Amiloride evokes significant natriuresis and weight loss in kidney transplant recipients with and without albuminuria.

Albuminuria in kidney transplant recipients (KTRs) is associated with hypertension and aberrant glomerular filtration of serine proteases that may proteolytically activate the epithelial Na+ channel (ENaC). The present nonrandomized, pharmacodynamic intervention study aimed to investigate if inhibition of ENaC increases Na+ excretion and reduces extracellular volume in KTRs dependent on the presence of albuminuria. KTRs with and without albuminuria (albumin-to-creatinine ratio > 300 mg/g, n = 7, and <30 mg/g, n = 7, respectively) were included and ingested a diet with fixed Na+ content (150 mmol/day) for 5 days. On the last day, amiloride at 10 mg was administered twice. Body weight, 24-h urine electrolyte excretion, body water content, and ambulatory blood pressure as well as plasma renin, angiotensin II, and aldosterone concentrations were determined before and after amiloride. Amiloride led to a significant decrease in body weight, increase in 24-h urinary Na+ excretion, and decrease in 24-h urinary K+ excretion in both groups. Urine output increased in the nonalbuminuric group only. There was no change in plasma renin, aldosterone, and angiotensin II concentrations after amiloride, whereas a significant decrease in nocturnal systolic blood pressure and increase in 24-h urine aldosterone excretion was observed in albuminuric KTRs only. There was a significant correlation between 24-h urinary albumin excretion and amiloride-induced 24-h urinary Na+ excretion. In conclusion, ENaC activity contributes to Na+ and water retention in KTRs with and without albuminuria. ENaC is a relevant pharmacological target in KTRs; however, larger and long-term studies are needed to evaluate whether the magnitude of this effect depends on the presence of albuminuria.NEW & NOTEWORTHY Amiloride has a significant natriuretic effect in kidney transplant recipients (KTRs) that relates to urinary albumin excretion. The epithelial Na+ channel may be a relevant direct pharmacological target to counter Na+ retention and hypertension in KTRs. Epithelial Na+ channel blockers should be further investigated as a mean to mitigate Na+ and water retention and to potentially obtain optimal blood pressure control in KTRs.

Effect of Oral Intake of Carrot Juice on Cyclooxygenases and Cytokines in Healthy Human Blood Stimulated by Lipopolysaccharide.

In vitro studies and animal studies have shown that chemical compounds contained in carrots, such as falcarinol and falcarindiol, can prevent inflammation. The present study was designed to test whether the oral intake of carrot juice containing falcarinol and falcarindiol affects the activity of cyclooxygenase (COX) enzymes and the secretion of inflammatory cytokines in human blood. Carrot juice (500 mL) was administered orally to healthy volunteers, and blood samples were drawn before and 1 h after juice intake at the time point when peak concentrations of falcarinol and falcariondiol have been shown in the blood. The blood samples were divided, and one sample was allowed to coagulate for 1 h at room temperature before analyzing the synthesis of thromboxane B2 (TBX2) by the COX1 enzyme using an enzyme linked immunosorbent assay (ELISA). The other blood samples were stimulated ex vivo with lipopolysaccharide and incubated at 37 °C for 24 h. The ELISA and cytokine multiplex analysis assessed the levels of COX-2-induced prostaglandin E2 (PGE2) and inflammatory markers interleukin (IL) 1α, IL1ß, IL6, IL16, and tumor necrosis factor α (TNFα). Inflammatory cytokines such as IL1α and IL16 were significantly reduced in the LPS stimulated blood samples with higher concentrations of falcarinol and falcariondiol compared to the control samples taken before the intake of carrot juice. The levels of TBX2, PGE2, IL1ß, IL6, and TNFα were not affected by the carrot juice intake blood samples not stimulated with LPS. In conclusion, carrot juice rich in the polyacetylens falcarinol and falcarindiol affects blood leukocytes, priming them to better cope with inflammatory conditions, evident by the reduced secretion of the proinflammatory cytokines IL1α and IL16.

Mannan-binding lectin serine protease-2 (MASP-2) in human kidney and its relevance for proteolytic activation of the epithelial sodium channel.

