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Vasoactive peptides often serve a multitude of functions aside from their direct effects on vasodynamics. This article will review the existing literature on two vasoactive peptides and their involvement in skin homeostasis: adiponectin and—as the main representative of the kallikrein-kinin system—bradykinin. Adiponectin is the most abundantly expressed adipokine in the human organism, where it is mainly localized in fat depots including subcutaneous adipose tissue, from where adiponectin can exert paracrine effects. The involvement of adiponectin in skin homeostasis is supported by a number of studies reporting the effects of adiponectin in isolated human keratinocytes, sebocytes, fibroblasts, melanocytes, and immune cells. Regarding skin pathology, the potential involvement of adiponectin in psoriasis, atopic dermatitis, scleroderma, keloid, and melanogenesis is discussed in this article. The kallikrein-kinin system is composed of a variety of enzymes and peptides, most of which have been identified to be expressed in the skin. This also includes the expression of bradykinin receptors on most skin cells. Bradykinin is one of the very few hormones that is targeted by treatment in routine clinical use in dermatology—in this case for the treatment of hereditary angioedema. The potential involvement of bradykinin in wound healing, psoriasis, and melanoma is further discussed in this article. This review concludes with a call for additional preclinical and clinical studies to further explore the therapeutic potential of adiponectin supplementation (for psoriasis, atopic dermatitis, wound healing, scleroderma, and keloid) or pharmacological interference with the kallikrein-kinin system (for wound healing, psoriasis, and melanoma).

This commentary on the article “Relative affinity of angiotensin peptides and novel ligands at AT1 and AT2 receptors” by Sanja Bosnyak et al. (Clini. Sci. (Lond.) (2011) 121(7): 297–303. https://doi.org/10.1042/CS20110036) summarises the main findings of the study, followed by a discussion of the findings and their relevance for various aspects of the biology of receptors of the renin-angiotensin system in the context of the current state of knowledge.

Angiotensin (1–7) production increases during AT1R (angiotensin type-1 receptor) blockade. The contribution of Ang (1–7) (angiotensin [1–7]) and its receptor (MasR) to the favorable effect of angiotensin receptor blockers on remodeling and function of resistance arteries remains unclear. We sought to determine whether MasR contributes to the improvement of vascular structure and function during chronic AT1R blockade. Spontaneously hypertensive rats were treated with Ang (1–7) or olmesartan ± MasR antagonist A-779, or vehicle, for 14 days. Blood pressure was measured by tail cuff methodology. Mesenteric arteries were dissected and mounted on a pressurized micromyograph to evaluate media-to-lumen ratio (M/L) and endothelial function. Expression of MasR and eNOS (endothelial nitric oxide synthase) was evaluated by immunoblotting, plasma nitrate by colorimetric assay, and reactive oxygen species production by dihydroethidium staining. Independently of blood pressure, olmesartan significantly reduced M/L and improved NO bioavailability, A-779 prevented these effects. Likewise, Ang (1–7) significantly reduced M/L and NO bioavailability. MasR expression was significantly increased by Ang (1–7) as well as by olmesartan, and it was blunted in the presence of A-779. Both Ang (1–7) and olmesartan increased eNOS expression and plasma nitrite which were reduced by A-779. Superoxide generation was attenuated by olmesartan and Ang (1–7) and was blunted in the presence of A-779. These MasR-mediated actions were independent of AT2R activation since olmesartan and Ang (1–7) increased MasR expression and reduced M/L in Ang II (angiotensin II)–infused AT2R knockout mice, independently of blood pressure control. A-779 prevented these effects. Hence, MasR activation may contribute to the favorable effects of AT1R antagonism on NO bioavailability and microvascular remodeling, independently of AT2R activation and blood pressure control.

The angiotensin AT

Objective The receptor MAS, encoded by Mas1, is expressed in microglia and its activation has been linked to anti-inflammatory actions. However, microglia are involved in several different processes in the central nervous system, including the promotion of angiogenesis. We therefore hypothesized that the receptor MAS also plays a role in angiogenesis via microglia. Approach and results To assess the role of MAS on vascular network development, flat-mounted retinas from 3-day-old wild-type (WT) and -Mas1(-/-) mice were subjected to Isolectin B4 staining. The progression of the vascular front was reduced (- 24%, p < 0.0001) and vascular density decreased (- 38%, p < 0.001) in -Mas1(-/-) compared to WT mice with no change in the junction density. The number of filopodia and filopodia bursts were decreased in -Mas1(-/-) mice at the vascular front (- 21%, p < 0.05; - 29%, p < 0.0001, respectively). This was associated with a decreased number of vascular loops and decreased microglial density at the vascular front in -Mas1(-/-) mice (-32%, p < 0.001; - 26%, p < 0.05, respectively). As the front of the developing vasculature is characterized by reduced oxygen levels, we determined the expression of Mas1 following hypoxia in primary microglia from 3-day-old WT mice. Hypoxia induced a 14-fold increase of Mas1 mRNA expression (p < 0.01). Moreover, stimulation of primary microglia with a MAS agonist induced expression of Notch1 (+ 57%, p < 0.05), Dll4 (+ 220%, p < 0.001) and Jag1 (+ 137%, p < 0.001), genes previously described to mediate microglia/endothelial cell interaction during angiogenesis. Conclusions Our study demonstrates that the activation of MAS is important for microglia recruitment and vascular growth in the developing retina. Foulquier, S (reprint author), Maastricht Univ, Dept Pharmacol Toxicol, POB 616, NL-6200 MD Maastricht, Netherlands, CARIM, Cardiovasc Res Inst Maastricht, Maastricht, Netherlands, Maastricht Univ, Sch Mental Hlth & Neurosci, MH&NS, Maastricht, Netherlands. s.foulquier@maastrichtuniversity.nl

