Epidermal growth factors in the kidney and relationship to hypertension

The presence of xanthine dehydrogenase is crucial for the maturation of the rat kidneys

The development of the kidney involves essential cellular processes, such as cell proliferation and differentiation, which are led by interactions between multiple signaling pathways. Xanthine dehydrogenase (XDH) catalyzes the reaction producing uric acid in the purine catabolism, which plays a multifaceted role in cellular metabolism. Our previous study revealed that the genetic ablation of the Xdh gene in rats leads to smaller kidneys, kidney damage, decline of renal functions, and failure to thrive. Rats, unlike humans, continue their kidney development postnatally. Therefore, we explored whether XDH plays a critical role in kidney development using SS-/- rats during postnatal development phase. XDH expression was significantly increased from postnatal day 5 to 15 in wild-type but not homozygote rat kidneys. The transcriptomic profile of renal tissue revealed several dysregulated pathways due to the lack of Xdh expression with the remodeling in inflammasome, purinergic signaling, and redox homeostasis. Further analysis suggested that lack of Xdh affects kidney development, likely via dysregulation of epidermal growth factor and its downstream STAT3 signaling. The present study showed that Xdh is essential for kidney maturation. Our data, alongside the previous research, suggests that loss of Xdh function leads to developmental issues, rendering them vulnerable to kidney diseases in adulthood.

Nontargeted Plasma Proteomic Analysis of Renal Disease and Pulmonary Hypertension in Patients with Sickle Cell Disease

Sickle cell disease (SCD) is characterized by red blood cell sickling, vaso-occlusion, hemolytic anemia, damage to multiple organ systems, and, as a result, shortened life expectancy. Sickle cell disease nephropathy (SCDN) and pulmonary hypertension (pHTN) are common and frequently co-occurring complications of SCD; both are associated with markedly accelerated mortality. To identify candidate circulating biomarkers of SCDN and pHTN, we used mass spectrometry to quantify the relative abundance of >1000 proteins in plasma samples from 189 adults with SCD from the Outcome Modifying Genes in SCD (OMG-SCD) cohort (ProteomeXchange identifier PXD048716). Forty-four proteins were differentially abundant in SCDN, most significantly cystatin-C and collagen α-1(XVIII) chain (COIA1), and 55 proteins were dysregulated in patients with SCDN and pHTN, most significantly insulin-like growth factor-binding protein 6 (IBP6). Network analysis identified a module of 133 coregulated proteins significantly associated with SCDN, that was enriched for extracellular matrix proteins, insulin-like growth factor binding proteins, cell adhesion proteins, EGF-like calcium binding proteins, and several cadherin family members. Collectively, these data provide a comprehensive understanding of plasma protein changes in SCDN and pHTN which validate numerous studies of chronic kidney disease and suggest shared profiles of protein disruption in kidney dysfunction and pHTN among SCD patients.

The Association between Urinary Sodium-Potassium Ratio, Kidney Function, and Blood Pressure in a Cohort from the General Population

INTRODUCTION

Subclinical kidney dysfunction may contribute to salt-sensitive hypertension. We assessed the association between the urinary sodium-potassium ratio (Na/K ratio) and blood pressure (BP) in a general population cohort without diabetes, chronic kidney disease, cardiovascular disease, or treated hypertension. We investigated whether any such association was mediated by the kidney function markers measured glomerular filtration rate (mGFR), urinary albumin-creatinine ratio (ACR), and urinary epidermal growth factor-creatinine ratio (EGF-Cr).

METHODS

The Tromsø Study is a population-based study of inhabitants of the municipality of Tromsø, Northern Norway. Participants aged 50-62 years, without diabetes, chronic kidney disease, or cardiovascular disease, were invited to the substudy Renal Iohexol Clearance Survey in Tromsø 6 (RENIS-T6; 2007-09). For the present study, we excluded participants reporting the use of 1 or more antihypertensive agents, leaving 1,311 RENIS-T6 participants for a cross-sectional analysis. We measured office BP, 24-h ambulatory blood pressure (ABP), and mGFR using iohexol clearance. Na/K ratio, ACR, and EGF-Cr were measured in morning urine samples.

RESULTS

Urinary Na/K ratio was significantly associated with systolic office BP and ABP independently of cardiovascular risk factors and kidney function markers. A one-standard deviation unit increase in the Na/K ratio was associated with increased systolic ABP by 1.0 (0.3-1.6) mm Hg. Urinary Na/K ratio showed a stronger association with office BP than ABP. EGF-Cr, ACR, and mGFR did not mediate the relationship between urinary Na/K ratio and systolic BP.

CONCLUSIONS

In a representative sample of the middle-aged North-European population without diabetes, chronic kidney disease, cardiovascular disease, or treated hypertension, there was a consistent association between urinary Na/K ratio and BP. The association with BP was not mediated through kidney function measures, suggesting a relationship between a diet with high sodium and low potassium and higher BP regardless of kidney function.

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.

