Oxidative stress in juvenile essential hypertension

Systemic Inflammation, Oxidative Stress and Cardiovascular Health in Children and Adolescents: A Systematic Review

Recent studies indicate that cerebrovascular diseases and processes of atherosclerosis originate in the childhood era and are largely influenced by chronic inflammation. Some features of vascular dysfunction in adulthood may even be programmed prenatally via genetic influences and an unfavorable intrauterine milieu. Oxidative stress, defined by an imbalance between the production and generation of reactive oxygen species (ROS) in cells and tissues and the capability of an organism to scavenge these molecules via antioxidant mechanisms, has been linked to adverse cardiovascular health in adults, yet has not been systematically reviewed in the pediatric population. We performed a systematic search as per the PRISMA guidelines in PubMed/Medline and Cochrane Reviews and detected, in total, 1228 potentially eligible pediatric articles on systemic inflammation, oxidative stress, antioxidant use, cardiovascular disease and endothelial dysfunction. The abstracts and full-text manuscripts of these were screened for inclusion and exclusion criteria, and a total of 160 articles were included. The results indicate that systemic inflammation and oxidative stress influence cardiovascular health in many chronic pediatric conditions, including hypertension, obesity, diabetes mellitus types 1 and 2, chronic kidney disease, hyperlipidemia and obstructive sleep apnea. Exercise and diet may diminish ROS formation and enhance the total serum antioxidant capacity. Antioxidant supplementation may, in selected conditions, contribute to the diminution of the oxidative state and improve endothelial function; yet, in many areas, studies provide unsatisfactory results.

Inhibition effect of nicotinamide (vitamin B3) and reduced glutathione (GSH) peptide on angiotensin-converting enzyme activity purified from sheep kidney

Angiotensin-converting enzyme (ACE, EC 3.4.15.1) plays a significant role in blood pressure regulation and inhibition of this enzyme is one of the significant drug targets for the treatment of hypertension. In this work, ACE was purified from sheep kidneys with the affinity chromatography method in one step. The purity and molecular weight of ACE were designated using the SDS-PAGE method and observed two bands at around 60 kDa and 70 kDa on the gel. The effects of nicotinamide (vitamin B₃) and reduced glutathione (GSH) peptide on purified ACE were researched. Nicotinamide and GSH peptide on purified ACE showed an inhibition effect. IC₅₀ values for nicotinamide and GSH were calculated as 14.3 μM and 7.3 μM, respectively. Type of inhibition and K_i values for nicotinamide and GSH from the Lineweaver-Burk graph were determined. The type of inhibition for nicotinamide and GSH was determined as non-competitive inhibition. K_i value was calculated as 15.4 μM for nicotinamide and 6.7 μM for GSH. Also, GSH peptide showed higher inhibitory activity on ACE activity than nicotinamide. In this study, it was concluded that nicotinamide and GSH peptide compounds, which show an inhibition effect on ACE activity, may have both protective and therapeutic effects against hypertension.

Racial differences of early vascular aging in children and adolescents

The prevalence of non-communicable disease (NCDs) is rising globally, with a large burden recorded in sub-Saharan countries and populations of black race/ethnicity. Accelerated vascular deterioration, otherwise known as early vascular aging (EVA), is the underlying factor for highly prevalent NCDs such as hypertension. The etiology of EVA is multifactorial with a central component being arterial stiffness with subsequent development of hypertension and cardiovascular complications. Although arterial stiffness develops with increasing age, many children and adolescents are subjected to the premature development of arterial stiffness, due to genetic or epigenetic predispositions, lifestyle and behavioral risk factors, and early life programming. Race/ethnic differences in pediatric populations have also been reported with higher aortic stiffness in black (African American) compared with age-matched white (European American) counterparts independent of blood pressure, body mass index, or socioeconomic status. With known evidence of race/ethnic differences in EVA, the pathophysiological mechanisms underlying graded differences in the programming of EVA are still sparse and rarely explored. This educational review aims to address the early life determinants of EVA in children and adolescents with a particular focus on racial or ethnic differences.

Origins of Primary Hypertension in Children

Although relatively rare in childhood, primary hypertension (PH) is thought to have originated in childhood and may be even determined perinatally. PH prevalence increases in school-age children and affects 11% of 18-year-old adolescents. Associated with metabolic risk factors, elevated blood pressure in childhood is carried into adulthood. Analysis of the phenotype of hypertensive children has revealed that PH is a complex of anthropometric and neuro-immuno-metabolic abnormalities, typically found in hypertensive adults. Children with elevated blood pressure have shown signs of accelerated biological development, which are closely associated with further development of PH, metabolic syndrome, and cardiovascular disease in adulthood. At the time of diagnosis, hypertensive children were reported to have significant arterial remodelling expressed as significantly increased carotid intima-media thickness, increased stiffness of large arteries, lower area of microcirculation, and decreased endothelial function. These changes indicate that their biological age is 4 to 5 years older than their normotensive peers. All these abnormalities are typical features of early vascular aging described in adults with PH. However, as these early vascular changes in hypertensive children are closely associated with features of accelerated biological development and neuro-immuno-metabolic abnormalities observed in older subjects, it seems that PH in childhood is not only an early vascular aging event, but also an early biological maturation phenomenon.

Elevated blood pressure-associated cardiometabolic risk factors and biomarkers in 16-23 years old students with or without metabolic abnormalities

In obesity, cardiometabolic risk markers show worsening trends with increasing blood pressure (BP). We assumed that risk markers show similar trends across BP categories (normotension, high normal BP, hypertension) in metabolic abnormalities-free subjects (without obesity, insulin resistance, atherogenic dyslipidemia, hyperuricemia, microinflammation) and those presenting them. Data from 2547 (48.1% males) subjects aged 16-23 years were analyzed. The prevalence of males increased across BP categories. Forty-seven percent of individuals with elevated BP were metabolic abnormalities-free. Among 1461 metabolic abnormalities-free subjects, 9% had high normal BP, and 4% hypertension; among 1086 individuals presenting metabolic abnormalities, the prevalence reached 13% and 6%, respectively, (p < 0.001). Both groups displayed similar BP values in corresponding BP categories and significant trends in markers of adiposity, insulin resistance, HDL-cholesterol, atherogenic index of plasma, uric acid, adiponectinemia, and antioxidant capacity of plasma across BP categories. In metabolic abnormalities-free individuals, also significant trends in soluble receptors for advanced glycation end products were revealed. Continuous metabolic syndrome score, a measure of cardiometabolic risk, increased across BP categories regardless of presence or absence of metabolic abnormalities. Multivariate regression models selected male gender, fat-free mass, and uric acid as significant independent predictors for determining BP. Our data emphasize that having a BP outside the normal range significantly worsens risk for cardiometabolic disease in young individuals even if the thresholds for any of the risk factors are not exceeded. Longitudinal studies are needed to assess whether in patients with elevated BP the prognosis of adverse outcomes differs between those presenting and not presenting metabolic abnormalities.

