Autophagy balances inflammation in innate immunity

BHRF1, a BCL2 viral homolog, disturbs mitochondrial dynamics and stimulates mitophagy to dampen type I IFN induction

Mitochondria respond to many cellular functions and act as central hubs in innate immunity against viruses. This response is notably due to their role in the activation of interferon (IFN) signaling pathways through the activity of MAVS (mitochondrial antiviral signaling protein) present at the mitochondrial surface. Here, we report that the BHRF1 protein, a BCL2 homolog encoded by Epstein-Barr virus (EBV), inhibits IFNB/IFN-β induction by targeting the mitochondria. Indeed, we have demonstrated that BHRF1 expression modifies mitochondrial dynamics and stimulates DNM1L/Drp1-mediated mitochondrial fission. Concomitantly, we have shown that BHRF1 is pro-autophagic because it stimulates the autophagic flux by interacting with BECN1/Beclin 1. In response to the BHRF1-induced mitochondrial fission and macroautophagy/autophagy stimulation, BHRF1 drives mitochondrial network reorganization to form juxtanuclear mitochondrial aggregates known as mito-aggresomes. Mitophagy is a cellular process, which can specifically sequester and degrade mitochondria. Our confocal studies uncovered that numerous mitochondria are present in autophagosomes and acidic compartments using BHRF1-expressing cells. Moreover, mito-aggresome formation allows the induction of mitophagy and the accumulation of PINK1 at the mitochondria. As BHRF1 modulates the mitochondrial fate, we explored the effect of BHRF1 on innate immunity and showed that BHRF1 expression could prevent IFNB induction. Indeed, BHRF1 inhibits the IFNB promoter activation and blocks the nuclear translocation of IRF3 (interferon regulatory factor 3). Thus, we concluded that BHRF1 can counteract innate immunity activation by inducing fission of the mitochondria to facilitate their sequestration in mitophagosomes for degradation.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; BCL2: BCL2 apoptosis regulator; CARD: caspase recruitment domain; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; CI: compaction index; CQ: chloroquine; DAPI: 4',6-diamidino-2-phenylindole, dihydrochloride; DDX58/RIG-I: DExD/H-box helicase 58; DNM1L/Drp1: dynamin 1 like; EBSS: Earle's balanced salt solution; EBV: Epstein-Barr virus; ER: endoplasmic reticulum; EV: empty vector; GFP: green fluorescent protein; HEK: human embryonic kidney; IFN: interferon; IgG: immunoglobulin G; IRF3: interferon regulatory factor 3; LDHA: lactate dehydrogenase A; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAVS: mitochondrial antiviral signaling protein; MMP: mitochondrial membrane potential; MOM: mitochondrial outer membrane; PINK1: PTEN induced kinase 1; RFP: red fluorescent protein; ROS: reactive oxygen species; SQSTM1/p62: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TOMM20: translocase of outer mitochondrial membrane 20; VDAC: voltage dependent anion channel.

Niacin Alleviates Dairy Cow Mastitis by Regulating the GPR109A/AMPK/NRF2 Signaling Pathway

Mastitis is one of three bovine diseases recognized as a cause of substantial economic losses every year throughout the world. Niacin is an important feed additive that is used extensively for dairy cow nutrition. However, the mechanism by which niacin acts on mastitis is not clear. The aim of this study is to investigate the mechanism of niacin in alleviating the inflammatory response of mammary epithelial cells and in anti-mastitis. Mammary glands, milk, and blood samples were collected from mastitis cows not treated with niacin (n = 3) and treated with niacin (30 g/d, n = 3) and healthy cows (n = 3). The expression of GPR109A, IL-6, IL-1β, and TNF-α in the mammary glands of the dairy cows with mastitis was significantly higher than it was in the glands of the healthy dairy cows. We also conducted animal experiments in vivo by feeding rumen-bypassed niacin. Compared with those in the untreated mastitis group, the somatic cell counts (SCCs) and the expression of IL-6, IL-1β, and TNF-α in the blood and milk were lower. In vitro, we isolated the primary bovine mammary epithelial cells (BMECs) from the mammary glands of the healthy cows. The mRNA levels of IL-6, IL-1β, TNF-α, and autophagy-related genes were detected after adding niacin, shRNA, compound C, trans retinoic acid, 3-methyladenine to BMECs. Then GPR109A, AMPK, NRF-2, and autophagy-related proteins were detected by Western blot. We found that niacin can activate GPR109A and phosphorylate AMPK, and promote NRF-2 nuclear import and autophagy to alleviate LPS-induced inflammatory response in BMECs. In summary, we found that niacin can reduce the inflammatory response of BMECs through GPR109A/AMPK/NRF-2/autophagy. We also preliminarily explored the alleviative effect of niacin on mastitis in dairy cows.

The CoV-2 outbreak: how hematologists could help to fight Covid-19

COVID-19 is a medical emergency, with 20 % of patients presenting with severe clinical manifestations. From the pathogenetic point of view, COVID-19 mimics two other well-known diseases characterized by cytokine storm and hyper-activation of the immune response, with consequent organ damage: acute graft-versus-host disease (aGVHD) and macrophage activation syndrome (MAS). Hematologists are confident with these situations requiring a prompt therapeutic approach for switching off the uncontrolled cytokine release; here, we discuss pros and cons of drugs that are already employed in hematology in the light of their possible application in COVID-19. The most promising drugs might be: Ruxolitinib, a JAK1/2 inhibitor, with a rapid and powerful anti-cytokine effect, tyrosine kinase inhibitors (TKIs), with their good anti-inflammatory properties, and perhaps the anti-Cd26 antibody Begelomab. We also present immunological data from gene expression experiments where TKIs resulted effective anti-inflammatory and pro-immune drugs. A possible combined treatment algorithm for COVID-19 is here proposed.

Roles of Autophagy in Oxidative Stress

Autophagy is a catabolic process for unnecessary or dysfunctional cytoplasmic contents by lysosomal degradation pathways. Autophagy is implicated in various biological processes such as programmed cell death, stress responses, elimination of damaged organelles and development. The role of autophagy as a crucial mediator has been clarified and expanded in the pathological response to redox signalling. Autophagy is a major sensor of the redox signalling. Reactive oxygen species (ROS) are highly reactive molecules that are generated as by-products of cellular metabolism, principally by mitochondria. Mitochondrial ROS (mROS) are beneficial or detrimental to cells depending on their concentration and location. mROS function as redox messengers in intracellular signalling at physiologically low level, whereas excessive production of mROS causes oxidative damage to cellular constituents and thus incurs cell death. Hence, the balance of autophagy-related stress adaptation and cell death is important to comprehend redox signalling-related pathogenesis. In this review, we attempt to provide an overview the basic mechanism and function of autophagy in the context of response to oxidative stress and redox signalling in pathology.

Danger matrix molecules orchestrate CD14/CD44 signaling in cancer development

The tumor matrix together with inflammation and autophagy are crucial regulators of cancer development. Embedded in the tumor stroma are numerous proteoglycans which, in their soluble form, act as danger-associated molecular patterns (DAMPs). By interacting with innate immune receptors, the Toll-like receptors (TLRs), DAMPs autonomously trigger aseptic inflammation and can regulate autophagy. Biglycan, a known danger proteoglycan, can regulate the cross-talk between inflammation and autophagy by evoking a switch between pro-inflammatory CD14 and pro-autophagic CD44 co-receptors for TLRs. Thus, these novel mechanistic insights provide some explanation for the plethora of reports indicating that the same matrix-derived DAMP acts either as a promoter or suppressor of tumor growth. In this review we will summarize and critically discuss the role of the matrix-derived DAMPs biglycan, hyaluronan, and versican in regulating the TLR-, CD14- and CD44-signaling dialogue between inflammation and autophagy with particular emphasis on cancer development.