Genome-wide Meta-analysis Reveals New Gene Signatures and Potential Drug Targets of Hypertension

The prevalence of hypertension reported around the world is increasing and is an important public health challenge. This study was designed to explore the disease's genetic variations and to identify new hypertension-related genes and target proteins. We analyzed 22 publicly available Affymetrix cDNA datasets of hypertension using an integrated system-level framework involving differential expression genetic (DEG) analysis, data mining, gene enrichment, protein-protein interaction, microRNA analysis, toxicogenomics, gene regulation, molecular docking, and simulation studies. We found potential DEGs after screening out the extracellular proteins. We studied the functional role of seven shortlisted DEGs (ADM, EDN1, ANGPTL4, NFIL3, MSR1, CEBPD, and USP8) in hypertension after disease gene curation analysis. The expression profiling and cluster analysis showed significant variations and enriched GO terms. hsa-miR-365a-3p, hsa-miR-2052, hsa-miR-3065-3p, hsa-miR-603, hsa-miR-7113-3p, hsa-miR-3923, and hsa-miR-524-5p were identified as hypertension-associated miRNA targets for each gene using computational algorithms. We found functional interactions of source DEGs with target and important gene signatures including EGFR, AGT, AVP, APOE, RHOA, SRC, APOB, STAT3, UBC, LPL, APOA1, and AKT1 associated with the disease. These DEGs are mainly involved in fatty acid metabolism, myometrial pathways, MAPK, and G-alpha signaling pathways linked with hypertension pathogenesis. We predicted significantly disordered regions of 71.2, 48.8, and 45.4% representing the mutation in the sequence of NFIL3, USP8, and ADM, respectively. Regulation of gene expression was performed to find upregulated genes. Molecular docking analysis was used to evaluate Food and Drug Administration-approved medicines against the four DEGs that were overexpressed. For each elevated target protein, the three best drug candidates were chosen. Furthermore, molecular dynamics (MD) simulation using the target's active sites for 100 ns was used to validate these 12 complexes after docking. This investigation establishes the worth of systems genetics for finding four possible genes as potential drug targets for hypertension. These network-based approaches are significant for finding genetic variant data, which will advance the understanding of how to hasten the identification of drug targets and improve the understanding regarding the treatment of hypertension.

Epidermal growth factor deficiency predisposes to progressive renal disease

Epidermal growth factor (EGF) is produced in the kidney by thick ascending limbs of the loop of Henle and by distal convoluted tubules (DCTs). Reduced urinary EGF levels have been associated with chronic kidney disease but it is not known whether physiological levels of EGF protect the kidney from progressive renal disease. Here, we show that EGF-deficient mice on a mixed genetic background had increased urinary microalbumin, and a subset of these mice developed severe progressive renal disease with azotemia that was not seen in WT or TGFα-deficient littermates with this mixed genetic background. These azotemic EGF-deficient mice developed crescentic glomerulonephritis linked to HB-EGF/EGFR hyperactivation in glomeruli, as well as attenuation of the proximal tubule brush border, distal convoluted tubule (DCT) dilatation, and kidney fibrosis associated with renal β-catenin/mTOR hyperactivation. The observation of these severe renal pathologies only in a subset of EGF-deficient mice suggests that independent segregation of strain-specific modifier alleles contributes to the severity of the renal abnormalities that only manifest when EGF is lacking. These findings link the lack of EGF to renal pathologies in the adult mammalian kidney, in support of a role of physiological levels of EGF for maintaining the function of glomeruli, proximal tubules, and DCTs. These observations suggest that diminished EGF levels predispose kidneys to progressive renal disease.

GPCR-ErbB transactivation pathways and clinical implications

Cell surface receptors including the epidermal growth factor receptor (EGFR) family and G-protein coupled receptors (GPCRs) play quintessential roles in physiology, and in diseases, including cardiovascular diseases. While downstream signaling from these individual receptor families has been well studied, the cross-talk between EGF and GPCR receptor families is still incompletely understood. Including members of both receptor families, the number of receptor and ligand combinations for unique interactions is vast, offering a frontier of pharmacologic targets to explore for preventing and treating disease. This molecular cross-talk, called receptor transactivation, is reviewed here with a focus on the cardiovascular system featuring the well-studied GPCR receptors, but also discussing less-studied receptors from both families for a broad understanding of context of expansile interactions, repertoire of cellular signaling, and disease consequences. Attention is given to cell type, level of chronicity, and disease context given that transactivation and comorbidities, including diabetes, hypertension, coronavirus infection, impact cardiovascular disease and health outcomes.

