The role of the Janus kinase family/signal transducer and activator of transcription signaling pathway in fibrotic renal disease

Recent Advances of MSCs in Renal IRI: From Injury to Renal Fibrosis

Renal fibrosis is a pathological endpoint of maladaptation after ischemia-reperfusion injury (IRI), and despite many attempts, no good treatment has been achieved so far. At the core of renal fibrosis is the differentiation of various types of cells into myofibroblasts. MSCs were once thought to play a protective role after renal IRI. However, growing evidence suggests that MSCs have a two-sided nature. In spite of their protective role, in maladaptive situations, MSCs start to differentiate towards myofibroblasts, increasing the myofibroblast pool and promoting renal fibrosis. Following renal IRI, it has been observed that Bone Marrow-Derived Mesenchymal Stem Cells (BM-MSCs) and Renal Resident Mesenchymal Stem Cells (RR-MSCs) play important roles. This review presents evidence supporting their involvement, discusses their potential mechanisms of action, and suggests several new targets for future research.

Pioglitazone Protects Tubular Epithelial Cells during Kidney Fibrosis by Attenuating miRNA Dysregulation and Autophagy Dysfunction Induced by TGF-β

Excessive renal TGF-β production and pro-fibrotic miRNAs are important drivers of kidney fibrosis that lack any efficient treatment. Dysfunctional autophagy might play an important role in the pathogenesis. We aimed to study the yet unknown effects of peroxisome proliferator-activated receptor-γ (PPARγ) agonist pioglitazone (Pio) on renal autophagy and miRNA dysregulation during fibrosis. Mouse primary tubular epithelial cells (PTEC) were isolated, pre-treated with 5 µM pioglitazone, and then stimulated with 10 ng/mL TGF-β1 for 24 h. Male 10-week-old C57Bl6 control (CTL) and TGF-β overexpressing mice were fed with regular chow (TGF) or Pio-containing chow (20 mg/kg/day) for 5 weeks (TGF + Pio). PTEC and kidneys were evaluated for mRNA and protein expression. In PTEC, pioglitazone attenuated (p < 0.05) the TGF-β-induced up-regulation of Col1a1 (1.4-fold), Tgfb1 (2.2-fold), Ctgf (1.5-fold), Egr2 (2.5-fold) mRNAs, miR-130a (1.6-fold), and miR-199a (1.5-fold), inhibited epithelial-to-mesenchymal transition, and rescued autophagy function. In TGF mice, pioglitazone greatly improved kidney fibrosis and related dysfunctional autophagy (increased LC3-II/I ratio and reduced SQSTM1 protein content (p < 0.05)). These were accompanied by 5-fold, 3-fold, 12-fold, and 2-fold suppression (p < 0.05) of renal Ccl2, Il6, C3, and Lgals3 mRNA expression, respectively. Our results implicate that pioglitazone counteracts multiple pro-fibrotic processes in the kidney, including autophagy dysfunction and miRNA dysregulation.

Erythropoietin mitigated thioacetamide-induced renal injury via JAK2/STAT5 and AMPK pathway

The kidney flushes out toxic substances and metabolic waste products, and homeostasis is maintained owing to the kidney efforts. Unfortunately, kidney disease is one of the illnesses with a poor prognosis and a high death rate. The current investigation was set out to assess erythropoietin (EPO) potential therapeutic benefits against thioacetamide (TAA)-induced kidney injury in rats. EPO treatment improved kidney functions, ameliorated serum urea, creatinine, and malondialdehyde, increased renal levels of reduced glutathione, and slowed the rise of JAK2, STAT5, AMPK, and their phosphorylated forms induced by TAA. EPO treatment also greatly suppressed JAK2, Phosphatidylinositol 3-kinases, and The Protein Kinase R-like ER Kinase gene expressions and mitigated the histopathological alterations brought on by TAA toxicity. EPO antioxidant and anti-inflammatory properties protected TAA-damaged kidneys. EPO regulates AMPK, JAK2/STAT5, and pro-inflammatory mediator synthesis.

Exploration of the possible mechanisms of Ling Gui Zhu Gan decoction in nephrotic syndrome based on network pharmacology, molecular docking and molecular dynamics simulation

This study aimed to explore the possible mechanisms of Ling Gui Zhu Gan decoction (LGZGD) in the treatment of nephrotic syndrome (NS) using network pharmacology combined with molecular docking and molecular dynamics simulation. The active ingredients of LGZGD and their targets were retrieved from Traditional Chinese Medicine Systems Pharmacology Database and Swiss Target Prediction database. The NS targets were retrieved from Genecards, OMIM and Drugbank databases. Next, the intersecting targets of drug and disease were imported into the String database for protein-protein interaction network analysis, and the core targets were identified through topological analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed in the Metascape platform. Finally, molecular docking and molecular dynamics simulation were performed for further validation. The network analysis showed that 109 active ingredients of LGZGD were associated with 105 targets in NS. The key active ingredients (quercetin, kaempferol, naringenin, licochalcone A, formononetin, beta-sitosterol) and the core targets (IL6, AKT1, TNF, VEGFA, TP53, JUN, IL1B, CASP3, EGFR, and STAT3) were further identified. Enrichment analysis indicated that multiple biological processes and pathways, including AGE-RAGE, PI3K-Akt, JAK-STAT, and HIF-1 signaling pathways, might be regulated by LGZGD in the treatment of NS. Molecular docking and molecular dynamics simulation results further indicated that the key active ingredients of LGZGD could stably bind to the core targets through hydrogen bonding and hydrophobic interaction. This study demonstrates that the active ingredients of LGZGD may regulate multiple targets, biological processes and signaling pathways in NS. Our findings may provide a theoretical basis for further studies on LGZGD in the treatment of NS.

L-Carnitine and Chronic Kidney Disease: A Comprehensive Review on Nutrition and Health Perspectives

Progressive segmental glomerulosclerosis is acknowledged as a characteristic of Chronic Kidney Disease (CKD). It is a major health issue that exponentially reduces health and economy and also causes serious morbidity and mortality across the globe. This review is aimed at comprehending the health perspectives of L-Carnitine (LC) as an adjuvant regimen for alleviating CKD and its associated complications. The data were gathered from different online databases such as Science Direct, Google Scholar, ACS publication, PubMed, Springer, etc., using keywords such as CKD/Kidney disease, current epidemiology and its prevalence, LC supplementations, sources of LC, anti-oxidant and anti-inflammatory potential of LC and its supplementation for mimicking the CKD and its associated problem, etc. Various items of literature concerning CKD were gathered and screened by experts based on their inclusion and exclusion criteria. The findings suggest that, among the different comorbidities such as oxidative stress and inflammatory stress, erythropoietin-resistant anemia, intradialytic hypotension, muscle weakness, myalgia, etc., are considered as the most significant onset symptoms in CKD or hemodialysis patients. LC or creatine supplementation provides an effective adjuvant or therapeutic regimen that significantly reduces oxidative and inflammatory stress and erythropoietin-resistant anemia and evades comorbidities such as tiredness, impaired cognition, muscle weakness, myalgia, and muscle wasting. However, no significant changes were found in biochemical alteration such as creatinine, uric acid, urea, etc., after creatine supplementation in a patient with renal dysfunction. The expert-recommended dose of LC or creatine to a patient is approached for better outcomes of LC as a nutritional therapy regimen for CKD-associated complications. Hence, it can be suggested that LC provides an effective nutritional therapy to ameliorate impaired biochemicals and kidney function and to treat CKD and its associated complications.

The Role of JAK/STAT Pathway in Fibrotic Diseases: Molecular and Cellular Mechanisms

There are four members of the JAK family and seven of the STAT family in mammals. The JAK/STAT molecular pathway could be activated by broad hormones, cytokines, growth factors, and more. The JAK/STAT signaling pathway extensively mediates various biological processes such as cell proliferation, differentiation, migration, apoptosis, and immune regulation. JAK/STAT activation is closely related to growth and development, homeostasis, various solid tumors, inflammatory illness, and autoimmune diseases. Recently, with the deepening understanding of the JAK/STAT pathway, the relationship between JAK/STAT and the pathophysiology of fibrotic diseases was noticed, including the liver, renal, heart, bone marrow, and lung. JAK inhibitor has been approved for myelofibrosis, and subsequently, JAK/STAT may serve as a promising target for fibrosis in other organs. Therefore, this article reviews the roles and mechanisms of the JAK/STAT signaling pathway in fibrotic diseases.

