Role of inflammation in túbulo-interstitial damage associated to obstructive nephropathy

Two distinct phenotypes of calcium oxalate stone formers could imply different long-term risks for renal function

Endoscopic and biopsy findings have identified two distinct phenotypes among individuals with calcium oxalate (CaOx) kidney stones. The first type has normal renal papillae but shows interstitial mineral deposition, known as Randall's plaque. The other phenotype presents with collecting duct plugging and a higher incidence of loss of papilla tissue mass. With Randall's plaque, renal papilla injury involves the loss of small patches of calcified tissue (Randall's plaque detaching with the stone), which likely results in damage to only a few nephrons. In contrast, collecting duct mineral plugs are very large, causing obstruction to tubular flow. Since each terminal collecting duct drains thousands of nephrons, ductal plugs could lead to the degeneration of many nephrons and a significant loss of renal glomeruli. New visualization techniques for immune cells in papillary biopsies have revealed that the Randall's plaque phenotype is marked by the accumulation of macrophages around the plaque regions. In contrast, preliminary data on the plugging phenotype shows collecting duct damage with mineral plugs and increased T-lymphocytes throughout the papilla. These regions also show tubulitis, i.e., T-cell infiltration into nearby collecting duct epithelium. This suggests that while some CaOx stone formers may have some papillary inflammation but with minimal damage to nephrons, others suffer from obstruction to flow for many nephrons that may also include destructive inflammation in the renal tissue. We propose that CaOx stone formers with the plugging phenotype will have a higher long-term risk for loss of renal function.

Ultrathin semirigid retrograde ureteroscopy versus antegrade flexible ureteroscopy in treating proximal ureteric stones 1-2 cm, a prospective randomized multicenter study

To compare the outcomes of using Ultrathin semirigid retrograde ureteroscopy and antegrade flexible ureteroscopy to treat proximal ureteric stones of sizes 1-2 cm. A prospective randomized multicenter study included patients who had proximal ureteric stones 1-2 cm, amenable for ureteroscopy and laser lithotripsy between August 2023 and February 2024. Two hundred thirty patients were divided evenly into two treatment groups. Group I included patients treated with antegrade flexible ureteroscopy and holmium laser stone fragmentation, and Group II included patients treated with retrograde ultrathin semirigid ureteroscopy. The study groups were compared in terms of patient demographics, stone access success, operation time, reoperation rates, peri-operative complications, and stone-free status. Group I included 114 patients, while Group II included 111. The mean age of the patients was 33.92 ± 10.37 years, and the size of the stones was 15.88 ± 3 mm. The study groups had comparable demographics and stone characteristics. The mean operative time was significantly longer in group I than in group II (102.55 ± 72.46 min vs. 60.98 ± 14.84 min, respectively, P < 0.001). Most reported complications were MCCS grades I and II, with no significant difference between the study groups. The stone-free rate after four weeks was 92.1% and 81.1% for groups I and II, respectively, which increased to 94.7% and 85.6% after eight weeks (P > 0.05). Antegrade flexible ureteroscopy is equivalent to retrograde ultrathin semirigid ureteroscopy in treating proximal ureteric stones regarding stone-free status and procedure-related morbidity. However, the antegrade approach has a longer operative time, greater fluoroscopy exposure, and longer hospital stays.

Two distinct phenotypes of calcium oxalate stone formers could imply different long-term risks for renal function

Endoscopic and biopsy findings have identified two distinct phenotypes among individuals with calcium oxalate (CaOx) kidney stones. One phenotype exhibits normal renal papillae but shows interstitial mineral deposition, known as Randall's plaque. The other phenotype presents with collecting duct plugging and a higher incidence of loss of papilla tissue mass. With Randall's plaque, renal papilla injury involves the loss of small patches of calcified tissue (Randall's plaque detaching with the stone), which likely results in damage to only a few nephrons. In contrast, collecting duct mineral plugs are very large, causing obstruction to tubular flow. Since each terminal collecting duct drains thousands of nephrons, ductal plugs could lead to the degeneration of many nephrons and a significant loss of renal glomeruli. New visualization techniques for immune cells in papillary biopsies have revealed that the Randall's plaque phenotype is marked by the accumulation of macrophages around the plaque regions. In contrast, preliminary data on the plugging phenotype shows collecting duct damage with mineral plugs, increased T-lymphocytes throughout the papilla, and tubulitis, characterized by T-cell infiltration into nearby collecting duct epithelium. This suggests that while some CaOx stone formers may have some papillary inflammation but with minimal damage to nephrons, others suffer from obstruction to flow for many nephrons that may also include destructive inflammation in the renal tissue. We propose that the long-term risks for loss of renal function will be greater for CaOx stone formers with the plugging phenotype.

TREM2 deficiency aggravates renal injury by promoting macrophage apoptosis and polarization via the JAK-STAT pathway in mice

The triggering receptor expressed on myeloid cells 2 (TREM2) is an immune receptor that affects cellular phenotypes by modulating phagocytosis and metabolism, promoting cell survival, and counteracting inflammation. Its role in renal injury, in particular, unilateral ureteral obstruction (UUO) or ischemia-reperfusion injury (IRI)-induced renal injury remains unclear. In our study, WT and Trem2-/- mice were employed to evaluate the role of TREM2 in renal macrophage infiltration and tissue injury after UUO. Bone marrow-derived macrophages (BMDM) from both mouse genotypes were cultured and polarized for in vitro experiments. Next, the effects of TREM2 on renal injury and macrophage polarization in IRI mice were also explored. We found that TREM2 expression was upregulated in the obstructed kidneys. TREM2 deficiency exacerbated renal inflammation and fibrosis 3 and 7 days after UUO, in association with reduced macrophage infiltration. Trem2-/- BMDM exhibited increased apoptosis and poorer survival compared with WT BMDM. Meanwhile, TREM2 deficiency augmented M1 and M2 polarization after UUO. Consistent with the in vivo observations, TREM2 deficiency led to increased polarization of BMDM towards the M1 proinflammatory phenotype. Mechanistically, TREM2 deficiency promoted M1 and M2 polarization via the JAK-STAT pathway in the presence of TGF-β1, thereby affecting cell survival by regulating mTOR signaling. Furthermore, cyclocreatine supplementation alleviated cell death caused by TREM2 deficiency. Additionally, we found that TREM2 deficiency promoted renal injury, fibrosis, and macrophage polarization in IRI mice. The current data suggest that TREM2 deficiency aggravates renal injury by promoting macrophage apoptosis and polarization via the JAK-STAT pathway. These findings have implications for the role of TREM2 in the regulation of renal injury that justify further evaluation.

Effects of the Surgical Ligation of the Ureter in Different Locations on the Kidney over Time in the Rat Model

Purpose

To evaluate the effects of the surgical ligation of the ureter in different locations on the kidney over time in the rat model.

Methods

A total of 155 rats were enrolled and randomly divided into the case (n = 150) and control (n = 5) groups. The case group included three separate groups (fifty rats in each group) that underwent surgical ureteral ligation at the proximal, middle, and distal ureter. The laboratory tests, and tumor necrosis factor α (TNF-α), were measured in groups. The pathological evaluation for glomerular changes, tubular dilation, interstitial fibrosis, and interstitial infiltration of the inflammatory cells following the obstruction was performed (severity of tubular atrophy categorized too mild (+), moderate (++), and severe (+++)). To compare the continuous variables between the groups and between the measurement times, the analysis of variance (ANOVA) was used.

Results

Our results revealed that the creatinine four weeks after the obstruction was significantly higher in the proximal group obstruction (p value: 0.046). The three groups had no significant differences regarding urine creatinine, serum sodium, and serum TNF (p value: 0.261). Obstruction did not change the glomerular morphology in three intervention groups after six weeks. The commencing of severe tubular atrophy in proximal, middle, and distal ureteral obstruction was at weeks three, four, and six, respectively.

Conclusion

The location of ureteral obstruction is also crucial in deciding to intervene to relieve the complete ureteral obstruction. Severe tubular damage occurs in weeks three, four, and six in proximal, middle, and distal ureteral obstruction, respectively.

Insights into Kidney Dysplasia in Duplex Kidneys: From Radiologic Diagnosis to Histopathologic Understanding

Duplex kidney is a urinary tract anomaly commonly associated with a wide range of primary and secondary parenchymal structural abnormalities. We present a unique comparison of US and MRI findings with histopathology following partial resection of duplex kidneys due to nephropathy. We examined a group of 21 children with duplex kidneys who were qualified for heminephrectomy (24 kidney units (KU)). All patients underwent US and MRI prior to the surgery. The imaging results were compared with histopathologic findings. In 21/24 KU, dysplastic changes were found on histopathology, including all with obstructive nephropathy and 7/10 specimens with refluxing uropathy. The loss of corticomedullary differentiation on US and increased signal on T2-weighted images (T2WI) on MRI were the imaging findings that best correlated with fibrosis. In children with megaureter, there were no statistical differences in histopathological findings between primary megaureter, megaureter with ureterocele, and megaureter with ectopia (p > 0.05). The extent of dysplasia of the affected pole correlated negatively with residual function in MRI. Kidney dysplasia and inflammation in the kidney with obstructive nephropathy are the most important histopathologic findings of this study. US is a valuable screening tool, and MRI enables morphologic and functional assessments of the nephropathy in duplex kidneys.

