Selective activation of epidermal growth factor receptor in renal proximal tubule induces tubulointerstitial fibrosis

Targeting the epidermal growth factor receptor (EGFR/ErbB) for the potential treatment of renal pathologies

Epidermal growth factor receptor (EGFR), which is referred to as ErbB1/HER1, is the prototype of the EGFR family of receptor tyrosine kinases which also comprises ErbB2 (Neu, HER2), ErbB3 (HER3), and ErbB4 (HER4). EGFR, along with other ErbBs, is expressed in the kidney tubules and is physiologically involved in nephrogenesis and tissue repair, mainly following acute kidney injury. However, its sustained activation is linked to several kidney pathologies, including diabetic nephropathy, hypertensive nephropathy, glomerulonephritis, chronic kidney disease, and renal fibrosis. This review aims to provide a summary of the recent findings regarding the consequences of EGFR activation in several key renal pathologies. We also discuss the potential interplay between EGFR and the reno-protective angiotensin-(1-7) (Ang-(1-7), a heptapeptide member of the renin-angiotensin-aldosterone system that counter-regulates the actions of angiotensin II. Ang-(1-7)-mediated inhibition of EGFR transactivation might represent a potential mechanism of action for its renoprotection. Our review suggests that there is a significant body of evidence supporting the potential inhibition of EGFR/ErbB, and/or administration of Ang-(1-7), as potential novel therapeutic strategies in the treatment of renal pathologies. Thus, EGFR inhibitors such as Gefitinib and Erlinotib that have an acceptable safety profile and have been clinically used in cancer chemotherapy since their FDA approval in the early 2000s, might be considered for repurposing in the treatment of renal pathologies.

Emodin inhibits M1 macrophage activation that related to acute and chronic kidney injury through EGFR/MAPK pathway

BACKGROUND

Macrophages are the main inflammatory cells involved in kidney injury and play a significant role in the development of acute kidney injury (AKI) and progression of chronic kidney disease (CKD). Emodin is believed to stabilize macrophage homeostasis under pathological conditions. The objective of this study aimed to explore the underlying mechanisms and effects of Emodin on M1 macrophages.

METHODS

Network pharmacology methods were used to predict target proteins associated with renal injury and identify the pathways affected by emodin. RAW264.7 macrophages were induced into M1 polarization using LPS and then treated with emodin at 20, 40, and 80 µM. The effects of emodin on cell viability, cytokines (IL-1β, IL-6, TNF-α), M1 macrophage markers (F4/80 + CD86+), and the EGFR/MAPK pathway were evaluated. Additionally, we transfected RAW264.7 cells with an EGFR shRNA interference lentivirus to assess its effects on RAW264.7 cells function and MAPK pathway. After RAW264.7 cells were passaged to expanded culture and transfected with EGFR-interfering plasmid, macrophages were induced to polarize towards M1 with LPS and then treated with 80 µM emodin. CKD modeling was performed to test how emodin is regulated during CKD.

RESULTS

There are 15 common targets between emodin and kidney injury, of which the EGFR/MAPK pathway is the pathway through which emodin affects macrophage function. Emodin significantly reduced the levels of IL-6, IL-1β and TNF-α (p < 0.05) and the ratio of M1 macrophage surface markers F4/80 + CD86+ (p < 0.01) in the supernatant of RAW264.7 cells in a dose-dependent manner. Furthermore, the inhibitory effect of emodin on RAW264.7 cells was achieved by interfering with the EGFR/MAPK pathway. Moreover, emodin also affected the mRNA and protein expression of EGFR and Ras, leading to a decrease in the rate of M1 macrophages, thus inhibiting the pro-inflammatory effect of M1 macrophages. The addition of emodin reduced the rate of M1 macrophages in CKD and inhibited the further polarization of M1 macrophages, thus maintaining the pro-inflammatory and anti-inflammatory homeostasis in CKD, and these effects were achieved by emodin through the control of the EGRF/ERK pathway.

CONCLUSION

Emodin attenuates M1 macrophage polarization and pro-inflammatory responses via the EGFR/MAPK signalling pathway. And the addition of emodin maintains pro- and anti-inflammatory homeostasis, which is important for maintaining organ function and tissue repair.

Clinical significance of amphiregulin in patients with chronic kidney disease

BACKGROUND

Amphiregulin (AREG) is a ligand of epidermal growth factor receptor (EGFR), which plays an important role in injury-induced kidney fibrosis. However, the clinical significance of serum soluble AREG in chronic kidney disease (CKD) is unclear. In this study, we elucidated the clinical significance of serum soluble AREG in CKD by analyzing the association of serum soluble AREG levels with renal function and other clinical parameters in patients with CKD.

METHODS

In total, 418 Japanese patients with CKD were enrolled, and serum samples were collected for the determination of soluble AREG and creatinine (Cr) levels, and other clinical parameters. Additionally, these parameters were evaluated after 2 and 3 years. Moreover, immunohistochemical assay was performed ate AREG expression in the kidney tissues of patients with CKD.

RESULTS

Soluble AREG levels were positively correlated with serum Cr (p < 0.0001). Notably, initial AREG levels were positively correlated with changes in renal function (ΔCr) after 2 (p < 0.0001) and 3 years (P = 0.048). Additionally, soluble AREG levels were significantly higher (p < 0.05) in patients with diabetic nephropathy or primary hypertension. Moreover, AREG was highly expressed in renal tubular cells in patients with advanced CKD, but only weakly expressed in patients with preserved renal function.

CONCLUSION

Serum soluble AREG levels were significantly correlated with renal function, and changes in renal function after 2 and 3 years, indicating that serum soluble AREG levels might serve as a biomarker of renal function and renal prognosis in CKD.

Identification of STAT3 as a biomarker for cellular senescence in liver fibrosis: A bioinformatics and experimental validation study

BACKGROUND

Cellular senescence is associated with a dysregulated inflammatory response, which is an important driver of the development of liver fibrosis (LF). This study aimed to investigate the effect of cellular senescence on LF and identify potential key biomarkers through bioinformatics analysis combined with validation experiments in vivo and in vitro.

METHODS

The Gene Expression Omnibus (GEO) database and GeneCards database were used to download the LF dataset and the aging-related gene set, respectively. Functional enrichment analysis of differential genes was then performed using GO and KEGG. Hub genes were further screened using Cytoscape's cytoHubba. Diagnostic values for hub genes were evaluated with a receiver operating characteristic (ROC) curve. Next, CIBERSORTx was used to estimate immune cell types and ratios. Finally, in vivo and in vitro experiments validated the results of the bioinformatics analysis. Moreover, molecular docking was used to simulate drug-gene interactions.

RESULTS

A total of 44 aging-related differentially expressed genes (AgDEGs) were identified, and enrichment analysis showed that these genes were mainly enriched in inflammatory and immune responses. PPI network analysis identified 6 hub AgDEGs (STAT3, TNF, MMP9, CD44, TGFB1, and TIMP1), and ROC analysis showed that they all have good diagnostic value. Immune infiltration suggested that hub AgDEGs were significantly associated with M1 macrophages or other immune cells. Notably, STAT3 was positively correlated with α-SMA, COL1A1, IL-6 and IL-1β, and was mainly expressed in hepatocytes (HCs). Validation experiments showed that STAT3 expression was upregulated and cellular senescence was increased in LF mice. A co-culture system of HCs and hepatic stellate cells (HSCs) further revealed that inhibiting STAT3 reduced HCs senescence and suppressed HSCs activation. In addition, molecular docking revealed that STAT3 was a potential drug therapy target.

CONCLUSIONS

STAT3 may be involved in HCs senescence and promote HSCs activation, which in turn leads to the development of LF. Our findings suggest that STAT3 could be a potential biomarker for LF.

Crosstalk between proximal tubular epithelial cells and other interstitial cells in tubulointerstitial fibrosis after renal injury

The energy needs of tubular epithelial components, especially proximal tubular epithelial cells (PTECs), are high and they heavily depend on aerobic metabolism. As a result, they are particularly vulnerable to various injuries caused by factors such as ischemia, proteinuria, toxins, and elevated glucose levels. Initial metabolic and phenotypic changes in PTECs after injury are likely an attempt at survival and repair. Nevertheless, in cases of recurrent or prolonged injury, PTECs have the potential to undergo a transition to a secretory state, leading to the generation and discharge of diverse bioactive substances, including transforming growth factor-β, Wnt ligands, hepatocyte growth factor, interleukin (IL)-1β, lactic acid, exosomes, and extracellular vesicles. By promoting fibroblast activation, macrophage recruitment, and endothelial cell loss, these bioactive compounds stimulate communication between epithelial cells and other interstitial cells, ultimately worsening renal damage. This review provides a summary of the latest findings on bioactive compounds that facilitate the communication between these cellular categories, ultimately leading to the advancement of tubulointerstitial fibrosis (TIF).

