Regulation of cardiovascular remodeling by the counter-regulatory axis of the renin-angiotensin system

Targeting the Renin-angiotensin-aldosterone System (RAAS) for Cardiovascular Protection and Enhanced Oncological Outcomes: Review

OPINION STATEMENT

The renin-angiotensin-aldosterone system (RAAS) is a crucial regulator of the cardiovascular system and a target for widely used therapeutic drugs. Dysregulation of RAAS, implicated in prevalent diseases like hypertension and heart failure, has recently gained attention in oncological contexts due to its role in tumor biology and cardiovascular toxicities (CVTs). Thus, RAAS inhibitors (RAASi) may be used as potential supplementary therapies in cancer treatment and CVT prevention. Oncological treatments have evolved significantly, impacting patient survival and safety profiles. However, they pose cardiovascular risks, necessitating strategies for mitigating adverse effects. The main drug classes used in oncology include anthracyclines, anti-HER2 therapies, immune checkpoint inhibitors (ICIs), and vascular endothelial growth factor (VEGF) signaling pathway inhibitors (VSPI). While effective against cancer, these drugs induce varying CVTs. RAASi adjunctive therapy shows promise in enhancing clinical outcomes and protecting the cardiovascular system. Understanding RAAS involvement in cancer and CVT can inform personalized treatment approaches and improve patient care.

Pathological cardiac remodeling seen by the eyes of proteomics

Cardiac remodeling involves cellular and structural changes that occur as consequence of multifactorial events to maintain the homeostasis. The progression of pathological cardiac remodeling involves a transition from adaptive to maladaptive changes that eventually leads to impairment of ventricular function and heart failure. In this scenario, proteins are key elements that orchestrate molecular events as increased expression of fetal genes, neurohormonal and second messengers' activation, contractile dysfunction, rearrangement of the extracellular matrix and alterations in heart geometry. Mass spectrometry based-proteomics has emerged as a sound method to study protein dysregulation and identification of cardiac diseases biomarkers in plasma. In this review, we summarize the main findings related to large-scale proteome modulation of cardiac cells and extracellular matrix occurred during pathological cardiac remodeling. We describe the recent proteomic progresses in the selection of protein targets and introduce the renin-angiotensin system as an interesting target for the treatment of pathological cardiac remodeling.

Bioactive peptides attenuate cardiac hypertrophy and fibrosis in spontaneously hypertensive rat hearts

Alcalase potato protein hydrolysate (APPH), a nutraceutical food, might an have important role in anti-obesity activity. Recent studies from our lab indicated that APPH treatment had lipolysis stimulating activity and identified was an efficient anti-obesity diet ingredient. In this study we aim to investigate the beneficial effects of pure peptide amino acid sequences (DIKTNKPVIF (DI) and IF) from APPH supplement in the regulation of cardiac hypertrophy and fibrosis on spontaneously hypertensive rats (SHR). We examined hematoxylin and eosin staining, Masson's trichrome staining, echocardiographic parameters, serum parameters, hypertrophy, inflammation and fibrotic marker expression to demonstrate efficacy of bioactive peptides in a SHR model. There was a significant upregulation between SHR and bioactive peptides treated groups in left heart weight (LHW), LHW/WHW, LHW/Tibia, LVIDd, and LVd mass. In addition, the bioactive peptides repress the protein expression of hypertrophy markers (BNP, MYH7), inflammation (TLR-4, p-NFkB, TNF-α, IL-6), and fibrotic markers (uPA, MMP-2, TIMP1, CTGF). In summary, these results indicate that DI and IF bioactive peptides from APPH attenuate cardiac hypertrophy, inflammation and fibrosis in the SHR model.

Time Series Gene Expression Profiling and Temporal Regulatory Pathway Analysis of Angiotensin II Induced Atrial Fibrillation in Mice

Background/Aim: Angiotensin II (Ang II) and hypertension play critical roles in the pathogenesis of the atrial remodeling that contributes to atrial fibrillation (AF). However, the gene expression profiles and signaling pathways in atria during the development of AF induced by Ang II remain unknown.

Methods: Wild-type male mice (C57BL/6 background, 10 weeks old) were administered an infusion of Ang II (2000 ng/kg/min) using an osmotic pump for 1, 2, and 3 weeks. Blood pressure (BP) was measured by the tail-cuff method. AF was induced and recorded. Atrial enlargement and remodeling were examined by echocardiography and Masson’s trichrome staining. Time-series microarray analyses were conducted to examine gene expression profiles and pathways.

