Soluble uric acid induces myocardial damage through activating the NLRP3 inflammasome

Potential Biomarkers for Neurobrucellosis Diagnosis and Treatment Based on Cerebrospinal Fluid Metabolomics Analysis

BACKGROUND

Zhenzhu Tongluo pills (ZZTL) have been utilized for the treatment of neurobrucellosis (NB) in the Inner Mongolia region of China. However, the specific mechanism underlying the neuroprotective effects of ZZTL in NB remains insufficiently explored. Therefore, this study aimed to analyze the metabolite profiles across different groups to identify potential biomarkers for the diagnosis and treatment of NB.

METHODS

LC-MS analysis was used to screen differential metabolites in cerebrospinal fluid (CSF) samples from control subjects, NB patients, and NB patients undergoing ZZTL therapy.

RESULTS

We identified 225 common metabolites across two comparison groups (NB vs. control group and NB + ZZTL vs. NB group). Among these metabolites, 138 were downregulated, and 87 were upregulated in the NB group compared to the control group, while the levels of these metabolites were reversed by ZZTL therapy. Creatinine exhibited the highest VIP score in both comparison groups, with elevated levels observed in CSF samples from NB patients compared to controls; however, its levels were reduced following ZZTL therapy. Additionally, hypoxanthine and uric acids levels were also increased in CSF samples from NB patients, indicating dysregulation of purine metabolism in NB; however, these changes were reversed by ZZTL. Furthermore, pantothenic acid (vitamin B5) and niacinamide (vitamin B3) levels were decreased in CSF samples from NB patients, suggesting a potential link between NB and vitamin B3 and B5 deficiency; however, these changes were reversed by ZZTL.

CONCLUSION

Collectively, CSF metabolomics may effectively differentiate NB patients from control subjects, providing valuable insights for NB diagnosis and treatment.

Hyperuricemia and its related diseases: mechanisms and advances in therapy

Hyperuricemia, characterized by elevated levels of serum uric acid (SUA), is linked to a spectrum of commodities such as gout, cardiovascular diseases, renal disorders, metabolic syndrome, and diabetes, etc. Significantly impairing the quality of life for those affected, the prevalence of hyperuricemia is an upward trend globally, especially in most developed countries. UA possesses a multifaceted role, such as antioxidant, pro-oxidative, pro-inflammatory, nitric oxide modulating, anti-aging, and immune effects, which are significant in both physiological and pathological contexts. The equilibrium of circulating urate levels hinges on the interplay between production and excretion, a delicate balance orchestrated by urate transporter functions across various epithelial tissues and cell types. While existing research has identified hyperuricemia involvement in numerous biological processes and signaling pathways, the precise mechanisms connecting elevated UA levels to disease etiology remain to be fully elucidated. In addition, the influence of genetic susceptibilities and environmental determinants on hyperuricemia calls for a detailed and nuanced examination. This review compiles data from global epidemiological studies and clinical practices, exploring the physiological processes and the genetic foundations of urate transporters in depth. Furthermore, we uncover the complex mechanisms by which the UA induced inflammation influences metabolic processes in individuals with hyperuricemia and the association with its relative disease, offering a foundation for innovative therapeutic approaches and advanced pharmacological strategies.

Co-delivery of indomethacin and uricase as a new strategy for inflammatory diseases associated with high uric acid

