Peripheral blood RNA biomarkers for cardiovascular disease from bench to bedside: a position paper from the EU-CardioRNA COST action CA17129

Despite significant advances in the diagnosis and treatment of cardiovascular diseases, recent calls have emphasized the unmet need to improve precision-based approaches in cardiovascular disease. Although some studies provide preliminary evidence of the diagnostic and prognostic potential of circulating coding and non-coding RNAs, the complex RNA biology and lack of standardization have hampered the translation of these markers into clinical practice. In this position paper of the CardioRNA COST action CA17129, we provide recommendations to standardize the RNA development process in order to catalyse efforts to investigate novel RNAs for clinical use. We list the unmet clinical needs in cardiovascular disease, such as the identification of high-risk patients with ischaemic heart disease or heart failure who require more intensive therapies. The advantages and pitfalls of the different sample types, including RNAs from plasma, extracellular vesicles, and whole blood, are discussed in the sample matrix, together with their respective analytical methods. The effect of patient demographics and highly prevalent comorbidities, such as metabolic disorders, on the expression of the candidate RNA is presented and should be reported in biomarker studies. We discuss the statistical and regulatory aspects to translate a candidate RNA from a research use only assay to an in-vitro diagnostic test for clinical use. Optimal planning of this development track is required, with input from the researcher, statistician, industry, and regulatory partners.

Rictor is a central target of the molecular network of cardiac ProtectomiRs

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Office of Hungary (NKFIA; NVKP-16-1-2016-0017 National Heart Program and OTKA-FK 134751); MTA-SE System Pharmacology Research Group, Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary

We have previously identified several cardiac microRNAs that are involved in cardioprotection and termed them as ProtectomiRs. mRNA targets of these ProtectomiRs may reveal new drug targets for cardioprotection.

Here we aimed to identify key molecular targets of ProtectomiRs and confirm their association with cardioprotection in a translational pig model of acute myocardial infarction.

Network theoretical approach was utilized to identify 882 potential target genes of 18 previously described protectomiRs. Rictor gene was the most central and it was ranked first in the protectomiR-target mRNA molecular network with the highest node degree of 5. Therefore, expression of Rictor and its targeting microRNAs were further validated in heart samples obtained from a translational pig model of acute myocardial infarction and cardioprotection induced by pre- or postconditioning. Three out of five Rictor-targeting pig homologue of rat ProtectomiRs showed significant upregulation in postconditioned but not in preconditioned pig hearts. Rictor was downregulated at the mRNA and protein level in ischemic postconditioning but not in ischemic preconditioning.

This is the first demonstration that Rictor is the central molecular target of ProtectomiRs and that decreased Rictor expression may regulate ischemic postconditioning-, but not preconditioning-induced acute cardioprotection. We conclude that Rictor is a potential novel drug target for acute cardioprotection.

Helium conditioning increases cardiac fibroblast migration which effect is not propagated via soluble factors or extracellular vesicles

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Project was supported by the National Research, Development and Innovation Office of Hungary

Background

Helium inhalation induces cardioprotection against ischemia/reperfusion injury, of which cellular mechanism is not fully elucidated. Extracellular vesicles (EVs) are cell-derived, nano-sized membrane vesicles which play role in cardioprotective mechanisms, but their function in helium-conditioning (HeC) is not elucidated.

Purpose

To investigate, how HeC affects cardiac fibroblasts and if their HeC-induced EVs or other secreted factors mediates remodeling of the cardiac tissue.

Methods

Neonatal rat cardiac fibroblasts (NRCF) were exposed to glucose deprivation and HeC rendered by four cycles of 95% helium + 5% CO2 for one hour, followed by one hour of normal culturing conditions. 40 hours later, NRCF migration was analyzed and Western Blot and quantitative PCR were used to analyze the expression of fibroblast to myofibroblast transformation markers. From the cell supernatant, medium-sized extracellular vesicles (mEVs) were isolated with differential centrifugation and analyzed with WB, transmission electron microscopy and nanoparticle tracking analysis. Supernatant of HeC-treated NRCF was transferred to naïve NRCF or immortalized human umbilical vein endothelia cells (HUVEC/TERT2) and migration and in vitro angiogenesis assay was performed.

