Fluorofenidone attenuates oxidative stress and renal fibrosis in obstructive nephropathy via blocking NOX2 (gp91phox) expression and inhibiting ERK/MAPK signaling pathway

BMAL1 inhibits renal fibrosis and renal interstitial inflammation by targeting the ERK1/2/ELK-1/Egr-1 axis

RATIONALE

Renal fibrosis and renal interstitial inflammation due to hydronephrosis are associated with progressive chronic kidney disease (CKD). The clock gene BMAL1 is thought to be involved in various diseases, including hypertension, diabetes, etc. However, little is known about how BMAL1 regulates renal fibrosis and renal interstitial inflammation in obstructed kidneys.

METHODS

The expression level of BMAL1 in UUO was examined using the GEO database. Lentivirus, siRNA and adeno-associated virus were used to modulate BMAL1 levels in HK-2 cells and mouse kidney. qRT-PCR, immunofluorescence staining, histological analysis, ELISA and Western blot were used to determine the level of fibrin deposition and the release of inflammatory factors. Immunofluorescence staining and western blotting were used to examine the interaction between BMAL1 and the ERK1/2/ELK-1/Egr-1 axis.

RESULTS

Bioinformatics analysis and in vivo experiments in this study showed that the expression level of BMAL1 in UUO model kidneys was higher than that in normal kidneys. We then found that downregulation of BMAL1 promoted the production of extracellular matrix (ECM) proteins and proinflammatory factors in vivo and in vitro, whereas upregulation inhibited this process. In addition, we demonstrated that the ERK1/2/ELK-1/Egr-1 axis is an important pathway for BMAL1 to play a regulatory role, and the use of PD98059 abolished the promoting effect of down-regulation of BMAL1 on fibrosis and inflammation.

CONCLUSIONS

Our findings suggest that BAML1 can target the ERK1/2/ELK-1/Egr-1 axis to suppress fibrotic progression and inflammatory events in obstructed kidneys, thereby inhibiting the development of CKD.

Fluorofenidone Attenuates Renal Interstitial Fibrosis by Enhancing Autophagy and Retaining Mitochondrial Function

BACKGROUND

Fluorofenidone (AKF-PD) is a novel pyridone agent and has potent anti-NLRP3 inflammasome and anti-fibrotic activities. However, the mechanisms underlying its pharmacological actions are not fully understood.

METHODS

A renal fibrosis rat model was established by the unilateral ureteral obstruction (UUO) procedure and the rats were randomized and treated with, or without, AKF-PD for 3 and 7 days. The levels of renal fibrosis, NLRP3 inflammasome activation, mitochondrial function, and autophagy were tested in rat kidney tissues. Macrophages following lipopolysaccharides (LPS) and adenosine 5'-triphosphate (ATP) stimulation were examined by Western blot, spectrophotometry, and TEM.

RESULTS

Compared with the untreated UUO rats, AKF-PD treatment significantly mitigated the UUO procedure-induced renal fibrosis in rats. AKF-PD treatment decreased mitochondrial dysfunction and IL-Iβ and caspase-1 expression in rat kidney tissues and reduced mitochondrial reactive oxygen species production in activated macrophages. Mechanistically, AKF-PD treatment significantly attenuated the PI3K/AKT/mTOR signaling, increased Beclin-1 and LC3 II expression and autophagosome formation, and ameliorated the mitochondrial damage in renal tissues and activated macrophages.

CONCLUSION

The results indicated that AKF-PD treatment inhibited renal interstitial fibrosis by regulating the autophagy-mitochondria-NLRP3 inflammasome pathway.

Suppression of LMCD1 ameliorates renal fibrosis by blocking the activation of ERK pathway

Tubulointerstitial fibrosis is a common pathway of chronic kidney disease (CKD) and is closely related to the progression of CKD. LMCD1, acting as an intermediary, has been reported to play a role in cardiac fibrosis. However, its role in renal fibrosis is yet to be deciphered. Based on the GEO database, we found the expression of LMCD1 is increased in kidney tissues of CKD patients and in human proximal tubular epithelial (HK-2) cells treated with transforming growth factor-β1 (TGF-β1), suggesting that LMCD1 may be involved in tubulointerstitial fibrosis. Herein, we investigated the role of LMCD1 in mice with unilateral ureteral obstruction (UUO) and in TGF-β1-stimulated HK-2 cells. In the UUO model, the expression of LMCD1 was upregulated. UUO-induced renal histopathological changes were mitigated by knockdown of LMCD1. LMCD1 silence alleviated renal interstitial fibrosis in UUO mice by decreasing the expression of TGF-β1, fibronectin, collagen I, and collagen III. LMCD1 deficiency suppressed cell apoptosis in kidney to prevent UUO-triggered renal injury. Furthermore, LMCD1 deficiency blocked the activation of ERK signaling in UUO mice. In vitro, LMCD1 was upregulated in HK-2 cells after TGF-β1 stimulation. LMCD1 silence abrogated TGF-β1-mediated upregulation of fibrotic genes. Treatment of HK-2 cells with ERK-specific inhibitor SCH772984 and agonist TPA validated LMCD1 exerted its function via activating ERK signaling. Together, our findings suggest that inhibition of LMCD1 protects against renal interstitial fibrosis by impeding ERK activation.