Uric acid is the final metabolite in humans. High level of uric acid chronically induces urate deposition, aggravates kidney damage, and concomitantly causes an increase in inflammatory factors. Alleviating acute inflammation and decreasing uric acid levels are the key points in the treatment of inflammatory diseases associated with high uric acid. However, a drug delivery system that combines anti-inflammatory and uric acid reduction functions at the same time remains a challenge to be settled. Here, we designed a nanocrystal-based co-delivery platform, IND Nplex, characterized by loading of indomethacin (IND) and uricase. Compared with free IND or uricase, IND Nplex possessed a better anti-inflammatory effect by restraining the release of inflammation-related factors in vitro. In addition, pharmacokinetic and biodistribution studies revealed that IND Nplex significantly prolonged the retention time in vivo and was more concentrated in the kidney. In acute gouty arthritis model rats, IND Nplex markedly relieved ankle joint swelling and mitigated synovial inflammation. In acute kidney injury model rats, IND Nplex indicated better biocompatibility and significant amelioration of renal fibrosis. Moreover, IND Nplex showed the effect of anti-inflammatory and improved renal function via determination of inflammatory factors and biochemical markers in the serum and kidney. In conclusion, these results indicate that IND Nplex exerts anti-inflammatory activity and uric acid-lowering effect and could become a promising candidate for the treatment of uric acid-related diseases.

The Role of Hyperuricemia in Cardiac Diseases: Evidence, Controversies, and Therapeutic Strategies

Hyperuricemia (HUA) may lead to myocardial cell damage, thereby promoting the occurrence and adverse outcomes of heart diseases. In this review, we discuss the latest clinical research progress, and explore the impact of HUA on myocardial damage-related diseases such as myocardial infarction, arrhythmias, and heart failure. We also combined recent findings from basic research to analyze potential mechanisms linking HUA with myocardial injury. In different pathological models (such as direct action of high uric acid on myocardial cells or combined with myocardial ischemia-reperfusion model), HUA may cause damage by activating the NOD-like receptor protein 3 inflammasome-induced inflammatory response, interfering with cardiac cell energy metabolism, affecting antioxidant defense systems, and stimulating reactive oxygen species production to enhance the oxidative stress response, ultimately resulting in decreased cardiac function. Additionally, we discuss the impact of lowering uric acid intervention therapy and potential safety issues that may arise. However, as the mechanism underlying HUA-induced myocardial injury is poorly defined, further research is warranted to aid in the development novel therapeutic strategies for HUA-related cardiovascular diseases.

Raising serum uric acid with a uricase inhibitor worsens PKD in rat and mouse models

Humans are predisposed to gout because they lack uricase that converts uric acid to allantoin. Rodents have uricase, resulting in low basal serum uric acid. A uricase inhibitor raises serum uric acid in rodents. There were two aims of the study in polycystic kidney disease (PKD): 1) to determine whether increasing serum uric acid with the uricase inhibitor, oxonic acid, resulted in faster cyst growth and 2) to determine whether treatment with the xanthine oxidase inhibitor, oxypurinol, reduced the cyst growth caused by oxonic acid. Orthologous models of human PKD were used: PCK rats, a polycystic kidney and hepatic disease 1 (Pkhd1) gene model of autosomal recessive PKD (ARPKD) and Pkd1RC/RC mice, a hypomorphic Pkd1 gene model. In PCK rats and Pkd1RC/RC mice, oxonic acid resulted in a significant increase in serum uric acid, kidney weight, and cyst index. Mechanisms of increased cyst growth that were investigated were proinflammatory cytokines, the inflammasome, and crystal deposition in the kidney. Oxonic acid resulted in an increase in proinflammatory cytokines in the serum and kidney in Pkd1RC/RC mice. Oxonic acid did not cause activation of the inflammasome or uric acid crystal deposition in the kidney. In Pkd1RC/RC male and female mice analyzed together, oxypurinol decreased the oxonic acid-induced increase in cyst index. In summary, increasing serum uric acid by inhibiting uricase with oxonic acid results in an increase in kidney weight and cyst index in PCK rats and Pkd1RC/RC mice. The effect is independent of inflammasome activation or crystal deposition in the kidney.NEW & NOTEWORTHY This is the first reported study of uric acid measurements and xanthine oxidase inhibition in polycystic kidney disease (PKD) rodents. Raising serum uric acid with a uricase inhibitor resulted in increased kidney weight and cyst index in Pkd1RC/RC mice and PCK rats, elevated levels of proinflammatory cytokines in the serum and kidney in Pkd1RC/RC mice, and no uric acid crystal deposition or activation of the caspase-1 inflammasome in the kidney.

