Salt Sensitivity Of Blood Pressure Research Articles

#2577 Sodium-mediated blood pressure rise is associated with a lower vasodilation response to nitroglycerin in healthy controls, but not in CKD

Abstract Background and Aims Chronic kidney disease (CKD) is characterized by endothelial dysfunction, that is partly caused by reduced bioavailability of NO. In addition to volume overload, endothelial dysfunction may contribute to hypertension in CKD. High sodium consumption affects NO levels, potentially leading to impaired vasorelaxation and a salt-sensitive blood pressure (BP) response. Whether salt-sensitivity in CKD is related to impaired NO bioavailability remains unknown. In this randomized-crossover-study, the vasoresponse to the NO donor nitroglycerin (NTG) during a high sodium diet in both CKD and healthy controls (HC) was assessed. Method CKD-patients (KDIGO stage G2-3A, proteinuria >0.5 g/d) and HC followed a 7-day low sodium control diet (<50 mmol/d) and high sodium diet (>200 mmol/d) in random order. After each diet, the hemodynamic profile was assessed by daytime BP and cardiac output (CO) measurements, by which systemic vascular resistance (SVR) was calculated. Nitroglycerin was administered to assess SVR changes. Results We included 15 CKD-patients (mean age, 49 yrs; median (IQR) proteinuria 0.7 (0.6-1.4) g/d; and plasma creatinine 129 (105-160) µmol/l) and 16 HC (41 yrs). Dietary salt intervention was comparable in the CKD and HC groups. After HSD, mean (SD) systolic BP increased in CKD by 9.7 mmHg (9.8; p < 0.01) as compared to 3.1 mmHg ((6.0), p = 0.07)) in HC (between-group difference p = 0.04). After HSD, changes in body weight and CO did not differ between groups. Median (IQR) SVR change after HSD was 163.0 (−34.9-275.7) in CKD and −13.8 ((−299.4–61.4),p = 0.03) dyn⋅sec⋅cm-5 in HC. In HC, salt-mediated blood pressure change was positively associated with a NTG-induced SVR change during HSD (r = 0.70, p = 0.01). This association was not present in CKD (r = −0.24, p = 0.34) and significantly different from that in HC (p < 0.01). Conclusion CKD-patients have a higher sodium-mediated BP response with comparable change of fluid status but a different SVR change as compared to HC. In HC, impaired sensitivity to the NO donor nitro-glycerin associates with higher BP response to sodium. No such association was found in CKD-patients, suggesting that persistent endothelial dysfunction is pivotal for salt sensitivity in CKD.

Salt Sensitivity of Blood Pressure.

The year 2024 marks the centennial of the initiation of the American Heart Association. Over the past 100 years, the American Heart Association has led groundbreaking discoveries in cardiovascular disease including salt sensitivity of blood pressure, which has been studied since the mid-1900s. Salt sensitivity of blood pressure is an important risk factor for cardiovascular events, but the phenotype remains unclear because of insufficient understanding of the underlying mechanisms and lack of feasible diagnostic tools. In honor of this centennial, we commemorate the initial discovery of salt sensitivity of blood pressure and chronicle the subsequent scientific discoveries and efforts to mitigate salt-induced cardiovascular disease with American Heart Association leading the way. We also highlight determinants of the pathophysiology of salt sensitivity of blood pressure in humans and recent developments in diagnostic methods and future prospects.

Metabolomics signature of blood pressure salt sensitivity and its link to cardiovascular disease: A dietary salt-intervention trial.

Individuals with a high degree of salt sensitivity (SS) have a greater risk of cardiovascular disease (CVD), but whether SS fosters CVD by influencing metabolomics homeostasis remains unclear. This study aimed to reveal the role of the SS-related metabolomics signature in the development of CVDs, based on the MetaSalt study, which was a dietary salt-intervention trial conducted at four centers in China in 2019. A total of 528 participants were recruited and underwent 3 days of baseline observations, a 10-day low-salt intervention, and a 10-day high-salt intervention. Plasma untargeted metabolomics, lipidomics, and BP measurements were scheduled at each stage. Participants were grouped into extreme SS, moderate SS, and salt-resistant (SR) individuals according to their BP responses to salt. Linear mixed models were used to identify SS-related metabolites and determine the relationship between the SS-related metabolomics signature and arterial stiffness. Mendelian randomization (MR) analyses were applied to establish the causal pathways among the SS-related metabolites, BP, and CVDs. Among the 713 metabolites, 467 were significantly changed after the high-salt intervention. Among them, the changes in 30 metabolites from the low-salt to the high-salt intervention differed among the SS groups. Of the remaining nonsalt-related metabolites, the baseline levels of 11 metabolites were related to SS. These 41 metabolites explained 23% of the variance in SS. Moreover, SS and its metabolomics signature were positively correlated with arterial stiffness. MR analyses demonstrated that the SS-related metabolites may affect CVD risk by altering BP, indicating that the increase in BP was the consequence of the changes in SS-related metabolites rather than the cause. Our study revealed that the metabolomics signature of SS individuals differs from that of SR individuals and that the changes in SS-related metabolites may increase arterial stiffness and foster CVDs. This study provides insight into understanding the biology and targets of SS and its role in CVDs.

