Angiotensin-converting enzyme 2: a key enzyme in key organs.

2020 marked the 20th anniversary of the discovery of the angiotensin-converting enzyme 2 (ACE2). This major event that changed the way we see the renin-angiotensin system today could have passed quietly. Instead, the discovery that ACE2 is a major player in the severe acute respiratory syndrome coronavirus 2 pandemic has blown up the literature regarding this enzyme. ACE2 connects the classical arm renin-angiotensin system, consisting mainly of angiotensin II peptide and its AT1 receptor, with a protective arm, consisting mainly of the angiotensin 1-7 peptide and its Mas receptor. In this brief article, we have reviewed the literature to describe how ACE2 is a key protective arm enzyme in the function of many organs, particularly in the context of brain and cardiovascular function, as well as in renal, pulmonary and digestive homeostasis. We also very briefly review and refer to recent literature to present an insight into the role of ACE2 in determining the course of coronavirus diseases 2019.

Activation of the angiotensin II receptor promotes autophagy in renal proximal tubular cells and affords protection from ischemia/reperfusion injury.

Roles of the renin-angiotensin system in autophagy and ischemia/reperfusion (I/R) injury in the kidney have not been fully characterized. Here we examined the hypothesis that modest activation of the angiotensin II (Ang II) receptor upregulates autophagy and increases renal tolerance to I/R injury. Sprague-Dawley rats were assigned to treatment with a vehicle or a non-pressor dose of Ang II (200 ng/kg/min) for 72 h before 30-min renal I/R. LC3-immunohistochemistry showed that Ang II treatment increased autophagosomes in proximal tubular cells by 2.7 fold. In Ang II-pretreated rats, autophagosomes were increased by 2.5 fold compared to those in vehicle-treated rats at 4 h after I/R, when phosphorylation of Akt and S6 was suppressed and ULK1-Ser555 phosphorylation was increased. Serum creatinine and urea nitrogen levels, incidence of oliguria, and histological score of tubular necrosis at 24 h after I/R were attenuated by Ang II-pretreatment. In NRK-52E cells, Ang II induced LC3-II upregulation, which was inhibited by losartan but not by A779. The results indicate that a non-pressor dose of Ang-II promotes autophagy via ULK1-mediated signaling in renal tubular cells and attenuates renal I/R injury. The AT1 receptor, but not the Mas receptor, contributes to Ang-II-induced autophagy and presumably also to the renoprotection.

Angiotensin Receptor-Neprilysin Inhibition Based on History of Heart Failure and Use of Renin-Angiotensin System Antagonists.

BACKGROUND: The PIONEER-HF (comParIson Of sacubitril/valsartaN versus Enalapril on Effect on nt-pRo-bnp in patients stabilized from an acute Heart Failure episode) trial demonstrated the efficacy and safety of sacubitril/valsartan (S/V) in stabilized patients with acute decompensated heart failure (HF) and reduced ejection fraction. OBJECTIVES: The study sought to determine whether and how prior HF history and treatment with an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) affected the results. METHODS: The PIONEER-HF trial was a prospective, multicenter, double-blind, randomized clinical trial enrolling 881 patients with an ejection fraction ≤40%. Patients were randomly assigned 1:1 to in-hospital initiation of S/V (n = 440) versus enalapril (n = 441). Pre-specified subgroup analyses were performed based on prior HF history (i.e., de novo HF vs. worsening chronic HF) and treatment with an ACE inhibitor or ARB (i.e., ACE inhibitor or ARB-yes vs. ACE inhibitor or ARB-no) at admission. RESULTS: At enrollment, 303 (34%) patients presented with de novo HF and 576 (66%) patients with worsening chronic HF. A total of 421 (48%) patients had been treated with an ACE inhibitor or ARB, while 458 (52%) had not been treated with an ACE inhibitor or ARB. N-terminal pro-B-type natriuretic peptide declined significantly in all 4 subgroups (p < 0.001), with greater decreases in the S/V versus the enalapril arm (p < 0.001). There was no interaction between prior HF history (p = 0.350) or ACE inhibitor or ARB treatment (p = 0.880) and the effect of S/V versus enalapril on cardiovascular death or rehospitalization for HF. The incidences of adverse events were comparable between S/V and enalapril across all 4 subgroups. CONCLUSIONS: Among patients admitted for acute decompensated HF, S/V was safe and well tolerated, led to a significantly greater reduction in N-terminal pro-B-type natriuretic peptide, and improved clinical outcomes compared with enalapril irrespective of previous HF history or ACE inhibitor or ARB treatment. (Comparison of Sacubitril/Valsartan Versus Enalapril on Effect of NT-proBNP in Patients Stabilized From an Acute Heart Failure Episode [PIONEER-HF]; NCT02554890).

