Controversies and practical management of patients with gout and chronic kidney disease.

Uric acid is a toxin retained with advancing kidney disease. Clinical manifestations of hyperuricemia include gout and systemic inflammation that are associated with increased risk of cardiovascular mortality. As many as one-third of all patients with chronic kidney disease have a history of gout, yet <25% of these patients are effectively treated to target serum urate levels of ≤6 mg/dl. A major reason for ineffective management of gout and hyperuricemia is the complexity in managing these patients, with some medications contraindicated and others requiring special dosing, potential drug interactions, and other factors. Consequently, many nephrologists do not primarily manage gout despite it being a common complication of chronic kidney disease, leaving management to the primary physician or rheumatologist. We believe that kidney specialists should consider gout as a major complication of chronic kidney disease and actively manage it in their patients. Here, we present insights from nephrologists and rheumatologists for a team approach to gout management that includes the nephrologist.

Monosodium Urate Crystal-Induced Pyroptotic Cell Death in Neutrophil and Macrophage Facilitates the Pathological Progress of Gout.

Monosodium urate (MSU) crystal deposition in joints can lead to the infiltration of neutrophils and macrophages, and their activation plays a critical role in the pathological progress of gout. However, the role of MSU crystal physicochemical properties in inducing cell death in neutrophil and macrophage is still unclear. In this study, MSU crystals of different sizes are synthesized to explore the role of pyroptosis in gout. It is demonstrated that MSU crystals induce size-dependent pyroptotic cell death in bone marrow-derived neutrophils (BMNs) and bone marrow-derived macrophages (BMDMs) by triggering NLRP3 inflammasome-dependent caspase-1 activation and subsequent formation of N-GSDMD. Furthermore, it is demonstrated that the size of MSU crystal also determines the formation of neutrophil extracellular traps (NETs) and aggregated neutrophil extracellular traps (aggNETs), which are promoted by the addition of interleukin-1ß (IL-1ß). Based on these mechanistic understandings, it is shown that N-GSDMD oligomerization inhibitor, dimethyl fumarate (DMF), inhibits MSU crystal-induced pyroptosis in BMNs and J774A.1 cells, and it further alleviates the acute inflammatory response in MSU crystals-induced gout mice model. This study elucidates that MSU crystal-induced pyroptosis in neutrophil and macrophage is critical for the pathological progress of gout, and provides a new therapeutic approach for the treatment of gout.

ML335 inhibits TWIK2 channel-mediated potassium efflux and attenuates mitochondrial damage in MSU crystal-induced inflammation.

BACKGROUND: Activation of the NLRP3 inflammasome is critical in the inflammatory response to gout. Potassium ion (K+) efflux mediated by the TWIK2 channel is an important upstream mechanism for NLRP3 inflammasome activation. Therefore, the TWIK2 channel may be a promising therapeutic target for MSU crystal-induced inflammation. In the present study, we investigated the effect of ML335, a known K2P channel modulator, on MSU crystal-induced inflammatory responses and its underlying molecular mechanisms. METHODS: By molecular docking, we calculated the binding energies and inhibition constants of five K2P channel modulators (Hydroxychloroquine, Fluoxetine, DCPIB, ML365 and ML335) with TWIK2. Intracellular potassium ion concentration and mitochondrial function were assessed by flow cytometry. The interaction between MARCH5 and SIRT3 was demonstrated by immunoprecipitation and Western blotting assay. MSU suspensions were injected into mouse paw and peritoneal cavity to induce acute gout model. RESULTS: ML335 has the highest binding energy and the lowest inhibition constant with TWIK2 in the five calculated K2P channel modulators. In comparison, among these five compounds, ML335 efficiently inhibited the release of IL-1ß from MSU crystal-treated BMDMs. ML335 decreased MSU crystal-induced K+ efflux mainly dependent on TWIK2 channel. More importantly, ML335 can effectively inhibit the expression of the mitochondrial E3 ubiquitin ligase MARCH5 induced by MSU crystals, and MARCH5 can interact with the SIRT3 protein. ML335 blocked MSU crystal-induced ubiquitination of SIRT3 protein by MARCH5. In addition, ML335 improved mitochondrial dynamics homeostasis and mitochondrial function by inhibiting MARCH5 protein expression. ML335 attenuated the inflammatory response induced by MSU crystals in vivo and in vitro. CONCLUSION: Inhibition of TWIK2-mediated K+ efflux by ML335 alleviated mitochondrial injury via suppressing March5 expression, suggesting that ML335 may be an effective candidate for the future treatment of gout.

