Insights into Alzheimer disease pathogenesis from studies in transgenic animal models

VEEV TC-83 Triggers Dysregulation of the Tryptophan-Kynurenine Pathway in the Central Nervous System That Correlates with Cognitive Impairment in Tg2576 Mice

Neurodegenerative diseases are chronic conditions affecting the central nervous system (CNS). Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid beta in the limbic and cortical brain regions. AD is presumed to result from genetic abnormalities or environmental factors, including viral infections, which may have deleterious, long-term effects. In this study, we demonstrate that the Venezuelan equine encephalitis virus (VEEV) commonly induces neurodegeneration and long-term neurological or cognitive sequelae. Notably, the effects of VEEV infection can persistently influence gene expression in the mouse brain, suggesting a potential link between the observed neurodegenerative outcomes and long-term alterations in gene expression. Additionally, we show that alphavirus encephalitis exacerbates the neuropathological profile of AD through crosstalk between inflammatory and kynurenine pathways, generating a range of metabolites with potent effects. Using a mouse model for β-amyloidosis, Tg2576 mice, we found that cognitive deficits and brain pathology were more severe in Tg2576 mice infected with VEEV TC-83 compared to mock-infected controls. Thus, during immune activation, the kynurenine pathway plays a more active role in the VEEV TC-83-infected cells, leading to increases in the abundance of transcripts related to the kynurenine pathway of tryptophan metabolism. This pathway generates several metabolites with potent effects on neurotransmitter systems as well as on inflammation, as observed in VEEV TC-83-infected animals.

Extracts of Sideritis scardica and Clinopodium vulgare Alleviate Cognitive Impairments in Scopolamine-Induced Rat Dementia

Sideritis scardica Griseb. and Clinopodium vulgare L., belonging to the Lamiaceae family, are rich in terpenoids and phenolics and exhibit various pharmacological effects, including antioxidant, anti-inflammatory and anti-cancer activities. While the memory-enhancing impacts of S. scardica are well documented, the cognitive benefits of C. vulgare remain unexplored. This study assessed the potential effect of C. vulgare on learning and memory in healthy and scopolamine (Sco)-induced memory-impaired male Wistar rats, comparing it with the effects of S. scardica. Over a 21-day period, rats orally received extracts of cultivated S. scardica (200 mg/kg) and C. vulgare (100 mg/kg), either individually or in combination, with administration starting 10 days before and continuing 11 days simultaneously with Sco injection at a dose of 2 mg/kg intraperitoneally. The results showed that both extracts effectively mitigated Sco-induced memory impairment. Their combination significantly improved recognition memory and maintained monoaminergic function. S. scardica excelled in preserving spatial working memory, while C. vulgare exhibited comparable retention of recognition memory, robust antioxidant activity and acetylcholinesterase inhibitory activity. The extracts alleviated Sco-induced downregulation of p-CREB/BDNF signaling, suggesting neuroprotective mechanisms. The extract combination positively affected most of the Sco-induced impairments, underscoring the potential for further investigation of these extracts for therapeutic development.

Insight into the emerging and common experimental in-vivo models of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial, rapidly progressing neurodegenerative disorder. As the exact cause of the disease is still unclear, the drug development is very challenging. This review encompasses the commonly used AD models involving various chemicals, heavy metals and endogenous substances induced models and the transgenic models. It also provides insight into the reliable emerging models of AD that may overcome the shortcomings associated with available models. Chemicals like streptozotocin, scopolamine, colchicine and okadaic acid render the animal susceptible to neuroinflammation and oxidative stress induced neurodegeneration along with amyloid-β deposition and tau hyperphosphorylation. Similarly, endogenous substances like acrolein and amyloid-β 1-42 are efficient in inducing the major pathologies of AD. Heavy metals like aluminum and fluoride and mixture of these have been reported to induce neurotoxicity therefore are used as animal models for AD. Transgenic models developed as a result of knock-in or knock-out of certain genes associated with AD including PDAPP, APP23, Tg2576, APP/PS1, 3 × Tg and 5 × FAD have also been incorporated in this study. Further, emerging and advanced pathomimetic models of AD are provided particular interest here which will add on to the current knowledge of animal models and may aid in the drug development process and deepen our understanding related to AD pathogenesis. These newly discovered models include oAβ25-35 model, transgenic model expressing 82-kDa ChAT, oDGal mouse and APP knock-in rat. This study may aid in the selection of suitable model for development of novel potent therapeutics and for exploring detailed pathogenic mechanism of AD.

Current emerging novel therapies for Alzheimer's disease and the future prospects of magneto-mechanical force therapy

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly, and the morbidity increases with the aging population aggravation. The clinical symptoms of AD mainly include cognitive impairment and memory loss, which undoubtedly bring a huge burden to families and society. Currently, the drugs in clinical use only improve the symptoms of AD but do not cure or prevent the progression of the disease. Therefore, it is urgent for us to develop novel therapeutic strategies for effective AD treatment. To provide a better theoretical basis for exploring novel therapeutic strategies in future AD treatment, this review introduces the recent AD treatment technologies from three aspects, including nanoparticle (NP) based drug therapy, biological therapy and physical therapy. The nanoparticle-mediated therapeutic approaches at the nanomaterial-neural interface and biological system are described in detail, and in particular the magneto-regulated strategies by magnetic field actuating magnetic nanoparticles are highlighted. Promising application of magneto-mechanical force regulated strategy in future AD treatment is also addressed, which offer possibilities for the remote manipulation in a precise manner. In the future, it may be possible for physicians to realize a remote, precise and effective therapy for AD using magneto-mechanical force regulated technology based on the combination of magnetic nanoparticles and an external magnetic field.

Evidence of disturbed insulin signaling in animal models of Alzheimer's disease

Since glucose reuptake by neurons is mostly independent of insulin, it has been an intriguing question whether insulin has or not any roles in the brain. Consequently, the identification of insulin receptors in the central nervous system has fueled investigations of insulin functions in the brain. It is also already known that insulin can influence glucose reuptake by neurons, mostly during activities that have the highest energy demand. The identification of high density of insulin receptors in the hippocampus also suggests that insulin may present important roles related to memory. In this context, studies have reported worse performance in cognitive tests among diabetic patients. In addition, alterations in the regulation of central insulin pathways have been observed in the brains of Alzheimer's disease (AD) patients. In fact, some authors have proposed AD as a third type of diabetes and recently, our group proposed insulin resistance as a common link between different AD hypotheses. Therefore, in the present narrative review, we intend to revise and gather the evidence of disturbed insulin signaling in experimental animal models of AD.

Effects of Sideritis scardica Extract on Scopolamine-Induced Learning and Memory Impairment in Mice

BACKGROUND

The neurodegenerative process in Alzheimer's disease, one of the most common types of dementia worldwide, mostly affects the cholinergic neurotransmitter system and, to a lesser extent, the monoaminergic one. The antioxidant acetylcholinesterase (AChE) and triple monoamine reuptake inhibitory activity of Sideritis scardica (S. scardica) and other Sideritis species has already been reported.

OBJECTIVE

To investigate the effects of S. scardica water extracts on the learning and memory processes, anxiety-like behavior, and locomotor activities in scopolamine (Sco)-induced dementia in mice.

