The Future Challenge of Reactive Oxygen Species (ROS) in Hypertension: From Bench to Bed Side

Redox control of vascular biology

Redox control is lost when the antioxidant defense system cannot remove abnormally high concentrations of signaling molecules, such as reactive oxygen species (ROS). Chronically elevated levels of ROS cause oxidative stress that may eventually lead to cancer and cardiovascular and neurodegenerative diseases. In this review, we focus on redox effects in the vascular system. We pay close attention to the subcompartments of the vascular system (endothelium, smooth muscle cell layer) and give an overview of how redox changes influence those different compartments. We also review the core aspects of redox biology, cardiovascular physiology, and pathophysiology. Moreover, the topic-specific knowledgebase DES-RedoxVasc was used to develop two case studies, one focused on endothelial cells and the other on the vascular smooth muscle cells, as a starting point to possibly extend our knowledge of redox control in vascular biology.

Functional potato bioactive peptide intensifies Nrf2-dependent antioxidant defense against renal damage in hypertensive rats

Hypertension, which is known as a silent killer, is the second leading cause of kidney failure worldwide. Elevated blood pressure causes approximately 7.6 million deaths, which account for ~13.5% of the total deaths and will continue to rise. High blood pressure is the prime risk factor associated with complications in major organs, including the heart, brain and kidney. High blood pressure accelerates oxidative stress and thereby causes organ dysfunction through the production of reactive oxygen species. In this study, we investigated the renal-protective effects of the bioactive peptide IF from alcalase potato protein hydrolysate in spontaneously hypertensive rat kidney. Sixteen-week-old spontaneously hypertensive rats were divided into three groups (n = 6), and Sixteen-week-old Wistar Kyoto rats (n = 6) served as the control group. The rats were administered IF and captopril via oral gavage for 8 weeks and then sacrificed, and their kidneys were harvested. The kidney sections from the rats treated with IF showed restoration of the structure of the glomerulus and Bowman's capsule. The expression levels of Nrf2-mediated antioxidants were also increased, as confirmed by 4-hydroxynonenal immunohistochemical staining. The TUNEL assay revealed a significant reduction in the number of apoptotic cells in the IF-treated groups, which was consistent with the western blot results. Thus, the bioactive peptide IF exerts potential protective effects against hypertension-associated ROS-mediated renal damage via the Nrf2-dependent antioxidant pathway along the DJ-1 and AKT axes. Hence, we speculate that IF might have promising therapeutic effects on renal damage associated with hypertension.

Effect of experimentally induced hypertension on cerebellum of postmenopausal rat

Cerebellum seems to be a specific target for both the decrease of estrogen and hypertension in menopause. The aim of this study was to investigate the hypertension and menopause-induced changes in rat's cerebellar cortex and the possible mechanisms of these changes. Rats were divided into four groups: the sham-operated control (SC-group), the ovariectomized (OVX-group), the hypertensive (H-group), and the ovariectomized-hypertensive (OVX-H-group) group. The mean arterial pressure (MAP), serum nitric oxide (NO), lipid peroxides and antioxidant catalase enzyme levels were assayed. Cerebellar tissue homogenization for analysis of lipid peroxides, antioxidant catalase enzyme, tumor necrosis factor-α (TNF-α), and estradiol was done. Quantification of adrenomedullin (AM) and interleukin-10 (IL-10) mRNA was also done. Cerebella were processed for histological, immunohistochemical and transmission electron microscopic examination. In the OVX-group, insignificant structural and biochemical changes were observed compared with the SC-group apart from the significantly increased lipid peroxides and decreased NO and catalase levels in serum. The H-group showed an elevated lipid peroxides and TNF-α levels, reduced catalase level, numerous degenerated Purkinje cells, vacuolations of the neuropil, some axonal degeneration, and few ghosts in the granular cell layer (GL). However, in OVX-H-group, oxidative stress, inflammation, and cerebellar damage were exacerbated and cerebellar estrogen was reduced associated with reduction in GL thickness and decreased Purkinje cells number. Most axoplasms had degenerated neurofilaments with abnormal myelination. The immunoexpression of glial fibrillary acidic protein were significantly increased in both OVX-group and H-group and significantly decreased in OVX-H group. Gene expression of AM and IL-10 were increased in cerebellar tissues of H-group compared with the SC-group but it was significantly decreased in OVX-H-group compared with H-group. Taken together, postmenopausal rats with hypertension suffered from structural cerebellar changes than rats with only hypertension or estrogen deficiency separately due to augmentation of the increased oxidative stress markers and the proinflammatory cytokines (TNF-α) with down regulation of the anti-inflammatory cytokine (IL-10) and the blood pressure regulator, AM. These suggested that high blood pressure is a critical factor for postmenopausal cerebellum.

