How does autophagy impact neurological function?

Autophagies describe a set of processes in which cells degrade their cytoplasmic contents via various routes that terminate with the lysosome. In macroautophagy (the focus of this review, henceforth autophagy), cytoplasmic contents, including misfolded proteins, protein complexes, dysfunctional organelles, and various pathogens, are captured within double membranes called autophagosomes, which ultimately fuse with lysosomes, after which their contents are degraded. Autophagy is important in maintaining neuronal and glial function; consequently, disrupted autophagy is associated with various neurologic diseases. This review provides a broad perspective on the roles of autophagy in the CNS, highlighting recent literature that furthers our understanding of the multifaceted role of autophagy in maintaining a healthy nervous system.

CIRBP Increases the synthesis and secretion of steroid hormones by in yak granulaso cells

As a regulatory protein that upregulates transcription in response to various stresses, cold-induced RNA-binding protein (CIRBP) is involved in a variety of physiological pathological processes in cells. However, little is known about the role of CIRBP in regulating autophagy and the synthesis and secretion of ovarian steroid hormones (estradiol E2 and progesterone P4). This study aimed to explore whether the synthetic secretion of ovarian steroid hormones is related to CIRBP-regulated autophagy. We detected the differential expression of CIRBP, LC3, E2 and P4 in YGCs cultured at mild low temperature (32 °C) for 6 and 12 h. CIRBP, LC3, E2 and P4 expression was increased in response to low temperature in YGCs. In order to illustrate that the changes in secretion of E2/P4 and autophagy might be caused by CIRBP induced by low temperature, we overexpressed CIRBP in YGCs cultured in vitro to detect its effects on autophagy and steroid hormone synthesis and secretion. We found that overexpression of CIRBP can induce autophagy of YGCs and enhance the synthesis and secretion of E2 and P4, suggesting that mild hypothermia may activate autophagy by inducing the expression of CIRBP and enhance the synthesis and secretion of E2 and P4. To further explore the relationship between CIRBP regulated autophagy and steroid hormone synthesis and secretion, we verified it by regulating autophagy. The results showed that Inhibition of autophagy significantly reversed CIRBP overexpression-enhanced autophagy and synthetic secretion of E2, P4 in YGCs, while activated autophagy showed similar results to overexpression of CIRBP. In conclusion, our data suggest that autophagy is involved in the synthesis and secretion of YGCs E2 and P4 and is associated with overexpression of CIRBP.

Diet-induced hyperhomocysteinemia causes sex-dependent deficiencies in offspring musculature and brain function

Hyperhomocysteinemia (HHcy), characterized by elevated homocysteine (Hcy) levels, is a known risk factor for cardiovascular, renal, and neurological diseases, as well as pregnancy complications. Our study aimed to investigate whether HHcy induced by a high-methionine (high-Met) diet exacerbates cognitive and behavioral deficits in offspring and leads to other breeding problems. Dietary HHcy was induced four weeks before mating and continued throughout gestation and post-delivery. A battery of behavioral tests was conducted on offspring between postnatal days (PNDs) 5 and 30 to assess motor function/activity and cognition. The results were correlated with brain morphometric measurements and quantitative analysis of mammalian target of rapamycin (mTOR)/autophagy markers. The high-Met diet significantly increased parental and offspring urinary tHcy levels and influenced offspring behavior in a sex-dependent manner. Female offspring exhibited impaired cognition, potentially related to morphometric changes observed exclusively in HHcy females. Male HHcy pups demonstrated muscle weakness, evidenced by slower surface righting, reduced hind limb suspension (HLS) hanging time, weaker grip strength, and decreased activity in the beaker test. Western blot analyses indicated the downregulation of autophagy and the upregulation of mTOR activity in HHcy cortexes. HHcy also led to breeding impairments, including reduced breeding rate, in-utero fetal death, lower pups' body weight, and increased mortality, likely attributed to placental dysfunction associated with HHcy. In conclusion, a high-Met diet impairs memory and cognition in female juveniles and weakens muscle strength in male pups. These effects may stem from abnormal placental function affecting early neurogenesis, the dysregulation of autophagy-related pathways in the cortex, or epigenetic mechanisms of gene regulation triggered by HHcy during embryonic development.

Aging Differentially Affects Axonal Autophagosome Formation and Maturation

Misregulation of neuronal macroautophagy/autophagy has been implicated in age-related neurodegenerative diseases. We compared autophagosome formation and maturation in primary murine neurons during development and through aging to elucidate how aging affects neuronal autophagy. We observed an age-related decrease in the rate of autophagosome formation leading to a significant decrease in the density of autophagosomes along the axon. Next, we identified a surprising increase in the maturation of autophagic vesicles in neurons from aged mice. While we did not detect notable changes in endolysosomal content in the distal axon during early aging, we did observe a significant loss of acidified vesicles in the distal axon during late aging. Interestingly, we found that autophagic vesicles were transported more efficiently in neurons from adult mice than in neurons from young mice. This efficient transport of autophagic vesicles in both the distal and proximal axon is maintained in neurons during early aging, but is lost during late aging. Our data indicate that early aging does not negatively impact autophagic vesicle transport nor the later stages of autophagy. However, alterations in autophagic vesicle transport efficiency during late aging reveal that aging differentially impacts distinct aspects of neuronal autophagy.Abbreviations: ACAP3: ArfGAP with coiled-coil, ankyrin repeat and PH domains 3; ARF6: ADP-ribosylation factor 6; ATG: autophagy related; AVs: autophagic vesicles; DCTN1/p150Glued: dynactin 1; DRG: dorsal root ganglia; GAP: GTPase activating protein; GEF: guanine nucleotide exchange factor; LAMP2: lysosomal-associated protein 2; LysoT: LysoTracker; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAPK8IP1/JIP1: mitogen-activated protein kinase 8 interacting protein 1; MAPK8IP3/JIP3: mitogen-activated protein kinase 8 interacting protein 3; mCh: mCherry; PE: phosphatidylethanolamine.