Inhibition of JAK1,2 Prevents Fibrotic Remodeling of Pulmonary Vascular Bed and Improves Outcomes in the Rat Model of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare complication of acute pulmonary embolism with poor clinical outcomes. Therapeutic approaches to prevention of fibrotic remodeling of the pulmonary vascular bed in CTEPH are limited. In this work, we tested the hypothesis that Janus kinase 1/2 (JAK1/2) inhibition with ruxolitinib might prevent and attenuate CTEPH in a rat model. CTEPH was induced by repeated embolization of the pulmonary artery with partially biodegradable 180 ± 30 μm alginate microspheres. Two weeks after the last injection of microspheres, ruxolitinib was administered orally at doses of 0.86, 2.58, and 4.28 mg/kg per day for 4 weeks. Prednisolone (1.475 mg/kg, i.m.) was used as a reference drug. Ruxolitinib in all doses as well as prednisolone reduced pulmonary vascular wall hypertrophy. Ruxolitinib at a dose of 2.58 mg/kg and prednisolone reduced vascular wall fibrosis. Prednisolone treatment resulted in decreased right ventricular systolic pressure. Pulmonary vascular resistance was lower in the prednisolone and ruxolitinib (4.28 mg/kg) groups in comparison with the placebo group. The plasma level of brain natriuretic peptide was lower in groups receiving ruxolitinib at doses of 2.58 and 4.28 mg/kg versus placebo. This study demonstrated that JAK1/2 inhibitor ruxolitinib dose-dependently reduced pulmonary vascular remodeling, thereby preventing CTEPH formation in rats.

Pharmacological and Genetic Inhibition of HDAC4 Alleviates Renal Injury and Fibrosis in Mice

Histone deacetylase 4 (HDAC4) has been shown to be involved in cell proliferation, differentiation, and migration and is associated with a variety of cancers. However, the role of HDAC4 in renal fibrogenesis and its mechanisms are unclear. We assessed the role of HDAC4 and possible mechanisms of fibrosis in a murine model of kidney injury induced by unilateral ureteral obstruction (UUO) using tasquinimod, a highly selective HDAC4 inhibitor, and knockout mice with depletion of HDAC4 in renal tubular cells. UUO injury resulted in increased expression of HDAC4 and fibrotic proteins fibronectin and α-smooth muscle actin, while treatment with tasquinimod or knockout of HDAC4 significantly reduced their expression. Pharmacological and genetic inhibition of HDAC4 also decreased tubular epithelial cell arrest in the G2/M phase of the cell cycle, expression of transforming growth factor-β1 and phosphorylation of Smad3, signal transducer and activator of transcription 3, and extracellular signal-regulated kinase 1/2 in the injured kidney. Moreover, tasquinimod treatment or HDAC4 deletion inhibited UUO-induced renal tubular cell injury and apoptosis as indicated by reduced expression of neutrophil gelatinase-associated lipocalin, Bax, and inhibition of caspase-3. Finally, administration of tasquinimod or knockdown of HDAC4 prevented injury-related repression of Klotho, a renoprotective protein. Our results indicate that HDAC4 is critically involved in renal tubular injury and fibrosis and suggest that HDAC4 is a potential therapeutic target for treatment of chronic fibrotic kidney disease.

Isolation and identification of the components in Cybister chinensis Motschulsky against inflammation and their mechanisms of action based on network pharmacology and molecular docking

ETHNOPHARMACOLOGICAL RELEVANCE

Cybister chinensis Motschulsky belongs to the family Dytiscidae. As a traditional Chinese medicine, the insect is called Longshi in the folk and is commonly used to treat enuresis in children and frequent urination in the elderly.

AIM OF THE STUDY

Inflammation is involved in chronic kidney disease. The previous study proved ethanol extract of C. chinensis exhibited anti-inflammation effects in the Doxorubicin-induced kidney disease. However, the material basis and their possible mechanism of the insect were still unclear. Thus, we aimed to separate the active compounds of the ethanol extract from C. chinensis and to investigate their possible mechanism of anti-inflammation by network pharmacology and molecular docking.

MATERIALS AND METHODS

The insect was extracted with 75% ethanol to produce ethanol extracts and then were extracted by petroleum ether, ethyl acetate and n-butanol respectively. Silica gel column chromatography and preparative HPLC were applied to separate the compounds of the extract. The compounds were characterized and identified by NMR and mass. The compound associated genes were collected by BATMAN-TCM database and the inflammation associated genes were obtained through DigSee database. The protein-protein interaction (PPI) network was carried out via Search Tool for the Retrieval of Interacting Genes/Protein (STRING) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) target pathway analysis was performed in Database for Annotation, Visualization and Integrated Discovery (DAVID). The possible mechanism of compounds against inflammation was investigated by molecular docking. Finally, the anti-inflammatory effect of the representative compound was verified by the LPS-induced Raw 264.7 cell inflammatory model. TNF-α, IL-1β and IL-6 of the cell supernatants were analyzed via using ELISA kits and the key proteins in JAK2/STAT3 signaling pathway were verified via the Western blot assays.

RESULTS

Among crude extracts from C. chinensis, ethyl acetate extract showed the obvious anti-inflammatory effects. Nine compounds were isolated from ethyl acetate extract of Cybister chinensis for the first time, including benzoic acid (1), hydroxytyrosol (2), protocatechualdehyde (3), N-[2-(4-hydroxyphenyl)ethyl]acetamide (4), (2E)-3-phenylprop-2-enoic acid (5), 3-phenylpropionic acid (6), methyl 3,4-dihydroxybenzoate (7), 1,4-diphenyl butane-2,3-diol (8) and p-N,N-dimethylaminobenzaldehyde (9). After searching in the database, 1079 compound associated genes and 467 inflammation associated genes were found. The 137 common targets covered 77 signaling pathways, in which HIF-1 signaling pathway, TNF signaling pathway, influenza A, PI3K/Akt signaling pathway, NOD-like receptor signaling pathway, MAPK signaling pathway, Toll-like receptor signaling pathway and Jak-STAT signaling pathway were important for inflammation. Molecular docking studies showed compound 1, 4, 5, 6, 7 and 8 were the potential inhibitors of JAK2 protein. In addition, the in vitro test showed compound 5 reduced the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β in lipopolysaccharide (LPS)-stimulated RAW264.7 cells in a dose-dependent manner. Furthermore, it was found that compound 5 inhibited the expression of p-JAK2 and p-STAT3 in LPS-induced RAW264.7 cells in a dose-dependent manner.

CONCLUSIONS

Based on the network pharmacology and molecular docking, the study suggested that C. chinensis could relieve the inflammation based on the multi-compounds and multi-pathways, which provided the foundation for the medicinal application of C. chinensis.

Alamandine alleviates hypertension and renal damage via oxidative-stress attenuation in Dahl rats

Alamandine (Ala) is a novel member of the renin-angiotensin-system (RAS) family. The present study aimed to explore the effects of Ala on hypertension and renal damage of Dahl salt-sensitive (SS) rats high-salt diet-induced, and the mechanisms of Ala on renal-damage alleviation. Dahl rats were fed with high-salt diets to induce hypertension and renal damage in vivo, and HK-2 cells were treated with sodium chloride (NaCl) to induce renal injury in vitro. Ala administration alleviated the high-salt diet-induced hypertension, renal dysfunction, and renal fibrosis and apoptosis in Dahl SS rats. The HK-2 cells' damage, and the increases in the levels of cleaved (c)-caspase3, c-caspase8, and c-poly(ADP-ribose) polymerase (PARP) induced by NaCl were inhibited by Ala. Ala attenuated the NaCl-induced oxidative stress in the kidney and HK-2 cells. DETC, an inhibitor of SOD, reversed the inhibitory effect of Ala on the apoptosis of HK-2 cells induced by NaCl. The NaCl-induced increase in the PKC level was suppressed by Ala in HK-2 cells. Notably, PKC overexpression reversed the moderating effects of Ala on the NaCl-induced apoptosis of HK-2 cells. These results show that Ala alleviates high-salt diet-induced hypertension and renal dysfunction. Ala attenuates the renal damage via inhibiting the PKC/reactive oxygen species (ROS) signaling pathway, thereby suppressing the apoptosis in renal tubular cells.

A systematic review on nephron protective AYUSH drugs as constituents of NEERI-KFT (A traditional Indian polyherbal formulation) for the management of chronic kidney disease

Chronic Kidney Disease (CKD) is a major health problem characterized by kidney dysfunction with progressive segmental glomerulosclerosis to end-stage renal disease (ESRD). Due to lack of scientific data and comprehensive reports, the current systematic review provides an inclusive understanding and prospective associated with phytopharmacology of NEERI-KFT in CKD. The data was collected from more than five databases such as Science Direct, Google Scholar, Elsevier, PubMed, Springer, ACS publication etc using keywords like CKD/Kidney disease, epidemiology/prevalence, modern therapies for CKD management, NEERI-KFT and its role in kidney disease. The study was performed based on scientific reports screened by experts according to inclusion and exclusion criteria. The pre-clinical and clinical findings suggested that NEERI-KFT has promising effects as nephroprotective and considered safe and well effective in primary care of kidney against disease. Phytopharmacological evaluation of NEERI-KFT suggest that it exhibit substantial potential against oxidative and inflammatory stress induced apoptosis by exerting antioxidants, nephroprotective and immunomodulatory effects. Hence, it can be enlighten that NEERI-KFT have potential herbs which exerts significant antioxidants, nephroprotective and immunomodulatory effects in the patients associated with renal dysfunction or CKD thus improving altered renal architecture and renal physiology. Clinically, it is concluded that NEERI-KFT works kidney malfunction and cease ESRD progression or even reduce the number of dialysis.

