Selective autophagy as a potential therapeutic target for neurodegenerative disorders

Autophagic mechanisms in longevity intervention: role of natural active compounds

The term 'autophagy' literally translates to 'self-eating' and alterations to autophagy have been identified as one of the several molecular changes that occur with aging in a variety of species. Autophagy and aging, have a complicated and multifaceted relationship that has recently come to light thanks to breakthroughs in our understanding of the various substrates of autophagy on tissue homoeostasis. Several studies have been conducted to reveal the relationship between autophagy and age-related diseases. The present review looks at a few new aspects of autophagy and speculates on how they might be connected to both aging and the onset and progression of disease. Additionally, we go over the most recent preclinical data supporting the use of autophagy modulators as age-related illnesses including cancer, cardiovascular and neurodegenerative diseases, and metabolic dysfunction. It is crucial to discover important targets in the autophagy pathway in order to create innovative therapies that effectively target autophagy. Natural products have pharmacological properties that can be therapeutically advantageous for the treatment of several diseases and they also serve as valuable sources of inspiration for the development of possible new small-molecule drugs. Indeed, recent scientific studies have shown that several natural products including alkaloids, terpenoids, steroids, and phenolics, have the ability to alter a number of important autophagic signalling pathways and exert therapeutic effects, thus, a wide range of potential targets in various stages of autophagy have been discovered. In this review, we summarised the naturally occurring active compounds that may control the autophagic signalling pathways.

Acupuncture inhibits autophagy and repairs synapses by activating the mTOR pathway in Parkinson's disease depression model rats

Acupuncture is a good treatment for depression in Parkinson's disease (DPD), so the possible mechanism of acupuncture in the treatment of DPD was explored in this study. Firstly, observing the behavioral changes of the DPD rat model, the regulation of monoamine neurotransmitters dopamine (DA) and 5-hydroxytryptamine (5-HT) in the midbrain, the change of α-synuclein (α-syn) in the striatum, the efficacy of acupuncture in the treatment of DPD was discussed. Secondly, autophagy inhibitors and activators were selected to judge the effect of acupuncture on autophagy in the DPD rat model. Finally, an mTOR inhibitor was used to observe the effect of acupuncture on the mTOR pathway in the DPD rat model. The results showed that acupuncture could improve the motor and depressive symptoms of DPD model rats, increase the content of DA and 5-HT, and decrease the content of ɑ-syn in the striatum. Acupuncture inhibited the expression of autophagy in the striatum of DPD model rats. At the same time, acupuncture upregulates p-mTOR expression, inhibits autophagy, and promotes synaptic protein expression. Therefore, we concluded that acupuncture might improve the behavior of DPD model rats by activating the mTOR pathway, inhibiting autophagy from removing α-syn and repairing synapses.

Digest it all: the lysosomal turnover of cytoplasmic aggregates

Aggrephagy describes the selective lysosomal transport and turnover of cytoplasmic protein aggregates by macro-autophagy. In this process, protein aggregates and conglomerates are polyubiquitinated and then sequestered by autophagosomes. Soluble selective autophagy receptors (SARs) are central to aggrephagy and physically bind to both ubiquitin and the autophagy machinery, thus linking the cargo to the forming autophagosomal membrane. Because the accumulation of protein aggregates is associated with cytotoxicity in several diseases, a better molecular understanding of aggrephagy might provide a conceptual framework to develop therapeutic strategies aimed at delaying the onset of these pathologies by preventing the buildup of potentially toxic aggregates. We review recent advances in our knowledge about the mechanism of aggrephagy.

Discovery of Small-Molecule Autophagy Inhibitors by Disrupting the Protein-Protein Interactions Involving Autophagy-Related 5

One possible strategy for modulating autophagy is to disrupt the critical protein-protein interactions (PPIs) formed during this process. Our attention is on the autophagy-related 12 (ATG12)-autophagy-related 5 (ATG5)-autophagy-related 16-like 1 (ATG16L1) heterotrimer complex, which is responsible for ATG8 translocation from ATG3 to phosphatidylethanolamine. In this work, we discovered a compound with an (E)-3-(2-furanylmethylene)-2-pyrrolidinone core moiety (T1742) that blocked the ATG5-ATG16L1 and ATG5-TECAIR interactions in the in vitro binding assay (IC₅₀ = 1-2 μM) and also exhibited autophagy inhibition in cellular assays. The possible binding mode of T1742 to ATG5 was predicted through molecular modeling, and a batch of derivatives sharing essentially the same core moiety were synthesized and tested. The outcomes of the in vitro binding assay and the flow cytometry assay of those newly synthesized compounds were generally consistent. This work has validated our central hypothesis that small-molecule inhibitors of the PPIs involving ATG5 can tune down autophagy effectively, and their pharmaceutical potential may be further explored.

Manganese-induced neuronal apoptosis: new insights into the role of endoplasmic reticulum stress in regulating autophagy-related proteins

Manganese (Mn) is an essential trace element that participates in various physiological and pathological processes. However, epidemiological observations indicate that overexposure to Mn is strongly associated with neurodegenerative disorders and has been recognized as a potential risk factor of neuronal apoptosis. Many mechanisms are involved in the pathogenesis of Mn-induced neuronal apoptosis, such as reactive oxygen species generation, neuroinflammation reactions, protein accumulation, endoplasmic reticulum stress (ER stress), and autophagy, all of which collectively accelerate the process of nerve cell damage. As sophisticated cellular processes for maintaining intracellular homeostasis, ER-mediated unfolded protein response and autophagy both play bilateral roles including cell protection and cell injury under pathophysiological conditions, which might interact with each other. Although emerging evidence suggests that ER stress is involved in regulating the compensatory activation of autophagy to promote cell survival, the inherent relationship between ER stress and autophagy on Mn-induced neurotoxicity remains obscure. Here, our review focuses on discussing the existing mechanisms and connections between ER stress, autophagy, and apoptosis, which provide a new perspective on Mn-induced neuronal apoptosis, and the pathogenesis of neurodegenerative diseases.

Pathogenic Aspects and Therapeutic Avenues of Autophagy in Parkinson's Disease

The progressive aging of the population and the fact that Parkinson's disease currently does not have any curative treatment turn out to be essential issues in the following years, where research has to play a critical role in developing therapy. Understanding this neurodegenerative disorder keeps advancing, proving the discovery of new pathogenesis-related genes through genome-wide association analysis. Furthermore, the understanding of its close link with the disruption of autophagy mechanisms in the last few years permits the elaboration of new animal models mimicking, through multiple pathways, different aspects of autophagic dysregulation, with the presence of pathological hallmarks, in brain regions affected by Parkinson's disease. The synergic advances in these fields permit the elaboration of multiple therapeutic strategies for restoring autophagy activity. This review discusses the features of Parkinson's disease, the autophagy mechanisms and their involvement in pathogenesis, and the current methods to correct this cellular pathway, from the development of animal models to the potentially curative treatments in the preclinical and clinical phase studies, which are the hope for patients who do not currently have any curative treatment.

Application of Novel Degraders Employing Autophagy for Expediting Medicinal Research

Targeted protein degradation (TPD) technology is based on a unique pharmacological mechanism that has profoundly revolutionized medicinal research by overcoming limitations associated with traditional small-molecule drugs. Autophagy, a mechanism for intracellular waste disposal and recovery, is an important biological process in medicinal research. Recently, studies have demonstrated that several emerging autophagic degraders can treat human diseases. Herein we summarize the progress in medicinal research on autophagic degraders, including autophagosome-tethering compounds (ATTEC), autophagy-targeting chimeras (AUTAC), and AUTOphagy-TArgeting chimeras (AUTOTAC), for treating human diseases. These autophagic degraders exhibit excellent potential for treating neurodegenerative diseases. Our research on autophagic degraders provides a new avenue for medicinal research on TPD via autophagy.

