E. Cavanagh

Angiotensin II blockade: a strategy to slow ageing by protecting mitochondria?

Protein and lipid oxidation-mainly by mitochondrial reactive oxygen species (mtROS)-was proposed as a crucial determinant of health and lifespan. Angiotensin II (Ang II) enhances ROS production by activating NAD(P)H oxidase and uncoupling endothelial nitric oxide synthase (NOS). Ang II also stimulates mtROS production, which depresses mitochondrial energy metabolism. In rodents, renin-angiotensin system blockade (RAS blockade) increases survival and prevents age-associated changes. RAS blockade reduces mtROS and enhances mitochondrial content and function. This suggests that Ang II contributes to the ageing process by prompting mitochondrial dysfunction. Since Ang II is a pleiotropic peptide, the age-protecting effects of RAS blockade are expected to involve a variety of other mechanisms. Caloric restriction (CR)-an age-retarding intervention in humans and animals-and RAS blockade display a number of converging effects, i.e. they delay the manifestations of hypertension, diabetes, nephropathy, cardiovascular disease, and cancer; increase body temperature; reduce body weight, plasma glucose, insulin, and insulin-like growth factor-1; ameliorate insulin sensitivity; lower protein, lipid, and DNA oxidation, and mitochondrial H(2)O(2) production; and increase uncoupling protein-2 and sirtuin expression. A number of these overlapping effects involve changes in mitochondrial function. In CR, peroxisome proliferator-activated receptors (PPARs) seem to contribute to age-retardation partly by regulating mitochondrial function. RAS inhibition up-regulates PPARs; therefore, it is feasible that PPAR modulation is pivotal for mitochondrial protection by RAS blockade during rodent ageing. Other potential mechanisms that may underlie RAS blockades mitochondrial benefits are TGF-β down-regulation and up-regulation of Klotho and sirtuins. In conclusion, the available data suggest that RAS blockade deserves further research efforts to establish its role as a potential tool to mitigate the growing problem of age-associated chronic disease.

Vascular Structure and Oxidative Stress in Salt-Loaded Spontaneously Hypertensive Rats: Effects of Losartan and Atenolol

BACKGROUND Renin-angiotensin system (RAS) modulation by high dietary sodium may contribute to salt-induced hypertension, oxidative stress, and target organ damage. We investigated whether angiotensin II (Ang-II) type 1 (AT1)-receptor blockade (losartan) could protect the aorta and renal arteries from combined hypertension- and high dietary salt-related oxidative stress. METHODS Spontaneously hypertensive rats (3-month-old, n = 10/group) received tap water (SHR), water containing 1.5% NaCl (SHR+S), 1.5% NaCl and 30 mg losartan/kg/day (SHR+S+L), or 50 mg atenolol/kg/day (SHR+S+A). Atenolol was used for comparison. Ten Wistar-Kyoto rats (WKY) were controls. Systolic blood pressure (SBP) was determined by tail plethysmography. After 5 months of treatment, vascular remodeling and oxidative stress (superoxide production and NAD(P)H-oxidase activity (chemiluminescence), malondialdehyde (MDA) content (high-performance liquid chromatography), endothelial nitric oxide synthase (eNOS) activity [(14)C-arginine to (14)C citrulline], CuZn-SOD activity (spectrophotometry)) were studied. RESULTS In SHR, salt-loading significantly aggravated hypertension, urinary protein excretion, intraparenchymal renal artery (IPRArt) perivascular fibrosis, aortic and renal artery oxidative stress, and induced endothelial cell loss in IPRArts. In salt-loaded SHR, 5-month losartan and atenolol treatments similarly reduced SBP, but only losartan significantly prevented (i) urinary protein excretion increase, (ii) or attenuated hypertension-related vascular remodeling, (iii) aortic MDA accumulation, (iv) renal artery eNOS activity lowering, and (v) aortic and renal artery superoxide dismutase (SOD) activity reduction. In SHR+S, the contributions to aortic superoxide production were as follows: uncoupled eNOS > xanthine oxidase (XO) > NAD(P)H oxidase. CONCLUSIONS In this salt-sensitive genetic hypertension model, losartan protects from hypertension- and high dietary salt-related vascular oxidative stress, exceeding the benefits of BP reduction. Also, during salt overload, BP-independent factors contribute to vascular remodeling, at least part of which derive from AT1-receptor activation.

