Longitudinal follow-up of autophagy and inflammation in brain of APPswePS1dE9 transgenic mice

Calcium (Ca2+) hemostasis, mitochondria, autophagy, and mitophagy contribute to Alzheimer's disease as early moderators

This review rigorously investigates the early cerebral changes associated with Alzheimer's disease, which manifest long before clinical symptoms arise. It presents evidence that the dysregulation of calcium (Ca2+) homeostasis, along with mitochondrial dysfunction and aberrant autophagic processes, may drive the disease's progression during its asymptomatic, preclinical stage. Understanding the intricate molecular interplay that unfolds during this critical period offers a window into identifying novel therapeutic targets, thereby advancing the treatment of neurodegenerative disorders. The review delves into both established and emerging insights into the molecular alterations precipitated by the disruption of Ca2+ balance, setting the stage for cognitive decline and neurodegeneration.

Corydalis ternata Nakai Alleviates Cognitive Decline in Alzheimer's Disease by Reducing β-Amyloid and Neuroinflammation

Recently, natural herbs have gained increasing attention owing to their comparatively low toxicity levels and the abundance of historical medical documentation regarding their use. Nevertheless, owing to a lack of knowledge regarding these herbs and their compounds, attempts to find those that could be beneficial for treating diseases have often been ad hoc; thus, there is now a growing demand for an in silico method to identify beneficial herbs. In this study, we present a computational approach for identifying natural herbs specifically effective in treating cognitive decline in Alzheimer's disease (AD) sufferers, which analyzes the similarities between herbal compounds and known drugs targeting AD-related proteins. Our in silico method suggests that Corydalis ternata can improve cognitive decline in AD sufferers. Behavioral tests with an AD mouse model for the confirmation of the in silico prediction reveals that C. ternata significantly alleviated the cognitive decline (memory and motor functions) caused by neurodegeneration. Further pathology analyses reveal that C. ternata decreases the level of Aβ plaques, reduces neuroinflammation, and promotes autophagy flux, and thus C. ternata can be clinically effective for preventing mild cognitive impairment during the early stages of AD. These findings highlight the potential utility of our in silico method and the potential clinical application of the identified natural herb in treating and preventing AD.

Neuroinflammation increases oxygen extraction in a mouse model of Alzheimer's disease

BACKGROUND

Neuroinflammation, impaired metabolism, and hypoperfusion are fundamental pathological hallmarks of early Alzheimer's disease (AD). Numerous studies have asserted a close association between neuroinflammation and disrupted cerebral energetics. During AD progression and other neurodegenerative disorders, a persistent state of chronic neuroinflammation reportedly exacerbates cytotoxicity and potentiates neuronal death. Here, we assessed the impact of a neuroinflammatory challenge on metabolic demand and microvascular hemodynamics in the somatosensory cortex of an AD mouse model.

METHODS

We utilized in vivo 2-photon microscopy and the phosphorescent oxygen sensor Oxyphor 2P to measure partial pressure of oxygen (pO2) and capillary red blood cell flux in cortical microvessels of awake mice. Intravascular pO2 and capillary RBC flux measurements were performed in 8-month-old APPswe/PS1dE9 mice and wildtype littermates on days 0, 7, and 14 of a 14-day period of lipopolysaccharide-induced neuroinflammation.

RESULTS

Before the induced inflammatory challenge, AD mice demonstrated reduced metabolic demand but similar capillary red blood cell flux as their wild type counterparts. Neuroinflammation provoked significant reductions in cerebral intravascular oxygen levels and elevated oxygen extraction in both animal groups, without significantly altering red blood cell flux in capillaries.

CONCLUSIONS

This study provides evidence that neuroinflammation alters cerebral oxygen demand at the early stages of AD without substantially altering vascular oxygen supply. The results will guide our understanding of neuroinflammation's influence on neuroimaging biomarkers for early AD diagnosis.

Ataxin-2 sequesters Raptor into aggregates and impairs cellular mTORC1 signaling

Ataxin-2 (Atx2) is a polyglutamine (polyQ) protein, in which abnormal expansion of the polyQ tract can trigger protein aggregation and consequently cause spinocerebellar ataxia type 2 (SCA2), but the mechanism underlying how Atx2 aggregation leads to proteinopathy remains elusive. Here, we investigate the molecular mechanism and cellular consequences of Atx2 aggregation by molecular cell biology approaches. We have revealed that either normal or polyQ-expanded Atx2 can sequester Raptor, a component of mammalian target of rapamycin complex 1 (mTORC1), into aggregates based on their specific interaction. Further research indicates that the polyQ tract and the N-terminal region (residues 1-784) of Atx2 are responsible for the specific sequestration. Moreover, this sequestration leads to suppression of the mTORC1 activity as represented by down-regulation of phosphorylated P70S6K, which can be reversed by overexpression of Raptor. As mTORC1 is a key regulator of autophagy, Atx2 aggregation and sequestration also induces autophagy by upregulating LC3-II and reducing phosphorylated ULK1 levels. This study proposes that Atx2 sequesters Raptor into aggregates, thereby impairing cellular mTORC1 signaling and inducing autophagy, and will be beneficial for a better understanding of the pathogenesis of SCA2 and other polyQ diseases.

Neuroinflammation increases oxygen extraction in a mouse model of Alzheimer's disease

Neuroinflammation, impaired metabolism, and hypoperfusion are fundamental pathological hallmarks of early Alzheimer's disease (AD). Numerous studies have asserted a close association between neuroinflammation and disrupted cerebral energetics. During AD progression and other neurodegenerative disorders, a persistent state of chronic neuroinflammation reportedly exacerbates cytotoxicity and potentiates neuronal death. Here, we assessed the impact of a neuroinflammatory challenge on metabolic demand and microvascular hemodynamics in the somatosensory cortex of an AD mouse model. We utilized in vivo 2-photon microscopy and the phosphorescent oxygen sensor Oxyphor 2P to measure partial pressure of oxygen (pO2) and capillary red blood cell flux in cortical microvessels of awake mice. Intravascular pO2 and capillary RBC flux measurements were performed in 8-month-old APPswe/PS1dE9 mice and wildtype littermates on days 0, 7, and 14 of a 14-day period of lipopolysaccaride-induced neuroinflammation. Before the induced inflammatory challenge, AD mice demonstrated reduced metabolic demand but similar capillary red blood cell flux as their wild type counterparts. Neuroinflammation provoked significant reductions in cerebral intravascular oxygen levels and elevated oxygen extraction in both animal groups, without significantly altering red blood cell flux in capillaries. This study provides evidence that neuroinflammation alters cerebral oxygen demand at the early stages of AD without substantially altering vascular oxygen supply. The results will guide our understanding of neuroinflammation's influence on neuroimaging biomarkers for early AD diagnosis.

