精氨酸增加大鼠海马脑片可溶性淀粉样前体蛋白的释放

目的：观察兴奋性神经递质精氨酸对于可溶性淀粉样前体蛋白(sAPP)释放的影响。方法：雄性SD大鼠断头取海马后于0～4℃：Krebs-Ringer液中快速振动切片，切片于370C预孵育后置含精氨酸或不含精氨酸Krebs-Ringer液(对照)中孵育后于15000g离心取上清液，应用二辛可宁酸法测定上清液总蛋白含量；释放入孵育液中的sAPP以Western blot方法测定。结果：正常孵育的海马脑片能够分泌基础量的sAPP，精氨酸刺激能够导致海马脑片释放sAPP增加，但是没有导致新蛋白的产生。结论：精氨酸在10^-9～10μmol／L浓度范围内，均能够导致海马脑片分泌sAPP增加。     

APP17肽对APP转基因小鼠突触相关蛋白表达的影响

目的研究APP17肽对APP转基因小鼠(APP V717 I)海马神经元突触相关蛋白表达的影响。方法将3 mon龄的APP转基因小鼠随机分为模型组和APP17肽治疗组(皮下注射0.16 mg.kg-1.d-1,每周3次),并以相同年龄和背景的C57BL/6 J小鼠做正常对照组。7 mon后行Morris水迷宫测定,小鼠脑组织灌注固定后进行PSD-95、Shank1蛋白的免疫组化染色。结果模型组小鼠水迷宫实验的逃避潜伏期明显长于治疗组和正常对照组,且模型组小鼠大脑海马CA4区中的PSD-95、Shank1阳性反应神经元明显减少,染色浅;APP17肽治疗组与正常对照组相近。结论APP转基因小鼠大脑中存在突触后致密区蛋白表达异常,由此引起突触功能损害,进而导致记忆、学习能力的改变;而APP17肽能通过提高PSD-95、Shank1的表达,使突触的损伤接近恢复正常。并能改善小鼠的记忆、学习能力。     

雌激素抑制淀粉样蛋白前体羧基端片段在雌性去势大鼠海马和脑皮质的表达

目的　探讨雌激素对♀去势大鼠海马和脑皮质神经细胞中神经毒性的淀粉样蛋白前体 (amyloidprecursorpro tein ,APP)羧基端片段 (carboxyl terminalfragment,C端片段 )表达的调节作用。方法　♀去势大鼠分别给予倍美力或补加乐 3个生理周期后 ,采用免疫组化法检测APP C端片段在两种组织中的分布 ,并以H score法对其表达进行半定量分析。结果　去势后♀大鼠海马和脑皮质组织中APP C端片段的表达升高。和去势对照组相比 ,倍美力组和补加乐组同一组织中APP C端片段的表达均明显下降 ,且补加乐组中APP C端片段的表达量低于倍美力组。结论　倍美力和补加乐对♀去势大鼠海马和脑皮质中APP C端片段的表达均起降调节作用 ,且补加乐的作用强于倍美力。     

Role of acetylcholinesterase inhibitors in the metabolism of amyloid precursor protein

Potentiation of central cholinergic activity has been proposed as a therapeutic approach for improving the cognitive function in patients with Alzheimer's disease (AD). Increasing the acetylcholine concentration in the brain by modulating acetylcholine-sterase (AChE) activity is among the most promising therapeutic strategies. Efforts to treat the underlying pathology based on the modulation of amyloid precursor protein (APP) processing in order to decrease the accumulation of beta-amyloid are also very important. Alterations in APP metabolism have recently been proposed to play a key role in the long-lasting effects of AChE inhibitors. This review surveys recent data from in vivo and in vitro studies that have contributed to our understanding of the role of AChE inhibitors in APP processing. The regulatory mechanisms relating to the muscarinic agonist effect, protein kinase C activation and mitogen-activated protein kinase phosphorylation, involving the alpha-secretase or the 5 -UTR region of the APP gene, are also discussed. Further work is warranted to elucidate the exact roles in APP metabolism of the AChE inhibitors used in AD therapy at present.     

