miR-486-5p protects against rat ischemic kidney injury and prevents the transition to chronic kidney disease and vascular dysfunction.

AIM: Acute kidney injury (AKI) increases the risk for progressive chronic kidney disease (CKD). MicroRNA (miR)-486-5p protects against kidney ischemia-reperfusion (IR) injury in mice, although its long-term effects on the vasculature and development of CKD are unknown. We studied whether miR-486-5p would prevent the AKI to CKD transition in rat, and affect vascular function. METHODS: Adult male rats were subjected to bilateral kidney IR followed by i.v. injection of liposomal-packaged miR-486-5p (0.5 mg/kg). Kidney function and histologic injury were assessed after 24 h and 10 weeks. Kidney endothelial protein levels were measured by immunoblot and immunofluorescence, and mesenteric artery reactivity was determined by wire myography. RESULTS: In rats with IR, miR-486-5p blocked kidney endothelial cell increases in intercellular adhesion molecule-1 (ICAM-1), reduced neutrophil infiltration and histologic injury, and normalized plasma creatinine (P<0.001). However, miR-486-5p attenuated IR-induced kidney endothelial nitric oxide synthase (eNOS) expression (P<0.05). At 10 weeks, kidneys from rats with IR alone had decreased peritubular capillary density and increased interstitial collagen deposition (P<0.0001), and mesenteric arteries showed impaired endothelium-dependent vasorelaxation (P<0.001). These changes were inhibited by miR-486-5p. Delayed miR-486-5p administration (96 h, 3 weeks after IR) had no impact on kidney fibrosis, capillary density, or endothelial function. CONCLUSION: In rats, administration of miR-486-5p early after kidney IR prevents injury, and protects against CKD development and systemic endothelial dysfunction. These protective effects are associated with inhibition of endothelial ICAM-1 and occur despite reduction in eNOS. miR-486-5p holds promise for the prevention of ischemic AKI and its complications.

Protecting the kidney in sepsis: resident macrophages to the rescue.

Kidney resident macrophages exert pro-inflammatory or reparative effects in experimental acute kidney injury, but their role in sepsis is unclear. In a mouse model of sepsis, Privratsky et al. show that kidney resident F4/80hi macrophages protect against kidney injury by expressing interleukin-1 receptor antagonist, which blocks interleukin-6 production selectively from endothelial cells. Discovery of this novel autocrine loop enhances opportunities for targeted therapies to diminish kidney injury during sepsis.

Comparative Analysis of Hypertensive Tubulopathy in Animal Models of Hypertension and Its Relevance to Human Pathology.

Assessment of hypertensive tubulopathy for more than fifty animal models of hypertension in experimental pathology employs criteria that do not correspond to lesional descriptors for tubular lesions in clinical pathology. We provide a critical appraisal of experimental hypertension with the same approach used to estimate hypertensive renal tubulopathy in humans. Four models with different pathogenesis of hypertension were analyzed-chronic angiotensin (Ang) II-infused and renin-overexpressing (TTRhRen) mice, spontaneously hypertensive (SHR), and Goldblatt two-kidney one-clip (2K1C) rats. Mouse models, SHR, and the nonclipped kidney in 2K1C rats had no regular signs of hypertensive tubulopathy. Histopathology in animals was mild and limited to variations in the volume density of tubular lumen and epithelium, interstitial space, and interstitial collagen. Affected kidneys in animals demonstrated lesion values that are significantly different compared with healthy controls but correspond to mild damage if compared with hypertensive humans. The most substantial human-like hypertensive tubulopathy was detected in the clipped kidney of 2K1C rats. For the first time, our study demonstrated the regular presence of chronic progressive nephropathy (CPN) in relatively young mice and rats with induced hypertension. Because CPN may confound the assessment of rodent models of hypertension, proliferative markers should be used to verify nonhypertensive tubulopathy.

miRNA-486-5p: signaling targets and role in non-malignant disease.

