Autophagy gone awry in neurodegenerative diseases

Phospholipid peroxidation inhibits autophagy via stimulating the delipidation of oxidized LC3-PE

Phospholipid peroxidation of polyunsaturated fatty acids at the bis-allylic position drives ferroptosis. Here we identify a novel role for phospholipid peroxidation in the inhibition of autophagy. Using in vitro and in vivo models, we report that phospholipid peroxidation induced by glutathione peroxidase-4 inhibition and arachidonate 15-lipoxygenase overexpression leads to overload of peroxidized phospholipids and culminate in inhibition of autophagy. Functional and lipidomics analysis further demonstrated that inhibition of autophagy was associated with an increase of peroxidized phosphatidylethanolamine (PE) conjugated LC3. We further demonstrate that autophagy inhibition occurred due to preferential cleavage of peroxidized LC3-PE by ATG4B to yield delipidated LC3. Mouse models of phospholipid peroxidation and autophagy additionally supported a role for peroxidized PE in autophagy inhibition. Our results agree with the recognized role of endoplasmic reticulum as the primary source for autophagosomal membranes. In summary, our studies demonstrated that phospholipid peroxidation inhibited autophagy via stimulating the ATG4B-mediated delipidation of peroxidized LC3-PE.

Proteolysis dysfunction in the process of aging and age-related diseases

In this review, we discuss in detail the most relevant proteolytic systems that together with chaperones contribute to creating the proteostasis network that is kept in dynamic balance to maintain overall functionality of cellular proteomes. Data accumulated over decades demonstrate that the effectiveness of elements of the proteostasis network declines with age. In this scenario, failure to degrade misfolded or faulty proteins increases the risk of protein aggregation, chronic inflammation, and the development of age-related diseases. This is especially important in the context of aging-related modification of functions of the immune system.

Crosstalk between regulatory non-coding RNAs and oxidative stress in Parkinson’s disease

Parkinson’s disease is the second most common neurodegenerative disease after Alzheimer’s disease, which imposes an ever-increasing burden on society. Many studies have indicated that oxidative stress may play an important role in Parkinson’s disease through multiple processes related to dysfunction or loss of neurons. Besides, several subtypes of non-coding RNAs are found to be involved in this neurodegenerative disorder. However, the interplay between oxidative stress and regulatory non-coding RNAs in Parkinson’s disease remains to be clarified. In this article, we comprehensively survey and overview the role of regulatory ncRNAs in combination with oxidative stress in Parkinson’s disease. The interaction between them is also summarized. We aim to provide readers with a relatively novel insight into the pathogenesis of Parkinson’s disease, which would contribute to the development of pre-clinical diagnosis and treatment.

The interplay of epilepsy with impaired mitophagy and autophagy linked dementia (MAD): A review of therapeutic approaches

The duration and, age of dementia have been linked to a higher risk of seizures. The exact mechanism that drives epileptogenesis in impaired mitophagy and autophagy linked dementia (MAD) is fully defined after reviewing the Scopus, Publon, and Pubmed databases. The epileptogenesis in patients with Alzheimer's disease dementia (ADD) and Parkinson's disease dementia (PDD) is due to involvement of amyloid plaques (Aβ), phosphorylated tau (pTau), Parkin, NF-kB and NLRP3 inflammasome. Microglia, the prime protective and inflammatory cells in the brain exert crosstalk between mitophagy and inflammation. Several researchers believed that the inflammatory brain cells microglia could be a therapeutic target for the treatment of a MAD associated epilepsy. There are conventional antiepileptic drugs such as gabapentin, lamotrigine, phenytoin sodium, carbamazepine, oxcarbazepine, felbamate, lamotrigine, valproate sodium, and topiramate are prescribed by a psychiatrist to suppress seizure frequency. Also, the conventional drugs generate serious adverse effects and synergises dementia characteristics. The adverse effect of carbamazepine is neurotoxic and also, damages haemopoietic system and respiratory tract. The phenytoin treatment causes cerebellar defect and anemia. Dementia and epilepsy have a complicated relationship, thus targeting mitophagy for cure of epileptic dementia makes sense. Complementary and alternative medicine (CAM) is one of the rising strategies by many patients of the world, not only to suppress seizure frequency but also to mitigate dementia characteristics of patients. Therefore our present review focus on the interplay between epilepsy and MAD and their treatment with CAM approaches.

Activation of LXRs Reduces Oxysterol Lipotoxicity in RPE Cells by Promoting Mitochondrial Function

Effective treatments for age-related macular degeneration (AMD), the most prevalent neurodegenerative form of blindness in older adults, are lacking. Genome-wide association studies have identified lipid metabolism and inflammation as AMD-associated pathogenic changes. Liver X receptors (LXRs) play a critical role in intracellular homeostases, such as lipid metabolism, glucose homeostasis, inflammation, and mitochondrial function. However, its specific role in AMD and its underlying molecular mechanisms remain unknown. In this study, we investigated the effects of lipotoxicity in human retinal pigmental epithelial (ARPE-19) cells and evaluated how LXRs reduce 7-ketocholesterol (7KCh) lipotoxicity in RPE cells using models, both in vivo and in vitro. A decrease in oxidative lipid accumulation was observed in mouse retinas following the activation of the LXRs; this result was also confirmed in cell experiments. At the same time, LXRs activation reduced RPE cell apoptosis induced by oxysterols. We found that oxysterols decreased the mitochondrial membrane potential in ARPE-19 cells, while LXR agonists counteracted these effects. In cultured ARPE-19 cells, activating LXRs reduced p62, mTOR, and LC3I/II levels, and the knockdown of LXRs elevated the expression of these proteins, indicating that activating LXRs could boost mitophagy. The findings of this study suggest LXR-active pharmaceuticals as a potential therapeutic target for dry AMD.

Identifying genetic determinants of inflammatory pain in mice using a large-scale gene-targeted screen

ABSTRACT

Identifying the genetic determinants of pain is a scientific imperative given the magnitude of the global health burden that pain causes. Here, we report a genetic screen for nociception, performed under the auspices of the International Mouse Phenotyping Consortium. A biased set of 110 single-gene knockout mouse strains was screened for 1 or more nociception and hypersensitivity assays, including chemical nociception (formalin) and mechanical and thermal nociception (von Frey filaments and Hargreaves tests, respectively), with or without an inflammatory agent (complete Freund's adjuvant). We identified 13 single-gene knockout strains with altered nocifensive behavior in 1 or more assays. All these novel mouse models are openly available to the scientific community to study gene function. Two of the 13 genes (Gria1 and Htr3a) have been previously reported with nociception-related phenotypes in genetically engineered mouse strains and represent useful benchmarking standards. One of the 13 genes (Cnrip1) is known from human studies to play a role in pain modulation and the knockout mouse reported herein can be used to explore this function further. The remaining 10 genes (Abhd13, Alg6, BC048562, Cgnl1, Cp, Mmp16, Oxa1l, Tecpr2, Trim14, and Trim2) reveal novel pathways involved in nociception and may provide new knowledge to better understand genetic mechanisms of inflammatory pain and to serve as models for therapeutic target validation and drug development.

