Isoflurane Exposure during Mid-Adulthood Attenuates Age-Related Spatial Memory Impairment in APP/PS1 Transgenic Mice

Many in vitro findings suggest that isoflurane exposure might accelerate the process of Alzheimer Disease (AD); however, no behavioral evidence exists to support this theory. In the present study, we hypothesized that exposure of APP/PS1 transgenic mice to isoflurane during mid-adulthood, which is the pre-symptomatic phase of amyloid beta (Abeta) deposition, would alter the progression of AD. Seven-month-old Tg(APPswe,PSEN1dE9)85Dbo/J transgenic mice and their wild-type littermates were exposed to 1.1% isoflurane for 2 hours per day for 5 days. Learning and memory ability was tested 48 hours and 5 months following isoflurane exposure using the Morris Water Maze and Y maze, respectively. Abeta deposition and oligomers in the hippocampus were measured by immunohistochemistry or Elisa 5 months following isoflurane exposure. We found that the performance of both the transgenic and wild-type mice in the Morris Water Maze significantly improved 48 hours following isoflurane exposure. The transgenic mice made significantly fewer discrimination errors in the Y maze following isoflurane exposure, and no differences were found between wild-type littermates 5 months following isoflurane exposure. For the transgenic mice, the Abeta plaque and oligomers in the hippocampus was significantly decreased in the 5 months following isoflurane exposure. In summary, repeated isoflurane exposure during the pre-symptomatic phase not only improved spatial memory in both the APP/PS1 transgenic and wild-type mice shortly after the exposure but also prevented age-related decline in learning and memory and attenuated the Abeta plaque and oligomers in the hippocampus of transgenic mice.     

Electroacupuncture Attenuates Reference Memory Impairment Associated with Astrocytic NDRG2 Suppression in APP/PS1 Transgenic Mice

Electroacupuncture (EA) has demonstrated therapeutic potential for the treatment of Alzheimer's disease (AD). A previous study reported that N-myc downstream-regulated gene 2 (NDRG2) was upregulated in the brain of patients with AD. In the present study, we investigated the effects of repeated EA administration on reference memory impairment and the role of NDRG2 in an amyloid precursor protein (APP)/presenilin-1 (PS1) double transgenic mouse model. Age-matched wild-type and transgenic mice were treated with EA (once per day for 30 min) for 4 weeks (four courses of 5 days EA administration and 2 days rest) beginning at 10 months of age. At seven and ten postnatal months of age and following a 4-week EA treatment regime, mice received training in the Morris water maze (MWM) and a probe test. Brain tissue was analyzed via Western blot and double-label immunofluorescence. Beginning at 7 months of age, APP/PS1 mice began to exhibit deficits in reference memory in the MWM test, an impairment associated with upregulation of glial fibrillary acidic protein (GFAP) and NDRG2. Four weeks of EA administration significantly ameliorated cognitive impairments and suppressed GFAP and NDRG2 upregulation. In conclusion, our findings demonstrated that EA administration can alleviate reference memory deficits and suppress NDRG2 upregulation in an AD transgenic mouse model. This study provides supportive evidence for EA as an effective therapeutic intervention for AD, as well as NDRG2 as a novel target for AD treatment.     

Partial Hospitalization: An Intervention for Youth with Poorly Controlled Diabetes Mellitus

