氧葡萄糖剥夺-再恢复后抑制小胶质细胞TLR9激活对神经元的保护作用

目的:观察氧葡萄糖剥夺-再恢复(OGDR)后小胶质细胞BV-2 Toll样受体9(TLR9)激活对神经元凋亡的影响。方法:对BV-2细胞或TLR9-siRNA转染的BV-2细胞进行OGDR处理4 h后,将细胞上清添加至OGDR处理4 h的小鼠原代皮层神经元中,继续正常培养24 h后,倒置显微镜下观察神经元形态变化,TUNEL染色检测神经元凋亡,Western blotting检测神经元caspase-3蛋白的表达。实验分为正常BV-2组、negative control-siRNA组、TLR9-siRNA组、OGDR组、OGDR+NC-siRNA组、OGDR+TLR9-siRNA组和对照组(神经元OGDR后不添加BV-2细胞上清)。结果:OGDR后神经元胞体肿胀,折光性下降,出现空泡样变,轴突变细、扭曲、断裂。TUNEL染色各组均可见绿染凋亡小体。与对照组比较,其它组的caspase-3蛋白表达升高(P0.05);与正常BV-2组比较,OGDR组和TLR9-siRNA组的caspase-3蛋白表达升高(P0.05);OGDR+TLR9-siRNA转染组与TLR9-siRNA转染组和OGDR组比较,caspase-3蛋白表达下降(P0.05)。结论:OGDR后BV-2细胞TLR9激活致神经元凋亡增多,caspase-3蛋白表达升高;抑制TLR9表达后,神经元损伤减轻。     

Decreased expression of mGluR5 within the dorsolateral prefrontal cortex in autism and increased microglial number in mGluR5 knockout mice: Pathophysiological and neurobehavioral implications

Metabotropic glutamate receptor 5 (mGluR5) and microglial abnormalities have been implicated in autism spectrum disorder (ASD). However, controversy exists as to whether the receptor is down or upregulated in functioning in ASD. In addition, whilst activation of mGluR5 has been shown to attenuate microglial activation, its role in maintaining microglial homeostasis during development has not been investigated. We utilised published microarray data from the dorsolateral prefrontal cortex (DLPFC) of control (n = 30) and ASD (n = 27) individuals to carry out regression analysis to assess gene expression of mGluR5 downstream signalling elements. We then conducted a post-mortem brain stereological investigation of the DLPFC, to estimate the proportion of mGluR5-positive neurons and glia. Finally, we carried out stereological investigation into numbers of microglia in mGluR5 knockout mice, relative to wildtype littermates, together with assessment of changes in microglial somal size, as an indicator of activation status. We found that gene expression of mGluR5 was significantly decreased in ASD versus controls (p = 0.018) as well as downstream elements SHANK3 (p = 0.005) and PLCB1 (p = 0.009) but that the pro-inflammatory marker NOS2 was increased (p = 0.047). Intensity of staining of mGluR5-positive neurons was also significantly decreased in ASD versus controls (p = 0.016). Microglial density was significantly increased in mGluR5 knockout animals versus wildtype controls (p = 0.011). Our findings provide evidence for decreased expression of mGluR5 and its signalling components representing a key pathophysiological hallmark in ASD with implications for the regulation of microglial number and activation during development. This is important in the context of microglia being considered to play key roles in synaptic pruning during development, with preservation of appropriate connectivity relevant for normal brain functioning.     

Endocannabinoids drive the acquisition of an alternative phenotype in microglia

The ability of microglia to acquire diverse states of activation, or phenotypes, reflects different features that are determinant for their contribution to homeostasis in the adult CNS, and their activity in neuroinflammation, repair or immunomodulation. Despite the widely reported immunomodulatory effects of cannabinoids in both the peripheral immune system and the CNS, less is known about how the endocannabinoid signaling system (eCBSS) influence the microglial phenotype. The general aim of the present study was to investigate the role of endocannabinoids in microglia polarization by using microglia cell cultures. We show that alternative microglia (M2a) and acquired deactivated microglia (M2c) exhibit changes in the eCB machinery that favor the selective synthesis of 2-AG and AEA, respectively. Once released, these eCBs might be able to act through CB1 and/or CB2 receptors in order to influence the acquisition of an M2 phenotype. We present three lines of evidence that the eCBSS is critical for the acquisition of the M2 phenotype: (i) M2 polarization occurs on exposure to the two main endocannabinoids 2-AG and AEA in microglia cultures; (ii) cannabinoid receptor antagonists block M2 polarization; and (iii) M2 polarization is dampened in microglia from CB2 receptor knockout mice. Taken together, these results indicate the interest of eCBSS for the regulation of microglial activation in normal and pathological conditions.     