Association of serum uric acid with functional disability in older subjects: a population-based study

BACKGROUND

The role of serum uric acid (SUA) in the development of adverse health outcomes in advanced age is still uncertain.

AIMS

The aim of the study was to assess the association of disability with SUA levels in older community-dwelling subjects.

METHODS

We assessed the association of disability with SUA in all 351 inhabitants of Tuscania (Italy) aged 75+. Functional ability was estimated using the instrumental activities of daily living (IADLs).

RESULTS

In logistic regression, increasing SUA levels were associated with disability (OR = 1.22; 95%CI = 1.01-1.48; P = .036), after adjusting. The association was independent of both gender and age (P for interaction > 0.050). SUA levels above 5.5 mg/dL best predicted disability.

CONCLUSIONS

In older subjects, SUA levels are associated with disability; the cut off level above 5.5 mg/dL might be adopted in pharmacological trials aiming at reducing the incidence and progression of disability by reducing SUA, and for identifying subjects at increased risk of disability.

Robust positive association between serum urate and the risk of chronic obstructive pulmonary disease: hospital-based cohort and Mendelian randomisation study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and hyperuricaemia are both characterised by systemic inflammation. Preventing chronic diseases among the population with common metabolic abnormality is an effective strategy. However, the association of hyperuricaemia with the higher incidence and risk of COPD remains controversial. Therefore, replicated researches in populations with distinct characteristics or demographics are compellingly warranted.

METHODS

This cohort study adopted a design of ambispective hospital-based cohort. We used propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) to minimise the effects of potential confounding factors. A Cox regression model and restricted cubic spline (RCS) model were applied further to assess the effect of serum urate on the risk of developing COPD. Finally, we conducted a two-sample Mendelian randomisation (MR) analysis to explore evidence of causal association.

RESULTS

There is a higher incidence in the population with hyperuricaemia compared with the population with normal serum urate (22.29/1000 person-years vs 8.89/1000 person-years, p=0.009). This result is robust after performing PSM (p=0.013) and IPTW (p<0.001). The Cox model confirms that hyperuricaemia is associated with higher risk of developing COPD (adjusted HR=3.35 and 95% CI=1.61 to 6.96). Moreover, RCS shows that the risk of developing COPD rapidly increases with the concentration of serum urate when it is higher than the reference (420 µmol/L). Finally, in MR analysis, the inverse variance weighted method evidences that a significant causal effect of serum urate on COPD (OR=1.153, 95% CI=1.034 to 1.289) is likely to be true. The finding of MR is robust in the repeated analysis using different methods and sensitivity analysis.

CONCLUSIONS

Our study provides convincing evidence suggesting a robust positive association between serum urate and the risk of developing COPD, and indicates that the population with hyperuricaemia is at high risk of COPD in the Chinese population who seek medical advice or treatment in the hospital.

A Possible Therapeutic Application of the Selective Inhibitor of Urate Transporter 1, Dotinurad, for Metabolic Syndrome, Chronic Kidney Disease, and Cardiovascular Disease

The reabsorption of uric acid (UA) is mainly mediated by urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) in the kidneys. Dotinurad inhibits URAT1 but does not inhibit other UA transporters, such as GLUT9, ATP-binding cassette transporter G2 (ABCG2), and organic anion transporter 1/3 (OAT1/3). We found that dotinurad ameliorated the metabolic parameters and renal function in hyperuricemic patients. We consider the significance of the highly selective inhibition of URAT1 by dotinurad for metabolic syndrome, chronic kidney disease (CKD), and cardiovascular disease (CVD). The selective inhibition of URAT1 by dotinurad increases urinary UA in the proximal tubules, and this un-reabsorbed UA may compete with urinary glucose for GLUT9, reducing glucose reabsorption. The inhibition by dotinurad of UA entry via URAT1 into the liver and adipose tissues increased energy expenditure and decreased lipid synthesis and inflammation in rats. Such effects may improve metabolic parameters. CKD patients accumulate uremic toxins, including indoxyl sulfate (IS), in the body. ABCG2 regulates the renal and intestinal excretion of IS, which strongly affects CKD. OAT1/3 inhibitors suppress IS uptake into the kidneys, thereby increasing plasma IS, which produces oxidative stress and induces vascular endothelial dysfunction in CKD patients. The highly selective inhibition of URAT1 by dotinurad may be beneficial for metabolic syndrome, CKD, and CVD.