Genetic polymorphisms associated with reactive oxygen species and blood pressure regulation

Hypertension is the most prevalent cause of cardiovascular disease and kidney failure, but only about 50% of patients achieve adequate blood pressure control, in part, due to inter-individual genetic variations in the response to antihypertensive medication. Significant strides have been made toward the understanding of the role of reactive oxygen species (ROS) in the regulation of the cardiovascular system. However, the role of ROS in human hypertension is still unclear. Polymorphisms of some genes involved in the regulation of ROS production are associated with hypertension, suggesting their potential influence on blood pressure control and response to antihypertensive medication. This review provides an update on the genes associated with the regulation of ROS production in hypertension and discusses the controversies on the use of antioxidants in the treatment of hypertension, including the antioxidant effects of antihypertensive drugs.

Sex, Oxidative Stress, and Hypertension: Insights From Animal Models

One of the mechanisms responsible for blood pressure (BP) regulation is thought to be oxidative stress. In this review, we highlight preclinical studies that strongly support a role for oxidative stress in development and maintenance of hypertension in male animals, based on depressor responses to antioxidants, particularly tempol and apocynin. In females, oxidative stress seems to be important in the initial development of hypertension. However, whether maintenance of hypertension in females is mediated by oxidative stress is not clear. In clinical studies, pharmacological intervention to reduce BP with antioxidants has conflicting results, mostly negative. This review will discuss the uncertainties regarding blood pressure control and oxidative stress and potential reasons for these outcomes.

Oxidative stress in chronic kidney disease

Oxidative stress (OS), defined as disturbances in the pro-/antioxidant balance, is harmful to cells due to the excessive generation of highly reactive oxygen (ROS) and nitrogen (RNS) species. When the balance is not disturbed, OS has a role in physiological adaptations and signal transduction. However, an excessive amount of ROS and RNS results in the oxidation of biological molecules such as lipids, proteins, and DNA. Oxidative stress has been reported in kidney disease, due to both antioxidant depletions as well as increased ROS production. The kidney is a highly metabolic organ, rich in oxidation reactions in mitochondria, which makes it vulnerable to damage caused by OS, and several studies have shown that OS can accelerate kidney disease progression. Also, in patients at advanced stages of chronic kidney disease (CKD), increased OS is associated with complications such as hypertension, atherosclerosis, inflammation, and anemia. In this review, we aim to describe OS and its influence on CKD progression and its complications. We also discuss the potential role of various antioxidants and pharmacological agents, which may represent potential therapeutic targets to reduce OS in both pediatric and adult CKD patients.

Chronic Treatment With Acetylcholinesterase Inhibitors Attenuates Vascular Dysfunction in Spontaneously Hypertensive Rats

BACKGROUND

Acetylcholinesterase inhibition prevents autonomic imbalance, reduces inflammation, and attenuates the development of hypertension. Considering that vascular dysfunction is a crucial feature of arterial hypertension, we investigated the effects of chronic administration of acetylcholinesterase inhibitors-pyridostigmine or donepezil-on vascular reactivity of spontaneously hypertensive rats (SHR).

