Deletion of the epidermal growth factor receptor in renal proximal tubule epithelial cells delays recovery from acute kidney injury

Renal toxicity of Aconitum plants? A study based on a new mass spectrometry scanning strategy and computer virtual screening

BACKGROUND

Radix Aconiti Lateralis (Fuzi), a mono-herbal preparation of Aconitum herbs in the genus Aconitum, is commonly used in traditional Chinese medicine (TCM) to treat critical illnesses. The curative effect of Fuzi is remarkable. However, the toxic effects of Fuzi are still a key clinical focus, and the substances inducing nephrotoxicity are still unclear. Therefore, this study proposes a research model combining "in vitro and in vivo component mining-virtual multi-target screening-active component prediction-literature verification" to screen potential nephrotoxic substances rapidly.

METHOD

The UHPLC-Q-Exactive-Orbitrap MS analysis method was used for the correlation analysis of Fuzi's in vitro-in vivo chemical substance groups. On this basis, the key targets of nephrotoxicity were screened by combining online disease databases and a protein-protein interaction (PPI) network. The computer screening technique was used to verify the binding mode and affinity of Fuzi's components with nephrotoxic targets. Finally, the potential material basis of Fuzi-induced nephrotoxicity was screened.

RESULTS

Eighty-one Fuzi components were identified. Among them, 35 components were absorbed into the blood. Based on the network biology method, 21 important chemical components and three potential key targets were screened. Computer virtual screening revealed that mesaconine, benzoylaconine, aconitine, deoxyaconitine, hypaconitine, benzoylhypaconine, benzoylmesaconine, and hypaconitine may be potential nephrotoxic substances of Fuzi.

CONCLUSIONS

Fuzi may interact with multiple components and targets in the process of inducing nephrotoxicity. In the future, experiments can be designed to explore further. This study provides a reference for screening Fuzi nephrotoxic components and has certain significance for the safe use of Fuzi.

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.

Tubuloid differentiation to model the human distal nephron and collecting duct in health and disease

Organoid technology is rapidly gaining ground for studies on organ (patho)physiology. Tubuloids are long-term expanding organoids grown from adult kidney tissue or urine. The progenitor state of expanding tubuloids comes at the expense of differentiation. Here, we differentiate tubuloids to model the distal nephron and collecting ducts, essential functional parts of the kidney. Differentiation suppresses progenitor traits and upregulates genes required for function. A single-cell atlas reveals that differentiation predominantly generates thick ascending limb and principal cells. Differentiated human tubuloids express luminal NKCC2 and ENaC capable of diuretic-inhibitable electrolyte uptake and enable disease modeling as demonstrated by a lithium-induced tubulopathy model. Lithium causes hallmark AQP2 loss, induces proliferation, and upregulates inflammatory mediators, as seen in vivo. Lithium also suppresses electrolyte transport in multiple segments. In conclusion, this tubuloid model enables modeling of the human distal nephron and collecting duct in health and disease and provides opportunities to develop improved therapies.

Exploring the mechanism of Dahuang-Tusizi drug pair in the treatment of diabetes nephropathy based on network pharmacology and immune infiltration analysis

The study aimed to explore the key targets and molecular mechanisms of Dahuang-Tusizi drug pair (DTDP) in the treatment of diabetes nephropathy (DN) based on the GEO database by using network pharmacology combined with molecular docking and immune infiltration. The active components of the DTDP were screened using the Traditional Chinese Medicine Systems Pharmacology database and the Swiss Target Prediction database. The differential genes of DN were retrieved from GEO databases. Next, the intersecting targets of drug and disease were imported into the String database for protein-protein interactions network analysis, and the core targets were identified through topological analysis. Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed with the help of the Metascape database and gene set enrichment analysis database. Subsequently, molecular docking was performed to verify the binding activity of the key component and the key target. The Nephroseq V5 database was used to verify the clinical relevance of DN and core genes. Finally, the Using CIBERSORT Algorithm to analyze the immune Infiltration of DN Gene Chip. The network analysis showed that 25 active ingredients of DTDP were associated with 22 targets in DN. The key active ingredients (Sesamin, quercetin, EUPATIN, matrine, beta-sitosterol, isorhamnetin, etc.) and the core targets (JUN, EGF, CD44, FOS, KDR, CCL2, PTGS2, and MMP2) were further identified. Enrichment analysis revealed signaling pathways including TNF, MAPK, and IL-17 signaling pathway. Molecular docking results showed that there was a strong affinity between the key components and core targets. The results of immune infiltration found that the proportion of macrophages in DN tissues was significantly increased. Our findings demonstrated that the characteristics of DTDP in treating DN are "multiple components, multiple targets and multiple pathways." We predicted that DTDP may inhibit inflammation related pathways by regulating key genes, reducing macrophage infiltration. Thus, inhibiting inflammatory response to reduce glomerular damage and delay the development of DN.

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.

Pharmacological inhibition of the mixed lineage leukemia 1-menin interaction aggravates acute kidney injury induced by folic acid and ischemia-reperfusion in mice

Mixed lineage leukemia 1 (MLL1) is a methyltransferase that induces histone H3 lysine 4 trimethylation (H3K4me3) and partially exerts its untoward functional effects by interacting with multiple subunits including menin and WD repeat-containing protein 5 (WDR5). In this study, we investigated the role and mechanisms of MLL1 in murine models of acute kidney injury induced by folic acid (FA) and ischemia-reperfusion. Injury to the kidney elevated the expression of MLL1, menin, WDR5, and H3K4Me3, which was accompanied by increased serum creatinine and blood urea nitrogen, renal tubular injury, and apoptosis. Pharmacological inhibition of MLL1 activity with MI503 to disrupt the interaction between MLL1 with menin further increased serum creatinine and blood urea nitrogen levels, enhanced expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1, and induced more apoptosis in the kidney following FA and ischemia-reperfusion injury. In contrast, MI503 treatment decreased the expression of vimentin and proliferating cell nuclear antigens. Similarly, treatment with MM102 to disrupt the interaction between MLL1 and WDR5 also worsened renal dysfunction, aggravated tubular cell injury, increased apoptosis, and inhibited cellular dedifferentiation and proliferation in mice following FA injection. Moreover, MI503 inhibited FA-induced phosphorylation of epidermal growth factor receptor, signal transducer and activator of transcription 3, and extracellular signal-regulated kinase-1/2 in injured kidneys. Collectively, these data suggest that MLL1 contributes to renal protection and functional recovery and promotes renal regeneration through a mechanism associated with activation of the epidermal growth factor receptor signaling pathway.NEW & NOTEWORTHY Mixed lineage leukemia 1 (MLL1) is a methyltransferase that induces histone H3 lysine 4 trimethylation and exerts its functional roles by interacting with multiple subunits. In this study, we demonstrated that inhibition of MLL1 activity by MI503 or MM102 aggravated renal injury and apoptosis and suppressed renal tubular cell dedifferentiation and proliferation, suggesting that MLL1 activation during acute kidney injury acts as an intrinsic protective mechanism to mediate renal tubular cell survival and regeneration.

