Hyperuricaemia elevates circulating CCL2 levels and primes monocyte trafficking in subjects with inter-critical gout

Association Between Hyperuricemia and Ultrasound-Detected Hand Synovitis

OBJECTIVE

Although hand synovitis is prevalent in the older population, the etiology remains unclear. Hyperuricemia, a modifiable metabolic disorder, may serve as an underlying mechanism of hand synovitis, but little is known about their relationship. We assessed the association between hyperuricemia and hand synovitis in a large population-based sample.

METHODS

We performed a cross-sectional study in Longshan County, Hunan Province, China. Hyperuricemia was defined as a serum urate level >420 μmol/L in men and >360 μmol/L in women. Ultrasound examinations were performed on both hands of 4,080 participants, and both gray-scale synovitis and the Power Doppler signal (PDS) were assessed using semiquantitative scores (grades 0-3). We evaluated the association of hyperuricemia with hand gray-scale synovitis (grade ≥2) and PDS (grade ≥1), respectively, adjusting for age, sex, and body mass index.

RESULTS

All required assessments for analysis were available for 3,286 participants. The prevalence of hand gray-scale synovitis was higher among participants with hyperuricemia (30.0%) than those with normouricemia (23.3%), with an adjusted odds ratio (aOR) of 1.28 (95% confidence interval [CI] 1.00-1.62). Participants with hyperuricemia also had a higher prevalence of PDS (aOR 2.36; 95% CI 1.15-4.81). Furthermore, hyperuricemia positively associated, both at the hand and joint levels, with the presence of gray-scale synovitis (aOR 1.27; 95% CI 1.00-1.60 and adjusted prevalence ratio [aPR] 1.26; 95% CI 1.10-1.44, respectively) and PDS (aOR 2.35; 95% CI 1.15-4.79 and aPR 2.34; 95% CI 1.28-4.30, respectively).

CONCLUSION

This population-based study provides more evidence for a positive association between hyperuricemia and prevalent hand synovitis.

Association between urate-lowering therapy initiation and all-cause mortality in patients with type 2 diabetes and asymptomatic hyperuricemia

AIMS

To assess the relationships between urate-lowering therapy (ULT) initiation with all-cause mortality in patients with asymptomatic hyperuricemia and Type 2 Diabetes (T2D).

METHODS

This nationwide retrospective cohort study involved patients with T2D and asymptomatic hyperuricemia from 19 academic hospitals across China between 2000 and 2021. The primary exposure was ULT initiation, including allopurinol, febuxostat, or benzbromarone. The primary outcome was all-cause mortality. The secondary outcomes were cardiovascular (CV) and non-CV mortality. Propensity score matching was employed to create a 1:2 matched cohort with balanced likelihood of ULT initiation. Associations between ULT initiation with all-cause and CV mortality were assessed in the matched cohort.

RESULTS

Among 42 507 patients, 5028 initiated ULT and 37 479 did not. In the matched cohort, comprising 4871 ULT initiators and 9047 noninitiators, ULT initiation was significantly associated with reduced risk of all-cause mortality (hazard ratio [HR] 0.77; 95% confidence interval [CI], 0.71-0.84), CV mortality (HR 0.86; 95% CI, 0.76-0.97), and non-CV mortality (HR 0.72; 95% CI, 0.64-0.80) over an average 3.0 years of follow-up. Among the ULT initiators, post-treatment SUA levels of 360-420 μmol/L was related to a significantly lower risk for all-cause mortality compared to levels >420 μmol/L (HR 0.74; 95% CI, 0.59-0.94) while levels ≤360 μmol/L did not (HR, 0.96; 95% CI, 0.81-1.14), suggesting a U-shaped relationship.

CONCLUSIONS

Initiating ULT was associated with a significant reduction in all-cause mortality in patients with T2D and asymptomatic hyperuricemia. Notably, maintaining post-treatment SUA concentrations within 360-420 μmol/L could potentially enhance this reduced mortality.

Exploration of circulating metabolic signature of erythrodermic psoriasis based on LC-MS metabolomics

Erythrodermic psoriasis (EP) is a rare and life-threatening disease, the pathogenesis of which remains to be largely unknown. Metabolomics analysis can provide global information on disease pathophysiology, candidate biomarkers, and potential intervention strategies. To gain a better understanding of the mechanisms of EP and explore the serum metabolic signature of EP, we conducted an untargeted metabolomics analysis from 20 EP patients and 20 healthy controls. Furthermore, targeted metabolomics for focused metabolites were identified in the serum samples of 30 EP patients and 30 psoriasis vulgaris (PsV) patients. In the untargeted analysis, a total of 2992 molecular features were extracted from each sample, and the peak intensity of each feature was obtained. Principal component analysis (PCA), orthogonal partial least squares-discriminant analysis (OPLS-DA) revealed significant difference between groups. After screening, 98 metabolites were found to be significantly dysregulated in EP, including 67 down-regulated and 31 up-regulated. EP patients had lower levels of L-tryptophan, L-isoleucine, retinol, lysophosphatidylcholine (LPC), and higher levels of betaine and uric acid. KEGG analysis showed differential metabolites were enriched in amino acid metabolism and glycerophospholipid metabolism. The targeted metabolomics showed lower L-tryptophan in EP than PsV with significant difference and L-tryptophan levels were negatively correlated with the PASI scores. The serum metabolic signature of EP was discovered. Amino acid and glycerophospholipid metabolism were dysregulated in EP. The metabolite differences provide clues for pathogenesis of EP and they may provide insights for therapeutic interventions.

Associations between hyperuricemia and ultrasound-detected knee synovial abnormalities in middle-aged and older population: a cross-sectional study

OBJECTIVES

Knee synovial abnormalities, potentially treatment targets for knee pain and osteoarthritis, are common in middle-aged and older population, but its etiology remains unclear. We examined the associations between hyperuricemia and knee synovial abnormalities detected by ultrasound in a general population sample.

METHODS

Participants aged ≥ 50 years were from a community-based observational study. Hyperuricemia was defined as serum urate (SU) level > 416 µmol/L in men and > 357 µmol/L in women. Ultrasound of both knees was performed to determine the presence of synovial abnormalities, i.e., synovial hypertrophy, effusion, or Power Doppler signal (PDS). We examined the relation of hyperuricemia to prevalence of knee synovial abnormalities and its laterality, and the dose-response relationships between SU levels and the prevalence of knee synovial abnormalities.

RESULTS

In total, 3,405 participants were included in the analysis. Hyperuricemia was associated with higher prevalence of knee synovial abnormality (adjusted odds ratio [aOR] = 1.21, 95% confidence interval [CI]: 1.02 to 1.43), synovial hypertrophy (aOR = 1.33, 95% CI: 1.05 to 1.68), and effusion (aOR = 1.21, 95% CI: 1.02 to 1.44), respectively. There were dose-response relationships between SU levels and synovial abnormalities. Additionally, the hyperuricemia was more associated with prevalence of bilateral than with that of unilateral knee synovial abnormality, synovial hypertrophy, or effusion; however, no significant association was observed between hyperuricemia and PDS.

CONCLUSION

In this population-based study we found that hyperuricemia was associated with higher prevalence of knee synovial abnormality, synovial hypertrophy and effusion, suggesting that hyperuricemia may play a role in pathogenesis of knee synovial abnormalities.

Sustained xanthine oxidase inhibitor treat to target urate lowering therapy rewires a tight inflammation serum protein interactome

Background

Effective xanthine oxidoreductase inhibition (XOI) urate-lowering treatment (ULT) to target significantly reduces gout flare burden and synovitis between 1-2 years therapy, without clearing all monosodium urate crystal deposits. Paradoxically, treat to target ULT is associated with increased flare activity for at least 1 year in duration on average, before gout flare burden decreases. Since XOI has anti-inflammatory effects, we tested for biomarkers of sustained, effective ULT that alters gouty inflammation.

Methods

We characterized the proteome of febuxostat-treated murine bone marrow macrophages. Blood samples (baseline and 48 weeks ULT) were analyzed by unbiased proteomics in febuxostat and allopurinol ULT responders from two, independent, racially and ethnically distinct comparative effectiveness trial cohorts (n=19, n=30). STRING-db and multivariate analyses supplemented determinations of significantly altered proteins via Wilcoxon matched pairs signed rank testing.

Results

The proteome of cultured IL-1b-stimulated macrophages revealed febuxostat-induced anti-inflammatory changes, including for classical and alternative pathway complement activation pathways. At 48 weeks ULT, with altered purine metabolism confirmed by serum metabolomics, serum urate dropped >30%, to normal (<6.8 mg/dL) in all the studied patients. Overall, flares declined from baseline. Treated gout patient sera and peripheral blood mononuclear cells (PBMCs) showed significantly altered proteins (p<0.05) in clustering and proteome networks. CRP was not a useful therapy response biomarker. By comparison, significant serum proteome changes included decreased complement C8 heterotrimer C8A and C8G chains essential for C5b-9 membrane attack complex assembly and function; increase in the NLRP3 inflammasome activation promoter vimentin; increased urate crystal phagocytosis inhibitor sCD44; increased gouty inflammation pro-resolving mediator TGFB1; decreased phagocyte-recruiting chemokine PPBP/CXCL7, and increased monocyte/macrophage-expressed keratin-related proteins (KRT9,14,16) further validated by PBMC proteomics. STRING-db analyses of significantly altered serum proteins from both cohorts revealed a tight interactome network including central mediators of gouty inflammation (eg, IL-1B, CXCL8, IL6, C5).

