Cf-02, a novel benzamide-linked small molecule, blunts NF-κB activation and NLRP3 inflammasome assembly and improves acute onset of accelerated and severe lupus nephritis in mice

In the present study, acute onset of severe lupus nephritis was successfully treated in mice using a new, benzamide-linked, small molecule that targets immune modulation and the NLRP3 inflammasome. Specifically, 6-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenyl)-2H-benzo[e][1,3]oxazine-2,4(3H)-dione (Cf-02) (a) reduced serum levels of IgG anti-dsDNA, IL-1β, IL-6, and TNF-α, (b) inhibited activation of dendritic cells and differentially regulated T cell functions, and (c) suppressed the NF-κB/NLRP3 inflammasome axis, targeting priming and activating signals of the inflammasome. Moreover, treatment with Cf-02 significantly inhibited secretion of IL-1β in lipopolysaccharide-stimulated macrophages, but this effect was abolished by autophagy induction. These results recommend Cf-02 as a promising drug candidate for the serious renal conditions associated with systemic lupus erythematosus. Future investigations should examine whether Cf-02 may also be therapeutic in other types of chronic kidney disease involving NLRP3 inflammasome-driven signaling.

1-Deoxysphingolipids cause autophagosome and lysosome accumulation and trigger NLRP3 inflammasome activation

1-Deoxysphingolipids (deoxySLs) are atypical sphingolipids of clinical relevance as they are elevated in plasma of patients suffering from hereditary sensory and autonomic neuropathy (HSAN1) or type 2 diabetes. Their neurotoxicity is described best but they inflict damage to various cell types by an uncertain pathomechanism. Using mouse embryonic fibroblasts and an alkyne analog of 1-deoxysphinganine (doxSA), the metabolic precursor of all deoxySLs, we here study the impact of deoxySLs on macroautophagy/autophagy, the regulated degradation of dysfunctional or expendable cellular components. We find that deoxySLs induce autophagosome and lysosome accumulation indicative of an increase in autophagic flux. The autophagosomal machinery targets damaged mitochondria that have accumulated N-acylated doxSA metabolites, presumably deoxyceramide and deoxydihydroceramide, and show aberrant swelling and tubule formation. Autophagosomes and lysosomes also interact with cellular lipid aggregates and crystals that occur upon cellular uptake and N-acylation of monomeric doxSA. As crystals entering the lysophagosomal apparatus in phagocytes are known to trigger the NLRP3 inflammasome, we also treated macrophages with doxSA. We demonstrate the activation of the NLRP3 inflammasome by doxSLs, prompting the release of IL1B from primary macrophages. Taken together, our data establish an impact of doxSLs on autophagy and link doxSL pathophysiology to inflammation and the innate immune system.Abbreviations: alkyne-doxSA: (2S,3R)-2-aminooctadec-17yn-3-ol; alkyne-SA: (2S,3R)-2- aminooctadec-17yn-1,3-diol; aSA: alkyne-sphinganine; ASTM-BODIPY: azido-sulfo-tetramethyl-BODIPY; CerS: ceramide synthase; CMR: clonal macrophage reporter; deoxySLs: 1-deoxysphingolipids; dox(DH)Cer: 1-deoxydihydroceramide; doxCer: 1-deoxyceramide; doxSA: 1-deoxysphinganine; FB1: fumonisin B1; HSAN1: hereditary sensory and autonomic neuropathy type 1; LC3: MAP1LC3A and MAP1LC3B; LPS: lipopolysaccharide; MEF: mouse embryonal fibroblasts; MS: mass spectrometry; N3635P: azido-STAR635P; N3Cy3: azido-cyanine 3; N3picCy3: azido-picolylcyanine 3; NLRP3: NOD-like receptor pyrin domain containing protein 3; P4HB: prolyl 4-hydroxylase subunit beta; PINK1: PTEN induced putative kinase 1; PYCARD/ASC: PYD and CARD domain containing; SPTLC1: serine palmitoyltransferase long chain base subunit 1; SQSTM1: sequestosome 1; TLC: thin layer chromatography.

The Pathways Underlying the Multiple Roles of p62 in Inflammation and Cancer

p62 is a highly conserved, multi-domain, and multi-functional adaptor protein critically involved in several important cellular processes. Via its pronounced domain architecture, p62 binds to numerous interaction partners, thereby influencing key pathways that regulate tissue homeostasis, inflammation, and several common diseases including cancer. Via binding of ubiquitin chains, p62 acts in an anti-inflammatory manner as an adaptor for the auto-, xeno-, and mitophagy-dependent degradation of proteins, pathogens, and mitochondria. Furthermore, p62 is a negative regulator of inflammasome complexes. The transcription factor Nrf2 regulates expression of a bundle of ROS detoxifying genes. p62 activates Nrf2 by interaction with and autophagosomal degradation of the Nrf2 inhibitor Keap1. Moreover, p62 activates mTOR, the central kinase of the mTORC1 sensor complex that controls cell proliferation and differentiation. Through different mechanisms, p62 acts as a positive regulator of the transcription factor NF-κB, a central player in inflammation and cancer development. Therefore, p62 represents not only a cargo receptor for autophagy, but also a central signaling hub, linking several important pro- and anti-inflammatory pathways. This review aims to summarize knowledge about the molecular mechanisms underlying the roles of p62 in health and disease. In particular, different types of tumors are characterized by deregulated levels of p62. The elucidation of how p62 contributes to inflammation and cancer progression at the molecular level might promote the development of novel therapeutic strategies.

Autophagic Degradation of Gasdermin D Protects against Nucleus Pulposus Cell Pyroptosis and Retards Intervertebral Disc Degeneration In Vivo

Intervertebral disc degeneration (IDD) is the primary culprit of low back pain and renders heavy social burden worldwide. Pyroptosis is a newly discovered form of programmed cell death, which is also involved in nucleus pulposus (NP) cells during IDD progression. Moderate autophagy activity is critical for NP cell survival, but its relationship with pyroptosis remains unknown. This study is aimed at investigating the relationship between autophagy and pyroptotic cell death. The pyroptosis executor N-terminal domain of gasdermin D (GSDMD-N) and inflammation-related proteins were measured in lipopolysaccharide- (LPS-) treated human NP cells. Inhibition of autophagy by siRNA transfection and chemical drugs aggravated human NP cell pyroptosis. Importantly, we found that the autophagy-lysosome pathway and not the proteasome pathway mediated the degradation of GSDMD-N as lysosome dysfunction promoted the accumulation of cytoplasmic GSDMD-N. Besides, P62/SQSTM1 colocalized with GSDMD-N and mediated its degradation. The administration of the caspase-1 inhibitor VX-765 could reduce cell pyroptosis as confirmed in a rat disc IDD model in vivo, whereas ATG5 knockdown significantly accelerated the progression of IDD. In conclusion, our study indicated that autophagy protects against LPS-induced human NP cell pyroptosis via a P62/SQSTM1-mediated degradation mechanism and the inhibition of pyroptosis retards IDD progression in vivo. These findings deepen the understanding of IDD pathogenesis and hold implications in unraveling therapeutic targets for IDD treatment.

Aberrant NLRP3 Inflammasome Activation Ignites the Fire of Inflammation in Neuromuscular Diseases

Inflammasomes are molecular hubs that are assembled and activated by a host in response to various microbial and non-microbial stimuli and play a pivotal role in maintaining tissue homeostasis. The NLRP3 is a highly promiscuous inflammasome that is activated by a wide variety of sterile triggers, including misfolded protein aggregates, and drives chronic inflammation via caspase-1-mediated proteolytic cleavage and secretion of proinflammatory cytokines, interleukin-1β and interleukin-18. These cytokines further amplify inflammatory responses by activating various signaling cascades, leading to the recruitment of immune cells and overproduction of proinflammatory cytokines and chemokines, resulting in a vicious cycle of chronic inflammation and tissue damage. Neuromuscular diseases are a heterogeneous group of muscle disorders that involve injury or dysfunction of peripheral nerves, neuromuscular junctions and muscles. A growing body of evidence suggests that dysregulation, impairment or aberrant NLRP3 inflammasome signaling leads to the initiation and exacerbation of pathological processes associated with neuromuscular diseases. In this review, we summarize the available knowledge about the NLRP3 inflammasome in neuromuscular diseases that affect the peripheral nervous system and amyotrophic lateral sclerosis, which affects the central nervous system. In addition, we also examine whether therapeutic targeting of the NLRP3 inflammasome components is a viable approach to alleviating the detrimental phenotype of neuromuscular diseases and improving clinical outcomes.