Multi-Organ Nutrigenomic Effects of Dietary Grapes in a Mouse Model

As a whole food, the potential health benefits of table grapes have been widely studied. Some individual constituents have garnered great attention, particularly resveratrol, but normal quantities in the diet are meniscal. On the other hand, the grape contains hundreds of compounds, many of which have antioxidant potential. Nonetheless, the achievement of serum or tissue concentrations of grape antioxidants sufficient to mediate a direct quenching effect is not likely, which supports the idea of biological responses being mediated by an indirect catalytic-type response. We demonstrate herein with Hsd:ICR (CD-1® Outbred, 18-24 g, 3-4 weeks old, female) mice that supplementation of a semi-synthetic diet with a grape surrogate, equivalent to the human consumption of 2.5 servings per day for 12 months, modulates gene expression in the liver, kidney, colon, and ovary. As might be expected when sampling changes in a pool of over 35,000 genes, there are numerous functional implications. Analysis of some specific differentially expressed genes suggests the potential of grape consumption to bolster metabolic detoxification and regulation of reactive oxygen species in the liver, cellular metabolism, and anti-inflammatory activity in the ovary and kidney. In the colon, the data suggest anti-inflammatory activity, suppression of mitochondrial dysfunction, and maintaining homeostasis. Pathway analysis reveals a combination of up- and down-regulation in the target tissues, primarily up-regulated in the kidney and down-regulated in the ovary. More broadly, based on these data, it seems logical to conclude that grape consumption leads to modulation of gene expression throughout the body, the consequence of which may help to explain the broad array of activities demonstrated in diverse tissues such as the brain, heart, eye, bladder, and colon. In addition, this work further supports the profound impact of nutrigenomics on mammalian phenotypic expression.

Novel insights into STAT3 in renal diseases

Signal transducer and activator of transcription 3 (STAT3) is a cell-signal transcription factor that has attracted considerable attention in recent years. The stimulation of cytokines and growth factors can result in the transcription of a wide range of genes that are crucial for several cellular biological processes involved in pro- and anti-inflammatory responses. STAT3 has attracted considerable interest as a result of a recent upsurge in study because of their role in directing the innate immune response and sustaining inflammatory pathways, which is a key feature in the pathogenesis of many diseases, including renal disorders. Several pathological conditions which may involve STAT3 include diabetic nephropathy, acute kidney injury, lupus nephritis, polycystic kidney disease, and renal cell carcinoma. STAT3 is expressed in various renal tissues under these pathological conditions. To better understand the role of STAT3 in the kidney and provide a theoretical foundation for STAT3-targeted therapy for renal disorders, this review covers the current work on the activities of STAT3 and its mechanisms in the pathophysiological processes of various types of renal diseases.

Mitochondrial Oxidative Metabolism: An Emerging Therapeutic Target to Improve CKD Outcomes

Chronic kidney disease (CKD) predisposes one toward end-stage renal disease (ESRD) and its associated morbidity and mortality. Significant metabolic perturbations in conjunction with alterations in redox status during CKD may induce increased production of reactive oxygen species (ROS), including superoxide (O₂^●-) and hydrogen peroxide (H₂O₂). Increased O₂^●- and H₂O₂ may contribute to the overall progression of renal injury as well as catalyze the onset of comorbidities. In this review, we discuss the role of mitochondrial oxidative metabolism in the pathology of CKD and the recent developments in treating CKD progression specifically targeted to the mitochondria. Recently published results from a Phase 2b clinical trial by our group as well as recently released data from a ROMAN: Phase 3 trial (NCT03689712) suggest avasopasem manganese (AVA) may protect kidneys from cisplatin-induced CKD. Several antioxidants are under investigation to protect normal tissues from cancer-therapy-associated injury. Although many of these antioxidants demonstrate efficacy in pre-clinical models, clinically relevant novel compounds that reduce the severity of AKI and delay the progression to CKD are needed to reduce the burden of kidney disease. In this review, we focus on the various metabolic pathways in the kidney, discuss the role of mitochondrial metabolism in kidney disease, and the general involvement of mitochondrial oxidative metabolism in CKD progression. Furthermore, we present up-to-date literature on utilizing targets of mitochondrial metabolism to delay the pathology of CKD in pre-clinical and clinical models. Finally, we discuss the current clinical trials that target the mitochondria that could potentially be instrumental in advancing the clinical exploration and prevention of CKD.

Limonin, a natural ERK2 agonist, protects against ischemic acute kidney injury

Acute kidney injury (AKI) is a refractory clinical syndrome with limited effective treatments. Amid AKI, activation of the extracellular signal-regulated kinase (ERK) cascade plays a critical role in promoting kidney repair and regeneration. However, a mature ERK agonist in treating kidney disease remains lacking. This study identified limonin, a member of the class of compounds known as furanolactones, as a natural ERK2 activator. Employing a multidisciplinary approach, we systemically dissected how limonin mitigates AKI. Compared to vehicles, pretreatment of limonin significantly preserved kidney functions after ischemic AKI. We revealed that ERK2 is a significant protein linked to the limonin's active binding sites through structural analysis. The molecular docking study showed a high binding affinity between limonin and ERK2, which was confirmed by the cellular thermal shift assay and microscale thermophoresis. Mechanistically, we further validated that limonin promoted tubular cell proliferation and reduced cell apoptosis after AKI by activating ERK signaling pathway in vivo. In vitro and ex vivo, blockade of ERK abolished limonin's capacity of preventing tubular cell death under hypoxia stress. Our results indicated that limonin is a novel ERK2 activator with strong translational potential in preventing or mitigating AKI.

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.

Avasopasem manganese (GC4419) protects against cisplatin-induced chronic kidney disease: An exploratory analysis of renal metrics from a randomized phase 2b clinical trial in head and neck cancer patients

Head and neck squamous cell carcinoma (HNSCC) patients treated with high-dose cisplatin concurrently with radiotherapy (hdCis-RT) commonly suffer kidney injury leading to acute and chronic kidney disease (AKD and CKD, respectively). We conducted a retrospective analysis of renal function and kidney injury-related plasma biomarkers in a subset of HNSCC subjects receiving hdCis-RT in a double-blinded, placebo-controlled clinical trial (NCT02508389) evaluating the superoxide dismutase mimetic, avasopasem manganese (AVA), an investigational new drug. We found that 90 mg AVA treatment prevented a significant reduction in estimated glomerular filtration rate (eGFR) three months as well as six and twelve months after treatment compared to 30 mg AVA and placebo. Moreover, AVA treatment may have allowed renal repair in the first 22 days following cisplatin treatment as evidenced by an increase in epithelial growth factor (EGF), known to aid in renal recovery. An upward trend was also observed in plasma iron homeostasis proteins including total iron (Fe-blood) and iron saturation (Fe-saturation) in the 90 mg AVA group versus placebo. These data support the hypothesis that treatment with 90 mg AVA mitigates cisplatin-induced CKD by inhibiting hdCis-induced renal changes and promoting renal recovery.

Downregulation of KLF10 contributes to the regeneration of survived renal tubular cells in cisplatin-induced acute kidney injury via ZBTB7A-KLF10-PTEN axis

Acute kidney injury (AKI) is a common clinical dysfunction with complicated pathophysiology and limited therapeutic methods. Renal tubular injury and the following regeneration process play a vital role in the course of AKI, but the underlining molecular mechanism remains unclear. In this study, network-based analysis of online transcriptional data of human kidney found that KLF10 was closely related to renal function, tubular injury and regeneration in various renal diseases. Three classical mouse models confirmed the downregulation of KLF10 in AKI and its correlation with tubular regeneration and AKI outcome. The 3D renal tubular model in vitro and fluorescent visualization system of cellular proliferation were constructed to show that KLF10 declined in survived cells but increased during tubular formation or conquering proliferative impediment. Furthermore, overexpression of KLF10 significantly inhibited, whereas knockdown of KLF10 extremely promoted the capacity of proliferation, injury repairing and lumen-formation of renal tubular cells. In mechanism, PTEN/AKT pathway were validated as the downstream of KLF10 and participated in its regulation of tubular regeneration. By adopting proteomic mass spectrum and dual-luciferase reporter assay, ZBTB7A were found to be the upstream transcription factor of KLF10. Our findings suggest that downregulation of KLF10 positively contributed to tubular regeneration in cisplatin induced acute kidney injury via ZBTB7A-KLF10-PTEN axis, which gives insight into the novel therapeutic and diagnostical target of AKI.

