Uric acid induces the expression of TNF-α via the ROS-MAPK-NF-κB signaling pathway in rat vascular smooth muscle cells

Sex Differences in the Effects of Cadmium and Uric Acid Levels on Hypertension Risk: A Dose-Response Relationship and Synergistic Effect Study

OBJECTIVE

This study explored the independent and synergistic effects of cadmium (Cd) and uric acid (UA) levels on hypertension risk, with a focus on sex differences.

METHODS

Data from 8043 National Health and Nutrition Examination Survey participants were analyzed using logistic regression, restricted cubic spline (RCS), and interaction effect models. A meta-analysis of eight studies was also conducted.

RESULTS

Blood, urinary Cd, and UA levels were more strongly associated with hypertension in females than in males (p < 0.05). Among females, blood Cd (odds ratio [OR] = 1.84, 95% confidence interval [CI]: 1.20-2.83), urinary Cd (OR = 3.38, 95% CI: 2.15-5.30), and UA levels (OR = 3.67, 95% CI: 2.47-5.45) were significantly associated with increased hypertension risk. RCS analysis showed linear dose-response relationships for blood (Pnon-linear = 0.085) and urinary Cd (Pnon-linear = 0.070) levels, whereas UA levels (Pnon-linear = 0.031) exhibited a non-linear association with hypertension risk. Multiplicative interaction showed 176% (OR = 2.76, 95% CI: 2.00-3.80) and 370% (OR = 4.70, 95% CI: 3.49-6.33) increased hypertension risks for high blood Cd-UA and urinary Cd-UA levels, respectively. Additive interaction confirmed synergy (relative excess risk due to interaction [RERI] = 1.74, 95% CI: 0.37-3.10). The meta-analysis using a random-effects model confirmed that blood Cd (OR = 1.93, 95% CI: 1.28-2.93) and urinary Cd levels (OR = 1.81, 95% CI: 0.93-3.50) were significantly increased hypertension risk.

CONCLUSIONS

Elevated Cd and UA levels independently and synergistically increased hypertension risk, especially in females, highlighting the need for targeted prevention strategies.

A New Perspective on the Prediction and Treatment of Stroke: The Role of Uric Acid

Stroke, a major cerebrovascular disease, has high morbidity and mortality. Effective methods to reduce the risk and improve the prognosis are lacking. Currently, uric acid (UA) is associated with the pathological mechanism, prognosis, and therapy of stroke. UA plays pro/anti-oxidative and pro-inflammatory roles in vivo. The specific role of UA in stroke, which may have both neuroprotective and damaging effects, remains unclear. There is a U-shaped association between serum uric acid (SUA) levels and ischemic stroke (IS). UA therapy provides neuroprotection during reperfusion therapy for acute ischemic stroke (AIS). Urate-lowering therapy (ULT) plays a protective role in IS with hyperuricemia or gout. SUA levels are associated with the cerebrovascular injury mechanism, risk, and outcomes of hemorrhagic stroke. In this review, we summarize the current research on the role of UA in stroke, providing potential targets for its prediction and treatment.

Uric acid in diabetic microvascular complications: Mechanisms and therapy

Uric acid (UA) is mainly synthesized in the liver, intestine, and vascular endothelium and excreted by the kidney (70 %) and intestine (30 %). Hyperuricemia (HUA) occurs when UA production exceeds excretion. Many studies have found that elevated UA is associated with diabetic microvascular complications (DMC), including diabetic retinopathy (DR), diabetic nephropathy (DN), and diabetic peripheral neuropathy (DPN). In addition, too high or too low UA levels will promote the occurrence and development of chronic diseases, but the relationship between UA and diabetic microvascular complications (DMC) is not clear. Therefore, the rational treatment of UA in patients with diabetes is essential. In this review, we summarize and discuss the mechanism and treatment of UA and DMC and may provide potential advice for rational drug selection.

Effects of uric acid on oxidative stress in vascular smooth muscle cells

Hyperuricemia during hypertension is associated with aberrant vascular functions and increased oxidative stress, which affects endothelial dysfunction. Nevertheless, the molecular mechanisms underlying the effects of uric acid on vascular smooth muscle cells (VSMCs) through oxidative stress remain unclear. The aim of the present study was to investigate the dose- and time-dependent effects of uric acid on oxidative stress and p53 protein expression in VSMCs. VSMCs were incubated with various concentrations of uric acid (0-50 mg/dl) for different time periods (1-24 h). Thiobarbituric acid reactive substances (TBARs), protein carbonylation and nitric oxide (NO) levels were determined using appropriate assay kits. Superoxide anion release was detected using the Görlach method. Western blotting was performed to determine the protein expression levels of p53. The findings demonstrated that the application of uric acid led to an increase in protein carbonylation and superoxide anion levels while causing a decrease in NO levels. Conversely, no significant effect was observed on TBARS levels. Additionally, it was observed that high concentrations of uric acid suppressed p53 expression at 6, 12 and 24 h. The present study provided evidence that the influence of uric acid on oxidative stress was more closely associated with time than dose; however, not all effects observed were strictly time-dependent.

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.