Autophagy Impairment in App Knock-in Alzheimer's Model Mice

Alzheimer's disease (AD) is characterized by impaired protein homeostasis leading to amyloid-β peptide (Aβ) amyloidosis. Amyloid precursor protein (APP) knock-in mice exhibit robust Aβ pathology, providing possibilities to determine its effect on protein homeostasis including autophagy. Here we compared human AD postmortem brain tissue with brains from two different types of App knock-in mice, App NL-F and App NL-G-F mice, exhibiting AD-like pathology. In AD postmortem brains, p62 levels are increased and p62-positive staining is detected in neurons, including potential axonal beadings, as well as in the vasculature and in corpora amylacea. Interestingly, p62 is also increased in the neurons in 12-month-old App NL-G-F mice. In brain homogenates from 12-month-old App NL-G-F mice, both p62 and light chain 3 (LC3)-II levels are increased as compared to wildtype (WT) mice, indicating inhibited autophagy. Double immunostaining for LC3 and Aβ revealed LC3-positive puncta in hippocampus of 24-month-old App NL-F mice around the Aβ plaques which was subsequently identified by electron microscopy imaging as an accumulation of autophagic vacuoles in dystrophic neurites around the Aβ plaques. Taken together, autophagy is impaired in App knock-in mice upon increased Aβ pathology, indicating that App knock-in mouse models provide a platform for understanding the correlation between Aβ and autophagy.

Mitochondrial structural variations in the process of mitophagy

Mitochondrion is one of significant organelles inside cells because it serves as a hub for energy management and intracellular signaling. Internal/external damages on mitochondria would lead to mitochondrial stresses with the malfunctions, accompanying with the changes of morphological structure and abnormal local environments (pH values). Mitophagy is capable of degradation of damaged mitochondrial segments to restore its normal metabolism, dynamics, and biogenesis. The dynamic structural visualization and pH quantification can be helpful for the understanding of mitochondrial functions as well as the diagnosis of disorders linking with this process. In this work, we use confocal laser scanning microscopy, STED super-resolution nanoscopy and fluorescence lifetime imaging microscopy, in conjunction with a mitochondrial probe to image the dynamic changes in the mitochondrial morphology and microenvironmental pH values during mitophagy in live cells, in particular, the structural changes of mitochondrial cristae beyond optical diffraction can be distinguished by STED nanoscopy with/without treatment by CCCP, which will provide a new view for the diagnosis and personalized treatment of mitochondrial dysfunction-related diseases.

Disuse-induced skeletal muscle atrophy in disease and non-disease states in humans: mechanisms, prevention, and recovery strategies

Decreased skeletal muscle contractile activity (disuse) or unloading leads to muscle mass loss, also known as muscle atrophy. The balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB) is the primary determinant of skeletal muscle mass. A reduced mechanical load on skeletal muscle is one of the main external factors leading to muscle atrophy. However, endocrine and inflammatory factors can act synergistically in catabolic states, amplifying the atrophy process and accelerating its progression. Additionally, older individuals display aging-induced anabolic resistance, which can predispose this population to more pronounced effects when exposed to periods of reduced physical activity or mechanical unloading. Different cellular mechanisms contribute to the regulation of muscle protein balance during skeletal muscle atrophy. This review summarizes the effects of muscle disuse on muscle protein balance and the molecular mechanisms involved in muscle atrophy in the absence or presence of disease. Finally, a discussion of the current literature describing efficient strategies to prevent or improve the recovery from muscle atrophy is also presented.

The role of autophagy and mitophagy in cancers

Autophagy is an important life phenomenon in eukaryotic cells. Its main role is to remove and degrade its damaged organelles and excess biological macromolecules, and use degradation products to provide energy and rebuild the cell structure, playing an important role in maintaining cell homeostasis and cell life activities. Mitophagy is a form of macroautophagy. It has the beneficial effect of eliminating damaged mitochondria, thereby maintaining the integrity of the mitochondrial pool. Autophagy and mitophagy have a dual role in the development of cancer. On one hand, autophagy and mitophagy can maintain the normal physiological function of cells. On the other hand, excessive autophagy and mitophagy can lead to diseases. The present review introduces the mechanisms of autophagy and mitophagy, and the main related proteins, and introduce the correlation with cancers, providing a basis for the treatment of cancers through the understanding of these proteins.

Defects of Nutrient Signaling and Autophagy in Neurodegeneration

Neurons are post-mitotic cells that allocate huge amounts of energy to the synthesis of new organelles and molecules, neurotransmission and to the maintenance of redox homeostasis. In neurons, autophagy is not only crucial to ensure organelle renewal but it is also essential to balance nutritional needs through the mobilization of internal energy stores. A delicate crosstalk between the pathways that sense nutritional status of the cell and the autophagic processes to recycle organelles and macronutrients is fundamental to guarantee the proper functioning of the neuron in times of energy scarcity. This review provides a detailed overview of the pathways and processes involved in the balance of cellular energy mediated by autophagy, which when defective, precipitate the neurodegenerative cascade of Parkinson's disease, frontotemporal dementia, amyotrophic lateral sclerosis or Alzheimer's disease.

Regulatory Roles of Antimicrobial Peptides in the Nervous System: Implications for Neuronal Aging

Antimicrobial peptides (AMPs) are classically known as important effector molecules in innate immunity across all multicellular organisms. However, emerging evidence begins to suggest multifunctional properties of AMPs beyond their antimicrobial activity, surprisingly including their roles in regulating neuronal function, such as sleep and memory formation. Aging, which is fundamental to neurodegeneration in both physiological and disease conditions, interestingly affects the expression pattern of many AMPs in an infection-independent manner. While it remains unclear whether these are coincidental events, or a mechanistic relationship exists, previous studies have suggested a close link between AMPs and a few key proteins involved in neurodegenerative diseases. This review discusses recent literature and advances in understanding the crosstalk between AMPs and the nervous system at both molecular and functional levels, with the aim to explore how AMPs may relate to neuronal vulnerability in aging.

Subcellular proteomics of dopamine neurons in the mouse brain

Dopaminergic neurons modulate neural circuits and behaviors via dopamine (DA) release from expansive, long range axonal projections. The elaborate cytoarchitecture of these neurons is embedded within complex brain tissue, making it difficult to access the neuronal proteome using conventional methods. Here, we demonstrate APEX2 proximity labeling within genetically targeted neurons in the mouse brain, enabling subcellular proteomics with cell-type specificity. By combining APEX2 biotinylation with mass spectrometry, we mapped the somatodendritic and axonal proteomes of midbrain dopaminergic neurons. Our dataset reveals the proteomic architecture underlying proteostasis, axonal metabolism, and neurotransmission in these neurons. We find that most proteins encoded by DA neuron-enriched genes are localized within striatal dopaminergic axons, including ion channels with previously undescribed axonal localization. These proteomic datasets provide a resource for neuronal cell biology, and this approach can be readily adapted for study of other neural cell types.

Weakened interaction of ATG14 and the SNARE complex blocks autophagosome-lysosome fusion contributes to fluoride-induced developmental neurotoxicity

Fluoride is capable of inducing developmental neurotoxicity, but the mechanisms involved remain unclear. We aimed to explore the role of autophagosome-lysosome fusion in developmental fluoride neurotoxicity, particularly focusing on the interaction between ATG14 and the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex. We developed in vivo models of Sprague-Dawley rats exposed to sodium fluoride (NaF) from the pregnancy of parental rats until the offspring were two months old and in vitro models of NaF and/or Ad-ATG14-treated SH-SY5Y cells. We assessed neurobehavioral changes in offspring and further investigated the effects of NaF exposure on autophagic flux, apoptosis, autophagosome-lysosome fusion, and the interaction between ATG14 and the SNARE complex. NaF exposure impaired offspring learning and memory capabilities and induced the accumulation of autophagosomes and autophagic flux blockage and apoptosis, as indicated by increased LC3-II, p62, and cleaved-caspase-3 expression in vivo and in vitro. In addition, NaF treatment downregulated the protein expression of ATG14 and the SNARE complex and induced autophagosome-lysosome fusion blockage as evidenced by decreased ATG14, STX17, SNAP29, and VAMP8 expression and diminished colocalization of autophagosomes and lysosomes in vivo and in vitro. Furthermore, ATG14 upregulation enhanced the interaction of ATG14 and the SNARE complex to facilitate autophagosome-lysosome fusion, thereby restoring autophagic flux and alleviating NaF-induced apoptosis. In conclusion, NaF exhibited developmental neurotoxicity by restraining the interaction of ATG14 with the SNARE complex and hindering autophagosome-lysosome fusion, thereby participating in the occurrence and development of fluoride neurotoxicity. Notably, ATG14 upregulation protects against developmental fluoride neurotoxicity, and ATG14 may serve as a promising biomarker for further epidemiological investigation.

