Culture of Rodent Cortical, Hippocampal, and Striatal Neurons

Study of Effector CD8+ T Cell Interactions with Cortical Neurons in Response to Inflammation in Mouse Brain Slices and Neuronal Cultures

Cytotoxic CD8+ T cells contribute to neuronal damage in inflammatory and degenerative CNS disorders, such as multiple sclerosis (MS). The mechanism of cortical damage associated with CD8+ T cells is not well understood. We developed in vitro cell culture and ex vivo brain slice co-culture models of brain inflammation to study CD8+ T cell-neuron interactions. To induce inflammation, we applied T cell conditioned media, which contains a variety of cytokines, during CD8+ T cell polyclonal activation. Release of IFNγ and TNFα from co-cultures was verified by ELISA, confirming an inflammatory response. We also visualized the physical interactions between CD8+ T cells and cortical neurons using live-cell confocal imaging. The imaging revealed that T cells reduced their migration velocity and changed their migratory patterns under inflammatory conditions. CD8+ T cells increased their dwell time at neuronal soma and dendrites in response to added cytokines. These changes were seen in both the in vitro and ex vivo models. The results confirm that these in vitro and ex vivo models provide promising platforms for the study of the molecular details of neuron-immune cell interactions under inflammatory conditions, which allow high-resolution live microscopy and are readily amenable to experimental manipulation.

Modulation of Amyloid β-Induced Microglia Activation and Neuronal Cell Death by Curcumin and Analogues

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is not restricted to the neuronal compartment but includes important interactions with immune cells, including microglia. Protein aggregates, common pathological hallmarks of AD, bind to pattern recognition receptors on microglia and trigger an inflammatory response, which contributes to disease progression and severity. In this context, curcumin is emerging as a potential drug candidate able to affect multiple key pathways implicated in AD, including neuroinflammation. Therefore, we studied the effect of curcumin and its structurally related analogues cur6 and cur16 on amyloid-β (Aβ)-induced microglia activation and neuronal cell death, as well as their effect on the modulation of Aβ aggregation. Primary cortical microglia and neurons were exposed to two different populations of Aβ42 oligomers (Aβ42Os) where the oligomeric state had been assigned by capillary electrophoresis and ultrafiltration. When stimulated with high molecular weight Aβ42Os, microglia released proinflammatory cytokines that led to early neuronal cell death. The studied compounds exerted an anti-inflammatory effect on high molecular weight Aβ42O-stimulated microglia and possibly inhibited microglia-mediated neuronal cell toxicity. Furthermore, the tested compounds demonstrated antioligomeric activity during the process of in vitro Aβ42 aggregation. These findings could be investigated further and used for the optimization of multipotent candidate molecules for AD treatment.

Differences between cultured cortical neurons by trypsin and papain digestion

The objective of this study was to compare the efficiency of trypsin and papain in neuronal digestion and determine which enzyme is more efficient. Cortical tissues were obtained from Sprague-Dawley (SD) rats. According to the different digestive enzymes, the samples were divided into the trypsin group and the papain group. After being digested by each of the two enzymes, cortical neurons were collected from the samples. Then, the morphology of the cortical neurons was determined. Moreover, the cortical neurons were transfected with the negative control (NC) lentivirus. The transfection efficiency and morphology were determined and compared. Compared with the papain group, cortical neurons in the trypsin group were more in number, had larger cell size, had longer axonal length, and had fewer impurities. The transfection efficiency of the trypsin group (57.77%) was higher than that of the papain group (53.83%). The morphology of neurons that was displayed showed that the cell body of most neurons shrank and became smaller, and the axis mutation became shorter and less in the papain group 6 days after transfection with the NC lentivirus. Trypsin is more efficient in digesting neurons because the neurons digested by this enzyme are more in number, have a larger cell body, longer axons, and greater transfection efficiency.

