Reduction In Sodium Excretion Research Articles

#1642 Influence of potassium intake on the renoprotective response to sodium restriction and hydrochlorothiazide in patients with diabetic nephropathy

Abstract Background and Aims Both salt restriction and hydrochlorothiazide (HCT) potentiate the antihypertensive and antiproteinuric effects of renin-angiotensin-aldosterone-system inhibitors (RAASi) in chronic kidney disease (CKD). Potassium intake is another dietary component that influences blood pressure (BP) and albuminuria. The influence of potassium intake on the response to sodium restriction during RAASi treatment in diabetic nephropathy is unknown. Method We performed a post-hoc analysis of a randomised, double blind, placebo-controlled cross-over trial (n = 43) investigating the combined and separate effects of low sodium (LS; aim 50 mmol Na+/d) and HCT (50 mg/d) on BP and albuminuria during background ACE inhibition (ACEi; lisinopril 40 mg/d) in patients with diabetic nephropathy. Each treatment (normal sodium (NS), LS, NS+HCT, LS+HCT) period consisted of six weeks. Participants were categorised as above or below median 24-hour urinary potassium excretion (UKV) at baseline, stratified by sex. Effects on BP and albuminuria were defined as % reduction from baseline systolic BP (SBP) and urinary albumin-creatinine ratio (ACR). Changes over time within both UKV subgroups were compared to baseline using repeated measures ANOVA (SBP) or paired Wilcoxon rank sum analysis (log-transformed ACR). Post-hoc between-group comparison was performed using Bonferroni testing. Results 43 patients (6 female; mean age 64.9±1.4 yrs) had UKV data available and were included in analysis. 33 patients had complete ACR data. Mean estimated glomerular filtration rate (eGFR) was 65.2 (±3.9), mean SBP was 146.6±2.4 mmHg and median albuminuria 648.6 [251.2 - 1883.0] mg/24 h. Median UKV in the high and low potassium groups was 64 [IQR 49-71] and 94 [90 – 111] mmol/24 u, respectively (p<0.0001). Mean baseline sodium excretion was higher in the high potassium group (191 vs. 260 mmol/d; P = .002), but percentual reduction in sodium excretion at SR was comparable between the two groups. There were no significant differences in baseline SBP, ACR, age and estimated glomerular filtration rate between the groups. LS led to a significant reduction of ACR in the high potassium group (P = .011), whereas in the low potassium group the ACR reduction was not significant (P = .058; Fig. 1). Similarly, addition of HCT to background ACEi therapy without salt restriction reduced ACR compared to ACEi monotherapy in the high potassium group (P < .0001), not the low potassium group (P = .211). LS+HCT combined led to a reduction in ACR in both high (P < .0001) and low potassium (P = .034) groups. A post-hoc between-group analysis showed a significantly larger ACR reduction for the high potassium group (P = .01) upon HCT therapy, and a trend towards larger reduction for HCT+LS (P = .05). The effect of LS alone was similar between high and low potassium groups (P = .485). During LS, within-group analysis showed a significant reduction in SBP compared to baseline for the low potassium group (P = .003), but not for the high potassium group (P = .208). In all further conditions, SBP was significantly reduced from baseline in both groups. Post-hoc analysis showed no significant differences in SBP reduction between high and low potassium groups, although there was a trend towards larger SBP reduction in the low potassium group during LS (P = .07). Conclusion Higher baseline potassium excretion is associated with stronger albuminuria lowering effects of salt restriction and HCT in patients with diabetic nephropathy on background ACEi therapy. These effects were not driven by similar effects on BP.

Long-Term Sodium Deficiency Reduces Sodium Excretion but Impairs Renal Function and Increases Stone Formation in Hyperoxaluric Calcium Oxalate Rats.

Excessive sodium intake is associated with nephrolithiasis, but the impact of sodium-deficient (SD) diets is unknown. Hence, we investigated the effects of short- and long-term SD diets on the expression of renal aquaporins and sodium transporters, and thus calcium oxalate (CaOx) crystal formation in hyperoxaluria rats. In a short-term sodium balance study, six male rats received drinking water and six received 0.75% ethylene glycol (EG) to induce hyperoxaluria. After a 30-day period of feeding on normal chow, both groups were treated with a normal-sodium diet for 5 days, followed by a sodium-free diet for the next 5 days. In a long-term SD study (42 days), four groups, induced with EG or not, were treated with normal-sodium water and sodium-free drinking water, alternately. Short-term sodium restriction in EG rats reversed the daily positive sodium balance, but progressively caused a negative cumulative water balance. In the long-term study, the abundant levels of of Na/H exchanger, thiazide-sensitive Na-Cl cotransporter, Na-K-ATPase, and aquaporins-1 from SD + EG rats were markedly reduced, corresponding to a decrease in Uosm, as compared to SD rats. Increased urine calcium, AP(CaOx)index, and renal CaOx deposition were also noted in SD + EG rats. Although the SD treatment reduced sodium excretion, it also increased urinary calcium and impaired renal function, ultimately causing the formation of more CaOx crystals.

