Alpha-1-anti-trypsin-Fc fusion protein ameliorates gouty arthritis by reducing release and extracellular processing of IL-1β and by the induction of endogenous IL-1Ra

α‑1 Antitrypsin is a potential target of inflammation and immunomodulation (Review)

α‑1 Antitrypsin (AAT) is an acute phase protein encoded by the serine protease inhibitor family A member 1 gene. This multifunctional protein serves several roles, including anti‑inflammatory, antibacterial, antiapoptotic and immune regulatory functions. The primary role of AAT is to protect tissues and organs from protease‑induced damage due to its function as a serine protease inhibitor. AAT is associated with the development of lung inflammation, liver inflammation and immune‑mediated inflammatory diseases, which are influenced by environmental and genetic factors. For instance, AAT acts as an anti‑inflammatory protein to prevent and reverse type I diabetes. The present study briefly reviewed the molecular properties and mechanisms of AAT, as well as advances in the study of lung, liver and inflammatory diseases associated with AAT. The potential of AAT as a diagnostic and therapeutic target for inflammatory and immune‑mediated inflammatory diseases was reviewed. In addition, the damaging and protective effects of AAT, and its effects on organ function were discussed.

An update on the pharmacotherapy of gout

INTRODUCTION

Gout is a common form of acute inflammatory arthritis caused by the deposition of monosodium urate crystals within synovium of joints. This leads to severe pain, reducing quality of life for patients with this condition.

AREAS COVERED

This review summarizes the treatment of both acute flares of gout and urate-lowering therapy based on guidance from various major international societies. We have also covered new emerging therapies that have not yet reached clinical practice.

EXPERT OPINION

Standard pharmacotherapies for gout flares include the options of colchicine, NSAIDs and oral or intramuscular corticosteroids, with IL-1 inhibitors newly established as an option for flare refractory to standard therapies. Urate-lowering therapies aim to prevent gout flares, with an emphasis on treat-to-target strategy; the escalation of therapies until the target serum uric acid is reached. Initial treatments include allopurinol and febuxostat, with uricosuric agents, probenecid, sulfinpyrazone and benzbromarone, as adjuncts. There are also emerging therapies in development. However, there is increasing personalization of treatment, adjusting pharmacotherapy depending on comorbidities, such as chronic kidney disease and ischemic heart disease, as well as patient preference.

Food-derived bioactive peptides potentiating therapeutic intervention in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that affects the joints of the human body and is projected to have a prevalence age-standardized rate of 1.5 million new cases worldwide by 2030. Several conventional and non-conventional preventive and therapeutic interventions have been suggested but they have their side effects including nausea, abdominal pain, liver damage, ulcers, heightened blood pressure, coagulation, and bleeding. Interestingly, several food-derived peptides (FDPs) from both plant and animal sources are increasingly gaining a reputation for their potential in the management or therapy of RA with little or no side effects. In this review, the concept of inflammation, its major types (acute and chronic), and RA identified as a chronic type were discussed based on its pathogenesis and pathophysiology. The conventional treatment options for RA were briefly outlined as the backdrop of introducing the FDPs that potentiate therapeutic effects in the management of RA.

Uric acid en route to gout

Gout and hyperuricemia (HU) have generated immense attention due to increased prevalence. Gout is a multifactorial metabolic and inflammatory disease that occurs when increased uric acid (UA) induce HU resulting in monosodium urate (MSU) crystal deposition in joints. However, gout pathogenesis does not always involve these events and HU does not always cause a gout flare. Treatment with UA-lowering therapeutics may not prevent or reduce the incidence of gout flare or gout-associated comorbidities. UA exhibits both pro- and anti-inflammation functions in gout pathogenesis. HU and gout share mechanistic and metabolic connections at a systematic level, as shown by studies on associated comorbidities. Recent studies on the interplay between UA, HU, MSU and gout as well as the development of HU and gout in association with metabolic syndromes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular, renal and cerebrovascular diseases are discussed. This review examines current and potential therapeutic regimens and illuminates the journey from disrupted UA to gout.

Indirect effect of alpha-1-antitrypsin on endotoxin-induced IL-1β secretion from human PBMCs

Human alpha-1-antitrypsin (AAT) encoded by the SERPINA1 gene, is an acute phase glycoprotein that regulates inflammatory responses via both protease inhibitory and non-inhibitory activities. We previously reported that AAT controls ATP-induced IL-1β release from human mononuclear cells by stimulating the release of small bioactive molecules. In the current study, we aimed to elucidate the identity of these putative effectors released from human PBMCs in response to AAT, which may inhibit the LPS-induced release of IL-1β. We pre-incubated human PBMCs alone or with different preparations of AAT (4 mg/ml) for 30 min at 37°C, 5% CO₂, and collected cell supernatants filtered through centrifugal filters (cutoff 3 kDa) to eliminate AAT and other high molecular weight substances. Supernatants passed through the filters were used to culture PBMCs isolated from the autologous or a heterologous donors with or without adding LPS (1 μg/ml) for 6 h. Unexpectedly, supernatants from PBMCs pre-incubated with AAT (Zemaira^®), but not with other AAT preparations tested or with oxidized AAT (Zemaira^®), lowered the LPS-induced release of IL-1β by about 25%–60% without affecting IL1B mRNA. The reversed-phase liquid chromatography coupled with mass spectrometry did not confirm the hypothesis that small pro-resolving lipid mediators released from PBMCs after exposure to AAT (Zemaira^®) are responsible for lowering the LPS-induced IL-1β release. Distinctively from other AAT preparations, AAT (Zemaira^®) and supernatants from PBMCs pre-treated with this protein contained high levels of total thiols. In line, mass spectrometry analysis revealed that AAT (Zemaira^®) protein contains freer Cys232 than AAT (Prolastin^®). Our data show that a free Cys232 in AAT is required for controlling LPS-induced IL-1β release from human PBMCs. Further studies characterizing AAT preparations used to treat patients with inherited AAT deficiency remains of clinical importance.

Alpha-1 antitrypsin in autoimmune diseases: Roles and therapeutic prospects

Alpha-1 antitrypsin (A1AT) is a protease inhibitor in the serum. Its primary function is to inhibit the activity of a series of proteases, including proteinase 3, neutrophil elastase, metalloproteases, and cysteine-aspartate proteases. In addition, A1AT also has anti-inflammatory, anti-apoptotic, anti-oxidative stress, anti-viral, and anti-bacterial activities and plays essential roles in the regulation of tissue repair and lymphocyte differentiation and activation. The overactivation of the immune system characterizes the pathogenesis of autoimmune diseases. A1AT treatment shows beneficial effects on patients and animal models with autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. This review summarizes the functions and therapeutic prospects of A1AT in autoimmune diseases.