Objective: To examine the efficacy of an integrated medical/psychiatric partial hospitalization program (PHP) to improve glycemic control in youth with both diabetes mellitus and mental health disorders.Methods: This retrospective chart review is of patients admitted to a PHP between 2005–2015 with concerns about diabetes mellitus care. Clinical characteristics, laboratory data, diabetic ketoacidosis hospitalizations, and outpatient clinic visit frequency were collected from the year prior to the year after PHP admission.Results: A total of 43 individuals met inclusion criteria: 22 (51%) were female, 40 (93%) had type 1 diabetes, the mean age was 15.2 ± 2.3 years, and the mean diabetes mellitus duration was 4.6 ± 3.6 years. Of those individuals, 35 of these patients had hemoglobin A1c (HbA1c) data available at baseline, 6 months, and 1 year after PHP. The average HbA1c before PHP admission was 11.3 ± 2.3% (100.5 ± 25 mmol/mol), and decreased to 9.2 ± 1.3% (76.7 ± 14.8 mmol/mol) within 6 months of PHP admission (P<.001). The average HbA1c 1 year after PHP was 10.7 ± 1.7 % (93.3 ± 19.1 mmol/mol). Overall, 24 patients (68%) had lower HbA1c, and 75% of those with improvement maintained an HbA1c reduction of ≥1% (≥10 mmol/mol) at 1 year compared to before PHP.Conclusion: Most patients demonstrated improved glycemic control within 6 months of PHP admission, and many of those maintained a ≥1% (≥10 mmol/mol) reduction in HbA1c at 1 year following PHP admission. This program may represent a promising intervention that could serve as a model for intensive outpatient management of youth with poorly controlled diabetes mellitus.Abbreviations: ADA = American Diabetes Association; DKA = diabetic ketoacidosis; EMR = electronic medical record; HbA1c = hemoglobin A1c; ICD-9 = International Classification of Diseases, 9^th revision; PHP = partial hospitalization program     

Specific Serotonergic Denervation Affects tau Pathology and Cognition without Altering Senile Plaques Deposition in APP/PS1 Mice

Senile plaques and neurofibrillary tangles are major neuropathological features of Alzheimer''s Disease (AD), however neuronal loss is the alteration that best correlates with cognitive impairment in AD patients. Underlying neurotoxic mechanisms are not completely understood although specific neurotransmission deficiencies have been observed in AD patients and, in animal models, cholinergic and noradrenergic denervation may increase amyloid-beta deposition and tau phosphorylation in denervated areas. On the other hand brainstem neurodegeneration has been suggested as an initial event in AD, and serotonergic dysfunction, as well as reductions in raphe neurones density, have been reported in AD patients. In this study we addressed whether specific serotonergic denervation, by administering 5,7-dihydroxitriptamine (5,7-DHT) in the raphe nuclei, could also worsen central pathology in APPswe/PS1dE9 mice or interfere with learning and memory activities. In our hands specific serotonergic denervation increased tau phosphorylation in denervated cortex, without affecting amyloid-beta (Aβ) pathology. We also observed that APPswe/PS1dE9 mice lesioned with 5,7-DHT were impaired in the Morris water maze test, supporting a synergistic effect of the serotonergic denervation and the presence of APP/PS1 transgenes on learning and memory impairment. Altogether our data suggest that serotonergic denervation may interfere with some pathological aspects observed in AD, including tau phosphorylation or cognitive impairment, without affecting Aβ pathology, supporting a differential role of specific neurotransmitter systems in AD.     

Time-Dependent Increase of Chitinase1 in APP/PS1 Double Transgenic Mice

It is reported that chitinase1 increases in Alzheimer’s disease (AD). However, the alteration of chitinase1 in the progress of AD is still unclear. Thus, we designed the present study to detect chitinase1 level in different stages of APP/PS1 double transgenic mice. Experimental models were APP/PS1 double transgenic mice with 4, 12 and 22 months. Cognitive function was detected by Morris water maze test in APP/PS1 mice as well as controls. ELISA and the quantitative RT-PCR were used to detect chitinase1 level in different groups. The study displayed that expression of chitinase1 gradually increased in a time-dependent manner in APP/PS1 mice, while there were no statistical differences among the wild-type mice in varies ages. Moreover, chitnase1 increased significantly in APP/PS1 mice aged 12 and 22 months compared with the age matched wild-type group, respectively. However, no difference of chitnase1 was found between 4 months-old APP/PS1 mice and wild-type mice. Comparing with the age matched wild type group, the consequences of mRNA on the increase in chitnase1 is in accordance with protein in APP/PS1 mice. Furthermore, Morris water maze showed that 4 months-old APP/PS1 mice have normal spatial learning and impaired spatial memory; both spatial learning and spatial memory in 12 and 22 months-old APP/PS1 mice were declined. Time-dependent increase of chitnase1 in APP/PS1 double transgenic mice indicates that the level of chitinase1 is associated with decline of cognition. Therefore, chitinase1 might be a biomarker of disease progression in AD.     

