Cyclic GMP-AMP Synthase Is Required for Cell Proliferation and Inflammatory Responses in Rheumatoid Arthritis Synoviocytes

cGAS-STING pathway in pathogenesis and treatment of osteoarthritis and rheumatoid arthritis

Osteoarthritis (OA) and Rheumatoid Arthritis (RA) are significant health concerns with notable prevalence and economic impact. RA, affecting 0.5% to 1.0% of the global population, leads to chronic joint damage and comorbidities. OA, primarily afflicting the elderly, results in joint degradation and severe pain. Both conditions incur substantial healthcare expenses and productivity losses. The cGAS-STING pathway, consisting of cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING), is a crucial component of mammalian immunity. This pathway is responsible for detecting foreign DNA, particularly double-stranded DNA (dsDNA), triggering innate immune defense responses. When cGAS recognizes dsDNA, it catalyzes the synthesis of cyclic GMP-AMP (cGAMP), which then binds to and activates STING. Activated STING, in turn, initiates downstream signaling events leading to the production of interferons and other immune mediators. The cGAS-STING pathway is essential for defending against viral infections and maintaining cellular balance. Dysregulation of this pathway has been implicated in various inflammatory diseases, including arthritis, making it a target for potential therapeutic interventions. Understanding the intricate molecular signaling network of cGAS-STING in these arthritis forms offers potential avenues for targeted therapies. Addressing these challenges through improved early detection, comprehensive management, and interventions targeting the cGAS-STING pathway is crucial for alleviating the impact of OA and RA on individuals and healthcare systems. This review offers an up-to-date comprehension of the cGAS-STING pathway's role in the development and therapeutic approaches for these arthritis types.

IUPHAR ECR review: The cGAS-STING pathway: Novel functions beyond innate immune and emerging therapeutic opportunities

Stimulator of interferon genes (STING) is a crucial innate immune sensor responsible for distinguishing pathogens and cytosolic DNA, mediating innate immune signaling pathways to defend the host. Recent studies have revealed additional regulatory functions of STING beyond its innate immune-related activities, including the regulation of cellular metabolism, DNA repair, cellular senescence, autophagy and various cell deaths. These findings highlight the broader implications of STING in cellular physiology beyond its role in innate immunity. Currently, approximately 10 STING agonists have entered the clinical stage. Unlike inhibitors, which have a maximum inhibition limit, agonists have the potential for infinite amplification. STING signaling is a complex process that requires precise regulation of STING to ensure balanced immune responses and prevent detrimental autoinflammation. Recent research on the structural mechanism of STING autoinhibition and its negative regulation by adaptor protein complex 1 (AP-1) provides valuable insights into its different effects under physiological and pathological conditions, offering a new perspective for developing immune regulatory drugs. Herein, we present a comprehensive overview of the regulatory functions and molecular mechanisms of STING beyond innate immune regulation, along with updated details of its structural mechanisms. We discuss the implications of these complex regulations in various diseases, emphasizing the importance and feasibility of targeting the immunity-dependent or immunity-independent functions of STING. Moreover, we highlight the current trend in drug development and key points for clinical research, basic research, and translational research related to STING.

Macrophage extracellular traps promote tumor-like biologic behaviors of fibroblast-like synoviocytes through cGAS-mediated PI3K/Akt signaling pathway in patients with rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disease characterized by synovium hyperplasia and bone destruction. Macrophage extracellular traps are released from macrophages under various stimuli and may generate stable autoantigen-DNA complexes, as well as aggravate autoantibody generation and autoimmune responses. We aimed to investigate the role of macrophage extracellular traps on the biologic behaviors of rheumatoid arthritis fibroblast-like synoviocytes. Synovial tissues and fibroblast-like synoviocytes were obtained from patients with rheumatoid arthritis. Extracellular traps in synovium and synovial fluids were detected by immunofluorescence, immunohistochemistry, and SYTOX Green staining. Cell viability, migration, invasion, and cytokine expression of rheumatoid arthritis fibroblast-like synoviocytes were assessed by CCK-8, wound-healing assay, Transwell assays, and quantitative real-time polymerase chain reaction, respectively. RNA sequencing analysis was performed to explore the underlying mechanism, and Western blot was used to validate the active signaling pathways. We found that extracellular trap formation was abundant in rheumatoid arthritis and positively correlated to anti-CCP. Rheumatoid arthritis fibroblast-like synoviocytes stimulated with purified macrophage extracellular traps demonstrated the obvious promotion in tumor-like biologic behaviors. The DNA sensor cGAS in rheumatoid arthritis fibroblast-like synoviocytes was activated after macrophage extracellular trap stimuli. RNA sequencing revealed that differential genes were significantly enriched in the PI3K/Akt signaling pathway, and cGAS inhibitor RU.521 effectively reversed the promotion of tumor-like biologic behaviors in macrophage extracellular trap-treated rheumatoid arthritis fibroblast-like synoviocytes and downregulated the PI3K/Akt activation. In summary, our study demonstrates that macrophage extracellular traps promote the pathogenically biological behaviors of rheumatoid arthritis fibroblast-like synoviocytes through cGAS-mediated activation of the PI3K/Akt signaling pathway. These findings provide a novel insight into the pathogenesis of rheumatoid arthritis and the mechanisms of macrophages in modulating rheumatoid arthritis fibroblast-like synoviocyte tumor-like behaviors.