The panoramic view of amyotrophic lateral sclerosis: A fatal intricate neurological disorder

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurological disease affecting both upper and lower motor neurons. In the United States alone, there are 16,000-20,000 established cases of ALS. The early disease diagnosis is challenging due to many overlapping pathophysiologies with other neurological diseases. The etiology of ALS is unknown; however, it is divided into two categories: familial ALS (fALS) which occurs due to gene mutations & contributes to 5-10% of ALS, and sporadic ALS (sALS) which is due to environmental factors & contributes to 90-95% of ALS. There is still no curative treatment for ALS: palliative care and symptomatic treatment are therefore essential components in the management of these patients. In this review, we provide a panoramic view of ALS, which includes epidemiology, risk factors, pathophysiologies, biomarkers, diagnosis, therapeutics (natural, synthetic, gene-based, pharmacological, stem cell, extracellular vesicles, and physical therapy), controversies (in the clinical trials of ALS), the scope of nanomedicine in ALS, and future perspectives.

The Role of Chaperone-Mediated Autophagy in Hepatitis C Virus-Induced Pathogenesis

Lysosome incorporate and degrade proteins in a process known as autophagy. There are three types of autophagy; macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA). Although autophagy is considered a nonselective degradation process, CMA is known as a selective degradation pathway. All proteins internalized in the lysosome via CMA contain a pentapeptide KFERQ-motif, also known as a CMA-targeting motif, which is necessary for selectivity. CMA directly delivers a substrate protein into the lysosome lumen using the cytosolic chaperone HSC70 and the lysosomal receptor LAMP-2A for degradation. Hepatitis C virus (HCV) NS5A protein interacts with hepatocyte-nuclear factor 1α (HNF-1α) together with HSC70 and promotes the lysosomal degradation of HNF-1α via CMA, resulting in HCV-induced pathogenesis. HCV NS5A promotes recruitment of HSC70 to the substrate protein HNF-1α. HCV NS5A plays a crucial role in HCV-induced CMA. Further investigations of HCV NS5A-interacting proteins containing CMA-targeting motifs may help to elucidate HCV-induced pathogenesis.

Location, location, location: subcellular protein partitioning in proteostasis and aging

Somatic maintenance and cell survival rely on proper protein homeostasis to ensure reliable functions across the cell and to prevent proteome collapse. Maintaining protein folding and solubility is central to proteostasis and is coordinated by protein synthesis, chaperoning, and degradation capacities. An emerging aspect that influences proteostasis is the dynamic protein partitioning across different subcellular structures and compartments. Here, we review recent literature related to nucleocytoplasmic partitioning of proteins, nuclear and cytoplasmic quality control mechanisms, and their impact on the development of age-related diseases. We also highlight new points of entry to modulate spatially-regulated proteostatic mechanisms to delay aging.

SINEUPs: a novel toolbox for RNA therapeutics

RNA molecules have emerged as a new class of promising therapeutics to expand the range of druggable targets in the genome. In addition to ‘canonical’ protein-coding mRNAs, the emerging richness of sense and antisense long non-coding RNAs (lncRNAs) provides a new reservoir of molecular tools for RNA-based drugs. LncRNAs are composed of modular structural domains with specific activities involving the recruitment of protein cofactors or directly interacting with nucleic acids. A single therapeutic RNA transcript can then be assembled combining domains with defined secondary structures and functions, and antisense sequences specific for the RNA/DNA target of interest.

As the first representative molecules of this new pharmacology, we have identified SINEUPs, a new functional class of natural antisense lncRNAs that increase the translation of partially overlapping mRNAs. Their activity is based on the combination of two domains: an embedded mouse inverted SINEB2 element that enhances mRNA translation (effector domain) and an overlapping antisense region that provides specificity for the target sense transcript (binding domain). By genetic engineering, synthetic SINEUPs can potentially target any mRNA of interest increasing translation and therefore the endogenous level of the encoded protein.

In this review, we describe the state-of-the-art knowledge of SINEUPs and discuss recent publications showing their potential application in diseases where a physiological increase of endogenous protein expression can be therapeutic.

Gossypol, a novel modulator of VCP, induces autophagic degradation of mutant huntingtin by promoting the formation of VCP/p97-LC3-mHTT complex

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by toxic aggregates of mutant huntingtin protein (mHTT) in the brain. Decreasing mHTT is a potential strategy for therapeutic purpose of HD. Valosin-containing protein (VCP/p97) is a crucial regulator of proteostasis, which regulates the degradation of damaged protein through proteasome and autophagy pathway. Since VCP has been implicated in pathogenesis of HD as well as other neurodegenerative diseases, small molecules that specifically regulate the activity of VCP may be of therapeutic benefits for HD patients. In this study we established a high-throughput screening biochemical assay for VCP ATPase activity measurement and identified gossypol, a clinical approved drug in China, as a novel modulator of VCP. Gossypol acetate dose-dependently inhibited the enzymatic activity of VCP in vitro with IC₅₀ of 6.53±0.6 μM. We further demonstrated that gossypol directly bound to the interface between the N and D1 domains of VCP. Gossypol acetate treatment not only lowered mHTT levels and rescued HD-relevant phenotypes in HD patient iPS-derived Q47 striatal neurons and HD knock-in mouse striatal cells, but also improved motor function deficits in both Drosophila and mouse HD models. Taken together, gossypol acetate acted through a gain-of-function way to induce the formation of VCP-LC3-mHTT ternary complex, triggering autophagic degradation of mHTT. This study reveals a new strategy for treatment of HD and raises the possibility that an existing drug can be repurposed as a new treatment of neurodegenerative diseases.

Astrocytes, a Promising Opportunity to Control the Progress of Parkinson's Disease

At present, there is no efficient treatment to prevent the evolution of Parkinson’s disease (PD). PD is generated by the concurrent activity of multiple factors, which is a serious obstacle for the development of etio-pathogenic treatments. Astrocytes may act on most factors involved in PD and the promotion of their neuroprotection activity may be particularly suitable to prevent the onset and progression of this basal ganglia (BG) disorder. The main causes proposed for PD, the ability of astrocytes to control these causes, and the procedures that can be used to promote the neuroprotective action of astrocytes will be commented upon, here.

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.