Analysis of ATG4C function in vivo

ABBREVIATIONS

ATG4 (autophagy related 4 cysteine peptidase); ATG4A (autophagy related 4A cysteine peptidase); ATG4B (autophagy related 4B cysteine peptidase); ATG4C (autophagy related 4C cysteine peptidase); ATG4D (autophagy related 4D cysteine peptidase); Atg8 (autophagy related 8); GABARAP (GABA type A receptor-associated protein); GABARAPL1(GABA type A receptor-associated protein like 1); GABARAPL2 (GABA type A receptor-associated protein like 2); MAP1LC3A/LC3A (microtubule associated protein 1 light chain 3 alpha); MAP1LC3B/LC3B (microtubule associated protein 1 light chain 3 beta); mATG8 (mammalian Atg8); PE (phosphatidylethanolamine); PS (phosphatydylserine); SQSTM1/p62 (sequestosome 1).

Sindbis virus is suppressed in the yellow fever mosquito Aedes aegypti by ATG-6/Beclin-1 mediated activation of autophagy

Autophagy is a critical modulator of pathogen invasion response in vertebrates and invertebrates. However, how it affects mosquito-borne viral pathogens that significantly burden public health remains underexplored. To address this gap, we use a genetic approach to activate macroautophagy/autophagy in the yellow fever mosquito (Aedes aegypti), infected with a recombinant Sindbis virus (SINV) expressing an autophagy activator. We first demonstrate a 17-amino acid peptide derived from the Ae. aegypti autophagy-related protein 6 (ATG-6/beclin-1-like protein) is sufficient to induce autophagy in C6/36 mosquito cells, as marked by lipidation of ATG-8 and puncta formation. Next, we engineered a recombinant SINV expressing this bioactive beclin-1-like peptide and used it to infect and induce autophagy in adult mosquitoes. We find that modulation of autophagy using this recombinant SINV negatively regulated production of infectious viruses. The results from this study improve our understanding of the role of autophagy in arboviruses in invertebrate hosts and also highlight the potential for the autophagy pathway to be exploited for arboviral control.

Roles of TGF-β in cancer hallmarks and emerging onco-therapeutic design

Transforming growth factor-beta (TGF-β) is a double-edged sword in cancer treatment because of its pivotal yet complex and roles played during cancer initiation/development. Current anti-cancer strategies involving TGF-β largely view TGF-β as an onco-therapeutic target that not only substantially hinders its full utilisation for cancer control, but also considerably restricts innovations in this field. Thereby, how to take advantages of therapeutically favourable properties of TGF-β for cancer management represents an interesting and less investigated problem. Here, by categorising cancer hallmarks into four critical transition events and one enabling characteristic controlling cancer initiation and progression, and delineating TGF-β complexities according to these cancer traits, we identify the suppressive role of TGF-β in tumour initiation and early-stage progression and its promotive functionalities in cancer metastasis as well as other cancer hallmarks. We also propose the feasibility and possible scenarios of combining cold atmospheric plasma (CAP) with onco-therapeutics utilising TGF-β for cancer control given the intrinsic properties of CAP against cancer hallmarks.

Posaconazole inhibits the stemness of cancer stem-like cells by inducing autophagy and suppressing the Wnt/β-catenin/survivin signaling pathway in glioblastoma

Posaconazole (POS) has been reported to present potential antitumor activity for glioblastoma (GBM). However, its molecular mechanisms remain unclear. In this study, we found that POS has potent cytotoxicity and inhibits cell viability and proliferation in GBM. In addition, we adopted a sphere formation assay to detect the self-renewal capacity, performed western blotting to measure cancer stem-like cells (CSCs) marker proteins (CD133, SOX2, Nanog and Oct4) and applied flow cytometry to monitor the subpopulation of CD144⁺/CD33⁺ cells, and the results all demonstrated that POS can remarkably weaken CSCs stemness. Furthermore, western blotting, immunoflurescence, transmission electron microscopy and acridine orange staining were performed to detect autophagy-related proteins (LC3, SQSTM1, Beclin 1 and Atg5), count the numbers of endogenous LC3 puncta, visually observe the ultrastructural morphology of autophagosomes and judge the formation of acidic vesicular organelles, respectively, and the results validated that POS promotes autophagy induction. Importantly, the suppressive effect of POS on CSCs stemness was partially relieved when autophagy was blocked by the autophagy inhibitor chloroquine (CQ) or Atg5 shRNA. Bioinformatic techniques, including weighted gene coexpression network analysis (WGCNA), gene set difference analysis (GSVA) and KEGG pathway analysis, combined with experimental validations showed that survivin, which is implicated in both autophagy and the stem cell index, is one of the target proteins of POS and that POS weakens CSCs stemness via suppressing the Wnt/β-catenin signaling pathway in GBM. Besides, POS-induced autophagy and the Wnt/β-catenin signaling pathway are negative regulators for each other. Finally, the antitumor activity of POS was confirmed in GBM xenograft models in vivo. Consistent with the in vitro conclusions, POS upregulated the expression of LC3 and decreased the expression of CD133, survivin and β-catenin, as shown by the immunohistochemistry analysis. In summary, this work provides an experimental foundation for exploiting POS as a CSCs-targeting antitumor drug for GBM treatment.

Autophagy deficiency in neurodevelopmental disorders

Autophagy is a cell self-digestion pathway through lysosome and plays a critical role in maintaining cellular homeostasis and cytoprotection. Characterization of autophagy related genes in cell and animal models reveals diverse physiological functions of autophagy in various cell types and tissues. In central nervous system, by recycling injured organelles and misfolded protein complexes or aggregates, autophagy is integrated into synaptic functions of neurons and subjected to distinct regulation in presynaptic and postsynaptic neuronal compartments. A plethora of studies have shown the neuroprotective function of autophagy in major neurodegenerative diseases, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD) and amyotrophic lateral sclerosis (ALS). Recent human genetic and genomic evidence has demonstrated an emerging, significant role of autophagy in human brain development and prevention of spectrum of neurodevelopmental disorders. Here we will review the evidence demonstrating the causal link of autophagy deficiency to congenital brain diseases, the mechanism whereby autophagy functions in neurodevelopment, and therapeutic potential of autophagy.