Mitochondrial DNA enables AIM2 inflammasome activation and hepatocyte pyroptosis in nonalcoholic fatty liver disease

Mitochondria damage exacerbates NAFLD through trigerring AIM2 inflammasome activation and hepatocyte pyroptosis. This study provides novel insights into the underlying mechanisms of mitochondrial DNA synthesis in NAFLD and also suggests potential therapeutic targets for the treatment of NAFLD.

Lipoxin A4 promotes autophagy and inhibits overactivation of macrophage inflammasome activity induced by Pg LPS

Objective

To explore the role of lipoxin A4 (LXA4) on inflammasome and inflammatory activity in macrophages activated by Porphyromonas gingivalis lipopolysaccharide (PgLPS) one of the major causative agents of chronic periodontitis.

Methods

The mouse macrophage cell line RAW264.7 was used to produce an activated inflammation model. Markers of inflammasome and inflammatory activity and autophagy were assessed by ELISA, reverse transcription polymerase chain reaction (RT-PCR), and Western blot assay.

Results

Markers of inflammasome activity, inflammation and autophagy increased with Pg LPS concentration. They also increased with increasing exposure to Pg LPS up to 12h but decreased at 24h. However, markers of autophagy increased. Phosphorylated NF-κBp65 decreased with LXA4, which was similar to results obtained with the autophagy inducer, rapamycin.

Conclusions

LXA4 promoted autophagy and inhibited activation of inflammasomes and inflammation markers in macrophage inflammation induced by PgLPS and this action was linked to the phosphorylation of NF-κB.

PRAK Promotes the Pathogen Clearance by Macrophage Through Regulating Autophagy and Inflammasome Activation

The p38 regulated/activated protein kinase (PRAK) is a protein kinase downstream of p38MAPK. The present study investigated its function in the macrophage. Myeloid-specific deletion of Prak resulted in a significant reduction in F4/80⁺CD11b⁺ peritoneal macrophages with decreased expression of MHC-II and CD80. Upon infection with Listeria monocytogenes, Prak-deficient mice demonstrated an increased mortality, which was accompanied by a higher bacterial load in multiple tissues and elevated levels of proinflammatory cytokines in the serum. While the Prak-deficient macrophage showed similar potency in phagocytosis assays, its bactericidal activity was severely impaired. Moreover, Prak deficiency was associated with defects in ROS production, inflammasome activation as well as autophagy induction. Therefore, PRAK critically contributes to the clearance of intracellular pathogens by affecting multiple aspects of the macrophage function.

An update on the regulatory mechanisms of NLRP3 inflammasome activation

The NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a multiprotein complex involved in the release of mature interleukin-1β and triggering of pyroptosis, which is of paramount importance in a variety of physiological and pathological conditions. Over the past decade, considerable advances have been made in elucidating the molecular mechanisms underlying the priming/licensing (Signal 1) and assembly (Signal 2) involved in NLRP3 inflammasome activation. Recently, a number of studies have indicated that the priming/licensing step is regulated by complicated mechanisms at both the transcriptional and posttranslational levels. In this review, we discuss the current understanding of the mechanistic details of NLRP3 inflammasome activation with a particular emphasis on protein-protein interactions, posttranslational modifications, and spatiotemporal regulation of the NLRP3 inflammasome machinery. We also present a detailed summary of multiple positive and/or negative regulatory pathways providing upstream signals that culminate in NLRP3 inflammasome complex assembly. A better understanding of the molecular mechanisms underlying NLRP3 inflammasome activation will provide opportunities for the development of methods for the prevention and treatment of NLRP3 inflammasome-related diseases.

Pathogenic, but Not Nonpathogenic, Rickettsia spp. Evade Inflammasome-Dependent IL-1 Responses To Establish an Intracytosolic Replication Niche

Rickettsia species (spp.) are strict obligate intracellular bacteria, some of which are pathogenic in their mammalian host, including humans. One critical feature of these stealthy group of pathogens is their ability to manipulate hostile cytosolic environments to their benefits. Although our understanding of Rickettsia cell biology and pathogenesis is evolving, the mechanisms by which pathogenic Rickettsia spp. evade host innate immune detection remain elusive. Here, we show that disease severity in wild-type (WT) C57BL/6J mice infected with Rickettsia typhi (the etiologic agent of murine typhus) and Rickettsia rickettsii (the etiologic agent of Rocky Mountain spotted fever), but not with the nonpathogenic species Rickettsia montanensis, correlated with levels of bacterial burden as detected in the spleens of mice, as well as the serum concentrations of proinflammatory cytokine interleukin-1α (IL-1α) and, to a lesser extent, IL-1β. Antibody-mediated neutralization of IL-1α confirmed a key role in controlling mortality rates and bacterial burdens of rickettsia-infected WT mice. As macrophages are a primary source of both IL-1α and IL-1β cytokines, we determined the mechanism of the antirickettsial activities using bone marrow-derived macrophages. We found that pathogenic R. typhi and R. rickettsii, but not nonpathogenic R. montanensis, eluded pro-IL-1α induction and benefited predominantly from the reduced IL-1α secretion, via a caspase-11-gasdermin D (Gsdmd)-dependent pathway, to facilitate intracytosolic replication. Adoptive transfer experiments identified that IL-1α secretion by macrophages was critical for controlling rickettsiosis in WT mice. In sum, we identified a previously unappreciated pathway by which pathogenic, unlike nonpathogenic, rickettsiae preferentially target the caspase-11-Gsdmd-IL-1α signaling axis in macrophages, thus supporting their replication within the host. IMPORTANCE Currently, no vaccines are available to prevent rickettsioses, while vector-borne rickettsial infections in humans are on the rise globally. In fact, the insufficient understanding of how pathogenic Rickettsia species circumvent host immune defense mechanisms has significantly hindered the development of more effective therapeutics. Here, we identified a previously unappreciated role for the caspase-11-Gsdmd-IL-1α signaling axis in limiting the replication of pathogenic R. rickettsia and R. typhi species in murine macrophages and wild-type (WT) C57BL/6J mice. Adoptive transfer studies further identified IL-1α-secreting macrophages as critical mediators in controlling rickettsial infection in WT mice. Collectively, these findings provide insight into the potential mechanism of how pathogenic, but not nonpathogenic, Rickettsia spp. benefit from a reduction in the caspase-11-Gsdmd-mediated release of IL-1α to support host colonization.

Contradictory regulation of macrophages on atherosclerosis based on polarization, death and autophagy

The main pathological feature of atherosclerosis is lipid metabolism disorder and inflammation. Macrophages, as the most important immune cells in the body, run through the beginning and end of disease development. After macrophages overtake the atherosclerosis-susceptible area apolipoprotein low-density lipoprotein ox-LDL, they transform into foam cells that adhere to blood vessels and recruit a large number of pro-inflammatory factors to initiate the disease. Promoting the outflow of lipids in foam cells and alleviating inflammation have become the basic ideas for the study of atherosclerosis treatment strategies. The polarization of macrophages refers to the estimation of the activation of macrophages at a specific point in space and time. Determining the proportion of different macrophage phenotypes in the plaque can help identify delay or prevent disease development. However, the abnormal polarization of macrophages and the accumulation of lipid also affect the growth state of cells to some extent, thus aggravate the influence on plaque area and stability. Besides, overactive or deficient autophagy of macrophages may also lead to cell death and participate in lipid metabolism and inflammation regression. In this paper, the role of macrophages in atherosclerosis was discussed from three aspects: polarization, death, and autophagy.

