GSK3β activity alleviates epileptogenesis and limits GluA1 phosphorylation

BACKGROUND

Glycogen synthase kinase-3β (GSK3β) is a key regulator of cellular homeostasis. In neurons, GSK3β contributes to the control of neuronal transmission and plasticity, but its role in epilepsy remains to be defined.

METHODS

Biochemical and electrophysiological methods were used to assess the role of GSK3β in regulating neuronal transmission and epileptogenesis. GSK3β activity was increased genetically in GSK3β[S9A] mice. Its effects on neuronal transmission and epileptogenesis induced by kainic acid were assessed by field potential recordings in mice brain slices and video electroencephalography in vivo. The ion channel expression was measured in brain samples from mice and followed by analysis in samples from patients with temporal lobe epilepsy or focal cortical dysplasia in correlation to GSK3β phosphorylation.

FINDINGS

Higher GSK3β activity decreased the progression of kainic acid induced epileptogenesis. At the biochemical level, higher GSK3β activity increased the expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel 4 under basal conditions and in the epileptic mouse brain and decreased phosphorylation of the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA1 at Serine 831 under basal conditions. Moreover, we found a significant correlation between higher inhibitory GSK3β phosphorylation at Serine 9 and higher activating GluA1 phosphorylation at Serine 845 in brain samples from epileptic patients.

INTERPRETATION

Our data imply GSK3β activity in the protection of neuronal networks from hyper-activation in response to epileptogenic stimuli and indicate that the anti-epileptogenic function of GSK3β involves modulation of HCN4 level and the synaptic AMPA receptors pool.

Novel Phospho-Tau Monoclonal Antibody Generated Using a Liposomal Vaccine, with Enhanced Recognition of a Conformational Tauopathy Epitope

The microtubule-associated protein Tau is an intrinsically unfolded, very soluble neuronal protein. Under still unknown circumstances, Tau protein forms soluble oligomers and insoluble aggregates that are closely linked to the cause and progression of various brain pathologies, including Alzheimer's disease. Previously we reported the development of liposome-based vaccines and their efficacy and safety in preclinical mouse models for tauopathy. Here we report the use of a liposomal vaccine for the generation of a monoclonal antibody with particular characteristics that makes it a valuable tool for fundamental studies as well as a candidate antibody for diagnostic and therapeutic applications. The specificity and affinity of antibody ACI-5400 were characterized by a panel of methods: (i) measuring the selectivity for a specific phospho-Tau epitope known to be associated with tauopathy, (ii) performing a combination of peptide and protein binding assays, (iii) staining of brain sections from mouse preclinical tauopathy models and from human subjects representing six different tauopathies, and (iv) evaluating the selective binding to pathological epitopes on extracts from tauopathy brains in non-denaturing sandwich assays. We conclude that the ACI-5400 antibody binds to protein Tau phosphorylated at S396 and favors a conformation that is typically present in the brain of tauopathy patients, including Alzheimer's disease.

GSK3β Controls mTOR and Prosurvival Signaling in Neurons

Glycogen synthase kinases-3β (GSK3β) is a key regulator of cell homeostasis. In neurons, GSK3β contributes to control of neuronal transmission and plasticity. Despite extensive studies in non-neuronal cells, crosstalk between GSK3β and other signaling pathways remains not well defined in neurons. In the present study, we report that GSK3β positively affected the activity of effectors of mammalian target of rapamycin complex 1 (mTORC1) and complex 2 (mTORC2), in mature neurons in vitro and in vivo. GSK3β also promoted prosurvival signaling and attenuated kainic acid-induced apoptosis. Our study identified GSK3β as a positive regulator of prosurvival signaling, including the mTOR pathway, and indicates the possible neuroprotective role of GSK3β in models of pharmacologically induced excitotoxicity.

