Impaired autophagy in macrophages promotes inflammatory eye disease

Pathogenesis of gout: Exploring more therapeutic target

Gout is a chronic metabolic and immune disease, and its specific pathogenesis is still unclear. When the serum uric acid exceeds its saturation in the blood or tissue fluid, it is converted to monosodium urate crystals, which lead to acute arthritis of varying degrees, urinary stones, or irreversible peripheral joint damage, and in severe cases, impairment of vital organ function. Gout flare is a clinically significant state of acute inflammation in gout. The current treatment is mostly anti-inflammatory analgesics, which have numerous side effects with limited treatment methods. Gout pathogenesis involves many aspects. Therefore, exploring gout pathogenesis from multiple perspectives is conducive to identifying more therapeutic targets and providing safer and more effective alternative treatment options for patients with gout flare. Thus, this article is of great significance for further exploring the pathogenesis of gout. The author summarizes the pathogenesis of gout from four aspects: signaling pathways, inflammatory factors, intestinal flora, and programmed cell death, focusing on exploring more new therapeutic targets.

Ophthalmological Manifestations in Inflammatory Bowel Diseases: Keep an Eye on It

BACKGROUND AND AIMS

Inflammatory bowel diseases (IBD) are multifactorial chronic inflammatory disorders affecting the gastrointestinal tract. However, a broad spectrum of extraintestinal manifestations (EIMs) is associated with IBD, affecting several organs and systems, such as the skin, musculoskeletal and hepatobiliary systems, and, not least, the eye. Approximately 10% of IBD patients can develop ocular EIMs (O-EIMs) with a higher prevalence in Crohn's disease (CD). Eye-redness, photophobia, pain, and blurred vision are the common symptoms, with a wide rate of severity and clinical impact on the quality of life. This narrative review aims to summarize the prevalence, pathogenesis, and current evidence-based management of O-EIMs, underlying the importance of a holistic approach and specialties collaboration for a prompt diagnosis and treatment.

METHODS

PubMed was searched up to December 2023 to identify relevant studies investigating the pathogenesis, epidemiology, and treatment of O-EIMs in IBD patients.

RESULTS

The mechanisms underlying O-EIMs are partially unknown, encompassing immune dysregulation, shared antigens between the eye and the gut, genetic predisposition, and systemic inflammation driven by high levels of interleukins and cytokines in IBD patients. The complexity of O-EIMs' pathogenesis reflects in the management of these conditions, varying from topical and systemic steroids to immunomodulatory molecules and biologic therapy, such as anti-tumor necrosis factor (TNF)-alpha. A multidisciplinary approach is the backbone of the management of O-EIMs.

Loss of stearoyl-CoA desaturase 2 disrupts inflammatory response in macrophages

Macrophages are innate immune cells that patrol tissues and are the first responders to detect infection. They orchestrate the host immune response in eliminating invading pathogens and the subsequent transition from inflammation to tissue repair. Macrophage dysfunction contributes to age-related pathologies, including low-grade inflammation in advanced age that is termed "inflammaging." Our laboratory has previously identified that macrophage expression of a fatty acid desaturase, stearoyl-CoA desaturase 2 (SCD2), declines with age. Herein, we delineate the precise cellular effects of SCD2 deficiency in murine macrophages. We found that deletion of Scd2 from macrophages dysregulated basal and bacterial lipopolysaccharide (LPS)-stimulated transcription of numerous inflammation-associated genes. Specifically, deletion of Scd2 from macrophages decreased basal and LPS-induced expression of Il1b transcript that corresponded to decreased production of precursor IL1B protein and release of mature IL1B. Furthermore, we identified disruptions in autophagy and depletion of unsaturated cardiolipins in SCD2-deficient macrophages. To assess the functional relevance of SCD2 in the macrophage response to infection, we challenged SCD2-deficient macrophages with uropathogenic Escherichia coli and found that there was impaired clearance of intracellular bacteria. This increased burden of intracellular bacteria was accompanied by increased release of pro-inflammatory cytokines IL6 and TNF but decreased IL1B. Taken together, these results indicate that macrophage expression of Scd2 is necessary for maintaining the macrophage response to inflammatory stimuli. This link between fatty acid metabolism and fundamental macrophage effector functions may potentially be relevant to diverse age-related pathologies. IMPORTANCE Macrophages are immune cells that respond to infection, but their dysfunction is implicated in many age-related diseases. Recent evidence showed that macrophage expression of a fatty acid enzyme, stearoyl-CoA desaturase 2, declines in aged organisms. In this work, we characterize the effects when stearoyl-CoA desaturase 2 is deficient in macrophages. We identify aspects of the macrophage inflammatory response to infection that may be affected when expression of a key fatty acid enzyme is decreased, and these findings may provide cellular insight into how macrophages contribute to age-related diseases.

Role of macrophage autophagy in postoperative pain and inflammation in mice

BACKGROUND

Postoperative pain and inflammation are significant complications following surgery. Strategies that aim to prevent excessive inflammation without hampering natural wound-healing are required for the management of postoperative pain and inflammation. However, the knowledge of the mechanisms and target pathways involved in these processes is lacking. Recent studies have revealed that autophagy in macrophages sequesters pro-inflammatory mediators, and it is therefore being recognized as a crucial process involved in regulating inflammation. In this study, we tested the hypothesis that autophagy in macrophages plays protective roles against postoperative pain and inflammation and investigated the underlying mechanisms.

METHODS

Postoperative pain was induced by plantar incision under isoflurane anesthesia in mice lacking macrophage autophagy (Atg5flox/flox LysMCre +) and their control littermates (Atg5flox/flox). Mechanical and thermal pain sensitivity, changes in weight distribution, spontaneous locomotor activity, tissue inflammation, and body weight were assessed at baseline and 1, 3, and 7 days after surgery. Monocyte/macrophage infiltration at the surgical site and inflammatory mediator expression levels were evaluated.

RESULTS

Atg5flox/flox LysMCre + mice compared with the control mice exhibited lower mechanical and thermal pain thresholds and surgical/non-surgical hindlimb weight-bearing ratios. The augmented neurobehavioral symptoms observed in the Atg5flox/flox LysMCre + mice were associated with more severe paw inflammation, higher pro-inflammatory mediator mRNA expression, and more monocytes/macrophages at the surgical site.

CONCLUSION

The lack of macrophage autophagy augmented postoperative pain and inflammation, which were accompanied by enhanced pro-inflammatory cytokine secretion and surgical-site monocyte/macrophage infiltration. Macrophage autophagy plays a protective role in postoperative pain and inflammation and can be a novel therapeutic target.

Colitis in a transgenic mouse model of autoimmune uveitis may be induced by neoantigen presentation in the bowel

Undifferentiated uveitis (intraocular inflammation, IOI) is an idiopathic sight-threatening, presumed autoimmune disease, accountable for ~ 10% of all blindness in the developed world. We have investigated the association of uveitis with inflammatory bowel disease (IBD) using a mouse model of spontaneous experimental autoimmune uveoretinitis (EAU). Mice expressing the transgene (Tg) hen egg lysozyme (HEL) in the retina crossed with 3A9 mice expressing a transgenic HEL-specific TCR spontaneously develop uveoretinitis at post-partum day (P)20/21. Double transgenic (dTg TCR/HEL) mice also spontaneously develop clinical signs of colitis at ~ P30 with diarrhoea, bowel shortening, oedema and lamina propria (LP) inflammatory cell infiltration. Single (s)Tg TCR (3A9) mice also show increased histological LP cell infiltration but no bowel shortening and diarrhoea. dTg TCR/HEL mice are profoundly lymphopenic at weaning. In addition, dTg TCR/HEL mice contain myeloid cells which express MHC Class II-HEL peptide complexes (MHCII-HEL), not only in the inflamed retina but also in the colon and have the potential for antigen presentation. In this model the lymphopenia and reduction in the absolute Treg numbers in dTg TCR/HEL mice is sufficient to initiate eye disease. We suggest that cell-associated antigen released from the inflamed eye can activate colonic HEL-specific T cells which, in a microbial micro-environment, not only cause colitis but feedback to amplify IOI.

