Physiology of Local Renin-Angiotensin Systems

Involvement of the Renin-Angiotensin System in Stress: State of the Art and Research Perspectives

BACKGROUND

Along with other canonical systems, the renin-angiotensin system (RAS) has shown important roles in stress. This system is a complex regulatory proteolytic cascade composed of various enzymes, peptides, and receptors. Besides the classical (ACE/Ang II/AT1 receptor) and the counter-regulatory (ACE2/Ang-(1-7)/Mas receptor) RAS axes, evidence indicates that nonclassical components, including Ang III, Ang IV, AT₂ and AT₄, can also be involved in stress.

OBJECTIVE AND METHODS

This comprehensive review summarizes the current knowledge on the participation of RAS components in different adverse environmental stimuli stressors, including air jet stress, cage switch stress, restraint stress, chronic unpredictable stress, neonatal isolation stress, and post-traumatic stress disorder.

RESULTS AND CONCLUSION

In general, activation of the classical RAS axis potentiates stress-related cardiovascular, endocrine, and behavioral responses, while the stimulation of the counter-regulatory axis attenuates these effects. Pharmacological modulation in both axes is optimistic, offering promising perspectives for stress-related disorders treatment. In this regard, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are potential candidates already available since they block the classical axis, activate the counter-regulatory axis, and are safe and efficient drugs.

Flexible and multifaceted: the plasticity of renin-expressing cells

The protease renin, the key enzyme of the renin–angiotensin–aldosterone system, is mainly produced and secreted by juxtaglomerular cells in the kidney, which are located in the walls of the afferent arterioles at their entrance into the glomeruli. When the body’s demand for renin rises, the renin production capacity of the kidneys commonly increases by induction of renin expression in vascular smooth muscle cells and in extraglomerular mesangial cells. These cells undergo a reversible metaplastic cellular transformation in order to produce renin. Juxtaglomerular cells of the renin lineage have also been described to migrate into the glomerulus and differentiate into podocytes, epithelial cells or mesangial cells to restore damaged cells in states of glomerular disease. More recently, it could be shown that renin cells can also undergo an endocrine and metaplastic switch to erythropoietin-producing cells. This review aims to describe the high degree of plasticity of renin-producing cells of the kidneys and to analyze the underlying mechanisms.

Gastroprotective Effect of Azilsartan Through Ameliorating Oxidative Stress, Inflammation, and Restoring Hydroxyproline, and Gastrin Levels in Ethanol-Induced Gastric Ulcer

Objective

The present study was designed to evaluate the possible gastroprotective effects of different doses of azilsartan in ethanol-induced gastric ulcers in rats.

Methodology

Forty-eight male adult Wistar rats were used and allocated randomly into four groups: negative control treated with distilled water, positive control treated with ethanol, lansoprazole treated group, and azilsartan (1mg, 5mg, and 10mg/kg) treated group. The treatment protocol was for 15 days, and all the groups except for the negative control group received 1mL of ethanol on the last day 1hr before scarification. Gastric content was collected for measuring the volume, free acidity, and pH. The stomach was used for measuring the gastric lesion area and ulcer index. Blood samples were collected for measuring serum hydroxyproline, gastrin, CRP, TNF-α, MDA, and TAOC. Gastric tissues were sent for histopathological examinations.

Results

Ethanol administration significantly increased gastric lesion, gastric ulcer index, and gastric acidity. Ethanol also decreased serum levels of hydroxyproline and TAOC and increased serum gastrin, CRP, TNF-α, and MDA. Azilsartan 10mg/kg was able to decrease the lesion by 43.6% and increase gastric pH and significantly decreased MDA level. Both 5mg/kg and 10mg/kg azilsartan have successfully restored the level of hydroxyproline, gastrin, and TNF-α. The histopathological finding showed gastroprotection by azilsartan in a dose-dependent manner.

Conclusion

The study revealed that azilsartan possesses a gastroprotective effect. The proposed mechanisms could be increased blood flow to the stomach, antioxidant capacity, and anti-inflammatory activity along with restoring hydroxyproline and gastrin levels. These findings suggest azilsartan as a promising candidate to be tested in a clinical setting.

Renin-angiotensin system (RAS) enzymes and placental trophoblast syncytialisation

Placental renin-angiotensin system (RAS) components; prorenin, angiotensinogen, and angiotensin (Ang) II type 1 receptor (AT₁R) are upregulated during syncytialisation. This study examined whether angiotensin-converting enzyme (ACE), ACE2 and neprilysin (NEP) are also altered during syncytialisation. Two in vitro models of syncytialisation were used: forskolin-treated BeWo cells and spontaneously syncytialising primary human trophoblast cells. Term placentae and primary trophoblasts had the highest levels of ACE, ACE2 and NEP mRNA. In primary trophoblasts, ACE mRNA levels significantly increased with syncytialisation, ACE2 and NEP mRNA levels decreased. ACE, ACE2 and NEP protein levels and ACE2 activity did not change. Syncytialisation of primary trophoblasts decreased soluble (s)ACE and sNEP but not sACE2 levels. In primary trophoblasts, the balance between the enzymes controlling the two opposing pathways of the RAS was maintained. These findings were unable to be reproduced in BeWo cells. Future studies exploring placental levels of these enzymes in pregnancies complicated by placental insufficiency are warranted.

Insights into Cardiovascular Defects and Cardiac Epigenome in the Context of COVID-19

Although few in number, studies on epigenome of the heart of COVID-19 patients show that epigenetic signatures such as DNA methylation are significantly altered, leading to changes in expression of several genes. It contributes to pathogenic cardiac phenotypes of COVID-19, e.g., low heart rate, myocardial edema, and myofibrillar disarray. DNA methylation studies reveal changes which likely contribute to cardiac disease through unknown mechanisms. The incidence of severe COVID-19 disease, including hospitalization, requiring respiratory support, morbidity, and mortality, is disproportionately higher in individuals with co-morbidities. This poses unprecedented strains on the global healthcare system. While their underlying conditions make patients more susceptible to severe COVID-19 disease, strained healthcare systems, lack of adequate support, or sedentary lifestyles from ongoing lockdowns have proved detrimental to their underlying health conditions, thus pushing them to severe risk of congenital heart disease (CHD) itself. Prophylactic vaccines against COVID-19 have ushered new hope for CHD. A common connection between COVID-19 and CHD is SARS-CoV-2’s host receptor ACE2, because ACE2 regulates and protects organs, including the heart, in various ways. ACE2 is a common therapeutic target against cardiovascular disease and COVID-19 which damages organs. Hence, this review explores the above regarding CHDs, cardiovascular damage, and cardiac epigenetics, in COVID-19 patients.

Prognostic impact of angiotensin-converting enzyme inhibitors and angiotensin receptors blockers in esophageal or gastric cancer patients with hypertension - a real-world study

Background

Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are used in treating cardiovascular diseases. Previous studies indicated that ACEIs/ARBs may benefit cancer patients by inhibiting tumor angiogenesis and proliferation. The effect of ACEIs/ARBs on cancer survival in esophageal and gastric cancer is still unclear. This study is to investigate the association between ACEIs/ARBs usage and esophageal and gastric cancer prognosis.

Methods

This retrospective cohort study identified esophageal and gastric cancer patients during 2008–2016 from the Taiwan Cancer Registry, and obtained medication usage and follow-up information from the National Health Insurance Research Database and Death Registry. Analysis groups were defined as ACEIs/ARBs user or non-user based on the usage of ACEIs/ARBs within the 6 months after cancer diagnosis. The stabilized inverse probability of treatment weighting using propensity scores was applied to balance covariates between study groups. We also used Kaplan-Meier estimates and Cox regression to compare survival outcome and estimate hazard ratios (HRs).

Results

We identified 14,463 and 21,483 newly-diagnosed esophageal and gastric cancer patients during 2008–2016. ACEIs/ARBs users were associated with lower risk of cancer-specific mortality, although only significantly in gastric cancer (gastric: adjusted HR = 0.87, 95% CI = 0.78–0.97; esophageal: adjusted HR =0.88, 95% CI = 0.76–1.02). A better survival outcome was observed among patients who received higher cumulative defined daily dose of ACEIs/ARBs.

Conclusions

We found that using ACEIs/ARBs after cancer diagnosis were associated with lower risk of mortality. Our results add to the knowledge of the benefit of ACEIs/ARBs against mortality in individuals with esophageal/gastric cancer patients with hypertension.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09513-4.