The Key Role of the WNT/β-Catenin Pathway in Metabolic Reprogramming in Cancers under Normoxic Conditions

Simple Summary

The canonical WNT/β-catenin pathway is upregulated in cancers and plays a major role in proliferation, invasion, apoptosis and angiogenesis. Recent studies have shown that cancer processes are involved under normoxic conditions. These findings completely change the way of approaching the study of the cancer process. In this review, we focus on the fact that, under normoxic conditions, the overstimulation of the WNT/β-catenin pathway leads to modifications in the tumor micro-environment and the activation of the Warburg effect, i.e., aerobic glycolysis, autophagy and glutaminolysis, which in turn participate in tumor growth.

Abstract

The canonical WNT/β-catenin pathway is upregulated in cancers and plays a major role in proliferation, invasion, apoptosis and angiogenesis. Nuclear β-catenin accumulation is associated with cancer. Hypoxic mechanisms lead to the activation of the hypoxia-inducible factor (HIF)-1α, promoting glycolytic and energetic metabolism and angiogenesis. However, HIF-1α is degraded by the HIF prolyl hydroxylase under normoxia, conditions under which the WNT/β-catenin pathway can activate HIF-1α. This review is therefore focused on the interaction between the upregulated WNT/β-catenin pathway and the metabolic processes underlying cancer mechanisms under normoxic conditions. The WNT pathway stimulates the PI3K/Akt pathway, the STAT3 pathway and the transduction of WNT/β-catenin target genes (such as c-Myc) to activate HIF-1α activity in a hypoxia-independent manner. In cancers, stimulation of the WNT/β-catenin pathway induces many glycolytic enzymes, which in turn induce metabolic reprogramming, known as the Warburg effect or aerobic glycolysis, leading to lactate overproduction. The activation of the Wnt/β-catenin pathway induces gene transactivation via WNT target genes, c-Myc and cyclin D1, or via HIF-1α. This in turn encodes aerobic glycolysis enzymes, including glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production. The increase in lactate production is associated with modifications to the tumor microenvironment and tumor growth under normoxic conditions. Moreover, increased lactate production is associated with overexpression of VEGF, a key inducer of angiogenesis. Thus, under normoxic conditions, overstimulation of the WNT/β-catenin pathway leads to modifications of the tumor microenvironment and activation of the Warburg effect, autophagy and glutaminolysis, which in turn participate in tumor growth.

Valproic Acid: A Potential Therapeutic for Spinal Cord Injury

The lack of an effective pharmaceutical agent for spinal cord injury (SCI) is a current problematic situation for clinicians, as the rate of motor vehicle accidents among young adults is on the rise. SCI contributes to the high disability rate. Presently, evidences detailing the precise pathological mechanisms in SCI are limited, compounding to the unavailability of an effective treatment method. Surgery, though not a complete curative method, is useful in managing some of the associated symptoms of secondary SCI. Autophagy and inflammation are contributive factors to both exacerbation and improvement of SCI. The mammalian target of rapamycin (mTOR) signaling pathway is a key player in the regulation of inflammatory response and autophagy. Valproic acid (VPA), a clinically used antiepileptic drug, has been suggested to improve neurological conditions, including SCI. This report reviewed the correlation between mTOR and autophagy, as well as autophagy's role and the therapeutic effects of VPA in SCI. VPA regulates autophagy by potentially inhibiting mTORC1, a complex of mTOR, while also hindering inflammatory response. Conclusively, an effective treatment for SCI could lie in the timely regulation of mTOR signaling pathway, and VPA could be the potential drug that improves SCI owing to its propensity to regulate the mTOR signaling pathway.

Autophagy Deficiency by Atg4B Loss Leads to Metabolomic Alterations in Mice

Autophagy is an essential protective mechanism that allows mammalian cells to cope with a variety of stressors and contributes to maintaining cellular and tissue homeostasis. Due to these crucial roles and also to the fact that autophagy malfunction has been described in a wide range of pathologies, an increasing number of in vivo studies involving animal models targeting autophagy genes have been developed. In mammals, total autophagy inactivation is lethal, and constitutive knockout models lacking effectors of this route are not viable, which has hindered so far the analysis of the consequences of a systemic autophagy decline. Here, we take advantage of atg4b^−/− mice, an autophagy-deficient model with only partial disruption of the process, to assess the effects of systemic reduction of autophagy on the metabolome. We describe for the first time the metabolic footprint of systemic autophagy decline, showing that impaired autophagy results in highly tissue-dependent alterations that are more accentuated in the skeletal muscle and plasma. These changes, which include changes in the levels of amino-acids, lipids, or nucleosides, sometimes resemble those that are frequently described in conditions like aging, obesity, or cardiac damage. We also discuss different hypotheses on how impaired autophagy may affect the metabolism of several tissues in mammals.

Single-cell transcriptome analysis reveals that maternal obesity affects DNA repair, histone methylation, and autophagy level in mouse embryos

Obesity causes many reproductive dysfunctions such as reduced conception, infertility, and early pregnancy loss, and this is largely due to the negative effects of obesity on oocyte and embryo quality. In the present study, we employed single-cell RNA transcriptome sequencing to investigate the potential causes for the maternal obesity effects on mouse embryos. Our results showed that the 4-cell and morula/blastocyst rates were all significantly decreased during embryo development in obese mice. Genome-wide analysis indicated that obesity altered the expression of more than 1100 genes in 2-cell embryos, including the genes which were related to the p53 signaling pathway and apoptosis. Further analysis showed that the expression of 47 genes related to DNA damage was changed, and a positive γH2A signal and the altered expression of Rad51 and Tex15 were observed in the obese embryos. Obesity also affected histone methylation, shown by the decrease of the H3K4-me2 level. Besides this, we observed the occurrence of autophagy and apoptosis in the embryos of obese mice. There were 42 genes that were related to autophagy/apoptosis that showed aberrant expression, and the positive LC3 signal and the decrease of Clec16a, Rraga, and Atg10 level were also observed. In summary, our study suggested that obesity affected early embryonic development by inducing DNA damage, aberrant histone methylation, and autophagy levels in mice.