METHODS

Male Albino IRC mice were used. The plant extract was administered for 11 consecutive days in the presence or absence of Sco (1 mg/kg, i.p). The behavioural performance of the animals was evaluated by passive avoidance, T-maze, and hole-board tests. The effects of extract on AChE activity, brain noradrenalin (NA), and serotonin (Sero) content, and antioxidant status were also monitored.

RESULTS

Our experimental data revealed that the S. scardica water extract caused a reduction in degree of memory impairment and anxiety-like behaviour in mice with scopolamine-induced dementia. The extract did not affect changed by the Sco AChE activity but impact reduced brain NA and Sero levels and demonstrated moderate antioxidant activity. In healthy mice we did not confirm the presence of anxiolytic-like and AChE inhibitory effects of the S. scardica water extract. The extract did not change the control Sero brain levels and reduce those of NA.

CONCLUSION

S. scardica water extract demonstrated memory preserving effect in mice with scopolamine-induced dementia and deserve further attention.

APP/PS1 Gene-Environmental Cadmium Interaction Aggravates the Progression of Alzheimer's Disease in Mice via the Blood-Brain Barrier, Amyloid-β, and Inflammation

BACKGROUND

There is limited information about gene-environment interaction on the occurrence and the progression of Alzheimer's disease.

OBJECTIVE

To explore the effect of environmental low-dose cadmium (Cd) exposure on the progress of Alzheimer's disease and the underlining mechanism.

METHODS

We administered 1 mg/L, 10 mg/L cadmium chloride (treated groups), and water (control group) to C57BL/6J and APP/PS1 mice through drinking water, from one week before mating, until the offspring were sacrificed at 6 months of age. The behaviors, Cd level, blood-brain barrier (BBB) leakage, Aβ1-42 deposition, and inflammation expression were evaluated in these mice.

RESULTS

Mice of both genotypes had similar blood Cd levels after exposure to the same dose of Cd. The toxic effects of Cd on the two genotypes differed little in terms of neuronal histomorphology and BBB permeability. Cd caused a series of pathological morphological changes in the mouse brains and more fluorescent dye leakage at higher doses. Furthermore, the APP/PS1 mice had more severe damage than the C57BL/6J mice, based on the following five criteria. They were increasing anxiety-like behavior and chaos movement, spatial reference memory damage, Aβ plaque deposition in mouse brains, increasing microglia expression in the brain, and IL-6 higher expression in the cortex and in the serum.

CONCLUSION

Low-dose Cd exposure for 6 months increases Aβ plaque deposition and BBB permeability, exacerbates inflammatory responses, and activates microglia, in APP/PS1 mice. APP/PS1 gene-environmental Cd interaction aggravates the progression of Alzheimer's disease in mice.

Mesenchymal stem cell-derived extracellular vesicles ameliorate Alzheimer's disease-like phenotypes in a preclinical mouse model

Alzheimer's disease (AD) is an irreversible neurodegenerative disorder that affects more than 44 million people worldwide. Despite the high disease burden, there is no effective treatment for people suffering from AD. Mesenchymal stem cells (MSCs) are multipotent stromal cells that have been widely studied due to their therapeutic potential. However, administration of cells has been found to have a multitude of limitations. Recently, extracellular vesicles (EVs) derived from MSCs have been studied as a therapeutic candidate, as they exhibit similar immunoprotective and immunomodulatory abilities as the host human MSCs. Methods: To test the potential therapeutic effects of MSC EVs, human bone-marrow derived MSCs were grown in three-dimensional (3D) cell culture, and small EVs were harvested using differential ultracentrifugation. These small EVs were given to non-transgenic (NT) or 5XFAD (5 familial Alzheimer's disease mutations) mice intranasally (IN) every 4 days for 4 months. The mice were then required to perform a variety of behavioral assays to measure changes in learning and memory. Afterwards, immunohistochemistry was performed on brain slices to measure amyloid beta (Aβ) and glial fibrillary acidic protein (GFAP) levels. Results: The data revealed that 5XFAD mice that received hMSC-EV treatment behaved significantly better in cognitive tests than saline treated 5XFAD mice, with no significant change between EV-treated 5XFAD mice and NT mice. Additionally, we found lower Aβ plaque load in the hippocampus of the EV-treated mice. Finally, less colocalization between GFAP and Aβ plaques was found in the brain of EV-treated mice compared to saline. Conclusions: Taken together, these data suggest that IN administration of MSC-derived EVs can slow down AD pathogenesis.

Age and gender differences for the behavioral phenotypes of 3xTg alzheimer's disease mice

The triple transgenic Alzheimer's disease (3xTg-AD) strain is a common mouse model used for studying the pathology and mechanism of Alzheimer's disease (AD). The 3xTg-AD strain exhibits two hallmarks of AD, amyloid beta (Aβ) and neurofibrillary tangles. Several studies using different gender and age of 3xTg-AD mice to investigate their behavior phenotypes under the influence of various treatments have reported mixed results. Therefore, a comprehensive investigation on the optimal gender, age, and training paradigms used for behavioral studies of 3xTg-AD is necessary. In the present study, we investigated the behavioral phenotypes for the two genders of 3xTg-AD mice at 3, 6, 9, and 12 months old and compared the results with age-, gender-matched C57BL/6N control strain. All mice were subjected to tail flick, pinprick, open field, elevated plus maze, passive avoidance, and trace fear conditioning (TFC) tests to evaluate their sensory, locomotor, anxiety, and learning/memory functions. The results showed that TFC on male 3xTg-AD mice is optimal for studying the memory performance in AD. The sensory and locomotor functions of 3xTg-AD mice for two genders appear to be normal before 6 months, decline in fear memory afterwards. The differences between control and 3xTg-AD male mice in contextual and cued memory are robust, thus they are ideal for evaluating the effect of a treatment. Since it is costly and time consuming to obtain wildtype littermates as controls, C57BL/6N strain is suggested to be used as control mice because their baseline performance of sensorimotor functions are similar to that of 3xTg-AD mice.

Mural Cells: Potential Therapeutic Targets to Bridge Cardiovascular Disease and Neurodegeneration

Mural cells collectively refer to the smooth muscle cells and pericytes of the vasculature. This heterogenous population of cells play a crucial role in the regulation of blood pressure, distribution, and the structural integrity of the vascular wall. As such, dysfunction of mural cells can lead to the pathogenesis and progression of a number of diseases pertaining to the vascular system. Cardiovascular diseases, particularly atherosclerosis, are perhaps the most well-described mural cell-centric case. For instance, atherosclerotic plaques are most often described as being composed of a proliferative smooth muscle cap accompanied by a necrotic core. More recently, the role of dysfunctional mural cells in neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease, is being recognized. In this review, we begin with an exploration of the mechanisms underlying atherosclerosis and neurodegenerative diseases, such as mural cell plasticity. Next, we highlight a selection of signaling pathways (PDGF, Notch and inflammatory signaling) that are conserved across both diseases. We propose that conserved mural cell signaling mechanisms can be exploited for the identification or development of dual-pronged therapeutics that impart both cardio- and neuroprotective qualities.