Neuroprotective Effect of Ramipril Is Mediated by AT2 in a Mouse MODEL of Paclitaxel-Induced Peripheral Neuropathy

Paclitaxel (PTX)-induced peripheral neuropathy (PIPN) induces numerous symptoms affecting patient quality of life, leading to decreased doses or even to cessation of anticancer therapy. Previous studies have reported that a widely used drug, ramipril, improves neuroprotection in several rodent models of peripheral neuropathy. The protective role of the angiotensin II type 2 receptor (AT2) in the central and peripheral nervous systems is well-established. Here, we evaluate the effects of ramipril in the prevention of PIPN and the involvement of AT2 in this effect. Paclitaxel was administered in wild type or AT2-deficient mice on alternate days for 8 days, at a cumulative dose of 8 mg/kg (2 mg/kg per injection). Ramipril, PD123319 (an AT2 antagonist), or a combination of both were administered one day before PTX administration, and daily for the next twenty days. PTX-administered mice developed mechanical allodynia and showed a loss of sensory nerve fibers. Ramipril prevented the functional and morphological alterations in PTX mice. The preventive effect of ramipril against tactile allodynia was completely absent in AT2-deficient mice and was counteracted by PD123319 administration in wild type mice. Our work highlights the potential of ramipril as a novel preventive treatment for PIPN, and points to the involvement of AT2 in the neuroprotective role of ramipril in PIPN.

Renin Angiotensin Blockers and Cardiac Protection: From Basis to Clinical Trials

Despite a similar beneficial effect on blood pressure lowering observed with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 receptor (AT1R) blocker (ARBs), several clinical trials and meta-analyses have reported higher cardiovascular mortality and lower protection against myocardial infarction with ARBs when compared with ACEIs. The European guidelines for the management of coronary syndromes and European guidelines on diabetes recommend using ARBs in patients who are intolerant to ACEIs. We reviewed the main pharmacological differences between ACEIs and ARBs, which could provide insights into the differences in the cardiac protection offered by these 2 drug classes. The effect of ACEIs on the tissue and plasma levels of bradykinin and on nitric oxide production and bioavailability is specific to the mechanism of action of ACEIs; it could account for the different effects of ACEIs and ARBs on endothelial function, atherogenesis, and fibrinolysis. Moreover, chronic blockade of AT1 receptors by ARBs induces a significant and permanent increase in plasma angiotensin II and an overstimulation of its still available receptors. In animal models, AT4 receptors have vasoconstrictive, proliferative, and inflammatory effects. Moreover, in models with kidney damage, atherosclerosis, and/or senescence, activation of AT2 receptors could have deleterious fibrotic, vasoconstrictive, and hypertrophic effects and seems prudent and reasonable to reserve the use of ARBs for patients who have presented intolerance to ACE inhibitors.

Functional ACE2 deficiency leading to angiotensin imbalance in the pathophysiology of COVID-19

SARS-CoV-2, the virus responsible for COVID-19, uses angiotensin converting enzyme 2 (ACE2) as its primary cell-surface receptor. ACE2 is a key enzyme in the counter-regulatory pathway of the broader renin-angiotensin system (RAS) that has been implicated in a broad array of human pathology. The RAS is composed of two competing pathways that work in opposition to each other: the "conventional" arm involving angiotensin converting enzyme (ACE) generating angiotensin-2 and the more recently identified ACE2 pathway that generates angiotensin (1-7). Following the original SARS pandemic, additional studies suggested that coronaviral binding to ACE2 resulted in downregulation of the membrane-bound enzyme. Given the similarities between the two viruses, many have posited a similar process with SARS-CoV-2. Proponents of this ACE2 deficiency model argue that downregulation of ACE2 limits its enzymatic function, thereby skewing the delicate balance between the two competing arms of the RAS. In this review we critically examine this model. The available data remain incomplete but are consistent with the possibility that the broad multisystem dysfunction of COVID-19 is due in large part to functional ACE2 deficiency leading to angiotensin imbalance with consequent immune dysregulation and endothelial cell dysfunction.

Synergistic actions between angiotensin-converting enzyme inhibitors and statins in atherosclerosis

AIMS

Hypertension and hypercholesterolemia are independent risk factors for atherosclerotic cardiovascular disease (ASCVD) by acting directly on the endothelium and activating the renin-angiotensin aldosterone system (RAAS) and mevalonate pathways. This review examines how the severity and duration of these risk factors may influence the cardiovascular risk through a reciprocal interplay leading to oxidative stress and pro-inflammatory response.

DATA SYNTHESIS

The review highlights the clinical evidence supporting the benefits of statins and angiotensin-converting enzyme (ACE) inhibitors for hypertension, lipid disorders and ASCVD management, both individually and combined, at all stages of the cardiovascular continuum.

CONCLUSION

Drug strategies incorporating an ACE-inhibitor and a statin, and in particular perindopril and atorvastatin, have consistently demonstrated reductions in the rate of ASCVD events in patients with hypertension and lipid disorders, cementing their position as first-line therapies for the management of atherosclerosis complications.

Treatment with Angiotensin-(1-7) Prevents Development of Oral Papilloma Induced in K-ras Transgenic Mice

Oral Squamous Cell Carcinoma (OSCC) is the most common malignant cancer affecting the oral cavity. It is characterized by high morbidity and very few therapeutic options. Angiotensin (Ang)-(1-7) is a biologically active heptapeptide, generated predominantly from AngII (Ang-(1-8)) by the enzymatic activity of angiotensin-converting enzyme 2 (ACE 2). Previous studies have shown that Ang-(1-7) counterbalances AngII pro-tumorigenic actions in different pathophysiological settings, exhibiting antiproliferative and anti-angiogenic properties in cancer cells. However, the prevailing effects of Ang-(1-7) in the oral epithelium have not been established in vivo. Here, we used an inducible oral-specific mouse model, where the expression of a tamoxifen-inducible Cre recombinase (CreER^tam), which is under the control of the cytokeratin 14 promoter (K14-CreER^tam), induces the expression of the K-ras oncogenic variant KrasG12D (LSLK-ras^G12D). These mice develop highly proliferative squamous papilloma in the oral cavity and hyperplasia exclusively in oral mucosa within one month after tamoxifen treatment. Ang-(1-7) treated mice showed a reduced papilloma development accompanied by a significant reduction in cell proliferation and a decrease in pS6 positivity, the most downstream target of the PI3K/Akt/mTOR signaling route in oral papilloma. These results suggest that Ang-(1-7) may be a novel therapeutic target for OSCC.

Angiotensin II Type I Receptor (AT1R): The Gate towards COVID-19-Associated Diseases

The binding of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein to its cellular receptor, the angiotensin-converting enzyme 2 (ACE2), causes its downregulation, which subsequently leads to the dysregulation of the renin-angiotensin system (RAS) in favor of the ACE-angiotensin II (Ang II)-angiotensin II type I receptor (AT1R) axis. AT1R has a major role in RAS by being involved in several physiological events including blood pressure control and electrolyte balance. Following SARS-CoV-2 infection, pathogenic episodes generated by the vasoconstriction, proinflammatory, profibrotic, and prooxidative consequences of the Ang II-AT1R axis activation are accompanied by a hyperinflammatory state (cytokine storm) and an acute respiratory distress syndrome (ARDS). AT1R, a member of the G protein-coupled receptor (GPCR) family, modulates Ang II deleterious effects through the activation of multiple downstream signaling pathways, among which are MAP kinases (ERK 1/2, JNK, p38MAPK), receptor tyrosine kinases (PDGF, EGFR, insulin receptor), and nonreceptor tyrosine kinases (Src, JAK/STAT, focal adhesion kinase (FAK)), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. COVID-19 is well known for generating respiratory symptoms, but because ACE2 is expressed in various body tissues, several extrapulmonary pathologies are also manifested, including neurologic disorders, vasculature and myocardial complications, kidney injury, gastrointestinal symptoms, hepatic injury, hyperglycemia, and dermatologic complications. Therefore, the development of drugs based on RAS blockers, such as angiotensin II receptor blockers (ARBs), that inhibit the damaging axis of the RAS cascade may become one of the most promising approaches for the treatment of COVID-19 in the near future. We herein review the general features of AT1R, with a special focus on the receptor-mediated activation of the different downstream signaling pathways leading to specific cellular responses. In addition, we provide the latest insights into the roles of AT1R in COVID-19 outcomes in different systems of the human body, as well as the role of ARBs as tentative pharmacological agents to treat COVID-19.

The Role of Angiotensin II in Poisoning-Induced Shock-a Review

Background

Shock in drug poisoning is a life-threatening condition and current management involves fluid resuscitation and vasopressor therapy. Management is limited by the toxicity of high-dose vasopressors such as catecholamines. Clinical trials have shown the efficacy of angiotensin II as an adjunct vasopressor in septic shock. The aim of this review is to assess the use of angiotensin II in patients with shock secondary to drug overdose.

Methods

Medline (from 1946), Embase (from 1947) and PubMed (from 1946) databases were searched until July 2021 via OVID. Included studies were those with shock due to drug poisoning and received angiotensin II as part of their treatment regimen. Of the 481 articles identified, 13 studies (case reports and scientific abstracts) were included in the final analysis with a total of 14 patients. Extracted data included demographics, overdose drug and dosage, angiotensin II dosage, time of angiotensin II administration, haemodynamic changes, length of hospital stay, mortality, complications, cardiac function and other treatment agents used.