Antigen Presenting Cell activator protein 1 (AP-1) complex contributes to Salt-sensitive Blood Pressure

Salt-sensitivity of blood pressure (SSBP) affects 50% of the hypertensive and 25% of the normotensive population and is a major independent risk factor for cardiovascular morbidity and mortality. We previously found that SSBP is associated with activation of the NLRP3 inflammasome in antigen presenting cells (APCs) via increased oxidated stress and isolevuglandin (IsoLG) formation, but the underlying mechanisms are unknown. The activator protein 1 (AP-1) (FOS/JUN) has been implicated in activation of the NLRP3 inflammasome but its role in SSBP is not known. We hypothesized that AP-1 transcription factor in APCs senses elevated sodium and contributes to SSBP. We further hypothesize that antioxidant flavonoid, diosmetin prevents AP-1 activation and SSBP. Using bulk RNA-sequencing in human monocytes, we found elevated sodium increases expression of the AP-1 gene family when compared to normal sodium concentration, including cFOS (2378.18 ± 480.7 vs 6494.09 ± 945.55, p= 0.0009), FOSB (53.63 ± 17. 55 vs 131.06 ± 10.30, p= 0.397), cJUN (7313.90 ± 984.93 vs 11370.09 ± 1286.35, p= 0.2563) JUNB (4218.4.36 ± 199.17 vs 570.45 ± 200.91, p= 0.0445) and JUND (3309. 63 ± 270.64 vs 8057.90 ± 1043.05, p= 0.00006). In additional experiments, we enrolled people with hypertension and phenotype them for SSBP using an established in-patient protocol of salt-loading/depletion and performed single-cell transcriptomic analyses in vivo on peripheral blood mononuclear cells (PBMCs). We found that expression of the FOSB and JUNB genes are more sensitive in concert with blood pressure in salt-sensitive (SS) but not salt-resistant (SR) humans. Moreover, diosmetin attenuated high salt-induced hypertension, 123.5 ± 4.1 vs 146.8 ± 2.5 mm Hg in controls, **p< 0.01). In addition, diosmetin also reduced high salt-induced inflammation including APC production of IsoLG-protein adducts, IL-1β, and NLRP3 inflammasome expression. These findings reveal a role for immune cell AP-1 (FOS/JUN) signaling in salt-sensitive hypertension and diosmetin may provide a potential therapeutic target for treatment of SSBP. 1R01HL144941-01A1. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Myeloid Specific Hypoxia Inducible Factor 1 Alpha contributes to Immune Metabolic Reprogramming in Human Salt Sensitive Hypertension

Salt-sensitivity of blood pressure (SSBP), acute changes in blood pressure that mirror dietary salt intake, is a major risk factor for cardiovascular disease independent of hypertension. We previously found that oxidative lipid protein modification via NADPH oxidase (NOX2) reactive oxygen species (ROS) production in antigen presenting cells (APCs) contributes to SSBP. Hypoxia Inducible Factor 1 Subunit Alpha (HIF1α) plays a role in metabolic reprogramming and maturation of dendritic cells but its role in the pathogenesis of SSBP is not known. I hypothesize that HIF1α expression specifically in APCs contributes to SSBP by promoting a switch to anaerobic energy production through glycolytic enzyme induction. To test this hypothesis, we performed both bulk and single cell transcriptomic analysis in circulating immune cells following both in vitro and in vivo salt-loading/depletion protocols to phenotype people for SSBP. We found that compared to normal (150 mMol/L), isolated monocytes from women (N =11) treated with high sodium (190 mMol/L) in vitro for 72 hours exhibited a marked increase in expression of HIF1α (16149 ± 6246.1 vs. 42233 ± 20836, p = 2.28E-05). This was associated with increased downstream expression of glycolytic enzymes LdhA (29600 ± 12391 vs. 55998 ± 17118, p = 0.013928), which catalyzes the conversion of pyruvate to lactate under anaerobic conditions, and PDK1 (1422.2 ± 880.80 vs. 2651.3 ± 1216.2, p = 0.0091) which attenuates the conversion of pyruvate to acetyl-CoA through inhibition of pyruvate dehydrogenase, stopping its entry to the citric acid cycle. Moreover monocyte-specific expression of PDK1 correlated with a decrease in systolic blood pressure from salt-loading to salt-depletion (r = 0.6753, p = 0.06608). Our data indicate that HIF1α may play a role the pathogenesis of SSBP by contributing to immune metabolic reprogramming. 1R03HL155041-01 (Kirabo, PI)1R01HL144941-01A1 (Kirabo, PI). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