Conclusions

Rewiring of inflammation mediators in a tight serum protein interactome was a biomarker of sustained XOI-based ULT that effectively reduced serum urate and gout flares. Monitoring of the serum and PBMC proteome, including for changes in the complement pathway could help determine onset and targets of anti-inflammatory changes in response to effective, sustained XOI-based ULT.Trial Registration: ClinicalTrials.gov Identifier: NCT02579096.

Association between hyperuricaemia and hand osteoarthritis: data from the Xiangya Osteoarthritis Study

OBJECTIVE

The pathogenesis of hand osteoarthritis (OA) remains unknown. Hyperuricaemia, which is related to inflammation, may play a role in hand OA, but evidence is lacking. In a large population-based study, we examined the association between hyperuricaemia and hand OA.

METHODS

Participants were from the Xiangya OA Study, a community-based observational study. Hyperuricaemia was defined as serum urate >416 µmol/L in men and >357 µmol/L in women. Radiographic hand OA (RHOA) was defined as presence of the modified Kellgren-Lawrence grade ≥2 in any hand joint. Symptomatic hand OA (SHOA) was defined as presence of both self-reported symptoms and RHOA in the same hand. The associations of hyperuricaemia with RHOA or SHOA were examined using generalised estimating equations.

RESULTS

Among 3628 participants, the prevalence of RHOA was higher in participants with hyperuricaemia than those with normouricaemia (26.9% vs 20.9%), with an adjusted OR (aOR) of 1.34 (95% CI 1.11 to 1.61). The associations were consistent in men (aOR 1.33, 95% CI 1.01 to 1.74) and women (aOR 1.35, 95% CI 1.05 to 1.74). Hyperuricaemia was mainly associated with bilateral RHOA (aOR 1.54, 95% CI 1.18 to 2.01) but not unilateral RHOA (aOR 1.13, 95% CI 0.89 to 1.45). Prevalence of SHOA was higher, although statistically insignificant, in participants with hyperuricaemia (aOR 1.39, 95% CI 0.94 to 2.07).

CONCLUSION

In this population-based study, hyperuricaemia was associated with a higher prevalence of hand OA. Future prospective studies are required to investigate the temporal relationship.

TRIAL REGISTRATION NUMBER

NCT04033757.

Sirt3 improves monosodium urate crystal-induced inflammation by suppressing Acod1 expression

BACKGROUND

Previous studies have revealed that Sirt3 deficiency is associated with several inflammatory responses. The purpose of this study is to investigate the role and potential molecular mechanisms of Sirt3 in the inflammation induced by monosodium urate (MSU) crystals.

METHODS

The Sirt3 expression level in the peripheral blood mononuclear cells (PBMCs) of patients with gout was measured. Function and molecular mechanism of Sirt3 in MSU crystal-induced inflammation were investigated in bone marrow-derived macrophages (BMDMs), C57BL/6 mouse, and Sirt3^-/- mouse.

RESULTS

Sirt3 expression was decreased in the PBMCs of patients with gout. Sirt3 agonist (Viniferin) inhibited the acetylation levels of mitochondrial proteins including the SOD2 protein. RNA sequencing, bio-informatics analysis, RT-PCR, and Western blot demonstrated that Sirt3 could suppress the expression of Acod1 (Irg1), which plays an important role in gout. In BMDMs treated with palmitic acid (C16:0) plus MSU crystals, Acod1 knockdown repressed mitochondrial reactive oxygen species (mtROS) over-production, macrophage migration, and mitochondrial fragmentation, and Acod1 improved AMPK activity. The over-expression of Acod1 did not significantly affect the level of itaconic acid, but greatly decreased the levels of some important intermediate metabolites of the tricarboxylic acid (TCA) cycle. These data indicate that Acod1 exerts a pro-inflammatory role in MSU crystal-induced inflammation and is independent of the metabolic level of itaconic acid. Sirt3 deficiency exacerbates inflammatory response induced by MSU crystals in vitro and in vivo.

CONCLUSION

The current study has shown that Sirt3 can alleviate the MSU crystal-induced inflammation by inhibiting the expression of Acod1.

Anti-hyperuricemia effect of hesperetin is mediated by inhibiting the activity of xanthine oxidase and promoting excretion of uric acid

Hesperetin is a natural flavonoid with many biological activities. In view of hyperuricemia treatment, the effects of hesperetin in vivo and in vitro, and the underlying mechanisms, were explored. Hyperuricemia models induced by yeast extract (YE) or potassium oxonate (PO) in mice were created, as were models based on hypoxanthine and xanthine oxidase (XOD) in L-O2 cells and sodium urate in HEK293T cells. Serum level of uric acid (UA), creatinine (CRE), and urea nitrogen (BUN) were reduced significantly after hesperetin treatment in vivo. Hesperetin provided hepatoprotective effects and inhibited xanthine oxidase activity markedly, altered the level of malondialdehyde (MDA), glutathione peroxidase (GSH-PX) and catalase (CAT), downregulated the XOD protein expression, toll-like receptor (TLR)4, nucleotide binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, interleukin-18 (IL-18), upregulated forkhead box O3a (FOXO3a), manganese superoxide dismutase (MnSOD) in a uric acid-synthesis model in mice. Protein expression of organic anion transporter 1 (OAT1), OAT3, organic cationic transporter 1 (OCT1), and OCT2 was upregulated by hesperetin intervention in a uric acid excretion model in mice. Our results proposal that hesperetin exerts a uric acid-lowering effect through inhibiting xanthine oxidase activity and protein expression, intervening in the TLR4-NLRP3 inflammasome signaling pathway, and up-regulating expression of FOXO3a, MnSOD, OAT1, OAT3, OCT1, and OCT2 proteins. Thus, hesperetin could be a promising therapeutic agent against hyperuricemia.

Uric Acid and Chronic Kidney Disease: Still More to Do

Gout and hyperuricemia are present in 25% and 60% of patients with chronic kidney disease (CKD), respectively. Despite the common association, the role of uric acid in the progression of kidney disease and in metabolic complications remains contested. Some authorities argue that the treatment of asymptomatic hyperuricemia in CKD is not indicated, and some have even suggested hyperuricemia may be beneficial. Here, we review the various arguments both for and against treatment. The weight of the evidence suggests asymptomatic hyperuricemia is likely injurious, but it may primarily relate to subgroups, those who have systemic crystal deposits, those with frequent urinary crystalluria or kidney stones, and those with high intracellular uric acid levels. We recommend carefully designed clinical trials to test if lowering uric acid in hyperuricemic subjects with cardiometabolic complications is protective.

Gout and the COVID-19 pandemic

PURPOSE OF REVIEW

This review gives an overview of recently published articles on COVID-19 and gout.

RECENT FINDINGS

People with gout are likely to be at an increased risk of poor outcomes after COVID-19 infection due to comorbid cardiometabolic conditions. The effects of chronic hyperuricemia on trained immunity, and the hyperinflammatory state induced by gout itself may also play a role. Frequent courses of glucocorticoids for gout flares may be associated with adverse outcomes after COVID-19 infection and reduced immunogenicity to the COVID-19 vaccination. Similarities between the pathophysiology of gout flares and the dysregulated inflammatory response of severe COVID-19 have been identified. Medications used in the treatment of gout, including colchicine and interleukin-1 inhibitors, have shown promise in the treatment of COVID-19 in clinical trials. Overall, the COVID-19 pandemic has had a negative impact on gout care, with patients reporting more difficulty with disease control, accessing medications and healthcare, and poorer quality of life.

SUMMARY

The COVID-19 pandemic has created many challenges for people with gout. At present, there is a lack of guidance on the management of gout during the pandemic and paucity of research assessing outcomes of COVID-19 infection in people with gout.

Purine-Induced IFN-γ Promotes Uric Acid Production by Upregulating Xanthine Oxidoreductase Expression

OBJECTIVE

Limiting purine intake, inhibiting xanthine oxidoreductase (XOR) and inhibiting urate reabsorption in proximal tubule by uricosuric drugs, to reduce serum uric acid (UA) levels, are recognized treatments for gout. However, the mechanism of increased how XOR expression and activity in hyperuricemia and gout remains unclear. This study aims to explore whether exogenous purines are responsible for increased XOR expression and activity.

METHODS

HepG2 and Bel-7402 human hepatoma cells were stimulated with exogenous purine, or were exposed to conditioned growth medium of purine-stimulated Jurkat cells, followed by measurement of XOR expression and UA production to determine the effect of lymphocyte-secreted cytokines on XOR expression in hepatocytes. The expression of STAT1, IRF1 and CBP and their binding on the XDH promoter were detected by western blotting and ChIP-qPCR. The level of DNA methylation was determined by bisulfite sequencing PCR. Blood samples from 117 hyperuricemia patients and 119 healthy individuals were collected to analyze the correlation between purine, UA and IFN-γ concentrations.