Dietary Vitamin E Supplementation Attenuates Hypertension in Dahl Salt-Sensitive Rats

There is strong evidence that excess dietary salt (NaCl) is a major factor contributing to the development of hypertension. Salt-sensitive humans and rats develop hypertension even on a normal-salt diet. Salt sensitivity is associated with glucose intolerance and insulin resistance in both humans and animal models, including Dahl salt-sensitive (DSS) rats. In insulin resistance, impaired glucose metabolism leads to elevated endogenous aldehydes that bind sulfhydryl groups of membrane proteins, altering calcium channels, and increasing cytosolic free calcium ([Ca2+] i) and blood pressure. Vitamin E lowers tissue aldehyde conjugates, cytosolic [Ca2+] i, and blood pressure in spontaneously hypertensive rats and fructose-induced hypertensive Wistar Kyoto rats, models of insulin resistance. This study investigated the effect of a normal-salt diet on tissue aldehyde conjugates, cytosolic [Ca2+] i, and blood pressure in DSS rats and the effect of vitamin E supplementation on blood pressure and associated biochemical changes in these animals. Seven-week-old DSS rats were divided into 3 groups of 6 animals each and treated for 6 weeks with diets as follows: low-salt (0.4% NaCl); normal-salt (0.7% NaCl) and normal salt (0.7% NaCl) plus vitamin E (34 mg/kg feed). At completion, animals in the normal-salt group had significantly elevated systolic blood pressure, cytosolic [Ca2+] i, and tissue aldehyde conjugates compared with the low-salt group. They also showed smooth muscle cell hyperplasia in small arteries and arterioles of the kidney. Dietary vitamin E supplementation significantly attenuated the increase in systolic blood pressure and associated biochemical and histopathologic changes.

Vascular Aging: Lessons From Pediatric Hypertension

Hypertension (HTN) in children is associated with early vascular aging (EVA) and underlying immunologic-metabolic abnormalities and accelerated biological maturation. Morphologic and functional vascular changes underlying EVA and HTN in children resemble those seen in the elderly including but not limited to an increase in intima-media thickness (IMT) and arterial stiffness and endothelial dysfunction. Although progeria syndrome leading to EVA and the development of clinically manifested cardiovascular (CV) disease in the second decade of life is a rare hereditary disorder, primary HTN, which is also associated with EVA, is much more common (reported in up to 10% in adolescents). EVA associated with HTN in children leads to the premature development of target organ injury in childhood and CV events in early adulthood. Limited evidence from prospective observational studies in children and adolescents indicates that early lifestyle measures (low salt/low sugar intake and exercise) or pharmacologic treatment of HTN, or both, partially reverses morphologic and functional changes underlying EVA such as an increase in carotid IMT and pulse wave velocity, a decrease in flow-mediated dilation of the brachial artery, and an increase in oxidative stress and visceral fat. Future mechanistic and therapeutic clinical trials are desirable to assess the mechanisms and treatment strategies of EVA in the context of HTN in children and their effect on CV events in early adulthood.

Primary hypertension is a disease of premature vascular aging associated with neuro-immuno-metabolic abnormalities

There is an increasing amount of data indicating that primary hypertension (PH) is not only a hemodynamic phenomenon but also a complex syndrome involving abnormal fat tissue distribution, over-activity of the sympathetic nervous system (SNS), metabolic abnormalities, and activation of the immune system. In children, PH usually presents with a typical phenotype of disturbed body composition, accelerated biological maturity, and subtle immunological and metabolic abnormalities. This stage of the disease is potentially reversible. However, long-lasting over-activity of the SNS and immuno-metabolic alterations usually lead to an irreversible stage of cardiovascular disease. We describe an intermediate phenotype of children with PH, showing that PH is associated with accelerated development, i.e., early premature aging of the immune, metabolic, and vascular systems. The associations and determinants of hypertensive organ damage, the principles of treatment, and the possibility of rejuvenation of the cardiovascular system are discussed.

A sensitive method for the analysis of glutathione in porcine hepatocytes

BACKGROUND

Reduced glutathione (γ-glutamylcysteinylglycine), GSH, is essential when protecting cells from oxidative stress and also an indicator of disease risk. Reported concentrations of GSH and its oxidized form, glutathione disulfide (GSSG), varies considerably, primarily due to the instability of GSH and various analytical methods.

METHODS

We designed a sensitive method to analyze GSH and GSSG in porcine hepatocytes using liquid chromatography-tandem mass spectrometry (LC-MS/MS) after stabilization with N-ethylmaleimide (NEM). This method includes stable isotope labeled internal standards and simple synthesis of labeled GSSG which commercial sources rarely offer. GSH and GSSG were analyzed in porcine liver biopsies giving a reference interval based on a large number of samples (26 pigs; 3 parallels).

RESULTS

The LC-MS/MS results revealed excellent linearity for both GSH and GSSG, with interday coefficient of variation (%CV) for GSH-NEM and GSSG <10 %. Accuracy for recovery tests was between 95.6% and 106.7% (n = 3) for GSH and between 92.3% and 107.7% (n = 3) for GSSG. The limits of quantification were 0.1 μM for GSH-NEM and 0.08 μM for GSSG. The mean concentration of GSH was 3.5 (95% CI = 1.5-8.1) mmol/liter and of GSSG 0.0023 (95% CI = 0.0003-0.019) mmol/liter.

CONCLUSION

For the first time GSH and GSSG are analyzed in porcine hepatocytes by LC-MS/MS yielding a reference level of GSH and GSSG. The method is reproducible in any laboratory with LC-MS/MS service and will probably be applicable in all soft tissues and cell suspensions, essentially with no modification.

Lipid peroxidation, nitric oxide metabolites, and their ratio in a group of subjects with metabolic syndrome

Our aim was to evaluate lipid peroxidation, expressed as thiobarbituric acid-reactive substances (TBARS), nitric oxide metabolites (nitrite + nitrate) expressed as NOx, and TBARS/NOx ratio in a group of subjects with metabolic syndrome (MS). In this regard we enrolled 106 subjects with MS defined according to the IDF criteria, subsequently subdivided into diabetic (DMS) and nondiabetic (NDMS) and also into subjects with a low triglycerides/HDL-cholesterol (TG/HDL-C) index or with a high TG/HDL-C index. In the entire group and in the four subgroups of MS subjects we found an increase in TBARS and NOx levels and a decrease in TBARS/NOx ratio in comparison with normal controls. Regarding all these parameters no statistical difference between DMS and NDMS was evident, but a significant increase in NOx was present in subjects with a high TG/HDL-C index in comparison with those with a low index. In MS subjects we also found a negative correlation between TBARS/NO x ratio and TG/HDL-C index. Considering the hyperactivity of the inducible NO synthase in MS, these data confirm the altered redox and inflammatory status that characterizes the MS and suggest a link between lipid peroxidation, inflammation, and insulin resistance, evaluated as TG/HDL-C index.

Primary hypertension in children and adolescents is an immuno-metabolic disease with hemodynamic consequences

With the rise in obesity epidemic primary hypertension (PH) is now one of the most common chronic diseases in adolescence. In contrast to hypertensive adults, hypertensive children usually are not exposed to other comorbidities such as diabetes, chronic kidney disease and atherosclerosis. Thus, PH in children and adolescents can be treated as the early stage of development of cardiovascular disease. There is increasing amount of data indicating that PH is not only hemodynamic phenomenon but a complex syndrome involving disturbed activity of sympathetic nervous system, metabolic abnormalities and activation of innate and adaptive immune system. We discuss results of the studies on clinical, metabolic and immunological phenotype of hypertensive children, associations between metabolic and immunological abnormalities with target organ damage and results of antihypertensive treatment.

