α‐tocopherol pretreatment alleviates cerebral ischemia‐reperfusion injury in rats

α‐tocopherol showed antioxidant, anti‐inflammatory and anti‐apoptotic abilities in rat brain tissue, thus alleviating cerebral ischemia‐reperfusion injury‐induced nerve damage.     

Zinc improves neurological recovery by promoting angiogenesis via the astrocyte‐mediated HIF‐1α/VEGF signaling pathway in experimental stroke

BackgroundIschemic stroke is a serious cerebrovascular disease with high morbidity and disability. Zinc accumulation has been shown to play a vital role in neuronal death and blood–brain barrier damage following ischemia in acute stage. However, almost nothing is known about whether zinc is involved in neurological recovery in ischemic prolonged period. This study investigates whether zinc promotes neurological recovery through astrocytes‐induced angiogenesis during ischemic repair phase.MethodsSprague–Dawley rats were subjected to 2 h ischemia/14, 21, and 28 days reperfusion by middle cerebral artery occlusion, then administered ZnCl₂ (10 mg/kg) via intraperitoneally daily from 7 days to tissue collection to observe brain tissue morphology, neurological function recovery by cortical width index, Adhesive removal test, and Forelimb placing test. Angiogenesis, astrocyte activation, and HIF‐1α/VEGF pathway were assessed via Western blot, immunofluorescence, and BrdU method in vivo and in vitro.ResultsThe results showed that zinc significantly alleviated brain atrophy and improved neurological function recovery during the cerebral ischemia repair stage. Zinc significantly increased the protein levels of HIF‐1α, VEGF‐A, and VEGF‐R2 in astrocytes, and promoted angiogenesis during cerebral ischemia repair. In vitro and in vivo studies confirmed that zinc promoted angiogenesis via the astrocyte‐mediated HIF‐1α/VEGF signaling pathway.ConclusionsZinc significantly improves neurological function recovery during the cerebral ischemia repair stage, providing new evidence supporting zinc as a potential therapeutic target for ischemic stroke by promoting astrocyte induced angiogenesis.     

Evidence that spinal endorphin mediates intraventricular β-endorphin-induced tail flick inhibition and catalepsy

Naloxone injected intrathecally had a different effect on the inhibition of the tail flick response produced by β-endorphin and morphine injected intraventricularly. The intrathecal naloxone completely antagonized the effect of β-endorphin but had only a very weak effect on morphine. In the same rats the cataleptic response to β-endorphin was antagonized as well; however no definitive conclusion could be made regarding the antagonism of the morphine-induced catalepsy. The results indicate that spinal endorphin is involved in the production of intraventricular β-endorphin-induced spinal tail flick inhibition and suggest that intraventricular β-endorphin and morphine elicit their pharmacological action via the activation of different descending inhibitory systems.     

Cross Talk between α7 and α3β4 Nicotinic Receptors Prevents Their Desensitization in Human Chromaffin Cells

The physical interaction and functional cross talk among the different subtypes of neuronal nicotinic acetylcholine receptors (nAChRs) expressed in the various tissues is unknown. Here, we have investigated this issue between the only two nAChRs subtypes expressed, the α7 and α3β4 subtypes, in a human native neuroendocrine cell (the chromaffin cell) using electrophysiological patch-clamp, fluorescence, and Förster resonance energy transfer (FRET) techniques. Our data show that α7 and α3β4 receptor subtypes require their mutual and maximal efficacy of activation to increase their expression, to avoid their desensitization, and therefore, to increase their activity. In this way, after repetitive stimulation with acetylcholine (ACh), α7 and α3β4 receptor subtypes do not desensitize, but they do with choline. The nicotinic current increase associated with the α3β4 subtype is dependent on Ca²⁺. In addition, both receptor subtypes physically interact. Interaction and expression of both subtypes are reversibly reduced by tyrosine and serine/threonine phosphatases inhibition, not by Ca²⁺. In addition, expression is greater in human chromaffin cells from men compared to women, but FRET efficiency is not affected. Together, our findings indicate that human α7 and α3β4 subtypes mutually modulate their expression and activity, providing a promising line of research to pharmacologically regulate their activity.SIGNIFICANCE STATEMENT Desensitization of nicotinic receptors is accepted to occur with repetitive agonist stimulation. However, here we show that human native α3β4 and α7 nicotinic acetylcholine receptor (nAChR) subtypes do not desensitize, and instead, increase their activity when they are activated by the physiological agonist acetylcholine (ACh). An indispensable requirement is the activation of the other receptor subtype with maximal efficacy, and the presence of Ca²⁺ to cooperate in the case of the α3β4 current increase. Because choline is an α3β4 partial agonist, it will act as a limiting factor of nicotinic currents enhancement in the absence of ACh, but in its presence, it will further potentiate α7 currents.     