Autophagy in the Regulation of Tissue Differentiation and Homeostasis

Autophagy is a constitutive pathway that allows the lysosomal degradation of damaged components. This conserved process is essential for metabolic plasticity and tissue homeostasis and is crucial for mammalian post-mitotic cells. Autophagy also controls stem cell fate and defective autophagy is involved in many pathophysiological processes. In this review, we focus on established and recent breakthroughs aimed at elucidating the impact of autophagy in differentiation and homeostasis maintenance of endothelium, muscle, immune system, and brain providing a suitable framework of the emerging results and highlighting the pivotal role of autophagic response in tissue functions, stem cell dynamics and differentiation rates.

Perfluorooctane sulfonate induced toxicity in embryonic stem cell-derived cardiomyocytes via inhibiting autophagy-lysosome pathway

Perfluorooctane sulfonate (PFOS), a classic environmental pollutant, is reported to cause cardiotoxicity in animals and humans. It has been demonstrated that PFOS exposure down-regulates expression of cardiac-development related genes and proteins. However, the related mechanism of PFOS has not been fully elucidated. In the present study, the embryonic stem (ES) cells-derived cardiomyocytes (ESC-CMs) was employed to investigate PFOS-mediated mechanism in developmental toxicity of cardiomyocytes. Our previous study shows that PFOS induces cardiomyocyte toxicity via causing mitochondrial damage. Nevertheless, the underlying mechanism by which PFOS affects the autophagy-related mitochondrial toxicity in ESC-CMs remains unclear. Here, we found that PFOS induced the swelling of mitochondria and the autophagosome accumulation in ESC-CMs at 40 μM concentration. PFOS increased the levels of LC3-II, p62, and ubiquitinated proteins. PFOS also induced an increase of LC3 and p62 localization into mitochondria, indicating that mitophagy degradation was impaired. The results of autophagic flux using chloroquine and RFP-GFP-LC3 analysis showed that the accumulation of autophagosome was not caused by the formation but by the impaired degradation. PFOS was capable of blocking the fusion between autophagosome and lysosome. PFOS caused dysfunction of lysosomes because it down-regulated Lamp2a and cathepsin D, but it did not induced lysosome membrane permeabilization. Meanwhile, PFOS-mediated lysosomal function and the inhibitory effect of autophagic flux could be reversed by PP242 at 40 nM concentration, an mTOR inhibitor. Furthermore, PP242 restored PFOS-induced ATP depletion and mitochondrial membrane potential. In conclusion, PFOS induced mitochondrial dysfunction via blocking autophagy-lysosome degradation, leading to cardiomyocyte toxicity from ES cells.

Autophagy in Neuronal Development and Plasticity

Autophagy is a highly conserved intracellular clearance pathway in which cytoplasmic contents are trafficked to the lysosome for degradation. Within neurons, it helps to remove damaged organelles and misfolded or aggregated proteins and has therefore been the subject of intense research in relation to neurodegenerative disease. However, far less is understood about the role of autophagy in other aspects of neuronal physiology. Here we review the literature on the role of autophagy in maintaining neuronal stem cells and in neuronal plasticity in adult life and we discuss how these contribute to structural and functional deficits observed in a range of human disorders.

Quantitative Proteome Analysis of Atg5-Deficient Mouse Embryonic Fibroblasts Reveals the Range of the Autophagy-Modulated Basal Cellular Proteome

Autophagy performs housekeeping functions for cells and maintains a functional mode by degrading damaged proteins and organelles and providing energy under starvation conditions. The process is tightly regulated by the evolutionarily conserved Atg genes, of which Atg5 is one such crucial mediator. Here, we have done a comprehensive quantitative proteome analysis of mouse embryonic fibroblasts that lack a functional autophagy pathway (Atg5 knockout). We observe that 14% of the identified cellular proteome is remodeled, and several proteins distributed across diverse cellular processes with functions in signaling, cell adhesion, development, and immunity show either higher or lower levels under autophagy-deficient conditions. These cells have lower levels of crucial immune proteins that are required to mount a protective inflammatory response. This study will serve as a valuable resource to determine the role of autophagy in modulating specific protein levels in cells.

Basal autophagy is crucial for maintenance of cellular homeostasis. ATG5 is an essential protein for autophagosome formation, and its depletion has been extensively used as a tool to disrupt autophagy. Here, we characterize the impact of Atg5 deficiency on the cellular proteome of mouse embryonic fibroblasts (MEFs). Using a tandem mass tagging (TMT)-based quantitative proteomics analysis, we observe that 14% of identified proteins show dysregulated levels in atg5^−/− MEFs. These proteins were distributed across diverse biological processes, such as cell adhesion, development, differentiation, transport, metabolism, and immune responses. Several of the upregulated proteins were receptors involved in transforming growth factor β (TGF-β) signaling, JAK-STAT signaling, junction adhesion, and interferon/cytokine-receptor interactions and were validated as autophagy substrates. Nearly equal numbers of proteins, including several lysosomal proteins and enzymes, were downregulated, suggesting a complex role of autophagy/ATG5 in regulating their levels. The atg5^−/− MEFs had lower levels of key immune sensors and effectors, including Toll-like receptor 2 (TLR2), interferon regulatory factor 3 (IRF3), IRF7, MLKL, and STAT1/3/5/6, which were restored by reexpression of ATG5. While these cells could efficiently mount a type I interferon response to the double-stranded RNA (dsRNA) mimic poly(I·C), they were compromised in their inflammatory response to the bacterial pathogen-associated molecular patterns (PAMPs) lipopolysaccharide (LPS) and Pam3CSK4. Transcriptional activation and secretion of interleukin-6 (IL-6) in these cells could be recovered by ATG5 expression, supporting the role of autophagy in the TLR2-induced inflammatory response. This study provides a key resource for understanding the effect of autophagy/ATG5 deficiency on the fibroblast proteome.

