Salt-sensitive Hypertension Research Articles

PS-R05-9: A CASE IN WHICH A MINERALOCORTICOID RECEPTOR ANTAGONIST COULD IMPROVE ARB-RESISTANT PROTEINURIA IN NON-DIABETIC HYPERTENSION

The patient is a 53-year-old man with hyperetension, obesity (Body mass index 32–34), dyslipidemia and hyperuricemia, without diabetes mellitus, who has been received antihypertensive agents since age 40. At his initial visit to our hospital at age 40, he exhibited severe hypertension of 244/163 mmHg and proteinuria of about 1000 mg/gram creatinine. According to medical interview, he had been pointed out hypertension since age 32, but denied antihypertensive therapy. Accelerated cardiac and renal damage was not shown. In addition, secondary hypertension such as renovascular hypertension, primary aldosteronism and PPGL were ruled out. He was administered 50 mg losartan and 12.5 mg hydrochlotiazide, and his blood pressure was gradually downregulated, However, his proteinuria of about 700 mg/gram creatinine remained, and so entered a double-blind, randomized, placebo-controlled trial: the Eplerenone Combination versus Conventional Agents to Lower Blood Pressure on Urinary Antialbuminuric Treatment Effect (EVALUATE) study: (Ando K, et al. Lancet Diabetes Endocrinol. 2014; 2: 944). He was randomized to treatment with eplerenone (50 mg/day) or placebo for 52 weeks, and his assigned treatment turned out the eplerenone, associated with anti-alubuminuric effect at the end of EVALUATE study. After that, antihypertensive treatment with 25 or 50 mg eplerenone plus ARB: telmisartan or irbesartan has been continued on his agreement. He avoided excess intake of potassium-containing food, and his plasma potassium level was carefully checked every hospital visit. After 13 years, his proteinuria has not been increased (500–900 mg/gram creatinine). Nishimoto, et al. has reported that eplerenone plus renin-angiotensin system blockade may be effective for CKD in hypertensive patients, especially those with excessive salt intake by EVALUATE study (Hypertens Res 2019; 42: 514). Obesity is related to salt-sensitive hypertension (Nagae A, Fujita M, et al. Circulation 2009; 119: 978.). This obesity-related hypertensive case suggests that a mineralocorticoid receptor antagonist may improve ARB-resistant proteinuria in non-diabetic hypertension for more than 10 years, longer than EVALUATE study for about 1 year period.

S-51-2: ROLE OF THE SYMPATHETIC NERVOUS SYSTEM IN HYPERTENSION: FOCUSED ON THE CENTRAL NERVOUS SYSTEM

Activation of the sympathetic nervous system plays a critical role in the pathogenesis of hypertension. In particular, the central nervous system (CNS) organizes the sympathetic outflow and various inputs from the periphery. These include afferent neural inputs, circulating hormone, cellular factors, and inflammatory and immune responses. Also, within the brain, several factors affect and determine the central sympathetic outflow. Interestingly, these factors are activated particularly in the autonomic nuclei such as the paraventricular nucleus of the hypothalamus and rostral ventrolateral medulla of the brainstem. I will review what and how these factors are altered in various stages of hypertension from the results of basic studies using animal models of hypertension including our own and other investigators. I will address topics such as imbalance of nitric oxide and reactive oxygen species, activation of the brain renin-angiotensin pathway, and altered immunity including Toll-like receptor activation, regulatory T cell inhibition, and perivascular macrophages. In addition, activation of the mineral corticoid receptors in the CNS could be responsible for salt-sensitive hypertension. Finally, I will introduce some new aspects of neural mechanisms of hypertension in the recent progress in the field of research. These experimental studies regarding CNS mechanisms of hypertension can be translated to clinical practice and novel therapies.

Fumarate hydratase as a potential target to ameliorate salt sensitive hypertension

Salt sensitive hypertension is a major risk factor for stroke, heart failure, and end-stage renal disease. The development of salt sensitive hypertension is involved in genetic and environmental factors. Excessive dietary salt intake is known as a main risk factor and one of the most important environmental determinants, exacerbates the salt sensitive hypertension by a renal redox metabolism.

