Autophagy and the immune system

Endoplasmic Reticulum Stress Induced Synthesis of a Novel Viral Factor Mediates Efficient Replication of Genotype-1 Hepatitis E Virus

Hepatitis E virus (HEV) causes acute hepatitis in many parts of the world including Asia, Africa and Latin America. Though self-limiting in normal individuals, it results in ~30% mortality in infected pregnant women. It has also been reported to cause acute and chronic hepatitis in organ transplant patients. Of the seven viral genotypes, genotype-1 virus infects humans and is a major public health concern in South Asian countries. Sporadic cases of genotype-3 and 4 infection in human and animals such as pigs, deer, mongeese have been reported primarily from industrialized countries. Genotype-5, 6 and 7 viruses are known to infect animals such as wild boar and camel, respectively. Genotype-3 and 4 viruses have been successfully propagated in the laboratory in mammalian cell culture. However, genotype-1 virus replicates poorly in mammalian cell culture and no other efficient model exists to study its life cycle. Here, we report that endoplasmic reticulum (ER) stress promotes genotype-1 HEV replication by inducing cap-independent, internal initiation mediated translation of a novel viral protein (named ORF4). Importantly, ORF4 expression and stimulatory effect of ER stress inducers on viral replication is specific to genotype-1. ORF4 protein sequence is mostly conserved among genotype-1 HEV isolates and ORF4 specific antibodies were detected in genotype-1 HEV patient serum. ORF4 interacted with multiple viral and host proteins and assembled a protein complex consisting of viral helicase, RNA dependent RNA polymerase (RdRp), X, host eEF1α1 (eukaryotic elongation factor 1 isoform-1) and tubulinβ. In association with eEF1α1, ORF4 stimulated viral RdRp activity. Furthermore, human hepatoma cells that stably express ORF4 or engineered proteasome resistant ORF4 mutant genome permitted enhanced viral replication. These findings reveal a positive role of ER stress in promoting genotype-1 HEV replication and pave the way towards development of an efficient model of the virus.

Hepatitis E virus (HEV) is one of the most common causes of acute and sporadic viral hepatitis. It is a small positive strand RNA virus, which is transmitted through the feco-oral route. Owing to lack of sanitation and unavailibility of safe drinking water, populations of developing and resource starved countries are prone towards HEV infection. Recent reports also indicate HEV induced acute and chronic hepatitis in organ transplant patients. Another peculiar characteristic of HEV is attributed to its ability to cause high mortality (~30%) in infected pregnant women. Even after 30 years of discovery of the virus, little information exists regarding viral life cycle and replication machinery. HEV is divided into seven genotypes. Genotype-3 and 4 viruses infect humans and a few animals (such as pigs, deer, mongeese) and have been reported from industrialized countries. Genotype-3 and 4 viruses have been successfully propagated in the laboratory in mammalian cell culture. However, genotype-1 virus, which is known to infect human and is a major public health concern in south Asian countries, replicates poorly in mammalian cell culture and no other efficient model exists to investigate the viral life cycle. With the goal of developing an efficient laboratory model of genotype-1 HEV, we attempted to identify a permissive cellular condition that would allow efficient viral replication in human hepatoma cells. Here, we report that endoplasmic reticulum stress inducing agents promote genotype-1 HEV replication by initiating cap-independent, internal translation mediated synthesis of a novel viral factor, which we have named ORF4. Further investigations revealed that ORF4 is expressed only in genotype-1 and it acts by interacting with multiple viral and host proteins and cooperates with host eEF1α1 (eukaryotic elongation factor 1 isoform 1) to control the activity of viral RNA dependent RNA polymerase. Moreover, a proteasome resistant ORF4 mutant significantly enhanced viral replication. Thus, our study identifies an optimal condition required for efficient replication of genotype-1 HEV and dissects out the molecular mechanism governing that. Data presented here will be instrumental in developing an efficient model of the virus.

New Potential Pharmacological Functions of Chinese Herbal Medicines via Regulation of Autophagy

Autophagy is a universal catabolic cellular process for quality control of cytoplasm and maintenance of cellular homeostasis upon nutrient deprivation and environmental stimulus. It involves the lysosomal degradation of cellular components such as misfolded proteins or damaged organelles. Defects in autophagy are implicated in the pathogenesis of diseases including cancers, myopathy, neurodegenerations, infections and cardiovascular diseases. In the recent decade, traditional drugs with new clinical applications are not only commonly found in Western medicines, but also highlighted in Chinese herbal medicines (CHM). For instance, pharmacological studies have revealed that active components or fractions from Chaihu (Radix bupleuri), Hu Zhang (Rhizoma polygoni cuspidati), Donglingcao (Rabdosia rubesens), Hou po (Cortex magnoliae officinalis) and Chuan xiong (Rhizoma chuanxiong) modulate cancers, neurodegeneration and cardiovascular disease via autophagy. These findings shed light on the potential new applications and formulation of CHM decoctions via regulation of autophagy. This article reviews the roles of autophagy in the pharmacological actions of CHM and discusses their new potential clinical applications in various human diseases.

Roles of Autophagy and Autophagy-Related Proteins in Antifungal Immunity

Autophagy was initially characterized as a process to digest cellular components, including damaged cell organelles or unused proteins. However, later studies showed that autophagy plays an important role to protect hosts from microbial infections. Accumulating evidences showed the contribution of autophagy itself and autophagy-related proteins (ATGs) in the clearance of bacteria, virus, and parasites. A number of studies also revealed the molecular mechanisms by which autophagy is initiated and developed. Furthermore, it is now understood that some ATGs are shared between two distinct processes; autophagy and LC3-associated phagocytosis (LAP). Thus, our understanding on autophagy has been greatly enhanced in the last decade. By contrast, roles of autophagy and ATGs in fungal infections are still elusive relative to those in bacterial and viral infections. Based on limited numbers of reports, ATG-mediated host responses appear to significantly vary depending on invading fungal species. In this review, we discuss how autophagy and ATGs are involved in antifungal immune responses based on recent discoveries.

Carboxyl-functionalized polyurethane nanoparticles with immunosuppressive properties as a new type of anti-inflammatory platform

The interaction of nanoparticles (NPs) with the body immune system is critically important for their biomedical applications. Most NPs stimulate the immune response of macrophages. Here we show that synthetic polyurethane nanoparticles (PU NPs, diameter 34-64 nm) with rich surface COO(-) functional groups (zeta potential -70 to -50 mV) can suppress the immune response of macrophages. The specially-designed PU NPs reduce the gene expression levels of proinflammatory cytokines (IL-1β, IL-6, and TNF-α) for endotoxin-treated macrophages. The PU NPs increase the intracellular calcium of macrophages (4.5-6.5 fold) and activate autophagy. This is in contrast to the autophagy dysfunction generally observed upon NP exposure. These PU NPs may further decrease the nuclear factor-κB-related inflammation via autophagy pathways. The immunosuppressive activities of PU NPs can prevent animal death by inhibiting the macrophage recruitment and proinflammatory responses, confirmed by an in vivo zebrafish model. Therefore, the novel biodegradable PU NPs demonstrate COO(-) dependent immunosuppressive properties without carrying any anti-inflammatory agents. This study suggests that NP surface chemistry may regulate the immune response, which provides a new paradigm for potential applications of NPs in anti-inflammation and immunomodulation.