Multifaceted Role of Matrix Metalloproteinases in Neurodegenerative Diseases: Pathophysiological and Therapeutic Perspectives

Neurodegeneration is the pathological condition, in which the nervous system or neuron loses its structure, function, or both, leading to progressive degeneration or the death of neurons, and well-defined associations of tissue system, resulting in clinical manifestations. Neuroinflammation has been shown to precede neurodegeneration in several neurodegenerative diseases (NDs). No drug is yet known to delay or treat neurodegeneration. Although the etiology and potential causes of NDs remain widely indefinable, matrix metalloproteinases (MMPs) evidently have a crucial role in the progression of NDs. MMPs, a protein family of zinc (Zn²⁺)-containing endopeptidases, are pivotal agents that are involved in various biological and pathological processes in the central nervous system (CNS). The current review delineates the several emerging evidence demonstrating the effects of MMPs in the progression of NDs, wherein they regulate several processes, such as (neuro)inflammation, microglial activation, amyloid peptide degradation, blood brain barrier (BBB) disruption, dopaminergic apoptosis, and α-synuclein modulation, leading to neurotoxicity and neuron death. Published papers to date were searched via PubMed, MEDLINE, etc., while using selective keywords highlighted in our manuscript. We also aim to shed a light on pathophysiological effect of MMPs in the CNS and focus our attention on its detrimental and beneficial effects in NDs, with a special focus on Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), multiple sclerosis (MS), and Huntington's disease (HD), and discussed various therapeutic strategies targeting MMPs, which could serve as potential modulators in NDs. Over time, several agents have been developed in order to overcome challenges and open up the possibilities for making selective modulators of MMPs to decipher the multifaceted functions of MMPs in NDs. There is still a greater need to explore them in clinics.

Metabolic, Phenotypic, and Neuropathological Characterization of the Tg4-42 Mouse Model for Alzheimer's Disease

BACKGROUND

Preclinical Alzheimer's disease (AD) research strongly depends on transgenic mouse models that display major symptoms of the disease. Although several AD mouse models have been developed representing relevant pathologies, only a fraction of available mouse models, like the Tg4-42 mouse model, display hippocampal atrophy caused by the death of neurons as the key feature of AD. The Tg4-42 mouse model is therefore very valuable for use in preclinical research. Furthermore, metabolic biomarkers which have the potential to detect biochemical changes, are crucial to gain deeper insights into the pathways, the underlying pathological mechanisms and disease progression.

OBJECTIVE

We thus performed an in-depth characterization of Tg4-42 mice by using an integrated approach to analyze alterations of complex biological networks in this AD in vivo model.

METHODS

Therefore, untargeted NMR-based metabolomic phenotyping was combined with behavioral tests and immunohistological and biochemical analyses.

RESULTS

Our in vivo experiments demonstrate a loss of body weight increase in homozygous Tg4-42 mice over time as well as severe impaired learning behavior and memory deficits in the Morris water maze behavioral test. Furthermore, we found significantly altered metabolites in two different brain regions and metabolic changes of the glutamate/4-aminobutyrate-glutamine axis. Based on these results, downstream effects were analyzed showing increased Aβ42 levels, increased neuroinflammation as indicated by increased astro- and microgliosis as well as neuronal degeneration and neuronal loss in homozygous Tg4-42 mice.

CONCLUSION

Our study provides a comprehensive characterization of the Tg4-42 mouse model which could lead to a deeper understanding of pathological features of AD. Additionally this study reveals changes in metabolic biomarker which set the base for future preclinical studies or drug development.

Invasive and non-invasive therapies for Alzheimer's disease and other amyloidosis

Advancements in medical science have facilitated in extending human lives. The increased life expectancy, though, has come at a cost. The cases of an aging population suffering from degenerative diseases like Alzheimer's disease (AD) are presently at its all-time high. Amyloidosis disorders such as AD are triggered by an abnormal transition of soluble proteins into their highly ordered aggregated forms. The landscape of amyloidosis treatment remains unchanged, and there is no cure for such disorders. However, an increased understanding of the mechanism of amyloid self-assembly has given hope for a possible therapeutic solution. In this review, we will discuss the current state of molecular and non-molecular options for therapeutic intervention of amyloidosis. We highlight the efficacy of non-invasive physical therapies as possible alternatives to their molecular counterparts. Graphical abstract.

Race- and Sex-Based Disparities in Alzheimer's Disease Clinical Trial Enrollment in the United States and Canada: An Indigenous Perspective

Randomized clinical trials (RCT) involve labor-intensive, highly regulated, and controlled processes intended to transform scientific concepts into clinical outcomes. To be effective and targeted, it is imperative they include those populations who would most benefit from those outcomes. Alzheimer's disease (AD) is most detrimental to the aging population, and its clinical manifestation is influenced by socio-economic factors such as poverty, poor education, stress, and chronic co-morbidities. Indigenous populations in the United States and Canada are among the minority populations most influenced by poor socio-economic conditions and are prone to the ravages of AD, with Indigenous women carrying the added burden of exposure to violence, caregiving stresses, and increased risk by virtue of their sex. Race- and sex-based disparities in RCT enrollment has occurred for decades, with Indigenous men and women very poorly represented. In this review, we examined literature from the last twenty years that reinforce these disparities and provide some concrete suggestions and guidelines to increase the enrollment numbers in AD RCT among this vulnerable and poorly represented population.

Alix and Syntenin-1 direct amyloid precursor protein trafficking into extracellular vesicles

BACKGROUND

Endosomal trafficking and amyloidogenic cleavage of amyloid precursor protein (APP) is believed to play a role in the neurodegeneration observed in Alzheimer's disease (AD). Recent evidence has suggested that packaging and secretion of APP and its amyloidogenic cleaved products into small extracellular vesicles (EVs) may facilitate uptake of these neurotoxic factors during disease progression. However, the molecular mechanisms underlying trafficking of APP into EVs are poorly understood.

RESULTS

In this study, the mechanism and impact of APP trafficking into extracellular vesicles (EVs) were assessed by a series of inducible gene knockdowns. We demonstrate that vesicle-associated proteins Alix and Syntenin-1 are essential for proper subcellular localization and efficient EV secretion of APP via an endosomal sorting complexes required for transport (ESCRT)-independent pathway. The neurotoxic C-terminal fragment (CTFβ) of APP is similarly secreted in association with small vesicles. These mechanisms are conserved in terminally differentiated neuron-like cells. Furthermore, knockdown of Alix and Syntenin-1 alters the subcellular localization of APP, sequestering the precursor protein to endoplasmic reticulum and endolysosomal compartments, respectively. Finally, transfer of small EVs containing mutant APP confers an increase in reactive oxygen species production and neurotoxicity to human induced pluripotent stem cell-derived cortical neurons and naïve primary neurons, an effect that is ameliorated by Alix and Syntenin-1 depletion.

CONCLUSIONS

Altogether these findings elucidate a novel mechanism for understanding the intracellular trafficking of APP and CTFβ into secreted extracellular vesicles, and the resultant potential impact on neurotoxicity in the context of Alzheimer's disease amyloidopathy.

