Search Results (113)

Prior research suggests a connection between osteoarthritis and gout at sites commonly affected by gouty attacks. Whether this connection exists at sites with known monosodium urate crystal deposition but less commonly affected by gouty attacks, such as the lumbosacral spine, has not been previously investigated. We assessed whether lumbosacral osteoarthritis is more prevalent and more severe in subjects with gout compared with controls, and whether lumbosacral osteoarthritis is associated with higher levels of spinal monosodium urate deposition. Fifty gout subjects and 25 controls underwent dual-energy computed tomography imaging of the lumbosacral spine. We assessed lumbosacral osteoarthritis using a modification of a validated computed tomography scoring system, incorporating grade of intervertebral disc narrowing and facet joint osteoarthritis, and presence of spondylolysis and spondylolisthesis. We quantified spinal monosodium urate deposition using the default post-processing algorithm, plus a maximally specific algorithm to exclude potential artefacts. Forty-six gout subjects and 25 controls, average age 62 years, were included in the final analysis. Both gout and control subjects exhibited high rates of facet joint osteoarthritis and degenerative disc disease, with no difference in prevalence or severity between groups. Gout subjects did not have differing prevalence of spondylolysis and spondylolisthesis vs. controls. Subjects with lumbosacral osteoarthritis did not have higher levels of spinal monosodium urate deposition. Overall, lumbosacral osteoarthritis was not more prevalent or more severe in gout patients compared with controls, and spinal monosodium urate crystal deposition did not differ between patients with and without lumbosacral osteoarthritis. Full article

Gout is the most common form of inflammatory arthritis in men, driven by hyperuricemia and the deposition of monosodium urate (MSU) crystals. The innate immune response to these crystals leads to acute inflammatory episodes, called flares, characterized by intense joint pain, swelling, and temporary disability. Although gout flares are self-limiting, they impose a considerable burden on patients’ quality of life and contribute to increased healthcare utilization. A detailed understanding of the inflammatory processes triggered by MSU crystals is critical for developing targeted therapies to prevent and manage flares effectively. This review provides an overview of experimental models used to study the inflammatory phase of gout, with a focus on both in vivo and in vitro models of MSU crystal-induced inflammation. We concentrate on models that reproduce the acute inflammatory response following MSU crystal deposition, including the air pouch, intraarticular injection, and peritonitis rodent models, alongside the larval zebrafish model. In addition, we discuss in vitro approaches using primary immune cells and cell lines. We discuss the strengths, limitations, and translational relevance of these models and highlight some examples of how they have contributed to our understanding of the etiology of gout. Of note, models of hyperuricemia are not included here as these have been extensively reviewed elsewhere. Full article

Background: Inonotus obliquus (Chaga), a medicinal and edible macrofungus abundant in bioactive polyphenols, is a potential source of natural antioxidants and anti-inflammatory agents for functional foods. This study aimed to evaluate the antioxidant capacity of three key polyphenols (osmundacetone [OS], protocatechuic aldehyde [PAH], protocatechuic acid [PA]) from I. obliquus and decipher their anti-inflammatory mechanisms via the MyD88/TLR4/NF-κB pathway in a gout-related model. Methods: Antioxidant activity was assessed by xanthine oxidase (XO) inhibition (IC₅₀), superoxide anion (O₂⁻) scavenging, and structure–activity relationship (SAR) analysis; in a monosodium urate (MSU)-induced acute gout cell model, reactive oxygen species (ROS), nitric oxide (NO), lactate dehydrogenase (LDH), superoxide dismutase (SOD), pro-inflammatory cytokines (TNF-α, IL-1β) were quantified, and MyD88/TLR4/NF-κB pathway proteins were analyzed by Western blot. Results: OS showed the strongest XO inhibition (IC₅₀ = 4.91 mM), followed by PAH (IC₅₀ = 5.92 mM) and PA (IC₅₀ = 26.53 mM); OS exerted dual redox effects by scavenging O₂⁻ and suppressing XO-mediated O₂⁻ generation, with its conjugated C=C-carbonyl system and PAH’s aldehyde group enhancing XO binding. All polyphenols and I. obliquus crude extract significantly reduced ROS, NO, LDH, and cytokines (p < 0.05), increased SOD, and downregulated TLR4, MyD88, and NF-κB expression. Conclusions: I. obliquus-derived polyphenols exhibit obvious antioxidant and xanthine oxidase inhibitory effects, and regulate oxidative stress, pro-inflammatory mediators, and the MyD88/TLR4/NF-κB signaling pathway in monosodium urate-stimulated RAW 264.7 inflammatory macrophages, supporting their development as natural functional food ingredients and potential candidates for gout-related and oxidative stress-associated inflammatory cellular disorders. Full article

