New frontiers in the intrarenal Renin-Angiotensin system: a critical review of classical and new paradigms

Analytical Methods and Effects of Bioactive Peptides Derived from Animal Products: A Mini-Review

Peptides with bioactive effects are being researched for various purposes. However, there is a lack of overall research on pork-derived peptides. In this study, we reviewed the process of obtaining bioactive peptides, available analytical methods, and the study of bioactive peptides derived from pork. Pepsin and trypsin, two representative protein digestive enzymes in the body, are hydrolyzed by other cofactors to produce peptides. Bicinchoninic acid assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, chromatography, and in vitro digestion simulation systems are utilized to analyze bioactive peptides for protein digestibility and molecular weight distribution. Pork-derived peptides mainly exhibit antioxidant and antihypertensive activities. The antioxidant activity of bioactive peptides increases the accessibility of amino acid residues by disrupting the three-dimensional structure of proteins, affecting free radical scavenging, reactive oxygen species inactivation, and metal ion chelating. In addition, the antihypertensive activity decreases angiotensin II production by inhibiting angiotensin converting enzyme and suppresses blood pressure by blocking the AT1 receptor. Pork-derived bioactive peptides, primarily obtained using papain and pepsin, exhibit significant antioxidant and antihypertensive activities, with most having low molecular weights below 1 kDa. This study may aid in the future development of bioactive peptides and serve as a valuable reference for pork-derived peptides.

Glucocorticoids with or without fludrocortisone in septic shock: a narrative review from a biochemical and molecular perspective

Two randomised controlled trials have reported a reduction in mortality when adjunctive hydrocortisone is administered in combination with fludrocortisone compared with placebo in septic shock. A third trial did not support this finding when hydrocortisone administered in combination with fludrocortisone was compared with hydrocortisone alone. The underlying mechanisms for this mortality benefit remain poorly understood. We review the clinical implications and potential mechanisms derived from laboratory and clinical data underlying the beneficial role of adjunctive fludrocortisone with hydrocortisone supplementation in septic shock. Factors including distinct biological effects of glucocorticoids and mineralocorticoids, tissue-specific and mineralocorticoid receptor-independent effects of mineralocorticoids, and differences in downstream signalling pathways between mineralocorticoid and glucocorticoid binding at the mineralocorticoid receptor could contribute to this interaction. Furthermore, pharmacokinetic and pharmacodynamic disparities exist between aldosterone and its synthetic counterpart fludrocortisone, potentially influencing their effects. Pending publication of well-designed, randomised controlled trials, a molecular perspective offers valuable insights and guidance to help inform clinical strategies.

Evaluation of the Expression and Localization of the Multifunctional Protein CacyBP/SIP and Elements of the MAPK Signaling Pathway in the Adrenal Glands of Rats with Primary and Secondary Hypertension

Hypertension is a global civilization disease and one of the most common causes of death in the world. Organ dysfunction is a serious health consequence of hypertension, which involves damage to the heart, kidneys and adrenals. The interaction of recently discovered multifunctional protein-CacyBP/SIP with ERK1/2 and p38 kinases by regulating the activity and intracellular localization of these kinases may play an important role in the signaling pathways involved in the pathogenesis of hypertension. Due to the lack of data on this subject, we decided to investigate the localization, expression and possible relationship between the studied parameters in the adrenals under arterial hypertension. The study was conducted on the adrenals of rats with spontaneous and DOCA-salt hypertension. The expression of CacyBP/SIP, p-ERK1/2 and p-p38 was detected by immunohistochemistry and qRT-PCR. The results show a statistically significant decrease in CacyBP/SIP expression in the adrenal glands of hypertensive rats. With ERK1/2, there was a decrease in cortical immunoreactivity and an increase in the adrenal medulla of primary hypertensive rats. In contrast, in the adrenals of DOCA-salt rats, ERK1/2 immunoreactivity increased in the cortex and decreased in the medulla. In turn, p38 expression was higher in the adrenal glands of rats with primary and secondary hypertension. The obtained results may suggest the involvement of CacyBP/SIP in the regulation of signaling pathways in which MAP kinases play an important role and provide new insight into molecular events in hypertension. Moreover, they show the participation of CacyBP/SIP in response to oxidative stress.

All-trans retinoic acid inhibits oxidative stress via ACE2/Ang (1-7)/MasR pathway in renal tubular epithelial cells stimulated with high glucose

The aim of this study was to investigate the effects of all-trans retinoic acid (atRA) on oxidative stress in renal tubular epithelial cells induced by high glucose (HG) and its potential mechanism. We investigated the effects of atRA in HG-induced renal epithelial cell line HK-2. Seven groups were designed for this experiment: negative control, mannitol, high-glucose (HG), HG combined with a low concentration of atRA, HG combined with a middle concentration of atRA, HG combined with a high concentration of atRA, and HG combined with captopril. After 48 h of incubation, oxidative stress factor expression in the supernatant was detected by enzyme-linked immunosorbent assay. Reactive oxygen species and cell apoptosis expression were assessed by flow cytometry. NADPH oxidase, fibrosis factor, and angiotensin-converting enzyme 2/angiotensin (1-7)/mas receptor (ACE2/Ang (1-7)/MasR) pathway-related protein expressions were determined by western blot analysis. The expressions of oxidative stress factors, NADPH oxidase components, and fibrosis factors were significantly higher after HG treatment. Apoptosis of HK2 cells in the HG group was also significantly higher. AtRA could reverse the above abnormal changes in a concentration-dependent manner. HG significantly promoted the expression of ACE, Ang II, and Ang II type 1 receptor (AT1R), whereas it inhibited the expression of ACE2, Ang (1-7), and MasR. With the elevation of concentration, atRA could gradually suppress the expression of ACE, Ang II, and AT1R, but facilitate ACE2, Ang (1-7), and MasR. These results were statistically significant. AtRA could significantly inhibit oxidative stress and apoptosis of renal tubular epithelial cells induced by HG. The mechanism may inhibit the ACE/Ang II/AT1R pathway and/or activate ACE2/Ang (1-7)/MasR pathway.

Sex differences in the renin-angiotensin-aldosterone system and its roles in hypertension, cardiovascular, and kidney diseases

Cardiovascular disease is a pathology that exhibits well-researched biological sex differences, making it possible for physicians to tailor preventative and therapeutic approaches for various diseases. Hypertension, which is defined as blood pressure greater than 130/80 mmHg, is the primary risk factor for developing coronary artery disease, stroke, and renal failure. Approximately 48% of American men and 43% of American women suffer from hypertension. Epidemiological data suggests that during reproductive years, women have much lower rates of hypertension than men. However, this protective effect disappears after the onset of menopause. Treatment-resistant hypertension affects approximately 10.3 million US adults and is unable to be controlled even after implementing ≥3 antihypertensives with complementary mechanisms. This indicates that other mechanisms responsible for modulating blood pressure are still unclear. Understanding the differences in genetic and hormonal mechanisms that lead to hypertension would allow for sex-specific treatment and an opportunity to improve patient outcomes. Therefore, this invited review will review and discuss recent advances in studying the sex-specific physiological mechanisms that affect the renin-angiotensin system and contribute to blood pressure control. It will also discuss research on sex differences in hypertension management, treatment, and outcomes.