Silica Nanoparticles Trigger Chaperone HSPB8-Assisted Selective Autophagy via TFEB Activation in Hepatocytes

Silica nanoparticles (SiNPs) are one of the most common inorganic nanomaterials. Autophagy is the predominant biological response to nanoparticles and transcription factor EB (TFEB) is a master regulator of the autophagy-lysosome pathway. Previous studies show that SiNPs induce autophagosome accumulation, yet the precise underlying mechanisms remain uncertain. The present study investigates the role of TFEB during SiNP-induced autophagy. SiNP-induced TFEB nuclear translocation is verified using immunofluorescence and western blot assay. The regulation of TFEB is proved to be via EIF2AK3 pathway. A TFEB knockout (KO) cell line is constructed to validate the TFEB involvement in SiNP-induced autophagy. The transcriptomes of wild-type and TFEB KO cells are compared using RNA-sequencing to identify genes of the TFEB-mediated autophagy and lysosome pathways affected by SiNPs. Based on these data and the Human Autophagy Database, four candidate autophagic genes are identified, including HSPB8, ATG4D, CTSB and CTSD. Specifically, that the chaperone HSPB8 is upregulated through SiNP-mediated TFEB activation and forms a chaperone-assisted selective autophagy (CASA) complex with BAG3 and HSC70, triggering HSPB8-assisted selective autophagy, is found. Thus, this study characterizes a novel mechanism underlying SiNP-induced autophagy that helps pave the way for further research on the toxicity and risk assessment of SiNPs.

Neuroprotective effect of astragalin via activating PI3K/Akt-mTOR-mediated autophagy on APP/PS1 mice

As a small molecule flavonoid, astragalin (AST) has anti-inflammatory, anti-cancer, and anti-oxidation effects. However, the impact and molecular mechanism of AST in Alzheimer's disease (AD) are still not clear. This study aims to investigate the neuroprotective effect and mechanism of AST on APP/PS1 mice and Aβ25-35-injured HT22 cells. In this study, we found that AST ameliorated cognitive dysfunction, reduced hippocampal neuronal damage and loss, and Aβ pathology in APP/PS1 mice. Subsequently, AST activated autophagy and up-regulated the levels of autophagic flux-related protein in APP/PS1 mice and Aβ25-35-induced injury in HT22 cells. Interestingly, AST down-regulated the phosphorylation level of PI3K/Akt-mTOR pathway-related proteins, which was reversed by autophagy inhibitors 3-Methyladenine (3-MA) or Bafilomycin A1 (Baf A1). At the same time, consistent with the impacts of Akt inhibitor MK2206 and mTOR inhibitor rapamycin, inhibited levels of autophagy in Aβ25-35-injured HT22 cells were activated by the administration of AST. Taken together, these results suggested that AST played key neuroprotective roles on AD via stimulating PI3K/Akt-mTOR pathway-mediated autophagy and autophagic flux. This study revealed a new mechanism of autophagy regulation behind the neuroprotection impact of AST for AD treatment.

Oligodendrocyte Progenitors Display Enhanced Proliferation and Autophagy after Space Flight

Intracranial hypertension (ICP) and visual impairment intracranial pressure (VIIP) are some of the consequences of long-term space missions. Here we examined the behavior of oligodendrocyte progenitors (OLPs) after space flight using time-lapse microscopy. We show that most OLPs divided more than ground control (GC) counterparts did. Nonetheless, a subpopulation of OLPs flown to space presented a significant increase in autophagic cell death. Examination of the proteomic profile of the secretome of space flown OLPs (SPC-OLPs) revealed that the stress protein heat shock protein-90 beta "HSP-90β" was the 5^th most enriched (6.8 times) and the secreted protein acidic and rich in cysteine "SPARC" was the 7^th most enriched (5.2 times), with respect to ground control cells. SPARC induces endoplasmic reticulum stress, which leads to autophagy. Given the roles and importance of these two proteins in mammalian cells' metabolism, their upregulation may hold the key to modulating cell proliferation and autophagy, in order to mitigate ICP and VIIP during and after space missions.

Recent advances of tanshinone in regulating autophagy for medicinal research

Initially described as an ancient and highly conserved catabolic biofunction, autophagy plays a significant role in disease pathogenesis and progression. As the bioactive ingredient of Salvia miltiorrhiza, tanshinone has recently shown profound effects in alleviating and treating various diseases by regulating autophagy. However, compared to the remarkable achievements in the known pharmacological effects of this traditional Chinese medicine, there is a lack of a concise and comprehensive review deciphering the mechanism by which tanshinone regulates autophagy for medicinal research. In this context, we concisely review the advances of tanshinone in regulating autophagy for medicinal research, including human cancer, the nervous system, and cardiovascular diseases. The pharmacological effects of tanshinone targeting autophagy involve the regulation of autophagy-related proteins, such as Beclin-1, LC3-II, P62, ULK1, Bax, ATG3, ATG5, ATG7, ATG9, and ATG12; the regulation of the PI3K/Akt/mTOR, MEK/ERK/mTOR, Beclin-1-related, and AMPK-related signaling pathways; the accumulation of reactive oxygen species (ROS); and the activation of AMPK. Notably, we found that tanshinone played a dual role in human cancers in an autophagic manner, which may provide a new avenue for potential clinical application. In brief, these findings on autophagic tanshinone and its derivatives provide a new clue for expediting medicinal research related to tanshinone compounds and autophagy.

Age-related changes in tau and autophagy in human brain in the absence of neurodegeneration

Tau becomes abnormally hyper-phosphorylated and aggregated in tauopathies like Alzheimers disease (AD). As age is the greatest risk factor for developing AD, it is important to understand how tau protein itself, and the pathways implicated in its turnover, change during aging. We investigated age-related changes in total and phosphorylated tau in brain samples from two cohorts of cognitively normal individuals spanning 19-74 years, without overt neurodegeneration. One cohort utilised resected tissue and the other used post-mortem tissue. Total soluble tau levels declined with age in both cohorts. Phosphorylated tau was undetectable in the post-mortem tissue but was clearly evident in the resected tissue and did not undergo significant age-related change. To ascertain if the decline in soluble tau was correlated with age-related changes in autophagy, three markers of autophagy were tested but only two appeared to increase with age and the third was unchanged. This implies that in individuals who do not develop neurodegeneration, there is an age-related reduction in soluble tau which could potentially be due to age-related changes in autophagy. Thus, to explore how an age-related increase in autophagy might influence tau-mediated dysfunctions in vivo, autophagy was enhanced in a Drosophila model and all age-related tau phenotypes were significantly ameliorated. These data shed light on age-related physiological changes in proteins implicated in AD and highlights the need to study pathways that may be responsible for these changes. It also demonstrates the therapeutic potential of interventions that upregulate turnover of aggregate-prone proteins during aging.

Lysosomal Pathogenesis of Parkinson's Disease: Insights From LRRK2 and GBA1 Rodent Models

The discovery of mutations in LRRK2 and GBA1 that are linked to Parkinson's disease provided further evidence that autophagy and lysosome pathways are likely implicated in the pathogenic process. Their protein products are important regulators of lysosome function. LRRK2 has kinase-dependent effects on lysosome activity, autophagic efficacy and lysosomal Ca2+ signaling. Glucocerebrosidase (encoded by GBA1) is a hydrolytic enzyme contained in the lysosomes and contributes to the degradation of alpha-synuclein. PD-related mutations in LRRK2 and GBA1 slow the degradation of alpha-synuclein, thus directly implicating the dysfunction of the process in the neuropathology of Parkinson's disease. The development of genetic rodent models of LRRK2 and GBA1 provided hopes of obtaining reliable preclinical models in which to study pathogenic processes and perform drug validation studies. Here, I will review the extensive characterization of these models, their impact on understanding lysosome alterations in the course of Parkinson's disease and what novel insights have been obtained. In addition, I will discuss how these models fare with respect to the features of a "gold standard" animal models and what could be attempted in future studies to exploit LRRK2 and GBA1 rodent models in the fight against Parkinson's disease.