Results

HeC accelerated the migration of NRCF. Meanwhile, HeC did not increase the expression of myofibroblast markers. HeC tended to decrease mEV secretion of NRCFs, but supernatant of HeC-NRCF neither accelerate the migration of naïve NRCF, nor affect the angiogenic potential of HUVEC/TERT2.

Conclusion

Since HeC increased the migration of NRCF but HeC-NRCF mEVs did not affect the function of remote cells, HeC may exert its cardioprotective effect via NRCFs, but not affect cardiac remodeling remotely, via NRCF mEVs.

Involvement of Oxidative Stress in the Development of Subcellular Defects and Heart Disease

It is now well known that oxidative stress promotes lipid peroxidation, protein oxidation, activation of proteases, fragmentation of DNA and alteration in gene expression for producing myocardial cell damage, whereas its actions for the induction of fibrosis, necrosis and apoptosis are considered to result in the loss of cardiomyocytes in different types of heart disease. The present article is focused on the discussion concerning the generation and implications of oxidative stress from various sources such as defective mitochondrial electron transport and enzymatic reactions mainly due to the activation of NADPH oxidase, nitric oxide synthase and monoamine oxidase in diseased myocardium. Oxidative stress has been reported to promote excessive entry of Ca²⁺ due to increased permeability of the sarcolemmal membrane as well as depressions of Na⁺-K⁺ ATPase and Na⁺-Ca²⁺ exchange systems, which are considered to increase the intracellular of Ca²⁺. In addition, marked changes in the ryanodine receptors and Ca²⁺-pump ATPase have been shown to cause Ca²⁺-release and depress Ca²⁺ accumulation in the sarcoplasmic reticulum as a consequence of oxidative stress. Such alterations in sarcolemma and sarcoplasmic reticulum are considered to cause Ca²⁺-handling abnormalities, which are associated with mitochondrial Ca²⁺-overload and loss of myofibrillar Ca²⁺-sensitivity due to oxidative stress. Information regarding the direct effects of different oxyradicals and oxidants on subcellular organelles has also been outlined to show the mechanisms by which oxidative stress may induce Ca²⁺-handling abnormalities. These observations support the view that oxidative stress plays an important role in the genesis of subcellular defects and cardiac dysfunction in heart disease.

Quercetin alleviates diastolic dysfunction and suppresses adverse pro-hypertrophic signaling in diabetic rats

INTRODUCTION

Quercetin (Que) is a potent anti-inflammatory and antioxidant flavonoid with cardioprotective potential. However, very little is known about the signaling pathways and gene regulatory proteins Que may interfere with, especially in diabetic cardiomyopathy. Therefore, we aimed to study the potential cardioprotective effects of Que on the cardiac phenotype of type 2 diabetes mellitus (T2DM) accompanied by obesity.

METHODS

For this experiment, we used Zucker Diabetic Fatty rats (fa/fa) and their age-matched lean controls (fa/+) that were treated with either vehicle or 20 mg/kg/day of Que for 6 weeks. Animals underwent echocardiographic (echo) examination before the first administration of Que and after 6 weeks.

RESULTS

After the initial echo examination, the diabetic rats showed increased E/A ratio, a marker of left ventricular (LV) diastolic dysfunction, in comparison to the control group which was selectively reversed by Que. Following the echo analysis, Que reduced LV wall thickness and exhibited an opposite effect on LV luminal area. In support of these results, the total collagen content measured by hydroxyproline assay was decreased in the LVs of diabetic rats treated with Que. The follow-up immunoblot analysis of proteins conveying cardiac remodeling pathways revealed that Que was able to interfere with cardiac pro-hypertrophic signaling. In fact, Que reduced relative protein expression of pro-hypertrophic transcriptional factor MEF2 and its counter-regulator HDAC4 along with pSer²⁴⁶-HDAC4. Furthermore, Que showed potency to decrease GATA4 transcription factor, NFAT3 and calcineurin, as well as upstream extracellular signal-regulated kinase Erk5 which orchestrates several pro-hypertrophic pathways.

