Mechanism of macrophages in gout: Recent progress and perspective.

Gout represents an autoinflammatory disorder instigated by monosodium urate crystals. Its primary manifestation involves the recruitment of diverse immune cell populations, including neutrophils and macrophages. Macrophages assume a pivotal role in the initiation of acute gouty inflammation and subsequent inflammatory cascades. However, recent investigations have revealed that the impact of macrophages on gout is nuanced, extending beyond a solely detrimental influence. Macrophages, characterized by different subtypes, exhibit distinct functionalities that either contribute to the progression or regression of gout. A strategy aimed at modulating macrophage polarization, rather than merely inhibiting inflammation, holds promise for enhancing the efficacy of acute gout treatment. This review centres on elucidating potential mechanisms underlying macrophage polarization in the onset and resolution of gouty inflammation, offering novel insights into the immune equilibrium of macrophages in the context of gout.

Deficiency of histone deacetylases 3 in macrophage alleviates monosodium urate crystals-induced gouty inflammation in mice.

BACKGROUND: Gout is caused by monosodium urate (MSU) crystals deposition to trigger immune response. A recent study suggested that inhibition of Class I Histone deacetylases (HDACs) can significantly reduce MSU crystals-induced inflammation. However, which one of HDACs members in response to MSU crystals was still unknown. Here, we investigated the roles of HDAC3 in MSU crystals-induced gouty inflammation. METHODS: Macrophage specific HDAC3 knockout (KO) mice were used to investigate inflammatory profiles of gout in mouse models in vivo, including ankle arthritis, foot pad arthritis and subcutaneous air pouch model. In the in vitro experiments, bone marrow-derived macrophages (BMDMs) from mice were treated with MSU crystals to assess cytokines, potential target gene and protein. RESULTS: Deficiency of HDAC3 in macrophage not only reduced MSU-induced foot pad and ankle joint swelling but also decreased neutrophils trafficking and IL-1ß release in air pouch models. In addition, the levels of inflammatory genes related to TLR2/4/NF-κB/IL-6/STAT3 signaling pathway were significantly decreased in BMDMs from HDAC3 KO mice after MSU treatment. Moreover, RGFP966, selective inhibitor of HDAC3, inhibited IL-6 and TNF-α production in BMDMs treated with MSU crystals. Besides, HDAC3 deficiency shifted gene expression from pro-inflammatory macrophage (M1) to anti-inflammatory macrophage (M2) in BMDMs after MSU challenge. CONCLUSIONS: Deficiency of HDAC3 in macrophage alleviates MSU crystals-induced gouty inflammation through inhibition of TLR2/4 driven IL-6/STAT3 signaling pathway, suggesting that HDAC3 could contribute to a potential therapeutic target of gout.

The Clinical Significance of Serum Interleukin-36α Levels in Patients with Gout.

BACKGROUND: Gout is a chronic inflammatory diseases caused by monosodium urate crystal deposition. However, the role of interleukin (IL)-36 in gout has not dbeen elucidated. METHODS: We enrolled 75 subjects, including 20 healthy controls (HC), 30 patients with acute gout attack and 25 patients in remission. Baseline data were obtained through clinical interrogation and laboratory data were obtained through tests of blood samples. Serum levels of IL-36α were detected using enzyme-linked immunosorbent assay. Spearman correlation analysis was used to investigate the correlation of IL-36α with other parameters. The diagnostic value of IL-36α was demonstrated using a receiver operating characteristic curve. RESULTS: The serum IL-36α level of gout patients in acute attack and remission stage was significantly higher than that of HC. Serum IL-36α was positively correlated with alanine transaminase (ALT) and aspartate transaminase (AST). Serum amyloid A (SAA) levels positively correlated with C-reactive protein levels and erythrocyte sedimentation rates. Glutamyl transpeptidase levels positively correlated with AST and ALT levels. CONCLUSION: In conclusion, serum IL-36α levels were elevated in patients with gout and correlated with the clinical markers of inflammation. Our findings suggest that IL-36α may be a novel inflammatory indicator for gout.