IMPORTANCE Autophagy performs housekeeping functions for cells and maintains a functional mode by degrading damaged proteins and organelles and providing energy under starvation conditions. The process is tightly regulated by the evolutionarily conserved Atg genes, of which Atg5 is one such crucial mediator. Here, we have done a comprehensive quantitative proteome analysis of mouse embryonic fibroblasts that lack a functional autophagy pathway (Atg5 knockout). We observe that 14% of the identified cellular proteome is remodeled, and several proteins distributed across diverse cellular processes with functions in signaling, cell adhesion, development, and immunity show either higher or lower levels under autophagy-deficient conditions. These cells have lower levels of crucial immune proteins that are required to mount a protective inflammatory response. This study will serve as a valuable resource to determine the role of autophagy in modulating specific protein levels in cells.

Author Video: An author video summary of this article is available.

Expression of WIPI2B counteracts age-related decline in autophagosome biogenesis in neurons

Autophagy defects are implicated in multiple late-onset neurodegenerative diseases including Amyotrophic Lateral Sclerosis (ALS) and Alzheimer's, Huntington's, and Parkinson's diseases. Since aging is the most common shared risk factor in neurodegeneration, we assessed rates of autophagy in mammalian neurons during aging. We identified a significant decrease in the rate of constitutive autophagosome biogenesis during aging and observed pronounced morphological defects in autophagosomes in neurons from aged mice. While early stages of autophagosome formation were unaffected, we detected the frequent production of stalled LC3B-negative isolation membranes in neurons from aged mice. These stalled structures recruited the majority of the autophagy machinery, but failed to develop into LC3B-positive autophagosomes. Importantly, ectopically expressing WIPI2B effectively restored autophagosome biogenesis in aged neurons. This rescue is dependent on the phosphorylation state of WIPI2B at the isolation membrane, suggesting a novel therapeutic target in age-associated neurodegeneration.

Glycine Protects against Hypoxic-Ischemic Brain Injury by Regulating Mitochondria-Mediated Autophagy via the AMPK Pathway

Hypoxic-ischemic encephalopathy (HIE) is detrimental to newborns and is associated with high mortality and poor prognosis. Thus, the primary aim of the present study was to determine whether glycine could (1) attenuate HIE injury in rats and hypoxic stress in PC12 cells and (2) downregulate mitochondria-mediated autophagy dependent on the adenosine monophosphate- (AMP-) activated protein kinase (AMPK) pathway. Experiments conducted using an in vivo HIE animal model and in vitro hypoxic stress to PC12 cells revealed that intense autophagy associated with mitochondrial function occurred during in vivo HIE injury and in vitro hypoxic stress. However, glycine treatment effectively attenuated mitochondria-mediated autophagy. Additionally, after identifying alterations in proteins within the AMPK pathway in rats and PC12 cells following glycine treatment, cyclosporin A (CsA) and 5-aminoimidazole-4-carboxamide-1-b-4-ribofuranoside (AICAR) were administered in these models and indicated that glycine protected against HIE and CoCl₂ injury by downregulating mitochondria-mediated autophagy that was dependent on the AMPK pathway. Overall, glycine attenuated hypoxic-ischemic injury in neurons via reductions in mitochondria-mediated autophagy through the AMPK pathway both in vitro and in vivo.

Islr regulates canonical Wnt signaling-mediated skeletal muscle regeneration by stabilizing Dishevelled-2 and preventing autophagy

Satellite cells are crucial for skeletal muscle regeneration, but the molecular mechanisms regulating satellite cells are not entirely understood. Here, we show that the immunoglobulin superfamily containing leucine-rich repeat (Islr), a newly identified marker for mesenchymal stem cells, stabilizes canonical Wnt signaling and promote skeletal muscle regeneration. Loss of Islr delays skeletal muscle regeneration in adult mice. In the absence of Islr, myoblasts fail to develop into mature myotubes due to defective differentiation. Islr interacts with Dishevelled-2 (Dvl2) to activate canonical Wnt signaling, consequently regulating the myogenic factor myogenin (MyoG). Furthermore, Islr stabilizes Dvl2 by reducing the level of LC3-labeled Dvl2 and preventing cells from undergoing autophagy. Together, our findings identify Islr as an important regulator for skeletal muscle regeneration.

“Satellite cells are crucial for skeletal muscle regeneration. Here the authors show that immunoglobulin superfamily containing leucine-rich repeat (Islr) promotes skeletal muscle regeneration via a mechanism involving Dishevelled-2 stabilization in satellite cells and protection from autophagy.

A protective role of autophagy in TDCIPP-induced developmental neurotoxicity in zebrafish larvae

Tris (1, 3-dichloro-2-propyl) phosphate (TDCIPP), an extensively used organophosphorus flame retardant, is frequently detected in various environmental media and biota, and has been demonstrated as neurotoxic. Autophagy has been proposed as a protective mechanism against toxicant-induced neurotoxicity. The purpose of the present study was to investigate the effect of TDCIPP exposure on autophagy, and its role in TDCIPP-induced developmental neurotoxicity. Zebrafish embryos (2-120 h post-fertilization [hpf]) were exposed to TDCIPP (0, 5, 50 and 500 μg/l) and a model neurotoxic chemical, chlorpyrifos (CPF, 100 μg/l). The developmental endpoints, locomotive behavior, cholinesterase activities, gene and protein expression related to neurodevelopment and autophagy were measured in the larvae. Our results demonstrate that exposure to TDCIPP (500 μg/l) and CPF causes developmental toxicity, including reduced hatching and survival rates and increased malformation rate (e.g., spinal curvature), as well as altered locomotor behavior. The expression of selected neurodevelopmental gene and protein markers (e.g., mbp, syn2a, and α1-tubulin) was significantly down-regulated in CPF and TDCIPP exposed zebrafish larvae. Treatment with CPF significantly inhibits AChE and BChE, while TDCIPP (0-500 μg/l) exerts no effects on these enzymes. Furthermore, the conversion of microtubule-associated protein I (LC3 I) to LC3 II was significantly increased in TDCIPP exposed zebrafish larvae. In addition, exposure to TDCIPP also activates transcription of several critical genes in autophagy (e.g. Becn1, atg3, atg5, map1lc3b and sqstm1). To further investigate the role of autophagy in TDCIPP induced developmental neurotoxicity, an autophagy inducer (rapamycin, Rapa, 1 nM) and inhibitor (chloroquine, CQ, 1 μM) were used. The results demonstrate that the hatching rate, survival rate, and the expression of mbp and а1-tubulin proteins were all significantly increased in larvae treated with TDCIPP (500 μg/l) and Rapa compared to TDCIPP alone. In contrast, co-treatment with the autophagy inhibitor CQ results in exacerbated neurodevelopmental toxicity. Taken together, our results confirm that exposure to TDCIPP induces autophagy, which plays a protective role in TDCIPP-induced developmental neurotoxicity in zebrafish embryos and larvae.