Generation of mouse model of TGFBI-R124C corneal dystrophy using CRISPR/Cas9-mediated homology-directed repair

Mutations in transforming growth factor-beta-induced (TGFBI) gene cause clinically distinct types of corneal dystrophies. To delineate the mechanisms driving these dystrophies, we focused on the R124C mutation in TGFBI that causes lattice corneal dystrophy type1 (LCD1) and generated novel transgenic mice harbouring a single amino acid substitution of arginine 124 with cysteine in TGFBI via ssODN-mediated base-pair substitution using CRISPR/Cas9 technology. Eighty percent of homozygous and 9.1% of heterozygous TGFBI-R124C mice developed a corneal opacity at 40 weeks of age. Hematoxylin and eosin and Masson trichrome staining showed eosinophilic deposits in subepithelial corneal stroma that stained negative for Congo-red. Although amyloid deposition was not observed in TGFBI-R124C mice, irregular amorphous deposits were clearly observed via transmission electron microscopy near the basement membrane. Interestingly, we found that the corneal deposition of TGFBI protein (TGFBIp) was significantly increased in homozygous TGFBI-R124C mice, suggesting a pathogenic role for the mutant protein accumulation. Furthermore, as observed in the LCD1 patients, corneal epithelial wound healing was significantly delayed in TGFBI-R124C mice. In conclusion, our novel mouse model of TGFBI-R124C corneal dystrophy reproduces features of the human disease. This mouse model will help delineate the pathogenic mechanisms of human corneal dystrophy.

Spatial Lipidomics Reveals Region and Long Chain Base Specific Accumulations of Monosialogangliosides in Amyloid Plaques in Familial Alzheimer's Disease Mice (5xFAD) Brain

Ganglioside metabolism is significantly altered in Alzheimer's disease (AD), which is a progressive neurodegenerative disease prominently characterized by one of its pathological hallmarks, amyloid deposits or "senile plaques". While the plaques mainly consist of aggregated variants of amyloid-β protein (Aβ), recent studies have revealed a number of lipid species including gangliosides in amyloid plaques along with Aβ peptides. It has been widely suggested that long chain (sphingosine) base (LCBs), C18:1-LCB and C20:1-LCB, containing gangliosides might play different roles in neuronal function in vivo. In order to elucidate region-specific aspects of amyloid-plaque associated C18:1-LCB and C20:1-LCB ganglioside accumulations, high spatial resolution (10 μm per pixel) matrix assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) of gangliosides in amyloid plaques was performed in hippocampal and adjacent cortical regions of 12 month old 5xFAD mouse coronal brain sections from two different stereotaxic coordinates (bregma points, -2.2 and -2.7 mm). MALDI-IMS uncovered brain-region (2 and 3D) and/or LCB specific accumulations of monosialogangliosides (GMs): GM1, GM2, and GM3 in the hippocampal and cortical amyloid plaques. The results reveal monosialogangliosides to be an important component of amyloid plaques and the accumulation of different gangliosides is region and LCB specific in 12 month old 5xFAD mouse brain. This is discussed in relation to amyloid-associated AD pathogenesis such as lipid related immune changes in amyloid plaques, AD specific ganglioside metabolism, and, notably, AD-associated impaired neurogenesis in the subgranular zone.

Environmental lead exposure aggravates the progression of Alzheimer's disease in mice by targeting on blood brain barrier

Alzheimer's disease (AD) is a neurodegenerative disease that can be induced by heavy metals such as lead. However, there is limited information on the role of blood-brain barrier (BBB) in lead induced AD-like pathology. This study investigates the potential mechanism of lead exposure aggravating the progression of Alzheimer's disease in mice through the BBB. 200 mg/L and 500 mg/L lead acetate were given to C57BL/6J and APP/PS1 mice through drinking water from a week before mating, until the offspring were 7-months-old. 8 female juvenile mice in each group were selected for this investigation. Lead exposure increased blood lead concentration which revealed the internal exposure level, accelerated Aβ1-42 deposition in APP/PS1 mouse cortexes and abnormal change in Zonula Occludin-1 (ZO-1) and Claudin-5 protein. It also increased the expression of p-tau in both the C57BL/6J and APP/PS1 mice, and decreased mRNA and protein expression in low-density lipoprotein receptor (LRP-1). Additionally, it increased the mRNA and protein expression of amyloid beta precursor protein (APP) and beta secretase 1 (BACE-1). The activated astrocytes increased in the brains of APP/PS1 mice, and coalesced around the Aβ1-42 deposition after lead exposure. The main vessels in deutocerebrum were attached with Aβ1-42 deposition. These results offer insight into the mechanism of preventing lead induced AD through cerebrovascular pathways.

Dietary Intake of Green Nut Oil or DHA Ameliorates DHA Distribution in the Brain of a Mouse Model of Dementia Accompanied by Memory Recovery

Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, has significant health benefits. Previous studies reported decreased levels of DHA and DHA-containing phosphatidylcholines in the brain of animals suffering from Alzheimer’s disease, the most common type of dementia; furthermore, DHA supplementation has been found to improve brain DHA levels and memory efficiency in dementia. Oil extracted from the seeds of Plukenetia volubilis (green nut oil; GNO) is also expected to have DHA like effects as it contains approximately 50% α-linolenic acid, a precursor of DHA. Despite this, changes in the spatial distribution of DHA in the brain of animals with dementia following GNO or DHA supplementation remain unexplored. In this study, desorption electrospray ionization imaging mass spectrometry (DESI-IMS) was applied to observe the effects of GNO or DHA supplementation upon the distribution of DHA in the brain of male senescence-accelerated mouse-prone 8 (SAMP8) mice, a mouse model of dementia. DESI-IMS revealed that brain DHA distribution increased 1.85-fold and 3.67-fold in GNO-fed and DHA-fed SAMP8 mice, respectively, compared to corn oil-fed SAMP8 mice. Memory efficiency in SAMP8 mice was also improved by GNO or DHA supplementation. In summary, this study suggests the possibility of GNO or DHA supplementation for the prevention of dementia.

Short-term fish oil supplementation applied in presymptomatic stage of Alzheimer's disease enhances microglial/macrophage barrier and prevents neuritic dystrophy in parietal cortex of 5xFAD mouse model

Dystrophic neurites and activated microglia are one of the main neuropathological characteristics of Alzheimer's disease (AD). Although the use of supplements with omega-3 fatty acids has been associated with reduced risk and lessened AD pathology, it still remains elusive whether such a treatment could affect dystrophic neurites (DNs) formation and microglia/macrophage behavior in the early phase of disease. We analyzed the effects of short-term (3 weeks) fish oil supplementation on DNs formation, tau hyperphosphorylation, Amyloid-beta peptide 1–42 (Aβ42) levels and microglial/macrophage response to AD pathology in the parietal cortex of 4-month-old 5xFAD mice, a mouse model of AD. The present study shows for the first time that short-term FO supplementation applied in presymptomatic stage of AD, alters the behaviour of microglia/macrophages prompting them to establish a physical barrier around amyloid plaques. This barrier significantly suppresses DNs formation through the reduction of both Aβ content and tau hyperphosphorylation. Moreover, the short-term FO treatment neither suppresses inflammation nor enhances phagocytic properties of microglia/macrophages in the response to Aβ pathology, the effects most commonly attributed to the fish oil supplementation. Our findings suggest that fish oil consumption may play an important role in modulating microglial/macrophage response and ameliorating the AD pathology in presymptomatic stage of Alzheimer's disease.

