Dysregulation Of Renin-angiotensin System Research Articles

Role of brain renin-angiotensin system in depression: A new perspective.

Depression is a mood disorder characterized by abnormal thoughts. The pathophysiology of depression is related to the deficiency of serotonin (5HT), which is derived from tryptophan (Trp). Mitochondrial dysfunction, oxidative stress, and neuroinflammation are involved in the pathogenesis of depression. Notably, the renin-angiotensin system (RAS) is involved in the pathogenesis of depression, and different findings revealed that angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) may be effective in depression. However, the underlying mechanism for the role of dysregulated brain RAS-induced depression remains speculative. Therefore, this review aimed to revise the conceivable role of ACEIs and ARBs and how these agents ameliorate the pathophysiology of depression. Dysregulation of brain RAS triggers the development and progression of depression through the reduction of brain 5HT and expression of brain-derived neurotrophic factor (BDNF) and the induction of mitochondrial dysfunction, oxidative stress, and neuroinflammation. Therefore, inhibition of central classical RAS by ARBS and ACEIs and activation of non-classical RAS prevent the development of depression by regulating 5HT, BDNF, mitochondrial dysfunction, oxidative stress, and neuroinflammation.

Age-related reduction in brain ACE-2 is not exacerbated by Alzheimer's disease pathology in mouse models of Alzheimer's disease.

An imbalance in the circulatory and organ-specific renin-angiotensin system (RAS) pathways is associated with age-related dysfunction and disease including cardiovascular burden and more recently Alzheimer's disease (AD). It is currently unclear whether an age-associated imbalance in components of the RAS within the brain precedes the onset of AD or whether a RAS imbalance is associated with the onset of disease pathology and cognitive decline. Angiotensin-converting enzyme-1 (ACE-1) and -2 (ACE-2) protein (ELISA) and enzyme activity (FRET assay), markers of the classical and counter-regulatory RAS axis respectively, and Ang-II and Ang-(1-7) peptide levels (ELISA), were measured in the left cortex across four transgenic AD mouse models of amyloid pathology (5xFAD - 2, 6, and 12months of age; Apd9 - 3-4, 12, and 18months of age; Tg2576 - 3-4 and 24months of age; and PDAPP - 3-4, 7, 11, 15, and 18months of age) and littermate wild-type (WT) controls. ACE-1 level, and enzyme activity, was unaltered in relation to age in WT mice and across all four models. In contrast, ACE-2 level and enzyme activity, was reduced and Ang-II increased with ageing in both WT animals and disease models. The changes in ACE-2 and Ang-II in AD models mirrored WT mice, except for the 5xFAD model, when the reduction in ACE-2 (and elevated Ang-II) was observed at a younger age. These data indicate an age-related dysregulation of brain RAS is likely to be driven by a reduction in ACE-2. The reduction in ACE-2 occurs at a young age, coinciding with early pathological changes and the initial deposition of Aβ, and preceding neuronal loss and cognitive decline, in the transgenic AD models. However, the age-related loss was mirrored in WT mice suggesting that the change was independent of pathological Aβ deposition.

Targeting the renin angiotensin system for respiratory diseases.

Renin-angiotensin system (RAS) plays an indispensable role in regulating blood pressure through its effects on fluid and electrolyte balance. As an aside, cumulative evidence from experimental to clinical studies supports the notion that dysregulation of RAS contributes to the pro-inflammatory, pro-oxidative, and pro-fibrotic processes that occur in pulmonary diseases like asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute lung injury (ALI). Pharmacological intervention of the various RAS components can be a novel therapeutic strategy for the treatment of these respiratory diseases. In this chapter, we first give a recent update on the RAS, and then compile, review, and analyse recent reports on targeting RAS components as treatments for respiratory diseases. Inhibition of the pro-inflammatory renin, angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and Ang II type 1 receptor (AT1R) axis, and activation of the protective ACE2, AT2R, Ang (1-7), and Mas receptor axis have demonstrated varying degrees of efficacies in experimental respiratory disease models or in human trials. The newly identified alamandine/Mas-related G-protein-coupled receptor member D pathway has shown some therapeutic promise as well. However, our understanding of the RAS ligand-and-receptor interactions is still inconclusive, and the modes of action and signaling cascade mediating the newly identified RAS receptors remain to be better characterized. Clinical data are obviously lacking behind the promising pre-clinical findings of certain well-established molecules targeting at different pathways of the RAS in respiratory diseases. Translational human studies should be the focus for RAS drug development in lung diseases in the next decade.