GSK-3β and MMP-9 Cooperate in the Control of Dendritic Spine Morphology

Changes in the morphology of dendritic spines are prominent during learning and in different neurological and neuropsychiatric diseases, including those in which glycogen synthase kinase-3β (GSK-3β) has been implicated. Despite much evidence of the involvement of GSK-3β in functional synaptic plasticity, it is unclear how GSK-3β controls structural synaptic plasticity (i.e., the number and shape of dendritic spines). In the present study, we used two mouse models overexpressing and lacking GSK-3β in neurons to investigate how GSK-3β affects the structural plasticity of dendritic spines. Following visualization of dendritic spines with DiI dye, we found that increasing GSK-3β activity increased the number of thin spines, whereas lacking GSK-3β increased the number of stubby spines in the dentate gyrus. Under conditions of neuronal excitation, increasing GSK-3β activity caused higher activity of extracellularly acting matrix metalloproteinase-9 (MMP-9), and MMP inhibition normalized thin spines in GSK-3β overexpressing mice. Administration of the nonspecific GSK-3β inhibitor lithium in animals with active MMP-9 and animals lacking MMP-9 revealed that GSK-3β and MMP-9 act in concert to control dendritic spine morphology. Altogether, our data demonstrate that the dysregulation of GSK-3β activity has dramatic consequences on dendritic spine morphology, implicating MMP-9 as a mediator of GSK-3β-induced synaptic alterations.

Increasing brain protein O-GlcNAc-ylation mitigates breathing defects and mortality of Tau.P301L mice

The microtubule associated protein tau causes primary and secondary tauopathies by unknown molecular mechanisms. Post-translational O-GlcNAc-ylation of brain proteins was demonstrated here to be beneficial for Tau.P301L mice by pharmacological inhibition of O-GlcNAc-ase. Chronic treatment of ageing Tau.P301L mice mitigated their loss in body-weight and improved their motor deficits, while the survival was 3-fold higher at the pre-fixed study endpoint at age 9.5 months. Moreover, O-GlcNAc-ase inhibition significantly improved the breathing parameters of Tau.P301L mice, which underpinned pharmacologically the close correlation of mortality and upper-airway defects. O-GlcNAc-ylation of brain proteins increased rapidly and stably by systemic inhibition of O-GlcNAc-ase. Conversely, biochemical evidence for protein Tau.P301L to become O-GlcNAc-ylated was not obtained, nor was its phosphorylation consistently or markedly affected. We conclude that increasing O-GlcNAc-ylation of brain proteins improved the clinical condition and prolonged the survival of ageing Tau.P301L mice, but not by direct biochemical action on protein tau. The pharmacological effect is proposed to be located downstream in the pathological cascade initiated by protein Tau.P301L, opening novel venues for our understanding, and eventually treating the neurodegeneration mediated by protein tau.

Efficacy and safety of a liposome-based vaccine against protein Tau, assessed in tau.P301L mice that model tauopathy

Progressive aggregation of protein Tau into oligomers and fibrils correlates with cognitive decline and synaptic dysfunction, leading to neurodegeneration in vulnerable brain regions in Alzheimer's disease. The unmet need of effective therapy for Alzheimer's disease, combined with problematic pharmacological approaches, led the field to explore immunotherapy, first against amyloid peptides and recently against protein Tau. Here we adapted the liposome-based amyloid vaccine that proved safe and efficacious, and incorporated a synthetic phosphorylated peptide to mimic the important phospho-epitope of protein Tau at residues pS396/pS404. We demonstrate that the liposome-based vaccine elicited, rapidly and robustly, specific antisera in wild-type mice and in Tau.P301L mice. Long-term vaccination proved to be safe, because it improved the clinical condition and reduced indices of tauopathy in the brain of the Tau.P301L mice, while no signs of neuro-inflammation or other adverse neurological effects were observed. The data corroborate the hypothesis that liposomes carrying phosphorylated peptides of protein Tau have considerable potential as safe and effective treatment against tauopathies, including Alzheimer's disease.

