Renal interstitial fibrosis is reduced in angiotensin II type 1a receptor-deficient mice

Therapeutic potential for renal fibrosis by targeting Smad3-dependent noncoding RNAs

Renal fibrosis is a characteristic hallmark of chronic kidney disease (CKD) that ultimately results in renal failure, leaving patients with few therapeutic options. TGF-β is a master regulator of renal fibrosis and mediates progressive renal fibrosis via both canonical and noncanonical signaling pathways. In the canonical Smad signaling, Smad3 is a key mediator in tissue fibrosis and mediates renal fibrosis via a number of noncoding RNAs (ncRNAs). In this regard, targeting Smad3-dependent ncRNAs may offer a specific therapy for renal fibrosis. This review highlights the significance and innovation of TGF-β/Smad3-associated ncRNAs as biomarkers and therapeutic targets in renal fibrogenesis. In addition, the underlying mechanisms of these ncRNAs and their future perspectives in the treatment of renal fibrosis are discussed.

Obstructive nephropathy and molecular pathophysiology of renal interstitial fibrosis

The kidneys play a key role in maintaining total body homeostasis. The complexity of this task is reflected in the unique architecture of the organ. Ureteral obstruction greatly affects renal physiology by altering hemodynamics, changing glomerular filtration and renal metabolism, and inducing architectural malformations of the kidney parenchyma, most importantly renal fibrosis. Persisting pathological changes lead to chronic kidney disease, which currently affects ∼10% of the global population and is one of the major causes of death worldwide. Studies on the consequences of ureteral obstruction date back to the 1800s. Even today, experimental unilateral ureteral obstruction (UUO) remains the standard model for tubulointerstitial fibrosis. However, the model has certain limitations when it comes to studying tubular injury and repair, as well as a limited potential for human translation. Nevertheless, ureteral obstruction has provided the scientific community with a wealth of knowledge on renal (patho)physiology. With the introduction of advanced omics techniques, the classical UUO model has remained relevant to this day and has been instrumental in understanding renal fibrosis at the molecular, genomic, and cellular levels. This review details key concepts and recent advances in the understanding of obstructive nephropathy, highlighting the pathophysiological hallmarks responsible for the functional and architectural changes induced by ureteral obstruction, with a special emphasis on renal fibrosis.

The Genomic Response to TGF-β1 Dictates Failed Repair and Progression of Fibrotic Disease in the Obstructed Kidney

Tubulointerstitial fibrosis is a common and diagnostic hallmark of a spectrum of chronic renal disorders. While the etiology varies as to the causative nature of the underlying pathology, persistent TGF-β1 signaling drives the relentless progression of renal fibrotic disease. TGF-β1 orchestrates the multifaceted program of kidney fibrogenesis involving proximal tubular dysfunction, failed epithelial recovery or re-differentiation, capillary collapse and subsequent interstitial fibrosis eventually leading to chronic and ultimately end-stage disease. An increasing complement of non-canonical elements function as co-factors in TGF-β1 signaling. p53 is a particularly prominent transcriptional co-regulator of several TGF-β1 fibrotic-response genes by complexing with TGF-β1 receptor-activated SMADs. This cooperative p53/TGF-β1 genomic cluster includes genes involved in cellular proliferative control, survival, apoptosis, senescence, and ECM remodeling. While the molecular basis for this co-dependency remains to be determined, a subset of TGF-β1-regulated genes possess both p53- and SMAD-binding motifs. Increases in p53 expression and phosphorylation, moreover, are evident in various forms of renal injury as well as kidney allograft rejection. Targeted reduction of p53 levels by pharmacologic and genetic approaches attenuates expression of the involved genes and mitigates the fibrotic response confirming a key role for p53 in renal disorders. This review focuses on mechanisms underlying TGF-β1-induced renal fibrosis largely in the context of ureteral obstruction, which mimics the pathophysiology of pediatric unilateral ureteropelvic junction obstruction, and the role of p53 as a transcriptional regulator within the TGF-β1 repertoire of fibrosis-promoting genes.

Alteration of N6-methyladenosine epitranscriptome profile in unilateral ureteral obstructive nephropathy

Aim: To reveal the alterations of N⁶-methyladenosine (m⁶A) epitranscriptome profile in kidney after unilateral ureteral obstruction in mice. Materials & methods: Total renal m⁶A and expressions of methyltransferases and demethylases were detected by colorimetric quantification method, real-time PCR and western blot, respectively. Methylated RNA immunoprecipitation sequencing was performed to map epitranscriptome-wide m⁶A profile. Results: Total m⁶A levels were time-dependent decreased within 1 week, with the lowest level detected at day 7. A total of 823 differentially methylated transcripts in 507 genes were identified. Specifically, demethylated mRNAs selectively acted on multiple pathways, including TGF-β and WNT. Conclusion: m⁶A modification has a functional importance in renal interstitial fibrosis during obstructive nephropathy and might be a promising therapeutic target.

The MicroRNA MiR-29c Alleviates Renal Fibrosis via TPM1-Mediated Suppression of the Wnt/β-Catenin Pathway

Purpose

This study aimed to evaluate the mechanism by which miR-29c expression in fibroblasts regulates renal interstitial fibrosis.

Methods

We stimulated NRK-49F cells with TGF-β1 to mimic the effects of fibrosis in vitro, while unilateral ureteral obstruction (UUO) was performed to obstruct the mid-ureter in mice. MiR-29c mimic or miR-29c inhibitor was used to mediate genes expressions in vitro. The recombinant adeno associated virus (rAAV) vectors carrying a FSP1 promoter that encodes miR-29c precursor or miR-29c inhibitor was used to mediate genes expressions in vivo, and a flank incision was made to expose the left kidney of each animal.

Results

In the present study, TGF-β1 was demonstrated to regulate miR-29c expression through Wnt/β-catenin signaling. In contrast, miR-29c appears to inhibit the Wnt/β-catenin pathway by suppressing TPM1 expression. As suggested by this feedback mechanism, miR-29c may be a key fibrosis-related microRNA expressed by fibroblasts in TGF-β1/Wnt/β-catenin-driven renal fibrosis, and manipulation of miR-29c action may accordingly offer a potential therapeutic pathway for renal fibrosis treatment.

Conclusion

MiR-29c expression was downregulated in UUO mouse kidneys as well as TGF-β1-treated NRK-49F cells, which thus inhibits myofibroblast formation via targeting of TPM1. Additionally, the production of extracellular matrix (ECM) in renal fibroblasts appears to be controlled by the reciprocal regulation of miR-29c action and the Wnt/β-catenin pathway.

Collagen receptor- and metalloproteinase-dependent hypertensive stress response in mesangial and glomerular endothelial cells

Progressive alteration of the extracellular matrix (ECM) is the characteristic of hypertensive nephropathy (HN). Both mesangial and endothelial cells have the ability to synthesize and degrade ECM components, including collagens through the activation of matrix metalloproteinases (MMPs) in stress conditions, such as in hypertension. On the other hand, hydrogen sulfide (H2S) has been shown to mitigate hypertensive renal matrix remodeling. Surprisingly, whether H2S ameliorates receptor-mediated (urokinase plasminogen activator receptor-associated protein, uPARAP/Endo180) collagen dysregulation in Ang-II hypertension is not clear. The purpose of this study was to determine whether Ang-II alters the expression of Endo180, tissue plasminogen activator (tPA), MMPs, and their tissue inhibitors (TIMPs) leading to the dysregulation of cellular collagen homeostasis and whether H2S mitigates the collagen turnover. Mouse mesangial cells (MCs) and glomerular endothelial cells (MGECs) were treated without or with Ang-II and H2S donor GYY (GYY4137) for 48 h. Cell lysates were analyzed by Western blot and RT-PCR, and cells were analyzed by immunocytochemistry. The results indicated that, while Ang-II differentially expressed MMP-13 and TIMP-1 in MCs and in MGECs, it predominantly decreased tPA, Endo 180, and increased plasminogen activator inhibitor-1 (PAI-1), MMP-14, and collagen IIIA and IV in both the cell types. Interestingly, H2S donor GYY treatment normalized the above changes in both the cell types. We conclude that Ang-II treatment causes ECM remodeling in MCs and MGECs through PAI-1/tPA/Endo180 and MMP/TIMP-dependent collagen remodeling, and H2S treatment mitigates remodeling, in part, by modulating these pathways.

