Qi-Zhu-Xie-Zhuo-Fang reduces serum uric acid levels and ameliorates renal fibrosis in hyperuricemic nephropathy rats

Gut microecology: effective targets for natural products to modulate uric acid metabolism

Gut microecology,the complex community consisting of microorganisms and their microenvironments in the gastrointestinal tract, plays a vital role in maintaining overall health and regulating various physiological and pathological processes. Recent studies have highlighted the significant impact of gut microecology on the regulation of uric acid metabolism. Natural products, including monomers, extracts, and traditional Chinese medicine formulations derived from natural sources such as plants, animals, and microorganisms, have also been investigated for their potential role in modulating uric acid metabolism. According to research, The stability of gut microecology is a crucial link for natural products to maintain healthy uric acid metabolism and reduce hyperuricemia-related diseases. Herein, we review the recent advanced evidence revealing the bidirectional regulation between gut microecology and uric acid metabolism. And separately summarize the key evidence of natural extracts and herbal formulations in regulating both aspects. In addition,we elucidated the important mechanisms of natural products in regulating uric acid metabolism and secondary diseases through gut microecology, especially by modulating the composition of gut microbiota, gut mucosal barrier, inflammatory response, purine catalyzation, and associated transporters. This review may offer a novel insight into uric acid and its associated disorders management and highlight a perspective for exploring its potential therapeutic drugs from natural products.

Bi Xie Fen Qing Yin decoction alleviates potassium oxonate and adenine induced-hyperuricemic nephropathy in mice by modulating gut microbiota and intestinal metabolites

This study aimed to evaluate the preventive effect of Bi Xie Fen Qing Yin (BXFQY) decoction on hyperuricemic nephropathy (HN). Using an HN mouse model induced by oral gavage of potassium oxonate and adenine, we found that BXFQY significantly reduced plasma uric acid levels and improved renal function. Further study shows that BXFQY suppressed the activation of the NLRP3 inflammasome and decreased the mRNA expressions of pro-inflammatory and fibrosis-associated factors in renal tissues of HN mice. Also, BXFQY prevented the damage to intestinal tissues of HN mice, indicative of suppressed colonic inflammation and increased gut barrier integrity. By 16 S rDNA sequencing, BXFQY significantly improved gut microbiota dysbiosis of HN mice. On the one hand, BXFQY down-regulated the abundance of some harmful bacteria, like Desulfovibrionaceae, Enterobacter, Helicobacter, and Desulfovibrio. On the other hand, BXFQY up-regulated the contents of several beneficial microbes, such as Ruminococcaceae, Clostridium sensu stricto 1, and Streptococcus. Using gas or liquid chromatography-mass spectrometry (GC/LC-MS) analysis, BXFQY reversed the changes in intestinal bacterial metabolites of HN mice, including indole and BAs. The depletion of intestinal flora from HN or HN plus BXFQY mice confirmed the significance of gut microbiota in BXFQY-initiated treatment of HN. In conclusion, BXFQY can alleviate renal inflammation and fibrosis of HN mice by modulating gut microbiota and intestinal metabolites. This study provides new insight into the underlying mechanism of BXFQY against HN.

Study of hispidulin in the treatment of uric acid nephropathy based on NF-κB signaling pathway

Uric acid nephropathy (UAN) is caused by purine metabolism disorders. UAN rat models were established in SD rats. The modeling rats received different doses of hispidulin (10, 20, 50 mg/mL). Febuxostat was applied as the positive drug. Serum creatinine, uric acid (UA), and cystatin-C (cys-C), neutrophil gelatinase-associated lipocalin (NGAL), IL-1β, IL-8, TNF-α, and IL-6 in rats were detected. HE staining was done to assess kidney injury. UAN rats possessed prominent levels of serum creatinine, UA, cys-C, and NGAL, which all reduced after hispidulin treatment in a dose-dependent manner. HE staining determined the improvement of kidney injury after treatment, which was comparable to the efficacy of febuxostat. Hispidulin inhibited the release of IL-1β, IL-8, TNF-α, and IL-6 in UAN rats. Hispidulin enhanced autophagy in UAN rats, presenting as ascending LC3II/I ratio and downregulated P62. The increasing trend of inflammasome-related proteins of NLRP3 and Caspase-1 was changeovered by hispidulin. The activation of NF-kB signaling was intercepted by hispidulin in UAN rats. Hispidulin can effectively improve renal function injury caused by UAN in rats. The mechanism may be related to the inhibition of inflammatory response induced by autophagy and activation of NF-κB pathway.