Gender variations in the impact of hyperuricemia on thyroid disorders

This study aimed to examine the impact of hyperuricemia on various thyroid disorders with emphasized focus on differences resulting from different genders. 16094 adults aged ≥18 years were enrolled in this cross-sectional study using a randomized stratified sampling strategy. Clinical data including thyroid function and antibodies, uric acid, and anthropometric measurements were measured. Multivariable logistic regression was used to determine the association between hyperuricemia and thyroid disorders. Women who have hyperuricemia are at a significantly increased risk of developing hyperthyroidism. Women's risk of overt hyperthyroidism and Graves' disease may be markedly increased by hyperuricemia. Men with hyperuricemia did not differ significantly in their chance of acquiring any thyroid disorders.

Inhibition of the uric acid efflux transporter ABCG2 enhances stimulating effect of soluble uric acid on IL-1β production in murine macrophage-like J774.1 cells

Soluble uric acid (UA) absorbed by cells through UA transporters (UATs) accumulates intracellularly, activates the NLRP3 inflammasome and thereby increases IL-1β secretion. ABCG2 transporter excludes intracellular UA. However, it remains unknown whether ABCG2 inhibition leads to intracellular accumulation of UA and increases IL-1β production. In this study, we examined whether genetic and pharmacological inhibition of ABCG2 could increase IL-1β production in mouse macrophage-like J774.1 cells especially under hyperuricemic conditions. We determined mRNA and protein levels of pro-IL-1β, mature IL-1β, caspase-1 and several UATs in culture supernatants and lysates of J774.1 cells with or without soluble UA pretreatment. Knockdown experiments using an shRNA against ABCG2 and pharmacological experiments with an ABCG2 inhibitor were conducted. Extracellularly applied soluble UA increased protein levels of pro-IL-1β, mature IL-1β and caspase-1 in the culture supernatant from lipopolysaccharide (LPS)-primed and monosodium urate crystal (MSU)-stimulated J774.1 cells. J774.1 cells expressed UATs of ABCG2, GLUT9 and MRP4, and shRNA knockdown of ABCG2 increased protein levels of pro-IL-1β and mature IL-1β in the culture supernatant. Soluble UA increased mRNA and protein levels of ABCG2 in J774.1 cells without either LPS or MSU treatment. An ABCG2 inhibitor, febuxostat, but not a urate reabsorption inhibitor, dotinurad, enhanced IL-1β production in cells pretreated with soluble UA. In conclusion, genetic and pharmacological inhibition of ABCG2 enhanced IL-1β production especially under hyperuricemic conditions by increasing intracellularly accumulated soluble UA that activates the NLRP3 inflammasome and pro-IL-1β transcription in macrophage-like J774.1 cells.

URAT1 is expressed in cardiomyocytes and dotinurad attenuates the development of diet-induced metabolic heart disease

We recently reported that the selective inhibition of urate transporter-1 (URAT1), which is primarily expressed in the kidneys, ameliorates insulin resistance by attenuating hepatic steatosis and improving brown adipose tissue function in diet-induced obesity. In this study, we evaluated the effects of dotinurad, a URAT1-selective inhibitor, on the hearts of high-fat diet (HFD)-fed obese mice for 16-20 weeks and on neonatal rat cardiomyocytes (NRCMs) exposed to palmitic acid. Outside the kidneys, URAT1 was also expressed in cardiomyocytes and indeed worked as a uric acid transporter. Dotinurad substantially attenuated HFD-induced cardiac fibrosis, inflammatory responses, and cardiac dysfunction. Intriguingly, among various factors related to the pathophysiology of diet-induced obesity, palmitic acid significantly increased URAT1 expression in NRCMs and subsequently induced apoptosis, oxidative stress, and inflammatory responses via MAPK pathway, all of which were reduced by dotinurad. These results indicate that URAT1 is a potential therapeutic target for metabolic heart disease.

