Computational investigation of the impact of potential AT2R polymorphism on small molecule binding

For more than a century, the renin-angiotensin system (RAS) has been acknowledged for playing a crucial part in the physiological control of arterial pressure, as well as sodium and fluid balance. It is now generally acknowledged that one of the receptor of RAS system i.e. angiotensin type 2 receptor (AT2R) functions as a repair system during pathophysiologic circumstances and performs a significant protective role. Efforts have been made previously to design suitable agonist and antagonist molecules to potentially modulate AT2R. One of the agonists and antagonists, named C21 and EMA401, has been studied in a number of pathological conditions. Additionally, a wide panel of single nucleotide polymorphisms (SNPs) has been reported for AT2R, which might potentially affect the efficacy of these molecules. Therefore, computational investigations have been carried out to analyze all the SNPs (1151) reported in NCBI to find potential SNPs affecting the active site of AT2R, as this domain is still unexplored. Structures of these polymorphic forms were modeled, and in silico drug interaction studies with C21 and EMA401 were carried out. The two mutants (rs868939201 and rs1042852794) that significantly affect the binding affinity as that of the wild type were subjected to molecular dynamics simulations. Our analysis of native and mutant AT2R and their complexes with C21 and EMA401 indicated that the occurrence of these mutations affects the conformation of the protein and has affected the binding of these ligand molecules. The study's findings will aid in the development of better, more versatile medications in the near future, and also in vitro and in vivo studies might be planned in accordance with recent findings.Communicated by Ramaswamy H. Sarma.

Unlocking the protective potential of the angiotensin type 2 receptor (AT2R) in acute lung injury and age-related pulmonary dysfunction

Despite its known importance in the cardiovascular system, the specific role and impact of the angiotensin type 2 receptor (AT2R) in lung physiology and pathophysiology remain largely elusive. In this study, we highlight the distinct and specialized lung-specific roles of AT2R, primarily localized to an alveolar fibroblast subpopulation, in contrast to the angiotensin type 1 receptor (AT1R), which is almost exclusively expressed in lung pericytes. Evidence from our research demonstrates that the disruption of AT2R (AT2R-/y), is associated with a surge in oxidative stress and impaired lung permeability, which were further intensified by Hyperoxic Acute Lung Injury (HALI). With aging, AT2R-/y mice show an increase in oxidative stress, premature enlargement of airspaces, as well as increased mortality when exposed to hyperoxia as compared to age-matched WT mice. Our investigation into Losartan, an AT1R blocker, suggests that its primary HALI lung-protective effects are channeled through AT2R, as its protective benefits are absent in AT2R-/y mice. Importantly, a non-peptide AT2R agonist, Compound 21 (C21), successfully reverses lung oxidative stress and TGFβ activation in wild-type (WT) mice exposed to HALI. These findings suggest a possible paradigm shift in the therapeutic approach for lung injury and age-associated pulmonary dysfunction, from targeting AT1R with angiotensin receptor blockers (ARBs) towards boosting the protective function of AT2R.

Angiotensin II type 2 receptor as a novel activator of brown adipose tissue in obesity

The angiotensin II type 2 receptor (AT2R) exerts vasorelaxant, anti-inflammatory, and antioxidant properties. In obesity, its activation counterbalances the adverse cardiovascular effects of angiotensin II mediated by the AT1R. Preliminary results indicate that it also promotes brown adipocyte differentiation in vitro. Our hypothesis is that AT2R activation could increase BAT mass and activity in obesity. Five-week-old male C57BL/6J mice were fed a standard or a high-fat (HF) diet for 6 weeks. Half of the animals were treated with compound 21 (C21), a selective AT2R agonist, (1 mg/kg/day) in the drinking water. Electron transport chain (ETC), oxidative phosphorylation, and UCP1 proteins were measured in the interscapular BAT (iBAT) and thoracic perivascular adipose tissue (tPVAT) as well as inflammatory and oxidative parameters. Differentiation and oxygen consumption rate (OCR) in the presence of C21 was tested in brown preadipocytes. In vitro, C21-differentiated brown adipocytes showed an AT2R-dependent increase of differentiation markers (Ucp1, Cidea, Pparg) and increased basal and H+ leak-linked OCR. In vivo, HF-C21 mice showed increased iBAT mass compared to HF animals. Both their iBAT and tPVAT showed higher protein levels of the ETC protein complexes and UCP1, together with a reduction of inflammatory and oxidative markers. The activation of the AT2R increases BAT mass, mitochondrial activity, and reduces markers of tissue inflammation and oxidative stress in obesity. Therefore, insulin reduction and better vascular responses are achieved. Thus, the activation of the protective arm of the renin-angiotensin system arises as a promising tool in the treatment of obesity.

The effect of AT1R-1166A/C and AT2R-1675A/G polymorphisms on susceptibility to preeclampsia: A systematic review and meta-analysis

BACKGROUND

The aim of this meta-analysis is to investigate the association between Angiotensin II type 1 receptor (AT1R)-1166A/C, Angiotensin II type 2 receptor (AT2R)-1675A/G polymorphisms and susceptibility to preeclampsia (PE).

METHODS

Online databases, including Web of Science, PubMed, EMBASE, CINAHL, CENTRAL, Scopus, Lilacs/SciELO, and Chinese National Knowledge Infrastructure, China Wan Fang, China Science and Technology Journal Database, were used to perform the literature search up to April 2022. The odds ratio (OR) and 95% confidence interval (CI) were used as effect size. The data was analyzed by Stata 15.0 software.

RESULTS

According to the inclusion and exclusion criteria, a total of 22 case-control studies were identified, including 3524 cases and 6308 controls. Our meta-analysis showed that the AT1R -1166 A/C allele was significantly associated with susceptibility to PE (A vs C: OR = 0.82, 95% CI: 0.69-0.96, P = .013), and there was significant difference in recessive gene model (AA vs AC + CC: OR = 0.81, 95% CI: 0.67-0.97, P = .021). However, no association was found between AT2R-1675A/G polymorphism and susceptibility to PE.

CONCLUSION

our meta-analysis suggested that AT1R-1166A/C polymorphism had an association with susceptibility to PE, but AT2R-1675A/G polymorphism had no association with susceptibility to PE.

Increased Arterial Responsiveness to Angiotensin II in Mice Conceived by Assisted Reproductive Technologies

Since the first report in 1978, the number of individuals conceived by Assisted Reproductive Technologies (ART) has grown incessantly. In parallel, with the recent emergence of possible underlying mechanisms of ART-induced epigenetic changes in the renin-angiotensin system, the cardiovascular repercussions of ART in mice and human offspring (including arterial hypertension, vascular dysfunction, and cardiac remodeling) have become increasingly recognized. Here, we hypothesized that ART may increase arterial responsiveness to angiotensin II (ANG II) by epigenetically modifying the expression of its receptors. To test this hypothesis, we assessed the vasoconstrictor responsiveness to ANG II in isolated aortas from ART and control mice. We also examined ANG II receptor (ATR) type 1 and 2 expression and the promoter methylation of the At1aR, At1bR and At2R genes. We found that the vasoconstrictor response to ANG II was markedly increased in ART mice compared to controls. This exaggerated vasoconstrictor responsiveness in ART mice correlated with a significant increase in the ANG II receptor (ATR) type 1 to ATR type 2 protein expression ratio in the aorta; this was mainly driven by an increase in AT1R expression, and by hypomethylation of two CpG sites located in the At1bR gene promoter leading to increased transcription of the gene. We conclude that in mice, ART increase the vasoconstrictor response to ANG II in the aorta by epigenetically causing an imbalance between the expression of vasoconstrictor (AT1R) and vasodilator (AT2R) ANG II receptors. Unbalanced expression of AT1R and AT2R receptors seems to be a novel mechanism contributing to ART-induced arterial hypertension in mice.

Aging modifies receptor expression but not muscular contractile response to angiotensin II in rat jejunum

The involvement of renin-angiotensin system in the modulation of gut motility and age-related changes in mRNA expression of angiotensin (Ang II) receptors (ATR) are well accepted. We aimed to characterize, in vitro, the contractile responses induced by Ang II, in jejunum from young (3–6 weeks old) and old rats (≥ 1 year old), to evaluate possible functional differences associated to changes in receptor expression. Mechanical responses to Ang II were examined in vitro as changes in isometric tension. ATR expression was assessed by qRT-PCR. Ang II induced a contractile effect, antagonized by losartan, AT1R antagonist, and increased by PD123319, AT2R antagonist, as well by neural blocker ω-conotoxin and by nitric oxide (NO) synthase inhibitor. No difference in the response was observed between young and old groups. AT1 receptor-mediated contractile response was decreased by U-73122, phospholipase C (PLC) inhibitor; or 2-aminoethoxy-diphenylborate (2-APB), inositol triphosphate (IP₃) receptor inhibitor; or nifedipine, l-type calcium channel blocker. Age-related changes in the expression of both AT1 receptor subtypes, AT1a and AT1b, and of AT2 receptors were detected. In conclusion, Ang II modulates the spontaneous contractility of rat jejunum via postjunctional AT1 receptors, involving Ca²⁺ mobilization from intracellular stores, via PLC/IP₃ pathway, and Ca²⁺ influx from extracellular space, via l-type channels. Prejunctional AT2 receptors would counteract AT1 receptor effects, via NO synthesis. The observed age-related differences in the expression of all AT receptor subtypes are not reflected in the muscular contractile response to Ang II.

