Phase I/II dose escalation study of angiotensin 1-7 [A(1-7)] administered before and after chemotherapy in patients with newly diagnosed breast cancer

The potential role of renin angiotensin system in acute leukemia: a narrative review

Acute leukemias (ALs) are the most common cancers in pediatric population. There are two types of ALs: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Some studies suggest that the Renin Angiotensin System (RAS) has a role in ALs. RAS signaling modulates, directly and indirectly, cellular activity in different cancers, affecting tumor cells and angiogenesis. Our review aimed to summarize the role of RAS in ALs and to explore future perspectives for the treatment of these hematological malignancies by modulating RAS molecules. The database including Pubmed, Scopus, Cochrane Library, and Scielo were searched to find articles about RAS molecules in ALL and in pediatric patients. The search terms were "RAS", "Acute Leukemia", "ALL", "Angiotensin-(1-7)", "Pediatric", "Cancer", "Angiotensin II", "AML". In the bone marrow, RAS has been found to play a key role in blood cell formation, affecting several processes including apoptosis, cell proliferation, mobilization, intracellular signaling, angiogenesis, fibrosis, and inflammation. Local tissue RAS modulates tumor growth and metastasis through autocrine and paracrine actions. RAS mainly acts via two molecules, Angiotensin II (Ang II) and Angiotensin (1-7) [Ang-(1-7)]. While Ang II promotes tumor cell growth and stimulates angiogenesis, Ang-(1-7) inhibits the proliferation of neoplastic cells and the angiogenesis, suggesting a potential therapeutic role of this molecule in ALL. The interaction between ALs and RAS reveals a complex network of molecules that can affect the hematopoiesis and the development of hematological cancers. Understanding these interactions could pave the way for innovative therapeutic approaches targeting RAS components.

Diverse biological functions of the renin-angiotensin system

The renin-angiotensin system (RAS) has been widely known as a circulating endocrine system involved in the control of blood pressure. However, components of RAS have been found to be localized in rather unexpected sites in the body including the kidneys, brain, bone marrow, immune cells, and reproductive system. These discoveries have led to steady, growing evidence of the existence of independent tissue RAS specific to several parts of the body. It is important to understand how RAS regulates these systems for a variety of reasons: It gives a better overall picture of human physiology, helps to understand and mitigate the unintended consequences of RAS-inhibiting or activating drugs, and sets the stage for potential new therapies for a variety of ailments. This review fulfills the need for an updated overview of knowledge about local tissue RAS in several bodily systems, including their components, functions, and medical implications.

LP2, a stable lanthipeptide derived from cAng-(1-7), exerts myeloprotective action in mice

OBJECTIVES

Linear unstable angiotensins stimulate hematopoiesis. Here we address: (1) Is cyclic angiotensin-(1-7) myeloprotective in mice? (2) Is cyclic angiotensin-(1-7) stable in rat? (3) Does LP2, a cyclic angiotensin-(1-7) with an N-terminal d-lysine, exert myeloprotective action in tumor-bearing mice?

MATERIALS AND METHODS

Cyclic angiotensin-(1-7)'s capacity to restore levels of blood platelets and white blood cells was studied in gemcitabine-treated mice. The stability of cyclic angiotensin-(1-7) in rat was measured in blood samples taken after injection or infusion. The capacity of LP2 to restore total bone marrow cell levels in mice after treatment with 5-fluoruracil was measured. In addition, the capacity of LP2 to counter anemia in tumor-bearing mice treated with erlotinib was measured.

RESULTS

Cyclic angiotensin-(1-7) dose-dependently restored blood platelet levels in gemcitabine-treated mice, whereas its capacity to restore levels of white blood cells was less. In vivo aminoterminal breakdown of cyclic angiotensin-(1-7) yielded cyclic angiotensin-(2-7) and cyclic angiotensin-(3-7). LP2 significantly (p < .0001 at 100 μg/kg/day) restored bone marrow cell counts in mice after treatment with 5-fluoruracil. LP2 also significantly (p < .05) countered anemia in tumor-bearing mice treated with erlotinib.

CONCLUSIONS

LP2 exerts myeloprotective action with perspectives for continuation of its clinical development.

The fibrotic niche impairs satellite cell function and muscle regeneration in mouse models of Marfan syndrome

AIM

It has been suggested that the proliferation and early differentiation of myoblasts are impaired in Marfan syndrome (MFS) mice during muscle regeneration. However, the underlying cellular and molecular mechanisms remain poorly understood. Here, we investigated muscle regeneration in MFS mouse models by analyzing the influence of the fibrotic niche on satellite cell function.

METHODS

In vivo, ex vivo, and in vitro experiments were performed. In addition, we evaluated the effect of the pharmacological inhibition of fibrosis using Ang-(1-7) on regenerating skeletal muscles of MFS mice.

RESULTS

The skeletal muscle of MFS mice shows an increased accumulation of collagen fibers (81.2%), number of fibroblasts (157.1%), and Smad2/3 signaling (110.5%), as well as an aberrant number of fibro-adipogenic progenitor cells in response to injury compared with wild-type mice. There was an increased number of proinflammatory and anti-inflammatory macrophages (3.6- and 3.1-fold, respectively) in regenerating muscles of wild-type mice, but not in the regenerating muscles of MFS mice. Our data show that proliferation and differentiation of satellite cells are altered (p ≤ 0.05) in MFS mice. Myoblast transplantation assay revealed that the regenerating muscles from MFS mice have reduced satellite cell self-renewal capacity (74.7%). In addition, we found that treatment with Ang-(1-7) reduces fibrosis (71.6%) and ameliorates satellite cell dysfunction (p ≤ 0.05) and muscle contractile function (p ≤ 0.05) in MFS mice.

CONCLUSION

The fibrotic niche, caused by Fbn1 mutations, reduces the myogenic potential of satellite cells, affecting structural and functional muscle regeneration. In addition, the fibrosis inhibitor Ang-(1-7) partially counteracts satellite cell abnormalities and restores myofiber size and contractile force in regenerating muscles.

Mitigating Cardiotoxicity of Dendrimers: Angiotensin-(1-7) via Its Mas Receptor Ameliorates PAMAM-Induced Cardiac Dysfunction in the Isolated Mammalian Heart

AIM

The influence of the physiochemical properties of dendrimer nanoparticles on cardiac contractility and hemodynamics are not known. Herein, we investigated (a) the effect of polyamidoamine (PAMAM) dendrimer generation (G7, G6, G5, G4 and G3) and surface chemistry (-NH₂, -COOH and -OH) on cardiac function in mammalian hearts following ischemia-reperfusion (I/R) injury, and (b) determined if any PAMAM-induced cardiotoxicity could be mitigated by Angiotensin-(1-7) (Ang-(1-7), a cardioprotective agent.

METHODS

Hearts isolated from male Wistar rats underwent regional I/R and/or treatment with different PAMAM dendrimers, Ang-(1-7) or its MAS receptors antagonists. Thirty minutes of regional ischemia through ligation of the left anterior descending coronary artery was followed by 30 min of reperfusion. All treatments were initiated 5 min prior to reperfusion and maintained during the first 10 min of reperfusion. Cardiac function parameters for left ventricular contractility, hemodynamics and vascular dynamics data were acquired digitally, whereas cardiac enzymes and infarct size were used as measures of cardiac injury.

RESULTS

Treatment of isolated hearts with increasing doses of G7 PAMAM dendrimer progressively exacerbated recovery of cardiac contractility and hemodynamic parameters post-I/R injury. Impairment of cardiac function was progressively less on decreasing dendrimer generation with G3 exhibiting little or no cardiotoxicity. Cationic PAMAMs (-NH₂) were more toxic than anionic (-COOH), with neutral PAMAMs (-OH) exhibiting the least cardiotoxicity. Cationic G7 PAMAM-induced cardiac dysfunction was significantly reversed by Ang-(1-7) administration. These cardioprotective effects of Ang-(1-7) were significantly revoked by administration of the MAS receptor antagonists, A779 and D-Pro⁷-Ang-(1-7).

CONCLUSIONS

PAMAM dendrimers can impair the recovery of hearts from I/R injury in a dose-, dendrimer-generation-(size) and surface-charge dependent manner. Importantly, PAMAM-induced cardiotoxicity could be mitigated by Ang-(1-7) acting through its MAS receptor. Thus, this study highlights the activation of Ang-(1-7)/Mas receptor axis as a novel strategy to overcome dendrimer-induced cardiotoxicity.

