The mechanisms of inflammation in gout and pseudogout (CPP-induced arthritis)

Titanium Dioxide Promotes the Growth and Aggregation of Calcium Phosphate and Monosodium Urate Mixed Crystals

The increased utilization of titanium dioxide (TiO2) nanoparticles (TNPs) in various industrial and consumer products has raised concerns regarding its harmful effect due to its accumulation within the different systems of the human body. Here, we focused on the influence of TNPs on the growth and aggregation of two crucial crystalline substances, calcium phosphate (CaP) and monosodium urate (MSU), particularly its implications in gout disease. In this study, we adopted microscopic techniques and generated kinetic models to examine the interactions between TNPs, CaP and MSU, and crystallization, under controlled laboratory conditions. Our findings reveal that TNPs not only facilitate the growth of these crystals but also promote their co-aggregations. Crystal dissolution kinetics also exhibit that an increase in TNPs concentration corresponds to a reduction in the dissolution rate of CaP and MSU crystals in presence of the dissoluting agent hydroxycitrate (Hcit). These observations suggest that TNPs can stabilize CaP+MSU mixed crystals, which underscores the significance of TNPs' exposure in the pathogenesis of gout disease.

Potential anti-gout properties of Wuwei Shexiang pills based on network pharmacology and pharmacological verification

ETHNOPHARMACOLOGICAL RELEVANCE

Wuwei Shexiang Pills (WWSX), a classic Tibetan medicine, consists of Chebulae Fructus (removed pit), Aucklandiae Radix, Moschus, Aconiti Fiavi Radix, and Acori Calami Rhizoma. It is used clinically in China to treat joint pain, swelling and other symptoms, and has the function of dispelling wind and relieving pain. However, to date, the mechanism of how it works against gout is still unclear.

AIMS OF THE STUDY

Using network pharmacology, molecular docking and pharmacological verification to explore the potential anti-gout properties of WWSX.

MATERIALS AND METHODS

With the use of UPLC-Q/TOF-MS, the main components of WWSX were obtained and screened for potential anti-inflammatory components by network pharmacology and molecular docking. The anti-inflammatory activity of the components screened from WWSX was also tested by in vitro assays. The anti-gout mechanism of WWSX was predicted by network pharmacology, and the pharmacological validation experiments using gouty arthritis model and mouse air pouch model were used to explore the multifaceted mechanism of WWSX to modify gout.

RESULT

Thirty-eight active ingredients were obtained from the UPLC-Q/TOF-MS detection. The network pharmacology and molecular docking analysis showed that 104 co-targets were participated in the treatment of gout, and the main signaling pathways involved were NOD-like receptor pathway, NF-κB pathway and MAPK pathway. Pharmacological evaluation showed that WWSX could significantly improve gout in gouty arthritis models and mouse air pouch models by modulating the above pathways.

CONCLUSION

This work has predicted and validated the anti-inflammatory material basis and predicted the anti-gout mechanism of WWSX which was verified by network pharmacology, molecular docking and in vitro cellular studies. The results reveal the mechanism of WWSX in the treatment of gout and provide a theoretical basis for its clinical application.

Network pharmacology and in vivo experiments reveal the pharmacological effects and molecular mechanisms of Simiao Powder in prevention and treatment for gout

Background

Gout is a common disease with high incidence due to unhealthy diet and living habits. Simiao Powder, as a classic formula consisted of four common herbs, has been widely used in clinical practice since ancient times to prevent and treat gout. However, the pharmacological mechanism of Simiao Powder is still unclear.

Methods

Based on network pharmacology, Simiao Powder active compounds were identified in TCMSP, ETCM and BATMAN database, used to establish a network of interaction between potential targets of Simiao Powder and known therapeutic targets of gout. Subsequently, the key potential targets are being used for protein–protein interaction, GO enrichment analysis and KEGG pathway enrichment analysis through several authoritative open databases. Molecular docking through AutoDockTools software can verify interaction between molecules. Finally, to validate the predicted results, in vivo experiments based on hyperuricemic-gout mice model were designed and treated with Simiao powder and allopurinol. Serum levels of uric acid (UA), creatinine (Cr), blood urea nitrogen (BUN) and xanthine oxidase (XOD) were determined using a customized assay kit while the expression of PPAR-γ, PTGS1, IL-6 and Bcl2 mRNA were analyzed through qRT-PCR.