Cimetidine-induced androgenic failure causes cell death and changes in actin, EGF and V-ATPase immunoexpression in rat submandibular glands

Submandibular gland (SMG) is responsive to androgens via androgen receptor (AR). We verified whether cimetidine induces androgenic dysfunction in SMG, and evaluated the structural integrity, cell death and immunoexpression of actin, EGF and V-ATPase in androgen-deficient SMG. Male rats received cimetidine (CMTG) and control animals (CG) received saline. Granular convoluted tubules (GCTs) diameter and number of acinar cell nuclei were evaluated. TUNEL and immunofluorescence reactions for detection of AR, testosterone, actin, EGF and V-ATPase were quantitatively analysed. In CG, testosterone immunolabelling was detected in acinar and ductal cells cytoplasm. AR-immunolabelled nuclei were observed in acinar cells whereas ductal cells showed AR-immunostained cytoplasm, indicating a non-genomic AR action. In CMTG, the weak testosterone and AR immunoexpression confirmed cimetidine-induced androgenic failure. A high cell death index was correlated with decreased number of acinar cells, GCTs diameter and EGF immunoexpression under androgenic dysfunction. Actin immunofluorescence decreased in the SMG cells, but an increased and diffuse cytoplasmic V-ATPase immunolabelling was observed in striated ducts, suggesting a disruption in the actin-dependent V-ATPase recycling due to androgenic failure. Our findings reinforce the androgenic role in the maintenance of SMG histophysiology, and point to a potential clinical use of cimetidine against androgen-dependent glandular tumour cells.

Urinary proteomics reveals key markers of salt sensitivity in hypertensive patients during saline infusion

BACKGROUND

Hypertension is a complex disease and is the major cause of cardiovascular complications. In the vast majority of individuals, the aetiology of elevated blood pressure (BP) cannot be determined, thus impairing optimized therapies and prognosis for individual patients. A more precise understanding of the molecular pathogenesis of hypertension remains a pressing priority for both basic and translational research. Here we investigated the effect of salt on naive hypertensive patients in order to better understand the salt intake-blood pressure relationship.

METHODS

Patients underwent an acute saline infusion and were defined as salt-sensitive or salt-resistant according to mean blood pressure changes. Urinary proteome changes during the salt load test were analysed by a label-free quantitative proteomics approach.

RESULTS

Our data show that salt-sensitive patients display equal sodium reabsorption as salt-resistant patients, as major sodium transporters show the same behaviour during the salt load. However, salt-sensitive patients regulate the renin angiotensin system (RAS) differently from salt-resistant patients, and upregulate proteins, as epidermal growth factor (EGF) and plasminogen activator, urokinase (PLAU), involved in the regulation of epithelial sodium channel ENaC activity.

CONCLUSIONS

Salt-sensitive and salt-resistant subjects have similar response to a saline/volume infusion as detected by urinary proteome. However, we identified glutamyl aminopeptidase (ENPEP), PLAU, EGF and Xaa-Pro aminopeptidase 2 precursor XPNPEP2 as key molecules of salt-sensitivity, through modulation of ENaC-dependent sodium reabsorption along the distal tubule.

Anti-Metastatic Activity of an Anti-EGFR Monoclonal Antibody against Metastatic Colorectal Cancer with KRAS p.G13D Mutation

The now clinically-used anti-epidermal growth factor receptor (EGFR) monoclonal antibodies have demonstrated significant efficacy only in patients with metastatic colorectal cancer (mCRC), with wild-type Kirsten rat sarcoma viral oncogene homolog (KRAS). However, no effective treatments for patients with mCRC with KRAS mutated tumors have been approved yet. Therefore, a new strategy for targeting mCRC with KRAS mutated tumors is desired. In the present study, we examined the anti-tumor activities of a novel anti-EGFR monoclonal antibody, EMab-17 (mouse IgG_2a, kappa), in colorectal cancer (CRC) cells with the KRAS p.G13D mutation. This antibody recognized endogenous EGRF in CRC cells with or without KRAS mutations, and showed a high sensitivity for CRC cells in flow cytometry, indicating that EMab-17 possesses a high binding affinity to the endogenous EGFR. In vitro experiments showed that EMab-17 exhibited antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity activities against CRC cells. In vivo analysis revealed that EMab-17 inhibited the metastases of HCT-15 and HCT-116 cells in the livers of nude mouse metastatic models, unlike the anti-EGFR monoclonal antibody EMab-51 of subtype mouse IgG₁. In conclusion, EMab-17 may be useful in an antibody-based therapy against mCRC with the KRAS p.G13D mutation.

NOX4-dependent regulation of ENaC in hypertension and diabetic kidney disease

NADPH oxidase 4 (NOX4) is the most abundant NOX isoform in the kidney; however, its importance for renal function has only recently emerged. The NOX4-dependent pathway regulates many factors essential for proper sodium handling in the distal nephron. However, the functional significance of this pathway in the control of sodium reabsorption during the initiation of chronic kidney disease is not established. The goal of this study was to test Nox4-dependent ENaC regulation in two models: SS hypertension and STZ-induced type 1 diabetes. First, we showed that genetic ablation of Nox4 in Dahl salt-sensitive (SS) rat attenuated a high-salt (HS)-induced increase in epithelial Na⁺ channel (ENaC) activity in the cortical collecting duct. We also found that H₂ O₂ upregulated ENaC activity, and H₂ O₂ production was reduced in both the renal cortex and medulla in SS^Nox4-/- rats fed an HS diet. Second, in the streptozotocin model of hyperglycemia-induced renal injury ENaC activity in hyperglycemic animals was elevated in SS but not SS^Nox4-/- rats. NaCl cotransporter (NCC) expression was increased compared to healthy controls, while expression values between SS and SS^Nox4-/- groups were similar. These data emphasize a critical contribution of the NOX4-mediated pathway in maladaptive upregulation of ENaC-mediated sodium reabsorption in the distal nephron in the conditions of HS- and hyperglycemia-induced kidney injury.