Crystal structure of the complex of CLEC12A and an antibody that interferes with binding of diverse ligands.

C-type lectin receptors (CLRs) are a family of pattern recognition receptors, which detect a broad spectrum of ligands via small carbohydrate-recognition domains (CRDs). CLEC12A is an inhibitory CLR that recognizes crystalline structures such as monosodium urate crystals. CLEC12A also recognizes mycolic acid, a major component of mycobacterial cell walls, and suppresses host immune responses. Although CLEC12A could be a therapeutic target for mycobacterial infection, structural information on CLEC12A was not available. We report here the crystal structures of human CLEC12A (hCLEC12A) in ligand-free form and in complex with 50C1, its inhibitory antibody. 50C1 recognizes human-specific residues on the top face of hCLEC12A CRD. A comprehensive alanine scan demonstrated that the ligand-binding sites of mycolic acid and monosodium urate crystals may overlap with each other, suggesting that CLEC12A utilizes a common interface to recognize different types of ligands. Our results provide atomic insights into the blocking and ligand-recognition mechanisms of CLEC12A and leads to the design of CLR-specific inhibitors.

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.

Gouty arthritis involves impairment of autophagic degradation via cathepsin D inactivation-mediated lysosomal dysfunction that promotes apoptosis in macrophages.

This study examined autophagy-lysosome pathway (ALP) perturbations in synovial monocytes/macrophages from patients with gouty arthritis (GA) and the associations of ALP perturbations with cell death. Synovial fluid mononuclear cells (SFMCs) and synovial tissues (STs) from patients with GA, as well as monosodium urate (MSU) crystal-exposed macrophages, underwent immunoblotting, quantitative polymerase chain reaction, and immunofluorescence analyses of markers linked to the ALP (microtubule-associated protein 1 light chain 3B [LC3B], p62, cathepsin D [CTSD], and lysosome-associated membrane protein 2 [LAMP2]) and cell death (caspase-3). GA STs underwent immunohistochemistry and immunofluorescence analyses to determine the distributions of LC3B-positive autophagosomes and macrophages. GA SFMCs and STs exhibited impaired autophagic degradation, indicated by elevated levels of LC3B and p62, along with CTSD upregulation and caspase-3 activation. Macrophages from GA STs exhibited significant accumulation of LC3B-positive autophagosomes. The temporal effects of MSU crystals on the ALP and the associations of these effects with cell death were investigated using a macrophage model of GA. MSU crystal-exposed macrophages exhibited early (2 h) autophagosome formation but later (6-24 h) autophagic flux impairment, demonstrated by p62 accumulation, lysosomal inhibitor failure to increase LC3B accumulation, and LC3B colocalization with p62. These macrophages exhibited autophagic flux impairment because of CTSD inactivation-mediated lysosomal dysfunction, which caused immature CTSD to accumulate within damaged LAMP2-positive lysosomes. This accumulation coincided with caspase-3-dependent cell death (24 h) that was unaffected by CTSD inhibition. These findings indicate that GA involves MSU crystal-induced impairment of autophagic degradation via CTSD inactivation-mediated lysosomal dysfunction, which promotes apoptosis in macrophages.

Novel perception of neutrophil extracellular traps in gouty inflammation.

The self-limiting nature of the inflammatory flare is a feature of gout. The effects of neutrophil extracellular traps (NETs) on gout have remarkably attracted researchers' attention. Aggregated NETs promote the resolution of gouty inflammation by packing monosodium urate (MSU) crystals, degrading cytokines and chemokines, and blocking neutrophil recruitment and activation. Deficiency of NETs aggravates experimental gout. Thus, aggregated NETs are assumed to be a possible mechanism for the spontaneous resolution of gout. It is feasible to envisage therapeutic strategies for targeting NETosis (NET formation process) in gout. However, recent studies have demonstrated that levels of NETs are not associated with disease activity and inflammation in human gout. Moreover, the process of MSU crystal trapping is not affected in the absence of neutrophils. This review has concentrated on the mechanisms and associations between NETs and gout.