Results

Thirteen studies were included consisting of 6 case reports, 6 scientific abstracts and 1 case series. Overdose drugs included antihypertensives (n = 8), psychotropics (n = 4), isopropanol (n = 1) and tamsulosin (n = 1). Out of a total of 14 patients, 3 patients died. Ten patients had their haemodynamic changes reported. In terms of MAP or SBP changes, three patients (30%) had an immediate response to angiotensin II, four patients (40%) had responses within 30 min, one patient (10%) within two hours and two patients (20%) did not have their time reported. Two patients were shown to have direct chronotropic effects within 30 min of angiotensin II administration. The median hospital stay for patients was 5 days (IQR = 4). The time from overdose until angiotensin II administration ranged from 5 to 56 h. Other vasopressors used included phenylephrine, noradrenaline, adrenaline, vasopressin, dobutamine, dopamine, methylene blue and ephedrine. A median of 3 vasopressors were used before initiation of angiotensin II. Twelve patients received angiotensin II as their final treatment.

Conclusions

Angiotensin II may be useful as an adjunct vasopressor in treating shock secondary to drug poisoning. However, the current literature consisted of only very low-quality studies. To truly assess the utility of angiotensin II use in drug-induced poisoned patients, further well-designed prospective studies are required.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13181-022-00885-4.

COVID-19 and the Vasculature: Current Aspects and Long-Term Consequences

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) was first identified in December 2019 as a novel respiratory pathogen and is the causative agent of Corona Virus disease 2019 (COVID-19). Early on during this pandemic, it became apparent that SARS-CoV-2 was not only restricted to infecting the respiratory tract, but the virus was also found in other tissues, including the vasculature. Individuals with underlying pre-existing co-morbidities like diabetes and hypertension have been more prone to develop severe illness and fatal outcomes during COVID-19. In addition, critical clinical observations made in COVID-19 patients include hypercoagulation, cardiomyopathy, heart arrythmia, and endothelial dysfunction, which are indicative for an involvement of the vasculature in COVID-19 pathology. Hence, this review summarizes the impact of SARS-CoV-2 infection on the vasculature and details how the virus promotes (chronic) vascular inflammation. We provide a general overview of SARS-CoV-2, its entry determinant Angiotensin-Converting Enzyme II (ACE2) and the detection of the SARS-CoV-2 in extrapulmonary tissue. Further, we describe the relation between COVID-19 and cardiovascular diseases (CVD) and their impact on the heart and vasculature. Clinical findings on endothelial changes during COVID-19 are reviewed in detail and recent evidence from in vitro studies on the susceptibility of endothelial cells to SARS-CoV-2 infection is discussed. We conclude with current notions on the contribution of cardiovascular events to long term consequences of COVID-19, also known as “Long-COVID-syndrome”. Altogether, our review provides a detailed overview of the current perspectives of COVID-19 and its influence on the vasculature.

Drug Treatment of Heart Failure in Children: Gaps and Opportunities

Medical therapy for pediatric heart failure is based on a detailed mechanistic understanding of the underlying causes, which are diverse and unlike those encountered in most adult patients. Diuresis and improved perfusion are the immediate goals of care in the child with acute decompensated heart failure. Conversion to maintenance oral therapy for heart failure is based on the results of landmark studies in adults, as well as recent pediatric clinical trials and heart failure guidelines. There will continue to be an important role for newer drugs, some of which are in active trials in adults, and some of which are already approved for use in children. The need to plan for clinical trials in children during drug development for heart failure is emphasized.

Use of angiotensin converting enzyme inhibitors is associated with reduced risk of late bladder toxicity following radiotherapy for prostate cancer

BACKGROUND AND PURPOSE

Genome-wide association studies (GWAS) of late hematuria following prostate cancer radiotherapy identified single nucleotide polymorphisms (SNPs) near AGT, encoding angiotensinogen. We tested the hypothesis that patients taking angiotensin converting enzyme inhibitors (ACEi) have a reduced risk of late hematuria. We additionally tested genetically-defined hypertension.

MATERIALS AND METHODS

Prostate cancer patients undergoing potentially-curative radiotherapy were enrolled onto two multi-center observational studies, URWCI (N = 256) and REQUITE (N = 1,437). Patients were assessed pre-radiotherapy and followed prospectively for development of toxicity for up to four years. The cumulative probability of hematuria was estimated by the Kaplan-Meier method. Multivariable grouped relative risk models assessed the effect of ACEi on time to hematuria adjusting for clinical factors and stratified by enrollment site. A polygenic risk score (PRS) for blood pressure was tested for association with hematuria in REQUITE and our Radiogenomics Consortium GWAS.

RESULTS

Patients taking ACEi during radiotherapy had a reduced risk of hematuria (HR 0.51, 95%CI 0.28 to 0.94, p = 0.030) after adjusting for prior transurethral prostate and/or bladder resection, heart disease, pelvic node radiotherapy, and bladder volume receiving 70 Gy, which are associated with hematuria. A blood pressure PRS was associated with hypertension (odds ratio per standard deviation 1.38, 95%CI 1.31 to 1.46, n = 5,288, p < 0.001) but not hematuria (HR per standard deviation 0.96, 95%CI 0.87 to 1.06, n = 5,126, p = 0.41).

CONCLUSIONS

Our study is the first to show a radioprotective effect of ACEi on bladder in an international, multi-site study of patients receiving pelvic radiotherapy. Mechanistic studies are needed to understand how targeting the angiotensin pathway protects the bladder.

Angiotensin converting enzyme and angiotensin converting enzyme inhibitors in dermatology: a narrative review

INTRODUCTION

Angiotensin converting enzyme inhibitors (ACEI) are commonly used for cardiovascular diseases. The evidence supporting the use of ACEI in dermatology is limited.

AREAS COVERED

This review article was divided into three parts. The first part discusses ACEI in clinical use in dermatology. The second part reveals the relationship between angiotensin converting enzyme (ACE) and immune diseases, and further discusses the possible relationship between ACEI in clinical use in these diseases and ACE. The third part focuses on cutaneous adverse reactions of ACEI.

EXPERT OPINION

The use of ACEI in dermatology is mainly based on its properties as regulation of renin angiotensin system (RAS), but currently, with limited clinical use. The association of ACE and several diseases are well discussed, including COVID-19, psoriasis, sarcoidosis, systemic lupus erythematosus and vitiligo. The main cutaneous adverse effects of ACEI include angioedema, psoriasis and pemphigus. Plausible factors for these adverse reactions include accumulation of vasoactive mediators, preventing angiotension from binding to AT₁ receptor and AT₂ receptor and presence of circulating antibodies.

Diabetes, heart damage, and angiotensin II. What is the relationship link between them? A minireview

Cardiovascular complications are the main cause of mortality and morbidity in the diabetic patients, in whom changes in myocardial structure and function have been described. Numerous molecular mechanisms have been proposed that could contribute to the development of a cardiac damage. In this regard, angiotensin II (Ang II), a proinflammatory peptide that constitutes the main effector of the renin-angiotensin system (RAS) has taken a relevant role. The aim of this review was to analyze the role of Ang II in the different biochemical pathways that could be involved in the development of cardiovascular damage during diabetes. We performed an exhaustive review in the main databases, using the following terms: angiotensin II, cardiovascular damage, renin angiotensin system, inflammation, and diabetes mellitus. Classically, the RAS has been defined as a complex system of enzymes, receptors, and peptides that help control the blood pressure and the fluid homeostasis. However, in recent years, this concept has undergone substantial changes. Although this system has been known for decades, recent discoveries in cellular and molecular biology, as well as cardiovascular physiology, have introduced a better understanding of its function and relationship to the development of the diabetic cardiomyopathy.

The Association Between Angiotensin II and Renin Kinetics in Patients After Cardiac Surgery

BACKGROUND

Hyperreninemia after cardiac surgery is associated with cardiovascular instability. Angiotensin II (AT-II) could potentially attenuate hyperreninemia while maintaining target blood pressure. This study assesses the association between AT-II usage and renin levels in cardiac surgery patients with postoperative hyperreninemia and vasoplegia.

METHODS

Between September 2020 and March 2021, we retrospectively identified 40 cardiac surgery patients with high Δ-renin levels (4 hours after cardiopulmonary bypass [CPB] minus preoperative levels) (defined as higher than 3.7 µU/mL) and vasopressor use who received a vasopressor therapy with either AT-II or continued norepinephrine alone. The primary outcome was the renin plasma level at 12 hours after surgery, adjusted by the renin plasma level at 4 hours after surgery.

RESULTS

Overall, the median renin plasma concentration increased from a baseline with median of 44.3 µU/mL (Q1-Q3, 14.6-155.5) to 188.6 µU/mL (Q1-Q3, 29.8-379.0) 4 hours after CPB. High Δ-renin (difference between postoperation and preoperation) patients (higher than 3.7 µU/mL) were then treated with norepinephrine alone (median dose of 3.25 mg [Q1-Q3, 1.00-4.75]) or with additional AT-II (norepinephrine dose: 1.33 mg [Q1-Q3, 0.78-2.04]; AT-II dose: 0.34 mg [Q1-Q3, 0.29-0.78]). At 12 hours after surgery, AT-II patients had lower renin levels than standard of care patients (71.7 µU/mL [Q1-Q3, 21.9-211.4] vs 130.6 µU/mL [Q1-Q3, 62.9-317.0]; P = .034 adjusting for the renin plasma level at 4 hours after surgery).