The aim of the present study was to evaluate the effect of Compound 21 (C21), a selective AT2R agonist, on the prevention of endothelial dysfunction, extracellular matrix (ECM) remodeling and arterial stiffness associated with diet-induced obesity (DIO). Five-week-old male C57BL/6J mice were fed a standard (Chow) or high-fat diet (HF) for 6 weeks. Half of the animals of each group were simultaneously treated with C21 (1 mg/kg/day, in the drinking water), generating four groups: Chow C, Chow C21, HF C, and HF C21. Vascular function and mechanical properties were determined in the abdominal aorta. To evaluate ECM remodeling, collagen deposition and TGF-β1 concentrations were determined in the abdominal aorta and the activity of metalloproteinases (MMP) 2 and 9 was analyzed in the plasma. Abdominal aortas from HF C mice showed endothelial dysfunction as well as enhanced contractile but reduced relaxant responses to Ang II. This effect was abrogated with C21 treatment by preserving NO availability. A left-shift in the tension–stretch relationship, paralleled by an augmented β-index (marker of intrinsic arterial stiffness), and enhanced collagen deposition and MMP-2/-9 activities were also detected in HF mice. However, when treated with C21, HF mice exhibited lower TGF-β1 levels in abdominal aortas together with reduced MMP activities and collagen deposition compared with HF C mice. In conclusion, these data demonstrate that AT2R stimulation by C21 in obesity preserves NO availability and prevents unhealthy vascular remodeling, thus protecting the abdominal aorta in HF mice against the development of endothelial dysfunction, ECM remodeling and arterial stiffness.

The angiotensin AT2-receptor (AT2R) is a key component within the protective arm of the renin-angiotensin system (RAS), being involved in nitric oxide (NO) production and vasodilation. To this date, no quantitative high-throughput assay is available to identify AT2R agonists in vitro , which may be a reason for the low number of AT2R selective ligands in drug development programs. Objective: To design and validate a high-throughput method for detection of AT2R activation in vitro . Methods and Results: NO release was selected as readout for AT2R activation in AT2R transfected (CHO-AT2) and non-transfected (CHO-NT) CHO cells using DAF-FM (5x10-6 mol/L) as NO probe. Cells were seeded on 96-well plates and stimulated for 15 minutes with C21 or Ang II (established AT2R agonists, 10-6mol/L), Ang-(1-5) (molecule with unknown biological status, 10-6 mol/L) or Ang-(1-7) (Mas-receptor agonist, 10-7 mol/L). After fixation of cells, fluorescence signals were captured by fluorescence microscopy using an automated imaging system (ImageXpress Pico, Molecular Devices, San Jose, USA) and image analysis by ImageJ. In CHO-AT2, C21 (+34.78 ± 12.09%), Ang II (+28.76 ± 17.65%) and Ang-(1-5) (+78.00 ± 23.82%) increased NO release (one-way ANOVA, p < 0.05 vs control, at least 3 independent experiments), while Ang-(1-7) had no effect (+ 0.13 ± 4.74%). In CHO-NT, none of the compounds stimulated release of NO (C21 -4.91 ±10.24%; Ang II -4.79 ± 12.44%; Ang (1-5) -8.88 ± 18.16%; Ang-(1-7) -11.57 ± 19.95%) indicating that the responses in CHO-AT2 were AT2R specific. Conclusion: Measurement of NO release from AT2R transfected CHO cells by DAF-FM fluorescence in an automated way is suitable as high-throughput assay for the identification of AT2R-agonistic compounds in vitro , Application of the assay revealed that Ang-(1-5), which is commonly regarded as an inactive metabolite of Ang II, has AT2R agonistic properties.

BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) is an antibody-mediated autoimmune inflammatory disease of the central nervous system (CNS), resulting in primary astrocytopathy. We have previously shown that Angiotensin AT2-receptor (AT2R) stimulation with the specific agonist Compound 21 (C21) attenuated NMOSD-like pathology. Recent studies have proposed that the mechanism behind protective effects of AT2R includes induction of brain derived neurotrophic factor (BDNF). Astrocytes are a major cellular source of BDNF. In this study we used mice with conditional BDNF deficiency in astrocytes (GfapF) to examine the involvement of astrocyte-derived BDNF in NMOSD-like pathology and in mediating the protective effect of AT2R stimulation.METHODS: Anti-aquaporin-4 IgG (AQP4-IgG) from an NMOSD patient and human complement (C) were co-injected intrastriatally to GfapF and wildtype littermate BDNFfl/fl mice (WT), together with either C21 or vehicle at day 0, followed by intrathecal injection of C21 or vehicle at day 2 and tissue collection at day 4.RESULTS: Intracerebral/intrathecal injection of C21, alone or in combination with AQP4-IgG + C, induced BDNF expression in WT mice. Injection of AQP4-IgG + C induced NMOSD-like pathology, including loss of AQP4 and GFAP. There was no difference in the severity of pathological changes between GfapF and WT mice. C21 treatment significantly and equally ameliorated NMOSD-like pathology in both WT and GfapF mice.CONCLUSION: Our findings indicate that astrocyte-derived BDNF neither reduces the severity of NMOSD-like pathology nor is it necessary for the protective effect of AT2R stimulation in NMOSD-like pathology.

Compound 21 (C21), a selective agonist of angiotensin II type 2 receptor (AT2R), induces vasodilation through NO release. Since AT2R seems to be overexpressed in obesity, we hypothesize that C21 prevents the development of obesity-related vascular alterations. The main goal of the present study was to assess the effect of C21 on thoracic aorta endothelial function in a model of diet-induced obesity (DIO) and to elucidate the potential cross-talk among AT2R, Mas receptor (MasR) and/or bradykinin type 2 receptor (B2R) in this response. Five-week-old male C57BL6J mice were fed a standard (CHOW) or a high-fat diet (HF) for 6 weeks and treated daily with C21 (1 mg/kg p.o) or vehicle, generating four groups: CHOW-C, CHOW-C21, HF-C, HF-C21. Vascular reactivity experiments were performed in thoracic aorta rings. Human endothelial cells (HECs; EA.hy926) were used to elucidate the signaling pathways, both at receptor and intracellular levels. Arteries from HF mice exhibited increased contractions to Ang II than CHOW mice, effect that was prevented by C21. PD123177, A779 and HOE-140 (AT2R, Mas and B2R antagonists) significantly enhanced Ang II-induced contractions in CHOW but not in HF-C rings, suggesting a lack of functionality of those receptors in obesity. C21 prevented those alterations and favored the formation of AT2R/MasR and MasR/B2R heterodimers. HF mice also exhibited impaired relaxations to acetylcholine (ACh) due to a reduced NO availability. C21 preserved NO release through PKA/p-eNOS and AKT/p-eNOS signaling pathways. In conclusion, C21 favors the interaction among AT2R, MasR and B2R and prevents the development of obesity-induced endothelial dysfunction by stimulating NO release through PKA/p-eNOS and AKT/p-eNOS signaling pathways.

