Aldosterone and angiotensin II synergistically induce mitogenic response in vascular smooth muscle cells

Mineralocorticoid Receptors in Vascular Smooth Muscle: Blood Pressure and Beyond

After half a century of evidence suggesting the existence of mineralocorticoid receptors (MR) in the vasculature, the advent of technology to specifically knockout the MR from smooth muscle cells (SMCs) in mice has elucidated contributions of SMC-MR to cardiovascular function and disease, independent of the kidney. This review summarizes the latest understanding of the molecular mechanisms by which SMC-MR contributes to (1) regulation of vasomotor function and blood pressure to contribute to systemic and pulmonary hypertension; (2) vascular remodeling in response to hypertension, vascular injury, obesity, and aging, and the impact on vascular calcification; and (3) cardiovascular pathologies including aortic aneurysm, heart valve dysfunction, and heart failure. Data are reviewed from in vitro studies using SMCs and in vivo findings from SMC-specific MR-knockout mice that implicate target genes and signaling pathways downstream of SMC-MR. By regulating expression of the L-type calcium channel subunit Cav1.2 and angiotensin II type-1 receptor, SMC-MR contributes to myogenic tone and vasoconstriction, thereby contributing to systemic blood pressure. MR activation also promotes SMC proliferation, migration, production and degradation of extracellular matrix, and osteogenic differentiation by regulating target genes including connective tissue growth factor, osteopontin, bone morphogenetic protein 2, galectin-3, and matrix metallopeptidase-2. By these mechanisms, SMC-MR promotes disease progression in models of aging-associated vascular stiffness, vascular calcification, mitral and aortic valve disease, pulmonary hypertension, and heart failure. While rarely tested, when sexes were compared, the mechanisms of SMC-MR-mediated disease were sexually dimorphic. These advances support targeting SMC-MR-mediated mechanisms to prevent and treat diverse cardiovascular disorders.

Sinapine targeting PLCβ3 EF hands disrupts Gαq-PLCβ3 interaction and ameliorates cardiovascular diseases

BACKGROUND

The renin-angiotensin-aldosterone system (RAAS) over-activation is highly involved in cardiovascular diseases (CVDs), with the Gαq-PLCβ3 axis acting as a core node of RAAS. PLCβ3 is a potential target of CVDs, and the lack of inhibitors has limited its drug development.

PURPOSE

Sinapine (SP) is a potential leading compound for treating CVDs. Thus, we aimed to elucidate the regulation of SP towards the Gαq-PLCβ3 axis and its molecular mechanism.

STUDY DESIGN

Aldosteronism and hypertension animal models were employed to investigate SP's inhibitory effect on the abnormal activation of the RAAS through the Gαq-PLCβ3 axis. We used chemical biology methods to identify potential targets and elucidate the underlying molecular mechanisms.

METHODS

The effects of SP on aldosteronism and hypertension were evaluated using an established animal model in our laboratory. Target identification and underlying molecular mechanism research were performed using activity-based protein profiling with a bio-orthogonal click chemistry reaction and other biochemical methods.

RESULTS

SP alleviated aldosteronism and hypertension in animal models by targeting PLCβ3. The underlying mechanism for blocking the Gαq-PLCβ3 interaction involves targeting the EF hands through the Asn-260 amino acid residue. SP regulated the Gαq-PLCβ3 axis more precisely than the Gαq-GEFT or Gαq-PKCζ axis in the cardiovascular system.

CONCLUSION

SP alleviated RAAS over-activation via Gαq-PLCβ3 interaction blockade by targeting the PLCβ3 EF hands domain, which provided a novel PLC inhibitor for treating CVDs. Unlike selective Gαq inhibitors, SP reduced the risk of side effects compared to Gαq inhibitors in treating CVDs.

Nicotinamide Mononucleotide Alleviates Angiotensin II-Induced Human Aortic Smooth Muscle Cell Senescence in a Microphysiological Model

ABSTRACT

The occurrence and development of aortic aneurysms are accompanied by senescence of human aortic smooth muscle cells (HASMCs). Because the mechanism of HASMC senescence has not been fully elucidated, the efficacy of various antisenescence treatments varies. Decreased nicotinamide adenine dinucleotide (NAD + ) levels are one of the mechanisms of cell senescence, and there is a lack of evidence on whether increasing NAD + levels could alleviate HASMC senescence and further retard the progression of aortic aneurysms.We constructed an HASMC-based organ-on-a-chip microphysiological model. RNA sequencing was performed on cell samples from the vehicle control and angiotensin II groups to explore biological differences. We detected cellular senescence markers and NAD + levels in HASMC-based organ-on-a-chip. Subsequently, we pretreated HASMC using the synthetic precursor of NAD + , nicotinamide mononucleotide, and angiotensin II treatment, and used rhythmic stretching to investigate whether nicotinamide mononucleotide could delay HASMC senescence.The HASMC-based organ-on-a-chip model can simulate the biomechanical microenvironment of HASMCs in vivo, and the use of angiotensin II in the model replicated senescence in HASMCs. The senescence of HASMCs was accompanied by downregulation of the expression level of nicotinamide phosphoribosyltransferase and NAD + . Pretreatment with nicotinamide mononucleotide significantly increased the NAD + level and alleviated the senescence of HASMCs, but did not change the expression level of nicotinamide phosphoribosyltransferase.Our study provides a complementary research platform between traditional cell culture and animal experiments to explore HASMC senescence in aortic aneurysms. Furthermore, it provides evidence for NAD + boosting therapy in the clinical treatment of aortic aneurysms.

Aldosterone: Renal Action and Physiological Effects

Aldosterone exerts profound effects on renal and cardiovascular physiology. In the kidney, aldosterone acts to preserve electrolyte and acid-base balance in response to changes in dietary sodium (Na+ ) or potassium (K+ ) intake. These physiological actions, principally through activation of mineralocorticoid receptors (MRs), have important effects particularly in patients with renal and cardiovascular disease as demonstrated by multiple clinical trials. Multiple factors, be they genetic, humoral, dietary, or otherwise, can play a role in influencing the rate of aldosterone synthesis and secretion from the adrenal cortex. Normally, aldosterone secretion and action respond to dietary Na+ intake. In the kidney, the distal nephron and collecting duct are the main targets of aldosterone and MR action, which stimulates Na+ absorption in part via the epithelial Na+ channel (ENaC), the principal channel responsible for the fine-tuning of Na+ balance. Our understanding of the regulatory factors that allow aldosterone, via multiple signaling pathways, to function properly clearly implicates this hormone as central to many pathophysiological effects that become dysfunctional in disease states. Numerous pathologies that affect blood pressure (BP), electrolyte balance, and overall cardiovascular health are due to abnormal secretion of aldosterone, mutations in MR, ENaC, or effectors and modulators of their action. Study of the mechanisms of these pathologies has allowed researchers and clinicians to create novel dietary and pharmacological targets to improve human health. This article covers the regulation of aldosterone synthesis and secretion, receptors, effector molecules, and signaling pathways that modulate its action in the kidney. We also consider the role of aldosterone in disease and the benefit of mineralocorticoid antagonists. © 2023 American Physiological Society. Compr Physiol 13:4409-4491, 2023.