Nerve Growth Factor-Based Therapy in Alzheimer's Disease and Age-Related Macular Degeneration

Alzheimer's disease (AD) is an age-associated neurodegenerative disease which is the most common cause of dementia among the elderly. Imbalance in nerve growth factor (NGF) signaling, metabolism, and/or defect in NGF transport to the basal forebrain cholinergic neurons occurs in patients affected with AD. According to the cholinergic hypothesis, an early and progressive synaptic and neuronal loss in a vulnerable population of basal forebrain involved in memory and learning processes leads to degeneration of cortical and hippocampal projections followed by cognitive impairment with accumulation of misfolded/aggregated Aβ and tau protein. The neuroprotective and regenerative effects of NGF on cholinergic neurons have been largely demonstrated, both in animal models of AD and in living patients. However, the development of this neurotrophin as a disease-modifying therapy in humans is challenged by both delivery limitations (inability to cross the blood-brain barrier (BBB), poor pharmacokinetic profile) and unwanted side effects (pain and weight loss). Age-related macular degeneration (AMD) is a retinal disease which represents the major cause of blindness in developed countries and shares several clinical and pathological features with AD, including alterations in NGF transduction pathways. Interestingly, nerve fiber layer thinning, degeneration of retinal ganglion cells and changes of vascular parameters, aggregation of Aβ and tau protein, and apoptosis also occur in the retina of both AD and AMD. A protective effect of ocular administration of NGF on both photoreceptor and retinal ganglion cell degeneration has been recently described. Besides, the current knowledge about the detection of essential trace metals associated with AD and AMD and their changes depending on the severity of diseases, either systemic or locally detected, further pave the way for a promising diagnostic approach. This review is aimed at describing the employment of NGF as a common therapeutic approach to AMD and AD and the diagnostic power of detection of essential trace metals associated with both diseases. The multiple approaches employed to allow a sustained release/targeting of NGF to the brain and its neurosensorial ocular extensions will be also discussed, highlighting innovative technologies and future translational prospects.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

Tau Seeds in Extracellular Vesicles Induce Tau Accumulation in Degradative Organelles of Cells

Clinical progression of tauopathies may result from transcellular propagation of pathogenic Tau seeds with the possible involvement of extracellular vesicles (EVs) as transport vectors. We established a cell model for investigating EV delivery of proteins, since the mechanism regulating EV cargo delivery to recipient cells is poorly understood. In our cell model, EVs are readily internalized and accumulate in degradative organelles (DOs). We then show for the first time that in this acidic compartment, profibrillogenic Tau delivered by EVs interacts with Tau expressed by the recipient cells and cause its accumulation by a process that involves the participation of autophagy. Thus, the degradative compartment of cells may represent the subcellular site initiating a cascade of events resulting in early hallmarks of tauopathies. These are characterized by seeded Tau accumulation, pathology-associated epitopes, DO stress, and cytotoxicity. The involvement of autophagy to this process and the relative accessibility of the degradative pathway for extracellular agents, support possible modes of intervention to slow down the progression of neurodegeneration.

Development of a specific live-cell assay for native autophagic flux

Autophagy is an evolutionarily conserved pathway mediating the breakdown of cellular proteins and organelles. Emphasizing its pivotal nature, autophagy dysfunction contributes to many diseases; nevertheless, development of effective autophagy modulating drugs is hampered by fundamental deficiencies in available methods for measuring autophagic activity or flux. To overcome these limitations, we introduced the photoconvertible protein Dendra2 into the MAP1LC3B locus of human cells via CRISPR/Cas9 genome editing, enabling accurate and sensitive assessments of autophagy in living cells by optical pulse labeling. We used this assay to perform high-throughput drug screens of four chemical libraries comprising over 30,000 diverse compounds, identifying several clinically relevant drugs and novel autophagy modulators. A select series of candidate compounds also modulated autophagy flux in human motor neurons modified by CRISPR/Cas9 to express GFP-labeled LC3. Using automated microscopy, we tested the therapeutic potential of autophagy induction in several distinct neuronal models of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). In doing so, we found that autophagy induction exhibited discordant effects, improving survival in disease models involving the RNA binding protein TDP-43, while exacerbating toxicity in neurons expressing mutant forms of UBQLN2 and C9ORF72 associated with familial ALS/FTD. These studies confirm the utility of the Dendra2-LC3 assay, while illustrating the contradictory effects of autophagy induction in different ALS/FTD subtypes.

Research Progress on the Mechanism of Mitochondrial Autophagy in Cerebral Stroke

Mitochondrial autophagy is an early defense and protection process that selectively clears dysfunctional or excessive mitochondria through a distinctive mechanism to maintain intracellular homeostasis. Mitochondrial dysfunction during cerebral stroke involves metabolic disbalance, oxidative stress, apoptosis, endoplasmic reticulum stress, and abnormal mitochondrial autophagy. This article reviews the research progress on the mechanism of mitochondrial autophagy in ischemic stroke to provide a theoretical basis for further research on mitochondrial autophagy and the treatment of ischemic stroke.

Cell competition from development to neurodegeneration

Cell competition is a process by which suboptimal cells are eliminated to the benefit of cells with higher fitness. It is a surveillance mechanism that senses differences in the fitness status by several modes, such as expression of fitness fingerprints, survival factor uptake rate and resistance to mechanical stress. Fitness fingerprints-mediated cell competition recognizes isoforms of the transmembrane protein Flower, and translates the relative fitness of cells into distinct fates through the Flower code. Impairments in cell competition potentiate the development of diseases like cancer and ageing-related pathologies. In cancer, malignant cells acquire a supercompetitor behaviour, killing the neighbouring cells and overtaking the tissue, thus avoiding elimination. Neurodegenerative disorders affect millions of people and are characterized by cognitive decline and locomotor deficits. Alzheimer's disease is the most common form of dementia, and one of the largely studied diseases. However, the cellular processes taking place remain unclear. Drosophila melanogaster is an emerging neurodegeneration model due to its versatility as a tool for genetic studies. Research in a Drosophila Alzheimer's disease model detected fitness markers in the suboptimal and hyperactive neurons, thus establishing a link between cell competition and Alzheimer's disease. In this Review, we overview cell competition and the new insights related to neurodegenerative disorders, and discuss how research in the field might contribute to the development of new therapeutic targets for these diseases.

Ischemia-induced upregulation of autophagy preludes dysfunctional lysosomal storage and associated synaptic impairments in neurons

Macroautophagy/autophagy is vital for neuronal homeostasis and functions. Accumulating evidence suggest that autophagy is impaired during cerebral ischemia, contributing to neuronal dysfunction and neurodegeneration. However, the outcomes after transient modification in autophagy machinery are not fully understood. This study investigated the effects of ischemic stress on autophagy and synaptic structures using a rat model of oxygen-glucose deprivation (OGD) in hippocampal neurons and a mouse model of middle cerebral artery occlusion (MCAO). Upon acute ischemia, an initial autophagy modification occurred in an upregulation manner. Following, the number of lysosomes increased, as well as lysosomal volume, indicating dysfunctional lysosomal storage. These changes were prevented by inhibiting autophagy via 3-methyladenine (3-MA) treatment or ATG7 (autophagy related 7) knockdown, or were mimicked by rapamycin (RAPA), a known activator of autophagy. This suggests that dysfunctional lysosomal storage is associated with the early burst of autophagy. Dysfunctional lysosomal storage contributed to autophagy dysfunction because the basal level of MTOR-dependent lysosomal biogenesis in the reperfusion was not sufficient to clear undegraded cargoes after transient autophagy upregulation. Further investigation revealed that impairment of synaptic ultra-structures, accompanied by dysfunctional lysosomal storage, may result from a failure in dynamic turnover of synaptic proteins. This indicates a vital role of autophagy-lysosomal machinery in the maintenance of synaptic structures. This study supports previous evidence that dysfunctional lysosomal storage may occur following the upregulation of autophagy in neurons. Appropriate autophagosome-lysosomal functioning is vital for maintenance of neuronal synaptic function and impacts more than the few known synaptic proteins.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; AD: Alzheimer disease; ALR: autophagic lysosome reformation; ATG7: autophagy related 7; CTSB: cathepsin B; CTSD: cathepsin D; DAPI: 4',6-diamidino-2-phenylindole; DEGs: differentially expressed genes; DMEM: Dulbecco's modified Eagle's medium; DMSO: dimethyl sulfoxide; GO: Gene Ontology; HBSS: Hanks' balanced salt solution; HPCA: hippocalcin; i.c.v: intracerebroventricular; KEGG: kyoto encyclopedia of genes and genomes; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3: microtubule-associated protein 1 light chain 3 beta; LSDs: lysosomal storage disorders; MAP2: microtubule-associated protein 2; MCAO: middle cerebral artery occlusion; mCTSB: mature CTSB; mCTSD: mature CTSD; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; OGD/R: oxygen-glucose deprivation/reoxygenation; PBS: phosphate-buffered saline; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; proCTSD: pro-cathepsin D; RAPA: rapamycin; RNA-seq: RNA sequencing; RPS6KB/p70S6K: ribosomal protein S6 kinase; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SIM: Structured Illumination Microscopy; SNAP25: synaptosomal-associated protein 25; SQSTM1/p62: sequestosome 1; SYN1: synapsin I; SYT1: synaptotagmin I; TBST: tris-buffered saline Tween-20; TEM: transmission electron microscopy; TFEB: transcription factor EB; tMCAO: transient middle cerebral artery occlusion; TTC: 2,3,5-triphenyltetrazolium chloride; TUBB3: tubulin, beta 3 class III.