Differential behavior of NF-κB, IκBα and EGFR during the renal carcinogenic process in an experimental model in vivo

Renal cell carcinoma (RCC) is the most common type of cancer of the adult kidney. It is generally asymptomatic even at advanced stages, so opportune diagnosis is rare, making it almost impossible to study this cancer at its early stages. RCC tumors induced by ferric nitrilotriacetate (FeNTA) in rats histologically correspond to the human clear cell RCC subtype (ccRCC) and the exposure to this carcinogen during either one or two months leads to different early stages of neoplastic development. High levels of nuclear factor kappa B (NF-κB) and epidermal growth factor receptor (EGFR) as well as low levels of NF-κB inhibitor alpha (IκBα) are frequent in human RCC, but their status in FeNTA-induced tumors and their evolution along renal carcinogenesis is unclear. On this basis, in the present study NF-κB, IκBα and EGFR behavior was analyzed at different stages of the experimental renal carcinogenesis model. Similar to patients with RCC, neoplastic tissue showed high levels of p65, one of the predominant subunits of NF-κB in ccRCC and of EGFR (protein and mRNA), as well as a decrease in the levels of NF-κB's main inhibitor, IκBα, resulting in a classic oncogenic combination. Conversely, different responses were observed at early stages of carcinogenesis. After one month of FeNTA-exposure, NF-κB activity and EGFR levels augmented; but unexpectedly, IκBα also did. While after two months, NF-κB activity diminished, but EGFR and IκBα levels remained elevated. In conclusion, FeNTA-induced tumors and RCC human neoplasms are analogues regarding to the classic NF-κB, IκBα and EGFR behavior, and distinctive non-conventional combination of changes is developed at each early stage studied. The results obtained suggest that the dysregulation of the analyzed molecules could be related to different signaling pathways and therefore, to particular effects depending on the phase of the carcinogenic process.

Serum amphiregulin and cerebellin-1 levels in severe preeclampsia

PURPOSE

Preeclampsia is a form of hypertensive disorders of pregnancy and defined as the presence of new-onset hypertension and proteinuria or other end organ damage occurring after 20-week gestation. Preeclampsia can be a destructive process that can cause maternal and infant mortality. The exact etiopathogenesis of preeclampsia is still undefined. We aimed to compare serum amphiregulin and cerebellin-1 levels of severe preeclampsia patients with healthy pregnant women and healthy control subjects.

MATERIALS AND METHODS

A total of 88 women were enrolled in this study. Patients diagnosed with severe preeclampsia were group 1 (n = 28), healthy non-pregnant normotensive women group 2 (n = 30), and healthy pregnant women group 3 (n = 30). The participants in each group were matched for age. Pregnant women in groups 1 and 3 were also matched for gestational age. Serum amphiregulin and cerebellin-1 levels were measured using ELISA.

RESULTS

Serum amphiregulin levels were 3413 ± 1.38 ng/ml (1748-7739), 8510 ± 7213 ng/ml (2019-24,000), and 6580 ± 5360 ng/ml (2484-24,000) in preeclampsia patients, controls and healthy pregnant women, respectively. Amphiregulin levels were significantly lower in preeclampsia patients than healthy pregnant women (p=.008) and controls (p = .015). Amphiregulin levels were similar between healthy controls and healthy pregnant women (p  =  1.00). Cerebellin-1 levels were 222.039 ± 92.681 pg/ml (138,580-557,757) in preeclamptic patients, 537.043 ± 525.117 pg/ml (150,432-1,600,000) in controls and 415.091 ± 436.580 pg/ml (137,284-1,600,000) in healthy pregnant women. Cerebellin-1 levels were similar among groups (p = .272). Serum amphiregulin and cerebellin-1 levels were significantly and positively correlated with each other in preeclampsia patients (r  =  0.693, p < .001), controls (r  =  0.882, p < .001), and healthy pregnant women (r  =  0.591, p = .001). Serum level of amphiregulin ≤3590 pg/ml had a sensitivity of 67.9% and specificity of 63.3% in the diagnosis of preeclampsia (AUC: 0.751; p = .001).

CONCLUSIONS

Serum amphiregulin decreases in severe preeclampsia patients.