Results: Ang II infusion resulted in marked elevation of systolic BP, increased AF incidence and duration, atrial enlargement, fibrosis, and atrial infiltration of myofibroblasts and F4/80-positive macrophages in a time-dependent manner. Microarray results showed that 1,719 genes were differentially expressed in the atrium at weeks 1, 2, and 3 after Ang II infusion. Gene ontology showed that these genes participate mainly in immune system processes, and regulation of cell migration, cell adhesion, complement activation, and the inflammatory response. Significant pathways included lysosomal and phagosomal pathways, which are involved in antigen processing and presentation, as well as chemokine signaling, and extracellular matrix–receptor interaction, which are known to play important roles in Ang II-induced AF. Moreover, these differentially expressed genes were classified into 50 profiles by hierarchical cluster analysis. Of these, eight profiles were significant and contained a total of 1,157 genes. Gene co-expression network analysis identified that Pik3cg (also known as phosphoinositide-3-kinase regulatory subunit 3) was localized in the core of the gene network, and was the most highly expressed among the Pik3 isoforms at different time points.

Conclusion: The present findings revealed that many genes are involved in Ang II-induced AF, and highlighted that Pik3cg may play a central role in this disease.

The role of arterial hypertension in development heart failure with preserved ejection fraction: just a risk factor or something more?

Heart failure with preserved ejection fraction (HFpEF) is an entity that still raises many questions. The agreement about definition, pathophysiology, and therapeutic approach is still missing. Arterial hypertension is present in majority of patients with HFpEF, and it is still not clear if it represent a risk factor or "sine qua non" condition for HFpEF development. The underlying mechanisms of hypertension and HFpEF involve the same biohumoral systems: renin-angiotensin-aldosterone, sympathetic nervous system, and oxidative stress. However, not all hypertensive patients have HFpEF. The predisposition of some hypertensive patients to develop HFpEF needs to be resolved. Large randomized controlled trials did not prove the usefulness of renin-angiotensin-aldosterone inhibitors, diuretics, calcium channel blockers, and beta-blockers in HFpEF patients. The majority of studies did not succeed to demonstrate the reduction of cardiovascular and all-cause mortality in HFpEF individuals. One of the major limitations in these investigations was the inconsistency of HFpEF definition, which mainly refers to left ventricular ejection fraction (LVEF) cut-off that ranged from 40 to 50% in different studies. This review article provides the available data about pathophysiology and mechanisms that connect hypertension and HFpEF, investigations and therapy used in both conditions.

Angiotensin-(1-9) reduces cardiovascular and renal inflammation in experimental renin-independent hypertension

Hypertension-induced cardiovascular and renal damage can be mediated by activation of the renin-angiotensin-aldosterone system. There are different factors beyond renin-angiotensin-aldosterone system involved in hypertension and renal damage. Inflammation has emerged as an important mediator of hypertension and cardiovascular and kidney damage. Angiotensin-(1-9), a peptide of the renin-angiotensin system, counter-regulates both the physiological and pathological actions of angiotensin II. Recent data has shown that angiotensin-(1-9) protects the heart and blood vessels from adverse cardiovascular remodeling in experimental models of hypertension and/or heart failure and reduces cardiac fibrosis in stroke-prone, spontaneously hypertensive rats. These effects are mediated by the angiotensin II type 2 receptor (AT2R). However, it remains unknown whether angiotensin-(1-9) also has an anti-inflammatory effect. In the present study, we investigate whether angiotensin-(1-9) reduces inflammation and fibrosis in the heart, arteries, and kidney in a DOCA-salt hypertensive model and explore the mechanisms underlying the amelioration of end-organ damage. DOCA-salt hypertensive rats received: a) vehicle, b) angiotensin-(1-9), c) PD123319 (AT2R blocker), d) angiotensin-(1-9) plus A779 (a Mas receptor blocker) or e) angiotensin-(1-9) plus PD123319, and sham rats were used as a control. Our results showed that angiotensin-(1-9) decreased hypertension and increased vasodilation in DOCA-salt hypertensive rats. These actions were partially inhibited by PD123319. Moreover, angiotensin-(1-9) decreased diuresis, fibrosis, and inflammation. These beneficial effects were not mediated by Mas or AT2R blockers. We concluded that angiotensin-(1-9) protects against volume overload-induced hypertensive cardiovascular and kidney damage by decreasing inflammation in the heart, aortic wall, and kidney, through mechanisms independent of the Mas or AT2R.

