Innate and adaptive immunity through autophagy

Carboplatin restricts peste des petits ruminants virus replication by suppressing the STING-mediated autophagy

Peste des petits ruminants virus (PPRV) is a morbillivirus that causes the acute and highly pathogenic infectious disease peste des petits ruminants (PPR) in small ruminants and poses a major threat to the goat and sheep industries. Currently, there is no effective treatment for PPRV infection. Here, we propose Carboplatin, a platinum-based regimen designed to treat a range of malignancies, as a potential antiviral agent. We showed that Carboplatin exhibits significant antiviral activity against PPRV in a cell culture model. The mechanism of action of Carboplatin against PPRV is mainly attributed to its ability to block STING mediated autophagy. Together, our study supports the discovery of Carboplatin as an antiviral against PPRV and potentially other closely related viruses, sheds light on its mode of action, and establishes STING as a valid and attractive target to counteract viral infection.

Friends and Foes: The Ambivalent Role of Autophagy in HIV-1 Infection

Autophagy has emerged as an integral part of the antiviral innate immune defenses, targeting viruses or their components for lysosomal degradation. Thus, successful viruses, like pandemic human immunodeficiency virus 1 (HIV-1), evolved strategies to counteract or even exploit autophagy for efficient replication. Here, we provide an overview of the intricate interplay between autophagy and HIV-1. We discuss the impact of autophagy on HIV-1 replication and report in detail how HIV-1 manipulates autophagy in infected cells and beyond. We also highlight tissue and cell-type specifics in the interplay between autophagy and HIV-1. In addition, we weigh exogenous modulation of autophagy as a putative double-edged sword against HIV-1 and discuss potential implications for future antiretroviral therapy and curative approaches. Taken together, we consider both antiviral and proviral roles of autophagy to illustrate the ambivalent role of autophagy in HIV-1 pathogenesis and therapy.

Calcineurin suppresses rat H9c2 cardiomyocyteprotective autophagy under chronic intermittent hypoxia by downregulating the AMPK pathway

Calcineurin plays a key role in cardiovascular pathogenesis by exerting pro-apoptotic effects in cardiomyocytes. However, whether calcineurin can regulate cardiomyocyte autophagy under conditions of chronic intermittent hypoxia (CIH) remains unclear. Here, we showed that CIH induced calcineurin activity in H9c2 cells, which attenuated adenosine monophosphate-activated protein kinase (AMPK) signaling and inhibited autophagy. In H9c2 cells, autophagy levels, LC3 expression, and AMPK phosphorylation were significantly elevated under conditions of CIH within 3 days. However, after 5 days of CIH, these effects were reversed and calcineurin activity and apoptosis were significantly increased. The calcineurin inhibitor 17-Allyl-1,14-dihydroxy-12-[2-(4-hydroxy-3-methoxycyclohexyl) -1-methylvinyl]-23,25-dimethoxy-13,19,21,27-tetramethyl-11,28-dioxa-4-azatricyclo- [22.3.1.04,9]octacos-18- ene-2,3,10,16-tetrone (FK506) restored AMPK activation and LC3 expression and attenuated CIH-induced H9c2 cell apoptosis. In contrast, calcineurin overexpression significantly attenuated the increase in LC3 expression and enhanced H9c2 cell apoptosis under conditions of CIH. Calcineurin inhibition failed to induce autophagy or alleviate apoptosis in H9c2 cells expressing a kinase-dead K45R AMPK mutant. Autophagy inhibition abrogated the protective effects of FK506-mediated calcineurin inhibition. These results indicate that calcineurin suppresses adaptive autophagy during CIH by downregulating AMPK activation. Our findings reveal the underlying mechanism of calcineurin and autophagy regulation during H9c2 cell survival under conditions of CIH and may provide a new strategy for preventing CIH-induced cardiomyocyte damage.

METTL14-m6A-FOXO3a axis regulates autophagy and inflammation in ankylosing spondylitis

The role of m6A in ankylosing spondylitis (AS) remains largely obscure. In this study, we found that m6A modification was decreased in T cells of AS, and the abnormal m6A modification was attributed to the downregulation of methyltransferase-like 14 (METTL14). METTL14 exerted a critical role in regulating autophagy activity and inflammation via targeting Forkhead box O3a (FOXO3a). Mechanistically, the loss of METTL14 decreased the expression of FOXO3a, leading to the damage of autophagic flux and the aggravation of inflammation. Inversely, the forced expression of METTL14 upregulated the expression of FOXO3a, thereby activating autophagy and alleviating inflammation. Furthermore, our results revealed that METTL14 targeted FOXO3a mRNA and regulated its expression and stability in a m6A-dependent manner. These findings uncovered the functional importance of m6A methylation mechanisms in the regulation of autophagy and inflammation, which expanded our understanding of this interaction and was critical for the development of therapeutic strategies for AS.

Autophagy and its consequences for platelet biology

Autophagy, the continuous recycling of intracellular building blocks, molecules, and organelles is necessary to preserve cellular function and homeostasis. In this context, it was demonstrated that autophagy plays an important role in megakaryopoiesis, the development and differentiation of hematopoietic progenitor cells into megakaryocytes. Furthermore, in recent years, autophagic proteins were detected in platelets, anucleate cells generated by megakaryocytes, responsible for hemostasis, thrombosis, and a key cell in inflammation and host immune responses. In the last decade studies have indicated the occurrence of autophagy in platelets. Moreover, autophagy in platelets was subsequently demonstrated to be involved in platelet aggregation, adhesion, and thrombus formation. Here, we review the current knowledge about autophagy in platelets, its function, and clinical implications. However, at the advent of platelet autophagy research, additional discoveries derived from evolving work will be required to precisely define the contributions of autophagy in platelets, and to expand the ever increasing physiologic and pathologic roles these remarkable and versatile blood cells play.

A autophagy related-like protein 16-1 promotes the formation of autophagosomes and autolysosomes in antibacterial immune response of Pacific oyster Crassostrea gigas

Autophagy related 16-like (ATG16L) protein is a core autophagy protein, which promotes the extension of autophagosome membrane through microtubule-associated protein light chain 3 (LC3). In the present study, an ATG16L was identified from oyster Crassostrea gigas (defined as CgATG16L1). The full-length cDNA of CgATG16L1 was of 3184 bp with an open reading frame of 1650 bp that encoded a polypeptide of 549 amino acids. There was an ATG5-interacting motif (AFIM) domain, a coiled-coil (CC) domain and seven tryptophan-aspartic acid 40 (WD40) repeats in CgATG16L1. ATG16L1 mRNA was expressed in all the examined tissues with the highest expression in haemolymph (11.22-fold of that in hepatopancreas, p < 0.05). The mRNA expressions of CgATG16L1 in haemocytes increased significantly at 3, 6, 12, 24 and 72 h after lipopolysaccharide (LPS) stimulation, which were 81.15-fold, 24.95-fold, 6.02-fold, 3.90-fold and 5.97-fold (p < 0.05) of that in control group, respectively. The green positive signals of CgATG16L1 protein and the red positive signals of CgLC3 protein were dotted in the cytoplasm of agranulocytes, semi-granulocytes and granulocytes. The co-localization of CgATG16L1 and CgLC3 was observed in haemocytes after Vibrio splendidus stimulation. In CgATG16L1-RNAi oysters, the number of autophagosomes and autolysosomes in haemocytes was reduced. All these results suggested that CgATG16L1 participated in the bacteria-induced autophagy process in the haemocytes of oyster response to bacteria invasion.

Bidirectional interplay between SARS-CoV-2 and autophagy

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as the causative agent of the recent COVID-19 pandemic, continues representing one of the main health concerns worldwide. Autophagy, in addition to its role in cellular homeostasis and metabolism, plays an important part for the host antiviral immunity. However, viruses including SARS-CoV-2 have evolved diverse mechanisms to not only overcome autophagy's antiviral pressure but also manipulate its machinery in order to enhance viral replication and propagation. Here, we discuss our current knowledge on the impact that autophagy exerts on SARS-CoV-2 replication, as well as the different counteracting measures that this virus has developed to manipulate autophagy's complex machinery. Some of the elements regarding this interplay may become future therapeutic targets in the fight against SARS-CoV-2.

Role of Macroautophagy in Mammalian Male Reproductive Physiology

Physiologically, autophagy is an evolutionarily conserved and self-degradative process in cells. Autophagy carries out normal physiological roles throughout mammalian life. Accumulating evidence shows autophagy as a mechanism for cellular growth, development, differentiation, survival, and homeostasis. In male reproductive systems, normal spermatogenesis and steroidogenesis need a balance between degradation and energy supply to preserve cellular metabolic homeostasis. The main process of autophagy includes the formation and maturation of the phagophore, autophagosome, and autolysosome. Autophagy is controlled by a group of autophagy-related genes that form the core machinery of autophagy. Three types of autophagy mechanisms have been discovered in mammalian cells: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy is classified as non-selective or selective. Non-selective macroautophagy randomly engulfs the cytoplasmic components in autophagosomes that are degraded by lysosomal enzymes. While selective macroautophagy precisely identifies and degrades a specific element, current findings have shown the novel functional roles of autophagy in male reproduction. It has been recognized that dysfunction in the autophagy process can be associated with male infertility. Overall, this review provides an overview of the cellular and molecular basics of autophagy and summarizes the latest findings on the key role of autophagy in mammalian male reproductive physiology.