Potential of soluble (pro)renin receptor in kidney disease: can it go beyond a biomarker?

(Pro)renin receptor (PRR), also termed ATPase H+-transporting accessory protein 2 (ATP6AP2), is a type I transmembrane receptor and is capable of binding and activating prorenin and renin. Apart from its association with the renin-angiotensin system, PRR has been implicated in diverse developmental, physiological, and pathophysiological processes. Within the kidney, PRR is predominantly expressed in the distal nephron, particularly the intercalated cells, and activation of renal PRR contributes to renal injury in various rodent models of chronic kidney disease. Moreover, recent evidence demonstrates that PRR is primarily cleaved by site-1 protease to produce 28-kDa soluble PRR (sPRR). sPRR seems to mediate most of the known pathophysiological functions of renal PRR through modulating the activity of the intrarenal renin-angiotensin system and provoking proinflammatory and profibrotic responses. Not only does sPRR activate renin, but it also directly binds and activates the angiotensin II type 1 receptor. This review summarizes recent advances in understanding the roles and mechanisms of sPRR in the context of renal pathophysiology.

The Pathophysiology of Long COVID throughout the Renin-Angiotensin System

COVID-19 has expanded across the world since its discovery in Wuhan (China) and has had a significant impact on people’s lives and health. Long COVID is a term coined by the World Health Organization (WHO) to describe a variety of persistent symptoms after acute SARS-CoV-2 infection. Long COVID has been demonstrated to affect various SARS-CoV-2-infected persons, independently of the acute disease severity. The symptoms of long COVID, like acute COVID-19, consist in the set of damage to various organs and systems such as the respiratory, cardiovascular, neurological, endocrine, urinary, and immune systems. Fatigue, dyspnea, cardiac abnormalities, cognitive and attention impairments, sleep disturbances, post-traumatic stress disorder, muscle pain, concentration problems, and headache were all reported as symptoms of long COVID. At the molecular level, the renin-angiotensin system (RAS) is heavily involved in the pathogenesis of this illness, much as it is in the acute phase of the viral infection. In this review, we summarize the impact of long COVID on several organs and tissues, with a special focus on the significance of the RAS in the disease pathogenesis. Long COVID risk factors and potential therapy approaches are also explored.

The Na+/H+ Exchanger 3 in the Intestines and the Proximal Tubule of the Kidney: Localization, Physiological Function, and Key Roles in Angiotensin II-Induced Hypertension

The sodium (Na⁺)/hydrogen (H⁺) exchanger 3 (NHE3) is one of the most important Na⁺/H⁺ antiporters in the small intestines of the gastrointestinal tract and the proximal tubules of the kidney. The roles of NHE3 in the regulation of intracellular pH and acid-base balance have been well established in cellular physiology using in vitro techniques. Localized primarily on the apical membranes in small intestines and proximal tubules, the key action of NHE3 is to facilitate the entry of luminal Na⁺ and the extrusion of intracellular H⁺ from intestinal and proximal tubule tubular epithelial cells. NHE3 is, directly and indirectly, responsible for absorbing the majority of ingested Na⁺ from small and large intestines and reabsorbing >50% of filtered Na⁺ in the proximal tubules of the kidney. However, the roles of NHE3 in the regulation of proximal tubular Na⁺ transport in the integrative physiological settings and its contributions to the basal blood pressure regulation and angiotensin II (Ang II)-induced hypertension have not been well studied previously due to the lack of suitable animal models. Recently, novel genetically modified mouse models with whole-body, kidney-specific, or proximal tubule-specific deletion of NHE3 have been generated by us and others to determine the critical roles and underlying mechanisms of NHE3 in maintaining basal body salt and fluid balance, blood pressure homeostasis, and the development of Ang II-induced hypertension at the whole-body, kidney, or proximal tubule levels. The objective of this invited article is to review, update, and discuss recent findings on the critical roles of intestinal and proximal tubule NHE3 in maintaining basal blood pressure homeostasis and their potential therapeutic implications in the development of angiotensin II (Ang II)-dependent hypertension.

Unraveling the Differentially Articulated Axes of the Century-Old Renin-Angiotensin-Aldosterone System: Potential Therapeutic Implications

Among numerous choices in cardiovascular therapies used for the management of hypertension and heart failure, drugs affecting the renin-angiotensin-aldosterone system (RAAS) hold substantial therapeutic roles. Therapies aimed at modifying the RAAS and its overactivation are employed for the management of various insidious disorders. In the pharmacologic perspective, RAAS is one of the frequently manipulated systems for the management of hypertension, heart failure, myocardial infarction, and renal disease. The RAAS pharmacologic interventions principally include the ACE inhibitors, the angiotensin II-AT1 receptor blockers, the mineralocorticoid receptor antagonists, and the direct renin inhibitors. In addition, therapeutic implication of ACE2/angiotensin (1-7)/Mas receptor activation using various ligands is being explored owing to their anti-inflammatory, anti-fibrotic, vasodilatory, and cardiovascular defensive roles. Moreover, being considered as the counter-regulatory arm of AT1 receptor, the potential role of AT2 receptor activation using selective AT2 receptor agonist is currently investigated for its efficacy in pulmonary complications. As an important regulator of fluid volume, blood pressure, and cardiovascular-renal function, the RAAS has been documented as a diversified intricate system with several therapeutic possibilities coupled with their fundamental structural and functional modulatory roles in cardiovascular, renal, and other systems. The RAAS possesses a number of regulatory, deregulatory, and counter-regulatory axes of physiopathologic importance in health and disease. The counter-regulatory arms of the RAAS might play an essential role in mitigating cardiovascular, renal, and pulmonary pathologies. In light of this background, we sought to explore the classical and counter-regulatory axes/arms of the RAAS and their imperative roles in physiologic functions and disease pathogenesis.

Suspected primary hyperreninism in a cat with malignant renal sarcoma and global renin-angiotensin-aldosterone system upregulation

A 14-year-old male castrated domestic medium-hair cat with diabetes mellitus was evaluated for vomiting, diarrhea, and anorexia. Two weeks before presentation, the cat had been diagnosed with congestive heart failure and started on furosemide. Initial diagnostic testing identified hypokalemia, systemic hypertension, and hypertrophic cardiomyopathy phenotype, and plasma aldosterone concentration was moderately increased. Abdominal ultrasound examination disclosed bilateral adrenomegaly and a right renal mass, and cytology of a needle aspirate of the mass was consistent with malignant neoplasia. The cat was treated with amlodipine and spironolactone. Because of the unusual presentation for hyperaldosteronism, a comprehensive profile of renin-angiotensin-aldosterone system (RAAS) peptides was performed. Results from multiple timepoints indicated persistently and markedly increased plasma renin activity and generalized RAAS upregulation. In addition to the lack of adrenal tumor, the markedly increased plasma renin activity was atypical for primary hyperaldosteronism. These clinical findings are suggestive of primary hyperreninism, a condition previously unreported in cats. The concurrent presence of a renal neoplasm suggests the possibility of a renin-secreting tumor.

