretory phenotype (SASP), including C-C motif ligand 2 (CCL2), CCL20, C-X-C motif chemokine ligand 2 (CXCL2), and interleukin-6 (IL-6). Here, we further demonstrated that HuD regulates the expression of CCL2, a SASP candidate upregulated in cells following HuD knockdown, by binding to the 3′-untranslated region (UTR) of Ccl2 mRNA. Downregulation of HuD increased the level of CCL2 in N2a cells and the brain tissues of HuD knockout (KO) mice. Exposure to γ-irradiation induced cellular senescence in N2a cells and HuD knockdown facilitated stress-induced cellular senescence. Our results reveal that HuD acts as a novel regulator of CCL2 expression, and its aberrant expression may contribute to cellular senescence by regulating SASP production.

Palmitic acid-induced defects in cell cycle progression and cytokinesis in Neuro-2a cells

ABSTRACT Obesity is associated with elevated levels of free fatty acids (FFAs). Excessive saturated fatty acids (SFAs) exhibit significant deleterious cytotoxic effects in many types of cells. However, the effects of palmitic acid (PA), the most common circulating SFA, on cell cycle progression in neuronal cells have not been well-examined. The aim of this study was to examine whether PA affects the proliferation and cell cycle progression in mouse neuroblastoma Neuro-2a (N2a) cells. Our studies found that 200 µM PA significantly decreased DNA synthesis and mitotic index in N2a cells as early as 4 h following treatment. 24 h treatment with 200 µM PA significantly decreased the percentage of diploid (2 N) cells while dramatically increasing the percentage of tetraploid (4 N) cells as compared to the BSA control. Moreover, our studies found that 24 h treatment with 200 µM PA increased the percentage of binucleate cells as compared to the BSA control. Our studies also found that unsaturated fatty acids (UFAs), including linoleic acid, oleic acid, α-linolenic acid, and docosahexaenoic acid, were able to abolish PA-induced decrease of 2 N cells, increase of 4 N cells, and accumulation of binucleate cells. Taken together, these results suggest that PA may affect multiple aspects of the cell cycle progression in N2a cells, including decreased DNA synthesis, G2/M arrest, and cytokinetic failure, which could be abolished by UFAs. Abbreviations: 4-PBA, 4-Phenylbutyric Acid; ALA, α-linolenic acid; BrdU, 5-bromo-2’-deoxyuridine; DAPI, 4′,6-diamidino-2-phenylindole; ER, endoplasmic reticulum; FFA, free fatty acids; FITC, fluorescein isothiocyanate; LA, linoleic acid; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; N2a, Neuro-2a; NAC, N-acetyl cysteine; OA, oleic acid; PA, palmitic acid; pHH3, Phosphorylation of histone H3; PI, propidium iodide; SFA, saturated fatty acids; PUFA, polyunsaturated fatty acids; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; UFA, unsaturated fatty acids

Ginsenoside F1 Protects the Brain against Amyloid Beta-Induced Toxicity by Regulating IDE and NEP.

Ginsenoside F1, the metabolite of Rg1, is one of the most important constituents of Panax ginseng. Although the effects of ginsenosides on amyloid beta (Aβ) aggregation in the brain are known, the role of ginsenoside F1 remains unclear. Here, we investigated the protective effect of ginsenoside F1 against Aβ aggregation in vivo and in vitro. Treatment with 2.5 μM ginsenoside F1 reduced Aβ-induced cytotoxicity by decreasing Aβ aggregation in mouse neuroblastoma neuro-2a (N2a) and human neuroblastoma SH-SY5Y neuronal cell lines. Western blotting, real-time PCR, and siRNA analysis revealed an increased level of insulin-degrading enzyme (IDE) and neprilysin (NEP). Furthermore, liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis confirmed that ginsenoside F1 could pass the blood–brain barrier within 2 h after administration. Immunostaining results indicate that ginsenoside F1 reduces Aβ plaques in the hippocampus of APPswe/PSEN1dE9 (APP/PS1) double-transgenic Alzheimer’s disease (AD) mice. Consistently, increased levels of IDE and NEP protein and mRNA were observed after the 8-week administration of 10 mg/kg/d ginsenoside F1. These data indicate that ginsenoside F1 is a promising therapeutic candidate for AD.