Immunological characterization and diagnostic models of RNA N6-methyladenosine regulators in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia, and it displays both clinical and molecular variability. RNA N6-methyladenosine (m6A) regulators are involved in a wide range of essential cellular processes. In this study, we aimed to identify molecular signatures associated with m6A in Alzheimer's disease and use those signatures to develop a predictive model. We examined the expression patterns of m6A regulators and immune features in Alzheimer's disease using the GSE33000 dataset. We examined the immune cell infiltration and molecular groups based on m6A-related genes in 310 Alzheimer's disease samples. The WGCNA algorithm was utilized to determine differently expressed genes within each cluster. After evaluating the strengths and weaknesses of the random forest model, the support vector machine model, the generalized linear model, and eXtreme Gradient Boosting, the best machine model was selected. Methods such as nomograms, calibration curves, judgment curve analysis, and the use of independent data sets were used to verify the accuracy of the predictions made. Alzheimer's disease and non-disease Alzheimer's groups were compared to identify dysregulated m6A-related genes and activated immune responses. In Alzheimer's disease, two molecular clusters linked to m6A were identified. Immune infiltration analysis indicated substantial variation in protection between groups. Cluster 1 included processes like the Toll-like receptor signaling cascade, positive regulation of chromatin binding, and numerous malignancies; cluster 2 included processes like the cell cycle, mRNA transport, and ubiquitin-mediated proteolysis. With a lower residual and root mean square error and a larger area under the curve (AUC = 0.951), the Random forest machine model showed the greatest discriminative performance. The resulting random forest model was based on five genes, and it performed well (AUC = 0.894) on external validation datasets. Accuracy in predicting Alzheimer's disease subgroups was also shown by analyses of nomograms, calibration curves, and decision curves. In this research, we methodically outlined the tangled web of connections between m6A and AD and created a promising prediction model for gauging the correlation between m6A subtype risk and AD pathology.

Inhibition of NLRP1 inflammasome improves autophagy dysfunction and Aβ disposition in APP/PS1 mice

Increasing evidence has shown that the NOD-like receptor protein 1 (NLRP1) inflammasome is associated with Aβ generation and deposition, which contributes to neuronal damage and neuronal-inflammation in Alzheimer's disease (AD). However, the specific mechanism of NLRP1 inflammasome in the pathogenesis of AD is still unclear. It has been reported that autophagy dysfunction can aggravate the pathological symptoms of AD and plays an important role in regulating Aβ generation and clearance. We hypothesized that NLRP1 inflammasome activation may induce autophagy dysfunction contributing to the progression of AD. In the present study, we observed the relationship between Aβ generation and NLRP1 inflammasome activation, as well as AMPK/mTOR mediated-autophagy dysfunction in WT 9-month-old (M) mice, APP/PS1 6 M and APP/PS1 9 M mice. Additionally, we further studied the effect of NLRP1 knockdown on cognitive function, Aβ generation, neuroinflammation and AMPK/mTOR mediated autophagy in APP/PS1 9 M mice. Our results indicated that NLRP1 inflammasome activation and AMPK/mTOR mediated-autophagy dysfunction are closely implicated in Aβ generation and deposition in APP/PS1 9 M mice, but not in APP/PS1 6 M mice. Meanwhile, we found that knockdown of NLRP1 significantly improved learning and memory impairments, decreased the expressions of NLRP1, ASC, caspase-1, p-NF-κB, IL-1β, APP, CTF-β, BACE1 and Aβ_1-42, and decreased the level of p-AMPK, Beclin 1 and LC3 II, and increased the level of p-mTOR and P62 in APP/PS1 9 M mice. Our study suggested that inhibition of NLRP1 inflammasome activation improves AMPK/mTOR mediated-autophagy dysfunction, resulting in the decrease of Aβ generation, and NLRP1 and autophagy might be important targets to delay the progression of AD.

Defective proteostasis in Alzheimer's disease

The homeostasis of cellular proteins, or proteostasis, is critical for neuronal function and for brain processes, including learning and memory. Increasing evidence indicates that defective proteostasis contributes to the progression of neurodegenerative disorders, including Alzheimer's disease (AD), the most prevalent form of dementia in the elderly. Proteostasis comprises a set of cellular mechanisms that control protein synthesis, folding, post-translational modification and degradation, all of which are deregulated in AD. Importantly, deregulation of proteostasis plays a key role in synapse dysfunction and in memory impairment, the major clinical manifestation of AD. Here, we discuss molecular pathways involved in protein synthesis and degradation that are altered in AD, and possible pharmacological approaches to correct these defects.

3, 14, 19-Triacetyl Andrographolide alleviates the cognitive dysfunction of 3 × Tg-AD mice by inducing initiation and promoting degradation process of autophagy

The present study aims to investigate the cognition-enhancing effect of 3, 14, 19-Triacetyl andrographolide (ADA) on learning and memory deficits in 3 × Tg-AD mice and to explore its underlying mechanism. Eight-month-old 3 × Tg-AD mice and C57BL/6J mice were randomly divided into three groups, namely wild-type group, 3 × Tg-AD group, and 3 × Tg-AD+ADA group (5 mg/kg, for 21 days, i.p.). We found that ADA significantly improved learning and cognition impairment, inhibited the loss of Nissl body, and reduced Aβ load in the brains of 3 × Tg-AD mice. In addition, ADA enhanced the levels of PSD95 and SYP, which were closely associated with synaptic plasticity. Accumulated autophagosomes, LC3II, and P62 in hippocampus and cortex of 3 × Tg-AD mice were decreased by ADA treatment. Furthermore, ADA administration further down-regulated the expressions of p-AKT and p-mTOR, reduced the level of CTSB, and increased the co-localization of LC3 and LAMP1 in the brains of 3 × Tg-AD mice, implying that ADA-induced autophagy initiation and also promoted the degradation process. In Aβ_25-35 -induced HT22 cells, ADA displayed similar effects on autophagy flux as observed in 3 × Tg-AD mice. Our finding verified that ADA could improve synaptic plasticity and cognitive function, which is mainly attributed to the key roles of ADA in autophagy induction and degradation.

From attention-deficit hyperactivity disorder to sporadic Alzheimer's disease-Wnt/mTOR pathways hypothesis

Alzheimer's disease (AD) is the most common neurodegenerative disorder with the majority of patients classified as sporadic AD (sAD), in which etiopathogenesis remains unresolved. Though sAD is argued to be a polygenic disorder, apolipoprotein E (APOE) ε4, was found three decades ago to pose the strongest genetic risk for sAD. Currently, the only clinically approved disease-modifying drugs for AD are aducanumab (Aduhelm) and lecanemab (Leqembi). All other AD treatment options are purely symptomatic with modest benefits. Similarly, attention-deficit hyperactivity disorder (ADHD), is one of the most common neurodevelopmental mental disorders in children and adolescents, acknowledged to persist in adulthood in over 60% of the patients. Moreover, for ADHD whose etiopathogenesis is not completely understood, a large proportion of patients respond well to treatment (first-line psychostimulants, e.g., methylphenidate/MPH), however, no disease-modifying therapy exists. Interestingly, cognitive impairments, executive, and memory deficits seem to be common in ADHD, but also in early stages of mild cognitive impairment (MCI), and dementia, including sAD. Therefore, one of many hypotheses is that ADHD and sAD might have similar origins or that they intercalate with one another, as shown recently that ADHD may be considered a risk factor for sAD. Intriguingly, several overlaps have been shown between the two disorders, e.g., inflammatory activation, oxidative stress, glucose and insulin pathways, wingless-INT/mammalian target of rapamycin (Wnt/mTOR) signaling, and altered lipid metabolism. Indeed, Wnt/mTOR activities were found to be modified by MPH in several ADHD studies. Wnt/mTOR was also found to play a role in sAD and in animal models of the disorder. Moreover, MPH treatment in the MCI phase was shown to be successful for apathy including some improvement in cognition, according to a recent meta-analysis. In several AD animal models, ADHD-like behavioral phenotypes have been observed indicating a possible interconnection between ADHD and AD. In this concept paper, we will discuss the various evidence in human and animal models supporting the hypothesis in which ADHD might increase the risk for sAD, with common involvement of the Wnt/mTOR-pathway leading to lifespan alteration at the neuronal levels.