藏药七十味珍珠丸改善APP/PS1小鼠学习记忆能力

藏药七十味珍珠丸（ratanasampil,RNSP）可改善大脑氧化应激水平,改善大脑功能,有安神和促进学习记忆的功效,然而RNSP是否可改善阿尔茨海默症（AD）小鼠的学习记忆功能,尚缺乏系统研究。本研究采用APP/PS 1转基因小鼠为研究对象,并随机将其分为实验组和对照组。对实验组进行为期12周的RNSP灌胃给药,对照组进行12周的蒸馏水灌胃,采用Morris水迷宫与开场实验评价小鼠学习记忆能力,比较小鼠体重与相关器官质量,并比较器官质量指数,通过分子生物学检测指标评价小鼠脑内老年斑数量,Aβ生成量及BACE1表达水平。本研究证实,与对照组相比,给药组小鼠定位航行潜伏期明显缩短（22.60±13.26 vs. 46.44±8.41, P<0.01, day 5）,穿越平台次数明显增加（1.29±0.37 vs. 0.54±0.29, P<0.01）,探洞次数明显增加（32.11±9.85 vs. 20.89±8.78, P<0.05）,表明RNSP提高了APP/PS 1小鼠的学习记忆能力和空间探索能力。与对照组相比,给药组小鼠大脑重量及脑质量指数均增高（0.4135±0.0102 vs. 0.3833±0.0254, P<0.05;2.04±0.08 vs. 1.84±0.15, P<0.05）,脑内老年斑数量减少（18.70±7.88 vs. 38.83±6.15, P<0.05）,Aβ1- 42水平及BACE1表达均显著降低（0.19±0.08 vs. 0.41±0.12, P<0.05; 0.136±0.04 vs. 0.206±0.02, P<0.05）,表明RNSP延缓了APP/PS 1小鼠的脑萎缩进程,降低脑内老年斑的形成,下调脑内Aβ1-42水平和BACE1裂解酶的蛋白质表达量。本研究提示,RNSP可改善APP/PS 1小鼠的学习记忆能力,其机制可能和RNSP抑制脑萎缩,降低BACE1蛋白表达以及减少脑内Aβ沉积有关。     

Nicotinamide Effects Oxidative Burst Activity of Neutrophils in Patients with Poorly Controlled Type 2 Diabetes Mellitus

Neutrophil functions are impaired in patients with diabetes mellitus. Bacterial phagocytosis and oxidative burst activity are reduced at high glucose concentrations in diabetic patients. Defects in neutrophil oxidative burst capacity are of multifactorial origin in diabetes mellitus and correlate with glucose levels. It has been reported that neutrophil NADPH oxidase activity is impaired and superoxide production is reduced in diabetic patients with or without any infections. Nicotinamide is a vitamin B3 derivative and a NAD precursor with immunomodulatory effects. In vitro studies demonstrated that nicotinamide increases NAD and NADH content of beta cells. The authors hypothesized that nicotinamide may restore the impaired oxidative burst capacity of neutrophils in diabetic patients by increasing the NADH content as an electron donor and possibly through NADPH oxidase activity of the cell. In order to test the hypothesis, this placebo-controlled and open study was designed to evaluate neutrophil functions in infection-free poorly controlled type 2 diabetic patients as compared to healthy subjects and assess the effects of nicotinamide on neutrophil phagocytosis as well as oxidative burst activity. Thirty patients with type 2 diabetes mellitus were enrolled in the study. Sixteen were females and 14 were males, with a mean age 58 ± 10. All patients were on sulphonylurea treatment and their hemoglobin A_1c (HbA_1c) levels were above 7.5%. The control group consisted of 10 voluntary healthy subjects. Diabetic and control subjects were not significantly different in terms of age, body mass index (BMI), leucocyte and neutrophil counts, C-reactive protein (CRP) level, and erythrocyte sedimentation rate (ESR), but HbA_1c and fasting glucose levels were significantly higher in patients with diabetes mellitus. Phagocytic activity and respiratory burst indexes were measured by flow cytometric analyses as previously described by Rothe and Valet (Methods Enzyml., 233, 539–548, 1994) and compared in diabetic subjects and healthy controls. Diabetic patients were grouped to receive either 50 mg/kg oral nicotinamide (n = 15) or placebo (n = 15) for a period of 1 month. The 2 groups did not differ in terms of treatment, frequency of hypertension, BMI, diabetes duration, age, fasting plasma glucose (FPG), HbA_1c, CRP, ESR, polymorphonuclear leukocyte (PNL) and neutrophil counts. Neutrophil functions were reassessed after the treatment period. Phagocytic activity represented as indexes were lower in diabetic patients when compared to healthy subjects, but the differences were not statistically significant (P > .05). Patients with diabetes mellitus had significantly lower oxidative burst indexes when compared to healthy controls (P values < .05). In diabetic patients, a negative correlation between neutrophil functions and HbA_1c was found which was not statistically significant (P values > .05). Phagocytic indexes were similar in nicotinamide and placebo groups after treatment period (P > .05). But oxidative burst activity in patients receiving nicotinamide was greater when compared with placebo and the difference was statistically significant at 30 and 45 minutes (P values .04 and .03). This effect of nicotinamide may be due to increased NADH content and NADPH oxidase activity of the cell, which needs to be further studied. Impaired neutrophil functions may aggravate various infections in patients with diabetes mellitus and blood glucose regulation is an important target of treatment to improve neutrophil functions. But nicotinamide treatment may help to improve prognosis in diabetic patients with severe infections.     

