Ivonne Hernandez Schulman

Postovariectomy Hypertension Is Linked to Increased Renal AT1 Receptor and Salt Sensitivity

Abstract—The functional balance between angiotensin II (Ang II) and nitric oxide (NO) plays a key role in modulating salt sensitivity. Estrogen has been shown to downregulate angiotensin type 1 (AT1) receptor expression and to increase the bioavailability of endothelium-derived NO, which decreases AT1 receptor expression. The present study tests the hypothesis that in the presence of genetic salt sensitivity, deficiency of endogenous estrogens after ovariectomy (OVX) fosters an upregulation of Ang II. Female Dahl salt-resistant (DR), Dahl salt-sensitive (DS), Wistar-Kyoto (WKY), and spontaneously hypertensive (SHR) rats underwent bilateral OVX or sham surgery (SHX) and were fed a normal salt diet (0.5% NaCl) for 14 weeks. Systolic blood pressures were measured every 2 weeks and were not significantly different between OVX and SHX for DR, WKY, and SHR groups. However, at the end of 14 weeks of normal salt diet, hypertension developed in DS OVX but not SHX rats (160±3 versus 136±3 mm Hg; P <0.05). Hypertension also developed in DS OVX rats pair-fed a normal salt diet (166±7 mm Hg). Development of hypertension in DS OVX rats was prevented by estrogen replacement (132±3 mm Hg), AT1 receptor blockade (119±3 mm Hg), or feeding a very low salt diet (0.1% NaCl; 129±4 mm Hg). Renal AT1 receptor protein expression was significantly elevated 2-fold in DS OVX relative to SHX rats and was prevented by estrogen replacement. These data strongly suggest that after OVX in salt-sensitive rats there is a lower threshold for the hypertensinogenic effect of salt that is linked to an activation of Ang II.

Reduced NAD(P)H Oxidase in Low Renin Hypertension: Link Among Angiotensin II, Atherogenesis, and Blood Pressure

Endothelial dysfunction (ED) complicates hypertension and is a precursor of atherosclerosis. Reduced NO bioactivity, because of increased reduced NAD(P)H oxidase–derived reactive oxygen species (ROS), plays a critical role in ED. gp91phox, predominantly expressed in the endothelium and adventitia, is a subunit of NAD(P)H oxidase important for its activation in response to angiotensin (Ang) II. Human atherosclerotic plaques are heavy laden with gp91phox. We have shown that in Dahl salt-sensitive (DS) rats, a paradigm of low renin salt-sensitive (SS) hypertension in humans, Ang II receptor blockade normalizes ROS production and endothelium-dependent relaxation (EDR) without significantly affecting systolic blood pressure (SBP). To additionally elucidate the mechanisms involved in the functional association of Ang II in SS hypertension, we administered a cell-permeable inhibitor of the assembly of p47phox with gp91phox in NAD(P)H oxidase, gp91ds-tat (10 mg/kg body weight, 3 weeks by minipump), to DS rats fed a 4% salt diet. Control rats received either vehicle or an inactive scramb-tat peptide. Vehicle-treated DS developed hypertension (SBP 168±5 mm Hg), left ventricular hypertrophy (LVH), proteinuria, impaired EDR, and increased aortic ROS production (superoxide 115% and peroxynitrite 157%) and expression of the proatherogenic molecules LOX-1 (130%) and MCP-1 (166%). gp91ds-tat, but not scramb-tat, normalized ROS and EDR, as well as LOX-1 and MCP-1, despite nonsignificant effects on SBP (159±5 mm Hg; P>0.05), left ventricular hypertrophy, and proteinuria. Our findings support the notion that in SS hypertension, activation of NAD(P)H oxidase promotes ED and atherogenesis via decreased nitric oxide bioactivity and increased LOX-1 and MCP-1, independent of blood pressure.