Rationalizing a pharmacological intervention on the amyloid precursor protein metabolism.

The treatment of Alzheimer's disease remains a major challenge because of our incomplete understanding of the triggering events that lead to the selective neurodegeneration characteristic of Alzheimer's brains. The rational design of a pharmacological intervention is therefore a great theoretical challenge. One approach involves the study of the pharmacological modulation of the amyloid precursor protein metabolism, in which the goal is to reduce the formation of beta-amyloid in the hope of reducing the formation of a potentially neurotoxic peptide. Such an approach has led to the identification of a complex intracellular mechanism that can be regulated by neurotransmitters and other ligands.     

神经传递与β-淀粉样蛋白前体的加工调控

淀粉样蛋白沉积是阿尔采末病（Ａｌｚｈｅｉｍｅｒｓｄｉｓｅａｓｅ,ＡＤ）中重要的组织病理学特征,其前体ＡＰＰ在加工代谢过程中生成两类作用相反的产物。有些神经递质受体参与调控这一加工过程,提示神经传递活动在ＡＤ发生发展机制中起了作用。     

氯丙烯对大鼠神经组织神经丝亚单位蛋白含量的影响

目的　为了进一步探讨氯丙烯引起的周围神经病的发病机理。方法　用Western印迹方法测定了亚慢性中毒大鼠大脑、脊髓、坐骨神经组织低分子量神经丝 (NF L)、中分子量神经丝 (NF M)和高分子量神经丝 (NF H) 3个亚单位相对含量的变化。结果　氯丙烯使脑组织沉淀和上清液中神经丝 3个亚单位的相对含量明显降低 ;在脊髓组织沉淀和上清液中 ,NF M均降低。NF H在沉淀增加 ,在上清液中降低。NF L在沉淀增加 ;在坐骨神经组织沉淀和上清液中 ,氯丙烯使NF M含量降低 ,而使NF H含量增加。NF L在沉淀中降低、在上清液中明显增加。结论　氯丙烯引起的中毒性周围神经病与神经丝亚单位紊乱有关。     

Estrogen stimulates release of secreted amyloid precursor protein from primary rat cortical neurons via protein kinase C pathway

Aim: To investigate the mechanism of the action of estrogen, which stimulates the release of secreted amyloid precursor protein α (sAPPα) and decreases the generation of amyloid-β protein (Aβ), a dominant component in senile plaques in the brains of Alzheimer‘s disease patients. Methods: Experiments were carried out in primary rat cortical neurons, and Western blot was used to detect sAPPα in aculture medium and the total amount of cellular amyloid precursor protein (APP) in neurons. Results: 17β-Estradiol (but not 17α-estradiol) and β-estradiol 6-(0-carboxymethyl) oxime: BSA increased the secretion of sAPPα and this effect was blocked by protein kinase C (PKC) inhibitor caiphostin C, but not by the classical estrogen receptor antagonist ICI 182,780. Meanwhile, 17β-estradiol did not alter the synthesis of cellular APP. Conclusion: The effect of 17β-estradiol on sAPPα secretion is likely mediated through the membrane binding sites, and needs molecular configuration specificity of the ligand. Furthermore, the action of the PKCdependent pathway might be involved in estrogen-induced sAPPα secretion.     

银杏叶提取物对正常大鼠海马caspase—3和淀粉样前体蛋白水平的影响

AIM:To explre the effect of Ginkgo biloba extract (GbE)on the levels of caspase-3 and amyloid precursor protein(APP)in normal rats' hippocampus.METHODS:Immunohistochemistry method was used for qualitative analysis of the expressions of caspase-3 and APP,and an image analysis method was used for the quantification of the levels of caspase-3and APP atfer GbE was administered to rats of different ages for 14d.RESULTS:The mean absorbance of staining of caspase-3 and APP was markedly higher in GbE group than that in control groups.The expressions of caspase-3 and APP were intersified in the hipocampus of rats after GbE administration.CONCLUSION:GbE can raise the levels of caspase-3and APP in the hippocampus of normal ras.     