Updated roles of cGAS-STING signaling in autoimmune diseases

Natural immunity, the first line for the body to defense against the invasion of pathogen, serves as the body's perception of the presence of pathogens depends on nucleic acid recognition mechanisms. The cyclic GMP-AMP synthase-stimulator of the interferon gene (cGAS-STING) signaling pathway is considered an essential pattern recognition and effector pathway in the natural immune system and is mainly responsible for recognizing DNA molecules present in the cytoplasm and activating downstream signaling pathways to generate type I interferons and some other inflammatory factors. STING, a crucial junction protein in the innate immune system, exerts an essential role in host resistance to external pathogen invasion. Also, STING, with the same character of inflammatory molecules, is inseparable from the body's inflammatory response. In particular, when the expression of STING is upregulated or its related signaling pathways are overactivated, the body may develop serious infectious disorders due to the generation of excessive inflammatory responses, non-infectious diseases, and autoimmune diseases. In recent years, accumulating studies indicated that the abnormal activation of the natural immune cGAS-STING signaling pathway modulated by the nucleic acid receptor cGAS closely associated with the development and occurrence of autoimmune diseases (AID). Thereof, to explore an in-depth role of STING and its related signaling pathways in the diseases associated with inflammation may be helpful to provide new avenues for the treatment of these diseases in the clinic. This article reviews the activation process of the cGAS-STING signaling pathways and its related important roles, and therapeutic drugs in AID, aiming to improve our understanding of AID and achieve better diagnosis and treatment of AID.

Beyond DNA sensing: expanding the role of cGAS/STING in immunity and diseases

Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) is a DNA sensor that elicits a robust type I interferon response by recognizing ubiquitous danger-associated molecules. The cGAS/stimulator of interferon genes (cGAS/STING) is activated by endogenous DNA, including DNA released from mitochondria and extranuclear chromatin, as well as exogenous DNA derived from pathogenic microorganisms. cGAS/STING is positioned as a key axis of autoimmunity, the inflammatory response, and cancer progression, suggesting that the cGAS/STING signaling pathway represents an efficient therapeutic target. Based on the accumulated evidence, we present insights into the prevention and treatment of cGAS/STING-related chronic immune and inflammatory diseases. This review presents the current state of clinical and nonclinical development of modulators targeting cGAS/STING, providing useful information on the design of therapeutic strategies.

Discovery and characterization of a novel cGAS covalent inhibitor for the treatment of inflammatory bowel disease

Cyclic GMP-AMP synthase (cGAS), a cytosolic DNA sensor, acts as a nucleotidyl transferase that catalyzes ATP and GTP to form cyclic GMP-AMP (cGAMP) and plays a critical role in innate immunity. Hyperactivation of cGAS-STING signaling contributes to hyperinflammatory responses. Therefore, cGAS is considered a promising target for the treatment of inflammatory diseases. Herein, we report the discovery and identification of several novel types of cGAS inhibitors by pyrophosphatase (PPiase)-coupled activity assays. Among these inhibitors, 1-(1-phenyl-3,4-dihydro-1H-pyrrolo[1,2-a]pyrazin-2-yl)prop-2-yn-1-one (compound 3) displayed the highest potency and selectivity at the cellular level. Compound 3 exhibited better inhibitory activity and pathway selectivity than RU.521, which is a selective cGAS inhibitor with anti-inflammatory effects in vitro and in vivo. Thermostability analysis, nuclear magnetic resonance and isothermal titration calorimetry assays confirmed that compound 3 directly binds to the cGAS protein. Mass spectrometry and mutation analysis revealed that compound 3 covalently binds to Cys419 of cGAS. Notably, compound 3 demonstrated promising therapeutic efficacy in a dextran sulfate sodium (DSS)-induced mouse colitis model. These results collectively suggest that compound 3 will be useful for understanding the biological function of cGAS and has the potential to be further developed for inflammatory disease therapies.

