Treatment Of Salt-sensitive Hypertension Research Articles

Efficacy of the calcium channel blocker amlodipine in the treatment of salt-sensitive hypertension in patients with different genetic status

Aim. To study the effectiveness of the calcium channel blocker amlodipine in the treatment of salt-sensitive hypertension (HTN) and compare it with the genotypes of patients.Material and methods. The study involved 96 patients aged 42,7±5,2 years. There were following inclusion criteria: diagnosis — grade 1, stage 1 hypertension with low risk of cardiovascular events (CVEs). Before inclusion in the study, patients had not taken regular antihypertensive therapy for 3 months. Next, all patients underwent assessment of salt sensitivity of blood pressure according to the M. H. Weinberger method and, based on it, the participants were divided into salt-sensitive and salt-resistant. Regardless of the result, all patients were recommended to have a low-salt diet of 3-5 g/day, with subsequent 24-hour ambulatory blood pressure monitoring (ABPM) during the diet. In patients with ineffective diet, amlodipine was prescribed on day 26 at a dose of 2,5-5 mg once a day. The effectiveness of the drug was assessed by repeated ABPM. In addition, a genetic study was performed on 4 polymorphic variants of the genes AGT (T704C), AGT (C521T), AGTR1 (A1166C), AGTR2 (G1675A), ADD1 (G1378T), CYP11B2 (C344T), GNB3 (C825T), NOS3 (T786C), NOS3 (G894T), to determine their association with the effectiveness of a low-salt diet and amplodipine therapy.Results. In patients with grade 1, stage 1 hypertension with low risk of CVEs, the effectiveness of a low-salt diet and amlodipine monotherapy at a dose of 2,55 mg/day was revealed. The results of the study were confirmed by achieving target values of office blood pressure and ABPM. In hypertensive patients not sensitive to salt, amlodipine monotherapy was ineffective. The genotyping revealed a relationship between antihypertensive therapy with amlodipine in salt-sensitive patients and carriage of the GG polymorphism of the AGTR2 gene.Conclusion. The effectiveness of amlodipine and a low-salt diet in salt-sensitive patients with grade 1 hypertension, stage 1, low risk of CVEs with carriage of the GG genotype of the AGTR2 gene.

Hypothalamic kinin B1 receptor mediates orexin system hyperactivity in neurogenic hypertension

Brain orexin system hyperactivity contributes to neurogenic hypertension. We previously reported upregulated neuronal kinin B1 receptor (B1R) expression in hypertension. However, the role of central B1R activation on the orexin system in neurogenic hypertension has not been examined. We hypothesized that kinin B1R contributes to hypertension via upregulation of brain orexin-arginine vasopressin signaling. We utilized deoxycorticosterone acetate (DOCA)-salt hypertension model in wild-type (WT) and B1R knockout (B1RKO) mice. In WT mice, DOCA-salt-treatment increased gene and protein expression of orexin A, orexin receptor 1, and orexin receptor 2 in the hypothalamic paraventricular nucleus and these effects were attenuated in B1RKO mice. Furthermore, DOCA-salt- treatment increased plasma arginine vasopressin levels in WT mice, but not in B1RKO mice. Cultured primary hypothalamic neurons expressed orexin A and orexin receptor 1. B1R specific agonist (LDABK) stimulation of primary neurons increased B1R protein expression, which was abrogated by B1R selective antagonist R715 but not by the dual orexin receptor antagonist, ACT 462206, suggesting that B1R is upstream of the orexin system. These data provide novel evidence that B1R blockade blunts orexin hyperactivity and constitutes a potential therapeutic target for the treatment of salt-sensitive hypertension.