Epidermal growth factor receptor activation is essential for kidney fibrosis development

Fibrosis is the progressive accumulation of excess extracellular matrix and can cause organ failure. Fibrosis can affect nearly every organ including kidney and there is no specific treatment currently. Although Epidermal Growth Factor Receptor (EGFR) signaling pathway has been implicated in development of kidney fibrosis, underlying mechanisms by which EGFR itself mediates kidney fibrosis have not been elucidated. We find that EGFR expression increases in interstitial myofibroblasts in human and mouse fibrotic kidneys. Selective EGFR deletion in the fibroblast/pericyte population inhibits interstitial fibrosis in response to unilateral ureteral obstruction, ischemia or nephrotoxins. In vivo and in vitro studies and single-nucleus RNA sequencing analysis demonstrate that EGFR activation does not induce myofibroblast transformation but is necessary for the initial pericyte/fibroblast migration and proliferation prior to subsequent myofibroblast transformation by TGF-ß or other profibrotic factors. These findings may also provide insight into development of fibrosis in other organs and in other conditions.

A single administration of FGF2 after renal ischemia-reperfusion injury alleviates post-injury interstitial fibrosis

BACKGROUND

Despite lack of clinical therapy in acute kidney injury (AKI) or its progression to chronic kidney disease (CKD), administration of growth factors shows great potential in the treatment of renal repair and further fibrosis. At an early phase of AKI, administration of exogenous fibroblast growth factor 2 (FGF2) protects against renal injury by inhibition of mitochondrial damage and inflammatory response. Here, we investigated whether this treatment attenuates the long-term renal interstitial fibrosis induced by ischemia-reperfusion (I/R) injury.

METHODS

Unilateral renal I/R with contralateral nephrectomy was utilized as an in vivo model for AKI and subsequent CKD. Rats were randomly divided into four groups: Sham-operation group, I/R group, I/R-FGF2 group and FGF2-3D group. These groups were monitored for up to 2 months. Serum creatinine, inflammatory response and renal histopathology changes were detected to evaluate the role of FGF2 in AKI and followed renal interstitial fibrosis. Moreover, the expression of vimentin, α-SMA, CD31 and CD34 were examined.

RESULTS

Two months after I/R injury, the severity of renal interstitial fibrosis was significantly attenuated in both of I/R-FGF2 group and FGF2-3D group, compared with the I/R group. The protective effects of FGF2 administration were associated with the reduction of high-mobility group box 1 (HMGB1)-mediated inflammatory response, the inhibition of transforming growth factor beta (TGF-β1)/Smads signaling-induced epithelial-mesenchymal transition and the maintenance of peritubular capillary structure.

CONCLUSIONS

A single dose of exogenous FGF2 administration 1 h or 3 days after reperfusion inhibited renal fibrogenesis and thus blocked the transition of AKI to CKD. Our findings provided novel insight into the role of FGF signaling in AKI-to-CKD progression and underscored the potential of FGF-based therapy for this devastating disease.

Potential therapeutic target of EGF on bile duct ligation model and biliary atresia children

BACKGROUND

The pathogenesis of liver fibrosis in biliary atresia (BA) is unclear. Epidermal growth factor (EGF) plays a vital role in liver fibrosis. This study aims to investigate the expression of EGF and the mechanisms of its pro-fibrotic effects in BA.

METHODS

EGF levels in serum and liver samples of BA and non-BA children were detected. Marker proteins of EGF signaling and epithelial-mesenchymal transition (EMT) in liver sections were evaluated. Effects of EGF on intrahepatic cells and the underlying mechanisms were explored in vitro. Bile duct ligation (BDL) mice with/without EGF antibody injection were used to verify the effects of EGF on liver fibrosis.

RESULTS

Serum levels and liver expression of EGF elevated in BA. Phosphorylated EGF receptor (p-EGFR) and extracellular regulated kinase 1/2 (p-ERK1/2) increased. In addition, EMT and proliferation of biliary epithelial cells were present in BA liver. In vitro, EGF induced EMT and proliferation of HIBEpic cells and promoted IL-8 expression in L-02 cells by phosphorylating ERK1/2. And EGF activated LX-2 cells. Furthermore, EGF antibody injection reduced p-ERK1/2 levels and alleviated liver fibrosis in BDL mice.

CONCLUSION

EGF is overexpressed in BA. It aggravates liver fibrosis through EGF/EGFR-ERK1/2 pathway, which may be a therapeutic target for BA.

IMPACT

The exact pathogenesis of liver fibrosis in BA is unknown, severely limiting the advancement of BA treatment strategies. This study revealed that serum and liver tissue levels of EGF were increased in BA, and its expression in liver tissues was correlated with the degree of liver fibrosis. EGF may promote EMT and proliferation of biliary epithelial cells and induce IL-8 overexpression in hepatocytes through EGF/EGFR-ERK1/2 signaling pathway. EGF can also activate HSCs in vitro. The EGF/EGFR-ERK1/2 pathway may be a potential therapeutic target for BA.

Analysis of the potential biological mechanisms of diosmin against renal fibrosis based on network pharmacology and molecular docking approach

BACKGROUND

Interstitial fibrosis is involved in the progression of various chronic kidney diseases and renal failure. Diosmin is a naturally occurring flavonoid glycoside that has antioxidant, anti-inflammatory, and antifibrotic activities. However, whether diosmin protects kidneys by inhibiting renal fibrosis is unknown.

METHODS

The molecular formula of diosmin was obtained, targets related to diosmin and renal fibrosis were screened, and interactions among overlapping genes were analyzed. Overlapping genes were used for gene function and KEGG pathway enrichment analysis. TGF-β1 was used to induce fibrosis in HK-2 cells, and diosmin treatment was administered. The expression levels of relevant mRNA were then detected.

RESULTS

Network analysis identified 295 potential target genes for diosmin, 6828 for renal fibrosis, and 150 hub genes. Protein-protein interaction network results showed that CASP3, SRC, ANXA5, MMP9, HSP90AA1, IGF1, RHOA, ESR1, EGFR, and CDC42 were identified as key therapeutic targets. GO analysis revealed that these key targets may be involved in the negative regulation of apoptosis and protein phosphorylation. KEGG indicated that pathways in cancer, MAPK signaling pathway, Ras signaling pathway, PI3K-Akt signaling pathway, and HIF-1 signaling pathway were key pathways for renal fibrosis treatment. Molecular docking results showed that CASP3, ANXA5, MMP9, and HSP90AA1 stably bind to diosmin. Diosmin treatment inhibited the protein and mRNA levels of CASP3, MMP9, ANXA5, and HSP90AA1. Network pharmacology analysis and experimental results suggest that diosmin ameliorates renal fibrosis by decreasing the expression of CASP3, ANXA5, MMP9, and HSP90AA1.

CONCLUSIONS

Diosmin has a potential multi-component, multi-target, and multi-pathway molecular mechanism of action in the treatment of renal fibrosis. CASP3, MMP9, ANXA5, and HSP90AA1 might be the most important direct targets of diosmin.

TNF or EGFR inhibition equally block AKI-to-CKD transition: opportunities for etanercept treatment

BACKGROUND

Inflammation is a key driver of the transition of acute kidney injury to progressive fibrosis and chronic kidney disease (AKI-to-CKD transition). Blocking a-disintegrin-and-metalloprotease-17 (ADAM17)-dependent ectodomain shedding, in particular of epidermal growth factor receptor (EGFR) ligands and of the type 1 inflammatory cytokine tumor necrosis factor (TNF), reduces pro-inflammatory and pro-fibrotic responses after ischemic AKI or unilateral ureteral obstruction (UUO), a classical fibrosis model. Metalloprotease or EGFR inhibition show significant undesirable side effects in humans. In retrospective studies anti-TNF biologics reduce the incidence and progression of CKD in humans. Whether TNF has a role in AKI-to-CKD transition and how TNF inhibition compares to EGFR inhibition is largely unknown.

METHODS

Mice were subjected to bilateral renal ischemia-reperfusion injury or unilateral ureteral obstruction. Kidneys were analyzed by histology, immunohistochemistry, qPCR, western blot, mass cytometry, scRNA sequencing, and cytokine profiling.