CONCLUSIONS

In cardiac surgery patients with hypotonia and postoperative high Δ-renin levels, AT-II was associated with reduced renin plasma levels for at 12 hours and significantly decreased norepinephrine use, while norepinephrine alone was associated with increased renin levels. Further studies of AT-II in cardiac surgery appear justified.

Multiple Aspects of Inappropriate Action of Renin-Angiotensin, Vasopressin, and Oxytocin Systems in Neuropsychiatric and Neurodegenerative Diseases

The cardiovascular system and the central nervous system (CNS) closely cooperate in the regulation of primary vital functions. The autonomic nervous system and several compounds known as cardiovascular factors, especially those targeting the renin–angiotensin system (RAS), the vasopressin system (VPS), and the oxytocin system (OTS), are also efficient modulators of several other processes in the CNS. The components of the RAS, VPS, and OTS, regulating pain, emotions, learning, memory, and other cognitive processes, are present in the neurons, glial cells, and blood vessels of the CNS. Increasing evidence shows that the combined function of the RAS, VPS, and OTS is altered in neuropsychiatric/neurodegenerative diseases, and in particular in patients with depression, Alzheimer’s disease, Parkinson’s disease, autism, and schizophrenia. The altered function of the RAS may also contribute to CNS disorders in COVID-19. In this review, we present evidence that there are multiple causes for altered combined function of the RAS, VPS, and OTS in psychiatric and neurodegenerative disorders, such as genetic predispositions and the engagement of the RAS, VAS, and OTS in the processes underlying emotions, memory, and cognition. The neuroactive pharmaceuticals interfering with the synthesis or the action of angiotensins, vasopressin, and oxytocin can improve or worsen the effectiveness of treatment for neuropsychiatric/neurodegenerative diseases. Better knowledge of the multiple actions of the RAS, VPS, and OTS may facilitate programming the most efficient treatment for patients suffering from the comorbidity of neuropsychiatric/neurodegenerative and cardiovascular diseases.

AMPA and angiotensin type 1 receptors are necessary for hemorrhage-induced vasopressin secretion

Hypovolemia induced by hemorrhage is a common clinical complication, which stimulates vasopressin (AVP) secretion by the neurohypophysis in order to retain body water and maintain blood pressure. To evaluate the role of brain L-glutamate and angiotensin II on AVP secretion induced by hypovolemia we induced hemorrhage (∼25% of blood volume) after intracerebroventricular (icv) administration of AP5, NBQX, or losartan, which are NMDA, AMPA, and AT1 receptor antagonists, respectively. Hemorrhage significantly increased plasma AVP levels in all groups. The icv injection of AP5 did not change AVP secretion in response to hemorrhage. Conversely, icv administration of both NBQX and losartan significantly decreased plasma AVP levels after hemorrhage. Therefore, the blockade of AMPA and AT1 receptors impaired AVP secretion in response to hemorrhage, suggesting that L-glutamate and angiotensin II acted in these receptors to increase AVP secretion in response to hemorrhage-induced hypovolemia.

Fetal Undernutrition Modifies Vascular RAS Balance Enhancing Oxidative Damage and Contributing to Remodeling

Fetal stress is known to increase susceptibility to cardiometabolic diseases and hypertension in adult age in a process known as fetal programming. This study investigated the relationship between vascular RAS, oxidative damage and remodeling in fetal programming. Six-month old Sprague-Dawley offspring from mothers that were fed ad libitum (CONTROL) or with 50% intake during the second half of gestation (maternal undernutrition, MUN) were used. qPCR or immunohistochemistry were used to obtain the expression of receptors and enzymes. Plasma levels of carbonyls were measured by spectrophotometry. In mesenteric arteries from MUN rats we detected an upregulation of ACE, ACE2, AT₁ receptors and NADPH oxidase, and lower expression of AT₂, Mas and MrgD receptors compared to CONTROL. Systolic and diastolic blood pressure and plasma levels of carbonyls were higher in MUN than in CONTROL. Vascular morphology evidenced an increased media/lumen ratio and adventitia/lumen ratio, and more connective tissue in MUN compared to CONTROL. In conclusion, fetal undernutrition indices RAS alterations and oxidative damage which may contribute to the remodeling of mesenteric arteries, and increase the risk of adverse cardiovascular events and hypertension.

Characterization of the intrarenal renin-angiotensin system in cats with naturally occurring chronic kidney disease

Background

The role of the renin‐angiotensin‐aldosterone system in cats with chronic kidney disease (CKD) is incompletely understood.

Objective

To characterize components of the intrarenal renin‐angiotensin system (RAS) in cats with CKD.

Animals

Eleven cats with naturally occurring CKD (CKD group) and 8 healthy control cats.

Methods

Renal tissue samples were evaluated by reverse‐transcription polymerase chain reaction for renin, angiotensinogen, angiotensin‐converting enzyme (ACE), and angiotensin II type 1 receptor transcript levels, and by liquid chromatography‐mass spectrometry for quantification of angiotensin I, II, III, and IV concentrations. Linear mixed models were used to compare gene transcript levels and concentrations of angiotensin peptides between groups.

Results

Cats of the CKD group were significantly older (P < .001) and more likely to be neutered (P = .007) than healthy control cats. Kidneys from cats with CKD had significantly higher transcript levels of angiotensinogen (P < .001) and lower transcript levels of ACE (P < .001) than those from control cats. Renal angiotensin I concentrations were increased in CKD compared with control kidneys (P = .001). No other significant differences in renal transcript levels or angiotensin peptide concentrations were noted between groups.

Conclusion and Clinical Importance

The intrarenal RAS might be activated in cats with CKD. Small sample size and differences in age, neuter status, and dietary sodium intake between groups might have limited the ability to identify a significant difference in concentration of renal angiotensin II.

Mechanisms for the development of heart failure and improvement of cardiac function by angiotensin-converting enzyme inhibitors

Angiotensin-converting enzyme (ACE) inhibitors, which prevent the conversion of angiotensin I to angiotensin II, are well-known for the treatments of cardiovascular diseases, such as heart failure, hypertension and acute coronary syndrome. Several of these inhibitors including captopril, enalapril, ramipril, zofenopril and imidapril attenuate vasoconstriction, cardiac hypertrophy and adverse cardiac remodeling, improve clinical outcomes in patients with cardiac dysfunction and decrease mortality. Extensive experimental and clinical research over the past 35 years has revealed that the beneficial effects of ACE inhibitors in heart failure are associated with full or partial prevention of adverse cardiac remodeling. Since cardiac function is mainly determined by coordinated activities of different subcellular organelles, including sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils, for regulating the intracellular concentration of Ca2+ and myocardial metabolism, there is ample evidence to suggest that adverse cardiac remodelling and cardiac dysfunction in the failing heart are the consequence of subcellular defects. In fact, the improvement of cardiac function by different ACE inhibitors has been demonstrated to be related to the attenuation of abnormalities in subcellular organelles for Ca2+-handling, metabolic alterations, signal transduction defects and gene expression changes in failing cardiomyocytes. Various ACE inhibitors have also been shown to delay the progression of heart failure by reducing the formation of angiotensin II, the development of oxidative stress, the level of inflammatory cytokines and the occurrence of subcellular defects. These observations support the view that ACE inhibitors improve cardiac function in the failing heart by multiple mechanisms including the reduction of oxidative stress, myocardial inflammation and Ca2+-handling abnormalities in cardiomyocytes.

Implications of testicular ACE2 and the renin-angiotensin system for SARS-CoV-2 on testis function

Although many studies have focused on SARS-CoV-2 infection in the lungs, comparatively little is known about the potential effects of the virus on male fertility. SARS-CoV-2 infection of target cells requires the presence of furin, angiotensin-converting enzyme 2 (ACE2) receptors, and transmembrane protease serine 2 (TMPRSS2). Thus, cells in the body that express these proteins might be highly susceptible to viral entry and downstream effects. Currently, reports regarding the expression of the viral entry proteins in the testes are conflicting; however, other members of the SARS-CoV family of viruses - such as SARS-CoV - have been suspected to cause testicular dysfunction and/or orchitis. SARS-CoV-2, which displays many similarities to SARS-CoV, could potentially cause similar adverse effects. Commonalities between SARS family members, taken in combination with sparse reports of testicular discomfort and altered hormone levels in patients with SARS-CoV-2, might indicate possible testicular dysfunction. Thus, SARS-CoV-2 infection has the potential for effects on testis somatic and germline cells and experimental approaches might be required to help identify potential short-term and long-term effects of SARS-CoV-2 on male fertility.