Local and Systemic Cellular Immunity in Early Renal Artery Atherosclerosis

BACKGROUND AND OBJECTIVES Modern imaging techniques have increased the incidental detection of renal atherosclerotic disease (RAD). Because immune activation may hasten RAD progression, identifying cellular immune markers might provide clues to clinical activity. In this study, cellular immune markers were assessed in early RAD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Immune cell markers in peripheral blood of two groups of hypertensive patients with normal carotid and coronary arteries were evaluated: 28 patients had incidental RAD and 22 patients had normal renal arteries; 21 renal arteries obtained at necropsy from individuals with history of hypertension and tissue evidence of RAD were examined and matched with 21 individuals with normal renal arteries. Cell subpopulations were measured by flow cytometry in peripheral blood and direct cell count, respectively, using T and dendritic cells monoclonal antibodies. RESULTS Peripheral blood of RAD patients showed increased numbers of cells expressing CD3, CD4, CD83, and CD86. CD4 to CD8 ratio was 8.3 ± 1.4 (RAD) to 3.4 ± 0.9 (normal; P<0.001). No differences were found in CD25, CD8, and S100 among groups. Postmortem samples from RAD showed increased CD3+, CD4+, CD86+, and S100+ cells, whereas CD25+ and CD8+ were unmodified between groups. CD4+ to CD8+ ratio was higher in the RAD(PM) group. CONCLUSIONS These results are consistent with an increased expression of immune cell markers in early RAD. Additional studies will explore if they may potentially turn into treatment targets to prevent disease progression.

Sympathetic predominance is associated with impaired endothelial progenitor cells and tunneling nanotubes in controlled-hypertensive patients

Early endothelial progenitor cells (early EPC) and late EPC are involved in endothelial repair and can rescue damaged endothelial cells by transferring organelles through tunneling nanotubes (TNT). In rodents, EPC mobilization from the bone marrow depends on sympathetic nervous system activity. Indirect evidence suggests a relation between autonomic derangements and human EPC mobilization. We aimed at testing whether hypertension-related autonomic imbalances are associated with EPC impairment. Thirty controlled-essential hypertensive patients [systolic blood pressure/diastolic blood pressure = 130(120-137)/85(61-88) mmHg; 81.8% male] and 20 healthy normotensive subjects [114(107-119)/75(64-79) mmHg; 80% male] were studied. Mononuclear cells were cultured on fibronectin- and collagen-coated dishes for early EPC and late EPC, respectively. Low (LF)- and high (HF)-frequency components of short-term heart rate variability were analyzed during a 5-min rest, an expiration/inspiration maneuver, and a Stroop color-word test. Modulations of cardiac sympathetic and parasympathetic activities were evaluated by LF/HF (%) and HF power (ms(2)), respectively. In controlled-hypertensive patients, the numbers of early EPC, early EPC that emitted TNT, late EPC, and late EPC that emitted TNT were 41, 77, 50, and 88% lower than in normotensive subjects (P < 0.008), respectively. In controlled-hypertensive patients, late EPC number was positively associated with cardiac parasympathetic reserve during the expiration/inspiration maneuver (rho = 0.45, P = 0.031) and early EPC with brachial flow-mediated dilation (rho = 0.655; P = 0.049); also, late TNT number was inversely related to cardiac sympathetic response during the stress test (rho = -0.426, P = 0.045). EPC exposure to epinephrine or norepinephrine showed negative dose-response relationships on cell adhesion to fibronectin and collagen; both catecholamines stimulated early EPC growth, but epinephrine inhibited late EPC growth. In controlled-hypertensive patients, sympathetic overactivity/parasympathetic underactivity were negatively associated with EPC, suggesting that reducing sympathetic/increasing parasympathetic activation might favor endothelial repair.