Treatment of Ulcerative Colitis by Cationic Liposome Delivered NLRP3 siRNA

Purpose

The abnormal activation of NLRP3 inflammasome is related to the occurrence and development of ulcerative colitis (UC). However, the ideal drug and delivery system remain important factors limiting the targeting of NLRP3 inflammasome in UC therapy. Gene therapy by delivering siRNA is effective in treating various diseases. Therefore, delivering siNLRP3 using an ideal vector for UC treatment is necessary.

Materials and Methods

Nanoparticles delivering siNLRP3 were developed based on cationic liposome (CLP/siNLRP3). Their ability to inhibit NLRP3 inflammasome activation was monitored using Western blot (WB) and Enzyme-linked Immunosorbent Assay (ELISA). The ASC oligomerization in LPS-primed peritoneal macrophages (PMs) was detected by WB and immunofluorescence. Moreover, we assessed the role of CLP/siNLRP3 on dextran sodium sulfate (DSS)-induced UC by examining NLRP3 levels, pro-inflammatory cytokines expression, and disease-associated index (DAI). Flow cytometry (FCM) was used to detect the contents of macrophages and T cells. Finally, we assessed the safety of CLP/siNLRP3.

Results

The prepared CLP was spherical, with a small particle size (94 nm) and low permeability. The CLP could efficiently protect siNLRP3 from degradation and then deliver siNLRP3 into PMs, inhibiting NLRP3 inflammasome activation. Also, the CLP/siNLRP3 could inhibit the secretion of mature IL-1β and IL-18 from PMs, thereby achieving a favorable anti-inflammation effect. In vivo, CLP/siNLRP3 could effectively alleviate intestinal injury in UC mice, which was attributed to down-regulating levels of IL-1β and IL-18, inhibiting infiltration of macrophages and other immune cells, and the polarization of M1 macrophages. Finally, pathological testing of tissue sections and blood biochemical tests showed no significant toxic effects of CLP/siNLRP3.

Conclusion

We introduced a prospective approach for the efficient delivery of siRNA in vitro and in vivo with high safety and stability, which was found to have great potential in treating NLRP3-driven diseases in an RNA-silencing manner.

The association between serum uric acid and creatine phosphokinase in the general population: NHANES 2015-2018

BACKGROUND

The association between serum creatine phosphokinase (CPK), a standard biochemical measure of acute myocardial infarction, and serum uric acid (sUA) has not been studied. This study aimed to determine the association between sUA and CPK in the general population of the US.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) 2015-2018 were used, including a total of 8,431 subjects aged ≥ 30 years. Weighted multiple regression analysis was used to estimate the independent relationship between sUA and CPK. Fitted smoothing curves and weighted generalized additive models were also performed.

RESULTS

We found a positive relationship between sUA and CPK after adjusting for potential confounders. In subgroup analyses stratified by sex and race/ethnicity, sUA was positively correlated with CPK in each subgroup. The association between sUA and CPK followed an inverted U-shaped curve in females (turning point: sUA = 428.3 μmol/L).

CONCLUSIONS

Our study suggested that sUA level was positively correlated with CPK in the general population of the US. However, CPK increased with sUA until the turning point (sUA = 428.3 μmol/L) in females. Fundamental research and large sample prospective studies are needed to determine the exact mechanism of the association between sUA and CPK.

