Obstructive nephropathy and renal fibrosis

GSDME-mediated pyroptosis promotes inflammation and fibrosis in obstructive nephropathy

Renal tubular cell (RTC) death and inflammation contribute to the progression of obstructive nephropathy, but its underlying mechanisms have not been fully elucidated. Here, we showed that Gasdermin E (GSDME) expression level and GSDME-N domain generation determined the RTC fate response to TNFα under the condition of oxygen-glucose-serum deprivation. Deletion of Caspase-3 (Casp3) or Gsdme alleviated renal tubule damage and inflammation and finally prevented the development of hydronephrosis and kidney fibrosis after ureteral obstruction. Using bone marrow transplantation and cell type-specific Casp3 knockout mice, we demonstrated that Casp3/GSDME-mediated pyroptosis in renal parenchymal cells, but not in hematopoietic cells, played predominant roles in this process. We further showed that HMGB1 released from pyroptotic RTCs amplified inflammatory responses, which critically contributed to renal fibrogenesis. Specific deletion of Hmgb1 in RTCs alleviated caspase11 and IL-1β activation in macrophages. Collectively, our results uncovered that TNFα/Casp3/GSDME-mediated pyroptosis is responsible for the initiation of ureteral obstruction-induced renal tubule injury, which subsequentially contributes to the late-stage progression of hydronephrosis, inflammation, and fibrosis. This novel mechanism will provide valuable therapeutic insights for the treatment of obstructive nephropathy.

Unilateral Ureteral Obstruction for 28 Days in Rats Is Not Associated with Changes in Cardiac Function or Alterations in Mitochondrial Function

Our work evaluated cardiac function and mitochondrial bioenergetics parameters in hearts from male Wistar rats subjected to the UUO model during 28 days of progression. We measured markers of kidney damage and inflammation in plasma and renal fibrosis by histological analysis and Western blot. Cardiac function was evaluated by echocardiography and proteins involved in cardiac damage by Western blot. Oxygen consumption and transmembrane potential were monitored in cardiac mitochondria using high-resolution respirometry. We also determined the activity of ATP synthase and antioxidant enzymes such as glutathione peroxidase, glutathione reductase, and catalase. Our results show that, although renal dysfunction is established in animals subjected to ureteral obstruction, cardiac function is maintained along with mitochondrial function and antioxidant enzymes activity after 28 days of injury evolution. Our results suggest that renocardiac syndrome might develop but belatedly in obstruction-induced renal damage, opening the opportunity for treatment to prevent this condition.

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.

MRTF: Basic Biology and Role in Kidney Disease

A lesser known but crucially important downstream effect of Rho family GTPases is the regulation of gene expression. This major role is mediated via the cytoskeleton, the organization of which dictates the nucleocytoplasmic shuttling of a set of transcription factors. Central among these is myocardin-related transcription factor (MRTF), which upon actin polymerization translocates to the nucleus and binds to its cognate partner, serum response factor (SRF). The MRTF/SRF complex then drives a large cohort of genes involved in cytoskeleton remodeling, contractility, extracellular matrix organization and many other processes. Accordingly, MRTF, activated by a variety of mechanical and chemical stimuli, affects a plethora of functions with physiological and pathological relevance. These include cell motility, development, metabolism and thus metastasis formation, inflammatory responses and—predominantly-organ fibrosis. The aim of this review is twofold: to provide an up-to-date summary about the basic biology and regulation of this versatile transcriptional coactivator; and to highlight its principal involvement in the pathobiology of kidney disease. Acting through both direct transcriptional and epigenetic mechanisms, MRTF plays a key (yet not fully appreciated) role in the induction of a profibrotic epithelial phenotype (PEP) as well as in fibroblast-myofibroblast transition, prime pathomechanisms in chronic kidney disease and renal fibrosis.

The Innovative Use of Ureter Catheter in the Surgery of Obstructive Uropathy

Purpose

Relieving obstruction and protecting renal function are the main therapeutic purposes of obstructive uropathy which often involve surgical treatment, and the ureter catheter is one of the surgical instruments commonly used in surgery. We aimed to explore the innovative use of a ureter catheter in the surgery of obstructive uropathy.

Methods

We used a ureteral catheter to innovate the surgical procedure of the most common causes of obstructive uropathy: ureteral calculi and stricture, establishing an internal circulation system (ICS), proposing a three-step dilatation method, and reviewing their effects on patients. Furthermore, we introduced a simple real-time intrapelvic pressure measurement device to monitor intrarenal pressure during operation.

Results

Postoperative laboratory examination showed that blood CRP, leukocyte neutrophil level, changes in the hemoglobin, urine occult blood, and positive rate of urine culture in the ICS group are significantly lower than those in the control group, corresponding to a lower incidence of bleeding and infection-related complications clinically. A three-month follow-up revealed 1/3 rate of ureteral stricture in the ICS group comparing to the control. We applied the three-step dilatation in patients with severe stenosis in which the balloon could not pass; the overall effective rate was 90.9%. The pressure of the renal pelvis was displayed on the monitor in real time. The surgeon could estimate the degree of filling of the renal pelvis and adjust the intake volume through the data.

Conclusion

The innovative application of ureteral catheters in the operation of obstructive uropathy can realize the real-time monitor of intraoperative renal pelvis pressure, reduce the incidence of lithotripsy postoperative complications, and expand the indications of balloon dilatation in ureteral stricture, which has certain clinical significance.

IDH2 gene deficiency accelerates unilateral ureteral obstruction-induced kidney inflammation through oxidative stress and activation of macrophages

Mitochondrial NADP⁺-dependent isocitrate dehydrogenase 2 (IDH2) produces NADPH, which is known to inhibit mitochondrial oxidative stress. Ureteral obstruction induces kidney inflammation and fibrosis via oxidative stress. Here, we investigated the role and underlying mechanism of IDH2 in unilateral ureteral obstruction (UUO)-induced kidney inflammation using IDH2 gene deleted mice (IDH2^-/-). Eight- to 10-week-old female IDH2^-/- mice and wild type (IDH2^+/+) littermates were subjected to UUO and kidneys were harvested 5 days after UUO. IDH2 was not detected in the kidneys of IDH2^-/- mice, while UUO decreased IDH2 in IDH2^+/+ mice. UUO increased the expressions of markers of oxidative stress in both IDH2^+/+ and IDH2^-/- mice, and these changes were greater in IDH2^-/- mice compared to IDH2^+/+ mice. Bone marrow-derived macrophages of IDH2^-/- mice showed a more migrating phenotype with greater ruffle formation and Rac1 distribution than that of IDH2^+/+ mice. Correspondently, UUO-induced infiltration of monocytes/macrophages was greater in IDH2^-/- mice compared to IDH2^+/+ mice. Taken together, these data demonstrate that IDH2 plays a protective role against UUO-induced inflammation through inhibition of oxidative stress and macrophage infiltration.

Interleukin-18 in Inflammatory Kidney Disease

Interleukin (IL)-18, a member of the IL-1 superfamily, is a pro-inflammatory cytokine that is structurally similar to IL-1β. IL-18 promotes the production of interferon gamma (IFN-γ) and strongly induces a Th1 response. IL-18 drives the same myeloid differentiation factor 88 (MyD88)/nuclear factor kappa B (NF-κB) signaling pathway as IL-1β. In physiological conditions, IL-18 is regulated by the endogenous inhibitor IL-18 binding protein (IL-18BP), and the activity of IL-18 is balanced. It is reported that in several inflammatory diseases, the IL-18 activity is unbalanced, and IL-18 neutralization by IL-18BP is insufficient. IL-18 acts synergistically with IL-12 to induce the production of IFN-γ as a Th1 cytokine, and IL-18 acts alone to induce the production of Th2 cytokines such as IL-4 and IL-13. In addition, IL-18 alone enhances natural killer (NK) cell activity and FAS ligand expression. The biological and pathological roles of IL-18 have been studied in many diseases. Here we review the knowledge regarding IL-18 signaling and the role of IL-18 in inflammatory kidney diseases. Findings on renal injury in coronavirus disease 2019 (COVID-19) and its association with IL-18 will also be presented.