The dual role of autophagy in periprosthetic osteolysis

Periprosthetic osteolysis (PPO) induced by wear particles is an important cause of aseptic loosening after artificial joint replacement, among which the imbalance of osteogenesis and osteoclastic processes occupies a central position. The cells involved in PPO mainly include osteoclasts (macrophages), osteoblasts, osteocytes, and fibroblasts. RANKL/RANK/OGP axis is a typical way for osteolysis. Autophagy, a mode of regulatory cell death and maintenance of cellular homeostasis, has a dual role in PPO. Although autophagy is activated in various periprosthetic cells and regulates the release of inflammatory cytokines, osteoclast activation, and osteoblast differentiation, its beneficial or detrimental role remains controversy. In particular, differences in the temporal control and intensity of autophagy may have different effects. This article focuses on the role of autophagy in PPO, and expects the regulation of autophagy to become a powerful target for clinical treatment of PPO.

In vitro methods in autophagy research: Applications in neurodegenerative diseases and mood disorders

Background

Autophagy is a conserved physiological intracellular mechanism responsible for the degradation and recycling of cytoplasmic constituents (e.g., damaged organelles, and protein aggregates) to maintain cell homeostasis. Aberrant autophagy has been observed in neurodegenerative diseases, including Alzheimer's Disease (AD), Parkinson's Disease (PD), Amyotrophic Lateral Sclerosis (ALS), and Huntington's Disease (HD), and recently aberrant autophagy has been associated with mood disorders, such as depression. Several in vitro methods have been developed to study the complex and tightly regulated mechanisms of autophagy. In vitro methods applied to autophagy research are used to identify molecular key players involved in dysfunctional autophagy and to screen autophagy regulators with therapeutic applications in neurological diseases and mood disorders. Therefore, the aims of this narrative review are (1) to compile information on the cell-based methods used in autophagy research, (2) to discuss their application, and (3) to create a catalog of traditional and novel in vitro methods applied in neurodegenerative diseases and depression.

Methods

Pubmed and Google Scholar were used to retrieve relevant in vitro studies on autophagy mechanisms in neurological diseases and depression using a combination of search terms per mechanism and disease (e.g., "macroautophagy" and "Alzheimer's disease"). A total of 37 studies were included (14 in PD, 8 in AD, 5 in ALS, 5 in %, and 5 in depression).

Results

A repertoire of traditional and novel approaches and techniques was compiled and discussed. The methods used in autophagy research focused on the mechanisms of macroautophagy, microautophagy, and chaperone-mediated autophagy. The in vitro tools presented in this review can be applied to explore pathophysiological mechanisms at a molecular level and to screen for potential therapeutic agents and their mechanism of action, which can be of great importance to understanding disease biology and potential therapeutic options in the context of neurodegenerative disorders and depression.

Conclusion

This is the first review to compile, discuss, and provide a catalog of traditional and novel in vitro models applied to neurodegenerative disorders and depression.

The participation of non-canonical autophagic proteins in the autophagy process and their potential as therapeutic targets

INTRODUCTION

Autophagy is a conserved catabolic process that helps recycle intracellular components to maintain homeostasis. The completion of autophagy requires the synergistic effect of multiple canonical autophagic proteins. Defects in autophagy machinery have been reported to promote diseases, rendering autophagy a bone fide health-modifying agent. However, the clinical implication of canonical pan-autophagic activators or inhibitors has often led to undesirable side effects, making it urgent to find a safer autophagy-related therapeutic target. The discovery of non-canonical autophagic proteins has been found to specifically affect the development of diseases without causing a universal impact on autophagy and has shed light on finding a safer way to utilize autophagy in the therapeutic context.

AREAS COVERED

This review summarizes recently discovered non-canonical autophagic proteins, how these proteins influence autophagy, and their potential therapeutic role in the disease due to their interaction with autophagy.

EXPERT OPINION

Several therapies have been studied thus far and continued research is needed to identify the potential that non-canonical autophagic proteins have for treating certain diseases. In the meantime, continue to uncover new non-canonical autophagic proteins and examine which are likely to have therapeutic implications.

KEAP1-NRF2 protein-protein interaction inhibitors: Design, pharmacological properties and therapeutic potential

The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is considered the master regulator of the phase II antioxidant response. It controls a plethora of cytoprotective genes related to oxidative stress, inflammation, and protein homeostasis, among other processes. Activation of these pathways has been described in numerous pathologies including cancer, cardiovascular, respiratory, renal, digestive, metabolic, autoimmune, and neurodegenerative diseases. Considering the increasing interest of discovering novel NRF2 activators due to its clinical application, initial efforts were devoted to the development of electrophilic drugs able to induce NRF2 nuclear accumulation by targeting its natural repressor protein Kelch-like ECH-associated protein 1 (KEAP1) through covalent modifications on cysteine residues. However, off-target effects of these drugs prompted the development of an innovative strategy, the search of KEAP1-NRF2 protein-protein interaction (PPI) inhibitors. These innovative activators are proposed to target NRF2 in a more selective way, leading to potentially improved drugs with the application for a variety of diseases that are currently under investigation. In this review, we summarize known KEAP1-NRF2 PPI inhibitors to date and the bases of their design highlighting the most important features of their respective interactions. We also discuss the preclinical pharmacological properties described for the most promising compounds.

S1PR2 Regulates Autophagy Through the AKT/mTOR Pathway to Promote Pathological Damage in Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a fatal and debilitating neurodegenerative disease. Sphingosine-1-phosphate receptor 2 (S1PR2), one of the receptors of S1P, is a key regulatory factor for various diseases.

OBJECTIVE

This study aimed to explore the role and possible mechanism of S1PR2 in AD.

METHODS

S1PR2 expression in the AD mice was detected, and after intervening S1PR2 expression with sh-S1PR2 in AD mice, the behavioral changes, pathological lesions of the hippocampus, autophagy level, and AKT/mTOR pathway activation were analyzed. Furthermore, SH-SY5Y cells were induced by Aβ25-35 to construct an AD cell model, and the effects of sh-S1PR2 on proliferation, apoptosis, autophagy, and AKT/mTOR pathway of AD cells were investigated. In addition, the effects of pathway inhibitor rapamycin on model cells were further analyzed.

RESULTS

The expression of S1PR2 was significantly increased in AD mice, the sh-S1PR2 significantly improved behavioral dysfunction, alleviated pathological injury of the hippocampus, increased the number of neurons, and inhibited Aβ production and p-tau expression, showing a positive effect on the AD pathology. In addition, silencing of S1PR2 expression significantly promoted the autophagy level and inhibited the activation of the AKT/mTOR pathway in AD model mice. In vitro experiments further confirmed that sh-S1PR2 promoted cell proliferation, inhibited apoptosis, relieved cytopathology, promoted autophagy, and inhibited the activation of the AKT/mTOR pathway in the cell model. The use of rapamycin further confirmed the role of AKT/mTOR pathway-mediated autophagy in the regulation of AD by S1PR2.

CONCLUSION

S1PR2 promoted AD pathogenesis by inhibiting autophagy through the activation of AKT/mTOR pathway.

From Association to Intervention: The Alzheimer's Disease-Associated Processes and Targets (ADAPT) Ontology

BACKGROUND

Many putative causes and risk factors have been associated with outcomes in Alzheimer's disease (AD) but all attempts at disease-modifying treatment have failed to be clinically significant. Efforts to address this "association-intervention" mismatch have tended to focus on the novel design of interventions.

