Hydatid fluid from Echinococcus granulosus induces autophagy in dendritic cells and promotes polyfunctional T-cell responses.

Parasites possess remarkable abilities to evade and manipulate the immune response of their hosts. Echinococcus granulosus is a parasitic tapeworm that causes cystic echinococcosis in animals and humans. The hydatid fluid released by the parasite is known to contain various immunomodulatory components that manipulate host´s defense mechanism. In this study, we focused on understanding the effect of hydatid fluid on dendritic cells and its impact on autophagy induction and subsequent T cell responses. Initially, we observed a marked downregulation of two C-type lectin receptors in the cell membrane, CLEC9A and CD205 and an increase in lysosomal activity, suggesting an active cellular response to hydatid fluid. Subsequently, we visualized ultrastructural changes in stimulated dendritic cells, revealing the presence of macroautophagy, characterized by the formation of autophagosomes, phagophores, and phagolysosomes in the cell cytoplasm. To further elucidate the underlying molecular mechanisms involved in hydatid fluid-induced autophagy, we analyzed the expression of autophagy-related genes in stimulated dendritic cells. Our results demonstrated a significant upregulation of beclin-1, atg16l1 and atg12, indicating the induction of autophagy machinery in response to hydatid fluid exposure. Additionally, using confocal microscopy, we observed an accumulation of LC3 in dendritic cell autophagosomes, confirming the activation of this catabolic pathway associated with antigen presentation. Finally, to evaluate the functional consequences of hydatid fluid-induced autophagy in DCs, we evaluated cytokine transcription in the splenocytes. Remarkably, a robust polyfunctional T cell response, with inhibition of Th2 profile, is characterized by an increase in the expression of il-6, il-10, il-12, tnf-α, ifn-γ and tgf-ß genes. These findings suggest that hydatid fluid-induced autophagy in dendritic cells plays a crucial role in shaping the subsequent T cell responses, which is important for a better understanding of host-parasite interactions in cystic echinococcosis.

Therapeutic Antitumor Efficacy of Cancer Stem Cell-Derived DRibble Vaccine on Colorectal Carcinoma.

Dendritic cell (DC)-based immunotherapy has been a promising strategy for colon cancer therapy, but the efficacy of dendritic cell vaccines is in part limited by immunogenicity of loaded antigens. In this study, we aimed to identify a putative tumor antigen that can generate or enhance anti-tumor immune responses against colon cancer. CD44+ colon cancer stem cells (CCSCs) were isolated from mouse colorectal carcinoma CT-26 cell cultures and induced to form defective ribosomal products-containing autophagosome-rich blebs (DRibbles) by treatment with rapamycin, bortezomib, and ammonium chloride. DRibbles were characterized by western blot and transmission electron microscopy. DCs generated from the mice bone marrow monocytes were cocultured with DRibbles, then surface markers of DCs were analyzed by flow cytometry. Meanwhile, the efficacy of DRibble-DCs was examined in vivo. Our results showed that CCSC-derived DRibbles upregulated CD80, CD86, major histocompatibility complex (MHC)-I, and MHC-II on DCs and induced proliferation of mouse splenic lymphocytes and CD8+ T cells. In a model of colorectal carcinoma using BALB/c mice with robust tumor growth and mortality, DC vaccine pulsed with CCSC-derived DRibbles suppressed tumor growth and extended survival. A lactate dehydrogenase test indicated a strong cytolytic activity of cytotoxic T-cells derived from mice vaccinated with CCSC-derived DRibbles against CT-26 cells. Furthermore, flow cytometry analyses showed that the percentages of IFN-γ-producing CD8+ T-cells were increased in SD-DC group compare with the other groups. These findings provide a rationale for novel immunotherapeutic anti-tumor approaches based on DRibbles derived from colon cancer stem cells.

Modulation of the mTOR pathway plays a central role in dendritic cell functions after Echinococcus granulosus antigen recognition.

