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Abstract: Aim: Cyclosporine A (CsA) induces renal vasoconstriction and hypoxia and enhances the expression of endothelin‐1 (ET‐1) pro‐hormone (pre‐pro‐ET‐1), plausibly leading to a feed‐forward loop of renal vasoconstriction, hypoxia and enhanced synthesis of the potent vasoconstrictor ET‐1. Endothelin‐converting enzyme (ECE)‐1 cleaves big endothelin to generate endothelin (ET)‐1 and is upregulated by hypoxia via hypoxia‐inducible factor (HIF). We hypothesized that in addition to the direct induction of ET‐1 synthesis, CsA might also intensify renal ECE‐1 expression, thus contributing to enhanced ET‐1 synthesis following CsA. Methods: CsA was administered to Sprague Dawley rats (120 mg/kg/SC) for 4 days, and renal HIF and ECE‐1 expression were assessed with Western blots and immunostaining. Human umbilical vein endothelial cells (HUVEC) and proximal tubular cell line (HK‐2) were subjected to CsA, and ECE‐1 induction was evaluated using real‐time mRNA PCR and Western blots. Results: Cyclosporine A intensified renal parenchymal ECE‐1 expression in the rat kidney, particularly in distal nephron segments, along with renal hypoxia (detected by pimonidazole adducts) and HIF expression, in line with our recent observations showing episodic hypoxia in mice subjected to CsA. Furthermore, in cultured normoxic HUVEC and HK‐2 cells, CsA dose‐dependently induced both pre‐pro‐ET‐1 and ECE‐1 mRNA and protein expression, with enhanced ET‐1 generation. Conclusion: CsA induces ECE‐1 via both hypoxic and non‐hypoxic pathways. ECE‐1 may contribute to increased renal ET‐1 generation following CsA, participating in a feed‐forward loop of renal parenchymal hypoxia and ET synthesis. [ABSTRACT FROM AUTHOR]

Introduction: Similarities of the rat to the human placenta make rat pregnancy models relevant to the study of human gestational diseases. Understanding of species differences is necessary to extrapolate from animal models to humans. We observed alpha-smooth muscle actin (αSMA) expression in rat endovascular trophoblasts (EVasT) and investigated the spatial and temporal expression of smooth muscle (SM) proteins and their potential function in remodeled spiral artery. Methods: Rat placentas were examined from gestational day 13 to term, and were immunostained for cytokeratin, αSMA, alpha heavy chain of SM myosin, non-muscle myosin, Rho proteins, regulators of SM gene expression, myocardin, an early marker of SM differentiation and endothelin receptors A and B (ETA, ETB). Transmission electron microscopy (TEM) was performed. Modified spiral artery rings were studied ex vivo for endothelin-1- induced contraction. Results: EVasT expressed SM proteins co-localizing with cytokeratin confirming their trophoblastic origin from gestational day 13 to term. Thin fibers, consistent with actin fibers, were observed by TEM, in the cellular localization of αSMA in EVasT. Functional experiments revealed that addition of 10-7 M endothelin-1 ex vivo reduced vascular lumen area by 11.1% ± 1.8% compared with control. This effect was reduced to only 1.0 ± 1.7% with ETA antagonist, and to 5.4 ± 1.7% contraction by ETB antagonist, p < 0.002, for all. Discussion: The expression of SM proteins in EVasT along with the contractibility of the rat remodeled spiral artery ex vivo, suggest that some vascular tone is potentially maintained by endothelin-1, and may play a role in situations of dysregulation of the vasoactive systems. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor about post-splenectomy pseudohyperkalemia in patients with chronic idiopathic myelofibrosis and thrombocytosis.

Abstract Background Angiogenic therapy with vascular endothelial growth factor (VEGF) has been proposed as a treatment paradigm for patients suffering from an insufficiency of collateral vessels. Diabetes is associated with increase in the production of VEGF and therefore additional VEGF may not be beneficial. Accordingly, we sought to determine the efficacy of VEGF therapy to augment collateral formation and tissue perfusion in a diabetic mouse ischemic hindlimb model. Methods Diabetic and non-diabetic mice were studied in parallel for the efficacy of VEGF administration. Diabetes was induced with streptozotocin. Hindlimb ischemia was produced by severing the left iliac artery. An outlet tube from an osmotic infusion pump with placebo/ 500 micrograms of plasmid-DNA encoding VEGF was fenestrated and tunneled into the left quadriceps muscle. Results VEGF induced more rapid and complete restoration of blood flow in normal mice. However, in the setting of diabetes there was no difference between VEGF Vs. placebo in the rate or adequacy of flow restoration. There was a significant increase in smooth muscle actin and Factor-VIII antigen densities in diabetic animals and in animals which received VEGF. Conclusions Angiogenic therapy with VEGF in the setting of diabetes does not appear to have the beneficial effects seen in the absence of diabetes.

Hypoxia of the kidney in diabetes could predispose it to develop acute and chronic renal failure. To examine the relationship between renal hypoxia and renal failure, we measured hypoxia (as a pimonidazole adducts), hypoxia-inducible factors (HIFs), and a hypoxia target gene heme oxygenase-1. The studies were performed in rats with streptozotocin (STZ)-induced diabetes, Cohen diabetes sensitive rats, and during short-term artificial hyperglycemia in rats induced by intravenous glucose and octreotide. STZ-treated rats received insulin, the superoxide dismutase mimetic tempol, or contrast medium. Radiocontrast media causes hypoxia and HIF induction. Hypoxia, HIFs, and heme oxygenase were undetectable in controls, but transiently activated in STZ-treated and the Cohen diabetes sensitive rats. Different patterns of HIFs and pimonidazole were observed between the three models. Insulin abolished pimonidazole and HIF induction, whereas tempol lead to increased HIFs and heme oxygenase induction at similar levels of pimonidazole. When compared with control rats, STZ-treated rats exhibited more intense and protracted renal pimonidazole, with augmented hypoxia inducible factor production and reduced GFR following contrast media. Our data suggest that both regional hypoxia and hypoxia adaptation transiently occur in early stages of experimental diabetes, largely dependent on hyperglycemia or after contrast media. Tempol may augment the HIF response in diabetes.Kidney International (2008) 73, 34–42; doi:10.1038/sj.ki.5002567; published online 3 October 2007 [ABSTRACT FROM AUTHOR]