DISCUSSION

In summary, we showed for the first time that Que ameliorated pro-hypertrophic signaling on the level of epigenetic regulation and targeted specific upstream pathways which provoked inhibition of pro-hypertrophic signals in ZDF rats. Moreover, Que mitigated T2DM and obesity-induced diastolic dysfunction, therefore, might represent an interesting target for future research on novel cardioprotective agents.

Beneficial Effect of Quercetin on Erythrocyte Properties in Type 2 Diabetic Rats

Diabetes mellitus is characterized by tissue oxidative damage and impaired microcirculation, as well as worsened erythrocyte properties. Measurements of erythrocyte deformability together with determination of nitric oxide (NO) production and osmotic resistance were used for the characterization of erythrocyte functionality in lean (control) and obese Zucker diabetic fatty (ZDF) rats of two age categories. Obese ZDF rats correspond to prediabetic (younger) and diabetic (older) animals. As antioxidants were suggested to protect erythrocytes, we also investigated the potential effect of quercetin (20 mg/kg/day for 6 weeks). Erythrocyte deformability was determined by the filtration method and NO production using DAF-2DA fluorescence. For erythrocyte osmotic resistance, we used hemolytic assay. Erythrocyte deformability and NO production deteriorated during aging-both were lower in older ZDF rats than in younger ones. Three-way ANOVA indicates improved erythrocyte deformability after quercetin treatment in older obese ZDF rats only, as it was not modified or deteriorated in both (lean and obese) younger and older lean animals. NO production by erythrocytes increased post treatment in all experimental groups. Our study indicates the potential benefit of quercetin treatment on erythrocyte properties in condition of diabetes mellitus. In addition, our results suggest potential age-dependency of quercetin effects in diabetes that deserve additional research.

Age- and Phenotype-Dependent Changes in Circulating MMP-2 and MMP-9 Activities in Normotensive and Hypertensive Rats

Matrix metalloproteinases (MMPs) are important in the pathogenesis of numerous diseases. The present study aimed to monitor the activation of MMP-2 and MMP-9 in spontaneously hypertensive rats (SHR) and their normotensive counterparts-Wistar-Kyoto rats (WKY). The animals were divided according to age (7, 20, and 52 weeks) and phenotype into: WKY-7, WKY-20, WKY-52, SHR-7, SHR-20 and SHR-52 groups. MMP plasma activities were determined by gelatine zymography. We monitored selected parameters of oxidative stress and antioxidant status. N-terminal pro-brain natriuretic peptide (NT-proBNP) was determined as a marker of heart function and neurohumoral activation. SHR-7 showed higher MMP-2 activity compared with WKY-7, while SHR-52 showed lower MMP-2 and MMP-9 activities compared with WKY-52. Examining age-dependent changes in MMP activities, we found a decrease in MMP-2 activity and increase in MMP-9 activity with increasing age in both phenotypes. Parameters of oxidative stress and antioxidant status as well as NT-proBNP levels were not significantly worsened due to aging in SHR. Our results suggest that hypertension is accompanied by varying MMP activation during aging. The results of our study may indicate that MMP-2 inhibition is therapeutically applicable during the development of hypertension, while in developed, stabilized and uncomplicated hypertension, systemic MMP-2 and MMP-9 inhibition may not be desirable.