LCC18, a benzamide-linked small molecule, ameliorates IgA nephropathy in mice

IgA nephropathy (IgAN), an immune complex-mediated process and the most common primary glomerulonephritis, can progress to end-stage renal disease in up to 40% of patients. Accordingly, a therapeutic strategy targeting a specific molecular pathway is urgently warranted. Aided by structure characterisation and target identification, we predicted that a novel ring-fused 6-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenyl)-2H-benzo[e][1,3]oxazine-2,4(3H)-dione (LCC18) targets the NLRP3 inflammasome, which participates in IgAN pathogenesis. We further developed biomarkers for the disease. We used two complementary IgAN models in C57BL/6 mice, involving TEPC-15 hybridoma-derived IgA, and in gddY mice. Moreover, we created specific cell models to validate therapeutic effects of LCC18 on IgAN and to explain its underlying mechanisms. IgAN mice benefited significantly from treatment with LCC18, showing dramatically improved renal function, including greatly reduced proteinuria and renal pathology. Mechanistic studies showed that the mode of action specifically involved: (1) blocking of the MAPKs/COX-2 axis-mediated priming of the NLRP3 inflammasome; (2) inhibition of ASC oligomerisation and NLRP3 inflammasome assembly by inhibiting NLRP3 binding to PKR, NEK7 and ASC; and (3) activation of autophagy. LCC18 exerts therapeutic effects on murine IgAN by differentially regulating NLRP3 inflammasome activation and autophagy induction, suggesting this new compound as a promising drug candidate to treat IgAN. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Role of Mitochondria in Pyroptosis

Pyroptosis is a recently discovered aspartic aspart-specific cysteine protease (Caspase-1/4/5/11) dependent mode of gene-regulated cell death cell death, which is represented by the rupture of cell membrane perforations and the production of proinflammatory mediaters like interleukin-18(IL-18) and interleukin-1β (IL-1β). Mitochondria also play an important role in apoptotic cell death. When it comes to apoptosis of mitochondrion, mitochondrial outer membrane permeabilization (MOMP) is commonly known to cause cell death. As a downstream pathological process of apoptotic signaling, MOMP participates in the leakage of cytochrome-c from mitochondrion to the cytosol and subsequently activate caspase proteases. Hence, targeting MOMP for the sake of manipulating cell death presents potential therapeutic effects among various types of diseases, such as autoimmune disorders, neurodegenerative diseases, and cancer. In this review, we highlights the roles and significance of mitochondria in pyroptosis to provide unexplored strategies that target the mitochondria to regulate cell death for clinical benefits.

Effect of Sirolimus on the Level of Peripheral Blood Lymphocyte Autophagy in Children With Systemic Lupus Erythematosus

Background: To observe the changes of autophagy-related protein levels in peripheral blood lymphocytes before and after sirolimus treatment in children with systemic lupus erythematosus (SLE). Methods: Children with SLE were randomly divided into two groups, 28 in the traditional treatment group and 28 in the sirolimus group. Fifteen healthy children who were in the same period were collected as the normal control group. Clinical laboratory indexes, the percentage of routine lymphocytes, complement C3, complement C4, serum Anti-dsDNA and SLEDAI were detected. Results: At 3 and 6 months after treatment, compared with the traditional treatment group, the percentage of routine lymphocytes in the sirolimus group increased (P = 0.03), SLEDAI score and positive rate of Anti-dsDNA decreased (P = 0.01). Compared with normal children, the expression of microtubule-associated protein 1 light chain 3 (LC3) protein in peripheral blood lymphocytes was significantly higher (P = 0.006); peripheral blood expression of P62/SQSTM1 (sequestosome 1) protein in lymphocytes decreased (P = 0.02). Conclusion: Sirolimus can play a role in the treatment of systemic lupus erythematosus by regulating the level of autophagy.

A Synthetic Small Molecule F240B Decreases NLRP3 Inflammasome Activation by Autophagy Induction

Conjugated polyenes are a class of widely occurring natural products with various biological functions. We previously identified 4-hydroxy auxarconjugatin B (4-HAB) as anti‐inflammatory agent with an IC₅₀ of ~20 µM. In this study, we synthesized a new anti‐inflammatory 4-HAB analogue, F240B, which has an IC₅₀ of less than 1 µM. F240B dose-dependently induced autophagy by increasing autophagic flux, LC3 speck formation and acidic vesicular organelle formation. F240B inhibited NACHT, LRR and PYD domain-containing protein 3 (NLRP3) inflammasome activation through autophagy induction. In a mechanistic study, F240B inhibited interleukin (IL)-1β (IL-1β) precursor expression, promoted degradation of NLRP3 and IL-1β, and reduced mitochondrial membrane integrity loss in an autophagy-dependent manner. Additionally, F240B inhibited apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization and speck formation without affecting the interaction between NLRP3 and ASC or NIMA-related kinase 7 (NEK7) and double-stranded RNA-dependent kinase (PKR). Furthermore, F240B exerted in vivo anti-inflammatory activity by reducing the intraperitoneal influx of neutrophils and the levels of IL-1β, active caspase-1, IL-6 and monocyte chemoattractant protein-1 (MCP-1) in lavage fluids in a mouse model of uric acid crystal-induced peritonitis. In conclusion, F240B attenuated the NLRP3 inflammasome through autophagy induction and can be developed as an anti-inflammatory agent in the future.

The Role of Soluble Uric Acid in Modulating Autophagy Flux and Inflammasome Activation during Bacterial Infection in Macrophages

Autophagy is a homeostatic process that regulates and recycles intracellular structures and is a host defense mechanism that facilitates bacterial clearance. Uric acid in plasma is a major antioxidant but in certain conditions acts as an inflammatory danger signal. The aim of this study is to investigate the effect of soluble uric acid on autophagy and the inflammatory responses in macrophages during bacterial infection. Herein, we employed murine RAW264.7 macrophages that express uricase enzyme and human THP-1 cells that are uricase-deficient. Three different strains of Staphylococcus aureus and two different strains of Klebsiella pneumoniae were used to infect macrophages in presence and absence of soluble uric acid. We found that soluble uric acid enhanced autophagy flux in infected macrophages. We observed that IL-1β increased during bacterial infection but decreased when macrophages were co-stimulated with bacteria and uric acid. In contrast to IL-1β, soluble uric acid did not affect TNFα release and there were no dramatic differences when macrophages were infected with S. aureus or K. pneumoniae. In conclusion, uric acid enhances autophagy flux during bacterial infection, consequently reducing inflammasome activation in macrophages. Understanding the effect of uric acid on the interplay between autophagy and inflammation will facilitate therapeutic design.

Interplay Between Autophagy and Zinc

Autophagy is a conserved catabolic process that plays an important role in cellular homeostasis. The study of the interplay between autophagy and zinc has gained interest over the last years. Multiple studies have indicated that zinc stimulates autophagy and is critical for basal and induced autophagy in mammalian cells. Conversely, autophagy is induced by zinc starvation in yeast. There are no studies analyzing the role of zinc in either Microautophagy or Chaperone-Mediated-Autophagy. The mechanisms by which zinc modulates autophagy are still poorly understood. Studies examining loss of function of genes involved in cellular zinc homeostasis have provided novel insights into the role of zinc in autophagy. Autophagy may help cells adapt to changes in zinc availability in medium by controlling zinc mobilization, recycling, and secretion. Zinc is a key player in toxic and protective autophagy.

Focus on the Multimodal Role of Autophagy in Rheumatoid Arthritis

Autophagy exerts its dual role in eukaryotic cells and exerts its cytoprotective action through degradation mechanism and by regulating catabolic processes which results in elimination of pathogens. Under suitable conditions, autophagy is associated with recycling of cytoplasmic components which causes regeneration of energy whereas deregulated autophagy exerts its implicated role in development and pathogenesis of auto-immune diseases such as rheumatoid arthritis. The immune, innate, and adaptive responses are regulated through the development, proliferation, and growth of lymphocytes. Such innate and adaptive responses can act as mediator of arthritis; along with this, stimulation of osteoclast-mediated bone resorption takes place via transferring citrullinated peptides towards MHC (major histocompatibility complex) compartments, thereby resulting in degradation of bone. Processes such as apoptosis resistance are also regulated through autophagy. In this review, the current knowledge based on role of autophagy in pathogenesis of rheumatoid arthritis is summarized along with proteins associated.

Endoplasmic reticulum stress and autophagy in HIV-1-associated neurocognitive disorders

Although antiretroviral therapy (ART) affects virologic suppression and prolongs life expectancies among HIV-positive patients; HIV-1-associated neurocognitive disorders (HAND) continue to be diagnosed in patients with HIV-1 undergoing treatment. The extensive clinical manifestations of HAND include behavioral, cognitive, and motor dysfunctions that severely affect the patients' quality of life. The pathogenesis of HAND has received increasing attention as a potential avenue by which to improve the treatment of the condition. Many studies have shown that endoplasmic reticulum (ER) stress, autophagy, and their interaction play important roles in the onset and development of neurodegenerative diseases. While the accumulation of misfolded proteins can induce ER stress, autophagy can effectively remove accumulated toxic proteins, reduce ER stress, and thus inhibit the development of neuropathy. Through the in-depth study of ER stress and autophagy, both have been recognized as promising targets for pharmacotherapeutic intervention in the treatment of HAND. This review will highlight the effects of ER stress, autophagy, and their interaction in the context of HAND, thereby helping to inform the future development of targeted treatments for patients with HAND.