Potential Therapeutic Value of the STING Inhibitors

The stimulator of interferon genes (STING) is a critical protein in the activation of the immune system in response to DNA. It can participate the inflammatory response process by modulating the inflammation-preferred translation program through the STING-PKR-like endoplasmic reticulum kinase (PERK)-eIF2α pathway or by inducing the secretion of type I interferons (IFNs) and a variety of proinflammatory factors through the recruitment of TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) or the regulation of the nuclear factor kappa-B (NF-κB) pathway. Based on the structure, location, function, genotype, and regulatory mechanism of STING, this review summarizes the potential value of STING inhibitors in the prevention and treatment of infectious diseases, psoriasis, systemic lupus erythematosus, non-alcoholic fatty liver disease, and other inflammatory and autoimmune diseases.

Role of Liquid Biopsies in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease caused by genetic and environmental factors. Early diagnosis is crucial for effective therapy and prognosis of RA, while biomarkers play important roles in early diagnosis. Traditional laboratory tests include rheumatoid factor, anti-cyclic citrullinated peptide antibody, which are inadequate in the ability of early diagnosis. Liquid biopsy technology is a technique using biomarkers found in the blood, urine, and other biological samples from patients, including DNA, RNA, exosome, etc. Evidence indicates that these biomarkers are involved in pathological and physiological conditions of RA. We reviewed the effects of liquid biopsy technology in the early diagnosis of RA and may provide new ideas for effective and precise treatment.

DNA damage repair kinase DNA-PK and cGAS synergize to induce cancer-related inflammation in glioblastoma

Cytosolic DNA promotes inflammatory responses upon detection by the cyclic GMP-AMP (cGAMP) synthase (cGAS). It has been suggested that cGAS downregulation is an immune escape strategy harnessed by tumor cells. Here, we used glioblastoma cells that show undetectable cGAS levels to address if alternative DNA detection pathways can promote pro-inflammatory signaling. We show that the DNA-PK DNA repair complex (i) drives cGAS-independent IRF3-mediated type I Interferon responses and (ii) that its catalytic activity is required for cGAS-dependent cGAMP production and optimal downstream signaling. We further show that the cooperation between DNA-PK and cGAS favors the expression of chemokines that promote macrophage recruitment in the tumor microenvironment in a glioblastoma model, a process that impairs early tumorigenesis but correlates with poor outcome in glioblastoma patients. Thus, our study supports that cGAS-dependent signaling is acquired during tumorigenesis and that cGAS and DNA-PK activities should be analyzed concertedly to predict the impact of strategies aiming to boost tumor immunogenicity.

Alternative pathways driven by STING: From innate immunity to lipid metabolism

The Stimulator of Interferon Genes (STING) is a major adaptor protein that is central to the initiation of type I interferon responses and proinflammatory signalling. STING-dependent signalling is triggered by the presence of cytosolic nucleic acids that are generated following pathogen infection or cellular stress. Beyond this central role in controlling immune responses through the production of cytokines and chemokines, recent reports have uncovered inflammation-independent STING functions. Amongst these, a rapidly growing body of evidence demonstrates a key role of STING in controlling metabolic pathways at several levels. Since immunity and metabolic homeostasis are tightly interconnected, these findings deepen our understanding of the involvement of STING in human pathologies. Here, we discuss these findings and reflect on their impact on our current understanding of how nucleic acid immunity controls homeostasis and promotes pathological outcomes.

Crosstalk between xanthine oxidase (XO) inhibiting and cancer chemotherapeutic properties of comestible flavonoids- a comprehensive update

Gout is an inflammatory disease caused by metabolic disorder or genetic inheritance. People throughout the world are strongly dependent on ethnomedicine for the treatment of gout and some receive satisfactory curative treatment. The natural remedies as well as established drugs derived from natural sources or synthetically made exert their action by mechanisms that are closely associated with anticancer treatment mechanisms regarding inhibition of xanthine oxidase, feedback inhibition of de novo purine synthesis, depolymerization and disappearance of microtubule, inhibition of NF-ĸB activation, induction of TRAIL, promotion of apoptosis, and caspase activation and proteasome inhibition. Some anti-gout and anticancer novel compounds interact with same receptors for their action, e.g., colchicine and colchicine analogues. Dietary flavonoids, i.e., chrysin, kaempferol, quercetin, fisetin, pelargonidin, apigenin, luteolin, myricetin, isorhamnetin, phloretinetc etc. have comparable IC₅₀ values with established anti-gout drug and effective against both cancer and gout. Moreover, a noticeable number of newer anticancer compounds have already been isolated from plants that have been using by local traditional healers and herbal practitioners to treat gout. Therefore, the anti-gout plants might have greater potentiality to become selective candidates for screening of newer anticancer leads.