Potential Implications of Quercetin and its Derivatives in Cardioprotection

Quercetin (QCT) is a natural polyphenolic compound enriched in human food, mainly in vegetables, fruits and berries. QCT and its main derivatives, such as rhamnetin, rutin, hyperoside, etc., have been documented to possess many beneficial effects in the human body including their positive effects in the cardiovascular system. However, clinical implications of QCT and its derivatives are still rare. In the current paper we provide a complex picture of the most recent knowledge on the effects of QCT and its derivatives in different types of cardiac injury, mainly in ischemia-reperfusion (I/R) injury of the heart, but also in other pathologies such as anthracycline-induced cardiotoxicity or oxidative stress-induced cardiac injury, documented in in vitro and ex vivo, as well as in in vivo experimental models of cardiac injury. Moreover, we focus on cardiac effects of QCT in presence of metabolic comorbidities in addition to cardiovascular disease (CVD). Finally, we provide a short summary of clinical studies focused on cardiac effects of QCT. In general, it seems that QCT and its metabolites exert strong cardioprotective effects in a wide range of experimental models of cardiac injury, likely via their antioxidant, anti-inflammatory and molecular pathways-modulating properties; however, ageing and presence of lifestyle-related comorbidities may confound their beneficial effects in heart disease. On the other hand, due to very limited number of clinical trials focused on cardiac effects of QCT and its derivatives, clinical data are inconclusive. Thus, additional well-designed human studies including a high enough number of patients testing different concentrations of QCT are needed to reveal real therapeutic potential of QCT in CVD. Finally, several negative or controversial effects of QCT in the heart have been reported, and this should be also taken into consideration in QCT-based approaches aimed to treat CVD in humans.

Chronic inflammatory diseases, myocardial function and cardioprotection

The association between chronic inflammatory diseases (CIDs) and increased cardiovascular (CV) risk is well documented and can be a most threatening complication in these patients. However, the pathogenetic mechanisms underlying increased CV risk remain elusive, especially in their cellular and biochemical pathways. Using animal models to understand mechanisms underlying cardiac involvement are limited. Additionally, treatments may influence cardiovascular events through different outcomes. Some drugs used to treat CIDs can negatively affect cardiac function by a direct toxicity, whereas others may protect the myocardium. In the present article, we focus on the cardiac manifestations and risk factors, the pathogenetic mechanisms, and the effect of treatments on myocardial function and cardioprotection for five common worldwide CIDs (rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, psoriasis and inflammatory bowel disease). We also give recommendations in order to evaluate common targets between CID and CV disease (CVD) and to design therapies to alleviate CID-related CVD. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Potential Clinical Implications of miR-1 and miR-21 in Heart Disease and Cardioprotection

The interest in non-coding RNAs, which started more than a decade ago, has still not weakened. A wealth of experimental and clinical studies has suggested the potential of non-coding RNAs, especially the short-sized microRNAs (miRs), to be used as the new generation of therapeutic targets and biomarkers of cardiovascular disease, an ever-growing public health issue in the modern world. Among the hundreds of miRs characterized so far, microRNA-1 (miR-1) and microRNA-21 (miR-21) have received some attention and have been associated with cardiac injury and cardioprotection. In this review article, we summarize the current knowledge of the function of these two miRs in the heart, their association with cardiac injury, and their potential cardioprotective roles and biomarker value. While this field has already been extensively studied, much remains to be done before research findings can be translated into clinical application for patient’s benefit.

Emerging role of non-coding RNAs and extracellular vesicles in cardioprotection by remote ischemic conditioning of the heart

Remote ischemic conditioning of the heart (including pre-, per-, and post-conditioning) is a phenomenon where short episodes of non-lethal ischemia in the distant vessels within the heart or distant organs from the heart protects the myocardium against sustained ischemia/reperfusion injury. Several pathways have been proposed to be involved in the mechanisms of Remote ischemic conditioning. While triggers of Remote ischemic conditioning act in preconditioned areas, its mediators transduce protective signals via humoral or neuronal pathways to the heart. Remote ischemic conditioning is mediated via receptor and nonreceptor signaling through secondary mediators, which transfer the signal within the cardiomyocyte and activate cardioprotective pathways that lead to higher resistance of the heart to ischemia/reperfusion. Apparently, identification of endogenous signal molecules involved in the mechanisms of Remote ischemic conditioning have therapeutic implications in the management of patients suffering from myocardial ischemia through the development of diverse beneficial effects. Recently, different non-coding RNAs such as microRNAs or long non-coding RNAs have been identified as emerging factors that trigger protective mechanisms in the heart. These non-coding RNAs are transferred to the heart via extracellular vesicles that exert remote cardioprotection. This review is intended to summarize the existing knowledge about the potential role of extracellular vesicles as humoral transmitters of Remote ischemic conditioning and emphasize the involvement of non-coding RNAs in the mechanism of cardioprotection by Remote ischemic conditioning.

