Heparin binding epidermal growth factor in renal ischaemia/reperfusion injury

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.

Role of tRNA derived fragments in renal ischemia-reperfusion injury

Background

Ischemia–reperfusion injury (IRI) is one of the major causes of acute kidney injury (AKI). tRNA derived fragments (tRFs/tiRNAs) are groups of small noncoding RNAs derived from tRNAs. To date, the role of tRFs/tiRNAs in renal IRI has not been reported. Herein, we aimed to investigate the involvement of tRFs/tiRNAs in the occurrence and development of ischemia–reperfusion-induced AKI.

Methods

Moderate/severe renal IRI mouse models were established by bilateral renal pedicle clamping. The tRF/tiRNA profiles of healthy controls and moderate/severe IRI-stressed kidney tissues were sequenced by Illumina NextSeq 500. Candidate differentially expressed tiRNAs were further verified by RT-qPCR. Biological analysis was also performed.

Results

Overall, 152 tRFs/tiRNAs were differentially expressed in the moderate ischemic injury group compared with the normal control group (FC > 2, p < 0.05), of which 47 were upregulated and 105 were downregulated; in the severe ischemic injury group, 285 tRFs/tiRNAs were differentially expressed (FC > 2, p < 0.05), of which 157 were upregulated, and 128 were downregulated. RT-qPCR determination of eight abundantly expressed tiRNAs was consistent with the sequencing results. Gene Ontology analysis for target genes of the tRFs/tiRNAs showed that the most enriched cell components, molecular functions and biological processes were Golgi apparatus, cytoplasmic vesicles, protein binding, cellular protein localization and multicellular organism development. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that these target genes were mainly involved in the natural killer cell mediated cytotoxicity pathway, citrate cycle, and regulation of actin cytoskeleton signaling pathway.

Conclusion

Our results indicated that tRFs/tiRNAs were involved in renal IRI. These tRFs/tiRNAs may be effective partly via regulation of renal immunity, inflammation and metabolism processes. Candidate genes, including tiRNA-Gly-GCC-003, tiRNA-Lys-CTT-003, and tiRNA-His-GTG-002, might be potential biomarkers and therapeutic targets of ischemia–reperfusion injury-induced acute 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.

The renal microcirculation in chronic kidney disease: novel diagnostic methods and therapeutic perspectives

Chronic kidney disease (CKD) affects 8–16% of the population worldwide and is characterized by fibrotic processes. Understanding the cellular and molecular mechanisms underpinning renal fibrosis is critical to the development of new therapeutics. Microvascular injury is considered an important contributor to renal progressive diseases. Vascular endothelium plays a significant role in responding to physical and chemical signals by generating factors that help maintain normal vascular tone, inhibit leukocyte adhesion and platelet aggregation, and suppress smooth muscle cell proliferation. Loss of the rich capillary network results in endothelial dysfunction, hypoxia, and inflammatory and oxidative effects and further leads to the imbalance of pro- and antiangiogenic factors, endothelial cell apoptosis and endothelial-mesenchymal transition. New techniques, including both invasive and noninvasive techniques, offer multiple methods to observe and monitor renal microcirculation and guide targeted therapeutic strategies. A better understanding of the role of endothelium in CKD will help in the development of effective interventions for renal microcirculation improvement. This review focuses on the role of microvascular injury in CKD, the methods to detect microvessels and the novel treatments to ameliorate renal fibrosis.

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.

Molecular characterization of the transition from acute to chronic kidney injury following ischemia/reperfusion

Though an acute kidney injury (AKI) episode is associated with an increased risk of chronic kidney disease (CKD), the mechanisms determining the transition from acute to irreversible chronic injury are not well understood. To extend our understanding of renal repair, and its limits, we performed a detailed molecular characterization of a murine ischemia/reperfusion injury (IRI) model for 12 months after injury. Together, the data comprising RNA-sequencing (RNA-seq) analysis at multiple time points, histological studies, and molecular and cellular characterization of targeted gene activity provide a comprehensive profile of injury, repair, and long-term maladaptive responses following IRI. Tubular atrophy, interstitial fibrosis, inflammation, and development of multiple renal cysts were major long-term outcomes of IRI. Progressive proximal tubular injury tracks with de novo activation of multiple Krt genes, including Krt20, a biomarker of renal tubule injury. RNA-seq analysis highlights a cascade of temporal-specific gene expression patterns related to tubular injury/repair, fibrosis, and innate and adaptive immunity. Intersection of these data with human kidney transplant expression profiles identified overlapping gene expression signatures correlating with different stages of the murine IRI response. The comprehensive characterization of incomplete recovery after ischemic AKI provides a valuable resource for determining the underlying pathophysiology of human CKD.