Results

Disease-target-compound network was visualized basing on the 20 bioactive compounds and the 19 potential targets using Cytoscape software. The results of PPI analysis, GO enrichment and KEGG pathway enrichment analysis indicate that the potential mechanism of Simiao Powder in treating gout may be achieved by regulating immune and inflammatory reactions, improving metabolism and endocrine. The results of molecular docking show that most of the targets and components have good binding activity. In vivo experiments revealed that Simiao powder can decreased serum UA and XOD levels in hyperuricemic-gout mice, and improved renal function. Furthermore, Simiao powder certainly regulates the expression of PPAR-γ, PTGS1, IL-6 and Bcl2 mRNA in ankle tissue in hyperuricemic-gout mice.

Conclusion

Collectively, this research predicted a multiple compounds, targets, and pathways model mechanism of Simiao Powder in the prevention and treatment of gout, providing new ideas and methods for in-depth research, via vivo experiments.

Tear Function Alterations and Conjunctival Impression Cytology Findings in Patients With Gout

OBJECTIVES

The aim of this study was to evaluate the tear functions and conjunctival impression cytology (CIC) findings of patients with gout and compare them with healthy controls.

METHODS

Thirty-four patients with gout (group 1) and 32 age-matched and gender-matched healthy individuals (group 2) were included in this cross-sectional study. Schirmer 1 test, tear breakup time (TBUT), Ocular Surface Disease Index (OSDI) score, and CIC grade were evaluated and compared between the groups.

RESULTS

There was no significant difference between the groups in gender and age (P=0.923 and P=0.078, respectively). The mean of Schirmer 1 test result was significantly lower in group 1 (9.74±6.03 mm) than that in group 2 (17.16±9.33 mm) (P<0.001). The TBUT was also significantly lower in group 1 (7.00±2.09 seconds) than that in group 2 (12.75±5.25 seconds) (P<0.001). The OSDI score (20.04±12.92) was significantly higher in group 1 than that in group 2 (6.19±10.07) (P<0.001). Although 10 patients (29.4%) in group 1 had the CIC grade of 2 to 3, none of the controls had CIC grade 2 to 3. The mean CIC grade in group 1 (1.15±0.89) was significantly higher than that in group 2 (0.47±0.51) (P<0.001).

CONCLUSIONS

The results of this study suggest that ocular surface alterations assessed by CIC and tear function abnormalities are more common in patients with gout.

A brief review on in vivo models for Gouty Arthritis

Gout is more common in men than in women, by a factor of 3.1–10.1. Gout prevalence and incidence have increased in recent decades, with prevalence reaching 11–13% and incidence reaching 0.4% in people over the age of 80. Age-related renal impairment, altered drug distribution, and increased prevalence of comorbidities have significant consequences for safe and effective gout pharmacotherapy. The Discovery of Fruitful in-vivo animal models needs the effective screening of drugs or formulations used in the treatment of gout. In vivo animal models of Gouty arthritis are extensively used to investigate pathogenic mechanisms governing inflammation-driven bone and cartilage damage. Four commonly utilized models include the Potassium oxonate induced hyperuricemic model, MSU crystals induced gouty arthritis animal model, Animal Model of Acute Gouty Arthritis with Hyperuricemia, and Diet-induced hyperuricemia. These offer unique advantages for correlating different aspects of gouty arthritis with human disease. In-vivo animal models served as testing beds for novel biological therapies, including cytokine blockers and small molecule inhibitors of intracellular signaling that have revolutionized gouty arthritis treatment. This review highlights a brief overview of in vivo experimental models for assessment of hypouricemic, anti-inflammatory, as well as renal protective effects of test compounds with some evaluation parameters in detail.

The role of Interleukin-1 receptor antagonist as a treatment option in calcium pyrophosphate crystal deposition disease

Calcium Pyrophosphate Crystal Deposition (CPPD) disease is characterized by the deposition of calcium pyrophosphate crystals in the cartilage. In most cases, it can manifest as a subclinical condition named chondrocalcinosis, often revealed by joint x-ray examination. In other cases, deposition can cause flares of arthritis, known as acute CPP crystal arthritis. In the last few years, many pathogenic pathways have been discovered. Interleukin-1 (IL-1) plays a key role in the pathogenesis of CPPD disease, both as a mediator of inflammatory response to crystals and as a promoter of damage to articular cartilage. In this review, we investigated the role of IL-1R inhibitor, such as Anakinra, as an alternative to the various therapeutic strategies for CPPD disease, especially among patients resistant to traditional treatment with NSAIDs, corticosteroids and colchicine.

Gout and AA-Amyloidosis: A Case-Based Review

Background:

AA-amyloidosis complicates many chronic infections and inflammatory diseases, including rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis, but its relationship to gout is extremely rare. As it is unknown definitely what the pathophysiological connections between gout and amyloidosis are, treatment issues of the diseases are open for discussion.

Aim:

To establish a link between gout and AA-amyloidosis, and to improve the quality of treatment in patients suffering from gout and AA-amyloidosis.

