Obstructive nephropathy and renal fibrosis

Renoprotective effect and mechanism of polysaccharide from Polyporus umbellatus sclerotia on renal fibrosis

As a fungal polysaccharide, polysaccharide (PPUS) from Polyporus umbellatus sclerotia have showed remarkable anti-inflammatory activities. In view of the closely relationship between inflammation and renal fibrosis, and considering the significant role of other fungal polysaccharides on treatment of renal fibrosis, we speculated that PPUS may have therapeutic effects on renal fibrosis. However, there was not any reports about PPUS treatment this disease. The purpose of this paper is to investigate renoprotective effect and mechanism of PPUS on renal fibrosis. The results indicated that PPUS can improve renal function and ameliorate the degree of renal collagen deposition and further fibrosis. Its mechanism was found to be related with decreased inflammation, suppressive epithelial-mesenchymal transition, reconstructed the balance of matrix metalloproteinases and tissue inhibitor of metalloproteinases, and pro-fibrotic and anti-fibrotic factors. The data implied that PPUS can serve as a clinical candidate on treatment of renal interstitial fibrosis.

Peroxiredoxin 3 deficiency accelerates chronic kidney injury in mice through interactions between macrophages and tubular epithelial cells

Chronic kidney disease (CKD) has become epidemic worldwide. Mitochondrial reactive oxygen species (ROS)-induced oxidative stress is an important mediator of CKD, and Prx3 plays a critical role in maintenance of mitochondrial ROS. The present study examined the role of Prx3 in the context of fibrosis, a common feature of CKD, using Prx3 KO mice under obstructive and diabetic stress. Prx3 deficiency accelerated fibrosis and inflammation accompanied by mitochondrial oxidative stress in obstructed and diabetic kidneys as well as in proximal tubular epithelial (mProx) cells. In addition, Prx3 deficiency induced Raw264.7 macrophages activation, leading to upregulation of proinflammatory cytokines. Conditioned media from LPS-stimulated Prx3 deficient macrophages accelerated proinflammatory and profibrotic cytokines in mProx cells. Interestingly, Prx3 deficiency induced most inflammatory and fibrotic cytokines at basal condition in both tissues and cells. Taken together, these results demonstrate that Prx3 deficiency can accelerate CKD through interactions between macrophages and tubular epithelial cells.

Hydronephrosis and risk of later development of hypertension

AIM

Congenital ureteral obstruction is a fairly common condition in infants, and its clinical management has been long debated during the last decade. The long-term physiological consequences of today's conservative non-surgical management in many asymptomatic hydronephrotic children are unclear.

METHODS

Experimental studies in rats and mice, retrospective studies in children and adults, as well as prospective studies in children are included in this mini review.

RESULTS

Experimental models of hydronephrosis in rats and mice have demonstrated that partial ureteropelvic junction obstruction (UPJO) is casually linked with development of hypertension and renal injuries in later life. The mechanisms are multifactorial and involve increased activity of the renin-angiotensin-aldosterone system and renal sympathetic nerve activity. Furthermore, oxidative stress and nitric oxide deficiency in the affected kidney appear to play important roles in the development and maintenance of hypertension. Clinical case reports in adults and recent prospective studies in children have associated hydronephrosis with elevated blood pressure, which could be reduced by surgical management of the obstruction.

CONCLUSION

Based on current experimental and clinical knowledge regarding the link between partial UPJO and changes in blood pressure, it is proposed that today's non-operative management of hydronephrosis should be reconsidered to reduce the risk of developing elevated blood pressure or hypertension in later life.

Connective Tissue Growth Factor and Renal Fibrosis

CCN2, also known as connective tissue growth factor (CTGF), is one of important members of the CCN family. Generally, CTGF expresses at low levels in normal adult kidney, while increases significantly in various kidney diseases, playing an important role in the development of glomerular and tubulointerstitial fibrosis in progressive kidney diseases. CTGF is involved in cell proliferation, migration, and differentiation and can promote the progression of fibrosis directly or act as a downstream factor of transforming growth factor β (TGF-β). CTGF also regulates the expression and activity of TGF-β and bone morphogenetic protein (BMP), thereby playing an important role in the process of kidney repair. In patients with chronic kidney disease, elevated plasma CTGF is an independent risk factor for progression to end-stage renal disease and is closely related to glomerular filtration rate. Therefore, CTGF may be a potential biological marker of kidney fibrosis, but more clinical studies are needed to confirm this view. This section briefly describes the role and molecular mechanisms of CTGF in renal fibrosis and also discusses the potential value of targeting CCN2 for the treatment of renal fibrosis.

Protein kinase C inhibitor chelerythrine attenuates partial unilateral ureteral obstruction induced kidney injury in neonatal rats

The present study aimed to evaluate the renoprotective effects of chelerythrine (CHE), a protein kinase C inhibitor, on neonatal rats after partial unilateral ureteral obstruction (UUO) surgery. New born Sprague Dawley rats were subjected to partial UUO 48 h after birth and received a daily intraperitoneal injection of 5 mg/kg CHE. At 21-day age, the rats were scarified and the kidneys were collected for analysis. Results showed that CHE treatment significantly increased kidney weight and restored renal function in the obstructed kidney. Histological examination demonstrated that CHE attenuated renal injury by reducing renal parenchymal loss and preventing glomerular and tubular degeneration. In addition, CHE inhibited partial UUO-induced upregulated kidney injury molecule-1 expression and apoptosis and renal fibrosis. Moreover, as a PKC inhibitor, CHE significantly inhibited PKCα and PKCβ membrane translocation. This action may be associated with its effects of anti-apoptosis and anti-fibrosis and contribute to the renoprotection. This short-term study suggests that CHE is beneficial for obstructive nephropathy in neonatal rats and provides foundation for further studies to reveal the long-term effects of CHE on obstructive nephropathy in children and infants.

The role of klotho in chronic kidney disease

Chronic kidney disease (CKD) is an inherently systemic disease that refers to a long-term loss of kidney function. The progression of CKD has repercussions for other organs, leading to many kinds of extrarenal complications. Intensive studies are now being undertaken to reveal the risk factors and pathophysiological mechanism of this disease. During the past 20 years, increasing evidence from clinical and basic studies has indicated that klotho, which was initially known as an anti-aging gene and is mainly expressed in the kidney, is significantly correlated with the development and progression of CKD and its complications. Here, we discuss in detail the role and pathophysiological implications of klotho in ion disorders, the inflammation response, vascular calcification, mineral bone disorders, and renal fibrosis in CKD. Based on the pathogenic mechanism of klotho deficiency and klotho decline in urine early in CKD stage 2 and even earlier in CKD stage 1, it is not difficult to understand that soluble klotho can serve as an early and sensitive marker of CKD. Moreover, the prevention of klotho decline by several mechanisms can attenuate renal injuries, retard CKD progression, ameliorate extrarenal complications, and improve renal function. In this review, we focus on the functions and pathophysiological implications of klotho in CKD and its extrarenal complications as well as its potential applications as a diagnostic and/or prognostic biomarker for CKD and as a novel treatment strategy to improve and decrease the burden of comorbidity in CKD.

Serum-Free Medium Enhances the Immunosuppressive and Antifibrotic Abilities of Mesenchymal Stem Cells Utilized in Experimental Renal Fibrosis

Serum used in culture medium brings risks of immune reactions or infections and thus may hinder using ex vivo expanded mesenchymal stem cells (MSCs) for medical treatment. Here, we cultured MSCs in a serum-free medium (SF-MSCs) and in a medium containing 10% fetal bovine serum (10%MSCs) and investigated their effects on inflammation and fibrosis. MSC-conditioned medium suppressed transforming growth factor-β1-induced phosphorylation of Smad2 in HK-2 cells, with no significant difference between the two MSCs. This finding suggests that the direct antifibrotic effect of SF-MSCs is similar to that of 10%MSCs. However, immunohistochemistry revealed that renal fibrosis induced by unilateral ureteral obstruction in rats was more significantly ameliorated by the administration of SF-MSCs than by that of 10%MSCs. Coculture of MSCs and monocytic THP-1 cell-derived macrophages using a Transwell system showed that SF-MSCs significantly induced polarization from the proinflammatory M1 to the immunosuppressive M2 phenotype macrophages, suggesting that SF-MSCs strongly suppress the persistence of inflammation. Furthermore, the gene expression of tumor necrosis factor-α-induced protein 6 (TSG-6), which inhibits the recruitment of inflammatory cells, was higher in SF-MSCs than in 10%MSCs, and TSG-6 knockdown in SF-MSCs attenuated the anti-inflammatory responses in unilateral ureteral obstruction rats. These findings imply that SF culture conditions can enhance the immunosuppressive and antifibrotic abilities of MSCs and the administration of ex vivo expanded SF-MSCs has the potential to be a useful therapy for preventing the progression of renal fibrosis. Stem Cells Translational Medicine 2018;7:893-905.