Abstract MP57: Chronic Inhibition Of Brain Rhomboid-like Protein 2 (irhom2) Activity Decreases Arterial Blood Pressure In Salt-sensitive Hypertension In Mice

We previously reported that ADAM17 (aka tumor necrosis factor-α convertase) is critical for the development of hypertension in experimental models and patients. Recent studies highlighted that ADAM17’s formation of TNF-α relies on prior maturation of this sheddase, controlled by the rhomboid-like protein 2 (iRhom2) specifically in microglia. Genetic deletion of iRhom2 in mice shows significant attenuation of TNF-α and ADAM17 activity in a tissue specific manner. Here, we hypothesized that silencing iRhom2 activity specifically in the brain would decrease blood pressure (BP) in the DOCA-salt model of hypertension, in mice. Uninephrectomized mice were implanted subcutaneously (sc) with DOCA-pellets (50 mg) and provided with 1% saline in drinking water. In addition, mice were chronically implanted with an icv cannula connected to a sc osmotic minipump for delivery of: (1) iRhom2-siRNA (9.6 μg/kg/day), (2) scrambled siRNA (SCR 0.2 μg/kg/day), (3) ADAM17 antibody (ADAM17-Ab; 23.8 μg/kg/day) or (4) artificial cerebrospinal fluid (aCSF) for 2 weeks while BP was recorded by telemetry. DOCA-salt treatment led to a significant increase in BP in the control groups (SCR: 156 ±3 mmHg and aCSF: 161 ±1 mmHg; n=3/group; p<0.001) compared to baseline values (122 ±2 mmHg; n=12). ICV infusion of iRhom2-siRNA or ADAM17 neutralizing antibody for 2-weeks in DOCA-salt-treated mice resulted in a significant attenuation of BP (iRhom2-siRNA: 152 ±2 mmHg and ADAM17-Ab: 151 ±2 mmHg n=3/group, p<0.001). These data suggest that: 1) Selective silencing of iRhom2 from microglia is as potent as ADAM17 neutralization throughout the brain in lowering BP and 2) iRhom2 is a potential new therapeutic target for the treatment of salt-sensitive hypertension.

Chlorthalidone or Hydrochlorothiazide for Treatment of Hypertension

Chlorthalidone or Hydrochlorothiazide for Treatment of Hypertension

Insufficient fumarase contributes to hypertension by an imbalance of redox metabolism in Dahl salt-sensitive rats.

Fumarase insufficiencies can increase reactive oxygen species (ROS). This study will further dissect the imbalance of redox metabolism and the mechanism of ROS production using proteomic technology in fumarase knockdown HK-2 cells. The contribution of fumarase was further confirmed by supplementation of fumarate and malate in Dahl salt-sensitive rats. Proteomic analysis indicated that fumarase knockdown in HK-2 cells changed the expression or activity of NADPH oxidase (NOX), mitochondrial respiratory chain Complex I and III, ATP synthase subunits, and α-oxoglutarate dehydrogenase (OGDH). Meanwhile, the activities of key antioxidant enzymes, including glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione reductase, glutathione peroxidase, and glutathione S-transferase, increased significantly. The apparent activation of antioxidant defense appeared insufficient as the glutathione and GSH/GSSG ratio were decreased significantly. Dahl salt-sensitive rats exhibited changes in redox metabolism similar to HK-2 cells with fumarase knockdown. Supplementation with fumarate and malate increased and decreased, respectively, blood pressure and H2O2 and malondialdehyde in salt-sensitive rats. These results indicated that insufficient fumarase activity increased ROS by regulating NOX, Complex I and III, ATPase alpha, and OGDH and the imbalance of glutathione metabolism, which may be one of the main reasons for salt-sensitive hypertension. Malate may be a potentially effective drug for the prevention and treatment of salt-sensitive hypertension.

Abstract P118: The Complexity of the Albuminuria Development in Salt-sensitive Hypertension

Hypertension is one of the most prevalent diseases worldwide, and is a major risk factor for developing albuminuria, renal failure and cardiovascular diseases. The goal of this study was to investigate the mechanisms leading to albuminuria in the kidney of a canonical rat model of hypertension, the Dahl salt-sensitive (SS) rat. To determine the relative contributions of the glomerulus and proximal tubule (PT) to albuminuria, we applied intravital two-photon-based imaging to investigate complex changes in renal function that occur during salt-induced hypertension. Following a high salt (HS) diet, SS rats exhibited elevated blood pressure, accompanied by increased glomerular sieving of albumin (GSC alb =0.0686) and decreased serum albumin (-Δ0.54 g/dL), which corresponded to increased daily filtered albumin up to 3.7 vs 0.8 g at normal diet. Pathologically, hypertensive animals had significant tubular damage as indicated by increased prevalence of granular casts (+Δ2.20 casts/image), dilation/expansion and necrosis of PT epithelial cells, increased vascular injury (+Δ0.61 leakage/image), and progressive inflammation. HS diet significantly reduced total PT uptake of albumin, which also coincided with reduced transcellular transport of albumin back into circulation. Collectively, these results indicate that both the glomerulus and the proximal tubule contribute to albuminuria and dual treatment of glomerular filtration and albumin reabsorption may represent an effective treatment of salt-sensitive hypertension.