Thymoquinone: An Effective Natural Compound for Kidney Protection

Kidney disease is a common health problem worldwide. Acute or chronic injuries may interfere with kidney functions, eventually resulting in irreversible kidney damage. A number of recent studies have shown that the plant-derived natural products have an extensive potential for renal protection. Thymoquinone (TQ) is an essential compound derived from Nigella Sativa (NS), which is widely applied in the Middle East as a folk medicine. Previous experiments have demonstrated that TQ has a variety of potential pharmacological effects, including anti-oxidant, antibacterial, antitumor, immunomodulatory, and neuroprotective activities. In particular, the prominent renal protective efficacy of TQ has been demonstrated in both in vivo and in vitro experiments. TQ can prevent acute kidney injuries from various xenobiotics through anti-oxidation, anti-inflammatory, and anti-apoptosis effects. In addition, TQ exhibited significant pharmacological effects on renal cell carcinoma, renal fibrosis, and urinary calculi. The essential mechanisms involve scavenging ROS and increasing anti-oxidant activity, decreasing inflammatory mediators, inducing apoptosis, and inhibiting migration and invasion. The purpose of this review is to conclude the pharmacological effects and the potential mechanisms of TQ in renal protection, shedding new light on the exploration of medicinal phyto-protective agents targeting kidneys.

[18F] AlF-NOTA-FAPI-04 PET/CT for non-invasive assessment of tubular injury in kidney diseases

Background

[18F] AlF-NOTA-FAPI-04 is a novel positron emission tomography (PET) ligand, which specifically targets fibroblast activation protein (FAP) expression as a FAP inhibitor (FAPI). We analysed the diagnostic value of [18F] AlF-NOTA-FAPI-04 PET/CT for the non-invasive assessment of kidney interstitial inflammation and fibrosis in different renal pathologies.

Methods

Twenty-six patients (14 males and 12 females; mean age, 50.5 ± 16.5 years) with a wide range of kidney diseases and 10 patients (six males and four females; mean age, 55.4 ± 8.6 years) without known evidence of renal disease as disease controls underwent [18F] AlF-NOTA-FAPI-04 PET/CT imaging. Kidney tissues obtained from kidney biopsies were stained with haematoxylin and eosin, periodic acid-Schiff, Masson's trichome, and periodic acid-silver methenamine. Immunohistochemical staining was also performed to assess the expression of α-smooth muscle actin (αSMA) and FAP. Renal parenchymal FAPI uptake reflected by maximum standardized uptake value (SUVmax) and mean standardized uptake value (SUVmean) measurements on PET/CT was analysed against pathohistological findings.

Results

We found that renal parenchymal FAPI uptake was significantly higher in patients with various kidney diseases than in control patients in this study (SUVmax = 4.3 ± 1.8 vs 1.9 ± 0.4, SUVmean=3.9 ± 1.7 vs 1.5 ± 0.4, respectively; all P < 0.001). All kidney diseases, both in acute and chronic kidney disease, had increased renal parenchymal uptake to varying degrees. The correlation analysis indicated a positive association between the SUVmax and the tubulointerstitial inflammation (TII), interstitial fibrosis and tubular atrophy (IF/TA), and TII + IF/TA scores (r = 0.612, 0.681, and 0.754, all P < 0.05), and between the SUVmean and the TII, IF/TA, and TII + IF/TA scores (r = 0.603, 0.700, and 0.748, all P < 0.05). Furthermore, we found significant positive correlations between both SUVmax and the SUVmean with SMA and FAP staining scores (r = 0.686 and 0.732, r = 0.667 and 0.739, respectively; both P < 0.001).

Conclusions

[18F] AlF-NOTA-FAPI-04 PET/CT is clinically available for the comprehensive and non-invasive assessment of tubular injury in various kidney diseases.

Critical Role of histone deacetylase 3 in the regulation of kidney inflammation and fibrosis

Chronic kidney disease (CKD) is characterized by kidney inflammation and fibrosis. However, the precise mechanisms leading to kidney inflammation and fibrosis are poorly understood. Since histone deacetylase is involved in inflammation and fibrosis in other tissues, we examined the role of histone deacetylase 3 (HDAC3) in the regulation of inflammation and kidney fibrosis. HDAC3 is induced in the kidneys of animal models of CKD but mice with conditional HDAC3 deletion exhibit significantly reduced fibrosis in the kidneys compared with control mice. The expression of proinflammatory and profibrotic genes was significantly increased in the fibrotic kidneys of control mice, which was impaired in mice with HDAC3 deletion. Genetic deletion or pharmacological inhibition of HDAC3 reduced the expression of proinflammatory genes in cultured monocytes/macrophages. Mechanistically, HDAC3 deacetylates Lys122 of NF-κB p65 subunit turning on transcription. RGFP966, a selective HDAC3 inhibitor, reduced fibrosis in cells and in animal models by blocking NF-κB p65 binding to κB-containing DNA sequences. Thus, our study identified HDAC3 as a critical regulator of inflammation and fibrosis of the kidney through deacetylation of NF-κB unlocking its transcriptional activity. Hence, targeting HDAC3 could serve as a novel therapeutic strategy for CKD.

Management of de novo nephrolithiasis after kidney transplantation: a comprehensive review from the European Renal Association CKD-MBD working group

The lifetime incidence of kidney stones is 6%-12% in the general population. Nephrolithiasis is a known cause of acute and chronic kidney injury, mediated via obstructive uropathy or crystal-induced nephropathy, and several modifiable and non-modifiable genetic and lifestyle causes have been described. Evidence for epidemiology and management of nephrolithiasis after kidney transplantation is limited by a low number of publications, small study sizes and short observational periods. Denervation of the kidney and ureter graft greatly reduces symptomatology of kidney stones in transplant recipients, which may contribute to a considerable underdiagnosis. Thus, reported prevalence rates of 1%-2% after kidney transplantation and the lack of adverse effects on allograft function and survival should be interpreted with caution. In this narrative review we summarize current state-of-the-art knowledge regarding epidemiology, clinical presentation, diagnosis, prevention and therapy of nephrolithiasis after kidney transplantation, including management of asymptomatic stone disease in kidney donors. Our aim is to strengthen clinical nephrologists who treat kidney transplant recipients in informed decision-making regarding management of kidney stones. Available evidence, supporting both surgical and medical treatment and prevention of kidney stones, is presented and critically discussed. The specific anatomy of the transplanted kidney and urinary tract requires deviation from established interventional approaches for nephrolithiasis in native kidneys. Also, pharmacological and lifestyle changes may need adaptation to the specific situation of kidney transplant recipients. Finally, we point out current knowledge gaps and the need for additional evidence from future studies.

Macrophages polarization in renal inflammation and fibrosis animal models (Review)

Chronic kidney disease (CKD) is a significant public health concern. Renal fibrosis is the final common pathway in the progression of kidney diseases, irrespective of the initial injury. Substantial evidence underscores the pivotal role of renal inflammation in the genesis of renal fibrosis. The presence of macrophages within normal renal tissue is significantly increased within diseased renal tissue, indicative of their crucial regulatory function in inflammation and fibrosis. Macrophages manifest a high degree of heterogeneity, exhibiting distinct phenotypic and functional traits in response to diverse stimuli within the local microenvironment in various types of kidney diseases. Broadly, macrophages are categorized into two principal groups: Classically activated, designated as M1 macrophages and alternatively activated, designated as M2 macrophages. A number of experimental models are widely used to study the underlying mechanisms driving renal inflammation and fibrosis progression. The present review delineated the phenotypic and functional attributes of macrophages present in diverse induced models, analyzing their disposition in relation to M1 and M2 polarization states.

Natural products in traditional Chinese medicine: molecular mechanisms and therapeutic targets of renal fibrosis and state-of-the-art drug delivery systems

Renal fibrosis (RF) is the end stage of several chronic kidney diseases. Its series of changes include excessive accumulation of extracellular matrix, epithelial-mesenchymal transition (EMT) of renal tubular cells, fibroblast activation, immune cell infiltration, and renal cell apoptosis. RF can eventually lead to renal dysfunction or even renal failure. A large body of evidence suggests that natural products in traditional Chinese medicine (TCM) have great potential for treating RF. In this article, we first describe the recent advances in RF treatment by several natural products and clarify their mechanisms of action. They can ameliorate the RF disease phenotype, which includes apoptosis, endoplasmic reticulum stress, and EMT, by affecting relevant signaling pathways and molecular targets, thereby delaying or reversing fibrosis. We also present the roles of nanodrug delivery systems, which have been explored to address the drawback of low oral bioavailability of natural products. This may provide new ideas for using natural products for RF treatment. Finally, we provide new insights into the clinical prospects of herbal natural products.

