Effects of concentrated ambient ultrafine particulate matter on hallmarks of Alzheimer’s disease in the 3xTgAD mouse model

BackgroundExposure to air pollution has been identified as a possible environmental contributor to Alzheimer’s Disease (AD) risk. As the number of people with AD worldwide continues to rise, it becomes vital to understand the nature of this potential gene-environment interaction. This study assessed the effects of short-term exposures to concentrated ambient ultrafine particulates (UFP, <100 nm) on measurements of amyloid-β, tau, and microglial morphology.MethodsTwo cohorts of aged (12.5–14 months) 3xTgAD and NTg mice were exposed to concentrated ambient UFP or filtered air for 2 weeks (4-h/day, 4 days/week). Bronchoalveolar lavage fluid and brain tissue were collected twenty-four hours following the last exposure to evaluate lung inflammation, tau pathology, amyloid-β pathology, and glial cell morphology.ResultsNo exposure- or genotype-related changes were found with any of the measures of lung inflammation or in the hippocampal staining density of astrocyte marker glial fibrillary acidic protein. The microglia marker, ionized calcium binding adaptor molecule 1, and amyloid-β marker, 6E10, exhibited significant genotype by exposure interactions such that levels were lower in the UFP-exposed as compared to filtered air-exposed 3xTgAD mice. When microglia morphology was assessed by Sholl analysis, microglia from both NTg mouse groups were ramified. The 3xTgAD air-exposed mice had the most ameboid microglia, while the 3xTgAD UFP-exposed mice had microglia that were comparatively more ramified. The 3xTgAD air-exposed mice had more plaques per region of interest as measured by Congo red staining as well as more plaque-associated microglia than the 3xTgAD UFP-exposed mice. The number of non-plaque-associated microglia was not affected by genotype or exposure. Levels of soluble and insoluble human amyloid-β₄₂ protein were measured in both 3xTgAD groups and no exposure effect was found. In contrast, UFP-exposure led to significant elevations in phosphorylated tau in 3xTgAD mice as compared to those that were exposed to air, as measured by pT205 staining.ConclusionsExposure to environmentally relevant levels of ultrafine particulates led to changes in tau phosphorylation and microglial morphology in the absence of overt lung inflammation. Such changes highlight the need to develop greater mechanistic understanding of the link between air pollution exposure and Alzheimer’s disease.     

Gene expression changes in aging retinal microglia: relationship to microglial support functions and regulation of activation

Microglia, the resident immune cells of the central nervous system (CNS), are thought to contribute to the pathogenesis of age-related neurodegenerative disorders. It has been hypothesized that microglia undergo age-related changes in gene expression patterns that give rise to pathogenic phenotypes. We compared the gene expression profiles in microglia isolated ex vivo from the retinas of mice ranging from early adulthood to late senescence. We discovered that microglial gene expression demonstrated progressive change with increasing age, and involved genes that regulate microglial supportive functions and immune activation. Molecular pathways involving immune function and regulation, angiogenesis, and neurotrophin signaling demonstrated age-related change. In particular, expression levels of complement genes, C3 and CFB, previously associated with age-related macular degeneration (AMD), increased with aging, suggesting that senescent microglia may contribute to complement dysregulation during disease pathogenesis. Taken together, senescent microglia demonstrate age-related gene expression changes capable of altering their constitutive support functions and regulation of their activation status in ways relating to neuroinflammation and neurodegeneration in the CNS.     

Neuroinflammatory phenotype in early Alzheimer's disease

Alzheimer's disease (AD) involves progressive neurodegeneration in the presence of misfolded proteins and poorly-understood inflammatory changes. However, research has shown that AD is genetically, clinically, and pathologically heterogeneous. In frozen brain samples of frontal cortex (diseased) and cerebellum (nondiseased) from the University of Kentucky Alzheimer's Disease Center autopsy cohort, we performed gene expression analysis for genes categorizing inflammatory states (termed M1 and M2) from early and late stage AD, and age-matched nondemented controls. We performed analysis of the serum samples for a profile of inflammatory proteins and examined the neuropathologic data on these samples. Striking heterogeneity was found in early AD. Specifically, early-stage AD brain samples indicated apparent polarization toward either the M1 or M2 brain inflammatory states when compared with age-matched nondisease control tissue. This polarization was observed in the frontal cortex and not in cerebellar tissue. We were able to detect differences in AD neuropathology, and changes in serum proteins that distinguished the individuals with apparent M1 versus M2 brain inflammatory polarization.     