The skin is the first line of defence against most infections, including those by arthropod-borne viruses (arboviruses). The skin is a compartmentalised organ populated by a variety of immune cells that play a critical role in coordinating immune responses after skin infection. Arboviruses such as Ross River virus (RRV) and Chikungunya virus (CHIKV) cause debilitating musculoskeletal and arthritic disease and are considered significant public health threats of major global concern due to the scale of outbreaks, and the limited treatment options available. To understand the dynamics of arthritogenic arbovirus dissemination following skin infection, we developed a pathogenic model of RRV infection to mimic a mosquito bite. We found that inflammatory monocytes, neutrophils and dermal macrophages dominated the early inflammatory response in the skin. In addition, we found that RRV-infected CD11b+ migratory cells translocate to the skin draining lymph nodes. Importantly, we unveiled a critical role for viral envelope glycosylation in driving viral dissemination kinetics and disease severity. Intradermal infection with RRV derived from mosquito cells resulted in more severe disease compared to RRV derived from mammalian cells. This difference in disease was accompanied by glycosylationspecific transcriptional response in the skin after intradermal infection. Interestingly we also show evidence indicating that viral envelope glycosylation dictates the dissemination of RRV to target tissues in muscle and joint. Using a new model of cutaneous arboviral infection, we show previously unappreciated mechanisms of immune response and viral dissemination that, in future, will help develop novel approaches to limit arboviral dissemination and ameliorate disease outcomes.

IntroductionWhether ACE inhibitors (ACEi) or angiotensin II receptor blocker (ARB) therapy should be continued, initiated or ceased in patients with COVID-19 is uncertain. Given the widespread use of ACEi/ARBs worldwide, guidance on the use of these drugs is urgently needed. This prospective meta-analysis aims to pool data from randomised controlled trials (RCTs) to assess the safety and efficacy of ACEi/ARB therapy in adults infected with SARS-CoV-2.Methods and analysisRCTs will be eligible if they compare patients with COVID-19 randomised to ACEi/ARB continuation or commencement versuss no ACEi/ARB therapy; study duration ≥14 days; recruitment completed between March 2020 and May 2021. The primary outcome will be all-cause mortality at ≤30 days. Secondary outcomes will include mechanical ventilation, admission to intensive care or cardiovascular events at short-term follow-up (≤30 days) and all-cause mortality at longer-term follow-up (>1 month). Prespecified subgroup analyses will assess the effect of sex; age; comorbidities; smoking status; ethnicity; country of origin on all-cause mortality. A search of ClinicalTrials.gov has been performed, which will be followed by a formal search of trial registers, preprint servers, MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials to identify RCTs that meet inclusion criteria. To date, a search of ClinicalTrials.gov identified 21 potentially eligible trials for this meta-analysis. We will request trial investigators/sponsors to contribute standardised grouped tabular outcome data.Ethics and disseminationEthics approval and informed consent will be the responsibility of the individual RCTs. Dissemination of results will occur by peer-reviewed publication. The results of our analysis can inform public health policy and clinical decision making regarding ACEi/ARB use in patients with COVID-19 on a global scale.

Background and Purpose: The AT 2 receptor plays a role in metabolism by opposing the actions triggered by the AT 1 receptors. Activation of AT 2 receptors has been shown to enhance insulin sensitivity in both normal and insulin resistance animal models. In this study, we investigated the mechanism by which AT 2 receptors activation improves metabolism in diabetic mice. Experimental Approach: Female diabetic (db/db) and non-diabetic (db/+) mice were treated for 1 month with the selective AT 2 agonist, compound 21 (C21, 0.3 mg·kg −1·day −1, s.c.). To evaluate whether the effects of C21 depend on NO production, a subgroup of mice was treated with C21 plus a sub-pressor dose of the NOS inhibitor l-NAME (0.1 mg·ml −1, drinking water). Key Results: C21-treated db/db mice displayed improved glucose and pyruvate tolerance compared with saline-treated db/db mice. Also, C21-treated db/db mice showed reduced liver weight and decreased hepatic lipid accumulation compared with saline-treated db/db mice. Insulin signalling analysis showed increased phosphorylation of the insulin receptor, Akt and FOXO1 in the livers of C21-treated db/db mice compared with saline-treated counterparts. These findings were associated with increased adiponectin levels in plasma and adipose tissue and reduced adipocyte size in inguinal fat. The beneficial effects of AT 2 receptors activation were associated with increased eNOS phosphorylation and higher levels of NO metabolites and were abolished by l-NAME. Conclusion and Implications: Chronic C21 infusion exerts beneficial metabolic effects in female diabetic db/db mice, alleviating type 2 diabetes complications, through a mechanism that involves NO production.

Background: Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing inflammatory central nervous system (CNS) disease for which there is no cure. Immunoglobulin G autoantibodies specific for the water channel aquaporin-4 are a serum biomarker, believed to induce complement-dependent astrocyte damage with secondary demyelination. Objective: To investigate the effect of angiotensin AT2 receptor (AT2R) stimulation on NMOSD-like pathology and its underlying mechanism. Methods: NMOSD-like pathology was induced in mice by intracerebral injection of immunoglobulin-G isolated from NMOSD patient serum, with complement. This mouse model produces the characteristic histological features of NMOSD. A specific AT2R agonist, Compound 21 (C21), was given intracerebrally at day 0 and by intrathecal injection at day 2. Results: Loss of aquaporin-4 and glial fibrillary acidic protein was attenuated by treatment with C21. Administration of C21 induced mRNA for interleukin-10 in the brain. NMOSD-like pathology was exacerbated in interleukin-10-deficient mice, suggesting a protective role. C21 treatment did not attenuate NMOSD-like pathology in interleukin-10-deficient mice, indicating that the protective effect of AT2R stimulation was dependent on interleukin-10. Conclusion: Our findings identify AT2R as a novel potential therapeutic target for the treatment of NMOSD. Interleukin-10 signaling is an essential part of the protective mechanism counteracting NMOSD pathology.

