实验性血管性痴呆小鼠中枢神经系统细胞凋亡与迟发性神经元坏死

目的:探讨实验性血管性痴呆小鼠中枢神经系统细胞凋亡与迟发性神经元坏死的关系。方法:实验于1998-01/1999-07在白求恩医科大学实验动物中心完成。选用6～7周龄雄性昆明小鼠40只,随机分为假手术组和缺血再灌流组;假手术组5只作为对照,缺血再灌流组根据再灌注提取标本的时间不同并分7组,即术后1h,1,3,7,14,28,42d组,每小组5只。制备动物模型,选用跳台,避暗反应等行为学检测确定。评价采用卒中指数评分和神经病学症状评分标准。制作病理切片,应用光镜,电镜,流式细胞仪,原位末端标记等方法检测神经细胞凋亡在不同时间缺血再灌注时与迟发性神经元坏死发生、发展关系。结果:在整个实验过程中无动物死亡,全部进入结果分析。①动物模型卒中指数及神经病学指数评价:缺血再灌注1d时卒中指数及神经病学指数与对照组比较差异显著(3.5±0.53,0,P<0.05),(4.6±0.54,0,P<0.05)。②各组病理形态学改变:重复缺血再灌注24h神经细胞间质水肿,核浓染固缩,顶树突延长。再灌注3d,皮质少量小胶质细胞增生,海马可见颗粒细胞变性呈空泡样。再灌注7d,皮质胶质细胞增生聚集成堆,海马CA1区锥体细胞变性,部分坏死。再灌注28d,皮质神经细胞大量缺失代之胶质细胞,海马CA1、CA4区锥体细胞大量缺失、变性、坏死。电镜观察可见细胞核基质肿胀,破坏。排列紊乱,并有空泡形成。粗面内质网扩张,小胶质细胞核染色质凝聚,可见变形。③额叶、海马区细胞凋亡变化:重复缺血再灌注3d流式细胞仪检测额叶皮质、海马神经细胞凋亡百分率最高。随再灌注时间的延长,海马神经细胞凋亡数逐渐下降至42d最低点。各不同时间点再灌注细胞凋亡数百分比与对照组比较差异显著性(P<0.05)。原位末端标记法正常阳性对照组可见少量散在阳性细胞,缺血再灌注1h后原位末端标记法染色阳性细胞增多,3d后皮质、海马阳性细胞明显增多达高峰,核固缩,染色质聚集,一些细胞可见凋亡小体,阳性染色细胞核呈深棕色,缺血再灌注7d时皮质、海马区阳性细胞逐渐减少。至再灌注42d时阳性细胞数略有增多,但仍少于再灌注3d。电镜下受累神经细胞多单个存在,早期为染色质固缩,常聚集于核膜呈境界分明的颗粒、块状或新月形小体,细胞浆浓缩。核内细胞器和致密染色质保持完整。细胞周围无炎性细胞浸润。结论:脑缺血再灌注损伤全过程中均伴随着神经细胞凋亡,但细胞凋亡的高峰期在缺血再灌注后的两三天,随缺血再灌注时间延长,神经细胞坏死加重,凋亡数量减少。迟发性神经元死亡是通过细胞凋亡完成的,且细胞凋亡作为一种主要表现形式。

Maresin 1 alleviates neuroinflammation and cognitive decline in a mouse model of cecal ligation and puncture