Epidermal growth factor receptors and their ligands are expressed in the spleen of the Japanese Quail (Coturnix coturnix japonica) during the post-hatch period

1. The epidermal growth factor (EGF) family plays an important role in the development, differentiation, migration and apoptosis of cells, as well as in wound healing, which are all essential to the viability of multicellular organisms. The avian spleen is a principal organ of systemic immunity and its importance in disease resistance is presumably accentuated by the scarcity of avian lymph nodes.2. The aim of this study was to determine whether EGF receptors (ErbB1-4) and their ligands (EGF, AREG and NRG) are expressed in the structural components of the quail spleen during the post-hatch period. At each selected age, from 1 d to 7, 14, 21 and 60 d, 10 quails were euthanised under ether anaesthesia and their spleens were fixed in a 10% formaldehyde-alcohol solution. Following routine histological processing, the streptavidin-biotin-peroxidase method was used for immunohistochemical examination.3. Strong cytoplasmic immunoreactions for ErbB2, ErbB4 and NRG were observed in the ellipsoid associated cells (EAC) of the quail spleen throughout the post-hatch period. This immunoreactivity in the EAC increased after the 7th d post-hatch. ErbB1 and ErbB3 immunoreactions were relatively similar and weak in all components of the spleen during the post-hatch period. Some immune cells of the peri-arterial lymphatic sheath (PALS) and peri-ellipsoidal lymphatic sheath (PELS) showed positive immunoreactivity for the ErbB receptors and their ligands. In the vascular smooth muscle cells, immunoreactivity for ErbB2 was stronger than that for the other ErbB receptors and their ligands.4. The data showed that ErbB receptors and their ligands (EGF, AREG and NRG) are expressed by different structural components of the quail spleen during the post-hatch period.

Mineralocorticoid Receptor Antagonism by Finerenone Attenuates Established Pulmonary Hypertension in Rats

BACKGROUND

We studied the ability of the nonsteroidal MR (mineralocorticoid receptor) antagonist finerenone to attenuate vascular remodeling and pulmonary hypertension using two complementary preclinical models (the monocrotaline and sugen/hypoxia rat models) of severe pulmonary hypertension.

METHODS

We first examined the distribution pattern of MR in the lungs of patients with pulmonary arterial hypertension (PAH) and in monocrotaline and sugen/hypoxia rat lungs. Subsequent studies were performed to explore the effect of MR inhibition on proliferation of pulmonary artery smooth muscle cells derived from patients with idiopathic PAH. To validate the functional importance of MR activation in the pulmonary vascular remodeling characteristic of pulmonary hypertension, mice overexpressing MR (hMR+) were studied, and curative treatments with finerenone (1 mg/kg per day by gavage), started 2 weeks after monocrotaline injection or 5 weeks after Sugen injection were realized.

RESULTS

We demonstrated that MR is overexpressed in experimental and human PAH and that its inhibition following siRNA-mediated MR silencing or finerenone treatment attenuates proliferation of pulmonary artery smooth muscle cells derived from patients with idiopathic PAH. In addition, we obtained evidence that hMR+ mice display increased right ventricular systolic pressure, right ventricular hypertrophy, and remodeling of pulmonary arterioles. Consistent with these observations, curative treatments with finerenone partially reversed established pulmonary hypertension, reducing total pulmonary vascular resistance and vascular remodeling. Finally, we found that continued finerenone treatment decreases inflammatory cell infiltration and vascular cell proliferation in monocrotaline and sugen/hypoxia rat lungs.

CONCLUSIONS

Finerenone treatment appears to be a potential therapy for PAH worthy of investigation and evaluation for clinical use in conjunction with current PAH treatments.

Aldosterone breakthrough from a pharmacological perspective

Aldosterone (Aldo) breakthrough is a well-known phenomenon that occurs in patients with long-term renin-angiotensin aldosterone system (RAAS) blockade using inhibitors of renin or angiotensin converting enzyme or angiotensin II type 1 receptor blockers. The blockade of the mineralocorticoid receptor (MR), an Aldo binding receptor, is effective in managing patients with resistant hypertension, defined as uncontrollable blood pressure despite the concurrent use of three antihypertensive drugs. In other words, MR inhibitors are not used as first-line antihypertensive drugs in most guidelines for hypertension management. Aldo breakthrough puts hypertensive patients at higher risk of cardiovascular disease and worsens future outcomes. This review discusses Aldo secretion and the mechanism of Aldo breakthrough, dependent or independent of the RAAS, with consideration of the pharmacological aspects of this phenomenon, as well as hypothetical views.

Targeting the renin angiotensin system for the treatment of anxiety and depression

Emotional disorders like anxiety and depression are responsible for considerable morbidity and mortality all over the world. Several antidepressant and anxiolytic medications are available for the treatment of anxiety and depression. However, a significant number of patients either do not respond to these medications or respond inadequately. Hence, there is a need to identify novel targets for the treatment of anxiety and depression. In this review we focus on the renin angiotensin system (RAS) as a potential target for the treatment of these disorders. We review work that has evaluated the effects of various compounds targeting the RAS on anxiety- and depression-like behaviors. Further, we suggest future work that must be carried out to fully exploit the RAS for the treatment of anxiety and depression. The RAS provides an attractive target for both the identification of novel anxiolytic and antidepressant medications and/or for enhancing the efficacy of currently available medications used for the treatment of anxiety and depression.

Extracellular matrix induced by steroids and aging through a G-protein-coupled receptor in a Drosophila model of renal fibrosis

Aldosterone is produced by the mammalian adrenal cortex to modulate blood pressure and fluid balance; however, excessive, prolonged aldosterone promotes fibrosis and kidney failure. How aldosterone triggers disease may involve actions independent of its canonical mineralocorticoid receptor. Here, we present a Drosophila model of renal pathology caused by excess extracellular matrix formation, stimulated by exogenous aldosterone and by insect ecdysone. Chronic administration of aldosterone or ecdysone induces expression and accumulation of collagen-like Pericardin in adult nephrocytes - podocyte-like cells that filter circulating hemolymph. Excess Pericardin deposition disrupts nephrocyte (glomerular) filtration and causes proteinuria in Drosophila, hallmarks of mammalian kidney failure. Steroid-induced Pericardin production arises from cardiomyocytes associated with nephrocytes, potentially reflecting an analogous role of mammalian myofibroblasts in fibrotic disease. Remarkably, the canonical ecdysteroid nuclear hormone receptor, Ecdysone receptor (EcR), is not required for aldosterone or ecdysone to stimulate Pericardin production or associated renal pathology. Instead, these hormones require a cardiomyocyte-associated G-protein-coupled receptor, Dopamine-EcR (DopEcR), a membrane-associated receptor previously characterized in the fly brain to affect behavior. DopEcR in the brain is known to affect behavior through interactions with the Drosophila Epidermal growth factor receptor (Egfr), referred to as dEGFR. Here, we find that the steroids ecdysone and aldosterone require dEGFR in cardiomyocytes to induce fibrosis of the cardiac-renal system. In addition, endogenous ecdysone that becomes elevated with age is found to foster age-associated fibrosis, and to require both cardiomyocyte DopEcR and dEGFR. This Drosophila renal disease model reveals a novel signaling pathway through which steroids may modulate mammalian fibrosis through potential orthologs of DopEcR.