Immune evasion is a hallmark of persistent echinococcal infection, comprising modulation of innate immune cells and antigen-specific T cell responses. However, recognition of Echinococcus granulosus by dendritic cells (DCs) is a key determinant of the host's response to this parasite. Given that mTOR signaling pathway has been described as a regulator linking metabolism and immune function in DCs, we reported for the first time in these cells, global translation levels, antigen uptake, phenotype, cytokine transcriptional levels, and splenocyte priming activity upon recognition of the hydatid fluid (HF) and the highly glycosylated laminar layer (LL). We found that LL induced a slight up-regulation of CD86 and MHC II in DCs and also stimulated the production of IL-6 and TNF-α. By contrast, HF did not increase the expression of any co-stimulatory molecules, but also down-modulated CD40 and stimulated the expression of the anti-inflammatory cytokine IL-10. Both parasitic antigens promoted protein synthesis through mTOR activation. The use of rapamycin decreased the expression of the cytokines tested, empowered the down-modulation of CD40 and also reduced splenocyte proliferation. Finally, we showed that E. granulosus antigens increase the amounts of LC3-positive structures in DCs which play critical roles in the presentation of these antigens to T cells.

Signaling through polymerization and degradation: Analysis and simulations of T cell activation mediated by Bcl10.

The adaptive immune system serves as a potent and highly specific defense mechanism against pathogen infection. One component of this system, the effector T cell, facilitates pathogen clearance upon detection of specific antigens by the T cell receptor (TCR). A critical process in effector T cell activation is transmission of signals from the TCR to a key transcriptional regulator, NF-κB. The transmission of this signal involves a highly dynamic process in which helical filaments of Bcl10, a key protein constituent of the TCR signaling cascade, undergo competing processes of polymeric assembly and macroautophagy-dependent degradation. Through computational analysis of three-dimensional, super-resolution optical micrographs, we quantitatively characterize TCR-stimulated Bcl10 filament assembly and length dynamics, and demonstrate that filaments become shorter over time. Additionally, we develop an image-based, bootstrap-like resampling method that demonstrates the preferred association between autophagosomes and both Bcl10-filament ends and punctate-Bcl10 structures, implying that autophagosome-driven macroautophagy is directly responsible for Bcl10 filament shortening. We probe Bcl10 polymerization-depolymerization dynamics with a stochastic Monte-Carlo simulation of nucleation-limited filament assembly and degradation, and we show that high probabilities of filament nucleation in response to TCR engagement could provide the observed robust, homogeneous, and tunable response dynamic. Furthermore, we demonstrate that the speed of filament disassembly preferentially at filament ends provides effective regulatory control. Taken together, these data suggest that Bcl10 filament growth and degradation act as an excitable system that provides a digital response mechanism and the reliable timing critical for T cell activation and regulatory processes.

Systematic functional analysis of SARS-CoV-2 proteins uncovers viral innate immune antagonists and remaining vulnerabilities.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evades most innate immune responses but may still be vulnerable to some. Here, we systematically analyze the impact of SARS-CoV-2 proteins on interferon (IFN) responses and autophagy. We show that SARS-CoV-2 proteins synergize to counteract anti-viral immune responses. For example, Nsp14 targets the type I IFN receptor for lysosomal degradation, ORF3a prevents fusion of autophagosomes and lysosomes, and ORF7a interferes with autophagosome acidification. Most activities are evolutionarily conserved. However, SARS-CoV-2 Nsp15 antagonizes IFN signaling less efficiently than the orthologs of closely related RaTG13-CoV and SARS-CoV-1. Overall, SARS-CoV-2 proteins counteract autophagy and type I IFN more efficiently than type II or III IFN signaling, and infection experiments confirm potent inhibition by IFN-γ and -λ1. Our results define the repertoire and selected mechanisms of SARS-CoV-2 innate immune antagonists but also reveal vulnerability to type II and III IFN that may help to develop safe and effective anti-viral approaches.