Osteogenic Potential of Monosodium Urate Crystals in Synovial Mesenchymal Stem Cells.

Background and Objectives: Deposits of monosodium urate (MSU) crystals due to increased levels of uric acid (UA) have been associated with bone formation and erosion, mainly in patients with chronic gout. The synovial membrane (SM) comprises several types of cells, including mesenchymal stem cells (SM-MSCs); however, it is unknown whether UA and MSU induce osteogenesis through SM-MSCs. Materials and Methods: Cultures of SM were immunotyped with CD44, CD69, CD90, CD166, CD105, CD34, and CD45 to identify MSCs. CD90+ cells were isolated by immunomagnetic separation (MACS), colony-forming units (CFU) were identified, and the cells were exposed to UA (3, 6.8, and 9 mg/dL) and MSU crystals (1, 5, and 10 µg/mL) for 3 weeks, and cellular morphological changes were evaluated. IL-1ß and IL-6 were determined by ELISA, mineralization was assessed by alizarin red, and the expression of Runx2 was assessed by Western blot. Results: Cells derived from SM and after immunomagnetic separation were positive for CD90 (53 ± 8%) and CD105 (52 ± 18%) antigens, with 53 ± 5 CFU identified. Long-term exposure to SM-MSCs by UA and MSU crystals did not cause morphological damage or affect cell viability, nor were indicators of inflammation detected. Mineralization was observed at doses of 6.8 mg/dL UA and 5 µg/mL MSU crystals; however, the differences were not significant with respect to the control. The highest dose of MSU crystals (10 µg/mL) induced significant Runx2 expression with respect to the control (1.4 times greater) and SM-MSCs cultured in the osteogenic medium. Conclusions: MSU crystals may modulate osteogenic differentiation of SM-MSCs through an increase in Runx2.

Bactericidal/Permeability-Increasing Protein Downregulates the Inflammatory Response in In Vivo Models of Arthritis.

We investigated the effects of bactericidal/permeability-increasing protein (BPI) alone or in combination with hyaluronic acid (HA) in two animal models: collagen-induced arthritis (CIA) and crystal-induced inflammation. In CIA, mice were intraperitoneally injected with PBS, HA, or BPI plus or minus HA, twice a week for 2 months, and then euthanized to collect paw and blood. Arthritis was assessed in ankle joints by clinical and histological evaluation. Pathogenic crystals were intraperitoneally injected in mice plus or minus BPI, or with a composition of BPI and HA. After sacrifice, total and differential leukocyte counts were determined. Cytokine levels were measured in serum and peritoneal fluids. In CIA mice, BPI improved clinical and histological outcomes (histological scores ≥2-fold), and downregulated inflammatory mediators (47-93%). In crystal-induced inflammation, BPI reduced leukocyte infiltration (total count: ≥60%; polymorphonuclear cells: ≥36%) and inhibited cytokine production (35-74%). In both models, when mice were co-treated with BPI and HA, the improvement of all parameters was greater than that observed after administration of the two substances alone. Results show that BPI attenuates CIA and inflammation in mice, and this effect is enhanced by HA co-administration. Combined use of BPI and HA represents an interesting perspective for new potential treatments in arthritis.

Angiotensin type 2 receptor antagonism as a new target to manage gout.

