The cytoskeleton as a novel target for treatment of renal fibrosis

The PI3K-AKT-mTOR signaling pathway mediates the cytoskeletal remodeling and epithelial-mesenchymal transition in bladder outlet obstruction

Objective

Partial bladder outlet obstruction(pBOO) is the most common cause of lower urinary tract symptoms (LUTS) and significantly affects the quality of life. Long-term pBOO can cause changes in bladder structure and function, referred to as bladder remodeling. The pathogenesis of pBOO-induced bladder remodeling has yet to be fully understood, so effective treatment options are lacking. Our study aimed to explore how pBOO-induced bladder remodeling brings new strategies for treating pBOO.

Methods

A rat model of pBOO was established by partial ligation of the bladder neck, and the morphological changes and fibrosis changes in the bladder tissues were detected by H&E and Masson trichrome staining. Furthermore, EMT(epithelial-mesenchymal transition) related indicators and related pathway changes were further examined after TGF- β treatment of urothelial cells SV-HUC-1. Finally, the above indicators were tested again after using the PI3K inhibitor. Subsequently, RNA sequencing of bladder tissues to identify differential genes and related pathways enrichment and validated by immunofluorescence and western blotting analysis.

Results

The pBOO animal model was successfully established by partially ligating the bladder neck. H&E staining showed significant changes in the bladder structure, and Masson trichrome staining showed significantly increased collagen fibers. RNA sequencing results significantly enriched in the cytoskeleton, epithelial-mesenchymal transformation, and the PI3K-AKT-mTOR signaling pathway. Immunofluorescence and western blotting revealed EMT and cytoskeletal remodeling in SV-HUC-1 cells after induction of TGF- β and in the pBOO bladder tissues. The western blotting showed significant activation of the PI3K-AKT-mTOR signaling pathway in SV-HUC-1 cells after induction of TGF-β and in pBOO bladder tissues. Furthermore, EMT and cytoskeletal damage were partially reversed after PI3K pathway inhibition using PI3K inhibitors.

Conclusions

In the pBOO rat model, the activation of the PI3K-AKT-mTOR signaling pathway can mediate the cytoskeletal remodeling and the EMT to induce fibrosis in the bladder tissues. PI3K inhibitors partially reversed EMT and cytoskeletal damage.

Ion channels as a therapeutic target for renal fibrosis

Renal ion channel transport and electrolyte disturbances play an important role in the process of functional impairment and fibrosis in the kidney. It is well known that there are limited effective drugs for the treatment of renal fibrosis, and since a large number of ion channels are involved in the renal fibrosis process, understanding the mechanisms of ion channel transport and the complex network of signaling cascades between them is essential to identify potential therapeutic approaches to slow down renal fibrosis. This review summarizes the current work of ion channels in renal fibrosis. We pay close attention to the effect of cystic fibrosis transmembrane conductance regulator (CFTR), transmembrane Member 16A (TMEM16A) and other Cl− channel mediated signaling pathways and ion concentrations on fibrosis, as well as the various complex mechanisms for the action of Ca2+ handling channels including Ca2+-release-activated Ca2+ channel (CRAC), purinergic receptor, and transient receptor potential (TRP) channels. Furthermore, we also focus on the contribution of Na+ transport such as epithelial sodium channel (ENaC), Na+, K+-ATPase, Na+-H+ exchangers, and K+ channels like Ca2+-activated K+ channels, voltage-dependent K+ channel, ATP-sensitive K+ channels on renal fibrosis. Proposed potential therapeutic approaches through further dissection of these mechanisms may provide new therapeutic opportunities to reduce the burden of chronic kidney disease.