有氧运动改善AD模型APP/PS1双转基因小鼠中枢神经元线粒体融合分裂动态平衡

线粒体融合分裂平衡是线粒体动力学的需要。本研究观察12周规律有氧运动对APP/PS1双转基因小鼠中枢神经元线粒体融合分裂动态平衡的影响。本研究采用3月龄雄性APP/PS1小鼠（AD模型）随机分为AD安静组（AS）、AD运动组（AE）,同月龄雄性C57BL/6J小鼠做正常对照组（CS）。AE组进行12周规律跑台运动,5 d/周,60 min/d。前10 min运动速度12 m/min,后50 min运动速度15 m/min,跑台坡度为0°。八臂迷宫实验检测小鼠工作记忆错误频率和参考记忆错误频率;Western印迹检测小鼠皮层、海马组织中线粒体分裂蛋白Drp1和Fis1的含量,以及Drp1的活性（p-Drp1-Ser616）、线粒体融合蛋白Mfn1、Mfn2、Opa1的表达水平;透射电镜观察皮层、海马线粒体形态结构、健康线粒体比率及线粒体平均直径。本研究证实AS组较CS组工作记忆错误频率显著提高（P<0.05）,12周有氧运动显著降低工作记忆错误频率（P<0.05）。AS组小鼠皮层Fis1蛋白和海马脑区Drp1、Fis1蛋白表达水平及皮层、海马脑区Drp1蛋白的活性增加（P<0.05）。而皮层Mfn1和海马Mfn1、Mfn2蛋白表达水平显著降低（P<0.05）。12周有氧运动显著减低Fis1、Drp1蛋白表达及Drp1蛋白的活性,提高Mfn1、Mfn2蛋白表达水平（P<0.05）。AS组小鼠皮层、海马线粒体多呈现球形,部分线粒体膜结构消失,线粒体嵴结构紊乱。且AS组较CS组小鼠健康线粒体比率降低、直径缩短。12周规律有氧运动可明显改善线粒体形态和结构,提高健康线粒体比率及直径。本研究提示,12周规律有氧运动可有效抑制皮层、海马脑区线粒体分裂蛋白Drp1和 Fis1的表达,降低Drp1的活性（p-Drp1-Ser616）,上调线粒体融合蛋白Mfn1、Mfn2的蛋白表达水平,改善线粒体形态和结构以促进线粒体质量控制,是有氧运动改善AD模型空间学习记忆能力的分子机制之一。     

游泳运动对APP/PS1转基因小鼠学习记忆能力的影响

探讨游泳运动对APP/PS1转基因小鼠学习记忆能力的影响。选择11月龄的雄性APP/PS1转基因小鼠,随机平均分为对照组和游泳组,对照组常规饲养而游泳组进行1个月的游泳运动训练。分别采用刚果红染色、Tunel检测、Western Blot和Morris水迷宫等实验方法观察小鼠大脑皮层Aβ斑形成、神经元凋亡、线粒体生成相关蛋白表达和学习记忆能力的变化情况。结果发现,游泳运动可以减少APP/PS1转基因小鼠大脑皮层Aβ斑的形成、抑制神经元凋亡、促进线粒体生成、增强小鼠的学习记忆能力。由此可见,游泳运动可作为一项防治阿尔茨海默病的行为治疗候选方案。     