Patients with severe COVID‐19 have reduced circulating levels of angiotensin‐(1–7): A cohort study

Background and Aims

Angiotensin‐converting enzyme 2 (ACE2) acts as a functional receptor for the entry of severe acute respiratory syndrome coronavirus 2 into host cells. Angiotensin (1–7) (Ang (1–7)) obtained from the function of ACE2 improves heart and lung function. We investigated the relationship between Ang (1–7) level and disease severity in patients with coronavirus disease 2019 (COVID‐19).

Methods

This cohort study was carried out at Masih Daneshvari Hospital in Tehran, Iran from September 2020 to October 2020. To do so, the Ang (1–7) levels of 331 hospitalized COVID‐19 patients with and without underlying disease were measured by ELISA kit. The need for oxygen, intubation, and mechanical ventilation were recorded for all the patients.

Results

Results showed a significant inverse relationship between the levels of Ang 1–7 and the severity of the disease (needed oxygen, intubation, and mechanical ventilation). According to the results, median (interquartile range) of Ang (1–7) levels was significantly lower in patients who needed oxygen versus those who needed no oxygen (44.50 (91) vs. 82.25 (68), p = 0.002), patients who needed intubation and mechanical ventilation versus those who did not (9.80 (62) vs. 68.70 (102), p < 0.000) and patients hospitalized in an intensive care unit (ICU) than people hospitalized in other wards. We also found that the older patients were more in need of ICU and mechanical ventilation than younger patients.

Conclusions

Higher levels of Ang (1–7) have been associated with decreased disease severity. Besides this, we perceived that synthetic Ang 1–7 peptides may be useful to treat and reduce the complications of COVID‐19.

Pharmacological Blockade of NLRP3 Inflammasome/IL-1β-Positive Loop Mitigates Endothelial Cell Senescence and Dysfunction

The clinical relevance of IL-1β in chronic inflammation underlying atherosclerosis has been reinforced by recent evidence associating pharmacological inhibition of the cytokine with lower cardiovascular risk. Previously, we have demonstrated a direct involvement of IL-1β in endothelial senescence. Therefore, this can be a key mechanism contributing to the sterile inflammatory milieu associated with aging, termed inflammaging. In the present study, we have evaluated whether a positive feedback of IL-1β in the NLRP3 inflammasome via NF-κB could promote human endothelial senescence in vitro and murine endothelial dysfunction in vivo. Our results indicate that the NLRP3 inflammasome is pivotal in mediating the detrimental effects of IL-1β, showing that auto-activation is a crucial feature boosting endothelial cell senescence in vitro, which is paralleled by vascular dysfunction in vivo. Hence, the inhibitor of NLRP3 inflammasome assembly, MCC 950, was able to disrupt the aforementioned positive loop, thus alleviating inflammation, cell senescence and vascular dysfunction. Besides, we explored alternative NLRP3 inflammasome inhibitory agents such as the RAS heptapeptide Ang-(1-7) and the anti-aging protein klotho, both of which demonstrated protective effects in vitro and in vivo. Altogether, our results highlight a fundamental role for the hereby described NLRP3 inflammasome/IL-1β positive feedback loop in stress-induced inflammaging and the associated vascular dysfunction, additionally providing evidence of a potential therapeutic use of MCC 950, Ang-(1-7) and recombinant klotho to block this loop and its deleterious effects.

Neurofilament light: a possible prognostic biomarker for treatment of vascular contributions to cognitive impairment and dementia

Background

Decreased cerebral blood flow and systemic inflammation during heart failure (HF) increase the risk for vascular contributions to cognitive impairment and dementia (VCID) and Alzheimer disease-related dementias (ADRD). We previously demonstrated that PNA5, a novel glycosylated angiotensin 1–7 (Ang-(1–7)) Mas receptor (MasR) agonist peptide, is an effective therapy to rescue cognitive impairment in our preclinical model of VCID. Neurofilament light (NfL) protein concentration is correlated with cognitive impairment and elevated in neurodegenerative diseases, hypoxic brain injury, and cardiac disease. The goal of the present study was to determine (1) if treatment with Ang-(1–7)/MasR agonists can rescue cognitive impairment and decrease VCID-induced increases in NfL levels as compared to HF-saline treated mice and, (2) if NfL levels correlate with measures of cognitive function and brain cytokines in our VCID model.

Methods

VCID was induced in C57BL/6 male mice via myocardial infarction (MI). At 5 weeks post-MI, mice were treated with daily subcutaneous injections for 24 days, 5 weeks after MI, with PNA5 or angiotensin 1–7 (500 microg/kg/day or 50 microg/kg/day) or saline (n = 15/group). Following the 24-day treatment protocol, cognitive function was assessed using the Novel Object Recognition (NOR) test. Cardiac function was measured by echocardiography and plasma concentrations of NfL were quantified using a Quanterix Simoa assay. Brain and circulating cytokine levels were determined with a MILLIPLEX MAP Mouse High Sensitivity Multiplex Immunoassay. Treatment groups were compared via ANOVA, significance was set at p < 0.05.

Results

Treatment with Ang-(1–7)/MasR agonists reversed VCID-induced cognitive impairment and significantly decreased NfL levels in our mouse model of VCID as compared to HF-saline treated mice. Further, NfL levels were significantly negatively correlated with cognitive scores and the concentrations of multiple pleiotropic cytokines in the brain.

Conclusions

These data show that treatment with Ang-(1–7)/MasR agonists rescues cognitive impairment and decreases plasma NfL relative to HF-saline-treated animals in our VCID mouse model. Further, levels of NfL are significantly negatively correlated with cognitive function and with several brain cytokine concentrations. Based on these preclinical findings, we propose that circulating NfL might be a candidate for a prognostic biomarker for VCID and may also serve as a pharmacodynamic/response biomarker for therapeutic target engagement.

Angiotensin-(1-7) Peptide Hormone Reduces Inflammation and Pathogen Burden during Mycoplasma pneumoniae Infection in Mice

The peptide hormone, angiotensin (Ang-(1–7)), produces anti-inflammatory and protective effects by inhibiting production and expression of many cytokines and adhesion molecules that are associated with a cytokine storm. While Ang-(1–7) has been shown to reduce inflammation and airway hyperreactivity in models of asthma, little is known about the effects of Ang-(1–7) during live respiratory infections. Our studies were developed to test if Ang-(1–7) is protective in the lung against overzealous immune responses during an infection with Mycoplasma pneumonia (Mp), a common respiratory pathogen known to provoke exacerbations in asthma and COPD patients. Wild type mice were treated with infectious Mp and a subset of was given either Ang-(1–7) or peptide-free vehicle via oropharyngeal delivery within 2 h of infection. Markers of inflammation in the lung were assessed within 24 h for each set of animals. During Mycoplasma infection, one high dose of Ang-(1–7) delivered to the lungs reduced neutrophilia and Muc5ac, as well as Tnf-α and chemokines (Cxcl1) associated with acute respiratory distress syndrome (ARDS). Despite decreased inflammation, Ang-(1-7)-treated mice also had significantly lower Mp burden in their lung tissue, indicating decreased airway colonization. Ang-(1–7) also had an impact on RAW 264.7 cells, a commonly used macrophage cell line, by dose-dependently inhibiting TNF-α production while promoting Mp killing. These new findings provide additional support to the protective role(s) of Ang1-7 in controlling inflammation, which we found to be highly protective against live Mp-induced lung inflammation.

Breast cancer and the renin-angiotensin system (RAS): Therapeutic approaches and related metabolic diseases

The Renin-Angiotensin System (RAS) is classically recognized for regulating blood pressure and fluid balance. Recently, this role has extended to other areas including inflammation, obesity, diabetes, as well as breast cancer. RAS components are expressed in normal and cancerous breast tissues, and downregulation of RAS inhibits metastasis, proliferation, angiogenesis, and desmoplasia in the tumor microenvironment. Therefore, RAS inhibitors (Angiotensin receptor blockers, ARBs, or angiotensin converting enzyme inhibitors, ACE-I) may be beneficial as preventive adjuvant therapies to thwart breast cancer development and improve outcomes, respectively. Given the beneficial effects of RAS inhibitors in metabolic diseases, which often co-exist in breast cancer patients, combining RAS inhibitors with other breast cancer therapies may enhance the effectiveness of current treatments. This review scrutinizes above associations, to advance our understanding of the role of RAS in breast cancer and its potential for repurposing of RAS inhibitors to improve the therapeutic approach for breast cancer patients.