RESULTS

Here we show that TNF or EGFR inhibition reduce AKI-to-CKD transition and fibrosis equally by about 25%, while combination has no additional effect. EGFR inhibition reduced kidney TNF expression by about 50% largely by reducing accumulation of TNF expressing immune cells in the kidney early after AKI, while TNF inhibition did not affect EGFR activation or immune cell accumulation. Using scRNAseq data we show that TNF is predominantly expressed by immune cells in AKI but not in proximal tubule cells (PTC), and PTC-TNF knockout did not affect AKI-to-CKD transition in UUO. Thus, the anti-inflammatory and anti-fibrotic effects of the anti-TNF biologic etanercept in AKI-to-CKD transition rely on blocking TNF that is released from immune cells recruited or accumulating in response to PTC-EGFR signals.

CONCLUSION

Short-term anti-TNF biologics during or after AKI could be helpful in the prevention of AKI-to-CKD transition.

YY1-induced upregulation of LncRNA-ARAP1-AS2 and ARAP1 promotes diabetic kidney fibrosis via aberrant glycolysis associated with EGFR/PKM2/HIF-1α pathway

Objectives: Dimeric pyruvate kinase (PK) M2 (PKM2) plays an important role in promoting the accumulation of hypoxia-inducible factor (HIF)-1α, mediating aberrant glycolysis and inducing fibrosis in diabetic kidney disease (DKD). The aim of this work was to dissect a novel regulatory mechanism of Yin and Yang 1 (YY1) on lncRNA-ARAP1-AS2/ARAP1 to regulate EGFR/PKM2/HIF-1α pathway and glycolysis in DKD. Materials and methods: We used adeno-associated virus (AAV)-ARAP1 shRNA to knocked down ARAP1 in diabetic mice and overexpressed or knocked down YY1, ARAP1-AS2 and ARAP1 expression in human glomerular mesangial cells. Gene levels were assessed by Western blotting, RT-qPCR, immunofluorescence staining and immunohistochemistry. Molecular interactions were determined by RNA pull-down, co-immunoprecipitation, ubiquitination assay and dual-luciferase reporter analysis. Results: YY1, ARAP1-AS2, ARAP1, HIF-1α, glycolysis and fibrosis genes expressions were upregulated and ARAP1 knockdown could inhibit dimeric PKM2 expression and partly restore tetrameric PKM2 formation, while downregulate HIF-1α accumulation and aberrant glycolysis and fibrosis in in-vivo and in-vitro DKD models. ARAP1 knockdown attenuates renal injury and renal dysfunction in diabetic mice. ARAP1 maintains EGFR overactivation in-vivo and in-vitro DKD models. Mechanistically, YY1 transcriptionally upregulates ARAP1-AS2 and indirectly regulates ARAP1 and subsequently promotes EGFR activation, HIF-1α accumulation and aberrant glycolysis and fibrosis. Conclusion: Our results first highlight the role of the novel regulatory mechanism of YY1 on ARAP1-AS2 and ARAP1 in promoting aberrant glycolysis and fibrosis by EGFR/PKM2/HIF-1α pathway in DKD and provide potential therapeutic strategies for DKD treatments.

The uPA/uPAR System Orchestrates the Inflammatory Response, Vascular Homeostasis, and Immune System in Fibrosis Progression

Fibrotic diseases, such as systemic sclerosis (SSc), idiopathic pulmonary fibrosis, renal fibrosis and liver cirrhosis are characterized by tissue overgrowth due to excessive extracellular matrix (ECM) deposition. Fibrosis progression is caused by ECM overproduction and the inhibition of ECM degradation due to several events, including inflammation, vascular endothelial dysfunction, and immune abnormalities. Recently, it has been reported that urokinase plasminogen activator (uPA) and its receptor (uPAR), known to be fibrinolytic factors, orchestrate the inflammatory response, vascular homeostasis, and immune homeostasis system. The uPA/uPAR system may show promise as a potential therapeutic target for fibrotic diseases. This review considers the role of the uPA/uPAR system in the progression of fibrotic diseases.

Recombinant Human Prolidase (rhPEPD) Induces Wound Healing in Experimental Model of Inflammation through Activation of EGFR Signalling in Fibroblasts

The potential of recombinant human prolidase (rhPEPD) to induce wound healing in an experimental model of IL-1β-induced inflammation in human fibroblasts was studied. It was found that rhPEPD significantly increased cell proliferation and viability, as well as the expression of the epidermal growth factor receptor (EGFR) and downstream signaling proteins, such as phosphorylated PI3K, AKT, and mTOR, in the studied model. Moreover, rhPEPD upregulated the expression of the β1 integrin receptor and its downstream signaling proteins, such as p-FAK, Grb2 and p-ERK 1/2. The inhibition of EGFR signaling by gefitinib abolished rhPEPD-dependent functions in an experimental model of inflammation. Subsequent studies showed that rhPEPD augmented collagen biosynthesis in IL-1β-treated fibroblasts as well as in a wound healing model (wound closure/scratch test). Although IL-1β treatment of fibroblasts increased cell migration, rhPEPD significantly enhanced this process. This effect was accompanied by an increase in the activity of MMP-2 and MMP-9, suggesting extracellular matrix (ECM) remodeling during the inflammatory process. The data suggest that rhPEPD may play an important role in EGFR-dependent cell growth in an experimental model of inflammation in human fibroblasts, and this knowledge may be useful for further approaches to the treatment of abnormalities of wound healing and other skin diseases.

Quercetin inhibits the amphiregulin/EGFR signaling-mediated renal tubular epithelial-mesenchymal transition and renal fibrosis in obstructive nephropathy

Quercetin is a widely distributed, bioactive flavonoid compound, which displays potential to inhibit fibrosis in several diseases. The purpose of our study was to determine the effect of quercetin treatment on renal fibrosis and investigate the mechanism. Human proximal tubular epithelial cells (HK-2) stimulated by transforming growth factor-β1 (TGF-β1) and a rat model of unilateral ureter obstruction (UUO) that contributes to fibrosis were used to investigate the role and molecular mechanism of quercetin. PD153035 (N-[3-Bromophenyl]-6,7-dimethoxyquinazolin-4-amine) was used to inactivate EGFR (epidermal growth factor receptor). The level of fibrosis, proliferation, apoptosis, and oxidative stress in HK-2 were measured. All data are presented as means ± standard deviation (SD). p-value < .05 was considered statistically significant. In UUO rats, quercetin reduced the area of fibrosis as well as inflammation, oxidative stress, and cell apoptosis. In cultured HK-2 cells, quercetin significantly ameliorated the EMT induced by TGF-β1, which was accompanied by increased amphiregulin (AREG) expression. Moreover, quercetin inhibited AREG binding to the EGFR receptor, thereby further affecting other downstream pathways. Quercetin may alleviate fibrosis in vitro and in vivo by inhibiting the activation of AREG/EGFR signaling indicating a potential therapeutic effect of quercetin in renal fibrosis.

EGFR-mediated activation of adipose tissue macrophages promotes obesity and insulin resistance

Obesity and obesity-related health complications are increasing in prevalence. Adipose tissue from obese subjects has low-grade, chronic inflammation, leading to insulin resistance. Adipose tissue macrophages (ATMs) are a source of proinflammatory cytokines that further aggravate adipocyte dysfunction. In response to a high fat diet (HFD), ATM numbers initially increase by proliferation of resident macrophages, but subsequent increases also result from infiltration in response to chemotactic signals from inflamed adipose tissue. To elucidate the underlying mechanisms regulating the increases in ATMs and their proinflammatory phenotype, we investigated the role of activation of ATM epidermal growth factor receptor (EGFR). A high fat diet increased expression of EGFR and its ligand amphiregulin in ATMs. Selective deletion of EGFR in ATMs inhibited both resident ATM proliferation and monocyte infiltration into adipose tissue and decreased obesity and development of insulin resistance. Therefore, ATM EGFR activation plays an important role in adipose tissue dysfunction.