Effects of low-sodium bread on dietary compliance and fecal cultivable bacteria in a randomized controlled pilot trial in hypertensive subjects

High salt intake and compliance to low-sodium (LS) diets are critical in hypertension. Salt reduction in processed foods can help to achieve the target sodium intake. To verify the hypothesis that an innovative LS formulation of a traditional bread could result in a reduction of sodium intake and blood pressure, we performed a 6-month randomized controlled pilot trial on hypertensive patients. We additionally explored the effects of sodium restriction on blood pressure and fecal cultivable bacteria.Fifty-seven patients were randomized in three groups. Group A (n = 19) followed a free diet using standard bread (750 mg Na/100 g), group B (n = 18) followed a LS diet (2300 mg Na/die) using standard bread, group C (n = 20) followed a LS diet (2300 mg Na/die) using LS bread (280 mg Na/100 g). We measured 24-h urinary sodium, blood pressure, routine parameters, fecal microbial counts (26 patients).After 6 months, as compared to group A, group C showed a reduction of 24-h urinary sodium excretion (-908 mg/24 h), diastolic pressure (-9 mmHg) and microbial counts of Bacteroides, Porphyromonas, Prevotella, Enterobacteriaceae, Staphylococcus, Micrococcus. These results suggest that LS bread could increase the adherence to a LS diet, reducing sodium excretion, diastolic pressure and abundance of some fecal cultivable bacteria.Trial registration Registration nr. NCT03127553, on 25/04/2017.

Dynamic changes in renal sodium handling during sympathetic stimulation in healthy human males

The temporal response of changes in renal sodium reabsorption during increased renal sympathetic nerve activity has not been investigated. Central hypovolemia by application of lower-body negative-pressure (LBNP) elicits baroreceptor mediated sympathetic reflexes to maintain arterial blood pressure. We hypothesized, that during 90 min LBNP, the renal sodium retention would increase rapidly, remain increased during intervention, and return to baseline immediately after end of intervention. Methods30 young, healthy, sodium loaded, non-obese males were exposed to −15 mmHg LBNP, −30 mmHg LBNP, −15 mmHg LBNP + renin blockade or time-control (0 mmHg LBNP) for 90 min. Urine was collected every 15 min during 90 min of intervention and 60 min of recovery to identify a possible relation between time of intervention and renal response. ResultsAll intervention groups exhibited a comparable reduction in distal sodium excretion at the end of the intervention (P = 0.46 between groups; −15 mmHg: −3.1 ± 0.9 %, −30 mmHg: −2.9 ± 0.6 %, −15 mmHg + aslikiren: −1.8 ± 0.6 %). −15 mmHg+Aliskiren resulted in a slower onset, but all groups exhibited a continued reduction in sodium excretion after 1 h of recovery despite return to baseline of renin, aldosterone, diuresis and cardiovascular parameters. ConclusionSympathetic stimulation for 90 min via LBNP at −30 mmHg LBNP compared to −15 mmHg did not result in a greater response in fractional Na+ excretion, suggesting that additional baroreceptor unloading did not cause further increases in renal sodium reabsorption. Changes in distal Na+ excretion were linear with respect to time (dose) of intervention, but seem to exhibit a saturation-like effect at a level around 4 %. The lack of recovery after 1 h is also a new finding that warrants further investigation.

Dietary sodium restriction reduces blood pressure in patients with treatment resistant hypertension

PurposePatients with treatment resistant hypertension (TRH) are at particular risk of cardiovascular disease. Life style modification, including sodium restriction, is an important part of the treatment of these patients. We aimed to analyse if self-performed dietary sodium restriction could be implemented in patients with TRH and to evaluate the effect of this intervention on blood pressure (BP). Moreover, we aimed to examine if mechanisms involving nitric oxide, body water content and BNP, renal function and handling of sodium were involved in the effect on nocturnal and 24-h BP. Also, measurement of erythrocyte sodium sensitivity was included as a possible predictor for the effect of sodium restriction on BP levels.Patients and methodsTRH patients were included for this interventional four week study: two weeks on usual diet and two weeks on self-performed sodium restricted diet with supplementary handed out sodium-free bread. At the end of each period, 24-h BP and 24-h urine collections (sodium, potassium, ENaC) were performed, blood samples (BNP, NOx, salt blood test) were drawn, and bio impedance measurements were made.ResultsFifteen patients, 11 males, with a mean age of 59 years were included. After sodium restriction, urinary sodium excretion decreased from 186 (70) to 91 [51] mmol/24-h, and all but one reduced sodium excretion. Nocturnal and 24-h systolic BP were significantly reduced (− 8 and − 10 mmHg, respectively, p < 0.05). NOx increased, BNP and extracellular water content decreased, all significantly. Change in NOx correlated to the change in 24-h systolic BP. BP response after sodium restriction was not related to sodium sensitivity examined by salt blood test.ConclusionSelf-performed dietary sodium restriction was feasible in a population of patients with TRH, and BP was significantly reduced. Increased NOx synthesis may be involved in the BP lowering effect of sodium restriction.Trial registrationThe study was registered in Clinical trials with ID: NCT06022133.

RANDOMIZED PILOT STUDY ON THE EFFECTS OF SARCOCORNIA AS A SALTSUBSTITUTE IN ARTERIAL BLOOD PRESSURE AND VASCULAR FUNCTION INHEALTHY YOUNG ADULTS

Objective: Previous studies have shown that excessive salt intake is strongly associated with highblood pressure (HT), vascular dysfunction, and the overall risk of cardiovascular diseases. The aimof this study was to evaluate Sarcocornia effectiveness as a salt substitute, addressing its effect oncardiovascular function in healthy young individuals. Design and method: Thirty healthy participants, aged 18 to 26 years,were randomized into two groups: the control group (CG) and the intervention group (IG). The IGused Sarcocornia powder as a salt substitute for cooking, and the CG used regular salt, during a periodof 1 month. A baseline evaluation was performed before the participants started the interventionphase, and was repeated after a 30-day intervention period. Each evaluation included blood pressure (BP) measurement, carotid-femoral pulse wave velocity (PWV), and carotid pulse wave analysis(PWA), and blood samples were also collected for analysis. Sodium excretion was measured atbaseline and after intervention through spot urine collection and analysis, a method suitable forthis population but with known limitations. Results: Baseline parameters were similar between groups and were within normal range. Sodium excretion remained unchanged in the two evaluations in the CG, but significantly decreased after intervention in the IG. The reduction in sodium excretion in the IG was followed by a significant reduction in brachial and aortic systolic (-7.0± 0.9 mmHg and -5.6 ± 1.0 mmHg, respectively; p&lt;.001) and diastolic (-5.9 ± 1.0 mmHg; p&lt;.001) blood pressure, with no differences observed in the CG. Also in the IG, PWV decreased from 6.0 ± 0.6 m/s at baseline to 5.7 ± 0.6 m/s after intervention (p = .042), with no significant changes in the CG. Conclusions: This preliminary study conveys positive results in favor of Sarcocornia as a dietary substitute for regular salt, providing added evidence on the negative cardiovascular effects of high salt intake in young and healthy adults. The overall nutritional value of Sarcocornia, also known for its high phenolic content, may also add to the observed benefits.