The New Investigators Committee (NIC) of the International Society of Hypertension (ISH) is a dynamic group of junior doctors and scientists, actively involved in various society activities. This report highlights the events (scientific meetings and summer schools) and activities (social media, mentorship and networking) during 2019 including May Measurement Month and collaborative efforts with the ISH Women in Hypertension Research Committee (WiHRC). The ISH NIC is proud to sponsor awards for outstanding work by junior and emerging researchers at hypertension conferences and also provides opportunities to showcase their work on our social media features such as 'Our Fellows Work' and the New Investigator Spotlight of the month. In 2020, the ISH NIC aims to promote women in leadership roles and to foster strong collaborations with and between society committees and other scientific organizations.

Since its first description around the year 2000, the local renin angiotensin system (RAS) in skin has been subject of an increasing number of studies with many additions over the last two to three years. A focus of research has been investigations on the role of cutaneous angiotensin receptors and locally synthesised angiotensin II in wound healing, in dermatoses associated with skin fibrosis and in melanoma. This review will provide an introduction into the RAS with emphasis on information relevant for the cutaneous RAS. It will discuss the role of the RAS in skin physiology, followed by a detailed review of the existing literature addressing the role of local angiotensin II and angiotensin AT1 - and AT2 -receptors in wound healing and in various skin diseases such as hypertrophic scars/keloids, scleroderma, dystrophic epidermolysis bullosa, Dupuytren's disease, squamous cell carcinoma, melanoma and psoriasis. In a final section, the potential relevance of drugs, which interfere with the RAS, for future therapy of dermatological disorders is discussed. Collectively, research about the RAS in skin can currently be described as an area, which has gained increasing attention by basic researchers, thus resulting in a multitude of preclinical studies pointing to the potential relevance of components of the RAS as drug targets in dermatological diseases. With a few small clinical studies already performed successfully for indications such as hypertrophic scars and keloids, it can be said that the skin RAS is now in the critical phase of translation from preclinical evidence to clinical use.

Hypertrophic scar and keloid are two types of fibroproliferative conditions that result from excessive extracellular matrix production. The underlying pathological mechanism is not entirely clear. Activation of the renin-angiotensin system (RAS) is associated with fibrosis in various organs. RAS components including angiotensin II (Ang II), angiotensin AT1 and AT2 receptors, and angiotensin-converting enzyme (ACE) are expressed in the skin and act independently from the plasma RAS. AT1 receptors, which are usually the dominating receptor subtype, promote fibrosis and scar formation, while AT2 receptors inhibit the aforementioned AT1 receptor-coupled effects. Elevated angiotensin II (Ang II) levels acting on the AT1 receptor contribute to skin scar formation through increased expression of inflammatory factors such as interleukin-6 (IL-6), angiogenic factors such as vascular endothelial growth factor (VEGF) and fibrinogenic factors such as transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF), while at the same time suppressing the anti-fibrotic tissue inhibitors of matrix metalloproteinase (TIMPs). First, small clinical trials have provided evidence that inhibition of the ACE/Ang II/ AT1 receptor axis may be effective in the treatment of hypertrophic scars/keloids. This review provides a detailed overview of the current literature on the RAS in skin, wound healing and scar formation and discusses the translational potential of targeting this hormonal system for treatment and prevention of hypertrophic scars and keloids.

Significant neuroprotective effects of angiotensin II type 2 (AT 2 ) receptor (AT 2 receptor) agonists in ischemic stroke have been previously demonstrated in multiple studies. However, the routes of agonist application used in these pre-clinical studies, direct intracerebroventricular (ICV) and systemic administration, are unsuitable for translation into humans; in the latter case because AT 2 receptor agonists are blood-brain barrier (BBB) impermeable. To circumvent this problem, in the current study we utilized the nose-to-brain (N2B) route of administration to bypass the BBB and deliver the selective AT 2 receptor agonist Compound 21 (C21) to näive rats or rats that had undergone endothelin 1 (ET-1)-induced ischemic stroke. The results obtained from the present study indicated that C21 applied N2B entered the cerebral cortex and striatum within 30 min in amounts that are therapeutically relevant (8.4-9 nM), regardless of whether BBB was intact or disintegrated. C21 was first applied N2B at 1.5 h after stroke indeed provided neuroprotection, as evidenced by a highly significant, 57% reduction in cerebral infarct size and significant improvements in Bederson and Garcia neurological scores. N2B-administered C21 did not affect blood pressure or heart rate. Thus, these data provide proof-of-principle for the idea that N2B application of an AT 2 receptor agonist can exert neuroprotective actions when administered following ischemic stroke. Since N2B delivery of other agents has been shown to be effective in certain human central nervous system diseases, the N2B application of AT 2 receptor agonists may become a viable mode of delivering these neuroprotective agents for human ischemic stroke patients.

The angiotensin AT2 -receptor is a main receptor of the protective arm of the renin-angiotensin-system. Understanding of this unconventional G-protein coupled receptor has significantly advanced during the past decade, largely because of the availability of a selective non-peptide AT2 -receptor agonist, which allowed the conduct of a multitude of studies in animal disease models. This article reviews such preclinical studies that in their entirety provide strong evidence for an anti-fibrotic effect mediated by activation of the AT2 -receptor. Prevention of the development of fibrosis by AT2 -receptor stimulation has been demonstrated in lung, heart, blood vessels, kidney, pancreas and skin. In lung, AT2 -receptor stimulation was even able to reverse existing fibrosis. The article further discusses intracellular signalling mechanisms mediating the AT2 -receptor coupled anti-fibrotic effect, including activation of phosphatases and subsequent interference with pro-fibrotic signalling pathways, induction of matrix-metalloproteinases, and hetero-dimerisation with the AT1 -receptor, the TGF-βRII-receptor or the RXFP1-receptor for relaxin. Knowledge of the anti-fibrotic effects of the AT2 -receptor is of particular relevance, because drugs targeting this receptor have entered clinical development for indications involving fibrotic diseases. This article is protected by copyright. All rights reserved.