MicroRNA‐140‐5p inhibitor attenuates memory impairment induced by amyloid‐ß oligomer in vivo possibly through Pin1 regulation

AimsThe peptidyl‐prolyl cis/trans isomerase, Pin1, has a protective role in age‐related neurodegeneration by targeting different phosphorylation sites of tau and the key proteins required to produce Amyloid‐β, which are the well‐known molecular signatures of Alzheimer''s disease (AD) neuropathology. The direct interaction of miR‐140‐5p with Pin1 mRNA and its inhibitory role in protein translation has been identified. The main purpose of this study was to investigate the role of miRNA‐140‐5p inhibition in promoting Pin1 expression and the therapeutic potential of the AntimiR‐140‐5p in the Aß oligomer (AßO)‐induced AD rat model.MethodsSpatial learning and memory were assessed in the Morris water maze. RT‐PCR, western blot, and histological assays were performed on hippocampal samples at various time points after treatments. miRNA‐140‐5p inhibition enhanced Pin1 and ADAM10 mRNA expressions but has little effect on Pin1 protein level.ResultsThe miRNA‐140‐5p inhibitor markedly ameliorated spatial learning and memory deficits induced by AßO, and concomitantly suppressed the mRNA expression of inflammatory mediators TNFα and IL‐1β, and phosphorylation of tau at three key sites (thr231, ser396, and ser404) as well as increased phosphorylated Ser473‐Akt.ConclusionAccording to our results, Antimir‐140‐mediated improvement of AβO‐induced neuronal injury and memory impairment in rats may provide an appropriate rationale for evaluating miR‐140‐5p inhibitors as a promising agent for the treatment of AD.     

The effect of propofol on hypoxia‐ and TNF‐α‐mediated BDNF/TrkB pathway dysregulation in primary rat hippocampal neurons

AimsHypoxia and inflammation may lead to BDNF/TrkB dysregulation and neurological disorders. Propofol is an anesthetic with neuroprotective properties. We wondered whether and how propofol affected BDNF/TrkB pathway in hippocampal neurons and astrocytes.MethodsPrimary rat hippocampal neurons and astrocytes were cultured and exposed to propofol followed by hypoxia or TNF‐α treatment. The expression of BDNF and the expression/truncation/phosphorylation of TrkB were measured. The underlying mechanisms were investigated.ResultsHypoxia and TNF‐α reduced the expression of BDNF, which was reversed by pretreatment of 25 μM propofol in hippocampal neurons. Furthermore, hypoxia and TNF‐α increased the phosphorylation of ERK and phosphorylation of CREB at Ser142, while reduced the phosphorylation of CREB at Ser133, which were all reversed by 25 μM propofol and 10 μM ERK inhibitor. In addition, hypoxia or TNF‐α did not affect TrkB expression, truncation, or phosphorylation in hippocampal neurons and astrocytes. However, in hippocampal neurons, 50 μM propofol induced TrkB phosphorylation, which may be mediated by p35 expression and Cdk5 activation, as suggested by the data showing that blockade of p35 or Cdk5 expression mitigated propofol‐induced TrkB phosphorylation.ConclusionsPropofol modulated BDNF/TrkB pathway in hippocampal neurons via ERK/CREB and p35/Cdk5 under the condition of hypoxia or TNF‐α exposure.     