Autophagy in graves' ophthalmopathy

Graves' ophthalmopathy (GO) is an inflammatory autoimmune disease that affects the eyes. It can significantly alter the quality of life in patients because of its distinctive pathological appearance and the effect on vision. To date, the exact pathological mechanism of GO has not been explicitly discovered. However, several studies have associated autophagy with this disease. Autophagy is a catabolic process that helps maintain homeostasis in all organisms by protecting the cells and tissues from various endogenous and exogenous stress factors. Based on our results, patients affected with GO have comparatively elevated levels of autophagy, which critically affects the pathological mechanism of the GO. In this review, we have summarized the autophagy mechanism in the pathogenesis of GO.

Optimization of determinant factors associated with the efficiency of experimental autoimmune uveitis induction in C57BL/6 mice

Background

Experimental autoimmune uveitis (EAU) is a widely used animal model for uveitis research. The C57BL/6 mouse strain is the most commonly used mouse strain in the research of genetic modification, but C57BL/6 mice are not sufficiently susceptible to EAU induction, partly due to experimental factors. This work aims to optimize relevant factors to improve the efficiency of EAU induction in C57BL/6 mice.

Methods

To induce EAU, mice were immunized via intraperitoneal injection with pertussis (PTX) and subcutaneous injection with interphotoreceptor retinoid-binding protein peptide 1-20 (IRBP_1-20) emulsified with complete Freund's adjuvant (CFA). The severity of inflammation was assessed using several approaches. The relevant experimental factors were evaluated, including methods of emulsification and doses of peptide and PTX.

Results

Uveitis occurred at 8-12 days after immunization and reached its peak at 18-20 days, while T helper type 17 (Th17) cells peaked earlier at 14-18 days after immunization. Based on clinical and histological scores, 500 µg of IRBP peptide was the optimal dose required to induce EAU. The PTX dose demonstrated no influence on EAU incidence, but potentially affected the severity of uveitis. A single injection of 1,000 ng of PTX induced the most severe EAU and the highest proportion of Th17 cells. Compared to extruded emulsion, sonicated emulsion produced a higher incidence, higher histological score, and a 2-day-earlier onset of EAU. Electron microscopy showed a significantly different microstructure between the 2 emulsions.

Conclusions

This work optimized the protocols of EAU induction and obtained a high and stable induction rate with severe inflammation in the C57BL/6 mouse strain. Our results facilitate future experimental research involving uveitis.

The Prevalence of Ocular Extra-Intestinal Manifestations in Adults Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

Patients with inflammatory bowel disease (IBD) have a greater frequency of ocular extra-intestinal manifestations (O-EIMs) than the general population, while Crohn's disease (CD) and ulcerative colitis (UC) have inconsistent prevalence, according to previous studies. This study aimed to examine the prevalence of O-EIMs in CD and UC, respectively. We systemically reviewed O-EIMs and IBD across several online databases. Inclusion criteria are as follows: (1) observational studies examining the association between O-EIMs and IBD, such as cross-sectional, case-control, or cohort studies; (2) human and adult individuals; and (3) with case and control groups consisting of patients with and without O-EIMs, respectively. Patients under the age of 18 or any study on pediatric IBD will be excluded. The prevalence of uveitis in adults was determined by 21 studies comprising 190,941 individuals with IBD, including 62,874 CD and 128,067 UC. The pooled analysis revealed significantly increased odds of uveitis in patients with CD than with UC (pooled odd ratio (OR) 1.603, 95% confidence interval 1.254-2.049). The subgroup analysis revealed that European populations had significantly higher odds of developing uveitis and episcleritis in patients with CD than UC (pooled OR 1.683 and 2.401, respectively). Although O-EIMs may be the prodrome of IBD, no consistent finding was obtained as a result of the high heterogeneity from the two included studies. This meta-analysis indicates the significantly increased odds of uveitis in adults with CD than those with UC. In subgroup analysis, European with CD seemed to have higher odds of uveitis and episcleritis than those with UC. Nonetheless, the link between O-EIMs and IBD remained unclear.

Interactions of Autophagy and the Immune System in Health and Diseases

Autophagy is a highly conserved process that utilizes lysosomes to selectively degrade a variety of intracellular cargo, thus providing quality control over cellular components and maintaining cellular regulatory functions. Autophagy is triggered by multiple stimuli ranging from nutrient starvation to microbial infection. Autophagy extensively shapes and modulates the inflammatory response, the concerted action of immune cells, and secreted mediators aimed to eradicate a microbial infection or to heal sterile tissue damage. Here, we first review how autophagy affects innate immune signaling, cell-autonomous immune defense, and adaptive immunity. Then, we discuss the role of non-canonical autophagy in microbial infections and inflammation. Finally, we review how crosstalk between autophagy and inflammation influences infectious, metabolic, and autoimmune disorders.

Selenomethionine alleviates NF-κB-mediated inflammation in bovine mammary epithelial cells induced by Escherichia coli by enhancing autophagy

Autophagy is crucial for the maintenance of homeostasis under stimuli related to infection. Selenium (Se) plays variable roles in defence against infection and Selenomethionine (Se-Met) is a common Se supplementation. This study aimed to understand whether Se-Met could regulate the nuclear factor-kappa B (NF-κB) signaling pathway through autophagy. Mammary alveolar cell-T (MAC-T) was challenged with Escherichia coli (E. coli). Western blotting and real-time quantitative PCR (RT-qPCR) were used to detect the protein expression and mRNA expression of cytokines. Immunofluorescence assays were performed to observe the expression of intracellular LC3. The results showed that E. coli inhibited autophagy by decreasing the LC3-Ⅱ protein levels, and the Atg5 and Beclin1 protein levels were increased after 4 h. Infection also decreased the number of LC3 puncta. E. coli increased the phosphorylation of p65 and IκBα protein. Concomitantly, the levels of interleukin (IL)-1β, IL-6, IL-8 and tumour necrosis factor (TNF)-α mRNA increased at 3 and 4 h post-infection. We further explored the regulatory role of autophagy on NF-κB-mediated inflammation with autophagy modulators and shAtg5. The results indicated that the autophagy activator reduced the phosphorylation of p65 and IκBα and the mRNA expression of IL-1β, IL-6, IL-8 and TNF-α. Additionally, activating autophagy weakened the adhesion to MAC-T of E. coli. Autophagy inhibitors exacerbated NF-κB-mediated inflammation and strengthened the adhesion of E. coli to cells. We then examined the effects of Se-Met on NF-κB-mediated inflammation through autophagy. The data suggested that Se-Met enhanced LC3-II expression, inhibited the E. coli-induced phosphorylation of p65 and IκBα, and suppressed the adhesion ability of E. coli to MAC-T and that the effects of Se-Met in attenuating NF-κB-mediated inflammation were partially blocked by an autophagy inhibitor. In summary, Se-Met alleviated NF-κB-mediated inflammation induced by E. coli by enhancing autophagy in bovine mammary epithelial cells.

Lysosomal dysfunction is associated with NLRP3 inflammasome activation in chronic unpredictable mild stress-induced depressive mice

NLRP3 inflammasome pathway-mediated inflammatory response is closely associated with depression. Increasing attention has been recently paid to the links between autophagy and depression, however, the relationship between autophagy and NLRP3 inflammasome in depressive behavior remain poorly understood. In the present study, the potential roles of autophagy-lysosome pathway in NLRP3 inflammasome regulation were investigated both in vivo (chronic unpredictable mild stress (CUMS)-induced depressive mouse model) and in vitro (LPS-induced cellular model) model. It demonstrated that CUMS induces depressive-like behaviors in mice, accompanied by increased expression of NLRP3 inflammasome and inflammatory responses. Meanwhile, it promoted the autophagosome marker LC3 and autophagic adaptor protein p62 accumulation, accompanied by the decrease of lysosomal cathepsins B and D expression in the prefrontal cortex of mice. Notably, a significant colocalization of NLRP3 and LC3 in CUMS mice by immunofluorescence co-staining were observed. For the in vitro study, disrupting the lysosomal function with Baf A1 significantly increased the LPS-induced NLRP3 inflammasome accumulation and pro-inflammatory factors (IL-1β and IL-18) production in BV2 cells. Collectively, our results suggested that the autophagic process is related to NLRP3 inflammasome activation, and dysfunctional lysosome in autophagy-lysosomal pathway may retard NLRP3 inflammasome degradation, facilitating the production of pro-inflammatory factors, thereby contributing to depressive behavior in CUMS mice.