Plasma endothelin-1 levels rise in diabetes and after exposure to contrast media suggesting a role in progressive diabetic and acute radiocontrast nephropathies. Here we studied individual and combined effects of streptozotocin-induced diabetes and contrast media on renal endothelin converting enzyme-1 levels in the rat. In vivo, medullary (but not cortical) endothelin converting enzyme protein gradually increased 4 to 5-fold following the induction of diabetes or after the administration of contrast media but rose 15-fold when diabetic rats were given contrast media. Changes in mRNA expression paralleled those of the protein. Immunohistochemistry confirmed that increased tubular and endothelial cell endothelin converting enzyme-1 were most pronounced in the medulla. In vitro, endothelin-1 levels increased 3-fold following incubation of endothelial cells with media high in glucose or with contrast and 4-fold with their combination. Endothelin converting enzyme-1 protein and mRNA expression changed in a similar pattern while prepro endothelin-1 mRNA increased with each insult but not in an additive way. Our study shows that diabetes and contrast media up-regulate renal medullary endothelin converting enzyme-1 expression and synthesis.Kidney International (2008) 74, 91–100; doi:10.1038/ki.2008.112; published online 2 April 2008 [ABSTRACT FROM AUTHOR]

Background: Heart failure (HF) is considered a putative factor predisposing to acute renal failure (ARF). Since outer medullary hypoxic injury may play an important role in the pathogenesis of acute tubular necrosis, we explored the impact of experimental HF on the propensity to develop ARF with hypoxic medullary injury following the inhibition of prostaglandin and nitric oxide synthesis. Methods: Compensated, high-output HF was induced in Sprague-Dawley rats by aorto-caval fistula. At the eighth to ninth postoperative day, the rats were injected with indomethacin and N(omega) nitro-L-arginine methyl ester (L-NAME; ARF protocol) and were sacrificed 24 hours later for morphologic evaluation. Results: Kidney function comparably declined in HF-ARF rats and in control sham operated animals (CTR-ARF). Nevertheless, outer medullary hypoxic damage with medullary thick ascending limb (mTAL) necrosis occurred almost exclusively in the HF-ARF group (11 +/- 4% vs. 0.2 +/- 0.2% of tubules in CTR-ARF, P < 0.03). In a third group of HF animals subjected to vehicles only (HF-Nil), kidney function was preserved and renal morphology remained intact. Papillary-tip necrosis was consistently found in all animals subjected to indomethacin and L-NAME, irrespective of preconditioning. Morphometric evaluation disclosed that HF was not associated with mTAL hypertrophy. Conclusions: Incipient HF predisposes to hypoxic outer medullary injury, probably reflecting the impact of regional vasoconstrictive stimuli rather than tubular hypertrophy when protective local vasodilating mechanisms are hampered. The presence and extent of outer medullary hypoxic damage cannot be predicted from the functional derangement, which in the experimental settings may also represent prerenal azotemia or papillary damage. [ABSTRACT FROM AUTHOR]

Gaucher disease (GD) has a high carrier rate among Ashkenazi Jews.The most common disease-causing variant in this population N370S, is also prevalent pan-ethnically. This has led to speculations of some protective effect for carriers of this variant. During the recent COVID-19 pandemic, GD patients reportedly had a surprisingly low infection rate and mild symptoms considering their disease status. As SARS-CoV-2 gains entry into the cell via membrane-bound angiotensin-converting enzyme 2 (ACE2), we speculated that differences in levels of soluble ACE2 in GD patients could contribute to this protective state. While ACE is known to be elevated in GD, to our knowledge, ACE2 levels have not been explored. We measured serum and macrophage-bound levels of ACE and ACE2 by ELISA and western blot, respectively, in GD patients and age- and sex-matched controls. Our results reveal a significant elevation of both serum and macrophage-bound ACE and ACE2 in GD patients compared to healthy controls. This elevation appears to be mitigated by GD treatment. Moreover, the most robust ACE2 elevation was observed in N370S homozygotes, and was not effected by treatment. Since coronaviruses use the ACE2 receptor as a gateway for host cell entry, we speculate that elevated circulating ACE2 may serve as a decoy. This might explain the observed mild infections in GD patients during the COVID-19 pandemic., Competing Interests: Declaration of competing interest HBF received support from Genzyme for attending meetings, participation on a data safety monitoring board and ICGG scientific advisory board. TH received honoraria for lectures from Takeda. All other authors have no conflicts of interest to declare., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The central role of natriuretic peptides (NPs) in the complex cardio-renal integrated physiology and organ failure has been revealed over the last four decades. Atrial natriuretic peptide (ANP), the oldest representative of the NPs family, is produced through conversion of proANP to the mature peptide by corin, a trans-membrane protease localized to the cardiac myocyte membrane. Similarly, brain natriuretic peptide (BNP) is generated by furin, which cleaves proBNP to BNP in myocytes. Though the components of NPs system, their synthesis and target organs are well established, understanding their role in the interplay between the heart and the kidney is steadily evolving. In this context, Feldman et al. (New England Journal of Medicine, 389, 1685) recently described patients with hypertension, cardiomyopathy, atrial arrhythmia and left atrial fibrosis, associated with a homozygous loss-of-function variant of the gene encoding corin (Cor -/- ). Notably, reduced baseline urinary electrolyte and creatinine excretion have been observed in one of the studied patients. This renal excretory functional impairment could be attributed to the lack of cardiac-derived ANP in these patients, as implied by Feldman et al. Yet, in this mini-review we suggest that this aberrant renal manifestation may principally stem from lack of local ANP production at renal tissue, as corin is normally expressed in proximal tubules, Henle's loop and collecting ducts, with locally produced ANP provoking Na + and water exertion. Collectively, it seems that beside the classic well-established cardio-renal axis, the renal NPs system functions as local endocrine machinery in the regulation of sodium excretion., (© 2024 The Author(s). Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)