Glucose Transporter Glut1-Dependent Metabolic Reprogramming Regulates Lipopolysaccharide-Induced Inflammation in RAW264.7 Macrophages

This study investigated the critical role of Glut1-mediated glucose metabolism in the inflammatory response of macrophages, which are energy-intensive cells within the innate immune system. Inflammation leads to increased Glut1 expression, ensuring sufficient glucose uptake to support macrophage functions. We demonstrated that using siRNA to knock down Glut1 reduces the expression of various pro-inflammatory cytokines and markers, such as IL-6, iNOS, MHC II/CD40, reactive oxygen species, and the hydrogen sulfide (H₂S)-producing enzyme cystathionine γ-lyase (CSE). Glut1 activates a pro-inflammatory profile through a nuclear factor (NF)-κB, while silencing Glut1 can prevent lipopolysaccharide (LPS)-induced IκB degradation, blocking NF-κB activation. Glut1's role in autophagy, an essential process for macrophage functions such as antigen presentation, phagocytosis, and cytokine secretion, was also measured. The findings show that LPS stimulation decreases autophagosome formation, but Glut1 knockdown reverses this effect, increasing autophagy beyond control levels. The study highlights Glut1's importance in macrophage immune responses and its regulation of apoptosis during LPS stimulation. Knocking down Glut1 negatively impacts cell viability and mitochondrial intrinsic pathway signaling. These findings collectively suggest that targeting macrophage glucose metabolism through Glut1 could potentially serve as a target for controlling inflammation.

Evidence of the Autophagic Process during the Fish Immune Response of Skeletal Muscle Cells against Piscirickettsia salmonis

Autophagy is a fundamental cellular process implicated in the health of the cell, acting as a cytoplasmatic quality control machinery by self-eating unfunctional organelles and protein aggregates. In mammals, autophagy can participate in the clearance of intracellular pathogens from the cell, and the activity of the toll-like receptors mediates its activation. However, in fish, the modulation of autophagy by these receptors in the muscle is unknown. This study describes and characterizes autophagic modulation during the immune response of fish muscle cells after a challenge with intracellular pathogen Piscirickettsia salmonis. For this, primary cultures of muscle cells were challenged with P. salmonis, and the expressions of immune markers il-1β, tnfα, il-8, hepcidin, tlr3, tlr9, mhc-I and mhc-II were analyzed through RT-qPCR. The expressions of several genes involved in autophagy (becn1, atg9, atg5, atg12, lc3, gabarap and atg4) were also evaluated with RT-qPCR to understand the autophagic modulation during an immune response. In addition, LC3-II protein content was measured via Western blot. The challenge of trout muscle cells with P. salmonis triggered a concomitant immune response to the activation of the autophagic process, suggesting a close relationship between these two processes.

Relish regulates innate immunity via mediating ATG5 activity in Antheraea pernyi

In innate immunity, autophagy is an important molecular mechanism that plays a critical role in the animal defense system. Given the importance of anti-microbial autophagy in the innate immune processes, the relationship between anti-microbial autophagy and LPS-induced innate immunity in A. pernyi was investigated. Quantitative RT-PCR analysis revealed that autophagy-related genes (ATG6, ATG5, and ATG12) were induced following LPS injection. LPS treatment in the Relish knockdown larvae reduced the expression of autophagy-related genes, especially ATG5. Furthermore, ATG5 depletion decreased the innate immune effect, while its over-expression with ATG12 was induced after the LPS challenge. The dual-luciferase assay revealed that Relish could regulate ATG5 expression by binding directly to the promoter of the ATG5 gene. Overall, our findings show that Relish regulates the ATG5 transcription to eliminate Gram-negative bacteria by anti-microbial autophagy, implying a strong connection between autophagy and innate immunity in immunologic homeostasis.

Human platelets display dysregulated sepsis-associated autophagy, induced by altered LC3 protein-protein interaction of the Vici-protein EPG5

Platelets mediate central aspects of host responses during sepsis, an acute profoundly systemic inflammatory response due to infection. Macroautophagy/autophagy, which mediates critical aspects of cellular responses during inflammatory conditions, is known to be a functional cellular process in anucleate platelets, and is essential for normal platelet functions. Nevertheless, how sepsis may alter autophagy in platelets has never been established. Using platelets isolated from septic patients and matched healthy controls, we show that during clinical sepsis, the number of autophagosomes is increased in platelets, most likely due to an accumulation of autophagosomes, some containing mitochondria and indicative of mitophagy. Therefore, autophagy induction or early-stage autophagosome formation (as compared to decreased later-stage autophagosome maturation or autophagosome-late endosome/lysosome fusion) is normal or increased. This was consistent with decreased fusion of autophagosomes with lysosomes in platelets. EPG5 (ectopic P-granules autophagy protein 5 homolog), a protein essential for normal autophagy, expression did increase, while protein-protein interactions between EPG5 and MAP1LC3/LC3 (which orchestrate the fusion of autophagosomes and lysosomes) were significantly reduced in platelets during sepsis. Furthermore, data from a megakaryocyte model demonstrate the importance of TLR4 (toll like receptor 4), LPS-dependent signaling for regulating this mechanism. Similar phenotypes were also observed in platelets isolated from a patient with Vici syndrome: an inherited condition caused by a naturally occurring, loss-of-function mutation in EPG5. Together, we provide evidence that autophagic functions are aberrant in platelets during sepsis, due in part to reduced EPG5-LC3 interactions, regulated by TLR4 engagement, and the resultant accumulation of autophagosomes.Abbreviations: ACTB: beta actin; CLP: cecal ligation and puncture; Co-IP: co-immunoprecipitation; DAP: death associated protein; DMSO: dimethyl sulfoxide; EPG5: ectopic P-granules autophagy protein 5 homolog; ECL: enhanced chemiluminescence; HBSS: Hanks' balanced salt solution; HRP: horseradish peroxidase; ICU: intensive care unit; LPS: lipopolysaccharide; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; MKs: megakaryocytes; PFA: paraformaldehyde; PBS: phosphate-buffered saline; PLA: proximity ligation assay; pRT-PCR: quantitative real-time polymerase chain reaction; RT: room temperature; SQSTM1/p62: sequestosome 1; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TLR4: toll like receptor 4; TEM: transmission electron microscopy; WGA: wheat germ agglutinin.

Limited Heme Oxygenase Contribution to Modulating the Severity of Salmonella enterica serovar Typhimurium Infection

An important virulence trait of Salmonella enterica serovar Typhimurium (S. Typhimurium) is the ability to avoid the host immune response, generating systemic and persistent infections. Host cells play a crucial role in bacterial clearance by expressing the enzyme heme oxygenase 1 (Hmox1), which catalyzes the degradation of heme groups into Fe2+, biliverdin, and carbon monoxide (CO). The role of Hmox1 activity during S. Typhimurium infection is not clear and previous studies have shown contradictory results. We evaluated the effect of pharmacologic modulation of Hmox1 in a mouse model of acute and persistent S. Typhimurium infection by administering the Hmox1 activity inductor cobalt protoporphyrin-IX (CoPP) or inhibitor tin protoporphyrin-IX (SnPP) before infection. To evaluate the molecular mechanism involved, we measured the colocalization of S. Typhimurium and autophagosome and lysosomal markers in macrophages. Administering CoPP reduced the bacterial burden in organs of mice 5 days post-infection, while SnPP-treated mice showed bacterial loads similar to vehicle-treated mice. Furthermore, CoPP reduced bacterial loads when administered after infection in macrophages in vitro and in a persistent infection model of S. Typhimurium in vivo, while tin protoporphyrin-IX (SnPP) treatment resulted in a bacterial burden similar to vehicle-treated controls. However, we did not observe significant differences in co-localization of green fluorescent protein (GFP)-labeled S. Typhimurium with the autophagic vesicles marker microtubule-associated protein 1A/1B-light chain 3 (LC3) and the lysosomal marker lysosomal-associated membrane protein 1 (LAMP-1) in macrophages treated with CoPP. Our results suggest that CoPP can enhance antimicrobial activity in response to Salmonella infection, reducing bacterial dissemination and persistence in mice, in a CO and autophagy- independent manner.

Molecular Determinants Regulating the Plasticity of the MHC Class II Immunopeptidome

In the last few years, advancement in the analysis of the MHC class II (MHC-II) ligandome in several mouse and human haplotypes has increased our understanding of the molecular components that regulate the range and selection of the MHC-II presented peptides, from MHC class II molecule polymorphisms to the recognition of different conformers, functional differences in endosomal processing along the endocytic tract, and the interplay between the MHC class II chaperones DM and DO. The sum of all these variables contributes, qualitatively and quantitatively, to the composition of the MHC II ligandome, altogether ensuring that the immunopeptidome landscape is highly sensitive to any changes in the composition of the intra- and extracellular proteome for a comprehensive survey of the microenvironment for MHC II presentation to CD4 T cells.