Regulation of autophagy by E3 ubiquitin ligase RNF216 through BECN1 ubiquitination

Autophagy is an evolutionarily conserved biological process involved in an array of physiological and pathological events. Without proper control, autophagy contributes to various disorders, including cancer and autoimmune and inflammatory diseases. It is therefore of vital importance that autophagy is under careful balance. Thus, additional regulators undoubtedly deepen our understanding of the working network, and provide potential therapeutic targets for disorders. In this study, we found that RNF216 (ring finger protein 216), an E3 ubiquitin ligase, strongly inhibits autophagy in macrophages. Further exploration demonstrates that RNF216 interacts with BECN1, a key regulator in autophagy, and leads to ubiquitination of BECN1, thereby contributing to BECN1 degradation. RNF216 was involved in the ubiquitination of lysine 48 of BECN1 through direct interaction with the triad (2 RING fingers and a DRIL [double RING finger linked]) domain. We further showed that inhibition of autophagy through overexpression of RNF216 in alveolar macrophages promotes Listeria monocytogenes growth and distribution, while knockdown of RNF216 significantly inhibited these outcomes. These effects were confirmed in a mouse model of L. monocytogenes infection, suggesting that manipulating RNF216 expression could be a therapeutic approach. Thus, our study identifies a novel negative regulator of autophagy and suggests that RNF216 may be a target for treatment of inflammatory diseases.

Epigenetics and miRNA during bacteria-induced host immune responses

Various cellular processes including the pathogen-specific immune responses, host-pathogen interactions and the related evasion mechanisms rely on the ability of the immune cells to be reprogrammed accurately and in many cases instantaneously. In this context, the exact functions of epigenetic and miRNA-mediated regulation of genes, coupled with recent advent in techniques that aid such studies, make it an attractive field for research. Here, we review examples that involve the epigenetic and miRNA control of the host immune system during infection with bacteria. Interestingly, many pathogens utilize the epigenetic and miRNA machinery to modify and evade the host immune responses. Thus, we believe that global epigenetic and miRNA mapping of such host-pathogen interactions would provide key insights into their cellular functions and help to identify various determinants for therapeutic value.

The Role of Autophagy in Lupus Nephritis

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease characterized by the generation of immune responses to self-antigens. Lupus nephritis is one of the most common and severe complications in SLE patients. Though the pathogenesis of lupus nephritis has been studied extensively, unresolved questions are still left and new therapeutic methods are needed for disease control. Autophagy is a conserved catabolic process through which cytoplasmic constituents can be degraded in lysosome and reused. Autophagy plays vital roles in maintaining cell homeostasis and is involved in the pathogenesis of many diseases. In particular, autophagy can affect almost all parts of the immune system and is involved in autoimmune diseases. Based on genetic analysis, cell biology, and mechanism studies of the classic and innovative therapeutic drugs, there are growing lines of evidence suggesting the relationship between autophagy and lupus nephritis. In the present review, we summarize the recent publications investigating the relationship between autophagy and lupus nephritis and provide a new perspective towards the pathogenesis of lupus nephritis.

Autophagy in Helicobacter pylori Infection and Related Gastric Cancer

BACKGROUND

Autophagy, a degradation pathway in which cytoplasmic content is engulfed and degraded by lysosomal hydrolases, plays a pivotal role in infection and inflammation. Given that defects in autophagy lead to increased susceptibility to infection, we investigated the role of autophagy in Helicobacter pylori-related gastric cancer (GC).

MATERIALS AND METHODS

Gene expression of 84 molecules was examined through quantitative real-time PCR in gastric epithelial cells (AGS) and macrophages (THP-1) upon exposure to H. pylori GC026 (GC) and 26695 (gastritis). Further, ATG16L1 rs2241880, IRGM rs13361189, and IRGM rs4958847, polymorphisms that have been investigated in relation to H. pylori infection or GC in Caucasians, were detected by MALDI-TOF mass spectrometry in 304 ethnic Chinese (86 noncardia GC cases/218 functional dyspepsia controls).

RESULTS

Gene expression analyses showed twenty-eight molecules involved in vesicle nucleation, elongation, and maturation to be significantly down-regulated in H. pylori GC026-challenged AGS cells. Further, core autophagy proteins and autophagy regulators were differentially expressed in H. pylori-challenged THP-1-derived macrophages. Analyses of the selected polymorphisms showed that ATG16L1 rs2241880 increased the risk of GC (OR: 2.38, 95% CI: 1.34-4.24) and H. pylori infection (OR: 1.49, 95% CI: 1.02-2.16) while IRGM rs4958847 decreased GC risk (OR: 0.26, 95% CI: 0.09-0.74) in ethnic Chinese, these effect sizes being especially strong in H. pylori-infected individuals (ATG16L1 rs2241880 and IRGM rs13361189).

CONCLUSIONS

Our findings indicate that highly virulent H. pylori strains markedly modulate autophagy in the host cell. Further, for the first time, autophagy polymorphisms were associated with GC in Chinese, a high GC-risk population.

Diphenyldifluoroketone EF24 Suppresses Pro-inflammatory Interleukin-1 receptor 1 and Toll-like Receptor 4 in lipopolysaccharide-stimulated dendritic cells

Background

Unresolved and prolonged inflammation is a pathological basis of many disorders such as cancer and multiple organ failure in shock. Interleukin-1 receptor (IL-1R) superfamily consists of IL-1R1 and pathogen pattern recognition receptor toll-like receptor-4 (TLR4) which, upon ligand binding, initiate pro-inflammatory signaling. The study objective was to investigate the effect of a diphenyldifluoroketone EF24 on the expression of IL-1R1 and TLR4 in lipopolysaccharide (LPS)-stimulated dendritic cells (DCs).

Methods

Immortalized murine bone marrow-derived JAWS II dendritic cells (DC) were challenged with LPS (100 ng/ml) for 4 h. The LPS-stimulated DCs were treated with 10 μM of EF24 for 1 h. The expression levels of IL-1R1 and TLR4 were monitored by RT-PCR, immunoblotting, and confocal microscopy. The effect of EF24 on the viability and cell cycle of DCs was examined by lactate dehydrogenase assay and flow cytometry, respectively.