Nrf2/HO-1 as a therapeutic target in renal fibrosis

Chronic kidney disease (CKD) is one of the most prevalent chronic diseases and affects between 10 and 14 % of the world's population. The World Health Organization estimates that by 2040, the disease will be fifth in prevalence. End-stage CKD is characterized by renal fibrosis, which can eventually lead to kidney failure and death. Renal fibrosis develops due to multiple injuries and involves oxidative stress and inflammation. In the human body, nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the expression of antioxidant, anti-inflammatory, and cytoprotective genes, which prevents oxidative stress and inflammation damage. Heme oxygenase (HO-1) is an inducible homolog influenced by heme products and after exposure to cellular stress inducers such as oxidants, inflammatory chemokines/cytokines, and tissue damage as an outcome or downstream of Nrf2 activation. HO-1 is known for its antioxidative properties, which play an important role in regulating oxidative stress. In renal diseases-induced tissue fibrosis and xenobiotics-induced renal fibrosis, Nrf2/HO-1 has been targeted with promising results. This review summarizes these studies and highlights the interesting bioactive compounds that may assist in attenuating renal fibrosis mediated by HO-1 activation. In conclusion, Nrf2/HO-1 signal activation could have a renoprotective effect strategy against CKD caused by oxidative stress, inflammation, and consequent renal fibrosis.

Biochemical aspects of the inflammatory process: A narrative review

Inflammation is a protective response of the body potentially caused by microbial, viral, or fungal infections, tissue damage, or even autoimmune reactions. The cardinal signs of inflammation are consequences of immunological, biochemical, and physiological changes that trigger the release of pro-inflammatory chemical mediators at the local of the injured site thus, increasing blood flow, vascular permeability, and leukocyte recruitment. The aim of this study is to give an overview of the inflammatory process, focusing on chemical mediators. The literature review was based on a search of journals published between the years 2009 and 2023, regarding the role of major chemical mediators in the inflammatory process and current studies in pathogenesis, diagnosis, and therapy. Some of the recent contributions in the study of inflammatory pathologies and their mediators, including cytokines and chemokines, the kinin system, free radicals, nitric oxide, histamine, cell adhesion molecules, leukotrienes, prostaglandins and the complement system and their role in human health and chronic diseases.

Identification of the key immune-related genes and immune cell infiltration changes in renal interstitial fibrosis

Background

Chronic kidney disease (CKD) is the third-leading cause of premature mortality worldwide. It is characterized by rapid deterioration due to renal interstitial fibrosis (RIF) via excessive inflammatory infiltration. The aim of this study was to discover key immune-related genes (IRGs) to provide valuable insights and therapeutic targets for RIF in CKD.

Materials and methods

We screened differentially expressed genes (DEGs) between RIF samples from CKD patients and healthy controls from a public database. Least absolute shrinkage and selection operator regression analysis and receiver operating characteristic curve analysis were applied to identify significant key biomarkers. The single-sample Gene Set Enrichment Analysis (ssGSEA) algorithm was used to analyze the infiltration of immune cells between the RIF and control samples. The correlation between biomarkers and immune cell composition was assessed.

Results

A total of 928 DEGs between CKD and control samples from six microarray datasets were found, 17 overlapping immune-correlated DEGs were identified by integration with the ImmPort database, and six IRGs were finally identified in the model: apolipoprotein H (APOH), epidermal growth factor (EGF), lactotransferrin (LTF), lysozyme (LYZ), phospholipid transfer protein (PLTP), and secretory leukocyte peptidase inhibitor (SLPI). Two additional datasets and in vivo experiments indicated that the expression levels of APOH and EGF in the fibrosis group were significantly lower than those in the control group, while the expression levels of LTF, LYZ, PLTP, and SLPI were higher (all P < 0.05). These IRGs also showed a significant correlation with renal function impairment. Moreover, four upregulated IRGs were positively associated with various T cell populations, which were enriched in RIF tissues, whereas two downregulated IRGs had opposite results. Several signaling pathways, such as the "T cell receptor signaling pathway" and "positive regulation of NF-κB signaling pathway", were discovered to be associated not only with immune cell infiltration, but also with the expression levels of six IRGs.

Conclusion

In summary, six IRGs were identified as key biomarkers for RIF, and exhibited a strong correlation with various T cells and with the NF-κB signaling pathway. All these IRGs and their signaling pathways may evolve as valuable therapeutic targets for RIF in CKD.

Currently Used Methods to Evaluate the Efficacy of Therapeutic Drugs and Kidney Safety

Kidney diseases with kidney failure or damage, such as chronic kidney disease (CKD) and acute kidney injury (AKI), are common clinical problems worldwide and have rapidly increased in prevalence, affecting millions of people in recent decades. A series of novel diagnostic or predictive biomarkers have been discovered over the past decade, enhancing the investigation of renal dysfunction in preclinical studies and clinical risk assessment for humans. Since multiple causes lead to renal failure, animal studies have been extensively used to identify specific disease biomarkers for understanding the potential targets and nephropathy events in therapeutic insights into disease progression. Mice are the most commonly used model to investigate the mechanism of human nephropathy, and the current alternative methods, including in vitro and in silico models, can offer quicker, cheaper, and more effective methods to avoid or reduce the unethical procedures of animal usage. This review provides modern approaches, including animal and nonanimal assays, that can be applied to study chronic nonclinical safety. These specific situations could be utilized in nonclinical or clinical drug development to provide information on kidney disease.

Renal tubular function and morphology revealed in kidney without labeling using three-dimensional dynamic optical coherence tomography

Renal tubule has distinct metabolic features and functional activity that may be altered during kidney disease. In this paper, we present label-free functional activity imaging of renal tubule in normal and obstructed mouse kidney models using three-dimensional (3D) dynamic optical coherence tomography (OCT) ex vivo. To create an obstructed kidney model, we ligated the ureter of the left kidney for either 7 or 14 days. Two different dynamic OCT (DOCT) methods were implemented to access the slow and fast activity of the renal tubules: a logarithmic intensity variance (LIV) method and a complex-correlation-based method. Three-dimensional DOCT data were acquired with a 1.3 [Formula: see text]m swept-source OCT system and repeating raster scan protocols. In the normal kidney, the renal tubule appeared as a convoluted pipe-like structure in the DOCT projection image. Such pipe-like structures were not observed in the kidneys subjected to obstruction of the ureter for several days. Instead of any anatomical structures, a superficial high dynamics appearance was observed in the perirenal cortex region of the obstructed kidneys. These findings suggest that volumetric LIV can be used as a tool to investigate kidney function during kidney diseases.

Causal effects of systemic inflammatory regulators on chronic kidney diseases and renal function: a bidirectional Mendelian randomization study

Background

While targeted systemic inflammatory modulators show promise in preventing chronic kidney disease (CKD) progression, the causal link between specific inflammatory factors and CKD remains uncertain.

Methods

Using a genome-wide association study of 41 serum cytokines from 8,293 Finnish individuals, we conducted a bidirectional two-sample Mendelian randomization (MR) analysis. In addition, we genetically predicted causal associations between inflammatory factors and 5 phenotypes, including CKD, estimated glomerular filtration rate (eGFR), dialysis, rapid progression of CKD, and rapid decline in eGFR. Inverse variance weighting (IVW) served as the primary MR method, while MR-Egger, weighted median, and MR-pleiotropy residual sum and outlier (MR-PRESSO) were utilized for sensitivity analysis. Cochrane's Q test for heterogeneity. Leave-one-out method ensured stability of MR results, and Bonferroni correction assessed causal relationship strength.

Results

Seventeen cytokines were associated with diverse renal outcomes. Among them, after Bonferroni correction test, higher tumor necrosis factor alpha levels were associated with a rapid decrease in eGFR (OR = 1.064, 95% CI 1.028 - 1.103, P = 0.001), higher interleukin-4 levels were associated with an increase in eGFR (β = 0.003, 95% CI 0.001 - 0.005, P = 0.002), and higher growth regulated oncogene alpha (GROα) levels were associated with an increased risk of CKD (OR=1.035, 95% CI 1.012 - 1.058, P = 0.003). In contrast, genetic susceptibility to CKD was associated with an increase in GROa, and a decrease in eGFR may lead to an increase in stem cell factor. We did not find the presence of horizontal pleiotropy during the analysis.

Conclusion

We discovered causally related inflammatory factors that contribute to the initiation and progression of CKD at the genetic prediction level.

NQO1 alleviates renal fibrosis by inhibiting the TLR4/NF-κB and TGF-β/Smad signaling pathways in diabetic nephropathy

OBJECTIVE

Diabetic nephropathy (DN) is one of the main complications of diabetes, and inflammation and fibrosis play an important role in its progression. NAD(P)H: quinone oxidoreductase 1 (NQO1) protects cells from oxidative stress and damage caused by toxic quinones. In the present study, we aimed to investigate the protective effects of NQO1 against diabetes-induced renal inflammation and fibrosis and the underlying mechanisms.

