Connective tissue growth factor: potential role in glomerulosclerosis and tubulointerstitial fibrosis

Novel Approaches in Chronic Renal Failure without Renal Replacement Therapy: A Review

Chronic kidney disease (CKD) is characterized by renal parenchymal damage leading to a reduction in the glomerular filtration rate. The inflammatory response plays a pivotal role in the tissue damage contributing to renal failure. Current therapeutic options encompass dietary control, mineral salt regulation, and management of blood pressure, blood glucose, and fatty acid levels. However, they do not effectively halt the progression of renal damage. This review critically examines novel therapeutic avenues aimed at ameliorating inflammation, mitigating extracellular matrix accumulation, and fostering renal tissue regeneration in the context of CKD. Understanding the mechanisms sustaining a proinflammatory and profibrotic state may offer the potential for targeted pharmacological interventions. This, in turn, could pave the way for combination therapies capable of reversing renal damage in CKD. The non-replacement phase of CKD currently faces a dearth of efficacious therapeutic options. Future directions encompass exploring vaptans as diuretics to inhibit water absorption, investigating antifibrotic agents, antioxidants, and exploring regenerative treatment modalities, such as stem cell therapy and novel probiotics. Moreover, this review identifies pharmaceutical agents capable of mitigating renal parenchymal damage attributed to CKD, targeting molecular-level signaling pathways (TGF-β, Smad, and Nrf2) that predominate in the inflammatory processes of renal fibrogenic cells.

The role of the mesangium in glomerular function

When discussing glomerular function, one cell type is often left out, the mesangial cell (MC), probably since it is not a part of the filtration barrier per se. The MCs are instead found between the glomerular capillaries, embedded in their mesangial matrix. They are in direct contact with the endothelial cells and in close contact with the podocytes and together they form the glomerulus. The MCs can produce and react to a multitude of growth factors, cytokines, and other signaling molecules and are in the perfect position to be a central hub for crosstalk communication between the cells in the glomerulus. In certain glomerular diseases, for example, in diabetic kidney disease or IgA nephropathy, the MCs become activated resulting in mesangial expansion. The expansion is normally due to matrix expansion in combination with either proliferation or hypertrophy. With time, this expansion can lead to fibrosis and decreased glomerular function. In addition, signs of complement activation are often seen in biopsies from patients with glomerular disease affecting the mesangium. This review aims to give a better understanding of the MCs in health and disease and their role in glomerular crosstalk and inflammation.

CCN2 Activates RIPK3, NLRP3 Inflammasome, and NRF2/Oxidative Pathways Linked to Kidney Inflammation

Inflammation is a key characteristic of both acute and chronic kidney diseases. Preclinical data suggest the involvement of the NLRP3/Inflammasome, receptor-interacting protein kinase-3 (RIPK3), and NRF2/oxidative pathways in the regulation of kidney inflammation. Cellular communication network factor 2 (CCN2, also called CTGF in the past) is an established fibrotic biomarker and a well-known mediator of kidney damage. CCN2 was shown to be involved in kidney damage through the regulation of proinflammatory and profibrotic responses. However, to date, the potential role of the NLRP3/RIPK3/NRF2 pathways in CCN2 actions has not been evaluated. In experimental acute kidney injury induced with folic acid in mice, CCN2 deficiency diminished renal inflammatory cell infiltration (monocytes/macrophages and T lymphocytes) as well as the upregulation of proinflammatory genes and the activation of NLRP3/Inflammasome-related components and specific cytokine products, such as IL-1β. Moreover, the NRF2/oxidative pathway was deregulated. Systemic administration of CCN2 to C57BL/6 mice induced kidney immune cell infiltration and activated the NLRP3 pathway. RIPK3 deficiency diminished the CCN2-induced renal upregulation of proinflammatory mediators and prevented NLRP3 modulation. These data suggest that CCN2 plays a fundamental role in sterile inflammation and acute kidney injury by modulating the RIKP3/NLRP3/NRF2 inflammatory pathways.

Pyruvate kinase M2 modification by a lipid peroxidation byproduct acrolein contributes to kidney fibrosis

Renal fibrosis is a hallmark of diabetic nephropathy (DN) and is characterized by an epithelial-to-mesenchymal transition (EMT) program and aberrant glycolysis. The underlying mechanisms of renal fibrosis are still poorly understood, and existing treatments are only marginally effective. Therefore, it is crucial to comprehend the pathophysiological mechanisms behind the development of renal fibrosis and to generate novel therapeutic approaches. Acrolein, an α-,β-unsaturated aldehyde, is endogenously produced during lipid peroxidation. Acrolein shows high reactivity with proteins to form acrolein-protein conjugates (Acr-PCs), resulting in alterations in protein function. In previous research, we found elevated levels of Acr-PCs along with kidney injuries in high-fat diet-streptozotocin (HFD-STZ)-induced DN mice. This study used a proteomic approach with an anti-Acr-PC antibody followed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis to identify several acrolein-modified protein targets. Among these protein targets, pyruvate kinase M2 (PKM2) was found to be modified by acrolein at Cys358, leading to the inactivation of PKM2 contributing to the pathogenesis of renal fibrosis through HIF1α accumulation, aberrant glycolysis, and upregulation of EMT in HFD-STZ-induced DN mice. Finally, PKM2 activity and renal fibrosis in DN mice can be reduced by acrolein scavengers such as hydralazine and carnosine. These results imply that acrolein-modified PKM2 contributes to renal fibrosis in the pathogenesis of DN.

Selonsertib Enhances Kidney Protection Beyond Standard of Care in a Hypertensive, Secondary Glomerulosclerosis CKD Model

Background

Despite widespread use of renin-aldosterone-angiotensin system inhibitors and the benefits of lowering glomerular pressure in patients with CKD, there remains a major unmet need for therapies targeting underlying causes of CKD progression. Apoptosis signal-regulating kinase 1 (ASK1) promotes apoptosis and glomerulosclerosis, and is implicated in the progression of diabetic kidney disease (DKD), a major cause of CKD. Selonsertib is a selective ASK1 inhibitor currently in clinical development for the treatment of DKD. We examined the added benefits of selonsertib on existing glomerulosclerosis and related molecular pathways in the nondiabetic 5/6 nephrectomy (5/6 Nx) rat model in combination with the angiotensin-converting enzyme inhibitor (ACEI) enalapril.

Methods

Male Sprague Dawley rats underwent 5/6 Nx with kidney biopsy 8 weeks later for assessment of glomerulosclerosis, and were randomized to four treatment groups with equal glomerulosclerosis: selonsertib, enalapril, combination (selonsertib plus enalapril), and untreated controls. Serum creatinine, systolic BP (SBP), and urinary albumin were measured at intervals. Animals were euthanized at week 12 for histologic, biochemical, and molecular analyses.

Results

All rats developed hypertension, albuminuria, and glomerulosclerosis by week 8. Kidney function further declined, and glomerulosclerosis and albuminuria progressively increased in controls from week 8 to 12. Enalapril treatment alone from week 8 to 12 reduced SBP versus controls, decreased albuminuria, and resulted in numerically lower glomerulosclerosis. Selonsertib alone had no effect on SBP but preserved kidney function. Combined treatment significantly reduced glomerulosclerosis, with more regression than either monotherapy. Enalapril treatment resulted in fewer interstitial macrophages, whereas selonsertib treatment reduced apoptosis and podocyte loss. RNA-seq revealed that combined treatment influenced pathways related to extracellular matrix and wound healing.

Conclusions

Selonsertib targets a novel, nonhemodynamic pathway in CKD. Our data suggest that ASK1 inhibition, when combined with ACEI, has additive effects to reduce progression of glomerulosclerosis, attenuate kidney function decline, and reduce podocyte loss.

Mitochondrial Pathophysiology on Chronic Kidney Disease

In healthy kidneys, interstitial fibroblasts are responsible for the maintenance of renal architecture. Progressive interstitial fibrosis is thought to be a common pathway for chronic kidney diseases (CKD). Diabetes is one of the boosters of CKD. There is no effective treatment to improve kidney function in CKD patients. The kidney is a highly demanding organ, rich in redox reactions occurring in mitochondria, making it particularly vulnerable to oxidative stress (OS). A dysregulation in OS leads to an impairment of the Electron transport chain (ETC). Gene deficiencies in the ETC are closely related to the development of kidney disease, providing evidence that mitochondria integrity is a key player in the early detection of CKD. The development of novel CKD therapies is needed since current methods of treatment are ineffective. Antioxidant targeted therapies and metabolic approaches revealed promising results to delay the progression of some markers associated with kidney disease. Herein, we discuss the role and possible origin of fibroblasts and the possible potentiators of CKD. We will focus on the important features of mitochondria in renal cell function and discuss their role in kidney disease progression. We also discuss the potential of antioxidants and pharmacologic agents to delay kidney disease progression.