The renal protect function of erythropoietin after release of bilateral ureteral obstruction in a rat model

Congenital urinary tract obstruction is one of the most frequent malformations in fetuses or neonates, which usually causes profound impairment of renal function including reductions in both glomerular filtration rate (GFR) and tubular handling of water and solutes. Although obstruction can be released by surgical operation, the child will suffer from diuresis for sometime. It has been reported that erythropoietin (EPO) could prevent the down-regulation of aquaporin-2 (AQP2) and urinary-concentrating defects induced by renal ischemia/reperfusion (I/R) injury. However, whether EPO could promote the recovery of renal function and AQP2 expression after releasing of ureteral obstruction has not been reported yet. The purposes of the present study were to investigate the effects of EPO on renal function and AQP2 expression after release of bilateral ureteral obstruction (BUO-R) in rats. The results showed that EPO could promote interleukin (IL) 10 (IL-10) expression; inhibit tumor necrosis factor-α (TNF-α), IL-6, and inducible nitric oxide synthase (iNOS) expressions; reduce the fractional excretion of sodium (FENa) and plasma creatinine (CREA) and urea; and promote the recovery of water and salt handling and AQP2 expression in BUO-R rats, especially in the high dose of EPO-treated group rats. In conclusion, EPO could promote the recovery of renal function and AQP2 expression in BUO-R rats, which may partially associate with its anti-inflammation effect.

Thioredoxin-interacting protein deficiency ameliorates kidney inflammation and fibrosis in mice with unilateral ureteral obstruction

Thioredoxin-interacting protein (TXNIP) is associated with inflammation, tubulointerstitial fibrosis, and oxidative stress in diabetic kidney disease, yet the potential role of TXNIP in nondiabetic renal injury is not well known. This study aimed to investigate the effect of TXNIP on renal injury by creating a unilateral ureteral obstruction (UUO) model in TXNIP knockout (TKO) mice. We performed sham or UUO surgery in 8-week-old TXNIP KO male mice and age and sex-matched wild-type (WT) mice. Animals were killed at 3, 5, 7, or 14 days after surgery, and renal tissues were obtained for RNA, protein, and other analysis. Our results show that the expression of TXNIP was increased in a time-dependent manner in the ligated kidneys. TXNIP deletion reduced renal fibrosis, apoptosis, α-SMA, TGF-β1 and CTGF expression, and activation of Smad3, p38 MAPK, and ERK1/2 in UUO kidneys. We also found UUO-induced renal F4/80+ macrophage infiltration, MCP-1 expression and activation of NF-κB and NLRP3 inflammasome were attenuated in TKO mice. Furthermore, our study revealed that TXNIP deficiency inhibited the expression of 8-OHdG, heme oxygenase-1 (HO-1) and NADPH oxidase 4 (Nox4) in UUO kidney. In summary, our study suggests that TXNIP plays a key role in the renal inflammation and fibrosis induced by UUO. Inhibition of TXNIP may be a strategy to slow the progression of chronic kidney diseases.

HL156A, a novel pharmacological agent with potent adenosine-monophosphate-activated protein kinase (AMPK) activator activity ameliorates renal fibrosis in a rat unilateral ureteral obstruction model

Background

Renal fibrosis is characterized by excessive production and deposition of extracellular matrix (ECM), which leads to progressive renal failure. Adenosine-monophosphate-activated protein kinase (AMPK) is a highly conserved kinase that plays a key role in Smad-3 signaling. Here, we examined the effect of a novel AMPK activator, HL156A, on the inhibition of renal fibrosis in in vivo and in vitro models.

Methods

Unilateral ureteral obstruction (UUO) was induced in male Wistar rats. Rats with UUO were administered HL156A (20mg/kg/day), and then the kidneys were harvested 10 days after ligation for further analysis.

Results

In the rat UUO model, HL156A attenuated ECM protein deposition. After HL156A treatment, expressions of TGF-β1, p-Smad3, α-SMA, fibronectin, and type IV collagen were suppressed, and E-cadherin expression was up-regulated. In the in vitro experiment, NRK52E cells were treated with HL156A before TGF-β1 stimulation. The inhibitory effects of HL156A upon the signaling pathways and markers of the epithelial-to-mesenchymal transition (EMT) were analyzed. In TGF-β1-treated NRK-52E cells, HL156A co-treatment inhibited the TGF-β1-induced Smad3 signaling pathway and EMT markers.

Conclusion

Taken together, the above findings suggest that HL156A, a novel AMPK activator, ameliorates renal fibrosis in vivo and in vitro.

Taxus chinensis ameliorates diabetic nephropathy through down-regulating TGF-β1/Smad pathway

Diabetic nephropathy (DN) is one of the common microvascular complications of diabetes mellitus. Renal fibrosis is closely related to the deterioration of renal function. The present study aimed to investigate protective effect of Taxus chinensis on high-fat diet/streptozotocin-induced DN in rats and explore the underlying mechanism of action. The rat DN model was established via feeding high fat diet for 4 weeks and subsequently injecting streptozotocin (30 mg·kg^-1 body weight) intraperitoneally. The rats with blood glucose levels higher than 16.8 mmol·L^-1 were selected for experiments. The DN rats were treated with Taxus chinensis orally (0.32, 0.64, and 1.28 g·kg^-1) once a day for 8 weeks. Taxus chinensis significantly improved the renal damage, which was indicated by the decreases in 24-h urinary albumin excretion rate, blood serum creatinine, and blood urea nitrogen. Histopathological examination confirmed the protective effect of Taxus chinensis. The thickness of glomerular basement membrane was reduced, and proliferation of mesangial cells and podocytes cells and increase in mesangial matrix were attenuated. Further experiments showed that Taxus chinensis treatment down-regulated the expression of TGF-β1 and α-SMA, inhibited phosphorylation of Smad2 and Smad3. These results demonstrated that Taxus chinensis alleviated renal injuries in DN rats, which may be associated with suppressing TGF-β1/Smad signaling pathway.

Nigella sativa extract is a potent therapeutic agent for renal inflammation, apoptosis, and oxidative stress in a rat model of unilateral ureteral obstruction

Unilateral ureteral obstruction (UUO) is a well-established experimental model to evaluate renal interstitial fibrosis. Current study is aimed to investigate the effects of Nigella sativa (NS) extract and renin-angiotensin system (RAS) blockade against kidney damage following UUO in rats. In this study, the rats received intraperitoneal injection of losartan (15 mg/kg), captopril (30 mg/kg), and two doses of NS extract (200 and 400 mg/kg) for 18 consecutive days. At the fourth day of the experiment, laparotomy was performed, and the left ureter was ligated. Sham-operated animals received saline as vehicle, and laparotomy without ureteral ligation was done. UUO was associated with significant increase in the expression of renal angiotensin II and monocyte chemoattractant protein-1, concentration of malondialdehyde and tumor necrosis factor-α, and the number of apoptotic cells when compared with sham group. Renal total thiol content and the activity of antioxidant enzymes were significantly reduced as compared with the sham group. However, treatment of obstructed rats with losartan, captopril, and NS extract significantly improved these renal impairments when compared with UUO group. Thus, NS extract, a potent antioxidant and anti-inflammatory herb, is a therapeutic agent to treat the UUO-induced kidney damage comparable with the well-known RAS inhibitors captopril and losartan.

Novel inhibitors of the cellular renin-angiotensin system components, poricoic acids, target Smad3 phosphorylation and Wnt/β-catenin pathway against renal fibrosis

BACKGROUND AND PURPOSE

Tubulo-interstitial fibrosis is the final pathway in the progression of chronic kidney disease (CKD) to kidney failure. The renin-angiotensin system (RAS) plays a major role in CKD progression. Hence, we determined the efficacy of novel RAS inhibitors isolated from Poria cocos against renal fibrosis.

EXPERIMENTAL APPROACH

Effects of three novel tetracyclic triterpenoid compounds, poricoic acid ZC (PZC), poricoic acid ZD (PZD) and poricoic acid ZE (PZE), were investigated on TGFβ1- and angiotensin II (AngII)-treated HK-2 cells and unilateral ureteral obstruction (UUO) in mice. Immunofluorescence staining, quantitative real-time PCR, siRNA, co-immunoprecipitation and Western blot analyses were used to evaluate expression of key molecules in RAS, Wnt/β-catenin and TGFβ/Smad pathways.