The Growth Factors: Potential Biomarkers and Therapeutic Targets in Kidney Diseases

BACKGROUND

Kidney diseases are a prevalent health problem worldwide. Although substantial progress has been made in understanding the pathophysiology of kidney disease, currently there is no satisfactory clinical treatment available to prevent or treat kidney disease. Therefore, strategies to establish early diagnosis, identify the key molecules, and develop novel therapeutic interventions to slow the progression of kidney diseases and reduce their complications are encouraged.

SUMMARY

The growth factors play a crucial role in the development of kidney diseases. The altered levels of growth factors are usually detected in circulation and urine in the disease course. A growing body of studies has suggested that growth factors, receptors, and related regulators are promising biomarkers for the diagnosis and/or prognosis and potential therapeutic targets for the treatment of kidney diseases. In this review, we summarize recent advances in the potential applications of growth factors for diagnostic biomarkers and therapeutic targets in kidney diseases and highlight their performances in clinical trials.

KEY MESSAGES

Most diagnostic and therapeutic strategies targeting growth factors are still far from clinical implementation. The better understanding of growth factor-regulated pathophysiology and the progress of new intervention approaches are expected to facilitate the clinical translation of growth factor-based diagnosis and therapy of kidney diseases.

Tenovin-1 Ameliorates Renal Fibrosis in High-Fat-Diet-Induced Diabetic Nephropathy via Antioxidant and Anti-Inflammatory Pathways

High-fat diet (HFD)-induced obesity has been involved in the development of diabetic nephropathy (DN). Tenovin-1, a potent selective SIRT1/2 inhibitor, regulates various target proteins. The present study evaluated the protective effect of Tenovin-1 against renal fibrosis in HFD-induced Zucker diabetic fatty (ZDF) rats. Rats were fed a normal chow diet or HFD. Tenovin-1 (45 mg/kg) administered to HFD-fed rats decreased inflammatory cytokine expression in the serum of the rats. The antioxidant status and oxidative damage to lipids or DNA were significantly restored by Tenovin-1. Additionally, Tenovin-1 reduced the levels of blood urea nitrogen (BUN), serum creatinine (sCr), microalbumin, and urinary protein-based biomarkers in the urine of HFD-fed rats. The abnormal architecture of the kidney and pancreas was restored by Tenovin-1 administration. Tenovin-1 also reduced apoptosis in the kidneys of the HFD-fed rats and HG-treated NRK-52E cells. It significantly lowered the levels of ECM proteins in the kidneys of HFD-fed rats and HG-treated NRK-52E cells. Additionally, Tenovin-1 markedly reduced claudin-1, SIRT1, and SIRT2, but increased SIRT3 and SIRT4 in HFD-fed rats and NRK-52E cells treated with HG. Furthermore, Tenovin-1 altered epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor-β (PDGFR-β), and signal transducer and activator of transcription 3 (STAT3) levels in the kidneys of HFD-fed rats. Conclusively, this study shows that Tenovin-1 can be a potential candidate drug for the treatment of HFD-induced renal fibrosis, in vivo and in vitro models.

Molecular Mechanisms and Biomarkers Associated with Chemotherapy-Induced AKI

Acute kidney injury (AKI) is a life-threatening condition characterized by a rapid and transient decrease in kidney function. AKI is part of an array of conditions collectively defined as acute kidney diseases (AKD). In AKD, persistent kidney damage and dysfunction lead to chronic kidney disease (CKD) over time. A variety of insults can trigger AKI; however, chemotherapy-associated nephrotoxicity is increasingly recognized as a significant side effect of chemotherapy. New biomarkers are urgently needed to identify patients at high risk of developing chemotherapy-associated nephrotoxicity and subsequent AKI. However, a lack of understanding of cellular mechanisms that trigger chemotherapy-related nephrotoxicity has hindered the identification of effective biomarkers to date. In this review, we aim to (1) describe the known and potential mechanisms related to chemotherapy-induced AKI; (2) summarize the available biomarkers for early AKI detection, and (3) raise awareness of chemotherapy-induced AKI.

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.

In vivo evidence for therapeutic applications of beclin 1 to promote recovery and inhibit fibrosis after acute kidney injury

Autophagy regulator beclin 1 activity determines the severity of kidney damage induced by ischemia reperfusion injury, but its role in kidney recovery and fibrosis are unknown and its therapeutic potentials have not been tested. Here, we explored beclin 1 effects on kidney fibrosis in three models of acute kidney injury (AKI)-ischemia reperfusion injury, cisplatin kidney toxicity, and unilateral ureteric obstruction in mouse strains with three levels of beclin 1 function: normal (wild type), low (heterozygous global deletion of beclin 1, Becn1^+/-), and high beclin 1 activity (knockin gain-of-function mutant Becn1, Becn1^FA). Fourteen days after AKI induction, heterozygous mice had more, but knockin mice had less kidney fibrosis than wild-type mice did. One day after ischemia reperfusion injury, heterozygous pan-kidney tubular Becn1 null mice had more severe kidney damage than homozygous distal tubular Becn1 null mice did, which was similar to the wild-type mice, implying that proximal tubular beclin 1 protects the kidney against ischemia reperfusion injury. By 14 days, both pan-kidney heterozygous Becn1 null and distal tubular homozygous Becn1 null mice had poorer kidney recovery than wild-type mice did. Injection of beclin 1 peptides increased cell proliferation in kidney tubules in normal mice. Beclin 1 peptides injection either before or after (2-5 days) ischemia reperfusion injury protected the kidney from injury and suppressed kidney fibrosis. Thus, both endogenous beclin 1 protein expression in kidney tubules and exogenous beclin 1 peptides are kidney protective via attenuation of acute kidney damage, promotion of cell proliferation, and inhibition of kidney fibrosis, consequently improving kidney recovery post-AKI. Hence, exogenous beclin 1 peptide may be a potential new therapy for AKI.

Discovery of Novel Proteomic Biomarkers for the Prediction of Kidney Recovery from Dialysis-Dependent AKI Patients

BACKGROUND

AKI requiring dialysis (AKI-D) is associated with prolonged hospitalization, mortality, and progressive CKD among survivors. Previous studies have examined only select urine or serum biomarkers for predicting kidney recovery from AKI.

METHODS

Serum samples collected on day 8 of randomized RRT from 72 patients enrolled in the Veteran's Affairs/National Institutes of Health Acute Renal Failure Trial Network study were analyzed by the SOMAscan proteomic platform to profile 1305 proteins in each sample. Of these patients, 38 recovered kidney function and dialysis was discontinued, whereas another 34 patients remained on dialysis by day 28.