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

The angiotensin AT

Cardiovascular and metabolic disorders, such as hypertension, insulin resistance, dyslipidemia or obesity are linked with chronic low-grade inflammation and dysregulation of the renin-angiotensin system (RAS). Consequently, RAS inhibition by ACE inhibitors or angiotensin AT1 receptor (AT1R) blockers is the evidence-based standard for cardiovascular risk reduction in high-risk patients, including diabetics with albuminuria. In addition, RAS inhibition reduces the new onset of diabetes mellitus. Yet, the high and increasing prevalence of metabolic disorders, and the high residual risk even in properly treated patients, calls for additional means of pharmacological intervention. In the past decade, the stimulation of the angiotensin AT2 receptor (AT2R) has been shown to reduce inflammation, improve cardiac and vascular remodeling, enhance insulin sensitivity and increase adiponectin production. Therefore, a concept of dual AT1R/AT2R modulation emerges as a putative means for risk reduction in cardio-metabolic diseases. The approach employing simultaneous RAS blockade (AT1R) and RAS stimulation (AT2R) is distinct from previous attempts of double intervention in the RAS by dual blockade. Dual blockade abolishes the AT1R-linked RAS almost completely with subsequent risk of hypotension and hypotension-related events, i.e. syncope or renal dysfunction. Such complications might be especially prominent in patients with renal impairment or patients with isolated systolic hypertension and normal-to-low diastolic blood pressure values. In contrast to dual RAS blockade, the add-on of AT2R stimulation does not exert significant blood pressure effects, but it may complement and enhance the anti-inflammatory and antifibrotic/de-stiffening effects of the AT1R blockade and improve the metabolic profile. Further studies will have to investigate these putative effects in particular for settings in which blood pressure reduction is not primarily desired.

Objectives: The angiotensin AT2-receptor (AT2R) is a main component of the protective arm of the renin-angiotensin system. In order to get new and deeper insights into AT2R mediated signalling, this study mapped the AT2R-coupled phosphoproteome in human aortic endothelial cells (HAEC) by quantitative phosphoproteomics. Methods: HAEC were stimulated with the AT2R agonist C21 (1 μM) for 1, 3, 5 or 20 minutes. Following protein digestion and TMT peptide labelling, samples were subjected to TiO2–SIMAC phospho-peptide enrichment and LC–MS/MS. Data were analysed using Proteome Discoverer and the human sequence libraries SwissProt and UniProt. For confirmation of phosphoproteomics results, expression of p53 and phosphorylation of HDAC-1 were determined by Western Blot. Cellular translocation of HDAC-1 and p53 was assessed by immunofluorescence and activity of HDAC-1 by deacetylation assay. HAEC proliferation was determined by resazurin assay and apoptosis by caspase 3/7 assay. Results: AT2R stimulation of HAEC changed the phosphorylation status of 265 proteins at 471 sites (281 phosphorylations and 190 dephosphorylations). Gene Ontology and STRING analysis revealed the predominant phospho-modification of proteins involved in anti-proliferation, cell differentiation and apoptosis including HDAC-1, p53, BCL2 or HSP90. AT2R-mediated inhibition of HDAC-1 and activation of p53 were confirmed by additional experiments demonstrating changes in cellular localisation of HDAC-1 and p53, in total expression of p53, and in enzymatic activity and phosphorylation of HDAC1. Conclusion: This study mapped the AT2R coupled phospho-signalling network. It identified dephosphorylation and deactivation of HDAC-1 as well as nuclear importation and increased expression of p53 as novel, potential mediators of AT2R-coupled anti-proliferation.

The renin–angiotensin system modulates insulin action. Angiotensin type 1 receptor exerts a deleterious effect, whereas the angiotensin type 2 receptor (AT2R) appears to have beneficial effects providing protection against insulin resistance and type 2 diabetes. To further explore the role of the AT2R on insulin action and glucose homeostasis, in this study we administered C57Bl/6 mice with the synthetic agonist of the AT2R C21 for 12 weeks (1 mg/kg per day; ip). Vehicle-treated animals were used as control. Metabolic parameters, glucose, and insulin tolerance, in vivo insulin signaling in main insulin-target tissues as well as adipose tissue levels of adiponectin, and TNF-α were assessed. C21-treated animals displayed decreased glycemia together with unaltered insulinemia, increased insulin sensitivity, and increased glucose tolerance compared to nontreated controls. This was accompanied by a significant decrease in adipocytes size in epididymal adipose tissue and significant increases in both adiponectin and UCP-1 expression in this tissue. C21-treated mice showed an increase in both basal Akt and ERK1/2 phosphorylation levels in the liver, and increased insulin-stimulated Akt activation in adipose tissue. This positive modulation of insulin action induced by C21 appeared not to involve the insulin receptor. In C21-treated mice, adipose tissue and skeletal muscle became unresponsive to insulin in terms of ERK1/2 phosphorylation levels. Present data show that chronic pharmacological activation of AT2R with C21 increases insulin sensitivity in mice and indicate that the AT2R has a physiological role in the conservation of insulin action. Fil: Quiroga, Diego Tomás. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Muñoz, Marina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina Fil: Gil, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina Fil: Pffeifer, Marlies. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Toblli, Jorge Eduardo. Hospital Aleman. Laboratorio de Medicina Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Steckelings, Ulrike M.. Southern Denmark University; Dinamarca Fil: Giani, Jorge Fernando. Cedars Sinai Medical Center; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Dominici, Fernando Pablo. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