Alleviating air pollutant-associated hypertension by potassium intake in Korean adults: a cross-sectional study from the 2012-2016 Korea National Health and Nutrition Examination Survey.

Air pollution may increase the risk of hypertension (HTN) by increasing oxidative stress and inflammation, and reducing sodium excretion. Potassium intake may reduce the risk of HTN through sodium excretion and reduce inflammation and oxidative stress. This study is aimed at investigating the association between air pollutants and HTN and whether these associations differ based on the potassium intake data of Korean adults from the 2012-2016 Korean National Health and Nutrition Examination Survey (KNHANES). This cross-sectional study used data from KNHANES (2012-2016) combined with annual air pollutant data from the Ministry of Environment using administrative units. We included 15,373 adults who responded to the semi-food frequency questionnaire. Associations between ambient PM10, SO2, NO2, CO, and O3 with HTN according to potassium intake were assessed using the survey logistic regression model for complex samples analysis. After adjusting for potential covariates such as, age, sex, education level, smoking status, family income, alcohol consumption, body mass index (BMI), exercise status, and survey year, as the air pollutant score considering the five air pollutants increased (severe air pollution), the prevalence of HTN increased in a dose-dependent manner (p for trend < 0.001). Meanwhile, in the adults with higher potassium intake and who were exposed to lowest levels of air pollutants score (score = 0), the ORs of HTN were significantly lower (OR = 0.56, 95% CI: 0.32-0.97). In conclusion, our study suggests that exposure to air pollutants may increase the prevalence of HTN among Korean adults. However, high potassium intake may help prevent HTN caused by air pollutants.

Reducing dietary sodium of dairy cows fed a low-roughages diet affect intake and feed efficiency, but not yield.

Wastewater from dairy farms has become a major environmental and economical concern. Sodium residue in treated and untreated wastewater from dairy farms used for irrigation can lead to soil and groundwater salinization, with the risk of soil degradation. We examined the effect of reducing sodium fed to mid to late lactating cows from 0.61% (high sodium [HS]) to 0.45% (low sodium [LS]) of dry matter on dry matter intake (DMI), milk and milk-component yields, eating behavior, apparent total track digestibility, feed efficiency, and sodium excretion into the environment. We randomly assigned 28 multiparous high-yielding ( > 35kg milk/d) cows to 1 of 2 treatment groups (LS or HS) in a crossover design, with 7d of adaptation and 28d of data collection. Reducing sodium in the diet reduced sodium intake from 171 to 123g/d while lowering sodium excreted in the manure by 22%. Energy corrected milk (ECM) yield (37.4kg/d) and sodium excretion in the milk (33.7g/d) were similar for both groups. The DMI of LS cows was lower than that of HS cows (27.3 vs. 28kg/d) and consequently, feed efficiency of the LS cows was higher (1.40 vs. 1.35 ECM/DMI). Eating rate, meal and visit frequency, and eating time were similar for both treatments; meal and visit duration were longer for the HS cows, and meal and visit sizes tended to be larger. Digestibility of DM and amylase-treated neutral detergent fiber remained similar. Based on the results of this study, and discussed considerations, we recommend lowering the dietary sodium content for mid to late lactating cows in commercial herds to 0.52% of DM, in order to reduce sodium excretion to the environment via urine.

Randomized Pilot Study on the Effects of Sarcocornia as a Salt Substitute in Arterial Blood Pressure and Vascular Function in Healthy Young Adults.

Previous studies have shown that excessive salt intake is strongly associated with high blood pressure (HT), vascular dysfunction, and the overall risk of cardiovascular diseases. The aim of this study was to evaluate Sarcocornia effectiveness as a salt substitute, addressing its effect on cardiovascular function in healthy young individuals. Thirty healthy participants, aged 18 to 26 years, were randomized into two groups: the control group (CG) and the intervention group (IG). The IG used Sarcocornia powder as a salt substitute for cooking, and the CG used regular salt, during a period of 1 month. A baseline evaluation was performed before the participants started the intervention phase, and was repeated after a 30-day intervention period. Each evaluation included blood pressure (BP) measurement, carotid-femoral pulse wave velocity (PWV), and carotid pulse wave analysis (PWA), and blood samples were also collected for analysis. Sodium excretion was measured at baseline and after intervention through spot urine collection and analysis, a method suitable for this population but with known limitations. Baseline parameters were similar between groups and were within the normal range. Sodium excretion remained unchanged in the two evaluations in the CG, but significantly decreased after intervention in the IG. The reduction in sodium excretion in the IG was followed by a significant reduction in brachial and aortic systolic (SBP) and diastolic blood pressure (DBP), and also in PWV. No significant changes were observed in the CG in terms of cardiovascular parameters. This preliminary study conveys positive results in favor of Sarcocornia as a dietary substitute for regular salt, providing added evidence of the negative cardiovascular effects of high salt intake in young and healthy adults.