A new LC-MS/MS method for the clinical determination of reduced and oxidized glutathione from whole blood

Reduced levels of glutathione (γ-glutamylcysteinylglycine, GSH) and the ratio of GSH to glutathione disulfide (GSSG) can serve as important indicators of oxidative stress and disease risk. Measured concentrations of GSH and GSSG vary widely between laboratories, largely due to the instability of GSH during sample handling and variables arising from different analytical methods. We have developed a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for measuring whole blood GSH and GSSG that minimizes preanalytic and analytic variability, reliably eliminates interference from ion suppression, and can easily be implemented in clinical laboratories. Samples were deproteinized with sulfosalicylic acid (SSA) and derivatized with N-ethylmaleimide (NEM) in a single preparative step, and the resulting supernatants combined with stable-isotope internal standards (GSH-(13)C, (15)N-NEM and GSSG-(13)C,(15)N), subjected to chromatographic separation using a Hypercarb column, and analyzed by MS/MS in the positive-ion mode. Results showed excellent linearity for both GSH and GSSG over the ranges of physiologic normal, with inter- and intra-assay CV's of 3.1-4.3% and accuracy between 95% and 101%. The lower limits of detection (LLOD) were 0.4μM for GSH and 0.1μM for GSSG and the lower limits of quantitation (LLOQ) were 1.5μM for GSH and 0.1μM for GSSG. Derivatized samples are stable for at least 3 years when stored at -80°C, and underivatized samples for at least 24h at either 4°C or room temperature. Reference intervals were determined for 59 control samples, and were (mean±SD): GSH 900±140μM; GSSG 1.17±0.43μM; GSH/GSSG 880±370.

Role of the immune system in hypertension: modulation by dietary antioxidants

Hypertension is a major health problem worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease, and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Insulin resistance is a common feature of hypertension in both humans and animal models affecting glucose and lipid metabolism producing excess aldehydes including methylglyoxal. These aldehydes react with proteins to form conjugates called advanced glycation end products (AGEs). This alters protein structure and function and can affect vascular and immune cells leading to their activation and secretion of inflammatory cytokines. AGEs also act via receptors for advanced glycation end products on these cells altering the function of antioxidant and metabolic enzymes, and ion channels. This results in an increase in cytosolic free calcium, decrease in nitric oxide, endothelial dysfunction, oxidative stress, peripheral vascular resistance, and infiltration of vascular and kidney tissue with inflammatory cells leading to hypertension. Supplementation with dietary antioxidants including vitamins C, E, or B(6), thiols such as cysteine and lipoic acid, have been shown to lower blood pressure and plasma inflammatory cytokines in animal models and humans with essential hypertension. A well-balanced diet rich in antioxidants that includes vegetables, fruits, low fat dairy products, low salt, and includes whole grains, poultry, fish and nuts, lowers blood pressure and vascular inflammation. These antioxidants may achieve their antihypertensive and anti-inflammatory/immunomodulatory effects by reducing AGEs and improving insulin resistance and associated alterations. Dietary supplementation with antioxidants may be a beneficial, inexpensive, front-line alterative treatment modality for hypertension.

Non-alcoholic fatty liver disease and metabolic syndrome in adolescents: pathogenetic role of genetic background and intrauterine environment

In the last three decades the incidence of metabolic syndrome (MetS) has been growing worldwide along with an increase of obesity, type 2 diabetes mellitus, and non-alcoholic fatty liver disease (NAFLD). In children and adolescents such epidemics are particularly worrisome, since the metabolic consequences in adulthood will significantly burden the health care system. Although the definition of MetS in childhood is still controversial, there is agreement with respect to NAFLD being the hepatic manifestation of MetS. However, the molecular pathogenesis of MetS and its contribution to NAFLD is complex and closely related to the pre- and postnatal environment as well as to genetic predisposing factors. The analysis of the possible relationships between NAFLD and MetS is particularly interesting, not only from an epidemiological point of view, but also to better understand the genetic and environmental factors contributing to the development of both diseases. We here summarize the most recent epidemiological data on the incidence of both diseases in adolescents, and several aspects linking MetS with NAFLD, discussing the possible role played by genetics and intrauterine environment.

Oxidative stress in hypertensive children before and after 1 year of antihypertensive therapy

BACKGROUND

The relation between primary hypertension (PH), target organ damage (TOD) and oxidative stress (SOX) is not known.

METHODS

We assessed SOX in 86 children with PH before and after 12 months of standard non-pharmacological and pharmacological therapy based on renin-angiotensin system blockade.

RESULTS

Patients with left ventricular hypertrophy (LVH) and with carotid intima-media thickness (cIMT) >2SDS had higher thiobarbituric acid reactive substances (TBARS) concentrations in comparison to patients without LVH or with normal cIMT. Patients with metabolic syndrome (MS) had lower activity of gluthatione peroxidase, higher asymmetric dimethyloarginine (ADMA) and oxidized LDL cholesterol (oxyLDL) in comparison to patients without MS. TBARS correlated with left ventricular concentric hypertrophy, cIMT, albuminuria and SBP/24 h. ADMA and oxyLDL correlated with CRP and TG/HDL ratio. After 1 year of antihypertensive treatment blood pressure, TOD and prevalence of MS decreased. TBARS decreased and glutathione concentrations increased. The decrease of TBARS concentration correlated with the decrease of body mass index (BMI). Decrease of oxyLDL and ADMA correlated with increased insulin sensitivity, however markers of SOX did not correlate with BP decrease.

CONCLUSION

SOX in children with PH correlates with TOD, metabolic abnormalities, changes in fat amount and improvement of insulin sensitivity, but not with BP decrease.

Nontraditional risk factors and biomarkers for cardiovascular disease: mechanistic, research, and clinical considerations for youth: a scientific statement from the American Heart Association

The rapid increase in the prevalence and severity of obesity in children is likely to lower the age of onset and increase the incidence of cardiovascular disease worldwide. Understanding the pathophysiology and improving the clinical management of cardiovascular disease involve a knowledge of novel risk factors and biomarkers. The clinical and mechanistic roles of these novel biological factors during childhood are currently being investigated. The goals of this scientific statement are to present the existing knowledge and theoretical framework of nontraditional risk factors for cardiovascular disease as they relate to children and adolescents, to describe the relevance and weight of available experimental and clinical evidence and the therapeutic implications pertaining to nontraditional risk factors in the pediatric population, and to stimulate further research with a goal of developing valid and reliable approaches to identify and validate novel risk factors that will aid in the clinical evaluation and perhaps prediction of cardiovascular disease in the pediatric population. Although several biomarkers are promising, substantial research is required before nontraditional risk factors can be used to identify and reduce cardiovascular disease risk in children and adolescents.

Association between oxidative stress and masked hypertension in a multi-ethnic population of obese children and adolescents

OBJECTIVE

To evaluate whether oxidative stress is correlated with adiposity, obesity-related metabolic abnormalities, and ambulatory blood pressure (ABP) in a multi-ethnic pediatric population.

STUDY DESIGN

We conducted a prospective study enrolling 42 obese children (age, 12.8 ± 2.4 years) and 34 non-obese children (age, 11.8 ± 3.4 years). We measured urine 8-isoprostane and hydrogen peroxide (markers of oxidative stress) in both obese and non-obese groups. In the obese group, we measured the 24-hour ABP and obtained an oral glucose tolerance test, lipid panel, interleukin-6, and tumor necrosis factor-α.