Blocking cell cycle progression through CDK4/6 protects against chronic kidney disease

Acute and chronic kidney injuries induce increased cell cycle progression in renal tubules. While increased cell cycle progression promotes repair after acute injury, the role of ongoing tubular cell cycle progression in chronic kidney disease is unknown. Two weeks after initiation of chronic kidney disease, we blocked cell cycle progression at G1/S phase by using an FDA-approved, selective inhibitor of CDK4/6. Blocking CDK4/6 improved renal function and reduced tubular injury and fibrosis in 2 murine models of chronic kidney disease. However, selective deletion of cyclin D1, which complexes with CDK4/6 to promote cell cycle progression, paradoxically increased tubular injury. Expression quantitative trait loci (eQTLs) for CCND1 (cyclin D1) and the CDK4/6 inhibitor CDKN2B were associated with eGFR in genome-wide association studies. Consistent with the preclinical studies, reduced expression of CDKN2B correlated with lower eGFR values, and higher levels of CCND1 correlated with higher eGFR values. CDK4/6 inhibition promoted tubular cell survival, in part, through a STAT3/IL-1β pathway and was dependent upon on its effects on the cell cycle. Our data challenge the paradigm that tubular cell cycle progression is beneficial in the context of chronic kidney injury. Unlike the reparative role of cell cycle progression following acute kidney injury, these data suggest that blocking cell cycle progression by inhibiting CDK4/6, but not cyclin D1, protects against chronic kidney injury.

Matrix Metalloproteinase-10 in Kidney Injury Repair and Disease

Matrix metalloproteinase-10 (MMP-10) is a zinc-dependent endopeptidase with the ability to degrade a broad spectrum of extracellular matrices and other protein substrates. The expression of MMP-10 is induced in acute kidney injury (AKI) and chronic kidney disease (CKD), as well as in renal cell carcinoma (RCC). During the different stages of kidney injury, MMP-10 may exert distinct functions by cleaving various bioactive substrates including heparin-binding epidermal growth factor (HB-EGF), zonula occludens-1 (ZO-1), and pro-MMP-1, -7, -8, -9, -10, -13. Functionally, MMP-10 is reno-protective in AKI by promoting HB-EGF-mediated tubular repair and regeneration, whereas it aggravates podocyte dysfunction and proteinuria by disrupting glomerular filtration integrity via degrading ZO-1. MMP-10 is also involved in cancerous invasion and emerges as a promising therapeutic target in patients with RCC. As a secreted protein, MMP-10 could be detected in the circulation and presents an inverse correlation with renal function. Due to the structural similarities between MMP-10 and the other MMPs, development of specific inhibitors targeting MMP-10 is challenging. In this review, we summarize our current understanding of the role of MMP-10 in kidney diseases and discuss the potential mechanisms of its actions.

Renal tubular dilation and fibrosis after unilateral ureter obstruction revealed by relaxometry and spin-lock exchange MRI

We evaluated the use of quantitative MRI relaxometry, including the dispersion of spin-lock relaxation with different locking fields, for detecting and assessing tubular dilation and fibrosis in a mouse model of unilateral ureter obstruction (UUO). C57BL/6 J and BALB/c mice that exhibit different levels of tubular dilation and renal fibrosis after UUO were subjected to MR imaging at 7 T. Mice were imaged before UUO surgery, and at 5, 10 and 15 days after surgery. We acquired maps of relaxation rates and fit the dispersion of spin-lock relaxation rates R1ρ at different locking fields (frequencies) to a model of exchanging water pools, and assessed the sensitivity of the derived quantities for detecting tubular dilation and fibrosis in kidney. Histological scores for tubular dilation and fibrosis, based on luminal space and positive fibrotic areas in sections, were obtained for comparison. Histology detected extensive tubular dilation and mild to moderate fibrosis in the UUO kidneys, in which enlargement of luminal space, deposition of collagen, and reductions in capillary density were observed in the cortex and outer stripe of the outer medulla. Relaxation rates R1 , R2 and R1ρ clearly decreased in these regions of UUO kidneys longitudinally. While R1 showed the highest detectability to tubular dilation and overall changes in UUO kidneys, Sρ , a parameter derived from R1ρ dispersion data, showed the highest correlation with renal fibrosis in UUO. While relaxation parameters are sensitive to tubular dilation in UUO kidneys, Sρ depends primarily on the average exchange rate between water and other chemically shifted resonances such as hydroxyls and amides, and provides additional specific information for evaluating fibrosis in kidney disease.

Both Specific Endothelial and Proximal Tubular Adam17 Deletion Protect against Diabetic Nephropathy

ADAM17 is a disintegrin and metalloproteinase capable of cleaving the ectodomains of a diverse variety of molecules including TNF-α, TGF-α, L-selectin, and ACE2. We have previously demonstrated that renal ADAM17 is upregulated in diabetic mice. The role of endothelial (eAdam17) and proximal tubular (tAdam17) Adam17 deletion in renal histology, modulation of the renin angiotensin system (RAS), renal inflammation, and fibrosis was studied in a mouse model of type 1 Diabetes Mellitus. Moreover, the effect of Adam17 deletion in an in vitro 3D cell culture from human proximal tubular cells under high glucose conditions was evaluated. eAdam17 deletion attenuates renal fibrosis and inflammation, whereas tAdam17 deletion decreases podocyte loss, attenuates the RAS, and decreases macrophage infiltration, α-SMA and collagen accumulation. The 3D in vitro cell culture reinforced the findings obtained in tAdam17KO mice with decreased fibrosis in the Adam17 knockout spheroids. In conclusion, Adam17 deletion either in the endothelial or the tubular cells mitigates kidney injury in the diabetic mice by targeting different pathways. The manipulation of Adam17 should be considered as a therapeutic strategy for treating DN.

The Role of Tubule-Interstitial Crosstalk in Renal Injury and Recovery

Renal epithelial cells show remarkable regenerative capacity to recover from acute injury, which involves specific phenotypic changes, but also significant profibrotic tubule-interstitial crosstalk. Tubule-derived profibrotic stimuli and subsequent myofibroblast activation and extracellular matrix deposition have been linked closely with decline of renal function and nephron loss. However, recent data have questioned the view of purely detrimental effects of myofibroblast activation in the injured kidney and even suggested its beneficial role for epithelial regeneration. This article reviews the current understanding of the underlying mechanisms of tubular cell turnover, new suggested pathways of proregenerative tubular-interstitial crosstalk, and relevant insights of proliferation-enhancing effects of myofibroblasts on epithelial cells in nonrenal tissues.

The epidermal growth factor receptor axis and kidney fibrosis

PURPOSE OF REVIEW

The aim of this study was to summarize recent findings about the role of the epidermal growth factor receptor (EGFR) in acute kidney injury and in progression of chronic kidney injury.

RECENT FINDINGS

There is increasing evidence that EGFR activation occurs as a response to either ischemic or toxic kidney injury and EGFR signalling plays an important role in recovery of epithelial integrity. However, with incomplete recovery or in conditions predisposing to progressive glomerular and tubulointerstitial injury, aberrant persistent EGFR signalling is a causal mediator of progressive fibrotic injury. New studies have implicated activation of HIPPO/YAP signalling as a component of EGFR's actions in the kidney. There is also new evidence for sex disparities in kidney EGFR expression and activation after injury, with a male predominance that is mediated by androgens.

SUMMARY

There is increasing evidence for an important role for EGFR signalling in mediation of kidney injury, raising the possibility that interruption of the signalling cascade could limit progression of development of progressive kidney fibrosis.

Epidermal Growth Factor Receptor: A Potential Therapeutic Target for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease worldwide and the major cause of renal failure among patients on hemodialysis. Numerous studies have demonstrated that transient activation of epidermal growth factor receptor (EGFR) pathway is required for promoting kidney recovery from acute injury whereas its persistent activation is involved in the progression of various chronic kidney diseases including DKD. EGFR-mediated pathogenesis of DKD is involved in hemodynamic alteration, metabolic disturbance, inflammatory response and parenchymal cellular dysfunction. Therapeutic intervention of this receptor has been available in the oncology setting. Targeting EGFR might also hold a therapeutic potential for DKD. Here we review the functional role of EGFR in the development of DKD, mechanisms involved and the perspective about use of EGFR inhibitors as a treatment for DKD.

Extracellular Prolidase (PEPD) Induces Anabolic Processes through EGFR, β1-integrin, and IGF-1R Signaling Pathways in an Experimental Model of Wounded Fibroblasts

The role of prolidase (PEPD) as a ligand of the epidermal growth factor receptor (EGFR) was studied in an experimental model of wound healing in cultured fibroblasts. The cells were treated with PEPD (1-100 nM) and analysis of cell viability, proliferation, migration, collagen biosynthesis, PEPD activity, and the expressions of EGFR, insulin-like growth factor 1 (IGF-1), and β₁-integrin receptor including downstream signaling proteins were performed. It has been found that PEPD stimulated proliferation and migration of fibroblasts via activation of the EGFR-downstream PI3K/Akt/mTOR signaling pathway. Simultaneously, PEPD stimulated the expression of β₁-integrin and IGF-1 receptors and proteins downstream to these receptors such as FAK, Grb2, and ERK1/2. Collagen biosynthesis was increased in control and "wounded" fibroblasts under PEPD treatment. The data suggest that PEPD-induced EGFR signaling may serve as a new attempt to therapy wound healing.