Hypoxia Induces Autophagy in Human Dendritic Cells: Involvement of Class III PI3K/Vps34

Hypoxia is a component of both physiological and pathological conditions, including inflammation, solid tumors, and lymphoid tissues, where O2 demand is not balanced by O2 supply. During their lifespan, dendritic cells (DCs) are exposed to different pO2 and activate different adaptive responses, including autophagy, to preserve their viability and functions. Autophagy plays multiple roles in DC physiology. Very recently, we demonstrated that hypoxia shapes autophagy in DCs upon their differentiation state. Here, we proposed a role for PI3Ks, and especially class III PI3K/Vps34, that could be relevant in hypoxia-induced autophagy, in either immature or mature DCs. Hypoxia inhibited mTOR phosphorylation and activated a pro-autophagic program. By using different pharmacological inhibitors, we demonstrated that hypoxia-induced autophagy was mediated by PI3Ks, especially by Vps34. Furthermore, Vps34 expression was enhanced by LPS, a TLR4 ligand, along with the promotion of autophagy under hypoxia. The Vps34 inhibitor, SAR405, abolished hypoxia-induced autophagy, inhibited pro-survival signaling and viability, and increased the expression of proinflammatory cytokines. Our results underlined the impact of autophagy in the maintenance of DC homeostasis at both cell survival and inflammatory response levels, therefore, contributing to a better understanding of the significance of autophagy in DC physiology and pathology.

Polymorphisms of ATG5 Gene Are Associated with Autoimmune Thyroid Diseases, Especially Thyroid Eye Disease

Objective

To explore the association of ATG5 gene polymorphisms with autoimmune thyroid diseases (AITDs) including Hashimoto's thyroiditis (HT) and Graves' illness (GD) as well as their clinical features.

Methods

rs6568431, rs548234, and rs6937876 were selected to investigate the correlation of single-nucleotide polymorphisms of ATG5 gene with AITDs. Their frequencies in 824 AITD patients, including 271 HT patients and 553 GD patients, and 764 healthy controls were tested using both ligase detection reaction and multiplex polymerase chain reaction.

Results

Allele A frequency of rs6568431 in AITDs patients (p = 0.016, OR = 1.201, 95% CI = 1.034 - 1.394) and allele G frequency of rs6937876 in AITDs patients (p = 0.009, OR = 1.223, 95% CI = 1.052 - 1.422) and in GD patients (p = 0.009, OR = 1.247, 95% CI = 1.056 - 1.473) were significantly higher than those in the healthy controls. The frequency of G allele (p = 5.42E - 18, OR = 0.242, 95% CI = 0.173 - 0.339) of rs6937876 was significantly higher in GD patients with ophthalmopathy. However, no relationship was found between family history, age onset, and the three SNPs.

Conclusion

The study is the first to reveal the association between AITDs and ATG5 polymorphisms, and ATG5 gene is considered as a predisposing gene to AITDs, especially GDs.

UV Protection in the Cornea: Failure and Rescue

Simple Summary

The sun is a deadly laser, and its damaging rays harm exposed tissues such as our skin and eyes. The skin’s protection and repair mechanisms are well understood and utilized in therapeutic approaches while the eye lacks such complete understanding of its defenses and therefore often lacks therapeutic support in most cases. The aim here was to document the similarities and differences between the two tissues as well as understand where current research stands on ocular, particularly corneal, ultraviolet protection. The objective is to identify what mechanisms may be best suited for future investigation and valuable therapeutic approaches.

Abstract

Ultraviolet (UV) irradiation induces DNA lesions in all directly exposed tissues. In the human body, two tissues are chronically exposed to UV: the skin and the cornea. The most frequent UV-induced DNA lesions are cyclobutane pyrimidine dimers (CPDs) that can lead to apoptosis or induce tumorigenesis. Lacking the protective pigmentation of the skin, the transparent cornea is particularly dependent on nucleotide excision repair (NER) to remove UV-induced DNA lesions. The DNA damage response also triggers intracellular autophagy mechanisms to remove damaged material in the cornea; these mechanisms are poorly understood despite their noted involvement in UV-related diseases. Therapeutic solutions involving xenogenic DNA-repair enzymes such as T4 endonuclease V or photolyases exist and are widely distributed for dermatological use. The corneal field lacks a similar set of tools to address DNA-lesions in photovulnerable patients, such as those with genetic disorders or recently transplanted tissue.

Autophagy in Extracellular Matrix and Wound Healing Modulation in the Cornea

Autophagy is a robust cellular mechanism for disposing of harmful molecules or recycling them to cells, which also regulates physiopathological processes in cornea. Dysregulated autophagy causes inefficient clearance of unwanted proteins and cellular debris, mitochondrial disorganization, defective inflammation, organ dysfunctions, cell death, and diseases. The cornea accounts for two-thirds of the refraction of light that occurs in the eyes, but is prone to trauma/injury and infection. The extracellular matrix (ECM) is a noncellular dynamic macromolecular network in corneal tissues comprised of collagens, proteoglycans, elastin, fibronectin, laminins, hyaluronan, and glycoproteins. The ECM undergoes remodeling by matrix-degrading enzymes and maintains corneal transparency. Autophagy plays an important role in the ECM and wound healing maintenance. Delayed/dysregulated autophagy impacts the ECM and wound healing, and can lead to corneal dysfunction. Stromal wound healing involves responses from the corneal epithelium, basement membrane, keratocytes, the ECM, and many cytokines and chemokines, including transforming growth factor beta-1 and platelet-derived growth factor. Mild corneal injuries self-repair, but greater injuries lead to corneal haze/scars/fibrosis and vision loss due to disruptions in the ECM, autophagy, and normal wound healing processes. Presently, the precise role of autophagy and ECM remodeling in corneal wound healing is elusive. This review discusses recent trends in autophagy and ECM modulation in the context of corneal wound healing and homeostasis.

Ocular transmissibility of COVID-19: possibilities and perspectives

Since the initial outbreak of coronavirus disease 2019 (COVID-19), extensive research has emerged from across the globe to understand the pathophysiology of this novel coronavirus. Transmission of this virus is a subject of particular interest as researchers work to understand which protective and preventative measures are most effective. Despite the well understood model of aerosol-respiratory mediated transmission, the exact mechanism underlying the inoculation, infection and spread of COVID-19 is currently unknown. Given anatomical positioning and near constant exposure to aerosolized pathogens, the eye may be a possible gateway for COVID-19 infection. This critical review explores the possibility of an ocular-systemic or ocular-nasal-pulmonic pathway of COVID-19 infection and includes novel insights into the possible immunological mechanisms leading to cytokine surge.

Genetic association of primary nonresponse to anti-TNFα therapy in patients with inflammatory bowel disease

OBJECTIVES

Primary nonresponse (PNR) to antitumor necrosis factor-α (TNFα) biologics is a serious concern in patients with inflammatory bowel disease (IBD). We aimed to identify the genetic variants associated with PNR.

PATIENTS AND METHODS

Patients were recruited from outpatient GI clinics and PNR was determined using both clinical and endoscopic findings. A case-control genome-wide association study was performed in 589 IBD patients and associations were replicated in an independent cohort of 293 patients. Effect of the associated variant on gene expression and TNFα secretion was assessed by cell-based assays. Pleiotropic effects were investigated by Phenome-wide association study (PheWAS).

