Bilateral Paraventricular Nucleus Upregulation of Extracellular Superoxide Dismutase Decreases Blood Pressure by Regulation of the NLRP3 and Neurotransmitters in Salt-Induced Hypertensive Rats

Aims: Long-term salt diet induces the oxidative stress in the paraventricular nucleus (PVN) and increases the blood pressure. Extracellular superoxide dismutase (Ec-SOD) is a unique antioxidant enzyme that exists in extracellular space and plays an essential role in scavenging excessive reactive oxygen species (ROS). However, the underlying mechanism of Ec-SOD in the PVN remains unclear. Methods: Sprague-Dawley rats (150-200 g) were fed either a high salt diet (8% NaCl, HS) or normal salt diet (0.9% NaCl, NS) for 6 weeks. Each group of rats was administered with bilateral PVN microinjection of AAV-Ec-SOD (Ec-SOD overexpression) or AAV-Ctrl for the next 6 weeks. Results: High salt intake not only increased mean arterial blood pressure (MAP) and the plasma noradrenaline (NE) but also elevated the NAD(P)H oxidase activity, the NAD(P)H oxidase components (NOX2 and NOX4) expression, and ROS production in the PVN. Meanwhile, the NOD-like receptor protein 3 (NLRP3)-dependent inflammatory proteins (ASC, pro-cas-1, IL-β, CXCR, CCL2) expression and the tyrosine hydroxylase (TH) expression in the PVN with high salt diet were higher, but the GSH level, Ec-SOD activity, GAD67 expression, and GABA level were lower than the NS group. Bilateral PVN microinjection of AAV-Ec-SOD decreased MAP and the plasma NE, reduced NAD(P)H oxidase activity, the NOX2 and NOX4 expression, and ROS production, attenuated NLRP3-dependent inflammatory expression and TH, but increased GSH level, Ec-SOD activity, GAD67 expression, and GABA level in the PVN compared with the high salt group. Conclusion: Excessive salt intake not only activates oxidative stress but also induces the NLRP3-depensent inflammation and breaks the balance between inhibitory and excitability neurotransmitters in the PVN. Ec-SOD, as an essential anti-oxidative enzyme, eliminates the ROS in the PVN and decreases the blood pressure, probably through inhibiting the NLRP3-dependent inflammation and improving the excitatory neurotransmitter release in the PVN in the salt-induced hypertension.

Salt Intake and Risk of Disaster Hypertension Among Evacuees in a Shelter After the Great East Japan Earthquake

This study investigated the association between salt intake and risk of disaster hypertension. We analyzed the data of surveys evaluating the health condition of evacuees in shelters after the Great East Japan Earthquake on April 30 and May 5, 2011. Among 272 subjects who completed the basic health condition questionnaire and underwent a medical examination, 158 (58%) had disaster hypertension (systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg). Average estimated sodium intake assessed by spot urine was significantly associated with disaster hypertension (odds ratio per 1 g/d, 1.16; 95% CI, 1.05-1.30). When we defined the high risk factors for salt-sensitive hypertension as older age (≥65 years), obesity (body mass index, ≥25 kg/m²), chronic kidney disease, and diabetes mellitus, estimated sodium intake was found to be a risk factor for disaster hypertension in the total group (odds ratio per 1 g/d, 1.27; 95% CI, 1.12-1.43) and even in the group without prevalent hypertension before disaster (n=146; odds ratio per 1 g/d, 1.46; 95% CI, 1.19-1.79). There was an interaction between estimated sodium intake and disaster hypertension according to the presence or absence of high risk of salt-sensitive hypertension in the group without prevalent hypertension (P=0.03). Disaster hypertension conferred a risk of microalbuminuria (odds ratio, 3.00; 95% CI, 1.71-5.26; P<0.001). We conclude that increased estimated sodium intake was associated with disaster hypertension in evacuees after disaster. This association was noted in the population with high risk of salt-sensitive hypertension and without prevalent hypertension before natural disaster. Additionally, disaster hypertension was associated with subclinical organ damage.

Postulating the major environmental condition resulting in the expression of essential hypertension and its associated cardiovascular diseases: Dietary imprudence in daily selection of foods in respect of their potassium and sodium content resulting in oxidative stress-induced dysfunction of the vascular endothelium, vascular smooth muscle, and perivascular tissues