NG2‐glia crosstalk with microglia in health and disease

Neurodegenerative diseases are increasingly becoming a global problem. However, the pathological mechanisms underlying neurodegenerative diseases are not fully understood. NG2‐glia abnormalities and microglia activation are involved in the development and/or progression of neurodegenerative disorders, such as multiple sclerosis, Alzheimer''s disease, Parkinson''s disease, and cerebrovascular diseases. In this review, we summarize the present understanding of the interaction between NG2‐glia and microglia in physiological and pathological states and discuss unsolved questions concerning their fate and potential fate. First, we introduce the NG2‐glia and microglia in health and disease. Second, we formulate the interaction between NG2‐glia and microglia. NG2‐glia proliferation, migration, differentiation, and apoptosis are influenced by factors released from the microglia. On the other hand, NG2‐glia also regulate microglia actions. We conclude that NG2‐glia and microglia are important immunomodulatory cells in the brain. Understanding the interaction between NG2‐glia and microglia will help provide a novel method to modulate myelination and treat neurodegenerative disorders.     

Lithium attenuates blood–brain barrier damage and brain edema following intracerebral hemorrhage via an endothelial Wnt/β‐catenin signaling‐dependent mechanism in mice

BackgroundVasogenic cerebral edema resulting from blood–brain barrier (BBB) damage aggravates the devastating consequences of intracerebral hemorrhage (ICH). Although augmentation of endothelial Wnt/β‐catenin signaling substantially alleviates BBB breakdown in animals, no agents based on this mechanism are clinically available. Lithium is a medication used to treat bipolar mood disorders and can upregulate Wnt/β‐catenin signaling.MethodsWe evaluated the protective effect of lithium on the BBB in a mouse model of collagenase IV‐induced ICH. Furthermore, we assessed the effect and dependency of lithium on Wnt/β‐catenin signaling in mice with endothelial deletion of the Wnt7 coactivator Gpr124.ResultsLithium treatment (3 mmol/kg) significantly decreased the hematoma volume (11.15 ± 3.89 mm³ vs. 19.97 ± 3.20 mm³ in vehicle controls, p = 0.0016) and improved the neurological outcomes of mice following ICH. Importantly, lithium significantly increased the BBB integrity, as evidenced by reductions in the levels of brain edema (p = 0.0312), Evans blue leakage (p = 0.0261), and blood IgG extravasation (p = 0.0009) into brain tissue around the hematoma. Mechanistically, lithium upregulated the activity of endothelial Wnt/β‐catenin signaling in mice and increased the levels of tight junction proteins (occludin, claudin‐5 and ZO‐1). Furthermore, the protective effect of lithium on cerebral damage and BBB integrity was abolished in endothelial Gpr124 knockout mice, suggesting that its protective effect on BBB function was mainly dependent on Gpr124‐mediated endothelial Wnt/β‐catenin signaling.ConclusionOur findings indicate that lithium may serve as a therapeutic candidate for treating BBB breakdown and brain edema following ICH.     

Minocycline and fluorocitrate suppress spinal nociceptive signaling in intrathecal IL‐1β–induced thermal hyperalgesic rats

We previously demonstrated that intrathecal IL‐1β caused thermal hyperalgesia in rats. This study was conducted to examine the effects and cellular mechanisms of glial inhibitors on IL‐1β–induced nociception in rats. The effects of minocycline (20 μg), fluorocitrate (1 nmol), and SB203580 (5 μg) on IL‐1β (100 ng) treatment in rats were measured by nociceptive behaviors, western blotting of p38 mitogen‐activated protein kinase (MAPK) and inducible nitric oxide synthase (iNOS) expression, cerebrospinal fluid nitric oxide (NO) levels, and immunohistochemical analyses. The results demonstrated that intrathecal IL‐1β activated microglia and astrocytes, but not neurons, in the dorsal horn of the lumbar spinal cord, as evidenced by morphological changes and increased immunoreactivity, phosphorylated p38 (P‐p38) MAPK, and iNOS expression; the activation of microglia and astrocytes peaked at 30 min and lasted for 6 h. The immunoreactivities of microglia and astrocytes were significantly increased at 30 min (6.6‐ and 2.7‐fold, respectively) and 6 h (3.3‐ and 4.0‐fold, respectively) following IL‐1β injection, as compared with saline controls at 30 min (all P < 0.01). IL‐1β induced P‐p38 MAPK and iNOS expression predominantly in microglia and less in astrocytes. Minocycline, fluorocitrate, or SB203580 pretreatment suppressed this IL‐1β–upregulated P‐p38 MAPK mainly in microglia and iNOS mainly in astrocytes; minocycline exhibited the most potent effect. Minocycline and fluorocitrate pretreatment abrogated IL‐1β–induced NO release and thermal hyperalgesia in rats. In conclusion, minocycline, fluorocitrate, and SB203580 effectively suppressed the IL‐1β–induced central sensitization and hyperalgesia in rats. © 2012 Wiley Periodicals, Inc.     

