Alpha lipoic acid supplementation attenuates reactive oxygen species in hypothalamic paraventricular nucleus and sympathoexcitation in high salt-induced hypertension

Cardiovascular and Renal Effects Induced by Alpha-Lipoic Acid Treatment in Two-Kidney-One-Clip Hypertensive Rats

α-Lipoic acid (LA) is an antioxidant of endogenous production, also obtained exogenously. Oxidative stress is closely associated with hypertension, which causes kidney injury and endothelial dysfunction. Here, we evaluated the cardiovascular and renal effects of LA in the two-kidney-one-clip (2K1C) hypertension model. The rats were divided into four groups: Sham surgery (Sham), the two-kidneys-one-clip (2K1C) group, and groups treated with LA for 14 days (Sham-LA and 2K1C-LA). No changes were observed in the pattern of food, water intake, and urinary volume. The left/right kidney weight LKw/RKw ratio was significantly higher in 2K1C animals. LA treatment did not reverse the increase in cardiac mass. In relation to vascular reactivity, there was an increase in the potency of phenylephrine (PHE) curve in the hypertensive animals treated with LA compared to the 2K1C group and also compared to the Sham group. Vasorelaxation induced by acetylcholine (Ach) and sodium nitroprusside (SNP) were not improved by treatment with LA. Urea and creatinine levels were not altered by the LA treatment. In conclusion, the morphological changes in the aorta and heart were not reversed; however, the treatment with LA mitigated the contraction increase induced by the 2K1C hypertension.

Central administration of AICAR attenuates hypertension via AMPK/Nrf2 pathway in the hypothalamic paraventricular nucleus of hypertensive rats

BACKGROUND

Oxidative stress and inflammatory cytokines in the hypothalamus paraventricular nucleus (PVN) have been implicated in sympathetic nerve activity and the development of hypertension, but the specific mechanisms underlying their production in the PVN remains to be elucidated. Previous studies have demonstrated that activation of nuclear transcription related factor-2 (Nrf2) in the PVN reduced the production of reactive oxygen species (ROS) and inflammatory mediators. Moreover, AMP-activated protein kinase (AMPK), has been observed to decrease ROS and inflammatory cytokine production when activated in the periphery. 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide (AICAR) is an AMPK agonist. However, little research has been conducted on the role of AMPK in the PVN during hypertension. Therefore, we hypothesized that AICAR in the PVN is involved in regulating AMPK/Nrf2 pathway, affecting ROS and inflammatory cytokine expression, influencing sympathetic nerve activity.

METHODS

Adult male Sprague-Dawley rats were utilized to induce two-kidney, one-clip (2K1C) hypertension via constriction of the right renal artery. Bilateral PVN was microinjected with either artificial cerebrospinal fluid or AICAR once a day for 4 weeks.

RESULTS

Compared to the SHAM group, the PVN of 2K1C hypertensive rats decreased p-AMPK and p-Nrf2 expression, increased Fra-Like, NAD(P)H oxidase (NOX)2, NOX4, tumor necrosis factor-α and interleukin (IL)-1β expression, elevated ROS levels, decreased superoxide dismutase 1 and IL-10 expression, and elevated plasma norepinephrine levels. Bilateral PVN microinjection of AICAR significantly ameliorated these changes.

CONCLUSION

These findings suggest that repeated injection of AICAR in the PVN suppresses ROS and inflammatory cytokine production through the AMPK/Nrf2 pathway, reducing sympathetic nerve activity and improving hypertension.

Angiotensin-converting enzyme inhibitory peptide IVGFPAYGH protects against liver injury in mice fed a high‑sodium diet by inhibiting the RAS and remodeling gut microbial communities

Consuming a high‑sodium diet carries serious health risks and significantly influences the activation state of the renin-angiotensin system (RAS). This study evaluates the protective effect of angiotensin-converting enzyme (ACE) inhibitory peptide IVGFPAYGH on a high‑sodium diet-induced liver injury. IVGFPAYGH supplementation increased the activities of liver antioxidase and decreased the levels of liver inflammatory factor in mice fed a high‑sodium diet (8 % NaCl). IVGFPAYGH supplementation also reduced liver fatty acid synthesis and promoted fatty acid oxidation, increased the expression of low-density lipoprotein receptor, and improved liver dyslipidemia. Furthermore, IVGFPAYGH supplementation inhibited the activation of the liver RAS via inhibiting ACE activity and reducing angiotensin II levels in mice fed a high‑sodium diet. Moreover, IVGFPAYGH supplementation could alter the gut microbiota composition toward a normal gut microbiota composition and increase the abundance of the Lactobacillus genus. IVGFPAYGH supplementation also increased the expression levels of small intestinal tight junction protein and cecum short-chain fatty acids. Thus, IVGFPAYGH supplementation may maintain intestinal homeostasis and improve high‑sodium diet-induced liver injury by altering the gut microbiota composition and inhibiting the RAS. IVGFPAYGH is a promising functional ingredient for protecting liver damage caused by a high‑sodium diet.

Research trends and hotpots on the relationship between high salt and hypertension: A bibliometric and visualized analysis

INTRODUCTION

A high salt diet is a significant risk factor for hypertension, and scholarly investigations into this relationship have garnered considerable attention worldwide. However, bibliometric analyses in this field remain underdeveloped. This study aimed to conduct a bibliometric and visual analysis of research progress on the link between high salt and hypertension from 2011 to 2022 with the goal of identifying future research trends and providing valuable insights for this field.

METHODS

High salt and hypertension data were obtained from the Web of Science Core Collection database. Microsoft Excel, Scimago Graphica, CiteSpace, and VOSviewer software were employed to analyze publication output trends, the most productive countries or regions, journals, authors, co-cited references, and keywords.

RESULTS

After screening, 1470 papers met the inclusion criteria. Relevant publications increased annually by 3.66% from 2011 to 2022. The United States led in research productivity, with The Journal of Hypertension publishing the most papers, and David L. Mattson as the most prolific author. Oxidative stress has emerged as a prominent research topic, and extensive investigations have been conducted on related mechanisms. "Oxidative stress," "gut microbiota," and "kidney injury" are recent hotspots that are expected to remain so, and this study carefully characterizes the mechanism of high salt-induced hypertension based on these hotspots.

CONCLUSION

This study utilized bibliometric and visualization analysis to identify the development trends and hotspots of publications related to high salt and hypertension. The findings of this study offer valuable insights into the forefront of emerging trends and future directions in this field.

Oxidative Stress, Antioxidants and Hypertension

As a major cause of morbidity and mortality globally, hypertension remains a serious threat to global public health. Despite the availability of many antihypertensive medications, several hypertensive individuals are resistant to standard treatments, and are unable to control their blood pressure. Regulation of the renin-angiotensin-aldosterone system (RAAS) controlling blood pressure, activation of the immune system triggering inflammation and production of reactive oxygen species, leading to oxidative stress and redox-sensitive signaling, have been implicated in the pathogenesis of hypertension. Thus, besides standard antihypertensive medications, which lower arterial pressure, antioxidant medications were tested to improve antihypertensive treatment. We review and discuss the role of oxidative stress in the pathophysiology of hypertension and the potential use of antioxidants in the management of hypertension and its associated organ damage.