Mechanism of Xiezhuo Huayu Yiqi Tongluo Formula in the Treatment of Uric Acid Nephropathy Based on Network Pharmacology, Molecular Docking, and In Vivo Experiments

Background

Xiezhuo Huayu Yiqi Tongluo Formula (XHYTF) consists of 14 Chinese herbal medicines. In this study, we investigated the potential mechanism of XHYTF in the treatment of uric acid nephropathy (UAN) through network pharmacology, molecular docking, and in vivo methods.

Methods

Using various pharmacological databases and analysis platforms, information on the active ingredients and targets of Chinese herbal medicine was collected, and UAN disease targets were retrieved using OMIM, Gene Cards, and NCBI. Then common target proteins were integrated. A Drug-Component-Target (D-C-T) map was constructed to screen core compounds and build a protein-protein interaction (PPI) network. Further, Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed for common targets, and a Drug-Component-Target-Pathway (D-C-T-P) network diagram was constructed. The molecular docking simulation was performed to verify the binding affinity between core components and hub targets. Subsequently, the UAN rat model was established, followed by the collection of serum and renal tissues. The expression levels of indicators in the serum were determined using an enzyme-linked immunosorbent assay. The pathological changes of renal tissues were detected using H & E staining and Masson staining. The expression of related proteins in renal tissue was detected by western blot.

Results

In the study, 216 active ingredients and 439 targets in XHYTF were screened, and 868 targets were identified as being related to UAN. Among them, 115 were common targets. Based on the D-C-T network, quercetin, luteolin, β-sitosterol, and stigmasterol were observed to be the key active ingredients of XHYTF that were effective against UAN. The analysis of the PPI network revealed TNF, IL6, AKT1, PPARG, and IL1β as the 5 key targets. GO enrichment analysis revealed that the pathways were mainly concentrated in cell killing, regulation of signaling receptor activity, and other activities. Subsequently, KEGG pathway analysis revealed that multiple signaling pathways, including the HIF-1, PI3K-Akt, IL-17, and other signaling pathways, were closely related to the action of XHYTF. All 5 key targets were confirmed to interact with all core active ingredients. In vivo experiments indicated that XHYTF significantly reduced blood uric acid and creatinine levels, alleviated inflammatory cell infiltration in kidney tissues, reduced the levels of serum inflammatory factors such as TNF-α and IL1β, and ameliorated renal fibrosis in rats with UAN. Finally, western blot revealed decreased levels of PI3K and AKT1 proteins in the kidney, which confirmed the hypothesis.

Conclusion

Collectively, our observations demonstrated that XHYTF significantly protects kidney function, including alleviation of inflammation and renal fibrosis via multiple pathways. This study provided novel insights into the treatment of UAN using traditional Chinese medicines.

A Novel Approach Based on Gut Microbiota Analysis and Network Pharmacology to Explain the Mechanisms of Action of Cichorium intybus L. Formula in the Improvement of Hyperuricemic Nephropathy in Rats

Background

Cichorium intybus L. formula (CILF) is a traditional Chinese medicine (TCM) widely used in the treatment of gout and hyperuricemic nephropathy (HN). The aim of this research was to investigate the potential protective effect of CILF against HN and elucidated the underlying mechanism.

Methods

CILF water extract was administered to an HN rat model established by adenine combined with ethambutol. The levels of uric acid (UA), serum urea nitrogen (UREA), and creatinine (CREA) were detected. Changes in the pathology and histology of the kidney were observed by hematoxylin-eosin staining. The 16S rRNA of the gut microbiota was sequenced. The binding ability of the main ingredients of CILF to key targets was analyzed by network pharmacology and molecular docking. The expression levels of the related mRNAs and proteins in the kidney were evaluated by RT-qPCR and immunohistochemistry analysis.