跑台运动改善海马线粒体功能提高APP/PS1小鼠学习记忆能力

为研究跑台运动对APP/PS1小鼠海马线粒体融合、分裂作用的影响,将遗传背景为C57BL/6的3月龄APP/PS1小鼠和野生小鼠各42只分别随机分为APP/PS1安静对照组（ADC,n=21）和运动组（ADE,n=21）,野生安静对照组（WTC,n=21）和运动组（WTE,n=21）。ADE、WTE组进行12周跑台运动,同时ADC、WTC组置于安静跑台环境。水迷宫实验检测小鼠的空间学习记忆能力,RT-PCR法检测线粒体功能关键酶的mRNA水平,Western印迹检测海马融合、分裂及线粒体关键酶的蛋白质表达情况,透射电镜观察海马线粒体融合、分裂状态。结果发现,6月龄APP/PS1小鼠学习记忆能力降低（P<0.05）;海马线粒体融合蛋白质Mfn1、Mfn2、Opa1表达降低（P<0.05）,线粒体分裂蛋白质Drp1、Mff表达增高（P<0.05）;线粒体膜结构模糊,嵴不明显,线粒体碎片增多,空泡化线粒体增多;线粒体呼吸关键酶COX IV及ATP合酶表达均下调（P<0.05）。12周跑台运动可逆转APP/PS1小鼠的上述变化,改善海马线粒体结构和功能,提高学习记忆能力。综上提示：12周跑台运动改善APP/PS1小鼠学习记忆能力的机制可能与其对线粒体结构与功能的改善有关。     

动态观察姜黄素对APP/PS1双转基因小鼠尿液AD7C-NTP浓度的影响

目的通过动态检测小鼠尿液中AD7C-NTP的浓度变化,了解姜黄素在阿尔茨海默病治疗方面的作用。方法 3月龄APP/PS1双转基因小鼠35只,随机分为5组,每组7只,分别为模型组,阳性对照组(罗格列酮组),姜黄素大、中、小剂量组;另选用同月龄同背景的C57BL/6J小鼠7只作为正常对照组。以上6组连续灌胃3个月,分别于灌胃前、灌胃30d、灌胃60d和灌胃90d收集小鼠尿液,应用酶联免疫吸附试验(ELISA)检测尿AD7C-NTP浓度的变化。结果不同时间点各组小鼠尿AD7C-NTP浓度的动态存在波动,各治疗组治疗2个月与治疗1个月相比,AD7C-NTP浓度均有所下降(P0.05,P0.01);同一时间点小鼠尿AD7C-NTP浓度组间比较:治疗2个月后,西药组,姜黄素大、小剂量组与模型组相比AD7C-NTP浓度有所下降(P0.05,P0.01)。结论姜黄素可降低AD模型小鼠尿液内AD7C-NTP浓度,延缓AD的进展。     