Isolation, identification, and pathogenicity of two novel goose astrovirus from goslings with severe gout in China.

Goose astroviruses (GAstVs) are important pathogens which can cause gout in goslings leading to huge economic losses for the goose farming industry in China. In 2023, an infectious disease characterized by visceral gout broke out in commercial goose farms in Guangxi and Guangdong provinces of China. In this study, two GAstV strains of GXNN and GDCS were successfully isolated from these two disease-ridden goose farms. The complete genomic lengths of these two strains were 7166 bp, and phylogenetic analysis showed that they were both GAstV-2 subtypes. The 3-dimensional structures of the capsid protein were predicted and six characteristic mutation sites at amino acid positions 60, 61, 228, 229, 456 and 523 were found within the strong antigenic regions. A recombination event occurred at 6833-7070 nt between the GAstV TZ03 and Turkey astrovirus CA/00 and this was detected in both the GXNN and GDCS strains. Another recombinant event occurred at 63-2747 nt between the GAstV XT1 and GAstV SDPY and this was detected in the GDCS strain. When 1-day-old goslings were infected with the novel GXNN and GDCS strains, they showed severe visceral gout. This was accompanied by enlarged spleens, liver hemorrhages and urate deposits in the kidneys and ureters and their blood urea nitrogen levels were significantly elevated. The mortality rates of the GXNN- and GDCS-infected groups were pathogenically high at 80 % and 60 %, respectively. These results will promote our understanding of the evolution and epidemic potential of GAstVs in China.

Inactivation of mitochondrial pyruvate carrier promotes NLRP3 inflammasome activation and gout development via metabolic reprogramming.

The nucleotide-binding and oligomerization domain, leucine-rich repeats, and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a crucial role in innate immunity and is involved in the pathogenesis of autoinflammatory diseases. Glycolysis regulates NLRP3 inflammasome activation in macrophages. However, how lactic acid fermentation and pyruvate oxidation controlled by the mitochondrial pyruvate carrier (MPC) affect NLRP3 inflammasome activation and autoinflammatory disease remains elusive. We found that the inactivation of MPC with genetic depletion or pharmacological inhibitors, MSDC-0160 or pioglitazone, increased NLRP3 inflammasome activation and IL-1ß secretion in macrophages. Glycolytic reprogramming induced by MPC inhibition skewed mitochondrial ATP-associated oxygen consumption into cytosolic lactate production, which enhanced NLRP3 inflammasome activation in response to monosodium urate (MSU) crystals. As pioglitazone is an insulin sens MSDC-itizer used for diabetes, its MPC inhibitory effect in diabetic individuals was investigated. The results showed that MPC inhibition exacerbated MSU-induced peritonitis in diabetic mice and increased the risk of gout in patients with diabetes. Altogether, we found that glycolysis controlled by MPC regulated NLRP3 inflammasome activation and gout development. Accordingly, prescriptions for medications targeting MPC should consider the increased risk of NLRP3-related autoinflammatory diseases.

[Tophaceous gout as a differential diagnosis of preauricular tumor]. / Tophöse Gicht als Differenzialdiagnose eines präaurikulären Tumors.

Primary gout is a hereditary disorder in nucleotide metabolism. In addition to typical manifestations in the feet, hands, and large joints, there may be rare manifestations in the head and neck. We report a case of tophaceous gout in the temporomandibular joint in a patient who presented with preauricular swelling and progressive hearing impairment. Physical examination showed obliteration of the auditory canal and imaging revealed a destructive process involving the skull base. The diagnosis was confirmed by imaging and biopsy.

Genomic dissection of 43 serum urate-associated loci provides multiple insights into molecular mechanisms of urate control.