Icaritin Exacerbates Mitophagy and Synergizes with Doxorubicin to Induce Immunogenic Cell Death in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) resistant to both chemotherapy and immunotherapy is among the deadliest malignancies. Doxorubicin widely used in transarterial chemotherapy in HCC can induce immunogenic cell death (ICD), but the resulting immunogenicity is still weak. We aim to seek a strategy for improving the efficacy of ICD in HCC based on an immunoregulatory drug called icaritin. Icaritin induced mitophagy and apoptosis to provoke ICD both in mouse Hepa1-6 and human Huh7 HCC cells. A combination of icaritin and doxorubicin with a molar ratio of 1:2 played a synergistic role in ICD induction. The poly lactic-co-glycolic acid (PLGA)-polyethylene glycol (PEG)-aminoethyl anisamide (AEAA) nanoparticle (NP) targeted codelivery of icaritin and doxorubicin remodeled the immunosuppressive tumor microenvironment and triggered a robust immune memory response, which efficiently improved anti-HCC effect at an early stage in mouse HCC model. In addition, the combo PLGA-PEG-AEAA NP together with lenvatinib significantly prolonged survival time of mice at the advanced stage of HCC. Collectively, our findings reveal an anti-HCC mechanism of icaritin on mitophagy and provide an effective immune-based therapeutic strategy for HCC.

Identification of 3',4',5'-trihydroxyflavone as an mammalian target of rapamycin inhibitor and its suppressive effects on dextran sulfate sodium-induced ulcerative colitis

Flavone derivatives have been shown to possess anti-inflammatory properties in various inflammation model systems; however, their underlying molecular mechanisms remain elusive. In this study, a flavone derivative 3',4',5'-trihydroxyflavone (THF; NJK16003) was synthesized, and its anti-inflammatory effects and molecular targets were investigated using in vitro systems and an in vivo colitis model. NJK16003 showed potent anti-inflammatory activities in cell-based assays using macrophages. In vitro enzyme activity assays using various inflammation-related kinases revealed the mammalian target of rapamycin (mTOR) as a possible molecular target. Treatment of RAW264.7 cells with NJK16003 resulted in an increase in light chain 3B protein lipidation and a decrease in p62 protein levels and ribosomal S6 kinase phosphorylation, indicating that NJK16003 induces autophagy through mTOR inhibition. NJK16003 treatment resulted in significant induction of autophagy and suppression of inflammatory responses in intestinal epithelial cells. Autophagy induction has been shown to alleviate colitis by suppressing inflammatory responses and apoptotic cell death of intestinal epithelial cells. Indeed, inflammatory responses and intestinal epithelial cell death in our DSS-induced colitis mouse model were significantly suppressed by NJK16003 treatment. Our results indicate that NJK16003 could suppress inflammation by inducing autophagy through its mTOR inhibitory activity. These results suggest that NJK16003 could be a possible therapeutic agent for the treatment of inflammatory bowel diseases including colitis.

Mitophagy in the Pathogenesis of Liver Diseases

Autophagy is a catabolic process involving vacuolar sequestration of intracellular components and their targeting to lysosomes for degradation, thus supporting nutrient recycling and energy regeneration. Accumulating evidence indicates that in addition to being a bulk, nonselective degradation mechanism, autophagy may selectively eliminate damaged mitochondria to promote mitochondrial turnover, a process termed “mitophagy”. Mitophagy sequesters dysfunctional mitochondria via ubiquitination and cargo receptor recognition and has emerged as an important event in the regulation of liver physiology. Recent studies have shown that mitophagy may participate in the pathogenesis of various liver diseases, such as liver injury, liver steatosis/fatty liver disease, hepatocellular carcinoma, viral hepatitis, and hepatic fibrosis. This review summarizes the current knowledge on the molecular regulations and functions of mitophagy in liver physiology and the roles of mitophagy in the development of liver-related diseases. Furthermore, the therapeutic implications of targeting hepatic mitophagy to design a new strategy to cure liver diseases are discussed.

IL28A protein homotetramer structure is required for autolysosomal degradation of HCV-NS5A in vitro

Interferon lambda-2 (IL28A) has a wide antiviral effect with fewer side-effects. Autophagy is a host mechanism to maintain intracellular homeostasis and defends invasion of pathogenic microorganisms. HCV NS5A can disable host defense systems to support HCV replication. Thus, molecular mechanism of interaction among interferon lambda, autophagy, and HCV was concerned and explored in this study. We report that HCV NS5A activated an incomplete autophagy by promoting the autophagic ubiquitylation-like enzymes ATG3, ATG5, ATG7, ATG10, and autophagosome maker LC3B, but blocked autophagy flux; IL28A bound to NS5A at NS5A-ISDR region, and degraded HCV-NS5A by promoting autolysosome formations in HepG2 cells. A software prediction of IL28A protein conformation indicated a potential structure of IL28A homotetramer; the first α-helix of IL28A locates in the interfaces among the four IL28A chains to maintain IL28A homotetrameric conformation. Co-IP and cell immunofluorescence experiments with sequential deletion mutants demonstrate that IL28A preferred a homotetramer conformation to a monomer in the cells; the IL28A homotetramer is positively correlated with autolysosomal degradation of HCV NS5A and the other HCV proteins. Summarily, the first α-helix of IL28A protein is the key domain for maintaining IL28A homotetramer which is required for promoting formation of autolysosomes and degradation of HCV proteins in vitro.

Therapeutic Potential of Volatile Terpenes and Terpenoids from Forests for Inflammatory Diseases

Forest trees are a major source of biogenic volatile organic compounds (BVOCs). Terpenes and terpenoids are known as the main BVOCs of forest aerosols. These compounds have been shown to display a broad range of biological activities in various human disease models, thus implying that forest aerosols containing these compounds may be related to beneficial effects of forest bathing. In this review, we surveyed studies analyzing BVOCs and selected the most abundant 23 terpenes and terpenoids emitted in forested areas of the Northern Hemisphere, which were reported to display anti-inflammatory activities. We categorized anti-inflammatory processes related to the functions of these compounds into six groups and summarized their molecular mechanisms of action. Finally, among the major 23 compounds, we examined the therapeutic potentials of 12 compounds known to be effective against respiratory inflammation, atopic dermatitis, arthritis, and neuroinflammation among various inflammatory diseases. In conclusion, the updated studies support the beneficial effects of forest aerosols and propose their potential use as chemopreventive and therapeutic agents for treating various inflammatory diseases.

Perturbation of bulk and selective macroautophagy, abnormal UPR activation and their interplay pave the way to immune dysfunction, cancerogenesis and neurodegeneration in ageing

A plethora of studies has indicated that ageing is characterized by an altered proteostasis, ROS accumulation and a status of mild/chronic inflammation, in which macroautophagy reduction and abnormal UPR activation play a pivotal role. The dysregulation of these inter-connected processes favors immune dysfunction and predisposes to a variety of several apparently unrelated pathological conditions including cancer and neurodegeneration. Given the progressive ageing of the population, a better understanding of the mechanisms regulating autophagy, UPR and their interplay is needed in order to design new therapeutic strategies able to counteract the effects of ageing and concomitantly restrain the onset/progression of age-related diseases that represent a private and public health problem.