MicroRNA-302b mitigates renal fibrosis via inhibiting TGF-β/Smad pathway activation

Renal fibrosis is one of the most significant pathological changes after ureteral obstruction. Transforming growth factor-β (TGF-β) signaling pathway plays essential roles in kidney fibrosis regulation. The aims of the present study were to investigate effects of microRNA-302b (miR-302b) on renal fibrosis, and interaction between miR-302b and TGF-β signaling pathway in murine unilateral ureteral obstruction (UUO) model. Microarray dataset GSE42716 was downloaded by retrieving Gene Expression Omnibus database. In accordance with bioinformatics analysis results, miR-302b was significantly down-regulated in UUO mouse kidney tissue and TGF-β1-treated HK-2 cells. Masson's trichrome staining showed that miR-302b mimics decreased renal fibrosis induced by UUO. The increased mRNA expression of collagen I and α-smooth muscle actin (α-SMA) and decreased expression of E-cadherin were reversed by miR-302b mimics. In addition, miR-302b up-regulation also inhibited TGF-β1-induced epithelial mesenchymal transition (EMT) of HK-2 cells by restoring E-cadherin expression and decreasing α-SMA expression. miR-302b mimics suppressed both luciferase activity and protein expression of TGF-βR2. However, miR-302b inhibitor increased TGF-βR2 luciferase activity and protein expression. Meanwhile, miR-302b mimics inhibited TGF-βR2 mRNA expression and decreased Smad2 and Smad3 phosphorylation in vivo and in vitro. Furthermore, over-expression of TGF-βR2 restored the miR-302b-induced decrease of collagen I and α-SMA expression. In conclusion, this study demonstrated that miR-302b attenuated renal fibrosis by targeting TGF-βR2 to suppress TGF-β/Smad signaling activation. Our findings showed that elevating renal miR-302b levels may be a novel therapeutic strategy for preventing renal fibrosis.

Red ginger-extract nanoemulsion modulates high blood pressure in rats by regulating angiotensin-converting enzyme production

Background and Aim:

Red ginger (RG) has reportedly been used in folk medicine for the management and prevention of hypertension. One of the hypertension study models in experimental animals is the unilateral ureteral obstruction (UUO). This study aimed at evaluating the effect of RG-extract (RGE) nanoemulsion on UUO-induced hypertension and angiotensin-converting enzyme (ACE) production in rats.

Materials and Methods:

RG was extracted using ethanol, combined with virgin coconut oil, polysorbate 80, and polyethylene glycol 400 to form the oil phase. The particle sizes of RGE nanoemulsions were analyzed using a particle size analyzer. The UUO method was used to induce chronic kidney disease in rats (504 mg/200 g and 360 mg/200 g b/w per oral for 7 days). The systolic and diastolic blood pressure was determined non-invasively in conscious state by tail plethysmography using an automated blood pressure monitor. ACE in serum was measured using enzyme-linked immunosorbent assay.

Results:

The RGE nanoemulsions exhibited a particle size of32.8 nm and a polydispersity index (PI) of 0.268, indicating a homogenous nanoemulsion. UUO rats treated with RGE nanoemulsion (360 mg/200 g b/w) experienced a significant decrease in both their systolic blood pressure (p<0.05) from 142±1 mmHg to 107±6 mmHg and their diastolic blood pressure from 106±1 mmHg to 84±4 mmHg. Furthermore, treatment with RGE resulted in a 10.80% decrease in the level of ACE.

Conclusion:

The size and the PI of the RGE used in this study suggest a stable and effective distribution of the particle size in the emulsions. RGE nanoemulsions at the dose of 360 mg/200 g bw can be used as potential ACE inhibitors because they were found to decrease the blood pressure of hypertensive UUO rats.

Fluorofenidone Alleviates Renal Fibrosis by Inhibiting Necroptosis Through RIPK3/MLKL Pathway

Cell death and sterile inflammation are major mechanisms of renal fibrosis, which eventually develop into end-stage renal disease. “Necroptosis” is a type of caspase-independent regulated cell death, and sterile inflammatory response caused by tissue injury is strongly related to necrosis. Fluorofenidone (AKF-PD) is a novel compound shown to ameliorate renal fibrosis and associated inflammation. We investigated whether AKF-PD could alleviate renal fibrosis by inhibiting necroptosis. Unilateral ureteral obstruction (UUO) was used to induce renal tubulointerstitial fibrosis in C57BL/6J mice. AKF-PD (500 mg/kg) or necrostatin-1 (Nec-1; 1.65 mg/kg) was administered simultaneously for 3 and 7 days. Obstructed kidneys and serum were harvested after euthanasia. AKF-PD and Nec-1 ameliorated renal tubular damage, inflammatory-cell infiltration, and collagen deposition, and the expression of proinflammatory factors (interlukin-1β, tumor necrosis factor [TNF]-α) and chemokines (monocyte chemoattractant protein-1) decreased. AKF-PD or Nec-1 treatment protected renal tubular epithelial cells from necrosis and reduced the release of lactate dehydrogenase in serum. Simultaneously, production of receptor-interacting protein kinase (RIPK)3 and mixed lineage kinase domain-like protein (MLKL) was also reduced 3 and 7 days after UUO. AKF-PD and Nec-1 significantly decreased the percentage of cell necrosis, inhibiting the phosphorylation of MLKL and RIPK3 in TNF-α- and Z-VAD–stimulated human proximal tubular epithelial (HK-2) cells. In conclusion, AKF-PD and Nec-1 have effective anti-inflammatory and antifibrotic activity in UUO-induced renal tubulointerstitial fibrosis, potentially mediated by the RIPK3/MLKL pathway.

Exaggerated renal fibrosis in lncRNA Gas5-deficient mice after unilateral ureteric obstruction

AIMS

Abnormal expression of long non-coding RNAs (lncRNAs) occurs in several diseases including renal fibrosis. Notably, growth arrest-specific 5 (Gas5) is a lncRNA, which functions as an essential modulator of cell proliferation and growth. However, the role and expression of lncRNA Gas5 associated with renal fibrosis remains controversial. Herein, we investigate the effect of lncRNA Gas5 deficiency in renal fibrosis induced by the operation of unilateral ureteric obstruction (UUO) in mice.

MAIN METHODS

Sera and urine of mice were used to detect markers of renal function. Further, Masson and immunohistochemical staining, western blotting as well as qRT-PCR were performed to observe the distribution and expression of fibrosis marker in the kidney tissue of the mice.

KEY FINDINGS

Unlike the wild type mice, the obstructed kidney in Gas5+/- mice showed more severe renal fibrosis and collagen deposition. In the UUO-Gas5+/- group, the serum levels of uric acid, serum creatinine, and the urine levels of albumin-to-creatinine ratio were higher. Moreover, the expression of mRNA and protein of α-smooth muscle actin (α-SMA), vimentin, collagen IV, fibronectin, and matrix metalloproteinase 9 (MMP9) were higher, whereas that of phosphatase and tensin homolog (PTEN) were lower with the difference being statistically significant (p < 0.05).

SIGNIFICANCE

lncRNA Gas5 was up-regulated in renal fibrosis tissues, and its deficiency exacerbated renal fibrosis in the UUO mice model.

Mast Cell Chymase and Kidney Disease

A sizable part (~2%) of the human genome encodes for proteases. They are involved in many physiological processes, such as development, reproduction and inflammation, but also play a role in pathology. Mast cells (MC) contain a variety of MC specific proteases, the expression of which may differ between various MC subtypes. Amongst these proteases, chymase represents up to 25% of the total proteins in the MC and is released from cytoplasmic granules upon activation. Once secreted, it cleaves the targets in the local tissue environment, but may also act in lymph nodes infiltrated by MC, or systemically, when reaching the circulation during an inflammatory response. MC have been recognized as important components in the development of kidney disease. Based on this observation, MC chymase has gained interest following the discovery that it contributes to the angiotensin-converting enzyme's independent generation of angiotensin II, an important inflammatory mediator in the development of kidney disease. Hence, progress regarding its role has been made based on studies using inhibitors but also on mice deficient in MC protease 4 (mMCP-4), the functional murine counterpart of human chymase. In this review, we discuss the role and actions of chymase in kidney disease. While initially believed to contribute to pathogenesis, the accumulated data favor a more subtle view, indicating that chymase may also have beneficial actions.

Huoxue Jiedu Huayu Recipe Ameliorates Mesangial Cell Pyroptosis in Contralateral Kidney of UUO Rats

OBJECTIVES

To observe the effects of the Huoxue Jiedu Huayu Recipe (HJHR) on pyroptosis of glomerular mesangial cells in the contralateral unobstructed kidney (CK) of unilateral ureteral obstruction (UUO) rats.

METHODS

Sprague-Dawley rats were randomly divided into 4 groups: sham group, UUO group (10 days of left ureter ligation), UUO treated with eplerenone (EPL) (UUO + EPL) group, and UUO treated with HJHR (UUO + HJHR) group. The CKs of all rats were collected for studies.

