Elderly Patients Exhibit Stronger Inflammatory Responses during Gout Attacks

Clinical Features and Risk Factors of Fever in Acute Gouty Arthritis

Objectives

This study aimed to investigate the clinical characteristics and risk factors of fever in hospitalised patients with acute gouty arthritis (AGA).

Methods

The clinical data of 167 hospitalised patients with AGA who met the inclusion criteria were retrospectively analysed. The demographic, clinical, and medication data of patients with and without fever were compared, and risk factors associated with fever were identified via logistic regression analysis.

Results

The incidence of fever in hospitalised patients with AGA was 31.1%, with low-grade fever being predominant. Visual analogue scale (VAS) scores, white blood cell counts, neutrophil proportion, C-reactive protein (CRP) levels, and erythrocyte sedimentation rate (ESR) were higher in the fever group than in the non-fever group (P < 0.05 for all). In addition, the incidence rates of arthritis of single knee and polyarthritis were higher in patients in the fever group (P < 0.05). The proportion of patients who received betamethasone injection and combination therapy were higher in the fever group (P < 0.05). However, no significant differences were observed in age; sex; uric acid (UA) levels; and the incidence rate of hypertension, diabetes mellitus, cardiovascular disease, and renal function abnormalities between the two groups. Logistic regression analysis revealed that arthritis of single knee, polyarthritis, age of ≥65 years, CRP levels, and VAS scores were risk factors for concomitant AGA and fever. Among these factors, CRP levels and VAS scores were identified as independent risk factors (odds ratio [OR], 1.014 and 1.686, respectively; 95% confidence interval [CI], 1.004-1.025 and 1.115-2.549, respectively; P < 0.05 for both).

Conclusion

The incidence of fever is high in hospitalised patients with AGA. Elderly patients, patients with arthritis affecting only one knee, and those with polyarthritis are predisposed to fever. In addition, the risk of developing fever increases with increasing VAS scores and CRP levels, and patients presenting with fever require enhanced anti-inflammatory and analgesic therapy.

Raised total methylated arginine load in patients with gout

Aim: The aim of this study was to measure serum levels of methylarginine derivatives and related metabolites in patients with gout. Materials & methods: This study enrolled 100 patients with gout and 80 patients in the control group. Serum asymmetric dimethylarginine, symmetric dimethylarginine, L-N-monomethylarginine, arginine, homoarginine, citrulline and ornithine levels were measured with tandem mass spectrometry. Results: Serum ornithine, citrulline and total methylated arginine load levels were statistically significantly higher in patients with gout compared with the control group, while serum arginine and homoarginine levels and global arginine bioavailability ratio were statistically significantly lower. Conclusion: There may be an association between gout, methylarginine levels and hyperuricemia and increased risk of cardiovascular disease.

Recent Insights Into the Role of Macrophages in Acute Gout

Gout is a common type of inflammatory arthritis characterized by the presence of monosodium urate crystals (MSU) in the joints. Macrophages are believed to be involved in gout flares. It has long been recognized that resident macrophage and monocyte derived macrophages are distinct subsets and there have been attempts to investigate their roles in acute gout, respectively. Previous studies revealed that resident macrophages initiate and drive the inflammation, while monocyte derived macrophages differentiated into M1-like macrophages in response to MSU crystals. With the advancement of technologies, subpopulations of synovial resident macrophages have been defined with the characteristics more accurately described. Resident macrophages in the synovial lining layer showed an anti-inflammatory effect in rheumatoid arthritis, but specific Trpv4 depletion of them reduced MSU crystals induced murine arthritis. CD14+ monocytes in the synovial fluid from patients with gout exhibit phenotypes of anti-inflammatory as well as pro-inflammatory characteristics. Here, we review the main aspects of macrophages in the initiation and resolution of acute gout and try to clarify the specific role of each subpopulation. Building a reliable diagram of the effect of monocytes and macrophages during MSU crystals induced arthritis will bring us closer to targeting macrophages for improving the management of gout.

Inflammatory Response to Regulated Cell Death in Gout and Its Functional Implications

Gout, a chronic inflammatory arthritis disease, is characterized by hyperuricemia and caused by interactions between genetic, epigenetic, and metabolic factors. Acute gout symptoms are triggered by the inflammatory response to monosodium urate crystals, which is mediated by the innate immune system and immune cells (e.g., macrophages and neutrophils), the NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome activation, and pro-inflammatory cytokine (e.g., IL-1β) release. Recent studies have indicated that the multiple programmed cell death pathways involved in the inflammatory response include pyroptosis, NETosis, necroptosis, and apoptosis, which initiate inflammatory reactions. In this review, we explore the correlation and interactions among these factors and their roles in the pathogenesis of gout to provide future research directions and possibilities for identifying potential novel therapeutic targets and enhancing our understanding of gout pathogenesis.