Volume of β-Bursts,But Not Their Rate,Predicts Successful Response Inhibition

In humans, impaired response inhibition is characteristic of a wide range of psychiatric diseases and of normal aging. It is hypothesized that the right inferior frontal cortex (rIFC) plays a key role by inhibiting the motor cortex via the basal ganglia. The electroencephalography (EEG)-derived β-rhythm (15–29 Hz) is thought to reflect communication within this network, with increased right frontal β-power often observed before successful response inhibition. Recent literature suggests that averaging spectral power obscures the transient, burst-like nature of β-activity. There is evidence that the rate of β-bursts following a Stop signal is higher when a motor response is successfully inhibited. However, other characteristics of β-burst events, and their topographical properties, have not yet been examined. Here, we used a large human (male and female) EEG Stop Signal task (SST) dataset (n = 218) to examine averaged normalized β-power, β-burst rate, and β-burst “volume” (which we defined as burst duration × frequency span × amplitude). We first sought to optimize the β-burst detection method. In order to find predictors across the whole scalp, and with high temporal precision, we then used machine learning to (1) classify successful versus failed stopping and to (2) predict individual stop signal reaction time (SSRT). β-burst volume was significantly more predictive of successful and fast stopping than β-burst rate and normalized β-power. The classification model generalized to an external dataset (n = 201). We suggest β-burst volume is a sensitive and reliable measure for investigation of human response inhibition.SIGNIFICANCE STATEMENT The electroencephalography (EEG)-derived β-rhythm (15–29 Hz) is associated with the ability to inhibit ongoing actions. In this study, we sought to identify the specific characteristics of β-activity that contribute to successful and fast inhibition. In order to search for the most relevant features of β-activity, across the whole scalp and with high temporal precision, we employed machine learning on two large datasets. Spatial and temporal features of β-burst “volume” (duration × frequency span × amplitude) predicted response inhibition outcomes in our data significantly better than β-burst rate and normalized β-power. These findings suggest that multidimensional measures of β-bursts, such as burst volume, can add to our understanding of human response inhibition.     

Inhibition of phosphodiesterase‐4 in the spinal dorsal horn ameliorates neuropathic pain via cAMP‐cytokine‐Cx43 signaling in mice

BackgroundThe spinal phosphodiesterase‐4 (PDE4) plays an important role in chronic pain. Inhibition of PDE4, an enzyme catalyzing the hydrolysis of cyclic adenosine monophosphate AMP (cAMP), produces potent antinociceptive activity. However, the antinociceptive mechanism remains largely unknown. Connexin43 (Cx43), a gap junction protein, has been shown to be involved in controlling pain transduction at the spinal level; restoration of Cx43 expression in spinal astrocytes to the normal levels reduces nerve injury‐induced pain. Here, we evaluate the novel mechanisms involving spinal cAMP‐Cx43 signaling by which PDE4 inhibitors produce antinociceptive activity.MethodsFirst, we determined the effect of PDE4 inhibitors rolipram and roflumilast on partial sciatic nerve ligation (PSNL)‐induced mechanical hypersensitivity. Next, we observed the role of cAMP‐Cx43 signaling in the effect of PDE4 inhibitors on PSNL‐induced mechanical hypersensitivity.ResultsSingle or repeated, intraperitoneal or intrathecal administration of rolipram or roflumilast significantly reduced mechanical hypersensitivity in mice following PSNL. In addition, repeated intrathecal treatment with either of PDE4 inhibitors reduced PSNL‐induced downregulation of cAMP and Cx43, and upregulation of proinflammatory cytokines tumor necrosis factor‐α (TNF‐α) and interleukin‐1β. Furthermore, the antinociceptive effects of PDE4 inhibitors were attenuated by the protein kinase A (PKA) inhibitor H89, TNF‐α, or Cx43 antagonist carbenoxolone. Finally, PSNL‐induced upregulation of PDE4B and PDE4D, especially the PDE4B subtype, was reduced by treatment with either of the PDE4 inhibitors.ConclusionsThe results suggest that the antinociceptive effect of PDE4 inhibitors is contributed by increasing Cx43 expression via cAMP‐PKA‐cytokine signaling in the spinal dorsal horn.     