Methods:

We reviewed the English-language literature sources, searching not only for rare cases of the combination of gout and AA amyloidosis, but also detailed descriptions of the medical treatments for the two pathologies.

Results:

By July 2020, we had identified 14 cases describing AA amyloidosis in patients with gout. Most of those patients had been suffering tophaceous gout for at least 10 years, and were prescribed various methods of treatment; however, not all patients took colchicine regularly. In some cases, therapy with allopurinol and colchicine was effective against attacks of gouty arthritis, although amyloidogenic inflammation was not controlled sufficiently. However, there were no cases that described in detail the successful treatment of both diseases. Besides those 14 patients described in literature, we examined one more patient with amyloidosis that is secondary to gout, in whom the protein of amyloid A (AA) had affected the kidneys, intestines, and adrenal glands. The patient has been successfully treated with the combination of canakinumab, prednisone, colchicine and allopurinol.

Conclusion:

Clinicians should be aware that patients may have atypical combinations of diseases like gout and amyloidosis. The obtained results help to explain some pathogenic processes associated with AA-amyloidosis. Further research is necessary to confirm the effectiveness of different treatment options such as lifestyle biologic agents or other medicines with anti-inflammatory properties.

Acute pseudogout presenting as an exception to Musculoskeletal Infection Society criteria in total knee arthroplasty: a case report

In this case, a 78-year-old female with no previous medical history of crystalline arthropathy presented with pain, effusion, and erythema about a total knee arthroplasty (TKA) performed 13 years prior. Implementation of a novel synovial fluid alpha-defensin assay ruled out periprosthetic joint infection (PJI) despite a positive 2018 Musculoskeletal Infection Society (MSIS) minor criteria score of 8 points, a significant diagnostic differentiation which prevented secondary invasive debridement or joint irrigation intervention. Confirmatory histologic study was positive for calcium pyrophosphate crystals, indicative of acute pseudogout inflammation rather than PJI or septic arthritis manifestation. The patient was then conservatively managed medically for a pseudogout flare and had no evidence of infection with normal physical exam and laboratory study at one- and two-years post treatment, respectively. Given the predominantly clinical nature of current PJI assessment in-clinic coupled with notable risks associated with aggressive re-intervention in the setting of suspected infection, critical need exists for the maturation of sensitive, reliable empiric measures which may assist in guiding orthopaedic surgeon evaluation of patients presenting with inflammatory symptomology around a previous surgical site. In this case, we conclude that patients with a negative alpha-defensin assay alongside crystalline arthropathy on histology may be cautiously yet successfully treated non-operatively despite clinical MSIS criteria concerning for PJI.

Involvement of inflammasome activation via elevation of uric acid level in nociception in a mouse model of muscle pain

Muscle pain is a common condition in many diseases and is induced by muscle overuse. Muscle overuse induces an increase in uric acid, which stimulates the nucleotide-binding oligomerization domain-like receptor (NLR). This receptor contains the pyrin domain NLRP-3 inflammasome which when activated, results in the secretion of potent pro-inflammatory cytokines such as interleukin-1β (IL-1β). The aim of this study was to investigate the involvement of inflammasome activation via the elevation of uric acid level in nociception in a mouse model of muscle pain. The right hind leg muscles of BALB/c mice were stimulated electrically to induce excessive muscle contraction. The left hind leg muscles were not stimulated as a control. Mechanical withdrawal thresholds, levels of uric acid, IL-1β, and NLRP3, caspase-1 activity, and the number of macrophages were investigated. Furthermore, the effects of xanthine oxidase inhibitors, such as Brilliant Blue G, caspase-1 inhibitor, and clodronate liposome, on pain were investigated. In the stimulated muscles, mechanical withdrawal thresholds decreased, and the levels of uric acid, NLRP3, and IL-1β, caspase-1 activity, and the number of macrophages increased compared to that in the non-stimulated muscles. Administration of the inhibitors attenuated hyperalgesia caused by excessive muscle contraction. These results suggested that IL-1β secretion and NLRP3 inflammasome activation in macrophages produced mechanical hyperalgesia by elevating uric acid level, and xanthine oxidase inhibitors may potentially reduce over-exercised muscle pain.

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.