Notopterol Ameliorates Hyperuricemia-Induced Cardiac Dysfunction in Mice

Notopterol is a naturally occurring furanocoumarin compound found in the root of Notopterygium incisum. Hyperuricemia involves the activation of chronic inflammation and leads to cardiac damage. Whether notopterol has cardioprotective potential in hyperuricemia mice remains elusive. The hyperuricemic mouse model was constructed by administration of potassium oxonate and adenine every other day for six weeks. Notopterol (20 mg/kg) and allopurinol (10 mg/kg) were given daily as treatment, respectively. The results showed that hyperuricemia dampened heart function and reduced exercise capacity. Notopterol treatment improved exercise capacity and alleviated cardiac dysfunction in hyperuricemic mice. P2X7R and pyroptosis signals were activated both in hyperuricemic mice and in uric acid-stimulated H9c2 cells. Additionally, it was verified that inhibition of P2X7R alleviated pyroptosis and inflammatory signals in uric acid-treated H9c2 cells. Notopterol administration significantly suppressed expression levels of pyroptosis associated proteins and P2X7R in vivo and in vitro. P2X7R overexpression abolished the inhibition effect of notopterol on pyroptosis. Collectively, our findings suggested that P2X7R played a critical role in uric acid-induced NLRP3 inflammatory signals. Notopterol inhibited pyroptosis via inhibiting the P2X7R/NLRP3 signaling pathway under uric acid stimulation. Notopterol might represent a potential therapeutic strategy against pyroptosis and improve cardiac function in hyperuricemic mice.

L-carnitine attenuated hyperuricemia-associated left ventricular remodeling through ameliorating cardiomyocytic lipid deposition

Hyperuricemia (HUA) is associated with left ventricular remodeling (LVR) and thereby causes the initiation and development of a large number of cardiovascular diseases. LVR is typically accompanied by cardiomyocyte energy metabolic disorder. The energy supply of cardiomyocytes is provided by glucose and fatty acid (FA) metabolism. Currently, the effect of HUA on cardiomyocytic FA metabolism is unclear. In this study, we demonstrate that UA-induced cardiomyocyte injury is associated with cytoplasmic lipid deposition, which can be ameliorated by the FA metabolism-promoting drug L-carnitine (LC). UA suppresses carnitine palmitoyl transferase 1B (CPT1B), thereby inhibiting FA transport into the mitochondrial inner matrix for elimination. LC intervention can ameliorate HUA-associated left ventricular anterior wall thickening in mice. This study showed that FA transport dysfunction plays is a critical mechanism in both cardiomyocytic injury and HUA-associated LVR and promoting cytoplasmic FA transportation through pharmacological treatment by LC is a valid strategy to attenuate HUA-associated LVR.

Sirtuin deficiency and the adverse effects of fructose and uric acid synthesis

Fructose metabolism and hyperuricemia have been shown to drive insulin resistance, metabolic syndrome, hepatic steatosis, hypertension, inflammation, and innate immune reactivity in experimental studies. We suggest that these adverse effects are at least in part the result of suppressed activity of sirtuins, particularly Sirtuin1. Deficiency of sirtuin deacetylations is a consequence of reduced bioavailability of its cofactor nicotinamide adenine dinucleotide (NAD+). Uric acid-induced inflammation and oxidative stress consume NAD+ and activation of the polyol pathway of fructose and uric acid synthesis also reduces the NAD+-to-NADH ratio. Variability in the compensatory regeneration of NAD+ could result in variable recovery of sirtuin activity that may explain the inconsistent benefits of treatments directed to reduce uric acid in clinical trials. Here, we review the pathogenesis of the metabolic dysregulation driven by hyperuricemia and their potential relationship with sirtuin deficiency. In addition, we discuss therapeutic options directed to increase NAD+ and sirtuins activity that may improve the adverse effects resulting from fructose and uric acid synthesis.

Serum Uric Acid Levels at Admission Could Predict the Chronic Post-stroke Fatigue

Background

Post-stroke fatigue (PSF) is a frequent complication of stroke. Serum uric acid (SUA) is frequently thought to be a risk factor for stroke. This study aimed to investigate whether SUA also played a role in PSF.