Angiotensin receptor-neprilysin inhibitior (thiorphan/irbesartan) decreased ischemia-reperfusion induced ventricular arrhythmias in rat; in vivo study.

Ventricular arrhythmias are considered as a major risk of sudden cardiac death. This study was designed to investigate the potential effects of angiotensin receptor neprilysin inhibitor; thiorphan/irbesartan (TH/IRB) combination therapy on myocardial ischemic-reperfusion (I/R)-induced arrhythmia. Fifty male Wistar rats were divided into 5 groups; (I, II): Sham, I/R both received DMSO intraperitoneally before the procedure. (III, IV, V): TH/IRB + IR (0.1/5 mg/kg, 0.1/10 mg/kg and 0.1/15 mg/kg). The drugs were injected intraperitoneally 15 min before I/R induction. Electrocardiograms changes, mean arterial blood pressure, incidence of ventricular tachycardia (VT), incidence of ventricular fibrillation (VF) and arrhythmia score were assessed. Cardiac levels of creatinine kinase-MB (CK-MB), Malondialdehyde (MDA), superoxide dismutase (SOD), endothelin-1 (ET-1), ATP content, and Na+/K+-ATPase pump activity were measured. TH (0.1 mg/kg) in combination with IRB (5, 10 and 15 mg/kg) produced significant decrease in QTc interval duration, ST height, incidence of VT and VF, duration of VT + VF, and arrhythmia score compared to I/R group. All treated groups showed significant decrease in the cardiac levels of: CK-MB, MDA and ET-1 and significant increase in SOD, ATP content, and Na+/K+-ATPase pump activity compared to I/R. TH/IRB + IR (0.1/10 mg/kg) group produced significant decrease in CK-MB, MDA and ET-1 and a significant increase in SOD, ATP content, and Na+/K+-ATPase pump activity compared to other treated groups. In conclusion, angiotensin receptor neprilysin inhibitor (thiorphan/irbesartan) decreased arrhythmia score and decreased cardiac damage. These could be explained in part by its ability to decrease oxidative stress and ET-1, increase ATP, and Na+/K+-ATPase pump activity in this rat model of I/R-induced arrhythmia.

Effects of NLRP6 in Cerebral Ischemia/Reperfusion (I/R) Injury in Rats.

The NOD-like receptor protein 6 (NLRP6), an intracytoplasmic pattern recognition receptor in the nucleotide-binding domain, leucine-rich repeat-containing (NLR) innate immune receptor family, influences the inflammation reaction. The role of NLRP6 in cerebral ischemia-reperfusion (I/R) injury in rats is unclear. We explore the function of NLRP6 in cerebral I/R injury. The investigators used a middle cerebral artery occlusion/reperfusion model (MCAO) to imitate ischemic injury. We found the peak expression of NLRP6 is in 48-h post-cerebral I/R injury. The expression of NLRP6 siRNA, as well as the expression of protein and mRNA, was detected by Western blot and qRT-PCR. The degree of IL-1ß and IL-18 was assessed by ELISA. After downregulating NLRP6, the expression of IL-1ß, IL-18, cleaved Caspase-1, and myeloperoxidase (MPO) were reduced. In HE and Nissl staining, pathological injury of brain tissue after downregulating NLRP6 was improved. NLRP6 siRNA decreased the NLRP6-ASC binding states by CO-IP. NRP6 has a pro-inflammatory effect in cerebral I/R injury, which may provide a new target for the treatment of cerebral I/R injury.