The Kidney and Hypertension: Pathogenesis of Salt-Sensitive Hypertension

Salt-sensitive hypertension is closely related with natriuretic capacity of the kidney. Besides several genome-wide research reported candidate gene or gene polymorphism responsible for salt-sensitive hypertension, recently, several new factors for acquired salt-sensitive hypertension are reported. Among them, we have identified that rac1, a small GTPase, activates mineralocorticoid receptor in aldosterone-independent fashion and induces salt-sensitive hypertension in several rodent model. On the other hand, sympathoactivation in the brain and/or kidney regulate sodium handlings in the kidney. Recently it is reported that oxidative stress in the brain or in the kidney may modulate sympathetic tone. Moreover, we reported that β2 adrenoceptor alters histone acetylation and further regulates sodium resorption at distal tubules via activating glucocorticoid receptor. These regulations are to be confirmed in humans and the future, and may open a new door for diagnosis and treatment of salt-sensitive hypertension or moreover preventing development of salt-sensitive hypertension.

The genetic deletion of Mas abolishes salt induced hypertension in mice

The G protein-coupled receptor Mas is a physiological antagonist of the angiotensin II type 1 receptor and is associated with angiotensin-(1–7) signaling. We investigated the effect of Mas-deficiency on blood pressure regulation under physiological conditions and salt load using radiotelemetry. Mas-knockout mice and their wild-type controls received a telemetry implant in the carotid artery. One week after surgery, animals were monitored for 3 days receiving normal diet (0.6% NaCl) followed by one-week high-salt diet (8% NaCl). Under same high-salt diet, another set of mice was placed in individual metabolic cages for 4 days. Basal mean arterial pressure, heart rate and locomotor activity displayed normal day–night rhythm in Mas-deficient mice. Mas-knockout mice were normotensive. High dietary NaCl ingestion did not alter heart rate or locomotor activity in both groups, but significantly increased night time mean arterial pressure in control mice whereas this increase was blunted in Mas-deficient mice. Baseline food and water intake and urine osmolality were not different between both genotypes. Under high-salt diet, water consumption and food intake were equally increased in wild-type controls and Mas-knockout, but urinary electrolytes and osmolality were significantly higher in Mas-knockout. Taken together, basal hemodynamic parameters are unchanged in Mas-knockout mice. In contrast to wild-type controls, telemetric mean arterial pressure measurement revealed salt resistance in Mas-deficient animals, probably due to their higher urinary NaCl excretion. This is the first direct proof that Mas blockade might be a new option in the treatment of salt-sensitive hypertension.

The role of incretins in salt-sensitive hypertension

Incretin mimetics, such as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), as well as dipeptidyl peptidase-IV (DPP-IV) inhibitors, are used in the treatment of type 2 diabetes mellitus (T2DM). In addition to stimulating insulin secretion from pancreatic β cells, incretins have apparent extrapancreatic functions beyond glycemic control. This review summarizes the recent findings regarding the blood-pressure-lowering effects of incretins and DPP-IV inhibitors in patients who are obese, diabetic, or have metabolic syndrome. Clinical studies have indicated that GLP-1 and its analogues lower blood pressure in patients with T2DM, particularly in patients with moderate-to-severe hypertension. DPP-IV inhibitors also appear to elicit a similar blood-pressure-lowering effect. In animal models of salt-sensitive hypertension, incretins appear to induce their antihypertensive effects by inhibiting the proximal tubular sodium reabsorption, and thereby increasing urinary excretion of sodium. These data suggest that the local actions of incretins may be via their key role in regulating natriuresis and lowering blood pressure. Incretin mimetics and DPP-IV inhibitors are a novel class of antihypertensive drugs with natriuretic properties. They can be used in the treatment of salt-sensitive hypertension, which is characterized by edema.