IGF IIRα-triggered pathological manifestations in the heart aggravate renal inflammation in STZ-induced type-I diabetes rats

Pathological manifestations in either heart or kidney impact the function of the other and form the basis for the development of cardiorenal syndrome. However, the mechanism or factors involved in such scenario are not completely elucidated. In our study, to find the correlation between late fetal gene expression in diabetic hearts and their influence on diabetic nephropathy, we created a rat model with cardiac specific overexpression of IGF-IIRα, which is an alternative splicing variant of IGFIIR, expressed in pathological hearts. In this study, transgenic rats over expressing cardiac specific IGF-IIRα and non-transgenic animal models established in SD rats were administered with single dose of streptozotocin (STZ, 55 mg/Kg) to induce Type I diabetes. The correlation between IGF-IIRα and kidney damages were further determined based on their intensity of damage in the kidneys. The results show that cardiac specific overexpression of IGF-IIRα elevates the diabetes associated inflammation and morphological changes in the kidneys. The diabetic transgenic rats showed advancement in the pathological features such a renal tubular damage, collagen accumulation and enhancement in STAT3 associated mechanism of renal fibrosis. The results therefore show that that IGF-IIRα expression in the heart during pathological condition may worsen symptoms of diabetic nephropathy in rats.

Vitamin D protects glomerular mesangial cells from high glucose-induced injury by repressing JAK/STAT signaling

Aim

High glucose (HG) induces the production of transforming growth factor (TGF)-β and reactive oxygen species, which further activates JAK/STAT signaling and promotes the synthesis of matrix proteins, contributes to the pathophysiological processes of diabetic nephropathy. This study aims to investigate the protection role of vitamin D (VD) in the kidney in high glucose condition.

Methods

Rat glomerular mesangial cells were cultured in high glucose medium, with or without VD or VD receptor (VDR) siRNAs treatment. The levels of TGF-β and fibronectin were detected by qRT-PCR, immunoblotting and enzyme-linked immunosorbent assay (ELISA). The levels of phosphorylated JAK2, STAT1 and STAT3, and JAK/STAT signaling downstream genes were examined by immunoblotting and qRT-PCR.

Results

In rat glomerular mesangial cells, VD treatment can repress the tyrosine phosphorylation of JAK2, STAT1 and STAT3. VD inhibited TGF-β and fibronectin expression which was rescued by vitamin d receptor (VDR) siRNA and STATs inhibitor perficitinib. The JAK/STAT signaling downstream protein coding genes including SOCS1, SOCS3 and type IV collagen were repressed by VD. Meanwhile, the expression of non-coding RNAs such as miR-181a, miR-181b, was repressed by VD, and the expression of miR-34a and Let-7b was upregulated by VD.

Conclusion

Vitamin D (VD) treatment inhibits the function of HG on fibronectin production through regulating JAK/STAT pathway. These results provide direct evidences that VD protects glomerular mesangial cells from high glucose-induced injury through repressing JAK/STAT signaling, which has the potential for clinical DN treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-020-02728-z.

Immunomodulatory Approaches in Diabetes-Induced Cardiorenal Syndromes

Immunomodulatory approaches are defined as all interventions that modulate and curb the immune response of the host rather than targeting the disease itself with the aim of disease prevention or treatment. A better understanding of the immune system continues to offer innovative drug targets and methods for immunomodulatory interventions. Cardiorenal syndrome is a clinical condition that defines disorders of the heart and kidneys, both of which communicate with one another through multiple pathways in an interdependent relationship. Cardiorenal syndrome denotes the confluence of heart-kidney relationships across numerous interfaces. As such, a dysfunctional heart or kidney has the capacity to initiate disease in the other organ via common hemodynamic, neurohormonal, immunological, and/or biochemical feedback pathways. Understanding how immunomodulatory approaches are implemented in diabetes-induced cardiovascular and renal diseases is important for a promising regenerative medicine, which is the process of replacing cells, tissues or organs to establish normal function. In this article, after a brief introduction on the immunomodulatory approaches in diseases, we will be reviewing the epidemiology and classifications of cardiorenal syndrome. We will be emphasizing on the hemodynamic factors and non-hemodynamic factors linking the heart and the kidneys. In addition, we will be elaborating on the immunomodulatory pathways involved in diabetes-induced cardiorenal syndrome namely, RAS, JAK/STAT, and oxidative stress. Moreover, we will be addressing possible therapeutic approaches that target the former pathways in an attempt to modulate the immune system.

LncRNA NEAT1 Promotes High Glucose-Induced Mesangial Cell Hypertrophy by Targeting miR-222-3p/CDKN1B Axis

Glomerular hypertrophy is an early morphological alteration in diabetic nephropathy. Cyclin-Dependent Kinases have been shown to be required for high glucose (HG)-induced hypertrophy; however, the upstream regulators of CDKN1B in glomerular hypertrophy remain unclear. Herein we describe a novel pathway in which Long noncoding RNA (lncRNA) NEAT1 regulates the progression of mesangial cell hypertrophy via a competing endogenous RNA (ceRNA) mechanism. Real-time PCR was performed to detect the relative NEAT1 and miR-222-3p expressions and further confirmed the relationship between NEAT1 and miR-222-3p. Cell cycle was evaluated by flow cytometry. The related mechanisms were explored by Western blot, RNA immunoprecipitation and chromatin immunoprecipitation assay. We show that NEAT1 forms double stranded RNA (dsRNA) with miR-222-3p, thus limiting miR-222-3p's binding with CDKN1B. This release of CDKN1B mRNA leads to elevated CDKN1B protein expression, resulting in hypertrophy. In addition, we demonstrated that STAT3 which is activated by HG induces the transcription of NEAT1 by binding to its promoter. Our findings underscore an unexpected role of lncRNAs on gene regulation and introduce a new mode of proliferation regulation in mesangial cells.

Effect of Shenkang on renal fibrosis and activation of renal interstitial fibroblasts through the JAK2/STAT3 pathway

BACKGROUND

Activation of renal fibroblasts is a critical mechanism in the process of renal fibrosis. As a commonly used herbal formula, Shenkang (SK) has been found to attenuate renal fibrosis and renal parenchyma destruction. However, the effect of SK on renal fibroblast activation in unilateral ureteral obstruction (UUO) mice and its molecular mechanism remain undetermined. The present study was performed to elucidate the effect of SK on renal fibroblast activation and renal fibrosis, as well as the potential underlying mechanism, in both NRK-49F cells and UUO mice.

METHODS

NRK-49F cells were stimulated with 10 ng/ml TGF-β1 for 48 h. After SK treatment, the CCK-8 method was used to evaluate cell viability. Thirty-six C57BL/6 mice were randomly divided into the sham group, UUO group, angiotensin receptor blocker (ARB) group, and SK high-, moderate- and low-dose groups. UUO was induced in mice except those in the sham group. Drugs were administered 1 day later. On the 13th day, the fractional anisotropy (FA) value was determined by MRI to evaluate the degree of renal fibrosis. After 14 days, serum indexes were assessed. Hematoxylin and eosin (HE) and Sirius red staining were used to observe pathological morphology and the degree of fibrosis of the affected kidney. Western blotting and PCR were used to assess the expression of related molecules in both cells and animals at the protein and gene levels.

RESULTS

Our results showed that SK reduced extracellular matrix (ECM) and α-smooth muscle actin (α-SMA) expression both in vitro and in vivo and attenuated renal fibrosis and the pathological lesion degree after UUO, suppressing JAK2/STAT3 activation. Furthermore, we found that SK regulated the JAK2/STAT3 pathway regulators peroxiredoxin 5 (Prdx5) in vitro and suppressor of cytokine signaling protein 1 (SOCS1) and SOCS3 in vivo.

CONCLUSIONS

These results indicated that SK inhibited fibroblast activation by regulating the JAK2/STAT3 pathway, which may be a mechanism underlying its protective action in renal fibrosis.

PERK-Dependent Activation of the JAK2/STAT3 Pathway Contributes to High Glucose-Induced Extracellular Matrix Deposition in Renal Tubular Epithelial Cells

BACKGROUND

Although the deposition of extracellular matrix (ECM) is critical leading to tubular damage in diabetic kidney disease (DKD), the mechanism still remains unclear. The purpose of this study was to demonstrate a role for protein kinase R-like endoplasmic reticulum kinase (PERK) (a protein located in the endoplasmic reticulum membrane) in this pathologic process.

METHODS

NRK-52E cells were grown in the media containing different concentrations of glucose or thapsigargin for different durations. Cells were subsequently incubated with or without AG490, a selective inhibitor of Janus kinase 2 (JAK2) or GSK2606414 (a selective PERK inhibitor). We evaluated the production of TGF-β1, fibronectin, and collagen I proteins by ELISA. The levels of 78 kD-glucose-regulated protein (GRP78) and PERK, as well as the phosphorylation statues of PERK and JAK2/signal transducer and activator of transcription (STAT3), were determined by western blotting analysis.