MicroRNAs (miRNAs) are short non-coding RNAs, highly conserved between species, that are powerful regulators of gene expression. Aberrant expression of miRNAs alters biological processes and pathways linked to human disease. miR-486-5p is a muscle-enriched miRNA localized to the cytoplasm and nucleus, and is highly abundant in human plasma and enriched in small extracellular vesicles. Studies of malignant and non-malignant diseases, including kidney diseases, have found correlations with circulating miR-486-5p levels, supporting its role as a potential biomarker. Pre-clinical studies of non-malignant diseases have identified miR-486-5p targets that regulate major signaling pathways involved in cellular proliferation, migration, angiogenesis, and apoptosis. Validated miR-486-5p targets include phosphatase and tensin homolog (PTEN) and FoXO1, whose suppression activates phosphatidyl inositol-3-kinase (PI3K)/Akt signaling. Targeting of Smad1/2/4 and IGF-1 by miR-486-5p inhibits transforming growth factor (TGF)-ß and insulin-like growth factor-1 (IGF-1) signaling, respectively. Other miR-486-5p targets include matrix metalloproteinase-19 (MMP-19), Sp5, histone acetyltransferase 1 (HAT1), and nuclear factor of activated T cells-5 (NFAT5). In this review, we examine the biogenesis, regulation, validated gene targets and biological effects of miR-486-5p in non-malignant diseases.

Performance of the 2021 Race-Free CKD-EPI Creatinine- and Cystatin C-Based Estimated GFR Equations Among Kidney Transplant Recipients.

RATIONALE & OBJECTIVE: Race-free estimated glomerular filtration rate (eGFR) equations incorporating creatinine with and without cystatin C were recently developed and recommended for routine use. However, the performance of these equations among kidney transplant recipients (KTRs) remains unknown. STUDY DESIGN: Cross-sectional study to validate the 2021 race-free Chronic Kidney Disease (CKD) Epidemiology Collaboration (CKD-EPI) eGFR equation based on creatinine alone (eGFRcr) or based on creatinine and cystatin C (eGFRcr-cys) among KTRs. SETTING & PARTICIPANTS: KTRs in stable condition (N = 415) from Canada and New Zealand with same-day measurements of creatinine, cystatin C, and glomerular filtration rate (GFR) using radiolabeled diethylenetriaminepentaacetic acid. TESTS COMPARED: The 2009 CKD-EPI eGFRcr, 2021 CKD-EPI eGFRcr, 2012 CKD-EPI eGFRcr-cys, 2021 CKD-EPI eGFRcr-cys, 2012 CKD-EPI eGFRcys, and Modification of Diet in Renal Disease (MDRD) Study eGFR equations were compared with measured GFR. OUTCOMES: Bias, precision, accuracy, and correct classification by CKD stage. Bias was defined as the difference between estimated and measured GFR. Precision was represented by the interquartile range. Accuracy was defined as the percentages of participants with eGFRs within 10%/20%/30% (P10/P20/P30) of measured GFR, root mean square error, and mean absolute error. RESULTS: 87% of patients studied were White, 3% Black, and 10% other races. Mean measured GFR was 53 ± 19 (SD) mL/min/1.73 m2. The 2009 and 2021 CKD-EPI eGFRcr equations demonstrated similar median bias (-2.3 vs -0.2 mL/min/1.73 m2, respectively), precision (14.5 vs 14.9 mL/min/1.73 m2), and accuracy (P10/P20/P30, 32%/65%/84% vs 33%/63%/84%). The 2012 and 2021 CKD-EPI eGFRcr-cys equations also demonstrated similar median bias (-3.6 vs 0.3 mL/min/1.73 m2, respectively), precision (13.3 vs 14.3 mL/min/1.73 m2), and accuracy (P10/P20/P30, 32%/63%/80% vs 32%/67%/83%). No clear difference in performance was detected between the 2021 CKD-EPI eGFRcr and eGFRcr-cys equations among KTRs. The proportion of correct classification by CKD stage was similar across all eGFR equations. LIMITATIONS: Moderate sample size, few patients had a GFR <30 mL/min/1.73 m2, and the large majority of patients were White. CONCLUSIONS: Among KTRs, the 2021 race-free CKD-EPI eGFR equations perform similarly to the previous CKD-EPI equations that included race correction terms. No significant difference in performance was observed between the 2021 CKD-EPI eGFRcr and eGFRcr-cys equations in the kidney transplant population.

Renal Hemodynamics and Renin-Angiotensin-Aldosterone System Profiles in Patients With Heart Failure.