Abstract P117: MECHANISMS OF SIGNALING PATHWAYS TRIGGERED BY ANGIOTENSIN I CONVERTING ENZYME IN CHO ECA CELLS TREATED WITH CAPTOPRIL

Renin-Angiotensin System (RAS) is a hormonal system associated with hydroelectrolytic homeostasis and blood pressure control. Angiotensin II (Ang II) is the main and most potent biologically active product in the system, which is produced by the action of Angiotensin Converting Enzyme (ACE) on Ang I. Dysregulation of RAS is an important factor in the development and progression of cardiovascular/renal diseases and diabetes. Experiments and clinical practice have shown that the use of an ACE inhibitor (ACEi) is an effective treatment to attenuate hypertension and diabetic renal damage. In addition, recently the use of ACEi has also been associated with the activation of signaling pathways thus suggesting that ACE can act as a signal transductional molecule. The purpose of this study is to demonstrate the proteins that are differentially regulated when CHO-ECA cells are treated with the ACE inhibitor, captopril. The CHO-ACE cells were cultured in DMEM-SILAC medium in different media: Medium with light chain lysine (LV), medium with heavy chain lysine (P), and control (CT), with DMEM-High Glucose medium. At the 75% confluency, the cells were deprived of serum and then stimulated with captopril (1μM) or vehicle for 2 and 5 minutes (min). CHO-ACE cells were also cultured for the assay analysis of the Kinase Array. ACE activity was determined spectrofluorimetrically using ZPhe-His-Leu as substrate. With the SILAC medium, it was not possible to detect the differently modulated proteins by captopril. The kinase array demonstrated that some signaling pathways were not modulated after Captopril (eg, MSK1/2 and CREB). Other kinases were positively modulated after 2 min stimulation (eg, AMPKa1, HSP27, Akt 1/2/3 T308) and 5 min stimulation (STATa/b, HSP60, b-Catenin) with Captopril. Our screening also has shown that some kinases were negatively modulated following Captopril (eg, p53, PLC-γ1, Pyk2, eNOS). ACE activity in cell lysate group was inexpressive when treated with captopril. Our results expanded the repertoire of kinases modulated by the binding of Captopril to ACE, as well as, the role of ACE as a receptor and the modulation of signaling pathways triggered by this binding, which may imply in the treatment of hypertension.

LC/MS/MS assessment of changes in placental angiotensin I metabolism in preeclampsia.

Preeclampsia (PE) is a condition characterized by high blood pressure and significant proteinuria in pregnant women. It affects about 7% pregnancies and can be cause of fetal and maternal morbidity and mortality. During pregnancy, a physiological overexpression of the Renin-Angiotensin System (RAS) components is observed, including increased plasma Ang II level. Dysregulation of RAS in placenta may contribute to preeclampsia and uterine growth retardation. The aim of the study was to evaluate the Ang I metabolism in human preeclamptic placentas and to compare to normal pregnancies condition. Fragments of placental tissues were collected right after ceasarian section from PE and physiological pregnancies. Tissues were incubated in Krebs buffer in the presence of Ang I. Evaluation of Ang I metabolites in incubating fluid was performed by LC/MS/MS method. mRNA expression of main RAS components was measured by RT-PCR. Pattern of angiotensin metabolites did not differ between groups. The main products were Ang 1-7 and Ang II. Comparing to control group, more than 3-fold lower production of Ang II and Ang 1-7 in preeclampsia was observed. mRNA expressions of ACE and AT1 were significantly decreased in pre- eclamptic placentas, whereas higher expression of mRNA of ACE2 and MAS receptor were observed. Production of Ang 1-7 by PE placentas was significantly lower than in control group. Significantly decreased mRNA expression of ACE and AT1 receptor and lower production of Ang II in placentas of PE patients suggest that placental Ang II/ACE/AT1r pathway could be less important than Ang 1-7/ACE-2/MASr pathway in development of preeclampsia, but this requires further investigations.