Caspase抑制剂F1013对大鼠肝CYPs含量及其主要亚型mRNA表达的影响

目的:探讨Caspase抑制剂F1013对大鼠肝CYPs含量及其主要亚型CYP1A2,CYP2D1,CYP2E1,CYP2C11,CYP3A1 mRNA相对表达水平的影响。方法:Wistar大鼠40只,随机分成空白组、诱导剂组、F1013低、中、高剂量组。空白组和诱导剂组分别灌胃给予0.9%氯化钠溶液和地塞米松50 mg·kg-1.d-1,F1013低、中、高组分别肌内注射F1013 1.25,2.5,5.0 mg·kg-1.d-1,每日1次,连续6 d。取大鼠肝组织制备肝微粒体,测定微粒体蛋白浓度及CYP总酶含量。并采用实时定量荧光RT-PCR法分析大鼠CYP各主要亚型mRNA的相对表达水平。结果:F1013低、中、高组肝微粒体CYP总酶含量与空白组比有显著增高(P<0.05),提示该药对CYP总酶有诱导作用。低剂量组CYP2D1酶活性显著升高(为空白组2.54倍,P<0.05);中剂量组CYP1A2及CYP2E1酶活性显著升高,分别为空白组4.24和2.46倍(P<0.05);3个剂量的F1013对CYP2C11均无显著诱导作用。结论:F1013在1.25,2.5,5.0 mg.kg-1剂量范围内,可显著诱导CYP总酶活性。F1013 1.25 mg·kg-1可诱导CYP 2D1 mRNA表达,2.5 mg·kg-1剂量可诱导CYP1A2及CYP2E1 mRNA的表达,其诱导机制可能与升高各主要亚酶mRNA相对表达水平有关。     

Effect of eritadenine on cholesterol metabolism in the rat

Eritadenine, a hypocholesterolemic adenine derivative occurring in the Japanese mushroom Lentinus edodes, had no effect on hepatic cholesterol biosynthesis from 1-¹⁴C-acetate and 2-¹⁴C-mevalonate but accelerated tissue uptake of plasma cholesterol.     

高脂饲料中胆固醇含量对大鼠非酒精性脂肪肝动物模型建立的影响

目的观察大鼠非酒精性脂肪肝动物模型构建中肝脏脂变程度与高脂饲料内胆固醇含量和造模时间的动态关系,以找到合适的非酒精性脂肪肝的造模方法。方法 SD雄性大鼠70只,饲喂不同胆固醇含量的高脂饲料,分别检测14,21和28d大鼠血清ALT,AST,TC,TG,LDL-C和HDL-C,并观察肝脏脂变情况。结果造模2,3和4周后高脂饲料中胆固醇质量分数1%组与1.5%组大鼠的肝脏脂肪变性均无显著区别。其中21d后,所有的大鼠均发生了肝脏脂肪变性;28d后,大部分大鼠发生了肝脏重度脂肪变性,质量分数1.5%胆固醇组大鼠肝脏发生了炎症浸润和点状坏死。结论实验较好再现了高脂饮食引起的非酒精性脂肪肝发展的全过程,其中高胆固醇的质量分数为1%和1.5%的高脂饲料对大鼠肝脏脂变程度的影响无明显差别。     

Involvement of notch signaling pathway in amyloid precursor protein induced glial differentiation

The amyloid precursor protein (APP) has been mainly studied in its role in the production of amyloid β peptides (Aβ), because Aβ deposition is a hallmark of Alzheimer's disease. Although several studies suggest APP has physiological functions, it is still controversial. We previously reported that APP increased glial differentiation of neural progenitor cells (NPCs). In the current study, NPCs transplanted into APP23 transgenic mice primarily differentiated into glial cells. In vitro treatment with secreted APP (sAPP) dose-dependently increased glial fibrillary acidic protein (GFAP) immuno-positive cells in NPCs and over expression of APP caused most NPCs to differentiate into GFAP immuno-positive cells. Treatment with sAPP also dose-dependently increased expression levels of GFAP in NT-2/D1 cells along with the generation of Notch intracellular domain (NICD) and expression of Hairy and enhancer of split 1 (Hes1). Treatment with γ-secretase inhibitor suppressed the generation of NICD and reduced Hes1 and GFAP expressions. Treatment with the N-terminal domain of APP (APP 1–205) was enough to induce up regulation of GFAP and Hes1 expressions, and application of 22 C11 antibodies recognizing N-terminal APP suppressed these changes by sAPP. These results indicate APP induces glial differentiation of NPCs through Notch signaling.     

