Sodium Sensitivity Research Articles

Enabling SENSE accelerated 2D CSI for hyperpolarized carbon-13 imaging

As hyperpolarized (HP) carbon-13 (13C) metabolic imaging is clinically translated, there is a need for easy-to-implement, fast, and robust imaging techniques. However, achieving high temporal resolution without decreasing spatial and/or spectral resolution, whilst maintaining the usability of the imaging sequence is challenging. Therefore, this study looked to accelerate HP 13C MRI by combining a well-established and robust sequence called two-dimensional Chemical Shift Imaging (2D CSI) with prospective under sampling and SENSitivity Encoding (SENSE) reconstruction. Due to the low natural abundance of 13C, the sensitivity maps cannot be pre-acquired for the reconstruction. As such, the implementation of sodium (23Na) sensitivity maps for SENSE reconstructed 13C CSI was demonstrated in a phantom and in vivo in the pig kidney. Results showed that SENSE reconstruction using 23Na sensitivity maps corrected aliased images with a four-fold acceleration. With high temporal resolution, the kidney spectra produced a detailed metabolic arrival and decay curve, useful for further metabolite kinetic modelling or denoising. Metabolic ratio maps were produced in three pigs demonstrating the technique’s ability for repeat metabolic measurements. In cases with unknown metabolite spectra or limited HP MRI specialist knowledge, this robust acceleration method ensures comprehensive capture of metabolic signals, mitigating the risk of missing spectral data.

#1405 Salt sensitivity and hypertensive nephropathy: a link to be discovered

Abstract Background and Aims Sodium sensitivity (SS) is a change in blood pressure (BP) depending on Na+ intake, 30% of population has it. Either a salt load test or a sodium dietary protocol can be used to stratify the population into 3 groups based on BP variation: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on an increase, a non-significant variation or a decrease in BP following the administration of Na+. SNPs located in genes related with Na+ metabolism, aldosterone synthesis and kidney tubular Na+ reabsorption are related to this phenotype. Method We analyzed data collected from the follow-up (FUP) of 127 subjects with a new diagnosis of hypertension, categorized by their profile through acute salt load test. We analyzed the kidney damage by annual decline of eGFR and development of microalbuminuria. Genetic polymorphism analysis has been executed. Results No differences in the decline of eGFR are observed among the groups (−1.3084 ml/min ± 0.16 p-Value 0.372). SR subjects seem to be more prone to develop earlier microalbuminuria (χ 2 10.682, p = 0.005) even with an adequate BP control (P-Anova SBP 0.766; P-Anova DBP 0.856). An inverse correlation exists between pressure-natriuresis ratio and decline in eGFR (R −0.194 p = 0.016). Polymorphism in CYP11B2 (0.72 OR p = 0.045) and NEDD4L (0.74 OR p = 0.027) are protective against eGFR decline. ADD3 polymorphism (3.73 OR p = 0.049) is a risk factor for development of microalbuminuria. KL (0.15 OR p = 0.034), PKD and TRPC6 (p-Value 0.037, p-Value 0.009) polymorphism are protective factor against microalbuminuria. Conclusion SR patients are more at risk of developing hypertensive nephropathy earlier than other groups; steeper pressure natriuresis ratio is involved in quicker decline in renal function possibly accelerating development of hypertensive nephropathy. Further studies with larger sample and standardization in salt sensitivity test are needed to translate this knowledges into clinical setting.

Da-Chuan-Xiong Decoction Ameliorates Sodium Sensitivity and Plasma Norepinephrine via Attenuation of Brain Oxidative Stress in the DOCA-Salt Hypertensive Rats.