High Salt Diet Induces Aldosterone Synthase Elevation in Adrenal and Visceral Adipose Tissue - A Potential Culprit for Unsuppressed Aldosterone Levels in Female BALB/c Mice

Women are more salt-sensitive than men, irrespective of age, menopausal status, or ethnic background. Nonetheless, the mechanisms predisposing women to salt sensitivity of blood pressure (SSBP) are poorly understood, notably due to the diffculty in finding appropriate animal models. Previously, we demonstrated that female BALB/c mice spontaneously develop SSBP, likely through an inability to reduce the expression of adrenal aldosterone synthase (CYP11B2) appropriately, which leads to unsuppressed aldosterone levels in response to high salt intake. Herein, we aim to decipher the mechanism involved in SSBP in female BALB/c mice by comparing them to female salt-resistant C57BL/6 mice. Eleven-week-old female BALB/c and C57BL/6J mice were fed either a normal (0.4%, NSD) or a high salt diet (4%, HSD) for seven days. HSD significantly reduced adrenal aldosterone synthase transcript and protein expression in female C57BL/6 mice compared to those on a NSD. Conversely, HSD substantially increased CYP11B2 levels in BALB/c female mice when compared to strain-matched NSD and C57BL/6 NSD mice (2-way ANOVA, p<0.05). HSD induced a more significant aldosterone drop in C57BL/6 versus BALB/c mice (C57BL/6: 72% vs. BALB/c: 49%). Remarkably, HSD led to an increase in CYP11B2 in the visceral adipose tissue (VAT) of BALB/c mice in comparison to strain-matched NSD mice, while no such alteration was observed between C57BL/6 NSD and HSD. We previously showed that leptin regulates CYP11B2 expression. We report here that HSD increased leptin receptor (lepR) expression in adrenal and VAT from BALB/c mice in comparison to both strain-matched NSD and C57BL/6 NSD. Baseline levels of leptin were similar in C57BL/6 and BALB/c mice. However, BALB/c mice on HSD displayed increased levels of leptin compared to its strain-matched NSD mice, while no such alteration was observed in C57BL/6 mice. Furthermore, female BALB/c mice on HSD displayed elevated endothelial cell-specific mineralocorticoid receptor (ECMR) expression compared to female C57BL/6 NSD and HSD mice (2-way ANOVA, p<0.05). Endothelium-dependent relaxation to acetylcholine was significantly reduced in the female BALB/c mice on HSD compared to strain-matched NSD and C57BL/6 NSD (n = 3, 2-way ANOVA, P < 0.05). Interestingly, on NSD, C57BL/6 mice present a better endothelial function than BALB/c, which was not altered by HSD. Collectively, our data supports an overactivation of the leptin-CYP11B2-aldosterone axis in both adrenals and VAT, leading to inappropriate aldosterone levels, which, associated with higher ECMR expression, induce endothelial dysfunction in BALB/c mice. Together, these mechanisms are likely the cause of SSBP in female BALB/c mice. Funding: R01HL130301, R01HL155265 (E.J.B.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Immune Metabolic Reprogramming by Excess Dietary Salt in Salt Sensitive Hypertension via CXCL8