Evolutionary information helps understand distinctive features of the angiotensin II receptors AT1 and AT2 in amniota

In vertebrates, the octopeptide angiotensin II (AngII) is an important in vivo regulator of the cardiovascular system. It acts mainly through two G protein-coupled receptors, AT1 and AT2. To better understand distinctive features of these receptors, we carried out a phylogenetic analysis that revealed a mirror evolution of AT1 and AT2, each one split into two clades, separating fish from terrestrial receptors. It also revealed that hallmark mutations occurred at, or near, the sodium binding site in both AT1 and AT2. Electrostatics computations and molecular dynamics simulations support maintained sodium binding to human AT1 with slow ingress from the extracellular side and an electrostatic component of the binding free energy around -3kT, to be compared to around -2kT for human AT2 and the δ opioid receptor. Comparison of the sodium binding modes in wild type and mutated AT1 and AT2 from humans and eels indicates that the allosteric control by sodium in both AT1 and AT2 evolved during the transition from fish to amniota. The unusual S7.46N mutation in AT1 is mirrored by a L3.36M mutation in AT2. In the presence of sodium, the N7.46 pattern in amniota AT1 stabilizes the inward orientation of N3.35 in the apo receptor, which should contribute to efficient N3.35 driven biased signaling. The M3.36 pattern in amniota AT2 favours the outward orientation of N3.35 and the receptor promiscuity. Both mutations have physiological consequences for the regulation of the renin-angiotensin system.

The analysis of protein sequences from different species can reveal interesting trends in the structural and functional evolution of a protein family. Here, we analyze the evolution of two G protein-coupled receptors, AT1 and AT2, which bind the angiotensin II peptide and are important regulators of the cardiovascular system. We show that these receptors underwent a mirror evolution. Specific mutations at, or near, the sodium binding pocket occurred in both AT1 and AT2 during the transition to terrestrial life. We carried out electrostatics computations and molecular dynamics simulations to decipher the details of the sodium binding mode in eel and human receptors, as prototypes of fish and amniota receptors. Our results indicate that sodium binding is kinetically slow but thermodynamically stable. Comparison of the sodium binding modes in eel and human receptors reveals that an unusual mutation in the sodium binding pocket of AT1 is critical for biased signaling of amniota AT1 whereas a mutation in AT2 promotes promiscuity of amniota AT2. In turn, these data indicate that a few mutations at a strategic position (here the sodium binding pocket) are an efficient way to gain functional evolution.

Fetal Undernutrition Modifies Vascular RAS Balance Enhancing Oxidative Damage and Contributing to Remodeling

Fetal stress is known to increase susceptibility to cardiometabolic diseases and hypertension in adult age in a process known as fetal programming. This study investigated the relationship between vascular RAS, oxidative damage and remodeling in fetal programming. Six-month old Sprague-Dawley offspring from mothers that were fed ad libitum (CONTROL) or with 50% intake during the second half of gestation (maternal undernutrition, MUN) were used. qPCR or immunohistochemistry were used to obtain the expression of receptors and enzymes. Plasma levels of carbonyls were measured by spectrophotometry. In mesenteric arteries from MUN rats we detected an upregulation of ACE, ACE2, AT₁ receptors and NADPH oxidase, and lower expression of AT₂, Mas and MrgD receptors compared to CONTROL. Systolic and diastolic blood pressure and plasma levels of carbonyls were higher in MUN than in CONTROL. Vascular morphology evidenced an increased media/lumen ratio and adventitia/lumen ratio, and more connective tissue in MUN compared to CONTROL. In conclusion, fetal undernutrition indices RAS alterations and oxidative damage which may contribute to the remodeling of mesenteric arteries, and increase the risk of adverse cardiovascular events and hypertension.

Angiotensin II biphasically regulates cell differentiation in human iPSC-derived kidney organoids

Human kidney organoid technology holds promise for novel kidney disease treatment strategies and utility in pharmacological and basic science. Given the crucial roles of the intrarenal renin-angiotensin system (RAS) and angiotensin II (ANG II) in the progression of kidney development and injury, we investigated the expression of RAS components and effects of ANG II on cell differentiation in human kidney organoids. Human induced pluripotent stem cell-derived kidney organoids were induced using a modified 18-day Takasato protocol. Gene expression analysis by digital PCR and immunostaining demonstrated the formation of renal compartments and expression of RAS components. The ANG II type 1 receptor (AT1R) was strongly expressed in the early phase of organoid development (around day 0), whereas ANG II type 2 receptor (AT2R) expression levels peaked on day 5. Thus, the organoids were treated with 100 nM ANG II in the early phase on days 0-5 (ANG II-E) or during the middle phase on days 5-10 (ANG II-M). ANG II-E was observed to decrease levels of marker genes for renal tubules and proximal tubules, and the downregulation of renal tubules was inhibited by an AT1R antagonist. In contrast, ANG II-M increased levels of markers for podocytes, the ureteric tip, and the nephrogenic mesenchyme, and an AT2R blocker attenuated the ANG II-M-induced augmentation of podocyte formation. These findings demonstrate RAS expression and ANG II exertion of biphasic effects on cell differentiation through distinct mediatory roles of AT1R and AT2R, providing a novel strategy to establish and further characterize the developmental potential of human induced pluripotent stem cell-derived kidney organoids.NEW & NOTEWORTHY This study demonstrates angiotensin II exertion of biphasic effects on cell differentiation through distinct mediatory roles of angiotensin II type 1 receptor and type 2 receptor in human induced pluripotent stem cell-derived kidney organoids, providing a novel strategy to establish and further characterize the developmental potential of the human kidney organoids.

Colon adenocarcinoma-derived cells possessing stem cell function can be modulated using renin-angiotensin system inhibitors

The cancer stem cell (CSC) concept proposes that cancer recurrence and metastasis are driven by CSCs. In this study, we investigated whether cells from colon adenocarcinoma (CA) with a CSC-like phenotype express renin-angiotensin system (RAS) components, and the effect of RAS inhibitors on CA-derived primary cell lines. Expression of RAS components was interrogated using immunohistochemical and immunofluorescence staining in 6 low-grade CA (LGCA) and 6 high-grade CA (HGCA) tissue samples and patient-matched normal colon samples. Primary cell lines derived from 4 HGCA tissues were treated with RAS inhibitors to investigate their effect on cellular metabolism, tumorsphere formation and transcription of pluripotency genes. Immunohistochemical and immunofluorescence staining showed expression of AT2R, ACE2, PRR, and cathepsins B and D by cells expressing pluripotency markers. β-blockers and AT2R antagonists reduced cellular metabolism, pluripotency marker expression, and tumorsphere-forming capacity of CA-derived primary cell lines. This study suggests that the RAS is active in CSC-like cells in CA, and further investigation is warranted to determine whether RAS inhibition is a viable method of targeting CSCs.

Double Deletion of Angiotensin II Type 2 and Mas Receptors Accelerates Aging-Related Muscle Weakness in Male Mice

Background The activation of AT2 (angiotensin II type 2 receptor ) and Mas receptor by angiotensin II and angiotensin-(1-7), respectively, is the primary process that counteracts activation of the canonical renin-angiotensin system (RAS). Although inhibition of canonical RAS could delay the progression of physiological aging, we recently reported that deletion of Mas had no impact on the aging process in mice. Here, we used male mice with a deletion of only AT2 or a double deletion of AT2 and Mas to clarify whether these receptors contribute to the aging process in a complementary manner, primarily by focusing on aging-related muscle weakness. Methods and Results Serial changes in grip strength of these mice up to 24 months of age showed that AT2/Mas knockout mice, but not AT2 knockout mice, had significantly weaker grip strength than wild-type mice from the age of 18 months. AT2/Mas knockout mice exhibited larger sizes, but smaller numbers and increased frequency of central nucleation (a marker of aged muscle) of single skeletal muscle fibers than AT2 knockout mice. Canonical RAS-associated genes, inflammation-associated genes, and senescence-associated genes were highly expressed in skeletal muscles of AT2/Mas knockout mice. Muscle angiotensin II content increased in AT2/Mas knockout mice. Conclusions Double deletion of AT2 and Mas in mice exaggerated aging-associated muscle weakness, accompanied by signatures of activated RAS, inflammation, and aging in skeletal muscles. Because aging-associated phenotypes were absent in single deletions of the receptors, AT2 and Mas could complement each other in preventing local activation of RAS during aging.

AGTR2, One Possible Novel Key Gene for the Entry of SARS-CoV-2 Into Human Cells

Recently, it was confirmed that ACE2 is the receptor of SARS-CoV-2, the pathogen causing the recent outbreak of severe pneumonia around the world. It is confused that ACE2 is widely expressed across a variety of organs and is expressed moderately but not highly in lung, which, however, is the major infected organ. Therefore, we hypothesized that there could be some other genes playing key roles in the entry of SARS-CoV-2 into human cells. Here we found that AGTR2 (angiotensin II receptor type 2), a G-protein coupled receptor, has interaction with ACE2 and is highly expressed in lung with a high tissue specificity. More importantly, simulation of 3D structure based protein-protein interaction reveals that AGTR2 shows a higher binding affinity with the Spike protein of SARS-CoV-2 than ACE2 (energy: -8.2 vs. -5.1 [kcal/mol]). A number of compounds, biologics and traditional Chinese medicine that could decrease the expression level of AGTR2 were predicted. Finally, we suggest that AGTR2 could be a putative novel gene for the entry of SARS-CoV-2 into human cells, which could provide different insight for the research of SARS-CoV-2 proteins with their receptors.