OBJECTIVE: Understanding cardiorenal pathophysiology in heart failure (HF) is of clinical importance. We sought to characterize the renal hemodynamic function and the transrenal gradient of the renin-angiotensin-aldosterone system (RAAS) markers in patients with HF and in controls without HF. METHODS: In this post hoc analysis, the glomerular filtration rate (GFRinulin), effective renal plasma flow (ERPFPAH) and transrenal gradients (arterial-renal vein) of angiotensin converting enzyme (ACE), aldosterone, and plasma renin activity (PRA) were measured in 47 patients with HF and in 24 controls. Gomez equations were used to derive afferent (RA) and efferent (RE) arteriolar resistances. Transrenal RAAS gradients were also collected in patients treated with intravenous dobutamine (HF, n = 11; non-HF, n = 11) or nitroprusside (HF, n = 18; non-HF, n = 5). RESULTS: The concentrations of PRA, aldosterone and ACE were higher in the renal vein vs the artery in patients with HF vs patients without HF (P < 0.01). In patients with HF, a greater ACE gradient was associated with greater renal vascular resistance (r = 0.42; P 0.007) and greater arteriolar resistances (RA: r = 0.39; P = 0.012; RE: r = 0.48; P = 0.002). Similarly, a greater aldosterone gradient was associated with lower GFR (r = -0.51; P = 0.0007) and renal blood flow (RBF), r = -0.32; P = 0.042) whereas greater PRA gradient with lower ERPF (r = -0.33; P = 0.040), GFR (r = -0.36; P = 0.024), and RBF (r = -0.33; P = 0.036). Dobutamine and nitroprusside treatment decreased the transrenal gradient of ACE (P = 0.012, P < 0.0001, respectively), aldosterone (P = 0.005, P = 0.030) and PRA (P = 0.014, P = 0.002) in patients with HF only. CONCLUSIONS: A larger transrenal RAAS marker gradient in patients with HF suggests a renal origin for neurohormonal activation associated with a vasoconstrictive renal profile.

Implementation of Baltimore City's COVID-19 Isolation Hotel.

In May 2020, Baltimore City, Maryland, implemented the Lord Baltimore Triage, Respite, and Isolation Center (LBTC), a multiagency COVID-19 isolation and quarantine site tailored for people experiencing homelessness. In the first year, 2020 individuals were served, 78% completed isolation at LBTC, and 6% were transferred to a hospital. Successful isolation can mitigate outbreaks in shelters and residential recovery programs, and planning for sustainable isolation services integrated within these settings is critical as the COVID-19 pandemic continues. (Am J Public Health. 2022;112(6):876-880. https://doi.org/10.2105/AJPH.2022.306778).

micro-RNA-486-5p protects against kidney ischemic injury and modifies the apoptotic transcriptome in proximal tubules.

Acute kidney injury (AKI) carries high morbidity and mortality, and effective treatments are lacking. Preclinical models support involvement of micro-RNAs (miRs) in AKI pathogenesis, although effects on the kidney transcriptome are unclear. We previously showed that injection of cord blood endothelial colony forming cell-derived exosomes, enriched in miR-486-5p, prevented ischemic AKI in mice. To further define this, we studied direct effects of miR-486-5p in mice with kidney ischemia-reperfusion injury. RNA-Seq was used to compare the impact of miR-486-5p and exosomes on the transcriptome of proximal tubules and kidney endothelial cells 24 hours after ischemia-reperfusion. In mice with AKI, injection of miR-486-5p mimic increased its levels in proximal tubules and endothelial cells, and improved plasma creatinine, histological injury, neutrophil infiltration, and apoptosis. Additionally, miR-486-5p inhibited expression of its target phosphatase and tensin homolog, and activated protein kinase B. In proximal tubules, miR-486-5p or exosomes reduced expression of genes associated with ischemic injury and the tumor necrosis factor (TNF) pathway, and altered distinct apoptotic genes. In endothelial cells, genes associated with metabolic processes were altered by miR-486-5p or exosomes, although TNF pathway genes were not affected. Thus, our results suggest that miR-486-5p may have therapeutic potential in AKI.

Kidney, Cardiac, and Safety Outcomes Associated With α-Blockers in Patients With CKD: A Population-Based Cohort Study.