Acute kidney injury (AKI) is a serious health concern with high morbidity and high mortality worldwide. Recently, sexual dimorphism has become increasingly recognized as a factor influencing the severity of the disease. This study explores the gender-specific renoprotective pathways in αMUPA transgenic mice subjected to AKI. αMUPA transgenic male and female mice were subjected to ischemia-reperfusion (I/R)-AKI in the presence or absence of orchiectomy, oophorectomy, and L-NAME administration. Blood samples and kidneys were harvested 48 h following AKI for the biomarkers of kidney function, renal injury, inflammatory response and intracellular pathway sensing of or responding to AKI. Our findings show differing responses to AKI, where female αMUPA mice were remarkably protected against AKI as compared with males, as was evident by the lower SCr and BUN, normal renal histologically and attenuated expression of NGAL and KIM-1. Moreover, αMUPA females did not show a significant change in the renal inflammatory and fibrotic markers following AKI as compared with wild-type (WT) mice and αMUPA males. Interestingly, oophorectomized females eliminated the observed resistance to renal injury, highlighting the central protective role of estrogen. Correspondingly, orchiectomy in αMUPA males mitigated their sensitivity to renal damage, thereby emphasizing the devastating effects of testosterone. Additionally, treatment with L-NAME proved to have significant deleterious impacts on the renal protective mediators, thereby underscoring the involvement of eNOS. In conclusion, gender-specific differences in the response to AKI in αMUPA mice include multifaceted and keen interactions between the sex hormones and key biochemical mediators (such as estrogen, testosterone and eNOS). These novel findings shed light on the renoprotective pathways and mechanisms, which may pave the way for development of therapeutic interventions.

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects one-third of the global population. Understanding the metabolic pathways involved can provide insights into disease progression and treatment. Untargeted metabolomics of livers from mice with early-stage steatosis uncovered decreased methylated metabolites, suggesting altered one-carbon metabolism. The levels of glycine, a central component of one-carbon metabolism, were lower in mice with hepatic steatosis, consistent with clinical evidence. Stable-isotope tracing demonstrated that increased serine synthesis from glycine via reverse serine hydroxymethyltransferase (SHMT) is the underlying cause for decreased glycine in steatotic livers. Consequently, limited glycine availability in steatotic livers impaired glutathione synthesis under acetaminophen-induced oxidative stress, enhancing acute hepatotoxicity. Glycine supplementation or hepatocyte-specific ablation of the mitochondrial SHMT2 isoform in mice with hepatic steatosis mitigated acetaminophen-induced hepatotoxicity by supporting de novo glutathione synthesis. Thus, early metabolic changes in MASLD that limit glycine availability sensitize mice to xenobiotics even at the reversible stage of this disease., Competing Interests: Declaration of interests E.G. is a founder and shareholder at MetaboMed Ltd, Israel. Y.E.C. is the founder and O.R. is a scientific advisor at Diapin Therapeutics LLC. They are the inventors of PCT/US2019/046052 (Tri-peptides and treatment of metabolic, cardiovascular, and inflammatory disorders)., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Despite the high prevalence of acute kidney injury (AKI), the therapeutic approaches for AKI are disappointing. This deficiency stems from the poor understanding of the pathogenesis of AKI. Recent studies demonstrate that αMUPA, alpha murine urokinase-type plasminogen activator (uPA) transgenic mice, display a cardioprotective pathway following myocardial ischemia. We hypothesize that these mice also possess protective renal pathways. Male and female αMUPA mice and their wild type were subjected to 30 min of bilateral ischemic AKI. Blood samples and kidneys were harvested 48 h following AKI for biomarkers of kidney function, renal injury, inflammatory response, and intracellular pathways sensing or responding to AKI. αMUPA mice, especially females, exhibited attenuated renal damage in response to AKI, as was evident from lower SCr and BUN, normal renal histology, and attenuated expression of NGAL and KIM-1. Notably, αMUPA females did not show a significant change in renal inflammatory and fibrotic markers following AKI as compared with wild-type (WT) mice and αMUPA males. Moreover, αMUPA female mice exhibited the lowest levels of renal apoptotic and autophagy markers during normal conditions and following AKI. αMUPA mice, especially the females, showed remarkable expression of PGC1α and eNOS following AKI. Furthermore, MUPA mice showed a significant elevation in renal leptin expression before and following AKI. Pretreatment of αMUPA with leptin-neutralizing antibodies prior to AKI abolished their resistance to AKI. Collectively, the kidneys of αMUPA mice, especially those of females, are less susceptible to ischemic I/R injury compared to WT mice, and this is due to nephroprotective actions mediated by the upregulation of leptin, eNOS, ACE2, and PGC1α along with impaired inflammatory, fibrotic, and autophagy processes.

The introduction of gliflozins in the management of type 2 diabetes mellitus leads to a better control of hyperglycemia, obesity, hypertension, dyslipidemia, and fluid retention. Most importantly, it also improves renal survival and reduces major cardiovascular events and mortality. Gliflozins were also found to induce erythropoietin (EPO) synthesis, leading to reticulocytosis and erythropoiesis. The mechanism(s) by which gliflozins induce erythropoiesis is a matter of debate. Although the canonical pathway of triggering EPO synthesis is through renal tissue hypoxia, it has been suggested that improved renal oxygenation may facilitate EPO synthesis via non-canonical routes. The latter proposes that the recovery of peritubular interstitial fibroblasts producing erythropoietin (EPO) is responsible for enhanced erythropoiesis. According to this hypothesis, enhanced glucose/sodium re-uptake by proximal tubules in uncontrolled diabetes generates cortical hypoxia, with injury to these cells. Once transport workload declines with the use of SGLT2i, they recover and regain their capacity to produce EPO. In this short communication, we argue that this hypothesis may be wrong and propose that gliflozins likely induce EPO through the documented intensification of renal hypoxia at the corticomedullary junction, related to the translocation of tubular transport from cortical segments to medullary thick ascending limbs. We propose that gliflozins, through intensified hypoxia in this region, trigger local EPO synthesis in peritubular interstitial cells via the canonical pathway of blocking HIF-prolyl hydroxylases (that initiate HIF alpha degradation), with the consequent stabilization of HIF-2 signal and an apocrinic induction of EPO in these same cells.