Lactobacillus johnsonii L531 Ameliorates Escherichia coli-Induced Cell Damage via Inhibiting NLRP3 Inflammasome Activity and Promoting ATG5/ATG16L1-Mediated Autophagy in Porcine Mammary Epithelial Cells

Escherichia coli (E. coli), a main mastitis-causing pathogen in sows, leads to mammary tissue damage. Here, we explored the effects of Lactobacillus johnsonii L531 on attenuating E. coli-induced inflammatory damage in porcine mammary epithelial cells (PMECs). L. johnsonii L531 pretreatment reduced E. coli adhesion to PMECs by competitive exclusion and the production of inhibitory factors and decreased E. coli-induced destruction of cellular morphology and ultrastructure. E. coli induced activation of NLRP3 inflammasome associated with increased expression of NLRP3, ASC, and cleaved caspase-1, however, L. johnsonii L531 inhibited E. coli-induced activation of NLRP3 inflammasome. Up-regulation of interleukin (Il)-1β, Il-6, Il-8, Il-18, tumor necrosis factor alpha, and chemokine Cxcl2 expression after E. coli infection was attenuated by L. johnsonii L531. E. coli infection inhibited autophagy, whereas L. johnsonii L531 reversed the inhibitory effect of E. coli on autophagy by decreasing the expression of autophagic receptor SQSTM1/p62 and increasing the expression of autophagy-related proteins ATG5, ATG16L1, and light chain 3 protein by Western blotting analysis. Our findings suggest that L. johnsonii L531 pretreatment restricts NLRP3 inflammasome activity and induces autophagy through promoting ATG5/ATG16L1-mediated autophagy, thereby protecting against E. coli-induced inflammation and cell damage in PMECs.

NLRP3 Inflammasome in Acute Myocardial Infarction

Acute myocardial infarction (AMI) is associated with the induction of a sterile inflammatory response that leads to further injury. The NACHT, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a macromolecular structure responsible for the inflammatory response to injury or infection. NLRP3 can sense intracellular danger signals, such as ischemia and extracellular or intracellular alarmins during tissue injury. The NLRP3 inflammasome is primed and triggered by locally released damage-associated molecular patterns and amplifies the inflammatory response and cell death through caspase-1 activation. Here, we examine the scientific evidence supporting a role for NLRP3 in AMI and the available strategies to inhibit the effects of the inflammasome. Our focus is on the beneficial effects seen in experimental models of AMI in preclinical animal models and the initial results of clinical trials.

Preconditioning with cell-free DNA prevents DSS-colitis by promoting cell protective autophagy

Presence of cell-free DNA (cfDNA) in sera of patients with inflammatory bowel diseases (IBD) is a long-known fact. The biological effect of cfDNA administration on cellular autophagy within normal and inflammatory circumstances remains unclear. In this study, the effects of intravenous cfDNA pretreatment on autophagy response were studied in dextran sulfate sodium (DSS)-induced acute experimental colitis. Selected proinflammatory cytokine and autophagy-related gene and protein expressions were compared with clinical and histological activity parameters, and with transmission electron microscopic evaluations. A single intravenous dose of cfDNA pretreatment with cfDNA from colitis exhibited beneficial response concerning the clinical and histological severity of DSS-colitis as compared with effects of normal cfDNA. Pretreatment with colitis-derived cfDNA substantially altered the gene and protein expression of several autophagy and inflammatory cytokine genes in a clinically favorable manner. Autophagy in splenocytes is also altered after colitis-derived cfDNA pretreatment. During the process of acute colitis, the subsequent inflammatory environment presumably results in changes of cfDNA with the potential to facilitate cell protective autophagy. Understanding the molecular mechanisms behind the impact of colitis-associated autophagy, and elucidating alterations of the interaction between autophagy and innate immunity caused by nucleic acids may provide further insight into the etiology of IBD. By targeting or modifying cfDNA, novel anti-inflammatory therapies may be developed.

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.

Pharmacological modulation of mitochondrial calcium uniporter controls lung inflammation in cystic fibrosis

Mitochondria physically associate with the endoplasmic reticulum to coordinate interorganelle calcium transfer and regulate fundamental cellular processes, including inflammation. Deregulated endoplasmic reticulum-mitochondria cross-talk can occur in cystic fibrosis, contributing to hyperinflammation and disease progression. We demonstrate that Pseudomonas aeruginosa infection increases endoplasmic reticulum-mitochondria associations in cystic fibrosis bronchial cells by stabilizing VAPB-PTPIP51 (vesicle-associated membrane protein-associated protein B-protein tyrosine phosphatase interacting protein 51) tethers, affecting autophagy. Impaired autophagy induced mitochondrial unfolding protein response and NLRP3 inflammasome activation, contributing to hyperinflammation. The mechanism by which VAPB-PTPIP51 tethers regulate autophagy in cystic fibrosis involves calcium transfer via mitochondrial calcium uniporter. Mitochondrial calcium uniporter inhibition rectified autophagy and alleviated the inflammatory response in vitro and in vivo, resulting in a valid therapeutic strategy for cystic fibrosis pulmonary disease.

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 Protects Against Developing Increased Lung Permeability and Hypoxemia by Down Regulating Inflammasome Activity and IL-1β in LPS Plus Mechanical Ventilation-Induced Acute Lung Injury

Targeting inflammasome activation to modulate interleukin (IL)-1β is a promising treatment strategy against acute respiratory distress syndrome and ventilator-induced lung injury (VILI). Autophagy is a key regulator of inflammasome activation in macrophages. Here, we investigated the role of autophagy in the development of acute lung injury (ALI) induced by lipopolysaccharide (LPS) and mechanical ventilation (MV). Two hours before starting MV, 0.2 mg/kg LPS was administered to mice intratracheally. Mice were then placed on high-volume MV (30 ml/kg with 3 cmH₂O positive end-expiratory pressure for 2.5 h without additional oxygen application). Mice with myeloid-specific deletion of the autophagic protein ATG16L1 (Atg16l1^fl/flLysM^Cre) suffered severe hypoxemia (adjusted p < 0.05) and increased lung permeability (p < 0.05, albumin level in bronchoalveolar lavage fluid) with significantly higher IL-1β release into alveolar space (p < 0.05). Induction of autophagy by fasting-induced starvation led to improved arterial oxygenation (adjusted p < 0.0001) and lung permeability (p < 0.05), as well as significantly suppressed IL-1β production (p < 0.01). Intratracheal treatment with anti-mouse IL-1β monoclonal antibody (mAb; 2.5 mg/kg) significantly improved arterial oxygenation (adjusted p < 0.01) as well as lung permeability (p < 0.05). On the other hand, deletion of IL-1α gene or use of anti-mouse IL-1α mAb (2.5 mg/kg) provided no significant protection, suggesting that the LPS and MV-induced ALI is primarily dependent on IL-1β, but independent of IL-1α. These observations suggest that autophagy has a protective role in controlling inflammasome activation and production of IL-1β, which plays a critical role in developing hypoxemia and increased lung permeability in LPS plus MV-induced acute lung injury.

The evaluation of cytokines to help establish diagnosis and guide treatment of autoinflammatory and autoimmune diseases

Our knowledge of the role of cytokines in pathologic conditions has increased considerably with the emergence of molecular and genetic studies, particularly in the case of autoinflammatory monogenic diseases. Many rare disorders, considered orphan until recently, are directly related to abnormal gene regulation, and the treatment with biologic agents (biologics) targeting cytokine receptors, intracellular signaling or specific cytokines improve the symptoms of an increasing number of chronic inflammatory diseases. As it is currently impossible to systematically conduct genetic studies for all patients with autoinflammatory and autoimmune diseases, the evaluation of cytokines can be seen as a simple, less time consuming, and less expensive alternative. This approach could be especially useful when the diagnosis of syndromes of diseases of unknown etiology remains problematic. The evaluation of cytokines could also help avoid the current trial-and-error approach, which has the disadvantages of exposing patients to ineffective drugs with possible unnecessary side effects and permanent organ damages. In this review, we discuss the various possibilities, as well as the limitations of evaluating the cytokine profiles of patients suffering from autoinflammatory and autoimmune diseases, with methods such as direct detection of cytokines in the plasma/serum or following ex vivo stimulation of PBMCs leading to the production of their cytokine secretome. The patients' secretome, combined with biomarkers ranging from genetic and epigenetic analyses to immunologic biomarkers, may help not only the diagnosis but also guide the choice of biologics for more efficient and rapid treatments.