The Mechanism of the NLRP3 Inflammasome Activation and Pathogenic Implication in the Pathogenesis of Gout

The NACHT, LRR, and PYD-domains-containing protein 3 (NLRP3) inflammasome is an intracellular multi-protein signaling platform that is activated by cytosolic pattern-recognition receptors such as NLRs against endogenous and exogenous pathogens. Once it is activated by a variety of danger signals, recruitment and assembly of NLRP3, ASC, and pro-caspase-1 trigger the processing and release of pro-inflammatory cytokines including interleukin-1β (IL-1β) and IL-18. Multiple intracellular and extracellular structures and molecular mechanisms are involved in NLRP3 inflammasome activation. Gout is an autoinflammatory disease induced by inflammatory response through production of NLRP3 inflammasome-mediated proinflammatory cytokines such as IL-1β by deposition of monosodium urate (MSU) crystals in the articular joints and periarticular structures. NLRP3 inflammasome is considered a main therapeutic target in MSU crystal-induced inflammation in gout. Novel therapeutic strategies have been proposed to control acute flares of gouty arthritis and prophylaxis for gout flares through modulation of the NLRP3/IL-1 axis pathway. This review discusses the basic mechanism of NLRP3 inflammasome activation and the IL-1-induced inflammatory cascade and explains the NLRP3 inflammasome-induced pathogenic role in the pathogenesis of gout.

Kidney Normothermic Machine Perfusion Can Be Used as a Preservation Technique and a Model of Reperfusion to Deliver Novel Therapies and Assess Inflammation and Immune Activation

Ischaemia-reperfusion injury (IRI) is an inevitable process in transplantation and results in inflammation and immune system activation. Alpha-1 antitrypsin (AAT) has anti-inflammatory properties. Normothermic machine perfusion (NMP) can be used to deliver therapies and may help in assessing the effects of IRI and immunity. This study investigated the effects of AAT on IRI and inflammation in pig kidneys when administered during preservation, followed by normothermic reperfusion (NR) with autologous whole blood, as a surrogate for transplant. Two different models were used to deliver AAT or placebo to paired slaughterhouse pig kidneys: Model 1: 7-h static cold storage (SCS) + 3-h NR (n = 5 pairs), where either AAT (10 mg/ml) or placebo was delivered in the flush following retrieval; Model 2: 4-h SCS + 3-h NMP + 3-h NR (n = 5 pairs), where either AAT or placebo was delivered during NMP. Injury markers and cytokines levels were analysed in the perfusate, and heat shock protein 70 KDa (HSP-70) was analysed in biopsies. AAT delivered to kidneys showed no adverse effects on perfusion parameters. HSP-70 fold changes were significantly lower in the AAT group during NMP (P < 0.01, paired t-test) but not during NR. Interleukin-1 receptor antagonist (IL-1ra) fold changes were significantly higher in the AAT group during NR model 1 (p < 0.05, two-way ANOVA). In contrast to the AAT group, significant upregulation of interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) between t = 90 min and t = 180 min and interleukin-8 (IL-8) between baseline and t = 90 min was observed in the control group in NR model 2 (p < 0.05, Tukey's multiple comparison test). However, overall inflammatory cytokines and injury markers showed similar levels between groups. Delivery of AAT to pig kidneys was safe without any detrimental effects. NMP and NR provided excellent methods for comparison of inflammation and immune activation in the delivery of a novel therapy.

Active Flavonoids From Lagotis brachystachya Attenuate Monosodium Urate-Induced Gouty Arthritis via Inhibiting TLR4/MyD88/NF-κB Pathway and NLRP3 Expression

Lagotis brachystachya Maxim is a characteristic herb commonly used in Tibetan medicine. Tibetan medicine records it as an important medicine for the clinical treatment of "Yellow Water Disease," the symptoms of which are similar to that of arthritis. Our previous study showed that the flavonoid fraction extracted from L. brachystachya could attenuate hyperuricemia. However, the effects of the active flavonoids on gouty arthritis remain elusive, and the underlying mechanism is not understood. In the present study, the effects of the active flavonoids were evaluated in rats or Raw264.7 cells with gouty arthritis induced by monosodium urate (MSU) crystal, followed by the detection of TLR4, MyD88, pNF-κB, and NLR family pyrin domain-containing 3 (NLRP3) expression. The swelling of the ankle joint induced by MSU crystal began to be relieved 6 h post the administration with the active flavonoids. In addition, the active flavonoids not only alleviated MSU crystal-induced inflammation in synovial tissues by histopathological examination but also reduced tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) levels in the joint tissue fluid of MSU crystal-induced rats. Furthermore, Western blot analysis indicated that the active flavonoids reduced the production of these cytokines by inhibiting the TLR4/MyD88/NF-κB pathway and decreasing NLRP3 expression in synovial tissues of rats. More importantly, the inhibition of TLR4/MyD88/NF-κB pathway and NLRP3 expression was also confirmed in MSU-induced Raw264.7 cells. In conclusion, these results indicated that the active flavonoids from L. brachystachya could effectively attenuate gouty arthritis induced by MSU crystal through the TLR4/MyD88/NF-κB pathway and NLRP3 expression in vivo and in vitro, suggesting several potential candidates for the treatment of gouty arthritis.

Where Epigenetics Meets Food Intake: Their Interaction in the Development/Severity of Gout and Therapeutic Perspectives

Gout is the most frequent form of inflammatory arthritis in the world. Its prevalence is particularly elevated in specific geographical areas such as in the Oceania/Pacific region and is rising in the US, Europe, and Asia. Gout is a severe and painful disease, in which co-morbidities are responsible for a significant reduction in life expectancy. However, gout patients remain ostracized because the disease is still considered "self-inflicted", as a result of unhealthy lifestyle and excessive food and alcohol intake. While the etiology of gout flares is clearly associated with the presence of monosodium urate (MSU) crystal deposits, several major questions remain unanswered, such as the relationships between diet, hyperuricemia and gout flares or the mechanisms by which urate induces inflammation. Recent advances have identified gene variants associated with gout incidence. Nevertheless, genetic origins of gout combined to diet-related possible uric acid overproduction account for the symptoms in only a minor portion of patients. Hence, additional factors must be at play. Here, we review the impact of epigenetic mechanisms in which nutrients (such as ω-3 polyunsaturated fatty acids) and/or dietary-derived metabolites (like urate) trigger anti/pro-inflammatory responses that may participate in gout pathogenesis and severity. We propose that simple dietary regimens may be beneficial to complement therapeutic management or contribute to the prevention of flares in gout patients.

Neutrophil elastase and its inhibitors-overlooked players in osteoarthritis

Cartilage homeostasis is maintained by a delicate balance between anabolism and catabolism. In osteoarthritis, pathological biomechanics or injury triggers cartilage breakdown, nonresolving synovial inflammation, and bone changes, causing reduced joint mobility and incapacitating pain. Undoubtedly, the most important cartilage degrading collagenase during osteoarthritis, matrix metalloproteinase (MMP)-13, is activated by an unlikely player: neutrophil elastase. Although primarily associated with inflammatory arthritis, neutrophil elastase is present in the osteoarthritic joint, and through activating MMP-13, spurs a cascade of events leading not just to the aberrant destruction of the cartilage itself, but to the proteolysis of its own inhibitor, alpha-1-antitrypsin, as described in the new study by Wilkinson et al. Endowed with potent chondrogenic and cartilage-protective properties, the loss of alpha-1-antitrypsin from cartilage will have major consequences for osteoarthritis progression, and strategies to prevent its loss, or replace it, might provide an innovative treatment opportunity that should not be ignored. Comment on: https://doi.org/10.1111/febs.16127.