RESULTS

Differential serum levels of 119 proteins, with 53 higher and 66 lower, were detected in samples from patients who discontinued dialysis, compared with patients who remained on dialysis by day 28. Patients were classified into tertiles on the basis of SOMAscan protein measurements for the 25 proteins most differentially expressed. The association of serum levels of each protein with kidney recovery was further evaluated using logistic regression analysis. Higher serum levels of CXCL11, CXCL2/CXCL3, CD86, Wnt-7a, BTK, c-Myc, TIMP-3, CCL5, ghrelin, PDGF-C, survivin, CA2, IL-9, EGF, and neuregulin-1, and lower levels of soluble CXCL16, IL1RL1, stanniocalcin-1, IL-6, and FGF23 when classified in tertiles were significantly associated with better kidney recovery. This significant association persisted for each of these proteins after adjusting for potential confounding risk factors including age, sex, cardiovascular SOFA score, congestive heart failure, diabetes, modality of intensive dialysis treatment, cause of AKI, baseline serum creatinine, day 8 urine volume, and estimated 60-day mortality risk.

CONCLUSIONS

These results suggest concerted changes between survival-related proteins and immune-regulatory chemokines in regulating angiogenesis, endothelial and epithelial remodeling, and kidney cell regeneration, illustrating potential mechanisms of kidney recovery. Thus, this study identifies potential novel predictive biomarkers of kidney recovery in patients with AKI-D.

miR-141 mediates recovery from acute kidney injury

Acute kidney injury (AKI) is a global clinical problem characterised by a sudden decline in renal function and mortality as high as 60%. Current AKI biomarkers have limited ability to classify disease progression and identify underlying pathological mechanisms. Here we hypothesised that alterations in urinary microRNA profiles could predict AKI recovery/nonrecovery after 90 days, and that injury-specific changes would signify microRNA mediators of AKI pathology. Comparison of urinary microRNA profiles from AKI patients with controls detected significant injury-specific increases in miR-21, miR-126 and miR-141 (p < 0.05) and decreases in miR-192 (p < 0.001) and miR-204 (p < 0.05). Expression of miR-141 increased in renal proximal tubular epithelial cells (PTECs) under oxidative stress in vitro and unilateral ischaemic reperfusion injury in vivo. Forced miR-141 expression in the presence of H₂O₂ increased PTEC death and decreased cell viability. Of nine messenger RNA targets with two or more miR-141 3'-untranslated region binding sites, we confirmed protein tyrosine phosphatase receptor type G (PTPRG) as a direct miR-141 target in PTECs. PTPRG-specific siRNA knockdown under oxidative stress increased PTEC death and decreased cell viability. In conclusion, we detected significant alterations in five urinary microRNAs following AKI, and identified proximal tubular cell PTPRG as a putative novel therapeutic target.

Pyruvate kinase M2 mediates fibroblast proliferation to promote tubular epithelial cell survival in acute kidney injury

Acute kidney injury (AKI) is a devastating condition with high morbidity and mortality rates. The pathological features of AKI are tubular injury, infiltration of inflammatory cells, and impaired vascular integrity. Pyruvate kinase is the final rate-limiting enzyme in the glycolysis pathway. We previously showed that pyruvate kinase M2 (PKM2) plays an important role in regulating the glycolytic reprogramming of fibroblasts in renal interstitial fibrosis. The present study aimed to determine the role of PKM2 in fibroblast activation during the pathogenesis of AKI. We found increased numbers of S100A4 positive cells expressing PKM2 in renal tissues from mice with AKI induced via folic acid or ischemia/reperfusion (I/R). The loss of PKM2 in fibroblasts impaired fibroblast proliferation and promoted tubular epithelial cell death including apoptosis, necroptosis, and ferroptosis. Mechanistically, fibroblasts produced less hepatocyte growth factor (HGF) in response to a loss of PKM2. Moreover, in two AKI mouse models, fibroblast-specific deletion of PKM2 blocked HGF signal activation and aggravated AKI after it was induced in mice via ischemia or folic acid. Fibroblast proliferation mediated by PKM2 elicits pro-survival signals that repress tubular cell death and may help to prevent AKI progression. Fibroblast activation mediated by PKM2 in AKI suggests that targeting PKM2 expression could be a novel strategy for treating AKI.

Wnt/β-Catenin in Acute Kidney Injury and Progression to Chronic Kidney Disease

Acute kidney injury (AKI) portends a poor clinical prognosis and increases the risk for the development of chronic kidney disease (CKD). Currently, there are no therapies to treat AKI or prevent its progression to CKD. Wnt/β-catenin is a critical regulator of kidney development that is up-regulated after injury. Most of the literature support a beneficial role for Wnt/β-catenin in AKI, but suggest that this pathway promotes the progression of tubulointerstitial fibrosis, the hallmark of CKD progression. We review the role of Wnt/β-catenin in renal injury with a focus on its potential as a therapeutic target in AKI and in AKI to CKD transition.

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.

Urine Biomarkers of Kidney Tubule Health and Incident CKD Stage 3 in Women Living With HIV: A Repeated Measures Study

Rationale & Objective

Single measurements of urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in HIV infection, but the prognostic value of repeat measurements over time is unknown.

Study Design

Cohort study.

Setting & Participants

647 women living with HIV infection enrolled in the Women’s Interagency Health Study.

Exposures

14 urinary biomarkers of kidney tubule health measured at 2 visits over a 3-year period.

Outcome

Incident CKD, defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² at two 6-month visits and an average eGFR decline ≥ 3% per year.

Analytical Approach

We used multivariable generalized estimating equations adjusting for CKD risk factors to evaluate baseline, time-updated, and change-over-time biomarker associations with incident CKD. We compared CKD discrimination between models with and without a parsimoniously selected set of biomarkers.

Results

During a median 7 years of follow-up, 9.7% (63/647) developed CKD. In multivariable-adjusted analyses, 3 of 14 baseline biomarkers associated with incident CKD. In contrast, 10 of 14 time-updated biomarkers and 9 of 14 biomarkers modeled as change over time associated with incident CKD. Urinary epidermal growth factor (EGF), α₁-microglobulin (A1M), and albumin were selected using penalized regression methods. In the time-updated model, lower urinary EGF (risk ratio [RR] per 2-fold higher time-updated biomarker levels, 0.69; 95% CI, 0.58-0.81), higher urinary A1M (RR, 1.47; 95% CI, 1.25-1.73), and higher urinary albumin excretion (RR, 1.21; 95% CI, 1.03-1.42) were jointly associated with increased risk for CKD. Compared with a base model (C statistic, 0.75), CKD discrimination improved after adding urinary EGF, A1M, and albumin values across baseline (C = 0.81), time-updated (C = 0.83), and change-over-time (C = 0.83) models (P < 0.01 for all).

Limitations

Observational design, incident CKD definition limited to eGFR.

Conclusions

Repeat urinary biomarker measurements for kidney tubule health have stronger associations with incident CKD compared with baseline measurements and moderately improve CKD discrimination in women living with HIV infection.