L-Alpha-glycerylphosphorylcholine can be cytoprotective or cytotoxic in neonatal rat cardiac myocytes: a double-edged sword phenomenon

l-Alpha-glycerylphosphorylcholine (GPC) is a widely used food supplement. GPC has been shown to exert beneficial effects in several organs; however, the cardiac effects of GPC have yet to be investigated. The aim of the present study was therefore to map out the effects of GPC on cardiac myocytes, with or without ischemia–reperfusion insult. Neonatal rat cardiac myocytes were treated with GPC at 1, 10, 80, and 100 µM concentrations for 15 min, 3 h, or 24 h, respectively. Cell viability by calcein assay and the degree of oxidative stress by DHE (superoxide level) and H₂DCF (total ROS accumulation) staining were measured. In separate experiments, cardiomyocytes were pre-treated with the optimal concentration of GPC for 3 h and then cells were exposed to 4 h of simulated ischemia followed by 2 h of reperfusion (SI/R). Cell viability was measured at the end of the SI/R protocol. In normoxic conditions, the 15-min and the 3-h GPC treatment did not affect cell viability, total ROS, and superoxide levels. Under SI/R conditions, the 3-h GPC treatment protected the cardiac myocytes from SI/R-induced cell death and did not alter the level of oxidative stress. The 24-h GPC treatment in normoxic conditions resulted in significant cell death and increased oxidative stress at each concentration. Here we provide the first evidence for the cytoprotective effect of short-term GPC treatment. However, long-term administration of GPC may exert cytotoxicity in a wide concentration range in cardiac myocytes. These results may draw attention to a comprehensive cardiac safety protocol for the testing of GPC.

Role of cytokines and inflammation in heart function during health and disease

By virtue of their actions on NF-κB, an inflammatory nuclear transcription factor, various cytokines have been documented to play important regulatory roles in determining cardiac function under both physiological and pathophysiological conditions. Several cytokines including TNF-α, TGF-β, and different interleukins such as IL-1 IL-4, IL-6, IL-8, and IL-18 are involved in the development of various inflammatory cardiac pathologies, namely ischemic heart disease, myocardial infarction, heart failure, and cardiomyopathies. In ischemia-related pathologies, most of the cytokines are released into the circulation and serve as biological markers of inflammation. Furthermore, there is an evidence of their direct role in the pathogenesis of ischemic injury, suggesting cytokines as potential targets for the development of some anti-ischemic therapies. On the other hand, certain cytokines such as IL-2, IL-4, IL-6, IL-8, and IL-10 are involved in the post-ischemic tissue repair and thus are considered to exert beneficial effects on cardiac function. Conflicting reports regarding the role of some cytokines in inducing cardiac dysfunction in heart failure and different types of cardiomyopathies seem to be due to differences in the nature, duration, and degree of heart disease as well as the concentrations of some cytokines in the circulation. In spite of extensive research work in this field of investigation, no satisfactory anti-cytokine therapy for improving cardiac function in any type of heart disease is available in the literature.

Beneficial Effects of N-acetylcysteine and N-mercaptopropionylglycine on Ischemia Reperfusion Injury in the Heart

BACKGROUND

Ischemia-reperfusion (I/R) injury of the heart as a consequence of myocardial infarction or cardiac surgery represents a serious clinical problem. One of the most prominent mechanisms of I/R injury is the development of oxidative stress in the heart. In this regard, I/R has been shown to enhance the production of reactive oxygen/nitrogen species in the heart which lead to the imbalance between the pro-oxidants and antioxidant capacities of the endogenous radical-scavenging systems.