OBJECTIVE

Here, we instead deal with the notion of association in depth. We introduce the concept of disease-associated process (DAP) as a flexible concept that can unite different areas of study of AD from genetics to epidemiology to identify disease-modifying targets.

METHODS

We sort DAPs using three properties: specificity for AD, frequency in patients, and pathogenic intensity for dementia before using a literature review to apply these properties in three ways. Firstly, we describe and visualize known DAPs. Secondly, we exemplify qualitative specificity analysis with the DAPs of tau protein pathology and autophagy to reveal their differential implication in AD. Finally, we use DAP properties to define the terms "risk factor," "cause," and "biomarker."

RESULTS

We show how DAPs fit into our collaborative disease ontology, the Alzheimer's Disease-Associated Processes and Targets (ADAPT) ontology. We argue that our theoretical system can serve as a democratic research forum, offering a more biologically adequate view of dementia than reductionist models.

CONCLUSION

The ADAPT ontology is a tool that could help to ground debates around priority setting using objective criteria for the identifying of targets in AD. Further efforts are needed to address issues of how biomedical research into AD is prioritized and funded.

The HERC proteins and the nervous system

The HERC protein family is one of three subfamilies of Homologous to E6AP C-terminus (HECT) E3 ubiquitin ligases. Six HERC genes have been described in humans, two of which encode Large HERC proteins -HERC1 and HERC2- with molecular weights above 520 kDa that are constitutively expressed in the brain. There is a large body of evidence that mutations in these Large HERC genes produce clinical syndromes in which key neurodevelopmental events are altered, resulting in intellectual disability and other neurological disorders like epileptic seizures, dementia and/or signs of autism. In line with these consequences in humans, two mice carrying mutations in the Large HERC genes have been studied quite intensely: the tambaleante mutant for Herc1 and the Herc2^+/530 mutant for Herc2. In both these mutant mice there are clear signs that autophagy is dysregulated, eliciting cerebellar Purkinje cell death and impairing motor control. The tambaleante mouse was the first of these mice to appear and is the best studied, in which the Herc1 mutation elicits: (i) delayed neural transmission in the peripheral nervous system; (ii) impaired learning, memory and motor control; and (iii) altered presynaptic membrane dynamics. In this review, we discuss the information currently available on HERC proteins in the nervous system and their biological activity, the dysregulation of which could explain certain neurodevelopmental syndromes and/or neurodegenerative diseases.

miR-17-92 cluster in osteoarthritis: Regulatory roles and clinical utility

Osteoarthritis (OA) is the most prevalent articular disease, especially in aged population. Caused by multi-factors (e.g., trauma, inflammation, and overloading), OA leads to pain and disability in affected joints, which decreases patients' quality of life and increases social burden. In pathophysiology, OA is mainly characterized by cartilage hypertrophy or defect, subchondral bone sclerosis, and synovitis. The homeostasis of cell-cell communication is disturbed as well in such pro-inflammatory microenvironment, which provides clues for the diagnosis and treatment of OA. MicoRNAs (miRNAs) are endogenous non-coding RNAs that regulate various processes via post-transcriptional mechanisms. The miR-17-92 cluster is an miRNA polycistron encoded by the host gene called MIR17HG. Mature miRNAs generated from MIR17HG participate in biological activities such as oncogenesis, neurogenesis, and modulation of the immune system. Accumulating evidence also indicates that the expression level of miRNAs in the miR-17-92 cluster is tightly related to the pathological processes of OA, such as chondrocyte apoptosis, extracellular matrix degradation, bone remodeling, and synovitis. In this review, we aim to summarize the roles of the miR-17-92 cluster in the underlying molecular mechanism during the development and progression of OA and shed light on the new avenue of the diagnosis and treatment of OA.

Role of Proteostasis Regulation in the Turnover of Stress Granules

RNA-binding proteins (RBPs) and RNAs can form dynamic, liquid droplet-like cytoplasmic condensates, known as stress granules (SGs), in response to a variety of cellular stresses. This process is driven by liquid-liquid phase separation, mediated by multivalent interactions between RBPs and RNAs. The formation of SGs allows a temporary suspension of certain cellular activities such as translation of unnecessary proteins. Meanwhile, non-translating mRNAs may also be sequestered and stalled. Upon stress removal, SGs are disassembled to resume the suspended biological processes and restore the normal cell functions. Prolonged stress and disease-causal mutations in SG-associated RBPs can cause the formation of aberrant SGs and/or impair SG disassembly, consequently raising the risk of pathological protein aggregation. The machinery maintaining protein homeostasis (proteostasis) includes molecular chaperones and co-chaperones, the ubiquitin-proteasome system, autophagy, and other components, and participates in the regulation of SG metabolism. Recently, proteostasis has been identified as a major regulator of SG turnover. Here, we summarize new findings on the specific functions of the proteostasis machinery in regulating SG disassembly and clearance, discuss the pathological and clinical implications of SG turnover in neurodegenerative disorders, and point to the unresolved issues that warrant future exploration.

The Interplay between Ghrelin and Microglia in Neuroinflammation: Implications for Obesity and Neurodegenerative Diseases

Numerous studies have shown that microglia are capable of producing a wide range of chemokines to promote inflammatory processes within the central nervous system (CNS). These cells share many phenotypical and functional characteristics with macrophages, suggesting that microglia participate in innate immune responses in the brain. Neuroinflammation induces neurometabolic alterations and increases in energy consumption. Microglia may constitute an important therapeutic target in neuroinflammation. Recent research has attempted to clarify the role of Ghre signaling in microglia on the regulation of energy balance, obesity, neuroinflammation and the occurrence of neurodegenerative diseases. These studies strongly suggest that Ghre modulates microglia activity and thus affects the pathophysiology of neurodegenerative diseases. This review aims to summarize what is known from the current literature on the way in which Ghre modulates microglial activity during neuroinflammation and their impact on neurometabolic alterations in neurodegenerative diseases. Understanding the role of Ghre in microglial activation/inhibition regulation could provide promising strategies for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

The crosstalk among autophagy, apoptosis, and pyroptosis in cardiovascular disease

In recent years, the mechanism of cell death has become a hotspot in research on the pathogenesis and treatment of cardiovascular disease (CVD). Different cell death modes, including autophagy, apoptosis, and pyroptosis, are mosaic with each other and collaboratively regulate the process of CVD. This review summarizes the interaction and crosstalk of key pathways or proteins which play a critical role in the entire process of CVD and explores the specific mechanisms. Furthermore, this paper assesses the interrelationships among these three cell deaths and reviews how they regulate the pathogenesis of CVD. By understanding how these three cell death modes go together we can learn about the pathogenesis of CVD, which will enable us to identify new targets for preventing, controlling, and treating CVD. It will not only reduce mortality but also improve the quality of life.