LncRNA ARAP1-AS2 promotes high glucose-induced human proximal tubular cell injury via persistent transactivation of the EGFR by interacting with ARAP1

The persistent transactivation of epidermal growth factor receptor (EGFR) causes subsequent activation of the TGF-β/Smad3 pathway, which is closely associated with fibrosis and cell proliferation in diabetic nephropathy (DN), but the exact mechanism of persistent EGFR transactivation in DN remains unclear. ARAP1, a susceptibility gene for type 2 diabetes, can regulate the endocytosis and ubiquitination of membrane receptors, but the effect of ARAP1 and its natural antisense long non-coding RNA (lncRNA), ARAP1-AS2, on the ubiquitination of EGFR in DN is not clear. In this study, we verified that the expression of ARAP1 and ARAP1-AS2 was significantly up-regulated in high glucose-induced human proximal tubular epithelial cells (HK-2 cells). Moreover, we found that overexpression or knockdown of ARAP1-AS2 could regulate fibrosis and HK-2 cell proliferation through EGFR/TGF-β/Smad3 signalling. RNA pulldown assays revealed that ARAP1-AS2 directly interacts with ARAP1. Coimmunoprecipitation, dual-immunofluorescence and ubiquitination assays showed that ARAP1 may maintain persistent EGFR activation by reducing EGFR ubiquitination through competing with Cbl for CIN85 binding. Taken together, our results suggest that the lncRNA ARAP1-AS2 may promote high glucose-induced proximal tubular cell injury via persistent EGFR/TGF-β/Smad3 pathway activation by interacting with ARAP1.

Erlotinib can halt adenine induced nephrotoxicity in mice through modulating ERK1/2, STAT3, p53 and apoptotic pathways

Renal fibrosis is a failed regenerative process that facilitates chronic kidney disease progression. The current study was designed to study the effect of erlotinib, a receptor tyrosine kinase inhibitor, on the progression of renal fibrosis. The study included four groups of mice: control group; adenine group: received adenine (0.2% w/w) daily with food for 4 weeks; erlotinib group: received 80 mg/kg/day erlotinib orally (6 ml/kg/day, 1.3% w/v suspension in normal saline 0.9%) for 4 weeks; adenine + erlotinib group: received adenine and erlotinib concurrently. Kidney function and antioxidant biomarkers were measured. Renal expression of Bcl2 and p53 and histopathological changes (tubular injury and renal fibrosis) were scored. Renal tissue levels of transforming growth factor-β₁, p-ERK1/2 and p-STAT3 were measured. Results obtained showed significant decrease (P < 0.001) in serum creatinine, urea and uric acid in erlotinib + adenine group. Level of malondialdehyde was decreased significantly (P < 0.001) while reduced glutathione and catalase levels were increased (P < 0.01) by erlotinib concurrent administration. Erlotinib markedly reduced fibrosis and tubular injury and decreased TGF-β1, p-ERK1/2 and p-STAT3 (P < 0.5). In addition, expression level of Bcl-2 was elevated (P < 0.001) while that of p53-was reduced compared to adenine alone. Erlotinib can attenuate renal fibrosis development and progression through anti-fibrotic, antioxidant and anti-apoptotic pathways.

Spin-lock relaxation rate dispersion reveals spatiotemporal changes associated with tubulointerstitial fibrosis in murine kidney

PURPOSE

To develop and evaluate a reliable non-invasive means for assessing the severity and progression of fibrosis in kidneys. We used spin-lock MR imaging with different locking fields to detect and characterize progressive renal fibrosis in an hHB-EGF^Tg/Tg mouse model.

METHODS

Male hHB-EGF^Tg/Tg mice, a well-established model of progressive fibrosis, and age-matched normal wild type (WT) mice, were imaged at 7T at ages 5-7, 11-13, and 30-40 weeks. Spin-lock relaxation rates R_{1 ρ} were measured at different locking fields (frequencies) and the resultant dispersion curves were fit to a model of exchanging water pools. The obtained MRI parameters were evaluated as potential indicators of tubulointerstitial fibrosis in kidney. Histological examinations of renal fibrosis were also carried out post-mortem after MRI.

RESULTS

Histology detected extensive fibrosis in the hHB-EGF^Tg/Tg mice, in which collagen deposition and reductions in capillary density were observed in the fibrotic regions of kidneys. R₂ and R_{1 ρ} values at different spin-lock powers clearly dropped in the fibrotic region as fibrosis progressed. There was less variation in the asymptotic locking field relaxation rate R 1 ρ ∞ between the groups. The exchange parameter S_ρ and the inflection frequency ω_infl changed by larger factors.

CONCLUSION

Both S_ρ and ω_infl depend primarily on the average exchange rate between water and other chemically shifted resonances such as hydroxyls and amides. Spin-lock relaxation rate dispersion, rather than single measurements of relaxation rates, provides more comprehensive and specific information on spatiotemporal changes associated with tubulointerstitial fibrosis in murine kidney.

Role of Heparin-Binding Epidermal Growth Factor-Like Growth Factor in Oxidative Stress-Associated Metabolic Diseases

Heparin-binding EGF-like growth factor (HB-EGF) is an EGF family member that interacts with epidermal growth factor receptor (EGFR) and ERBB4. Since HB-EGF was first identified as a novel growth factor secreted from a human macrophage cell line, numerous pathological and physiological functions related to cell proliferation, migration, and inflammation have been reported. Notably, the expression of HB-EGF is sensitively upregulated by oxidative stress in the endothelial cells and functions for auto- and paracrine-EGFR signaling. Overnutrition and obesity cause elevation of HB-EGF expression and EGFR signaling in the hepatic and vascular systems. Modulations of HB-EGF signaling showed a series of protections against phenotypes related to metabolic syndrome and advanced metabolic diseases, suggesting HB-EGF as a potential target against metabolic diseases.

Long noncoding RNA NEAT1 is involved in the protective effect of Klotho on renal tubular epithelial cells in diabetic kidney disease through the ERK1/2 signaling pathway

Klotho, an antiaging protein, has been shown to play a protective role in renal tubular epithelial-mesenchymal transition (EMT) during the development of diabetic kidney disease (DKD). Long noncoding RNAs (lncRNAs) participate in the progression of EMT in many diseases. However, the effect of Klotho on lncRNAs during the development of DKD is still unknown. In this study, we found that Klotho overexpression in high-fat diet (HFD)- and streptozotocin (STZ)-induced DKD mice significantly inhibited the expression of lncRNA nuclear-enriched abundant transcript 1 (Neat1). We demonstrated that NEAT1 was significantly upregulated in both bovine serum albumin (BSA)-stimulated HK2 cells and mice with HFD- and STZ-induced diabetes. In addition, we observed that Klotho displays colocalization with NEAT1. Furthermore, overexpression of Klotho can inhibit the high expression of NEAT1 in BSA-stimulated HK2 cells, while silencing Klotho can further upregulate the expression of NEAT1. Silencing NEAT1 in HK2 cells resulted in inhibition of the EMT-related markers alpha smooth muscle actin (α-SMA) and vimentin (VIM) and the renal fibrosis-related markers transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF). The effect of NEAT1 on DKD was partly mediated by regulation of the ERK1/2 signaling pathway. Finally, we found that silencing NEAT1 can reverse the activation of EMT and fibrosis caused by Klotho silencing in a manner dependent on the ERK1/2 signaling pathway. These findings reveal a new regulatory pathway by which Klotho regulates ERK1/2 signaling via NEAT1 to protect against EMT and renal fibrosis, suggesting that NEAT1 is a potential therapeutic target for DKD.

An anti-ageing protein called Klotho helps protect against kidney failure in mice and human cells by silencing a long non-coding RNA molecule. The regulatory RNA involved, known as NEAT1, promotes cellular transformations associated with the disease process. A team led by Yao-Ming Xue from Southern Medical University in Guangdong, China, showed that levels of NEAT1 are elevated in mouse models of diabetic kidney disease and in injured human kidney calls. The identification of NEAT1 in kidney disease thus provides a novel therapeutic target. After demonstrating that Klotho and NEAT1 interact directly with each other in cells, they experimentally boosted Klotho expression and observed suppressed levels of NEAT1. As a consequence, the cells displayed lower levels of the proteins linked to the progressive deposition of fibrosis in the kidneys.