BACKGROUND: There is a growing search for therapeutic targets in the treatment of gout. The present study aimed to evaluate the analgesic and anti-inflammatory potential of angiotensin type 2 receptor (AT2R) antagonism in an acute gout attack mouse model. METHODS: Male wild-type (WT) C57BL/6 mice either with the AT2R antagonist, PD123319 (10 pmol/joint), or with vehicle injections, or AT2R KO mice, received intra-articular (IA) injection of monosodium urate (MSU) crystals (100 µg/joint), that induce the acute gout attack, and were tested for mechanical allodynia, thermal hyperalgesia, spontaneous nociception and ankle edema development at several times after the injections. To test an involvement of AT2R in joint pain, mice received an IA administration of angiotensin II (0.05-5 nmol/joint) with or without PD123319, and were also evaluated for pain and edema development. Ankle joint tissue samples from mice undergoing the above treatments were assessed for myeloperoxidase activity, IL-1ß release, mRNA expression analyses and nitrite/nitrate levels, 4 h after injections. RESULTS: AT2R antagonism has robust antinociceptive effects on mechanical allodynia (44% reduction) and spontaneous nociception (56%), as well as anti-inflammatory effects preventing edema formation (45%), reducing myeloperoxidase activity (54%) and IL-1ß levels (32%). Additionally, Agtr2tm1a mutant mice have largely reduced painful signs of gout. Angiotensin II administration causes pain and inflammation, which was prevented by AT2R antagonism, as observed in mechanical allodynia 4 h (100%), spontaneous nociception (46%), cold nociceptive response (54%), edema formation (83%), myeloperoxidase activity (48%), and IL-1ß levels (89%). PD123319 treatment also reduces NO concentrations (74%) and AT2R mRNA levels in comparison with MSU untreated mice. CONCLUSION: Our findings show that AT2R activation contributes to acute pain in experimental mouse models of gout. Therefore, the antagonism of AT2R may be a potential therapeutic option to manage gout arthritis.

The Clinical Utility of Dual-Energy Computed Tomography in the Diagnosis of Gout-A Cross-Sectional Study.

Dual-energy computed tomography (DECT) is an imaging technique that detects monosodium urate (MSU) deposits. This study aimed to assess the clinical utility of DECT in the diagnosis of gout. A total of 120 patients with clinical suspicion of gout who underwent DECT were retrospectively enrolled. The sensitivity and specificity of DECT alone, American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) classification criteria without DECT, and ACR/EULAR criteria with DECT were assessed. Additionally, an analysis of gout risk factors was performed. When artifacts were excluded, any MSU volume provided the best diagnostic value of DECT (AUC = 0.872, 95% CI 0.806−0.938). DECT alone had a sensitivity of 90.4% and specificity of 74.5%. Although ACR/EULAR criteria without DECT provided better diagnostic accuracy than DECT alone (AUC = 0.926, 95% CI 0.878−0.974), the best value was obtained when combing both (AUC = 0.957, 95% CI 0.924−0.991), with 100% sensitivity and 76.6% specificity. In univariate analysis, risk factors for gout were male sex, presence of tophi, presence of MSU deposits on DECT, increased uric acid in serum (each p < 0.001), and decreased glomerular filtration rate (GFR) (p = 0.029). After logistic regression, only increased serum uric acid (p = 0.034) and decreased GFR (p = 0.018) remained independent risk factors for gout. Our results suggest that DECT significantly increases the sensitivity of the ACR/EULAR criteria in the diagnosis of gout.

The Inhibition of Osteoblast Viability by Monosodium Urate Crystal-Stimulated Neutrophil-Derived Exosomes.

