Angiotensin II induces nuclear factor- kappa B activation in cultured neonatal rat cardiomyocytes through protein kinase C signaling pathway

Intricate relationship between SARS-CoV-2-induced shedding and cytokine storm generation: A signaling inflammatory pathway augmenting COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), through its ability to induce cytokine release syndrome, can set up a generalized inflammatory response together with activating multiple inflammatory pathways, which contributes to a dramatic increase in the number of mortalities and morbidities worldwide. Reportedly, the manipulative nature of coronavirus disease 2019 (COVID-19), which targets the immune system, often focuses on specific inflammation-related pathways, usually confined to interleukins and tumor necrosis factor-α (TNF-α), with a great emphasis on therapeutic approaches targeting the inhibition of these inflammatory mediators. The involvement of a disintegrin and metalloprotease 17 (ADAM-17) and matrix metalloproteinase-9 (MMP-9) in the pathogenesis of COVID-19, through their ability to potentiate the cytokine storm during an episode of SARS-CoV-2 infection, often goes unnoticed. In this review, the intricate relationship between ADAM-17 and MMP-9 together with angiotensin-converting enzyme 2 (ACE-2) as the main target for SARS-CoV-2 is highlighted in detail through a compilation of evidence-based literature; thus, we shed light on a proposed inflammatory pathway that COVID-19 may exploit to provoke an inflammatory response of a complex nature. Conclusively, our proposed mechanism acts as a means to developing a therapeutic approach aimed at modulating the intricate communication between ADAM-17 and MMP-9, where a great emphasis on the role of ACE-2 shedding and subsequent elevation in angiotensin II (Ang-II) levels is crucial to understanding the awry inflammatory response in patients with COVID-19. From this concept, designing a therapeutic strategy targeting multiple inflammatory mediators and enzymes simultaneously is another approach to unravel this global pandemic.

The Role of Matrix Proteins in Cardiac Pathology

The extracellular matrix (ECM) and ECM-regulatory proteins mediate structural and cell-cell interactions that are crucial for embryonic cardiac development and postnatal homeostasis, as well as organ remodeling and repair in response to injury. These proteins possess a broad functionality that is regulated by multiple structural domains and dependent on their ability to interact with extracellular substrates and/or cell surface receptors. Several different cell types (cardiomyocytes, fibroblasts, endothelial and inflammatory cells) within the myocardium elaborate ECM proteins, and their role in cardiovascular (patho)physiology has been increasingly recognized. This has stimulated robust research dissecting the ECM protein function in human health and disease and replicating the genetic proof-of-principle. This review summarizes recent developments regarding the contribution of ECM to cardiovascular disease. The clear importance of this heterogeneous group of proteins in attenuating maladaptive repair responses provides an impetus for further investigation into these proteins as potential pharmacological targets in cardiac diseases and beyond.

Cardiomyocyte-Specific Snrk Prevents Inflammation in the Heart

Background The SNRK (sucrose-nonfermenting-related kinase) enzyme is critical for cardiac function. However, the underlying cause for heart failure observed in Snrk cardiac conditional knockout mouse is unknown. Methods and Results Previously, 6-month adult mice knocked out for Snrk in cardiomyocytes (CMs) displayed left ventricular dysfunction. Here, 4-month adult mice, on angiotensin II (Ang II) infusion, show rapid decline in cardiac systolic function, which leads to heart failure and death in 2 weeks. These mice showed increased expression of nuclear factor κ light chain enhancer of activated B cells (NF-κB), inflammatory signaling proteins, proinflammatory proteins in the heart, and fibrosis. Interestingly, under Ang II infusion, mice knocked out for Snrk in endothelial cells did not show significant systolic or diastolic dysfunction. Although an NF-κB inflammation signaling pathway was increased in Snrk knockout endothelial cells, this did not lead to fibrosis or mortality. In hearts of adult mice knocked out for Snrk in CMs, we also observed NF-κB pathway activation in CMs, and an increased presence of Mac2+ macrophages was observed in basal and Ang II-infused states. In vitro analysis of Snrk knockdown HL-1 CMs revealed similar upregulation of the NF-κB signaling proteins and proinflammatory proteins that was exacerbated on Ang II treatment. The Ang II-induced NF-κB pathway-mediated proinflammatory effects were mediated in part through protein kinase B or AKT, wherein AKT inhibition restored the proinflammatory signaling protein levels to baseline in Snrk knockdown HL-1 CMs. Conclusions During heart failure, SNRK acts as a cardiomyocyte-specific repressor of cardiac inflammation and fibrosis.

Assigning matrix metalloproteinase roles in ischaemic cardiac remodelling

Matrix metalloproteinases (MMPs) and their endogenous inhibitors have been studied in the myocardium for the past 2 decades. An incomplete knowledge base and experimental design issues with inhibitors have hampered attempts at translation, but clinical interest remains high because of strong associations between MMPs and outcomes after myocardial infarction (MI) as well as mechanistic studies showing MMP involvement at multiple stages of the MI wound-healing process. This Review focuses on how our understanding of MMPs has evolved from a one-dimensional early focus on measuring MMP activity, monitoring MMP:inhibitor ratios, and evaluating one MMP-substrate pair to the current use of systems biology approaches to integrate the whole MMP repertoire of roles in the left ventricular response to MI. MMP9 is used as an example MMP to explain these concepts and to provide a template for examining MMPs as mechanistic mediators of cardiac remodelling.

Left ventricular remodelling in chronic primary mitral regurgitation: implications for medical therapy

Surgical repair or replacement of the mitral valve is currently the only recommended therapy for severe primary mitral regurgitation. The chronic elevation of wall stress caused by the resulting volume overload leads to structural remodelling of the muscular, vascular and extracellular matrix components of the myocardium. These changes are initially compensatory but in the long term have detrimental effects, which ultimately result in heart failure. Understanding the changes that occur in the myocardium due to volume overload at the molecular and cellular level may lead to medical interventions, which potentially could delay or prevent the adverse left ventricular remodelling associated with primary mitral regurgitation. The pathophysiological changes involved in left ventricular remodelling in response to chronic primary mitral regurgitation and the evidence for potential medical therapy, in particular beta-adrenergic blockers, are the focus of this review.

S-nitrosylation of transglutaminase 2 impairs fatty acid-stimulated contraction in hypertensive cardiomyocytes

The myocardium in hypertensive heart exhibits decreased fatty acid utilization and contractile dysfunction, leading to cardiac failure. However, the causal relationship between metabolic remodeling and cardiomyocyte contractility remains unestablished. Transglutaminase 2 (TG2) has been known to promote ATP production through the regulation of mitochondrial function. In this study, we investigated the involvement of TG2 in cardiomyocyte contraction under fatty acid supplementation. Using TG2 inhibitor and TG2-deficient mice, we demonstrated that fatty acid supplementation activated TG2 and increased ATP level and contractility of cardiac myocyte from the normal heart. By contrast, in cardiac myocytes from angiotensin-II-treated rats and mice, the effects of fatty acid supplementation on TG2 activity, ATP level, and myocyte contraction were abolished. We found that TG2 was inhibited by S-nitrosylation and its level increased in hypertensive myocytes. Treatment with inhibitor for neuronal NOS restored fatty acid-induced increase of TG2 activity and myocyte contraction. Moreover, intracellular Ca²⁺ levels were increased by fatty acid supplementation in both normal and hypertensive myocytes, showing that S-nitrosylation of TG2 but not alteration of intracellular Ca²⁺ levels is responsible for contractile dysfunction. These results indicate that TG2 plays a critical role in the regulation of myocyte contractility by promoting fatty acid metabolism and provide a novel target for preventing contractile dysfunction in heart with high workload.