LncRNA MIAT enhances cerebral ischaemia/reperfusion injury in rat model via interacting with EGLN2 and reduces its ubiquitin-mediated degradation

Long non-coding RNA (lncRNA) MIAT (myocardial infarction associated transcript) has been characterized as a functional lncRNA modulating cerebral ischaemic/reperfusion (I/R) injury. However, the underlying mechanisms remain poorly understood. This study explored the functional partners of MIAT in primary rat neurons and their regulation on I/R injury. Sprague-Dawley rats were used to construct middle cerebral artery occlusion (MCAO) models. Their cerebral cortical neurons were used for in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) models. Results showed that MIAT interacted with EGLN2 in rat cortical neurons. MIAT overexpression or knockdown did not alter EGLN2 transcription. In contrast, MIAT overexpression increased EGLN2 stability after I/R injury via reducing its ubiquitin-mediated degradation. EGLN2 was a substrate of MDM2, a ubiquitin E3 ligase. MDM2 interacted with the N-terminal of EGLN2 and mediated its K48-linked poly-ubiquitination, thereby facilitating its proteasomal degradation. MIAT knockdown enhanced the interaction and reduced EGLN2 stability. MIAT overexpression enhanced infarct volume and induced a higher ratio of neuronal apoptosis. EGLN2 knockdown significantly reversed the injury. MIAT overexpression reduced oxidative pentose phosphate pathway flux and increased oxidized/reduced glutathione ratio, the effects of which were abrogated by EGLN2 knockdown. In conclusion, MIAT might act as a stabilizer of EGLN2 via reducing MDM2 mediated K48 poly-ubiquitination. MIAT-EGLN2 axis exacerbates I/R injury via altering redox homeostasis in neurons.

Bilirubin Oxidation End Products (BOXes) Induce Neuronal Oxidative Stress Involving the Nrf2 Pathway

Delayed ischemic neurological deficit (DIND) is a severe complication after subarachnoid hemorrhage (SAH). Previous studies have suggested that bilirubin oxidation end products (BOXes) are probably associated with the DIND after SAH, but there is a lack of direct evidence yet even on cellular levels. In the present study, we aim to explore the potential role of BOXes and the involved mechanisms in neuronal function. We synthesized high-purity (>97%) BOX A and BOX B isomers. The pharmacokinetics showed they are permeable to the blood-brain barrier. Exposure of a moderate concentration (10 or 30 μM) of BOX A or BOX B to isolated primary cortical neurons increased the production of reactive oxygen species. In the human neuroblastoma SH-SY5Y cells, BOX A and BOX B decreased the mitochondrial membrane potential and enhanced nuclear accumulation of the protein Nrf2 implicated in oxidative injury repair. In addition, both chemicals increased the mRNA and protein expression levels of multiple antioxidant response genes including Hmox1, Gsta3, Blvrb, Gclm, and Srxn1, indicating that the antioxidant response element (ARE) transcriptional cascade driven by Nrf2 is activated. In conclusion, we demonstrated that primary cortical neurons and neuroblastoma cells undergo an adaptive response against BOX A- and BOX B-mediated oxidative stress by activation of multiple antioxidant responses, in part through the Nrf2 pathway, which provides in-depth insights into the pathophysiological mechanism of DIND after SAH or other neurological dysfunctions related to cerebral hemorrhage.

Silencing TRPV4 partially reverses the neurotoxic effects caused by excess Ketamine

Excessive use of Ketamine (KET) has a neurotoxic effect on the brain. This study explored the effect of Transient Receptor Potential Vanilloid 4 (TRPV4) on KET-induced neurotoxicity in the hippocampus. We extracted and identified rat hippocampal neuronal cells. The hippocampal neurons were treated with different concentrations (0, 0.1, 1, 10, 100, 300 and 1000 μmol/L) of KET (6, 12 and 24 hr). Cell viability was detected by cell counting Kit-8 (CCK-8), and TRPV4 expression was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) and western blot. After silencing TRPV4, we tested cell viability and apoptosis. The contents of superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), and catalase (CAT) were detected by colorimetry, and the contents of TNF-α, IL-1β, IL-6 and reactive oxygen species (ROS) were detected by Enzyme-Linked ImmunoSorbent Assay (ELISA). Finally, the expression levels of apoptosis-related proteins Bcl-2, Bax and Cleaved caspase-3, and phosphorylated-p65 (p-65), p65, phosphorylated-IκBα (p-IκBα) and IκBα were detected by qRT-PCR and western blot. KET inhibited the viability of hippocampal neurons in a dose-dependent manner, and up-regulated TRPV4 expression. SiTRPV4 inhibits KET-induced decrease in cell viability and promotes apoptosis. SiTRPV4 reduced MDA and ROS content, increased SOD, GSH and CAT levels. The release of proinflammatory factors TNF-α, IL-1β and IL-6 was also inhibited by siTRPV4. In addition, siTRPV4 up-regulated KET-induced Bcl-2 expression in hippocampal neurons, down-regulated Bax and Cleaved caspase-3, and inhibited the activation of the inflammatory pathway. Silencing TRPV4 partially reverses the neurotoxic effects induced by KET through regulating apoptosis-related proteins and p65/IκBα pathway.