RESULTS

We identified rs34767465 as associated with PNR to anti-TNFα therapy (odds ratio: 2.07, 95% CI, 1.46-2.94, P = 2.43 × 10-7, [replication odds ratio: 1.8, 95% CI, 1.04-3.16, P = 0.03]). rs34767465 is a multiple-tissue expression quantitative trait loci for FAM114A2. Using RNA-sequencing and protein quantification from HapMap lymphoblastoid cell lines (LCLs), we found a significant decrease in FAM114A2 mRNA and protein expression in both heterozygous and homozygous genotypes when compared to wild type LCLs. TNFα secretion was significantly higher in THP-1 cells [differentiated into macrophages] with FAM114A2 knockdown versus controls. Immunoblotting experiments showed that depletion of FAM114A2 impaired autophagy-related pathway genes suggesting autophagy-mediated TNFα secretion as a potential mechanism. PheWAS showed rs34767465 was associated with comorbid conditions found in IBD patients (derangement of joints [P = 3.7 × 10-4], pigmentary iris degeneration [P = 5.9 × 10-4], diverticulum of esophagus [P = 7 × 10-4]).

CONCLUSIONS

We identified a variant rs34767465 associated with PNR to anti-TNFα biologics, which increases TNFα secretion through mechanism related to autophagy. rs34767465 may also explain the comorbidities associated with IBD.

Loss of Mir146b with aging contributes to inflammation and mitochondrial dysfunction in thioglycollate-elicited peritoneal macrophages

Macrophages undergo programmatic changes with age, leading to altered cytokine polarization and immune dysfunction, shifting these critical immune cells from protective sentinels to disease promoters. The molecular mechanisms underlying macrophage inflammaging are poorly understood. Using an unbiased RNA sequencing (RNA-seq) approach, we identified Mir146b as a microRNA whose expression progressively and unidirectionally declined with age in thioglycollate-elicited murine macrophages. Mir146b deficiency led to altered macrophage cytokine expression and reduced mitochondrial metabolic activity, two hallmarks of cellular aging. Single-cell RNA-seq identified patterns of altered inflammation and interferon gamma signaling in Mir146b-deficient macrophages. Identification of Mir146b as a potential regulator of macrophage aging provides novel insights into immune dysfunction associated with aging.

Advanced oxidation protein products impair autophagic flux in macrophage by inducing lysosomal dysfunction via activation of PI3K-Akt-mTOR pathway in Crohn's disease

Dysfunction in macrophages is involved in the pathogenesis of various diseases, including Crohn's disease (CD). Previously, we found that advanced oxidation protein products (AOPPs) were predominantly deposited in macrophages in the intestinal lamina propria of CD patients. However, whether AOPPs contributes to macrophage dysfunction in CD and the underlying mechanism remains unknown. This study aimed to investigate the effects of AOPPs on macrophages functions in CD. In the present study, we discovered increased AOPPs levels were positively correlated with impaired autophagy in macrophages of CD patients. AOPPs could impair autophagic flux by inducing lysosomal dysfunction in RAW264.7 cell line and macrophages in AOPPs-treated mice, evidenced by increased number of autophagosomes, blocked degradation of autophagy-related proteins (LC3B-II and SQSTM1/p62), and decreased activity of lysosomal proteolytic enzymes after AOPPs challenge. Besides, AOPPs could also promote M1 polarization in RAW264.7 cells and bone marrow derived macrophages (BMDMs) in AOPPs-treated mice. In addition, our study revealed that PI3K-AKT-mTOR-TFEB pathway was activated by AOPPs in macrophages. Inhibition of the PI3K pathway effectively alleviated AOPPs-induced autophagy impairment and M1 polarization both in vitro and in vivo, thus reducing intestinal inflammation in AOPPs-challenged mice. Together, this study demonstrates that AOPPs-induced autophagy impairment in macrophages is crucial for CD progression.

New insights into crosstalk between pyroptosis and autophagy co-induced by molybdenum and cadmium in duck renal tubular epithelial cells

Pyroptosis and autophagy are two different biological processes that determine cell fates. Our previous studies revealed that pyroptosis and autophagy were involved in cytotoxicity co-induced by molybdenum (Mo) and cadmium (Cd) in duck renal tubular epithelial cells, but crosstalk between them is unclear. Hence, the cells were treated with 500.0 μM Mo, 4.0 μM Cd, 10.0 μM Z-YVAD-fluoromethylketone (YVAD), 2.5 μM 3-methyladenine (3-MA) and 10.0 μM chloroquine (CQ) alone or in combination for 12 h (CQ for the last 4 h). Under Mo and Cd co-stress, data evidenced that YVAD addition decreased the number of autophagosomes, LC3 puncta, and AMPKα-1, Atg5, Beclin-1, LC3A, LC3B mRNA levels and LC3-II/LC3-I, Beclin-1 protein levels, and increased p62 expression levels. Besides, both 3-MA and CQ addition increased NLRP3, Caspase-1, NEK7, ASC, GSDMA, GSDME, IL-1β, IL-18 mRNA levels, NLRP3, Caspase-1 p20, ASC, GSDMD protein and ROS levels, and NO, LDH, IL-1β, IL-18 releases. Collectively, our results revealed that pyroptosis and autophagy co-induced by Mo and Cd were interrelated in duck renal tubular epithelial cells, and inhibiting pyroptosis might attenuate Mo and Cd co-induced autophagy, but inhibiting autophagy might promote Mo and Cd co-induced pyroptosis.

Self-eating and Heart: The Emerging Roles of Autophagy in Calcific Aortic Valve Disease

Autophagy is a self-degradative pathway by which subcellular elements are broken down intracellularly to maintain cellular homeostasis. Cardiac autophagy commonly decreases with aging and is accompanied by the accumulation of misfolded proteins and dysfunctional organelles, which are undesirable to the cell. Reduction of autophagy over time leads to aging-related cardiac dysfunction and is inversely related to longevity. However, despite the increasing interest in autophagy in cardiac diseases and aging, the process remains an undervalued and disregarded object in calcific valvular disease. Neither the nature through which autophagy is triggered nor the interplay between autophagic machinery and targeted molecules during aortic valve calcification are fully understood. Recently, the upregulation of autophagy has been shown to result in cardioprotective effects against cell death as well as its origin. Here, we review the evidence that shows how autophagy can be both beneficial and detrimental as it pertains to aortic valve calcification in the heart.

Insight Into Polysaccharides From Panax ginseng C. A. Meyer in Improving Intestinal Inflammation: Modulating Intestinal Microbiota and Autophagy

Polysaccharides from Panax ginseng C. A. Meyer (P. ginseng) are the main active component of P. ginseng and exhibit significant intestinal anti-inflammatory activity. However, the therapeutic mechanism of the ginseng polysaccharide is unclear, and this hinders the application for medicine or functional food. In this study, a polysaccharide was isolated from P. ginseng (GP). The primary structure and morphology of the GP were studied by HPLC, FT-IR spectroscopy, and scanning electron microscopy (SEM). Further, its intestinal anti-inflammatory activity and its mechanism of function were evaluated in experimental systems using DSS-induced rats, fecal microbiota transplantation (FMT), and LPS-stimulated HT-29 cells. Results showed that GP modulated the structure of gut microbiota and restored mTOR-dependent autophagic dysfunction. Consequently, active autophagy suppressed inflammation through the inhibition of NF-κB, oxidative stress, and the release of cytokines. Therefore, our research provides a rationale for future investigations into the relationship between microbiota and autophagy and revealed the therapeutic potential of GP for inflammatory bowel disease.

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

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

Extraintestinal Manifestations in Patients with Inflammatory Bowel Disease: Study Based on the ENEIDA Registry

BACKGROUND

Patients with inflammatory bowel disease (IBD) may present extraintestinal manifestations (EIMs) that affect the joints, skin, eyes, and hepatobiliary area, among others.