Inhibiting ATP6V0D2 Aggravates Liver Ischemia-Reperfusion Injury by Promoting NLRP3 Activation via Impairing Autophagic Flux Independent of Notch1/Hes1.

At present, liver ischemia-reperfusion (IR) injury is still a great challenge for clinical liver partial resection and liver transplantation. The innate immunity regulated by liver macrophages orchestrates the cascade of IR inflammation and acts as a bridge. As a specific macrophage subunit of vacuolar ATPase, ATP6V0D2 (V-ATPase D2 subunit) has been shown to promote the formation of autophagolysosome in vitro. Our research fills a gap which has existed in the study of inflammatory stress about the V-ATPase subunit ATP6V0D2 in liver macrophages. We first found that the expression of specific ATP6V0D2 in liver macrophages was upregulated with the induction of inflammatory cascade after liver IR surgery, and knockdown of ATP6V0D2 resulted in increased secretion of proinflammatory factors and chemokines, which enhanced activation of NLRP3 and aggravation of liver injury. Further studies found that the exacerbated activation of NLRP3 was related to the autophagic flux regulated by ATP6V0D2. Knocking down ATP6V0D2 impaired the formation of autophagolysosome and aggravated liver IR injury through nonspecific V-ATPase activation independent of V-ATPase-Notchl-Hesl signal axis. In general, we illustrated that the expression of ATP6V0D2 in liver macrophages was upregulated after liver IR, and by gradually promoting the formation of autophagolysosomes to increase autophagy flux to limit the activation of liver inflammation, this regulation is independent of the Notch1-Hes1 signal axis.

Impaired ATG16L-Dependent Autophagy Promotes Renal Interstitial Fibrosis in Chronic Renal Graft Dysfunction Through Inducing EndMT by NF-κB Signal Pathway.

Chronic renal graft dysfunction (CAD) is caused by multiple factors, including glomerular sclerosis, inflammation, interstitial fibrosis and tubular atrophy (IF/TA). However, the most prominent elements of CAD are IF/TA. Our studies have confirmed that endothelial-mesenchymal transition (EndMT) is an important source to allograft IF/TA. The characteristic of EndMT is the loss of endothelial marker and the acquisition of mesenchymal or fibroblastic phenotypes. Autophagy is an intracellular degradation pathway that is regulated by autophagy-related proteins and plays a vital role in many fibrotic conditions. However, whether or not autophagy contributes to fibrosis of renal allograft and how such mechanism occurs still remains unclear. Autophagy related 16 like gene (ATG16L) is a critical autophagy-related gene (ARG) necessary for autophagosome formation. Here, we first analyzed kidney transplant patient tissues from Gene Expression Omnibus (GEO) datasets and 60 transplant patients from our center. Recipients with stable kidney function were defined as non-CAD group and all patients in CAD group were histopathologically diagnosed with CAD. Results showed that ATG16L, as one significant differential ARG, was less expressed in CAD group compared to the non-CAD group. Furthermore, we found there were less autophagosomes and autolysosomes in transplanted kidneys of CAD patients, and downregulation of autophagy is a poor prognostic factor. In vitro, we found out that the knockdown of ATG16L enhanced the process of EndMT in human renal glomerular endothelial cells (HRGECs). In vivo, the changes of EndMT and autophagic flux were then detected in rat renal transplant models of CAD. We demonstrated the occurrence of EndMT, and indicated that abundance of ATG16L was accompanied by the dynamic autophagic flux change along different stages of kidney transplantation. Mechanistically, knockdown of ATG16L, specifically in endothelial cells, reduced of NF-κB degradation and excreted inflammatory cytokines (IL-1ß, IL-6 and TNF-α), which could facilitate EndMT. In conclusion, ATG16L-dependent autophagic flux causing by transplant showed progressive loss increase over time. Inflammatory cytokines from this process promoted EndMT, thereby leading to progression of CAD. ATG16L served as a negative regulator of EndMT and development of renal graft fibrosis, and autophagy can be explored as a potential therapeutic target for chronic renal graft dysfunction.