Dynamic denitrosylation via S-nitrosoglutathione reductase regulates cardiovascular function

Although protein S-nitrosylation is increasingly recognized as mediating nitric oxide (NO) signaling, roles for protein denitrosylation in physiology remain unknown. Here, we show that S-nitrosoglutathione reductase (GSNOR), an enzyme that governs levels of S-nitrosylation by promoting protein denitrosylation, regulates both peripheral vascular tone and β-adrenergic agonist-stimulated cardiac contractility, previously ascribed exclusively to NO/cGMP. GSNOR-deficient mice exhibited reduced peripheral vascular tone and depressed β-adrenergic inotropic responses that were associated with impaired β-agonist–induced denitrosylation of cardiac ryanodine receptor 2 (RyR2), resulting in calcium leak. These results indicate that systemic hemodynamic responses (vascular tone and cardiac contractility), both under basal conditions and after adrenergic activation, are regulated through concerted actions of NO synthase/GSNOR and that aberrant denitrosylation impairs cardiovascular function. Our findings support the notion that dynamic S-nitrosylation/denitrosylation reactions are essential in cardiovascular regulation.

Interaction between nitric oxide and angiotensin II in the endothelium: role in atherosclerosis and hypertension.

Background Although there is overwhelming evidence that hypertension promotes atherosclerosis, the relative contribution and/or interaction of vasoactive and hemodynamic factors remain undefined. Endothelial dysfunction complicates hypertension and is a precursor of atherosclerosis. It is characterized by a reduction in the bioavailability of vasodilators, particularly nitric oxide, and an increase in the activity of vasoconstrictors, including angiotensin (Ang) II and reactive oxygen species (ROS). Nitric oxide antagonizes the vasoconstrictive and pro-atherosclerotic effects of Ang II, whereas Ang II decreases nitric oxide bioavailability by promoting oxidative stress. Objectives The present review will focus on the interaction among nitric oxide, Ang II, and ROS in the endothelium and will examine their role in vascular tone and atherogenesis. In this context, studies from our laboratory will be reviewed demonstrating that salt-sensitive hypertension is a vascular diathesis characterized by a local activation of Ang II and NAD(P)H oxidase-derived ROS in the setting of insufficient nitric oxide. In hypertensive Dahl salt-sensitive rats, a paradigm of human salt-sensitive hypertension, inhibition of Ang II type 1 receptor or NAD(P)H oxidase-derived ROS prevented the development of endothelial dysfunction, upregulation of pro-atherogenic molecules, and vascular ROS generation, independently of blood pressure. Conclusions Salt sensitivity, an independent risk factor for increased cardiovascular morbidity and mortality, affects approximately 50% of hypertensives. Our studies suggest that, in salt-sensitive hypertension, atherogenesis is more closely linked to oxidative stress than to the hemodynamic stress of hypertension. To prevent or arrest atherosclerosis, antihypertensive therapy should aim at restoring the homeostatic balance between vasoactive factors in the vascular wall.

Surgical Menopause Increases Salt Sensitivity of Blood Pressure

Salt sensitivity of blood pressure is associated with an elevated risk of developing hypertension (HTN) and is an independent risk factor for cardiovascular disease. The prevalence of HTN increases after menopause. The aim of this study was to investigate prospectively whether the loss of ovarian hormones increases the occurrence of salt sensitivity among healthy premenopausal women. We enrolled 40 normotensive, nondiabetic women (age 47.2±3.5), undergoing hysterectomy–oophorectomy for nonneoplastic processes and not on hormone replacement, to determine the effect of changes in sodium intake on blood pressure the day before and subsequently 4 months after surgical menopause. Salt loading was achieved using a 2-L normal saline infusion and salt depletion produced by 40 mg of intravenous furosemide. A decrease >10 mm Hg in systolic blood pressure between salt loading and salt depletion was used to define salt sensitivity. Before and after menopause, salt-sensitive women exhibited higher waist/hip and waist/thigh ratios (P<0.01). Although all of the women remained normotensive, the prevalence of salt sensitivity was significantly higher after surgical menopause (21 women; 52.5%) than before (9 women; 22.5%; P=0.01), because 12 (38.7%) salt-resistant women developed salt sensitivity after menopause. In summary, we demonstrated that the prevalence of salt sensitivity doubled as early as 4 months after surgical menopause, without an associated increase in blood pressure. Epidemiological studies indicate that development of HTN may not occur until 5 to 10 years after menopause. The loss of ovarian hormones may unmask a population of women prone to salt sensitivity who, with aging, would be at higher risk for the subsequent development of HTN and cardiovascular disease.

