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

Identification of Hyperuricemia Alleviating Peptides from Yellow Tuna Thunnus albacares

The development of food-derived antihyperuricemic substances is important for alleviating hyperuricemia (HUA) and associated inflammation. Here, novel peptides fromThunnus albacares (TAP) with strong antihyperuricemic activity were prepared. TAP was prepared by alkaline protease (molecular weight <1000 Da), with an IC50 value of xanthine oxidase inhibitory activity of 2.498 mg/mL, and 5 mg/mL TAP could reduce uric acid (UA) by 33.62% in human kidney-2 (HK-2) cells (P < 0.01). Mice were fed a high-purine diet and injected with potassium oxonate to induce HUA. Oral administration of TAP (600 mg/kg/d) reduced serum UA significantly by 42.22% and increased urine UA by 79.02% (P < 0.01) via regulating urate transporters GLUT9, organic anion transporter 1, and ATP-binding cassette subfamily G2. Meantime, TAP exhibited hepatoprotective and nephroprotective effects, according to histological analysis. Besides, HUA mice treated with TAP showed anti-inflammatory activity by decreasing the levels of toll-like receptor 4, nuclear factors-κB p65, NLRP3, ASC, and Caspase-1 in the kidneys (P < 0.01). According to serum non-targeted metabolomics, 91 differential metabolites between the MC and TAP groups were identified, and purine metabolism was considered to be the main pathway for TAP alleviating HUA. In a word, TAP exhibited strong antihyperuricemic activity both in vitro and in vivo.

Epithelial-mesenchymal transition in tissue repair and degeneration

Epithelial-mesenchymal transitions (EMTs) are the epitome of cell plasticity in embryonic development and cancer; during EMT, epithelial cells undergo dramatic phenotypic changes and become able to migrate to form different tissues or give rise to metastases, respectively. The importance of EMTs in other contexts, such as tissue repair and fibrosis in the adult, has become increasingly recognized and studied. In this Review, we discuss the function of EMT in the adult after tissue damage and compare features of embryonic and adult EMT. Whereas sustained EMT leads to adult tissue degeneration, fibrosis and organ failure, its transient activation, which confers phenotypic and functional plasticity on somatic cells, promotes tissue repair after damage. Understanding the mechanisms and temporal regulation of different EMTs provides insight into how some tissues heal and has the potential to open new therapeutic avenues to promote repair or regeneration of tissue damage that is currently irreversible. We also discuss therapeutic strategies that modulate EMT that hold clinical promise in ameliorating fibrosis, and how precise EMT activation could be harnessed to enhance tissue repair.

Possible correlated signaling pathways with chronic urate nephropathy: A review

Hyperuricemia nephropathy, also known as gouty nephropathy, refers to renal damage induced by hyperuricemia caused by excessive production of serum uric acid or low excretion of uric acid. the persistence of symptoms will lead to changes in renal tubular phenotype and accelerate the progress of renal fibrosis. The existence and progressive aggravation of symptoms will bring a heavy burden to patients, their families and society, affect their quality of life and reduce their well-being. With the increase of reports on hyperuricemia nephropathy, the importance of related signal pathways in the pathogenesis of hyperuricemia nephropathy is becoming more and more obvious, but most studies are limited to the upper and lower mediating relationship between 1 or 2 signal pathways. The research on the comprehensiveness of signal pathways and the breadth of crosstalk between signal pathways is limited. By synthesizing the research results of signal pathways related to hyperuricemia nephropathy in recent years, this paper will explore the specific mechanism of hyperuricemia nephropathy, and provide new ideas and methods for the treatment of hyperuricemia nephropathy based on a variety of signal pathway crosstalk and personal prospects.

Baicalin alleviates silica-induced lung inflammation and fibrosis by inhibiting TLR4/NF-?B pathway in rats

Silicosis is an occupational lung disease caused by inhaling silica dust. The disease is characterized by early lung inflammation and late irreversible pulmonary fibrosis. Here we report the effect of Baicalin, a main flavonoid compound from the roots of Chinese herbal medicine Huang Qin on silicosis in a rat model. Results showed Baicalin (50 or 100 mg/kg/day) can mitigate the silica-induced lung inflammation and reduce the harm of alveolar structure and the blue region of collagen fibers in rat lung at 28 days after administration. At the same time, Baicalin also diminished the level of interleukin-1beta (IL-1beta, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1) in lung tissues. The protein expression of collagen I (Col-1), alpha-smooth muscle actin (alpha-SMA) and vimentin were down-regulated while E-cadherin (E-cad) was increased in Baicalin-treated rats. In addition, the Toll Like Receptor 4 (TLR4)/ nuclear factor kappaB (NF-kappaB) pathway was enabled at 28 days after silica infusion, and the treatment of Baicalin diminished the expression of TLR4 and NF-?B in the lungs of rat with silicosis. These results suggested that Baicalin inhibited the pulmonary inflammatory and fibrosis in a rat model of silicosis, which could be attributed to inhibition of the TLR4/NF-kappaB pathway.

Therapeutic effects of traditional Chinese medicine on gouty nephropathy: Based on NF-κB signalingpathways

As the final product of purine metabolism, excess serum uric acid (SUA) aggravates the process of some metabolic diseases. SUA causes renal tubule damage, interstitial fibrosis, and glomerular hardening, leading to gouty nephropathy (GN). A growing number of investigations have shown that NF-κB mediated inflammation and oxidative stress have been directly involved in the pathogenesis of GN. Traditional Chinese medicine's treatment methods of GN have amassed a wealth of treatment experience. In this review, we first describe the mechanism of NF-κB signaling pathways in GN. Subsequently, we highlight traditional Chinese medicine that can treat GN through NF-κB pathways. Finally, commenting on promising candidate targets of herbal medicine for GN treatment via suppressing NF-κB signaling pathways was summarized.

The Nephroprotective Effects of Hibiscus sabdariffa Leaf and Ellagic Acid in Vitro and in Vivo Models of Hyperuricemic Nephropathy

Hyperuricemic nephropathy (HN) is caused by urate crystals that get deposited in the kidney and contribute to renal fibrosis. Uric acid (UA) has been proven to directly cause renal mesangial cell oxidative stress and fibrosis in the pathogenesis of HN. Some antioxidants can be used as chemopreventive agents of HN. Hibiscus sabdariffa leaf extracts (HLE), rich in polyphenol, have been shown to possess hypoglycemic, antioxidant, hypolipidemic, antiatherosclerotic, and anticancer effects. The aim of the study is to examine the inhibitory effect of HLE and its main component ellagic acid (EA) on renal fibrosis. In vitro, mouse renal glomerular mesangial SV40MES13 cells pretreated with UA were demonstrated to trigger obvious morphological changes and viability loss, as well as affect matrix metalloproteinases (MMPs) activities. Noncytotoxic doses of HLE and EA abolished the UA-induced cell injury and MMP-2/9 secretion. In addition, HLE and EA exhibited antioxidant and anti-inflammatory effects on the UA-treated cells with a reduction in transforming growth factor-beta (TGF-β) production. Next, the UA-activated pro-fibrotic factors, extracellular matrix (ECM) deposition, and epithelial-mesenchymal-transition (EMT) were inhibited by HLE or EA. Mechanistic assays indicated that antifibrotic effects of HLE might be mediated via TGF-β/Smad signaling, as confirmed by the transfection of Smad7 siRNA. In vivo, HLE and EA supplementations significantly alleviated HN development, which may result from inhibiting adenine-induced TGF-β production accompanying oxidative stress and inflammation, as well as fibrogenesis. Our data imply that EA-enriched HLE regulates the TGF-β/Smad signaling, which in turn led to reduced renal mesangial cell injury and fibrosis in HN and provided a new mechanism for its nephroprotective activity.