Methods

Subjects with ischemic stroke were screened from The First Affiliated Hospital of Wenzhou Medical University between January 2020 and October 2020. Patients' fatigue symptoms were assessed by the Fatigue severity scale (FSS). To investigate the relationship between SUA and PSF, binary logistic regression analysis was conducted, with the confounders being controlled. SUA levels were divided into four layers (Q1 ≤ 245 μmol/L; Q2 246–308 μmol/L; Q3 309–365 μmol/L; Q4 ≥366 μmol/L) based on the quartiles.

Results

SUA levels were significantly higher in the PSF group (345.96 ± 73.78 μmol/L) than the non-PSF group (295.97 ± 87.8 μmol/L, P < 0.001). There were no differences in any other variables between these two groups. After adjusting the confounders, the risk of PSF in the Q4 layer (≥366 μmol/L) was 6.05 times (95% CI 1.79–20.43, P = 0.004) higher than that in Q1 (≤245 μmol/L).

Conclusion

High SUA at admission was an independent risk factor for fatigue 1 year after stroke onset. High SUA (≥366 μmol/L) during stroke deserves more attention, and active control of high SUA levels may be beneficial to reduce the incidence of PSF in the chronic stage following stroke.

Ellagic Acid Exerts Beneficial Effects on Hyperuricemia by Inhibiting Xanthine Oxidase and NLRP3 Inflammasome Activation

Hyperuricemia is a metabolic disease caused by impaired uric acid (UA) metabolism. Ellagic acid (EA) is a natural small-molecule polyphenolic compound with known antioxidative and anti-inflammatory properties. Here, we evaluated the regulatory effects of EA on hyperuricemia and explored the underlying mechanisms. We found that EA is an effective xanthine oxidase (XOD) inhibitor (IC₅₀ = 165.6 μmol/L) and superoxide anion scavenger (IC₅₀ = 27.66 μmol/L). EA (5 and 10 μmol/L) treatment significantly and dose-dependently reduced UA levels in L-O2 cells; meanwhile, intraperitoneal EA administration (50 and 100 mg/kg) also significantly reduced serum XOD activity and UA levels in hyperuricemic mice and markedly improved their liver and kidney histopathology. EA treatment significantly reduced the degree of foot edema and inhibited the expression of NLPR3 pathway-related proteins in foot tissue of monosodium urate (MSU)-treated mice. The anti-inflammatory effect was also observed in lipopolysaccharide-stimulated RAW-264.7 cells. Furthermore, EA significantly inhibited the expressions of XOD and NLRP3 pathway-related proteins (TLR4, p-p65, caspase-1, TNF-α, and IL-18) in vitro and in vivo. Our results indicated that EA exerts ameliorative effects in experimental hyperuricemia and foot edema via regulating the NLRP3 signaling pathway and represents a promising therapeutic option for the management of hyperuricemia.

Reactive oxygen species induced by uric acid promote NRK‑52E cell apoptosis through the NEK7‑NLRP3 signaling pathway

Increasing uric acid (UA) could induce renal tubular epithelial cell (NRK-52E) injury. However, the specific mechanism by which UA induces renal tubular epithelial cell injury remains unknown. It was hypothesized that UA induces renal tubular epithelial cell injury through reactive oxygen species (ROS) and the Never in mitosis gene A (NIMA)-related kinase 7 (NEK7)/NLR family pyrin domain containing 3 (NLRP3) signaling pathway. TUNEL assay and flow cytometry were applied to measure apoptosis, and the results of the present study showed that UA treatment induced apoptosis of NRK-52E cells in a concentration-dependent manner. Western blotting was performed to determine the expression levels of cleaved caspase-3, Bax and Bcl-xl, it was found that levels were significantly increased after UA treatment in NRK-52E cells. ROS and apoptosis were predominantly induced in NRK-52E cells and there was an association between ROS and apoptosis. Enhanced expression of NEK7, NLRP3, apoptosis-associated speck-like and caspase-1 were observed in NRK-52E cells treated with UA. The ROS inhibitor, N-acetyl-l-cysteine, exerted a protective effect on the UA-induced apoptosis of tubular epithelial cells by reducing excess ROS production, which significantly inhibited NEK7 and NLRP3 inflammasome activation. These results indicated that UA activates ROS and induces apoptosis of NRK-52E cells. The mechanism might be related to the regulation of the NEK7/NLRP3 signaling pathway.