Antigen Presentation and Autophagy in Teleost Adaptive Immunity

Infectious diseases are a burden for aquaculture. Antigen processing and presentation (APP) to the immune effector cells that fight pathogens is key in the adaptive immune response. At the core of the adaptive immunity that appeared in lower vertebrates during evolution are the variable genes encoding the major histocompatibility complex (MHC). MHC class I molecules mainly present peptides processed in the cytosol by the proteasome and transported to the cell surface of all cells through secretory compartments. Professional antigen-presenting cells (pAPC) also express MHC class II molecules, which normally present peptides processed from exogenous antigens through lysosomal pathways. Autophagy is an intracellular self-degradation process that is conserved in all eukaryotes and is induced by starvation to contribute to cellular homeostasis. Self-digestion during autophagy mainly occurs by the fusion of autophagosomes, which engulf portions of cytosol and fuse with lysosomes (macroautophagy) or assisted by chaperones (chaperone-mediated autophagy, CMA) that deliver proteins to lysosomes. Thus, during self-degradation, antigens can be processed to be presented by the MHC to immune effector cells, thus, linking autophagy to APP. This review is focused on the essential components of the APP that are conserved in teleost fish and the increasing evidence related to the modulation of APP and autophagy during pathogen infection.

Surface carboxylation of iron oxide nanoparticles brings reduced macrophage inflammatory response through inhibiting macrophage autophagy

Macrophage autophagy is a common biological response triggered by nanomaterials, which is closely related to the regulation of inflammation. Superparamagnetic iron oxide (SPIO) nanoparticles have been used for study of autophagy response due to their broad biomedical applications. However, few reports have focused on how to regulate the macrophage autophagy response induced by SPIO nanoparticles. In this study, SPIO nanoparticles grafted with carboxyl groups were synthesized and for the comparison of macrophage autophagy with unmodified nanoparticles. The study on the correlation between autophagy and inflammation induced by the two kinds of SPIO nanoparticles was also included, and the one that grafted with carboxyl groups shows a reduction of autophagy and thereby caused a milder inflammatory response. We proposed that the increased amount of albumin adsorption on the surface of carboxylated SPIO nanoparticles, a protein previously proven to attenuate autophagy, can be considered an important reason for reducing autophagy and inflammation. In general, the carboxyl modification of SPIO nanoparticles has been demonstrated to reduce inflammation by inhibiting macrophage autophagy, which may provide some insights for the design of nanomaterials in the future.

Mechanisms and Therapeutic Strategies of Viral Myocarditis Targeting Autophagy

Viral myocarditis is caused by infection with viruses or bacteria, including coxsackievirus B3 (CVB3), and is characterized by acute or chronic inflammatory responses in the heart. The mortality associated with severe viral myocarditis is considerable. In some patients, viral myocarditis may develop into dilated cardiomyopathy or heart failure. Autophagy is involved in a wide range of physiological processes, including viral infection and replication. In the present review, we focus on the responses of cardiac tissues, cardiomyocytes, and cardiac fibroblasts to CVB3 infection. Subsequently, the effects of altered autophagy on the development of viral myocarditis are discussed. Finally, this review also examined and assessed the use of several popular autophagy modulating drugs, such as metformin, resveratrol, rapamycin, wortmannin, and 3-methyladenine, as alternative treatment strategies for viral myocarditis.

The ATG5 interactome links clathrin-mediated vesicular trafficking with the autophagosome assembly machinery

Autophagosome formation involves the sequential actions of conserved ATG proteins to coordinate the lipidation of the ubiquitin-like modifier Atg8-family proteins at the nascent phagophore membrane. Although the molecular steps driving this process are well understood, the source of membranes for the expanding phagophore and their mode of delivery are only now beginning to be revealed. Here, we have used quantitative SILAC-based proteomics to identify proteins that associate with the ATG12-ATG5 conjugate, a crucial player during Atg8-family protein lipidation. Our datasets reveal a strong enrichment of regulators of clathrin-mediated vesicular trafficking, including clathrin heavy and light chains, and several clathrin adaptors. Also identified were PIK3C2A (a phosphoinositide 3-kinase involved in clathrin-mediated endocytosis) and HIP1R (a component of clathrin vesicles), and the absence of either of these proteins alters autophagic flux in cell-based starvation assays. To determine whether the ATG12-ATG5 conjugate reciprocally influences trafficking within the endocytic compartment, we captured the cell surface proteomes of autophagy-competent and autophagy-incompetent mouse embryonic fibroblasts under fed and starved conditions. We report changes in the relative proportions of individual cell surface proteins and show that cell surface levels of the SLC7A5-SLC3A2 amino acid transporter are influenced by autophagy capability. Our data provide evidence for direct regulatory coupling between the ATG12-ATG5 conjugate and the clathrin membrane trafficking system and suggest candidate membrane proteins whose trafficking within the cell may be modulated by the autophagy machinery. Abbreviations: ATG, autophagy related; BafA1, bafilomycin A1; GFP, green fluorescent protein; HIP1R, huntingtin interacting protein 1 related; MEF, mouse embryo fibroblast; PIK3C2A, phosphatidylinositol-4-phosphate 3-kinase catalytic subunit type 2 alpha; SILAC, stable isotope labelling with amino acids in culture; SQSTM1, sequestosome 1; STRING, search tool for the retrieval of interacting genes/proteins.

Monitoring Autophagy at Cellular and Molecular Level in Crassostrea gigas During an Experimental Ostreid Herpesvirus 1 (OsHV-1) Infection

Mortality outbreaks of young Pacific oysters, Crassostrea gigas, have seriously affected the oyster-farming economy in several countries around the world. Although the causes of these mortality outbreaks appear complex, a viral agent has been identified as the main factor: a herpesvirus called ostreid herpesvirus 1 (OsHV-1). Autophagy is an important degradation pathway involved in the response to several pathologies including viral diseases. In C. gigas, recent studies indicate that this pathway is conserved and functional in at least haemocytes and the mantle. Furthermore, an experimental infection in combination with compounds known to inhibit or induce autophagy in mammals revealed that autophagy is involved in the response to OsHV-1 infection. In light of these results, the aim of this study was to determine the role of autophagy in the response of the Pacific oyster to infection by virus OsHV-1. For this purpose, an experimental infection in combination with a modulator of autophagy was performed on Pacific oysters known to have intermediate susceptibility to OsHV-1 infection. In haemolymph and the mantle, the autophagy response was monitored by flow cytometry, western blotting, and real-time PCR. At the same time, viral infection was evaluated by quantifying viral DNA and RNA amounts by real-time PCR. Although the results showed activation of autophagy in haemolymph and the mantle 14 hours post infection (after viral replication was initiated), they were also indicative of different regulatory mechanisms of autophagy in the two tissues, thus supporting an important function of autophagy in the response to virus OsHV-1.

Autophagy modulation in rainbow trout Oncorhynchus mykiss L. and resistance to experimental infection with Flavobacterium psychrophilum

Previously, rainbow trout fed deoxynivalenol (DON) or partially fed (pair-fed) for 4 weeks before and during experimental infection with Flavobacterium psychrophilum had significantly decreased mortality rates. Similar results were obtained in the present study after 12 days, but not after 6 days, feeding 5 ppm DON or pair-fed before infection. Furthermore, feeding 250 ppm chloroquine (CQ) also reduced mortality (p = .052) compared with controls and may have promise for treatment of some fish disease. Parallel groups of fish were maintained on the respective treatments for 15 days, with an additional group that was fasted, but were not infected to monitor autophagy. Fish that were fasted or fed DON had significantly increased LC3II in the liver and fasted fish had significantly decreased LC3II in muscle compared with controls using western blot. There was no difference in LC3II signal in the spleen of any treatment group. Fish that were fasted or pair-fed had significant up-regulation of the Atg genes atg4, atg7, lc3, gabarap and atg12 in muscle using quantitative PCR. Less alteration of Atg expression was seen in liver. Fish treated with CQ had significantly increased expression of atg4, becn1, lc3 and atg12 in the liver. Fish fed DON for 15 days had few alterations of Atg genes in either the liver or muscle. It is still not clear if autophagy is responsible for the resistance of rainbow trout fed DON, CQ or pair-fed before F. psychrophilum infection.