A companion to the preclinical common data elements and case report forms for neuropathology studies in epilepsy research. A report of the TASK3 WG2 Neuropathology Working Group of the ILAE/AES Joint Translational Task Force

The International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force initiated the TASK3 working group to create common data elements (CDEs) for various aspects of preclinical epilepsy research studies, which could help improve the standardization of experimental designs. This article addresses neuropathological changes associated with seizures and epilepsy in rodent models of epilepsy. We discuss CDEs for histopathological parameters for neurodegeneration, changes in astrocyte morphology and function, mechanisms of inflammation, and changes in the blood-brain barrier and myelin/oligodendrocytes resulting from recurrent seizures in rats and mice. We provide detailed CDE tables and case report forms (CRFs), and with this companion manuscript, we discuss the rationale and methodological aspects of individual neuropathological examinations. The CDEs, CRFs, and companion paper are available to all researchers, and their use will benefit the harmonization and comparability of translational preclinical epilepsy research. The ultimate hope is to facilitate the development of rational therapy concepts for treating epilepsies, seizures, and comorbidities and the development of biomarkers assessing the pathological state of the disease.

Echinacoside alleviates sevoflurane-induced cognitive dysfunction by activating FOXO1-mediated autophagy

The current study aimed to examine the effects of echinacoside on cognitive impairment in mice after exposure to sevoflurane. To examine the role of FOXO1, si-FOXO1 and si-con were injected into the hippocampus through the left lateral cerebral ventricles. Sevoflurane-induced mice had serious cognitive dysfunction. However, pretreatment with echinacoside alleviated the cognitive dysfunction, as measured by a shortened escape latency time, and increased platform crossing times, the percentage of distance in the target quadrant and Y-maze spontaneous alternations. In addition, we found that echinacoside elevated FOXO1 expression in the hippocampus, increased the expression of autophagy-related proteins including Beclin 1, ATG5, ATG7 and LC3, and reduced P62 expression. Silencing of FOXO1 aggravated the cognitive deficits and reduced expression of the autophagy-related markers, while the effects of si-FOXO1 on memory were abrogated by echinacoside. Echinacoside attenuated the cognitive impairment in sevoflurane-induced mice through FOXO1-mediated autophagy.

Alzheimer’s Disease: From Pathogenesis to Mesenchymal Stem Cell Therapy – Bridging the Missing Link

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disease worldwide. With the increasing trend of population aging, the estimated number of AD continues to climb, causing enormous medical, social and economic burden to the society. Currently, no drug is available to cure the disease or slow down its progression. There is an urgent need to improve our understanding on the pathogenesis of AD and develop novel therapy to combat it. Despite the two well-known pathological hallmarks (extracellular amyloid plaques and intracellular Neurofibrillary Tangles), the exact mechanisms for selective degeneration and loss of neurons and synapses in AD remain to be elucidated. Cumulative studies have shown neuroinflammation plays a central role in pathogenesis of AD. Neuroinflammation is actively involved both in the onset and the subsequent progression of AD. Microglia are the central player in AD neuroinflammation. In this review, we first introduced the different theories proposed for the pathogenesis of AD, focusing on neuroinflammation, especially on microglia, systemic inflammation, and peripheral and central immune system crosstalk. We explored the possible mechanisms of action of stem cell therapy, which is the only treatment modality so far that has pleiotropic effects and can target multiple mechanisms in AD. Mesenchymal stem cells are currently the most widely used stem cell type in AD clinical trials. We summarized the ongoing major mesenchymal stem cell clinical trials in AD and showed how translational stem cell therapy is bridging the gap between basic science and clinical intervention in this devastating disorder.

Trans ε-Viniferin Decreases Amyloid Deposits With Greater Efficiency Than Resveratrol in an Alzheimer's Mouse Model

In a previous study, we showed that viniferin decreased amyloid deposits and reduced neuroinflammation in APPswePS1dE9 transgenic mice between 3 and 6 months of age. In the present study, wild type and APPswePS1dE9 transgenic mice were treated from 7 to 11 or from 3 to 12 months by a weekly intraperitoneal injection of either 20 mg/kg viniferin or resveratrol or their vehicle, the polyethylene glycol 200 (PEG 200). The cognitive status of the mice was evaluated by the Morris water maze test. Then, amyloid burden and neuroinflammation were quantified by western-blot, Enzyme-Linked ImmunoSorbent Assay (ELISA), immunofluorescence, and in vivo micro-Positon Emission Tomography (PET) imaging. Viniferin decreased hippocampal amyloid load and deposits with greater efficiency than resveratrol, and both treatments partially prevented the cognitive decline. Furthermore, a significant decrease in brain uptake of the TSPO PET tracer [¹⁸F]DPA-714 was observed with viniferin compared to resveratrol. Expression of GFAP, IBA1, and IL-1β were decreased by viniferin but PEG 200, which was very recently shown to be a neuroinflammatory inducer, masked the neuroprotective power of viniferin.

Rifampicin Suppresses Amyloid-β Accumulation Through Enhancing Autophagy in the Hippocampus of a Lipopolysaccharide-Induced Mouse Model of Cognitive Decline

BACKGROUND

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) deposition. The metabolism of Aβ is critically affected by autophagy. Although rifampicin is known to mediate neuroinflammation, the underlying mechanism by which rifampicin regulates the cognitive sequelae remains unknown.

OBJECTIVE

Based on our previous findings that rifampicin possesses neuroprotective effects on improving cognitive function after neuroinflammation, we aimed to examine in this study whether rifampicin can inhibit Aβ accumulation by enhancing autophagy in a mouse model of lipopolysaccharide (LPS)-induced cognitive impairment.

METHODS

Adult C57BL/6 mice were intraperitoneally injected with rifampicin, chloroquine, and/or LPS every day for 7 days. Pathological and biochemical assays and behavioral tests were performed to determine the therapeutic effect and mechanism of rifampicin on the hippocampus of LPS-induced mice.

RESULTS

We found that rifampicin ameliorated cognitive impairments in the LPS-induced mice. In addition, rifampicin attenuated the inhibition of autophagosome formation, suppressed the accumulation of Aβ1-42, and protected the hippocampal neurons against LPS-induced damage. Our results further demonstrated that rifampicin improved the neurological function by promoting autophagy through the inhibition of Akt/mTOR/p70S6K signaling pathway in the hippocampus of LPS-induced mice.

CONCLUSION

Rifampicin ameliorates cognitive impairment by suppression of Aβ1-42 accumulation through inhibition of Akt/mTOR/p70S6K signaling and enhancement of autophagy in the hippocampus of LPS-induced mice.

Calcium Signaling Regulates Autophagy and Apoptosis

Calcium (Ca²⁺) functions as a second messenger that is critical in regulating fundamental physiological functions such as cell growth/development, cell survival, neuronal development and/or the maintenance of cellular functions. The coordination among various proteins/pumps/Ca²⁺ channels and Ca²⁺ storage in various organelles is critical in maintaining cytosolic Ca²⁺ levels that provide the spatial resolution needed for cellular homeostasis. An important regulatory aspect of Ca²⁺ homeostasis is a store operated Ca²⁺ entry (SOCE) mechanism that is activated by the depletion of Ca²⁺ from internal ER stores and has gained much attention for influencing functions in both excitable and non-excitable cells. Ca²⁺ has been shown to regulate opposing functions such as autophagy, that promote cell survival; on the other hand, Ca²⁺ also regulates programmed cell death processes such as apoptosis. The functional significance of the TRP/Orai channels has been elaborately studied; however, information on how they can modulate opposing functions and modulate function in excitable and non-excitable cells is limited. Importantly, perturbations in SOCE have been implicated in a spectrum of pathological neurodegenerative conditions. The critical role of autophagy machinery in the pathogenesis of neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and Huntington’s diseases, would presumably unveil avenues for plausible therapeutic interventions for these diseases. We thus review the role of SOCE-regulated Ca²⁺ signaling in modulating these diverse functions in stem cell, immune regulation and neuromodulation.