RESULTS

8-isoprostane and hydrogen peroxide were correlated with body mass index standard deviation score and waist circumference. The mean 8-isoprostane and hydrogen peroxide levels of the obese group were higher than those of the non-obese group. In the subset of obese subjects who underwent ABP monitoring, 8-isoprostane was correlated with mean 24-hour systolic blood pressure: within the obese group, 8-isoprostane was higher in obese children with elevated mean 24-hour systolic blood pressure.

CONCLUSIONS

Our findings provide evidence of a significant correlation between oxidative stress, adiposity, and blood pressure in children. Longitudinal studies in a larger population sample are needed to validate the association between elevated urine 8-isoprostane level and cardiovascular risk factors in an obese pediatric population.

Microvascular reactivity in lean, overweight, and obese hypertensive adolescents

The microvascular responses to endothelium-dependent vasodilators (e.g., acetylcholine), endothelium-independent vasodilators (e.g., sodium nitroprusside), and to local heating were studied (for the first time) in adolescents with essential hypertension, grouped according to their body mass index. The forearm microvascular reactivities of thirty-three hypertensive adolescents (ten lean, 13 overweight, and ten obese) and 19 healthy controls were assessed by means of laser Doppler flowmetry. Blood levels of enzymatic and nonenzymatic antioxidants and malondialdehyde were determined. The perfusion increments in response to acetylcholine iontophoresis were not significantly attenuated in the patient groups as compared with the controls. Sodium nitroprusside (SNP) iontophoresis resulted in significantly smaller perfusion increments in the lean and obese hypertensives than in the controls (both p < 0.05). Similar responses to local heating (44°C) performed after either acetylcholine or SNP iontophoresis were observed at the respective measurement sites. As compared with the controls, we found elevated ratios of the whole blood oxidized and reduced glutathione in all the patient groups (all p < 0.001), increased erythrocyte catalase activities in the overweight hypertensives (p < 0.05), and decreased ratios of the plasma alpha-tocopherol and triglycerides in the obese hypertensive group (p < 0.05).

CONCLUSION

The endothelium-dependent microvascular reactivity was not significantly attenuated in the hypertensive adolescents in contrast with the impaired endothelium-independent vasorelaxation in the lean and obese hypertensives.

Biomarkers of inflammation and oxidative stress in atherosclerosis

Increasing evidence has highlighted the roles of oxidative stress and inflammation in the promotion of atherosclerotic cardiovascular disease. Recent pathological studies have elucidated specific mediators that appear to link these pathways to the progression and rupture of atherosclerotic plaque in the artery wall. The ability to measure levels of these mediators in the systemic circulation has provoked interest in their development as biomarkers for potential use in risk assessment and in evaluation of the response to the use of preventive therapies. The discovery of these pathological mediators and their potential translation to the clinical arena will be reviewed.

Diagnostic and Therapeutic Significance of the Oxidative Stress Parameters in Children

Pharmacotherapy of pediatric diseases represents a major challenge considering that the majority of medicines in everyday practice have not been pediatrically evaluated. The efficacy of therapy depends to a large extent on the knowledge of pathophysiological processes in the children organism at different ages. Therefore, research in that direction is of the utmost importance. An imbalance in the production of free oxygen/nitrogen species and parameters of antioxidative protection is a significant factor in many diseases (e.g. heart failure, pulmonary hypertension, asthma, neonatal sepsis, cancer etc.) in children of different age groups. Reactive oxygen/nitrogen species serve as cell signaling molecules for normal biologic processes. An increase in their generation can cause damages which can disrupt normal physiological cellular processes and eventually cause cell death. This review outlines the previous assessments of oxidative stress parameters in children of different ages for some diseases. Also, the potential diagnostic and therapeutic possibilities for the oxydative stress parameters in children have been considered.

Pulmonary oxidative stress, inflammation, and dysregulated iron homeostasis in rat models of cardiovascular disease

Underlying cardiovascular disease (CVD) is a risk factor for the exacerbation of air pollution health effects. Pulmonary oxidative stress, inflammation, and altered iron (Fe) homeostasis secondary to CVD may influence mammalian susceptibility to air pollutants. Rodent models of CVD are increasingly used to examine mechanisms of variation in susceptibility. Baseline cardiac and pulmonary disease was characterized in healthy normotensive Wistar Kyoto (WKY) rats, cardiovascular compromised spontaneously hypertensive rats (SHR), and spontaneously hypertensive heart failure (SHHF) rats. Blood pressure, heart rate, and breathing frequencies were measured in rats 11 to 12 wk of age, followed by necropsy at 14 to 15 wk of age. Blood pressure and heart rate were increased in SHR and SHHF relative to WKY rats (SHR > SHHF > WKY). Increased breathing frequency in SHHF and SHR (SHR > SHHF > WKY) resulted in greater minute volume relative to WKY. Bronchoalveolar lavage fluid (BALF) protein and neutrophils were higher in SHHF and SHR relative to WKY (SHHF >> SHR > WKY). Lung ascorbate and glutathione levels were low in SHHF rats. BALF Fe-binding capacity was decreased in SHHF relative to WKY rats and was associated with increased transferrin (Trf) and ferritin. However, lung ferritin was lower and Trf was higher in SHHF relative to WKY or SHR rats. mRNA for markers of inflammation and oxidative stress (macrophage inflammatory protein [MIP]-2, interleukin [IL]-1alpha, and heme oxygenase [HO]-1) were greater in SHHF and SHR relative to WKY rats. Trf mRNA rose in SHR but not SHHF relative to WKY rats, whereas transferrin receptors 1 and 2 mRNA was lower in SHHF rats. Four of 12 WKY rats exhibited cardiac hypertrophy despite normal blood pressure, while demonstrating some of the pulmonary complications noted earlier. This study demonstrates that SHHF rats display greater underlying pulmonary complications such as oxidative stress, inflammation, and impaired Fe homeostasis than WKY or SHR rats, which may play a role in SHHF rats' increased susceptibility to air pollution.

Evaluation of a urinary multi-parameter biomarker set for oxidative stress in children, adolescents and young adults

The involvement of reactive oxygen species (ROS) and oxidative stress in pediatric diseases is an important concern, but oxidative stress status in healthy young subjects and appropriate methods for its measurement remain unclear. This study evaluated a comprehensive set of urinary biomarkers for oxidative stress in healthy children, adolescents and young adults. Results show that urinary excretion of acrolein-lysine, 8-hydroxy-2'-deoxyguanosine (8-OHdG), nitrite/nitrate and pentosidine were highest in the youngest subjects and decreased to constant levels by early adolescence. Urinary acrolein-lysine, 8-OHdG, nitrite/nitrate and pentosidine showed significant inverse correlations with age, but pyrraline did not change significantly with age. No significant differences in biomarkers were apparent between males and females. Younger subjects grow rapidly and sustain immune activation, and are probably exposed to high concentrations of ROS and nitric oxide. Consequently, they are more vulnerable to oxidation of lipids, proteins, DNA and carbohydrates. Normal reported values in this study are a basis for future studies of disease mechanisms involving oxidative stress and for future trials using antioxidant therapies for oxidative stress-related diseases in the pediatric field.

