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Modulation of the renin-angiotensin-aldosterone system is a foundation of therapy for cardiovascular and kidney diseases. Excess aldosterone plays an important role in cardiovascular disease, contributing to inflammation, fibrosis, and dysfunction in the heart, kidneys, and vasculature through both genomic and mineralocorticoid receptor (MR)-mediated as well as nongenomic mechanisms. MR antagonists have been a key therapy for attenuating the pathologic effects of aldosterone but are associated with some side effects and may not always adequately attenuate the nongenomic effects of aldosterone. Aldosterone is primarily synthesized by the CYP11B2 aldosterone synthase enzyme, which is very similar in structure to other enzymes involved in steroid biosynthesis including CYP11B1, a key enzyme involved in glucocorticoid production. Lack of specificity for CYP11B2, off-target effects on the hypothalamic-pituitary-adrenal axis, and counterproductive increased levels of bioactive steroid intermediates such as 11-deoxycorticosterone have posed challenges in the development of early aldosterone synthase inhibitors such as osilodrostat. In early-phase clinical trials, newer aldosterone synthase inhibitors demonstrated promise in lowering blood pressure in patients with treatment-resistant and uncontrolled hypertension. It is therefore plausible that these agents offer protection in other disease states including heart failure or chronic kidney disease. Further clinical evaluation will be needed to clarify the role of aldosterone synthase inhibitors, a promising class of agents that represent a potentially major therapeutic advance. [ABSTRACT FROM AUTHOR]

Plasma soluble prorenin receptor (sPRR) displays sexual dimorphism and is higher in women with type 2 diabetes mellitus (T2DM). However, the contribution of plasma sPRR to the development of vascular complications in T2DM remains unclear. We investigated if plasma sPRR contributes to sex differences in the activation of the systemic renin-angiotensin-aldosterone system (RAAS) and vascular damage in a model of high-fat diet (HFD)-induced T2DM. Male and female C57BL/6J mice were fed either a normal fat diet (NFD) or an HFD for 28 wk to assess changes in blood pressure, cardiometabolic phenotype, plasma prorenin/renin, sPRR, and ANG II. After completing dietary protocols, tissues were collected from males to assess vascular reactivity and aortic reactive oxygen species (ROS). A cohort of male mice was used to determine the direct contribution of increased systemic sPRR by infusion. To investigate the role of ovarian hormones, ovariectomy (OVX) was performed at 32 wk in females fed either an NFD or HFD. Significant sex differences were found after 28 wk of HFD, where only males developed T2DM and increased plasma prorenin/renin, sPRR, and ANG II. T2DM in males was accompanied by nondipping hypertension, carotid artery stiffening, and aortic ROS. sPRR infusion in males induced vascular thickening instead of material stiffening caused by HFD-induced T2DM. While intact females were less prone to T2DM, OVX increased plasma prorenin/renin, sPRR, and systolic blood pressure. These data suggest that sPRR is a novel indicator of systemic RAAS activation and reflects the onset of vascular complications during T2DM regulated by sex. NEW & NOTEWORTHY High-fat diet (HFD) for 28 wk leads to type 2 diabetes mellitus (T2DM) phenotype, concomitant with increased plasma soluble prorenin receptor (sPRR), nondipping blood pressure, and vascular stiffness in male mice. HFD-fed female mice exhibiting a preserved cardiometabolic phenotype until ovariectomy revealed increased plasma sPRR and blood pressure. Plasma sPRR may indicate the status of systemic renin-angiotensin-aldosterone system (RAAS) activation and the onset of vascular complications during T2DM in a sex-dependent manner. [ABSTRACT FROM AUTHOR]

Peripherally or centrally administered TNF-α elicits a prolonged sympathetically mediated pressor response, but the underlying molecular mechanisms are unknown. Activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in cardiovascular regions of the brain has recently been recognized as a key mediator of sympathetic excitation, and ERK1/2 signaling is induced by activation of epidermal growth factor receptor (EGFR) tyrosine kinase activity. The present study examined the role of EGFR and ERK1/2 signaling in the sympathetic response to TNF-α. In urethane-anesthetized rats, intracarotid artery injection of TNF-α increased phosphorylation of EGFR and ERK1/2 in the subfornical organ (SFO) and the hypothalamic paraventricular nucleus (PVN); upregulated the gene expression of excitatory mediators in SFO and PVN; and increased blood pressure (BP), heart rate (HR), and renal sympathetic nerve activity (RSNA). A continuous intracerebroventricular infusion of the selective EGFR tyrosine kinase inhibitor AG1478 or the ERK1/2 inhibitor PD98059 significantly attenuated these responses. Bilateral PVN microinjections of TNF-α also increased phosphorylated ERK1/2 and the gene expression of excitatory mediators in PVN, along with increases in BP, HR, and RSNA, and these responses were substantially reduced by prior bilateral PVN microinjections of AG1478. These results identify activation of EGFR in cardiovascular regulatory regions of the forebrain as an important molecular mediator of TNF-α-driven sympatho-excitatory responses and suggest that EGFR activation of the ERK1/2 signaling pathway plays an essential role. These mechanisms likely contribute to sympathetic excitation in pathophysiological states like heart failure and hypertension, in which circulating and brain TNF-α levels are increased. NEW & NOTEWORTHY Proinflammatory cytokines contribute to the augmented sympathetic nerve activity in hypertension and heart failure, but the central mechanisms involved are largely unknown. The present study reveals that TNF-α transactivates EGFR in the subfornical organ and the hypothalamic paraventricular nucleus to initiate ERK1/2 signaling, upregulate the gene expression of excitatory mediators, and increase sympathetic nerve activity. These findings identify EGFR as a gateway to sympathetic excitation and a potential target for intervention in cardiovascular disease states. [ABSTRACT FROM AUTHOR]

South AM, Diz DI, Chappell MC. COVID-19, ACE2, and the cardiovascular consequences. Am J Physiol Heart Circ Physiol 318: H1084-H1090, 2020. First published March 31, 2020; doi:10.1152/ajpheart.00217.2020.--The novel SARS coronavirus SARS-CoV-2 pandemic may be particularly deleterious to patients with underlying cardiovascular disease (CVD). The mechanism for SARS-CoV-2 infection is the requisite binding of the virus to the membrane-bound form of angiotensin-converting enzyme 2 (ACE2) and internalization of the complex by the host cell. Recognition that ACE2 is the coreceptor for the coronavirus has prompted new therapeutic approaches to block the enzyme or reduce its expression to prevent the cellular entry and SARS-CoV-2 infection in tissues that express ACE2 including lung, heart, kidney, brain, and gut. ACE2, however, is a key enzymatic component of the renin-angiotensin-aldosterone system (RAAS); ACE2 degrades ANG II, a peptide with multiple actions that promote CVD, and generates Ang-(1-7), which antagonizes the effects of ANG II. Moreover, experimental evidence suggests that RAAS blockade by ACE inhibitors, ANG II type 1 receptor antagonists, and mineralocorticoid antagonists, as well as statins, enhance ACE2 which, in part, contributes to the benefit of these regimens. In lieu of the fact that many older patients with hypertension or other CVDs are routinely treated with RAAS blockers and statins, new clinical concerns have developed regarding whether these patients are at greater risk for SARS-CoV-2 infection, whether RAAS and statin therapy should be discontinued, and the potential consequences of RAAS blockade to COVID-19-related pathologies such as acute and chronic respiratory disease. The current perspective critically examines the evidence for ACE2 regulation by RAAS blockade and statins, the cardiovascular benefits of ACE2, and whether ACE2 blockade is a viable approach to attenuate COVID-19. [ABSTRACT FROM AUTHOR]

Accumulating evidence supports that the brain renin-angiotensin system (RAS), including prorenin (PR) and its receptor (PRR), two newly discovered RAS players, contribute to sympathoexcitation in salt-sensitive hypertension. Still, whether PR also contributed to elevated circulating levels of neurohormones such as vasopressin (VP) during salt-sensitive hypertension, and if so, what are the precise underlying mechanisms, remains to be determined. To address these questions, we obtained patch-clamp recordings from hypothalamic magnocellular neurosecretory neurons (MNNs) that synthesize the neurohormones oxytocin and VP in acute hypothalamic slices obtained from sham and deoxycorticosterone acetate (DOCA)-salt-treated hypertensive rats. We found that focal application of PR markedly increased membrane excitability and firing responses in MNNs of DOCA-salt, compared with sham rats. This effect included a shorter latency to spike initiation and increased numbers of spikes in response to depolarizing stimuli and was mediated by a more robust inhibition of A-type K+ channels in DOCA-salt compared with sham rats. On the other hand, the afterhyperpolarizing potential mediated by the activation of Ca2+ dependent K+ channel was not affected by PR. mRNA expression of PRR, VP, and the Kv4.3 K+ channel subunit in the supraoptic nucleus of DOCA-salt hypertensive rats was increased compared with sham rats. Finally, we report a significant decrease of plasma VP levels in neuron-selective PRR knockdown mice treated with DOCA-salt, compared with wild-type DOCA-salt-treated mice. Together, these results support that activation of PRR contributes to increased excitability and firing discharge of MNNs and increased plasma levels of VP in DOCA-salt hypertension. [ABSTRACT FROM AUTHOR]