Genistein Alleviates Oxidative Stress and Inflammation in the Hypothalamic Paraventricular Nucleus by Activating the Sirt1/Nrf2 Pathway in High Salt-Induced Hypertension

Hypertension caused by a high-salt (HS) diet is one of the major causes of cardiovascular diseases. Underlining pathology includes oxidative stress and inflammation in the hypothalamic paraventricular nucleus (PVN). This study investigates genistein's (Gen) role in HS-induced hypertension and the underlying molecular mechanism. We placed male Wistar rats on HS (8% NaCl) or normal salt diet (0.3% NaCl). Then, we injected bilateral PVN in rats with Gen, vehicle, or nicotinamide (NAM) for 4 weeks. Tail cuff was used weekly to assess the systolic pressure, diastolic pressure, and mean arterial pressure (MAP). Cardiac hypertrophy was analyzed by heart weight/body weight ratio and wheat germ agglutinin staining. ELISA kits, Western blot, or dihydroethidium staining determined the levels of inflammatory cytokines and oxidative stress markers. Western blot measured protein levels of Sirt1, Ac-FOXO1, Nrf2, NQO-1, HO-1, and gp91^phox. Our result showed that PVN infusion of Gen significantly reduced the increase of systolic pressure, diastolic pressure, and MAP induced by an HS diet. Additionally, there was a decrease in cardiac hypertrophy and the levels of inflammatory cytokines in PVN and plasma. Meanwhile, PVN infusion of Gen notably inhibited the levels of oxidized glutathione and superoxide dismutase and improved the glutathione level and total antioxidant capacities and superoxide dismutase activities. It also decreased the level of reactive oxygen species and gp91^phox expression in PVN. Furthermore, Gen infusion markedly increases the Sirt1, Nrf2, HO-1, and NQO-1 levels and decreases the Ac-FOXO1 level. However, PVN infusion of NAM could significantly block these changes induced by Gen in HS diet rats. Our results demonstrated that PVN infusion of Gen could inhibit the progression of hypertension induced by an HS diet by activating the Sirt1/Nrf2 pathway.

Blockade of Microglial Activation in Hypothalamic Paraventricular Nucleus Improves High Salt-Induced Hypertension

BACKGROUND

It has been shown that activated microglia in brain releasing proinflammatory cytokines (PICs) contribute to the progression of cardiovascular diseases. In this study, we tested the hypothesis that microglial activation in hypothalamic paraventricular nucleus (PVN), induced by high-salt diet, increases the oxidative stress via releasing PICs and promotes sympathoexcitation and development of hypertension.

METHODS

High-salt diet was given to male Dahl salt-sensitive rats to induce hypertension. Those rats were bilaterally implanted with cannula for PVN infusion of minocycline, a selective microglial activation blocker, or artificial cerebrospinal fluid for 4 weeks.

RESULTS

High-salt diet elevated mean arterial pressure of Dahl salt-sensitive rats. Meanwhile, elevations of renal sympathetic nerve activity and central prostaglandin E2, as well as increase of plasma norepinephrine, were observed in those hypertensive rats. Tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6 increased in the PVN of those rats, associated with a significant activation of microglia and prominent disruption of redox balance, which was demonstrated by higher superoxide and NAD(P)H oxidase 2 (NOX-2) and NAD(P)H oxidase 4 (NOX-4), and lower Cu/Zn superoxide dismutase in PVN. PVN infusion of minocycline attenuated all hypertension-related alterations described above.

CONCLUSION

This study indicates that high salt leads to microglial activation within PVN of hypertensive rats, and those activated PVN microglia release PICs and trigger the production of reactive oxygen species, which contributes to sympathoexcitation and development of hypertension. Blockade of PVN microglial activation inhibits inflammation and oxidative stress, therefore attenuating the development of hypertension induced by high-salt diet.

The Protective Effect of α-Lipoic Acid against Gold Nanoparticles (AuNPs)-Mediated Liver Damage Is Associated with Upregulating Nrf2 and Suppressing NF-κB

This study examined if regulating the keap-1? Nrf2 antioxidant pathway mediated gold nanoparticles (AuNPs) induced liver damage, and examined the protective effect of co-supplement of α-lipoic acid (α-LA). Rats were separated into 4 groups (n = 8/each) as control, α-LA (200 mg/kg), AuNPs (5 µg/2.85 × 10¹¹), and AuNPs (5 µg/2.85 × 10¹¹) + α-LA (200 mg/kg). After 7 days, AuNPs induced severe degeneration in the livers of rats with the appearance of some fatty changes. In addition, it increased serum levels of alanine aminotransferase (ALT) and gamma-glutamyl transferase (ɣ-GTT), and aspartate aminotransferase (AST), as well as liver levels of malondialdehyde (MDA). Concomitantly, AuNPs significantly depleted hepatic levels of total glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) but increased hepatic levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). It also reduced mRNA levels of B-cell lymphoma 2 (Bcl2) and heme oxygenase-1 (HO-1) but significantly increased those of Bax and cleaved caspase-3, as well as the ratio of Bax/Bcl2. In addition, AuNPs enhanced the total and nuclear levels of NF-κB p65 but reduced the mRNA and total and nuclear protein levels of Nrf2. Of note, AuNPs did not affect the mRNA levels of keap-1. All these events were reversed by α-LA in the AuNPs-treated rats. In conclusion, α-LA attenuated AuNPs-mediated liver damage in rats by suppressing oxidative stress and inflammation, effects that are associated with upregulation/activation of Nrf2.

Inhibition of Microbiota-dependent Trimethylamine N-Oxide Production Ameliorates High Salt Diet-Induced Sympathetic Excitation and Hypertension in Rats by Attenuating Central Neuroinflammation and Oxidative Stress

