Academic literature on the topic 'Transgenic mouse Tg2576'

Abstract The efficacy of antihypertensive agents in Alzheimer's disease (AD) is controversial. It has been tested here whether some antihypertensive drugs might influence AD through mechanisms independent of blood pressure-lowering activity. The effects of treatment with the antihypertensive propranolol on cognition and AD-related markers have been studied in the Tg2576 mouse model of AD. Propranolol, at a lower dose than that used as antihypertensive (5 mg/kg, 6 wk), attenuated cognitive impairments shown by Tg2576 mice aged 9 months in the novel object recognition and fear conditioning tests. Propranolol was also able to counteract the increases in hippocampal levels of Aβ42 present in Tg2576 mice. This effect was accompanied by an increased expression of insulin degrading enzyme. Changes in markers of synaptic pathology, as shown by decreases in phosphorylation of Akt and in the expression of BDNF in Tg2676 mice, were also counteracted by propranolol treatment. Tau hyperphosphorylation shown by Tg2576 mice was also decreased in the hippocampus of propranolol-treated mice, an effect probably related to an increase of GSK3β phosphorylation (inactive form) and a decreased JNK1 expression. Overall, these data further strengthen the potential of propranolol as a therapeutic agent for AD.

Hypertension and cerebral amyloid angiopathy (CAA) are major risk factors for intracerebral hemorrhage (ICH); however the mechanisms of interplay between the two are not fully understood. We investigated the effect of hypertension in a transgenic mouse model with Alzheimer’s-like pathology (Tg2576) treating them with angiontensin II and L-NG-nitroarginine methyl ester. A similar increase in systolic blood pressure was observed in both Tg2576 and control mice; however Tg2576 mice developed signs of stroke with a markedly shorter latency. Cerebral deposition of amyloid beta promotes the hypertension-induced ICH, thus supporting the notion that hypertension is a risk factor for ICH among patients with CAA.

In order to clarify the pathophysiological role of presenilin-2 (PS2) carrying the Volga German Kindred mutation (N141I) in a conventional mouse model of Alzheimer's disease (AD) expressing amyloid precursor protein (APP) with the Swedish mutation (Tg2576 line), we generated a double transgenic mouse (PS2Tg2576) by crossbreeding the PS2 mutant with Tg2576 mice. Here, we demonstrate that the PS2 mutation induced the early deposition of amyloid β-protein (Aβ) at 2-3 months of age and progressive accumulation at 4-5 months of age in the brains of the mutant mice. The PS2 mutation also accelerated learning and memory impairment associated with Aβ accumulation at 4-5 months of age in Tg2576 mice. These results suggest that the PS2 mutation causes early cerebral amyloid accumulation and memory dysfunction. PS2Tg2576 mice are a suitable mouse model for studying amyloid-lowering therapies.

Presenilin 1 and presenilin 2 (PS1 and PS2) play a critical role inγ-secretase-mediated cleavage of amyloid-βprecursor protein (APP) and the subsequent generation ofβ-amyloid peptides. The purpose of the present study was to test whether PS2 mutation accelerates the onset of contextual fear memory deficits in a mouse model of AD that expresses a mutation (K670N/M671L) of the human APP with the Swedish mutation (Tg2576 mice). In the present study, an APP/PS2 double-transgenic mouse model (PS2Tg2576) was generated by crossbreeding transgenic mice carrying the human mutant PS2 (N141I) with Tg2576 mice. Contextual fear conditioning was tested in PS2Tg2576 mice aged 3, 4, 6, and 10–12 months. PS2Tg2576 mice showed a tendency of lower freezing behavior as early as 3 months of age, but significant memory impairment was observed from the age of 4 months. The cognitive impairment was more prominent at ages of 6 and 10–12 months. In contrast, Tg2576 mice aged 3 and 4 months exhibited successful acquisition of contextual fear learning, but Tg2576 mice aged 6 months or older showed significantly impaired fear memory. These results show that PS2 mutation significantly accelerates the onset of fear memory deficits in the APP AD model mice.