Novel Therapeutic Approaches for Alzheimer's Disease: An Updated Review

Alzheimer’s disease (AD) is a progressive neurodegenerative disease and accounts for most cases of dementia. The prevalence of AD has increased in the current rapidly aging society and contributes to a heavy burden on families and society. Despite the profound impact of AD, current treatments are unable to achieve satisfactory therapeutic effects or stop the progression of the disease. Finding novel treatments for AD has become urgent. In this paper, we reviewed novel therapeutic approaches in five categories: anti-amyloid therapy, anti-tau therapy, anti-neuroinflammatory therapy, neuroprotective agents including N-methyl-D-aspartate (NMDA) receptor modulators, and brain stimulation. The trend of therapeutic development is shifting from a single pathological target to a more complex mechanism, such as the neuroinflammatory and neurodegenerative processes. While drug repositioning may accelerate pharmacological development, non-pharmacological interventions, especially repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), also have the potential for clinical application. In the future, it is possible for physicians to choose appropriate interventions individually on the basis of precision medicine.

Mammalian/mechanistic target of rapamycin (mTOR) complexes in neurodegeneration

Novel targets to arrest neurodegeneration in several dementing conditions involving misfolded protein accumulations may be found in the diverse signaling pathways of the Mammalian/mechanistic target of rapamycin (mTOR). As a nutrient sensor, mTOR has important homeostatic functions to regulate energy metabolism and support neuronal growth and plasticity. However, in Alzheimer's disease (AD), mTOR alternately plays important pathogenic roles by inhibiting both insulin signaling and autophagic removal of β-amyloid (Aβ) and phospho-tau (ptau) aggregates. It also plays a role in the cerebrovascular dysfunction of AD. mTOR is a serine/threonine kinase residing at the core in either of two multiprotein complexes termed mTORC1 and mTORC2. Recent data suggest that their balanced actions also have implications for Parkinson's disease (PD) and Huntington's disease (HD), Frontotemporal dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS). Beyond rapamycin; an mTOR inhibitor, there are rapalogs having greater tolerability and micro delivery modes, that hold promise in arresting these age dependent conditions.

Alzheimer's Disease Pathogenesis: Role of Autophagy and Mitophagy Focusing in Microglia

Alzheimer's disease (AD) is a debilitating neurological disorder, and currently, there is no cure for it. Several pathologic alterations have been described in the brain of AD patients, but the ultimate causative mechanisms of AD are still elusive. The classic hallmarks of AD, including amyloid plaques (Aβ) and tau tangles (tau), are the most studied features of AD. Unfortunately, all the efforts targeting these pathologies have failed to show the desired efficacy in AD patients so far. Neuroinflammation and impaired autophagy are two other main known pathologies in AD. It has been reported that these pathologies exist in AD brain long before the emergence of any clinical manifestation of AD. Microglia are the main inflammatory cells in the brain and are considered by many researchers as the next hope for finding a viable therapeutic target in AD. Interestingly, it appears that the autophagy and mitophagy are also changed in these cells in AD. Inside the cells, autophagy and inflammation interact in a bidirectional manner. In the current review, we briefly discussed an overview on autophagy and mitophagy in AD and then provided a comprehensive discussion on the role of these pathways in microglia and their involvement in AD pathogenesis.

Chronic intraperitoneal injection of polyethylene glycol 200 in mice induces hippocampal neuroinflammation

In vivo treatment of hydrophobic substances requires the use of organic solvents, which are often toxic. Consequently, polyethylene glycols (PEGs), which are considered as nontoxic, have been widely used for many years in chemistry and biology. We used PEG 200, which was administrated by intraperitoneal (i.p.) injection once a week to mice. After 4 months of injections, at the dose of 1.67 mL/kg, a surprising increase in expression of GFAP (glial fibrillary acidic protein) and IBA1 (ionized calcium binding adaptor molecule 1), glial markers of astrocytes and microglia respectively, was observed in the mice's hippocampus. These results were associated with a dramatic increase in pro-inflammatory cytokine interleukin-1β (IL-1β) expression, all together suggesting an inflammatory process. It is important to communicate these results to the scientific community to provide awareness of this potential effect when PEG 200 is used under similar conditions as a vehicle in mice.

Enhanced Autolysosomal Function Ameliorates the Inflammatory Response Mediated by the NLRP3 Inflammasome in Alzheimer's Disease

The pathogenesis of Alzheimer’s disease (AD) involves activation of many NLRP3 inflammatory bodies, which may be related to amyloid β peptide and aggregation of misfolded proteins. Autophagy is an important regulator of inflammatory bodies. However, autophagy shows dynamic changes in the development of AD, and its role in inflammation remains controversial. In this study, the key link between autophagic disorders and the NLRP3 inflammasome in AD was investigated. APP/PS1 double transgenic mice and C57 mice with Aβ_25–35 injected into the lateral ventricle were used as two animal models of AD. Immunofluorescence staining and Western blot analysis showed that NLRP3 inflammasome-related proteins and inflammatory cytokines, such as IL-1α, IL-1β, IL-6, IL-12, and TNF-α, were increased and microglia were activated in the brains of both AD animal models. Endogenous overexpression of the APPswe gene and exogenous addition of Aβ_25–35 increased the expression of NLRP3 inflammasome-related proteins, while exogenous Aβ_25–35 intervention more significantly activated inflammation. Furthermore, LC3 was increased in the AD animal and cell models, and the level of Lamp1 decreased. After overexpression of the primary regulator of lysosomal biogenesis, TFEB, the lysosome protein Lamp1 was increased, and LC3 and inflammatory protein expression were decreased. These results suggest that the NLRP3 inflammasome-mediated inflammatory response is activated in AD animal and cell models, which may be related to the decline in autolysosome function. Overexpression of the TFEB protein can reduce the inflammatory response by improving autolysosome function in AD model cells.

Huanglian Jiedu decoction remodels the periphery microenvironment to inhibit Alzheimer's disease progression based on the "brain-gut" axis through multiple integrated omics

BACKGROUND

In recent years, excellent results have suggested an association between the "brain-gut" axis and Alzheimer's disease (AD) progression, yet the role of the "brain-gut" axis in AD pathogenesis still remains obscure. Herein, we provided a potential link between the central and peripheral neuroinflammatory disorders in AD progression.

METHODS

The Morris water maze (MWM) test, immunohistochemistry, ELISA, ProcartaPlex Multiplex immunoassay, multiple LC-MS/MS methods, and the V3-V4 regions of 16S rRNA genes were applied to explore potential biomarkers.

RESULTS

In Tg-APP/PS1 mice, gut dysbiosis and lipid metabolism were highly associated with AD-like neuroinflammation. The combination of inflammatory factors (IL-6 and INF-γ), phosphatidylcholines (PCs) and SCFA-producing bacteria were expected to be early diagnostic biomarkers for AD. Huanglian Jiedu decoction (HLJDD) suppressed gut dysbiosis and the associated Aβ accumulation, harnessed neuroinflammation and reversed cognitive impairment.

CONCLUSION

Together, our findings highlighted the roles of neuroinflammation induced by gut dysbiosis and lipid metabolism disorder in AD progression. This integrated metabolomics approach showed its potential to understand the complex mechanisms of HLJDD in the treatment of AD.