Brain Vasculature and Cognition.

There is a complex interaction between the brain and the cerebral vasculature to meet the metabolic demands of the brain for proper function. Preservation of cerebrovascular function and integrity has a central role in this sophisticated communication within the brain, and any derangements can have deleterious acute and chronic consequences. In almost all forms of cognitive impairment, from mild to Alzheimer disease, there are changes in cerebrovascular function and structure leading to decreased cerebral blood flow, which may initiate or worsen cognitive impairment. In this focused review, we discuss the contribution of 2 major vasoactive pathways to cerebrovascular dysfunction and cognitive impairment in an effort to identify early intervention strategies.

Contributions by the Brain Renin-Angiotensin System to Memory, Cognition, and Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive neuron losses in memory-associated brain structures that rob patients of their dignity and quality of life. Five drugs have been approved by the FDA to treat AD but none modify or significantly slow disease progression. New therapies are needed to delay the course of this disease with the ultimate goal of preventing neuron losses and preserving memory functioning. In this review we describe the renin-angiotensin II (AngII) system (RAS) with specific regard to its deleterious contributions to hypertension, facilitation of neuroinflammation and oxidative stress, reduced cerebral blood flow, tissue remodeling, and disruption of memory consolidation and retrieval. There is evidence that components of the RAS, AngIV and Ang(1-7), are positioned to counter such damaging influences and these systems are detailed with the goal of drawing attention to their importance as drug development targets. Ang(1-7) binds at the Mas receptor, while AngIV binds at the AT4 receptor subtype, and these receptor numbers are significantly decreased in AD patients, accompanied by declines in brain aminopeptidases A and N, enzymes essential for the synthesis of AngIV. Potent analogs may be useful to counter these changes and facilitate neuronal functioning and reduce apoptosis in memory associated brain structures of AD patients.

Distinct roles of angiotensin receptors in autonomic dysreflexia following high-level spinal cord injury in mice.

Autonomic dysreflexia (AD), a syndrome caused by loss of supraspinal control over sympathetic activity and amplified vascular reflex upon sensory stimuli below injury level, is a major health problem in high-level spinal cord injury (SCI). After supraspinal sympathetic control of the vasculature below the lesion is lost, the renin-angiotensin system (RAS) is thought to be involved in AD by regulating blood pressure and vascular reactivity. In this study, we aimed to assess the role of different RAS receptors during AD following SCI. Therefore, we induced AD by colorectal distention (CRD) in wild-type mice and mice deficient in the RAS components angiotensin (Ang) II type 1a receptor (AT1a) (Agtr1a-/-) and Ang-(1-7) receptor Mas (Mas-/-) four weeks after complete transection of spinal cord at thoracic level 4 (T4). Systemic blood pressure measurements and wire myography technique were performed to assess hemodynamics and the reactivity of peripheral arteries, respectively. CRD increased mean arterial blood pressure (MAP) and decreased heart rate (HR) in all three animal groups. However, we found less increases in MAP in Mas-/- mice compared to control mice after CRD, whereas AT1a deficiency did not affect the hemodynamic response. We found that the reactivity of wild-type and Mas-/- mesenteric arteries, which are innervated from ganglia distal but close to thoracic level T4, was diminished in response to Ang II in AD after T4-SCI, but this difference was not observed in the absence of AT1a receptors. CRD did not influence the reactivity of femoral arteries which are innervated from ganglia more distal to thoracic level T4, in response to Ang II in AD. In conclusion, we identified a specific role of the Ang-(1-7) receptor Mas in regulating the systemic blood pressure increase in AD in T4-SCI mice. Furthermore, AT1a signaling is not involved in this hemodynamic response, but underlies increased vascular reactivity in mesenteric arteries in response to Ang II, where it may contribute to adaptive changes in regional blood flow.

[Mitochondrial signaling of G protein-coupled receptors]. / Signalisation mitochondriale des récepteurs couplés aux protéines G.

