Alamandine and Its Receptor MrgD Pair Up to Join the Protective Arm of the Renin-Angiotensin System

Alamandin and especially melatonin attenuate pulmonary arterial hypertension induced by monocrotalin

BACKGROUND

Despite the available treatments, pulmonary arterial hypertension (PAH) prognosis is poor.

OBJECTIVES

We aimed to investigate the effects of the alamandine (ALA), melatonin (MEL), and ALA + MEL in PAH.

METHODS

The rats were randomly divided into Control (n = 10), monocrotaline (MCT) (n = 12), ALA (n = 12), MEL (n = 12), and ALA + MEL (n = 12) groups. PAH was induced by MCT. The ALA, MEL, and ALA + MEL groups received 50 μg/kg/day ALA, 10 mg/kg/day MEL, and ALA + MEL, respectively, for 35 days. Echocardiographic and hemodynamic measurements and tissue analyses (morphometric, histopathological, ELISA, and western blot) were performed.

RESULTS

Monotherapies, especially MEL, reduced the right ventricular (RV) systolic pressure. Only MEL increased the pulmonary artery acceleration time. MCT increased the RV/left ventricle (LV) + interventricular septum (IVS) ratio. While ALA and ALA + MEL slightly decreased the RV/(LV + IVS), MEL significantly restored it. MCT increased the tunica intima-media (TIM) thickness, PCNA and α-SMA of pulmonary arterioles, histopathological score (HS) (inflammatory infiltration etc.) of the lung, and RV. All treatments reduced the TIM thickness (especially MEL), PCNA, and α-SMA. All treatments significantly decreased the HS of the lung; however, MEL and ALA + MEL produced greater benefits. All treatments attenuated the HS of RV. MCT caused a significant increase in lung lysyl oxidase (LOX) activity. All treatments restored the LOX; however, MEL and ALA + MEL provided greater improvement. While lung Nrf-2 was increased in MCT-treated rats, MEL reduced it.

CONCLUSION

ALA, MEL, and ALA + MEL attenuate PAH and protect RV via antiproliferative, anti-remodeling, antihypertrophic, anti-inflammatory, and free radical scavenging (only MEL) capabilities. Overall, MEL produced the best outcomes.

Mas-related G protein-coupled receptors in gastrointestinal dysfunction and inflammatory bowel disease: A review

Inflammatory bowel disease (IBD) is a chronic debilitating condition, hallmarked by persistent inflammation of the gastrointestinal tract. Despite recent advances in clinical treatments, the aetiology of IBD is unknown, and a large proportion of patients are refractory to pharmacotherapy. Understanding IBD immunopathogenesis is crucial to discern the cause of IBD and optimise treatments. Mas-related G protein-coupled receptors (Mrgprs) are a family of approximately 50 G protein-coupled receptors that were first identified over 20 years ago. Originally known for their expression in skin nociceptors and their role in transmitting the sensation of itch in the periphery, new reports have described the presence of Mrgprs in the gastrointestinal tract. In this review, we consider the impact of these findings and assess the evidence that suggests that Mrgprs may be involved in the disrupted homeostatic processes that contribute to gastrointestinal disorders and IBD. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Adaptive and maladaptive roles of different angiotensin receptors in the development of cardiac hypertrophy and heart failure

Angiotensin II (Ang II) is formed by the action of angiotensin-converting enzyme (ACE) in the renin-angiotensin system. This hormone is known to induce cardiac hypertrophy and heart failure and its actions are mediated by the interaction of both pro- and antihypertrophic Ang II receptors (AT1R and AT2R). Ang II is also metabolized by ACE 2 to Ang-(1-7), which elicits the activation of Mas receptors (MasR) for inducing antihypertrophic actions. Since heart failure under different pathophysiological situations is preceded by adaptive and maladaptive cardiac hypertrophy, we have reviewed the existing literature to gain some information regarding the roles of AT1R, AT2R, and MasR in both acute and chronic conditions of cardiac hypertrophy. It appears that the activation of AT1R may be involved in the development of adaptive and maladaptive cardiac hypertrophy as well as subsequent heart failure because both ACE inhibitors and AT1R antagonists exert beneficial effects. On the other hand, the activation of both AT2R and MasR may prevent the occurrence of maladaptive cardiac hypertrophy and delay the progression of heart failure, and thus therapy with different activators of these antihypertrophic receptors under chronic pathological stages may prove beneficial. Accordingly, it is suggested that a great deal of effort should be made to develop appropriate activators of both AT2R and MasR for the treatment of heart failure subjects.

ACE inhibitors and their interaction with systems and molecules involved in metabolism

The main function of the renin-angiotensin-aldosterone system (RAAS) is the regulation of blood pressure; therefore, researchers have focused on its study to treat cardiovascular and renal diseases. One of the most widely used treatments derived from the study of RAAS, is the use of angiotensin-converting enzyme inhibitors (ACEi). Since it was discovered, the main target of ACEi has been the cardiovascular and renal systems. However, being the RAAS expressed locally in several specialized tissues and cells such as pneumocytes, hepatocytes, spleenocytes, enterocytes, adipocytes, and neurons the effect of inhibitors has expanded, because it is expected that RAAS has a role in the specific function of those cells. Many chronic degenerative diseases compromise the correct function of those organs, and in most of them, the RAAS is overactivated. Therefore, the use of ACEi must exert a benefit on an impaired system. Accordingly, the objective of this review is to present a brief overview of the cardiovascular and renal actions of ACEi and its effects in organs that are not the classic targets of ACEi that carry on glucose and lipid metabolism.