Hirsutella sinensis mycelium regulates autophagy of alveolar macrophages via TLR4/NF-κB signaling pathway.

Background: Hirsutella sinensis mycelium (HSM) has potent anti-pulmonary fibrotic activities and has been proposed as an effective treatment for idiopathic pulmonary fibrosis. Macrophages are the main innate immune cells in the lung tissue, playing key roles in pulmonary fibrosis repair and homeostasis. Excessive macrophage autophagy plays a vital role in pulmonary fibrosis. The protective effect of HSM on macrophages of bleomycin (BLM)-induced pulmonary fibrotic mice remain unclear. Methods: In this study, we collected lung tissue and bronchoalveolar lavage fluid (BALF) samples from pulmonary fibrotic mice. Meanwhile, alveolar macrophages were isolated and murine macrophage RAW264.7 cell line was cultured for further study of HSM autophagy. Results: First, we found that HSM decreased the number of autophagosomes, as well as the levels of LC3B and ATG5, and increased the protein level of P62 during the development of pulmonary fibrosis. Meanwhile, HSM reduced alveolar macrophages infiltration into the BALF and inhibited their accumulation in the fibrotic lung tissue. Flow cytometry analysis showed that HSM administration inhibited the autophagy marker LC3B expression in CD11bloCD11chi alveolar macrophages in BLM-induced lung fibrosis without affecting CD11bhiCD11clo interstitial macrophages. Transmission electron microscopy and JC-1 staining for mitochondrial membrane potential of alveolar macrophages also verified that the HSM significantly decreased autophagy in the alveolar macrophages of BLM-treated mice. In vitro, autophagosomes-lysosome fusion inhibitor chloroquine (CQ) was pre-incubated with RAW264.7 cells, and HSM reduced CQ-induced autophagosomes accumulation. TLR4 signaling inhibitor CLI095 reversed the above effects, suggesting HSM could reduce the cumulation of autophagosomes dependent on TLR4. Furthermore, lipopolysaccharide (LPS)-stimulated TLR4-related autophagy was significantly inhibited by HSM treatment. In addition, the protein expressions of TLR4 and phospho-NF-κB p65 were markedly inhibited in cells treated with HSM. Conclusions: These results indicated that HSM could inhibit the autophagy of alveolar macrophages through TLR4/NF-κB signaling pathway to achieve anti-fibrotic effect.

IL-17 deficiency aggravates the streptozotocin-induced diabetic nephropathy through the reduction of autophagosome formation in mice.

BACKGROUND: Diabetic nephropathy (DN) is one of the most important medical complications of diabetes mellitus. Autophagy is an important mediator of pathological response and plays a critical role in inflammation during the progression of diabetic nephropathy. Interleukin (IL)-17A favorably modulates inflammatory disorders including DN. In this study, we examined whether IL-17A deficiency affected the autophagy process in the kidneys of mice with streptozotocin (STZ)-induced DN. METHODS: The autophagic response of IL-17A to STZ-induced nephrotoxicity was evaluated by analyzing STZ-induced functional and histological renal injury in IL-17A knockout (KO) mice. RESULTS: IL-17A KO STZ-treated mice developed more severe nephropathy than STZ-treated wild-type (WT) mice, with increased glomerular damage and renal interstitial fibrosis at 12 weeks. IL-17A deficiency also increased the up-regulation of proinflammatory cytokines and fibrotic gene expression after STZ treatment. Meanwhile, autophagy-associated proteins were induced in STZ-treated WT mice. However, IL-17A KO STZ-treated mice displayed a significant decrease in protein expression. Especially, the levels of LC3 and ATG7, which play crucial roles in autophagosome formation, were notably decreased in the IL-17A KO STZ-treated mice compared with their WT counterparts. CONCLUSIONS: IL-17 deficiency aggravates of STZ-induced DN via attenuation of autophagic response. Our study demonstrated that IL-17A mediates STZ-induced renal damage and represents a potential therapeutic target in DN.