RATIONALE & OBJECTIVES: Alpha-blockers (ABs) are commonly prescribed for control of resistant or refractory hypertension in patients with and without chronic kidney disease (CKD). The association between AB use and kidney, cardiac, mortality, and safety-related outcomes in CKD remains unknown. STUDY DESIGN: Population-based retrospective cohort study. SETTINGS & PARTICIPANTS: Ontario (Canada) residents 66 years and older treated for hypertension in 2007 to 2015 without a prior prescription for an AB. EXPOSURES: New use of an AB versus new use of a non-AB blood pressure (BP)-lowering medication. OUTCOMES: 30% or greater estimated glomerular filtration rate (eGFR) decline; dialysis initiation or kidney transplantation (kidney replacement therapy); composite of acute myocardial infarction, coronary revascularization, congestive heart failure, or atrial fibrillation; safety (hypotension, syncope, falls, and fractures) events; and mortality. ANALYTICAL APPROACH: New users of ABs (doxazosin, terazosin, and prazosin) were matched to new users of non-ABs by a high dimensional propensity score. Cox proportional hazards and Fine and Gray models were used to examine the association of AB use with kidney, cardiac, mortality, and safety outcomes. Interactions by eGFR categories (≥90, 60-89, 30-59, and<30mL/min/1.73m2) were explored. RESULTS: Among 381,120 eligible individuals, 16,088 were dispensed ABs and matched 1:1 to non-AB users. AB use was associated with higher risk for≥30% eGFR decline (HR, 1.14; 95% CI, 1.08-1.21) and need for kidney replacement therapy (HR, 1.28; 95% CI, 1.13-1.44). eGFR level did not modify these associations, P interaction=0.3and 0.3, respectively. Conversely, AB use was associated with lower risk for cardiac events, which was also consistent across eGFR categories (HR, 0.92; 95% CI, 0.89-0.95; P interaction=0.1). AB use was also associated with lower mortality risk, but only among those with eGFR<60mL/min/1.73m2 (P interaction<0.001): HRs were 0.85 (95% CI, 0.78-0.93) and 0.71 (95% CI, 0.64-0.80) for eGFR of 30 to 59 and<30mL/min/1.73m2, respectively. LIMITATIONS: Observational design, BP measurement data unavailable. CONCLUSIONS: AB use in CKD is associated with higher risk for kidney disease progression but lower risk for cardiac events and mortality compared with alternative BP-lowering medications.

Prostaglandin E2 receptor EP1 (PGE2/EP1) deletion promotes glomerular podocyte and endothelial cell injury in hypertensive TTRhRen mice.

Prostaglandin E2 receptor EP1 (PGE2/EP1) promotes diabetic renal injury, and EP1 receptor deletion improves hyperfiltration, albuminuria, and fibrosis. The role of EP1 receptors in hypertensive kidney disease (HKD) remains controversial. We examined the contribution of EP1 receptors to HKD. EP1 null (EP1-/-) mice were bred with hypertensive TTRhRen mice (Htn) to evaluate kidney function and injury at 24 weeks. EP1 deletion had no effect on elevation of systolic blood pressure in Htn mice (HtnEP1-/-) but resulted in pronounced albuminuria and reduced FITC-inulin clearance, compared with Htn or wild-type (WT) mice. Ultrastructural injury to podocytes and glomerular endothelium was prominent in HtnEP1-/- mice; including widened subendothelial space, subendothelial lucent zones and focal lifting of endothelium from basement membrane, with focal subendothelial cell debris. Cortex COX2 mRNA was increased by EP1 deletion. Glomerular EP3 mRNA was reduced by EP1 deletion, and EP4 by Htn and EP1 deletion. In WT mice, PGE2 increased chloride reabsorption via EP1 in isolated perfused thick ascending limb (TAL), but PGE2 or EP1 deletion did not affect vasopressin-mediated chloride reabsorption. In WT and Htn mouse inner medullary collecting duct (IMCD), PGE2 inhibited vasopressin-water transport, but not in EP1-/- or HtnEP1-/- mice. Overall, EP1 mediated TAL and IMCD transport in response to PGE2 is unaltered in Htn, and EP1 is protective in HKD.

Sex diversity in proximal tubule and endothelial gene expression in mice with ischemic acute kidney injury.