Excessive dietary salt intake induces neuroinflammation and oxidative stress in the brain, which lead to sympathetic excitation, contributing to hypertension. However, the underlying mechanisms remain elusive. Accumulating evidence reveals that trimethylamine-N-oxide (TMAO), a gut microbiota-derived metabolite, is implicated in the pathogenesis of multiple cardiovascular diseases. The present study sought to determine whether central TMAO is elevated and associated with neuroinflammation and oxidative stress in the brain after long-term high salt (HS) diet intake and, if so, whether inhibition of TMAO generation ameliorates HS-induced sympathetic excitation and hypertension. Sprague-Dawley rats were fed either a HS diet or a normal salt (NS) diet and simultaneously treated with vehicle (VEH) or 1.0% 3,3-Dimethyl-1-butanol (DMB, an inhibitor of trimethylamine formation) for 8 weeks. HS + VEH rats, compared with NS + VEH rats, had elevated TMAO in plasma and cerebrospinal fluid (CSF), increased blood pressure (BP), and increased sympathetic drive as indicated by the BP response to ganglionic blockade and plasma norepinephrine levels. HS-induced these changes were attenuated by DMB, which significantly reduced TMAO in plasma and CSF. Neuroinflammation as assessed by proinflammatory cytokine expression and NF-κB activity and microglial activity, and oxidative stress as measured by NAD(P)H oxidase subunit expression and NAD(P)H activity and reactive oxygen species (ROS) production in the hypothalamic paraventricular nucleus (PVN) were increased in HS + VEH rats but were decreased by DMB. DMB had no effects on above measured parameters in NS rats. The results suggest that long-term HS diet intake causes elevation in TMAO in the circulation and brain, which is associated with increased neuroinflammation and oxidative stress in the PVN, an important cardiovascular regulatory center. Inhibition of TMAO generation ameliorates HS-induced sympathetic excitation and hypertension by reducing neuroinflammation and oxidative stress in the PVN.

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.

Apigenin Improves Hypertension and Cardiac Hypertrophy Through Modulating NADPH Oxidase-Dependent ROS Generation and Cytokines in Hypothalamic Paraventricular Nucleus

Apigenin, identified as 4', 5, 7-trihydroxyflavone, is a natural flavonoid compound that has many interesting pharmacological activities and nutraceutical potential including anti-inflammatory and antioxidant functions. Chronic, low-grade inflammation and oxidative stress are involved in both the initiation and progression of hypertension and hypertension-induced cardiac hypertrophy. However, whether or not apigenin improves hypertension and cardiac hypertrophy through modulating NADPH oxidase-dependent reactive oxygen species (ROS) generation and inflammation in hypothalamic paraventricular nucleus (PVN) has not been reported. This study aimed to investigate the effects of apigenin on hypertension in spontaneously hypertensive rats (SHRs) and its possible central mechanism of action. SHRs and Wistar-Kyoto (WKY) rats were randomly assigned and treated with bilateral PVN infusion of apigenin or vehicle (artificial cerebrospinal fluid) via osmotic minipumps (20 μg/h) for 4 weeks. The results showed that after PVN infusion of apigenin, the mean arterial pressure (MAP), heart rate, plasma norepinephrine (NE), Beta 1 receptor in kidneys, level of phosphorylation of PKA in the ventricular tissue and cardiac hypertrophy, perivascular fibrosis, heart level of oxidative stress, PVN levels of oxidative stress, interleukin 1β (IL-1β), interleukin 6 (IL-6), iNOS, monocyte chemotactic protein 1 (MCP-1), tyrosine hydroxylase (TH), NOX2 and NOX4 were attenuated and PVN levels of interleukin 10 (IL-10), superoxide dismutase 1 (Cu/Zn-SOD) and the 67-kDa isoform of glutamate decarboxylase (GAD67) were increased. These results revealed that apigenin improves hypertension and cardiac hypertrophy in SHRs which are associated with the down-regulation of NADPH oxidase-dependent ROS generation and inflammation in the PVN.

Central Blockade of E-Prostanoid 3 Receptor Ameliorated Hypertension Partially by Attenuating Oxidative Stress and Inflammation in the Hypothalamic Paraventricular Nucleus of Spontaneously Hypertensive Rats

Hypertension, as one of the major risk factors for cardiovascular disease, significantly affects human health. Prostaglandin E2 (PGE2) and the E3-class prostanoid (EP3) receptor have previously been demonstrated to modulate blood pressure and hemodynamics in various animal models of hypertension. The PGE2-evoked pressor and biochemical responses can be blocked with the EP3 receptor antagonist, L-798106 (N-[(5-bromo-2methoxyphenyl)sulfonyl]-3-[2-(2-naphthalenylmethyl) phenyl]-2-propenamide). In the hypothalamic paraventricular nucleus (PVN), sympathetic excitation can be introduced by PGE2, which can activate EP3 receptors located in the PVN. In such a case, the central knockdown of EP3 receptor can be considered as a potential therapeutic modality for hypertension management. The present study examined the efficacy of the PVN infusion of L-798106, by performing experiments on spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKYs). The rats were administered with chronic bilateral PVN infusion of L-798106 (10 μg/day) or the vehicle for 28 days. The results indicated that the SHRs had a higher mean arterial pressure (MAP), an increased Fra-like (Fra-LI) activity in the PVN, as well as a higher expression of gp91phox, mitogen-activated protein kinase (MAPK), and proinflammatory cytokines in the PVN compared with the WKYs. Additionally, the expression of Cu/Zn-SOD in the PVN of the SHRs was reduced compared with the WKYs. The bilateral PVN infusion of L-798106 significantly reduced MAP, as well as plasma norepinephrine (NE) levels in the SHRs. It also inhibited Fra-LI activity and reduced the expression of gp91phox, proinflammatory cytokines, and MAPK, whereas it increased the expression of Cu/Zn-SOD in the PVN of SHRs. In addition, L-798106 restored the balance of the neurotransmitters in the PVN. On the whole, the findings of the present study demonstrate that the PVN blockade of EP3 receptor can ameliorate hypertension and cardiac hypertrophy partially by attenuating ROS and proinflammatory cytokines, and modulating neurotransmitters in the PVN.

Effects of Aqueous Extract of Lycopersicum esculentum L. var. “Camone” Tomato on Blood Pressure, Behavior and Brain Susceptibility to Oxidative Stress in Spontaneously Hypertensive Rats

Behavioral disorders affect millions of people worldwide. Hypertension contributes to both the development and progression of brain damage and cognitive dysfunction and could represent the most powerful modifiable risk factor for cerebral vessel dysfunction and consequent behavioral impairment. Tomato contains antioxidants and bioactive molecules that might play an important role in the prevention of cardiovascular and brain diseases. The effects of the combined gel and serum from Lycopersicum esculentum L. var. “Camone” tomatoes and those of purified tomato glycoalkaloids (tomatine) and an antihypertensive drug (captopril) were investigated in male spontaneously hypertensive rats (SHRs) and compared with normotensive Wistar Kyoto (WKY) rats. Body weight, systolic blood pressure, behavioral parameters, as well as brain susceptibility to oxidative stress and brain cytokine contents, were assessed. Treating hypertensive rats with tomato gel/serum or captopril for four weeks caused a significant reduction in blood pressure, decreased locomotor activity and increased grooming behavior; the last two parameters were also significantly affected by tomatine treatment. Brain slices obtained from hypertensive rats treated with tomato gel/serum were more resistant to oxidative stress and contained lower levels of inflammatory cytokines than vehicle-treated ones. In contrast, tomatine treatment had no effect. In conclusion, the tomato-derived gel/serum can be considered a dietary supplement able to drive in vivo blood pressure towards healthier values and also control some central effects such as behavior and brain oxidative stress.