Fluorofenidone protects liver against inflammation and fibrosis by blocking the activation of NF-κB pathway

Despite the increasing understanding of the pathophysiology of hepatic fibrosis, the therapies to combat it remain inadequate. Fluorofenidone (AKF-PD) is a novel pyridone agent able to ameliorate hepatic fibrosis in an experimental hepatic fibrosis model induced by dimethylnitrosamine. However, the underlying mechanism remains to be further elucidated. In light of the critical role of the NF-κB pathway in inflammation and hepatic fibrosis, together with the preliminary finding that AKF-PD decreases the release of proinflammatory cytokines in the endotoxemia and unilateral ureteral occlusion model, the aim of this study was to explore whether AKF-PD exerts an antifibrotic effect in hepatic fibrosis by inhibiting inflammation and suppressing the activation of the NF-κB pathway in vivo and in vitro. To test this possibility, the effect of AKF-PD on hepatic fibrosis models induced by both carbon tetrachloride (CCL₄ ) and porcine serum (PS) was investigated. Our results showed that AKF-PD treatment ameliorated hepatic injury and fibrosis in both models. Furthermore, the administration of AKF-PD induced a robust anti-inflammatory reaction revealed by the downregulation of the proinflammatory cytokines as well as the suppression of the infiltration of inflammatory cells in the fibrotic liver. The analysis of the mechanism of action demonstrated that the attenuation of the production of proinflammatory cytokines and chemokines mediated by AKF-PD in vivo and in vitro were accompanied by the suppression in the activation of the NF-κB signaling pathway. In conclusion, AKF-PD might be considered as an antifibrotic agent attenuating hepatic inflammation and fibrosis potentially through the suppression of the NF-κB pathway.

NMDA receptor-mediated CaMKII/ERK activation contributes to renal fibrosis

Background

This study aimed to understand the mechanistic role of N-methyl-D-aspartate receptor (NMDAR) in acute fibrogenesis using models of in vivo ureter obstruction and in vitro TGF-β administration.

Methods

Acute renal fibrosis (RF) was induced in mice by unilateral ureteral obstruction (UUO). Histological changes were observed using Masson’s trichrome staining. The expression levels of NR1, which is the functional subunit of NMDAR, and fibrotic and epithelial-to-mesenchymal transition markers were measured by immunohistochemical and Western blot analysis. HK-2 cells were incubated with TGF-β, and NMDAR antagonist MK-801 and Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) antagonist KN-93 were administered for pathway determination. Chronic RF was introduced by sublethal ischemia–reperfusion injury in mice, and NMDAR inhibitor dextromethorphan hydrobromide (DXM) was administered orally.

Results

The expression of NR1 was upregulated in obstructed kidneys, while NR1 knockdown significantly reduced both interstitial volume expansion and the changes in the expression of α-smooth muscle actin, S100A4, fibronectin, COL1A1, Snail, and E-cadherin in acute RF. TGF-β1 treatment increased the elongation phenotype of HK-2 cells and the expression of membrane-located NR1 and phosphorylated CaMKII and extracellular signal–regulated kinase (ERK). MK801 and KN93 reduced CaMKII and ERK phosphorylation levels, while MK801, but not KN93, reduced the membrane NR1 signal. The levels of phosphorylated CaMKII and ERK also increased in kidneys with obstruction but were decreased by NR1 knockdown. The 4-week administration of DXM preserved renal cortex volume in kidneys with moderate ischemic–reperfusion injury.

Conclusions

NMDAR participates in both acute and chronic renal fibrogenesis potentially via CaMKII-induced ERK activation.