Simiao pill inhibits epithelial mesenchymal transition in a mouse model of chronic hyperuricemic nephropathy by inhibiting NLRP3 inflammasome activation

Background

Simiao pill module (SMM), a traditional Chinese medicine formula, has been widely used to treat gout and gouty arthritis. The goal of this study was to investigate the effects of SMM on epithelial-mesenchymal transition (EMT) and activation of NLR family pyrin domain containing 3 (NLRP3) inflammasome in a mouse model of potassium oxonate (PO)-induced chronic hyperuricemic nephropathy (HN).

Methods

Mice were randomly divided into the following four groups: control, HN model (PO), febuxostat (FEB)-treated (PO + FEB), and SMM-treated (PO + SMM) groups. Following 6 weeks of treatment, blood samples were collected and mice were sacrificed to collect kidney samples to study the biochemical parameters associated with renal function and histopathological changes associated with HN, respectively. The samples were analyzed for the expression of markers of EMT (collagen type 3, α-smooth muscle actin [α-SMA], fibronectin, vimentin and E-cadherin) and activation of NLRP3 inflammasome (NLRP3, apoptosis-associated speck-like protein [ASC], caspase-1, interleukin [IL]-1β, and IL-18).

Results

Our results showed that hyperuricemia, impaired kidney function, and renal pathological characteristics induced by PO treatment were improved following treatment with SMM and FEB. Additionally, treatment with SMM and FEB decreased the expression of vimentin, collagen 3, fibronectin, and α-SMA, and increased the expression of E-cadherin. Moreover, NLRP3 inflammasome activation, as assessed by the increased expression of NLRP3, ASC, and caspase-1, and secretion of IL-1β and IL-18, was inhibited by treatment with SMM and FEB.

Conclusion

These results suggest that SMM inhibited EMT and NLRP3 inflammasome activation in chronic HN mice, and the beneficial effect of SMM was compared with a standard drug, FEB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03757-0.

Persistent Purine Metabolic Abnormality Induces the Aggravation of Visceral Inflammation and Intestinal Microbiota Dysbiosis in Magang Goose

Gout is a disease involving abnormal purine metabolism that is widespread in mammals and birds. Goose is especially susceptible for gout in early stage. However, a few studies investigated the ontogenetic pattern of goslings with purine metabolic abnormality. Our studies were conducted to investigate whether persistent purine metabolic abnormality would lead to aggravation of visceral inflammation and intestinal microbiota dysbiosis in goose. A total of 132 1-day-old Magang geese were randomly divided into six replicates and fed a high-calcium and protein meal-based diet from 1 to 28 days. The experiment lasted for 28 days. Liver and kidney damages were observed in 14- and 28-day-old Magang geese, and liver inflammation increased with increasing age. In 28-day-old Magang geese, serum CAT and liver GSH-Px activity were significantly reduced. Furthermore, jejunum intestinal barrier was impaired and the abundance of Bacteroides was significantly reduced at the genus level. Collectively, the high-calcium and high-protein (HCP) meal-based diet caused liver and kidney damage in 28-day-old Magang geese, leading to hyperuricemia and gout symptoms, and the intestinal barrier is impaired and the intestinal flora is disrupted.

Eriodictyol attenuates TNBS-induced ulcerative colitis through repressing TLR4/NF-kB signaling pathway in rats

Ulcerative colitis (UC) is a chronic disease characterized by mucosal and submucosal inflammation, which has a low cure rate and is prone to relapse, due to the immune imbalance of the body. Inhibition of inflammation-related pathways can delay the progression of UC. Toll-like receptor 4 (TLR4) pathway is considered to be one of the important signaling pathways involved in colon inflammation. Eriodictyol (EDT) is a natural flavonoid widely distributed in foodborne plants. EDT plays an important role in the regulation of inflammation and related signaling pathways. However, whether EDT plays a role in UC remains unknown. Herein, we established a TNBS induced animal model of enteritis in Wistar rats. Our data confirmed the establishment of TNBS induced animal model of enteritis and the administration Eriodictyol in Wistar rats. EDT treatment alleviated TNBS-induced intestinal tissue injury in rats. We further found that EDT reduced MPO expression and regulated the cytokine parameters in TNBS-induced intestinal tissues of rats. The levels of TNF-α, IL-1β, IL-6, IL-10, IL-2, and IL-12 were also affected by the treatment of EDT. EDT also affected SOD, CAT, GSH-Px, and MDA level in rats with colitis. Moreover, EDT regulated TNBS-induced TLR4/NF-κB pathway activation, therefore inhibiting the progression of UC. Our results suggest that EDT could be a potential therapeutic agent for UC.

The Rho kinase signaling pathway participates in tubular mitochondrial oxidative injury and apoptosis in uric acid nephropathy

Introduction

Oxidative stress is a pathologic feature of hyperuricemia that is highly prevalent and that contributes to kidney tubular interstitial fibrosis. Rho-kinase is closely related to mitochondrial-induced oxidative stress. Herein, we designed a study to explore the expression and role of Rho-kinase in hyperuricemia nephropathy. The secondary objective was to investigate whether the Rho-kinase signaling pathway regulates hyperuricemic tubular oxidative injury and apoptosis via the mitochondrial pathway in addition to the mechanisms that are involved.

Materials and methods

HK-2 cells were divided into the following five groups: normal; uric acid (UA); UA+Fasudil; UA+ROCK1 si-RNA; and UA+sc-siRNA. Rho-kinase activity, mitochondrial oxidative injury, and apoptosis-related protein levels were measured in each group. A t-test was used to analyze the difference between groups.

Results

Myosin phosphatase target subunit 1 (MYPT1) overexpression was shown in HK-2 cells, which was caused by UA. High concentrations of UA also up-regulated Rho-kinase expression and mitochondrial and apoptosis-related protein expression, while treatment with fasudil and ROCK1 si-RNA significantly attenuated these responses.

Conclusion

The Rho-kinase signaling pathway participates in tubular mitochondrial oxidative injury and apoptosis via regulating mitochondrial dyneins/biogenic genes in UA nephropathy, which suggests that the mitochondrial pathway might be a potential therapeutic target for hyperuricemia nephropathy.

Cross talk between autophagy and oncogenic signaling pathways and implications for cancer therapy

Autophagy is a highly conserved metabolic process involved in the degradation of intracellular components including proteins and organelles. Consequently, it plays a critical role in recycling metabolic energy for the maintenance of cellular homeostasis in response to various stressors. In cancer, autophagy either suppresses or promotes cancer progression depending on the stage and cancer type. Epithelial-mesenchymal transition (EMT) and cancer metastasis are directly mediated by oncogenic signal proteins including SNAI1, SLUG, ZEB1/2, and NOTCH1, which are functionally correlated with autophagy. In this report, we discuss the crosstalk between oncogenic signaling pathways and autophagy followed by possible strategies for cancer treatment via regulation of autophagy. Although autophagy affects EMT and cancer metastasis, the overall signaling pathways connecting cancer progression and autophagy are still illusive. In general, autophagy plays a critical role in cancer cell survival by providing a minimum level of energy via self-digestion. Thus, cancer cells face nutrient limitations and challenges under stress during EMT and metastasis. Conversely, autophagy acts as a potential cancer suppressor by degrading oncogenic proteins, which are essential for cancer progression, and by removing damaged components such as mitochondria to enhance genomic stability. Therefore, autophagy activators or inhibitors represent possible cancer therapeutics. We further discuss the regulation of autophagy-dependent degradation of oncogenic proteins and its functional correlation with oncogenic signaling pathways, with potential applications in cancer therapy.