RESULTS

Cell pyroptosis and macrophage infiltration was found in contralateral glomeruli, and nucleotide-binding oligomerization domain-like pyrin domain containing protein 3 (NLRP3) and interleukin (IL)-1β expression was upregulated in the CK of UUO rats. All of these changes were inhibited by HJHR and eplerenone. To determine how aldosterone (Aldo) activated the mineralocorticoid receptor (MR) and then induced mesangial cell pyroptosis with NLRP3-caspase-1-IL-1β pathway, human mesangial cells (HMCs) were treated with HJHR and eplerenone, which were examined to detect the expression of NLRP3 inflammasome-associated proteins following treatment with Aldo.

CONCLUSION

These results suggest that HJHR and eplerenone suppressed HMC pyroptosis via the MR/NLRP3 pathway.

Deletion of Akt1 Promotes Kidney Fibrosis in a Murine Model of Unilateral Ureteral Obstruction

We investigated the role of Akt1, one of the three isoforms of Akt, in renal fibrosis using the murine model of unilateral ureteral obstruction (UUO). We subjected wild type and Akt1^−/− mice to UUO. The Akt1 gene was silenced in vitro using short hairpin RNA delivered via a lentiviral vector in human proximal tubular cells (HK2 cells) and kidney fibroblasts (NRK-49F cells). The obstructive kidneys of Akt1^−/− mice showed more severe tubulointerstitial fibrosis than those of wild type mice. The expression of fibronectin and type I collagen was significantly increased in obstructed kidneys of Akt1^−/− mice compared to those of wild type mice. The important finding was that the expression of transforming growth factor β1 (TGFβ1) was significantly increased in the Akt1^−/− mice compared to the wild type mice. The knockdown of Akt1 enhanced the expression of TGFβ1 in HK2 cells. Interestingly, the upregulation of TGFβ1 due to genetic knockdown of Akt1 was associated with activation of signal transducer and activator of transcript 3 (STAT3) independently of the Smad pathway in NRK-49F and HK2 cells. Immunohistochemical staining also showed that expression of phosphorylated STAT3 was more increased in Akt1^−/− mice than in wild type mice after UUO. Additionally, the deletion of Akt1 led to apoptosis of the renal tubular cells in both in vivo and in vitro studies. Conclusively, these results suggest that the deletion of Akt1 may contribute to renal fibrosis via induction of the TGFβ1/STAT3 pathway in a murine model of UUO.

Genistein Ameliorates Renal Fibrosis Through Regulation Snail via m6A RNA Demethylase ALKBH5

Renal tubule-interstitial fibrosis is related to chronic kidney disease progression and a typical feature of the aging kidney. Epigenetic modifications of fibrosis-prone genes regulate the development of renal fibrosis. As a kind of “epigenetic diet”, soy isoflavone genistein was reported to have renal protective action and epigenetic-modulating effects. However, its renal protection role and underlying mechanisms are yet to be fully clarified. Herein, we showed that genistein exhibits a demonstrable anti-fibrotic effect on kidney in vivo UUO (unilateral ureteral occlusion) model and renal epithelial cells in vitro model. The mechanism is strongly associated with epithelial-to-mesenchymal transition and m6A RNA demethylase ALKBH5. Mouse fibrotic kidneys induced by UUO exhibited adverse expression of renal fibrosis-related proteins and significant increases in the total m6A level. As an eraser, ALKBH5 showed severer suppression in the renal fibrosis process. However, genistein pretreatment restored ALKBH5 loss remarkably and reduced renal fibrosis, abnormal protein, and inflammatory markers. The examination of possible mechanisms revealed that genistein promoted ALKBH5 and maybe induced the level of mRNA m6A methylation in some epithelial-to-mesenchymal transition-related transcription factors. We found snail was the critical regulator and critical for the protective role of genistein. To verify the relationship between ALKBH5 and snail, we generated knockdown and overexpression of ALKBH5 cells in vitro. ALKBH5 knockdown enhanced the mesenchymal phenotype marker α-smooth muscle actin and snail expression. In agreement, overexpression ALKBH5 increased epithelial adhesion molecule E-cadherin and reduced snail expression. In conclusion, genistein increased renal ALKBH5 expression in UUO-induced renal fibrosis and reduced RNA m6A levels and ameliorates renal damages.

DAMPs in Unilateral Ureteral Obstruction

Damage-associated molecular patterns (DAMPs) are released from tubular and interstitial cells in the kidney after unilateral ureteral obstruction (UUO). DAMPs are recognized by pattern recognition receptors (PRRs), which mediate the initiation of an immune response and the release of inflammatory cytokines. The animal model of UUO is used for various purposes. UUO in adult mice serves as a model for accelerated renal fibrosis, which is a hallmark of progressive renal disease. UUO in adult mice enables to study cell death, inflammation, and extracellular matrix deposition in the kidney. Neonatal UUO is a model for congenital obstructive nephropathies. It studies inflammation, apoptosis, and interstitial fibrosis in the neonatal kidney, when nephrogenesis is still ongoing. Following UUO, several DAMPs as well as DAMP receptors are upregulated. In adult UUO, soluble uric acid is upregulated and activates the NOD-like receptor family, pyrin domain containing-3 (NLRP3) inflammasome, which promotes fibrosis, apoptosis, and reactive oxygen species (ROS) injury. Further DAMPs associated with UUO are uromodulin, members of the IL-1 family, and necrotic cell DNA, all of which promote sterile inflammation. In neonatal UUO, the receptor for advanced glycation endproducts (RAGE) is highly upregulated. RAGE is a ligand for several DAMPs, including high mobility group box 1 (HMGB1) and S100 proteins, which play an important role in renal fibrosis. Additionally, necroptosis is an important mechanism of cell death, besides apoptosis, in neonatal UUO. It is highly inflammatory due to release of cytokines and specific DAMPs. The release and recognition of DAMPs initiate sterile inflammation, which makes them good candidates to develop and improve diagnostic and therapeutic strategies in renal fibrosis and congenital obstructive nephropathies.

Calcium dobesilate mediates renal interstitial fibrosis and delay renal peritubular capillary loss through Sirt1/p53 signaling pathway

Calcium dobesilate (Cad), a protective agent, protects against microvascular damage, and diseases such as diabetic retinopathy and diabetic nephropathy. However, these vascular protective effects have not been demonstrated in chronic kidney disease (CKD). In this study, we aimed to determine the ability of Cad to protect against renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO) and identify the underlying therapeutic mechanisms of Cad during hypoxia/serum deprivation (H/SD) in human umbilical vein endothelial cells (HUVECs). A total of 36 male mice were randomly assigned into 3 groups (12 mice in each group): the Sham-operated group (Sham), the saline solution-treated UUO mice group (UUO), and the Cad administration (intragastrically) group (Cad). The mice in Cad group were administered Cad (100 mg/kg) daily by oral gavage and slaughtered on the 7th and 14th days post-surgery. Six mice from each group were sacrificed by sodium pentobarbital injection on the 7th and 14th day after surgery. Tissue hypoxia, cell apoptosis and fibrotic lesions were detected by Immunostaining and Western blot. Peritubular capillaries (PTCs) injury was measured by a novel technique of fluorescent microangiography (FMA). Endothelial cell-to-mesenchymal transition (EndMT) were identified by immunofluorescence and Western blot. HUVECs proliferation was measured via Cell Counting Kit‑8 assays and Edu staining. Sirt1 and its downstream gene in Cad regulation of endothelial were detected. Hematoxylin-eosin (HE), Masson-trichrome stains and Histological findings showed that Cad administration markedly reduced hypoxia and renal interstitial fibrosis at each time point in UUO. Meanwhile, Cad protect against EndMT process of PTCs by increasing CD31 expression and decreasing α-smooth muscle actin and fibronectin expression. in vitro studies showed that there was a proliferative response of the HUVECs incubated with Cad (10 μM) in H/SD. Sirt1 was suppressed after small interfering RNA (siRNA) was transfected in HUVECs. Mechanistically, Cad enhanced Sirt1 signaling, which was accompanied by increased levels of p53 acetylation (ac-p53). Meanwhile, protein expression of Bcl-2, and VE-cadherin were downregulated, Bax, and α-SMA were upregulated. In summary, the therapeutic effect of Cad in obstructive nephropathy were likely through suppressing EndMT progression and promoting anti-apoptotic effects after via activating the Sirt1/p53 signaling pathway.

