Identification of Scopoletin and Chlorogenic Acid as Potential Active Components in Sunflower Calathide Enzymatically Hydrolyzed Extract towards Hyperuricemia

It is known that sunflower (Helianthus annuus L.) calathide enzymatically hydrolyzed extract (SCHE) contributes to the regulation of serum uric acid (UA); however, evidence regarding its bioactive components and mechanism are lacking. We identified two water-soluble components (scopoletin and chlorogenic acid) that are abundant in sunflower calathide, especially evaluated for the inhibition of xanthine oxidase (XO) and the expression levels of urate transporters with SCHE. Molecular docking of a chlorogenic acid–XO complex was more stable than that of the Scopoletin–XO, and its binding pockets, which closed the Mo = S center, was similar to xanthine pockets. Moreover, chlorogenic acid exhibited stronger inhibition than that of the scopoletin below 260 μM, despite the IC50 of scopoletin (577.7 μM) being lower than that chlorogenic acid (844.7 μM) on the UA generation assessed by a spectrophotometer in vitro. It revealed that chlorogenic acid and scopoletin were competitive inhibitors of XO. In addition, the SCHE (300 μg/mL) and chlorogenic acid (0.75 mM) obviously inhibited urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) expression levels, while scopoletin significantly upregulated the expression of GLUT9. To summarize, chlorogenic acid served a crucial role in UA regulation consistent with the SCHE and functioned as an important ingredient of SCHE. The strategic analysis of SCHE combined with scopoletin and chlorogenic acid may contribute to the development of food supplemental alternatives on UA metabolism and the reduction of agricultural byproduct waste.

The effects of hyperuricemia on endothelial cells are mediated via GLUT9 and the JAK2/STAT3 pathway

Background Uric acid (UA) transporters mediate the uptake and outflow of UA, and are greatly involved in the control of UA concentrations. Glucose transporter 9 (GLUT9), one of the UA transporters, has been confirmed to be expressed in human umbilical vein endothelial cells (HUVECs). This study aimed to characterize GLUT9’s effect on intracellular UA accumulation in HUVECs in a high-UA environment and to explore the mechanism of cellular dysfunction. Methods and results HUVECs were treated with UA to establish a model of cellular dysfunction. Then, UA uptake, GLUT9 expression and endothelial nitric oxide synthase (eNOS) and reactive oxygen species (ROS) amounts were measured. UA uptake was concentration- and time-dependent, and UA treatment significantly reduced nitric oxide (NO) levels and eNOS activity. UA also upregulated pro-inflammatory molecules and GLUT9, and increased intracellular ROS amounts in HUVECs. GLUT9 knockdown reduced UA uptake and ROS content, but antioxidant treatment did not reduce GLUT9 expression. To assess the function of JAK2/STAT3 signaling, HUVECs were treated with UA, and the phosphorylation levels of JAK2, STAT3, IL-6 and SOCS3 were increased by a high concentration of UA. In addition, GLUT9 knockdown reduced the phosphorylation of JAK2/STAT3 intermediates and increased p-eNOS amounts. Conclusions GLUT9 mediated the effects of high UA levels on HUVECs by increasing the cellular uptake of UA, activating JAK2/STAT3 signaling, and reduced the production of active eNOS and NO in HUVECs.

Effects of Macroporous Resin Extract of Dendrobium officinale Leaves in Rats with Hyperuricemia Induced by Fructose and Potassium Oxonate

Aim and Objective: Fructose, as a ubiquitous monosaccharide, can promote ATP consumption and elevate circulating uric acid (UA) levels. Our previous studies confirmed that the macroporous resin extract of Dendrobium officinale leaves (DoMRE) could reduce the UA level of rats with hyperuricemia induced by a high-purine diet. This study aimed to investigate whether DoMRE had a UA-lowering effect on rats with hyperuricemia caused by fructose combined with potassium oxonate, so as to further clarify the UA-lowering effect of DoMRE, and to explore the UA-lowering effect of DoMRE on both UA production and excretion. Materials and Methods: Rats with hyperuricemia induced by fructose and potassium oxonate were administered with DoMRE and vehicle control, respectively, to compare the effects of the drugs. At the end of the experiment, the serum uric acid (SUA) and creatinine (Cr) levels were measured using an automatic biochemical analyzer, the activities of xanthine oxidase (XOD) were measured using an assay kit, and the protein expression of urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), and ATP-binding cassette superfamily G member 2 (ABCG2) were assessed using immunohistochemical and western blot analyses. Hematoxylin and eosin staining was used to assess the histological changes in the kidney, liver, and intestine. Results: Rats with hyperuricemia were induced by fructose and potassiumFructose and potassium induced hyperuricemia in rats. Meanwhile, the activities of XOD were markedly augmented, the expression of URAT1 and GLUT9 was promoted, and the expression of ABCG2 was reduced, which were conducive to the elevation of UA. However, exposure to DoMRE reversed these fructose- and potassium oxonate-induced negative alternations in rats. The activities of XOD were recovered to the normal level, reducing UA formation; the expression of URAT1, ABCG2, and GLUT9 returned to the normal level, resulting in an increase in renal urate excretion. Conclusion: DoMRE reduces UA levels in rats with hyperuricemia induced by fructose combined with potassium oxonate by inhibiting XOD activity and regulating the expression of ABCG2, URAT1, and GLUT9. DoMRE is a potential therapeutic agent for treating hyperuricemia through inhibiting UA formation and promoting UA excretion.