Angiotensin (1-7) Alleviates Postresuscitation Myocardial Dysfunction by Suppressing Oxidative Stress Through the Phosphoinositide 3-Kinase, Protein Kinase B, and Endothelial Nitric Oxide Synthase Signaling Pathway

ABSTRACT

There is increasing evidence that angiotensin (1-7) [Ang (1-7)] is an endogenous biologically active component of the renin-angiotensin system. However, the role of the Ang (1-7)-MasR axis in postresuscitation myocardial dysfunction (PRMD) and its associated mechanism are still unclear. In this study, we investigated the effect of the Ang (1-7)-MasR axis on myocardial injury after cardiac arrest-cardiopulmonary resuscitation-restoration of spontaneous circulation. We established a model of oxygen/glucose deprivation-reperfusion in myocardial cells in vitro and a rat model of cardiac arrest-cardiopulmonary resuscitation-restoration of spontaneous circulation in vivo. The cell apoptosis rate and the expression of the superoxide anion 3-nitrotyrosine were decreased in the Ang (1-7) group in vitro and in vivo. The mean arterial pressure was decreased, whereas +LVdp/dtmax and -LVdp/dtmax were increased in rats in the Ang (1-7) group. The mRNA and protein levels of Ang II type 1 receptor, MasR, phosphoinositide 3-kinase, protein kinase B, and endothelial nitric oxide synthase were increased in the Ang (1-7) group in vivo. These results indicate that the Ang (1-7)-MasR axis can alleviate PRMD by reducing myocardial tissue damage and oxidative stress through activation of the phosphoinositide 3-kinase-protein kinase B-endothelial nitric oxide synthase signaling pathway and provide a new direction for the clinical treatment of PRMD.

Advances in use of mouse models to study the renin-angiotensin system

The renin-angiotensin system (RAS) is a highly complex hormonal cascade that spans multiple organs and cell types to regulate solute and fluid balance along with cardiovascular function. Much of our current understanding of the functions of the RAS has emerged from a series of key studies in genetically-modified animals. Here, we review key findings from ground-breaking transgenic models, spanning decades of research into the RAS, with a focus on their use in studying blood pressure. We review the physiological importance of this regulatory system as evident through the examination of mouse models for several major RAS components: angiotensinogen, renin, ACE, ACE2, and the type 1 A angiotensin receptor. Both whole-animal and cell-specific knockout models have permitted critical RAS functions to be defined and demonstrate how redundancy and multiplicity within the RAS allow for compensatory adjustments to maintain homeostasis. Moreover, these models present exciting opportunities for continued discovery surrounding the role of the RAS in disease pathogenesis and treatment for cardiovascular disease and beyond.

Angiotensin receptors in the kidney and vasculature in hypertension and kidney disease

Kidney disease, blood pressure determination, hypertension pathogenesis, and the renin-angiotensin system (RAS) are inextricably linked. Hence, understanding the RAS is pivotal to unraveling the pathophysiology of hypertension and the determinants to maintaining normal blood pressure. The RAS has been the subject of intense investigation for over a century. Moreover, medications that block the RAS are mainstay therapies in clinical medicine and have been shown to reduce morbidity and mortality in patients with diabetes, cardiovascular, and kidney diseases. The main effector peptide of the RAS is the interaction of the octapeptide- Ang II with its receptor. The type 1 angiotensin receptor (AT₁R) is the effector receptor for Ang II. These G protein-coupled receptors (GPCRs) are ubiquitously expressed in a variety of cell lineages and tissues relevant to cardiovascular disease throughout the body. The advent of cell specific deletion of genes using Cre LoxP technology in mice has allowed for the identification of discreet actions of AT₁Rs in blood pressure control and kidney disease. The kidney is one of the major targets of the RAS, which is responsible in maintaining fluid, electrolyte balance, and blood pressure. In this review we will discuss the role of AT₁Rs in the kidney, vasculature, and immune cells and address their effects on hypertension and kidney disease.

Renin-angiotensin system and inflammation update

The most classical view of the renin-angiotensin system (RAS) emphasizes its role as an endocrine regulator of sodium balance and blood pressure. However, it has long become clear that the RAS has pleiotropic actions that contribute to organ damage, including modulation of inflammation. Angiotensin II (Ang II) activates angiotensin type 1 receptors (AT1R) to promote an inflammatory response and organ damage. This represents the pathophysiological basis for the successful use of RAS blockers to prevent and treat kidney and heart disease. However, other RAS components could have a built-in capacity to brake proinflammatory responses. Angiotensin type 2 receptor (AT2R) activation can oppose AT1R actions, such as vasodilatation, but its involvement in modulation of inflammation has not been conclusively proven. Angiotensin-converting enzyme 2 (ACE2) can process Ang II to generate angiotensin-(1-7) (Ang-(1-7)), that activates the Mas receptor to exert predominantly anti-inflammatory responses depending on the context. We now review recent advances in the understanding of the interaction of the RAS with inflammation. Specific topics in which novel information became available recently include intracellular angiotensin receptors; AT1R posttranslational modifications by tissue transglutaminase (TG2) and anti-AT1R autoimmunity; RAS modulation of lymphoid vessels and T lymphocyte responses, especially of Th17 and Treg responses; interactions with toll-like receptors (TLRs), programmed necrosis, and regulation of epigenetic modulators (e.g. microRNAs and bromodomain and extraterminal domain (BET) proteins). We additionally discuss an often overlooked effect of the RAS on inflammation which is the downregulation of anti-inflammatory factors such as klotho, peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), transient receptor potential ankyrin 1 (TRPA1), SNF-related serine/threonine-protein kinase (SNRK), serine/threonine-protein phosphatase 6 catalytic subunit (Ppp6C) and n-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP). Both transcription factors, such as nuclear factor κB (NF-κB), and epigenetic regulators, such as miRNAs are involved in downmodulation of anti-inflammatory responses. A detailed analysis of pathways and targets for downmodulation of anti-inflammatory responses constitutes a novel frontier in RAS research.

Dysregulation of COVID-19 related gene expression in the COPD lung

BACKGROUND

Chronic obstructive pulmonary disease (COPD) patients are at increased risk of poor outcome from Coronavirus disease (COVID-19). Early data suggest elevated Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) receptor angiotensin converting enzyme 2 (ACE2) expression, but relationships to disease phenotype and downstream regulators of inflammation in the Renin-Angiotensin system (RAS) are unknown. We aimed to determine the relationship between RAS gene expression relevant to SARS-CoV-2 infection in the lung with disease characteristics in COPD, and the regulation of newly identified SARS-CoV-2 receptors and spike-cleaving proteases, important for SARS-CoV-2 infection.

METHODS

We quantified gene expression using RNA sequencing of epithelial brushings and bronchial biopsies from 31 COPD and 37 control subjects.

RESULTS

ACE2 gene expression (log2-fold change (FC)) was increased in COPD compared to ex-smoking (HV-ES) controls in epithelial brushings (0.25, p = 0.042) and bronchial biopsies (0.23, p = 0.050), and correlated with worse lung function (r = - 0.28, p = 0.0090). ACE2 was further increased in frequent exacerbators compared to infrequent exacerbators (0.51, p = 0.00045) and associated with use of ACE inhibitors (ACEi) (0.50, p = 0.0034), having cardiovascular disease (0.23, p = 0.048) or hypertension (0.34, p = 0.0089), and inhaled corticosteroid use in COPD subjects in bronchial biopsies (0.33, p = 0.049). Angiotensin II receptor type (AGTR)1 and 2 expression was decreased in COPD bronchial biopsies compared to HV-ES controls with log2FC of -0.26 (p = 0.033) and - 0.40, (p = 0.0010), respectively. However, the AGTR1:2 ratio was increased in COPD subjects compared with HV-ES controls, log2FC of 0.57 (p = 0.0051). Basigin, a newly identified potential SARS-CoV-2 receptor was also upregulated in both brushes, log2FC of 0.17 (p = 0.0040), and bronchial biopsies, (log2FC of 0.18 (p = 0.017), in COPD vs HV-ES. Transmembrane protease, serine (TMPRSS)2 was not differentially regulated between control and COPD. However, various other spike-cleaving proteases were, including TMPRSS4 and Cathepsin B, in both epithelial brushes (log2FC of 0.25 (p = 0.0012) and log2FC of 0.56 (p = 5.49E-06), respectively) and bronchial biopsies (log2FC of 0.49 (p = 0.00021) and log2FC of 0.246 (p = 0.028), respectively).

CONCLUSION

This study identifies key differences in expression of genes related to susceptibility and aetiology of COVID-19 within the COPD lung. Further studies to understand the impact on clinical course of disease are now required.

Gene Polymorphisms of the Renin-Angiotensin-Aldosterone System as Risk Factors for the Development of In-Stent Restenosis in Patients with Stable Coronary Artery Disease

This study investigated the renin-angiotensin-aldosterone system (RAAS) gene polymorphisms as possible genetic risk factors for the restenosis development in patients with drug-eluting stents. 113 participants had coronary artery disease and underwent stenting. The control group consisted of 62 individuals with intact coronary arteries. Patients were divided into two groups: with in-stent restenosis (ISR) and without it. The patients with ISR were classified into subgroups by the terms of the restenosis development and age. Real-time PCR and Restriction Fragment Length Polymorphism-PCR were used to genotype the study participants for RAAS gene polymorphisms. We found that the development of restenosis is generally associated with the minor A allele for renin (REN) rs2368564 and the major TT genotype for angiotensinogen (AGT) rs699. The heterozygous genotype for AGT rs4762 acts as a protective marker. A minor A allele for angiotensin II type 2 receptor (AGTR2) rs1403543 is associated with a risk of restenosis in people under 65 years old. Among patients with the early ISR, heterozygotes for angiotensin II type 1 receptor (AGTR1) rs5186 are more frequent, as well as A allele carriers for AGTR2 rs1403543. A minor homozygous genotype for REN rs41317140 and heterozygous genotype for aldosterone synthase (CYP11B2) rs1799998 are predisposed to the late restenosis. Thus, to choose the effective treatment tactics for patients with coronary artery disease, it is necessary to genotype patients for the RAAS polymorphisms, which, along with age and clinical characteristics, will allow a comprehensive assessment of the risk of the restenosis development after stenting.

AT1 and AT2 Receptor Knockout Changed Osteonectin and Bone Density in Mice in Periodontal Inflammation Experimental Model

BACKGROUND

The aim of this study was to evaluate the role of AT1 and AT2 receptors in a periodontal inflammation experimental model.