NADPH Oxidase Inhibition in Fibrotic Pathologies

Significance: Fibrosis is a stereotypic, multicellular tissue response to diverse types of injuries that fundamentally result from a failure of cell/tissue regeneration. This complex tissue remodeling response disrupts cellular/matrix composition and homeostatic cell-cell interactions, leading to loss of normal tissue architecture and progressive loss of organ structure/function. Fibrosis is a common feature of chronic diseases that may affect the lung, kidney, liver, and heart. Recent Advances: There is emerging evidence to support a combination of genetic, environmental, and age-related risk factors contributing to susceptibility and/or progression of fibrosis in different organ systems. A core pathway in fibrogenesis involving these organs is the induction and activation of nicotinamide adenine dinucleotide phosphate oxidase (NOX) family enzymes. Critical Issues: We explore current pharmaceutical approaches to targeting NOX enzymes, including repurposing of currently U.S. Food and Drug Administration (FDA)-approved drugs. Specific inhibitors of various NOX homologs will aid establishing roles of NOXs in the various organ fibroses and potential efficacy to impede/halt disease progression. Future Directions: The discovery of novel and highly specific NOX inhibitors will provide opportunities to develop NOX inhibitors for treatment of fibrotic pathologies.

Development of small molecule inhibitors targeting TGF-β ligand and receptor: Structures, mechanism, preclinical studies and clinical usage

Transforming growth factor-β (TGF-β) is a member of a superfamily of pleiotropic proteins that regulate multiple cellular processes such as growth, development and differentiation. Following binding to type I and II TGF-β serine/threonine kinase receptors, TGF-β activates downstream signaling cascades involving both SMAD-dependent and -independent pathways. Aberrant TGF-β signaling is associated with a variety of diseases, such as fibrosis, cardiovascular disease and cancer. Hence, the TGF-β signaling pathway is recognized as a potential drug target. Various organic molecules have been designed and developed as TGF-β signaling pathway inhibitors and they function by either down-regulating the expression of TGF-β or by inhibiting the kinase activities of the TGF-β receptors. In this review, we discuss the current status of research regarding organic molecules as TGF-β inhibitors, focusing on the biological functions and the binding poses of compounds that are in the market or in the clinical or pre-clinical phases of development.

Enhancer of zeste homolog 2 modulates oxidative stress-mediated pyroptosis in vitro and in a mouse kidney ischemia-reperfusion injury model

Enhancer of zeste homolog 2 (EZH2), a well-known methyltransferase, mediates histone H3 lysine 27 trimethylation (H3K27me3) and plays a crucial role in several kidney disease models. However, its role in renal ischemia/reperfusion (I/R) injury still remains unclear. In this study, we found that EZH2 was positively related to renal I/R injury and inhibition of EZH2 with DZNeP alleviated I/R injury and blocked the activation of oxidative stress and pyroptosis in vivo. Similarly, inhibition of EZH2 with either DZNeP or si-RNA also exerted an inhibitory effect on hypoxia/reoxygenation (H/R)-induced oxidative stress and pyroptosis in vitro. Moreover, further study revealed that ablation of reactive oxygen species (ROS) with N-acetyl-cysteine (NAC) suppressed pyroptosis in human renal proximal tubular epithelial cell line cells exposed to H/R stimulation. Furthermore, Nox4, which was positively related to the generation of ROS, was upregulated during H/R process, while it could be reversed by EZH2 inhibition. Consistently, Nox4-mediated ROS generation was attenuated upon inhibition of EZH2 with DZNeP or si-RNA. Additionally, the transcriptional activity of Nox4 was enhanced by the activation of ALK5/Smad2/3 signaling pathway, which was abolished by ALK5 knockdown in vitro. Finally, EZH2 inhibition blocked H/R and I/R-activated ALK5/Smad2/3 pathway and also resulted in an obvious decrease in the transcriptional activity and protein expression levels of Nox4. In conclusion, our results proved that EZH2 inhibition alleviated renal pyroptosis by blocking Nox4-dependent ROS generation through ALK5/Smad2/3 signaling pathway, indicating that EZH2 could be a potential therapeutic target for renal I/R injury.

Fluorofenidone inhibits apoptosis of renal tubular epithelial cells in rats with renal interstitial fibrosis

This study aimed to investigate the mechanism of fluorofenidone (AKF-PD) in treating renal interstitial fibrosis in rats with unilateral urinary obstruction (UUO). Thirty-two male Sprague-Dawley rats were randomly divided into sham, UUO, UUO + enalapril, and UUO + AKF-PD groups. All rats, except sham, underwent left urethral obstruction surgery to establish the animal model. Rats were sacrificed 14 days after surgery, and serum was collected for renal function examination. Kidneys were collected to observe pathological changes. Immunohistochemistry was performed to assess collagen I (Col I) protein expression, and terminal deoxynucleotidyl transferase-mediated nick end-labeling staining to observe the apoptosis of renal tubular epithelial cells. The expression of Fas-associated death domain (FADD), apoptotic protease activating factor-1 (Apaf-1), and C/EBP homologous protein (CHOP) proteins was evaluated by immunohistochemistry and western blot analysis. AKF-PD showed no significant effect on renal function in UUO rats. The pathological changes were alleviated significantly after enalapril or AKF-PD treatment, but with no significant differences between the two groups. Col I protein was overexpressed in the UUO group, which was inhibited by both enalapril and AKF-PD. The number of apoptotic renal tubular epithelial cells was much higher in the UUO group, and AKF-PD significantly inhibited epithelial cells apoptosis. The expression of FADD, Apaf-1, and CHOP proteins was significantly upregulated in the UUO group and downregulated by enalapril and AKF-PD. In conclusion, AKF-PD improved renal interstitial fibrosis by inhibiting apoptosis of renal tubular epithelial cells in rats with UUO.