Alpha-1-antitrypsin reduces inflammation and exerts chondroprotection in arthritis

While new treatments have been developed to control joint disease in rheumatoid arthritis, they are partially effective and do not promote structural repair of cartilage. Following an initial identification of α-1-Antitrypsin (AAT) during the resolution phase of acute inflammation, we report here the properties of this protein in the context of cartilage protection, joint inflammation, and associated pain behavior. Intra-articular and systemic administration of AAT reversed joint inflammation, nociception, and cartilage degradation in the KBxN serum and neutrophil elastase models of arthritis. Ex vivo analyses of arthritic joints revealed that AAT promoted transcription of col2a1, acan, and sox9 and downregulated mmp13 and adamts5 gene expression. In vitro studies using human chondrocytes revealed that SERPINA1 transfection and rAAT protein promoted chondrogenic differentiation through activation of PKA-dependent CREB signaling and inhibition of Wnt/β-catenin pathways. Thus, AAT is endowed with anti-inflammatory, analgesic, and chondroprotective properties that are partially inter-related. We propose that AAT could be developed for new therapeutic strategies to reduce arthritic pain and repair damaged cartilage.

Regulation of crystal induced inflammation: current understandings and clinical implications

Introduction: Accumulation of abnormal crystals in the body, derived from endogenous or exogenous materials can drive a wide spectrum of inflammatory disease states. It is well established that intra-articular deposition of monosodium urate (MSU) and calcium pyrophoshate (CPP) crystals contributes to joint destruction through pro-inflammatory processes.Areas covered: This review will focus on current understanding and recent novelty about the mechanisms and the clinical implications of the inflammation induced by MSU and CPP crystals.Expert opinion: Advances in molecular biology reveal that at the base of the inflammatory cascade, stimulated by MSU or CPP crystals, there are many complex cellular mechanisms mainly involving the NLRP3 inflammasome, the hallmark of autoinflammatory syndromes. The extensive studies carried out through in vitro and in vivo models along with a better clinical definition of the disease has led to an optimized use of existing drugs and the introduction of novel therapeutic strategies. In particular, the identification of IL-1 as the most important target in gout and pseudogout has made it possible to expand the pharmacological indications of anti-IL-1 biological drugs, opening new therapeutic perspectives for patients.

Interleukin-6: obstacles to targeting a complex cytokine in critical illness

Circulating concentrations of the pleiotropic cytokine interleukin-6 (IL-6) are known to be increased in pro-inflammatory critical care syndromes, such as sepsis and acute respiratory distress syndrome. Elevations in serum IL-6 concentrations in patients with severe COVID-19 have led to renewed interest in the cytokine as a therapeutic target. However, although the pro-inflammatory properties of IL-6 are widely known, the cytokine also has a series of important physiological and anti-inflammatory functions. An adequate understanding of the complex processes by which IL-6 signalling occurs is crucial for the correct interpretation of IL-6 concentrations in the blood or lung, the use of IL-6 as a critical care biomarker, or the design of effective anti-IL-6 strategies. Here, we outline the role of IL-6 in health and disease, explain the different types of IL-6 signalling and their contribution to the net biological effect of the cytokine, describe the approaches to IL-6 inhibition that are currently available, and discuss implications for the future use of treatments such as tocilizumab in the critical care setting.

Augmentation therapy with alpha 1-antitrypsin: present and future of production, formulation, and delivery

Alpha 1-antitrypsin is one of the first protein therapeutics introduced on the market - more than 30 years ago - and, to date, it is indicated only for the treatment of the severe forms of a genetic condition known as alpha-1 antitrypsin deficiency. The only approved preparations are derived from plasma, posing potential problems associated with its limited supply and high processing costs. Moreover, augmentation therapy with alpha 1-antitrypsin is still limited to intravenous infusions, a cumbersome regimen for patients. Here, we review the recent literature on its possible future developments, focusing on i) the recombinant alternatives to the plasma-derived protein, ii) novel formulations, and iii) novel administration routes. Regulatory issues and the still unclear noncanonical functions of alpha 1-antitrypsin - possibly associated with the glycosylation pattern found only in the plasma-derived protein - have hindered the introduction of new products. However, potentially new therapeutic indications other than the treatment of alpha-1 antitrypsin deficiency might open the way to new sources and new formulations.

A Systematic Review of the Anti-inflammatory Effects of Gallium Compounds

BACKGROUND

Inflammation is an essential response provided by the immune system, ensuring the survival during microbial infection, tissue injury and other noxious conditions. However, prolonged inflammatory processes are often associated with severe side effects on health.

OBJECTIVE

This systematic review aimed to provide the evidence in the literature of the preclinical and human anti-inflammatory activity of gallium compounds from 2000 to 2019 focused on elucidating the mechanisms involved in the inflammatory process.

METHODS

Seven bibliographical databases were consulted (PubMed, Medline, ScienceDirect, Scopus, Springer, Web of Science, and EBSCOhost). The selection of appropriate publications and writing of this systematic review were based on the guidelines mentioned in the PRISMA statement. Moreover, the assessment of the methodological quality of the selected studies was also performed.

RESULTS

From a total of 3018 studies, 16 studies were included in this paper based on our eligibility criteria, which showed promising and consistent results.

CONCLUSION

Further research concerning specific inflammatory conditions is required.

An atlas connecting shared genetic architecture of human diseases and molecular phenotypes provides insight into COVID-19 susceptibility

BACKGROUND

While genome-wide associations studies (GWAS) have successfully elucidated the genetic architecture of complex human traits and diseases, understanding mechanisms that lead from genetic variation to pathophysiology remains an important challenge. Methods are needed to systematically bridge this crucial gap to facilitate experimental testing of hypotheses and translation to clinical utility.

RESULTS

Here, we leveraged cross-phenotype associations to identify traits with shared genetic architecture, using linkage disequilibrium (LD) information to accurately capture shared SNPs by proxy, and calculate significance of enrichment. This shared genetic architecture was examined across differing biological scales through incorporating data from catalogs of clinical, cellular, and molecular GWAS. We have created an interactive web database (interactive Cross-Phenotype Analysis of GWAS database (iCPAGdb)) to facilitate exploration and allow rapid analysis of user-uploaded GWAS summary statistics. This database revealed well-known relationships among phenotypes, as well as the generation of novel hypotheses to explain the pathophysiology of common diseases. Application of iCPAGdb to a recent GWAS of severe COVID-19 demonstrated unexpected overlap of GWAS signals between COVID-19 and human diseases, including with idiopathic pulmonary fibrosis driven by the DPP9 locus. Transcriptomics from peripheral blood of COVID-19 patients demonstrated that DPP9 was induced in SARS-CoV-2 compared to healthy controls or those with bacterial infection. Further investigation of cross-phenotype SNPs associated with both severe COVID-19 and other human traits demonstrated colocalization of the GWAS signal at the ABO locus with plasma protein levels of a reported receptor of SARS-CoV-2, CD209 (DC-SIGN). This finding points to a possible mechanism whereby glycosylation of CD209 by ABO may regulate COVID-19 disease severity.

CONCLUSIONS

Thus, connecting genetically related traits across phenotypic scales links human diseases to molecular and cellular measurements that can reveal mechanisms and lead to novel biomarkers and therapeutic approaches. The iCPAGdb web portal is accessible at http://cpag.oit.duke.edu and the software code at https://github.com/tbalmat/iCPAGdb .