METHODS

In vivo, the kidneys of type 2 diabetes model db/db mice were infected with adeno-associated virus vectors to induce NQO1 overexpression. In vitro, human renal tubular epithelial (HK-2) cells transfected with NQO1 pcDNA3.1(+) were cultured under high-glucose (HG) conditions. Gene and protein expression was assessed by quantitative real-time PCR, Western blotting, immunofluorescence, and immunohistochemical staining. Mitochondrial reactive oxygen species (ROS) were detected with MitoSOX Red.

RESULT

Our study revealed that the expression of NQO1 was markedly downregulated and that Toll-like receptor (TLR)4 and TGF-β1 expression was upregulated in vivo and in vitro under diabetic conditions. Overexpression of NQO1 suppressed proinflammatory cytokine (IL-6, TNF-α, MCP-1) secretion, extracellular matrix (ECM) (collagen IV, fibronectin) accumulation and epithelial-mesenchymal transition (EMT) (α-SMA, E-cadherin) in the db/db mouse kidneys and HG-cultured HK-2 cells. Furthermore, NQO1 overexpression ameliorated HG-induced TLR4/NF-κB and TGF-β/Smad pathways activation. Mechanistic studies demonstrated that a TLR4 inhibitor (TAK-242) suppressed the TLR4/NF-κB signaling pathway, proinflammatory cytokine secretion, EMT and ECM-related protein expression in HG-exposed HK-2 cells. In addition, we found that the antioxidants N-acetylcysteine (NAC) and tempol increased the expression of NQO1 and decreased the expression of TLR4, TGF-β1, Nox1, and Nox4 and ROS production in HK-2 cells cultured under HG conditions.

CONCLUSIONS

These data suggest that NQO1 alleviates diabetes-induced renal inflammation and fibrosis by regulating the TLR4/NF-κB and TGF-β/Smad signaling pathways.

Renal tubular function and morphology revealed in kidney without labeling using three-dimensional dynamic optical coherence tomography.. [DOI: 10.1101/2023.05.01.539010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Renal tubule has distinct metabolic features and functional activity that may be altered during kidney disease. In this paper, we present label-free functional activity imaging of renal tubule in normal and obstructed mouse kidney models using three-dimensional (3D) dynamic optical coherence tomography (OCT)ex vivo. To create an obstructed kidney model, we ligated the ureter of the left kidney for either 7 or 14 days. Two different dynamic OCT (DOCT) methods were implemented to access the slow and fast activity of the renal tubules: a logarithmic intensity variance (LIV) method and a complex-correlation-based method. Three-dimensional DOCT data were acquired with a 1.3 μm swept-source OCT system and repeating raster scan protocols. In the normal kidney, the renal tubule appeared as a convoluted pipe-like structure in the DOCT projection image. Such pipe-like structures were not observed in the kidneys subjected to obstruction of the ureter for several days. Instead of any anatomical structures, a superficial high dynamics appearance was observed in the perirenal cortex region of the obstructed kidneys. These findings suggest that volumetric DOCT can be used as a tool to investigate kidney function during kidney diseases.

A potential link between fibroblast growth factor-23 and the progression of AKI to CKD

BACKGROUND

Patients who recover from acute kidney injury (AKI) have a 25% increase in the risk of chronic kidney disease (CKD) and a 50% increase in mortality after a follow-up of approximately 10 years. Circulating FGF-23 increases significantly early in the development of AKI, is significantly elevated in patients with CKD and has become a major biomarker of poor clinical prognosis in CKD. However, the potential link between fibroblast growth factor-23 levels and the progression of AKI to CKD remains unclear.

METHOD

Serum FGF-23 levels in AKI patients and ischaemia‒reperfusion injury (IRI) mice were detected with ELISA. Cultured HK2 cells were incubated with FGF-23 and PD173074, a blocker of FGFR, and then TGFβ/Smad and Wnt/β-catenin were examined with immunofluorescence and immunoblotting. Quantitative real-time polymerase chain reaction was used to detect the expression of COL1A1 and COL4A1. Histologic staining confirmed renal fibrosis.

RESULTS

The level of serum FGF-23 was significantly different between AKI patients and healthy controls (P < 0.01). Moreover, serum FGF-23 levels in the CKD progression group were significantly higher than those in the non-CKD progression group of AKI patients (P < 0.01). In the AKI-CKD mouse model, serum FGF-23 levels were increased, and renal fibrosis occurred; moreover, the protein expression of β-catenin and p-Smad3 was upregulated. PD173074 downregulated the expression of β-catenin and p-Smad3 and reduced fibrosis in both mice and HK2 cells.

CONCLUSION

The increase in FGF-23 may be associated with the progression of AKI to CKD and may mediate renal fibrosis via TGF-β and Wnt/β-catenin activation.

Role of Cannabinoid Type 2 Receptor Activation in Renal Fibrosis Induced by Unilateral Ureteric Obstruction in Rats

Background

Chronic kidney disease (CKD) ends mostly with renal fibrosis. The effect of CB2 receptor on renal fibrosis has been unclear. The aim of this study was to investigate the effect of CB2 receptor on renal fibrosis and the mechanisms behind it.

Methods

50 adult male Sprague-Dawley rats were divided into 5 groups; normal, sham; rats had their ureters only manipulated, UUO; rats had their left ureters ligated, and JWH post; rats had their left ureters ligated and they received JWH 133 for 14 days, JWH pre+post; rats received JWH 133 for 14 days before and after UUO procedure. Serum creatinine and BUN were assessed together with tissue MDA, GSH, and catalase. Histopathological evaluation of the renal tissue by H&E and Masson's trichrome was done. Immunohistochemical staining for TGF-β1, AQP1, Caspase-3, LC3B and p62 was performed. AQP1 and CB2 receptors genes expression was detected by quantitative RT-PCR.

Results

UUO had caused severe damage in the renal tissue with reduction of the renal function parameter accompanied by increase in the collagen deposition with increase TGF-β1 and decrease AQP1 expression.

Conclusions

The improvement of these parameters with JWH-133 suggests an anti-fibrotic role of CB2 receptor activation through reduction of oxidative stress, apoptosis, and autophagy.

Renal-Protective Roles of Lipoic Acid in Kidney Disease

The kidney is a crucial organ that eliminates metabolic waste and reabsorbs nutritious elements. It also participates in the regulation of blood pressure, maintenance of electrolyte balance and blood pH homeostasis, as well as erythropoiesis and vitamin D maturation. Due to such a heavy workload, the kidney is an energy-demanding organ and is constantly exposed to endogenous and exogenous insults, leading to the development of either acute kidney injury (AKI) or chronic kidney disease (CKD). Nevertheless, there are no therapeutic managements to treat AKI or CKD effectively. Therefore, novel therapeutic approaches for fighting kidney injury are urgently needed. This review article discusses the role of α-lipoic acid (ALA) in preventing and treating kidney diseases. We focus on various animal models of kidney injury by which the underlying renoprotective mechanisms of ALA have been unraveled. The animal models covered include diabetic nephropathy, sepsis-induced kidney injury, renal ischemic injury, unilateral ureteral obstruction, and kidney injuries induced by folic acid and metals such as cisplatin, cadmium, and iron. We highlight the common mechanisms of ALA’s renal protective actions that include decreasing oxidative damage, increasing antioxidant capacities, counteracting inflammation, mitigating renal fibrosis, and attenuating nephron cell death. It is by these mechanisms that ALA achieves its biological function of alleviating kidney injury and improving kidney function. Nevertheless, we also point out that more comprehensive, preclinical, and clinical studies will be needed to make ALA a better therapeutic agent for targeting kidney disorders.

Grape Seed Extract and Urolithiasis: Protection Against Oxidative Stress and Inflammation

Background

Grape seed extract (GSE) has demonstrated various pharmacological actions. Urolithiasis is the occurrence of calculus in the renal system. The present study evaluated the anti-urolithic effect of GSE on ethylene glycol (EG) and ammonium chloride (AC)-induced experimental urolithiasis in rats.

Materials and Methods

Rats were assigned into six groups; Normal control and Normal + GSE, in which rats received standard drinking water and GSE orally daily, respectively; Urolithiatic animals received EG with AC in drinking water for 28 days; Urolithiatic animals + GSE, in which rats were administered EG with AC in drinking water and GSE 100 and 200 mg/kg orally; and Urolithiatic + cystone, where rats received EG with AC in drinking water and 750 g/kg of cystone as a standard drug orally.

Results

Urolithiatic animals showed a significant decrease in excreted magnesium and citrate and antioxidant enzymes, whereas they exhibited amplified oxalate crystal numbers, urinary excreted calcium, phosphate, oxalate ions, uric acid, intensified renal function parameters, lipid peroxidation, and inflammatory mediators. Management with GSE and cystone significantly augmented urolithiasis inhibitors (excreted magnesium and citrate) and amplified the antioxidant enzymes’ activities. GSE reduced oxalate crystal numbers and urolithiasis promoters, including excreted calcium, oxalate, phosphate, and uric acid excretion, lessened renal function parameters, and declined lipid peroxidation and the inflammatory mediators.