Female sex protects against development of acute kidney injury (AKI). While sex hormones may be involved in protection, the role of differential gene expression is unknown. We conducted gene profiling in male and female mice with or without kidney ischemia-reperfusion injury (IRI). Mice underwent bilateral renal pedicle clamping (30 min), and tissues were collected 24 h after reperfusion. RNA-sequencing (RNA-Seq) was performed on proximal tubules (PTs) and kidney endothelial cells. Female mice were resistant to ischemic injury compared with males, determined by plasma creatinine and neutrophil gelatinase-associated lipocalin (NGAL), histologic scores, neutrophil infiltration, and extent of apoptosis. Sham mice had sex-specific gene disparities in PT and endothelium, and male mice showed profound gene dysregulation with ischemia-reperfusion compared with females. After ischemia PTs from females exhibited smaller increases compared with males in injury-associated genes lipocalin-2 (Lcn2), hepatitis A virus cellular receptor 1 (Havcr1), and keratin 18 (Krt18), and no up-regulation of SRY-Box transcription factor 9 (Sox9) or keratin 20 (Krt20). Endothelial up-regulation of adhesion molecules and cytokines/chemokines occurred in males, but not females. Up-regulated genes in male ischemic PTs were linked to tumor necrosis factor (TNF) and Toll-like receptor (TLR) pathways, while female ischemic PTs showed up-regulated genes in pathways related to transport. The data highlight sex-specific gene expression differences in male and female PTs and endothelium before and after ischemic injury that may underlie disparities in susceptibility to AKI.

PGE2 EP1 receptor inhibits vasopressin-dependent water reabsorption and sodium transport in mouse collecting duct.

PGE2 regulates glomerular hemodynamics, renin secretion, and tubular transport. This study examined the contribution of PGE2 EP1 receptors to sodium and water homeostasis. Male EP1-/- mice were bred with hypertensive TTRhRen mice (Htn) to evaluate blood pressure and kidney function at 8 weeks of age in four groups: wildtype (WT), EP1-/-, Htn, HtnEP1-/-. Blood pressure and water balance were unaffected by EP1 deletion. COX1 and mPGE2 synthase were increased and COX2 was decreased in mice lacking EP1, with increases in EP3 and reductions in EP2 and EP4 mRNA throughout the nephron. Microdissected proximal tubule sglt1, NHE3, and AQP1 were increased in HtnEP1-/-, but sglt2 was increased in EP1-/- mice. Thick ascending limb NKCC2 was reduced in the cortex but increased in the medulla. Inner medullary collecting duct (IMCD) AQP1 and ENaC were increased, but AVP V2 receptors and urea transporter-1 were reduced in all mice compared to WT. In WT and Htn mice, PGE2 inhibited AVP-water transport and increased calcium in the IMCD, and inhibited sodium transport in cortical collecting ducts, but not in EP1-/- or HtnEP1-/- mice. Amiloride (ENaC) and hydrochlorothiazide (pendrin inhibitor) equally attenuated the effect of PGE2 on sodium transport. Taken together, the data suggest that EP1 regulates renal aquaporins and sodium transporters, attenuates AVP-water transport and inhibits sodium transport in the mouse collecting duct, which is mediated by both ENaC and pendrin-dependent pathways.

High glucose increases the formation and pro-oxidative activity of endothelial microparticles.

AIMS/HYPOTHESIS: Individuals with diabetes exhibit increases in circulating endothelial microparticles (eMPs, also referred to as endothelial microvesicles), which are associated with endothelial dysfunction and a heightened risk of cardiovascular complications. We have shown that eMPs are markers and mediators of vascular injury although their role in diabetes is unclear. We hypothesised that the composition and biological activity of eMPs are altered in response to high glucose exposure. We assessed the effects of high glucose on eMP formation, composition and signalling in cultured HUVECs. METHODS: eMPs were isolated from the media of HUVECs cultured under conditions of normal glucose (eMPNG), high glucose (eMPHG) or osmotic control of L-glucose (eMPLG). eMP size, concentration and surface charge were assessed by nanoparticle tracking analysis and flow cytometry. eMP protein composition was assessed by liquid chromatography-tandem mass spectrometry, and eMP-mediated effects on coagulation, reactive oxygen species (ROS) production and vessel function were assessed. RESULTS: Exposure of HUVECs to high glucose for 24 h caused a threefold increase in eMP formation, increased mean particle size (269 ± 18 nm vs 226 ± 11 nm) and decreased surface charge. Compared with eMPNG or eMPLG, eMPHG possessed approximately threefold greater pro-coagulant activity, stimulated HUVEC ROS production to a greater extent (~250% of eMPNG) and were more potent inhibitors of endothelial-dependent relaxation. Proteomic analysis of eMPs identified 1212 independent proteins of which 68 were exclusively found in eMPHG. Gene ontology analysis revealed that eMPHG-exclusive proteins were associated with signalling pathways related to blood coagulation, cell signalling and immune cell activation. CONCLUSIONS/INTERPRETATION: Our results indicate that elevated glucose is a potent stimulus for eMP formation that also alters their molecular composition leading to increased bioactivity. Such effects may contribute to progressive endothelial injury and subsequent cardiovascular complications in diabetes.