CCN2 Binds to Tubular Epithelial Cells in the Kidney

Cellular communication network-2 (CCN2), also called connective tissue growth factor (CTGF), is considered a fibrotic biomarker and has been suggested as a potential therapeutic target for kidney pathologies. CCN2 is a matricellular protein with four distinct structural modules that can exert a dual function as a matricellular protein and as a growth factor. Previous experiments using surface plasmon resonance and cultured renal cells have demonstrated that the C-terminal module of CCN2 (CCN2(IV)) interacts with the epidermal growth factor receptor (EGFR). Moreover, CCN2(IV) activates proinflammatory and profibrotic responses in the mouse kidney. The aim of this paper was to locate the in vivo cellular CCN2/EGFR binding sites in the kidney. To this aim, the C-terminal module CCN2(IV) was labeled with a fluorophore (Cy5), and two different administration routes were employed. Both intraperitoneal and direct intra-renal injection of Cy5-CCN2(IV) in mice demonstrated that CCN2(IV) preferentially binds to the tubular epithelial cells, while no signal was detected in glomeruli. Moreover, co-localization of Cy5-CCN2(IV) binding and activated EGFR was found in tubules. In cultured tubular epithelial cells, live-cell confocal microscopy experiments showed that EGFR gene silencing blocked Cy5-CCN2(IV) binding to tubuloepithelial cells. These data clearly show the existence of CCN2/EGFR binding sites in the kidney, mainly in tubular epithelial cells. In conclusion, these studies show that circulating CCN2(IV) can directly bind and activate tubular cells, supporting the role of CCN2 as a growth factor involved in kidney damage progression.

Renoprotective Effects of Maslinic Acid on Experimental Renal Fibrosis in Unilateral Ureteral Obstruction Model via Targeting MyD88

Maslinic acid (MA), also named crategolic acid, is a pentacyclic triterpene extracted from fruits and vegetables. Although various beneficial pharmacological effects of MA have been revealed, its effect on renal fibrosis remains unclear. This study was designed to clarify whether MA could attenuate renal fibrosis and determine the putative underlying molecular mechanisms. We demonstrated that MA-treated mice with unilateral ureteral obstruction (UUO) developed a histological injury of low severity and exhibited downregulated expression of fibrotic markers, including α-smooth muscle actin (α-SMA), vimentin, and fibronectin by 38, 44 and 40%, and upregulated expression of E-cadherin by 70% as compared with untreated UUO mice. Moreover, MA treatment restored the expression levels of α-SMA, connective tissue growth factor, and vimentin to 10, 7.8 and 38% of those induced by transforming growth factor (TGF)-β in NRK49F cells. MA decreased expression of Smad2/3 phosphorylation and Smad4 in UUO kidneys and TGF-β treated NRK49F cells (p < 0.05, respectively). Notably, MA specifically interferes with MyD88, an adaptor protein, thereby mitigating Smad4 nuclear expression (p < 0.01 compared to TGF-β treated group) and ameliorating renal fibrotic changes (p < 0.01 for each fibrotic markers compared to TGF-β induced cells). In addition, in the UUO model and lipopolysaccharide-induced NRK49F cells, MA treatment decreased the expression of IL-1β, TGF-α and MCP-1, ICAM-1, associated with the suppression of NF-κB signaling. These findings suggest that MA is a potential agent that can reduce renal interstitial fibrosis, to some extent, via targeting TGF-β/Smad and MyD88 signaling.

Integrated Bioactive Scaffold with Polydeoxyribonucleotide and Stem-Cell-Derived Extracellular Vesicles for Kidney Regeneration

Kidney tissue engineering and regeneration approaches offer great potential for chronic kidney disease treatment, but kidney tissue complexity imposes an additional challenge in applying regenerative medicine for renal tissue regeneration. In this study, a porous pneumatic microextrusion (PME) composite scaffold consisting of poly(lactic-co-glycolic acid) (PLGA, P), magnesium hydroxide (MH, M), and decellularized porcine kidney extracellular matrix (kECM, E) is functionalized with bioactive compounds, polydeoxyribonucleotide (PDRN), and tumour necrosis factor-α (TNF-α)/interferon-γ (IFN-γ)-primed mesenchymal stem-cell-derived extracellular vesicles (TI-EVs) to improve the regeneration and maintenance of a functional kidney tissue. The combination of PDRN and TI-EVs showed a significant synergistic effect in regenerative processes including cellular proliferation, angiogenesis, fibrosis, and inflammation. In addition, the PME/PDRN/TI-EV scaffold induced an effective glomerular regeneration and restoration of kidney function compared to the existing PME scaffold in a partial nephrectomy mouse model. Therefore, such an integrated bioactive scaffold that combines biochemical cues from PDRN and TI-EVs and biophysical cues from a porous PLGA scaffold containing MH and kECM can be used as an advanced tissue engineering platform for kidney tissue regeneration.

Involvement of FATP2-mediated tubular lipid metabolic reprogramming in renal fibrogenesis

Following a chronic insult, renal tubular epithelial cells (TECs) contribute to the development of kidney fibrosis through dysregulated lipid metabolism that lead to lipid accumulation and lipotoxicity. Intracellular lipid metabolism is tightly controlled by fatty acids (FAs) uptake, oxidation, lipogenesis, and lipolysis. Although it is widely accepted that impaired fatty acids oxidation (FAO) play a crucial role in renal fibrosis progression, other lipid metabolic pathways, especially FAs uptake, has not been investigated in fibrotic kidney. In this study, we aim to explore the potential mechanically role of FAs transporter in the pathogenesis of renal fibrosis. In the present study, the unbiased gene expression studies showed that fatty acid transporter 2 (FATP2) was one of the predominant expressed FAs transport in TECs and its expression was tightly associated with the decline of renal function. Treatment of unilateral ureteral obstruction (UUO) kidneys and TGF-β induced TECs with FATP2 inhibitor (FATP2i) lipofermata restored the FAO activities and alleviated fibrotic responses both in vivo and in vitro. Moreover, the expression of profibrotic cytokines including TGF-β, connective tissue growth factor (CTGF), fibroblast growth factor (FGF), and platelet-derived growth factor subunit B (PDGFB) were all decreased in FATP2i-treated UUO kidneys. Mechanically, FATP2i can effectively attenuate cell apoptosis and endoplasmic reticulum (ER) stress induced by TGF-β treatment in cultured TECs. Taking together, these findings reveal that FATP2 elicits a profibrotic response to renal interstitial fibrosis by inducing lipid metabolic reprogramming including abnormal FAs uptake and defective FAO in TECs.

Effects of thromboxane prostanoid receptor deficiency on diabetic nephropathy induced by high fat diet and streptozotocin in mice

Diabetic nephropathy (DN), one of the main causes of end-stage renal disease, still remains as a challenge of clinical management. This study aimed to determine whether deficiency of the thromboxane (TX) prostanoid receptor (TP), which mediates the contractile activities of all prostanoids, alleviates the development of DN and if so, to examine the underlying mechanism(s). Diabetes was induced by high fat diet and streptozotocin injection in wild-type (WT) mice and those with TP deficiency (TP^-/-). Here we show that WT and TP^-/- mice developed diabetes with a similar blood glucose level; however, signs of renal functional impairments and pathologies occurred to a lesser extent in TP^-/- than in WT mice. Also, the extent of an increase in the expression level of transforming growth factor-β1 (TGF-β1), a common pathological mediator of DN, in diabetic renal cortexes of TP^-/- mice was lower than that of WT counterparts. Moreover, we noted that expression levels of cyclooxygenase (COX)-2 and calcium-dependent phospholipase A₂ (cPLA₂) as well as levels of prostaglandin E₂ and TXA₂ in diabetic renal cortexes were increased as compared to those of non-diabetic conditions. These results thus demonstrate that possibly due to up-regulated cPLA₂ and COX-2 that lead to increased prostanoid syntheses in diabetic renal cortexes, TP^-/- alleviates DN development. In addition, our results suggest that such an effect of TP^-/- might be related to the suppression of TGF-β1 up-regulation that is commonly associated with the disease condition.