Efecto de la exposición a bajas dosis de ozono en la expresión de la interleucina 17A durante el proceso de neurodegeneración progresiva en el hipocampo de ratas

IntroductionChronic exposure to low doses of ozone causes oxidative stress and loss of regulation of the inflammatory response, leading to progressive neurodegeneration.ObjectiveWe studied the effect of chronic exposure to low doses of ozone on IL-17A concentration and expression in neurons, microglia, astrocytes, and T cells in the rat hippocampus.MethodsWe used 72 Wistar rats, divided into 6 groups (n = 12): a control group (no ozone exposure) and 5 groups exposed to ozone (0.25 ppm, 4 h daily) for 7, 15, 30, 60, and 90 days. We processed 6 rats from each group to quantify IL-17A by ELISA; the remaining 6 were processed for immunohistochemistry (against IL-17A and GFAP, Iba1, NeuN, and CD3).ResultsThe ELISA study data showed a significant increase in IL-17A concentrations in the 7-, 15-, 30-, and 60-day exposure groups, with regard to the control group (P < .05). Furthermore, they indicate that hippocampal neurons were the cells showing greatest immunoreactivity against IL-17A between 60 and 90 days of exposure to ozone; we also observed an increase in activated astrocytes in the 30- and 60-day exposure groups.ConclusionExposure to ozone in rats induces an increase in IL-17A expression, mainly in hippocampal neurons, accompanied by hippocampal astrocyte activation during chronic neurodegeneration, similar to that observed in Alzheimer disease in humans.     

Graded peripheral nerve injury creates mechanical allodynia proportional to the progression and severity of microglial activity within the spinal cord of male mice

The reactivity of microglia within the spinal cord in response to nerve injury, has been associated with the development and maintenance of neuropathic pain. However, the temporal changes in microglial reactivity following nerve injury remains to be defined. Importantly, the magnitude of behavioural allodynia displayed and the relationship to the phenotypic microglial changes is also unexplored. Using a heterozygous CX₃CR₁ ^gfp+ transgenic mouse strain, we monitored microglial activity as measured by cell density, morphology, process movement and process length over 14 days following chronic constriction of the sciatic nerve via in vivo confocal microscopy. Uniquely this relationship was explored in groups of male mice which had graded nerve injury and associated graded behavioural mechanical nociceptive sensitivity. Significant mechanical allodynia was quantified from the ipsilateral hind paw and this interacted with the extent of nerve injury from day 5 to day 14 (p < 0.009). The extent of this ipsilateral allodynia was proportional to the nerve injury from day 5 to 14 (Spearman rho = −0.58 to −0.77; p < 0.002). This approach allowed for the assessment of the association of spinal microglial changes with the magnitude of the mechanical sensitivity quantified behaviourally. Additionally, the haemodynamic response in the somatosensory cortex was quantified as a surrogate measure of neuronal activity. We found that spinal dorsal horn microglia underwent changes unilateral to the injury in density (Spearman rho = 0.47; p = 0.01), velocity (Spearman rho = −0.68; p = 0.00009), and circularity (Spearman rho = 0.55; p = 0.01) proportional to the degree of the neuronal injury. Importantly, these data demonstrate for the first time that the mechanical allodynia behaviour is not a binary all or nothing state, and that microglial reactivity change proportional to this behavioural measurement. Increased total haemoglobin levels in the somatosensory cortex of higher-grade injured animals was observed when compared to sham controls suggesting increased neuronal activity in this brain region. The degree of phenotypic microglial changes quantified here, may explain how microglia can induce both rapid onset and sustained functional changes in the spinal cord dorsal horn, following peripheral injury.     

粒细胞集落刺激因子通过调节小胶质细胞活化改善缺氧致脑室周围白质损伤

目的 探讨粒细胞集落刺激因子通过影响小胶质细胞的活化对缺氧导致的脑室周围白质损伤（PWMD）的保护作用。方法 将1d龄新生小鼠108只随机分为对照组、损伤组及治疗组,后两组经缺氧箱缺氧法制备脑室周围白质损伤模型,造模前及造模后2h给予治疗组存活鼠腹腔注射粒细胞集落刺激因子,之后每日1次,1d、3d、7d后各处死3组部分动物。取全脑切片进行免疫荧光双标检测小胶质细胞的募集以及炎性因子的分泌情况;取脑室周围白质,采用酶联免疫吸附剂测定法检测炎性因子分泌水平;利用RT-PCR法检测致炎因子和抑炎因子的分泌以及两类活化小胶质细胞的数量和比例变化情况;治疗组结束给药于7d,分别于5d、8d、10d、12d、30d进行神经行为学实验,观察其感觉运动功能的发育。结果 粒细胞集落刺激因子能够促进小鼠运动功能恢复,改善脑瘫症状,改变活化小胶质细胞中M1型细胞和M2型细胞的数量和比例,使促炎性因子分泌降低,抑炎因子及神经营养因子分泌升高,改善损伤导致的神经发育异常及神经行为缺陷。结论 利用粒细胞集落刺激因子干预脑室周围白质损伤可以抗炎,并可以诱导小胶质细胞向神经保护方向转化,调节炎性因子和神经营养因子的分泌。     