Recent Advances in Hypertension: Epigenetic Mechanism Involved in Development of Salt-Sensitive Hypertension.

This review highlights recent insights into the epigenetic mechanism of salt-sensitive hypertension from the fetus to the elderly population, mainly focusing on the DNA methylation and histone modification-mediated regulation of hypertension-associated genes. Maternal malnutrition during pregnancy induces upregulation of AT1a (angiotensin receptor 1a) by aberrant DNA methylation, and increased AT1A activity in the hypothalamus develops prenatally programmed salt-sensitive hypertension through renal sympathetic overactivity. In addition, maternal lipopolysaccharide exposure during pregnancy induces upregulation of the Rac1 gene through histone modification by H3K9me2 across generations, resulting in salt-induced activation of the Rac1-MR (mineralocorticoid receptor) pathway in the kidney and the development of salt-sensitive hypertension in F4 and F5 offspring. In mice, aberrant DNA methylation of the Klotho gene, which regulates aging-associated hypertension, decreases the circulating soluble Klotho levels, leading to activation of the vascular Wnt5a-RhoA pathway and vasoconstriction and development of salt-sensitive hypertension because of decreased renal blood flow. A detailed understanding of the environmentally-induced epigenetic modulations related to salt-induced hypertension could be promising for developing preventive and therapeutic approaches to hypertension.

Inflammation and oxidative stress in salt sensitive hypertension; The role of the NLRP3 inflammasome.

Salt-sensitivity of blood pressure is an independent risk factor for cardiovascular disease and affects approximately half of the hypertensive population. While the precise mechanisms of salt-sensitivity remain unclear, recent findings on body sodium homeostasis and salt-induced immune cell activation provide new insights into the relationship between high salt intake, inflammation, and hypertension. The immune system, specifically antigen-presenting cells (APCs) and T cells, are directly implicated in salt-induced renal and vascular injury and hypertension. Emerging evidence suggests that oxidative stress and activation of the NLRP3 inflammasome drive high sodium-mediated activation of APCs and T cells and contribute to the development of renal and vascular inflammation and hypertension. In this review, we summarize the recent insights into our understanding of the mechanisms of salt-sensitive hypertension and discuss the role of inflammasome activation as a potential therapeutic target.

Salt-sensitive hypertension: modern pathogenetic mechanisms and prospects

The article presents the recent data on the pathogenic links and potential targets for the treatment of salt-sensitive hypertension (HTN). Distinguishing salt-sensitive and salt-resistant phenotypes is one approach to personalized medicine. In the review, special attention is paid to the intestinal microbiota as an etiological factor in salt-sensitive HTN, which, along with the imbalance of neurohumoral systems and the subsequent dysregulatory hemodynamic response to salt load, plays a leading role in the development of salt sensitivity. The advantages and limitations of methods for quantitative assessment of sodium intake are discussed, ways of their optimization are indicated, which is necessary for a more accurate determination of the optimal threshold for salt intake.

The circadian clock protein PER1 is important in maintaining endothelin axis regulation in Dahl salt-sensitive rats.

Endothelin-1 (ET-1) is a peptide hormone that acts on its receptors to regulate sodium handling in the kidney's collecting duct. Dysregulation of the endothelin axis is associated with various diseases, including salt-sensitive hypertension and chronic kidney disease. Previously, our lab has shown that the circadian clock gene PER1 regulates ET-1 levels in mice. However, the regulation of ET-1 by PER1 has never been investigated in rats. Therefore, we used a novel model where knockout of Per1 was performed in Dahl salt-sensitive rat background (SS Per1 -/-) to test a hypothesis that PER1 regulates the ET-1 axis in this model. Here, we show increased renal ET-1 peptide levels and altered endothelin axis gene expression in several tissues, including the kidney, adrenal glands, and liver in SS Per1 -/- compared with control SS rats. Edn1 antisense lncRNA Edn1-AS, which has previously been suggested to be regulated by PER1, was also altered in SS Per1 -/- rats compared with control SS rats. These data further support the hypothesis that PER1 is a negative regulator of Edn1 and is important in the regulation of the endothelin axis in a tissue-specific manner.