The role of distal tubule and collecting duct sodium reabsorption in sunitinib-induced hypertension

OBJECTIVE

Antiangiogenic receptor tyrosine kinase inhibitors (RTKI) induce arterial hypertension which may limit their use. Renal fractional sodium excretion (FENa) is reduced in early RTKI-induced hypertension, whereas fractional lithium excretion is unaltered. Therefore, we tested the hypothesis that activated distal tubule and collecting duct sodium reabsorption contributes to RTKI-induced hypertension.

METHODS

Amiloride-sensitive and hydrochlorothiazide (HCTZ)-sensitive fractional sodium reabsorption (FRNa) and renal epithelial sodium channel (ENaC) as well as sodium chloride cotransporter (NCC) abundances were determined in sunitinib-treated and control rats. The antihypertensive effects of amiloride and HCTZ were investigated by radiotelemery.

RESULTS

After 4 days of treatment, mean arterial pressure was 20 mmHg higher, FENa was lower (0.32 ± 0.08% vs. 0.65 ± 0.14%; P < 0.05), and renal medullary-ENaC protein abundance was higher in sunitinib-treated rats than in controls. Amiloride-sensitive FRNa was 2.37 ± 0.52% in sunitinib-treated rats vs. 2.66 ± 0.44% in controls (n.s.). HCTZ increased FENa by a similar magnitude without affecting amiloride-sensitive FRNa in both groups. After 14 days of treatment, renal medullary β-ENaC protein abundance was higher in rats that received sunitinib than in controls, whereas α-ENaC, γ-ENaC, and NCC abundances were similar in both groups. Amiloride and HCTZ reduced the sunitinib-induced mean arterial pressure rise by 8 ± 3 mmHg (P < 0.05) and 12 ± 2 mmHg (P < 0.05), respectively, without additive effects when combined.

CONCLUSION

ENaC-dependent and thiazide-sensitive sodium-retaining mechanisms are not overactive in sunitinib-induced hypertension but ENaC blockers and in particular thiazides may be suitable for its treatment.

Sex-specific and pleiotropic effects underlying kidney function identified from GWAS meta-analysis

Chronic kidney disease (CKD) is a growing health burden currently affecting 10–15% of adults worldwide. Estimated glomerular filtration rate (eGFR) as a marker of kidney function is commonly used to diagnose CKD. We analyze eGFR data from the Nord-Trøndelag Health Study and Michigan Genomics Initiative and perform a GWAS meta-analysis with public summary statistics, more than doubling the sample size of previous meta-analyses. We identify 147 loci (53 novel) associated with eGFR, including genes involved in transcriptional regulation, kidney development, cellular signaling, metabolism, and solute transport. Additionally, sex-stratified analysis identifies one locus with more significant effects in women than men. Using genetic risk scores constructed from these eGFR meta-analysis results, we show that associated variants are generally predictive of CKD with only modest improvements in detection compared with other known clinical risk factors. Collectively, these results yield additional insight into the genetic factors underlying kidney function and progression to CKD.

Estimated glomerular filtration rate (eGFR) is a measure of kidney function and used to characterize chronic kidney disease. Here, Graham et al. identify 53 novel loci for eGFR in a GWAS meta-analysis, a subset of which are associated with other common diseases, such as diabetes and hypertension, based on PheWAS.

PPARγ maintains the metabolic heterogeneity and homeostasis of renal tubules

Background

The renal tubules, which have distant metabolic features and functions in different segments, reabsorb >99% of approximately 180 l of water and 25,000 mmol of Na ⁺ daily. Defective metabolism in renal tubules is involved in the pathobiology of kidney diseases. However, the mechanisms underlying the metabolic regulation in renal tubules remain to be defined.

Methods

We quantitatively compared the proteomes of the isolated proximal tubules (PT) and distal tubules (DT) from C57BL/6 mouse using tandem mass tag (TMT) labeling-based quantitative mass spectrometry. Bioinformatics analysis of the differentially expressed proteins revealed the significant differences between PT and DT in metabolism pathway. We also performed in vitro and in vivo assays to investigate the molecular mechanism underlying the distant metabolic features in PT and DT.

Findings

We demonstrate that the renal proximal tubule (PT) has high expression of lipid metabolism enzymes, which is transcriptionally upregulated by abundantly expressed PPARα/γ. In contrast, the renal distal tubule (DT) has elevated glycolytic enzyme expression, which is mediated by highly expressed c-Myc. Importantly, PPARγ transcriptionally enhances the protease iRhom2 expression in PT, which suppresses EGF expression and secretion and subsequent EGFR-dependent glycolytic gene expression and glycolysis. PPARγ inhibition reduces iRhom2 expression and increases EGF and GLUT1 expression in PT in mice, resulting in renal tubule hypertrophy, tubulointerstitial fibrosis and damaged kidney functions, which are rescued by 2-deoxy-d-glucose treatment.