OBJECTIVES

Increasing the antioxidant capacity of the heart by the administration of exogenous antioxidants is considered beneficial for the heart exposed to I/R. N-acetylcysteine (NAC) and Nmercaptopropionylglycine (MPG) are two sulphur containing amino acid substances, which belong to the broad category of exogenous antioxidants that have been tested for their protective potential in cardiac I/R injury.

OBSERVATIONS

Pretreatment of hearts with both NAC and MPG has demonstrated that these agents attenuate the I/R-induced alterations in sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils in addition to improving cardiac function. While experimental studies have revealed promising data suggesting beneficial effects of NAC and MPG in cardiac I/R injury, the results of clinical trials are not conclusive because both positive and no effects of these substances have been reported on the post-ischemic recovery of heart following cardiac surgery or myocardial infarction.

CONCLUSION

It is concluded that both NAC and MPG exert beneficial effects in preventing the I/Rinduced injury; however, further studies are needed to establish their effectiveness in reversing the I/R-induced abnormalities in the heart.

Extracellular Vesicles in Cardiovascular Theranostics

Extracellular vesicles (EVs) are small bilayer lipid membrane vesicles that can be released by most cell types and detected in most body fluids. EVs exert key functions for intercellular communication via transferring their bioactive cargos to recipient cells or activating signaling pathways in target cells. Increasing evidence has shown the important regulatory effects of EVs in cardiovascular diseases (CVDs). EVs secreted by cardiomyocytes, endothelial cells, fibroblasts, and stem cells play essential roles in pathophysiological processes such as cardiac hypertrophy, cardiomyocyte survival and apoptosis, cardiac fibrosis, and angiogenesis in relation to CVDs. In this review, we will first outline the current knowledge about the physical characteristics, biological contents, and isolation methods of EVs. We will then focus on the functional roles of cardiovascular EVs and their pathophysiological effects in CVDs, as well as summarize the potential of EVs as therapeutic agents and biomarkers for CVDs. Finally, we will discuss the specific application of EVs as a novel drug delivery system and the utility of EVs in the field of regenerative medicine.

Changes in activities of circulating MMP-2 and MMP-9 in patients suffering from heart failure in relation to gender, hypertension and treatment: a cross-sectional study

Matrix metalloproteinases (MMPs) play an important role in the pathogenesis of heart failure (HF). Our aim was to determine the activities of circulating MMP-2 and MMP-9 in patients with HF in respect of gender, comorbidities and treatment (n=51). We did not reveal any differences in circulating pro-MMP-2 and pro-MMP-9 activities between the patients with HF and without it. However, there was a decrease in activity of pro-MMP-2 in treated hypertensive participants versus healthy ones. In contrast, we observed increased pro-MMP-2 activity in hypertensive participants with coexistent HF versus hypertensive participants without HF. In addition, a decrease in pro-MMP-2 activity was shown in women suffering from HF versus men suffering from HF. In conclusion, potential inhibitory effect of antihypertensive treatment on pro-MMP-2 activity was found. Coexistent HF with hypertension probably reduces the inhibitory effect of antihypertensive treatment on pro-MMP-2 activity. Our data also suggest the role of potential cardioprotective factors influencing the activity of pro-MMP-2 in women.

Remote preconditioning as a novel "conditioning" approach to repair the broken heart: potential mechanisms and clinical applications

Remote ischemic preconditioning (RIPC) is a novel strategy of protection against ischemia-reperfusion (IR) injury in the heart (and/or other organs) by brief episodes of non-lethal IR in a distant organ/tissue. Importantly, RIPC can be induced noninvasively by limitation of blood flow in the extremity implying the applicability of this method in clinical situations. RIPC (and its delayed phase) is a form of relatively short-term adaptation to ischemia, similar to ischemic PC, and likely they both share triggering mechanisms, whereas mediators and end-effectors may differ. It is hypothesized that communication between the signals triggered in the remote organs and protection in the target organ may be mediated through substances released from the preconditioned organ and transported via the circulation (humoral pathways), by neural pathways and/or via systemic anti-inflammatory and antiapoptotic response to short ischemic bouts. Identification of molecules involved in RIPC cascades may have therapeutic and diagnostic implications in the management of myocardial ischemia. Elucidation of the mechanisms of endogenous cardioprotection triggered in the remote organ could lead to the development of diverse pharmacological RIPC mimetics. In the present article, the authors provide a short overview of RIPC-induced protection, proposed underlying mechanisms and factors modulating RIPC as a promising cardioprotective strategy.