Abstract 15331: Epigenetic Interaction of Grk4 and Slc4a5 Variants Regulates Gene Transcription and Blood Pressure

Salt sensitive hypertension is associated with variants of G protein-coupled receptor kinase 4γ (GRK4), as well as with activating variants of the solute carrier family 4 member 5 (rs7571842 and rs10177833; SLC4a5), which encodes the sodium bicarbonate transporter 2 (NBCe2). We tested the hypothesis that the effect of the R65L variant (rs2960306) of GRK4 (GRK4γ 65L) on salt-sensitivity involves a gene-gene interaction with SLC4a5 variants. We found that the renal expression of SLC4a5 is increased in salt sensitive transgenic mice expressing GRK4γ 65L and is higher (50%; n=4; P<0.02) than that in GRK4 γ expressing the wild type variant (WT). Moreover, that AAV9-mediated renal specific overexpression of SLC4a5 in GRK4γ 65L mice increases the blood pressure (BP) response to a high salt diet compared with mice expressing empty vector (n=3; P<0.05). We studied human renal proximal tubule cells (hRPTCs) endogenously expressing GRK4 WT and SLC4a5 WT, GRK4 65L, SLC4a5 variants and both GRK4 65L and SLC4a5 variants. SLC4A5 expression is increased in hRPTCs expressing GRK4 65L and in cells expressing both GRK4 65L and SLC4a5 variants (n=5, P<0.05) compared with GRK4 WT. GRK4 can interact with nuclear histone deacetylases (HDACs) and co-immunoprecipitates with HDAC1 in nuclear fractions of hRPTCs. Renal-selective downregulation of HDAC1 increases BP in C57Bl/6J (P<0.05) mice. hRPTCs carrying both GRK4 65L and SLC4a5 variants have decreased expression (60%; n=4; P<0.05) of HDAC1 compared with cells expressing GRK4 WT and SLC4a5 WT or GRK4 65L This correlates with increased histone H4 acetylation but unchanged H2A, H2B and H3 acetylation in cells carrying both variants. Our results indicate a complex interaction between these variants in the regulation not only of SLC4a5 expression but that of other genes involved in salt sensitivity.

Revealing the Pathogenesis of Salt-Sensitive Hypertension in Dahl Salt-Sensitive Rats through Integrated Multi-Omics Analysis.

Salt-induced renal metabolism dysfunction is an important mechanism of salt-sensitive hypertension. Given that the gut-liver axis is the first hit of a high-salt diet (HSD), we aimed to identify the extra-renal mechanism from hepatic metabolism and gut microbiota, and attempted to relieve the salt-induced metabolic dysfunctions by curcumin. Untargeted metabolomics analysis was performed to identify the changes in hepatic metabolic pathways, and integrated analysis was employed to reveal the relationship between hepatic metabolic dysfunction and gut microbial composition. HSD induced significant increase in fumaric acid, l-lactic acid, creatinine, l-alanine, glycine, and l-cysteine levels, and amino acids metabolism pathways associated with glycolysis were significantly altered, including alanine, aspartate, and glutamate metabolism; glycine, serine, and threonine metabolism, which were involved in the regulation of blood pressure. Integrated multi-omics analysis revealed that changes in Paraprevotella, Erysipelotrichaceae, and genera from Clostridiales are associated with metabolic disorders. Gene functional predication analysis based on 16S Ribosomal RNA sequences showed that the dysfunction in hepatic metabolism were correlated with enhanced lipopolysaccharide (LPS) biosynthesis and apoptosis in gut microbes. Curcumin (50 mg/kg/d) might reduce gut microbes-associated LPS biosynthesis and apoptosis, partially reverse metabolic dysfunction, ameliorate renal oxidative stress, and protect against salt-sensitive hypertension.

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.

