The Influence of Angiotensin Peptides on Survival and Motility of Human High-Grade Serous Ovarian Cancer Cells in Serum Starvation Conditions

High-grade serous ovarian carcinoma (HGSOC) is the most frequent and malignant form of ovarian cancer. A local renin–angiotensin system (RAS) has been found in the ovary, and changes in selected components of this system were observed in pathological states and also in ovarian cancer. In the present study, we examined the effect of three peptides, Ang-(1-7), Ang-(1-9) and Ang-(3-7), on proliferation and motility of the OVPA8 cell line, a new well-defined and preclinical model of HGSOC. We confirmed the presence of mRNA for all angiotensin receptors in the tested cells. Furthermore, our findings indicate that all tested angiotensin peptides increased the metabolic serum in the medium by activation of cell defense mechanisms such as nuclear factor kappaB signaling pathway andapoptosis. Moreover, tested angiotensin peptides intensified serum starvation-induced cell cycle arrest at the G0/G1 phase. In the case of Ang-(3-7), a significant decrease in the number of Ki67 positive cells (Ki67+) and reduced percentage of activated ERK1/2 levels in ovarian cancer cells were additionally reported. The angiotensin-induced effect of the accumulation of cells in the G0/G1 phase was not observed in OVPA8 cells growing on the medium with 10% FBS. Moreover, in the case of Ang-(3-7), the tendency was quite the opposite. Ang-(1-7) but not Ang-(1-9) or Ang-(3-7) increased the mobility of reluctant-to-migrate OVAP8 cells cultured in the serum-free medium. In any cases, the changes in the expression of VIM and HIF1A gene, associated with epithelial–mesenchymal transition (EMT), were not observed. In conclusion, we speculate that the adaptation to starvation in nutrient-deprived tumors can be modulated by peptides from the renin–angiotensin system. The influence of angiotensin peptides on cancer cells is highly dependent on the availability of growth factors and nutrients.

Dysregulation of ACE (Angiotensin-Converting Enzyme)-2 and Renin-Angiotensin Peptides in SARS-CoV-2 Mediated Mortality and End-Organ Injuries

ACE (angiotensin-converting enzyme)-2 as the target for SARS-CoV-2 also negatively regulates the renin-angiotensin system. Pathological activation of ADAM17 (A disintegrin and metalloproteinase-17) may potentiate inflammation and diminish ACE2-mediated tissue protection through proteolytic shedding, contributing to SARS-CoV-2 pathogenesis. We aim to examine plasma soluble ACE2 and angiotensin profiles in relation to outcomes by enrolling consecutive patients admitted for COVID-19 with baseline blood collection at admission and repeated sampling at 7 days. The primary outcome was 90-day mortality, and secondary outcomes were the incidence of end-organ injuries. Overall, 242 patients were included, the median age was 63 (52–74) years, 155 (64.0%) were men, and 57 (23.6%) patients reached the primary end point. Baseline soluble ACE2 was elevated in COVID-19 but was not associated with disease severity or mortality. In contrast, an upward trajectory of soluble ACE2 at repeat sampling was independently associated with an elevated risk of mortality and incidence of acute myocardial injury and circulatory shock. Similarly, an increase in soluble tumor necrosis factor receptor levels was also associated with adverse outcomes. Plasma Ang I, Ang 1-7 (angiotensin 1–7) levels, and the Ang 1-7/Ang II (angiotensin II) ratio were elevated during SARS-CoV-2 infection related to downregulation of ACE activity at baseline. Moreover, patients having an upward trajectory of soluble ACE2 were characterized by an imbalance in the Ang 1-7/Ang II ratio. The observed dysregulation of ACE2 and angiotensin peptides with disease progression suggest a potential role of ADAM17 inhibition and enhancing the beneficial Ang 1-7/Mas axis to improve outcomes against SARS-CoV-2 infection.

Molecular basis of a redox switch: molecular dynamics simulations and surface plasmon resonance provide insight into reduced and oxidised angiotensinogen

Angiotensinogen fine-tunes the tightly controlled activity of the renin-angiotensin system by modulating the release of angiotensin peptides that control blood pressure. One mechanism by which this modulation is achieved is via angiotensinogen’s Cys18 – Cys138 disulfide bond that acts as a redox switch. Molecular dynamics simulations of each redox state of angiotensinogen reveal subtle dynamic differences between the reduced and oxidised forms, particularly at the N-terminus. Surface plasmon resonance data demonstrate that the two redox forms of angiotensinogen display different binding kinetics to an immobilised anti-angiotensinogen monoclonal antibody. Mass spectrometry mapped the epitope for the antibody to the N-terminal region of angiotensinogen. We therefore provide evidence that the different redox forms of angiotensinogen can be detected by an antibody-based detection method.