AIMS

Our aim was to analyse the prevalence and characteristics of EIMs in patients with IBD and to identify the possible risk factors associated with the development of EIMs in the largest series published to date.

METHODS

Observational, cross-sectional study including patients from the Spanish ENEIDA registry promoted by GETECCU. We retrospectively identified all cases of EIMs in the ENEIDA registry until January 2018.

RESULTS

The study included 31,077 patients, 5779 of whom had at least one EIM (global prevalence 19%; 95% CI 18.2-19.0). Among the different types of EIMs, rheumatic manifestations had a prevalence of 13% (95% CI 12.9-13.7; 63% of EIMs), with a prevalence of 5% (95% CI 4.7-5.2) for mucocutaneous manifestations, 2.1% (95% CI 1.9-2.2) for ocular manifestations, and 0.7% (95% CI 0.6-0.8) for hepatobiliary manifestations. The multivariable analysis showed that the type of IBD (Crohn's disease, p < 0.001), gender (female, p < 0.001), the need for an immunomodulator (p < 0.001) or biologic drugs (p < 0.001), a previous family history of IBD (p < 0.001), and an extensive location of IBD (p < 0.001) were risk factors for the presence of EIMs.

CONCLUSIONS

One-fifth of patients with IBD may have associated EIMs, with rheumatic manifestations as the most frequent (> 60% of EIMs). Female patients with severe Crohn's disease represent the group with the highest risk of developing EIMs. These patients should therefore be specially monitored and referred to the corresponding specialist when suggestive symptoms appear.

The role of the inflammasomes in the pathogenesis of uveitis

Uveitis is a diverse group of sight-threatening intraocular inflammatory diseases usually causing eye redness, pain, blurred vision, and sometimes blindness. Although the exact pathogenesis of uveitis is not yet clear, accumulating evidences have shown that an imbalanced regulation of immune responses caused by a combination of genetic and environmental factors are implicated in the pathogenesis of this disease. As critical regulators of inflammation, inflammasomes have been assumed to play a role in the pathogenesis of uveitis. Recent studies have reported the association between a number of genetic variants in inflammasome related genes (such as NLRP3, NLRP1, NLRC4 and AIM2) with increased risk to uveitis. Mounting evidence have shown an aberrant activation of the NLRP3 inflammasome in both uveitis patients and murine models of uveitis. Some studies explored the intervention of uveitis via modulating inflammasome activity in the eye. This review aims at summarizing the main findings of these studies, proposing the possible mechanism whereby inflammasomes affect the susceptibility to develop uveitis, and giving a perspective for future studies, which may further improve our understanding about the role of inflammasomes and related cytokines in the pathogenesis of uveitis, and may hopefully lead to new therapeutics by targeting inflammasomes.

Decreased microRNA-155 in Behcet's disease leads to defective control of autophagy thereby stimulating excessive proinflammatory cytokine production

BACKGROUND

Earlier, we reported that the microRNA (miR)-155 expression in dendritic cells (DCs) from Behcet's disease (BD) patients was decreased and affected cytokine production of DCs. In this study, we investigated the mechanisms whereby miR-155 regulates cytokine production by DCs.

METHODS

The formation of autophagosomes in DCs was detected by transmission electron microscopy. Western blotting was used to detect the protein levels of LC3, Beclin-1, P62, p-mTOR, and p-Akt in DCs. TNF-α, IL-6, and IL-1β expression were investigated by ELISA. MiR-155 mimics were transfected to DCs to evaluate its effects on autophagy and cytokine production. RNA interference was used to downregulate the expression of TAB2.

RESULTS

The formation of autophagosomes was found in DCs of active BD patients. The expressions of LC3-II, Beclin-1, and P62 were significantly increased in DCs of active BD patients compared to that of inactive BD patients and healthy controls. The expressions of IL-6, IL-1β, and TNF-α were significantly increased in DCs of active BD patients compared to that of healthy controls. The autophagy promoter (3-MA) and inhibitor (rapamycin) significantly decreased or increased the expression of TNF-α, IL-6, and IL-1β by DCs. The expression of LC3-II and Beclin-1 was significantly increased, but the expression of P62 proteins was decreased in DCs transfected with miR-155 mimics or after TAB2 was downregulated. The expression of TNF-α, IL-6, and IL-1β was decreased in DCs after miR-155 was upregulated or TAB2 was downregulated. The ratios of p-Akt/Akt and p-mTOR/mTOR were decreased in DCs after miR-155 was upregulated.

CONCLUSIONS

These results suggest that miR-155 affects the production of TNF-α, IL-6, and IL-1β by DCs through activation of the Akt/mTOR signaling pathway and by affecting the process of autophagy.

The interaction between autophagy and neuroinflammation in major depressive disorder: From pathophysiology to therapeutic implications

The past decade has revealed neuroinflammation as an important mechanism of major depressive disorder (MDD). Nod-like receptors family pyrin domain containing 3 (NLRP3) inflammasome is the key regulator interleukin-1β (IL-1β) maturation, whose activation has been reported in MDD patients and various animal models. Function as a dominant driver of neuroinflammation, NLRP3 bridges the gap between immune activation with stress exposure, and further leads to subsequent occurrence of neuropsychiatric disorders such as MDD. Of note, autophagy is a tightly regulated cellular degradation pathway that removes damaged organelles and intracellular pathogens, and maintains cellular homeostasis from varying insults. Serving as a critical cellular monitoring system, normal functioned autophagy signaling prevents excessive NLRP3 inflammasome activation and subsequent release of IL-1 family cytokines. This review will describe the current understanding of how autophagy regulates NLRP3 inflammasome activity and discuss the implications of this regulation on the pathogenesis of MDD. The extensive crosstalk between autophagy pathway and NLRP3 inflammasome is further discussed, as it is critical for developing new therapeutic strategies for MDD aimed at modulating the neuroinflammatory responses.

Panuveitis in a patient with active Crohn's disease

A 14-year-old girl presented to the ophthalmology clinic with progressive diminution of vision, redness, pain and photophobia in both eyes for the last 1 month. She had abdominal pain, diarrhoea and weight loss during that period. Ocular examination revealed features of anterior uveitis, vitritis and retinal vasculitis. In view of gastrointestinal symptoms, abdominal imaging was done, which showed multiple enhancing bowel wall thickening with skip lesions in the terminal ileum and ascending colon. Colonoscopy showed ulcers in the ascending colon, caecum and terminal ileum. Histopathology revealed microgranulomas in lamina propria and submucosal granulomas suggestive of Crohn's disease. The patient was started on topical steroid eye drops and oral budesonide and mesalazine. Her vision improved after 3 weeks and bowel symptoms attained remission after 8 weeks, and at present, she is doing well.

Regulation of Innate Immune Responses by Autophagy: A Goldmine for Viruses

Autophagy is a lysosomal degradation pathway for intracellular components and is highly conserved across eukaryotes. This process is a key player in innate immunity and its activation has anti-microbial effects by directly targeting pathogens and also by regulating innate immune responses. Autophagy dysfunction is often associated with inflammatory diseases. Many studies have shown that it can also play a role in the control of innate immunity by preventing exacerbated inflammation and its harmful effects toward the host. The arms race between hosts and pathogens has led some viruses to evolve strategies that enable them to benefit from autophagy, either by directly hijacking the autophagy pathway for their life cycle, or by using its regulatory functions in innate immunity. The control of viral replication and spread involves the production of anti-viral cytokines. Controlling the signals that lead to production of these cytokines is a perfect way for viruses to escape from innate immune responses and establish successful infection. Published reports related to this last viral strategy have extensively grown in recent years. In this review we describe several links between autophagy and regulation of innate immune responses and we provide an overview of how viruses exploit these links for their own benefit.