KEY RESULTS

Addition of the above compounds to culture media and their administration to UUO mice: (i) significantly attenuated epithelial-to-mesenchymal transition and extracellular matrix production in TGFβ1- and AngII-treated HK-2 cells and UUO mice by inhibiting Wnt/β-catenin pathway activation and Smad3 phosphorylation; (ii) selectively inhibited Smad3 phosphorylation by blocking the interaction of TGFBR1 with Smad3; and (iii) specifically inhibited Smad3 activation. PZC and PZD showed a strong inhibitory effect on all RAS components, and PZE showed a strong inhibitory effect on renin. Furthermore, the secolanostane tetracyclic triterpenoids, PZC and PZD, showed a stronger inhibitory effect than the lanostane tetracyclic triterpenoid PZE. Therefore, compounds with secolanostance skeleton showed stronger bioactivity than those with lanostance skeleton.

CONCLUSION AND IMPLICATIONS

The secolanostane tetracyclic triterpenoids effectively blocked RAS by simultaneously targeting multiple RAS components and lanostane tetracyclic triterpenoids inhibited renin and protected against tubulo-interstitial fibrosis.

IL-33/ST2 axis mediates hyperplasia of intrarenal urothelium in obstructive renal injury

The monolayered intrarenal urothelium covers the renal papilla and ureteropelvic junction (UPJ). In response to increased renal pressure during obstruction or ischemic injuries, intrarenal urothelial cells begin to proliferate and form a multilayered urothelium. Little is known regarding the mechanism and pathophysiological role of urothelium hyperplasia during renal obstruction. In this study, we investigated the expression of interleukin (IL)-33, an IL-1 family cytokine, in kidneys with unilateral ureteral obstruction (UUO)-induced obstructive injury. IL-33 levels in hydronephrotic urine and serum were upregulated 2 days after UUO. The number of ST2-expressing immune cells was increased in the UUO kidney. We found that IL-33 was upregulated in vimentin-positive cells in the cortical and medullar layers and the UPJ stroma. Moreover, IL-33 expression was predominantly induced in multilayered keratin 5-positive urothelial cells in the UPJ. IL-33 was not detected in terminally differentiated superficial umbrella cells expressing uroplakin 3a. In vivo, we confirmed that deficiency of IL33 or its receptor ST2 attenuated UUO-induced hyperplasia of the UPJ urothelium. Deficiency of IL33 attenuated the expression of UUO-induced type 2 inflammatory cytokines and upregulated uroplakins and urothelial differentiation signaling in UPJ tissues. Our results collectively suggest that the IL-33/ST2 axis mediates the activation of innate immune responses and contributes to urothelial hyperplasia by regulating urothelial differentiation in obstructive kidney injury.

Nephrotoxicity Induced by Cisplatin Intake in Experimental Rats and Therapeutic Approach of Using Mesenchymal Stem Cells and Spironolactone

Chronic kidney disease may lead to subsequent tissue fibrosis. However, many factors can combat injurious stimuli in these tissues aiming to repair, heal, and alleviate any disturbance. Chemokines release, migration of inflammatory cells to the affected site, and activation of fibroblasts for the production of extracellular matrix are commonly observed in this disease. In the last years, many studies have focused on spironolactone (SPL), a mineralocorticoid receptor antagonist, and its pharmacological effects. In the present study, SPL was selected as an anti-inflammatory agent to combat nephrotoxicity and renal fibrosis induced by cisplatin. Mesenchymal stem cells (MSCs) were also selected in addition as a referring agent. Renal fibrosis induced by cisplatin intake significantly increased creatinine, urea, nuclear factor kappa B, insulin-like growth factor-1, fibroblast growth factor-23, and kidney malondialdehyde (MDA) content. Hepatocyte growth factor and renal content of reduced glutathione demonstrated a significant decrease. Histopathological examination of kidney tissues demonstrated marked cellular changes which are correlated with the biochemical results. Oral SPL intake (20 mg/kg/body weight) daily for 4 weeks and MSCs administration (3 × 106 cell/rat) intravenous to the experimental rats resulted in a significant improvement of both the biomarkers studied and the histopathological profile of the renal tissue. Individual administration of spironolactone and MSCs exhibited a marked anti-inflammatory potential and alleviated to a great extent the nephrotoxicity and renal fibrotic pattern induced by cisplatin.

Thrombospondin immune regulation and the kidney

Most therapeutic attempts to prevent the progression of kidney diseases have been based on interventions to inhibit the production of transforming growth factor-β (TGF-β). Thrombospondins (TSPs) play an important role in activating TGF-β. In the healthy kidney, two TSPs are expressed, TSP1 and TSP2, which exert contrasting effects. While TSP1 is a major activator of TGF-β in renal cells and exerts pro-inflammatory effects both in vitro and in vivo, TSP2 lacks the ability for TGF-β activation but regulates matrix remodeling and inflammation in experimental kidney disease. The effects of TSPs in the kidney have been mostly investigated by using the murine model of unilateral ureteral obstruction. In this model, TSP1 expression is increased along with the development of interstitial fibrosis and TGF-β. Relief of the obstruction gradually improves renal function and decreases the expression in TSP1 and TGF-β1. Several inhibitors of TSP1 prevented progressive interstitial fibrosis in murine models of ureteral obstruction, suggesting that control of latent TGF-β activation by inhibiting TSP1 might represent a novel potential target for preventing renal interstitial fibrosis. However, further studies are needed to assess whether TSP1-mediated TGF-β activation can be safely used in humans. In fact, TSPs normally act to suppress tumors in vivo. Moreover, TGF-β can exert a pivotal function in the immune system, as it may induce the production of regulatory T cells and suppress B cell responses. Knowledge of the molecular mechanisms involved in TGF-β regulation may help in finding effective treatments of tissue fibrosis, cancer and autoimmune disease.

RIPK3 promotes kidney fibrosis via AKT-dependent ATP citrate lyase

Renal fibrosis is a common pathogenic response to injury in chronic kidney disease (CKD). The receptor-interacting protein kinase-3 (RIPK3), a regulator of necroptosis, has been implicated in disease pathogenesis. In mice subjected to unilateral ureteral obstruction-induced (UUO-induced) or adenine diet-induced (AD-induced) renal fibrosis, models of progressive kidney fibrosis, we demonstrate increased kidney expression of RIPK3. Mice genetically deficient in RIPK3 displayed decreased kidney fibrosis and improved kidney function relative to WT mice when challenged with UUO or AD. In contrast, mice genetically deficient in mixed-lineage kinase domain-like protein (MLKL), a downstream RIPK3 target, were not protected from UUO-induced kidney fibrosis. We demonstrate a pathway by which RIPK3 promotes fibrogenesis through the AKT-dependent activation of ATP citrate lyase (ACL). Genetic or chemical inhibition of RIPK3 suppressed the phosphorylation of AKT and ACL in response to TGF-β1 in fibroblasts. Inhibition of AKT or ACL suppressed TGF-β1-dependent extracellular matrix production and myofibroblast differentiation in fibroblasts. Pharmacological inhibition of ACL suppressed UUO-induced kidney fibrosis. RIPK3 expression was highly regulated in human CKD kidney. In conclusion, we identify a pathway by which RIPK3 promotes kidney fibrosis independently of MLKL-dependent necroptosis as a promising therapeutic target in CKD.

Long non-coding RNA-H19 antagonism protects against renal fibrosis

Although long non-coding RNAs (lncRNAs) are important players in the initiation and progression of many pathological processes, the role of lncRNAs in renal fibrosis still remains unclear. We showed that lncRNA-H19 expression was significantly up-regulated in TGF-β2-induced HK-2 cell fibrosis and unilateral ureteral obstruction (UUO)-induced renal fibrosis in vivo. H19 knockdown significantly attenuated renal fibrosis in vitro and in vivo. LncRNA-H19, miR-17, and fibronectin constituted to a regulatory network involved in renal fibrosis. We also detected up-regulated H19 expression and down-regulated miR-17 expression in the early and advanced animal models of renal fibrosis. This study indicates that H19 up-regulation contributes to renal fibrosis. H19 inhibition might represent a novel anti-fibrotic treatment in renal diseases.