Proteolytic activation of the renal epithelial sodium channel (ENaC) is increased by aldosterone. The aldosterone-sensitive protease remains unidentified. In humans, elevated circulating aldosterone is associated with increased urinary extracellular vesicle (uEVs) excretion of mannan-binding lectin associated serine protease-2 (MASP-2). We hypothesized that MASP-2 is a physiologically relevant ENaC-activating protease. It was confirmed that MASP2 mRNA is abundantly present in liver but not in human and mouse kidneys. Aldosterone-stimulation of murine cortical colleting duct (mCCD) cells did not induce MASP-2 mRNA. In human kidney collecting duct, MASP-2 protein was detected in AQP2-negative/ATP6VB1-positive intercalated cells suggestive of MASP2 protein uptake. Plasma concentration of full-length MASP-2 and the short splice variant MAp19 were not changed in a cross-over intervention study in healthy humans with low (70 mmol/day) versus high (250 mmol/day) Na+ intake despite changes in aldosterone. The ratio of MAp19/MASP-2 in plasma was significantly increased with a high Na+ diet and the ratio correlated with changes in aldosterone and fractional Na+ excretion. MASP-2 was not detected in crude urine or in uEVs. MASP2 activated an amiloride-sensitive current when co-expressed with ENaC in Xenopus oocytes, but not when added to the bath solution. In monolayers of collecting duct M1 cells, MASP2 expression did not increase amiloride-sensitive current and in HEK293 cells, MASP-2 did not affect γENaC cleavage. MASP-2 is neither expressed nor co-localized and co-regulated with ENaC in the human kidney or in urine after low Na+ intake. MASP-2 does not mediate physiological ENaC cleavage in low salt/high aldosterone settings.

Low Plasma Sodium Concentration Predicts Perforated Acute Appendicitis in Children: A Prospective Diagnostic Accuracy Study.

INTRODUCTION: Early differentiation between perforated and nonperforated acute appendicitis (AA) in children is of major benefit for the selection of proper treatment. Based on pilot study data, we hypothesized that plasma sodium concentration at hospital admission is a diagnostic marker for perforation in children with AA. MATERIALS AND METHODS: This was a prospective diagnostic accuracy study, including previously healthy children, 1 to 14 years of age, with AA. Blood sampling included plasma sodium concentration, plasma glucose, base excess, white blood cell count, plasma arginine vasopressin (AVP), and C-reactive protein. RESULTS: Eighty children with histopathologically confirmed AA were included in the study. Median plasma sodium concentration on admission in patients with perforated AA (134 mmol/L, [interquartile range 132-136]) was significantly lower than in children with nonperforated AA (139 mmol/L, [137-140]). The receiver operating characteristic curve of plasma sodium concentration identifying patients with perforated AA showed an area under the curve of 0.93 (95% confidence interval, 0.87-0.99), with a sensitivity and specificity of 0.82 (0.70-0.90) and 0.87 (0.60-0.98), respectively. Plasma sodium concentrations ≤136 mmol/L resulted in an odds ratio of 31.9 (6.3-161.9) for perforation. The association between low plasma sodium concentration and perforated AA was confirmed in a multivariate logistic regression analysis. Median plasma AVP on admission was higher in patients with perforated (8.6 pg/mL [5.0-14.6]) as compared with nonperforated AA (3.4 pg/mL [2.5-6.6]). CONCLUSION: In children with AA, there is a strong association between low plasma sodium concentration and perforation, a novel and not previously described finding.

Pazopanib-Induced Hypertension in Patients With Renal Cell Carcinoma Is Associated With Low Urine Excretion of NO Metabolites.

Drugs targeting VEGF (vascular endothelial growth factor) are often associated with rapid development of hypertension by a yet not fully understood mechanism. VEGF is expressed in renal epithelial cells and stimulates NO production. In the renal medulla, inhibition of NO formation by local L-NAME or by impaired endothelin-1 leads to hypertension. The present study was designed to test the hypothesis that VEGF receptor inhibitor treatment leads to hypertension through decreased renal medullary formation of NO and endothelin-1. With a single-center prospective observational design, patients with metastatic renal cell carcinoma (n=27) treated with the receptor tyrosine kinase inhibitor pazopanib were included in the study. Home blood pressure was measured, and plasma and urine samples were collected at baseline and after 4 and 8 weeks of treatment. After 4 weeks, systolic and diastolic blood pressures increased, whereas heart rate decreased significantly; urine protein/creatinine ratio increased significantly, whereas estimated glomerular filtration rate was unchanged. Urine nitrite/nitrate (NOx) and cGMP/creatinine ratios decreased significantly, whereas urine endothelin-1/creatinine ratio and FENa+ were unchanged. In plasma, NOx, cGMP, and brain natriuretic peptide decreased significantly, whereas endothelin-1 was significantly elevated. Blood leukocyte count decreased significantly with unchanged CRP (C-reactive protein). In summary, pazopanib treatment of patients with advanced renal cell carcinoma is associated with hypertension, proteinuria, myelosuppression, and decreased urine and plasma NO metabolites. Results are compatible with a significant role of reduced renal medullary NO bioavailability in VEGF inhibitor-induced hypertension.