Background and Objective: Bone erosion is common in patients with gout. The role of neutrophil-derived exosomes in gouty bone erosion remains elusive. This study aimed to investigate the functions of the neutrophil-derived exosomes in the development of bone erosion in gout. Methods: Neutrophil-derived exosomes were collected and assessed by transmission electron microscopy and nanoparticle tracking analysis. Cell counting kit-8 assay was applied to evaluate cell viability, and cell apoptosis was assessed by flow cytometry. In addition, quantitative Real-time PCR and Western blotting were used to determine the expression levels of alkaline phosphatase (ALP), osteoprotegerin (OPG), and receptor activator of nuclear factor-κB ligand (RANKL). Neutrophil-derived exosomes were tagged with PKH67. The miRNA expression profiles of exosomes and human fetal osteoblasts (hFOB) were compared using high-throughput sequencing. Functional miRNAs transfected into hFOB after co-incubation with exosomes were selected and validated by preliminary qPCR. Results: Neutrophil-derived exosomes were stimulated by monosodium urate (MSU). The exosomes could inhibit the viability of the hFOB, and the expression levels of ALP and OPG were down-regulated, while the expression level of RANKL was up-regulated. However, there was no significant difference in the viability of osteoclasts and the expression of nuclear factor of activated T cells 1. Exosomes were observed in the cytoplasm under a confocal microscopy, confirming that exosomes could be taken up by hFOB. In total, 2590 miRNAs were found, of which 47 miRNAs were differentially expressed. Among the delivered miRNAs, miR-1246 exhibited the highest level of differential expression. The viability of hFOB was reduced by miR-1246 mimics and increased by miR-1246 inhibitors. There was no significant difference in hFOB apoptosis rate between the miR-1246 mimic and miR-1246 inhibitor group. MiR-1246 overexpression decreased the expression levels of ALP and OPG, whereas increasing the expression level of RANKL. In contrast, miR-1246 inhibitor increased the expression levels of ALP and OPG, while decreasing the expression level of RANKL. Neutrophil-derived exosomes stimulated by MSU could increase the expression of miR-1246. Conclusion: Neutrophil-derived exosomes stimulated by MSU could inhibit the viability of osteoblasts.

Case Report: Articular Gout in Four Dogs and One Cat.

Background: There is widespread prejudice in veterinary medicine that gout does not occur in non-human mammalians. However, we recently discovered monosodium urate crystals in the synovial fluid obtained from a few dogs and a cat. Since it is the definitive and gold standard to diagnose gout, we report these cases as newly emerging diseases in companion animals. Case Presentation: Four dogs and one cat were presented at our hospital because of lameness due to an unknown cause. Even after the routine examinations, including radiographic imaging, laboratory examination, and arthrocentesis, we were unable to find a clear cause of polyarthritis. However, we later discovered monosodium urate crystals in the synovial fluid of the animals, confirmed by polarized microscopy. In one of the two dogs treated with immunosuppressants, the disease relapsed, and the other did not show any symptoms for 3 months. The other two dogs were treated with xanthine oxidase inhibitor, where one died, and the other did not show any symptoms for 3 years. The cat was treated with drainage and intra-articular dexamethasone injection, but the disease recurred after 6 months. Conclusion: This is the first report to confirm that articular gout can occur in dogs and cats. Care must be taken not to neglect needle-shaped materials in the synovial fluid. Gout should also be included in the differential diagnosis of arthritis and further research is needed in these animals.

Carvacrol Alleviates Hyperuricemia-Induced Oxidative Stress and Inflammation by Modulating the NLRP3/NF-κB Pathwayt.

Purpose: Gouty arthritis is generally induced by the accumulation of monosodium urate (MSU) crystals in the joints due to elevated serum uric acid levels, potentially leading to serious pathological disorders such as nephrolithiasis, renal failure, and acute gouty arthritis. In this study, we aimed to validate the anti-gout effects of carvacrol, a phenolic monoterpene. Materials and Methods: Male Sprague-Dawley rats were divided into normal saline, disease group by injecting potassium mono-oxonate (PO) at a dose of 250 mg/kg, and three treatment groups, either with carvacrol 20 mg/kg or 50 mg/kg and 10 mg/kg allopurinol. The blood and tissue samples were subsequently collected and analyzed using different biochemical and histopathological techniques. Results: Our results revealed a significant increase in the serum levels of oxidative stress-related markers, namely, uric acid and C-reactive protein (CRP), and NLRP3 inflammasome-dependent inflammatory mediators, including nuclear factor kappa B (NF-κB) and tumor necrosis factor-alpha (TNF-α). Carvacrol administration for seven consecutive days exhibited significant anti-hyperuricemic and anti-inflammatory effects in a dose-dependent manner. Notably, the 50 mg/kg carvacrol treatment was observed to produce results similar to the allopurinol treatment. Furthermore, the renal safety of carvacrol was confirmed by the renal function test. Conclusion: Carvacrol potentially alleviates hyperuricemia-induced oxidative stress and inflammation by regulating the ROS/NRLP3/NF-κB pathway, thereby exerting protective effects against joint degeneration.