MO093: Dietary Sodium Restriction Reduces Nocturnal Blood Pressure in Treatment Resistant Hypertensive Patients

Abstract BACKGROUND AND AIMS High blood pressure (BP) is an essential contributor to the risk of cardiovascular disease (CVD) and death. Hence, diagnosing and treating patients with high BP is paramount if the number of cardiovascular related death should be reduced. High nocturnal BP and blunting of normal nocturnal BP decrease have stronger correlation to the risk of CVD than high day time BP. Lowering nocturnal BP is assumed to reduce the risk of CVD. Patients with treatment resistant hypertension (TRH) represent a subgroup of hypertensive patients characterized by lack of BP control despite antihypertensive treatment. These patients are at particular risk of CVD and target organ damage. Patients with TRH are more likely to experience BP increase as a response to sodium loading than other individuals. Lifestyle modification is an important treatment angle in hypertensive patients. It is, in particular, central to reduce sodium intake, as high sodium intake increases the risk of TRH. Thus, in this study we aimed to analyse if self-performed dietary sodium restriction could be implemented in patients with TRH. Moreover, we aimed to analyse the effect of this attempted restriction on nocturnal BP and 24 h BP, on plasma levels of BNP and nitric oxide, and on body water content. METHOD Patients with TRH from 20 to 70 years with normal renal function were invited for participation in this cross-over interventional study. Patients were screened with 24 h ambulatory BP monitoring initiated after observed intake of usual antihypertensive medication, and they were included if 24 h systolic BP/diastolic BP ≥ 130/80 mmHg. Study participation included two periods of 14 days; a standard period with usual diet and an interventional period with instructed dietary sodium restriction and handed-out sodium-reduced bread. For both periods, all antihypertensive medication was dosed and handed out and ingested in the morning. At the end of each period, patients were examined with 24 h BP monitoring, 24 h urine collection (sodium excretion), blood samples (nitric oxide and BNP) and bioimpedance measurement (body water content). RESULTS Baseline characteristics of the fifteen included patients are shown in Table 1. Eleven of the patients were male. Patients had been treated for hypertension for a mean of 12.5 (7) years and excreted a mean of 11.2 grams of salt at baseline [192 (86) mmol sodium]. All patients but one reduced sodium excretion at follow up. Table 2 shows the effect of sodium restriction on BP, nitric oxide, BNP and body water content. Sodium excretion was reduced to 91 mmol/24 h, which equals 5.3 g of salt. BP (24 h, day and nocturnal) decreased significantly as well as body water content and plasma levels of BNP. These changes were, however, not correlated. Plasma levels of nitric oxide increased, but it was not related to the changes in BP. Nocturnal fraction of 24 h sodium excretion increased after sodium restriction; however, this was not correlated to changes in nocturnal BP. Renal function and urinary potassium excretion both remained unchanged. Four patients experienced side effects; three reported newly onset dizziness at follow-up; two of them had 24 h BP reduction &amp;gt; 10 mmHg systolic. One patient had increased creatinine and potassium at follow-up. CONCLUSION In a population of 15 treatment resistant hypertensive patients, we demonstrated that self-performed dietary sodium restriction could be implemented. Urinary sodium excretion was reduced significantly to 5.3 g/24 h. Nocturnal BP was reduced significantly; dipping status was, however, unchanged. Increased plasma levels of nitric oxide may be evidence of improved endothelial function. Hence, by the local vasodilating effect, NO may be one of the involved mechanisms in BP decrease following a sodium restriction. Reduced extracellular water content and BNP may be other explainable effects of BP reduction after inducing sodium restriction.

Effects of Potassium Supplementation and Kir7.1 Knockout on Renal Function During the Progression of Salt‐Sensitive Hypertension

The inward‐rectifying potassium channel (Kir) family has been shown to play an important role in the kidney’s ability to maintain electrolyte homeostasis as well as blood pressure. Kir7.1 (encoded by the Kcnj13 gene) is expressed in the kidney, though its role in renal function is rudimentary. To examine the role of Kir7.1 in renal electrolyte handling and the development of salt‐induced hypertension, we generated a knockout of Kcnj13 on the Dahl salt‐sensitive (SS) rat background. Rats with the knockout of Kcnj13 were embryonically lethal; therefore, to study the Kir7.1 channel, we used heterozygous (SSKcnj13+/‐) rats. Immunohistochemistry staining for Kir7.1 revealed basolateral staining in the cortical sections of the kidneys in wild‐type littermates (WT), while SSKcnj13+/‐ rats showed little to no staining. In addition, immunofluorescence analysis confirmed that Kir7.1 was localized on the basolateral side in tubules and revealed that Kir7.1 co‐localized with aquaporin 2 and sodium‐chloride cotransporter (NCC). This data indicates that Kir7.1 is expressed in the cortical collecting duct (CCD) and the distal convoluted tubule (DCT). SSKcnj13+/‐ rats were further used to measure blood pressure and electrolyte handling changes during the development of salt‐induced hypertension. DSI telemeters were implanted in animals at 8 weeks of age; after a week to recover from surgery, animals were fed a high salt 4% NaCl diet (HS) for three weeks. Both WT and SSKcnj13+/‐rats become hypertensive after three weeks of HS; no difference between mean arterial pressures (153.1 ± 5.7 vs. 159.2 ± 6.9 mmHg for WT and SSKcnj13+/‐rats, respectively) was identified. Serum electrolytes were measured and also showed no difference in the amount of potassium (3.4 ± 0.1 vs. 3.5 ± 0.1 mmol/L) or sodium (142 ± 0.8 vs. 142 ± 0.4 mmol/L). Furthermore, urinary electrolyte excretion was measured and revealed no differences between WT and SSKcnj13+/‐ animals for potassium (14.0 ± 0.6 vs. 15.6 ± 1.9 K+/Cre) or sodium excretion (91 ± 11 vs. 117 ± 16 Na+/Cre). Potassium supplementation has previously been shown to augment renal Kir7.1 expression. Thus, we repeated the previous protocol but instead using a high salt and high potassium 4% NaCl and 2% KCl (HSHK) diet. After three weeks on this diet, animals exhibited no difference in blood pressure (154.2 ± 9.1 vs 145.6 ± 4.1 mmHg) and no differences in plasma potassium (4.0 ± 0.1 vs 4.0 ± 0.1 mmol/L) or sodium (139 ± 1 vs 139 ± 1 mmol/L). Urinary electrolyte excretion showed no differences in potassium excretion (60.9 ± 3.3 vs 54.8 ± 1.1 K+/Cre), but SSKcnj13+/‐ animals did have a significant decrease in sodium excretion (130 ± 8 vs 103 ± 3 Na+/Cre). Altogether, we have confirmed the presence of Kir7.1 in the CCD and DCT, found that heterozygous knockout of Kir7.1 does not affect the development of blood pressure on a HS or HSHK diet. However, we do see a reduction in sodium excretion in SSKcnj13+/‐rats on the HSHK diet, suggesting that Kir7.1’s role may be more pronounced under conditions of higher potassium.