Necrostatin-1 Alleviates Bleomycin-Induced Pulmonary Fibrosis and Extracellular Matrix Expression in Interstitial Pulmonary Fibrosis

Background

Interstitial pulmonary fibrosis (IPF) is harmful for patients’ life and health. The effective treatment of IPF is lacking because of unclear pathogenesis. Necrostatin-1 has protective effects on lung injury and can suppress the fibrosis development. I this study we investigated whether necrostatin-1 could decrease the proliferation of pulmonary fibroblasts, pulmonary fibrosis and expression of extracellular matrix (ECM) in IPF.

Material/Methods

The IPF mice model was conducted by intra-tracheal injection of bleomycin (BLM) (2 mg/kg) for C57BL/6N mice. Necrostatin-1 treatment was performed with 1 mg/kg necrostatin-1 by an intravenous injection for C57BL/6N mice. Lung tissue structures and collagen deposition were observed by hematoxylin and eosin staining and Masson staining. IPF in vitro model was constructed by MRC-5 cells induced by transforming growth factor beta 1 (TGF-β1). And, 20 μM necrostatin-1 was used to treat the TGF-β1 induced MRC-5 cells. Cell Counting Kit-8 (CCK-8) assay detected the viability of MRC-5 cells. The expression of receptor-interacting protein kinase-1 and -3 (RIPK1 and RIPK3), α smooth muscle actin (α-SMA), collagen IV, collagen I, fibronectin (FN), and transforming growth factor-β (TGF-β) in lung tissues and MRC-5 cells was measured by western blot analysis. The α-SMA expression in lung tissues was also analyzed by immunohistochemistry.

Results

The expression of RIPK1 and RIPK3 in lung tissues of BLM induced mice was increased. The degree of pulmonary fibrosis and expression of α-SMA, collagen IV, collagen I, FN, and TGF-β in lung tissues of BLM induced mice was enhanced. The proliferation of MRC-5 cells was increased when MRC-5 cells were induced by TGF-β. The expression of RIPK1, RIPK3, α-SMA, collagen IV, collagen I, and FN was increased in TGF-β induced MRC-5 cells. And, necrostatin-1 could effectively reverse the changes of pulmonary fibrosis, RIPK1, RIPK3, and ECM in vivo and in vitro experiments.

Conclusions

Necrostatin-1 attenuated pulmonary fibrosis in lung tissues of BLM induced mice and inhibited the fibroblast proliferation. And, necrostatin-1 also decreased the expression of RIPK1, RIPK3, and ECM in lung tissues of BLM induced mice and TGF-β induced fibroblasts. Necrostatin-1 could be a new effective drug for the treatment of IPF.

Thymoquinone alleviates renal interstitial fibrosis and kidney dysfunction in rats with unilateral ureteral obstruction

Unilateral ureteral obstruction (UUO) causes severe renal tubulointerstitial fibrosis. Because of many pharmacologic properties of thymoquinone (TQ), in this study, the effects of TQ against kidney fibrosis and dysfunction were investigated in rats with UUO. Forty male Wistar rats were divided into five groups: Sham operated, UUO, and the animals with UUO treated with losartan, captopril, or TQ. Collagen IV and transforming growth factor (TGF)-β1 expressions, interstitial fibrosis, histological changes, and kidney function were assessed. UUO markedly increased renal expression of TGF-β1 and collagen I and induced interstitial fibrosis (p < .001). Losartan, captopril, or TQ significantly downregulated the expression of these fibrotic markers and interstitial fibrosis (p < .01-p < .001). In UUO group, serum levels of urea and creatinine and protein excretion rate significantly increased, but glomerular filtration rate (GFR) and urine osmolarity showed a significant decrease (p < .001-p < .05). Administration of captopril and TQ caused no significant change in serum urea and protein excretion rate. Unlike losartan and captopril, TQ caused no significant alteration in GFR compared with Day 1. Losartan caused significant increases in serum urea and creatinine but significant decrease in urine osmolarity. TQ could be regarded as a potent therapeutic agent for treatment of UUO-induced kidney fibrosis and dysfunction.

The protective arm of the renin-angiotensin system may counteract the intense inflammatory process in fetuses with posterior urethral valves

OBJECTIVE

Posterior urethral valve is the most common lower urinary tract obstruction in male children. A high percentage of patients with posterior urethral valve evolve to end-stage renal disease. Previous studies showed that cytokines, chemokines, and components of the renin-angiotensin system contribute to the renal damage in obstructive uropathies. The authors recently found that urine samples from fetuses with posterior urethral valve have increased levels of inflammatory molecules. The aim of this study was to measure renin-angiotensin system molecules and to investigate their correlation with previously detected inflammatory markers in the same urine samples of fetuses with posterior urethral valve.

METHODS

Urine samples from 24 fetuses with posterior urethral valve were collected and compared to those from 22 healthy male newborns at the same gestational age (controls). Renin-angiotensin system components levels were measured by enzyme-linked immunosorbent assay.

RESULTS

Fetuses with posterior urethral valve presented increased urinary levels of angiotensin (Ang) I, Ang-(1-7) and angiotensin-converting enzyme 2 in comparison with controls. ACE levels were significantly reduced and Ang II levels were similar in fetuses with posterior urethral valve in comparison with controls.

CONCLUSIONS

Increased urinary levels of angiotensin-converting enzyme 2 and of Ang-(1-7) in fetuses with posterior urethral valve could represent a regulatory response to the intense inflammatory process triggered by posterior urethral valve.

Stimulating Type 1 Angiotensin Receptors on T Lymphocytes Attenuates Renal Fibrosis

Most forms of chronic kidney disease culminate in renal fibrosis that heralds organ failure. In contrast to the protective effects of globally blocking type 1 angiotensin (AT₁) receptors throughout the body, activating AT₁ receptors directly on immune cells may serve protective functions. However, the effects of stimulating the T-cell AT₁ receptor on the progression of renal fibrosis remain unknown. In this study, mice with T-cell-specific deletion of the dominant murine AT₁ receptor isoform Lck-Cre Agtra^flox/flox [total knockout (TKO)] and wild-type (WT) controls were subjected to the unilateral ureteral obstruction model of kidney fibrosis. Compared with WT controls, obstructed kidneys from TKO mice at day 14 had increased collagen 1 deposition. CD4⁺ T cells, CD11b⁺Ly6C^hi myeloid cells, and mRNA levels of Th1 inflammatory cytokines are elevated in obstructed TKO kidneys, suggesting that augmented Th1 responses in the TKO mice may exaggerate renal fibrosis by driving proinflammatory macrophage differentiation. In turn, T-bet deficient (T-bet knockout) mice lacking Th1 responses have attenuated collagen deposition after unilateral ureteral obstruction. We conclude that activating the AT₁ receptor on T cells mitigates renal fibrogenesis by inhibiting Th1 differentiation and renal accumulation of profibrotic macrophages.

Losartan treatment enhances chemotherapy efficacy and reduces ascites in ovarian cancer models by normalizing the tumor stroma

In ovarian cancer patients, tumor fibrosis and angiotensin-driven fibrogenic signaling have been shown to inversely correlate with survival. We sought to enhance drug delivery and therapeutic efficacy by remodeling the dense extracellular matrix in two orthotopic human ovarian carcinoma xenograft models. We hypothesized that targeting the angiotensin signaling axis with losartan, an approved angiotensin system inhibitor, could reduce extracellular matrix content and the associated "solid stress," leading to better anticancer therapeutic effect. We report here four translatable findings: (i) losartan treatment enhances the efficacy of paclitaxel-a drug used for ovarian cancer treatment-via normalizing the tumor microenvironment, resulting in improved vessel perfusion and drug delivery; (ii) losartan depletes matrix via inducing antifibrotic miRNAs that should be tested as candidate biomarkers of response or resistance to chemotherapy; (iii) although losartan therapy alone does not reduce tumor burden, it reduces both the incidence and the amount of ascites formed; and (iv) our retrospective analysis revealed that patients receiving angiotensin system inhibitors concurrently with standard treatment for ovarian cancer exhibited 30 mo longer overall survival compared with patients on other antihypertensives. Our findings provide the rationale and supporting data for a clinical trial on combined losartan and chemotherapy in ovarian cancer patients.

Angiotensin receptor-binding molecule in leukocytes in association with the systemic and leukocyte inflammatory profile

BACKGROUND AND AIMS

The components of the renin-angiotensin system in leukocytes is involved in the pathophysiology of non-communicable diseases (NCDs), including hypertension, atherosclerosis and chronic kidney disease. Angiotensin II type 1 receptor (AT1R)-associated protein (ATRAP) is an AT1R-specific binding protein, and is able to inhibit the pathological activation of AT1R signaling in certain animal models of NCDs. The aim of the present study was to investigate the expression and regulation of ATRAP in leukocytes.