Chronic Infusion of Astaxanthin Into Hypothalamic Paraventricular Nucleus Modulates Cytokines and Attenuates the Renin-Angiotensin System in Spontaneously Hypertensive Rats

ABSTRACT

Oxidative stress, the renin-angiotensin system (RAS), and inflammation are some of the mechanisms involved in the pathogenesis of hypertension. The aim of this study is to examine the protective effect of the chronic administration of astaxanthin, which is extracted from the shell of crabs and shrimps, into hypothalamic paraventricular nucleus (PVN) in spontaneously hypertensive rats. Animals were randomly assigned to 2 groups and treated with bilateral PVN infusion of astaxanthin or vehicle (artificial cerebrospinal fluid) through osmotic minipumps (Alzet Osmotic Pumps, Model 2004, 0.25 μL/h) for 4 weeks. Spontaneously hypertensive rats had higher mean arterial pressure and plasma level of norepinephrine and proinflammatory cytokine; higher PVN levels of reactive oxygen species, NOX2, NOX4, IL-1β, IL-6, ACE, and AT1-R; and lower PVN levels of IL-10 and Cu/Zn SOD, Mn SOD, ACE2, and Mas receptors than Wistar-Kyoto rats. Our data showed that chronic administration of astaxanthin into PVN attenuated the overexpression of reactive oxygen species, NOX2, NOX4, inflammatory cytokines, and components of RAS within the PVN and suppressed hypertension. The present results revealed that astaxanthin played a role in the brain. Our findings demonstrated that astaxanthin had protective effect on hypertension by improving the balance between inflammatory cytokines and components of RAS.

Deciphering the Mechanism of the Anti-Hypertensive Effect of Isorhynchophylline by Targeting Neurotransmitters Metabolism of Hypothalamus in Spontaneously Hypertensive Rats

Essential hypertension is a major risk factor for cardiovascular disease that can lead eventually to structural and functional alterations in the brain. Accumulating evidence has suggested that the increased activities in renin-angiotensin system and sympathetic nerve participated in the pathogenesis of hypertension that is related to the imbalance between neurotransmitters. The potential role in essential hypertension arising from alterations of neurotransmitters in the central nervous system remains understudied. Isorhynchophylline is a major oxindole alkaloid extracted from Uncaria rhynchophylla, which has been widely used for treating hypertension and neurodegenerative diseases. Whether isorhynchophylline acts on neurotransmitters to lower blood pressure has been hypothesized but rarely demonstrated unequivocally. Here, we studied the metabolic neurotransmitter profiles in the hypothalamus using a targeted metabolomic approach in spontaneously hypertensive rats after isorhynchophylline intervention. Our study demonstrated that isorhynchophylline exhibited a strong anti-hypertensive effect in spontaneously hypertensive rats by improving the neurotransmitter imbalance in the hypothalamus and inhibiting the overactivation of the renin-angiotensin system and sympathetic nerve system. Overall, this study played an essential role in enhancing our understanding of the mechanism of isorhynchophylline in essential hypertension and in providing theoretical evidence for future research and clinical application.

Antihypertensive, cardio- and neuro-protective effects of Tenebrio molitor (Coleoptera: Tenebrionidae) defatted larvae in spontaneously hypertensive rats

In pre-hypertension, moderate control of blood pressure (BP) can be obtained by a nutritional approach. The effects of a diet enriched with defatted larvae of the mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) (TM) endowed with ACE inhibitory activity was studied in both spontaneously hypertensive rats (SHR) and in the age-matched normotensive Wistar Kyoto strain. These were fed for 4 weeks with standard laboratory rodent chow supplemented with or without TM or captopril. In SHR, the TM diet caused a significant reduction in BP, heart rate and coronary perfusion pressure, as well as an increase in red blood cell glutathione/glutathione disulphide ratio. Rat brain slices of SHR were more resistant to oxidative stress and contained lower levels of inflammatory cytokines, while vascular and liver enzyme-activities were not affected. These results suggest that TM can be considered a new functional food that can lower BP in vivo and thus control cardiovascular-associated risk factors such as hypertension.

Irisin lowers blood pressure by activating the Nrf2 signaling pathway in the hypothalamic paraventricular nucleus of spontaneously hypertensive rats

Exercise training is one of the major non-pharmacological treatments for hypertension. However, the central mechanism by which exercise training attenuates the hypertensive responses remains unclear. Irisin is a muscle-secreted cytokine derived from fibronectin type III domain containing 5 (FNDC5) that will be released into the circulation during exercise. We hypothesized that irisin may play a role in the blood pressure regulation by exercise. To examine the hypothesis, our study investigated the effect of irisin on hypertension and its central mechanism. The study was performed in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats. We found that intravenous injection of irisin effectively reduced blood pressure, plasma norepinephrine, paraventricular nucleus (PVN) levels of neuronal activation, oxidative stress and inflammation in SHRs. Moreover, irisin activated nuclear factor E2-related factor-2 (Nrf2) and restored the imbalance of neurotransmitters in the PVN. Our study also found PVN knockdown of Nrf2 abolished the protective effects of irisin on hypertension. These findings demonstrate irisin can improve hypertension via Nrf2-mediated antioxidant in the PVN.

Calcitriol ameliorated autonomic dysfunction and hypertension by down-regulating inflammation and oxidative stress in the paraventricular nucleus of SHR

The hypothalamic paraventricular nucleus (PVN) plays crucial roles in central cardiovascular regulation. Increasing evidence in humans and rodents shows that vitamin D intake is important for achieving optimal cardiovascular function. The purpose of this study was to investigate whether calcitriol, an active form of vitamin D, improves autonomic and cardiovascular function in hypertensive rats and whether PVN oxidative stress and inflammation are involved in these beneficial effects. Male spontaneously hypertensive rats (SHR) and normotensive control Wistar Kyoto (WKY) rats were treated with either calcitriol (40 ng/day) or vehicle (0.11 μL/h) through chronic PVN infusion for 4 weeks. Blood pressure and heart rate were recorded continuously by radiotelemetry. PVN tissue, heart and plasma were collected for molecular and histological analysis. Compared to WKY rats, SHR exhibited increased systolic blood pressure, sympathetic drive, and cardiac hypertrophy and remodeling. These were associated with higher mRNA and protein expression levels of high mobility box 1 (HMGB1), receptor for advanced glycation end products (RAGE), toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB), proinflammatory cytokines, NADPH oxidase subunit in the PVN. In addition, increased norepinephrine in plasma, elevated reactive oxygen species levels and activation of microglia in the PVN were also observed in SHR. Chronic calcitriol treatment ameliorated these changes but not in WKY rats. Our results demonstrate that chronic infusion of calcitriol in the PVN ameliorates hypertensive responses, sympathoexcitation and retains cardiovascular function in SHR. Reduced inflammation and oxidative stress within the PVN are involved in these calcitriol-induced effects.