Conclusion

GSE could protect against EG-induced renal stones as evidenced by mitigated kidney dysfunction, histological alterations, and oxalate crystal formation. This action may be related to the antioxidant as well as anti-inflammatory activities of the extracts.

Identification of an unrecognized circRNA associated with development of renal fibrosis

Backgroud: Renal fibrosis is the common characteristic of chronic kidney disease. Circular RNA plays an essential role in the occurrence and development of Renal fibrosis, but its regulative mechanism remains elusive. Methods: The animal and cell model of Renal fibrosis was established, and RNA-sequencing and real-time polymerase chain reaction (qRT-PCR) experiments were implemented. Subsequently, experiments for detecting apoptosis and proliferation of cell, were carried out, and the isobaric tags for relative and absolute quantification proteomics analyses were performed accordingly. Results: It was found that a newly discovered Circular RNA (circRNA_0002158), is highly expressed in kidneys or cells with fibrosis, implying that this Circular RNA might be associated with the occurrence and development of Renal fibrosis. Subsequently, the overexpression and knockdown of circRNA_0002158 were conducted in the human kidney epithelial cell line (HK-2) cells, and the results indicated that the circRNA_0002158 could inhibit apoptosis, and promote proliferation of cells. The kidney injury-related factors, including Fibronectin and plasminogen activator inhibitor-1 (PAI-1), were decreased in HK-2 cells with overexpression of circRNA_0002158, while the results were reversed in cells with knockdown of circRNA_0002158. Finally, to explore the regulative mechanism of circRNA_0002158, the iTRAQ proteomics analyses were implemented for the cell samples with OE of circRNA_0002158 and its control, it showed that multiple genes and functional pathways were associated with the occurrence and development of Renal fibrosis. Conclusion: CircRNA_0002158 is associated with regulating Renal fibrosis, and may contribute to ameliorating the progression of Renal fibrosis in the future.

Protective role for C3aR in experimental chronic pyelonephritis

Emerging evidence suggest that C3aR plays important roles in homeostasis, host defense and disease. Although it is known that C3aR is protective in several models of acute bacterial infections, the role for C3aR in chronic infection is largely unknown. Here we show that C3aR is protective in experimental chronic pyelonephritis. Global C3aR deficient (C3ar^-/- ) mice had higher renal bacterial load, more pronounced renal histological lesions, increased renal apoptotic cell accumulation, tissue inflammation and extracellular matrix deposition following renal infection with uropathogenic E. coli (UPEC) strain IH11128, compared to WT control mice. Myeloid C3aR deficient (Lyz2-C3ar^-/- ) mice exhibited a similar disease phenotype to global C3ar^-/- mice. Pharmacological treatment with a C3aR agonist reduced disease severity in experimental chronic pyelonephritis. Furthermore, macrophages of C3ar^-/- mice exhibited impaired ability to phagocytose UPEC. Our data clearly demonstrate a protective role for C3aR against experimental chronic pyelonephritis, macrophage C3aR plays a major role in the protection, and C3aR is necessary for phagocytosis of UPEC by macrophages. Our observation that C3aR agonist curtailed the pathology suggests a therapeutic potential for activation of C3aR in chronic infection.

Chrysophanol, a main anthraquinone from Rheum palmatum L. (rhubarb), protects against renal fibrosis by suppressing NKD2/NF-κB pathway

PURPOSE

Chronic kidney disease (CKD), characterized as renal dysfunction and multi-system damage, has become a serious public health problem with high prevalence and mortality. Rheum palmatum L. (rhubarb) is one of the most widely used Chinese herb with renal protective activity. However, the active components and underlying mechanisms of rhubarb remain unknown. In this work, we tried to explore the pharmacological mechanism of chrysophanol, a main anthraquinone from rhubarb, against CKD by in vivo and in vitro models.

STUDY DESIGN

The therapeutic effect of chrysophanol and its underlying mechanism were investigated using CKD mouse model induced by unilateral ureteral occlusion (UUO), and human kidney 2 (HK-2) cells stimulated by TGF-β1 in vivo.

METHODS

The impact of chrysophanol on renal function, inflammation, fibrosis of CKD mice were evaluated. Then, the protein expressions of FN1, collagen ɑI, α-SMA, NF-κB and naked keratinocyte homolog 2 (NKD2) were investigated. In vitro studies, the inhibition on inflammation and fibrogenesis by chrysophanol was further validated in TGF-β1-stimulated HK2 cells, and the regulation of chrysophanol on NKD2/NF-κB pathway was analyzed. Moreover, NKD2 was overexpressed in HK-2 cells to confirm the role of NKD2/NF-κB pathway in chrysophanol-mediated efficacy. Finally, the binding mode of chrysophanol with NKD2 was studied using in silico molecular docking and microscale thermophoresis (MST) assay.

RESULTS

Chrysophanol could significantly improve the kidney dysfunction, alleviate renal pathology, and reverse the elevated levels of renal fibrosis markers such as FN1, collagen ɑI and α-SMA. Furthermore, chrysophanol effectively inhibited TNF-α, IL-6, and IL-1β production, and suppressed NF-κB activation and NKD2 expression. The findings of in vitro study were consistent with those of animal expriment. Using NKD2-overexpressing HK-2 cells, we also demonstrated that overexpression of NKD2 significantly compromised the anti-fibrotic effects of chrysophanol. In addition, molecular docking and MST analysis revealed that NKD2 was a direct target of chrysophanol.

CONCLUSION

Together, our work demonstrated for the first time that chrysophanol could effectively ameliorate renal fibrosis by inhibiting NKD2/NF-κB pathway. Chrysophanol can potentially prevent CKD by suppressing renal NKD2 expression directly.

Modified Gexiazhuyu decoction alleviates chronic salpingitis p38 signaling pathway

OBJECTIVE

To investigate pharmacodynamic effects of modified Gexiazhuyu decoction (MGXZYD) and explore the underlying mechanism in the treatment of chronic salpingitis METHODS: Chronic salpingitis model rats were firstly constructed and the blood was collected to detect the whole blood viscosity and plasma viscosity. Rat oviduct were collected to evaluate the macroscopic damage and the pathological injury and fibrosis of oviduct by hematoxylin-eosin (HE) and Masson staining. Elisa assay was to detect the production interleukin-1 β (IL-1β) in serum and collagen I (COL-1), matrix metalloprotein 9 (MMP-9), tissue inhibitor of metalloproteinases 1 (TIMP-1) in oviduct tissue. And immunohistochemical staining with MMP-9 and TIMP-1 in oviduct tissue were examined. Western blot was used to detect the expressions of p38 mitogen-activated protein kinases (p38MAPK), phospho-p38MPAK (p-p38MPAK), transforming growth factor-β1 (TGF-β1) in oviduct. The expression of α-smooth muscle actin (α-SMA), p-p38MPAK, in oviduct tissue were detected by immunofluorescence method. The mRNA of p-p38MAPK, α -SMA, COL-1, MMP-9, TIMP-1 was measured by reverse transcription-polymerase chain reaction.

RESULTS

Rats administrated with MGXZYD demonstrated decreased the whole blood viscosity and plasma viscosity. MGXZYD obviously improved the tubal wall thickening, swelling and pelvic adhesion. And HE and Masson staining showed MGXZYD improved the pathological injury and fibrosis of oviduct. The results of MTT assay and flow cytometry indicated that MGXZYD could decreased the NIN-3T3 cells viability and improved the apoptosis. Besides, MGXZYD inhibited the protein and / or mRNA of TGF-β1, IL-1β, COL-1, α-SMA, p-p38MAPK expressions and increased the production of MMP-9/TIMP-1.

CONCLUSION

MGXZYD could prevent the progression of chronic salpingitis by inhibited the fibrocyte and inflammation which inhibited the p38 MAPK signaling pathway.

Inhibition of renal fibrosis with a human CXCL9‐derived glycosaminoglycan‐binding peptide

Objectives

Renal fibrosis accompanies all chronic kidney disorders, ultimately leading to end‐stage kidney disease and the need for dialysis or even renal replacement. As such, renal fibrosis poses a major threat to global health and the search for effective therapeutic strategies to prevent or treat fibrosis is highly needed. We evaluated the applicability of a highly positively charged human peptide derived from the COOH‐terminal domain of the chemokine CXCL9, namely CXCL9(74–103), for therapeutic intervention. Because of its high density of net positive charges at physiological pH, CXCL9(74–103) competes with full‐length chemokines for glycosaminoglycan (GAG) binding. Consequently, CXCL9(74–103) prevents recruitment of inflammatory leucocytes to sites of inflammation.

Methods

CXCL9(74–103) was chemically synthesised and tested in vitro for anti‐fibrotic properties on human fibroblasts and in vivo in the unilateral ureteral obstruction (UUO) mouse model.