ZDHHC18 negatively regulates cGAS-mediated innate immunity through palmitoylation

Double-stranded DNA is recognized as a danger signal by cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS), triggering innate immune responses. Palmitoylation is an important post-translational modification (PTM) catalyzed by DHHC-palmitoyl transferases, which participate in the regulation of diverse biological processes. However, whether palmitoylation regulates cGAS function has not yet been explored. Here, we found that palmitoylation of cGAS at C474 restricted its enzymatic activity in the presence of double-stranded DNA. cGAS palmitoylation was catalyzed mainly by the palmitoyltransferase ZDHHC18 and double-stranded DNA promoted this modification. Mechanistically, palmitoylation of cGAS reduced the interaction between cGAS and double-stranded DNA, further inhibiting cGAS dimerization. Consistently, ZDHHC18 negatively regulated cGAS activation in human and mouse cell lines. In a more biologically relevant model system, Zdhhc18-deficient mice were found to be resistant to infection by DNA viruses, in agreement with the observation that ZDHHC18 negatively regulated cGAS mediated innate immune responses in human and mouse primary cells. In summary, the negative role of ZDHHC18-mediated cGAS palmitoylation may be a novel regulatory mechanism in the fine-tuning of innate immunity.

The cGAS-STING pathway: more than fighting against viruses and cancer

In the classic Cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway, downstream signals can control the production of type I interferon and nuclear factor kappa-light-chain-enhancer of activated B cells to promote the activation of pro-inflammatory molecules, which are mainly induced during antiviral responses. However, with progress in this area of research, studies focused on autoimmune diseases and chronic inflammatory conditions that may be relevant to cGAS–STING pathways have been conducted. This review mainly highlights the functions of the cGAS–STING pathway in chronic inflammatory diseases. Importantly, the cGAS–STING pathway has a major impact on lipid metabolism. Different research groups have confirmed that the cGAS–STING pathway plays an important role in the chronic inflammatory status in various organs. However, this pathway has not been studied in depth in diabetes and diabetes-related complications. Current research on the cGAS–STING pathway has shown that the targeted therapy of diseases that may be caused by inflammation via the cGAS–STING pathway has promising outcomes.

Drosophila STING protein has a role in lipid metabolism

Stimulator of interferon genes (STING) plays an important role in innate immunity by controlling type I interferon response against invaded pathogens. In this work, we describe a previously unknown role of STING in lipid metabolism in Drosophila. Flies with STING deletion are sensitive to starvation and oxidative stress, have reduced lipid storage, and downregulated expression of lipid metabolism genes. We found that Drosophila STING interacts with lipid synthesizing enzymes acetyl-CoA carboxylase (ACC) and fatty acid synthase (FASN). ACC and FASN also interact with each other, indicating that all three proteins may be components of a large multi-enzyme complex. The deletion of Drosophila STING leads to disturbed ACC localization and decreased FASN enzyme activity. Together, our results demonstrate a previously undescribed role of STING in lipid metabolism in Drosophila.

Cell-Free DNA in Rheumatoid Arthritis

Endogenous DNA derived from the nuclei or mitochondria is released into the bloodstream following cell damage or death. Extracellular DNA, called cell-free DNA (cfDNA), is associated with various pathological conditions. Recently, multiple aspects of cfDNA have been assessed, including cfDNA levels, integrity, methylation, and mutations. Rheumatoid arthritis (RA) is the most common form of autoimmune arthritis, and treatment of RA has highly varied outcomes. cfDNA in patients with RA is elevated in peripheral blood and synovial fluid and is associated with disease activity. Profiling of cfDNA in patients with RA may then be utilized in various aspects of clinical practice, such as the prediction of prognosis and treatment responses; monitoring disease state; and as a diagnostic marker. In this review, we discuss cfDNA in patients with RA, particularly the sources of cfDNA and the correlation of cfDNA with RA pathogenesis. We also highlight the potential of analyzing cfDNA profiles to guide individualized treatment approaches for RA.