Neurological characterization of mice deficient in GSK3α highlight pleiotropic physiological functions in cognition and pathological activity as Tau kinase

BACKGROUND

GSK3β is involved in a wide range of physiological functions, and is presumed to act in the pathogenesis of neurological diseases, from bipolar disorder to Alzheimer's disease (AD). In contrast, the GSK3α isozyme remained largely ignored with respect to both aspects.

RESULTS

We generated and characterized two mouse strains with neuron-specific or with total GSK3α deficiency. Behavioral and electrophysiological analysis demonstrated the physiological importance of neuronal GSK3α, with GSK3β not compensating for impaired cognition and reduced LTP. Interestingly, the passive inhibitory avoidance task proved to modulate the phosphorylation status of both GSK3 isozymes in wild-type mice, further implying both to function in cognition. Moreover, GSK3α contributed to the neuronal architecture of the hippocampal CA1 sub-region that is most vulnerable in AD. Consequently, practically all parameters and characteristics indicated that both GSK3 isoforms were regulated independently, but that they acted on the same physiological functions in learning and memory, in mobility and in behavior.

CONCLUSIONS

GSK3α proved to be regulated independently from GSK3β, and to exert non-redundant physiological neurological functions in general behavior and in cognition. Moreover, GSK3α contributes to the pathological phosphorylation of protein Tau.

Tauopathy differentially affects cell adhesion molecules in mouse brain: early down-regulation of nectin-3 in stratum lacunosum moleculare

Cell adhesion molecules are important structural substrates, required for synaptic plasticity and synaptogenesis. CAMs differ widely in their expression throughout different brain regions and their specific structural and functional roles in the brain remain to be elucidated. Here, we investigated selected cell adhesion molecules for alterations in expression levels and neuronal localization in validated mouse models for Alzheimer's disease that mimic the age-related progression of amyloid accumulation and tauopathy. Among the cell adhesion molecules analyzed, Nectin-3 expression was affected most and specifically in all mouse models with tauopathy. In particular was Nectin-3 depleted from the specific region of the hippocampus, known as the stratum lacunosum and moleculare, in mice that express wild-type or mutant human protein Tau, either chronically or sub-acutely. Tauopathy progresses from the entorhinal cortex to the hippocampus by unknown mechanisms that could involve transport by the myelinated axons of the temporoammonic and perforant pathways. The decreased expression of Nectin-3 in the stratum lacunosum moleculare is an early marker of impaired transport, and eventual synaptic problems, caused by beginning tauopathy.

GSK-3α/β kinases and amyloid production in vivo

Arising from C. J. Phiel, C. A. Wilson, V. M.-Y. Lee & P. S. Klein 423, 435-439 (2003)A major unresolved issue in Alzheimer's disease is identifying the mechanisms that regulate proteolytic processing of amyloid precursor protein (APP)-glycogen synthase kinase-3 (GSK-3) isozymes are thought to be important in this regulation. Phiel et al. proposed that GSK-3α, but not GSK-3β, controls production of amyloid. We analysed the proteolytic processing of mouse and human APP in mouse brain in vivo in five different genetic and viral models. Our data do not yield evidence for either GSK-3α-mediated or GSK-3β-mediated control of APP processing in brain in vivo.

Synaptic dysfunction in hippocampus of transgenic mouse models of Alzheimer's disease: a multi-electrode array study

APP.V717I and Tau.P301L transgenic mice develop Alzheimer's disease pathology comprising important aspects of human disease including increased levels of amyloid peptides, cognitive and motor impairment, amyloid plaques and neurofibrillary tangles. The combined model, APP.V717I×Tau.P301L bigenic mice (biAT mice) exhibit aggravated amyloid and tau pathology with severe cognitive and behavioral defects. In the present study, we investigated early changes in synaptic function in the CA1 and CA3 regions of acute hippocampal slices of young APP.V717I, Tau.P301L and biAT transgenic animals. We have used planar multi-electrode arrays (MEA) and improved methods for simultaneous multi-site recordings from two hippocampal sub-regions. In the CA1 region, long-term potentiation (LTP) was severely impaired in all transgenic animals when compared with age-matched wild-type controls, while basal synaptic transmission and paired-pulse facilitation were minimally affected. In the CA3 region, LTP was normal in Tau.P301L and APP.V717I but clearly impaired in biAT mice. Surprisingly, frequency facilitation in CA3 was significantly enhanced in Tau.P301L mice, while not affected in APP.V717I mice and depressed in biAT mice. The findings demonstrate important synaptic changes that differ considerably in the hippocampal sub-regions already at young age, well before the typical amyloid or tau pathology is evident.