Salt sensitivity of blood pressure (SSBP) is when blood pressure changes parallel to salt loading/ depletion and is an independent risk factor for cardiovascular disease. Despite its importance, there is no feasible diagnosis, which limits investigational studies to identify therapeutic targets. We have found that immune cells mediate SSBP via Epithelial Sodium Channel (ENaC). CXCL8/(IL-8), a known chemoattractant plays a well-known role in glycolysis. We hypothesize that CXCL8 mediates immune metabolic reprogramming of immune cells to glycolysis via ENaC. To test this hypothesis, we performed bulk and single cell RNA sequencing in human monocytes from individuals from a modified Weinberger inpatient salt loading/ depletion protocol. The participants were instructed to refrain from taking their blood pressure medication for 2 weeks prior to the salt loading/depletion protocol. Blood and urine samples were collected, as well as ambulatory blood pressure recording. We found that changes in immune cell activation via isolevuglandin (IsoLG) protein-adducts mirror changes in salt balance and blood pressure in salt sensitive but not salt resistant individuals. We confirmed that these in vivo changes can be recapitulated in vitro. In addition, we found that salt-loading both in vivo and in vitro increases antigen presenting cell production of IL-8, which was reversed after salt depletion in salt sensitive, but not salt resistant people. ENaC inhibition by amiloride prevented the high salt-induced production of IL-8. Moreover, high salt induced blood pressure changes of expression of CXCL8 (p = 0.01553, r = 0.8067) were significant along with varying expression of glycolytic genes, including hexokinase 1(HK1)(p = 0.04190, r = -0.7249), phosphofructokinase (PFKP)(p = 0.05932, r = 0.6879) and galactose mutarotase (GALM) (p = 0.04176, r = 0.5138). Seahorse analysis revealed increased extracellular acidification rate (ECAR) in high salt conditioned monocytes, which was associated with mitochondrial dysfunction. Our results suggest that high salt intake reprograms antigen presenting cell metabolism to glycolysis via IL-8 signaling. Furthermore, targeting IL-8 and mitochondrial switching to glycolysis may not only provide novel therapeutic approaches, but also important biomarkers for diagnosis of salt sensitivity of blood pressure. 1R03HL155041-01 (Kirabo, PI), 1R01HL144941-01A1 (Kirabo, PI), 5R01HL147818-22 (Kleyman & Kirabo), 1R01HL157584-01 (Shibao, Kirabo — MPI), R01DK135764 (Kon, Shelton, Kirabo — MPI), R21TW012635 (Kirabo, Masenga — MPI), Meharry Medical College: School of Graduate Studies T32AI007281, T32GM14492, andT32HL00773. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endoplasmic Reticulum Stress in Hypertension and Salt Sensitivity of Blood Pressure.

Hypertension is a principal risk factor for cardiovascular morbidity and mortality, with its severity exacerbated by high sodium intake, particularly in individuals with salt-sensitive blood pressure. However, the mechanisms underlying hypertension and salt sensitivity are only partly understood. Herein, we review potential interactions in hypertension pathophysiology involving the immune system, endoplasmic reticulum (ER) stress, the unfolded protein response (UPR), and proteostasis pathways; identify knowledge gaps; and discuss future directions. Recent advancements by our research group and others reveal interactions within and between adaptive and innate immune responses in hypertension pathophysiology. The salt-immune-hypertension axis is further supported by the discovery of the role of dendritic cells in hypertension, marked by isolevuglandin (IsoLG) formation. Alongside these broadened understandings of immune-mediated salt sensitivity, the contributions of T cells to hypertension have been recently challenged by groups whose findings did not support increased resistance of Rag-1-deficient mice to Ang II infusion. Hypertension has also been linked to ER stress and the UPR. Notably, a holistic approach is needed because the UPR engages in crosstalk with autophagy, the ubiquitin proteasome, and other proteostasis pathways, that may all involve hypertension. There is a critical need for studies to establish cause and effect relationships between ER stress and the UPR in hypertension pathophysiology in humans and to determine whether the immune system and ER stress function mainly to exacerbate or initiate hypertension and target organ injury. This review of recent studies proposes new avenues for future research for targeted therapeutic interventions.

Salt-Sensitive Hypertension and the Kidney.

Salt-sensitive hypertension (SS-HT) is characterized by blood pressure elevation in response to high dietary salt intake and is considered to increase the risk of cardiovascular and renal morbidity. Although the mechanisms responsible for SS-HT are complex, the kidneys are known to play a central role in the development of SS-HT and the salt sensitivity of blood pressure (SSBP). Moreover, several factors influence renal function and SSBP, including the renin-angiotensin-aldosterone system, sympathetic nervous system, obesity, and aging. A phenotypic characteristic of SSBP is aberrant activation of the renin-angiotensin system and sympathetic nervous system in response to excessive salt intake. SSBP is also accompanied by a blunted increase in renal blood flow after salt loading, resulting in sodium retention and SS-HT. Obesity is associated with inappropriate activation of the aldosterone mineralocorticoid receptor pathway and renal sympathetic nervous system in response to excessive salt, and mineralocorticoid receptor antagonists and renal denervation attenuate sodium retention and inhibit salt-induced blood pressure elevation in obese dogs and humans. SSBP increases with age, which has been attributed to impaired renal sodium handling and a decline in renal function, even in the absence of kidney disease. Aging-associated changes in renal hemodynamics are accompanied by significant alterations in renal hormone levels and renal sodium handling, resulting in SS-HT. In this review, we focus mainly on the contribution of renal function to the development of SS-HT.

Role of Raptor Gene Variants in Hypertension: Influence on Blood Pressure Independent of Salt Intake in White Population.