Da-Chuan-Xiong Decoction (DCXD) is an aqueous extract from a classic Chinese herbal formula composed of dried rhizomes of Ligusticum chuanxiong Hort and Gastrodia elata Bl. in the mass ratio of 4 : 1. It has been long used to treat chronic cardiovascular disease caused by blood stasis and wind pathogen in the clinic. This experimental study aimed to investigate the blood pressure (BP)-lowering effect of DCXD treatment on hypertension and underlying mechanisms. Male Sprague-Dawley rats were used in the experiment, and the hypertensive models were created by administering deoxycorticosterone acetate (DOCA) in conjunction with a high salt intake in uninephrectomized rats. DCXD was administered to hypertensive rats by oral gavage daily at a dose of 5 g/kg or 2.5 g/kg bodyweight for 28 days. The brain sodium sensitivity, ENaC function, superoxide anion level, NADPH oxidase activity, and expression of ENaC, p67phox, p47phox, and Rac1 in the paraventricular nucleus were assessed by using the appropriate methods. The 28 days of DCXD (5 g/kg) treatment significantly reduced the increased BP effectively, inhibited the enhanced heart index, kidney index, and 24 h urinary protein, and improved the progressive pathological changes of heart and kidney, which was comparable to that of the positive control amlodipine. DCXD treatment also caused a marked reduction in plasma norepinephrine and induced a significant improvement in brain sodium sensitivity and ENaC function in DOCA-salt hypertensive rats. Rats in DCXD-treated groups also exhibited decreased superoxide anion levels and NADPH oxidase activity in the paraventricular nucleus. The level of ENaC, p67phox, and Rac1 protein expression in the paraventricular nucleus was significantly downregulated by DCXD treatment in DOCA-salt hypertensive rats. These findings indicate that the depressor action and sympathetic inhibition of DCXD on salt-sensitive hypertension may be by ameliorating brain sodium sensitivity, modulating ENaC function, and inhibiting the expression of ENaC and NADPH oxidase in the hypothalamic paraventricular nucleus.

Alpha-adducin 1 (rs4961) gene and its expression associated with sodium sensitivity in hypertensive patients: a cohort study in the western Ukrainian population.

Objective. The aim of this study was to evaluate the association of the α-adducin-1 gene (ADD1) (Gly460Trp [rs4961]) polymorphism and its expression in association with renal dysfunction and sodium sensitivity in hypertensive patients in western Ukrainian population. Methods. One-hundred patients with essential arterial hypertension (EAH) and hypertensive-mediated target organ damage (stage 2), moderate, high, and very high cardiovascular risk were enrolled in case-control study. Sixty healthy individuals were assigned as controls. Sodium sensitivity and sodium resistance were determined by salt load reaction. The ADD1 (rs4961) genotyping was performed in RT-PCR. Results. The expression of the quantitative trait loci (eQTL) of ADD1 gene (rs4961) (chr4:2906707 [hg19]) was confirmed in 37 tissues and organs with 23 phenotypic traits. Two hundred eQTL associations revealed - all cis-variants (cis-QTL); 73 methylation QTL (mQTL), 34 splicing QTL (sQTL), 14 histone modification QTL (hQTL), 2 protein QTL (pQTL), 23 transcript utilization QTL (tuQTL), and 4 loci of incorporated long noncoding areas of RNA (lncRNA). GG-genotype unreliably enhances EAH risk (OR=1.92; 95%CI: 0.90-4.10; p=0.066). Sodium sensitivity was observed in 54.0% of patients and in 20.0% of controls (c2=17.89; p<0.001). Sodium sensitivity in T-allele carriers of the ADD1 gene (1378G>T; rs4961) dominated 12-fold in general (OR 95%CI: 2.24-64.29; p=0.001), in women - 4.71 times (OR 95%CI: 1.92-11.56; p<0.001), and in men - 4.09 times (OR 95%CI: 1.03-16.28; p=0.041). Sodium sensitivity elevated the likelihood of severe EAH twice (OR=2.19; OR 95%CI: 1.00-5.05; p=0.049). Conclusion. T-allele associates with sodium sensitivity in essential arterial hypertension patients and increases the risk of hypertension regardless the gender. Sodium sensitivity enhances the probability of severe essential arterial hypertension in observed population.

Single-molecule visualization of human A2A adenosine receptor activation by a G protein and constitutively activating mutations

Mutations that constitutively activate G protein-coupled receptors (GPCRs), known as constitutively activating mutations (CAMs), modify cell signaling and interfere with drugs, resulting in diseases with limited treatment options. We utilize fluorescence imaging at the single-molecule level to visualize the dynamic process of CAM-mediated activation of the human A2A adenosine receptor (A2AAR) in real time. We observe an active-state population for all CAMs without agonist stimulation. Importantly, activating mutations significantly increase the population of an intermediate state crucial for receptor activation, notably distinct from the addition of a partner G protein. Activation kinetics show that while CAMs increase the frequency of transitions to the intermediate state, mutations altering sodium sensitivity increase transitions away from it. These findings indicate changes in GPCR function caused by mutations may be predicted based on whether they favor or disfavor formation of an intermediate state, providing a framework for designing receptors with altered functions or therapies that target intermediate states.