Stroke-prone salt-sensitive spontaneously hypertensive rats show higher susceptibility to spreading depolarization (SD) and altered hemodynamic responses to SD

Spreading depolarization (SD) occurs in a plethora of clinical conditions including migraine aura, delayed ischemia after subarachnoid hemorrhage and malignant hemispheric stroke. It describes waves of near-breakdown of ion homeostasis, particularly Na+ homeostasis in brain gray matter. SD induces tone alterations in resistance vessels, causing either hyperperfusion in healthy tissue; or hypoperfusion (inverse hemodynamic response = spreading ischemia) in tissue at risk. Observations from mice with genetic dysfunction of the ATP1A2-encoded α2-isoform of Na+/K+-ATPase (α2NaKA) suggest a mechanistic link between (1) SD, (2) vascular dysfunction, and (3) salt-sensitive hypertension via α2NaKA. Thus, α2NaKA-dysfunctional mice are more susceptible to SD and show a shift toward more inverse hemodynamic responses. α2NaKA-dysfunctional patients suffer from familial hemiplegic migraine type 2, a Mendelian model disease of SD. α2NaKA-dysfunctional mice are also a genetic model of salt-sensitive hypertension. To determine whether SD thresholds and hemodynamic responses are also altered in other genetic models of salt-sensitive hypertension, we examined these variables in stroke-prone spontaneously hypertensive rats (SHRsp). Compared with Wistar Kyoto control rats, we found in SHRsp that electrical SD threshold was significantly reduced, propagation speed was increased, and inverse hemodynamic responses were prolonged. These results may have relevance to both migraine with aura and stroke.

Gut-Immune-Kidney Axis: Influence of Dietary Protein in Salt-Sensitive Hypertension.

Humans with salt-sensitive hypertension demonstrate increased morbidity, increased mortality, and renal end-organ damage when compared with normotensive subjects or those with salt-resistant hypertension. Substantial evidence from humans and animals has also demonstrated the role of dietary components other than salt to modulate hypertension. Evidence presented in this review provides support for the view that immunity and inflammation serve to amplify the development of salt-sensitive hypertension and leads to malignant disease accompanied by end-organ damage. Interestingly, salt-sensitive disease is modulated by changes in dietary protein intake, which also influences immune mechanisms. Together, the evidence presented in this review from animal and human studies indicates that changes in dietary protein source have profound effects on the gut microbiota, microbiota-derived metabolites, DNA methylation, gene expression, immune cell activation, the production of cytokines and other factors, and the development of salt-sensitive hypertension and related disease phenotypes.

Genetic Engineering of Lymphangiogenesis in Skin Does Not Affect Blood Pressure in Mouse Models of Salt-Sensitive Hypertension.

Recent studies have indicated that sodium storage is influenced by macrophages that secrete VEGF-C (vascular endothelial growth factor) during salt stress thus stimulating lymphangiogenesis, thereby acting as a buffer against increased blood pressure (BP). We aimed to explore the role of dermal lymphatics in BP and sodium homeostasis. Our hypothesis was that mice with reduced dermal lymphatic vessels were more prone to develop salt-sensitive hypertension, and that mice with hyperplastic vessels were protected. Mice with either hypoplastic (Chy), absent (K14-VEGFR3 [vascular endothelial growth factor receptor 3]-Ig), or hyperplastic (K14-VEGF-C) dermal lymphatic vessels and littermate controls were given high-salt diet (4% NaCl in the chow), deoxycorticosterone acetate (DOCA)-salt diet and 1% saline to drink or nitric oxide blocker diet L-NG-nitro arginine methyl ester (followed by high salt diet). BP was measured by telemetric recording, and tissue sodium content by ion chromatography. In contrast to previous studies, high salt diet did not induce an increase in BP or sodium storage in any of the mouse strains investigated. DOCA-salt, on the other hand, gave an increase in BP in Chy and K14-VEGFR3-Ig not different from their corresponding WT controls. DOCA induced salt storage in skin and muscle, but to the same extent in mice with dysfunctional lymphatic vessels and WT controls. Lymph flow as assessed by tracer washout was not affected by the diet in any of the mouse strains. Our results suggest that dermal lymphatic vessels are not involved in salt storage or blood pressure regulation in these mouse models of salt-sensitive hypertension.