MiR-155-5p promotes renal interstitial fibrosis in obstructive nephropathy via inhibiting SIRT1 signaling pathway

Protection against renal fibrosis is important for the management of obstructive nephropathy. We researched the roles and possible mechanism of miR-155-5p in renal interstitial fibrosis, which may provide a potential endogenous target for renal interstitial fibrosis in obstructive nephropathy. Herein, NRK-49F cells were transfected with miR-155-5p mimic, miR-155-5p inhibitor, SIRT1 plasmid and/or SIRT1 siRNA. The unilateral ureteral obstruction (UUO) model was built with male C57 black mice and administrated with SRT1720 by tail vein injection. Levels of miR-155-5p, SIRT1 and relative proteins (TGF-β1, α-SMA, Collage I and fibronectin) in NRK-49F cells or mice kidney tissues were measured with quantitative reverse transcription polymerase chain reaction or Western blot. The target gene of miR-155-5p was analyzed through TargetScan and dual-luciferase reporter assay. Mice kidney tissue was stained with Masson trichrome. It was found that miR-155-5p overexpression promoted the expressions of fibroblast related proteins expression and inhibited the SIRT1 expression in NRK-49F cells, while miR-155-5p silencing had an opposite effect. SIRT1 can bind with miR-155-5p. MiR-155-5p inhibited the level of SIRT1. Fibroblast related proteins were up-regulated by miR-155-5p and down-regulated by SIRT1 in NRK-49F cells, while the up-regulatory effect of miR-155-5p was reversed by SIRT1. MiR-155-5p expression was up-regulated and SIRT1 expression was down-regulated in the kidney tissue of UUO mice. SRT1720 attenuated the fiber deposition, up-regulated SIRT1 level and down-regulated the levels of fibroblast related proteins in UUO model mice. To conclude, miR-155-5p promotes renal interstitial fibrosis in obstructive nephropathy via inhibiting SIRT1 signaling pathway.

Tripartite motif-containing 35 (TRIM35) is up-regulated in UUO-induced renal fibrosis animal model

Renal fibrosis has been recognized as a serious health threat in the world because of the high cost of treatment and poor prognosis. However, the molecular mechanism of renal fibrosis is still largely unknown. In this study, we aimed at illustrating the role of TRIM35 in the renal fibrosis process. A UUO mouse model and a TGF-β1-induced tubulointerstitial fibrosis model were constructed for the research of renal fibrosis at animal and cell level, respectively. Hematoxylin-eosin and Masson staining were used for visualizing the pathological change. qRT-PCR, Western blot analysis and immunohistochemical staining were used to detect the expression of fibrosis-associated proteins and TRIM35. The results showed that, after the modeling, the expressions of α-SMA, Collagen I, Collagen III, Fibronectin and Snail1 were up-regulated, while the expression of E-cadherin was down-regulated, indicating the successful construction of animal and cell models. More importantly, TRIM35 was proved to be up-regulated in both animal and cell models. Therefore, this study demonstrates the potential promotional effect of TRIM35 in the renal fibrosis process, which may prove to be a new biomarker for the diagnosis and development of new treatments of renal fibrosis.

DsbA-L mediated renal tubulointerstitial fibrosis in UUO mice

Recent studies have reported that upregulation of disulfide-bond A oxidoreductase-like protein (DsbA-L) prevented lipid-induced renal injury in diabetic nephropathy (DN). However, the role and regulation of proximal tubular DsbA-L for renal tubulointerstitial fibrosis (TIF) remains unclear. In current study, we found that a proximal tubules-specific DsbA-L knockout mouse (PT-DsbA-L-KO) attenuated UUO-induced TIF, renal cell apoptosis and inflammation. Mechanistically, the DsbA-L interacted with Hsp90 in mitochondria of BUMPT cells which activated the signaling of Smad3 and p53 to produce connective tissue growth factor (CTGF) and then resulted in accumulation of ECM of BUMPT cells and mouse kidney fibroblasts. In addition, the progression of TIF caused by UUO, ischemic/reperfusion (I/R), aristolochic acid, and repeated acute low-dose cisplatin was also alleviated in PT-DsbA-L-KO mice via the activation of Hsp90 /Smad3 and p53/CTGF axis. Finally, the above molecular changes were verified in the kidney biopsies from patients with obstructive nephropathy (Ob). Together, these results suggest that DsbA-L in proximal tubular cells promotes TIF via activation of the Hsp90 /Smad3 and p53/CTGF axis.

DsbA-L upregulation prevents lipid-induced renal injury in diabetic nephropathy. Here, the authors show that DsbA-L knockout attenuates tubulointerstitial fibrosis in mice, and show that this occurs via activation of Smad3 and p53, which result in modulation of CTGF, a regulator of kidney fibrosis.

Biomarkers in vesicoureteral reflux: an overview

Aim: This article aimed to review the role of cytokines, chemokines, growth factors and cellular adhesion molecules as biomarkers for vesicoureteral reflux (VUR) and reflux nephropathy (RN). Methods: We reviewed articles from 1979 onward by searching PubMed and Scopus utilizing the combination of words: 'VUR' or 'RN' and each one of the biomarkers. Results: Genetic, inflammatory, fibrogenic, environmental and epigenetic factors responsible for renal scarring need to be better understood. TGF-β, IL-10, IL-6, IL-8 and TNF seem to exert a role in VUR particularly in RN based on the current literature. Serum levels of procalcitonin have been also associated with high-grade VUR and RN. These molecules should be more intensively evaluated as potential biomarkers for renal scarring in VUR. Conclusion: Further studies are necessary to define which molecules will really be of utility in clinical decisions and as therapeutic targets for VUR and RN.

Ablation of Gadd45β ameliorates the inflammation and renal fibrosis caused by unilateral ureteral obstruction

The growth arrest and DNA damage‐inducible beta (Gadd45β) protein have been associated with various cellular functions, but its role in progressive renal disease is currently unknown. Here, we examined the effect of Gadd45β deletion on cell proliferation and apoptosis, inflammation, and renal fibrosis in an early chronic kidney disease (CKD) mouse model following unilateral ureteral obstruction (UUO). Wild‐type (WT) and Gadd45β‐knockout (KO) mice underwent either a sham operation or UUO and the kidneys were sampled eight days later. A histological assay revealed that ablation of Gadd45β ameliorated UUO‐induced renal injury. Cell proliferation was higher in Gadd45β KO mouse kidneys, but apoptosis was similar in both genotypes after UUO. Expression of pro‐inflammatory cytokines after UUO was down‐regulated in the kidneys from Gadd45β KO mice, whereas UUO‐mediated immune cell infiltration remained unchanged. The expression of pro‐inflammatory cytokines in response to LPS stimulation decreased in bone marrow‐derived macrophages from Gadd45β KO mice compared with that in WT mice. Importantly, UUO‐induced renal fibrosis was ameliorated in Gadd45β KO mice unlike in WT mice. Gadd45β was involved in TGF‐β signalling pathway regulation in kidney fibroblasts. Our findings demonstrate that Gadd45β plays a crucial role in renal injury and may be a therapeutic target for the treatment of CKD.

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.

Protective role of renal proximal tubular alpha-synuclein in the pathogenesis of kidney fibrosis

Kidney fibrosis is a highly deleterious process and a final manifestation of chronic kidney disease. Alpha-(α)-synuclein (SNCA) is an actin-binding neuronal protein with various functions within the brain; however, its role in other tissues is unknown. Here, we describe the expression of SNCA in renal epithelial cells and demonstrate its decrease in renal tubules of murine and human fibrotic kidneys, as well as its downregulation in renal proximal tubular epithelial cells (RPTECs) after TGF-β1 treatment. shRNA-mediated knockdown of SNCA in RPTECs results in de novo expression of vimentin and α-SMA, while SNCA overexpression represses TGF-β1-induced mesenchymal markers. Conditional gene silencing of SNCA in RPTECs leads to an exacerbated tubulointerstitial fibrosis (TIF) in two unrelated in vivo fibrotic models, which is associated with an increased activation of MAPK-p38 and PI3K-Akt pathways. Our study provides an evidence that disruption of SNCA signaling in RPTECs contributes to the pathogenesis of renal TIF by facilitating partial epithelial-to-mesenchymal transition and extracellular matrix accumulation.

Pharmacologic inhibition of RGD-binding integrins ameliorates fibrosis and improves function following kidney injury

Fibrosis is a final common pathway for many causes of progressive chronic kidney disease (CKD). Arginine-glycine-aspartic acid (RGD)-binding integrins are important mediators of the pro-fibrotic response by activating latent TGF-β at sites of injury and by providing myofibroblasts information about the composition and stiffness of the extracellular matrix. Therefore, blockade of RGD-binding integrins may have therapeutic potential for CKD. To test this idea, we used small-molecule peptidomimetics that potently inhibit a subset of RGD-binding integrins in a murine model of kidney fibrosis. Acute kidney injury leading to fibrosis was induced by administration of aristolochic acid. Continuous subcutaneous administration of CWHM-12, an RGD integrin antagonist, for 28 days improved kidney function as measured by serum creatinine. CWHM-12 significantly reduced Collagen 1 (Col1a1) mRNA expression and scar collagen deposition in the kidney. Protein and gene expression markers of activated myofibroblasts, a major source of extracellular matrix deposition in kidney fibrosis, were diminished by treatment. RNA sequencing revealed that inhibition of RGD integrins influenced multiple pathways that determine the outcome of the response to injury and of repair processes. A second RGD integrin antagonist, CWHM-680, administered once daily by oral gavage was also effective in ameliorating fibrosis. We conclude that targeting RGD integrins with such small-molecule antagonists is a promising therapeutic approach in fibrotic kidney disease.