G protein-coupled receptors (GPCRs) are the largest family of integral membrane receptors with 800 members in humans that are expressed at the cell surface responding to a large panel of extracellular stimuli. Recent advances indicate that GPCRs are also expressed in intracellular compartments where they fulfil important functions. Here, we will report on the mitochondrial localization and function of GPCRs.

Novel Cardiac Intracrine Mechanisms Based on Ang-(1-12)/Chymase Axis Require a Revision of Therapeutic Approaches in Human Heart Disease.

PURPOSE OF THE REVIEW: Drugs targeting the renin-angiotensin system (RAS), namely angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers, are the most commonly prescribed drugs for patients with or at risk for cardiovascular events. However, new treatment strategies aimed at mitigating the rise of the heart failure pandemic are warranted because clinical trials show that RAS blockers have limited benefits in halting disease progression. The main goal of this review is to put forward the concept of an intracrine RAS signaling through the novel angiotensin-(1-12)/chymase axis as the main source of deleterious angiotensin II (Ang II) in cardiac maladaptive remodeling leading to heart failure (HF). RECENT FINDINGS: Expanding traditional knowledge, Ang II can be produced in tissues independently from the circulatory renin-angiotensin system. In the heart, angiotensin-(1-12) [Ang-(1-12)], a recently discovered derivative of angiotensinogen, is a precursor of Ang II, and chymase rather than ACE is the main enzyme contributing to the direct production of Ang II from Ang-(1-12). The Ang-(1-12)/chymase axis is an independent intracrine pathway accounting for the trophic, contractile, and pro-arrhythmic Ang II actions in the human heart. Ang-(1-12) expression and chymase activity have been found elevated in the left atrial appendage of heart disease subjects, suggesting a pivotal role of this axis in the progression of HF. Recent meta-analysis of large clinical trials on the use of ACE inhibitors and angiotensin receptor blockers in cardiovascular disease has demonstrated an imbalance between patients that significantly benefit from these therapeutic agents and those that remain at risk for heart disease progression. Looking to find an explanation, detailed investigation on the RAS has unveiled a previously unrecognized complexity of substrates and enzymes in tissues ultimately associated with the production of Ang II that may explain the shortcomings of ACE inhibition and angiotensin receptor blockade. Discovery of the Ang-(1-12)/chymase axis in human hearts, capable of producing Ang II independently from the circulatory RAS, has led to the notion that a tissue-delimited RAS signaling in an intracrine fashion may account for the deleterious effects of Ang II in the heart, contributing to the transition from maladaptive cardiac remodeling to heart failure. Targeting intracellular RAS signaling may improve current therapies aimed at reducing the burden of heart failure.

Angiotensin IV protects cardiac reperfusion injury by inhibiting apoptosis and inflammation via AT4R in rats.

Angiotensin IV (Ang IV) is formed by aminopeptidase N from Ang III by removing the first N-terminal amino acid. Previously, we reported that Ang III has some cardioprotective effects against global ischemia in Langendorff heart. However, it is not clear whether Ang IV has cardioprotective effects. The aim of the present study was to evaluate the effect of Ang IV on myocardial ischemia-reperfusion (I/R) injury in rats. Before ischemia, male Sprague-Dawley rats received Ang IV (1mg/kg/day) for 3 days. Anesthetized rats were subjected to 45min of ischemia by ligation of left anterior descending coronary artery followed by reperfusion and then, sacrificed 1 day or 1 week after reperfusion. Plasma creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations, and infarct size were measured. Quantitative analysis of apoptotic and inflammatory proteins in ventricles were performed using Western blotting. Pretreatment with Ang IV attenuated I/R-induced increases in plasma CK and LDH levels, and infarct size, which were blunted by Ang IV receptor (AT4R) antagonist and but not by antagonist for AT1R, AT2R, or Mas receptor. I/R increased Bax, caspase-3 and caspase-9 protein levels, and decreased Bcl-2 protein level in ventricles, which were blunted by Ang IV. I/R-induced increases in TNF-α, MMP-9, and VCAM-1 protein levels in ventricles were also blunted by Ang IV. Ang IV increased the phosphorylation of Akt and mTOR. These effects were attenuated by co-treatment with AT4R antagonist or inhibitors of downstream signaling pathway. Myocardial dysfunction after reperfusion was improved by Ang IV. These results suggest that Ang IV has cardioprotective effect against I/R injury by inhibiting apoptosis via AT4R and PI3K-Akt-mTOR pathway.