Enhancing activity of an enzyme that promotes healthy heart contraction could benefit patients at risk of serious heart conditions. Chronic high blood pressure can cause excessive thickening of heart muscle tissue, reducing the heart’s ability to contract correctly and leading to heart failure. A healthy heart fuels itself by oxidizing fatty acids to trigger production of the key energy transfer molecule ATP. Yin Hua Zhang and In-Gyu Kim at Seoul National University College of Medicine, Korea and co-workers have highlighted how S-nitrosylation, addition of nitric oxide, affects transglutaminase 2 (TG2), an enzyme that promotes ATP production. Experiments on rats and mice showed that fatty acids activate TG2, increasing ATP production and maintaining contractibility in healthy hearts. However, in pressure-overloaded hearts, TG2 activity is inhibited by S-nitrosylation, which stops heart muscle cells contracting properly.

Combined Effects of ACE and MMP-3 Polymorphisms On Migraine Development

Migraine is a primary headache disorder which involves both genetic and environmental components. Since angiotensin-converting enzyme (ACE) and matrix metalloproteinase (MMP) share the same homology, we investigated whether the MMP-3 and ACE I/D gene variants are involved in migraine risk and whether the ACE variant might act in combination with the MMP-3 genetic variant in patients with migraine. This is the first study to evaluate the association between MMP-3 and ACE polymorphisms, and migraine. Genotypes were determined by polymerase chain reaction. The frequencies of 5A5A genotypes of the MMP-3 and D allele of ACE were significantly elevated, but II genotypes of the ACE and 6A allele of MMP-3 significantly decreased in all patients. The combined DD/5A5A and ID/5A5A genotypes increased the risk of migraine. Individuals who were homozygous for the deletion (D) allele showed increased ACE activity. Subjects with the 5A5A genotype and/or D allele or with the combined DD/5A5A or ID/5A5A might be more susceptible to migraine development. In contrast, subjects with the II and/or 6A6A genotypes may be protected from migraine development. The greater activity of the 5A5A and DD genotypes might result in vascular reactivity that is more pronounced in migraine. Taken together, our data suggest that numerous genes may influence ACE activity. Discovery of new genes might better clarify the pathogenesis of migraine and open an avenue to therapeutic strategies against migraine.

Can heart function lost to disease be regenerated by therapeutic targeting of cardiac scar tissue?

Myocardial infarction results in scar tissue that cannot actively contribute to heart mechanical function and frequently causes lethal arrhythmias. The healing response after infarction involves inflammation, biochemical signaling, changes in cellular phenotype, activity, and organization, and alterations in electrical conduction due to variations in cell and tissue geometry and alterations in protein expression, organization, and function - particularly in membrane channels. The intensive research focus on regeneration of myocardial tissues has, as of yet, only met with modest success, with no near-term prospect of improving standard-of-care for patients with heart disease. An alternative concept for novel therapeutic approach is the rejuvenation of cardiac electrical and mechanical properties through the modification of scar tissue. Several peptide therapeutics, locally applied genetic therapies, or delivery of genetically modified cells have shown promise in improving the characteristics of the fibrous scar and post-myocardial infarction prognosis in experimental models. This review highlights several factors that contribute to arrhythmogenesis in scar formation and how these might be targeted to regenerate some of the electrical and mechanical function of the post-MI scar.

A Dipeptidyl Peptidase-4 Inhibitor but not Incretins Suppresses Abdominal Aortic Aneurysms in Angiotensin II-Infused Apolipoprotein E-Null Mice

AIM

The main pathophysiology of abdominal aortic aneurysm (AAA) considerably overlaps with that of atherosclerosis. We reported that incretins [glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP)] or a dipeptidyl peptidase-4 inhibitor (DPP-4I) suppressed atherosclerosis in apolipoprotein E-null (Apoe－/－) mice. Here we investigated the effects of incretin-related agents on AAA in a mouse model.

METHODS

Apoe－/－ mice maintained on an atherogenic diet were subcutaneously infused with saline, Ang II (2000 ng/kg/min), Ang II, and native GLP-1 (2.16 nmol/kg/day) or Ang II and native GIP (25 nmol/kg/day) for 4 weeks. DPP-4I (MK0626, 6 mg/kg/day) was provided in the diet to the Ang II-infused mice with or without incretin receptor antagonists [(Pro3) GIP and exendin (9-39)].

RESULTS

AAA occurred in 70% of the animals receiving Ang II. DPP-4I reduced this rate to 40% and significantly suppressed AAA dilatation, fibrosis, and thrombosis. In contrast, incretins failed to attenuate AAA. Incretin receptor blockers did not reverse the suppressive effects of DPP-4I on AAA. In the aorta, DPP-4I significantly reduced the expression of Interleukin-1β and increased that of tissue inhibitor of metalloproteinase (TIMP)-2. In addition, DPP-4I increased the ratio of TIMP-2 to matrix metalloproteinases-9.

CONCLUSIONS

DPP-4I, MK0626, but not native incretins has protective effects against AAA in Ang II-infused Apoe－/－ mice via suppression of inflammation, proteolysis, and fibrosis in the aortic wall.

Novel therapeutic targets in the management of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, contributing to increased morbidity and reduced survival through its associations with stroke and heart failure. AF contributes to a four- to fivefold increase in the risk of stroke in the general population and is responsible for 10-15 % of all ischemic strokes. Diagnosis and treatment of AF require considerable health care resources. Current therapies to restore sinus rhythm in AF are suboptimal and are limited either by their pro-arrhythmic effects or by their procedure-related complications. These limitations have necessitated identification of newer therapeutic targets to expand the treatment options. There has been a considerable amount of research interest in investigating the mechanisms of initiation and propagation of AF. Despite extensive research focused on the pathogenesis of AF, a thorough understanding of various pathways mediating initiation and propagation of AF still remains limited. Research efforts focused on the identification of these pathways and molecular mediators have generated a great degree of interest for developing more targeted therapies. This review discusses the potential therapeutic targets and the results from experimental and clinical research investigating these targets.

Matrix metalloproteinase-9: Many shades of function in cardiovascular disease

Matrix metalloproteinase (MMP)-9, one of the most widely investigated MMPs, regulates pathological remodeling processes that involve inflammation and fibrosis in cardiovascular disease. MMP-9 directly degrades extracellular matrix (ECM) proteins and activates cytokines and chemokines to regulate tissue remodeling. MMP-9 deletion or inhibition has proven overall beneficial in multiple animal models of cardiovascular disease. As such, MMP-9 expression and activity is a common end point measured. MMP-9 cell-specific overexpression, however, has also proven beneficial and highlights the fact that little information is available on the underlying mechanisms of MMP-9 function. In this review, we summarize our current understanding of MMP-9 physiology, including structure, regulation, activation, and downstream effects of increased MMP-9. We discuss MMP-9 roles during inflammation and fibrosis in cardiovascular disease. By concentrating on the substrates of MMP-9 and their roles in cardiovascular disease, we explore the overall function and discuss future directions on the translational potential of MMP-9 based therapies.

The ocular renin-angiotensin system: a therapeutic target for the treatment of ocular disease

The renin-angiotensin system (RAS) is most well-known for its role in regulation and dysregulation of blood pressure as well as fluid and electrolyte homeostasis. Due to its ability to cause cardiovascular disease, the RAS is the target of a multitude of drugs that antagonize its pathophysiological effects. While the "classical" RAS is a systemic hormonal system, there is an increasing awareness of the existence and functional significance of local RASs in a number of organs, e.g., liver, kidney, heart, lungs, reproductive organs, adipose tissue and adrenal. The eye is one of these organs where a compelling body of evidence has demonstrated the presence of a local RAS. Individual components of the RAS have been shown to be present in many structures of the eye and their potential functional significance in ocular disease states is described. Because the eye is one of the most important and complex organs in the body, this review also discusses the implications of dysregulation of the systemic RAS on the pathogenesis of ocular diseases and how pharmacological manipulation of the RAS might lead to novel or adjunctive therapies for ocular disease states.