Ovarian hormones-autophagy-immunity axis in menstruation and endometriosis.

Menstruation occurs in few species and involves a cyclic process of proliferation, breakdown and regeneration under the control of ovarian hormones. Knowledge of normal endometrial physiology, as it pertains to the regulation of menstruation, is essential to understand disorders of menstruation. Accumulating evidence indicates that autophagy in the endometrium, under the regulation of ovarian hormones, can result in the infiltration of immune cells, which plays an indispensable role in the endometrium shedding, tissue repair and prevention of infections during menstruation. In addition, abnormal autophagy levels, together with resulting dysregulated immune system function, are associated with the pathogenesis and progression of endometriosis. Considering its potential value of autophagy as a target for the treatment of menstrual-related and endometrium-related disorders, we review the activity and function of autophagy during menstrual cycles. The role of the estrogen/progesterone-autophagy-immunity axis in endometriosis are also discussed.

Autophagy regulates long-term cross-presentation by murine dendritic cells.

Autophagy has been reported to be involved in supporting antigen cross-presentation by dendritic cells (DCs). We have shown that DCs have the ability to store antigen for a prolonged time in endolysosomal compartments and thereby sustain MHCI antigen cross-presentation to CD8+ T cells. In the current study, we investigated the role of autophagy in long-term antigen presentation. We show that the autophagy machinery has a negative impact on storage of antigen in DCs. Atg5-/- DCs which are deficient in autophagy or DCs treated with common autophagy inhibitors showed enhanced antigen storage and antigen cross-presentation. This augmented antigen cross-presentation effect is independent of altered proteasome enzyme activity or MHCI surface expression on DCs. We visualized that the storage compartments are in close proximity to LC3 positive autophagosomes. Our results indicate that autophagosomes disrupt antigen storage in DCs and thereby regulate long-term MHCI cross-presentation.

Tumor cell-derived autophagosomes (DRibbles)-activated B cells induce specific naïve CD8+ T cell response and exhibit antitumor effect.

Dendritic cell (DC) vaccine has been proved to be an effective way in cancer immunotherapy in both preclinical and clinical studies. However, limitations in DC isolation and culture have hampered its practice and promoted the development of other antigen-presenting cells (APCs) sources to fulfill that role. Our previous studies have shown that B cells loaded by tumor cell-derived autophagosomes, which we named as DRibbles (defective ribosomal products-containing blebs), could reactivate DC-induced effector T cell response. In this study, the roles of DRibble-loaded B cells in priming naïve CD8+ T cell responses and controlling tumors were investigated. We found that high-mobility group box 1 protein (HMGB1) on DRibbles was involved in DRibble-induced B cell activation, and the DRibble-triggered B cell phagocytosis via the caveolae-mediated endocytosis pathway. By using OT-I mouse-derived T cells, we demonstrated that DRibble-loaded B cells could activate specific naïve CD8+ T cells in vitro and ex vivo. In a tumor-bearing mouse model, DRibble-loaded B cells elicited systemic antitumor immunity and significantly suppressed the tumor growth. Moreover, the antitumor efficacy of DRibble-loaded B cells was enhanced when they were combined with CpG and anti-CD40 stimulation. These results suggest that DRibble-loaded B cells represent a viable and practical therapeutic vaccination strategy that might have important clinical implications for tumor immunotherapy.

Eating the unknown: Xenophagy and ER-phagy are cytoprotective defenses against pathogens.