METHODS

Periodontal inflammation was induced by LPS/Porphyromonas gingivalis. Maxillae, femur, and vertebra were scanned using Micro-CT. Maxillae were analyzed histopathologically, immunohistochemically, and by RT-PCR.

RESULTS

The vertebra showed decreased BMD in AT1 H compared with WT H (p < 0.05). The femur showed increased Tb.Sp for AT1 H and AT2 H, p < 0.01 and p < 0.05, respectively. The Tb.N was decreased in the vertebra (WT H-AT1 H: p < 0.05; WT H-AT2 H: p < 0.05) and in the femur (WT H-AT1 H: p < 0.01; WT H-AT2 H: p < 0.05). AT1 PD increased linear bone loss (p < 0.05) and decreased osteoblast cells (p < 0.05). RANKL immunostaining was intense for AT1 PD and WT PD (p < 0.001). OPG was intense in the WT H, WT PD, and AT2 PD when compared to AT1 PD (p < 0.001). AT1 PD showed weak immunostaining for osteocalcin compared with WT H, WT PD, and AT2 PD (p < 0.001). AT1 H showed significantly stronger immunostaining for osteonectin in fibroblasts compared to AT2 H (p < 0.01).

CONCLUSION

AT1 receptor knockout changed bone density, the quality and number of bone trabeculae, decreased the number of osteoblast cells, and increased osteonectin in fibroblasts.

Blockade of bradykinin receptors or angiotensin II type 2 receptor prevents paclitaxel-associated acute pain syndrome in mice

BACKGROUND

Paclitaxel (PCX) is the first-line choice for the treatment of several types of cancer, including breast, ovarian, and lung cancers. However, patients who receive even a single dose with PCX commonly develop mechanical and cold allodynia, a symptom known as PCX-associated acute pain syndrome (P-APS). Here, we assessed possible involvement of kinin-kallikrein and renin-angiotensin systems in P-APS in mice.

METHODS

Male mice C57Bl/6 wild type (WT) and knockouts for bradykinin receptors, B1 (B1^-/- ) and B2 (B2^-/- ), were used. Mechanical and cold allodynia were evaluated by using von Frey filaments and acetone test, respectively. P-APS was induced by administration of PCX 4 mg/kg, i.v.. ACE inhibitors (captopril and enalapril), antagonists for angiotensin II type 1 (losartan) and type 2 ([AT2R]; PD123319 and EMA 401) receptors were administrated prior the treatment with PCX. RT-PCR was used to analyse the expression of mRNA for B1, B2 and AT2R receptors.

RESULTS

Administration of PCX in B1^-/- and B2^-/- mice induced lower mechanical and cold allodynia compared to the WT. However, the pre-treatment with ACE inhibitors reduced the development of mechanical and cold allodynia in P-APS. Surprisingly, we found that mice pre-treatment with the PD123319 or EMA401, but not losartan, prevented the development of mechanical and cold allodynia induced by PCX.

CONCLUSION

Our results demonstrated the involvement of bradykinin receptors B1 and B2 as well as AT2R in the induction of P-APS in mice, and suggest the use of AT2R antagonists as a potential therapy for the prevention of P-APS in humans.

SIGNIFICANCE

Kinin-kallikrein and renin-angiotensin systems, through B1, B2 and AT2 receptors, potentiates paclitaxel-associated acute pain syndrome (P-APS) in mice. Antagonists for AT2R are potential alternatives to prevent P-APS.

Estrogens and the Angiotensin II Type 2 Receptor Control Flow-Mediated Outward Remodeling in the Female Mouse Mesenteric Artery

Flow-mediated outward remodeling (FMR) is involved in postischemic revascularization. Angiotensin II type 2 receptor (AT2R), through activation of T-cell-mediated IL-17 production, and estrogens are involved in FMR. Thus, we investigated the interplay between estrogens and AT2R in FMR using a model of ligation of feed arteries supplying collateral pathways in mouse mesenteric arteries in vivo. Arteries were collected after 2 (inflammatory phase), 4 (diameter expansion phase), and 7 days (remodeling completed). We used AT2R+/+ and AT2R-/- ovariectomized (OVX) female mice treated or not with 17-beta-estradiol (E2). Seven days after ligation, arterial diameter was larger in high flow (HF) compared to normal flow (NF) arteries. FMR was absent in OVX mice and restored by E2. AT2R gene expression was higher in HF than in NF arteries only in E2-treated OVX AT2R+/+ mice. CD11b and TNF alpha levels (inflammatory phase), MMP2 and TIMP1 (extracellular matrix digestion), and NOS3 (diameter expansion phase) expression levels were higher in HF than in NF arteries only in E2-treated AT2R+/+ mice, not in the other groups. Thus, E2 is necessary for AT2R-dependent diameter expansion, possibly through activation of T-cell AT2R, in arteries submitted chronically to high blood flow.

Comparing the Binding Interactions in the Receptor Binding Domains of SARS-CoV-2 and SARS-CoV

SARS-CoV-2, since emerging in Wuhan, China, has been a major concern because of its high infection rate and has left more than six million infected people around the world. Many studies endeavored to reveal the structure of the SARS-CoV-2 compared to the SARS-CoV, in order to find solutions to suppress this high infection rate. Some of these studies showed that the mutations in the SARS-CoV spike (S) protein might be responsible for its higher affinity to the ACE2 human cell receptor. In this work, we used molecular dynamics simulations and Monte Carlo sampling to compare the binding affinities of the S proteins of SARS-CoV and SARS-CoV-2 to the ACE2. Our results show that the protein surface of the ACE2 at the receptor binding domain (RBD) exhibits negative electrostatic potential, while a positive potential is observed for the S proteins of SARS-CoV/SARS-CoV-2. In addition, the binding energies at the interface are slightly higher for SARS-CoV-2 because of enhanced electrostatic interactions. The major contributions to the electrostatic binding energies result from the salt bridges forming between R426 and ACE-2-E329 in the case of SARS-CoV and K417 and ACE2-D30 in the SARS-CoV-2. In addition, our results indicate that the enhancement in the binding energy is not due to a single mutant but rather because of the sophisticated structural changes induced by all these mutations together. This finding suggests that it is implausible for the SARS-CoV-2 to be a lab-engineered virus.

Ablation of angiotensin type 2 receptor prevents endothelial nitric oxide synthase glutathionylation and nitration in ischaemic abductor muscle of diabetic mice

Peripheral artery disease is a severe complication of diabetes. We have reported that the deletion of angiotensin type 2 receptor in diabetic mice promoted vascular angiogenesis in the ischaemic muscle 4 weeks following ischaemia. However, the angiotensin type 2 receptor deletion beneficial effects occurred 2 weeks post surgery suggesting that angiotensin type 2 receptor may regulate other pro-angiogenic signalling pathways during the early phases of ischaemia. Nondiabetic and diabetic angiotensin type 2 receptor-deficient mice (Agtr2^-/Y) underwent femoral artery ligation after 2 months of diabetes. Blood perfusion was measured every week up to 2 weeks post surgery. Expression of vascular endothelial growth factor, vascular endothelial growth factor receptor and endothelial nitric oxide synthase expression and activity were evaluated. Blood flow reperfusion in the ischaemic muscle of diabetic Agtr2^+/Y mice was recovered at 35% as compared to a 68% recovery in diabetic Agtr2^-/Y mice. The expression of vascular endothelial growth factor and its receptors was diminished in diabetic Agtr2^+/Y mice, an observation not seen in diabetic Agtr2^-/Y mice. Interestingly, Agtr2^-/Y mice were protected from diabetes-induced glutathionylation, nitration and decreased endothelial nitric oxide synthase expression, which correlated with reduced endothelial cell death and enhanced vascular density in diabetic ischaemic muscle. In conclusion, our results suggest that the deletion of angiotensin type 2 receptor promotes blood flow reperfusion in diabetes by favouring endothelial cell survival and function.

Angiotensin II inhibits P-glycoprotein in intestinal epithelial cells

AIM

P-glycoprotein (Pgp/MDR1) plays a major role in intestinal homeostasis. Decrease in Pgp function and expression has been implicated in the pathogenesis of IBD. However, inhibitory mechanisms involved in the decrease of Pgp in inflammation are not fully understood. Angiotensin II (Ang II), a peptide hormone predominantly expressed in the epithelial cells of the crypt-villus junction of the intestine, has been shown to exert pro-inflammatory effects in the gut. It is increased in IBD patients and animals with experimental colitis. Whether Ang II directly influences Pgp is not known.

METHODS

Pgp activity was measured as verapamil-sensitive 3 H-digoxin flux. Pgp surface expression and exocytosis were measured by cell surface biotinylation studies. Signalling pathways were elucidated by Western blot analysis and pharmacological approaches.

RESULTS

Ang II (10 nM) significantly inhibited Pgp activity at 60 minutes. Ang II-mediated effects on Pgp function were receptor-mediated as the Ang II receptor 1 (ATR1) antagonist, losartan, blocked Pgp inhibition. Ang II effects on Pgp activity appeared to be mediated via PI3 kinase, p38 MAPK and Akt signalling. Ang II-mediated inhibition of Pgp activity was associated with a decrease in the surface membrane expression of Pgp protein via decreased exocytosis and was found to be dependent on the Akt pathway. Short-term treatment of Ang II (2 mg/kg b.wt., 2 hours) to mice also decreased the membrane expression of Pgp protein levels in ileum and colon.

CONCLUSION

Our findings provide novel insights into the role of Ang II and ATR1 in decreasing Pgp expression in intestinal inflammation.