Results

CXCL9(74–103) significantly reduced the mRNA and/or protein expression of connective tissue growth factor (CTGF), alpha‐smooth muscle actin (α‐SMA) and collagen III by transforming growth factor (TGF)‐β1‐stimulated human fibroblasts. In addition, administration of CXCL9(74–103) inhibited fibroblast migration towards platelet‐derived growth factor (PDGF), without affecting cell viability. In the UUO model, CXCL9(74–103) treatment significantly decreased renal α‐SMA, vimentin, and fibronectin mRNA and protein expression. Compared with vehicle, CXCL9(74–103) attenuated mRNA expression of TGF‐β1 and the inflammatory markers/mediators MMP‐9, F4/80, CCL2, IL‐6 and TNF‐α. Finally, CXCL9(74–103) treatment resulted in reduced influx of leucocytes in the UUO model and preserved tubular morphology. The anti‐fibrotic and anti‐inflammatory effects of CXCL9(74–103) were mediated by competition with chemokines and growth factors for GAG binding.

Conclusions

Our findings provide a scientific rationale for targeting GAG–protein interactions in renal fibrotic disease.

Cyclo(Val-Pro) and Cyclo(Leu-Hydroxy-Pro) from Pseudomonas sp. (ABS-36) alleviates acute and chronic renal injury under in vitro and in vivo models (Ischemic reperfusion and unilateral ureter obstruction)

The study aimed to identify small molecules having potentiality in alleviating renal injury. Two natural compounds cyclo(Val-Pro) (1) and cyclo(Leu-Hydroxy-Pro) (2) were first evaluated under acute renal injury model of ischemic reperfusion at different doses of 25, 50 and 75 mg/kg body weight. Further, the compounds were subjected to antimycin A-induced ischemic in vitro study (NRK-52E cell lines). Both the compounds significantly decreased plasma IL-1β levels (P < 0.05). Also, the mRNA expression levels of inflammatory markers (TNF-α, IL-6 and IL-1β) and renal injury markers (KIM-1, NGAL, α-GST and π-GST) in the renal tissues were significantly alleviated (P < 0.01) along with the improvement in histological damage and control over neutrophil infiltration as a result of ischemic reperfusion. The in vitro study revealed the protective effect against antimycin A-induced cytotoxicity (P < 0.05) and antiapoptotic effect acting through the regulation of Bax, caspase 3 (pro and cleaved) and BCL2 with reduction in Annexin⁺PI⁺ cells. Further, the compound cyclo(Val-Pro) (1) was evaluated (50 mg/kg body weight dose) in chronic unilateral ureter obstruction model of renal injury in mice and TGF-β-induced in vitro fibrotic model (NRK-49F cell lines). Cyclo(Val-Pro) (1) significantly reduced the expression levels of fibrotic markers (collagen-1, α-SMA and TGF-β) and showed marked alleviation of renal fibrosis (sirius red staining). Also, the proliferation of TGF-β-induced NRK-49F cells was significantly reduced along with decreased levels of collagen-1 and α-SMA in immunohistochemistry studies. In conclusion, the compounds significantly abrogated ischemic injury by inhibiting renal inflammation and tubular epithelial apoptosis. Further, cyclo (Val-Pro) (1) exhibited significant anti-fibrotic activity through the inhibition of fibroblast activation and proliferation. Thus, these proline-based cyclic dipeptides are recommended as drug leads for treating renal injury.

IL-15 Prevents Renal Fibrosis by Inhibiting Collagen Synthesis: A New Pathway in Chronic Kidney Disease?

Chronic kidney disease (CKD), secondary to renal fibrogenesis, is a public health burden. The activation of interstitial myofibroblasts and excessive production of extracellular matrix (ECM) proteins are major events leading to end-stage kidney disease. Recently, interleukin-15 (IL-15) has been implicated in fibrosis protection in several organs, with little evidence in the kidney. Since endogenous IL-15 expression decreased in nephrectomized human allografts evolving toward fibrosis and kidneys in the unilateral ureteral obstruction (UUO) model, we explored IL-15's renoprotective role by pharmologically delivering IL-15 coupled or not with its soluble receptor IL-15Rα. Despite the lack of effects on myofibroblast accumulation, both IL-15 treatments prevented tubulointerstitial fibrosis (TIF) in UUO as characterized by reduced collagen and fibronectin deposition. Moreover, IL-15 treatments inhibited collagen and fibronectin secretion by transforming growth factor-β (TGF-β)-treated primary myofibroblast cultures, demonstrating that the antifibrotic effect of IL-15 in UUO acts, in part, through a direct inhibition of ECM synthesis by myofibroblasts. In addition, IL-15 treatments resulted in decreased expression of monocyte chemoattractant protein 1 (MCP-1) and subsequent macrophage infiltration in UUO. Taken together, our study highlights a major role of IL-15 on myofibroblasts and macrophages, two main effector cells in renal fibrosis, demonstrating that IL-15 may represent a new therapeutic option for CKD.

Apamin inhibits renal fibrosis via suppressing TGF-β1 and STAT3 signaling in vivo and in vitro

Renal fibrosis is a progressive and chronic process that influences kidneys with chronic kidney disease (CKD), irrespective of cause, leading to irreversible failure of renal function and end-stage kidney disease. Among the signaling related to renal fibrosis, transforming growth factor-β1 (TGF-β1) signaling is a major pathway that induces the activation of myofibroblasts and the production of extracellular matrix (ECM) molecules. Apamin, a component of bee venom (BV), has been studied in relation to various diseases. However, the effect of apamin on renal interstitial fibrosis has not been investigated. The aim of this study was to estimate the beneficial effect of apamin in unilateral ureteral obstruction (UUO)-induced renal fibrosis and TGF-β1-induced renal fibroblast activation. This study revealed that obstructive kidney injury induced an inflammatory response, tubular atrophy, and ECM accumulation. However, apamin treatment suppressed the increased expression of fibrotic-related genes, including α-SMA, vimentin, and fibronectin. Administration of apamin also attenuated the renal tubular cells injury and tubular atrophy. In addition, apamin attenuated fibroblast activation, ECM synthesis, and inflammatory cytokines such as TNF-α, IL-1β, and IL-6 by suppressing the TGF-β1-canonical and non-canonical signaling pathways. This study showed that apamin inhibits UUO-induced renal fibrosis in vivo and TGF-β1-induced renal fibroblasts activation in vitro. Apamin inhibited the inflammatory response, tubular atrophy, ECM accumulation, fibroblast activation, and renal interstitial fibrosis through suppression of TGF-β1/Smad2/3 and STAT3 signaling pathways. These results suggest that apamin might be a potential therapeutic agent for renal fibrosis. KEY MESSAGES: UUO injury can induce renal dysfunction; however, apamin administration prevents renal failure in UUO mice. Apamin inhibited renal inflammatory response and ECM deposition in UUO-injured mice. Apamin suppressed the activation of myofibroblasts in vivo and in vitro. Apamin has the anti-fibrotic effect on renal fibrosis via regulation of TGF-β1 canonical and non-canonical signaling.

Redox signaling pathways in unilateral ureteral obstruction (UUO)-induced renal fibrosis

Unilateral ureteral obstruction (UUO) is an experimental rodent model that mimics renal fibrosis associated with obstructive nephropathy in an accelerated manner. After UUO, the activation of the renin-angiotensin system (RAS), nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and mitochondrial dysfunction lead to reactive oxygen species (ROS) overproduction in the kidney. ROS are secondary messengers able to induce post-translational modifications (PTMs) in redox-sensitive proteins, which activate or deactivate signaling pathways. Therefore, in UUO, it has been proposed that ROS overproduction causes changes in said pathways promoting inflammation, oxidative stress, and apoptosis that contribute to fibrosis development. Furthermore, mitochondrial metabolism impairment has been associated with UUO, contributing to renal damage in this model. Although ROS production and oxidative stress have been studied in UUO, the development of renal fibrosis associated with redox signaling pathways has not been addressed. This review focuses on the current information about the activation and deactivation of signaling pathways sensitive to a redox state and their effect on mitochondrial metabolism in the fibrosis development in the UUO model.

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.

Chronic Inflammation in Chronic Kidney Disease Progression: Role of Nrf2

Despite recent advances in the management of chronic kidney disease (CKD), morbidity and mortality rates in these patients remain high. Although pressure-mediated injury is a well-recognized mechanism of disease progression in CKD, emerging data indicate that an intermediate phenotype involving chronic inflammation, oxidative stress, hypoxia, senescence, and mitochondrial dysfunction plays a key role in the etiology, progression, and pathophysiology of CKD. A variety of factors promote chronic inflammation in CKD, including oxidative stress and the adoption of a proinflammatory phenotype by resident kidney cells. Regulation of proinflammatory and anti-inflammatory factors through NF-κB- and nuclear factor, erythroid 2 like 2 (Nrf2)-mediated gene transcription, respectively, plays a critical role in the glomerular and tubular cell response to kidney injury. Chronic inflammation contributes to the decline in glomerular filtration rate (GFR) in CKD. Whereas the role of chronic inflammation in diabetic kidney disease (DKD) has been well-elucidated, there is now substantial evidence indicating unresolved inflammatory processes lead to fibrosis and eventual end-stage kidney disease (ESKD) in several other diseases, such as Alport syndrome, autosomal-dominant polycystic kidney disease (ADPKD), IgA nephropathy (IgAN), and focal segmental glomerulosclerosis (FSGS). In this review, we aim to clarify the mechanisms of chronic inflammation in the pathophysiology and disease progression across the spectrum of kidney diseases, with a focus on Nrf2.