FOXM1 drives proximal tubule proliferation during repair from acute ischemic kidney injury

The proximal tubule has a remarkable capacity for repair after acute injury, but the cellular lineage and molecular mechanisms underlying this repair response are incompletely understood. Here, we developed a Kim1-GFPCreERt2 knockin mouse line (Kim1-GCE) in order to perform genetic lineage tracing of dedifferentiated cells while measuring the cellular transcriptome of proximal tubule during repair. Acutely injured genetically labeled clones coexpressed KIM1, VIMENTIN, SOX9, and KI67, indicating a dedifferentiated and proliferative state. Clonal analysis revealed clonal expansion of Kim1+ cells, indicating that acutely injured, dedifferentiated proximal tubule cells, rather than fixed tubular progenitor cells, account for repair. Translational profiling during injury and repair revealed signatures of both successful and unsuccessful maladaptive repair. The transcription factor Foxm1 was induced early in injury, was required for epithelial proliferation in vitro, and was dependent on epidermal growth factor receptor (EGFR) stimulation. In conclusion, dedifferentiated proximal tubule cells effect proximal tubule repair, and we reveal an EGFR/FOXM1-dependent signaling pathway that drives proliferative repair after injury.

Anti-fibrotic effects of synthetic TGF-β1 and Smad oligodeoxynucleotide on kidney fibrosis in vivo and in vitro through inhibition of both epithelial dedifferentiation and endothelial-mesenchymal transitions

Kidney fibrosis is a common process of various kidney diseases leading to end-stage renal failure irrespective of etiology. Myofibroblasts are crucial mediators in kidney fibrosis through production of extracellular matrix (ECM), but their origin has not been clearly identified. Many study proposed that epithelial and endothelial cells become myofibroblasts by epithelial dedifferentiation and endothelial-mesenchymal transition (EndoMT). TGF-β1/Smad signaling plays a crucial role in partly epithelial-mensencymal transition (EMT) and EndoMT. Thus, we designed the TGF-β1/Smad oligodeoxynucleotide (ODN), a synthetic short DNA containing complementary sequence for Smad transcription factor and TGF-β1 mRNA. Therefore, this study investigated the anti-fibrotic effect of synthetic TGF-β1/Smad ODN on UUO-induced kidney fibrosis in vivo model and TGF-β1-induced in vitro model. To examine the effect of TGF-β1/Smad ODN, we performed various experiments to evaluate kidney fibrosis. The results showed that UUO induced inflammation, ECM accumulation, epithelial dedifferentiation and EndoMT processes, and tubular atrophy. However, synthetic TGF-β1/Smad ODN significantly suppressed UUO-induced fibrosis. Furthermore, synthetic ODN attenuated TGF-β1-induced epithelial dedifferentiation and EndoMT program via blocking TGF-β1/Smad signaling. In conclusion, this study demonstrated that administration of synthetic TGF-β1/Smad ODN attenuates kidney fibrosis, epithelial dedifferentiation, and EndoMT processes. The findings propose the possibility of synthetic ODN as a new effective therapeutic tool for kidney fibrosis.

Proximal Tubule-Derived Amphiregulin Amplifies and Integrates Profibrotic EGF Receptor Signals in Kidney Fibrosis

BACKGROUND

Sustained activation of EGF receptor (EGFR) in proximal tubule cells is a hallmark of progressive kidney fibrosis after AKI and in CKD. However, the molecular mechanisms and particular EGFR ligands involved are unknown.

METHODS

We studied EGFR activation in proximal tubule cells and primary tubular cells isolated from injured kidneys in vitro. To determine in vivo the role of amphiregulin, a low-affinity EGFR ligand that is highly upregulated with injury, we used ischemia-reperfusion injury or unilateral ureteral obstruction in mice with proximal tubule cell-specific knockout of amphiregulin. We also injected soluble amphiregulin into knockout mice with proximal tubule cell-specific deletion of amphiregulin's releasing enzyme, the transmembrane cell-surface metalloprotease, a disintegrin and metalloprotease-17 (ADAM17), and into ADAM17 hypomorphic mice.

RESULTS

Yes-associated protein 1 (YAP1)-dependent upregulation of amphiregulin transcript and protein amplifies amphiregulin signaling in a positive feedback loop. YAP1 also integrates signals of other moderately injury-upregulated, low-affinity EGFR ligands (epiregulin, epigen, TGFα), which also require soluble amphiregulin and YAP1 to induce sustained EGFR activation in proximal tubule cells in vitro. In vivo, soluble amphiregulin injection sufficed to reverse protection from fibrosis after ischemia-reperfusion injury in ADAM17 hypomorphic mice; injected soluble amphiregulin also reversed the corresponding protective proximal tubule cell phenotype in injured proximal tubule cell-specific ADAM17 knockout mice. Moreover, the finding that proximal tubule cell-specific amphiregulin knockout mice were protected from fibrosis after ischemia-reperfusion injury or unilateral ureteral obstruction demonstrates that amphiregulin was necessary for the development of fibrosis.

CONCLUSIONS

Our results identify amphiregulin as a key player in injury-induced kidney fibrosis and suggest therapeutic or diagnostic applications of soluble amphiregulin in kidney disease.

Noninvasive quantitative magnetization transfer MRI reveals tubulointerstitial fibrosis in murine kidney

Excessive tissue scarring, or fibrosis, is a critical contributor to end stage renal disease, but current clinical tests are not sufficient for assessing renal fibrosis. Quantitative magnetization transfer (qMT) MRI provides indirect information about the macromolecular composition of tissues. We evaluated measurements of the pool size ratio (PSR, the ratio of immobilized macromolecular to free water protons) obtained by qMT as a biomarker of tubulointerstitial fibrosis in a well-established murine model with progressive renal disease. MR images were acquired from 16-week-old fibrotic hHB-EGF^Tg/Tg mice and normal wild-type (WT) mice (N = 12) at 7 T. QMT parameters were derived using a two-pool five-parameter fitting model. A normal range of PSR values in the cortex and outer stripe of outer medulla (CR + OSOM) was determined by averaging across voxels within WT kidneys (mean ± 2SD). Regions in diseased mice whose PSR values exceeded the normal range above a threshold value (tPSR) were identified and measured. The spatial distribution of fibrosis was confirmed using picrosirius red stains. Compared with normal WT mice, scattered clusters of high PSR regions were observed in the OSOM of hHB-EGF^Tg/Tg mouse kidneys. Moderate increases in mean PSR (mPSR) of CR + OSOM regions were observed across fibrotic kidneys. The abnormally high PSR regions (% area) detected by the tPSR were significantly increased in hHB-EGF^Tg/Tg mice, and were highly correlated with regions of fibrosis detected by histological fibrosis indices measured from picrosirius red staining. Renal tubulointerstitial fibrosis in OSOM can thus be assessed by qMT MRI using an appropriate analysis of PSR. This technique may be used as an imaging biomarker for chronic kidney diseases.

The Role of the EGF Receptor in Sex Differences in Kidney Injury

BACKGROUND

Sex differences mediating predisposition to kidney injury are well known, with evidence indicating lower CKD incidence rates and slower decline in renal function in nondiabetic CKD for premenopausal women compared with men. However, signaling pathways involved have not been elucidated to date. The EGF receptor (EGFR) is widely expressed in the kidney in glomeruli and tubules, and persistent and dysregulated EGFR activation mediates progressive renal injury.

METHODS

To investigate the sex differences in response to renal injury, we examined EGFR expression in mice, in human kidney tissue, and in cultured cell lines.

RESULTS

In wild type mice, renal mRNA and protein EGFR levels were comparable in males and females at postnatal day 7 but were significantly lower in age-matched adult females than in adult males. Similar gender differences in renal EGFR expression were detected in normal adult human kidneys. In Dsk5 mutant mice with a gain-of-function allele that increases basal EGFR kinase activity, males had progressive glomerulopathy, albuminuria, loss of podocytes, and tubulointerstitial fibrosis, but female Dsk5 mice had minimal kidney injury. Oophorectomy had no effect on renal EGFR levels in female Dsk5 mice, while castration protected against the kidney injury in male Dsk5 mice, in association with a reduction in EGFR expression to levels seen in females. Conversely, testosterone increased EGFR expression and renal injury in female Dsk5 mice. Testosterone directly stimulated EGFR expression in cultured kidney cells.

CONCLUSIONS

These studies indicate that differential renal EGFR expression plays a role in the sex differences in susceptibility to progressive kidney injury that may be mediated at least in part by testosterone.