Role of microRNA 690 in Mediating Angiotensin II Effects on Inflammation and Endoplasmic Reticulum Stress

Overactivation of the renin–angiotensin system (RAS) during obesity disrupts adipocyte metabolic homeostasis and induces endoplasmic reticulum (ER) stress and inflammation; however, underlying mechanisms are not well known. We propose that overexpression of angiotensinogen (Agt), the precursor protein of RAS in adipose tissue or treatment of adipocytes with Angiotensin II (Ang II), RAS bioactive hormone, alters specific microRNAs (miRNA), that target ER stress and inflammation leading to adipocyte dysfunction. Epididymal white adipose tissue (WAT) from B6 wild type (Wt) and transgenic male mice overexpressing Agt (Agt-Tg) in adipose tissue and adipocytes treated with Ang II were used. Small RNA sequencing and microarray in WAT identified differentially expressed miRNAs and genes, out of which miR-690 and mitogen-activated protein kinase kinase 3 (MAP2K3) were validated as significantly up- and down-regulated, respectively, in Agt-Tg, and in Ang II-treated adipocytes compared to respective controls. Additionally, the direct regulatory role of miR-690 on MAP2K3 was confirmed using mimic, inhibitors and dual-luciferase reporter assay. Downstream protein targets of MAP2K3 which include p38, NF-κB, IL-6 and CHOP were all reduced. These results indicate a critical post-transcriptional role for miR-690 in inflammation and ER stress. In conclusion, miR-690 plays a protective function and could be a useful target to reduce obesity.

Endothelial Dysfunction in Primary Aldosteronism

Primary aldosteronism (PA) is characterized by excess production of aldosterone from the adrenal glands and is the most common and treatable cause of secondary hypertension. Aldosterone is a mineralocorticoid hormone that participates in the regulation of electrolyte balance, blood pressure, and tissue remodeling. The excess of aldosterone caused by PA results in an increase in cardiovascular and cerebrovascular complications, including coronary artery disease, myocardial infarction, stroke, transient ischemic attack, and even arrhythmia and heart failure. Endothelial dysfunction is a well-established fundamental cause of cardiovascular diseases and also a predictor of worse clinical outcomes. Accumulating evidence indicates that aldosterone plays an important role in the initiation and progression of endothelial dysfunction. Several mechanisms have been shown to contribute to aldosterone-induced endothelial dysfunction, including aldosterone-mediated vascular tone dysfunction, aldosterone- and endothelium-mediated vascular inflammation, aldosterone-related atherosclerosis, and vascular remodeling. These mechanisms are activated by aldosterone through genomic and nongenomic pathways in mineralocorticoid receptor-dependent and independent manners. In addition, other cells have also been shown to participate in these mechanisms. The complex interactions among endothelium, inflammatory cells, vascular smooth muscle cells and fibroblasts are crucial for aldosterone-mediated endothelial dysregulation. In this review, we discuss the association between aldosterone and endothelial function and the complex mechanisms from a molecular aspect. Furthermore, we also review current clinical research of endothelial dysfunction in patients with PA.

PKCδ Mediates Mineralocorticoid Receptor Activation by Angiotensin II to Modulate Smooth Muscle Cell Function

Angiotensin II (AngII) and the mineralocorticoid receptor (MR) ligand aldosterone both contribute to cardiovascular disorders, including hypertension and adverse vascular remodeling. We previously demonstrated that AngII activates MR-mediated gene transcription in human vascular smooth muscle cells (SMCs), yet the mechanism and the impact on SMC function are unknown. Using an MR-responsive element-driven transcriptional reporter assay, we confirm that AngII induces MR transcriptional activity in vascular SMCs and endothelial cells, but not in Cos1 or human embryonic kidney-293 cells. AngII activation of MR was blocked by the MR antagonist spironolactone or eplerenone and the protein kinase C-δ (PKCδ) inhibitor rottlerin, implicating both in the mechanism. Similarly, small interfering RNA knockdown of PKCδ in SMCs prevented AngII-mediated MR activation, whereas knocking down of MR blocked both aldosterone- and AngII-induced MR function. Coimmunoprecipitation studies reveal that endogenous MR and PKCδ form a complex in SMCs that is enhanced by AngII treatment in association with increased serine phosphorylation of the MR N terminus. AngII increased mRNA expression of the SMC-MR target gene, FKBP51, via an MR-responsive element in intron 5 of the FKBP51 gene. The impact of AngII on FKBP51 reporter activity and gene expression in SMCs was inhibited by spironolactone and rottlerin. Finally, the AngII-induced increase in SMC number was also blocked by the MR antagonist spironolactone and the PKCδ inhibitor rottlerin. These data demonstrate that AngII activates MR transcriptional regulatory activity, target gene regulation, and SMC proliferation in a PKCδ-dependent manner. This new mechanism may contribute to synergy between MR and AngII in driving SMC dysfunction and to the cardiovascular benefits of MR and AngII receptor blockade in humans.

Role of Aldosterone in Renal Fibrosis

Aldosterone is a mineralocorticoid hormone, as its main renal effect has been considered as electrolyte and water homeostasis in the distal tubule, thus maintaining blood pressure and extracellular fluid homeostasis through the activation of mineralocorticoid receptor (MR) in epithelial cells. However, over the past decade, numerous studies have documented the significant role of aldosterone in the progression of chronic kidney disease (CKD) which has become a subject of interest. It is being studied that aldosterone can affect cardiovascular and renal system, thereby contributing to tissue inflammation, injury, glomerulosclerosis, and interstitial fibrosis. Aldosterone acts on renal vessels, renal cells (glomerular mesangial cells, podocytes, vascular smooth muscle cells, tubular epithelial cells, and interstitial fibroblasts), and infiltrating inflammatory cells, inducing reactive oxygen species (ROS) production, upregulated epithelial growth factor receptor (EGFR), and type 1 angiotensin (AT1) receptor expressions, and activating nuclear factor kappa B (NF-κB), activator protein-1 (AP-1), and EGFR to further promote cell proliferation, apoptosis, and proliferation. Phenotypic transformation of epithelial cells stimulates the expression of transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), osteopontin (OPN), and plasminogen activator inhibitor-1 (PAI-1), eventually leading to renal fibrosis. MR antagonisms are related to inhibition of aldosterone-mediated pro-inflammatory and pro-fibrotic effect. In this review, we will summarize the important role of aldosterone in the pathogenesis of renal injury and fibrosis, emphasizing on its multiple underlying mechanisms and advances in aldosterone research along with the potential therapeutics for targeting MR in a renal fibrosis.

Molecular and genetic aspects of guanylyl cyclase natriuretic peptide receptor-A in regulation of blood pressure and renal function

Natriuretic peptides (NPs) exert diverse effects on several biological and physiological systems, such as kidney function, neural and endocrine signaling, energy metabolism, and cardiovascular function, playing pivotal roles in the regulation of blood pressure (BP) and cardiac and vascular homeostasis. NPs are collectively known as anti-hypertensive hormones and their main functions are directed toward eliciting natriuretic/diuretic, vasorelaxant, anti-proliferative, anti-inflammatory, and anti-hypertrophic effects, thereby, regulating the fluid volume, BP, and renal and cardiovascular conditions. Interactions of NPs with their cognate receptors display a central role in all aspects of cellular, biochemical, and molecular mechanisms that govern physiology and pathophysiology of BP and cardiovascular events. Among the NPs atrial and brain natriuretic peptides (ANP and BNP) activate guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) and initiate intracellular signaling. The genetic disruption of Npr1 (encoding GC-A/NPRA) in mice exhibits high BP and hypertensive heart disease that is seen in untreated hypertensive subjects, including high BP and heart failure. There has been a surge of interest in the NPs and their receptors and a wealth of information have emerged in the last four decades, including molecular structure, signaling mechanisms, altered phenotypic characterization of transgenic and gene-targeted animal models, and genetic analyses in humans. The major goal of the present review is to emphasize and summarize the critical findings and recent discoveries regarding the molecular and genetic regulation of NPs, physiological metabolic functions, and the signaling of receptor GC-A/NPRA with emphasis on the BP regulation and renal and cardiovascular disorders.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: Nongenomic effects via the mineralocorticoid receptor