Central regulation of body fluid homeostasis

Extracellular fluids, including blood, lymphatic fluid, and cerebrospinal fluid, are collectively called body fluids. The Na⁺ concentration ([Na⁺]) in body fluids is maintained at 135-145 mM and is broadly conserved among terrestrial animals. Homeostatic osmoregulation by Na⁺ is vital for life because severe hyper- or hypotonicity elicits irreversible organ damage and lethal neurological trauma. To achieve "body fluid homeostasis" or "Na homeostasis", the brain continuously monitors [Na⁺] in body fluids and controls water/salt intake and water/salt excretion by the kidneys. These physiological functions are primarily regulated based on information on [Na⁺] and relevant circulating hormones, such as angiotensin II, aldosterone, and vasopressin. In this review, we discuss sensing mechanisms for [Na⁺] and hormones in the brain that control water/salt intake behaviors, together with the responsible sensors (receptors) and relevant neural pathways. We also describe mechanisms in the brain by which [Na⁺] increases in body fluids activate the sympathetic neural activity leading to hypertension.

Hamster organotypic kidney culture model of early-stage SARS-CoV-2 infection highlights a two-step renal susceptibility

Kidney pathology is frequently reported in patients hospitalized with COVID-19, the pandemic disease caused by the Severe acute respiratory coronavirus 2 (SARS-CoV-2). However, due to a lack of suitable study models, the events occurring in the kidney during the earliest stages of infection remain unknown. We have developed hamster organotypic kidney cultures (OKCs) to study the early stages of direct renal infection. OKCs maintained key renal structures in their native three-dimensional arrangement. SARS-CoV-2 productively replicated in hamster OKCs, initially targeting endothelial cells and later disseminating into proximal tubules. We observed a delayed interferon response, markers of necroptosis and pyroptosis, and an early repression of pro-inflammatory cytokines transcription followed by a strong later upregulation. While it remains an open question whether an active replication of SARS-CoV-2 takes place in the kidneys of COVID-19 patients with AKI, our model provides new insights into the kinetics of SARS-CoV-2 kidney infection and can serve as a powerful tool for studying kidney infection by other pathogens and testing the renal toxicity of drugs.

Activation of the intestinal tissue renin-angiotensin system by transient sodium loading in salt-sensitive rats

BACKGROUND

The renal tissue renin-angiotensin system is known to be activated by salt loading in salt-sensitive rats; however, the response in other organs remains unclear.

METHOD

Spontaneously hypertensive rats were subjected to normal tap water or transient high-salt-concentration water from 6 to 14 weeks of age and were thereafter given normal tap water. From 18 to 20 weeks of age, rats given water with a high salt concentration were treated with an angiotensin II type 1 receptor blocker, valsartan.

RESULTS

Sustained blood pressure elevation by transient salt loading coincided with a persistent decrease in the fecal sodium content and sustained excess of the circulating volume in spontaneously hypertensive rats. Administration of valsartan sustainably reduced the blood pressure and normalized the fecal sodium levels. Notably, transient salt loading persistently induced the intestinal tissue renin-angiotensin system and enhanced sodium transporter expression exclusively in the small intestine of salt-sensitive rats, suggesting the potential connection of intestinal sodium absorption to salt sensitivity.

CONCLUSION

These results reveal the previously unappreciated contribution of the intestinal tissue renin-angiotensin system to sodium homeostasis and blood pressure regulation in the pathophysiology of salt-sensitive hypertension.

DAD3 targets ACE2 to inhibit the MAPK and NF-κB signalling pathways and protect against LPS-induced inflammation in bovine mammary epithelial cells

The protective arm of the renin-angiotensin system (RAS), the ACE 2/Ang-(1-7)/MasR axis, has become a new anti-inflammatory target. As a specific activator of ACE2, diminazene aceturate (DA) can promote anti-inflammatory effects by regulating the ACE2/Ang-(1-7)/MasR axis. However, due to the reported toxicity of DA, its application has been limited. In the current study, we synthesized a low toxicity DA derivative 3 (DAD3) and sought to determine whether DAD3 can also activate ACE2 in bovine mammary epithelial cells (BMEC) and regulate the RAS system to inhibit inflammation. We found that both DA and DAD3 can activate and promote ACE2 expression in BMEC. iRNA-mediated knockdown of ACE2 demonstrated that DAD3 activates the ACE2/Ang-(1-7)/MasR axis and plays an anti-inflammatory role in BMEC. Furthermore, the inhibitory effects of DA and DAD3 on the protein phosphorylation of MAPK and NF-κB pathways were reduced in ACE2-silenced BMEC. Our findings show that ACE2 is a target of DAD3, which leads to inhibition of the MAPK and NF-κB signalling pathways and protects against LPS-induced inflammation in BMEC. Thus, DAD3 may provide a new strategy to treat dairy cow mastitis.

(Pro)renin Receptor and Blood Pressure Regulation: A Focus on the Central Nervous System

The renin-angiotensin system (RAS) is classically described as a hormonal system in which angiotensin II (Ang II) is one of the main active peptides. The action of circulating Ang II on its cognate Ang II type-1 receptor (AT1R) in circumventricular organs has important roles in regulating the autonomic nervous system, blood pressure (BP) and body fluid homeostasis, and has more recently been implicated in cardiovascular metabolism. The presence of a local or tissue RAS in various tissues, including the central nervous system (CNS), is well established. However, because the level of renin, the rate-limiting enzyme in the systemic RAS, is very low in the brain, how endogenous angiotensin peptides are generated in the CNS-the focus of this review-has been the subject of considerable debate. Notable in this context is the identification of the (pro)renin receptor (PRR) as a key component of the brain RAS in the production of Ang II in the CNS. In this review, we highlight cellular and anatomical locations of the PRR in the CNS. We also summarize studies using gain- and loss-of function approaches to elucidate the functional importance of brain PRR-mediated Ang II formation and brain RAS activation, as well as PRR-mediated Ang II-independent signaling pathways, in regulating BP. We further discuss recent developments in PRR involvement in cardiovascular and metabolic diseases and present perspectives for future directions.

Mineralocorticoid receptor in non-alcoholic fatty liver disease

Liver diseases are the fourth common death in Europe responsible for about 2 million death per year worldwide. Among the known detrimental causes for liver dysfunction are virus infections, intoxications and obesity. The mineralocorticoid receptor (MR) is a ligand-dependent transcription factor activated by aldosterone or glucocorticoids but also by pathological milieu factors. Canonical actions of the MR take place in epithelial cells of kidney, colon and sweat glands and contribute to sodium reabsorption, potassium secretion and extracellular volume homeostasis. The non-canonical functions can be initiated by inflammation or an altered micro milieu leading to fibrosis, hypertrophy and remodeling in various tissues. This narrative review summarizes the evidence regarding the role of MR in portal hypertension, non-alcoholic fatty liver disease, liver fibrosis and cirrhosis, demonstrating that inhibition of the MR in vivo seems to be beneficial for liver function and not just for volume regulation. Unfortunately, the underlying molecular mechanisms are still not completely understood.

Interactions of renin-angiotensin system and COVID-19: the importance of daily rhythms in ACE2, ADAM17 and TMPRSS2 expression

Angiotensin-converting enzyme 2 (ACE2) was identified as a molecule that mediates the cellular entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several membrane molecules of the host cell must cooperate in this process. While ACE2 serves in a membrane receptor-mediating interaction with the surface spike (S) glycoprotein of SARS-CoV-2 located on the virus envelope, enzyme A disintegrin and metalloproteinase 17 (ADAM17) regulates ACE2 availability on the membrane and transmembrane protease serine 2 (TMPRSS2) facilitates virus-cell membrane fusion. Interestingly, ACE2, ADAM17 and TMPRSS2 show a daily rhythm of expression in at least some mammalian tissue. The circadian system can also modulate COVID-19 progression via circadian control of the immune system (direct, as well as melatonin-mediated) and blood coagulation. Virus/ACE2 interaction causes ACE2 internalization into the cell, which is associated with suppressed activity of ACE2. As a major role of ACE2 is to form vasodilatory angiotensin 1-7 from angiotensin II (Ang II), suppressed ACE2 levels in the lung can contribute to secondary COVID-19 complications caused by up-regulated, pro-inflammatory vasoconstrictor Ang II. This is supported by the positive association of hypertension and negative COVID-19 prognosis although this relationship is dependent on numerous comorbidities. Hypertension treatment with inhibitors of renin-angiotensin system does not negatively influence prognosis of COVID-19 patients. It seems that tissue susceptibility to SARS-CoV-2 shows negative correlation to ACE2 expression. However, in lungs of infected patient, a high ACE2 expression is associated with better outcome, compared to low ACE2 expression. Manipulation of soluble ACE2 levels is a promising COVID-19 therapeutic strategy.

Effect of the Renin-Angiotensin-Aldosterone System Reactivity on Endothelial Function and Modulative Role of Valsartan in Male Subjects with Essential Hypertension

BACKGROUND

The aim of the study was to evaluate the relationship between renin-angiotensin-aldosterone (RAA) system activity and reactivity, and the endothelial function profile in normotensive subjects (N), and in essential hypertensives (H), followed by analysis of the modulatory role of an angiotensin receptor blocker (ARB): valsartan, administered in the management of hypertension.