Proteomic analysis of hepatic fibrosis induced by a high starch diet in largemouth bass (Micropterus salmoides)

Largemouth bass is sensitive to the dietary starch level and excess starch can induce metabolic liver diseases (MLD). Hepatic fibrosis is a typical pathological phenotype of MLD in largemouth bass, but the molecular basis underlying is largely unclear. This study fed fish with a low or high starch diet for 4 weeks. Liver tissues with or without fibrotic symptoms were recognized through histopathological and molecular markers analysis of hepatic fibrosis, following TMT Quantitative proteomics and conducted Parallel Reaction Monitoring (PRM) analyses. 2455 differentially expressed proteins with 1618 up-regulated and 837 down-regulated were identified in this study. In GO terms, up-regulated proteins were correlated with cytoskeleton organization, supramolecular fiber, cytoskeleton protein binding, and actin-binding, while down-regulated proteins were involved in mainly metabolism-related processes, and molecular binding activity. Down-regulated proteins were enriched in 63 KEGG pathways and concentrated in metabolism-related pathways, especially glucose, lipid, and amino acid metabolism. 70 KEGG pathways of up-regulated proteins mainly included immunity and inflammation-related pathways. The expression trends of 11 differentially expressed proteins were consistent with proteome results by PRM analysis. In conclusion, the development of hepatic fibrosis induced by high starch may be related to multi-signaling pathways, metabolism processes, and targets, which provides important data for further study on revealing the molecular mechanism of hepatic fibrosis.

Transcriptomic analysis of bladder tissue in a rat model of ketamine-induced bladder fibrosis

INTRODUCTION

Ketamine-induced cystitis (KIC) is a disease caused by ketamine that can cause lower urinary tract symptoms (LUTS). Its end-stage is bladder contracture, which is related to bladder fibrosis and poses a serious burden to patient lives.

METHODS

We established a KIC model in female Sprague Dawley rats and verified bladder fibrosis in the model by Masson trichrome staining and western blot analysis. The bladders of the rats from the ketamine and control groups were used to perform transcriptome analysis. In particular, association analysis with metabolomics was also used to determine the potential mechanisms of ketamine-induced bladder fibrosis.

RESULTS

A total of 685 differentially expressed messenger RNAs, 71 differentially expressed long noncoding RNAs, 23 differentially expressed microRNAs, and 68 differentially expressed circular RNAs were identified. We found that ribosome, Wnt signaling, vascular endothelial growth factor signaling, cytoskeleton organization, and cytoskeletal protein binding may be potential pathways in ketamine-induced bladder fibrosis as identified by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. In addition, the mitogen-activated protein kinase pathway appeared to be closely related to the development of ketamine-induced bladder fibrosis according to association analysis.

CONCLUSIONS

In this study, using transcriptomic and correlation analyses of metabolomics, we identified pathways that may be potential targets for the prevention and treatment of ketamine-induced bladder fibrosis.

Extracellular Vesicles and Renal Fibrosis: An Odyssey toward a New Therapeutic Approach

Renal fibrosis is a complex disorder characterized by the destruction of kidney parenchyma. There is currently no cure for this devastating condition. Extracellular vesicles (EVs) are membranous vesicles released from cells in both physiological and diseased states. Given their fundamental role in transferring biomolecules to recipient cells and their ability to cross biological barriers, EVs have been widely investigated as potential cell-free therapeutic agents. In this review, we provide an overview of EVs, focusing on their functional role in renal fibrosis and signaling messengers responsible for EV-mediated crosstalk between various renal compartments. We explore recent findings regarding the renoprotective effect of EVs and their use as therapeutic agents in renal fibrosis. We also highlight advantages and future perspectives of the therapeutic applications of EVs in renal diseases.