Congestive heart failure (CHF) is often associated with impaired kidney function. Over- activation of the renin-angiotensin-aldosterone system (RAAS) contributes to avid salt/water retention and cardiac hypertrophy in CHF. While the deleterious effects of angiotensin II (Ang II) in CHF are well established, the biological actions of angiotensin 1-7 (Ang 1-7) are not fully characterized. In this study, we assessed the acute effects of Ang 1-7 (0.3, 3, 30 and 300 ng/kg/min, IV) on urinary flow (UF), urinary Na + excretion (UNaV), glomerular filtration rate (GFR) and renal plasma flow )RPF) in rats with CHF induced by the placement of aortocaval fistula. Additionally, the chronic effects of Ang 1-7 (24 µg/kg/h, via intra-peritoneally implanted osmotic minipumps) on kidney function, cardiac hypertrophy and neurohormonal status were studied. Acute infusion of either Ang 1-7 or its agonist, AVE 0991, into sham controls, but not CHF rats, increased UF, UNaV, GFR, RPF and urinary cGMP. In the chronic protocols, untreated CHF rats displayed lower cumulative UF and UNaV than their sham controls. Chronic administration of Ang 1-7 and AVE 0991 exerted significant diuretic, natriuretic and kaliuretic effects in CHF rats, but not in sham controls. Serum creatinine and aldosterone levels were significantly higher in vehicle-treated CHF rats as compared with controls. Treatment with Ang 1-7 and AVE 0991 reduced these parameters to comparable levels observed in sham controls. Notably, chronic administration of Ang 1-7 to CHF rats reduced cardiac hypertrophy. In conclusion, Ang 1-7 exerts beneficial renal and cardiac effects in rats with CHF. Thus, we postulate that ACE2/Ang 1-7 axis represents a compensatory response to over-activity of ACE/AngII/AT1R system characterizing CHF and suggest that Ang 1-7 may be a potential therapeutic agent in this disease state.

Background: Concern exists regarding the renal safety of blocking the renin-angiotensin system (RAS) during acute illness, especially in the presence of volume depletion and hemodynamic instability., Methods: We explored the impact of loop diuretics and RAS blockers on the likelihood of developing acute kidney injury (AKI) or acute kidney functional recovery (AKR) among inpatients. Adjusted odds ratio for AKI, AKR and mortality was calculated, using logistic regression models, with subgroup analysis for patients with estimated glomerular filtration rate (eGFR) <30 ml/min/1.73 m2, corrected for blood pressure measurements., Results: 53,289 patients were included. RAS blockade was associated with reduced adjusted odds ratio for both AKI (0.76, CI 0.70-0.83) AKR (0.55, 0.52-0.58), and mortality within 30 days (0.44, 0.41-0.48), whereas loop diuretics were associated with increased risk of AKI (3.75, 3.42-4.12) and mortality (1.71, 1.58-1.85) and reduced AKR (0.71, 0.66-0.75). Comparable impact of RAS blockers and loop diuretics on renal outcomes and death was found among 6,069 patients with eGFR < 30 ml/min/1.73m 2 . RAS inhibition and diuretics tended to increase the adjusted odds ratios for AKI and to reduce the likelihood of AKR in hypotensive patients., Conclusions: Reduced blood pressure, RAS blockers and diuretics affect the odds of developing AKI or AKR among inpatients, suggesting possible disruption in renal functional reserve (RFR). As long as blood pressure is maintained, RAS inhibition seems to be safe and renoprotective in this population, irrespective of kidney function upon admission, and is associated with reduced mortality.

The kidney glomerular filtration barrier (GFB) is enriched with heparan sulfate (HS) proteoglycans, which contribute to its permselectivity. The endoglycosidase heparanase cleaves HS and hence appears to be involved in the pathogenesis of kidney injury and glomerulonephritis. We have recently reported, nonetheless, that heparanase overexpression preserved glomerular structure and kidney function in an experimental model of Adriamycin-induced nephropathy. To elucidate mechanisms underlying heparanase function in podocytes-key GFB cells, we utilized a human podocyte cell line and transgenic mice overexpressing heparanase. Notably, podocytes overexpressing heparanase (H) demonstrated significantly higher survival rates and viability after exposure to Adriamycin or hydrogen peroxide, compared with mock-infected (V) podocytes. Immunofluorescence staining of kidney cryo-sections and cultured H and V podocytes as well as immunoblotting of proteins extracted from cultured cells, revealed that exposure to toxic injury resulted in a significant increase in autophagic flux in H podocytes, which was reversed by the heparanase inhibitor, Roneparstat (SST0001). Heparanase overexpression was also associated with substantial transcriptional upregulation of autophagy genes BCN1, ATG5, and ATG12 , following Adriamycin treatment. Moreover, cleaved caspase-3 was attenuated in H podocytes exposed to Adriamycin, indicating lower apoptotic cell death in H vs. V podocytes. Collectively, these findings suggest that in podocytes, elevated levels of heparanase promote cytoprotection., Competing Interests: The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Congestive heart failure (HF) is a complex disease state characterized by impaired ventricular function and insufficient peripheral blood supply. The resultant reduced blood flow characterizing HF promotes activation of neurohormonal systems which leads to fluid retention, often exhibited as pulmonary congestion, peripheral edema, dyspnea, and fatigue. Despite intensive research, the exact mechanisms underlying edema formation in HF are poorly characterized. However, the unique relationship between the heart and the kidneys plays a central role in this phenomenon. Specifically, the interplay between the heart and the kidneys in HF involves multiple interdependent mechanisms, including hemodynamic alterations resulting in insufficient peripheral and renal perfusion which can lead to renal tubule hypoxia. Furthermore, HF is characterized by activation of neurohormonal factors including renin-angiotensin-aldosterone system (RAAS), sympathetic nervous system (SNS), endothelin-1 (ET-1), and anti-diuretic hormone (ADH) due to reduced cardiac output (CO) and renal perfusion. Persistent activation of these systems results in deleterious effects on both the kidneys and the heart, including sodium and water retention, vasoconstriction, increased central venous pressure (CVP), which is associated with renal venous hypertension/congestion along with increased intra-abdominal pressure (IAP). The latter was shown to reduce renal blood flow (RBF), leading to a decline in the glomerular filtration rate (GFR). Besides the activation of the above-mentioned vasoconstrictor/anti-natriuretic neurohormonal systems, HF is associated with exceptionally elevated levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). However, the supremacy of the deleterious neurohormonal systems over the beneficial natriuretic peptides (NP) in HF is evident by persistent sodium and water retention and cardiac remodeling. Many mechanisms have been suggested to explain this phenomenon which seems to be multifactorial and play a major role in the development of renal hyporesponsiveness to NPs and cardiac remodeling. This review focuses on the mechanisms underlying the development of edema in HF with reduced ejection fraction and refers to the therapeutic maneuvers applied today to overcome abnormal salt/water balance characterizing HF., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Abassi, Khoury, Karram and Aronson.)