Lamp1 Deficiency Enhances Sensitivity to α-Synuclein and Oxidative Stress in Drosophila Models of Parkinson Disease

Parkinson disease (PD) is a common neurodegenerative condition affecting people predominantly at old age that is characterized by a progressive loss of midbrain dopaminergic neurons and by the accumulation of α-synuclein-containing intraneuronal inclusions known as Lewy bodies. Defects in cellular degradation processes such as the autophagy-lysosomal pathway are suspected to be involved in PD progression. The mammalian Lysosomal-associated membrane proteins LAMP1 and LAMP2 are transmembrane glycoproteins localized in lysosomes and late endosomes that are involved in autophagosome/lysosome maturation and function. Here, we show that the lack of Drosophila Lamp1, the homolog of LAMP1 and LAMP2, severely increased fly susceptibility to paraquat, a pro-oxidant compound known as a potential PD inducer in humans. Moreover, the loss of Lamp1 also exacerbated the progressive locomotor defects induced by the expression of PD-associated mutant α-synuclein A30P (α-synA30P) in dopaminergic neurons. Remarkably, the ubiquitous re-expression of Lamp1 in a mutant context fully suppressed all these defects and conferred significant resistance towards both PD factors above that of wild-type flies. Immunostaining analysis showed that the brain levels of α-synA30P were unexpectedly decreased in young adult Lamp1-deficient flies expressing this protein in comparison to non-mutant controls. This suggests that Lamp1 could neutralize α-synuclein toxicity by promoting the formation of non-pathogenic aggregates in neurons. Overall, our findings reveal a novel role for Drosophila Lamp1 in protecting against oxidative stress and α-synuclein neurotoxicity in PD models, thus furthering our understanding of the function of its mammalian homologs.

Bromo-protopine, a novel protopine derivative, alleviates tau pathology by activating chaperone-mediated autophagy for Alzheimer’s disease therapy

Emerging evidence from Alzheimer’s disease (AD) patients suggests that reducing tau pathology can restore cognitive and memory loss. To reduce tau pathology, it is critical to find brain-permeable tau-degrading small molecules that are safe and effective. HDAC6 inhibition has long been considered a safe and effective therapy for tau pathology. Recently, we identified protopine as a dibenzazecine alkaloid with anti-HDAC6 and anti-AD activities. In this study, we synthesized and tested novel protopine derivatives for their pharmacological action against AD. Among them, bromo-protopine (PRO-Br) demonstrated a two-fold increase in anti-HDAC6 activity and improved anti-tau activities compared to the parent compound in both in vitro and in vivo AD models. Furthermore, molecular docking results showed that PRO-Br binds to HDAC6, with a ∆G value of −8.4 kcal/mol and an IC₅₀ value of 1.51 µM. In neuronal cell lines, PRO-Br reduced pathological tau by inducing chaperone-mediated autophagy (CMA). In 3xTg-AD and P301S tau mice models, PRO-Br specifically decreased the pathogenic hyperphosphorylated tau clumps and led to the restoration of memory functions. In addition, PRO-Br treatment promoted the clearance of pathogenic tau by enhancing the expression of molecular chaperones (HSC70) and lysosomal markers (LAMP2A) via CMA in AD models. Our data strongly suggest that administration of the brain-permeable protopine derivative PRO-Br, could be a viable anti-tau therapeutic strategy for AD.

Advances in Treatment of Frontotemporal Dementia

In this review, the authors explored the clinical features of frontotemporal dementia (FTD), focusing on treatment. The clinical features of FTD are unique, with disinhibition, apathy, loss of empathy, and compulsions common. Motor changes occur later in the illness. The two major proteins that aggregate in the brain with FTD are tau and TDP-43, whereas a minority of patients aggregate FET proteins, primarily the FUS protein. Genetic causes include mutations in MAPT, GRN, and C9orf72. There are no medications that can slow FTD progression, although new therapies for the genetic forms of FTD are moving into clinical trials. Once a diagnosis is made, therapies should begin, focusing on the family and the patient. In the setting of FTD, families experience a severe burden associated with caregiving, and the clinician should focus on alleviating this burden. Advice around legal and financial issues is usually helpful. Careful consideration of environmental changes to cope with abnormal behaviors is essential. Most compounds that have been used to treat dementia of the Alzheimer's disease type are not effective in FTD, and cholinesterase inhibitors and memantine should be avoided. Although the data are scant, there is some evidence that antidepressants and second-generation antipsychotics may help individual patients.

Autophagy regulates neuronal excitability by controlling cAMP/protein kinase A signaling at the synapse

Autophagy provides nutrients during starvation and eliminates detrimental cellular components. However, accumulating evidence indicates that autophagy is not merely a housekeeping process. Here, by combining mouse models of neuron-specific ATG5 deficiency in either excitatory or inhibitory neurons with quantitative proteomics, high-content microscopy, and live-imaging approaches, we show that autophagy protein ATG5 functions in neurons to regulate cAMP-dependent protein kinase A (PKA)-mediated phosphorylation of a synapse-confined proteome. This function of ATG5 is independent of bulk turnover of synaptic proteins and requires the targeting of PKA inhibitory R1 subunits to autophagosomes. Neuronal loss of ATG5 causes synaptic accumulation of PKA-R1, which sequesters the PKA catalytic subunit and diminishes cAMP/PKA-dependent phosphorylation of postsynaptic cytoskeletal proteins that mediate AMPAR trafficking. Furthermore, ATG5 deletion in glutamatergic neurons augments AMPAR-dependent excitatory neurotransmission and causes the appearance of spontaneous recurrent seizures in mice. Our findings identify a novel role of autophagy in regulating PKA signaling at glutamatergic synapses and suggest the PKA as a target for restoration of synaptic function in neurodegenerative conditions with autophagy dysfunction.

Lamp1 mediates lipid transport, but is dispensable for autophagy in Drosophila

The endolysosomal system not only is an integral part of the cellular catabolic machinery that processes and recycles nutrients for synthesis of biomaterials, but also acts as signaling hub to sense and coordinate the energy state of cells with growth and differentiation. Lysosomal dysfunction adversely influences vesicular transport-dependent macromolecular degradation and thus causes serious problems for human health. In mammalian cells, loss of the lysosome associated membrane proteins LAMP1 and LAMP2 strongly affects autophagy and cholesterol trafficking. Here we show that the previously uncharacterized Drosophila Lamp1 is a bona fide ortholog of vertebrate LAMP1 and LAMP2. Surprisingly and in contrast to lamp1 lamp2 double-mutant mice, Drosophila Lamp1 is not required for viability or autophagy, suggesting that fly and vertebrate LAMP proteins acquired distinct functions, or that autophagy defects in lamp1 lamp2 mutants may have indirect causes. However, Lamp1 deficiency results in an increase in the number of acidic organelles in flies. Furthermore, we find that Lamp1 mutant larvae have defects in lipid metabolism as they show elevated levels of sterols and diacylglycerols (DAGs). Because DAGs are the main lipid species used for transport through the hemolymph (blood) in insects, our results indicate broader functions of Lamp1 in lipid transport. Our findings make Drosophila an ideal model to study the role of LAMP proteins in lipid assimilation without the confounding effects of their storage and without interfering with autophagic processes.Abbreviations: aa: amino acid; AL: autolysosome; AP: autophagosome; APGL: autophagolysosome; AV: autophagic vacuole (i.e. AP and APGL/AL); AVi: early/initial autophagic vacuoles; AVd: late/degradative autophagic vacuoles; Atg: autophagy-related; CMA: chaperone-mediated autophagy; Cnx99A: Calnexin 99A; DAG: diacylglycerol; eMI: endosomal microautophagy; ESCRT: endosomal sorting complexes required for transport; FB: fat body; HDL: high-density lipoprotein; Hrs: Hepatocyte growth factor regulated tyrosine kinase substrate; LAMP: lysosomal associated membrane protein; LD: lipid droplet; LDL: low-density lipoprotein; Lpp: lipophorin; LTP: Lipid transfer particle; LTR: LysoTracker Red; MA: macroautophagy; MCC: Manders colocalization coefficient; MEF: mouse embryonic fibroblast MTORC: mechanistic target of rapamycin kinase complex; PV: parasitophorous vacuole; SNARE: soluble N-ethylmaleimide sensitive factor attachment protein receptor; Snap: Synaptosomal-associated protein; st: starved; TAG: triacylglycerol; TEM: transmission electron microscopy; TFEB/Mitf: transcription factor EB; TM: transmembrane domain; tub: tubulin; UTR: untranslated region.