Results

CILF administration significantly alleviated increases in UA, UREA, and CREA, structural damage, and kidney dysfunction. Gut microbiota analysis was applied to explore the pharmacological mechanism of the effects of CILF on bacterial diversity and microbiota structure in HN. CILF decreased the abundance of Bacteroides. In addition, it increased the abundance of Lactobacillaceae, Erysipelotrichaceae, Lachnospiraceae, Ruminococcaceae, and Bifidobacterium. Based on network pharmacology and molecular docking analysis, CILF profoundly influenced the IL17, TNF and AGE-RAGE signaling pathway. Additionally, CILF inhibited the expression of STAT3, VEGFA and SIRT1 to improve the symptoms of nephropathy. Our research suggested that CILF protects against kidney dysfunction in rats with HN induced by adenine combined with ethambutol.

Conclusion

Our findings on the anti-HN effects of CILF and its mechanism of action, from the viewpoint of systems biology, and elaborated that CILF can alter the diversity and community structure of the gut microbiota in HN, providing new approaches for the prevention and treatment of HN.

Integrating network pharmacology and pharmacological validation to explore the effect of Shi Wei Ru Xiang powder on suppressing hyperuricemia

ETHNOPHARMACOLOGICAL RELEVANCE

Shi Wei Ru Xiang powder (SWR) is a traditional Tibetan medicinal formula with the effect of dispelling dampness and dispersing cold. In clinical practice, SWR is generally used for the treatment of hyperuricemia (HUA). However, its exact pharmacological mechanism remains unclear.

AIMS OF THE STUDY

To preliminarily elucidate the regulatory effects and possible mechanisms of SWR on hyperuricemia using network pharmacology and experimental validation.

MATERIALS AND METHODS

A mouse model of hyperuricemia was used to evaluate the alleviating effect of SWR on hyperuricemia. The major components of SWR were acquired by UPLC-Q/TOF-MS. The potential molecular targets and associated signaling pathways were predicted through network pharmacology. The mechanism of action of SWR in ameliorating hyperuricemia was further investigated by pharmacological evaluation.

RESULTS

Mice with hyperuricemia and renal dysfunction were ameliorated by SWR. The 36 components of SWR included phenolic acids, terpenoids, alkaloids and flavonoids were identified. Network pharmacological analysis showed the involvement of the above compounds, and 115 targets were involved to treat hyperuricemia, involving multiple biological processes and different signaling pathways. Pharmacological experiments validated that SWR ameliorated hyperuricemic nephropathy in mice by modulating the mitogen-activated protein kinase (MAPK) signaling pathway, nuclear factor kappaB (NF-κB) signaling pathway and NOD-like receptor signaling pathway.

CONCLUSION

MAPK signaling pathway, NF-κB signaling pathway and NOD-like receptor signaling pathway play important roles in the therapeutic effects of SWR on hyperuricemia.

Traditional Chinese herbs and natural products in hyperuricemia-induced chronic kidney disease

Hyperuricemia is a common biochemical disorder, which resulted from both excessive uric acid (UA) production and/or absolute or relative impairment of urinary UA excretion. Growing evidence has indicated that hyperuricemia is an independent risk factor for the development and progression of chronic kidney disease (CKD), causing hyperuricemia-induced CKD (hyperuricemic nephropathy, HN). The therapeutic strategy of HN is managing hyperuricemia and protecting kidney function. Adverse effects of commercial drugs make persistent treatment of HN challenging. Traditional Chinese medicine (TCM) has exact efficacy in lowering serum UA without serious adverse effects. In addition, TCM is widely applied for the treatment of CKD. This review aimed to provide an overview of efficacy and mechanisms of traditional Chinese herbs and natural products in hyperuricemia-induced CKD.

Apigenin ameliorates hyperuricemic nephropathy by inhibiting URAT1 and GLUT9 and relieving renal fibrosis via the Wnt/β-catenin pathway

BACKGROUND

Hyperuricemia (HUA) is characterized by abnormal serum uric acid (UA) levels and demonstrated to be involved in renal injury leading to hyperuricemic nephropathy (HN). Apigenin (API), a flavonoid naturally present in tea, berries, fruits, and vegetables, exhibits various biological functions, such as antioxidant and anti-inflammatory activity.

PURPOSE

To investigate the effect of API treatment in HN and to reveal its underlying mechanisms.

METHODS

The mice with HN were induced by potassium oxonate intraperitoneally and orally administered for two weeks. The effects of API on renal function, inflammation, fibrosis, and uric acid (UA) metabolism in mice with HN were evaluated. The effects of API on urate transporters were further examined in vitro.