RESULTS

We showed that the increased phosphorylation of JAK2 and STAT3 was accompanied by overexpression of TGF-β1 and ECM deposition in high glucose medium. Disruption of the JAK2/STAT3 pathway with AG490 significantly prevents the high glucose-induced increase in TGF-β1, fibronectin, and collagen I. High glucose induced the overproduction of GRP78 and phosphorylation of PERK, which indicated that endoplasmic reticulum stress (ERS) was triggered in NRK-52E cells cultured under high glucose condition. Inhibition of PERK phosphorylation with GSK2606414, however, blocked the effect of JAK2/STAT3 on the production of TGF-β1 and ECM components in NRK-52E cells.

CONCLUSION

Our data indicated that the ECM accumulation induced by high glucose arouse via the PERK-dependent JAK2/STAT3-signaling pathway in renal tubular epithelial cells.

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.

The Emerging Role of Innate Immunity in Chronic Kidney Diseases

Renal fibrosis is a common fate of chronic kidney diseases. Emerging studies suggest that unsolved inflammation will progressively transit into tissue fibrosis that finally results in an irreversible end-stage renal disease (ESRD). Renal inflammation recruits and activates immunocytes, which largely promotes tissue scarring of the diseased kidney. Importantly, studies have suggested a crucial role of innate immunity in the pathologic basis of kidney diseases. This review provides an update of both clinical and experimental information, focused on how innate immune signaling contributes to renal fibrogenesis. A better understanding of the underlying mechanisms may uncover a novel therapeutic strategy for ESRD.

The Effects of Sidt2 on the Inflammatory Pathway in Mouse Mesangial Cells

In patients with chronic kidney disease, the abnormal activation of inflammatory pathways is usually an important factor leading to renal fibrosis and further deterioration of renal function. Finding effective intervention targets of the inflammatory signaling pathway is an important way to treat chronic kidney disease. As a newly discovered lysosomal membrane protein, the correlation between SID1 transmembrane family member 2 (Sidt2) and the inflammatory signaling pathway has not been reported. The aim of this study was to investigate the effect of Sidt2 on inflammation by inhibiting the expression of the Sidt2 gene in a mouse mesangial cell line mediated by a lentiviral CRISPR/Cas9 vector. Hematoxylin and eosin staining and microscopy found that the mesangial cells lost their normal morphology after inhibiting the expression of Sidt2, showing that the cell body became smaller, the edge between the cells was unclear, and part of the nucleus was pyknotic and fragmented, appearing blue-black. The expressions of IKK β, p-IKK α/β, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the NF-κB pathway of the Sidt2^−/− group were higher than those of the Sidt2^+/+ group. p-Jak2 and IL6 increased in the Jak/Stat pathway, and p-ERK and p-P38 increased in the MAPK pathway. The expressions of IKK β, p-IKK α/β, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the NF-κB pathway of the Sidt2^+/++LPS group were significantly higher than those in the Sidt2^+/+ group. The expressions of IKK β, p-IKK α/β, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the Sidt2^−/−+LPS group were higher than those in the Sidt2^−/− group. The expressions of p-IKK α/β, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the Sidt2^−/−+LPS group were higher than those in the Sidt2^+/++LPS group. In the Jak/Stat pathway, the protein expressions of p-Jak2 and IL6 in the Sidt2^+/++LPS group were higher than those in the Sidt2^+/+ group. The expressions of p-Jak2 and IL6 in the Sidt2^−/−+LPS group were higher than those in the Sidt2^−/− group. The expressions of p-Jak2 and IL6 in the Sidt2^−/−+LPS group were higher than those in the Sidt2^+/++LPS group. The expressions of p-JNK, p-ERK, p-P38, and ERK in the MAPK pathway in the Sidt2^+/++LPS group were higher than those in the Sidt2^+/+ group. The expressions of p-JNK, p-ERK, p-P38, and ERK in the Sidt2^−/−+LPS group were higher than those in the Sidt2^−/− group. The expressions of p-JNK, p-ERK, p-P38, and ERK in the Sidt2^−/−+LPS group were higher than those in the Sidt2^+/++LPS group. These data suggested that deletion of the Sidt2 gene changed the three inflammatory signal pathways, eventually leading to the damage of glomerular mesangial cells in mice.

Identification of histone deacetylase 8 as a novel therapeutic target for renal fibrosis

Histone deacetylases (HDACs) have been shown to alleviate renal fibrosis, however, the role of individual HDAC isoforms in this process is poorly understood. In this study, we examined the role of HDAC8 in the development of renal fibrosis and partial epithelial-mesenchymal transitions (EMT). In a murine model of renal fibrosis induced by unilateral ureteral obstruction (UUO), HDAC8 was primarily expressed in renal tubular epithelial cells and time-dependently upregulated. This occurred in parallel with the deacetylation of cortactin, a nonhistone substrate of HDAC8, and increased expression of three fibrotic markers: α-smooth muscle actin, collagen 1, and fibronectin. Administration of PCI34051, a highly selective inhibitor of HDAC8, restored acetylation of contactin and reduced expression of those proteins. PCI34051 treatment also reduced the number of renal tubular epithelial cells arrested at the G2/M phase of the cell cycle and suppressed phosphorylation of Smad3, STAT3, β-catenin, and expression of Snail after ureteral obstruction. In contrast, HDAC8 inhibition reversed UUO-induced downregulation of BMP7 and Klotho, two renoprotective proteins. In cultured murine proximal tubular cells, treatment with PCI34051 or specific HDAC8 siRNA was also effective in inhibiting transforming growth factor β1 (TGFβ1)-induced deacetylation of contactin, EMT, phosphorylation of Smad3, STAT3, and β-catenin, upregulation of Snail, and downregulation of BMP7 and Klotho. Collectively, these results suggest that HDAC8 activation is required for the EMT and renal fibrogenesis by activation of multiple profibrotic signaling and transcription factors, and suppression of antifibrotic proteins. Therefore, targeting HDAC8 may be novel therapeutic approach for treatment of renal fibrosis.

Targeting the progression of chronic kidney disease

Chronic kidney disease (CKD) is a devastating condition that is reaching epidemic levels owing to the increasing prevalence of diabetes mellitus, hypertension and obesity, as well as ageing of the population. Regardless of the underlying aetiology, CKD is slowly progressive and leads to irreversible nephron loss, end-stage renal disease and/or premature death. Factors that contribute to CKD progression include parenchymal cell loss, chronic inflammation, fibrosis and reduced regenerative capacity of the kidney. Current therapies have limited effectiveness and only delay disease progression, underscoring the need to develop novel therapeutic approaches to either stop or reverse progression. Preclinical studies have identified several approaches that reduce fibrosis in experimental models, including targeting cytokines, transcription factors, developmental and signalling pathways and epigenetic modulators, particularly microRNAs. Some of these nephroprotective strategies are now being tested in clinical trials. Lessons learned from the failure of clinical studies of transforming growth factor β1 (TGFβ1) blockade underscore the need for alternative approaches to CKD therapy, as strategies that target a single pathogenic process may result in unexpected negative effects on simultaneously occurring processes. Additional promising avenues include preventing tubular cell injury and anti-fibrotic therapies that target activated myofibroblasts, the main collagen-producing cells.

Inhibition of STAT3 in tubular epithelial cells prevents kidney fibrosis and nephropathy in STZ-induced diabetic mice

Recent evidences indicate that signal transducer and activator of transcription 3 (STAT3) is one of the crucial signaling pathways in the progression of diabetic nephropathy (DN). Here, we investigated the hypothesis that pharmacological blockade of STAT3 limits the progression of DN. Treatment with selective STAT3 inhibitor, S3I-201 for 16 weeks significantly attenuated kidney injuries in streptozotocin (STZ) induced diabetic mice, associated with downregulated expression of TGF-β1, ACE/AT1, and VEGF in diabetic mouse kidneys. Similar results were confirmed using genetic knockdown of STAT3 in mouse kidneys by injections of AAV2 expressing STAT3 shRNA in diabetic mouse. Further, STAT3 localization in kidney tissue was evaluated using immunofluorescent double-staining analysis, which indicated that STAT3 expression was mainly in the tubular epithelial cells. As expected, in renal tubular epithelial NRK-52E cells, high glucose (HG)-induced overexpression of TGF-β1, ACE/AT1, and VEGF were abrogated by S3I-201 pretreatment, as well as by genetic knockdown of STAT3 using specific siRNA sequence. This study found that renal tubular epithelial cells contributed to STAT3-mediated progression of DN and provided the first evidence that pharmacological inhibition of STAT3 attenuates DN.

The PPARγ agonist pioglitazone prevents TGF-β induced renal fibrosis by repressing EGR-1 and STAT3

Background

It has been proposed that peroxisome proliferator-activated receptor-γ (PPARγ) agonists might reduce renal fibrosis, however, several studies had contradictory results. Moreover, the possible interaction of TGF-β₁, PPARγ, and transcription factors in renal fibrosis have not been investigated. We hypothesized that oral pioglitazone treatment would inhibit TGF-β–driven renal fibrosis and its progression, by modulating profibrotic transcription factors in TGF-β₁ transgenic mice.