Cardioprotective effects of quercetin against ischemia-reperfusion injury are age-dependent

Quercetin, a polyphenolic compound present in various types of food, has been shown to exert beneficial effects in different cardiac as well as non-cardiac ischemia/reperfusion (I/R) models in adult animals. However, there is no evidence about the effects of quercetin on I/R injury in non-mature animals, despite the fact that efficiency of some interventions against I/R is age-dependent. This study was aimed to investigate the effects of chronic quercetin treatment on I/R injury in juvenile and adult rat hearts. Juvenile (4-week-old) as well as adult (12-week-old) rats were treated with quercetin (20 mg/kg/day) for 4 weeks, hearts were excised and exposed to 25-min global ischemia followed by 40-min reperfusion. Functional parameters of hearts and occurrence of reperfusion arrhythmias were registered to assess the cardiac function. Our results have shown that quercetin improved post-ischemic recovery of LVDP, as well as recovery of markers of contraction and relaxation, +(dP/dt)max and -(dP/dt)max, respectively, in juvenile hearts, but not in adult hearts. Quercetin had no impact on incidence as well as duration of reperfusion arrhythmias in animals of both ages. We conclude that the age of rats plays an important role in heart response to quercetin treatment in the particular dose and duration of the treatment. Therefore, the age of the treated subjects should be taken into consideration when choosing the dose of quercetin and duration of its application in prevention and/or treatment of cardiovascular diseases.

Effect of yeast biomass with high content of carotenoids on erythrocyte deformability, NO production and Na,K-ATPase activity in healthy and LPS treated rats

Measurements of red blood cell (RBC) deformability together with estimation of NO-synthase activity and Na,K-ATPase activity were used for characterization of RBC functionality in rats subjected to single dose of Escherichia coli lipopolysaccharides (LPS) at a dose of 1 mg/kg. We hypothesized that LPS might initiate a malfunction of RBC. We also investigated the potential effect of carotenoids (10 mg/kg/day) produced in red yeast biomass of Rhodotorula glutinis on RBC in LPS-challenged rats. LPS significantly reduced the deformability of RBC (by 14%) together with decrease of NO-synthase activity by 20%. Daily supplementation of carotenoids for 10 days attenuated the LPS-induced injury, as observed by 22% increase of RBC deformability and 23% increase of NO-synthase activity. The activity of Na,K-ATPase was also improved probably due to increased number of active enzyme molecules as indicated by 66% enhancement of Vmax value, hence maintaining the activity of erythrocyte Na,K-ATPase to the level even higher as compared with healthy control animals. It may be concluded that administration of yeast biomass with high content of carotenoids resulted in advanced function of erythrocytes as concerns their ability to squeeze through narrow capillaries of the circulation, better intrinsic production of NO and improvement of intracellular homeostasis of sodium.

MMP Activity Detection in Zymograms

Matrix metalloproteinases (MMP) belong to a distinguished class of zinc-dependent endopeptidases. Zymography is a semi-quantitative tool for determining the activity of different MMP isoenzymes in a variety of biological samples. In substrate gel zymography, protein samples of different origin (tissue, cell lysates, plasma/serum, perfusates, other liquids) are separated in sodium dodecyl sulfate (SDS) polyacrylamide gels containing copolymerized substrate (gelatin, casein, elastin, etc.), and after incubation-enabling substrate cleavage by MMPs, MMP activities are detected after the gel staining as transparent bands against a dark-blue background. In situ zymography is a histological modification of substrate zymography in frozen sections, allowing detection of the localization of the MMP activities within the tissue. Here, we describe detailed experimental protocols of all abovementioned techniques and provide examples for several sample measurements.