Autophagy is an evolutionary conserved catabolic process devoted to the removal of unnecessary and harmful cellular components. In its general form, autophagy governs cellular lifecycle through the formation of double membrane vesicles, termed autophagosomes, that enwrap and deliver unwanted intracellular components to lysosomes. In addition to this omniscient role, forms of selective autophagy, relying on specialized receptors for cargo recognition, exert fine-tuned control over cellular homeostasis. In this regard, xenophagy plays a pivotal role in restricting the replication of intracellular pathogens, thus acting as an ancient innate defense system against infections. Recently, selective autophagy of the endoplasmic reticulum (ER), more simply ER-phagy, has been uncovered as a critical mechanism governing ER network shape and function. Six ER-resident proteins have been characterized as ER-phagy receptors and their orchestrated function enables ER homeostasis and turnover overtime. Unfortunately, ER is also the preferred site for viral replication and several viruses hijack ER machinery for their needs. Thus, it is not surprising that some ER-phagy receptors can act to counteract viral replication and minimize the spread of infection throughout the organism. On the other hand, evolutionary pressure has armed pathogens with strategies to evade and subvert xenophagy and ER-phagy. Although ER-phagy biology is still in its infancy, the present review aims to summarize recent ER-phagy literature, with a special focus on its role in counteracting viral infections. Moreover, we aim to offer some hints for future targeted approaches to counteract host-pathogen interactions by modulating xenophagy and ER-phagy pathways.

DUSP5 (dual-specificity protein phosphatase 5) suppresses BCG-induced autophagy via ERK 1/2 signaling pathway.

Autophagy is considered as an effective strategy for host cells to eliminate intracellular Mycobacterium tuberculosis (Mtb). Dual-specificity phosphatase 5 (DUSP5) is an endogenous phosphatase of ERK1/2, and plays an important role in host innate immune responses, its function in autophagy regulation however remains unexplored. In the present study, the function of DUSP5 in autophagy in Mycobacterium bovis Bacillus Calmette-Guerin (BCG)-infected RAW264.7 cells, a murine macrophage-like cell line, was examined by assessing the alteration of the cell morphology, expression of autophagy markers, and ERK1/2 signaling activation. The results demonstrated that the BCG infection could induce DUSP5 expression and activate ERK1/2 signaling in RAW264.7 cells; an activation of ERK1/2 signaling contributed to autophagic process in RAW264.7 cells. Moreover, DUSP5 knockdown increased the expression of autophagy-related proteins (Atgs), including LC3-II, Beclin1, Atg5 and Atg7. However, an overexpression of DUSP5 exhibited an opposite effect. Mechanistically, DUSP5 could inhibit the formation of autophagosome by suppressing the phosphorylation of signaling molecules in ERK1/2 signaling cascade. This study thus demonstrated a novel role of DUSP5 in modulating autophagy inRAW264.7 cells in response to BCG infection in particular, and autophagy macrophage to Mtb in general.

Identification of Group A Streptococcus-Containing Autophagosome-Like Vacuoles.

Group A Streptococcus (GAS) is one of the major human pathogens that can invade nonphagocytic cells. GAS internalized through endocytosis secretes the pore-forming toxin Streptolysin O (SLO) to escape into the cytoplasm. The cytosolic GAS is selectively captured by autophagic membranes (GAS-containing autophagosome-like vacuoles, GcAVs) and delivered to lysosomes for degradation. Macroautophagy (referred to as autophagy hereafter) is a highly conserved lysosome-mediated catabolic process, which is critical for cellular homeostasis. Autophagy also acts as an intracellular immune system. In this section, we describe how to identify GcAVs in infected cells using fluorescent microscopy.

Target of rapamycin signaling inhibits autophagy in sea cucumber Apostichopus japonicus.