NF-κB-mediated miR-30b regulation in cardiomyocytes cell death by targeting Bcl-2

Angiotensin II(Ang II)-stimulated cardiomyocytes hypertrophy and apoptosis are associated with nuclear factor-κB (NF-κB) activation. NF-κB, a redox-sensitive transcription factor, contributes a critical role in cell death, but, Ang II-stimulated NF-κB-mediated cardiomyocytes apoptosis remains less understood. Recently, microRNAs (miRNAs) have been shown to be critical regulators in various cardiac remodeling processes; however, NF-κB-mediated miRNA's role in cardiomyocytes apoptosis remains undetermined. The miR-30b has been implicated in diverse cardiac remodeling; but, NF-κB-mediated miR-30b modulation in Ang II-induced cardiomyocytes death is currently unknown. In the present study, neonatal cardiomyocytes were pretreated with SN50, a selective cell permeable peptide inhibitor of NF-κB, or transfected with miR-30b mimetic and inhibitors separately, and then challenged with Ang II. The target gene, Bcl-2, and NF-κB transcriptional activity were analyzed. Our results demonstrated that NF-κB positively regulated miR-30b expression in Ang II-induced cardiomyocytes apoptosis, and Bcl-2 was a direct target for miR-30b. NF-κB further regulated the expression of Bcl-2 in the above setting. Furthermore, Ang II-induced cardiomyocytes apoptosis rescued by inhibiting either NF-κB or miR-30b provided an important role in cardiomyocytes cell death. We evaluated a critical role of NF-κB-mediated miR-30b modulation in Ang II-stimulated cardiomyocytes targeting Bcl-2. Our data may provide a new insight of miR-30b's role in myocardial infarction or ischemia.

Pivotal role of mouse mast cell protease 4 in the conversion and pressor properties of Big-endothelin-1

The serine protease chymase has been reported to generate intracardiac angiotensin-II (Ang-II) from Ang-I as well as an intermediate precursor of endothelin-1 (ET-1), ET-1 (1-31) from Big-ET-1. Although humans possess only one chymase, several murine isoforms are documented, each with its own specific catalytic activity. Among these, mouse mast cell protease 4 (mMCP-4) is the isoform most similar to the human chymase for its activity. The aim of this study was to characterize the capacity of mMCP-4 to convert Big-ET-1 into its bioactive metabolite, ET-1, in vitro and in vivo in the mouse model. Basal mean arterial pressure did not differ between wild-type (WT) and mMCP-4(-/-) mice. Systemic administration of Big-ET-1 triggered pressor responses and increased blood levels of immunoreactive (IR) ET-1 (1-31) and ET-1 that were reduced by more than 50% in mMCP-4 knockout (-/-) mice compared with WT controls. Residual responses to Big-ET-1 in mMCP-4(-/-) mice were insensitive to the enkephalinase/neutral endopeptidase inhibitor thiorphan and the specific chymase inhibitor TY-51469 {2-[4-(5-fluoro-3-methylbenzo[b]thiophen-2-yl)sulfonamido-3-methanesulfonylphenyl]thiazole-4-carboxylic acid}. Soluble fractions from the lungs, left cardiac ventricle, aorta, and kidneys of WT but not mMCP-4(-/-) mice generated ET-1 (1-31) from exogenous Big-ET-1 in a TY-51469-sensitive fashion as detected by high-performance liquid chromatography/ matrix-assisted laser desorption/ionization-mass spectrometry. Finally, pulmonary endogenous levels of IR-ET-1 were reduced by more than 40% in tissues derived from mMCP-4(-/-) mice compared with WT mice. Our results show that mMCP-4 plays a pivotal role in the dynamic conversion of systemic Big-ET-1 to ET-1 in the mouse model.

LOX-1 transcription

The importance of the lectin-like oxidized LDL receptor (LOX-1) gene in cardiovascular and other diseases is slowly being revealed. LOX-1 gene expression appears to be a "canary in a coal mine" for atherogenesis, being strongly up-regulated early on in a number of cell types when they are activated, and predicting the sites of future disease. From this early time point the LOX-1 protein often participates in the disease process itself. While gene/protein expression can be regulated on a multiplicity of levels, the most basic and important mode of regulation is usually transcriptional. There are very few studies on the transcriptional regulation of the human LOX-1 promoter; fewer still on definitive mapping of the transcription factors involved. It is known that a wide variety of stimuli up-regulate LOX-1, usually/probably on the transcriptional level. Angiotensin II (Ang II) is one important regulator of renin-angiotensin system and stimulator LOX-1. Ang II is known to up-regulate LOX-1 transcription through an NF-kB motif located at nt -2158. Oxidized low density lipoprotein (ox-LDL) is another important cardiovascular regulator, particularly of atherosclerotic disease, and a strong stimulator of LOX-1. Ox-LDL is known to up-regulate LOX-1 transcription through an Oct-1 motif located at nt -1556. The subsequent enhanced LOX-1 receptor numbers and their binding by ox-LDL ligand triggers a positive feedback loop, increasing further LOX-1 expression, with a presently unknown regulatory governor. The Oct-1 gene also has its own Oct-1-driven positive feedback loop, which likely also contributes to LOX-1 up-regulation. There is also data which suggests the involvement of the transcription factor AP-1 during stimulation with Phorbol 12-myristate acetate. While the importance of NF-κB as a transcriptional regulator of cardiovascular-relevant genes is well known, the importance of Oct-1 is not. Data suggests that Oct-1-mediated up-regulation of transcription is an early event in the stimulation of LOX-1 by ox-LDL. Yet Oct-1 also down-regulates cardiovascular-relevant genes by suppressing NF-κB transactivation. Thus, Oct-1 is presently somewhat of an enigma, up-regulating and down-regulating genes seemingly at random without an overall theme (with the exception of cell cycle). Yet the up-regulation of LOX-1 by ox-LDL is a very important event in atherogenesis (both early and late) and Oct-1 is, therefore, an important transcriptional gatekeeper of this important atherogenic trigger.

Novel association patterns of cardiac remodeling markers in patients with essential hypertension and atrial fibrillation

BACKGROUND

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are essential for the cardiac extracellular matrix (ECM) remodeling. We investigated differences in serum levels of these markers between patients with atrial fibrillation (AF) and sinus rhythm (SR).

METHODS

Serum levels of MMP-2, MMP-3, MMP-9 and TIMP-1 were measured in 86 patients: 27 on SR without any AF history, 33 with paroxysmal and 26 with permanent AF. All subjects had essential hypertension, normal systolic function and no coronary artery disease.

RESULTS

Patients with AF had higher MMP-2, MMP-3 and MMP-9 and lower TIMP-1 compared to SR subjects (all p < 0.001). Paroxysmal AF was associated with higher MMP-2 levels compared to permanent AF (p < 0.001). Matrix metalloproteinase-9 but not MMP-3 was higher in permanent compared to paroxysmal AF group (p < 0.001). Patients with AF had lower levels of TIMP-1 compared to those with SR while permanent AF subjects had lower TIMP-1 levels than those with paroxysmal AF (p < 0.001 for both comparisons). Lower TIMP-1 was the only independent factor associated with AF (OR: 0.259, 95%CI: 0.104-0.645, p = 0.004).

CONCLUSIONS

In hypertensives, paroxysmal AF and permanent AF differ with respect to serum MMPs. Increased MMP-2 is associated with paroxysmal, whereas increased MMP-9 with permanent AF. Additionally, lower levels of TIMP-1 had a strong association with AF incidence.