Establishment of pelvic inflammatory disease model induced by vaginal injection of Ureaplasma urealyticum liquids combined with fatigue and hunger

Pelvic inflammatory disease (PID) is an inflammation of the upper genital tract. PID is the leading cause of some severe sequelae in the absence of timely and accurate diagnosis and treatment. An appropriate animal model is needed to explore the underlying mechanism of PID sequelae. This study introduced an animal model of PID by vaginal injection of liquid Ureaplasma urealyticum combined with fatigue and hunger (UVF). This study was designed to test the feasibility of a rat model. A rat model was established using UVF irradiation. Levels of some inflammatory cytokines in the serum and the homogenates of the fallopian tubes were measured by ELISA, RT-PCR, and flow cytometry and compared with another rat model of Ureaplasma urealyticum liquids injected into the two uterus horns during laparotomy. Inflammatory alterations and adhesions were observed after hematoxylin and eosin (H&E) staining and detected using the Blauer scoring system. The results showed that the combined UVF and rat model caused apparent obstruction, edema, and adhesion in the fallopian tubes and connective tissues. The rat model showed upregulated CD4, CD8, and CD4/CD8 in peripheral blood mononuclear cells (PBMCs) and significantly increased levels of IL-4, IL-6, IL-10, and IL-17. UVF also enhanced the expression of tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, vascular endothelial growth factor (VEGF) β, and matrix metalloproteinase (MMP)-2 (P<0.05). The UVF rat model can induce inflammatory alterations in the fallopian tubes and connective tissues, and can be used as a model of PID.

Hyperuricemia remodels the serum proteome toward a higher inflammatory state

Gout is an autoinflammatory disease triggered by a complex innate immune response to MSU crystals and inflammatory triggers. While hyperuricemia is an obligatory risk factor for the development of gout, the majority of individuals with hyperuricemia never develop gout but have an increased risk of developing cardiometabolic disorders. Current management of gout aims at MSU crystal dissolution by lowering serum urate. We apply a targeted proteomic analysis, using Olink inflammation panel, to a large group of individuals with gout, asymptomatic hyperuricemia, and normouricemic controls, and we show a urate-driven inflammatory signature. We add in vivo evidence of persistent immune activation linked to urate exposure and describe immune pathways involved in the pathogenesis of gout. Our results support a pro-inflammatory effect of asymptomatic hyperuricemia and pave the way for new research into targetable mechanisms in gout and cardiometabolic complications of asymptomatic hyperuricemia.

CXCL12 and CXCR4 as Novel Biomarkers in Uric Acid-Induced Inflammation and Patients with Gouty Arthritis

The aim of this study was to evaluate the expression of chemokine receptor CXCR4 and its ligand CXCL12 in patients with gout and uric acid-induced inflammation. A total of 40 patients with intercritical gout and 27 controls were consecutively enrolled. The serum levels of interleukin-1β (IL-1β), IL-18, CXCL12, and CXCR4 were assessed using an enzyme-linked immunosorbent assay. The gene and protein expressions for these target molecules were measured in human U937 cells incubated with monosodium urate (MSU) crystals using a real-time reverse transcription polymerase chain reaction and Western blot analysis. Patients with intercritical gout showed higher serum IL-1β, IL-18, and CXCL12 levels, but not the serum CXCR4 level, than in the controls.The serum CXCR4 level in gout patients was associated with the serum IL-18 level, uric acid level, and uric acid/creatinine ratio (r = 0.331, p = 0.037; r = 0.346, p = 0.028; and r = 0.361, p = 0.022, respectively). U937 cells treated with MSU crystals significantly induced the CXCL12 and CXCR4 mRNA and protein expression in addition to IL-1β and IL-18. In cells transfected with IL-1β siRNA or IL-18 siRNA, the CXCL12 and CXCR4 expression was downregulated compared with the non-transfected cells in MSU crystal-induced inflammation. In this study, we revealed that CXCL12 and CXCR4 were involved in the pathogenesis of uric acid-induced inflammation and gouty arthritis.

Soluble klotho as an effective biomarker to characterize inflammatory states

BACKGROUND & AIMS

Soluble α-Klotho (s-Klotho) is a circulating protein with pleiotropic effects that mainly induce protective effects. Our study investigates the associations between s-Klotho and several established inflammatory biomarkers, with the aim of examining whether s-Klotho levels are representative of inflammatory states.

METHODS

A total of 11,128 eligible participants from NHANES 2007-2016 were included in our study. Levels of four inflammatory biomarkers, uric acid (UA), C-reactive protein (CRP), white blood cell (WBC) count, and mean platelet volume (MPV), were examined for their relationship with s-Klotho levels. Sub-analyses sorted the total population by gender and into four quartiles. Linear regression models were used to evaluate the strengths of associations.

RESULTS

All four inflammatory biomarkers were significantly associated with s-Klotho levels. UA, CRP, and WBC count showed an inverse association, while MPV showed a direct one. Of the four markers, UA was most strongly correlated with s-Klotho levels (β coefficient: -28.89 in unadjusted model, p<.001), and this relationship was stronger in women than in men (β coefficient of UA in men: -22.01, p<.001; in women: -31.54, p<.001). In addition, all four biomarkers manifested stronger associations with s-Klotho in higher quartiles, and the highest absolute values of β coefficients appeared in Q4 vs. Q1.