Anti-inflammatory and Antioxidant Effect of Poly-gallic Acid (PGAL) in an In Vitro Model of Synovitis Induced by Monosodium Urate Crystals.

Gout is a chronic and degenerative disease that affects the joints and soft tissues because of the crystalline deposit of monosodium urate. The interaction between monosodium urate crystals (MSU) and synoviocytes generates oxidative and inflammatory states. These physiological characteristics have promoted the study of poly-gallic acid (PGAL), a poly-oxidized form of gallic acid reported to be effective in in vitro models of inflammation. The effect of PGAL in an in vitro model of oxidation and synovial inflammation induced by MSU was evaluated after 24 h of stimulation through the morphological changes, the determination of oxidative stress (OS), IL-1ß, and the phagocytosis of the MSU. A 20% reduction in synovial viability and the generation of vesicles were observed when they were exposed to MSU. When PGAL was used at 100 and 200 µg/ml, cell death was reduced by 30% and 17%, respectively. PGAL both doses reduce the vesicles generated by MSU. OS generation in synoviocytes exposed to 100 µg/ml and 200 µg/ml PGAL decreased by 1.28 and 1.46 arbitrary fluorescence units (AFU), respectively, compared to the OS in synoviocytes exposed to MSU (1.9 AFU). PGAL at 200 µg/ml inhibited IL-1ß by 100%, while PGAL at 100 µg/ml inhibited IL-1ß by 66%. The intracellular MSU decreased in synoviocytes stimulated with 100 µg/ml PGAL. The PGAL has a cytoprotective effect against damage caused by MSU in synoviocytes and can counteract the oxidative and inflammatory response induced by the crystals probably because it exerts actions at the membrane level that prevent phagocytosis of the crystals.

Influence of Pinealectomy and Long-term Melatonin Administration on Inflammation and Oxidative Stress in Experimental Gouty Arthritis.

Gout is an inflammatory arthritis characterized by the deposition of monosodium urate (MSU) crystals in the joints or soft tissue. MSU crystals are potent inflammation inducers. Melatonin (MLT) is a powerful endogenous anti-inflammatory agent and effective in reducing cellular damage. In the present study, possible underlying mechanisms associated with anti-inflammatory and antioxidative effects were investigated in rats with gouty arthritis and melatonin deprivation treated with MLT. Fifty-six rats were divided into seven groups: control, sham control, pinealectomy (PNX), MSU (on the 30th day, single-dose 20 mg/ml, intraperitoneal), MSU + MLT (10 mg/kg/day for 30 days, intraperitoneal), MSU + PINX and MSU + PINX + MLT. PNX procedure was performed on the first day of the study. As compared to the controls, the results showed that MSU administration caused significant increases in oxidative stress parameters (malondialdehyde and total oxidant status). Besides, significant decreases in antioxidant defense systems (glutathione, superoxide dismutase and total antioxidant status) were observed. A statistically significant increase was found in the mean histopathological damage score in the groups that received MSU injection. It was found that histopathological changes were significantly reduced in the MSU + MLT group given MLT. In our study, it was determined that many histopathological changes, as well as swelling and temperature increase in the joint, which are markers of inflammation, were significantly reduced with MLT supplementation. These results suggest that melatonin ameliorates MSU-induced gout in the rat through inhibition of oxidative stress and proinflammatory cytokine production.

Gout-associated monosodium urate crystal-induced necrosis is independent of NLRP3 activity but can be suppressed by combined inhibitors for multiple signaling pathways.