Arsenic Exposure Contributes to the Bioenergetic Damage in an Alzheimer's Disease Model

Worldwide, every year there is an increase in the number of people exposed to inorganic arsenic (iAs) via drinking water. Human populations present impaired cognitive function as a result of prenatal and childhood iAs exposure, while studies in animal models demonstrate neurobehavioral deficits accompanied by neurotransmitter, protein, and enzyme alterations. Similar impairments have been observed in close association with Alzheimer's disease (AD). In order to determine whether iAs promotes the pathophysiological progress of AD, we used the 3xTgAD mouse model. Mice were exposed to iAs in drinking water from gestation until 6 months (As-3xTgAD group) and compared with control animals without arsenic (3xTgAD group). We investigated the behavior phenotype on a test battery (circadian rhythm, locomotor behavior, Morris water maze, and contextual fear conditioning). Adenosine triphosphate (ATP), reactive oxygen species, lipid peroxidation, and respiration rates of mitochondria were evaluated, antioxidant components were detected by immunoblots, and immunohistochemical studies were performed to reveal AD markers. As-3xTgAD displayed alterations in their circadian rhythm and exhibited longer freezing time and escape latencies compared to the control group. The bioenergetic profile revealed decreased ATP levels accompanied by the decline of complex I, and an oxidant state in the hippocampus. On the other hand, the cortex showed no changes of oxidant stress and complex I; however, the antioxidant response was increased. Higher immunopositivity to amyloid isoforms and to phosphorylated tau was observed in frontal cortex and hippocampus of exposed animals. In conclusion, mitochondrial dysfunction may be one of the triggering factors through which chronic iAs exposure exacerbates brain AD-like pathology.

18F-FDG-PET Detects Drastic Changes in Brain Metabolism in the Tg4-42 Model of Alzheimer's Disease

The evaluation of new therapeutic strategies in Alzheimer’s disease (AD) relies heavily on in vivo imaging and suitable animal models that mimic the pathological changes seen in patients. ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG)-positron-emission tomography (PET) is a well-established non-invasive imaging tool for monitoring changes in cerebral brain glucose metabolism in vivo. ¹⁸F-FDG-PET is used as a functional biomarker for AD as patients show an early and progressive reduction of cerebral glucose metabolism. However, earlier studies in preclinical models of AD showed conflicting results. The aim of this study was the evaluation of cerebral glucose metabolism in the Tg4–42 mouse model of AD using ¹⁸F-FDG-PET/magnetic resonance imaging (MRI). Tg4–42 mice show an age-dependent reduction in glucose metabolism together with severe neuron loss and memory deficits. Similar to AD patients early decrease in ¹⁸F-FDG uptake was already detected in young (3 months) Tg4–42 mice. The altered glucose metabolism coupled with age- and disease related cognitive decline of Tg4–42 mice make it a well-suited model for preclinical testing of AD-relevant therapeutics.

L-Norvaline, a new therapeutic agent against Alzheimer's disease

Growing evidence highlights the role of arginase activity in the manifestation of Alzheimer’s disease (AD). Upregulation of arginase was shown to contribute to neurodegeneration. Regulation of arginase activity appears to be a promising approach for interfering with the pathogenesis of AD. Therefore, the enzyme represents a novel therapeutic target. In this study, we administered an arginase inhibitor, L-norvaline (250 mg/L), for 2.5 months to a triple-transgenic model (3×Tg-AD) harboring PS1M146V, APPSwe, and tauP301L transgenes. Then, the neuroprotective effects of L-norvaline were evaluated using immunohistochemistry, proteomics, and quantitative polymerase chain reaction assays. Finally, we identified the biological pathways activated by the treatment. Remarkably, L-norvaline treatment reverses the cognitive decline in AD mice. The treatment is neuroprotective as indicated by reduced beta-amyloidosis, alleviated microgliosis, and reduced tumor necrosis factor transcription levels. Moreover, elevated levels of neuroplasticity related postsynaptic density protein 95 were detected in the hippocampi of mice treated with L-norvaline. Furthermore, we disclosed several biological pathways, which were involved in cell survival and neuroplasticity and were activated by the treatment. Through these modes of action, L-norvaline has the potential to improve the symptoms of AD and even interferes with its pathogenesis. As such, L-norvaline is a promising neuroprotective molecule that might be tailored for the treatment of a range of neurodegenerative disorders. The study was approved by the Bar-Ilan University Animal Care and Use Committee (approval No. 82-10-2017) on October 1, 2017.

Shedding Light on the Molecular Pathology of Amyloid Plaques in Transgenic Alzheimer's Disease Mice Using Multimodal MALDI Imaging Mass Spectrometry

Senile plaques formed by aggregated amyloid β peptides are one of the major pathological hallmarks of Alzheimer's disease (AD) which have been suggested to be the primary influence triggering the AD pathogenesis and the rest of the disease process. However, neurotoxic Aβ aggregation and progression are associated with a wide range of enigmatic biochemical, biophysical and genetic processes. MALDI imaging mass spectrometry (IMS) is a label-free method to elucidate the spatial distribution patterns of intact molecules in biological tissue sections. In this communication, we utilized multimodal MALDI-IMS analysis on 18 month old transgenic AD mice (tgArcSwe) brain tissue sections to enhance molecular information correlated to individual amyloid aggregates on the very same tissue section. Dual polarity MALDI-IMS analysis of lipids on the same pixel points revealed high throughput lipid molecular information including sphingolipids, phospholipids, and lysophospholipids which can be correlated to the ion images of individual amyloid β peptide isoforms at high spatial resolutions (10 μm). Further, multivariate image analysis was applied in order to probe the multimodal MALDI-IMS data in an unbiased way which verified the correlative accumulations of lipid species with dual polarity and Aβ peptides. This was followed by the lipid fragmentation obtained directly on plaque aggregates at higher laser pulse energies which provided tandem MS information useful for structural elucidation of several lipid species. Majority of the amyloid plaque-associated alterations of lipid species are for the first time reported here. The significance of this technique is that it allows correlating the biological discussion of all detected plaque-associated molecules to the very same individual amyloid plaques which can give novel insights into the molecular pathology of even a single amyloid plaque microenvironment in a specific brain region. Therefore, this allowed us to interpret the possible roles of lipids and amyloid peptides in amyloid plaque-associated pathological events such as focal demyelination, autophagic/lysosomal dysfunction, astrogliosis, inflammation, oxidative stress, and cell death.

Intracerebroventricular Administration of L-arginine Improves Spatial Memory Acquisition in Triple Transgenic Mice Via Reduction of Oxidative Stress and Apoptosis

Arginine is one of the most versatile semi-essential amino acids. Further to the primary role in protein biosynthesis, arginine is involved in the urea cycle, and it is a precursor of nitric oxide. Arginine deficiency is associated with neurodegenerative diseases such as Parkinson's, Huntington's and Alzheimer's diseases (AD). In this study, we administer arginine intracerebroventricularly in a murine model of AD and evaluate cognitive functions in a set of behavioral tests. In addition, the effect of arginine on synaptic plasticity was tested electrophysiologically by assessment of the hippocampal long-term potentiation (LTP). The effect of arginine on β amyloidosis was tested immunohistochemically. A role of arginine in the prevention of cytotoxicity and apoptosis was evaluated in vitro on PC-12 cells. The results indicate that intracerebroventricular administration of arginine improves spatial memory acquisition in 3xTg-AD mice, however, without significantly reducing intraneuronal β amyloidosis. Arginine shows little or no impact on LTP and does not rescue LTP deterioration induced by Aβ. Nevertheless, arginine possesses neuroprotective and antiapoptotic properties.