Targeting hepatic heparin-binding EGF-like growth factor (HB-EGF) induces anti-hyperlipidemia leading to reduction of angiotensin II-induced aneurysm development

Objective

The upregulated expression of heparin binding EGF-like growth factor (HB-EGF) in the vessel and circulation is associated with risk of cardiovascular disease. In this study, we tested the effects of HB-EGF targeting using HB-EGF-specific antisense oligonucleotide (ASO) on the development of aortic aneurysm in a mouse aneurysm model.

Approach and results

Low-density lipoprotein receptor (LDLR) deficient mice (male, 16 weeks of age) were injected with control and HB-EGF ASOs for 10 weeks. To induce aneurysm, the mice were fed a high fat diet (22% fat, 0.2% cholesterol; w/w) at 5 week point of ASO administration and infused with angiotensin II (AngII, 1,000ng/kg/min) for the last 4 weeks of ASO administration. We confirmed that the HB-EGF ASO administration significantly downregulated HB-EGF expression in multiple tissues including the liver. Importantly, the HB-EGF ASO administration significantly suppressed development of aortic aneurysms including thoracic and abdominal types. Interestingly, the HB-EGF ASO administration induced a remarkable anti-hyperlipidemic effect by suppressing very low density lipoprotein (VLDL) level in the blood. Mechanistically, the HB-EGF targeting suppressed hepatic VLDL secretion rate without changing heparin-releasable plasma triglyceride (TG) hydrolytic activity or fecal neutral cholesterol excretion rate.

Conclusion

This result suggested that the HB-EGF targeting induced protection against aneurysm development through anti-hyperlipidemic effects. Suppression of hepatic VLDL production process appears to be a key mechanism for the anti-hyperlipidemic effects by the HB-EGF targeting.

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

Epidermal growth factor receptor (EGFR) has been implicated in the pathogenesis of diabetic nephropathy and renal fibrosis; however, the causative role of sustained EGFR activation is unclear. Here, we generated a novel kidney fibrotic mouse model of persistent EGFR activation by selectively expressing the EGFR ligand, human heparin-binding EGF-like growth factor (hHB-EGF), in renal proximal tubule epithelium. hHB-EGF expression increased tyrosine kinase phosphorylation of EGFR and the subsequent activation of downstream signaling pathways, including ERK and AKT, as well as the profibrotic TGF-β1/SMAD pathway. Epithelial-specific activation of EGFR was sufficient to promote spontaneous and progressive renal tubulointerstitial fibrosis, as characterized by increased collagen deposition, immune cell infiltration, and α-smooth muscle actin (α-SMA)-positive myofibroblasts. Tubule-specific EGFR activation promoted epithelial dedifferentiation and cell-cycle arrest. Furthermore, EGFR activation in epithelial cells promoted the proliferation of α-SMA⁺ myofibroblasts in a paracrine manner. Genetic or pharmacologic inhibition of EGFR tyrosine kinase activity or downstream MEK activity attenuated the fibrotic phenotype. This study provides definitive evidence that sustained activation of EGFR in proximal epithelia is sufficient to cause spontaneous, progressive renal tubulointerstitial fibrosis, evident by epithelial dedifferentiation, increased myofibroblasts, immune cell infiltration, and increased matrix deposition.-Overstreet, J. M., Wang, Y., Wang, X., Niu, A., Gewin, L. S., Yao, B., Harris, R. C., Zhang, M.-Z. Selective activation of epidermal growth factor receptor in renal proximal tubule induces tubulointerstitial fibrosis.

Expression and Function of the Epidermal Growth Factor Receptor in Physiology and Disease

The epidermal growth factor receptor (EGFR) is the prototypical member of a family of membrane-associated intrinsic tyrosine kinase receptors, the ErbB family. EGFR is activated by multiple ligands, including EGF, transforming growth factor (TGF)-α, HB-EGF, betacellulin, amphiregulin, epiregulin, and epigen. EGFR is expressed in multiple organs and plays important roles in proliferation, survival, and differentiation in both development and normal physiology, as well as in pathophysiological conditions. In addition, EGFR transactivation underlies some important biologic consequences in response to many G protein-coupled receptor (GPCR) agonists. Aberrant EGFR activation is a significant factor in development and progression of multiple cancers, which has led to development of mechanism-based therapies with specific receptor antibodies and tyrosine kinase inhibitors. This review highlights the current knowledge about mechanisms and roles of EGFR in physiology and disease.