Caspase-11 Mediates Neutrophil Chemotaxis and Extracellular Trap Formation During Acute Gouty Arthritis Through Alteration of Cofilin Phosphorylation

Gout is characterized by attacks of arthritis with hyperuricemia and monosodium urate (MSU) crystal-induced inflammation within joints. Innate immune responses are the primary drivers for tissue destruction and inflammation in gout. MSU crystals engage the Nlrp3 inflammasome, leading to the activation of caspase-1 and production of IL-1β and IL-18 within gout-affected joints, promoting the influx of neutrophils and monocytes. Here, we show that caspase-11^−/− mice and their derived macrophages produce significantly reduced levels of gout-specific cytokines including IL-1β, TNFα, IL-6, and KC, while others like IFNγ and IL-12p70 are not altered. IL-1β induces the expression of caspase-11 in an IL-1 receptor-dependent manner in macrophages contributing to the priming of macrophages during sterile inflammation. The absence of caspase-11 reduced the ability of macrophages and neutrophils to migrate in response to exogenously injected KC in vivo. Notably, in vitro, caspase-11^−/− neutrophils displayed random migration in response to a KC gradient when compared to their WT counterparts. This phenotype was associated with altered cofilin phosphorylation. Unlike their wild-type counterparts, caspase-11^−/− neutrophils also failed to produce neutrophil extracellular traps (NETs) when treated with MSU. Together, this is the first report demonstrating that caspase-11 promotes neutrophil directional trafficking and function in an acute model of gout. Caspase-11 also governs the production of inflammasome-dependent and -independent cytokines from macrophages. Our results offer new, previously unrecognized functions for caspase-11 in macrophages and neutrophils that may apply to other neutrophil-mediated disease conditions besides gout.

Polydatin and Resveratrol Inhibit the Inflammatory Process Induced by Urate and Pyrophosphate Crystals in THP-1 Cells

Resveratol (RES) and its natural precursor polydatin (PD) are polyphenols that may display a broad variety of beneficial effects including anti-inflammatory properties. This study aimed to investigate the role of RES and PD in the inflammatory process induced by monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals in vitro. A monocytic cell line (THP-1) was primed for 3 hours with phorbol myristate acetate (100 ng/mL) and stimulated with synthetic MSU (0.05 mg/mL) and CPP (0.025 mg/mL) crystals. RES and PD were added to cultures concurrently with the crystals, or as 2-hour pretreatment. The effect of the two polyphenols was evaluated on intracellular and extracellular IL-1β levels, NACHT-LRRPYD-containing protein-3 (NLRP3) inflammasome expression, reactive oxygen species (ROS) and nitric oxide (NO) production, and the assessment of crystal phagocytosis. RES and PD strongly inhibited IL-1β induced by crystals after cell pretreatment. Cell pretreatment was effective also in reducing IL-1 mRNA expression while no effect was observed on NLRP3 gene expression. RES and PD had no effect on crystal phagocytosis when used as pretreatment. Both polyphenols were significantly effective in inhibiting ROS and NO production. Our results demonstrated that RES and PD are effective in inhibiting crystal-induced inflammation. Data obtained after cell pretreatment allow us to hypothesize that these polyphenols act on specific signaling pathways, preventing inflammation.

Calcium crystal-associated arthropathy mimicking a febrile systemic inflammatory disease in an elderly patient

Crystal formation and deposition in the joints is an important and common cause of acute arthritis. The disease may present with fever and systemic signs. In this report, we describe the case of a 70-year-old man, who presented with a sudden and incapacitating polyarthritis of large and small joints, fever, asthenia and leukocytosis. After extensive investigation, radiography of the joints showed the presence of chondrocalcinosis. A few days after the beginning of the treatment with colchicine, he became completely asymptomatic, drawing one’s attention of calcium crystal-associated arthropathy as a cause of febrile systemic inflammatory disease particularly in elderly population.

Decreased Expression of CD14 in MSU-Mediated Inflammation May Be Associated with Spontaneous Remission of Acute Gout

Gout is a common metabolic disease in humans, and it is due to persistently elevated levels of uric acid in the blood. At high levels, uric acid crystallizes and the crystals deposit in joints and surrounding tissues, resulting in an attack of gout. Interestingly, the gout attack can spontaneously resolve within a few days. However, the self-limited mechanism of gout remains elusive. It has been demonstrated that CD14 plays an important role in self-remission of gout. In this study, we found that the proportion of CD14-positive PBMCs was decreased in gout patients when compared with healthy controls and the serum sCD14 level was also considerably decreased in gout patients in comparison to healthy controls. In addition, sCD14 levels were positively correlated with CRP levels. Furthermore, the effect of MSU on the levels of CD14 in healthy volunteer's PBMC was explored in in vitro experiment. The results showed that CD14 expression on macrophage and sCD14 levels in the culture supernatants were significantly decreased after MSU treatment. However, there was no significance in the levels of membrane CD14 and sCD14 in healthy volunteer's PBMC stimulated by LPS. Taken together, these results suggest that CD14 might play an important role in self-remission of gout.