Gut microbiota and neuroinflammation in pathogenesis of hypertension: A potential role for hydrogen sulfide

Inflammation and gut dysbiosis are hallmarks of hypertension (HTN). Hydrogen sulfide (H2S) is an important freely diffusing molecule that modulates the function of neural, cardiovascular and immune systems, and circulating levels of H2S are reduced in animals and humans with HTN. While most research to date has focused on H₂S produced endogenously by the host, H2S is also produced by the gut bacteria and may affect the host homeostasis. Here, we review an association between neuroinflammation and gut dysbiosis in HTN, with special emphasis on a potential role of H2S in this interplay.

Role of brain renin angiotensin system in neurodegeneration: An update

Renin angiotensin system (RAS) is an endocrine system widely known for its physiological roles in electrolyte homeostasis, body fluid volume regulation and cardiovascular control in peripheral circulation. However, brain RAS is an independent form of RAS expressed locally in the brain, which is known to be involved in brain functions and disorders. There is strong evidence for a major involvement of excessive brain angiotensin converting enzyme (ACE)/Angiotensin II (Ang II)/Angiotensin type-1 receptor (AT-1R) axis in increased activation of oxidative stress, apoptosis and neuroinflammation causing neurodegeneration in several brain disorders. Numerous studies have demonstrated strong neuroprotective effects by blocking AT1R in these brain disorders. Additionally, the angiotensin converting enzyme 2 (ACE2)/Angiotensin (1–7)/Mas receptor (MASR), is another axis of brain RAS which counteracts the damaging effects of ACE/Ang II/AT1R axis on neurons in the brain. Thus, angiotensin II receptor blockers (ARBs) and activation of ACE2/Angiotensin (1–7)/MASR axis may serve as an exciting and novel method for neuroprotection in several neurodegenerative diseases. Here in this review article, we discuss the expression of RAS in the brain and highlight how altered RAS level may cause neurodegeneration. Understanding the pathophysiology of RAS and their links to neurodegeneration has enormous potential to identify potentially effective pharmacological tools to treat neurodegenerative diseases in the brain.

Blockade of c-Src Within the Paraventricular Nucleus Attenuates Inflammatory Cytokines and Oxidative Stress in the Mechanism of the TLR4 Signal Pathway in Salt-Induced Hypertension

Toll-like receptor 4 (TLR4) and cellular Src (c-Src) are closely associated with inflammatory cytokines and oxidative stress in hypertension, so we designed this study to explore the exact role of c-Src in the mechanism of action of the TLR4 signaling pathway in salt-induced hypertension. Salt-sensitive rats were given a high salt diet for 10 weeks to induce hypertension. This resulted in higher levels of TLR4, activated c-Src, pro-inflammatory cytokines, oxidative stress, and arterial pressure. Infusion of a TLR4 blocker into the hypothalamic paraventricular nucleus (PVN) decreased the activated c-Src, while microinjection of a c-Src inhibitor attenuated the PVN levels of nuclear factor-kappa B, pro-inflammatory cytokines, and oxidative stress. Our findings suggest that a long-term high-salt diet increases TLR4 expression in the PVN and this promotes the activation of c-Src, which upregulates the expression of pro-inflammatory cytokines and results in the overproduction of reactive oxygen species. Therefore, inhibiting central c-Src activity may be a new target for treating hypertension.

Protective effect of Coleus forskohlii leaf-extract compound on progression of cataract against Fructose-Induced experimental cataract in rats

The present study was designed to determine protective effects of Coleus forskohlii hydroalcoholic leaf-extract along with its fractions against fructose-induced cataract rat model. The Coleus forskolii leaf extract was subjected to silica gel column chromatography and fractions were collected. A major high yielding fraction of the leaf extract, designated as fraction B6 was pharmacologically evaluated in Sprague Dawley albino rats at three doses 0.1, 1 and 10 mg/kg respectively. Compound B2; isolated from B6 fraction, identified as 'gallic acid' was also pharmacologically evaluated at three different doses. Cataract was induced by concurrent administration of fructose solution (10% w/v, per oral, dissolved in drinking water) for eight consecutive weeks. Mean arterial pressure, blood glucose level and lenticular opacity were determined. At the end of eight weeks, C. forskohlii leaf extract fraction and gallic acid reduced mean arterial pressure and glucose level in a dose dependent manner. In addition, C. forskohlii led to significant restoration of lens antioxidants enzyme level and reduced cataract formation in rats. These results showed the concentration dependent protective effect by C. forskohlii leaf extract against cataract formation due to restoration of oxidative stress markers.

Infiltrating T helper 17 cells in the paraventricular nucleus are pathogenic for stress-induced hypertension

Central neuroinflammation produced by both innate and adaptive immunities plays a major role in the development of stress-induced hypertension (SIH), but successful T cell immunoregulation for SIH requires that the T cells can access brain tissues. So far, both the effects of T helper 17 (Th17) cells on SIH and the pathway for T cells entry into the brain were unknown. Here we show that the blood pressure (BP), heart rate (HR) and the norepinephrine(NE) of the SIH rats were considerably higher, the numbers of Th17 cells and IL-17 were higher, relative to control. Anti-IL-17 attenuated the elevation of BP and HR of the SIH rats when microinjected into the paraventricular nucleus (PVN).Alb-FITC, after infusion into the carotid artery, were found in the brain parenchyma of the PVN in the SIH rats. We concluded that Th17 cells infiltrated the parenchyma of the paraventricular nucleus (PVN) via a compromised blood brain barrier (BBB) in response to stress and Th17 cells and IL-17 play an important role in the pathophysiology of SIH.

Neuroinflammation in hypertension: the renin-angiotensin system versus pro-resolution pathways

Overstimulation of the pro-inflammatory pathways within brain areas responsible for sympathetic outflow is well evidenced as a primary contributing factor to the establishment and maintenance of neurogenic hypertension. However, the precise mechanisms and stimuli responsible for promoting a pro-inflammatory state are not fully elucidated. Recent work has unveiled novel compounds derived from omega-3 polyunsaturated fatty acids (ω-3 PUFAs), termed specialized pro-resolving mediators (SPMs), which actively regulate the resolution of inflammation. Failure or dysregulation of the resolution process has been linked to a variety of chronic inflammatory and neurodegenerative diseases. Given the pathologic role of neuroinflammation in the hypertensive state, SPMs and their associated pathways may provide a link between hypertension and the long-standing association of dietary ω-3 PUFAs with cardioprotection. Herein, we review recent progress in understanding the RAS-driven pathophysiology of neurogenic hypertension, particularly in regards to the chronic low-grade neuroinflammatory response. In addition, we examine the potential for an impaired resolution of inflammation process in the context of hypertension.