Foe and friend in the COVID-19-associated acute kidney injury: an insight on intrarenal renin-angiotensin system

Since the first reported case in December of 2019, the coronavirus disease 2019 (COVID-19) has became an international public health emergency. So far, there are more than 228,206,384 confirmed cases including 4,687,066 deaths. Kidney with high expression of angiotensin-converting enzyme 2 (ACE2) is one of the extrapulmonary target organs affected in patients with COVID-19. Acute kidney injury (AKI) is one of the independent risk factors for the death of COVID-19 patients. The imbalance between ACE2-Ang(1-7)-MasR and ACE-Ang II-AT1R axis in the kidney may contribute to COVID-19-associated AKI. Although series of research have shown the inconsistent effects of multiple common RAS inhibitors on ACE2 expression and enzyme activity, most of the retrospective cohort studies indicated the safety and protective effects of ACEI/ARB in COVID-19 patients. This review article highlights the current knowledge on the possible involvement of intrarenal RAS in COVID-19-associated AKI with a primary focus on the opposing effects of ACE2-Ang(1-7)-MasR and ACE-Ang II-AT1R signaling in the kidney. Human recombinant soluble ACE2 or ACE2 variants with preserved ACE2-enzymatic activity may be the best options to improve COVID-19-associated AKI.

High-Salt Diet Accelerated the Decline of Residual Renal Function in Patients With Peritoneal Dialysis

Objective: This study aims to investigate the relationship between dietary salt intake and residual renal function in peritoneal dialysis (PD) patients.

Methods: The daily salt intake of the patients was calculated based on a 3 day dietary record. Sixty-two patients were divided into three groups: 33 patients in the low salt intake group (salt intake <6.0 g/day), 17 in the medium salt intake group (salt intake 6.0 to <8.0 g/day), and 12 in the high salt intake group (salt intake ≥8.0 g/day). Regular follow-up was conducted every 3 months. Urine volume, peritoneal ultrafiltration volume, and other clinical indicators were recorded. Biochemical indexes were detected to evaluate the changes in residual renal function and peritoneal function during follow-up.

Results: A positive correlation between dietary sodium intake and sodium excretion was found. During 12-month follow-up, a decrease of residual renal function showed a significant difference among the three groups (p = 0.041) (15.3 ± 27.5 vs. 12.5 ± 11.5 vs. 32.9 ± 18.4 L/W/1.73 m² in the low-, medium-, and high salt intake groups, respectively). Consistently, a higher decline of residual renal function (adjusted β, 20.37; 95% CI, 2.83, 37.91) was found in participants with high salt intake (salt intake ≥8 g/day) compared with those in non-high salt intake.

Conclusion: Our study showed that the sodium excretion by peritoneal dialysis was positively correlated with dietary sodium intake in PD patients. The high salt intake diet (salt intake ≥8 g/day) may lead to a faster decline of residual renal function in PD patients.

A Contemporary View of Natriuretic Peptides in the SARS-CoV-2 Era

The heart releases natriuretic peptides (NPs) which represent an important hormonal axis with cardiorenal protective effects. In view of their properties, NPs have pathophysiologic, diagnostic and prognostic implications in several cardiovascular diseases (CVDs). Severe pulmonary inflammation, as induced by the SARS-COV2, may increase pulmonary pressure with potential influence on NPs release, whereby normal cardiovascular integrity becomes impaired. Moreover, pre-existing CVDs are strong negative prognostic factors since they exacerbate the effects of the viral infection and lead to worse outcomes. In this context, it may be expected that NPs exert a key protective role toward the virus infection whereas an impairment of NPs release contributes to the virus deleterious effects. In this review article we explore the potential involvement of NPs in the COVID-19 disease. To this aim, we will first focus on the interactions between NPs and the Ang II/ATIR arm of the renin-angiotensin-aldosterone system (RAAS) as well as with the protective ACE2/Ang (1-7) arm of the RAAS. Subsequently, we will review evidence that strongly supports the role of increased NT-proBNP level as a marker of cardiac damage and of worse prognosis in the COVID-19 affected patients. Finally, we will discuss the potential therapeutic benefits of these protective hormones toward the viral infection through their endothelial protective function, anti-inflammatory and anti-thrombotic effects. In conclusion, the potential implications of NPs in the SARS-CoV-2 infection, as discussed in our article, represent an important issue that deserves to be fully investigated.

Novel roles of the renal angiotensin-converting enzyme

The observation that all components of the renin angiotensin system (RAS) are expressed in the kidney and the fact that intratubular angiotensin (Ang) II levels greatly exceed the plasma concentration suggest that the synthesis of renal Ang II occurs independently of the circulating RAS. One of the main components of this so-called intrarenal RAS is angiotensin-converting enzyme (ACE). Although the role of ACE in renal disease is demonstrated by the therapeutic effectiveness of ACE inhibitors in treating several conditions, the exact contribution of intrarenal versus systemic ACE in renal disease remains unknown. Using genetically modified mouse models, our group demonstrated that renal ACE plays a key role in the development of several forms of hypertension. Specifically, although ACE is expressed in different cell types within the kidney, its expression in renal proximal tubular cells is essential for the development of high blood pressure. Besides hypertension, ACE is involved in several other renal diseases such as diabetic kidney disease, or acute kidney injury even when blood pressure is normal. In addition, studies suggest that ACE might mediate at least part of its effect through mechanisms that are independent of the Ang I conversion into Ang II and involve other substrates such as N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), Ang-(1-7), and bradykinin, among others. In this review, we summarize the recent advances in understanding the contribution of intrarenal ACE to different pathological conditions and provide insight into the many roles of ACE besides the well-known synthesis of Ang II.

Advances in use of mouse models to study the renin-angiotensin system

The renin-angiotensin system (RAS) is a highly complex hormonal cascade that spans multiple organs and cell types to regulate solute and fluid balance along with cardiovascular function. Much of our current understanding of the functions of the RAS has emerged from a series of key studies in genetically-modified animals. Here, we review key findings from ground-breaking transgenic models, spanning decades of research into the RAS, with a focus on their use in studying blood pressure. We review the physiological importance of this regulatory system as evident through the examination of mouse models for several major RAS components: angiotensinogen, renin, ACE, ACE2, and the type 1 A angiotensin receptor. Both whole-animal and cell-specific knockout models have permitted critical RAS functions to be defined and demonstrate how redundancy and multiplicity within the RAS allow for compensatory adjustments to maintain homeostasis. Moreover, these models present exciting opportunities for continued discovery surrounding the role of the RAS in disease pathogenesis and treatment for cardiovascular disease and beyond.

The Involvement of MicroRNAs in SARS-CoV-2 Infection Comorbid with HIV-Associated Preeclampsia

Purpose of Review

This review investigated the potential role of microRNAs (miRNAs) in the synergy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, preeclampsia (PE), and human immunodeficiency virus (HIV) infection. Maternal health is a great concern when treating pregnant women fighting this triad of diseases, which is highly prevalent in South Africa. MicroRNAs are involved in fine-tuning of physiological processes. Disruptions to the balance of this minute protein can lead to various physiological changes that are sometimes pathological.

Recent Findings

MicroRNAs have recently been implicated in PE and have been linked to the anti-angiogenic imbalance evident in PE. Recent in silico studies have identified potential host miRNAs with anti-viral properties against SARS-CoV-2 infection. Studies have demonstrated dysregulated expression of several miRNAs in HIV-1 infection along with the ability of HIV-1 to downregulate anti-viral host microRNAs.