The Association of Serum Anti-Lysosomal-Associated Membrane Protein-2 Antibody with Vasculitis Combined with Hypertension

The aim of this study was to explore the association of serum anti-lysosomal-associated membrane protein-2 (anti-LAMP-2) antibody with vasculitis combined with hypertension (VAS-HTN). A total of 51 VAS-HTN patients, 46 essential hypertension (EH) patients, and 46 healthy controls (HC) were included in the study. Serum anti-LAMP-2 antibody levels are increased in VAS-HTN patients as compared with EH and HC (all $P<0.05$ ). Serum anti-LAMP-2 antibody levels were significantly higher in active stage patients than those in non-active stage patients and HC (all $P<0.05$ ). The correlation analysis showed a significant positive correlation between serum anti-LAMP-2 antibody levels and the Birmingham Vasculitis Activity Score (BVAS) and hypersensitive C-reactive protein (Hs-CRP) (all $P<0.05$ ). Among the subsets of VAS-HTN, the levels of serum anti-LAMP-2 antibody were remarkably higher in all VAS-HTN subsets compared with HC (all $P<0.05$ ). More interestingly, the levels of serum anti-LAMP-2 antibody were remarkably increased in polyarteritis nodosa (PAN) patients compared with ANCA-associated vasculitis and Takayasu arteritis patients (all $P<0.05$ ). In addition, there was a significant positive correlation between serum anti-LAMP-2 antibody levels and BAVS and Hs-CRP in PAN patients (all $P<0.05$ ). Multivariate logistic regression analysis showed that the anti-LAMP-2 antibody was independently associated with VAS-HTN. The levels of serum anti-LAMP-2 antibody were remarkably increased in VAS-HTN patients compared to EH and HC and might reflect the disease activity. The anti-LAMP-2 antibody may be a potential biomarker for diagnosis and estimating the disease activity in VAS-HTN.

Interferon Alpha Induces Cellular Autophagy and Modulates Hepatitis B Virus Replication

Hepatitis B virus (HBV) infection causes acute and chronic liver diseases, including severe hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). Interferon alpha 2a (IFNα-2a) is commonly used for treating chronic HBV infection. However, its efficacy remains relatively low. Yet, the immunological and molecular mechanisms for successful IFNα-2a treatment remain elusive. One issue is whether the application of increasing IFNα doses may modulate cellular processes and HBV replication in hepatic cells. In the present study, we focused on the interaction of IFNα signaling with other cellular signaling pathways and the consequence for HBV replication. The results showed that with the concentration of 6000 U/ml IFNα-2a treatment downregulated the activity of not only the Akt/mTOR signaling but also the AMPK signaling. Additionally, IFNα-2a treatment increased the formation of the autophagosomes by blocking autophagic degradation. Furthermore, IFNα-2a treatment inhibited the Akt/mTOR signaling and initiated autophagy under low and high glucose concentrations. In reverse, inhibition of autophagy using 3-methyladenine (3-MA) and glucose concentrations influenced the expression of IFNα-2a-induced ISG15 and IFITM1. Despite of ISGs induction, HBV replication and gene expression in HepG2.2.15 cells, a cell model with continuous HBV replication, were slightly increased at high doses of IFNα-2a. In conclusion, our study indicates that IFNα-2a treatment may interfere with multiple intracellular signaling pathways, facilitate autophagy initiation, and block autophagic degradation, thereby resulting in slightly enhanced HBV replication.

The S100A10-AnxA2 complex is associated with the exocytosis of hepatitis B virus in intrauterine infection

Mother-to-child transmission (MTCT) is the major cause of chronic infection of hepatitis B virus (HBV) in patients. However, whether and how HBV crosses the placenta to cause infection in utero remains unclear. In this study, we investigate the mechanism as to how the HBV virions pass through layers of the trophoblast. Our data demonstrate the exocytosis of virions from the trophoblast after exposure to HBV where the endocytosed HBV virions co-localized with an S100A10/AnxA2 complex and LC3, an autophagosome membrane marker. Knockdown of either AnxA2 or S100A10 in trophoblast cells led to a reduction of the amount of exo-virus in Transwell assay. Immunohistochemistry also showed a high expression of AnxA2 and S100A10 in the placental tissue samples of HBV-infected mothers with congenital HBV-positive infants (HBV+/+). We conclude that in HBV intrauterine infection and mother-to-child transmission, a proportion of HBV hijacks autophagic protein secretion pathway and translocate across the trophoblast via S100A10/AnxA2 complex and multivesicular body (MVB)-mediated exocytosis. Our study provides a potential target for the interference of the mechanisms of HBV intrauterine infection and mother-to-child transmission.

ATG12 is involved in the antiviral immune response in large yellow croaker (Larimichthys crocea)

ATG12, a core autophagy protein, forms a conjugate with ATG5 to promote the formation of autophagosome membrane, and plays an important role in antiviral immunity. However, little is known about the function of ATG12 in fish. Here, we cloned the open reading frame (ORF) of large yellow croaker (Larimichthys crocea) ATG12 (LcATG12), which is 354 nucleotides long and encodes a protein of 117 amino acids. The deduced LcATG12 possesses a conserved APG12 domain (residues 31 to 117), and shares 91.45% identities with ATG12 in orange-spotted grouper (Epinephelus coioides). LcATG12 was constitutively expressed in all examined tissues, with the highest level in intestine. Its transcript was also detected in primary head kidney granulocytes (PKG), primary head kidney macrophages (PKM), primary head kidney lymphocytes (PKL), and large yellow croaker head kidney (LYCK) cell line, and was significantly up-regulated by poly(I:C). LcATG12 was regularly distributed in both cytoplasm and nucleus of LYCK and epithelioma papulosum cyprinid (EPC) cells. Overexpression of LcATG12 in EPC cells significantly inhibited the replication of spring viremia of carp virus (SVCV). Further studies reveled that LcATG12 could induce the occurrence of autophagy in LYCK cells. Furthermore, overexpression of LcATG12 in LYCK cells increased the expression levels of large yellow croaker type I interferons (IFNs, IFNc, IFNd, and IFNh), IFN regulatory factors (IRF3 and IRF7), and IFN-stimulated genes (PKR, Mx, and Viperin). All these data indicated that LcATG12 plays a role in the antiviral immunity possibly by inducing both autophagy and type I IFN response in large yellow croaker.

Loss of Hsp67Bc leads to autolysosome enlargement in the Drosophila brain

Hsp67Bc is a small heat shock protein found in Drosophila melanogaster. Apart from performing a function (common for all small heat shock proteins) of preventing aggregation of misfolded proteins, it is involved in macroautophagy regulation alongside the Starvin protein. Overexpression of the D. melanogaster Hsp67Bc gene has been shown to stimulate macroautophagy in S2 cell culture. Nonetheless, it has been unknown how the absence of the Hsp67Bc gene may affect it. Here, we studied the effect of Hsp67Bc gene deletion on the macroautophagy induced by the pathogenic Wolbachia wMelPop strain in D. melanogaster. We detected Wolbachia inside autophagic vacuoles in fly neurons, thereby proving that these endosymbionts were being eliminated via macroautophagy. Nevertheless, we did not register any difference in brain bacterial load between Hsp67Bc-null and control flies at all tested stages of ontogenesis. Moreover, the abundance of autophagic vacuoles was similar between neurons of the mutant and control flies, yet the cross-sectional area of autolysosomes on ultrathin sections was more than 1.5-fold larger in Hsp67Bc-null fly brains than in the control line. Our findings suggest that the product of the Hsp67Bc gene does not participate in the initiation of endosymbiont-induced macroautophagy but may mediate autophagosome maturation: the deletion of the Hsp67Bc gene leads to the increase in autolysosome size.

Residues T48 and A49 in HIV-1 NL4-3 Nef are responsible for the counteraction of autophagy initiation, which prevents the ubiquitin-dependent degradation of Gag through autophagosomes

BACKGROUND

Autophagy plays an important role as a cellular defense mechanism against intracellular pathogens, like viruses. Specifically, autophagy orchestrates the recruitment of specialized cargo, including viral components needed for replication, for lysosomal degradation. In addition to this primary role, the cleavage of viral structures facilitates their association with pattern recognition receptors and MHC-I/II complexes, which assists in the modulation of innate and adaptive immune responses against these pathogens. Importantly, whereas autophagy restricts the replicative capacity of human immunodeficiency virus type 1 (HIV-1), this virus has evolved the gene nef to circumvent this process through the inhibition of early and late stages of the autophagy cascade. Despite recent advances, many details of the mutual antagonism between HIV-1 and autophagy still remain unknown. Here, we uncover the genetic determinants that drive the autophagy-mediated restriction of HIV-1 as well as the counteraction imposed by Nef. Additionally, we also examine the implications of autophagy antagonism in HIV-1 infectivity.

RESULTS

We found that sustained activation of autophagy potently inhibits HIV-1 replication through the degradation of HIV-1 Gag, and that this effect is more prominent for nef-deficient viruses. Gag re-localizes to autophagosomes where it interacts with the autophagosome markers LC3 and SQSTM1. Importantly, autophagy-mediated recognition and recruitment of Gag requires the myristoylation and ubiquitination of this virus protein, two post-translational modifications that are essential for Gag's central role in virion assembly and budding. We also identified residues T48 and A49 in HIV-1 NL4-3 Nef as responsible for impairing the early stages of autophagy. Finally, a survey of pandemic HIV-1 transmitted/founder viruses revealed that these isolates are highly resistant to autophagy restriction.