Renal Inflammation and Fibrosis: A Double-edged Sword

Renal tissue injury initiates inflammatory and fibrotic processes that occur to promote regeneration and repair. After renal injury, damaged tissue releases cytokines and chemokines, which stimulate activation and infiltration of inflammatory cells to the kidney. Normal tissue repair processes occur simultaneously with activation of myofibroblasts, collagen deposition, and wound healing responses; however, prolonged activation of pro-inflammatory and pro-fibrotic cell types causes excess extracellular matrix deposition. This review focuses on the physiological and pathophysiological roles of specialized cell types, cytokines/chemokines, and growth factors, and their implications in recovery or exacerbation of acute kidney injury.

YY1: A novel therapeutic target for diabetic nephropathy orchestrated renal fibrosis

BACKGROUND

Renal fibrosis promotes the development of diabetic nephropathy (DN). A growing number of studies have reported that Yin Yang 1 (YY1), which is involved in cellular proliferation and differentiation, plays a crucial role in the pathogenesis of many diseases, such as pulmonary fibrosis, hepatic steatosis and cancer.

METHODS

We detected the expression of YY1 under various glucose concentration and time gradient conditions. Rapamycin was used to verify the mTORC1/p70S6K/YY1 signaling pathway in HK-2 cells. We used db/db mice to examine the connection between renal fibrosis and YY1. A luciferase assay and chromatin immunoprecipitation (ChIP) assay were used to identify whether YY1 directly regulated α-SMA by binding to the α-SMA promoter. RNA silencing and overexpression were performed by using a YY1 expression/knockdown plasmid to investigate the function of YY1 in renal fibrosis of DN.

RESULTS

YY1 expression and subsequent nuclear translocation were upregulated in a glucose- and time-dependent manner via the mTORC1/p70S6K signaling pathway in HK-2 cells. YY1 expression and nuclear translocation was significantly upregulated in db/db mice. Furthermore, YY1 upregulated α-SMA expression and activity in high-glucose-cultured HK-2 cells. Overexpression of YY1 promoted renal fibrosis in db/m mice mainly by upregulating α-SMA expression and inducing epithelial-mesenchymal transition (EMT) in vitro and in vivo. Finally, downregulation of YY1 reversed renal fibrosis by improving EMT in vivo and in vitro.

CONCLUSIONS

These results reveal that upregulation of YY1 plays a critical role in HG-induced deregulation of EMT-associated protein expression, which finally results in renal fibrosis of DN. Therefore, decreasing YY1 expression might represent a new therapeutic target for diabetic nephropathy-induced renal fibrosis.

Ergosterol Ameliorates Diabetic Nephropathy by Attenuating Mesangial Cell Proliferation and Extracellular Matrix Deposition via the TGF-β1/Smad2 Signaling Pathway

(1) Background: Diabetic nephropathy, a microvascular complication of diabetes, is one of the principal causes of end-stage renal disease worldwide. The aim of this study was to explore the therapeutic effects of ergosterol on diabetic nephropathy. (2) Methods: Streptozotocin (STZ)-induced C57BL/6 diabetic mice were treated with ergosterol (10, 20, 40 mg/kg/day) for 8 weeks by oral gavage. The in vitro study employed rat mesangial cells exposed to 30 mM glucose for 48 h in the presence of 10 or 20 μM ergosterol. (3) Results: Ergosterol treatment improved body weights, ameliorated the majority of biochemical and renal functional parameters and histopathological changes, and reduced extracellular matrix (ECM) deposition in diabetic mice. In vitro, ergosterol suppressed proliferation, reduced the levels of ECM proteins, and increased the expression of matrix metalloproteinase-2 and -9 in high glucose-induced mesangial cells; Furthermore, ergosterol markedly improved transforming growth factor-β1 (TGF-β1) expression, enhanced phosphorylation levels of drosophila mothers against decapentaplegic 2 (Smad2), and regulated the downstream factors in vivo and in vitro. (4) Conclusions: Ergosterol alleviated mesangial cell proliferation and the subsequent ECM deposition by regulating the TGF-β1/Smad2 signaling pathway.

Epidermal growth factor receptor and podocin predict nephropathy progression in type 2 diabetic patients through interaction with the autophagy influencer ULK-1

AIMS

Diabetic nephropathy (DN) that progress to end stage renal failure is a serious health problem. Autophagy is involved in DN pathogenesis. Finding renal prognostic biomarkers can help in the future renal status prevision. Therefore, the aim of current study was to evaluate and correlate circulating levels of autophagy regulator protein Unc-51-like kinase 1 (ULK-1) with the widely expressed receptor in mammalian kidney; epidermal growth factor receptor (EGFR); and the key functional podocyte protein podocin (PDCN).

METHODS

Serum levels were assessed by ELISA in 72 type 2 diabetic patients classified according to their urinary albumin/creatinine ratio; 19 normoalbuminuric, 37 microalbuminuric and 16 macroalbuminuric patients; age and sex matched with 18 healthy controls.

RESULTS

Microalbuminuria and macroalbuminuria patients exhibited decreased ULK-1, EGFR and PDCN levels. Only EGFR showed lower levels in normoalbuminuria compared with controls. ULK-1 and EGFR were significantly higher in normoalbuminuria compared with microalbuminuria and macroalbuminuria patients. ULK-1, EGFR and PDCN were correlated with each other and with some metabolic parameters.

CONCLUSIONS

ULK-1 with EGFR can predict early impairment in DN while PDCN can highlight progressive DN risk EGFR and PDCN may interact synergistically with ULK-1 in autophagy dysregulation as a pathogenic mechanism of DN induction and progression.

Renal tubular epithelial cells: the neglected mediator of tubulointerstitial fibrosis after injury

Renal fibrosis, especially tubulointerstitial fibrosis, is the inevitable outcome of all progressive chronic kidney diseases (CKDs) and exerts a great health burden worldwide. For a long time, interests in renal fibrosis have been concentrated on fibroblasts and myofibroblasts. However, in recent years, growing numbers of studies have focused on the role of tubular epithelial cells (TECs). TECs, rather than a victim or bystander, are probably a neglected mediator in renal fibrosis, responding to a variety of injuries. The maladaptive repair mechanisms of TECs may be the key point in this process. In this review, we will focus on the role of TECs in tubulointerstitial fibrosis. We will follow the fate of a tubular cell and depict the intracellular changes after injury. We will then discuss how the repair mechanism of tubular cells becomes maladaptive, and we will finally discuss the intercellular crosstalk in the interstitium that ultimately proceeds tubulointerstitial fibrosis.

TGF-β promotes fibrosis after severe acute kidney injury by enhancing renal macrophage infiltration

TGF-β signals through a receptor complex composed of 2 type I and 2 type II (TGF-βRII) subunits. We investigated the role of macrophage TGF-β signaling in fibrosis after AKI in mice with selective monocyte/macrophage TGF-βRII deletion (macrophage TGF-βRII-/- mice). Four weeks after injury, renal TGF-β1 expression and fibrosis were higher in WT mice than macrophage TGF-βRII-/- mice, which had decreased renal macrophages. The in vitro chemotactic response to f-Met-Leu-Phe was comparable between bone marrow-derived monocytes (BMMs) from WT and macrophage TGF-βRII-/- mice, but TGF-βRII-/- BMMs did not respond to TGF-β. We then implanted Matrigel plugs suffused with either f-Met-Leu-Phe or TGF-β1 into WT or macrophage TGF-βRII-/- mice. After 6 days, f-Met-Leu-Phe induced similar macrophage infiltration into the Matrigel plugs of WT and macrophage TGF-βRII-/- mice, but TGF-β induced infiltration only in WT mice. We further determined the number of labeled WT or TGF-βRII-/- BMMs infiltrating into WT kidneys 20 days after ischemic injury. There were more labeled WT BMMs than TGF-βRII-/- BMMs. Therefore, macrophage TGF-βRII deletion protects against the development of tubulointerstitial fibrosis following severe ischemic renal injury. Chemoattraction of macrophages to the injured kidney through a TGF-β/TGF-βRII axis is a heretofore undescribed mechanism by which TGF-β can mediate renal fibrosis during progressive renal injury.