Melatonin and Melatonergic Influence on Neuronal Transcription Factors: Implications for the Development of Novel Therapies for Neurodegenerative Disorders

Melatonin is a multifunctional signalling molecule that is secreted by the mammalian pineal gland, and also found in a number of organisms including plants and bacteria. Research has continued to uncover an ever-increasing number of processes in which melatonin is known to play crucial roles in mammals. Amongst these functions is its contribution to cell multiplication, differentiation and survival in the brain. Experimental studies show that melatonin can achieve these functions by influencing transcription factors which control neuronal and glial gene expression. Since neuronal survival and differentiation are processes that are important determinants of the pathogenesis, course and outcome of neurodegenerative disorders; the known and potential influences of melatonin on neuronal and glial transcription factors are worthy of constant examination. In this review, relevant scientific literature on the role of melatonin in preventing or altering the course and outcome of neurodegenerative disorders, by focusing on melatonin's influence on transcription factors is examined. A number of transcription factors whose functions can be influenced by melatonin in neurodegenerative disease models have also been highlighted. Finally, the therapeutic implications of melatonin's influences have also been discussed and the potential limitations to its applications have been highlighted.

Phanginin R Induces Cytoprotective Autophagy via JNK/c-Jun Signaling Pathway in Non-Small Cell Lung Cancer A549 Cells

BACKGROUND

Cassane-type diterpenoids are widely distributed in the medical plants of genus Caesalpinia. To date, plenty of cassane diterpenoids have been isolated from the genus Caesalpinia, and some of them were documented to exhibit multiple biological activities. However, the effects of these compounds on autophagy have never been reported.

OBJECTIVE

To investigate the effects and mechanisms of the cassane diterpenoids including Phanginin R (PR) on autophagy in Non-Small Cell Lung Cancer (NSCLC) A549 cells.

METHODS

Western blot analysis and immunofluorescence assay were performed to investigate the effects of the compounds on autophagic flux in A549 cells. The pathway inhibitor and siRNA interference were used to investigate the mechanism of PR. MTT assay was performed to detect cell viability.

RESULTS

PR treatment upregulated the expression of phosphatidylethanolamine-modified microtubule-associated protein Light-Chain 3 (LC3-II) in A549 cells. Immunofluorescence assay showed that PR treatment increased the production of red-fluorescent puncta in mRFP-GFP-LC3 plasmid-transfected cells, indicating PR promoted autophagic flux in A549 cells. PR treatment activated the c-Jun N-terminal Kinase (JNK) signaling pathway while it did not affect the classical Akt/mammalian Target of Rapamycin (mTOR) pathway. Pretreatment with the JNK inhibitor SP600125 or siRNA targeting JNK or c-Jun suppressed PR-induced autophagy. In addition, cotreatment with the autophagy inhibitor Chloroquine (CQ) or inhibition of the JNK/c-Jun signaling pathway increased PR-induced cytotoxicity.

CONCLUSION

PR induced cytoprotective autophagy in NSCLC A549 cells via the JNK/c-Jun signaling pathway, and autophagy inhibition could further improve the anti-cancer potential of PR.

Evidence Linking Protein Misfolding to Quality Control in Progressive Neurodegenerative Diseases

Several proteolytic systems including ubiquitin (Ub)-proteasome system (UPS), chaperonemediated autophagy (CMA), and macroautophagy are used by the mammalian cells to remove misfolded proteins (MPs). UPS mediates degradation of most of the MPs, where Ub-conjugated substrates are deubiquitinated, unfolded, and passed through the proteasome's narrow chamber, and eventually break into smaller peptides. It has been observed that the substrates that show a specific degradation signal, the KFERQ sequence motif, can be delivered to and go through CMA-mediated degradation in lysosomes. Macroautophagy can help in the degradation of substrates that are prone to aggregation and resistant to both the CMA and UPS. In the aforesaid case, cargoes are separated into autophagosomes before lysosomal hydrolase-mediated degradation. Even though the majority of the aggregated and MPs in the human proteome can be removed via cellular protein quality control (PQC), some mutant and native proteins tend to aggregate into β-sheet-rich oligomers that exhibit resistance to all identified proteolytic processes and can, therefore, grow into extracellular plaques or inclusion bodies. Indeed, the buildup of protease-resistant aggregated and MPs is a usual process underlying various protein misfolding disorders, including neurodegenerative diseases (NDs) for example Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and prion diseases. In this article, we have focused on the contribution of PQC in the degradation of pathogenic proteins in NDs.

Mini-review: Amyloid degradation toxicity hypothesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia affecting millions of people. Neuronal death in AD is initiated by oligomeric amyloid-β (Aβ) peptides. The amyloid channel hypothesis readily explains the primary molecular damage but does not address major observations associated with AD such as autophagy failure and decreased metabolism. The amyloid degradation toxicity hypothesis provides the interpretation as a sequence of molecular events. Aβ enters a cell by endocytosis, and the endocytic vesicle is merged with a lysosome. Lysosomal peptidases degrade the peptide. Fragments form membrane channels in lysosomal membranes that have a significant negative charge due to the presence of acidic phospholipids. Amyloid channels can transfer various ions (including protons) and even relatively large compounds, which explains lysosomal permeabilization. The neutralization of lysosomal content inactivates degradation enzymes, results in an accumulation of undigested amyloid, and stalls autophagy. Inadequate quality control of mitochondria is associated with an increased production of reactive oxygen species and decreased energy production. Also, the passage of lysosomal proteases through rare extremely large channels results in cell death. Proposed hypothesis identifies biochemical pathways involved in the initiation and progression of cellular damage induced by beta-amyloid and provides new potential pharmacological targets to treat Alzheimer's disease.

Targeting impaired nutrient sensing with repurposed therapeutics to prevent or treat age-related cognitive decline and dementia: A systematic review

BACKGROUND

Dementia is a debilitating syndrome that significantly impacts individuals over the age of 65 years. There are currently no disease-modifying treatments for dementia. Impairment of nutrient sensing pathways has been implicated in the pathogenesis of dementia, and may offer a novel treatment approach for dementia.

AIMS

This systematic review collates all available evidence for Food and Drug Administration (FDA)-approved therapeutics that modify nutrient sensing in the context of preventing cognitive decline or improving cognition in ageing, mild cognitive impairment (MCI), and dementia populations.