Alzheimer's disease: old problem, new views from transgenic and viral models

Alzheimer's dementia is developing ever more as a complex syndrome with various unknown genetic and epigenetic contributions. These are compounded on and exacerbating the underlying amyloid and tau pathology that remain the basis of the pathological definition of Alzheimer's disease. Here, we present a selection of aspects of recent bigenic and virus-based mouse strains, developed as pre-clinical models for Alzheimer's disease. We discuss newer features in the context of the characteristics defined in previously validated transgenic models. We focus on specific aspects of single and multiple transgenic mouse models for Alzheimer's disease and for tauopathies, rather than providing an exhaustive list of all available models. We concentrate on the content of information related to neurodegeneration and disease mechanisms. We pay attention to aspects and defects that are predicted by the models and can be tested in humans. We discuss implications that help translate the fundamental knowledge into clinical, diagnostic and therapeutic applications. We elaborate on the increasing knowledge extracted from transgenic models and from newer adeno-associated viral models. We advocate this combination as a valuable strategy to study molecular, cellular and system-related pathogenic mechanisms in AD and tauopathies. We believe that innovative animal models remain needed to critically test current views, to identify and validate therapeutic targets, to allow testing of compounds, to help understand and eventually treat tauopathies, including Alzheimer's disease.

AAV-tau mediates pyramidal neurodegeneration by cell-cycle re-entry without neurofibrillary tangle formation in wild-type mice

In Alzheimer's disease tauopathy is considered secondary to amyloid, and the duality obscures their relation and the definition of their respective contributions.Transgenic mouse models do not resolve this problem conclusively, i.e. the relative hierarchy of amyloid and tau pathology depends on the actual model and the genes expressed or inactivated. Here, we approached the problem in non-transgenic models by intracerebral injection of adeno-associated viral vectors to express protein tau or amyloid precursor protein in the hippocampus in vivo. AAV-APP mutant caused neuronal accumulation of amyloid peptides, and eventually amyloid plaques at 6 months post-injection, but with only marginal hippocampal cell-death. In contrast, AAV-Tau, either wild-type or mutant P301L, provoked dramatic degeneration of pyramidal neurons in CA1/2 and cortex within weeks. Tau-mediated neurodegeneration proceeded without formation of large fibrillar tau-aggregates or tangles, but with increased expression of cell-cycle markers.We present novel AAV-based models, which demonstrate that protein tau mediates pyramidal neurodegeneration in vivo. The data firmly support the unifying hypothesis that post-mitotic neurons are forced to re-enter the cell-cycle in primary and secondary tauopathies, including Alzheimer's disease.

Glycogen synthase kinase-3beta, or a link between amyloid and tau pathology?

Phosphorylation is the most common post-translational modification of cellular proteins, essential for most physiological functions. Deregulation of phosphorylation has been invoked in disease mechanisms, and the case of Alzheimer's disease (AD) is no exception: both in the amyloid pathology and in the tauopathy are kinases deeply implicated. The glycogen synthase kinase-3 (GSK-3) isozymes participate in diverse cellular processes and important signalling pathways and have been implicitly linked to diverse medical problems, i.e. from diabetes and cancer to mood disorders and schizophrenia, and in the neurodegeneration of AD. Here, we review specific aspects of GSK-3 isozymes in the framework of recent data that we obtained in novel transgenic mouse models that robustly recapitulate the pathology and mechanistical problems of AD.