Autophagy and Protein Secretion

Autophagy - conventional for macroautophagy - is a major recycling strategy that ensures cellular homeostasis through the selective engulfment of cytoplasmic supramolecular cargos in double membrane vesicles and their rapid dispatch to the lysosome for digestion. As autophagy operates in the cytoplasm, its interference with secretory proteins, that is, proteins destined to the plasma membrane or the extracellular space, generally synthesized and routed within the endoplasmic reticulum (ER), has been relatively overlooked in the past. However, mounting evidence reveals that autophagy in fact heavily regulates protein secretion through diverse mechanisms. First, autophagy is closely involved in the unconventional secretion of leaderless proteins, a pool of proteins destined extracellularly, but lacking an ER-targeted leader sequence, and thus manufactured in the cytosol. Autophagy-related (ATG) genes now appear instrumental to the underlying pathways, hence the recently coined concept of secretory autophagy, or better ATG gene-dependent secretion. Indeed, ATG genes regulate unconventional protein secretion at multiple levels, ranging from intracellular inflammatory signaling, for example, through the control of mitochondrial health and inflammasome activity, to trafficking of leaderless proteins. Moreover, perhaps less expectedly, autophagy also participates in the control of conventional secretion, intersecting the secretory apparatus at multiple points, though with surprising differences among professional secretory cell types that disclose remarkable and unpredicted specificity. This review synopsizes the multiple mechanisms whereby autophagy interfaces with conventional and unconventional protein secretory pathways and discusses the relative teleology. Altogether, the diverse controls exerted on protein secretion broaden and deepen the homeostatic significance of autophagy within the cell.

New insights into the interplay between autophagy, gut microbiota and inflammatory responses in IBD

One of the most significant challenges of inflammatory bowel disease (IBD) research is to understand how alterations in the symbiotic relationship between the genetic composition of the host and the intestinal microbiota, under impact of specific environmental factors, lead to chronic intestinal inflammation. Genome-wide association studies, followed by functional studies, have identified a role for numerous autophagy genes in IBD, especially in Crohn disease. Studies using in vitro and in vivo models, in addition to human clinical studies have revealed that autophagy is pivotal for intestinal homeostasis maintenance, gut ecology regulation, appropriate intestinal immune responses and anti-microbial protection. This review describes the latest researches on the mechanisms by which dysfunctional autophagy leads to disrupted intestinal epithelial function, gut dysbiosis, defect in anti-microbial peptide secretion by Paneth cells, endoplasmic reticulum stress response and aberrant immune responses to pathogenic bacteria. A better understanding of the role of autophagy in IBD pathogenesis may provide better sub-classification of IBD phenotypes and novel approaches for disease management.Abbreviations: AIEC: adherent-invasive Escherichia coli; AMPK: AMP-activated protein kinase; ATF6: activating transcription factor 6; ATG: autophagy related; Atg16l1[ΔIEC] mice: mice with Atg16l1 depletion specifically in intestinal epithelial cells; Atg16l1[HM] mice: mice hypomorphic for Atg16l1 expression; BCL2: B cell leukemia/lymphoma 2; BECN1: beclin 1, autophagy related; CALCOCO2: calcium binding and coiled-coil domain 2; CASP: caspase; CD: Crohn disease; CGAS: cyclic GMP-AMP synthase; CHUK/IKKA: conserved helix-loop-helix ubiquitous kinase; CLDN2: claudin 2; DAPK1: death associated protein kinase 1; DCs: dendritic cells; DSS: dextran sulfate sodium; EIF2A: eukaryotic translation initiation factor 2A; EIF2AK: eukaryotic translation initiation factor 2 alpha kinase; ER: endoplasmic reticulum; ERBIN: Erbb2 interacting protein; ERN1/IRE1A: ER to nucleus signaling 1; FNBP1L: formin binding protein 1-like; FOXP3: forkhead box P3; GPR65: G-protein coupled receptor 65; GSK3B: glycogen synthase kinase 3 beta; IBD: inflammatory bowel disease; IECs: intestinal epithelial cells; IFN: interferon; IL: interleukin; IL10R: interleukin 10 receptor; IRGM: immunity related GTPase M; ISC: intestinal stem cell; LAMP1: lysosomal-associated membrane protein 1; LAP: LC3-associated phagocytosis; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; LPS: lipopolysaccharide; LRRK2: leucine-rich repeat kinase 2; MAPK: mitogen-activated protein kinase; MHC: major histocompatibility complex; MIF: macrophage migration inhibitory factor; MIR/miRNA: microRNA; MTMR3: myotubularin related protein 3; MTOR: mechanistic target of rapamycin kinase; MYD88: myeloid differentiation primary response gene 88; NLRP3: NLR family, pyrin domain containing 3; NOD2: nucleotide-binding oligomerization domain containing 2; NPC: Niemann-Pick disease type C; NPC1: NPC intracellular cholesterol transporter 1; OMVs: outer membrane vesicles; OPTN: optineurin; PI3K: phosphoinositide 3-kinase; PRR: pattern-recognition receptor; PTPN2: protein tyrosine phosphatase, non-receptor type 2; PTPN22: protein tyrosine phosphatase, non-receptor type 22 (lymphoid); PYCARD/ASC: PYD and CARD domain containing; RAB2A: RAB2A, member RAS oncogene family; RELA: v-rel reticuloendotheliosis viral oncogene homolog A (avian); RIPK2: receptor (TNFRSF)-interacting serine-threonine kinase 2; ROS: reactive oxygen species; SNPs: single nucleotide polymorphisms; SQSTM1: sequestosome 1; TAX1BP1: Tax1 binding protein 1; Th: T helper 1; TIRAP/TRIF: toll-interleukin 1 receptor (TIR) domain-containing adaptor protein; TLR: toll-like receptor; TMEM173/STING: transmembrane protein 173; TMEM59: transmembrane protein 59; TNF/TNFA: tumor necrosis factor; Treg: regulatory T; TREM1: triggering receptor expressed on myeloid cells 1; UC: ulcerative colitis; ULK1: unc-51 like autophagy activating kinase 1; WT: wild-type; XBP1: X-box binding protein 1; XIAP: X-linked inhibitor of apoptosis.

Bacterial Manipulation of Autophagic Responses in Infection and Inflammation

Eukaryotes have cell-autonomous defenses against environmental stress and pathogens. Autophagy is one of the main cellular defenses against intracellular bacteria. In turn, bacteria employ diverse mechanisms to interfere with autophagy initiation and progression to avoid elimination and even to subvert autophagy for their benefit. This review aims to discuss recent findings regarding the autophagic responses regulated by bacterial effectors. Effectors manipulate autophagy at different stages by using versatile strategies, such as interfering with autophagy-initiating signaling, preventing the recognition of autophagy-involved proteins, subverting autophagy component homeostasis, manipulating the autophagy process, and impacting other biological processes. We describe the barriers for intracellular bacteria in host cells and highlight the role of autophagy in the host-microbial interactions. Understanding the mechanisms through which bacterial effectors manipulate host responses will provide new insights into therapeutic approaches for prevention and treatment of chronic inflammation and infectious diseases.

Astrocytes autophagy in aging and neurodegenerative disorders

Astrocytes can serve multiple functions in maintaining cellular homeostasis of the central nervous system (CNS), and normal functions for autophagy in astrocytes is considered to have very vital roles in the pathogenesis of aging and neurodegenerative diseases. Autophagy is a major intracellular lysosomal (or its yeast analog, vacuolar) clearance pathways involved in the degradation and recycling of long-lived proteins, oxidatively damaged proteins and dysfunctional organelles by lysosomes. Current evidence has shown that autophagy might influence inflammation, oxidative stress, aging and function of astrocytes. Although the interrelation between autophagy and inflammation, oxidative stress, aging or neurological disorders have been addressed in detail, the influence of astrocytes mediated-autophagy in aging and neurodegenerative disorders has yet to be fully reviewed. In this review, we will summarize the most up-to-date findings and highlight the role of autophagy in astrocytes and link autophagy of astrocytes to aging and neurodegenerative diseases. Due to the prominent roles of astrocytic autophagy in age-related neurodegenerative diseases, we believe that we can provide new suggestions for the treatment of these disorders.