MiR-132 down-regulates high glucose-induced β-dystroglycan degradation through Matrix Metalloproteinases-9 up-regulation in primary neurons

Cognitive dysfunction is one of the complications of diabetes. Unfortunately, there is no effective methods to block its progression currently. One of the pathophysiological mechanisms is synaptic protein damage and neuronal signal disruption because of glucose metabolism disorder. Dystroglycan protein, located in the post‐synaptic membrane of neurons, links the intracellular cytoskeleton with extracellular matrix. Abnormal expression of dystroglycan protein affects neuronal biological functions and leads to cognitive impairment. However, there are no relevant studies to observe the changes of β‐dystroglycan protein in diabetes rat brain and in primary neurons under high glucose exposure. Our data demonstrated the alterations of cognitive abilities in the diabetic rats; β‐dystroglycan protein degradation occurred in hippocampal and cortical tissues in diabetic rat brain. We further explored the mechanisms underlying of this phenomenon. When neurons are exposed to high glucose environment in long‐term period, microRNA‐132 (miR‐132) would be down‐regulated in neurons. Matrix Metalloproteinases‐9 (MMP‐9) mRNA, as a target of miR‐132, could be up‐regulated; higher expression and overlay activity of MMP‐9 protein could increase β‐DG protein degradation. In this way, β‐DG degradation may affect structure and functions among the synapses, which related to cognition decline. It may provide some theoretical basis for elucidating the molecular mechanism of diabetes‐induced cognitive dysfunction.

Aβ1-16 controls synaptic vesicle pools at excitatory synapses via cholinergic modulation of synapsin phosphorylation

Amyloid beta (Aβ) is linked to the pathology of Alzheimer’s disease (AD). At physiological concentrations, Aβ was proposed to enhance neuroplasticity and memory formation by increasing the neurotransmitter release from presynapse. However, the exact mechanisms underlying this presynaptic effect as well as specific contribution of endogenously occurring Aβ isoforms remain unclear. Here, we demonstrate that Aβ1-42 and Aβ1-16, but not Aβ17-42, increased size of the recycling pool of synaptic vesicles (SV). This presynaptic effect was driven by enhancement of endogenous cholinergic signalling via α7 nicotinic acetylcholine receptors, which led to activation of calcineurin, dephosphorylation of synapsin 1 and consequently resulted in reorganization of functional pools of SV increasing their availability for sustained neurotransmission. Our results identify synapsin 1 as a molecular target of Aβ and reveal an effect of physiological concentrations of Aβ on cholinergic modulation of glutamatergic neurotransmission. These findings provide new mechanistic insights in cholinergic dysfunction observed in AD.

Acid Sphingomyelinase Impacts Canonical Transient Receptor Potential Channels 6 (TRPC6) Activity in Primary Neuronal Systems

: The acid sphingomyelinase (ASM)/ceramide system exhibits a crucial role in the pathology of major depressive disorder (MDD). ASM hydrolyzes the abundant membrane lipid sphingomyelin to ceramide that regulates the clustering of membrane proteins via microdomain and lipid raft organization. Several commonly used antidepressants, such as fluoxetine, rely on the functional inhibition of ASM in terms of their antidepressive pharmacological effects. Transient receptor potential canonical 6 (TRPC6) ion channels are located in the plasma membrane of neurons and serve as receptors for hyperforin, a phytochemical constituent of the antidepressive herbal remedy St. John's wort. TRPC6 channels are involved in the regulation of neuronal plasticity, which likely contributes to their antidepressant effect. In this work, we investigated the impact of reduced ASM activity on the TRPC6 function in neurons. A lipidomic analysis of cortical brain tissue of ASM deficient mice revealed a decrease in ceramide/sphingomyelin molar ratio and an increase in sphingosine. In neurons with ASM deletion, hyperforin-mediated Ca2+-influx via TRPC6 was decreased. Consequently, downstream activation of nuclear phospho-cAMP response element-binding protein (pCREB) was changed, a transcriptional factor involved in neuronal plasticity. Our study underlines the importance of balanced ASM activity, as well as sphingolipidome composition for optimal TRPC6 function. A better understanding of the interaction of the ASM/ceramide and TRPC6 systems could help to draw conclusions about the pathology of MDD.