Effects of angiotensin receptor blocker and calcium channel blocker on experimental abdominal aortic aneurysms in a hamster model

Remodeling in the abdominal aortic wall results in abdominal aortic aneurysm (AAA) formation. Many patients with AAA are prescribed antihypertensive drugs. However, the effects of antihypertensive drugs other than their effects on blood pressure control are rarely reported. In this study, we investigated the effects of these drugs on changes in the levels of matrix metalloproteinases (MMPs) and on AAA formation. Experimental AAAs were created in a hamster model by wrapping the abdominal aorta with elastase gauze. Olmesartan medoxomil (angiotensin II receptor antagonist) or azelnidipine (calcium channel antagonist) was administered to the hamsters and then we evaluated the aortic diameter, performed histological analysis, and analyzed the production of MMP-2 and MMP-9 by gelatin zymography. The expansion rate of the aortic diameter was smaller in both treatment groups than in the control group. Elastica van Gieson (EVG) staining showed structural preservation of elastin lamellae in both treatment groups. The active MMP-9 level decreased in both the olmesartan group and the azelnidipine group. Reducing MMP-9 production is important for suppression of AAA formation. Both olmesartan medoxomil and azelnidipine decreased MMP-9 activity, which suppressed degradation of the MMPs and inhibited AAA formation. There are different cascades that determine the production of MMP-9.

Tear me down: role of calpain in the development of cardiac ventricular hypertrophy

Cardiac hypertrophy develops most commonly in response to hypertension and is an independent risk factor for the development of heart failure. The mechanisms by which cardiac hypertrophy may be reversed to reduce this risk have not been fully determined to the point where mechanism-specific therapies have been developed. Recently, proteases in the calpain family have been implicated in the regulation of the development of cardiac hypertrophy in preclinical animal models. In this review, we summarize the molecular mechanisms by which calpain inhibition has been shown to modulate the development of cardiac (specifically ventricular) hypertrophy. The context within which calpain inhibition might be developed for therapeutic intervention of cardiac hypertrophy is then discussed.

Protective effects of angiotensin-converting enzyme I/I and matrix metalloproteinase-3 6A/6A polymorphisms on dilatative pathology within the ascending thoracic aorta

OBJECTIVE

Activation of matrix metalloproteinases and the renin/angiotensin signaling pathways is under investigation with regard to their potential pathogenesis in dilatative pathology of the aorta. The purpose of this study was to explore matrix metalloproteinase-3 5A/6A and angiotensin-converting enzyme I/D polymorphisms as predisposing factors to dilatative pathology of the aorta.

METHODS

We studied 107 patients who underwent aortic reconstruction surgery due to dilatative pathology of ascending thoracic aorta and a random sample of the population (n = 773), all from Lithuania. The insertion/deletion (-1171 5A/6A) polymorphism in the promoter region of matrix metalloproteinase-3 studied by real-time polymerase-chain-reaction amplification and the D and I alleles were identified on the basis of standard polymerase-chain-reaction amplification of the respective fragments from intron 16 of the angiotensin-converting enzyme gene.

RESULTS

The frequency of the angiotensin-converting enzyme D allele was significantly higher in dilatative pathology of ascending thoracic aorta patients than in the reference group subjects (0.55 vs 0.48, respectively). The latter group had a significantly higher frequency of the angiotensin-converting enzyme I/I genotype than in dilatative pathology of ascending thoracic aorta patients (27.4% vs 16.5%, respectively). In the reference group, the frequency of combined angiotensin-converting enzyme I/I and matrix metalloproteinase-3 6A/6A genotypes was 7.5%, while in the dilatative pathology of ascending thoracic aorta patient group, there was no one carrying that combined genotype (p = 0.001).

CONCLUSIONS

The present study showing a role of angiotensin-converting enzyme and matrix metalloproteinase-3 in the development of dilatative pathology of ascending thoracic aorta permits us to entertain a possible protective mechanism for the combined effects of the angiotensin-converting enzyme I/I and the matrix metalloproteinase-3 6A/6A genotypes.

Left ventricular remodeling in the post-infarction heart: a review of cellular, molecular mechanisms, and therapeutic modalities

As more patients survive myocardial infarctions, the incidence of heart failure increases. After an infarction, the human heart undergoes a series of structural changes, which are governed by cellular and molecular mechanisms in a pathological metamorphosis termed "remodeling." This review will discuss the current developments in our understanding of these molecular and cellular events in remodeling and the various pharmacological, cellular and device therapies used to treat, and potentially retard, this condition. Specifically, this paper will examine the neurohormonal activity of the renin-angiotensin-aldosterone axis and its molecular effects on the heart. The emerging understanding of the extra-cellular matrix and the various active molecules within it, such as the matrix metalloproteinases, elicits new appreciation for their role in cardiac remodeling and as possible future therapeutic targets. Cell therapy with stem cells is another recent therapy with great potential in improving post-infarcted hearts. Lastly, the cellular and molecular effects of left ventricular assist devices on remodeling will be reviewed. Our increasing knowledge of the cellular and molecular mechanisms underlying cardiac remodeling enables us not only to better understand how our more successful therapies, like angiotensin-converting enzyme inhibitors, work, but also to explore new therapies of the future.

Expression of toll-like receptor 4, tumor necrosis factor- alpha, matrix metalloproteinase-9 and effects of benazepril in patients with acute coronary syndromes

OBJECTIVES

The study aims to explore the relationship between expressions of toll-like receptor 4 (TLR4) on peripheral blood monocytes, serum tumor necrosis factor-alpha (TNF-α) and matrix metalloproteinase-9 (MMP-9) in patients with acute coronary syndromes(ACS), and to investigate the possible mechanisms of Benazepril stabilizing atherosclerosis plaques.

METHODS

70 patients selected were randomly divided into Benazepril treatment group (35 patients) and regular treatment group (35 patients). Meanwhile, Stable angina pectoris (SAP) group of 32 patients and control group of 22 patients were also set up. With the help of flow-cytometry, expressions of TLR4 on peripheral blood monocytes of the four groups were analyzed and compared to show differences, correlations and changes of the above mentioned indicators. The concentration of TNF-α and MMP-9 in serum were measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

(1) Expressions of TLR4, levels of TNF-α and MMP-9 were increased and the rate was rising from the control group, to SAP group and then to ACS group. All these indicators in ACS group are significantly higher than those in other groups (P < 0.05). (ACS versus SAP, control; all (P < 0.05). (2) Multi-linear regression analysis indicates that there was a positive correlation between the expression level of TLR4 and serum levels of TNF-α and MMP-9 in patients with ACS (P < 0.01). (3) There is no significant differences between the expression level of TLR4 and serum levels of TNF-α and MMP-9 in Benazepril treatment group and regular treatment group before treatment (P > 0.05) while they all fell after treatment (P < 0.05). In addition, all the indicators decreased more greatly than the regular treatment group.

CONCLUSIONS

TLR4 on peripheral blood monocytes and serum TNF-α and MMP-9 in patients with coronary arteriosclerosis disease may be effective markers of the vulnerable plaque. Benazepril can inhibit over-expression of TLR4 and reduce serum levels of TNF-α and MMP-9, thus stabilize the vulnerable plaques and improve the condition of the patients with ACS.

Stimulation of reactive oxygen species and collagen synthesis by angiotensin II in cardiac fibroblasts

Superoxide anion generated by NAD(P)H-oxidase has an important role in the pathogenesis of cardiovascular diseases and scavenging superoxide anion can be considered as a reasonable therapeutic strategy. In hypertensive heart diseases there is a mutual reinforcement of reactive oxygen species (ROS) and angiotensin II (ANG II). ANG II increases the NAD(P)H-dependent superoxide anion production and the intracellular generation of ROS in cardiac fibroblasts and apocynin, a membrane NAD(P)H oxidase inhibitor, abrogates this rise. ANG II also stimulates the collagen production, the collagen I and III content and mRNA expression in cardiac fibroblasts and apocynin abolishes this induction. In this review we demonstrate that scavenging superoxide anion by tempol or EUK-8 or administration of PEG-superoxide dismutase (SOD) inhibits collagen production in cardiac fibroblasts. On the contrary increasing superoxide anion formation by inhibition of SOD stimulates collagen production. A vital role of SOD and the generated ROS can be suggested in the regulation and organization of collagen in cardiac fibroblasts. Specific pharmacological intervention with SOD mimetics can probably be an alternative approach for reducing myocardial fibrosis.