Schisandrin A protects against lipopolysaccharide-induced mastitis through activating Nrf2 signaling pathway and inducing autophagy

Schisandrin A (Sch A), a dibenzocyclooctadiene lignan extracted from Schisandra chinensis (Turcz.) Baill., has anti-oxidant and anti-inflammatory effects, but the effect on masitits has not been studied. Therefore, we investigated the effect of Sch A in cell and mouse models of lipopolysaccharide (LPS)-induced mastitis. Studies in vivo showed that Sch A reduced LPS-induced mammary injury and the production of pro-inflammatory mediators. Sch A also decreased the levels of pro-inflammatory mediators and activated nuclear factor-E2 associated factor 2 (Nrf2) signaling pathway in mouse mammary epithelial cells (mMECs). The Nrf2 inhibitor partially abrogated the downregulation of Sch A on LPS-induced inflammatory response. In addition, LPS stimulation suppressed autophagy, while both Sch A and the autophagy inducer rapamycin activated autophagy in mMECs, which down-regulated inflammatory response. Sch A also restrained LPS-induced phosphorylation of mammalian target of rapamycin (mTOR) and activated AMP-activated protein kinase (AMPK) and unc-51 like kinase 1 (ULK1). In summary, these results suggest that Sch A exerts protective effects in LPS-induced mastitis models by activating Nrf2 signaling pathway and inducing autophagy and the autophagy is initiated by suppressing mTOR signaling pathway and activating AMPK-ULK1 signaling pathway.

Activation of NLRP3 inflammasome by lymphocytic microparticles via TLR4 pathway contributes to airway inflammation

The presence of elevated T lymphocytic microparticles (TLMPs) during respiratory illness is associated with airway and lung inflammation and epithelial injuries. Although inflammasome and IL-1β signaling are crucial in airway inflammation, little was known about their regulatory mechanism. We hypothesized that TLMPs trigger inflammasome activation and IL-1β production in bronchial and alveolar epithelial cells to induce airway and lung inflammation. In this study, TLMPs induced IL-1β and IL-18 secretion through NLRP3 inflammasome activation and upregulated TLR4 mRNA and protein expression in alveolar (A549) and human airway epithelial (16HBE) cells. Pretreatment with CLI-095, a specific inhibitor of TLR4 signaling, dramatically diminished the TLMP-induced release of IL-1β and IL-18 by inhibiting the formation of NLRP3/ASC/pro-caspase-1 inflammasome in a dose-dependent manner. The TLMP-induced autophagy inhibition in epithelial cells was dependent on the PI3K/Akt signaling pathway, which significantly increased NLRP3 expression and enhanced TLMP-induced inflammation. TLR4, IL-1β, and IL-18 proteins harbored in TLMPs were nonessential for the pro-inflammatory effect. In conclusion, TLMPs induce bronchial and alveolar epithelial cell secretion of IL-1β and IL-18 cytokines by activating the TLR4 and PI3K/Akt signaling pathways and inhibiting autophagy. These effects lead to NLRP3 inflammasome formation and accumulation. TLMPs may be regarded as deleterious markers of airway and lung damage in respiratory diseases.

Hyperglycemia aggravates acute liver injury by promoting liver-resident macrophage NLRP3 inflammasome activation via the inhibition of AMPK/mTOR-mediated autophagy induction

Although the detrimental effects of diabetes mellitus/hyperglycemia have been observed in many liver disease models, the function and mechanism of hyperglycemia regulating liver‐resident macrophages, Kupffer cells (KCs), in thioacetamide (TAA)‐induced liver injury remain largely unknown. In this study, we evaluated the role of hyperglycemia in regulating NOD‐like receptor family pyrin domain‐containing 3 protein (NLRP3) inflammasome activation by inhibiting autophagy induction in KCs in the TAA‐induced liver injury model. Type I diabetes/hyperglycemia was induced by streptozotocin treatment. Compared with the control group, hyperglycemic mice exhibited a significant increase in intrahepatic inflammation and liver injury. Enhanced NLRP3 inflammasome activation was detected in KCs from hyperglycemic mice, as shown by increased gene induction and protein levels of NLRP3, cleaved caspase‐1, apoptosis‐associated speck‐like protein containing a caspase recruitment domain and interleukin‐1β, compared with control mice. NLRP3 inhibition by its antagonist CY‐09 effectively suppressed inflammasome activation in KCs and attenuated liver injury in hyperglycemic mice. Furthermore, inhibited autophagy activation was revealed by transmission electron microscope detection, decreased LC3B protein expression and p‐62 protein degradation in KCs isolated from TAA‐stressed hyperglycemic mice. Interestingly, inhibited 5′ AMP‐activated protein kinase (AMPK) but enhanced mammalian target of rapamycin (mTOR) activation was found in KCs from TAA‐stressed hyperglycemic mice. AMPK activation by its agonist 5‐aminoimidazole‐4‐carboxamide ribonucleotide (AICAR) or mTOR signaling knockdown by small interfering RNA restored autophagy activation, and subsequently, inhibited NLRP3 inflammasome activation in KCs, leading to ultimately reduced TAA‐induced liver injury in the hyperglycemic mice. Our findings demonstrated that hyperglycemia aggravated TAA‐induced acute liver injury by promoting liver‐resident macrophage NLRP3 inflammasome activation via inhibiting AMPK/mTOR‐mediated autophagy. This study provided a novel target for prevention of toxin‐induced acute liver injury under hyperglycemia.

Trichostatin A modulates the macrophage phenotype by enhancing autophagy to reduce inflammation during polymicrobial sepsis

Sepsis is a syndrome of life-threatening organ dysfunction caused by dysregulated host responses to infection. Macrophage polarization is a key process involved in the pathogenesis of sepsis. Recent evidence has demonstrated that autophagy participates in the regulation of macrophage polarization in different phases of inflammation. Here, we investigated whether trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, promotes the macrophage M2 phenotype by enhancing autophagy to counteract excessive inflammation in a cecal ligation and puncture (CLP) mouse model. TSA stimulation increased the proportions of M2 marker (CD206, CD124 and CD23)-labeled RAW264.7 macrophages. Furthermore, with increasing TSA doses, autophagy was enhanced gradually. Interestingly, the autophagy activator rapamycin (Rap), also known as an mTOR inhibitor, unexpectedly decreased the proportions of M2 marker-labeled macrophages. However, TSA treatment reversed the Rap-induced decreases in CD206-labeled macrophages. Next, we stimulated different groups of RAW264.7 cells with the autophagy inhibitors MHY1485 or 3-methyladenine (3-MA). Inhibition of autophagy at any stage in the process suppressed TSA-induced macrophage M2 polarization, but the effect was not associated with mTOR activity. In vivo, TSA administration promoted peritoneal macrophage M2 polarization, increased LC3 II expression, attenuated sepsis-induced organ (lung, liver and kidney) injury, and altered systemic inflammatory cytokine secretion. However, 3-MA abolished the protective effects of TSA in CLP mice and decreased the number of M2 peritoneal macrophages. Therefore, TSA promotes the macrophage M2 phenotype by enhancing autophagy to reduce systemic inflammation and ultimately improves the survival of mice with polymicrobial sepsis.

Sepsis roadmap: What we know, what we learned, and where we are going

Sepsis is a life-threatening condition originating as a result of systemic blood infection causing, one or more organ damage due to the dysregulation of the immune response. In 2017, the world health organization (WHO) declared sepsis as a disease of global health priority, needing special attention due to its high prevalence and mortality around the world. Most of the therapeutics targeting sepsis have failed in the clinics. The present review highlights the history of the sepsis, its immunopathogenesis, and lessons learned after the failure of previously used immune-based therapies. The subsequent section, where to go describes in details the importance of the complement system (CS), autophagy, inflammasomes, and microbiota along with their targeting to manage sepsis. These systems are interconnected to each other, thus targeting one may affect the other. We are in an urgent need for a multi-targeting therapeutic approach for sepsis.