The Advancing Field of Cell‐Based Therapy: Insights and Lessons From Clinical Trials

Stem cell therapy aimed at restoring organ function, notably myocardial repair and regeneration postmyocardial infarction (MI), is one of the most exciting and promising frontiers of medical research. While new pharmacotherapies and advances in interventional cardiology have significantly reduced the mortality of ischemic heart disease and heart failure, there remains an ongoing need for innovative cellbased therapies that can prevent or reverse cardiac ventricular remodeling post-MI. Although questions remain on how to best implement cell-based interventions, a growing number of preclinical studies and clinical trials have demonstrated the safety of a variety of adult stem cell types. This review will focus on the collective progress in cardiovascular regenerative medicine, with particular emphasis on the findings from the most recently published or announced clinical trials: the

Cell-based therapy for prevention and reversal of myocardial remodeling

Although pharmacological and interventional advances have reduced the morbidity and mortality of ischemic heart disease, there is an ongoing need for novel therapeutic strategies that prevent or reverse progressive ventricular remodeling following myocardial infarction, the process that forms the substrate for ventricular failure. The development of cell-based therapy as a strategy to repair or regenerate injured tissue offers extraordinary promise for a powerful anti-remodeling therapy. In this regard, the field of cell therapy has made major advancements in the past decade. Accumulating data from preclinical studies have provided novel insights into stem cell engraftment, differentiation, and interactions with host cellular elements, as well as the effectiveness of various methods of cell delivery and accuracy of diverse imaging modalities to assess therapeutic efficacy. These findings have in turn guided rationally designed translational clinical investigations. Collectively, there is a growing understanding of the parameters that underlie successful cell-based approaches for improving heart structure and function in ischemic and other cardiomyopathies.

Does Transendocardial Injection of Mesenchymal Stem Cells Improve Myocardial Function Locally or Globally? An Analysis From the Percutaneous Stem Cell Injection Delivery Effects on Neomyogenesis (POSEIDON) Randomized Trial