Breviscapine protects against cardiac hypertrophy through blocking PKC-alpha-dependent signaling

Breviscapine is a mixture of flavonoid glycosides extracted from the Chinese herbs. Previous studies have shown that breviscapine possesses comprehensive pharmacological functions. However, very little is known about whether breviscapine have protective role on cardiac hypertrophy. The aim of the present study was to determine whether breviscapine attenuates cardiac hypertrophy induced by angiotensin II (Ang II) in cultured neonatal rat cardiac myocytes in vitro and pressure-overload-induced cardiac hypertrophy in mice in vivo. Our data demonstrated that breviscapine (2.5-15 microM) dose-dependently blocked cardiac hypertrophy induced by Ang II (1 microM) in vitro. The results further revealed that breviscapine (50 mg/kg/day) prevented cardiac hypertrophy induced by aortic banding as assessed by heart weight/body weight and lung weight/body weight ratios, echocardiographic parameters, and gene expression of hypertrophic markers. The inhibitory effect of breviscapine on cardiac hypertrophy is mediated by disrupting PKC-alpha-dependent ERK1/2 and PI3K/AKT signaling. Further studies showed that breviscapine inhibited inflammation by blocking NF-kappaB signaling, and attenuated fibrosis and collagen synthesis through abrogating Smad2/3 signaling. Therefore, these findings indicate that breviscapine, which is a potentially safe and inexpensive therapy for clinical use, has protective potential in targeting cardiac hypertrophy and fibrosis through suppression of PKC-alpha-dependent signaling.

Loss of STAT1 is associated with increased aortic rupture in an experimental model of aortic dissection and aneurysm formation

BACKGROUND

Transcription factor signal transducer and activator of transcription (STAT) 1 has been linked to a variety of pathologic states involved with matrix remodeling, but its role in aortic pathology has not been previously described. The current study hypothesized that STAT1 regulates aneurysmal degeneration and its role was evaluated in human abdominal aortic aneurysm (AAA) and in a mouse model of aortic dissection.

METHODS

Apolipoprotein E knockout mice (ApoE-/-) or ApoE/STAT1 double knockout mice (ApoE/STAT1-/-) were infused with 1000 ng/kg/min of angiotensin II. Systolic blood pressure (SBP) was measured in the rodent tail. At sacrifice, aortic diameters and extent of aneurysm formation were measured by digital microscopy. STAT1 and phosphorylated-STAT1 protein levels were assessed in ApoE-/- mice at 0, 7, 14, and 28 days (n = 8/time point) by enzyme-linked immunosorbent assay. Histology was performed using hematoxylin and eosin (H&E) and Movat stains. Statistical analyses included chi(2) test, t test, and analysis of variance.

RESULTS

STAT1 messenger RNA and total protein were greater in human AAA vs non-AAA controls. In addition, aneurysms occurred in 8%, 50%, and 80% of ApoE-/- mice at 7, 14, and 28 days, respectively. Total STAT1 levels were not altered during the course of angiotensin II infusion. Phosphorylated STAT1 levels peaked at 7 days with a 1.4-fold increase over baseline (P < .05). Aneurysms occurred in 0%, 100%, and 100% of ApoE/STAT1-/- mice at 3, 5, and 28 days. In mice infused with angiotensin II for >3 days, aortic rupture occurred more frequently in ApoE/STAT-/- mice (53% vs 19%, P < .05) and at earlier time points (4.0 +/- 0.5 vs 9.2 +/- 0.77 days, P < .05) vs ApoE-/- mice. SBP did not differ between the groups during angiotensin II infusion. By 28 days, aneurysms were larger in ApoE/STAT1-/- mice compared with ApoE-/- mice (2.7 +/- 0.4 vs 1.9 +/- 0.1 mm, P < .05) and were more extensive. H&E and Movat stain did not reveal differences in aortic wall structural content at baseline between ApoE-/- and ApoE/STAT1-/- mice. Both groups demonstrated equal disorganization in the aneurysmal state.

CONCLUSIONS

Phosphorylated STAT1 is elevated during aneurysmal degeneration. Its loss is associated with a higher rate of acute aortic rupture and more extensive aneurysms in a mouse model of aortic dissection. Further investigation is necessary to determine whether these observations are secondary to an underlying aortic wall abnormality or alterations in vessel wall matrix remodeling.

Influence of p53 in the transition of myotrophin-induced cardiac hypertrophy to heart failure

AIMS

Cardiac-specific overexpression of myotrophin (myo) protein in transgenic (myo-Tg) mice results in hypertrophy at 4 weeks that progresses to heart failure (HF) by 36 weeks. Gene profiling showed that p53 expression increases as hypertrophy worsens to HF, suggesting that p53 may influence myo-induced HF. We aimed to define how the p53 signalling cascade affects the spectrum of cardiac hypertrophy (CH)/HF.

METHODS AND RESULTS

Immunoblot analysis showed that in myo-Tg mice (Mus musculus), upregulation of p53 occurs only when hypertrophy transitions to HF (16 weeks onward). To elucidate the role of p53, a double-Tg mouse line (p53(-/-)/myo(+/+)) was developed by crossing myo-Tg mice with p53-null mice. A significant reduction in cardiac mass with improved cardiac function was observed in p53(-/-)/myo(+/+) mice, suggesting that absence of p53 prevents hypertrophy from turning into HF. Analysis via real-time reverse-transcription PCR revealed changes in transcripts of the p53 pathway in p53(-/-)/myo(+/+) mice. Ingenuity Pathway Analysis indicated that cross-talk among several key nodal molecules (e.g. cyclin-dependent kinase inhibitor 1A, caspase-3, nuclear factor kappa-light-chain enhancer of activated B cells etc.) may play a regulatory role in the transition of CH to HF.

CONCLUSION

Our data provide evidence, for the first time, that the coherence of p53 with myo plays an active role during the transition of CH to HF in a model of HF induced by myo overexpression. Transition from CH to HF can be prevented in the absence of p53 in myo-induced hypertrophy. Therefore, deletion/inhibition of p53 could be a therapeutic strategy to prevent CH from transitioning to HF.

Sodium tanshinone IIA sulfonate attenuates angiotensin II-induced collagen type I expression in cardiac fibroblasts in vitro

Cardiac fibrosis occurs after pathological stimuli to the cardiovascular system. One of the most important factors that contribute to cardiac fibrosis is angiotensin II (AngII). Accumulating studies have suggested that reactive oxygen species (ROS) plays an important role in cardiac fibrosis and sodium tanshinone IIA sulfonate (STS) possesses antioxidant action. We therefore examined whether STS depresses Ang II-induced collagen type I expression in cardiac fibroblasts. In this study, Ang II significantly enhanced collagen type I expression and collagen synthesis. Meanwhile, Ang II depressed matrix metalloproteinase-1 (MMP-1) expression and activity. These responses were attenuated by STS. Furthermore, STS depressed the intracellular generation of ROS, NADPH oxidase activity and subunit p47(phox) expression. In addition, N-acetylcysteine the ROS scavenger, depressed effects of Ang II in a manner similar to STS. In conclusion, the current studies demonstrate that anti-fibrotic effects of STS are mediated by interfering with the modulation of ROS.