Δ9-Tetrahydrocannabinol Suppresses Monocyte-Mediated Astrocyte Production of Monocyte Chemoattractant Protein 1 and Interleukin-6 in a Toll-Like Receptor 7-Stimulated Human Coculture

Cannabis is widely used in the United States, with an estimated prevalence of 9.5%. Certain cannabinoids in Cannabis sativa, Δ9-tetrahydrocannabinol (THC) in particular, possess immune-modulating and anti-inflammatory activity. Depending on the context, the anti-inflammatory activity of cannabinoids may be beneficial (e.g., in treating inflammatory diseases) or detrimental to normal immune defense against pathogens. The potential beneficial effect of cannabinoids on chronic neuroinflammation has gained recent attention. Monocyte migration to the brain has been implicated as a key event in chronic neuroinflammation and in the etiology of central nervous system diseases including viral infection (e.g., human immunodeficiency virus-associated neurocognitive disorder). In the brain, monocytes can contribute to neuroinflammation through interactions with astrocytes, including inducing astrocyte secretion of cytokines and chemokines. In a human coculture system, monocyte-derived interleukin (IL)-1β due to Toll-like receptor 7 (TLR7) activation has been identified to promote astrocyte production of monocyte chemoattractant protein (MCP)-1 and IL-6. THC treatment of the TLR7-stimulated coculture suppressed monocyte secretion of IL-1β, resulting in decreased astrocyte production of MCP-1 and IL-6. Furthermore, THC displayed direct inhibition of monocytes, as TLR7-stimulated monocyte monocultures treated with THC also showed suppressed IL-1β production. The cannabinoid receptor 2 (CB2) agonist, JWH-015, impaired monocyte IL-1β production similar to that of THC, suggesting that THC acts, in part, through CB2. THC also suppressed key elements of the IL-1β production pathway, including IL1B mRNA levels and caspase-1 activity. Collectively, this study demonstrates that the anti-inflammatory properties of THC suppress TLR7-induced monocyte secretion of IL-1β through CB2, which results in decreased astrocyte secretion of MCP-1 and IL-6. SIGNIFICANCE STATEMENT: Because cannabis use is highly prevalent in the United States and has putative anti-inflammatory properties, it is important to investigate the effect of cannabinoids on immune cell function. Furthermore, cannabinoids have garnered particular interest due to their potential beneficial effects on attenuating viral-induced chronic neuroinflammation. This study utilized a primary human coculture system to demonstrate that the major psychotropic cannabinoid in cannabis, Δ9-tetrahydrocannabinol, and a cannabinoid receptor-2 selective agonist suppress specific monocyte-mediated astrocyte inflammatory responses.

SQSTM1-dependent autophagic degradation of PKM2 inhibits the production of mature IL1B/IL-1β and contributes to LIPUS-mediated anti-inflammatory effect

Synovitis is implicated in the pathology of osteoarthritis (OA) and significantly contributes to the development of OA. As a noninvasive physical therapy, low-intensity pulsed ultrasound (LIPUS) has been reported to possess anti-inflammatory effect in recent years. However, the role of LIPUS on synovitis of OA and the underlying mechanisms are little known. The present study showed that LIPUS ameliorated synovial inflammation in destabilization of the medial meniscus (DMM) mouse model and air pouch model, and alleviated pain gait patterns of DMM mouse. LIPUS dramatically inhibited the production of mature IL1B/IL-1β (interleukin 1 beta) in vitro and in vivo. In addition, LIPUS upregulated the macroautophagy/autophagy level as well as accelerated the formation of an SQSTM1 (sequestosome1)-PKM (pyruvate kinase, muscle) complex in the lipopolysaccharide (LPS)-adenosine triphosphate (ATP)-treated macrophages. Besides, LIPUS downregulated the level of PKM2 in LPS-ATP-treated macrophages, which could be reversed by SQSTM1 knockdown. In brief, the present study for the first time demonstrates that LIPUS inhibits the production of mature IL1B partially via SQSTM1-dependent autophagic degradation of PKM2 in LPS-ATP-treated macrophages, which may further ameliorate the synovial inflammation and gait patterns in animal models. Our data provide new clues for the treatments of synovitis and other inflammatory diseases using LIPUS.

ABBREVIATIONS

3-MA: 3-methyladenene; ATG7: autophagy-related 7; ATP: adenosine triphosphate; BafA1: bafilomycin A₁; BMDMs: bone marrow derived macrophages; CHX: cycloheximide; DMM: destabilization of the medial meniscus; ELISA: enzyme-linked immunosorbent assay; GFP: green fluorescent protein; IL1B/IL-1β: interleukin 1 beta; LIPUS: low-intensity pulsed ultrasound; LIR: LC3-interacting region; LPS: lipopolysaccharide; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MDP: muramyl dipeptide; NFKB/NF-κB: nuclear factor kappa B; NLRP3: NLR family, pyrin domain containing 3; OA: osteoarthritis; PKM/PKM2: pyruvate kinase M1/2; PMA: phorbol-12-myristate-13-acetate; PYCARD/ASC; PYD and CARD domain containing; RFP: red fluorescent protein; siRNAs: small interfering RNAs; SQSTM1: sequestosome 1; TEM: transmission electron microscopy.

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.

An evolutionary perspective on immunometabolism

Metabolism is at the core of all biological functions. Anabolic metabolism uses building blocks that are either derived from nutrients or synthesized de novo to produce the biological infrastructure, whereas catabolic metabolism generates energy to fuel all biological processes. Distinct metabolic programs are required to support different biological functions. Thus, recent studies have revealed how signals regulating cell quiescence, proliferation, and differentiation also induce the appropriate metabolic programs. In particular, a wealth of new studies in the field of immunometabolism has unveiled many examples of the connection among metabolism, cell fate decisions, and organismal physiology. We discuss these findings under a unifying framework derived from the evolutionary and ecological principles of life history theory.

Role of mTORC1 in intestinal epithelial repair and tumorigenesis

mTORC1 signaling is the prototypical pathway regulating protein synthesis and cell proliferation. mTORC1 is active in stem cells located at the base of intestinal crypts but silenced as transit-amplifying cells differentiate into enterocytes or secretory cells along the epithelium. After an insult or injury, self-limiting and controlled activation of mTORC1 is critical for the renewal and repair of intestinal epithelium. mTORC1 promotes epithelial cell renewal by driving cryptic stem cell division, and epithelial cell repair by supporting the dedifferentiation and proliferation of enterocytes or secretory cells. Under repeated insult or injury, mTORC1 becomes constitutively active, triggering an irreversible return to stemness, cell division, proliferation, and inflammation among dedifferentiated epithelial cells. Epithelium-derived cytokines promulgate inflammation within the lamina propria, which in turn releases inflammatory factors that act back on the epithelium where undamaged intestinal epithelial cells participate in the pervading state of inflammation and become susceptible to tumorigenesis.

A novel potent autophagy inhibitor ECDD-S27 targets vacuolar ATPase and inhibits cancer cell survival

Autophagy is a conserved lysosomal-dependent cellular degradation process and its dysregulation has been linked to numerous diseases including neurodegeneration, infectious diseases, and cancer. Modulation of autophagy is therefore considered as an attractive target for disease intervention. We carried out a high-content image analysis screen of natural product-derived compounds to discover novel autophagy modulating molecules. Our screen identified ECDD-S27 as the most effective compound for increasing the number of autophagic vacuoles inside cells. The structure of ECDD-S27 revealed that it is a derivative of cleistanthin A, a natural arylnaphthalene lignan glycoside found in plants. ECDD-S27 increases the number of autophagic vacuoles by inhibiting the autophagic flux and is able to restrict the survival of different cancer cells at low nanomolar concentrations. Molecular docking and SERS analysis showed that ECDD-S27 may potentially target the V-ATPase. Upon treatment of various cancer cells with ECDD-S27, the V-ATPase activity is potently inhibited thereby resulting in the loss of lysosomal acidification. Taken together, these data indicated that ECDD-S27 retards the autophagy pathway by targeting the V-ATPase and inhibits cancer cell survival. The observed antitumor activity without cytotoxicity to normal cells suggests the therapeutic potential warranting further studies on lead optimization of the compound for cancer treatment.

Experimental autoimmune encephalomyelitis in the common marmoset: a translationally relevant model for the cause and course of multiple sclerosis

Aging Western societies are facing an increasing prevalence of chronic autoimmune-mediated inflammatory disorders (AIMIDs) for which treatments that are safe and effective are scarce. One of the main reasons for this situation is the lack of animal models, which accurately replicate clinical and pathological aspects of the human diseases. One important AIMID is the neuroinflammatory disease multiple sclerosis (MS), for which the mouse experimental autoimmune encephalomyelitis (EAE) model has been frequently used in preclinical research. Despite some successes, there is a long list of experimental treatments that have failed to reproduce promising effects observed in murine EAE models when they were tested in the clinic. This frustrating situation indicates a wide validity gap between mouse EAE and MS. This monography describes the development of an EAE model in nonhuman primates, which may help to bridge the gap.