SKLB023 hinders renal interstitial fibrosis in obstructive nephropathy by interfering TGF-β1/Smad3 signaling

Renal fibrosis is the principal process underlying the progression of chronic kidney disease to end-stage renal disease. It is a relatively uniform response involving glomerulosclerosis, tubulointerstitial fibrosis and changes in renal vasculature. A considerable number of studies have confirmed that inducible nitric oxide synthase (iNOS) was highly expressed in renal interstitial fibrosis and the overexpression of iNOS played a negative role in kidney disease progression. In our previous study, SKLB023 as a novel small-molecule inhibitor of iNOS, blocked joint inflammation and cartilage destruction in arthritis. However, the pharmacological role and function of SKLB023 in renal fibrosis remained poorly understood. In the study, oral administration of SKLB023 (25 and 50 mg per kg per day) for 7 day exhibited potent anti-fibrotic effects against the model UUO using the pathological assessment of H & E and Masson's trichrome staining. SKLB023 inhibited the expression of α-SMA, col I, col IV, fibronectin and further decreased iNOS expression as well as TGF-β1/Smad3 phosphorylation in the injured kidney tissues of UUO mice. Similarly, SKLB023 suppressed in vitro features of fibrosis in TGF-β1-induced NRK-49F by the inhibition of the corresponding fibrotic protein expression. These findings confirmed that SKLB023 hindered renal interstitial fibrosis by interfering with TGF-β1/Smad3 signaling, highlighting that SKLB023 has potential in therapeutic strategies.

The novel small-molecule inhibitor of iNOS (SKLB023) hindered renal interstitial fibrosis in vivo and in vitro by interfering with TGF-β1/Smad3 signaling, highlighting that SKLB023 has potential in the therapeutic strategy for renal fibrosis.

Evaluation of renal metabolic response to partial ureteral obstruction with hyperpolarized 13 C MRI

Hyperpolarized 13 C magnetic resonance imaging (MRI) may be used to non-invasively image the transport and chemical conversion of 13 C-labeled compounds in vivo. In this study, we utilize hyperpolarized 13 C MRI to evaluate metabolic markers in the kidneys longitudinally in a mouse model of partial unilateral ureteral obstruction (pUUO). Partial obstruction was surgically induced in the left ureter of nine adult mice, leaving the right ureter as a control. 1 H and hyperpolarized [1-13 C]pyruvate MRI of the kidneys was performed 2 days prior to surgery (baseline) and at 3, 7 and 14 days post-surgery. Images were evaluated for changes in renal pelvis volume, pyruvate, lactate and the lactate to pyruvate ratio. After 14 days, mice were sacrificed and immunohistological staining of both kidneys for collagen fibrosis (picrosirius red) and macrophage infiltration (F4/80) was performed. Statistical analysis was performed using a linear mixed effects model. Significant kidney × time interaction effects were observed for both lactate and pyruvate, indicating that these markers changed differently between time points for the obstructed and unobstructed kidneys. Both kidneys showed an increase in the lactate to pyruvate ratio after obstruction, suggesting a shift towards glycolytic metabolism. These changes were accompanied by marked hydronephrosis, fibrosis and macrophage infiltration in the obstructed kidney, but not in the unobstructed kidney. Our results show that pUUO is associated with increased pyruvate to lactate metabolism in both kidneys, with injury and inflammation specific to the obstructed kidney. The work also demonstrates the feasibility of the use of hyperpolarized 13 C MRI to study metabolism in renal disease.

Role of Sirolimus in renal tubular apoptosis in response to unilateral ureteral obstruction

Renal tubule cell apoptosis plays a pivotal role in the progression of chronic renal diseases. The previous study indicates that Sirolimus is effective on unilateral ureteral obstruction (UUO)-induced renal fibrosis. However, the role of Sirolimus in renal tubular apoptosis induced by UUO has not yet been addressed. The aim of this study was to determine the role of Sirolimus in renal tubular apoptosis induced by UUO. Male Sprague-Dawley rats were divided into three groups, sham-operated rats, and after which unilateral ureteral obstruction (UUO) was performed: non-treated and sirolimus-treated (1mg/kg). After 4, 7 and 14 d, animals were sacrificed and blood, kidney tissue samples were collected for analyses. Histologic changes and interstitial collagen were determined microscopically following HE and Masson's trichrome staining. The expression of PCNA was investigated using immunohistochemistry and the expression of Bcl-2, Bax, caspase-9, and caspase-3 were investigated using Western blot in each group. Tubular apoptotic cell deaths were assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. Sirolimus administration resulted in a significant reduction in tubulointerstitial fibrosis scores. After UUO, there was an increase in tubular and interstitial apoptosis in untreated controls as compared to Sirolimus treatment rats (P<0.05). In addition, the expression of PCNA, Bcl-2, Bax, caspase-9, and caspase-3 in obstructed kidney was characterized by immunohistochemistry and Western blot analyses demonstrating that sirolimus treatment significantly reduced PCNA, Bax, caspase-9 and cleaved caspase-3 expression compared to those observed in controls (P<0.05), whereas, Bcl-2 in the obstructed kidney were decreased in untreated controls compared to Sirolimus treatment rats subjected to the same time course of obstruction (P<0.05). We demonstrated a marked renoprotective effect of sirolimus by inhibition of UUO-induced renal tubular apoptosis in vivo.

Sevelamer hydrochloride suppresses proliferation of parathyroid cells during the early phase of chronic renal failure in rats

AIM

We examined the effects of sevelamer on parathyroid cell proliferation and secondary hyperparathyroidism in rats following induction of early-phase of chronic renal failure (CRF) by unilateral ureteral obstruction (UUO).

METHODS

For 5 days, rats in the control group received normal food, rats in the sevelamer group (SH) received control food plus 5% sevelamer, and rats in the low protein group (LP) received low protein food. Five rats of each group were killed at baseline (day 0). All other rats were given UUO, and five rats per group were killed on days 3, 7, 14, and 28 after UUO. Changes in body weight, serum phosphorus, calcium, intact-parathyroid hormone (i-PTH), creatinine (SCr), creatinine clearance rate (CCR), blood urea nitrogen (BUN), and 24-h urinary phosphorus were determined. Parathyroid tissues were removed for histological examination of proliferating cell nuclear antigen-positive (PCNA+) cells.

RESULTS

Measurement of body weight, BUN, and SCr in the controls indicated successful establishment of this model of early-phase CRF. The controls also had remarkable proliferation of PCNA+ cells beginning on day 3, but this did not occur in the SH or LP groups. After 28 days, serum phosphorus had decreased more in the SH and LP groups than in the control group, and phosphorus excretion was much greater in the control group than in the SH and LP groups. The three groups had similar increases in serum i-PTH.

CONCLUSION

Sevelamer rapidly lowered the serum phosphorus and inhibited the proliferation of PCNA+ cells in this experimental model of early-phase CRF.

Telbivudine attenuates UUO-induced renal fibrosis via TGF-β/Smad and NF-κB signaling

Renal fibrosis yields decreased renal function and is a potent contributor to chronic kidney disease (CKD). Telbivudine (LdT) is an anti-hepatitis B virus (HBV) drug that has been found to steadily improve renal function, but the mechanism of drug action is unclear. One explanation is that LdT impacts inflammatory or fibrotic pathways. In this study, we investigated renal protection by LdT in a rat model of unilateral ureteral obstruction (UUO). UUO rats received oral gavage of LdT (1, 1.5, or 2g/kg/day) for 5weeks. Kidney tissues were examined histopathologically with hematoxylin and eosin and Masson's trichrome stain. To assess proliferation of myofibroblasts and matrix accumulation, α-smooth muscle actin (α-sma) and collagen type I and III were detected. Interleukin-1 (IL-1) and tumor necrosis factor (TNF)-α were evaluated as a measure of proinflammatory cytokines. Transforming growth factor (TGF)-β and nuclear factor-κB (NF-κB) were considered the canonical signaling components in our investigation of the underlying mechanism of LdT action. Histopathology results indicated that LdT ameliorates renal injury and matrix accumulation. Expression of α-sma and collagen I/III as well as key fibrotic signaling factors in the TGF-β/Smad pathway were downregulated. In addition, LdT suppressed the release of IL-1 and TNF-α and decreased the expression of NF-κB by inhibiting toll-like receptor 4. Taken together, these findings indicate that LdT can attenuate renal fibrosis and inflammation via TGF-β/Smad and NF-κB pathways in UUO.