RESULTS

The mice with HN exhibited abnormal renal urate excretion and renal dysfunction accompanied by increased renal inflammation and fibrosis. In contrast, API reduced the levels of serum UA, serum creatinine (CRE), blood urea nitrogen (BUN) and renal inflammatory factors in mice with HN. Besides, API ameliorated the renal fibrosis via Wnt/β-catenin pathway suppression. Furthermore, API potently promoted urinary UA excretion and inhibited renal urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) in mice with HN. In vitro, API competitively inhibited URAT1 and GLUT9 in a dose-dependent manner, with IC₅₀ values of 0.64 ± 0.14 μM and 2.63 ± 0.69 μM, respectively.

CONCLUSIONS

API could effectively attenuate HN through co-inhibiting UA reabsorption and Wnt/β-catenin pathway, and thus it might be a potential therapy to HN.

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.

Plantaginis Semen polysaccharides ameliorate renal damage through regulating NLRP3 inflammasome in gouty nephropathy rats

Gouty nephropathy (GN) is considered to be a prevalent renal disease and is an inflammatory event mainly induced by MSU crystals. Plantaginis Semen is a traditional Chinese herb that has been used in the treatment of gout, gouty arthritis and GN, but the mechanism and ingredients have been unclear. In this study, we explored and evaluated the preliminary structural characterizations of Plantaginis Semen polysaccharides (PSPs) and the activity of protecting against renal damage in GN rats. Three polysaccharide fractions, PSP-D, PSP-H and PSP-S, were sequentially extracted by different processes from the seed of Plantago asiatica L. The Fourier transform infrared spectral (FTIR) results showed that there were significant differences between PSP-S and the other two polysaccharides (PSP-D and PSP-H). PSP-D and PSP-H have pyrene monomers and linkages of β-glycosides in their structures, and PSP-S has furanoside in the molecular structure. The scanning electron microscope (SEM) images of three polysaccharides showed that PSP-D has a smooth surface and a small curve, PSP-H is block-like and uneven in magnitude, whereas PSP-S is sea-tent-like and its surface is very distinct from the others. Main components and molar ratios are also different. Rats were randomly divided into six groups (n^1/6 8 per group): the control group, model group, positive group, and three treatment groups (PSP-D, PSP-H and PSP-S). For all groups except the control group, rats were intragastrically administered the adenine suspension (50 mg kg^-1 d^-1) and fed with a high-yeast diet (15 g kg^-1 d^-1) for 28 days. On the 9th day, the control group and the model group were administered normal saline at the same time. Treatment groups were individually given corresponding drugs for 20 days. We found that PSPs could prevent renal damage, including decreasing the inflammatory response and regulating the (NOD)-like receptor protein 3 (NLRP3) protein in renal tissue. The underlying mechanism was related to NLRP3 inflammasome signal pathways, and it could take effect through the down-regulation of the protein expression levels of NLRP3, ASC and caspase-1 and inhibit the release of downstream inflammatory factors. PSPs are promising polysaccharides that could protect against renal injury through ameliorating renal inflammation in GN rats. Plantaginis Semen polysaccharides are potential functional food ingredients or pharmacological agents for treating GN in clinical practice.

Pharmacologic Targeting of BET Proteins Attenuates Hyperuricemic Nephropathy in Rats

Hyperuricemia is an independent risk factor for renal damage and promotes the progression of chronic kidney disease. In this study, we investigated the effect of I-BET151, a small-molecule inhibitor targeting the bromodomain and extraterminal (BET) proteins, on the development of hyperuricemic nephropathy (HN), and the mechanisms involved. Expression levels of bromodomain-containing protein 2 and 4, but not 3 were increased in the kidney of rats with HN; administration of I-BET151 effectively prevented renal dysfunction, decreased urine microalbumin, and attenuated renal fibrosis as indicated by reduced activation of renal interstitial fibroblasts and expression of fibronectin and collagen I in HN rats. Mechanistic studies show that I-BET151 treatment inhibited transition of renal epithelial cells to a mesenchymal cell type as evidenced by preservation of E-cadherin and reduction of vimentin expression. This was coincident with reduced expression of TGF-β1 and dephosphorylation of Smad3 and ERK1/2. I-BET151 was also effective in inhibiting phosphorylation of NF-κB, expression of multiple cytokines and chemokines, and infiltration of macrophages to the injured kidney. Although there were increased serum levels of uric acid and xanthine oxidase, an enzyme that catalyzes production of uric acid, and decreased expression of renal organic anion transporter 1 and 3 that promote urate excretion in the model of HN, and reduced expression levels of urine uric acid, I-BET151 treatment did not affect these responses. Collectively, our results indicate that I-BET151 alleviates HN by inhibiting epithelial to mesenchymal transition and inflammation in association with blockade of TGF-β, ERK1/2 and NF-κB signaling.