Silencing salusin β ameliorates heart failure in aged spontaneously hypertensive rats by ROS-relative MAPK/NF-κB pathways in the paraventricular nucleus

OBJECTIVE

Sustained hypertension is a major cause of heart failure in aging hypertensive patients. Salusin β, a novel bioactive peptide of 20 amino acids, has been reported to participate in various cardiovascular diseases, including hypertension. We therefore hypothesized that central knockdown of salusin β might be effective for hypertension-induced heart failure treatment.

METHODS AND RESULTS

Eighteen-month-old male aged spontaneously hypertensive rats (SHR) with heart failure and WKY rats were microinjected with either a specific adenoviral vector encoding salusin β shRNA (Ad-Sal-shRNA) or a scramble shRNA (Ad-Scr-shRNA) in the hypothalamic paraventricular nucleus (PVN) for 4 weeks. Radiotelemetry and echocardiography were used for measuring blood pressure and cardiac function, respectively. Blood samples and heart were harvested for evaluating plasma norepinephrine, tyrosine hydroxylase, and cardiac morphology, respectively. The mesenteric arteries were separated for measurement of vascular responses. The PVN was analyzed for salusin β, proinflammatory cytokines (PICs), mitogen-activated protein kinase (MAPK), NF-κB, and reactive oxygen species (ROS) levels. Compared with normotensive rats, aging SHR with heart failure had dramatically increased salusin β expression. Silencing salusin β with Ad-Sal-shRNA attenuated arterial pressure and improved autonomic function, cardiac and vascular dysfunction in aging SHR with heart failure, but not in aging WKY rats. Knockdown of salusin β significantly reduced paraventricular nucleus PICs levels, MAPK and NF-κB activity, and ROS levels in aging SHR with heart failure.

CONCLUSION

These data demonstrate that in aging SHR, the heart failure that was developed during the end stage of hypertension could be ameliorated by silencing salusin β.

Superoxide via Sp3 mechanism increases renal renin activity, renal AT1 receptor function, and blood pressure in rats

We tested a hypothesis that superoxide, by inducing Sp3, increases renal renin activity, renal angiotensin II type 1 receptor (AT1R) function, and blood pressure (BP) in rats. Group 1 rats were treated with vehicle, saline. Group 2 rats were treated with superoxide dismutase (SOD) inhibitor diethylthiocarbamate (DETC). Group 3 rats were treated with DETC and an SOD mimetic, tempol. Group 4 rats were treated with tempol only. All four groups of rats were treated for 2 wk then anesthetized, and BP was recorded. Thereafter, diuresis and natriuresis in response to AT1R blocker candesartan were determined. When compared with vehicle rats, BP increased in DETC rats. The increased BP in DETC rats decreased with tempol. Diuresis and natriuresis in response to candesartan increased in controls, and this further increased in DETC rats and decreased with tempol. A second set of four groups of rats underwent the same treatment as above and were anesthetized, and their kidneys were obtained for biochemical studies. The levels of superoxide but not hydrogen peroxide increased, whereas SOD activities decreased further in the renal cortical tissues of DETC rats than vehicle rats. These effects were attenuated with tempol in DETC rats. Moreover, tissue renin activity and abundance of membranous AT1R proteins increased more in DETC rats than vehicle rats, and decreased with tempol in DETC rats. Furthermore, the levels of lysine-acetylated, but not serine-phosphorylated, Sp3 increased more in the nuclei of DETC rats than vehicle rats. The increased levels of Sp3 lysine acetylation decreased in DETC rats with tempol. Taken together, our results suggest that superoxide activates renal Sp3 via lysine acetylation increasing renin activity, AT1R function, and BP in rats.

Mitochondria and Reactive Oxygen Species Contribute to Neurogenic Hypertension

Beyond its primary role as fuel generators, mitochondria are engaged in a variety of cellular processes, including redox homeostasis. Mitochondrial dysfunction, therefore, may have a profound impact on high-energy-demanding organs such as the brain. Here, we review the roles of mitochondrial biogenesis and bioenergetics, and their associated signaling in cellular redox homeostasis, and illustrate their contributions to the oxidative stress-related neural mechanism of hypertension, focusing on specific brain areas that are involved in the generation or modulation of sympathetic outflows to the cardiovascular system. We also highlight future challenges of research on mitochondrial physiology and pathophysiology.

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.

Therapeutic potential of α-lipoic acid derivative, sodium zinc histidine dithiooctanamide, in a mouse model of allergic rhinitis

BACKGROUND

Oxidative stress is involved in various diseases, including allergies. Several studies have pointed to the preventive and therapeutic potential of antioxidants in allergic disorders. However, little is known about the immunomodulatory effects of antioxidants in type I hypersensitivity. In this study we aimed to explore the impact of a water-soluble antioxidant and α-lipoic acid derivative, sodium zinc histidine dithiooctanamide (DHL-HisZn), on mast-cell- and T-cell-mediated allergic and immune responses both in vitro and in vivo.

METHODS

The therapeutic impact of DHL-HisZn on mast-cell-mediated type I hypersensitivity was evaluated by a mast-cell degranulation assay using bone marrow-derived mast cells and by a mouse model of ovalbumin (OVA)-induced allergic rhinitis. The effect of DHL-HisZn on the proportion of regulatory T cells (Tregs) was evaluated using flow cytometry.

RESULTS

During the course of OVA-induced allergic rhinitis in mice, serum nitrate was elevated, suggesting the involvement of oxidative stress in allergic responses. DHL-HisZn not only suppressed mast-cell degranulation but also ameliorated OVA-induced nasal hypersensitivity, with significant suppression of serum nitrate. DHL-HisZn treatment significantly suppressed OVA-specific immunoglobulin E (IgE) but enhanced OVA-specific IgG2a in OVA-sensitized and nasal-challenged mice. Furthermore, DHL-HisZn treatment suppressed interleukin-17 production in OVA-stimulated splenocytes. Finally, we demonstrated the induction of Tregs by DHL-HisZn in concanavalin A blasts.

CONCLUSIONS

These findings suggest that DHL-HisZn may regulate mast-cell-, T-helper 2 (Th2)-, and Th17-mediated allergic and immune responses by induction of Tregs.

Tert-butylhydroquinone attenuates oxidative stress and inflammation in hypothalamic paraventricular nucleus in high salt-induced hypertension

Excessive oxidative stress and inflammation in hypothalamic paraventricular nucleus (PVN) are implicated in the pathogenesis of hypertension. It is reported that tert-butylhydroquinone (tBHQ), a nuclear factor erythroid 2-related factor 2(Nrf2)-inducer, has a variety of pharmacological activities such as anti-oxidation and anti-inflammatory effect. The objective of this study was to investigate the effects of tBHQ in high salt induced hypertension and to identify whether the beneficial effects were induced by inhibiting PVN oxidative stress and inflammation. Male Sprague-Dawley rats were fed with high salt diet (HS, 8% NaCl) or normal salt diet (NS, 0.3% NaCl). These rats were administration of tBHQ (150mg/kg/d) by oral gavage for 16 weeks. Our results showed that high salt intake resulted in higher mean arterial pressure, cardiac hypertrophy as well as increased plasma level of norepinephrine and interleukin (IL)-1β, IL-6 compared with NS rats. It increased PVN level of reactive oxygen species, gp91^phox, IL-1β, IL-6, p-IKKβ and nuclear factor-kappa B (NF-κB) activity, decreased PVN level of Nrf2 and Cu/Zn-SOD. Chronic administration of tBHQ significantly attenuated these changes in HS rats. These data suggest that the protective effects of tBHQ in salt induced hypertension are partly due to inhibiting oxidative stress and inflammation in PVN.