The Angiotensin II type 2 receptor (AT 2R) promotes vasodilation by nitric oxide (NO) release from endothelial cells. However, the mechanisms underlying the AT 2R-induced stimulation of endothelial NO synthase (eNOS) is still not completely understood. Therefore, we investigated whether in addition to the known AT 2R-mediated phosphorylation of eNOS at Ser 1177, activation of phosphatases and dephosphorylation of eNOS at Tyr 657 and Thr 495 are also involved. Human aortic endothelial cells (HAEC) were stimulated with the AT 2R-agonist Compound 21 (C21) (1 μM) in the presence or absence of either PD123319 (10 μM; AT 2R antagonist), L-NG-Nitroarginine methyl ester (L-NAME) (10 μM; eNOS inhibitor), MK-2206 (100 nM; protein kinase B (Akt) inhibitor) sodium fluoride (NaF) (1 nM; serine/threonine phosphatase inhibitor) or sodium orthovanadate (Na 3VO 4) (10 nM; tyrosine phosphatase inhibitor). NO release was estimated by quantifying 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM) fluorescence. The phosphorylation status of activating (eNOS-Ser 1177) or inhibitory eNOS residues (eNOS-Tyr 657, eNOS-Thr 495) was determined by Western blotting. Phosphorylation of Akt at Ser 473 was measured to estimate Akt activity. AT 2R stimulation significantly increased NO release from HAEC, which was blocked by PD123319, L-NAME and both phosphatase inhibitors. Intracellular calcium transients were not changed by C21. AT 2R stimulation resulted in phosphorylation of eNOS-Ser 1177 and dephosphorylation of eNOS-Tyr 657 and eNOS-Thr 495. Phosphorylation at eNOS-Ser 1177 was prevented by inhibition of Akt with MK-2206. From these data, we conclude that AT 2R stimulation in human endothelial cells increases eNOS activity through phosphorylation of activating eNOS residues (eNOS-Ser 1177) by Akt, and through dephosphorylation of inactivating eNOS residues (eNOS-Tyr 657, eNOS-Thr 495) by serine/threonine and tyrosine phosphatases, thus increasing NO release.

Significant neuroprotective effects of angiotensin II type 2 (AT

Renin is a key enzyme of the renin-angiotensin-aldosterone-system (RAAS), a complex hormone system which regulates the sodium balance, the blood vessel tone and the glomerular filtration. Therefore, it plays a crucial role in the pathology of hypertension. This chapter reviews the structure, the biosynthesis, the processing and the expression of renin along with its main actions and the mechanisms controlling its release. Further, the components of the RAAS — angiotensinogen, the angiotensin-converting enzyme (ACE), angiotensin II and its receptor subtypes (the AT1 and the AT2) — are shortly discussed. Finally, drugs affecting the RAAS and providing benefits for the treatment of hypertension, such as renin inhibitors, ACE inhibitors, the AT1 receptor antagonists and the aldosterone antagonists, are reviewed.

The Angiotensin II type 2 receptor (AT

Recently, AT2 receptors have been discovered on the surface of human immunocompetent cells such as monocytes. Data on regulative properties of this receptor on the cellular immune response are poor. We hypothesized that direct stimulation of the AT2 receptor mediates anti-inflammatory responses in these cells. Human monocytic THP-1 and U937 cells were stimulated with lipopolysaccharide (LPS) and the selective AT2 receptor agonist Compound 21 (C21). Expression of pro- and anti-inflammatory cytokines IL-6, IL-10, tumor necrosis factor-alpha (TNF alpha), and IL-1 beta were analyzed on both the transcriptional and the translational level over course of time. Treatment with C21 attenuated the expression of TNF alpha, IL-6, and IL-10 after LPS challenge in both cell lines in a time- and dose-dependent manner. We conclude that selective AT2 receptor stimulation acts anti-inflammatory in human monocytes. Modulation of cytokine response by AT2 receptor activation might be a beneficial and novel treatment concept in inflammatory conditions.

Background and Purpose Angiotensin AT2 receptors are upregulated in disease states such as atherosclerosis and blockade of the AT2 receptors exacerbates plaque formation. Direct stimulation of these receptors is anti-atherogenic but the mechanisms and pathways involved remain unknown. We examined the effect of direct AT2 receptor stimulation with Compound 21 (C21) on the leukocyte adhesion cascade in vitro, right through to plaque formation in vivo. Experimental Approach Effects of C21 on TNFα-induced inflammation were assessed in human umbilical vein endothelial cells (HUVECs), activation of monocytes, polarisation of monocyte-derived macrophages and in intact mouse aortae. Key Results C21 attenuated TNFα-induced: monocyte adhesion to cultured HUVECs, adhesion molecule expression and abolished TNFα-induced ROS production. TNFα-induced NFκB translocation from the cytoplasm to the nucleus, essential for cytokine production, was prevented by C21. C21 did not influence monocyte activation or macrophage polarisation but did reduce TNFα and IL-6 mRNA expression in M1 macrophages. The anti-inflammatory effects of C21 were abolished by an AT2 receptor antagonist confirming that the effects of C21 were AT2 receptor-mediated. Also, leukocyte adhesion and cytokine gene expression, induced by high-fat diet (HFD), was attenuated in ApoE-/- mice treated with C21. Plaque size and stability were improved with C21 treatment with increased smooth muscle cell composition and decreased lipid size, compared with HFD-saline treated mice. Conclusion and Implications C21 prevented TNFα-induced and HFD-induced vascular inflammation in vitro and in vivo. Our data provide strong evidence that the anti-atherosclerotic actions of C21 were due to vascular anti-inflammatory effects, mediated by AT2 receptors.

In most situations, the angiotensin AT2-receptor (AT2R) mediates physiological actions opposing those mediated by the AT1-receptor (AT1R), including a vasorelaxant effect. Nevertheless, experimental evidence vastly supports that systemic application of AT2R-agonists is blood pressure neutral. However, stimulation of AT2R locally within the brain or the kidney apparently elicits a systemic blood pressure lowering effect. A systemic effect of AT2R stimulation on blood pressure can also be achieved, when the prevailing effect of continuous background AT1R-stimulation is attenuated by low-dose AT1R blockade. Despite a lack of effect on blood pressure, AT2R stimulation still protects from hypertensive end-organ damage. Current data and evidence therefore suggest that AT2R agonists will not be suitable as future anti-hypertensive drugs, but that they may well be useful for end-organ protection in combination with established anti-hypertensives.