METHODS

Endothelium-dependent relaxant responses to acetylcholine (ACh) and contractile responses induced by electric field stimulation (EFS) and alpha-adrenergic agonist were studied in mesenteric resistance arteries from SHR and Wistar Kyoto rats. SHR were treated for 16 weeks with vehicle, pyridostigmine (1.5 mg/kg/day) or donepezil (1.4 mg/kg/day).

RESULTS

Pyridostigmine and donepezil decreased the vasoconstrictor responses to EFS, which were increased in vehicle-treated SHR. Acetylcholinesterase inhibition increased the modulatory effects of nitric oxide (NO) on SHR vascular reactivity, that is, N(ω)-nitro-(L)-arginine methyl ester (L-NAME) increased EFS-induced contractions and reduced ACh-induced relaxation, with more significant effects in pyridostigmine- and donepezil-treated SHR. The acetylcholinesterase inhibitors also decreased vascular reactive oxygen species levels.

CONCLUSIONS

This study demonstrates for the first time that long-term administration of acetylcholinesterase inhibitors, pyridostigmine or donepezil, attenuates vascular reactivity dysfunction in SHR by decreasing reactive oxygen species generation and increasing NO bioavailability; possibly via increased endothelial NO synthase activity, and inhibition of NADPH oxidase activity.

Oxidative stress and vascular stiffness in hypertension: A renewed interest for antioxidant therapies?

Since the first successful launch of the Veterans Administration(VA) cooperative studies in the late 1960s, the increasing access to blood pressure lowering medications has significantly contributed to improving longevity and quality of life in hypertensive patients. Since then, insights into the pathogenesis of hypertension have shown a mechanistic role for reactive oxygen species (ROS) in all phases of disease progression, suggesting the potential utility of antioxidant therapies to counteract symptoms and, at the same time, treat a fundamental mechanism of the disease. Despite these progresses, hypertension still remains the main contributor to the global incidence of cardiovascular disease and the leading cause of morbidity and mortality worldwide. We here briefly review and update the role of ROS and ROS-dependent metalloproteinase activation in the maladaptive remodeling of the vascular wall in hypertension. Such understanding should provide new Potential sites of action for antioxidant therapies as an integrated therapeutic approach to hypertension and its consequences.

γ-Pyrone compounds: flavonoids and maltol glucoside derivatives from Herniaria glabra L. collected in the Ternopil region of the Ukraine

The phytochemical investigation of the whole plant extracts of Herniaria glabra L. (Caryophyllaceae) led to the identification and isolation of four known flavonoids, one known and three undescribed maltol derivatives, and benzyl β-gentiobioside. The structures were established by extensive 1D and 2D NMR spectroscopic analyses, as well as HRESIMS data. For the first time in Herniaria genus, as well as in Caryophylaceae family the presence of apiorutin {quercetin 3-O-[(D-apio-β-d-furanosyl-(1 → 2)-O-[-α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside]} and licoagroside B {maltol 3-O-[6-O-(3-hydroxy-3-methylglutaroyl)]-β-d-glucopyranoside} were revealed. Additionally, antioxidant actions of apiorutin, rutin, narcissin (isorhamentin 3-O-β-d-rutinoside) and licoagroside B were assessed in human blood plasma, exposed to the peroxynitrite-induced oxidative stress in vitro. The isolates partly reduced oxidative (oxidation of thiol groups) and nitrative (tyrosine nitration) damage to blood plasma proteins, decreased plasma lipid peroxidation as well as enhanced the non-enzymatic antioxidant capacity of blood plasma. No cytotoxicity of the examined substances towards peripheral blood mononuclear cells was found.