Single-cell RNA sequencing reveals the role of immune-related autophagy in spinal cord injury in rats

Spinal cord injury refers to damage to the spinal cord due to trauma, disease, or degeneration; and the number of new cases is increasing yearly. Significant cellular changes are known to occur in the area of spinal cord injury. However, changes in cellular composition, trajectory of cell development, and intercellular communication in the injured area remain unclear. Here, we used single-cell RNA sequencing to evaluate almost all the cell types that constitute the site of spinal cord injury in rats. In addition to mapping the cells of the injured area, we screened the expression of immune autophagy-related factors in cells and identified signaling pathways by the measuring the expression of the receptor−ligand pairs to regulate specific cell interactions during autophagy after spinal cord injury. Our data set is a valuable resource that provides new insights into the pathobiology of spinal cord injury and other traumatic diseases of the central nervous system.

Targeting of biomolecular condensates to the autophagy pathway

Biomolecular condensates are membraneless compartments formed by liquid-liquid phase separation. They can phase transit into gel-like and solid states. The amount and state of biomolecular condensates must be tightly regulated to maintain normal cellular function. Autophagy targets biomolecular condensates to the lysosome for degradation or other purposes, which we term biocondensophagy. In biocondensophagy, autophagy receptors recognize biomolecular condensates and target them to the autophagosome, the vesicle carrier of autophagy. Multiple types of autophagy receptors have been identified and they are specifically involved in targeting biomolecular condensates with different phase transition states. The receptors also organize the phase transition of biomolecular condensate to facilitate biocondensophagy. Here, we briefly discuss the latest discoveries regarding how biomolecular condensates are recognized by autophagy receptors.

Progress and Challenges in Targeted Protein Degradation for Neurodegenerative Disease Therapy

Neurodegenerative diseases (NDs) are currently incurable diseases that cause progressive degeneration of nerve cells. Many of the disease-causing proteins of NDs are "undruggable" for traditional small-molecule inhibitors (SMIs). None of the compounds that attenuated the amyloid-β (Aβ) accumulation process have entered clinical practice, and many phase III clinical trials of SMIs for Alzheimer's disease (AD) have failed. In recent years, emerging targeted protein degradation (TPD) technologies such as proteolysis-targeting chimeras (PROTACs), lysosome-targeting chimaeras (LYTACs), and autophagy-targeting chimeras (AUTACs) with TPD-assistive technologies such as click-formed proteolysis-targeting chimeras (CLIPTACs) and deubiquitinase-targeting chimera (DUBTAC) have developed rapidly. In vitro and in vivo experiments have also confirmed that TPD technology can target the degradation of ND pathogenic proteins, bringing hope for the treatment of NDs. Herein, we review the latest TPD technologies, introduce their targets and technical characteristics, and discuss the emerging TPD technologies with potential in ND research, with the hope of providing a new perspective for the development of TPD technology in the NDs field.

Autophagy in Rat Müller Glial Cells Is Modulated by the Sirtuin 4/AMPK/mTOR Pathway and Induces Apoptosis under Oxidative Stress

Müller glial cells (MGCs) are a group of glial cells in the retina that provide essential support to retinal neurons; however, the understanding of MGC apoptosis and autophagy remains limited. This study was aimed at investigating the role of autophagy in MGCs under normal and oxidative conditions, and identifying the underlying mechanisms. In addition, the sirtuin 4 (SIRT4)-mediated signaling pathway was observed to regulate the autophagic process in MGCs. To assess the effect of autophagy on MGC mitochondrial function and survival, we treated rMC-1 cells—rat-derived Müller glial cells—with rapamycin and 3-methyladenine (3-MA), and found that MGC death was not induced by such treatment, while autophagic dysfunction could increase MGC apoptosis under oxidative stress, as reflected by the expression level of cleaved caspase 3 and PI staining. In addition, the downregulation of autophagy by 3-MA could influence the morphology of the mitochondrial network structure, the mitochondrial membrane potential, and generation of reactive oxygen species (ROS) under oxidative stress. Moreover, SIRT4 depletion enhanced autophagosome formation, as verified by an increase in the LC3 II/I ratio and a decrease in the expression of SQSTM1/p62, and vice versa. The inhibition of AMPK phosphorylation by compound C could reverse these changes in LC3 II/I and SQSTM1/p62 caused by SIRT4 knockdown. Our research concludes that MGCs can endure autophagic dysfunction in the absence of oxidative stress, while the downregulation of autophagy can cause MGCs to become more sensitized to oxidative stress. Simultaneous exposure to oxidative stress and autophagic dysfunction in MGCs can result in a pronounced impairment of cell survival. Mechanically, SIRT4 depletion can activate the autophagic process in MGCs by regulating the AMPK–mTOR signaling pathway.

PD-L1 maintains neutrophil extracellular traps release by inhibiting neutrophil autophagy in endotoxin-induced lung injury

Programmed death ligand 1 (PD-L1) is not only an important molecule in mediating tumor immune escape, but also regulates inflammation development. Here we showed that PD-L1 was upregulated on neutrophils in lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS). Neutrophil specific knockout of PD-L1 reduced lung injury in ARDS model induced by intratracheal LPS injection. The level of NET release was reduced and autophagy is elevated by PD-L1 knockout in ARDS neutrophils both in vivo and in vitro. Inhibition of autophagy could reverse the inhibitory effect of PD-L1 knockout on NET release. PD-L1 interacted with p85 subunit of PI3K at the endoplasmic reticulum (ER) in neutrophils from ARDS patients, activating the PI3K/Akt/mTOR pathway. An extrinsic neutralizing antibody against PD-L1 showed a protective effect against ARDS. Together, PD-L1 maintains the release of NETs by regulating autophagy through the PI3K/Akt/mTOR pathway in ARDS. Anti-PD-L1 therapy may be a promising measure in treating ARDS.

The prognostic value and clinical significance of mitophagy-related genes in hepatocellular carcinoma

Background: Mitophagy has been found to play a significant part in the cancer process in a growing number of studies in recent years. However, there is still a lack of study on mitophagy-related genes' (MRGs) prognostic potential and clinical significance in hepatocellular carcinoma (HCC). Methods: We employed bioinformatics and statistical knowledge to examine the transcriptome data of HCC patients in the TCGA and GEO databases, with the goal of constructing a multigene predictive model. Then, we separated the patients into high- and low-risk groups based on the score. The model's dependability was determined using principal components analysis (PCA), survival analysis, independent prognostic analysis, and receiver operating characteristic (ROC) analysis. Following that, we examined the clinical correlations, pharmacological treatment sensitivity, immune checkpoint expression, and immunological correlations between patients in high and low risk groups. Finally, we evaluated the variations in gene expression between high- and low-risk groups and further analyzed the network core genes using protein-protein interaction network analysis. Results: Prognostic models were built using eight genes (OPTN, ATG12, CSNK2A2, MFN1, PGAM5, SQSTM1, TOMM22, TOMM5). During validation, the prognostic model demonstrated high reliability, indicating that it could accurately predict the prognosis of HCC patients. Additionally, we discovered that typical HCC treatment medicines had varying impacts on patients classified as high or low risk, and that individuals classified as high risk are more likely to fail immunotherapy. Additionally, the high-risk group expressed more immunological checkpoints. The immunological status of patients in different risk categories varies as well, and patients with a high-risk score have a diminished ability to fight cancer. Finally, PPI analysis identified ten related genes with potential for research. Conclusion: Our prognostic model had good and reliable predictive ability, as well as clinical diagnosis and treatment guiding significance. Eight prognostic MRGs and ten network core genes merited further investigation.