Relaxin deficiency attenuates pregnancy-induced adaptation of the mesenteric artery to angiotensin II in mice.

Pregnancy is associated with reduced peripheral vascular resistance, underpinned by changes in endothelial and smooth muscle function. Failure of the maternal vasculature to adapt correctly leads to serious pregnancy complications, such as preeclampsia. The peptide hormone relaxin regulates the maternal renal vasculature during pregnancy; however, little is known about its effects in other vascular beds. This study tested the hypothesis that functional adaptation of the mesenteric and uterine arteries during pregnancy will be compromised in relaxin-deficient (Rln(-/-)) mice. Smooth muscle and endothelial reactivity were examined in small mesenteric and uterine arteries of nonpregnant (estrus) and late-pregnant (day 17.5) wild-type (Rln(+/+)) and Rln(-/-) mice using wire myography. Pregnancy per se was associated with significant reductions in contraction to phenylephrine, endothelin-1, and ANG II in small mesenteric arteries, while sensitivity to endothelin-1 was reduced in uterine arteries of Rln(+/+) mice. The normal pregnancy-associated attenuation of ANG II-mediated vasoconstriction in mesenteric arteries did not occur in Rln(-/-) mice. This adaptive failure was endothelium-independent and did not result from altered expression of ANG II receptors or regulator of G protein signaling 5 (Rgs5) or increases in reactive oxygen species generation. Inhibition of nitric oxide synthase with l-NAME enhanced ANG II-mediated contraction in mesenteric arteries of both genotypes, whereas blockade of prostanoid production with indomethacin only increased ANG II-induced contraction in arteries of pregnant Rln(+/+) mice. In conclusion, relaxin deficiency prevents the normal pregnancy-induced attenuation of ANG II-mediated vasoconstriction in small mesenteric arteries. This is associated with reduced smooth muscle-derived vasodilator prostanoids.

Elevated Transglutaminase Activity Triggers Angiotensin Receptor Activating Autoantibody Production and Pathophysiology of Preeclampsia.

BACKGROUND: Preeclampsia (PE) is a life-threatening hypertensive disorder of pregnancy associated with autoantibodies, termed AT1-AA, that activate the AT1 angiotensin receptor. Although the pathogenic nature of these autoantibodies has been extensively studied, little is known about the molecular cause of their generation. METHODS AND RESULTS: Here we show that tissue transglutaminase (TG2), an enzyme that conducts posttranslational modification of target proteins, directly modified the 7-amino acid (7-aa) epitope peptide that localizes to the second extracellular loop of the AT1 receptor. These findings led us to further discover that plasma transglutaminase activity was induced and contributed to the production of AT1-AA and disease development in an experimental model of PE induced by injection of LIGHT, a tumor necrosis factor superfamily member. Key features of PE were regenerated by adoptive transfer of purified IgG from LIGHT-injected pregnant mice and blocked by the 7-amino acid epitope peptide. Translating our mouse research to humans, we found that plasma transglutaminase activity was significantly elevated in PE patients and was positively correlated with AT1-AA levels and PE features. CONCLUSIONS: Overall, we provide compelling mouse and human evidence that elevated transglutaminase underlies AT1-AA production in PE and highlight novel pathogenic biomarkers and innovative therapeutic possibilities for the disease.

Ubiquitin Ligase TRIM62 Regulates CARD9-Mediated Anti-fungal Immunity and Intestinal Inflammation.