Endothelial dysfunction in patients with noncomplicated and complicated hypertension

Endothelial dysfunction plays an important role in the pathogenesis of hypertension. Other risk factors of atherosclerosis also affect its development. The aim of the study was to assess nitric oxide metabolites concentration (nitrites and nitrates No(x)) and endothelin (ET-1) in plasma and cyclic 3,5-guanosine monophosphate (cGMP) in 24 h-urine collection in patients with noncomplicated hypertension without risk factors of atherosclerosis and in hypertensive patients with coronary artery disease (CAD). Sixty-eight subjects were included in the study (44 men, 24 women), aged 47 +/- 76 years, allotted into four groups: I - controls (18 clinically healthy subjects); II - 12 subjects with hypertension without risk factors of atherosclerosis; III - 16 subjects with hypertension and risk factors of atherosclerosis; and IV - 22 subjects with hypertension and CAD. Plasma NO(x) concentration was determined using the Greiss method, plasma ET-1 by ELISA, and urine cGMP using the immunoenzymatic method. Plasma NO(x) concentration was 14.00 +/- 6.88 micromol/L in group I, in group II - 18.62 +/- 5.84 micromol, in group III - 9.96 +/- 4.72 micromol/L, and in group IV - 8.78 +/- 3.72 micromol/L. Statistically significant differences were between groups I and III (p < 0.05) and I and IV (p < 0.04) and groups II and III (p < 0.01) and II and IV (p < 0.01). The concentration of cGMP in 24 h urine collection was in group I - 40 +/- 24 pmol/L; in group II - 54 +/- 41 pmol/L; in group III - 38 +/- 32 pmol/L; and in group IV - 42 +/- 36 pmol/L. There were no significant differences between the groups. Plasma ET-1 concentration was 3.86 +/- 0.52 pg/mL in group I, in group II - 4.05 +/- 0.71 pg/mL, in group III - 4.22 +/- 0.79 pg/mL and in group IV - 4.38 +/- 0.75 pg/mL. Statistically significant differences were between group I and III (p < 0.05), I and IV (p < 0.03), and between group II and IV (p < 0.04). Endothelial dysfunction was not found in hypertensive patients without a family history of cardiovascular diseases and without other risk factors of atherosclerosis. Deterioration of endothelial function was observed in patients with hypertension with risk factors of atherosclerosis. It was most pronounced in those with CAD.

Targeting reactive oxygen species in hypertension

Oxidative stress plays an important role in the pathogenesis of hypertension. A number of sources of reactive oxygen species have been identified including NADPH oxidase, endothelial NO synthase, and xanthine oxidase. Inhibitors of these systems reduce blood pressure in experimental models. Targeted overexpression of antioxidant systems and interference with expression of oxidant systems has also been successfully used in animal models of hypertension. It is expected that these strategies will eventually be translated to human disease, but currently, the specificity and toxicity of such measures are not yet fulfilling quality criteria for treatment of humans. In the meantime, presumably nontoxic measures, such as administration of antioxidant vitamins, are the only available treatments for oxidative stress in humans. In this review, we discuss strategies to target oxidative stress both in experimental models and in humans. We also discuss how patients could be selected who particularly benefit from antioxidant treatment. In clinical practice, diagnostic procedures beyond measurement of blood pressure will be necessary to predict the response to antioxidants; these procedures will include measurement of antioxidant status and detailed assessment of vascular structure and function.

Roles of Paraoxonase and Oxidative Stress in Adolescents with Uraemic, Essential or Obesity-Induced Hypertension

BACKGROUND/AIMS

Paraoxonase 1 (PON1) is associated with high-density lipoproteins in the plasma, and is capable of hydrolysing oxidized lipids and preventing the oxidation of low-density lipoproteins. Oxidative stress and the PON1 (activity and Q192R polymorphism) were analysed in adolescent patients with essential (n = 49) or obesity-induced hypertension (n = 79), uraemic patients (n = 20), and also in obese normotensive patients (n = 60) and age-matched controls (n = 57).

METHODS

The PON1 activity was measured via paraoxon hydrolysis. The PON1 genotype was determined by real-time PCR. The levels of oxidized and reduced glutathione, the end-products of nitric oxide, cysteine, homocysteine and lipid peroxidation in the plasma were measured and related to the PON1 status.

RESULTS

There were no significant differences between the patient groups and the control group in the genotype distributions and the allele frequencies of the Q192R polymorphism. The PON activity was significantly lower (p < 0.001) in the uraemic hypertensive group than in the controls. The MDA concentration was significantly higher in the uraemic hypertensive (p < 0.001) and obese hypertensive (p < 0.05) patients. The plasma NOx concentrations were significantly lower (p < 0.001) and the ratio MDA/NOx were significantly higher in all four patient groups. The GSH levels were significantly lower in the patients with hypertension (p < 0.001) and obesity-induced hypertension (p < 0.05) than in the controls, while the GSSG level (p < 0.01) and the ratio GSSG/GSH (p < 0.05) was significantly higher in the uraemic hypertensive group. The plasma homocysteine level was significantly higher (p < 0.001) in the uraemic hypertensive patients as compared with the controls.

CONCLUSIONS

We found no significant correlation between the biochemical parameters and neither genotypes nor enzyme activities. The PON1 status and the levels of certain biochemical parameters are independently associated with the hypertension in hypertensive and obese hypertensive patients, and the elevated levels of lipid peroxides and plasma homocysteine may contribute to the increased risk of cardiovascular complications in patients on haemodialysis.

Different pathomechanisms of essential and obesity-associated hypertension in adolescents

Obesity-induced hypertension and essential hypertension in lean patients are two different forms of hypertension. The main goal of this study was to test whether there are differences in biochemical parameters between subjects with obesity-associated hypertension and those with essential hypertension. We examined whether the biochemical responses to angiotensin-converting enzyme inhibitor (ACEI) ramipril therapy reveal properties of these two conditions that might explain the differences in clinical outcome. Before ramipril therapy, the hypertensive group exhibited increases in ACE activity (p<0.05), plasma malondialdehyde (MDA) concentration and the malondialdehyde/nitric oxide end-product ratio (MDA/NO(x)) (p<0.05), and decreases in xanthine oxidase (XO) activity (p<0.05) and plasma nitric oxide end-product (NO(x)) level (p<0.01). Before medication, plasma endothelin-1 (ET-1), plasma leptin, and leptin receptor levels were normal. Following ramipril treatment, ACE activity normalized. Before ACE inhibitor treatment, the obese-hypertensive group exhibited elevated levels of plasma ET-1 (p<0.05), plasma leptin (p<0.01), XO activity (p<0.05), plasma MDA and MDA/NO(x) (p<0.05), and reduced levels of plasma NO(x)(p<0.01) and leptin receptors (p<0.001). Following medication, the plasma NO(x) level, MDA/NO(x), and XO activity returned to normal while ACE activity decreased (p<0.001). In patients with essential hypertension, NO availability and ACE activity, and in those with obesity-associated hypertension, hyperleptinemic effects, NO level, endothelin-1 concentration and XO activity, may be important factors in the pathology.

Oxidative stress and post-transplant hypertension in pediatric kidney-transplanted patients

OBJECTIVE

To test the hypothesis that oxidative stress signaling contributes to post-transplant endothelial dysfunction and hypertension in pediatric post-transplant hypertension.

STUDY DESIGN

This study evaluated in 16 pediatric renal transplant patients, divided in two groups based on the presence of post-transplant hypertension, the oxidative stress status measuring the gene expression (reverse transcription-polymerase chain reaction) of two major oxidative stress-related proteins, p22(phox) and heme oxygenase-1 (HO-1). Total plasma antioxidant power (ELISA) was also evaluated.