Rationale: Transendocardial stem cell injection (TESI) with mesenchymal stem cells improves remodeling in chronic ischemic cardiomyopathy, but the effect of the injection site remains unknown. Objective: To address whether TESI exerts its effects at the site of injection only or also in remote areas, we hypothesized that segmental myocardial scar and segmental ejection fraction improve to a greater extent in injected than in noninjected segments. Methods and Results: Biplane ventriculographic and endocardial tracings were recorded. TESI was guided to 10 sites in infarct-border zones. Sites were mapped according to the 17-myocardial segment model. As a result, 510 segments were analyzed in 30 patients before and 13 months after TESI. Segmental early enhancement defect (a measure of scar size) was reduced by TESI in both injected (−43.7±4.4%; n=95; P<0.01) and noninjected segments (−25.1±7.8%; n=148; P<0.001; between-group comparison P<0.05). Conversely, segmental ejection fraction (a measure of contractile performance) improved in injected scar segments (19.9±3.3–26.3±3.5%; P=0.003) but not in noninjected scar segments (21.3±2.6–23.5±3.2%; P=0.20; between-group comparison P<0.05). Furthermore, segmental ejection fraction in injected scar segments improved to a greater degree in patients with baseline segmental ejection fraction <20% (12.1±1.2–19.9±2.7%; n=18; P=0.003), versus <20% (31.7±3.4–35.5±3.3%; n=12; P=0.33, between-group comparison P<0.0001). Conclusions: These findings illustrate a dichotomy in regional responses to TESI. Although scar size reduction was evident in all scar segments, scar size reduction and ventricular functional responses preferentially occurred at the sites of TESI versus non-TESI sites. Furthermore, improvement was greatest when segmental left ventricular dysfunction was severe.Rationale: Transendocardial stem cell injection (TESI) with mesenchymal stem cells improves remodeling in chronic ischemic cardiomyopathy, but the effect of the injection site remains unknown. Objective: To address whether TESI exerts its effects at the site of injection only or also in remote areas, we hypothesized that segmental myocardial scar and segmental ejection fraction improve to a greater extent in injected than in noninjected segments. Methods and Results: Biplane ventriculographic and endocardial tracings were recorded. TESI was guided to 10 sites in infarct-border zones. Sites were mapped according to the 17-myocardial segment model. As a result, 510 segments were analyzed in 30 patients before and 13 months after TESI. Segmental early enhancement defect (a measure of scar size) was reduced by TESI in both injected (−43.7±4.4%; n=95; P <0.01) and noninjected segments (−25.1±7.8%; n=148; P <0.001; between-group comparison P <0.05). Conversely, segmental ejection fraction (a measure of contractile performance) improved in injected scar segments (19.9±3.3–26.3±3.5%; P =0.003) but not in noninjected scar segments (21.3±2.6–23.5±3.2%; P =0.20; between-group comparison P <0.05). Furthermore, segmental ejection fraction in injected scar segments improved to a greater degree in patients with baseline segmental ejection fraction <20% (12.1±1.2–19.9±2.7%; n=18; P =0.003), versus <20% (31.7±3.4–35.5±3.3%; n=12; P =0.33, between-group comparison P <0.0001). Conclusions: These findings illustrate a dichotomy in regional responses to TESI. Although scar size reduction was evident in all scar segments, scar size reduction and ventricular functional responses preferentially occurred at the sites of TESI versus non-TESI sites. Furthermore, improvement was greatest when segmental left ventricular dysfunction was severe. # Novelty and Significance {#article-title-37}

Vascular inflammation, insulin resistance, and endothelial dysfunction in salt-sensitive hypertension: role of nuclear factor kappa B activation

Objectives Activation of the nuclear factor kappa B (NFκB) inflammatory pathway by angiotensin II and reactive oxygen species may play an important role in the development of insulin resistance and cardiovascular injury in hypertensive and metabolic diseases. We have shown that in hypertensive Dahl salt-sensitive rats, upregulation of angiotensin II and reactive oxygen species contributed to increased vascular inflammatory gene expression, endothelial dysfunction, and insulin resistance. Herein, we investigated whether activation of NFκB contributes to the development of endothelial dysfunction, vascular injury, and vascular and peripheral insulin resistance in salt-sensitive hypertension. Methods Dahl salt-sensitive rats were fed a normal (0.5% NaCl) or high-salt diet (4% NaCl), or high-salt diet and pyrrolidine dithiocarbamat (150 mg/kg in drinking water), an inhibitor of NFκB activation, for 6 weeks. Results Hypertensive Dahl salt-sensitive rats manifested impaired endothelium-dependent relaxation to acetylcholine, aortic hypertrophy (35%), increased plasma C-reactive protein (25%), vascular superoxide (O2−) production (148%), and expression of monocyte chemoattractant protein-1, tumor necrosis factor alpha, phospho-IκBα, and phospho-(Ser536)-p65NFκB. Pyrrolidine dithiocarbamat significantly improved endothelium-dependent relaxation, reduced vascular O2−, and normalized aortic hypertrophy and systemic and local inflammation, despite only mildly reducing blood pressure. Hypertensive Dahl salt-sensitive rats also manifested impaired insulin-mediated vasorelaxation and Akt/endothelial nitric oxide synthase phosphorylation and decreased insulin sensitivity by hyperinsulinemic–euglycemic clamp (glucose infusion rate, −32%). Pyrrolidine dithiocarbamat significantly improved insulin-mediated vascular relaxation and Akt/endothelial nitric oxide synthase phosphorylation as well as insulin sensitivity. Conclusion The current findings strongly suggest that activation of the NFκB inflammatory pathway by angiotensin II-induced reactive oxygen species generation may importantly contribute to vascular injury, systemic inflammation, as well as vascular and peripheral insulin resistance in salt-sensitive hypertension.