High serum urate is a prerequisite for gout and associated with metabolic disease. Genome-wide association studies (GWAS) have reported dozens of loci associated with serum urate control; however, there has been little progress in understanding the molecular basis of the associated loci. Here, we employed trans-ancestral meta-analysis using data from European and East Asian populations to identify 10 new loci for serum urate levels. Genome-wide colocalization with cis-expression quantitative trait loci (eQTL) identified a further five new candidate loci. By cis- and trans-eQTL colocalization analysis, we identified 34 and 20 genes, respectively, where the causal eQTL variant has a high likelihood that it is shared with the serum urate-associated locus. One new locus identified was SLC22A9 that encodes organic anion transporter 7 (OAT7). We demonstrate that OAT7 is a very weak urate-butyrate exchanger. Newly implicated genes identified in the eQTL analysis include those encoding proteins that make up the dystrophin complex, a scaffold for signaling proteins and transporters at the cell membrane; MLXIP that, with the previously identified MLXIPL, is a transcription factor that may regulate serum urate via the pentose-phosphate pathway and MRPS7 and IDH2 that encode proteins necessary for mitochondrial function. Functional fine mapping identified six loci (RREB1, INHBC, HLF, UBE2Q2, SFMBT1 and HNF4G) with colocalized eQTL containing putative causal SNPs. This systematic analysis of serum urate GWAS loci identified candidate causal genes at 24 loci and a network of previously unidentified genes likely involved in control of serum urate levels, further illuminating the molecular mechanisms of urate control.

Retrospective longitudinal assessment of ultrasound gout lesions using the OMERACT semi-quantitative scoring system.

OBJECTIVES: The objectives of this study were (i) to evaluate the responsiveness of gout-specific US lesions representing urate deposition in patients receiving treat-to-target urate-lowering therapy using a binary and the OMERACT-defined semi-quantitative scoring systems; (ii) to determine the most responsive US measure for urate deposition and the optimal joint/tendon set for monitoring this. METHODS: US (28 joints, 14 tendons) was performed in microscopically verified gout patients initiating/increasing urate-lowering therapy and repeated after 6 and 12 months. Static images/videos of pathologies were stored and scored binarily and semi-quantitatively for tophus, double contour sign (DC) and aggregates. Lesion scores were calculated at patient level, as were combined crystal sum scores. Responsiveness of lesions-scored binarily and semi-quantitatively-was calculated at both patient and joint/tendon levels. RESULTS: Sixty-three patients underwent longitudinal evaluation. The static images/videos assessed retrospectively showed statistically significant decreases in tophus and DC, when scored binarily and semi-quantitatively, whereas aggregates were almost unchanged during follow-up. The responsiveness of the semi-quantitative tophus and DC sum scores were markedly higher than when using binary scoring. The most responsive measure for urate deposition was a combined semi-quantitative tophus-DC-sum score. A feasible joint/tendon set for monitoring included knee and first-second MTP joints and peroneus and distal patella tendons (all bilateral), representing the most prevalent and responsive sites. CONCLUSION: The OMERACT consensus-based semi-quantitative US gout scoring system showed longitudinal validity with both tophus and DC being highly responsive to treatment when assessed in static images/videos. A responsive US measure for urate deposition and a feasible joint/tendon set for monitoring were proposed and may prove valuable in future longitudinal studies.

Components of tart cherry juice inhibit NFκB activation and inflammation in acute gout.

OBJECTIVES: To identify the anthocyanin content in tart cherry juice concentrate (TCJC) and establish the anti-inflammatory effect of in a murine acute gout model. METHODS: The main anthocyanins in the TCJC were identified by liquid chromatography mass spectroscopy (LCMS). TCJC or phosphate-buffered saline (PBS) as control were administered daily by oral gavage to BALB/C-Tg(NFκB-RE-luc)-Xen mice that harbour a firefly luciferase cDNA reporter under the regulation of 3 Nuclear factor-κB (NF-κB) response elements. After 14 days, gouty inflammation was induced by intra-articular injection of monosodium urate (MSU) crystals into the tibio-tarsal joint (ankle). NF-κB activity was measured locally in the injected ankle using the Xenogen in vivo imaging system (IVIS), and decalcified feet/ankles were paraffin-embedded and analysed histopathologically. RESULTS: The major anthocyanin compound present in TCJC was cyanidin 3-glucosylrutinoside followed by cyanidin 3-rutinoside. In the murine acute gout model, MSU injection increased NF-κB activity and oral administration of TCJC significantly reduced NF-κB activity in mouse foot, and ankle joints as assessed by IVIS analysis. Bioluminescent imaging detection of NF-κB activation was inhibited approximately 2-fold relative to control mice receiving PBS. Histopathologic examination showed suppression of infiltrates into the tibio-tarsal joint space of the mice receiving TCJC compared to PBS-treated control counterparts. CONCLUSIONS: The major anthocyanin in TCJC was cyanidin 3-glucosylrutinoside. Clinically relevant doses of TCJC significantly inhibit inflammation and NF-κB activation induced by MSU crystals.