Fetal exposure to betamethasone (BMX) as a consequence of glucocorticoid administration to women threatening premature delivery may lead to long-term deleterious effects on the cardiovascular system and dysregulation of blood pressure in exposed adults. Indeed, adult offspring of BMX sheep exhibit increased mean arterial pressure (MAP) and attenuated baroreflex sensitivity (BRS) that are associated with lower medullary and cerebrospinal fluid (CSF) angiotensin-(1-7) [(ANG-(1-7)] content. Thus we determined the effects of ANG-(1-7) supplementation in the CSF on MAP, BRS, blood pressure (BPV) and heart rate variability (HRV) in conscious animals. The peptide or artificial CSF (aCSF) was infused continuously into the lateral ventricle (intracerebroventricular) of 4-mo-old male and female BMX sheep for 2 wk. Analysis of data from males and females combined revealed that intracerebroventricular ANG-(1-7) significantly lowered MAP and heart rate and improved BRS as compared with baseline; intracerebroventricular aCSF did not change these indexes. Similar patterns were observed for altered hemodynamics and autonomic function produced by intracerebroventricular ANG-(1-7) in both sexes. Oxidative stress and MAP kinase (MAPK) activation were lower in tissues from the dorsomedial medulla (DMM) of ANG-(1-7)-treated males but were unchanged in the treated females, when assessed at the end of the treatment period. We conclude that in the face of ANG-(1-7) deficiency in CSF and medullary tissue in BMX sheep intracerebroventricular supplementation of ANG-(1-7) lowers MAP and restores the impaired autonomic function to a similar degree in both males and females; however, the attenuation of MAPK and oxidative stress within the DMM was evident only in males. [ABSTRACT FROM AUTHOR]

Activation of the brain renin-angiotensin system (RAS) is a pivotal step in the pathogenesis of hypertension. The paraventricular nucleus (PVN) of the hypothalamus is a critical part of the angiotensinergic sympatho-excitatory neuronal network involved in neural control of blood pressure and hypertension. However, the importance of the PVN (pro)renin receptor (PVN-PRR)-a key component of the brain RAS-in hypertension development has not been examined. In this study, we investigated the involvement and mechanisms of the PVN-PRR in DOCA-salt-induced hypertension, a mouse model of hypertension. Using nanoinjection of adeno-associated virus-mediated Cre recombinase expression to knock down the PRR specifically in the PVN, we report here that PVN-PRR knockdown attenuated the enhanced blood pressure and sympathetic tone associated with hypertension. Mechanistically, we found that PVN-PRR knockdown was associated with reduced activation of ERK (extracellular signalregulated kinase)-1/2 in the PVN and rostral ventrolateral medulla during hypertension. In addition, using the genetically encoded Ca2+ biosensor GCaMP6 to monitor Ca2+-signaling events in the neurons of PVN brain slices, we identified a reduction in angiotensin II type 1 receptor-mediated Ca2+ activity as part of the mechanism by which PVN-PRR knockdown attenuates hypertension. Our study demonstrates an essential role of the PRR in PVN neurons in hypertension through regulation of ERK1/2 activation and angiotensin II type 1 receptor-mediated Ca2+ activity. [ABSTRACT FROM AUTHOR]

A growing body of data provides strong evidence that intracellular angiotensin II (ANG II) plays an important role in mammalian cell function and is involved in the pathogenesis of human diseases such as hypertension, diabetes, inflammation, fibrosis, arrhythmias, and kidney disease, among others. Recent studies also suggest that intracellular ANG II exerts protective effects in cells during high extracellular levels of the hormone or during chronic stimulation of the local tissue reninangiotensin system (RAS). Notably, the intracellular RAS (iRAS) described in neurons, fibroblasts, renal cells, and cardiomyocytes provided new insights into regulatory mechanisms mediated by intracellular ANG II type 1 (AT1Rs) and 2 (AT2Rs) receptors, particularly, in mitochondria and nucleus. For instance, ANG II through nuclear AT1Rs promotes protective mechanisms by stimulating the AT2R signaling cascade, which involves mitochondrial AT2Rs and Mas receptors. The stimulation of nuclear ANG II receptors enhances mitochondrial biogenesis through peroxisome proliferator-activated receptor-γ coactivator-1α and increases sirtuins activity, thus protecting the cell against oxidative stress. Recent studies in ANG II-induced preconditioning suggest that plasma membrane AT2R stimulation exerts protective effects against cardiac ischemia-reperfusion by modulating mitochondrial AT1R and AT2R signaling. These studies indicate that iRAS promotes the protection of cells through nuclear AT1R signaling, which, in turn, promotes AT2R-dependent processes in mitochondria. Thus, despite abundant data on the deleterious effects of intracellular ANG II, a growing body of studies also supports a protective role for iRAS that could be of relevance to developing new therapeutic strategies. This review summarizes and discusses previous studies on the role of iRAS, particularly emphasizing the protective and counterbalancing actions of iRAS, mitochondrial ANG II receptors, and their implications for organ protection. [ABSTRACT FROM AUTHOR]

Sex differences in blood pressure and the prevalence of hypertension are found in humans and animal models. Moreover, there has been a recent explosion of data concerning sex differences in nitric oxide, the renin-angiotensin-aldosterone system, inflammation, and kidney function. These data have the potential to reveal the mechanisms underlying male-female differences in blood pressure control. To elucidate the interactions among the multitude of physiological processes involved, one may apply computational models. In this review, we describe published computational models that represent key players in blood pressure regulation, and highlight sex-specific models and their findings. [ABSTRACT FROM AUTHOR]

Thirty years ago, a novel axis of the renin-angiotensin system (RAS) was unveiled by the discovery of angiotensin- (1-7) [ANG-(1-7)] generation in vivo. Later, angiotensin-converting enzyme 2 (ACE2) was shown to be the main mediator of this reaction, and Mas was found to be the receptor for the heptapeptide. The functional analysis of this novel axis of the RAS that followed its discovery revealed numerous protective actions in particular for cardiovascular diseases. In parallel, similar protective actions were also described for one of the two receptors of ANG II, the ANG II type 2 receptor (AT2R), in contrast to the other, the ANG II type 1 receptor (AT1R), which mediates deleterious actions of this peptide, e.g., in the setting of cardiovascular disease. Very recently, another branch of the RAS was discovered, based on angiotensin peptides in which the amino-terminal aspartate was replaced by alanine, the alatensins. Ala-ANG-(1-7) or alamandine was shown to interact with Mas-related G protein-coupled receptor D, and the first functional data indicated that this peptide also exerts protective effects in the cardiovascular system. This review summarizes the presentations given at the International Union of Physiological Sciences Congress in Rio de Janeiro, Brazil, in 2017, during the symposium entitled "The Renin-Angiotensin System: Going Beyond the Classical Paradigms," in which the signaling and physiological actions of ANG-(1-7), ACE2, AT2R, and alatensins were reported (with a focus on noncentral nervous system-related tissues) and the therapeutic opportunities based on these findings were discussed. [ABSTRACT FROM AUTHOR]

Deletion of the prorenin receptor (PRR) in adipose tissue elevates systolic blood pressure (SBP) and the circulating soluble form of PRR (sPRR) in male mice fed a high-fat (HF) diet. However, sex differences in the contribution of adipose- PRR and sPRR to the regulation of the renin-angiotensin system (RAS) in key organs for blood pressure control are undefined. Therefore, we assessed blood pressure and the systemic and intrarenal RAS status in adipose-PRR knockout (KO) female mice. Blockade of RAS with losartan blunted SBP elevation in HF diet-fed adipose-PRR KO mice. ANG II levels were significantly increased in the renal cortex of HF diet-fed adipose-PRR KO female mice, but not systemically. HF diet-fed adipose-PRR KO mice exhibited higher vasopressin levels, water retention, and lower urine output than wild-type (WT) mice. The results also showed that deletion of adipose-PRR increased circulating sPRR and total hepatic sPRR contents, suggesting the liver as a major source of elevated plasma sPRR in adipose-PRR KO mice. To mimic the elevation of circulating sPRR and define the direct contribution of systemic sPRR to the regulation of the RAS and vasopressin, C57BL/6 female mice fed a standard diet were infused with recombinant sPRR. sPRR infusion increased plasma renin levels, renal and hepatic angiotensinogen expression, and vasopressin. Together, these results demonstrate that the deletion of adipose-PRR induced an elevation of SBP likely mediated by an intrarenal ANG II-dependent mechanism and that sPRR participates in RAS regulation and body fluid homeostasis via its capacity to activate the RAS and increase vasopressin levels. [ABSTRACT FROM AUTHOR]

Although anticancer systemic therapy agents clearly lead to improved survival in patients with cancer, these can come at the cost of serious complications including cardiotoxicity. Two types of targeted systemic therapies currently in use for colorectal cancer (CRC) and renal cell cancer (RCC), respectively, include the vascular endothelial growth factor inhibitor bevacizumab (BVZ) and the tyrosine kinase inhibitor sunitinib (SNT). Despite the beneficial effects of BVZ and SNT in improving clinical outcomes in the settings of CRC and RCC, there is an increased risk of cardiac dysfunction. The aim of the present study was to determine whether prophylactic administration of renin-angiotensin system (RAS) inhibitors would attenuate the cardiotoxic side effects of BVZ or SNT in a chronic in vivo murine model. A total of 194 wild-type C57Bl/6 male mice received: 1) 0.9% saline, 2) BVZ (10 mg·kg-1·wk-1), or 3) SNT (40 mg·kg-1·day-1) for 4 wk. Within each arm, mice received daily prophylactic treatment with hydralazine (0.05 mg/ml), aliskiren (50 mg/kg), perindopril (4 mg/kg), or valsartan (2 mg/kg). Although hydralazine effectively lowered blood pressure in BVZ- or SNTtreated mice, it did not prevent left ventricular systolic dysfunction. Prophylactic administration of aliskiren, perindopril, or valsartan prevented adverse cardiovascular remodeling in mice treated with either BVZ or SNT. The addition of RAS antagonists also downregulated expression of phosphorylated p38 and Bcl-2-like 19-kDa interacting protein 3 in SNT-treated mice. In our chronic in vivo murine model, RAS antagonists partially attenuated the development of BVZor SNT-mediated cardiac dysfunction. Future clinical studies are warranted to investigate the cardioprotective effects of prophylactic treatment with RAS inhibitors in the settings of CRC and RCC. [ABSTRACT FROM AUTHOR]