The Drosophila amyloid precursor protein homologue mediates neuronal survival and neuroglial interactions

The amyloid precursor protein (APP) is a structurally and functionally conserved transmembrane protein whose physiological role in adult brain function and health is still unclear. Because mutations in APP cause familial Alzheimer's disease (fAD), most research focuses on this aspect of APP biology. We investigated the physiological function of APP in the adult brain using the fruit fly Drosophila melanogaster, which harbors a single APP homologue called APP Like (APPL). Previous studies have provided evidence for the implication of APPL in neuronal wiring and axonal growth through the Wnt signaling pathway during development. However, like APP, APPL continues to be expressed in all neurons of the adult brain where its functions and their molecular and cellular underpinnings are unknown. We report that APPL loss of function (LOF) results in the dysregulation of endolysosomal function in neurons, with a notable enlargement of early endosomal compartments followed by neuronal cell death and the accumulation of dead neurons in the brain during a critical period at a young age. These defects can be rescued by reduction in the levels of the early endosomal regulator Rab5, indicating a causal role of endosomal function for cell death. Finally, we show that the secreted extracellular domain of APPL interacts with glia and regulates the size of their endosomes, the expression of the Draper engulfment receptor, and the clearance of neuronal debris in an axotomy model. We propose that APP proteins represent a novel family of neuroglial signaling factors required for adult brain homeostasis.

Can We Treat Neuroinflammation in Alzheimer's Disease?

Alzheimer's disease (AD), considered the most common type of dementia, is characterized by a progressive loss of memory, visuospatial, language and complex cognitive abilities. In addition, patients often show comorbid depression and aggressiveness. Aging is the major factor contributing to AD; however, the initial cause that triggers the disease is yet unknown. Scientific evidence demonstrates that AD, especially the late onset of AD, is not the result of a single event, but rather it appears because of a combination of risk elements with the lack of protective ones. A major risk factor underlying the disease is neuroinflammation, which can be activated by different situations, including chronic pathogenic infections, prolonged stress and metabolic syndrome. Consequently, many therapeutic strategies against AD have been designed to reduce neuro-inflammation, with very promising results improving cognitive function in preclinical models of the disease. The literature is massive; thus, in this review we will revise the translational evidence of these early strategies focusing in anti-diabetic and anti-inflammatory molecules and discuss their therapeutic application in humans. Furthermore, we review the preclinical and clinical data of nutraceutical application against AD symptoms. Finally, we introduce new players underlying neuroinflammation in AD: the activity of the endocannabinoid system and the intestinal microbiota as neuroprotectors. This review highlights the importance of a broad multimodal approach to treat successfully the neuroinflammation underlying AD.

Royal Jelly as an Intelligent Anti-Aging Agent-A Focus on Cognitive Aging and Alzheimer's Disease: A Review

The astronomical increase of the world's aged population is associated with the increased prevalence of neurodegenerative diseases, heightened disability, and extremely high costs of care. Alzheimer's Disease (AD) is a widespread, age-related, multifactorial neurodegenerative disease that has enormous social and financial drawbacks worldwide. The unsatisfactory outcomes of available AD pharmacotherapy necessitate the search for alternative natural resources that can target various the underlying mechanisms of AD pathology and reduce disease occurrence and/or progression. Royal jelly (RJ) is the main food of bee queens; it contributes to their fertility, long lifespan, and memory performance. It represents a potent nutraceutical with various pharmacological properties, and has been used in a number of preclinical studies to target AD and age-related cognitive deterioration. To understand the mechanisms through which RJ affects cognitive performance both in natural aging and AD, we reviewed the literature, elaborating on the metabolic, molecular, and cellular mechanisms that mediate its anti-AD effects. Preclinical findings revealed that RJ acts as a multidomain cognitive enhancer that can restore cognitive performance in aged and AD models. It promotes brain cell survival and function by targeting multiple adversities in the neuronal microenvironment such as inflammation, oxidative stress, mitochondrial alterations, impaired proteostasis, amyloid-β toxicity, Ca excitotoxicity, and bioenergetic challenges. Human trials using RJ in AD are limited in quantity and quality. Here, the limitations of RJ-based treatment strategies are discussed, and directions for future studies examining the effect of RJ in cognitively impaired subjects are noted.

A Systematic Bioinformatics Workflow With Meta-Analytics Identified Potential Pathogenic Factors of Alzheimer's Disease

Potential pathogenic factors, other than well-known APP, APOE4, and PSEN, can be further identified from transcriptomics studies of differentially expressed genes (DEGs) that are specific for Alzheimer’s disease (AD), but findings are often inconsistent or even contradictory. Evidence corroboration by combining meta-analysis and bioinformatics methods may help to resolve existing inconsistencies and contradictions. This study aimed to demonstrate a systematic workflow for evidence synthesis of transcriptomic studies using both meta-analysis and bioinformatics methods to identify potential pathogenic factors. Transcriptomic data were assessed from GEO and ArrayExpress after systematic searches. The DEGs and their dysregulation states from both DNA microarray and RNA sequencing datasets were analyzed and corroborated by meta-analysis. Statistically significant DEGs were used for enrichment analysis based on KEGG and protein–protein interaction network (PPIN) analysis based on STRING. AD-specific modules were further determined by the DIAMOnD algorithm, which identifies significant connectivity patterns between specific disease-associated proteins and non-specific proteins. Within AD-specific modules, the nodes of highest degrees (>95th percentile) were considered as potential pathogenic factors. After systematic searches of 225 datasets, extensive meta-analyses among 25 datasets (21 DNA microarray datasets and 4 RNA sequencing datasets) identified 9,298 DEGs. The dysregulated genes and pathways in AD were associated with impaired amyloid-β (Aβ) clearance. From the AD-specific module, Fyn, and EGFR were the most statistically significant and biologically relevant. This meta-analytical study suggested that the reduced Aβ clearance in AD pathogenesis was associated with the genes encoding Fyn and EGFR, which were key receptors in Aβ downstream signaling.

Pharmacological Tools to Modulate Autophagy in Neurodegenerative Diseases

Considerable evidences suggest a link between autophagy dysfunction, protein aggregation, and neurodegenerative diseases. Given that autophagy is a conserved intracellular housekeeping process, modulation of autophagy flux in various model organisms have highlighted its importance for maintaining proteostasis. In postmitotic cells such as neurons, compromised autophagy is sufficient to cause accumulation of ubiquitinated aggregates, neuronal dysfunction, degeneration, and loss of motor coordination-all hallmarks of neurodegenerative diseases. Reciprocally, enhanced autophagy flux augments cellular and organismal health, in addition to extending life span. These genetic studies not-withstanding a plethora of small molecule modulators of autophagy flux have been reported that alleviate disease symptoms in models of neurodegenerative diseases. This review summarizes the potential of such molecules to be, perhaps, one of the first autophagy drugs for treating these currently incurable diseases.