The mineralocorticoid receptor (MR) belongs to the steroid hormone receptor family and classically functions as a ligand-dependent transcription factor. It is involved in water-electrolyte homeostasis and blood pressure regulation but independent from these effects also furthers inflammation, fibrosis, hypertrophy and remodeling in cardiovascular tissues. Next to genomic effects, aldosterone elicits very rapid actions within minutes that do not require transcription or translation and that occur not only in classical MR epithelial target organs like kidney and colon but also in nonepithelial tissues like heart, vasculature and adipose tissue. Most of these effects can be mediated by classical MR and its crosstalk with different signaling cascades. Near the plasma membrane, the MR seems to be associated with caveolin and striatin as well as with receptor tyrosine kinases like EGFR, PDGFR and IGF1R and G protein-coupled receptors like AT1 and GPER1, which then mediate nongenomic aldosterone effects. GPER1 has also been named a putative novel MR. There is a close interaction and functional synergism between the genomic and the nongenomic signaling so that nongenomic signaling can lead to long-term effects and support genomic actions. Therefore, understanding nongenomic aldosterone/MR effects is of potential relevance for modulating genomic aldosterone effects and may provide additional targets for intervention.

Cellular distribution and interaction between extended renin-angiotensin-aldosterone system pathways in atheroma

The importance of the renin-angiotensin-aldosterone system (RAAS) in the development of atherosclerotic has been experimentally documented. In fact, RAAS components have been shown to be locally expressed in the arterial wall and to be differentially regulated during atherosclerotic lesion progression. RAAS transcripts and proteins were shown to be differentially expressed and to interact in the 3 main cells of atheroma: endothelial cells, vascular smooth muscle cells, and macrophages. This review describes the local expression and cellular distribution of extended RAAS components in the arterial wall and their differential regulation during atherosclerotic lesion development.

Expression and Function of the Epidermal Growth Factor Receptor in Physiology and Disease

The epidermal growth factor receptor (EGFR) is the prototypical member of a family of membrane-associated intrinsic tyrosine kinase receptors, the ErbB family. EGFR is activated by multiple ligands, including EGF, transforming growth factor (TGF)-α, HB-EGF, betacellulin, amphiregulin, epiregulin, and epigen. EGFR is expressed in multiple organs and plays important roles in proliferation, survival, and differentiation in both development and normal physiology, as well as in pathophysiological conditions. In addition, EGFR transactivation underlies some important biologic consequences in response to many G protein-coupled receptor (GPCR) agonists. Aberrant EGFR activation is a significant factor in development and progression of multiple cancers, which has led to development of mechanism-based therapies with specific receptor antibodies and tyrosine kinase inhibitors. This review highlights the current knowledge about mechanisms and roles of EGFR in physiology and disease.

Aldosterone-Induced Vascular Remodeling and Endothelial Dysfunction Require Functional Angiotensin Type 1a Receptors

We investigated the role of angiotensin type 1a receptors (AGTR1a) in vascular injury induced by aldosterone activation of mineralocorticoid receptors in Agtr1a(-/-) and wild-type (WT) mice infused with aldosterone for 14 days while receiving 1% NaCl in drinking water. Aldosterone increased systolic blood pressure (BP) by ≈30 mm Hg in WT mice and ≈50 mm Hg in Agtr1a(-/-) mice. Aldosterone induced aortic and small artery remodeling, impaired endothelium-dependent relaxation in WT mice, and enhanced fibronectin and collagen deposition and vascular inflammation. None of these vascular effects were observed in Agtr1a(-/-) mice. Aldosterone effects were prevented by the AGTR1 antagonist losartan in WT mice. In contrast to aldosterone, norepinephrine caused similar BP increase and mesenteric artery remodeling in WT and Agtr1a(-/-) mice. Agtr1a(-/-) mice infused with aldosterone did not increase sodium excretion in response to a sodium chloride challenge, suggesting that sodium retention could contribute to the exaggerated BP rise induced by aldosterone. Agtr1a(-/-) mice had decreased mesenteric artery expression of the calcium-activated potassium channel Kcnmb1, which may enhance myogenic tone and together with sodium retention, exacerbate BP responses to aldosterone/salt in Agtr1a(-/-) mice. We conclude that although aldosterone activation of mineralocorticoid receptors raises BP more in Agtr1a(-/-) mice, AGTR1a is required for mineralocorticoid receptor stimulation to induce vascular remodeling and inflammation and endothelial dysfunction.

Update on RAAS Modulation for the Treatment of Diabetic Cardiovascular Disease

Since the advent of insulin, the improvements in diabetes detection and the therapies to treat hyperglycemia have reduced the mortality of acute metabolic emergencies, such that today chronic complications are the major cause of morbidity and mortality among diabetic patients. More than half of the mortality that is seen in the diabetic population can be ascribed to cardiovascular disease (CVD), which includes not only myocardial infarction due to premature atherosclerosis but also diabetic cardiomyopathy. The importance of renin-angiotensin-aldosterone system (RAAS) antagonism in the prevention of diabetic CVD has demonstrated the key role that the RAAS plays in diabetic CVD onset and development. Today, ACE inhibitors and angiotensin II receptor blockers represent the first line therapy for primary and secondary CVD prevention in patients with diabetes. Recent research has uncovered new dimensions of the RAAS and, therefore, new potential therapeutic targets against diabetic CVD. Here we describe the timeline of paradigm shifts in RAAS understanding, how diabetes modifies the RAAS, and what new parts of the RAAS pathway could be targeted in order to achieve RAAS modulation against diabetic CVD.

Towards the emerging crosstalk: ERBB family and steroid hormones

Growth factors acting through receptor tyrosine kinases (RTKs) of ERBB family, along with steroid hormones (SH) acting through nuclear receptors (NRs), are critical signalling mediators of cellular processes. Deregulations of ERBB and steroid hormone receptors are responsible for several diseases, including cancer, thus demonstrating the central role played by both systems. This review will summarize and shed light on an emerging crosstalk between these two important receptor families. How this mutual crosstalk is attained, such as through extensive genomic and non-genomic interactions, will be addressed. In light of recent studies, we will describe how steroid hormones are able to fine-tune ERBB feedback loops, thus impacting on cellular output and providing a new key for understanding the complexity of biological processes in physiological or pathological conditions. In our understanding, the interactions between steroid hormones and RTKs deserve further attention. A system biology approach and advanced technologies for the analysis of RTK-SH crosstalk could lead to major advancements in molecular medicine, providing the basis for new routes of pharmacological intervention in several diseases, including cancer.

Angiotensin-II induced hypertension and renovascular remodelling in tissue inhibitor of metalloproteinase 2 knockout mice

BACKGROUND

Sustained hypertension induces renovascular remodelling by altering extracellular matrix (ECM) components. Matrix metalloproteinases (MMPs) are Zn-dependent enzymes that regulate ECM turnover in concert with their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). Increased MMP-2 and MMP-9 have been implicated in hypertensive complications; however, the contribution of individual MMPs/TIMPs in renal remodelling has not been fully elucidated. The purpose of this study was to determine the effect of TIMP2 deficiency and thus MMP-2 on angiotensin-II (Ang-II) induced renal remodelling.

METHOD

C57BL/6J (wild-type) and TIMP2 knockout mice were infused with Ang-II at 250 ng/kg per min for 4 weeks. Blood pressure was measured weekly and end-point laser Doppler flowmetry was done to assess cortical blood flow. Immunohistochemical staining was performed for collagen and elastin analyses. The activity of MMP-9 and MMP-2 was determined by Gelatin zymography.