TRIM proteins in autophagy: selective sensors in cell damage and innate immune responses

Autophagy, a main intracellular catabolic process, is induced in response to a variety of cellular stresses to promptly degrade harmful agents and to coordinate the activity of prosurvival and prodeath processes in order to determine the fate of the injured cells. While the main components of the autophagy machinery are well characterized, the molecular mechanisms that confer selectivity to this process both in terms of stress detection and cargo engulfment have only been partly elucidated. Here, we discuss the emerging role played by the E3 ubiquitin ligases of the TRIM family in regulating autophagy in physiological and pathological conditions, such as inflammation, infection, tumorigenesis, and muscle atrophy. TRIM proteins employ different strategies to regulate the activity of the core autophagy machinery, acting either as scaffold proteins or via ubiquitin-mediated mechanisms. Moreover, they confer high selectivity to the autophagy-mediated degradation as described for the innate immune response, where TRIM proteins mediate both the engulfment of pathogens within autophagosomes and modulate the immune response by controlling the stability of signaling regulators. Importantly, the elucidation of the molecular mechanisms underlying the regulation of autophagy by TRIMs is providing important insights into how selective types of autophagy are altered under pathological conditions, as recently shown in cancer and muscular dystrophy.

Regulation of Autophagy Orchestrates Pyroptotic Cell Death in Molybdenum Disulfide Quantum Dot-Induced Microglial Toxicity

Molybdenum disulfide quantum dots (MoS₂ QDs) represent an emerging class of two-dimensional (2D) atomically layered transition metal dichalcogenide nanostructures with few nanometers in lateral size, which show attractive potential as versatile platforms for theranostic applications in various neurological disorders. However, the potential impacts of MoS₂ QDs on microglia remain unclear. In this report, we showed that exposure of microglia to MoS₂ QDs triggered NLRP3 inflammasome activation as revealed by the cleavage of the inactive precursor of caspase-1 to its active form and the increased release of downstream pro-inflammatory cytokines, resulting in microglia cell death that occurred through caspase-1-dependent pyroptosis. We also found that MoS₂ QDs activated autophagy, and suppression of autophagy by specific inhibitors potentiated MoS₂ QD-induced pyroptosis. Additionally, MoS₂ QDs stimulated mitochondria-derived reactive oxygen species (mtROS) generation in BV-2 cells. However, ROS scavengers could diminish the MoS₂ QD-mediated NLRP3 inflammasome activation and pyroptotic cell death in microglia. Overall, our findings identified pyroptosis as a cellular response to MoS₂ QD exposure in microglial cells, affording novel insights into the neurotoxicity of MoS₂ QDs and facilitating the rational design and application of functional MoS₂ QDs in neuroscience.

Intestinal Alkaline Phosphatase Exerts Anti-Inflammatory Effects Against Lipopolysaccharide by Inducing Autophagy

Intestinal alkaline phosphatase (IAP) regulates bicarbonate secretion, detoxifies lipopolysaccharide (LPS), regulates gut microbes, and dephosphorylates proinflammatory nucleotides. IAP also exhibits anti-inflammatory effects in a Toll-like Receptor-4 (TLR-4) dependent manner. However, it is not known whether IAP induces autophagy. We tested the hypothesis that IAP may induce autophagy which may mediate the anti-inflammatory effects of IAP. We found that exogenous IAP induced autophagy in intestinal epithelial cells and in macrophages. TLR4INC34 (C34), a TLR4 signaling inhibitor, suppressed IAP-induced autophagy. IAP also inhibited LPS-induced IL-1β mRNA expression and activation of NF-κB. When autophagy was blocked by 3-methyladenine (3MA) or by Atg5 siRNA, IAP failed to block LPS-mediated effects. IAP also upregulated autophagy-related gene expression in small intestine in mice. We administered either vehicle or IAP (100 U/ml) in drinking water for 14 days in C57BL/6 mice. Mice were sacrificed and ileal tissues collected. Increased expression of Atg5, Atg16, Irgm1, Tlr4, and Lyz genes was observed in the IAP treated group compared to the vehicle treated group. Increase in Atg16 protein expression and fluorescence intensity of LC3 was also observed in IAP-treated tissues compared to the vehicle-treated tissues. Thus, our study lays the framework for investigating how IAP and autophagy may act together to control inflammatory conditions.

Lysosomotropic drugs enhance pro-inflammatory responses to IL-1β in macrophages by inhibiting internalization of the IL-1 receptor

Interleukin (IL)-1 signaling leads to production of pro-inflammatory mediators and is regulated by receptor endocytosis. Lysosomotropic drugs have been linked to increased pro-inflammatory responses under sterile inflammatory conditions but the underlying mechanisms have not been fully elucidated. Here, we report that lysosomotropic drugs potentiate pro-inflammatory effects in response to IL-1β via a mechanism involving reactive oxygen species, p38 mitogen-activated protein kinase and reduced IL-1 receptor internalization. Chloroquine and hydroxychloroquine increased IL-1β-induced CXCL8 secretion in macrophages which was critically dependent on the lysosomotropic character and inhibition of macroautophagy but independent from the NLRP3 inflammasome. Co-stimulation with the autophagy inducer interferon gamma attenuated CXCL8 release. Other lysosomotropic drugs like bafilomycin A₁, fluoxetine and chlorpromazine but also the endocytosis inhibitor dynasore showed similar pro-inflammatory responses. Increased cell surface expression of IL-1 receptor suggests reduced receptor degradation in the presence of lysosomotropic drugs. Our findings provide new insights into a potentially crucial immunoregulatory mechanism in macrophages that may explain how lysosomotropic drugs drive sterile inflammation.

Autophagy-based unconventional secretion of HMGB1 by keratinocytes plays a pivotal role in psoriatic skin inflammation