Microglia Express Insulin-Like Growth Factor-1 in the Hippocampus of Aged APPswe/PS1ΔE9 Transgenic Mice

Insulin-like growth factor-1 (IGF-1) is a pleiotropic molecule with neurotrophic and immunomodulatory functions. Knowing the capacity of chronically activated microglia to produce IGF-1 may therefore show essential to promote beneficial microglial functions in Alzheimer's disease (AD). Here, we investigated the expression of IGF-1 mRNA and IGF-1 along with the expression of tumor necrosis factor (TNF) mRNA, and the amyloid-β (Aβ) plaque load in the hippocampus of 3- to 24-month-old APPswe/PS1ΔE9 transgenic (Tg) and wild-type (WT) mice. As IGF-1, in particular, is implicated in neurogenesis we also monitored the proliferation of cells in the subgranular zone (sgz) of the dentate gyrus. We found that the Aβ plaque load reached its maximum in aged 21- and 24-month-old APPswe/PS1ΔE9 Tg mice, and that microglial reactivity and hippocampal IGF-1 and TNF mRNA levels were significantly elevated in aged APPswe/PS1ΔE9 Tg mice. The sgz cell proliferation decreased with age, regardless of genotype and increased IGF-1/TNF mRNA levels. Interestingly, IGF-1 mRNA was expressed in subsets of sgz cells, likely neuroblasts, and neurons in both genotypes, regardless of age, as well as in glial-like cells. By double in situ hybridization these were shown to be IGF1 mRNA+ CD11b mRNA+ cells, i.e., IGF-1 mRNA-expressing microglia. Quantification showed a 2-fold increase in the number of microglia and IGF-1 mRNA-expressing microglia in the molecular layer of the dentate gyrus in aged APPswe/PS1ΔE9 Tg mice. Double-immunofluorescence showed that IGF-1 was expressed in a subset of Aβ plaque-associated CD11b+ microglia and in several subsets of neurons. Exposure of primary murine microglia and BV2 cells to Aβ42 did not affect IGF-1 mRNA expression. IGF-1 mRNA levels remained constant in WT mice with aging, unlike TNF mRNA levels which increased with aging. In conclusion, our results suggest that the increased IGF-1 mRNA levels can be ascribed to a larger number of IGF-1 mRNA-expressing microglia in the aged APPswe/PS1ΔE9 Tg mice. The finding that subsets of microglia retain the capacity to express IGF-1 mRNA and IGF-1 in the aged APPswe/PS1ΔE9 Tg mice is encouraging, considering the beneficial therapeutic potential of modulating microglial production of IGF-1 in AD.

Autophagy in Neurotrauma: Good, Bad, or Dysregulated

Autophagy is a physiological process that helps maintain a balance between the manufacture of cellular components and breakdown of damaged organelles and other toxic cellular constituents. Changes in autophagic markers are readily detectable in the spinal cord and brain following neurotrauma, including traumatic spinal cord and brain injury (SCI/TBI). However, the role of autophagy in neurotrauma remains less clear. Whether autophagy is good or bad is under debate, with strong support for both a beneficial and detrimental role for autophagy in experimental models of neurotrauma. Emerging data suggest that autophagic flux, a measure of autophagic degradation activity, is impaired in injured central nervous systems (CNS), and interventions that stimulate autophagic flux may provide neuroprotection in SCI/TBI models. Recent data demonstrating that neurotrauma can cause lysosomal membrane damage resulting in pathological autophagosome accumulation in the spinal cord and brain further supports the idea that the impairment of the autophagy-lysosome pathway may be a part of secondary injury processes of SCI/TBI. Here, we review experimental work on the complex and varied responses of autophagy in terms of both the beneficial and detrimental effects in SCI and TBI models. We also discuss the existing and developing therapeutic options aimed at reducing the disruption of autophagy to protect the CNS after injuries.

NRBF2 is involved in the autophagic degradation process of APP-CTFs in Alzheimer disease models

Alzheimer disease (AD) is the most common neurodegenerative disease characterized by the deposition of amyloid plaque in the brain. The autophagy-associated PIK3C3-containing phosphatidylinositol 3-kinase (PtdIns3K) complex has been shown to interfere with APP metabolism and amyloid beta peptide (Aβ) homeostasis via poorly understood mechanisms. Here we report that NRBF2 (nuclear receptor binding factor 2), a key component and regulator of the PtdIns3K, is involved in APP-CTFs homeostasis in AD cell models. We found that NRBF2 interacts with APP in vivo and its expression levels are reduced in hippocampus of 5XFAD AD mice; we further demonstrated that NRBF2 overexpression promotes degradation of APP C-terminal fragments (APP-CTFs), and reduces Aβ_1-40 and Aβ_1-42 levels in human mutant APP-overexpressing cells. Conversely, APP-CTFs, Aβ_1-40 and Aβ_1-42 levels were increased in Nrbf2 knockdown or nrbf2 knockout cells. Furthermore, NRBF2 positively regulates autophagy in neuronal cells and NRBF2-mediated reduction of APP-CTFs levels is autophagy dependent. Importantly, nrbf2 knockout attenuates the recruitment of APP and APP-CTFs into phagophores and the sorting of APP and APP-CTFs into endosomal intralumenal vesicles, which is accompanied by the accumulation of the APP and APP-CTFs into RAB5-positive early endosomes. Collectively, our results reveal the potential connection between NRBF2 and the AD-associated protein APP by showing that NRBF2 plays an important role in regulating degradation of APP-CTFs through modulating autophagy.

Endo-lysosomal pathway and ubiquitin-proteasome system dysfunction in Alzheimer's disease pathogenesis

Several lines of evidence have shown that defects in the endo-lysosomal autophagy degradation pathway and the ubiquitin-proteasome system play a role in Alzheimer's Disease (AD) pathogenesis and pathophysiology. Early pathological changes, such as marked enlargement of endosomal compartments, gradual accumulation of autophagic vacuoles (AVs) and lysosome dyshomeostasis, are well-recognized in AD. In addition to these pathological indicators, many genetic variants of key regulators in the endo-lysosomal autophagy networks and the ubiquitin-proteasome system have been found to be associated with AD. Furthermore, altered expression levels of key proteins in these pathways have been found in AD human brain tissues, primary cells and AD mouse models. In this review, we discuss potential disease mechanisms underlying the dysregulation of protein homeostasis governing systems. While the importance of two major protein degradation pathways in AD pathogenesis has been highlighted, targeted therapy at key components of these pathways has great potential in developing novel therapeutic interventions for AD. Future investigations are needed to define molecular mechanisms by which these complex regulatory systems become malfunctional at specific stages of AD development and progression, which will facilitate future development of novel therapeutic interventions. It is also critical to investigate all key components of the protein degradation pathways, both upstream and downstream, to improve our abilities to manipulate transport pathways with higher efficacy and less side effects.

Melatonin attenuates expression of cyclooxygenase-2 (COX-2) in activated microglia induced by lipopolysaccharide (LPS)

Lipopolysaccharide (LPS) is a known neurotoxin and utilized most extensively as a microglial activator for induction of inflammatory neurodegeneration. Melatonin (MEL) is the main secretory product of pineal gland reported to be responsible for a variety of physiological functions. However, the molecular mechanisms underlying the influence of MEL on microglia activation remain unclear. The aim of this study was to investigate the effect of MEL on cyclooxygenase-2 (COX-2) levels in LPS-induced microglia. The results of RT-PCR and Western blot analysis showed that MEL significantly inhibited LPS-mediated upregulation of COX-2 in microglia. Data from ELISA demonstrated that prostaglandin E2 (PGE2), the downstream effector of COX-2, concentrations were also reduced. In addition, MEL was found to decrease activation of ERK1/2, JNK, p38 MAPK, and NF-κB, the upstream signal pathways of COX-2. Taken together, evidence indicates that MEL may attenuate upregulation of COX-2 by blocking the MAPK/NF-κB signaling pathway in LPS-stimulated microglia.

Trans ε viniferin decreases amyloid deposits and inflammation in a mouse transgenic Alzheimer model

As Alzheimer’s disease (AD) induces several cellular and molecular damages, it could be interesting to use multi-target molecules for therapeutics. We previously published that trans ε-viniferin induced the disaggregation of Aβ₄₂ peptide and inhibited the inflammatory response in primary cellular model of AD. Here, effects of this stilbenoid were evaluated in transgenic APPswePS1dE9 mice. We report that trans ε-viniferin could go through the blood brain barrier, reduces size and density of amyloid deposits and decreases reactivity of astrocytes and microglia, after a weekly intraperitoneal injection at 10 mg/kg from 3 to 6 months of age.