Results

EF24 treatment suppressed the LPS-induced TLR4 and IL-1R1 expression in DCs. However, the expression levels of IL-1RA and IL-1R2 were not influenced by either LPS or EF24 treatments. These effects of EF24 were associated with a decrease in LPS-induced expression of phospho-NF-kB p65, indicative of its role in the transcriptional control of IL-1R superfamily members. We did not find any significant effect of EF24 on the proliferation or cell cycle of DCs.

Conclusions

The results suggest that EF24 influences IL-1R superfamily signaling pathway in ways that could have salutary effects in inflammation. The pluripotent anti-inflammatory actions of EF24 warrant further investigation of EF24 in inflammatory conditions of systemic nature.

Recent insights into the role of autophagy in the pathogenesis of rheumatoid arthritis

Autophagy appears to play a dual role in eukaryotic cells. It manifests cytoprotective effects through the regulation of catabolic processes and the clearance of pathogens; however, a correlation between autophagy and the pathogenesis of autoimmune/autoinflammatory conditions has recently been described. Autophagy has emerged as a mediator in the pathogenesis of RA. Autophagy may regulate apoptosis resistance and hyperplasia in synovial fibroblasts, promote osteoclastogenesis and stimulate osteoclast-mediated bone resorption through the delivery of citrullinated peptides to MHC compartments, which results in the activation of the innate and adaptive immune response, thereby resulting in RA. Given the likely importance of autophagy in the pathogenesis of RA, here we reviewed the detailed mechanisms concerning the pathogenicity of autophagy and autophagy proteins in RA.

The Legionella Anti-autophagy Effector RavZ Targets the Autophagosome via PI3P- and Curvature-Sensing Motifs

Autophagy is a conserved membrane transport pathway used to destroy pathogenic microbes that access the cytosol of cells. The intracellular pathogen Legionella pneumophila interferes with autophagy by delivering an effector protein, RavZ, into the host cytosol. RavZ acts by cleaving membrane-conjugated Atg8/LC3 proteins from pre-autophagosomal structures. Its remarkable efficiency allows minute quantities of RavZ to block autophagy throughout the cell. To understand how RavZ targets pre-autophagosomes and specifically acts only on membrane-associated Atg8 proteins, we elucidated its structure. Revealed is a catalytic domain related in fold to Ulp family deubiquitinase-like enzymes and a C-terminal PI3P-binding module. RavZ targets the autophagosome via the PI3P-binding module and a catalytic domain helix, and it preferentially binds high-curvature membranes, intimating localization to highly curved domains in autophagosome intermediate membranes. RavZ-membrane interactions enhance substrate affinity, providing a mechanism for interfacial activation that also may be used by host autophagy proteins engaging only lipidated Atg8 proteins.

Autophagy is involved in oral rAAV/Aβ vaccine-induced Aβ clearance in APP/PS1 transgenic mice

The imbalance between ß-amyloid (Aß) generation and clearance plays a fundamental role in the pathogenesis of Alzheimer's disease (AD). The sporadic form of AD is characterized by an overall impairment in Aß clearance. Immunotherapy targeting Aß clearance is believed to be a promising approach and is under active clinical investigation. Autophagy is a conserved pathway for degrading abnormal protein aggregates and is crucial for Aß clearance. We previously reported that oral vaccination with a recombinant AAV/Aß vaccine increased the clearance of Aß from the brain and improved cognitive ability in AD animal models, while the underlying mechanisms were not well understood. In this study, we first demonstrated that oral vaccination with rAAV/Aß decreased the p62 level and up-regulated the LC3B-II/LC3B-I ratio in APP/PS1 mouse brain, suggesting enhanced autophagy. Further, inhibition of the Akt/mTOR pathway may account for autophagy enhancement. We also found increased anti-Aß antibodies in the sera of APP/PS1 mice with oral vaccination, accompanied by elevation of complement factors C1q and C3 levels in the brain. Our results indicate that autophagy is closely involved in oral vaccination-induced Aß clearance, and modulating the autophagy pathway may be an important strategy for AD prevention and intervention.

Modulation of inflammation by autophagy: Consequences for human disease

Autophagy and inflammation are 2 fundamental biological processes involved in both physiological and pathological conditions. Through its crucial role in maintaining cellular homeostasis, autophagy is involved in modulation of cell metabolism, cell survival, and host defense. Defective autophagy is associated with pathological conditions such as cancer, autoimmune disease, neurodegenerative disease, and senescence. Inflammation represents a crucial line of defense against microorganisms and other pathogens, and there is increasing evidence that autophagy has important effects on the induction and modulation of the inflammatory reaction; understanding the balance between these 2 processes may point to important possibilities for therapeutic targeting. This review focuses on the crosstalk between autophagy and inflammation as an emerging field with major implications for understanding the host defense on the one hand, and for the pathogenesis and treatment of immune-mediated diseases on the other hand.

Small-molecule enhancers of autophagy modulate cellular disease phenotypes suggested by human genetics

Studies of human genetics and pathophysiology have implicated the regulation of autophagy in inflammation, neurodegeneration, infection, and autoimmunity. These findings have motivated the use of small-molecule probes to study how modulation of autophagy affects disease-associated phenotypes. Here, we describe the discovery of the small-molecule probe BRD5631 that is derived from diversity-oriented synthesis and enhances autophagy through an mTOR-independent pathway. We demonstrate that BRD5631 affects several cellular disease phenotypes previously linked to autophagy, including protein aggregation, cell survival, bacterial replication, and inflammatory cytokine production. BRD5631 can serve as a valuable tool for studying the role of autophagy in the context of cellular homeostasis and disease.

Resveratrol inhibits NLRP3 inflammasome activation by preserving mitochondrial integrity and augmenting autophagy

The NLRP3 inflammasome is a caspase-1-containing multi-protein complex that controls the release of IL-1β and plays important roles in the development of inflammatory disease. Here, we report that resveratrol, a polyphenolic compound naturally produced by plants, inhibits NLRP3 inflammasome-derived IL-1β secretion and pyroptosis in macrophages. Resveratrol inhibits the activation step of the NLRP3 inflammasome by suppressing mitochondrial damage. Resveratrol also induces autophagy by activating p38, and macrophages treated with an autophagy inhibitor are resistant to the suppressive effects of resveratrol. In addition, resveratrol administration mitigates glomerular proliferation, glomerular sclerosis, and glomerular inflammation in a mouse model of progressive IgA nephropathy. These findings were associated with decreased renal mononuclear leukocyte infiltration, reduced renal superoxide anion levels, and inhibited renal NLRP3 inflammasome activation. Our data indicate that resveratrol suppresses NLRP3 inflammasome activation by preserving mitochondrial integrity and by augmenting autophagy.