A novel role of glutathione S-transferase A3 in inhibiting hepatic stellate cell activation and rat hepatic fibrosis

Background and aims

Glutathione S-transferase A3 (GSTA3) is known as an antioxidative protease, however, the crucial role of GSTA3 in liver fibrosis remains unclear. As a recently we developed water-soluble pyridone agent with antifibrotic features, fluorofenidone (AKF-PD) can attenuate liver fibrosis, present studies were designed to explore the role of GSTA3 in liver fibrosis and its modulation by AKF-PD in vivo and in vitro.

Methods

Rats liver fibrosis models were induced by dimethylnitrosamine (DMN) or carbon tetrachloride (CCl4). The two activated hepatic stellate cells (HSCs) lines, rat CFSC-2G and human LX2 were treated with AKF-PD respectively. The lipid peroxidation byproduct malondialdehyde (MDA) in rat serum was determined by ELISA. The accumulation of reactive oxygen species (ROS) was measured by dichlorodihydrofluorescein fluorescence analysis. The expression of α-smooth muscle actin (α-SMA), fibronectin (FN), and phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2), p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK) and glycogen synthase kinase 3 beta (GSK-3β) were detected by western blotting (WB).

Results

GSTA3 was substantially reduced in the experimental fibrotic livers and transdifferentiated HSCs. AKF-PD alleviated rat hepatic fibrosis and potently inhibited HSCs activation correlated with restoring GSTA3. Moreover, GSTA3 overexpression prevented HSCs activation and fibrogenesis, while GSTA3 knockdown enhanced HSCs activation and fibrogenesis resulted from increasing accumulation of ROS and subsequent amplified MAPK signaling and GSK-3β phosphorylation.

Conclusions

We demonstrated firstly that GSTA3 inhibited HSCs activation and liver fibrosis through suppression of the MAPK and GSK-3β signaling pathways. GSTA3 may represent a promising target for potential therapeutic intervention in liver fibrotic diseases.

Amiodarone induces cell proliferation and myofibroblast differentiation via ERK1/2 and p38 MAPK signaling in fibroblasts

Amiodarone is a potent antidysrhythmic agent that can cause potentially life-threatening pulmonary fibrosis. Accumulating evidence has demonstrated that myofibroblast differentiation is related to the pathogenesis of pulmonary fibrosis. In the present study, we treated human embryonic lung fibroblasts (HELFs) with amiodarone, and investigated the relative molecular mechanism of amiodarone-induced pulmonary fibrosis and pathway determinants PD98059 (extracellular signal-regulated kinase (ERK) inhibitor) and SB203580 (p38 mitogen-activated protein kinase (MAPK) inhibitor). Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8). The secretion of collagen Ⅰ was detected by ELISA. The expressions of α-smooth muscle actin (α-SMA), vimentin, phosphorylated ERK1/2 (p-ERK1/2), ERK1/2, phosphorylated p38 MAPK (p-p38), and p38 MAPK were investigated using Western blot analysis. The levels of α-SMA and vimentin were also determined by immunofluorescence and qRT-PCR. We report that amiodarone promoted cell proliferation and collagen Ⅰ secretion, induced α-SMA and vimentin protein and mRNA expression accompanied by increased phosphorylation of ERK1/2 and p38 MAPK, and furthermore, PD98059 and SB203580 remarkably reduced the proliferative response of HELFs compared with amiodarone group and greatly attenuated α-SMA, vimentin and collagen Ⅰ protein production induced by amiodarone. Taken together, our study suggests that amiodarone regulates cell proliferation and myofibroblast differentiation in HELFs through modulating ERK1/2 and p38 MAPK pathways, and these signal pathways may therefore represent an attractive treatment modality in amiodarone-induced pulmonary fibrosis.