The precise mechanism through which macroautophagy/autophagy affects psoriasis is poorly understood. Here, we found that keratinocyte (KC) autophagy, which was positively correlated with psoriatic severity in patients and mouse models and could be inhibited by mitogen-activated protein kinase (MAPK) family inactivation. The impairment of autophagic flux alleviated psoriasisform inflammation. We also found that an autophagy-based unconventional secretory pathway (autosecretion) dependent on ATG5 (autophagy related 5) and GORASP2 (golgi reassembly stacking protein 2) promoted psoriasiform KC inflammation. Moreover, the alarmin HMGB1 (high mobility group box 1) was more effective than other autosecretory proteins in regulating psoriasiform cutaneous inflammation. HMGB1 neutralization in autophagy-efficient KCs eliminated the differences in psoriasiform inflammation between Krt14^+/+-Atg5^f/f KCs and Krt14^Cre/+-atg5^f/f KCs, and conversely, recombinant HMGB1 almost completely restored psoriasiform inflammation in Krt14^Cre/+-atg5^f/f KCs in vivo. These results suggest that HMGB1-associated autosecretion plays a pivotal role in cutaneous inflammation. Finally, we demonstrated that Krt14^Cre/+-hmgb1^f/f mice displayed attenuated psoriatic inflammation due to the essential crosstalk between KC-specific HMGB1-associated autosecretion and γδT cells. Thus, this study uncovered a novel autophagy mechanism in psoriasis pathogenesis, and the findings imply the clinical significance of investigating and treating psoriasis.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; AGER: advanced glycosylation end-product specific receptor; Anti-HMGB1: anti-HMGB1 neutralizing antibody; Anti-IL18: anti-IL18 neutralizing antibody; Anti-IL1B: anti-IL1B neutralizing antibody; ATG5: autophagy related 5; BAF: bafilomycin A₁; BECN1: beclin 1; CASP1: caspase 1; CCL: C-C motif chemokine ligand; CsA: cyclosporine A; ctrl shRNA: lentivirus harboring shRNA against control; CXCL: C-X-C motif chemokine ligand; DCs: dendritic cells; DMEM: dulbecco's modified Eagle's medium; ELISA: enzyme-linked immunosorbent assay; EM: electron microscopy; FBS: fetal bovine serum; GORASP2 shRNA: lentivirus harboring shRNA against GORASP2; GORASP2/GRASP55: golgi reassembly stacking protein 2; GR1: a composite epitope between LY6 (lymphocyte antigen 6 complex) locus C1 and LY6 locus G6D antigens; H&E: hematoxylin and eosin; HMGB1: high mobility group box 1; HMGB1 shRNA: lentivirus harboring shRNA against HMGB1; IFNG/IFN-γ: interferon gamma; IL17A: interleukin 17A; IL18: interleukin 18; IL1A/IL-1α: interleukin 1 alpha; IL1B/IL-1β: interleukin 1 beta; IL22/IL-22: interleukin 22; IL23A: interleukin 23 subunit alpha; IL23R: interleukin 23 receptor; IMQ: imiquimod; ITGAM/CD11B: integrin subunit alpha M; ITGAX/CD11C: integrin subunit alpha X; IVL: involucrin; KC: keratinocyte; KD: knockdown; KO: knockout; Krt14^+/+-Atg5^f/f mice: mice bearing an Atg5 flox allele, in which exon 3 of the Atg5 gene is flanked by two loxP sites; Krt14^+/+-Hmgb1^f/f: mice bearing an Hmgb1 flox allele, in which exon 2 to 4 of the Hmgb1 gene is flanked by two loxP sites; Krt14^Cre/+-atg5^f/f mice: keratinocyte-specific atg5 knockout mice generated by mating Atg5-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt4; Krt14^Cre/+-hmgb1^f/f mice: keratinocyte-specific hmgb1 knockout mice generated by mating Hmgb1-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt14; Krt14-Vegfa mice: mice expressing 164-amino acid Vegfa splice variant recombinase under the control of promoter of Krt14; LAMP1: lysosomal associated membrane protein 1; LDH: lactate dehydrogenase; LORICRIN: loricrin cornified envelope precursor protein; M5: TNF, IL1A, IL17A, IL22 and OSM in combination; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MKI67: marker of proliferation Ki-67; MTT: thiazolyl blue tetrazolium bromide; NFKB/NF-κB: nuclear factor kappa B; NHEKs: primary normal human epidermal keratinocytes; NS: not significant; OSM: oncostatin M; PASI: psoriasis area and severity index; PtdIns3K: class III phosphatidylinositol 3-kinase; qRT-PCR: quantitative RT-PCR; RELA/p65: RELA proto-oncogene, NF-kB subunit; rHMGB1: recombinant HMGB1; rIL18: recombinant interleukin 18; rIL1B: recombinant interleukin 1 beta; S100A: S100 calcium binding protein A; SQSTM1/p62: sequestosome 1; T17: IL17A-producing T; TCR: T-cell receptor; tcrd KO mice: tcrd (T cell receptor delta chain) knockout mice, which show deficient receptor expression in all adult lymphoid and epithelial organs; TLR: toll-like receptor; TNF/TNF-α: tumor necrosis factor; WOR: wortmannin; WT: wild-type; γδT17 cells: IL17A-producing γδ T cells.

Vitamin D-Cathelicidin Axis: at the Crossroads between Protective Immunity and Pathological Inflammation during Infection

Vitamin D signaling plays an essential role in innate defense against intracellular microorganisms via the generation of the antimicrobial protein cathelicidin. In addition to directly binding to and killing a range of pathogens, cathelicidin acts as a secondary messenger driving vitamin D-mediated inflammation during infection. Recent studies have elucidated the biological and clinical functions of cathelicidin in the context of vitamin D signaling. The vitamin D-cathelicidin axis is involved in the activation of autophagy, which enhances antimicrobial effects against diverse pathogens. Vitamin D studies have also revealed positive and negative regulatory effects of cathelicidin on inflammatory responses to pathogenic stimuli. Diverse innate and adaptive immune signals crosstalk with functional vitamin D receptor signals to enhance the role of cathelicidin action in cell-autonomous effector systems. In this review, we discuss recent findings that demonstrate how the vitamin D-cathelicidin pathway regulates autophagy machinery, protective immune defenses, and inflammation, and contributes to immune cooperation between innate and adaptive immunity. Understanding how the vitamin D-cathelicidin axis operates in the host response to infection will create opportunities for the development of new therapeutic approaches against a variety of infectious diseases.

Autophagy stimulation and intracellular sodium reduction as mediators of the cardioprotective effect of sodium-glucose cotransporter 2 inhibitors

In five large-scale trials involving >40 000 patients, sodium-glucose cotransporter 2 (SGLT2) inhibitors decreased the risk of serious heart failure events by 25-40%. This effect cannot be explained by control of hyperglycaemia, since it is not observed with antidiabetic drugs with greater glucose-lowering effects. It cannot be attributed to ketogenesis, since it is not causally linked to ketone body production, and the benefit is not enhanced in patients with diabetes. The effect cannot be ascribed to a natriuretic action, since SGLT2 inhibitors decrease natriuretic peptides only modestly, and they reduce cardiovascular death, a benefit that diuretics do not possess. Although SGLT2 inhibitors increase red blood cell mass, enhanced erythropoiesis does not favourably influence the course of heart failure. By contrast, experimental studies suggest that SGLT2 inhibitors may reduce intracellular sodium, thereby preventing oxidative stress and cardiomyocyte death. Additionally, SGLT2 inhibitors induce a transcriptional paradigm that mimics nutrient and oxygen deprivation, which includes activation of adenosine monophosphate-activated protein kinase, sirtuin-1, and/or hypoxia-inducible factors-1α/2α. The interplay of these mediators stimulates autophagy, a lysosomally-mediated degradative pathway that maintains cellular homeostasis. Autophagy-mediated clearance of damaged organelles reduces inflammasome activation, thus mitigating cardiomyocyte dysfunction and coronary microvascular injury. Interestingly, the action of hypoxia-inducible factors-1α/2α to both stimulate erythropoietin and induce autophagy may explain why erythrocytosis is strongly correlated with the reduction in heart failure events. Therefore, the benefits of SGLT2 inhibitors on heart failure may be mediated by a direct cardioprotective action related to modulation of pathways responsible for cardiomyocyte homeostasis.

Autophagy in hepatic adaptation to stress

Autophagy is an evolutionarily ancient process whereby eukaryotic cells eliminate disposable or potentially dangerous cytoplasmic material, to support bioenergetic metabolism and adapt to stress. Accumulating evidence indicates that autophagy operates as a critical quality control mechanism for the maintenance of hepatic homeostasis in both parenchymal (hepatocytes) and non-parenchymal (stellate cells, sinusoidal endothelial cells, Kupffer cells) compartments. In line with this notion, insufficient autophagy has been aetiologically involved in the pathogenesis of multiple liver disorders, including alpha-1-antitrypsin deficiency, Wilson disease, non-alcoholic steatohepatitis, liver fibrosis and hepatocellular carcinoma. Here, we critically discuss the importance of functional autophagy for hepatic physiology, as well as the mechanisms whereby defects in autophagy cause liver disease.

Autophagy in the Immunosuppressive Perivascular Microenvironment of Glioblastoma

Glioblastoma (GB) has been shown to up-regulate autophagy with anti- or pro-oncogenic effects. Recently, our group has shown how GB cells aberrantly up-regulate chaperone-mediated autophagy (CMA) in pericytes of peritumoral areas to modulate their immune function through cell-cell interaction and in the tumor’s own benefit. Thus, to understand GB progression, the effect that GB cells could have on autophagy of immune cells that surround the tumor needs to be deeply explored. In this review, we summarize all the latest evidence of several molecular and cellular immunosuppressive mechanisms in the perivascular tumor microenvironment. This immunosuppression has been reported to facilitate GB progression and may be differently modulated by several types of autophagy as a critical point to be considered for therapeutic interventions.