Mesenchymal Stem Cells Protect Against Hypoxia-Ischemia Brain Damage by Enhancing Autophagy Through Brain Derived Neurotrophic Factor/Mammalin Target of Rapamycin Signaling Pathway

Hypoxic-ischemic encephalopathy (HIE) is a serious disease for neonates. However, present therapeutic strategies are not effective enough for treating HIE. Previous study showed that mesenchymal stem cells (MSCs) can exert neuroprotective effects for brain damage, but its mechanism remains elusive. Using in vitro coculture of rat cortical primary neurons and MSCs in HI conditions, we demonstrated that MSCs help increase brain derived neurotrophic factor (BDNF) and autophagy markers (LC3II and Beclin1) in the cultures and decrease cells death (lactate dehydrogenase levels). We demonstrated a similar mechanism using an in vivo rat model of HI in combination with MSCs transplantation. Using a behavioral study, we further showed that MSCs transplantation into the rat brain after HI injury can attenuate behavioral deficits. Finally, we found that the increase in BDNF and autophagy related factors after HI injury combined with MSCs transplantation can be reversed by anti-BDNF treatment and strengthen the point that the protective effects of BDNF work through inhibition of the mammalin target of rapamycin (mTOR) pathway. Collectively, we proposed that coculture/transplantation of MSCs after HI injury leads to increased BDNF expression and a subsequent reduction in mTOR pathway activation that results in increased autophagy and neuroprotection. This finding gives a hint to explore new strategies for treating neonates with HIE. Stem Cells 2018;36:1109-1121.

Autophagy couteracts weight gain, lipotoxicity and pancreatic β-cell death upon hypercaloric pro-diabetic regimens

In the last years, autophagy has been revealed as an essential pathway for multiple biological processes and physiological functions. As a catabolic route, autophagy regulation by nutrient availability has been evolutionarily conserved from yeast to mammals. On one hand, autophagy induction by starvation is associated with a significant loss in body weight in mice. Here, we demonstrate that both genetic and pharmacological inhibition of the autophagy process compromise weight loss induced by starvation. Moreover, autophagic potential also impacts on weight gain induced by distinct hypercaloric regimens. Atg4b-deficient mice, which show limited autophagic competence, exhibit a major increase in body weight in response to distinct obesity-associated metabolic challenges. This response is characterized by the presence of larger adipocytes in visceral fat tissue, increased hepatic steatosis, as well as reduced glucose tolerance and attenuated insulin responses. Similarly, autophagy-deficient mice are more vulnerable to experimentally induced type-I diabetes, showing an increased susceptibility to acute streptozotocin administration. Notably, pharmacological stimulation of autophagy in wild-type mice by spermidine reduced both weight gain and obesity-associated alterations upon hypercaloric regimens. Altogether, these results indicate that systemic autophagic activity influences the resilience of the organism to weight gain induced by high-calorie diets, as well as to the obesity-associated features of both type-1 and type-2 diabetes.

Understanding cell cycle and cell death regulation provides novel weapons against human diseases

Cell division, cell differentiation and cell death are the three principal physiological processes that regulate tissue homoeostasis in multicellular organisms. The growth and survival of cells as well as the integrity of the genome are regulated by a complex network of pathways, in which cell cycle checkpoints, DNA repair and programmed cell death have critical roles. Disruption of genomic integrity and impaired regulation of cell death may both lead to uncontrolled cell growth. Compromised cell death can also favour genomic instability. It is becoming increasingly clear that dysregulation of cell cycle and cell death processes plays an important role in the development of major disorders such as cancer, cardiovascular disease, infection, inflammation and neurodegenerative diseases. Research achievements in these fields have led to the development of novel approaches for treatment of various conditions associated with abnormalities in the regulation of cell cycle progression or cell death. A better understanding of how cellular life-and-death processes are regulated is essential for this development. To highlight these important advances, the Third Nobel Conference entitled 'The Cell Cycle and Cell Death in Disease' was organized at Karolinska Institutet in 2016. In this review we will summarize current understanding of cell cycle progression and cell death and discuss some of the recent advances in therapeutic applications in pathological conditions such as cancer, neurological disorders and inflammation.

Vitexin alleviates ox-LDL-mediated endothelial injury by inducing autophagy via AMPK signaling activation

Endothelial cell injury plays a crucial role in the development and pathogenesis of cardiovascular disease. Vitexin is a natural flavonoid characterized by anti-oxidative and anti-inflammatory properties. The purpose of this study was to investigate the effects of vitexin on ox-LDL-induced endothelial dysfunction and to explore the underlying molecular mechanisms. In the present study, vitexin was found to play a protective role against ox-LDL-induced endothelial injury. Vitexin significantly promoted cell viability and inhibited apoptosis in ox-LDL-treated HUVECs. The up-regulation of cleaved Caspase-3, cleaved Caspase-9 and Bax induced by ox-LDL were inhibited by treatment with vitexin; meanwhile, the down-regulation of Bcl-2 was suppressed by vitexin. Pretreatment with vitexin was found to inhibit the ox-LDL-induced overexpression of IL-1β, IL-6, TNF-α, E-selectin, ICAM1 and VCAM1. Moreover, vitexin reduced ox-LDL-induced oxidative stress by inhibiting the production of ROS and MDA, and by promoting the expression of SOD. Furthermore, we had shown that vitexin protected against the ox-LDL induced cell injury by activating autophagy. The protective effects of vitexin in ox-LDL-treated HUVECs were all reversed following treatment with the autophagy inhibitor 3-MA. In addition, we found that vitexin increased the expression of p-AMPK and decreased the expression of p-mTOR. The combination of the AMPK inhibitor Compound C plus vitexin significantly reversed the effects of vitexin in ox-LDL-treated HUVECs, such as the inhibition of autophagy, reduction in cell viability, increase in apoptosis and ROS production. In conclusion, these data suggest that vitexin ameliorates ox-LDL-mediated endothelial injury by inducing autophagy via AMPK signaling.