Pathophysiology of Gout

Multiple interacting checkpoints are involved in the pathophysiology of gout. Hyperuricemia is the key risk factor for gout and is considered a prerequisite for monosodium urate (MSU) crystal formation. Urate underexcretion through renal and gut mechanisms is the major mechanism for hyperuricemia in most people. Multiple genetic, environmental, and metabolic factors are associated with serum urate and alter urate transport or synthesis. Urate supersaturation is the most important factor for MSU crystal formation, and other factors such as temperature, pH, and connective tissue components also play a role. The nucleotide-binding oligomerization domain leucine-rich repeats and pyrin domain-containing protein 3 inflammasome plays a pivotal role in the inflammatory response to MSU crystals, and interleukin 1β is the key cytokine mediating the inflammatory cascade. Variations in the regulatory mechanisms of this inflammatory response may affect an individual's susceptibility to developing gout. Tophus formation is the cardinal feature of advanced gout, and both MSU crystals and the inflammatory tissue component of the tophus contribute to the development of structural joint damage owing to gout. In this article, we review the pathophysiologic mechanisms of hyperuricemia, MSU crystal formation and the associated inflammatory response, tophus formation, and structural joint damage in gout.

Alpha-1 antitrypsin deficiency and recombinant protein sources with focus on plant sources: Updates, challenges and perspectives

Alpha-1 antitrypsin deficiency (A1ATD) is an autosomal recessive disease characterized by low plasma levels of A1AT, a serine protease inhibitor representing the most abundant circulating antiprotease normally present at plasma levels of 1-2 g/L. The dominant clinical manifestations include predispositions to early onset emphysema due to protease/antiprotease imbalance in distal lung parenchyma and liver disease largely due to unsecreted polymerized accumulations of misfolded mutant A1AT within the endoplasmic reticulum of hepatocytes. Since 1987, the only FDA licensed specific therapy for the emphysema component has been infusions of A1AT purified from pooled human plasma at the 2020 cost of up to US $200,000/year with the risk of intermittent shortages. In the past three decades various, potentially less expensive, recombinant forms of human A1AT have reached early stages of development, one of which is just reaching the stage of human clinical trials. The focus of this review is to update strategies for the treatment of the pulmonary component of A1ATD with some focus on perspectives for therapeutic production and regulatory approval of a recombinant product from plants. We review other competitive technologies for treating the lung disease manifestations of A1ATD, highlight strategies for the generation of data potentially helpful for securing FDA Investigational New Drug (IND) approval and present challenges in the selection of clinical trial strategies required for FDA licensing of a New Drug Approval (NDA) for this disease.

Human recombinant interleukin-38 suppresses inflammation in mouse models of local and systemic disease

Interleukin (IL)-38 belongs to the IL-1 family and is part of the IL-36 subfamily due to its binding to the IL-36 Receptor (IL-1R6). In the current study, we assessed the anti-inflammatory properties of IL-38 in murine models of arthritis and systemic inflammation. First, the anti-inflammatory properties of mouse and human IL-38 precursors were compared to forms with a truncated N-terminus. In mouse bone marrow derived dendritic cells (BMDC), human and mouse IL-38 precursors with a truncation of the two N-terminal amino acids (3-152) suppressed LPS-induced IL-6. Recombinant human IL-38 (3-152) was further investigated for its immunomodulatory potential using four murine models of inflammatory disease: streptococcal cell wall (SCW)-induced arthritis, monosodium urate (MSU) crystal-induced arthritis, MSU crystal-induced peritonitis, and systemic endotoxemia. In each of these models IL-38 significantly reduced inflammation. In SCW and MSU crystal-induced arthritis, joint swelling, inflammatory cell influx, and synovial levels of IL-1β, IL-6, and KC were reduced by 50% or greater. These suppressive properties of IL-38 in SCW-induced arthritis were independent of the anti-inflammatory co-receptor IL-1R8, as IL-38 reduced arthritis equally in IL-1R8 deficient and WT mice. In MSU crystal-induced peritonitis, IL-38 reduced hypothermia, while plasma IL-6 and KC and peritoneal KC levels were reduced by 65-70%. In the LPS endotoxemia model, IL-38 pretreatment reduced systemic IL-6, TNFα and KC. Furthermore, in ex vivo cultured bone marrow, LPS-induced IL-6, TNFα and KC were reduced by 75-90%. Overall, IL-38 exhibits broad anti-inflammatory properties in models of systemic and local inflammation and therefore may be an effective cytokine therapy.

An atlas connecting shared genetic architecture of human diseases and molecular phenotypes provides insight into COVID-19 susceptibility

While genome-wide associations studies (GWAS) have successfully elucidated the genetic architecture of complex human traits and diseases, understanding mechanisms that lead from genetic variation to pathophysiology remains an important challenge. Methods are needed to systematically bridge this crucial gap to facilitate experimental testing of hypotheses and translation to clinical utility. Here, we leveraged cross-phenotype associations to identify traits with shared genetic architecture, using linkage disequilibrium (LD) information to accurately capture shared SNPs by proxy, and calculate significance of enrichment. This shared genetic architecture was examined across differing biological scales through incorporating data from catalogs of clinical, cellular, and molecular GWAS. We have created an interactive web database (interactive Cross-Phenotype Analysis of GWAS database (iCPAGdb); http://cpag.oit.duke.edu) to facilitate exploration and allow rapid analysis of user-uploaded GWAS summary statistics. This database revealed well-known relationships among phenotypes, as well as the generation of novel hypotheses to explain the pathophysiology of common diseases. Application of iCPAGdb to a recent GWAS of severe COVID-19 demonstrated unexpected overlap of GWAS signals between COVID-19 and human diseases, including with idiopathic pulmonary fibrosis driven by the DPP9 locus. Transcriptomics from peripheral blood of COVID-19 patients demonstrated that DPP9 was induced in SARS-CoV-2 compared to healthy controls or those with bacterial infection. Further investigation of cross-phenotype SNPs with severe COVID-19 demonstrated colocalization of the GWAS signal of the ABO locus with plasma protein levels of a reported receptor of SARS-CoV-2, CD209 (DC-SIGN), pointing to a possible mechanism whereby glycosylation of CD209 by ABO may regulate COVID-19 disease severity. Thus, connecting genetically related traits across phenotypic scales links human diseases to molecular and cellular measurements that can reveal mechanisms and lead to novel biomarkers and therapeutic approaches.

The role of interleukin-1 family members in hyperuricemia and gout

BACKGROUND

Interleukin (IL)-1 family cytokines and their receptors have important roles in innate and partly in adaptive immunity. The family consists of 11 members of which IL-1α, IL-1β, IL-18, IL-33, IL-36α, IL-36β and IL-36γ are considered pro-inflammatory and IL-1Ra, IL-36Ra, IL-37 and IL-38 anti-inflammatory. Whereas IL-1β has a known pivotal role in gout, increasing evidence suggests other IL-1 family members are also involved in the pathogenesis of hyperuricemia and gout flares.

FINDINGS

Studies indicate IL-1α, like IL-1β, plays an essential role in the pathogenesis of gout flares. IL-18, although elevated in patients with gout, does not contribute to MSU crystal-induced inflammation, but may be involved in the subsequent development of cardiovascular disease in individuals with gout. The role of the pro-inflammatory cytokine IL-36 in gout remains elusive. In contrast, IL-1Ra, IL-33, IL-37 and IL-38 inhibit MSU crystal-induced inflammation and therefore have therapeutic potential for treatment of gout flares. In addition to existing IL-1β blockers, several new therapeutics to treat gout are being developed either inhibiting the transcription or maturation of IL-1β.