Beta-site amyloid precursor protein-cleaving enzyme-1 (BACE1)-mediated changes of endogenous amyloid beta in wild-type and transgenic mice in vivo

Beta-site amyloid precursor protein-cleaving enzyme-1 (BACE1) initiates generation of amyloid beta (Abeta), a pathological hallmark of Alzheimer's disease. We investigated the impact of BACE1 protein level on endogenous Abeta. Endogenous Abeta and BACE1 protein levels were concurrently and significantly reduced during early life. However, Abeta levels were similar between BACE1 transgenic and wildtype mice. This suggests that BACE1 protein level has a minimal effect on the level of endogenous Abeta. Consequently, other factors must be involved in modulation of Abeta production in adult and ageing brain and investigation of such factors may yield therapeutic targets. Further, these results suggest that substantial inhibition of BACE1 in brain may be required for clinical benefit in Alzheimer's disease.

Amyloid activates GSK-3beta to aggravate neuronal tauopathy in bigenic mice

The hypothesis that amyloid pathology precedes and induces the tau pathology of Alzheimer's disease is experimentally supported here through the identification of GSK-3 isozymes as a major link in the signaling pathway from amyloid to tau pathology. This study compares two novel bigenic mouse models: APP-V717I x Tau-P301L mice with combined amyloid and tau pathology and GSK-3beta x Tau-P301L mice with tauopathy only. Extensive and remarkable parallels were observed between these strains including 1) aggravation of tauopathy with highly fibrillar tangles in the hippocampus and cortex; 2) prolonged survival correlated to alleviated brainstem tauopathy; 3) development of severe cognitive and behavioral defects in young adults before the onset of amyloid deposition or tauopathy; and 4) presence of pathological phospho-epitopes of tau, including the characteristic GSK-3beta motif at S396/S404. Both GSK-3 isozymes were activated in the brain of parental APP-V717I amyloid mice, even at a young age when cognitive and behavioral defects are evident but before amyloid deposition. The data indicate that amyloid induces tauopathy through activation of GSK-3 and suggest a role for the kinase in maintaining the functional integrity of adult neurons.

Neurodegeneration and neuroinflammation in cdk5/p25-inducible mice: a model for hippocampal sclerosis and neocortical degeneration

The cyclin-dependent kinase cdk5 is atypically active in postmitotic neurons and enigmatic among the kinases proposed as molecular actors in neurodegeneration. We generated transgenic mice to express p25, the N-terminally truncated p35 activator of cdk5, in forebrain under tetracycline control (TET-off). Neuronal expression of p25 (p25(ON)) caused high mortality postnatally and early in life. Mortality was completely prevented by administration of doxycycline in the drinking water of pregnant dams and litters until P42, allowing us to study the action of p25 in adult mouse forebrain. Neuronal p25 triggered neurodegeneration and also microgliosis, rapidly and intensely in hippocampus and cortex. Progressive neurodegeneration was severe with marked neuron loss, causing brain atrophy (40% loss at age 5 months) with nearly complete elimination of the hippocampus. Neurodegeneration did not involve phosphorylation of protein tau or generation of amyloid peptide. Degenerating neurons did not stain for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling or activated caspase-3 but were marked by FluoroJadeB in early stages. Diseased neurons were always closely associated with activated microglia already very early in the disease process. Primary neurons derived from p25 embryos were more prone to apoptosis than wild-type neurons, and they activated microglial cells in co-culture. The inducible p25 mice present as a model for neurodegeneration in hippocampal sclerosis and neocortical degeneration, with important contributions of activated microglia.