Novel Medical Treatments for Hypertension and Related Comorbidities

Purpose of Review

The purpose of this review is to summarize the most recent data available on advances in development of novel medical treatments for hypertension and related comorbidities.

Recent Findings

Approximately half of all hypertensive patients have not achieved goal blood pressure with current available antihypertensive medications. Recent landmark studies and new hypertension guidelines have called for stricter blood pressure control, creating a need for better strategies for lowering blood pressure. This has led to a shift in focus, in recent years, to the development of combination pills as a means of achieving improved blood pressure control by increasing adherence to prescribed medications along with further research and development of promising novel drugs based on discovery of new molecular targets such as the counter-regulatory renin-angiotensin system.

Summary

Fixed-dose combination pills and novel treatments based on recently discovered pathogenic mechanisms of hypertension that have demonstrated promising results as treatments for hypertension and related comorbidities will be discussed in this review.

Hypotensive and Angiotensin-Converting Enzyme Inhibitory Activities of Eisenia fetida Extract in Spontaneously Hypertensive Rats

Objectives. This study aimed to investigate the antihypertensive effects of an Eisenia fetida extract (EFE) and its possible mechanisms in spontaneously hypertensive rats (SHR rats). Methods. Sixteen-week-old SHR rats and Wistar-Kyoto rats (WKY rats) were used in this study. Rats were, respectively, given EFE (EFE group), captopril (captopril group), or phosphate-buffered saline (PBS) (normal control group and SHR group) for 4 weeks. ACE inhibitory activity of EFE in vitro was determined. The systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using a Rat Tail-Cuff Blood Pressure System. Levels of angiotensin II (Ang II), aldosterone (Ald), and 6-keto-prostaglandin F1 alpha (6-keto-PGF1α ) in plasma were determined by radioimmunoassay, and serum nitric oxide (NO) concentration was measured by Griess reagent systems. Results. EFE had marked ACE inhibitory activity in vitro (IC50 = 2.5 mg/mL). After the 4-week drug management, SHR rats in EFE group and in captopril group had lower SBP and DBP, lower levels of Ang II and Ald, and higher levels of 6-keto-PGF1α and NO than the SHR rats in SHR group. Conclusion. These results indicate that EFE has hypotensive effects in SHR rats and its effects might be associated with its ACE inhibitory activity.

An update of the role of renin angiotensin in cardiovascular homeostasis

The renin angiotensin system (RAS) is thought to be the body's main vasoconstrictor system, with physiological effects mediated via the interaction of angiotensin II with angiotensin I receptors (the "classic" RAS model). However, since the discovery of the heptapeptide angiotensin 1-7 and the development of the concept of the "alternate" RAS system, with its ability to reduce arterial blood pressure, our understanding of this physiologic system has changed dramatically. In this review, we focus on the newly discovered functions of the RAS, particularly the potential clinical significance of these developments, especially in the realm of new pharmacologic interventions for treating cardiovascular disease.

Angiotensin-(1-12): a chymase-mediated cellular angiotensin II substrate

The classical view of biochemical pathways for the formation of biologically active angiotensins continues to undergo significant revision as new data uncovers the existence of important species differences between humans and rodents. The discovery of two novel substrates that, cleaved from angiotensinogen, can lead to direct tissue angiotensin II formation has the potential of radically altering our understanding of how tissues source angiotensin II production and explain the relative lack of efficacy that characterizes the use of angiotensin converting enzyme inhibitors in cardiovascular disease. This review addresses the discovery of angiotensin-(1-12) as an endogenous substrate for the production of biologically active angiotensin peptides by a non-renin dependent mechanism and the revealing role of cardiac chymase as the angiotensin II convertase in the human heart. This new information provides a renewed argument for exploring the role of chymase inhibitors in the correction of cardiac arrhythmias and left ventricular systolic and diastolic dysfunction.

Dipeptidyl peptidase inhibition prevents diastolic dysfunction and reduces myocardial fibrosis in a mouse model of Western diet induced obesity

OBJECTIVE

Consumption of a high-fat/high-fructose Western diet (WD) is linked to rising obesity and heart disease, particularly diastolic dysfunction which characterizes early obesity/metabolic cardiomyopathy. Mounting evidence supports a role for inflammation, oxidative stress and fibrosis in the pathophysiology of metabolic cardiomyopathy. Dipeptidyl peptidase-4 (DPP-4) is a circulating exopeptidase recently reported to be elevated in the plasma of patients with insulin resistance (IR), obesity and heart failure. We hypothesized that a model of WD induced obesity/metabolic cardiomyopathy would exhibit increased DPP-4 activity and cardiac fibrosis with DPP-4 inhibition preventing cardiac fibrosis and the associated diastolic dysfunction.