Alzheimer’s disease (AD), a progressive neurodegenerative disorder, is characterized clinically by cognitive decline and pathologically by the development of amyloid plaques. AD is the most common cause of dementia among older people. However, there is currently no cure for AD. In this study, we aimed to elucidate the therapeutic effects of human amniotic epithelial stem cells (hAESCs) in a transgenic mouse model of AD. Tg2576 transgenic (Tg) mice underwent behavioral tests, namely the Morris water maze and Y-maze tests, to assess their cognitive function. In the Morris water maze test, hAESC-treated Tg mice exhibited significantly shorter escape latencies than vehicle-treated Tg mice. In the Y-maze test, hAESC-treated Tg mice exhibited significantly higher rate of spontaneous alteration than vehicle-treated Tg mice, while the total number of arm entries did not differ between the groups. Furthermore, Congo red staining revealed that hAESCs injection reduced the number of amyloid plaques present in the brains of Tg mice. Finally, beta-secretase (BACE) activity was significantly decreased in Tg mice at 60 min after hAESCs injection. In this study, we found that intracerebral injection of hAESCs alleviated cognitive impairment in a Tg2576 mouse model of AD. Our results indicate that hAESCs injection reduced amyloid plaques caused by reduced BACE activity. These results indicate that hAESCs may be a useful therapeutic agent for the treatment of AD-related memory impairment.

Recent studies suggest that hyperinsulinemia and insulin resistance are linked to Alzheimer’s disease (AD). In this study, we used Tg2576 transgenic (Tg) mice, a widely used transgenic mouse model for AD, to explore the relationship between increased amyloid β-peptide (Aβ) and insulin resistance. When fed a high-fat diet (HFD), Tg mice developed obesity and insulin resistance at 16 wk of age. Furthermore, HFD-fed Tg mice displayed abnormal feeding behavior and increased caloric intake with time. Although caloric intake of HFD-fed Tg mice was similar to that of normal diet-fed Tg or wild-type mice during 4 to 8 wk of age, it increased sharply at 12 wk, and went up further at 16 wk, which paralleled changes in the level of Aβ40 and Aβ42 in the brain of these mice. Limiting food intake in HFD-fed Tg mice by pair-feeding a caloric intake identical with that of normal diet-fed mice completely prevented the obesity and insulin intolerance of HFD-fed Tg mice. The hypothalamus of HFD-fed Tg mice had a significant decrease in the expression of the anorexigenic neuropeptide, brain-derived neurotrophic factor, at both the mRNA and protein levels. These findings suggest that the increased Aβ in the brain of HFD-fed Tg2576 mice is associated with reduced brain-derived neurotrophic factor expression, which led to abnormal feeding behavior and increased food intake, resulting in obesity and insulin resistance in these animals.

Thesis (M.A.)--George Mason University, 2008.
Vita: p. 68. Thesis director: Jane M. Flinn. Submitted in partial fulfillment of the requirements for the degree of Master of Arts in Psychology. Title from PDF t.p. (viewed June 30, 2008). Includes bibliographical references (p. 62-67). Also issued in print.

Grundlage der vorgelegten Arbeit sind die bei der Alzheimerschen Erkrankung beobachtbaren pathologischen Merkmale, wie die progressive Akkumulation von β-Amyloid-Plaques, cholinerger Dysfunktion und zerebrovaskuläre Abnormalitäten. Die in englischer Sprache verfasste Dissertation ist eine tierexperimentelle Studie, die versucht, den Zusammenhang von β-Amyloid, cholinerger Neurotransmission und zerebralem Gefäßsystem bei der Alzheimerschen Erkrankung näher zu charakterisieren. An Hirnmaterial aus der transgenen Maus Tg2576, die die schwedische Mutation des humanen Amyloidpräkursorproteins als Transgen trägt und ab dem 10. Lebensmonat durch humane β-Amyloid-Plaqueablagerungen in der Hirnrinde imponiert, wurden im Altersverlauf (4 bis 18 Monate) immunhistochemische Untersuchungen zur morphologischen Integrität der zerebralen Mikrogefäße, der kortikalen cholinergen Nervterminalen und der intrazerebralen cholinergen neurovaskulären Innervation durchgeführt. Am somatosensorischen Kortex werden beispielhaft die Expression des Glukosetransporters 1 oder Solanum tuberosum Lektin als Kapillarmarker und des vesikulären Acetylcholintransporters als Marker für cholinerge Fasern mittels Immunfluoreszenz und Laser-Scanning Mikroskopie erfasst, einer semiquantitativen Computer-gestützten Bildanalytischen Auswertung unterzogen und mit dem Ausmaß der kortikalen Plaquebeladung korreliert. So konnte gezeigt werden, dass die Dichte der Blutgefäße und cholinergen Fasern im somatosensorischen Kortex von transgenen Tieren mit dem Alter im Vergleich zu nichttransgenen Kontrolltieren abnimmt, was mit einer Reduktion der perivaskulären cholinergen Innervation einhergeht. Die erhobenen Befunde stützen die von J.C. de la Torre und T. Mussivand schon im Jahre 1993 formulierte „vaskuläre Hypothese“, wonach bei der sporadischen Form der Alzheimerschen Erkrankung alters- und Lebensstil-bedingte Schädigungen des zerebralen Gefäßsystems eine zentrale Rolle bei der Manifestierung der Erkrankung spielen.