Methods

Male C57Bl/6 J mice (control, CTL, n = 14) and TGF-β overexpressing transgenic mice (TGFβ, n = 14, having elevated plasma TGF-β₁ level) were divided in two sets at 10 weeks of age. Mice in the first set were fed with regular rodent chow (CTL and TGFβ, n = 7/group). Mice in the second set were fed with chow containing pioglitazone (at a dose of 20 mg/kg/day, CTL + Pio and TGFβ+Pio, n = 7/group). After 5 weeks of treatment, blood pressure was assessed and urine samples were collected, and the kidneys were analyzed for histology, mRNA and protein expression.

Results

TGF-β₁ induced glomerulosclerosis and tubulointerstitial damage were significantly reduced by pioglitazone. Pioglitazone inhibited renal mRNA expression of all the profibrotic effectors: type-III collagen, TGF-β₁, CTGF and TIMP-1, and alike transcription factors cFos/cJun and protein expression of EGR-1, and STAT3 protein phosphorylation.

Conclusions

Oral administration of PPARγ agonist pioglitazone significantly reduces TGF-β₁-driven renal fibrosis, via the attenuation of EGR-1, STAT3 and AP-1. This implies that PPARγ agonists might be effective in the treatment of chronic kidney disease patients.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1431-x) contains supplementary material, which is available to authorized users.

A high-fat diet rich in corn oil induces cardiac fibrosis in rats by activating JAK2/STAT3 and subsequent activation of ANG II/TGF-1β/Smad3 pathway: The role of ROS and IL-6 trans-signaling

This study compared the effect of low-fat diet (LFD) and high-fat diet rich in corn oil (HFD-CO) on left ventricular (LV) fibrosis in rats and examined their effect of angiotensin II (ANG II), JAK/STAT, and TGF-1β/smad3 pathways. As compared to LFD which didn't affect any of the measured parameters, HFD-CO-induced type 2 diabetes phenotype and increased LV collagen synthesis. Mechanistically, it increased LV levels of ROS, ANG II, ACE, IL-6, s-IL-6Rα, TGF-β1, Smad-3, and activities of JAK1/2 and STAT1/3. AG490, a JAK2 inhibitor, partially ameliorated these effect while Losartan, an AT1 inhibitor completely abolished collagen synthesis. However, with both treatments, levels of ANG II, IL-6, and s-IL-6Rα, and activity of JAK1/STAT3 remained high, all of which were normalized by co-administration of NAC or IL-6 neutralizing antibody. In conclusion: HFD-CO enhances LV collage synthesis by activation of JAK1/STAT3/ANG II/TGF-1β/smad3 pathway. PRACTICAL APPLICATIONS: We report that chronic consumption of a high-fat diet rich in corn oil (HFD-CO) induces diabetes mellitus phenotype 2 associated with left ventricular (LV) cardiac fibrosis in rats. The findings of this study show that HFD-CO, and through the increasing generation of ROS and IL-6 levels and shedding, could activate LV JAK1/2-STAT1/3  and  renin-angiotensin system (RAS) signaling pathways, thus creating a positive feedback between the two which ultimately leads to activation of TGF-1β/Smad3 fibrotic pathway. Herein, we also report a beneficial effect of the antioxidant, NAC, or IL-6 neutralizing antibody in preventing such adverse effects of such HFD-CO. However, this presents a warning message to the current sudden increase in idiopathic cardiac disorders, especially with the big shift in our diets toward n-6 PUFA.

Inhibition of JAK2/STAT3 and activation of caspase‑9/3 are involved in KYS05090S‑induced apoptosis in ovarian cancer cells

To overcome the poor prognosis of patients with ovarian cancer, attempting to target ovarian cancer with effective antitumor compounds has been conducted for numerous years. Although the 3,4‑dihydroquinazoline derivative KYS05090S was known to exert antitumor effects in A549 and ovarian cancer cells by inhibition of T‑type Ca2+ channels, the complete underlying antitumor mechanism of this compound remains unclear. Thus, in the present study, the potential apoptotic mechanism of KYS05090S was elucidated in SKOV3 and OVCAR3 ovarian cancer cells. KYS05090S exerted significant cytotoxicity in SKOV3 and OVCAR3 ovarian cancer cells, and also increased the number of apoptotic bodies, and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling positive cells and the sub‑G1 population as a feature of apoptosis. Consistently, KYS05090S induced cleavage of poly(ADP‑ribose) polymerase and caspase‑9/3 in ovarian cancer cells. Notably, KYS05090S attenuated the expression of anti‑apoptotic proteins, including cyclin D1 and B‑cell lymphoma‑2 (Bcl‑2), and reduced the phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) in ovarian cancer cells. Additionally, KYS05090S blocked the nuclear translocation of STAT3 and suppressed the signaling of JAK2/STAT3 in interleukin‑6‑treated SKOV3 cells, as a STAT3 activator. Overall, these observations indicated that inhibition of JAK2/STAT3 signaling and activation of caspase‑9/3 are critically involved in the effects of KYS05090S on apoptosis in ovarian cancer types, and the compound may be beneficial as a potent antitumor agent.

PTPN2 improved renal injury and fibrosis by suppressing STAT-induced inflammation in early diabetic nephropathy

Diabetic nephropathy (DN) is a chronic inflammatory disease triggered by disordered metabolism. Recent studies suggested that protein tyrosine phosphatase non‐receptor type 2 (PTPN2) could ameliorate metabolic disorders and suppress inflammatory responses. This study investigated PTPN2's role in modulating DN and the possible cellular mechanisms involved. In a mouse model combining hyperglycaemia and hypercholesterolaemia (streptozotocin diabetic, ApoE^‐/‐ mice), mice showed severe insulin resistance, renal dysfunction, micro‐inflammation, subsequent extracellular matrix expansion and decreased expression of PTPN2. We found that mice treated with PTPN2 displayed reduced serum creatinine, serum BUN and proteinuria. PTPN2 gene therapy markedly attenuated metabolic disorders and hyperglycaemia. In addition, PTPN2 gene transfer significantly suppressed renal activation of signal transducers and activators of transcription (STAT), STAT‐dependent pro‐inflammatory and pro‐fibrotic genes expression, and influx of lymphocytes in DN, indicating anti‐inflammatory effects of PTPN2 by inhibiting the activation of STAT signalling pathway in vivo. Furthermore, PTPN2 overexpression inhibited the high‐glucose induced phosphorylation of STAT, target genes expression and proliferation in mouse mesangial and tubuloepithelial cells, suggesting that the roles of PTPN2 on STAT activation was independent of glycaemic changes. Our results demonstrated that PTPN2 gene therapy could exert protective effects on DN via ameliorating metabolic disorders and inhibiting renal STAT‐dependent micro‐inflammation, suggesting its potential role for treatment of human DN.

CXCL6 Promotes Renal Interstitial Fibrosis in Diabetic Nephropathy by Activating JAK/STAT3 Signaling Pathway

In this study the role of CXCL6 in diabetic nephropathy (DN) was investigated. It was found to be overexpression in DN patients and DN rat model. And the expression of fibrosis-related cytokines was consistent with the expression of CXCL6. High glucose significantly increased the proliferation of rat renal fibroblasts NRK-49F cell and the expression of CXCL6. Knockdown of CXCL6 ameliorated the pro-proliferation effect of high glucose and decreased the expression of fibrosis-related cytokines, while CXCL6 overexpression exhibited the opposite phenomenon. Gene set enrichment analysis, Western blot and ELISA showed that Janus kinase-signal transducer and activator of transcription (JAK-STAT) and CYTOKINE_CYTOKINE_RECEPTOR_INTERACTION signaling pathways were correlative with CXCL6. This data indicates that CXCL6 may promote fibrosis-related factors to accelerate the development of DN renal interstitial fibrosis by activating JAK/STAT3 signaling pathway. CXCL6 is promising to be a potential novel therapeutic target and candidate biomarker for JAK/STAT3 signaling for the treatment of DN.

Molecular mechanisms of protein-bound uremic toxin-mediated cardiac, renal and vascular effects: underpinning intracellular targets for cardiorenal syndrome therapy

Cardiorenal syndrome (CRS) remains a global health burden with a lack of definitive and effective treatment. Protein-bound uremic toxin (PBUT) overload has been identified as a non-traditional risk factor for cardiac, renal and vascular dysfunction due to significant albumin-binding properties, rendering these solutes non-dialyzable upon the state of irreversible kidney dysfunction. Although limited, experimental studies have investigated possible mechanisms in PBUT-mediated cardiac, renal and vascular effects. The ultimate aim is to identify relevant and efficacious targets that may translate beneficial outcomes in disease models and eventually in the clinic. This review will expand on detailed knowledge on mechanisms involved in detrimental effects of PBUT, specifically affecting the heart, kidney and vasculature, and explore potential effective intracellular targets to abolish their effects in CRS initiation and/or progression.