Matrix metalloproteinase-10 protects against acute kidney injury by augmenting epidermal growth factor receptor signaling

Matrix metalloproteinase-10 (MMP-10) is a zinc-dependent endopeptidase involved in regulating a wide range of biologic processes, such as apoptosis, cell proliferation, and tissue remodeling. However, the role of MMP-10 in the pathogenesis of acute kidney injury (AKI) is unknown. In this study, we show that MMP-10 was upregulated in the kidneys and predominantly localized in the tubular epithelium in various models of AKI induced by ischemia/reperfusion (IR) or cisplatin. Overexpression of exogenous MMP-10 ameliorated AKI, manifested by decreased serum creatinine, blood urea nitrogen, tubular injury and apoptosis, and increased tubular regeneration. Conversely, knockdown of endogenous MMP-10 expression aggravated kidney injury. Interestingly, alleviation of AKI by MMP-10 in vivo was associated with the activation of epidermal growth factor receptor (EGFR) and its downstream AKT and extracellular signal-regulated kinase-1 and 2 (ERK1/2) signaling. Blockade of EGFR signaling by erlotinib abolished the MMP-10-mediated renal protection after AKI. In vitro, MMP-10 potentiated EGFR activation and protected kidney tubular cells against apoptosis induced by hypoxia/reoxygenation or cisplatin. MMP-10 was colocalized with heparin-binding EGF-like growth factor (HB-EGF) in vivo and activated it by a process of proteolytical cleavage in vitro. These studies identify HB-EGF as a previously unrecognized substrate of MMP-10. Our findings also underscore that MMP-10 can protect against AKI by augmenting EGFR signaling, leading to promotion of tubular cell survival and proliferation after injury.

Epidermal Growth Factor Protects Against High Glucose-Induced Podocyte Injury Possibly via Modulation of Autophagy and PI3K/AKT/mTOR Signaling Pathway Through DNA Methylation

AIM

Diabetic nephropathy (DN) is a serious health problem worldwide. Epidermal growth factor (EGF) has suggested as a potential biomarker for the progression of chronic kidney disease. In this study, we examined the effects of EGF on the high glucose (HG)-induced podocyte injury and explored the underlying molecular mechanisms.

METHODS

The cell proliferation, toxicity, and cell apoptosis of podocytes were determined by CCK-8 assay, lactate dehydrogenase release assay, and flow cytometry, respectively, and protein levels in the podocytes were determined by Western blot assay. Mechanistically, DNA methylation analysis, bioinformatic analysis, methylation‑specific PCR and quantitative real-time PCR were used to analyze functional pathways in differentially methylated genes and the expression of the key methylated genes in the podocytes after different interventions.

RESULTS

EGF treatment significantly increased the protein expression level of LC3 and decreased the protein level of P62 in HG-stimulated podocytes, which was attenuated by autophagy inhibitor, 3-methyladenine. EGF increased the cell proliferation and the protein expression levels of nephrin and synaptopodin, but reduced cell toxicity and cell apoptosis and protein expression level of cleaved caspase-3, which was partially antagonized by 3-methyladenine. DNA methylation expression profiles revealed the differential hypermethylation sites and hypomethylation sites among podocytes treated with normal glucose, HG and HG+EGF. GO enrichment analysis showed that DNA methylation was significantly enriched in negative regulation of phosphorylation, cell-cell junction and GTPase binding. KEGG pathway analysis showed that these genes were mainly enriched in PI3K-Akt, Hippo and autophagy pathways. Further validation studies revealed that six hub genes (ITGB1, GRB2, FN1, ITGB3, FZD10 and FGFR1) may be associated with the protective effects of EGF on the HG-induced podocyte injury.

CONCLUSION

In summary, our results demonstrated that EGF exerted protective effects on HG-induced podocytes injury via enhancing cell proliferation and inhibiting cell apoptosis. Further mechanistic studies implied that EGF-mediated protective effects in HG-stimulated podocytes may be associated with modulation of autophagy and PI3K/AKT/mTOR signaling pathway.

The endoplasmic reticulum stress and the unfolded protein response in kidney disease: Implications for vascular growth factors

Acute kidney injury (AKI) and chronic kidney disease (CKD) represent an important challenge for healthcare providers. The identification of new biomarkers/pharmacological targets for kidney disease is required for the development of more effective therapies. Several studies have shown the importance of the endoplasmic reticulum (ER) stress in the pathophysiology of AKI and CKD. ER is a cellular organelle devolved to protein biosynthesis and maturation, and cellular detoxification processes which are activated in response to an insult. This review aimed to dissect the cellular response to ER stress which manifests with activation of the unfolded protein response (UPR) with its major branches, namely PERK, IRE1α, ATF6 and the interplay between ER and mitochondria in the pathophysiology of kidney disease. Further, we will discuss the relationship between mediators of renal injury (with specific focus on vascular growth factors) and ER stress and UPR in the pathophysiology of both AKI and CKD with the aim to propose potential new targets for treatment for kidney disease.

Urine biomarkers for monitoring acute kidney injury in premature infants

Background

Premature infants are at high risk for acute kidney injury (AKI). Serum creatinine (Cr) has limitations for evaluating kidney function in premature infants. We evaluated whether urine biomarkers could be used to monitor AKI in premature infants.

Methods

A prospective cohort study was conducted among infants born at < 37 weeks. Urine biomarkers and serum Cr were measured on postnatal days 1, 3, 5, 7, 10, and 14. Infants were divided into 3 groups according to gestational age (GA); < 28, 28 to < 32 and 32 to < 37 weeks.

Results

AKI occurred in 17 of 83 (20.5%) recruited infants at a median age of 7 (interquartile range 5–10) days. While the most common cause of AKI was hemodynamically significant patent ductus arteriosus (53.8%) in infants of GA < 28 weeks, necrotizing enterocolitis was the leading cause (50.0%) in infants of GA 28 to < 32 weeks. Urinary levels of neutrophil-gelatinase-associated lipocalin/Cr were higher and epidermal growth factor/Cr were lower in AKI group before the onset of AKI in infants of GA < 28 weeks. In infants of GA 28 to < 32 weeks, urinary interleukin-8/Cr levels were higher in AKI group at approximately the time of AKI onset.

Conclusion

Several urine biomarkers were significantly different between AKI and no AKI groups, and some had changed before the onset of AKI. These groups were distinct according to causative factors of AKI and GA. Urine biomarkers could be useful for monitoring the development of AKI in premature infants.

Glycogen synthase kinase-3β inhibits tubular regeneration in acute kidney injury by a FoxM1-dependent mechanism

Acute kidney injury (AKI) is characterized by injury to the tubular epithelium that leads to the sudden loss of renal function. Proper tubular regeneration is essential to prevent progression to chronic kidney disease. In this study, we examined the role of FoxM1, a forkhead box family member transcription factor in tubular repair after AKI. Renal FoxM1 expression increased after renal ischemia/reperfusion (I/R)-induced AKI in mouse kidneys. Treatment with thiostrepton, a FoxM1 inhibitor, reduced FoxM1 regulated pro-proliferative factors and cell proliferation in vitro, and tubular regeneration in mouse kidneys after AKI. Glycogen synthase kinase-3 (GSK3) was found to be an upstream regulator of FoxM1 because GSK3 inhibition or renal tubular GSK3β gene deletion significantly increased FoxM1 expression, and improved tubular repair and renal function. GSK3 inactivation increased β-catenin, Cyclin D1, and c-Myc, and reduced cell cycle inhibitors p21 and p27. Importantly, thiostrepton treatment abolished the improved tubular repair in GSK3β knockout mice following AKI. These results demonstrate that FoxM1 is important for renal tubular regeneration following AKI and that GSK3β suppresses tubular repair by inhibiting FoxM1.