利拉鲁肽对二甲双胍控制不佳的肥胖/超重2型糖尿病患者氧化应激、NLRP3炎症小体及脂肪因子水平的影响

摘要 目的：探讨利拉鲁肽对二甲双胍控制不佳的肥胖/超重2型糖尿病（T2DM）患者氧化应激、NLRP3炎症小体及脂肪因子水平的影响。方法：选择2018年2月-2020年1月期间河北北方学院附属第一医院收治的二甲双胍控制不佳的肥胖/超重T2DM患者160例。按照随机数字表法将患者分为对照组（80例,阿卡波糖治疗）和研究组（80例,阿卡波糖联合利拉鲁肽治疗）。观察两组的收缩压（SBP）、腰臀比（WHR）、体质量指数（BMI）、胰岛素抵抗指标、糖脂代谢指标、氧化应激指标、核苷酸结合寡聚化结构域样受体蛋白3（NLRP3）炎症小体及脂肪因子水平变化情况。结果：两组治疗后BMI、WHR、SBP均下降,且研究组的下降幅度更大（P<0.05）。两组治疗后胰岛?茁细胞分泌功能指数（HOMA-?茁）升高,胰岛素抵抗指数（HOMA-IR）下降,且研究组的改变幅度更大（P<0.05）。两组治疗后甘油三酯（TG）、总胆固醇（TC）、糖化血红蛋白（HbA1c）、低密度脂蛋白胆固醇（LDL-C）、空腹血糖（FPG）下降,高密度脂蛋白胆固醇（HDL-C）升高,且研究组的改变幅度更大（P<0.05）。两组治疗后丙二醛（MDA）下降,谷胱甘肽过氧化物酶（GSH-PX）、超氧化物歧化酶（SOD）升高,且研究组的改变幅度更大（P<0.05）。两组治疗后NLRP3炎症小体均下降,且研究组的改变幅度更大（P<0.05）。两组治疗后脂联素升高,瘦素下降,且研究组的改变幅度更大（P<0.05）。结论：利拉鲁肽应用于治疗二甲双胍控制不佳的肥胖/超重T2DM患者,可减轻氧化应激,有效改善糖脂代谢,调节NLRP3炎症小体及脂肪因子水平。     

GLP-1 Receptor Agonist Inhibited the Activation of RIPK1 for Alleviation the Neuronal Death and Neuroinflammation in APP/PS1 Mice

International Journal of Peptide Research and Therapeutics - Alzheimer’s disease (AD) is characterized by neuronal necroptosis and neuroinflammation, retardation of these pathological...     

An Individualized Inpatient Diabetes Education and Hospital Transition Program for Poorly Controlled Hospitalized Patients with Diabetes

ObjectiveTo evaluate predictors of outcomes associated with an inpatient diabetes education and discharge support program for hospitalized patients with poorly controlled diabetes (glycated hemoglobin [HbA1c]>9%).MethodsPatients participated in individualized diabetes education conducted by a certified diabetes educator (CDE) that included an exploration of barriers and goal setting during hospitalization with telephone follow-up and communication with primary providers at discharge. Predictors of HbA1c reduction, successful follow-up, and readmission were analyzed.ResultsThere were 82 subjects, and 48% were insulin naïve. Patients with type 2 diabetes (T2D, n = 58) had a significant decrease in HbAlc at follow-up (-2.8%, P < .0001), while those with type 1 diabetes (T1D, n = 19) did not (+ 0.02%, P = .96). However, after adjustment for other factors, only increasing age, higher baseline HbA1c, earlier education, and initiation of basal insulin were significant predictors of reduction in HbA1c. Higher area level income and empowerment and earlier education were significant predictors of outpatient follow-up within 30 days. While 28% were admitted for severe hyperglycemia, only 1 patient was readmitted with severe hyperglycemia. Successful phone contact was 77% and 57% with and without the support of non-CDE assistants respectively, but all outcomes were similar.ConclusionThe study suggests that an individualized inpatient diabetes education and transition program is associated with a significant reduction in HbA1c that is dependent on baseline HbA1c, older age, initiation of insulin, and earlier enrollment. Additional interventions are needed to ensure better continuity of care. (Endocr Pract. 2014;20:1265-1273)     

Neuregulin1beta1 Antagonizes Apoptosis Via ErbB4-Dependent Activation of PI3-Kinase/Akt in APP/PS1 Transgenic Mice

Alzheimer’s disease (AD) is characterized by the deposition of beta-amyloid protein (Aβ) and extensive neuronal cell death. Apoptosis plays a crucial role in loss of neurons in AD. Neuregulin1 (NRG1) has been found to protect neurons from oxygen glucose deprivation induced apoptosis and hypoxia ischemia induced apoptosis. However, the relationship between NRG1 and apoptosis related protein expression in AD and its mechanism remain uncertain. The present study explores the effects of NRG1 on Aβ-induced apoptosis in AD. In this study, extracellular domain of NRG1beta1 (NRG1β1-ECD) promoted the expression of p-ErbB4 receptor, p-Akt and increased the level of Bcl-2 both in APP/PS1 transgenic mice and in vitro. In primary culture of neurons, the level of Bcl-2 protein decreased significantly after Aβ treatment. These changes were inhibited by pretreatment of neurons with NRG1β1-ECD. A specific inhibitor of PI3-kinase/Akt pathway, wortmannin, significantly abrogated the effects of NRG1β1-ECD on p-Akt and Bcl-2 levels. Furthermore, the expression of PI3-kinase/Akt by NRG1β1-ECD was ErbB4-dependent. Our data demonstrated that NRG1β1-ECD might serve as an obvious neuroprotection in AD, and the possible protective mechanism occurs most likely via ErbB4-dependent activation of PI3-kinase/Akt pathway.     