METHODS

PubMed, Embase and Web of Science databases were searched using key search terms focusing on available therapeutics such as 'metformin', 'GLP1', 'insulin' and the dementias including 'Alzheimer's disease' and 'Parkinson's disease'. Articles were screened using Covidence systematic review software (Veritas Health Innovation, Melbourne, Australia). The risk of bias was assessed using the Cochrane Risk of Bias tool v 2.0 for human studies and SYRCLE's risk of bias tool for animal studies.

RESULTS

Out of 2619 articles, 114 were included describing 31 different 'modulation of nutrient sensing pathway' therapeutics, 13 of which specifically were utilized in human interventional trials for normal ageing or dementia. Growth hormone secretagogues improved cognitive outcomes in human mild cognitive impairment, and potentially normal ageing populations. In animals, all investigated therapeutic classes exhibited some cognitive benefits in dementia models. While the risk of bias was relatively low in human studies, this risk in animal studies was largely unclear.

CONCLUSIONS

Modulation of nutrient sensing pathway therapeutics, particularly growth hormone secretagogues, have the potential to improve cognitive outcomes. Overall, there is a clear lack of translation from animal models to human populations.

Exposure to PM2.5 aggravates Parkinson's disease via inhibition of autophagy and mitophagy pathway

Extensive health studies had declared that exposure to particulate matter (PM) was closely associated with neurodegenerative diseases, i.e. Parkinson's disease (PD). Our aim was to clarify the potential molecular mechanism by which PM2.5 aggravated PD symptoms using in vitro and in vivo PD models. In this study, PC12 cells treated with rotenone (1 μM) and/or PM2.5 (50 μg/mL) for 4 days was used as the in vitro model. C57BL/6 J mice expored to PM2.5 (inhalation, 2.5 mg/kg) and rotenone (intraperitoneal injection, 30 mg/kg) for 28 days was used as the in vivo model. Rapamycin was used to promote the level of autophagy. The results showed that after exposure to PM2.5, the apoptosis of rotenone-treated PC12 cells were increased by increasing the ROS levels and decreasing the levels of mitochondrial membrane potential. In rotenone-treated PC12 cells, exposure to PM2.5 could decrease the expression levels of LC3II and Atg5, and increase the expression level of mTOR, suggesting that PM2.5 exposure inhibited autophagy. Furthermore, the mitophagy related genes, including PINK1 and Parkin, were decreased. At the same time, inhalation of PM2.5 could relieve the behavioral abnormalities of PD mouse induced by rotenone. The levels of inflammatory factors (TNF-α, IL-1β, and IL-6) were significantly increased. Inhalation of PM2.5 could induce the oxidative stress and apoptosis in the substantia nigra of PD mouse, as well as the key markers of autophagy and mitophagy were also changed, which was consistent with the cell model. Besides, rapamycin would relieve the damaging effect of PM2.5 by triggering autophagy and mitophagy in rotenone-induced PD models. These results indicated that exposure to PM2.5 aggravated the behavioral abnormalities of PD symptoms through increasing oxidative stress, decreasing autophagy and mitophagy, and inducing mitochondria-mediated neuronal apoptosis. These findings not only revealed the effects and mechanism of PM2.5 exposure on PD, but also provided fundamental data that can be exploited to develop environmental safety policies.

Defects in early secretory pathway transport machinery components and neurodevelopmental disorders

The early secretory pathway, provisionally comprising of vesicular traffic between the endoplasmic reticulum (ER) and the Golgi apparatus, occurs constitutively in mammalian cells. Critical for a constant supply of secretory and plasma membrane (PM) materials, the pathway is presumably essential for general cellular function and survival. Neurons exhibit a high intensity in membrane dynamics and protein/lipid trafficking, with differential and polarized trafficking towards the somatodendritic and axonal PM domains. Mutations in genes encoding early secretory pathway membrane trafficking machinery components are known to result in neurodevelopmental or neurological disorders with disease manifestation in early life. Here, such rare disorders associated with autosomal recessive mutations in coat proteins, membrane tethering complexes and membrane fusion machineries responsible for trafficking in the early secretory pathway are summarily discussed. These mutations affected genes encoding subunits of coat protein complex I and II, subunits of transport protein particle (TRAPP) complexes, members of the YIP1 domain family (YIPF) and a SNAP receptor (SNARE) family member. Why the ubiquitously present and constitutively acting early secretory pathway machinery components could specifically affect neurodevelopment is addressed, with the plausible underlying disease etiologies and neuropathological mechanisms resulting from these mutations explored.

Is targeting autophagy mechanism in cancer a good approach? The possible double-edge sword effect

Autophagy is a conserved cellular process required to maintain homeostasis. The hallmark of autophagy is the formation of a phagophore that engulfs cytosolic materials for degradation and recycling to synthesize essential components. Basal autophagy is constitutively active under normal conditions and it could be further induced by physiological stimuli such as hypoxia, nutrient starvation, endoplasmic reticulum stress,energy depletion, hormonal stimulation and pharmacological treatment. In cancer, autophagy is highly context-specific depending on the cell type, tumour microenvironment, disease stage and external stimuli. Recently, the emerging role of autophagy as a double-edged sword in cancer has gained much attention. On one hand, autophagy suppresses malignant transformation by limiting the production of reactive oxygen species and DNA damage during tumour development. Subsequently, autophagy evolved to support the survival of cancer cells and promotes the tumourigenicity of cancer stem cells at established sites. Hence, autophagy is an attractive target for cancer therapeutics and researchers have been exploiting the use of autophagy modulators as adjuvant therapy. In this review, we present a summary of autophagy mechanism and controlling pathways, with emphasis on the dual-role of autophagy (double-edged sword) in cancer. This is followed by an overview of the autophagy modulation for cancer treatment and is concluded by a discussion on the current perspectives and future outlook of autophagy exploitation for precision medicine.

Understanding the Potential Role of Sirtuin 2 on Aging: Consequences of SIRT2.3 Overexpression in Senescence

Sirtuin 2 (SIRT2) has been associated to aging and age-related pathologies. Specifically, an age-dependent accumulation of isoform 3 of SIRT2 in the CNS has been demonstrated; however, no study has addressed the behavioral or molecular consequences that this could have on aging. In the present study, we have designed an adeno-associated virus vector (AAV-CAG-Sirt2.3-eGFP) for the overexpression of SIRT2.3 in the hippocampus of 2 month-old SAMR1 and SAMP8 mice. Our results show that the specific overexpression of this isoform does not induce significant behavioral or molecular effects at short or long term in the control strain. Only a tendency towards a worsening in the performance in acquisition phase of the Morris Water Maze was found in SAMP8 mice, together with a significant increase in the pro-inflammatory cytokine Il-1β. These results suggest that the age-related increase of SIRT2.3 found in the brain is not responsible for induction or prevention of senescence. Nevertheless, in combination with other risk factors, it could contribute to the progression of age-related processes. Understanding the specific role of SIRT2 on aging and the underlying molecular mechanisms is essential to design new and more successful therapies for the treatment of age-related diseases.