Mechanisms of NLRP3 Inflammasome Activation: Its Role in the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a common neurodegenerative disease of progressive dementia which is characterized pathologically by extracellular neuritic plaques containing aggregated amyloid beta (Aβ) and intracellular hyperphosphorylated tau protein tangles in cerebrum. It has been confirmed that microglia-specific nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome-mediated chronic neuroinflammation plays a crucial role in the pathogenesis of AD. Stimulated by Aβ deposition, NLRP3 assembles and activates within microglia in the AD brain, leading to caspase-1 activation along with downstream interleukin (IL)-1β secretion, and subsequent inflammatory events. Activation of the NLRP3 inflammasome mediates microglia to exhibit inflammatory M1 phenotype, with high expression of caspase-1 and IL-1β. This leads to Aβ deposition and neuronal loss in the amyloid precursor protein (APP)/human presenilin-1 (PS1) mouse model of AD. However, NLRP3 or caspase-1 deletion in APP/PS1 mice promotes microglia to transform to an anti-inflammatory M2 phenotype, with decreased secretion of caspase-1 and IL-1β. It also results in improved cognition, enhanced Aβ clearance, and a lower cerebral inflammatory response. This result suggests that the NLRP3 inflammasome may be an appropriate target for reducing neuroinflammation and alleviating pathological processes in AD. In the present review, we summarize the generally accepted regulatory mechanisms of NLRP3 inflammasome activation, and explore its role in neuroinflammation. Furthermore, we speculate on the possible roles of microglia-specific NLRP3 activation in AD pathogenesis and consider potential therapeutic interventions targeting the NLRP3 inflammasome in AD.

"Repair Me if You Can": Membrane Damage, Response, and Control from the Viral Perspective

Cells are constantly challenged by pathogens (bacteria, virus, and fungi), and protein aggregates or chemicals, which can provoke membrane damage at the plasma membrane or within the endo-lysosomal compartments. Detection of endo-lysosomal rupture depends on a family of sugar-binding lectins, known as galectins, which sense the abnormal exposure of glycans to the cytoplasm upon membrane damage. Galectins in conjunction with other factors orchestrate specific membrane damage responses such as the recruitment of the endosomal sorting complex required for transport (ESCRT) machinery to either repair damaged membranes or the activation of autophagy to remove membrane remnants. If not controlled, membrane damage causes the release of harmful components including protons, reactive oxygen species, or cathepsins that will elicit inflammation. In this review, we provide an overview of current knowledge on membrane damage and cellular responses. In particular, we focus on the endo-lysosomal damage triggered by non-enveloped viruses (such as adenovirus) and discuss viral strategies to control the cellular membrane damage response. Finally, we debate the link between autophagy and inflammation in this context and discuss the possibility that virus induced autophagy upon entry limits inflammation.

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.

Role of Autophagy in Lung Inflammation

Autophagy is a cellular recycling system found in almost all types of eukaryotic organisms. The system is made up of a variety of proteins which function to deliver intracellular cargo to lysosomes for formation of autophagosomes in which the contents are degraded. The maintenance of cellular homeostasis is key in the survival and function of a variety of human cell populations. The interconnection between metabolism and autophagy is extensive, therefore it has a role in a variety of different cell functions. The disruption or dysfunction of autophagy in these cell types have been implicated in the development of a variety of inflammatory diseases including asthma. The role of autophagy in non-immune and immune cells both lead to the pathogenesis of lung inflammation. Autophagy in pulmonary non-immune cells leads to tissue remodeling which can develop into chronic asthma cases with long term effects. The role autophagy in the lymphoid and myeloid lineages in the pathology of asthma differ in their functions. Impaired autophagy in lymphoid populations have been shown, in general, to decrease inflammation in both asthma and inflammatory disease models. Many lymphoid cells rely on autophagy for effector function and maintained inflammation. In stark contrast, autophagy deficient antigen presenting cells have been shown to have an activated inflammasome. This is largely characterized by a T_H17 response that is accompanied with a much worse prognosis including granulocyte mediated inflammation and steroid resistance. The cell specificity associated with changes in autophagic flux complicates its targeting for amelioration of asthmatic symptoms. Differing asthmatic phenotypes between T_H2 and T_H17 mediated disease may require different autophagic modulations. Therefore, treatments call for a more cell specific and personalized approach when looking at chronic asthma cases. Viral-induced lung inflammation, such as that caused by SARS-CoV-2, also may involve autophagic modulation leading to inflammation mediated by lung resident cells. In this review, we will be discussing the role of autophagy in non-immune cells, myeloid cells, and lymphoid cells for their implications into lung inflammation and asthma. Finally, we will discuss autophagy's role viral pathogenesis, immunometabolism, and asthma with insights into autophagic modulators for amelioration of lung inflammation.

The role of Neu1 in the protective effect of dipsacoside B on acetaminophen-induced liver injury

Background

Pharmacological induction of autophagy can protect against acetaminophen (APAP) induced acute liver failure (ALF) by removing APAP adducts (APAP-AD), but its mechanism is not well understood. Hepatoprotective effect of saponins from traditional Chinese medicine has attracted widespread attention from all over the world. The content of saponins in Lonicerae Flos (Shanyinhua in Chinese) is up to 15–25%. Dipsacoside B (DB) is a common bioactive ingredient of different Shanyinhua, but its hepatoprotective effect and mechanism are still unknown. The present investigation aimed to study the benefit of DB in APAP-induced hepatotoxicity mouse model and different cell model.

Methods

Mice were treated with DB by intraperitoneal injection 1 h before treated with 500 mg/kg APAP, which caused ALF after 4 h. HepG2 cells were treated with DB for 1 h before treated with 10 mM APAP for 12 h. Hepatotoxicity was assessed via ALT and AST. Neuraminidase 1 (Neu1), lysosomal autophagy marker LC3 and P62 were examined by western blot. Neu1 activity was assayed using its substrate 2-(4-methylumbelliferyl)-D-N-acetylneuraminic acid. Apoptosis level was examined by TUNEL and caspase 3 activity. Molecular docking was used to predict the interaction between DB and protein Neu1.

Results

Our results demonstrated that pretreatment with 0.5 μM DB (in vitro) and 50 mg/kg DB (in vivo) respectively reversed increased level of AST and ALT induced by APAP. Histopathological examinations showed reduced necrosis and apoptosis in the liver of DB-treated APAP mice. DB promoted the removal of APAP-AD by lysosomal autophagy. These effects were associated with significant decrease in the level of Neuraminidase 1 (Neu1), a negative regulator of lysosomal exocytosis. Molecular docking results showed that DB could bind to Neu1 protein (binding energy =−7.86 kcal/mol). Akt/mTOR-mediated autophagy and inhibition of apoptosis may be the main mechanisms for the hepatoprotective effects of DB in acetaminophen-induced liver injury.

Conclusions

These data indicate that DB alleviated hepatotoxicity caused by APAP at least in part via Neu1 inhibition, Akt/mTOR pathway is involved in the detoxification effect of DB on acetaminophen-induced hepatotoxicity.

Select autophagy genes maintain quiescence of tissue-resident macrophages and increase susceptibility to Listeria monocytogenes

Innate and adaptive immune responses that prime myeloid cells, such as macrophages, protect against pathogens^1,2. However, if left uncontrolled, these responses may lead to detrimental inflammation³. Macrophages, particularly those resident in tissues, must therefore remain quiescent between infections despite chronic stimulation by commensal microorganisms. The genes required for quiescence of tissue-resident macrophages are not well understood. Autophagy, an evolutionarily conserved cellular process by which cytoplasmic contents are targeted for lysosomal digestion, has homeostatic functions including maintenance of protein and organelle integrity and regulation of metabolism⁴. Recent research has shown that degradative autophagy, as well as various combinations of autophagy genes, regulate immunity and inflammation^5-12. Here, we delineate a function of the autophagy proteins Beclin 1 and FIP200-but not of other essential autophagy components ATG5, ATG16L1 or ATG7-in mediating quiescence of tissue-resident macrophages by limiting the effects of systemic interferon-γ. The perturbation of quiescence in mice that lack Beclin 1 or FIP200 in myeloid cells results in spontaneous immune activation and resistance to Listeria monocytogenes infection. While antibiotic-treated wild-type mice display diminished macrophage responses to inflammatory stimuli, this is not observed in mice that lack Beclin 1 in myeloid cells, establishing the dominance of this gene over effects of the bacterial microbiota. Thus, select autophagy genes, but not all genes essential for degradative autophagy, have a key function in maintaining immune quiescence of tissue-resident macrophages, resulting in genetically programmed susceptibility to bacterial infection.