Albuminuria, a hallmark of diabetic nephropathy, reflects not only injury and dysfunction of the filtration apparatus, but is also affected by altered glomerular hemodynamics and hyperfiltration, as well as by the inability of renal tubular cells to fully retrieve filtered albumin. Albuminuria further plays a role in the progression of diabetic nephropathy, and the suppression of glomerular albumin leak is a key factor in its prevention. Although microalbuminuria is a classic manifestation of diabetic nephropathy, often progressing to macroalbuminuria or overt proteinuria over time, it does not always precede renal function loss in diabetes. The various components leading to diabetic albuminuria and their associations are herein reviewed, and the physiologic rationale and efficacy of therapeutic interventions that reduce glomerular hyperfiltration and proteinuria are discussed. With these perspectives, we propose that these measures should be initiated early, before microalbuminuria develops, as substantial renal injury may already be present in the absence of proteinuria. We further advocate that the inhibition of the renin-angiotensin axis or of sodium-glucose co-transport likely permits the administration of a normal recommended or even high-protein diet, highly desirable for sarcopenic diabetic patients.

A rise in serum creatinine (SCr) is widely used for the detection and definition of evolving acute kidney injury (AKI). Yet, it takes time for SCr to re-adjust in response to changes in glomerular filtration rate (GFR), and subtle transient changes in GFR may remain concealed. Additionally, it cannot differentiate altered glomerular hemodynamics and pre-renal failure from true renal tissue injury, necessitating additional clinical and laboratory diagnostic tools. While these features limit the usefulness of SCr and subsequently estimated GFR (eGFR) at a single time point for the individual patient, their overall pattern of changes along time in a large cohort of hospitalized patients may provide a powerful perspective regarding the detection and assessment of shifting kidney function in this population. Herein we review our experience running large data analyses, evaluating patterns of day-to-day changes in SCr among inpatients, occurring around the exposure to iodinated radiocontrast agents. These large data evaluations helped substantiating the existence of contrast-induced nephropathy in patients with advanced renal failure, underscoring the impact of predisposing and confounding factors. It also provides novel insights regarding a phenomenon of "acute kidney functional recovery" (AKR), and illustrate that the incidence of AKI and AKR along the scale of baseline kidney function co-associates and is inversely proportional to kidney function. This can be attributed to renal functional reserve, which serves as a buffer for up-and-down changes in GFR, forming the physiologic explanation for concealed subclinical AKI., (© 2022 The Authors. Published by Elsevier B.V.)

Renal functional reserve (RFR) reflects the ability of the kidney to enhance glomerular filtration rate (GFR) in response to a protein load. Chronic kidney disease (CKD) leads to diminished RFR, since the capacity for whole-body GFR to increase through hyperfiltration of remaining nephrons is limited. Evaluating 41,456 inpatients following computerised tomography we reported many exhibiting acute kidney injury (AKI) but more patients with recovering kidney function (AKR), presumably reflecting resolution of their critical conditions. The incidences of AKI and AKR were closely co-associated and were both inversely correlated with baseline kidney function. We discuss this phenomenon, arguing that AKR among inpatients with an acute illness, like AKI, may often reflect underlying subtle CKD with diminished RFR., (© 2021 John Wiley & Sons Australia, Ltd.)

Congestive heart failure (CHF) often leads to progressive cardiac hypertrophy and salt/water retention. However, its pathogenesis remains largely unclarified. Corin, a cardiac serine protease, is responsible for converting proANP and proBNP to biologically active peptides. Although the involvement of corin in cardiac hypertrophy and heart failure was extensively studied, the alterations in corin and proprotein convertase subtilisin/kexin-6 (PCSK6), a key enzyme in the conversion of procorin to corin, has not been studied simultaneously in the cardiac and renal tissues in cardiorenal syndrome. Thus, this study aims to examine the status of PCSK6/corin in the cardiac and renal tissues of rats with CHF induced by the creation of aorto-caval fistula (ACF). We divided rats with ACF into two subgroups based on the pattern of their urinary sodium excretion, namely, compensated and decompensated. Placement of ACF led to cardiac hypertrophy, pulmonary congestion, and renal dysfunction, which were more profound in the decompensated subgroup. Corin immunoreactive peptides were detected in all heart chambers at the myocyte membranal and cytosolic localization and in the renal tissue, especially in the apical membrane of the proximal tubule, mTAL, and the collecting duct. Interestingly, the expression and abundance of corin in both the cardiac ventricles and renal tissues were significantly increased in compensated animals as compared with the decompensated state. Noteworthy, the abundance of PCSK6 in these tissues followed a similar pattern as corin. In contrast, furin expression was upregulated in the cardiac and renal tissues in correlation with CHF severity. We hypothesize that the obtained upregulation of cardiac and renal PCSK6/corin in rats with compensated CHF may represent a compensatory response aiming at maintaining normal Na + balance, whereas the decline in these two enzymes may contribute to the pathogenesis of avid sodium retention, cardiac hypertrophy, and blunted atrial natriuretic peptide/brain natriuretic peptide actions in decompensated CHF., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Khoury, Fokra, Kinaneh, Knaney, Aronson and Abassi.)

Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest.

Na+/H+ exchangers (NHEs), encoded by Solute Carrier 9A (SLC9A) genes in human, are ubiquitous integral membrane ion transporters that mediate the electroneutral exchange of H+ with Na+ or K+. NHEs, found in the kidney and intestine, play a major role in the process of fluid reabsorption together via Na+,K+-ATPase pump and Na+ channels. Nevertheless, the expression pattern of NHE in the lung and its role in alveolar fluid homeostasis has not been addressed. Therefore, we aimed to examine the expression of NHE specific isoforms in alveolar epithelial cells (AECs), and assess their role in congestive heart failure (CHF). Three NHE isoforms were identified in AEC and A549 cell line, at the level of protein and mRNA; NHE1, NHE2 and mainly NHE8, the latter was shown to be localized in the apical membrane of AEC. Treating A549 cells with angiotensin (Ang) II for 3, 5 and 24 hours displayed a significant reduction in NHE8 protein abundance. Moreover, the abundance of NHE8 protein was downregulated in A549 cells that were treated overnight with Ang II. NHE8 abundance in whole lung lysate was increased in rats with 1-week CHF compared to sham operated rats. However, lower abundance of NHE8 was observed in 4-week CHF group. In conclusion, we herein show for the first time, the expression of a novel NHE isoform in AEC, namely NHE8. Notably, Ang II decreased NHE8 protein levels. Moreover, NHE8 was distinctly affected in CHF rats, probably depending on the severity of the heart failure., Competing Interests: The authors have declared that no competing interests exist.

Congestive heart failure (CHF) is often associated with kidney and pulmonary dysfunction. Activation of the renin-angiotensin-aldosterone system (RAAS) contributes to avid sodium retention, cardiac hypertrophy and oedema formation, including lung congestion. While the status of the classic components of RAAS such as renin, angiotensin converting enzyme (ACE), angiotensin II (Ang II) and angiotensin II receptor AT-1 is well studied in CHF, the expression of angiotensin converting enzyme-2 (ACE2), a key enzyme of angiotensin 1-7 (Ang 1-7) generation in the pulmonary, cardiac and renal systems has not been studied thoroughly in this clinical setting. This issue is of a special interest as Ang 1-7 counterbalance the vasoconstrictory, pro-inflammatory and pro-proliferative actions of Ang II. Furthermore, CHF predisposes to COVID-19 disease severity, while ACE2 also serves as the binding domain of SARS-CoV-2 in human host-cells, and acts in concert with furin, an important enzyme in the synthesis of BNP in CHF, in permeating viral functionality along TMPRSST2. ADAM17 governs ACE2 shedding from cell membranes. Therefore, the present study was designed to investigate the expression of ACE2, furin, TMPRSS2 and ADAM17 in the lung, heart and kidneys of rats with CHF to understand the exaggerated susceptibility of clinical CHF to COVID-19 disease. Heart failure was induced in male Sprague Dawley rats by the creation of a surgical aorto-caval fistula. Sham-operated rats served as controls. One week after surgery, the animals were subdivided into compensated and decompensated CHF according to urinary sodium excretion. Both groups and their controls were sacrificed, and their hearts, lungs and kidneys were harvested for assessment of tissue remodelling and ACE2, furin, TMPRSS2 and ADAM17 immunoreactivity, expression and immunohistochemical staining. ACE2 immunoreactivity and mRNA levels increased in pulmonary, cardiac and renal tissues of compensated, but not in decompensated CHF. Furin immunoreactivity was increased in both compensated and decompensated CHF in the pulmonary, cardiac tissues and renal cortex but not in the medulla. Interestingly, both the expression and abundance of pulmonary, cardiac and renal TMPRSS2 decreased in CHF in correlation with the severity of the disease. Pulmonary, cardiac and renal ADAM17 mRNA levels were also downregulated in decompensated CHF. Circulating furin levels increased in proportion to CHF severity, whereas plasma ACE2 remained unchanged. In summary, ACE2 and furin are overexpressed in the pulmonary, cardiac and renal tissues of compensated and to a lesser extent of decompensated CHF as compared with their sham controls. The increased expression of the ACE2 in heart failure may serve as a compensatory mechanism, counterbalancing the over-activity of the deleterious isoform, ACE. Downregulated ADAM17 might enhance membranal ACE2 in COVID-19 disease, whereas the suppression of TMPRSS2 in CHF argues against its involvement in the exaggerated susceptibility of CHF patients to SARS-CoV2., (© 2021 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

COVID-19 is a complex disease with a multifaceted set of disturbances involving several mechanisms of health and disease in the human body. Sex hormones, estrogen, and testosterone, seem to play a major role in its pathogenesis, development, spread, severity, and mortalities. Examination of factors such as age, gender, ethnic background, genetic prevalence, and existing co-morbidities, may disclose the mechanisms underlying SARS-CoV-2 infection, morbidity, and mortality, paving the way for COVID-19 amelioration and substantial flattening of the infection curve. In this mini-review, we focus on the role of testosterone through a discussion of the intricate mechanisms of disease development and deterioration. Accumulated evidence suggests that there are links between high level (normal male level) as well as low level (age-related hypogonadism) testosterone in disease progression and expansion, supporting its role as a double-edged sword. Unresolved questions point to the essential need for further targeted studies to substantiate these contrasting mechanisms., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Younis, Skorecki and Abassi.)