Summary

This review has highlighted the significant gap in literature on the potential of miRNAs in women with HIV-associated PE in synergy with the novel SARS-CoV-2 infection. In addition, this review has provided evidence of the critical role that the epigenetic regulatory mechanism of miRNA plays in viral infections and PE, thereby providing a foundation for further research investigating the potential of therapeutic miRNA development with fewer side-effects for pregnant women.

Effects of SGLT2 Inhibitors and GLP-1 Receptor Agonists on Renin-Angiotensin-Aldosterone System

Sodium-glucose cotransporters inhibitors (SGLT2-i) and GLP-1 receptor agonists (GLP1-RA) are glucose-lowering drugs that are proved to reduce the cardiovascular (CV) risk in type 2 diabetes mellitus (T2DM). In this process, the renin-angiotensin-aldosterone system (RAAS) is assumed to play a role. The inhibition of SGLT2 improves hyperglycemia hampering urinary reabsorption of glucose and inducing glycosuria. This "hybrid" diuretic effect, which couples natriuresis with osmotic diuresis, potentially leads to systemic RAAS activation. However, the association between SGLT2-i and systemic RAAS activation is not straightforward. Available data indicate that SGLT2-i cause plasma renin activity (PRA) increase in the early phase of treatment, while PRA and aldosterone levels remain unchanged in chronic treated patients. Furthermore, emerging studies provide evidence that SGLT2-i might have an interfering effect on aldosterone/renin ratio (ARR) in patients with T2DM, due to their diuretic and sympathoinhibition effects. The cardio- and reno-protective effects of GLP-1-RA are at least in part related to the interaction with RAAS. In particular, GLP1-RA counteract the action of angiotensin II (ANG II) inhibiting its synthesis, increasing the inactivation of its circulating form and contrasting its action on target tissue like glomerular endothelial cells and cardiomyocytes. Furthermore, GLP1-RA stimulate natriuresis inhibiting Na+/H+ exchanger NHE-3, which is conversely activated by ANG II. Moreover, GLP1 infusion acutely reduces circulating aldosterone, but this effect does not seem to be chronically maintained in patients treated with GLP1-RA. In conclusion, both SGLT2-i and GLP1-RA seem to have several effects on RAAS, though additional studies are needed to clarify this relationship.

Nonclassical Axis of the Renin-Angiotensin System and Neprilysin: Key Mediators That Underlie the Cardioprotective Effect of PPAR-Alpha Activation during Myocardial Ischemia in a Metabolic Syndrome Model

The activation of the renin-angiotensin system (RAS) participates in the development of metabolic syndrome (MetS) and in heart failure. PPAR-alpha activation by fenofibrate reverts some of the effects caused by these pathologies. Recently, nonclassical RAS components have been implicated in the pathogenesis of hypertension and myocardial dysfunction; however, their cardiac functions are still controversial. We evaluated if the nonclassical RAS signaling pathways, directed by angiotensin III and angiotensin-(1-7), are involved in the cardioprotective effect of fenofibrate during ischemia in MetS rats. Control (CT) and MetS rats were divided into the following groups: (a) sham, (b) vehicle-treated myocardial infarction (MI-V), and (c) fenofibrate-treated myocardial infarction (MI-F). Angiotensin III and angiotensin IV levels and insulin increased the aminopeptidase (IRAP) expression and decreased the angiotensin-converting enzyme 2 (ACE2) expression in the hearts from MetS rats. Ischemia activated the angiotensin-converting enzyme (ACE)/angiotensin II/angiotensin receptor 1 (AT1R) and angiotensin III/angiotensin IV/angiotensin receptor 4 (AT4R)-IRAP axes. Fenofibrate treatment prevented the damage due to ischemia in MetS rats by favoring the angiotensin-(1-7)/angiotensin receptor 2 (AT2R) axis and inhibiting the angiotensin III/angiotensin IV/AT4R-IRAP signaling pathway. Additionally, fenofibrate downregulated neprilysin expression and increased bradykinin production. These effects of PPAR-alpha activation were accompanied by a reduction in the size of the myocardial infarct and in the activity of serum creatine kinase. Thus, the regulation of the nonclassical axis of RAS forms part of a novel protective effect of fenofibrate in myocardial ischemia.

The Counter Regulatory Axis of the Lung Renin-Angiotensin System in Severe COVID-19: Pathophysiology and Clinical Implications

The severe acute respiratory syndrome coronavirus (SARS-CoV)-2, which is responsible for coronavirus disease 2019 (COVID-19), uses angiotensin (ANG)-converting enzyme 2 (ACE2) as the entrance receptor. Although most COVID-19 cases are mild, some are severe or critical, predominantly due to acute lung injury. It has been widely accepted that a counter regulatory renin-angiotensin system (RAS) axis including the ACE2/ANG [1-7]/Mas protects the lungs from acute lung injury. However, recent evidence suggests that the generation of protective ANG [1-7] in the lungs is predominantly mediated by proinflammatory prolyl oligopeptidase (POP), which has been repeatedly demonstrated to be involved in lung pathology. This review contends that acute lung injury in severe COVID-19 is characterised by a) ACE2 downregulation and malfunction (inflammatory signalling) due to viral occupation, and b) dysregulation of the protective RAS axis, predominantly due to increased activity of proinflammatory POP. It follows that a reasonable treatment strategy in COVID-19-related acute lung injury would be delivering functional recombinant (r) ACE2 forms to trap the virus. Additionally, or alternatively to rACE2 delivery, the potential benefits resulting from lowering POP activity should also be explored. These treatment strategies deserve further investigation.

The interaction partners of (pro)renin receptor in the distal nephron

The (pro)renin receptor (PRR), a key regulator of intrarenal renin-angiotensin system (RAS), is predominantly presented in podocytes, proximal tubules, distal convoluted tubules, and the apical membrane of collecting duct A-type intercalated cells, and plays a crucial role in hypertension, cardiovascular disease, kidney disease, and fluid homeostasis. In addition to its well-known renin-regulatory function, increasing evidence suggests PRR can also act in a variety of intracellular signaling cascades independently of RAS in the renal medulla, including Wnt/β-catenin signaling, cyclooxygenase-2 (COX-2)/prostaglandin E₂ (PGE₂ ) signaling, and the apelinergic system, and work as a component of the vacuolar H⁺ -ATPase. PRR and these pathways regulate the expression/activity of each other that controlling blood pressure and renal functions. In this review, we highlight recent findings regarding the antagonistic interaction between PRR and ELABELA/apelin, the mutually stimulatory relationship between PRR and COX-2/PGE₂ or Wnt/β-catenin signaling in the renal medulla, and their involvement in the regulation of intrarenal RAS thereby control blood pressure, renal injury, and urine concentrating ability in health and patho-physiological conditions. We also highlight the latest progress in the involvement of PRR for the vacuolar H⁺ -ATPase activity.