Cytosolic DNA sensing by cGAS: regulation, function, and human diseases

Sensing invasive cytosolic DNA is an integral component of innate immunity. cGAS was identified in 2013 as the major cytosolic DNA sensor that binds dsDNA to catalyze the synthesis of a special asymmetric cyclic-dinucleotide, 2′3′-cGAMP, as the secondary messenger to bind and activate STING for subsequent production of type I interferons and other immune-modulatory genes. Hyperactivation of cGAS signaling contributes to autoimmune diseases but serves as an adjuvant for anticancer immune therapy. On the other hand, inactivation of cGAS signaling causes deficiency to sense and clear the viral and bacterial infection and creates a tumor-prone immune microenvironment to facilitate tumor evasion of immune surveillance. Thus, cGAS activation is tightly controlled. In this review, we summarize up-to-date multilayers of regulatory mechanisms governing cGAS activation, including cGAS pre- and post-translational regulations, cGAS-binding proteins, and additional cGAS regulators such as ions and small molecules. We will also reveal the pathophysiological function of cGAS and its product cGAMP in human diseases. We hope to provide an up-to-date review for recent research advances of cGAS biology and cGAS-targeted therapies for human diseases.

Extract from Ascaris suum and N-acetyl-L-cysteine induces an immunosuppressant effect in model of autoimmune hepatitis

BACKGROUND

Extract of adult Ascaris suum (ASC) worms attenuated the liver damage in experimental autoimmune hepatitis (EAH) with induction of Th2 immune response, but fibrosis occurred. N-acetyl-L-cysteine (NAC) has protective effects against liver fibrosis.

OBJECTIVES

Evaluate the association ASC + NAC on the T- and B-cell activation, inflammation and fibrogenic markers in the liver in EAH.

METHODS

Experimental autoimmune hepatitis was induced intravenously with concanavalin A in BALB/c mice. EAH + ASC+NAC group received NAC and ASC; EAH + ASC group received ASC; EAH group received PBS. Doubly labelled CD4⁺ T (CD28, CTLA-4, CD40L or IL-10) and CD45R⁺ B lymphocytes (IL-10) and CD4⁺ CD25⁺ FoxP3⁺ cells were evaluated, along with gene expression of Col1a1, α-SMA, Fizz1, Arg1 and PPAR-γ and histomorphometry.

RESULTS

Experimental autoimmune hepatitis group showed high frequency of CD28⁺ and CD40L⁺  T lymphocytes, but not the EAH + ASC group. In relation to EAH group, the Fizz1 expression was lower in both groups treated, but Arg1 expression was lower in only EAH + ASC+NAC group. In the EAH + ASC+NAC group, there were higher frequencies of CD4⁺ IL-10⁺ and CD4⁺ CD25⁺ FoxP3⁺ cells, but not CD45R⁺ IL-10⁺ , along with mitigated inflammation and collagen production.

CONCLUSIONS

Ascaris suum favoured immunosuppression in EAH limiting the T cells activation. However, association ASC and NAC was necessary for attenuating the inflammatory process and collagen production.

cGAS-STING pathway in oncogenesis and cancer therapeutics

The host innate immunity offers the first line of defense against infection. However, recent evidence shows that the host innate immunity is also critical in sensing the presence of cytoplasmic DNA derived from genomic instability events, such as DNA damage and defective cell cycle progression. This is achieved through the cyclic GMP-AMP synthase (cGAS)/Stimulator of interferon (IFN) genes (STING) pathway. Here we discuss recent insights into the regulation of this pathway in cancer immunosurveillance, and the downstream signaling cascades that coordinate immune cell recruitment to the tumor microenvironment to destroy transformed cells through cellular senescence or cell death programs. Its central role in immunosurveillance positions the cGAS-STING pathway as an attractive anti-cancer immunotherapeutic drug target for chemical agonists or vaccine adjuvants and suggests a key node to be targeted in a synthetic lethal approach. We also discuss adaptive mechanisms used by cancer cells to circumvent cGAS-STING signaling and present evidence linking chronic cGAS-STING activation to inflammation-induced carcinogenesis, cautioning against the use of activating the cGAS-STING pathway as an anti-tumor immunotherapy. A deeper mechanistic understanding of the cGAS-STING pathway will aid in the identification of potentially efficacious anti-cancer therapeutic targets.

Urate-induced immune programming: Consequences for gouty arthritis and hyperuricemia

Trained immunity is a process in which innate immune cells undergo functional reprogramming in response to pathogens or damage-associated molecules leading to an enhanced non-specific immune response to subsequent stimulation. While this capacity to respond more strongly to stimuli is beneficial for host defense, in some circumstances it can lead to maladaptive programming and chronic inflammation. Gout is characterized by persistent low-grade inflammation and is associated with an increased number of comorbidities. Hyperuricemia is the main risk factor for gout and is linked to the development of comorbidities. Several experimental studies have shown that urate can mechanistically alter the inflammatory capacity of myeloid cells, while observational studies have indicated an association of hyperuricemia to a wide spectrum of common adult inflammatory diseases. In this review, we argue that hyperuricemia is a main culprit in the development of the long-term systemic inflammation seen in gout. We revisit existing evidence for urate-induced transcriptional and epigenetic reprogramming that could lead to an altered functional state of circulating monocytes consisting in enhanced responsiveness and maladaptive immune responses. By discussing specific functional adaptations of monocytes and macrophages induced by soluble urate or monosodium urate crystals and their contribution to inflammation in vitro and in vivo, we further enforce that urate is a metabolite that can induce innate immune memory and we discuss future research and possible new therapeutic approaches for gout and its comorbidities.