METHODS

Human leukocyte ATRAP mRNA was measured with droplet digital polymerase chain reaction system, and analyzed in relation to the clinical variables. We also examined the leukocyte cytokines mRNA in bone-marrow ATRAP-deficient and wild-type chimeric mice after injection of low-dose lipopolysaccharide.

RESULTS

The ATRAP mRNA was abundantly expressed in leukocytes, predominantly granulocytes and monocytes, of healthy subjects. In 86 outpatients with NCDs, leukocyte ATRAP mRNA levels correlated positively with granulocyte and monocyte counts and serum C-reactive protein levels. These positive relationships remained significant even after adjustment. Furthermore, the leukocyte ATRAP mRNA was significantly associated with the interleukin-1β, tumor necrosis factor-α and monocyte chemotactic protein-1 mRNA levels in leukocytes of NCDs patients. In addition, the leukocyte interleukin-1β mRNA level was significantly upregulated in bone marrow ATRAP-deficient chimeric mice in comparison to wild-type chimeric mice after injection of lipopolysaccharide.

CONCLUSIONS

These results suggest that leukocyte ATRAP is an emerging marker capable of reflecting the systemic and leukocyte inflammatory profile, and plays a role as an anti-inflammatory factor in the pathophysiology of NCDs.

Ulinastatin inhibits renal tubular epithelial apoptosis and interstitial fibrosis in rats with unilateral ureteral obstruction

The effect of ulinastatin (UTI) on renal tubular epithelial apoptosis and interstitial fibrosis in rats with unilateral ureteral obstruction (UUO) was investigated. A total of 18 male Wistar rats were randomly divided into the following 3 groups: The Sham group (n=6), the UUO group (n=6), and the UTI group (n=6). In the UUO and UTI groups, the left ureter was ligated to establish a UUO model. Starting from day 1 after surgery, an intervention treatment was performed using normal saline (1 ml/kg/d) and UTI (40,000 unit/kg/d). On day 7 after surgery, 6 rats from each group were sacrificed. In the Sham group, the left ureter was only freed, not ligated; after 7 days of abdominal closure, all of the rats were sacrificed. Blood samples were collected prior to sacrificing the animals to measure the blood urea nitrogen (BUN) and serum creatinine (Scr). The incidence of renal interstitial lesions on the obstruction side was observed by hematoxylin and eosin, and Masson staining. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and immunohistochemical detection of apoptosis regulator Bax (Bax), apoptosis regulator Bcl-2 (Bcl-2) and caspase-3 were performed to observe the presence of renal tubular epithelial cell apoptosis. The UTI did not have a significant influence on the mouse BUN and Scr levels in any of the groups (P>0.05). Compared with that in the Sham group, renal tissue injury in the UUO group was significantly aggravated with renal tubular dilation, epithelial cell atrophy, renal interstitial inflammatory cell infiltration and fibrous tissue hyperplasia (P<0.01). Furthermore, the renal tubular epithelial TUNEL+ cell number and Bax and caspase-3 levels were increased, and the expression of Bcl-2 was decreased (P<0.01). Following the UTI treatment, the renal interstitial injury at the obstruction side was significantly attenuated (P<0.05), the renal tubular epithelial TUNEL+ cell number, and Bax and caspase-3 levels significantly decreased, and the expression of Bcl-2 was restored (P<0.05). UTI inhibited renal tubular epithelial apoptosis and interstitial fibrosis in UUO rats.

Graphene Oxide/Ag Nanoparticles Cooperated with Simvastatin as a High Sensitive X-Ray Computed Tomography Imaging Agent for Diagnosis of Renal Dysfunctions

Graphene oxides (GO) are attracting much attention in the diagnosis and therapy of the subcutaneous tumor as a novel biomaterial, but its diagnosis to tissue dysfunction is yet to be found. Here, a novel application of GO for diagnosis of renal dysfunction via contrast-enhanced computed tomography (CT) is proposed. In order to serve as contrast-enhanced agent, Ag nanoparticles (AgNPs) are composited on the surface of GO to promote its X-ray absorption, and then simvastatin is coinjected for eliminating in vivo toxicity induced by AgNPs. It is found that GO/AgNPs can enhance the imaging of CT into the lung, liver, and kidney of mice for a long circulation time (≈24 h) and a safety profile in vivo in the presence of simvastatin. Interestingly, the lower dose of GO/AgNPs (≈0.5 mg per kg bw) shows an excellent performance for CT imaging of renal perfusion, and visually exhibits the right renal dysfunction in model mice. Hence, this work suggests that graphene nanoparticles will play a vital role for the future medical translational development including drug carrier, biosensing, and disease therapy.

Differential synchrotron X-ray imaging markers based on the renal microvasculature for tubulointerstitial lesions and glomerulopathy

High resolution synchrotron microtomography capable of revealing microvessels in three dimensional (3D) establishes distinct imaging markers of mouse kidney disease strongly associated to renal tubulointerstitial (TI) lesions and glomerulopathy. Two complementary mouse models of chronic kidney disease (CKD), unilateral ureteral obstruction (UUO) and focal segmental glomerulosclerosis (FSGS), were used and five candidates of unique 3D imaging markers were identified. Our characterization to differentially reflect the altered microvasculature of renal TI lesions and/or glomerulopathy demonstrated these image features can be used to differentiate the disease status and the possible cause therefore qualified as image markers. These 3D imaging markers were further correlated with the histopathology and renal microvessel-based molecular study using antibodies against vascular endothelial cells (CD31), the connective tissue growth factor or the vascular endothelial growth factor. We also found that these 3D imaging markers individually characterize the development of renal TI lesions or glomerulopathy, quantitative and integrated use of all of them provide more information for differentiating the two renal conditions. Our findings thus establish a practical strategy to characterize the CKD-associated renal injuries by the microangiography-based 3D imaging and highlight the impact of dysfunctional microvasculature as a whole on the pathogenesis of the renal lesions.

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.

Baicalin ameliorates renal fibrosis via inhibition of transforming growth factor β1 production and downstream signal transduction

Previous studies have demonstrated the potential antifibrotic effects of baicalin in vitro, via examination of 21 compounds isolated from plants. However, its biological activity and underlying mechanisms of action in vivo remain to be elucidated. The present study aimed to evaluate the effect of baicalin on renal fibrosis in vivo, and the potential signaling pathways involved. A unilateral ureteral obstruction (UUO)‑induced renal fibrosis model was established using Sprague‑Dawley rats. Baicalin was administrated intraperitoneally every 2 days for 10 days. The degree of renal damage and fibrosis was investigated by histological assessment, and detection of fibronectin and collagen I mRNA expression levels. Epithelial‑mesenchymal transition (EMT) markers, transforming growth factor-β1 (TGF-β1) levels and downstream phosphorylation of mothers against decapentaplegic 2/3 (Smad2/3) were examined in vivo and in an NRK‑52E rat renal tubular cell line in vitro. Baicalin was demonstrated to markedly ameliorate renal fibrosis and suppress EMT, as evidenced by reduced interstitial collagen accumulation, decreased fibronectin and collagen I mRNA expression levels, upregulation of N‑ and E‑cadherin expression levels, and downregulation of α‑smooth muscle actin and vimentin expression. Furthermore, baicalin decreased TGF‑β1 expression levels in serum and kidney tissue following UUO, and suppressed Smad2/3 phosphorylation in rat kidney tissue. In vitro studies identified that baicalin may inhibit the phosphorylation of Smad2/3 under the same TGF‑β1 concentration. In conclusion, baicalin may protect against renal fibrosis, potentially via inhibition of TGF‑β1 production and its downstream signal transduction.

Downregulation of angiotensin type 1 receptor and nuclear factor-κB by sirtuin 1 contributes to renoprotection in unilateral ureteral obstruction

Activation of sirtuin 1 (Sirt1) attenuates unilateral ureteral obstruction (UUO)-induced inflammation and fibrosis, suggesting that Sirt1 may prevent tubulointerstitial fibrosis. In this study, we explored changes in the expression of Sirt1 in the kidneys of UUO-treated rats and evaluated the effects of Sirt1 activation or inhibition on renal pathology and mediators of UUO pathogenesis, especially angiotensin II and nuclear factor (NF)-κB, in rats and rat renal fibroblasts. Sirt1 expression increased in the obstructed kidney but not in the contralateral kidney and was mainly detected in tubulointerstitial cells. Resveratrol, a Sirt1 activator, decreased UUO-induced inflammation and fibrosis, while sirtinol, a Sirt1 inhibitor, enhanced UUO-induced inflammation. UUO increased renal angiotensin type 1 receptor (AT1R), NF-κB, monocyte chemotactic protein 1 (MCP-1), and fibronectin expression. Resveratrol attenuated these UUO-induced changes, whereas sirtinol enhanced them, with the exception of fibronectin. In renal fibroblasts, Sirt1 overexpression reduced AT1R and NF-κB levels, while Sirt1 knockdown had the opposite effects. Sirtinol increased the levels of AT1R, NF-κB, MCP-1, and connective tissue growth factor (CTGF), while resveratrol reduced AT1R levels. Our results suggested that Sirt1 inhibited AT1R and NF-κB expression in renal fibroblasts and that these mechanisms may play roles in alleviating UUO-induced damages.