Emerging Roles of Autophagy and Inflammasome in Ehrlichiosis

Human monocytic ehrlichiosis (HME) is a potentially life-threatening tick-borne rickettsial disease (TBRD) caused by the obligate intracellular Gram-negative bacteria, Ehrlichia. Fatal HME presents with acute ailments of sepsis and toxic shock-like symptoms that can evolve to multi-organ failure and death. Early clinical and laboratory diagnosis of HME are problematic due to non-specific flu-like symptoms and limitations in the current diagnostic testing. Several studies in murine models showed that cell-mediated immunity acts as a “double-edged sword” in fatal ehrlichiosis. Protective components are mainly formed by CD4 Th1 and NKT cells, in contrast to deleterious effects originated from neutrophils and TNF-α-producing CD8 T cells. Recent research has highlighted the central role of the inflammasome and autophagy as part of innate immune responses also leading to protective or pathogenic scenarios. Recognition of pathogen-associated molecular patterns (PAMPS) or damage-associated molecular patterns (DAMPS) triggers the assembly of the inflammasome complex that leads to multiple outcomes. Recognition of PAMPs or DAMPs by such complexes can result in activation of caspase-1 and -11, secretion of the pro-inflammatory cytokines IL-1β and IL-18 culminating into dysregulated inflammation, and inflammatory cell death known as pyroptosis. The precise functions of inflammasomes and autophagy remain unexplored in infections with obligate intracellular rickettsial pathogens, such as Ehrlichia. In this review, we discuss the intracellular innate immune surveillance in ehrlichiosis involving the regulation of inflammasome and autophagy, and how this response influences the innate and adaptive immune responses against Ehrlichia. Understanding such mechanisms would pave the way in research for novel diagnostic, preventative and therapeutic approaches against Ehrlichia and other rickettsial diseases.

Podocytes and autophagy: a potential therapeutic target in lupus nephritis

Recent studies suggest that defects in macroautophagy/autophagy contribute to the pathogenesis of systemic lupus erythamatosus (SLE), especially in adaptive immunity. The occurrence and progression of lupus nephritis (LN) is the end result of complex interactions between regulation of immune responses and pathological process by renal resident cells, but there is still a lot of missing information for establishing the role of autophagy in the pathogenesis of LN, and as a therapy target. In our recent study, we observed that autophagy is activated in LN, especially in podocytes. Based on in vitro assays, many of the most important mediators of the disease - patients' sera, patients' IgG and IFNA/IFN-α - can induce autophagy in both murine and human podocytes, by reactive oxygen species production or MTORC1 inhibition; autophagy activation negatively associates with podocyte injury. With regard to intervention, autophagy activators can protect against podocyte injury, whereas autophagy inhibitors aggravate injury. Taken together, our findings suggest that podocyte autophagy is involved in lupus renal protection and may be a therapeutic target. These data shed new light on the role of rapamycin and autophagy inducers in the treatment of SLE. Abbreviations: ALB: albumin; ARHGDIB: Rho GDP dissociation inhibitor beta; APOL1: apolipoprotein L1; ATG5: autophagy related 5; ATG7: autophagy related 7; ATG16L2: autophagy related 16 like 2; BECN1: beclin 1; CDKN1B: cyclin dependent kinase inhibitor 1B; CLEC16A, C-type lectin domain containing 16A; CYBB: cytochrome b-245 beta chain; DC: dendritic cell; DRAM1: DNA damage regulated autophagy modulator 1; eQTL: expression quantitative trait loci; GWAS: genome-wide association study; IFNA: interferon alpha; IRGM: immunity related GTPase M; LRRK2: leucine rich repeat kinase 2; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MTMR3: myotubularin related protein 3; LAP" LC3-associated phagocytosis; LN: lupus nephritis; NOD: non-obese diabetic; NPHS2: NPHS2, podocin; PBMC: peripheral blood mononuclear cell; RUBCN: rubicon autophagy regulator; SLE: systemic lupus erythematosus.

Methylomic correlates of autophagy activity in cystic fibrosis

Autophagy is a highly regulated, biological process that provides energy during periods of stress and starvation. This conserved process also acts as a defense mechanism and clears microbes from the host cell. Autophagy is impaired in Cystic Fibrosis (CF) patients and CF mice, as their cells exhibit low expression levels of essential autophagy molecules. The genetic disorder in CF is due to mutations in the cystic fibrosis transmembrane conductance regulator (cftr) gene that encodes for a chloride channel. CF patients are particularly prone to infection by pathogens that are otherwise cleared by autophagy in healthy immune cells including Burkholderia cenocepacia (B. cenocepacia). The objective of this study is to determine the mechanism underlying weak autophagic activity in CF macrophages and find therapeutic targets to correct it. Using reduced representation bisulfite sequencing (RRBS) to determine DNA methylation profile, we found that the promoter regions of Atg12 in CF macrophages are significantly more methylated than in the wild-type (WT) immune cells, accompanied by low protein expression. The natural product epigallocatechin-3-gallate (EGCG) significantly reduced the methylation of Atg12 promoter improving its expression. Accordingly, EGCG restricted B. cenocepacia replication within CF mice and their derived macrophages by improving autophagy and preventing dissemination. In addition, EGCG improved the function of CFTR protein. Altogether, utilizing RRBS for the first time in the CF field revealed a previously unrecognized mechanism for reduced autophagic activity in CF. Our data also offers a mechanism by which EGCG exerts its positive effects in CF.

Resistance to lysosomotropic drugs used to treat kidney and breast cancers involves autophagy and inflammation and converges in inducing CXCL5

Lysosomotropic agents such as sunitinib, lapatinib, and chloroquine belong to a drug family that is being used more frequently to treat advanced cancers. Sunitinib is standard care for metastatic renal cell carcinomas (mRCC) and lapatinib is used for trastuzumab/pertuzumab-refractory cancers. However, patients ineluctably relapse with a delay varying from a few months to a few years. To improve reactivity prior to relapse it is essential to identify the mechanisms leading to such variability. We showed previously that sunitinib became sequestered in lysosomes because of its basic pKa.

Methods: Modifications to gene expression in response to sunitinib and in sunitinib resistant cells were analyzed by transcriptomic and proteomic analysis. ROS production was evaluated by FACS. Nuclear Factor kappa B (NFkB)-dependent transcriptional regulation of inflammatory gene expression was evaluated with a reporter gene. Correlation of CXCL5 with survival was analyzed with an online available data base (TCGA) and using a cohort of patients enrolled in the SUVEGIL clinical trial (NCT00943839).

Results: We now show that sunitinib sequestration in lysosomes induced an incomplete autophagic process leading to activation of the NFkB inflammatory pathway. We defined a subset of inflammatory cytokines that were up-regulated by the drug either after an acute or chronic stimulus. One of the most up-regulated genes in sunitinib-resistant cells was the CXCL5 cytokine. CXCL5 was also induced in RCC by chloroquine and in a model of HER2 positive breast cancer cell lines after acute or chronic treatment with lapatinib. CXCL5 correlated to shorter survival in RCC and to the most aggressive forms of breast cancers. The levels of CXCL5 present in the plasma of patients treated with sunitinib were predictive of the efficacy of sunitinib but not of the VEGF-directed antibody bevacizumab.

Conclusion: This translational study identified CXCL5 as a biomarker of efficacy of lysosomotropic drugs, a potential asset for personalized medicine.

Thymosin β4 limits inflammation through autophagy

INTRODUCTION

Thymosin β4 (Tβ4) is a thymic hormone with multiple and different intracellular and extracellular activities affecting wound healing, inflammation, fibrosis and tissue regeneration. As the failure to resolve inflammation leads to uncontrolled inflammatory pathology which underlies many chronic diseases, the endogenous pathway through which Tβ4 may promote inflammation resolution becomes of great interest. In this review, we discuss data highlighting the efficacy of Tβ4 in resolving inflammation by restoring autophagy.

AREAS COVERED

The authors provide an overview of the Tβ4's anti-inflammatory properties in several pathologies and provide preliminary evidence on the ability of Tβ4 to resolve inflammation via the promotion of non-canonical autophagy associated with the activation of the DAP kinase anti-inflammatory function.

EXPERT OPINION

Based on its multitasking activity in various animal studies, including tissue repair and prevention of chronic inflammation, Tβ4 may represent a potential, novel treatment for inflammatory diseases associated with defective autophagy.