The Association of Blood-Based Inflammatory Factors IL-1β, TGF-β and CRP with Cognitive Function in Alzheimer’s Disease and Mild Cognitive Impairment

Objective Many patients suffer from dementia in its most common form, Alzheimer’s disease (AD). In this study, the levels of IL-1β, TGF-β and CRP, which are involved in the inflammatory response in Alzheimer’s disease and its mild cognitive impairment (MCI), were measured and analyzed. Methods Seventy nine subjects participated in this study (mean age: 75.56 years, female: 54.3%, AD: 26, MCI: 28, normal: 25). The overall cognitive function of the subjects and the severity of the disease stage were assessed using the Mini-Mental State Examination (MMSE-K), the Clinical Dementia Rating (CDR), the Global Deterioration Scale (GDS) and the Geriatric Depression Scale-Korean (GDS-K). Results It was observed that patients with AD had significantly higher levels of IL-1β and TGF-β than the patients with MCI and normal controls. In addition, the MCI group showed a statistically significantly higher TGF-β concentration than the normal group. Conclusion These results suggest that IL-1β and TGF-β may be useful biological markers for patients with Alzheimer’s disease.     

Inflammatory mechanisms of Ginkgo Biloba extract in improving memory functions through lncRNA‐COX2/NF‐κB pathway in mice with status epilepticus

PurposeThis study was to explore whether Ginkgo biloba extract (GBE) improve memory impairment by alleviating neuroinflammation signaling in mice with status epilepticus.MethodsThe status epilepticus (SE) mice model was established by pilocarpine and treated with 100 mg / kg of GBE for 14 days. Spontaneous alternation of Y‐maze and new object recognition were used to explore memory impairment. To examine glial cell activation, we performed immunohistochemistry and immunofluorescence staining. The activation of NF‐κB signaling and the expression level of lncRNA‐COX2 were detected by Western blot and qRT‐PCR, respectively. Adeno‐associated virus lncRNA‐COX2 was injected into mice for overexpression of lncRNA‐COX2.ResultsAfter GBE treatment, the spontaneous alternation rate and the recognition coefficient in SE mice were both increased. Moreover, activation of glial cells, NF‐κB signaling and lncRNA‐COX2 were significantly decreased in SE mice.In the GBE‐treated SE mice with lncRNA‐COX2 overexpression, NF‐κB signaling was up‐regulated again; the reduced level of inflammation factors was reversed; the GBE‐rescued spontaneous alternation rate of Y‐maze was eliminated.ConclusionOur results suggested that GBE reduces the hippocampal inflammation by down‐regulating lncRNA‐COX2 / NF‐κB signaling in the SE mice, leading to the decrease of neuronal damage and the improvement of memory functions.     

Reading and Modulating Cortical β Bursts from Motor Unit Spiking Activity

β Oscillations (13–30 Hz) are ubiquitous in the human motor nervous system. Yet, their origins and roles are unknown. Traditionally, β activity has been treated as a stationary signal. However, recent studies observed that cortical β occurs in “bursting events,” which are transmitted to muscles. This short-lived nature of β events makes it possible to study the main mechanism of β activity found in the muscles in relation to cortical β. Here, we assessed whether muscle β activity mainly results from cortical projections. We ran two experiments in healthy humans of both sexes (N = 15 and N = 13, respectively) to characterize β activity at the cortical and motor unit (MU) levels during isometric contractions of the tibialis anterior muscle. We found that β rhythms observed at the cortical and MU levels are indeed in bursts. These bursts appeared to be time-locked and had comparable average durations (40–80 ms) and rates (approximately three to four bursts per second). To further confirm that cortical and MU β have the same source, we used a novel operant conditioning framework to allow subjects to volitionally modulate MU β. We showed that volitional modulation of β activity at the MU level was possible with minimal subject learning and was paralleled by similar changes in cortical β activity. These results support the hypothesis that MU β mainly results from cortical projections. Moreover, they demonstrate the possibility to decode cortical β activity from MU recordings, with a potential translation to future neural interfaces that use peripheral information to identify and modulate activity in the central nervous system.SIGNIFICANCE STATEMENT We show for the first time that β activity in motor unit (MU) populations occurs in bursting events. These bursts observed in the output of the spinal cord appear to be time-locked and share similar characteristics of β activity at the cortical level, such as the duration and rate at which they occur. Moreover, when subjects were exposed to a novel operant conditioning paradigm and modulated MU β activity, cortical β activity changed in a similar way as peripheral β. These results provide evidence for a strong correspondence between cortical and peripheral β activity, demonstrating the cortical origin of peripheral β and opening the pathway for a new generation of neural interfaces.     