CONCLUSION

s-Klotho is significantly associated with well-recognized inflammatory biomarkers. A decrease in s-Klotho levels implies a general inflammatory status; therefore, s-Klotho serves as a potential biomarker that is inversely correlated with inflammatory conditions. Further applications in clinical practice will provide us with a better understanding of its role.Key messagesSoluble α-Klotho (s-Klotho) levels are significantly associated with the inflammatory markers uric acid, C-reactive protein, white blood cell count, and mean platelet volume.S-Klotho is involved in inflammatory processes and plays a protective role.S-Klotho may serve as an inverse indicator of inflammation.

3-Arylcoumarin inhibits vascular calcification by inhibiting the generation of AGEs and anti-oxidative stress

Objective

This work aims to screen drugs for preventing and treating vascular calcification. Method: We screened a series of 3-arylcoumarins for the detection of vascular calcification-associated factors using human aortic vascular smooth muscle cells.

Results

We found that compounds 14 and 32 significantly inhibited alkaline phosphatase (ALP) activity similar to aminoguanidine hydrochloride (AGH) in a cellular model of AGEs-induced calcification. We also found that compounds 14 and 32 could significantly decrease the levels of factors such as AGEs, intracellular calcium ions, and total ROS in the calcified cell model. Further study indicates that compound 14 could significantly inhibit the expression of P-ERK1/2, PKC, NF-κB, RAGE and OPN proteins and increased the expression of SM22-α and PPAR-γ proteins in the calcified cells.

Conclusion

We speculate that compound 14 inhibits vascular calcification by inhibiting oxidative stress and inhibiting AGEs production, suggesting that 3-arylcoumarin derivatives are potential candidates for the treatment of vascular calcification.

Vascular calcification is a process similar to bone formation, which is highly adjustable and active. Currently, there are no specific drugs to delay or reverse vascular calcification. Through the screening of 44 coumarin compounds synthesised by our group, compound 14 was obtained to dose-dependently inhibit the calcification of vascular smooth muscle cells without affecting the normal proliferation of cells, decreasing the intracellular calcium concentration, inhibiting the activity of ALP enzyme. In conclusion, the calcium lowering effect of compound 14 is a potential candidate for drugs for the treatment of vascular calcification.

Integration of network pharmacology and intestinal flora to investigate the mechanism of action of Chinese herbal Cichorium intybus formula in attenuating adenine and ethambutol hydrochloride-induced hyperuricemic nephropathy in rats

CONTEXT

Cichorium intybus L. (Asteraceae) formula (CF) has been applied as a folk medicine to treat hyperuricemic nephropathy (HN). However, the exact mechanism remains unclear.

OBJECTIVE

To explore the therapeutic effect and mechanism of CF on HN.

MATERIALS AND METHODS

Through network pharmacological methods, the targets of the active component of CF against HN were obtained. Subsequently, Male Wistar rats were divided into control, HN, allopurinol (50 mg/kg), CF high-dose (8.64 g/kg) and CF low-dose (2.16 g/kg) groups. The HN model was induced via intragastric administration of adenine (100 mg/kg) and ethambutol hydrochloride (250 mg/kg) for 3 weeks. After CF treatment, biochemical indicators including UA, UREA and CREA were measured. Then, HE staining, qRT-PCR and gut microbiota analysis were conducted to further explore the mechanism.

RESULTS

The network pharmacology identified 83 key targets, 6 core genes and 200 signalling pathways involved in the treatment of HN. Compared to the HN group, CF (8.64 g/kg) significantly reduced the levels of UA, UREA and CREA (from 2.4 to 1.57 μMol/L, from 15.87 to 11.05 mMol/L and from 64.83 to 54.83 μMol/L, respectively), and mitigated renal damage. Furthermore, CF inhibited the expression of IL-6, TP53, TNF and JUN. It also altered the composition of gut microbiota, and ameliorated HN by increasing the relative abundance of some probiotics.

CONCLUSIONS

This work elucidated the therapeutic effect and underlying mechanism by which CF protects against HN from the view of the biodiversity of the intestinal flora, thus providing a scientific basis for the usage of CF.

Aberrant messenger RNA expression in peripheral blood mononuclear cells is associated with gouty arthritis

AIM

Gouty arthritis (GA) is a type of self-limiting inflammatory arthritis caused by deposition of monosodium urate (MSU). This study aimed to analyze the expression variation of messenger RNAs (mRNAs) in GA patients and investigated the role of mRNAs in GA pathogenesis.

METHODS

Five patients with acute GA (AGA), 5 with non-acute GA (NAGA), and 5 healthy controls (HC) were recruited to examine differential mRNA expression profiles in peripheral blood mononuclear cells (PBMCs) and explore whether mRNA is involved in the pathogenesis of AGA. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used to study the biological functions of differentially expressed mRNA and the relationship between genes and signal pathways.

RESULTS

Compared with HC, the AGA group had 1456 differentially expressed mRNAs, while the NAGA group had 437 differentially expressed mRNAs and compared with the NAGA group, 115 differentially expressed mRNAs were found in the AGA group. GO analysis showed that the differentially expressed mRNA in the AGA group was mainly enriched in processes related to leukocyte activation and immune response, while KEGG analysis showed that "Staphylococcus aureus infection" and "Cytokine-cytokine receptor interaction" are enriched in the up-regulated mRNAs in the AGA group.

CONCLUSION

This study identified genes and pathways that are differentially expressed during the onset of AGA, which might reveal part of the pathogenesis of the disease and provide clues to explaining the severe pain associated with disease onset and the rapid development of inflammatory response that subsides by itself.