The dynamic expression of canonical Wnt/β-catenin signalling pathway in the pathologic process of experimental autoimmune neuritis

Background: Guillain-Barré syndrome (GBS), an autoimmune disease and an acute inflammation disorder, is currently the most frequent cause of acute flaccid paralysis worldwide. EAN, an animal model of GBS, is a CD4+ T cell-mediated autoimmune disease of the PNS. Wnt/β-catenin signals are critically important to several fundamental aspects of peripheral nerve development and play a crucial role in Schwann cell proliferation. Here, we investigate the role of Wnt/β-catenin signalling cascades in EAN rats.Methods: 28 male Lewis rats weighing 170 ± 10 g were randomly divided into control group (n = 7) and EAN groups (Early group; Peak group and Recovery group. n = 7 per group). EAN rats were immunized with P2_57-81 peptide; weighed daily, and the neurologic signs of EAN were evaluated every day. The sciatic nerve was taken on the days 10, 17, and 30 p.i. for H&E staining, transmission electron microscopy and immunohistochemical staining; blood samples were collected weekly from caudal vein to detect IFN-γ, IL-4, TGF-β1; and the sciatic nerve was taken to examinate the dynamics expression of Wnt/β-catenin pathway molecules.Results: In our study, we chose tail-root injection to better model GBS. Moreover, we observed that IFN-γ levels paralleled clinical EAN, and the levels of TGF-β1 and IL-4 gradually increased and peaked in the recovery phase. In addition, we have shown that canonical Wnt signalling is upregulated and reached a peak in the late recovery phase.Conclusion: Our findings suggest that Wnt/β-catenin signalling is associated with the promotion of remyelination in EAN rats.

Airway Epithelial cGAS Is Critical for Induction of Experimental Allergic Airway Inflammation

DNA damage could lead to the accumulation of cytosolic DNA, and the cytosolic DNA-sensing pathway has been implicated in multiple inflammatory diseases. However, the role of cytosolic DNA-sensing pathway in asthma pathogenesis is still unclear. This article explored the role of airway epithelial cyclic GMP-AMP synthase (cGAS), the major sensor of cytosolic dsDNA, in asthma pathogenesis. Cytosolic dsDNA accumulation in airway epithelial cells (ECs) was detected in the setting of allergic inflammation both in vitro and in vivo. Mice with cGAS deletion in airway ECs were used for OVA- or house dust mite (HDM)-induced allergic airway inflammation. Additionally, the effects of cGAS knockdown on IL-33-induced GM-CSF production and the mechanisms by which IL-33 induced cytosolic dsDNA accumulation in human bronchial epithelial (HBE) cells were explored. Increased accumulation of cytosolic dsDNA was observed in airway epithelium of OVA- or HDM-challenged mice and in HBE cells treated with IL-33. Deletion of cGAS in the airway ECs of mice significantly attenuated the allergic airway inflammation induced by OVA or HDM. Mechanistically, cGAS participates in promoting T_H2 immunity likely via regulating the production of airway epithelial GM-CSF. Furthermore, Mito-TEMPO could reduce IL-33-induced cytoplasmic dsDNA accumulation in HBE cells possibly through suppressing the release of mitochondrial DNA into the cytosol. In conclusion, airway epithelial cGAS plays an important role via sensing the cytosolic dsDNA in asthma pathogenesis and could serve as a promising therapeutic target against allergic airway inflammation.