Circulating Hemocytes from Larvae of the Japanese Rhinoceros Beetle Allomyrina dichotoma (Linnaeus) (Coleoptera: Scarabaeidae) and the Cellular Immune Response to Microorganisms

Hemocytes of the last larva of the Japanese rhinoceros beetle A. dichotoma (Linnaeus) (Coleoptera: Scarabaeidae) were classified as granulocytes, plasmatocytes, oenocytoids, spherulocytes, prohemocytes, and adipohemocytes. Among these cell types, only the granulocytes became immunologically activated with obvious morphological changes, displaying large amoeba-like, lobopodia-like, and fan-like structures. In addition, their cytoplasmic granules became larger and greatly increased in number. To explore whether these granules could be immunologically generated as phagosomes, total hemocytes were stained with LysoTracker. Greater than 90% of the granulocytes retained the LysoTracker dye at 4 h post-bacterial infection. In flow cytometry analysis, the red fluorescent signal was highly increased at 4 h post-bacterial infection (60.36%) compared to controls (5.08%), as was confirmed by fluorescent microscopy. After 12 h post-infection, these signals returned to basal levels. The uptake of pathogens by granulocytes rapidly triggered the translocation of the microtubule-associated protein 1 light chain 3 alpha (LC3) to the phagosome, which may result in enhanced pathogen killing.

Alternaria extract activates autophagy that induces IL-18 release from airway epithelial cells

Alternaria alternata is a major outdoor allergen that causes allergic airway diseases. Alternaria extract (ALT-E) has been shown to induce airway epithelial cells to release IL-18 and thereby initiate Th2-type responses. We investigated the underlying mechanisms involved in IL-18 release from ALT-E-stimulated airway epithelial cells. Normal human bronchial epithelial cells and A549 human lung adenocarcinoma cells were stimulated with ALT-E in the presence of different inhibitors of autophagy or caspases. IL-18 levels in culture supernatants were measured by ELISA. The numbers of autophagosomes, an LC3-I to LC3-II conversion, and p62 degradation were determined by immunofluorescence staining and immunoblotting. 3-methyladenine and bafilomycin, which inhibit the formation of preautophagosomal structures and autolysosomes, respectively, suppressed ALT-E-induced IL-18 release by cells, whereas caspase 1 and 8 inhibitors did not. ALT-E-stimulation increased autophagosome formation, LC-3 conversion, and p62 degradation in airway epithelial cells. LPS-stimulation induced the LC3 conversion in A549 cells, but did not induce IL-18 release or p62 degradation. Unlike LPS, ALT-E induced airway epithelial cells to release IL-18 via an autophagy dependent, caspase 1 and 8 independent pathway. Although autophagy has been shown to negatively regulate canonical inflammasome activity in TLR-stimulated macrophages, our data indicates that this process is an unconventional mechanism of IL-18 secretion by airway epithelial cells.

Herpes Simplex Virus-1 Fine-Tunes Host's Autophagic Response to Infection: A Comprehensive Analysis in Productive Infection Models

Herpes simplex virus-1 (HSV-1) infection causes severe conditions, with serious complications, including corneal blindness from uncontrolled ocular infections. An important cellular defense mechanism against HSV-1 infection is autophagy. The autophagic response of the host cell was suggested to be regulated by HSV-1. In this study, we performed a detailed analysis of autophagy in multiple HSV-1-targeted cell types, and under various infection conditions that recapitulate a productive infection model. We found that autophagy was slightly inhibited in one cell type, while in other cell types autophagy maintained its basal levels mostly unchanged during productive infection. This study refines the concept of HSV-1-mediated autophagy regulation to imply either inhibition, or prevention of activation, of the innate immune pathway.

Autophagy stimulation abrogates herpes simplex virus-1 infection

Herpes simplex virus-1 (HSV-1) is a double-stranded DNA virus that causes life-long infections. HSV-1 infections may lead to herpetic stromal keratitis that may advance to corneal blindness. HSV-1 infections can also cause fatal conditions, such as herpes encephalitis, or neonatal disease. A major virulence mechanism of HSV-1 is the control of autophagy, an innate immune defense strategy that could otherwise degrade viral particles. Here, to investigate a new mechanism for antiviral therapy, we tested the effect of various autophagy inducers (physiological and pharmacological) on infection. Autophagy stimulation was confirmed to significantly suppress HSV-1 infection in various cell types, without affecting cell viability. This study establishes the importance of autophagy for regulating HSV-1 infection, and provides a proof-of-principle evidence for a novel antiviral mechanism.

B cell Rab7 mediates induction of activation-induced cytidine deaminase expression and class-switching in T-dependent and T-independent antibody responses

Class switch DNA recombination (CSR) is central to the maturation of the Ab response because it diversifies Ab effector functions. Like somatic hypermutation, CSR requires activation-induced cytidine deaminase (AID), whose expression is restricted to B cells, as induced by CD40 engagement or dual TLR-BCR engagement (primary CSR-inducing stimuli). By constructing conditional knockout Igh(+/C)γ(1-cre)Rab7(fl/fl) mice, we identified a B cell-intrinsic role for Rab7, a small GTPase involved in intracellular membrane functions, in mediating AID induction and CSR. Igh(+/C)γ(1-cre)Rab7(fl/fl) mice displayed normal B and T cell development and were deficient in Rab7 only in B cells undergoing Igh(C)γ(1-cre) Iγ1-Sγ1-Cγ1-cre transcription, as induced--like Igh germline Iγ1-Sγ1-Cγ1 and Iε-Sε-Cε transcription--by IL-4 in conjunction with a primary CSR-inducing stimulus. These mice could not mount T-independent or T-dependent class-switched IgG1 or IgE responses while maintaining normal IgM levels. Igh(+/C)γ(1-cre)Rab7(fl/fl) B cells showed, in vivo and in vitro, normal proliferation and survival, normal Blimp-1 expression and plasma cell differentiation, as well as intact activation of the noncanonical NF-κB, p38 kinase, and ERK1/2 kinase pathways. They, however, were defective in AID expression and CSR in vivo and in vitro, as induced by CD40 engagement or dual TLR1/2-, TLR4-, TLR7-, or TLR9-BCR engagement. In Igh(+/C)γ(1-cre)Rab7(fl/fl) B cells, CSR was rescued by enforced AID expression. These findings, together with our demonstration that Rab7-mediated canonical NF-κB activation, as critical to AID induction, outline a novel role of Rab7 in signaling pathways that lead to AID expression and CSR, likely by promoting assembly of signaling complexes along intracellular membranes.