ACE2/Angiotensin-(1-7)/Mas Receptor Axis in Human Cancer: Potential Role for Pediatric Tumors

BACKGROUND

Pediatric tumors remain the highest cause of death in developed countries. Research on novel therapeutic strategies with lesser side effects is of utmost importance. In this scenario, the role of Renin-Angiotensin System (RAS) axes, the classical one formed by angiotensinconverting enzyme (ACE), Angiotensin II and AT1 receptor and the alternative axis composed by ACE2, Angiotensin-(1-7) and Mas receptor, have been investigated in cancer.

OBJECTIVE

This review aimed to summarize the pathophysiological role of RAS in cancer, evidence for anti-tumor effects of ACE2/Angiotensin-(1-7)/Mas receptor axis and future therapeutic perspectives for pediatric cancer.

METHODS

Pubmed, Scopus and Scielo were searched in regard to RAS molecules in human cancer and pediatric patients. The search terms were "RAS", "ACE", "Angiotensin-(1-7)", "ACE2", "Angiotensin II", "AT1 receptor", "Mas receptor", "Pediatric", "Cancer".

RESULTS

Experimental studies have shown that Angiotensin-(1-7) inhibits the growth of tumor cells and reduces local inflammation and angiogenesis in several types of cancer. Clinical trials with Angiotensin-( 1-7) or TXA127, a pharmaceutical grade formulation of the naturally occurring peptide, have reported promising findings, but not enough to recommend medical use in human cancer. In regard to pediatric cancer, only three articles that marginally investigated RAS components were found and none of them evaluated molecules of the alternative RAS axis.

CONCLUSION

Despite the potential applicability of Angiotensin-(1-7) in pediatric tumors, the role of this molecule was never tested. Further clinical trials are necessary, also including pediatric patients, to confirm safety and efficiency and to define therapeutic targets.

Improved pharmacokinetics and bone tissue accumulation of Angiotensin-(1-7) peptide through bisphosphonate conjugation

The renin-angiotensin system (RAS) has a central role in renal and cardiovascular homeostasis. Angiotensin-(1-7) (Ang1-7), one of the RAS active peptides, exerts beneficial effects through different mechanisms. These biological actions suggest that Ang1-7 is an effective therapeutic agent for treating various diseases associated with activated RAS. However, its short half-life and poor pharmacokinetics restrict its therapeutic utility. Our laboratory has successfully synthesized and characterized an Ang1-7 conjugate (Ang Conj.) with a prolonged half-life and improved pharmacokinetics profile. The Ang Conj. has been prepared by PEGylation of Ang1-7 and conjugation with a bisphosphonate using solid-phase peptide synthesis and characterized by HPLC and mass spectrometer. The compound's stability has been tested in different storage conditions. The bone binding capacity was evaluated using a hydroxyapatite assay. Pharmacokinetic and tissue distribution studies were performed using iodinated peptides in rats. Ang Conj. was synthesized with > 90% purity. Bone mineral affinity testing showed Ang Conj. exhibited significantly higher bone mineral affinity than Ang1-7. The Ang Conj. remained stable for more than a month using all tested storage conditions. The Ang Conj. demonstrated higher affinity to bone, a longer half-life, and better bioavailability when compared with the native peptide. These results support that conjugation of Ang1-7 with bisphosphonate enables it to utilize bone as a reservoir for the sustained delivery of Ang1-7 to maintain therapeutic plasma levels. High chemical stability and about five to tenfold prolongation of Ang Conj. plasma half-life after administrations into rats proves the effectiveness of our approach.

Combination of Angiotensin (1-7) Agonists and Convalescent Plasma as a New Strategy to Overcome Angiotensin Converting Enzyme 2 (ACE2) Inhibition for the Treatment of COVID-19

Coronavirus disease-2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently the most concerning health problem worldwide. SARS-CoV-2 infects cells by binding to angiotensin-converting enzyme 2 (ACE2). It is believed that the differential response to SARS-CoV-2 is correlated with the differential expression of ACE2. Several reports proposed the use of ACE2 pharmacological inhibitors and ACE2 antibodies to block viral entry. However, ACE2 inhibition is associated with lung and cardiovascular pathology and would probably increase the pathogenesis of COVID-19. Therefore, utilizing ACE2 soluble analogs to block viral entry while rescuing ACE2 activity has been proposed. Despite their protective effects, such analogs can form a circulating reservoir of the virus, thus accelerating its spread in the body. Levels of ACE2 are reduced following viral infection, possibly due to increased viral entry and lysis of ACE2 positive cells. Downregulation of ACE2/Ang (1-7) axis is associated with Ang II upregulation. Of note, while Ang (1-7) exerts protective effects on the lung and cardiovasculature, Ang II elicits pro-inflammatory and pro-fibrotic detrimental effects by binding to the angiotensin type 1 receptor (AT1R). Indeed, AT1R blockers (ARBs) can alleviate the harmful effects associated with Ang II upregulation while increasing ACE2 expression and thus the risk of viral infection. Therefore, Ang (1-7) agonists seem to be a better treatment option. Another approach is the transfusion of convalescent plasma from recovered patients with deteriorated symptoms. Indeed, this appears to be promising due to the neutralizing capacity of anti-COVID-19 antibodies. In light of these considerations, we encourage the adoption of Ang (1-7) agonists and convalescent plasma conjugated therapy for the treatment of COVID-19 patients. This therapeutic regimen is expected to be a safer choice since it possesses the proven ability to neutralize the virus while ensuring lung and cardiovascular protection through modulation of the inflammatory response.

Optimal biological dose: a systematic review in cancer phase I clinical trials

BACKGROUND

Classical phase 1 dose-finding designs based on a single toxicity endpoint to assess the maximum tolerated dose were initially developed in the context of cytotoxic drugs. With the emergence of molecular targeted agents and immunotherapies, the concept of optimal biological dose (OBD) was subsequently introduced to account for efficacy in addition to toxicity. The objective was therefore to provide an overview of published phase 1 cancer clinical trials relying on the concept of OBD.

METHODS

We performed a systematic review through a computerized search of the MEDLINE database to identify early phase cancer clinical trials that relied on OBD. Relevant publications were selected based on a two-step process by two independent readers. Relevant information (phase, type of therapeutic agents, objectives, endpoints and dose-finding design) were collected.

RESULTS

We retrieved 37 articles. OBD was clearly mentioned as a trial objective (primary or secondary) for 22 articles and was traditionally defined as the smallest dose maximizing an efficacy criterion such as biological target: biological response, immune cells count for immunotherapies, or biological cell count for targeted therapies. Most trials considered a binary toxicity endpoint defined in terms of the proportion of patients who experienced a dose-limiting toxicity. Only two articles relied on an adaptive dose escalation design.

CONCLUSIONS

In practice, OBD should be a primary objective for the assessment of the recommended phase 2 dose (RP2D) for a targeted therapy or immunotherapy phase I cancer trial. Dose escalation designs have to be adapted accordingly to account for both efficacy and toxicity.

Synthesis and Biological Evaluation of N-Aminoimidazolidin-2-one-Containing Angiotensin-(1-7) Peptidomimetics

N-Aminoimidazolidin-2-one (Aid)-containing peptides with a constrained backbone present a novel class of peptidomimetics for drug discovery. The introduction of Aid residues into peptide sequences has been achieved by intramolecular Mitsunobu cyclization of a serine side chain onto the α-NH of an aza-glycine residue. The effectiveness of this new strategy was demonstrated by synthesizing six Aid-containing analogues of angiotensin-(1-7) on solid support. The Aid analogues of angiotensin-(1-7) exhibited increased peptidase stability against human ACE and DPP3 and improved anti-inflammation and antiproliferation activity.