CONCLUSIONS

This study provides evidence that autophagy antagonism is important for virus replication and suggests that the ability of Nef to counteract autophagy may have played an important role in mucosal transmission. Hence, disabling Nef in combination with the pharmacological manipulation of autophagy represents a promising strategy to prevent HIV spread.

Identification of a TRIM32 from Penaeus monodon is involved in autophagy and innate immunity during white spot syndrome virus infection

Many tripartite motif (TRIM) family proteins played an important role in regulating innate immune and autophagy pathway and were important for host defenses against viral pathogens. However, the role of TRIM proteins in autophagy and innate immunity during virus infection was seldom studied in crustaceans. In this study, a novel TRIM32 homolog was identified from Penaeus monodon (named PmTRIM32). PmTRIM32 was significantly upregulated by rapamycin stimulation and WSSV infection. RNA interference experiments showed that PmTRIM32 could restrict WSSV replication and lead P. monodon more resistance to WSSV challenge. Autophagy could be induced by WSSV or rapamycin challenge and has been proved to play a positive role in restricting WSSV replication in P. monodon. The autophagy activity induced by WSSV or rapamycin challenge could be obviously inhibited by silence of PmTRIM32 in P. monodon. Further studies revealed that PmTRIM32 positively regulated the expression of nuclear transcription factor (NF-κB) and it mediated antimicrobial peptides. Moreover, Pull-down and in vitro ubiquitination assay demonstrated that PmTRIM32 could interact with WSSV envelope protein and target it for ubiquitination in vitro. Collectively, this study demonstrated that PmTRIM32 restricted WSSV replication and was involved in positively regulating autophagy and NF-κB pathway during WSSV infection in P. monodon.

Class I PI3K Provide Lipid Substrate in T Cell Autophagy Through Linked Activity of Inositol Phosphatases

Autophagy, a highly conserved intracellular process, has been identified as a novel mechanism regulating T lymphocyte homeostasis. Herein, we demonstrate that both starvation- and T cell receptor-mediated autophagy induction requires class I phosphatidylinositol-3 kinases to produce PI(3)P. In contrast, common gamma chain cytokines are suppressors of autophagy despite their ability to activate the PI3K pathway. T cells lacking the PI3KI regulatory subunits, p85 and p55, were almost completely unable to activate TCR-mediated autophagy and had concurrent defects in PI(3)P production. Additionally, T lymphocytes upregulate polyinositol phosphatases in response to autophagic stimuli, and the activity of the inositol phosphatases Inpp4 and SHIP are required for TCR-mediated autophagy induction. Addition of exogenous PI(3,4)P₂ can supplement cellular PI(3)P and accelerate the outcome of activation-induced autophagy. TCR-mediated autophagy also requires internalization of the TCR complex, suggesting that this kinase/phosphatase activity is localized in internalized vesicles. Finally, HIV-induced bystander CD4⁺ T cell autophagy is dependent upon PI3KI. Overall, our data elucidate an important pathway linking TCR activation to autophagy, via induction of PI3KI activity and inositol phosphatase upregulation to produce PI(3)P.

Ginsenoside Rg1 Ameliorates Neuroinflammation via Suppression of Connexin43 Ubiquitination to Attenuate Depression

Depression is an inflammation-associated disease that results in major depression as inflammation increases and progresses. Ginsenoside Rg1 (Rg1), the major bioactive ingredient derived from ginseng, possesses remarkable anti-depressant and anti-inflammatory effects. Our previous studies showed that the pathogenesis of depression was concomitant with the acceleration of connexin43 (Cx43) ubiquitin degradation, while Rg1 could upregulate Cx43 expression to attenuate depression. However, whether the ubiquitination of Cx43 is the specific correlation between depression and inflammation, and how Rg1 ameliorates neuroinflammation to attenuate depression, are still under investigation. In in vivo experiments, Rg1 treatment significantly ameliorated depression-like behaviors in rats subjected to chronic unpredictable stress (CUS). Moreover, these CUS rats treated with Rg1 exhibited attenuated neuroinflammation, together with the suppression of Cx43 ubiquitination. In in vitro experiments, Rg1 reduced the secretion of inflammatory cytokines and the ubiquitination of Cx43 in lipopolysaccharide-induced glial cells. Furthermore, treatment with ubiquitin-proteasome inhibitor MG132 suppressing the ubiquitination of Cx43 ameliorated lipopolysaccharide-induced neuroinflammation. The results suggest that Rg1 attenuates depression-like behavioral performances in CUS-exposed rats; and the main mechanism of the antidepressant-like effects of Rg1 appears to involve protection against neuroinflammation via suppression of Cx43 ubiquitination. In conclusion, Rg1 could ameliorate neuroinflammation via suppression of Cx43 ubiquitination to attenuate depression, which represents the perspective of an innovative therapy of Rg1 in the treatment of inflammation-associated depression.

Assessment of changes in autophagic vesicles in human immune cell lines exposed to nano particles

Background

Safe and rational development of nanomaterials for clinical translation requires the assessment of potential biocompatibility. Autophagy, a critical homeostatic pathway intrinsically linked to cellular health and inflammation, has been shown to be affected by nanomaterials. It is, therefore, important to be able to assess possible interactions of nanomaterials with autophagic processes.

Results

CEM (T cell), Raji (B lymphocyte), and THP-1 (human monocyte) cell lines were subject to treatment with rapamycin and chloroquine, known to affect the autophagic process, in order to evaluate cell line-specific responses. Flow cytometric quantification of a fluorescent autophagic vacuole stain showed that maximum observable effects (105%, 446%, and 149% of negative controls) were achieved at different exposure durations (8, 6, and 24 h for CEM, Raji, and THP-1, respectively). THP-1 was subsequently utilised as a model to assess the autophagic impact of a small library of nanomaterials. Association was observed between hydrodynamic size and autophagic impact (r² = 0.11, p = 0.004). An ELISA for p62 confirmed the greatest impact by 10 nm silver nanoparticles, abolishing p62, with 50 nm silica and 180 nm polystyrene also lowering p62 to a significant degree (50%, 74%, and 55%, respectively, p < 0.05).

Conclusions

This data further supports the potential for a variety of nanomaterials to interfere with autophagic processes which, in turn, may result in altered cellular function and viability. The association of particle size with impact on autophagy now warrants further investigation.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00648-8.

IIIM-941, a Stilbene Derivative Inhibits NLRP3 Inflammasome Activation by Inducing Autophagy

Aberrant activation of NLRP3 inflammasome has been implicated in several inflammatory diseases. Autophagy is one of the primary mechanisms that regulate NLRP3 inflammasome activity. In this study, we attempted to target NLRP3 inflammasome activity by a synthetic compound IIIM-941. We found that IIIM-941 inhibits ATP induced NLRP3 inflammasome by induction of autophagy through AMPK pathway in bone marrow derived macrophages (BMDMs) and J774A.1 cells. It was interesting to observe that IIIM-941 did not show any inhibitory activity against LPS induced pro-inflammatory cytokines TNF-α and IL-6. The anti-NLRP3 activity of IIIM-941 was significantly reversed when we attempted to block autophagy by using either pharmacological inhibitor bafilomycin A1or by using siRNA against AMPK. Further, we found that IIIM-941 downregulated the expression of NLRP3 and prevented the oligomerization of ASC to exert its anti-NLRP3 inflammasome effect in J774A.1 cells. We validated inhibitory activity of IIIM-941 against NLRP3 in three different mice models. The anti-inflammatory effect of IIIM-941 was highly significant in ATP induced peritoneal inflammation model. IIIM-941 was similarly effective in suppressing MSU induced IL-1β in the air pouch model of inflammation without affecting the levels of TNF-α and IL-6. Finally, oral efficacy of IIIM-941 was also proved in MSU indued foot paw edema model of inflammation in mice at 10 and 20 mg/kg (b.w.). The compounds like IIIM-941 can be explored further for the development of therapies against diseases such as Alzheimer's disease and Parkinson's disease, where hampered autophagy and NLRP3 activation play a crucial role in the pathological development.

Identification of a Shrimp E3 Ubiquitin Ligase TRIM50-Like Involved in Restricting White Spot Syndrome Virus Proliferation by Its Mediated Autophagy and Ubiquitination

Most tripartite motif (TRIM) family proteins are critical components of the autophagy machinery and play important roles in host defense against viral pathogens in mammals. However, the roles of TRIM proteins in autophagy and viral infection have not been studied in lower invertebrates, especially crustaceans. In this study, we first identified a TRIM50-like gene from Penaeus monodon (designated PmTRIM50-like), which, after a white spot syndrome virus (WSSV) challenge, was significantly upregulated at the mRNA and protein levels in the intestine and hemocytes. Knockdown of PmTRIM50-like led to an increase in the WSSV quantity in shrimp, while its overexpression led to a decrease compared with the controls. Autophagy can be induced by WSSV or rapamycin challenge and has been shown to play a positive role in restricting WSSV replication in P. monodon. The mRNA and protein expression levels of PmTRIM50-like significantly increased with the enhancement of rapamycin-induced autophagy. The autophagy activity induced by WSSV or rapamycin challenge could be inhibited by silencing PmTRIM50-like in shrimp. Further studies showed that rapamycin failed to induce autophagy or inhibit WSSV replication after knockdown of PmTRIM50-like. Moreover, pull-down and in vitro ubiquitination assays demonstrated that PmTRIM50-like could interact with WSSV envelope proteins and target them for ubiquitination in vitro. Collectively, this study demonstrated that PmTRIM50-like is required for autophagy and is involved in restricting the proliferation of WSSV through its ubiquitination. This is the first study to report the role of a TRIM family protein in virus infection and host autophagy in crustaceans.