Only the Fastest Corticospinal Fibers Contribute to β Corticomuscular Coherence

Human corticospinal transmission is commonly studied using brain stimulation. However, this approach is biased to activity in the fastest conducting axons. It is unclear whether conclusions obtained in this context are representative of volitional activity in mild-to-moderate contractions. An alternative to overcome this limitation may be to study the corticospinal transmission of endogenously generated brain activity. Here, we investigate in humans (N = 19; of either sex), the transmission speeds of cortical β rhythms (∼20 Hz) traveling to arm (first dorsal interosseous) and leg (tibialis anterior; TA) muscles during tonic mild contractions. For this purpose, we propose two improvements for the estimation of corticomuscular β transmission delays. First, we show that the cumulant density (cross-covariance) is more accurate than the commonly-used directed coherence to estimate transmission delays in bidirectional systems transmitting band-limited signals. Second, we show that when spiking motor unit activity is used instead of interference electromyography, corticomuscular transmission delay estimates are unaffected by the shapes of the motor unit action potentials (MUAPs). Applying these improvements, we show that descending corticomuscular β transmission is only 1–2 ms slower than expected from the fastest corticospinal pathways. In the last part of our work, we show results from simulations using estimated distributions of the conduction velocities for descending axons projecting to lower motoneurons (from macaque histologic measurements) to suggest two scenarios that can explain fast corticomuscular transmission: either only the fastest corticospinal axons selectively transmit β activity, or else the entire pool does. The implications of these two scenarios for our understanding of corticomuscular interactions are discussed.SIGNIFICANCE STATEMENT We present and validate an improved methodology to measure the delay in the transmission of cortical β activity to tonically-active muscles. The estimated corticomuscular β transmission delays obtained with this approach are remarkably similar to those expected from transmission in the fastest corticospinal axons. A simulation of β transmission along a pool of corticospinal axons using an estimated distribution of fiber diameters suggests two possible mechanisms by which fast corticomuscular transmission is achieved: either a very small fraction of the fastest descending axons transmits β activity to the muscles or, alternatively, the entire population does and natural cancellation of slow channels occurs because of the distribution of axon diameters in the corticospinal tract.     

β2 glycoprotein I participates in phagocytosis of apoptotic neurons and in vascular injury in experimental brain stroke

Beta-2 Glycoprotein I (β2-GPI) is the main target of anti-phospholipid antibodies (aPL) in the autoimmune anti-phospholipid syndrome, characterized by increased risk of stroke. We here investigated the antibody independent role of β2-GPI after ischemia/reperfusion, modeled in vivo by transient middle cerebral artery occlusion (tMCAo) in male C57Bl/6J mice; in vitro by subjecting immortalized human brain microvascular endothelial cells (ihBMEC) to 16 h hypoxia and 4 h re-oxygenation. ApoH (coding for β2-GPI) was upregulated selectively in the liver at 48 h after tMCAo. At the same time β2-GPI circulating levels increased. β2-GPI was detectable in brain parenchyma and endothelium at all time points after tMCAo. Parenchymal β2-GPI recognized apoptotic neurons (positive for annexin V, C3 and TUNEL) cleared by CD68+ brain macrophages. Hypoxic ihBMEC showed increased release of IL-6, over-expression of thrombomodulin and IL-1α after re-oxygenation with β2-GPI alone. β2-GPI interacted with mannose-binding lectin in mouse plasma and ihBMEC medium, potentially involved in formation of thrombi. We show for the first time that brain ischemia triggers the hepatic production of β2-GPI. β2-GPI is present in the ischemic endothelium, enhancing vascular inflammation, and extravasates binding stressed neurons before their clearance by phagocytosis. Thus β2-GPI may be a new mediator of brain injury following ischemic stroke.     