GEF-H1 Is Required for Colchicine Inhibition of Neutrophil Rolling and Recruitment in Mouse Models of Gout.

Gout is a painful arthritic inflammatory disease caused by buildup of monosodium urate (MSU) crystals in the joints. Colchicine, a microtubule-depolymerizing agent that is used in prophylaxis and treatment of acute gout flare, alleviates the painful inflammatory response to MSU crystals. Using i.p. and intra-articular mouse models of gout-like inflammation, we found that GEF-H1/GEF-H1/AHRGEF2, a microtubule-associated Rho-GEF, was necessary for the inhibitory effect of colchicine on neutrophil recruitment. GEF-H1 was required for neutrophil polarization in response to colchicine, characterized by uropod formation, accumulation of F-actin and myosin L chain at the leading edge, and accumulation of phosphorylated myosin L chain, flotillin-2, and P-selectin glycoprotein ligand-1 (PSGL-1) in the uropod. Wild-type neutrophils that were pre-exposed to colchicine failed to roll or accumulate on activated endothelial monolayers, whereas GEF-H1 knockout (GEF-H1-/-) neutrophils were unaffected by treatment with colchicine. In vivo, colchicine blocked MSU-induced recruitment of neutrophils to the peritoneum and the synovium in wild-type mice, but not in GEF-H1-/- mice. Inhibition of macrophage IL-1ß production by colchicine was independent of GEF-H1, supporting a neutrophil-intrinsic mode of action. Our results suggest that the anti-inflammatory effects of colchicine in acute gout-like inflammation can be accounted for by inhibition of neutrophil-rolling interactions with the inflamed vasculature and occurs through GEF-H1-dependent neutrophil stimulation by colchicine. These results contribute to our understanding of the therapeutic action of colchicine, and could inform the application of this drug in other conditions.

Kv1.5 channel mediates monosodium urate-induced activation of NLRP3 inflammasome in macrophages and arrhythmogenic effects of urate on cardiomyocytes.

BACKGROUND: Gout is usually found in patients with atrial fibrillation (AF). K+ efflux is a common trigger of NLRP3 inflammasome activation which is involved in the pathogenesis of AF. We investigated the role of the K+ channel Kv1.5 in monosodium urate crystal (MSU)-induced activation of the NLRP3 inflammasome and electrical remodeling in mouse and human macrophages J774.1 and THP-1, and mouse atrial myocytes HL-1. METHODS AND RESULTS: Macrophages, primed with lipopolysaccharide (LPS), were stimulated by MSU. HL-1 cells were incubated with the conditioned medium (CM) from MSU-stimulated macrophages. Western blot, ELISA and patch clamp were used. MSU induced caspase-1 expression in LPS-primed J774.1 cells and IL-1ß secretion, suggesting NLRP3 inflammasome activation. A selective Kv1.5 inhibitor, diphenyl phosphine oxide-1 (DPO-1), and siRNAs against Kv1.5 suppressed the levels of caspase-1 and IL-1ß. MSU reduced intracellular K+ concentration which was prevented by DPO-1 and siRNAs against Kv1.5. MSU increased expression of Hsp70, and Kv1.5 on the plasma membrane. siRNAs against Hsp70 were suppressed but heat shock increased the expression of Hsp70, caspase-1, IL-1ß, and Kv1.5 in MSU-stimulated J774.1 cells. The CM from MSU-stimulated macrophages enhanced the expression of caspase-1, IL-1ß and Kv1.5 with increased Kv1.5-mediated currents that shortened action potential duration in HL-1 cells. These responses were abolished by DPO-1 and a siRNA against Kv1.5. CONCLUSIONS: Kv1.5 regulates MSU-induced activation of NLRP3 inflammasome in macrophages. MSUrelated activation of NLRP3 inflammasome and electrical remodeling in HL-1 cells are via macrophages. Kv1.5 may have therapeutic value for diseases related to gout-induced activation of the NLRP3 inflammsome, including AF.