Sex differences in the presentation, outcome, and responses to treatment of systolic heart failure (HF) have been reported. In the present study, we examined the effect of sex on central neural mechanisms contributing to neurohumoral excitation and its peripheral manifestations in rats with HF. Male and female Sprague-Dawley rats underwent coronary artery ligation (CL) to induce HF. Age-matched rats served as controls. Ischemic zone and left ventricular function were similar 24 h and 4 wk after CL. Female rats with HF had a lower mortality rate and less hemodynamic compromise, pulmonary congestion, and right ventricular remodeling 4 wk after CL. Plasma angiotensin II (ANG II), arginine vasopressin (AVP), and norepinephrine levels were increased in HF rats in both sexes, but AVP and norepinephrine levels increased less in female rats. In the hypothalamic paraventricular nucleus, a key cardiovascular-related nucleus contributing to neurohumoral excitation in HF, mRNA levels for the proinflammatory cytokines tumor necrosis factor-α and interleukin- 1β as well as cyclooxygenase-2 and the ANG II type 1a receptor were increased in HF rats of both sexes, but less so in female rats. Angiotensin-converting enzyme 2 protein levels increased in female HF rats but decreased in male HF rats. mRNA levels of AVP were lower in female rats in both control and HF groups compared with the respective male groups. Activation of extracellular signal-regulated protein kinases 1 and 2 increased similarly in both sexes in HF. The results suggest that female HF rats have less central neural excitation and less associated hemodynamic compromise than male HF rats with the same degree of initial ischemic cardiac injury. [ABSTRACT FROM AUTHOR]

Diseases of the cardiovascular system are the leading cause of morbidity and mortality in men and women in developed countries, and cardiovascular disease (CVD) is becoming more prevalent in developing countries. The prevalence of atherosclerotic CVD in men is greater than in women until menopause, when the prevalence of CVD increases in women until it exceeds that of men. Endothelial function is a barometer of vascular health and a predictor of atherosclerosis that may provide insights into sex differences in CVD as well as how and why the CVD risk drastically changes with menopause. Studies of sex differences in endothelial function are conflicting, with some studies showing earlier decrements in endothelial function in men compared with women, whereas others show similar age-related declines between the sexes. Because the increase in CVD risk coincides with menopause, it is generally thought that female hormones, estrogens in particular, are cardioprotective. Moreover, it is often proposed that androgens are detrimental. In truth, the relationships are more complex. This review first addresses female and male sex hormones and their receptors and how these interact with the cardiovascular system, particularly the endothelium, in healthy young women and men. Second, we address sex differences in sex steroid receptor-independent mechanisms controlling endothelial function, focusing on vascular endothelin and the reninangiotensin systems, in healthy young women and men. Finally, we discuss sex differences in age-associated endothelial dysfunction, focusing on the role of attenuated circulating sex hormones in these effects. [ABSTRACT FROM AUTHOR]

Accumulating evidence indicates that maternal high-fat diet (HFD) is associated with metabolic syndrome and cardiovascular disease in adult offspring. The present study tested the hypothesis that maternal HFD modulates the brain reninangiotensin system (RAS), oxidative stress, and proinflammatory cytokines that alter angiotensin II (ANG II) and TNF-α actions and sensitize the ANG II-elicited hypertensive response in adult offspring. All offspring were cross fostered by dams on the same or opposite diet to yield the following four groups: offspring from normal-fat control diet-fed dams suckled by control diet-fed dams (OCC group) or by HFD-fed dams (OCH group) and offspring from HFD-fed dams fed a HFD suckled by control diet-fed dams (OHC group) or by HFD-fed dams (OHH group). RT-PCR analyses of the lamina terminalis and paraventricular nucleus indicated upregulation of mRNA expression of several RAS components, NADPH oxidase, and proinflammatory cytokines in 10-wk-old male offspring of dams fed a HFD during either pregnancy, lactation, or both (OHC, OCH, and OHH groups). These offspring also showed decreased cardiac baroreflex sensitivity and increased pressor responses to intracerebroventricular microinjection of either ANG II or TNF-α. Furthermore, chronic systemic infusion of ANG II resulted in enhanced upregulation of mRNA expression of RAS components, NADPH oxidase, and proinflammatory cytokines in the lamina terminalis and paraventricular nucleus and an augmented hypertensive response in the OHC, OCH, and OHH groups compared with the OCC group. The results suggest that maternal HFD blunts cardiac baroreflex function and enhances pressor responses to ANG II or proinflammatory cytokines through upregulation of the brain RAS, oxidative stress, and inflammation. NEW & NOTEWORTHY The results of our study indicate that a maternal high-fat diet during either pregnancy or lactation is sufficient for perinatal programming of sensitization for hypertension, which is associated with hyperreactivity of central cardiovascular nuclei that, in all likelihood, involves elevated expression of the renin-angiotensin system, NADPH oxidase, and proinflammatory cytokines. The present study demonstrates, for the first time, the central mechanism underlying maternal high-fat diet sensitization of the hypertensive response in adult offspring. [ABSTRACT FROM AUTHOR]

The central nervous system plays an important role in essential hypertension in humans and in animal models of hypertension through modulation of sympathetic activity and Na and body fluid homeostasis. Data from animal models of hypertension suggest that the renin-angiotensin system in the subfornical organ (SFO) of the brain is critical for hypertension development. We recently reported that the brain (pro) renin receptor (PRR) is a novel component of the brain reninangiotensin system and could be a key initiator of the pathogenesis of hypertension. Here, we examined the expression level and cellular distribution of PRR in the SFO of postmortem human brains to assess its association with the pathogenesis of human hypertension. Postmortem SFO tissues were collected from hypertensive and normotensive human subjects. Immunolabeling for the PRR and a retrospective analysis of clinical data were performed. We found that human PRR was prominently expressed in most neurons and microglia, but not in astrocytes, in the SFO. Importantly, PRR levels in the SFO were elevated in hypertensive subjects. Moreover, PRR immunoreactivity was significantly correlated with systolic blood pressure but not body weight, age, or diastolic blood pressure. Interestingly, this correlation was independent of antihypertensive drug therapy. Our data indicate that PRR in the SFO may be a key molecular player in the pathogenesis of human hypertension and, as such, could be an important focus of efforts to understand the neurogenic origin of hypertension. [ABSTRACT FROM AUTHOR]

An activated renin-angiotensin system (RAS) within the central nervous system has been implicated in sympathoexcitation during various disease conditions including congestive heart failure (CHF). In particular, activation of the RAS in the paraventricular nucleus (PVN) of the hypothalamus has been recognized to augment sympathoexcitation in CHF. We observed a 2.6-fold increase in angiotensinogen (AGT) in the PVN of CHF. To elucidate the molecular mechanism for increased expression of AGT, we performed in silico analysis of the 3=-untranslated region (3=-UTR) of AGT and found a potential binding site for microRNA (miR)-133a. We hypothesized that decreased miR-133a might contribute to increased AGT in the PVN of CHF rats. Overexpression of miR-133a in NG108 cells resulted in 1.4- and 1.5-fold decreases in AGT and angiotensin type II (ANG II) type 1 receptor (AT1R) mRNA levels, respectively. A luciferase reporter assay performed on NG108 cells confirmed miR-133a binding to the 3=-UTR of AGT. Consistent with these in vitro data, we observed a 1.9-fold decrease in miR-133a expression with a concomitant increase in AGT and AT1R expression within the PVN of CHF rats. Furthermore, restoring the levels of miR-133a within the PVN of CHF rats with viral transduction resulted in a significant reduction of AGT (1.4-fold) and AT1R (1.5-fold) levels with a concomitant decrease in basal renal sympathetic nerve activity (RSNA). Restoration of miR-133a also abrogated the enhanced RSNA responses to microinjected ANG II within the PVN of CHF rats. These results reveal a novel and potentially unique role for miR-133a in the regulation of ANG II within the PVN of CHF rats, which may potentially contribute to the commonly observed sympathoexcitation in CHF. [ABSTRACT FROM AUTHOR]

Stimulation of the renin-angiotensin- aldosterone system (RAAS) and β-adrenergic receptors plays an important role in adult heart failure (HF). Despite the demonstrated benefits of RAAS inhibition and β-adrenergic receptor blockade in adult HF patients, no substantial improvement in survival rate has been observed in children with HF. This suggests that the underlying disease mechanism is uniquely regulated in pediatric HF. Here, we show that treatment of human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and neonatal rat ventricular myocytes (NRVMs) with serum from pediatric dilated cardiomyopathy (DCM) patients induces pathological changes in gene expression, which occur independently of the RAAS and adrenergic systems, suggesting that serum circulating factors play an important role in cardiac remodeling. Furthermore, exosomes purified from DCM serum induced pathological changes in gene expression in NRVMs and iPSC-CMs. Our results suggest that DCM serum exosomes mediate pathological responses in cardiomyocytes and may propagate the pediatric HF disease process, representing a potential novel therapeutic target specific to this population. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the genetic mechanisms of the defense vascular reactions in response to the diving reflex in humans with polymorphisms in the genes ADBR2, ACE, AGTR1, BDKRB2, and REN. We hypothesized that protective vascular reactions, in response to the diving reflex, are genetically determined and are distinguished in humans with gene polymorphisms of the renin-angiotensin and kinin-bradykinin system. A total of 80 subjects (19 ± 1.4 yr) participated in the study. The intensity of the vascular response was estimated using photoplethysmogram. The I/D polymorphism (rs4340) of ACE was analyzed by PCR. REN (G/A, rs2368564), AGTR1 (A/C, rs5186), BDKRB2 (T/C, rs1799722), and ADBR2 (A/G, rs1042713) polymorphisms were examined using the two-step multiplex PCR followed by carrying allele hybridization on the biochip. Subjects with the BDKRB2 (C/C), ACE (D/D), and ADBR2 (G/G, G/A) genotypes exhibited the strongest peripheral vasoconstriction in response to diving. In subjects with a combination of the BDKRB2 (C/C) plus ACE (D/D) genotypes, we observed the lowest pulse wave amplitude and pulse transit time values and the highest arterial blood pressure during face immersion compared with the heterozygous individuals, suggesting that these subjects are more susceptible to diving hypoxia. This study observed that humans with gene polymorphisms of the renin-angiotensin and kinin-bradykinin systems demonstrate various expressions of protective vascular reactions in response to the diving reflex. The obtained results might be used in estimation of resistance to hypoxia of any origin in human beings or in a medical practice. NEW & NOTEWORTHY Our study demonstrates that the vascular reactions in response to the diving reflex are genetically determined and depend on gene polymorphisms of the kinin-bradykinin and the renin-angiotensin systems. [ABSTRACT FROM AUTHOR]