NADPH Oxidase Inhibition in Fibrotic Pathologies

Significance: Fibrosis is a stereotypic, multicellular tissue response to diverse types of injuries that fundamentally result from a failure of cell/tissue regeneration. This complex tissue remodeling response disrupts cellular/matrix composition and homeostatic cell-cell interactions, leading to loss of normal tissue architecture and progressive loss of organ structure/function. Fibrosis is a common feature of chronic diseases that may affect the lung, kidney, liver, and heart. Recent Advances: There is emerging evidence to support a combination of genetic, environmental, and age-related risk factors contributing to susceptibility and/or progression of fibrosis in different organ systems. A core pathway in fibrogenesis involving these organs is the induction and activation of nicotinamide adenine dinucleotide phosphate oxidase (NOX) family enzymes. Critical Issues: We explore current pharmaceutical approaches to targeting NOX enzymes, including repurposing of currently U.S. Food and Drug Administration (FDA)-approved drugs. Specific inhibitors of various NOX homologs will aid establishing roles of NOXs in the various organ fibroses and potential efficacy to impede/halt disease progression. Future Directions: The discovery of novel and highly specific NOX inhibitors will provide opportunities to develop NOX inhibitors for treatment of fibrotic pathologies.

A CTGF-YAP Regulatory Pathway Is Essential for Angiogenesis and Barriergenesis in the Retina

Connective tissue growth factor (CTGF) or cellular communication network 2 (CCN2) is a matricellular protein essential for normal embryonic development and tissue repair. CTGF exhibits cell- and context-dependent activities, but CTGF function in vascular development and barrier function is unknown. We show that endothelial cells (ECs) are one of the major cellular sources of CTGF in the developing and adult retinal vasculature. Mice lacking CTGF expression either globally or specifically in ECs exhibit impaired vascular cell growth and morphogenesis and blood barrier breakdown. The global molecular signature of CTGF includes cytoskeletal and extracellular matrix protein, growth factor, and transcriptional co-regulator genes such as yes-associated protein (YAP). YAP, itself a transcriptional activator of CTGF, mediates several CTGF-controlled angiogenic and barriergenic transcriptional programs. Re-expression of YAP rescues, at least partially, angiogenesis and barriergenesis in CTGF mutant mouse retinas. Thus, the CTGF-YAP regulatory loop is integral to retinal vascular development and barrier function.

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CTGF has a strong and persistent expression in the retinal vasculature

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Mice lacking CTGF exhibit defects in angiogenesis and blood barrier integrity

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CTGF-targeted genes include matrix, growth, and transcription co-factors like YAP

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YAP re-expression partly rescues angiogenic and barriergenic defects of CTGF loss

Targeting the progression of chronic kidney disease

Chronic kidney disease (CKD) is a devastating condition that is reaching epidemic levels owing to the increasing prevalence of diabetes mellitus, hypertension and obesity, as well as ageing of the population. Regardless of the underlying aetiology, CKD is slowly progressive and leads to irreversible nephron loss, end-stage renal disease and/or premature death. Factors that contribute to CKD progression include parenchymal cell loss, chronic inflammation, fibrosis and reduced regenerative capacity of the kidney. Current therapies have limited effectiveness and only delay disease progression, underscoring the need to develop novel therapeutic approaches to either stop or reverse progression. Preclinical studies have identified several approaches that reduce fibrosis in experimental models, including targeting cytokines, transcription factors, developmental and signalling pathways and epigenetic modulators, particularly microRNAs. Some of these nephroprotective strategies are now being tested in clinical trials. Lessons learned from the failure of clinical studies of transforming growth factor β1 (TGFβ1) blockade underscore the need for alternative approaches to CKD therapy, as strategies that target a single pathogenic process may result in unexpected negative effects on simultaneously occurring processes. Additional promising avenues include preventing tubular cell injury and anti-fibrotic therapies that target activated myofibroblasts, the main collagen-producing cells.

Transdermal delivery of small interfering RNAs with topically applied mesoporous silica nanoparticles for facile skin cancer treatment

Small interfering RNA (siRNA) is a promising tool for the treatment of skin disorders including skin squamous cell carcinoma (SCC). This article develops a topical formulation for the transdermal delivery of siRNA. The formulation is built on mesoporous silica nanoparticles (MSNPs) with a loading capacity of 1.4 μg of oligonucleotide per mg of MSNPs. Cell experiments are employed to study the functionality of the formulation including the cellular uptake, the qualitative and quantitative detection of specific gene biomarkers. The clinical potential of this system is examined by topically delivering siRNA targeting TGFβR-1 (TGFβR-1) to the SCC in a mouse xenograft model. In comparison to the controls, MSNPs containing TGFβR-1 siRNA show a 2-fold suppression of TGFβR-1.

BMP-7/Smads-induced inhibitor of differentiation 2 (Id2) upregulation and Id2/Twist interaction was involved in attenuating diabetic renal tubulointerstitial fibrosis

Renal tubular epithelial-mesenchymal transition (EMT) is the main pathological change in diabetic renal tubulointerstitial fibrosis. Mounting evidence indicates that the inhibitor of differentiation 2 (Id2) protein acts as a negative regulatory factor in organ fibrosis and can inhibit or reverse the process of fibrosis. However, its specific regulatory mechanism is not clear. Diabetes mellitus (DM) rat models were established by injecting rats with streptozotocin and sacrificing them after 16 weeks. Rat renal tubular epithelial cells (NRK-52E) were cultured with normal and high glucose. Immunohistochemical analysis, double immunofluorescence staining, co-immunoprecipitation, Western blot analysis, and real-time polymerase chain reaction were used to determine the expression of Id2, Twist, Smad1/5/8, E-cadherin, α-smooth muscle actin (α-SMA), and collagen Ⅳ. The results showed that bone morphogenetic protein-7 (BMP-7) upregulated the expression of Id2 against high-glucose-induced EMT and extracellular matrix secretion. Moreover, only the simultaneous knockdown of Smad1, Smad5, and Smad8 downregulated the expression of Id2, which was not altered by the individual knockdown of Smad1, Smad5, and Smad8. Basic helix-loop-helix (bHLH) transcription factors were essential for Id2 to regulate the role of downstream target genes, and Twist was a bHLH transcription factor. Therefore, the expression of Twist was examined in this study. Twist was found to be highly expressed in the kidney of DM rats and renal tubular epithelial cells cultured with high glucose. The overexpression of Id2 did not alter the expression of Twist, but the interaction between Id2 and Twist was enhanced. In conclusion, the data showed the specific mechanism underlying Id2 negative regulation in diabetic renal tubulointerstitial fibrosis.

Glomerular Expression of Some Profibrotic Factors in Progressive Childhood Lupus Nephritis

BACKGROUND

Lupus nephritis (LN) is a major cause of mortality and morbidity in both adult and pediatric patients. However, studies regarding pathogenesis and predictors of renal outcomes in childhood LN are limited. Transforming growth factor-β1 (TGF-β1) and Connective tissue growth factor (CTGF) have an important role in proliferative and fibrotic changes in many renal diseases. We aim to evaluate the role of such two profibrotic factors in the progression of childhood onset LN and to detect if their glomerular expression could represent an early predictor of future deterioration of renal function.

METHODS

34 children with new onset of LN were included. Glomerular expressions of TGF-β1 and CTGF were evaluated by immunohistochemical analysis in the renal tissue of such patients and in control tissue. GFR was estimated at time of renal biopsy at the onset of LN and after 2 years of follow-up. Rate of GFR change (ΔGFR) was calculated and used as indicative of degree of renal disease progression.

RESULTS

Glomerular TGF-β1 and CTGF expressions in children with LN were significantly higher than in control tissue (LN 15.41 ± 9.84 and 15.56 ± 10.51 vs. 2.15 ± 1.45 and 1.35 ± 1.07 in control respectively, with p < 0.001 in both). In addition, the glomerular expressions of TGF-β1 and CTGF were significantly higher in patients with further decline in GFR (20.68 ± 7.73 and 21.05 ± 8.75) versus (5.75 ± 4.37 and 5.50 ± 3.78) in those without change in GFR with (p = 0.000 for both of them).

CONCLUSIONS

Patients with LN have increased glomerular expressions of TGF-β1 and CTGF, which were higher in those with further decline in GFR. These profibrotic factors are suspected to be involved in pathogenesis of LN and could be evaluated as a target for therapeutic intervention to stop progression of LN. In addition, their glomerular expression could be used as an early predictor of progression of LN, to justify early aggressive therapy in those with suspected rapid progression.