Regulation of immune response by S-1-propenylcysteine through autophagy-mediated protein degradation

Autophagy is a key event in cellular recycling processes due to its involvement in the intracellular degradation of proteins. It has been demonstrated that S−1-propenylcysteine (S1PC), a characteristic sulfur compound in aged garlic extract, induces the activation of autophagy. S1PC degrades the adaptor protein myeloid differentiation response protein 88 (MyD88) of downstream of Toll-like receptor (TLR) by activating autophagy in vitro and in vivo. The degradation of MyD88 inhibits the TLR signaling pathway, including the phosphorylation of interleukin 1 receptor associated kinase 4 (IRAK4) and nuclear factor (NF)-κB p65 in vitro, and eventually leads to the inhibition of interleukin (IL)-6 production in vitro and C-C motif chemokine ligand 2 (Ccl2) mRNA expression in vivo. S1PC also increases the level of intestinal immunoglobulin A (IgA) and the number of IgA-producing cells in Peyer's patches in vivo. In addition, S1PC triggers the mRNA expression of X-box binding protein 1 (Xbp1), an inducer of IgA-producing cell differentiation via the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and the degradation of paired box protein 5 (Pax5), a suppressor of Xbp1 mRNA expression. The present review summarizes the mechanisms through which the activation of autophagy by S1PC modulates the immune response.

Lactobacillus johnsonii L531 ameliorates enteritis via elimination of damaged mitochondria and suppression of SQSTM1-dependent mitophagy in a Salmonella infantis model of piglet diarrhea

Newly weaned piglets challenged with Salmonella infantis were particularly susceptible, whereas oral preadministration of Lactobacillus johnsonii L531 alleviated enteritis and promoted intestinal secretory IgA production. Salmonella infantis-induced activation of NLRC4 and NLRP3 inflammasomes and (nuclear factor kappa B) NF-κB signaling in the small intestine was also inhibited by L. johnsonii L531 pretreatment, thus limiting inflammation. An IPEC-J2 cell model of S. infantis infection yielded similar results. Salmonella infantis infection also resulted in mitochondrial damage and impaired mitophagy in the ileum and IPEC-J2 cells, as demonstrated by immunofluorescence colocalization of mitochondria with microtubule-binding protein light chain 3 (LC3) and high expression of autophagy-related proteins PTEN-induced putative kinase 1 (PINK1), sequestosome 1 (SQSTM1/p62), optineurin (OPTN), and LC3 by Western blotting analysis. However, L. johnsonii L531 pretreatment reduced both the extent of mitochondrial damage and autophagy-related protein expression. Our findings suggest that the amelioration of S. infantis-associated enteritis by L. johnsonii L531 is associated with regulation of NLRC4 and NLRP3 inflammasomes and NF-κB signaling pathway activation and suppression of mitochondrial damage. Amelioration of impaired mitophagy by L. johnsonii L531 could involve eliminating damaged mitochondria and regulating S. infantis-induced activation of the NF-κB-SQSTM1mitophagy signaling pathway in host cells to prevent the further mitochondrial damage and S. infantis dissemination.

Shufengjiedu capsules protect against neuronal loss in olfactory epithelium and lung injury by enhancing autophagy in rats with allergic rhinitis

Shufengjiedu capsules (SFJDCs), a traditional Chinese medicine, have been widely used as an antiviral, antibacterial, antitumor, and anti-inflammatory drug. However, the roles of SFJDCs in allergic rhinitis remain unclear. The purpose of this study was to investigate the effects of SFJDCs in olfaction and lung injury in rats with allergic rhinitis. An animal model of allergic rhinitis was created by intraperitoneal injection and intranasal administration of ovalbumin to rats. All rats were divided into seven groups: a model group, a low-dose SFJDC group, a medium-dose SFJDC group, a high-dose SFJDC group, a cetirizine group, and a control group. Hematoxylin and eosin (HE) staining was used to observe pathological changes in rat lung and olfactory epithelium (OE) tissue, and peripheral blood was collected and subjected to an enzyme-linked immunosorbent assay (ELISA) to detect IgE, tumor necrosis factor alpha (TNF-α), and IL-1ꞵ levels. Western blotting, immunohistochemistry staining, and immunofluorescence staining were performed to detect inflammatory cytokines and levels of the autophagy biomarker beclin1 and the apoptosis biomarker cleaeved-caspased3 in lung and OE tissue. ELISA indicated that SFJDCs significantly decreased IgE, TNF-α, and IL-1ꞵ levels in peripheral blood, the lungs, and OE tissue. In addition, Western blotting and staining indicated that SFJDCs repair lung injury, protect against neuronal apoptosis in OE, and rescue impaired autophagy in the lungs and OE tissue. In conclusion, results indicated that SFJDCs might protect against neuronal loss in the OE and lung injury by enhancing autophagy and decreasing apoptosis in rats with allergic rhinitis. Therefore, SFJDCs might serve as an alternative treatment for allergic rhinitis.

Autophagy in the renewal, differentiation and homeostasis of immune cells

Across all branches of the immune system, the process of autophagy is fundamentally important in cellular development, function and homeostasis. Strikingly, this evolutionarily ancient pathway for intracellular recycling has been adapted to enable a high degree of functional complexity and specialization. However, although the requirement for autophagy in normal immune cell function is clear, the mechanisms involved are much less so and encompass control of metabolism, selective degradation of substrates and organelles and participation in cell survival decisions. We review here the crucial functions of autophagy in controlling the differentiation and homeostasis of multiple immune cell types and discuss the potential mechanisms involved.

Imaging the adenovirus infection cycle

Incoming adenoviruses seize control of cytosolic transport mechanisms to relocate their genome from the cell periphery to specialized sites in the nucleoplasm. The nucleus is the site for viral gene expression, genome replication, and the production of progeny for the next round of infection. By taking control of the cell, adenoviruses also suppress cell-autonomous immunity responses. To succeed in their production cycle, adenoviruses rely on well-coordinated steps, facilitated by interactions between viral proteins and cellular factors. Interactions between virus and host can impose remarkable morphological changes in the infected cell. Imaging adenoviruses has tremendously influenced how we delineate individual steps in the viral life cycle, because it allowed the development of specific optical markers to label these morphological changes in space and time. As technology advances, innovative imaging techniques and novel tools for specimen labeling keep uncovering previously unseen facets of adenovirus biology emphasizing why imaging adenoviruses is as attractive today as it was in the past. This review will summarize past achievements and present developments in adenovirus imaging centered on fluorescence microscopy approaches.

The Cross-Regulation Between Autophagy and Type I Interferon Signaling in Host Defense

The production of type I interferons (IFNs) is one of the hallmarks of intracellular antimicrobial program. Typical type I IFN response activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway, which results in the transcription of plentiful IFN-stimulated genes (ISGs) to establish the comprehensive antiviral states. Type I IFN signaling should initiate timely to provoke innate and adaptive immune responses for effective elimination of the invading pathogens. Meanwhile, a precise control must come on the stage to restrain the persistent activation of type I IFN responses to avoid attendant toxicity. Autophagy, a conserved eukaryotic degradation system, mediated by a number of autophagy-related (ATG) proteins, plays an essential role in the clearance of invading microorganism and manipulation of type I responses. Autophagy modulates type I IFN responses through regulatory integration with innate immune signaling pathways, and by removing endogenous ligands of innate immune sensors. Moreover, selective autophagy governs the choice of innate immune factors as specific cargoes for degradation, thus tightly monitoring the type I IFN responses. This review will focus on the cross-regulation between autophagy and type I IFN signaling in host defense.