The Expression of Alamandine Receptor MrgD in Clear Cell Renal Cell Carcinoma Is Associated with a Worse Prognosis and Unfavorable Response to Antiangiogenic Therapy

Renal cell carcinoma (RCC) ranks among the most prevalent malignancies in Western countries, marked by its notable heterogeneity, which contributes to an unpredictable clinical trajectory. The insufficiency of dependable biomarkers adds complexity to assessing this tumor progression. Imbalances of several components of the intrarenal renin-angiotensin system (iRAS) significantly impact patient prognoses and responses to first-line immunotherapies. In this study, we analyzed the immunohistochemical expression of the Mas-related G-protein-coupled receptor D (MrgD), which recognizes the novel RAS peptide alamandine (ALA), in a series of 87 clear cell renal cell (CCRCCs), 19 papillary (PRCC), 7 chromophobe (ChRCC) renal cell carcinomas, and 11 renal oncocytomas (RO). MrgD was expressed in all the renal tumor subtypes, with a higher mean staining intensity in the PRCCs, ChRCCs, and ROs. A high expression of MrgD at the tumor center and at the infiltrative front of CCRCC tissues was significantly associated with a high histological grade, large tumor diameter, local invasion, and locoregional node and distant metastasis. Patients with worse 5-year cancer-specific survival and a poorer response to antiangiogenic tyrosine-kinase inhibitors (TKIs) showed higher MrgD expression at the center of their primary tumors. These findings suggest a possible role of MrgD in renal carcinogenetic processes. Further studies are necessary to unveil its potential as a novel biomarker for CCRCC prognosis and response to frontline therapies.

Novel Insights into the Cardioprotective Effects of the Peptides of the Counter-Regulatory Renin-Angiotensin System

Currently, cardiovascular diseases are a major contributor to morbidity and mortality worldwide, having a significant negative impact on both the economy and public health. The renin-angiotensin system contributes to a high spectrum of cardiovascular disorders and is essential for maintaining normal cardiovascular homeostasis. Overactivation of the classical renin-angiotensin system is one of the most important pathophysiological mechanisms in the progression of cardiovascular diseases. The counter-regulatory renin-angiotensin system is an alternate pathway which favors the synthesis of different peptides, including Angiotensin-(1-7), Angiotensin-(1-9), and Alamandine. These peptides, via the angiotensin type 2 receptor (AT2R), MasR, and MrgD, initiate multiple downstream signaling pathways that culminate in the activation of various cardioprotective mechanisms, such as decreased cardiac fibrosis, decreased myocardial hypertrophy, vasodilation, decreased blood pressure, natriuresis, and nitric oxide synthesis. These cardioprotective effects position them as therapeutic alternatives for reducing the progression of cardiovascular diseases. This review aims to show the latest findings on the cardioprotective effects of the main peptides of the counter-regulatory renin-angiotensin system.

Alamandine attenuates ovariectomy-induced osteoporosis by promoting osteogenic differentiation via AMPK/eNOS axis

BACKGROUND

Alamandine is a newly characterized peptide of renin angiotensin system. Our study aims to investigate the osteo-preservative effects of alamandine, explore underlying mechanism and bring a potential preventive strategy for postmenopausal osteoporosis in the future.

METHODS

An ovariectomy (OVX)-induced rat osteoporosis model was established for in vivo experiments. Micro-computed tomography and three-point bending test were used to evaluate bone strength. Histological femur slices were processed for immunohistochemistry (IHC). Bone turnover markers and nitric oxide (NO) concentrations in serum were determined with enzyme-linked immunosorbent assay (ELISA). The mouse embryo osteoblast precursor (MC3T3-E1) cells were used for in vitro experiments. The cell viability was analysed with a Cell Counting Kit‑8. We performed Alizarin Red S staining and alkaline phosphatase (ALP) activity assay to observe the differentiation status of osteoblasts. Western blotting was adopted to detect the expression of osteogenesis related proteins and AMP-activated protein kinase/endothelial nitric oxide synthase (AMPK/eNOS) in osteoblasts. DAF-FM diacetate was used for semi-quantitation of intracellular NO.

RESULTS

In OVX rats, alamandine alleviated osteoporosis and maintained bone strength. The IHC showed alamandine increased osteocalcin and collagen type I α1 (COL1A1) expression. The ELISA revealed alamandine decreased bone turnover markers and restored NO level in serum. In MC3T3-E1 cells, alamandine promoted osteogenic differentiation. Western blotting demonstrated that alamandine upregulated the expression of osteopontin, Runt-related transcription factor 2 and COL1A1. The intracellular NO was also raised by alamandine. Additionally, the activation of AMPK/eNOS axis mediated the effects of alamandine on MC3T3-E1 cells and bone tissue. PD123319 and dorsomorphin could repress the regulating effect of alamandine on bone metabolism.

CONCLUSION

Alamandine attenuates ovariectomy-induced osteoporosis by promoting osteogenic differentiation via AMPK/eNOS axis.

Multi-omics Investigations in Endocrine Systems and Their Clinical Implications

Innovative techniques such as the "omics" can be a powerful tool for the understanding of intracellular pathways involved in homeostasis maintenance and identification of new potential therapeutic targets against endocrine-metabolic disorders. Over the last decades, proteomics has been extensively applied in the study of a wide variety of human diseases, including those involving the endocrine system. Among the most endocrine-related disorders investigated by proteomics in humans are diabetes mellitus and thyroid, pituitary, and reproductive system disorders. In diabetes, proteins implicated in insulin signaling, glucose metabolism, and β-cell activity have been investigated. In thyroid diseases, protein expression alterations were described in thyroid malignancies and autoimmune thyroid illnesses. Additionally, proteomics has been used to investigate the variations in protein expression in adrenal cancers and conditions, including Cushing's syndrome and Addison's disease. Pituitary tumors and disorders including acromegaly and hypopituitarism have been studied using proteomics to examine changes in protein expression. Reproductive problems such as polycystic ovarian syndrome and endometriosis are two examples of conditions where alterations in protein expression have been studied using proteomics. Proteomics has, in general, shed light on the molecular underpinnings of many endocrine-related illnesses and revealed promising biomarkers for both their detection and treatment. The capacity of proteomics to thoroughly and objectively examine complex protein mixtures is one of its main benefits. Mass spectrometry (MS) is a widely used method that identifies and measures proteins based on their mass-to-charge ratio and their fragmentation pattern. MS can perform the separation of proteins according to their physicochemical characteristics, such as hydrophobicity, charge, and size, in combination with liquid chromatography. Other proteomics techniques include protein arrays, which enable the simultaneous identification of several proteins in a single assay, and two-dimensional gel electrophoresis (2D-DIGE), which divides proteins depending on their isoelectric point and molecular weight. This chapter aims to summarize the most relevant proteomics data from targeted tissues, as well as the daily rhythmic variation of relevant biomarkers in both physiological and pathophysiological conditions within the involved endocrine system, especially because the actual modern lifestyle constantly imposes a chronic unentrained condition, which virtually affects all the circadian clock systems within human's body, being also correlated with innumerous endocrine-metabolic diseases.