[Ru(bpy)2(NO)SO3](PF6), a Nitric Oxide Donating Ruthenium Complex, Reduces Gout Arthritis in Mice

Monosodium urate crystals (MSU) deposition induces articular inflammation known as gout. This disease is characterized by intense articular inflammation and pain by mechanisms involving the activation of the transcription factor NFκB and inflammasome resulting in the production of cytokines and oxidative stress. Despite evidence that MSU induces iNOS expression, there is no evidence on the effect of nitric oxide (NO) donors in gout. Thus, the present study evaluated the effect of the ruthenium complex donor of NO {[Ru(bpy)₂(NO)SO₃](PF₆)} (complex I) in gout arthritis. Complex I inhibited in a dose-dependent manner MSU-induced hypersensitivity to mechanical stimulation, edema and leukocyte recruitment. These effects were corroborated by a decrease of histological inflammation score and recruitment of Lysm-eGFP⁺ cells. Mechanistically, complex I inhibited MSU-induced mechanical hypersensitivity and joint edema by triggering the cGMP/PKG/ATP-sensitive K (+) channels signaling pathway. Complex I inhibited MSU-induced oxidative stress and pro-inflammatory cytokine production in the knee joint. These data were supported by the observation that complex I inhibited MSU-induced NFκB activation, and IL-1β expression and production. Complex I also inhibited MSU-induced activation of pro-IL-1β processing. Concluding, the present data, to our knowledge, is the first evidence that a NO donating ruthenium complex inhibits MSU-induced articular inflammation and pain. Further, complex I targets the main physiopathological mechanisms of gout arthritis. Therefore, it is envisaged that complex I and other NO donors have therapeutic potential that deserves further investigation.

Urate crystal deposition, prevention and various diagnosis techniques of GOUT arthritis disease: a comprehensive review

Gout is described as difficult in joint sore, uttermost ordinarily in the principal metatarsophalangeal joint, attend from formation of urate monosodium crystallization in a joint space. Analysis might be affirmed by recognizable proof of urate monosodium precious stones in synovial liquid of the influenced joint. There has been expanded enthusiasm for gout in common scholarly and clinical practice settings. The pervasiveness of both hyperuricemia and gout has ascended as most recent decade of time in created nations and in this way weight of gout as expanded. The relationship of hyperuricemia and gout with cardio results for chance of added advantages in mediation on hyperuricemia was featured in this audit. Imaging procedures have ended up being helpful for location of urate statement, even before the primary clinical indications, empowering the assessment of the degree of testimony and giving target estimation of precious stone exhaustion amid urate-bringing down treatment. In advancement, the indication defines the pre diagnostic of gout and associated commodities is advised to prevent the inflammation, that image procedures will assess the weight on statement as well reaction to urinary bringing down clinical procedure in chose patients, lastly amongst last key goal on social insurance for clinical evaluation with gout is to totally project urate gem stores. In spite of the fact that the formal determination is defined with arthrocentesis and resulting examination, CT and ultrasound discoveries on addition of evaluation and execution of infection administration. The standard therapy methodology is available for the patients and whose disease is refractory to standard therapy.

Blocking fatty acid-fueled mROS production within macrophages alleviates acute gouty inflammation

Gout is the most common inflammatory arthritis affecting men. Acute gouty inflammation is triggered by monosodium urate (MSU) crystal deposition in and around joints that activates macrophages into a proinflammatory state, resulting in neutrophil recruitment. A complete understanding of how MSU crystals activate macrophages in vivo has been difficult because of limitations of live imaging this process in traditional animal models. By live imaging the macrophage and neutrophil response to MSU crystals within an intact host (larval zebrafish), we reveal that macrophage activation requires mitochondrial ROS (mROS) generated through fatty acid oxidation. This mitochondrial source of ROS contributes to NF-κB-driven production of IL-1β and TNF-α, which promote neutrophil recruitment. We demonstrate the therapeutic utility of this discovery by showing that this mechanism is conserved in human macrophages and, via pharmacologic blockade, that it contributes to neutrophil recruitment in a mouse model of acute gouty inflammation. To our knowledge, this study is the first to uncover an immunometabolic mechanism of macrophage activation that operates during acute gouty inflammation. Targeting this pathway holds promise in the management of gout and, potentially, other macrophage-driven diseases.