The Prospective Effect of Allopurinol on the Oxidative Stress Index and Endothelial Dysfunction in Covid-19

SARS-CoV-2 by the direct cytopathic effect or indirectly through the propagation of pro-inflammatory cytokines could cause endothelial dysfunction (ED) and oxidative stress (OS). It has been reported that OS is triggered by various types of viral infections, including SARS-CoV-2. Into the bargain, allopurinol is regarded as a potent antioxidant that acts through inhibition of xanthine oxidase (XO), which is an essential enzyme of purine metabolism. Herein, the present study aimed to find the potential protective effects of allopurinol on the biomarkers of OS and ED in patients with severe Covid-19. This single-center cohort study recruited 39 patients with mild-moderate Covid-19 compared with 41 patients with severe Covid-19. Nineteen patients with severe Covid-19 were on the allopurinol treatment because of underlying chronic gout 3 years ago compared with 22 Covid-19 patients not on this treatment. The recruited patients were allocated into three groups: group I, mild-moderate Covid-19 on the standard therapy (n = 39); group II, severe Covid-19 patients on the standard therapy only (n = 22); and group III, severe Covid-19 patients on the standard therapy plus allopurinol (n = 19). The duration of the study was 3 weeks from the time of hospitalization till the time of recovery. In addition, inflammatory biomarkers (D-dimer, LDH, ferritin, CRP, procalcitonin), neutrophil-lymphocyte ratio (NLR), endothelin-1 (ET-1), uric acid and oxidative stress index (OSI), CT scan score, and clinical score were evaluated at the time of admission and discharge regarding the effect of allopurinol treatment adds to the standard treatment of Covid-19. Allopurinol plus standard treatment reduced LDH, ferritin, CRP, procalcitonin, and ET-1 serum level significantly (P < 0.05) compared with Covid-19 patients on standard treatment. Besides, neutrophil (%), lymphocyte (%), and neutrophil-lymphocyte ratio (NLR) were reduced in patients with severe Covid-19 on standard treatment plus allopurinol compared with Covid-19 patients on standard treatment alone (P < 0.01). OSI was higher in patients with severe Covid-19 than mild-moderate Covid-19 patients (P = 0.00001) at admission. At the time of discharge, the oxidative status of Covid-19 patients was significantly improved compared with that at admission (P = 0.01). In conclusion, Covid-19 severity is linked with high OS and inflammatory reaction with ED development. High uric acid in patients with severe Covid-19 is correlated with high OS and inflammatory biomarkers. Allopurinol with standard treatment in patients with severe Covid-19 reduced oxidative and inflammatory disorders with significant amelioration of ED and clinical outcomes.

Serum uric acid and diabetic peripheral neuropathy: a double-edged sword

BACKGROUND AND OBJECTIVES

Research suggests that diabetic peripheral neuropathy (DPN) is related to high serum uric acid (SUA) level, although its correlation with low SUA level has not been reported. Here, diabetic patients with hyperuricemia were excluded, and the correlation between low SUA level and DPN was explored.

SUBJECTS AND METHODS

This prospective observational clinical study enrolled 525 type 2 diabetes mellitus (T2DM) patients without hyperuricemia, who were divided into the diabetes with symptomatic neuropathy (150 cases), diabetes with asymptomatic neuropathy (125 cases) and diabetes with no neuropathy (250 cases) groups.

RESULTS

The SUA slightly decreased in subjects with asymptomatic DPN compared with those with no neuropathy and greatly decreased in subjects with symptomatic DPN compared with those without (P < 0.001). The association of the SUA with diabetic neuropathy was independent of the hyperglycemic state and other potential confounders (odds ratio 0.985 [0.981-0.988], P < 0.001). The SUA was closely correlated with the means of motor/sensory nerve amplitude and CV (all P < 0.001). The optimal cut-off point for SUA to distinguish patients with diabetic neuropathy from those without was 324 umol/L, with a sensitivity of 76.0% and a specificity of 79.2% (AUC = 0.806).

CONCLUSIONS

The low SUA level is closely associated with DPN. Future studies are warranted to clarify the relationship.

Important Functions and Molecular Mechanisms of Mitochondrial Redox Signaling in Pulmonary Hypertension

Mitochondria are important organelles that act as a primary site to produce reactive oxygen species (ROS). Additionally, mitochondria play a pivotal role in the regulation of Ca²⁺ signaling, fatty acid oxidation, and ketone synthesis. Dysfunction of these signaling molecules leads to the development of pulmonary hypertension (PH), atherosclerosis, and other vascular diseases. Features of PH include vasoconstriction and pulmonary artery (PA) remodeling, which can result from abnormal proliferation, apoptosis, and migration of PA smooth muscle cells (PASMCs). These responses are mediated by increased Rieske iron–sulfur protein (RISP)-dependent mitochondrial ROS production and increased mitochondrial Ca²⁺ levels. Mitochondrial ROS and Ca²⁺ can both synergistically activate nuclear factor κB (NF-κB) to trigger inflammatory responses leading to PH, right ventricular failure, and death. Evidence suggests that increased mitochondrial ROS and Ca²⁺ signaling leads to abnormal synthesis of ketones, which play a critical role in the development of PH. In this review, we discuss some of the recent findings on the important interactive role and molecular mechanisms of mitochondrial ROS and Ca²⁺ in the development and progression of PH. We also address the contributions of NF-κB-dependent inflammatory responses and ketone-mediated oxidative stress due to abnormal regulation of mitochondrial ROS and Ca²⁺ signaling in PH.