Association between epidermal growth factor (EGF) and EGF receptor gene polymorphisms and end-stage renal disease and acute renal allograft rejection in a Korean population

Purpose

Epidermal growth factor (EGF) has been found to be associated with the development and repair mechanisms of several renal diseases. In this study, we hypothesized that single nucleotide polymorphisms (SNPs) in EGF or its receptor genes might have an association with end-stage renal disease (ESRD) or acute renal allograft rejection (AR) in a Korean population.

Methods

Three-hundred and forty seven recipients of the first renal transplants for ESRD, including 63 AR patients along with 289 healthy adults were included in the study. Five EGF gene SNPs (rs11568835, rs11568943, rs2237051, rs11569017, and rs3756261) and four EGFR gene SNPs (rs1140475, rs2293347, rs1050171, and rs6965469) were analyzed. The genotypes of these SNPs were analyzed using the AxiomTM genome-wide human assay. Statistical analysis was performed using SNPStats and Haploview version 4.2 software. Multiple logistic regression models (codominant, dominant, recessive, and Log-additive) were used to estimate the odds ratio (OR), 95% confidence interval (CI), and P value.

Results

One SNP (rs11569017) in the EGF gene showed significant association with ESRD but not with AR. Another SNP (rs11568835) in the EGF gene showed significant association with susceptibility to AR but not with ESRD. One SNP (rs1050171) in the EGFR gene showed significant association with susceptibility to AR but not with ESRD.

Conclusion

Our findings suggest that SNPs in the EGF and EGFR gene may be associated with the risk of ESRD and AR development in the Korean population.

Potential targeted therapy and diagnosis based on novel insight into growth factors, receptors, and downstream effectors in acute kidney injury and acute kidney injury-chronic kidney disease progression

Acute kidney injury (AKI) is defined as a rapid decline in renal function and is characterized by excessive renal inflammation and programmed death of resident cells. AKI shows high morbidity and mortality, and severe or repeated AKI can transition to chronic kidney disease (CKD) or even end-stage renal disease (ESRD); however, very few effective and specific therapies are available, except for supportive treatment. Growth factors, such as epidermal growth factor (EGF), insulin-like growth factor (IGF), and transforming growth factor-β (TGF-β), are significantly altered in AKI models and have been suggested to play critical roles in the repair process of AKI because of their roles in cell regeneration and renal repair. In recent years, a series of studies have shown evidence that growth factors, receptors, and downstream effectors may be highly involved in the mechanism of AKI and may function in the early stage of AKI in response to stimuli by regulating inflammation and programmed cell death. Moreover, certain growth factors or correlated proteins act as biomarkers for AKI due to their sensitivity and specificity. Furthermore, growth factors originating from mesenchymal stem cells (MSCs) via paracrine signaling or extracellular vesicles recruit leukocytes or repair intrinsic cells and may participate in AKI repair or the AKI-CKD transition. In addition, growth factor-modified MSCs show superior therapeutic potential compared to that of unmodified controls. In this review, we summarized the current therapeutic and diagnostic strategies targeting growth factors to treat AKI in clinical trials. We also evaluated the possibilities of other growth factor-correlated molecules as therapeutic targets in the treatment of AKI and the AKI-CKD transition.

Cathelicidin-related antimicrobial peptide protects against ischaemia reperfusion-induced acute kidney injury in mice

BACKGROUND AND PURPOSE

Despite recent advances in understanding its pathophysiology, treatment of acute kidney injury (AKI) remains a major unmet medical need, and novel therapeutic strategies are needed. Cathelicidin-related antimicrobial peptide (CRAMP) with immunomodulatory properties has an emerging role in various disease contexts. Here, we aimed to investigate the role of CRAMP and its underlying mechanisms in AKI.

EXPERIMENTAL APPROACH

The human homologue LL-37 and CRAMP were measured in blood samples of AKI patients and in experimental AKI mice respectively. Experimental AKI was induced in wild-type and CRAMP-deficient (Cnlp^-/- ) mice by ischaemia/reperfusion (I/R). Therapeutic evaluation of CRAMP was performed with exogenous CRAMP (5 mg·kg^-1 , i.p.) treatment.

KEY RESULTS

Cathelicidin expression was inversely related to clinical signs in patients and down-regulated in renal I/R-induced injury in mice. Cnlp^-/- mice exhibited exacerbated I/R-induced renal dysfunction, aggravated inflammatory responses and apoptosis. Moreover, over-activation of the NLRP3 inflammasome in Cnlp^-/- mice was associated with I/R-induced renal injury. Exogenous CRAMP treatment markedly attenuated I/R-induced renal dysfunction, inflammatory response and apoptosis, correlated with modulation of immune cell infiltration and phenotype. Consistent with Cnlp^-/- mouse data, CRAMP administration suppressed renal I/R-induced NLRP3 inflammasome activation, and its renal protective effects were mimicked by a specific NLRP3 inhibitor CY-09. The reno-protective and NLRP3 inhibitory effects of CRAMP required the EGF receptor.

CONCLUSION AND IMPLICATIONS

Our results suggest that CRAMP acts as a novel immunomodulatory mediator of AKI and modulation of CRAMP may represent a potential therapeutic strategy.

FGF/FGFR2 Protects against Tubular Cell Death and Acute Kidney Injury Involving Erk1/2 Signaling Activation

Background

Fibroblast growth factors (FGFs) are heparin-binding proteins involved in a variety of biological processes, and part of them may act through binding with cell membrane receptor FGFR2.

Objectives

To clarify the role and mechanisms of FGFR2 signaling in tubular cell survival and acute kidney injury (AKI).

Method

In this study, kidney ischemia/reperfusion (IR) or cisplatin injection was used to induce AKI in mice.

Results

In the kidneys after IR or cisplatin injection, the expression of FGFs and Erk1/2 phosphorylation were elevated. To investigate the role of FGFs in tubular cell survival and AKI, a mouse model with tubular cell specific FGFR2 gene disruption was generated. The knockouts were born normal. At 2 months of age, about one-third of the knockouts developed mild hydronephrosis. Ablation of FGFR2 in tubular cells aggravated acute kidney dysfunction as well as tubular cell apoptosis induced by IR or cisplatin. In addition, Erk1/2 phosphorylation was less in the knockout kidneys than in control littermates at day 1 after cisplatin injection. In cultured NRK-52E cells, recombinant FGF2 protein induced Erk1/2 phosphorylation and inhibited cisplatin-induced cell death. PD98059 abolished Erk1/2 phosphorylation and partly reversed the protective effect of FGF2 on cisplatin-induced cell death.

Conclusions

This study indicates that FGF/FGFR2 signaling plays an important role in protecting against tubular cell death and AKI, which is partly through stimulating Erk1/2 activation.