Live bacterial vaccine vectors: an overview

Genetically attenuated microorganisms, pathogens, and some commensal bacteria can be engineered to deliver recombinant heterologous antigens to stimulate the host immune system, while still offering good levels of safety. A key feature of these live vectors is their capacity to stimulate mucosal as well as humoral and/or cellular systemic immunity. This enables the use of different forms of vaccination to prevent pathogen colonization of mucosal tissues, the front door for many infectious agents. Furthermore, delivery of DNA vaccines and immune system stimulatory molecules, such as cytokines, can be achieved using these special carriers, whose adjuvant properties and, sometimes, invasive capacities enhance the immune response. More recently, the unique features and versatility of these vectors have also been exploited to develop anti-cancer vaccines, where tumor-associated antigens, cytokines, and DNA or RNA molecules are delivered. Different strategies and genetic tools are constantly being developed, increasing the antigenic potential of agents delivered by these systems, opening fresh perspectives for the deployment of vehicles for new purposes. Here we summarize the main characteristics of the different types of live bacterial vectors and discuss new applications of these delivery systems in the field of vaccinology.

Palmitate induces endoplasmic reticulum stress and autophagy in mature adipocytes: implications for apoptosis and inflammation

Endoplasmic reticulum (ER) stress and inflammation induced by obesity lead to adipocyte dysfunction, with the impairment of the insulin pathway. Recent studies have indicated that understanding the physiological role of autophagy is of great significance. In the present study, an in vitro model was used in which 3T3-L1 adipocytes were pre-loaded with palmitate (PA) to generate artificially hypertrophied mature adipocytes. PA induced an autophagic flux, determined by an increased microtubule-associated protein 1 light chain 3 (LC3)-II formation, as shown by western blot analysis and fluorescence microscopy, and was confirmed using transmission electron microscopy (TEM). Using TEM and western blot analysis, we observed increased ER stress in response to PA, as indicated by the increased levels of the ER stress markers, BiP, activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP), and the phosphoralytion of eukaryotic translation initiation factor 2α and c-Jun N-terminal kinase (JNK). Of note, we observed that the PA-induced ER stress occurred prior to the activation of autophagy. We confirmed that autophagy was induced in response to JNK-dependent ER stress, as autophagy was suppressed by treatment with the ER stress inhibitor, 4-phenyl butyrate (4-PBA), and the JNK inhibitor, SP600125. Upon the inhibition of autophagy using chloroquine (CQ), we observed exacerbated ER stress and an increased level of cell death. Importantly, to determine whether autophagy is linked to inflammation, the autophagy inhibitor, 3-methyladenine (3-MA) was used. The inhibition of autophagy led to a further increase in the PA-induced expression of monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6). Consistently, such an increase was also observed following treatment with SP600125. In conclusion, our data indicate that PA elicits a ER stress-JNK-autophagy axis, and that this confers a pro-survival effect against PA-induced cell death and stress in hypertrophied adipocytes. The JNK-dependent activation of autophagy diminishes PA-induced inflammation. Therefore, the stimulation of autophagy may become a method with which to attenuate adipocyte dysfunction and inflammation.

New insights into the interaction of Mycobacterium tuberculosis and human macrophages

Mycobacterium tuberculosis is a facultative intracellular pathogen. It infects macrophages where it avoids elimination by interfering with host defense mechanisms. Until recently, it was assumed that the acidification of phagosomes is the major strategy of macrophages to eliminate M. tuberculosis. However, there is emerging evidence demonstrating that human macrophages are equipped with additional antimicrobial effector functions. Specifically, autophagy, efferocytosis and antimicrobial peptides have been identified as mechanisms to restrict mycobacterial proliferation. Here we review recent findings on effector functions of human macrophages and mechanisms of the pathogen to interfere with them.

STAT3 in arsenic lung carcinogenicity

We recently found that the chronic sterile inflammation contributes to arsenic lung tumorigenesis which is inhibited by autophagy. STAT3 regulates the interaction between inflammation and autophagy. STAT3 may also play a critical role in mediating the crosstalk between lung epithelial cells and their microenvironment, including immune cells, during arsenic lung carcinogenesis.

Rapamycin improves palmitate-induced ER stress/NF κ B pathways associated with stimulating autophagy in adipocytes

Obesity-induced endoplasmic reticulum (ER) stress and inflammation lead to adipocytes dysfunction. Autophagy helps to adapt to cellular stress and involves in regulating innate inflammatory response. In present study, we examined the activity of rapamycin, a mTOR kinase inhibitor, against endoplasmic reticulum stress and inflammation in adipocytes. An in vitro model was used in which 3T3-L1 adipocytes were preloaded with palmitate (PA) to generate artificial hypertrophy mature adipocytes. Elevated autophagy flux and increased number of autophagosomes were observed in response to PA and rapamycin treatment. Rapamycin attenuated PA-induced PERK and IRE1-associated UPR pathways, evidenced by decreased protein levels of eIF2α phosphorylation, ATF4, CHOP, and JNK phosphorylation. Inhibiting autophagy with chloroquine (CQ) exacerbated these ER stress markers, indicating the role of autophagy in ameliorating ER stress. In addition, cotreatment of CQ abolished the anti-ER stress effects of rapamycin, which confirms the effect of rapamycin on ERs is autophagy-dependent. Furthermore, rapamycin decreased PA-induced nuclear translocation of NFκB P65 subunit, thereby NFκB-dependent inflammatory cytokines MCP-1 and IL-6 expression and secretion. In conclusion, rapamycin attenuated PA-induced ER stress/NFκB pathways to counterbalance adipocytes stress and inflammation. The beneficial of rapamycin in this context partly depends on autophagy. Stimulating autophagy may become a way to attenuate adipocytes dysfunction.

Atg5 but not Atg7 in dendritic cells enhances IL-2 and IFN-γ production by Toxoplasma gondii-reactive CD4+ T cells

The autophagy proteins (Atg) modulate not only innate but also adaptive immunity against pathogens. We examined the role of dendritic cell Atg5 and Atg7 in the production of IL-2 and IFN-γ by Toxoplasma gondii-reactive CD4(+) T cells. T. gondii-reactive mouse CD4(+) T cells exhibited unimpaired production of IL-2 and IFN-γ when stimulated with Atg7-deficient mouse dendritic cells that were infected with T. gondii or pulsed with T. gondii lysate antigens. In marked contrast, dendritic cells deficient in Atg5 induced diminished CD4(+) T cell production of IL-2 and IFN-γ. This defect was not accompanied by changes in costimulatory ligand expression on dendritic cells or impaired production of IL-12 p70, IL-1β or TNF-α. Knockdown of Irg6a in dendritic cells did not affect CD4(+) T cell cytokine production. These results indicate that Atg5 and Atg7 in dendritic cells play differential roles in the modulation of IL-2 and IFN-γ production by T. gondii-reactive CD4(+) T cells.