A negative feedback loop involving NF-κB/TIR8 regulates IL-1β-induced epithelial- myofibroblast transdifferentiation in human tubular cells

Renal tubular epithelial-myofibroblast transdifferentiation (EMT) plays a central role in the development of renal interstitial fibrosis (RIF). The profibrotic cytokine interleukin (IL)-1 and the IL-1 receptor (IL-1R) also participate in RIF development, and Toll/IL-1R 8 (TIR8), a member of the Toll-like receptor superfamily, has been identified as a negative regulator of IL-1R signaling. However, the functions of TIR8 in IL-1-induced RIF remain unknown. Here, human embryonic kidney epithelial cells (HKC) and unilateral ureteric obstruction (UUO)-induced RIF models on SD rats were used to investigate the functions of TIR8 involving IL-1β-induced EMT. We showed that IL-1β primarily triggers TIR8 expression by activating nuclear factor-κB (NF-κB) in HKC cells. Conversely, high levels of TIR8 in HKC cells repress IL-1β-induced NF-κB activation and inhibit IL-1β-induced EMT. Moreover, in vitro and in vivo findings revealed that TIR8 downregulation facilitated IL-1β-induced NF-κB activation and contributed to TGF-β1-mediated EMT in renal tubular epithelial cells. These results suggested that TIR8 exerts a protective role in IL-1β-mediated EMT and potentially represents a new target for RIF treatment.

[Exploring the therapeutic mechanism of Simiao pills for hyperuricemia based on network pharmacology and molecular docking]

OBJECTIVE

To explore the mechanism of Simiao pills for treatment of hyperuricemia based on network pharmacology and molecular docking.

OBJECTIVE

The active ingredients of Simiao pills and their targets of action were predicted using TCMSP, SEA, Swiss and PharmMapper databases. GeneCards and TCD databases were searched for the disease targets related to hyperuricemia. Cytoscape 3.6.1 was used to construct a protein-protein interaction network. GO enrichment analysis and KEGG pathway analysis were carried out on the STRING platform. The binding between the main compounds and the key targets were predicted using the SwissDock platform for molecular docking.

OBJECTIVE

We identified 28 active ingredients and 429 potential targets in Simiao pills, 494 disease targets related to hyperuricemia, and 118 common targets between Simiao pills and hyperuricemia. Several key targets including AKT1, IL- 6, JUN, TNF and CASP3 were screened for molecular docking, which had good binding activities with berberrubine, epiberberine, stigmasterol and sitosterol. AKT1, IL-6, JUN, TNF and CASP3 were predicted to be the key targets for Simiao pills for treating hyperuricemia. KEGG pathway enrichment analysis showed that Simiao pills produced therapeutic effects on hyperuricemia through multiple signaling pathways including the TNF signaling pathway, apoptosis signaling pathway and IL-17 signaling pathway.

OBJECTIVE

Simiao pills produces therapeutic effects on hyperuricemia through multiple components and targets and the synergy of several pathways. Our finding provides a theoretical basis for further study of the active ingredients and therapeutic mechanism of Simiao pills for treating hyperuricemia.

CTP-CM enhances osteogenic differentiation of hPDLSCs via NF-κB pathway

OBJECTIVE

The conditioned medium of calcined tooth powder (CTP-CM) is a type of biomimetic mineralized material and well contributing to bone healing and bone formation in vivo. However, little is known about the effect of CTP-CM on human periodontal ligament stem cells (hPDLSCs) as well as the underlying mechanisms.

METHODS

ALP activity assay was conducted to select the concentration with the highest ALP level, which was used for the following experiments. Cell proliferation was measured by cell counting kit-8 assay and flow cytometry analysis. Expression levels of osteogenic markers in CTP-CM-induced hPDLSCs were evaluated with real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunofluorescence staining, and Western blot. Mineralization of CTP-CM-induced hPDLSCs was evaluated by alizarin red staining. Furthermore, the involvement of NF-κB pathway was examined by immunofluorescence staining and Western blot.

RESULTS

20 μg/ml was selected for the further experiments. Functional studies demonstrated that CTP-CM exerted almost no influence on the proliferation of hPDLSCs and CTP-CM increased the osteogenic differentiation of hPDLSCs. Mechanistically, CTP-CM leads to activation of NF-κB signaling pathway. When treated with BMS345541, the osteogenic differentiation of CTP-CM-treated hPDLSCs was significantly attenuated.

CONCLUSION

CTP-CM can promote the osteogenic differentiation of hPDLSCs via activating NF-κB pathway.

Natural flavonol fisetin attenuated hyperuricemic nephropathy via inhibiting IL-6/JAK2/STAT3 and TGF-β/SMAD3 signaling

BACKGROUND

The naturally occurring flavonol fisetin (3,3',4',7-tetrahydroxyflavone), widely dispersed in fruits, vegetables and nuts, has been reported to exert anti-inflammatory, antioxidant and anti-angiogenic effects. Our previous study indicated fisetin ameliorated inflammation and apoptosis in septic kidneys. However, the potential nephroprotective effect of fisetin in hyperuricemic mice remains unknown.

PURPOSE

The current study was designed to investigate the effect of fisetin on hyperuricemic nephropathy (HN) and explore the underlying mechanisms.

METHODS

The HN was induced in mice by mixing of potassium oxonate (2400 mg/kg) and adenine (160 mg/kg) in male C57BL/6J mice. Fisetin (50 or 100 mg/kg) was orally administrated either simultaneously with the establishment of HN or after HN was induced. As a positive control, allopurinol of 10 mg/kg was included. Uric acid levels in the serum and urine as well as renal function parameters were measured. Renal histological changes were measured by periodic acid-Schiff (PAS) and Masson's trichrome stainings. The expression of gene/protein in relation to inflammation, fibrosis, and uric acid excretion in the kidneys of HN mice or uric acid-treated mouse tubular epithelial (TCMK-1) cells were measured by RNA-seq, RT-PCR, western blot and immunohistochemical analysis.

RESULTS

Treatment with fisetin, regardless of administration regimen, dose-dependently attenuated hyperuricemia-induced kidney injury as indicated by the improved renal function, preserved tissue architecture, and decreased urinary albumin-to-creatinine ratio. Additionally, fisetin lowered uricemia by modulating the expression of kidney urate transporters including urate transporter 1(URAT1), organic anion transporter 1 (OAT1), organic anion transporter 3 (OAT3) and ATP binding cassette subfamily G member 2 (ABCG2). Moreover, hyperuricemia-induced secretions of proinflammatory factors including tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6) and monocyte chemoattractant protein-1(MCP-1) in HN mice and uric acid-stimulated TCMK-1 cells were mitigated by fisetin treatment. Meanwhile, fisetin attenuated kidney fibrosis in HN mice with restored expressions of alpha-smooth muscle actin (α-SMA), collagen I and fibronectin. Mechanistically, fisetin regulated the aberrant activation of signal transducer and activator of transcription-3 (STAT3) signaling and transforming growth factor-β (TGF-β) signaling in the HN kidneys and uric acid-stimulated TCMK-1 cells.

CONCLUSION

Fisetin lowered uricemia, suppressed renal inflammatory response, and improved kidney fibrosis to protect against hyperuricemic nephropathy via modulation of STAT3 and TGF-β signaling pathways. The results highlighted that fisetin might represent a potential therapeutic strategy against hyperuricemic nephropathy.

The Management of Gout in Renal Disease

Gout, a debilitating inflammatory arthritis, currently affects more than 9 million Americans. Hyperuricemia, the laboratory abnormality associated with the development of gout, also occurs in a significant number of patients with chronic kidney disease (CKD), a condition that affects approximately 14% of the US population. Several recent studies have attempted to provide a definitive link between the presence of hyperuricemia and progression of CKD; however, the treatment of asymptomatic hyperuricemia in CKD is not supported by recent randomized controlled trials. The pharmacology of acute gout flares and urate lowering is complicated in patients who also have evidence of CKD, primarily because of an increased risk of medication toxicity. Recipients of kidney transplants are particularly at risk of debilitating gout and medication toxicity. We review the available data linking CKD, gout, and hyperuricemia, providing practice guidelines on managing gout in CKD patients and kidney transplant recipients. We advocate for much greater involvement of nephrologists in the management of gout in renal patients.

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 protective effect of 1-methyltryptophan isomers in renal ischemia-reperfusion injury is not exclusively dependent on indolamine 2,3-dioxygenase inhibition

BACKGROUND AND PURPOSE

Indolamine 2,3-dioxygenase (IDO), an enzyme that catalyses the metabolism of tryptophan, may play a detrimental role in ischemia-reperfusion injury (IRI). IDO can be inhibited by 1-methyl-tryptophan, which exists in a D (D-MT) or L (L-MT) isomer. These forms show different pharmacological effects besides IDO inhibition. Therefore, we sought to investigate whether these isomers can play a protective role in renal IRI, either IDO-dependent or independent.