CARD9 is a central component of anti-fungal innate immune signaling via C-type lectin receptors, and several immune-related disorders are associated with CARD9 alterations. Here, we used a rare CARD9 variant that confers protection against inflammatory bowel disease as an entry point to investigating CARD9 regulation. We showed that the protective variant of CARD9, which is C-terminally truncated, acted in a dominant-negative manner for CARD9-mediated cytokine production, indicating an important role for the C terminus in CARD9 signaling. We identified TRIM62 as a CARD9 binding partner and showed that TRIM62 facilitated K27-linked poly-ubiquitination of CARD9. We identified K125 as the ubiquitinated residue on CARD9 and demonstrated that this ubiquitination was essential for CARD9 activity. Furthermore, we showed that similar to Card9-deficient mice, Trim62-deficient mice had increased susceptibility to fungal infection. In this study, we utilized a rare protective allele to uncover a TRIM62-mediated mechanism for regulation of CARD9 activation.

Pleiotropic Effects of Angiotensin II Receptor Signaling in Cardiovascular Homeostasis and Aging.

Most of the pathophysiological actions of angiotensin II (Ang II) are mediated through the Ang II type 1 (AT1) receptor, a member of the seven-transmembrane G protein-coupled receptor family. Essentially, AT1 receptor signaling is beneficial for organismal survival and procreation, because it is crucial for normal organ development, and blood pressure and electrolyte homeostasis. On the other hand, AT1 receptor signaling has detrimental effects, such as promoting various aging-related diseases that include cardiovascular diseases, diabetes, chronic kidney disease, dementia, osteoporosis, and cancer. Pharmacological or genetic blockade of AT1 receptor signaling in rodents has been shown to prevent the progression of aging-related phenotypes and promote longevity. In this way, AT1 receptor signaling exerts antagonistic and pleiotropic effects according to the ages and pathophysiological conditions. Here we review the pleiotropic effects of AT1 receptor signaling in cardiovascular homeostasis and aging.

Update on the role of angiotensin in the pathophysiology of coronary atherothrombosis.

BACKGROUND: Coronary atherothrombosis due to atherosclerotic plaque rupture or erosion is frequently associated with acute coronary syndromes (ACS). Significant efforts have been made to elucidate the pathophysiological mechanisms underlying acute coronary events. MATERIALS AND METHODS: This narrative review is based on the material searched for and obtained via PubMed up to August 2014. The search terms we used were as follows: 'angiotensin, acute coronary syndromes, acute myocardial infarction' in combination with 'atherosclerosis, vulnerability, clinical trial, ACE inhibitors, inflammation'. RESULTS: Among several regulatory components, the renin-angiotensin system (RAS) was shown as a key pathway modulating coronary atherosclerotic plaque vulnerability. Indeed, these molecules are involved in all stages of atherogenesis. Classically, the RAS is composed by a series of enzymatic reactions leading to the angiotensin (Ang) II generation and activity. However, the knowledge of RAS has expanded and become more complex. The discovery of novel components and their functions has revealed additional pathways that contribute to or counterbalance the actions of Ang II. In this review, we discussed on recent findings concerning the role of different angiotensin peptides in the pathophysiology of ACS and coronary atherothrombosis, exploring the link between these molecules and atherosclerotic plaque vulnerability. CONCLUSIONS: Treatments selectively targeting angiotensins (including Mas and AT2 agonists, ACE2 recombinant, or Ang-(1-7) and almandine in oral formulations) have been tested in animal studies or in small human subgroups, expanding the perspective in the ACS prevention. These novel strategies, especially in the counter-regulatory axis ACE2/Ang-(1-7)/Mas, might be promising to reduce plaque vulnerability and inflammation.

Angiotensin II in paraventricular nucleus contributes to sympathoexcitation in renal ischemia-reperfusion injury by AT1 receptor and oxidative stress.