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.

Autophagy Regulation of Mammalian Immune Cells

Autophagy is a fully competent cellular machinery able to carry out the clearance of macromolecules via fusion with the lysosome. Many studies conducted in recent years have revealed that autophagy not only plays a critical role in maintaining cell homeostasis, but can also promote bacterial elimination. Additionally, autophagy exists in most eukaryotic cells including immune cells, such as lymphocytes, neutrophils, eosinophils, mast cells, and natural killer cells. Presently, there are numerous studies focusing on the roles of autophagy in regulating immune response. Autophagy regulates the innate and adaptive immunity by modulating cell differentiation, survival, phagocytosis, antigen presentation, degranulation, and cytokine production. In this chapter, we will summarize how autophagy participates explicitly in the survival and function of the mammalian adaptive and innate immune cells.

ULK1-mediated phosphorylation of ATG16L1 promotes xenophagy, but destabilizes the ATG16L1 Crohn's mutant

Autophagy is a highly regulated catabolic pathway that is potently induced by stressors including starvation and infection. An essential component of the autophagy pathway is an ATG16L1-containing E3-like enzyme, which is responsible for lipidating LC3B and driving autophagosome formation. ATG16L1 polymorphisms have been linked to the development of Crohn's disease (CD), and phosphorylation of CD-associated ATG16L1 T300A (caATG16L1) has been hypothesized to contribute to cleavage and autophagy dysfunction. Here we show that ULK1 kinase directly phosphorylates ATG16L1 in response to infection and starvation. Phosphorylated ATG16L1 localizes to the site of internalized bacteria and stable cell lines harbouring a phospho-dead mutant of ATG16L1 have impaired xenophagy, indicating a role for ATG16L1 phosphorylation in the promotion of anti-bacterial autophagy. In contrast to wild-type ATG16L1, ULK1-mediated phosphorylation of caATG16L1 drives its destabilization in response to stress. In summary, our results show that ATG16L1 is a novel target of ULK1 kinase and that ULK1 signalling to ATG16L1 is a double-edged sword, enhancing the function of the wild-type ATG16L1, but promoting degradation of caATG16L1.

Regulation of the innate immune system by autophagy: monocytes, macrophages, dendritic cells and antigen presentation

Autophagy is well equipped functionally to isolate microbial pathogens in autophagosomes and to carry out their clearance by dismemberment in the course of catabolic processes in the lysosome. Clearly, this is a non-metabolic function of autophagy that impacts strongly on the immune system. While in a preceding article on neutrophils, eosinophils, mast cells, and natural killer cells our focus was on the role of autophagy in regulating innate immune cell differentiation, degranulation, phagocytosis and extracellular trap formation, here we discuss monocytes/macrophages and dendritic cells, specifically, the influence of autophagy on functional cellular responses, such as phagocytosis, antigen presentation, cytokine production, control of inflammasome activation, tolerance and the consequences for overall host defense.

Beclin1-driven autophagy modulates the inflammatory response of microglia via NLRP3

Alzheimer's disease is characterized not only by extracellular amyloid plaques and neurofibrillary tangles, but also by microglia-mediated neuroinflammation. Recently, autophagy has been linked to the regulation of the inflammatory response. Thus, we investigated how an impairment of autophagy mediated by BECN1/Beclin1 reduction, as described in Alzheimer's disease patients, would influence cytokine production of microglia. Acutely stimulated microglia from Becn1 ^+/- mice exhibited increased expression of IL-1beta and IL-18 compared to wild-type microglia. Becn1 ^+/- APPPS1 mice also contained enhanced IL-1beta levels. The investigation of the IL-1beta/IL-18 processing pathway showed an elevated number of cells with inflammasomes and increased levels of NLRP3 and cleaved CASP1/Caspase1 in Becn1 ^+/- microglia. Super-resolation microscopy revealed a very close association of NLRP3 aggregates and LC3-positive vesicles. Interestingly, CALCOCO2 colocalized with NLRP3 and its downregulation increased IL-1beta release. These data support the notion that selective autophagy can impact microglia activation by modulating IL-1beta and IL-18 production via NLRP3 degradation and thus present a mechanism how impaired autophagy could contribute to neuroinflammation in Alzheimer's disease.

Chemokine and Adhesion Molecule Profiles in Aqueous Humor of Clinically Quiescent Uveitic Cataracts

PURPOSE

To investigate the chemokine and adhesion molecule profiles in aqueous humor (AH) of eyes with inactive uveitis and their correlations with inflammation relapse after cataract surgery.

METHODS

Patients with inactive uveitis who underwent cataract surgery between July 2014 and January 2016 at our center were included. Undiluted AH samples (100-120 µl) were obtained through lateral corneal incisions during surgery, and concentrations of monocyte chemoattractant protein 1 (MCP-1/CCL2), macrophage inflammatory protein 1 (MIP-1), interleukin 8 (IL-8), regulated on activation, normal T cell expressed and secreted (RANTES/CCL5), soluble vascular cell adhesion molecule (sVCAM) and soluble intercellular adhesion molecule (sICAM) were measured by cytometric bead array (BD Bioscience, San Jose, CA). AH levels of these inflammatory factors were compared between different uveitis entities and non-inflammatory control. Risk factors for postoperative inflammation relapse were also analysed in uveitic eyes.

RESULTS

As compared with the control group, the panuveitis group had significantly higher aqueous concentrations of MCP-1, IL-8, sVCAM, sICAM; the anterior uveitis group had significantly higher concentrations of MCP-1, MIP-1, sVCAM. Uveitic cataracts with postoperative inflammation relapse had significantly higher levels of MCP-1 and IL-8 in AH than those without. And multivariate cox regression analysis revealed that high AH levels of MCP-1 was an independent predictor for postoperative inflammation relapse.

CONCLUSIONS

Clinically quiescent uveitic eyes have elevated levels of chemokines and soluble adhesion molecules in AH, of which MCP-1 is associate with inflammation relapses after cataract surgery.

Impaired monocyte cholesterol clearance initiates age-related retinal degeneration and vision loss

Advanced age-related macular degeneration (AMD), the leading cause of blindness among people over 50 years of age, is characterized by atrophic neurodegeneration or pathologic angiogenesis. Early AMD is characterized by extracellular cholesterol-rich deposits underneath the retinal pigment epithelium (RPE) called drusen or in the subretinal space called subretinal drusenoid deposits (SDD) that drive disease progression. However, mechanisms of drusen and SDD biogenesis remain poorly understood. Although human AMD is characterized by abnormalities in cholesterol homeostasis and shares phenotypic features with atherosclerosis, it is unclear whether systemic immunity or local tissue metabolism regulates this homeostasis. Here, we demonstrate that targeted deletion of macrophage cholesterol ABC transporters A1 (ABCA1) and -G1 (ABCG1) leads to age-associated extracellular cholesterol-rich deposits underneath the neurosensory retina similar to SDD seen in early human AMD. These mice also develop impaired dark adaptation, a cardinal feature of RPE cell dysfunction seen in human AMD patients even before central vision is affected. Subretinal deposits in these mice progressively worsen with age, with concomitant accumulation of cholesterol metabolites including several oxysterols and cholesterol esters causing lipotoxicity that manifests as photoreceptor dysfunction and neurodegeneration. These findings suggest that impaired macrophage cholesterol transport initiates several key elements of early human AMD, demonstrating the importance of systemic immunity and aging in promoting disease manifestation. Polymorphisms in genes involved with cholesterol transport and homeostasis are associated with a significantly higher risk of developing AMD, thus making these studies translationally relevant by identifying potential targets for therapy.