RESULTS

Ang-II induced similar elevation in mean blood pressure in TIMP2 and wild-type mice. In TIMP2 mice, Ang-II treatment was associated with a greater reduction in renal cortical blood flow and barium angiography demonstrated decreased vascular density compared with Ang-II treated wild-type mice. Peri-glomerular and vascular collagen deposition was increased and elastin content was decreased causing increased wall-to-lumen ratio in TIMP2 mice compared with wild-type mice receiving Ang-II. Ang-II increased the expression and activity of MMP-9 predominantly in TIMP2 mice than in wild-type mice.

CONCLUSION

These results suggest that TIMP2 deficiency exacerbates renovascular remodelling in agonist-induced hypertension by a mechanism that may, in part, be attributed to increased activity of MMP-9.

Epidermal Growth Factor Receptor Transactivation: Mechanisms, Pathophysiology, and Potential Therapies in the Cardiovascular System

Epidermal growth factor receptor (EGFR) activation impacts the physiology and pathophysiology of the cardiovascular system, and inhibition of EGFR activity is emerging as a potential therapeutic strategy to treat diseases including hypertension, cardiac hypertrophy, renal fibrosis, and abdominal aortic aneurysm. The capacity of G protein-coupled receptor (GPCR) agonists, such as angiotensin II (AngII), to promote EGFR signaling is called transactivation and is well described, yet delineating the molecular processes and functional relevance of this crosstalk has been challenging. Moreover, these critical findings are dispersed among many different fields. The aim of our review is to highlight recent advancements in defining the signaling cascades and downstream consequences of EGFR transactivation in the cardiovascular renal system. We also focus on studies that link EGFR transactivation to animal models of the disease, and we discuss potential therapeutic applications.

Salusin-β contributes to vascular remodeling associated with hypertension via promoting vascular smooth muscle cell proliferation and vascular fibrosis

Vascular smooth muscle cell (VSMC) proliferation and vascular fibrosis are closely linked with hypertension and atherosclerosis. Salusin-β is a bioactive peptide involved in the pathogenesis of atherosclerosis. However, it is still largely undefined whether salusin-β is a potential candidate in the VSMC proliferation and vascular fibrosis. Experiments were carried out in human vascular smooth muscle cells (VSMCs) and in rats with intravenous injection of lentivirus expressing salusin-β. In vitro, salusin-β promoted VSMCs proliferation, which was attenuated by adenylate cyclase inhibitor SQ22536, PKA inhibitor Rp-cAMP, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478, ERK inhibitor U0126 or cAMP response element binding protein (CREB) inhibitor KG501. It promoted the phosphorylation of ERK1/2, CREB and EGFR, which were abolished by SQ22536 or Rp-cAMP. Furthermore, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478 diminished the salusin-β-evoked ERK1/2 and CREB phosphorylation. On the other hand, salusin-β increased collagen-I, collagen-III, fibronectin and connective tissue growth factor (CTGF) mRNA and phosphorylation of Smad2/3, which were prevented by ALK5 inhibitor A83-01. In vivo, salusin-β overexpression increased the media thickness, media/lumen ratio coupled with ERK1/2, CREB, EGFR and Smad2/3 phosphorylation, as well as the mRNA of collagen-I, collagen-III, fibronectin, transforming growth factor-β1 (TGF-β1) and CTGF in arteries. Moreover, salusin-β overexpression in rats caused severe hypertension. Intravenous injection of salusin-β dose-relatedly increased blood pressure, but excessive salusin-β decreased blood pressure and heart rate. These results indicate that salusin-β promotes VSMC proliferation via cAMP-PKA-EGFR-CREB/ERK pathway and vascular fibrosis via TGF-β1-Smad pathway. Increased salusin-β contributes to vascular remodeling and hypertension.

ADAMTS-7 promotes vascular smooth muscle cells proliferation in vitro and in vivo

Vascular smooth muscle cell (VSMC) proliferation and migration are pivotal for the pathogenesis of atherosclerosis and post-angioplasty restenosis. We have recently reported that a disintegrin and metalloproteinase with thrombospondin motifs-7 (ADAMTS-7), a novel metalloproteinase, contributes directly to neointima formation by mediating VSMC migration. However, whether ADAMTS-7 affects VSMC proliferation remains unclear. In this study, we found that luminal adenoviral delivery of ADAMTS-7 aggravated intimal hyperplasia 7 d after injury, paralleled by an increased percentage of PCNA-positive cells in both intima and media. In contrast, perivascular administration of ADAMTS-7 siRNA, but not scrambled siRNA to injured arteries attenuated intimal thickening at day 7, paralleled with reduced intimal VSMC replication, without alteration of VSMC proliferation in the media. In accordance, [(3)H]-thymidine incorporation assay in primary cultured rat VSMCs revealed an enhanced replication rate (by 61%) upon ADAMTS-7 overexpression and retarded proliferation (by 23%) upon ADAMTS-7 siRNA administration. Our data demonstrates that ADAMTS-7 promotes VSMC proliferation both in vitro and in vivo. ADAMTS-7 may therefore serve as a novel therapeutic target for atherosclerosis and post-angioplasty restenosis.

Aldosterone synthase inhibition: cardiorenal protection in animal disease models and translation of hormonal effects to human subjects

Background

Aldosterone synthase inhibition provides the potential to attenuate both the mineralocorticoid receptor-dependent and independent actions of aldosterone. In vitro studies with recombinant human enzymes showed LCI699 to be a potent, reversible, competitive inhibitor of aldosterone synthase (K_i = 1.4 ± 0.2 nmol/L in humans) with relative selectivity over 11β-hydroxylase.

Methods

Hormonal effects of orally administered LCI699 were examined in rat and monkey in vivo models of adrenocorticotropic hormone (ACTH) and angiotensin-II-stimulated aldosterone release, and were compared with the mineralocorticoid receptor antagonist eplerenone in a randomized, placebo-controlled study conducted in 99 healthy human subjects. The effects of LCI699 and eplerenone on cardiac and renal sequelae of aldosterone excess were investigated in a double-transgenic rat (dTG rat) model overexpressing human renin and angiotensinogen.

Results

Rat and monkey in vivo models of stimulated aldosterone release predicted human dose– and exposure–response relationships, but overestimated the selectivity of LCI699 in humans. In the dTG rat model, LCI699 dose-dependently blocked increases in aldosterone, prevented development of cardiac and renal functional abnormalities independent of blood pressure changes, and prolonged survival. Eplerenone prolonged survival to a similar extent, but was less effective in preventing cardiac and renal damage. In healthy human subjects, LCI699 0.5 mg selectively reduced plasma and 24 h urinary aldosterone by 49 ± 3% and 39 ± 6% respectively (Day 1, mean ± SEM; P < 0.001 vs placebo), which was associated with natriuresis and an increase in plasma renin activity. Doses of LCI699 greater than 1 mg inhibited basal and ACTH-stimulated cortisol. Eplerenone 100 mg increased plasma and 24 h urinary aldosterone while stimulating natriuresis and increasing renin activity. In contrast to eplerenone, LCI699 increased the aldosterone precursor 11-deoxycorticosterone and urinary potassium excretion.

Conclusions

These results provide new insights into the cardiac and renal effects of inhibiting aldosterone synthase in experimental models and translation of the hormonal effects to humans. Selective inhibition of aldosterone synthase appears to be a promising approach to treat diseases associated with aldosterone excess.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0340-9) contains supplementary material, which is available to authorized users.