Therapeutic effect of liraglutide on expression of CTGF and BMP-7 in induced diabetic nephropathy

INTRODUCTION

Diabetic nephropathy (DN) is one of the critical complications of diabetes mellitus and the main cause of chronic renal dysfunction. The pathogenic mechanism causing the disease remains unclear and there is a lack of effective treatment methods so novel strategies are needed for DN management. The aim of this study, therefore, is to evaluate the effect of liraglutide as glucagon-like peptide-1 analogue and its underlying mechanisms on induced DN in rats MATERIALS AND METHODS: Sixty rats were divided into control group, diabetic group, and liraglutide-treated group. At the end of experiment, renal CTGF and BMP-7 messeger RNA expression were determined. Blood sugar, serum urea, and creatinine were measured. Also, histopathological changes were studied.

RESULTS

Liraglutide can improve renal alterations associated with diabetes as it reduced CTGF expression and increased BMP-7 expression. In the same time, it could improve histopathological changes and renal function tests.

CONCLUSION

These findings influence the beneficial use of liraglutide for the management of DN in patients with diabetes mellitus.

Participation of the SMAD2/3 signalling pathway in the down regulation of megalin/LRP2 by transforming growth factor beta (TGF-ß1)

Megalin/LRP2 is a receptor that plays important roles in the physiology of several organs, such as kidney, lung, intestine, and gallbladder and also in the physiology of the nervous system. Megalin expression is reduced in diseases associated with fibrosis, including diabetic nephropathy, hepatic fibrosis and cholelithiasis, as well as in some breast and prostate cancers. One of the hallmarks of these conditions is the presence of the cytokine transforming growth factor beta (TGF-ß). Although TGF-ß has been implicated in the reduction of megalin levels, the molecular mechanism underlying this regulation is not well understood. Here, we show that treatment of two epithelial cell lines (from kidney and gallbladder) with TGF-ß1 is associated with decreased megalin mRNA and protein levels, and that these effects are reversed by inhibiting the TGF-ß1 type I receptor (TGF-ßRI). Based on in silico analyses, the two SMAD-binding elements (SBEs) in the megalin promoter are located at positions -57 and -605. Site-directed mutagenesis of the SBEs and chromatin immunoprecipitation (ChIP) experiments revealed that SMAD2/3 transcription factors interact with SBEs. Both the presence of SMAD2/3 and intact SBEs were associated with repression of the megalin promoter, in the absence as well in the presence of TGF-ß1. Also, reduced megalin expression and promoter activation triggered by high concentration of albumin are dependent on the expression of SMAD2/3. Interestingly, the histone deacetylase inhibitor Trichostatin A (TSA), which induces megalin expression, reduced the effects of TGF-ß1 on megalin mRNA levels. These data show the significance of TGF-ß and the SMAD2/3 signalling pathway in the regulation of megalin and explain the decreased megalin levels observed under conditions in which TGF-ß is upregulated, including fibrosis-associated diseases and cancer.

Hypoxia causes important changes of extracellular matrix biomarkers and ADAMTS proteinases in the adriamycin-induced renal fibrosis model

AIM

Renal fibrosis is a common cause of renal dysfunction with chronic kidney diseases. This process is characterized by excessive production of extracellular matrix (ECM) or inhibition of ECM degradation. A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) proteinases, which are widely presented in mammals, have very critical roles in ECM remodelling. We aimed to study the role of ADAMTS proteinases and some of the ECM markers in the pathogenesis of renal fibrosis and to investigate the effects of hypoxia on these biomarkers.

METHODS

In addition to the control group, Adriamycin (ADR) treated rats were divided into four groups as ADR, sham and two hypoxia groups. Renal nephropathy was assessed biochemical assays, pathological and immunohistochemical staining methods. The expression of ADAMTSs and mRNA were determined using Western blotting and real-time PCR, respectively.

RESULTS

Renal dysfuntion and tissue damage in favour of ECM accumulation and renal fibrosis were observed in the ADR group. This was approved by remarkable changes in the expression of ADAMTS such as increased ADAMTS-1, -12 and -15. In addition, it was found that hypoxia and duration of hypoxia enhanced markers of tubulointerstitial fibrosis in the rat kidney tissues. Also, expression differences especially in ADAMTS-1, -6 and -15 were observed in the hypoxia groups. The variable and different expression patterns of ADAMTS proteinases in the ADR-induced renal fibrosis suggest that ADAMTS family members are involved in the development and progression of fibrosis.

CONCLUSION

The expression changes of ADAMTS proteinases in kidney and association with hypoxia have potential clues to contribute to the early diagnosis and treatment options of renal fibrosis.

Protective effects of Pai-Du-Yang-Shen formula on chronic renal failure in rats

This study aimed to elucidate the therapeutic effects of a traditional Chinese medicine, Pai-Du-Yang-Shen (PDYS) Formula, in 5/6 nephrectomy-induced chronic renal failure (CRF). The CRF model was established via 5/6 nephrectomy (Nx) in rats. Then, PDYS (0.9 and 1.8 g/kg/day), or an equal amount of normal saline, was administrated to the rats in respective groups. Our results showed that PDYS treatment improved degeneration, fibrosis, and histopathological abnormalities of renal tissues in 5/6 Nx rats. Furthermore, the increase in serum creatinine (Scr), blood urea nitrogen (BUN), and total urinary protein (TUP) in 5/6 Nx rats was reduced by PDYS treatment. In addition, the levels of tumor necrosis factor (TNF), fibronectin (FN), and laminin (LN) that were induced in 5/6 Nx rats were also decreased by PDYS treatment. Finally, relative mRNA expression of α-smooth muscle actin (α-SMA), FN, transforming growth factor-β (TGF-β), and TNF as well as protein levels of TGF-β, NF-κB p65, and phosphorylated NF-κB p65 (p-p65) in renal tissues correlated with the concentration of TNF. In conclusion, PDYS shows therapeutic effects against CRF as determined by a reduction in markers for inflammation and fibrosis.

Isoliquiritigenin alleviated the Ang II-induced hypertensive renal injury through suppressing inflammation cytokines and oxidative stress-induced apoptosis via Nrf2 and NF-κB pathways

PURPOSE

Hypertensive renal injury plays important role in the pathogenesis of end-stage nephropathy and the need for dialysis. Isoliquiritigenin (ISL) is a natural compound with antioxidant and anti-inflammatory activities. In this study, the protective effects of ISL on Angiotensin II (Ang II)- induced apoptosis, inflammation and extracellular matrix production in HK-2 cells were observed and its mechanisms were elucidated.

METHODS

Cell survival was determined with MTT assay. Cell cycle and apoptosis was assessed with flow cytometric analysis. The production of cytokines including IL-1β and TNF-α were evaluated with Elisa. Western blotting assay was used to determine protein levels of apoptosis related signaling, oxidative stress, NF-κB and ECM related molecules. mRNA levels of fibronectin and collagen Ⅳ were detected by RT-qPCR.

RESULTS

Ang II significantly inhibited cell survival, induced cell cycle arrest and enhanced cell apoptosis. However, the above effects were markedly alleviated by ISL treatment in a dose-dependent manner. In addition, Ang II significantly induced oxidative stress and NF-κB signaling activation, as well as inflammatory cytokines release. In contrast, these effects were remarkably reversed by ISL via regulation of Nrf2. Notably, Ang II also triggered generation of extracellular matrix, including fibronectin and collagen Ⅳ, which was abolished upon ISL treatment.

CONCLUSIONS

Taken together, ISL alleviated the Ang II-induced hypertensive renal injury through suppressing inflammation cytokines, excessive deposition of extracellular matrix and oxidative stress-induced apoptosis via Nrf2 and NF-κB pathways. Our findings provided the evidences for exploring the possible mechanism of hypertensive renal injury pathogenesis and identifying novel therapeutic targets.

The Role of Trio, a Rho Guanine Nucleotide Exchange Factor, in Glomerular Podocytes

Nephrotic syndrome is a kidney disease featured by heavy proteinuria. It is caused by injury to the specialized epithelial cells called “podocytes” within the filtration unit of the kidney, glomerulus. Previous studies showed that hyperactivation of the RhoGTPase, Rac1, in podocytes causes podocyte injury and glomerulosclerosis (accumulation of extracellular matrix in the glomerulus). However, the mechanism by which Rac1 is activated during podocyte injury is unknown. Trio is a guanine nucleotide exchange factor (GEF) known to activate Rac1. By RNA-sequencing, we found that Trio mRNA is abundantly expressed in cultured human podocytes. Trio mRNA was also significantly upregulated in humans with minimal change disease and focal segmental glomerulosclerosis, two representative causes of nephrotic syndrome. Reduced expression of Trio in cultured human podocytes decreased basal Rac1 activity, cell size, attachment to laminin, and motility. Furthermore, while the pro-fibrotic cytokine, transforming growth factor β1 increased Rac1 activity in control cells, it decreases Rac1 activity in cells with reduced Trio expression. This was likely due to simultaneous activation of the Rac1-GTPase activation protein, CdGAP. Thus, Trio is important in the basal functions of podocytes and may also contribute to glomerular pathology, such as sclerosis, via Rac1 activation.