Autophagy mediated by mTOR pathway is a particularly important immune defense mechanism in the pathogens infected mammals. However, the role of TOR in echinoderm autophagy is largely unknown. Here, a cDNA encoding TOR protein was cloned and characterized from sea cucumber Apostichopus japonicus (designated as AjTOR) and its biological functions were also investigated. The AjTOR gene encoded a peptide of 2499 amino acids with the representative domains of DUF3385, FAT, FRB, PI3Kc, and FATC, which exhibited highly conservation with vertebrate orthologs. Phylogenetic analysis supported that AjTOR belonged to a new member of TOR family. Moreover, tissues distribution analysis indicated that AjTOR was ubiquitously expressed in all the tested tissues, with the highest transcription in muscle. Vibrio splendidus infection in vivo and LPS challenge in vitro could both significantly down-regulate the mRNA expression of AjTOR. What's more, transmission electron microscopy observations showed that rapamycin treatment resulted in rapid formation of autophagosomes in coelomocytes both at 3 and 6 h, however, injection with mTOR activator of MHY1485 showed an inhibitory effect on autophagosomes formation compared to the control, suggesting blocking the expression of AjTOR could accelerates autophagy signals. Our findings supported that AjTOR served as a negative regulator in sea cucumber authophay.

Staphylococcus aureus facilitates its survival in bovine macrophages by blocking autophagic flux.

Staphylococcus aureus is a pathogen that is the causative agent of several human and veterinary infections and plays a critical role in the clinical and subclinical mastitis of cattle. Autophagy is a conserved pathogen defence mechanism in eukaryotes. Studies have reported that S aureus can subvert autophagy and survive in cells. Staphylococcus aureus survival in cells is an important cause of chronic persistent mastitis infection. However, it is unclear whether S aureus can escape autophagy in innate immune cells. In this study, initiation of autophagy due to the presence of S aureus was detected in bovine macrophages. We observed autophagic vacuoles increased after S aureus infection of bovine macrophages by transmission electron microscopy (TEM). It was also found that S aureus-infected bovine macrophages increased the expression of LC3 at different times(0, 0.5, 1, 1.5, 2, 2.5, 3 and 4 hours). Data also showed the accumulation of p62 induced by S aureus infection. Application of autophagy regulatory agents showed that the degradation of p62 was blocked in S aureus induced bovine macrophages. In addition, we also found that the accumulation of autophagosomes promotes S aureus to survive in macrophage cells. In conclusion, this study indicates that autophagy occurs in S aureus-infected bovine macrophages but is blocked at a later stage of autophagy. The accumulation of autophagosomes facilitates the survival of S aureus in bovine macrophages. These findings provide new insights into the interaction of S aureus with autophagy in bovine macrophages.

Lipopolysaccharide induces neuroinflammation in microglia by activating the MTOR pathway and downregulating Vps34 to inhibit autophagosome formation.

BACKGROUND: Microglial activation is a prominent feature of neuroinflammation, which is present in almost all neurodegenerative diseases. While an initial inflammatory response mediated by microglia is considered to be protective, excessive pro-inflammatory response of microglia contributes to the pathogenesis of neurodegeneration. Although autophagy is involved in the suppression of inflammation, its role and mechanism in microglia are unclear. METHODS: In the present study, we studied the mechanism by which lipopolysaccharide (LPS) affects microglial autophagy and the effects of autophagy on the production of pro-inflammatory factors in microglial cells by western blotting, immunocytochemistry, transfection, transmission electron microscopy (TEM), and real-time PCR. In a mouse model of neuroinflammation, generated by intraventricular injection of LPS (5 µg/animal), we induced autophagy by rapamycin injection and investigated the effects of enhanced autophagy on microglial activation by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. RESULTS: We found that autophagic flux was suppressed in LPS-stimulated N9 microglial cells, as evidenced by decreased expression of the autophagy marker LC3-II (lipidated form of MAP1LC3), as well as increased levels of the autophagy adaptor protein SQSTM1. LPS significantly decreased Vps34 expression in N9 microglial cells by activating the PI3KI/AKT/MTOR pathway without affecting the levels of lysosome-associated proteins and enzymes. More importantly, overexpression of Vps34 significantly enhanced the autophagic flux and decreased the accumulation of SQSTM1 in LPS-stimulated N9 microglial cells. Moreover, our results revealed that an LPS-induced reduction in the level of Vps34 prevented the maturation of omegasomes to phagophores. Furthermore, LPS-induced neuroinflammation was significantly ameliorated by treatment with the autophagy inducer rapamycin both in vitro and in vivo. CONCLUSIONS: These data reveal that LPS-induced neuroinflammation in N9 microglial cells is associated with the inhibition of autophagic flux through the activation of the PI3KI/AKT/MTOR pathway, while enhanced microglial autophagy downregulates LPS-induced neuroinflammation. Thus, this study suggests that promoting the early stages of autophagy might be a potential therapeutic approach for neuroinflammation-associated diseases.