Changes of renal function after retrograde intrarenal surgery using flexible ureteroscope in renal stone patients

Background

Retrograde intrarenal surgery (RIRS) is widely performed for renal stones. Theoretically, removing renal stones could prevent the deterioration of renal function. However, two studies reported that not all patients would see an increase in renal function after RIRS. The aim of our study was to evaluate the change of renal function of the operative site, and to identify predictors of improvement or deterioration of renal function after RIRS.

Methods

We retrospectively reviewed renal stones patients who received RIRS and single-photon emission computed tomography (SPECT) before and after surgery. Improved renal function was defined as the change of glomerular filtration rate (GFR) >10% postoperatively, and that <−10% was regarded as deteriorated renal function. Logistic and least absolute shrinkage and selection operator regression analyses were used to identify predictors for the improvement or deterioration of renal function, and predictive nomogram models were built.

Results

A total of 120 renal stone patients were included. Twenty-one (17.5%), 79 (65.8%) and 20 (16.7%) patients had improved, stable and deteriorated renal function of operative site after surgery, respectively. Lower alkaline phosphatase, lower low-density lipoprotein, lower GFR of the operative site, thicker renal parenchyma, higher serum creatinine, and extracorporeal shock wave lithotripsy (SWL) history were associated with the improved renal function. The predictive accuracy of the model for the improved renal function was 0.800. Additionally, older age, longer flexible ureteroscopic time, thinner renal parenchyma and existence of ureteral stones were risk factors for deteriorated renal function. The predictive accuracy of the model for the deteriorated renal function was 0.725.

Conclusions

The renal function of most renal stone patients did not decrease after RIRS. For patients with potential deterioration of renal function postoperatively, urologists could shorten flexible ureteroscopic time to prevent the occurrence of this outcome.

Dissecting the Involvement of Ras GTPases in Kidney Fibrosis

Many different regulatory mechanisms of renal fibrosis are known to date, and those related to transforming growth factor-β1 (TGF-β1)-induced signaling have been studied in greater depth. However, in recent years, other signaling pathways have been identified, which contribute to the regulation of these pathological processes. Several studies by our team and others have revealed the involvement of small Ras GTPases in the regulation of the cellular processes that occur in renal fibrosis, such as the activation and proliferation of myofibroblasts or the accumulation of extracellular matrix (ECM) proteins. Intracellular signaling mediated by TGF-β1 and Ras GTPases are closely related, and this interaction also occurs during the development of renal fibrosis. In this review, we update the available in vitro and in vivo knowledge on the role of Ras and its main effectors, such as Erk and Akt, in the cellular mechanisms that occur during the regulation of kidney fibrosis (ECM synthesis, accumulation and activation of myofibroblasts, apoptosis and survival of tubular epithelial cells), as well as the therapeutic strategies for targeting the Ras pathway to intervene on the development of renal fibrosis.

Dasatinib mitigates renal fibrosis in a rat model of UUO via inhibition of Src/STAT-3/NF-κB signaling

This research aimed to investigate the reno-protective impact of the tyrosine kinase inhibitor dasatinib (DAS) against renal fibrosis induced by unilateral ureteral obstruction (UUO) in rats. DAS administration improved renal function and mitigated renal oxidative stress with paralleled reduction in the ligated kidney mass index, significant retraction in renal histopathological alterations and suppression of renal interstitial fibrosis. Nevertheless, DAS administration attenuated renal expression of phosphorylated Src (p-Src), Abelson (c-Abl) tyrosine kinases, nuclear factor-kappaB (NF-κB) p65, and phosphorylated signal transducer and activator of transcription-3 (p-STAT-3)/STAT-3 with paralleled reduction in renal contents of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1). DAS diminished interstitial macrophage infiltration and decreased renal profibrotic transforming growth factor-β1 (TGF-β1) levels and suppressed interstitial expression of renal α-smooth muscle actin (α-SMA) and fibronectin. Collectively, DAS slowed the progression of renal interstitial fibrosis, possibly via attenuating renal oxidative stress, impairing Src/STAT-3/NF-κB signaling, and reducing renal inflammation.

An Indole-2-Carboxamide Derivative, LG4, Alleviates Diabetic Kidney Disease Through Inhibiting MAPK-Mediated Inflammatory Responses

Aim

Elevated inflammatory signaling has been shown to play an important role in diabetic kidney disease (DKD). We previously developed a new anti-inflammatory compound LG4. In the present study, we have tested the hypothesis that LG4 could prevent DKD by suppressing inflammation and identified the underlying mechanism.

Methods

Streptozotocin-induced type 1 diabetic mice were used to develop DKD and evaluate the effects of LG4 against DKD. To identify the potential targets of LG4, biotin-linked LG4 was synthesized and subjected to proteome microarray screening. The cellular mechanism of LG4 was investigated in HG-challenged SV40MES13 cells.

Results

Although LG4 treatment had no effect on the body weight and blood glucose levels, it remarkably reversed the hyperglycemia-induced pathological changes and fibrosis in the kidneys of T1DM mice. Importantly, hyperglycemia-induced renal inflammation evidenced by NF-κB activation and TNFα and IL-6 overexpression was greatly ameliorated with LG4 treatment. Proteosome microarray screening revealed that JNK and ERK were the direct binding proteins of LG4. LG4 significantly reduced HG-induced JNK and ERK phosphorylation and subsequent NF-κB activation in vivo and in vitro. In addition, LG4 did not show further anti-inflammatory effect in HG-challenged mesangial cells with the presence of JNK or ERK inhibitor.

Conclusion

LG4 showed renoprotective activity through inhibiting ERK/JNK-mediated inflammation in diabetic mice, indicating that LG4 may be a therapeutic agent for DKD.

Nifuroxazide suppresses UUO-induced renal fibrosis in rats via inhibiting STAT-3/NF-κB signaling, oxidative stress and inflammation

The current work explored the influences of nifuroxazide, an in vivo inhibitor of signal transducer and activator of transcription-3 (STAT-3) activation, on tubulointerstitial fibrosis in rats with obstructive nephropathy using unilateral ureteral obstruction (UUO) model. Thirty-two male Sprague Dawley rats were assigned into 4 groups (n = 8/group) at random. Sham and UUO groups were orally administered 0.5% carboxymethyl cellulose (CMC) (2.5 mL/kg/day), while Sham-NIF and UUO-NIF groups were treated with 20 mg/kg/day of NIF (suspended in 0.5% CMC, orally). NIF or vehicle treatments were started 2 weeks after surgery and continued for further 2 weeks. NIF treatment ameliorated kidney function in UUO rats, where it restored serum creatinine, blood urea, serum uric acid and urinary protein and albumin to near-normal levels. NIF also markedly reduced histopathological changes in tubules and glomeruli and attenuated interstitial fibrosis in UUO-ligated kidneys. Mechanistically, NIF markedly attenuated renal immunoexpression of E-cadherin and α-smooth muscle actin (α-SMA), diminished renal oxidative stress (↓ malondialdehyde (MDA) levels and ↑ superoxide dismutase (SOD) activity), lessened renal protein expression of phosphorylated-STAT3 (p-STAT-3), phosphorylated-Src (p-Src) kinase, the Abelson tyrosine kinase (c-Abl) and phosphorylated nuclear factor-kappaB p65 (pNF-κB p65), decreased renal cytokine levels of transforming growth factor-β1 (TGF-β1), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and monocyte chemoattractant protein-1 (MCP-1) and reduced number of cluster of differentiation 68 (CD68) immunolabeled macrophages in UUO renal tissues, compared to levels in untreated UUO kidneys. Taken together, NIF treatment suppressed interstitial fibrosis in UUO renal tissues, probably via inhibiting STAT-3/NF-κB signaling and attenuating renal oxidative stress and inflammation.