TNFAIP3-DEPTOR complex regulates inflammasome secretion through autophagy in ankylosing spondylitis monocytes

Ankylosing spondylitis (AS) is a chronic autoimmune inflammatory disease with severe inflammatory symptoms in the axial skeleton. The cause of ankylosing spondylitis is unknown. TNFAIP3, also named A20, uses ubiquitin-related functions to regulate immune activation, deficiency of which is highly related to autoimmune disease. However, the role of TNFAIP3 in human AS has not been reported. Our objective was to study the role and mechanism of TNFAIP3 in ankylosing spondylitis. TNFAIP3 expression on different types of immunocytes from AS peripheral blood was measured by flow cytometry. In vitro, monocytes were transfected with a TNFAIP3 shRNA lentivirus, and IL6 and IL1B activation was tested using real-time PCR and ELISA. The novel interaction complex TNFAIP3-DEPTOR was determined through GST pull-down, yeast two-hybrid system, confocal microscopy, and co-immunoprecipitation. Transmission electron microscopy, the RFP-GFP-LC3 adenovirus, and LC3 expression were used for autophagy detection. Here, we show that TNFAIP3 expression in AS peripheral blood non-classical monocytes was decreased. In normal monocytes, TNFAIP3 induced autophagy, which restricted inflammasome activation to the early stage of LPS stimulation. Zinc-finger domains of TNFAIP3 were able to interact and stabilize DEPTOR. TNFAIP3 and DEPTOR together rapidly promoted autophagy after LPS treatment to prevent NLRP3 inflammasome formation. Finally, TNFAIP3 and DEPTOR deficiency in AS non-classical monocytes facilitated inflammasome activation. Our study indicates that TNFAIP3-DEPTOR complex-induced early-onset autophagy is vital for immune inhibition in autoimmune disease.

Disrupted cholesterol metabolism promotes age-related photoreceptor neurodegeneration

Photoreceptors have high intrinsic metabolic demand and are exquisitely sensitive to metabolic perturbation. In addition, they shed a large portion of their outer segment lipid membranes in a circadian manner, increasing the metabolic burden on the outer retina associated with the resynthesis of cell membranes and disposal of the cellular cargo. Here, we demonstrate that deletion of both ABCA1 and ABCG1 in rod photoreceptors leads to age-related accumulation of cholesterol metabolites in the outer retina, photoreceptor dysfunction, degeneration of rod outer segments, and ultimately blindness. A high-fat diet significantly accelerates rod neurodegeneration and vision loss, further highlighting the role of lipid homeostasis in regulating photoreceptor neurodegeneration and vision.

Aryl Hydrocarbon Receptor Regulates Apoptosis and Inflammation in a Murine Model of Experimental Autoimmune Uveitis

Uveitis is characterized as a common cause of blindness worldwide. Aryl hydrocarbon receptor (AhR), a ligand-activated nuclear receptor, has been implicated to play a role in human uveitis, although the exact mechanisms remain poorly understood. The purpose of this study was to enhance our knowledge concerning the role of AhR during intraocular inflammation. We immunized wild-type and AhR-knockout C57BL/6J mice with IRBP_651–670 to induce experimental autoimmune uveitis (EAU). Disease severity was evaluated with both clinical and histopathological grading. Blood–retinal barrier (BRB) integrity was tested by Evans blue and tight junction proteins qualifications. Apoptosis was measured using TdT-mediated dUTP nick end labeling staining. Macrophage/microglia activation and polarization were studied by immunofluorescence and Western blot. Following EAU induction, AhR^−/− mice had more severe clinical and histopathological manifestations of uveitis than AhR^+/+ mice. Increased vascular permeability and apoptotic cells were observed in AhR^−/− EAU mice when compared with AhR^+/+ EAU mice. In addition, AhR^−/− EAU mice showed evidence of a significantly increased macrophage/microglia cells and a stronger polarization from the M2 to the M1 phenotype as compared to AhR^+/+ EAU mice. The levels of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β were increased in AhR^−/− EAU mice, which was associated with the activation of NF-κB and signal transducers and activators of transcription (STAT) pathways. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an agonist of AhR, caused a significant decrease in the clinical and histopathological manifestations, preserved BRB integrity, reduced apoptotic cells, inhibited macrophage/microglia activation, and shifted their polarization from M1 toward M2. Moreover, decreased expression of pro-inflammatory cytokines including TNF-α, IL-6, and IL-1β and inhibition of NF-κB and STAT pathways were found in EAU mice following TCDD treatment. In conclusion, AhR activation with TCDD exhibits an immunomodulatory effect by reducing BRB breakdown, inhibiting retinal cell apoptosis, and reducing pro-inflammatory cytokine expression during EAU. The underlying mechanism may involve the modulation of macrophages/microglia polarization and the downregulation of NF-κB and STAT pathways.

Rapamycin regulates macrophage activation by inhibiting NLRP3 inflammasome-p38 MAPK-NFκB pathways in autophagy- and p62-dependent manners

Excessive and prolonged activation of macrophages underlies many inflammatory and autoimmune diseases. To regulate activation and maintain homeostasis, macrophages have multiple intrinsic mechanisms, one of which is modulation through autophagy. Here we demonstrate that autophagy induction by rapamycin suppressed the production of IL-1β and IL-18 in lipopolysaccharide- and adenosine triphosphate-activated macrophages at the post-transcriptional level by eliminating mitochondrial ROS (mtROS) and pro-IL1β in a p62/SQSTM1-dependent manner. In addition, rapamycin activated Nrf2 through up-regulation of p62/SQSTM1, which further contributed to the reduction of mtROS. Reduced IL-1β subsequently diminished the activation of p38 MAPK-NFκB pathways, leading to transcriptional down-regulation of IL-6, IL-8, MCP-1, and IκBα in rapamycin-treated macrophages. Therefore, our results suggest that rapamycin negatively regulates macrophage activation by restricting a feedback loop of NLRP3 inflammasome-p38 MAPK-NFκB pathways in autophagy- and p62/SQSTM1-dependent manners.

TANK-Binding Kinase 1-Dependent Responses in Health and Autoimmunity

The pathogenesis of autoimmune diseases, such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) is driven by genetic predisposition and environmental triggers that lead to dysregulated immune responses. These include the generation of pathogenic autoantibodies and aberrant production of inflammatory cytokines. Current therapies for RA and other autoimmune diseases reduce inflammation by targeting inflammatory mediators, most of which are innate response cytokines, resulting in generalized immunosuppression. Overall, this strategy has been very successful, but not all patients respond, responses can diminish over time and numerous side effects can occur. Therapies that target the germinal center (GC) reaction and/or antibody-secreting plasma cells (PC) potentially provide a novel approach. TANK-binding kinase 1 (TBK1) is an IKK-related serine/threonine kinase best characterized for its involvement in innate antiviral responses through the induction of type I interferons. TBK1 is also gaining attention for its roles in humoral immune responses. In this review, we discuss the role of TBK1 in immunological pathways involved in the development and maintenance of antibody responses, with particular emphasis on its potential relevance in the pathogenesis of humoral autoimmunity. First, we review the role of TBK1 in the induction of type I IFNs. Second, we highlight how TBK1 mediates inducible T cell co-stimulator signaling to the GC T follicular B helper population. Third, we discuss emerging evidence on the contribution of TBK1 to autophagic pathways and the potential implications for immune cell function. Finally, we discuss the therapeutic potential of TBK1 inhibition in autoimmunity.

Autophagy balances inflammation in innate immunity

Macroautophagy/autophagy is a homeostatic process with multiple effects on immunity. One of the pivotal contributions of autophagy in immunity is the cell autonomous control of inflammation. This property leads to systemic consequences and thereby influences the development of innate and adaptive immunity, which promotes or suppresses pathology in various disease contexts. In this review we focus on the intersections between autophagy and inflammasome activation, autophagy and interferons, and autophagy and inflammation in association with infection.