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.

Role of Female Sex Hormones and Immune Response in Salt-Sensitive Hypertension Development: Evidence from Experimental Models.

Female sex hormones have systemic effects unrelated to their reproductive function. We describe experiences of different research groups and our own, on aspects related to the importance of female sex hormones on blood pressure (BP) regulation and salt-sensitivity-mediated BP response and salt sensitivity without alterations in BP, as well as renal sodium handling and interactions with the immune system. Changes in sodium intake in normotensive premenopausal women cause more BP variations than in men. After menopause, women often develop arterial hypertension (HT) with a profile of sodium sensitivity. Besides, experimental results have shown that in adult rat models resembling the postmenopausal hormonal state induced by ovariectomy, controlling BP is not enough to avoid renal and other tissue infiltration with immune cells, which does not occur when sodium intake is low or normal. Therefore, excess sodium promotes an inflammatory state with the involvement of immune cells. The evidence of activation of adaptive immunity, besides changes in T cell subpopulations, includes changes in sodium transporters and receptors. More studies are needed to evaluate the particular sodium sensitivity of women and its meaning. Changes in lifestyle and sodium intake reduction are the main therapeutic steps. However, to face the actual burden of salt-sensitive HT in postmenopausal women and its associated inflammatory/immune changes, it seems reasonable to work on immune cell activity by considering the peripheral blood mononuclear cell phenotypes of molecules and transport proteins related to sodium handle, both to screen for and treat cell activation.

The Integral Role of Chloride & With-No-Lysine Kinases in Cell Volume Regulation & Hypertension.

Chloride anions are the most abundant in humans. For many years, it has been believed that chloride is simply a counterion of all other cations, ensuring the electroneutrality of the extracellular space. Recent data suggests that chloride anions possess a broad spectrum of important activities that regulate vital cellular functions. It is now evident that, apart from its contribution to the electroneutrality of the extracellular space, it acts as an osmole and contributes to extracellular and intracellular volume regulation. Its anionic charge also contributes to the generation of cell membrane potential. The most interesting action of chloride anions is their ability to regulate the activity of with-no-lysine kinases, which in turn regulate the activity of sodium chloride and potassium chloride cotransporters and govern the reabsorption of salt and excretion of potassium by nephron epithelia. Chloride anions seem to play a crucial role in cell functions, such as cell volume regulation, sodium reabsorption in the distal nephron, potassium balance, and sodium sensitivity, which lead to hypertension. All of these functions are accomplished on a molecular level via complicated metabolic pathways, many of which remain poorly defined. We attempted to elucidate some of these pathways in light of recent advances in our knowledge, obtained mainly from experimental studies.

#5537 GENETIC VARIABILITY IN THE PROSTAGLANDIN E2 PATHWAY IS RELATED TO SALT SENTIVITY IN TREATMENT-NAïVE HYPERTENSIVE PATIENTS