Monosodium urate (MSU) crystals, the etiological agent of gout, are formed in joints and periarticular tissues due to long-lasting hyperuricemia. Although MSU crystal-triggered NLRP3 inflammasome activation and interleukin 1ß (IL-1ß) release are known to have key roles in gouty arthritis, recent studies revealed that MSU crystal-induced necrosis also plays a critical role in this process. However, it remains unknown what forms of necrosis have been induced and whether combined cell death inhibitors can block such necrosis. Here, we showed that MSU crystal-induced necrosis in murine macrophages was not dependent on NLRP3 inflammasome activation, as neither genetic deletion nor pharmacological blockade of the NLRP3 pathway inhibited the necrosis. Although many cell death pathways (such as ferroptosis and pyroptosis) inhibitors or reactive oxygen species inhibitors did not have any suppressive effects, necroptosis pathway inhibitors GSK'872 (RIPK3 inhibitor), and GW806742X (MLKL inhibitor) dose-dependently inhibited MSU crystal-induced necrosis. Moreover, a triple combination of GSK'872, GW806742X, and IDN-6556 (pan-caspase inhibitor) displayed enhanced inhibition of the necrosis, which was further fortified by the addition of MCC950 (NLRP3 inhibitor), suggesting that multiple cell death pathways might have been triggered by MSU crystals. Baicalin, a previously identified inhibitor of NLRP3, inhibited MSU crystal-induced inflammasome activation and suppressed the necrosis in macrophages. Besides, baicalin gavage significantly ameliorated MSU crystal-induced peritonitis in mice. Altogether, our data indicate that MSU crystals induce NLRP3-independent necrosis, which can be inhibited by combined inhibitors for multiple signaling pathways, highlighting a new avenue for the treatment of gouty arthritis.

Dual-energy Computed Tomography for the Diagnosis of Acute Gouty Arthritis.

AIMS: To investigate the diagnostic value of Dual-energy Computed Tomography (DECT) in Acute Gouty Arthritis (AGA) or patients presenting suspected gouty arthritis. METHODS: This retrospective study was performed in a single centre from May 2017 to August 2018. Two hundred and twenty-six patients with an initial diagnosis of AGA in the preceding 15 days were included. All patients were referred for a DECT scan of the affected joints. The diagnosis criteria of gout with the American College of Rheumatology Classification Standard were regarded as the reference standard. RESULTS: After filtration, two hundred patients were included in the present study. The sensitivity, specificity, positive predictive value, and negative predictive value of DECT in the diagnosis of all AGA were 83.83%, 60.61%, 91.5%, and 42.55%, respectively. When AGA was subdivided according to the joint site, the sensitivity, specificity, positive predictive value, and negative predictive value were 80.68%, 61.11%, 91.03%, and 39.29% in feet, 93.55%, 40%, 93.55%, and 40% in knees and 87.5%, 71.43%, 91.3%, and 62.5% in ankles, respectively. CONCLUSION: DECT had a high sensitivity for the diagnosis of AGA. However, the specificity was limited, particularly for the diagnosis of acute gouty knee arthritis. Prospective multicenter studies of large samples will enhance the application of DECT among AGA patients in the future.

Appraisal of anti-gout potential of colchicine-loaded chitosan nanoparticle gel in uric acid-induced gout animal model.

Present study is aimed at transdermal delivery of colchicine-loaded chitosan nanoparticles. The nanoformulations were prepared utilising spontaneous emulsification method and optimised through 23 factorial designs. The optimised formulation (CHNP-OPT) displayed an average particle size of 294 ± 3.75 nm, entrapment efficiency 92.89 ± 1.1% and drug content 83.45 ± 2.5%, respectively. In vitro release study demonstrated 89.34 ± 2.90% release over a period of 24 h. Further, CHNP-OPT incorporated into HPMC-E4M (hydroxypropyl methylcellulose) to form transdermal gel. CHNPgel displayed 74.65 ± 1.90% permeation and stability over a period of 90 days. The anti-gout potential of CHNPgel formulation was evaluated in vivo against monosodium urate (MSU) crystal-induced gout in animal model. There was significant reduction in uric acid level, during MSU administration, when compared with the conventional gel of colchicine. The enhanced therapeutic potential was witnessed through X-ray. The study revealed that colchicine-loaded CHNPgel proved their supremacy over plain colchicine and can be an efficient delivery system for gout treatment.