Stress sounds the alarmin: The role of the danger-associated molecular pattern HMGB1 in stress-induced neuroinflammatory priming

High mobility group box-1 (HMGB1) is an endogenous danger signal or alarmin that mediates activation of the innate immune response including chemotaxis and pro-inflammatory cytokine release. HMGB1 has been implicated in the pathophysiology of several neuroinflammatory conditions including ischemia, traumatic brain injury, seizure and chronic ethanol use. In the present review, the unique structural and functional properties of HMGB1 will be explored including its affinity for multiple pattern recognition receptors (TLR2/TLR4), redox sensitivity and adjuvant-like properties. In light of recent evidence suggesting that HMGB1 may also mediate stress-induced sensitization of neuroinflammatory responses, mechanisms of HMGB1 action in neuroinflammatory priming are explored. A model of neuroinflammatory priming is developed wherein glucocorticoids induce synthesis and release of HMGB1 from microglia, which signals through TLR2/TLR4, thereby priming the NLRP3 inflammasome. We propose that if GCs reach a critical threshold as during a fight/flight response, they may thus function as an alarmin by inducing HMGB1, thereby preparing an organism’s innate immune system (NLRP3 inflammasome priming) for subsequent immune challenges such as injury, trauma or infection, which are more likely to occur during a fight/flight response. In doing so, GCs may confer a significant survival advantage by enhancing the central innate immune and sickness response to immune challenges.     

CORM-3介导小胶质细胞ICAM-1抑制放射性脑损伤炎症反应

目的本研究旨在探讨水溶性一氧化碳分子释放剂(CORM-3)对放射性脑损伤炎症反应的影响及其分子机制。方法 BV2系小胶质细胞,随机分为正常对照组、单纯照射组和照射加CORM干预组,通过ELISA法测定各组照射后24 h炎症因子TNF-α、IL-1β的表达情况;采用免疫荧光法判断各组小胶质细胞激活形态,TUNEL染色比较各组共培养后原代神经元凋亡情况,并用Western blot法检测P38 MAPK通路对CORM干预放射后细胞间黏附分子1(ICAM-1)蛋白表达的影响。结果 BV2细胞放射后24 h TNF-α、IL-1β表达明显增高;CORM-3可减轻放射后小胶质细胞活化程度及炎症表达,降低了放射后TUNEL阳性细胞百分比;CORM-3抑制了放射后BV2细胞磷酸化P38及ICAM-1蛋白的表达增加,而P38抑制剂进一步下调放射后BV2细胞ICAM-1的表达。结论 CORM-3通过P38 MAPK-ICAM-1通路抑制内源性小胶质细胞活化和外源性白细胞趋化的双重调控方式改善放射后脑损伤炎症反应,进而减轻放射后炎症所致神经元损伤,这为改善鼻咽癌放疗后脑损伤的治疗提供了有潜在前景的新途径。     

AMPK对氧糖剥夺再灌注后小胶质细胞介导炎性反应的影响

目的：探讨氧糖剥夺再灌注（OGD／R）损伤后腺苷酸活化蛋白激酶（AM PK ）对小胶质细胞介导的炎性介质释放及信号传导的影响。方法培养BV2细胞株,应用OGD 6 h再灌注24 h建立缺血再灌注损伤离体模型,AICAR（5μmol／L、50μmol／L、100μmol／L）或 Compound C（0．1μmol／L、1μmol／L、10μmol／L）不同程度激活或抑制AMPK磷酸化,MTT法检测细胞活性,免疫印迹及ELISA方法,检测OGD／R后BV2细胞AMPK活性变化,以及对NF－κB信号通路中IκB磷酸化、TNF－α释放的影响。结果各浓度AICAR均能够促进OGD／R后BV2细胞存活（P ＜0．05）,抑制IκB磷酸化水平（P ＜0．05）,AICAR（100μmol／L）能够增加AMPK磷酸化水平（P ＜0．05）,抑制TNF －α的释放（P＜0．01）。而Compound C（10μmol／L）促进BV2细胞死亡（P＜0．01）,降低OGD／R后AMPK及IκB磷酸化水平（P ＜0．05）,促进 TNF －α释放（P ＜0．05）。结论 AMPK 磷酸化激活能够减轻OGD／R后BV2细胞介导的炎性损伤作用,而抑制AM PK磷酸化能够加重神经炎性反应。     