RESULTS

Excess of purine was metabolized to UA in hepatocyte metabolism by XOR that was induced by IFN-γ secreted in the conditioned growth medium of Jurkat cells in response to exogenous purine, but it did not directly induce XOR expression. IFN-γ upregulated XOR expression due to the enhanced binding of STAT1 to IRF1 to further recruit CBP to the XDH promoter. Clinical data showed positive correlation of serum IFN-γ with both purine and UA, and associated risk of hyperuricemia.

CONCLUSION

Purine not only acts as a metabolic substrate of XOR for UA production, but it induces inflammation through IFN-γ secretion that stimulates UA production through elevation of XOR expression.

Circulating microRNA alternations in primary hyperuricemia and gout

OBJECTIVES

MicroRNAs (miRNAs) are short single-stranded RNAs that play a role in the post-transcriptional regulation of gene expression. Their deregulation can be associated with various diseases, such as cancer, neurodegenerative, and immune-related diseases. The aim of our study was to compare miRNA levels in plasma that could potentially influence the progression of hyperuricemia to gout, since the mechanism of progression is still unclear.

METHODS

Total RNA, including miRNA, was isolated from the plasma of 45 patients with asymptomatic hyperuricemia, 131 patients with primary gout (including 16 patients having a gout attack), and 130 normouricemic controls. The expression of 18 selected miRNAs (cel-miR-39 and cel-miR-54 as spike-in controls, hsa-miR-16-5p and hsa-miR-25-3p as endogenous controls, hsa-miR-17-5p, hsa-miR-18a-5p, hsa-miR-30a-3p, hsa-miR-30c-5p, hsa-miR-126-3p, hsa-miR-133a-3p, hsa-miR-142-3p, hsa-miR-143-3p, hsa-miR-146a-5p, hsa-miR-155-5p, hsa-miR-222-3p, hsa-miR-223-3p, hsa-miR-488-3p and hsa-miR-920) was measured using qPCR.

RESULTS

We found that hsa-miR-17-5p, hsa-miR-18a-5p, hsa-miR-30c-5p, hsa-miR-142-3p, and hsa-miR-223-3p were significantly upregulated (p < 0.001) in the plasma of hyperuricemia and gout patients compared to normouricemic individuals. As part of the follow-up of our previous study, we found a negative correlation between hsa-miR-17-5p, hsa-miR-30c-5p, hsa-miR-126-3p, hsa-miR-142-3p, and hsa-miR-223-3p with plasma levels of chemokine MCP-1. Additionally, we found a positive correlation between CRP and plasma levels of hsa-miR-17-5p, hsa-miR-18a-5p, hsa-miR-30c-5p, hsa-miR-126-3p, hsa-miR-142-3p, hsa-miR-146a-5p, hsa-miR-155-5p, hsa-miR-222-3p, and hsa-miR-223-3p. Five of those miRNAs (hsa-miR-126-3p, hsa-miR-142-3p, hsa-miR-146a-5p, hsa-miR-155-5p, and hsa-miR-222-3p) also had a positive correlation with serum creatinine and therefore a negative correlation with eGFR.

CONCLUSION

Five miRNAs were significantly upregulated in the plasma of patients with hyperuricemia and gout (and those during a gout attack) compared to normouricemic controls. We also found a correlation between the plasma levels of several miRNA and plasma levels of MCP-1, CRP, serum creatinine, and eGFR.

Updated Evidence of the Association Between Elevated Serum Uric Acid Level and Psoriasis

Background: Our earlier meta-analysis showed that the correlation between psoriasis and hyperuricemia might be region-dependent and that hyperuricemia was more common in patients with psoriasis in Western Europe. However, no further analysis could be conducted owing to the scarcity of data. Objective: Our study aimed to further explore the association between psoriasis and hyperuricemia. Methods: Six databases (PubMed, Embase, the Cochrane Central Register of Controlled Trials, the China National Knowledge Infrastructure database, the Chinese Scientific Journals Full Text Database, and the Wanfang Data Knowledge Service Platform) were searched for studies published between January 1980 and February 2021. Results: The search strategy yielded 291 relevant studies, of which 27 observational studies were included in this analysis. Serum uric acid (SUA) levels (mean difference [MD] 0.99, 95% confidence interval [CI] 0.48-1.49, P = 0.0001) and hyperuricemia frequency (odds ratio [OR] 5.39, 95% CI 1.88-15.40, P = 0.002) were higher in the psoriasis group than in the control group, and the subgroup differences were significant. In addition, SUA levels were significantly higher in patients with moderate to severe psoriasis from European and American countries (MD 0.89, 95% CI 0.18-1.60, P = 0.01) and Southeast Asia (MD 1.79, 95% CI 0.55-3.02, P = 0.004), while no significant differences were found between the Middle East subgroup (MD 0.63, 95% CI -0.33 to 1.59, P = 0.20). Similar results were obtained from the meta-analysis of SUA levels in patients with metabolic syndrome, obesity, or a special type of psoriasis (such as arthritic or erythrodermic psoriasis). Conclusions: Our meta-analysis study provides extended data regarding the correlation between psoriasis and hyperuricemia and the differences in SUA levels between psoriasis patients and controls in Southeast Asia, the Middle East, and European and American countries. Patients with moderate to severe psoriasis in European and American countries and Southeast Asia or those with metabolic syndrome and obesity were more likely to have higher uric acid levels. Systematic Review Registration: PROSPERO, identifier: CRD42014015091.

[Analysis of the effect of asymptomatic hyperuricemia on the effectiveness after arthroscopic rotator cuff repair]

Objective

To investigate the effect of asymptomatic hyperuricemia on the effectiveness of arthroscopic rotator cuff repair.

Methods

The clinical data of 80 patients who underwent arthroscopic rotator cuff repair and met the selection criteria between March 2018 and December 2019 were retrospectively analyzed. According to the serum uric acid level, the patients were divided into hyperuric acid group (46 cases, the serum uric acid level was more than 417 μmol/L in males and was more than 357 μmol/L in females) and normal group (34 cases, serum uric acid level was lower than the above standard). There was no significant difference in gender, age, side, body mass index, blood glucose level, total cholesterol level, rotator cuff tear size, and preoperative shoulder motion, visual analogue scale (VAS) score, University of California-Los Angeles (UCLA) score, Constant score, American Shoulder and Elbow Surgeons (ASES) score, and other general data between the two groups ( P>0.05). The range of motion of abduction, forward flexion, and external rotation at 90° abduction were recorded and compared between the two groups before operation and at last follow-up; the improvement of shoulder pain was evaluated by VAS score; the improvement of shoulder function was evaluated by UCLA score, Constant score, and ASES score; and the shoulder joint MRI grade was evaluated according to Sugaya evaluation criteria.

Results

All patients were followed up 9-16 months, with an average of 11.9 months; there was no significant difference in the follow-up time between the two groups ( t=0.968, P=0.336). There were 2 cases of retear in the hyperuric acid group (including 1 case of severe tear) and 1 case of light retear in the normal group. The remaining patients in the two groups had no early-related complications. At last follow-up, the range of motion of the shoulder joints (abduction, forward flexion, external rotation at 90° abduction), VAS score, UCLA score, Constant score, and ASES score of the two groups were significantly improved when compared with preoperative ones ( P<0.05); the above indicators in the normal group were significantly better than those in the hyperuric acid group ( P<0.05). The MRI grade of the shoulder joint in the normal group was significantly better than that in the hyperuric acid group ( Z=-2.000, P=0.045).

Conclusion

Compared with patients with normal serum uric acid level, asymptomatic hyperuricemia can lead to worse recovery after arthroscopic rotator cuff repair in patients with rotator cuff tears.

The inflammatory role of silent urate crystal deposition in intercritical gout

OBJECTIVE

To study subclinical inflammation in intercritical gout patients and its relation to the estimated size of monosodium urate crystal deposition and cardiovascular risk factors.

METHODS

We performed a secretome analysis and the quantification of cytokine and adipokine plasma levels (IL-1β, IL-18, IL-6, sIL-6R, TNFα, CXCL5, RANTES, leptin, resistin and adiponectin) to analize subclinical inflammation in intercritical gout patients. Since it is currently not feasible to determinate the whole body deposit of monosodium urate crystals, we created an indirect clinical classification to estimate it. Then, we compared cytokine levels in controls and gout patients, and in patients with different crystal deposition size. We also studied the association between cytokine-levels and the number of cardiovascular risk factors.

RESULTS

Ninety consecutive patients attending a Crystal Arthritis Unit were studied. IL-18, sIL-6R, RANTES, leptin and adiponectin were higher in intercritical gout patients than in controls. An association was observed between IL-18, sIL6-R and RANTES levels and the size of crystal deposition. IL-18, sIL6-R, RANTES and leptin were higher in patients with no cardiovascular risk factors when compared with controls with no risk factors.

CONCLUSION

Our results showed that the levels of some proinflammatory cytokines and metabolic proteins are elevated in intercritical gout patients. The levels of certain cytokines was related to the estimated size of the monosodium urate crystal deposition and to the number of cardiovascular risk factors. These cytokine changes may help to explain the increase of the cardiovascular events in gout patients.