The relationship between urinary renin-angiotensin system markers, renal function, and blood pressure in adolescents with type 1 diabetes.

The relationship between the renal renin-angiotensin aldosterone system (RAAS) and cardiorenal pathophysiology is unclear. Our aims were to assess 1) levels of urinary RAAS components and 2) the association between RAAS components and HbA1c, the urine albumin/creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), and blood pressure (BP) in otherwise healthy adolescents with type 1 diabetes mellitus (TID) vs. healthy controls (HC). Urinary angiotensinogen and angtionsin-converting enzyme (ACE) 2 levels, activity of ACE and ACE2, BP, HbA1c, ACR, and eGFR were measured in 65 HC and 194 T1D from the Adolescent Type 1 Diabetes Cardio-Renal Intervention Trial (AdDIT). Urinary levels of all RAAS components were higher in T1D vs. HC (P < 0.0001). Higher HbA1c was associated with higher urinary angiotensinogen, ACE2, and higher activity of ACE and ACE2 (P < 0.0001, P = 0.0003, P = 0.003, and P = 0.007 respectively) in T1D. Higher ACR (within the normal range) was associated with higher urinary angiotensinogen (P < 0.0001) and ACE activity (P = 0.007), but not with urinary ACE2 activity or ACE2 levels. These observations were absent in HC. Urinary RAAS components were not associated with BP or eGFR in T1D or HC. Otherwise healthy adolescents with T1D exhibit higher levels of urinary RAAS components compared with HC. While levels of all urinary RAAS components correlate with HbA1c in T1D, only urinary angiotensinogen and ACE activity correlate with ACR, suggesting that these factors reflect an intermediary pathogenic link between hyperglycemia and albuminuria within the normal range.

PGE2 receptor EP3 inhibits water reabsorption and contributes to polyuria and kidney injury in a streptozotocin-induced mouse model of diabetes.

AIMS/HYPOTHESIS: The first clinical manifestation of diabetes is polyuria. The prostaglandin E2 (PGE2) receptor EP3 antagonises arginine vasopressin (AVP)-mediated water reabsorption and its expression is increased in the diabetic kidney. The purpose of this work was to study the contribution of EP3 to diabetic polyuria and renal injury. METHODS: Male Ep 3 (-/-) (also known as Ptger3 (-/-)) mice were treated with streptozotocin (STZ) to generate a mouse model of diabetes and renal function was evaluated after 12 weeks. Isolated collecting ducts (CDs) were microperfused to study the contribution of EP3 to AVP-mediated fluid reabsorption. RESULTS: Ep 3 (-/-)-STZ mice exhibited attenuated polyuria and increased urine osmolality compared with wild-type STZ (WT-STZ) mice, suggesting enhanced water reabsorption. Compared with WT-STZ mice, Ep 3 (-/-)-STZ mice also had increased protein expression of aquaporin-1, aquaporin-2, and urea transporter A1, and reduced urinary AVP excretion, but increased medullary V2 receptors. In vitro microperfusion studies indicated that Ep 3 (-/-) and WT-STZ CDs responded to AVP stimulation similarly to those of wild-type mice, with a 60% increase in fluid reabsorption. In WT non-injected and WT-STZ mice, EP3 activation with sulprostone (PGE2 analogue) abrogated AVP-mediated water reabsorption; this effect was absent in mice lacking EP3. A major finding of this work is that Ep 3 (-/-)-STZ mice showed blunted renal cyclooxygenase-2 protein expression, reduced renal hypertrophy, reduced hyperfiltration and reduced albuminuria, as well as diminished tubular dilation and nuclear cysts. CONCLUSIONS/INTERPRETATION: Taken together, the data suggest that EP3 contributes to diabetic polyuria by inhibiting expression of aquaporins and that it promotes renal injury during diabetes. EP3 may prove to be a promising target for more selective management of diabetic kidney disease.

Transfer of microRNA-486-5p from human endothelial colony forming cell-derived exosomes reduces ischemic kidney injury.