Interaction between Angiotensin Type 1, Type 2, and Mas Receptors to Regulate Adult Neurogenesis in the Brain Ventricular-Subventricular Zone

The renin-angiotensin system (RAS), and particularly its angiotensin type-2 receptors (AT2), have been classically involved in processes of cell proliferation and maturation during development. However, the potential role of RAS in adult neurogenesis in the ventricular-subventricular zone (V-SVZ) and its aging-related alterations have not been investigated. In the present study, we analyzed the role of major RAS receptors on neurogenesis in the V-SVZ of adult mice and rats. In mice, we showed that the increase in proliferation of cells in this neurogenic niche was induced by activation of AT2 receptors but depended partially on the AT2-dependent antagonism of AT1 receptor expression, which restricted proliferation. Furthermore, we observed a functional dependence of AT2 receptor actions on Mas receptors. In rats, where the levels of the AT1 relative to those of AT2 receptor are much lower, pharmacological inhibition of the AT1 receptor alone was sufficient in increasing AT2 receptor levels and proliferation in the V-SVZ. Our data revealed that interactions between RAS receptors play a major role in the regulation of V-SVZ neurogenesis, particularly in proliferation, generation of neuroblasts, and migration to the olfactory bulb, both in young and aged brains, and suggest potential beneficial effects of RAS modulators on neurogenesis.

The angiotensin converting enzyme 2/angiotensin-(1-7)/Mas Receptor axis as a key player in alveolar bone remodeling

The renin-angiotensin system (RAS), aside its classical hormonal properties, has been implicated in the pathogenesis of inflammatory disorders. The angiotensin converting enzyme 2/angiotensin-(1-7)/Mas Receptor (ACE2/Ang-(1-7)/MasR) axis owns anti-inflammatory properties and was recently associated with bone remodeling in osteoporosis. Thus, the aim of this study was to characterize the presence and effects of the ACE2/Ang-(1-7)/MasR axis in osteoblasts and osteoclasts in vitro and in vivo. ACE2 and MasR were detected by qPCR and western blotting in primary osteoblast and osteoclast cell cultures. Cells were incubated with different concentrations of Ang-(1-7), diminazene aceturate (DIZE - an ACE2 activator), A-779 (MasR antagonist) and/or LPS in order to evaluate osteoblast alkaline phosphatase and mineralized matrix, osteoclast differentiation and cytokine expression, and mRNA levels of osteoblasts and osteoclasts markers. An experimental model of alveolar bone resorption triggered by dysbiosis in rats was used to evaluate bone remodeling in vivo. Rats were treated with Ang-(1-7), DIZE and/or A-779 and periodontal samples were collected for immunohistochemistry, morphometric analysis, osteoblast and osteoclast count and cytokine evaluation. Human gingival samples from healthy and periodontitis patients were also evaluated for detection of ACE2 and MasR expression. Osteoblasts and osteoclasts expressed ACE2 and MasR in vitro and in vivo. LPS stimulation or alveolar bone loss induction reduced ACE2 expression. Treatment of bone cells with Ang-(1-7) or DIZE stimulated osteoblast ALP, matrix synthesis, upregulated osterix, osteocalcin and collagen type 1 transcription, reduced IL-6 expression, and decreased osteoclast differentiation, RANK and IL-1β mRNA transcripts, and IL-6 and IL-1β levels, in a MasR-dependent manner. In vivo, Ang-(1-7) and DIZE decreased alveolar bone loss through improvement of osteoblast/osteoclast ratio. A-779 reversed such phenotype. ACE2/Ang-(1-7)/MasR axis activation reduced IL-6 expression, but not IL-1β. ACE2 and MasR were also detected in human gingival samples, with higher expression in the healthy than in the inflamed tissues. These findings show that the ACE2/Ang-(1-7)/MasR is an active player in alveolar bone remodeling.

AMPK: a balancer of the renin-angiotensin system

The renin-angiotensin system (RAS) is undisputedly well-studied as one of the oldest and most critical regulators for arterial blood pressure, fluid volume, as well as renal function. In recent studies, RAS has also been implicated in the development of obesity, diabetes, hyperlipidemia, and other diseases, and also involved in the regulation of several signaling pathways such as proliferation, apoptosis and autophagy, and insulin resistance. AMP-activated protein kinase (AMPK), an essential cellular energy sensor, has also been discovered to be involved in these diseases and cellular pathways. This would imply a connection between the RAS and AMPK. Therefore, this review serves to draw attention to the cross-talk between RAS and AMPK, then summering the most recent literature which highlights AMPK as a point of balance between physiological and pathological functions of the RAS.

Altered expression of renin-angiotensin system receptors throughout colorectal adenoma-adenocarcinoma sequence

Background and Objective: Colorectal cancer (CRC) is a major health problem in developed countries. Adenomatous lesions in the large bowel are the main precursors of CRC and the adenoma-adenocarcinoma sequence still provides a solid model for research on carcinogenesis. The finding of local renin-angiotensin systems (RAS) has been crucial to understand the role of this peptidergic system in cancer and has opened new perspectives in the study of colorectal carcinogenetic processes. Methods: In this study we analyzed the immunohistochemical expression of three main RAS receptors (AT1, AT2 and MAS) in a large series of CRC samples (n=161), including uninvolved intestinal mucosa-adenoma-adenocarcinoma sequences from the same patients (n=50). Results: 1) AT1 and AT2 showed a biphasic expression pattern along the sequence. The expression significantly decreased in adenomas with respect to uninvolved mucosa but increased in CRCs. 2) AT2 expression was lower in advanced CRCs with high local invasion (pT4), high stage (IV), high nodal (N2) and vascular invasion. 3) MAS receptor was moderately expressed in the uninvolved mucosa and in adenomas. This expression increased very significantly in CRC tissues. Conclusions: These results suggest that: 1) RAS receptors are differentially regulated as the genetic and epigenetic alterations accumulate throughout the uninvolved mucosa-adenoma-CRC sequence. 2) Loss of AT2 expression could contribute to the aggressive behavior of advanced CRC cells.

Angiotensin II type 2 receptor stimulation with compound 21 improves neurological function after stroke in female rats: a pilot study

The angiotensin II type 2 receptor (AT2R) agonist, compound 21 (C21), has been shown to be neurovascularly protective after ischemic stroke in male rats. In the current study, we aim to study the impact of C21 treatment on female rats. Young female Wistar rats were subjected to different durations of middle cerebral artery occlusion (MCAO) (3 h, 2 h, and 1 h) using a silicone-coated monofilament, treated at reperfusion with 0.03 mg/kg ip of C21 and followed up for different times (1, 3, and 14 days) after stroke. Behavioral tests were performed (Bederson, paw grasp, beam walk, and rotarod), and animals were euthanized for infarct size analysis and Western blot analysis. In vitro, primary male and female brain microvascular endothelial cells (ECs) were grown in culture, and the expression of the AT2R was compared between males and females. At 1 day, C21 treatment resulted in an improvement in Bederson scores. However, at 3 days and 14 days, the impact of C21 on stroke outcomes was less robust. In vitro, the expression of the AT2R was significantly higher in female ECs compared with male ECs. In conclusion, C21 improves Bederson scores after stroke in female rats when administered early at reperfusion. The ability of C21 to exert its neuroprotective effects might be affected by fluctuating levels of female hormones. NEW & NOTEWORTHY The present study shows the neuroprotective impact of C21 on ischemic stroke in female rats and how the protective effects of C21 can be influenced by the hormonal status of female rodents.

Nrf2 Deficiency Upregulates Intrarenal Angiotensin-Converting Enzyme-2 and Angiotensin 1-7 Receptor Expression and Attenuates Hypertension and Nephropathy in Diabetic Mice

We investigated the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in renin-angiotensin system (RAS) gene expression in renal proximal tubule cells (RPTCs) and in the development of systemic hypertension and kidney injury in diabetic Akita mice. We used adult male Akita Nrf2 knockout mice and Akita mice treated with trigonelline (an Nrf2 inhibitor) or oltipraz (an Nrf2 activator). We also examined rat immortalized RPTCs (IRPTCs) stably transfected with control plasmids or plasmids containing rat angiotensinogen (Agt), angiotensin-converting enzyme (ACE), angiotensin-converting enzyme-2 (Ace2), or angiotensin 1-7 (Ang 1-7) receptor (MasR) gene promoters. Genetic deletion of Nrf2 or pharmacological inhibition of Nrf2 in Akita mice attenuated hypertension, renal injury, tubulointerstitial fibrosis, and the urinary albumin/creatinine ratio. Furthermore, loss of Nrf2 upregulated RPTC Ace2 and MasR expression, increased urinary Ang 1-7 levels, and downregulated expression of Agt, ACE, and profibrotic genes in Akita mice. In cultured IRPTCs, Nrf2 small interfering RNA transfection or trigonelline treatment prevented high glucose stimulation of Nrf2 nuclear translocation, Agt, and ACE transcription with augmentation of Ace2 and MasR transcription, which was reversed by oltipraz. These data identify a mechanism, Nrf2-mediated stimulation of intrarenal RAS gene expression, by which chronic hyperglycemia induces hypertension and renal injury in diabetes.

Direct Activation of Angiotensin II Type 2 Receptors Enhances Muscle Microvascular Perfusion, Oxygenation, and Insulin Delivery in Male Rats

Angiotensin II receptors regulate muscle microvascular recruitment and the delivery of nutrients, oxygen, and insulin to muscle. Although angiotensin type 1 receptor antagonism increases muscle microvascular perfusion and insulin action, angiotensin type 2 receptor blockade markedly restricts muscle microvascular blood volume and decreases muscle delivery of insulin. To examine the effects of direct type 2 receptor stimulation using Compound 21 (C21) on microvascular perfusion, insulin delivery and action, and tissue oxygenation in muscle, overnight-fasted adult male rats were infused with C21 systemically. C21 potently increased microvascular blood volume without altering microvascular flow velocity or blood pressure, resulting in a net increase in microvascular blood flow in muscle. This was associated with a substantial increase in muscle interstitial oxygen saturation and insulin delivery into the skeletal and cardiac muscle. These effects were neutralized by coinfusion of the type 2 receptor antagonist or nitric oxide synthase inhibitor. Superimposing C21 infusion on insulin infusion increased insulin-mediated whole body glucose disposal by 50%. C21 significantly relaxed the preconstricted distal saphenous artery ex vivo. We have concluded that direct type 2 receptor stimulation markedly increases muscle microvascular perfusion through nitric oxide biosynthesis and enhances insulin delivery and action in muscle. These findings provide a physiologic mechanistic insight into type 2 receptor modulation of insulin action and suggest that type 2 receptor agonists might have therapeutic potential in the management of diabetes and its associated complications.