Lack of RAAS inhibition by high-salt intake is associated with arterial stiffness in hypertensive patients

Hypothesis/introduction: The relationship between salt intake, blood pressure and RAAS activation is still controversial, being that both high- and low-salt intakes are associated with cardiovascular events in a J-shaped curve pattern. We hypothesized that different patterns of RAAS response to dietary salt intake among hypertensives could be identified, while vascular damage would be related to high-salt intake plus absence of expected RAAS inhibition. Objective: We aim to assess the relationship between sodium intake, RAAS and vascular stiffness in hypertension. Materials and methods: We screened 681 hypertensive patients for urinary/plasma electrolytes, renin, aldosterone and pulse wave velocity (PWV) under their usual salt intake level. Results: After applying exclusion criteria, an inverse relation between urinary sodium and RAAS was observed in the 300 remaining subjects. Additionally, four types of response were identified: 1) Low (L) sodium (S)-Low RAAS, 2) LS-High (H) SRAAS, 3) HS-Low RAAS, 4) HS-High RAAS. We found no differences in age/BP among groups, but type 4 response individuals included more females and a higher pulse wave velocity. Conclusions: We showed a) an inverse salt-RAAS relation, b) an association between HS plus high RAAS with increased PWV that could identify a higher-risk hypertensive condition.

DEPRESSION-MEDIATED ARTERIAL STIFFNESS AND AUTONOMIC DISBALANCE IN YOUNG HYPERTENSIVE PATIENTS: A PATHWAY TO STROKE?: PP.4.144

Systemic hypertension and depression are currently considered risk factors for cardio-cerebral-vascular disease and particularly for stroke. The mechanisms how depression increases the risk of stroke have not been fully elucidated. It is also well known that elevated pulse wave velocity (PWV) as evidence of arterial stiffness and target organ damage (TOD) increases risk of cerebral events. Furthermore, autonomic disbalance has been related as a physiopatological mechanism in depression and cardiovascular disease. Based on this unexplored issue, we explored the hyphotesis that the association between hypertension and depression is related to greater PWV increase, and that autonomic disbalance could be one of the pathways involved. Objective: To evaluate PWV and the autonomic balance in young hipertensive patients with depression. Methods: We studied 34 consecutive hypertensive patients (39 ± 9,1 years; 68 % men) admitted for TOD assessment. All patients completed voluntarily a sheet with two questions validated for depression screening and validated scales (CES-D/Hamilton) to obtain a severity score of depression. Arterial stiffness was determined by non-invasive PWV measurement and autonomic response by heart rate variability, previously described by others, during stress test recovery period. Results: This population was analyzed in a 2:1 ratio, classified as depressive (n:11) when at least one question was positive, and non-depressive (n:23) when both were negative. Results were analyzed with chi2 and T-test. There were no significative differences in baseline characteristics. Depressive patients showed a significative higher PWV (11 ± 2,1 vs 9,2 ± 1,6 m/s; p = 0.025). There was also found a difference in stress test recovery period, showing a faster recovery in the same group (p = 0.006). Figure 1. No caption available. Conclusions: An association between an increased arterial stiffness, autonomic disbalance and depression was found in the young hypertensive population we evaluated. Further studies would be necessary to identify their contribution to the increased risk of stroke previously reported (MRFIT/WHI). Autonomic disbalance could be a probable physiopathological pathway while arterial stiffness would be a marker of its early atherosclerotic impact.