Autophagy: Guardian of Skin Barrier

Autophagy is a major degradation pathway that removes harmful intracellular substances to maintain homeostasis. Various stressors, such as starvation and oxidative stress, upregulate autophagy, and the dysregulation of autophagy is associated with various human diseases, including cancer and skin diseases. The skin is the first defense barrier against external environmental hazards such as invading pathogens, ultraviolet rays, chemical toxins, and heat. Although the skin is exposed to various stressors that can activate autophagy, the roles of autophagy in the skin have not yet been fully elucidated. Accumulating evidence suggests that autophagy is closely associated with pathogenesis and the treatment of immune-related skin diseases. In this study, we review how autophagy interacts with skin cells, including keratinocytes and immune cells, enabling them to successfully perform their protective functions by eliminating pathogens and maintaining skin homeostasis. Furthermore, we discuss the implications of autophagy in immune-related skin diseases, such as alopecia areata, psoriasis, and atopic dermatitis, and suggest that a combination of autophagy modulators with conventional therapies may be a better strategy for the treatment of these diseases.

Autophagy: A Key Regulator of Homeostasis and Disease: An Overview of Molecular Mechanisms and Modulators

Autophagy is a highly conserved lysosomal degradation pathway active at basal levels in all cells. However, under stress conditions, such as a lack of nutrients or trophic factors, it works as a survival mechanism that allows the generation of metabolic precursors for the proper functioning of the cells until the nutrients are available. Neurons, as post-mitotic cells, depend largely on autophagy to maintain cell homeostasis to get rid of damaged and/or old organelles and misfolded or aggregated proteins. Therefore, the dysfunction of this process contributes to the pathologies of many human diseases. Furthermore, autophagy is highly active during differentiation and development. In this review, we describe the current knowledge of the different pathways, molecular mechanisms, factors that induce it, and the regulation of mammalian autophagy. We also discuss its relevant role in development and disease. Finally, here we summarize several investigations demonstrating that autophagic abnormalities have been considered the underlying reasons for many human diseases, including liver disease, cardiovascular, cerebrovascular diseases, neurodegenerative diseases, neoplastic diseases, cancers, and, more recently, infectious diseases, such as SARS-CoV-2 caused COVID-19 disease.

Targeting retinoic acid receptor alpha-corepressor interaction activates chaperone-mediated autophagy and protects against retinal degeneration

Chaperone-mediated autophagy activity, essential in the cellular defense against proteotoxicity, declines with age, and preventing this decline in experimental genetic models has proven beneficial. Here, we have identified the mechanism of action of selective chaperone-mediated autophagy activators previously developed by our group and have leveraged that information to generate orally bioavailable chaperone-mediated autophagy activators with favorable brain exposure. Chaperone-mediated autophagy activating molecules stabilize the interaction between retinoic acid receptor alpha - a known endogenous inhibitor of chaperone-mediated autophagy - and its co-repressor, nuclear receptor corepressor 1, resulting in changes of a discrete subset of the retinoic acid receptor alpha transcriptional program that leads to selective chaperone-mediated autophagy activation. Chaperone-mediated autophagy activators molecules activate this pathway in vivo and ameliorate retinal degeneration in a retinitis pigmentosa mouse model. Our findings reveal a mechanism for pharmacological targeting of chaperone-mediated autophagy activation and suggest a therapeutic strategy for retinal degeneration.

Activation of Atg7-dependent autophagy by a novel inhibitor of the Keap1-Nrf2 protein-protein interaction from Penthorum chinense Pursh. attenuates 6-hydroxydopamine-induced ferroptosis in zebrafish and dopaminergic neurons

The death of dopaminergic neurons is a dominant factor during the occurrence and development of Parkinson's disease (PD). Previous studies demonstrated that ferroptosis is implicated in the death of dopaminergic neurons. Besides, polyphenols have been proven to be effective in preventing the death of dopaminergic neurons. This work aims to explore the neuroprotective effect and mechanism of thonningianin A (Th A), a polyphenolic compound in natural plant foods, against 6-hydroxydopamine (6-OHDA)-induced ferroptosis in dopaminergic cells. The results of molecular docking and other binding assays collectively demonstrated that Th A can strongly target the Kelch domain of Keap1. Th A treatment significantly facilitated the nuclear factor erythroid 2-like 2 (Nrf2) nuclear translocation and subsequently increased the heme oxygenase-1 (HO-1) protein level through inhibiting the protein-protein interaction (PPI) of Keap1 and Nrf2. Compared with the nomifensine (Nomi) treatment, Th A had a more potent protective effect on 6-OHDA-induced ferroptosis during PD pathology in zebrafish, which was associated with assuaging the reduction of the total swimming distance, glutathione (GSH) depletion, iron accumulation, lipid peroxidation, and aggregation of α-synuclein (α-syn). Furthermore, Th A also exhibited a strong protective effect against 6-OHDA-induced ferroptosis in vitro in the human neuroblastoma cell line SH-SY5Y. Th A degraded Keap1 protein through activating Atg7-dependent autophagy. Additionally, Th A treatment facilitated the degradation of Keap1 protein by promoting the interaction between p62/SQSTM1 (sequestosome 1, hereafter referred to as p62) and Keap1. Taken together, our findings indicated that Th A protects dopaminergic cells against 6-OHDA-induced ferroptosis through activating the Nrf2-based cytoprotective system, thus enabling a potential application of Keap1-Nrf2 PPI inhibitors in the restraint of ferroptosis and treatment of PD.

Unbalanced Regulation of Sec22b and Ykt6 Blocks Autophagosome Axonal Retrograde Flux in Neuronal Ischemia-Reperfusion Injury

Cerebral ischemia-reperfusion (I/R) injury in ischemic penumbra is accountable for poor outcome of ischemic stroke patients receiving recanalization therapy. Compelling evidence previously demonstrated a dual role of autophagy in stroke. This study aimed to understand the traits of autophagy in the ischemic penumbra and the potential mechanism that switches the dual role of autophagy. We found that autophagy induction by rapamycin and lithium carbonate performed before ischemia reduced neurologic deficits and infarction, while autophagy induction after reperfusion had the opposite effect in the male murine middle cerebral artery occlusion/reperfusion (MCAO/R) model, both of which were eliminated in mice lacking autophagy (Atg7flox/flox; Nestin-Cre). Autophagic flux determination showed that reperfusion led to a blockage of axonal autophagosome retrograde transport in neurons, which then led to autophagic flux damage. Then, we found that I/R induced changes in the protein levels of Sec22b and Ykt6 in neurons, two autophagosome transport-related factors, in which Sec22b significantly increased and Ykt6 significantly decreased. In the absence of exogenous autophagy induction, Sec22b knock-down and Ykt6 overexpression significantly alleviated autophagic flux damage, infarction, and neurologic deficits in neurons or murine exposed to cerebral I/R in an autophagy-dependent manner. Furthermore, Sec22b knock-down and Ykt6 overexpression switched the outcome of rapamycin posttreatment from deterioration to neuroprotection. Thus, Sec22b and Ykt6 play key roles in neuronal autophagic flux, and modest regulation of Sec22b and Ykt6 may help to reverse the failure of targeting autophagy induction to improve the prognosis of ischemic stroke.SIGNIFICANCE STATEMENT The highly polarized architecture of neurons with neurites presents challenges for material transport, such as autophagosomes, which form at the neurite tip and need to be transported to the cell soma for degradation. Here, we demonstrate that Sec22b and Ykt6 act as autophagosome porters and play an important role in maintaining the integrity of neuronal autophagic flux. Ischemia-reperfusion (I/R)-induced excess Sec22b and loss of Ykt6 in neurons lead to axonal autophagosome retrograde trafficking failure, autophagic flux damage, and finally neuronal injury. Facilitated axonal autophagosome retrograde transport by Sec22b knock-down and Ykt6 overexpression may reduce I/R-induced neuron injury and extend the therapeutic window of pharmacological autophagy induction for neuroprotection.