Brain MAPK signaling pathways are activated in heart failure (HF) induced by myocardial infarction and contribute to augmented sympathetic nerve activity. We tested whether decreasing ERK1/2 (also known as p44/42 MAPK) signaling in the hypothalamic paraventricular nucleus (PVN), a forebrain source of presympathetic neurons, would reduce the upregulation of sympathoexcitatory mediators in the PVN and augmented sympathetic nerve activity in rats with HF. Sprague-Dawley rats underwent left anterior descending coronary artery ligation to induce HF, with left ventricular dysfunction confirmed by echocardiography. One week after coronary artery ligation or sham operation, small interfering (si)RNAs targeting ERK1/2 or a nontargeting control siRNA was microinjected bilaterally into the PVN. Experiments were conducted 5-7 days later. Confocal images revealed reduced phosphorylated ERK1/2 immunofluorescence in the PVN of HF rats treated with ERK1/2 siRNAs compared with HF rats treated with control siRNA. Western blot analysis confirmed significant reductions in both total and phosphorylated ERK1/2 in the PVN of HF rats treated with ERK1/2 siRNAs along with reduced expression of renin-angiotensin system components and inflammatory mediators. HF rats treated with ERK1/2 siRNAs also had reduced PVN neuronal excitation (fewer Fos-related antigen-like-immunoreactive neurons), lower plasma norepinephrine levels, and improved peripheral manifestations of HF compared with HF rats treated with control siRNAs. These results demonstrate that ERK1/2 signaling in the PVN plays a pivotal role in mediating sympathetic drive in HF induced by myocardial infarction and may be a novel target for therapeutic intervention. [ABSTRACT FROM AUTHOR]

The reninangiotensin system (RAS) constitutes a key hormonal system in the physiological regulation of blood pressure through peripheral and central mechanisms. Indeed, dysregulation of the RAS is considered a major factor in the development of cardiovascular pathologies, and pharmacological blockade of this system by the inhibition of angiotensin-converting enzyme (ACE) or antagonism of the angiotensin type 1 receptor (AT1R) offers an effective therapeutic regimen. The RAS is now defined as a system composed of different angiotensin peptides with diverse biological actions mediated by distinct receptor subtypes. The classic RAS comprises the ACE-ANG II-AT1R axis that promotes vasoconstriction; water intake; sodium retention; and increased oxidative stress, fibrosis, cellular growth, and inflammation. In contrast, the nonclassical RAS composed primarily of the ANG II/ANG III-AT2R and the ACE2-ANG-(1-7)-AT7R pathways generally opposes the actions of a stimulated ANG II-AT1R axis. In lieu of the complex and multifunctional aspects of this system, as well as increased concerns on the reproducibility among laboratories, a critical assessment is provided on the current biochemical approaches to characterize and define the various components that ultimately reflect the status of the RAS. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine whether long-term high salt intake in the drinking water induces hypertension in wild-type (WT) mice and whether a chymase inhibitor or other antihypertensive drugs could reverse the increase of blood pressure. Eight-week-old male WT mice were supplied with drinking water containing 2% salt for 12 wk (high-salt group) or high-salt drinking water plus an oral chymase inhibitor (TPC-806) at four different doses (25, 50, 75, or 100 mg/kg), captopril (75 mg/kg), losartan (100 mg/kg), hydrochlorothiazide (3 mg/kg), eplerenone (200 mg/kg), or amlodipine (6 mg/kg). Control groups were given normal water with or without the chymase inhibitor. Blood pressure and heart rate gradually showed a significant increase in the high-salt group, whereas a dose-dependent depressor effect of the chymase inhibitor was observed. There was also partial improvement of hypertension in the losartan- and eplerenone-treated groups but not in the captopril-, hydrochlorothiazide-, and amlodipine- treated groups. A high salt load significantly increased chymasedependent ANG II-forming activity in the alimentary tract. In addition, the relative contribution of chymase to ANG II formation, but not actual average activity, showed a significant increase in skin and skeletal muscle, whereas angiotensin-converting enzyme-dependent ANG II-forming activity and its relative contribution were reduced by high salt intake. Plasma and urinary renin-angiotensin system components were significantly increased in the high-salt group but were significantly suppressed in the chymase inhibitor-treated group. In conclusion, 2% salt water drinking for 12 wk caused moderate hypertension and activated the renin-angiotensin system in WT mice. A chymase inhibitor suppressed both the elevation of blood pressure and heart rate, indicating a definite involvement of chymase in salt-sensitive hypertension. [ABSTRACT FROM AUTHOR]

ANG II type 2 receptor (AT2) and ANG I-converting enzyme 2 (ACE2) are important components of the renin-ANG system. Activation of AT2 and ACE2 reportedly counteracts proinflammatory effects of ANG II. However, the possible interaction between AT2 and ACE2 has never been established. We hypothesized that activation of AT2 increases ACE2 activity, thereby preventing TNF-α-stimulated ICAM-1 expression via inhibition of NF-κB signaling. Human coronary artery endothelial cells were pretreated with AT2 antagonist PD123319 (PD) or ACE2 inhibitor DX600 and then stimulated with TNF-α in the presence or absence of AT2 agonist CGP42112 (CGP). We found that AT2 agonist CGP increased both ACE2 protein expression and activity. This effect was blunted by AT2 antagonist PD. ICAM-1 expression was very low in untreated cells but greatly increased by TNF-α. Activation of AT2 with agonist CGP or with ANG II under concomitant AT1 antagonist reduced TNF-α-induced ICAM-1 expression, which was reversed by AT2 antagonist PD or ACE2 inhibitor DX600 or knockdown of ACE2 with small interfering RNA. AT2 activation also suppressed TNF-α-stimulated phosphorylation of inhibitory κB (p-IκB) and NF-κB activity. Inhibition of ACE2 reversed the inhibitory effect of AT2 on TNF-α-stimulated p-IκB and NF-κB activity. Our findings suggest that stimulation of AT2 reduces TNF-α-stimulated ICAM-1 expression, which is partly through ACE2-mediated inhibition of NF-κB signaling. [ABSTRACT FROM AUTHOR]

Caloric restriction (CR), renin angiotensin system blockade (RAS-bl), and rapamycin-mediated mechanistic target of rapamycin (mTOR) inhibition increase survival and retard aging across species. Previously, we have summarized CR and RAS-bl's converging effects, and the mitochondrial function changes associated with their physiological benefits. mTOR inhibition and enhanced sirtuin and KLOTHO signaling contribute to the benefits of CR in aging. mTORC1/mTORC2 complexes contribute to cell growth and metabolic regulation. Prolonged mTORC1 activation may lead to age-related disease progression; thus, rapamycin-mediated mTOR inhibition and CR may extend lifespan and retard aging through mTORC1 interference. Sirtuins by deacetylating histone and transcription-related proteins modulate signaling and survival pathways and mitochondrial functioning. CR regulates several mammalian sirtuins favoring their role in aging regulation. KLOTHO/fibroblast growth factor 23 (FGF23) contribute to control Ca2+, phosphate, and vitamin D metabolism, and their dysregulation may participate in age-related disease. Here we review how mTOR inhibition extends lifespan, how KLOTHO functions as an aging suppressor, how sirtuins mediate longevity, how vitamin D loss may contribute to age-related disease, and how they relate to mitochondrial function. Also, we discuss how RAS-bl downregulates mTOR and upregulates KLOTHO, sirtuin, and vitamin D receptor expression, suggesting that at least some of RAS-bl benefits in aging are mediated through the modulation of mTOR, KLOTHO, and sirtuin expression and vitamin D signaling, paralleling CR actions in age retardation. Concluding, the available evidence endorses the idea that RAS-bl is among the interventions that may turn out to provide relief to the spreading issue of age-associated chronic disease. [ABSTRACT FROM AUTHOR]

In experimental animal models of hypertension, angiotensin (1-7) [ANG-(1-7)] is higher in females compared with males; however, it is less clear whether the same applies to humans. Therefore, this study sought to compare circulating concentrations of ANG-(1-7) in apparently healthy men and women under normal physiological conditions. With the use of a cross-sectional experimental design, blood was collected in EDTA anticoagulant from 42 volunteers (21 men and 21 women; and age range, 19-48 yr) for analysis of plasma concentrations of ANG-(1-7) and ANG II. Blood pressure was measured and vascular endothelial function was determined (n = 25) using the brachial artery flow-mediated dilation (FMD) test. As a result, women exhibited a higher circulating concentration of ANG-(1-7) (P = 0.04) compared with men, whereas values of ANG II were similar between groups. Baseline arterial diameter, peak diameter, and shear rate were significantly greater (P < 0.02) in men compared with women. No significant differences in FMD, FMD normalized for shear, or time to peak dilation were observed between men and women. In addition, a positive correlation between ANG-(1-7) and FMD (P = 0.04) and negative association between ANG-(1-7) with ANG II (P = 0.01) were only identified in men, whereas a positive relationship between ANG-(1-7) and diastolic blood pressure (P = 0.03) was observed in women. [ABSTRACT FROM AUTHOR]