Berberrubine attenuates potassium oxonate- and hypoxanthine-induced hyperuricemia by regulating urate transporters and JAK2/STAT3 signaling pathway

Phellodendri Chinensis Cortex (PC) is a traditional medicinal material used to treat gout and hyperuricemia (HUA) in China. Berberine (BBR), the main component of PC, possesses anti-hyperuricemic and anti-gout effects. However, BBR exhibits low bioavailability due to its extensive metabolism and limited absorption. Thus, the metabolites of BBR are believed to be the potential active forms responsible for its in vivo biological activities. Berberrubine (BRB), one of the major metabolites of BBR, exhibits appreciable biological activities even superior to BBR. In this work, the anti-hyperuricemic efficacy of BRB was investigated in HUA model mice induced by co-administration with intraperitoneal potassium oxonate (PO) and oral hypoxanthine (HX) for 7 days. Results showed that administration with BRB (6.25, 12.5, and 25.0 mg/kg) significantly decreased the serum levels of uric acid (UA) by 49.70%, 75.35%, and 75.96% respectively, when compared to the HUA group. In addition, BRB sharply decreased the levels of blood urea nitrogen (BUN) (by 19.62%, 28.98%, and 38.72%, respectively) and serum creatinine (CRE) (by 16.19%, 25.07%, and 52.08%, respectively) and reversed the PO/HX-induced renal histopathological damage dose-dependently. Additionally, BRB lowered the hepatic XOD activity, downregulated the expressions of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1), upregulated expressions of organic anion transporter 1/3 (OAT1/3) and ATP-binding cassette transporter subfamily G member 2 (ABCG2) at both protein and mRNA levels, and suppressed the activation of the JAK2/STAT3 signaling pathway. In addition, BRB significantly decreased the levels of inflammatory mediators (IL-1β, IL-6, and TNF-α). In conclusion, our study indicated that BRB exerted anti-hyperuricemic effect, at least in part, via regulating the urate transporter expressions and suppressing the JAK2/STAT3 signaling pathway. BRB was believed to be promising for further development into a potential therapeutic agent for HUA treatment.

Upregulated Guanine Deaminase Is Involved in Hyperpigmentation of Seborrheic Keratosis via Uric Acid Release

Seborrheic keratosis, which is a benign tumor composed of epidermal keratinocytes, develops common in the elderly. Uric acid generated by upregulated guanine deaminase (GDA) has been identified to cause UV-induced keratinocyte senescence in seborrheic keratosis. Seborrheic keratosis is also frequently pigmented. Growing evidences indicate that hyperuricemia is a risk factor of acanthosis nigricans, an acquired skin hyperpigmentation. The objective of this study was to investigate role of GDA and its metabolic end product, uric acid, in hyperpigmentation of patients with seborrheic keratosis using their lesional and non-lesional skin specimen sets and cultured primary human epidermal keratinocytes with or without GDA overexpression or uric acid treatment. GDA-overexpressing keratinocytes or their conditioned media containing uric acid increased expression levels of MITF and tyrosinase in melanocytes. Uric acid released from keratinocytes was facilitated by ABCG2 transporter with the help of PDZK1 interaction. Released uric acid was taken by URAT1 transporter in melanocytes, stimulating melanogenesis through p38 MAPK activation. Overall, GDA upregulation in seborrheic keratosis plays a role in melanogenesis via its metabolic end product uric acid, suggesting that seborrheic keratosis as an example of hyperpigmentation associated with photoaging.

Serum and pulmonary uric acid in pulmonary arterial hypertension

Previous studies have suggested an association between uric acid (UA) and the severity of pulmonary arterial hypertension (PAH), but it is unknown whether UA contributes to disease pathogenesis.The aim of this study was to determine the prognostic value of circulating UA in the era of current management of PAH and to investigate the role of UA in pulmonary vascular remodelling.Serum UA levels were determined in idiopathic, heritable or anorexigen PAH at baseline and first re-evaluation in the French Pulmonary Hypertension Network. We studied protein levels of xanthine oxidase (XO) and the voltage-driven urate transporter 1 (URATv1) in lungs of control and PAH patients and of monocrotaline (MCT) and Sugen/hypoxia (SuHx) rats. Functional studies were performed using human pulmonary artery smooth muscle cells (PA-SMCs) and two animal models of pulmonary hypertension (PH).High serum UA levels at first follow-up, but not at baseline, were associated with a poor prognosis. Both the generating enzyme XO and URATv1 were upregulated in the wall of remodelled pulmonary arteries in idiopathic PAH patients and MCT and SuHx rats. High UA concentrations promoted a mild increase in cell growth in idiopathic PAH PA-SMCs, but not in control PA-SMCs. Consistent with these observations, oxonic acid-induced hyperuricaemia did not aggravate MCT-induced PH in rats. Finally, chronic treatment of MCT and SuHx rats with benzbromarone mildly attenuated pulmonary vascular remodelling.UA levels in idiopathic PAH patients were associated with an impaired clinical and haemodynamic profile and might be used as a non-invasive indicator of clinical prognosis during follow-up. Our findings also indicate that UA metabolism is disturbed in remodelled pulmonary vascular walls in both experimental and human PAH.