Therapeutic role of rifampicin in Alzheimer's disease

Rifampicin exerts significant brain protective functions in multiple experimental models. Here we summarize the underlying mechanisms of the neuroprotective and pro-cognitive effects of rifampicin that are mediated by its anti-inflammatory, anti-tau, anti-amyloid, and cholinergic effects. Beyond suggesting that rifampicin shows strong brain protective effects in preclinical models of Alzheimer's disease, we also provide substantial clinical evidence for the neuroprotective and pro-cognitive effects of rifampicin. Future neuroimaging studies combined with clinical assessment scores are the following steps to be taken in this field of research.

The effect of dietary supplementation on brain-derived neurotrophic factor and cognitive functioning in Alzheimer's dementia

BACKGROUND AND AIM

The objective of the present study was to investigate the effect of an aloe polymannose multinutrient complex (APMC) on pro brain-derived neurotrophic factor (BDNF) and mature BDNF in persons with moderate to severe Alzheimer's dementia.

METHODS

A 12-month open-label trial was utilized to evaluate the effect of the APMC on proBDNF and BDNF and their relationship to cognitive functioning. Thirty-four adults were enrolled and consumed 4 teaspoons/day of APMC for 12 months. Subjects were assessed at baseline and twelve months follow-up for proBDNF and BDNF and with a neuropsychological battery to measure cognitive functioning. Cognitive functioning was correlated with proBDNF and BDNF.

RESULTS

Few adverse effects were reported. While proBDNF (baseline M = 6,108.9, SD = 854.9 and 12 months M = 5,799.2, SD = 573.4; p = 0.57) and BDNF (baseline M = 5,673.8, SD = 3,342.3 and 12 months M = 6,312.9, SD = 2,830.9; p = 0.29) did not significantly change, the correlations between the ADAS-cog total score and BDNF (r = -0.53, p = 0.04) and BDNF/proBDNF ratio (r = -0.58, p = 0.05) became statistically significant after 12 months of dietary supplementation. Other correlations were noted for various cognitive functioning assessments and BDNF and/or BDNF/proBDNF ratio at both baseline and 12 months.

CONCLUSIONS

These findings suggest that the relationship between cognitive functioning and BDNF and BDNF/proBDNF ratio improved in response to consumption of a dietary supplement in persons with Alzheimer's dementia, which is consistent with our previous findings on cognitive functioning.

RELEVANCE FOR PATIENTS

Overall, our results showed modest improvements in clinical outcomes for a disease that otherwise has no standard conventional approach to treatment with proven efficacy.

Therapeutic potential of Bifidobacterium breve strain A1 for preventing cognitive impairment in Alzheimer's disease

It has previously been shown that the consumption of probiotics may have beneficial effects not only on peripheral tissues but also on the central nervous system and behavior via the microbiota-gut-brain axis, raising the possibility that treatment with probiotics could be an effective therapeutic strategy for managing neurodegenerative disorders. In this study, we investigated the effects of oral administration of Bifidobacterium breve strain A1 (B. breve A1) on behavior and physiological processes in Alzheimer's disease (AD) model mice. We found that administration of B. breve A1 to AD mice reversed the impairment of alternation behavior in a Y maze test and the reduced latency time in a passive avoidance test, indicating that it prevented cognitive dysfunction. We also demonstrated that non-viable components of the bacterium or its metabolite acetate partially ameliorated the cognitive decline observed in AD mice. Gene profiling analysis revealed that the consumption of B. breve A1 suppressed the hippocampal expressions of inflammation and immune-reactive genes that are induced by amyloid-β. Together, these findings suggest that B. breve A1 has therapeutic potential for preventing cognitive impairment in AD.

The neuroprotective effect of focused ultrasound: New perspectives on an old tool

INTRODUCTION

Transcranial focused ultrasound (tFUS) is a novel technique that can noninvasively modulate the cortical function. Moreover, there are rapidly replicating evidence suggesting the role of tFUS for targeted neuroprotective drug delivery by increasing the permeability of the central nervous system barrier that results with increased neuroprotective activity. In contrast to the indirect neuroprotective effect, there is rare evidence suggesting the direct parenchymal neuroprotective effect of transcranial focused ultrasound (tFUS). In the light of these findings, we aimed to review the direct and indirect neuroprotective effect of FUS in various animal models of Stroke, Parkinson's Disease, Alzheimer's Disease and Major Depressive Disorder.

METHODS

A literary search was conducted, utilizing search terms "animal", "focused ultrasound", "neuroprotection", "Alzheimer's Disease", "Parkinson's Disease ", "Stroke", "Neurodegenerative disease" and "Major Depressive Disorder". Items were excluded if they failed to: (1) include patients, (2) editorials, and letters.

RESULTS

This mini-review article presents an up-to-date review of the neuroprotective effects of tFUS in animal studies and suggests the dual neurotherapeutic role of tFUS in various neurodegenerative diseases.

CONCLUSION

Future well-conducted human studies are emergently needed to assess the neuroprotective effects of FUS.

Delineating Amyloid Plaque Associated Neuronal Sphingolipids in Transgenic Alzheimer's Disease Mice (tgArcSwe) Using MALDI Imaging Mass Spectrometry

The major pathological hallmarks of Alzheimer’s disease (AD) are the progressive aggregation and accumulation of beta-amyloid (Aβ) and hyperphosphorylated tau protein into neurotoxic deposits. Aβ aggregation has been suggested as the critical early inducer, driving the disease progression. However, the factors that promote neurotoxic Aβ aggregation remain elusive. Imaging mass spectrometry (IMS) is a powerful technique to comprehensively elucidate the spatial distribution patterns of lipids, peptides, and proteins in biological tissue sections. In the present study, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS)-based imaging was used on transgenic Alzheimer’s disease mouse (tgArcSwe) brain tissue to investigate the sphingolipid microenvironment of individual Aβ plaques and elucidate plaque-associated sphingolipid alterations. Multivariate data analysis was used to interrogate the IMS data for identifying pathologically relevant, anatomical features based on their lipid chemical profile. This approach revealed sphingolipid species that distinctly located to cortical and hippocampal deposits, whose Aβ identity was further verified using fluorescent amyloid staining and immunohistochemistry. Subsequent multivariate statistical analysis of the spectral data revealed significant localization of gangliosides and ceramides species to Aβ positive plaques, which was accompanied by distinct local reduction of sulfatides. These plaque-associated changes in sphingolipid levels implicate a functional role of sphingolipid metabolism in Aβ plaque pathology and AD pathogenesis. Taken together, the presented data highlight the potential of imaging mass spectrometry as a powerful approach for probing Aβ plaque-associated lipid changes underlying AD pathology.

Rationally Designed Peptides and Peptidomimetics as Inhibitors of Amyloid-β (Aβ) Aggregation: Potential Therapeutics of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease with no clinically accepted treatment to cure or halt its progression. The worldwide effort to develop peptide-based inhibitors of amyloid-β (Aβ) aggregation can be considered an unplanned combinatorial experiment. An understanding of what has been done and achieved may advance our understanding of AD pathology and the discovery of effective therapeutic agents. We review here the history of such peptide-based inhibitors, including those based on the Aβ sequence and those not derived from that sequence, containing both natural and unnatural amino acid building blocks. Peptide-based aggregation inhibitors hold significant promise for future AD therapy owing to their high selectivity, effectiveness, low toxicity, good tolerance, low accumulation in tissues, high chemical and biological diversity, possibility of rational design, and highly developed methods for analyzing their mode of action, proteolytic stability (modified peptides), and blood-brain barrier (BBB) permeability.