Angiotensin receptor blocker selectivity at the AT1- and AT2-receptors: conceptual and clinical effects

The advent of specific angiotensin II (Ang II) receptor blockers (ARBs) some ten years ago has provided substantial information on the specific actions of the AT1- and AT2-receptors. Most of the early research concentrated on the AT1-receptor, and the actions and biological roles of the AT2-receptor are much less well characterised. The AT2-receptor is involved in the inhibition of cell proliferation, and in cell differentiation and development, regeneration and apoptosis. By raising local Ang II concentrations at the AT2-receptor, selective blocking of the AT1-receptor may therefore have beneficial effects. This concept may be important for antihypertensive therapy and in cardiovascular disease in general.

Deletion of AT2 Receptor Prevents SHP-1-Induced VEGF Inhibition and Improves Blood Flow Reperfusion in Diabetic Ischemic Hindlimb

OBJECTIVE

Ischemia caused by narrowing of femoral artery is a major cause of peripheral arterial disease and morbidity affecting patients with diabetes mellitus. We have previously reported that the inhibition of the angiogenic response to VEGF (vascular endothelial growth factor) in diabetic mice was associated with the increased expression of SHP-1 (SH2 domain-containing phosphatase 1), a protein that can be activated by the AT2 (angiotensin II type 2) receptor. Deletion of AT2 receptor has been shown to promote angiogenesis within the ischemic muscle. However, the relative impact of AT2 receptor in diabetic condition remains unknown.

APPROACH AND RESULTS

Nondiabetic and diabetic AT2 null (Atgr2^-/Y) mice underwent femoral artery ligation after 2 months of diabetes mellitus. Blood perfusion was measured every week ≤4 weeks post-surgery. Expression of the VEGF, SHP-1, and renin-angiotensin pathways was evaluated. Blood flow in the ischemic muscle of diabetic Atgr2^-/Y mice recovered faster and ≤80% after 4 weeks compared with 51% recovery in diabetic control littermates. Diabetic Atgr2^-/Y had reduced apoptotic endothelial cells and elevated small vessel formation compared with diabetic Atgr2^+/Y mice, as well as increased SHP-1 expression and reduced VEGF receptor activity. In endothelial cells, high glucose levels and AT2 agonist treatment did not change SHP-1, VEGF, and VEGF receptor expression. However, the activity of SHP-1 and its association with the VEGF receptors were increased, causing inhibition of the VEGF action in endothelial cell proliferation and migration.

CONCLUSIONS

Our results suggest that the deletion of AT2 receptor reduced SHP-1 activity and restored VEGF actions, leading to an increased blood flow reperfusion after ischemia in diabetes mellitus.

Effects of early overnutrition on the renal response to Ang II and expression of RAAS components in rat renal tissue

BACKGROUND AND AIMS

The aim of this study was to analyze the effects of early overnutrition (EON) on the expression of the renin angiotensin aldosterone system (RAAS) components in renal cortex, renal arteries and renal perivascular adipose tissue (PVAT), as well as the vascular response of renal arteries to Angiotensin II (Ang II).

METHODS AND RESULTS

On birth day litters were adjusted to twelve (L12-control) or three (L3-overfed) pups per mother. Half of the animals were sacrificed at weaning (21 days old) and the other half at 5 months of age. Ang II-induced vasoconstriction of renal artery segments increased in young overfed rats and decreased in adult overfed rats. EON decreased the gene expression of angiotensinogen (Agt), Ang II receptors AT1 and AT2 and eNOS in renal arteries of young rats, while it increased the mRNA levels of AT-2 and ET-1 in adult rats. In renal PVAT EON up-regulated the gene expression of COX-2 and TNF-α in young rats and the mRNA levels of renin receptor both in young and in adult rats. On the contrary, Ang II receptors mRNA levels were downregulated at both ages. Renal cortex of overfed rats showed increased gene expression of Agt in adult rats and of AT1 in young rats. However the mRNA levels of AT1 were decreased in the renal cortex of overfed adult rats.

CONCLUSION

EON is associated with alterations in the vascular response of renal arteries to Ang II and changes in the gene expression of RAAS components in renal tissue.

Genetic Associations with Gestational Duration and Spontaneous Preterm Birth

BACKGROUND

Despite evidence that genetic factors contribute to the duration of gestation and the risk of preterm birth, robust associations with genetic variants have not been identified. We used large data sets that included the gestational duration to determine possible genetic associations.

METHODS

We performed a genomewide association study in a discovery set of samples obtained from 43,568 women of European ancestry using gestational duration as a continuous trait and term or preterm (<37 weeks) birth as a dichotomous outcome. We used samples from three Nordic data sets (involving a total of 8643 women) to test for replication of genomic loci that had significant genomewide association (P<5.0×10^-8) or an association with suggestive significance (P<1.0×10^-6) in the discovery set.

RESULTS

In the discovery and replication data sets, four loci (EBF1, EEFSEC, AGTR2, and WNT4) were significantly associated with gestational duration. Functional analysis showed that an implicated variant in WNT4 alters the binding of the estrogen receptor. The association between variants in ADCY5 and RAP2C and gestational duration had suggestive significance in the discovery set and significant evidence of association in the replication sets; these variants also showed genomewide significance in a joint analysis. Common variants in EBF1, EEFSEC, and AGTR2 showed association with preterm birth with genomewide significance. An analysis of mother-infant dyads suggested that these variants act at the level of the maternal genome.

CONCLUSIONS

In this genomewide association study, we found that variants at the EBF1, EEFSEC, AGTR2, WNT4, ADCY5, and RAP2C loci were associated with gestational duration and variants at the EBF1, EEFSEC, and AGTR2 loci with preterm birth. Previously established roles of these genes in uterine development, maternal nutrition, and vascular control support their mechanistic involvement. (Funded by the March of Dimes and others.).

Angiotensin receptor signaling and prostate tumor growth in mice

The renin-angiotensin system, through its type 1 and type 2 angiotensin receptors (AT1R and AT2R, respectively) may have a role in prostate cancer. The objective of this pilot study was to explore that potential role by determining whether the AT1R blocker, losartan, would reduce the growth of LAPC-4 prostate cancer xenografts in nude mice. We also evaluated the tumor growth effects of using angiotensin II to activate both AT1R and AT2R simultaneously. Our data showed that losartan decreased tumor volumes by 56% versus control. This decrease reached statistical significance at day 54 (p = 0.0014). By day 54, Ki67 was also reduced in the losartan group, though not significantly so (p = 0.077). Losartan had no significant effect on AT1R or AT2R expression. Despite significant increases in both AT1R and AT2R at day 29 (p = 0.043 and 0.038, respectively), the administration of angiotensin II did not result in any significant differences in tumor volumes or ki67 at any time point. These data suggest that selective activation and induction of AT2R coupled with blockade of AT1R may slow prostate cancer growth. Future larger studies are needed to confirm these results.

Sex chromosome complement involvement in angiotensin receptor sexual dimorphism

This study aimed to define whether sex chromosome complement (SCC) may differentially modulate sex differences in relative gene expression of basal Agtr1a, Agtr2, and Mas1 receptors at fore/hindbrain nuclei and at medulla/cortical kidney. Samples were collected from gonadectomized male (XX and XY) and female (XX and XY) mice of the "four core genotypes" model. At brain level, a SCC effect at the area postrema was demonstrated. An increase in mRNA level of Agtr1a and Agtr1a/Agtr2 ratio in XY-SCC mice was associated with a decrease in Mas1 compared to XX-SCC mice. In the renal cortex, a SCC effect for Agtr2 and Mas1 was observed. Regardless of sex (male or female), XX-SCC mice expressed higher levels of mRNA Agtr2 and Mas1 than XY-SCC mice {F(1,12) = 6,126,p < 0.05; F(1,21) = 5,143,p < 0.05}. Furthermore, XX-female mice showed a significant increase in Mas1 expression compared to XY-female mice. These results reveal a SCC modulatory effect at central and kidney level on angiotensin receptor expression, with an enhancement of the vasodilatory arm in XX-mice and an increase in the vasoconstriction arm in XY-mice, which may underlie sex differences in the regulation of arterial pressure.

Chronic blockade of the AT2 receptor with PD123319 impairs insulin signaling in C57BL/6 mice

The renin-angiotensin system modulates insulin action. Angiotensin type 1 receptor exerts a deleterious effects while the angiotensin type 2 receptor (AT2R) appears to have beneficial effects providing protection against insulin resistance and type 2 diabetes. Although recent reports indicate that agonism of AT2R ameliorates diabetes and insulin resistance, the phenotype of AT2R-knockout mice seems to be controversial relating this aspect. Thus, in this study we have explored the role of AT2R in the control of insulin action. To that end, C57Bl/6 mice were administered the synthetic AT2R antagonist PD123319 for 21days (10mg/kg/day ip); vehicle treated animals were used as control. Glucose tolerance, metabolic parameters, in vivo insulin signaling in main insulin-target tissues as well as levels of adiponectin, TNF-α, MCP-1 and IL-6 in adipose tissue were assessed. AT2R blockade with PD123319 induced a marginal effect on glucose homeostasis but an important reduction in the insulin-induced phosphorylation of the insulin receptor and Akt in both liver and adipose tissue. Insulin signaling in skeletal muscle remained unaltered after treatment with PD123319, which could explain the minimal effect on glucose homeostasis induced by PD123319. Our current results reinforce the notion that the AT2R has a physiological role in the conservation of insulin action.