Role of the renin-angiotensin-aldosterone system and inflammatory processes in the development and progression of diastolic dysfunction

Left ventricular diastolic dysfunction represents a frequent clinical condition and is associated with increased cardiovascular morbidity and mortality. Diastolic dysfunction is the most common cause of HF-PSF (heart failure with preserved ejection fraction). Therefore it becomes important to understand the pathophysiological mechanisms underlying diastolic dysfunction, as well as the effective therapeutic strategies able to antagonize its development and progression. Among the complex pathophysiological factors that may contribute to the development of diastolic dysfunction, the RAAS (renin-angiotensin-aldosterone system) has been shown to play a significant role. Paracrine and autocrine signals of the RAAS promote structural and functional changes in the heart largely linked to increased myocardial fibrosis. Enhanced and dysregulated activity of the RAAS also contributes to the development of volume overload and vasoconstriction with subsequent increases in left ventricular diastolic filling pressures and a higher susceptibility of developing CHF (congestive heart failure). More recently, it has also been suggested that the RAAS may play a role in triggering myocardial and vascular inflammation through the activation of different cell types and the secretion of cytokines and chemokines. RAAS-induced myocardial inflammation leads to perivascular myocardial fibrosis and to the development or progression of diastolic dysfunction. For these reasons pharmacological blockade of the RAAS has been proposed as a rational approach for the treatment of diastolic dysfunction. In fact, ACEIs (angiotensin-converting enzyme inhibitors), ARBs (angiotensin II receptor blockers) and AAs (aldosterone antagonists) have been demonstrated to delay the development and progression from pre-clinical diastolic dysfunction towards CHF, as well as to reduce the morbidity and mortality associated with this condition.

Nuclear co-translocation of myotrophin and p65 stimulates myocyte growth. Regulation by myotrophin hairpin loops

Myotrophin, a 12-kDa ankyrin repeat protein, stimulates protein synthesis and cardiomyocyte growth to initiate cardiac hypertrophy by activating the NF-kappaB signaling cascade. We found that, after internalization into myocytes, myotrophin cotranslocates into the nucleus with p65 to stimulate myocyte growth. We used structure-based mutations on the hairpin loops of myotrophin to determine the effect of the loops on myotrophin and p65 localization, induction of protein synthesis, and cardiac hypertrophy. Loop mutants, most prominently glutamic acid 33-->alanine (E33A), stimulated protein synthesis much less than wild type. Myotrophin-E33A internalized into myocytes but did not translocate into the nucleus and failed to promote nuclear translocation of p65. In addition, two cardiac hypertrophy marker genes, atrial natriuretic factor and beta-myosin heavy chain, were not up-regulated in E33A-treated cells. Myotrophin-induced myocyte growth and initiation of hypertrophy thus require nuclear co-translocation of myotrophin and p65, in a manner that depends crucially on the myotrophin hairpin loops.

Propofol depresses angiotensin II-induced cardiomyocyte hypertrophy in vitro

Cardiomyocyte hypertrophy is formed in response to pressure or volume overload, injury, or neurohormonal activation. The most important vascular hormone that contributes to the development of hypertrophy is angiotensin II (Ang II). Accumulating studies have suggested that reactive oxygen species (ROS) may play an important role in cardiac hypertrophy. Propofol is a general anesthetic that possesses antioxidant action. We therefore examined whether propofol inhibited Ang II-induced cardiomyocyte hypertrophy. Our results showed that both ROS formation and hypertrophic responses induced by Ang II in cardiomyocytes were partially blocked by propofol. Further studies showed that propofol inhibited the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and mitogen-activated protein kinase/ERK kinase 1/2 (MEK1/2) induced by Ang II via a decrease in ROS production. In addition, propofol also markedly attenuated Ang II-stimulated nuclear factor-kappaB (NF-kappaB) activation via a decrease in ROS production. In conclusion, propofol prevents cardiomyocyte hypertrophy by interfering with the generation of ROS and involves the inhibition of the MEK/ERK signaling transduction pathway and NF-kappaB activation.

Interplay of angiotensin II and angiotensin(1-7) in the regulation of matrix metalloproteinases of human cardiocytes

Angiotensin II (Ang II) is a critical effector in the renin-angiotensin system (RAS), which modulates cardiovascular homeostasis, and the matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) related metabolism of extracellular matrix (ECM). Angiotensin(1-7) [Ang(1-7)] is another bioactive peptide in the RAS and is considered to have opposite effects to Ang II. However, the modulation of MMPs and TIMPs by Ang(1-7) is largely unclear in cardiocytes, and the antagonistic effects of Ang(1-7) on Ang II-mediated expression of MMPs and TIMPs have yet to be identified. In the present study, we examined the transcript expression of MMPs and TIMPs in human cardiac fibroblasts (HCF) and myocytes (HCM) after Ang II or Ang(1-7) stimulation, and analysed the antagonistic effects of Ang(1-7) to Ang II. The results show that Ang II decreased transcript expression of MMP-1, MMP-2, TIMP-1, TIMP-2 and TIMP-3, but upregulated MMP-9 expression in the HCF cells. Transcript expression of MMP-9 and TIMP-2 was downregulated by Ang(1-7) in the same cells. In the HCM cells, Ang II induced MMP-1 and MMP-9 overexpression but MMP-2 was downregulated. All of the examined MMPs and TIMPs, except MMP-9, were markedly decreased by Ang(1-7). In the studies of antagonistic effects of Ang(1-7) to Ang II, Ang(1-7) counteracted the effects of Ang II-mediated regulation on MMP-9 and TIMP-1 in the HCF cells compared with the control group. The regulations of all examined MMPs by Ang II were reversed to basal expression by Ang(1-7) in the HCM cells. Our results suggest that Ang(1-7) and Ang II have opposite and antagonistic effects on regulation of transcription of MMPs and TIMPs in primary cultures of human cardiocytes. These effects lead to increased ratios of MMPs to TIMPs after Ang II stimulation and decreased ratios of MMPs to TIMPs after Ang(1-7) stimulation; effects which may partly depend of the type of cardiac cells. These results suggest a potential role for Ang(1-7) in attenuatating cardiac damage in Ang II-induced ECM remodelling.

NF-kappaB-dependent transcriptional regulation of the cardiac scn5a sodium channel by angiotensin II

Angiotensin II (ANG II) increases oxidative stress and is associated with increased risk of sudden cardiac death. The cardiac Na(+) channel promoter contains elements that confer redox sensitivity. We tested the hypothesis that ANG II-mediated oxidative stress may modulate Na(+) channel current through altering channel transcription. In H9c2 myocytes treated for 48 h with ANG II (100 nmol/l) or H(2)O(2) (10 micromol/l) showed delayed macroscopic inactivation, increased late current, and 59.6% and 53.8% reductions in Na(+) current, respectively (P < or = 0.01). By quantitative real-time RT-PCR, the cardiac Na(+) channel (scn5a) mRNA abundance declined by 47.3% (P < 0.01) in H9c2 myocytes treated for 48 h with 100 nmol/l ANG II. A similar change occurred with 20 micromol/l H(2)O(2) (46.9%, P < 0.01) after 48 h. Comparable effects were seen in acutely isolated ventricular myocytes. The effects of ANG II could be inhibited by prior treatment of H9c2 cells with scavengers of reactive oxygen species or an inhibitor of the NADPH oxidase. Mutation of the scn5a promoter NF-kappaB binding site prevented decreased activity in response to ANG II and H(2)O(2). Gel shift and chromosomal immunoprecipitation assays confirmed that nuclear factor (NF)-kappaB bound to the scn5a promoter in response to ANG II and H(2)O(2). Overexpression of the p50 subunit of NF-kappaB in H9c2 cells reduced scn5a mRNA (77.3%, P < 0.01). In conclusion, ANG II can decrease scn5a transcription and current. This effect appears to be through production of H(2)O(2) resulting in NF-kappaB binding to the Na(+) channel promoter.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