Angiotensin type-1 receptor and ACE2 autoantibodies in Parkinson´s disease

The role of autoimmunity in neurodegeneration has been increasingly suggested. The renin-angiotensin system (RAS) autoantibodies play a major role in several peripheral inflammatory processes. Dysregulation of brain RAS has been involved in neuroinflammation and neurodegeneration. We aimed to know whether angiotensin type-1 receptor (AT1) autoantibodies (AT1 agonists) and angiotensin-converting enzyme 2 (ACE2) autoantibodies (ACE2 antagonists) may be involved in Parkinson’s disease (PD) progression and constitute a new therapeutical target. Both AT1 and ACE2 serum autoantibodies were higher in a group of 117 PD patients than in a group of 106 controls. Serum AT1 autoantibodies correlated with several cytokines, particularly Tumor Necrosis Factor Ligand Superfamily Member 14 (TNFSF14, LIGHT), and 27-hydroxycholesterol levels. Serum ACE2 autoantibodies correlated with AT1 autoantibodies. Both autoantibodies were found in cerebrospinal fluid (CSF) of four PD patients with CSF samples. Consistent with the observations in patients, experimental dopaminergic degeneration, induced by 6-hydroxydopamine, increased levels of autoantibodies in serum and CSF in rats, as well as LIGHT levels and transglutaminase activity in rat substantia nigra. In cultures, administration of AT1 autoantibodies enhanced dopaminergic neuron degeneration and increased levels of neuroinflammation markers, which was inhibited by the AT1 antagonist candesartan. The results suggest dysregulation of RAS autoantibodies as a new mechanism that can contribute to PD progression. Therapeutical strategies blocking the production, or the effects of these autoantibodies may be useful for PD treatment, and the results further support repurposing AT1 blockers (ARBs) as treatment against PD progression.

Sequencing ACE2 in Bos Taurus: A Comparison of Bovine and Human ACE 2’s interaction with SARS‐CoV‐2

The World Health Organization’s (WHO) 2018 blueprint of priority diseases, based upon their potential to cause epidemics and public health emergencies included two respiratory illnesses, severe acute respiratory syndrome (SARS‐CoV) and middle east respiratory syndrome (MERS‐CoV), both caused by members of the Coronaviridae family (BioDefense, 2018). Now three years later, we are amid an ongoing worldwide pandemic caused by another Coronavirus, SARS‐Cov‐2. This virus has rapidly spread across the globe causing over 5.4 million deaths throughout the world. Symptoms of the viral infection include shortness of breath, fever, fatigue, muscle and body aches, headaches and most importantly acute lung injury (ALI) caused by dysregulation of pulmonary RAS (Renin‐Angiotensin System). RAS, the main network controlling blood pressure is regulated by ACE (Angiotensin Converting Enzyme) and its homolog ACE2. It is now known that the SARS‐CoV‐2, uses ACE2 as the cell receptor to enter and infiltrate the host cell. While ACE promotes atrophy, fibrosis, inflammation, oxidants, and vasoconstriction, ACE2 through its metabolism of angiotensin I, restricts excessive atrophy, fibrosis and causes vasodilation. Furthermore, ACE2 with its anti‐inflammatory and antioxidant role protects lung tissues and therefore a downregulation of ACE2 by SARS‐Cov‐2 infection can result in development of acute respiratory distress syndrome (ARDS) (Imai, Kuba, & Penninger, 2008). The Spike (S) protein of SARS‐Cov‐2 binds to ACE2, and recent studies have identified several residues in Exon 1 of ACE‐2, that mediate this binding (Rehman & Tabish, 2020). Our study aims to sequence ACE2 Exon 1 from Bos taurus and then compare it to human ACE2 Exon 1 using a variety of bioinformatics tools to understand and possibly identify polymorphisms that could determine species susceptibility to Covid‐19 infection. This investigation began with genomic DNA extraction from calf thymus. The genomic DNA was then analyzed using spectrophotometry (Biophotometer and Nanodrop) and gel electrophoresis. Thereafter, ACE2 target primers were designed using Primer BLAST and Primer Quest. We are now getting ready to run PCR to amplify our ACE2 Exon 1 target from Bos taurus, and after purifying the PCR products, we will sequence the ACE2 Exon 1 using our SeqStudio genetic analyzer. The sequence will then be analyzed and compared to its human counterpart using a variety of bioinformatics tools to gain a better understanding of polymorphisms that might influence SARS‐Cov‐2’s initial interaction with its host as well as pathogenesis of COVID‐19 in general.ReferencesBioDefense, G. (2018, February 12). https://globalbiodefense.com/2018/02/12/who‐updates‐blueprint‐list‐of‐priority‐diseases/. Retrieved May 14, 2020Imai, Y., Kuba, K., & Penninger, J. M. (2008). The discovery of angiotensin‐converting enzyme 2 and its role in acute lung injury in mice. Exp Physiol 93.5, pp 543–548.Rehman, S. u., & Tabish, M. (2020). Alternative splicing of ACE2 possibly generates variants that may limit the entry of SARS‐CoV‐2: a potential therapeutic approach using SSOs. Clinical Science, 134, 1143–1150.