Overexpression of AT2R in the solitary-vagal complex improves baroreflex in the spontaneously hypertensive rat

The aim of this study was to investigate the physiological effects of increased angiotensin II type 2 receptor (AT2R) expression in the solitary-vagal complex (nucleus of the solitary tract/dorsal motor nucleus of the vagus; NTS/DVM) on baroreflex function in non-anaesthetised normotensive (NT) and spontaneously hypertensive rats (SHR). Ten week old NT Holtzman and SHR were microinjected with either an adeno-associated virus expressing AT2R (AAV2-CBA-AT2R) or enhanced green fluorescent protein (control; AAV2-CBA-eGFP) into the NTS/DVM. Baroreflex and telemetry recordings were performed on four experimental groups: 1) NTeGFP, 2) NTAT2R, 3) SHReGFP and 4) SHRAT2R (n=4-7/group). Following in-vivo experimental procedures, brains were harvested for gene expression analysis. Impaired bradycardia in SHReGFP was restored in SHR rats overexpressing AT2R in the NTS/DMV. mRNA levels of angiotensin converting enzyme decreased and angiotensin converting enzyme 2 increased in the NTS/DMV of SHRAT2R compared to SHReGFP. Increased levels of pro-inflammatory cytokine mRNA levels in the SHReGFP group also decreased in the SHRAT2R group. AT2R overexpression did not elicit any significant change in mean arterial pressure (MAP) in all groups from baseline to 4weeks post viral transfection. Both SHReGFP and SHRAT2R showed a significant elevation in MAP compared to the NTeGFP and NTAT2R groups. Increased AT2R expression within the NTS/DMV of SHR was effective at improving baroreflex function but not MAP. We propose possible mediators involved in improving baroreflex are in the ANG II/ACE2 axis, suggesting a potential beneficial modulatory effect of AT2R overexpression in the NTS/DMV of neurogenic hypertensive rats.

Nicotine Mediates CD161a+ Renal Macrophage Infiltration and Premature Hypertension in the Spontaneously Hypertensive Rat

RATIONALE

Renal inflammation contributes to the pathophysiology of hypertension. CD161a+ immune cells are dominant in the (SHR) spontaneously hypertensive rat and expand in response to nicotinic cholinergic activation.

OBJECTIVE

We aimed to phenotype CD161a+ immune cells in prehypertensive SHR after cholinergic activation with nicotine and determine if these cells are involved in renal inflammation and the development of hypertension.

METHODS AND RESULTS

Studies used young SHR and WKY (Wistar-Kyoto) rats. Splenocytes and bone marrow cells were exposed to nicotine ex vivo, and nicotine was infused in vivo. Blood pressures, kidney, serum, and urine were obtained. Flow cytometry, Luminex/ELISA, immunohistochemistry, confocal microscopy, and Western blot were used. Nicotinic cholinergic activation induced proliferation of CD161a+/CD68+ macrophages in SHR-derived splenocytes, their renal infiltration, and premature hypertension in SHR. These changes were associated with increased renal expression of MCP-1 (monocyte chemoattractant protein-1) and VLA-4 (very-late antigen-4). LLT1 (lectin-like transcript 1), the ligand for CD161a, was overexpressed in SHR kidney, whereas vascular cellular and intracellular adhesion molecules were similar to those in WKY. Inflammatory cytokines were elevated in SHR kidney and urine after nicotine infusion. Nicotine-mediated renal macrophage infiltration/inflammation was enhanced in denervated kidneys, not explained by angiotensin II levels or expression of angiotensin type-1/2 receptors. Moreover, expression of the anti-inflammatory α7-nAChR (α7-nicotinic acetylcholine receptor) was similar in young SHR and WKY rats.

CONCLUSIONS

A novel, inherited nicotinic cholinergic inflammatory effect exists in young SHR, measured by expansion of CD161a+/CD68+ macrophages. This leads to renal inflammation and premature hypertension, which may be partially explained by increased renal expression of LLT-1, MCP-1, and VLA-4.

Combined Local Pulmonary and Systemic Delivery of AT2R Gene by Modified TAT Peptide Nanoparticles Attenuates Both Murine and Human Lung Carcinoma Xenografts in Mice

To evaluate the potential of cell-penetrating peptide-based delivery of apoptosis-inducer gene in cancer therapy, a modified HIV-1 TAT peptide (dimerized TAT peptide, dTAT) was studied. The dTAT and plasmid DNA (pDNA) complexes (dTAT-pDNA) were condensed using calcium chloride (dTAT-pDNA-Ca²⁺). This simple nonviral formulation approach showed high levels of gene expression in vitro without any cytotoxicity. In mouse studies, a single intratracheal (IT) aerosol spray or 2 intravenous (IV) injections of the dTAT, apoptosis-inducer gene, angiotensin II type 2 receptor (AT2R), and Ca²⁺ complexes (dTAT-pAT2R-Ca²⁺) significantly attenuated the acutely growing mouse Lewis lung carcinoma allografts in mouse lungs. Furthermore, single IT (p = 0.054) and the combination of IT and IV (p < 0.05) administrations of dTAT-pAT2R-Ca²⁺ markedly attenuated slowly growing and relatively large-sized H358 human bronchioloalveolar carcinoma xenografts in mouse lungs. These results indicate that the dTAT-pDNA-Ca²⁺ effectively delivered the gene to cancer cells by either IT or IV administration although the local pulmonary delivery of the dTAT-pAT2R-Ca²⁺ showed more effective growth inhibition of orthotopic lung cancer grafts. Thus, the present study offers preclinical proof of concept that a dTAT-based nonviral gene delivery method via IT administration may be an effective lung cancer gene therapy.

The angiotensin II type 2 receptor gene polymorphism and body mass index in healthy Japanese women

Background: Angiotensin II (AngII), through the AngII type 2 receptor (AT2-R), might exert some effect on adipocyte-and lipogenesis-related biology. The Adenine/Cytosine 3123 (A/C3123) polymorphism in the AT2-R gene is reportedly involved in some diseases, such as hypertension.

Methods: A total of 201 healthy Japanese women (mean age 43.2 years) were enrolled in the study to investigate the association among the AT2-R A/C3123 polymorphism detected by polymerase chain reaction methods, body mass index (BMI) and other obesity-linked metabolic parameters (blood pressure, serum lipid/lipoprotein, plasma glucose).

Results: Homozygotes of the C-allele in the AT2-R A/C3123 polymorphism were associated with small but significant increases in BMI levels. There were no differences between genotype-based groups in the obesity-linked metabolic parameters.

Conclusion: These findings suggest that the AT2-R A/C3123 polymorphism could be a polymorphic marker related to BMI in Japanese women.

Angiotensin Type-2 Receptors Influence the Activity of Vasopressin Neurons in the Paraventricular Nucleus of the Hypothalamus in Male Mice

It is known that angiotensin-II acts at its type-1 receptor to stimulate vasopressin (AVP) secretion, which may contribute to angiotensin-II-induced hypertension. Less well known is the impact of angiotensin type-2 receptor (AT2R) activation on these processes. Studies conducted in a transgenic AT2R enhanced green fluorescent protein reporter mouse revealed that although AT2R are not themselves localized to AVP neurons within the paraventricular nucleus of the hypothalamus (PVN), they are localized to neurons that extend processes into the PVN. In the present set of studies, we set out to characterize the origin, phenotype, and function of nerve terminals within the PVN that arise from AT2R-enhanced green fluorescent protein-positive neurons and synapse onto AVP neurons. Initial experiments combined genetic and neuroanatomical techniques to determine that γ-aminobutyric acid (GABA)ergic neurons derived from the peri-PVN area containing AT2R make appositions onto AVP neurons within the PVN, thereby positioning AT2R to negatively regulate neuroendocrine secretion. Subsequent patch-clamp electrophysiological experiments revealed that selective activation of AT2R in the peri-PVN area using compound 21 facilitates inhibitory (ie, GABAergic) neurotransmission and leads to reduced activity of AVP neurons within the PVN. Final experiments determined the functional impact of AT2R activation by testing the effects of compound 21 on plasma AVP levels. Collectively, these experiments revealed that AT2R expressing neurons make GABAergic synapses onto AVP neurons that inhibit AVP neuronal activity and suppress baseline systemic AVP levels. These findings have direct implications in the targeting of AT2R for disorders of AVP secretion and also for the alleviation of high blood pressure.

Changes of gene expression profiles in macrophages stimulated by angiotensin II — Angiotensin II induces MCP-2 through AT1-receptor

Introduction. Macrophages play critical roles in the development of atherosclerosis and diabetic nephropathy as well as many inflammatory diseases. Angiotensin II type 1 receptor antagonists (AIIA) are beneficial for the prevention of atherosclerosis and diabetic nephropathy suggesting that angiotensin II (Ang II) promotes the development of these diseases. It has recently been reported that Ang II exerts proinflammatory actions in vivo and in vitro. This study was aimed to clarify the direct effects of Ang II on monocytes/macrophages.

Materials and methods. PMA-treated THP-1 cells, a human monocytic leukaemia cell line, were treated with Ang II (10-6 mol/L) for 24 hours with or without AIIA (CV11974). We evaluated gene expression profiles of these cells using DNA microarray system and quantified them by real-time RT-PCR.

Results. DNA microarray revealed that in total 19 genes, including monocyte chemoattractant protein (MCP)-2, were up-regulated by Ang II and down-regulated by AIIA. Real-tim D e RT-PCR showed that up-regulation of MCP-2 with Ang II is blocked by the AIIA (CV11974) but not by an AT2-receptor antagonist.