Timosaponin alleviates oxidative stress in rats with high fat diet-induced obesity via activating Nrf2/HO-1 and inhibiting the NF-κB pathway

Anemarrhena asphodeloides originated from the rhizome of Liliaceae Anemarrhena asphodeloides. One of the active pharmacological components of Anemarrhena asphodeloides is timosaponin (TSA), which reduces blood lipids and shows antioxidation and anti-inflammatory effects, but its mechanism is unclear. The objective of this study was to investigate the effect of TSA on oxidative stress induced by a long-term high-fat diet in obese rats. Body weight and the obesity index of the rats were measured during the experiment. Total antioxidant capacity (T-AOC), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) were used to detect oxidative stress indexes in serum and liver tissue. To observe the effect of TSA on the liver and adipose tissue of rats with oxidative stress, hematoxylin & eosin (H&E) staining was used. The p-NF-κB, NAD(P)H: quinone oxidoreductase 1 (NQO-1), Heme oxygenase 1 (HO-1), and Nrf2 in Nrf2/HO-1 and NF-κB pathways were assayed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. TSA was found to improve oxidative stress in obese rats by reducing MDA levels and increasing T-AOC and GSH-Px levels. Histological examination revealed that TSA effectively attenuated liver damage and improved obesity in rats. TSA was found to down-regulate the protein level of p-NF-κB and up-regulate the protein level of Nrf2/HO-1. These results suggested that TSA could effectively block inflammation and dyslipidemia in obese rats, thus improving oxidative stress, and its mechanism could be related to the Nrf2/HO-1 and NF-κB pathways.

Resveratrol, a novel inhibitor of GLUT9, ameliorates liver and kidney injuries in a D-galactose-induced ageing mouse model via the regulation of uric acid metabolism

Accumulating evidence has shown that chronic injection of d-galactose (d-gal) can mimic natural ageing and induce liver and kidney injury. Previous studies showed that d-gal increased uric acid (UA) levels in mice. The increase in UA levels caused inflammation, accelerated oxidative stress, and aggravated liver and kidney injury. Oxidative stress and inflammation play vital roles in the ageing process. Therefore, reducing the levels of UA in ageing mice improved liver and kidney injury. Glucose transporter 9 (GLUT9) is responsible for the reabsorption of UA in the body, and its inhibition helps downregulate UA levels. The present study investigated the UA-lowering activity of the GLUT9 inhibitor resveratrol (RSV) using the patch clamping technique established in our laboratory in vitro. This research is the first study to demonstrate that RSV effectively inhibits UA uptake via GLUT9 (IC50 = 68.77 μM) in vitro. An in vivo study was also performed to investigate the possible protective effect of RSV on d-gal-induced liver and kidney injury. RSV significantly reduced serum UA levels via the downregulation of GLUT9 mRNA and protein expression and promoted the excretion of excess UA through urine. Biochemical analysis showed that RSV significantly downregulated abnormal increases in serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN) and creatinine (CRE) caused by long-term d-gal treatment, which effectively improved pathological damage, increased superoxide dismutase (SOD) activity and decreased the content of malondialdehyde (MDA) in the liver and kidneys. RSV also downregulated the expression of the inflammatory cytokines, interleukin IL-6, IL-1β and tumor necrosis factor (TNF)-α in the liver and kidneys of ageing mice. Our findings provide new insights into the treatment strategies for ageing-induced liver and kidney injury and reveal a new mechanism of RSV-induced reduction in UA levels in ageing individuals.

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.