The Identikit of Patient at Risk for Severe COVID-19 and Death: The Dysregulation of Renin-Angiotensin System as the Common Theme.

Since the first months of the coronavirus disease 2019 (COVID-19) pandemic, several specific physiologic traits, such as male sex and older age, or health conditions, such as overweight/obesity, arterial hypertension, metabolic syndrome, and type 2 diabetes mellitus, have been found to be highly prevalent and associated with increased risk of adverse outcomes in hospitalized patients. All these cardiovascular morbidities are widespread in the population and often coexist, thus identifying a common patient phenotype, characterized by a hyper-activation of the “classic” renin-angiotensin system (RAS) and mediated by the binding of angiotensin II (Ang II) to the type 1-receptor. At the same time, the RAS imbalance was proved to be crucial in the genesis of lung injury after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, where angiotensin-converting-enzyme-2 (ACE2) is not only the receptor for SARS-CoV-2, but its down-regulation through internalization and shedding, caused by the virus binding, leads to a further dysregulation of RAS by reducing angiotensin 1-7 (Ang 1-7) production. This focused narrative review will discuss the main available evidence on the role played by cardiovascular and metabolic conditions in severe COVID-19, providing a possible pathophysiological link based on the disequilibrium between the two opposite arms of RAS.

Brain angiotensin converting enzyme-2 in central cardiovascular regulation.

The brain renin-angiotensin system (RAS) plays an important role in the regulation of autonomic and neuroendocrine functions, and maintains cardiovascular homeostasis. Ang-II is the major effector molecule of RAS and exerts most of its physiological functions, including blood pressure (BP) regulation, via activation of AT1 receptors. Dysregulation of brain RAS in the central nervous system results in increased Ang-II synthesis that leads to sympathetic outflow and hypertension. Brain angiotensin (Ang) converting enzyme-2 (ACE2) was discovered two decades ago as an RAS component, exhibiting a counter-regulatory role and opposing the adverse cardiovascular effects produced by Ang-II. Studies using synthetic compounds that can sustain the elevation of ACE2 activity or genetically overexpressed ACE2 in specific brain regions found various beneficial effects on cardiovascular function. More recently, ACE2 has been shown to play critical roles in neuro-inflammation, gut dysbiosis and the regulation of stress and anxiety-like behaviors. In the present review, we aim to highlight the anatomical locations and functional implication of brain ACE2 related to its BP regulation via modulation of the sympathetic nervous system and discuss the recent developments and future directions in the ACE2-mediated central cardiovascular regulation.

Maternal Adenine-Induced Chronic Kidney Disease Programs Hypertension in Adult Male Rat Offspring: Implications of Nitric Oxide and Gut Microbiome Derived Metabolites.