Gouty arthritis (GA) is a debilitating autoinflammatory disorder precipitated by the deposition of monosodium urate (MSU) crystals, leading to intense, recurrent joint inflammation and systemic metabolic dysregulation. While hyperuricemia is a prerequisite, the transition to clinical gout involves complex intercellular signaling cascades that are not fully understood. Emerging evidence has identified exosomes,— nanoscale extracellular vesicles, —as critical mediators in this pathological process. Exosomes function as intercellular carriers, transporting a diverse cargo of bioactive molecules, including proteins, lipids, and nucleic acids (e.g., microRNAs), which profoundly influence immune cell activation, inflammasome regulation, and metabolic pathways. This review provides a critical analysis of the dual role of exosomes in both propagating and potentially resolving inflammation in GA. We delve into the intricate mechanisms of exosome-mediated pathogenesis, including the modulation of purine metabolism, lysosomal function, and complement–inflammasome crosstalk. Furthermore, we explore the burgeoning field of exosome-based therapeutics, critically evaluating strategies such as engineered exosomes for targeted drug delivery, mesenchymal stem cell (MSC)-derived exosomes for immunomodulation, and the development of exosomal biomarkers for diagnostics. Additionally, we examine how chemical drugs and herbal compounds may exert therapeutic effects by modulating exosome pathways, offering new insights into integrative treatment approaches. By synthesizing recent findings from proteomic, transcriptomic, and functional studies, we aim to unravel the complexities of exosome signaling in GA and to propose innovative therapeutic avenues that target these pathways to improve patient outcomes. Full article

This review introduces and elaborates a novel temporal paradigm, the “Gout Inflammation Time Programming” model, conceptualized through the Gout-STAT™ framework. This model redefines gout inflammation as a dynamic continuum progressing through three precisely timed phases: an acute Perception phase (0–24 h) initiated by monosodium urate (MSU) crystal recognition, triggering the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome and neutrophil-driven burst; a critical Adaptation phase (24–72 h) where outcomes are determined by immunometabolic reprogramming of macrophages and synovial fibroblasts; and a chronic Tissue Injury phase (>72 h) driven by epigenetic memory, leading to irreversible osteoarticular destruction. Deciphering this programmed timeline reveals distinct therapeutic windows. We propose a shift towards stage-specific precision interventions, targeting upstream triggers (e.g., mitochondrial reactive oxygen species(ROS), neutrophil extracellular trap formation (NETosis)) in the acute phase, correcting metabolic checkpoints (e.g., succinate accumulation, impaired autophagy) during adaptation, and employing tissue-protective strategies (e.g., epigenetic modulators) in the chronic phase. Furthermore, we highlight the pivotal role of cutting-edge translational technologies, such as intelligent drug delivery systems and digital twin joint models, in achieving spatiotemporal precision. Understanding this intrinsic molecular clock is fundamental for advancing gout management from reactive treatment to a predictive, preventive, and personalized 4P medicine approach. Full article

Background: d-Limonene (LIM) is a food-derived monoterpenoid phytocompound predominantly found in citrus peels, endowed with potent antioxidant and anti-inflammatory properties, and has been reported to inhibit xanthine oxidase (XO) activity in vitro. This study investigated the dose-sparing efficacy of this dietary bioactive compound in combination with low-dose allopurinol (ALP) using a dual rat model combining potassium oxonate (PO)-induced hyperuricemia and monosodium urate (MSU)-triggered gouty arthritis, thereby capturing both metabolic and inflammatory dimensions of gout. Methods: Female Wistar rats were PO-primed and MSU-challenged, then treated with LIM (50 mg/kg), ALP (5 or 10 mg/kg), or LIM + ALP. Outcomes included paw thickness, dysfunction and inflammation indices, serum uric acid, urea, creatinine, AST/ALT, cytokines (IL-1β, TNF-α, IL-6), oxidative stress markers (MDA, SOD, catalase, GSH), and NLRP3 immunoreactivity, supported by radiographic and histopathological analyses. Data were analyzed by one-way ANOVA with Tukey’s post hoc test. Results: LIM improved clinical and biochemical outcomes versus monotherapies. However, LIM + low-dose ALP exhibited the greatest overall efficacy. On Day 30, paw thickness was significantly lower with LIM + ALP than with LIM alone (3.25 ± 0.31 vs. 3.98 ± 0.72 mm; p < 0.001). Serum uric acid and hepatic transaminases declined most with the combination (p < 0.0001 vs. LIM), accompanied by improved renal indices (p < 0.001). Pro-inflammatory cytokines were markedly reduced, NLRP3 immunostaining was minimal, and oxidative balance shifted toward homeostasis (↓ MDA; ↑ SOD, catalase, GSH). Radiographic and histological evaluations corroborated attenuation of joint inflammation and tissue damage. Conclusions: In the PO + MSU gout model, co-administration of the food-derived compound LIM with low-dose ALP achieved additive, dose-sparing benefits across metabolic, inflammatory, and histological endpoints. While in vivo XO activity was not directly assessed, the findings are consistent with XO-pathway modulation, NLRP3–IL-1β suppression, and redox restoration. These results highlight the potential of dietary bioactives such as d-Limonene to complement standard urate-lowering therapy, warranting further pharmacokinetic and safety validation. Full article