Activation of NF-κB signaling in the heart may be protective or deleterious depending on the pathological context. In diabetes, the role of NF-κB in cardiac dysfunction has been investigated using pharmacological approaches that have a limitation of being nonspecific. Furthermore, the specific cellular pathways by which NF-κB modulates heart function in diabetes have not been identified. To address these questions, we used a transgenic mouse line expressing mutated IκB-α in the heart (3M mice), which prevented activation of canonical NF-κB signaling. Diabetes was developed by streptozotocin injections in wild-type (WT) and 3M mice. Diabetic WT mice developed systolic and diastolic cardiac dysfunction by the 12th week, as measured by echocardiography. In contrast, cardiac function was preserved in 3M mice up to 24 wk of diabetes. Diabetes induced an elevation in cardiac oxidative stress in diabetic WT mice but not 3M mice compared with nondiabetic control mice. In diabetic WT mice, an increase in the phospholamban/ sarco(endo)plasmic reticulum Ca2+-ATPase 2 ratio and decrease in ryanodine receptor expression were observed, whereas diabetic 3M mice showed an opposite effect on these parameters of Ca2+ handling. Significantly, renin-angiotensin system activity was suppressed in diabetic 3M mice compared with an increase in WT animals. In conclusion, these results demonstrate that inhibition of NF-κB signaling in the heart prevents diabetes-induced cardiac dysfunction through preserved Ca2+ handling and inhibition of the cardiac renin-angiotensin system. [ABSTRACT FROM AUTHOR]

The rostral ventrolateral medulla (RVLM) plays a key role in cardiovascular regulation. It has been reported that tonically active glutamatergic input to the RVLM is increased in hypertensive rats, whereas angiotensin-converting enzyme 2 (ACE2) in the brain has been suggested to be beneficial to hypertension. This study was designed to determine the effect of ACE2 gene transfer into the RVLM on tonically active glutamatergic input in spontaneously hypertensive rats (SHRs). Lentiviral particles containing enhanced green fluorescent protein (lenti-GFP) or ACE2 (lenti-ACE2) were injected bilaterally into the RVLM. Both protein expression and activity of ACE2 in the RVLM were increased in SHRs after overexpression of ACE2. A significant reduction in blood pressure and heart rate in SHRs was observed 6 wk after lenti-ACE2 injected into the RVLM. The concentration of glutamate in microdialysis fluid from the RVLM was significantly reduced by an average of 61% in SHRs with lenti-ACE2 compared with lenti-GFP. ACE2 overexpression significantly attenuated the decrease in blood pressure and renal sympathetic nerve activity evoked by bilateral injection of the glutamate receptor antagonist kynurenic acid (2.7 nmol in 100 nl) into the RVLM in SHRs. Therefore, we suggest that ACE2 overexpression in the RVLM attenuates the enhanced tonically active glutamatergic input in SHRs, which may be an important mechanism underlying the beneficial effect of central ACE2 to hypertension. [ABSTRACT FROM AUTHOR]

Inreased intraluminal pressure can reduce endothelial function in resistance arterioles; however, the mechanism of this impairment is unknown. The purpose of this study was to determine the effect of local renin-angiotensin system inhibition on the pressure-induced blunting of endothelium-dependent vasodilation in human adipose arterioles. Arterioles (100-200 μm) were dissected from fresh adipose surgical specimens, cannulated onto glass micropipettes, pressurized to an intraluminal pressure of 60 mmHg, and constricted with endothelin-1. Vasodilation to ACh was assessed at 60 mmHg and again after a 30-min exposure to an intraluminal pressure of 150 mmHg. The vasodilator response to ACh was significantly reduced in vessels exposed to 150 mmHg. Exposure of the vessels to the superoxide scavenger polyethylene glycol-SOD (100 U/ml), the ANG II type 1 receptor antagonist losartan (10-6 mol/l), or the angiotensin-converting enzyme inhibitor captopril (10-5 mol/l) prevented the pressureinduced reduction in ACh-dependent vasodilation observed in untreated vessels. High intraluminal pressure had no effect on papaverine- induced vasodilation or ANG II sensitivity. Increased intraluminal pressure increased dihydroethidium fluorescence in cannulated vessels, which could be prevented by polyethylene glycol-SOD or losartan treatment and endothelial denudation. These data indicate that high intraluminal pressure can increase vascular superoxide and reduce nitric oxide-mediated vasodilation via activation of the vascular renin-angiotensin system. This study provides evidence showing that the local renin-angiotensin system in the human microvasculature may be pressure sensitive and contribute to endothelial dysfunction after acute bouts of hypertension. [ABSTRACT FROM AUTHOR]

Aminopeptidase-A (APA) is a less well-studied enzyme of the renin-angiotensin system. We propose that it is involved in cardiac angiotensin (ANG) metabolism and its pathologies. ANG-(1-7) can ameliorate remodeling after myocardial injury. The aims of this study are to 1) develop mass spectrometric (MS) approaches for the assessment of ANG processing by APA within the myocardium; and 2) investigate the role of APA in cardiac ANG-(1-7) metabolism after myocardial infarction (MI) using sensitive MS techniques. MI was induced in C57Bl/6 male mice by ligating the left anterior descending (LAD) artery. Frozen mouse heart sections (in situ assay) or myocardial homogenates (in vitro assay) were incubated with the endogenous APA substrate, ANG II. Results showed concentration- and time-dependent cardiac formation of ANG III from ANG II, which was inhibited by the specific APA inhibitor, 4-amino-4-phosphonobutyric acid. Myocardial APA activity was significantly increased 24 h after LAD ligation (0.82 ± 0.02 vs. 0.32 ± 0.02 ρmol·min-1·μg-1, MI vs. sham, P < 0.01). Both MS enzyme assays identified the presence of a new peptide, ANG-(2-7), m/z 784, which accumulated in the MI (146.45 ± 6.4 vs. 72.96 ± 7.0%, MI vs. sham, P < 0.05). Use of recombinant APA enzyme revealed that APA is responsible for ANG-(2-7) formation from ANG-(1-7). APA exhibited similar substrate affinity for ANG-(1-7) compared with ANG II {Km (ANG II) 14.67 ± 1.6 vs. Km [ANG-(1-7)] 6.07 ± 1.12 μmol/l, P < 0.05}. Results demonstrate a novel role of APA in ANG-(1-7) metabolism and suggest that the upregulation of APA, which occurs after MI, may deprive the heart of cardioprotective ANG-(1-7). Thus APA may serve as a potentially novel therapeutic target for management of tissue remodeling after MI. [ABSTRACT FROM AUTHOR]

Angiotensin II favors the development of atherosclerosis. Our goal was to determine if foam cell formation increases angiotensin II generation by the endogenous renin-angiotensin system (RAS) and if endogenously produced angiotensin II promotes lipid accumulation in macrophages. Differentiated THP-1 cells were treated with acetylated low-density lipoproteins (ac-LDL), native LDL (n-LDL), or no LDL. Expression of RAS genes was assessed and angiotensin I/II levels were quantified in media and cell lysate. Ac-LDL increased angiotensin I/II levels and the angiotensin II/I ratio in cells and media after foam cell formation. Renin mRNA or activity did not change, but renin blockade completely inhibited the increase in angiotensin II. Angiotensinogen mRNA but not protein level was increased. Angiotensin-converting enzyme (ACE) and cathepsin G mRNA and activities were enhanced by ac-LDL. Inhibition of renin, ACE, or the angiotensin II receptor 1 (AT1-receptor) largely abolished cholesteryl ester formation in cells exposed to ac-LDL and decreased scavenger receptor A (SR-A) and acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT-1) protein levels. Inhibition of renin or the AT1-receptor in cells treated with oxidized LDL also decreased SR-A and ACAT-1 protein and foam cell formation. ac-LDL also increased angiotensin II by human peripheral blood monocyte-derived macrophages, whereas blockade of renin decreased cholesterol ester formation in these macrophages. These findings indicate that, during foam cell formation, angiotensin II generation by the endogenous RAS is stimulated and that endogenously generated angiotensin II is crucial for cholesterol ester accumulation in macrophages exposed to modified LDL. [ABSTRACT FROM AUTHOR]

Chronic kidney disease (CKD) is an independent risk factor for the development of cardiovascular disease. The perivascular adipose tissue is closely implicated in the development of atherosclerosis; however, the contribution to CKDassociated atherogenesis remains undefined. Eight-week-old apoEdeficient mice were uninephrectomized and fed a high-cholesterol diet starting at 12 wk of age. The atherosclerotic lesion area in the thoracic aorta was comparable in 16-wk-old uninephrectomized (UNX) mice and sham control mice; however, the lesion area was markedly exaggerated in 20-wk-old UNX mice compared with the control (54%, P < 0.05). While the accumulation of monocytes/macrophages and the mRNA expression levels of inflammatory cytokines/chemokines in the thoracic periaortic adipose tissue (PAT) did not differ between the two groups, angiotensinogen (AGT) mRNA expression and the angiotensin II (ANG II) concentration in the PAT were significantly higher in 16-wk-old UNX mice than in the control (1.9- and 1.5-fold increases vs. control, respectively; P < 0.05). ANG II concentrations in both the plasma and epididymal white adipose tissue (WAT) were comparable between the two groups, suggesting that PAT-specific activation of the renin-angiotensin system (RAS) is primarily involved in CKD-associated atherogenesis. The homeostasis model assessment-insulin resistance (HOMA-IR) index and plasma insulin level after glucose loading were significantly elevated in 16-wk-old UNX mice. In vitro stimulation of preadipocytes with insulin exaggerated the AGT mRNA expression along with increased mRNA expression of PPAR. These findings suggest that PATspecific RAS activation probably primarily contributes in accelerating atherosclerotic development in UNX mice and could thus represent a therapeutic target for preventing CKD-associated atherogenesis. [ABSTRACT FROM AUTHOR]