The role of autophagy in microbial infection and immunity

The autophagy pathway represents an evolutionarily conserved cell recycling process that is activated in response to nutrient deprivation and other stress signals. Over the years, it has been linked to an array of cellular functions. Equally, a wide range of cell-intrinsic, as well as extracellular, factors have been implicated in the induction of the autophagy pathway. Microbial infections represent one such factor that can not only activate autophagy through specific mechanisms but also manipulate the response to the invading microbe’s advantage. Moreover, in many cases, particularly among viruses, the pathway has been shown to be intricately involved in the replication cycle of the pathogen. Conversely, autophagy also plays a role in combating the infection process, both through direct destruction of the pathogen and as one of the key mediating factors in the host defense mechanisms of innate and adaptive immunity. Further, the pathway also plays a role in controlling the pathogenesis of infectious diseases by regulating inflammation. In this review, we discuss various interactions between pathogens and the cellular autophagic response and summarize the immunological functions of the autophagy pathway.

Autophagy, a major adaptation pathway shaping cancer cell death and anticancer immunity responses following photodynamic therapy

Autophagy is fundamentally a cytoprotective and pro-survival process yet studies have shown that it has an exceedingly contextual role in cancer biology; depending on the phase, location or type of oncogenic trigger and/or therapy, its role could fluctuate from pro- to anti-tumourigenic.

Essential role for autophagy during invariant NKT cell development

Autophagy is an evolutionarily conserved cellular homeostatic pathway essential for development, immunity, and cell death. Although autophagy modulates MHC antigen presentation, it remains unclear whether autophagy defects impact on CD1d lipid loading and presentation to invariant natural killer T (iNKT) cells and on iNKT cell differentiation in the thymus. Furthermore, it remains unclear whether iNKT and conventional T cells have similar autophagy requirements for differentiation, survival, and/or activation. We report that, in mice with a conditional deletion of the essential autophagy gene Atg7 in the T-cell compartment (CD4 Cre-Atg7(-/-)), thymic iNKT cell development--unlike conventional T-cell development--is blocked at an early stage and mature iNKT cells are absent in peripheral lymphoid organs. The defect is not due to altered loading of intracellular iNKT cell agonists; rather, it is T-cell-intrinsic, resulting in enhanced susceptibility of iNKT cells to apoptosis. We show that autophagy increases during iNKT cell thymic differentiation and that it developmentally regulates mitochondrial content through mitophagy in the thymus of mice and humans. Autophagy defects result in the intracellular accumulation of mitochondrial superoxide species and subsequent apoptotic cell death. Although autophagy-deficient conventional T cells develop normally, they show impaired peripheral survival, particularly memory CD8(+) T cells. Because iNKT cells, unlike conventional T cells, differentiate into memory cells while in the thymus, our results highlight a unique autophagy-dependent metabolic regulation of adaptive and innate T cells, which is required for transition to a quiescent state after population expansion.

Autophagy, inflammation and innate immunity in inflammatory myopathies

Autophagy has a large range of physiological functions and its dysregulation contributes to several human disorders, including autoinflammatory/autoimmune diseases such as inflammatory myopathies (IIMs). In order to better understand the pathogenetic mechanisms of these muscular disorders, we sought to define the role of autophagic processes and their relation with the innate immune system in the three main subtypes of IIM, specifically sporadic inclusion body myositis (sIBM), polymyositis (PM), dermatomyositis (DM) and juvenile dermatomyositis (JDM). We found that although the mRNA transcript levels of the autophagy-related genes BECN1, ATG5 and FBXO32 were similar in IIM and controls, autophagy activation in all IIM subgroups was suggested by immunoblotting results and confirmed by immunofluorescence. TLR4 and TLR3, two potent inducers of autophagy, were highly increased in IIM, with TLR4 transcripts significantly more expressed in PM and DM than in JDM, sIBM and controls, and TLR3 transcripts highly up-regulated in all IIM subgroups compared to controls. Co-localization between autophagic marker, LC3, and TLR4 and TLR3 was observed not only in sIBM but also in PM, DM and JDM muscle tissues. Furthermore, a highly association with the autophagic processes was observed in all IIM subgroups also for some TLR4 ligands, endogenous and bacterial HSP60, other than the high-mobility group box 1 (HMGB1). These findings indicate that autophagic processes are active not only in sIBM but also in PM, DM and JDM, probably in response to an exogenous or endogenous 'danger signal'. However, autophagic activation and regulation, and also interaction with the innate immune system, differ in each type of IIM. Better understanding of these differences may lead to new therapies for the different IIM types.

Autophagy as a pro-death pathway

The evolutionarily conserved catabolic process of autophagy involves the degradation of cytoplasmic components through lysosomal enzymes. Basal levels of autophagy maintain cellular homeostasis and under stress conditions high levels of autophagy are induced. It is often under such stress conditions that high levels of autophagy and cell death have been observed, leading to the idea that autophagy may act as an executioner of cell death. However the notion of autophagy as a cell death mechanism has been controversial and remains mechanistically undefined. There is now growing evidence that in specific contexts autophagy can indeed facilitate cell death. The pro-death role of autophagy is however complicated due to the extensive cross-talk between different signalling pathways. This review summarises the examples of where autophagy acts as a means of cell death and discusses the association of autophagy with the different cell death pathways.

Coronavirus membrane-associated papain-like proteases induce autophagy through interacting with Beclin1 to negatively regulate antiviral innate immunity

Autophagy plays important roles in modulating viral replication and antiviral immune response. Coronavirus infection is associated with the autophagic process, however, little is known about the mechanisms of autophagy induction and its contribution to coronavirus regulation of host innate responses. Here, we show that the membrane-associated papain-like protease PLP2 (PLP2-TM) of coronaviruses acts as a novel autophagy-inducing protein. Intriguingly, PLP2-TM induces incomplete autophagy process by increasing the accumulation of autophagosomes but blocking the fusion of autophagosomes with lysosomes. Furthermore, PLP2-TM interacts with the key autophagy regulators, LC3 and Beclin1, and promotes Beclin1 interaction with STING, the key regulator for antiviral IFN signaling. Finally, knockdown of Beclin1 partially reverses PLP2-TM's inhibitory effect on innate immunity which resulting in decreased coronavirus replication. These results suggested that coronavirus papain-like protease induces incomplete autophagy by interacting with Beclin1, which in turn modulates coronavirus replication and antiviral innate immunity.