RESULTS

Mononuclear cell p22(phox) gene expression was higher in hypertensive patients compared with the normotensive group (0.91 +/- 0.06 vs 0.79 +/- 0.08 densitometric units, P < .02), whereas HO-1 RNA production and total plasma antioxidant power were higher in the normotensive group (0.38 +/- 0.04 vs 0.20 +/- 0.11 d.u., P < .006, and 1189.35 +/- 145.75 vs 772.71 +/- 196.03 micromol/L, P < .01, respectively).

CONCLUSIONS

Oxidative stress is associated with post-transplant hypertension in hypertensive pediatric kidney-transplant patients, who therefore are at risk of oxidative stress-induced organ damage. They might benefit from treatments addressing not only hypertension but also oxidant-related complications.

Oxidized Forms of Glutathione in Peripheral Blood as Biomarkers of Oxidative Stress

Background: Reduced glutathione (GSH) and its redox forms, glutathione disulfide (GSSG) and glutathionylated proteins (PSSG), are biomarkers of oxidative stress, but methodologic artifacts can interfere with their measurement. We evaluated the importance of correct sample handling during the preanalytical phase for GSH, GSSG, and PSSG measurement.

Methods: We used human blood for in vitro experiments with oxidants [tert-butylhydroperoxide (t-BOOH), diamide, and menadione]. For in vivo experiments, we used rats in which we cannulated the jugular and femoral veins for both oxidant administration and blood collection. We measured GSH, GSSG, and PSSG with HPLC with or without sample pretreatment with N-ethylmaleimide (NEM) to prevent artifacts. We also measured malondialdehyde (MDA) with HPLC, and protein carbonyls (PCO) with spectrophotometric procedures.

Results: When methodologic artifacts were prevented by pretreatment with NEM, GSSG results increased up to 3-fold over the basal concentrations, even in the presence of 5 μmol/L t-BOOH or diamide and 20 μmol/L menadione. PSSG increased by ∼50% at 20 μmol/L t-BOOH or diamide and at 50 μmol/L menadione. PCO and MDA remained unchanged. In vivo oxidation treatments elicited immediate and significant increases in GSSG and PSSG over basal values (up to 200-fold), whereas PCO and MDA showed only slight variation 120 or 180 min after treatment.

Conclusions: With the use of artifact-free measurement methods, GSH, GSSG, and PSSG are potentially powerful and reliable biomarkers of oxidative stress status and can be used to evaluate whether, and to what extent, oxidative stress may be involved in various diseases.

Low ethanol intake prevents salt-induced hypertension in WKY rats

Low alcohol intake in humans lowers the risk of coronary heart disease and may lower blood pressure. In hypertension, insulin resistance with altered glucose metabolism leads to increased formation of aldehydes. We have shown that chronic low alcohol intake decreased systolic blood pressure (SBP) and tissue aldehyde conjugates in spontaneously hypertensive rats and demonstrated a strong link between elevated tissue aldehyde conjugates and hypertension in salt-induced hypertensive Wistar-Kyoto (WKY) rats. This study investigated the antihypertensive effect of chronic low alcohol consumption in high salt-treated WKY rats and its effect on tissue aldehyde conjugates, platelet cytosolic free calcium ([Ca2+]i, and renal vascular changes. Animals, aged 7 weeks, were divided into three groups of six animals each. The control group was given normal salt diet (0.7% NaCl) and regular drinking water; the high salt group was given a high salt diet (8% NaCl) and regular drinking water; the high salt + ethanol group was given a high salt diet and 0.25% ethanol in drinking water. After 10 weeks, SBP, platelet [Ca2+]i, and tissue aldehyde conjugates were significantly higher in rats in the high salt group as compared with controls. Animals on high salt diets also showed smooth muscle cell hyperplasia in the small arteries and arterioles of the kidney. Ethanol supplementation prevented the increase in SBP and platelet [Ca2+]i and aldehyde conjugates in liver and aorta. Kidney aldehyde conjugates and renal vascular changes were attenuated. These results suggest that chronic low ethanol intake prevents salt-induced hypertension and attenuates renal vascular changes in WKY rats by preventing an increase in tissue aldehyde conjugates and cytosolic [Ca2+]i.

Byproducts of oxidative protein damage and antioxidant enzyme activities in plasma of patients with different degrees of essential hypertension

Despite evidence that essential hypertension (EH) is a state of increased oxidative stress, the data on oxidative protein modifications is lacking. Besides, the role of extracellular antioxidant enzymes in EH has not been systematically studied. Study was performed in 45 subjects with EH and 25 normotensive controls. Patients were divided into three groups according to the 2003 ESH/ESC guidelines (grade 1-3). Plasma protein reactive carbonyl derivatives (RCD) and SH-groups (as byproducts of oxidative protein damage) as well as antioxidant enzyme activities superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase were studied spectrophotometrically and correlated with blood pressure (BP). RCD levels were increased in EH patients compared to controls and correlated significantly with both systolic blood pressure (SBP) (r = 0.495, P<0.01) and diastolic blood pressure (DBP) (r = 0.534, P<0.01). Plasma SH-groups content was significantly lower in all patients with EH, with no correlation with BP. SOD and catalase activity in patients with grade 1 EH were similar to that of controls. Patients with grade 2 and 3 of EH had lower SOD and catalase activity. However, significant correlation with SBP and DBP was observed for catalase only (r = -0.331; P<0.05 and r = -0.365; P<0.05, respectively). EH patients exhibited higher plasma GPX activity compared to those in controls, and it correlated with SBP (r = 0.328; P<0.05). The results presented show that increased oxidative protein damage is present in all grades of EH. In mild hypertension extracellular antioxidant enzyme activities are not decreased, suggesting they are probably not critical in early EH, but could be important in moderate to severe EH.

Assessing cardiovascular risk in children with chronic kidney disease. B-type natriuretic peptide: a potential new marker

Elevated plasma B-type natriuretic peptide (BNP) level is a hallmark of altered left ventricular (LV) structure and function. Measurement of circulating BNP has proved to be a sensitive and specific diagnostic test for congestive heart failure (CHF) and coronary syndrome in adults. Further, BNP levels constitute a strong predictive marker for future cardiovascular (CV) events. In high CV risk populations, such as adults with hypertension or chronic kidney disease (CKD), increased BNP predicts CV morbidity and mortality in symptomatic or asymptomatic patients. However, caution is needed in interpreting plasma BNP levels, as they increase with both age and decreased renal function. Despite increasing evidence of the value of BNP in the medical literature in adults, data in children are limited to those with congenital heart disease. It is appropriate to analyze the potential application of this tool in children with CKD, a well-known factor for CV disease.

Effects of ageing on carbonyl stress and antioxidant defense in RBCs of obese Type 2 diabetic patients

In this study we investigated the effects of ageing on the carbonyl stress (protein carbonyls and 4-hydroxy-2-nonenal groups) and glutathione antioxidant defense in red blood cells (RBCs) of obese Type 2 diabetic patients with/without hypertensive complications. To this purpose the following methods were used: spectrophotometry (protein carbonyls, glutathione and glutathione peroxidase assays), immunofluorescence (4-hydroxy-2-nonenal localization), western blotting (immunodetection of carbonylated proteins). The results showed that compared to RBCs of healthy subjects, in obese Type 2 diabetics, ageing is associated with: (i) an increase in the concentration and expression of carbonylated proteins, a marker of oxidative stress; (ii) a decrease of both non-enzymatic and enzymatic endogenous glutathione defenses; (iii) a severely disturbed oxidant/antioxidant balance when obesity was associated with hypertension. The simultaneous insults of high blood pressure, obesity, and diabetes conducted to the highest carbonyl stress, exposure of 4-hydroxy-2-nonenal Michel adducts at the outer leaflet of RBCs plasmalemma, and the lowest glutathione antioxidant potential, particularly in elderly patients. These results can explain the gradual age-dependent diminishment of the detoxification potential of RBCs that at the old age can not overcome the deleterious effects of the high systemic oxidative stress.