Angiotensin-(ANG)-(1-7) is known by its central and peripheral actions, which mainly oppose the deleterious effects induced by accumulation of ANG II during pathophysiological conditions. In the present study we evaluated whether a chronic increase in ANG-(1-7) levels in the brain would modify the progression of hypertension. After DOCA-salt hypertension was induced for seven days, Sprague- Dawley rats were subjected to 14 days of intracerebroventricular (ICV) infusion of ANG-(1-7) (200 ng/h, DOCA-A7) or 0.9% sterile saline. As expected, on the 21st day, DOCA rats presented increased mean arterial pressure (MAP) (≈40%), and impaired baroreflex control of heart rate (HR) and baroreflex renal sympathetic nerve activity (RSNA) in comparison with that in normotensive control rats (CTL). These changes were followed by an overactivity of the cardiac sympathetic tone and reduction of the cardiac parasympathetic tone, and exaggerated mRNA expression of collagen type I (≈9-fold) in the left ventricle. In contrast, DOCA rats treated with ANG-(1-7) ICV had an improvement of baroreflex control of HR, which was even higher than that in CTL, and a restoration of the baroreflex control of RSNA, the balance of cardiac autonomic tone, and normalized mRNA expression of collagen type I in the left ventricle. Furthermore, DOCA-A7 had MAP lowered significantly. These effects were not accompanied by significant circulating or cardiac changes in angiotensin levels. Taken together, our data show that chronic increase in ANG-(1-7) in the brain attenuates the development of DOCA-salt hypertension, highlighting the importance of this peptide in the brain for the treatment of cardiovascular diseases. [ABSTRACT FROM AUTHOR]

The aim of this investigation was to evaluate sex differences in baroreflex and heart rate variability (HRV) dysfunction and indexes of end-organ damage in the TG(mRen2)27 (Ren2) rat, a model of renin overexpression and tissue renin-angiotensin-aldosterone system overactivation. Blood pressure (via telemetric monitoring), blood pressure variability [BPV; SD of systolic blood pressure (SBP)], spontaneous baroreflex sensitivity, HRV [HRV Triangular Index (HRV-TI), standard deviation of the average NN interval (SDNN), low and high frequency power (LF and HF, respectively), and Poincaré plot analysis (SD1, SD2)], and cardiovascular function (pressure-volume loop analysis and proteinuria) were evaluated in male and female 10-wk-old Ren2 and Sprague Dawley rats. The severity of hypertension was greater in Ren2 males (R2-M) than in Ren2 females (R2-F). Increased BPV, suppression of baroreflex gain, decreased HRV, and associated end-organ damage manifested as cardiac dysfunction, myocardial remodeling, elevated proteinuria, and tissue oxidative stress were more pronounced in R2-M compared with R2-F. During the dark cycle, HRV-TI and SDNN were negatively correlated with SBP within R2-M and positively correlated within R2-F; within R2-M, these indexes were also negatively correlated with end-organ damage [left ventricular hypertrophy (LVH)]. Furthermore, within R2-M only, LVH was strongly correlated with indexes of HRV representing predominantly vagal (HF, SD1), but not sympathetic (LF, SD2), variability. These data demonstrated relative protection in females from autonomic dysfunction and end-organ damage associated with elevated blood pressure in the Ren2 model of hypertension. [ABSTRACT FROM AUTHOR]

This study determined the effect of ANG-(1-7) on salt-induced suppression of endothelium-dependent vasodilatation in the mesenteric arteries of male Sprague-Dawley rats. Chronic intravenous infusion of ANG-(1-7), oral administration of the nonpeptide mas receptor agonist AVE-0991, and acute preincubation of the arteries with ANG-(1-7) and AVE-0991 all restored vasodilator responses to both ACh and histamine that were absent in the arteries of rats fed a high-salt (4% NaCl) diet. The protective effects of ANG-(1-7) and AVE-0991 were inhibited by acute or chronic administration of the mas receptor antagonist A-779, the ANG II type 2 (AT2) receptor blocker PD-123319, or N-nitro-l-arginine methyl ester, but not the ANG II type 1 receptor antagonist losartan. Preincubation with the antioxidant tempol or the nitric oxide (NO) donor diethylenetriamine NONOate and acute and chronic administration of the AT2 receptor agonist CGP-42112 mimicked the protective effect of ANG-(1-7) to restore vascular relaxation. Acute preincubation with ANG-(1-7) and chronic infusion of ANG-(1-7) ameliorated the elevated superoxide levels in rats fed a high-salt diet, but the expression of Cu/Zn SOD and Mn SOD enzyme proteins in the vessel wall was unaffected by ANG-(1-7) infusion. These results indicate that both acute and chronic systemic administration of ANG-(1-7) or AVE-0991 restore endothelium-dependent vascular relaxation in salt-fed Sprague-Dawley rats by reducing vascular oxidant stress and enhancing NO availability via mas and AT2 receptors. These findings suggest a therapeutic potential for mas/AT2 receptor activation in preventing the vascular oxidant stress and endothelial dysfunction associated with elevated dietary salt intake. [ABSTRACT FROM AUTHOR]

Experimental studies have suggested a role for the local renin-angiotensin-aldosterone system in the response to vascular injury. Clinical data support that aldosterone, via activation of the mineralocorticoid receptor (MR), is an important mediator of vascular damage in humans with cardiovascular disease. In mineralocorticoid-sensitive target tissue, aldosterone specificity for MR is conferred enzymatically by the cortisol-inactivating enzyme 11β-hydroxysteroid-dehydrogenase-2 (11βHSD2). However, the role of MR/aldosterone signaling in the venous system has not been explored. We hypothesized that MR expression and signaling in venous smooth muscle cells contributes to the arterialization of venous conduits and the injury response in vein bypass grafts. MR immunostaining was observed in all samples of excised human peripheral vein graft lesions and in explanted experimental rabbit carotid interposition vein grafts, with minimal staining in control greater saphenous vein. We also found upregulated transcriptional expression of both MR and 11βHSD2 in human vein graft and rabbit vein graft, whereas control greater saphenous vein expressed minimal MR and no detectable 11βHSD2. The expression of MR and 11βHSD2 was confirmed in cultured human saphenous venous smooth muscle cells (hSVSMCs). Using an adenovirus containing a MR response element-driven reporter gene, we demonstrate that MR in hSVSMCs is capable of mediating aldosterone-induced gene activation. The functional significance for MR signaling in hSVSMCs is supported by the aldosterone-induced increase of angiotensin II type-1 receptor gene expression that was inhibited by the MR antagonist spironolactone. The upregulation of MR and 11βHSD2 suggests that aldosterone-mediated tissue injury plays a role in vein graft arterialization. [ABSTRACT FROM AUTHOR]

Endothelial cells exert an enormous influence on blood vessels throughout the circulation, but their impact is particularly pronounced in the brain. New concepts have emerged recently regarding the role of this cell type and mechanisms that contribute to endothelial dysfunction and vascular disease. Activation of the renin-angiotensin system plays a prominent role in producing these abnormalities. Both oxidative stress and local inflammation are key mechanisms that underlie vascular disease of diverse etiology. Endogenous mechanisms of vascular protection are also present, including antioxidants, anti-inflammatory molecules, and peroxisome proliferator-activated receptor-γ. Despite their clear importance, studies of mechanisms that underlie cerebrovascular disease continue to lag behind studies of vascular biology in general. Identification of endogenous molecules and pathways that protect the vasculature may result in targeted approaches to prevent or slow the progression of vascular disease that causes stroke and contributes to the vascular component of dementia and Alzheimer's disease. [ABSTRACT FROM AUTHOR]

This study evaluated endothelium-dependent vascular relaxation in response to acetylcholine (ACh) in isolated middle cerebral arteries (MCA) from Dahl salt-sensitive (Dahl SS) rats and three different congenic strains that contain a portion of Brown Norway (BN) chromosome 13 introgressed onto the Dahl SS genetic background through marker-assisted breeding. Two of the congenic strains carry a 3.5-Mbp portion and a 2.6-Mbp portion of chromosome 13 that lie on opposite sides of the renin locus, while the third contains a 2.0-Mbp overlapping region that includes the BN renin allele. While maintained on a normal salt (0.4% NaCl) diet, MCAs from Dahl SS rats and the congenic strains retaining the Dahl SS renin allele failed to dilate in response to ACh, whereas MCAs from the congenic strain carrying the BN renin allele exhibited normal vascular relaxation. In congenic rats receiving the BN renin allele, vasodilator responses to ACh were eliminated by nitric oxide synthase inhibition with NG-nitro-l-arginine methyl ester, angiotensin-converting enzyme inhibition with captopril, and AT1 receptor blockade with losartan. NG-nitro-l-arginine methyl ester-sensitive vasodilation in response to ACh was restored in MCAs of Dahl SS rats that received either a 3-day infusion of a subpressor dose of angiotensin II (3 ng·kg-1·min-1 iv), or chronic treatment with the superoxide dismutase mimetic tempol (15 mg·kg-1·day-1). These findings indicate that the presence of the Dahl SS renin allele plays a crucial role in endothelial dysfunction present in the cerebral circulation of the Dahl SS rat, even in the absence of elevated dietary salt intake, and that introgression of the BN renin allele rescues endothelium-dependent vasodilator responses by restoring normal activation of the renin-angiotensin system. [ABSTRACT FROM AUTHOR]