Effects of repeated increasing doses of cisplatin as models of acute kidney injury and chronic kidney disease in rats

Cisplatin (CP) is nephrotoxic, and this side effect is used as an animal model for acute kidney injury (AKI). Earlier research has been focused on CP-induced AKI, with relatively little attention being paid to its ability to progress to chronic kidney disease (CKD) on repeated administration. We aimed here to test the dose dependency of its nephrotoxic actions by comparing various physiological, biochemical, molecular, and histopathological indices using repeated increasing doses of CP in rats. Furthermore, we investigated whether these doses of CP would result in the development of CKD. Biochemical, molecular, and histopathological measurements were conducted in plasma, urine, and/or kidneys of rats treated with increasing doses of CP at 1.6, 3.2, and 4.8 mg kg-1 weekly for four consecutive weeks. These doses induced significant and dose-dependent elevations in most of the measured renal indices. These included increased renal fibrosis, as suggested histopathologically and biochemically by the significant increase in transforming growth factor-β1, significant decrease in actin alpha 2, and variable actions of collagen I and IV. CP also dose-dependently increased nuclear factor (erythroid-derived 2)-like 2 and caspase-3. Multiple repeated doses of CP (1.6 to 4.8 mg kg-1) induced multiple episodes of AKI, leading to CKD after the 4th weekly dose and confirmed that this dosage regimen could be used as an experimental animal model of AKI progressing to CKD. These actions were driven by inflammation, oxidative, and nitrosative stress.

Formin mDia1 contributes to migration and epithelial-mesenchymal transition of tubular epithelial cells exposed to TGF-β1

Renal tubular epithelial cells may undergo epithelial-mesenchymal transition (EMT) in response to stimuli, such as transforming growth factor (TGF)-β1, leading to myofibroblast activation and renal fibrosis. The formin mDia1 is required for nucleation and polymerization of actin and the microtubule cytoskeleton. The present study sought to explore the role of mDia1 in EMT of tubular epithelial cells. A rat model of unilateral ureteral obstruction (UUO) was established. The expression of TGF-β1, collagen I, collagen III, and mDia1 in the kidneys was examined at day 7 after surgery. The effect of mDia1 on EMT was explored in NRK-52E cells by exposing them to TGF-β1. Increased expression of TGF-β1, collagen I, collagen III, and mDia1 was found in obstructive kidneys of UUO model rats. Exposing rat tubular epithelial cells to TGF-β1 promoted collagen I and collagen III expression but had no effect on mDia1 expression. Silencing mDia1 expression impeded epithelial cell migration as well as reduced TGF-β1, collagen, and Profilin1 expression, whereas mDia1 overexpression exerted an opposite effect. Furthermore, mDia1 regulated the expression of vimentin, α-smooth muscle actin, and E-cadherin and focal adhesion-kinase (FAK)/Src activation through Profilin1. Inhibition of the mDia1 activator RhoA by fasudil reversed EMT, and FAK/Src activation induced by mDia1. In conclusion, mDia1 regulated tubular epithelial cell migration, collagen expression, and EMT in NRK-52E cells exposed to TGF-β1. Thus, suppression of mDia1 activation might be a strategy to counteract renal fibrosis.

Time-series proteomic study of the response of HK-2 cells to hyperglycemic, hypoxic diabetic-like milieu

During diabetes, renal proximal tubular cells (PTC) are exposed to a combination of high glucose and hypoxic conditions, which plays a relevant role in the development of diabetic kidney disease (DKD). In this work, a time-series proteomic study was performed to analyse the effect of a diabetic-like microenvironment induced changes on HK-2 cells, a human cell line derived from normal proximal tubular epithelial cells. Cells simultaneously exposed to high glucose (25 mM) and hypoxia (1% O₂) were compared to cells in control conditions for up to 48 h. Diabetic conditions increased the percentage of death cells after 24 and 48 h, but no differences in the protein/cell ratio were found. The relative protein quantification using dimethyl-labeling and UHPLC-MS/MS analysis allowed the identification of 317, 296 and 259 proteins at 5, 24 and 48 h, respectively. The combination of statistical and time expression profile analyses indicated an increased expression of proteins involved in glycolysis, and a decrease of cytoskeletal-related proteins. The exposure of HK-2 cells to high glucose and hypoxia reproduces some of the effects of diabetes on PTC and, with the limitations inherent to in vitro studies, propose new mechanisms and targets to be considered in the management of DKD.