ERK1/2 mediates the lipopolysaccharide-induced upregulation of FGF-2, uPA, MMP-2, MMP-9 and cellular migration in cardiac fibroblasts

Myocardial fibrosis is a critical event during septic shock. Upregulation in the fibrosis signaling cascade proteins such as fibroblast growth factor (FGF), urokinase plasminogen activator (uPA), tissue plasminogen activator (tPA) and activation of matrix metalloproteinases (MMPs) are widely associated with the development of myocardial infarction, dilated cardiomyopathy, cardiac fibrosis and heart failure. However, evidences suggest that the common upstream mediators of fibrosis cascade play little role in cardiac fibrosis induced by LPS; further, it is unknown if LPS directly triggers the expressions and/or activity of FGF-2, uPA, tPA, MMP-2 and MMP-9 in cardiac fibroblasts. In the present study, we treated primary cultures of cardiac fibroblasts with LPS to explore whether LPS upregulates FGF-2, uPA, tPA, MMP-2, MMP-9 and enhance cellular migration. Further the precise molecular and cellular mechanisms behind these LPS induced responses were identified. Inhibition assays on MAPKs using U0126 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor), CsA (calcineurin inhibitor) and QNZ (NFκB inhibitor) show that LPS-induced upregulation of FGF-2, uPA, MMP-2 and MMP-9 in cardiac fibroblasts was mediated through ERK1/2 signaling. Collectively, our results provide a link between LPS-induced cardiac dysfunction and ERK1/2 signaling pathway and thereby implies ERK1/2 as a possible target to regulate LPS induced upregulation of FGF-2, uPA, MMP-2, MMP-9 and cellular migration in cardiac fibroblasts.

AKF-PD alleviates diabetic nephropathy via blocking the RAGE/AGEs/NOX and PKC/NOX Pathways

Diabetic nephropathy (DN) is a major complication of diabetes. Currently, drugs are not available to effectively control the disease. Fluorofenidone (AKF-PD) is a recently developed drug; it possesses activities in reducing DN progression in preclinical research. Nonetheless, its renal protection and the underlying mechanisms have not been thoroughly investigated. We report here that AKF-PD significantly alleviatesrenal oxidative stress (OS) in db/dbmice through downregulation of Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase and upregulation of glutathione peroxidase and superoxide dismutase, thereby protecting kidney from DN pathogenesis. AKF-PD likely reduces OS through the advanced glycation end products (AGE) and protein kinase C (PKC) pathways. While renal AGEs, PKCα, PKCβ, and NADPH oxidase 4 (NOX4) were all substantially upregulated in db/db mice compared to db/m animals, AKF-PD robustly downregulated all these events to the basal levelsdetected in db/m mice. In primary human renal mesangial cells (HMCs), high glucose (HG) elevated receptor for advanced glycation endproducts (RAGE), PKCα, PKCβ and NOX4 activity, and induced the production of reactive oxygen species (ROS); these events were all inhibited by AKF-PD. Furthermore, HG led to mitochondrial damagein HMCs;AKF-PD conferred protection on the damage. Knockdown of either PKCα or PKCβ reduced HG-induced ROS production and mitochondrial damage in HMCs. The knockdown significantly enhanced AKF-PD-mediated inhibition of ROS production and mitochondrial damage in HG-treated HMCs. Collectively, our study demonstrates that AKF-PD protects renal function under diabetes conditions in part through inhibition of OS during DN pathogenesis. AKF-PD can be explored for clinical applications in DN therapy.

Blockade of ERK1/2 by U0126 alleviates uric acid-induced EMT and tubular cell injury in rats with hyperuricemic nephropathy

Extracellular signal-regulated kinases 1 and 2 (ERK1/2) are serine/threonine kinases and function as regulators of cellular proliferation and differentiation. Recently, we demonstrated that inhibition of ERK1/2 alleviates the development and progression of hyperuricemia nephropathy (HN). However, its potential roles in uric acid-induced tubular epithelial-mesenchymal transition (EMT) and tubular epithelial cell injury are unknown. In this study, we showed that hyperuricemic injury induced EMT as characterized by downregulation of E-cadherin and upregulation of vimentin and Snail1 in a rat model of HN. This was coincident with epithelial cells arrested at the G₂/M phase of cell cycle, activation of Notch1/Jagged-1 and Wnt/β-catenin signaling pathways, and upregulation of matrix metalloproteinase-2 (MMP-2) and MMP-9. Administration of U0126, a selective inhibitor of ERK1/2, blocked all these responses. U0126 was also effective in inhibiting renal tubular cell injury, as shown by decreased expression of lipocalin-2 and kidney injury molecule-1 and active forms of caspase-3. U0126 or ERK1/2 siRNA can inhibit tubular cell EMT and cell apoptosis as characterized with decreased expression of cleaved caspase-3. Moreover, ERK1/2 inhibition suppressed hyperuricemic injury-induced oxidative stress as indicated by decreased malondialdehyde and increased superoxide dismutase. Collectively, ERK1/2 inhibition-elicited renal protection is associated with inhibition of EMT through inactivation of multiple signaling pathways and matrix metalloproteinases, as well as attenuation of renal tubule injury by enhancing cellular resistance to oxidative stress.