TGF-β1/p53 signaling in renal fibrogenesis

Fibrotic disorders of the renal, pulmonary, cardiac, and hepatic systems are associated with significant morbidity and mortality. Effective therapies to prevent or curtail the advancement to organ failure, however, remain a major clinical challenge. Chronic kidney disease, in particular, constitutes an increasing medical burden affecting >15% of the US population. Regardless of etiology (diabetes, hypertension, ischemia, acute injury, urologic obstruction), persistently elevated TGF-β1 levels are causatively linked to the activation of profibrotic signaling networks and disease progression. TGF-β1 is the principal driver of renal fibrogenesis, a dynamic pathophysiologic process that involves tubular cell injury/apoptosis, infiltration of inflammatory cells, interstitial fibroblast activation and excess extracellular matrix synthesis/deposition leading to impaired kidney function and, eventually, to chronic and end-stage disease. TGF-β1 activates the ALK5 type I receptor (which phosphorylates SMAD2/3) as well as non-canonical (e.g., src kinase, EGFR, JAK/STAT, p53) pathways that collectively drive the fibrotic genomic program. Such multiplexed signal integration has pathophysiological consequences. Indeed, TGF-β1 stimulates the activation and assembly of p53-SMAD3 complexes required for transcription of the renal fibrotic genes plasminogen activator inhibitor-1, connective tissue growth factor and TGF-β1. Tubular-specific ablation of p53 in mice or pifithrin-α-mediated inactivation of p53 prevents epithelial G₂/M arrest, reduces the secretion of fibrotic effectors and attenuates the transition from acute to chronic renal injury, further supporting the involvement of p53 in disease progression. This review focuses on the pathophysiology of TGF-β1-initiated renal fibrogenesis and the role of p53 as a regulator of profibrotic gene expression.

Chronic kidney disease-associated cardiovascular disease: scope and limitations of animal models

Chronic kidney disease (CKD) is a heterogeneous range of disorders affecting up to 11% of the world's population. The majority of patients with CKD die of cardiovascular disease (CVD) before progressing to end-stage renal disease. CKD patients have an increased risk of atherosclerotic disease as well as a unique cardiovascular phenotype. There remains no clear aetiology for these issues and a better understanding of the pathophysiology of CKD-associated CVD is urgently needed. Although nonanimal studies can provide insights into the nature of disease, the whole-organism nature of CKD-associated CVD means that high-quality animal models, at least for the immediate future, are likely to remain a key tool in improving our understanding in this area. We will discuss the methods used to induce renal impairment in rodents and the methods available to assess cardiovascular phenotype and in each case describe the applicability to humans.

The loss of Krüppel-like factor 15 in Foxd1+ stromal cells exacerbates kidney fibrosis

Large epidemiological studies clearly demonstrate that multiple episodes of acute kidney injury contribute to the development and progression of kidney fibrosis. Although our understanding of kidney fibrosis has improved in the past two decades, we have limited therapeutic strategies to halt its progression. Myofibroblast differentiation and proliferation remain critical to the progression of kidney fibrosis. Although canonical Wnt signaling can trigger the activation of myofibroblasts in the kidney, mediators of Wnt inhibition in the resident progenitor cells are unclear. Recent studies demonstrate that the loss of a Krüppel-like factor 15 (KLF15), a kidney-enriched zinc-finger transcription factor, exacerbates kidney fibrosis in murine models. Here, we tested whether Klf15 mRNA and protein expression are reduced in late stages of fibrosis in mice that underwent unilateral ureteric obstruction, a model of progressive renal fibrosis. Knockdown of Klf15 in Foxd1-expressing cells (Foxd1-Cre Klf15fl/fl) increased extracellular matrix deposition and myofibroblast proliferation as compared to wildtype (Foxd1-Cre Klf15+/+) mice after three and seven days of ureteral obstruction. This was validated in mice receiving angiotensin II treatment for six weeks. In both these murine models, the increase in renal fibrosis was found in Foxd1-Cre Klf15fl/fl mice and accompanied by the activation of Wnt/β-catenin signaling. Furthermore, knockdown of Klf15 in cultured mouse embryonic fibroblasts activated canonical Wnt/β-catenin signaling, increased profibrotic transcripts, and increased proliferation after treatment with a Wnt1 ligand. Conversely, the overexpression of KLF15 inhibited phospho-β-catenin (Ser552) expression in Wnt1-treated cells. Thus, KLF15 has a critical role in attenuating kidney fibrosis by inhibiting the canonical Wnt/β-catenin pathway.

Puerarin attenuates renal fibrosis by reducing oxidative stress induced-epithelial cell apoptosis via MAPK signal pathways in vivo and in vitro

Puerarin (PR) is an isoflavonoid isolated from the root of the plant Pueraria lobata and has been widely used in traditional Chinese herbal medicine for the treatment of various diseases. Oxidative stress and epithelial cell apoptosis play important roles in the renal fibrotic process. The present study aimed to determine whether or not PR inhibits renal fibrosis by reducing oxidative stress induced-epithelial cell apoptosis. In vivo, unilateral ureteral obstruction (UUO) induced renal fibrosis, and epithelial cell apoptosis. A total of 24 mice were randomly assigned to four experimental groups: sham, UUO alone, UUO +50 mg/kg PR, and UUO +100 mg/kg PR. In vitro, 200 μM hydrogen peroxide (H₂O₂) induced epithelial cell apoptosis. The experiments were dived into four groups: control, H₂O₂ alone, H₂O₂+50 μM PR, and H₂O₂+100 μM PR. Tubular injury was measured in the renal cortex of the mice through periodic acid-Schiff (PAS) staining, and the extracellular matrix (ECM) was measured through Sirius red (SR), immunohistochemistry (IHC) staining, and Western blot. Renal epithelial cell apoptosis was measured through terminal deoxynucleotidyl transferase-mediated dUTP Nick-End labeling (TUNEL), flow cytometry (FCM), and Hoechst assays. The protein expression of NOX4, caspase3, ERK, P38, and JNK was assessed through Western blot. PAS staining showed that PR decreased renal tubular injury in UUO mice. SR and IHC staining demonstrated that PR decreased the accumulation of ECM. PR treatment significantly inhibited epithelial cell apoptosis according to the results of TUNEL, FCM, Hoechst, and Western blot. Furthermore, NOX4 increased in UUO mice and decreased with PR treatment. H₂O₂-derived oxidative stress activated epithelial apoptosis and mitogen-activated protein kinases (MAPK), and PR treatment significantly reversed it. These results suggest that PR treatment ameliorates renal fibrosis by inhibiting oxidative stress induced-epithelial cell apoptosis through MAPK signaling.

Pressure and stretch differentially affect proliferation of renal proximal tubular cells

Renal obstruction is frequently found in adults and children. Mechanical stimuli, including pressure and stretch in the obstructed kidney, contribute to damage; animal models of obstruction are characterized by increased cellular proliferation. We were interested in the direct effects of pressure and stretch on renal tubular cell proliferation. Human HKC-8 or rat NRK-52E proximal tubule cells were subjected to either pressure [0, 60 or 90 mmHg] or static stretch [0 or 20%] for 24 or 48 h. Cell proliferation was measured by cell counting, cell cycle analyzed by flow cytometry, and PCNA and Skp2 expression were determined by qPCR or western blot. Blood gases were determined in an iSTAT system. Proliferation was also assessed in vivo after 24 h of ureteral obstruction. There was a significant increase in HKC-8 cell number after 48 h of exposure to either 60 or 90 mmHg pressure. Western blot and qPCR confirmed increased expression of PCNA and Skp2 in pressurized cells. Cell cycle measurements demonstrated an increase in HKC-8 in S phase. Mechanical stretching increased PCNA protein expression in HKC-8 cells after 48 h while no effect was observed on Skp2 and cell cycle measurements. Increased PCNA expression was found at 24 h after ureteral obstruction. We demonstrate direct transduction of pressure into a proliferative response in HKC-8 and NRK-52E cells, measured by cell number, PCNA and Skp2 expression and increase in cells in S phase, whereas stretch had a less robust effect on proliferation.

Protective Role of Melatonin and Coenzyme Q10 in Ochratoxin A Toxicity in Rat Liver and Kidney

Melatonin (MEL) and coenzyme Q10 (CoQ10) both display antioxidant and free radical scavenger properties. In the present study, the effect of MEL and CoQ10 on the oxidative stress and fibrosis induced by ochratoxin A (OTA) administration in rats was investigated. Rats were divided into five equal groups, each consisting of seven rats: (1) controls; (2) OTA-treated rats (289 μg/kg/day); (3) OTA+MEL–treated rats (289 μg/kg/day OTA + 10 mg/kg/day MEL); and (4) OTA+CoQ10–treated rats (289 μg/kg/day OTA +1 mg/100 g/day body weight (bw) CoQ10). After 4 weeks of treatment, the level of malondialdehyde (MDA), glutathione peroxidase (GPx), and hydroxyproline (Hyp) were measured in the homogenates of liver and kidney. In the OTA-treated group, the levels of MDA and Hyp in both liver and kidney were significantly increased when compared with the levels of control, whereas GPx activities decreased. In OTA+MEL–treated rats, the levels of MDA and Hyp in both liver and kidney were significantly decreased when compared with the levels of OTA-treated rats; however; GPX activities increased. In the OTA+CoQ10–treated group, the levels of MDA and Hyp were decreased when compared with the levels of OTA-treated rats, whereas GPx activities increased. In the OTA+CoQ 10–treated group, the levels of MDA, Hyp, and GPx were not significantly changed in kidney when compared with OTA-treated group. MEL has a protective effect against OTA toxicity through an inhibition of the oxidative damage and fibrosis both liver and kidney. Although CoQ10 has protective effect against OTA toxicity in liver tissue, it has no effect in kidney tissue.