Roles of Mesenchymal Stem Cells in Tissue Regeneration and Immunomodulation

Mesenchymal stem cells are classified as multipotent stem cells, due to their capability to transdifferentiate into various lineages that develop from mesoderm. Their popular appeal as cell-based therapy was initially based on the idea of their ability to restore tissue because of their differentiation potential in vitro; however, the lack of evidence of their differentiation to target cells in vivo led researchers to focus on their secreted trophic factors and their role as potential powerhouses on regulation of factors under different immunological environments and recover homeostasis. To date there are more than 800 clinical trials on humans related to MSCs as therapy, not to mention that in animals is actively being applied as therapeutic resource, though it has not been officially approved as one. But just as how results from clinical trials are important, so is to reveal the biological mechanisms involved on how these cells exert their healing properties to further enhance the application of MSCs on potential patients. In this review, we describe characteristics of MSCs, evaluate their benefits as tissue regenerative therapy and combination therapy, as well as their immunological properties, activation of MSCs that dictate their secreted factors, interactions with other immune cells, such as T cells and possible mechanisms and pathways involved in these interactions.

Hydrogen sulfide attenuates myocardial fibrosis in diabetic rats through the JAK/STAT signaling pathway

The aim of the present study was to determine the role of hydrogen sulfide (H₂S) in improving myocardial fibrosis and its effects on oxidative stress, endoplasmic reticulum (ER) stress and cell apoptosis in diabetic rats, by regulating the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway. A total of 40 male Sprague-Dawley rats were randomly divided into four groups (n=10) as follows: Normal (control group), diabetes mellitus [streptozotocin (STZ) group], diabetes mellitus treated with H₂S (STZ + H₂S group), and normal rats treated with H₂S (H₂S group). Diabetes in rats was induced by intra-peritoneal (i.p.) injection of STZ at a dose of 40 mg/kg. NaHS (100 µmol/kg, i.p.), which was used as an exogenous donor of H₂S, was administered to rats in the STZ + H₂S and H₂S groups. After 8 weeks, the pathological morphological changes in myocardial fibers were observed following hematoxylin and eosin and Masson's trichrome staining. Apoptosis of myocardial tissue was analyzed by the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Oxidative stress was evaluated through detecting the content of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), glutathione (GSH) and superoxide dismutase (SOD) in the myocardial cells by ELISA. The expression of collagen III, matrix metalloproteinase (MMP)8, MMP14, tissue inhibitor of metalloproteinase (TIMP)2, transforming growth factor (TGF)-β, cystathionine-γ-lyase (CSE), eukaryotic initiation factor 2α (eIF2α), GRP94, Bcl-2, caspase-3, tumor necrosis factor (TNF)-α, nuclear factor-κB (NF-κB) and proteins related to the JAK/STAT pathway, was detected by western blot analysis. The results indicated that the array of myocardial cells was markedly disordered in STZ group rats; compared with the control group, both myocardial interstitial fibrosis and the deposition of collagen III were increased. Furthermore, the expression ratio of MMPs/TIMPs was dysregulated, while the expression levels of TGF-β, eIF2α, GRP94, caspase-3, TNF-α, NF-κB, MDA and 4-HNE were significantly increased. Furthermore, the expressions of JAK-1/2 and STAT1/3/5/6 were also markedly upregulated, while those of CSE, SOD, GSH and Bcl-2 were downregulated. Compared with the STZ group, these changes were reversed in the STZ + H₂S group. The results of the present study demonstrated that H₂S can improve myocardial fibrosis in diabetic rats, and the underlying mechanism may be associated with the downregulation of the JAK/STAT signaling pathway, thereby suppressing oxidative stress and ER stress, inflammatory reaction and cell apoptosis.

Acute downregulation of miR-155 leads to a reduced collagen synthesis through attenuating macrophages inflammatory factor secretion by targeting SHIP1

Fibrosis, tightly associated with fibroblasts collagen synthesis, is related closely with inflammatory response. Our previously study found that acute downregulation of miR-155 at wound sites leads to a reduced fibrosis, however its particular mechanism is unclear. Herein, we aimed to explore the mechanism of miR-155 in reducing fibrosis. We first found that down-regulation of miR-155 inhibited macrophages transforming growth factor-β1 (TGF-β1) and IL-1β secretion. Next, we found that co-cultured with macrophages increased the proliferation and collagen synthesis of fibroblasts, and downregulation of miR-155 in macrophages could effectively attenuate the accelerative effects. We further identified SH2 domain containing inositol-5-phosphatase 1 (SHIP1) as a direct target of miR-155 in macrophages, and the expression of SHIP1 was negatively correlated with the level of miR-155. We further confirmed that PI3K/Akt pathway was involved in this process. Last, we found that downregulation of miR-155 leads to a reduced fibrosis in sever burn rat. Taken together, these results indicate that down-regulation of miR-155 leads to a reduced fibroblasts proliferation and collagen synthesis through attenuating macrophages TGF-β1 and IL-1β secretion by targeting SHIP1 via PI3K/Akt pathway, suggesting its potential therapeutic effects on the treatment of skin fibrosis.

Connective tissue growth factor induces renal fibrosis via epidermal growth factor receptor activation

Connective tissue growth factor (CCN2/CTGF) is a matricellular protein that is overexpressed in progressive human renal diseases, mainly in fibrotic areas. In vitro studies have demonstrated that CCN2 regulates the production of extracellular matrix (ECM) proteins and epithelial-mesenchymal transition (EMT), and could therefore contribute to renal fibrosis. CCN2 blockade ameliorates experimental renal damage, including diminution of ECM accumulation. We have reported that CCN2 and its C-terminal degradation product CCN2(IV) bind to epidermal growth factor receptor (EGFR) to modulate renal inflammation. However, the receptor involved in CCN2 profibrotic actions has not been described so far. Using a murine model of systemic administration of CCN2(IV), we have unveiled a fibrotic response in the kidney that was diminished by EGFR blockade. Additionally, in conditional CCN2 knockout mice, renal fibrosis elicited by folic acid-induced renal damage was prevented, and this was linked to inhibition of EGFR pathway activation. Our in vitro studies demonstrated a direct effect of CCN2 via the EGFR pathway on ECM production by fibroblasts and the induction of EMT in tubular epithelial cells. Our studies clearly show that the EGFR regulates CCN2 fibrotic signalling in the kidney, and suggest that EGFR pathway blockade could be a potential therapeutic option to block CCN2-mediated profibrotic effects in renal diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

PDGF signaling pathway in hepatic fibrosis pathogenesis and therapeutics (Review)

The platelet‑derived growth factor (PDFG) signaling pathway exerts persistent activation in response to a variety of stimuli and facilitates the progression of hepatic fibrosis. Since this pathway modulates a broad spectrum of cellular processes, including cell growth, differentiation, inflammation and carcinogenesis, it has emerged as a therapeutic target for hepatic fibrosis and liver‑associated disorders. The present review exhibits the current knowledge of the role of the PDGF signaling pathway and its pathological profiles in hepatic fibrosis, and assesses the potential of inhibitors which have been investigated in the experimental hepatic fibrosis model, in addition to the clinical challenges associated with these inhibitors.

The pathogenesis of diclofenac induced immunoallergic hepatitis in a canine model of liver injury

Hypersensitivity to non-steroidal anti-inflammatory drugs is a common adverse drug reaction and may result in serious inflammatory reactions of the liver. To investigate mechanism of immunoallergic hepatitis beagle dogs were given 1 or 3 mg/kg/day (HD) oral diclofenac for 28 days. HD diclofenac treatment caused liver function test abnormalities, reduced haematocrit and haemoglobin but induced reticulocyte, WBC, platelet, neutrophil and eosinophil counts. Histopathology evidenced hepatic steatosis and glycogen depletion, apoptosis, acute lobular hepatitis, granulomas and mastocytosis. Whole genome scans revealed 663 significantly regulated genes of which 82, 47 and 25 code for stress, immune response and inflammation. Immunopathology confirmed strong induction of IgM, the complement factors C3&B, SAA, SERPING1 and others of the classical and alternate pathway. Alike, marked expression of CD205 and CD74 in Kupffer cells and lymphocytes facilitate antigen presentation and B-cell differentiation. The highly induced HIF1A and KLF6 protein expression in mast cells and macrophages sustain inflammation. Furthermore, immunogenomics discovered 24, 17, 6 and 11 significantly regulated marker genes to hallmark M1/M2 polarized macrophages, lymphocytic and granulocytic infiltrates; note, the latter was confirmed by CAE staining. Other highly regulated genes included alpha-2-macroglobulin, CRP, hepcidin, IL1R1, S100A8 and CCL20. Diclofenac treatment caused unprecedented induction of myeloperoxidase in macrophages and oxidative stress as shown by SOD1/SOD2 immunohistochemistry. Lastly, bioinformatics defined molecular circuits of inflammation and consisted of 161 regulated genes.

Altogether, the mechanism of diclofenac induced liver hypersensitivity reactions involved oxidative stress, macrophage polarization, mastocytosis, complement activation and an erroneous programming of the innate and adaptive immune system.