C-C Motif Chemokine 5 Attenuates Angiotensin II-Dependent Kidney Injury by Limiting Renal Macrophage Infiltration

Inappropriate activation of the renin angiotensin system (RAS) is a key contributor to the pathogenesis of essential hypertension. During RAS activation, infiltration of immune cells into the kidney exacerbates hypertension and renal injury. However, the mechanisms underpinning the accumulation of mononuclear cells in the kidney after RAS stimulation remain unclear. C-C motif chemokine 5 (CCL5) drives recruitment of macrophages and T lymphocytes into injured tissues, and we have found that RAS activation induces CCL5 expression in the kidney during the pathogenesis of hypertension and renal fibrosis. We therefore evaluated the contribution of CCL5 to renal damage and fibrosis in hypertensive and normotensive models of RAS stimulation. Surprisingly, during angiotensin II-induced hypertension, CCL5-deficient (knockout, KO) mice exhibited markedly augmented kidney damage, macrophage infiltration, and expression of proinflammatory macrophage cytokines compared with wild-type controls. When subjected to the normotensive unilateral ureteral obstruction model of endogenous RAS activation, CCL5 KO mice similarly developed more severe renal fibrosis and greater accumulation of macrophages in the kidney, congruent with enhanced renal expression of the macrophage chemokine CCL2. In turn, pharmacologic inhibition of CCL2 abrogated the differences between CCL5 KO and wild-type mice in kidney fibrosis and macrophage infiltration after unilateral ureteral obstruction. These data indicate that CCL5 paradoxically limits macrophage accumulation in the injured kidney during RAS activation by constraining the proinflammatory actions of CCL2.

Renal Medullary and Cortical Correlates in Fibrosis, Epithelial Mass, Microvascularity, and Microanatomy Using Whole Slide Image Analysis Morphometry

Renal tubulointerstitial injury often leads to interstitial fibrosis and tubular atrophy (IF/TA). IF/TA is typically assessed in the renal cortex and can be objectively quantitated with computerized image analysis (IA). However, the human medulla accounts for a substantial proportion of the nephron; therefore, medullary scarring will have important cortical consequences and may parallel overall chronic renal injury. Trichrome, periodic acid-Schiff (PAS), and collagen III immunohistochemistry (IHC) were visually examined and quantitated on scanned whole slide images (WSIs) (N = 67 cases). When tuned to measure fibrosis, IA of trichrome and Trichrome-PAS (T-P) WSIs correlated for all anatomic compartments (among cortex, medulla, and entire tissue, r = 0.84 to 0.89, P all <0.0001); and collagen III deposition correlated between compartments (r = 0.69 to 0.89, P <0.0001 to 0.0002); however, trichrome and T-P measures did not correlate with collagen deposition, suggesting heterogeneous contributions to extracellular matrix deposition. Epithelial cell mass (EPCM) correlated between cortex and medulla when measured with cytokeratin IHC and with the trichrome red portion (r = 0.85 and 0.66, respectively, all P < 0.0001). Visual assessment also correlated between compartments for fibrosis and EPCM. Correlations were found between increasing medullary inner stripe (IS) width and fibrosis in all of the tissue and the medulla by trichrome morphometry (r = 0.56, P < 0.0001, and r = 0.48, P = 0.00008, respectively). Weak correlations were found between increasing IS width and decreasing visual assessment of all tissue EPCM. Microvessel density (MVD) and microvessel area (MVA) measured using a MVD algorithm applied to CD34 IHC correlated significantly between all compartments (r = 0.76 to 0.87 for MVD and 0.71 to 0.87 for MVA, P all < 0.0001). Overall, these findings demonstrate the interrelatedness of the cortex and medulla and the importance of considering the renal parenchyma as a whole.

The renin-angiotensin system in lupus: physiology, genes and practice, in animals and humans

Although multiple studies suggest a potential role for angiotensin II in inflammation, most were performed either in vitro or in animals with non-immune-complex-mediated diseases. Extrapolation of these findings to humans, particularly patients with lupus, which involves multiple immunoregulatory pathways, is unclear. In autoimmune-prone MRL/lpr mice, angiotensin-converting-enzyme (ACE) inhibition improved survival although to a lesser degree than cyclophosphamide and diminished the glomerular histopathologic damage, proteinuria, lymphoid hyperplasia, dermatitis, and hypergammaglobulinemia, with a reduction in TGF-beta1 and beta 2 expression in the kidneys and renal chemokine mRNA expression. Spleen levels of IL-4 and IL-10 were also reduced. Uncontrolled studies in patients with treatment-refractory lupus nephritis showed a significant reduction in proteinuria with ACE-inhibitors and Angiotensin receptor blockers treatment. The ‘masking’ effect of ACE-inhibitors should be taken into consideration, as an exacerbation of lupus nephritis may be missed when estimated by the magnitude of proteinuria, which is decreased by these treatments. No single ACE genotype was consistently associated with subsets of SLE patients. In retrospective analyses, ACE-inhibitor use predicted a favourable outcome in 94 cases of pauci-immune vasculitis. The attenuating effect of angiotensin II inhibitors on the progression of chronic renal disease is well recognized. The data on the role of this intervention in lupus is limited.

Quantification and Comparison of Anti-Fibrotic Therapies by Polarized SRM and SHG-Based Morphometry in Rat UUO Model

Renal interstitial fibrosis (IF) is an important pathologic manifestation of disease progression in a variety of chronic kidney diseases (CKD). However, the quantitative and reproducible analysis of IF remains a challenge, especially in experimental animal models of progressive IF. In this study, we compare traditional polarized Sirius Red morphometry (SRM) to novel Second Harmonic Generation (SHG)-based morphometry of unstained tissues for quantitative analysis of IF in the rat 5 day unilateral ureteral obstruction (UUO) model. To validate the specificity of SHG for detecting fibrillar collagen components in IF, co-localization studies for collagens type I, III, and IV were performed using IHC. In addition, we examined the correlation, dynamic range, sensitivity, and ability of polarized SRM and SHG-based morphometry to detect an anti-fibrotic effect of three different treatment regimens. Comparisons were made across three separate studies in which animals were treated with three mechanistically distinct pharmacologic agents: enalapril (ENA, 15, 30, 60 mg/kg), mycophenolate mofetil (MMF, 2, 20 mg/kg) or the connective tissue growth factor (CTGF) neutralizing antibody, EX75606 (1, 3, 10 mg/kg). Our results demonstrate a strong co-localization of the SHG signal with fibrillar collagens I and III but not non-fibrillar collagen IV. Quantitative IF, calculated as percent cortical area of fibrosis, demonstrated similar response profile for both polarized SRM and SHG-based morphometry. The two methodologies exhibited a strong correlation across all three pharmacology studies (r² = 0.89–0.96). However, compared with polarized SRM, SHG-based morphometry delivered a greater dynamic range and absolute magnitude of reduction of IF after treatment. In summary, we demonstrate that SHG-based morphometry in unstained kidney tissues is comparable to polarized SRM for quantitation of fibrillar collagens, but with an enhanced sensitivity to detect treatment-induced reductions in IF. Thus, performing SHG-based morphometry on unstained kidney tissue is a reliable alternative to traditional polarized SRM for quantitative analysis of IF.