The immune system in the oxidative stress conditions of aging and hypertension: favorable effects of antioxidants and physical exercise

Several studies have shown that both oxidative stress and inflammation are linked to the process of hypertension and that the immune system is also involved in this age-related process. More specifically, the oxygen stress related to immune system dysfunction seems to have a key role in senescence, in agreement with the oxidation/ inflammation theory of aging. From a practical point of view, and according to our own research, the immune functions change in a similar fashion in hypertension and aging. As antioxidant diet supplementation decreases oxidative stress, it may be useful to treat hypertension and increase longevity. Probably, these favorable effects are mediated by an antioxidant-induced improvement of the immune function. The practice of moderate physical exercise shows similar favorable effects, and indeed our studies on exercising hypertensive women demonstrate an improved immune function, probably linked to raised levels of intracellular antioxidant defenses. The present review summarizes a selection of data related to the above from other authors as well as some findings from our own work.

NADPH oxidase-mediated oxidative stress: genetic studies of the p22(phox) gene in hypertension

Increased vascular production of reactive oxygen species, especially superoxide anion, significantly contributes to the oxidative stress associated with hypertension. An enhanced superoxide production causes an increased inactivation of nitric oxide that diminishes nitric oxide bioavailability, thus contributing to endothelial dysfunction and hypertrophy of vascular cells. It has been shown that NADPH oxidases play a major role as the most important sources of superoxide anion in phagocytic and vascular cells. Several experimental observations have described an enhanced superoxide generation as a result of NADPH oxidase activation in hypertension. Although these enzymes respond to stimuli such as vasoactive factors, growth factors, and cytokines, recent data suggest a significant role of the genetic background in the modulation of the expression of its different components. Several polymorphisms have been identified in the promoter and in the coding region of CYBA, the gene that encodes the essential subunit of the NADPH oxidase p22phox, some of which seem to influence significantly the activity of these enzymes in the context of cardiovascular diseases. Among CYBA polymorphisms, genetic investigations have provided a novel marker, the -930(A/G) polymorphism, which determines the genetic susceptibility of hypertensive patients to oxidative stress.

Effect of antihypertensive treatment with candesartan or amlodipine on glutathione and its redox status, homocysteine and vitamin concentrations in patients with essential hypertension

OBJECTIVE

To compare the effect of candesartan or amlodipine on concentrations of cellular markers of oxidative stress, plasma homocysteine and vitamins in hypertensive patients.

METHODS

Forty-nine middle-aged patients with untreated stage I-II essential hypertension were recruited in a randomized double-blind double-dummy study to receive a daily dose either of 8 mg candesartan (n = 25) or 5 mg amlodipine (n = 24) for 16 weeks. Blood pressure, reduced glutathione (GSH) and oxidized glutathione (GSSG), glutathione redox ratio (GSSG : GSH) in red blood cells, plasma homocysteine, vitamin B12 and folic acid status were measured at baseline, at week 2 and at week 16. The same parameters were measured in 32 healthy age- and sex-matched controls. An increase in homocysteine of at least 2 micromol/l was considered significant.

RESULTS

Hypertensive patients had significantly greater oxidative stress and homocysteine concentrations than controls. In addition to a significant decrease in blood pressure, in both treatment groups GSSG decreased (P < 0.03), GSSG : GSH had a tendency to decrease (P = 0.054), but homocysteine did not change. An increase in homocysteine concentration of at least 2 micromol/l was found in 12 patients (five in the candesartan group, seven in the amlodipine group), with a significant decrease in folic acid concentration and no changes in cellular oxidative stress. In patients with no increase in homocysteine concentration, both GSSG (P < 0.02) and GSSG : GSH (P = 0.051) decreased. GSH and vitamin B12 did not change in any of the groups studied.

CONCLUSION

Untreated hypertension is associated with disturbed glutathione redox status and increased plasma homocysteine concentrations. Both candesartan and amlodipine had favourable effects on cellular oxidative stress, but the oxidative stress status did not decrease in patients with adverse changes in homocysteine.

Oxidative Stress Status in Kidney Tissue after Losartan and Atenolol Treatment in Experimental Renal Failure

BACKGROUND/AIMS

Rats with subtotal nephrectomy (5/6NPX) rapidly develop systemic hypertension and proteinuria. The aim of our study was to evaluate the changes in oxidative stress parameters after 2 and 4 weeks of treatment with renin-angiotensin system (RAS)-blocking agent losartan and beta-blocking agent atenolol in experimental chronic renal failure (CRF).

METHODS

After 5/6NPX, rats were immediately treated with losartan or atenolol. The lipid peroxidation (LPO) products malondialdehyde and 4-hydroxyalkenals and oxidized and reduced glutathione values were measured in the renal cortex tissue and in blood; isoprostanes in urine.

RESULTS

There were no differences in the blood pressure values, serum creatinine levels or in daily proteinuria using both antihypertensive treatments. Losartan treatment lowered significantly LPO in kidney tissue after 2 and 4 weeks of treatment compared with untreated and atenolol-treated animals and induced the decrease of excretion of isoprostanes in urine at the end of the study. There was no ameliorating impact of losartan or atenolol observed in the blood status of oxidative stress in this period of time.

CONCLUSION

In the early period of experimental CRF, losartan treatment but not atenolol treatment induces significant decline in LPO grade in the kidney tissue of nephrectomized rats. RAS blockade in the kidney influences local tissue LPO in a much greater extent than in blood.

Association of increased phagocytic NADPH oxidase-dependent superoxide production with diminished nitric oxide generation in essential hypertension

OBJECTIVE

Oxidative stress has been implicated in the pathogenesis of hypertension and its complications through alterations in nitric oxide (NO) metabolism. This study was designed to investigate whether a relationship exists between phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent superoxide anion (*O2-) production and NO generation in patients with essential hypertension.

METHODS

Superoxide production was assayed by chemiluminescence under baseline and stimulated conditions on mononuclear cells obtained from hypertensives (n=51) and normotensives (n=43). NO production was evaluated by determining serum NO metabolites, nitrate plus nitrite (NOx).

RESULTS

Although there were no differences in baseline *O2- production between normotensives and hypertensives, the *O2- production in phorbol myristate acetate (PMA)-stimulated mononuclear cells was increased (P <0.05) in hypertensives compared with normotensives. The PMA-induced *O2- production was completely abolished by apocynin, a specific inhibitor of NADPH oxidase. Moreover, stimulation of *O2- production by angiotensin II and endothelin-1 was higher (P <0.05) in cells from hypertensives than in cells from normotensives. In addition, diminished (P <0.001) serum NOx was detected in hypertensives compared with normotensives. Interestingly, an inverse correlation (r=0.493, P <0.01) was found between *O2- production and NOx in hypertensives.

CONCLUSIONS

Generation of *O2- mainly dependent on NADPH oxidase is abnormally enhanced in stimulated mononuclear cells from hypertensives. It is suggested that this alteration could be involved in the diminished NO production observed in these patients.