Serum Uric Acid Levels and Risk of Eight Site-Specific Cancers: A Mendelian Randomization Study

The relationship between serum uric acid (UA) levels and cancer risk remains controversial. Here, a two-sample Mendelian randomization analysis was performed to identify a causal effect of serum UA levels on cancer risk. Twenty-six single nucleotide polymorphisms strongly associated with serum UA levels were screened as genetic variants from large-scale meta-analysis data of a genome-wide association study of 110,347 European individuals. Genetic associations with eight common site-specific cancers were subsequently explored. A total of six Mendelian randomization methods were used to estimate the potential effect of serum UA levels on cancer risk, including random effects inverse variance weighting, fix effects inverse variance weighting, MR-Egger, median weighting, mode weighting, and simple mode analysis. Our primary random effects inverse variance weighted analysis revealed that no significant associations with cancers was found (all p > 0.05). Sensitivity analyses and additional analyses also showed similar pooled results. In conclusion, no significant causality between serum UA levels and cancer risk was evidenced.

The effect of baseline serum uric acid on chronic kidney disease in normotensive, normoglycemic, and non-obese individuals: A health checkup cohort study

Introduction

The independent role of serum uric acid (SUA) on kidney disease is controversial due to its association with metabolic syndrome. The objective of this study was to investigate the association of baseline SUA with development of chronic kidney disease and eGFR decline in normotensive, normoglycemic and non-obese individuals during follow up period.

Materials and methods

We included non-hypertensitive, non-diabetic, and non-obese 13,133 adults with estimated glomerular filtration rate (eGFR) ≥ 60ml/min/1.73m² who had a voluntary health check-up during 2004–2017.

Results

SUA was positively related to adjusted means of systolic blood pressure (SBP), triglyceride, body mass index, and body fat percent. SUA was inversely associated with high density lipoprotein HDL (P for trend ≤0.001). SUA was an independent risk factor for the development of diabetes, hypertension, and obesity. During 45.0 [24.0–76.0] months of median follow up, the highest quartiles of SUA showed significant risks of 30% eGFR decline compared than the lowest quartile (RR:3.701; 95% CI: 1.504–9.108). The highest quartile had a 2.2 fold (95% CI: 1.182–4.177) increase in risk for incident chronic kidney disease (CKD).

Conclusions

SUA is an independent risk factor for the development of diabetes, hypertension, and obesity in the healthy population. High SUA is associated with increased risk of CKD development and eGFR decline in participants with intact renal function.

Sustained expression of MCP-1 induced low wall shear stress loading in conjunction with turbulent flow on endothelial cells of intracranial aneurysm

Shear stress was reported to regulate the expression of AC007362, but its underlying mechanisms remain to be explored. In this study, to isolate endothelial cells of blood vessels, unruptured and ruptured intracranial aneurysm (IA) tissues were collected from IA patients. Subsequently, quantitative real‐time PCR (qRT‐PCR), Western blot and luciferase assay were performed to investigate the relationships between AC007362, miRNAs‐493 and monocyte chemoattractant protein‐1 (MCP‐1) in human umbilical vein endothelial cells (HUVECs) exposed to shear stress. Reduced representation bisulphite sequencing (RRBS) was performed to assess the level of DNA methylation in AC007362 promoter. Accordingly, AC007362 and MCP‐1 were significantly up‐regulated while miR‐493 was significantly down‐regulated in HUVECs exposed to shear stress. AC007362 could suppress the miR‐493 expression and elevate the MCP‐1 expression, and miR‐493 was shown to respectively target AC007362 and MCP‐1. Moreover, shear stress in HUVECs led to the down‐regulated DNA methyltransferase 1 (DNMT1), as well as the decreased DNA methylation level of AC007362 promoter. Similar results were also observed in ruptured IA tissues when compared with unruptured IA tissues. In conclusion, this study presented a deep insight into the operation of the regulatory network of AC007362, miR‐493 and MCP‐1 upon shear stress. Under shear stress, the expression of AC007362 was enhanced by the inhibited promoter DNA methylation, while the expression of MCP‐1 was enhanced by sponging the expression of miR‐493.

Fingolimod Phosphate (FTY720-P) Activates Protein Phosphatase 2A in Human Monocytes and Inhibits Monosodium Urate Crystal-Induced Interleukin-1β Production

Gout is a chronic inflammatory arthritis caused by monosodium urate monohydrate (MSU) crystal deposits in joints of lower limbs. Phagocytic uptake of MSU crystals by joint-resident macrophages and recruited circulating monocytes results in IL-1β expression and production. Current acute gout treatments have serious toxicities and suffer suboptimal clinical outcomes. Protein phosphatase 2A (PP2A) plays an important role in regulating signaling pathways relevant to inflammation. We hypothesized that innate immune danger signals, e.g., lipopolysaccharide (LPS) and soluble uric acid (sUA), prime human monocytes toward MSU crystal phagocytosis and that increased IL-1β production mediated by a reduction in PP2A activity and restoring PP2A activity exerts an anti-inflammatory effect in this setting. Priming monocytes with LPS + sUA increased cytosolic pro-IL-1β and mature IL-1β and enhanced MSU crystal phagocytosis and its downstream IL-1β expression (P < 0.001). A combination of LPS + sUA priming and MSU crystals reduced PP2A activity in monocytes by 60% (P = 0.013). PP2A catalytic subunit gene knockdown reduced PP2A activity and exacerbated MSU crystal-induced IL-1β expression and secretion (P < 0.0001). Fingolimod (FTY720) and its active metabolite, fingolimod phosphate (FTY720-P), were evaluated for their ability to activate PP2A in human monocytes over 24 hours. FTY720 and FTY720-P activated PP2A to a similar extent, and maximal enzyme activity occurred at 24 hours for FTY720 and at 6 hours for FTY720-P. FTY720-P (2.5 μM) reduced pro-IL-1β production and IL-1β secretion in primed and MSU crystal-stimulated monocytes (P < 0.0001) without changing the magnitude of crystal phagocytosis. We conclude that PP2A is a promising new target in acute gout. SIGNIFICANCE STATEMENT: The activity of protein phosphatase 2A (PP2A) is implicated in the enhanced expression and production of IL-1β by human monocytes in response to priming with soluble uric acid and lipopolysaccharide and phagocytosis of monosodium urate monohydrate (MSU) crystals. Fingolimod phosphate activates PP2A in human monocytes and reduces cytosolic pro-IL-1β content and its conversion to biologically active IL-1β in human monocytes exposed to MSU crystals.

Isoorientin exerts a urate-lowering effect through inhibition of xanthine oxidase and regulation of the TLR4-NLRP3 inflammasome signaling pathway

Isoorientin (ISO), a natural flavonoid compound, has been identified in several plants and its biological activity is determined and the study on lowering uric acid has not been reported. In view of the current status of treatment of hyperuricemia, we evaluated the hypouricemic effects of ISO in vivo and in vitro, and explored the underlying mechanisms. Yeast extract-induced hyperuricemia animal model as well as hypoxanthine and xanthine oxidase (XOD) co-induced high uric acid L-O2 cell model and enzymatic experiments in vitro were selected. The XOD activity and uric acid (UA) level were inhibited after the treatment of ISO in vitro and in vivo. Furthermore, serum creatinine (CRE) and blood urea nitrogen (BUN) levels were also significantly reduced and liver damage was recovered in pathological histology after the ISO administration in hyperuricemia animal model. The results of mechanism illustrated that protein expressions such as XOD, toll-like receptor 4 (TLR4), cathepsin B (CTSB), NLRP3, and its downstream caspase-1 as well as interleukin-18 (IL-18) were markedly downregulated by ISO intervention in vitro and in vivo. Our results suggest that ISO exerts a urate-lowering effect through inhibiting XOD activity and regulating TLR4-NLRP3 inflammasome signal pathway, thus representing a promising candidate therapeutic agent for hyperuricemia. Both animal models and in vitro experiments suggested that ISO may effectively lower uric acid produce. The mechanism might be the inhibition of XOD activity and NLRP3 inflammasome of upregulation.

Metabolism-Associated Molecular Patterns (MAMPs)

Metabolic diseases pose a tremendous health threat in both developed and developing countries. The pathophysiology of metabolic diseases is complex but has been shown to be closely associated with sterile inflammation, which is initiated by various danger molecules derived from metabolic overload, such as oxidized low-density lipoproteins (OxLDLs), free fatty acids (FFAs), glucose, advanced glycation end products (AGEs), and cholesterol. These danger signals are sensed by pattern recognition receptors (PRRs) to activate proinflammatory signaling pathways and promote the release of proinflammatory mediators, leading to chronic low-grade inflammation. Although these harmful metabolic stimuli are generally regarded as damage-associated molecular patterns (DAMPs), a more specific definition and accurate classification for these DAMPs is still missing. In this opinion, we classify the harmful metabolic stimuli that can incite inflammatory responses and tissue damage via instigating PRRs as metabolism-associated molecular patterns (MAMPs), and we summarize their roles in metaflammation-mediated metabolic diseases.