Abstract Background and Aims Hypertensive nephropathy is a common aging-related disorder. One of the main factors that contributes to the development of hypertension is salt intake. Based on blood pressure (BP) variation after sodium intake in an acute salt load test, individuals can be grouped in: sodium sensitive (SS), sodium resistant (SR) or inverse sodium sensitivity (ISS). Prostaglandin E2 (PGE2) is the main renal metabolite of the cyclooxygenase pathway, a major actor mediating renal injury and it has also been related to renal blood flow and hemodynamic changes. Our aim was to determine common, functional variants in genes involved in the PGE2 pathway to identify associations with the sodium sensitivity phenotype of hypertensive patients, as well as with parameters of renal function and BP traits. Method We studied 511 treatment-naïve hypertensive patients, who were subjected to an acute salt load test and consequently stratified into 173 SR patients, 172 SS patients and 166 ISS, after they showed an increase in BP values (SS), no substantial variation (SR) or a paradoxical decrease (ISS). Renal function was established by estimated glomerular filtration rate (eGFR) using the MDRD-4 formula. All participants were screened for 216 tag-SNPs that define the variability of 12 genes of the PGE2 pathway, namely PLA2G4A, PLA2G7, SCARB1, PTGS1, PTGS2, PGTES, PTGES2, PTGES3, PTGER1, PTGER2, PTGER3 and PTGER4. Regression models were utilized to evaluate associations with clinical parameters. Results Using the SS group as a reference, eleven variants in genes coding for two phospholipases (PLA2G4A, PLA2G7), cyclooxygenase-1 (PGTS1) and PGE2 receptors (PTGER1 and PTGER4) were linked to the susceptibility of becoming SR or ISS patients. Seven of these variants produced protective odds ratios, whilst four of them were associated with increased risk (Table 1). Next, we analyzed BP traits in each cohort. In SR, PTGES3 rs12824563 was associated with variability in nighttime BP values (p&amp;lt;0.001, p&amp;lt;0.01, p&amp;lt;0.001 and p&amp;lt;0.05 for systolic BP, diastolic BP, mean BP and nighttime BP fall, respectively). For the SS group, two variants in PTGER3, rs61777123 and rs12410289, were also associated with the same parameters (p&amp;lt;0.01). Finally, in the ISS group, the most significant finding was that PTGES2 rs13283456 was strongly linked to daytime and nighttime measurements (p&amp;lt;0.001 for each parameter). Regarding renal function, we examined the 511 patients as a whole and observed that several variants affected eGFR. Most significantly, carriers of PTGER3 rs6424406 and rs1409986 were found to be associated with higher values [Mean difference vs. non carriers: 6.34 (2.42-10.26), p&amp;lt;0.01 and 6.20 (1.76-10.64) ml/min/1,73 m2, p&amp;lt;0.01]. Conclusion Variability in genes that participate in the PGE2 pathway, is associated with the response of treatment-naïve hypertensive patients to salt intake. In addition, these genetic variants may also modify BP traits and eGFR values in these patients.

#4391 SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Abstract Background and Aims Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Method A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up &amp;gt; 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (P = .002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusion Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting.

SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Objective: Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Design and method: A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up &gt; 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results: No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (p = 0.002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusions: Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting

Identification of sodium- and chloride-sensitive sites in the Slack channel.

The Slack channel (KCNT1, Slo2.2) is a sodium and chloride-activated potassium channel that regulates heart rate and maintains the normal excitability of the nervous system. Despite intense interest in the sodium gating mechanism, a comprehensive investigation to identify the sodium-sensitive and chloride-sensitive sites has been missing. In the present study, we identified two potential sodium-binding sites in the C-terminal domain of the rat Slack channel by conducting electrophysical recordings and systematic mutagenesis of cytosolic acidic residues in the rat Slack channel C-terminus. In particular, by taking advantage of the M335A mutant, which results in the opening of the Slack channel in the absence of cytosolic sodium, we found that among the screened ninety-two negatively charged amino acids, E373 mutants could completely remove sodium sensitivity of the Slack channel. In contrast, several other mutants showed dramatic decreases in sodium sensitivity but did not abolish it altogether. Furthermore, Molecular Dynamics (MD) simulations performed at the hundreds of nanoseconds time scale revealed one or two sodium ions at the E373 position or an acidic pocket composed of several negatively charged residues. Moreover, the MD simulations predicted possible chloride interaction sites. By screening predicted positively charged residues, we identified R379 as a chloride interaction site. Thus, we conclude that the E373 site and the D863/E865 pocket are two potential sodium-sensitive sites, while R379 is a chloride interaction site in the Slack channel.Significance Statement:The research presented here identified two distinct sodium and one chloride interaction sites located in the intracellular C-terminal domain of the Slack (Slo2.2, KCNT1) channel. Identification of the sites responsible for the sodium and chloride activation of the Slack channel sets its gating property apart from other potassium channels in the BK channel family. This finding sets the stage for this channel's future functional and pharmacological studies.