Posterior urethral valve in fetuses: evidence for the role of inflammatory molecules

BACKGROUND

The aim of this cross-sectional study was to investigate inflammatory biomarkers in urine samples of 24 fetuses with posterior urethral valve (PUV) collected at 22 ± 4 weeks of gestation and to compare the findings with measurements in urine samples of 22 male healthy preterm neonates at 23 ± 4 weeks (control group).

METHODS

Inflammatory biomarkers in urine were measured using a cytometric bead array [interleukin (IL)-2, IL-4, IL-6, IL-10, interferon (IFN)-γ, soluable tumor necrosis factor receptor (TNFR) 1, sTNFR2, monocyte chemoattractant protein-1/chemokine ligand 2 (MCP-1/CCL2), eotaxin/CCL11 and interferon gamma-induced protein/10/C-X-C motif chemokine 10 (IP-10/CXCL10)] and ELISA assays [TNF, IL-8/CXCL8 and transforming growth factor-beta (TGF-β)]. The Mann-Whitney test was used to compare medians. Markers of glomerular (creatinine) and tubular [beta 2 (β2)-microglobulin, uromodulin, osmolality] functions were correlated with inflammatory biomarkers (Spearman test).

RESULTS

An intense inflammatory profile was identified, with significantly increased concentrations of urinary IL-2, IL-4, IL-6, TNF, sTNFRI, sTNFRII, IFN-γ, MCP-1/CCL2, eotaxin/CCL11 and IL-8/CXCL8 in the PUV group compared to the controls. The same was observed for the anti-inflammatory cytokine IL-10 and for the fibrogenic mediator TGF-β. In the correlation analysis, β2-microglobulin positively correlated with the presence of MCP-1/CCL2, sTNFRI and eotaxin/CCL11 and negatively correlated with the presence of creatinine.

CONCLUSIONS

This study shows that inflammatory molecules are already increased in fetuses with PUV at the mean gestational age of 22 weeks, suggesting a physiopathological role for inflammation just after the embryological formation of the urethral membrane.

PKC/Nedd4-2 Signaling Pathway Regulates the Cell Surface Expression of Drug Transporter hOAT1

Human organic anion transporter-1 (hOAT1) regulates the absorption, distribution, and excretion of a wide range of clinically important drugs. Our previous work demonstrated that hOAT1 is a dynamic membrane transporter, constitutively internalizing from and recycling back to the cell plasma membrane. Short-term activation (<30 minutes) of protein kinase C (PKC) promotes the attachment of a lysine 48-linked polyubiquitin chain to hOAT1, a process catalyzed by ubiquitin ligase neural precursor cell expressed developmentally down-regulated 4-2 (Nedd4-2). The ubiquitination of hOAT1 then triggers an accelerated endocytosis of the transporter from plasma membrane, which results in reduced hOAT1 expression at the cell surface and decreased hOAT1 transport activity. In the present study, we investigated the long-term effect of PKC on hOAT1. We showed that long-term activation (>2 hours) of PKC significantly enhanced hOAT1 degradation, and such action was partially blocked by ubiquitin mutant Ub-K48R, which has its lysine (K) 48 mutated to arginine (R) and is incapable of forming a K48-linked polyubiquitin chain. The ubiquitin ligase Nedd4-2 was also found to augment hOAT1 degradation. These results suggest that PKC-regulated and Nedd4-2-catalyzed attachment of a lysine 48-linked polyubiquitin chain to hOAT1 is important for hOAT1 stability. We further showed through coimmunoprecipitation experiments that there was a direct association between hOAT1 and Nedd4-2, and such interaction was weakened when the WW3 and WW4 domains of the ligase were mutated. Mutating WW3 and WW4 domains of the ligase also impaired its ability to ubiquitinate hOAT1. Therefore, WW3 and WW4 domains of Nedd4-2 are critical for its association with and modulation of the transporter.

Pharmacological effects of a vitamin K1 2,3-epoxide reductase (VKOR) inhibitor, 3-acetyl-5-methyltetronic acid, on cisplatin-induced fibrosis in rats

Cisplatin (CDDP) is a chemotherapeutic agent that is widely used in the treatment of lymphomas and solid malignancies. However, its clinical usage is limited by its severe side effects in the kidneys. Glomerular and tubular injuries in the kidneys commonly progress to interstitial fibrosis and, ultimately, the end stage of renal failure. We previously reported that 3-acetyl-5-methyltetronic acid (AMT) had inhibitory effects on rat renal vitamin K₁ 2,3-epoxide reductase (VKOR) in vitro and also suppressed mesangial cell proliferation and, consequently, the formation of fibrosis via the vitamin K-dependent activation of the growth arrest-specific 6 (Gas6)/Axl pathway in anti-Thy-1 glomerulonephritis (Thy-1 GN) in rats. In the present study, we demonstrated that AMT alleviated the progression of renal fibrosis in CDDP-treated rats. The repeated intravenous administration of AMT for 28 days dose-dependently suppressed increases in plasma urea nitrogen and plasma creatinine levels as well as creatinine clearance in CDDP-treated rats. Furthermore, the treatment suppressed the expression of α-smooth muscle actin (SMA)-positive cells and ameliorated the extracellular matrix accumulation of collagen III, indicating an antifibrotic effect. In conclusion, our toxicological and histopathological results demonstrated quantitatively the pharmacological inhibitory effects of AMT on the progression of renal fibrosis in CDDP-treated rats.

Intermedin attenuates renal fibrosis by induction of heme oxygenase-1 in rats with unilateral ureteral obstruction

BACKGROUND

Intermedin [IMD, adrenomedullin-2 (ADM-2)] attenuates renal fibrosis by inhibition of oxidative stress. However, the precise mechanisms remain unknown. Heme oxygenase-1 (HO-1), an antioxidant agent, is associated with antifibrogenic effects. ADM is known to induce HO-1. Whether IMD has any effect on HO-1 is unclear. Herein, we determined whether the antifibrotic properties of IMD are mediated by induction of HO-1.

METHODS

Renal fibrosis was induced by unilateral ureteral obstruction (UUO) performed on male Wistar rats. Rat proximal tubular epithelial cell line (NRK-52E) was exposed to rhTGF-β1 (10 ng/ml) to establish an in vitro model of epithelial-mesenchymal transition (EMT). IMD was over-expressed in vivo and in vitro using the vector pcDNA3.1-IMD. Zinc protoporphyrin (ZnPP) was used to block HO-1 enzymatic activity. IMD effects on HO-1 expression in the obstructed kidney of UUO rat and in TGF-β1-stimulated NRK-52E were analyzed by real-time RT-PCR, Western blotting or immunohistochemistry. HO activity in the obstructed kidney, contralateral kidney of UUO rat and NRK-52E was examined by measuring bilirubin production. Renal fibrosis was determined by Masson trichrome staining and collagen I expression. Macrophage infiltration and IL-6 expression were evaluated using immunohistochemical analysis. In vivo and in vitro EMT was assessed by measuring α-smooth muscle actin (α-SMA) and E-cadherin expression using Western blotting or immunofluorescence, respectively.

RESULTS

HO-1 expression and HO activity were increased in IMD-treated UUO kidneys or NRK-52E. The obstructed kidneys of UUO rats demonstrated significant interstitial fibrosis on day 7 after operation. In contrast, kidneys that were treated with IMD gene transfer exhibited minimal interstitial fibrosis. The obstructed kidneys of UUO rats also had greater macrophage infiltration and IL-6 expression. IMD restrained infiltration of macrophages and expression of IL-6 in UUO kidneys. The degree of EMT was extensive in obstructed kidneys of UUO rats as indicated by decreased expression of E-cadherin and increased expression of α-SMA. In vitro studies using NRK-52E confirmed these observations. EMT was suppressed by IMD gene delivery. However, all of the above beneficial effects of IMD were eliminated by ZnPP, an inhibitor of HO enzyme activity.

CONCLUSION

This study demonstrates that IMD attenuates renal fibrosis by induction of HO-1.