Central administration of tert-butylhydroquinone attenuates hypertension via regulating Nrf2 signaling in the hypothalamic paraventricular nucleus of hypertensive rats

Reactive oxygen species (ROS) in the paraventricular nucleus (PVN) play a pivotal role in the pathogenesis of hypertension. Nuclear factor E2-related factor-2 (Nrf2) is an important transcription factor that modulates cell antioxidant defense response against oxidative stress. The present study aimed to explore the efficacy of PVN administration of tert-butylhydroquinone (tBHQ), a selective Nrf2 activator, in hypertensive rats. 16-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were used in this study. These rats were chronic bilateral PVN infusion of tBHQ (0.8μg/day), or oxygen free radical scavenger tempol (20μg/h), or vehicle for 2weeks. SHR rats had higher mean arterial pressure (MAP), plasma norepinephrine (NE) levels, and sympathetic nerve activity (RSNA) and lower PVN levels of Nrf2, hemeoxygenase-1 (HO-1), superoxide dismutase-1 (SOD1) and catalase (CAT) as compared with those in the WKY group. Bilateral PVN infusion of tBHQ or tempol significantly reduced MAP, RSNA, plasma NE levels in SHR rats. In addition, tBHQ treatment enhanced the nuclear accumulation of Nrf2 and increased the expression of HO-1, CAT and SOD1 in SHR rats. Furthermore, tBHQ attenuated PVN levels of ROS, the expression of proinflammatory cytokines and restored the imbalance of neurotransmitters in PVN. Knockdown of Nrf2 in the PVN by adeno-associated virus mediated small interfering RNA abrogated the protective effects of tBHQ on hypertension. These findings suggest that PVN administration of tBHQ can attenuate hypertension by activation of the Nrf2-mediated signaling pathway.

Does Alpha-lipoic Acid Supplement Regulate Blood Pressure? A Systematic Review of Randomized, Double-blind Placebo-controlled Clinical Trials

Although several animal and human studies have investigated the effect of alpha-lipoic acid (ALA) on blood pressure (BP), these findings are inconsistent. This systematic review of randomized clinical trials was conducted to summarize the evidence on the effect of ALA on BP. PubMed, SCOPUS, and Google Scholar databases were searched based on MESH term (“Thioctic acid” in combination with “Hypertension” and “Blood pressure”) to identify related papers published up to December 2015. We summarized the results of the relevant studies in this review. In total, nine studies included in this review, seven parallel-designed trials and two crossover-designed trials. The results of parallel-designed studies are inconsistent. Five studies indicate no significant effects for ALA supplementation on BP, but two trials show effects on BP. Unlike parallel-designed trials, two crossover-designed trials have shown similar results and both report no effect for ALA on BP. Several studies investigated the effect of ALA on BP. Most of the papers show no significant effect for supplementation and the studies have shown that associations are limited. However, these findings are limited and there is a need for further and more accurate researches to be clarified.

Interaction between interleukin‑6 and angiotensin II receptor 1 in the hypothalamic paraventricular nucleus contributes to progression of heart failure

The association between interleukin‑6 (IL‑6) and angiotensin II receptor 1 (AT1‑R) in modulating the progression of heart failure (HF) remains to be fully elucidated. The aim of the present study was to investigate the mechanism of IL‑6 and AT1‑R in a model of HF induced by surgery. Male Sprague‑Dawley rats were randomly divided into five groups, including sham surgery and vehicle groups. The animals were treated for 4 weeks via paraventricular nucleus infusion with either vehicle, losartan (LOS; 200 µg/day), IL‑6 (1 µg/day) or LOS and IL‑6 together (LOS+IL‑6). The rats with HF had higher levels of IL‑6, corticotropin‑releasing hormone (CRH) and norepinephrine (NE), and a lower level of neuronal nitric oxide synthase (nNOS), compared with the rats in the sham surgery group. Treatment with LOS attenuated the decrease in nNOS and the increases in IL‑6, CRH and NE; whereas treatment with IL‑6 facilitated the lower expression of nNOS and higher expression levels of IL‑6, CRH and NE. No differences in the expression levels of nNOS, CRH or NE were found between the LOS group and LOS+IL‑6 group. The results of the study demonstrated that IL‑6 contributed to the progression of HF via the AT1‑R pathway.

Renin-angiotensin system acting on reactive oxygen species in paraventricular nucleus induces sympathetic activation via AT1R/PKCγ/Rac1 pathway in salt-induced hypertension

Brain renin-angiotensin system (RAS) could regulate oxidative stress in the paraventricular nucleus (PVN) in the development of hypertension. This study was designed to explore the precise mechanisms of RAS acting on reactive oxygen species (ROS) in salt-induced hypertension. Male Wistar rats were administered with a high-salt diet (HS, 8.0% NaCl) for 8 weeks to induced hypertension. Those rats were received PVN infusion of AT1R antagonist losartan (LOS, 10 μg/h) or microinjection of small interfering RNAs for protein kinase C γ (PKCγ siRNA) once a day for 2 weeks. High salt intake resulted in higher levels of AT1R, PKCγ, Rac1 activity, superoxide and malondialdehyde (MDA) activity, but lower levels of copper/zinc superoxide dismutase (Cu/Zn-SOD), superoxide dismutase (SOD) and glutathione (GSH) in PVN than control animals. PVN infusion of LOS not only attenuated the PVN levels of AT1R, PKCγ, Rac1 activity, superoxide and decreased the arterial pressure, but also increased the PVN antioxidant capacity in hypertension. PVN microinjection of PKCγ siRNA had the same effect on LOS above responses to hypertension but no effect on PVN level of AT1R. These results, for the first time, identified that the precise signaling pathway of RAS regulating ROS in PVN is via AT1R/PKCγ/Rac1 in salt-induced hypertension.