Maternal chronic kidney disease (CKD) during pregnancy causes adverse fetal programming. Nitric oxide (NO) deficiency, gut microbiota dysbiosis, and dysregulated renin-angiotensin system (RAS) during pregnancy are linked to the development of hypertension in adult offspring. We examined whether maternal adenine-induced CKD can program hypertension and kidney disease in adult male offspring. We also aimed to identify potential mechanisms, including alterations of gut microbiota composition, increased trimethylamine-N-oxide (TMAO), reduced NO bioavailability, and dysregulation of the RAS. To construct a maternal CKD model, female Sprague-Dawley rats received regular chow (control group) or chow supplemented with 0.5% adenine (CKD group) for 3 weeks before pregnancy. Mother rats were sacrificed on gestational day 21 to analyze placentas and fetuses. Male offspring (n = 8/group) were sacrificed at 12 weeks of age. Adenine-fed rats developed renal dysfunction, glomerular and tubulointerstitial damage, hypertension, placental abnormalities, and reduced fetal weights. Additionally, maternal adenine-induced CKD caused hypertension and renal hypertrophy in adult male offspring. These adverse pregnancy and offspring outcomes are associated with alterations of gut microbiota composition, increased uremic toxin asymmetric and symmetric dimethylarginine (ADMA and SDMA), increased microbiota-derived uremic toxin TMAO, reduced microbiota-derived metabolite acetate and butyrate levels, and dysregulation of the intrarenal RAS. Our results indicated that adenine-induced maternal CKD could be an appropriate model for studying uremia-related adverse pregnancy and offspring outcomes. Targeting NO pathway, microbiota metabolite TMAO, and the RAS might be potential therapeutic strategies to improve maternal CKD-induced adverse pregnancy and offspring outcomes.

Dysregulation of the Renin-Angiotensin System and Cardiometabolic Status in Mice Fed a Long-Term High-Fat Diet.

BackgroundThis study aimed to investigate the renin-angiotensin system (RAS) and cardiometabolic status in mice fed a long-term high-fat diet (HFD).Material/MethodsC57BL/6J mice were randomly assigned to the control group on a normal diet (ND) (n=15) and the HFD group (n=15). Serum biomarkers were measured, including total cholesterol (TC), triglyceride (TG), insulin, glycated hemoglobin (HbA1c), brain natriuretic peptide (BNP), renin, angiotensin-converting enzyme (ACE), angiotensin II (Ang-II), Ang-II type 1 receptor (AT1R), and aldosterone. Cardiac histology was measured by the cross-sectional area (CSA) of cardiomyocytes and collagen deposition. Levels of myocardial intercalated disc (ICD) proteins and mRNA were analyzed by Western blot and real-time quantitative polymerase chain reaction (RT-qPCR), respectively. The localization of ICD proteins was evaluated by immunohistochemistry (IHC).ResultsCompared with ND, HFD resulted in increased blood glucose, body weight, TC, TG, HbA1c, insulin, and BNP and levels of serum ACE, Ang-II, aldosterone, AT1R, cardiomyocyte CSA, and interstitial collagen in the myocardium compared. Also, HFD significantly down-regulated connexin-43, and upregulated β-catenin, N-cadherin, and plakoglobin in the hearts of HFD mice compared with ND mice. However, the deposition of ICD proteins was not changed in the hearts of HFD mice compared with ND mice.ConclusionsLong-term HFD in mice resulted in left ventricular hypertrophy, interstitial fibrosis, dysregulation of RAS, and abnormal expression of ICD proteins compared with ND mice, but did not affect the distribution of cardiomyocyte ICD proteins. Long-term HFD resulted in cardiac remodeling and altered expression of ICD proteins through RAS activation.

Renoprotective effect of irbesartan in a rat model of gentamicin-induced nephrotoxicity: Role of oxidative stress.