Antecedent hypertension and the effect of captopril on the risk of adverse cardiovascular outcomes after acute myocardial infarction with left ventricular systolic dysfunction: Insights from the Survival and Ventricular Enlargement Trial

BACKGROUND

Hypertension is a well-established risk factor for myocardial infarction (MI), but its prognostic importance in survivors of an acute MI is less clear.

METHODS

We used Cox proportional hazards models to examine the risk of any major cardiovascular event (cardiovascular death, heart failure, recurrent MI, or stroke)-combined or individual components-and all-cause death and evaluate the efficacy of captopril in 906 patients with hypertension and 1325 patients without hypertension in the Survival and Ventricular Enlargement (SAVE) clinical trial. All patients had survived an acute MI with resultant left ventricular (LV) systolic dysfunction, but without overt heart failure, and were randomized within 3 to 16 days after the index MI to receive either captopril or placebo. The mean (+/- SD) follow-up period was 42 +/- 10 months.

RESULTS

After adjustment for known risk factors, medication use at enrollment, and baseline systolic blood pressure, patients with hypertension had a significant increase in the risk of experiencing a combined cardiovascular event (47.7% vs 31.3%; hazard ratio [HR], 1.49; 95% CI, 1.28-1.74), cardiovascular death (23.4% vs 15.9%; HR, 1.40; 95% CI, 1.12-1.74), heart failure (27.7% vs 15.5%; HR, 1.64; 95% CI, 1.34-2.02), and all-cause death (27.4 vs 19.3%; HR, 1.25; 95% CI, 1.02-1.53), and a similar but statistically non-significant increase in the risk of non-fatal or fatal recurrent MI (17.4% vs 10.9%; HR, 1.27; 95% CI, 0.98-1.65), and non-fatal or fatal stroke (5.0% vs 3.6%; HR, 1.31; 95% CI, 0.81-2.09). Captopril resulted in similar benefits for both patients with and patients without hypertension. The number of combined cardiovascular events prevented for every 100 patients treated with captopril was 7.0 (95% CI, 0.5-13.5) in patients with hypertension and 7.5 (95% CI, 2.6-12.5) in patients without hypertension.

CONCLUSIONS

In survivors of an acute MI with LV systolic dysfunction, antecedent hypertension was associated with a greater risk of subsequent adverse cardiovascular events, not directly explained by elevated blood pressure levels. Captopril use was beneficial in both patients with and patients without hypertension.

Effect of antecedent systemic hypertension on subsequent left ventricular dilation after acute myocardial infarction (from the Survival and Ventricular Enlargement trial)

Whether antecedent systemic hypertension influences the risk of subsequent left ventricular (LV) dilation in patients after an acute myocardial infarction with LV systolic dysfunction is unclear. We assessed echocardiographic evidence of ventricular remodeling from baseline (mean +/- SD 11 +/- 3 days) to 2 years after an acute myocardial infarction in 122 hypertensive (defined as a history of treated hypertension, baseline systolic blood pressure > or =140 or baseline diastolic blood pressure > or =90 mm Hg) and 334 nonhypertensive patients in the Survival and Ventricular Enlargement echocardiographic substudy. Compared with nonhypertensives, baseline heart size, defined as the sum of the average short- and long-axis LV cavity areas, was similar (70.1 +/- 11.9 vs 68.8 +/- 11.2 cm(2), p = 0.33 at end-diastole; 50.1 +/- 11.3 vs 48.8 +/- 10.8 cm(2), p = 0.31 at end-systole), but short-axis LV myocardial area (24.7 +/- 4.3 vs 25.7 +/- 5.0 cm(2), p = 0.043) and wall thickness (1.15 +/- 0.16 vs 1.21 +/- 0.17 cm, p = 0.004) at end-diastole were greater among hypertensives. The myocardial infarct segment lengths were similar in the 2 groups (p = 0.22). Although LV cavity areas increased significantly in the 2 groups from baseline to 2 years (p < or =0.001), the increase was significantly greater in hypertensives than in nonhypertensives (+5.6 +/- 11.5 vs +2.2 +/- 10.7 cm(2), p = 0.005 at end-diastole; +6.23 +/- 12.75 vs +2.94 +/- 11.4 cm(2), p = 0.012 at end-systole). There was no concomitant difference in the change in LV myocardial area or LV wall thickness between the 2 groups (p >0.30). After adjusting for known confounders, antecedent hypertension was associated with a doubling of the risk of LV dilation (50.8% vs 37.7%, odds ratio 2.09, 95% confidence interval 1.27 to 3.45, p = 0.004). This association was not modified by diabetes mellitus, myocardial infarct segment length, or captopril use (all p values for interaction >0.10). We conclude that antecedent hypertension is associated with subsequent LV dilation in patients after acute myocardial infarction with LV systolic dysfunction.

The current epidemic of primary aldosteronism

Until recently, primary aldosteronism was considered to be a rare cause of identifiable or secondary hypertension. Over the past 10 years, a steadily growing number of reports have claimed that this condition is much more common, present in 5-40% of all hypertensive patients, which translates into many millions of patients. The primary basis for this current epidemic is the application of a relatively simple screening test, the plasma aldosterone to renin ratio (ARR). Despite growing recognition that the ARR is neither sensitive nor specific, its advocates recommend that it should be a routine procedure in evaluation of all hypertensives. Evidence is provided that this recommendation will lead to massive increases in costs, both in money and in morbidity, while providing benefit to only a very small number of patients who would not be aided by continuation of previous diagnostic protocols.

Homocysteine and red blood cell glutathione as indices for middle-aged untreated essential hypertension patients

OBJECTIVE

Intracellular glutathione in its reduced state is a principal cellular biomolecule with antioxidant activity. Glutathione and homocysteine metabolism are closely associated. As both oxidative stress and hyperhomocystinemia are associated with hypertension, we assessed the relationships between these variables.

DESIGN AND SETTING

An observation-based case-control study, performed at a university teaching hospital.

PATIENTS

Middle-aged male patients with untreated uncomplicated essential hypertension (mean +/- standard deviation age 53.0 +/- 7.2 years, n = 48) before any treatment and controls with similar age distributions (age 51.6 +/- 5.5 years, n = 28) were evaluated.

METHODS

In all subjects, the plasma levels of homocysteine, lipids, creatinine, protein, and glucose were measured. Reduced and oxidized glutathione and folic acid were measured from red blood cells (RBC).

RESULTS

The hypertensive patients had decreased levels of red blood cell reduced glutathione (RBC-GSH) and increased levels of oxidized glutathione, which resulted in elevated ratio of oxidized/reduced glutathione as compared to controls (P < 0.001). Plasma homocysteine levels were significantly higher in the hypertensive patients versus the age-matched controls (P < 0.004). In the hypertensive patients, RBC-GSH correlated inversely with systolic blood pressure, serum creatinine, protein and RBC folic acid. No correlation was detected between RBC-GSH and homocysteine. In the controls, RBC-GSH correlated inversely with homocysteine, RBC folic acid and creatinine. According to multiple regression, in the hypertensive patients RBC-GSH was related to systolic blood pressure, hemoglobin, plasma homocysteine, creatinine and protein. Such a relationship was not detected for the controls.

CONCLUSION

In untreated hypertensive patients both homocysteine and systolic blood pressure are associated with intracellular oxidative stress as determined by RBC-GSH.