PVN Blockade of p44/42 MAPK Pathway Attenuates Salt-induced Hypertension through Modulating Neurotransmitters and Attenuating Oxidative Stress

The imbalance of neurotransmitters and excessive oxidative stress responses contribute to the pathogenesis of hypertension. In this study, we determined whether blockade of p44/42 MAPK pathway in the hypothalamic paraventricular nucleus (PVN) ameliorates the development of hypertension through modulating neurotransmitters and attenuating oxidative stress. Dahl salt-sensitive (S) rats received a high-salt diet (HS, 8% NaCl) or a normal-salt diet (NS, 0.3% NaCl) for 6 weeks and were treated with bilateral PVN infusion of PD-98059 (0.025 μg/h), a p44/42 MAPK inhibitor, or vehicle via osmotic minipump. HS resulted in higher mean arterial pressure (MAP) and Fra-like (Fra-LI) activity, and plasma and PVN levels of norepinephrine (NE), tyrosine hydroxylase (TH), NOX2 and NOX4, lower PVN levels of gamma-aminobutyric acid (GABA), copper/zinc superoxide dismutase (Cu/Zn-SOD) and the 67-kDa isoform of glutamate decarboxylase (GAD67), as compared with NS group. PD-98059 infusion reduced NE, TH, NOX2 and NOX4 in the PVN, and induced Cu/Zn-SOD and GAD67 in the PVN. It suggests that PVN blockade of p44/42 MAPK attenuates hypertension through modulating neurotransmitters and attenuating oxidative stress.

Superoxide increases angiotensin II AT1 receptor function in human kidney-2 cells

The redox-sensitive Sp family transcription factor has been linked to the regulation of angiotensin II type 1 receptor (AT1R). However, the exact mechanism of AT1R regulation in renal cells is poorly understood. We tested the specificity of reactive oxygen species (ROS), superoxide vs. hydrogen peroxide (H₂O₂), and the specific role of Sp3 transcription factor, if any, in the regulation of AT1R in human kidney cells (HK2 cells). Superoxide dismutase (SOD) inhibitor diethyldithiocarbamate (DETC), but not H₂O₂ treatment, increased fluorescence levels of superoxide probe dihydroethidium (DHE). H₂O_2, but not DETC, treatment increased the fluorescence of the H₂O₂-sensitive probe dichloro-dihydro-fluorescein (DCFH). These data suggest that SOD inhibition by DETC increases the superoxide but not H₂O₂ and exogenously added H₂O₂ is not converted to superoxide in renal cells. Furthermore, DETC, but not H₂O₂, treatment increased nuclear accumulation of Sp3, which was attenuated with the superoxide dismutase (SOD)-mimetic tempol. DETC treatment also increased AT1R mRNA and protein levels that were attenuated with tempol, whereas H₂O₂ did not have any effects on AT1R mRNA. Moreover, Sp3 overexpression increased, while Sp3 depletion by siRNA decreased, protein levels of AT1R. In addition, Sp3 siRNA in the presence of DETC decreased AT1R protein expression. Furthermore, DETC treatment increased the levels of cell surface AT1R as measured by biotinylation and immunofluorescence studies. Angiotensin II increased PKC activity in vehicle-treated cells that further increased in DETC-treated cells, which was attenuated by AT1R blocker candesartan and SOD-mimetic tempol. Taken together, our results suggest that superoxide, but not H₂O₂, via Sp3 up-regulates AT1R expression and function in the renal cells.

Inhibitory effects of alpha-lipoic acid on oxidative stress in the rostral ventrolateral medulla in rats with salt-induced hypertension

Oxidative stress in the rostral ventrolateral medulla (RVLM) plays an important role in the pathophysiology of hypertension. Alpha‑lipoic acid (ALA) is widely recognized for its potent superoxide inhibitory properties, and it can safely penetrate deep into the brain. The aim of this study was to explore whether ALA supplementation attenuates hypertensive responses and cardiac hypertrophy by decreasing the NAD(P)H oxidase (NOX)-derived overproduction of reactive oxygen species (ROS) in the mitochondria in the RVLM, and thus attenuating the development of salt‑induced hypertension. For this purpose, male Wistar rats were randomly divided into 2 groups and either fed a high-salt diet or not. After 8 weeks, the rats were either administered ALA or an equal volume of the vehicle for 8 weeks. The rats fed a high‑salt diet exhibited higher mean arterial pressure (MAP) and higher plasma noradrenaline (NE) levels, as well as cardiac hypertrophy, as evidence by the increased whole heart weight/body weight (WHW/BW) ratio, WHW/tibia length (TL) ratio and left‑ventricular weight (LVW)/TL ratio. Compared with the rats in the NS group, the rats in the HS group only exhibited increased levels of superoxide, NOX2, NOX4 and mitochondrial malondialdehyde (MDA), but also decreased levels of copper/zinc (Cu/Zn)-superoxide dismutase (SOD), mitochondrial SOD and glutathione (GSH) in the RVLM. The supplementation of ALA decreased MAP, plasma NE levels and the levels of cardiac hypertrophy indicators. It also decreased the levels of superoxide, NOX2, NOX4 and mitochondrial MDA, and increased the levels of Cu/Zn‑SOD, mitochondrial SOD and GSH in the RVLM compared with the rats fed a high-salt diet and not treated with ALA. On the whole, our findings indicate that long‑term ALA supplementation attenuates hypertensive responses and cardiac hypertrophy by decreasing the expression of NAD(P)H subunits (NOX2 and NOX4), increasing the levels of mitochondrial bioenergetic enzymes, and enhancing the intracellular antioxidant capacity in the RVLM during the development of hypertension.

Chronic infusion of epigallocatechin-3-O-gallate into the hypothalamic paraventricular nucleus attenuates hypertension and sympathoexcitation by restoring neurotransmitters and cytokines

Reactive oxygen species (ROS) in the brain are involved in the pathogenesis of hypertension. Epigallocatechin-3-O-gallate (EGCG), one of the active compounds in green tea, has anti-oxidant, anti-inflammatory and vascular protective properties. This study was designed to determine whether chronic infusion of EGCG into the hypothalamic paraventricular nucleus (PVN) attenuates ROS and sympathetic activity and delays the progression of hypertension by up-regulating anti-inflammatory cytokines, reducing pro-inflammatory cytokines (PICs) and decreasing nuclear factor-kappa B (NF-κB) activity, as well as restoring the neurotransmitters balance in the PVN of spontaneously hypertensive rats (SHR). Adult normotensive Wistar-Kyoto (WKY) rats and SHR received bilateral PVN infusion of EGCG (20μg/h) or vehicle via osmotic minipumps for 4 weeks. SHR showed higher mean arterial pressure, plasma proinflammatory cytokines and circulating norepinephrine (NE) levels compared with WKY rats. SHR also had higher PVN levels of the subunit of NAD(P)H oxidase (gp91^phox), ROS, tyrosine hydroxylase, and PICs; increased NF-κB activity; and lower PVN levels of interleukin-10 (IL-10) and 67kDa isoform of glutamate decarboxylase (GAD67) than WKY rats. PVN infusion of EGCG attenuated all these changes in SHR. These findings suggest that SHR have an imbalance between excitatory and inhibitory neurotransmitters, as well as an imbalance between pro- and anti-inflammatory cytokines in the PVN. Chronic inhibition of ROS in the PVN restores the balance of neurotransmitters and cytokines in the PVN, thereby attenuating hypertensive response and sympathetic activity.