Interaction between Angiotensinase Activities in Pituitary and Adrenal Glands of Wistar–Kyoto and Spontaneously Hypertensive Rats under Hypotensive or Hypertensive Treatments

In the present study, we analyzed the activity of several aminopeptidases (angiotensinases) involved in the metabolism of various angiotensin peptides, in pituitary and adrenal glands of untreated Wistar–Kyoto (WKY) and spontaneously hypertensive rats (SHR) or treated with the antihypertensive drugs captopril and propranolol or with the L-Arginine hypertensive analogue L-NG-Nitroarginine Methyl Ester (L-NAME). Intra- and inter-gland correlations between angiotensinase activities were also calculated. Membrane-bound alanyl-, cystinyl-, and glutamyl-aminopeptidase activities were determined fluorometrically using aminoacyl-β-naphthylamide as substrates. Depending on the type of angiotensinase analyzed, the results reflect a complex picture showing substantial differences between glands, strains, and treatments. Alanyl-aminopeptidase responsible for the metabolism of Ang III to Ang IV appears to be the most active angiotensinase in both pituitary and adrenals of WKY and particularly in SHR. Independently of treatment, most positive correlations are observed in the pituitary gland of WKY whereas such positive correlations are predominant in adrenals of SHR. Negative inter-gland correlations were observed in control SHR and L-NAME treated WKY. Positive inter-gland correlations were observed in captopril-treated SHR and propranolol-treated WKY. These results may reflect additional mechanisms for increasing or decreasing systolic blood pressure in WKY or SHR.

Loss of Hepatic Angiotensinogen Attenuates Sepsis-Induced Myocardial Dysfunction

Rationale: The renin-angiotensin system (RAS) is a complex regulatory network that maintains normal physiological functions. The role of the RAS in sepsis-induced myocardial dysfunction (SIMD) is poorly defined. Angiotensinogen (AGT) is the unique precursor of the RAS and gives rise to all angiotensin peptides. The effects and mechanisms of AGT in development of SIMD have not been defined. Objective: To determine a role of AGT in SIMD and investigate the underlying mechanisms. Methods and Results: Either intraperitoneal injection of lipopolysaccharide (LPS) or cecal ligation and puncture (CLP) significantly enhanced AGT abundances in liver, heart, and plasma. Deficiency of hepatocyte-derived AGT (hepAGT), rather than cardiomyocyte-derived AGT (carAGT), alleviated septic cardiac dysfunction in mice and prolonged survival time. Further investigations revealed that the effects of hepAGT on SIMD were partially associated with augmented angiotensin II (AngII) production in circulation. In addition, hepAGT was internalized by LDL receptor-related protein 1 (LRP1) in cardiac fibroblasts (CF), and subsequently activated NLRP3 inflammasome via an AngII-independent pathway, ultimately promoting SIMD by suppressing Sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) abundances in cardiomyocytes (CM). Conclusions: HepAGT promoted SIMD via both AngII-dependent and AngII-independent pathways. We identified a liver-heart axis by which AGT regulated development of SIMD. Our study may provide a potential novel therapeutic target for SIMD.

Angiotensinogen and the Modulation of Blood Pressure

The angiotensin peptides that control blood pressure are released from the non-inhibitory plasma serpin, angiotensinogen, on cleavage of its extended N-terminal tail by the specific aspartyl-protease, renin. Angiotensinogen had previously been assumed to be a passive substrate, but we describe here how recent studies reveal an inherent conformational mechanism that is critical to the cleavage and release of the angiotensin peptides and consequently to the control of blood pressure. A series of crystallographic structures of angiotensinogen and its derivative forms, together with its complexes with renin show in molecular detail how the interaction with renin triggers a profound shift of the amino-terminal tail of angiotensinogen with modulation occurring at several levels. The tail of angiotensinogen is restrained by a labile disulfide bond, with changes in its redox status affecting angiotensin release, as demonstrably so in the hypertensive complication of pregnancy, pre-eclampsia. The shift of the tail also enhances the binding of renin through a tail-in-mouth allosteric mechanism. The N-terminus is now seen to insert into a pocket equivalent to the hormone-binding site on other serpins, with helix H of angiotensinogen unwinding to form key interactions with renin. The findings explain the precise species specificity of the interaction with renin and with variant carbohydrate linkages. Overall, the studies provide new insights into the physiological regulation of angiotensin release, with an ability to respond to local tissue and temperature changes, and with the opening of strategies for the development of novel agents for the treatment of hypertension.

Increased circulating levels of angiotensin-(1-7) in severely ill COVID-19 patients

The mono-carboxypeptidase Angiotensin-Converting Enzyme 2 (ACE2) is an important “player” of the renin-angiotensin system (RAS). ACE2 is also the receptor for SARS-CoV-2, the new coronavirus that causes COVID-19. It has been hypothesized that following SARS-CoV-2/ACE2 internalization Ang II level would increase in parallel to a decrease of Ang-(1-7) in COVID-19 patients. In this preliminary report, we analyzed the plasma levels of angiotensin peptides in 19 severe COVID-19 patients and 19 non-COVID-19 volunteers, to assess potential outcome associations. Unexpectedly, a significant increase in circulating Ang-(1-7) and lower Ang II plasma level were found in critically ill COVID-19 patients. Accordingly, an increased Ang-(1-7)/ Ang II ratio was observed in COVID-19 suggesting a RAS dysregulation toward an increased formation of Ang-(1-7) in these patients.