BACKGROUND:The renin–angiotensin system (RAS) is essential in renal physiology; however, disturbance of the RAS is one of the chief pathways involved in renal injury. Dysregulation of RAS may result in both glomerular and tubulointerstitial injuries through direct effects of angiotensin II (Ang II) type 1 receptor. Irbesartan and other Ang II blockers have renoprotective effect through reduction of on renal inflammations. Therefore, the aim of the present study was to demonstrate the renoprotective effect of irbesartan on gentamicin-induced nephrotoxicity in rats concerning the oxidative stress.MATERIALS AND METHODS:Thirty Sprague-Dawley Male rats divided into three groups, Group I (10 rats) treated with distilled water, Group II (10 rats) treated with gentamicin, and Group III (10 rats) treated with gentamicin plus irbesartan for 12 days. Blood urea, serum creatinine, serum malondialdehyde (MDA), superoxide dismutase (SOD), glutathione reductase (GSH), neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecules (KIM-1), and cystatin-c were measured in each group.RESULTS:Irbesartan significantly reduced blood urea, serum creatinine, serum MDA, NGAL, KIM-1, and cystatin-c P < 0.05. Irbesartan significantly increases SOD P < 0.05 without significant effect in elevation of GSH serum levels.CONCLUSION:Irbesartan has renoprotective effect in attenuation of acute nephrotoxicity through modulation of oxidative stress and antioxidant capacity in rats.

Brain Renin-Angiotensin System and Microglial Polarization: Implications for Aging and Neurodegeneration.

Microglia can transform into proinflammatory/classically activated (M1) or anti-inflammatory/alternatively activated (M2) phenotypes following environmental signals related to physiological conditions or brain lesions. An adequate transition from the M1 (proinflammatory) to M2 (immunoregulatory) phenotype is necessary to counteract brain damage. Several factors involved in microglial polarization have already been identified. However, the effects of the brain renin-angiotensin system (RAS) on microglial polarization are less known. It is well known that there is a “classical” circulating RAS; however, a second RAS (local or tissue RAS) has been observed in many tissues, including brain. The locally formed angiotensin is involved in local pathological changes of these tissues and modulates immune cells, which are equipped with all the components of the RAS. There are also recent data showing that brain RAS plays a major role in microglial polarization. Level of microglial NADPH-oxidase (Nox) activation is a major regulator of the shift between M1/proinflammatory and M2/immunoregulatory microglial phenotypes so that Nox activation promotes the proinflammatory and inhibits the immunoregulatory phenotype. Angiotensin II (Ang II), via its type 1 receptor (AT1), is a major activator of the NADPH-oxidase complex, leading to pro-oxidative and pro-inflammatory effects. However, these effects are counteracted by a RAS opposite arm constituted by Angiotensin II/AT2 receptor signaling and Angiotensin 1–7/Mas receptor (MasR) signaling. In addition, activation of prorenin-renin receptors may contribute to activation of the proinflammatory phenotype. Aged brains showed upregulation of AT1 and downregulation of AT2 receptor expression, which may contribute to a pro-oxidative pro-inflammatory state and the increase in neuron vulnerability. Several recent studies have shown interactions between the brain RAS and different factors involved in microglial polarization, such as estrogens, Rho kinase (ROCK), insulin-like growth factor-1 (IGF-1), tumor necrosis factor α (TNF)-α, iron, peroxisome proliferator-activated receptor gamma, and toll-like receptors (TLRs). Metabolic reprogramming has recently been involved in the regulation of the neuroinflammatory response. Interestingly, we have recently observed a mitochondrial RAS, which is altered in aged brains. In conclusion, dysregulation of brain RAS plays a major role in aging-related changes and neurodegeneration by exacerbation of oxidative stress (OS) and neuroinflammation, which may be attenuated by pharmacological manipulation of RAS components.

Hypoxia induces dysregulation of local renin-angiotensin system in mouse Lewis lung carcinoma cells

The renin-angiotensin system (RAS) influences cancer biology and is frequently dysregulated in malignancy. However, regulation of tumor local RAS remains poorly understood. Hypoxia is a hallmark of solid tumors and affects nearly every major aspect of cancer biology. Previous studies have shown that hypoxia can regulate RAS expression in somatic tissues and cells. The aim of this study was to investigate the influence of hypoxia on local RAS expression in mouse Lewis lung carcinoma (LLC) cells. For hypoxia treatment, LLC cells were cultured in a hypoxia incubator or treated with hypoxia-mimetic cobalt chloride. Hypoxia up-regulated angiotensin II, angiotensin-converting enzyme (ACE), and angiotensin II type 1 receptor (AT1R), and down-regulated ACE2 and angiotensin II type 2 receptor in LLC cells. Captopril, an ACE inhibitor, and losartan, an AT1R blocker, decreased expression of ACE and AT1R, but increased expression of ACE2 and angiotensin II type 2 receptor in LLC cells under hypoxia. Captopril and losartan also suppressed vascular endothelial growth factor-A expression in LLC cells under hypoxia. These findings suggest that hypoxia induces dysregulation of local RAS in LLC cells. The pathophysiological importance of hypoxia-induced RAS dysregulation and potentially therapeutic effects of RAS inhibitors on hypoxic tumor cells should be further examined.