Alamandine injection in the periaqueductal gray and rostral ventromedial medulla attenuates allodynia induced by sciatic nerve ligation in rats

Alamandine, a peptide known to interact with Mas-related G protein-coupled receptor subtype D (MrgD), has been implicated in moderating inflammatory signals. MrgD receptors are abundantly found in pain transmission pathways, but the role of alamandine/MrgD in pain modulation has not been thoroughly explored. This study aimed to investigate the effects of alamandine (10, 40, and 100 pmol) in a rat model of allodynia induced by sciatic nerve ligation, with a specific focus on examining the involvement of MrgD receptors, NMDAR1, and serotonin transporter (SERT) in the ventrolateral periaqueductal gray (vlPAG) and rostral ventromedial medulla (RVM). Microinjection of alamandine into the vlPAG at a dose of 100 pmol and into the RVM at doses of 40 and 100 pmol resulted in a significant increase in paw withdrawal threshold (PWT). Additionally, co-administration of D-Pro7-Ang-(1-7) at 50 pmol, an MrgD receptor antagonist, effectively blocked the analgesic effects of alamandine. Immunofluorescence analysis confirmed the presence of MrgD receptors in both the vlPAG and RVM regions. Importantly, an upregulation of MrgD receptor expression was observed following allodynia induction, suggesting a potential compensatory mechanism in response to pain. Our findings support the co-localization of MrgD receptors with NMDAR1 in vlPAG neurons, suggesting their ability to initiate analgesic pathways similar to those activated by NMDA receptors in the vlPAG. Furthermore, our results underscore a significant co-localization of MrgD receptors with the SERT in the RVM, underscoring their potential impact on serotonergic neurons involved in promoting analgesic effects.

Nuclear import of Mas-related G protein-coupled receptor member D induces pathological cardiac remodeling

Alamandine (Ala), a ligand of Mas-related G protein-coupled receptor, member D (MrgD), alleviates angiotensin II (AngII)-induced cardiac hypertrophy. However, the specific physiological and pathological role of MrgD is not yet elucidated. Here, we found that MrgD expression increased under various pathological conditions. Then, MrgD knockdown prevented AngII-induced cardiac hypertrophy and fibrosis via inactivating Gα_i-mediacted downstream signaling pathways, including the phosphorylation of p38 (p-P38), while MrgD overexpression induced pathological cardiac remodeling. Next, Ala, like silencing MrgD, exerted its cardioprotective effects by inhibiting Ang II-induced nuclear import of MrgD. MrgD interacted with p-P38 and promoted its entry into the nucleus under Ang II stimulation. Our results indicated that Ala was a blocking ligand of MrgD that inhibited downstream signaling pathway, which unveiled the promising cardioprotective effect of silencing MrgD expression on alleviating cardiac remodeling. Video Abstract.

The AT1/AT2 Receptor Equilibrium Is a Cornerstone of the Regulation of the Renin Angiotensin System beyond the Cardiovascular System

The AT₁ receptor has mainly been associated with the pathological effects of the renin-angiotensin system (RAS) (e.g., hypertension, heart and kidney diseases), and constitutes a major therapeutic target. In contrast, the AT₂ receptor is presented as the protective arm of this RAS, and its targeting via specific agonists is mainly used to counteract the effects of the AT₁ receptor. The discovery of a local RAS has highlighted the importance of the balance between AT₁/AT₂ receptors at the tissue level. Disruption of this balance is suggested to be detrimental. The fine tuning of this balance is not limited to the regulation of the level of expression of these two receptors. Other mechanisms still largely unexplored, such as S-nitrosation of the AT₁ receptor, homo- and heterodimerization, and the use of AT₁ receptor-biased agonists, may significantly contribute to and/or interfere with the settings of this AT₁/AT₂ equilibrium. This review will detail, through several examples (the brain, wound healing, and the cellular cycle), the importance of the functional balance between AT₁ and AT₂ receptors, and how new molecular pharmacological approaches may act on its regulation to open up new therapeutic perspectives.

Renin-Angiotensin System: Updated Understanding and Role in Physiological and Pathophysiological States

The classical view of the renin-angiotensin system (RAS) is that of the circulating hormone pathway involved in salt and water homeostasis and blood pressure regulation. It is also involved in the pathogenesis of cardiac and renal disorders. This led to the creation of drugs blocking the actions of this classical pathway, which improved cardiac and renal outcomes. Our understanding of the RAS has significantly expanded with the discovery of new peptides involved in this complex pathway. Over the last two decades, a counter-regulatory or protective pathway has been discovered that opposes the effects of the classical pathway. Components of RAS are also implicated in the pathogenesis of obesity and its metabolic diseases. The continued discovery of newer molecules also provides novel therapeutic targets to improve disease outcomes. This article aims to provide an overview of an updated understanding of the RAS, its role in physiological and pathological processes, and potential novel therapeutic options from RAS for managing cardiorenal disorders, obesity, and related metabolic disorders.

Targeting the renin angiotensin system for respiratory diseases

Renin-angiotensin system (RAS) plays an indispensable role in regulating blood pressure through its effects on fluid and electrolyte balance. As an aside, cumulative evidence from experimental to clinical studies supports the notion that dysregulation of RAS contributes to the pro-inflammatory, pro-oxidative, and pro-fibrotic processes that occur in pulmonary diseases like asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute lung injury (ALI). Pharmacological intervention of the various RAS components can be a novel therapeutic strategy for the treatment of these respiratory diseases. In this chapter, we first give a recent update on the RAS, and then compile, review, and analyse recent reports on targeting RAS components as treatments for respiratory diseases. Inhibition of the pro-inflammatory renin, angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and Ang II type 1 receptor (AT1R) axis, and activation of the protective ACE2, AT2R, Ang (1-7), and Mas receptor axis have demonstrated varying degrees of efficacies in experimental respiratory disease models or in human trials. The newly identified alamandine/Mas-related G-protein-coupled receptor member D pathway has shown some therapeutic promise as well. However, our understanding of the RAS ligand-and-receptor interactions is still inconclusive, and the modes of action and signaling cascade mediating the newly identified RAS receptors remain to be better characterized. Clinical data are obviously lacking behind the promising pre-clinical findings of certain well-established molecules targeting at different pathways of the RAS in respiratory diseases. Translational human studies should be the focus for RAS drug development in lung diseases in the next decade.