Gout: An old disease in new perspective - A review

Gout is a picturesque presentation of uric acid disturbance. It is the most well understood and described type of arthritis. Its epidemiology is studied. New insights into the pathophysiology of hyperuricemia and gouty arthritis; acute and chronic allow for an even better understanding of the disease. The role of genetic predisposition is becoming more evident. The clinical picture of gout is divided into asymptomatic hyperuricemia, acute gouty arthritis, intercritical period, and chronic tophaceous gout. Diagnosis is based on laboratory and radiological features. The gold standard of diagnosis is identification of characteristic MSU crystals in the synovial fluid using polarized light microscopy. Imaging modalities include conventional radiography, ultrasonography, conventional CT, Dual-Energy CT, Magnetic Resonance Imaging, nuclear scintigraphy, and positron emission tomography. There is remarkable progress in the application of ultrasonography and Dual-Energy CT which is bound to influence the diagnosis, staging, follow-up, and clinical research in the field. Management of gout includes management of flares, chronic gout and prevention of flares, as well as management of comorbidities. Newer drugs in the pharmacological armamentarium are proving successful and supplement older ones. Other important points in its management include patient education, diet and life style changes, as well as cessation of hyperuricemic drugs.

Physiological functions and pathogenic potential of uric acid: A review

Uric acid is synthesized mainly in the liver, intestines and the vascular endothelium as the end product of an exogenous pool of purines, and endogenously from damaged, dying and dead cells, whereby nucleic acids, adenine and guanine, are degraded into uric acid. Mentioning uric acid generates dread because it is the established etiological agent of the severe, acute and chronic inflammatory arthritis, gout and is implicated in the initiation and progress of the metabolic syndrome. Yet, uric acid is the predominant anti-oxidant molecule in plasma and is necessary and sufficient for induction of type 2 immune responses. These properties may explain its protective potential in neurological and infectious diseases, mainly schistosomiasis. The pivotal protective potential of uric acid against blood-borne pathogens and neurological and autoimmune diseases is yet to be established.

Neutrophil Extracellular Traps and Microcrystals

Neutrophil extracellular traps represent a fascinating mechanism by which PMNs entrap extracellular microbes. The primary purpose of this innate immune mechanism is thought to localize the infection at an early stage. Interestingly, the ability of different microcrystals to induce NET formation has been recently described. Microcrystals are insoluble crystals with a size of 1-100 micrometers that have different composition and shape. Microcrystals have it in common that they irritate phagocytes including PMNs and typically trigger an inflammatory response. This review is the first to summarize observations with regard to PMN activation and NET release induced by microcrystals. Gout-causing monosodium urate crystals, pseudogout-causing calcium pyrophosphate dehydrate crystals, cholesterol crystals associated with atherosclerosis, silicosis-causing silica crystals, and adjuvant alum crystals are discussed.

P2Y6 Receptor Antagonist MRS2578 Inhibits Neutrophil Activation and Aggregated Neutrophil Extracellular Trap Formation Induced by Gout-Associated Monosodium Urate Crystals

Human neutrophils (polymorphonuclear leukocytes [PMNs]) generate inflammatory responses within the joints of gout patients upon encountering monosodium urate (MSU) crystals. Neutrophil extracellular traps (NETs) are found abundantly in the synovial fluid of gout patients. The detailed mechanism of MSU crystal-induced NET formation remains unknown. Our goal was to shed light on possible roles of purinergic signaling and neutrophil migration in mediating NET formation induced by MSU crystals. Interaction of human neutrophils with MSU crystals was evaluated by high-throughput live imaging using confocal microscopy. We quantitated NET levels in gout synovial fluid supernatants and detected enzymatically active neutrophil primary granule enzymes, myeloperoxidase, and human neutrophil elastase. Suramin and PPADS, general P2Y receptor blockers, and MRS2578, an inhibitor of the purinergic P2Y6 receptor, blocked NET formation triggered by MSU crystals. AR-C25118925XX (P2Y2 antagonist) did not inhibit MSU crystal-stimulated NET release. Live imaging of PMNs showed that MRS2578 represses neutrophil migration and blocked characteristic formation of MSU crystal-NET aggregates called aggregated NETs. Interestingly, the store-operated calcium entry channel inhibitor (SK&F96365) also reduced MSU crystal-induced NET release. Our results indicate that the P2Y6/store-operated calcium entry/IL-8 axis is involved in MSU crystal-induced aggregated NET formation, but MRS2578 could have additional effects affecting PMN migration. The work presented in the present study could lead to a better understanding of gouty joint inflammation and help improve the treatment and care of gout patients.

Macrophage-derived IL-1β enhances monosodium urate crystal-triggered NET formation

OBJECTIVE AND DESIGN

Arthritic gout is caused by joint inflammation triggered by the damaging effects of monosodium uric acid (MSU) crystal accumulation in the synovial space. Neutrophils play a major role in mediating joint inflammation in gout. Along with neutrophils, other immune cells, such as macrophages, are present in inflamed joints and contribute to gout pathogenesis. Neutrophils form neutrophil extracellular traps (NETs) in response to MSU crystals. In the presence of MSU crystals, macrophages release IL-1β, a cytokine crucial to initiate gout pathogenesis and neutrophil recruitment. Our research investigated interactions between human macrophages and neutrophils in an in vitro model system and asked how macrophages affect NET formation stimulated by MSU crystals.