Protective effect of EX-527 against high-fat diet-induced diabetic nephropathy in Zucker rats

High-fat diet (HFD)-induced obesity is implicated in diabetic nephropathy (DN). EX-527, a selective Sirtuin 1 (SIRT1) inhibitor, has multiple biological functions; however, its protective effect against DN is yet to be properly understood. This study was aimed to explore the protective effect of EX-527 against DN in HFD-induced diabetic Zucker (ZDF) rats. After 21 weeks of continually feeding HFD to the rats, the apparent characteristics of progressive DN were observed, which included an increase in kidney weight (~160%), hyperglycemia, oxidative stress, and inflammatory cytokines, and subsequent renal cell damage. However, the administration of EX-527 for 10 weeks significantly reduced the blood glucose concentration and kidney weight (~59%). Furthermore, EX-527 significantly reduced the serum concentration of transforming growth factor-β1 (49%), interleukin (IL)-1β (52%), and IL-6 in the HFD-fed rats. Overall, the antioxidant activities significantly increased, and oxidative damage to lipids or DNA was suppressed. Particularly, EX-527 significantly reduced blood urea nitrogen (81%), serum creatinine (71%), microalbumin (43%), and urinary excretion of protein-based biomarkers. Histopathological examination revealed expansion of the extracellular mesangial matrix and suppression of glomerulosclerosis following EX-527 administration. EX-527 downregulated the expression of α-SMA (~64%), TGF-β (25%), vimentin, α-tubulin, fibronectin, and collagen-1 in the kidneys of the HFD-fed rats. Additionally, EX-527 substantially reduced claudin-1 and SIRT1 expression, but increased the expression of SIRT3 in the kidneys of the HFD-fed rats. EX-527 also inhibited the growth factor receptors, including EGFR, PDGFR-β, and STAT3, which are responsible for the anti-fibrotic effect of SIRT-1. Therefore, the administration of EX-527 protects against HFD-induced DN.

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.

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.

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.

Early activation of fibroblasts is required for kidney repair and regeneration after injury

Acute kidney injury (AKI) is a devastating condition with high morbidity and mortality. AKI is characterized by tubular injury, inflammation, and vascular impairment. However, the role of interstitial fibroblasts in the pathogenesis of AKI is largely unknown. Here, we show that fibroblasts were activated, as defined by vimentin expression, at 1 h after AKI triggered by ischemia-reperfusion injury (IRI). They rapidly entered the cell cycle with Ki-67-positive staining, which started at 1 h and peaked at 12 h after IRI, whereas tubular cell proliferation peaked at 3 d. The trigger for such an early activation of fibroblasts was identified as sonic hedgehog (Shh), which was rapidly induced in renal tubules and could target interstitial fibroblasts. Tubule-specific knockout of Shh in mice inhibited fibroblast activation and aggravated kidney injury and functional decline after IRI. Likewise, pharmacologic inhibition of Shh signaling with cyclopamine also hindered fibroblast activation and exacerbated kidney damage. These studies uncover that tubule-derived Shh triggers the early activation of fibroblasts, which is required for kidney repair and regeneration. Our findings for the first time illustrate a previously unrecognized importance of interstitial fibroblasts in conferring renal protection in AKI.-Zhou, D., Fu, H., Liu, S., Zhang, L., Xiao, L., Bastacky, S. I., Liu, Y. Early activation of fibroblasts is required for kidney repair and regeneration after injury.

Proximal Tubular Development Is Impaired with Downregulation of MAPK/ERK Signaling, HIF-1α, and Catalase by Hyperoxia Exposure in Neonatal Rats

Supplemental oxygen therapy (hyperoxia) is a widely used treatment for alveolar hypoxia in preterm infants. Despite being closely monitored, hyperoxia exposure is believed to undermine neonatal nephrogenesis and renal function caused by elevated oxidative stress. Previous studies have mostly focused on the hyperoxia-induced impairment of glomerular development, while the long-term impact of neonatal hyperoxia on tubular development and the regulatory component involved in this process remain to be clarified. Here, we examined tubular histology and apoptosis, along with the expression profile of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling, hypoxia-inducible factor 1α (HIF-1α), and catalase, following hyperoxia exposure in neonatal rats. Hematoxylin and eosin (H&E) staining revealed the early disappearance of the nephrogenic zone, as well as dilated lumens and reduced epithelial cells, of mature proximal tubules following neonatal hyperoxia. A robust increase in tubular cell apoptosis caused by neonatal hyperoxia was found using a TUNEL assay. Moreover, neonatal hyperoxia altered renal MAPK/ERK signaling activity and downregulated the expression of HIF-1α and catalase in the proximal tubules throughout nephrogenesis from S-shaped bodies to mature proximal tubules. Cell apoptosis in the proximal tubules was positively correlated with HIF-1α expression on the 14th postnatal day. Our data indicates that proximal tubular development is impaired by neonatal hyperoxia, which is accompanied by altered MAPK/ERK signaling as well as downregulated HIF-1α and catalase. Therapeutic management that targets MAPK/ERK signaling, HIF-1α, or catalase may serve as a protective agent against hyperoxia-induced oxidative damage to neonatal proximal tubules.

EGFR drives the progression of AKI to CKD through HIPK2 overexpression

The molecular mechanism underlying the transition of acute kidney injury (AKI) to chronic kidney disease (CKD) induced by vancomycin (VAN) remains largely unknown. Methods: The mice model of VAN drives AKI to CKD was developed to investigate the role and molecular mechanism of epidermal growth factor receptor (EGFR). The EGF receptor mutant (Wa-2) mice and gefitinib were used to inactivation of EGFR. The homeodomain interacting protein kinase 2 (HIPK2) siRNA was applied to silence of HIPK2. Human proximal tubular epithelial cells (HK-2) were used to explore the molecular regulation methanism of EGFR. ChIp analysis was used to investigate if STAT3 interaction with the promoter of HIPK2. Results: A novel VAN-induced AKI mouse model was established for the first time. Moreover, the expression levels collagen I&IV, α-SMA, p-EGFR and the expression of HIPK2 proteins were upregulated in this model. Interestingly, AKI caused by VAN was markedly attenuated in waved-2 mice at the early stage, as evidenced by the suppression of renal dysfunction, renal cell apoptosis and caspase3 activation. In the latter stage, renal fibrosis and inflammation were significantly ameliorated in Wa-2 mice, accompanied by the downregulation of profibrotic molecules and F4/80. Besides, the expression levels of HIPK2 and p-STAT3 were suppressed in Wa-2 mice during VAN-induced transition of AKI to CKD. In addition, renal fibrosis and inflammation, profibrotic molecules, and EGFR/STAT3/HIPK2 signaling were ameliorated by gefitinib treatment after VAN-induced AKI. These results were consistent with the findings of Wa-2 mice. EGFR/STAT3 signaling mediated VAN-induced HIPK2 expression in HK-2 cells. ChIp analysis revealed that STAT3 directly bound to the promoter region of HIPK2. Finally, inhibition of HIPK2 attenuated the VAN drove the progression of AKI to CKD. Conclusion: These data suggest that EGFR plays an important role in VAN-driven progression of AKI to CKD.

Apoptosis repressor with caspase recruitment domain deficiency accelerates ischemia/reperfusion (I/R)-induced acute kidney injury by suppressing inflammation and apoptosis: The role of AKT/mTOR signaling

Acute kidney injury (AKI) is a significant medical problem worldwide. Ischemia-reperfusion (I/R) injury of the kidney is a major cause of AKI. However, the pathogenesis that contributes to renal I/R injury is still unclear. Apoptosis repressor with caspase recruitment domain (ARC) is abundantly expressed in various tissues, and has been reported to play a strong protective role during pathological processes. Our results indicated that ARC expression was decreased in the reperfused kidneys. ARC deficiency markedly accelerated renal dysfunction, promoted reperfusion-regulated tubular epithelial cell apoptosis, and enhanced the vulnerability of kidney to I/R damage. Furthermore, in the kidney samples of mice underwent renal I/R injury, ARC knockout significantly accelerated the expression levels of inflammatory factors, including interleukin (IL)-1β, IL-6, tumor necrosis factor a (TNF-α), monocyte chemoattractant protein-1 (MCP-1) and IL-2. In addition, renal I/R injury-induced apoptosis was further exacerbated in ARC-deficient mice through promoting the expression of cleaved Caspase-3 and poly (ADP-ribose) polymerase (PARP). From the molecular level, ARC deletion obviously accelerated mitochondrial injury, as evidenced by the further decreased adenosine triphosphate (ATP) levels and mitochondrial potential in hypoxia-reoxygenation (H/R)-treated cells. Moreover, ARC knockout exacerbated AKI through activating phosphorylated protein kinase B (AKT), mammalian target of Rapamycin (mTOR) and p53, whereas reducing phosphorylated glycogen synthase kinase 3β (GSK3β). Of note, blocking AKT/mTOR signaling markedly attenuated inflammation, mitochondrial damage and apoptosis stimulated by H/R in ARC knockdown cells. In summary, our results suggested that ARC played a pivotal role in the pathogenesis of AKI induced by renal I/R operation through regulating AKT/mTOR signaling.