Galectin-4 expression is down-regulated in response to autophagy during differentiation of rat trophoblast cells

Placental development and trophoblast invasion of the maternal endometrium establish the maternal-fetal interface, which is critical for the developing embryo and fetus. Herein we show that overexpression of Galectin-4 (Gal-4) during trophoblast differentiation inhibited the enlargement of Rcho-1 cells (a model for rat trophoblast differentiation) and promoted cell-cell adhesion, whereas trophoblast specific markers and MMP-9 activity were not affected. In the rat placenta, microtubule associated protein 1 light chain 3 alpha (LC3) protein, an autophagy marker, is highly expressed on the maternal side of the decidua where Gal-4 expression is weak. In vitro assays showed that the expression of trophoblast-specific differentiation markers was reduced by 3-Methyladenine (3-MA) and Bafilomycin A1, known as autophagy inhibitors, compared to control cells. Furthermore, Gal-4 expression in Rcho-1 cells, which is normally down-regulated during differentiation, was not attenuated in the presence of autophagy inhibitors, suggesting that autophagy is upstream of Gal-4 expression. We herein describe a possible mechanism by which autophagy regulates trophoblast differentiation via regulation of Gal-4 expression in order to establish the maternal-fetal interface.

Effect of autophagy induced by dexamethasone on senescence in chondrocytes

The aim of the current study was to explore the effects of dexamethasone (DXM) on autophagy and senescence in chondrocytes. Collagen II and aggrecan were examined in normal chondrocytes isolated from Sprague‑Dawley rats. Following stimulation with DXM, LysoTracker Red staining, monodansylcadaverine (MDC) staining, green fluorescent protein‑red fluorescent protein‑light chain 3 (LC3) and western blotting were used to detect autophagy levels in the chondrocytes. Mechanistic target of rapamycin (mTOR) pathway‑associated molecules were investigated by western blotting. Cell senescence was analyzed by senescence‑associated (SA)‑β‑galactosidase (β‑gal) staining. A dose‑dependent increase in the number of autophagic vacuoles was observed in the DXM‑treated chondrocytes, as demonstrated by LysoTracker Red and MDC staining. A dose‑dependent increase in autophagosome formation was observed in the DXM‑treated chondrocytes. Expression of LC3‑II and beclin‑1 was increased by DXM, in particular in the cells treated with DXM for 4 days. However, P62 expression was reduced as a result of treatment. SA‑β‑gal staining indicated that DXM increased cell senescence. Notably, DXM‑induced cell senescence was exacerbated by the autophagic inhibitor 3‑MA. Autophagy induced by DXM protected chondrocytes from senescence, and it is suggested that the mTOR pathway may be involved in the activation of DXM‑induced autophagy.

KIF1A/UNC-104 Transports ATG-9 to Regulate Neurodevelopment and Autophagy at Synapses

Autophagy is a cellular degradation process important for neuronal development and survival. Neurons are highly polarized cells in which autophagosome biogenesis is spatially compartmentalized. The mechanisms and physiological importance of this spatial compartmentalization of autophagy in the neuronal development of living animals are not well understood. Here we determine that, in Caenorhabditis elegans neurons, autophagosomes form near synapses and are required for neurodevelopment. We first determine, through unbiased genetic screens and systematic genetic analyses, that autophagy is required cell autonomously for presynaptic assembly and for axon outgrowth dynamics in specific neurons. We observe autophagosome biogenesis in the axon near synapses, and this localization depends on the synaptic vesicle kinesin, KIF1A/UNC-104. KIF1A/UNC-104 coordinates localized autophagosome formation by regulating the transport of the integral membrane autophagy protein, ATG-9. Our findings indicate that autophagy is spatially regulated in neurons through the transport of ATG-9 by KIF1A/UNC-104 to regulate neurodevelopment.

Autophagy, Innate Immunity and Tissue Repair in Acute Kidney Injury

Kidney is a vital organ with high energy demands to actively maintain plasma hemodynamics, electrolytes and water homeostasis. Among the nephron segments, the renal tubular epithelium is endowed with high mitochondria density for their function in active transport. Acute kidney injury (AKI) is an important clinical syndrome and a global public health issue with high mortality rate and socioeconomic burden due to lack of effective therapy. AKI results in acute cell death and necrosis of renal tubule epithelial cells accompanied with leakage of tubular fluid and inflammation. The inflammatory immune response triggered by the tubular cell death, mitochondrial damage, associative oxidative stress, and the release of many tissue damage factors have been identified as key elements driving the pathophysiology of AKI. Autophagy, the cellular mechanism that removes damaged organelles via lysosome-mediated degradation, had been proposed to be renoprotective. An in-depth understanding of the intricate interplay between autophagy and innate immune response, and their roles in AKI pathology could lead to novel therapies in AKI. This review addresses the current pathophysiology of AKI in aspects of mitochondrial dysfunction, innate immunity, and molecular mechanisms of autophagy. Recent advances in renal tissue regeneration and potential therapeutic interventions are also discussed.