Counter-regulatory renin-angiotensin system in hypertension: Review and update in the era of COVID-19 pandemic

Cardiovascular disease is the major cause of mortality and disability, with hypertension being the most prevalent risk factor. Excessive activation of the renin-angiotensin system (RAS) under pathological conditions, leading to vascular remodeling and inflammation, is closely related to cardiovascular dysfunction. The counter-regulatory axis of the RAS consists of angiotensin-converting enzyme 2 (ACE2), angiotensin (1-7), angiotensin (1-9), alamandine, proto-oncogene Mas receptor, angiotensin II type-2 receptor and Mas-related G protein-coupled receptor member D. Each of these components has been shown to counteract the effects of the overactivated RAS. In this review, we summarize the latest insights into the complexity and interplay of the counter-regulatory RAS axis in hypertension, highlight the pathophysiological functions of ACE2, a multifunctional molecule linking hypertension and COVID-19, and discuss the function and therapeutic potential of targeting this counter-regulatory RAS axis to prevent and treat hypertension in the context of the current COVID-19 pandemic.

IgA Nephropathy with Macroproteinuria and a GFR of 20-30 ml/min/1.73 m2 May Still Benefit from RAS Inhibition

Introduction

There has been controversy about renin-angiotensin system (RAS) inhibition in IgAN patients with advanced (stage 4) chronic kidney disease (CKD). Therefore, we investigated the effect of RAS blockade in these patients.

Methods

Renal specimens of 50 IgAN patients who underwent renal biopsy during stage 4 CKD between 2010 and 2020, were stained using immunohistochemistry to detect the expression of RAS receptors (AT1R, AT2R, MasR, and MrgD). The primary endpoint was a composite of end-stage renal disease (ESRD) and death. Main baseline information and the administration of angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) were collected.

Results

During a median follow-up time of 25.5 months, 21 (42.0%) patients reached ESRD and none died. Six patients had a baseline eGFR of 15-20 ml/min/1.73m², and reached ESRD with a median renal survival time of 7.0 (range 6.0-23.0) months. Among patients with a baseline eGFR of 20-30 ml/min/1.73m², the percentage of patients using ACEI/ARB in progressive group was much lower than that in stable group (33.3% vs. 62.1%, P = 0.045), together with a shorter renal survival time in progressive group (26.0 vs. 30.5 months, P = 0.033). Macroproteinuria (24 h - UP ≥ 2.5 g) was also associated with a shorter renal survival time, as well as a significant decline in eGFR of stable group (24.4 vs. 26.4 ml/min/1.73 m², P = 0.026). Lower eGFR [hazards ratio (HR), 0.829, 95% confidence interval (CI), 0.724-0.950; P = 0.007] and use of ACEI/ARB (HR, 0.356, 95% CI, 0.133-0.953; P = 0.040) were predictive of time to ESRD in this stage. No differences were found in the expression of AT1R, AT2R, MasR, and MrgD of renal tissues at the time of biopsy between stable and progressive groups.

Conclusion

Contingent on monitoring serum creatinine and potassium levels, IgAN with macroproteinuria and a GFR of 20-30 ml/min/1.73m² may still benefits from intrarenal RAS inhibition.

Inhibition of angiotensin II type 1 receptor partially prevents acute elevation of pulmonary arterial pressure induced by endovascular ethanol injection

This study aimed to examine whether the administration of losartan can prevent acute elevation of pulmonary arterial pressure (AEPAP) induced by endovascular ethanol injection and to assess its related mechanisms. Male swine were selected and performed with absolute ethanol endovascular injection. Saline was used as the negative control. Losartan was administered preoperatively. Pulmonary arterial pressure (PAP), femoral arterial pressure (FAP) and heart rate (HR) were monitored during operations. Venous plasma and pulmonary artery (PA) tissue were harvested for analyses. Protein level was detected by Western blotting and ELISA, whereas qRT-PCR was used in mRNA detection. H & E staining and immunohistochemistry were conducted to evaluate histopathology. Ethanol injection elevated PAP in swine. The concentration of RAS ligands was elevated in plasma (all P < 0.0001) but not in PA. The level of oxidative stress increased in both plasma and PA. MRNA level of AT1R (P < 0.01, 95% CI: 0.251-1.006), not AT2R increased in PA. Losartan failed to inhibit AEPAP after all sessions of ethanol injection, and partially reversed the ethanol-induced PA remodeling. The P38 MAPK was activated after ethanol injection and could be inhibited by losartan (P < 0.01, 95% CI: -0.391 to -0.164). Ethanol also promoted the translocation of the P40-PHOX/P47-PHOX/P67-PHOX complex and the activation of NOX, which was independent from RAS. Endovascular ethanol injection can induce AEPAP mainly by activating RAS and P38 MAPK signaling. Losartan can partially prevent AEPAP and vascular remodeling owing to the promotion of NOX activity by ethanol. Mechanism diagram of endovascular ethanol injection-induced acute elevation of pulmonary arterial pressure (AEPAP) partially prevented by losartan. RAS: Renin-angiotensin system; AGT: angiotensinogen; Ang I: angiotensin I; ACE: angiotensin I converting enzyme; Ang II: angiotensin II. AT1R: angiotensin II type 1 receptor. NOX2: NADPH oxidase 2. PA: pulmonary artery.

Olmesartan medoxomil self-microemulsifying drug delivery system reverses apoptosis and improves cell adhesion in trinitrobenzene sulfonic acid-induced colitis in rats