PS-BPB10-2: MOLECULAR INSIGHT INTO SALT-SENSITIVITY; THE ROLE OF ATF3 AND THE GENERATION OF TUBULAR SPECIFIC KO MICE. (1)

Objectives: Current research including ours suggested pivotal roles of expressions of and regulations of tubular ion transporters for developments of sodium sensitivity and hypertension. Orlov et al. demonstrated using rat cardiomyocytes three different genes which are activated according to the elevation of intra-cellular Na ion concentration. (2015) To elucidate detailed biological roles of these genes in tubules, we performed current experiments. Methods: We tested expressions of three genes for cDNA from kidneys of Nedd4 2 C2 KO mice using quantitative RT PCR methods. Subsequently, we performed crossbreeding experiments between floxed target gene mice (generous gift from Prof. Kitamura, Tokyo Medical and Dental University) and Ksp-cre mice (Jackson Laboratory), which cre-recombinase expresses specifically along urinary tubules to generate mice with cre+, flox/flox genotype. Results: We found expressions of Atf3 are significantly changed due to oral sodium intake and diuretics treatment in Nedd4–2 C2 KO mice. We successfully generated mice with cre+, Atf3 flox/flox mice for current experiments. Under normal salt diet, we could not find any significant differences between cre + and minus mice in terms of systolic blood pressure, water intake, urine volume, urinary sodium excretions, urinary pH, and urinary osmotic pressures using metabolic cage experiments. We found, under high salt intake, gene expressions of both classic renin and tubular alternative renin are significantly suppressed for 30 to 70% in KO mice by quantitative RT PCR and immunohistochemistry imaging. Conclusions: Tubular epithelial Atf3 genes are involved in regulations of renin gene expressions in accordance with intracellular Na ion concentrations. Therefore, there are possibilities that tubular specific Atf3 KO mice shows blood pressure change under various salt intake and diuretics treatment.

Inverse Salt Sensitivity of Blood Pressure Is Associated with an Increased Renin-Angiotensin System Activity.

High and low sodium diets are associated with increased blood pressure and cardiovascular morbidity and mortality. The paradoxical response of elevated BP in low salt diets, aka inverse salt sensitivity (ISS), is an understudied vulnerable 11% of the adult population with yet undiscovered etiology. A linear relationship between the number of single nucleotide polymorphisms (SNPs) in the dopamine D2 receptor (DRD2, rs6276 and 6277), and the sodium myo-inositol cotransporter 2 (SLC5A11, rs11074656), as well as decreased expression of these two genes in urine-derived renal proximal tubule cells (uRPTCs) isolated from clinical study participants suggest involvement of these cells in ISS. Insight into this newly discovered paradoxical response to sodium is found by incubating cells in low sodium (LS) conditions that unveil cell physiologic differences that are then reversed by mir-485-5p miRNA blocker transfection and bypassing the genetic defect by DRD2 re-expression. The renin-angiotensin system (RAS) is an important counter-regulatory mechanism to prevent hyponatremia under LS conditions. Oversensitive RAS under LS conditions could partially explain the increased mortality in ISS. Angiotensin-II (AngII, 10 nmol/L) increased sodium transport in uRPTCs to a greater extent in individuals with ISS than SR. Downstream signaling of AngII is verified by identifying lowered expression of nuclear factor erythroid 2-related factor 2 (NRF2), CCCTC-binding factor (CTCF), and manganese-dependent mitochondrial superoxide dismutase (SOD2) only in ISS-derived uRPTCs and not SR-derived uRPTCs when incubated in LS conditions. We conclude that DRD2 and SLC5A11 variants in ISS may cause an increased low sodium sensitivity to AngII and renal sodium reabsorption which can contribute to inverse salt-sensitive hypertension.

Abstract P247: Altered Renal Sodium Transporters Expression Is Associated With Cholinergic-mediated Salt Sensitive Hypertension In Young Spontaneously Hypertensive Rats