Oxidative Stress: A Major Player in Cerebrovascular Alterations Associated to Neurodegenerative Events

The brain is one of the most exquisite organs in the body with high metabolic demands, and requires a tight regulation of the surrounding environment. This tight control is exerted by the neurovascular unit (NVU) comprising different cell types, where endothelial cells play the commander-in-chief role. Thus, it is assumable that even slight perturbations in NVU might affect, in some cases irreversibly, brain homeostasis and health. In this line, recent findings support the two-hit vascular hypothesis for neurodegenerative conditions, where vascular dysfunction underlies the development of neurodegenerative diseases, such as Alzheimer’s disease (AD). Knowing that endothelial cells are rich in mitochondria and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, two major reactive oxygen species (ROS) sources, this review aims to gather information on how oxidative stress is in the front line of vascular alterations observed in brain aging and neurodegenerative conditions, particularly AD. Also, a brief discussion about the therapeutic strategies aimed to protect against cerebrovascular diseases is included.

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.

Redox status of patients before cardiac surgery

Objectives: Redox regulation plays a crucial role in balancing the cardiovascular system. In this prospective study we aimed to identify currently unknown correlations valuable to cardiovascular research and patient management.

Methods: Blood samples from 500 patients were collected directly before cardiosurgical interventions (Ethics Committee reference number 85/11). Four central redox parameters were determined together with about 30 clinical, anthropometric, and metabolic parameters.

Results: Creatinine levels and pulmonary hypertension were significant predictors of the total antioxidant status (TAOS) in the patients; total glutathione levels were linked to C-peptide, and creatinine, gender, and ventricular arrhythmia influenced nitrate/nitrite levels. Notably, significant interactions were found between medication and redox parameters. Calcium channel blockers (CCBs) were positive predictors of total glutathione levels, whereas angiotensin-converting enzyme inhibitors and CCBs were negative predictors of NOx levels. Age showed the highest correlation with the duration of the intensive care stay, followed by NOx levels, creatinine, TAOS, and C-reactive protein.

Discussion: In this prospective study we determined multiple correlations between redox markers and parameters linked to cardiovascular diseases. The data point towards so far unknown interdependencies, particularly between antihypertensive drugs and redox metabolism. A thorough follow-up to these data has the potential to improve patient management.

Abbreviations: A: absorption; ΔA: absorption difference; ABTS: 2,2′-azino-di(3-ethylbenzothiazoline sulfonate); ACE: angiotensin-converting enzyme; AO: antioxidant; ARB: angiotensin receptor blocker; BMI: body mass index; CAD: coronary artery disease; CCB: calcium channel blocker; CDC: coronary heart diseases; COPD: chronic obstructive pulmonary disease; CRP: C-reactive protein; CVD: cardiovascular diseases; Cu-OOH: cumene hydroperoxide; D: dilution factor; DAN: 2,3-diaminonaphtalene; DMSO: dimethylsulfoxide; DNA: deoxyribonucleic acid; DTNB: 5,5-dithiobis(2-nitrobenzoate); ϵ: extinction coefficient; EDRF: endothelium-derived relaxing factor; fc: final concentration; GPx: glutathione peroxidases; (h)GR: (human) glutathione reductase; GSH: (reduced) glutathione; GSSG: glutathione disulfide; GST: glutathione-S-transferase; Hb: hemoglobin; HDL: high-density lipoprotein; Hk: hematocrit; H₂O₂: hydrogen peroxide; ICS: intensive care stay; LDH: lactate dehydrogenase; LDL: low-density lipoprotein; MI: myocardial infarction; NED: N-(1-naphthyl)-ethylendiamine-dihydrochloride; NOS: nitric oxide synthase; NOx: nitrate/nitrite; NR: nitrate reductase; PBS: phosphate buffered saline; PCA: principle component analysis; PH: pulmonary hypertension; ROS: reactive oxygen species; RNS: reactive nitrogen species; RT: room temperature (25°C); SA: sulfanilamide; SOD: superoxide dismutase; SSA: sulfosalicylic acid; TAC: total antioxidant capacity; TAOS: total antioxidant status; TEAC: trolox equivalent antioxidative capacity; TG: triglycerides; tGSH: total glutathione; TNB-: 2-nitro-5-thiobenzoate; U: unit; UV: ultraviolet; VA: volume activity; Wc: working concentration; WHR: waist-hip ratio.