Intermittent hypoxia causes histological kidney damage and increases growth factor expression in a mouse model of obstructive sleep apnea

Epidemiological studies demonstrate an association between obstructive sleep apnea (OSA) and accelerated loss of kidney function. It is unclear whether the decline in function is due to OSA per se or to other confounding factors such as obesity. In addition, the structural kidney abnormalities associated with OSA are unclear. The objective of this study was to determine whether intermittent hypoxia (IH), a key pathological feature of OSA, induces renal histopathological damage using a mouse model. Ten 8-week old wild-type male CB57BL/6 mice were randomly assigned to receive either IH or intermittent air (IA) for 60 days. After euthanasia, one kidney per animal was paraformaldehyde-fixed and then sectioned for histopathological and immunohistochemical analysis. Measurements of glomerular hypertrophy and mesangial matrix expansion were made in periodic acid–Schiff stained kidney sections, while glomerular transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF) and vascular endothelial growth factor-A (VEGF-A) proteins were semi-quantified by immunohistochemistry. The antigen-antibody reaction was detected by 3,3′-diaminobenzidine chromogen where the color intensity semi-quantified glomerular protein expression. To enhance the accuracy of protein semi-quantification, the percentage of only highly-positive staining was used for analysis. Levels of TGF-β, CTGF and VEGF-A proteins in the kidney cortex were further quantified by western blotting. Cellular apoptosis was also investigated by measuring cortical antiapoptotic B-cell lymphoma 2 (Bcl-2) and apoptotic Bcl-2-associated X (Bax) proteins by western blotting. Further investigation of cellular apoptosis was carried out by fluorometric terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) staining. Finally, the levels of serum creatinine and 24-hour urinary albumin were measured as a general index of renal function. Our results indicate that mice exposed to IH have an increased glomerular area (by 1.13 fold, p< 0.001) and expansion of mesangial matrix (by 1.8 fold, p< 0.01). Moreover, the glomerular expressions of TGF-β1, CTGF and VEGF-A proteins were 2.7, 2.2 and 3.8-fold higher in mice exposed to IH (p< 0.05 for all). Furthermore, western blotting protein analysis demonstrates that IH-exposed mice express higher levels of TGF-β1, CTGF and VEGF-A proteins by 1.9, 4.0 and 1.6-fold (p< 0.05 for all) respectively. Renal cellular apoptosis was greater in the IH group as shown by an increased cortical Bax/Bcl-2 protein ratio (p< 0.01) and higher fluorometric TUNEL staining (p< 0.001). Finally, 24-hr urinary albumin levels were higher in mice exposed to IH (43.4 μg vs 9.7 μg, p< 0.01), while there were no differences in serum creatinine levels between the two groups. We conclude that IH causes kidney injury that is accompanied by glomerular hypertrophy, mesangial matrix expansion, increased expression of glomerular growth factors and an increased cellular apoptosis.

Connective tissue growth factor induces renal fibrosis via epidermal growth factor receptor activation

Connective tissue growth factor (CCN2/CTGF) is a matricellular protein that is overexpressed in progressive human renal diseases, mainly in fibrotic areas. In vitro studies have demonstrated that CCN2 regulates the production of extracellular matrix (ECM) proteins and epithelial-mesenchymal transition (EMT), and could therefore contribute to renal fibrosis. CCN2 blockade ameliorates experimental renal damage, including diminution of ECM accumulation. We have reported that CCN2 and its C-terminal degradation product CCN2(IV) bind to epidermal growth factor receptor (EGFR) to modulate renal inflammation. However, the receptor involved in CCN2 profibrotic actions has not been described so far. Using a murine model of systemic administration of CCN2(IV), we have unveiled a fibrotic response in the kidney that was diminished by EGFR blockade. Additionally, in conditional CCN2 knockout mice, renal fibrosis elicited by folic acid-induced renal damage was prevented, and this was linked to inhibition of EGFR pathway activation. Our in vitro studies demonstrated a direct effect of CCN2 via the EGFR pathway on ECM production by fibroblasts and the induction of EMT in tubular epithelial cells. Our studies clearly show that the EGFR regulates CCN2 fibrotic signalling in the kidney, and suggest that EGFR pathway blockade could be a potential therapeutic option to block CCN2-mediated profibrotic effects in renal diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Endothelin A receptor blocker and calcimimetic in the adenine rat model of chronic renal insufficiency

BACKGROUND

We studied whether endothelin receptor antagonist and calcimimetic treatments influence renal damage and kidney renin-angiotensin (RA) components in adenine-induced chronic renal insufficiency (CRI).

METHODS

Male Wistar rats (n = 80) were divided into 5 groups for 12 weeks: control (n = 12), 0.3% adenine (Ade; n = 20), Ade + 50 mg/kg/day sitaxentan (n = 16), Ade + 20 mg/kg/day cinacalcet (n = 16), and Ade + sitaxentan + cinacalcet (n = 16). Blood pressure (BP) was measured using tail-cuff, kidney histology was examined, and RA components measured using RT-qPCR.

RESULTS

Adenine caused tubulointerstitial damage with severe CRI, anemia, hyperphosphatemia, 1.8-fold increase in urinary calcium excretion, and 3.5-fold and 18-fold increases in plasma creatinine and PTH, respectively. Sitaxentan alleviated tubular atrophy, while sitaxentan + cinacalcet combination reduced interstitial inflammation, tubular dilatation and atrophy in adenine-rats. Adenine diet did not influence kidney angiotensin converting enzyme (ACE) and AT₄ receptor mRNA, but reduced mRNA of renin, AT_1a, AT₂, (pro)renin receptor and Mas to 40-60%, and suppressed ACE2 to 6% of that in controls. Sitaxentan reduced BP by 8 mmHg, creatinine, urea, and phosphate concentrations by 16-24%, and PTH by 42%. Cinacalcet did not influence BP or creatinine, but reduced PTH by 84%, and increased hemoglobin by 28% in adenine-rats. The treatments further reduced renin mRNA by 40%, while combined treatment normalized plasma PTH, urinary calcium, and increased ACE2 mRNA 2.5-fold versus the Ade group (p < 0.001).

CONCLUSIONS

In adenine-induced interstitial nephritis, sitaxentan improved renal function and tubular atrophy. Sitaxentan and cinacalcet reduced kidney renin mRNA by 40%, while their combination alleviated tubulointerstitial damage and urinary calcium loss, and increased kidney tissue ACE2 mRNA.

Dencichine ameliorates kidney injury in induced type II diabetic nephropathy via the TGF-β/Smad signalling pathway

Diabetic nephropathy (DN), a common complication associated with both type I and type II diabetes mellitus (DM), is a major cause of chronic nephropathy and a common cause of end-stage renal diseases (ESRD) throughout the world. This study is aimed to determine whether dencichine (De) can ameliorate renal damage in high-glucose-and-fat diet combined STZ (streptozocin) induced DN in type II DM rats and to investigate the potential underlying mechanisms. Markers of metabolism, diabetes, and renal function, and levels of extracellular matrix (ECM) collagen I (Col I), collagen IV (Col IV), fibronectin (FN) and laminin (LN), and of proteins in the TGF-β/Smad pathway were analysed through RT-PCR, western blot, immunofluorescence and immunohistochemistry. The results show that De significantly alleviates metabolism disorder, improved renal function, relieved pathological alterations in the glomerulus of DN rats, decreased ECM deposition and increased the ratio of matrix metalloproteinase (MMP)-9 to tissue inhibitor of metalloproteinase (TIMP)-1 both in vivo and in vitro. Moreover, De negatively regulated TGF-β/Smad signalling pathway and increased the expression of Smad7, an endogenic inhibitory Smad located downstream of the signalling pathway. In conclusion, we provide experimental evidence indicating that the renoprotective effect of De could significantly prevent the progression of DN possibly attribute to down-regulation of the TGF-β/Smad pathway and rebalance the deposition and degradation of ECM proteins.

ARISTOLOCHIA BRACTEOLATE RETZ. ATTENUATES HYPERURICEMIA IN A METABOLIC ARTHRITIS RAT MODEL

Background:

The leaves of Aristolochia bracteolata Retz. has been documented in the folk medicine literature for its anti-arthritic activity. The target of the research envisaged was to elucidate the activity of A. bracteolata extract on hyperuricemic condition in arthritis rat model.