Grundlage der vorgelegten Arbeit sind die bei der Alzheimerschen Erkrankung beobachtbaren pathologischen Merkmale, wie die progressive Akkumulation von β-Amyloid-Plaques, cholinerger Dysfunktion und zerebrovaskuläre Abnormalitäten. Die in englischer Sprache verfasste Dissertation ist eine tierexperimentelle Studie, die versucht, den Zusammenhang von β-Amyloid, cholinerger Neurotransmission und zerebralem Gefäßsystem bei der Alzheimerschen Erkrankung näher zu charakterisieren. An Hirnmaterial aus der transgenen Maus Tg2576, die die schwedische Mutation des humanen Amyloidpräkursorproteins als Transgen trägt und ab dem 10. Lebensmonat durch humane β-Amyloid-Plaqueablagerungen in der Hirnrinde imponiert, wurden im Altersverlauf (4 bis 18 Monate) immunhistochemische Untersuchungen zur morphologischen Integrität der zerebralen Mikrogefäße, der kortikalen cholinergen Nervterminalen und der intrazerebralen cholinergen neurovaskulären Innervation durchgeführt. Am somatosensorischen Kortex werden beispielhaft die Expression des Glukosetransporters 1 oder Solanum tuberosum Lektin als Kapillarmarker und des vesikulären Acetylcholintransporters als Marker für cholinerge Fasern mittels Immunfluoreszenz und Laser-Scanning Mikroskopie erfasst, einer semiquantitativen Computer-gestützten Bildanalytischen Auswertung unterzogen und mit dem Ausmaß der kortikalen Plaquebeladung korreliert. So konnte gezeigt werden, dass die Dichte der Blutgefäße und cholinergen Fasern im somatosensorischen Kortex von transgenen Tieren mit dem Alter im Vergleich zu nichttransgenen Kontrolltieren abnimmt, was mit einer Reduktion der perivaskulären cholinergen Innervation einhergeht. Die erhobenen Befunde stützen die von J.C. de la Torre und T. Mussivand schon im Jahre 1993 formulierte „vaskuläre Hypothese“, wonach bei der sporadischen Form der Alzheimerschen Erkrankung alters- und Lebensstil-bedingte Schädigungen des zerebralen Gefäßsystems eine zentrale Rolle bei der Manifestierung der Erkrankung spielen.:CHAPTER 1: INTRODUCTION 1.1 Alzheimer’s disease 1 1.2 APP processing and β-amyloid production 2 1.3 Cholinergic dysfunction in Alzheimer’s disease 5 1.4 Cerebrovascular abnormalities in Alzheimer’s disease 8 1.5 Cholinergic innervation of intracortical cerebral microvessels 9 1.6 Transgenic Tg2576 mouse model of Alzheimer’s disease 11 1.7 Aim of study 14 CHAPTER 2: MATERIALS AND METHODS 2.1 Materials 15 2.1.1 Chemical reagents used 15 2.1.2 Biological reagents used 15 2.1.3 Preparation of solutions and buffers 15 2.1.4 Antibodies and reagents used for immunohistochemistry 17 2.1.5 Transgenic animals 19 2.2 Methods 20 2.2.1 Tissue preparation and sampling of sections 20 2.2.2 Immunohistochemistry 20 2.2.2.1 Protocol of immunofluorescent labeling 20 2.2.2.2 Protocol of immunoperoxidase labeling (ABC technique) 21 2.2.2.3 Combination of primary and secondary antibodies 22 2.2.2.4 Protocol of β–amyloid immunolabeling (Formic acid epitope retrieval method) 23 2.2.3 Histochemistry 23 2.2.3.1 Thioflavin S staining 23 2.2.3.2 Nissl staining 23 2.2.3.3 Solanum Tuberosum Lectin (STL) staining 24 2.2.4 Double and triple-coloured