Gout is an inflammatory arthritis triggered by monosodium urate crystal deposition, especially in obese patients. However, distinctions between the characteristics of obese and non-obese patients with gout remain unclear. We aimed to investigate the clinical differences by body mass index (BMI) with gout. We conducted a single-center retrospective cross-sectional study of 269 patients with gout from March 2020 to May 2024. Patients were classified into two groups: underweight/normal BMI and overweight/obesity. Baseline demographics, laboratory data, and clinical outcomes were compared between these groups. Stepwise logistic regression analysis was performed to identify predictors of underweight/normal BMI in gout patients. The underweight/normal BMI group included 35 patients (13.0%), characterized by older age, a higher proportion of females, and a lower prevalence of hypertension and alcohol consumption. This group also demonstrated lower uric acid, lipid profile, and alanine aminotransferase (ALT) levels but had a higher erythrocyte sedimentation rate. Logistic regression analysis identified female sex (odds ratio [OR] 3.831, 95% confidence interval [CI] 1.254–11.705, p = 0.018), presence of hypertension (OR 0.367, 95% CI 0.166–0.809, p = 0.013), total cholesterol (OR 0.990, 95% CI 0.982–0.999, p = 0.031), and ALT (OR 0.967, 95% CI 0.941–0.995, p = 0.019) as significant predictors of underweight/normal BMI gout. Understanding these characteristics may improve the identification of underweight/normal BMI subgroups, leading to improved approaches for gout management. Full article

Objective: Monosodium urate (MSU) crystallization in human joints is poorly understood. This study aimed to investigate whether the length of MSU crystals varies in relation to organized ultrasound deposits, which may lead to longer crystals. Methods: Observational, cross-sectional study analyzing MSU crystals from synovial fluid samples of patients with crystal-proven gout. Using light microscopy, we measured crystal lengths (in µm) and noted the presence of long crystals, defined by cutoffs at the 66th, 75th, and 90th percentiles. We evaluated their association with two ultrasound-defined crystal deposition models: (1) grade 2–3 double-contour (DC) sign, tophi, and/or aggregates; and (2) grade 2–3 DC sign and/or tophi. Results: In a total of 1076 MSU crystals from 28 joints, median length was 23.3 µm (95% confidence interval 22.1–24.5). MSU crystal length was similar regardless of ultrasound deposition: in model 1 (20 joints, 71.4%), 22.5 µm in joints with deposits vs. 21.7 µm without; p = 0.42; in model 2 (15 joints, 53.6%), 22.8 µm vs. 21.2 µm, respectively; p = 0.12. Joints fulfilling model 2 criteria had more long crystals (>66th percentile), both in absolute and relative terms. Long crystals mildly correlated with serum urate levels and were numerically more frequent in patients with tophaceous gout. Conclusions: Most MSU crystals in synovial fluid gathered around a common length, regardless of ultrasound deposition. Long crystals were more common in joints with DC signs or tophi. Our finding is in keeping with two different mechanisms of MSU crystallization in humans. Full article

Interferon Regulatory Factor 5 plays an important role in the regulation of innate immune responses by amplifying the Nuclear Factor κB response, which is critical in gout inflammation. Furthermore, the rs4728141 polymorphism C allele was associated with both increased IRF5 expression and susceptibility to gout. We examine the association between rs4728141 and cytokine production in response to various Toll-Like Receptor ligands and describe the transcriptomic and proteomic changes observed in patients with gout and controls in relation to this polymorphism. We examine the transcriptome of freshly isolated peripheral blood mononuclear cells (PBMCs) from 93 normouricemic donors and 63 gout patients as well as serum inflammatory proteome in 197 control and 195 gout samples. Stimulation experiments of freshly isolated human PBMCs were performed over 24 h, followed by RNA-sequencing in gout patients and cytokine production measurement by ELISA in normouricemic donors and gout patients. The rs4728141 C allele was associated with increased IL-1β expression in unstimulated PBMCs of controls, but not in gout. No association between the polymorphism and serum inflammatory proteome was found. As expected, an increased IRF5 expression was observed in stimulated PBMCs of rs4728141 C allele carriers in response to several stimulations. Interestingly, IL-1β production was specifically enhanced in association to the rs4728141 C allele when cells were stimulated with palmitate with or without monosodium urate crystals. This pattern of cytokine production shows a functional impact of rs4728141 in gout through altered IL-1β production. Full article