The mTOR (mechanistic target of rapamycin) is an essential regulator of fundamental biological processes. mTOR forms 2 distinct complexes, mTORC1 (mTOR complex 1) when it binds with RAPTOR (Regulatory-associated Protein of mTOR) and mTORC2 (mTOR complex 2) when it associates with RICTOR (Rapamycin-insesitive companion of mTOR). Due to the previous link between the mTOR pathway, aldosterone, and blood pressure (BP), we anticipated that variants in the mTOR complex might be associated with salt-sensitive BP. BP and other parameters were assessed after a one-week liberal Na+ (200 mmol/d) and a one-week restricted Na+ (10 mmol/d) diet in 608 White subjects from the Hypertensive Pathotype cohort, single-nucleotide variants in MTOR, RPTOR, and RICTOR genes were obtained for candidate genes analyses. The analysis revealed a significant association between a single nucleotide variants within the RPTOR gene and BP. Individuals carrying the RPTOR rs9901846 homozygous risk allele (AA) and heterozygous risk allele (GA) exhibited a 5 mm Hg increase in systolic BP on a liberal diet compared with nonrisk allele individuals (GG), but only in women. This single nucleotide variants effect was more pronounced on the restricted diet and present in both sexes, with AA carriers having a 9 mm Hg increase and GA carriers having a 5 mm Hg increase in systolic BP compared with GG. Interestingly, there were no significant associations between MTOR or RICTOR gene variants and BP. The RPTOR gene variation is associated with elevated BP in White participants, regardless of salt intake, specifically in females.

Erythrocyte glycocalyx sensitivity to sodium is associated with salt sensitivity of blood pressure in women but not men.

While salt sensitivity of blood pressure (SSBP) is a risk factor for hypertension, end-organ damage and death, most studies are conducted in western countries and in White people. We previously found that the prevalence of SSBP in Blacks living in Sub-Saharan Africa is as high as 75-80% like what has been reported in the west. Erythrocyte glycocalyx sensitivity to sodium (eGCSS), a marker of sodium-induced damage to the erythrocyte and vascular endothelial glycocalyx is thought to be related to blood pressure perturbations associated with salt intake. We hypothesized that SSBP correlates with eGCSS differently in men and women in Black people. We conducted a cross sectional study using data from our recent clinical trial from Livingstone University Teaching Hospital among 117 normotensive young adults. We used a "salt blood test" to determine eGCSS and an immediate pressor response to oral salt (IPROS) for the diagnosis of SSBP. The proportion of males were equal to females and the median age (interquartile range) of the participants was 29 (22-45) years. The eGCSS scores were higher in salt-resistant females compared to salt-sensitive females and males. eGCSS correlated negatively with SSBP (AOR 0.98, 95% CI 0.97-0.99, p = 0.008), however, this relationship was driven by female sex and abrogated by male sex. Although blood pressure elevations exhibited a sustained bimodal pattern in both sexes, in males, systolic and diastolic blood pressure never returned to baseline during the time course as it did in females. In this study, eGCSS correlated negatively with SSBP in black women but not in black men and the pressor response to dietary salt was significantly higher in men compared to women. These results suggest that women tend to have a higher disruption of the vascular endothelial glycocalyx by an acute salt load, implying that acute changes in blood pressure may not be driven directly by the endothelial glycocalyx. Our findings suggest a novel mechanism linking eGCSS and SSBP with potential implications for sex differences in salt-induced cardiovascular disease.Clinical trial registration: https://clinicaltrials.gov/, identifier [NCT04844255].

Recent Advances in Understanding Peripheral and Gut Immune Cell-Mediated Salt-Sensitive Hypertension and Nephropathy.

Hypertension is the primary modifiable risk factor for cardiovascular, renal, and cerebrovascular diseases and is considered the main contributing factor to morbidity and mortality worldwide. Approximately 50% of hypertensive and 25% of normotensive people exhibit salt sensitivity of blood pressure, which is an independent risk factor for cardiovascular disease. Human and animal studies demonstrate that the immune system plays an important role in the etiology and pathogenesis of salt sensitivity of blood pressure, kidney damage, and vascular diseases. Antigen-presenting and adaptive immune cells are implicated in salt-sensitive hypertension and salt-induced renal and vascular injury. Elevated sodium activates antigen-presenting cells to release proinflammatory cytokines including IL (interleukin) 6, tumor necrosis factor-α, IL-1β, and accumulate isolevuglandin-protein adducts. In turn, these activate T cells release prohypertensive cytokines including IL-17A. Moreover, high-salt intake is associated with gut dysbiosis, leading to inflammation, oxidative stress, and blood pressure elevation but the mechanistic contribution to salt-sensitivity of blood pressure is not clearly understood. Here, we discuss recent advances in research investigating the cause, potential biomarkers, and therapeutic targets for salt-sensitive hypertension as they pertain to the gut microbiome, immunity, and inflammation.