Refining the unilateral ureteral obstruction mouse model: No sham, no shame

Fibrosis, as a common final pathway in many renal diseases, contributes significantly to the decline of organ function and to progression to end-stage renal disease. To establish therapeutic interventions that target fibrosis, animal models are essential. The most widely used model of renal fibrosis is the unilateral ureteral obstruction (UUO) model. Typically, the control for this model is a sham-operated animal. Sham surgery causes pain and distress to these control animals, and here we aim to show that there is no difference in the main read-outs of this model between sham-operated animals and non-operated C57BL/6J mice. In five experiments, quantification of Picro Sirius Red stained collagen in the renal cortex did not show any difference between 15 sham and 25 non-operated individuals. A comparison of the regulation of genes involved with fibrosis did not show any difference between sham and non-operated groups at 21 days post surgery either. We conclude that there are no significant differences between non-operated controls and sham animals with respect to collagen deposition and fibrosis pathways in the UUO mouse model.

A modified relief of unilateral ureteral obstruction model

Objectives: To improve the mouse model of relief for unilateral ureteral obstruction (RUUO) and explore the pathological process of renal fibrosis after the obstruction was relieved. Methods: C57BL/6 mice in model group were randomly divided into RUUO group, improved RUUO group, and UUO group. After leaving Unilateral Ureteral Obstruction (UUO) for 3 days, the obstruction was released by reimplantation way in RUUO group and in reimplantation + catheter way in improved RUUO group. C57BL/6 mice in observation group were randomly divided into 1d RUUO group, 3d RUUO group, 7d RUUO group, and 14d RUUO group. Three days after UUO, the obstruction was released by reimplantation + catheter in four groups. We detected the renal volume, H&E, Masson staining, and immunohistochemistry of kidney pathology on the seventh day after RUUO in model group and on the 1st, 3rd, 7th, and 14th day after RUUO in observation group. Results: Comparing with mice in RUUO group, mice in improved RUUO group had lower renal volume, tubular damage score, and collagen area percentage. After the obstruction was relieved, the renal volume decreased gradually within 2 weeks. The tubular damage score in 7d RUUO group was lower than that in 1d RUUO and 3d RUUO group. However, the tubular damage score in 14d RUUO group was higher than that in 7d RUUO group. The tendency of collagen area percentage and α-SMA IOD value were consistent with the tubular damage score. Conclusions: Using the method of reimplantation + catheter, a reliable mice model of RUUO can be got. After RUUO, the de-obstructed kidneys are still in damage and fibrosis state.

Deletion of discoidin domain receptor 2 attenuates renal interstitial fibrosis in a murine unilateral ureteral obstruction model

Background: Renal interstitial fibrosis is a common pathway of chronic kidney disease to end-stage renal disease, which is characterized by an imbalance between the synthesis and degradation of the collagen-rich extracellular matrix (ECM). While, discoidin domain receptor 2 (DDR2) can be activated when it binds to some types of collagen. Therefore, we hypothesized that DDR2 may be a major player in renal interstitial fibrosis.

Methods: Renal histologic analysis, real-time PCR analyses and hydroxyproline assay were performed in DDR2-deficient mice and wild-type mice after unilateral ureteral obstruction; C57 mice were randomly divided into sham operation group (Sham group, n = 4), renal interstitial fibrosis model group (UUO group, n = 4), and calcium dobesilate treatment group (CDT group, n = 4), preparation of renal interstitial fibrosis model by unilateral ureteral obstruction (UUO), CDT Group was treated with calcium dobesilate orally, Sham group and UUO group were given double distilled water, HE staining, Masson staining, real-time quantitative PCR were detected after 14 days of UUO in mice to observe the renal interstitial fibrosis degree.

Results: DDR2 expression was dramatically increased in the obstructed kidney; In contrast to wild-type mice that developed severe interstitial fibrosis, the DDR2-deficient mice displayed only moderate fibrotic changes; Compared with the UUO group, the degree of renal interstitial fibrosis in CDT group was relieved after operation 14 day.

Conclusion: DDR2 might play an important role in the development of RIF; Calcium dobesilate can affect the expression of DDR2 and improve the renal interstitial fibrosis in mice.

Renal elasticity and perfusion changes associated with fibrosis on ultrasonography in a rabbit model of obstructive uropathy

PURPOSE

To evaluate elasticity and perfusion change associated with fibrosis in a rabbit model of unilateral ureter obstruction using shear wave elastography (SWE) and contrast-enhanced ultrasonography (CEUS).

METHODS

Complete unilateral ureter obstruction by ligation was performed in the left kidney of 15 rabbits. Renal elasticity on SWE and perfusion change on CEUS at the renal cortex were measured before and after the operation. Histopathological renal fibrosis was quantified by the stained area ratio with Masson trichrome and Picrosirius red using ImageJ analysis. Renal elasticity and perfusion values were compared by the Mann-Whitney U test and Proc Mixed as a function of time. Spearman's correlation was used to analyze differences between imaging values and fibrosis.

RESULTS

The duration of imaging follow-up was up to 49 days, with interval imaging performed 1-3 times. Renal elasticity values were higher in obstructed kidneys compared to contralateral kidneys (31.0 kPa vs 16.4 kPa, p < 0.001) and increased according to postoperative time (0.46 kPa/day). With respect to renal fibrosis, SWE values were positively correlated with Masson trichrome (ρ = 0.651, p < 0.001) and Picrosirius red (ρ = 0.514, p = 0.007). Among CEUS parameters, mean transit time was negatively correlated with renal fibrosis by Masson trichrome (ρ = - 0.639, p = 0.001) and Picrosirius red (ρ = - 0.625, p = 0.001). Rise time and time to peak were positively correlated with renal fibrosis.

CONCLUSION

Obstructive uropathy resulted in changes to both renal elasticity and perfusion. Renal fibrosis was moderately associated with increased renal cortical stiffness and both delayed and decreased cortical perfusion.

KEY POINTS

• Obstructive uropathy causes changes in elasticity and perfusion in a rabbit model. • Renal fibrosis from obstructive uropathy increases renal cortical stiffness, and both delay and decrease cortical perfusion.

BMP1 inhibitor UK383,367 attenuates renal fibrosis and inflammation in CKD

Renal fibrosis is a key pathological phenomenon of chronic kidney disease (CKD) contributing to the progressive loss of renal function. UK383,367 is a procollagen C proteinase inhibitor that has been selected as a candidate for dermal antiscarring agents, whereas its role in renal fibrosis is unclear. In the present study, UK383,367 was applied to a CKD mouse model of unilateral ureteral obstruction (UUO) and cell lines of renal tubular epithelial cells (mouse proximal tubular cells) and renal fibroblast cells (NRK-49F cells) challenged by transforming growth factor-β1. In vivo, bone morphogenetic protein 1, the target of UK383,367, was significantly enhanced in UUO mouse kidneys and renal biopsies from patients with CKD. Strikingly, UK383,367 administration ameliorated tubulointerstitial fibrosis as shown by Masson’s trichrome staining in line with the blocked expression of collagen type I/III, fibronectin, and α-smooth muscle actin in the kidneys from UUO mice. Similarly, the enhanced inflammatory factors in obstructed kidneys were also blunted. In vitro, UK383,367 pretreatment inhibited the induction of collagen type I/III, fibronectin, and α-smooth muscle actin in both mouse proximal tubular cells and NRK-49F cells treated with transforming growth factor-β1. Taken together, these findings indicate that the bone morphogenetic protein 1 inhibitor UK383,367 could serve as a potential drug in antagonizing CKD renal fibrosis by acting on the maturation and deposition of collagen and the subsequent profibrotic response and inflammation.