The inflammatory event of birth: How oxytocin signaling may guide the development of the brain and gastrointestinal system

The role of oxytocin (OT) as a neuropeptide that modulates social behavior has been extensively studied and reviewed, but beyond these functions, OT’s adaptive functions at birth are quite numerous, as OT coordinates many physiological processes in the mother and fetus to ensure a successful delivery. In this review we explore in detail the potential adaptive roles of oxytocin as an anti-inflammatory, protective molecule at birth for the developing fetal brain and gastrointestinal system based on evidence that birth is a potent inflammatory/immune event. We discuss data with relevance for a number of neurodevelopmental disorders, as well as the emerging role of the gut-brain axis for health and disease. Finally, we discuss the potential relevance of sex differences in OT signaling present at birth in the increased male vulnerability to neurodevelopmental disabilities.     

Corticosterone-mediated microglia activation affects dendritic spine plasticity and motor learning functions in minimal hepatic encephalopathy

Minimal hepatic encephalopathy (MHE) is characterized as cognitive deficits including memory and learning dysfunctions after liver injuries or hepatic diseases. Our understandings of neurological mechanisms of MHE-associated cognitive syndromes, however, are far from complete. In the current study we generated a mouse MHE model by repetitive administrations of thioacetamide (TAA), which induced hyperammonemia plus elevated proinflammatory cytokines in both the general circulation and motor cortex. MHE mice presented prominent motor learning deficits, which were associated with excess dendritic spine pruning in the motor cortex under 2-photon in vivo microscopy. The pharmaceutical blockade of glucocorticoid receptor or suppression of its biosynthesis further rescued motor learning deficits and synaptic protein loss. Moreover, MHE mice presented microglial activation, which can be alleviated after glucocorticoid pathway inhibition. In sum, our data demonstrates corticosterone-induced microglial activation, synaptic over-pruning and motor learning impairments in MHE, providing new insights for MHE pathogenesis and potential targets of clinical interventions.     

白藜芦醇对氧糖剥夺/再复氧损伤后体外小胶质细胞极化的影响

目的 探讨白藜芦醇对氧糖剥夺/再复氧损伤（OGD/R）后小胶质细胞极化的影响。方法 对体外培养的N9小胶质细胞进行氧糖剥夺150 min，复氧培养24 h。实验分为正常组、对照组和白藜芦醇预处理24 h组。细胞计数盒-8(CCK-8)法检测细胞活力，硫代巴比妥酸（TBA）和水溶性四唑盐（WST-1）法分别检测细胞上清液中丙二醛（MDA）含量和总超氧化物歧化酶（SOD）活性，免疫荧光法检测核因子-E2-相关因子2（Nrf2）的核移位，Western blotting和Real-time PCR法检测CD206、诱导型一氧化氮合酶（iNOS）、Nrf2、血红素加氧酶1（HO-1）和苯醌还原酶（NQO1）蛋白和mRNA表达水平。 结果 OGD/R损伤后，白藜芦醇组细胞活力、SOD活力、CD206、Nrf2、HO-1、NQO1蛋白或mRNA表达均显著高于对照组（P<0.05,n=3），而MDA含量和iNOS蛋白或mRNA表达均显著低于对照组（P<0.05,n=3），白藜芦醇组Nrf2 蛋白较对照组明显移位到细胞核。 结论 白藜芦醇预处理可能通过增强Nrf2的激活，调控M1/M2型小胶质细胞极化，从而减轻OGD/R后小胶质细胞的氧化应激损伤。