Striatin Gene Variants Are Associated With Salt Sensitivity of Blood Pressure by Mechanisms That Differ in Women and Men.

Salt sensitivity of blood pressure (SSBP) is a substantial risk factor for cardiovascular morbidity and mortality. Striatin (STRN) is critical for estrogen and aldosterone nongenomic signaling. However, the role of biological sex on the SSBP phenotype associated with STRN gene variants remains unexplored. Data from 1306 subjects participating in the Hypertensive Pathotype (HyperPATH) Consortium were used to identify STRN gene single-nucleotide variants associated with SSBP. Haploblock analysis revealed a novel diplotype in the upstream regulatory region of STRN (rs888083 and rs6744560), with 31% of subjects being homozygous for the risk diplotype. Individuals homozygous for the risk diplotype had significantly greater SSBP than nonrisk diplotypes (P<0.009). While a significant genotype/SSBP association was present in both sexes, their potential mechanisms differed. Women, but not men homozygous risk diplotypes, had significantly greater aldosterone levels than nonrisk diplotypes (5.8±0.4 versus 3.2±0.7 ng/dl; P=0.01; liberal Na+ diet, adjusted). Men, but not women, homozygous risk diplotypes, had significantly reduced renal plasma flow response to Angiotensin II than nonrisk diplotypes (delta 95.2±5.2 versus 122.9±10.2 mL/min per 1.73 m2; P=0.01; liberal Na+ diet, adjusted). The single-nucleotide variants composing the risk diplotype were associated with lower STRN mRNA expression in human tissues (in silico). In women, the primary driver of SSBP is increased aldosterone, while in men, it is reduced renal plasma flow responses. Thus, despite a common hypertensive phenotype (SSBP) in both sexes, the specific treatment approaches might differ to increase therapeutic gain and mitigate adverse effects. These genetic- and sex-based observational results require confirmation in a prospective clinical study.

Associations of genetic variations in the M3 receptor with salt sensitivity, longitudinal changes in blood pressure and the incidence of hypertension in Chinese adults.

Recent studies have reported the role of the M3 muscarinic acetylcholine receptor (M3R), a member of the G-protein coupled receptor superfamily, encoded by the CHRM3 gene, in cardiac function and the regulation of blood pressure (BP). The aim of this study was to investigate the associations of CHRM3 genetic variants with salt sensitivity, longitudinal BP changes, and the development of hypertension in a Chinese population. We conducted a chronic dietary salt intervention experiment in a previously established Chinese cohort to analyze salt sensitivity of BP. Additionally, a 14-year follow-up was conducted on all participants in the cohort to evaluate the associations of CHRM3 polymorphisms with longitudinal BP changes, as well as the incidence of hypertension. The single nucleotide polymorphism (SNP) rs10802811 within the CHRM3 gene displayed significant associations with low salt-induced changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), while rs373288072, rs114677844, and rs663148 exhibited significant associations with SBP and MAP responses to a high-salt diet. Furthermore, the SNP rs58359377 was associated with changes in SBP and pulse pressure (PP) over the course of 14 years. Additionally, the 14-year follow-up revealed a significant association between the rs619288 polymorphism and an increased risk of hypertension (OR=1.74, 95% CI: 1.06-2.87, p=.029). This study provides evidence that CHRM3 may have a role in salt sensitivity, BP progression, and the development of hypertension.

Integrated analysis of the lncRNA-associated competing endogenous RNA network in salt sensitivity of blood pressure

Accumulating evidence showed that competing endogenous RNA (ceRNA) mechanism plays a pivotal role in salt sensitivity of blood pressure (SSBP). We constructed a ceRNA network based on SSBP-related differently expressed lncRNAs (2), mRNAs (73) and miRNAs (18). Bioinformatic analyses were utilized to analyze network and found network genes participate in biological pathways related to SSBP pathogenesis such as regulation of nitric oxide biosynthetic process (GO:0045,428) and cellular response to cytokine stimulus (GO:0071,345). Fourteen candidate ceRNA pathways were selected from network to perform qRT-PCR validation and found nine RNAs (KCNQ1OT1, SLC8A1-AS1, IL1B, BCL2L11, KCNJ15, CX3CR1, KLF2, hsa-miR-362–5p and hsa-miR-423–5p) differently expressed between salt-sensitive (SS) and salt-resistant (SR) groups (P < 0.05). Four ceRNA pathways were further validated by luciferase reporter assay and found KCNQ1OT1→hsa-miR-362–5p/hsa-miR-423–5p→IL1B pathways may influence the pathogenic mechanism of SS. Our findings suggested the ceRNA pathway and network may affect SS occurrence mainly through endothelial dysfunction and inflammatory activation.