Punicalagin Prevents Inflammation in LPS-Induced RAW264.7 Macrophages by Inhibiting FoxO3a/Autophagy Signaling Pathway

Punicalagin, a hydrolysable tannin of pomegranate juice, exhibits multiple biological effects, including inhibiting production of pro-inflammatory cytokines in macrophages. Autophagy, an intracellular self-digestion process, has been recently shown to regulate inflammatory responses. In this study, we investigated the anti-inflammatory potential of punicalagin in lipopolysaccharide (LPS) induced RAW264.7 macrophages and uncovered the underlying mechanisms. Punicalagin significantly attenuated, in a concentration-dependent manner, LPS-induced release of NO and decreased pro-inflammatory cytokines TNF-α and IL-6 release at the highest concentration. We found that punicalagin inhibited NF-κB and MAPK activation in LPS-induced RAW264.7 macrophages. Western blot analysis revealed that punicalagin pre-treatment enhanced LC3II, p62 expression, and decreased Beclin1 expression in LPS-induced macrophages. MDC assays were used to determine the autophagic process and the results worked in concert with Western blot analysis. In addition, our observations indicated that LPS-induced releases of NO, TNF-α, and IL-6 were attenuated by treatment with autophagy inhibitor chloroquine, suggesting that autophagy inhibition participated in anti-inflammatory effect. We also found that punicalagin downregulated FoxO3a expression, resulting in autophagy inhibition. Overall these results suggested that punicalagin played an important role in the attenuation of LPS-induced inflammatory responses in RAW264.7 macrophages and that the mechanisms involved downregulation of the FoxO3a/autophagy signaling pathway.

Biological Functions of Autophagy Genes: A Disease Perspective

The lysosomal degradation pathway of autophagy plays a fundamental role in cellular, tissue, and organismal homeostasis and is mediated by evolutionarily conserved autophagy-related (ATG) genes. Definitive etiological links exist between mutations in genes that control autophagy and human disease, especially neurodegenerative, inflammatory disorders and cancer. Autophagy selectively targets dysfunctional organelles, intracellular microbes, and pathogenic proteins, and deficiencies in these processes may lead to disease. Moreover, ATG genes have diverse physiologically important roles in other membrane-trafficking and signaling pathways. This Review discusses the biological functions of autophagy genes from the perspective of understanding-and potentially reversing-the pathophysiology of human disease and aging.

At a glance: A history of autophagy and cancer

Since the first discovery of the lysosome and the definition of autophagy by Christian de Duve more than 60 years ago, research on autophagy, a process targeting cytoplasmic materials for lysosomal degradation and recycling, has expanded dramatically. This research has extended our understanding of the basic mechanism of autophagy as well as its role in pathophysiology. Autophagy deficiency has been reported to be involved in numerous diseases, among which cancer has been extensively studied, in part because autophagy appears to play a dual role, depending on the stage of tumorigenesis. In this review, we will briefly revisit the intriguing history of autophagy and cancer, underscoring the importance of harnessing this pathway for the benefit of human health.

Deciphering the Role Played by Autophagy in Leishmania Infection

In recent decades, studies have shown that, depending on parasite species and host background, autophagy can either favor infection or promote parasite clearance. To date, relatively few studies have attempted to assess the role played by autophagy in Leishmania infection. While it has been consistently shown that Leishmania spp. induce autophagy in a variety of cell types, published results regarding the effects of autophagic modulation on Leishmania survival are contradictory. The present review, after a short overview of the general aspects of autophagy, aims to summarize the current body of knowledge surrounding how Leishmania spp. adaptively interact with macrophages, the host cells mainly involved in controlling leishmaniasis. We then explore the scarce studies that have investigated interactions between these parasite species and the autophagic pathway, and finally present a critical perspective on how autophagy influences infection outcome.

Autophagy in Kidney Disease

Autophagy is a cellular homeostatic program for the turnover of cellular organelles and proteins, in which double-membraned vesicles (autophagosomes) sequester cytoplasmic cargos, which are subsequently delivered to the lysosome for degradation. Emerging evidence implicates autophagy as an important modulator of human disease. Macroautophagy and selective autophagy (e.g., mitophagy, aggrephagy) can influence cellular processes, including cell death, inflammation, and immune responses, and thereby exert both adaptive and maladaptive roles in disease pathogenesis. Autophagy has been implicated in acute kidney injury, which can arise in response to nephrotoxins, sepsis, and ischemia/reperfusion, and in chronic kidney diseases. The latter includes comorbidities of diabetes and recent evidence for chronic obstructive pulmonary disease-associated kidney injury. Roles of autophagy in polycystic kidney disease and kidney cancer have also been described. Targeting the autophagy pathway may have therapeutic benefit in the treatment of kidney disorders.

Liraglutide ameliorates non-alcoholic steatohepatitis by inhibiting NLRP3 inflammasome and pyroptosis activation via mitophagy

Non-alcoholic steatohepatitis (NASH) is a key step in the progression of non-alcoholic fatty liver disease (NAFLD), which causes serious health problems worldwide. The nucleotide-binding oligomerization domain, leucine-rich repeat-containing receptor-containing pyrin domain 3 (NLRP3) inflammasome and pyroptosis play crucial roles in the progression of NASH. Our team has provided clinical evidence of the effects of glucagon-like peptide-1 (GLP-1) on the improvement in liver function and histological resolution of NAFLD. Preliminary work has demonstrated that GLP-1 inhibited NLRP3 inflammasome activation in a mouse model of NAFLD. We further explored the potential molecular mechanisms underlying the anti-inflammatory effect of liraglutide, a long-acting GLP-1 analog, in the treatment of NASH. We established a HepG2 cell model of NASH using double stimulation with palmitic acid and lipopolysaccharide to assess NLRP3 inflammasome and pyroptotic cell activity and to evaluate mitochondrial function and mitophagy. Liraglutide reduced lipid accumulation, inhibited NLRP3 inflammasome and pyroptosis activation, attenuated mitochondrial dysfunction and reactive oxygen species generation, augmented mitophagy in hepatocytes. Mitophagy inhibition with 3-methyladenine/PINK1-directed siRNA weakened the liraglutide-mediated suppression of inflammatory injury. We propose that liraglutide suppresses NLRP3 inflammasome-induced hepatocyte pyroptosis via mitophagy to slow the progression of NASH.

Autophagy in bone homeostasis and the onset of osteoporosis

Autophagy is an evolutionarily conserved intracellular process, in which domestic cellular components are selectively digested for the recycling of nutrients and energy. This process is indispensable for cell homeostasis maintenance and stress responses. Both genetic and functional studies have demonstrated that multiple proteins involved in autophagic activities are critical to the survival, differentiation, and functioning of bone cells, including osteoblasts, osteocytes, and osteoclasts. Dysregulation at the level of autophagic activity consequently disturbs the balance between bone formation and bone resorption and mediates the onset and progression of multiple bone diseases, including osteoporosis. This review aims to introduce the topic of autophagy, summarize the understanding of its relevance in bone physiology, and discuss its role in the onset of osteoporosis and therapeutic potential.

Autophagy in T Cell Function and Aging

Dysregulation of autophagy with age has been identified as a central mechanism of aging affecting many cells and tissues. T cells do also show decreased activity with age of different autophagic pathways. Here, we will review the current knowledge of the different functions that autophagy has in the regulation of T cell homeostasis, differentiation and function and explore how the age-associated decreased in autophagy activity may contribute to the altered T cell responses that characterize T cell immunosenescence.