Reduction of WDR81 impairs autophagic clearance of aggregated proteins and cell viability in neurodegenerative phenotypes

Neurodegenerative diseases are characterized by neuron loss and accumulation of undegraded protein aggregates. These phenotypes are partially due to defective protein degradation in neuronal cells. Autophagic clearance of aggregated proteins is critical to protein quality control, but the underlying mechanisms are still poorly understood. Here we report the essential role of WDR81 in autophagic clearance of protein aggregates in models of Huntington’s disease (HD), Parkinson’s disease (PD) and Alzheimer’s disease (AD). In hippocampus and cortex of patients with HD, PD and AD, protein level of endogenous WDR81 is decreased but autophagic receptor p62 accumulates significantly. WDR81 facilitates the recruitment of autophagic proteins onto Htt polyQ aggregates and promotes autophagic clearance of Htt polyQ subsequently. The BEACH and MFS domains of WDR81 are sufficient for its recruitment onto Htt polyQ aggregates, and its WD40 repeats are essential for WDR81 interaction with covalent bound ATG5-ATG12. Reduction of WDR81 impairs the viability of mouse primary neurons, while overexpression of WDR81 restores the viability of fibroblasts from HD patients. Notably, in Caenorhabditis elegans, deletion of the WDR81 homolog (SORF-2) causes accumulation of p62 bodies and exacerbates neuron loss induced by overexpressed α-synuclein. As expected, overexpression of SORF-2 or human WDR81 restores neuron viability in worms. These results demonstrate that WDR81 has crucial evolutionarily conserved roles in autophagic clearance of protein aggregates and maintenance of cell viability under pathological conditions, and its reduction provides mechanistic insights into the pathogenesis of HD, PD, AD and brain disorders related to WDR81 mutations.

In recent years, a group of clinical studies reported that mutations of WDR81 are related to pathogenesis of human brain disorders. However, the underlying mechanisms of pathogenesis are still unknown. In this study, WDR81 promotes the autophagic clearance of protein aggregates via facilitating the recruitment of autophagic proteins onto protein aggregates. The BEACH and MFS domains of WDR81 are sufficient for its recruitment onto Htt polyQ aggregates, and its WD40 repeats are essential for WDR81 interaction with covalent bound ATG5-ATG12. In hippocampus and cortex of patients with HD, PD and AD, protein level of WDR81 is decreased significantly. Reduction of WDR81 impairs the viability of mouse primary neurons, while overexpression of WDR81 restores the viability of fibroblasts from HD patients.

Mechanistic insights into the protective effects of chlorogenic acid against indomethacin-induced gastric ulcer in rats: Modulation of the cross talk between autophagy and apoptosis signaling

BACKGROUND

This study aimed to investigate the gastroprotective effect of chlorogenic acid (CGA) against Indomethacin (IND)-induced gastric ulcer (GU) in rats and its underlying mechanism, especially through autophagic and apoptotic pathways.

METHODS

Seventy-five rats were divided into five groups; control, IND (50 mg/kg, p.o.), CGA (100 mg/kg, p.o., 14 days), IND pretreated with CGA (50 mg/kg or 100 mg/kg, p.o., 14 days). The stomach tissues were examined to calculate the ulcer index and analyze markers of autophagy (beclin-1, LC3-II/LC3-I and p62), lysosomal function (cathepsin-D) and apoptosis (Bcl-2, Bax and caspase-3), along with expression of Akt/mTOR pathway using western blot or ELISA techniques. In addition, viability of gastric mucosal cells was detected by flowcytometry. Structural changes were assessed histologically, while autophagic and apoptotic changes of gastric mucosa were observed by transmission electron microscopy.

RESULTS

CGA exhibited a dose-dependent gastroprotective effect by reversing IND-induced accumulation of autophagic vacuoles, significant reduction in beclin-1, LC3-II/LC3-I, and p62 levels, and down-regulation of p-Akt/p-mTOR expression. CGA100 also restored normal autolysosomal function by modulation of cathepsin-D levels. Furthermore, pretreatment with CGA100 was significantly associated with an increase in antiapoptotic protein Bcl-2 along with a decrease in proapoptotic Bax and caspase-3 proteins in such a way that impairs IND-induced apoptosis. This was confirmed by CGA-induced significant decrease in annexin V⁺ cells.

CONCLUSIONS

The natural compound CGA offers a novel gastroprotective intervention against IND-induced GU through restoration of normal autophagic flux, impairment of apoptosis in a crosstalk mechanism mediated by Akt/mTOR pathway reactivation, and alleviation of IND-induced lysosomal dysfunction.

The effects of morphine, methadone, and fentanyl on mitochondria: A live cell imaging study

The important role of mitochondria in maintaining normal brain cell function has been demonstrated in several neurodegenerative diseases where mitochondrial dysfunction is a prominent feature. Accumulating evidence indicates that opioids may induce neuronal cell death and inhibit neurogenesis, two factors that are dependent on normal mitochondrial function. The aim of the present study was to examine the effects of morphine, methadone, and fentanyl on MitoTracker-stained mitochondria. Cells from the neuroblastoma/glioma hybrid cell-line NG108-15 were seeded on 96-well cell culture plates and treated with MitoTracker for 30 min prior to opioid treatment. Morphine, methadone, and fentanyl were added at various concentrations and images of mitochondria were acquired every 30 min for four hours using a high-content imaging device. The parameters total mitochondrial area, mitochondrial network, as well as the number and mean area of mitochondrial objects were analyzed using automated image analysis. Methadone and fentanyl, but not morphine, decreased the mitochondrial network, the number of mitochondrial objects, and increased the mean area of mitochondrial objects. Both methadone and fentanyl altered mitochondrial morphology with no effects seen from morphine treatment. These data suggest that methadone and fentanyl impact mitochondrial morphology negatively, which may be associated with neuronal cell death.

Hypothyroidism Induces Interleukin-1-Dependent Autophagy Mechanism as a Key Mediator of Hippocampal Neuronal Apoptosis and Cognitive Decline in Postnatal Rats

Thyroid hormone (TH) is essential for brain development, and hypothyroidism induces cognitive deficits in children and young adults. However, the participating mechanisms remain less explored. Here, we examined the molecular mechanism, hypothesizing the involvement of a deregulated autophagy and apoptosis pathway in hippocampal neurons that regulate cognitive functions. Therefore, we used a rat model of developmental hypothyroidism, generated through methimazole treatment from gestation until young adulthood. We detected that methimazole stimulated the autophagy mechanism, characterized by increased LC3B-II, Beclin-1, ATG7, and ATG5-12 conjugate and decreased p-mTOR/mTOR and p-ULK1/ULK1 autophagy regulators in the hippocampus of developing and young adult rats. This methimazole-induced hippocampal autophagy could be inhibited by thyroxine treatment. Subsequently, probing the upstream mediators of autophagy revealed an increased hippocampal neuroinflammation, marked by upregulated interleukin (IL)-1alpha and beta and activated microglial marker, Iba1, promoting neuronal IL-1 receptor-1 expression. Hence, IL-1R-antagonist (IL-1Ra), which reduced hippocampal neuronal IL-1R1, also inhibited the enhanced autophagy in hypothyroid rats. We then linked these events with hypothyroidism-induced apoptosis and loss of hippocampal neurons, where we observed that like thyroxine, IL-1Ra and autophagy inhibitor, 3-methyladenine, reduced the cleaved caspase-3 and TUNEL-stained apoptotic neurons and enhanced Nissl-stained neuronal count in methimazole-treated rats. We further related these molecular results with cognition through Y-maze and passive avoidance tests, demonstrating an IL-1Ra and 3-methyladenine-mediated improvement in learning-memory performances of the hypothyroid rats. Taken together, our study enlightens the critical role of neuroinflammation-dependent autophagy mechanism in TH-regulated hippocampal functions, disrupted in developmental hypothyroidism.