Amaranth as a Source of Antihypertensive Peptides

Amaranth is an ancestral crop used by pre-Columbian cultures for 6000 to 8000 years. Its grains have a relevant chemical composition not only from a nutritional point of view but also due to the contribution of components with good techno-functional properties and important potential as bioactive compounds. Numerous studies have shown that amaranth storage proteins possess encrypted sequences that, once released, exhibit different physiological activities. One of the most studied is antihypertensive activity. This review summarizes the progress made over the last years (2008-2020) related to this topic. Studies related to inhibition of different enzymes of the Renin-Angiotensin-Aldosterone system, in particular Angiotensin Converting Enzyme (ACE) and Renin, as well as those referring to potential modulation mechanisms of tissue or local Renin-Angiotensin-Aldosterone system, are analyzed, including in silico, in vitro, in vivo, and ex vivo assays. Furthermore, the potential use of these bioactive peptides or products containing them, in the elaboration of functional food matrices is discussed. Finally, the most relevant conclusions and future requirements in research and development of food products are presented.

Mineralocorticoid Dysfunction during Critical Illness: A Review of the Evidence

The recent demonstration of the significant reduction in mortality in patients with septic shock treated with adjunctive glucocorticoids combined with fludrocortisone and the effectiveness of angiotensin II in treating vasodilatory shock have renewed interest in the role of the mineralocorticoid axis in critical illness. Glucocorticoids have variable interactions at the mineralocorticoid receptor. Similarly, mineralocorticoid receptor-aldosterone interactions differ from mineralocorticoid receptor-glucocorticoid interactions and predicate receptor-ligand interactions that differ with respect to cellular effects. Hyperreninemic hypoaldosteronism or selective hypoaldosteronism, an impaired adrenal response to increasing renin levels, occurs in a subgroup of hemodynamically unstable critically ill patients. The suggestion is that there is a defect at the level of the adrenal zona glomerulosa associated with a high mortality rate that may represent an adaptive response aimed at increasing cortisol levels. Furthermore, cross-talk exists between angiotensin II and aldosterone, which needs to be considered when employing therapeutic strategies.

COVID's Razor: RAS Imbalance, the Common Denominator Across Disparate, Unexpected Aspects of COVID-19

A modern iteration of Occam's Razor posits that "the simplest explanation is usually correct." Coronavirus Disease 2019 involves widespread organ damage and uneven mortality demographics, deemed unexpected from what was originally thought to be "a straightforward respiratory virus." The simplest explanation is that both the expected and unexpected aspects of COVID-19 share a common mechanism. Silent hypoxia, atypical acute respiratory distress syndrome (ARDS), stroke, olfactory loss, myocarditis, and increased mortality rates in the elderly, in men, in African-Americans, and in patients with obesity, diabetes, and cancer-all bear the fingerprints of the renin-angiotensin system (RAS) imbalance, suggesting that RAS is the common culprit. This article examines what RAS is and how it works, then from that baseline, the article presents the evidence suggesting RAS involvement in the disparate manifestations of COVID-19. Understanding the deeper workings of RAS helps one make sense of severe COVID-19. In addition, recognizing the role of RAS imbalance suggests potential routes to mitigate COVID-19 severity.

Central angiotensin-(1-7) attenuates systemic inflammation via activation of sympathetic signaling in endotoxemic rats

Angiotensin-(1-7) [Ang-(1-7)] is an angiotensin-derived neuropeptide with potential anti-hypertensive and anti-inflammatory properties. However, a possible action of Ang-(1-7) in neuroimmune interactions to regulate inflammatory response has not been explored. Thus, the aim of this study was to determine whether the intracerebroventricular (i.c.v.) administration of Ang-(1-7) can modulate systemic inflammation via sympathetic efferent circuits. Wistar male rats received systemic administration of lipopolysaccharide (LPS) (1.5 mg/Kg). Ang-(1-7) (0.3 nmol in 2 µL) promoted the release of splenic norepinephrine and attenuated tumor necrosis factor (TNF) and nitric oxide (NO), but increased interleukin-10 (IL-10), levels in the serum, spleen, and liver in endotoxemic rats. Furthermore, 6-hydroxydopamine-induced chemical sympathectomy (100 mg/Kg, intravenous) or i.c.v. administration of Mas receptor antagonist A779 (3 nmol in 2 µL) abolished the anti-inflammatory effects of central Ang-(1-7) injection. Moreover, this treatment did not alter the plasmatic LPS-induced corticosterone and vasopressin. The administration of Ang-(1-7) reverted the low resistance in response to catecholamines of rings of thoracic aorta isolated from endotoxemic rats, treated or not, with this peptide by a mechanism dependent on the regulation of NO released from perivascular adipose tissue. Together, our results indicate that Ang-(1-7) regulates systemic inflammation and vascular hyporesponsiveness in endotoxemia via activation of a central Mas receptors/sympathetic circuits/norepinephrine axis and provide novel mechanistic insights into the anti-inflammatory Ang-(1-7) properties.

Qian Yang Yu Yin Granule protects against hypertension-induced renal injury by epigenetic mechanism linked to Nicotinamide N-Methyltransferase (NNMT) expression

ETHNOPHARMACOLOGICAL RELEVANCE

Qian Yang Yu Yin Granule (QYYY) is a Chinese herbal formulation. It is used to treat hypertensive nephropathy for decades in China, but it is unknown that the exact mechanism of QYYY on hypertensive nephropathy.

AIMS OF STUDY

The present study was to elucidate its epigenetic mechanism of QYYY on hypertensive nephropathy.

MATERIALS AND METHODS

In the current study, HEK293T cells' proliferation induced by Ang II was chosen to observe epigenetic mechanisms of QYYY on renal damage. The cell proliferation was examined by MTT assays and ethynyldeoxyuridine analysis. Cell cycle analysis was performed. After treatment with QYYY, expression of Nicotinamide N-methyltransferase (NNMT), sirtuin1(SIRT1), S-adenosylhomocysteine(SAH), histone H3K4 methylation, and cortactin acetylation(acetyl-cortactin,ac-cortactin) were further investigated by western-blotting and real time PCR. DNA methylation was detected by ELISA. The study also observed the changes of SIRT1, SAH, H3K4 methylation, acetyl-cortactin when NNMT over-expressed by lentivirus transfection. Angiotensin II(Ang II) induced renal damage in spontaneously hypertensive rats(SHR). After eight weeks treatment of QYYY, blood pressure, serum and urine creatinine, and urinary microalbumin(mAlb) were assessed. The concentration of N1 -methylnicotinamide were detected by liquid chromatography with tandem mass spectrometry. The protein of NNMT, ac-cortactin, H3K3me3 were also assessed in vivo.

RESULTS

QYYY inhibited HEK293T cells' proliferation, down-regulated the expression of NNMT, SAH, acetyl-cortactin and DNA methylation, up-regulated the expression of SIRT1, histone H3K4 trimethylation(H3K4me3). Over-expression of NNMT increased the expression of SAH and acetyl-cortactin, and reduced the expression of SIRT1 and H3K4me3. The study also demonstrated that QYYY promoted urinary creatinine excretion and reduced serum creatinine and urinary mAlb in SHR. QYYY decreased the concentration of N1 -methylnicotinamide in Ang II group. QYYY decreased the protein of NNMT, ac-cortactin and increased H3K4me3 in vivo.

CONCLUSION

The results showed that QYYY alleviated renal impairment of SHR and inhibited HEK293T cells' proliferation induced by Ang II through the pathway of epigenetic mechanism linked to Nicotinamide N-Methyltransferase (NNMT) expression, including histone methylation, DNA methylation and acetyl-cortactin. This study unveiled a novel molecular mechanism by which QYYY controlled the progression of hypertensive nephropathy.