Soluble uric acid induces myocardial damage through activating the NLRP3 inflammasome

Uric acid crystal is known to activate the NLRP3 inflammasome and to cause tissue damages, which can result in many diseases, such as gout, chronic renal injury and myocardial damage. Meanwhile, soluble uric acid (sUA), before forming crystals, is also related to these diseases. This study was carried out to investigate whether sUA could also activate NLRP3 inflammasome in cardiomyocytes and to analyse the mechanisms. The cardiomyocyte activity was monitored, along with the levels of mature IL-1β and caspase-1 from H9c2 cells following sUA stimulus. We found that sUA was able to activate NLRP3 inflammasome, which was responsible for H9c2 cell apoptosis induced by sUA. By elevating TLR6 levels and then activating NF-κB/p65 signal pathway, sUA promoted NLRP3, pro-caspase 1 and pro-IL-1β production and provided the first signal of NLRP3 inflammasome activation. Meanwhile, ROS production regulated by UCP2 levels also contributed to NLRP3 inflammasome assembly and subsequent caspase 1 activation and mature IL-1β secretion. In addition, the tlr6 knockdown rats suffering from hyperuricemia showed the lower level of IL-1β and an ameliorative cardiac function. These findings suggest that sUA activates NLRP3 inflammasome in cardiomyocytes and they may provide one therapeutic strategy for myocardial damage induced by sUA.

Friend or Foe? An Unrecognized Role of Uric Acid in Cancer Development and the Potential Anticancer Effects of Uric Acid-lowering Drugs

In recent years, metabolic syndrome (Mets) has been a hot topic among medical scientists. Mets has an intimate relationship with the incidence and development of various cancers. As a contributory factor of Mets, hyperuricemia actually plays an inseparable role in the formation of various metabolic disorders. Although uric acid is classically considered an antioxidant with beneficial effects, mounting evidence indicates that a high serum uric acid (SUA) level may serve as a pro-oxidant to generate inflammatory reactions and oxidative stress. In this review, we describe the unrecognized role of hyperuricemia in cancer development and summarize major mechanisms linking uric acid to carcinogenesis. Furthermore, we also discuss the potential mechanism of liver metastasis of cancer and list some types of uric acid-lowering agents, which may exert anticancer effects.

Uric acid pathway activation during respiratory virus infection promotes Th2 immune response via innate cytokine production and ILC2 accumulation

Respiratory syncytial virus (RSV) infects a majority of infants and can cause severe disease leading to increased risk to develop asthma later in life. In the present studies we detected high levels of uric acid pathway components during RSV infection and examined whether they altered the pathogenesis of RSV infection. Inhibition of uric acid (UA) pathway activation during RSV infection in airway epithelial cells using XOI decreased the expression of IL-33, thymic stromal lymphopoietin (TSLP), and CCL2. In addition, treatment of RSV infected bone marrow-derived macrophages with XOI decreased production of IL-1β. Thus, UA activation of different cell populations contributes different innate immune mediators that promote immunopathogenesis. When mice were treated with XOI or interleukin-1 receptor antagonist (IL1-ra) during RSV infection decreased pulmonary mucus was observed along with significantly reduced numbers of ILC2 and macrophages, accompanied by decreased IL-33 in bronchoalveolar lavage of the treated mice. These findings provide mechanistic insight into the development of RSV immunopathology and indicate that xanthine metabolites and UA are key immunoregulator molecules during RSV infection. Moreover, these findings suggest uric acid and IL-1β as possible therapeutic targets to attenuate severe RSV disease.

Advances in our understanding of gout as an auto-inflammatory disease

Gout, the most common inflammatory arthritis, is the result of hyperuricemia and inflammation induced by monosodium urate (MSU) crystal deposition. However, most people with hyperuricemia will never develop gout, implying a molecular-genetic contribution to the development of gout. Recent genomic studies reveal links between certain genetic variations and gout. We highlight recent advances in our understanding of gout as an auto-inflammatory disease. We review the auto-inflammatory aspects of gout, including the inflammasome and thirteen gout-associated inflammatory-pathway genes and associated comorbidities. This information provides important insights into emerging immune-modulating targets in the management of gout, and future novel therapeutic targets in gout treatment. Cumulatively, this has important implications for treating gout as an auto-inflammatory disease, as opposed to a purely metabolic disease.

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

BACKGROUND/OBJECTIVE

Although gout flares are featured by systemic signs of inflammation, cellular sources of inflammatory mediators are not yet properly characterized. Our objective was to evaluate serum levels and gene expression in peripheral blood mononuclear cells (PBMCs) of several molecules associated with the activation of NLRP3 inflammasome.

METHODS

Fifteen patients with gout flare and 15 individuals with asymptomatic hyperuricemia were cross-sectionally studied. Serum levels of interleukin 1β (IL-1β), IL-18, monocyte chemoattractant protein 1/chemokine (C-C motif) ligand 2 (CCL2), and vascular cell adhesion molecule 1 were measured as a reflection of systemic inflammation, whereas the expression of NLRP3, CASP1, IL18, and CCL2 genes was measured to assess the inflammatory characteristics of PBMCs.

RESULTS

Serum levels of IL-1β (1.27 [0.07-1.99] pg/mL vs. 0 [0-0.82] pg/mL, p = 0.032) and vascular cell adhesion molecule 1 (606 [435-748] pg/mL vs. 349 [305-422] pg/mL, p = 0.014) were significantly higher in patients with gout flare than in individuals with asymptomatic hyperuricemia, whereas differences in IL-18 and monocyte chemoattractant protein 1/CCL2 were not found. Notably, no differences were observed in the expression of NLRP3, CASP1, IL18, or CCL2 in PBMCs from individuals of one or another group.

CONCLUSIONS

Systemic inflammation during gout flares does not appear to be associated with NLRP3 inflammasome activation in PBMCs, suggesting that it may represent the systemic spread of local (synovial) inflammation to monosodium urate crystals, which provides a rationale for redirecting anti-inflammatory therapy from a systemic approach to one centered on the inflamed joint.

Studies on the Anti-Gouty Arthritis and Anti-hyperuricemia Properties of Astilbin in Animal Models

The purpose of this study was to investigate potential anti-gouty effect of astilbin (AS) and its possible mechanisms. In mice with hyperuricemia induced by potassium oxonate (OXO) and yeast extract powder (YEP), AS and febuxostat (FB) reduced the serum uric acid (UA) and xanthine oxidase (XO). Moreover, AS and FB reduced the levels of reactive oxygen species and increased the content of superoxide dismutase (SOD), glutathione peroxidase and catalase present in the serum. In acute gouty arthritis rats induced by intraarticular monosodium urate crystal injection, AS and Colchicine (COL) alleviated the ankle joints swelling, and reduced the inflammatory cell infiltration. AS also reduced the levels of interleukin 1β, interleukin 6, tumor necrosis factor alpha and monocyte chemoattractant protein 1 in liver. The present study first confirmed the anti-gouty effect of AS in mice with hyperuricemia and rats with acute gouty arthritis, which provides the experimental evidence for further evaluation of AS as a candidate for gout treatment.

Urate-induced immune programming: Consequences for gouty arthritis and hyperuricemia

Trained immunity is a process in which innate immune cells undergo functional reprogramming in response to pathogens or damage-associated molecules leading to an enhanced non-specific immune response to subsequent stimulation. While this capacity to respond more strongly to stimuli is beneficial for host defense, in some circumstances it can lead to maladaptive programming and chronic inflammation. Gout is characterized by persistent low-grade inflammation and is associated with an increased number of comorbidities. Hyperuricemia is the main risk factor for gout and is linked to the development of comorbidities. Several experimental studies have shown that urate can mechanistically alter the inflammatory capacity of myeloid cells, while observational studies have indicated an association of hyperuricemia to a wide spectrum of common adult inflammatory diseases. In this review, we argue that hyperuricemia is a main culprit in the development of the long-term systemic inflammation seen in gout. We revisit existing evidence for urate-induced transcriptional and epigenetic reprogramming that could lead to an altered functional state of circulating monocytes consisting in enhanced responsiveness and maladaptive immune responses. By discussing specific functional adaptations of monocytes and macrophages induced by soluble urate or monosodium urate crystals and their contribution to inflammation in vitro and in vivo, we further enforce that urate is a metabolite that can induce innate immune memory and we discuss future research and possible new therapeutic approaches for gout and its comorbidities.

The burden of subclinical intra-articular inflammation in gout

OBJECTIVE

To assess the burden of subclinical intra-articular inflammation using ultrasound in people with gout.

METHODS

A pilot, prospective longitudinal cohort of 28 participants with gout were examined twice, once during a gout flare (n = 25) and then during an inter-critical phase (n = 27). At each visit, a 52 joint count was done followed by ultrasound examination for detection of intra-articular power Doppler (PD) signal. Clinically active joints were defined as tender and swollen. Data was collected on patient reported gout pain - visual analog scale (VAS) (painVAS), physician global VAS (physicianVAS), Health Assessment Questionnaire (HAQ), serum uric acid, erythrocyte sedimentation rate (ESR), and high-sensitivity C-reactive protein (HsCRP).

RESULTS

At the flare visit, participants had a median of 1 clinically active joint (interquartile range [IQR] 1-2), and a median of 5 joints with a PD score ≥ 2 (IQR 4-10, P < .001). At the inter-critical visit, participants reported an median of 0 clinically active joints (IQR 0-0), and a median of 4 joints with a PD score ≥ 2 (IQR 3-7, P < .001). Physician VAS (5.69 vs 3.40, P < .001), painVAS (6 vs 0, P < .001), HAQ (0.75 vs 0.12, P = .032), and ESR (29 vs 13.5 mm/h, P = .02) were higher at the acute visit, but HsCRP levels were similar (8.88 vs 5.15 mg/L, P = .062).