Human rhomboid family-1 modulates clathrin coated vesicle-dependent pro-transforming growth factor α membrane trafficking to promote breast cancer progression

BACKGROUND

Epidermal growth factor receptor (EGFR) signalling is critical in epithelial cancer development. Human rhomboid family-1 (RHBDF1) facilitates the secretion of TGFα, an EGFR ligand, in breast cancer; however, the underlying mechanism remains unclear. We evaluated the role for RHBDF1 in clathrin-coated vesicle (CCV)-dependent pro-TGFα membrane trafficking in breast cancer cells upon stimulation by G-protein coupled receptor (GPCR) agonists.

METHODS

RHBDF1 was silenced in various breast cancer cells using shRNA. TGFα levels, subcellular localization, and secretion were evaluated using ELISA, immunofluorescent staining, and coimmunoprecipitation. Phosphorylation and expression of relevant proteins were measured by western blotting. RHBDF1-dependent cell viability and invasion were measured.

FINDINGS

RHBDF1 mediates GPCR agonist-induced EGFR phosphorylation by promoting TGFα secretion in various types of breast cancer cells. RHBDF1 not only mediates ADAM17-dependent shedding of TGFα, but is essential in membrane trafficking of pro-TGFα. RHBDF1 silencing results in blocking of clathrin uncoating from CCV, a crucial step for the plasma membrane release of pro-TGFα. Interaction of RHBDF1 with auxilin-2, a CCV protein, determines the recruitment of HSC70 to CCV to facilitate clathrin uncoating. RHBDF1 function is required for the proliferation and mobility of breast cancer cells upon stimulation by Sphingosine 1 Phosphate (S1P), a GPCR agonist. We demonstrate a significant correlation between RHBDF1 overexpression and EGFR activation in breast cancer tissues.

INTERPRETATION

RHBDF1 is an indispensable component of the protein trafficking machinery involved in GPCR-mediated EGFR transactivation, and is an attractive therapeutic target for cancer. FUND: National Natural Science Foundation of China (81,672,740 to ZSZ, 81,272,356 and 81,330,029 to LYL).

Inhibition of Epidermal Growth Factor Receptor Activation Is Associated With Improved Diabetic Nephropathy and Insulin Resistance in Type 2 Diabetes

Previous studies by us and others have indicated that renal epidermal growth factor receptors (EGFR) are activated in models of diabetic nephropathy (DN) and that inhibition of EGFR activity protects against progressive DN in type 1 diabetes. In this study we examined whether inhibition of EGFR activation would affect the development of DN in a mouse model of accelerated type 2 diabetes (BKS db/db with endothelial nitric oxide knockout [eNOS-/-db/db]). eNOS-/-db/db mice received vehicle or erlotinib, an inhibitor of EGFR tyrosine kinase activity, beginning at 8 weeks of age and were sacrificed at 20 weeks of age. In addition, genetic models inhibiting EGFR activity (waved 2) and transforming growth factor-α (waved 1) were studied in this model of DN in type 2 diabetes. Compared with vehicle-treated mice, erlotinib-treated animals had less albuminuria and glomerulosclerosis, less podocyte loss, and smaller amounts of renal profibrotic and fibrotic components. Erlotinib treatment decreased renal oxidative stress, macrophage and T-lymphocyte infiltration, and the production of proinflammatory cytokines. Erlotinib treatment also preserved pancreas function, and these mice had higher blood insulin levels at 20 weeks, decreased basal blood glucose levels, increased glucose tolerance and insulin sensitivity, and increased blood levels of adiponectin compared with vehicle-treated mice. Similar to the aforementioned results, both waved 1 and waved 2 diabetic mice also had attenuated DN, preserved pancreas function, and decreased basal blood glucose levels. In this mouse model of accelerated DN, inhibition of EGFR signaling led to increased longevity.

Selective pharmacological inhibition of DDR1 prevents experimentally-induced glomerulonephritis in prevention and therapeutic regime

Background

Discoidin domain receptor 1 (DDR1) is a collagen-activated receptor tyrosine kinase extensively implicated in diseases such as cancer, atherosclerosis and fibrosis. Multiple preclinical studies, performed using either a gene deletion or a gene silencing approaches, have shown this receptor being a major driver target of fibrosis and glomerulosclerosis.

Methods

The present study investigated the role and relevance of DDR1 in human crescentic glomerulonephritis (GN). Detailed DDR1 expression was first characterized in detail in human GN biopsies using a novel selective anti-DDR1 antibody using immunohistochemistry. Subsequently the protective role of DDR1 was investigated using a highly selective, novel, small molecule inhibitor in a nephrotoxic serum (NTS) GN model in a prophylactic regime and in the NEP25 GN mouse model using a therapeutic intervention regime.

Results

DDR1 expression was shown to be mainly limited to renal epithelium. In humans, DDR1 is highly induced in injured podocytes, in bridging cells expressing both parietal epithelial cell (PEC) and podocyte markers and in a subset of PECs forming the cellular crescents in human GN. Pharmacological inhibition of DDR1 in NTS improved both renal function and histological parameters. These results, obtained using a prophylactic regime, were confirmed in the NEP25 GN mouse model using a therapeutic intervention regime. Gene expression analysis of NTS showed that pharmacological blockade of DDR1 specifically reverted fibrotic and inflammatory gene networks and modulated expression of the glomerular cell gene signature, further validating DDR1 as a major mediator of cell fate in podocytes and PECs.

Conclusions

Together, these results suggest that DDR1 inhibition might be an attractive and promising pharmacological intervention for the treatment of GN, predominantly by targeting the renal epithelium.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1524-5) contains supplementary material, which is available to authorized users.

Fatty acid receptor modulator PBI-4050 inhibits kidney fibrosis and improves glycemic control

Extensive kidney fibrosis occurs in several types of chronic kidney diseases. PBI-4050, a potentially novel first-in-class orally active low-molecular weight compound, has antifibrotic and antiinflammatory properties. We examined whether PBI-4050 affected the progression of diabetic nephropathy (DN) in a mouse model of accelerated type 2 diabetes and in a model of selective tubulointerstitial fibrosis. eNOS-/- db/db mice were treated with PBI-4050 from 8-20 weeks of age (early treatment) or from 16-24 weeks of age (late treatment). PBI-4050 treatment ameliorated the fasting hyperglycemia and abnormal glucose tolerance tests seen in vehicle-treated mice. In addition, PBI-4050 preserved (early treatment) or restored (late treatment) blood insulin levels and increased autophagy in islets. PBI-4050 treatment led to significant improvements in lifespan in the diabetic mice. Both early and late PBI-4050 treatment protected against progression of DN, as indicated by reduced histological glomerular injury and albuminuria, slow decline of glomerular filtration rate, and loss of podocytes. PBI-4050 inhibited kidney macrophage infiltration, oxidative stress, and TGF-β-mediated fibrotic signaling pathways, and it also protected against the development of tubulointerstitial fibrosis. To confirm a direct antiinflammatory/antifibrotic effect in the kidney, further studies with a nondiabetic model of EGFR-mediated proximal tubule activation confirmed that PBI-4050 dramatically decreased the development of the associated tubulointerstitial injury and macrophage infiltration. These studies suggest that PBI-4050 attenuates development of DN in type 2 diabetes through improvement of glycemic control and inhibition of renal TGF-β-mediated fibrotic pathways, in association with decreases in macrophage infiltration and oxidative stress.

ErbB4 deletion accelerates renal fibrosis following renal injury

Tubulointerstitial fibrosis (TIF) is a prominent factor in the progression of chronic kidney disease regardless of etiology. Avian erythroblastic leukemia viral oncogene homolog 4 (ErbB4) expression levels were inversely correlated to renal fibrosis in human fibrotic kidneys. In both unilateral ureteral obstruction (UUO) and ischemia-reperfusion injury followed by uninephrectomy (IRI/UNx) mouse models, expression levels of ErbB4 were elevated in the early stage of renal injury. Using mice with global ErbB4 deletion except for transgenic rescue in cardiac tissue ( ErbB4-/-ht+), we determined that UUO induced similar injury in proximal tubules compared with wild-type mice but more severe injury in distal nephrons. TIF was apparent earlier and was more pronounced following UUO in ErbB4-/-ht+ mice. With ErbB4 deletion, UUO injury inhibited protein kinase B phosphorylation and increased the percentage of cells in G2/M arrest. There was also increased nuclear immunostaining of yes-associated protein and increased expression of phospho-Mothers against decapentaplegic homolog 3, snail1, and vimentin. These results indicate that ErbB4 deletion accelerates the development and progression of renal fibrosis in obstructive nephropathy. Similar results were found in a mouse IRI/UNx model. In conclusion, increased expression of ErbB4 in the early stages of renal injury may reflect a compensatory effect to lessen tubulointerstitial injury.

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.