Uric acid can enhance MAPK pathway-mediated proliferation in rat primary vascular smooth muscle cells via controlling of mitochondria and caspase-dependent cell death

Hyperuricemia may be a risk factor for cardiovascular diseases such as hypertension and atherosclerosis, but the mechanisms underlying uric acid-induced pathological conditions remain unknown. In this study, we investigated the effect of short time and long-term administration of increasing uric acid concentrations on cell viability, proliferative and apoptotic pathways in vascular smooth muscle cells (VSMCs). Cell viability/proliferation was determined with WST-1 assay. Expression levels of mitogen-activated protein kinases (MAPKs) (phosphorylated (p)-p38 and p-p44/42 MAPK), extrinsic (caspase 3, caspase 8), and intrinsic (B-cell lymphoma-extra-large (Bcl-xL)) apoptotic pathway proteins were measured by Western blotting. In order to assess the proliferative effects of uric acid incubations on VSMCs, we monitored the proliferative/apoptosis signaling pathways for up to 24 h. Our results indicated that uric acid increases cell viability at time and dose-dependently in VSMCs. Immunoblotting results showed that uric acid treatment elevated the expression level of p-p38 MAPK but did markedly reduce the protein levels of p-p44/42, compared with all the uric acid doses-treated VSMCs, especially at 1 h. Uric acid stimulation increased caspase-3 protein levels and decreased Bcl-xL, but did not alter caspase-8 protein expression at the same dose and time. Furthermore, low uric acid incubations (0-7.5 mg/dL) did not affect any signaling pathways for long time points (6-24 h). In conclusion, our study demonstrates for the first time that VSMCs induced with uric acid can affect cell viability, proliferative, and apoptosis pathways at the widest time and dose range. These findings provide a better understanding of the uric acid effects related to vascular impairments.

The Efficacy and Mechanism of Chinese Herbal Medicines in Lowering Serum Uric Acid Levels: A Systematic Review

Background. Chinese herbal medicines are widely used to lower serum uric acid levels. However, no systemic review summarizes and evaluates their efficacies and the underlying mechanisms of action. Objectives. To evaluate the clinical and experimental evidences for the effectiveness and the potential mechanism of Chinese herbal medicines in lowering serum uric acid levels. Methods. Four electronic databases PubMed, Wed of Science, the Cochrane Library and Embase were used to search for Chinese herbal medicines for their effects in lowering serum uric acid levels, dated from 1 January 2009 to 19 August 2020. For clinical trials, randomized controlled trials (RCTs) were included; and for experimental studies, original articles were included. The methodological quality of RCTs was assessed according to the Cochrane criteria. For clinical trials, a meta-analysis of continuous variables was used to obtain pooled effects. For experimental studies, lists were used to summarize and integrate the mechanisms involved. Results. A total of 10 clinical trials and 184 experimental studies were included. Current data showed that Chinese herbal medicines have promising clinical efficacies in patients with elevated serum uric acid levels (SMD: −1.65, 95% CI: −3.09 to −0.22; p = 0.024). There was no significant difference in serum uric acid levels between Chinese herbal medicine treatments and Western medicine treatments (SMD: −0.13, 95% CI: −0.99 to 0.74; p = 0.772). Experimental studies revealed that the mechanistic signaling pathways involved in the serum uric acid lowering effects include uric acid synthesis, uric acid transport, inflammation, renal fibrosis and oxidative stress. Conclusions. The clinical studies indicate that Chinese herbal medicines lower serum uric acid levels. Further studies with sophisticated research design can further demonstrate the efficacy and safety of these Chinese herbal medicines in lowering serum uric acid levels and reveal a comprehensive picture of the underlying mechanisms of action.

Network Pharmacology-Based Investigation of the Mechanism of Action of Plantaginis Herba in Hyperuricemia Treatment

This study used a network pharmacology approach to investigate the potential active ingredients of Plantaginis Herba and its underlying mechanisms in hyperuricemia treatment. The potential active ingredients of Plantaginis Herba were obtained from TCMSP and ETCM databases, and the potential targets of the active ingredients were predicted using the Swiss TargetPrediction database. The potential therapeutic targets of hyperuricemia were retrieved from the GeneCards, DisGeNET, and Online Mendelian Inheritance in Man (OMIM) databases. Then, the integrative bioinformatics analyses of candidates were performed by GO analysis, KEGG analysis, and PPI network construction. There were 15 predicted active ingredients in Plantaginis Herba and 41 common targets that may be involved in the treatment of hyperuricemia. A total of 61 GO annotations and 35 signaling pathways were identified by enrichment analysis (P < 0.01). The underlying mechanisms of Plantaginis Herba may be related to insulin resistance, PI3K/AKT, TNF, VEGF, AMPK, and glucagon signaling pathways. Thus, the present study provided potential and promising strategies of Plantaginis Herba for hyperuricemia treatment.