CONCLUSION

This pilot study established the presence of subclinical intra-articular inflammation in gout at both acute and inter-critical phases. Despite the apparent resolution of symptoms after an acute flare, a relatively high proportion of joints had subclinical inflammation in the inter-critical visit. The long-term implications of untreated subclinical joint inflammation are not clear.

Asymptomatic hyperuricaemia: a silent activator of the innate immune system

Asymptomatic hyperuricaemia affects ~20% of the general population in the USA, with variable rates in other countries. Historically, asymptomatic hyperuricaemia was considered a benign laboratory finding with little clinical importance in the absence of gout or kidney stones. Yet, increasing evidence suggests that asymptomatic hyperuricaemia can predict the development of hypertension, obesity, diabetes mellitus and chronic kidney disease and might contribute to disease by stimulating inflammation. Although urate has been classically viewed as an antioxidant with beneficial effects, new data suggest that both crystalline and soluble urate activate various pro-inflammatory pathways. This Review summarizes what is known about the role of urate in the inflammatory response. Further research is needed to define the role of asymptomatic hyperuricaemia in these pro-inflammatory pathways.

Interaction of the p.Q141K Variant of the ABCG2 Gene with Clinical Data and Cytokine Levels in Primary Hyperuricemia and Gout

Gout is an inflammatory arthritis influenced by environmental risk factors and genetic variants. The common dysfunctional p.Q141K allele of the ABCG2 gene affects gout development. We sought after the possible association between the p.Q141K variant and gout risk factors, biochemical, and clinical determinants in hyperuricemic, gouty, and acute gouty arthritis cohorts. Further, we studied the correlation of p.Q141K allele and levels of pro-/anti-inflammatory cytokines. Coding regions of the ABCG2 gene were analyzed in 70 primary hyperuricemic, 182 gout patients, and 132 normouricemic individuals. Their genotypes were compared with demographic and clinical parameters. Plasma levels of 27 cytokines were determined using a human multiplex cytokine assay. The p.Q141K variant was observed in younger hyperuricemic/gout individuals (p = 0.0003), which was associated with earlier disease onset (p = 0.004), trend toward lower BMI (p = 0.056), and C-reactive protein (CRP, p = 0.007) but a higher glomerular filtration rate (GFR, p = 0.035). Levels of 19 cytokines were higher, mainly in patients with acute gouty arthritis (p < 0.001), irrespective of the presence of the p.Q141K variant. The p.Q141K variant influences the age of onset of primary hyperuricemia or gout and other disease-linked risk factors and symptoms. There was no association with cytokine levels in the circulation.

A C-terminal CXCL8 peptide based on chemokine-glycosaminoglycan interactions reduces neutrophil adhesion and migration during inflammation

Leucocyte recruitment is critical during many acute and chronic inflammatory diseases. Chemokines are key mediators of leucocyte recruitment during the inflammatory response, by signalling through specific chemokine G-protein-coupled receptors (GPCRs). In addition, chemokines interact with cell-surface glycosaminoglycans (GAGs) to generate a chemotactic gradient. The chemokine interleukin-8/CXCL8, a prototypical neutrophil chemoattractant, is characterized by a long, highly positively charged GAG-binding C-terminal region, absent in most other chemokines. To examine whether the CXCL8 C-terminal peptide has a modulatory role in GAG binding during neutrophil recruitment, we synthesized the wild-type CXCL8 C-terminal [CXCL8 (54-72)] (Peptide 1), a peptide with a substitution of glutamic acid (E) 70 with lysine (K) (Peptide 2) to increase positive charge; and also, a scrambled sequence peptide (Peptide 3). Surface plasmon resonance showed that Peptide 1, corresponding to the core CXCL8 GAG-binding region, binds to GAG but Peptide 2 binding was detected at lower concentrations. In the absence of cellular GAG, the peptides did not affect CXCL8-induced calcium signalling or neutrophil chemotaxis along a diffusion gradient, suggesting no effect on GPCR binding. All peptides equally inhibited neutrophil adhesion to endothelial cells under physiological flow conditions. Peptide 2, with its greater positive charge and binding to polyanionic GAG, inhibited CXCL8-induced neutrophil transendothelial migration. Our studies suggest that the E70K CXCL8 peptide, may serve as a lead molecule for further development of therapeutic inhibitors of neutrophil-mediated inflammation based on modulation of chemokine-GAG binding.

Prognostic factors associated with early gout flare recurrence in patients initiating urate-lowering therapy during an acute gout flare

Lowering serum urate levels below the threshold for crystal formation with urate-lowering therapy (ULT) has been associated with a lower risk for gout flare reoccurrences. However, gout patients on ULT still commonly suffer from recurring gout flares. The purpose of this study was to explore prognostic factors associated with gout flare recurrence within the first 3 months, in gout patients starting ULT during an acute gout flare. Post-hoc analysis of trial data on acute gout patients randomized to either gout flare standard of care or anakinra treatment were used, including baseline demographic, laboratory, clinical, and patient-reported variables, as well as 3-month follow-up data on gout flare recurrences. Only patients starting ULT at baseline were included. Using variable selection based on clinical relevance, univariate, and multivariate binary logistic regression analyses were done to examine predictors of gout flare reoccurrence. A total of 75 patients were included in this study, of which 36 (48%) experienced a gout flare ≤ 3 months post baseline. The multivariate regression analysis revealed that CRP levels > 30 mg/L (OR 9.47) and lack of prophylaxis when starting ULT (OR 11.56) were independently associated with gout flare recurrence. Similar results were found for the univariate regression analyses. Our results show that CRP levels > 30 mg/L and lack of prophylaxis when starting ULT were prognostic factors for early gout flare reoccurrence in patients starting ULT during an acute gout flare. KEY POINTS: • Gout flare recurrences were common within the first 3 months after starting urate-lowering therapy in gout patients. • Intake of prophylaxis when starting ULT had a strong protective effect on gout flare recurrences. • C-reactive protein level > 30 mg/L was an additional prognostic factor for early (≤ 3 months) gout flare reoccurrence in patients starting ULT during an acute gout flare.

Inhibitors of Xanthine Oxidase: Scaffold Diversity and Structure-Based Drug Design

Xanthine oxidase (XO) is the enzyme responsible for the catabolism of purines and their conversion into uric acid. XO is thus the target for the treatment of hyperuricemia and gout. For more than 50 years the only XO inhibitor drug available on the market was the purine analogue allopurinol. In the last decade there has been a resurgence in the search for new inhibitors of XO, as the activity of XO and hyperuricemia have also been associated with a variety of conditions such as diabetes, hypertension, and other cardiovascular diseases. In recent years the non-purine inhibitor febuxostat was approved in Europe and the USA for the treatment of hyperuricemia. This drug was followed by another XO inhibitor called topiroxostat. This review discusses the molecular structures and activities of the multiple classes of inhibitors that have been developed since the discovery of allopurinol, with a brief review of the molecular interactions between inhibitors and XO active site residues for the most important molecules. The challenges ahead for the discovery of new inhibitors of XO with novel chemical structures are discussed.

A Randomized Controlled Trial of Chuanhutongfeng Mixture for the Treatment of Chronic Gouty Arthritis by Regulating miRNAs

Background

We investigated whether Chuanhutongfeng mixture has actions on chronic gouty arthritis (CGA) by regulating miRNAs.

Methods

A total of 255 patients with CGA and 30 controls were enrolled. miRNA expression profiles and cluster analysis were preformed; RT-qPCR was used to detect miRNAs associated with CGA. Patients were allocated into Chuanhutongfeng mixture, allopurinol (positive control), and control (etoricoxib) groups. Expression of plasma miRNAs was measured before and after treatments; expression of chemokine 2 (CCL2) and interleukin 8 (CXCL8) was determined by ELISA.

Results

48 miRNAs were differentially expressed and compared to controls. 36 miRNAs expression levels were > 1.5 times and 12 miRNAs < 1.5 times compared to the controls. miR-339-5p, miR-486-5p, and miR-361-5p levels in patients with CGA were lower than in controls (P < 0.05). This trial showed that the Chuanhutongfeng mixture and allopurinol groups had upregulated the expressions of miR-486-5, miR-339-5p, and miR-361-5p and decreased levels of CCL2 and CXCL8 proteins. After 8 weeks of treatment, Chuanhutongfeng mixture decreased serum uric acid levels more than allopurinol (P < 0.05) and reduced levels of CCL2 and CXCL8 protein significantly more than in the allopurinol and control groups.

Conclusions

The therapeutic actions of Chuanhutongfeng mixture inhibit the expression of proteins CCL2 and CXCL8 in plasma and upregulated the expressions of three miRNAs (miR-486-5p, miR-339-5p, and miR-361-5p).

Male asymptomatic hyperuricemia patients display a lower number of NKG2D+ NK cells before and after a low-purine diet

BACKGROUND

Aberrant activation of the immune system has been reported in asymptomatic hyperuricemia (HUA) patients. However, very few studies have elucidated the role of natural killer (NK) cells in this disease.

METHODS

In this study, we evaluated the relationship between NK cells and HUA in 16 control subjects and 20 patients, who were all on a low-purine diet. We analyzed the number of circulating NK cells, its subsets, interferon-γ, and CD107 NK cells, by flow cytometry, before and after 4 and 24 weeks of diet control. We also assessed the potential association of the NK cells with clinical measures.