[Toxicity of dibutyl phthalate in primary cultured rat hippocampal neurons and the toxicological mechanism]

OBJECTIVE

To investigate the neurotoxicity and toxicological mechanism of dibutyl phthalate (DBP) in primary cultured rat hippocampal neurons.

METHODS

Primary rat hippocampal neurons cultured for 4 days were exposed to 1 g/L DBP for 24, 48, or 96 h. Immunofluorescence assay and transmission electron microscopy (TEM) were used to observe the morphological changes of the axons and the ultrastructure of DBP-treated neurons. The action potential (AP) of the hippocampal neurons was measured with patch-clamp electrophysiology. CCK-8 assay was used to detect the viability of the hippocampal neurons, and Western blotting was performed to determine the mRNA and protein expressions of brain-derived neurotrophic factor (BDNF), neuropeptide Y (NPY) and estrogen receptor β (ERβ). High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) was employed to detect the release of the neurotransmitter GABA.

RESULTS

After exposure to DBP for 96 h, the cellular network of the hippocampal neurons became sparse, and the neurons showed significantly decreased axonal length (P < 0.01) and presented with round cell nuclei, chromatin aggregation and cytoplasmic vacuolization. Patch-clamp electrophysiology revealed depolarization drift and increased frequency of discharge in the exposed neurons (P < 0.01). The neurons with DBP exposure for 24, 48 and 96 h all showed significantly decreased cell viability (P < 0.01). DBP exposure for 48 and 96 h significantly lowered the protein expressions of ERβ, BDNF and NPY, and a 96-h exposure significantly reduced the release of the neurotransmitter GABA in the neurons (P < 0.05).

CONCLUSIONS

DBP exposure causes morphological and functional damages of primary cultured rat hippocampal neurons. DBP-induced neurotoxicity is probably associated with GABA-mediated blockage of the ERβ-BDNF-NPY signaling communication.

Assessing the Expression of Major Histocompatibility Complex Class I on Primary Murine Hippocampal Neurons by Flow Cytometry

Increasing evidence supports the hypothesis that neuro-immune interactions impact nervous system function in both homeostatic and pathologic conditions. A well-studied function of major histocompatibility complex class I (MHCI) is the presentation of cell-derived peptides to the adaptive immune system, particularly in response to infection. More recently it has been shown that the expression of MHCI molecules on neurons can modulate activity-dependent changes in the synaptic connectivity during normal development and neurologic disorders. The importance of these functions to the brain health supports the need for a sensitive assay that readily detects MHCI expression on neurons. Here we describe a method for primary culture of murine hippocampal neurons and then assessment of MHCI expression by flow cytometric analysis. Murine hippocampus is microdissected from prenatal mouse pups at the embryonic day 18. Tissue is dissociated into a single cell suspension using enzymatic and mechanical techniques, then cultured in a serum-free media that limits growth of non-neuronal cells. After 7 days in vitro, MHCI expression is stimulated by treating cultured cells pharmacologically with beta interferon. MHCI molecules are labeled in situ with a fluorescently tagged antibody, then cells are non-enzymatically dissociated into a single cell suspension. To confirm the neuronal identity, cells are fixed with paraformaldehyde, permeabilized, and labeled with a fluorescently tagged antibody that recognizes neuronal nuclear antigen NeuN. MHCI expression is then quantified on neurons by flow cytometric analysis. Neuronal cultures can easily be manipulated by either genetic modifications or pharmacologic interventions to test specific hypotheses. With slight modifications, these methods can be used to culture other neuronal populations or to assess expression of other proteins of interest.