Cell Autophagy in NASH and NASH-Related Hepatocellular Carcinoma

Autophagy, a cellular self-digestion process, involves the degradation of targeted cell components such as damaged organelles, unfolded proteins, and intracellular pathogens by lysosomes. It is a major quality control system of the cell and plays an important role in cell differentiation, survival, development, and homeostasis. Alterations in the cell autophagic machinery have been implicated in several disease conditions, including neurodegeneration, autoimmunity, cancer, infection, inflammatory diseases, and aging. In non-alcoholic fatty liver disease, including its inflammatory form, non-alcoholic steatohepatitis (NASH), a decrease in cell autophagic activity, has been implicated in the initial development and progression of steatosis to NASH and hepatocellular carcinoma (HCC). We present an overview of autophagy as it occurs in mammalian cells with an insight into the emerging understanding of the role of autophagy in NASH and NASH-related HCC.

Antiaging Mechanism of Natural Compounds: Effects on Autophagy and Oxidative Stress

Aging is a natural biological process that manifests as the progressive loss of function in cells, tissues, and organs. Because mechanisms that are meant to promote cellular longevity tend to decrease in effectiveness with age, it is no surprise that aging presents as a major risk factor for many diseases such as cardiovascular disease, neurodegenerative disorders, cancer, and diabetes. Oxidative stress, an imbalance between the intracellular antioxidant and overproduction of reactive oxygen species, is known to promote the aging process. Autophagy, a major pathway for protein turnover, is considered as one of the hallmarks of aging. Given the progressive physiologic degeneration and increased risk for disease that accompanies aging, many studies have attempted to discover new compounds that may aid in the reversal of the aging process. Here, we summarize the antiaging mechanism of natural or naturally derived synthetic compounds involving oxidative stress and autophagy. These compounds include: 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) derivatives (synthetic triterpenoids derived from naturally occurring oleanolic acid), caffeic acid phenethyl ester (CAPE, the active ingredient in honey bee propolis), xanthohumol (a prenylated flavonoid identified in the hops plant), guggulsterone (a plant steroid found in the resin of the guggul plant), resveratrol (a natural phenol abundantly found in grape), and sulforaphane (a sulfur-containing compound found in cruciferous vegetables).

The mitochondrial associated endoplasmic reticulum membranes: A platform for the pathogenesis of inflammation-mediated metabolic diseases

Mitochondria-associated endoplasmic reticulum membranes (MAM) are specialized subcellular compartments that are shaped by endoplasmic reticulum (ER) subdomains placed side by side to the outer membrane of mitochondria (OMM) being connected by tethering proteins in mammalian cells. Studies showed that MAM has multiple physiological functions. These include regulation of lipid synthesis and transport, Ca2+ transport and signaling, mitochondrial dynamics, apoptosis, autophagy, and formation and activation of an inflammasome. However, alterations of MAM integrity lead to deleterious effects due to an increased generation of mitochondrial reactive oxygen species (ROS) via increased Ca2+ transfer from the ER to mitochondria. This, in turn, causes mitochondrial damage and release of mitochondrial components into the cytosol as damage-associated molecular patterns which rapidly activate MAM-resident Nod-like receptor protein-3 (NLRP3) inflammasome components. This complex induces the release of pro-inflammatory cytokines that initiate low-grade chronic inflammation that subsequently causes the development of metabolic diseases. But, the mechanisms of how MAM is involved in the pathogenesis of these diseases are not exhaustively reviewed. Therefore, this review was aimed to highlight the contribution of MAM to a variety of cellular functions and consider its significance pertaining to the pathogenesis of inflammation-mediated metabolic diseases.

Retinoid Drugs Improve Autophagy of Medulloblastoma Cells via Hedgehog-Gli Signaling Pathway

Our study aims to discuss the effect of retinoid drug on autophagy of medulloblastoma cells. Targeted ferrocenoretinoic acid was prepared and identified. The MB cells were assigned into blank group, control group and transfection group followed by analysis of cell survival rate and expression of Rack1, Hedgehog-Gli, Beclin1 and LC3. The size and form of prepared ferrocenoretinoic acid was uniform. There was positive charge which can bind target. Ferrocenoretinoic acid treatment declined cell survival rate and increased cell apoptotic rate. The level of Rack1 and Hedgehog-Gli in transfection group was lower than other two group. The tendency in expression of Beclin1 and LC3 was reversed. In conclusion, the expression of Rack1 is restrained by nano-retinoid drug so as to restrain the Hedgehog-Gli signal activity. Therefore, the survival rate of medulloblastoma cells could be restrained and apoptotic rate could be prompted.

Rnd3 Expression is Necessary to Maintain Mitochondrial Homeostasis but Dispensable for Autophagy

Autophagy is a highly conserved process that mediates the targeting and degradation of intracellular components to lysosomes, contributing to the maintenance of cellular homeostasis and to obtaining energy, which ensures viability under stress conditions. Therefore, autophagy defects are common to different neurodegenerative disorders. Rnd3 belongs to the family of Rho GTPases, involved in the regulation of actin cytoskeleton dynamics and important in the modulation of cellular processes such as migration and proliferation. Murine models have shown that Rnd3 is relevant for the correct development and function of the Central Nervous System and lack of its expression produces several motor alterations and neural development impairment. However, little is known about the molecular events through which Rnd3 produces these phenotypes. Interestingly we have observed that Rnd3 deficiency correlates with the appearance of autophagy impairment profiles and irregular mitochondria. In this work, we have explored the impact of Rnd3 loss of expression in mitochondrial function and autophagy, using a Rnd3 KO CRISPR cell model. Rnd3 deficient cells show no alterations in autophagy and mitochondria turnover is not impaired. However, Rnd3 KO cells have an altered mitochondria oxidative metabolism, resembling the effect caused by oxidative stress. In fact, lack of Rnd3 expression makes these cells strictly dependent on glycolysis to obtain energy. Altogether, our results demonstrate that Rnd3 is relevant to maintain mitochondria function, suggesting a possible relationship with neurodegenerative diseases.

Bisdemethoxycurcumin inhibits VEGF-induced HUVECs proliferation, migration and invasion through AMPK/mTOR pathway-dependent autophagy activation and cell cycle arrest

Vascular endothelial growth factor (VEGF) is a key mediator of angiogenesis, which plays a key role in the proliferation, migration and invasion of endothelial cell. Bisdemethoxycurcumin (BDMC) is a natural demethoxy curcumin derivative. In this study, we explored the mechanisms whereby BDMC is able to influence the proliferative, migratory and invasive activity of human umbilical vein endothelial cells (HUVECs) in response to VEGF treatment. These experiments revealed that BDMC at 10 and 20μM suppressed HUVECs proliferation in response to VEGF (10 ng/mL) without impacting the proliferation in absence of VEGF. BDMC treatment also signifantly suppressed VEGF-induced migratory and invasive activity in HUVECs. However, the selective AMPK inhibitor compound C (3 μM) treatment signifantly reversed all of these effects. Flow cytometric assay showed BDMC treatment was found to induce G0/G1 phase cell cycle arrest. Western blotting further indicated that BDMC treatment increased the ratios of p-AMPK/AMPK and LC3B/LC3A, up-regulated the expression of Beclin-1, decreased the ratio of p-mTOR/mTOR, down-regulated the expression of cyclin D1 and CDK4. Overall, these data suggested that BDMC may exert benefical effect on HUVECs activation by activating autophagy and inducing cell cycle arrest through regulation of the AMPK/mTOR pathway, which could provide a potential compound candidate for the treatment of diseases related to VEGF overproduction.