Objective:Inflammation in the central nervous system plays a crucial role in the occurrence and development of sepsis-associated encephalopathy.This study aims to explore the effects of maresin 1(MaR1),an anti-inflammatory and pro-resolving lipid mediator,on sepsis-induced neuroinflammation and cognitive impairment.Methods:Mice were randomly assigned to 4 groups:A sham group(sham operation+vehicle),a cecal ligation and puncture(CLP)group(CLP operation+vehicle),a MaR1-LD group(CLP operation+1 ng MaR1),and a MaR1-HD group(CLP operation+10 ng MaR1).MaR1 or vehicle was intraperitoneally administered starting 1 h before CLP operation,then every other day for 7 days.Survival rates were monitored,and serum inflammatory cytokines[tumor necrosis factor alpha(TNF-α),interleukin(IL)-1β,and IL-6]were measured 24 h after operation using enzyme-linked immunosorbent assay(ELISA).Cognitive function was assessed 7 days after operation using the Morris water maze(MWM)test and novel object recognition(NOR)task.The mRNA expression of TNF-α,IL-1β,IL-6,inducible nitric oxide synthase(iNOS),IL-4,IL-10,and arginase 1(Arg1)in cortical and hippocampal tissues was determined by real-time reverse transcription PCR(RT-PCR).Western blotting was used to determine the protein expression of iNOS,Arg1,signal transducer and activator of transcription 6(STAT6),peroxisome proliferator-activated receptor gamma(PPARγ),and phosphorylated STAT6(p-STAT6)in hippocampal tissue.Microglia activation was visualized via immunofluorescence.Mice were also treated with the PPARγantagonist GW9662 to confirm the involvement of this pathway in MaR1’s effects.Results:CLP increased serum levels of TNF-α,IL-1β,and IL-6,and reduced body weight and survival rates(all P<0.05).Both 1 ng and 10 ng doses of MaR1 significantly reduced serum TNF-α,IL-1β,and IL-6 levels,improved body weight,and increased survival rates(all P<0.05).No significant difference in efficacy was observed between the 2 doses(all P>0.05).MWM test and NOR task indicated that CLP impaired spatial learning,which MaR1 mitigated.However,GW9662 partially reversed MaR1’s protective effects.Real-time RTPCR results demonstrated that,compared to the sham group,mRNA expression of TNF-α,IL-1β,and iNOS significantly increased in hippocampal tissues following CLP(all P<0.05),while IL-4,IL-10,and Arg1 showed a slight decrease,though the differences were not statistically significant(all P>0.05).Compared to the CLP group,both 1 ng and 10 ng MaR1 decreased TNF-α,IL-1β,and iNOS mRNA expression in hippocampal tissues and increased IL-4,IL-10,and Arg1 mRNA expression(all P<0.05).Immunofluorescence results indicated a significant increase in Iba1-positive microglia in the hippocampus after CLP compared to the sham group(P<0.05).Administration of 1 ng and 10 ng MaR1 reduced the percentage area of Iba1-positive cells in the hippocampus compared to the CLP group(both P<0.05).Western blotting results showed that,compared to the CLP group,both 1 ng and 10 ng MaR1 down-regulated the iNOS expression,while up-regulated the expression of Arg1,PPARγ,and p-STAT6(all P<0.05).However,the inclusion of GW9662 counteracted the MaR1-induced upregulation of Arg1 and PPARγcompared to the MaR1-LD group(all P<0.05).Conclusion:MaR1 inhibits the classical activation of hippocampal microglia,promotes alternative activation,reduces sepsis-induced neuroinflammation,and improves cognitive decline.

Triptolide protects against 1-methyl-4-phenyl pyridinium-induced dopaminergic neurotoxicity in rats:Implication for immunosuppressive therapy in Parkinson’s disease

Objective Neuroinflammation with microglial activation has been implicated to have a strong association with the progressive dopaminergic neuronal loss in Parkinson＇s disease （PD）. The present study was undertaken to evaluate the activation profile of microglia in 1-methyl-4-phenyl pyridinium （MPP^＋）-induced hemiparkinsonian rats. Triptolide, a potent immunosuppressant and microglia inhibitor, was then examined for its efficacy in protecting dopaminergic neurons from injury and ameliorating behavioral disabilities induced by MPP^＋. Methods The rat model of PD was established by intranigral microinjection of MPP^＋. At baseline and on day 1, 3, 7, 14, 21 following MPP^＋ injection, the degree of microglial activation was examined by detecting the immunodensity of OX-42 （microglia marker） in the substantia nigra （SN）. The number of viable dopaminergic neurons was determined by measuring tyrosine hydroxylase （TH） positive neurons in the SN. Behavioral performances were evaluated by counting the number of rotations induced by apomorphine, calculating scores of forelimb akinesia and vibrissae-elicited forelimb placing asymmetry. Results Intranigral injection of MPP^＋ resulted in robust activa- tion of microglia, progressive depletion of dopaminergic neurons, and ongoing aggravation of behavioral disabilities in rats. Triptolide significantly inhibited microglial activation, partially prevented dopaminergic cells from death and improved behavioral performances. Conclusion These data demonstrated for the first time a neuroprotective effect of triptolide on dopaminergic neurons in MPP^＋ induced hemiparkinsonian rats. The protective effect of triptolide may, at least partially, be related to the inhibition of MPP^＋-induced microglial activation. Our results lend strong support to the use of immunosuppressive agents in the management of PD.

