Activation Status of NLRP3 Inflammasome in Peripheral Blood Mononuclear Cells From Patients With Gout Flare

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.

Gout therapeutics and drug delivery

Gout is a common inflammatory arthritis caused by persistently elevated uric acid levels. With the improvement of people's living standards, the consumption of processed food and the widespread use of drugs that induce elevated uric acid, gout rates are increasing, seriously affecting the human quality of life, and becoming a burden to health systems worldwide. Since the pathological mechanism of gout has been elucidated, there are relatively effective drug treatments in clinical practice. However, due to (bio)pharmaceutical shortcomings of these drugs, such as poor chemical stability and limited ability to target the pathophysiological pathways, traditional drug treatment strategies show low efficacy and safety. In this scenario, drug delivery systems (DDS) design that overcome these drawbacks is urgently called for. In this review, we initially describe the pathological features, the therapeutic targets, and the drugs currently in clinical use and under investigation to treat gout. We also comprehensively summarize recent research efforts utilizing lipid, polymeric and inorganic carriers to develop advanced DDS for improved gout management and therapy.

Degenerative joint disease induced by repeated intra-articular injections of monosodium urate crystals in rats as investigated by translational imaging

The objective of this work was to assess the consequences of repeated intra-articular injection of monosodium urate (MSU) crystals with inflammasome priming by lipopolysaccharide (LPS) in order to simulate recurrent bouts of gout in rats. Translational imaging was applied to simultaneously detect and quantify injury in different areas of the knee joint. MSU/LPS induced joint swelling, synovial membrane thickening, fibrosis of the infrapatellar fat pad, tidemark breaching, and cartilage invasion by inflammatory cells. A higher sensitivity to mechanical stimulus was detected in paws of limbs receiving MSU/LPS compared to saline-injected limbs. In MSU/LPS-challenged joints, magnetic resonance imaging (MRI) revealed increased synovial fluid volume in the posterior region of the joint, alterations in the infrapatellar fat pad reflecting a progressive decrease of fat volume and fibrosis formation, and a significant increase in the relaxation time T2 in femoral cartilage, consistent with a reduction of proteoglycan content. MRI also showed cyst formation in the tibia, femur remodeling, and T2 reductions in extensor muscles consistent with fibrosis development. Repeated intra-articular MSU/LPS injections in the rat knee joint induced pathology in multiple tissues and may be a useful means to investigate the relationship between urate crystal deposition and the development of degenerative joint disease.

Active components from Lagotis brachystachya maintain uric acid homeostasis by inhibiting renal TLR4-NLRP3 signaling in hyperuricemic mice

Lagotis brachystachya Maxim is a herb widely used in traditional Tibetan medicine. Our previous study indicated that total extracts from Lagotis brachystachya could lower uric acid levels. This study aimed to further elucidate the active components (luteolin, luteoloside and apigenin) isolated from Lagotis brachystachya and the underlying mechanism in vitro and in vivo. The results showed that treatment with luteolin and luteoloside reversed the reduction of organic anion transporter 1 (OAT1) levels, while apigenin attenuated the elevation of urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) levels in uric acid-treated HK-2 cells, which was consistent with the finding in the kidneys of potassium oxonate (PO)-induced mice. On the other hand, hepatic xanthine oxidase activity was inhibited by the components. In addition, all of these active components improved the morphology of the kidney in hyperuricemic mice. Moreover, molecular docking showed that luteolin, luteoloside and apigenin could bind Toll-like receptor 4 (TLR4) and NLR family pyrin domain containing 3 (NLRP3). Congruently, western blot analysis showed that the components inhibited TLR4/myeloid differentiation primary response 88 (MyD88)/NLRP3 signaling. In conclusion, these results indicated that luteolin, luteoloside and apigenin could attenuate hyperuricemia by decreasing the production and increasing the excretion of uric acid, which were mediated by inhibiting inflammatory signaling pathways.