MP36-19 PROSTACYCLIN (TREPROSTINIL) THERAPY IMPROVES RENAL HEMODYNAMICS DURING RAT RENAL ISCHEMIA-REPERFUSION INJURY

You have accessJournal of UrologyCME1 May 2022MP36-19 PROSTACYCLIN (TREPROSTINIL) THERAPY IMPROVES RENAL HEMODYNAMICS DURING RAT RENAL ISCHEMIA-REPERFUSION INJURY Frances Kazal, Meiwen Ding, Dicken Ko, Reginald Gohh, and Nisanne Ghonem Frances KazalFrances Kazal More articles by this author , Meiwen DingMeiwen Ding More articles by this author , Dicken KoDicken Ko More articles by this author , Reginald GohhReginald Gohh More articles by this author , and Nisanne GhonemNisanne Ghonem More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002590.19AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Renal ischemia-reperfusion injury (IRI) is a crucial factor causing acute kidney injury (AKI). To date, no pharmacological treatments are available for the prevention of I/R-induced renal injury. Here, we investigate the renal hemodynamics and reno-protective effects of the prostacyclin analog, treprostinil, against renal IRI in vivo. METHODS: Male Sprague Dawley rats were subjected to bilateral renal ischemia (45 minutes) followed by reperfusion (1–48 hour). Treprostinil (100 ng/kg/min) was administered subcutaneously either (A) at the time of ischemia (IRI-immT) or (B) approximately 18-24 hours before renal IRI (IRI-preT). RESULTS: Serum and urine creatinine were elevated at 24 hours post-reperfusion in the IRI group vs. sham (P <0.001), which both the IRI-immT and IRI-preT reduced the peak of serum creatinine at 24 hours after renal IRI (P <0.001). Also, medullary and cortical renal blood flow (RBF) were significantly reduced in the IRI group vs. sham (P <0.001), whereas the IRI-immT (P <0.01) and IRI-preT (P <0.05) groups improved RBF at 90 minutes post-reperfusion and maintained throughout 120 minutes. In parallel, animals in the IRI injury group experienced a decreased eGFR, increased urinary sodium (UNa 2+) excretion and proteinuria during the first 24 hours post-reperfusion vs. sham (P <0.01). Meanwhile, treprostinil reduced the UNa 2+ and proteinuria and completely restored the eGRF to baseline by 48 hours post-reperfusion and, compared to the IRI group (P <0.01). CONCLUSIONS: This study demonstrates the efficacy of treprostinil in improving renal hemodynamics and kidney function early post-IRI in a clinically relevant rat model of AKI. Specifically, our data show that treprostinil remarkably increased renal blood flow and GFR, and reduced sodium excretion and proteinuria post-reperfusion. Importantly, these data suggest that treprostinil has the potential to serve as a therapeutic agent to protect the kidney against renal IRI. Source of Funding: Funding support for this project was provided in part by the Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health, which funds the University of Rhode Island Core Lab (P20GM103430). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e605 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Frances Kazal More articles by this author Meiwen Ding More articles by this author Dicken Ko More articles by this author Reginald Gohh More articles by this author Nisanne Ghonem More articles by this author Expand All Advertisement PDF DownloadLoading ...

Gs‐DREADD Regulation of ENaC

Activity of the epithelial Na+ channel (ENaC) fine-tunes renal Na+ excretion and consequently, contributes to the normal control of blood pressure. ENaC is expressed in the apical membrane of principal cells. Importantly, ENaC is activated by the hormone vasopressin via the V2 receptor, which is coupled to the heterotrimeric Gs protein. Stimulation of the V2 receptor rapidly activates adenylyl cyclase to increase intracellular cAMP levels. We have recently developed a mouse model with targeted expression of the Gs designer receptors exclusively activated by designer drugs (DREADD) in renal principal cells (GsD). Moreover, this mouse line has a luciferase reporter downstream of a cAMP response element binding protein site. As such, it allows in vivo reporting of cAMP levels. DREADD receptors are activated by clozapine N-oxide (CNO), which normally is an inert drug with no biological activity in the absence of DREADD receptors. We test here if CNO affects the activity of ENaC to influence renal salt and water excretion in GsD mice similarly to vasopressin. In these mice, we longitudinally monitored CNO-stimulated cAMP levels in principal cells using an IVIS Lumina XR. In parallel, we quantified CNO-dependent ENaC activity and renal sodium excretion. We observed that CNO increased ENaC activity in principal cells in freshly isolated tubules from GsD mice compared to control mice. Metabolic cages experiments demonstrated that CNO treatment (0.1 mg/kg) increased cAMP levels concomitantly with reducing sodium excretion similarly to dDAVP (1 µg) in GsD mice. Finally, in COS-7 cells expressing murine ENaC tagged with YFP, CPT-cAMP increased translocation of ENaC to the plasma membrane. Here we demonstrated the utility of a new principal cell-specific Gs-DREADD mouse line. This new mouse model will be an important tool for investigating the effects of abnormal cAMP signaling in principal cells possibly informing understanding of the cellular mechanism underpinning conditions like polycystic kidney disease.