HIV-1 Nef counteracts autophagy restriction by enhancing the association between BECN1 and its inhibitor BCL2 in a PRKN-dependent manner

Macroautophagy/autophagy is an auto-digestive pro-survival pathway activated in response to stress to target cargo for lysosomal degradation. In recent years, autophagy has become prominent as an innate antiviral defense mechanism through multiple processes, such as targeting virions and viral components for elimination. These exciting findings have encouraged studies on the ability of autophagy to restrict HIV. However, the role of autophagy in HIV infection remains unclear. Whereas some reports indicate that autophagy is detrimental for HIV, others have claimed that HIV deliberately activates this pathway to increase its infectivity. Moreover, these contrasting findings seem to depend on the cell type investigated. Here, we show that autophagy poses a hurdle for HIV replication, significantly reducing virion production. However, HIV-1 uses its accessory protein Nef to counteract this restriction. Previous studies have indicated that Nef affects autophagy maturation by preventing the fusion between autophagosomes and lysosomes. Here, we uncover that Nef additionally blocks autophagy initiation by enhancing the association between BECN1 and its inhibitor BCL2, and this activity depends on the cellular E3 ligase PRKN. Remarkably, the ability of Nef to counteract the autophagy block is more frequently observed in pandemic HIV-1 and its simian precursor SIVcpz infecting chimpanzees than in HIV-2 and its precursor SIVsmm infecting sooty mangabeys. In summary, our findings demonstrate that HIV-1 is susceptible to autophagy restriction and define Nef as the primary autophagy antagonist of this antiviral process.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin, beta; ATG16L1: autophagy related 16 like 1; BCL2: bcl2 apoptosis regulator; BECN1: beclin 1; cDNA: complementary DNA; EGFP: enhanced green fluorescence protein; ER: endoplasmic reticulum; Gag/p55: group-specific antigen; GFP: green fluorescence protein; GST: glutathione S transferase; HA: hemagglutinin; HIV: human immunodeficiency virus; IP: immunoprecipitation; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; Nef: negative factor; PRKN: parkin RBR E3 ubiquitin ligase; PtdIns3K: phosphatidylinositol 3 kinase; PtdIns3P: phosphatidylinositol 3 phosphate; PTM: post-translational modification; RT-qPCR: reverse transcription followed by quantitative PCR; RUBCN: rubicon autophagy regulator; SEM: standard error of the mean; SERINC3: serine incorporator 3; SERINC5: serine incorporator 5; SIV: simian immunodeficiency virus; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; UVRAG: UV radiation resistance associated gene; VSV: vesicular stomatitis virus; ZFYVE1/DFCP1: zinc finger FYVE-type containing 1.

Molecular chaperone function of stress inducible Hsp70 is critical for intracellular multiplication of Toxoplasma gondii

Intracellular pathogens like Toxoplasma gondii often target proteins and pathways critical for host cell survival and stress response. Molecular chaperones encoded by the evolutionary conserved Heat shock proteins (Hsps) maintain proteostasis and are vital to cell survival following exposure to any form of stress. A key protein of this family is Hsp70, an ATP-driven molecular chaperone, which is stress inducible and often indiscernible in normal cells. Role of this protein with respect to intracellular survival and multiplication of protozoan parasite like T. gondii remains to be examined. We find that T. gondii infection upregulates expression of host Hsp70. Hsp70 selective inhibitor 2-phenylethynesulfonamide (PES) attenuates intracellular T. gondii multiplication. Biotinylated PES confirms selective interaction of this small molecule inhibitor with Hsp70. We show that PES acts by disrupting Hsp70 chaperone function which leads to dysregulation of host autophagy. Silencing of host Hsp70 underscores its importance for intracellular multiplication of T. gondii, however, attenuation achieved using PES is not completely attributable to host Hsp70 indicating the presence of other intracellular targets of PES in infected host cells. We find that PES is also able to target T. gondii Hsp70 homologue which was shown using PES binding assay. Detailed molecular docking analysis substantiates PES targeting of TgHsp70 in addition to host Hsp70. While establishing the importance of protein quality control in infection, this study brings to the fore a unique opportunity of dual targeting of host and parasite Hsp70 demonstrating how structural conservation of these proteins may be exploited for therapeutic design.

The propagation of HSV-1 in high autophagic activity

Autophagy is an intracellular process involving double-membrane vacuoles that ultimately merge with the lysosomes and play a key role in the inhibition of herpessimplex virus 1 (HSV-1) proliferation. This virus is an agent of some lethal neuronal diseases like encephalitis. HSV-1 requires the expression of its latent proteins, such as ICP34.5, to promote cell infection, which disrupts the autophagy process. In this study, we aimed to evaluate the effect of autophagy induction on HSV-1 replication in host cells at the early and late stages of its replication. Furthermore, we explored the consequences of autophagy induction before and after cell infection.Cells were transfected through Beclin-1-expressing plasmids. Autophagy induction was performed with microtubule-associated protein 1 light chain 3 (LC3-II) as an autophagosome formation marker by using flow cytometry. In the first stage, HSV-1 was inoculated into transfected cells 18 hours post-transfection. Next, viral DNA was extracted 18 and 48 hours post-infection, and eventually viral copies per milliliter were calculated through real-time polymerase chain reaction (PCR). For the second stage, the plasmid containing Beclin-1 was transfected to the cells following virus inoculation to examine the influence of autophagy induction after cell infection.Study results have shown that in neuroblastoma cells autophagy activation reduces virus yield from 4×10 ⁵ copies/ml (control sample) to 9×10 ⁴ copies/ml at 24 h postinfection and viral load after 48 h declines up to 1×10 ⁶ copies/ml, which is less than that of the control sample about 5 logs. However, in HeLa cells, we observed a significant reduction in autophagy induction with reducing HSV-1 propagation. Despite these results, HSV-1 proliferation in both cell types increased and these viruses were able to maintain their ability to propagate even in high autophagic activity. Hyperactivation of autophagy can only slow the rate of virus replication. This study may provide new insight into the effect of autophagy on HSV-1 replication.

Autophagy Takes Center Stage as a Possible Cancer Hallmark

Cancer remains one of the leading causes of death worldwide, despite significant advances in cancer research and improvements in anticancer therapies. One of the major obstacles to curing cancer is the difficulty of achieving the complete annihilation of resistant cancer cells. The resistance of cancer cells may not only be due to intrinsic factors or factors acquired during the evolution of the tumor but may also be caused by chemotherapeutic treatment failure. Conversely, autophagy is a conserved cellular process in which intracellular components, such as damaged organelles, aggregated or misfolded proteins and macromolecules, are degraded or recycled to maintain cellular homeostasis. Importantly, autophagy is an essential mechanism that plays a key role in tumor initiation and progression. Depending on the cellular context and microenvironmental conditions, autophagy acts as a double-edged sword, playing a role in inducing apoptosis or promoting cell survival. In this review, we propose several scenarios in which autophagy could contribute to cell survival or cell death. Moreover, a special focus on novel promising targets and therapeutic strategies based on autophagic resistant cells is presented.

VHSV IVb infection and autophagy modulation in the rainbow trout gill epithelial cell line RTgill-W1

Autophagy modulation influences the success of intracellular pathogens, and an understanding of the mechanisms involved might offer practical options to reduce the impact of infectious disease. Viral haemorrhagic septicaemia virus (VHSV) can cause high mortality and economic loss in some commercial fish species. VHSV IVb was used to infect a rainbow trout gill cell line, RTgill-W1, followed by the treatment of the cells with different autophagy-modulating reagents. LC3II protein using Western blot was significantly (p < .05) decreased for two days following VHSV infection, and immunofluorescence confirmed that LC3II-positive intracytoplasmic puncta were also decreased. Infection with VHSV resulted in significantly decreased expression of the autophagy-related (Atg) genes atg4, at12, atg13 and becn1 after one day using quantitative PCR. Both viral gene copy number and VHSV N protein were significantly decreased by treating the cells with autophagy-blocking (chloroquine) and autophagy-inhibiting reagents (deoxynivalenol and 3-methyladenine) after three days, while autophagy induction (restricted nutrition and rapamycin) had limited effect. Only treatment of RTgill-W1 with deoxynivalenol resulted in a significant increase in expression of type I interferon. Therefore, the suppression of autophagy initially occurs after VHSV IVb infection, but the modulation of autophagy can also inhibit VHSV IVb infection in RTgill-W1 after three days.