The indole compound MA-35 attenuates tumorigenesis in an inflammation-induced colon cancer model

In inflammatory bowel disease, chronic inflammation results in the development of colon cancer known as colitis-associated cancer. This disease is associated with tumor necrosis factor-α (TNF-α) signaling. In addition, intestinal fibrosis is a common clinical complication that is promoted by transforming growth factor β1 (TGF-β₁). In our previous study, MA-35 attenuated renal fibrosis by inhibiting both TNF-α and TGF-β₁ signaling. This study aimed to identify the possible antitumor effects and antifibrotic effects of MA-35 using an AOM/DSS mouse model. MA-35 was orally administered every day for 70 days in the AOM/DSS mouse model. There was no difference in weight loss between the AOM/DSS group and the AOMDSS + MA-35 group, but the disease activity index score and the survival rate were improved by MA-35. MA-35 blocked the anemia and shortening of the colon induced by AOM/DSS. MA-35 reduced the macroscopic formation of tumors in the colon. In the microscopic evaluation, MA-35 reduced inflammation and fibrosis in areas with dysplasia. Furthermore, the TNF-α mRNA level in the colon tended to be reduced, and the interleukin 6, TGF-β₁ and fibronectin 1 mRNA levels in the colon were significantly reduced by MA-35. These results suggested that MA-35 inhibited AOM/DSS-induced carcinogenesis by reducing inflammation and fibrosis.

Claudin-2 suppresses GEF-H1, RHOA, and MRTF, thereby impacting proliferation and profibrotic phenotype of tubular cells

The tight junctional pore-forming protein claudin-2 (CLDN-2) mediates paracellular Na⁺ and water transport in leaky epithelia and alters cancer cell proliferation. Previously, we reported that tumor necrosis factor-α time-dependently alters CLDN-2 expression in tubular epithelial cells. Here, we found a similar expression pattern in a mouse kidney injury model (unilateral ureteral obstruction), consisting of an initial increase followed by a drop in CLDN-2 protein expression. CLDN-2 silencing in LLC-PK¹ tubular cells induced activation and phosphorylation of guanine nucleotide exchange factor H1 (GEF-H1), leading to Ras homolog family member A (RHOA) activation. Silencing of other claudins had no such effects, and re-expression of an siRNA-resistant CLDN-2 prevented RHOA activation, indicating specific effects of CLDN-2 on RHOA. Moreover, kidneys from CLDN-2 knockout mice had elevated levels of active RHOA. Of note, CLDN-2 silencing reduced LLC-PK1 cell proliferation and elevated expression of cyclin-dependent kinase inhibitor P27 (P27KIP1) in a GEF-H1/RHOA-dependent manner. P27KIP1 silencing abrogated the effects of CLDN-2 depletion on proliferation. CLDN-2 loss also activated myocardin-related transcription factor (MRTF), a fibrogenic RHOA effector, and elevated expression of connective tissue growth factor and smooth muscle actin. Finally, CLDN-2 down-regulation contributed to RHOA activation and smooth muscle actin expression induced by prolonged tumor necrosis factor-α treatment, because they were mitigated by re-expression of CLDN-2. Our results indicate that CLDN-2 suppresses GEF-H1/RHOA. CLDN-2 down-regulation, for example, by inflammation, can reduce proliferation and promote MRTF activation through RHOA. These findings suggest that the initial CLDN-2 elevation might aid epithelial regeneration, and CLDN-2 loss could contribute to fibrotic reprogramming.

Epithelial-fibroblast cross talk aggravates the impact of the nephrotoxin ochratoxin A

BACKGROUND

Chronic nephropathies result from different pathogenic agents, including nutritional factors triggering vicious pathophysiological cycles. Ochratoxin A (OTA) is a globally occurring nephrotoxic mycotoxin detectable in a variety of foodstuff and suspected to cause tubulointerstitial damage. The underlying mechanisms are not sufficiently understood, compromising risk assessment. Because crosstalk of proximal tubule cells with fibroblasts is crucial for tubulointerstitial damage, we investigated the effects of OTA in co-culture of these two cell types.

METHODS

Rat renal proximal tubule cells (NRK-52E) and renal fibroblasts (NRK-49F) were exposed to nanomolar OTA concentrations under mono- and/or co-culture conditions for up to 48 h. We determined the impact on inflammation-, EMT- and fibrosis-associated proteins as well as microRNAs by western blot or qPCR, respectively. Alterations in cell morphology were quantitatively assessed. The roles of miRs, COX-2 and ERK1/2 in OTA-induced effects were investigated by specific inhibition.

FINDINGS

Only under co-culture condition, OTA caused an increase of vimentin, fibronectin and miR-21 and a decrease of collagen III, E-cadherin, COX-2 and WISP1 mRNA abundance in NRK-52E cells. In NRK-49F cells, OTA induced an increase of N-cadherin, COX-2, WISP1 in co-culture only. The OTA-induced increase of fibronectin in NRK-52E cells was prevented by simultaneous inhibition of miR-21 and -200a, COX-2 or ERK1/2. The OTA-induced increase of COX-2 in NRK-49F cells was prevented by inhibition of miR-21 and -200a or ERK1/2.

INTERPRETATION

Our results show that the complete nephropathic potential of nanomolar OTA, leading to EMT, is unveiled when cellular crosstalk is possible. In monoculture, the nephropathic potential is underestimated.

RESEARCH IN CONTEXT

Chronic nephropathies are a severe health burden and the result of different pathogenic mechanisms, including nutritional factors that trigger vicious pathophysiological cycles. Ochratoxin A (OTA) is a ubiquitous, globally occurring nephrotoxic mycotoxin detectable in a variety of foodstuff and suspected to cause tubulointerstitial damage. Because underlying pathomechanisms are unclear, risk assessment is problematic. Crosstalk of proximal tubule cells (the main target of OTA) with fibroblasts is crucial for the development of tubulointerstitial damage. We show that during co-culture of proximal tubule cells and fibroblasts, OTA-induced effects (e.g. epithelial-mesenchymal transition (EMT)) change significantly as compared to monoculture. Our results show that the complete nephropathic potential of OTA is unveiled when cellular crosstalk is possible. In monoculture, the nephropathic potential of OTA is underestimated.

Losartan accelerates the repair process of renal fibrosis in UUO mouse after the surgical recanalization by upregulating the expression of Tregs

Obstructive nephropathy is a common cause for chronic kidney disease. Surgery, which is adopted to promptly relieve the obstruction, is the most important method to save damaged kidneys. However, earlier studies have shown that renal function will continue to deteriorate until the terminal stage after the obstruction' relief. The aim of this study is to explore the renal fibrosis and investigate the effect of losartan on renal fibrosis after the obstruction' relief using an improved mouse model of relief for unilateral ureteral obstruction (RUUO). Experiments carried out using C57BL/6 mice (n = 30) were randomly divided into RUUO + Losartan group, RUUO group and sham group. Using an improved mouse RUUO model, this study revealed that the mouse kidney for 3- or 7-day unilateral ureteral obstruction undergoing the RUUO surgery was still in a state of injury and fibrosis, while losartan could effectively ameliorate renal fibrosis by upregulating the expression of CD4 + CD25 + Foxp3 + regulatory T cells (Tregs) in kidney after the surgery of RUUO.

Human umbilical cord-derived mesenchymal stem cells conditioned medium attenuate interstitial fibrosis and stimulate the repair of tubular epithelial cells in an irreversible model of unilateral ureteral obstruction

AIM

The growing number of patients suffering from chronic renal disease (CKD) is a challenge for the development of innovative therapies. Researchers have studied the therapeutic effects of cell therapy in acute kidney injury (AKI). However, the therapeutic effect of conditional medium (CM) in the CKD models have been rarely reported. Here, we examined the effects of umbilical cord derived-mesenchymal stem cells (hUC-MSCs) CM on renal fibrosis in a rat model of unilateral ureteral obstruction (UUO).

METHODS

Animals were randomly divided into three groups: sham-operated, UUO, UUO + CM. CM was administered via the left renal artery after total ligation of the left ureter. Rats were killed after 14 days of obstruction. Histological changes and oxidative stress parameters were assessed. Western blotting and immunohistochemistry analysis were used to measure epithelial-mesenchymal transition (EMT) markers, including epithelial cadherin (E-cadherin), α-smooth muscle actin (α-SMA), tumour necrosis factor-α (TNF-α), Collagen-I, and transforming growth factor β1 (TGF-β1). Proliferation and apoptosis of renal tubular epithelial cells (RTEs) were also measured.

RESULTS

HucMSC-CM significantly reduced the levels of malondialdehyde (MDA) and reactive oxygen species (ROS), and increased the activity of glutathione (GSH) induced by UUO. Moreover, CM significantly reduced the expression of TGF-β1, α-SMA, TNF-α and Collagen-I in UUO kidney, promoted the proliferation of RTEs and inhibited its apoptosis. In addition, the increased expression of E-cadherin also reflects the effective improvement of renal interstitial fibrosis.

CONCLUSION

This study shows that CM protects UUO-induced kidney damage and therefore could be a potential tool to prevent CKD progression.