Thrombin-induced microglial activation contributes to the degeneration of nigral dopaminergic neurons in vivo

Objective To evaluate the role of thrombin-activated microglia in the neurodegeneration of nigral dopaminergic neurons in the rat substantia nigra （SN） in vivo. Methods After stereotaxic thrombin injection into unilateral SN of rats, immunostaining, reverse transcription polymerase chain reaction （RT-PCR） and biochemical methods were used to observe tyrosine hydroxylase （TH） irnmunoreactive positive cells, microglia activation, nitric oxide （NO） amount and inducible nitricoxide synthase （iNOS） expression. Results （1） Selective damage to dopaminergic neurons was produced after thrombin injection, which was evidenced by loss of TH imrnunostaining in time-dependent manner; （2） Strong microglial activation was observed in the SN; （3） RT-PCR demonstrated the early and transient expression of neurotoxic factors iNOS mRNA in the SN. Immunofluorescence results found that thrombin induced expression of iNOS in microglia. The NO production in the thrombininjected rats was significantly higher than that of controls （P 〈 0.05）. Conclusion Thrombin intranigral injection can injure the dopaminergic neurons in the SN. Thrombin-induced microglia activation precedes dopaminergic neuron degeneration, which suggest that activation of microglia and release of NO may play important roles in dopaminergic neuronal death in the SN.

Cyclooxygenase-2 inhibitor inhibits hippocampal synaptic reorganization in pilocarpine-induced status epilepticus rats

Objective： To examine modulations caused by cyclooxygenase-2 （COX-2） inhibitors on altered microenvironments and overbalanced neurotransmitters in pilocarpine-induced epileptic status rats and to investigate possible mechanisms. Methods： Celecoxib （a COX-2 inhibitor） was administered 45 min prior to pilocarpine administration. The effects of COX-2 inhibitors on mlPSCs （miniature GABAergic inhibitory postsynaptic currents） of CA3 pyramidal cells in the hippocampus were recorded. Expressions of COX-2, c-Fos, newly generated neurons, and activated microgliosis were analyzed by immunohistochemistry, and expressions of c^-subunit of y-amino butyric acid （GABAA） receptors and mitogen-activated protein kinase/extracellular signal-regulated protein kinase （MAPK/ERK） activity were detected by Western blotting. Results： Pretreatment with celecoxib showed protection against pilocarpine-induced seizures. Celecoxib prevented microglia activation in the hilus and inhibited the abnormal neurogenesis and astrogliosis in the hippocampus by inhibiting MAPK/ERK activity and c-Fos transcription. Celecoxib also up-regulated the expression of GABAA receptors. NS-398 （N-2-cyclohexyloxy-4-nitrophenyl-methanesulfonamide）, another COX-2 inhibitor, enhanced the frequency and decay time of mIPSCs. Conclusion： The COX-2 inhibitor celecoxib decreased neuronal excitability and prevented epileptogenesis in pilocarpine-induced status epilepticus rats. Celecoxib regulates synaptic reorganization by inhibiting astrogliosis and ectopic neurogenesis by attenuating MAPK/ERK signal activity, mediated by a GABAergic mechanism.

Lipopolysaccharide preconditioning induces protection against lipopolysac-charide -induced neurotoxicity in organotypic midbrain slice culture

Objective To identify the protective effect of lipopolysaccharide （LPS） preconditioning against LPS-induced inflammatory damage in dopaminergic neurons of midbrain slice culture and the possible mechanisms. Methods After cultured in vitro for 14 d, the rat organotypic midbrain slices were pretreated with different concentrations （0, 1, 3, 6 or 10 ng/mL） of LPS for 24 h followed by treatment with 100 ng/mL LPS for 72 h. The whole slice viability was detelmined by measurement of the activity of lactic acid dehydrogenase （LDH）. Tyrosine hydroxylase-immunoreactive （TH-IR） neurons and CD 1 1 b/c equivalent-immunoreactive （OX-42-IR） microglia in the slices were observed by immunohistochemical method, and tumor necrosis factor-α （TNF-α levels in the culture media were detected by enzymelinked immunosorbent assays （ELISA）. Results In the slices treated with 100 ng/mL LPS for 72 h, the number of TH-IR neurons reduced from 191± 12 in the control slices to 46±4, and the LDH activity elevated obviously （P 〈 0.01）, along with remarkably increased number of OX-42-IR cells and production of TNF-α （P 〈 0.01）. Preconditioning with 3 or 6 ng/mL LPS attenuated neuron loss （the number of TH-IR neurons increased to 126± 12 and 180± 13, respectively） and markedly reduced LDH levels （P 〈 0.05）, accompanied by significant decreases of OX-42-IR microglia activation and TNF-α production （P 〈 0.05）. Conclusion Low-dose LPS preconditioning could protect dopaminergic neurons against inflammatory damage in rat midbrain slice culture, and inhibition of microglial activation and reduction of the proinflammatory factor TNF-α production may contribute to this protective effect. Further understanding the underlying mechanism of LPS preconditioning may open a new window for treatment of Parkinson＇s disease.