Regulation of cytochrome P450 enzyme activity and expression by nitric oxide in the context of inflammatory disease

Many hepatic cytochrome P450 enzymes and their associated drug metabolizing activities are down-regulated in disease states, and much of this has been associated with inflammatory cytokines and their signaling pathways. One such pathway is the induction of inducible nitric oxide synthase (NOS2) and generation of nitric oxide (NO) in many tissues and cells including the liver and hepatocytes. Experiments in the 1990s demonstrated that NO could bind to and inhibit P450 enzymes, and suggested that inhibition of NOS could attenuate, and NO generation could mimic, the down-regulation by inflammatory stimuli of not only P450 catalytic activities but also of mRNA expression and protein levels of certain P450 enzymes. This review will summarize and examine the evidence that NO functionally inhibits and down-regulates P450 enzymes in vivo and in vitro, with a particular focus on the mechanisms by which these effects are achieved.

The Roles of Autophagy and Senescence in the Tumor Cell Response to Radiation

Radiation is a critical pillar in cancer therapeutics, exerting its anti-tumor DNA-damaging effects through various direct and indirect mechanisms. Radiation has served as an effective mode of treatment for a number of cancer types, providing both curative and palliative treatment; however, resistance to therapy persists as a fundamental limitation. While cancer cell death is the ideal outcome of any anti-tumor treatment, radiation induces several responses, including apoptotic cell death, mitotic catastrophe, autophagy and senescence, where autophagy and senescence may promote cell survival. In most cases, autophagy, a conventionally cytoprotective mechanism, is a "first" responder to damage incurred from chemotherapy and radiation treatment. The paradigm developed on the premise that autophagy is cytoprotective in nature has provided the rationale for current clinical trials designed with the goal of radiosensitizing cancer cells through the use of autophagy inhibitors; however, these have failed to produce consistent results. Delving further into pre-clinical studies, autophagy has actually been shown to take diverse, sometimes opposing, forms, such as acting in a cytotoxic or nonprotective fashion, which may be partially responsible for the inconsistency of clinical outcomes. Furthermore, autophagy can have both pro- and anti-tumorigenic effects, while also having an important immune modulatory function. Senescence often occurs in tandem with autophagy, which is also the case with radiation. Radiation-induced senescence is frequently followed by a phase of proliferative recovery in a subset of cells and has been proposed as a tumor dormancy model, which can contribute to resistance to therapy and possibly also disease recurrence. Senescence induction is often accompanied by a unique secretory phenotype that can either promote or suppress immune functions, depending on the expression profile of cytokines and chemokines. Novel therapeutics selectively cytotoxic to senescent cells (senolytics) may prove to prolong remission by delaying disease recurrence in patients. Accurate assessment of primary responses to radiation may provide potential targets that can be manipulated for therapeutic benefit to sensitize cancer cells to radiotherapy, while sparing normal tissue.

Minocycline Induces Autophagy and Inhibits Cell Proliferation in LPS-Stimulated THP-1 Cells

Excessive activation and proliferation of inflammatory cell and uncontrolled release of cytokines and chemokines, also known as cytokine storm, is considered to be the main cause of sepsis. Accumulating evidence has indicated that autophagy may play an important role in regulating immune response and controlling excessive inflammation. Recent studies have showed that minocycline has immunomodulatory effects on cytokine and chemokine production. It has also been reported that minocycline can induce autophagy, suggesting that autophagy may be involved in the process of minocycline regulating inflammation and immune response. However, the precise mechanism is unclear. In the present study, we used enzyme-linked immunosorbent assays (ELISA) to measure the production of cytokines following minocycline treatment of lipopolysaccharide- (LPS-) stimulated THP-1 cells. Western blotting analysis was performed to confirm autophagy and the mTOR signal pathway. Cell proliferation was measured by WST-1 cell proliferation assay. We demonstrated that LPS induced autophagy in a tumor necrosis factor- (TNF-) α-mediated manner, and simultaneously, LPS induced the release of TNF-α to trigger inflammation and activated mammalian target of rapamycin (mTOR) to potentiate cell proliferation. Minocycline, which induces autophagy by inhibiting mTOR, suppresses cytokine production and cell proliferation and protects THP-1 cells from LPS toxicity. Further study demonstrated that there might be an intimate crosstalk between the inhibitor kappa B kinase (IKK)/nuclear factor-kappa B (NF-κB) signaling pathway and autophagy flux in modification of inflammatory responses. In addition, rapamycin, the mTOR inhibitor, has cooperative effect with minocycline on suppression of TNF-α release and induction of autophagy by repressing mTOR. Our data brought a novel clue to evaluate minocycline using as a potential therapeutic medicine for sepsis.

Unraveling the regulatory role of endoplasmic-reticulum-associated degradation in tumor immunity

During malignant transformation and cancer progression, tumor cells face both intrinsic and extrinsic stress, endoplasmic reticulum (ER) stress in particular. To survive and proliferate, tumor cells use multiple stress response pathways to mitigate ER stress, promoting disease aggression and treatment resistance. Among the stress response pathways is ER-associated degradation (ERAD), which consists of multiple components and steps working together to ensure protein quality and quantity. In addition to its established role in stress responses and tumor cell survival, ERAD has recently been shown to regulate tumor immunity. Here we summarize current knowledge on how ERAD promotes protein degradation, regulates immune cell development and function, participates in antigen presentation, exerts paradoxical roles on tumorigenesis and immunity, and thus impacts current cancer therapy. Collectively, ERAD is a critical protein homeostasis pathway intertwined with cancer development and tumor immunity. Of particular importance is the need to further unveil ERAD's enigmatic roles in tumor immunity to develop effective targeted and combination therapy for successful treatment of cancer.

Mechanisms underlying astrocytic connexin-43 autophagy degradation during cerebral ischemia injury and the effect on neuroinflammation and cell apoptosis

Connexin-43 (Cx43) is the most abundant gap junction protein in the nervous system. It enables cell communication and has important physiological roles including ion transport and substrate exchange, all of which have been implicated in cerebral ischemia injury. Our previous in vitro and in vivo studies have demonstrated that Cx43 is internalized and degraded during ischemia stress. However, the significance of ischemia-induced degradation of Cx43 remains unclear. Herein, we demonstrated that Cx43 degradation during ischemia injury is mediated by selective autophagy; additionally, we identified two related autophagy receptors-OPTN and NDP52. Cx43 degradation during ischemia requires its phosphorylation and ubiquitination, which are mediated by PKC, Src kinases, and ubiquitin kinase PINK1. Using point mutagenesis, we identified three phosphorylation sites underlying Cx43 autophagy degradation under ischemic stress. Cx43 degradation inhibition promoted the transition of astrocytes from a pro-inflammatory to an anti-inflammatory status, based on the levels of IL-10 and TNF in ischemia. Knockdown or accelerated degradation of Cx43 protected astrocytes from apoptosis under ischemic stress. These findings elucidate the underlying mechanism of astrocytic Cx43 autophagic degradation during ischemia. The study has identified potentially novel therapeutic strategies against ischemic stroke and evidence of crosstalk between autophagic degradation of Cx43, astrocytic apoptosis, and neuroinflammation.

Bazedoxifene Suppresses Intracellular Mycobacterium tuberculosis Growth by Enhancing Autophagy

Since current strategies for the treatment of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) have low efficacy and highly negative side effects, research on new treatments including novel drugs is essential for curing drug-resistant tuberculosis. Host-directed therapy (HDT) has become a promising idea to modulate host cell responses to enhance protective immunity against pathogens. Bazedoxifene (BZA), which belongs to a new generation of SERMs, shows the ability to inhibit the growth of M. tuberculosis in macrophages and is associated with autophagy. Our findings reveal a previously unrecognized antibacterial function of BZA. We propose that the mechanism of SERMs action in macrophages may provide a new potential measure for host-directed therapies against TB.

Tuberculosis (TB) is still the leading killer caused by Mycobacterium tuberculosis infection. There is a clear need for new treatment strategy against TB. It has been reported that tamoxifen, known as a selective estrogen receptor modulator (SERM), exhibits antimycobacterial activity and inhibits M. tuberculosis growth in macrophages. However, it remains unknown whether such antimicrobial activity is a general property of all SERMs and how it works. In this study, we identified that bazedoxifene (BZA), a newer SERM, inhibits intracellular M. tuberculosis growth in macrophages. BZA treatment increases autophagosome formation and LC3B-II protein expression in M. tuberculosis-infected macrophages. We further demonstrated that the enhancement of autophagy by BZA is dependent on increased reactive oxygen species (ROS) production and associated with phosphorylation of Akt/mTOR signaling. In summary, our data reveal a previously unappreciated antimicrobial function of BZA and suggest that future investigation focusing on the mechanism of action of SERMs in macrophages may lead to new host-directed therapies against TB.