METHODS

A total of 101 male subjects were enrolled to the study: 31H and 70N. The nitric-oxide (NO) bioavailability (l-Arginine, asymmetric dimethylarginine (ADMA)), symmetric dimethylarginine (SDMA), endothelial vasodilative function (flow mediated dilation (FMD)), oxidative-stress markers (malonyldialdehyde (MDA), thiol index (GSH/GSSG), nitrotyrozine (N-Tyr)), and pro-inflammatory/angiogenic parameters (sICAM-1, sVCAM-1, PAI-1, sE-selectin, PAI-1, thromboxane -B2) were assessed at baseline, then after intravenous -l-arginine administration, which was repeated after the 4-day acetylsalicylic acid (ASA) administration (75 mg/24 h). In hypertensives, this whole protocol was repeated following 2 weeks of valsartan therapy.

RESULTS

No effect of valsartan and ASA on the flow-mediated vasodilation (FMD) and the NO bioavailability in hypertensives was observed. Administration of valsartan increased plasma renin activity (PRA), but without a decrease in the aldosterone levels. ASA treatment minimized the pre-existing differences between the groups, and increased the PRA in the N-subgroup with the highest ARR values. The blood concentrations of proinflammatory sICAM-1, sE-selectin, sVCAM-1, and PAI-1 were higher, whereas the anti-inflammatory 6-keto-PGF1 alpha level was lower in hypertensive subjects. The levels of angiogenic VEGF did not differ between groups.

CONCLUSIONS

Our study does not confirm the modulative effect of valsartan on endothelial function. Normotensive men showed an increase in FMD after l-arginine administration, possibly indicating baseline impairment of the NO synthesis.

Telmisartan impairs the in vitro osteogenic differentiation of mesenchymal stromal cells from spontaneously hypertensive male rats

Telmisartan (TELM) is an angiotensin II (Ang II) type 1 receptor (Agtr1) antagonist, with partial agonism for Pparg, and has been shown to affect bone metabolism. Therefore, the aim of this study was to investigate the effects of TELM in the in vitro osteogenic differentiation of bone marrow-derived mesenchymal stromal cells (BMSC) from spontaneously hypertensive rats (SHRs). BMSC were obtained from male SHR, and the osteogenic medium (OM) was added to the cells concomitantly with TELM (0.005, 0.05, and 0.5 μM). Undifferentiated BMSC, in control medium (CM), showed an increased viability, while the addition of OM reduced this parameter, and TELM did not show cytotoxicity in the concentrations used. BMSC in OM had an alkaline phosphatase (ALP) activity peak at d10, which decreased at d14 and d21, and TELM reduced ALP at d10 in a dose-dependent manner. Mineralization was observed in the OM at d14, which intensified at d21, but was inhibited by TELM. Agtr1b was increased in the OM, and TELM inhibited its expression. TELM reduced Opn, Ocn, and Bsp and increased Pparg expression, and at the higher concentration TELM also increased the expression of adipogenic markers, Fabp4 and Adipoq. In addition, TELM 0.5 μM increased Irs1 and Glut4, insulin and glucose metabolism markers, known to be regulated by Pparg and to be related to adipogenic phenotype. Our data shows that TELM inhibited the osteogenic differentiation and mineralization of SHR BMSC, by favoring an adipogenic prone phenotype due to Pparg upregulation.

COVID-19 in pregnancy: What we know from the first year of the pandemic

The COVID-19 pandemic has infected nearly 178 million people and claimed the lives of over 3.8 million in less than 15 months. This has prompted a flurry of research studies into the mechanisms and effects of SARS-CoV-2 viral infection in humans. However, studies examining the effects of COVID-19 in pregnant women, their placentae and their babies remain limited. Furthermore, reports of safety and efficacy of vaccines for SARS-CoV-2 in pregnancy are limited. This review concisely summarises the case studies and research on COVID-19 in pregnancy, to date. It also reviews the mechanism of infection with SARS-CoV-2, and its reliance and effects upon the renin-angiotensin-aldosterone system. Overall, the data suggest that infection during pregnancy can be dangerous at any time, but this risk to both the mother and fetus, as well as placental damage, increases during the third trimester. The possibility of vertical transmission, which is explored in this review, remains contentious. However, maternal infection with SARS-CoV-2 can increase risk of miscarriage, preterm birth and stillbirth, which is likely due to damage to the placenta.

Participation of angiotensin-(1-7) in exercise-induced analgesia in rats with neuropathic pain

Exercise reduces neuropathic pain in animals and humans. Recent studies indicate that training exercise favors the synthesis and action of angiotensin-(1-7) (Ang-(1-7)), a vasoactive peptide of the renin-angiotensin system (RAS), in various tissues. Interestingly, Ang-(1-7) also relieves neuropathic pain; however, it remains to be elucidated whether exercise mitigates this type of pain through Ang-(1-7). In this study, we investigated the role of Ang-(1-7) in exercise-induced analgesia in a neuropathic pain model. Male Wistar rats were ligated of lumbar spinal nerves (L5 and L6) or sham-operated. Then, they were subjected to acute (2-h) or chronic (4-week) exercise protocols. Tactile allodynia was evaluated before and after each exercise intervention. Microosmotic pumps were implanted subcutaneously for the release of Ang-(1-7) or A779 (selective Mas receptor (MasR; Ang-(1-7) receptor) antagonist). Plasma levels of Ang II and Ang-(1-7) were quantified by HPLC. Spinal nerve ligation (SNL) produced tactile allodynia. Both acute and chronic exercise reversed this neuropathic behavior. A779 treatment prevented the antiallodynic effect induced by each exercise protocol. SNL increased the plasma Ang II/Ang-(1-7) ratio; however, exercise did not modify it. Acute treatment with Ang-(1-7) via MasR mimicked exercise-mediated antinociception. Collectively, these results suggest that activation of the Ang-(1-7)/MasR axis of the RAS represents a potential novel mechanism by which exercise attenuates neuropathic pain in rats.

Common Inflammatory Mechanisms in COVID-19 and Parkinson's Diseases: The Role of Microbiome, Pharmabiotics and Postbiotics in Their Prevention

In the last decade, metagenomic studies have shown the key role of the gut microbiome in maintaining immune and neuroendocrine systems. Malfunction of the gut microbiome can induce inflammatory processes, oxidative stress, and cytokine storm. Dysfunction of the gut microbiome can be caused by short-term (virus infection and other infectious diseases) or long-term (environment, nutrition, and stress) factors. Here, we reviewed the inflammation and oxidative stress in neurodegenerative diseases and coronavirus infection (COVID-19). Here, we reviewed the renin-angiotensin-aldosterone system (RAAS) involved in the processes of formation of oxidative stress and inflammation in viral and neurodegenerative diseases. Moreover, the coronavirus uses ACE2 receptors of the RAAS to penetrate human cells. The coronavirus infection can be the trigger for neurodegenerative diseases by dysfunction of the RAAS. Pharmabiotics, postbiotics, and next-generation probiotics, are considered as a means to prevent oxidative stress, inflammatory processes, neurodegenerative and viral diseases through gut microbiome regulation.

Angiotensin II and the Cardiac Parasympathetic Nervous System in Hypertension

The renin-angiotensin-aldosterone system (RAAS) impacts cardiovascular homeostasis via direct actions on peripheral blood vessels and via modulation of the autonomic nervous system. To date, research has primarily focused on the actions of the RAAS on the sympathetic nervous system. Here, we review the critical role of the RAAS on parasympathetic nerve function during normal physiology and its role in cardiovascular disease, focusing on hypertension. Angiotensin (Ang) II receptors are present throughout the parasympathetic nerves and can modulate vagal activity via actions at the level of the nerve endings as well as via the circumventricular organs and as a neuromodulator acting within brain regions. There is tonic inhibition of cardiac vagal tone by endogenous Ang II. We review the actions of Ang II via peripheral nerve endings as well as via central actions on brain regions. We review the evidence that Ang II modulates arterial baroreflex function and examine the pathways via which Ang II can modulate baroreflex control of cardiac vagal drive. Although there is evidence that Ang II can modulate parasympathetic activity and has the potential to contribute to impaired baseline levels and impaired baroreflex control during hypertension, the exact central regions where Ang II acts need further investigation. The beneficial actions of angiotensin receptor blockers in hypertension may be mediated in part via actions on the parasympathetic nervous system. We highlight important unknown questions about the interaction between the RAAS and the parasympathetic nervous system and conclude that this remains an important area where future research is needed.

Zebrafish Model to Study Angiotensin II-Mediated Pathophysiology

Hypertension, a common chronic condition, may damage multiple organs, including the kidney, heart, and brain. Thus, it is essential to understand the pathology upon ectopic activation of the molecular pathways involved in mammalian hypertension to develop strategies to manage hypertension. Animal models play a crucial role in unraveling the disease pathophysiology by allowing incisive experimental procedures impossible in humans. Zebrafish, a small freshwater fish, have emerged as an important model system to study human diseases. The primary effector, Angiotensin II of the RAS pathway, regulates hemodynamic pressure overload mediated cardiovascular pathogenesis in mammals. There are various established mammalian models available to study pathophysiology in Angiotensin II-induced hypertension. Here, we have developed a zebrafish model to study pathogenesis by Angiotensin II. We find that intradermal Angiotensin II injection every 12 h can induce cardiac remodeling in seven days. We show that Angiotensin II injection in adult zebrafish causes cardiomyocyte hypertrophy and enhances cardiac cell proliferation. In addition, Angiotensin II induces ECM protein-coding gene expression and fibrosis in the cardiac ventricles. Thus, this study can conclude that Angiotensin II injection in zebrafish has similar implications as mammals, and zebrafish can be a model to study pathophysiology associated with AngII-RAS signaling.