Neuron-astrocyte signaling is preserved in the aging brain

Astrocytes play crucial roles in brain homeostasis and are emerging as regulatory elements of neuronal and synaptic physiology by responding to neurotransmitters with Ca²⁺ elevations and releasing gliotransmitters that activate neuronal receptors. Aging involves neuronal and astrocytic alterations, being considered risk factor for neurodegenerative diseases. Most evidence of the astrocyte-neuron signaling is derived from studies with young animals; however, the features of astrocyte-neuron signaling in adult and aging brain remain largely unknown. We have investigated the existence and properties of astrocyte-neuron signaling in physiologically and pathologically aging mouse hippocampal and cortical slices at different lifetime points (0.5 to 20 month-old animals). We found that astrocytes preserved their ability to express spontaneous and neurotransmitter-dependent intracellular Ca²⁺ signals from juvenile to aging brains. Likewise, resting levels of gliotransmission, assessed by neuronal NMDAR activation by glutamate released from astrocytes, were largely preserved with similar properties in all tested age groups, but DHPG-induced gliotransmission was reduced in aged mice. In contrast, gliotransmission was enhanced in the APP/PS1 mouse model of Alzheimer's disease, indicating a dysregulation of astrocyte-neuron signaling in pathological conditions. Disruption of the astrocytic IP₃ R2 mediated-signaling, which is required for neurotransmitter-induced astrocyte Ca²⁺ signals and gliotransmission, boosted the progression of amyloid plaque deposits and synaptic plasticity impairments in APP/PS1 mice at early stages of the disease. Therefore, astrocyte-neuron interaction is a fundamental signaling, largely conserved in the adult and aging brain of healthy animals, but it is altered in Alzheimer's disease, suggesting that dysfunctions of astrocyte Ca²⁺ physiology may contribute to this neurodegenerative disease. GLIA 2017 GLIA 2017;65:569-580.

Oxidative Stress and Amyloid Toxicity: Insights From Yeast

Alzheimer's disease is the most common neurodegenerative disorder. One of the factors that promotes neurodegeneration is the accumulation of senile plaques formed by Aβ peptide. In this paper, it was analyzed that if oxidative stress is cause or consequence of amyloid cascade and the role of antioxidant defense system in this process, using S. cerevisiae (with a multicopy plasmid containing the Aβ1-42 sequence) as experimental model. Cells grown on glycerol were more tolerant than when grown on glucose, strengthening the role of the antioxidant defense system against Aβ accumulation. Antioxidant defense deficiency did not change the pattern of amyloid aggregation. On the other hand, the presence of Aβ increased the level of intracellular oxidation and induced the activity of catalase, superoxide dismutase, and aconitase. Peroxissomal catalase deficient cells (Δcta1), were more sensitive to Aβ toxicity than the wild type strain, while mitochondrial superoxide dismutase (Sod2) deficient cells displayed the highest frequency of petites. Besides, Aβ alters the oxygen consumption and the activity of complex III and IV. Taken together, our results point out that the Aβ toxicity mechanism involves an oxidative stress induction by increasing ROS production into the mitochondria, where Cta1 and Sod2 play a crucial role in the regulation of the redox balance. J. Cell. Biochem. 118: 1442-1452, 2017. © 2016 Wiley Periodicals, Inc.

Early Changes in Hippocampal Neurogenesis in Transgenic Mouse Models for Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in the Western world and is characterized by a progressive loss of cognitive functions leading to dementia. One major histopathological hallmark of AD is the formation of amyloid-beta plaques, which is reproduced in numerous transgenic animal models overexpressing pathogenic forms of amyloid precursor protein (APP). In human AD and in transgenic amyloid plaque mouse models, several studies report altered rates of adult neurogenesis, i.e. the formation of new neurons from neural stem and progenitor cells, and impaired neurogenesis has also been attributed to contribute to the cognitive decline in AD. So far, changes in neurogenesis have largely been considered to be a consequence of the plaque pathology. Therefore, possible alterations in neurogenesis before plaque formation or in prodromal AD have been largely ignored. Here, we analysed adult hippocampal neurogenesis in amyloidogenic mouse models of AD at different points before and during plaque progression. We found prominent alterations of hippocampal neurogenesis before plaque formation. Survival of newly generated cells and the production of new neurons were already compromised at this stage. Moreover and surprisingly, proliferation of doublecortin (DCX) expressing neuroblasts was significantly and specifically elevated during the pre-plaque stage in the APP-PS1 model, while the Nestin-expressing stem cell population was unaffected. In summary, changes in neurogenesis are evident already before plaque deposition and might contribute to well-known early hippocampal dysfunctions in prodromal AD such as hippocampal overactivity.

Probing amyloid-β pathology in transgenic Alzheimer's disease (tgArcSwe) mice using MALDI imaging mass spectrometry

The pathological mechanisms underlying Alzheimer's disease (AD) are still not understood. The disease pathology is characterized by the accumulation and aggregation of amyloid-β (Aβ) peptides into extracellular plaques, however the factors that promote neurotoxic Aβ aggregation remain elusive. Imaging mass spectrometry (IMS) is a powerful technique to comprehensively elucidate the spatial distribution patterns of lipids, peptides and proteins in biological tissues. In the present study, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS)-based imaging was used to study Aβ deposition in transgenic mouse brain tissue and to elucidate the plaque-associated chemical microenvironment. The imaging experiments were performed in brain sections of transgenic Alzheimer's disease mice carrying the Arctic and Swedish mutation of amyloid-beta precursor protein (tgArcSwe). Multivariate image analysis was used to interrogate the IMS data for identifying pathologically relevant, anatomical features based on their chemical identity. This include cortical and hippocampal Aβ deposits, whose amyloid peptide content was further verified using immunohistochemistry and laser microdissection followed by MALDI MS analysis. Subsequent statistical analysis on spectral data of regions of interest revealed brain region-specific differences in Aβ peptide aggregation. Moreover, other plaque-associated protein species were identified including macrophage migration inhibitory factor suggesting neuroinflammatory processes and glial cell reactivity to be involved in AD pathology. The presented data further highlight the potential of IMS as a powerful approach in neuropathology. Hanrieder et al. described an imaging mass spectrometry based study on comprehensive spatial profiling of C-terminally truncated Aβ species within individual plaques in tgArcSwe mice. Here, brain region-dependent differences in Aβ truncation and other plaque-associated proteins, such as macrophage migration inhibitory factor, were observed. The data shed further light on plaque-associated molecular mechanisms implicated in Alzheimer's pathogenesis. Cover image for this issue: doi: 10.1111/jnc.13328.

Friends or Foes: Matrix Metalloproteinases and Their Multifaceted Roles in Neurodegenerative Diseases

Neurodegeneration is a chronic progressive loss of neuronal cells leading to deterioration of central nervous system (CNS) functionality. It has been shown that neuroinflammation precedes neurodegeneration in various neurodegenerative diseases. Matrix metalloproteinases (MMPs), a protein family of zinc-containing endopeptidases, are essential in (neuro)inflammation and might be involved in neurodegeneration. Although MMPs are indispensable for physiological development and functioning of the organism, they are often referred to as double-edged swords due to their ability to also inflict substantial damage in various pathological conditions. MMP activity is strictly controlled, and its dysregulation leads to a variety of pathologies. Investigation of their potential use as therapeutic targets requires a better understanding of their contributions to the development of neurodegenerative diseases. Here, we review MMPs and their roles in neurodegenerative diseases: Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and multiple sclerosis (MS). We also discuss MMP inhibition as a possible therapeutic strategy to treat neurodegenerative diseases.