High sodium diet is a major contributing factor and has been associated with inflammation in patients suffering from hypertension. Systemic infusion of nicotine induces renal inflammation and the development of premature hypertension in young spontaneously hypertensive rats (SHR) and leads to enhanced expression of the renal Na-K-Cl cotransporter (NKCC2). Sodium sensitivity also plays a role in the development of cholinergic hypertension. We hypothesized that these findings were related to alterations in renal sodium transporters expression. We continuously infused SHR and Wistar Kyoto (WKY, normotensive control) rats with saline or nicotine (15mg/kg/day) and fed either a low-salt (LSD, 0.01% NaCl) or high-salt (HSD, 4% NaCl) diet for 2 weeks. Renal homogenates were assessed by western blot for the presence of the epithelial sodium channel (ENaC), NKCC2, Na-Cl co-transporter (NCC) and Serum and glucocorticoid regulated kinase 1 (SGK-1). Nicotine infusion in WKY induced 1.9-fold increase (p=0.003) in renal expression of SGK-1 under LSD, compared to saline-infused controls. The sharp increase in SGK-1 in nicotine-infused WKY on LSD was accompanied by a 1.9-fold increase in NCC (p=0.004), a 1.3-fold increase in the cleaved alpha ENaC, a 1.2-fold increase in the uncleaved alpha ENaC, and a 1.5-fold increase in the beta-ENaC (p=0.02). Both saline and nicotine infused WKY showed very little expression of renal NKCC2 in either LSD or HSD. There was no effect of either diet or nicotine infusion on expression of SGK-1, NCC, or ENaC subunits in SHR. Nicotine had no effect on NKCC2 expression in SHR on LSD, but HSD alone induced a 2.25-fold increase in renal NKCC2 expression compared to LSD in saline infused SHR (p=0.006). Nicotine infusion further induced a 58% increase in renal NKCC2 expression for SHR fed HSD (p=0.004). Here we show an effect of nicotine to appropriately increase the expression of NCC and ENaC in WKY under LSD and a trend towards decreased expression under HSD. In contrast, nicotine not only has no effect on NCC and ENaC under LSD in SHR but leads to a paradoxical increase in NKCC2 under HSD. We conclude that inappropriate regulation of renal sodium transporters likely plays a role in cholinergic-mediated renal inflammation and hypertension.

Abstract P068: Dietary Sodium Restriction Prevents Vascular Endothelial Growth Factor Inhibitor-Induced Hypertension

Vascular endothelial growth factor tyrosine kinase inhibitors (VEGFIs) are effective anti-cancer agents which often induce hypertension. VEGFI-induced hypertension was demonstrated to be sodium-sensitive in preclinical studies, but the sodium sensitivity in humans and its potential as a preventive antihypertensive strategy in the clinical situation remains unknown. Therefore, the efficacy of dietary sodium restriction (DSR) to prevent VEGFI-induced hypertension was studied in patients with cancer. To this end, patients with cancer who developed VEGFI-induced hypertension (defined as daytime systolic blood pressure (SBP) &gt; 135 mmHg and/or diastolic blood pressure (DBP) &gt; 85 mmHg or a rise in SBP/DBP of ≥ 20 mmHg) were treated with DSR under supervision of a specialized dietician (aiming at &lt; 4 g salt/day). The primary endpoint was the difference in daytime mean arterial blood pressure (MAP) increase between the VEGFI treatment cycle with and without concomitant DSR. Of the forty-nine screened patients, twenty (41%) patients were eligible for the DSR intervention based on their VEGFI-induced blood pressure rise, of whom sixteen successfully completed the intervention. During the first VEGFI treatment cycle without DSR, mean daytime MAP increased from 95 mmHg to 110 mmHg. During the subsequent treatment cycle with concomitant DSR, mean daytime MAP increased from 94 mmHg to 102 mmHg. Therefore, DSR attenuated the increase in mean daytime MAP by 7 mmHg (95% CI 1.3 to 12.0, P = 0.009). DSR prevented the rise in the endothelin-1/renin ratio that normally accompanies VEGFI-induced hypertension ( P = 0.020) and slightly prevented the onset of proteinuria: 0.15 (0.10-0.25) g/24h with DSR versus 0.19 (0.11-0.32) g/24h without DSR; P = 0.005. For two patients, proteinuria decreased from common terminology criteria of adverse events (CTCAE) grade and 3 during the treatment cycle without DSR to grade 1 and grade 2 during DSR, respectively. In conclusion, DSR significantly attenuated the VEGFI-induced BP rise, the increase in the endothelin-1/renin ratio and the onset of proteinuria. Therefore, DSR is an effective and attractive non-pharmacological intervention for patients with VEGFI-induced hypertension and its sequelae.