NMDA receptor antagonist MK-801 reduces neuronal damage and preserves learning and memory in a rat model of traumatic brain injury

Objective NMDA receptor channel plays an important role in the pathophysiological process of traumatic brain injury （TBI）. The present study aims to study the pathological mechanism of TBI and the impairment of learning and memory after TBI, and to investigate the mechanism of the protective effect of NMDA receptor antagonist MK-801 on learning and memory disorder after TBI. Methods Forty Sprague-Dawley rats （weighing approximately 200 g） were randomized into 5 groups （n = 8 in each group）： control group, model group, low-dose group （MK-801 0.5 mg/kg）, middle-dose group （MK-801 2 mg/kg）, and high-dose group （MK-801 10 mg/kg）. TBI model was established using a weight-drop head injury mode. After 2-month drug treatment, learning and memory ability was evaluated by using Morris water maze test. Then the animals were sacrificed, and brain tissues were taken out for morphological and immunohistochemical assays. Results The ability of learning and memory was significantly impaired in the TBI model animals. Besides, the neuronal caspase-3 expression, neuronal nitric oxide synthase （nNOS）-positive neurons and OX-42-positive microglia were all increased in TBI animals. Meanwhile, the number of neuron synapses was decreased, and vacuoles degeneration could be observed in mitochondria. After MK-801 treatment at 3 different dosages, the ability of learning and memory was markedly improved, as compared to that of the TBI model animals. Moreover, neuronal caspase-3 expression, OX-42-positive microglia and nNOS-positive neurons were all significantly decreased. Meanwhile, the mitochondria degeneration was greatly inhibited. Conclusion MK-801 could significantly inhibit the degeneration and apoptosis of neurons in damaged brain areas. It could also inhibit TBI-induced increase in nNOS-positive neurons and OX-42-positive microglia. Impairment in learning and memory in TBI animals could be repaired by treatment with MK-801.

P2Y6 receptor and immunoinflammation

The immunocytes microglia in the central nervous system （CNS） were reported to play a crucial role in neurodegeneration. As a member of P2 receptors family, purinoceptor P2Y6 has attracted much attention recently. Previous studies showed that purinoceptor P2Y6 mainly contributed to microglia activation and their later phagocytosis in CNS, while in immune system, it participated in the secretion of interleukin （IL）-8 from monocytes and macrocytes. So there raises a question： whether purinoceptor P2Y6 also takes part in neuroinflammation？ Thus, this review mainly concerns about the properties and roles of purinoceptor P2Y6, including （1） structure of purinoceptor P2Y6; （2） distribution and properties of purinoceptor P2Y6; （3） relationships between purinoceptor P2Y6 and microglia; （4） relationships between purinoceptor P2Y6 and immunoinflammation. It＇s proposed that purinoceptor P2Y6 may play a role in neuroinflammation in CNS, although further research is still required.

2-Hydroxycircumdatin C inhibits LPS-induced BV2 cells inflammatory response via down-regulation of TLR4-mediated NF-κB/MAPK and JAK2/STAT3 pathways

2-Hydroxycircumdatin C(2-HCC) is a circumdatin-type alkaloid isolated from a coral-associated fungus Aspergillus ochraceus LZDX-32-15.In the present study,we aimed to assess the neuroprotective effects of 2-HCC on the microglia-mediated inflammatory response as well as underlining molecular mechanisms.2-HCC could significantly down-regulate the overproduction of tumor necrosis factor-α(TNF-α) and interleukin-1β(IL-1β) induced by lipopolysaccharide(LPS) both in BV2 cells and primary microglial cells without affecting cell viability.In addition,2-HCC exerted obvious neuroprotective effects against inflammatory injury in neurons when cocultured with LPS-induced microglia.Mechanism investigation indicated that the anti-inflammatory effect of 2-HCC involved the inhibition of inducible nitric oxide synthase(iNOS) and cyclooxygenase 2(COX-2) and alleviation of the LPS-induced TLR4-NF-κB/MAPK pathway.Furthermore,2-HCC treatment attenuated LPS-induced activation of the JAK2/STAT3 pathway.In conclusion,these results indicated that the anti-inflammatory and neuroprotective properties of 2-HCC,at least partially,depended upon TLR4-NF-κB/MAPK and JAK2/STAT3 signaling pathways.