EXPERIMENTAL APPROACH

We studied the effect of both isomers in a rat renal IRI model with a focus on IDO-dependent and independent effects.

KEY RESULTS

Both MT isomers reduced creatinine and BUN levels, with D-MT having a faster onset of action but shorter duration and L-MT a slower onset but longer duration (24 h and 48 h vs 48 h and 96 h reperfusion time). Interestingly, this effect was not exclusively dependent on IDO inhibition, but rather from decreased TLR4 signalling, mimicking changes in renal function. Additionally, L-MT increased the overall survival of rats. Moreover, both MT isomers interfered with TGF-β signalling and epithelial-mesenchymal transition. In order to study the effect of isomers in all mechanisms involved in IRI, a series of in vitro experiments was performed. The isomers affected signalling pathways in NK cells and tubular epithelial cells, as well as in dendritic cells and T cells.

CONCLUSION AND IMPLICATIONS

This study shows that both MT isomers have a renoprotective effect after ischemia-reperfusion injury, mostly independent of IDO inhibition, involving mutually different mechanisms. We bring novel findings in the pharmacological properties and mechanism of action of MT isomers, which could become a novel therapeutic target of renal IRI.

Serum Uric Acid Levels, but Not rs7442295 Polymorphism of SCL2A9 Gene, Predict Mortality in Clinically Stable Coronary Artery Disease

Serum uric acid (SUA) has been associated with cardiovascular disease, but up to now whether SUA is an independent cardiovascular risk factor or merely a disease-related epiphenomenon remains still controversial. within the framework of the Verona Heart Study, we prospectively followed 703 subjects with angiographically demonstrated and clinically stable coronary artery disease between May 1996 and March 2007. At baseline, SUA levels were measured in all the patients. Genotype data of SCL2A9 rs7442295 polymorphism, which has been associated with SUA by genome-wide association studies, were available for 686 subjects (97.6%). After a median follow-up of 57 months, 116 patients (16.5%) had died, 83 (11.8%) because of cardiovascular causes. Patients with hyperuricemia, defined by SUA levels above the 75th percentile (≥0.41 mmol/L), had an increased total and cardiovascular mortality rate than those with SUA below this threshold level (23.3% vs 14.1%, P = 0.048 and 19.4% vs 9.2%, P = 0.001, respectively, by Kaplan-Meier with Log-Rank test). These associations were confirmed by Cox regression after adjustment for sex, age, other predictors of mortality, coronary revascularization, and drug therapies at discharge (hazard ratio for total mortality 1.87 [1.05-3.34], P = 0.033; hazard ratio for cardiovascular mortality 2.09 [1.03-4.25], P = 0.041). Although associated with SUA levels, rs7442295 polymorphism did not predict total or cardiovascular mortality. our data support that SUA may be a prognostic cardiovascular biomarker, predicting total and cardiovascular mortality in the setting of secondary prevention of coronary artery disease. On the other hand, SCL2A9 gene polymorphism, notwithstanding a clear influence on SUA levels, was not associated with mortality.

The Role of the Unfolded Protein Response on Renal Lipogenesis in C57BL/6 Mice

Renal injury observed in several pathologies has been associated with lipid accumulation in the kidney. While it has been suggested that the accumulation of renal lipids depends on free fatty acids released from adipose tissue, it is not known whether in situ renal lipogenesis due to endoplasmic reticulum (ER) stress contributes to kidney injury. The aim of the present study was to elucidate the role of pharmacological ER stress in renal structure and function and its effect on renal lipid metabolism of C57BL/6 mice. ER stress increased serum creatinine and induced kidney structural abnormalities. Tunicamycin-administered mice developed hyperinsulinemia, augmented lipolysis and increased circulating leptin and adiponectin. Renal unfolded protein response (UPR) gene expression markers, the lipogenic transcription factor SREBP1 and the phosphorylation of eIF2α increased 8 h after tunicamycin administration. At 24 h, an increase in BiP protein content was accompanied by a reduction in p-eIF2α and increased SREBP-1 and FASn protein content, in addition to a significant increase in triglyceride content and a reduction in AMPK. Thus, ER stress induces in situ lipid synthesis, leading to renal lipid accumulation and functional alterations. Future pharmacological and/or dietary strategies must target renal ER stress to prevent kidney damage and the progression of metabolic diseases.

Serum uric acid level is correlated with the clinical, pathological progression and prognosis of IgA nephropathy: an observational retrospective pilot-study

Objectives

This study was aimed to assess the relationship between serum uric acid (SUA) level and the clinical, pathological phenotype of IgA nephropathy (IgAN), and to determine the role of SUA level in the progression and prognosis of IgAN.

Methods

A total of 208 patients with IgAN were included in this study, and were classified into the normo-uricemia group and hyperuricemia group according to the SUA level. The clinical data at baseline, IgAN Oxford classification scores (MEST-C scoring system), and other pathological features were collected and further analyzed. All patients were followed up and the prognosis was assessed using Kaplan-Meier survival curves. GraphPad Prism 7.0 and SPSS 23.0 were used for statistical analyses.

Results

In clinical indicators, patients with hyperuricemia had the significantly higher proportion of males to females, mean arterial pressure, the levels of total cholesterol, triglyceride, Scr, BUN, 24 hour-urine protein, C3, and C4, the lower levels of high-density lipoprotein cholesterol and eGFR than those without (p < 0.05). In terms of pathological characteristics, the tubular atrophy/interstitial fibrosis scores, vascular injury scores, and glomerular sclerosis percentage were significantly higher in patients with hyperuricemia compared with those without (p < 0.01). There was no significant difference in the scores of mesangial hypercellularity, endocapillary hypercellularity, focal segmental glomerulosclerosis, as well as crescents between the two groups (p > 0.05). As for the depositions of immune complexes deposition in IgAN, the hyperuricemia group had less deposition of immunoglobulin G and FRA than the normo-uricemia group (p < 0.05), while the deposition of immunoglobulin A, immunoglobulin M, and complement C3 in the two groups showed no statistical difference. The survival curve suggested that patients in the hyperuricemia group have significantly poorer renal outcome than those in the normo-uricemia group (p = 0.0147). Results also revealed that the SUA level is a valuable predictor of renal outcome in patients with IgAN. The optimal cutoff value was 361.1 µmol/L (AUC = 0.76 ± 0.08167) and 614 µmol/L (AUC = 0.5728 ± 0.2029) for female and male, respectively.

Conclusions

The level of SUA is associated with renal function level and pathological severity of IgAN, and maybe a prognostic indicator of IgAN.

Prothrombotic effects of high uric acid in mice via activation of MEF2C-dependent NF-κB pathway by upregulating let-7c

Serum uric acid is reportedly associated with thrombosis development. However, still unclear is the mechanism of high uric acid in thrombosis with the involvement of let-7c. In an aim to fill this void, we conducted this study by treating mice and human umbilical vein endothelial cells with high uric acid. Analysis indicated that let-7c was upregulated in hyperuricemia patients as well as in mice and human umbilical vein endothelial cells treated with high uric acid. Furthermore, high uric acid inhibited myocyte enhancer factor-2C, but activated nuclear factor-kappa B pathway in human umbilical vein endothelial cells. Then the targeting relationship between let-7c and myocyte enhancer factor-2C was verified. On the one hand, high uric acid shortened activated partial thromboplastin time and prothrombin time of mice and declined tissue plasminogen activator level. Additionally, the treatment prolonged thrombin time and elevated the levels of thrombosis related molecules or proteins such as Fibrinogen and D-dimer. Nevertheless, these alternations could be reversed by inhibition of let-7c and nuclear factor-kappa B pathway or overexpressing myocyte enhancer factor-2C. To sum up, our results uncovered the pro-thrombotic effect of high uric acid in mice by activating myocyte enhancer factor-2C-dependent nuclear factor-kappa B pathway via let-7c upregulation.