We hypothesize that the major environmental determinant of the expression of essential hypertension in America and other Westernized countries is dietary imprudence in respect of the consumption of daily combinations of foods containing suboptimal amounts of potassium and blood pressure-lowering phytochemicals, and supraphysiological amounts of sodium. We offer as premise that Americans on average consume suboptimal amounts of potassium and blood pressure-lowering phytochemicals, and physiologically excessive amounts of sodium, and that such dietary imprudence leads to essential hypertension through oxidative stress-induced vascular endothelial and smooth muscle dysfunction. Such dysfunctions restrict nitric oxide bioavailability, impairing endothelial cell-mediated relaxation of the underlying vascular smooth muscle, initiating and maintaining inappropriately increased peripheral and renal vascular resistance. The biochemical steps from oxidative stress to vascular endothelial dysfunction and its pernicious cardiovascular consequences are well established and generally accepted. The unique aspect of our hypothesis resides in the contention that Americans' habitual consumption of foods resulting in suboptimal dietary intake of potassium and supraphysiological intake of sodium result in oxidative stress, the degree of which, we suggest, will correlate with the degree of deviation of potassium and sodium intake from optimal. Because suboptimal intakes of potassium reflect suboptimal intakes of fruits and vegetables, associated contributors to oxidative stress include suboptimal intakes of magnesium, nitrate, polyphenols, carotenoids, and other phytochemical antioxidants for which fruits and vegetables contain abundant amounts. Currently Americans consume potassium-to-sodium in molar ratios of less than or close to 1.0 and the Institute of Medicine (IOM) recommends a molar ratio of 1.2. Ancestral diets to which we are physiologically adapted range from molar ratios of 5.0 to 10.0 or higher. Accordingly, we suggest that the average American is usually afflicted with oxidative stress-induced vascular endothelial dysfunction, and therefore the standards for normal blood pressure and pre-hypertension often reflect a degree of clinically significant hypertension. In this article, we provide support for those contentions, and indicate the findings that the hypothesis predicts.

Maternal high-salt diet alters redox state and mitochondrial function in newborn rat offspring's brain

Excessive salt intake is a common feature of Western dietary patterns, and has been associated with important metabolic changes including cerebral redox state imbalance. Considering that little is known about the effect on progeny of excessive salt intake during pregnancy, the present study investigated the effect of a high-salt diet during pregnancy and lactation on mitochondrial parameters and the redox state of the brains of resulting offspring. Adult female Wistar rats were divided into two dietary groups (n 20 rats/group): control standard chow (0·675 % NaCl) or high-salt chow (7·2 % NaCl), received throughout pregnancy and for 7 d after delivery. On postnatal day 7, the pups were euthanised and their cerebellum, hypothalamus, hippocampus, prefrontal and parietal cortices were dissected. Maternal high-salt diet reduced cerebellar mitochondrial mass and membrane potential, promoted an increase in reactive oxygen species allied to superoxide dismutase activation and decreased offspring cerebellar nitric oxide levels. A significant increase in hypothalamic nitric oxide levels and mitochondrial superoxide in the hippocampus and prefrontal cortex was observed in the maternal high-salt group. Antioxidant enzymes were differentially modulated by oxidant increases in each brain area studied. Taken together, our results suggest that a maternal high-salt diet during pregnancy and lactation programmes the brain metabolism of offspring, favouring impaired mitochondrial function and promoting an oxidative environment; this highlights the adverse effect of high-salt intake in the health state of the offspring.

Daily sodium intake influences the relationship between angiotensin-converting enzyme gene insertion/deletion polymorphism and hypertension in older adults

The angiotensin-converting enzyme insertion/deletion (I/D) gene polymorphism has been widely reported as being associated with hypertension; however, most studies do not consider environmental/behavioral factors. This study aimed to investigate the relationship among angiotensin-converting enzyme insertion/deletion gene polymorphism, environmental/behavioral factors, and hypertension in community-dwelling elderly individuals. All community-dwelling older adults from Aiquara, Bahia, Brazil, were invited to take part in this study. After exclusions, 234 elderly participants were submitted to a data collection, which included sociodemographics, lifestyle and health status questionnaires, clinical assessment, and blood withdrawal. From the blood samples, the gene polymorphism was identified through polymerase chain reaction and patients grouped as II or D allele carriers (ID and DD genotypes). Hypertension was defined by self-report of the condition and confirmed by antihypertensive drug treatment. Chi-square test was used to identify differences in the proportions distributed between groups of each dependent variable (ie, genotype, diagnosis of hypertension, and blood pressure state from medicated patients with hypertension). The prevalence of hypertension was 59.3% and was associated with diabetes mellitus and obesity, but not with angiotensin-converting enzyme insertion/deletion gene polymorphism. However, carriers of the II genotype, a salt-sensitivity genotype, exhibited a significantly greater estimated sodium intake. In addition, among medicated elderly patients with hypertension, II genotype carriers exhibited poor blood pressure control, despite similar antihypertensive drug treatment in D allele carriers, while exhibiting a greater estimated sodium intake. Our results provide new evidence regarding the interaction of genetic and environmental/behavioral factors in the genesis of hypertension among elderly patients, as well as in blood pressure control in medicated elderly patients with hypertension.