Specific endothelial heparin-binding EGF-like growth factor deletion ameliorates renal injury induced by chronic angiotensin II infusion

Transactivation of EGF receptor (EGFR) by angiotensin II (Ang II) plays important roles in the initiation and progression of chronic kidney diseases. Studies suggest that heparin-binding EGF-like factor (HB-EGF) may be a critical mediator in this process, but its role in vivo has not been investigated. In the current study, we found that in response to Ang II infusion, kidneys from endothelial HB-EGF deletion mice had significantly reduced EGFR activation compared with controls. Meanwhile, deletion of endothelial HB-EGF expression decreased Ang II infusion related renal injury, as demonstrated by 1) less albuminuria; 2) less glomerulosclerosis; 3) preserved endothelial integrity and decreased podocyte injury, as shown by greater glomerular tuft area and WT1-positive cells, and fewer apoptotic cells measured by cleaved caspase 3 staining; 4) reduced inflammation in the perivascular area and interstitium measured by F4/80 and CD3 immunostaining; and 5) reduced renal fibrosis. In conclusion, our results suggest that shedding of HB-EGF from endothelium plays an important role in Ang II-induced renal injury by linking Ang II-AT1R with EGFR transactivation. Inhibition of HB-EGF shedding could be a potential therapeutic strategy for chronic kidney disease.

Sodium thiosulfate ameliorates oxidative stress and preserves renal function in hyperoxaluric rats

Background

Hyperoxaluria causes crystal deposition in the kidney, which leads to oxidative stress and to injury and damage of the renal epithelium. Sodium thiosulfate (STS, Na₂S₂O₃) is an anti-oxidant, which has been used in human medicine for decades. The effect of STS on hyperoxaluria-induced renal damage is not known.

Methods

Hyperoxaluria and renal injury were induced in healthy male Wistar rats by chronic exposure to ethylene glycol (EG, 0.75%) in the drinking water for 4 weeks. The treatment effects of STS, NaCl or Na₂SO₄ were compared. Furthermore, the effects of STS on oxalate-induced oxidative stress were investigated in vitro in renal LLC-PK1 cells.

Results

Chronic EG exposure led to hyperoxaluria, oxidative stress, calcium oxalate crystalluria and crystal deposition in the kidneys. Whereas all tested compounds significantly reduced crystal load, only STS-treatment maintained tissue superoxide dismutase activity and urine 8-isoprostaglandin levels in vivo and preserved renal function. In in vitro studies, STS showed the ability to scavenge oxalate-induced ROS accumulation dose dependently, reduced cell-released hydrogen peroxide and preserved superoxide dismutase activity. As a mechanism explaining this finding, STS was able to directly inactivate hydrogen peroxide in cell-free experiments.

Conclusions

STS is an antioxidant, which preserves renal function in a chronic EG rat model. Its therapeutic use in oxidative-stress induced renal-failure should be considered.

Targeting CTGF, EGF and PDGF pathways to prevent progression of kidney disease

Chronic kidney disease (CKD) is a major health and economic burden with a rising incidence. During progression of CKD, the sustained release of proinflammatory and profibrotic cytokines and growth factors leads to an excessive accumulation of extracellular matrix. Transforming growth factor β (TGF-β) and angiotensin II are considered to be the two main driving forces in fibrotic development. Blockade of the renin-angiotensin-aldosterone system has become the mainstay therapy for preservation of kidney function, but this treatment is not sufficient to prevent progression of fibrosis and CKD. Several factors that induce fibrosis have been identified, not only by TGF-β-dependent mechanisms, but also by TGF-β-independent mechanisms. Among these factors are the (partially) TGF-β-independent profibrotic pathways involving connective tissue growth factor, epidermal growth factor and platelet-derived growth factor and their receptors. In this Review, we discuss the specific roles of these pathways, their interactions and preclinical evidence supporting their qualification as additional targets for novel antifibrotic therapies.

Essential roles of heparin-binding epidermal growth factor-like growth factor in the brain

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a member of the EGF family of growth factors, which interacts with the EGF receptor to exert mitogenic activity for various types of cells. Through its interactions with various molecules, it is involved in diverse biological processes, including wound healing, blast implantation, and tumor formation. At the same time, HB-EGF is widely expressed in the central nervous system, including the hippocampus and cerebral cortex, and is considered to play pivotal roles in the developing and adult nervous system. Because HB-EGF protein levels in the brain are much higher than those of TGF-α and EGF, it is possible that HB-EGF serves as a major physiologic ligand for the EGF receptor (ErbB1) within the central nervous system. Recent studies indicate that HB-EGF contributes to the neuronal survival and proliferation of glial/stem cells. HB-EGF also promotes the survival of dopaminergic neurons, an action mediated by mitogen-activated protein kinase (MAPK) as well as by the Akt signaling pathway. In this review, we discuss recent findings on the implications of HB-EGF in higher brain functions of the central nervous system.