IMMUNOLOGICAL ACTIVATION IN EARLY PHASES OF ATHEROSCLEROTIC RENOVASCULAR DISEASE: - A NEW THERAPEUTIC TARGET?: 1C.03

Introduction: An autoimmune component is present in atherosclerotic disease, cellular and humoral immunity are involved in its development. However most of the reports describing the presence of immune markers in clinical settings came from individuals with severe symptomatic carotid or coronary plaques and no previous reports described it in asymptomatic lesions from renovascular atherosclerosis (RVD). Basis in this unexplored field we examined the presence of immune markers in hypertensive patients with asymptomatic RVD. Aims: to identify immune activation in hypertensive patients with asymptomatic RVD. Methods: A prospective, controlled study was conducted including 50 patients with hypertension that underwent an evaluation of their renal arteries by digital arteriography. According to its results they were classified in 2 groups; a)RVD (n: 28); b) Normal arteries (NA, n: 22). Basal characteristics, cardiovascular risk factors distributions and blood pressure values(table 1) were similar between both groups, no carotid or coronary atherosclerotic lesions were found in any patient included. All patients were asymptomatic for RVD (as defined by AHA,2000: RVD not accompanied by severe, malignant or refractory hypertension, nor renal function impairment). Peripheral blood samples were obtained and incubation for primary and secondary antibodies were performed. Immunophenotyping was done using the following monoclonal antibodies: anti-CD4, anti-CD3, anti-CD83; anti-CD86; anti-CD8; anti-CD25 and all the appropriates isotypes controls. Results (table1): In the RVD group, CD3+ and CD4 T cell counts were approximately 2 times (P < 0.0001) and 3 times (P < 0.0001) higher respectively, the CD4+/CD8+ ratio was 2.4 times higher (P < 0.0001) and CD86+ and CD83+ cell count was approximately 5.15 times and 1.4 times higher (P < 0.0001, respectively). Conclusions: An increased significative immune activation was found in asymptomatic hypertensives with RVD suggesting that an active immune reaction is already present in these early phases. Further research would be necessary in interventions targeting this activation to reduce disease progression. Figure 1. No caption available.

IMPACT OF SALT BEYOND ARTERIAL PRESSURE: 9C.06

Although experimental data describes the relation between sodium intake and parasympathetic tone, its interaction still remains controversial. A recent clinical report from Coruzzi et al.1 identified an impaired parasympathetic cardiac control in hypertensives submitted to a high salt diet by describing a fall in their baroreflex sensitivity.The metabolic impact of these autonomic abnormalities has not been explored. Objective: To evaluate the effect of a high salt loading on parasympathetic tone and metabolic status in essential hypertension (EH). METHODS: We evaluated 1671 consecutive patients with mild EH (50.8 ± 12.9 years, 31.3 % female) without or after a 7 days wash out from any antihypertensive drugs. A final group of 490 patients(49.5 ± 13.9 years, 33.2% women) were included after application of exclusion criteria (treatment with hypoglucemiants and/or hypolipemiants; renal damage, congestive heart failure, rheumatic disease).The following determinations were done: BMI, SBP/DBP (OMROM HEM-781),urinary sodium excretion (UNa), lipid profile, glucose (colorimetric), insulin (radioinmunoanalysis), usCRP (inmunoturbidimetry). To evaluate parasympathetic tone we determined heart rate-recovery in the first minute after the end of stress-test (HRR). UNa was stratified by using tertiles(table). RESULTS (table): Patients with high levels of UNa presented lower levels of HRR and HDL, and higher levels of Tg, insulin, HOMAir and usCRP (univariate analysis) while HRR (p < 0.03) and HDL (p < 0.02) were the significant variables in multivariate analysis. Figure 1. No caption available. Conclusion: Higher levels of salt intake were associated with a reduction in parasympathetic tone and metabolic abnormalities (lower levels of HDL; and higher levels of triglycerides, insulin and HOMAir). Sympathetic activation secondary to a loss of parasympathetic modulation in the brainstem maybe the cause of metabolic and inflammatory abnormalities observed. A reduction in sodium intake would have a potential impact in the restoration of the autonomic balance and in the regression of these alterations beyond its benefits on blood pressure.