Renal chymase-dependent pathway for angiotensin II formation mediated acute kidney injury in a mouse model of aristolochic acid I-induced acute nephropathy

Angiotensin-converting enzyme (ACE) is the primary enzyme that converts angiotensin I (Ang I) to angiotensin II (Ang II) in the renin-angiotensin system (RAS). However, chymase hydrates Ang I to Ang II independently of ACE in some kidney diseases, and it may play an important role. The present study investigated whether chymase played a crucial role in aristolochic acid I (AAI)-induced nephropathy. C57BL/6 mice were treated with AAI via intraperitoneal injection for an accumulated AAI dosage of 45 mg/kg body weight (BW) (15 mg/kg BW per day for 3 days). The animals were sacrificed after acute kidney injury development, and blood, urine and kidneys were harvested for biochemical and molecular assays. Mice exhibited increased serum creatinine, BUN and urinary protein after the AAI challenge. Significant infiltrating inflammatory cells and tubular atrophy were observed in the kidneys, and high immunocytokine levels were detected. Renal RAS-related enzyme activities were measured, and a significantly increased chymase activity and slightly decreased ACE activity were observed in the AAI-treated mice. The renal Ang II level reflected the altered profile of RAS enzymes and was significantly increased in AAI-treated mice. Treatment of AAI-induced nephropathic mice with an ACE inhibitor (ACEI) or chymase inhibitor (CI; chymostatin) reduced renal Ang II levels. The combination of ACEI and CI (ACEI+CI) treatment significantly reversed the AAI-induced changes of Ang II levels and kidney inflammation and injuries. AAI treatment significantly increased renal p-MEK without increasing p-STAT3 and p-Smad3 levels, and p-MEK/p-ERK1/2 signalling pathway was significantly activated. CI and ACEI+CI treatments reduced this AAI-activated signaling pathway. AAI-induced nephropathy progression was significantly mitigated with CI and ACEI+CI treatment. This study elucidates the role of RAS in the pathogenesis of AAI-induced nephropathy.

Transplantation of Amniotic Fluid-Derived Stem Cells Preconditioned with Glial Cell Line-Derived Neurotrophic Factor Gene Alleviates Renal Fibrosis

Amniotic fluid-derived stem cells (AFSCs), which exhibit both embryonic and mesenchymal stem cell characteristics, have been shown to mitigate the degree of renal interstitial fibrosis. The aim of the present study was to determine whether transplantation of glial cell line-derived neurotrophic factor (GDNF)–modified AFSCs is more useful than transplantation of unmodified AFSCs for the treatment of renal interstitial fibrosis. Mice were randomly assigned to a sham-operation group (sham), a unilateral ureteral obstruction (UUO)-saline solution group (UUO), an AFSC transplantation group (AFSC) and a GDNF-modified AFSC transplantation group (GDNF-AFSC) and sacrificed at days 3 and 7 post-surgery (six in each group). We showed that GDNF-AFSCs noticeably suppressed oxidative stress and inflammation; additionally, GDNF-AFSCs positively regulated peritubular capillaries (PTCs), vascular endothelial growth factor (VEGF), hypoxia inducible factor-1α (HIF-1α), and transforming growth factor-β1 (TGF-β1) protein levels. Transmission electron microscopy (TEM) revealed that mitochondrial injury induced by the UUO model was significantly ameliorated after the mice were treated with GDNF-AFSCs. Therefore, we determined that GDNF gene promotes the abilities of AFSCs to inhibit inflammatory and oxidative stress effects, repair renal microvessels, relieve tissue hypoxia and mitochondrial damage, and, ultimately, alleviate renal interstitial fibrosis.

Loss of the Protein Cystathionine β-Synthase During Kidney Injury Promotes Renal Tubulointerstitial Fibrosis

BACKGROUND/AIMS

Renal tubulointerstitial fibrosis (TIF) is the common pathway of progressive chronic kidney disease. Inflammation has been widely accepted as the major driving force of TIF. Cystathionine β-synthase (CBS) is the first and rate-limiting enzyme in the transsulfuration pathway. CBS is considered to play protective role in liver and pulmonary fibrosis, but its role in TIF remains unknown. The purpose of this study was to investigate the potential role and mechanism of CBS in renal inflammation and TIF.