Experimental inhibition of porcupine-mediated Wnt O-acylation attenuates kidney fibrosis

Activated Wnt signaling is critical in the pathogenesis of renal fibrosis, a final common pathway for most forms of chronic kidney disease. Therapeutic intervention by inhibition of individual Wnts or downstream Wnt/β-catenin signaling has been proposed, but these approaches do not interrupt the functions of all Wnts nor block non-canonical Wnt signaling pathways. Alternatively, an orally bioavailable small molecule, Wnt-C59, blocks the catalytic activity of the Wnt-acyl transferase porcupine, and thereby prevents secretion of all Wnt isoforms. We found that inhibiting porcupine dramatically attenuates kidney fibrosis in the murine unilateral ureteral obstruction model. Wnt-C59 treatment similarly blunts collagen mRNA expression in the obstructed kidney. Consistent with its actions to broadly arrest Wnt signaling, porcupine inhibition reduces expression of Wnt target genes and bolsters nuclear exclusion of β-catenin in the kidney following ureteral obstruction. Importantly, prevention of Wnt secretion by Wnt-C59 blunts expression of inflammatory cytokines in the obstructed kidney that otherwise provoke a positive feedback loop of Wnt expression in collagen-producing fibroblasts and epithelial cells. Thus, therapeutic targeting of porcupine abrogates kidney fibrosis not only by overcoming the redundancy of individual Wnt isoforms but also by preventing upstream cytokine-induced Wnt generation. These findings reveal a novel therapeutic maneuver to protect the kidney from fibrosis by interrupting a pathogenic crosstalk loop between locally generated inflammatory cytokines and the Wnt/β-catenin signaling pathway.

The Protective Mechanism of Fluorofenidone in Renal Interstitial Inflammation and Fibrosis

BACKGROUND

Deregulated inflammation has been implicated in the development of renal interstitial fibrosis and progressive renal failure. Previous work has established that fluorofenidone, a pyridone agent, attenuates renal fibrosis. However, the mechanism by which fluorofenidone prevents renal fibrosis remains unclear. The aim of this study was to investigate the in vivo effects of fluorofenidone on unilateral ureteral obstruction-induced fibrosis and the involved molecular mechanism in mouse peritoneal macrophages.

METHODS

Renal fibrosis was induced in rat by unilateral ureteral obstruction for 3, 7 or 14 days. Ipsilateral kidneys were harvested for morphologic analysis. Leukocyte infiltration was assessed by immunohistochemistry staining. The expression of chemokines (MCP-1, RANTAS, IP-10, MIP-1α and MIP-1β) and pro-inflammatory cytokines (TNF-α and IL-1β) was measured by enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Mouse peritoneal macrophages and HK-2 cells were incubated with necrotic MES-13 cells or TNF-α in the presence or absence of fluorofenidone. The production of MCP-1 was measured by enzyme-linked immunosorbent assay, and phosphorylation of ERK1/2, p38 and JNK was quantified by Western blot.

RESULTS

Fluorofenidone treatment hampered renal pathologic change and interstitial collagen deposition. Leukocyte infiltration and the expression of chemokines (MCP-1, RANTES, IP-10, MIP-1α and MIP-1β) and pro-inflammatory cytokines (IL-1α) in kidney were significantly reduced by fluorofenidone treatment. Mechanistically, fluorofenidone significantly inhibited TNF-α or necrotic cell-induced activation of MAP kinase pathways in vitro.

CONCLUSIONS

Fluorofenidone serves as a novel anti-inflammatory agent that attenuates ureteral obstruction-induced renal interstitial inflammation and fibrosis, possibly through the inhibition of the microtubule-associated protein kinase pathways.

Evidence of a Role for Fibroblast Transient Receptor Potential Canonical 3 Ca2+ Channel in Renal Fibrosis

Transient receptor potential canonical (TRPC) Ca(2+)-permeant channels, especially TRPC3, are increasingly implicated in cardiorenal diseases. We studied the possible role of fibroblast TRPC3 in the development of renal fibrosis. In vitro, a macromolecular complex formed by TRPC1/TRPC3/TRPC6 existed in isolated cultured rat renal fibroblasts. However, specific blockade of TRPC3 with the pharmacologic inhibitor pyr3 was sufficient to inhibit both angiotensin II- and 1-oleoyl-2-acetyl-sn-glycerol-induced Ca(2+) entry in these cells, which was detected by fura-2 Ca(2+) imaging. TRPC3 blockade or Ca(2+) removal inhibited fibroblast proliferation and myofibroblast differentiation by suppressing the phosphorylation of extracellular signal-regulated kinase (ERK1/2). In addition, pyr3 inhibited fibrosis and inflammation-associated markers in a noncytotoxic manner. Furthermore, TRPC3 knockdown by siRNA confirmed these pharmacologic findings. In adult male Wistar rats or wild-type mice subjected to unilateral ureteral obstruction, TRPC3 expression increased in the fibroblasts of obstructed kidneys and was associated with increased Ca(2+) entry, ERK1/2 phosphorylation, and fibroblast proliferation. Both TRPC3 blockade in rats and TRPC3 knockout in mice inhibited ERK1/2 phosphorylation and fibroblast activation as well as myofibroblast differentiation and extracellular matrix remodeling in obstructed kidneys, thus ameliorating tubulointerstitial damage and renal fibrosis. In conclusion, TRPC3 channels are present in renal fibroblasts and control fibroblast proliferation, differentiation, and activation through Ca(2+)-mediated ERK signaling. TRPC3 channels might constitute important therapeutic targets for improving renal remodeling in kidney disease.

Application of GC-MS coupled with chemometrics for scanning serum metabolic biomarkers from renal fibrosis rat

Renal interstitial fibrosis closely relates to chronic kidney disease and is regarded as the final common pathway in most cases of end-stage renal disease. Metabolomic biomarkers can facilitate early diagnosis and allow better understanding of the pathogenesis underlying renal fibrosis. Gas chromatography-mass spectrometry (GC/MS) is one of the most promising techniques for identification of metabolites. However, the existence of the background, baseline offset, and overlapping peaks makes accurate identification of the metabolites unachievable. In this study, GC/MS coupled with chemometric methods was successfully developed to accurately identify and seek metabolic biomarkers for rats with renal fibrosis. By using these methods, seventy-six metabolites from rat serum were accurately identified and five metabolites (i.e., urea, ornithine, citric acid, galactose, and cholesterol) may be useful as potential biomarkers for renal fibrosis.

Tanshinone IIA attenuates renal fibrosis and inflammation via altering expression of TGF-β/Smad and NF-κB signaling pathway in 5/6 nephrectomized rats

PURPOSE

In traditional Chinese medicine, Tanshinone IIA is used to treat chronic kidney disease (CKD). However, its biological activity and mechanism of action in renal fibrosis and inflammation are not fully identified. The current study was conducted to determine the effects of Tanshinone IIA treatment on CKD by assessing potential modulation of the TGF-β/Smad and NF-κB signaling pathway.

METHODS

CKD was produced in rats by 5/6 nephrectomy. They were then divided into the following groups: control (sham operation); CKD (5/6 nephrectomy); 5/6 nephrectomy+Tanshinone IIA (10mg/kg in average, once a day for 16 weeks). Serum and urine samples were obtained from animals in each group, and serum creatinine (Scr), blood urea nitrogen (BUN) levels and 24h urinary protein excretion were measured. Tissue samples from the kidney were used for morphometric studies (Masson's trichrome). The expression of fibronectin protein and collagen types I, III, IV, and TGF-β, TNF-α, CXCL-1, MCP-1, RANTES mRNA were evaluated using immunohistochemistry and RT-PCR analysis; the TGF-β/Smad and NF-κB signaling pathway was detected by immunohistochemistry and Western blot analysis.

RESULTS

The following effects were observed in CKD rats treated with Tanshinone IIA: (1) marked improvements in Scr, and 24h urine protein excretion; (2) significant reductions in protein and mRNA levels of fibronectin, collagen III, and collagen IV and TNF-α, MCP-1, and CXCL-1; (3) significantly inhibited the TGF-β/Smad and NF-κB signaling activation.

CONCLUSIONS

These results suggest that Tanshinone IIA suppresses renal fibrosis and inflammation via altering expression of TGF-β/Smad and NF-κB pathway in the remnant kidney, thus supporting the potential of Tanshinone IIA as a new therapeutic agent for slowing the progression of CKD.

Epigallocatechin-3-gallate attenuates unilateral ureteral obstruction-induced renal interstitial fibrosis in mice

The severity of tubulointerstitial fibrosis is regarded as an important determinant of renal prognosis. Therapeutic strategies targeting tubulointerstitial fibrosis have been considered to have potential in the treatment of chronic kidney disease. This study aims to evaluate the protective effects of (-)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol, against renal interstitial fibrosis in mice. EGCG was administrated intraperitoneally for 14 days in a mouse model of unilateral ureteral obstruction (UUO). The results of our histological examination showed that EGCG alleviated glomerular and tubular injury and attenuated renal interstitial fibrosis in UUO mice. Furthermore, the inflammatory responses induced by UUO were inhibited, as represented by decreased macrophage infiltration and inflammatory cytokine production. Additionally, the expression of type I and III collagen in the kidney were reduced by EGCG, which indicated an inhibition of extracellular matrix accumulation. EGCG also caused an up-regulation in α-smooth muscle actin expression and a down-regulation in E-cadherin expression, indicating the inhibition of epithelial-to-mesenchymal transition. These changes were found to be in parallel with the decreased level of TGF-β1 and phosphorylated Smad. In conclusion, the present study demonstrates that EGCG could attenuate renal interstitial fibrosis in UUO mice, and this renoprotective effect might be associated with its effects of inflammatory responses alleviation and TGF-β/Smad signaling pathway inhibition.