Membrane-bound angiotensin converting enzyme (ACE) 2 serves as a receptor for the Sars-CoV-2 spike protein, permitting viral attachment to target host cells. The COVID-19 pandemic brought into light ACE2, its principal product angiotensin (Ang) 1-7, and the G protein-coupled receptor for the heptapeptide (MasR), which together form a still under-recognized arm of the renin-angiotensin system (RAS). This axis counteracts vasoconstriction, inflammation and fibrosis, generated by the more familiar deleterious arm of RAS, including ACE, Ang II and the ang II type 1 receptor (AT1R). The COVID-19 disease is characterized by the depletion of ACE2 and Ang-(1-7), conceivably playing a central role in the devastating cytokine storm that characterizes this disorder. ACE2 repletion and the administration of Ang-(1-7) constitute the therapeutic options currently tested in the management of severe COVID-19 disease cases. Based on their beneficial effects, both ACE2 and Ang-(1-7) have also been suggested to slow the progression of experimental diabetic and hypertensive chronic kidney disease (CKD). Herein, we report a further step undertaken recently, utilizing this type of intervention in the management of evolving acute kidney injury (AKI), with the expectation of renal vasodilation and the attenuation of oxidative stress, inflammation, renal parenchymal damage and subsequent fibrosis. Most outcomes indicate that triggering the ACE2/Ang-(1-7)/MasR axis may be renoprotective in the setup of AKI. Yet, there is contradicting evidence that under certain conditions it may accelerate renal damage in CKD and AKI. The nature of these conflicting outcomes requires further elucidation.

The unique clinical features of COVID-19 disease present a formidable challenge in the understanding of its pathogenesis. Within a very short time, our knowledge regarding basic physiological pathways that participate in SARS-CoV-2 invasion and subsequent organ damage have been dramatically expanded. In particular, we now better understand the complexity of the renin-angiotensin-aldosterone system (RAAS) and the important role of angiotensin converting enzyme (ACE)-2 in viral binding. Furthermore, the critical role of its major product, angiotensin (Ang)-(1-7), in maintaining microcirculatory balance and in the control of activated proinflammatory and procoagulant pathways, generated in this disease, have been largely clarified. The kallikrein-bradykinin (BK) system and chymase are intensively interwoven with RAAS through many pathways with complex reciprocal interactions. Yet, so far, very little attention has been paid to a possible role of these physiological pathways in the pathogenesis of COVID-19 disease, even though BK and chymase exert many physiological changes characteristic to this disorder. Herein, we outline the current knowledge regarding the reciprocal interactions of RAAS, BK, and chymase that are probably turned-on in COVID-19 disease and participate in its clinical features. Interventions affecting these systems, such as the inhibition of chymase or blocking BKB1R/BKB2R, might be explored as potential novel therapeutic strategies in this devastating disorder.

Purpose: We investigate the mechanism of intestinal cell apoptosis and its relation to the time of reperfusion in a rat model of intestinal ischemia-reperfusion (IR)., Methods: Rats were divided into 4 groups: Sham-24 and Sham-48 rats underwent laparotomy without an intentional ischemic intervention and were sacrificed 24 or 48 h hours later; IR-24 and IR-48 rats underwent occlusion of SMA and portal vein for 20 min followed by 24 or 48 h of reperfusion, respectively. Park's injury score, cell proliferation and apoptosis were determined at sacrifice. Proliferation and apoptosis-related gene and protein expression were determined using Real-Time PCR, Western Blot and Immunohistochemistry., Results: IR-24 rats demonstrated a strong increase in cell apoptosis along with an elevated Bax and decreased Bcl-2 expression and a decrease in cell proliferation (vs Sham-24). IR-48 group showed an increase in cell proliferation and a decrease in cell apoptosis compared to IR-24 animals. IR-48 rats demonstrated an increase in apoptotic rate that was accompanied by greater TNF-α mRNA, Fas mRNA and FasL mRNA compared to Sham-48 animals., Conclusion: While cell apoptosis in IR-24 rats is regulated mainly by intrinsic apoptotic pathway, 48 h followed ischemia extrinsic apoptotic pathway is responsible for pro-apoptotic effects of IR injury.

Endothelial dysfunction (ED) is a key feature of diabetes and is a major cause of diabetic vasculopathy. Diabetic patients who also exhibit hyperlipidaemia suffer from accelerated vascular complications. While the deleterious effects of high glucose levels (HG) and hyperlipidaemia alone on ED are well established, the effects of combined hyperlipidaemia and HG have not been thoroughly studied. Therefore, the current study examines whether HG and hyperlipidaemia exert synergistic ED, and explores the mechanisms underlying this phenomenon. We applied multi-disciplinary approaches including cultured HUVECs and HMEC-1 as well as knockout mice CByJ.129S7(B6)-Ldlrtm1Her/J (LDLR -/- ) to investigate the mechanisms underlying combined HG and hyperlipidaemia-induced ED. Incremental doses of glucose in the presence or absence of OxLDL were added to HUVECs and HMEC-1. After 5 days, the status of nitric oxide (NO) and endothelin (ET)-1 systems as well as their signal transduction were assessed using Western blot, ELISA and immunoreactive staining. The effects of chronic combination of HG and hyperlipidaemia on endothelial integrity and function as well as alterations in circulatory NO and ET-1 systems were examined in knockout mice LDLR -/- and their wild-type. HUVEC cells exposed to HG and OxLDL displayed enhanced ET-1 production, more than HG or OxLDL when added alone. Overproduction of ET-1 stems from up-regulation of endothelin converting enzyme (ECE)-1 as observed under these conditions. In contrast, combination of HG and OxLDL dramatically decreased both total endothelial NO synthase (eNOS) by 60%, and activated eNOS (peNOS) by 80%. Moreover, NRF2 decreased by 42% and its active form (pNRF2) by 56%, as compared to baseline. Likewise, ET B levels decreased by 64% from baseline on endothelial cells. Furthermore, diabetic LDLR -/- mice displayed a higher blood pressure, plasma triglycerides, cholesterol, ET-1 and NO2/NO3 levels, when compared with normoglycemic LDLR -/- and BALB mice. Combined hyperglycaemia and hyperlipidaemia activates the ET system and attenuates the nitric oxide system with the Nrf2 signalling pathway. These findings suggest that perturbations in these paracrine systems may contribute to ED., (© 2020 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Background: Inhibitors of sodium-glucose co-transporter-2 (SGLT2i) were found to improve renal outcome in diabetic patients in large prospective randomized trials. Yet, SGLT2i may acutely reduce kidney function through volume depletion, altered glomerular hemodynamics or intensified medullary hypoxia leading to acute tubular injury (ATI). The aim or this study was to prospectively assess the pathophysiology of acute kidney injury (AKI) in patients hospitalized while on SGLT2i, differing ATI from pre-renal causes using renal biomarkers., Methods: Serum and urine Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Kidney Ischemia Molecule (KIM)-1, markers of distal and proximal tubular injury, respectively, were determined in 46 diabetic patients who were on SGLT2i upon hospitalization with an acute illness., Results: Serum and urine NGAL, but not KIM-1, were significantly increased in 21 of the patients who presented with AKI upon admission, as compared with 25 patients that maintained kidney function. Both serum and urinary NGAL correlated with the degree of impaired renal function, which in many cases was likely the result of additional acute renal perturbations, such as sepsis., Conclusions: Increased urinary and serum NGAL indicates that ATI, principally affecting distal tubular segments, may develop in some of the patients hospitalized with an acute illness and AKI while on SGLT2i. It is suggested that intensified medullary hypoxia by SGLT2i might be detrimental in this injury. By contrast, concomitantly unaltered KIM-1 might reflect improved cortical oxygenation by SGLT2i, and may explain an overall reduced risk of AKI with SGLT1i in large series. The independent potential of SGLT2i to inflict medullary hypoxic damage should be explored further.