METHODS

Renal function, tubulointerstitium damage index score, extracellular matrix (ECM) deposition, and the expressions of collagen I, collagen III, fibronectin, CD3, CD68, IL-1β, TNF-α were measured in sham operation and unilateral ureteral obstruction (UUO) rats. Proteomics and gene array analysis were performed to screen differentially expressed molecules in the development of renal inflammation and TIF in UUO rats. The expression of CBS was detected in patients with obstructive nephropathy and UUO rats. We confirmed the expression of CBS using western blot and real-time PCR in HK-2 cells. Overexpression plasmid and siRNA were transfected specifically to study the possible function of CBS in HK-2 cells.

RESULTS

Abundant expression of CBS, localized in renal tubular epithelial cells, was revealed in human and rat renal tissue, which correlated negatively with the progression of fibrotic disease. Expression of CBS was dramatically decreased in the obstructed kidney from UUO rats as compared with the sham group (SHM). In addition, knocking down CBS exacerbated extracellular matrix (ECM) deposition, whereas CBS overexpression attenuated TGF-β1-induced ECM deposition in vitro. Inflammatory and chemotactic factors were also increased in CBS knockdown HK-2 cells stimulated by IL-1β.

CONCLUSIONS

These findings establish CBS as a novel inhibitor in renal fibrosis and as a new therapeutic target in patients with chronic kidney disease.

Microarray Analysis Reveals Increased Expression of Matrix Metalloproteases and Cytokines of Interleukin-20 Subfamily in the Kidneys of Neonate Rats Underwent Unilateral Ureteral Obstruction: A Potential Role of IL-24 in the Regulation of Inflammation and Tissue Remodeling

BACKGROUND/AIMS

Congenital obstructive nephropathy (CON) is the main cause of pediatric chronic kidney diseases leading to renal fibrosis. High morbidity and limited treatment opportunities of CON urge the better understanding of the underlying molecular mechanisms.

METHODS

To identify the differentially expressed genes, microarray analysis was performed on the kidney samples of neonatal rats underwent unilateral ureteral obstruction (UUO). Microarray results were then validated by real-time RT-PCR and bioinformatics analysis was carried out to identify the relevant genes, functional groups and pathways involved in the pathomechanism of CON. Renal expression of matrix metalloproteinase (MMP)-12 and interleukin (IL)-24 were evaluated by real-time RT-PCR, flow cytometry and immunohistochemical analysis. Effect of the main profibrotic factors on the expression of MMP-12 and IL-24 was investigated on HK-2 and HEK-293 cell lines. Finally, the effect of IL-24 treatment on the expression of pro-inflammatory cytokines and MMPs were tested in vitro.

RESULTS

Microarray analysis revealed 880 transcripts showing >2.0-fold change following UUO, enriched mainly in immune response related processes. The most up-regulated genes were MMPs and members of IL-20 cytokine subfamily, including MMP-3, MMP-7, MMP-12, IL-19 and IL-24. We found that while TGF-β treatment inhibits the expression of MMP-12 and IL-24, H2O2 or PDGF-B treatment induce the epithelial expression of MMP-12. We demonstrated that IL-24 treatment decreases the expression of IL-6 and MMP-3 in the renal epithelial cells.

CONCLUSIONS

This study provides an extensive view of UUO induced changes in the gene expression profile of the developing kidney and describes novel molecules, which may play significant role in the pathomechanism of CON.

Brd4 inhibition attenuates unilateral ureteral obstruction-induced fibrosis by blocking TGF-β-mediated Nox4 expression

Uncovering new therapeutic targets for renal fibrosis holds promise for the treatment of chronic kidney diseases. Bromodomain and extra-terminal (BET) protein inhibitors have been shown to effectively ameliorate pathological fibrotic responses. However, the pharmacological effects and underlying mechanisms of these inhibitors in renal fibrosis remain elusive. In this study, we determined that the inhibition of Brd4, a BET family member, with a selective potent chemical inhibitor, JQ1, could prevent the development of renal fibrosis and block the progression of fibrosis in rats that have undergone unilateral ureteral obstruction (UUO). Inhibiting Brd4 with either JQ1 or genetic knockdown resulted in decreased expression of fibrotic genes such as α-smooth muscle actin, collagen IV and fibronectin both in UUO-induced fibrosis and upon TGF-β1 stimulation in HK-2 cells. Brd4 inhibition also suppressed the oxidative stress induced by UUO in vivo or by TGF-β1 in HK-2 cells. Moreover, Nox4, which is constitutively active in renal cells and is involved in the generation of hydrogen peroxide, was up-regulated during UUO-mediated fibrosis and induced by TGF-β1 in HK-2 cells, and this up-regulation could be blunted by Brd4 inhibition. Consistently, Nox4-mediated ROS generation and fibrotic gene expression were attenuated upon Brd4 inhibition. Further, the transcriptional activity of Nox4 was suppressed by JQ1 or siRNA against Brd4. Additionally, Smad3 and ERK1/2 phosphorylation, which are upstream signals of Nox4 expression, were inhibited both in JQ1-administered UUO rats and Brd4-inhibited HK-2 cells. In conclusion, these results indicated that the inhibition of Brd4 might protect against renal fibrosis by blocking the TGF-β-Nox4-ROS-fibrosis axis, suggesting that Brd4 could be a promising therapeutic target.