Glycopeptide drugs: A pharmacological dimension between "Small Molecules" and "Biologics"

Peptides are an important class of molecules with diverse biological activities. Many endogenous peptides, especially neuropeptides and peptide hormones, play critical roles in development and regulating homeostasis. Furthermore, as drug candidates their high receptor selectivity and potent binding leads to reduced off-target interactions and potential negative side effects. However, the therapeutic potential of peptides is severely hampered by their poor stability in vivo and low permeability across biological membranes. Several strategies have been successfully employed over the decades to address these concerns, and one of the most promising strategies is glycosylation. It has been demonstrated in numerous cases that glycosylation is an effective synthetic approach to improve the pharmacokinetic profiles and membrane permeability of peptides. The effects of glycosylation on peptide stability and peptide-membrane interactions in the context of blood-brain barrier penetration will be explored. Numerous examples of glycosylated analogues of endogenous peptides targeting class A and B G-protein coupled receptors (GPCRs) with an emphasis on O-linked glycopeptides will be reviewed. Notable examples of N-, S-, and C-linked glycopeptides will also be discussed. A small section is devoted to synthetic methods for the preparation of glycopeptides and requisite amino acid glycoside building blocks.

Angiotensin II receptors: Impact for COVID-19 severity

COVID-19 is an outbreak of viral pneumonia which became a global health crisis, and the risk of morbidity and mortality of people with obesity are higher. SARS-CoV-2, the pathogen of COVID-19, enters into cells through binding to the Angiotensin Converting Enzyme (ACE) homolog-2 (ACE2). ACE2 is a regulator of two contrary pathways in renin angiotensin system (RAS): ACE-Ang-II-AT1R axis and ACE2-Ang 1-7-Mas axis. Viral entry process eventuates in downregulation of ACE2 and subsequent activation of ACE-Ang-II-AT1R axis. ACE-Ang II-AT1R axis increases lipid storage, reduces white-to-beige fat conversion and plays role in obesity. Conversely, adipose tissue is an important source of angiotensin, and obesity results in increased systemic RAS. ACE-Ang-II-AT1R axis, which has proinflammatory, profibrotic, prothrombotic, and vasoconstrictive effects, is potential mechanism of more severe SARS-CoV-2 infection. The link between obesity and severe COVID-19 may be attributed to ACE2 consumption and subsequent ACE-Ang-II-AT1R axis activation. Therefore, patients with SARS-CoV-2 infection may benefit from therapeutic strategies that activate ACE2-Ang 1-7-Mas axis, such as Ang II receptor blockers (ARBs), ACE inhibitors (ACEIs), Mas receptor agonists and ACE2.

Targeting the Protective Arm of the Renin-Angiotensin System to Reduce Systemic Lupus Erythematosus Related Pathologies in MRL-lpr Mice

Patients with Systemic Lupus Erythematosus (SLE) suffer from a chronic inflammatory autoimmune disease that results from the body's immune system targeting healthy tissues which causes damage to various organ systems. Patients with lupus are still in need of effective therapies to treat this complex, multi-system disease. Because polymorphisms in ACE are associated with the activity of SLE and lupus nephritis and based on well-documented renal-protective effects of Renin Angiotensin System (RAS)-modifying therapies, ACE-I are now widely used in patients with SLE with significant efficacy. Our research explores alternate ways of modifying the RAS as a potential for systemic therapeutic benefit in the MRL-lpr mouse model of SLE. These therapeutics include; angiotensin (1-7) [A(1-7)], Nor-Leu-3 Angiotensin (1-7) (NorLeu), Losartan (ARB), and Lisinopril (ACE-I). Daily systemic treatment with all of these RAS-modifying therapies significantly reduced the onset and intensity in rash formation and swelling of the paw. Further, histology showed a corresponding decrease in hyperkeratosis and acanthosis in skin sections. Important immunological parameters such as decreased circulating anti-dsDNA antibodies, lymph node size, and T cell activation were observed. As expected, the development of glomerular pathologies was also attenuated by RAS-modifying therapy. Improved number and health of mesenchymal stem cells (MSCs), as well as reduction in oxidative stress and inflammation may be contributing to the reduction in SLE pathologies. Several studies have already characterized the protective role of ACE-I and ARBs in mouse models of SLE, here we focus on the protective arm of RAS. A(1-7) in particular demonstrates several protective effects that go beyond those seen with ACE-Is and ARBs; an important finding considering that ACE-Is and ARBs are teratogenic and can cause hypotension in this population. These results offer a foundation for further pharmaceutical development of RAS-modifying therapies, that target the protective arm, as novel SLE therapeutics that do not rely on suppressing the immune system.

Urgent need for evaluating agonists of angiotensin-(1-7)/Mas receptor axis for treating patients with COVID-19

ACE2 is a receptor of entry of SARS-CoV-2 into the host cells, and its upregulation has been implicated in increasing susceptibility of individuals to this infection. The clinical picture of COVID-19 suggests a role of ACE2 blockade, rather than its overexpression, in causing the pathogenesis. ACE2 blockade results in increased angiotensin II activity with simultaneous hampering of functions of angiotensin-(1-7)/MasR axis. Acute respiratory distress due to interstitial pulmonary fibrosis, cardiomyopathy and shock reported in COVID-19 patients can be explained by imbalanced angiotensin II and angiotensin-(1-7) activities. Failure of angiotensin II type 1 receptor blockers to control the severity of SARS-CoV-2 infections indicates the importance of simultaneous induction of angiotensin-(1-7)/MasR axis for correcting pathological conditions in COVID-19 through its anti-fibrotic, anti-inflammatory, vasodilatory, and cardioprotective roles. MasR agonists have also shown organ protective effects in a number of animal studies. Unfortunately, these agonists have not been tested in clinical studies. Their evaluation in seriously ill COVID-19 patients is urgently warranted to reduce mortality due to infection.

Targeting Angiotensin-Converting Enzyme-2/Angiotensin-(1-7)/Mas Receptor Axis in the Vascular Progenitor Cells for Cardiovascular Diseases

Bone marrow-derived hematopoietic stem/progenitor cells are vasculogenic and play an important role in endothelial health and vascular homeostasis by participating in postnatal vasculogenesis. Progenitor cells are mobilized from bone marrow niches in response to remote ischemic injury and migrate to the areas of damage and stimulate revascularization largely by paracrine activation of angiogenic functions in the peri-ischemic vasculature. This innate vasoprotective mechanism is impaired in certain chronic clinical conditions, which leads to the development of cardiovascular complications. Members of the renin-angiotensin system-angiotensin-converting enzymes (ACEs) ACE and ACE2, angiotensin II (Ang II), Ang-(1-7), and receptors AT1 and Mas-are expressed in vasculogenic progenitor cells derived from humans and rodents. Ang-(1-7), generated by ACE2, is known to produce cardiovascular protective effects by acting on Mas receptor and is considered as a counter-regulatory mechanism to the detrimental effects of Ang II. Evidence has now been accumulating in support of the activation of the ACE2/Ang-(1-7)/Mas receptor pathway by pharmacologic or molecular maneuvers, which stimulates mobilization of progenitor cells from bone marrow, migration to areas of vascular damage, and revascularization of ischemic areas in pathologic conditions. This minireview summarizes recent studies that have enhanced our understanding of the physiology and pharmacology of vasoprotective axis in bone marrow-derived progenitor cells in health and disease. SIGNIFICANCE STATEMENT: Hematopoietic stem progenitor cells (HSPCs) stimulate revascularization of ischemic areas. However, the reparative potential is diminished in certain chronic clinical conditions, leading to the development of cardiovascular diseases. ACE2 and Mas receptor are key members of the alternative axis of the renin-angiotensin system and are expressed in HSPCs. Accumulating evidence points to activation of ACE2 or Mas receptor as a promising approach for restoring the reparative potential, thereby preventing the development of ischemic vascular diseases.