Collecting duct-specific knockout of sphingosine-1-phosphate receptor 1 aggravates DOCA-salt hypertension in mice.

We have previously reported that renal medullary sphingosine-1-phosphate (S1P) regulates sodium excretion via the S1P type-1 receptor (S1PR1). As S1PR1 is predominantly expressed in collecting ducts (CD), the present study tested the hypothesis that the CD-S1PR1 pathway plays a critical role in sodium excretion and contributes to salt-sensitive hypertension. CD-specific S1PR1 knockout mice were generated by crossing aquaporin-2-Cre mice with S1PR1-floxed mice. Renal sodium excretion and arterial pressure were compared between wild type and KO mice in response to high-salt challenges and treatment of deoxycorticosterone acetate (DOCA) salt. Protein levels of renal medullary S1PR1 were increased by 100% after high-salt intake, whereas DOCA treatment with high-salt intake blocked the increase of S1PR1 levels. Urinary sodium excretions in knockout mice were decreased by 60% compared with wild type mice after acute intravenous sodium loading (0.84 ± 0.16 vs. 2.22 ± 0.62 μmole/min per g kwt). The pressure natriuresis was impaired in knockout mice compared with wild type mice (4.32 ± 1.04 vs. 8.73 ± 0.19 μmole/min per g kwt). The chronic high-salt intake-induced positive sodium balance was enhanced in knockout mice compared with wild type mice (5.27 ± 0.39 vs. 2.38 ± 1.04 mmol/100 g BW per 24 h). After 10-day DOCA-salt treatment, knockout mice developed more severe hypertension than wild type mice (SBP 142 ± 8 vs. 115 ± 4 mmHg). The deletion of CD-S1PR1 reduced sodium excretion, promoted sodium retention, and accelerated DOCA-salt-induced salt-sensitive hypertension, suggesting that the CD-S1PR1 signaling is an important antihypertensive pathway by promoting sodium excretion and that impairment of renal medullary S1PR1 may represent a novel mechanism for salt-sensitive hypertension.

Abstract P005: GRK4 Inhibitors Suppress Breast Cancer Cell Growth And Potentiate The Inhibitory Effect Of Dopaminergic D 1 Receptor Agonist SKF38393

The renal dopaminergic D 1 receptor (D 1 R) regulates sodium excretion which is terminated by phosphorylation by G protein-coupled receptor kinases 4 (GRK4). GRK4 gene variants are associated with increased GRK4 activity and reduced sodium excretion resulting in hypertension. Breast cancer incidence is higher in hypertensive women. We found that GRK4 is a potential molecule linking these two diseases. We hypothesized that GRK4 inhibitors would be beneficial to patients with hypertension and breast cancer. Three potential GRK4 inhibitors (compounds A, B, and C) were tested for their effect on the growth of breast cancer cells MDA-MB-468, MCF-7, and benign mammary epithelial cells MCF-10A controls. These cell lines had high, low, and no GRK4 expression respectively. Growth of MDA-MB-468 and MCF-7 cells was effectively inhibited by compound C with IC 50 16.8±1.9 nM (n=2). MCF-10A cells were relatively resistant to compound C with IC 50 49.3±4.0 nM (n=3) that is significantly higher than the cancer cells (p&lt;0.001). Compound B was the least effective inhibitor in all three cell lines (IC 50 was 1.5-2.3 μM). Growth inhibition of compound A was similar in MCF-7 and MCF-10A cells but less effective in MDA-MB-468 cells indicating GRK4 inhibition may not be the only target for growth inhibition of this compound. It has been reported that D 1 R agonists inhibit growth of breast cancer cells. We hypothesized that blockade of GRK4 would increase sensitivity of breast cancer cells to the inhibitory effect of a D 1 R agonist. In MDA-MB-468 cells, SKF38393 (SKF) at 20 μM caused a 36% reduction in cell number (from 276.7±0.47E4 to 177.7±4.33E4). Compound C alone reduced cell number by 37% (172.4±0.04E4, 5 nM) and 51% (136.3±7.87E4, 10 nM) respectively. Combination treatment induced more reduction in cell number, 63% (100.4±5.54E4, 5 nM) and 84% (44.1±12.7E4, 10 nM). Similarly, Compound A also enhanced the inhibitory effect of SKF. A left-shift of the SKF dose-response curve in GKR4 knock-down MDA-MB-468 cells confirmed that inhibition of GRK4 increases sensitivity of breast cancer cells to SKF. Our preliminary results suggest that targeting GRK4 with compound C and a dopaminergic agonist could be a novel strategy for breast cancer therapy especially for the patients with hypertension.