The attenuation of renal fibrosis by histone deacetylase inhibitors is associated with the plasticity of FOXP3+IL-17+ T cells

BACKGROUND

The histone deacetylase (HDAC) inhibitor, which has potential effects on epigenetic modifications, had been reported to attenuate renal fibrosis. CD4⁺ forkhead box P3 (FOXP3)⁺ T regulatory (Treg) cells may be converted to inflammation-associated T helper 17 cells (Th17) with tissue fibrosis properties. The association between FOXP3⁺IL-17⁺ T cells and the attenuation of renal fibrosis by the HDAC inhibitor is not clear.

METHODS

This study evaluated the roles of the HDAC inhibitor, Treg cells and their differentiation into Th17 cells, which aggravate chronic inflammation and renal fibrosis in a unilateral ureteral obstruction (UUO) mouse model. The study groups included control and UUO mice that were monitored for 7, 14 or 21 days.

RESULTS

Juxtaglomerular (JG) hyperplasia, angiotensin II type 1 receptor (AT1R) expression and lymphocyte infiltration were observed in renal tissues after UUO but were decreased after trichostatin A (TSA) treatment, a HDAC inhibitor. The number of CD4⁺FOXP3⁺ T cells increased progressively, along with the number of FOXP3⁺interleukin (IL)-17⁺ T cells, after 14 days, and their numbers then progressively decreased with increasing CD4⁺IL-17⁺ T cell numbers, as demonstrated by double immunohistochemistry. Progressive renal fibrosis was associated with the loss of CD4⁺FOXP3⁺IL-17⁺ T cells in splenic single-cell suspensions. FOXP3⁺IL-17⁺ T cells expressed TGF-β1 both in vitro and in vivo, and TGF-β1 expression was significantly knockdown by IL-17 siRNA in vitro. These cells were found to play a role in converting Tregs into IL-17- and TGF-β1-producing cells.

CONCLUSIONS

TSA treatment decreased JG hyperplasia, the percentage of FOXP3⁺IL-17⁺ cells and the degree of fibrosis, suggesting that therapeutic benefits may result from epigenetic modifications.

A case of renal dysfunction caused by pelvic organ prolapse

Pelvic organ prolapse (POP) is the descent of pelvic organs through the vagina, and sometimes causes hydronephrosis. Although the association between POP and hydronephrosis has long been recognized, severe hydronephrosis and renal dysfunction are rarely seen. We report a case of 66-year-old woman who had a vaginal delivery presented with externalized uterine and bladder prolapse during the previous 2 years. She had a 3-day history of hypophagia and vomiting, and laboratory analysis resulted in serum creatinine of 5.75 mg/dL and blood urea of 78.1 mg/dL. The patient was treated urgently with vaginal pessary to return the uterine and bladder into the pelvis. After 2 weeks, her serum creatinine dropped to 3.66 mg/dL, but chronic renal failure persisted. Hydronephrosis caused by POP may lead to renal dysfunction and can advance to irreversible renal damage if left untreated. Important is early evaluation of renal function and images of the kidney and ureter.

A novel indole compound MA-35 attenuates renal fibrosis by inhibiting both TNF-α and TGF-β1 pathways

Renal fibrosis is closely related to chronic inflammation and is under the control of epigenetic regulations. Because the signaling of transforming growth factor-β₁ (TGF-β₁) and tumor necrosis factor-α (TNF-α) play key roles in progression of renal fibrosis, dual blockade of TGF-β₁ and TNF-α is desired as its therapeutic approach. Here we screened small molecules showing anti-TNF-α activity in the compound library of indole derivatives. 11 out of 41 indole derivatives inhibited the TNF-α effect. Among them, Mitochonic Acid 35 (MA-35), 5-(3, 5-dimethoxybenzyloxy)-3-indoleacetic acid, showed the potent effect. The anti-TNF-α activity was mediated by inhibiting IκB kinase phosphorylation, which attenuated the LPS/GaIN-induced hepatic inflammation in the mice. Additionally, MA-35 concurrently showed an anti-TGF-β₁ effect by inhibiting Smad3 phosphorylation, resulting in the downregulation of TGF-β₁-induced fibrotic gene expression. In unilateral ureter obstructed mouse kidney, which is a renal fibrosis model, MA-35 attenuated renal inflammation and fibrosis with the downregulation of inflammatory cytokines and fibrotic gene expressions. Furthermore, MA-35 inhibited TGF-β₁-induced H3K4me1 histone modification of the fibrotic gene promoter, leading to a decrease in the fibrotic gene expression. MA-35 affects multiple signaling pathways involved in the fibrosis and may recover epigenetic modification; therefore, it could possibly be a novel therapeutic drug for fibrosis.

Pathophysiological Mechanisms of Renal Fibrosis: A Review of Animal Models and Therapeutic Strategies

Chronic kidney disease (CKD) is a long-term condition in which the kidneys do not work correctly. It has a high prevalence and represents a serious hazard to human health and estimated to affects hundreds of millions of people. Diabetes and hypertension are the two principal causes of CKD. The progression of CKD is characterized by the loss of renal cells and their replacement by extracellular matrix (ECM), independently of the associated disease. Thus, one of the consequences of CKD is glomerulosclerosis and tubulointerstitial fibrosis caused by an imbalance between excessive synthesis and reduced breakdown of the ECM. There are many molecules and cells that are associated with progression of renal fibrosis e.g. angiotensin II (Ang II). Therefore, in order to understand the biopathology of renal fibrosis and for the evaluation of new treatments, the use of animal models is crucial such as: surgical, chemical and physical models, spontaneous models, genetic models and in vitro models. However, there are currently no effective treatments for preventing the progression of renal fibrosis. Therefore it is essential to improve our knowledge of the cellular and molecular mechanisms of the progress of renal fibrosis in order to achieve a reversion/elimination of renal fibrosis.

Alpha-lipoic acid ameliorates the epithelial mesenchymal transition induced by unilateral ureteral obstruction in mice

The epithelial-to-mesenchymal transition (EMT) is one of mechanisms that induce renal interstitial fibrosis. Understanding EMT in renal fibrosis has important therapeutic implications for patients with kidney disease. Alpha-lipoic acid (ALA) is a natural compound with antioxidant properties. Studies for ALA are performed in acute kidney injury with renal tubular apoptosis, renal inflammation, and oxidative stress. We investigated the effects of ALA on EMT-mediated renal interstitial fibrosis in mice with unilateral ureteral obstruction (UUO). UUO mice developed severe tubular atrophy and tubulointerstitial fibrosis, with a robust EMT response and ECM deposition after 7 postoperative days. In contrast, ALA-treated UUO mice showed only moderate injury and minimal fibrosis and also larger reductions in the expression of ECM proteins, inflammatory factors, and EMT markers. ALA was shown to be involved in the suppression of infiltrating macrophages associated with EMT and the progression of interstitial fibrosis. It also lessened the destruction of the tubular basement membrane, by reducing the expression of matrix metalloproteinases. This is the first study to show that ALA modulates EMT in a UUO mouse model. Our results suggest that ALA merits further exploration as a therapeutic agent in the prevention and treatment of chronic kidney disease.

The Sirt1 activator, SRT1720, attenuates renal fibrosis by inhibiting CTGF and oxidative stress

The transforming growth factor-β1 (TGF-β1)/connective tissue growth factor (CTGF) pathway plays an important role in the pathogenesis and progression of chronic kidney disease. Oxidative stress is also involved in TGF-β1 signalling. Sirtuin 1 (Sirt1) exerts a number of pleiotropic effects, protecting against renal disease, including inhibiting fibrosis and oxidative metabolism. In this study, we investigated the role of the Sirt1 activator, SRT1720, in unilateral ureteral obstruction (UUO)-induced tubulointerstitial fibrosis and aimed to determine whether this role depends on the inhibition of oxidative stress and the TGF-β1/CTGF pathway. Renal fibrosis was induced by UUO in CD1 mice. SRT1720 (100 mg/kg) was administered by intraperitoneal injection for 3 days prior to UUO and this was continued for 7 days following UUO. Histological changes were examined by Masson's trichrome staining. The expression of fibrosis-related factors was evaluated by immunohistochemistry, western blot analysis and RT-qPCR. Apoptosis was also examined. We also examined the superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GPx) and reduced glutathione (GSH) levels. UUO induced renal fibrosis and apoptosis and decreased Sirt1 expression. The administration of SRT1720 increased the Sirt1 levels and partially attenuated UUO-induced renal fibrosis and apoptosis. Furthermore, SRT1720 attenuated the levels of oxidative stress (it decreased the MDA levels, and increased the SOD, GPx and GSH levels), which suggests that it protected the cells against ROS-induced damage. Moreover, SRT1720 effectively inhibited the levels of TGF-β1/CTGF induced by UUO. On the whole, these findings indicate that the Sirt1 activator, SRT1720, exerts protective effects against UUO-induced tubulointerstitial fibrosis. The mechanisms of action of SRT1720 may include, at least in part, the suppression of renal oxidative stress and the TGF-β1/CTGF signalling pathway. The Sirt1 activator may therefore be prove to be a potent therapeutic agent for the treatment of fibrotic kidney disease.