BACKGROUND: To investigate the effect of angiotensin II (Ang II) in the hypothalamic paraventricular nucleus (PVN) on renal ischemia-reperfusion (IR) injury and to assay the role of renal sympathetic nerve activity (RSNA). METHODS: A cannula was inserted into the right side PVN in Sprague-Dawley rats for microinjection of Ang II (3, 30, and 300 ng); Ang II AT1 receptor antagonist, losartan (0.3 µg); and the superoxide dismutase (SOD) mimetic, tempol (20 nmol) before right side nephrectomy. After 1 wk, renal IR injury was induced by clamping the left renal artery for 45 min, and then reperfusion for 3 or 24 h. The extent of renal damage was determined by evaluation of renal functional indices. RSNA was recorded in all groups. Oxidative stress indices (SOD activity and malondialdehyde levels) were assayed in the PVN. RESULTS: Microinjection of pharmacologic doses of Ang II into the PVN exaggerated renal IR injury, increased RSNA and oxidative stress in the PVN dose dependently. The effects of Ang II (3 ng) was prevented by pretreatment with losartan into the PVN. Furthermore, the deleterious effects of Ang II on renal IR injury, RSNA, and oxidative stress were abolished by pretreatment with tempol. CONCLUSIONS: These results indicate that the PVN is a responsive site for central Ang II increment damage in renal ischemia-reperfusion injury. We suggested the central effects of Ang II in the PVN on renal IR injury are mediated by AT1 receptors and oxidative stress in the PVN, and the peripheral effects by a sympathetic pathway.

Perinatal nicotine exposure increases angiotensin II receptor-mediated vascular contractility in adult offspring.

UNLABELLED: Previous studies have reported that perinatal nicotine exposure causes development of hypertensive phenotype in adult offspring. AIMS: The present study was to determine whether perinatal nicotine exposure causes an epigenetic programming of vascular Angiotensin II receptors (ATRs) and their-mediated signaling pathway leading to heightened vascular contraction in adult offspring. MAIN METHODS: Nicotine was administered to pregnant rats via subcutaneous osmotic minipumps from day 4 of gestation to day 10 after birth. The experiments were conducted at 5 months of age of male offspring. KEY FINDINGS: Nicotine treatment enhanced Angitension II (Ang II)-induced vasoconstriction and 20-kDa myosin light chain phosphorylation (MLC20-P) levels. In addition, the ratio of Ang II-induced tension/MLC-P was also significantly increased in nicotine-treated group compared with the saline group. Nicotine-mediated enhanced constrictions were not directly dependent on the changes of [Ca2+]i concentrations but dependent on Ca2+ sensitivity. Perinatal nicotine treatment significantly enhanced vascular ATR type 1a (AT1aR) but not AT1bR mRNA levels in adult rat offspring, which was associated with selective decreases in DNA methylation at AT1aR promoter. Contrast to the effect on AT1aR, nicotine decreased the mRNA levels of vascular AT2R gene, which was associated with selective increases in DNA methylation at AT2R promoter. SIGNIFICANCE: Our results indicated that perinatal nicotine exposure caused an epigenetic programming of vascular ATRs and their-mediated signaling pathways, and suggested that differential regulation of AT1R/AT2R gene expression through DNA methylation mechanism may be involved in nicotine-induced heightened vasoconstriction and development of hypertensive phenotype in adulthood.

Role of inflammation and the angiotensin type 2 receptor in the regulation of arterial pressure during pregnancy in mice.

During normal pregnancy the renin-angiotensin system is activated, yet pregnant women are resistant to the pressor effects of angiotensin II. Our aim was to determine the role of the angiotensin type 2 receptor (AT2R) in the regulation of arterial pressure, natriuresis, and immune cell infiltration during pregnancy. Mean arterial pressure was measured via telemetry, and flow cytometry was used to enumerate immune cell infiltration in 14-week-old wild-type and AT2R knockout mice during gestation. In wild-type mice, mean arterial pressure decreased during gestation, reaching a nadir at gestational day 9 (-6±2 mm Hg) and returned to near preconception levels during late gestation. In AT2R-deficient mice, the midgestational decrease in mean arterial pressure was absent. Furthermore, mean arterial pressure was significantly increased during late gestation compared with wild-type mice (≈10 mm Hg). As expected, circulating immune cell activation was suppressed during pregnancy. However, this response was absent in AT2R-deficient mice. While renal immune cell infiltration was similar between the genotypes, there was a significant T cell phenotypic switch toward a proinflammatory T-helper 1 phenotype in AT2R-deficient mice. These data indicate that the AT2R plays an important role in arterial pressure regulation and may modulate T cell activation and renal cytokine production during pregnancy. Therefore, deficits in AT2R expression may contribute to pregnancy-induced hypertension and thus represents a potential therapeutic target.