Olmesartan medoxomil (OM) is an angiotensin receptor blocker. This study aimed to investigate the effects of OM self-microemulsifying drug delivery system (OMS) in trinitrobenzene sulfonic acid (TNBS)-induced acute colitis in rats. Besides two control groups, five TNBS-colitic-treated groups (n = 8) were given orally sulfasalazine (100 mg/kg/day), low and high doses of OM (3.0 and 10.0 mg/kg/day) (OML and OMH) and of OMS (OMSL and OMSH) for seven days. A colitis activity score was calculated. The colon was examined macroscopically. Colonic levels of myeloperoxidase, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), malondialdehyde, and reduced glutathione were measured. Plasma and colonic olmesartan levels were measured. Colonic sections were subjected to hematoxylin and eosin staining and immunohistochemical staining for E-cadherin, caspase-3, and matrix metalloproteinase-9 (MMP-9). Protein expression of E-cadherin, Bcl-2 associated X protein (Bax), and B-cell lymphoma 2 (Bcl-2), and cleaved caspase-3 by Western blot was done. TNBS-colitic rats showed increased colonic myeloperoxidase, TNF-α, IL-6, and malondialdehyde, decreased colonic glutathione, histopathological, immunohistochemical, and protein expression alterations. OMS, compared with OM, dose-dependently achieved higher colonic free olmesartan concentration, showed better anti-inflammatory, antioxidant, and anti-apoptotic effects, improved intestinal barrier, and decreased mucolytic activity. OMS more effectively up-regulated the reduced Bcl-2, Bcl-2/Bax ratio, and E-cadherin expression, and down-regulated the overexpressed Bax, cleaved caspase-3, and MMP-9. OMSL exerted effects comparable to OMH. Sulfasalazine exerted maximal colonic protective effects and almost completely reversed colonic damage, and OMSH showed nearly similar effects with non-significant differences in-between or compared with the normal control group. In conclusion, OMS could be a potential additive treatment for Crohn's disease colitis.

Alamandine alleviated heart failure and fibrosis in myocardial infarction mice

Alamandine (Ala) is the newest identified peptide of the renin-angiotensin system and has protective effect on myocyte hypertrophy. However, it is still unclear whether Ala can alleviate heart failure (HF). The aim of this study was to explore the effects of Ala on HF and the related cardiac fibrosis, and to probe the mechanism. HF model was induced by myocardial infarction (MI) in mice. Four weeks after MI, Ala was administrated by intraperitoneal injection for two weeks. Ala injection significantly improved cardiac dysfunction of MI mice in vivo. The cardiac fibrosis and the related biomarkers were attenuated after Ala administration in HF mice in vivo. The increases of collagen I, alpha-smooth muscle actin and transforming growth factor-beta induced by oxygen–glucose deprivation (OGD) in neonatal rat cardiac fibroblasts (NRCFs) were inhibited by Ala treatment in vitro. The biomarkers of apoptosis were elevated in NRCFs induced by OGD, which were attenuated after treating with Ala in vitro. The enhancement of oxidative stress in the heart of MI mice or in the NRCFs treated with OGD was suppressed by treating with Ala in vivo and in vitro. These effects of Ala were reversed by tBHP, an exogenous inducer of oxidative stress in vitro. These results demonstrated that Ala could alleviate cardiac dysfunction and attenuate cardiac fibrosis via inhibition of oxidative stress.

Myocardial effects of angiotensin II compared to norepinephrine in an animal model of septic shock

BACKGROUND

Angiotensin II is one of the vasopressors available for use in septic shock. However, its effects on the septic myocardium remain unclear. The aim of the study was to compare the effects of angiotensin II and norepinephrine on cardiac function and myocardial oxygen consumption, inflammation and injury in experimental septic shock.

METHODS

This randomized, open-label, controlled study was performed in 20 anesthetized and mechanically ventilated pigs. Septic shock was induced by fecal peritonitis in 16 animals, and four pigs served as shams. Resuscitation with fluids, antimicrobial therapy and abdominal drainage was initiated one hour after the onset of septic shock. Septic pigs were randomly allocated to receive one of the two drugs to maintain mean arterial pressure between 65 and 75 mmHg for 8 h.

RESULTS

There were no differences in MAP, cardiac output, heart rate, fluid balance or tissue perfusion indices in the two treatment groups but myocardial oxygen consumption was greater in the norepinephrine-treated animals. Myocardial mRNA expression of interleukin-6, interleukin-6 receptor, interleukin-1 alpha, and interleukin-1 beta was higher in the norepinephrine than in the angiotensin II group.

CONCLUSIONS

In septic shock, angiotensin II administration is associated with a similar level of cardiovascular resuscitation and less myocardial oxygen consumption, and inflammation compared to norepinephrine.

Alamandine, a new member of the renin-angiotensin system (RAS), attenuates collagen-induced arthritis in mice via inhibiting cytokine secretion in synovial fibroblasts

Alamandine is a novel component of the renin-angiotensin system (RAS) as well as an important biologically active peptide. It has predominantly been studied in cardiovascular context. However, its role in rheumatoid arthritis (RA) remains unknown. Here we illustrated its effects on inflammatory cytokines production by synovial fibroblasts from RA and pathological changes in collagen-induced arthritis (CIA) mice. Alamandine (0.1, 1 and 10 µg/ml) did not affect the survival of the synovial fibroblasts, but decreased the migration and proinflammatory cytokines expression in TNF-α (10 ng/ml) stimulated cells in vitro. Additionally, alamandine selectively decreased phosphorylated-JNK expression induced by TNF-a stimulation in RA FLS. DBA/1 J mice were induced arthritis by a primary injection with an emulsion of bovine type II collagen (CII) and complete Freund's adjuvant (day 0) and a booster injection of CII in incomplete Freund's adjuvant (day 21). Mice were then given alamandine intraperitoneally in saline (50 μg/kg/day) from days 21-42. Histology and multiplex immunobead assay showed that alamandine treatment inhibited the development of arthritis and reduced the joint damage. This effect was accompanied by the reduced inflammatory cytokines (IL-6, IL-23, IFN-γ) mRNA expression in local joints, the decreased TNF-α, IL-6, IL-17 and the increased IL-10 levels in the serum from alamandine administrated CIA mice. In conclusion, alamandine attenuates the development of arthritis by suppressing inflammatory cytokines expression in RA synovial fibroblasts via MAPK signaling pathway, suggesting a potential therapeutic role for RA.

Structural insight into the activation mechanism of MrgD with heterotrimeric Gi-protein revealed by cryo-EM

MrgD, a member of the Mas-related G protein-coupled receptor (MRGPR) family, has high basal activity for Gi activation. It recognizes endogenous ligands, such as β-alanine, and is involved in pain and itch signaling. The lack of a high-resolution structure for MrgD hinders our understanding of whether its activation is ligand-dependent or constitutive. Here, we report two cryo-EM structures of the MrgD-Gi complex in the β-alanine-bound and apo states at 3.1 Å and 2.8 Å resolution, respectively. These structures show that β-alanine is bound to a shallow pocket at the extracellular domains. The extracellular half of the sixth transmembrane helix undergoes a significant movement and is tightly packed into the third transmembrane helix through hydrophobic residues, creating the active form. Our structures demonstrate a structural basis for the characteristic ligand recognition of MrgD. These findings provide a framework to guide drug designs targeting the MrgD receptor.