Overexpression of phosphoprotein enriched in astrocytes 15 reverses the damage induced by propofol in hippocampal neurons

Propofol is a general anesthetic used in surgical operations. Phosphoprotein enriched in astrocytes 15(PEA15) was initially identified in astrocytes. The present study examined the role of PEA15 in the damage induced by propofol in hippocampal neurons. A model of hippocampal neuron damage was established using 50 µmol/l propofol. Cell viability, proliferation and apoptosis of hippocampal neurons were tested by Cell Counting Kit‑8 and flow cytometry. Western blotting and reverse transcription‑quantitative polymerase chain reaction analysis were performed to measure the expression levels of PEA15, and additional factors involved in apoptosis or in the signaling pathway downstream of PEA15. The present results suggested that propofol significantly decreased PEA15 expression levels in hippocampal neurons. Furthermore, overexpression of PEA15 significantly increased the cell viability and cell proliferation of cells treated with propofol. Additionally, PEA15 overexpression decreased apoptosis, which was promoted by propofol. Treatment with propofol significantly decreased the protein expression levels of pro‑caspase‑3, B‑cell lymphoma-2, phosphorylated extracellular signal‑regulated kinases (ERK)1/2, ribosomal S6 kinase 2 (RSK2) and phosphorylated cAMP responsive element binding protein 1 (CREB1). However, propofol upregulated active caspase‑3 and Bax expression levels. Notably, PEA15 overexpression was able to reverse the effects of propofol. Collectively, overexpression of PEA15 was able to attenuate the neurotoxicity of propofol in rat hippocampal neurons by increasing proliferation and repressing apoptosis via upregulation of the ERK‑CREB‑RSK2 signaling pathway.

Overexpression of COX6B1 protects against I/R‑induced neuronal injury in rat hippocampal neurons

Cerebrovascular disease (CVD) is one of the leading causes of mortality worldwide. The role of cytochrome c oxidase subunit 6B1 (COX6B1) in the central nervous system remains unclear. The present study aimed to analyze the role of COX6B1 in rat hippocampal neurons extracted from fetal rats. The subcellular localization of the neuron‑specific marker microtubule‑associated protein 2 was detected by immunofluorescence assay. Cell viability was assessed using a cell counting kit, and the levels of apoptosis and cytosolic Ca2+ were analyzed by flow cytometry. The expression levels of the molecular factors downstream to COX6B1 were determined using reverse transcription‑quantitative polymerase chain reaction and western blotting. Reoxygenation following oxygen‑glucose deprivation (OGD) decreased cell viability and the expression levels of COX6B1 in a time‑dependent manner, and 60 min of reoxygenation was identified as the optimal time period for establishing an ischemia/reperfusion (I/R) model. Overexpression of COX6B1 was demonstrated to reverse the viability of hippocampal neurons following I/R treatment. Specifically, COX6B1 overexpression decreased the cytosolic concentration of Ca2+ and suppressed neuronal apoptosis, which were increased following I/R treatment. Furthermore, overexpression of COX6B1 increased the protein expression levels of apoptosis regulator BCL‑2 and mitochondrial cytochrome c (cyt c), and decreased the protein expression levels of apoptosis regulator BCL2‑associated X and cytosolic cyt c in I/R model cells. Collectively, the present study results suggested that COX6B1 overexpression may reverse I/R‑induced neuronal damage by increasing the viability of neurons, by decreasing the cytosolic levels of Ca2+ and by suppressing apoptosis. These results may facilitate the development of novel strategies for the prevention and treatment of CVD.

Collapsin Response Mediator Protein-2 Ameliorates Sevoflurane-Mediated Neurocyte Injury by Targeting PI3K-mTOR-S6K Pathway

Background

Collapsin response mediator protein-2 (CRMP-2) is the first member of the CRMP family that has been identified in primary neuronal cells; it was originally found and identified in the regulation of microtubule dimerization into microtubules.

Material/Methods

In the present study, we aimed to investigate the roles and mechanisms of CRMP-2 in sevoflurane-induced neurocyte injury. Cell viability, proliferation, and apoptosis were measured by Cell Counting Kit-8 (CCK-8) assay and flow cytometry. Colorimetry was performed to measure the activity of caspase-3. Western blot and quantitative real-time reverse transcription assays were used to evaluate the related mRNAs and proteins expression.

Results

We found that CRMP-2 reversed the inhibitory effect of sevoflurane on the viability of nerve cells. Moreover, CRMP-2 accelerated the proliferation and suppressed the apoptosis of sevoflurane-induced nerve cells. CRMP-2 modulated the expression levels of apoptosis-associated protein in sevoflurane-induced nerve cells. Furthermore, it was demonstrated that CRMP-2 impacted the PI3K-mTOR-S6K pathway.

Conclusions

CRMP2 ameliorated sevoflurane-mediated neurocyte injury by targeting the PI3K-mTOR-S6K pathway. Thus, CRMP2 might be an effective target for sevoflurane-induced neurocyte injury therapies.