Uremic Toxins and Vascular Calcification-Missing the Forest for All the Trees

The cardiorenal syndrome relates to the detrimental interplay between the vascular system and the kidney. The uremic milieu induced by reduced kidney function alters the phenotype of vascular smooth muscle cells (VSMC) and promotes vascular calcification, a condition which is strongly linked to cardiovascular morbidity and mortality. Biological mechanisms involved include generation of reactive oxygen species, inflammation and accelerated senescence. A better understanding of the vasotoxic effects of uremic retention molecules may reveal novel avenues to reduce vascular calcification in CKD. The present review aims to present a state of the art on the role of uremic toxins in pathogenesis of vascular calcification. Evidence, so far, is fragmentary and limited with only a few uremic toxins being investigated, often by a single group of investigators. Experimental heterogeneity furthermore hampers comparison. There is a clear need for a concerted action harmonizing and standardizing experimental protocols and combining efforts of basic and clinical researchers to solve the complex puzzle of uremic vascular calcification.

Mechanistic Insights of Soluble Uric Acid-related Kidney Disease

Hyperuricemia, defined as the presence of elevated serum uric acid (sUA), could lead to urate deposit in joints, tendons, kidney and other tissues. Hyperuricemia as an independent risk factor was common in patients during the causation and progression of kidney disease. Uric acid is a soluble final product of endogenous and dietary purine metabolism, which is freely filtered in kidney glomeruli where approximately 90% of filtered uric acid is reabsorbed. Considerable studies have demonstrated that soluble uric acid was involved in the pathophysiology of renal arteriolopathy, tubule injury, tubulointerstitial fibrosis, as well as glomerular hypertrophy and glomerulosclerosis. In the review, we summarized the mechanistic insights of soluble uric acid related renal diseases.

Ethanol extract of Liriodendron chinense (Hemsl.) Sarg barks attenuates hyperuricemic nephropathy by inhibiting renal fibrosis and inflammation in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Liriodendron chinense (Hemsl.) Sarg, known as the Chinese tulip tree, has a long history of cultivation and utilization in many Asia countries, especially in China to use in traditional Chinese medicine for expelling "wind and dampness", a term corresponding to rheumatic fever and rheumatoid arthritis. Interestingly, the barks of Liriodendron chinense (Hemsl.) Sarg was also found in folk to treat gout. However, further experimental studies remained to confirm its uric acid-lowering effects.

AIM OF THE STUDY

The aim of the study was to evaluate the protective effect of ethanol extract of the barks of Liriodendron chinense (Hemsl.) Sarg (EELC) in a mouse model of hyperuricemic nephropathy (HN) and the involved mechanisms.

MATERIALS AND METHODS

EELC at a respective dose of 250 mg/kg/d or 500 mg/kg/d were orally administered to HN mice induced by a mixture of adenine (160 mg/kg/d)/potassium oxonate (2.4 g/kg/d) for 21 days. At the end of the treatment, serum uric acid, kidney functions (serum creatinine, blood urea nitrogen and urine microalbumin), 24-h urine uric acid excretion, as well as kidney pathological changes were investigated by biochemical assay, histopathological score, immunofluorescence and histochemistry, RT-qPCR, and western blotting analysis.

RESULTS AND DISCUSSION

Oral administration of EELC significantly lowered serum uric acid level at 500 mg/kg (185.75 ± 15.49 μmol/L of EELC vs. 238.28 ± 20.97 μmol/L of HN model, p < 0.01) in HN mice. EELC at 500 mg/kg also remarkably reduced the levels of serum creatinine (82.92 ± 7.86 μmol/L of EELC vs. 92.08 ± 6.13 μmol/L of HN model, p < 0.0001), blood urea nitrogen (21.50 ± 1.87 mmol/L of EELC vs. 29.40 ± 3.95 mmol/L of HN model, p < 0.001) and urine microalbumin (4.25 ± 0.40 mg/L of EELC vs. 5.95 ± 0.33 mg/L of HN model, p < 0.001) to improve renal function. It also attenuated renal fibrosis, especially the high-dose of EELC. Furthermore, EELC could inhibit the activation of NF-κB, ASK1/JNK/c-Jun, JAK2/STAT3 signaling pathways and reduce the release of pro-inflammatory cytokine TNF-α in the kidneys of HN mice. Additionally, EELC remarkably increased urine uric acid excretion of HN mice, which may be achieved by the upregulation of organic anion transporter 1 (OAT1), OAT3 and ATP-binding cassette subfamily G member 2 (ABCG2) proteins.

CONCLUSIONS

EELC alleviated the progression of HN by suppressing the activation of NF-κB, ASK1/JNK/c-Jun and JAK2/STAT3 signaling pathway, reducing the infiltration of inflammatory factors and uric acid accumulation in the kidney.

Lipoxin A4 attenuates uric acid-activated, NADPH oxidase-dependent oxidative stress by interfering with translocation of p47phox in human umbilical vein endothelial cells