Interpretation

These findings delineate instrumental mechanisms underlying the active lipid metabolism and suppressed glycolysis in PT and active glycolysis in DT and reveal critical roles for PPARs and c-Myc in maintaining renal metabolic homeostasis. FUND: This work was supported by the National Natural Science Foundation of China (grants 81572076 and 81873932; to Q.Z.), the Applied Development Program of the Science and Technology Committee of Chongqing (cstc2014yykfB10003; Q.Z.), the Program of Populace Creativities Workshops of the Science and Technology Committee of Chongqing (Q.Z.), the special demonstration programs for innovation and application of techniques (cstc2018jscx-mszdX0022) from the Science and Technology Committee of Chongqing (Q.Z.).

Overexpression of Epidermal Growth Factor Receptor (EGFR) and HER-2 in Bladder Carcinoma and Its Association with Patients' Clinical Features

BACKGROUND The aim of this study was to determine the expression of EGFR/HER-2 and investigate their association with patients' clinical features in bladder transitional cell carcinoma (BTCC). MATERIAL AND METHODS Immunohistochemistry was utilized in our study to explore the expression of EGFR/HER-2 of 56 human bladder cancer samples and 10 normal bladder samples. RESULTS EGFR and HER-2 expressions were both significantly higher in bladder transitional cell carcinoma (BTCC) than that in non-cancer bladder samples; the EGFR positivity rate was 55.4% among BTCC samples and 37.5% for HER-2a. A statistically significant correlation was also present between the increasing EGFR or HER-2 expression levels and the clinical stages, pathologic grades, and tumor recurrence. The expression level of EGFR increased along with higher clinical stages and pathologic grades of BTCC, and the obviously increased expression of HER-2 was statistically associated with clinical stages and tumor recurrence. In addition, the expression level of HER-2 increased along with the higher clinical stage of BTCC. EGFR expression and HER-2 levels were positively associated in BTCC samples. CONCLUSIONS Our findings demonstrate that high EGFR and HER-2 expressions are dramatically increased in the BTCC tissues and are closely related to the clinical stages, pathologic grades, and tumor recurrence. Therefore, the evaluation of EGFR and HER-2 expression in BTCC may contribute to identifying patients who are at increased risk of disease progression and recurrence.

Ticagrelor Improves Endothelial Function by Decreasing Circulating Epidermal Growth Factor (EGF)

Ticagrelor is one of the most powerful P2Y₁₂ inhibitor. We have recently reported that, in patients with concomitant Stable Coronary Artery Disease (SCAD) and Chronic Obstructive Pulmonary Disease (COPD) undergoing percutaneous coronary intervention (PCI), treatment with ticagrelor, as compared to clopidogrel, is associated with an improvement of the endothelial function (Clinical Trial NCT02519608). In the present study, we showed that, in the same population, after 1 month treatment with ticagrelor, but not with clopidogrel, there is a decrease of the circulating levels of epidermal growth factor (EGF) and that these changes in circulating levels of EGF correlate with on-treatment platelet reactivity. Furthermore, in human umbilical vein endothelial cells (HUVEC) incubated with sera of the patients treated with ticagrelor, but not with clopidogrel there is an increase of p-eNOS levels. Finally, analyzing the changes in EGF and p-eNOS levels after treatment, we observed an inverse correlation between p-eNOS and EGF changes only in the ticagrelor group. Causality between EGF and eNOS activation was assessed in vitro in HUVEC where we showed that EGF decreases eNOS activity in a dose dependent manner. Taken together our data indicate that ticagrelor improves endothelial function by lowering circulating EGF that results in the activation of eNOS in the vascular endothelium.

Genetic and ethnic modulation of cardiovascular toxicity of vascular endothelial growth factor inhibitors

Vascular endothelial growth factor (VEGF) inhibitors, including monoclonal antibodies and tyrosine kinase inhibitors (TKIs), are important as anticancer treatments through curbing tumour angiogenesis and growth. VEGF inhibitors have significant cardiovascular effects. By blocking VEGF receptors, ligands, or signal pathways, VEGF inhibitors disturb the balance between vasodilation and vasoconstriction, undermine endothelial cell integrity, and activate cardiomyocyte apoptosis. VEGF inhibitors increase risks of hypertension, heart failure, thromboembolism and arrhythmia. Genetic and geographic studies showed that genetic polymorphisms likely play significant predictive or prognostic roles in cardiovascular toxicity associated with VEGF inhibitors. This review updates current understandings of VEGF inhibitors on cardiovascular toxicity, explores potential mechanisms, and clarifies whether genetic or ethnic factors contribute to their adverse effects. Key Messages VEGF inhibitors disturb the balance between vasodilation and vasoconstriction, undermine endothelial cell integrity and activate cardiomyocyte apoptosis. VEGF inhibitors increase risks of hypertension, heart failure, thromboembolism and arrhythmia. Genetic and geographic studies showed that genetic polymorphisms likely play significant predictive or prognostic roles in cardiovascular toxicity associated with VEGF inhibitors.