Computed tomography and magnetic resonance imaging findings in gouty arthritis involving large joints of the upper extremities.

BACKGROUND: We aimed to analyze the computed tomography (CT) and magnetic resonance imaging (MRI) findings of gouty arthritis primarily involving the large joints of the upper limbs, signal or density characteristics of the tophi, growth patterns, involvement of the adjacent joints, and differentiation from other lesions occurring in this area and to discuss the causes of misdiagnosis. METHODS: CT and MRI data were collected from 14 patients with gouty arthritis, primarily involving the shoulder and elbow joints, and their imaging features were analyzed. RESULTS: All the patiens were ranged from 28-85 years old, and the tophi deposition can be observed on either CT or MRI.The tophi deposition apperas as slightly higher density nodules or masses on CT images,or nodules or masses on MRI with isosignal/hypointensity on T1WI and hyperintensity on T2WI. Five patients showed narrowing of the affected joint space, four had different degrees of bone erosion under the articular surface, eight developed joint effusion, and all showed surrounding soft tissue swelling. The tophi grew around the joint, with anterolateral and posterolateral tophi predominantly in the shoulder joint and dorsal tophi predominantly in the elbow joint on the MRI, with compression and edema of the surrounding soft tissues. CONCLUSIONS: Gouty arthritis occurs in the large joints of the upper limbs and is characterized by fluid accumulation in the joint capsule and the formation of tophi. These tophi are usually large, with subcutaneous bone resorption and erosion, with or without cartilage destruction. However, extensive edema appeared in the soft tissue around the tophi, but the edema only produced pressure without any obvious signs of soft tissue infiltration, which may be distinguished from the joint tumor. In addition, the gout incidence rate is increased in young patients. Therefore, when the patient has a large joint mass, it is important to confirm whether there is a history of gout.

Gout-like hands.

A 65-year-old man presented to our hospital with a 1-year history of multiple nodules on his arms and hands without itching or pain.

Miliarial gout: Clinical case and a brief review.

Miliarial gout is a rare clinical variant of chronic tophaceous gout characterised by tiny milia-like papules containing chalky tophaceous material. In this report, we present a case of miliarial gout in a patient with known history of gouty arthritis and review the reported cases of miliarial gout in the literature to discuss its characteristics, diagnosis and treatment.

Taxonomic variations in the gut microbiome of gout patients with and without tophi might have a functional impact on urate metabolism.

OBJECTIVE: To evaluate the taxonomic composition of the gut microbiome in gout patients with and without tophi formation, and predict bacterial functions that might have an impact on urate metabolism. METHODS: Hypervariable V3-V4 regions of the bacterial 16S rRNA gene from fecal samples of gout patients with and without tophi (n = 33 and n = 25, respectively) were sequenced and compared to fecal samples from 53 healthy controls. We explored predictive functional profiles using bioinformatics in order to identify differences in taxonomy and metabolic pathways. RESULTS: We identified a microbiome characterized by the lowest richness and a higher abundance of Phascolarctobacterium, Bacteroides, Akkermansia, and Ruminococcus_gnavus_group genera in patients with gout without tophi when compared to controls. The Proteobacteria phylum and the Escherichia-Shigella genus were more abundant in patients with tophaceous gout than in controls. Fold change analysis detected nine genera enriched in healthy controls compared to gout groups (Bifidobacterium, Butyricicoccus, Oscillobacter, Ruminococcaceae_UCG_010, Lachnospiraceae_ND2007_group, Haemophilus, Ruminococcus_1, Clostridium_sensu_stricto_1, and Ruminococcaceae_UGC_013). We found that the core microbiota of both gout groups shared Bacteroides caccae, Bacteroides stercoris ATCC 43183, and Bacteroides coprocola DSM 17136. These bacteria might perform functions linked to one-carbon metabolism, nucleotide binding, amino acid biosynthesis, and purine biosynthesis. Finally, we observed differences in key bacterial enzymes involved in urate synthesis, degradation, and elimination. CONCLUSION: Our findings revealed that taxonomic variations in the gut microbiome of gout patients with and without tophi might have a functional impact on urate metabolism.