Background and Purpose Pulmonary hypertension (PH) is a devastating disease characterized by increased pulmonary arterial pressure, which progressively leads to right-heart failure and death. A dys-regulated renin angiotensin system (RAS) has been implicated in the development and progression of PH. However, the role of the angiotensin AT2 receptor in PH has not been fully elucidated. We have taken advantage of a recently identified non-peptide AT2 receptor agonist, Compound 21 (C21), to investigate its effects on the well-established monocrotaline (MCT) rat model of PH. Experimental Approach A single s.c. injection of MCT (50 mg·kg−1) was used to induce PH in 8-week-old male Sprague Dawley rats. After 2 weeks of MCT administration, a subset of animals began receiving either 0.03 mg·kg−1 C21, 3 mg·kg−1 PD-123319 or 0.5 mg·kg−1 A779 for an additional 2 weeks, after which right ventricular haemodynamic parameters were measured and tissues were collected for gene expression and histological analyses. Key Results Initiation of C21 treatment significantly attenuated much of the pathophysiology associated with MCT-induced PH. Most notably, C21 reversed pulmonary fibrosis and prevented right ventricular fibrosis. These beneficial effects were associated with improvement in right heart function, decreased pulmonary vessel wall thickness, reduced pro-inflammatory cytokines and favourable modulation of the lung RAS. Conversely, co-administration of the AT2 receptor antagonist, PD-123319, or the Mas antagonist, A779, abolished the protective actions of C21. Conclusions and Implications Taken together, our results suggest that the AT2 receptor agonist, C21, may hold promise for patients with PH.

The presence of angiotensin type 2 (AT2) receptors in mitochondria and their role in NO generation and cell aging were recently demonstrated in various human and mouse non-tumour cells. We investigated the intracellular distribution of AT2 receptors including their presence in mitochondria and their role in the induction of apoptosis and cell death in cultured human uterine leiomyosarcoma (SK-UT-1) cells and control human uterine smooth muscle cells (HutSMC). The intracellular levels of the AT2 receptor are low in proliferating SK-UT-1 cells but the receptor is substantially up-regulated in quiescent SK-UT-1 cells with high densities in mitochondria. Activation of the cell membrane AT2 receptors by a concomitant treatment with angiotensin II and the AT1 receptor antagonist, losartan, induces apoptosis but does not affect the rate of cell death. We demonstrate for the first time that the high-affinity, non-peptide AT2 receptor agonist, Compound 21 (C21), penetrates the cell membrane of quiescent SK-UT-1 cells, activates intracellular AT2 receptors and induces rapid cell death; approximately 70% of cells died within 24 h. The cells, which escaped cell death, displayed activation of the mitochondrial apoptotic pathway, i.e. down-regulation of the Bcl-2 protein, induction of the Bax protein and activation of caspase-3. All quiescent SK-UT-1 cells died within 5 days after treatment with a single dose of C21. C21 was devoid of cytotoxic effects in proliferating SK-UT-1 cells and in quiescent HutSMC. Our results point to a new, unique approach enabling the elimination non-cycling uterine leiomyosarcoma cells providing that they over-express the AT2 receptor. Abbreviations: Ang, II, angiotensin II; AT1, angiotensin type 1; AT2, angiotensin type 2; ATIP, AT2 receptor interacting proteins; C21, Compound 21; DMEM, Dulbecco’s modified Eagle’s medium; 18F-FDG, [18F]2-fluoro-2-deoxy-D-glucose; HutSMC, human uterine smooth muscle cells; LC–MS, liquid chromatography–mass spectrometry; LDH, lactate dehydrogenase; RAS, renin–angiotensin system; RT, reverse transcription; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling

The angiotensin type 2 receptor (AT2R) and the receptor MAS are receptors of the protective arm of the renin–angiotensin system. They mediate strikingly similar actions. Moreover, in various studies, AT2R antagonists blocked the effects of MAS agonists and vice versa. Such cross-inhibition may indicate heterodimerization of these receptors. Therefore, this study investigated the molecular and functional interplay between MAS and the AT2R. Molecular interactions were assessed by fluorescence resonance energy transfer and by cross correlation spectroscopy in human embryonic kidney-293 cells transfected with vectors encoding fluorophore-tagged MAS or AT2R. Functional interaction of AT2R and MAS was studied in astrocytes with CX3C chemokine receptor-1 messenger RNA expression as readout. Coexpression of fluorophore-tagged AT2R and MAS resulted in a fluorescence resonance energy transfer efficiency of 10.8 ± 0.8%, indicating that AT2R and MAS are capable to form heterodimers. Heterodimerization was verified by competition experiments using untagged AT2R and MAS. Specificity of dimerization of AT2R and MAS was supported by lack of dimerization with the transient receptor potential cation channel, subfamily C-member 6. Dimerization of the AT2R was abolished when it was mutated at cysteine residue 35. AT2R and MAS stimulation with the respective agonists, Compound 21 or angiotensin-(1–7), significantly induced CX3C chemokine receptor-1 messenger RNA expression. Effects of each agonist were blocked by an AT2R antagonist (PD123319) and also by a MAS antagonist (A-779). Knockout of a single of these receptors made astrocytes unresponsive for both agonists. Our results suggest that MAS and the AT2R form heterodimers and that—at least in astrocytes—both receptors functionally depend on each other.

PURPOSE OF REVIEW: The goal of this review is to assess the evidence that activation of angiotensin type 2 receptors (AT2R) in the brain can lower blood pressure and possibly constitute an endogenous anti-hypertensive mechanism.RECENT FINDINGS: Recent studies that detail the location of AT2R in the brain, particularly within or near cardiovascular control centers, mesh well with findings from pharmacological and gene transfer studies which demonstrate that activation of central AT2R can influence cardiovascular regulation. Collectively, these studies indicate that selective activation of brain AT2R causes moderate decreases in blood pressure in normal animals and more profound anti-hypertensive effects, along with restoration of baroreflex function, in rodent models of neurogenic hypertension. These findings have opened the door to studies that can (i) assess the role of specific AT2R neuron populations in depressing blood pressure, (ii) determine the relevance of such mechanisms, and (iii) investigate interactions between AT2R and depressor angiotensin-(1-7)/Mas mechanisms in the brain.