Engulfed by the grave consequences of the coronavirus disease 2019 (COVID-19) pandemic, a better understanding of the unique pattern of viral invasion and virulence is of utmost importance. Angiotensin (Ang)-converting enzyme (ACE) 2 is a key component in COVID-19 infection. Expressed on cell membranes in target pulmonary and intestinal host cells, ACE2 serves as an anchor for initial viral homing, binding to COVID-19 spike-protein domains to enable viral entry into cells and subsequent replication. Viral attachment is facilitated by a multiplicity of membranal and circulating proteases that further uncover attachment loci. Inherent or acquired enhancement of membrane ACE2 expression, likely leads to a higher degree of infection and may explain the predisposition to severe disease among males, diabetics, or patients with respiratory or cardiac diseases. Additionally, once attached, viral intracellular translocation and replication leads to depletion of membranal ACE2 through degradation and shedding. ACE2 generates Ang 1-7, which serves a critical role in counterbalancing the vasoconstrictive, pro-inflammatory, and pro-coagulant effects of ACE-induced Ang II. Therefore, Ang 1-7 may decline in tissues infected by COVID-19, leading to unopposed deleterious outcomes of Ang II. This likely leads to microcirculatory derangement with endothelial damage, profound inflammation, and coagulopathy that characterize the more severe clinical manifestations of COVID-19 infection. Our understanding of COVID-ACE2 associations is incomplete, and some conceptual formulations are currently speculative, leading to controversies over issues such as the usage of ACE inhibitors or Ang-receptor blockers (ARBs). This highlights the importance of focusing on ACE2 physiology in the evaluation and management of COVID-19 disease., (Copyright © 2020 Abassi, Higazi, Kinaneh, Armaly, Skorecki and Heyman.)

Objectives: Corin is a protease that converts pro-atrial natriuretic peptide (pro-ANP) to ANP. While the involvement of ANP in the cardiovascular regulation is well established, there is increasing evidence that the pregnant uterus produces ANP, which promotes spiral artery remodeling. The present study examines the alterations in corin and PCSK6, a key enzyme in the conversion of pro-corin to corin, in the placenta of hyperinsulinemic dams (HD) featuring pregnancy-induced hypertension (PIH)., Materials and Methods: The study was conducted on female Wistar rats. Rats were rendered hyperinsulinemic by subcutaneous insulin pellet, mated and followed to the twenty-first day of pregnancy. Normal pregnant dams (NPD) served as controls. Both groups were sacrificed on day 21 of gestation and their placentas were dissected along with the mesometrial triangle (MT). The tissue was then sectioned from the maternal surface to the base of the MT, and processed for histological and molecular biology analysis of Corin, PCSK6 and ANP expression/immunoreactivity., Results: Hyperinsulinemic dams developed PIH, along lower placental and fetal weights. Corin expression and immunoreactivity were significantly decreased in the placenta by ~40-50%, but not in the MT. Similarly, placental but not MT PCSK6 immunoreactivity was lower in HD. Concomitantly with the downregulation of corin/PCSK6, proANP levels increased in the placenta of HD., Conclusions: Corin and PCSK6 are expressed in the placenta and MT. The decline in these two enzymes in the placenta of HD suggests a role of corin/PCSK6 machinery in the development of PIH and intrauterine growth restriction characterizing hyperinsulinemia., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 International Society for the Study of Hypertension in Pregnancy. Published by Elsevier B.V. All rights reserved.)

Respiratory, circulatory, and renal failure are among the gravest features of COVID-19 and are associated with a very high mortality rate. A common denominator of all affected organs is the expression of angiotensin-converting enzyme 2 (ACE2), a protease responsible for the conversion of Angiotensin 1-8 (Ang II) to Angiotensin 1-7 (Ang 1-7). Ang 1-7 acts on these tissues and in other target organs via Mas receptor (MasR), where it exerts beneficial effects, including vasodilation and suppression of inflammation and fibrosis, along an attenuation of cardiac and vascular remodeling. Unfortunately, ACE2 also serves as the binding receptor of SARS viral spike glycoprotein, enabling its attachment to host cells, with subsequent viral internalization and replication. Although numerous reports have linked the devastating organ injuries to viral homing and attachment to organ-specific cells widely expressing ACE2, little attention has been given to ACE-2 expressed by the immune system. Herein we outline potential adverse effects of SARS-CoV2 on macrophages and dendritic cells, key cells of the immune system expressing ACE2. Specifically, we propose a new hypothesis that, while macrophages play an important role in antiviral defense mechanisms, in the case of SARS-CoV, they may also serve as a Trojan horse, enabling viral anchoring specifically within the pulmonary parenchyma. It is tempting to assume that diverse expression of ACE2 in macrophages among individuals might govern the severity of SARS-CoV-2 infection. Moreover, reallocation of viral-containing macrophages migrating out of the lung to other tissues is theoretically plausible in the context of viral spread with the involvement of other organs., (Copyright © 2020 Abassi, Knaney, Karram and Heyman.)