Angiotensin-(1–7) reduces doxorubicin-induced cardiac dysfunction in male and female Sprague-Dawley rats through antioxidant mechanisms

Doxorubicin (Dox) is an effective chemotherapeutic for a variety of pediatric malignancies. Unfortunately, Dox administration often results in a cumulative dose-dependent cardiotoxicity that manifests with marked oxidative stress, leading to heart failure. Adjunct therapies are needed to mitigate Dox cardiotoxicity and enhance quality of life in pediatric patients with cancer. Angiotensin-(1–7) [Ang-(1–7)] is an endogenous hormone with cardioprotective properties. This study investigated whether adjunct Ang-(1–7) attenuates cardiotoxicity resulting from exposure to Dox in male and female juvenile rats. Dox significantly reduced body mass, and the addition of Ang-(1–7) had no effect. However, adjunct Ang-(1–7) prevented Dox-mediated diastolic dysfunction, including markers of decreased passive filling as measured by reduced early diastole mitral valve flow velocity peak ( E) ( P < 0.05) and early diastole mitral valve annulus peak velocity ( e′; P < 0.001) and increased E/e′ ( P < 0.001), an echocardiographic measure of diastolic dysfunction. Since Dox treatment increases reactive oxygen species (ROS), the effect of Ang-(1–7) on oxidative by-products and enzymes that generate or reduce ROS was investigated. In hearts of male and female juvenile rats, Dox increased NADPH oxidase 4 ( P < 0.05), a major cardiovascular NADPH oxidase isozyme that generates ROS, as well as 4-hydroxynonenal ( P < 0.001) and malondialdehyde ( P < 0.001), markers of lipid peroxidation; Ang-(1–7) prevented these effects of Dox. Cotreatment with Dox and Ang-(1–7) increased the antioxidant enzymes SOD1 (male: P < 0.05; female: P < 0.01) and catalase ( P < 0.05), which likely contributed to reduced ROS. These results demonstrate that Ang-(1–7) prevents diastolic dysfunction in association with a reduction in ROS, suggesting that the heptapeptide hormone may serve as an effective adjuvant to improve Dox-induced cardiotoxicity.

NEW & NOTEWORTHY Ang-(1–7) is a clinically safe peptide hormone with cardioprotective and antineoplastic properties that could be used as an adjuvant therapy to improve cancer treatment and mitigate the long-term cardiotoxicity associated with doxorubicin in pediatric patients with cancer.

Pathobiological Interactions of Local Bone Marrow Renin-Angiotensin System and Central Nervous System in Systemic Arterial Hypertension

Circulating renin-angiotensin system (RAS) and local paracrin-autocrin-intracrin tissue-based RAS participate in numerous pathobiological events. Pro-inflammatory, pro-fibrotic, and pro-thrombotic consequences associated with local RAS activation have been detected at cellular and molecular level. Regenerative progenitor cell therapy in response to RAS modulating pharmacotherapy has emerged as an adjunct in the context of endothelial cell injury and regeneration to improve regeneration of the vascular endothelium. Local hematopoietic bone marrow (BM) RAS symbolizes the place of cross-interaction between vascular biology and cellular events from embryogenesis to definitive hematopoiesis underlying vascular atherosclerosis. The BM microenvironment also contains Mas receptors, which control the proliferative role of Ang 1-7 on hematopoietic stem cells. Ang 1-7 is produced from Ang-II or Ang-I with the help of ACE2. Various tissues and organs also have an effect on the RAS system. The leukocytes contain and synthesize immunoreactive angiotensinogen species capable of producing angiotensin in the basal state or after incubation with renin. The significance of RAS employment in atherosclerosis and hypertension was indicated by novel bidirectional Central Nervous System (CNS) RAS-BM RAS communications. Myeloid cells generated within the context of hematopoietic BM RAS are considered as the initiators and decision shapers in atherosclerosis. Macrophages in the atherosclerotic lesions contain angiotensin peptides by which RAS blockers inhibit monocyte activation and adherence. Furthermore, vascular biology in relation to inflammation and neoplasia is also affected by local tissue RAS. The purpose of this article is to outline interactions of circulating and local angiotensin systems, especially local bone marrow RAS, in the vascular pathobiological microenvironment of CNS.

Therapeutic Targeting of Cancer Stem Cells via Modulation of the Renin-Angiotensin System

Cancer stem cells (CSCs) are proposed to be the cells that initiate tumorigenesis and maintain tumor development due to their self-renewal and multipotency properties. CSCs have been identified in many cancer types and are thought to be responsible for treatment resistance, metastasis, and recurrence. As such, targeting CSCs specifically should result in durable cancer treatment. One potential option for targeting CSCs is by manipulation of the renin-angiotensin system (RAS) and pathways that converge on the RAS with numerous inexpensive medications currently in common clinical use. In addition to its crucial role in cardiovascular and body fluid homeostasis, the RAS is vital for stem cell maintenance and differentiation and plays a role in tumorigenesis and cancer prevention, suggesting that these roles may converge and result in modulation of CSC function by the RAS. In support of this, components of the RAS have been shown to be expressed in many cancer types and have been more recently localized to the CSCs in some tumors. Given these roles of the RAS in tumor development, clinical trials using RAS inhibitors either singly or in combination with other therapies are underway in different cancer types. This review outlines the roles of the RAS, with respect to CSCs, and suggests that the presence of components of the RAS in CSCs could offer an avenue for therapeutic targeting using RAS modulators. Due to the nature of the RAS and its crosstalk with numerous other signaling pathways, a systems approach using traditional RAS inhibitors in combination with inhibitors of bypass loops of the RAS and other signaling pathways that converge on the RAS may offer a novel therapeutic approach to cancer treatment.

A Novel Angiotensin-(1-7) Glycosylated Mas Receptor Agonist for Treating Vascular Cognitive Impairment and Inflammation-Related Memory Dysfunction

Increasing evidence indicates that decreased brain blood flow, increased reactive oxygen species (ROS) production, and proinflammatory mechanisms accelerate neurodegenerative disease progression such as that seen in vascular contributions to cognitive impairment and dementia (VCID) and Alzheimer's disease and related dementias. There is a critical clinical need for safe and effective therapies for the treatment and prevention of cognitive impairment known to occur in patients with VCID and chronic inflammatory diseases such as heart failure (HF), hypertension, and diabetes. This study used our mouse model of VCID/HF to test our novel glycosylated angiotensin-(1-7) peptide Ang-1-6-O-Ser-Glc-NH2 (PNA5) as a therapy to treat VCID and to investigate circulating inflammatory biomarkers that may be involved. We demonstrate that PNA5 has greater brain penetration compared with the native angiotensin-(1-7) peptide. Moreover, after treatment with 1.0/mg/kg, s.c., for 21 days, PNA5 exhibits up to 10 days of sustained cognitive protective effects in our VCID/HF mice that last beyond the peptide half-life. PNA5 reversed object recognition impairment in VCID/HF mice and rescued spatial memory impairment. PNA5 activation of the Mas receptor results in a dose-dependent inhibition of ROS in human endothelial cells. Last, PNA5 treatment decreased VCID/HF-induced activation of brain microglia/macrophages and inhibited circulating tumor necrosis factor α, interleukin (IL)-7, and granulocyte cell-stimulating factor serum levels while increasing that of the anti-inflammatory cytokine IL-10. These results suggest that PNA5 is an excellent candidate and "first-in-class" therapy for treating VCID and other inflammation-related brain diseases.

Diversity-oriented submonomer synthesis of azapeptides mediated by the Mitsunobu reaction

A new approach featuring the Mitsunobu reaction for the convenient synthesis of azapeptides on a solid support.

The Role of Angiotensin–(1-7) in Cancer

The rationale to investigate the role of angiotensin-(1-7) [Ang-(1-7)] in cancer relies on the fact that the heptapeptide inhibits the growth of several cell lines. The first studies showed that Ang-(1-7) accelerated hematopoietic recovery in the peripheral blood and bone marrow after chemotherapy and inhibits lung cancer cell growth through the activation of Mas receptor. In this chapter, we summarize studies on the role of Ang-(1-7) in different types of cancer, especially lung, breast, prostate, hepatocellular cancers and in gliobalstoma multiforme (GBM). The antitumor effect of Ang-(1-7) was due to reduction of angiogenesis, cancer-associated fibrosis, osteoclastogenesis, tumor-induced inflammation, and metastasis as well as inhibition of cancer cell growth and proliferation. In clinical trials, Ang-(1-7) was well tolerated with limited toxic or quality-of-life side effects and showed clinical benefit in cancer patients with solid tumors. Further clinical trials are needed to confirm safety, to determine doses and clinical indications.

Long-Term Administration of Angiotensin (1-7) to db/db Mice Reduces Oxidative Stress Damage in the Kidneys and Prevents Renal Dysfunction

Aims

The goal of this study was to evaluate the effects of long-term (16 weeks) administration of angiotensin (1–7) [A(1–7)] on kidney function in db/db mice and to identify the protective mechanisms of this therapy.