Materials and Methods:

Dried and powdered plant leaves were extracted using ether and chloroform. Potassium oxonate was injected intra-articularly to produce arthritis. The hyperuricemic effect, of A. bracteolate was analyzed by studying levels of uric acid in serum as well as in urine of arthritis induced rats. Effects of plant extracts were also studied on BUN (blood urea nitrogen) levels and fraction of uric acid excreted.

Results:

Results indicate that administration of A. bracteolata presented substantial change in uric acid concentration, augmented by potassium oxonate administration in rats. The reduction in levels of uric acid levels was nearly same as allopurinol. The investigation also revealed that the primary plant extract has nephroprotective effect by enhancing the production of Prostaglandin E₂ and Interleukin-1. Histological studies of rat kidney slices indicated the safety of the present plant extract.

Conclusion:

The crude extract of A. bracteolate can be used to reduce hyperuricemia in metabolic arthritis produced in rat model, without inducing any potential damaging effects.

Exogenous CGRP upregulates profibrogenic growth factors through PKC/JNK signaling pathway in kidney proximal tubular cells

Kidney denervation prevents the development of tubulointerstitial fibrosis, but the neuropeptide calcitonin gene-related peptide (CGRP) in the denervated kidneys restores the fibrotic feature through the upregulation of profibrogenic growth factors. CGRP is involved in aggravation of inflammation by increasing the number of circulating cells and chemotactic factors. However, it is not clear how CGRP contributes to the upregulation of profibrogenic factors during fibrogenesis. In both human and pig kidney proximal tubular cell lines, administration of 1 nM CGRP significantly increased the levels of transforming growth factor-β1 (TGF-β1) production and connective tissue growth factor (CTGF) expression at 6 and 24 h after the administration. Exogenous CGRP also increased the TGF-β1 and CTGF protein levels in the incubation media, indicating release of these proteins from the cells. Treatment with 100 nM CGRP receptor antagonist (CGRP^8-37) for 24 h significantly inhibited the increase in intracellular levels and released levels of TGF-β1 and CTGF in CGRP-treated cells. Genetic inhibition of CGRP receptor using siRNA transfection also suppressed the increase in TGF-β1 production and release at 24 h after CGRP stimulation. Furthermore, treatment with a specific protein kinase C (PKC) inhibitor chelerythrine (1 thru 10 μM) markedly reduced the upregulation and release of TGF-β1 and CTGF 6 h after CGRP administration. Finally, inhibition of c-Jun N-terminal protein kinase (JNK) phosphorylation using 1 μM SP600125 prevented the increase in TGF-β1 and CTGF upregulation and release 6 h after CGRP administration. Consistent with the in vitro data, exogenous CGRP in denervated UUO kidneys upregulated and secreted TGF-β1 and CTGF in dependence on PKC activation and JNK phosphorylation. In conclusion, these data suggest that exogenous CGRP induces the upregulation and secretion of profibrogenic TGF-β1 and CTGF proteins through the CGRP receptor/PKC/JNK signaling pathway in kidney proximal tubular cells.

Connective tissue growth factor regulates fibrosis-associated renal lymphangiogenesis

Lymphangiogenesis is correlated with the degree of renal interstitial fibrosis. Pro-fibrotic transforming growth factor β induces VEGF-C production, the main driver of lymphangiogenesis. Connective tissue growth factor (CTGF) is an important determinant of fibrotic tissue remodeling, but its possible involvement in lymphangiogenesis has not been explored. We found prominent lymphangiogenesis during tubulointerstitial fibrosis to be associated with increased expression of CTGF and VEGF-C in human obstructed nephropathy as well as in diabetic kidney disease. Using CTGF knockout mice, we investigated the involvement of CTGF in development of fibrosis and associated lymphangiogenesis in obstructive nephropathy. The increase of lymphatic vessels and VEGF-C in obstructed kidneys was significantly reduced in CTGF knockout compared to wild-type mice. Also in mouse kidneys subjected to ischemia-reperfusion injury, CTGF knockdown was associated with reduced lymphangiogenesis. In vitro, CTGF induced VEGF-C production in HK-2 cells, while CTGF siRNA suppressed transforming growth factor β1-induced VEGF-C upregulation. Furthermore, surface plasmon resonance analysis showed that CTGF and VEGF-C directly interact. Interestingly, VEGF-C-induced capillary-like tube formation by human lymphatic endothelial cells was suppressed by full-length CTGF but not by naturally occurring proteolytic CTGF fragments. Thus, CTGF is significantly involved in fibrosis-associated renal lymphangiogenesis through regulation of, and direct interaction with, VEGF-C.

ATP-citrate lyase is essential for high glucose-induced histone hyperacetylation and fibrogenic gene upregulation in mesangial cells

The goal of this study was to address the role of ATP-citrate lyase (ACL), an enzyme that converts citrate to acetyl-CoA, in high glucose (HG)-induced histone acetylation and profibrotic gene expression. Our recent ChIP-Seq studies have demonstrated that HG induces genome-wide histone hyperacetylation in mesangial cells (MCs). Here, we showed that exposure of MCs to HG markedly increased histone acetylation at the H3K9/14 and H3K18 marks and induced the expression of potent profibrotic factors TGF-β1, TGF-β3, and connective tissue growth factor (CTGF). The induction of these profibrotic factors was further enhanced by histone deacetylase inhibitor but suppressed by histone acetyl-transferase inhibitor, confirming the importance of histone acetylation in this regulation. Interestingly, HG not only upregulated ACL expression but also promoted ACL nuclear translocation, evidenced by increased ACL concentration and activity in the nuclear extracts. Consistent with this observation, transfection of MCs with a plasmid-carrying green fluorescent protein (GFP)-ACL fusion protein led to GFP nuclear accumulation when cultured in HG condition. Silencing ACL with siRNAs alleviated HG-induced histone hyperacetylation, as well as upregulation of TGF-β1, TGF-β3, CTGF, and extracellular matrix (ECM) proteins fibronectin and collagen type IV, whereas ACL overexpression further enhanced HG induction of histone acetylation, as well as these profibrotic factors and ECM proteins. Collectively, these observations demonstrate that HG promotes ACL expression and translocation into the nucleus, where ACL converts citrate to acetyl-CoA to provide the substrate for histone acetylation, leading to upregulation of fibrogenic genes. Therefore, ACL plays a critical role in epigenetic regulation of diabetic renal fibrosis.

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

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

Prunella vulgaris Attenuates Diabetic Renal Injury by Suppressing Glomerular Fibrosis and Inflammation

Diabetic nephropathy is both the most common complication and the leading cause of mortality associated with diabetes. Prunella vulgaris, a well-known traditional medicinal plant, is used for the cure of abscess, scrofula, hypertension and urinary diseases. This study confirmed whether an aqueous extract of Prunella vulgaris (APV) suppresses renal inflammation and fibrosis. In human mesangial cell (HMC), pretreatment of APV attenuated 25[Formula: see text]mM HG-induced suppressed TGF-[Formula: see text] and Smad-2/4 expression; it increased the expression level of Smad-7. Connective tissue growth factor (CTGF) and collagen IV, fibrosis biomarkers, were significantly decreased by APV. APV suppressed inflammatory factors such as intracellular cell adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1). APV inhibited activation and translocation of nuclear factor kappa-B (NF-[Formula: see text]B) in HG-stimulated HMCs. Moreover, APV significantly improved HG-induced ROS in a dose-dependent manner. In diabetic rat models, APV significantly decreased blood glucose, blood urea nitrogen (BUN) and ameliorated plasma creatinine (PCr). APV reduced the PAS positivity staining intensity and basement membrane thickening in glomeruli of diabetic rats. Fibrosis related proteins such as collagen IV and TGF-[Formula: see text]1 were also inhibited by APV. These results suggest that APV has a significant protective effect against diabetic renal dysfunction including inflammation and fibrosis through disruption of the TGF-[Formula: see text]/Smad signaling. Therefore, APV may be useful in potential therapies that target glomerulonephritis and glomerulosclerosis, which lead to diabetic nephropathy.