To accelerate lung development and protect neonates from other early developmental problems, synthetic steroids are administered maternally in the third trimester, exposing fetuses that are candidates for premature delivery to them. However, steroid exposure at this point of gestation may lead to elevated blood pressure [mean arterial pressure (MAP)] during adolescence. We hypothesize that fetal exposure to steroids activates the renin-angiotensin system, inducing an elevation in blood pressure and attenuation of baroreflex sensitivity (BRS) that is angiotensin It dependent in early adulthood. To test this hypothesis, fetal sheep were exposedto betamethasone (Beta) or vehicle (control) administered to ewes at day 80 of gestation and delivered at full term. At 1.8 yr of age, male offspring were instrumented for conscious recording of MAP, heart rate, and measurement of BRS [as lowfrequency-a, high-frequency-a, sequence (seq) UP, seq DOWN, and seq TOTAL]. Beta-exposed sheep (n = 6) had higher MAP than control sheep (n = 5) (93 ± 2 vs. 84 ± 2 mmHg, P < 0.01). Acute blockade of angiotensin type I receptors with candesartan (0.3 mg/kg iv) normalized MAP in Beta-exposed sheep (85 ± 4 mmHg), with no effect in control sheep (82 ± 3 mmHg). Before angiotensin type 1 blockade, BRS maximum gain was significantly lower in Betaexposed vs. control sheep (11 ± 3 vs. 26 ± 3 ms/mmHg, P < 0.0.01). However, 45 mm after candesartan injection, BRS was increased in Beta-exposed (21 ± 5 ms/mmHg) and control (35 ± 4 ms/mmHg) sheep. Heart rate variability (HRV) and blood pressure variability (BPV) revealed lower HRV (SD of beat-to-beat interval and root mean square of successive beat-to-beat differences in R-R interval duration) and higher BPV (SD of MAP, systolic arterial pressure in low-frequency range) in Beta-exposed sheep. Candesartan partially restored HRV in Beta-exposed sheep and fully corrected BPV. Thus, in utero exposure to synthetic glucocorticoids causes long-lasting programming of the cardiovascular system via renin-angiotensin system-dependent mechanisms. [ABSTRACT FROM AUTHOR]

Following sinoaortic denervation, which eliminates arterial baroreceptor input into the brain, there are slowly developing adaptations that abolish initial sympathetic activation and hypertension. In comparison, electrical stimulation of the carotid sinus for 1 wk produces sustained reductions in sympathetic activity and arterial pressure. However, whether compensations occur subsequently to diminish these responses is unclear. Therefore, we determined whether there are important central and/or peripheral adaptations that diminish the sympathoinhibitory and blood pressure-lowering effects of more sustained carotid sinus stimulation. To this end, we measured whole body plasma norepinephrine spillover and ai-adrenergic vascular reactivity in six dogs over a 3-wk period of baroreflex activation. During the first week of baroreflex activation, there was an ∼45% decrease in plasma norepinephrine spillover, along with reductions in mean arterial pressure and heart rate of ∼20 mmHg and 15 beats/mm, respectively; additionally, plasma renin activity did not increase. Most importantly, these responses during week I were largely sustained throughout the 3 wk of baroreflex activation. Acute pressor responses to α-adrenergic stimulation during ganglionic blockade were similar throughout the study, indicating no compensatory increases in adrenergic vascular reactivity. These findings indicate that the sympathoinhibition and lowering of blood pressure and heart rate induced by chronic activation of the carotid barorefiex are not diminished by adaptations in the brain and peripheral circulation. Furthermore, by providing evidence that baroreflexes have long-term effects on sympathetic activity and arterial pressure, they present a perspective that is opposite from studies of sinoaortic denervation. [ABSTRACT FROM AUTHOR]

Myocardial fibrosis increases arrhythmia vulnerability of the diseased heart. The reninangiotensin-aldosterone system (RAAS) governs myocardial collagen synthesis. We hypothesized that reducing cardiac fibrosis by chronic RAAS inhibition would result in reduced arrhythmia vulnerability of the senescent mouse heart. Wild-type mice (52 wk old) were treated for 36 wk: 1) untreated control (C); 2) eplerenone (E); 3) losartan (L); and 4) cotreatment with eplerenone and losartan (EL). Ventricular epicardial activation mapping was performed on Langendorff-perfused hearts. Arrhythmia inducibility was tested by one to three premature stimuli and burst pacing. Longitudinal and transverse conduction velocity and dispersion of conduction were determined during pacing at a basic cycle length of 150 ms. Sirius red staining (collagen) was performed. As a result, in the RV of mice in the E, L, and EL groups, transverse conduction velocity was significantly increased and anisotropic ratio was significantly decreased compared with those values of mice in the C group. Anisotropic reentrant arrhythmias were induced in 52% of untreated mice and significantly reduced to 22%, 26%, and 16% in the E, L, and EL groups, respectively. Interstitial fibrosis was significantly decreased in both the RV and LV of all treated groups. Scattered patches of replacement fibrosis were found in 90% of untreated hearts, which were significantly reduced in the E, L, and EL groups. A strong correlation between the abundance of patchy fibrosis and arrhythmia inducibility was found. In conclusion, chronic RAAS inhibition limited aging-related interstitial fibrosis. The lower arrhythmogeneity of treated mice was directly correlated to the reduced amount of patchy fibrosis. [ABSTRACT FROM AUTHOR]

This study examined the role of the renin-angiotensin-aldosterone system (RAAS) in mediating cardiovascular and renal damage in spontaneously hypertensive rats (SHR) given salt excess. Since the circulating RAAS is inhibited in this model, it permits examination of the role of local tissue RAASs in mediating this injury. To this end, male 8-wk SHR were divided into 7 groups. The control group (C) received normal NaCi (0.6%) diet. All other groups were given 8% NaCl chow. In addition, group 2 was given placebo, group 3 the mineralocorticoid receptor blocker eplerenone (100 mg∙kg-1∙day-1), group 4 the angiotensin converting enzyme inhibitor quinapril (3 mg∙kg-1∙day-1), group 5 the angiotensin II type 1 receptor blocker candesartan (10 mg∙kg-1∙day-1), and groups 6 and 7 eplerenone and either quinapril or candesartan. The treatments lasted 8 wk. Compared with controls, mean arterial pressure (MAP), renal blood flow, coronary flow reserve, minimal coronary vascular resistance, diastolic time constant, and maximal rate of ventricular pressure fall were all adversely affected by salt loading. Left ventricular mass and fibrosis as well as proteinuria were also markedly increased by salt overload. Eplerenone induced only slight changes, whereas quinapril and candesartan normalized all indexes except MAP. Combination therapy also normalized all indexes, including MAP. These data suggest that 1) cardiovascular and renal damage induced by salt excess in the SHR were not pressure dependent; 2) mineralocorticoids were only marginally involved in this model; and 3) local tissue generation of angiotensin II may be, at least in part, responsible for the other adverse effects. [ABSTRACT FROM AUTHOR]

Neuropeptide Y (NPY) is a cotransmitter with norepinephrine (NE) and ATP in sympathetic nerves. There is evidence for increased activity of the sympathetic nervous system and the renin-angiotensin system (RAS), as well as a role for NPY in the development of hypertension in experimental animal models and in humans. Angiotensin II (ANG II) is known to facilitate sympathetic neurotransmission, an effect greater in spontaneously hypertensive rats (SHR) than normotensive WistarKyoto (WKY) rats. A newly discovered product of the RAS is angiotensin-(1-7) [ANG-(1-7)]. There is evidence suggesting that ANG-(1-7) opposes the actions of ANG II, resulting in hypotensive effects. The objective of this study was to investigate the role of ANG-(1-7) on the nerve-stimulated overflow of NE and NPY from the mesenteric arterial bed of SHR and the mechanisms involved in mediating any effects produced. ANG-(1-7) (0.001, 0.01, 0.1 μM) decreased nerve-stimulated NE and NPY overflow, as well as perfusion pressure in preparations obtained from SHR. This effect was greater in preparations of SHR than WKY controls. In addition, ANG-(1-7) decreased NE overflow to a greater extent than NPY overflow. Administration of the Mas receptor antagonist, D-Ala7 ANG-(1-7), attenuated the decrease in both NE and NPY overflow due to ANG-(1-7) administration. However, the angiotensin type 2 receptor antagonist, PD-123391, attenuated the effect of ANG-(1-7) on NE overflow without affecting the decrease in NPY overflow. Moreover, in the presence of NG-nitro-L-arginine methyl ester, ANG(1-7) decreased NPY overflow, but not NE overflow. ANG-(1-7) decreases the nerve-stimulated overflow of NE and NPY in preparations of SHR, whereas ANG II enhances it. Therefore, ANG-(1-7) may counteract the effects of ANG II by acting on ANG type 2 and Mas receptors. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Biochemical evaluation of the renin angiotensin system: the good, bad, and absolute?" by M.C. Chappell and colleagues in a 2016 issue.