EGF regulation of proximal tubule cell proliferation and VEGF-A secretion

Proximal tubule cell (PTC) proliferation is critical for tubular regeneration and recovery from acute kidney injury. Epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF‐A) are important for the maintenance of tubulointerstitial integrity and can stimulate PTC proliferation. We utilized HK‐2 cells, an immortalized human PTC line, to characterize the EGF‐dependent regulation of VEGF‐A secretion and proliferation in PTCs. We demonstrate that EGF stimulates VEGF‐A secretion via the EGF receptor (EGFR) and stimulates cell proliferation via activation of the VEGF receptor, VEGFR‐2. EGFR activation promotes MAPK (ERK1/2) activation and HIF‐1α expression, which are required for basal and EGF‐stimulated VEGF‐A secretion. EGF also stimulates the phosphorylation of P70S6 kinase (P70S6K), the downstream target of mTORC1. Rapamycin decreased basal and EGF stimulated HIF‐1α and enhanced MAPK (ERK1/2) activation, while MAPK (ERK/12) inhibition downregulated HIF‐1α expression and the phosphorylation of p70S6K. EGF stimulation of p70S6K was also independent of p‐AKT. Inhibition of the mTORC1 pathway with rapamycin abolished phosphorylation of p70S6K but had no effect on VEGF‐A secretion, indicating that EGF‐stimulated VEGF‐A secretion did not require mTORC1 pathway activation. We demonstrate evidence of a complex crosstalk between the MAPK/ERK and mTORC1 pathways, wherein MAPK (ERK1/2) activation stimulates p‐P70S6K, while p‐P70S6K activation seems to inhibit MAPK (ERK1/2) in EGF‐treated HK‐2 cells. Our results suggest that EGF stimulates MAPK (ERK1/2) in HK‐2 cells, which in turn increases HIF‐1α expression and VEGF‐A secretion, indicating that VEGF‐A mediates EGF‐stimulated cell proliferation as an autocrine proximal tubular epithelial cell growth factor.

Involvement of ENaC in the development of salt-sensitive hypertension

Salt-sensitive hypertension is associated with renal and vascular dysfunctions, which lead to impaired fluid excretion, increased cardiac output, and total peripheral resistance. It is commonly accepted that increased renal sodium handling and plasma volume expansion are necessary factors for the development of salt-induced hypertension. The epithelial sodium channel (ENaC) is a trimeric ion channel expressed in the distal nephron that plays a critical role in the regulation of sodium reabsorption in both normal and pathological conditions. In this mini-review, we summarize recent studies investigating the role of ENaC in the development of salt-sensitive hypertension. On the basis of experimental data obtained from the Dahl salt-sensitive rats, we and others have demonstrated that abnormal ENaC activation in response to a dietary NaCl load contributes to the development of high blood pressure in this model. The role of different humoral factors, such as the components of the renin-angiotensin-aldosterone system, members of the epidermal growth factors family, arginine vasopressin, and oxidative stress mediating the effects of dietary salt on ENaC are discussed in this review to highlight future research directions and to determine potential molecular targets for drug development.

EGF Receptor Inhibition by Erlotinib Increases Aquaporin 2-Mediated Renal Water Reabsorption

Nephrogenic diabetes insipidus (NDI) is caused by impairment of vasopressin (VP) receptor type 2 signaling. Because potential therapies for NDI that target the canonical VP/cAMP/protein kinase A pathway have so far proven ineffective, alternative strategies for modulating aquaporin 2 (AQP2) trafficking have been sought. Successful identification of compounds by our high-throughput chemical screening assay prompted us to determine whether EGF receptor (EGFR) inhibitors stimulate AQP2 trafficking and reduce urine output. Erlotinib, a selective EGFR inhibitor, enhanced AQP2 apical membrane expression in collecting duct principal cells and reduced urine volume by 45% after 5 days of treatment in mice with lithium-induced NDI. Similar to VP, erlotinib increased exocytosis and decreased endocytosis in LLC-PK1 cells, resulting in a significant increase in AQP2 membrane accumulation. Erlotinib increased phosphorylation of AQP2 at Ser-256 and Ser-269 and decreased phosphorylation at Ser-261 in a dose-dependent manner. However, unlike VP, the effect of erlotinib was independent of cAMP, cGMP, and protein kinase A. Conversely, EGF reduced VP-induced AQP2 Ser-256 phosphorylation, suggesting crosstalk between VP and EGF in AQP2 trafficking and a role of EGF in water homeostasis. These results reveal a novel pathway that contributes to the regulation of AQP2-mediated water reabsorption and suggest new potential therapeutic strategies for NDI treatment.

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.