Activation of α7-nAChRs Promotes the Clearance of α-Synuclein and Protects Against Apoptotic Cell Death Induced by Exogenous α-Synuclein Fibrils

Misfolding and abnormal aggregation of α-synuclein (αSyn) have been shown to increase the risk of developing Parkinson's disease (PD). Finding some way to reduce the aggregation of αSyn is particularly important for the treatment of PD. The main route in prion-like αSyn spreading is the cholinergic innervated vagus nervous system and central cholinergic neurons. Since the degenerative changes and death of cholinergic neurons also run through the pathological process of PD, we hypothesize an involvement of the cholinergic system in αSyn aggregation. The α7 nicotinic acetylcholine receptors (α7-nAChRs) are one of the most abundant nAChRs in the mammalian brain. Using nicotine and a selective α7-nAChRs agonist PNU-282987, we found a protective effect of α7-nAChRs on the cell damage induced by αSyn-PFF (preformed fibrils) through inhibiting apoptotic cell death. We further discovered an additive effect of α7-nAChRs on the clearance of αSyn in normal and αSyn stably transduced SH-SY5Y cells. Moreover, using α7-nAChRs knockout mice, we noticed that α7-nAChRs deficiency increased the deposition of αSyn and aggravated the loss of dopaminergic neurons in a chronic MPTP mouse model of PD. Our findings for the first time indicated that α7-nAChRs activation exhibited a neuroprotective effect on αSyn pathology and aggregation by promoting the clearance of αSyn.

Mechanisms and Therapeutic Implications of GSK-3 in Treating Neurodegeneration

Neurodegenerative disorders are spreading worldwide and are one of the greatest threats to public health. There is currently no adequate therapy for these disorders, and therefore there is an urgent need to accelerate the discovery and development of effective treatments. Although neurodegenerative disorders are broad ranging and highly complex, they may share overlapping mechanisms, and thus potentially manifest common targets for therapeutic interventions. Glycogen synthase kinase-3 (GSK-3) is now acknowledged to be a central player in regulating mood behavior, cognitive functions, and neuron viability. Indeed, many targets controlled by GSK-3 are critically involved in progressing neuron deterioration and disease pathogenesis. In this review, we focus on three pathways that represent prominent mechanisms linking GSK-3 with neurodegenerative disorders: cytoskeleton organization, the mammalian target of rapamycin (mTOR)/autophagy axis, and mitochondria. We also consider the challenges and opportunities in the development of GSK-3 inhibitors for treating neurodegeneration.

Impact of Chaperone-Mediated Autophagy in Brain Aging: Neurodegenerative Diseases and Glioblastoma

Brain aging is characterized by a time-dependent decline of tissue integrity and function, and it is a major risk for neurodegenerative diseases and brain cancer. Chaperone-mediated autophagy (CMA) is a selective form of autophagy specialized in protein degradation, which is based on the individual translocation of a cargo protein through the lysosomal membrane. Regulation of processes such as proteostasis, cellular energetics, or immune system activity has been associated with CMA, indicating its pivotal role in tissue homeostasis. Since first studies associating Parkinson’s disease (PD) to CMA dysfunction, increasing evidence points out that CMA is altered in both physiological and pathological brain aging. In this review article, we summarize the current knowledge regarding the impact of CMA during aging in brain physiopathology, highlighting the role of CMA in neurodegenerative diseases and glioblastoma, the most common and aggressive brain tumor in adults.

Hijacking Endocytosis and Autophagy in Extracellular Vesicle Communication: Where the Inside Meets the Outside

Extracellular vesicles, phospholipid bilayer-membrane vesicles of cellular origin, are emerging as nanocarriers of biological information between cells. Extracellular vesicles transport virtually all biologically active macromolecules (e.g., nucleotides, lipids, and proteins), thus eliciting phenotypic changes in recipient cells. However, we only partially understand the cellular mechanisms driving the encounter of a soluble ligand transported in the lumen of extracellular vesicles with its cytosolic receptor: a step required to evoke a biologically relevant response. In this context, we review herein current evidence supporting the role of two well-described cellular transport pathways: the endocytic pathway as the main entry route for extracellular vesicles and the autophagic pathway driving lysosomal degradation of cytosolic proteins. The interplay between these pathways may result in the target engagement between an extracellular vesicle cargo protein and its cytosolic target within the acidic compartments of the cell. This mechanism of cell-to-cell communication may well own possible implications in the pathogenesis of neurodegenerative disorders.

Adult Neural Plasticity in Naked Mole-Rats: Implications of Fossoriality, Longevity and Sociality on the Brain's Capacity for Change

Naked mole-rats (Heterocephalus glaber) are small African rodents that have many unique behavioral and physiological adaptations well-suited for testing hypotheses about mammalian neural plasticity. In this chapter, we focus on three features of naked mole-rat biology and how they impact neural plasticity in this species: (1) their fossorial lifestyle, (2) their extreme longevity with a lack of demonstrable senescence, and (3) their unusual social structure. Critically, each of these features requires some degree of biological flexibility. First, their fossorial habitat situates them in an environment with characteristics to which the central nervous system is particularly sensitive (e.g., oxygen content, photoperiod, spatial complexity). Second, their long lifespan requires adaptations to combat senescence and declines in neural functioning. Finally, their extreme reproductive skew and sustained ability for release from reproductive suppression indicates remarkable neural sensitivity to the sociosexual environment that is distinct from chronological age. These three features of naked mole-rat life are not mutually exclusive, but they do each offer unique considerations for the possibilities, constraints, and mechanisms associated with adult neural plasticity.

TP53-induced glycolysis and apoptosis regulator (TIGAR) ameliorates lysosomal damage in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine-mediated mouse model of Parkinson's disease

The progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) correlates with rupture of lysosome in Parkinson's disease (PD). It has been found that TP53-induced glycolysis and apoptosis regulator (TIGAR) has been attributed to the regulation of metabolic pathways and neuroprotective effect. In the present study, we showed in a mouse model that 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) caused lysosomal damage and DA neurons loss in the SNpc. MPTP only induced SP1-mediated TIGAR upregulation in the early stage of neurotoxin-induced pathology, and this compensatory mechanism was not enough to maintain normal lysosomal function. MPTP significantly decreased the levels of NADPH and GSH, and the effects were ameliorated by the expression of exogenous TIGAR but execerbated by knockdown of TIAGR. TIGAR or NADPH alleviated oxidative stress, rescued lysosomal dysfunction and attenuated DA neurons degeneration. Overexpression of TIGAR or NADPH supplement inhibited MPP⁺-mediated reactive oxygen species (ROS), lysosomal membrane permeabilization (LMP) and autophagic flux impairment in PC12 cells. Together, these findings suggest that TIGAR reduces MPTP-mediated oxidative stress, lysosomal depletion and DA neuron damage.

Isovitexin modulates autophagy in Alzheimer's disease via miR-107 signalling

Background:

Alzheimer’s disease (AD) is an ultimately fatal, degenerative brain disease in the elderly people. In the current work, we assessed the defensive capability of isovitexin (IVX) through an intracerebroventricular injection of streptozotocin (STZ)-induced AD mouse model.

Methods:

Mice were separated into four cohorts: sham-operated control mice; STZ-intoxicated Alzheimer’s mice; IVX cohort, IVX + STZ; and Ant-107 cohort, antagomiR-107 + IVX/STZ as in the IVX cohort.

Results:

The outcomes indicated that IVX administration ameliorated spatial memory loss and blunted a cascade of neuro-noxious episodes – including increased amyloid-beta (Aβ) and degraded myelin basic protein burden, neuroinflammation (represented by elevated caspase-1, TNF-α and IL-6 levels) and autophagic dysfunction (represented by altered LC3-II, Atg7 and beclin-1 expressions) – via the inhibition of PI3K/Akt/mTOR signalling axis. We considered the question of whether the epigenetic role of microRNA-107 (miR-107) has any impact on these events, by using antagomiR-107.

Conclusion:

This probing underscored that miR-107 could be a pivotal regulatory button in the activation of molecular signals linked with the beneficial autophagic process and anti-inflammatory activities in relation to IVX treatment. Hence, this report exemplifies that IVX could guard against Aβ toxicity and serve as an effectual treatment for patients afflicted with AD.