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.

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.

Research Advances in the Mechanisms of Hyperuricemia-Induced Renal Injury

Uric acid is the end product of purine metabolism in humans, and its excessive accumulation leads to hyperuricemia and urate crystal deposition in tissues including joints and kidneys. Hyperuricemia is considered an independent risk factor for cardiovascular and renal diseases. Although the symptoms of hyperuricemia-induced renal injury have long been known, the pathophysiological molecular mechanisms are not completely understood. In this review, we focus on the research advances in the mechanisms of hyperuricemia-caused renal injury, primarily on oxidative stress, endothelial dysfunction, renal fibrosis, and inflammation. Furthermore, we discuss the progress in hyperuricemia management.

Treatment with a PPAR-γ Agonist Protects Against Hyperuricemic Nephropathy in a Rat Model

Purpose

Hyperuricemia is an independent risk factor for renal damage and can promote the progression of chronic kidney disease (CKD). In the present study, we employ a rat model to investigate the effects of rosiglitazone (RGTZ), a peroxisome proliferator-activated receptor-gamma agonist, on the development of hyperuricemic nephropathy (HN), and we elucidate the mechanisms involved.

Methods

An HN rat model was established by oral administration of a mixture of adenine and potassium oxonate daily for 3 weeks. Twenty-four rats were divided into 4 groups: sham treatment, sham treatment plus RGTZ, HN, and HN treated with RGTZ.

Results

Administration of RGTZ effectively preserved renal function, decreased urine microalbumin, and inhibited interstitial fibrosis and macrophage infiltration in a rat HN model. RGTZ treatment also inhibited TGF-β and NF-κB pathway activation, decreased expression of fibronectin, collagen I, α-SMA, vimentin, MCP-1, RANTES, TNF-α, and IL-1β, and increased E-cadherin expression in the kidneys of HN rats. Furthermore, RGTZ treatment preserved expression of OAT1 and OAT3 in the kidney of HN rats.

Conclusion

RGTZ attenuates the progression of HN through inhibiting TGF-β signaling, suppressing epithelial-to-mesenchymal transition, reducing inflammation, and lowering serum uric acid levels by preserving expression of urate transporters.

Uric acid induced epithelial-mesenchymal transition of renal tubular cells through PI3K/p-Akt signaling pathway

The phenotypic changes of tubular epithelial cell are hallmark features of renal diseases caused by abnormal uric acid levels. We hereby intend to investigate whether PI3K/p-Akt signaling plays a role in uric-acid induced epithelial-mesenchymal transition process. The normal rat kidney cell line (NRK-52E) was used as a proximal tubular cell model in this study. NRK-52E cells were exposed to different concentrations of uric acid, or PI3K inhibitor LY294002, or both, respectively. The effects of uric acid on cell morphology were examined by phase contrast microscopy, while molecular alternations were assessed by western blot analysis and immunofluorescence staining. We found that uric acid induced visible morphological alterations in NRK-52E cells accompanied by increased expression of α-smooth muscle actin and reduced expression of E-cadherin. Moreover, phosphorylation of Akt protein was obviously increased, whereas Akt level remained stable. Furthermore, the above effects were abolished when PI3K/p-Akt pathway was blocked by the PI3K inhibitor. These findings demonstrated that high uric acid could induce phenotypic transition of cultured renal tubular cells, which was probably via activating PI3K/p-Akt signaling pathway.

Risk factors analysis for hyperuricemic nephropathy among CKD stages 3-4 patients: an epidemiological study of hyperuricemia in CKD stages 3-4 patients in Ningbo, China

Objective: Uric acid (UA) is a risk marker of CKD and SUA level in CKD 3–4 patients closely correlates with hyperuricemic nephropathy (HN) morbidity. This study was designed to evaluate the risk factors for HN in CKD 3–4 patients.