Effect of two storage solutions on proteolysis in isolated rat livers

One process identified as detrimental during liver preservation is proteolysis. The aim of this study was to test two preservation media, the University of Wisconsin (UW) solution and a simplified variant so-called Cochin (Co) solution with respect to their potential antiproteolytic effect. A model of isolated rat liver perfused after 24-h cold storage was used. Graft viability was assessed on biochemical and functional parameters. Proteolysis was assessed on amino acid metabolism. Survival of rats following orthotopic transplantation of 18-h cold-stored livers was determined. Proteolysis, assessed on valine release in the preservation solution, was limited in UW (0.12±0.01 versus 0.18±0.03 μmol/g liver, p<0.05). The protective effect of UW extended to reperfusion after storage and valine uptake was maintained in UW-stored livers but decreased in Co-stored organs (−12.39±5.93 versus −1.84±5.51 nmol/min/g liver). Enzyme release, portal flow rate and bile flow rate were similar in both groups. However, survival after orthotopic transplantation confirmed the superiority of UW over Co. These results demonstrated the antiproteolytic effect of UW solution in cold-stored rat livers. Amongst components omitted in the simplified UW solution, hydroxyethylstarch was identified as the more probable support of this effect.     

The metabolism of the amyloid precursor protein and its relevance to Alzheimer's disease

Summary The pathology of Alzheimer's disease is primarily characterized by the deposition of -amyloid/A peptide as the major component of senile or neuritic plaques. The A peptide is produced as a result of proteolytic cleavage of the transmembrane protein precursor, APP, during its normal cellular metabolism. The free amino terminus of the A peptide is generated by an endopeptidic cleavage between Met⁶⁷¹-Asp⁶⁷² by a protease termed -secretase. Increased cleavage at this site takes place in a rare, inherited double mutation (Lys⁶⁷⁰-Met⁶⁷¹ to Asn⁶⁷⁰-Leu⁶⁷¹), leading to increased A production and consequent development of Alzheimer's disease on an accelerated time scale in the affected individuals, underscoring the pathological importance of -secretase activity. Cellular studies provide direct evidence that inhibition of -secretase activity would appear to be effective in inhibiting A production as a rational approach to developing therapeutics for the disease.     

Cholinergic activity and amyloid precursor protein processing in aging and Alzheimer's disease

Among the neuropathological features of Alzheimer's disease (AD), are senile plaques and dysfunction of cholinergic neurotransmission are the major hallmarks. Senile plaques are formed by amyloid beta-peptides (Abeta), derived from amyloidogenic processing of a larger protein named amyloid precursor protein (APP). It has been suggested and also proved that cholinergic system plays an important role in the cognitive function of the brain and its deficit correlates well with the cognitive impairment of AD. Aging is the most important risk factor for AD. In normal aging, cholinergic system undergoes degeneration. APP processing changes with aging, probably resulting in higher amyloidogenic products. The current clinical treatments for Alzheimer's disease solely rely on cholinomimetic drugs i.e., acetylcholinesterase inhibitors. Recently, a great effort has been made to seek therapies that could reduce Abeta products by influencing APP processing. Through genetic engineering in cell lines and mice, in vitro and in vivo models for AD studies have been created. Experimental evidence obtained from the studies on these model organisms suggests that activity of cholinergic neurotransmission might have an impact on APP processing. On the other hand, the proteolytic products of APP have also been found able to influence the cholinergic system in both in vitro and in vivo models. To determine whether there exists a reciprocal interaction between cholinergic neurotransmission and APP processing is important for the development of new therapeutic strategies with high efficacy and specificity for AD.