CONCLUSION

In this review, IL-1 family cytokines are discussed in the context of hyperuricemia and gout. Finally, current and novel therapeutic options for targeting IL-1 are reviewed.

Characterization of the Inflammatory Response to Severe COVID-19 Illness

Rationale: Coronavirus disease (COVID-19) is a global threat to health. Its inflammatory characteristics are incompletely understood.Objectives: To define the cytokine profile of COVID-19 and to identify evidence of immunometabolic alterations in those with severe illness.Methods: Levels of IL-1β, IL-6, IL-8, IL-10, and sTNFR1 (soluble tumor necrosis factor receptor 1) were assessed in plasma from healthy volunteers, hospitalized but stable patients with COVID-19 (COVIDstable patients), patients with COVID-19 requiring ICU admission (COVIDICU patients), and patients with severe community-acquired pneumonia requiring ICU support (CAPICU patients). Immunometabolic markers were measured in circulating neutrophils from patients with severe COVID-19. The acute phase response of AAT (alpha-1 antitrypsin) to COVID-19 was also evaluated.Measurements and Main Results: IL-1β, IL-6, IL-8, and sTNFR1 were all increased in patients with COVID-19. COVIDICU patients could be clearly differentiated from COVIDstable patients, and demonstrated higher levels of IL-1β, IL-6, and sTNFR1 but lower IL-10 than CAPICU patients. COVID-19 neutrophils displayed altered immunometabolism, with increased cytosolic PKM2 (pyruvate kinase M2), phosphorylated PKM2, HIF-1α (hypoxia-inducible factor-1α), and lactate. The production and sialylation of AAT increased in COVID-19, but this antiinflammatory response was overwhelmed in severe illness, with the IL-6:AAT ratio markedly higher in patients requiring ICU admission (P < 0.0001). In critically unwell patients with COVID-19, increases in IL-6:AAT predicted prolonged ICU stay and mortality, whereas improvement in IL-6:AAT was associated with clinical resolution (P < 0.0001).Conclusions: The COVID-19 cytokinemia is distinct from that of other types of pneumonia, leading to organ failure and ICU need. Neutrophils undergo immunometabolic reprogramming in severe COVID-19 illness. Cytokine ratios may predict outcomes in this population.

The intrinsic and extrinsic elements regulating inflammation

Inflammation is a sophisticated biological tissue response to both extrinsic and intrinsic stimuli. Although the pathological aspects of inflammation are well appreciated, there are still rooms for understanding the physiological functions of the inflammation. Recent studies have focused on mechanisms, context and the role of physiological inflammation. Besides, there have been progress in the comprehension of commensal microbiota, immunometabolism, cancer and intracellular signaling events' roles that impact on the regulation of inflammation. Despite the fact that inflammatory responses are vital through tissue damage, understanding the mechanisms to turn off the finished or unnecessary inflammation is crucial for restoring homeostasis. Inflammation seems to be a smart process that acts like two edges of a sword, meaning that it has both protective and deleterious consequences. Knowing both edges and the regulation processes will help the future understanding and therapy for various diseases.

lncRNA‑MM2P downregulates the production of pro‑inflammatory cytokines in acute gouty arthritis

Acute gouty arthritis (AGA) is characterized by the accumulation of pro‑inflammatory cytokines, which are immunological responses to monosodium urate (MSU) crystals. It has been demonstrated that long non‑coding RNA (lncRNA)‑MM2P is a novel regulator of M2 polarization of macrophages. The aim of the present study was to investigate whether lncRNA‑MM2P regulates the MSU‑induced inflammatory process. In cell models of RAW 264.7 and THP‑1‑derived macrophages, decreased expression of lncRNA‑MM2P was observed in lipopolysaccharide‑ and MSU‑treated macrophages, which was accompanied with obvious inflammatory responses. Using small interfering RNA to knockdown lncRNA‑MM2P led to the upregulation of MSU‑mediated inflammatory responses, both in RAW 264.7 and THP‑1‑derived macrophages. In conclusion, lncRNA‑MM2P could be an important regulator of MSU‑induced inflammation, and therefore could be involved in the development of AGA.

Silencing of Gasdermin D by siRNA-Loaded PEI-Chol Lipopolymers Potently Relieves Acute Gouty Arthritis through Inhibiting Pyroptosis

Gasdermin D (GSDMD) plays a causal role in NOD-like receptor protein 3 (NLRP3) inflammasome-mediated pyroptosis eruption, which has been regarded as a potential therapeutic target for pyroptosis-related diseases including acute gouty arthritis. In the present study, the synthesized PEI-Chol (cholesterol grafted polyethylenimine) was assembled with GSDMD small interfering RNA (siRNA) to form PEI-Chol/siGSDMD polyplexes, which provided high transfection efficiency for siRNA-mediated GSDMD knockdown. Then we evaluated the effect of GSDMD siRNA-loaded PEI-Chol on inflammatory cascades in bone-marrow-derived macrophages (BMDMs) and acute gouty arthritis animal models under MSU exposure. When accompanied by pyroptosis blockade and decreased release of interleukin-1 beta (IL-1β), NLRP3 inflammasome activation was also suppressed by GSDMD knockdown in vivo and in vitro. Moreover, in MSU-induced acute gouty arthritis mice, blocking GSDMD with siRNA significantly improved ankle swelling and inflammatory infiltration observed in histopathological analysis. Furthermore, investigation using a mouse air pouch model verified the effect of siGSDMD-loaded PEI-Chol on pyroptosis of recruited macrophages and related signaling pathways in response to MSU. These novel findings exhibited that GSDMD knockdown relieved acute gouty arthritis through inhibiting pyroptosis, providing a possible therapeutic approach for MSU-induced acute gouty arthritis molecular therapy using PEI-Chol as a nucleic acid delivery carrier.

P2Y14 receptor has a critical role in acute gouty arthritis by regulating pyroptosis of macrophages

Nod-like receptor protein 3 (NLRP3)-mediated pyroptosis has a causal role in the pathogenesis of gout. P2Y₁₄ receptor (P2Y₁₄R) distributed in immune cells including macrophages is a Gi-coupled receptor that inhibits the synthesis of cAMP, which has been regarded as a potential regulator of inflammatory response. Nevertheless, the role of P2Y₁₄R in MSU-induced pyroptosis of macrophages involved in acute gouty arthritis is still unclear. In our present study, P2Y₁₄R knockout (P2Y₁₄R-KO) disrupted MSU-induced histopathologic changes in rat synoviums, accompanied with a significant inhibition of pyroptotic cell death characterized by Caspase-1/PI double-positive and blockade of NLRP3 inflammasome activation in synovial tissues, which was consistent with that observed in in vitro studies. Owing to the interaction of NLRP3 inflammasome and cAMP, we then investigated the effect of adenylate cyclase activator (Forskolin) on macrophage pyroptosis and gout flare caused by MSU stimulation. The reversal effect of Forskolin verified the negative regulatory role of cAMP in MSU-induced pyroptosis. More importantly, adenylate cyclase inhibitor (SQ22536) intervention led to a reversal of protection attributed to P2Y₁₄R deficiency. Findings in air pouch animal models also verified aforementioned experimental results. Our study first identified the role of P2Y₁₄R/cAMP/NLRP3 signaling pathway in acute gouty arthritis, which provides a novel insight into the pathological mechanisms of pyroptosis-related diseases.