Potential Role of Integrin α₅β₁/Focal Adhesion Kinase (FAK) and Actin Cytoskeleton in the Mechanotransduction and Response of Human Gingival Fibroblasts Cultured on a 3-Dimension Lactide-Co-Glycolide (3D PLGA) Scaffold

BACKGROUND The stability of orthodontic treatment is thought to be significantly affected by the compression and retraction of gingival tissues, but the underlying molecular mechanism is not fully elucidated. The objectives of our study were to explore the effects of mechanical force on the ECM-integrin-cytoskeleton linkage response in human gingival fibroblasts (HGFs) cultured on 3-dimension (3D) lactide-co-glycolide (PLGA) biological scaffold and to further study the mechanotransduction pathways that could be involved. MATERIAL AND METHODS A compressive force of 25 g/m² was applied to the HGFs-PLGA 3D co-cultured model. Rhodamine-phalloidin staining was used to evaluate the filamentous actin (F-actin) cytoskeleton. The expression level of type I collagen (COL-1) and the activation of the integrin alpha₅ß₁/focal adhesion kinase (FAK) signaling pathway were determined by using real-time PCR and Western blotting analysis. The impacts of the applied force on the expression levels of FAK, phosphorylated focal adhesion kinase (p-FAK), and COL-1 were also measured in cells treated with integrin alpha₅ß₁ inhibitor (Ac-PHSCN-NH 2, ATN-161). RESULTS Mechanical force increased the expression of integrin alpha₅ß₁, FAK (p-FAK), and COL-1 in HGFs, and induced the formation of stress fibers. Blocking integrin alpha₅ß₁ reduced the expression of FAK (p-FAK), while the expression of COL-1 was not fully inhibited. CONCLUSIONS The integrin alpha₅ß₁/FAK signaling pathway and actin cytoskeleton appear to be involved in the mechanotransduction of HGFs. There could be other mechanisms involved in the promotion effect of mechanical force on collagen synthesis in addition to the integrin alpha₅ß₁ pathway.

PRC1 promotes GLI1-dependent osteopontin expression in association with the Wnt/β-catenin signaling pathway and aggravates liver fibrosis

Background

PRC1 (Protein regulator of cytokinesis 1) regulates microtubules organization and functions as a novel regulator in Wnt/β-catenin signaling pathway. Wnt/β-catenin is involved in development of liver fibrosis (LF). We aim to investigate effect and mechanism of PRC1 on liver fibrosis.

Methods

Carbon tetrachloride (CCl₄)-induced mice LF model was established and in vitro cell model for LF was induced by mice primary hepatic stellate cell (HSC) under glucose treatment. The expression of PRC1 in mice and cell LF models was examined by qRT-PCR (quantitative real-time polymerase chain reaction), western blot and immunohistochemistry. MTT assay was used to detect cell viability, and western blot to determine the underlying mechanism. The effect of PRC1 on liver pathology was examined via measurement of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and hydroxyproline, as well as histopathological analysis.

Results

PRC1 was up-regulated in CCl₄-induced mice LF model and activated HSC. Knockdown of PRC1 inhibited cell viability and promoted cell apoptosis of activated HSC. PRC1 expression was regulated by Wnt3a signaling, and PRC1 could regulate downstream β-catenin activation. Moreover, PRC1 could activate glioma-associated oncogene homolog 1 (GLI1)-dependent osteopontin expression to participate in LF. Adenovirus-mediated knockdown of PRC1 in liver attenuated LF and reduced collagen deposition.

Conclusions

PRC1 aggravated LF through regulating Wnt/β-catenin mediated GLI1-dependent osteopontin expression, providing a new potential therapeutic target for LF treatment.