Mechanisms Associated with Type 2 Diabetes as a Risk Factor for Alzheimer-Related Pathology

Current evidence suggests dementia and pathology in Alzheimer's Disease (AD) are both dependent and independent of amyloid processing and can be induced by multiple 'hits' on vital neuronal functions. Type 2 diabetes (T2D) poses the most important risk factor for developing AD after ageing and dysfunctional IR/PI3K/Akt signalling is a major contributor in both diseases. We developed a model of T2D, coupling subdiabetogenic doses of streptozotocin (STZ) with a human junk food (HJF) diet to more closely mimic the human condition. Over 35 weeks, this induced classic signs of T2D (hyperglycemia and insulin dysfunction) and a modest, but stable deficit in spatial recognition memory, with very little long-term modification of proteins in or associated with IR/PI3K/Akt signalling in CA1 of the hippocampus. Intracerebroventricular infusion of soluble amyloid beta 42 (Aβ42) to mimic the early preclinical rise in Aβ alone induced a more severe, but short-lasting deficits in memory and deregulation of proteins. Infusion of Aβ on the T2D phenotype exacerbated and prolonged the memory deficits over approximately 4 months, and induced more severe aberrant regulation of proteins associated with autophagy, inflammation and glucose uptake from the periphery. A mild form of environmental enrichment transiently rescued memory deficits and could reverse the regulation of some, but not all protein changes. Together, these data identify mechanisms by which T2D could create a modest dysfunctional neuronal milieu via multiple and parallel inputs that permits the development of pathological events identified in AD and memory deficits when Aβ levels are transiently effective in the brain.

Cholesterol impairs autophagy-mediated clearance of amyloid beta while promoting its secretion

Macroautophagy/autophagy failure with the accumulation of autophagosomes is an early neuropathological feature of Alzheimer disease (AD) that directly affects amyloid beta (Aβ) metabolism. Although loss of presenilin 1 function has been reported to impair lysosomal function and prevent autophagy flux, the detailed mechanism leading to autophagy dysfunction in AD remains to be elucidated. The resemblance between pathological hallmarks of AD and Niemann-Pick Type C disease, including endosome-lysosome abnormalities and impaired autophagy, suggests cholesterol accumulation as a common link. Using a mouse model of AD (APP-PSEN1-SREBF2 mice), expressing chimeric mouse-human amyloid precursor protein with the familial Alzheimer Swedish mutation (APP695swe) and mutant presenilin 1 (PSEN1-dE9), together with a dominant-positive, truncated and active form of SREBF2/SREBP2 (sterol regulatory element binding factor 2), we demonstrated that high brain cholesterol enhanced autophagosome formation, but disrupted its fusion with endosomal-lysosomal vesicles. The combination of these alterations resulted in impaired degradation of Aβ and endogenous MAPT (microtubule associated protein tau), and stimulated autophagy-dependent Aβ secretion. Exacerbated Aβ-induced oxidative stress in APP-PSEN1-SREBF2 mice, due to cholesterol-mediated depletion of mitochondrial glutathione/mGSH, is critical for autophagy induction. In agreement, in vivo mitochondrial GSH recovery with GSH ethyl ester, inhibited autophagosome synthesis by preventing the oxidative inhibition of ATG4B deconjugation activity exerted by Aβ. Moreover, cholesterol-enrichment within the endosomes-lysosomes modified the levels and membrane distribution of RAB7A and SNAP receptors (SNAREs), which affected its fusogenic ability. Accordingly, in vivo treatment with 2-hydroxypropyl-β-cyclodextrin completely rescued these alterations, making it a potential therapeutic tool for AD.

Altered plasma arginine metabolome precedes behavioural and brain arginine metabolomic profile changes in the APPswe/PS1ΔE9 mouse model of Alzheimer's disease

While amyloid-beta (Aβ) peptides play a central role in the development of Alzheimer's disease (AD), recent evidence also implicates altered metabolism of L-arginine in the pathogenesis of AD. The present study systematically investigated how behavioural function and the brain and plasma arginine metabolic profiles changed in a chronic Aβ accumulation model using male APPswe/PS1ΔE9 transgenic (Tg) mice at 7 and 13 months of age. As compared to their wild-type (WT) littermates, Tg mice displayed age-related deficits in spatial water maze tasks and alterations in brain arginine metabolism. Interestingly, the plasma arginine metabolic profile was markedly altered in 7-month Tg mice prior to major behavioural impairment. Receiver operating characteristic curve analysis revealed that plasma putrescine and spermine significantly differentiated between Tg and WT mice. These results demonstrate the parallel development of altered brain arginine metabolism and behavioural deficits in Tg mice. The altered plasma arginine metabolic profile that preceded the behavioural and brain profile changes suggests that there may be merit in an arginine-centric set of ante-mortem biomarkers for AD.

The role of UNC5C in Alzheimer's disease

Alzheimer's disease (AD) is a chronic progressive neurodegenerative disease in adults characterized by the deposition of extracellular plaques of β-amyloid protein (Aβ), intracellular neurofibrillary tangles (NFTs), synaptic loss and neuronal apoptosis. AD has a strong and complex genetic component that involving into multiple genes. With recent advances in whole-exome sequencing (WES) and whole-genome sequencing (WGS) technology, UNC5C was identified to have association with AD. Emerging studies on cell and animal models identified that aberrant UNC5C may contribute to AD by activating death-associated protein kinase 1 (DAPK1) which is a new component involved in AD pathogenesis with an extensive involvement in aberrant tau, Aβ and neuronal apoptosis/autophagy. In this review, we briefly summarize the biochemical properties, genetics, epigenetics, and the speculative role of UNC5C in AD. We hope our review would bring comprehensive understandings of AD pathogenesis and provide new therapeutic targets for AD.

The mechanistic target of rapamycin (mTOR) and the silent mating-type information regulation 2 homolog 1 (SIRT1): oversight for neurodegenerative disorders

As a result of the advancing age of the global population and the progressive increase in lifespan, neurodegenerative disorders continue to increase in incidence throughout the world. New strategies for neurodegenerative disorders involve the novel pathways of the mechanistic target of rapamycin (mTOR) and the silent mating-type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1) that can modulate pathways of apoptosis and autophagy. The pathways of mTOR and SIRT1 are closely integrated. mTOR forms the complexes mTOR Complex 1 and mTOR Complex 2 and can impact multiple neurodegenerative disorders that include Alzheimer's disease, Huntington's disease, and Parkinson's disease. SIRT1 can control stem cell proliferation, block neuronal injury through limiting programmed cell death, drive vascular cell survival, and control clinical disorders that include dementia and retinopathy. It is important to recognize that oversight of programmed cell death by mTOR and SIRT1 requires a fine degree of precision to prevent the progression of neurodegenerative disorders. Additional investigations and insights into these pathways should offer effective and safe treatments for neurodegenerative disorders.