Methods

db/db mice and heterozygous controls were treated with A(1–7) or vehicle daily, subcutaneously for up to 16 weeks. Kidney injury was assessed by measuring blood flow in renal arteries, plasma creatinine levels, and proteinuria. Effects of treatment on oxidative stress were evaluated by histological staining and gene expression.

Results

16 weeks of daily administration of A(1–7) to a mouse model of severe type 2 diabetes (db/db) prevented the progression of kidney damage. Treatment with A(1–7) improved blood flow in the renal arteries, as well as decreased plasma creatinine levels and proteinuria in diabetic mice. Reduction of oxidative stress was identified as one of the mechanisms of the renoprotective action of A(1–7). Treatment prevented formation of nitrotyrosine residues, a marker of oxidative stress damage. A(1–7) also reduced the expression of two enzymes involved in formation of nitrotyrosine, namely, eNOS and NOX-4. A(1–7) regulated the phosphorylation pattern of eNOS to enhance production of NO in diabetic animals, possibly through the Akt pathway. However, these elevated levels of NO did not result in increased nitrosylation, possibly due to reduced NOX-4 levels.

Conclusions

Long-term administration of A(1–7) improved kidney function and reduced oxidative stress damage in db/db mice.

AAV-Mediated angiotensin 1-7 overexpression inhibits tumor growth of lung cancer in vitro and in vivo

Ang-(1-7) inhibits lung cancer cell growth both in vitro and in vivo. However, the molecular mechanism of action is unclear and also the rapid degradation of Ang-(1-7) in vivo limits its clinical application. Here, we have demonstrated that Ang- (1-7) inhibits lung cancer cell growth by interrupting pre-replicative complex assembly and restrains epithelial-mesenchymal transition via Cdc6 inhibition. Furthermore, we constructed a mutant adeno-associated viral vector AAV8 (Y733F) that produced stable and high efficient Ang-(1-7) expression in a xenograft tumor model. The results show that AAV8-mediated Ang-(1-7) over-expression can remarkably suppress tumor growth in vivo by down-regulating Cdc6 and anti-angiogenesis. Ang-(1-7) over-expression via the AAV8 method may be a promising strategy for lung cancer treatment.

Angiotensin 1-7 Overexpression Mediated by a Capsid-optimized AAV8 Vector Leads to Significant Growth Inhibition of Hepatocellular Carcinoma In vivo

Background: Angiotensin-(1-7) [Ang-(1-7)] has been identified to inhibit the growth of many types of tumor cells both in vitro and in vivo. However, the rapid degradation of Ang-(1-7) in vivo limits its clinical application. Adeno-associated virus (AAV) serotype-8 is a remarkable vector for long-term in vivo gene delivery. Method: This study was designed to investigate the effects of AAV-mediated Ang-(1-7) overexpression on hepatocellular carcinoma. We first generated three different tyrosine (Y) to phenylalanine (F) mutants of AAV8 (Y447F, Y703F, Y708F) and evaluated their in vivo transduction efficiencies. Results: The data indicated that the Y703F mutant elicited a significant enhancement of liver gene delivery when compared with wild-type AAV8 (wtAAV8). The anti-tumor effect of Ang-(1-7) mediated by this optimized vector was evaluated in H22 hepatoma-bearing mice. Our results demonstrated that AAV-Ang-(1-7) persistently inhibited the growth of hepatocellular carcinoma by significantly downregulating angiogenesis. This was confirmed by observed decreases in the levels of the proangiogenic factors VEGF and PIGF. Conclusion: Collectively, these data suggest that Ang-(1-7) overexpression mediated by the optimized vector may be an effective alternative for hepatocellular carcinoma therapy due to its long-term and significant anti-tumor activity.

Future drug discovery in renin-angiotensin-aldosterone system intervention

INTRODUCTION

Renin-angiotensin-aldosterone system inhibitors (RAASIs), including angiotensin-converting enzyme inhibitors, angiotensin AT1 receptor blockers and mineralocorticoid receptor antagonists (MRAs), are the cornerstone for the treatment of cardiovascular and renal diseases. Areas covered: The authors searched MEDLINE, PubMed and ClinicalTrials.gov to identify eligible full-text English language papers. Herein, the authors discuss AT2-receptor agonists and ACE2/angiotensin-(1-7)/Mas-receptor axis modulators, direct renin inhibitors, brain aminopeptidase A inhibitors, biased AT1R blockers, chymase inhibitors, multitargeted drugs, vaccines and aldosterone receptor antagonists as well as aldosterone synthase inhibitors. Expert opinion: Preclinical studies have demonstrated that activation of the protective axis of the RAAS represents a novel therapeutic strategy for treating cardiovascular and renal diseases, but there are no clinical trials supporting our expectations. Non-steroidal MRAs might become the third-generation of MRAs for the treatment of heart failure, diabetes mellitus and chronic kidney disease. The main challenge for these new drugs is that conventional RAASIs are safe, effective and cheap generics. Thus, the future of new RAASIs will be directed by economical/strategic reasons.

Renin angiotensin system in liver diseases: Friend or foe?

In the last three decades, the understanding of the renin angiotensin system (RAS) has been changed by the discoveries of functional local systems, novel biologically active peptides, additional specific receptors, alternative pathways of angiotensin (Ang) II generation, and new roles for enzymes and precursor components other than those in Ang II synthesis. In this regard, the discovery that Ang-(1-7) opposes the pressor, proliferative, pro-fibrotic, and pro-inflammatory effects mediated by Ang II has contributed to the realization that the RAS is composed of two axes. The first axis consists of the angiotensin-converting enzyme (ACE), with Ang II as the end product, and the angiotensin type 1 (AT₁) receptor as the main effector mediating the biological actions of Ang II. The second axis results from ACE2-mediated hydrolysis of Ang II, leading to the production of Ang-(1-7), with the Mas receptor as the main effector conveying the vasodilatory, anti-proliferative, anti-fibrotic, and anti-inflammatory effects of Ang-(1-7). Experimental and clinical studies have shown that both axes of the RAS may take part in the pathogenesis of liver diseases. In this manuscript, we summarize the current evidence regarding the role of RAS in hepatic cirrhosis and its complications, including hemodynamic changes and hepatorenal syndrome. The therapeutic potential of the modulation of RAS molecules in liver diseases is also discussed.

Therapeutic uses for Angiotensin-(1-7)

INTRODUCTION

Angiotensin-(1-7) is a key component of the Renin-Angiotensin System, which can counter-regulate several deleterious effects caused by angiotensin II. Due to the potential for therapeutic use, several of its actions are specifically described in patents.

AREAS COVERED

In this review, the authors describe a plethora of therapeutic uses for Angiotensin-(1-7), claimed and supported by experimental evidence in patent documents and applications.

EXPERT OPINION

The clinical potential of Angiotensin-(1-7) as a therapeutic agent to treat several pathologies is evidenced by the variety of patents and clinical trials involving this peptide. Cancer treatment is one of the most advanced therapeutic areas, but clinical studies are also available in several other areas, such as cardiovascular, hematological, transplantation, surgical and medical procedures.

Long-term administration of angiotensin (1-7) prevents heart and lung dysfunction in a mouse model of type 2 diabetes (db/db) by reducing oxidative stress, inflammation and pathological remodeling

Congestive heart failure is one of the most prevalent and deadly complications of type 2 diabetes that is frequently associated with pulmonary dysfunction. Among many factors that contribute to development and progression of diabetic complications is angiotensin II (Ang2). Activation of pathological arm of renin-angiotensin system results in increased levels of Ang2 and signaling through angiotensin type 1 receptor. This pathway is well recognized for its role in induction of oxidative stress (OS), inflammation, hypertrophy and fibrosis. Angiotensin (1-7) [A(1-7)], through activation of Mas receptor, opposes the actions of Ang2 which can result in the amelioration of diabetic complications; enhancing the overall welfare of diabetic patients. In this study, 8 week-old db/db mice were administered A(1-7) daily via subcutaneous injections. After 16 weeks of treatment, echocardiographic assessment of heart function demonstrated significant improvement in cardiac output, stroke volume and shortening fraction in diabetic animals. A(1-7) also prevented cardiomyocyte hypertrophy, apoptosis, lipid accumulation, and decreased diabetes-induced fibrosis and OS in the heart tissue. Treatment with A(1-7) reduced levels of circulating proinflammatory cytokines that contribute to the low grade inflammation observed in diabetes. In addition, lung pathologies associated with type 2 diabetes, including fibrosis and congestion, were decreased with treatment. OS and macrophage infiltration were also reduced in the lungs after treatment with A(1-7). Long-term administration of A(1-7) to db/db mice is effective in improving heart and lung function in db/db mice. Treatment prevented pathological remodeling of the tissues and reduced OS, fibrosis and inflammation.