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Brd4 was up-regulated in the progression of renal fibrosis.

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Brd4 inhibitor JQ1 prevented renal fibrosis and delayed the fibrotic progression.

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Brd4 inhibition blocked TGF-β1-induced oxidative stress and fibrosis through Nox4.

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Brd4 regulated Nox4 expression via Smad and ERK pathways.

Mammalian Metallothionein-2A and Oxidative Stress

Mammalian metallothionein-2A (MT2A) has received considerable attention in recent years due to its crucial pathophysiological role in anti-oxidant, anti-apoptosis, detoxification and anti-inflammation. For many years, most studies evaluating the effects of MT2A have focused on reactive oxygen species (ROS), as second messengers that lead to oxidative stress injury of cells and tissues. Recent studies have highlighted that oxidative stress could activate mitogen-activated protein kinases (MAPKs), and MT2A, as a mediator of MAPKs, to regulate the pathogenesis of various diseases. However, the molecule mechanism of MT2A remains elusive. A deeper understanding of the functional, biochemical and molecular characteristics of MT2A would be identified, in order to bring new opportunities for oxidative stress therapy.

Evaluating the Oxidative Stress in Renal Diseases: What Is the Role for S-Glutathionylation?

SIGNIFICANCE

Reactive oxygen species (ROS) have long been considered as toxic derivatives of aerobic metabolism displaying a harmful effect to living cells. Deregulation of redox homeostasis and production of excessive free radicals may contribute to the pathogenesis of kidney diseases. In line, oxidative stress increases in patients with renal dysfunctions due to a general increase of ROS paralleled by impaired antioxidant ability.

RECENT ADVANCES

Emerging evidence revealed that physiologically, ROS can act as signaling molecules interplaying with several transduction pathways such as proliferation, differentiation, and apoptosis. ROS can exert signaling functions by modulating, at different layers, protein oxidation since proteins have "cysteine switches" that can be reversibly reduced or oxidized, supporting the dynamic signaling regulation function. In this scenario, S-glutathionylation is a posttranslational modification involved in oxidative cellular response.

CRITICAL ISSUES

Although it is widely accepted that renal dysfunctions are often associated with altered redox signaling, the relative role of S-glutathionylation on the pathogenesis of specific renal diseases remains unclear and needs further investigations. In this review, we discuss the impact of ROS in renal health and diseases and the role of selective S-glutathionylation proteins potentially relevant to renal physiology.

FUTURE DIRECTIONS

The paucity of studies linking the reversible protein glutathionylation with specific renal disorders remains unmet. The growing number of S-glutathionylated proteins indicates that this is a fascinating area of research. In this respect, further studies on the association of reversible glutathionylation with renal diseases, characterized by oxidative stress, may be useful to develop new pharmacological molecules targeting protein S-glutathionylation. Antioxid. Redox Signal. 25, 147-164.

Antidiabetic and Antinephritic Activities of Aqueous Extract of Cordyceps militaris Fruit Body in Diet-Streptozotocin-Induced Diabetic Sprague Dawley Rats

Cordyceps militaris has long been used as a crude drug and folk tonic food in East Asia. The present study aims to evaluate the antidiabetic and antinephritic effects of the aqueous extract of the Cordyceps militaris fruit body (CM) in diet-streptozotocin- (STZ-) induced diabetic rats. During four weeks of continuous oral administration of CM at doses of 0.5, 1.0, and 2.0 g/kg and metformin at 100 mg/kg, the fasting blood glucose and bodyweight of each rat were monitored. Hypoglycemic effects of CM on diabetic rats were indicated by decreases in plasma glucose, food and water intake, and urine output. The hypolipidemic activity of CM was confirmed by the normalization of total cholesterol, triglycerides, and low- and high-density lipoprotein cholesterol in diabetic rats. Inhibitory effects on albuminuria, creatinine, urea nitrogen, and n-acetyl-β-d-glucosaminidase verified CM's renal protective activity in diabetic rats. Furthermore, CM exerted beneficial modulation of inflammatory factors and oxidative enzymes. Compared with untreated diabetic rats, CM decreased the expression of phosphor-AKT and phosphor-GSK-3β in the kidneys. Altogether, via attenuating oxidative stress, CM displayed antidiabetic and antinephritic activities in diet-STZ-induced diabetic rats.