Angiotensin II increases fibronectin and collagen I through the β-catenin-dependent signaling in mouse collecting duct cells

The contribution of angiotensin II (ANG II) to renal and tubular fibrosis has been widely reported. Recent studies have shown that collecting duct cells can undergo mesenchymal transition suggesting that collecting duct cells are involved in interstitial fibrosis. The Wnt/β-catenin signaling pathway plays an essential role in development, organogenesis, and tissue homeostasis; however, the dysregulation of this pathway has been linked to fibrosis. In this study, we investigated whether AT1 receptor activation induces the expression of fibronectin and collagen I via the β-catenin pathway in mouse collecting duct cell line M-1. ANG II (10(-7) M) treatment in M-1 cells increased mRNA, protein levels of fibronectin and collagen I, the β-catenin target genes (cyclin D1 and c-myc), and the myofibroblast phenotype. These effects were prevented by candesartan, an AT1 receptor blocker. Inhibition of the β-catenin degradation with pyrvinium pamoate (pyr; 10(-9) M) prevented the ANG II-induced expression of fibronectin, collagen I, and β-catenin target genes. ANG II treatment promoted the accumulation of β-catenin protein in a time-dependent manner. Because phosphorylation of glycogen synthase kinase-3β (GSK-3β) inhibits β-catenin degradation, we further evaluated the effects of ANG II and ANG II plus pyr on p-ser9-GSK-3β levels. ANG II-dependent upregulation of β-catenin protein levels was correlated with GSK-3β phosphorylation. These effects were prevented by pyr. Our data indicate that in M-1 collecting duct cells, the β-catenin pathway mediates the stimulation of fibronectin and collagen I in response to AT1 receptor activation.

What is the best way to measure renal fibrosis?: A pathologist's perspective

Interstitial fibrosis is a hallmark structural correlate of progressive and chronic kidney disease. There remain many uncertainties about how to best measure interstitial fibrosis both in research settings and in evaluations of renal biopsies performed for management of individual patients. Areas of uncertainty include determination of the composition of the matrix in a fibrotic parenchyma, the definition of how the interstitium is involved by fibrosing injuries, the choice of histologic stains for evaluation of renal fibrosis, and the reproducibility and robustness of measures currently employed by pathologists, both with and without the assistance of computerized imaging and assessments. In this review, we address some of these issues while citing the key studies that illustrate these difficulties. We point to future approaches that may allow a more accurate and meaningful assessment of renal interstitial fibrosis.

Vasohibin-1 deficiency enhances renal fibrosis and inflammation after unilateral ureteral obstruction

Tubulointerstitial injuries are known to predict the deterioration of renal function in chronic kidney disease (CKD). We recently reported the protective role of Vasohibin‐1(VASH‐1), a negative feedback regulator of angiogenesis, in diabetic nephropathy, but its impact on tubulointerstitial injuries remains to be elucidated. In the present study, we evaluated the role of endogenous VASH‐1 in regulating the tubulointerstitial alterations induced by unilateral ureteral obstruction (UUO), and assessed its role on fibrogenesis and the activation of Smad3 signaling in renal fibroblasts. UUO was induced in female Vasohibin‐1 heterozygous knockout mice (VASH‐1^+/−) or wild‐type (WT) (VASH‐1^+/+) littermates. Mice were sacrificed on Day 7 after left ureter ligation, and the kidney tissue was obtained. Interstitial fibrosis, the accumulation of type I and type III collagen and monocytes/macrophages infiltration in the obstructed kidneys (OBK) were significantly exacerbated in VASH‐1^+/− mice compared with WT mice (Day 7). The increases in the renal levels of TGF‐β1, pSmad3, NF‐κB pp65, CCL2 mRNA, and the number of interstitial fibroblast‐specific protein‐1 (FSP‐1)⁺ fibroblasts in the OBK were significantly aggravated in VASH‐1^+/− mice. In addition, treatment with VASH‐1 siRNA enhanced the TGF‐β1‐induced phosphorylation of Smad3, the transcriptional activation of the Smad3 pathway and the production of type I/type III collagen in fibroblasts, in vitro. Taken together, our findings demonstrate a protective role for endogenous VASH‐1 on tubulointerstitial alterations via its regulation of inflammation and fibrosis and also show the direct anti‐fibrotic effects of VASH‐1 on renal fibroblasts through its modulation of TGF‐β1 signaling.

In the present study, we evaluated the role of endogenous Vasohibn‐1 VASH‐1 in regulating tubulointerstitial alterations induced by unilateral ureteral obstruction (UUO), and assessed its regulatory role on fibrogenesis and the activation of TGF‐beta/Smad3 signaling in renal fibroblasts. This is the first study to demonstrate the potential protective role for endogenous VASH‐1 on tubulointerstitial alterations via regulating inflammation and fibrosis, partly mediated via its direct anti‐fibrotic effects on renal fibroblasts through modulating TGF‐β1 signaling.

Type 1 angiotensin receptors on macrophages ameliorate IL-1 receptor-mediated kidney fibrosis

In a wide array of kidney diseases, type 1 angiotensin (AT1) receptors are present on the immune cells that infiltrate the renal interstitium. Here, we examined the actions of AT1 receptors on macrophages in progressive renal fibrosis and found that macrophage-specific AT1 receptor deficiency exacerbates kidney fibrosis induced by unilateral ureteral obstruction (UUO). Macrophages isolated from obstructed kidneys of mice lacking AT1 receptors solely on macrophages had heightened expression of proinflammatory M1 cytokines, including IL-1. Evaluation of isolated AT1 receptor-deficient macrophages confirmed the propensity of these cells to produce exaggerated levels of M1 cytokines, which led to more severe renal epithelial cell damage via IL-1 receptor activation in coculture compared with WT macrophages. A murine kidney crosstransplantation concomitant with UUO model revealed that augmentation of renal fibrosis instigated by AT1 receptor-deficient macrophages is mediated by IL-1 receptor stimulation in the kidney. This study indicates that a key role of AT1 receptors on macrophages is to protect the kidney from fibrosis by limiting activation of IL-1 receptors in the kidney.

Construction of a CTGF and RFP-coexpressed renal tubular epithelial cell and its application on evaluation of CTGF-specific siRNAs on epithelial-mesenchymal transition

OBJECTIVE

To construct a connective tissue growth factor (CTGF) and red fluorescent protein (RFP)-coexpressed renal tubular epithelial cell that can be used to quantitatively evaluate the CTGF-induced epithelial-mesenchymal transition (EMT).

METHODS

The CTGF and RFP coding sequences were linked with a "2A" peptide, cloned into an expressing vector, and the HK-C2AR cell clone, which could express CTGF and RFP, were selected from the HK-2 cells after the recombinant plasmid transfection. Then, the CTGF-induced EMT in this cell line was determined, to further determine the association of RFP fluorescence intensity with the CTGF expression or CTGF-induced EMT. CTGF-specific ribonucleic acid (RNA) interference was also used to reconfirm the association.

RESULTS

The constructed HK-C2AR cells could stably express RFP and CTGF proportionally, and the CTGF expressed in the cell line could induce EMT of cells, whereas the RFP expressed in the cell could exhibit bright red fluorescence after excitation. After the silence in CTGF, the RFP expression was also decreased, and the CTGF-induced EMT was also inhibited.

CONCLUSION

The CTGF and RFP-coexpressing renal tubular epithelial cell, HK-C2AR, could be used to quantitatively evaluate CTGF-specific small interfering RNAs on EMT by quantitatively detecting the RFP expression. Also, this cell line could be used to quantitatively determine the mechanism of CTGF-induced EMT in renal tubular epithelial cells.