NF-κB blockade during short-term l-NAME and salt overload strongly attenuates the late development of chronic kidney disease

Nitric oxide synthase inhibition by N^ω-nitro-l-arginine methyl ester (l-NAME) plus a high-salt diet (HS) is a model of chronic kidney disease (CKD) characterized by marked hypertension and renal injury. With cessation of treatment, most of these changes subside, but progressive renal injury develops, associated with persistent low-grade renal inflammation. We investigated whether innate immunity, and in particular the NF-κB system, is involved in this process. Male Munich-Wistar rats received HS + l-NAME (32 mg·kg^-1·day^-1), whereas control rats received HS only. Treatment was ceased after week 4 when 30 rats were studied. Additional rats were studied at week 8 (n = 30) and week 28 (n = 30). As expected, HS + l-NAME promoted severe hypertension, albuminuria, and renal injury after 4 wk of treatment, whereas innate immunity activation was evident. After discontinuation of treatments, partial regression of renal injury and inflammation occurred, along with persistence of innate immunity activation at week 8. At week 28, glomerular injury worsened, while renal inflammation persisted and renal innate immunity remained activated. Temporary administration of the NF-κB inhibitor pyrrolidine dithiocarbamate, in concomitancy with the early 4-wk HS + l-NAME treatment, prevented the development of late renal injury and inflammation, an effect that lasted until the end of the study. Early activation of innate immunity may be crucial to the initiation of renal injury in the HS + l-NAME model and to the autonomous progression of chronic nephropathy even after cessation of the original insult. This behavior may be common to other conditions leading to CKD.

Application of Histone Deacetylase Inhibitors in Renal Interstitial Fibrosis

BACKGROUND

Renal interstitial fibrosis is characterized by the accumulation of extracellular matrix proteins, which is a common feature of chronic kidney diseases.

SUMMARY

Increasing evidence has shown the aberrant expression of histone deacetylases (HDACs) in the development and progression of renal fibrosis, suggesting the possibility of utilizing HDAC inhibitor (HDACi) as therapeutics for renal fibrosis. Recent studies have successfully demonstrated the antifibrotic effects of HDACis in various animal models, which are associated with multiple signaling pathways including TGF-β signaling, EGRF signaling, signal transducer and activator of transcription 3 pathway, and JNK/Notch2 signaling. This review will focus on the utilization of HDACi as antifibrotic agents and its relative molecular mechanisms.

KEY MESSAGES

HDACis have shown promising results in antifibrotic therapy, and it is rational to anticipate that HDACis will improve clinical outcomes of renal fibrosis in the future.

Effects of the NF‑κB/p53 signaling pathway on intervertebral disc nucleus pulposus degeneration

The incidence of intervertebral disc degeneration (IDD) is increasing, especially among elderly individuals. The present study aimed to investigate the effects of the NF-κB/p53 signaling pathway on IDD and its regulatory effect on associated cytokines. In the present study, human nucleus pulposus cells were isolated from patients with thoracic-lumbar fractures and patients with IDD to observe cellular morphology and detect phosphorylated (p)-p65/p53 expression levels. The locality and expression levels of p65 in interleukin (IL)-1β-stimulated nucleus pulposus cells, with or without the addition of ammonium pyrrolidinedithiocarbamate (PDTC; a NF-κB signaling pathway-specific blocker), were measured. Furthermore, the effects of IL-1β stimulation on the protein and gene expression levels of IDD-related cytokines were determined following p53 knockdown and inhibition of the NF-κB signaling pathway. The results suggested that p-p65 and p53 expression was significantly increased in IDD cells compared with normal nucleus pulposus cells. Moreover, nucleus pulposus cells isolated from patients with IDD contained less cytoplasm compared with normal nucleus pulposus cells, and p65 expression levels were higher in the cytoplasm than the nucleus of IL-1β-stimulated PDTC-treated healthy nucleus pulposus cells. Moreover, the p53 expression levels were significantly decreased following transfection with sip53. PDTC treatment and p53 knockdown significantly decreased matrix metallopeptidase (MMP)-3, MMP-13, metallopeptidases with thrombospondin type 1 motif (ADAMTS)-4 and ADAMTS-5 expression levels, and increased aggrecan and collagen type II expression levels in IL-1β-stimulated cells. The present study indicated that activation of the NF-κB/p53 signaling pathway might be related to the occurrence of IDD; therefore, the NF-κB/p53 signaling pathway may serve as a therapeutic target for IDD.

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.

The TLR4-MyD88-NF-κB pathway is involved in sIgA-mediated IgA nephropathy

Previous studies have shown that secretory IgA (sIgA) was critically involved in IgA nephropathy (IgAN) immune responses. Toll-like receptors (TLRs), especially TLR4 which participates in mucosal immunity, may be involved in the pathogenesis of IgAN. The purpose of this study was to investigate whether sIgA and TLR4 interact to mediate kidney damage in IgAN patients. IgAN patients with positive sIgA deposition in renal tissues were screened by immunofluorescence assay. Patient salivary sIgA (P-sIgA) was collected and purified by jacalin affinity chromatography. Salivary sIgA from healthy volunteers was used as a control (N-sIgA). Expression of TLR4, MyD88, NF-κB, TNF-α, IL-6, and MCP-1 were detected in the mesangial area of IgAN patients by immunohistochemistry, the expression levels in patients with positive sIgA deposition were higher than that with negative sIgA deposition. Human renal mesangial cells (HRMCs) were cultured in vitro, flow cytometry showed that P-sIgA bound HRMCs significantly better than N-sIgA. HRMCs were cultured in the presence of sIgA (400 μg/mL) for 24 h, compared with cells cultured with N-sIgA, HRMCs cultured in vitro with P-sIgA showed enhanced expression of TLR4, increased secretion of TNF-α, IL-6, and MCP-1, and increased expression of MyD88/NF-κB. TLR4 shRNA silencing and NF-κB inhibition both reduced the ability of HRMCs to synthesize TNF-α, IL-6, and MCP-1. Our results indicate that sIgA may induce high expression of TLR4 in HRMCs and further activate downstream signalling pathways, prompting HRMCs to secrete multiple cytokines and thereby mediating kidney damage in IgAN patients.

Immunological regulatory effect of flavonoid baicalin on innate immune toll-like receptors

As an essential component of the innate immune system, Toll-like receptors (TLRs) are a family of well-recognized ligand-binding receptors found in various organisms and initiate host immune responses. Activation of TLRs signaling pathways lead to the induction of numerous genes that function in host defense. Baicalin is a natural compound from the dry raw root of Scutellaria baicalensis (S. baicalensis) and it has been found to exhibit several pharmaceutical actions, such as anti-inflammation, anti-tumor and antivirus. These biological activities are mainly related to the regulatory effect of baicalin on the host immune response. In this review, we provide an overview of the regulation of baicalin on TLRs signaling pathways in various pathological conditions, and highlight potential targets for the development of the regulatory effect of natural compound from traditional Chinese medicine on innate immune system.

Role of NF-κB transcriptional factor activation during chronic fluoride intoxication in development of oxidative-nitrosative stress in rat's gastric mucosa

Fluoride compounds are known as hazardous environmental pollutants that can enter the body with drinking water. Chronic exposure to fluoride leads to development of oxidative stress and can lead to activation of nuclear factor κB (NF-κB). The aim of this work is to clarify the role of NF-kB activation in production of reactive nitrogen and oxygen species, activity of antioxidant enzymes and intensity of lipid peroxidation (LPO) in gastric mucosa of rats during chronic fluoride intoxication.