Methods: The 461 CKD 3–4 patients were recruited and all patients were divided into three groups (24 h UUA normal, underexeret, and overproduct type groups) according to the 24 h UUA level after receiving low purine food for five days. Clinical and biochemical characteristics of CKD patients were collected for the logistic regression analysis. Correlation analysis of the mRNA relative expression level of hUAT and hURAT1 with serum UA (SUA) level also was evaluated.

Results: There were significant increases in characteristics including average age, waist-to-height ratio (WHR), SUA levels, HN ratio, TG/HDL ratio, body mass index (BMI), blood pressure (BP), uNgal/Cr. ratio, and uKim-1/Cr. ratio in overproduct type group in comparison with the other two groups. Logistic regression analysis showed SUA, CHO, uKim-1/Cr. ratio and uNgal/Cr. ratio were independent and multiple risk factors for HN. Moreover, hUAT and hURAT1 mRNA relative expression levels were significantly correlated with SUA level in the underexeret type CKD 3–4 patients.

Conclusions: These results showed SUA and other characteristics contributed to HN morbidity in CKD 3–4 patients.

Antacids' side effect hyperuricaemia could be alleviated by long-term aerobic exercise via accelerating ATP turnover rate

Hyperuricemia is the term for an abnormally high serum uric acid level. Many factors contribute to hyperuricemia, however no definite correlation between proton pump inhibitors (PPIs) and hyperuricemia has been reported before. Physical exercise also decreases serum uric acid levels. However, the detailed biochemical-regulatory mechanisms remain unknown. Here we found that adenylate deaminase activities are much higher in hyperuricemia patients than in the healthy people. Therefore, the patients have higher levels of adenosine metabolites hypoxanthine and uric acid. Acid-inhibitory drugs (antacids) significantly increased serum uric acid level and may lead to gout in the hyperuricemia patient. Long-term aerobic exercise significantly increased serum phosphorus and decreased serum ATP and its metabolites, and therefore decreased serum uric acid. Antacids slow down the ATP turnover rate and result in serum uric acid elevation subsequently. While the long-term aerobic exercise decreases serum uric acid levels by accelerating ATP turnover rate. The results imply that long-term aerobic exercise may be a useful strategy to prevent and treat hyperuricaemia.

High Uric Acid-Induced Epithelial-Mesenchymal Transition of Renal Tubular Epithelial Cells via the TLR4/NF-kB Signaling Pathway

BACKGROUND

Hyperuricemia is an independent risk factor for causing chronic kidney disease and contributes to kidney fibrosis. After urate crystals get deposited in the kidney, they can cause hyperuricemia nephropathy, leading to glomerular hypertrophy and renal tubular interstitial fibrosis. Recent data showed that uric acid (UA) could induce epithelial mesenchymal transition (EMT) of renal tubular cells, in which NRLP3 inflammatory pathway was involved. However, whether TLR4/NF-κB signaling pathway is also involved in EMT of renal tubular cells induced by UA is not clear.

METHODS

Human renal tubular epithelial cells (HK-2) were directly treated with UA and the phenotypic transition was detected by morphological changes and the molecular markers of EMT. The activation of the TLR4/NF-κB signaling pathway induced by UA was measured by Western blot and its involvement was further confirmed by the inhibition of NF-κB activation or knockdown of toll like receptor 4 (TLR4) expression.

RESULTS

UA induced obvious morphological changes of HK-2 cell, accompanied with altered molecular markers of EMT including fibronectin, α-SMA and E-cadherin. In addition, UA significantly upregulated the gene expression of interleukin-1β and tumor necrosis factor-α in a time- and dose-dependent manner. Furthermore, UA significantly activated the TLR4/NF-κB signaling pathway in HK-2 cells, while the inhibition of the TLR4 expression by siRNA and NF-κB activation by PDTC significantly attenuated EMT induced by UA in HK-2 cells.

CONCLUSIONS

UA can induce EMT in renal tubular epithelial cells by the activation of the TLR4/NF-κB signaling pathway, and the targeted intervention of the TLR4/NF-κB signaling pathway might effectively inhibit UA-induced renal interstitial fibrosis mediated by EMT.