Effects of triiodo-thyronine on angiotensin-induced cardiomyocyte hypertrophy: reversal of increased beta-myosin heavy chain gene expression

Thyroid hormone-induced cardiac hypertrophy is similar to that observed in physiological hypertrophy, which is associated with high cardiac contractility and increased alpha-myosin heavy chain (alpha-MHC, the high ATPase activity isoform) expression. In contrast, angiotensin II (Ang II) induces an increase in myocardial mass with a compromised contractility accompanied by a shift from alpha-MHC to the fetal isoform beta-MHC (the low ATPase activity isoform), which is considered as a pathological hypertrophy and inevitably leads to the development of heart failure. The present study is designed to assess the effect of thyroid hormone on angiotensin II-induced hypertrophic growth of cardiomyocytes in vitro. Cardiomyocytes were prepared from hearts of neonatal Wistar rats. The effects of Ang II and 3,3',5-triiodo-thyronine (T3) on incorporations of [3H]-thymine and [3H]-leucine, MHC isoform mRNA expression, PKC activity, and PKC isoform protein expression were studied. Ang II enhanced [3H]-leucine incorporation, beta-MHC mRNA expression, PKC activity, and PKCepsilon expression and inhibited alpha-MHC mRNA expression in cardiomyocytes. T3 treatment prevented Ang II-induced increases in PKC activity, PKCepsilon, and beta-MHC mRNA overexpression and favored alpha-MHC mRNA expression. Thyroid hormone appears to be able to reprogram gene expression in Ang II-induced cardiac hypertrophy, and a PKC signal pathway may be involved in such remodeling process.

Role of subcellular remodeling in cardiac dysfunction due to congestive heart failure

Although alterations in the size and shape of the heart (cardiac remodeling) are considered in explaining cardiac dysfunction during the development of congestive heart failure (CHF), there are several conditions including initial stages of cardiac hypertrophy, where cardiac remodeling has also been found to be associated with either an increased or no change in heart function. Extensive studies have indicated that cardiac dysfunction is related to defects in one or more subcellular organelles such as myofibrils, sarcoplasmic reticulum and sarcolemma, depending upon the stage of CHF. Such subcellular abnormalities in the failing hearts have been shown to occur at both genetic and protein levels. Blockade of the renin-angiotensin system has been reported to partially attenuate changes in subcellular protein, gene expression, functional activities and cardiac performance in CHF. These observations provide support for the role of subcellular remodeling (alterations in molecular and biochemical composition of subcellular organelles) in cardiac dysfunction in the failing heart. On the basis of existing knowledge, it appears that subcellular remodeling during the process of cardiac remodeling plays a major role in the development of cardiac dysfunction in CHF.

Inhibition of Matrix Metalloproteinase-9 Activity by Trandolapril after Middle Cerebral Artery Occlusion in Rats

We investigated whether an angiotensin-converting enzyme (ACE) inhibitor could inhibit matrix metalloproteinase (MMP) activities in cerebral infarct lesions after middle cerebral artery occlusion (MCAO) in rats. After placebo or trandolapril (5 mg/kg per day) was administered orally for 7 days, we permanently occluded the right middle cerebral artery. ACE activity in extracts from the infarct side of placebo-treated rats was significantly higher than that in extracts from the non-infarct side from 5 days after MCAO, though they did not differ at 1 day. ACE activities in extracts from both hemispheric segments in the trandolapril-treated group were significantly decreased compared with those in the placebo-treated group before MCAO, and this significant reduction persisted even at 7 days after MCAO. In the placebo-treated group, MMP-9 and MMP-2 activities in the infarct side were significantly increased at 12 h and at 1 day after MCAO, respectively. Trandolapril treatment significantly reduced MMP-9 and MMP-2 activities to 68.5% and 53.2%, respectively. Seven days after MCAO, the ratios of infarct areas to the hemispheric sectional areas in placebo- and trandolapril-treated rats were 55.4+/-2.1% and 30.9+/-2.9%, respectively, and this difference was significant. Neurological severity scores were significantly improved from 1 to 7 days after MCAO in trandolapril-treated rats. Cumulative survival in trandolapril-treated rats was significantly increased compared with that in placebo-treated rats. Thus, the inhibition of MMP-9 by trandolapril might be part of the mechanism that prevents cerebral damage after cerebral ischemia.

CARMA3/Bcl10/MALT1-dependent NF-kappaB activation mediates angiotensin II-responsive inflammatory signaling in nonimmune cells

Angiotensin II (Ang II) is a peptide hormone that, like many cytokines, acts as a proinflammatory agent and growth factor. After injury to the liver, the hormone assists in tissue repair by stimulating hepatocytes and hepatic stellate cells to synthesize extracellular matrix proteins and secrete secondary cytokines and by stimulating myofibroblasts to proliferate. However, under conditions of chronic liver injury, all of these effects conspire to promote pathologic liver fibrosis. Much of this effect of Ang II results from activation of the proinflammatory NF-kappaB transcription factor in response to stimulation of the type 1 Ang II receptor, a G protein-coupled receptor. Here, we characterize a previously undescribed signaling pathway mediating Ang II-dependent activation of NF-kappaB, which is composed of three principal proteins, CARMA3, Bcl10, and MALT1. Blocking the function of any of these proteins, through the use of either dominant-negative mutants, RNAi, or gene targeting, effectively abolishes Ang II-dependent NF-kappaB activation in hepatocytes. In addition, Bcl10(-/-) mice show defective hepatic cytokine production after Ang II treatment. Evidence also is presented that this pathway activates NF-kappaB through ubiquitination of IKKgamma, the regulatory subunit of the IkappaB kinase complex. These results elucidate a concrete series of molecular events that link ligand activation of the type 1 Ang II receptor to stimulation of the NF-kappaB transcription factor. These findings also uncover a function of the CARMA, Bcl10, and MALT1 proteins in cells outside the immune system.

Spatial disruption and enhanced degradation of collagen with the transition from compensated ventricular hypertrophy to symptomatic congestive heart failure

The cardiac extracellular matrix (ECM) maintains the structural and mechanical integrity of the myocardium. We determined the alterations in the composition of the ECM coincident with the transition from compensated left ventricular (LV) hypertrophy (LVH) to symptomatic congestive heart failure (CHF) and the mechanisms underlying such changes. Heart failure was induced in ferrets by aortic banding. Myocardial collagen content was assessed by HPLC and histological analysis. Matrix metalloproteinase (MMP) activity and tissue inhibitor of metalloproteinase (TIMP) expression were evaluated using gelatin zymography and Western blotting, respectively. LV free wall thickness increased by 29% in asymptomatic LVH and was associated with a 20% increase in interstitial fibrosis (P < 0.05). CHF was coincident with increased plasma angiotensin II levels (149 +/- 48, 40 +/- 19, and 5.6 +/- 1 pg/ml for CHF, LVH, and sham, respectively; P < 0.01, CHF vs. sham and LVH), ventricular dilatation (LV internal diameter = 15 +/- 0.4 vs. 9 +/- 0.1 mm, P < 0.05), increased active MMP-9 (3.0- and 2.2-fold increase over sham and LVH, respectively, n = 5-10 animals per group, P < 0.01), and reduced myocardial total collagen content (3.5 +/- 0.4, 2.6 +/- 0.3, and 2.2 +/- 0.3% in sham, LVH, and CHF, respectively, P < 0.05). In CHF the distribution of collagen was markedly altered, becoming punctate in nature. No difference in MMP-2 activity, TIMP-1, TIMP-2, TIMP-3, or TIMP-4 expression, or collagen cross-linking was found at any time. The present work demonstrates structural reorganization and loss of collagen from cardiac ECM during the transition to decompensated CHF. The enhanced MMP-9 activity coincident with the transition to CHF provides potential therapeutic opportunities for managing the progression from asymptomatic LVH to symptomatic CHF.