Cell Death in the Kidney

Apoptotic cell death is usually a response to the cell's microenvironment. In the kidney, apoptosis contributes to parenchymal cell loss in the course of acute and chronic renal injury, but does not trigger an inflammatory response. What distinguishes necrosis from apoptosis is the rupture of the plasma membrane, so necrotic cell death is accompanied by the release of unprocessed intracellular content, including cellular organelles, which are highly immunogenic proteins. The relative contribution of apoptosis and necrosis to injury varies, depending on the severity of the insult. Regulated cell death may result from immunologically silent apoptosis or from immunogenic necrosis. Recent advances have enhanced the most revolutionary concept of regulated necrosis. Several modalities of regulated necrosis have been described, such as necroptosis, ferroptosis, pyroptosis, and mitochondrial permeability transition-dependent regulated necrosis. We review the different modalities of apoptosis, necrosis, and regulated necrosis in kidney injury, focusing particularly on evidence implicating cell death in ectopic renal calcification. We also review the evidence for the role of cell death in kidney injury, which may pave the way for new therapeutic opportunities.

Anti-Apoptotic Effect of G-Protein-Coupled Receptor 40 Activation on Tumor Necrosis Factor-α-Induced Injury of Rat Proximal Tubular Cells

G-protein-coupled receptor 40 (GPR40) has an anti-apoptotic effect in pancreatic β-cells. However, its role in renal tubular cell apoptosis remains unclear. To explore the role of GPR40 in renal tubular apoptosis, a two-week unilateral ureteral obstruction (UUO) mouse model was used. The protein expression of GPR40 was decreased, while the Bax/Bcl-2 protein expression ratio, the expression of tumor necrosis factor (TNF)-α mRNA, and angiotensin II type 1 receptor (AT1R) protein were increased in mice with UUO. In vitro, pretreatment of rat proximal tubular (NRK52E) cells with GW9508, a GPR40 agonist, attenuated the decreased cell viability, increased the Bax/Bcl-2 protein expression ratio, increased protein expression of cleaved caspase-3 and activated the nuclear translocation of nuclear factor-κB (NF-κB) p65 subunit induced by TNF-α treatment. TNF-α treatment significantly increased the expression of AT1R protein and the generation of reactive oxygen species (ROS), whereas GW9508 treatment markedly reversed these effects. Pretreatment with GW1100, a GPR40 antagonist, or silencing of GPR40 in NRK52E cells promoted the increased expression of the cleaved caspase-3 protein by TNF-α treatment. Our results demonstrate that decreased expression of GPR40 is associated with apoptosis via TNF-α and AT1R in the ureteral obstructed kidney. The activation of GPR40 attenuates TNF-α-induced apoptosis by inhibiting AT1R expression and ROS generation through regulation of the NF-κB signaling pathway.

Emerging strategies to disrupt the central TGF-β axis in kidney fibrosis

Chronic kidney disease (CKD) affects more than 20 million people in the United States and the global burden of this disorder is increasing. Many affected individuals will progress to end stage kidney disease necessitating dialysis or transplantation. CKD is also a major independent contributor to the risk of cardiovascular morbidity and mortality. Tubulointerstitial fibrosis is a final common pathway for most causes of progressive CKD. Currently, there are no clinically available therapies targeting fibrosis that can slow the decline in kidney function. Although it has long been known that TGF-β signaling is a critical mediator of kidney fibrosis, translating this knowledge to the clinic has been challenging. In this review, we highlight some recent insights into the mechanisms of TGF-β signaling that target activation of this cytokine at the site of injury or selectively inhibit pro-fibrotic gene expression. Molecules directed at these targets hold the promise of attaining therapeutic efficacy while limiting toxicity seen with global inhibition of TGF-β. Kidney injury has profound epigenetic effects leading to altered expression of more than a thousand genes. We discuss how drugs targeting epigenetic modifications, some of which are in use for cancer therapy, have the potential to reprogram gene regulatory networks to favor adaptive repair and prevent fibrosis. The lack of reliable biomarkers of kidney fibrosis is a major limitation in designing clinical trials for testing CKD treatments. We conclude by reviewing recent advances in fibrosis biomarker development.

Alterations in Lipid Profile of the Aging Kidney Identified by MALDI Imaging Mass Spectrometry

During aging, the kidney undergoes functional and physiological changes that are closely affiliated with chronic kidney disease (CKD). There is increasing evidence supporting the role of lipid or lipid-derived mediators in the pathogenesis of CKD and other aging-related diseases. To understand the role of lipids in various metabolic processes during kidney aging, we conducted matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS) analysis in kidneys harvested from young (2 months old, n = 3) and old mice (24 months old, n = 3). MALDI-IMS analysis showed an increase in ceramide level and a decrease in sphingomyelin (SM) and phosphatidylcholine (PC) levels in kidneys of old mice. The increased expression of cPLA2 and SMPD1 protein in aged kidney was confirmed by immunohistochemistry and Western blot analysis. Our MALDI-IMS data showed the altered distribution of lipids in aged kidney as indicative of aging-related functional changes of the kidney. Combined analysis of MALDI-IMS and IHC confirmed lipidomic changes and expression levels of responsible enzymes as well as morphological changes.

Noninvasive Monitoring and Evaluation of the Renal Structure and Function in a Mouse Model of Unilateral Ureteral Occlusion Using Microcomputed Tomography

Mouse unilateral ureteral occlusion (UUO) is widely used as a model of renal experimental obstructive nephropathy with interstitial fibrosis. Microcomputed tomography (micro-CT) imaging has the potential to produce quantitative images. The aim of this study was to establish standard images of micro-CT for renal anatomic and functional evaluations in a mouse model of UUO. UUO was induced in adult male mice BALB/c. In total, 27 mice were used in this study. Three mice per group (a total of 6 groups) were examined with contrast-enhanced micro-CT prior to UUO (day 0) and on days 1, 3, 5, 7, 10, and 14 after UUO. In order to determine the histopathologic correlations at each point in time, contrast-enhanced micro-CT imaging was performed in the 18 remaining mice. All animals were sacrificed, and both kidneys were harvested after the final micro-CT examination. UUO resulted in hydronephrosis and changes in the renal parenchyma. The predominant alteration was substantial changes in the hemodynamics of the renal vascular system after ureteral obstruction for 24 hours or longer, which may be resulting from increased action of vasoconstrictors versus vasodilators. The renal parenchyma was significantly reduced after 1 week, and the features of the histologic changes supported the findings of the micro-CT images. In the contralateral unobstructed kidneys, the images showed a normal structure and function and the pathohistology revealed a normal histoarchitecture. Micro-CT is a useful tool for providing noninvasive monitoring and evaluating the renal structure and function.

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.

Relaxin and extracellular matrix remodeling: Mechanisms and signaling pathways

Fibrosis is associated with accumulation of excess fibrillar collagen, leading to tissue dysfunction. Numerous processes, including inflammation, myofibroblast activation, and endothelial-to-mesenchymal transition, play a role in the establishment and progression of fibrosis. Relaxin is a peptide hormone with well-known antifibrotic properties that result from its action on numerous cellular targets to reduce fibrosis. Relaxin activates multiple signal transduction pathways as a mechanism to suppress inflammation and myofibroblast activation in fibrosis. In this review, the general mechanisms underlying fibrotic diseases are described, along with the current state of knowledge regarding cellular targets of relaxin. Finally, an overview is presented summarizing the signaling pathways activated by relaxin and other relaxin family peptide receptor agonists to suppress fibrosis.

Urinary microRNA in kidney disease: utility and roles

MicroRNAs (miRNAs) are small, noncoding single-stranded RNA oligonucleotides that modulate physiological and pathological processes by modulating target gene expression. Many miRNAs display tissue-specific expression patterns, the dysregulation of which has been associated with various disease states, including kidney disease. Mounting evidence implicates miRNAs in various biological processes, such as cell proliferation and differentiation and cancer. Because miRNAs are relatively stable in tissue and biological fluids, particularly when carried by extracellular vesicles, changes in their levels may reflect the development of human disease. Urinary miRNAs originate from primary kidney and urinary tract cells, cells infiltrating the renal tissue and shed in the urine, or the systemic circulation. Although their validity as biomarkers for kidney disease has not been fully established, studies have been applying analysis of miRNAs in the urine in an attempt to detect and monitor acute and chronic renal diseases. Because appreciation of the significance of miRNAs in the renal field is on the rise, an understanding of miRNA pathways that regulate renal physiology and pathophysiology is becoming critically important. This review aims to summarize new data obtained in this field of research. It is hoped that new developments in the use of miRNAs as biomarkers and/or therapy will help manage and contain kidney disease in affected subjects.