Endothelial dysfunction is an early driver of atherosclerosis, yet the direct impact of endogenous crystals such as cholesterol crystals and monosodium urate on endothelial activation remains incompletely understood. In this study, we examine how crystalline stimuli modulate human umbilical vein endothelial cells by assessing inflammatory signaling, mitochondrial respiration, and neutrophil recruitment. Using dose- and time-controlled experiments, we show that CC and MSU are internalized by endothelial cells, activating NF-κB and STAT3 signaling pathways and inducing a robust pro-inflammatory cytokine profile. Notably, CC caused marked mitochondrial dysfunction, evidenced by impaired respiratory capacity and loss of membrane potential, revealing a novel bioenergetic vulnerability in endothelial cells. Both direct crystal stimulation and exposure to crystal-primed conditioned media triggered endothelial adhesion molecule expression and promoted neutrophil adhesion, indicating that soluble mediators released upon crystal stimulation can propagate vascular inflammation. These findings demonstrate that crystalline stimuli are potent vascular danger signals capable of driving endothelial inflammation, mitochondrial impairment, and immune cell engagement, which are hallmarks of early atherogenesis. By elucidating these multifaceted endothelial responses, this study provides important mechanistic insights into how crystal-induced signals may contribute to vascular dysfunction and the early stages of atherogenesis. Full article

Gout is a form of sterile inflammatory arthritis in which monosodium urate (MSU) crystals deposit and provoke a neutrophil-predominant response, primarily driven by activation of the NACHT, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome. Here, we show that auranofin, a Food and Drug Administration (FDA)-approved anti-rheumatic agent, exerts anti-inflammatory effects in both in vitro and in vivo models of gout. Auranofin inhibited NLRP3 inflammasome activation in human THP-1 cells and murine macrophages, leading to reduced cleavage of caspase-1, interleukin-1β (IL-1β), and interleukin-18 (IL-18). In MSU crystal-induced mouse models, auranofin treatment reduced paw swelling, serum cytokine levels, and tissue inflammation. Notably, auranofin suppressed neutrophil migration and decreased expression of C-X-C motif chemokine ligand 1 (CXCL1) in inflamed foot tissue and air-pouch exudates. Mechanistically, auranofin disrupted the interleukin-33 (IL-33)/suppression of tumorigenicity 2 (ST2) axis, a key signaling pathway promoting neutrophil recruitment. Overexpression of IL-33 abolished the anti-inflammatory effects of auranofin, highlighting the central role of IL-33 in gout pathogenesis. Together, our findings suggest that auranofin alleviates MSU-induced inflammation by concurrently inhibiting NLRP3 inflammasome activation and IL-33-mediated neutrophil recruitment, supporting its potential as a dual-action therapeutic candidate for gout. Full article

Hyperuricemia has been increasingly recognized as a modifiable contributor to chronic kidney disease (CKD) progression. Although the traditional classification of hyperuricemia distinguished between renal underexcretion and renal overload types, recent studies suggest that hyperuricemia in patients with CKD can result from heterogeneous excretory defects, including glomerular under-filtration and tubular over-reabsorption. These distinct phenotypes may drive divergent renal injury mechanisms. Experimental and clinical data reveal that monosodium urate crystals and soluble uric acid independently induce renal damage through oxidative stress, inflammasome activation, and endothelial dysfunction. Furthermore, clinical investigations showed inconsistent associations between serum uric acid levels and renal outcomes, suggesting that serum levels alone may not fully reflect urate-related renal risk. This has prompted increasing interest in uricosuric agents, particularly the selective urate reabsorption inhibitors (SURIs), which target tubular urate handling. Urate transporter 1 inhibitors have shown promise in enhancing urinary uric acid excretion and potentially preserving kidney function, especially in patients with CKD. In this review, we summarize the current evidence linking the emerging pathophysiological classification of hyperuricemia, mechanisms or urate-induced kidney injury, and therapeutic interventions. These insights may inform individualized approaches to urate-lowering therapy in CKD and support future research into phenotype-guided treatment strategies. Full article