IMPORTANCE Since current strategies for the treatment of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) have low efficacy and highly negative side effects, research on new treatments including novel drugs is essential for curing drug-resistant tuberculosis. Host-directed therapy (HDT) has become a promising idea to modulate host cell responses to enhance protective immunity against pathogens. Bazedoxifene (BZA), which belongs to a new generation of SERMs, shows the ability to inhibit the growth of M. tuberculosis in macrophages and is associated with autophagy. Our findings reveal a previously unrecognized antibacterial function of BZA. We propose that the mechanism of SERMs action in macrophages may provide a new potential measure for host-directed therapies against TB.

The effects of Aeromonas hydrophila infection on oxidative stress, nonspecific immunity, autophagy, and apoptosis in the common carp

Although the toxicity of Aeromonas hydrophila infection to common carp has been characterized, the mechanisms underlying this toxicity have not been fully explored. The present study assessed the effects of A. hydrophila infection on oxidative stress, nonspecific immunity, autophagy, and apoptosis in the common carp (Cyprinus carpio). We measured the effects of 7.55 × 10⁵ CFU/mL and 4.87 × 10⁷ CFU/mL A. hydrophila on carp after 1, 3, 5, and 7 d of infection. GSH and SOD activity levels in the serum, liver, intestine, and gills generally increased during the early stage of infection, but significantly decreased (P < 0.05) on the seventh day. In addition, MDA levels were significantly increased throughout the infection period. The activity levels of ACP, AKP, and LZM in the liver and intestine increased on the first day after infection, then decreased on the fifth and seventh days. The mRNA expressions levels of the autophagy-associated genes atg12, atg5, LC3-II, and BECN1 in the liver, kidney, and brain substantially increased on the third day after infection (P < 0.05), while mTOR was significantly downregulated on the first and third days (P < 0.05). Western blot analysis indicated that the ratio of LC3B-ǁ/LC3B-ǀ significantly increased (P < 0.05) on days 3 and 5 post infection. Furthermore, the apoptosis-related gene Bcl-2 was significantly (P < 0.05) upregulated in the liver, kidney, and brain of the treatment group on the first and third days, while caspase3 was significantly downregulated (P < 0.05). In conclusion, our results demonstrate that A. hydrophila infection causes oxidative stress, stimulates nonspecific immune reactions, and results in autophagy in the common carp, possibly initiating apoptosis in the late stage of infection. The results of this study provide new insights into the mechanism of A. hydrophila infection in carp.

Autophagy Induced by Simian Retrovirus Infection Controls Viral Replication and Apoptosis of Jurkat T Lymphocytes

Autophagy and apoptosis are two important evolutionarily conserved host defense mechanisms against viral invasion and pathogenesis. However, the association between the two pathways during the viral infection of T lymphocytes remains to be elucidated. Simian type D retrovirus (SRV) is an etiological agent of fatal simian acquired immunodeficiency syndrome (SAIDS), which can display disease features that are similar to acquired immunodeficiency syndrome in humans. In this study, we demonstrate that infection with SRV-8, a newly isolated subtype of SRV, triggered both autophagic and apoptotic pathways in Jurkat T lymphocytes. Following infection with SRV-8, the autophagic proteins LC3 and p62/SQSTM1 interacted with procaspase-8, which might be responsible for the activation of the caspase-8/-3 cascade and apoptosis in SRV-8-infected Jurkat cells. Our findings indicate that autophagic responses to SRV infection of T lymphocytes promote the apoptosis of T lymphocytes, which, in turn, might be a potential pathogenetic mechanism for the loss of T lymphocytes during SRV infection.

Genetic polymorphisms of ATG16L1 and IRGM genes in Malaysian patients with Crohn's disease

OBJECTIVE

To investigate the association between genetic polymorphisms in ATG16L1 and IRGM genes and the development of Crohn's disease (CD) in Malaysian patients.

METHODS

Altogether 335 participants were recruited, including 85 patients with CD and 250 unrelated healthy controls, and their informed consent was obtained. Genomic DNA was extracted via a conventional phenol-chloroform extraction method. Six single nucleotide polymorphisms (SNPs) in ATG16L1 and IRGM genes were genotyped using TaqMan SNP genotyping assays. Associations between SNP and CD were determined using Fisher's exact test, odds ratio, and 95% confidence interval. Statistical power and the Hardy-Weinberg equilibrium were also calculated.

RESULTS

Two SNPs (rs2241880 and rs6754677) in the ATG16L1 gene were significantly associated with the onset of CD in the Malaysian population. The A allele and homozygous A/A genotype of the rs2241880 A/G polymorphism were protective against CD in the overall Malaysian and Malay population. The G allele and homozygous G/G genotype of the rs6754677 G/A polymorphism were protective in the Indian population, whereas the homozygous A/A genotype showed a risk of developing CD. The homozygous G/G genotype of IRGM rs11747270 was significantly present in the controls. However, this significance was not observed in a race-stratified analysis. All three ATG16L1 SNPs were associated with inflamed terminal ileum. IRGM rs4958847 and rs11747270 increased the risk of developing arthritis in patients with CD.

CONCLUSION

We found a significant association between SNP, which are located in autophagy-related genes, and CD in a Malaysian population.

Excessive ER-phagy mediated by the autophagy receptor FAM134B results in ER stress, the unfolded protein response, and cell death in HeLa cells

Autophagy is typically a prosurvival cellular process that promotes the turnover of long-lived proteins and damaged organelles, but it can also induce cell death. We have previously reported that the small molecule Z36 induces autophagy along with autophagic cell death in HeLa cells. In this study, we analyzed differential gene expression in Z36-treated HeLa cells and found that Z36-induced endoplasmic reticulum-specific autophagy (ER-phagy) results in ER stress and the unfolded protein response (UPR). This result is in contrast to the common notion that autophagy is generally activated in response to ER stress and the UPR. We demonstrate that Z36 up-regulates the expression levels of FAM134B, LC3, and Atg9, which together mediate excessive ER-phagy, characterized by forming increased numbers of autophagosomes with larger sizes. We noted that the excessive ER-phagy accelerates ER degradation and impairs ER homeostasis and thereby triggers ER stress and the UPR as well as ER-phagy-dependent cell death. Interestingly, overexpression of FAM134B alone in HeLa cells is sufficient to impair ER homeostasis and cause ER stress and cell death. These findings suggest a mechanism involving FAM134B activity for ER-phagy to promote cell death.

Transmembrane Protein 39A Promotes the Replication of Encephalomyocarditis Virus via Autophagy Pathway

Encephalomyocarditis virus (EMCV) causes encephalitis, myocarditis, neuropathy, reproductive disorders, and diabetes in animals. EMCV is known to induce cell autophagy; however, the molecular mechanisms underlying this remain unclear. Here, we show that the type III-transmembrane protein, transmembrane protein 39A (TMEM39A), plays a critical role in EMCV replication. We showed that EMCV GS01 strain infection upregulated TMEM39A expression. Importantly, EMCV induced autophagy in a range of host cells. The autophagy chemical inhibitor, 3-MA, inhibited EMCV replication and reduced TMEM39A expression. This is the first study demonstrating TMEM39A promoting the replication of EMCV via autophagy. Overall, we show that TMEM39A plays a positive regulatory role in EMCV proliferation and that TMEM39A expression is dependent on the autophagy pathway.

Downregulation of microRNA-30a-5p contributes to the replication of duck enteritis virus by regulating Beclin-1-mediated autophagy

BACKGROUND

MicroRNAs (miRNAs) is increasingly recognized as an important element in regulating virus-host interactions. Our previous results showed that cellular miR-30a-5p was significantly downregulated after duck enteritis virus (DEV) infection cell. However, whehter or not the miR-30a-5p is involved in DEV infection has not been known.

METHODS

Quantitative reverse-transcription PCR (qRT-PCR) was used to measure the expression levels of miRNAs(miR-30a-5p) and Beclin-1 mRNA. The miR-30a-5p - Beclin-1 target interactions were determined by Dual luciferase reporter assay (DLRA). Western blotting was utilized to analyze Beclin-1-mediated duck embryo fibroblast (DEF) cells autophagy activity. DEV titers were estimated by the median tissue culture infective dose (TCID50).

RESULTS

The miR-30a-5p was significantly downregulated and the Beclin-1 mRNA was significantly upregulated in DEV-infected DEF cells. DLRA confirmed that miR-30a-5p directly targeted the 3'- UTR of the Beclin-1 gene. Overexpression of miR-30a-5p significantly reduced the expression level of Beclin-1protein (p < 0.05), leading to the decrease of Beclin-1-mediated autophagy activity, which ultimately suppressed DEV replication (P < 0.05). Whereas transfection of miR-30a-5p inhibitor increased Beclin-1-mediated autophagy and triggered DEV replication during the whole process of DEV infection (P < 0.01).

CONCLUSIONS

This study shows that miR-30a-5p can inhibit DEV replication through reducing autophagy by targeting Beclin-1. These findings suggest a new insight into virus-host interaction during DEV infection and provide a potential new antiviral therapeutic strategy against DEV infection.