MATERIALS/METHODS

Four-week-old C57BL6/J mice were fed a high-fat/high-fructose WD with the DPP-4 inhibitor MK0626 for 16 weeks. Cardiac function was examined by high-resolution cine-cardiac magnetic resonance imaging (MRI). Phenotypic analysis included measurements of body and heart weight, systemic IR and DPP-4 activity. Immunohistochemistry and transmission electron microscopy (TEM) were utilized to identify underlying pathologic mechanisms.

RESULTS

We found that chronic WD consumption caused obesity, IR, elevated plasma DPP-4 activity, heart enlargement and diastolic dysfunction. DPP-4 inhibition with MK0626 in WD fed mice resulted in >75% reduction in plasma DPP-4 activity, improved IR and normalized diastolic relaxation. WD consumption induced myocardial oxidant stress and fibrosis with amelioration by MK0626. TEM of hearts from WD fed mice revealed abnormal mitochondrial and perivascular ultrastructure partially corrected by MK0626.

CONCLUSIONS

This study provides evidence of a role for increased DPP-4 activity in metabolic cardiomyopathy and a potential role for DPP-4 inhibition in prevention and/or correction of oxidant stress/fibrosis and associated diastolic dysfunction.

Mild Renal Artery Stenosis Can Induce Renovascular Hypertension and is Associated with Elevated Renal Vein Renin Secretion

Renovascular hypertension is a syndrome which encompasses the physiological response of the kidney to changes in renal blood flow and renal perfusion pressure. Such physiological changes can occur with renal artery occlusion irrespective of the severity of the lesion. We have analyzed hypertensive patients with mild renal artery stenosis and compared them to patients with no stenosis. Renal vein renin sampling from catheterization of the renal vein was performed in all these patients. Patients with mild stenosis had higher renal vein renin ratio (3.01 ± 1.5) than the patients with no stenosis (1.10 ± 0.29; p = 0.002). Patients with mild stenosis were also found to have higher diastolic blood pressure and renal artery resistive indices when compared to patients with no stenosis. We therefore conclude that mild stenosis can precipitate renin-mediated hypertension in renovascular stenosis and also emphasis that parameters pertinent to renal physiology need to be evaluated before considering treatment options in patients with renal artery stenosis and medical management with RAAS blockade is the preferred modality of therapy for patients with renin-mediated hypertension.

Protective effects of losartan in mice with chronic viral myocarditis induced by coxsackievirus B3

AIM

To investigate whether losartan has protective effects in mice with chronic viral myocarditis induced by coxsackievirus B3 (CVB3).

MAIN METHODS

Thirty two male Balb/c mice were intraperitoneally injected with CVB3 (10×TCID50) to induce chronic viral myocarditis (CVM). Losartan at 12.5mg/kg (n=16) or normal saline (n=16) were orally administered daily for 28 days to these mice. Uninfected mice (n=6) were used as controls. On day 29, all mice underwent anesthesia and echocardiography prior to sacrifice. Serum IL-17, IL-4, IFN-γ and TNF-α levels were measured by enzyme-linked immunosorbent assay, and cardiac tissues were histologically examined after hematoxylin & eosin staining. In addition, the effect of losartan on the virus titers in primary cultured neonatal rat cardiomyocytes infected with CVB3 was measured on Hep-2 cells at 72 h post infection.

KEY FINDINGS

Mice infected with CBV3 had significantly increased mortality, heart/body weight ratios, necrosis and inflammatory scores and decreased cardiac ejection fractions, compared with the controls (all P<0.05). Losartan significantly decreased mortality from 40.0% to 12.5%, heart/body weight ratios from 7.08 ± 2.17 to 4.15 ± 0.99, and necrosis and inflammatory scores from 3.33 ± 0.50 to 2.50 ± 0.65 (all P<0.05), and increased ejection fractions from 55.80 ± 9.25 to 72.31 ± 12.15 (P<0.05). Losartan significantly enhanced IL-4, and decreased IFN-γ, TNF-α and IL-17 (all P<0.05). In the in vitro experiment, losartan had no influence on virus titers.

SIGNIFICANCE

Losartan protects mice against CVB3-induced CVM, most likely through upregulating Th2 responses, and down-regulating Th1 and Th17 responses.