Membrane lipid therapy: Modulation of the cell membrane composition and structure as a molecular base for drug discovery and new disease treatment

Nowadays we understand cell membranes not as a simple double lipid layer but as a collection of complex and dynamic protein-lipid structures and microdomains that serve as functional platforms for interacting signaling lipids and proteins. Membrane lipids and lipid structures participate directly as messengers or regulators of signal transduction. In addition, protein-lipid interactions participate in the localization of signaling protein partners to specific membrane microdomains. Thus, lipid alterations change cell signaling that are associated with a variety of diseases including cancer, obesity, neurodegenerative disorders, cardiovascular pathologies, etc. This article reviews the newly emerging field of membrane lipid therapy which involves the pharmacological regulation of membrane lipid composition and structure for the treatment of diseases. Membrane lipid therapy proposes the use of new molecules specifically designed to modify membrane lipid structures and microdomains as pharmaceutical disease-modifying agents by reversing the malfunction or altering the expression of disease-specific protein or lipid signal cascades. Here, we provide an in-depth analysis of this emerging field, especially its molecular bases and its relevance to the development of innovative therapeutic approaches.

Animal models for prion-like diseases

Prion diseases or Transmissible Spongiform Encephalopathies (TSEs) are a group of fatal neurodegenerative disorders affecting several mammalian species being Creutzfeldt-Jacob Disease (CJD) the most representative in human beings, scrapie in ovine, Bovine Spongiform Encephalopathy (BSE) in bovine and Chronic Wasting Disease (CWD) in cervids. As stated by the "protein-only hypothesis", the causal agent of TSEs is a self-propagating aberrant form of the prion protein (PrP) that through a misfolding event acquires a β-sheet rich conformation known as PrP(Sc) (from scrapie). This isoform is neurotoxic, aggregation prone and induces misfolding of native cellular PrP. Compelling evidence indicates that disease-specific protein misfolding in amyloid deposits could be shared by other disorders showing aberrant protein aggregates such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Amyotrophic lateral sclerosis (ALS) and systemic Amyloid A amyloidosis (AA amyloidosis). Evidences of shared mechanisms of the proteins related to each disease with prions will be reviewed through the available in vivo models. Taking prion research as reference, typical prion-like features such as seeding and propagation ability, neurotoxic species causing disease, infectivity, transmission barrier and strain evidences will be analyzed for other protein-related diseases. Thus, prion-like features of amyloid β peptide and tau present in AD, α-synuclein in PD, SOD-1, TDP-43 and others in ALS and serum α-amyloid (SAA) in systemic AA amyloidosis will be reviewed through models available for each disease.

Attenuation of Aβ25-35-induced parallel autophagic and apoptotic cell death by gypenoside XVII through the estrogen receptor-dependent activation of Nrf2/ARE pathways

Amyloid-beta (Aβ) has a pivotal function in the pathogenesis of Alzheimer's disease. To investigate Aβ neurotoxicity, we used an in vitro model that involves Aβ25-35-induced cell death in the nerve growth factor-induced differentiation of PC12 cells. Aβ25-35 (20μM) treatment for 24h caused apoptotic cell death, as evidenced by significant cell viability reduction, LDH release, phosphatidylserine externalization, mitochondrial membrane potential disruption, cytochrome c release, caspase-3 activation, PARP cleavage, and DNA fragmentation in PC12 cells. Aβ25-35 treatment led to autophagic cell death, as evidenced by augmented GFP-LC3 puncta, conversion of LC3-I to LC3-II, and increased LC3-II/LC3-I ratio. Aβ25-35 treatment induced oxidative stress, as evidenced by intracellular ROS accumulation and increased production of mitochondrial superoxide, malondialdehyde, protein carbonyl, and 8-OHdG. Phytoestrogens have been proved to be protective against Aβ-induced neurotoxicity and regarded as relatively safe targets for AD drug development. Gypenoside XVII (GP-17) is a novel phytoestrogen isolated from Gynostemma pentaphyllum or Panax notoginseng. Pretreatment with GP-17 (10μM) for 12h increased estrogen response element reporter activity, activated PI3K/Akt pathways, inhibited GSK-3β, induced Nrf2 nuclear translocation, augmented antioxidant responsive element enhancer activity, upregulated heme oxygenase 1 (HO-1) expression and activity, and provided protective effects against Aβ25-35-induced neurotoxicity, including oxidative stress, apoptosis, and autophagic cell death. In conclusion, GP-17 conferred protection against Aβ25-35-induced neurotoxicity through estrogen receptor-dependent activation of PI3K/Akt pathways, inactivation of GSK-3β and activation of Nrf2/ARE/HO-1 pathways. This finding might provide novel insights into understanding the mechanism for neuroprotective effects of phytoestrogens or gypenosides.

Disrupted-In-Schizophrenia-1 (DISC1) interactome and mental disorders: impact of mouse models

Disrupted-In-Schizophrenia-1 (DISC1) has captured much attention because it predisposes individuals to a wide range of mental illnesses. Notably, a number of genes encoding proteins interacting with DISC1 are also considered to be relevant risk factors of mental disorders. We reasoned that the understanding of DISC1-associated mental disorders in the context of network principles will help to address fundamental properties of DISC1 as a disease gene. Systematic integration of behavioural phenotypes of genetic mouse lines carrying perturbation in DISC1 interacting proteins would contribute to a better resolution of neurobiological mechanisms of mental disorders associated with the impaired DISC1 interactome and lead to a development of network medicine. This review also makes specific recommendations of how to assess DISC1 associated mental disorders in mouse models and discuss future directions.

Effects of Fructus Akebiae on learning and memory impairment in a scopolamine-induced animal model of dementia

Fructus Akebiae (FAE) is a component of traditional Chinese medicines used for the clinical treatment of amnesia. The aim of the present study was to investigate the effects of FAE extract on scopolamine-induced learning and memory impairment in mice and Sprague-Dawley rats. Treatment with FAE (2.5, 5 and 10 mg/kg) was investigated in scopolamine-treated animals, and its effects on different types of memory were examined using the T-maze, the Morris water maze task, the novel object recognition test, the passive avoidance task and the step-down test. The results revealed that 5 and 10 mg/kg FAE attenuated scopolamine-mediated impairment of cognition, including spatial, episodic, aversive, and short- and long-term memory. Overall, these results suggest that FAE is an effective cognitive enhancer, and thus highlights the value of a multi-target strategy to address the complexity of cognitive dysfunction in Alzheimer’s disease.

RIFAMPICIN: an antibiotic with brain protective function

Besides its well known antibiotic activity rifampicin exerts multiple brain protective functions in acute cerebral ischemia and chronic neurodegeneration. The present mini-review gives an update of the unique activity of rifampicin in different diseases including Parkinson's disease, meningitis, stroke, Alzheimer's disease and optic nerve injury.