Preeclampsia: Molecular Mechanisms, Predisposition, and Treatment

Preeclampsia is a disorder characterised by vascular endothelial dysfunction and vasospasm that occurs after 20 weeks of gestation till 4–6 weeks postpartum. The global incidence of preeclampsia has been estimated at 2–14% of all pregnancies. Despite the advances made in the field, research is still organised to clarify the possible molecular mechanisms or predisposing factors of preeclampsia as well as the treatment options for such a significant disorder. Papers were selected on the basis of fundamental research ideas or reviews in the field. This special issue is comprising of seven papers which are focused on the better understanding of preeclapsia. One of the papers deals with the correlation of preeclampsia with hypoxia, thrombosis, and inflammation. The authors suggest that there is no accurate test for predicting preeclampsia. The role of markers such as sFLT, sEng, products of fetal and placental origin, markers of renal or endothelial damage, or markers of oxidative stress is presented by acting as secondary pathways to the pathophysiological changes that precede the clinical onset of preeclampsia. A combination of such markers is proposed in order to increase the detection accuracy earlier in the pregnancy and hopefully allow for more effective prophylactic strategies. Another paper sought to validate the use of urinary podocyte (podocyturia) as a single diagnostic marker in preeclampsia and in differentiating from other high-risk pregnancy states with similar presentations. The researchers discovered that podocyte loss is present not only in preeclampsia but in other high-risk pregnancy states. In addition, podocyturia was not found in a majority of patients diagnosed with preeclampsia. So, they realized that their findings had relatively low sensitivity and specificity, but they proposed further research regarding the predictive value of podocyturia in preeclampsia in larger studies. The authors of one of the paper investigated whether there is an association between angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism and preeclampsia in 236 pregnant women. They showed that there was significant difference in terms of genotype distribution between preeclampsia and controls, while it was not found any difference in allele frequency for ACE I/D polymorphism. A possible reason for the inconsistency could be the genetic basis that caused different susceptibilities among different populations. Moreover, one paper is mentioning that both women and children exposed to preeclampsia exhibit an adverse vascular phenotype, a propensity to subclinical atherosclerosis, and increased risk of adverse cardiac and vascular events in future life. They suggest that further studies into the mechanisms such as vascular dysfunction underlying the altered cardiovascular phenotype might provide unique insight into pathophysiological or molecular links between preeclampsia and cardiovascular disease which may direct us to novel treatment strategies for both conditions. Improvement in vascular function is also proposed as a valuable intermediate end point in studies aiming to reduce risk in this potentially young and generally asymptomatic population before the onset of clinical disease. F. J. Valenzuela and colleagues have recently reviewed some polymorphisms in important candidate genes involved in different pathogenic mechanisms related to preeclampsia and concluded that various studies in different populations have identified maternal polymorphisms associated with preeclampsia through candidate gene approaches. Luizon and colleagues with a Letter to the Editor add to the paper of F. J. Valenzuela et al. by further referring to candidate genes related to angiogenesis and endothelial dysfunction in preclampsia performed in the Brazilian population. Specifically, genotypes and haplotypes formed by polymorphisms of VEGF, eNOS, and MMP-9, along with an example of the interaction among these genes in the prediction of preeclampsia provide additional information with clinical relevance to its susceptibility. An additional paper is a review of the molecular mechanisms which are contributing to the pathogenesis of preeclampsia. Altered angiogenic balance, systemic inflammation, dysregulation of Renin-Angiotensin system, and placental hypoxia or ischemia are mechanisms leading to the pathogenesis of preeclampsia. However, it is unknown whether the mechanisms act independently or have synergistic effects.