The antihelmenthic phosphate niclosamide impedes renal fibrosis by inhibiting homeodomain-interacting protein kinase 2 expression

Renal fibrosis is the final common pathway of all varieties of progressive chronic kidney disease. However, there are no effective therapies to prevent or slow the progression of renal fibrosis. Niclosamide is a US Food and Drug Administration-approved oral antihelminthic drug used for treating most tapeworm infections. Here, we demonstrated that phosphate niclosamide, the water-soluble form of niclosamide, significantly reduced proteinuria, glomerulosclrotic lesions, and interstitial fibrosis in a murine model of adriamycin nephropathy. In addition, phosphate niclosamide significantly ameliorated established renal interstitial fibrosis a murine model of unilateral ureteral obstruction. Mechanistically, phosphate niclosamide directly inhibited TGF-β-induced expression of homeodomain-interacting protein kinase 2 (HIPK2) by interfering with the binding of Smad3 to the promoter of the HIPK2 gene, and subsequently mitigated the activation of its downstream signaling pathways including Smad, Notch, NF-κB and Wnt/β-catenin pathway both in vitro and in vivo. Thus, phosphate niclosamide mitigates renal fibrosis at least partially by inhibiting HIPK2 expression. Hence, phosphate niclosamide might be a potential therapeutic agent for renal fibrosis.

p53 induces miR199a-3p to suppress SOCS7 for STAT3 activation and renal fibrosis in UUO

The role of p53 in renal fibrosis has recently been suggested, however, its function remains controversial and the underlying mechanism is unclear. Here, we show that pharmacological and genetic blockade of p53 attenuated renal interstitial fibrosis, apoptosis, and inflammation in mice with unilateral urethral obstruction (UUO). Interestingly, p53 blockade was associated with the suppression of miR-215-5p, miR-199a-5p&3p, and STAT3. In cultured human kidney tubular epithelial cells (HK-2), TGF-β1 treatment induced fibrotic changes, including collagen I and vimentin expression, being associated with p53 accumulation, p53 Ser15 phosphorylation, and miR-199a-3p expression. Inhibition of p53 by pifithrin-α blocked STAT3 activation and the expression of miR-199a-3p, collagen I, and vimentin during TGF-β1 treatment. Over-expression of miR-199a-3p increased TGFβ1-induced collagen I and vimentin expression and restored SOCS7 expression. Furthermore, SOCS7 was identified as a target gene of miR-199a-3p, and silencing of SOCS7 promoted STAT3 activation. ChIp analyses indicated the binding of p53 to the promoter region of miR-199a-3p. Consistently, kidney biopsies from patients with IgA nephropathy and diabetic nephropathy exhibited substantial activation of p53 and STAT3, decreased expression of SOCS7, and increase in profibrotic proteins and miR-199a-3p. Together, these results demonstrate the novel p53/miR-199a-3p/SOCS7/STAT3 pathway in renal interstitial fibrosis.

Oligo-fucoidan prevents renal tubulointerstitial fibrosis by inhibiting the CD44 signal pathway

Tubulointerstitial fibrosis is recognized as a key determinant of progressive chronic kidney disease (CKD). Fucoidan, a sulphated polysaccharide extracted from brown seaweed, exerts beneficial effects in some nephropathy models. The present study evaluated the inhibitory effect of oligo-fucoidan (800 Da) on renal tubulointerstitial fibrosis. We established a mouse CKD model by right nephrectomy with transient ischemic injury to the left kidney. Six weeks after the surgery, we fed the CKD mice oligo-fucoidan at 10, 20, and 100 mg/kg/d for 6 weeks and found that the oligo-fucoidan doses less than 100 mg/kg/d improved renal function and reduced renal tubulointerstitial fibrosis in CKD mice. Oligo-fucoidan also inhibited pressure-induced fibrotic responses and the expression of CD44, β-catenin, and TGF-β in rat renal tubular cells (NRK-52E). CD44 knockdown downregulated the expression of β-catenin and TGF-β in pressure-treated cells. Additional ligands for CD44 reduced the anti-fibrotic effect of oligo-fucoidan in NRK-52E cells. These data suggest that oligo-fucoidan at the particular dose prevents renal tubulointerstitial fibrosis in a CKD model. The anti-fibrotic effect of oligo-fucoidan may result from interfering with the interaction between CD44 and its extracellular ligands.

Soluble Uric Acid Activates the NLRP3 Inflammasome

Uric acid is a damage-associated molecular pattern (DAMP), released from ischemic tissues and dying cells which, when crystalized, is able to activate the NLRP3 inflammasome. Soluble uric acid (sUA) is found in high concentrations in the serum of great apes, and even higher in some diseases, before the appearance of crystals. In the present study, we sought to investigate whether uric acid, in the soluble form, could also activate the NLRP3 inflammasome and induce the production of IL-1β. We monitored ROS, mitochondrial area and respiratory parameters from macrophages following sUA stimulus. We observed that sUA is released in a hypoxic environment and is able to induce IL-1β release. This process is followed by production of mitochondrial ROS, ASC speck formation and caspase-1 activation. Nlrp3^-/- macrophages presented a protected redox state, increased maximum and reserve oxygen consumption ratio (OCR) and higher VDAC protein levels when compared to WT and Myd88^-/- cells. Using a disease model characterized by increased sUA levels, we observed a correlation between sUA, inflammasome activation and fibrosis. These findings suggest sUA activates the NLRP3 inflammasome. We propose that future therapeutic strategies for renal fibrosis should include strategies that block sUA or inhibit its recognition by phagocytes.

Analysis of Pathological Activities of CCN Proteins in Fibrotic Diseases: Kidney Fibrosis

Renal fibrosis is characterized by glomerulosclerosis and tubulointerstitial fibrosis. Transforming growth factor-β (TGF-β) is postulated to play a central role in the development of both fibrotic processes. Extracellular matrix proteins, particularly type I collagen and fibronectin, accumulate in the tissue during renal fibrogenesis. CCN2, also known as connective tissue growth factor (CTGF), is increased in the setting of fibrosis and modulates a number of downstream signaling pathways involved in the fibrogenic properties of TGF-β. Unilateral ureteral obstruction is one of the most widely used models of renal tubulointerstitial fibrosis. Herein, we describe unilateral ureteral obstruction in mice as an animal model of renal fibrosis and methods for immunohistochemical analyses of extracellular matrix proteins and CCN2. In addition, we describe the construction of podocyte-specific CCN2-transgenic mice for analyzing mesangial matrix expansion and glomerulosclerosis.

Inhibition of TRPC6 channels ameliorates renal fibrosis and contributes to renal protection by soluble klotho

Fibrosis is an exaggerated form of tissue repair that occurs with serious damage or repetitive injury and ultimately leads to organ failure due to the excessive scarring. Increased calcium ion entry through the TRPC6 channel has been associated with the pathogenesis of heart and glomerular diseases, but its role in renal interstitial fibrosis is unknown. We studied this by deletion of Trpc6 in mice and found it decreased unilateral ureteral obstruction-induced interstitial fibrosis and blunted increased mRNA expression of fibrosis-related genes in the ureteral obstructed kidney relative to that in the kidney of wild-type mice. Administration of BTP2, a pyrazol derivative known to inhibit function of several TRPC channels, also ameliorated obstruction-induced renal fibrosis and gene expression in wild-type mice. BTP2 inhibited carbachol-activated TRPC3 and TRPC6 channel activities in HEK293 cells. Ureteral obstruction caused over a 10-fold increase in mRNA expression for TRPC3 as well as TRPC6 in the kidneys of obstructed relative to the sham-operated mice. The magnitude of protection against obstruction-induced fibrosis in Trpc3 and Trpc6 double knockout mice was not different from that in Trpc6 knockout mice. Klotho, a membrane and soluble protein predominantly produced in the kidney, is known to confer protection against renal fibrosis. Administration of soluble klotho significantly reduced obstruction-induced renal fibrosis in wild-type mice, but not in Trpc6 knockout mice, indicating that klotho and TRPC6 inhibition act in the same pathway to protect against obstruction-induced renal fibrosis. Thus klotho and TRPC6 may be pharmacologic targets for treating renal fibrosis.