Cross-talk between CD38 and TTP Is Essential for Resolution of Inflammation during Microbial Sepsis.

The resolution phase of acute inflammation is essential for tissue homeostasis, yet the underlying mechanisms remain unclear. We demonstrate that resolution of inflammation involves interactions between CD38 and tristetraprolin (TTP). During the onset of acute inflammation, CD38 levels are increased, leading to the production of Ca2+-signaling messengers, nicotinic acid adenine dinucleotide phosphate (NAADP), ADP ribose (ADPR), and cyclic ADPR (cADPR) from NAD(P)+. To initiate the onset of resolution, TTP expression is increased by the second messengers, NAADP and cADPR, which downregulate CD38 expression. The activation of TTP by Sirt1-dependent deacetylation, in response to increased NAD+ levels, suppresses the acute inflammatory response and decreases Rheb expression, inhibits mTORC1, and induces autophagolysosomes for bacterial clearance. TTP may represent a mechanistic target of anti-inflammatory agents, such as carbon monoxide. TTP mediates crosstalk between acute inflammation and autophagic clearance of bacteria from damaged tissue in the resolution of inflammation during sepsis.

Critical Role of TFEB-Mediated Lysosomal Biogenesis in Alcohol-Induced Pancreatitis in Mice and Humans.

BACKGROUND & AIMS: Alcohol abuse is the major cause of experimental and human pancreatitis but the molecular mechanisms remain largely unknown. We investigated the role of transcription factor EB (TFEB), a master regulator of lysosomal biogenesis, in the pathogenesis of alcoholic pancreatitis. METHODS: Using a chronic plus acute alcohol binge (referred to as Gao-binge) mouse model, we analyzed pancreas injury, autophagic flux, zymogen granule removal, TFEB nuclear translocation and lysosomal biogenesis in GFP-LC3 transgenic mice, acinar cell-specific Atg5 knockout (KO) and TFEB KO mice as well as their matched wild type mice. RESULTS: We found that Gao-binge alcohol induced typical features of pancreatitis in mice with increased serum amylase and lipase activities, pancreatic edema, infiltration of inflammatory cells, accumulation of zymogen granules (ZGs) and expression of inflammatory cytokines. While Gao-binge alcohol increased the number of autophagosomes, it also concurrently inhibited TFEB nuclear translocation and TFEB-mediated lysosomal biogenesis resulting in insufficient autophagy. Acinar cell-specific Atg5 KO and acinar cell-specific TFEB KO mice developed severe inflammatory and fibrotic pancreatitis in both Gao-binge alcohol and control diet-fed mice. In contrast, TFEB overexpression inhibited alcohol-induced pancreatic edema, accumulation of zymogen granules and serum amylase and lipase activities. In line with our findings in mice, decreased LAMP1 and TFEB nuclear staining were also observed in human alcoholic pancreatitis tissues. CONCLUSIONS: our results indicate that TFEB plays a critical role in maintaining pancreatic acinar cell homeostasis. Impairment of TFEB-mediated lysosomal biogenesis by alcohol may lead to insufficient autophagy and promote alcohol-induced pancreatitis.