Collecting Duct NOS1 is Necessary to Maintain Sodium Balance in Male, But Not Female Mice

Nitric oxide synthase 1 (NOS1) is a well‐established regulator of fluid and electrolyte balance in the collecting duct (CD). We previously reported that a loss of CDNOS1 in male mice results in reduced sodium excretion, urine volume, and nitric oxide (NO) excretion as well as increased plasma sodium compared to flox control mice after being challenged with 1 day of high salt diet. However, it is not yet known if this genotype difference is conserved in female mice. Therefore, we investigated whether collecting duct NOS1 is critical in maintaining homeostasis in female mice. Female CDNOS1KO and flox control mice were acclimated to metabolic cages and placed on a sodium deficient (LS, 1 week) then challenged with a high sodium (HS, 1 day) diet and urine collected. Female CDNOS1KO mice and flox control mice had similar sodium excretion (Flox: 3.24±0.32, KO: 2.62±0.31mmol/day; n=8–12/group, p&gt;0.05), urine volume (Flox: 7.69±0.75, KO: 6.42±0.82mL/day; n=8–12/group, p&gt;0.05), and NOx excretion (Flox: 1099±205, KO: 1339±389 μmol/day; n=8–12/group, p&gt;0.05) in addition to comparable plasma sodium levels (Flox: 146±1.0, KO: 147±0.5mmol/L; n=6/group, p&gt;0.05) after one day of a high salt challenge. Furthermore, urinary prostaglandin E metabolite excretion was similar between genotypes after a high salt challenge (Flox: 3187±382, KO: 2744±291pg/day; n=8–10/group, p&gt;0.05), suggesting that female mice are able to compensate for a loss of NOS1‐derived NO in the collecting duct. Additionally, we performed RT‐PCR on male and female renal vessels and found that unlike males, female CDNOS1KO mice have significantly elevated vascular endothelin 1 mRNA expression (Male‐ flox: 1.00±0.09, KO: 0.98±0.03; n=6/group, p&gt;0.05; Female‐ flox: 1.00±0.18, KO: 1.75±0.24; n=5–6/group, p=0.03). In conclusion, female mice do not rely on collecting duct NOS1‐derived NO to maintain fluid‐electrolyte balance. We propose that female mice utilize endothelin‐1 and/or NO production in other renal segments.Support or Funding InformationF31DK111067 to RSS, F31HL149235 to LSD, and P01HL136267, AHA 19SRG34930023 to JSP

Effects of Atrial Natriuretic Peptide knockout on renal mitochondrial bioenergetics in salt‐sensitive hypertension

BackgroundAtrial Natriuretic Peptide (ANP) encoded by Nppa, is a hormone known to promote salt excretion and BP reduction; there are clinical data implicating inherently low levels of ANP in the development of salt‐sensitive (SS) hypertension. In the heart and fat tissue, ANP is known to affect lipid peroxidation, mitochondrial bioenergetics and biogenesis. However, there is a gap in knowledge regarding the effects of ANP on mitochondria in the kidney. We hypothesized here that in SS hypertension ANP deficiency causes renal mitochondrial dysfunction.MethodsSS hypertension was induced in SSNPPA−/− (ANP knockout in Dahl SS background) and SSWT (wild type Dahl SS) rats by placing them on a high salt diet (HS, 4% NaCl) or a normal salt diet (control, NS, 0.4% NaCl) for 21 days. A combination of in vivo techniques with studies performed on isolated renal mitochondria (seahorse respiration and spectrofluorimetry assays) were used to test the role of ANP knockout in the mitochondria bioenergetics.ResultsOur previous studies demonstrated that during a HS challenge SSNPPA−/− rats exhibit exacerbated salt‐sensitivity of blood pressure, reduced sodium excretion, decreased urine flow, and aggravated kidney injury. In addition, there is a significant reduction in renal cortical cGMP production in the HS fed SSNPPA−/− rats vs SSWT. cGMP is known to exert protective effects in mitochondria; in order to test mitochondrial function in our model, we measured membrane potential and levels of superoxide and hydrogen peroxide (H2O2) in mitochondria isolated from kidney cortex. Specifically, TMRM, Amplex Red and MCLA were used to detect mitochondrial membrane potential, H2O2 and superoxide, respectively. We report a decrease in mitochondrial membrane potential in the SSNPPA−/− rats vs SSWT (both on NS and HS diets), and an increase in mitochondrial H2O2 and superoxide levels in the same groups. Swelling assay revealed a trend for an increased mitochondria swelling rate in the SSNPPA−/− rats. Pilot calcium uptake studies implicated calcium influx via MCU (mitochondrial calcium uniporter) and mitochondrial permeability transition pore (mPTP) opening in this process. Interestingly, seahorse respirometry performed on cortical mitochondria revealed elevation of the oxygen consumption rate (OCR) in the knockout rats on HS, while in SSWT rats HS diet feeding reduced OCR (both vs NS). In addition, we observed activation of the antioxidant system in the SSNPPA−/− rats as opposed to SSWT (on HS diet, assessed in a Trolox‐based assay).ConclusionsTaken together, our data indicate that lack of ANP, via disruption of protective cGMP‐mediated pathways, results in significant alterations in mitochondrial bioenergetics in the renal tissue. By establishing the mechanistic link between ANP and mitochondrial function, further studies will advance the understanding of the mitochondria‐mediated mechanisms affecting renal disease progression.Support or Funding InformationThe study was supported by NIH R00 DK105160 and Dialysis Clinic Inc Reserve Funds.