Molecular basis of the therapeutic properties of hemorphins

Hemorphins are endogenous peptides, 4-10 amino acids long, belonging to the family of atypical opioid peptides released during the sequential cleavage of hemoglobin protein. Hemorphins have been shown to exhibit diverse therapeutic effects in both human and animal models. However, the precise cellular and molecular mechanisms involved in such effects remain elusive. In this review, we summarize and propose potential mechanisms based on studies that investigated the biological activity of hemorphins of different lengths on multiple therapeutic targets. Special emphasis is given to molecular events related to renin-angiotensin system (RAS), opioid receptors and insulin-regulated aminopeptidase receptor (IRAP). This review provides a comprehensive coverage of the molecular mechanisms that underpin the therapeutic potential of hemorphins. Furthermore, it highlights the role of various hemorphin residues in pathological conditions, which could be explored further for therapeutic purposes.

"Bottom-Up" Strategy for the Identification of Novel Soybean Peptides with Angiotensin-Converting Enzyme Inhibitory Activity

IAVPTGVA (Soy1) and LPYP are two soybean peptides, which display a multifunctional behavior, showing in vitro hypocholesterolemic and hypoglycemic activities. A preliminary screening of their structures using BIOPEP suggested that they might be potential angiotensin-converting enzyme (ACE) inhibitors. Therefore, a bottom-up-aided approach was developed in order to clarify the in vitro hypotensive activity. Soy1 and LPYP dropped the intestinal and renal ACE enzyme activity with IC50 values equal to 14.7 ± 0.28 and 5.0 ± 0.28 μM (Caco-2 cells), and 6.0 ± 0.35 and 6.8 ± 0.20 μM (HK-2 cells), respectively. In parallel, a molecular modeling study suggested their capability to act as competitive inhibitors of this enzyme. Finally, in order to increase both their stability and hypotensive properties, a suitable strategy for the harmless control of their release from a nanomaterial was developed through their encapsulation into the RADA16-assembling peptide.

AMPK: a balancer of the renin-angiotensin system

The renin-angiotensin system (RAS) is undisputedly well-studied as one of the oldest and most critical regulators for arterial blood pressure, fluid volume, as well as renal function. In recent studies, RAS has also been implicated in the development of obesity, diabetes, hyperlipidemia, and other diseases, and also involved in the regulation of several signaling pathways such as proliferation, apoptosis and autophagy, and insulin resistance. AMP-activated protein kinase (AMPK), an essential cellular energy sensor, has also been discovered to be involved in these diseases and cellular pathways. This would imply a connection between the RAS and AMPK. Therefore, this review serves to draw attention to the cross-talk between RAS and AMPK, then summering the most recent literature which highlights AMPK as a point of balance between physiological and pathological functions of the RAS.

[Effect of dietary sodium intake on residual renal function in patients undergoing peritoneal dialysis: a prospective study of 33 cases]

OBJECTIVE

To explore the impact of dietary sodium-intake on residual renal function in patients undergoing peritoneal dialysis (PD).

METHODS

Thirty-three patients on PD with stable dialysis were regularly followed up for 12 months. The daily sodium intake of the patients was calculated based on the 3-day dietary record. Based on the mean daily sodium intake, the patients enrolled were divided into low-salt group (sodium intake≤3.0 g/day, 19 patients) and high-salt group (sodium intake&gt;3.0 g/day, 14 patients). The baseline data of the patients were recorded, and the indicators of residual renal function and peritoneal function were regularly tested. The patients were followed-up at 3-month intervals, and their urine volume, peritoneal ultrafiltration volume and other clinical indicators were recorded and the biochemical indexes were detected to evaluate the changes in the residual renal function and peritoneal function.

RESULTS

There was a positive correlation between the total sodium excretion and dietary sodium intake in these patients (r=0.536, P=0.0013), and sodium excretion by dialysis was positively correlated with their sodium intake (r=0.901, P=0.000). Regression analysis suggested that the total sodium excretion was correlated with dietary sodium intake (β=0.416, 95% CI: 0.170-0.666; P &lt; 0.0018); sodium excretion by dialysis was associated with dietary sodium intake (β=0.489, 95% CI: 0.395-0.582; P &lt; 0.001). The residual renal function was reduced by 17.48±11.22 L /(w·1.73 m²) in the low-salt group, as compared to 30.20±18.30 L /(w·1.73 m²) in the high-salt group (P=0.032). The reduction in the residual renal function was correlated with sodium intake in the PD patients (r=0.409, P=0.018). Multivariate regression analysis showed that sodium intake was an independent factor contributing to the reduction of residual renal function (β=14.646, 95% CI 7.426-21.866, P &lt; 0.001).

CONCLUSIONS

Sodium excretion by PD in patients with continuous ambulatory PD is positively correlated with their dietary sodium intake, which contribute to the decrease of residual renal function. A high dietary sodium intake may accelerate the reduction of residual renal function in these patients.

Perinatal changes in estradiol and Ang II concentrations in pregnant women with pulmonary arterial hypertension and their correlation

Objective: This study aimed to analyze the perinatal changes of plasma estradiol (E₂) and angiotensin II (Ang II) in pregnant women with pulmonary arterial hypertension before and after cesarean section. Methods: Depending on pulmonary arterial pressure, the subjects were divided into two groups, moderate group, and severe group. Plasma concentrations of E₂ and Ang II were determined at different time points using electrochemiluminescence immunoassay and ELISA, respectively. The correlation between E2 and Ang II concentrations was analyzed. Results: Intragroup comparison indicated that E2 levels at different time points after surgery decreased in the two groups than before, with a greater reduction in the severe group. Besides, both groups showed a reduction in Ang II concentrations after surgery. As indicated by intragroup comparison, there was a significant difference at each time point in the two groups. The reduction in Ang II concentrations was more conspicuous at 48 h and 72 h after surgery (cesarean section) than before for the two groups. Moreover, E₂ concentrations were correlated positively with AngII concentrations. Conclusion: Plasma concentrations of E₂ and Ang II decreased after delivery. The plasma concentrations of E₂ and Ang II were correlated with each other.

Preparation, Bioavailability, and Mechanism of Emerging Activities of Ile-Pro-Pro and Val-Pro-Pro

Ile-Pro-Pro and Val-Pro-Pro are two most well-known food-derived bioactive peptides, initially identified as inhibitors of angiotensin I-converting enzyme (ACE) from a sample of sour milk. These two peptides were identified in fermented and enzymatic hydrolyzed cow and non-cow (that is, goat, sheep, buffalo, yak, camel, mare, and donkey) milk, as well as sourdough prepared from wheat, rye, and malt. Similar to other bioactive peptides, bioavailability of these peptides is low (about 0.1%), reaching picomolar concentration in human plasma; they showed blood pressure lowering activity in animals and in human, via improved endothelial function, activation of ACE2, and anti-inflammatory property. Emerging bioactivities of these two peptides toward against metabolic syndrome and bone-protection received limited attention, but may open up new applications of these peptides as functional food ingredients. Further studies are warranted to determine the best source as well as to identify novel enzymes (particularly from traditional fermented milk products) to improve the efficiency of production, to characterize possible peptide receptors using a combination of omics technology with molecular methods to understand if these two peptides act as signal-like molecules, to improve their bioavailability, and to explore new applications based on emerging bioactivities.