An ACE2-Alamandine Axis Modulates the Cardiac Performance of the Goldfish Carassius auratus via the NOS/NO System

Alamandine is a peptide of the Renin Angiotensin System (RAS), either generated from Angiotensin A via the Angiotensin Converting Enzyme 2 (ACE2), or directly from Ang-(1-7). In mammals, it elicits cardioprotection via Mas-related G-protein-coupled receptor D (MrgD), and the NOS/NO system. In teleost fish, RAS is known to modulate heart performance. However, no information is available on the presence of a cardioactive ACE2/Alamandine axis. To fill this gap, we used the cyprinid teleost Carassius auratus (goldfish) for in silico and in vitro analyses. Via the NCBI Blast P suite we found that in cyprinids ace2 is phylogenetically detectable in a subcluster of proteins including ace2-like isoforms, and is correlated with a hypoxia-dependent pathway. By real-time PCR, Western Blotting, and HPLC, ACE2 and Alamandine were identified in goldfish heart and plasma, respectively. Both increased after chronic exposure to low O₂ (2.6 mg O₂ L^-1). By using an ex-vivo working goldfish-heart preparation, we observed that in vitro administration of exogenous Alamandine dose-dependently stimulates myocardial contractility starting from 10^-11 M. The effect that involved Mas-related receptors and PKA occurred via the NOS/NO system. This was shown by exposing the perfused heart to the NOS inhibitor L-NMMA (10^-5 M) that abolished the cardiac effect of Alamandine and was supported by the increased expression of the phosphorylated NOS enzyme in the extract from goldfish heart exposed to 10^-10 M Alamandine. Our data are the first to show that an ACE2/Alamandine axis is present in the goldfish C. auratus and, to elicit cardiac modulation, requires the obligatory involvement of the NOS/NO system.

Angiotensin-(1-7) as a Potential Therapeutic Strategy for Delayed Cerebral Ischemia in Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a substantial cause of mortality and morbidity worldwide. Moreover, survivors after the initial bleeding are often subject to secondary brain injuries and delayed cerebral ischemia, further increasing the risk of a poor outcome. In recent years, the renin-angiotensin system (RAS) has been proposed as a target pathway for therapeutic interventions after brain injury. The RAS is a complex system of biochemical reactions critical for several systemic functions, namely, inflammation, vascular tone, endothelial activation, water balance, fibrosis, and apoptosis. The RAS system is classically divided into a pro-inflammatory axis, mediated by angiotensin (Ang)-II and its specific receptor AT₁R, and a counterbalancing system, presented in humans as Ang-(1-7) and its receptor, MasR. Experimental data suggest that upregulation of the Ang-(1-7)/MasR axis might be neuroprotective in numerous pathological conditions, namely, ischemic stroke, cognitive disorders, Parkinson's disease, and depression. In the presence of SAH, Ang-(1-7)/MasR neuroprotective and modulating properties could help reduce brain damage by acting on neuroinflammation, and through direct vascular and anti-thrombotic effects. Here we review the role of RAS in brain ischemia, with specific focus on SAH and the therapeutic potential of Ang-(1-7).

Factors associated with the progression of mesangial lesions in IgA nephropathy: A comparative analysis of renal re-biopsies

OBJECTIVES

IgA nephropathy (IgAN) is the most common primary glomerular disease, and is the leading cause of chronic renal failure. Because mesangial lesions are the main pathological changes seen in IgAN, we investigated factors associated with the progression of mesangial lesions in IgAN.

METHODS

We enrolled participants with IgAN who underwent repeat renal biopsies. Based on the progression of mesangial proliferative lesions, the participants were divided into progressive and stable groups. The progression group included participants with a ratio of mesangial cell proliferation score ≥ 1.1 (i.e., proliferation of > 10%) in the second biopsy specimen compared to the first biopsy specimen. The stable group included participants who did not fulfill the aforementioned criteria. We recorded the laboratory parameters, expression of renin-angiotensin system (RAS) receptors (angiotensin II type 1 receptor [AT1R], angiotensin II type 2 receptor [AT2R], Mas receptor [MasR], and the Mas-related G protein-coupled receptor, member D [MrgD]) and mesangial matrix proteins (collagen [Col] IV, fibronectin [FN] and laminin) at the first and second renal biopsies, and the use of immunosuppressive therapy and/or RAS blockers after the first biopsy.

RESULTS

We enrolled 24 patients with IgAN who underwent repeat renal biopsies. Half of patients showed progression of mesangial lesions on repeat renal biopsy after a median of 4.3 (1-6) years. The progression group had significantly higher expression levels of AT1R and mesangial matrix proteins (Col IV and FN), and significantly lower expression of AT2R and MasR, compared to the stable group. Multivariate analysis showed that the use of RAS blockers (hazard ratio [HR], 0.27; 95% CI, 0.08-0.97; p < 0.05) and the level of proteinuria (HR, 1.8; 95% CI, 1.04-3.12; p < 0.05) were associated with progression of mesangial lesions. Additionally, the progression group exhibited a more rapid decline of renal function compared to the stable group (0.38 and 0.012 ml/min/1.73 m²/month, respectively; p = 0.004).

CONCLUSIONS

Continuous activation of the intrarenal RAS and massive proteinuria correlate with histological progression of mesangial lesions in IgAN patients, which may further accelerate the deterioration of renal function.

Localization and expression of the Mas-related G-protein coupled receptor member D (MrgD) in the mouse brain

Numerous studies in the last decades have provided evidence for the existence of a local renin-angiotensin system (RAS) in the central nervous system (CNS). Widespread distribution of the different RAS components in the brain demonstrates the pleiotropic role of this system in the structure and function of CNS. With the advent of new molecular techniques, a novel receptor has been identified within the beneficial arm of the RAS, the Mas-related G-protein coupled receptor D (MrgD), which can be stimulated by two heptapeptides, Ala¹-(Ang-(1-7), also named alamandine, and Ang-(1-7). However, the biological and physiological relevance of this interaction remains obscure. Since several recent studies hinted at a role of MrgD in the CNS, we determined the distribution pattern of MrgD receptors in the adult mouse brain by using a genetic mouse model with tracers of MrgD expression. MrgD-positive cells could be identified in some forebrain areas, including cortex, hippocampus, amygdala, hypothalamus, habenular nuclei, striatum and pallidum, as well as in some mid-brain nuclei in a region-specific manner. The specific localization of MrgD in the reward- and limbic-related areas can hint at a role of MrgD in processes such as pain perception/modulation, synaptic plasticity, learning, memory and cognition.