Mineralocorticoid receptor signaling: crosstalk with membrane receptors and other modulators

The mineralocorticoid receptor (MR) belongs to the steroid receptor superfamily. Classically, it acts as a ligand-bound transcription factor in epithelial tissues, where it regulates water and electrolyte homeostasis and controls blood pressure. Additionally, the MR has been shown to elicit pathophysiological effects including inflammation, fibrosis and remodeling processes in the cardiovascular system and the kidneys and MR antagonists have proven beneficial for patients with certain cardiovascular and renal disease. The underlying molecular mechanisms that mediate MR effects have not been fully elucidated but very likely rely on interactions with other signaling pathways in addition to genomic actions at hormone response elements. In this review we will focus on interactions of MR signaling with different membrane receptors, namely receptor tyrosine kinases and the angiotensin II receptor because of their potential relevance for disease. In addition, GPR30 is discussed as a new aldosterone receptor. To gain insights into the problem why the MR only seems to mediate pathophysiological effects in the presence of additional permissive factors we will also briefly discuss factors that lead to modulation of MR activity as well. Overall, MR signaling is part of an intricate network that still needs to be investigated further.

Direct role for smooth muscle cell mineralocorticoid receptors in vascular remodeling: novel mechanisms and clinical implications

The mineralocorticoid receptor (MR) is a key regulator of blood pressure. MR antagonist drugs are used to treat hypertension and heart failure, resulting in decreased mortality by mechanisms that are not completely understood. In addition to the kidney, MR is also expressed in the smooth muscle cells (SMCs) of the vasculature, where it is activated by the hormone aldosterone and affects the expression of genes involved in vascular function at the cellular and systemic levels. Following vascular injury due to mechanical or physiological stresses, vessels undergo remodeling resulting in SMC hypertrophy, migration, and proliferation, as well as vessel fibrosis. Exuberant vascular remodeling is associated with poor outcomes in cardiovascular patients. This review compiles recent findings on the specific role of SMC-MR in the vascular remodeling process. The development and characterization of a SMC-specific MR-knockout mouse has demonstrated a direct role for SMC-MR in vascular remodeling. Additionally, several novel mechanisms contributing to SMC-MR-mediated vascular remodeling have been identified and are reviewed here, including Rho-kinase signaling, placental growth factor signaling through vascular endothelial growth factor type 1 receptor, and galectin signaling.

Combined aliskiren and L-arginine treatment has antihypertensive effects and prevents vascular endothelial dysfunction in a model of renovascular hypertension

Angiotensin II is a key player in the pathogenesis of renovascular hypertension, a condition associated with endothelial dysfunction. We investigated aliskiren (ALSK) and L-arginine treatment both alone and in combination on blood pressure (BP), and vascular reactivity in aortic rings. Hypertension was induced in 40 male Wistar rats by clipping the left renal artery. Animals were divided into Sham, 2-kidney, 1-clip (2K1C) hypertension, 2K1C+ALSK (ALSK), 2K1C+L-arginine (L-arg), and 2K1C+ALSK+L-arginine (ALSK+L-arg) treatment groups. For 4 weeks, BP was monitored and endothelium-dependent and independent vasoconstriction and relaxation were assessed in aortic rings. ALSK+L-arg reduced BP and the contractile response to phenylephrine and improved acetylcholine relaxation. Endothelium removal and incubation with N-nitro-L-arginine methyl ester (L-NAME) increased the response to phenylephrine in all groups, but the effect was greater in the ALSK+L-arg group. Losartan reduced the contractile response in all groups, apocynin reduced the contractile response in the 2K1C, ALSK and ALSK+L-arg groups, and incubation with superoxide dismutase reduced the phenylephrine response in the 2K1C and ALSK groups. eNOS expression increased in the 2K1C and L-arg groups, and iNOS was increased significantly only in the 2K1C group compared with other groups. AT₁ expression increased in the 2K1C compared with the Sham, ALSK and ALSK+L-arg groups, AT₂ expression increased in the ALSK+L-arg group compared with the Sham and L-arg groups, and gp91phox decreased in the ALSK+L-arg group compared with the 2K1C and ALSK groups. In conclusion, combined ALSK+L-arg was effective in reducing BP and preventing endothelial dysfunction in aortic rings of 2K1C hypertensive rats. The responsible mechanisms appear to be related to the modulation of the local renin-angiotensin system, which is associated with a reduction in endothelial oxidative stress.

Antihypertensive medications, bone mineral density, and fractures: a review of old cardiac drugs that provides new insights into osteoporosis

Osteoporosis is increasing in prevalence and importance as society's age, with the clinical consequence of fractures of the hip, spine, and upper extremity, leading to impaired quality of life, loss of function and independence, and increased morbidity and mortality. A major risk factor for osteoporosis is older age, and cardiovascular diseases also share this risk factor; therefore, osteoporosis and cardiovascular disease often coexist and share risk factors. Medications used for the treatment of cardiovascular diseases, in particular antihypertensive drugs, have been shown in a variety of studies of varying designs to modulate bone health in both a positive or negative manner. In this article, we reviewed the pharmacology, potential mechanisms, and possible effects on bone mineral density and fracture risk of commonly prescribed antihypertensive medications, including thiazide and non-thiazide diuretics, beta-blockers, calcium channel blockers, renin-angiotensin-aldosterone system agents, and nitrates.

CaMKII protects MKP-1 from proteasome degradation in endothelial cells

CaMKs are a widely distributed family of kinases with multiple and often cell specific effects on intracellular signal transduction pathway. In endothelial cells, it has been recognized a role for CamKII in several pathways such as eNOS activation and nitric oxide production. It is not clear though, whether CaMKII interfere with other endothelial cell functions such as ERK activation and cell proliferation. We explored this issue in primary cultured rat endothelial cells and we evaluated the effect on endothelial cell proliferation and DNA synthesis. CaMKII inhibition through Cantide, conducted into the cell through Antoennapedia (ANT-CN), showed positive effects on proliferation and H(3)-thimdine incorporation similar to insulin stimulation. Accordingly, both CaMKII pharmacological inhibition and silencing through shRNA produced activation of the p44/42 MAPK. These observations leaded to the hypothesis that CamKII could regulate p44/p42 by interfering with specific ERK phosphatases. Indeed, we found that CaMKII interacts and protect the dual specific phosphatase MKP-1 from proteasome mediated degradation while this complex is disrupted by CaMKII inhibitors. This study reveals that CaMKII, besides phosphorylation through the known ras-raf-mek pathway, can regulate also dephosphorylation of p44/p42 by modulation of MKP-1 level. This novel finding opens to a novel scenario in regulation of endothelial cell functions.

The epidermal growth factor receptor and its ligands in cardiovascular disease

The epidermal growth factor receptor (EGFR) family and its ligands serve as a switchboard for the regulation of multiple cellular processes. While it is clear that EGFR activity is essential for normal cardiac development, its function in the vasculature and its role in cardiovascular disease are only beginning to be elucidated. In the blood vessel, endothelial cells and smooth muscle cells are both a source and a target of EGF-like ligands. Activation of EGFR has been implicated in blood pressure regulation, endothelial dysfunction, neointimal hyperplasia, atherogenesis, and cardiac remodeling. Furthermore, increased circulating EGF-like ligands may mediate accelerated vascular disease associated with chronic inflammation. Although EGFR inhibitors are currently being used clinically for the treatment of cancer, additional studies are necessary to determine whether abrogation of EGFR signaling is a potential strategy for the treatment of cardiovascular disease.

Cross-talk between mineralocorticoid receptor/angiotensin II type 1 receptor and mitogen-activated protein kinase pathways underlies aldosterone-induced atrial fibrotic responses in HL-1 cardiomyocytes

BACKGROUND

Aldosterone is increasingly recognized for its involvement in atrial structural remodeling. However, the precise molecular mechanisms and signal pathways underlying aldosterone-induced atrial fibrosis are unknown.