MATERIALS OR SUBJECTS

Human neutrophils and PBMCs were isolated from peripheral blood of healthy volunteers. PBMCs were differentiated into macrophages in vitro using human M-CSF.

TREATMENT

Human neutrophils were pretreated with macrophage-conditioned media, neutrophil-conditioned media, recombinant human IL-1β or anakinra prior to stimulation by MSU crystals.

METHOD

Interaction of neutrophils with MSU crystals was evaluated by live imaging using confocal microscopy. The presence of myeloperoxidase (MPO) and neutrophil elastase (NE) was measured by ELISA. NET formation was quantitated by Sytox Orange-based extracellular DNA release assay and NE-DNA ELISA. AggNET formation was assessed by macroscopic evaluation.

RESULTS

We found that crystal- and cell-free supernatants of macrophages stimulated with MSU crystals promote MSU crystal-stimulated NET formation in human neutrophils. This observation was confirmed by additional assays measuring the release of MPO, NE, and the enzymatic activity of NE. MSU crystal-induced NET formation remained unchanged when neutrophil supernatants were tested. IL-1β is a crucial cytokine orchestrating the onset of inflammation in gout and is known to be released in large amounts from macrophages following MSU crystal stimulation. We found that recombinant IL-1β strongly promoted MSU crystal-induced NET formation in human neutrophils. Interestingly, IL-1β alone did not induce any NET release. We also found that clinical grade anakinra, an IL-1 receptor blocker, strongly reduced the NETosis-enhancing effect of macrophage supernatants indicating that IL-1β is mainly responsible for this effect.

CONCLUSIONS

Macrophage-derived IL-1β enhances MSU crystal-induced NET release in neutrophils. We identified a new mechanism by which macrophages and IL-1β affect neutrophil functions, and could contribute to the inflammatory conditions present in gout. Our results also revealed a new anti-inflammatory mechanism of anakinra.

Expression of Caspase-1 Gene Transcript Variant mRNA in Peripheral Blood Mononuclear Cells of Patients with Primary Gout in Different TCM Syndromes

A large number of studies have shown that cysteinyl aspartate specific protease-1 (CASP1) played an important role in the inflammatory response of primary gout, but the decreased expression of different CASP1 transcript variant could inhibit the activation of IL-1β. Our study mainly analyzed the expression level and function of CASP1 gene transcript variant mRNA in peripheral blood mononuclear cells of patients with gout in different TCM syndromes. The expression of CASP1 gene transcript variant and IL-1β mRNA in PBMCs were detected in patients with PG [acute phase (AP: 44 cases); nonacute phase (NAP: 52 cases)] and healthy controls (HC: 30 cases) by reverse transcription-polymerase chain reaction and/or real-time quantitative polymerase chain reaction. The expressions of plasma IL-1β in patients with PG and HC were detected by enzyme-linked immunosorbent assay. Dysregulated expression of the CASP1 gene and its transcript variant, plasma proinflammatory cytokines in all patients with primary gout in different TCM syndromes, correlation analysis showed that there was negative correlation between the expression of CASP1-gamma gene transcript variant mRNA and IL-1β protein in APPG group. The study suggested that CASP1 gene and its transcript variant may play a critical role in the inflammatory response of patients with PG in different phases and TCM syndromes.

The role of oxidative stress during inflammatory processes

Abstract The production of various reactive oxidant species in excess of endogenous antioxidant defense mechanisms promotes the development of a state of oxidative stress, with significant biological consequences. In recent years, evidence has emerged that oxidative stress plays a crucial role in the development and perpetuation of inflammation, and thus contributes to the pathophysiology of a number of debilitating illnesses, such as cardiovascular diseases, diabetes, cancer, or neurodegenerative processes. Oxidants affect all stages of the inflammatory response, including the release by damaged tissues of molecules acting as endogenous danger signals, their sensing by innate immune receptors from the Toll-like (TLRs) and the NOD-like (NLRs) families, and the activation of signaling pathways initiating the adaptive cellular response to such signals. In this article, after summarizing the basic aspects of redox biology and inflammation, we review in detail the current knowledge on the fundamental connections between oxidative stress and inflammatory processes, with a special emphasis on the danger molecule high-mobility group box-1, the TLRs, the NLRP-3 receptor, and the inflammasome, as well as the transcription factor nuclear factor-κB.