Four-jointed knock-out delays renal failure in an ADPKD model with kidney injury

Autosomal Dominant Polycystic Kidney Disease is characterised by the development of fluid‐filled cysts in the kidneys which lead to end‐stage renal disease (ESRD). In the majority of cases, the disease is caused by a mutation in the Pkd1 gene. In a previous study, we demonstrated that renal injury can accelerate cyst formation in Pkd1 knock‐out (KO) mice. In that study, we found that after injury four‐jointed (Fjx1), an upstream regulator of planar cell polarity and the Hippo pathway, was aberrantly expressed in Pkd1 KO mice compared to WT. Therefore, we hypothesised a role for Fjx1 in injury/repair and cyst formation. We generated single and double deletion mice for Pkd1 and Fjx1, and we induced toxic renal injury using the nephrotoxic compound 1,2‐dichlorovinyl‐cysteine. We confirmed that nephrotoxic injury can accelerate cyst formation in Pkd1 mutant mice. This caused Pkd1 KO mice to reach ESRD significantly faster; unexpectedly, double KO mice survived significantly longer. Cyst formation was comparable in both models, but we found significantly less fibrosis and macrophage infiltration in double KO mice. Taken together, these data suggest that Fjx1 disruption protects the cystic kidneys against kidney failure by reducing inflammation and fibrosis. Moreover, we describe, for the first time, an interesting (yet unidentified) mechanism that partially discriminates cyst growth from fibrogenesis. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Neutrophil-to-lymphocyte ratio and incident end-stage renal disease in Chinese patients with chronic kidney disease: results from the Chinese Cohort Study of Chronic Kidney Disease (C-STRIDE)

BACKGROUND

Chronic kidney disease (CKD) leads to end-stage renal failure and cardiovascular events. An attribute to these progressions is abnormalities in inflammation, which can be evaluated using the neutrophil-to-lymphocyte ratio (NLR). We aimed to investigate the association of NLR with the progression of end stage of renal disease (ESRD), cardiovascular disease (CVD) and all-cause mortality in Chinese patients with stages 1-4 CKD.

METHODS

Patients with stages 1-4 CKD (18-74 years of age) were recruited at 39 centers in 28 cities across 22 provinces in China since 2011. A total of 938 patients with complete NLR and other relevant clinical variables were included in the current analysis. Cox regression analysis was used to estimate the association between NLR and the outcomes including ESRD, CVD events or all-cause mortality.

RESULTS

Baseline NLR was related to age, hypertension, serum triglycerides, total serum cholesterol, CVD history, urine albumin to creatinine ratio (ACR), chronic kidney disease-mineral and bone disorder (CKD-MBD), hyperlipidemia rate, diabetes, and estimated glomerular filtration rate (eGFR). The study duration was 4.55 years (IQR 3.52-5.28). Cox regression analysis revealed an association of NLR and the risk of ESRD only in patients with stage 4 CKD. We did not observe any significant associations between abnormal NLR and the risk of either CVD or all-cause mortality in CKD patients in general and CKD patients grouped according to the disease stages in particular.

CONCLUSION

Our results suggest that NLR is associated with the risk of ESRD in Chinese patients with stage 4 CKD. NLR can be used in risk assessment for ESRD among patients with advanced CKD; this application is appealing considering NLR being a routine test. Trial registration ClinicalTrials.gov Identifier NCT03041987. Registered January 1, 2012. (retrospectively registered) ( https://www.clinicaltrials.gov/ct2/show/NCT03041987?term=Chinese+Cohort+Study+of+Chronic+Kidney+Disease+%28C-STRIDE%29&rank=1 ).

Resveratrol exerts dose-dependent anti-fibrotic or pro-fibrotic effects in kidneys: A potential risk to individuals with impaired kidney function

BACKGROUND

Renal fibrosis is the pathological feature of chronic kidney disease (CKD) which leads to end-stage renal disease (ESRD) and renal failure. Resveratrol [3,5,4'-trihydroxy-trans-stilbene (RSV)] has shown benefits for metabolic diseases and anti-cancer therapy, but its potential risk on renal health has not been fully evaluated.