RESULTS

The patients consistently had a lower number of NKG2D NK cells before and after low-purine diet, even the serum uric acid (SUA) levels <7 mg/dL after diet control. Moreover, a lower number of NK cells and a higher number of CD107a NK cells were observed on recruitment. Low-purine diet was benefit on the improvement of the SUA levels, body mass index (BMI), and the number and functions of NK cells. Furthermore, the number of CD3CD56 NK cells and NKG2D NK cells negatively correlated with the BMI before and after diet control.

CONCLUSION

The consistent lower number of NKG2D NK cells and correlated with BMI before and after low-purine diet may be involved in the occurrence and development of HUA.

Soluble uric acid increases PDZK1 and ABCG2 expression in human intestinal cell lines via the TLR4-NLRP3 inflammasome and PI3K/Akt signaling pathway

BACKGROUND

In addition to the kidney, the intestine is one of the most important organs involved in uric acid excretion. However, the mechanism of urate excretion in the intestine remains unclear. Therefore, the relationship between soluble uric acid and the gut excretion in human intestinal cells was explored. The relevant signaling molecules were then also examined.

METHODS

HT-29 and Caco-2 cell lines were stimulated with soluble uric acid. Western blotting and qRT-PCR were used to measure protein and mRNA levels. Subcellular fractionation methods and immunofluorescence were used to quantify the proteins in different subcellular compartments. Flow cytometry experiments examined the function of ATP-binding cassette transporter, subfamily G, member 2 (ABCG2). Small interfering RNA transfection was used to assess the interaction between ABCG2 and PDZ domain-containing 1 (PDZK1).

RESULTS

Soluble uric acid increased the expression of PDZK1 and ABCG2. The stimulation of soluble uric acid also facilitated the translocation of ABCG2 from the intracellular compartment to the plasma membrane and increased its transport activity. Moreover, the upregulation of PDZK1 and ABCG2 by soluble uric acid was partially decreased by either TLR4-NLRP3 inflammasome inhibitors or PI3K/Akt signaling inhibitors. Furthermore, PDZK1 knockdown significantly inhibited the expression and transport activity of ABCG2 regardless of the activation by soluble uric acid, demonstrating a pivotal role for PDZK1 in the regulation of ABCG2.

CONCLUSIONS

These findings suggest that urate upregulates the expression of PDZK1 and ABCG2 for excretion in intestinal cells via activating the TLR4-NLRP3 inflammasome and PI3K/Akt signaling pathway.

CD14+ Cells with the Phenotype of Infiltrated Monocytes Consist of Distinct Populations Characterized by Anti-inflammatory as well as Pro-inflammatory Activity in Gouty Arthritis

It has been suggested that inflammasome-mediated IL-1β production in monocytic cells is responsible for the acute inflammatory response in gouty arthritis. However, phenotypical and functional analyses of monocytes during gouty arthritis have yet to be conducted. Therefore, we investigated the characteristics of monocytes/macrophages in the synovial fluid cells of patients with acute gout. The number and frequency of monocytes/macrophages in the synovial fluid mononuclear cells (SFMCs) of patients was examined. The expression of markers for monocyte recruitment and tissue-resident macrophages, the production of pro-inflammatory and anti-inflammatory cytokines, and phagocytosis were analyzed in the monocytes/macrophages of patients with acute gout attacks. The number and frequency of CD14⁺CD3⁻CD19⁻CD56⁻ monocytes/macrophages was markedly increased in the SFMCs of patients with gout compared to those of patients with rheumatoid arthritis (RA). CD14⁺ cells showed the phenotypes of infiltrated monocytes rather than tissue-resident macrophages, characterized by a high expression of CCR2, MRP8, and MRP14, but a low expression of MERTK and 25F9. These cells had the capacity to produce pro-inflammatory cytokines such as TNF-α and IL-1β after stimulation with lipopolysaccharides. In addition, anti-inflammatory features, including CD163 expression and IL-10 production from CD14⁺ cells, were significantly higher in patients with gout than in those with RA. CD14⁺ cells with phenotype of M2 macrophages had high phagocytic activity for monosodium urate crystals. Thus, our results indicate that monocytes/macrophages from patients with gout have the phenotype of infiltrated monocytes, and these cells consist of different populations characterized by anti-inflammatory activities as well as pro-inflammatory functions.

What makes gouty inflammation so variable?

Acute gout arthritis flares contribute dominantly to gout-specific impaired health-related quality of life, representing a progressively increasing public health problem. Flares can be complex and expensive to treat, partly due to the frequent comorbidities. Unmet needs in gout management are more pressing given the markedly increasing gout flare hospital admission rates. In addition, chronic gouty arthritis can cause joint damage and functional impairment. This review addresses new knowledge on the basis for the marked, inherent variability of responses to deposited urate crystals, including the unpredictable and self-limited aspects of many gout flares. Specific topics reviewed include how innate immunity and two-signal inflammasome activation intersect with diet, metabolism, nutritional biosensing, the microbiome, and the phagocyte cytoskeleton and cell fate. The paper discusses the roles of endogenous constitutive regulators of inflammation, including certain nutritional biosensors, and emerging genetic and epigenetic factors. Recent advances in the basis of variability in responses to urate crystals in gout provide information about inflammatory arthritis, and have identified potential new targets and strategies for anti-inflammatory prevention and treatment of gouty arthritis.

Ozonated autohemotherapy modulates the serum levels of inflammatory cytokines in gouty patients

Objectives

Ozonated autohemotherapy (O3-AHT) has been used to effectively treat gout, but the underlying therapeutic mechanisms remain unknown. In this study, as an initial effort to understand the therapeutic mechanisms of O3-AHT, we aim to examine the effect of O3-AHT on serum inflammatory cytokine levels in gouty patients.

Patients and methods

Three groups of patients and healthy subjects were recruited, including the gouty (n=10), hyperuricemia (n=10), and healthy control (n=11) groups. Cytometric bead array was applied to examine 12 cytokines before (T0), during (T1), and after (T2) therapies.

Results

Three cytokines, IL-8, IL-12, and MCP-1, were detectable in all participants. Before O3-AHT, the average serum levels of IL-8 and MCP-1 were higher in the gout group than in the hyperuricemia and healthy control groups, confirming the inflammation status in gouty patients. After the 5th course of O3-AHT (T1), IL-8 level was significantly increased compared to that at T0. IL-12 level was also raised at T1, although the difference did not reach statistical significance. After completing the therapy, both IL-8 and IL-12 levels decreased to levels lower than those at T0. MCP-1 level remained essentially unchanged during and after treatment.

Conclusion

Our results indicate that O3-AHT induces a significant change in serum cytokine levels, suggesting that modulating the inflammatory process is one of the therapeutic mechanisms underlying O3-AHT. In addition, the sensitive response of serum IL-8 and IL-12 levels to O3-AHT suggests that these cytokines may be developed as biomarkers to evaluate the therapeutic effect of O3-AHT in gouty patients.

Gout: an Asia-Pacific update

Even though, Hippocrates recognized gout as an affection of older men and a product of high living long back in 5th century BC, this painful condition promises to accompany humanity to the 21st century. The incidence is progressively rising and females are also affected in the modern era. There are also regional and ethnic variations in the incidence, the genetics of which is being studied. The recommended best therapy for the acute attacks and long term prophylaxis has improved remarkably in the recent years. However, patients are often treated inadequately and risk factors for their disease are not well explored in daily practice. Although well designed long term studies of current and newer treatment are welcomed, educating doctors especially the primary care physicians who manage majority of gout cases, in optimizing the currently available management options would improve the present care.

CXCL9-Derived Peptides Differentially Inhibit Neutrophil Migration In Vivo through Interference with Glycosaminoglycan Interactions

Several acute and chronic inflammatory diseases are driven by accumulation of activated leukocytes due to enhanced chemokine expression. In addition to specific G protein-coupled receptor-dependent signaling, chemokine-glycosaminoglycan (GAG) interactions are important for chemokine activity in vivo. Therefore, the GAG-chemokine interaction has been explored as target for inhibition of chemokine activity. It was demonstrated that CXCL9(74-103) binds with high affinity to GAGs, competed with active chemokines for GAG binding and thereby inhibited CXCL8- and monosodium urate (MSU) crystal-induced neutrophil migration to joints. To evaluate the affinity and specificity of the COOH-terminal part of CXCL9 toward different GAGs in detail, we chemically synthesized several COOH-terminal CXCL9 peptides including the shorter CXCL9(74-93). Compared to CXCL9(74-103), CXCL9(74-93) showed equally high affinity for heparin and heparan sulfate (HS), but lower affinity for binding to chondroitin sulfate (CS) and cellular GAGs. Correspondingly, both peptides competed with equal efficiency for CXCL8 binding to heparin and HS but not to cellular GAGs. In addition, differences in anti-inflammatory activity between both peptides were detected in vivo. CXCL8-induced neutrophil migration to the peritoneal cavity and to the knee joint were inhibited with similar potency by intravenous or intraperitoneal injection of CXCL9(74-103) or CXCL9(74-93), but not by CXCL9(86-103). In contrast, neutrophil extravasation in the MSU crystal-induced gout model, in which multiple chemoattractants are induced, was not affected by CXCL9(74-93). This could be explained by (1) the lower affinity of CXCL9(74-93) for CS, the most abundant GAG in joints, and (2) by reduced competition with GAG binding of CXCL1, the most abundant ELR+ CXC chemokine in this gout model. Mechanistically we showed by intravital microscopy that fluorescent CXCL9(74-103) coats the vessel wall in vivo and that CXCL9(74-103) inhibits CXCL8-induced adhesion of neutrophils to the vessel wall in the murine cremaster muscle model. Thus, both affinity and specificity of chemokines and the peptides for different GAGs and the presence of specific GAGs in different tissues will determine whether competition can occur. In summary, both CXCL9 peptides inhibited neutrophil migration in vivo through interference with GAG interactions in several animal models. Shortening CXCL9(74-103) from the COOH-terminus limited its GAG-binding spectrum.