DGMI alleviates OGD/R-induced cell injury by regulating inflammatory and apoptosis signaling pathways

Diterpene ginkgolides meglumine injection(DGMI),a kind of Ginkgo biloba special extract injection,is now used for the treatment of ischemic stroke in convalescence.In the present study,we aimed to confirm whether DGMI could suppress inflammatory responses and apoptosis and explore the potential mechanisms underlying these effects.Cell viability and lactate dehydrogenase(LDH)release were measured by MTS and LDH assays after the cells were exposed to oxygen-glucose deprivation/reoxygenation(OGD/R).The extent of anti-apoptotic effect of DGMI was detected by flow cytometry using Annexin V-FITC/PI double staining assay kit.Pro-inflammatory cytokines,including TNF-α,IL-1β,IL-6 and IL-10,were quantified by a specific Bio-Plex ProTM Reagent Kit.Additionally,activities of TLR2/4,NF-κB p65,MAPK pathway and apoptosis-related proteins as well as cellular localization of NF-κB p65 were determined by Western blotting analysis and immunofluorescence staining,respectively.DGMI at 50μg/mL significantly increased the cell viability and decreased the secretion of IL-1β,IL-6,IL-10 and TNF-αin OGD/R-induced BV2 microglia cells.These effects were also confirmed by LDH assay and Annexin V-FITC/PI staining.Meanwhile,DGMI not only inhibited the protein expressions of TLR2,TLR4,MyD88,p-TAK1,p-IkBα,p-IKKβand Bak,but also decreased the cleaved caspase-3/caspase-3,Bax/Bcl-2 and cleaved PARP-1/PARP-1 ratio in OGD/R-induced BV2 microglia cells.Furthermore,OGD/R-enhanced p-JNK1/2 and p-p38 MAPK expressions and nuclear translocation of NF-κB p65 were also partially inhibited by DGMI.The present study showed that inflammatory responses were triggered in BV2 microglia cells activated by OGD/R,leading to the release of pro-inflammatory cytokines and apoptosis.DGMI suppressed the inflammatory response and apoptosis by regulating the TLR/MyD88/NF-κB signaling pathways and down-regulation of p-JNK1/2 and p-p38 MAPK activation.

Regulatory mechanisms and therapeutic potential of microglial inhibitors in neuropathic pain and morphine tolerance

Microglia are important cells involved in the regulation of neuropathic pain(NPP)and morphine tolerance.Information on their plasticity and polarity has been elucidated after determining their physiological structure,but there is still much to learn about the role of this type of cell in NPP and morphine tolerance.Microglia mediate multiple functions in health and disease by controlling damage in the central nervous system(CNS)and endogenous immune responses to disease.Microglial activation can result in altered opioid system activity,and NPP is characterized by resistance to morphine.Here we investigate the regulatory mechanisms of microglia and review the potential of microglial inhibitors for modulating NPP and morphine tolerance.Targeted inhibition of glial activation is a clinically promising approach to the treatment of NPP and the prevention of morphine tolerance.Finally,we suggest directions for future research on microglial inhibitors.

Human endogenous retrovirus W env increases nitric oxide production and enhances the migration ability of microglia by regulating the expression of inducible nitric oxide synthase

Human endogenous retrovirus W env(HERV-W env) plays a critical role in many neuropsychological diseases such as schizophrenia and multiple sclerosis(MS). These diseases are accompanied by immunological reactions in the central nervous system(CNS). Microglia are important immunocytes in brain inflammation that can produce a gasotransmitter – nitric oxide(NO). NO not only plays a role in the function of neuronal cells but also participates in the pathogenesis of various neuropsychological diseases. In this study, we reported increased NO production in CHME-5 microglia cells after they were transfected with HERV-W env. Moreover, HERV-W env increased the expression and function of human inducible nitric oxide synthase(hi NOS) and enhanced the promoter activity of hi NOS. Microglial migration was also enhanced. These data revealed that HERV-W env might contribute to increase NO production and microglial migration ability in neuropsychological disorders by regulating the expression of inducible NOS. Results from this study might lead to the identification of novel targets for the treatment of neuropsychological diseases, including neuroinflammatory diseases, stroke, and neurodegenerative diseases.