CD38 activation by monosodium urate crystals contributes to inflammatory responses in human and murine macrophages.

Cluster of differentiation (CD) 38, a major enzyme for nicotinamide adenine dinucleotide (NAD+) degradation, plays a key role in inflammation. Meanwhile, intracellular NAD+ decline is also associated with inflammatory responses. However, whether CD38 activation is involved in gouty inflammation has not been elucidated. The present study aimed to clarify the role of CD38 in monosodium urate crystals (MSU)-triggered inflammatory responses. The results showed that MSU crystals increased the protein expression of CD38 in time- and concentration-dependent manner in THP-1 macrophages and mouse bone marrow-derived macrophages (BMDMs). Moreover, intracellular NAD+ levels were reduced by MSU crystals along with the increased IL-1ß release. However, CD38 inhibition by 78c elevated intracellular NAD+ levels and suppressed IL-1ß release in MSU crystals-treated THP-1 macrophages and BMDMs. Interestingly, CD38 inhibition without significant elevation of intracellular NAD+ also decreased IL-1ß release driven by MSU crystals in THP-1 macrophages. In conclusion, the present study revealed that MSU crystals could activate CD38 with the ensuing intracellular NAD+ decline to promote inflammatory responses in THP-1 macrophages and BMDMs, while CD38 inhibition could suppress MSU crystals-triggered inflammatory responses, indicating that CD38 is a potential therapeutic target for gout.

Trans-ancestral dissection of urate- and gout-associated major loci SLC2A9 and ABCG2 reveals primate-specific regulatory effects.

Gout is a complex inflammatory arthritis affecting ~20% of people with an elevated serum urate level (hyperuricemia). Gout and hyperuricemia are essentially specific to humans and other higher primates, with varied prevalence across ancestral groups. SLC2A9 and ABCG2 are major loci associated with both urate and gout in multiple ancestral groups. However, fine mapping has been challenging due to extensive linkage disequilibrium underlying the associated regions. We used trans-ancestral fine mapping integrated with primate-specific genomic information to address this challenge. Trans-ancestral meta-analyses of GWAS cohorts of either European (EUR) or East Asian (EAS) ancestry resulted in single-variant resolution mappings for SLC2A9 (rs3775948 for urate and rs4697701 for gout) and ABCG2 (rs2622621 for gout). Tests of colocalization of variants in both urate and gout suggested existence of a shared candidate causal variant for SLC2A9 only in EUR and for ABCG2 only in EAS. The fine-mapped gout variant rs4697701 was within an ancient enhancer, whereas rs2622621 was within a primate-specific transposable element, both supported by functional evidence from the Roadmap Epigenomics project in human primary tissues relevant to urate and gout. Additional primate-specific elements were found near both loci and those adjacent to SLC2A9 overlapped with known statistical epistatic interactions associated with urate as well as multiple super-enhancers identified in urate-relevant tissues. We conclude that by leveraging ancestral differences trans-ancestral fine mapping has identified ancestral and functional variants for SLC2A9 or ABCG2 with primate-specific regulatory effects on urate and gout.

Neutrophil extracellular traps release in gout and pseudogout depends on the number of crystals regardless of leukocyte count.