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.

Role of Epidermal Growth Factor Receptor (EGFR) and Its Ligands in Kidney Inflammation and Damage

Chronic kidney disease (CKD) is characterized by persistent inflammation and progressive fibrosis, ultimately leading to end-stage renal disease. Although many studies have investigated the factors involved in the progressive deterioration of renal function, current therapeutic strategies only delay disease progression, leaving an unmet need for effective therapeutic interventions that target the cause behind the inflammatory process and could slow down or reverse the development and progression of CKD. Epidermal growth factor receptor (EGFR) (ERBB1), a membrane tyrosine kinase receptor expressed in the kidney, is activated after renal damage, and preclinical studies have evidenced its potential as a therapeutic target in CKD therapy. To date, seven official EGFR ligands have been described, including epidermal growth factor (EGF) (canonical ligand), transforming growth factor-α, heparin-binding epidermal growth factor, amphiregulin, betacellulin, epiregulin, and epigen. Recently, the connective tissue growth factor (CTGF/CCN2) has been described as a novel EGFR ligand. The direct activation of EGFR by its ligands can exert different cellular responses, depending on the specific ligand, tissue, and pathological condition. Among all EGFR ligands, CTGF/CCN2 is of special relevance in CKD. This growth factor, by binding to EGFR and downstream signaling pathway activation, regulates renal inflammation, cell growth, and fibrosis. EGFR can also be “transactivated” by extracellular stimuli, including several key factors involved in renal disease, such as angiotensin II, transforming growth factor beta (TGFB), and other cytokines, including members of the tumor necrosis factor superfamily, showing another important mechanism involved in renal pathology. The aim of this review is to summarize the contribution of EGFR pathway activation in experimental kidney damage, with special attention to the regulation of the inflammatory response and the role of some EGFR ligands in this process. Better insights in EGFR signaling in renal disease could improve our current knowledge of renal pathology contributing to therapeutic strategies for CKD development and progression.

EGF Receptor-Dependent YAP Activation Is Important for Renal Recovery from AKI

BACKGROUND

Increasing evidence indicates that renal recovery from AKI stems from dedifferentiation and proliferation of surviving tubule epithelial cells. Both EGF receptor (EGFR) and the Hippo signaling pathway are implicated in cell proliferation and differentiation, and previous studies showed that activation of EGFR in renal proximal tubule epithelial cells (RPTCs) plays a critical role in recovery from ischemia-reperfusion injury (IRI). In this study, we explored RPTC activation of Yes-associated protein (YAP) and transcriptional coactivator with PDZ binding motif (TAZ), two key downstream effectors of the Hippo pathway, and their potential involvement in recovery from AKI.

METHODS

We used immunofluorescence to examine YAP expression in kidney biopsy samples from patients with clinical AKI and controls (patients with minimal change disease). Studies of RPTC activation of YAP and TAZ used cultured human RPTCs that were exposed to hypoxia-reoxygenation as well as knockout mice (with inducible deletions of Yap, Taz, or both occurring specifically in RPTCs) that were subjected to bilateral IRI.

RESULTS

YAP was activated in RPTCs in kidneys from post-AKI patients and post-IRI mouse kidneys. Inhibition of the interaction of YAP and the TEA domain (TEAD) transcription factor complex by verteporfin or conditional deletion of YAP in RPTCs delayed renal functional and structural recovery from IRI, whereas TAZ deletion had no effect. Activation of the EGFR-PI3K-Akt pathway in response to IRI signaled YAP activation, which promoted cell cycle progression.

CONCLUSIONS

This study shows that EGFR-PI3K-Akt-dependent YAP activation plays an essential role in mediating epithelial cell regeneration during kidney recovery from AKI.

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.

IL-22 sustains epithelial integrity in progressive kidney remodeling and fibrosis

IL-22, a member of the IL-10 cytokine family, accelerates tubule regeneration upon acute kidney injury, hence we speculated on a protective role also in chronic kidney disease. We quantified intrarenal IL-22 expression after unilateral ureteral (UUO) in wild-type mice and performed UUO in IL-22 knock-out animals. Obstruction phenotypic differences between IL22+/+ and IL22-/- mice were assessed by histology, immunohistochemistry, immunofluorescence as well as western blotting and reverse-transcriptase quantitative PCR ex vivo. Additionally, we performed in vitro experiments using both murine and human tubular cells to characterize IL-22 effects in epithelial healing. We found increasing IL-22 positivity in infiltrating immune cells over time upon UUO in wild-type mice. UUO in IL22-/- mice caused more tubular cell injury as defined by TUNEL positive cells and loss of tetragonolobus lectin staining. Instead, tubular dilation, loss of CD31+ perivascular capillaries, and interstitial fibrosis were independent of the Il22 genotype as assessed by standard histology, immunostaining, and mRNA expression profiling. In vitro experiments showed that recombinant human IL-22 significantly enhanced human tubular epithelial cell proliferation and wound closure upon mechanical injury, and electric cell-substrate impedance sensing studies revealed that recombinant IL-22 sustained tubular epithelial barrier function upon injury. In contrast, IL-22 had no such direct effects on human fibroblasts. Together, in progressive kidney remodeling upon UUO, infiltrating immune cells secrete IL-22, which augments tubular epithelial integrity and epithelial barrier function, but does not affect vascular rarefaction or fibrogenesis. We conclude that IL-22 could represent a molecular target to specifically modulate tubular atrophy.

Enhancing in vivo renal ischemia assessment by high-dynamic-range fluorescence molecular imaging

Fluorescence imaging has been used to evaluate the physiological features of renal ischemia in animal model. However, the fluorophore distribution details of the ischemia model could not be fully represented due to the limited dynamic range of the charged-couple device. A high-dynamic-range (HDR) strategy was adopted in renal ischemia fluorescence imaging, both ex vivo and in vivo. The HDR strategy successfully combined ischemia relevant biological features that could only be captured with different exposure times, and then presented these features in the HDR results. The HDR results effectively highlighted the renal ischemic areas with relatively better perfusion and diminished the saturation that resulted from long exposure time. The relative fluorescence intensities of the ischemic kidneys and the image entropy values were significantly higher in the HDR images than in the original images, therefore enhancing the visualization of the renal ischemia model. The results suggest that HDR could serve as a postprocessing strategy to enhance the assessment of in vivo renal ischemia, and HDR fluorescence molecular imaging could be a valuable imaging tool for future studies of clinical ischemia detection and evaluation.