Administration of human cord blood endothelial colony-forming cells (ECFCs) or their exosomes protects mice against kidney ischemia/reperfusion injury. Here we studied the microRNA (miRNA) content of ECFC exosomes and the role of miRNA transfer in kidney and endothelial cell protection. ECFC exosomes were enriched in miR-486-5p, which targets the phosphatase and tensin homolog (PTEN) and the Akt pathway. In cultured endothelial cells exposed to hypoxia, incubation with ECFC exosomes increased miR-486-5p, decreased PTEN, and stimulated Akt phosphorylation. Exposure of hypoxic endothelial cells to conditioned medium from ECFCs pretreated with anti-miR-486-5p blocked increases in miR-486-5p and phosphorylated Akt, restored expression of PTEN, and enhanced apoptosis. Coculture of endothelial cells with ECFCs enhanced endothelial miR-486-5p levels. Targeting of PTEN by miR-486-5p was observed in endothelial cells, and PTEN knockdown blocked apoptosis. In mice with ischemic kidney injury, infusion of ECFC exosomes induced potent functional and histologic protection, associated with increased kidney miR-486-5p levels, decreased PTEN, and activation of Akt. Infusion of exosomes from ECFCs transfected with anti-miR-486-5p had no protective effect. Thus, delivery of ECFC exosomes reduces ischemic kidney injury via transfer of miR-486-5p targeting PTEN. Exosomes enriched in miR-486-5p could represent a therapeutic tool in acute kidney injury.

The effect of angiotensin-(1-7) in mouse unilateral ureteral obstruction.

Angiotensin-(1-7) is a ligand for the Mas receptor and may protect against tissue injury associated with renin-angiotensin system activation. We determined the effects of endogenous or exogenous angiotensin-(1-7) in mice with unilateral ureteral obstruction (UUO). Mice with UUO were treated with or without the angiotensin-(1-7) antagonist A779 or with 6, 24, or 62 µg/kg per hour exogenous angiotensin-(1-7). After 10 days, kidneys were harvested for histology, immunoblots, and measurement of NADPH oxidase. Compared with controls, A779 treatment significantly increased fibronectin, transforming growth factor-ß, and α-smooth muscle actin expression in obstructed kidneys and enhanced tubulointerstitial injury, apoptosis, and NADPH oxidase. Unexpectedly, administration of angiotensin-(1-7) to mice with UUO caused injury in obstructed kidneys compared with controls and increased macrophage infiltration. In obstructed kidneys from mice with gene deletion of Mas (Mas(-/-)), apoptosis and macrophage infiltration were increased compared with wild-type mice. Angiotensin-(1-7) (but not A779) further increased apoptosis and macrophage influx in obstructed kidneys from Mas(-/-) mice, compared with untreated Mas(-/-) mice. These data indicate that endogenous angiotensin-(1-7) protects against kidney injury in UUO. In mice with or without the Mas receptor, however, delivery of exogenous angiotensin-(1-7) worsens kidney damage. The results suggest dose-dependent effects of angiotensin-(1-7) in the kidney in UUO, with endogenous angiotensin-(1-7) promoting repair pathways via interaction with Mas and higher amounts exacerbating injury.

Human endothelial colony-forming cells protect against acute kidney injury: role of exosomes.

The administration of certain progenitor cells is protective in experimental acute kidney injury (AKI), and mechanisms may involve the release of paracrine factors. Endothelial colony-forming cells (ECFCs) are endothelial precursor cells with a high proliferative capacity and pro-angiogenic potential. We examined the effects of human umbilical cord blood-derived ECFCs and their extracellular vesicles in a mouse model of ischemic AKI and in cultured human umbilical vein endothelial cells subjected to hypoxia/reoxygenation. In mice with ischemic AKI, administration of ECFCs (i.v.) at the time of reperfusion significantly attenuated increases in plasma creatinine, tubular necrosis, macrophage infiltration, oxidative stress, and apoptosis, without cell persistence in the kidneys. In cultured human umbilical vein endothelial cells, hypoxia/reoxygenation stimulated apoptosis. This effect was inhibited by incubation with conditioned medium or exosomes (40- to 100-nm diameter) derived from ECFCs, but not by microparticles (100- to 1000-nm diameter) or vesicle-depleted conditioned medium. Administration of exosomes (i.v.) directly to mice with ischemic AKI attenuated renal injury, as assessed by plasma creatinine, tubular necrosis, and apoptosis. Taken together, these studies indicate protective effects of human cord blood-derived ECFCs in experimental AKI and suggest that ECFC-derived exosomes may mediate the protective response via inhibition of endothelial cell apoptosis.