Deregulation of NMDA-receptor function and down-stream signaling in APP[V717I] transgenic mice

Evidence is accumulating for a role for amyloid peptides in impaired synaptic plasticity and cognition, while the underlying mechanisms remain unclear. We here analyzed the effects of amyloid peptides on NMDA-receptor function in vitro and in vivo. A synthetic amyloid peptide preparation containing monomeric and oligomeric A beta (1-42) peptides was used and demonstrated to bind to synapses expressing NMDA-receptors in cultured hippocampal and cortical neurons. Pre-incubation of primary neuronal cultures with A beta peptides significantly inhibited NMDA-receptor function, albeit not by a direct pharmacological inhibition of NMDA-receptors, since acute application of A beta peptides did not change NMDA-receptor currents in autaptic hippocampal cultures nor in xenopus oocytes expressing recombinant NMDA-receptors. Pre-incubation of primary neuronal cultures with A beta peptides however decreased NR2B-immunoreactive synaptic spines and surface expression of NR2B containing NMDA-receptors. Furthermore, we extended these findings for the first time in vivo, demonstrating decreased concentrations of NMDA-receptor subunit NR2B and PSD-95 as well as activated alpha-CaMKII in postsynaptic density preparations of APP[V717I] transgenic mice. This was associated with impaired NMDA-dependent LTP and decreased NMDA- and AMPA-receptor currents in hippocampal CA1 region in APP[V717I] transgenic mice. In addition, induction of c-Fos following cued and contextual fear conditioning was significantly impaired in the basolateral amygdala and hippocampus of APP[V717I] transgenic mice. Our data demonstrate defects in NMDA-receptor function and learning dependent signaling cascades in vivo in APP[V717I] transgenic mice and point to decreased surface expression of NMDA-receptors as a mechanism involved in early synaptic defects in APP[V717I] transgenic mice in vivo.

5-HT4 receptor agonists increase sAPPalpha levels in the cortex and hippocampus of male C57BL/6j mice

BACKGROUND AND PURPOSE

A strategy to treat Alzheimer's disease (AD) is to increase the soluble form of amyloid precursor protein (sAPPalpha), a promnesic protein, in the brain. Because strong evidence supports beneficial effects of 5-hydroxytryptamine 5-HT(4) receptor agonists in memory and learning, we investigated the role of 5-HT(4) receptors on APP processing in 8 weeks-old male C57BL/6j mice.

EXPERIMENTAL APPROACH

Mice were given, subcutaneously, prucalopride or ML 10302 (s.c.), two highly selective 5-HT(4) receptor agonists and, up to 240 min later, the hippocampus and cortex were analysed by Western blot for sAPPalpha determination.

KEY RESULTS

Prucalopride (5 or 10 mg kg(-1)) significantly increased sAPPalpha levels in the hippocampus and cortex, but did not modify the expression level of APP mRNA as detected by quantitative RT-PCR. A selective 5-HT(4) receptor antagonist, GR125487 (1 mg kg(-1), s.c.) inhibited prucalopride induced- increase in sAPPalpha levels. In addition, levels of sAPPalpha were increased by ML10302 only at 20 mg kg(-1) and was limited to the cortex. Also, prucalopride increased sAPPalpha levels in the cortex of a transgenic mouse model of AD, expressing the London mutation of APP. Furthermore, the combined injection of a selective acetylcholinesterase inhibitor, donepezil and prucalopride induced a synergic increase in sAPPalpha levels in the cortex and hippocampus.

CONCLUSIONS AND IMPLICATIONS

Our results demonstrate that the 5-HT(4) receptor plays a key role in the non-amyloidogenic pathway of APP metabolism in vivo and give support to the beneficial use of 5-HT(4) agonists for AD treatment.

Modulation of synaptic plasticity and Tau phosphorylation by wild-type and mutant presenilin1