Abstract 830: Angiotensin converting enzyme inhibitor and angiotensin receptor blocker suppress obesity-related colonic preneoplastic lesions in male C57BL/KsJ-db/db obese mice

Abstract Obesity and related metabolic abnormalities, including a state of chronic inflammation and oxidative stress, are risk factors for colon cancer. Dysregulation the renin-angiotensin system (RAS) also plays a critical role in obesity-related metabolic disorders and certain types of carcinogenesis. In the present study, we examined the effects of angiotensin converting enzyme (ACE) inhibitor and angiotensin receptor blocker (ARB), both of which target RAS, on the development of azoxymethane (AOM)-initiated colonic premalignant lesions in C57BL/KsJ-db/db (db/db) obese mice. Male db/db mice were given 4 weekly subcutaneous injections of AOM (15 mg/kg body weight) and then they received drinking water containing captopril (ACE inhibitor, 5 mg/kg/day) or telmisartan (ARB, 5 mg/kg/day) for 7 weeks. At sacrifice, administration of captopril and telmisartan significantly reduced the total number of colonic premalignant lesions, aberrant crypt foci and β-catenin accumulated crypts, compared with the control untreated-group. Both agents decreased the expression levels of TNF-α mRNA on the colonic mucosa of experimental mice. The expression levels of TNF-α, COX-2, IL-1β, IL-6, and PAI-1 mRNAs on the visceral fat were also decreased by administration of these agents. In addition, captopril and telmisartan significantly decreased the levels of urinary 8-OHdG, a surrogate marker of oxidative damage to DNA, in the experimental mice. These findings suggest that both ACE inhibitor and ARB suppress obesity-related colon carcinogenesis by attenuating chronic inflammation and reducing oxidative stress. Targeting the dysregulation of RAS might be, therefore, one of the effective strategies for the chemoprevention of obesity-related colon cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 830. doi:10.1158/1538-7445.AM2011-830

Functional interactions between 7TM receptors in the Renin-Angiotensin System—Dimerization or crosstalk?

The Renin-Angiotensin System (RAS) is important for the regulation of cardiovascular physiology, where it controls blood pressure, and salt- and water homeostasis. Dysregulation of RAS can lead to severe diseases including hypertension, diabetic nephropathy, and cardiac arrhythmia, and -failure. The importance of the RAS is clearly emphasised by the widespread use of drugs targeting this system in clinical practice. These include, renin inhibitors, angiotensin II receptor type I blockers, and inhibitors of the angiotensin converting enzyme. Some of the important effectors within the system are 7 transmembrane (7TM) receptors (or G-protein-coupled receptors) such as the angiotensin II Receptors type I and II (AT1R and AT2R) and the MAS-oncogene receptor. Several findings indicate that the 7TM receptors can form both homo- and heterodimers, or higher orders of oligomers. Furthermore, dimerization may be important for receptor function, and in the development of cardiovascular diseases. This is very significant, since "dimers" may provide pharmacologists with novel targets for improved drug therapy. However, we know that 7TM receptors can mediate signals as monomeric units, and so far it has been very difficult to establish if our observations reflect actual well-defined dimerization or merely reflect close proximity between the receptors and/or various types of functional interaction. In this review, we will present and critically discuss the current data on 7TM receptor dimerization with a clear focus on the RAS, and delineate future challenges within the field.

Association between a functional polymorphism in the renin-angiotensin system and completed suicide

Suicide has been suggested to involve disturbances in the stress response system and to be related to genetics. The renin-angiotensin system (RAS) has been shown to affect the stress response, and several functional polymorphisms in RAS-related genes have been predicted to alter protein function. We hypothesized that the dysregulation of RAS was involved in suicide, and examined the association between completed suicides and four functional polymorphisms of RAS-related genes: the angiotensinogen M235T, angiotensin-converting enzyme (ACE) insertion(I)/deletion(D), angiotensin type-1 receptor A1166C, and G-protein-beta3 C825T gene polymorphisms. The I allele of the ACE I/D polymorphism was found to be more frequent in completed suicides than in controls (P = 0.014). The I allele was also found to be more frequent in male completed suicides (P = 0.022) than in male controls, while this was not the case in females. These results suggest that the alteration of RAS function caused by the genetic polymorphism is involved in the susceptibility to suicide in males.