Erythropoietin promotes the differentiation of fetal neural stem cells into glial cells via the erythropoietin receptor‐β common receptor/Syne‐1/H3K9me3 pathway

AimsTo investigate the effect of erythropoietin (EPO) on the differentiation of neural stem cells (NSCs)/neural progenitors (NPs) in the treatment of hypoxic–ischemic injury and its potential mechanisms.MethodsFetal NSCs/NPs were treated with EPO after oxygen and glucose deprivation/reoxygenation (OGD/R). Cell viability, proliferation, and differentiation of NSCs/NPs were detected by CellTiter‐Glo, Edu assay, flow cytometry, and quantitative real‐time PCR (qPCR). Immunofluorescence staining, co‐immunoprecipitation (Co‐IP), and western blotting were used to test the existence of EPO receptor/β common receptor (EPOR/βCR) heterodimer on NSCs/NPs and the possible pathway.ResultsEPO treatment at different time points increased cell viability without affecting proliferation. EPO treatment immediately after OGD/R promoted oligodendrocyte and astrocyte differentiation, while decreasing neuronal differentiation of NSCs/NPs. EPOR/βCR heterodimer existed on the cell surface of the fetal cortical NSCs/NPs, EPO treatment significantly increased the mRNA expression of βCR and elevated the correlation between EPOR and βCR levels. In addition, mass spectrometry analysis identified Syne‐1 as a downstream signaling molecule of the EPOR/βCR heterodimer. Immunofluorescence staining and western blotting indicated that the βCR/Syne‐1/H3K9me3 pathway was possibly involved in the differentiation of fetal neural stem cells into the glial cell effect of EPO.ConclusionEPO treatment immediately after OGD/R could not facilitate fetal NSCs/NPs neurogenesis but promoted the formation of the EPOR/βCR heterodimer on fetal NSCs/NPs, which mediates its function in glial differentiation.     

Suppression of P2X3 receptor‐mediated currents by the activation of α2A‐adrenergic receptors in rat dorsal root ganglion neurons

AimsThe α₂‐adrenergic receptor (α₂‐AR) agonists have been shown to be effective in the treatment of various pain. For example, dexmedetomidine (DEX), a selective α_2A‐AR agonist, can be used for peripheral analgesia. However, it is not yet fully elucidated for the precise molecular mechanisms. P2X3 receptor is a major receptor processing nociceptive information in primary sensory neurons. Herein, we show that a functional interaction of α_2A‐ARs and P2X3 receptors in dorsal root ganglia (DRG) neurons could contribute to peripheral analgesia of DEX.MethodsElectrophysiological recordings were carried out on rat DRG neurons, and nociceptive behavior was quantified in rats.ResultsThe activation of α_2A‐ARs by DEX suppressed P2X3 receptor‐mediated and α,β‐methylene‐ATP (α,β‐meATP)‐evoked inward currents in a concentration‐dependent and voltage‐independent manner. Pre‐application of DEX shifted the α,β‐meATP concentration‐response curve downwards, with a decrease of 50.43 ± 4.75% in the maximal current response of P2X3 receptors to α,β‐meATP in the presence of DEX. Suppression of α,β‐meATP‐evoked currents by DEX was blocked by the α_2A‐AR antagonist BRL44408 and prevented by intracellular application of the G_i/o protein inhibitor pertussis toxin, the adenylate cyclase activator forskolin, and the cAMP analog 8‐Br‐cAMP. DEX also suppressed α,β‐meATP‐evoked action potentials through α_2A‐ARs in rat DRG neurons. Finally, the activation of peripheral α_2A‐ARs by DEX had an analgesic effect on the α,β‐meATP‐induced nociception.ConclusionsThese results suggested that activation of α_2A‐ARs by DEX suppressed P2X3 receptor‐mediated electrophysiological and behavioral activity via a G_i/o proteins and cAMP signaling pathway, which was a novel potential mechanism underlying analgesia of peripheral α_2A‐AR agonists.