Renin angiotensin aldosterone system in pulmonary fibrosis: Pathogenesis to therapeutic possibilities

Pulmonary fibrosis is a devastating lung disease with multifactorial etiology characterized by alveolar injury, fibroblast proliferation and excessive deposition of extracellular matrix proteins, which progressively results in respiratory failure and death. Accumulating evidence from experimental and clinical studies supports a central role of the renin angiotensin aldosterone system (RAAS) in the pathogenesis and progression of idiopathic pulmonary fibrosis. Angiotensin II (Ang II), a key vasoactive peptide of the RAAS mediates pro-inflammatory and pro-fibrotic effects on the lungs, adversely affecting organ function. Recent years have witnessed seminal discoveries in the field of RAAS. Identification of new enzymes, peptides and receptors has led to the development of several novel concepts. Of particular interest is the establishment of a protective axis of the RAAS comprising of Angiotensin converting enzyme 2 (ACE2), Angiotensin-(1-7) [Ang-(1-7)], and the Mas receptor (the ACE2/Ang-(1-7)/Mas axis), and the discovery of a functional role for the Angiotensin type 2 (AT₂) receptor. Herein, we will review our current understanding of the role of RAAS in lung fibrogenesis, provide evidence on the anti-fibrotic actions of the newly recognized RAAS components (the ACE2/Ang-(1-7)/Mas axis and AT₂ receptor), discuss potential strategies and translational efforts to convert this new knowledge into effective therapeutics for PF.

Biologia Futura: is ADAM 17 the reason for COVID-19 susceptibility in hyperglycemic and diabetic patients?

COVID-19 is a disease-causing current pandemic. It prevails in patients with pre-existing conditions such as diabetes and hypertension. Renin-angiotensin system was identified as a center of COVID-19 pathophysiology. There is a current controversy concerning the usage of ACE inhibitors and AR blockers in patients with COVID-19. Multiple clinical trials are on the way to determine the effect of RAS blockers in patients with COVID-19. ACE2 receptor is thought to be the point of entry utilized by a coronavirus. However, other factors have been identified which potentially facilitate SARS-CoV-2 entry into the cell. ADAM17 could facilitate viral entry in hyperglycemic and diabetic patients. Insulin is an ADAM17 inhibitor. Heme oxygenase (HO)-1 level is reduced in diabetic patients, contributing to the worst outcome for patients with poor glycemic control. The combined therapy of glycemic control and antioxidant response to oxidative stress could be explored in patients with COVID-19.

The Impact of microRNAs in Renin-Angiotensin-System-Induced Cardiac Remodelling

Current knowledge on the renin-angiotensin system (RAS) indicates its central role in the pathogenesis of cardiovascular remodelling via both hemodynamic alterations and direct growth and the proliferation effects of angiotensin II or aldosterone resulting in the hypertrophy of cardiomyocytes, the proliferation of fibroblasts, and inflammatory immune cell activation. The noncoding regulatory microRNAs has recently emerged as a completely novel approach to the study of the RAS. A growing number of microRNAs serve as mediators and/or regulators of RAS-induced cardiac remodelling by directly targeting RAS enzymes, receptors, signalling molecules, or inhibitors of signalling pathways. Specifically, microRNAs that directly modulate pro-hypertrophic, pro-fibrotic and pro-inflammatory signalling initiated by angiotensin II receptor type 1 (AT1R) stimulation are of particular relevance in mediating the cardiovascular effects of the RAS. The aim of this review is to summarize the current knowledge in the field that is still in the early stage of preclinical investigation with occasionally conflicting reports. Understanding the big picture of microRNAs not only aids in the improved understanding of cardiac response to injury but also leads to better therapeutic strategies utilizing microRNAs as biomarkers, therapeutic agents and pharmacological targets.

Alamandine improves cardiac remodeling induced by transverse aortic constriction in mice

Alamandine is the newest identified peptide of the renin-angiotensin system (RAS) and has protective effects in the cardiovascular system. Although the involvement of classical RAS components in the genesis and progression of cardiac remodeling is well known, less is known about the effects of alamandine. Therefore, in the present study we investigated the effects of alamandine on cardiac remodeling induced by transverse aortic constriction (TAC) in mice. Male mice (C57BL/6), 10-12 wk of age, were divided into three groups: sham operated, TAC, and TAC + ALA (30 µg/kg/day alamandine for 14 days). The TAC surgery was performed under ketamine and xylazine anesthesia. At the end of treatment, the animals were submitted to echocardiographic examination and subsequently euthanized for tissue collection. TAC induced myocyte hypertrophy, collagen deposition, and the expression of matrix metalloproteinase (MMP)-2 and transforming growth factor (TGF)-β in the left ventricle. These markers of cardiac remodeling were reduced by oral treatment with alamandine. Western blotting analysis showed that alamandine prevents the increase in ERK1/2 phosphorylation and reverts the decrease in 5'-adenosine monophosphate-activated protein kinase (AMPK)α phosphorylation induced by TAC. Although both TAC and TAC + ALA increased SERCA2 expression, the phosphorylation of phospholamban in the Thr17 residue was increased solely in the alamandine-treated group. The echocardiographic data showed that there are no functional or morphological alterations after 2 wk of TAC. Alamandine treatment prevents myocyte hypertrophy and cardiac fibrosis induced by TAC. Our results reinforce the cardioprotective role of alamandine and highlight its therapeutic potential for treating heart diseases related to pressure overload conditions.NEW & NOTEWORTHY Alamandine is the newest identified component of the renin-angiotensin system protective arm. Considering the beneficial effects already described so far, alamandine is a promising target for cardiovascular disease treatment. We demonstrated for the first time that alamandine improves many aspects of cardiac remodeling induced by pressure overload, including cell hypertrophy, fibrosis, and oxidative stress markers.