A miR-1207-5p binding site polymorphism abolishes regulation of HBEGF and is associated with disease severity in CFHR5 nephropathy

Heparin binding epidermal growth factor (HBEGF) is expressed in podocytes and was shown to play a role in glomerular physiology. MicroRNA binding sites on the 3′UTR of HBEGF were predicted using miRWalk algorithm and followed by DNA sequencing in 103 patients diagnosed with mild or severe glomerulopathy. A single nucleotide polymorphism, miRSNP C1936T (rs13385), was identified at the 3′UTR of HBEGF that corresponds to the second base of the hsa-miR-1207-5p seed region. When AB8/13 undifferentiated podocytes were transfected with miRNA mimics of hsa-miR-1207-5p, the HBEGF protein levels were reduced by about 50%. A DNA fragment containing the miRSNP allele-1936C was cloned into the pMIR-Report Luciferase vector and co-transfected with miRNA mimics of hsa-miR-1207-5p into AB8/13 podocytes. In agreement with western blot data, this resulted in reduced luciferase expression demonstrating the ability of hsa-miR-1207-5p to directly regulate HBEGF expression. On the contrary, in the presence of the miRSNP 1936T allele, this regulation was abolished. Collectively, these results demonstrate that variant 1936T of this miRSNP prevents hsa-miR-1207-5p from down-regulating HBEGF in podocytes. We hypothesized that this variant has a functional role as a genetic modifier. To this end, we showed that in a cohort of 78 patients diagnosed with CFHR5 nephropathy (also known as C3-glomerulopathy), inheritance of miRSNP 1936T allele was significantly increased in the group demonstrating progression to chronic renal failure on long follow-up. No similar association was detected in a cohort of patients with thin basement membrane nephropathy. This is the first report associating a miRSNP as genetic modifier to a monogenic renal disorder.

ADAM17 up-regulation in renal transplant dysfunction and non-transplant-related renal fibrosis

BACKGROUND

Interstitial fibrosis and tubular atrophy (IF/TA) is an important cause of renal function loss and ischaemia-reperfusion (I/R) injury is considered to play an important role in its pathophysiology. The aim of the present study was to investigate the role of a disintegrin and metalloproteinase 17 (ADAM17) in human renal allograft disease and in experimental I/R injury of the kidney.

METHODS

We studied the expression of ADAM17 messenger RNA (mRNA) in IF/TA and control kidneys by reverse transcription-polymerase chain reaction and in situ hybridization. Moreover, we assessed ADAM17-mediated heparin-binding epidermal growth factor (HB-EGF) shedding in immortalized human cells. Finally, we studied the effect of pharmacological ADAM17 inhibition in a model of renal I/R injury in rats.

RESULTS

ADAM17 mRNA was up-regulated in IF/TA when compared to control kidneys. In normal kidneys, ADAM17 mRNA was weakly expressed in proximal tubules, peritubular capillaries, glomerular endothelium and parietal epithelium. In IF/TA, tubular, capillary and glomerular ADAM17 expression was strongly enhanced with de novo expression in the mesangium. In interstitial fibrotic lesions, we observed co-localization of ADAM17 with HB-EGF protein. In vitro, inhibition of ADAM17 with TNF484 resulted in a dose-dependent reduction of HB-EGF shedding in phorbol 12-myrisate 13-acetate-stimulated cells and non-stimulated cells. In vivo, ADAM17 inhibition significantly reduced the number of glomerular and interstitial macrophages at Day 4 of reperfusion.

CONCLUSIONS

In conclusion, HB-EGF co-expresses with ADAM17 in renal interstitial fibrosis, suggesting a potential interaction in IF/TA. Targeting ADAM17 to reduce epidermal growth factor receptor phosphorylation could be a promising way of intervention in human renal disease.

Ischemic kidney injury and mechanisms of tissue repair

Acute kidney injury (AKI) may result from ischemia or by the use of nephrotoxic agents. The incidence of AKI is variable, depends on comorbidities, and ranges from 5 to 35% in all hospitalized patients. The mechanisms of kidney injury exist within a large network of signaling pathways driven by interplay of inflammatory cytokines/chemokines, reactive oxygen species (ROS), and apoptotic factors. The effects and progression of injury overlap extensively with the remarkable ability of the kidney to repair itself both by intrinsic and extrinsic mechanisms that involve specific cell receptors/ligands as well as possible paracrine influences. The fact that kidney injury is usually part of a generalized comorbid condition makes it all the more challenging in terms of assessment of severity. In this review, we attempt to analyze the mechanisms of ischemic injury and repair in acute and chronic kidney disease from the perspectives of both preclinical and human studies.