Linkage between endosomal escape of LNP-mRNA and loading into EVs for transport to other cells

RNA-based therapeutics hold great promise for treating diseases and lipid nanoparticles (LNPs) represent the most advanced platform for RNA delivery. However, the fate of the LNP-mRNA after endosome-engulfing and escape from the autophagy-lysosomal pathway remains unclear. To investigate this, mRNA (encoding human erythropoietin) was delivered to cells using LNPs, which shows, for the first time, a link between LNP-mRNA endocytosis and its packaging into extracellular vesicles (endo-EVs: secreted after the endocytosis of LNP-mRNA). Endosomal escape of LNP-mRNA is dependent on the molar ratio between ionizable lipids and mRNA nucleotides. Our results show that fractions of ionizable lipids and mRNA (1:1 molar ratio of hEPO mRNA nucleotides:ionizable lipids) of endocytosed LNPs were detected in endo-EVs. Importantly, these EVs can protect the exogenous mRNA during in vivo delivery to produce human protein in mice, detected in plasma and organs. Compared to LNPs, endo-EVs cause lower expression of inflammatory cytokines.

Bacterial Type I CRISPR-Cas systems influence inflammasome activation in mammalian host by promoting autophagy

The clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated systems (CRISPR-Cas) systems in prokaryotes function at defending against foreign DNAs, providing adaptive immunity to maintain homeostasis. CRISPR-Cas may also influence immune regulation ability in mammalian cells through alterations of pathogenic extent and nature. Recent research has implied that Type I CRISPR-Cas systems of Pseudomonas aeruginosa strain UCBPP-PA14 impede recognition by Toll-like receptor 4, and decrease pro-inflammatory responses both in vitro and in vivo. However, the molecular mechanism by which CRISPR-Cas systems affect host immunity is largely undemonstrated. Here, we explored whether CRISPR-Cas systems can influence autophagy to alter the activation of inflammasome. Using the wild-type PA14 and total CRISPR-Cas region deletion (∆TCR) mutant strain, we elucidated the role and underlying mechanism of Type I CRISPR-Cas systems in bacterial infection, and showed that CRISPR-Cas systems impacted the release of mitochondrial DNA and induction of autophagy. CRISPR-Cas deficiency led to an increase of mitochondrial DNA release, a decrease in autophagy, an increase of inflammasome activation and, ultimately, an elevation of pro-inflammatory response. Our findings illustrate a new important mechanism by which Type I CRISPR-Cas systems control their virulence potency to evade host defense.

Cloning and characterization of the target protein subunit lst8 of rapamycin in Apostichopus japonicus

Autophagy plays an important role in the immune defense systems of vertebrates through the interaction between the lethal with SEC13 protein 8 (lst8) and the mechanistic target of rapamycin. In the present study, a novel invertebrate lst8 homologue is identified from Apostichopus japonicus (designated as Ajlst8) via polymerase chain reaction. The full-length complementary DNA of Ajlst8 comprises a 5'-untranslated region (UTR) of 78 base pair (bp), a 3'-UTR of 479 bp, and a putative open reading frame of 951 bp; hence, 316 amino acids are encoded. Structural analysis shows that the deduced amino acid of Ajlst8 shares six typical WD40 domains (28 aa-248 aa). Spatial expression analysis indicates that Ajlst8 is ubiquitously expressed in all the examined tissues, with a larger magnitude in coelomocytes. Vibrio splendidus infection in vivo and lipopolysaccharide exposure in vitro can significantly upregulate the messenger RNA expression of Ajlst8 by 2.39-fold and 1.93-fold compared with the control group, respectively. LPS exposure could also significantly induced the protein level of Ajlst8 to 2.38-fold and the autophagy level was markedly increased by 3.08-fold under same condition. The RNA interference of Ajlst8 in primary coelomocytes also reduces the relative expression of autophagy with a 0.71-fold decrease in the ratio of LC3-II/LC3-I compared with that in the control group. These results indicate that Ajlst8 is a novel immune regulator that may be involved in the antibacterial response process of sea cucumber by regulating autophagy.

Decoding inflammation, its causes, genomic responses, and emerging countermeasures

Inflammation is the mechanism of diseases caused by microbial, autoimmune, allergic, metabolic and physical insults that produce distinct types of inflammatory responses. This aetiologic view of inflammation informs its classification based on a cause‐dependent mechanism as well as a cause‐directed therapy and prevention. The genomic era ushered in a new understanding of inflammation by highlighting the cell's nucleus as the centre of the inflammatory response. Exogenous or endogenous inflammatory insults evoke genomic responses in immune and non‐immune cells. These genomic responses depend on transcription factors, which switch on and off a myriad of inflammatory genes through their regulatory networks. We discuss the transcriptional paradigm of inflammation based on denying transcription factors’ access to the nucleus. We present two approaches that control proinflammatory signalling to the nucleus. The first approach constitutes a novel intracellular protein therapy with bioengineered physiologic suppressors of cytokine signalling. The second approach entails control of proinflammatory transcriptional cascades by targeting nuclear transport with a cell‐penetrating peptide that inhibits the expression of 23 out of the 26 mediators of inflammation along with the nine genes required for metabolic responses. We compare these emerging anti‐inflammatory countermeasures to current therapies. The transcriptional paradigm of inflammation offers nucleocentric strategies for microbial, autoimmune, metabolic, physical and other types of inflammation afflicting millions of people worldwide.

Mechanisms and Pathophysiological Roles of the ATG8 Conjugation Machinery

Since their initial discovery around two decades ago, the yeast autophagy-related (Atg)8 protein and its mammalian homologues of the light chain 3 (LC3) and γ-aminobutyric acid receptor associated proteins (GABARAP) families have been key for the tremendous expansion of our knowledge about autophagy, a process in which cytoplasmic material become targeted for lysosomal degradation. These proteins are ubiquitin-like proteins that become directly conjugated to a lipid in the autophagy membrane upon induction of autophagy, thus providing a marker of the pathway, allowing studies of autophagosome biogenesis and maturation. Moreover, the ATG8 proteins function to recruit components of the core autophagy machinery as well as cargo for selective degradation. Importantly, comprehensive structural and biochemical in vitro studies of the machinery required for ATG8 protein lipidation, as well as their genetic manipulation in various model organisms, have provided novel insight into the molecular mechanisms and pathophysiological roles of the mATG8 proteins. Recently, it has become evident that the ATG8 proteins and their conjugation machinery are also involved in intracellular pathways and processes not related to autophagy. This review focuses on the molecular functions of ATG8 proteins and their conjugation machinery in autophagy and other pathways, as well as their links to disease.

The exosome-like vesicles from osteoarthritic chondrocyte enhanced mature IL-1β production of macrophages and aggravated synovitis in osteoarthritis

Synovitis, a common clinical symptom for osteoarthritis (OA) patients, is highly related to OA pathological progression and pain manifestation. The activated synovial macrophages have been demonstrated to play an important role in synovitis, but the mechanisms about macrophage activation are still not clear. In this study, we found that the exosome-like vesicles from osteoarthritic chondrocytes could be a new biological factor to stimulate inflammasome activation and increase mature IL-1β production in macrophages. The degraded cartilage explants produced more exosome-like vesicles than the nondegraded ones, while the exosome-like vesicles from chondrocytes could enter into joint synovium tissue and macrophages. Moreover, the exosome-like vesicles from osteoarthritic chondrocytes enhanced the production of mature IL-1β in macrophages. These vesicles could inhibit ATG4B expression via miR-449a-5p, leading to inhibition of autophagy in LPS-primed macrophages. The decreased autophagy promoted the production of mitoROS, which further enhanced the inflammasome activation and subsequent IL-1β processing. Ultimately, the increase of mature IL-1β may aggravate synovial inflammation and promote the progression of OA disease. Our study provides a new perspective to understand the activation of synovial macrophages and synovitis in OA patients, which may be beneficial for therapeutic intervention in synovitis-related OA patients.