An autocrine role for leptin in mediating the cardiomyocyte hypertrophic effects of angiotensin II and endothelin-1

Leptin is a 16 kDa product of the obesity gene secreted primarily by adipocytes. We recently identified cardiomyocytes as a target for the direct hypertrophic effects of leptin and suggested that leptin may be a biological link between obesity and cardiovascular pathologies. Activation of the renin-angiotensin and endothelin systems is associated with development of cardiovascular diseases and plasma renin levels are elevated in obese individuals. We therefore determined possible interaction between these factors in mediating hypertrophy in cultured neonatal rat ventricular myocytes. Treatment for 24 h with leptin (3.1 nM), angiotensin II (100 nM) or endothelin-1 (ET-1, 10 nM) significantly increased cell area by 37%, 36% and 35%, respectively and significantly increased gene expression of myosin light chain-2 and alpha-skeletal actin as well as leucine incorporation. The hypertrophic effects of all three agents were prevented by leptin and a leptin triple mutant receptor antagonist whereas the AT(1) receptor blocker (Sar1-lle(8))-Ang II or the ET(A) receptor blocker BQ123 was ineffective against leptin-induced hypertrophy. Both angiotensin II and ET-1 significantly increased leptin levels in the culture medium by fivefold. Moreover, both angiotensin II and ET-1 increased the gene expression of the short form (OBRa) by 180% and long form (OBRb) of leptin receptors by 200%, and this increase was abolished by both leptin receptor and leptin antibodies and leptin triple mutant. Although both angiotensin II and ET-1 increased phosphorylation of MAPK (p38, ERK1/2 and JNK) and NF-kappaB, the ability of leptin blockade to attenuate the hypertrophic responses was generally dissociated from these effects suggesting an alternate, yet to be identified cellular pathway mediating this role of leptin. Our studies therefore suggest a novel autocrine function for leptin in mediating the hypertrophic effects of both angiotensin II and ET-1 in cardiac myocytes.

Mechanism of induction of muscle protein degradation by angiotensin II

Angiotensin I and II have been shown to directly induce protein degradation in skeletal muscle through an increased activity and expression of the ubiquitin-proteasome proteolytic pathway. This investigation determines the role of the nuclear transcription factor nuclear factor-kappaB (NF-kappaB) in this process. Using murine myotubes as a surrogate model system both angiotensin I and II were found to induce activation of protein kinase C (PKC), with a parabolic dose-response curve similar to the induction of total protein degradation. Activation of PKC was required for the induction of proteasome expression, since calphostin C, a highly specific inhibitor of PKC, attenuated both the increase in total protein degradation and in proteasome expression and functional activity increased by angiotensin II. PKC is known to activate I-kappaB kinase (IKK), which is responsible for the phosphorylation and subsequent degradation of I-kappaB. Both angiotensin I and II induced an early decrease in cytoplasmic I-kappaB levels followed by nuclear accumulation of NF-kappaB. Using an NF-kappaB luciferase construct this was shown to increase transcriptional activation of NF-kappaB regulated genes. Maximal luciferase expression was seen at the same concentrations of angiotensin I/II as those inducing protein degradation. Total protein degradation induced by both angiotensin I and II was attenuated by resveratrol, which prevented nuclear accumulation of NF-kappaB, confirming that activation of NF-kappaB was responsible for the increased protein degradation. These results suggest that induction of proteasome expression by angiotensin I/II involves a signalling pathway involving PKC and NF-kappaB.

Subcellular remodeling as a viable target for the treatment of congestive heart failure

It is now well known that congestive heart failure (CHF) is invariably associated with cardiac hypertrophy, and changes in the shape and size of cardiomyocytes (cardiac remodeling) are considered to explain cardiac dysfunction in CHF. However, the mechanisms responsible for the transition of cardiac hypertrophy to heart failure are poorly understood. Several lines of evidence both from various experimental models of CHF and from patients with different types of CHF have indicated that the functions of different subcellular organelles such as extracellular matrix, sarcolemma, sarcoplasmic reticulum, myofibrils, mitochondria, and nucleus are defective. Subcellular abnormalities for protein contents, gene expression, and enzyme activities in the failing heart become evident as a consequence of prolonged hormonal imbalance, metabolic derangements, and cation maldistribution. In particular, the occurrence of oxidative stress, development of intracellular Ca2+ overload, activation of proteases and phospholipases, and alterations in cardiac gene expression result in changes in the biochemical composition, molecular structure, and function of different subcellular organelles (subcellular remodeling). Not only does subcellular remodeling appear to be intimately involved in the transition of cardiac hypertrophy to heart failure, the mismatching of the function of different subcellular organelles leads to the development of cardiac dysfunction. Although blockade of the renin-angiotensin system, sympathetic nervous system, and various other hormonal actions have been reported to produce beneficial effects on cardiac remodeling and heart dysfunction in CHF, the actions of various cardiac drugs on subcellular remodeling have not been examined extensively. Some recent studies have indicated that both the angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists attenuate changes in sarcolemma, sarcoplasmic reticulum, and myofibril enzyme activities, protein contents, and gene expression, and partly improve cardiac function in the failing hearts. It is suggested that subcellular remodeling is an excellent target for the development of improved drug therapy for CHF. Furthermore, extensive studies should investigate the effects of different agents individually or in combination on reverse subcellular remodeling, cardiac remodeling, and cardiac dysfunction in various experimental models of CHF.

Angiotensin II-stimulated collagen production in cardiac fibroblasts is mediated by reactive oxygen species

OBJECTIVE

The aim of the present study was to determine whether inhibition of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] oxidase and of various superoxide generating systems could affect the collagen production, the mRNA and protein expression of collagen types I and III in control and angiotensin II-treated cardiac fibroblasts.

METHODS

Cardiac fibroblasts from passage 2 from normal male adult rats were cultured to confluency and incubated in serum-free Dulbecco's modified Eagle's medium for 24 h. The cells were then preincubated with(out) the tested inhibitors for 1 h and then further incubated with(out) angiotensin II (1 micromol/l) for 24 h. Collagen production was measured spectrophotometrically with picrosirius red as dye and with [3H]proline incorporation; collagen type I and III content by enzyme-linked immunosorbent assay and collagen type I and III mRNA expression by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). NAD(P)H-dependent superoxide anion production was assayed as superoxide dismutase-inhibitable cytochrome c reduction. Intracellular formation of reactive oxygen species was assessed with 2',7'-dichlorofluorescein diacetate as fluorescent probe.

RESULTS

Angiotensin II stimulated the collagen production, the collagen I and III content and mRNA expression in cardiac fibroblasts, and apocynin, a membrane NAD(P)H oxidase inhibitor, abolished this induction. Rotenone, allopurinol, indomethacin, nordihydroguiaretic acid, ketoconazole and nitro-L-arginine (inhibitors of mitochondrial NAD(P)H oxidase, xanthine oxidase, cyclooxygenase, lipoxygenase, cytochrome P450 oxygenase and nitric oxide synthase, respectively) did not affect the angiotensin II-induced collagen production. Angiotensin II increased the NAD(P)H-dependent superoxide anion production and the intracellular generation of reactive oxygen species in cardiac fibroblasts, and apocynin abrogated this rise.

CONCLUSIONS

Our data show that in adult rat cardiac fibroblasts the membrane-associated NAD(P)H oxidase complex is the predominant source of superoxide anion and reactive oxygen species generation in angiotensin II-stimulated adult cardiac fibroblasts. Inhibition of this NAD(P)H oxidase complex with apocynin completely blocked the angiotensin II-stimulated collagen production, and collagen I and III protein and mRNA expression.