Dapansutrile, an oral selective NLRP3 inflammasome inhibitor, for treatment of gout flares: an open-label, dose-adaptive, proof-of-concept, phase 2a trial

SUMMARY

BACKGROUND

Gout flares are driven by interleukin (IL)-1β. Dapansutrile inhibits the NLRP3 inflammasome and subsequent activation of IL-1β. In this study we aimed to investigate the safety and efficacy of orally administered dapansutrile in patients with a gout flare.

METHODS

In this open-label, proof-of-concept, phase 2a trial, adult patients (aged 18-80 years) with a monoarticular monosodium urate crystal-proven gout flare were enrolled at an outpatient clinic in the Netherlands and sequentially assigned using a dose-adaptive design to receive 100 mg/day, 300 mg/day, 1000 mg/day, or 2000 mg/day oral dapansutrile for 8 days. The coprimary outcomes were change in patient-reported target joint pain from baseline to day 3 and from baseline to day 7, assessed in the per-protocol population (all patients who received at least 80% of the study drug and had no major protocol deviations). Safety was assessed in the intention-to-treat population. This trial is registered with the EU Clinical Trials Register, EudraCT 2016-000943-14, and is completed.

FINDINGS

Between May 18, 2017, and Jan 21, 2019, 144 patients were assessed for eligibility, of whom 34 were enrolled and 29 were included in the per-protocol population (three patients were excluded due to receiving <80% of study drug and two had major protocol deviations): eight patients received 100 mg/day, seven received 300 mg/day, six received 1000 mg/day, and eight received 2000 mg/day. Between baseline and day 3, there was a mean reduction in patient-reported target joint pain of 52·4% (SD 32·94; p=0∙016) for the 100 mg/day group, 68·4% (34·29; p=0∙016) for the 300 mg/day group, 55·8% (44·90; p=0∙063) for the 1000 mg/day group, and 57·6% (38·72; p=0∙016) for the 2000 mg/day group. At day 7, there was a mean reduction of 82·1% (22·68; p=0∙031) for the 100 mg/day group, 84·2% (16·33; p=0∙016) for the 300 mg/day group, 68·9% (34·89; p=0∙031) for the 1000 mg/day group, and 83·9% (15·44; p=0∙008) for the 2000 mg/day group, compared to baseline. 25 (73·5%) of 34 patients reported a total of 45 treatment-emergent adverse events, most of which were metabolism and nutrition disorders (17 [37·8%]) and gastrointestinal disorders (ten [22·2%]). Two serious adverse events occurred during the study, admission to hospital because of worsening of gout flare at day 3, and admission to hospital because of coronary stenosis 18 days after the patient received their last dose; these were considered moderate in severity and unrelated to the study drug.

INTERPRETATION

Dapansutrile is a specific NLRP3 inflammasome inhibitor with a satisfactory safety profile and efficacy in the reduction of target joint pain in this study. Future studies are needed to confirm the clinical potential of dapansutrile.

Autoinflammatory Mechanisms in Crystal-Induced Arthritis

Crystal-induced arthritides have been classified as “type-1 autoinflammatory diseases” for their main features which resemble those of the monogenic autoinflammatory syndromes. They are in fact characterized by spontaneous onset, recurrence of the episodes, self-limitation and resolution, inflammasome activation with huge production of IL-1β and a prevalent involvement of the innate immune system. The term “auto” refers also to the induction of IL-1β gene expression, processing and secretion by IL-1β itself. The concept of autoinflammation in crystal-induced arthritis has been finally reinforced by the efficacy of IL-1 blockade in treating acute and chronic state of this disease. The aim of this article is to review the autoinflammatory mechanisms in crystal-induced arthritis, considering both clinical and molecular aspects.

Asymptomatic hyperuricaemia: a silent activator of the innate immune system

Asymptomatic hyperuricaemia affects ~20% of the general population in the USA, with variable rates in other countries. Historically, asymptomatic hyperuricaemia was considered a benign laboratory finding with little clinical importance in the absence of gout or kidney stones. Yet, increasing evidence suggests that asymptomatic hyperuricaemia can predict the development of hypertension, obesity, diabetes mellitus and chronic kidney disease and might contribute to disease by stimulating inflammation. Although urate has been classically viewed as an antioxidant with beneficial effects, new data suggest that both crystalline and soluble urate activate various pro-inflammatory pathways. This Review summarizes what is known about the role of urate in the inflammatory response. Further research is needed to define the role of asymptomatic hyperuricaemia in these pro-inflammatory pathways.

A mouse model of MSU-induced acute inflammation in vivo suggests imiquimod-dependent targeting of Il-1β as relevant therapy for gout patients

Rationale: The role of Monosodium Urate (MSU) crystals in gout pathophysiology is well described, as is the major impact of IL-1β in the inflammatory reaction that constitutes the hallmark of the disease. However, despite the discovery of the NLRP3 inflammasome and its role as a Pattern Recognition Receptor linking the detection of a danger signal (MSU) to IL-1β secretion in vitro, the precise mechanisms leading to joint inflammation in gout patients are still poorly understood. Methods: Acute urate crystal inflammation was obtained by subcutaneous injections of MSU crystals in mice. Symptoms were followed by scoring, cytokine quantification by ELISA and western blot, gene expression by RT-qPCR and RNAseq; Magnetic Resonance Imaging was also used to assess inflammation. Results: We provide an extensive clinical, biological and molecular characterization of an acute uratic inflammation mouse model which accurately mimics human gout. We report the efficacy of topical imiquimod treatment and its impact on Interferon-dependent down modulation of Il-1β gene expression in this experimental model. Conclusion: Our work reveals several key features of MSU-dependent inflammation and identifies novel therapeutic opportunities for gout patients.

Engineering the serpin α1 -antitrypsin: A diversity of goals and techniques

α₁ -Antitrypsin (α₁ -AT) serves as an archetypal example for the serine proteinase inhibitor (serpin) protein family and has been used as a scaffold for protein engineering for >35 years. Techniques used to engineer α₁ -AT include targeted mutagenesis, protein fusions, phage display, glycoengineering, and consensus protein design. The goals of engineering have also been diverse, ranging from understanding serpin structure-function relationships, to the design of more potent or more specific proteinase inhibitors with potential therapeutic relevance. Here we summarize the history of these protein engineering efforts, describing the techniques applied to engineer α₁ -AT, specific mutants of interest, and providing an appended catalog of the >200 α₁ -AT mutants published to date.

Experimental and investigational drugs for the treatment of alpha-1 antitrypsin deficiency

Introduction: Alpha-1 antitrypsin deficiency (AATD) is most often associated with chronic lung disease, early onset emphysema, and liver disease. The standard of care in lung disease due to AATD is alpha-1 antitrypsin augmentation but there are several new and emerging treatment options under investigation for both lung and liver manifestations. Areas covered: We review therapeutic approaches to lung and liver disease in alpha-1 antitrypsin deficiency (AATD) and the agents in clinical development according to their mode of action. The focus is on products in clinical trials, but data from pre-clinical studies are described where relevant, particularly where progression to trials appears likely. Expert opinion: Clinical trials directed at lung and liver disease separately are now taking place. Multimodality treatment may be the future, but this could be limited by treatment costs. The next 5-10 years may reveal new guidance on when to use therapeutics for slowing disease progression with personalized treatment regimes coming to the forefront.