EXPRESSION OF THE RENIN-ANGIOTENSIN SYSTEM COMPONENTS IN ONCOLOGIC DISEASES

The literature devoted to changes in the expression of the renin-angiotensin system (RAS) proteins of cancer cells was analyzed. The dynamics of RAS protein expression in malignant tumors and the possible role of epigenetic mechanisms in these processes are briefly reviewed. Through research of the epigenetic mechanisms in cancer, principally new techniques for their correction based on the use of selective regulatory systems of covalent modification of histone proteins (for example, deacetylase inhibitor) and microRNA synthesis technologies have been developed. Literature data show promising pharmacological correction of epigenetic modification of chromatin in the treatment of cancer.

MAPK/AP-1 pathway activation mediates AT1R upregulation and vascular endothelial cells dysfunction under PM2.5 exposure

Acute and chronic exposure to particulate matter (PM) 2.5 is associated with adverse health effect upon the cardiovascular (CV) system. However, the molecular mechanism by which PM2.5 evokes CV injuries has not been fully clarified. In our recent report, we demonstrate that exposure to PM2.5 leads to elevation of circulating angiotensin II (ANGII) levels and local expressions of angiotensinogen (AGT, the precursor of ANGII), angiotensin-converting enzyme (ACE) and ANGII type 1 receptor (AT1R) in the vascular endothelial cells, which subsequently instigates the oxidative stress and proinflammatory response in the vascular endothelium. In the present study, we disclosed that PM2.5 exposure induced the activation of the transcriptional factor AP-1 and its components, c-Jun and ATF2, in the human vascular endothelial cells. Although the DNA-binding sites for AP-1 were identified within the promoter regions of AGT, ACE and AT1R genes, RT-PCR and immunoblot assays indicated that AP-1 transactivation was only involved in AT1R upregulation, but did not affect the induction of AGT and ACE expression under the same conditions. Furthermore, ERKs and p38K functioned as the upstream protein kinases involving in AP-1 transactivation and AT1R upregulation under PM2.5 stimulation. In addition, the oxidative stress and proinflammatory responses in the PM2.5-treated vascular endothelial cells were significantly reduced when MAPKs and AP-1 activation were inhibited. Therefore, we conclude that PM2.5 exposure induces MAPK/AP-1 cascade activation, which contributes to AT1R upregulation and vascular endothelial dysfunction. Identifying novel therapeutic targets to alleviate AP-1 transactivation and restore AT1R expression may be helpful for the management of PM2.5-induced CV burden.

Inflammation as a Regulator of the Renin-Angiotensin System and Blood Pressure

PURPOSE OF REVIEW

Mechanisms facilitating progression of hypertension via cross stimulation of the renin-angiotensin system (RAS) and inflammation have been proposed. Accordingly, we review and update evidence for regulation of RAS components by pro-inflammatory factors.

RECENT FINDINGS

Angiotensin II (Ang II), which is produced by RAS, induces vasoconstriction and consequent blood pressure elevation. In addition to this direct action, chronically elevated Ang II stimulates several pathophysiological mechanisms including generation of oxidative stress, stimulation of the nervous system, alterations in renal hemodynamics, and activation of the immune system. In particular, an activated immune system has been shown to contribute to the development of hypertension. Recent studies have demonstrated that immune cell-derived pro-inflammatory cytokines regulate RAS components, further accelerating systemic and local Ang II formation. Specifically, regulation of angiotensinogen (AGT) production by pro-inflammatory cytokines in the liver and kidney is proposed as a key mechanism underlying the progression of Ang II-dependent hypertension.

Molecular interactions, bioavailability, and cellular mechanisms of angiotensin-converting enzyme inhibitory peptides

Food-derived angiotensin-converting enzyme inhibitory (ACEi) peptides have gained substantial interest as potential alternatives to synthetic drugs in the management of hypertension. Peptide size and sequence are two critical factors that determine their potency, bioavailability, and cellular mechanisms. Molecular interaction studies between ACE and ACEi peptides support that potent ACEi peptides are generally composed of hydrophobic, positively charged, and aromatic or cyclic amino acid residues at the third, second, and first position from the C-terminus, respectively. Small peptides containing N-terminal Tyr and/or C-terminal Pro could improve their stability against enterocyte peptidases, thus their bioavailability. Different ACEi peptides can reduce aberrant cellular proliferation, excessive inflammation, and oxidative stress but through different mechanisms. Further understanding the structure-activity-bioavailability relationships will help design novel potent ACEi peptides with improved bioavailability and in vivo efficacy. PRACTICAL APPLICATIONS: ACEi peptides have the potential for uses as functional food ingredients against hypertension.

Intratubular and intracellular renin-angiotensin system in the kidney: a unifying perspective in blood pressure control

The renin-angiotensin system (RAS) is widely recognized as one of the most important vasoactive hormonal systems in the physiological regulation of blood pressure and the development of hypertension. This recognition is derived from, and supported by, extensive molecular, cellular, genetic, and pharmacological studies on the circulating (tissue-to-tissue), paracrine (cell-to-cell), and intracrine (intracellular, mitochondrial, nuclear) RAS during last several decades. Now, it is widely accepted that circulating and local RAS may act independently or interactively, to regulate sympathetic activity, systemic and renal hemodynamics, body salt and fluid balance, and blood pressure homeostasis. However, there remains continuous debate with respect to the specific sources of intratubular and intracellular RAS in the kidney and other tissues, the relative contributions of the circulating RAS to intratubular and intracellular RAS, and the roles of intratubular compared with intracellular RAS to the normal control of blood pressure or the development of angiotensin II (ANG II)-dependent hypertension. Based on a lecture given at the recent XI International Symposium on Vasoactive Peptides held in Horizonte, Brazil, this article reviews recent studies using mouse models with global, kidney- or proximal tubule-specific overexpression (knockin) or deletion (knockout) of components of the RAS or its receptors. Although much knowledge has been gained from cell- and tissue-specific transgenic or knockout models, a unifying and integrative approach is now required to better understand how the circulating and local intratubular/intracellular RAS act independently, or with other vasoactive systems, to regulate blood pressure, cardiovascular and kidney function.

Molecular targets and mechanisms of bioactive peptides against metabolic syndromes

Bioactive peptides are present in all living organisms and have critical roles ranging from protection against infection as the key element of innate immunity, regulating blood pressure and glucose levels, to reducing signs of ageing by killing senescent cells. Bioactive peptides are also encrypted within food protein sequences that can be released during proteolysis or food processing. These specific food protein fragments are reported to have potential for improving human health and preventing metabolic diseases through their impact on inflammation, blood pressure, obesity, and type-2 diabetes. This review mainly focuses on the molecular targets and the underlying mechanisms of bioactive peptides against various metabolic syndromes including inflammation, high blood pressure, obesity, and type-2 diabetes, to provide new insights and perspectives on the potential of bioactive peptides for management of metabolic syndromes.