Background: Compound 21 (C21), a selective small-molecule angiotensin type 2 receptor (AT2R) agonist, has been proven in multiple preclinical studies to reduce infarct size and ameliorate neurological deficits, when administered after ischemic stroke via intracerebroventricular or intraperitoneal routes. However, C21 poorly penetrates the blood brain barrier (BBB). In this study, we used the novel and non-invasive approach of intranasal trans-olfactory (INTO) application, in order to bypass the BBB and deliver C21 directly into the brain. The therapeutic efficacy of INTO application of C21 was assessed in a model of transient middle cerebral artery occlusion (MCAO). Methods: (i) Male SD rats (12 weeks old) underwent ischemic stroke by endothelin-1-induced MCAO. They were randomly divided into two treatment groups, either receiving 0.9% saline or C21 (1.5 ug/kg) at 1.5, 4, 24 and 48 h post-stroke, using a rat intranasal catheter device (Impel Neuropharma, Seattle, WA) for INTO application. All rats underwent blinded neurological assessments at 4, 24 and 72 h after stroke, and immediately after the 72 h tests, were euthanized and cerebral infarct volumes were assessed by TTC staining. (ii) Male SD rats (12 weeks old) underwent implantation of a telemetry transducer (DSI, St. Paul, MN) into the abdominal aorta for measurement of blood pressure, heart rate and locomotor activity after INTO C21 (1.5 ug/kg) vs. 0.9% saline at baseline and post-ischemic stroke. Results: (i) Post-stroke INTO delivery of C21 (1.5 ug/kg) elicited a significant lowering of % cerebral infarct volume (25.4 ± 4.7; n=9) compared with saline-treated rats (48.4 ± 4.4; n=21) [p Conclusions: Our results demonstrate, that INTO delivery of C21 exerts protective effects after ischemic stroke. These studies suggest INTO administration as potential future route of application of C21 to stroke patients.

The actions of angiotensin II type 2 receptor (AT 2 R) and the receptor Mas (MasR) are complex but show similar pronatriuretic function; particularly, AT 2 R expression and natriuretic function are enhanced in obese/diabetic rat kidney. In light of some reports suggesting a potential positive interaction between these receptors, we tested hypothesis that renal AT 2 R and MasR physically interact and are interdependent to stimulate cell signaling and promote natriuresis in obese rats. We found that infusion of AT 2 R agonist C21 in obese Zucker rats (OZR) increased urine flow and urinary Na excretion which were attenuated by simultaneous infusion of the AT 2 R antagonist PD123319 or the MasR antagonist A-779. Similarly, infusion of MasR agonist Ang-(1–7) in OZR increased urine flow and urinary Na excretion, which were attenuated by simultaneous infusion of A-779 or PD123319. Experiment in isolated renal proximal tubules of OZR revealed that both the agonists C21 and Ang-(1–7) stimulated NO which was blocked by either of the receptor antagonists. Dual labeling of AT 2 R and MasR in OZR kidney sections and human proximal tubule epithelial cells showed that AT 2 R and MasR are colocalized. The AT 2 R also coimmunoprecipitated with MasR in cortical homogenate of OZR. Immunoblotting of cortical homogenate cross-linked with zero-length oxidative (sulfhydryl groups) cross-linker cupric-phenanthroline revealed a shift of AT 2 R and MasR bands upward with overlapping migration for their complexes which were sensitive to the reducing β-mercaptoethanol, suggesting involvement of -SH groups in cross-linking. Collectively, the study reveals that AT 2 R and MasR are colocalized and functionally interdependent in terms of stimulating NO and promoting diuretic/natriuretic response.

Left ventricular (LV) remodeling is the main reason for the development of progressive cardiac dysfunction after myocardial infarction (MI). This study investigated whether stimulation of the angiotensin type 2 receptor is able to ameliorate post-MI cardiac remodeling and what the underlying mechanisms may be. MI was induced in Wistar rats by permanent ligation of the left coronary artery. Treatment with the angiotensin type 2 receptor agonist compound 21 ( 0.03 mg/kg) was started 6 hours post-MI and continued for 6 weeks. Hemodynamic parameters were measured by echocardiography and intracardiac catheter. Effects on proteolysis were studied in heart tissue and primary cardiac fibroblasts. Compound 21 significantly improved systolic and diastolic functions, resulting in improved ejection fraction (71.2±4.7% versus 53.4±7.0%; P P P P P

1. In recent years it has been firmly established that apart from the classic renin-angiotensin system (RAS) comprising angiotensin (Ang) II, angiotensin converting enzyme (ACE; responsible for AngII generation) and the angiotensin AT(1) receptor (AT(1)R), there also exist protective arms of the RAS that comprise the angiotensin AT(2) receptor (AT(2)R), Ang-(1-7), ACE2 (mainly responsible for Ang-(1-7) synthesis) and Mas, the receptor for Ang-(1-7). 2. Stimulation of AT(2)R promotes neuronal differentiation, neurite outgrowth and axonal regeneration, which results in an acceleration of repair and improved functional outcome after injury of peripheral nerves or the spinal cord. 3. Stimulation of AT(2)R and the receptor Mas has been shown to reduce infarct size and ameliorate neurological deficits in various animal models of stroke. The underlying mechanisms of action are comprised of activation of direct neurotrophic, anti-inflammatory and anti-oxidant pathways, as well as the augmentation of cerebral blood flow. 4. Cognitive function is improved by AT(2)R stimulation due, at least in part, to increased cerebral blood flow. There is indirect evidence that Ang-(1-7) could also play a role in protection against cognitive decline, but studies confirming this have not yet been published. 5. In view of the data reviewed in this article, it can be assumed that the protective arms of the RAS are putative targets in the treatment of neurological diseases, which involve tissue damage or cognitive impairment.