Conclusions. These results suggest that Ang II directly stimulates MCP-2 expression through AT1-receptors in activated macrophages.Ang II may contribute to the persistence or amplification of microinflammation in vessel walls, heart and kidney.Vasculoprotective or renoprotective effects of AIIA might partly depend on direct antiinflammatory effects on macrophages.

Association of Genetic Polymorphisms of Renin-Angiotensin-Aldosterone System-Related Genes with Arterio-Venous Fistula Malfunction in Hemodialysis Patients

Hemodialysis (HD) is the most commonly-used renal replacement therapy for patients with end-stage renal disease worldwide. Arterio-venous fistula (AVF) is the vascular access of choice for HD patients with lowest risk of infection and thrombosis. In addition to environmental factors, genetic factors may also contribute to malfunction of AVF. Previous studies have demonstrated the effect of genotype polymorphisms of angiotensin converting enzyme on vascular access malfunction. We conducted a multicenter, cross-sectional study to evaluate the association between genetic polymorphisms of renin-angiotensin-aldosterone system and AVF malfunction. Totally, 577 patients were enrolled. Their mean age was 60 years old and 53% were male. HD patients with AVF malfunction had longer duration of HD (92.5 ± 68.1 vs. 61.2 ± 51.9 months, p < 0.001), lower prevalence of hypertension (44.8% vs. 55.3%, p = 0.025), right-sided (31.8% vs. 18.4%, p = 0.002) and upper arm AVF (26.6% vs. 9.7%, p < 0.001), and higher mean dynamic venous pressure (DVP) (147.8 ± 28.3 vs. 139.8 ± 30.0, p = 0.021). In subgroup analysis of different genders, location of AVF and DVP remained significant clinical risk factors of AVF malfunction in univariate and multivariate binary logistic regression in female HD patients. Among male HD patients, univariate binary logistic regression analysis revealed that right-side AVF and upper arm location are two important clinical risk factors. In addition, two single nucleotide polymorphisms (SNPs), rs275653 (Odds ratio 1.90, p = 0.038) and rs1492099 (Odds ratio 2.29, p = 0.017) of angiotensin II receptor 1 (AGTR1), were associated with increased risk of AVF malfunction. After adjustment for age and other clinical factors, minor allele-containing genotype polymorphisms (AA and CA) of rs1492099 still remained to be a significant risk factor of AVF malfunction (Odds ratio 3.63, p = 0.005). In conclusion, we demonstrated that rs1492099, a SNP of AGTR1 gene, could be a potential genetic risk factor of AVF malfunction in male HD patients.

Synergistic effect of angiotensin II on vascular endothelial growth factor-A-mediated differentiation of bone marrow-derived mesenchymal stem cells into endothelial cells

INTRODUCTION

Increased levels of angiotensin II (Ang II) and activity of Ang II receptor type 1 (AT1R) elicit detrimental effects in cardiovascular disease. However, the role of Ang II receptor type 2 (AT2R) remains poorly defined. Mesenchymal stem cells (MSCs) replenish and repair endothelial cells in the cardiovascular system. Herein, we investigated a novel role of angiotensin signaling in enhancing vascular endothelial growth factor (VEGF)-A-mediated differentiation of MSCs into endothelial cells (ECs).

METHODS

Bone marrow was aspirated from the femurs of Yucatan microswine. MSCs were extracted via ficoll density centrifugation technique and were strongly immunopositive for MSC markers, CD44, CD90, and CD105, but negative for hematopoietic markers, CD14 and CD45. Subsequently, naïve MSCs were differentiated for 10 days in varying concentrations and combinations of VEGF-A, Ang II, and AT1R or AT2R antagonists. Markers specific to ECs were determined by FACS analysis.

RESULTS

AT1R and AT2R expression and cellular localization was demonstrated in MSCs stimulated with VEGF-A and Ang II via quantitative RT-PCR and immunofluorescence, respectively. Differentiation of naïve MSCs in media containing Ang II (2 ng/ml) plus low-dose VEGF-A (2 ng/ml) produced a significantly higher percentage of cells that were positive for expression of EC markers (for example, platelet endothelial cell adhesion molecule, vascular endothelial Cadherin and von Willebrand factor) compared to VEGF-A alone. Ang II alone failed to induce EC marker expression. MSCs differentiated with the combination of Ang II and VEGF-A were capable of forming capillary tubes using an in vitro angiogenesis assay. Induction of EC marker expression was greatly attenuated by co-treatment of Ang II/VEGF-A with the AT2R antagonist PD123319, but not the AT1R antagonist telmisartan.

CONCLUSIONS

We report the presence of functional AT2R receptor on porcine bone marrow-derived MSCs, where it positively regulates EC differentiation. These findings have significant implications toward therapeutic approaches based on activation of AT2R, which could be a means to stimulate regeneration of damaged endothelium and prevent vascular thrombosis.

Analysis of White Adipose Tissue Gene Expression Reveals CREB1 Pathway Altered in Huntington's Disease

BACKGROUND

In addition to classical neurological symptoms, Huntington's disease (HD) is complicated by peripheral pathology and both the mutant gene and the protein are found in cells and tissues throughout the body. Despite the adipose tissue gene expression alterations described in HD mouse models, adipose tissue and its gene expression signature have not been previously explored in human HD.

OBJECTIVE

We investigated gene expression signatures in subcutaneous adipose tissue obtained from control subjects, premanifest HD gene carriers and manifest HD subjects with the aim to identify gene expression changes and signalling pathway alterations in adipose tissue relevant to HD.

METHODS

Gene expression was assessed using Affymetrix GeneChip® Human Gene 1.0 ST Array. Target genes were technically validated using real-time quantitative PCR and the expression signature was validated in an independent subject cohort.

RESULTS

In subcutaneous adipose tissue, more than 500 genes were significantly different in premanifest HD subjects as compared to healthy controls. Pathway analysis suggests that the differentially expressed genes found here in HD adipose tissue are involved in fatty acid metabolism pathways, angiotensin signalling pathways and immune pathways. Transcription factor analysis highlights CREB1. Using RT-qPCR, we found that MAL2, AGTR2, COBL and the transcription factor CREB1 were significantly upregulated, with CREB1 and AGT also being significantly upregulated in a separate cohort.

CONCLUSIONS

Distinct gene expression profiles can be seen in HD subcutaneous adipose tissue, with CREB1 highlighted as a key transcription factor.

Involvement of angiotensin II type 2 receptor (AT2R) signaling in human pancreatic ductal adenocarcinoma (PDAC): a novel AT2R agonist effectively attenuates growth of PDAC grafts in mice

We have recently discovered the potential involvement of angiotensin II type 2 receptor (AT2R) signaling in pancreatic cancer using AT2R deficient mice. To examine the involvement of AT2R expression in human PDAC, expressions of AT2R as well as the major angiotensin II receptor (type 1 receptor, AT1R) in human PDAC and adjacent normal tissue was evaluated by immunohistochemistry and real time PCR using surgically dissected human PDAC specimens. In immunohistochemical analysis, relatively strong AT1R expression was detected consistently in both normal pancreas and PDAC areas, whereas moderate AT2R expression was detected in 78.5% of PDAC specimens and 100% of normal area of the pancreas. AT1R, but not AT2R, mRNA levels were significantly higher in the PDAC area than in the normal pancreas. AT2R mRNA levels showed a negative correlation trend with overall survival. In cell cultures, treatment with a novel AT2R agonist significantly attenuated both murine and human PDAC cell growth with negligible cytotoxicity in normal epithelial cells. In a mouse study, administrations of the AT2R agonist in tumor surrounding connective tissue markedly attenuated growth of only AT2R expressing PAN02 murine PDAC grafts in syngeneic mice. The AT2R agonist treatment induced apoptosis primarily in tumor cells but not in stromal cells. Taken together, our findings offer clinical and preclinical evidence for the involvement of AT2R signaling in PDAC development and pinpoint that the novel AT2R agonist could serve as an effective therapeutic for PDAC treatment.

Transcriptional network analysis reveals that AT1 and AT2 angiotensin II receptors are both involved in the regulation of genes essential for glioma progression

Gliomas are aggressive primary brain tumors with high infiltrative potential. The expression of Angiotensin II (Ang II) receptors has been associated with poor prognosis in human astrocytomas, the most common type of glioma. In this study, we investigated the role of Angiotensin II in glioma malignancy through transcriptional profiling and network analysis of cultured C6 rat glioma cells exposed to Ang II and to inhibitors of its membrane receptor subtypes. C6 cells were treated with Ang II and specific antagonists of AT1 and AT2 receptors. Total RNA was isolated after three and six hours of Ang II treatment and analyzed by oligonucleotide microarray technology. Gene expression data was evaluated through transcriptional network modeling to identify how differentially expressed (DE) genes are connected to each other. Moreover, other genes co-expressing with the DE genes were considered in these analyses in order to support the identification of enriched functions and pathways. A hub-based network analysis showed that the most connected nodes in Ang II-related networks exert functions associated with cell proliferation, migration and invasion, key aspects for glioma progression. The subsequent functional enrichment analysis of these central genes highlighted their participation in signaling pathways that are frequently deregulated in gliomas such as ErbB, MAPK and p53. Noteworthy, either AT1 or AT2 inhibitions were able to down-regulate different sets of hub genes involved in protumoral functions, suggesting that both Ang II receptors could be therapeutic targets for intervention in glioma. Taken together, our results point out multiple actions of Ang II in glioma pathogenesis and reveal the participation of both Ang II receptors in the regulation of genes relevant for glioma progression. This study is the first one to provide systems-level molecular data for better understanding the protumoral effects of Ang II in the proliferative and infiltrative behavior of gliomas.