Smad3-dependent CCN2 mediates fibronectin expression in human skin dermal fibroblasts

The potential involvement of connective tissue growth factor (CCN2/CTGF) in extracellular matrix (ECM) production is recognized. However, the role CCN2 in fibronectin (FN) gene expression has remained incompletely understood and even controversial. Here we report that CCN2 is absolutely necessary for FN expression in primary human skin dermal fibroblasts, the major cells responsible for ECM production in skin. Gain- and loss-of-function approaches demonstrate that CCN2 is an essential component of FN expression in both basal and stimulation by TGF-β signaling, the major regulator of FN expression. CCN2 is significantly induced by Smad3, a critical mediator of TGF-β signaling. CCN2 acts as a downstream mediator of TGF-β/Smad signaling and acting synergistically with TGF-β to regulate FN gene expression. Finally, we observed that CCN2 and FN predominantly expressed in the dermis of normal human skin, stromal tissues of skin squamous cell carcinoma (SCC), and simultaneously induced in wounded human skin in vivo. These findings provide evidence that CCN2 is responsible for mediating the stimulatory effects of TGF-β/Smad on FN gene expression, and attenuation of CCN2 expression may benefit to reduce fibrotic ECM microenvironment in disease skin.

Critical role of the cAMP-PKA pathway in hyperglycemia-induced epigenetic activation of fibrogenic program in the kidney

Hyperglycemia is a major pathogenic factor that promotes diabetic nephropathy, but the underlying mechanism remains incompletely understood. Here, we show that high glucose induced cAMP response element-binding protein (CREB)-binding protein (CBP)-mediated H3K9/14 hyperacetylation in approximately 5000 gene promoters in glomerular mesangial cells, including those of Tgfb1, Tgfb3, and Ctgf, the major profibrotic factors that are known to drive diabetic renal fibrogenesis. In these promoters, H3K9/14 hyperacetylation was closely associated with NF-κB or CREB motifs. Chromatin immunoprecipitation assays confirmed that hyperglycemia promoted phospho-p65 or phospho-CREB and CBP bindings and RNA polymerase II recruitment to these promoters in mesangial cells as well as in glomeruli that were purified from type I and type II diabetic mice. Under hyperglycemia, cAMP production and PKA activity were markedly increased as a result of glucose transporter 1-mediated glucose influx that drives glucose metabolism and ATP production, which led to increased phosphorylation of p65 and CREB. Inhibition of adenylyl cyclase or PKA activity blocked p65 and CREB phosphorylation, CBP recruitment, and histone acetylation in these promoters. Collectively, these data demonstrate that the cAMP-PKA pathway plays a key role in epigenetic regulation of key profibrotic factors in diabetes.-Deb, D. K., Bao, R., Li, Y. C. Critical role of the cAMP-PKA pathway in hyperglycemia-induced epigenetic activation of fibrogenic program in the kidney.

Major review: Exfoliation syndrome; advances in disease genetics, molecular biology, and epidemiology

Exfoliation syndrome (XFS) is a common age-related disorder that leads to deposition of extracellular fibrillar material throughout the body. The most recognized disease manifestation is exfoliation glaucoma (XFG), which is a common cause of blindness worldwide. Recent developments in XFS genetics, cell biology and epidemiology have greatly improved our understanding of the etiology of this complex inherited disease. This review summarizes current knowledge of XFS pathogenesis, identifies gaps in knowledge, and discusses areas for future research.

Usp2-69 overexpression slows down the progression of rat anti-Thy1.1 nephritis

Mesangial proliferative glomerulonephritis is characterized by proliferation of mesangial cells (MCs) and transforming growth factor-β (TGF-β)-dependent stimulation of abnormal extracellular matrix (ECM) accumulation. We previously showed that Decorin--a leucine-rich proteoglycan inhibiting the progression of glomerulonephritis and glomerular sclerosis--can be degraded by the ubiquitin-proteasome pathway and deubiquitinated and stabilized by ubiquitin-specific processing protease 2-69(Usp2-69). Usp2-69 is highly expressed in the kidney and has been implicated in the regulation of cell proliferation and apoptosis. However, its role in mesangial proliferative glomerulonephritis remains unclear. Here, we explored the effect of Usp2-69 on MC proliferation and ECM deposition by transfecting Usp2-69 plasmid into rat anti-Thy1.1 nephritis model and into cultured MCs, as well as detected Usp2-69 and Decorin in rat anti-Thy1.1 nephritis model by western blot. Overexpressing Usp2-69 at the early stage, but not advanced stage, of anti-Thy1.1 nephritis alleviated cell proliferation and ECM deposition, which was shown by decreased Ki-67, Collagen IV and Fibronectin detected by immunohistochemistry. Overexpression also increased Decorin and decreased TGF-β1 and Collagen IV both in vitro and in vivo. In conclusion, our findings suggest that Usp2-69 overexpression alleviates the progression of rat anti-Thy1.1 nephritis and, therefore, that exogenous plasmid injection via the renal artery enhanced by electrotransfer technology could be a promising avenue for glomerular disease research.

Reduced expression of VAChT increases renal fibrosis

Chronic kidney disease (CKD) is associated with several other long-lasting conditions such as diabetes and cardiovascular diseases and it is a significant contributor to mortality worldwide. Obstructive kidney disease is one of the leading causes of CKD in children and may result from a wide variety of pathologic processes. Recent studies have shown that α7 nicotinic acetylcholine receptor (α7 nAChR) activation in the cholinergic anti-inflammatory pathway reduces production of inflammatory mediators and consequently prevents tissue injury and death. Here, we examined the role of endogenous release of acetylcholine on the development of fibrosis in renal tissue using a model of unilateral ureter obstruction (UUO)-induced CKD, in which obstruction promotes inflammation-mediated kidney damages. To interfere with acetylcholine secretion, we used mice in which the vesicular acetylcholine transporter is genetically reduced (VAChT KD(hom) mice). We observed a higher renal damage in VAChT mutant mice when compared to wild type controls, exemplified by higher proteinuria and increased amount of type 1 collagen in the kidney tissue, indicating accentuated fibrogenesis. These results were accompanied by enhanced localized kidney inflammation, with increased TH1/TH17 profile response. Administration of PNU-282987, a selective agonist of α7 nAChR, significantly attenuated kidney injury after UUO in VAChT KD(hom) mice, indicating that the lack of acetylcholine release decrease the action of the cholinergic anti-inflammatory pathway, promoting an up-regulation of pro-inflammatory and pro-fibrotic pathways. These results suggest that physiological activation of the cholinergic anti-inflammatory pathway regulates inflammatory responses in the kidney suggesting a new therapeutic approach for kidney disease.

New EGFR inhibitor, 453, prevents renal fibrosis in angiotensin II-stimulated mice

Chronic activation of renin-angiotensin system (RAS) greatly contributes to renal fibrosis through the over expression of angiotensin (Ang) II, ultimately leading to chronic kidney disease (CKD). As the main peptide in the RAS, Ang II is a key regulator of nephrotic inflammation, fibrogenic destruction and hypertensive nephropathy. Controlled by growth factors such as TGF-β, Ang II is thought to be affected by other such growth factors including epidermal growth factor (EGF) due to its ability to stimulate growth, regulate angiogenesis, and desensitize cells from apoptotic stimuli. Here we show that epidermal growth factor receptor (EGFR) plays a key role in Ang II induced renal fibrosis and its inhibition for the use as an effective treatment of CKD. 453, an AG1478 analog, was used to block the EGF-EGFR interaction in vivo in 4-week old mice treated with Ang II and 453. Along with the inhibition of EGFR and its downstream signaling pathways (AKT and ERK), 453 also prevented the activation of fibrotic (collagen, CFGF, TGF-β), inflammatory (COX2, IL-6, IL-1β, TNF-α), apoptosis and oxidative stress pathways. These findings suggest the use of 453 as a novel EGFR-inhibitor for therapeutic use in CKD kidney dysfunction.

Role of connective tissue growth factor in vascular and renal damage associated with hypertension in rats. Interactions with angiotensin II

We have evaluated the role of connective tissue growth factor (CTGF) in vascular and renal damage associated with hypertension and possible interactions with angiotensin II (Ang II). Spontaneously hypertensive rats (SHR) were treated with either the Ang II receptor antagonist candesartan (C;2 mg/Kg-1/day-1) or antihypertensive triple therapy (TT; in mg/Kg-1/day-1 ;20 hydralazine +7 hydrochlorothiazide +0.15 reserpine) for 10 weeks. Wistar Kyoto rats were used as a normotensive control group. Hypertension was associated with an increase in aortic media area, media-to-lumen ratio and collagen density. Kidneys from SHR showed minimum renal alterations. Aorta and renal gene expression and immunostaining of CTGF were higher in SHR. Candesartan decreased arterial pressure, aortic media area, media-to-lumen ratio and collagen density. However, although arterial pressure decrease was comparable for both treatments,TT partially reduced these parameters. Candesartantreated rats showed lower levels of vascular CTGF expression, aortic media area, media-to-lumen ratio and collagen density than TT-treated animals. Treatments improve renal damage and reduce renal gene exp Pression and CTGF immunostaining in SHR in a similar manner.The results show that vascular and renal damage is associated with stimulation of CTGF gene and protein content.These results also might suggest that CTGF could be one downstream mediator of Ang II in hypertension-associated organ damage in SHR.