PURPOSE

To investigate the global effects of RSV on renal fibrosis in human tubular epithelial cell (TEC) line HK-2, and in mice with unilateral ureteral obstruction (UUO).

METHODS

A TGF-β-induced in vitro model of epithelial-mesenchymal transition (EMT) in TEC was established. The effects of RSV on cell viability, pro-fibrotic factors, oxidative stress, mitochondria function, and underlying pathway proteins were analyzed. In vivo, the effects of RSV on renal function and fibrosis were assayed in UUO mice.

RESULTS

Our results showed that low concentrations of RSV (5-20 μM) decreased TGF-β-induced EMT via Sirt1-dependent deacetylation of Smad3/Smad4 mechanism. By contrast, long-term (72 h) exposure to high concentrations of RSV (≥ 40 μM) promoted EMT in HK-2 cells via mitochondrial oxidative stress and ROCK1-mediated disordered cytoskeleton remodeling. In vivo, low-dose treatment of RSV (≤ 25 mg/kg) partly improved renal function, whereas high-dose treatment of RSV (≥ 50 mg/kg) lost its anti-fibrotic role and even aggravated renal fibrosis. However, mice with UUO were more susceptible to high RSV-induced renal injury than normal mice.

CONCLUSION

Dependent on dose, RSV activated either anti-fibrotic or pro-fibrotic effects in kidneys. The risk of RSV consumption in individuals with impaired kidney function should be carefully considered.

Elevated serum levels of procollagen C-proteinase enhancer-1 in patients with chronic kidney disease is associated with a declining glomerular filtration rate

BACKGROUND

Procollagen C-proteinase enhancer-1 (PCPE-1) is a 55 kDa glycoprotein, which increases the activity of procollagen C-proteinases that break down C-terminal propeptides. Studies have shown that PCPE-1 is involved in the fibrotic process that occurs in various tissues and organs. Our review of the literature revealed no data concerning the relation between PCPE-1 and chronic kidney disease (CKD). The purpose of this study was to determine PCPE-1 levels in CKD.

METHODS

One hundred thirty-one CKD patients and 34 healthy controls were included in our study. Demographic data were recorded, and routine biochemical tests were performed. Blood specimens were collected for PCPE-1 investigation. Demographic data, biochemical test results and PCPE-1 levels were compared between the control and patient groups. Parameters affecting PCPE-1 levels in our patient group were assessed.

RESULTS

Procollagen C-proteinase enhancer-1 levels were significantly higher in our patient group compared to the control group. Parameters affecting PCPE-1 elevation in the patient group were identified as systolic blood pressure, blood urea nitrogen, phosphorus, haemoglobin, intact parathormone levels, glomerular filtration rate and body mass index.

CONCLUSION

We determined high PCPE-1 levels in CKD patients. PCPE-1 levels being negatively correlated with glomerular filtration rate suggests that PCPE-1 may be associated with progression in CKD patients.

FOXO1/3: Potential suppressors of fibrosis

Fibrosis is a universally age-related disease that involves nearly all organs. It is typically initiated by organic injury and eventually results in organ failure. There are still few effective therapeutic strategy targets for fibrogenesis. Forkhead box proteins O1 and O3 (FOXO1/3) have been shown to have favorable inhibitory effects on fibroblast activation and subsequent extracellular matrix production and can ameliorate fibrosis levels in numerous organs, including the heart, liver, lung, and kidney; they are therefore promising targets for anti-fibrosis therapy. Moreover, we can develop appropriate strategies to make the best use of FOXO1/3's anti-fibrosis properties. The information reviewed here should be significant for understanding the roles of FOXO1/3 in fibrosis and should contribute to the design of further studies related to FOXO1/3 and the fibrotic response and shed light on a potential treatment for fibrosis.