TSS-Seq analysis of low pH-induced gene expression in intercalated cells in the renal collecting duct

Metabolic acidosis often results from chronic kidney disease; in turn, metabolic acidosis accelerates the progression of kidney injury. The mechanisms for how acidosis facilitates kidney injury are not fully understood. To investigate whether low pH directly affects the expression of genes controlling local homeostasis in renal tubules, we performed transcription start site sequencing (TSS-Seq) using IN-IC cells, a cell line derived from rat renal collecting duct intercalated cells, with acid loading for 24 h. Peak calling identified 651 up-regulated and 128 down-regulated TSSs at pH 7.0 compared with those at pH 7.4. Among them, 424 and 38 TSSs were ≥ 1.0 and ≤ -1.0 in Log₂ fold change, which were annotated to 193 up-regulated and 34 down-regulated genes, respectively. We used gene ontology analysis and manual curation to profile the up-regulated genes. The analysis revealed that many up-regulated genes are involved in renal fibrosis, implying potential molecular mechanisms induced by metabolic acidosis. To verify the activity of the ubiquitin-proteasome system (UPS), a candidate pathway activated by acidosis, we examined the expression of proteins from cells treated with a proteasome inhibitor, MG132. The expression of ubiquitinated proteins was greater at pH 7.0 than at pH 7.4, suggesting that low pH activates the UPS. The in vivo study demonstrated that acid loading increased the expression of ubiquitin proteins in the collecting duct cells in mouse kidneys. Motif analysis revealed Egr1, the mRNA expression of which was increased at low pH, as a candidate factor that possibly stimulates gene expression in response to low pH. In conclusion, metabolic acidosis can facilitate renal injury and fibrosis during kidney disease by locally activating various pathways in the renal tubules.

Mesenchymal stem cells protect against obstruction-induced renal fibrosis by decreasing STAT3 activation and STAT3-dependent MMP-9 production

STAT3 is a transcription factor implicated in renal fibrotic injury, but the role of STAT3 in mesenchymal stem cell (MSC)-induced renoprotection during renal fibrosis remains unknown. We hypothesized that MSCs protect against obstruction-induced renal fibrosis by downregulating STAT3 activation and STAT3-induced matrix metalloproteinase-9 (MMP-9) expression. Male Sprague-Dawley rats underwent renal arterial injection of vehicle or MSCs (1 × 10⁶/rat) immediately before sham operation or induction of unilateral ureteral obstruction (UUO). The kidneys were harvested after 4 wk and analyzed for collagen I and III gene expression, collagen deposition (Masson's trichrome), fibronectin, α-smooth muscle actin, active STAT3 (p-STAT3), MMP-9, and tissue inhibitor of matrix metalloproteinases 1 (TIMP-1) expression. In a separate arm, the STAT3 inhibitor S3I-201 (10 mg/kg) vs. vehicle was administered to rats intraperitoneally just after induction of UUO and daily for 14 days thereafter. The kidneys were harvested after 2 wk and analyzed for p-STAT3 and MMP-9 expression, and collagen and fibronectin deposition. Renal obstruction induced a significant increase in collagen, fibronectin, α-SMA, p-STAT3, MMP-9, and TIMP-1 expression while exogenously administered MSCs significantly reduced these indicators of obstruction-induced renal fibrosis. STAT3 inhibition with S3I-201 significantly reduced obstruction-induced MMP-9 expression and tubulointerstitial fibrosis. These results demonstrate that MSCs protect against obstruction-induced renal fibrosis, in part, by decreasing STAT3 activation and STAT3-dependent MMP-9 production.

Myrciaria cauliflora extract improves diabetic nephropathy via suppression of oxidative stress and inflammation in streptozotocin-nicotinamide mice

Myrciaria cauliflora is a functional food rich in anthocyanins, possessing antioxidative and anti-inflammatory properties. Our previous results demonstrated M. cauliflora extract (MCE) had beneficial effects in diabetic nephropathy (DN) and via the inhibition of Ras/PI3K/Akt and kidney fibrosis-related proteins. The purpose of this study was to assess the benefit of MCE in diabetes associated with kidney inflammation and glycemic regulation in streptozotocin–nicotinamide (STZ/NA)-induced diabetic mice. Compared with the untreated diabetic group, MCE significantly improved blood glucose and serum biochemical characteristic levels. Exposure to MCE increased antioxidative enzyme activity and diminished reactive oxygen synthesis. Mice receiving MCE supplementation had reduced intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), monocyte chemoattractant protein 1 (MCP-1), colony stimulating factor 1 (CSF-1), interleukin-1β (IL-1β), IL-6 and tumor necrosis factor α (TNF-α) levels compared to the untreated diabetic mice. Inflammatory and fibrotic related proteins such as collagen IV, fibronectin, Janus kinase (JAK), phosphorylated signal transducer and activator of transcription 3 (STAT3), protein kinase C beta (PKC-β), and nuclear factor kappa B (NF-κB) were also inhibited by MCE treatment in STZ/NA mice. These results suggest that MCE may be used as a hypoglycemic agent and antioxidant in Type 2 diabetic mice.

Suppressor of Cytokine Signaling-1 Peptidomimetic Limits Progression of Diabetic Nephropathy

Diabetes is the main cause of CKD and ESRD worldwide. Chronic activation of Janus kinase and signal transducer and activator of transcription (STAT) signaling contributes to diabetic nephropathy by inducing genes involved in leukocyte infiltration, cell proliferation, and extracellular matrix accumulation. This study examined whether a cell-permeable peptide mimicking the kinase-inhibitory region of suppressor of cytokine signaling-1 (SOCS1) regulatory protein protects against nephropathy by suppressing STAT-mediated cell responses to diabetic conditions. In a mouse model combining hyperglycemia and hypercholesterolemia (streptozotocin diabetic, apoE-deficient mice), renal STAT activation status correlated with the severity of nephropathy. Notably, compared with administration of vehicle or mutant inactive peptide, administration of the SOCS1 peptidomimetic at either early or advanced stages of diabetes ameliorated STAT activity and resulted in reduced serum creatinine level, albuminuria, and renal histologic changes (mesangial expansion, tubular injury, and fibrosis) over time. Mice treated with the SOCS1 peptidomimetic also exhibited reduced kidney leukocyte recruitment (T lymphocytes and classic M1 proinflammatory macrophages) and decreased expression levels of proinflammatory and profibrotic markers that were independent of glycemic and lipid changes. In vitro, internalized peptide suppressed STAT activation and target gene expression induced by inflammatory and hyperglycemic conditions, reduced migration and proliferation in mesangial and tubuloepithelial cells, and altered the expression of cytokine-induced macrophage polarization markers. In conclusion, our study identifies SOCS1 mimicking as a feasible therapeutic strategy to halt the onset and progression of renal inflammation and fibrosis in diabetic kidney disease.

Combined administration of propranolol + AG490 offers better effects on portal hypertensive rats with cirrhosis

BACKGROUND AND AIMS

AG490, the specific inhibitor of JAK2/STAT3 signaling, has been shown to decrease portal pressure, splanchnic hyperdynamic circulation and liver fibrosis in cirrhotic rats. Nonselective betablockers such as propranolol are the only drugs recommended in the treatment of portal hypertension. The aim of this study was to explore the combinative effect of treatment with propranolol and AG490 on portal hypertension.

METHODS

Rats induced by common bile duct ligation were treated with vehicle, AG490, propranolol, or AG490 + propranolol for 2 weeks. Hemodynamics parameters were assessed. Expressions of phospho-STAT3 protein and its down-regulated cytokines in splanchnic organs were detected by ELISA or western blot. Lipopolysaccharide binding protein (LBP) and IL-6 were assessed by ELISA or western blot. Characterization of liver and mesentery was performed by histological analyses.

RESULTS

Highly expressed phospho-STAT3 protein in cirrhotic rats could successfully be inhibited by AG490 or AG490 + propranolol treatments but not by propranolol alone. Both AG490 and propranolol significantly reduced portal pressure and hyperdynamic splanchnic circulation, and combination of AG490 and propranolol achieved an additive effect than with either drug alone. AG490, alone or in combination with propranolol, inhibited liver fibrosis, splenomegaly and splanchnic angiogenesis. Increased markers of bacterial translocation (LBP and IL6) were greatly reduced by propranolol but not by AG490.

CONCLUSIONS

The combination of propranolol and AG490 caused a greater improvement of portal hypertension and might therefore offer a potentially promising therapy in the portal hypertension treatment.