Autophagy and modular restructuring of metabolism control germline tumor differentiation and proliferation in C. elegans

Autophagy can act either as a tumor suppressor or as a survival mechanism for established tumors. To understand how autophagy plays this dual role in cancer, in vivo models are required. By using a highly heterogeneous C. elegans germline tumor, we show that autophagy-related proteins are expressed in a specific subset of tumor cells, neurons. Inhibition of autophagy impairs neuronal differentiation and increases tumor cell number, resulting in a shorter life span of animals with tumors, while induction of autophagy extends their life span by impairing tumor proliferation. Fasting of animals with fully developed tumors leads to a doubling of their life span, which depends on modular changes in transcription including switches in transcription factor networks and mitochondrial metabolism. Hence, our results suggest that metabolic restructuring, cell-type specific regulation of autophagy and neuronal differentiation constitute central pathways preventing growth of heterogeneous tumors.

Autophagy in neonatal hypoxia ischemic brain is associated with oxidative stress

Autophagy is activated when the neonatal brain exposed to hypoxia ischemia (HI), but the mechanisms underlying its activation and its role in the neuronal cell death associated with HI is unclear. We have previously shown that reactive oxygen species (ROS) derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase play an important role in HI-mediated neuronal cell death. Thus, the aim of this study was to determine if ROS is involved in the activation of autophagy in HI-mediated neonatal brain injury and to determine if this is a protective or deleterious pathway. Initial electron microscopy data demonstrated that autophagosome formation is elevated in P7 hippocampal slice cultures exposed to oxygen-glucose deprivation (OGD). This corresponded with increased levels of LC3II mRNA and protein. The autophagy inhibitor, 3-methyladenine (3-MA) effectively reduced LC3II levels and autophagosome formation in hippocampal slice cultures exposed to OGD. Neuronal cell death was significantly attenuated. Finally, we found that the pharmacologic inhibition of NADPH oxidase using apocynin or gp91ds-tat decreased autophagy in hippocampal slice cultures and the rat brain respectively. Thus, our results suggest that an activation of autophagy contributes to neonatal HI brain injury this is oxidative stress dependent.

Endocytic Adaptor Protein Tollip Inhibits Canonical Wnt Signaling

Many adaptor proteins involved in endocytic cargo transport exhibit additional functions in other cellular processes which may be either related to or independent from their trafficking roles. The endosomal adaptor protein Tollip is an example of such a multitasking regulator, as it participates in trafficking and endosomal sorting of receptors, but also in interleukin/Toll/NF-κB signaling, bacterial entry, autophagic clearance of protein aggregates and regulation of sumoylation. Here we describe another role of Tollip in intracellular signaling. By performing a targeted RNAi screen of soluble endocytic proteins for their additional functions in canonical Wnt signaling, we identified Tollip as a potential negative regulator of this pathway in human cells. Depletion of Tollip potentiates the activity of β-catenin/TCF-dependent transcriptional reporter, while its overproduction inhibits the reporter activity and expression of Wnt target genes. These effects are independent of dynamin-mediated endocytosis, but require the ubiquitin-binding CUE domain of Tollip. In Wnt-stimulated cells, Tollip counteracts the activation of β-catenin and its nuclear accumulation, without affecting its total levels. Additionally, under conditions of ligand-independent signaling, Tollip inhibits the pathway after the stage of β-catenin stabilization, as observed in human cancer cell lines, characterized by constitutive β-catenin activity. Finally, the regulation of Wnt signaling by Tollip occurs also during early embryonic development of zebrafish. In summary, our data identify a novel function of Tollip in regulating the canonical Wnt pathway which is evolutionarily conserved between fish and humans. Tollip-mediated inhibition of Wnt signaling may contribute not only to embryonic development, but also to carcinogenesis. Mechanistically, Tollip can potentially coordinate multiple cellular pathways of trafficking and signaling, possibly by exploiting its ability to interact with ubiquitin and the sumoylation machinery.

Autophagy eliminates cytoplasmic β-catenin and NICD to promote the cardiac differentiation of P19CL6 cells

Autophagy plays important roles in adipogenesis and neuron development. However, how autophagy contributes to cardiac development is not well understood. The main aim of our study was to determine the association between autophagy and myocardial differentiation and its roles in this process. Using a well-established in vitro cardiomyocyte differentiation system, P19CL6 cells, we found that autophagy occurred from the early stage of cardiac differentiation. Blocking autophagy by knocking-down of autophagy-related gene Atg7 or Atg5 inhibited the cardiac differentiation of P19CL6 cells. Further investigation demonstrated that LC3 and P62 could form a complex with β-catenin and NICD, respectively, and promoted the degradation of β-catenin and NICD. Enhancing autophagy promoted the formation of complex, whereas blocking autophagy attenuated the degradation of β-catenin and NICD. Taken together, autophagy could facilitate P19CL6 cells to complete the cardiac differentiation process through blocking Wnt and Notch signaling pathways.

Linking pathways in the developing and aging brain with neurodegeneration

The molecular and cellular mechanisms, which coordinate the critical stages of brain development to reach a normal structural organization with appropriate networks, are progressively being elucidated. Experimental and clinical studies provide evidence of the occurrence of developmental alterations induced by genetic or environmental factors leading to the formation of aberrant networks associated with learning disabilities. Moreover, evidence is accumulating that suggests that also late-onset neurological disorders, even Alzheimer's disease, might be considered disorders of aberrant neural development with pathological changes that are set up at early stages of development before the appearance of the symptoms. Thus, evaluating proteins and pathways that are important in age-related neurodegeneration in the developing brain together with the characterization of mechanisms important during brain development with relevance to brain aging are of crucial importance. In the present review we focus on (1) aspects of neurogenesis with relevance to aging; (2) neurodegenerative disease (NDD)-associated proteins/pathways in the developing brain; and (3) further pathways of the developing or neurodegenerating brains that show commonalities. Elucidation of complex pathogenetic routes characterizing the earliest stage of the detrimental processes that result in pathological aging represents an essential first step toward a therapeutic intervention which is able to reverse these pathological processes and prevent the onset of the disease. Based on the shared features between pathways, we conclude that prevention of NDDs of the elderly might begin during the fetal and childhood life by providing the mothers and their children a healthy environment for the fetal and childhood development.