Fucoidan from Laminaria japonica Inhibits Expression of GLUT9 and URAT1 via PI3K/Akt, JNK and NF-κB Pathways in Uric Acid-Exposed HK-2 Cells

This work aimed to investigate the effect of fucoidan (FPS) on urate transporters induced by uric acid (UA). The results showed that UA stimulated the expression of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) in HK-2 cells, and FPS could reverse the effect. Moreover, UA could activate NF-κB, JNK and PI3K/Akt pathways, but both pathway inhibitors and FPS inhibited the UA-induced activation of these three pathways. These data suggested that FPS effectively inhibited the expression induction of reabsorption transporters URAT1 and GLUT9 by UA, through repressing the activation of NF-κB, JNK and PI3K/Akt signal pathways in HK-2 cells. The in vitro research findings support the in vivo results that FPS reduces serum uric acid content in hyperuricemia mice and rats through inhibiting the expression of URAT1 and GLUT9 in renal tubular epithelial cells. This study provides a theoretical basis for the application of FPS in the treatment of hyperuricemia.

Active Components from Lagotis Brachystachya Maintain Uric Acid Homeostasis by Inhibiting Renal TLR4-NLRP3 Signaling in Hyperuricemic Mice

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

Ameliorative Effects of Lesinurad (Zurampic) on Experimental Hyperuricemia, Biochemical, Molecular and Immunohistochemical Study

Background: The current study evaluates the potential ameliorative impact of Lesinurad (i.e. Zurampic (ZUR)) and Allopurinol (ALP) on the kidneys of hyperuricemic mice at the biochemical, molecular and cellular levels. Methods: ALP and ZUR in combination were orally administered to both hyperuricemic and control mice for seven consecutive days. Levels of uric acid and Blood Urea Nitrogen (BUN), along with antioxidants and inflammatory cytokines (IL-1β and TNF-a) were measured in serum. The mRNA expression of mouse urate anion transporter-1 (mURAT1), glucose transporter 9 (mGLUT9), organic anion transporters (mOAT1 and mOAT3), in renal tissues were examined using quantitative real time PCR (qRT-PCR). Simultaneously, the immunoreactivity of transforming growth factor-1 beta (TGF-β1) was examined immunohistochemically. Results: ALP and ZUR administration resulted in significantly reduced serum urate levels and decreased serum levels of uric acid, BUN, catalase, glutathione peroxidase (GPx) and inflammatory cytokines (IL-1β and TNF-a) in hyperuricemic mice. Both partially reversed oxonate-induced alterations in renal mURAT-1, mGLUT-9, mOAT-1 and mOAT-3 expressions, as well as leading to changes in the immunoreactivity of TGF- β1, resulting in the increase of renal uric acid secretion and excretion. The combined administration of ALP and ZUR restored all altered measurements in a synergistic manner, improving renal dysfunction in the hyperuricemic mouse model employed. Conclusion: This study therefore provides evidence for the synergistic hypouricemic impact of both ALP and ZUR in the treatment of HU in mice at the biochemical, molecular and cellular levels.

Anti-Hyperuricemic Effect of 2-Hydroxy-4-methoxy-benzophenone-5-sulfonic Acid in Hyperuricemic Mice through XOD

Conventionally, benzophenone-type molecules are beneficial for alleviating the UV exposure of humans. More importantly, various compounds with this skeleton have demonstrated various biological activities. In this paper, we report the anti-hyperuricemic effect of the benzophenone compound 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (HMS). Preliminarily, its molecular docking score and xanthine oxidase (XOD) inhibition suggested a good anti-hyperuricemic effect. Then, its anti-hyperuricemic effect, primary mechanisms and general toxicity were examined on a hyperuricemic mouse model which was established using potassium oxonate and hypoxanthine together. HMS demonstrated a remarkable anti- hyperuricemic effect which was near to that of the control drugs, showing promising perspective. General toxicity was assessed and it showed no negative effects on body weight growth and kidney function. Moreover, anti-inflammatory action was observed for HMS via spleen and thymus changes. Its anti-hyperuricemic mechanisms may be ascribed to its inhibition of XOD and its up-regulation of organic anion transporter 1 (OAT1) and down-regulation of glucose transporter 9 (GLUT9).