MATERIALS AND METHODS

We carried out the study on 18 mature male rats of the Wistar line. The animals were divided into 3 groups: control animals (6), group of chronic fluoride intoxication (6), and animals (6), which received the NF-κB inhibitor, namely ammonium pyrrolidine dithiocarbamate (PDTC) in a dose of 76 mg / kg (iNF-κB group) during modeling of chronic fluoride intoxication. To assess the development of oxidative stress we studied superoxide production (O2-), activity of superoxide dismutase (SOD), catalase (CAT) and concentration of free malondialdehyde (MDA). We also assessed NO production and concentration of its metabolites (peroxynitrite, nitrosilated thiol groups, nitrites).

RESULTS

Chronic fluoride intoxication leads to NO hyperproduction with subsequent increase in concentration of its later metabolites (peroxynitrite, nitrosilated thiol groups, nitrites). Production of O2- increases, SOD activity decreases, CAT activity increases and MDA concentration also increases. Inhibition of NF-kB activation by PDTC normalizes the parameters studied.

CONCLUSIONS

Activation of NF-κB during chronic fluoride intoxication leads to the development of hyperproduction of NO and development of oxidative-nitrosative stress.

The association of renal tubular inflammatory and injury markers with uric acid excretion in chronic kidney disease patients

AIM

To investigate the correlation of renal tubular inflammatory and injury markers with renal uric acid excretion in chronic kidney disease (CKD) patients.

METHODS

Seventy-three patients with CKD were enrolled. Fasting blood and morning urine sample were collected for routine laboratory measurements. At the same time, 24 h of urine was collected for urine biochemistry analyses, and 10 ml was extracted from the 24-h urine sample to further detect renal tubular inflammatory and injury markers, including interleukin-18 (IL-18), interleukin 1β (IL-1β), neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). The patients were divided into three tertile groups according to their 24-h urinary uric acid (24-h UUA) levels (UUA1: 24-h UUA ≤ 393.12 mg; UUA2: 393.12 < 24-h UUA ≤ 515.76 mg; UUA3: 24-h UUA > 515.76 mg). The general clinical and biochemical indexes were compared. Multivariable linear regression models were used to test the association of IL-18/Urinary creatinine concentration (IL-18/CR), IL-1β/CR, NGAL/CR and KIM-1/CR with renal uric acid excretion indicators.

RESULTS

All of tested renal tubular inflammation- and injury-related urinary markers were negatively associated with 24-h UUA and UEUA, and the negative correlation still persisted after adjusting for multiple influencing factors including urinary protein and eGFR. Further group analyses showed that these makers were significantly higher in the UUA1 than in the UUA3 group.

CONCLUSIONS

Our findings suggest that markers of urinary interstitial inflammation and injury in CKD patients are significantly correlated with 24-h UUA and Urinary excretion of uric acid (UEUA), and those with high 24-h UUA have lower levels of these markers. Renal uric acid excretion may also reflect the inflammation and injury of renal tubules under certain conditions.

Uric acid in CKD: has the jury come to the verdict?

Epidemiological studies show that hyperuricemia independently predicts the development of chronic kidney disease (CKD) in individuals with normal kidney function both in the general population and in subjects with diabetes. As a matter of fact, an unfavorable role of uric acid may somewhat be harder to identify in the context of multiple risk factors and pathogenetic mechanisms typical of overt CKD such as proteinuria and high blood pressure. Although the discrepancy in clinical results could mean that urate lowering treatment does not provide a constant benefit in all patients with hyperuricemia and CKD, we believe that the inconsistency in the results from available meta-analysis is mainly due to inadequate sample size, short follow-up times and heterogeneity in study design characterizing the randomized controlled trials included in the analyses. Therefore, available data support the view that hyperuricemia has a damaging impact on kidney function, while preliminary evidence suggests that treatment of so-called asymptomatic hyperuricemia may be helpful to slow or delay the progression of chronic kidney.

N-Butyrylated hyaluronic acid ameliorates gout and hyperuricemia in animal models

Context: Hyaluronic acid (HA) plays critical roles in the structural skeleton, joint lubrication, renal function and cell signaling. We previously showed that partially N-butyrylated, low molecular weight, hyaluronic acid (BHA) exhibited an anti-inflammatory effect in cultured human macrophage, where inflammation was induced either by a TL-4 agonist or the low molecular weight HA itself, in dose-dependent fashion. Objectives: To investigate the anti-inflammatory, antioxidative, and antihyperuricemic effects of BHA using animal models of acute gouty arthritis and hyperuricemia. Materials and methods: The anti-inflammatory effect of articular BHA (10 and 50 μg) injections was evaluated by measuring joint swelling and the serum levels of inflammatory cytokines in a model of acute gouty arthritis induced by intra-articular injection of monosodium urate crystals in Wistar rats (n = 10/group), in comparison to the control group with saline injection. Antioxidative and antihyperuricemic activities were investigated using intraperitoneal injections of oteracil potassium and yeast extract hyperuricemic Balb/C mice, which were treated with intraperitoneal injection of BHA at day 6-8 in the model. Results: In the gouty arthritis rat model, BHA at a higher dosage (50 μg) demonstrated a strong anti-inflammatory effect by reducing the degree of articular swelling and the serum levels of IL-1β, IL-8, IFN-γ, and MCP-1 by 5.56%, 6.55%, 15.58% and 33.18%. In the hyperuricemic mouse model, lower dosage BHA (10 μg) was sufficient to provide antioxidative activities by significantly decreasing the ROS levels in both serum and liver by 14.87% and 8.04%, while improving liver SOD by 12.77%. Intraperitoneal injection of BHA suppressed uric acid production through reducing liver XO activity by 19.78% and decreased the serum uric acid level in hyperuricemic mice by 30.41%. Conclusions: This study demonstrated for the first time that BHA exhibits anti-inflammatory, antioxidative and antihyperuricemic effects in vivo, suggesting a potential therapeutic application of BHA in gouty arthritis and hyperuricemia.

Male-biased zebrafish sex differentiation and metabolomics profile changes caused by dydrogesterone

Some progestins, including the widely used dydrogesterone (DDG), have been shown to cause male-biased sex ratio in teleost. However, there is a gap to fully understand the mechanisms of the sex differentiation disturbance by progestins, particularly from the metabolic aspect. We thus aimed to examine the sex changes by exposing zebrafish embryos to 4.4 (L), 44 (M) and 440 (H) ng/L DDG for up to 140 days, and investigated metabolomic profile changes during the critical period of sex differentiation at fry stage (35 dpf). DDG increased the percentage of male zebrafish in a dose-dependent manner, with 98% male fish in the high concentration group. In zebrafish fry, DDG increased the levels of some free fatty acids, monoglycerides, acylcarnitines, organic acids, free amino acids, while decreased lysophospholipids, uric acid and bile acids. DDG exposure also decreased the nucleoside monophosphates and UDP-sugars while increased nucleosides and their bases. These metabolite changes, namely increase in n-3 PUFAs (polyunsaturated fatty acids), myo-inositol, taurine, palmitoleic acid, oleic acid, lactic acid, fumaric acid, and uracil, and decrease in uric acid and bile acids, might account for the male-biased sex ratio in zebrafish. It appears that many of these metabolites could inhibit several pathways that regulate zebrafish gonad differentiation, including NF-κB/COX-2 and Wnt/β-catenin pathways, and activate p53 pathway. Thus we proposed a hypothesis that DDG might induce oocytes apoptosis through the above pathways and finally lead to female-to-male sex reversal. The results from this study suggest that DDG at environmentally relevant concentrations could affect zebrafish metabolomic profiles and finally disturb fish sex differentiation.