电针预处理对肢体缺血再灌注大鼠生存、脑损伤及认知功能的影响

 目的：观察电针（EA）预处理对肢体缺血再灌注（LI/R）大鼠生存情况、脑损伤及认知功能的影响,探讨相关机制。方法：清洁级、健康成年雄性SD大鼠132 只,体重255～300 g,采用随机数字表法,将其随机分为3 组：假手术(sham)组、LI/R组和LI/R+EA预处理 (LI/R+EA) 组。LI/R组采用动脉夹夹闭双后肢股动脉3 h,建立LI/R模型;sham组只暴露股动脉,不夹闭;LI/R+EA组于模型制备前14 d行电针治疗,针刺穴位为“百会”、“足三里”及“血海”。观察各组大鼠7 d生存率;于再灌注48 h,用Morris水迷宫方法测试大鼠认知功能的变化;其余大鼠于再灌注48 h后处死取材,用干湿重法测定脑含水量;免疫组织化学法测定小胶质细胞标志物Iba1;采用Western blotting检测cleaved caspase-3的表达水平;原位末端标记(TUNEL)法检测神经细胞凋亡并计算凋亡指数;光镜下观察海马病理结构变化;化学法测定活性氧（ROS）、丙二醛（MDA）含量及髓过氧化物酶(MPO)、超氧化物歧化酶(SOD)活性。结果：与sham组比较,LI/R组及LI/R+EA组大鼠7 d生存率下降,潜伏期和游泳距离增加,穿越平台次数减少,海马Iba1阳性细胞数增加,cleaved caspase-3蛋白表达量增加,凋亡指数明显增加,神经元减少,ROS、MDA含量及MPO活性增加,SOD活性降低(P<0.05或P<0.01);与LI/R组相比,LI/R+EA组上述指标得到明显改善(P<0.05或P<0.01)。结论：电针预处理能提高LI/R大鼠生存率,减轻脑损伤及改善大鼠认知功能障碍,其机制可能与抑制小胶质细胞激活、减轻氧化应激损伤有关。     

人参皂苷Rg1对癫痫大鼠海马神经元损伤和小胶质细胞活化的影响

目的探讨人参皂苷Rg1对癫痫大鼠海马神经元损伤和小胶质细胞活化的影响及其作用机制。方法 SD大鼠分为对照组(control组)、癫痫模型组(model组)、人参皂苷Rg1低剂量组(Rg1-L组)和人参皂苷剂量组(Rg1-H组),采用氯化锂-匹罗卡品腹腔注射制备癫痫大鼠模型;记录各组大鼠行为学发作情况;ELISA检测各组大鼠海马组织的氧化应激水平;qRT-PCR检测各组海马组织中炎症因子的表达;HE染色观察各组大鼠海马神经元结构和病理形态变化;免疫荧光组织化学染色检测各组大鼠小胶质细胞中iNOS、Arg-1蛋白表达。结果 model组大鼠症状达到Ⅲ级及Ⅲ级以上较control组显著增加,人参皂苷Rg1使大鼠的癫痫症状得到改善;与control组相比,model组大鼠海马组织中MDA(P<0.001)、TNF-αm RNA(P<0.001)、IL-1βmRNA(P<0.001)的表达水平上调,SOD(P<0.001)、IL-10 m RNA(P<0.001)的表达水平下调,而人参皂苷Rg1使大鼠海马组织中MDA(P<0.05)、TNF-αm RNA(P<0.05)、IL-1βmRNA(P<0.05)的表达水平下调,SOD(P<0.05)、IL-10 mRNA(P<0.05)的表达水平上调;model组大鼠海马神经元形态不完整,细胞间间隙增大和排列紊乱,人参皂苷Rg1组大鼠海马神经元形态明显改变,可见细胞排列较规则,大部分细胞形态正常;model组大鼠海马神经元凋亡率显著上升(P<0.001),人参皂苷Rg1组使大鼠海马神经元凋亡率下降(P<0.05);与control组相比,model组大鼠小胶质细胞数量显著增加(P<0.001),iNOS蛋白的表达显著升高(P<0.001),Arg-1蛋白表达显著降低(P<0.001),与model组相比,人参皂苷Rg1组大鼠小胶质细胞数量减少(P<0.05),iNOS蛋白的表达降低(P<0.05),Arg-1蛋白表达升高(P<0.05)。结论人参皂苷Rg1降低癫痫大鼠海马组织中iNOS蛋白的表达,增加Arg-1蛋白的表达,抑制小胶质细胞的激活,减轻氧化应激和炎症因子的表达,降低癫痫大鼠发作的等级。     