Banff fibrosis study: multicenter visual assessment and computerized analysis of interstitial fibrosis in kidney biopsies

Increasing interstitial fibrosis (IF) in native and kidney transplant biopsies is associated with functional decline and serves as a clinical trial end point. A Banff 2009 Conference survey revealed a range in IF assessment practices. Observers from multiple centers were asked to assess 30 renal biopsies with a range of IF and quantitate IF using two approaches on trichrome, Periodic acid-Schiff (PAS) and computer-assisted quantification of collagen III immunohistochemistry (C-IHC) slides, as well as assessing percent of cortical tubular atrophy% (TA%) and Banff total cortical inflammation score (ti-score). C-IHC using whole slide scans was performed. C-IHC assessment showed a higher correlation with organ function (r = -0.48) than did visual assessments (r = -0.32--0.42); computerized and visual C-IHC assessment also correlated (r = 0.64-0.66). Visual assessment of trichrome and C-IHC showed better correlations with organ function and C-IHC, than PAS, TA% and ti-score. However, visual assessment of IF, independent of approach, was variable among observers, and differences in correlations with organ function were not statistically significant among C-IHC image analysis and visual assessment methods. C-IHC image analysis correlated among three centers (r > 0.90, p < 0.0001, between all centers). Given the difficulty of visual IF assessment standardization, C-IHC image could potentially accomplish standardized IF assessment in multicenter settings.

MicroRNA-22 is a master regulator of bone morphogenetic protein-7/6 homeostasis in the kidney

Accumulating evidence suggests that microRNAs (miRNAs) contribute to a myriad of kidney diseases. However, the regulatory role of miRNAs on the key molecules implicated in kidney fibrosis remains poorly understood. Bone morphogenetic protein-7 (BMP-7) and its related BMP-6 have recently emerged as key regulators of kidney fibrosis. Using the established unilateral ureteral obstruction (UUO) model of kidney fibrosis as our experimental model, we examined the regulatory role of miRNAs on BMP-7/6 signaling. By analyzing the potential miRNAs that target BMP-7/6 in silica, we identified miR-22 as a potent miRNA targeting BMP-7/6. We found that expression levels of BMP-7/6 were significantly elevated in the kidneys of the miR-22 null mouse. Importantly, mice with targeted deletion of miR-22 exhibited attenuated renal fibrosis in the UUO model. Consistent with these in vivo observations, primary renal fibroblast isolated from miR-22-deficient UUO mice demonstrated a significant increase in BMP-7/6 expression and their downstream targets. This phenotype could be rescued when cells were transfected with miR-22 mimics. Interestingly, we found that miR-22 and BMP-7/6 are in a regulatory feedback circuit, whereby not only miR-22 inhibits BMP-7/6, but miR-22 by itself is induced by BMP-7/6. Finally, we identified two BMP-responsive elements in the proximal region of miR-22 promoter. These findings identify miR-22 as a critical miRNA that contributes to renal fibrosis on the basis of its pivotal role on BMP signaling cascade.

The effect of simvastatin and erythropoietin on renal fibrosis in rats with unilateral ureteral obstruction

Prevention of fibrosis is a very important therapeutic strategy in the treatment of obstructive nephropathy (ON). The aim of this study is to show and compare the actions of Simvastatin (Simv) and Erythropoietin (Epo) in renal expression of nuclear factor kappa B (NFκB), transforming growth factor-β (TGF-β), basic fibroblast growth factor (bFGF), platelet-derived growth factor B (PDGF-B), fibronectin and development of interstitial fibrosis in rats with unilateral ureteral obstruction (UUO). A total of 48 Sprague-Dawley rats were allocated to 4 groups of sham, Epo, Simv and control. Unilateral ureteral ligation was performed on all rats except the Sham group. For interstitial fibrosis Masson's trichrome stain and for the expression of TGF-β, PDGF-B, bFGF, NFκB and fibronectin, immunohistochemical methods were used. In the Epo and Simv groups, expression of TGF-β and fibronectin and staining with Masson's trichrome were less compared to the control group. In addition, fibronectin expression in the Epo group was less than the Simv group. Unlike the Simv group, NFκB and bFGF expression in the Epo group were less when compared to the control group. Consequently, it was seen that both Epo and Simv prevented fibrosis in ON. Epo was superior in this effect by suppressing the expressions of NFκB and bFGF more effectively than Simv. Based on this finding, Epo might be a better agent than Simv in the prevention of fibrosis in ON.

Unilateral ureteral obstruction: beyond obstruction

Unilateral ureteral obstruction is a popular experimental model of renal injury. However, the study of the kidney response to urinary tract obstruction is only one of several advantages of this model. Unilateral ureteral obstruction causes subacute renal injury characterized by tubular cell injury, interstitial inflammation and fibrosis. For this reason, it serves as a model both of irreversible acute kidney injury and of events taking place during human chronic kidney disease. Being a unilateral disease, it is not useful to study changes in global kidney function, but has the advantage of a low mortality and the availability of an internal control (the non-obstructed kidney). Experimental unilateral ureteral obstruction has illustrated the molecular mechanisms of apoptosis, inflammation and fibrosis, all three key processes in kidney injury of any cause, thus providing information beyond obstruction. Recently this model has supported key concepts on the role in kidney fibrosis of epithelial-mesenchymal transition, tubular epithelial cell G2/M arrest, the anti-aging hormone Klotho and renal innervation. We now review the experimental model and its contribution to identifying novel therapeutic targets in kidney injury and fibrosis, independently of the noxa.

Beneficial effects of the activation of the angiotensin-(1-7) MAS receptor in a murine model of adriamycin-induced nephropathy

Angiotensin-(1–7) [Ang-(1–7)] is a biologically active heptapeptide that may counterbalance the physiological actions of angiotensin II (Ang II) within the renin-angiotensin system (RAS). Here, we evaluated whether activation of the Mas receptor with the oral agonist, AVE 0991, would have renoprotective effects in a model of adriamycin (ADR)-induced nephropathy. We also evaluated whether the Mas receptor contributed for the protective effects of treatment with AT₁ receptor blockers. ADR (10 mg/kg) induced significant renal injury and dysfunction that was maximal at day 14 after injection. Treatment with the Mas receptor agonist AVE 0991 improved renal function parameters, reduced urinary protein loss and attenuated histological changes. Renoprotection was associated with reduction in urinary levels of TGF-β. Similar renoprotection was observed after treatment with the AT₁ receptor antagonist, Losartan. AT₁ and Mas receptor mRNA levels dropped after ADR administration and treatment with losartan reestablished the expression of Mas receptor and increased the expression of ACE2. ADR-induced nephropathy was similar in wild type (Mas^+/+) and Mas knockout (Mas^−/−) mice, suggesting there was no endogenous role for Mas receptor activation. However, treatment with Losartan was able to reduce renal injury only in Mas^+/+, but not in Mas^−/− mice. Therefore, these findings suggest that exogenous activation of the Mas receptor protects from ADR-induced nephropathy and contributes to the beneficial effects of AT₁ receptor blockade. Medications which target specifically the ACE2/Ang-(1–7)/Mas axis may offer new therapeutic opportunities to treat human nephropathies.

Angiotensin II type 1 receptor antagonist attenuates lacrimal gland, lung, and liver fibrosis in a murine model of chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD), a serious complication following allogeneic HSCT (hematopoietic stem cell transplantation), is characterized by systemic fibrosis. The tissue renin-angiotensin system (RAS) is involved in the fibrotic pathogenesis, and an angiotensin II type 1 receptor (AT1R) antagonist can attenuate fibrosis. Tissue RAS is present in the lacrimal gland, lung, and liver, and is known to be involved in the fibrotic pathogenesis of the lung and liver. This study aimed to determine whether RAS is involved in fibrotic pathogenesis in the lacrimal gland and to assess the effect of an AT1R antagonist on preventing lacrimal gland, lung, and liver fibrosis in cGVHD model mice. We used the B10.D2→BALB/c (H-2^d) MHC-compatible, multiple minor histocompatibility antigen-mismatched model, which reflects clinical and pathological symptoms of human cGVHD. First, we examined the localization and expression of RAS components in the lacrimal glands using immunohistochemistry and quantitative real-time polymerase chain reaction (PCR). Next, we administered an AT1R antagonist (valsartan; 10 mg/kg) or angiotensin II type 2 receptor (AT2R) antagonist (PD123319; 10 mg/kg) intraperitoneally into cGVHD model mice and assessed the fibrotic change in the lacrimal gland, lung, and liver. We demonstrated that fibroblasts expressed angiotensin II, AT1R, and AT2R, and that the mRNA expression of angiotensinogen was greater in the lacrimal glands of cGVHD model mice than in controls generated by syngeneic-HSCT. The inhibition experiment revealed that fibrosis of the lacrimal gland, lung, and liver was suppressed in mice treated with the AT1R antagonist, but not the AT2R antagonist. We conclude that RAS is involved in fibrotic pathogenesis in the lacrimal gland and that AT1R antagonist has a therapeutic effect on lacrimal gland, lung, and liver fibrosis in cGVHD model mice. Our findings point to AT1R antagonist as a possible target for therapeutic intervention in cGVHD.