Pathogenic role of innate immunity in a model of chronic NO inhibition associated with salt overload

Nitric oxide inhibition with N^ω-nitro-l-arginine methyl ester (l-NAME), along with salt overload, leads to hypertension, albuminuria, glomerulosclerosis, glomerular ischemia, and interstitial fibrosis, characterizing a chronic kidney disease (CKD) model. Previous findings of this laboratory and elsewhere have suggested that activation of at least two pathways of innate immunity, Toll-like receptor 4 (TLR4)/NF-κB and nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain containing 3 (NLRP3) inflammasome/IL-1β, occurs in several experimental models of CKD and that progression of renal injury can be slowed with inhibition of these pathways. In the present study, we investigated whether activation of innate immunity, through either the TLR4/NF-κB or NLRP3/IL-1β pathway, is involved in the pathogenesis of renal injury in chronic nitric oxide inhibition with the salt-overload model. Adult male Munich-Wistar rats that received l-NAME in drinking water with salt overload (HS + N group) were treated with allopurinol (ALLO) as an NLRP3 inhibitor (HS + N + ALLO group) or pyrrolidine dithiocarbamate (PDTC) as an NF-κB inhibitor (HS + N + PDTC group). After 4 wk, HS + N rats developed hypertension, albuminuria, and renal injury along with renal inflammation, oxidative stress, and activation of both the NLRP3/IL-1β and TLR4/NF-κB pathways. ALLO lowered renal uric acid and inhibited the NLRP3 pathway. These effects were associated with amelioration of hypertension, albuminuria, and interstitial inflammation/fibrosis but not glomerular injury. PDTC inhibited the renal NF-κB system and lowered the number of interstitial cells staining positively for NLRP3. PDTC also reduced renal xanthine oxidase activity and uric acid. Overall, PDTC promoted a more efficient anti-inflammatory and nephroprotective effect than ALLO. The NLRP3/IL-1β and TLR4/NF-κB pathways act in parallel to promote renal injury/inflammation and must be simultaneously inhibited for best nephroprotection.

1,25(OH)2 D3 attenuates indoxyl sulfate-induced epithelial-to-mesenchymal cell transition via inactivation of PI3K/Akt/β-catenin signaling in renal tubular epithelial cells

OBJECTIVES

Indoxyl sulfate (IS), a uremic toxin, has been shown to promote the epithelial-to-mesenchymal transition (EMT) of human proximal tubular cells and to accelerate the progression of chronic kidney disease (CKD). Despite the well-known protective role of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂ D₃] in EMT, the effect of 1,25(OH)₂ D₃ on IS-induced EMT in human proximal tubular epithelial cells and the underlying mechanism remain unclear. The aim of this study was to determine whether IS (0-1 mM) dose-dependently inhibited the protein expression of E-cadherin and increased the protein expression of alpha-smooth muscle actin, N-cadherin, and fibronectin.

METHODS

This study investigated the molecular mechanism by which 1,25(OH)₂ D₃ attenuates IS-induced EMT. HK-2 human renal tubular epithelial cells was used as the study model, and the MTT assay, Western Blotting, siRNA knockdown technique were used to explore the effects of 1,25(OH)₂ D₃ on EMT in the presence of IS.

RESULTS

Pretreatment with 1,25(OH)₂ D₃ inhibited the IS-induced EMT-associated protein expression in HK-2 cells. IS induced the phosphorylation of Akt (S473) and β-catenin (S552) and subsequently increased the nuclear accumulation of β-catenin. Pretreatment with 1,25(OH)₂ D₃ and LY294002 (phosphoinositide 3-kinase [PIK3] inhibitor) significantly inhibited the IS-induced phosphorylation of Akt and β-catenin, nuclear β-catenin accumulation, and EMT-associated protein expression.

CONCLUSIONS

Results from the present study revealed that the anti-EMT effect of 1,25(OH)₂ D₃ is likely through inhibition of the PI3K/Akt/β-catenin pathway, which leads to down-regulation of IS-driven EMT-associated protein expression in HK-2 human renal tubular epithelial cells.

Galangin Suppresses Renal Inflammation via the Inhibition of NF-κB, PI3K/AKT and NLRP3 in Uric Acid Treated NRK-52E Tubular Epithelial Cells

Renal inflammation can result in renal injury. Uric acid (UA) is the final product of purine metabolism in humans and because of the lack of urate oxidase, UA may accumulate in tissues, including kidney, causing inflammation. Galangin was isolated from a traditional Chinese medicine plant and possesses several beneficial effects, working as an anti-oxidant, anti-mutagenic, anti-tumor, anti-inflammatory, anti-microbial, and anti-viral agent. Therefore, this study aimed at investigating the molecular mechanism of galangin in the attenuation of UA induced renal inflammation in normal rat kidney epithelial cells NRK-52E. Our findings suggested that galangin treatment efficiently protected NRK-52E cells against UA induced renal inflammation by decreasing tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-18, prostaglandin E2 (PGE2), and nitric oxide (NO) release, and it inhibited nitric oxide synthase (iNOS), prostaglandin endoperoxide synthase 2 (PTGS2), TNF-α, IL-1β, and IL-18 mRNA expression. In addition, galangin was not exerting any cytotoxicity at the concentrations that were effective against inflammation as assessed by CCK8 assay. Moreover, western blotting showed that galangin treatment effectively inhibited nuclear factor-kappa B (NF-κB), phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT) and nucleotide-binding domain- (NOD-) like receptor protein 3 (NLRP3) signaling pathway activation. Taken together, these findings suggested that galangin plays a pivotal role in renal inflammation by suppressing inflammatory responses, which might be closely associated with the inhibition of NLRP3 inflammasome, NF-κB and PI3K/AKT signaling pathway activation.

Crosstalk between autophagy and epithelial-mesenchymal transition and its application in cancer therapy

Autophagy is a highly conserved catabolic process that mediates degradation of pernicious or dysfunctional cellular components, such as invasive pathogens, senescent proteins, and organelles. It can promote or suppress tumor development, so it is a “double-edged sword” in tumors that depends on the cell and tissue types and the stages of tumor. The epithelial-mesenchymal transition (EMT) is a complex biological trans-differentiation process that allows epithelial cells to transiently obtain mesenchymal features, including motility and metastatic potential. EMT is considered as an important contributor to the invasion and metastasis of cancers. Thus, clarifying the crosstalk between autophagy and EMT will provide novel targets for cancer therapy. It was reported that EMT-related signal pathways have an impact on autophagy; conversely, autophagy activation can suppress or strengthen EMT by regulating various signaling pathways. On one hand, autophagy activation provides energy and basic nutrients for EMT during metastatic spreading, which assists cells to survive in stressful environmental and intracellular conditions. On the other hand, autophagy, acting as a cancer-suppressive function, is inclined to hinder metastasis by selectively down-regulating critical transcription factors of EMT in the early phases. Therefore, the inhibition of EMT by autophagy inhibitors or activators might be a novel strategy that provides thought and enlightenment for the treatment of cancer. In this article, we discuss in detail the role of autophagy and EMT in the development of cancers, the regulatory mechanisms between autophagy and EMT, the effects of autophagy inhibition or activation on EMT, and the potential applications in anticancer therapy.

NFκB and Kidney Injury

The global burden of chronic kidney disease will increase during the next century. As NFκB, first described more than 30 years ago, plays a major role in immune and non-immune-mediated diseases and in inflammatory and metabolic disorders, this review article summarizes current knowledge on the role of NFκB in in vivo kidney injury and describes the new and so far not completely understood crosstalk between canonical and non-canonical NFκB pathways in T-lymphocyte activation in renal disease.

Telmisartan Attenuates Uric Acid-Induced Epithelial-Mesenchymal Transition in Renal Tubular Cells

We examined whether and how uric acid induces epithelial to mesenchymal transition (EMT) in renal tubular cells, along with the mechanism by which telmisartan acts on uric acid-induced renal injury. Rat renal proximal tubular epithelial cells (NRK-52E) were exposed to various concentrations of uric acid in the presence or absence of telmisartan. Treatment with uric acid increased the expression of α-SMA, decreased the expression of E-cadherin, and promoted EMT in NRK-52E cells. Uric acid treatment also led to increased endothelin-1 (ET-1) production, activation of extracellular-regulated protein kinase 1/2 (ERK1/2), and the upregulation of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). Use of ET-1 receptor inhibitor (BQ123 or BQ788) could inhibit uric acid-induced EMT in NRK-52E cells. Pretreatment with the ERK inhibitor (U0126 or PD98059) suppressed the release of ET-1 and EMT induced by uric acid. Additionally, pretreatment with a traditional antioxidant (diphenylene iodonium or apocynin) inhibited the activation of ERK1/2, release of ET-1, and uric acid-induced EMT in NRK-52E cells. These findings suggested that uric acid-induced EMT in renal tubular epithelial cells occurs through NADPH oxidase-mediated ERK1/2 activation and the subsequent release of ET-1. Furthermore, telmisartan (10² nmol/L to 10⁴ nmol/L) inhibited the expression of NOX4, intracellular reactive oxygen species (ROS), activation of ERK1/2, and the release of ET-1 in a dose-dependent manner, thereby preventing uric acid-induced EMT in NRK-52E. In conclusion, telmisartan could ameliorate uric acid-induced EMT in NRK-52E cells likely through inhibition of the NADPH oxidase/ERK1/2/ET-1 pathway.