The aortic blood pressure curve involves two components: a steady component, the mean arterial pressure (MAP), which is dependent on cardiac output and vascular resistance, and a pulsatile component pulse pressure (PP), which is dependent on arterial stiffness and pulse wave reflections. The transduction mechanisms of MAP and PP differ markedly, involving focal adhesion kinase for MAP and oxygen free radicals for PP. Angiotensin II (ANG II) and its blockade are associated with changed vascular resistance and MAP; however, their effects on PP (peripheral and mostly central PP) have been inadequately investigated. In hypertensive rats, when compared with their normotensive controls, ANG II blockade normalizes central PP (<50 rnmHg) but not MAP when the same drug dosage is used for each. In hypertensive patients, ANG II blockade reduces arterial stiffness and pulse wave reflections, but with the same reduction in MAP, there is a greater reduction in central than peripheral PP, thereby increasing carotid-brachial PP amplification. With long-term ANG II blockade, the hypertensive arteriolar hypertrophy observed at baseline is corrected in association with reduced arteriolar reflection coefficients, reduced carotid arterial attachments linking α5-integrin to its ligand fibronectin, and decreased circulating C-reactive protein. When given a normal salt diet, each of these factors contributes separately in reducing arterial stiffness and wave reflections. These responses disappear with a high-salt diet, a condition that usually involves the activation of the local vascular renin-angiotensin-aldosterone system and can be prevented by its selective blockade. Thus ANG II inhibition seems to contribute independently in reducing central PP and aortic stiffness. [ABSTRACT FROM AUTHOR]

This study identified, on the integrative level, two components of the ANG II signaling pathway that lay downstream from the ANG II type I (AT1) receptor and are critically involved in maintaining vascular relaxation in cerebral resistance arteries. In these experiments, the relaxation of isolated middle cerebral arteries (MCA) in response to ACh (10-9-10-5 M), iloprost (10-16-10-11 g/ml), and reduced PO2 was lost and the ratio of phospho-ERKIERK1/2 was significantly reduced in aortas of male Sprague-Dawley rats fed a high-salt (HS; 4% NaCI) diet to suppress plasma ANG II levels. In salt-fed rats, relaxation of MCA in response to these vasodilator stimuli was restored by chronic (3 days) intravenous infusion of either ANG 11(5 ng∙kg-1∙min-1) or epidermal growth factor (EGF; 2 μg/h). The protective effect of ANG II infusion to restore vascular relaxation was eliminated by coinfusion of either the EGF receptor kinase inhibitor AG-1478 (20 μg/h), the ERK1/2 inhibitor PD-98059 (10 μg/h), or the protein synthesis inhibitor cycloheximide (5 μg/h). In rats fed a low-salt (0.4% NaCl) diet, MCA relaxation in response to ACh, reduced PO2, and iloprost was eliminated by intravenous infusion of AG-1478, PD-98059, or cycloheximide. In ANG TI-infused rats fed HS diet, and in rats fed LS diet, vasodilator responses to reduced PO2 and iloprost were unaffected by the p38 MAP kinase inhibitor SB203580 and the phosphatidylinositol 3-kinase inhibitor wortmannin. These findings indicate that maintenance of normal vascular relaxation mechanisms by ANG II in rat MCA requires activation of the EGF receptor kinase and ERK1/2. [ABSTRACT FROM AUTHOR]

Aortic valve regurgitation (AR) imposes a severe volume overload to the left ventricle (LV), which results in dilation, eccentric hypertrophy, and eventually loss of function. Little is known about the impact of AR on LV gene expression. We, therefore, conducted a gene expression profiling study in the LV of rats with acute and severe AR. We identified 64 genes that were specifically upregulated and 29 that were downregulated out of 21,910 genes after 2 wk. Of the upregulated genes, a good proportion was related to the extracellular matrix. We subsequently studied a subset of 19 genes by quantitative RT-PCR (qRT-PCR) to see if the modulation seen in the LV after 2 wk persisted in the chronic phase (after 6 and 12 mo) and found that it did persist. Knowing that the adrenergic and renin-angiotensin systems are overactivated in our animal model, we were interested to see if blocking those systems using metoprolol (25 mg·kg-1·day-1) and captopril (100 mg· kg-1·day-1) would alter the expression of some upregulated LV genes in AR rats after 6 mo. By qRT-PCR, we observed that upregulations of LV mRNA levels encoding for procollagens type I and III, fibronectin, atrial natriuretic peptide, transforming growth factor-β2, and connective tissue growth factor were totally or partially reversed by this treatment. These observations provide a molecular rationale for a medical strategy aiming these systems in the medical treatment of AR and expand the paradigm in the study of this form of LV volume overload. [ABSTRACT FROM AUTHOR]

Malfunctioning mitochondria strongly participate in the pathogenesis of cardiovascular damage associated with hypertension and other disease conditions. Eukaryotic cells move, assume their shape, resist mechanical stress, accommodate their internal constituents, and transmit signals by relying on the constant remodeling of cytoskeleton filaments. Mitochondrial ATP is needed to support cytoskeletal dynamics. Conversely, mitochondria need to interact with cytoskeletal elements to achieve normal motility, morphology, localization, and function. Extracellular matrix (ECM) quantity and quality influence cellular growth, differentiation, morphology, survival, and mobility. Mitochondria can sense ECM composition changes, and changes in mitochondrial functioning modify the ECM. Maladaptive ECM and cytoskeletal alterations occur in a number of cardiac conditions and in most types of glomerulosclerosis, leading to cardiovascular and renal fibrosis, respectively. Angiotensin II (ANG II), a vasoactive peptide and growth factor, stimulates cytosolic and mitochondrial oxidant production, eventually leading to mitochondrial dysfunction. Also, by inducing integrinlfocal adhesion changes, ANG II regulates ECM and cytoskeletal composition and organization and, accordingly, contributes to the pathogenesis of cardiovascular remodeling. ANG II-initiated integrin signaling results in the release of transforming growth factor-β1 (TGF-β1), a cytokine that modifies ECM composition and structure, induces reorganization of the cytoskeleton, and modifies mitochondrial function. Therefore, it is possible to hypothesize that the depression of mitochondrial energy metabolism brought about by ANG II is preceded by ANG lI-induced integrin signaling and the consequent derangement of the cytoskeletal filament network and/or ECM organization. ANG TI-dependent TGF-β1 release is a potential link between ANG II, ECM, and cytoskeleton derangements and mitochondrial dysfunction. It is necessary to emphasize that the present hypothesis is among many other plausible explanations for ANG II- mediated mitochondrial dysfunction. A potential limitation of this proposal is that the results compiled here were obtained in different cells, tissues, and/or experimental models. [ABSTRACT FROM AUTHOR]

Identification of angiotensin-(1-12) as an intermediate precursor derived directly from angiotensinogen led us to explore whether the heart has the capacity to process angiotensin-(1-12) into biologically active angiotensin peptides. The generation of angiotensin I, angiotensin II, and angiotensin-(1-7) from exogenous angiotensin-(1-12) was evaluated in the effluent of isolated perfused hearts mounted on a Langendorff apparatus in three normotensive and two hypertensive strains: Sprague-Dawley, Lewis, congenic mRen2.Lewis, Wistar-Kyoto, and spontaneously hypertensive rats. Hearts were perfused with Krebs solution for 60 mm before and after the addition of angiotensin-(1-12) (10 nmol/l). Angiotensin-(1- 12) caused the rapid appearance of both angiotensin I and angiotensin II in the perfusate that peaked between 30 and 60 mm of recirculation. Production of angiotensin-(1-7) from exogenous angiotensin-(1-12) rose steadily over the course of the 60-mm experiment. These data directly demonstrate that angiotensin-(1-12) is a substrate for the formation of angiotensin peptides in cardiac tissue. This finding further suggests that this angiotensinogen-derived product is a previously unrecognized important precursor peptide to the renin-angiotensin system cascade. [ABSTRACT FROM AUTHOR]

The occurrence of a functional intracellular renin-angiotensin system (RAS) has emerged as a new paradigm. Recently, we and others demonstrated intracellular synthesis of ANG II in cardiac myocytes and vascular smooth muscle cells that was dramatically stimulated in high glucose conditions. Cardiac fibroblasts significantly contribute to diabetes-induced diastolic dysfunction. The objective of the present study was to determine the existence of the intracellular RAS in cardiac fibroblasts and its role in extracellular matrix deposition. Neonatal rat ventricular fibroblasts were serum starved and exposed to isoproterenol or high glucose in the absence or presence of candesartan, which was used to prevent receptor-mediated uptake of ANG II. Under these conditions, an increase in ANG 11 levels in the cell lysate represented intracellular synthesis. Both isoproterenol and high glucose significantly increased intracellular ANG II levels. Confocal microscopy revealed perinuclear and nuclear distribution of intracellular ANG II. Consistent with intracellular synthesis, Western analysis showed increased intracellular levels of renin following stimulation with isoproterenol and high glucose. ANG TI synthesis was catalyzed by renin and angiotensin- converting enzyme (ACE), but not chymase, as determined using specific inhibitors. High glucose resulted in increased transforming growth factor-~3 and collagen-I synthesis by cardiac fibroblasts that was partially inhibited by candesartan but completely prevented by renin and ACE inhibitors. In conclusion, cardiac fibroblasts contain a functional intracellular RAS that participates in extracellular matrix formation in high glucose conditions, an observation that may be helpful in developing an appropriate therapeutic strategy in diabetic conditions. [ABSTRACT FROM AUTHOR]

This study was designed to determine the effect of all-trans retinoic acid (RA) on the development of cardiac remodeling in a pressure overload rat model. Male Sprague-Dawley rats were subjected to sham operation and the aortic constriction procedure. A subgroup of sham control and aortic constricted rats were treated with RA for 5 mo after surgery. Pressure-overloaded rats showed significantly increased interstitial and perivascular fibrosis, heart weight-to-body weight ratio, and gene expression of atrial natriuretic peptide and brain natriuretic peptide. Echocardiographic analysis showed that pressure overload induced systolic and diastolic dysfunction, as evidenced by decreased fractional shortening, ejection fraction, stroke volume, and increased E-to-Ea ratio and isovolumic relaxation time. RA treatment prevented the above changes in cardiac structure and function and hypertrophic gene expression in pressure-overloaded rats. RA restored the ratio of Bcl-2 to Bax, inhibited cleavage of caspase-3 and -9, and prevented the decreases in the levels of SOD-1 and SOD-2. Pressure overload-induced phosphorylation of ERK1/2, JNK, and p38 was inhibited by RA, via upregulation of mitogen-activated protein kinase phosphatase (MKP)-1 and MKP-2. The pressure overload-induced production of angiotensin II was inhibited by RA via upregulation of expression of angiotensin-converting enzyme (ACE)2 and through inhibition of the expression of cardiac and renal renin, angiotensinogen, ACE, and angiotensin type 1 receptor. Similar results were observed in cultured neonatal cardiomyocytes in response to static stretch. These results demonstrate that RA has a significant inhibitory effect on pressure overload-induced cardiac remodeling, through inhibition of the expression of renin-angiotensin system components. [ABSTRACT FROM AUTHOR]