The role of interleukin 1 in the development of human diseases

Human immuno-inflammatory diseases (IID), depending on the predominant mechanisms of immune activation, are divided into two main categories: autoimmune and autoinflammatory. It is assumed that hyperproduction of "proinflammatory" and immunoregulatory cytokine-interleukin 1 (IL 1) largely determines the "intersection" between the mechanisms underlying autoimmunity and autoinflammation in many IID. This review discusses the role of IL1 in the pathogenesis of IID, primarily those associated with the activation of NLRP3-inflammasome, and therapeutic perspectives of IL1β inhibition with monoclonal antibodies to IL1β – canakinumab. The study of the IL1 role in the regulation of interactions between innate (TLR activation, inflammasome) and adaptive (Th1 – and Th17-types of immune response) immunity and the efficacy of IL1 inhibitors may be important in terms of decoding the pathogenetic mechanisms of IID and the development of new approaches to personalized therapy.

Therapy with canakinumab for gout

A significant part of patients with gout has contraindications to taking nonsteroidal anti-inflammatory drugs, colchicine and glucocorticoids. Such therapy is often ineffective, particularly in patients with the severe tophaceous gout what hampers treatment of acute arthritis attack assuming the need for other methods of therapy. During the last years several medications have been introduced the mechanism of anti-inflammatory action of which is associated with inhibition of interleukin 1 (IL1) playing a key role in the development of acute gouty arthritis. To date, the most well-studied and the only registered drug for relief of acute arthritis attack is canakinumab, recommended for use in situations where other therapy options are unacceptable. Despite these limitations, the use of IL1 inhibitors, in particular canakinumab, seems promising due to the high efficiency of the drug, the ability to use it in patients with comorbid diseases, as well as a favorable effect on the risk of cardiovascular disease.

S-Nitrosylation of α1-Antitrypsin Triggers Macrophages Toward Inflammatory Phenotype and Enhances Intra-Cellular Bacteria Elimination

Background: Human α1-antitrypsin (hAAT) is a circulating anti-inflammatory serine-protease inhibitor that rises during acute phase responses. in vivo, hAAT reduces bacterial load, without directly inhibiting bacterial growth. In conditions of excess nitric-oxide (NO), hAAT undergoes S-nitrosylation (S-NO-hAAT) and gains antibacterial capacity. The impact of S-NO-hAAT on immune cells has yet to be explored.

Aim: Study the effects of S-NO-hAAT on immune cells during bacterial infection.

Methods: Clinical-grade hAAT was S-nitrosylated and then compared to unmodified hAAT, functionally, and structurally. Intracellular bacterial clearance by THP-1 macrophages was assessed using live Salmonella typhi. Murine peritoneal macrophages were examined, and signaling pathways were evaluated. S-NO-hAAT was also investigated after blocking free mambranal cysteine residues on cells.

Results: S-NO-hAAT (27.5 uM) enhances intracellular bacteria elimination by immunocytes (up to 1-log reduction). S-NO-hAAT causes resting macrophages to exhibit a pro-inflammatory and antibacterial phenotype, including release of inflammatory cytokines and induction of inducible nitric oxide synthase (iNOS) and TLR2. These pro-inflammatory effects are dependent upon cell surface thiols and activation of MAPK pathways.

Conclusions: hAAT duality appears to be context-specific, involving S-nitrosylation in a nitric oxide rich environment. Our results suggest that S-nitrosylation facilitates the antibacterial activity of hAAT by promoting its ability to activate innate immune cells. This pro-inflammatory effect may involve transferring of nitric oxide from S-NO-hAAT to a free cysteine residue on cellular targets.

IL-1 Family Cytokine Pathways Underlying NAFLD: Towards New Treatment Strategies

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. Pathways responsible for the activation of IL-1 family cytokines are key in the development of NAFLD but underlying mechanisms are not fully understood. Many studies have focused on the inflammasome-caspase-1 pathway and have shown that this pathway is an important inducer of inflammation in NAFLD. However, this pathway is not solely responsible for the activation of proinflammatory cytokines. Also, neutrophil serine proteases (NSPs) are capable of activating cytokines and recent studies reported that these proteases also contribute to NAFLD. These studies provided, for the first time, evidence that this inflammasome-independent pathway is involved in NAFLD. In our opinion, these new insights open up new approaches for therapeutic intervention.

Regenerative approaches for cartilage repair in the treatment of osteoarthritis

Osteoarthritis (OA) as a debilitating affliction of joints currently affects millions of people and remains an unsolved problem. The disease involves multiple cellular and molecular pathways that converge on the progressive destruction of cartilage. Activation of cartilage regenerative potential and specific targeting pathogenic mediators have been the major focus of research efforts aimed at slowing the progression of cartilage degeneration and preserve joint function. This review will summarize recent key discoveries toward better understanding of the complex mechanisms behind OA development and highlight the latest advances in basic and clinical research in the approach for cartilage regeneration. Prospectively, more potent therapeutic strategies against progressive cartilage deterioration may use a combination of cytotherapy, pharmacotherapy, and bioscaffoldings for improved chondrogenic differentiation and stem/progenitor cell homing as well as the concomitant reduced enzymatic matrix degradation and inflammation. Further, treatments need to be provided with increased preciseness of targeted therapy. One might expect that the regenerative therapies could potentially control or even possibly cure OA if performed at early stages of the disease.

Inflammation in gout: mechanisms and therapeutic targets

The acute symptoms of gout are triggered by the inflammatory response to monosodium urate crystals, mediated principally by macrophages and neutrophils. Innate immune pathways are of key importance in the pathogenesis of gout, in particular the activation of the NLRP3 inflammasome, which leads to the release of IL-1β and other pro-inflammatory cytokines. The orchestration of this pro-inflammatory cascade involves multiple intracellular and extracellular receptors and enzymes interacting with environmental influences that modulate the inflammatory state. Furthermore, the resolution of inflammation in gout is becoming better understood. This Review highlights recent advances in our understanding of both positive and negative regulatory pathways, as well as the genetic and environmental factors that modulate the inflammatory response. Some of these pathways can be manipulated and present novel therapeutic opportunities for the treatment of acute gout attacks.

What makes gouty inflammation so variable?

Acute gout arthritis flares contribute dominantly to gout-specific impaired health-related quality of life, representing a progressively increasing public health problem. Flares can be complex and expensive to treat, partly due to the frequent comorbidities. Unmet needs in gout management are more pressing given the markedly increasing gout flare hospital admission rates. In addition, chronic gouty arthritis can cause joint damage and functional impairment. This review addresses new knowledge on the basis for the marked, inherent variability of responses to deposited urate crystals, including the unpredictable and self-limited aspects of many gout flares. Specific topics reviewed include how innate immunity and two-signal inflammasome activation intersect with diet, metabolism, nutritional biosensing, the microbiome, and the phagocyte cytoskeleton and cell fate. The paper discusses the roles of endogenous constitutive regulators of inflammation, including certain nutritional biosensors, and emerging genetic and epigenetic factors. Recent advances in the basis of variability in responses to urate crystals in gout provide information about inflammatory arthritis, and have identified potential new targets and strategies for anti-inflammatory prevention and treatment of gouty arthritis.