The function of presenilin1 (PS1) in intra-membrane proteolysis is undisputed, as is its role in neurodegeneration in FAD, in contrast to its exact function in normal conditions. In this study, we analyzed synaptic plasticity and its underlying mechanisms biochemically in brain of mice with a neuron-specific deficiency in PS1 (PS1(n-/-)) and compared them to mice that expressed human mutant PS1[A246E] or wild-type PS1. PS1(n-/-) mice displayed a subtle impairment in Schaffer collateral hippocampal long-term potentiation (LTP) as opposed to normal LTP in wild-type PS1 mice, and a facilitated LTP in mutant PS1[A246E] mice. This finding correlated with, respectively, increased and reduced NMDA receptor responses in PS1[A246E] mice and PS1(n-/-) mice in hippocampal slices. Postsynaptically, levels of NR1/NR2B NMDA-receptor subunits and activated alpha-CaMKII were reduced in PS1(n-/-) mice, while increased in PS1[A246E] mice. In addition, PS1(n-/-) mice, displayed reduced paired pulse facilitation, increased synaptic fatigue and lower number of total and docked synaptic vesicles, implying a presynaptic function for wild-type presenilin1, unaffected by the mutation in PS1[A246E] mice. In contrast to the deficiency in PS1, mutant PS1 activated GSK-3beta by decreasing phosphorylation on Ser-9, which correlated with increased phosphorylation of protein tau at Ser-396-Ser-404 (PHF1/AD2 epitope). The synaptic functions of PS1, exerted on presynaptic vesicles and on postsynaptic NMDA-receptor activity, were concluded to be independent of alterations in GSK-3beta activity and phosphorylation of protein tau.

Transgenic mouse models for Alzheimer's disease: the role of GSK-3β in combined amyloid and tau-pathology

Describing and understanding the pathological processes which devastate the brain of Alzheimer's disease (AD) patients remains a major target for experimental biology. We approached this problem by generating different types of single and double transgenic mice that develop pathological hallmarks of AD. In APP-V717 mice, the progression from intracellular amyloid to diffuse and senile plaques with vascular deposits, is preceded by early defects in cognition and LTP. In Tau-P301L mice, the morbid tauopathy with intracellular filaments, cause mortality before age 1 year. Ageing APP-V717IxTau-P301L double tg mice (14-17 months) have combined AD-like pathology in hippocampus and cortex consisting of amyloid plaques and neurofibrillary tangles. Remarkably, while Tau-P301L mice die before age 1 year, the APP-V717IxTau-P301L double tg mice survive much longer, which correlates with alleviation of tauopathy in hindbrain, despite aggravation in forebrain. This hypothesis is corroborated in Tau-P301LxGSK-3B double transgenic mice, which have also an extended lifespan relative to Tau-P301L mice, that correlates with reduction of brainstem tauopathy. At the same time, Tau-P301LxGSK-3B mice have dramatic forebrain tauopathy, with "tangles in almost all neurons", although without hyper-phosphorylation of Tau. The data corroborate the hypothesis that GSK-3B is the missing link between the amyloid and tau-pathology, and position GSK-3B as prominent player in the pathogenesis in AD.

Neuronal or glial expression of human apolipoprotein e4 affects parenchymal and vascular amyloid pathology differentially in different brain regions of double- and triple-transgenic mice

Apolipoprotein E4 (ApoE4) is associated with Alzheimer's disease by unknown mechanisms. We generated six transgenic mice strains expressing human ApoE4 in combination with mutant amyloid precursor protein (APP) and mutant presenilin-1 (PS1) in single-, double-, or triple-transgenic combinations. Diffuse, but not dense, amyloid plaque-load in subiculum and cortex was increased by neuronal but not glial ApoE4 in old (15 months) double-transgenic mice, whereas both diffuse and dense plaques formed in thalamus in both genotypes. Neuronal and glial ApoE4 promoted cerebral amyloid angiopathy as extensively as mutant PS1 but with pronounced regional differences: cortical angiopathy was induced by neuronal ApoE4 while thalamic angiopathy was again independent of ApoE4 source. Angiopathy correlated more strongly with soluble Abeta40 and Abeta42 levels in cortex than in thalamus throughout the six genotypes. Neither neuronal nor glial ApoE4 affected APP proteolytic processing, as opposed to mutant PS1. Neuronal ApoE4 increased soluble amyloid levels more than glial ApoE4, but the Abeta42/40 ratios were similar, although significantly higher than in single APP transgenic mice. We conclude that although the cellular origin of ApoE4 differentially affects regional amyloid pathology, ApoE4 acts on the disposition of amyloid peptides downstream from their excision from APP but without induction of tauopathy.