Egg White-Derived Antihypertensive Peptide IRW (Ile-Arg-Trp) Inhibits Angiotensin II-Stimulated Migration of Vascular Smooth Muscle Cells via Angiotensin Type I Receptor

Excessive proliferation, inflammation, oxidative stress, and migration induced by angiotensin II (Ang II), occurring in vascular smooth muscle cells (VSMCs) during vascular remodelling, are major pathogenesis of hypertension. Antihypertensive peptides derived from food proteins are promising alternatives in preventing/treating hypertension and associated complications. In addition to reducing high blood pressure in spontaneously hypertensive rats, egg white ovotransferrin-derived antihypertensive IRW (Ile-Arg-Trp) was shown to exert antiproliferative, antioxidant, and anti-inflammatory effects in A7r5 cells (a vascular smooth muscle cell line) against Ang II stimulation, further indicating its potential in retarding vascular remodelling. Since its regulatory role in migration of VSMC is unclear, the objective of this study was to evaluate the antimigrant activity of IRW in Ang II-stimulated A7r5 cells. It was found that IRW could downregulate matrix metallopeptidase 9 (MMP9) expression and inhibit migration of Ang II-stimulated A7r5 cells, which was associated with inactivation of p38/MAPK signaling. More importantly, the antimigrant activity of IRW in Ang II-stimulated A7r5 cells was dependent on angiotensin type I receptor (AT1R). Our study provided the first evidence that egg ovotransferrin-derived antihypertensive peptide IRW inhibited migration of VSMCs.

Egg Protein-Derived Bioactive Peptides: Preparation, Efficacy, and Absorption

The hen's egg is an important protein source of human diet. On average one large egg contains ~6g protein, which contributes to ~11% of daily protein intake. As a high-quality protein, egg proteins are well recognized as excellent sources of bioactive peptides. The objectives of this chapter are to introduce generation, bioactivities, and absorption of egg protein-derived bioactive peptides. Research on egg protein-derived bioactive peptides has been progressed during the past decades. Enzymatic hydrolysis is the major technique to prepare bioactive peptides from egg protein. Quantitative structure-activity relationships-aided in silico prediction is increasingly applied as a promising tool for efficient prediction of novel bioactive peptides. A number of bioactive peptides from egg proteins have been characterized for antioxidant, immunomodulatory, antihypertensive, antidiabetic, anticancer, and antimicrobial activities. Egg protein-derived peptides that can improve bone health have been reported as well. However, molecular mechanisms of many peptides are not fully understood. The stability and absorption routes, bioavailability, safety, and production of bioactive peptides await further investigation.

The Role of Renin-Angiotensin-Aldosterone System and Its New Components in Arterial Stiffness and Vascular Aging

Many cardiovascular diseases present renin-angiotensin-aldosterone system (RAAS) hyperactivity as an important pathophysiological mechanism to be target in the therapeutic approaches. Moreover, arterial stiffness is currently considered as a new independent risk factor for cardiovascular disease in different clinical conditions, including hypertension and chronic kidney disease. In fact, excessive stimulation of angiotensin type 1 (AT1) receptors, as well as mineralocorticoid receptors, results in cellular growth, oxidative stress and vascular inflammation, which may lead to arterial stiffness and accelerate the process of vascular aging. In the last decades, a vasoprotective axis of the RAAS has been discovered, and now it is well established that new components with antioxidant and anti-inflammatory properties play important roles promoting vasodilation, natriuresis and reducing collagen deposition, thus attenuating arterial stiffness and improving endothelial function. In this review, we will focus on these pathophysiological mechanisms and the relevance of RAAS inhibition by different strategies to increase arterial compliance and to decelerate vascular aging.

Biological activities of (-)-epicatechin and (-)-epicatechin-containing foods: Focus on cardiovascular and neuropsychological health

Recent studies have suggested that certain (-)-epicatechin-containing foods have a blood pressure-lowering capacity. The mechanisms underlying (-)-epicatechin action may help prevent oxidative damage and endothelial dysfunction, which have both been associated with hypertension and certain brain disorders. Moreover, (-)-epicatechin has been shown to modify metabolic profile, blood's rheological properties, and to cross the blood-brain barrier. Thus, (-)-epicatechin causes multiple actions that may provide unique synergy beneficial for cardiovascular and neuropsychological health. This review summarises the current knowledge on the biological actions of (-)-epicatechin, related to cardiovascular and brain functions, which may play a remarkable role in human health and longevity.

The vasoprotective axes of the renin-angiotensin system: Physiological relevance and therapeutic implications in cardiovascular, hypertensive and kidney diseases

The renin-angiotensin system (RAS) is undisputedly one of the most prominent endocrine (tissue-to-tissue), paracrine (cell-to-cell) and intracrine (intracellular/nuclear) vasoactive systems in the physiological regulation of neural, cardiovascular, blood pressure, and kidney function. The importance of the RAS in the development and pathogenesis of cardiovascular, hypertensive and kidney diseases has now been firmly established in clinical trials and practice using renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors, type 1 (AT₁) angiotensin II (ANG II) receptor blockers (ARBs), or aldosterone receptor antagonists as major therapeutic drugs. The major mechanisms of actions for these RAS inhibitors or receptor blockers are mediated primarily by blocking the detrimental effects of the classic angiotensinogen/renin/ACE/ANG II/AT₁/aldosterone axis. However, the RAS has expanded from this classic axis to include several other complex biochemical and physiological axes, which are derived from the metabolism of this classic axis. Currently, at least five axes of the RAS have been described, with each having its key substrate, enzyme, effector peptide, receptor, and/or downstream signaling pathways. These include the classic angiotensinogen/renin/ACE/ANG II/AT₁ receptor, the ANG II/APA/ANG III/AT₂/NO/cGMP, the ANG I/ANG II/ACE2/ANG (1-7)/Mas receptor, the prorenin/renin/prorenin receptor (PRR or Atp6ap2)/MAP kinases ERK1/2/V-ATPase, and the ANG III/APN/ANG IV/IRAP/AT₄ receptor axes. Since the roles and therapeutic implications of the classic angiotensinogen/renin/ACE/ANG II/AT₁ receptor axis have been extensively reviewed, this article will focus primarily on reviewing the roles and therapeutic implications of the vasoprotective axes of the RAS in cardiovascular, hypertensive and kidney diseases.

Physiology and Pathophysiology of the Intrarenal Renin-Angiotensin System: An Update

The renin-angiotensin system (RAS) has a pivotal role in the maintenance of extracellular volume homeostasis and blood pressure through complex mechanisms. Apart from the well known systemic RAS, occurrence of a local RAS has been documented in multiple tissues, including the kidney. A large body of recent evidence from pharmacologic and genetic studies, particularly those using various transgenic approaches to manipulate intrarenal levels of RAS components, has established the important role of intrarenal RAS in hypertension. Recent studies have also begun to unravel the molecular mechanisms that govern intrarenal RAS activity. This local system is under the control of complex regulatory networks consisting of positive regulators of (pro)renin receptor, Wnt/β-catenin signaling, and PGE₂/PGE₂ receptor EP₄ subtype, and negative regulators of Klotho, vitamin D receptor, and liver X receptors. This review highlights recent advances in defining the regulation and function of intrarenal RAS as a unique entity separate from systemic angiotensin II generation.