ARRB2 (β-Arrestin-2) Deficiency Alters Fluid Homeostasis and Blood Pressure Regulation

GPCRs (G protein-coupled receptors) are implicated in blood pressure (BP) and fluid intake regulation. There is a developing concept that these effects are mediated by both canonical G protein signaling and noncanonical β-arrestin mediated signaling, but the contributions of each remain largely unexplored. Here, we hypothesized that β-arrestin contributes to fluid homeostasis and blood pressure (BP) regulation in deoxycorticosterone acetate (DOCA) salt hypertension, a prototypical model of salt-sensitive hypertension. Global β-arrestin1 (Arrb1) and β-arrestin2 (Arrb2) knockout mice were employed to evaluate drinking behavior, and BP was evaluated in Arrb2-knockout mice. Age- and sex-matched C57BL/6 mice served as controls. We measured intake of water and different sodium chloride solutions and BP employing a 2-bottle choice paradigm with and without DOCA. Without DOCA (baseline), Arrb2-knockout mice exhibited a significant elevation in saline intake with no change in water intake. With DOCA treatment, Arrb2-knockout mice exhibited a significant increase in both saline and water intake. Although Arrb2-knockout mice exhibited hypernatremia at baseline conditions, we did not find significant changes in total body sodium stores or sodium palatability. In a separate cohort, BP was measured via telemetry in Arrb2-knockout and C57BL/6 mice with and without DOCA. Arrb2-knockout did not exhibit significant differences in BP before DOCA treatment when provided water alone, or when provided a choice of water and saline. However, Arrb2-knockout exhibited an increased pressor response to DOCA-salt. These findings suggest that in salt-sensitive hypertension, ARRB2, but not ARRB1 (β-arrestin 1), might counterbalance the canonical signaling of GPCRs.

Revealing Novel Signaling Pathways Affected in Glomeruli During Salt-Sensitive Hypertension

Revealing Novel Signaling Pathways Affected in Glomeruli During Salt-Sensitive Hypertension

Effects of Hyperuricemia on the Progression of Salt-Sensitive (SS) Hypertension in Dahl SS Rats

Effects of Hyperuricemia on the Progression of Salt-Sensitive (SS) Hypertension in Dahl SS Rats

Insights Into the Role of Atrial Natriuretic Peptide in Mitochondria-Mediated Metabolism in Salt-Sensitive (SS) Hypertension

Insights Into the Role of Atrial Natriuretic Peptide in Mitochondria-Mediated Metabolism in Salt-Sensitive (SS) Hypertension

Resident Renal Dendritic Cells Respond to Salt-Sensitive Hypertension via ToneBP, Leading to Increased Interleukin 6

Resident Renal Dendritic Cells Respond to Salt-Sensitive Hypertension via ToneBP, Leading to Increased Interleukin 6

Knockout of the Circadian Clock Protein PER1 (Period1) Exacerbates Hypertension and Increases Kidney Injury in Dahl Salt-Sensitive Rats.

Circadian rhythms play an essential role in physiological function. The molecular clock that underlies circadian physiological function consists of a core group of transcription factors, including the protein PER1 (Period1). Studies in mice show that PER1 plays a role in the regulation of blood pressure and renal sodium handling; however, the results are dependent on the strain being studied. Using male Dahl salt-sensitive (SS) rats with global knockout of PER1 (SSPer1-/-), we aim to test the hypothesis that PER1 plays a key role in the regulation of salt-sensitive blood pressure. The model was generated using CRISPR/Cas9 and was characterized using radiotelemetry and measures of renal function and circadian rhythm. SSPer1-/- rats had similar mean arterial pressure when fed a normal 0.4% NaCl diet but developed augmented hypertension after three weeks on a high-salt (4% NaCl) diet. Despite being maintained on a normal 12:12 light:dark cycle, SSPer1-/- rats exhibited desynchrony mean arterial pressure rhythms on a high-salt diet, as evidenced by increased variability in the time of peak mean arterial pressure. SSPer1-/- rats excrete less sodium after three weeks on the high-salt diet. Furthermore, SSPer1-/- rats exhibited decreased creatinine clearance, a measurement of renal function, as well as increased signs of kidney tissue damage. SSPer1-/- rats also exhibited higher plasma aldosterone levels. Altogether, our findings demonstrate that loss of PER1 in Dahl SS rats causes an array of deleterious effects, including exacerbation of the development of salt-sensitive hypertension and renal damage.

Gut Microbiome and Kidney Disease: Reconciling Optimism and Skepticism.

Gut Microbiome and Kidney Disease: Reconciling Optimism and Skepticism.