Abstract 19164: The Role of Klf6 in Hypertensive Inflammation

Salt-sensitivity of blood pressure (SSBP) is a major risk factor for cardiovascular morbidity and mortality in people with or without hypertension. We previously found that oxidative lipid protein modification via NADPH oxidase in antigen presenting cells (APCs) contributes to SSBP but the underlying mechanisms are not known. HIF1α, which codes glycolytic enzymes in APCs enhances expression of Kruppel like factor 6 (KLF6), promoting expression of PDGFB which binds to the PDGFB receptor to activate NADPH oxidase, leading to increased oxidative stress and activation of mTOR. We hypothesize that HIF2α contributes to SSBP through activating NADPH oxidase by enhancing KLF6. To test this hypothesis, we isolated monocytes from human participants (N =11) and treated them with either high (190 mMol/L) or normal (150 mMol/L) Na+ in vitro for 72 hours and subsequently performed bulk RNA sequencing. We found that elevated sodium increases expression of HIFα (16437 ± 1810 vs. 42233 ± 6282, p = 2.28E-05) and KLF6 (9058 ± 584.3 vs. 12817 ± 1108, p = 0.6768). Interestingly, while the PDGFB receptor was upregulated by elevated sodium ( 21.18 ± 4.600 vs. 566.3 ± 205.3, p = 3.91E-13), the ligand PDGFB was downregulated (1249 ± 215.9 vs. 610.5 ± 118.2, p = 6.11E-04). In additional experiments, we performed single cell transcriptomic analysis in on immune cells of people phenotyped for SSBP. We found that in monocytes, as salt goes up with blood pressure so does the expression of KLF6 (r = 0.3773, p = 0.3561), PDGFB (r = 0.5604, p = 0.1485), and PDGFB receptor (r = 0.4436, p = 0.2709). Our data demonstrate the HIF1α-KLF6 pathway contributes to inflammation and SSBP.

Abstract 19150: DUSP1 is Associated With Map-Kinase Signaling in Antigen Presenting Cells Contributing to Salt-Sensitivity of Blood Pressure

Salt sensitivity of blood pressure, a pathological response characterized by a marked increase in blood pressure following salt intake, acts independently of hypertension as a risk factor for cardiovascular morbidities. Our recent research has elucidated a mechanism of sodium entry into antigen presenting cells through epithelial sodium channels (ENaC), which leads to the formation of neoantigen presenting isolevuglandin protein adducts via oxidative stress. Reactive oxygen species present in the cell may impact inflammation response as well as other intracellular pathways, chiefly the MAPK pathway. Previous studies have established an inhibitory connection between the protein-coding phosphatase DUSP1 and MAPKs. We hypothesize that DUSP1 acts as a negative regulator of MAPK signaling pathways involved in the immune response to salt-sensitive hypertension. To test our hypothesis, we isolated human monocytes from healthy participants (N=11) and treated them with either normal (150 mMol/L) or high (190 mMol/L) Na+ for 72 hours in vitro. Analysis of bulk RNA sequence data points to a significant upregulation of DUSP1 in the high salt environments compared to normal salt levels (4339 ± 770.1 vs 2721 ± 546.4 , p=0.0192). We also found that the high salt treatment led to increased expression of ERK1 (HS:2066 ± 184.0 NS:1560 ± 136.7 p= 0.0652), ERK2 (HS:8364 ± 669.8 NS:6256 ± 578.3 p= 0.0281), JNK (HS:1069 + 102.2 NS:792.3 ± 74.85 p= 0.0336), and p38 (HS: 4062 ± 329.0 NS:3010 ± 292.5, p= 0.0336). To study further, we enrolled 9 hypertensive participants who discontinued anti-hypertensive therapy for 2 weeks in an inpatient protocol to phenotype them through rapid salt loading and depletion. Blood pressure was recorded and blood collected at baseline, after salt loading, and after salt depletion and CITE-Seq analysis was performed on isolated PBMCs. After salt loading, we found a negative correlation between both p38 expression and pulse pressure (r= -0.7564 p= 0.0299) and p38 expression and systolic blood pressure (r= -0.8371, p=0.0095). We found a positive correlation between DUSP1 expression and systolic blood pressure after salt depletion (r= 0.7089, p=0.0490). These results suggest that DUSP1 plays an important role in salt sensitivity of blood pressure.