Pattern of inflammatory immune response determines the clinical course and outcome of COVID-19: unbiased clustering analysis

The objective of the study was to identify distinct patterns in inflammatory immune responses of COVID-19 patients and to investigate their association with clinical course and outcome. Data from hospitalized COVID-19 patients were retrieved from electronic medical record. Supervised k-means clustering of serial C-reactive protein levels (CRP), absolute neutrophil counts (ANC), and absolute lymphocyte counts (ALC) was used to assign immune responses to one of three groups. Then, relationships between patterns of inflammatory responses and clinical course and outcome of COVID-19 were assessed in a discovery and validation cohort. Unbiased clustering analysis grouped 105 patients of a discovery cohort into three distinct clusters. Cluster 1 (hyper-inflammatory immune response) was characterized by high CRP levels, high ANC, and low ALC, whereas Cluster 3 (hypo-inflammatory immune response) was associated with low CRP levels and normal ANC and ALC. Cluster 2 showed an intermediate pattern. All patients in Cluster 1 required oxygen support whilst 61% patients in Cluster 2 and no patient in Cluster 3 required supplementary oxygen. Two (13.3%) patients in Cluster 1 died, whereas no patient in Clusters 2 and 3 died. The results were confirmed in an independent validation cohort of 116 patients. We identified three different patterns of inflammatory immune response to COVID-19. Hyper-inflammatory immune responses with elevated CRP, neutrophilia, and lymphopenia are associated with a severe disease and a worse outcome. Therefore, targeting the hyper-inflammatory response might improve the clinical outcome of COVID-19.

Expansion of Polymorphonuclear Myeloid-Derived Suppressor Cells in Patients With Gout

Gout is an inflammatory joint disease caused by monosodium urate (MSU) crystals; however, the mechanism underlying MSU-induced inflammation is unclear. Previous research has suggested that inflammation or cancer can drive the expansion of myeloid-derived suppressor cells (MDSCs). In this study, the role of MDSCs in MSU-induced gout inflammation was evaluated. A total of 28 patients with gout, and 20 healthy controls were recruited for the study. MDSCs, and their functions, were analyzed by flow cytometry and a T cell co-culture assay, respectively. We observed a higher frequency of PMN-MDSCs, and a stronger immunosuppressive function, in patients with gout compared to the controls. Moreover, circulating PMN-MDSCs were positively correlated with pathological indicators, including uric acid and C-reactive protein levels. We also demonstrated that MSU can induce significant PMN-MDSC expansion, using in vivo and in vitro experiments. Finally, MSU-induced PMN-MDSCs produced higher levels of IL-1β, which mediated gout inflammatory progression. Our results demonstrate that MSU modulates the expansion and suppressive function of PMN-MDSCs, providing insights into a novel mechanism underlying the pathogenesis of MSU-induced gout. Thus, MDSCs may be useful for the development of novel therapeutic strategies for the prevention and treatment of gout.

C-reactive protein (CRP) recognizes uric acid crystals and recruits proteases C1 and MASP1

Gout is caused by crystallization of uric acid in the form of monosodium urate (MSU) crystals, which induce a sterile inflammatory response that is hardly distinguishable from microbe-induced inflammatory responses. It is unclear, if MSU crystals (like microbes) are recognized by specific pattern recognition receptors. To identify possible soluble pattern recognition molecules for MSU crystals, we purified MSU-binding proteins from human body fluids. We identified C-reactive protein (CRP) as a major MSU-binding protein. Binding of CRP was strong enough to specifically deplete CRP from human serum. We found that CRP was required for fixation of complement components C1q, C1r, C1s and MASP1. Thus, we have identified a pattern recognition molecule for MSU crystals that links to the activation of complement. Notably, CRP does not show an even binding to the complete surface of the crystals. It rather binds to edges or distinct faces of the crystals.

Metabolic regulation of inflammasomes in inflammation

Inflammasome activation and subsequent inflammatory cytokine secretion are essential for innate immune defence against multiple stimuli and are regarded as a link to adaptive immune responses. Dysfunction of inflammasome activation has been discovered at the onset or progression of infectious diseases, autoimmune diseases and cancer, all of which are also associated with metabolic factors. Furthermore, many studies concerning the metabolic regulation of inflammasome activation have emerged in recent years, especially regarding the activity of the NLRP3 inflammasome under metabolic reprogramming. In this review, we discuss the molecular mechanisms of the interactions between metabolic pathways and inflammasome activation, which exerts further important effects on various diseases.