immuno-/ histochemical staining of brain sections 24 2.2.5 Microscopy and digital image processing 25 2.2.6 Morphological and morphometric analyses 25 2.2.6.1 Cortical microvessels 25 2.2.6.2 Cortical cholinergic innervation 27 2.2.6.2.1 Total density of VAChT-immunoreactivity 27 2.2.6.2.2 Estimation of the density of varicosities on cholinergic fibres 29 2.2.6.3 Estimation of cholinergic perivascular innervation of cortical microvessels 29 2.2.6.4 Three-dimensional-imaging of vessels innervation 30 2.2.7 Statistical analysis 30 CHAPTER 3: RESULTS 3.1 Developmental and amyloid plaque-related changes in cerebral cortical capillaries in transgenic Tg2576 Alzheimer mice 31 3.1.1 Morphological distribution of brain vessels in the cerebral cortex of wild type mice 31 3.1.2 Microvessel density under plaque burden 33 3.2 Developmental and amyloid plaque-related changes in cholinergic neurotransmission in cholinoceptive target regions of transgenic Tg2576 mice 39 3.2.1 Visualisation of cholinergic nerve terminals in mouse brain 39 3.2.2 VAChT-Expression in wild type and transgenic Tg2576 mice 40 3.3 Role of cholinergic system in β-amyloid-related changes in the cerebrovascular system of transgenic Tg2576 mice 46 3.3.1 Solanum tuberosum lectin (STL) histochemistry in visualisation of brain vessels, β-amyloid, and microglia 46 3.3.1.1 Solanum tuberosum lectin and brain vessels 46 3.3.1.2 Solanum tuberosum lectin and β-amyloid plaques 47 3.3.1.3 Solanum tuberosum lectin staining to visualize glial cells 48 3.3.2 Cholinergic perivascular innervation of cerebral cortical microvessels in transgenic Tg2576 and wild type mice 50 CHAPTER 4: DISCUSSION 4.1 β-Amyloid and brain vascular system: the vascular hypothesis of Alzheimer’s disease 55 4.1.1 Evidences of a role of vascular mechanisms in Alzheimer’s disease 55 4.1.2 Effect of β-amyloid on brain vascular system 57 4.1.3 Effect of ischemia and hypoperfusion on APP processing 59 4.1.4 Effect of β-amyloid on cholinergic function in brain vascular system 59 4.2 Aim of study and main results obtained 61 4.3 Age-related changes in cerebral cortical microvessels in the presence and absence of β-amyloid plaque load 62 4.4 Age-related changes of cholinergic terminals in cholinoceptive target regions in the presence and absence of β-amyloid plaque load 64 4.4.1 VAChT – a reliable marker for detection of cholinergic terminals in cerebral cortex 64 4.4.2 The barrel field of the somatosensory cortex 1 (S1BF) as a model region to reveal age-related changes in cholinergic innervation 65 4.4.3 VAChT expression: morphological and morphometric studies 66 4.5 Age-related changes in cholinergic innervation of cerebral cortical microvessels in the presence and absence of β-amyloid plaque load 69 4.5.1 STL – a mono-marker for detection of cortical vessels, senile amyloid plaques and activated microglia in cerebral cortex 69 4.5.2 Cholinergic perivascular innervation of cerebral cortical microvessels in transgenic Tg2576 mice 70 4.5.3 Quantitation of cholinergic input on cerebral microvessels of mouse brain 71 4.6 Summary and conclusions 75 REFERENCES 77