Factors secreted by monosodium urate crystal-stimulated macrophages promote a proinflammatory state in osteoblasts: a potential indirect mechanism of bone erosion in gout

Current Status of Gout Arthritis: Current Approaches to Gout Arthritis Treatment: Nanoparticles Delivery Systems Approach

The deposition of monosodium urate (MSU) crystals within joint spaces produces a painful inflammatory condition known as gout, a specific form of arthritis. The condition calls for a combined curative and preventive management model. A new development in the approach to gout is that of NLRP3-targeted biologic agents, such as monoclonal therapies, to provide more accurate treatment by blocking specific pro-inflammatory cytokines. Nanoparticle drug delivery enhances biological availability and delivery to targets, which may increase therapeutic efficacy and decrease general toxicity. The preventive approach again cannot be ignored, mainly keeping up certain modifications in diet and weight, along with pharmacological therapies to reduce uric acid (UA) levels and to decrease the frequency of acute attacks. The advancement of genetic profiling of patients and biomarker discoveries drives the trend towards building individualized medicine and care, quickly gaining ground as the most effective method of delivering treatments to individual patients, moving away from one-size-fits-all treatments. The following paper aims to provide an updated account of the management of gout with a focus on recent developments, in order to enhance these approaches, the quality of life for patients with gout, and the standard of gout treatment.

The pathogenesis of gout

Gout is the most common inflammatory arthritis in adults, associated with hyperuricemia and the chronic deposition of monosodium urate (MSU) crystals. Hyperuricemia results from increased production of uric acid and decreased excretion by the kidneys and intestines. Urate excretion is regulated by a group of urate transporters, and decreased renal or intestinal excretion is the primary mechanism of hyperuricemia in most people. Genetic variability in these urate transporters is strongly related to variances in serum urate levels. Not all individuals with hyperuricemia show deposition of MSU crystals or develop gout. The initiation of the inflammatory response to MSU crystals is mainly mediated by the nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing protein 3 (NLRP3) inflammasome. The activated NLRP3 inflammasome complex cleaves pro-interleukin-1β (IL-1β) into its active form, IL-1β, which is a key mediator of the inflammatory response in gout. IL-1β leads to the upregulation of cytokines and chemokines, resulting in the recruitment of neutrophils and other immune cells. Neutrophils recruited to the site of inflammation also play a role in resolving inflammation. Aggregated neutrophil extracellular traps (NETs) trap and degrade cytokines and chemokines through NET-bound proteases, promoting the resolution of inflammation. Advanced gout is characterized by tophi, chronic inflammatory responses, and structural joint damage. Tophi are chronic foreign body granuloma-like structures containing collections of MSU crystals encased by inflammatory cells and connective tissue. Tophi are closely related to chronic inflammation and structural damage.

Advancements in the study of IL-6 and its receptors in the pathogenesis of gout

Gout is an autoinflammatory disease characterized by the deposition of monosodium urate crystals in or around the joints, primarily manifesting as inflammatory arthritis that recurs and resolves spontaneously. Interleukin-6 (IL-6) is a versatile cytokine with both anti-inflammatory and pro-inflammatory capabilities, linked to a variety of inflammatory diseases such as gouty arthritis, rheumatoid arthritis, inflammatory bowel disease, vasculitis, and several types of cancer. The rapid production of IL-6 during infections and tissue damage aids in host defense. However, excessive synthesis of IL-6 and dysregulation of its receptor signaling (IL-6R) might contribute to the pathology of diseases. Recent advancements in clinical and basic research, along with developments in animal models, have established the significant role of IL-6 and its receptors in the pathogenesis of gout, although the precise mechanisms remain to be fully elucidated. This review discusses the role of IL-6 and its receptors in gout progression and examines contemporary research on modulating IL-6 and its signaling pathways for treatment. It aims to provide insights into the pathogenesis of gout and to advance the development of targeted therapies for gout-related inflammation.

Neoisoastilbin Ameliorates Acute Gouty Arthritis via Suppression of the NF-κB/NLRP3 Pathway

Acute gouty arthritis (AGA) is an acute inflammatory disease, whose occurrence and development mechanism are associated with inflammatory reaction of joint tissue. This study investigated the role of neoisoastilbin (NIA) in the treatment of AGA and explored the underlying mechanisms. C57BL/6 mice underwent intraarticular injection of monosodium urate (MSU) to establish an AGA model in vivo. Enzyme-linked immunosorbent assay, histopathological hematoxylin-eosin staining, western blotting, and other methods were used to observe the therapeutic effects of NIA on AGA and investigate the role of the NF-κB/NLRP3 pathway in the treatment. We found that NIA effectively reduced MSU-induced joint swelling and inflammatory cell infiltration in a concentration-dependent manner. NIA also significantly reduced interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) levels as compared with the respective values in the model mice group. In addition, administration of NIA significantly mitigated the phosphorylation of NF-κB-related proteins (IKKα, NF-κB, and IκBα) and the expression of NLRP3-related proteins (NLRP3, caspase-1, and ASC) in MSU-induced joint tissues. In conclusion, our research indicated that NIA significantly improved AGA, and its underlying mechanism was achieved by simultaneously inhibiting the NF-κB/NLRP3 pathway and the expression of inflammatory factors. This research preliminarily suggested the potential role of NIA in the treatment of AGA.

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-1β 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.