METHODS

Western blotting was used to investigate the effects of aldosterone on the expression of mineralocorticoid receptor (MR), angiotensin II type I receptor (AT1), mitogen-activated protein kinases (MAPKs), and fibrotic marker proteins in cultured HL-1 cardiomyocytes.

RESULTS

Aldosterone upregulated MR and AT1 expressions in a concentration-dependent and time-dependent manner. Aldosterone (10(-6)M) significantly and time-dependently increased activation of the extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p38MAPK pathways, and the protein expression of collagen 1A and 3A (COL1A and COL3A), transforming growth factor (TGF)-β1, and α-smooth muscle actin (SMA). Pre-treatment with eplerenone (10(-10)M) prevented the increased expression of MR, MAPK signals and the above profibrotic molecules, but amplified the increase in AT1 level stimulated by aldosterone (10(-6)M). Pre-treatment with losartan (10(-10)M) or MAPK pathway inhibitors (U0126 or SP600125) abolished aldosterone-induced MR upregulation and significantly inhibited the expression of the above fibrotic marker proteins, indicating the critical role of MR and the requirement for active AT1 in the development of aldosterone-induced atrial fibrosis.

CONCLUSIONS

Elevated MR activity plays a central role in aldosterone-mediated activation of the MAPK signaling pathway and subsequent profibrotic effects in HL-1 atrial cells. MR/AT1 and the MAPK signaling pathway interact to trigger the molecular mechanism underlying the aldosterone-induced atrial fibrotic response. Our results support the view that MR blockade in conjunction with AT1 blockade can prevent the occurrence of atrial fibrillation.

Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects

Small G proteins exist in eukaryotes from yeast to human and constitute the Ras superfamily comprising more than 100 members. This superfamily is structurally classified into five families: the Ras, Rho, Rab, Arf, and Ran families that control a wide variety of cell and biological functions through highly coordinated regulation processes. Increasing evidence has accumulated to identify small G proteins and their regulators as key players of the cardiovascular physiology that control a large panel of cardiac (heart rhythm, contraction, hypertrophy) and vascular functions (angiogenesis, vascular permeability, vasoconstriction). Indeed, basal Ras protein activity is required for homeostatic functions in physiological conditions, but sustained overactivation of Ras proteins or spatiotemporal dysregulation of Ras signaling pathways has pathological consequences in the cardiovascular system. The primary object of this review is to provide a comprehensive overview of the current progress in our understanding of the role of small G proteins and their regulators in cardiovascular physiology and pathologies.

High sodium augments angiotensin II-induced vascular smooth muscle cell proliferation through the ERK 1/2-dependent pathway

Angiotensin II (Ang II)-induced vascular injury is exacerbated by high-salt diets. This study examined the effects of high-sodium level on Ang II-induced cell proliferation in rat vascular smooth muscle cells (VSMCs). The cells were cultured in a standard medium containing 137.5 mmol l(-1) of sodium. The high-sodium medium (140 mmol l(-1)) contained additional sodium chloride. Extracellular signal-regulated kinase (ERK) 1/2 phosphorylation was determined by western blot analysis. Cell proliferation was evaluated by [(3)H]-thymidine incorporation. Ang II (100 nmol l(-1)) significantly increased ERK 1/2 phosphorylation and cell proliferation in the both medium containing standard sodium and high sodium. High-sodium level augmented Ang II-induced ERK 1/2 phosphorylation and cell proliferation compared with standard sodium. Pre-treatment with candesartan (1 μmol l(-1), Ang II type 1 receptor blocker) or PD98095 (10 μmol l(-1), ERK kinase iinhibitor) abolished the proliferative effect induced by high sodium/Ang II. Pre-treatment with 5-N,N-hexamethylene amiloride (30 μmol l(-1), Na(+)/H(+) exchanger type 1 (NHE-1) inhibitor), but not SN-6 (10 μmol l(-1), Na(+)/Ca(2+) exchanger inhibitor) or ouabain (1 mmol l(-1), Na(+)/K(+)-ATPase inhibitor) attenuated ERK 1/2 phosphorylation or cell proliferation. Osmotic pressure or chloride had no effect on Ang II-induced proliferative changes. High-sodium level did not affect Ang II receptor expression. Ang II increased intracellular pH via NHE-1 activation, and high-sodium level augmented the pH increase induced by Ang II. These data suggest that high-sodium level directly augments Ang II-induced VSMC proliferation through NHE-1- and ERK 1/2-dependent pathways and may offer new insights into the mechanisms of vascular remodeling by high-sodium/Ang II.

Pathophysiology of vascular remodeling in hypertension

Vascular remodeling refers to alterations in the structure of resistance vessels contributing to elevated systemic vascular resistance in hypertension. We start with some historical aspects, underscoring the importance of Glagov's contribution. We then move to some basic concepts on the biomechanics of blood vessels and explain the definitions proposed by Mulvany for specific forms of remodeling, especially inward eutrophic and inward hypertrophic. The available evidence for the existence of remodeled resistance vessels in hypertension comes next, with relatively more weight given to human, in comparison with animal data. Mechanisms are discussed. The impact of antihypertensive drug treatment on remodeling is described, again with emphasis on human data. Some details are given on the three mechanisms to date which point to remodeling resistance arteries as an independent predictor of cardiovascular risk in hypertensive patients. We terminate by considering the potential role of remodeling in the pathogenesis of endorgan damage and in the perpetuation of hypertension.

Contribution of aldosterone to cardiovascular and renal inflammation and fibrosis

The steroid hormone aldosterone regulates sodium and potassium homeostasis. Aldosterone and activation of the mineralocorticoid receptor also causes inflammation and fibrosis of the heart, fibrosis and remodelling of blood vessels and tubulointerstitial fibrosis and glomerular injury in the kidney. Aldosterone and mineralocorticoid-receptor activation initiate an inflammatory response by increasing the generation of reactive oxygen species by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and mitochondria. High salt intake potentiates these effects, in part by activating the Rho family member Rac1, a regulatory subunit of reduced NADPH oxidase that activates the mineralocorticoid receptor. Studies in mice in which the mineralocorticoid receptor has been deleted from specific cell types suggest a key role for macrophages in promoting inflammation and fibrosis. Aldosterone can exert mineralocorticoid-receptor-independent effects via the angiotensin II receptor and via G-protein-coupled receptor 30. Mineralocorticoid-receptor antagonists are associated with decreased mortality in patients with heart disease and show promise in patients with kidney injury, but can elevate serum potassium concentration. Studies in rodents genetically deficient in aldosterone synthase or treated with a pharmacological aldosterone-synthase inhibitor are providing insight into the relative contribution of aldosterone compared with the contribution of mineralocorticoid-receptor activation in inflammation, fibrosis, and injury. Aldosterone-synthase inhibitors are under development in humans.

Smooth muscle cell mineralocorticoid receptors: role in vascular function and contribution to cardiovascular disease

The mineralocorticoid receptor (MR), a member of the steroid receptor family, regulates blood pressure by mediating the effects of the hormone aldosterone on renal sodium handling. In recent years, it has become clear that MR is expressed in vascular smooth muscle cells (SMCs), and interest has grown in understanding the direct role of SMC MR in regulating vascular function. This interest stems from multiple clinical studies where MR inhibitor treatment reduced the incidence of cardiovascular events and mortality. This review summarizes the most recent advances in our understanding of SMC MR in regulating normal vascular function and in promoting vascular disease. Many new studies suggest a role for SMC MR activation in stimulating vascular contraction and contributing to vessel inflammation, fibrosis, and remodeling. These detrimental vascular effects of MR activation appear to be independent of changes in blood pressure and are synergistic with the presence of endothelial dysfunction or damage. Thus, in humans with underlying cardiovascular disease or cardiovascular risk factors, SMC MR activation may promote hypertension, atherosclerosis, and vascular aging. Further exploration of the molecular mechanisms for the effects of SMC MR activation has the potential to identify novel therapeutic targets to prevent or treat common cardiovascular disorders.