Balanced regulation of the CCN family of matricellular proteins: a novel approach to the prevention and treatment of fibrosis and cancer

The CCN family of matricellular signaling proteins is emerging as a unique common link across multiple diseases and organs related to injury and repair. They are now being shown to play a central role in regulating the pathways to the initiation and resolution of normal wound healing and fibrosis in response to multiple forms of injury. Similarly, it is also emerging that they play a key role in regulating the establishment, growth, metastases and tissue regeneration in many forms of cancer via the interaction of cancer cells with the tumor stroma. Evidence has been recently provided that these proteins do not act independently but are co-regulated working in a yin/yang manner to alter the outcome of both normal physiological processes as well as pathology. The purpose of this review is to twofold. First, it will summarize work to date supporting CCN2 as a therapeutic target in the formation and progression of renal, skin, and other organ fibrosis, as well as cancer stroma formation. Second, it will highlight recent evidence for CCN3 as a counter-regulator and a potential therapeutic agent in these diseases with an exciting, novel potential to both treat and then restore tissue homeostasis in those afflicted by these devastating disorders.

Cytokine Regulation of Microenvironmental Cells in Myeloproliferative Neoplasms

The term myeloproliferative neoplasms (MPN) refers to a heterogeneous group of diseases including not only polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), but also chronic myeloid leukemia (CML), and systemic mastocytosis (SM). Despite the clinical and biological differences between these diseases, common pathophysiological mechanisms have been identified in MPN. First, aberrant tyrosine kinase signaling due to somatic mutations in certain driver genes is common to these MPN. Second, alterations of the bone marrow microenvironment are found in all MPN types and have been implicated in the pathogenesis of the diseases. Finally, elevated levels of proinflammatory and microenvironment-regulating cytokines are commonly found in all MPN-variants. In this paper, we review the effects of MPN-related oncogenes on cytokine expression and release and describe common as well as distinct pathogenetic mechanisms underlying microenvironmental changes in various MPN. Furthermore, targeting of the microenvironment in MPN is discussed. Such novel therapies may enhance the efficacy and may overcome resistance to established tyrosine kinase inhibitor treatment in these patients. Nevertheless, additional basic studies on the complex interplay of neoplastic and stromal cells are required in order to optimize targeting strategies and to translate these concepts into clinical application.

MicroRNA-26a inhibits TGF-β-induced extracellular matrix protein expression in podocytes by targeting CTGF and is downregulated in diabetic nephropathy

AIMS/HYPOTHESIS

The accumulation of extracellular matrix (ECM) is a characteristic of diabetic nephropathy, and is partially caused by profibrotic proteins TGF-β and connective tissue growth factor (CTGF). We aimed to identify microRNAs (miRNAs) targeting CTGF on podocytes in diabetic nephropathy.

METHODS

We investigated miRNAs targeting CTGF on podocytes with miRNA array analysis and identified a candidate miRNA, miR-26a. Using overexpression and silencing of miR-26a in cultured podocytes, we examined changes of ECM and its host genes. We further investigated glomerular miR-26a expression in humans and in mouse models of diabetic nephropathy.

RESULTS

miR-26a, which was downregulated by TGF-β1, was expressed in glomerular cells including podocytes and in tubules by in situ hybridisation. Glomerular miR-26a expression was downregulated by 70% in streptozotocin-induced diabetic mice. Transfection of miR-26a mimics in cultured human podocytes decreased the CTGF protein level by 50%, and directly inhibited CTGF expression in podocytes, as demonstrated by a reporter assay with the 3'-untranslated region of the CTGF gene. This effect was abolished by a mutant plasmid. miR-26a mimics also inhibited TGF-β1-induced collagen expression, SMAD-binding activity and expression of its host genes CTDSP2 and CTDSPL. Knockdown of CTDSP2 and CTDSPL increased collagen expression in TGF-β-stimulated podocytes, suggesting that host genes also regulate TGF-β/SMAD signalling. Finally, we observed a positive correlation between microdissected glomerular miR-26a expression levels and estimated GFR in patients with diabetic nephropathy.

CONCLUSIONS/INTERPRETATION

The downregulation of miR-26a is involved in the progression of diabetic nephropathy both in humans and in mice through enhanced TGF-β/CTGF signalling.

Fibrosis Related Inflammatory Mediators: Role of the IL-10 Cytokine Family

Importance of chronic fibroproliferative diseases (FDs) including pulmonary fibrosis, chronic kidney diseases, inflammatory bowel disease, and cardiovascular or liver fibrosis is rapidly increasing and they have become a major public health problem. According to some estimates about 45% of all deaths are attributed to FDs in the developed world. Independently of their etiology the common hallmark of FDs is chronic inflammation. Infiltrating immune cells, endothelial, epithelial, and other resident cells of the injured organ release an orchestra of inflammatory mediators, which stimulate the proliferation and excessive extracellular matrix (ECM) production of myofibroblasts, the effector cells of organ fibrosis. Abnormal amount of ECM disturbs the original organ architecture leading to the decline of function. Although our knowledge is rapidly expanding, we still have neither a diagnostic tool to detect nor a drug to specifically target fibrosis. Therefore, there is an urgent need for the more comprehensive understanding of the pathomechanism of fibrosis and development of novel diagnostic and therapeutic strategies. In the present review we provide an overview of the common key mediators of organ fibrosis highlighting the role of interleukin-10 (IL-10) cytokine family members (IL-10, IL-19, IL-20, IL-22, IL-24, and IL-26), which recently came into focus as tissue remodeling-related inflammatory cytokines.

The Function of Matricellular Proteins in the Lamina Cribrosa and Trabecular Meshwork in Glaucoma

PURPOSE

To review the current literature regarding the role of matricellular proteins in glaucoma, specifically in the lamina cribrosa (LC) region of the optic nerve head (ONH) and the trabecular meshwork (TM).

METHODS

A literature search was performed for published articles describing the expression and function of matricellular proteins such as thrombospondin (TSP), connective tissue growth factor (CTGF), secreted protein acidic and rich in cysteine (SPARC), and periostin in glaucoma.

RESULTS

In glaucoma, there are characteristic extracellular matrix (ECM) changes associated with optic disc cupping in the ONH and subsequent visual field defects. Matricellular proteins are a family of nonstructural secreted glycoproteins, which enable cells to communicate with their surrounding ECM, including CTGF, also known as CCN2, TSPs, SPARC, periostin, osteonectin, and tenascin-C and -X, and other ECM proteins. Such proteins appear to play a role in fibrosis and increased ECM deposition. Importantly, most are widely expressed in tissues particularly in the TM and ONH, and deficiency of TSP1 and SPARC has been shown to lower intraocular pressure in mouse models of glaucoma through enhanced outflow facility.

CONCLUSION

This article highlights the role of matricellular proteins in glaucoma pathology. The potential role of these proteins in glaucoma is emerging as some have an association with the pathophysiology of the TM and LC region and might therefore be potential targets for therapeutic intervention in glaucoma.

Acetaminophen attenuates glomerulosclerosis in obese Zucker rats via reactive oxygen species/p38MAPK signaling pathways

Focal segmental glomerulosclerosis is a critical pathological lesion in metabolic syndrome-associated kidney disease that, if allowed to proceed unchecked, can lead to renal failure. However, the exact mechanisms underlying glomerulosclerosis remain unclear, and effective prevention strategies against glomerulosclerosis are currently limited. Herein, we demonstrate that chronic low-dose ingestion of acetaminophen (30 mg/kg/day for 6 months) attenuates proteinuria, glomerulosclerosis, podocyte injury, and inflammation in the obese Zucker rat model of metabolic syndrome. Moreover, acetaminophen treatment attenuated renal fibrosis and the expression of profibrotic factors (fibronectin, connective tissue growth factor, transforming growth factor β), reduced inflammatory cell infiltration into the glomeruli, and decreased the expression of monocyte chemoattractant protein, glutathione (GSH) reductase, and nuclear factor erythroid 2-related factor 2, but increased the level of GSH synthetase in obese animals. Further in vivo and in vitro studies using human renal mesangial cells exposed to high glucose or hydrogen peroxide suggested that the renoprotective effects of acetaminophen are characterized by diminished renal oxidative stress and p38MAPK hyperphosphorylation.