LipoxinA4 (LXA4) is a well-known key mediator of endogenous anti-inflammation and of the resolution of inflammation. Considerable oxidative stress occurs during inflammation due to the generation of reactive oxidative species (ROS). Moreover, high levels of uric acid (UA) contribute to endothelial cell dysfunction, which can promote disease-related morbidity, and NADPH oxidase-derived ROS are crucial regulatory factors in these responses. However, LXA4 also has the potential to reduce oxidative stress. The aim of the present study was to examine whether LXA4 could suppress UA-induced oxidative stress in human umbilical vein endothelial cells (HUVECs) and to investigate its mechanisms of action in vitro. HUVECs were incubated with or without LXA4, followed by the addition of UA. ROS levels were then measured using 2,7-dichlorodihydrofluorescein diacetate and lucigenin-enhanced chemiluminescence was used to evaluate NADPH oxidase activity. p47phox or p22phox small interfering (si)RNA were transfected into HUVECs and protein levels of p47phox were detected using western blot analysis. LXA4 significantly inhibited UA-induced generation of ROS to the same extent as the NADPH oxidase inhibitor, diphenyleneiodonium chloride. Notably, transfection of p47phox siRNA attenuated the generation of ROS and the activation of NADPH oxidase. Cells transfected with p22phox siRNA demonstrated a significant reduction in the expression of p47phox on the membrane. Further experiments demonstrated that LXA4 interfered with the transfer of p47phox from the cytoplasm to the cell membrane. These findings suggested that LXA4 inhibited the release of NADPH oxidase derived ROS in HUVECs stimulated by UA. A potential mechanism of action underlying this effect could be LXA4-mediated suppression of NADPH oxidase activity, leading to inhibition of p47phox translocation from the cytoplasm to the cell membrane.

Uric Acid Has Direct Proinflammatory Effects on Human Macrophages by Increasing Proinflammatory Mediators and Bacterial Phagocytosis Probably via URAT1

The relationship of uric acid with macrophages has not been fully elucidated. We investigated the effect of uric acid on the proinflammatory ability of human macrophages and then examined the possible molecular mechanism involved. Primary human monocytes were differentiated into macrophages for subsequent exposure to 0, 0.23, 0.45, or 0.9 mmol/L uric acid for 12 h, in the presence or absence of 1 mmol/L probenecid. Flow cytometry was used to measure proinflammatory marker production and phagocytic activity that was quantified as a percentage of GFP-labeled Escherichia coli positive macrophages. qPCR was used to measure the macrophage expression of the urate anion transporter 1 (URAT1). As compared to control cells, the production of tumor necrosis factor-alpha (TNF-alpha), toll-like receptor 4 (TLR4), and cluster of differentiation (CD) 11c was significantly increased by uric acid. In contrast, macrophages expressing CD206, CX3C-motif chemokine receptor 1 (CX3CR1), and C-C chemokine receptor type 2 (CCR2) were significantly reduced. Uric acid progressively increased macrophage phagocytic activity and downregulated URAT1 expression. Probenecid-a non-specific blocker of URAT1-dependent uric acid transport-inhibited both proinflammatory cytokine production and phagocytic activity in macrophages that were exposed to uric acid. These results suggest that uric acid has direct proinflammatory effects on macrophages possibly via URAT1.

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.

PP2A alleviates oxidized LDL-induced endothelial dysfunction by regulating LOX-1/ROS/MAPK axis

AIMS

The purpose of this study is to investigate the effect of PP2A on the progression of AS and the special molecular mechanism.

MAIN METHODS

The expression of PP2A in Human umbilical vein endothelial cells (HUVECs) induced by different concentrations of Ox-LDL was measured by RT-PCR and Western blot. The binding activity of PP2A and LOX-1 was determined by CoIP assay. Western blot was used to measure the protein expression of VCAM-1, ICAM-1 and MCP-1.

KEY FINDING

The results revealed that the expression of PP2A was decreased with the increase of Ox-LDL concentration in HUVECs. Overexpression of PP2A alleviated Ox-LDL-induced dysfunction and inflammatory response in HUVECs. The results of Co-immunoprecipitation (CoIP) showed that PP2A had direct effect on LOX-1, and PP2A inhibited the expression of LOX-1. In addition, overexpression of LOX-1 reversed the inhibitory effect of PP2A on Ox-LDL-induced dysfunction and inflammatory response in HUVECs. What is more, PP2A inhibited LOX-1/ROS/MAPK axis.

SIGNIFICANCE

it suggests that PP2A alleviates Ox-LDL-induced dysfunction and inflammatory response of HUVECs potentially by regulating the LOX-1/ROS/MAPK axis，which suggests that PP2A has anti-inflammatory effect during the formation of as, and the molecular therapy of PP2A provides a theoretical basis.

Anti‑gouty arthritis and anti‑hyperuricemia properties of celery seed extracts in rodent models

Gout is a type of serious arthritis that is caused by hyperuricemia. Celery is an umbelliferous plant that was shown to exhibit anti‑inflammatory activity in rodent. The present study aimed to investigate the effects and potential preliminary mechanisms of celery seed aqueous extract (CSAE) and celery seed oil extract (CSOL) for gout treatment. The components of CSAE and CSOL were systematically analyzed. In mice with hyperuricemia induced by potassium oxonate and yeast extract, CSAE and CSOL treatment reduced the serum levels of uric acid and xanthine oxidase. In addition, CSAE and CSOL reduced the levels of reactive oxygen species and increased the serum levels of superoxide dismutase and glutathione peroxidase in mouse serum. In rats with acute gouty arthritis induced by intra‑articular injection of monosodium urate crystals, CSAE and CSOL treatment alleviated the swelling of the ankle joints and reduced inflammatory cell infiltration around the ankle joints. In addition, CSAE and CSOL reduced the levels of interleukin (IL)‑1β and tumor necrosis factor α and increased the levels of IL‑10. The results of the present study suggested that celery seed extracts may have anti‑gout properties, partially through anti‑inflammatory and antioxidative effects.