Full age spectrum equation versus CKD-EPI and MDRD equations to estimate glomerular filtration rate in adults with obstructive nephropathy

Objective

To compare the full age spectrum (FAS) equation with the Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in predicting glomerular filtration rate (GFR) in patients with obstructive nephropathy.

Methods

Adult patients with obstructive nephropathy who had undergone a GFR measurement using technetium-99m diethylenetriaminepentaacetic acid radioisotope renography were enrolled in the study. The measured GFR was taken as the reference value. Bias, precision and accuracy were compared between the three equations. Kappa test and the Bland–Altman method were used to evaluate the classification and the agreement. Receiver operating characteristic (ROC) curve analysis was used to describe the diagnostic accuracy of each equation.

Results

A total of 327 patients were enrolled. The P30 value for the FAS equation was 60.2% in the overall study cohort. The FAS equation had the highest diagnostic accuracy (ROC^AUC = 0.87, 95% confidence interval [CI] 0.84, 0.91) compared with the MDRD equation (ROC^AUC = 0.86, 95% CI 0.82, 0.89). The median bias of the FAS equation was significantly higher than that of the MDRD equation (8.7 versus 7.6 ml/min/1.73 m², respectively).

Conclusions

Despite the drawbacks associated with each equation, the FAS equation was probably closer to ideal to estimate GFR in patients with obstructive nephropathy.

Profibrotic epithelial phenotype: a central role for MRTF and TAZ

Epithelial injury is a key initiator of fibrosis but - in contrast to the previous paradigm - the epithelium in situ does not undergo wide-spread epithelial-mesenchymal/myofibroblast transition (EMT/EMyT). Instead, it assumes a Profibrotic Epithelial Phenotype (PEP) characterized by fibrogenic cytokine production. The transcriptional mechanisms underlying PEP are undefined. As we have shown that two RhoA/cytoskeleton-regulated transcriptional coactivators, Myocardin-related transcription factor (MRTF) and TAZ, are indispensable for EMyT, we asked if they might mediate PEP as well. Here we show that mechanical stress (cyclic stretch) increased the expression of transforming growth factor-β1 (TGFβ1), connective tissue growth factor (CTGF), platelet-derived growth factor and Indian Hedgehog mRNA in LLC-PK1 tubular cells. These responses were mitigated by siRNA-mediated silencing or pharmacological inhibition of MRTF (CCG-1423) or TAZ (verteporfin). RhoA inhibition exerted similar effects. Unilateral ureteral obstruction, a murine model of mechanically-triggered kidney fibrosis, induced tubular RhoA activation along with overexpression/nuclear accumulation of MRTF and TAZ, and increased transcription of the above-mentioned cytokines. Laser capture microdissection revealed TAZ, TGFβ1 and CTGF induction specifically in the tubular epithelium. CCG-1423 suppressed total renal and tubular expression of these proteins. Thus, MRTF regulates epithelial TAZ expression, and both MRTF and TAZ are critical mediators of PEP-related epithelial cytokine production.

Salidroside Ameliorates Renal Interstitial Fibrosis by Inhibiting the TLR4/NF-κB and MAPK Signaling Pathways

Salidroside (Sal) is an active ingredient that is isolated from Rhodiola rosea, which has been reported to have anti-inflammatory activities and a renal protective effect. However, the role of Sal on renal fibrosis has not yet been elucidated. Here, the purpose of the current study is to test the protective effects of Sal against renal interstitial fibrosis (RIF), and to explore the underlying mechanisms using both in vivo and in vitro models. In this study, we establish the unilateral ureteric obstruction (UUO) or folic acid (FA)-induced mice renal interstitial fibrosis in vivo and the transforming growth factor (TGF)-β1-stimulated human proximal tubular epithelial cell (HK-2) model in vitro. The levels of kidney functional parameters and inflammatory cytokines in serum are examined. The degree of renal damage and fibrosis is determined by histological assessment. Immunohistochemistry and western blotting are used to determine the mechanisms of Sal against RIF. Our results show that treatment with Sal can ameliorate tubular injury and deposition of the extracellular matrix (ECM) components (including collagen Ш and collagen I). Furthermore, Sal administration significantly suppresses epithelial-mesenchymal transition (EMT), as evidenced by a decreased expression of α-SMA, vimentin, TGF-β1, snail, slug, and a largely restored expression of E-cadherin. Additionally, Sal also reduces the levels of serum biochemical markers (serum creatinine, Scr; blood urea nitrogen, BUN; and uric acid, UA) and decreases the release of inflammatory cytokines (IL-1β, IL-6, TNF-α). Further study revealed that the effect of Sal on renal interstitial fibrosis is associated with the lower expression of TLR4, p-IκBα, p-NF-κB and mitogen-activated protein kinases (MAPK), both in vivo and in vitro. In conclusion, Sal treatment improves kidney function, ameliorates the deposition of the ECM components and relieves the protein levels of EMT markers in mouse kidneys and HK-2 cells. Furthermore, Sal treatment significantly decreases the release of inflammatory cytokines and inhibits the TLR4/NF-κB and MAPK signaling pathways. Collectively, these results suggest that the administration of Sal could be a novel therapeutic strategy in treating renal fibrosis.

Ribes diacanthum Pall (RDP) ameliorates UUO-induced renal fibrosis via both canonical and non-canonical TGF-β signaling pathways in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ribes diacanthum Pall (RDP), a folk medicine, has been widely used in Mongolia to treat urinary system diseases.

AIM OF THE STUDY

To investigate the effectiveness of RDP on unilateral ureteral obstruction (UUO)-induced renal interstitial fibrosis and the underlying mechanisms.

MATERIALS AND METHODS

A total of 60 mice were randomly divided into six groups: sham group, sham plus RDP (40 mg/kg) group, UUO model group, and UUO model plus RDP (10, 20 or 40 mg/kg) groups. After surgery, aqueous extract of RDP were administrated intragastrically (i.g) daily for a week and ipsilateral kidneys were collected seven days after surgery. Levels of blood urea nitrogen (BUN) and serum creatinine (Scr) were detected to reflect the kidney injury. Hematoxylin & eosin and Masson's trichrome staining were used to evaluate the kidney morphological changes and fibrosis, respectively. ELISA was used to examine the levels of pro-inflammatory cytokines. Immunohistochemistry, western blot and PCR were used to examine the expression levels of key proteins involved in transforming growth factor (TGF-β)/Smad and mitogen-activated protein kinase (MAPK) signaling pathways.

RESULTS

RDP treatment attenuates the level of BUN and kidney fibrosis in UUO mice, decreases the expressions of interleukin-6, tumor necrosis factor-α, Interleukin-1α, TGF-β1, monocyte chemotactic protein-1, α-smooth muscle actin, collagen I, fibronectin, and vimentin, while increases the expressions of E-cadherin and hepatocyte growth factor. Moreover, RDP administration significantly decreases the levels of p-Smad2/3, p-ERK1/2, p-p38 and p-JNK, while increases the expression level of Smad7 in UUO models.

CONCLUSION

These data demonstrate that RDP ameliorates renal fibrosis through TGF-β/Smad and MAPK pathways in a UUO mouse model.

A Novel Biomarker for Acute Kidney Injury, Vanin-1, for Obstructive Nephropathy: A Prospective Cohort Pilot Study

Background: Vanin-1 is a novel acute kidney injury (AKI) biomarker that has not been clinically investigated as a biomarker for obstructive nephropathy. This study investigated the diagnostic value of vanin-1 as a biomarker for adult obstructive nephropathy by comparing it to existing AKI biomarkers. Methods: A total of 49 patients, 21 controls, and 28 hydronephrosis (HN) cases were assessed. AKI biomarkers in bladder (BL) urine and renal pelvic (RP) urine in the HN group were compared to each BL marker in the control group. In a subgroup of cases receiving interventions for obstructive nephropathy, the BL values of each biomarker were assessed after the intervention. Results: RP vanin-1 levels were significantly higher while BL vanin-1 levels were marginally higher in the HN group than in the control group. The area under the receiver operating characteristics curve values for RP and BL vanin-1 were 0.9778 and 0.6386, respectively. In multivariate analyses, BL vanin-1 and N-acetyl-β-D-glucosaminidase (NAG), but not kidney injury molecule-1 (KIM-1) or neutrophil gelatinase-associated lipocalin (NGAL), were independent factors for predicting the presence of HN. In cases receiving interventions, vanin-1 decreased significantly from 1 week after the intervention in cases of moderate to severe obstructive nephropathy compared to RP values at baseline. Conclusion: Urinary vanin-1 is a useful biomarker to detect and monitor the clinical course of obstructive nephropathy.