Peroxiredoxin 5 Protects TGF-β Induced Fibrosis by Inhibiting Stat3 Activation in Rat Kidney Interstitial Fibroblast Cells

Renal fibrosis is a common final pathway of end-stage kidney disease which is induced by aberrant accumulation of myofibroblasts. This process is triggered by reactive oxygen species (ROS) and proinflammatory cytokines generated by various source of injured kidney cells. Peroxiredoxin 5 (Prdx5) is a thiol-dependent peroxidase that reduces oxidative stress by catalyzing intramolecular disulfide bonds. Along with its antioxidant effects, expression level of Prdx5 also was involved in inflammatory regulation by immune stimuli. However, the physiological effects and the underlying mechanisms of Prdx5 in renal fibrosis have not been fully characterized. Sprague-Dawley rats were subjected to unilateral ureteral obstruction (UUO) for 1 or 7 days. For the in vitro model, NRK49F cells, a rat kidney interstitial fibroblast cell lines, were treated with transforming growth factor β (TGF-β) for 0, 1, 3, or 5 days. To access the involvement of its peroxidase activity in TGF-β induced renal fibrosis, wild type Prdx5 (WT) and double mutant Prdx5 (DM), converted two active site cysteines at Cys 48 and Cys 152 residue to serine, were transiently expressed in NRK49F cells. The protein expression of Prdx5 was reduced in UUO kidneys. Upregulation of fibrotic markers, such as fibronectin and alpha-smooth muscle actin (α-SMA), declined at 5 days in time point of higher Prdx5 expression in TGF-β treated NRK49F cells. The overexpression of wild type Prdx5 by transient transfection in NRK49F cells attenuated the TGF-β induced upregulation of fibronectin and α-SMA. On the other hand, the transient transfection of double mutant Prdx5 did not prevent the activation of fibrotic markers. Overexpression of Prdx5 also suppressed the TGF-β induced upregulation of Stat3 phosphorylation, while phosphorylation of Smad 2/3 was unchanged. In conclusion, Prdx5 protects TGF-β induced fibrosis in NRK49F cells by modulating Stat3 activation in a peroxidase activity dependent manner.

Cinnamaldehyde and nitric oxide attenuate advanced glycation end products-induced the Jak/STAT signaling in human renal tubular cells

Cinnamaldehyde is a major and a bioactive compound isolated from the leaves of Cinnamomum osmophloeum kaneh. It possesses anti-diabetic properties in vitro and in vivo and has anti-inflammatory and anti-cancer effects. To explore whether cinnamaldehyde was linked to altered advanced glycation end products (AGE)-mediated diabetic nephropathy, the molecular mechanisms of cinnamaldehyde responsible for inhibition of AGE-reduced nitric oxide (NO) bioactivity in human renal proximal tubular cells were examined. We found that raising the ambient AGE concentration causes a dose-dependent decrease in NO generation. Cinnamaldehyde significantly reverses AGE-inhibited NO generation and induces high levels of cGMP synthesis and PKG activation. Treatments with cinnamaldehyde, the NO donor S-nitroso-N-acetylpenicillamine, and the JAK2 inhibitor AG490 markedly attenuated AGE-inhibited NOS protein levels and NO generation. Moreover, AGE-induced the JAK2-STAT1/STAT3 activation, RAGE/p27(Kip1) /collagen IV protein levels, and cellular hypertrophy were reversed by cinnamaldehyde. The ability of cinnamaldehyde to suppress STAT activation was also verified by the observation that it significantly increased SCOS-3 protein level. These findings indicate for the first time that in the presence of cinnamaldehyde, the suppression of AGE-induced biological responses is probably mediated by inactivating the JAK2-STAT1/STAT3 cascade or activating the NO pathway.

Redox Signaling in Diabetic Nephropathy: Hypertrophy versus Death Choices in Mesangial Cells and Podocytes

This review emphasizes the role of oxidative stress in diabetic nephropathy, acting as trigger, modulator, and linker within the complex network of pathologic events. It highlights key molecular pathways and new hypothesis in diabetic nephropathy, related to the interferences of metabolic, oxidative, and inflammatory stresses. Main topics this review is addressing are biomarkers of oxidative stress in diabetic nephropathy, the sources of reactive oxygen species (mitochondria, NADPH-oxidases, hyperglycemia, and inflammation), and the redox-sensitive signaling networks (protein kinases, transcription factors, and epigenetic regulators). Molecular switches deciding on the renal cells fate in diabetic nephropathy are presented, such as hypertrophy versus death choices in mesangial cells and podocytes. Finally, the antioxidant response of renal cells in diabetic nephropathy is tackled, with emphasis on targeted therapy. An integrative approach is needed for identifying key molecular networks which control cellular responses triggered by the array of stressors in diabetic nephropathy. This will foster the discovery of reliable biomarkers for early diagnosis and prognosis, and will guide the discovery of new therapeutic approaches for personalized medicine in diabetic nephropathy.

Mefunidone attenuates tubulointerstitial fibrosis in a rat model of unilateral ureteral obstruction

BACKGROUND

Inflammation has a crucial role in renal interstitial fibrosis, which is the common pathway of chronic kidney diseases. Mefunidone (MFD) is a new compound which could effectively inhibit the proliferation of renal fibroblasts in vitro. However, the overall effect of Mefunidone in renal fibrosis remains unknown.

METHODS

Sprague-Dawley rats were randomly divided intro 6 groups: sham operation, unilateral ureteral obstruction (UUO), UUO/Mefunidone (25, 50, 100mg/kg/day) and UUO/PFD (500mg/kg/day). The rats were sacrificed respectively on days 3, 7, and 14 after the operation. Tubulointerstitial injury index, interstitial collagen deposition, expression of fibronectin (FN), α-smooth muscle actin (α-SMA), type I and III collagen and the number of CD3+ and CD68+ cells were determined. The expressions of proinflammatory cytokines, p-ERK, p-IκB, and p-STAT3 were measured in human renal proximal tubular epithelial cells of HK-2 or macrophages.

RESULTS

Mefunidone treatment significantly attenuated tubulointerstitial injury, interstitial collagen deposition, expression of FN, α-SMA, type I and III collagen in the obstructive kidneys, which correlated with significantly reduced the number of T cells and macrophages in the obstructive kidneys. Mechanistically, Mefunidone significantly inhibited tumor necrosis factor-α (TNF-α-) or lipopolysaccharide (LPS)-induced production of proinflammatory cytokines. This effect is possibly due to the inhibition of phosphorylation of ERK, IκB, and STAT3.

CONCLUSION

Mefunidone treatment attenuated tubulointerstitial fibrosis in a rat model of UUO, at least in part, through inhibition of inflammation.

Astaxanthin inhibits JAK/STAT-3 signaling to abrogate cell proliferation, invasion and angiogenesis in a hamster model of oral cancer

Identifying agents that inhibit STAT-3, a cytosolic transcription factor involved in the activation of various genes implicated in tumour progression is a promising strategy for cancer chemoprevention. In the present study, we investigated the effect of dietary astaxanthin on JAK-2/STAT-3 signaling in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model by examining the mRNA and protein expression of JAK/STAT-3 and its target genes. Quantitative RT-PCR, immunoblotting and immunohistochemical analyses revealed that astaxanthin supplementation inhibits key events in JAK/STAT signaling especially STAT-3 phosphorylation and subsequent nuclear translocation of STAT-3. Furthermore, astaxanthin downregulated the expression of STAT-3 target genes involved in cell proliferation, invasion and angiogenesis, and reduced microvascular density, thereby preventing tumour progression. Molecular docking analysis confirmed inhibitory effects of astaxanthin on STAT signaling and angiogenesis. Cell culture experiments with the endothelial cell line ECV304 substantiated the role of astaxanthin in suppressing angiogenesis. Taken together, our data provide substantial evidence that dietary astaxanthin prevents the development and progression of HBP carcinomas through the inhibition of JAK-2/STAT-3 signaling and its downstream events. Thus, astaxanthin that functions as a potent inhibitor of tumour development and progression by targeting JAK/STAT signaling may be an ideal candidate for cancer chemoprevention.

Ursolic acid ameliorates carbon tetrachloride-induced oxidative DNA damage and inflammation in mouse kidney by inhibiting the STAT3 and NF-κB activities

Ursolic acid (UA), a common pentacyclic triterpenoid compound, has been reported to have many benefits and medicinal properties. However, its protective effects against carbon tetrachloride (CCl4) induced injury in kidneys are not yet clear. In the current report, we investigated whether UA inhibited the oxidative stress and inflammation in the kidneys of CCl4 treated mice. Male ICR mice were injected with CCl4 with or without UA co-administration (25 and 50mg/kg intragastrically once daily) for six weeks. Our data showed that UA significantly prevented CCl4-induced nephrotoxicity in a dose-dependent manner, indicated by both diagnostic indicators of kidney damage and histopathological analysis. Moreover, CCl4-induced profound elevation of ROS and oxidative stress, as evidenced by the increase of lipid peroxidation level and the depletion of the total antioxidant capacity (TAC) level in the kidney, was suppressed by treatment with UA. UA also decreased 8-hydroxy-2-deoxyguanosine (one product of oxidative DNA damage) levels. Furthermore, protein expression by Western blot analysis showed that UA significantly decreased production of pro-inflammatory markers including tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-17 (IL-17) and cyclooxygenase-2 (COX-2) in CCl4-treated mouse kidney. In exploring the underlying mechanisms of UA action, we found that UA increased the phosphorylation of transcription 3 (STAT3), which in turn activated the nuclear factor kappa B (NF-kappaB) and the inflammatory cytokines in the kidneys. In conclusion, these results suggested that the inhibition of CCl4-induced inflammation by UA is due at least in part to its anti-oxidant activity and its ability to modulate the STAT3 and NF-κB signaling pathways.