Upstream stimulatory factors 1 and 2 mediate the transcription of angiotensin II binding and inhibitory protein

The angiotensin II type 1 receptor (AT1R)-associated protein (ATRAP/Agtrap) promotes constitutive internalization of the AT1R so as to specifically inhibit the pathological activation of its downstream signaling yet preserve the base-line physiological signaling activity of the AT1R. Thus, tissue-specific regulation of Agtrap expression is relevant to the pathophysiology of cardiovascular and renal disease. However, the regulatory mechanism of Agtrap gene expression has not yet been fully elucidated. In this study, we show that the proximal promoter region from −150 to +72 of the mouse Agtrap promoter, which contains the X-box, E-box, and GC-box consensus motifs, is able to elicit substantial transcription of the Agtrap gene. Among these binding motifs, we showed that the E-box specifically binds upstream stimulatory factor (Usf) 1 and Usf2, which are known E-box-binding transcription factors. It is indicated that the E-box-Usf1/Usf2 binding regulates Agtrap expression because of the following: 1) mutation of the E-box to prevent Usf1/Usf2 binding reduces Agtrap promoter activity; 2) knockdown of Usf1 or Usf2 affects both endogenous Agtrap mRNA and Agtrap protein expression, and 3) the decrease in Agtrap mRNA expression in the afflicted kidney by unilateral ureteral obstruction is accompanied by changes in Usf1 and Usf2 mRNA. Furthermore, the results of siRNA transfection in mouse distal convoluted tubule cells and those of unilateral ureteral obstruction in the afflicted mouse kidney suggest that Usf1 decreases but Usf2 increases the Agtrap gene expression by binding to the E-box. The results also demonstrate a functional E-box-USF1/USF2 interaction in the human AGTRAP promoter, thereby suggesting that a strategy of modulating the E-box-USF1/USF2 binding has novel therapeutic potential.

Ulinastatin inhibits unilateral ureteral obstruction-induced renal interstitial fibrosis in rats via transforming growth factor β (TGF-β)/Smad signalling pathways

This study aims to explore the protective effects and mechanisms of ulinastatin (UTI), which is a urinary trypsin inhibitor, of the renal interstitial fibrosis of rats subjected to unilateral ureteral obstruction (UUO). A total of 36 male Wistar rats were divided in random into three groups, namely, the sham operation (SOR) group (n=12), the UUO group (n=12), and the UTI treatment group (n=12). Six rats from each group were euthanised after unilateral ureteral obstruction operation on the seventh and fourteenth days, respectively. Blood samples were harvested for blood urea nitrogen (BUN) and serum creatinine (Scr) measurement. The interstitial pathological changes of the tissue from the obstructed kidneys were observed using haematoxylin-eosin (H&E) and Masson staining. The expression of the transforming growth factor β type 1 (TGF-β1), α-smooth muscle actin (α-SMA), type I collagen (Col-I), and phosphorylated Smad2/3 (p-Smad2/3) was determined using immunohistochemistry. The protein expression levels of TGF-β1, α-SMA, and p-Smad2/3 were examined using Western blot analysis. The results show that ulinastatin has no statistically significant effect on the BUN and Scr levels (P>0.05), but it can significantly reduce renal interstitial injury and suppress interstitial collagen deposits. The renoprotective effect of ulinastatin is likely realised through the TGF-β/Smad signalling pathways.

Klotho protects against mouse renal fibrosis by inhibiting Wnt signaling

Augmented Wnt signaling has been implicated in many fibrotic diseases including obstructive nephropathy. Soluble form Klotho has been reported to function as a secreted Wnt antagonist. In this study, we tested whether Klotho protein could reduce renal fibrosis by inhibition of Wnt signaling. Transgenic mice that overexpressed Klotho, wild-type mice, and Klotho hetero mutant mice underwent unilateral ureteral obstruction (UUO). In some Klotho hetero mutant mice, Klotho-encoding plasmid was transferred into the skeletal muscle by electroporation. UUO induced activation of Wnt signaling in wild-type but less in Klotho transgenic mice. Enhanced tubulointerstitial fibrosis in wild-type mice was also attenuated in Klotho transgenic mice. In contrast, Wnt signaling and concomitant tubulointerstitial fibrosis were further augmented in Klotho hetero mutant mice after UUO compared with wild-type mice. In Klotho-encoding plasmid-transfected Klotho hetero mutant mice, however, Wnt signaling was markedly reduced accompanied by a decrease in extracellular matrix deposition after UUO. In vitro studies showed that stimulation of Wnt3a induced prolonged cell cycle arrest at G(2)/M phase, with a resultant increase in production of fibrogenic cytokines. Cotreatment with Klotho bypassed the G(2)/M arrest and reduced fibrogenic cytokine production. In conclusion, Klotho is a critical negative regulator of Wnt signaling and a suppressor of renal fibrosis in the obstructed kidney model.

Gene expression profiling in glomeruli of diabetic nephropathy rat

Diabetic nephropathy (DN) remains the most common cause of end-stage renal disease (ESRD) as the burden of diabetes increases worldwide. To find improved intervention strategies for this disease, it is necessary to investigate the molecular mechanisms involved. To obtain more insight into processes that lead to DN, mRNA expression profiles of diabetic and normal glomeruli from rat kidneys were compared. Rats were divided into a control group and a DN group randomly. The DN group was injected with streptozotocin. Fasting blood glucose (FBG) and weight were measured monthly. On the 12th week, blood samples were collected and analyzed for plasma creatinine and blood urea nitrogen (BUN). Glomeruli were isolated and Illumina Rat Ref-12 V1.0 Expression Beadchip gene array was performed. Quantitative realtime polymerase chain reaction (Q-RT-PCR) was used to confirm the results of gene array for a selected number of genes. We found FBG, 24-h urinary albumin, serum creatinine and BUN were significantly increased, while urinary creatinine and body weight were significantly decreased in the DN group. Glomeruli from the DN group had 624 genes with differential expression. DAVID (Database for Annotation, Visualization and integrated Discovery) analysis showed that the three most enriched terms were 'cytosol' (GO:0005829), 'translational elongation' (GO:0006414) and 'mitochondion' (GO:0005739). Those genes could be mapped to eight pathways. The most common type of enriched pathway was related to 'extracellular matrix (ECM)-receptor interaction'. Other pathways included those for 'ribosome', 'focal adhesion', 'oxidative phosphorylation', 'transforming growth factor (TGF)-beta signaling pathway', 'Parkinson's disease', 'Alzheimer's disease' and 'renin-angiotensin system'. Q-RT-PCR verified that Atp5b (F1-ATPase beta subunit), Col1a1 (collagen type 1 alpha 1), Cox6c (cytochrome c oxidase subunit VIc), Ndufs3 (NADH dehydrogenase [ubiquinone] Fe-S protein 3) and Tgfb1 (transforming growth factor β1) were significantly up-regulated in the DN group. The expressions of NDUFS3 and TGF-β1 in DN rats were increased. Our findings suggested that the oxidative phosphorylation pathway, ECM-receptor interaction, TGF-β pathway and renin-angiotensin system may be involved in the development of DN.

Renal interstitial fibrosis: mechanisms and evaluation

PURPOSE OF REVIEW

Tubulointerstitial injury in the kidney is complex, involving a number of independent and overlapping cellular and molecular pathways, with renal interstitial fibrosis and tubular atrophy (IFTA) as the final common pathway. Furthermore, there are multiple ways to assess IFTA.

RECENT FINDINGS

Cells involved include tubular epithelial cells, fibroblasts, fibrocytes, myofibroblasts, monocyte/macrophages, and mast cells with complex and still incompletely characterized cell-molecular interactions. Molecular mediators involved are numerous and involve pathways such as transforming growth factor (TGF)-β, bone morphogenic protein (BMP), platelet-derived growth factor (PDGF), and hepatocyte growth factor (HGF). Recent genomic approaches have shed insight into some of these cellular and molecular pathways. Pathologic evaluation of IFTA is central in assessing the severity of chronic disease; however, there are a variety of methods used to assess IFTA. Most assessment of IFTA relies on pathologist assessment of special stains such as trichrome, Sirius Red, and collagen III immunohistochemistry. Visual pathologist assessment can be prone to intra and interobserver variability, but some methods employ computerized morphometery, without a clear consensus as to the best method.

SUMMARY

IFTA results from on orchestration of cell types and molecular pathways. Opinions vary on the optimal qualitative and quantitative assessment of IFTA.