SALT-SENSITIVITY IN HEALTHY NORMOTENSIVE MEN IS ASSOCIATED WITH IMPAIRED BAROREFLEX SENSITIVITY

Objective: Blood pressure (BP) responses to Na+ intake show great variability, discriminating sodium sensitive (SS) from salt resistant (SR) individuals. The pathophysiology behind salt-sensitivity is still not fully elucidated. A pivotal role for the sympathetic nervous system to BP increase after sodium loading is suggested. Therefore, we aimed to investigate the effect of the sympathovagal balance on Na+-induced BP effects and if Na+-induced effects on sympathetic activation contribute to salt-sensitivity. Design and method: We performed a randomized cross-over study in 31 young healthy men with normal BMI and eGFR. Subjects followed both an 8-day low Na+ diet (LSD, &lt; 50mmol/d) and high Na+ diet (HSD, &gt; 200mmol/d), in 18 subjects the diets were extended to 14-days. SS was defined as an increase of three or more mmHg standardized measured office MAP after HSD. Cardiac-output (CO) and cross correlation baroreflex sensitivity (xBRS) were measured with continuous non-invasive finger photoplethysmography. Systemic vascular resistance (SVR) was calculated as the ratio of MAP by CO. Results: After HSD, SS men (19%) showed a mean 6.2 (±2.1 SD) mmHg increase in MAP. No absolute differences in Na+-induced effects on CO and SVR could be observed between groups. After HSD, xBRS was 34% lower in SS men compared to SR men (Fig1A). Sodium loading resulted in a mean xBRS decrease of 3.4 (±6.5 SD) ms/mmHg in SS men, whilst xBRS increased with 2.3 (±6.3 SD) ms/mmHg in SR men (p = 0.06). HSD xBRS values were significantly correlated with Na+-induced BP changes in the complete group when corrected for age and BMI (Fig1B). Conclusions: Salt-sensitivity of BP in young normotensive men seems to be predominantly driven by changes in sympathovagal balance. The significant correlation between xBRS and delta BP further suggests a continuous relation between sympathetovagal balance and salt exposure. Further studies are needed to unravel pathophysiological mechanisms underlying Na+-effects on sympathetic regulation.

Erythrocyte sodium buffering capacity status correlates with self-reported salt intake in a population from Livingstone, Zambia.

Salt impairs endothelial function and increases arterial stiffness independent of blood pressure. The mechanisms are unknown. Recent evidence suggests that there is a possible link between salt consumption and sodium buffering capacity and cardiovascular disease but there is limited evidence in the populations living in Sub-Saharan Africa. The aim of our study was to explore the relationship between erythrocyte sodium buffering capacity and sociodemographic, clinical factors, and self-reported salt consumption at Livingstone Central Hospital. We conducted a cross sectional study at Livingstone Central hospital among 242 volunteers accessing routine medical checkups. Sociodemographic and dietary characteristics were obtained along with clinical measurements to evaluate their health status. Sodium buffering capacity was estimated by erythrocyte sodium sensitivity (ESS) test. We used descriptive and inferential statistics to describe and examine associations between erythrocyte sodium sensitivity and independent variables. The median age (interquartile range) of the study sample was 27 (22, 42) years. 54% (n = 202) and 46% (n = 169) were males and females, respectively. The majority (n = 150, 62%) had an ESS of >120%. High salt intake correlated positively with ESS or negatively with vascular sodium buffering capacity. Self-reported high salt intake was associated with poor vascular sodium buffering capacity or high ESS in the majority of middle-aged Zambians living in Livingstone. The poor vascular sodium buffering capacity implies a damaged vascular glycocalyx which may potentially lead to a leakage of sodium into the interstitium. This alone is a risk factor for the future development of hypertension and cardiovascular disease. However, future studies need to validate vascular function status when using ESS testing by including established vascular function assessments to determine its pathophysiological and clinical implications.

Abstract 10418: Complex Action Potential Regulation in Cardiomyocytes from Induced Pluripotent Stem Cells (iPSC-CMs) Reveals a Novel Arrhythmia Susceptibility Mechanism