The association of urinary sodium excretion and the need for renal replacement therapy in advanced chronic kidney disease: a cohort study.

BACKGROUND: Restriction of dietary sodium is routinely recommended for patients with chronic kidney disease (CKD). Whether or not sodium intake is associated with the progression of CKD and mortality remains controversial. We evaluated the association of urinary sodium excretion (as a surrogate for sodium intake) on the need for renal replacement therapy and mortality in patients with advanced CKD. METHODS: We conducted a retrospective study of patients followed at a CKD clinic of a tertiary care hospital from January 2010 to December 2012. Adult patients with advanced CKD (estimated glomerular filtration rate (eGFR) <30 ml/min/1.73 m(2)) were included. Using a time-to-event analysis, we examined the association of urinary sodium excretion as a continuous and also as a categorical variable (categorized as low sodium diet - LSD (<100 mEq/day), medium sodium diet - MSD (100-150 mEq/day), and high sodium diet - HSD (>150 mEq/day) and the outcomes of interest. The primary outcome was defined as composite of progression to end-stage renal disease requiring any type of renal replacement therapy and mortality. The secondary outcome was change in eGFR/year. RESULTS: 341 patients (82 LSD, 116 MSD and 143 HSD) were included in the study (mean follow up of 1.5 years) with a mean eGFR decline of 2.7 ml/min/1.73 m(2)/year. 105 patients (31 %) required renal replacement therapy and 10 (3 %) died. There was no association between urinary sodium excretion and change in the eGFR or need for renal replacement therapy and mortality in crude or adjusted models (unadjusted HR 1.002; 95%CI 1.000-1.004, adjusted HR 1.001; 95%CI 0.998-1.004). CONCLUSION: In patients with advanced CKD (eGFR < 30 ml/min/1.73 m(2)), sodium intake does not appear to impact the progression of CKD to end-stage renal disease; however, more definitive studies are needed.

Prostaglandin E2 increases proximal tubule fluid reabsorption, and modulates cultured proximal tubule cell responses via EP1 and EP4 receptors.

Renal prostaglandin (PG) E2 regulates salt and water transport, and affects disease processes via EP1-4 receptors, but its role in the proximal tubule (PT) is unknown. Our study investigates the effects of PGE2 on mouse PT fluid reabsorption, and its role in growth, sodium transporter expression, fibrosis, and oxidative stress in a mouse PT cell line (MCT). To determine which PGE2 EP receptors are expressed in MCT, qPCR for EP1-4 was performed on cells stimulated for 24 h with PGE2 or transforming growth factor beta (TGFß), a known mediator of PT injury in kidney disease. EP1 and EP4 were detected in MCT, but EP2 and EP3 are not expressed. EP1 was increased by PGE2 and TGFß, but EP4 was unchanged. To confirm the involvement of EP1 and EP4, sulprostone (SLP, EP1/3 agonist), ONO8711 (EP1 antagonist), and EP1 and EP4 siRNA were used. We first show that PGE2, SLP, and TGFß reduced H(3)-thymidine and H(3)-leucine incorporation. The effects on cell-cycle regulators were examined by western blot. PGE2 increased p27 via EP1 and EP4, but TGFß increased p21; PGE2-induced p27 was attenuated by TGFß. PGE2 and SLP reduced cyclinE, while TGFß increased cyclinD1, an effect attenuated by PGE2 administration. Na-K-ATPase α1 (NaK) was increased by PGE2 via EP1 and EP4. TGFß had no effect on NaK. Additionally, PGE2 and TGFß increased fibronectin levels, reaching 12-fold upon co-stimulation. EP1 siRNA abrogated PGE2-fibronectin. PGE2 also increased ROS generation, and ONO-8711 blocked PGE2-ROS. Finally, PGE2 significantly increased fluid reabsorption by 31 and 46% in isolated perfused mouse PT from C57BL/6 and FVB mice, respectively, and this was attenuated in FVB-EP1 null mice. Altogether PGE2 acting on EP1 and EP4 receptors may prove to be important mediators of PT injury, and salt and water transport.