"Hypothalamic Microinflammation" Paradigm in Aging and Metabolic Diseases

Under conditions leading to aging and metabolic syndrome, the hypothalamus atypically undergoes proinflammatory signaling activation leading to a chronic and stable background inflammation, referred to as "hypothalamic microinflammation." Through the past decade of research, progress has been made to causally link this hypothalamic inflammation to the mechanism of aging as well as metabolic syndrome, promoting the "hypothalamic microinflammation" theory, which helps characterize the consensus of these epidemic health problems. In general, it is consistently appreciated that hypothalamic microinflammation emerges during the early stages of aging and metabolic syndrome and evolves to be multifaceted and advanced alongside disease progression, while inhibition of key inflammatory components in the hypothalamus has a broad range of effects in counteracting these disorders. Herein, focusing on aging and metabolic syndrome, this writing aims to provide an overview of and insights into the mediators, signaling components, cellular impacts, and physiological significance of this hypothalamic microinflammation.

Autophagy dysfunctions associated with cancer cells and their therapeutic implications

Genomic analysis of human cancers indicates that the loss or mutation of core autophagy related genes, (ATG) is uncommon, whereas oncogenic events that activate autophagy and lysosomal biogenesis have been identified. Several studies have demonstrated that autophagy plays a wide variety of physiological and pathophysiological roles in cells: a cellular process that maintains the homeostasis of the normal cell, while self-defects can lead to a lawsuit to accelerate tumorigenesis and developing diseases, such as cancer. Depending on different contexts, autophagy dysfunctions may play a role: neutral, tumor-suppressive, or tumor-promoting. The process of autophagy may function in tumor suppression by mitigating metabolic stress and, in concert with apoptosis, by preventing tumor cell death by necrosis. In this case, optimal combination of autophagy inhibition (CQ, HCQ) with other conventional therapies - chemo or radiotherapy in a variety of tumor types in different phases can be successful approaches for improve the effect of anticancer therapies. This review examines recent insights of the molecular mechanism of autophagy and the potential roles of autophagy in cell death, cancer development, overview of the most recent therapeutic strategies involving autophagy modulators in cancer prevention and therapeutic opportunities.

Autophagy mediates the secretion of macrophage migration inhibitory factor from cardiomyocytes upon serum-starvation

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine. It is elevated early in the blood of acute myocardial infarction patients. However, it is unclear whether and how MIF is released. This study investigated the cellular source and mechanism of MIF release from hearts. An ischemia-mimic treatment induced the secretion of MIF from neonatal rat cardiomyocytes but not from fibroblasts. The treatment did not cause significant leakage of lactate dehydrogenase, suggesting that ischemia induced the MIF secretion without causing severe cell damage. Plasma samples from patients with acute chest pain at the emergency department were collected for the detection of MIF. MIF levels in patients with acute coronary syndrome (ACS) increased early, when cardiac injury markers were not yet elevated, suggesting that ischemia can induce MIF secretion before the occurrence of severe myocardial damage. Serum-starvation caused MIF secretion from rat cardiomyocytes and Langendorff-perfused rat hearts. The secretion was suppressed by the inhibition of autophagy by inhibitors or by silencing of Atg5. In conclusion, serum-starvation induces the secretion of MIF from cardiomyocytes via autophagy dependent pathway. Clarifying the mechanism of MIF secretion will be helpful for its application in the early diagnosis and treatment of ACS.

Autophagic induction modulates splenic plasmacytoid dendritic cell mediated immune response in cerebral malarial infection model

Splenic plasmacytoid dendritic cells (pDC) possess the capability to harbor live replicative Plasmodium parasite. Isolated splenic pDC from infected mice causes malaria when transferred to naïve mice. Incomplete autophagic degradation might cause poor antigen processing and poor immune response. Induction of autophagic flux by rapamycin treatment led to better prognosis by boosting pDC centered immune response against the pathogen. Splenic pDC from rapamycin-treated infected mice, caused less parasitemia in naïve mice. The downregulation of adhesion with unaltered phagocytic potential of the cells post autophagic induction restricted excessive parasite burden within them. Rapamycin-treated pDC played a better role in antigen presentation. They showed higher expression of co-stimulatory molecules CD80, CD86, DEC205, MHCI. Rapamycin-treated pDC induced CD28 expression on CD8⁺ T cells and suppressed FasL level. This cells also influenced differentiation of effector, memory T cell population. The increase in IL10: TNFα ratio, Treg: Th17 ratio and lowering of myeloid DC: plasmacytoid DC ratio was observed. It shifted the overaggressive inflammation mediated Th1 pathway that is reported to incur host damage, to a better well-balanced cytokine profile exhibiting Th2 pathway. Autophagic flux induction within pDC proved to be beneficial in combating malarial pathogenicity.

A Mycobacterium tuberculosis surface protein recruits ubiquitin to trigger host xenophagy

Ubiquitin-mediated xenophagy, a type of selective autophagy, plays crucial roles in host defense against intracellular pathogens including Mycobacterium tuberculosis (Mtb). However, the exact mechanism by which host ubiquitin targets invaded microbes to trigger xenophagy remains obscure. Here we show that ubiquitin could recognize Mtb surface protein Rv1468c, a previously unidentified ubiquitin-binding protein containing a eukaryotic-like ubiquitin-associated (UBA) domain. The UBA-mediated direct binding of ubiquitin to, but not E3 ubiquitin ligases-mediated ubiquitination of, Rv1468c recruits autophagy receptor p62 to deliver mycobacteria into LC3-associated autophagosomes. Disruption of Rv1468c-ubiquitin interaction attenuates xenophagic clearance of Mtb in macrophages, and increases bacterial loads in mice with elevated inflammatory responses. Together, our findings reveal a unique mechanism of host xenophagy triggered by direct binding of ubiquitin to the pathogen surface protein, and indicate a diplomatic strategy adopted by Mtb to benefit its persistent intracellular infection through controlling intracellular bacterial loads and restricting host inflammatory responses.

Ubiquitin (Ub)-mediated xenophagy is important in defense against Mycobacterium tuberculosis (Mtb). Here, Chai et al. describe autophagy triggering by Ub binding to the Mtb surface protein Rv1468c, and show that its deletion leads to increased bacterial loads and hyperinflammatory responses in mice.

Extracellular peptide Kratos restricts cell death during vascular development and stress in Arabidopsis

During plant vascular development, xylem tracheary elements (TEs) form water-conducting, empty pipes by genetically regulated cell death. Cell death is prevented from spreading to non-TEs by unidentified intercellular mechanisms, downstream of METACASPASE9 (MC9)-mediated regulation of autophagy in TEs. Here, we identified differentially abundant extracellular peptides in vascular-differentiating wild-type and MC9-down-regulated Arabidopsis cell suspensions. A peptide named Kratos rescued the abnormally high ectopic non-TE death resulting from either MC9 knockout or TE-specific overexpression of the ATG5 autophagy protein during experimentally induced vascular differentiation in Arabidopsis cotyledons. Kratos also reduced cell death following mechanical damage and extracellular ROS production in Arabidopsis leaves. Stress-induced but not vascular non-TE cell death was enhanced by another identified peptide, named Bia. Bia is therefore reminiscent of several known plant cell death-inducing peptides acting as damage-associated molecular patterns. In contrast, Kratos plays a novel extracellular cell survival role in the context of development and during stress response.

Significance of Autophagy in Dengue Virus Infection: A Brief Review

Dengue virus (DENV) causes asymptomatic to severe life-threatening infections and affects millions of people worldwide. Autophagy, a cellular degradative pathway, has both proviral and antiviral functions. Dengue virus triggers the autophagy pathway for the successful replication of its genome. However, the exact mechanism and the viral factors involved in activating this pathway remain unclear. This review summarizes the existing knowledge on the mechanism of autophagy induction and its significance during DENV infection.