Abstract 19133: Sodium Induced-RGMa Plays a Role in Salt-Sensitive Hypertension

Salt sensitivity of blood pressure, characterized by blood pressure fluctuations that mirror dietary sodium (Na + ) intake, is an independent risk factor for cardiovascular morbidity and mortality in people with and without hypertension. We previously found that elevated Na + uptake via the amiloride-sensitive epithelial sodium channel (ENaC) in antigen-presenting cells leads to the upregulation of isoleuvoglandins and proinflammatory cytokines ultimately leading to T cell activation and salt-sensitive hypertension. In addition, we also showed that SMAD3 activation plays a role in inflammation and salt-sensitive hypertension. In previous studies, RGMa has been shown to be upstream of SMAD3. Furthermore, previous studies have also shown that knockdown of RGMa leads to reduced levels of TGFβ1-induced SMAD3 phosphorylation. The exact mechanism by which elevated extracellular Na + leads to increased blood pressure remains unknown. We hypothesized that RGMa complexes with TGFβ1R1 to promote SMAD3 phosphorylation ultimately contributing to inflammation in salt-sensitive hypertension. To test our hypothesis, we isolated monocytes from human participants (N =11) and treated them with either high (190 mMol/L) or normal (150 mMol/L) Na + in vitro for 72 hours and subsequently performed bulk RNA sequencing. We found that TGFβ1R1 (8837 ± 780.9 vs. 9688 ± 942.5, p =0.350) and TGFβ1R2 (7012 ± 717.0 vs. 7176 ± 633.9, p = 0.059) were being similarly expressed between high or normal salt treatment. Interestingly, RGMa (2253 ± 441.0 vs. 516 ± 84.1, p &lt;0.001) and TGFβ1 (5118 ± 353.9 vs. 9067 ± 826.4, p = 0.073) were significantly upregulated in human monocytes after high Na + treatment compared to normal salt. To further investigate, we performed an in vivo high Na + treatment by utilizing a rigorous salt-loading/depletion protocol on human participants (N = 9) and conducted single-cell transcriptomic analyses. We found a positive correlation between the changes in pulse pressure and RGMa (r = 0.5154, p = 0.1911). Our data suggest that RGMa mediates Na + -induced inflammation and salt-sensitive hypertension which may reveal a novel therapeutic target.

Salty Subjects: Unpacking Racial Differences in Salt-Sensitive Hypertension.

To review underlying mechanisms and environmental factors that may influence racial disparities in the development of salt-sensitive blood pressure. Our group and others have observed racial differences in diet and hydration, which may influence salt sensitivity. Dietary salt elicits negative alterations to the gut microbiota and immune system, which may increase hypertension risk, but little is known regarding potential racial differences in these physiological responses. Antioxidant supplementation and exercise offset vascular dysfunction following dietary salt, including in Black adults. Furthermore, recent work proposes the role of racial differences in exposure to social determinants of health, and differences in health behaviors that may influence risk of salt sensitivity. Physiological and environmental factors contribute to the mechanisms that manifest in racial differences in salt-sensitive blood pressure. Using this information, additional work is needed to develop strategies that can attenuate racial disparities in salt-sensitive blood pressure.

CACNA1D Gene Polymorphisms Associate With Increased Blood Pressure and Salt Sensitivity of Blood Pressure in White Individuals.

Disease-causing mutations in CACNA1D gene occur in aldosterone-producing adenomas and familial hyperaldosteronism. We determined whether single nucleotide polymorphisms in CACNA1D gene associate with higher aldosterone resulting in salt sensitivity of blood pressure (BP) and increased BP in men and women. Data were obtained from the HyperPATH (International Hypertension Pathotypes) cohort, where participants completed a cross-over intervention of liberal and restricted sodium diets. Multi-Ethnic Genotyping Array identified 104 CACNA1D single nucleotide polymorphisms that met quality control. Single nucleotide polymorphism is rs7612148 strongly associated with systolic BP and was selected for study in 521 White participants in 3 scenarios ([1] hypertensives; [2] normotensives; [3] total population=hypertensives+normotensives) using multivariate regression analysis. In the total population and hypertensives, but not normotensives, risk allele carriers (CC, GC), as compared with nonrisk allele homozygotes (GG), exhibited higher salt sensitivity of BP and, on liberal sodium diet, higher systolic BP, lower baseline and angiotensin II-stimulated aldosterone, and lower plasma renin activity. On restricted sodium diet, BP was similar across genotypes, suggesting sodium restriction corrected/neutralized the genotype effect on BP. Because increased aldosterone did not seem to drive the increased salt sensitivity of BP and increased BP on liberal sodium diet, we assessed renal plasma flow. Renal plasma flow increase from restricted to liberal sodium diets was blunted in risk allele homozygotes in the total population and in hypertensives. A replication study in another cohort HyperPATH B (International Hypertension Pathotypes Cohort B) confirmed BP-genotype associations. CACNA1D rs7612148 risk allele associated with increased BP and salt sensitivity of BP, likely due to an impaired ability to increase renal plasma flow in response to a liberal sodium diet and not to excess aldosterone.