Brain angiotensin-(1-7)/Mas axis: A new target to reduce the cardiovascular risk to emotional stress

Emotional stress is now considered a risk factor for several diseases including cardiac arrhythmias and hypertension. It is well known that the activation of neuroendocrine and autonomic mechanisms features the response to emotional stress. However, its link to cardiovascular diseases and the regulatory mechanisms involved remain to be further comprehended. The renin-angiotensin system (RAS) plays an important role in homeostasis on all body systems. Specifically in the brain, the RAS regulates a number of physiological aspects. Recent data indicate that the activation of angiotensin-converting enzyme/angiotensin II/AT1 receptor axis facilitates the emotional stress responses. On the other hand, growing evidence indicates that its counterregulatory axis, the angiotensin-converting enzyme 2 (ACE2)/(Ang)iotensin-(1-7)/Mas axis, reduces anxiety and attenuates the physiological responses to emotional stress. The present review focuses on angiotensin-(1-7)/Mas axis as a promising target to attenuate the physiological response to emotional stress reducing the risk of cardiovascular diseases.

ACE inhibition, ACE2 and angiotensin-(1-7) axis in kidney and cardiac inflammation and fibrosis

The Renin Angiotensin System (RAS) is a pivotal physiological regulator of heart and kidney homeostasis, but also plays an important role in the pathophysiology of heart and kidney diseases. Recently, new components of the RAS have been discovered, including angiotensin converting enzyme 2 (ACE2), Angiotensin(Ang)-(1-7), Mas receptor, Ang-(1-9) and Alamandine. These new components of RAS are formed by the hydrolysis of Ang I and Ang II and, in general, counteract the effects of Ang II. In experimental models of heart and renal diseases, Ang-(1-7), Ang-(1-9) and Alamandine produced vasodilation, inhibition of cell growth, anti-thrombotic, anti-inflammatory and anti-fibrotic effects. Recent pharmacological strategies have been proposed to potentiate the effects or to enhance the formation of Ang-(1-7) and Ang-(1-9), including ACE2 activators, Ang-(1-7) in hydroxypropyl β-cyclodextrin, cyclized form of Ang-(1-7) and nonpeptide synthetic Mas receptor agonists. Here, we review the role and effects of ACE2, ACE2 activators, Ang-(1-7) and synthetic Mas receptor agonists in the control of inflammation and fibrosis in cardiovascular and renal diseases and as counter-regulators of the ACE-Ang II-AT1 axis. We briefly comment on the therapeutic potential of the novel members of RAS, Ang-(1-9) and alamandine, and the interactions between classical RAS inhibitors and new players in heart and kidney diseases.

Regulatory aspects of small molecule drugs for heart regeneration

Even though recent discoveries prove the existence of cardiac progenitor cells, internal regenerative capacity of the heart is minimal. As cardiovascular disease is the leading cause of deaths in the United States, a number of approaches are being used to develop treatments for heart repair and regeneration. Small molecule drugs are of particular interest as they are suited for oral administration and can be chemically synthesized. However, the regulatory process for the development of new treatment modalities is protracted, complex and expensive. One of the hurdles to development of appropriate therapies is the need for predictive preclinical models. The use of patient-derived cardiomyocytes from iPSC cells represents a novel tool for this purpose. Among other concepts for induction of heart regeneration, the most advanced is the combination of DPP-IV inhibitors with stem cell mobilizers. This review will focus on regulatory aspects as well as preclinical hurdles of development of new treatments for heart regeneration.

Identification of intracellular proteins and signaling pathways in human endothelial cells regulated by angiotensin-(1-7)

The study aimed to identify proteins regulated by the cardiovascular protective peptide angiotensin-(1-7) and to determine potential intracellular signaling cascades. Human endothelial cells were stimulated with Ang-(1-7) for 1 h, 3 h, 6 h, and 9 h. Peptide effects on intracellular signaling were assessed via antibody microarray, containing antibodies against 725 proteins. Bioinformatics software was used to identify affected intracellular signaling pathways. Microarray data was verified exemplarily by Western blot, Real-Time RT-PCR, and immunohistochemical studies. The microarray identified 110 regulated proteins after 1 h, 119 after 3 h, 31 after 6 h, and 86 after 9 h Ang-(1-7) stimulation. Regulated proteins were associated with high significance to several metabolic pathways like “Molecular Mechanism of Cancer” and “p53 signaling” in a time dependent manner. Exemplarily, Western blots for the E3-type small ubiquitin-like modifier ligase PIAS2 confirmed the microarray data and displayed a decrease by more than 50% after Ang-(1-7) stimulation at 1 h and 3 h without affecting its mRNA. Immunohistochemical studies with PIAS2 in human endothelial cells showed a decrease in cytoplasmic PIAS2 after Ang-(1-7) treatment. The Ang-(1-7) mediated decrease of PIAS2 was reproduced in other endothelial cell types. The results suggest that angiotensin-(1-7) plays a role in metabolic pathways related to cell death and cell survival in human endothelial cells.

New Approaches in the Treatment of Hypertension

Hypertension is the most common modifiable risk factor for cardiovascular disease and death, and lowering blood pressure with antihypertensive drugs reduces target organ damage and prevents cardiovascular disease outcomes. Despite a plethora of available treatment options, a substantial portion of the hypertensive population has uncontrolled blood pressure. The unmet need of controlling blood pressure in this population may be addressed, in part, by developing new drugs and devices/procedures to treat hypertension and its comorbidities. In this Compendium Review, we discuss new drugs and interventional treatments that are undergoing preclinical or clinical testing for hypertension treatment. New drug classes, eg, inhibitors of vasopeptidases, aldosterone synthase and soluble epoxide hydrolase, agonists of natriuretic peptide A and vasoactive intestinal peptide receptor 2, and a novel mineralocorticoid receptor antagonist are in phase II/III of development, while inhibitors of aminopeptidase A, dopamine β-hydroxylase, and the intestinal Na + /H + exchanger 3, agonists of components of the angiotensin-converting enzyme 2/angiotensin(1–7)/Mas receptor axis and vaccines directed toward angiotensin II and its type 1 receptor are in phase I or preclinical development. The two main interventional approaches, transcatheter renal denervation and baroreflex activation therapy, are used in clinical practice for severe treatment resistant hypertension in some countries. Renal denervation is also being evaluated for treatment of various comorbidities, eg, chronic heart failure, cardiac arrhythmias and chronic renal failure. Novel interventional approaches in early development include carotid body ablation and arteriovenous fistula placement. Importantly, none of these novel drug or device treatments has been shown to prevent cardiovascular disease outcomes or death in hypertensive patients.

Angiotensin-(1-7) improves oxygenation, while reducing cellular infiltrate and fibrosis in experimental Acute Respiratory Distress Syndrome

Background

The renin-angiotensin system (RAS) plays a role in the pathogenesis of ARDS, Angiotensin II (Ang-II) contributing to the pathogenesis of inflammation and fibrogenesis. Angiotensin-(1-7) (Ang-(1-7)) may antagonize the effects of Ang-II. This study was aimed at evaluating the potential for Ang-(1-7) to reduce injury, inflammation and fibrosis in an experimental model of ARDS in the acute and late phases.

Methods

Male Sprague Dawley rats underwent an instillation of 0.1 M hydrochloric acid (HCl, 2.5 ml/kg) into the right bronchus. In an acute ARDS study, acid-injured rats were subjected to high stretch mechanical ventilation (18 ml/kg) for 5 h and randomized to receive an intravenous infusion of either vehicle (saline), Ang-(1-7) at low dose(0.27 μg/kg/h) (ALD), or high dose (60 μg/kg/h) (AHD) starting simultaneously with injury or 2 h afterwards. Arterial blood gas analysis and bronchoalveolar lavage (BAL) were performed to assess the injury. For the late ARDS study, after HCl instillation rats were randomized to either vehicle or high dose Ang-(1-7) (300 μg/kg/day) infused by mini osmotic pumps for two weeks, and lung hydroxyproline content measured.