Autophagy and Alzheimer's Disease: From Molecular Mechanisms to Therapeutic Implications

Alzheimer’s disease (AD) is the most common cause of progressive dementia in the elderly. It is characterized by a progressive and irreversible loss of cognitive abilities and formation of senile plaques, composed mainly of amyloid β (Aβ), and neurofibrillary tangles (NFTs), composed of tau protein, in the hippocampus and cortex of afflicted humans. In brains of AD patients the metabolism of Aβ is dysregulated, which leads to the accumulation and aggregation of Aβ. Metabolism of Aβ and tau proteins is crucially influenced by autophagy. Autophagy is a lysosome-dependent, homeostatic process, in which organelles and proteins are degraded and recycled into energy. Thus, dysfunction of autophagy is suggested to lead to the accretion of noxious proteins in the AD brain. In the present review, we describe the process of autophagy and its importance in AD. Additionally, we discuss mechanisms and genes linking autophagy and AD, i.e., the mTOR pathway, neuroinflammation, endocannabinoid system, ATG7, BCL2, BECN1, CDK5, CLU, CTSD, FOXO1, GFAP, ITPR1, MAPT, PSEN1, SNCA, UBQLN1, and UCHL1. We also present pharmacological agents acting via modulation of autophagy that may show promise in AD therapy. This review updates our knowledge on autophagy mechanisms proposing novel therapeutic targets for the treatment of AD.

Natural polyphenols effects on protein aggregates in Alzheimer's and Parkinson's prion-like diseases

Alzheimer's and Parkinson's diseases are the most common neurodegenerative diseases. They are characterized by protein aggregates and so can be considered as prion-like disease. The major components of these deposits are amyloid peptide and tau for Alzheimer's disease, α-synuclein and synphilin-1 for Parkinson's disease. Drugs currently proposed to treat these pathologies do not prevent neurodegenerative processes and are mainly symptomatic therapies. Molecules inducing inhibition of aggregation or disaggregation of these proteins could have beneficial effects, especially if they have other beneficial effects for these diseases. Thus, several natural polyphenols, which have antioxidative, anti-inflammatory and neuroprotective properties, have been largely studied, for their effects on protein aggregates found in these diseases, notably in vitro. In this article, we propose to review the significant papers concerning the role of polyphenols on aggregation and disaggregation of amyloid peptide, tau, α-synuclein, synphilin-1, suggesting that these compounds could be useful in the treatments in Alzheimer's and Parkinson's diseases.

Selenium-enriched yeast inhibited β-amyloid production and modulated autophagy in a triple transgenic mouse model of Alzheimer's disease

Se-yeast reduced the burden of Aβ accumulation by both decreased the generation and inhibited the initiation of autophagy pathway, enhanced autophagic clearance of Aβ in the brains of AD mice.

Erythropoietin and mTOR: A "One-Two Punch" for Aging-Related Disorders Accompanied by Enhanced Life Expectancy

Life expectancy continues to increase throughout the world, but is accompanied by a rise in the incidence of non-communicable diseases. As a result, the benefits of an increased lifespan can be limited by aging-related disorders that necessitate new directives for the development of effective and safe treatment modalities. With this objective, the mechanistic target of rapamycin (mTOR), a 289-kDa serine/threonine protein, and its related pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), proline rich Akt substrate 40 kDa (PRAS40), AMP activated protein kinase (AMPK), Wnt signaling, and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), have generated significant excitement for furthering novel therapies applicable to multiple systems of the body. Yet, the biological and clinical outcome of these pathways can be complex especially with oversight of cell death mechanisms that involve apoptosis and autophagy. Growth factors, and in particular erythropoietin (EPO), are one avenue under consideration to implement control over cell death pathways since EPO can offer potential treatment for multiple disease entities and is intimately dependent upon mTOR signaling. In experimental and clinical studies, EPO appears to have significant efficacy in treating several disorders including those involving the developing brain. However, in mature populations that are affected by aging-related disorders, the direction for the use of EPO to treat clinical disease is less clear that may be dependent upon a number of factors including the understanding of mTOR signaling. Continued focus upon the regulatory elements that control EPO and mTOR signaling could generate critical insights for targeting a broad range of clinical maladies.

Autophagy impairment by caspase-1-dependent inflammation mediates memory loss in response to β-Amyloid peptide accumulation

β-Amyloid peptide accumulation in the cortex and in the hippocampus results in neurodegeneration and memory loss. Recently, it became evident that the inflammatory response triggered by β-Amyloid peptides promotes neuronal cell death and degeneration. In addition to inflammation, β-Amyloid peptides also induce alterations in neuronal autophagy, eventually leading to neuronal cell death. Thus, here we evaluated whether the inflammatory response induced by the β-Amyloid peptides impairs memory via disrupting the autophagic flux. We show that male mice overexpressing β-Amyloid peptides (5XFAD) but lacking caspase-1, presented reduced β-Amyloid plaques in the cortex and in the hippocampus; restored brain autophagic flux and improved learning and memory capacity. At the molecular level, inhibition of the inflammatory response in the 5XFAD mice restored LC3-II levels and prevented the accumulation of oligomeric p62 and ubiquitylated proteins. Furthermore, caspase-1 deficiency reinstates activation of the AMPK/Raptor pathway while down-regulating AKT/mTOR pathway. Consistent with this, we found an inverse correlation between the increase of autophagolysosomes in the cortex of 5XFAD mice lacking caspase-1 and the presence of mitochondria with altered morphology. Together our results indicate that β-Amyloid peptide-induced caspase-1 activation, disrupts autophagy in the cortex and in the hippocampus resulting in neurodegeneration and memory loss.

TNFα affects CREB-mediated neuroprotective signaling pathways of synaptic plasticity in neurons as revealed by proteomics and phospho-proteomics

Neuroinflammation is a hallmark of Alzheimer's disease and TNFα as the main inducer of neuroinflammation has neurodegenerative but also pro-regenerative properties, however, the dose-dependent molecular changes on signaling pathway level are not fully understood. We performed quantitative proteomics and phospho-proteomics to target this point.

In HT22 cells, we found that TNFα reduced mitochondrial signaling and inhibited mTOR protein translation signaling but also led to induction of neuroprotective MAPK-CREB signaling. Stimulation of human neurons with TNFα revealed similar cellular mechanisms. Moreover, a number of synaptic plasticity-associated genes were altered in their expression profile including CREB.

SiRNA-mediated knockdown of CREB in human neurons prior to TNFα stimulation led to a reduced number of protein/phospho-protein hits compared to siRNA-mediated knockdown of CREB or TNFα stimulation alone and countermeasured the reduced CREB signaling. In vivo data of TNFα knockout mice showed that learning ability did not depend on TNFα per se but that TNFα was essential for preserving the learning ability after episodes of lipopolysaccharide-induced neuroinflammation. This may be based on modulation of CREB/CREB signaling as revealed by the in vitro / in vivo data.

Our data show that several molecular targets and signaling pathways induced by TNFα in neurons resemble those seen in Alzheimer's disease pathology.

Type-I interferon pathway in neuroinflammation and neurodegeneration: focus on Alzheimer's disease

Past research in Alzheimer's disease (AD) has largely been driven by the amyloid hypothesis; the accompanying neuroinflammation seen in AD has been assumed to be consequential and not disease modifying or causative. However, recent data from both clinical and preclinical studies have established that the immune-driven neuroinflammation contributes to AD pathology. Key evidence for the involvement of neuroinflammation in AD includes enhanced microglial and astroglial activation in the brains of AD patients, increased pro-inflammatory cytokine burden in AD brains, and epidemiological evidence that chronic non-steroidal anti-inflammatory drug use prior to disease onset leads to a lower incidence of AD. Identifying critical mediators controlling this neuroinflammation will prove beneficial in developing anti-inflammatory therapies for the treatment of AD. The type-I interferons (IFNs) are pleiotropic cytokines that control pro-inflammatory cytokine secretion and are master regulators of the innate immune response that impact on disorders of the central nervous system. This review provides evidence that the type-I IFNs play a critical role in the exacerbation of neuroinflammation and actively contribute to the progression of AD.