Maintenance of glia in the optic lamina is mediated by EGFR signaling by photoreceptors in adult Drosophila

The late onset of neurodegeneration in humans indicates that the survival and function of cells in the nervous system must be maintained throughout adulthood. In the optic lamina of the adult Drosophila, the photoreceptor axons are surrounded by multiple types of glia. We demonstrated that the adult photoreceptors actively contribute to glia maintenance in their target field within the optic lamina. This effect is dependent on the epidermal growth factor receptor (EGFR) ligands produced by the R1-6 photoreceptors and transported to the optic lamina to act on EGFR in the lamina glia. EGFR signaling is necessary and sufficient to act in a cell-autonomous manner in the lamina glia. Our results suggest that EGFR signaling is required for the trafficking of the autophagosome/endosome to the lysosome. The loss of EGFR signaling results in cell degeneration most likely because of the accumulation of autophagosomes. Our findings provide in vivo evidence for the role of adult neurons in the maintenance of glia and a novel role for EGFR signaling in the autophagic flux.

Degeneration of the nervous system can be viewed as a failure to maintain cell survival or function in the nervous system. The late onset of neurodegeneration in humans indicates that the cell survival in the nervous system must be maintained throughout our lives. Neuronal survival is maintained by neurotrophic factors in adults; however, it is unclear whether glia survival is also maintained throughout adulthood. Here, we use the Drosophila visual system as a model to address the role played by adult neurons for the active maintenance of glia. We demonstrated that the adult photoreceptors secrete a signaling molecule, which is transported to the brain to act on the lamina glia and maintain its integrity. When this signaling pathway is blocked, the lamina glia undergoes a progressive and irreversible degeneration. The primary defect occurs in the trafficking from the late endosome and autophagosome to the lysosome. This defect leads to an accumulation of autophagosomes and subsequent cell degeneration as a result of autophagy. Our findings provide in vivo evidence for a novel aspect of the neuron-glia interaction and a novel role for EGFR signaling in regulating the maintenance and degeneration of the nervous system.

Inhibition of ENaC by endothelin-1

The amiloride-sensitive epithelial Na(+) channel (ENaC) is a key player in the regulation of Na(+) homeostasis. Its functional activity is under continuous control by a variety of signaling molecules, including bioactive peptides of endothelin family. Since ENaC dysfunction is causative for disturbances in total body Na(+) levels associated with the abnormal regulation of blood volume, blood pressure, and lung fluid balance, uncovering the molecular mechanisms of inhibitory modulation or inappropriate activation of ENaC is crucial for the successful treatment of a variety of human diseases including hypertension. The precise regulation of ENaC is particularly important for normal Na(+) and fluid homeostasis in organs where endothelins are known to act: the kidneys, lung, and colon. Inhibition of ENaC by endothelin-1 (ET-1) has been established in renal cells, and several molecular mechanisms of inhibition of ENaC by ET-1 are proposed and will be reviewed in this chapter.

Role of Rho GDP dissociation inhibitor α in control of epithelial sodium channel (ENaC)-mediated sodium reabsorption

The epithelial sodium channel (ENaC) is expressed in the aldosterone-sensitive distal nephron where it performs sodium reabsorption from the lumen. We have recently shown that ENaC activity contributes to the development of salt-induced hypertension as a result of deficiency of EGF level. Previous studies revealed that Rho GDP-dissociation inhibitor α (RhoGDIα) is involved in the control of salt-sensitive hypertension and renal injury via Rac1, which is one of the small GTPases activating ENaC. Here we investigated the intracellular mechanism mediating the involvement of the RhoGDIα/Rac1 axis in the control of ENaC and the effect of EGF on ENaC in this pathway. We demonstrated that RhoGDIα is highly expressed in the cortical collecting ducts of mice and rats, and its expression is down-regulated in Dahl salt-sensitive rats fed a high salt diet. Knockdown of RhoGDIα in cultured cortical collecting duct principal cells increased ENaC subunits expression and ENaC-mediated sodium reabsorption. Furthermore, RhoGDIα deficiency causes enhanced response to EGF treatment. Patch clamp analysis reveals that RhoGDIα significantly decreases ENaC current density and prevents its up-regulation by RhoA and Rac1. Inhibition of Rho kinase with Y27632 had no effects on ENaC response to EGF either in control or RhoGDIα knocked down cells. However, EGF treatment increased levels of active Rac1, which was further enhanced in RhoGDIα-deficient cells. We conclude that changes in the RhoGDIα-dependent pathway have a permissive role in the Rac1-mediated enhancement of ENaC activity observed in salt-induced hypertension.

Epidermal growth factor, from gene organization to bedside

In 1962, epidermal growth factor (EGF) was discovered by Dr. Stanley Cohen while studying nerve growth factor (NGF). It was soon recognized that EGF is the prototypical member of a family of peptide growth factors that activate the EGF receptors, and that the EGF/EGF receptor signaling pathway plays important roles in proliferation, differentiation and migration of a variety of cell types, especially in epithelial cells. After the basic characterization of EGF function in the first decade or so after its discovery, the studies related to EGF and its signaling pathway have extended to a broad range of investigations concerning its biological and pathophysiological roles in development and in human diseases. In this review, we briefly describe the gene organization and tissue distribution of EGF, with emphasis on its biological and pathological roles in human diseases.