Febuxostat inhibits TGF‑β1‑induced epithelial‑mesenchymal transition via downregulation of USAG‑1 expression in Madin‑Darby canine kidney cells in vitro

Our previous study demonstrated that febuxostat, a xanthine oxidase inhibitor, can alleviate kidney dysfunction and ameliorate renal tubulointerstitial fibrosis in a rat unilateral ureteral obstruction (UUO) model; however, the underlying mechanisms remain unknown. Increasing evidence has revealed that epithelial-mesenchymal transition (EMT) is one of the key mechanisms mediating the progression of renal tubulointerstitial fibrosis in chronic kidney disease (CKD). Uterine sensitization-associated gene-1 (USAG-1), a kidney-specific bone morphogenetic protein antagonist, is involved in the development of numerous types of CKDs. The present study aimed to investigate the role of febuxostat in the process of EMT in Madin-Darby canine kidney (MDCK) cells in vitro. Western blotting, reverse transcription-semiquantitative polymerase chain reaction analysis and immunofluorescence staining were used to evaluate the expression levels of bone morphogenetic protein 7, USAG-1, α-smooth muscle actin (α-SMA) and E-cadherin, respectively. The results demonstrated that the expression of USAG-1 and α-SMA increased, and that of E-cadherin decreased significantly in MDCK cells following treatment with transforming growth factor-β1 (TGF-β1). The application of small interfering RNA-USAG-1 potently inhibited TGF-β1-induced EMT. Subsequently, the effects of febuxostat on TGF-β1-induced EMT was investigated. The results demonstrated that febuxostat downregulated the expression of USAG-1, and reversed TGF-β1-induced EMT in MDCK cells. Furthermore, pretreatment with febuxostat significantly restored the decreased expression levels of phosphorylated Smad1/5/8 induced by TGF-β1 in MDCK cells. The results of the present study suggested that USAG-1 may be involved in the EMT process of MDCK cells induced by TGF-β1, and febuxostat inhibited EMT by activating the Smad1/5/8 signaling pathway via downregulating the expression of USAG-1 in MDCK cells.

Uric acid and angiotensin II additively promote inflammation and oxidative stress in human proximal tubule cells by activation of toll-like receptor 4

Renal proximal tubular cells (PTECs) participate in several mechanisms of innate immunity, express toll-like receptors (TLRs), and proinflammatory cytokines. Hyperuricemia may be a promoter of inflammation and renal damage. Angiotensin II (Ang II) modulate immune and inflammatory responses in renal tubular cells. With the aim to evaluate the effect of uric acid (UA) and Ang II on oxidative stress and inflammation mediated by toll-like receptor 4 (TLR4) activation in human PTECs, human kidney 2 (HK2) were incubated for 24 hr with UA (12 mg/dl) and Ang II (10 ^-7  M). HK2 were pretreated with an antagonist of TLR4 (TAK 242), valsartan or losartan. The genic expression of TLR4, monocyte chemoattractant protein-1 (MCP1), and Nox4 was quantified with reverse transcription polymerase chain reaction, proteins were evaluated with Western blot. The incubation of HK2 either with UA or with Ang II determines an increased expression of TLR4, production of proinflammatory cytokines as MCP1 and pro-oxidants as Nox4 ( p < 0.05). TAK 242 attenuates the expression of MCP1 induced both by UA and Ang II. Valsartan attenuated all the effects we described after exposure to Ang II but not those observed after UA exposure. At variance, pretreatment with losartan, which inhibits UA internalization, attenuates the expression of TLR4, MCP1, and Nox4 in cells previously treated with UA, Ang II, and UA plus Ang II. Proinflammatory pathways are induced in an additive manner by UA and Ang II ( p < 0.05) and might be mediated by TLR4 in PTECs. Renin-angiotensin-aldosterone system (RAAS) activation, hyperuricemia, and innate immunity interplay in the development of chronic tubular damage and the interaction of several nephrotoxic mechanisms blunt the protective effect of RAAS inhibition.

Early growth response protein-1 upregulates long noncoding RNA Arid2-IR to promote extracellular matrix production in diabetic kidney disease

Diabetic kidney disease (DKD) has surpassed chronic glomerulonephritis as the leading cause of end-stage renal disease. Previously, we showed that early growth response protein-1 (Egr1) plays a key role in DKD by enhancing mesangial cell proliferation and extracellular matrix (ECM) production. The long noncoding RNA (lncRNA) AT-rich interactive domain 2-IR (Arid2-IR) has been identified as a mothers against decapentaplegic homolog 3 (Smad3)-associated lncRNA in unilateral ureteral obstructive kidney disease. However, the effect of Egr1 on Arid2-IR in the development of DKD is still unknown. In this study, we found that Arid2-IR was increased in mice with high-fat diet and streptozotocin-induced type 2 diabetes and in mouse mesangial cells cultured with high glucose to mimic diabetes. Knockdown of Arid2-IR in mouse mesangial cells reduced the high expression levels of collagen-α₁(I) (Col1a1) and α-smooth muscle actin (α-SMA) induced by high glucose. Furthermore, Arid2-IR expression changed the increased expression of Col1a1 and α-SMA caused by overexpression of Egr1. Overall, these data suggest that increased Arid2-IR likely contributes to ECM production in DKD and that Egr1 promotes ECM production in DKD partly by upregulating Arid2-IR. Thus, Arid2-IR may be a new target in the treatment of DKD.

Pharmacological inhibition of autophagy by 3-MA attenuates hyperuricemic nephropathy

Autophagy has been identified as a cellular process of bulk degradation of cytoplasmic components and its persistent activation is critically involved in the renal damage induced by ureteral obstruction. However, the role and underlying mechanisms of autophagy in hyperuricemic nephropathy (HN) remain unknown. In the present study, we observed that inhibition of autophagy by 3-methyladenine (3-MA) abolished uric acid-induced differentiation of renal fibroblasts to myofibroblasts and activation of transforming growth factor-β1 (TGF-β1), epidermal growth factor receptor (EGFR), and Wnt signaling pathways in cultured renal interstitial fibroblasts. Treatment with 3-MA also abrogated the development of HN in vivo as evidenced by improving renal function, preserving renal tissue architecture, reducing the number of autophagic vacuoles, and decreasing microalbuminuria. Moreover, 3-MA was effective in attenuating renal deposition of extracellular matrix (ECM) proteins and expression of α-smooth muscle actin (α-SMA) and reducing renal epithelial cells arrested at the G₂/M phase of cell cycle. Injury to the kidney resulted in increased expression of TGF-β1 and TGFβ receptor I, phosphorylation of Smad3 and TGF-β-activated kinase 1 (TAK1), and activation of multiple cell signaling pathways associated with renal fibrogenesis, including Wnt, Notch, EGFR, and nuclear factor-κB (NF-κB). 3-MA treatment remarkably inhibited all these responses. In addition, 3-MA effectively suppressed infiltration of macrophages and lymphocytes as well as release of multiple profibrogenic cytokines/chemokines in the injured kidney. Collectively, these findings indicate that hyperuricemia-induced autophagy is critically involved in the activation of renal fibroblasts and development of renal fibrosis and suggest that inhibition of autophagy may represent a potential therapeutic strategy for HN.