μ-Opioid Receptor-Mediated AT1R-TLR4 Crosstalk Promotes Microglial Activation to Modulate Blood Pressure Control in the Central Nervous System

Opioids, a kind of peptide hormone involved in the development of hypertension, cause systemic and cerebral inflammation, and affects regions of the brain that are important for blood pressure (BP) control. A cause-and-effect relationship exists between hypertension and inflammation; however, the role of blood pressure in cerebral inflammation is not clear. Evidence showed that AT1R and μOR heterodimers’ formation in the NTS might lead to the progression of hypertension. In this study, we investigated the formation of the μOR/AT1R heterodimer, determined its correlation with μORs level in the NTS, and explored the role of TLR4-dependent inflammation in the development of hypertension. Results showed that Ang II increased superoxide and Iba-1 (microgliosis marker: ionized calcium-binding adaptor molecule (1) levels in the NTS of spontaneously hypertensive rats (SHRs). The AT1R II inhibitor, losartan, significantly decreased BP and abolished superoxide, Iba-1, TLR4 expression induced by Ang II. Furthermore, losartan significantly increased nNsOS^S1416 phosphorylation. Administration of a μOR agonist or antagonist in the NTS of WKY and SHRs increased endogenous μ-opioids, triggered the formation of μOR/AT1R heterodimers and the TLR4-dependent inflammatory pathway, and attenuated the effect of depressor nitric oxide (NO). These results imply an important link between neurotoxicity and superoxides wherein abnormal increases in NTS endogenous μ-opioids promote the interaction between Ang II and μOR, the binding of Ang II to AT1R, and the activation of microglia. In addition, the interaction between Ang II and μOR enhanced the formation of the AT1R and μOR heterodimers, and inactivated nNOS-derived NO, leading to the development of progressive hypertension.

The Role of Endothelium in COVID-19

The 2019 novel coronavirus, known as severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) or coronavirus disease 2019 (COVID-19), is causing a global pandemic. The virus primarily affects the upper and lower respiratory tracts and raises the risk of a variety of non-pulmonary consequences, the most severe and possibly fatal of which are cardiovascular problems. Data show that almost one-third of the patients with a moderate or severe form of COVID-19 had preexisting cardiovascular comorbidities such as diabetes mellitus, obesity, hypertension, heart failure, or coronary artery disease. SARS-CoV2 causes hyper inflammation, hypoxia, apoptosis, and a renin–angiotensin system imbalance in a variety of cell types, primarily endothelial cells. Profound endothelial dysfunction associated with COVID-19 can be the cause of impaired organ perfusion that may generate acute myocardial injury, renal failure, and a procoagulant state resulting in thromboembolic events. We discuss the most recent results on the involvement of endothelial dysfunction in the pathogenesis of COVID-19 in patients with cardiometabolic diseases in this review. We also provide insights on treatments that may reduce the severity of this viral infection.

Vitamin D Deficiency Exacerbates Colonic Inflammation Due to Activation of the Local Renin-Angiotensin System in the Colon

BACKGROUND

The renin-angiotensin system (RAS) is activated in inflammatory bowel disease (IBD), and vitamin D deficiency aggravates the development of colitis, but the relationship between the local colonic RAS and vitamin D is unclear with regard to the pathogenesis of IBD.

AIMS

To investigate whether vitamin D suppresses the local colonic RAS to prevent colonic mucosal inflammation in a mouse model of experimental colitis.

METHODS

C57BL/6 mice fed vitamin D-deficient (VDD) diet for 8 weeks were induced to colitis by 2,4,6-trinitrobenzenesulfonic acid (TNBS), with mice fed vitamin D-sufficient (VDS) diet as controls. Colitis severity was assessed by histology, and pro-inflammatory cytokines, RAS components, and signaling pathways were quantified by real-time RT-PCR and Western blotting.

RESULTS

C57BL/6 mice fed the VDD diet for 8 weeks exhibited significantly lower serum 25(OH)D₃ concentrations compared to mice fed the VDS diet. When these VDD mice were induced to colitis by TNBS, they exhibited more severe colonic inflammation and developed more severe colitis compared to the VDS counterparts. VDD diet feeding resulted in higher production of mucosal pro-inflammatory cytokines, higher activation of the myosin light chain kinase-tight junction regulatory pathway, and greater increases in mucosal permeability. VDD diet feeding also enhanced colonic RAS activation. Treatment with angiotensin II receptor blocker losartan markedly alleviated colitis in TNBS-induced VDD mice.

CONCLUSION

Vitamin D deficiency promotes colonic inflammation at least in part due to over activation of the local RAS in the colon.

RAAS, ACE2 and COVID-19; a mechanistic review

The use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in coronavirus disease 2019 (COVID-19) patients has been claimed as associated with the risk of COVID-19 infection and its subsequent morbidities and mortalities. These claims were resulting from the possibility of upregulating the expression of angiotensin-converting enzyme 2 (ACE2), facilitation of SARS-CoV-2 entry, and increasing the susceptibility of infection in such treated cardiovascular patients. ACE2 and renin-angiotensin-aldosterone system (RAAS) products have a critical function in controlling the severity of lung injury, fibrosis, and failure following the initiation of the disease. This review is to clarify the mechanisms beyond the possible deleterious effects of angiotensin II (Ang II), and the potential protective role of angiotensin 1-7 (Ang 1-7) against pulmonary fibrosis, with a subsequent discussion of the latest updates on ACEIs/ARBs use and COVID-19 susceptibility in the light of these mechanisms and biochemical explanation.

Renoprotective mechanisms of sodium-glucose co-transporter 2 (SGLT2) inhibitors against the progression of diabetic kidney disease

Sodium-glucose co-transporter 2 inhibitors (SGLT2-Is) have emerged as a promising class of antidiabetic drugs with cardioprotective and renoprotective effects in patients with type 2 diabetes (T2D). The sodium-glucose co-transporters 1 and 2 (SGLT 1 and SGLT2) located in the renal proximal tubules are responsible for glucose reabsorption from the glomerular filtrate back into the systemic circulation. Inhibition of SGLT2, which accounts for about 90% of the glucose reabsorption, leads to a significant reduction in blood glucose levels and a concomitant increase in the urinary excretion of glucose (glycosuria). Multiple mechanisms contribute to the nephroprotective effects of SGLT2-Is in T2D patients. These include: (1) Restoration of the tubuloglomerular feedback by increasing sodium delivery at macula densa, leading to afferent arteriolar constriction and reduced glomerular hyperfiltration, (2) Decreased activation of the intra-renal renin-angiotensin-aldosterone system, which also contributes to reducing glomerular hyperfiltration, (3) Increased production of ketone bodies, which serves as an alternate fuel for adenosine triphosphate production in mitochondria, which helps in attenuating inflammation, and (4) Protection against hypoxia, oxidative stress, and fibrosis. This review elaborates on the key mechanisms that underlie the nephroprotective effects and the adverse effects of SGLT2-Is in T2D patients with progressive diabetic kidney disease.

Age and genotype dependent erythropoietin protection in COVID-19

Erythropoietin (EPO) is the main mediator of erythropoiesis and an important tissue protective hormone that appears to mediate an ancestral neuroprotective innate immune response mechanism at an early age. When the young brain is threatened-prematurity, neonatal hyperbilirubinemia, malaria- EPO is hyper-secreted disproportionately to any concurrent anemic stimuli. Under eons of severe malarial selection pressure, neuroprotective EPO augmenting genetic determinants such as the various hemoglobinopathies, and the angiotensin converting enzyme (ACE) I/D polymorphism, have been positively selected. When malarial and other cerebral threats abate and the young child survives to adulthood, EPO subsides. Sustained high ACE and angiotensin II (Ang II) levels through the ACE D allele in adulthood may then become detrimental as witnessed by epidemiological studies. The ubiquitous renin angiotensin system (RAS) influences the α-klotho/fibroblast growth factor 23 (FGF23) circuitry, and both are interconnected with EPO. Here we propose that at a young age, EPO augmenting genetic determinants through ACE D allele elevated Ang II levels in some or HbE/beta thalassemia in others would increase EPO levels and shield against coronavirus disease 2019, akin to protection from malaria and dengue fever. Human evolution may use ACE2 as a “bait” for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) to gain cellular entry in order to trigger an ACE/ACE2 imbalance and stimulate EPO hypersecretion using tissue RAS, uncoupled from hemoglobin levels. In subjects without EPO augmenting genetic determinants at any age, ACE2 binding and internalization upon SARS-CoV-2 entry would trigger an ACE/ACE2 imbalance, and Ang II oversecretion leading to protective EPO stimulation. In children, low nasal ACE2 Levels would beneficially augment this imbalance, especially for those without protective genetic determinants. On the other hand, in predisposed adults with the ACE D allele, ACE/ACE2 imbalance, may lead to uncontrolled RAS overactivity and an Ang II induced proinflammatory state and immune dysregulation, with interleukin 6 (IL-6), plasminogen activator inhibitor, and FGF23 elevations. IL-6 induced EPO suppression, aggravated through co-morbidities such as hypertension, diabetes, obesity, and RAS pharmacological interventions may potentially lead to acute respiratory distress syndrome, cytokine storm and/or autoimmunity. HbE/beta thalassemia carriers would enjoy protection at any age as their EPO stimulation is uncoupled from the RAS system. The timely use of rhEPO, EPO analogs, acetylsalicylic acid, bioactive lipids, or FGF23 antagonists in genetically predisposed individuals may counteract those detrimental effects.