A guiding map for inflammation

Biologists, physicians and immunologists have contributed to the understanding of the cellular participants and biological pathways involved in inflammation. Here, we provide a general guide to the cellular and humoral contributors to inflammation as well as to the pathways that characterize inflammation in specific organs and tissues.

A Brief History of IL-1 and IL-1 Ra in Rheumatology

The history of what, in 1979, was called interleukin-1 (IL-1), orchestrator of leukocyte inter-communication, began many years before then, initially by the observation of fever induction via the endogenous pyrogen (EP) (1974) and then in rheumatology on the role in tissue destruction in rheumatoid diseases via the induction of collagenase and PGE₂ in human synovial cells by a mononuclear cell factor (MCF) (1977). Since then, the family has exploded to presently 11 members as well as many membrane-bound and soluble receptor forms. The discovery of a natural Interleukin-1 receptor antagonist (IL-1Ra) in human biological fluids has highlighted the importance of IL-1 and IL-1Ra in human diseases. Evidence delineating its role in autoinflammatory syndromes and the elucidation of the macromolecular complex referred to as "inflammasome" have been instrumental to our understanding of the link with IL-1. At present, the IL-1blockade as therapeutic approach is crucial for many hereditary autoinflammatory diseases, as well as for adult-onset Still's disease, crystal-induced arthropathies, certain skin diseases including neutrophil-triggered skin diseases, Behçet's disease and deficiency of IL-1Ra and other rare fever syndromes. Its role is only marginally important in rheumatoid arthritis and is still under debate with regard to osteoarthritis, type 2 diabetes mellitus, cardiovascular diseases and cancer. This brief historical review focuses on some aspects of IL-1, mainly IL-1β and IL-Ra, in rheumatology. There are many excellent reviews focusing on the IL-1 family in general or with regard to specific diseases or biological discoveries.

Uric acid priming in human monocytes is driven by the AKT-PRAS40 autophagy pathway

Metabolic triggers are important inducers of the inflammatory processes in gout. Whereas the high serum urate levels observed in patients with gout predispose them to the formation of monosodium urate (MSU) crystals, soluble urate also primes for inflammatory signals in cells responding to gout-related stimuli, but also in other common metabolic diseases. In this study, we investigated the mechanisms through which uric acid selectively lowers human blood monocyte production of the natural inhibitor IL-1 receptor antagonist (IL-1Ra) and shifts production toward the highly inflammatory IL-1β. Monocytes from healthy volunteers were first primed with uric acid for 24 h and then subjected to stimulation with lipopolysaccharide (LPS) in the presence or absence of MSU. Transcriptomic analysis revealed broad inflammatory pathways associated with uric acid priming, with NF-κB and mammalian target of rapamycin (mTOR) signaling strongly increased. Functional validation did not identify NF-κB or AMP-activated protein kinase phosphorylation, but uric acid priming induced phosphorylation of AKT and proline-rich AKT substrate 40 kDa (PRAS 40), which in turn activated mTOR. Subsequently, Western blot for the autophagic structure LC3-I and LC3-II (microtubule-associated protein 1A/1B-light chain 3) fractions, as well as fluorescence microscopy of LC3-GFP-overexpressing HeLa cells, revealed lower autophagic activity in cells exposed to uric acid compared with control conditions. Interestingly, reactive oxygen species production was diminished by uric acid priming. Thus, the Akt-PRAS40 pathway is activated by uric acid, which inhibits autophagy and recapitulates the uric acid-induced proinflammatory cytokine phenotype.

Host and Environmental Factors Influencing Individual Human Cytokine Responses

Differences in susceptibility to immune-mediated diseases are determined by variability in immune responses. In three studies within the Human Functional Genomics Project, we assessed the effect of environmental and non-genetic host factors of the genetic make-up of the host and of the intestinal microbiome on the cytokine responses in humans. We analyzed the association of these factors with circulating mediators and with six cytokines after stimulation with 19 bacterial, fungal, viral, and non-microbial metabolic stimuli in 534 healthy subjects. In this first study, we show a strong impact of non-genetic host factors (e.g., age and gender) on cytokine production and circulating mediators. Additionally, annual seasonality is found to be an important environmental factor influencing cytokine production. Alpha-1-antitrypsin concentrations partially mediate the seasonality of cytokine responses, whereas the effect of vitamin D levels is limited. The complete dataset has been made publicly available as a comprehensive resource for future studies. PAPERCLIP.

How Factors Involved in the Resolution of Crystal-Induced Inflammation Target IL-1β

One of the main clinical features characterizing crystal-induced inflammation is its spontaneous resolution. The aim of this review is to outline the various factors involved in the self-limiting course of crystal-induced inflammation focusing on their effect on IL-1β production. Endogenous molecules that are induced or locally recruited by the process itself, inhibitory proteins naturally present in the joint and exogenous dietary factors are discussed. Aside from the classical well-known molecules involved in the resolution of crystal-induced acute attack such as TGFβ, IL-10, IL-1Ra, and lipoproteins, particular attention is paid to recently uncovered mechanisms such as the aggregation of neutrophil extracellular traps, the release of ectosomes from neutrophil surface, and alpha-1-anti-trypsin-mediated IL-1 inhibition.

Identification of Novel Chondroprotective Mediators in Resolving Inflammatory Exudates

We hypothesized that exudates collected at the beginning of the resolution phase of inflammation might be enriched for tissue protective molecules; thus an integrated cellular and molecular approach was applied to identify novel chondroprotective bioactions. Exudates were collected 6 h (inflammatory) and 24 h (resolving) following carrageenan-induced pleurisy in rats. The resolving exudate was subjected to gel filtration chromatography followed by proteomics, identifying 61 proteins. Fractions were added to C28/I2 chondrocytes, grown in micromasses, ions with or without IL-1β or osteoarthritic synovial fluids for 48 h. Three proteins were selected from the proteomic analysis, α1-antitrypsin (AAT), hemopexin (HX), and gelsolin (GSN), and tested against catabolic stimulation for their effects on glycosaminoglycan deposition as assessed by Alcian blue staining, and gene expression of key anabolic proteins by real-time PCR. In an in vivo model of inflammatory arthritis, cartilage integrity was determined histologically 48 h after intra-articular injection of AAT or GSN. The resolving exudate displayed protective activities on chondrocytes, using multiple readouts: these effects were retained in low m.w. fractions of the exudate (46.7% increase in glycosaminoglycan deposition; ∼20% upregulation of COL2A1 and aggrecan mRNA expression), which reversed the effect of IL-1β. Exogenous administration of HX, GSN, or AAT abrogated the effects of IL-1β and osteoarthritic synovial fluids on anabolic gene expression and increased glycosaminoglycan deposition. Intra-articular injection of AAT or GSN protected cartilage integrity in mice with inflammatory arthritis. In summary, the strategy for identification of novel chondroprotective activities in resolving exudates identified HX, GSN and AAT as potential leads for new drug discovery programs.