Excitability and synaptic alterations in the cerebellum of APP/PS1 mice

In Alzheimer's disease (AD), the severity of cognitive symptoms is better correlated with the levels of soluble amyloid-beta (Aβ) rather than with the deposition of fibrillar Aβ in amyloid plaques. In APP/PS1 mice, a murine model of AD, at 8 months of age the cerebellum is devoid of fibrillar Aβ, but dosage of soluble Aβ(1-42), the form which is more prone to aggregation, showed higher levels in this structure than in the forebrain. Aim of this study was to investigate the alterations of intrinsic membrane properties and of synaptic inputs in Purkinje cells (PCs) of the cerebellum, where only soluble Aβ is present. PCs were recorded by whole-cell patch-clamp in cerebellar slices from wild-type and APP/PS1 mice. In APP/PS1 PCs, evoked action potential discharge showed enhanced frequency adaptation and larger afterhyperpolarizations, indicating a reduction of the intrinsic membrane excitability. In the miniature GABAergic postsynaptic currents, the largest events were absent in APP/PS1 mice and the interspike intervals distribution was shifted to the left, but the mean amplitude and frequency were normal. The ryanodine-sensitive multivescicular release was not altered and the postsynaptic responsiveness to a GABA(A) agonist was intact. Climbing fiber postsynaptic currents were normal but their short-term plasticity was reduced in a time window of 100-800 ms. Parallel fiber postsynaptic currents and their short-term plasticity were normal. These results indicate that, in the cerebellar cortex, chronically elevated levels of soluble Aβ(1-42) are associated with alterations of the intrinsic excitability of PCs and with alterations of the release of GABA from interneurons and of glutamate from climbing fibers, while the release of glutamate from parallel fibers and all postsynaptic mechanisms are preserved. Thus, soluble Aβ(1-42) causes, in PCs, multiple functional alterations, including an impairment of intrinsic membrane properties and synapse-specific deficits, with differential consequences even in different subtypes of glutamatergic synapses.     

TREM2 Overexpression has No Improvement on Neuropathology and Cognitive Impairment in Aging APPswe/PS1dE9 Mice

Previously, we showed that overexpression of triggering receptor expressed on myeloid cells 2 (TREM2), a microglia-specific immune receptor, in the brain of a middle-aged (7 months old) APPswe/PS1dE9 mice could ameliorate Alzheimer’s disease (AD)-related neuropathology by enhancement of microglial amyloid-β (Aβ) phagocytosis. Since AD is an age-related neurodegenerative disorder, it is critical to assess the efficacy of TREM2 overexpression in aging animals with an advanced disease stage. In vivo, we employed a lentiviral strategy to overexpress TREM2 in the brain of aging (18 months old) APPswe/PS1dE9 mice, and observed its efficacy on AD-related neuropathology and cognitive functions. Afterwards, we directly isolated microglia from middle-aged and aging APPswe/PS1dE9 mice and determined effects of TREM2 overexpression on microglial Aβ phagocytosis and Aβ-binding receptors expression in vitro. In aging APPswe/PS1dE9 mice, TREM2 overexpression has no beneficial effect on AD-related neuropathology and spatial cognitive functions. Of note, in vitro experiments showed a significant reduction of Aβ phagocytosis in microglia from aging APPswe/PS1dE9 mice, possibly attributing to the declined expression of Aβ-binding receptors. Meanwhile, this phagocytic deficit in microglia from aging APPswe/PS1dE9 mice cannot be rescued by TREM2 overexpression. Taken together, our study shows that TREM2 overexpression fails to provide neuroprotection in aging APPswe/PS1dE9 mice, possibly attributing to deficits in microglial Aβ phagocytosis at the late-stage of disease progression. These findings indicate that TREM2-mediated protection in AD is at least partially dependent on the reservation of microglial phagocytic functions, emphasizing the importance of early therapeutic interventions for this devastating disease.