Reduction of Cardiovascular Risk through Angiotensin II Type 1 Receptor Antagonism : Focus on Olmesartan Medoxomil

It is well recognized that angiotensin II is involved in the pathogenesis of hypertension. Less well recognized - until recently, at least - is its involvement in the pathogenesis of atherosclerosis. However, it is now evident that angiotensin II promotes oxidative stress, vascular remodelling, inflammation, and the formation of atherosclerotic lesions. These actions, which are mediated almost exclusively by the angiotensin II type 1 (AT(1)) receptor, can be blocked by administration of angiotensin II type 1 receptor antagonists (angiotensin receptor blockers [ARBs]). Of the seven ARBs currently in clinical use, olmesartan is one of the most effective. The rapid and consistent antihypertensive efficacy of this drug, which allows a high proportion of patients to achieve their target blood pressure (BP), is associated with beneficial effects on oxidative stress, vascular remodelling, inflammation, and atherosclerotic lesion formation. These effects appear to be independent of the BP-lowering activity of olmesartan. In clinical trials, olmesartan has been shown to control microinflammation in hypertensive patients, to reduce oxidative stress in patients with type 2 diabetes mellitus, and to normalize the wall: lumen ratio of small resistance arteries (a measure of vascular remodelling) in patients with hypertension. Moreover, in a 2-year study involving hypertensive patients with carotid atherosclerosis (the MORE [Multicentre Olmesartan atherosclerosis Regression Evaluation] trial), olmesartan reduced the intima-media thickness of the carotid artery and significantly reduced the volume of large atherosclerotic plaques. These data suggest that olmesartan may reduce cardiovascular risk by simultaneously normalizing BP and reversing the proatherogenic effects of angiotensin II.

Expression of Angiotensin II and Aldosterone in Radiation-induced Lung Injury

OBJECTIVE

Radiation-induced lung injury (RILI) is the most common, dose-limiting complication in thoracic malignancy radiotherapy. Considering its negative impact on patients and restrictions to efficacy, the mechanism of RILI was studied.

METHODS

Wistar rats were locally irradiated with a single dose of 0, 16, and 20 Gy to the right half of the lung to establish a lung injury model. Two and six months after irradiation, the right half of the rat lung tissue was removed, and the concentrations of TGF-β1, angiotensin II, and aldosterone were determined via enzyme-linked immunosorbent assay.

RESULTS

Statistical differences were observed in the expression levels of angiotensin II and aldosterone between the non-irradiation and irradiation groups. Moreover, the expression level of the angiotensin II-aldosterone system increased with increasing doses, and the difference was still observed as time progressed.

CONCLUSIONS

Angiotensin II-aldosterone system has an important pathophysiological function in the progression of RILI.

Corticosteroids, heart failure, and hypertension: a role for immune cells?

Aldosterone and its receptor the mineralocorticoid receptor (MR) are best known for their regulation of fluid and electrolyte homeostasis in epithelial cells. However, it is now clear that MR are also expressed in a broad range of nonepithelial tissues including the cardiovascular system. In the heart and vascular tissues, pathological activation of MR promotes cardiovascular inflammation and remodeling for which there is increasing evidence that macrophages and other immune cells (e.g. T cells and dendritic cells) play a significant role. While the glucocorticoids and their receptors have well-described antiinflammatory actions in immune cells, a role for aldosterone and/or the MR in these cells is largely undefined. Emerging evidence, however, suggests that MR signaling may directly or indirectly promote proinflammatory responses in these immune cells. This review will discuss the current understanding of the role of corticosteroid receptors in macrophages and their effect on cardiovascular diseases involving inflammation.

New evidence for vascular interactions between aldosterone, angiotensin II and antioxidants in isolated smooth muscle cells of rats

Accumulating evidence suggests that the nongenomic cardiovascular actions of aldosterone are produced by varied cellular pathways and mediated by a multitude of messenger systems including the reactive oxygen and nitrogen species. Considering the involvement of the oxidative and nitrosative stress in the pathways leading to the activation of the angiotensin — aldosterone system, in the current study we tried to evaluate the functional interactions between aldosterone, angiotensin II and antioxidants in isolated vascular smooth muscle of aortic rings from rats. Our data provide additional arguments that the nongenomic actions of aldosterone on aortic smooth muscle cells of rats are a question of cross-talk and balance between its rapid vasoconstrictor and vasodilator effects, as result of the activation of reactive oxygen species in the first case and of nitrogen species in the second. In this way, it seems that at low ambient oxidative stress, aldosterone promotes nitric oxide (NO) production and vasodilatation, while in situations with increased oxidative stress the endothelial dysfunction and detrimental effects induced by vasoconstriction will prevail. Thus, aldosterone could be considered both “friend and foe”. This could be relevant for the ways in which aldosterone damages cardiovascular functions and could lead to significant therapeutic improvements.

Vascular actions of aldosterone

Aldosterone exerts direct effects on the vascular system by inducing oxidative stress, inflammation, hypertrophic remodeling, fibrosis, and endothelial dysfunction. Aldosterone exerts its effects through genomic and nongenomic pathways in a mineralocorticoid receptor (MR)-dependent or independent manner. Other aldosterone receptors such as GPR30 have been identified. A tight relation exists between the aldosterone and angiotensin II pathways, as well as with the endothelin-1 system. There is a correlation between plasma levels of aldosterone and cardiovascular risk. Recently, an increasing body of evidence has underlined the importance of aldosterone in cardiovascular complications associated with the metabolic syndrome, such as arterial remodeling and endothelial dysfunction. Blockade of MR is an increasingly used evidence-based therapy for many forms of cardiovascular disease, including hypertension, heart failure, chronic kidney disease, and diabetes mellitus.

Influence of ovariectomy on cardiac oxidative stress in a renovascular hypertension model

The aim of this study was to evaluate the potential influence of endogenous ovarian hormones on cardiac oxidative stress in renovascular hypertension. Female Wistar rats (N = 10 per group) were divided among 4 groups: (i) normotensive control; (ii) hypertensive control; (iii) normotensive ovariectomized; and (iv) hypertensive ovariectomized rats. To induce hypertension, 2-kidney 1-clip (2K1C) Goldblatt's method was followed. Blood pressure (BP) was enhanced (25%) in 2K1C and it was not further altered in hypertensive ovariectomized animals. Lipid peroxidation (measured by thiobarbituric acid reactive substances; TBARS) increased in heart homogenates after ovariectomy (253%) and was additionally augmented when associated with hypertension (by 28%). Superoxide dismutase and catalase activities were similar in both hypertensive groups. Hypertension enhanced glutathione peroxidase activity (75%), but the association with ovariectomy prevented this change. Total radical trapping antioxidant potential (TRAP) decreased in hypertensive rats (34%) and was recovered when associated with ovariectomy. However, this adaptation seems not to be sufficient to avoid the increased oxidative damage in ovariectomized hypertensive animals. These results suggest a protective role for physiological ovarian hormones in the cardiac oxidative stress induced by 2K1C hypertension.