Accumulation of cytosolic dsDNA contributes to fibroblast-like synoviocytes-mediated rheumatoid arthritis synovial inflammation

The accumulation of cytosolic dsDNA plays important roles in the regulation of cellular processes. However, whether cytosolic dsDNA is involved in the pathogenesis of rheumatoid arthritis (RA) is not clear. Therefore, the present study investigated the roles of cytosolic dsDNA in the modulation of inflammatory responses of fibroblast-like synoviocytes (FLS) in patients with RA. FLS were obtained from active RA patients. dsDNA accumulation in the cytosol was detected by immunofluorescence staining and the Qubit® dsDNA HS Assay. Immunohistochemistry was employed to detect the dsDNA and cGMP-AMP synthase (cGAS) expression in the synovium. Short hairpin RNA (shRNA) was used to knockdown the expression of cGAS and stimulator of interferon genes (STING). Protein expression was detected by Western blotting and immunofluorescence staining. We observed increased cytosolic dsDNA and cGAS expression in FLS and synovium from RA patients. dsDNA and cGAS expression correlated with the severity of rheumatoid synovitis. Transfection of dsDNA into the cytosol of RA FLS promoted pro-inflammatory cytokines production. DNaseII overexpression downregulated cytosolic dsDNA expression and inhibited dsDNA-induced cytokines secretion. We also found that dsDNA and TNF-α enhanced cGAS and STING expression, and dsDNA-induced cytokine secretion was reduced by cGAS or STING knockdown. Furthermore, we determined that the dsDNA-induced phosphorylation of IRF3 and NF-κBp65 was decreased by DNaseII overexpression or cGAS/STING knockdown. Overall, our findings show that increased cytosolic dsDNA level promoted inflammatory responses via the cGAS/STING pathway in RA FLS, which suggests that cytosolic dsDNA accumulation is an important contributor to FLS-mediated rheumatoid synovial inflammation.

Astragalus polysaccharides inhibits cell growth and pro-inflammatory response in IL-1β-stimulated fibroblast-like synoviocytes by enhancement of autophagy via PI3K/AKT/mTOR inhibition

The hyperplastic growth of rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLSs) and inflammatory response are pathological hallmarks of RA. It has been reported that Astragalus polysaccharides (APS) possess appreciable anti-inflammatory activity against adjuvant-induced arthritis. Nevertheless, little is known about the role and detailed mechanism underlying the therapeutic effects of APS in RA. This study demonstrated that administration of APS dose-dependently impaired cell viability, increased cell apoptosis by decreasing Bcl-2 expression, increasing Bax expression and Caspase3 activity in IL-1β-stimulated RSC-364 cells and RA-FLS. Simultaneously, IL-1β-induced production of pro-inflammatory cytokines IL-6 and TNF-α was significantly decreased after APS treatment. Furthermore, preconditioning with APS dramatically enhanced autophagy activity by increasing Beclin-1 and LC3II/LC3I expression coupled with decreasing p62 expression and augmenting the number of LC3 puncta in IL-1β-stimulated RSC-364 cells. More importantly, autophagy inhibitor 3-methyladenine (3-MA) partly abolished APS-triggered inhibitory effects on cell growth and production of pro-inflammatory cytokines. APS also repressed the activation of PI3K/Akt/mTOR signaling pathway in IL-1β-stimulated RSC-364 cells. Moreover, treatment with insulin-like growth factor-1 (IGF-1), an activator of PI3K/Akt signaling, partly reversed the therapeutic effects of APS in IL-1β-stimulated RSC-364 cells. Collectively, we concluded that APS might attenuate the pathological progression of RA by exerting the pro-apoptotic and anti-inflammatory effects in IL-1β-stimulated FLSs by regulating the PI3K/AKT/mTOR-autophagy pathway.

Nitrolipids in kidney physiology and disease

The kidneys are vital organs responsible for maintaining body fluid homeostasis within proper physiologic ranges. Kidney disease is an epidemic clinical problem causing significant morbidity and mortality, and current treatments are limited to renin-angiotensin system blockade or renal replacement therapy for the majority of affected individuals. There is a critical, unmet need for novel pharmacological agents to improve the outcome of patients with kidney disease. Nitro-oleic acid (NO2-OA) is an endogenously generated electrophilic compound with the capacity to modify thiols in proteins, altering their function. The most important targets appear to be the Keap1/Nrf2 and NF-κB pathways, which have widespread effects on antioxidant, detoxifying, and inflammatory responses in cells and tissues. Through these and potentially additional protective actions, NO2-OA may be capable of preserving or enhancing kidney function in acute and chronic kidney diseases.

Post-Operative Cognitive Dysfunction: An exploration of the inflammatory hypothesis and novel therapies

Post-Operative Cognitive Dysfunction (POCD) is a highly prevalent condition with significant clinical, social and financial impacts for patients and their communities. The underlying pathophysiology is becoming increasingly understood, with the role of neuroinflammation and oxidative stress secondary to surgery and anaesthesia strongly implicated. This review aims to describe the putative mechanisms by which surgery-induced inflammation produces cognitive sequelae, with a focus on identifying potential novel therapies based upon their ability to modify these pathways.