Dioclea violacea lectin modulates the gentamicin activity against multi-resistant strains and induces nefroprotection during antibiotic exposure

Gentamicin is an aminoglycoside antibiotic used to treat infections of various origins. In the last few decades, the constant use of gentamicin has resulted in increased bacterial resistance and nephrotoxicity in some cases. In this study, we examined the ability of Dioclea violacea lectin (DVL) in modulate the antimicrobial activity of gentamicin and reduce the nephrotoxicity induced by this drug. The minimum inhibitory concentration (MIC) obtained for DVL against all strains studied was not clinically relevant (MIC ≥ 1024 μg/mL). However, when DVL was combined with gentamicin, a significant increase in antibiotic action was observed against Staphylococcus aureus and Escherichia coli. DVL also reduced antibiotic tolerance in S. aureus during 10 days of continuous treatment. In addition, DVL presented a nephroprotective effect, reducing sodium excretion, N-Gal expression and urinary protein, that are important markers of glomerular and tubular injuries. Taken together, studies of inhibition of hemagglutinating activity, fluorescence spectroscopy and molecular docking revealed that gentamicin can interact with DVL via the carbohydrate recognition domain (CRD), suggesting that the results obtained in this study may be directly related to the interaction of DVL-gentamicin and with the ability of the lectin to interact with glycans present in the cells of the peritoneum.

Abstract P2043: Role of GRK4, a Risk Factor for Hypertension, in Breast Cancer

Clinical studies have shown that breast cancer risk is increased in hypertensive women. The molecular mechanism linking hypertension and breast cancer remains undetermined. Several lines of evidence suggest that G-protein coupled receptor kinase 4 (GRK4) is a candidate protein. The link between high salt and hypertension has been well documented. Renal sodium excretion is regulated by dopaminergic D1-like receptor (D 1 R). Sustained activation of GRK4 impairs D 1 R function and causes hypertension. On the other hand, GRK4 expression is higher in breast cancer than in normal breast tissues. GRK4 variants A142V and R65L have been identified as both hypertension and breast cancer risk loci. To determine the role of GRK4 in breast cancer, we first examined GRK4 expression and SNPs in 7 breast cancer cell lines and benign breast epithelial cell line, MCF-10A. We found that MCF-10A cells do not express detectable level of GRK4 protein whereas all 7 breast cancer cell lines express different levels of GRK4. Except for BT20, all other breast cancer lines have 1-3 SNPs on GRK4 gene of which A142V occurs in all 6 lines. MDA-MB-468 cells contain both A142V and R65L at both alleles. These 2 SNPs have been demonstrated to be associated with enhanced GRK4 activity and reduced sodium excretion in the kidney. To further explore the function of GRK4 in breast cancer cells, we generated three stable GRK4 knock-down MDA-MB-468 lines using inducible lentiviral shRNA vectors. GRK4 knock-down induced by doxycycline (Dox) significantly reduced growth rates of these cells with greatest reduction in line 167 (68%). Growth rate changes correlated with that in GRK4 mRNA levels. 5-bromo-2-deoxyuridine (BrdU) incorporation test demonstrated that reduced growth rate was predominantly a result of reduced cell proliferation. Percentage of BrdU labeled cells were decreased from 45±3% in the cells without Dox to 32±5% in the cells treated with 0.1 μg/ml Dox (p&lt;0.005). There was no change in growth rate in the cells expressing non-targeting shRNA. Our results demonstrate that GRK4 plays a role in promoting breast cancer proliferation and suggest that GRK4 could be a new therapeutic target for the treatment of hypertension and breast cancer.

Collecting duct NOS1 activation is necessary for increased GFR in response to high salt diet

We previously reported that nitric oxide synthase‐1 (NOS1) in the collecting duct (CD) is critical for maintaining fluid‐electrolyte balance during high salt diet. Lack of NOS1 in the CD (CDNOS1KO) results in reduced sodium excretion, urine output, and urinary nitrite/nitrate excretion compared to control mice after 1 day of a high salt diet. By day 7 of a high salt diet, CDNOS1KO mice display significantly increased systolic blood pressure with normalized sodium excretion. We also previously reported that after 7 days of high salt diet there is inappropriate suppression of plasma and urinary aldosterone excretion, renal angiotensin II levels, and CD ENaC activity. This inability to appropriately suppress renal angiotensin II and systemic aldosterone with high salt diet in CDNOS1KO mice lead us to hypothesize that the loss of activation of CD NOS1 during high salt diet challenges blunts the physiological renal hemodynamic response to high salt diet. The purpose of the current study was to determine if CDNOS1KO mice on high salt diets have attenuated glomerular filtration rate (GFR) response. To test this, GFR was measured by transdermal FITC‐sinistrin clearance in conscious male control and CDNOS1KO mice on sodium deficient (LS, n=4), normal salt (NS, n=11) or after 1 day and 7 days of high salt (HS1, n=4 and HS7, n=10) diets. On LS and NS, GFR was similar between control (LS: 263 ± 14 ml/min, NS: 224 ± 6 ml/min) and CDNOS1KO mice (LS: 237.2 ± 10 ml/min, NS: 218 ± 10 ml/min) (Pgenotype = 0.4, Pdiet = 0.7, Pgenotypexdiet = 0.3). HS1 control mice had a significant increase in GFR (333 ± 10 ml/min, P=0.008), while GFR remained unchanged in CDNOS1KO mice (255 ± 23 ml/min, P=0.2) compared with LS. HS7 control and CDNOS1KO mice had similar levels of GFR (251 ± 16 and 291 ± 27 ml/min, respectively). Taken together these data indicate, that CD NOS1 is critical for the adaptation to a high salt diet, such that CDNOS1KO mice are volume expanded, have inappropriately high RAAS activation, and fail to increase GFR. After a few days of high salt diet, blood pressure is increased resulting in a rightward shift in the pressure natriuresis curve, with GFR and sodium excretion normalized to control levels. In conclusion, CD NOS1 activation is critical for regulation of tubular and hemodynamic pathways during consumption of HS diets.Support or Funding InformationK01‐DK‐105038 KAH, HL136936 JSP and DMP.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.