白细胞介素-11在小鼠脑缺血再灌注损伤中的保护作用及其机制

目的探讨白细胞介素-11(interleukin-11,IL-11)在小鼠脑缺血再灌注损伤中的保护作用及机制研究。方法选择SPF级C57BL/6雄性小鼠60只,随机分成为对照组、模型组和IL-11组,每组各20只,通过线栓法构建脑缺血再灌注损伤。应用TTC染色检测脑组织梗死面积,采用Longa评分法评估各组小鼠的神经功能,检测并计算各组小鼠的脑组织含水量。应用Western blot法检测脑组织诱导型一氧化氮合酶(iNOS)、IL-1β、CD206和精氨酸酶(Arginase)-1蛋白表达水平。应用酶联免疫吸附(ELISA)法检测IL-1、IL-6、IL-10和肿瘤坏死因子(TNF)-α水平。免疫荧光双染检测IL-11对小胶质细胞分化的影响。结果与对照组比较,模型组小鼠脑组织梗死面积、含水量和Longa评分均显著升高(均P<0.05);与模型组比较,IL-11组小鼠脑组织梗死面积、含水量和Longa评分均显著减低(均P<0.05);与对照组比较,模型组小鼠M1型小胶质细胞数量明显升高(均P<0.05);与模型组比较,IL-11组小鼠M1型小胶质细胞数量降低,M2型小胶质细胞数量升高(均P<0.05);与对照组比较,模型组小鼠M1型小胶质细胞标记物iNOS和IL-1β表达升高(均P<0.05);与模型组比较,IL-11组小鼠M1型小胶质细胞标记物iNOS和IL-1β表达降低,M2型小胶质细胞标记物CD206和Arginase-1表达升高(均P<0.05);与对照组比较,模型组小鼠脑组织IL1、IL-6、TNF-α水平明显升高,IL-10水平明显降低(均P<0.05);与模型组比较,IL-11组小鼠脑组织IL-1、IL-6和TNF-α水平明显降低,IL-10水平明显升高(P<0.05)。结论IL-11促进小胶质细胞由促炎表型M1型向抗炎表型M2型转化,降低脑组织炎症,发挥脑缺血保护作用。     

Unilateral facial injection of Botulinum neurotoxin A attenuates bilateral trigeminal neuropathic pain and anxiety-like behaviors through inhibition of TLR2-mediated neuroinflammation in mice

ObjectivesIn this study, we investigated the possible analgesic effects of Botulinum toxin type A (BoNT/A) on trigeminal neuralgia (TN). A modified TN mouse model was established by chronic constriction injury of the distal infraorbital nerve (dIoN-CCI) in mice, and the possible roles of microglia toll-like receptor 2 (TLR2) and neuroinflammation was investigated.MethodsMale C57BL/6 mice were divided into 3 groups, including sham group, vehicle-treated TN group and BoNT/A-treated TN group. Bilateral mechanical pain hypersensitivity, anxiety-like and depressive-like behaviors were evaluated by using von Frey test, open field, elevated plus-maze testing, and forced swimming test in mice, respectively. The mRNA or protein expression levels of toll-like receptors (TLRs), glia activation markers and proinflammatory factors in the trigeminal nucleus caudalis (TNC) were tested by RT-qPCR, immunofluorescence and Western blotting. We also tested the pain behaviors of TN in Tlr2^−/− mice.ResultsWe found that unilateral subcutaneous injection of BoNT/A into the whisker pad on the ipsilateral side of dIoN-CCI mice significantly attenuated bilateral mechanical pain hypersensitivity and anxiety-like behaviors induced by dIoN-CCI surgery in mice. The dIoN-CCI surgery significantly up-regulated the expression of TLR2, MyD88, CD11b (a microglia marker), IL-1β, TNF-α and IL-6 in the ipsilateral TNC in mice, and BoNT/A injection significantly inhibited the expression of these factors. Immunostaining results confirmed that BoNT/A injection significantly inhibited the microglia activation in the ipsilateral TNC in dIoN-CCI mice. TLR2 deficiency also alleviated bilateral mechanical pain hypersensitivity and the up-regulation of MyD88 expression in the TNC of dIoN-CCI mice.ConclusionThese results indicate that unilateral injection of BoNT/A attenuated bilateral mechanical pain hypersensitivity and anxiety-like behaviors in dIoN-CCI mice, and the analgesic effects of BoNT/A may be associated with the inhibition of TLR2-mediated neuroinflammation in the TNC.