Grouping annotations on the subcellular layered interactome demonstrates enhanced autophagy activity in a recurrent experimental autoimmune uveitis T cell line

Human uveitis is a type of T cell-mediated autoimmune disease that often shows relapse-remitting courses affecting multiple biological processes. As a cytoplasmic process, autophagy has been seen as an adaptive response to cell death and survival, yet the link between autophagy and T cell-mediated autoimmunity is not certain. In this study, based on the differentially expressed genes (GSE19652) between the recurrent versus monophasic T cell lines, whose adoptive transfer to susceptible animals may result in respective recurrent or monophasic uveitis, we proposed grouping annotations on a subcellular layered interactome framework to analyze the specific bioprocesses that are linked to the recurrence of T cell autoimmunity. That is, the subcellular layered interactome was established by the Cytoscape and Cerebral plugin based on differential expression, global interactome, and subcellular localization information. Then, the layered interactomes were grouping annotated by the ClueGO plugin based on Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases. The analysis showed that significant bioprocesses with autophagy were orchestrated in the cytoplasmic layered interactome and that mTOR may have a regulatory role in it. Furthermore, by setting up recurrent and monophasic uveitis in Lewis rats, we confirmed by transmission electron microscopy that, in comparison to the monophasic disease, recurrent uveitis in vivo showed significantly increased autophagy activity and extended lymphocyte infiltration to the affected retina. In summary, our framework methodology is a useful tool to disclose specific bioprocesses and molecular targets that can be attributed to a certain disease. Our results indicated that targeted inhibition of autophagy pathways may perturb the recurrence of uveitis.

Correlative light and electron microscopy imaging of autophagy in a zebrafish infection model

High-resolution imaging of autophagy has been used intensively in cell culture studies, but so far it has been difficult to visualize this process in detail in whole animal models. In this study we present a versatile method for high-resolution imaging of microbial infection in zebrafish larvae by injecting pathogens into the tail fin. This allows visualization of autophagic compartments by light and electron microscopy, which makes it possible to correlate images acquired by the 2 techniques. Using this method we have studied the autophagy response against Mycobacterium marinum infection. We show that mycobacteria during the progress of infection are frequently associated with GFP-Lc3-positive vesicles, and that 2 types of GFP-Lc3-positive vesicles were observed. The majority of these vesicles were approximately 1 μm in size and in close vicinity of bacteria, and a smaller number of GFP-Lc3-positive vesicles was larger in size and were observed to contain bacteria. Quantitative data showed that these larger vesicles occurred significantly more in leukocytes than in other cell types, and that approximately 70% of these vesicles were positive for a lysosomal marker. Using electron microscopy, it was found that approximately 5% of intracellular bacteria were present in autophagic vacuoles and that the remaining intracellular bacteria were present in phagosomes, lysosomes, free inside the cytoplasm or occurred as large aggregates. Based on correlation of light and electron microscopy images, it was shown that GFP-Lc3-positive vesicles displayed autophagic morphology. This study provides a new approach for injection of pathogens into the tail fin, which allows combined light and electron microscopy imaging in vivo and opens new research directions for studying autophagy process related to infectious diseases.

Characterization of the hemocytes in Larvae of Protaetia brevitarsis seulensis: involvement of granulocyte-mediated phagocytosis

Hemocytes are key players in the immune response against pathogens in insects. However, the hemocyte types and their functions in the white-spotted flower chafers, Protaetia brevitarsis seulensis (Kolbe), are not known. In this study, we used various microscopes, molecular probes, and flow cytometric analyses to characterize the hemocytes in P. brevitarsis seulensis. The circulating hemocytes were classified based on their size, morphology, and dye-staining properties into six types, including granulocytes, plasmatocytes, oenocytoids, spherulocytes, prohemocytes, and adipohemocytes. The percentages of circulating hemocyte types were as follows: 13% granulocytes, 20% plasmatocytes, 1% oenocytoids, 5% spherulocytes, 17% prohemocytes, and 44% adipohemocytes. Next, we identified the professional phagocytes, granulocytes, which mediate encapsulation and phagocytosis of pathogens. The granulocytes were immunologically or morphologically activated and phagocytosed potentially hazardous substances in vivo. In addition, we showed that the phagocytosis by granulocytes is associated with autophagy, and that the activation of autophagy could be an efficient way to eliminate pathogens in this system. We also observed a high accumulation of autophagic vacuoles in activated granulocytes, which altered their shape and led to autophagic cell death. Finally, the granulocytes underwent mitotic division thus maintaining their number in vivo.

Autophagy in antimicrobial immunity

Autophagy plays a key role in cellular homeostasis, responding to various environmental stresses. In particular, pathogen invasion leads to rapid induction of autophagy, which is critical for both innate and adaptive immune responses. In this review, we focus on the emerging molecular mechanisms of pathogen elimination by autophagy (a process known as xenophagy) and on the strategies developed by pathogens to subvert autophagy. We also address other functions of autophagy proteins in restricting pathogen invasion, independent of the formation of a canonical double-membrane autophagosome.

Autophagy regulates the therapeutic potential of mesenchymal stem cells in experimental autoimmune encephalomyelitis

Mesenchymal stem cell (MSC)-based therapy is a promising approach to treat various inflammatory disorders including multiple sclerosis. However, the fate of MSCs in the inflammatory microenvironment is largely unknown. Experimental autoimmune encephalomyelitis (EAE) is a well-studied animal model of multiple sclerosis. We demonstrated that autophagy occurred in MSCs during their application for EAE treatment. Inflammatory cytokines, e.g., interferon gamma and tumor necrosis factor, induced autophagy in MSCs synergistically by inducing expression of BECN1/Beclin 1. Inhibition of autophagy by knockdown of Becn1 significantly improved the therapeutic effects of MSCs on EAE, which was mainly attributable to enhanced suppression upon activation and expansion of CD4⁺ T cells. Mechanistically, inhibition of autophagy increased reactive oxygen species generation and mitogen-activated protein kinase 1/3 activation in MSCs, which were essential for PTGS2 (prostaglandin-endoperoxide synthase 2 [prostaglandin G/H synthase and cyclooxygenase]) and downstream prostaglandin E2 expression to exert immunoregulatory function. Furthermore, pharmacological treatment of MSCs to inhibit autophagy increased their immunosuppressive effects on T cell-mediated EAE. Our findings indicate that inflammatory microenvironment-induced autophagy downregulates the immunosuppressive function of MSCs. Therefore, modulation of autophagy in MSCs would provide a novel strategy to improve MSC-based immunotherapy.

Dectin-1 pathway activates robust autophagy-dependent unconventional protein secretion in human macrophages

Dectin-1 is a membrane-bound pattern recognition receptor for β-glucans, which are the main constituents of fungal cell walls. Detection of β-glucans by dectin-1 triggers an effective innate immune response. In this study, we have used a systems biology approach to provide the first comprehensive characterization of the secretome and associated intracellular signaling pathways involved in activation of dectin-1/Syk in human macrophages. Transcriptome and secretome analysis revealed that the dectin-1 pathway induced significant gene expression changes and robust protein secretion in macrophages. The enhanced protein secretion correlated only partly with increased gene expression. Bioinformatics combined with functional studies revealed that the dectin-1/Syk pathway activates both conventional and unconventional, vesicle-mediated, protein secretion. The unconventional protein secretion triggered by the dectin-1 pathway is dependent on inflammasome activity and an active autophagic process. In conclusion, our results reveal that unconventional protein secretion has an important role in the innate immune response against fungal infections.