Nephroprotective Effect of Pleurotus ostreatus and Agaricus bisporus Extracts and Carvedilol on Ethylene Glycol-Induced Urolithiasis: Roles of NF-κB, p53, Bcl-2, Bax and Bak

This study was designed to assess the nephroprotective effects of Pleurotus ostreatus and Agaricus bisporus aqueous extracts and carvedilol on hyperoxaluria-induced urolithiasis and to scrutinize the possible roles of NF-κB, p53, Bcl-2, Bax and Bak. Phytochemical screening and GC-MS analysis of mushrooms’ aqueous extracts were also performed and revealed the presence of multiple antioxidant and anti-inflammatory components. Hyperoxaluria was induced in Wistar rats through the addition of 0.75% (v/v) ethylene glycol in drinking water for nine weeks. The ethylene glycol-administered rats were orally treated with Pleurotus ostreatus and Agaricus bisporus aqueous extracts (100 mg/kg) and carvedilol (30 mg/kg) daily during the last seven weeks. The study showed that Pleurotus ostreatus, Agaricus bisporus and carvedilol all successfully inhibited ethylene glycol-induced histological perturbations and the elevation of serum creatinine, serum urea, serum and urinary uric acid, serum, urinary and kidney oxalate, urine specific gravity, kidney calcium, kidney NF-κB, NF-κB p65, NF-κB p50, p53, Bax and Bak expressions as well as serum TNF-α and IL-1β levels. Moreover, the treatment decreased the reduction in urinary creatinine, urinary urea, ratios of urinary creatinine to serum creatinine and urinary urea to serum urea, Fex Urea and Bcl-2 expression in kidney. In conclusion, although Pleurotus ostreatus and Agaricus bisporus extracts and carvedilol all significantly inhibited the progression of nephrolithiasis and showed nephroprotective effects against ethylene glycol-induced kidney dysfunction, Pleurotus ostreatus and Agaricus bisporus seemed to be more effective than carvedilol. Moreover, the nephroprotective effects may be mediated via affecting NF-κB activation, extrinsic apoptosis and intrinsic apoptosis pathways.

Are endourological procedures for nephrolithiasis treatment associated with renal injury? A review of potential mechanisms and novel diagnostic indexes

Nephrolithiasis is one of the most common urological conditions with a huge socio-economic impact. About 50% of recurrent stone-formers have just one lifetime recurrence and >10% of patients present with a high recurrent disease requiring subsequent and sometimes multiple surgical interventions. The advent of new technology has made endourological procedures the pinnacle of stone treatment, including procedures like percutaneous nephrolithotomy (PCNL), retrograde intrarenal surgery and miniaturized PCNL procedures. Researchers have primarily focused on comparisons with respect to stone-free rates, procedure parameters and post-operative complications. However, the effect of these three procedures on renal function or indexes of renal injury has not been sufficiently examined. This was only reported in a few studies as a secondary objective with the use of common and not the appropriate and detailed renal parameters. This review presents current literature regarding the use of novel and highly predictive biomarkers for diagnosing acute kidney injury, discusses potential mechanisms through which endourological procedures for renal stone treatment may affect renal function and proposes areas with open questions where future research efforts in the field should focus.

The Role of Autophagy and NLRP3 Inflammasome in Liver Fibrosis

Liver fibrosis is an intrinsic repair process of chronic injury with excessive deposition of extracellular matrix. As an early stage of various liver diseases, liver fibrosis is a reversible pathological process. Therefore, if not being controlled in time, liver fibrosis will evolve into cirrhosis, liver failure, and liver cancer. It has been demonstrated that hepatic stellate cells (HSCs) play a crucial role in the formation of liver fibrosis. In particular, the activation of HSCs is a key step for liver fibrosis. Recent researches have suggested that autophagy and inflammasome have biological effect on HSC activation. Herein, we review current studies about the impact of autophagy and NOD-like receptors containing pyrin domain 3 (NLRP3) inflammasome on liver fibrosis and the underlying mechanisms.

The NLRP3 Inflammasome Role in the Pathogenesis of Pregnancy Induced Hypertension and Preeclampsia

Pregnancy-induced hypertension and preeclampsia are associated with significant maternal and fetal mortality. A better understanding of these diseases, delineation of molecular pathomechanism, and efficient treatment development are some of the most urgent tasks in obstetrics and gynecology. Recent findings indicate the crucial role of inflammation in the development of hypertension and preeclampsia. Although the mechanism is very complex and needs further explanation, it appears that high levels of cholesterol, urate, and glucose activates NLRP3 inflammasome, which produces IL-1β, IL-18, and gasdermin D. Production of these proinflammatory chemokines is the beginning of a local and general inflammation, which results in sympathetic outflow, angiotensin II production, proteinuria, hemolysis, liver damage, immunothrombosis, and coagulopathy. The NLRP3 inflammasome is a critical complex in the mediation of the inflammatory response, which makes it crucial for the development of pregnancy-induced hypertension and preeclampsia, as well as its complications, such as placental abruption and HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome. Herein, the presented article delineates molecular mechanisms of these processes, indicating directions of future advance.

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.

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.

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.

Endothelial-specific deletion of Brahma-related gene 1 (BRG1) assuages unilateral ureteral obstruction induced renal injury in mice

Renal homeostasis is regulated by the interplay among different cell types in the kidneys including endothelial cells. In the present study we investigated the phenotypic regulation of endothelial cells by BRG1, a chromatin remodeling protein, in a mouse model of obstructive nephropathy (ON). We report that endothelial-specific deletion of BRG1 attenuated renal inflammation induced by unilateral ureteral tract obstruction (UUO) in mice, as evidenced by down-regulation of pro-inflammatory cytokines and diminished infiltration of immune cells. Moreover, endothelial BRG1 deficiency suppressed UUO-induced renal fibrosis in mice as measured by expression of pro-fibrogenic genes, picrosirius red staining of collagenous tissues, and quantification of hydroxylproline levels. Mechanistically, BRG1 activated the transcription of adhesion molecules and chemokines in endothelial cells by recruiting histone modifying enzymes leading to macrophage adhesion and chemotaxis. In conclusion, we propose that epigenetic regulation of endothelial function by BRG1 may play an active role in ON pathogenesis.

Nephropathy induced by renal microembolism: a characterization of biochemical and histopathological changes in rats

The aim of this study was to investigate some biochemical parameters of renal function and the vascular, glomerular, tubular, and interstitial manifestations in the progression of nephropathy induced by renal microembolism. Renal microembolism was induced by the arterial injection of polymethacrylate microspheres in the remnant kidney of nephrectomized rats. Animals 110-120 days old were randomly divided into three groups: the control group (C; normal), the nephrectomized group (S; nephrectomized that did not undergo renal microembolism), and the model group (M, nephrectomized animals that underwent renal arterial microembolism). The animals were evaluated 30, 60, and 90 days after the induction of a renal microembolism. Blood and urine samples were collected to determine serum creatinine (Cr) and urea (Ur) concentrations and urine total protein (Pt) concentrations. The kidneys were weighed and processed for histopathological analysis using hematoxylin and eosin (HE), periodic acid-Schiff (PAS), Mallory-Azan, and Picro-Sirius staining. The samples were also subjected to immunohistochemistry with a proliferating cell nuclear antigen (PCNA) and a vascular endothelial growth factor receptor (VEGFR). The data demonstrated evidence of the occurrence of vascular, glomerular, tubular, and interstitial abnormalities in the renal tissue, and changes in the biochemical parameters of renal function (serum Cr and Ur and of 24-h urine Pt) in this experimental model of nephropathy induced by renal microembolism, which may indicate the development of chronic kidney disease (CKD). Additionally, the findings indicate that this is a good reproducibility model that may be useful for studying the pathogenesis of CKD that is caused by atheroembolism and possible treatment alternatives.

Cardiotrophin-1 opposes renal fibrosis in mice: Potential prevention of chronic kidney disease

AIM

Chronic kidney disease is characterized by tubulointerstitial fibrosis involving inflammation, tubular apoptosis, fibroblast proliferation and extracellular matrix accumulation. Cardiotrophin-1, a member of the interleukin-6 family of cytokines, protects several organs from damage by promoting survival and anti-inflammatory effects. However, whether cardiotrophin-1 participates in the response to chronic kidney injury leading to renal fibrosis is unknown.

METHODS

We hypothesized and assessed the potential role of cardiotrophin-1 in a mice model of tubulointerstitial fibrosis induced by unilateral ureteral obstruction (UUO).

RESULTS

Three days after UUO, obstructed kidneys from cardiotrophin-1^-/- mice show higher expression of inflammatory markers IL-1β, Cd68, ICAM-1, COX-2 and iNOs, higher activation of NF-κB, higher amount of myofibroblasts and higher severity of tubular damage and apoptosis, compared with obstructed kidneys from wild-type littermates. In a later stage, obstructed kidneys from cardiotrophin-1^-/- mice show higher fibrosis than obstructed kidneys from wild-type mice. Interestingly, administration of exogenous cardiotrophin-1 prevents the increased fibrosis resulting from the genetic knockout of cardiotrophin-1 upon UUO, and supplementation of wild-type mice with exogenous cardiotrophin-1 further reduces the renal fibrosis induced by UUO. In vitro, renal myofibroblasts from cardiotrophin-1^-/- mice have higher collagen I and fibronectin expression and higher NF-κB activation than wild-type cells.

CONCLUSIONS

Cardiotrophin-1 participates in the endogenous response that opposes renal damage by counteracting the inflammatory, apoptotic and fibrotic processes. And exogenous cardiotrophin-1 is proposed as a candidate for the treatment and prevention of chronic renal fibrosis.