Serum uric acid and the risk of cardiovascular and renal disease

Substantial evidence suggests that chronic hyperuricemia is an independent risk factor for hypertension, metabolic syndrome, chronic kidney disease (CKD) and cardiovascular diseases. This highlights the need for greater attention to serum uric acid levels when profiling patients, and suggests that the threshold above which uricemia is considered abnormal is 6  mg/dl, in light of the available evidence. Another important question is whether lowering serum uric acid can improve cardiovascular and renal outcomes, and what therapeutic mechanism of action could provide more clinical benefits to patients; the available literature shows a trend toward improvement associated with administration of urate-lowering drugs, in particular for the xanthine oxidase inhibitors. The demonstrated efficacy of urate-lowering therapy on outcomes other than gout flares leads to the consideration that treatment may be beneficial even in the absence of overt gout when hyperuricemia accompanies other clinical conditions, such as urate deposition, advanced CKD or cardiovascular risk factors.

Presence of gout is associated with increased prevalence and severity of knee osteoarthritis among older men: results of a pilot study

BACKGROUND

Gout and osteoarthritis (OA) are the most prevalent arthritides, but their relationship is neither well established nor well understood.

OBJECTIVES

We assessed whether a diagnosis of gout or asymptomatic hyperuricemia (AH) is associated with increased prevalence/severity of knee OA.

METHODS

One hundred nineteen male patients aged 55 to 85 years were sequentially enrolled from the primary care clinics of an urban Veterans Affairs hospital, assessed and categorized into 3 groups: gout (American College of Rheumatology Classification Criteria), AH (serum urate ≥6.8 mg/dL, no gout), and control (serum urate <6.8 mg/dL, no gout). Twenty-five patients from each group subsequently underwent formal assessment of knee OA presence and severity (American College of Rheumatology Clinical/Radiographic Criteria, Kellgren-Lawrence grade). Musculoskeletal ultrasound was used to detect monosodium urate deposition at the knees and first metatarsophalangeal joints.

RESULTS

The study showed 68.0% of gout, 52.0% of AH, and 28.0% of age-matched control subjects had knee OA (gout vs control, P = 0.017). Odds ratio for knee OA in gout versus control subjects was 5.46 prior to and 3.80 after adjusting for body mass index. Gout subjects also had higher Kellgren-Lawrence grades than did the control subjects (P = 0.001). Subjects with sonographically detected monosodium urate crystal deposition on cartilage were more likely to have OA than those without (60.0 vs 27.5%, P = 0.037), with crystal deposition at the first metatarsophalangeal joints correlating most closely with OA knee involvement.

CONCLUSIONS

Knee OA was more prevalent in gout patients versus control subjects and intermediate in AH. Knee OA was more severe in gout patients versus control subjects.

Foot-related pain and disability and spatiotemporal parameters of gait during self-selected and fast walking speeds in people with gout: A two-arm cross sectional study

OBJECTIVES

To examine gait parameters in people with gout during different walking speeds while adjusting for body mass index (BMI) and foot-pain, and to determine the relationship between gait parameters and foot-pain and disability.

METHOD

Gait parameters were measured using the GAITRite™ walkway in 20 gout participants and 20 age- and sex-matched controls during self-selected and fast walking speeds. Foot-pain and disability was measured using the Manchester Foot Pain and Disability Index (MFPDI) which contains four domains relating to function, physical appearance, pain and work/leisure.

RESULTS

At the self-selected speed, gout participants demonstrated increased step time (p=0.017), and stance time (p=0.012), and reduced velocity (p=0.031) and cadence (p=0.013). At the fast speed, gout participants demonstrated increased step time (p=0.007), swing time (p=0.005) and stance time (p=0.019) and reduced velocity (p=0.036) and cadence (p=0.009). For participants with gout, step length was correlated with total MFPDI (r=-0.62, p=0.008), function (r=-0.65, p=0.005) and physical appearance (r=-0.50, p=0.041); stride length was correlated with total MFPDI (r=-0.62, p=0.008), function (r=-0.65, p=0.005) and physical appearance (r=-0.50, p=0.041); and velocity was correlated with total MFPDI (r=-0.60, p=0.011), function (r=-0.63, p=0.007) and work/leisure (r=-0.53, p=0.030).

CONCLUSION

Gait patterns exhibited by people with gout are different from controls during both self-selected and fast walking speeds, even after adjusting for BMI and foot-pain. Additionally, gait parameters were strongly correlated with patient-reported functional limitation, physical appearance and work/leisure difficulties, while pain did not significantly influence gait in people with gout.

Characteristics of the first metatarsophalangeal joint in gout and asymptomatic hyperuricaemia: a cross-sectional observational study

Background

This study aimed to identify patient-reported outcomes and clinician-assessed characteristics of the first metatarsophalangeal joint (1MTPJ) in people with gout and with asymptomatic hyperuricaemia by comparing them to normouricaemic controls.

Methods

Twenty four people with gout (without current symptoms of acute arthritis), 29 with asymptomatic hyperuricaemia and 34 age- and sex-matched controls participated in this cross-sectional observational study. Patient-reported outcomes included 1MTPJ pain, foot pain and disability, body pain, lower limb function, activity limitation and overall wellbeing. Clinician-assessed characteristics of the 1MTPJ included range of motion (ROM), plantar- and dorsi-flexion force, foot posture, temperature and hallux valgus severity.

Results

Compared to controls, participants with gout reported greater 1MTPJ pain (p = 0.014), greater foot pain and disability (p < 0.001), increased odds of having disabling foot pain (odds ratio (OR) 13.4, p < 0.001), decreased lower limb function for daily living (p = 0.002) and recreational (p < 0.001) activities, increased activity limitation (p = 0.002), reduced overall wellbeing (p = 0.034), reduced ROM (p < 0.001), reduced plantarflexion force (p = 0.012), increased 1MTPJ plantar (p = 0.004), dorsal (p = 0.003) and medial (p = 0.004) temperature and had increased odds of having more severe hallux valgus (OR 0.3 p = 0.041). Compared to controls, participants with asymptomatic hyperuricaemia had increased odds of having disabling foot pain (OR 4.2, p = 0.013), increased activity limitation (p = 0.033), decreased lower limb function for daily living (p = 0.026) and recreational (p = 0.010) activities, increased 1MTPJ plantarflexion force (p = 0.004) and a more pronated foot type (p = 0.036).

Conclusions

People with gout demonstrate 1MTPJ-specific changes indicative of subclinical inflammation, even in the absence of acute arthritis. People with asymptomatic hyperuricaemia, who exhibit no features or symptoms of gout, also report high levels of foot- and lower limb-related pain and disability.

Soluble monosodium urate, but not its crystal, induces toll like receptor 4-dependent immune activation in renal mesangial cells

BACKGROUND

Uric acid has emerged as a novel and potential modifiable risk factor for the incidence and progression of kidney diseases, however, the deteriorate effect of uric acid on renal mesangial cells remains unclear. The present study is to examine the immune activation of soluble and crystal forms of uric acid in human mesangial cells.

METHODS

We stimulated primary human mesangial cells (HMCs) with increasing concentrations (from 50 to 200 μg/ml) of soluble monosodium urate (MSU) or MSU crystals. We examined interleukin (IL)-1β protein expression levels in cell culture by ELISA. The stimulated HMCs were further stimulated with soluble MSU or MSU crystals at 200 μg/ml with or without the pre-incubation of toll like receptor (TLR) 4 inhibitor TAK242 (1μM). TLR4, nod-like receptor protein (NLRP3, also known as NALP3), IL-1β, human leukocyte antigen (HLA)-DR and CD40 were examined by Realtime-PCR, Western blot and ELISA, respectively.

RESULTS

We found that both soluble MSU and MSU crystals increased IL-1β protein expression levels in dose-dependent fashion. Soluble MSU significantly enhanced the expression of TLR4, NLRP3, IL-1β, HLA-DR and CD40 while MSU crystals only upregulated the expression of TLR4 and IL-1β. TLR4 inhibitor TAK242 significantly blocked the up-regulation of NLRP3, IL-1β, HLA-DR and CD40 induced by soluble MSU while no TAK242 suppression effect on MSU crystals induced IL-1β up-regulation was found.

CONCLUSIONS

Our results suggested that soluble MSU, but not MSU crystals, induce NLRP3, IL-1β, HLA-DR and CD40 upregulation in a TLR4-dependent manner. These findings indicate that soluble MSU may play a pathological role in hyperuricemia induced renal mesangial injury.