Does Transendocardial Injection of Mesenchymal Stem Cells Improve Myocardial Function Locally or Globally? An Analysis From the POSEIDON Randomized Trial

Rationale: Transendocardial stem cell injection (TESI) with mesenchymal stem cells improves remodeling in chronic ischemic cardiomyopathy, but the effect of the injection site remains unknown. Objective: To address whether TESI exerts its effects at the site of injection only or also in remote areas, we hypothesized that segmental myocardial scar and segmental ejection fraction improve to a greater extent in injected than in noninjected segments. Methods and Results: Biplane ventriculographic and endocardial tracings were recorded. TESI was guided to 10 sites in infarct-border zones. Sites were mapped according to the 17-myocardial segment model. As a result, 510 segments were analyzed in 30 patients before and 13 months after TESI. Segmental early enhancement defect (a measure of scar size) was reduced by TESI in both injected (−43.7±4.4%; n=95; P<0.01) and noninjected segments (−25.1±7.8%; n=148; P<0.001; between-group comparison P<0.05). Conversely, segmental ejection fraction (a measure of contractile performance) improved in injected scar segments (19.9±3.3–26.3±3.5%; P=0.003) but not in noninjected scar segments (21.3±2.6–23.5±3.2%; P=0.20; between-group comparison P<0.05). Furthermore, segmental ejection fraction in injected scar segments improved to a greater degree in patients with baseline segmental ejection fraction <20% (12.1±1.2–19.9±2.7%; n=18; P=0.003), versus <20% (31.7±3.4–35.5±3.3%; n=12; P=0.33, between-group comparison P<0.0001). Conclusions: These findings illustrate a dichotomy in regional responses to TESI. Although scar size reduction was evident in all scar segments, scar size reduction and ventricular functional responses preferentially occurred at the sites of TESI versus non-TESI sites. Furthermore, improvement was greatest when segmental left ventricular dysfunction was severe.Rationale: Transendocardial stem cell injection (TESI) with mesenchymal stem cells improves remodeling in chronic ischemic cardiomyopathy, but the effect of the injection site remains unknown. Objective: To address whether TESI exerts its effects at the site of injection only or also in remote areas, we hypothesized that segmental myocardial scar and segmental ejection fraction improve to a greater extent in injected than in noninjected segments. Methods and Results: Biplane ventriculographic and endocardial tracings were recorded. TESI was guided to 10 sites in infarct-border zones. Sites were mapped according to the 17-myocardial segment model. As a result, 510 segments were analyzed in 30 patients before and 13 months after TESI. Segmental early enhancement defect (a measure of scar size) was reduced by TESI in both injected (−43.7±4.4%; n=95; P <0.01) and noninjected segments (−25.1±7.8%; n=148; P <0.001; between-group comparison P <0.05). Conversely, segmental ejection fraction (a measure of contractile performance) improved in injected scar segments (19.9±3.3–26.3±3.5%; P =0.003) but not in noninjected scar segments (21.3±2.6–23.5±3.2%; P =0.20; between-group comparison P <0.05). Furthermore, segmental ejection fraction in injected scar segments improved to a greater degree in patients with baseline segmental ejection fraction <20% (12.1±1.2–19.9±2.7%; n=18; P =0.003), versus <20% (31.7±3.4–35.5±3.3%; n=12; P =0.33, between-group comparison P <0.0001). Conclusions: These findings illustrate a dichotomy in regional responses to TESI. Although scar size reduction was evident in all scar segments, scar size reduction and ventricular functional responses preferentially occurred at the sites of TESI versus non-TESI sites. Furthermore, improvement was greatest when segmental left ventricular dysfunction was severe. # Novelty and Significance {#article-title-37}