2020 update on the renin-angiotensin-aldosterone system in pediatric kidney disease and its interactions with coronavirus

The last decade was crucial for our understanding of the renin-angiotensin-aldosterone system (RAAS) as a two-axis, counter-regulatory system, divided into the classical axis, formed by angiotensin-converting enzyme (ACE), angiotensin II (Ang II), and the angiotensin type 1 receptor (AT1R), and the alternative axis comprising angiotensin-converting enzyme 2 (ACE2), angiotensin-(1-7) (Ang-(1-7)), and the Mas receptor. Breakthrough discoveries also took place, with other RAAS endopeptides being described, including alamandine and angiotensin A. In this review, we characterize the two RAAS axes and the role of their components in pediatric kidney diseases, including childhood hypertension (HTN), pediatric glomerular diseases, congenital abnormalities of the kidney and urinary tract (CAKUT), and chronic kidney disease (CKD). We also present recent findings on potential interactions between the novel coronavirus, SARS-CoV-2, and components of the RAAS, as well as potential implications of coronavirus disease 2019 (COVID-19) for pediatric kidney diseases.

Neuropsychiatric Properties of the ACE2/Ang-(1-7)/Mas Pathway: A Brief Review

The current pharmacological strategies for the management of anxiety disorders and depression, serious conditions which are gaining greater prevalence worldwide, depend on only two therapeutic classes of mood-stabilizing drugs: Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs). Although first line agents with proven efficacy, their clinical success in the management of anxiety disorders and depression is still considered highly complex due to the multifaceted nature of such conditions. Several studies have shown a possible therapeutic target could be found in the form of the Angiotensin-Converting Enzyme [ACE] type 2 (ACE2), Angiotensin [Ang]-(1-7) and Mas receptor pathway of the Renin- Angiotensin System (RAS), which as will be discussed, has been described to exhibit promising therapeutic properties for the management of anxiety disorders and depression. In this article, the literature to describe recent findings related to the role of the RAS in anxiety and depression disorders was briefly revised. The literature used covers a time range from 1988 to 2019 and were acquired from the National Center for Biotechnology Information's (NCBI) PubMed search engine. The results demonstrated in this review are promising and encourage the development of new research for the treatment of anxiety and depression disorders focusing on the RAS. In conclusion, the ACE2/Ang-(1-7)/Mas pathway may exhibit anxiolytic and anti-depressive effects through many possible biochemical mechanisms both centrally and peripherally, and result in highly promising mental health benefits which justifies further investigation into this system as a possible new therapeutic target in the management of neuropsychiatric disorders, including any as of yet undescribed risk-benefit analysis compared to currently-implemented pharmacological strategies.

Should ACE2 be given a chance in COVID-19 therapeutics: A semi-systematic review of strategies enhancing ACE2

The severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) has resulted in almost 28 million cases of COVID-19 (Corona virus disease-2019) and more than 900000 deaths worldwide since December 2019. In the absence of effective antiviral therapy and vaccine, treatment of COVID-19 is largely symptomatic. By making use of its spike (S) protein, the virus binds to its primary human cell receptor, angiotensin converting enzyme 2 (ACE2) which is present in the pulmonary epithelial cells as well as other organs. SARS-CoV-2 may cause a downregulation of ACE2. ACE2 plays a protective role in the pulmonary system through its Mas-receptor and alamandine-MrgD-TGR7 pathways. Loss of this protective effect could be a major component of COVID-19 pathogenesis. An attractive strategy in SARS-CoV-2 therapeutics would be to augment ACE2 either directly by supplementation or indirectly through drugs which increase its levels or stimulate its downstream players. In this semi-systematic review, we have analysed the pathophysiological interplay between ACE and ACE2 in the cardiopulmonary system, the modulation of these two proteins by SARS-CoV-2, and potential therapeutic avenues targeting ACE-Ang II and ACE2-Ang (1-7) axes, that can be utilized against COVID-19 disease progression.

Angiotensin Receptors Heterodimerization and Trafficking: How Much Do They Influence Their Biological Function?

G-protein–coupled receptors (GPCRs) are targets for around one third of currently approved and clinical prescribed drugs and represent the largest and most structurally diverse family of transmembrane signaling proteins, with almost 1000 members identified in the human genome. Upon agonist stimulation, GPCRs are internalized and trafficked inside the cell: they may be targeted to different organelles, recycled back to the plasma membrane or be degraded. Once inside the cell, the receptors may initiate other signaling pathways leading to different biological responses. GPCRs’ biological function may also be influenced by interaction with other receptors. Thus, the ultimate cellular response may depend not only on the activation of the receptor from the cell membrane, but also from receptor trafficking and/or the interaction with other receptors. This review is focused on angiotensin receptors and how their biological function is influenced by trafficking and interaction with others receptors.

Local ocular renin-angiotensin-aldosterone system: any connection with intraocular pressure? A comprehensive review

The renin-angiotensin system (RAS) is one of the oldest and most extensively studied human peptide cascades, well-known for its role in regulating blood pressure. When aldosterone is included, RAAS is involved also in fluid and electrolyte homeostasis. There are two main axes of RAAS: (1) Angiotensin (1-7), angiotensin converting enzyme 2 and Mas receptor (ACE2-Ang(1-7)-MasR), (2) Angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor (ACE1-AngII-AT1R). In its entirety, RAAS comprises dozens of angiotensin peptides, peptidases and seven receptors. The first mentioned axis is known to counterbalance the deleterious effects of the latter axis. In addition to the systemic RAAS, tissue-specific regulatory systems have been described in various organs, evidence that RAAS is both an endocrine and an autocrine system. These local regulatory systems, such as the one present in the vascular endothelium, are responsible for long-term regional changes. A local RAAS and its components have been detected in many structures of the human eye. This review focuses on the local ocular RAAS in the anterior part of the eye, its possible role in aqueous humour dynamics and intraocular pressure as well as RAAS as a potential target for anti-glaucomatous drugs.KEY MESSAGESComponents of renin-angiotensin-aldosterone system have been detected in different structures of the human eye, introducing the concept of a local intraocular renin-angiotensin-aldosterone system (RAAS).Evidence is accumulating that the local ocular RAAS is involved in aqueous humour dynamics, regulation of intraocular pressure, neuroprotection and ocular pathology making components of RAAS attractive candidates when developing new effective ways to treat glaucoma.