Results

In the acute ARDS study, Ang-(1-7) led to a significant improvement in oxygenation (PaO₂/FiO₂ : vehicle 359 ± 86; ALD 436 ± 72; AHD 44 442 ± 56; ANOVA p = 0.007) and reduced white blood cells counts (vehicle 4,519 ± 2,234; ALD 2,496 ± 621; AHD 2,744 ± 119/mm³; ANOVA p = 0.004). Only treatment with high dose Ang-(1-7) reduced inflammatory cell numbers in BAL (vehicle 127 ± 34; AHD 96 ± 34/ μl; p = 0.033). Interestingly also delayed administration of Ang-(1-7) was effective in reducing injury. In later ARDS, Ang-(1-7) decreased hydroxyproline content (649 ± 202 and 1,117 ± 297 μg/lung; p < 0.05).

Conclusions

Angiotensin-(1-7), decreased the severity of acute lung injury and inflammation induced by combined acid aspiration and high stretch ventilation. Furthermore, continuous infusion of Ang-(1-7) reduced lung fibrosis 2 weeks following acid aspiration injury. These results call for further research on Ang-(1-7) as possible therapy for ARDS.

G-protein coupled receptors of the renin-angiotensin system: new targets against breast cancer?

G-protein coupled receptors (GPCRs) constitute the largest family of membrane receptors, with high potential for drug discovery. These receptors can be activated by a panel of different ligands including ions, hormones, small molecules, and vasoactive peptides. Among those, angiotensins [angiotensin II (AngII) and angiotensin 1–7] are the major biologically active products of the classical and alternative renin-angiotensin system (RAS). These peptides bind and activate three different subtypes of GPCRs, namely AT1, AT2, and Mas receptors, to regulate cardiovascular functions. Over the past decade, the contribution of several RAS components in tumorigenesis has emerged as a novel important concept, AngII being considered as harmful and Ang1–7 as protective against cancer. Development of selective ligands targeting each RAS receptor may provide novel and efficient targeted therapeutic strategies against cancer. In this review, we focus on breast cancer to summarize current knowledge on angiotensin receptors (AT1, AT2, and Mas), and discuss the potential use of angiotensin receptor agonists and antagonists in clinics.

Effect of a stable Angiotensin-(1-7) analogue on progenitor cell recruitment and cardiovascular function post myocardial infarction

Background

Angiotensin‐(1–7) improves cardiac function and remodeling after myocardial infarction (MI). This may involve recruitment of hematopoietic progenitor cells that support angiogenesis. However, angiotensin‐(1–7) is rapidly metabolized in plasma and tissue. The authors investigated in mice the effect of a metabolically stable angiotensin‐(1–7) analogue, cyclic angiotensin‐(1–7), on progenitor cell recruitment and on the heart post MI, when given in the angiogenesis phase of remodeling.

Methods and Results

Angiogenic progenitor cell recruitment was measured by using flow cytometry 24 and 72 hours after a daily bolus injection of cyclic angiotensin‐(1–7) in healthy C57BL/6 mice. Further, mice underwent MI or sham surgery and subsequently received saline or 2 different doses of cyclic angiotensin‐(1–7) for 3 or 9 weeks. Cyclic angiotensin‐(1–7) increased circulating hematopoietic progenitor cells at 24 hours but not 72 hours. Post MI, cyclic angiotensin‐(1–7) diminished cardiomyocyte hypertrophy and reduced myogenic tone, without altering cardiovascular function or cardiac histology at 9 weeks. Importantly, cyclic angiotensin‐(1–7)–treated mice had reduced cardiac capillary density at 3 weeks after MI but not after 9 weeks. Finally, cyclic angiotensin‐(1–7) decreased tube formation by cultured human umbilical vein endothelial cells.

Conclusions

Our results suggest that cyclic angiotensin‐(1–7), when given early after MI, recruits progenitor cells but does not lead to improved angiogenesis, most likely because it simultaneously exerts antiangiogenic effect in adult endothelial cells. Apparently, optimal treatment with cyclic angiotensin‐(1–7) depends on the time point of onset of application after MI.

Angiotensin-(1-7): A Novel Peptide to Treat Hypertension and Nephropathy in Diabetes?

The renin-angiotensin system (RAS) plays a pivotal role in mammalian homeostasis physiology. The RAS can be delineated into a classical RAS (the pressor arm) including angiotensinogen (Agt), renin, angiotensin-converting enzyme (ACE), angiotensin II (Ang II) and angiotensin type 1 receptor (AT1R), and a counterbalancing novel RAS (the depressor arm) including Agt, renin, angiotensin-converting enzyme-2 (ACE-2), angiotensin-(1-7) (Ang 1-7) and Ang 1-7 receptor (or Mas receptor (MasR)). Hyperglycemia (diabetes) induces severe tissue oxidative stress, which stimulates the pressor arm of the renal RAS axis and leads to an increase in ACE/ACE-2 ratio, with excessive formation of Ang II. There is a growing body of evidence for beneficial effects of the depressor arm of RAS (ACE-2/Ang 1-7/MasR) axis in diabetes, hypertension and several other diseased conditions. Evidence from in vitro, in vivo and clinical studies reflects anti-oxidant, anti-fibrotic, and anti-inflammatory properties of Ang 1-7. Most of the currently available therapies only target suppression of the pressor arm of RAS with angiotensin receptor blockers (ARBs) and ACE inhibitors (ACEi). However, it is time to consider simultaneous activation of the depressor arm for more effective outcomes. This review summarizes the recent updates on the protective role of Ang 1-7 in hypertension and kidney injury in diabetes, as well as the possible underlying mechanism(s) of Ang 1-7 action, suggesting that the ACE-2/Ang 1-7/MasR axis can be developed as a therapeutic target for the treatment of diabetes-induced hypertension and renal damage.

Angiotensin-converting enzyme 2 and angiotensin 1-7: novel therapeutic targets

Angiotensin-converting enzyme (ACE) 2 and its product angiotensin 1–7 are thought to have effects that counteract the adverse actions of other, better-known renin–angiotensin system (RAS) components

Numerous experimental studies have suggested that ACE2 and angiotensin 1–7 have notable protective effects in the heart and blood vessels

ACE2-mediated catabolism of angiotensin II is likely to have a major role in cardiovascular protection, whereas the functional importance and signalling mechanisms of angiotensin-1–7-induced actions remain unclear

New pharmacological interventions targeting ACE2 are expected to be useful in clinical treatment of cardiovascular disease, especially those associated with overactivation of the conventional RAS

More studies, especially randomized controlled clinical trials, are needed to clearly delineate the benefits of therapies targeting angiotensin 1–7 actions

Angiotensin-converting enzyme 2, and its product angiotensin 1–7, are thought to have counteracting effects against the adverse actions of the better-known members of the renin–angiotensin system and might, therefore, be useful therapeutic targets in patients with cardiovascular disease. Professor Jiang and colleagues review the evidence for the potential roles of these proteins in various cardiovascular conditions, including hypertension, atherosclerosis, myocardial remodelling, heart failure, ischaemic stroke, and diabetes.

The renin–angiotensin system (RAS) has pivotal roles in the regulation of normal physiology and the pathogenesis of cardiovascular disease. Angiotensin-converting enzyme (ACE) 2, and its product angiotensin 1–7, are thought to have counteracting effects against the adverse actions of other, better known and understood, members of the RAS. The physiological and pathological importance of ACE2 and angiotensin 1–7 in the cardiovascular system are not completely understood, but numerous experimental studies have indicated that these components have protective effects in the heart and blood vessels. Here, we provide an overview on the basic properties of ACE2 and angiotensin 1–7 and a summary of the evidence from experimental and clinical studies of various pathological conditions, such as hypertension, atherosclerosis, myocardial remodelling, heart failure, ischaemic stroke, and diabetes mellitus. ACE2-mediated catabolism of angiotensin II is likely to have a major role in cardiovascular protection, whereas the relevant functions and signalling mechanisms of actions induced by angiotensin 1–7 have not been conclusively determined. The ACE2–angiotensin 1–7 pathway, however, might provide a useful therapeutic target for the treatment of cardiovascular disease, especially in patients with overactive RAS.