[Examination of cases of pseudogout in succession to inflammatory disease in the elderly]

AIM

Pseudogout is an important causative disease of febrile illness in elderly patients. We experienced cases of pseudogout during or after the progression of inflammatory disease.

METHODS

We investigated 14 patients with pseudogout admitted to the Department of Geriatric Medicine at Kyorin University Hospital. Seven patients who developed inflammatory disease prior to the onset of pseudogout are described in greater detail.

RESULTS

The affected joint was the knee joint in 12 of 14 cases. Other joints were affected in four cases, and four patients had more than two affected joints in this series. Clear joint cartilage calcification was noted on X-rays in nine of 14 cases, and CPPD crystals were detected in two patients treated with joint puncture. NSAIDs were administered in all cases for treatment. Seven patients had a preceding inflammatory disease, with infectious disease in all cases. Repeat elevation of temperature and inflammatory reactions were seen in seven cases, with progression to bimodal disease in two cases. The average duration of antimicrobial use was 11 days. In three cases, the average duration of antimicrobial use was 33 days, and two or more antimicrobials were used for long-term treatment.

CONCLUSIONS

Pseudogout appears as delayed infective disease and fever of unknown origin in the elderly. This condition may easily be overlooked until joint symptoms become apparent. It is extremely important to keep pseudogout in mind as a differential diagnosis of thermogenesis in elderly patients.

Phytochemical Compositions and Antioxidant and Anti-Inflammatory Activities of Crude Extracts from Ficus pandurata H. (Moraceae)

Background. Ficus pandurata H. (Moraceae) is widely used in traditional Chinese medicine as a healthy food condiment or a medicine for treatment of various diseases including inflammation. Objective. The purpose of the present study is to investigate the phytochemical compositions and antioxidant and anti-inflammatory activities of crude water (FPW) and ethanolic extracts (FPE) from Ficus pandurata H. Methods. Phytochemical compositions were identified by a high-performance liquid chromatography-electrospray ionization-mass spectrometry method (HPLC-ESI-MS). The antioxidant activities were evaluated by diphenylpicrylhydrazyl (DPPH) and hydroxyl radical assays, and the anti-inflammatory activities were evaluated by paw edema and levels of inflammatory mediator TNF-α and PGE2 in monosodium urate (MSU) crystal-induced rats. Results. Six compounds were identified by HPLC-MS method, and abundance of phenolics was found in FPE. The FPE showed concentration-dependent-significant scavenging of DPPH and hydroxyl radicals with IC50 values 118.4 and 192.9 μg/mL, respectively. The FPE treatment significantly inhibited the paw edema and the production of TNF-α and PGE2 in MSU crystal-induced rats. Conclusion. The FPE exerted stronger antioxidant and anti-inflammatory activities which may be attributed to its high phenolic content.

Epigallocatechin-3-gallate reduces inflammation induced by calcium pyrophosphate crystals in vitro

Although osteoarthritis (OA) is defined as a cartilage disease, synovitis involving mononuclear cell infiltration and overexpression of proinflammatory mediators is common in early and late OA. Calcium crystals deposition is thought to be a factor that likely contributes to synovial inflammation. In recent years, significant interest has emerged in the beneficial health effects attributed to the green tea polyphenols and in particular to epigallocatechin-3-gallate (EGCG). It has been demonstrated that some of the actions of EGCG are linked to its ability to interfere with cell membranes. The objective of this study was to evaluate the influence of EGCG in some inflammatory aspects of OA and whether EGCG is able to interfere with membrane organization. We assessed the effect of EGCG on the production of proinflammatory cytokines and chemokines released by human fibroblast-like synoviocytes (FLS) and THP-1 cells stimulated with calcium pyrophosphate (CPP) crystals in presence of methyl-β-cyclodextrin (MβCD), a cholesterol-removing agent that disturbs lipid raft structures. The chemotactic effect of culture supernatants was also evaluated. EGCG inhibited interleukin (IL)-1β, transforming growth factor beta, IL-8, and chemokine (C–C motif) ligand 2 (CCL2) release by stimulated FLS and/or THP-1 cells in a dose-dependent manner. Supernatants of CPP-stimulated cells induced the migration of neutrophils and mononuclear cells which decreased in a dose-dependent manner in the presence of EGCG. EGCG increased cell viability when added to THP-1 cells treated with MβCD. Furthermore, MβCD enhanced the inflammatory response to CPP crystals increasing IL-8 and CCL2 secretion which was inhibited by EGCG in a dose-dependent manner. This study showed that EGCG is able to reduce the inflammatory response induced by CPP crystals in vitro. The identification of EGCG as dietary supplement capable of affording protection or modulating the inflammatory response to CPP crystals may have important implications in the prevention and treatment of OA and crystal-related arthropathies.