Gout and calcium pyrophosphate crystal deposition disease (CPPD) are frequently associated with comorbid disorders, including coronary artery disease and osteoarthritis, in which ectopic calcification with basic calcium phosphate crystals commonly affects arteries and articular cartilage, respectively. Accepting the 2024 G-CAN Gold Medal, I review my research philosophy for translational etiopathogenesis investigation in gout and CPPD, atherosclerosis, responses to arterial injury, and osteoarthritis. Since molecular homeostasis points to pathophysiology and vice versa, I have followed selected molecular players and pathways to phenotypes. Typically, behind each disease target is another target. Illuminating passageways between etiopathogenic pathways is especially productive when using approaches beyond conventional “omics” to reveal the impact of specific post-translational protein modifications, and changes in protein conformation, complex assembly, and interactomes. Highlighting these concepts, I review my past studies on specific molecular pathways, and current perspectives for the following: (i) PP_i, NPP1, ANKH, and transglutaminase 2 (TG2); (ii) relationships between NPP1, ANKH, Vanin-1 Pantetheinase, and ectopic chondrogenesis; (iii) intersections between adenosine, AMPK, CXCL8 and its receptor CXCR2, the receptor for advanced glycation endproducts (RAGE) and chondrocyte hypertrophy; (iv) lubricin homeostasis and proteolysis; (v) receptor for advanced glycation endproducts (RAGE) and TG2-catalyzed post-translational calgranulin modification; (vi) complement activation and C5b-9 assembly, and the nucleotide-bound conformation of TG2. The inescapable conclusion is that these molecular pathways tightly knit crystal arthropathy with both arterial and osteoarthritis comorbidity. Full article

In this study, a novel polysaccharide (PSH) with potent anti-gout activity was extracted and separated from Sanghuangporus vaninii (S. vaninii). The structural characteristics of PSH were elucidated using analytical techniques. HPLC analysis revealed that PSH was a heteropolysaccharide with a molecular weight of 5.25 × 10⁴ Da. FT-IR, NMR, and GC-MS collectively demonstrated that PSH was a pyranose with both α and β configurations, primarily composed of Glcp-(1→, →4)-Glcp-(2→, →3)-Galp-(1→, and Araf-(1→ linkages. The cell viability confirmed the non-toxicity of PSH. CAT and SOD showed that compared with the model group, PSH significantly offset the oxidative damage induced by MSU (p < 0.01). The results from ROS and MDA mutually corroborated the antioxidant capacity of PSH. Furthermore, PSH effectively suppressed MSU-triggered inflammatory responses. The antioxidant and anti-inflammatory experiments provided evidence for the anti-gout efficacy of PSH. Collectively, these findings support the potential development of PSH as an anti-gout active substance. Full article

Gout is a chronic inflammatory disease characterized by the deposition of monosodium urate (MSU) crystals within joints, leading to recurrent acute flares and long-term tissue damage. While various hypotheses have been proposed to explain the self-limiting nature of acute gout attacks, we posit that aggregated neutrophil extracellular traps (aggNETs) play a central role in this process. This review focuses on the mechanisms underlying MSU crystal-induced formation of neutrophil extracellular traps (NETs) and explores their dual role in the clinical progression of gout. During the initial phase of acute flares, massive NET formation is accompanied by the release of preformed inflammatory mediators, which is a condition that amplifies inflammatory cascades. As neutrophil recruitment reaches a critical threshold, the NETs tend to form high-order aggregates (aggNETs). The latter encapsulate MSU crystals and further pro-inflammatory mediators within their three-dimensional scaffold. High concentrations of neutrophil serine proteases (NSPs) within the aggNETs facilitate the degradation of soluble inflammatory mediators and eventually promote the resolution of inflammation in a kind of negative inflammatory feedback loop. In advanced stages of gout, MSU crystal deposits are often visible via dual-energy computed tomography (DECT), and the formation of palpable tophi is frequently observed. Based on the mechanisms of resolution of inflammation and the clinical course of the disease, building on the traditional static model of “central crystal–peripheral fibrous encapsulation,” we have expanded the NETs component and refined the overall concept, proposing a more dynamic, multilayered, multicentric, and heterogeneous model of tophus maturation. Notably, in patients with late-stage gout, tophi exist in a stable state, referred to as “silent” tophi. However, during clinical tophus removal, the disruption of the structural or functional stability of “silent” tophi often leads to the explosive reactivation of inflammation. Considering these findings, we propose that future therapeutic strategies should focus on the precise modulation of NET dynamics, aiming to maintain immune equilibrium and prevent the recurrence of gout flares. Full article