Immune evasion strategies of pre-erythrocytic malaria parasites

Malaria is a mosquito-borne infectious disease of humans. It begins with a bite from an infected female Anopheles mosquito and leads to the development of the pre-erythrocytic and blood stages. Blood-stage infection is the exclusive cause of clinical symptoms of malaria. In contrast, the pre-erythrocytic stage is clinically asymptomatic and could be an excellent target for preventive therapies. Although the robust host immune responses limit the development of the liver stage, malaria parasites have also evolved strategies to suppress host defenses at the pre-erythrocytic stage. This paper reviews the immune evasion strategies of malaria parasites at the pre-erythrocytic stage, which could provide us with potential targets to design prophylactic strategies against malaria.

Autophagy mediates neutrophil responses to bacterial infection

Neutrophils constitute the first line of cellular defense against pathogens and autophagy is a fundamental cellular homeostasis pathway that operates with the intracellular degradation/recycling system. Induction of the autophagic process in neutrophils, in response to invading pathogens, constitutes a crucial mechanism in innate immunity. Exploration of autophagy has greatly progressed and diverse strategies have been reported for studying this molecular process in different biological systems; especially in infectious and inflammatory diseases. Furthermore, the role of autophagy in neutrophils, during pathogenic infection, continues to be of interest, due to the role of the cell in immunity function, its recruitment to the site of infection and its implication in inflammatory diseases. This review focuses on the known role of autophagy in neutrophils defence against pathogenic infections. A more detailed discussion will concern the recent findings highlighting the role of autophagy in inflammation and cell death in infected neutrophils.

Altered autophagy induction by sera from pregnant women with pre-eclampsia: a case-control study

OBJECTIVE

Mechanisms leading to pre-eclampsia remain incompletely defined. Autophagy is a conserved process necessary for cell survival under adverse conditions. We hypothesised that sera from women with healthy pregnancies and women with pre-eclampsia differed in autophagy induction.

DESIGN

A case-control study.

SETTING

Weill Cornell Medical College.

POPULATION

Twenty-four normotensive pregnant women and 20 women with pre-eclampsia.

METHODS

Sera were incubated with peripheral blood mononuclear cells (PBMCs) from female donors. After 48 hours the PBMCs were lysed and the intracellular concentration of p62 was determined by enzyme-linked immunosorbent assay (ELISA). Its concentration is inversely proportional to the extent of autophagy induction. Serum endoglin, interleukin 13 (IL-13), insulin-like growth factor 1 (IGF-1), and transforming growth factor β1 (TGF-β1) levels were quantitated by ELISA.

MAIN OUTCOME MEASURES

Differences in autophagy induction and serum mediator levels in the two groups.

RESULTS

Autophagy induction increased with gestational age in sera from normotensive women (P = 0.0045), but not in women with pre-eclampsia. In the presence of an autophagy inducer, the capacity for autophagy induction decreased with gestational age in sera from women with pre-eclampsia (P = 0.0235), but not from controls. Endoglin concentrations were positively associated with the extent of autophagy induction in controls only (P = 0.0141). There was no association between autophagy and serum IL-13, IGF-1, or TGF-β1 levels.

CONCLUSIONS

Sera from women with pre-eclampsia differ from normotensive women by their inability to induce autophagy as a function of gestational age.

Regulation of SIV antigen-specific CD4+ T cellular immunity via autophagosome-mediated MHC II molecule-targeting antigen presentation in mice

CD4+ T cell-mediated immunity has increasingly received attention due to its contribution in the control of HIV viral replication; therefore, it is of great significance to improve CD4+ T cell responses to enhance the efficacy of HIV vaccines. Recent studies have suggested that macroautophagy plays a crucial role in modulating adaptive immune responses toward CD4+ T cells or CD8+ T cells. In the present study, a new strategy based on a macroautophagy degradation mechanism is investigated to enhance CD4+ T cell responses against the HIV/SIV gag antigen. Our results showed that when fused to the autophagosome-associated LC3b protein, SIVgag protein can be functionally targeted to autophagosomes, processed by autophagy-mediated degradation in autolysosomes/lysosomes, presented to MHC II compartments and elicit effective potential CD4 T cell responses in vitro. Importantly, compared with the SIVgag protein alone, SIVgag-LC3b fusion antigen can induce a stronger antigen-specific CD4+ T cell response in mice, which is characterized by an enhanced magnitude and polyfunctionality. This study provides insight for the immunological modulation between viral and mammalian cells via autophagy, and it also presents an alternative strategy for the design of new antigens in the development of effective HIV vaccines.

Toxicity of carboxylated carbon nanotubes in endothelial cells is attenuated by stimulation of the autophagic flux with the release of nanomaterial in autophagic vesicles

Carbon nanotubes (CNTs) exhibit a number of unique properties that make them attractive for various nanomedicine applications including their intravascular use. Therefore, the vascular toxicity of CNTs is a critical safety concern and methods of CNTs toxicity modulation are of great interest. Here, we report that carboxylated multiwalled carbon nanotubes (MWCNTs) induce a decrease in viability of cultured human umbilical vein endothelial cells (HUVECs) associated with the profound accumulation of autophagosomes. This autophagosome accumulation was mTOR kinase independent and was caused by blockade of the autophagic flux rather than by activation of autophagy. Stimulation of the autophagic flux with 1nmol/L bafilomycin A1 attenuated the cytotoxicity of carboxylated MWCNTs in HUVECs and was associated with the extracellular release of the nanomaterial in autophagic microvesicles. Thus, pharmacological stimulation of the autophagic flux may represent a new method of cytoprotection against toxic effects of nanomaterials.

FROM THE CLINICAL EDITOR

This study investigates the mechanisms of toxicity of multiwalled carbon nanutubes on human endothelial cells, concluding that pharmacological stimulation of autophagic flux may represent a new method of cytoprotection against the toxic effects of these nanomaterials.

Emerging view of autophagy in systemic lupus erythematosus

Aberrations of both innate immunity and adaptive immunity in genetically predisposed individuals evoked by environmental factors are suggested to be implicated in pathophysiological processes of systemic lupus erythematosus (SLE). Autophagy, a degradation pathway in which cytoplasmic content is engulfed and degraded by the lysosome, has been recently demonstrated to be involved in multiple cytoplasmic homeostatic progresses and interact with nearly all parts of the innate and adaptive immune system. More recently, some lines of evidence from genetic, cell biology and model animal studies also suggests a pivotal role of autophagy in mediating the occurrence and development of SLE. We discuss and synthesize studies that have begun to demonstrate how autophagy cause and/or promote autoimmunity in SLE.