OBJECTIVES: Microcrystal-induced arthritis is still an unresolved paradigm for medicine. Overt inflammation may be absent even when crystals occur in SF. Recently, the production of neutrophil extracellular traps (NETs) embedding MSU crystals has been proposed as a possible mechanism of the auto-resolution of the inflammatory phase during gout. We aimed to verify and quantify the release of NETs in SFs during gout and pseudogout attacks and to compare any differences with respect to crystals and neutrophils number, and to analyse activation of necroptosis pathway in SF from crystal-induced arthritis. METHODS: SF samples were obtained by arthrocentesis from 22 patients presenting acute crystal-induced arthritis, gout or pseudogout (n = 11 each group), and from 10 patients with acute non-crystal arthritis as controls. NETosis was quantified in SF by nucleic acid stain and by quantification of human neutrophil elastase. Activation of phosphorylated MLKL was assessed by western blot. RESULTS: We observed that SF neutrophils encountering MSU and CPPD crystals during episodes of gout and pseudogout release NETs in relation to the number of crystals in SF and irrespective of neutrophil density and type of crystal. This release was accompanied by necroptosis through the activation of the MLKL pathway. CONCLUSIONS: Our findings suggest that a role of NETs in crystal-induced arthritis is to 'trap extracellular particles', including microcrystals. Embedding crystals in aggregates of NETs may be the basis of tophi and CPPD deposition, and may have implications for disease evolution rather than for spontaneous resolution of the acute attack.

Crystal deposition measured with dual-energy computed tomography: association with mortality and cardiovascular risks in gout.

OBJECTIVES: To determine whether the volume of monosodium urate (MSU) crystal deposition measured with dual-energy CT (DECT) is predictive of short-term mortality and development of cardiovascular comorbidities and diabetes mellitus. METHODS: Patients with a diagnosis of gout having had baseline DECT scans of their knees and feet to measure the volume of MSU crystal deposition were included to undergo a follow-up visit. Risk factors for mortality and a composite variable (onset of any cardio-metabolic event) were examined using multivariable Cox models. RESULTS: A total of 128 patients aged 66.1 (14.0) years with gout durations of 11.4 (10.4) years were included; most were naïve of urate lowering therapy (61.7%), with a follow-up visit at 24 (12, 36) months. Baseline serum urate (SU) level was 7.44 (2.29) mg/dl and DECT volume of MSU crystals was 0.2 (0, 0.9) cm3. A total of 14 patients died during follow-up, 6/14 from a cardiovascular cause, and 17 patients presented a new cardio-metabolic comorbidity. Factors associated with mortality risk were baseline DECT volume of MSU crystals [hazard ratio (HR) 1.02, 95% CI: 1.002, 1.03] and baseline SU level (HR 1.04, 95% CI: 1.003, 1.06). DECT volume of MSU crystals was the only factor associated with the onset of cardio-metabolic comorbidities with a HR of 1.014 (95% CI: 1.001, 1.03). CONCLUSIONS: Volume of MSU crystals measured with DECT is a biomarker for the risk of developing new cardio-metabolic diseases and for all-cause mortality.

Therapeutic potential of the FPR2/ALX agonist AT-01-KG in the resolution of articular inflammation.

The resolution of inflammation is a dynamic process, characterized by the biosynthesis of pro-resolving mediators, including the lipid Lipoxin A4 (LXA4). LXA4 acts on the N-formyl peptide receptor 2 (FPR2/ALX) to mediate anti-inflammatory and pro-resolving effects. In order to exploit the therapeutic potential of endogenous LXA4 in the context of inflammation we have recently developed synthetic LXA4 mimetics (sLXms) including a dimethyl-imidazole-containing FPR2/ALX agonist designated AT-01-KG. Here, we have investigated the effect of treatment with AT-01-KG in established models of articular inflammation. In a model of gout, mice were injected with MSU crystals and treated with AT-01-KG at the peak of inflammatory response. The treatment decreased the number of neutrophils in the knee exudate, an effect which was accompanied by low levels of myeloperoxidase, CXCL1 and IL-1ß in periarticular tissue. AT-01-KG treatment led to reduced tissue damage and hypernociception. The effects of AT-01-KG on neutrophil accumulation were not observed in MSU treated FPR2/3-/-mice. Importantly, AT-01-KG induced resolution of articular inflammation by increasing neutrophil apoptosis and subsequent efficient efferocytosis. In a model of antigen-induced arthritis, AT-01-KG treatment also attenuated inflammatory responses. These data suggest that AT-01-KG may be a potential new therapy for neutrophilic inflammation of the joints.