Anti-Inflammatory Effects of TRAF-Interacting Protein in Rheumatoid Arthritis Fibroblast-Like Synoviocytes

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease characterized by inflammatory cell infiltration, synovial inflammation, and cartilage destruction. Proliferative fibroblast-like synoviocytes (FLS) play crucial roles in both propagation of inflammation and joint damage because of their production of great amount of proinflammatory cytokines and proteolytic enzymes. In this study, we investigate the role of TRAF-interacting protein (TRIP) in regulating inflammatory process in RA-FLS. TRIP expression was attenuated in RA-FLS compared with osteoarthritis- (OA-) FLS. Overexpression of TRIP significantly inhibited the activation of NF-κB signaling and decreased the production of proinflammatory cytokines and matrix metalloproteinases (MMPs) in TNFα-stimulated RA-FLS. Furthermore, TRIP was found to interact with transforming growth factor β-activated kinase 1 (TAK1) and promoting K48-linked polyubiquitination of TAK1 in RA-FLS. Our results demonstrate that TRIP has anti-inflammatory effects on RA-FLS and suggest TRIP as a potential therapeutic target for human RA.

Effect of oleuropein against chemotherapy drug-induced histological changes, oxidative stress, and DNA damages in rat kidney injury

Cisplatin-based chemotherapy is responsible for a large number of renal failures, and it is still associated with high rates of mortality today. Oleuropein (OLE) presents a plethora of pharmacological beneficial properties. In this study we investigated whether OLE could provide sufficient protection against cisplatin-induced nephrotoxicity. With this aim, Sprague-Dawley rats were divided into eight groups: control; 7 mg/kg/d cisplatin, 50 mg/kg, 100 mg/kg, and 200 mg/kg OLE; and treatment with OLE for 3 days starting at 24 hours following cisplatin injection. After exposure to the chemotherapy agent and OLE, oxidative DNA damage was quantitated in the renal tissue of experimental animals by measuring the amount of 8-hydroxy-2′-deoxyguanosine (8-OHdG) adducts. Malondialdehyde (MDA) level, total oxidative stress (TOS), and total antioxidant status (TAS) were assessed to determine the oxidative injury in kidney cells. The histology of the kidney was examined using four different staining methods: hematoxylin-eosin (H&E), periodic acid Schiff (PAS), Masson trichrome, and amyloid. In addition, the blood urea nitrogen (BUN), uric acid (UA), and creatinine (CRE) levels were established. Our experimental data showed that tissue 8-OHdG levels were significantly higher in the cisplatin group when compared to the control group. The glomerular cells were sensitive to cisplatin as tubular cells. In addition, treatment with cisplatin elevated the levels of BUN, UA, CRE, and TOS, but lowered the level of TAS compared to the control group. The OLE therapy modulated oxidative stress in order to restore normal kidney function and reduced the formation of 8-OHdG induced by cisplatin. Furthermore, the OLE treatment significantly reduced pathological findings in renal tissue. We demonstrate for the first time that OLE presents significant cytoprotective properties against cisplatin-induced genotoxicity by restoring the antioxidant system of the renal tissue. According to our findings, OLE is a promising novel natural source for the prevention of serious kidney damage in current chemotherapies.

15d-PGJ2 alleviates ConA-induced acute liver injury in mice by up-regulating HO-1 and reducing hepatic cell autophagy

OBJECTIVE

In this study, we confirmed a protective effect of 15d-PGJ2 in concanavalin A (ConA)-induced fulminant hepatitis in mice and investigated the potential mechanism.

MATERIALS AND METHODS

Balb/C mice were injected with ConA (25mg/kg) to induce acute fulminant hepatitis, and 15d-PGJ2 (2.5-10μg) was administered 30min after the ConA injection. The histological grade, pro-inflammatory cytokine and ROS levels, apoptosis and autophagy activity, the expression of HO-1, Nrf2, JNK and Bcl-2 activity were determined 2, 4, and 8h after the ConA injection.

RESULTS

Following ConA challenge, the expression of cytokines tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) was up-regulated. Treatment with 15d-PGJ2 reduced the pathological effects of ConA-induced fulminant hepatitis and significantly reduced the levels of TNF-α, IL-1β and ROS after injection. 15d-PGJ2 inhibited apoptosis and autophagic cell death, facilitated Nrf2 nuclear translocation, increased HO-1 expression and suppressed the JNK activation.

CONCLUSION

15d-PGJ2 alleviates ConA-induced acute liver injury in mice by up-regulating the anti-oxidative stress factor HO-1 and reducing the production of cytokines and ROS, thereby inhibiting hepatic cell autophagy probably induced by ROS.