Quantifying Renin-Angiotensin-System Alterations in COVID-19

The renin-angiotensin system (RAS) plays a pivotal role in a wide series of physiological processes, among which inflammation and blood pressure regulation. One of its key components, the angiotensin-converting enzyme 2, has been identified as the entry point of the SARS-CoV-2 virus into the host cells, and therefore a lot of research has been devoted to study RAS dysregulation in COVID-19. Here we discuss the alterations of the regulatory RAS axes due to SARS-CoV-2 infection on the basis of a series of recent clinical investigations and experimental analyzes quantifying, e.g., the levels and activity of RAS components. We performed a comprehensive meta-analysis of these data in view of disentangling the links between the impaired RAS functioning and the pathophysiological characteristics of COVID-19. We also review the effects of several RAS-targeting drugs and how they could potentially help restore the normal RAS functionality and minimize the COVID-19 severity. Finally, we discuss the conflicting evidence found in the literature and the open questions on RAS dysregulation in SARS-CoV-2 infection whose resolution would improve our understanding of COVID-19.

Alterations in ACE and ACE2 Activities and Cardiomyocyte Signaling Underlie Improved Myocardial Function in a Rat Model of Repeated Remote Ischemic Conditioning

Post-ischemic left ventricular (LV) remodeling and its hypothetical prevention by repeated remote ischemic conditioning (rRIC) in male Sprague–Dawley rats were studied. Myocardial infarction (MI) was evoked by permanent ligation of the left anterior descending coronary artery (LAD), and myocardial characteristics were tested in the infarcted anterior and non-infarcted inferior LV regions four and/or six weeks later. rRIC was induced by three cycles of five-minute-long unilateral hind limb ischemia and five minutes of reperfusion on a daily basis for a period of two weeks starting four weeks after LAD occlusion. Sham operated animals served as controls. Echocardiographic examinations and invasive hemodynamic measurements revealed distinct changes in LV systolic function between four and six weeks after MI induction in the absence of rRIC (i.e., LV ejection fraction (LVEF) decreased from 52.8 ± 2.1% to 50 ± 1.6%, mean ± SEM, p < 0.05) and in the presence of rRIC (i.e., LVEF increased from 48.2 ± 4.8% to 55.2 ± 4.1%, p < 0.05). Angiotensin-converting enzyme (ACE) activity was about five times higher in the anterior LV wall at six weeks than that in sham animals. Angiotensin-converting enzyme 2 (ACE2) activity roughly doubled in post-ischemic LVs. These increases in ACE and ACE2 activities were effectively mitigated by rRIC. Ca²⁺-sensitivities of force production (pCa₅₀) of LV permeabilized cardiomyocytes were increased at six weeks after MI induction together with hypophosphorylation of 1) cardiac troponin I (cTnI) in both LV regions, and 2) cardiac myosin-binding protein C (cMyBP-C) in the anterior wall. rRIC normalized pCa₅₀, cTnI and cMyBP-C phosphorylations. Taken together, post-ischemic LV remodeling involves region-specific alterations in ACE and ACE2 activities together with changes in cardiomyocyte myofilament protein phosphorylation and function. rRIC has the potential to prevent these alterations and to improve LV performance following MI.

Scorpion bradykinin potentiating factor mitigates lung damage induced by γ-irradiation in rats: Insights on AngII/ACE/Ang(1-7) axis

The goal of this research is to study the mitigating impact of bradykinin potentiating factor (BPF) found in scorpion Androctonus bicolor venom on irradiation-induced lung damage as a new functional target for angiotensin-converting enzyme inhibitors (ACEIs). Male rats were exposed to 7 Gy of γ-radiation as a single dose, with a biweekly intraperitoneal injection of 1 μg/g BPF. Gamma irradiation not only boosted the ACE activity and angiotensin II (Ang II) level, in lung tissue but also significantly depressed the angiotensin (1-7) (Ang (1-7)) that, lead to lung toxicity through a significant elevation of pulmonary levels of CXC-chemokine receptor 4 (CXCR4), toll-like receptor 4 (TLR4), nitric oxide (NO) and lactate dehydrogenase (LDH) activity with a marked disruption in oxidative stress markers, via a reduction in the level of total thiol (tSH) and superoxide dismutase (SOD) activity associated with an elevation in protein carbonyl (PCO) contents. In addition, apoptotic consequences of gamma irradiation were evidenced by raising the levels of mitogen-activated protein kinase (MAPK), C-Jun N-Terminal Kinases (JNK), and cleaved caspase-3. BPF administration leads to ACE inhibition, consequently sustaining decreased Ang II alongside increased Ang (1-7) production. Those sensitive molecules reduce irradiated lung issues. In conclusion, BPF significantly diminished the biochemical and histopathological consequences of radiation through renin-angiotensin system (RAS) control and ACE suppression in the lung.

Irbesartan, an angiotensin II type 1 receptor blocker, inhibits colitis-associated tumourigenesis by blocking the MCP-1/CCR2 pathway

The introduction of anti-inflammatory therapies has enabled substantial improvement of disease activity in patients with inflammatory bowel diseases (IBD). However, IBD can lead to serious complications such as intestinal fibrosis and colorectal cancer. Therefore, novel therapies reducing the development of these complications are needed. Angiotensin II (Ang II) promotes tissue inflammation by stimulating the production of monocyte chemoattractant protein-1 (MCP-1) or proinflammatory cytokines. It plays a pivotal role in IBD progression. Although blockade of Ang II has been reported to ameliorate experimental colitis and reduce colorectal cancer risk, the cellular and molecular mechanisms remain poorly understood. Our previous work showed that irbesartan, an Ang II type 1 receptor blocker, reduced the number of C-C chemokine receptor 2-positive (CCR2+) monocytic cells in the inflamed pancreas. This study aimed to investigate the possible antifibrotic and antitumour effects of irbesartan using the azoxymethane/dextran sodium sulphate mouse model. Irbesartan suppressed MCP-1 production and the accumulation of Ly6C+CCR2+ monocytes and fibrocytes in the inflamed colon, downregulated the expression of type 1 collagen and matrix metalloproteinase 9 and inhibited the development of intestinal fibrosis and tumours. Our observations suggest that blocking the MCP-1/CCR2 pathway using irbesartan might be beneficial in preventing colitis-associated colon tumours.

Functions of the (pro)renin receptor (Atp6ap2) at molecular and system levels: pathological implications in hypertension, renal and brain development, inflammation, and fibrosis

The (pro)renin receptor [(P)RR, Atp6ap2] was initially discovered as a membrane-bound binding partner of prorenin and renin. A soluble (P)RR has additional paracrine effects and is involved in metabolic syndrome and kidney damage. Meanwhile it is clear that most of the effects of the (P)RR are independent of prorenin. In the kidney, (P)RR plays an important role in renal dysfunction by activating proinflammatory and profibrotic molecules. In the brain, (P)RR is expressed in cardiovascular regulatory nuclei and is linked to hypertension. (P)RR is known to be an essential component of the v-ATPase as a key accessory protein and plays an important role in kidney, brain and heart via regulating the pH of the extracellular space and intracellular compartments. V-ATPase and (P)RR together act on WNT and mTOR signalling pathways, which are responsible for cellular homeostasis and autophagy. (P)RR through its role in v-ATPase assembly and function is also important for fast recycling endocytosis by megalin. In the kidney, megalin together with v-ATPase and (P)RR is crucial for endocytic uptake of components of the RAS and their intracellular processing. In the brain, (P)RR, v-ATPases and megalin are important regulators both during development and in the adult. All three proteins are associated with diseases such as XLMR, XMRE, X-linked parkinsonism and epilepsy, cognitive disorders with Parkinsonism, spasticity, intellectual disability, and Alzheimer's Disease which are characterized by impaired neuronal function and/or neuronal loss. The present review focusses on the relevant effects of Atp6ap2 without assigning them necessarily to the RAS. Mechanistically, many effects can be well explained by the role of Atp6ap2 for v-ATPase assembly and function. Furthermore, application of a soluble (P)RR analogue as new therapeutic option is discussed.