Background: While the cardiac sodium channel ( SCN5A ) variants S1103Y and R1193Q have been associated with LQT3 and drug-induced arrhythmia, they are too common to be highly arrhythmogenic: S1103Y allele frequency is 8.1% in Africans and R1193Q 6.1% in East Asians. We have previously reported that S1103Y had no effect on QT in a large biobank or on action potential duration (APD) in iPSC-CMs. Here, we identify a mechanism underlying control of normal baseline repolarization with these variants and study whether the mechanism is generalizable. Methods: Late sodium current (I Na-L ), I Kr , and sensitivity to the blockers dofetilide (I Kr ) and GS967 (I Na-L ) were measured in natural or genome-edited iPSC-CMs carrying S1103Y, R1193Q, or R518X, a common KCNQ1 nonsense variant in the Jervell Lange-Nielsen (JLN) syndrome and unaffected family members. Results: Although APD was unaffected by S1103Y, I Na-L was increased 2~16-fold in SY/YY compared to SS cells (p&lt;0.01) and GS967 shortened APDs only in SY/YY but not in SS cells (p&lt;0.001). Further, I Kr was increased in SY/YY ([SY] 1.2 pA/pF, n=17, p&lt;0.001, [YY] 1.2 pA/pF, n=11, p&lt;0.01) compared to SS cells (0.67 pA/pF, n=20) and challenge with dofetilide prolonged APD by 100 msec at much lower concentrations in SY/YY (median 4.1 nM [SY], 4.2 [YY], n=5-11) compared to SS cells (249 nM, n=14, p&lt;0.001); afterdepolarizations were seen more often in SY/YY (8/16) than in SS cells (1/14). R1193Q also displayed no difference in baseline APD but increased I Kr and I Na-L and increased dofetilide sensitivity. In R518X JLN iPSC-CMs, I Ks was absent as expected but I Kr was increased (1.9 pA/pF, n=5), and editing R518X to wild-type increased I Ks (1.3 pA/pF, n=10) and dramatically decreased I Kr (0.2 pA/pF, n=4). Conclusions: S1103Y and R1193Q increase I Na-L but unexpectedly do not affect baseline repolarization. We hypothesize that increased I Kr through as yet undetermined mechanisms maintains normal repolarization but at the cost of increased sensitivity to I Kr block. The findings with R518X suggest this may be a general mechanism. Our data show that preposition to genetically- or drug-mediated arrhythmias is determined by a complex interaction among multiple repolarizing currents that is not fully captured by heterologous expression systems.

Abstract P216: Cholinergic-mediated Salt-Sensitive Hypertension In A Genetic Model Of Essential Hypertension

Inflammation plays a key role in the pathogenesis of hypertension. High dietary sodium intake has been associated with inflammation in patients suffering from high blood pressure &amp; atherosclerosis. Our lab has shown that development of hypertension in a genetic model of human essential hypertension, the Spontaneously Hypertensive Rat (SHR), is dependent on nicotinic acetylcholine receptor (nAChR) mediated renal inflammation, which leads to enhanced expression of the renal sodium-potassium chloride cotransporter (NKCC2). Based on these findings we hypothesized that sodium sensitivity may play a role in the development of cholinergic hypertension. To investigate this hypothesis, we infused young pre-hypertensive SHR and Wistar Kyoto (WKY, normotensive control) rats with either saline or nicotine (15mg/kg/day) and placed them on either low-salt (LSD, 0.01% NaCl) or high-salt (HSD, 4% NaCl) diet for 2 wks. There was no change in systolic blood pressure (SBP) in saline or nicotine infused WKY with either LSD or HSD. Similarly, there was no difference between the SBP of saline infused SHR with either LSD or HSD. Interestingly, nicotine infusion did not change SBP in LSD fed SHR, but did result in ~20% increase in SBP in HSD fed SHR (122.0 ± 0.7 vs. 146.2 ± 0.2mmHg, p= 0.01). HSD alone induced a 2.25-fold increase in renal NKCC2 expression compared to LSD in saline infused SHR (p=0.006). In comparison to saline, nicotine infusion further induced a 58% increase in renal NKCC2 expression in SHR fed HSD (p=0.004). Renal NKCC2 expression did not change in WKY with either diet or nicotine infusion. Nicotine infused SHR on a HSD also manifested a 16% sodium retention compared to saline infused SHR (2.1 ± 0.1 mM/gBW vs. 2.5 ± 0.1 mM/gBW, p = 0.017). Nicotine infused SHR had 1.7 times more renal IL-6 than saline-infused SHR (1442. ± 212 vs 826 ± 103 pg/25mg total protein, p=0.04) and 9 times more renal IL-6 than nicotine-infused WKY controls (1442. ± 212 vs 148. ± 71 pg/25mg total protein, p=0.0041) under HSD conditions. Taken together with our previously published data, we conclude that NKCC2 likely plays a role in cholinergic-mediated renal inflammation and hypertension.