Molecular changes induced by repeated restraint stress in the heart: the effect of oxytocin receptor antagonist atosiban

Even though stress belongs to the most common lifestyle risk factors of cardiovascular diseases, there are only limited data on direct influence of stressors on the heart. The aim of the present study was to explore selected protein signaling pathways in response to repeated immobilization stress in the heart tissue. Effects of simultaneous treatment with atosiban, an oxytocin receptor antagonist, on stress-induced changes in the heart were also investigated. Male Wistar rats were exposed to repeated immobilization (2 h daily, lasting 2 weeks). The results showed increased phosphorylation of Akt kinase, enhanced levels of Bcl-2, and decreased levels of cleaved caspase-3 in the left ventricle in response to chronic stress independently of the treatment. Exposure to restraint led to the rise of HSP-90 and p53 in vehicle-treated rats only. Stress failed to modify MMP-2 activity and ultrastructure of the heart tissue. Treatment with the oxytocin/vasopressin receptor antagonist atosiban reversed stress-induced rise in HSP-90 and p53 proteins. In conclusion, our data demonstrate that repeated restraint stress induces Akt kinase activation and this is associated with elevation of anti-apoptotic proteins (Bcl-2) and down-regulation of pro-apoptotic proteins (cleaved caspase-3). These findings suggest that activation of pro-survival anti-apoptotic Akt kinase pathway plays an important role in molecular mechanisms underlying responses and adaptation of the rat heart to repeated stress exposure. The results further indicate a regulatory role of oxytocin/vasopressin in the control of stress-induced activation in HSP-90 and related proteins.

Prolonged oxytocin treatment in rats affects intracellular signaling and induces myocardial protection against infarction

Oxytocin is a hormone, which is released into the circulation in response to acute or chronic stress stimuli. One of the important targets of oxytocin is cardiovascular system. Present studies were aimed at testing the hypothesis that prolonged treatment with oxytocin (simulation of stress-induced rise in circulating oxytocin) activates intracellular signaling pathways playing a role in ischemia/reperfusion injury. Furthermore, we tested protective effects of oxytocin treatment in vivo against cardiac injury induced by ischemia/reperfusion of isolated hearts. Male Wistar rats were treated with oxytocin or vehicle continuously via osmotic minipumps for 2 weeks. The hearts were used for biochemical measurements or isolated for Langendorff perfusion. Treatment with oxytocin resulted in a significant increase in specific phosphorylation (activation) of p38-MAPK and Akt kinase, an increase in phosphorylated Hsp27 and an elevation in atrial natriuretic peptide (ANP) levels in left ventricular heart tissue. There were no significant changes in the activation of MMP-2 and ERK in the left heart ventricle of oxytocin-treated rats. Postischemic recovery of functional parameters LVDP, RPP, +dP/dtmax and -dP/dtmax was better in the hearts of oxytocin-treated rats compared to that in the controls. Oxytocin treatment significantly reduced infarct size to 15.1 + 3.2% as compared to 32.4 + 3.5% in vehicle-treated rats (p < 0.01). This is the first evidence for cardioprotective effects of oxytocin administered in vivo simulating chronic stress-induced elevation in plasma oxytocin. The present results show that positive effects of oxytocin that may ameliorate negative consequences of stress on the heart are, at least in part, mediated through p38-MAPK and Akt kinase pathways.

Effect of quercetin on kinetic properties of renal Na,K-ATPase in normotensive and hypertensive rats

The effect of quercetin, a plant-derived bioflavonoid with documented positive effect on the cardiovascular system, was examined after 4-week supplementation in the dose of 20 mg kg(-1) x day(-1) to young male normotensive control (C) and to spontaneously hypertensive rats (SHR) over the period of their 5(th)-8(th) week of age. The study was focused on the influence of quercetin on properties of the renal Na,K-ATPase, a key system in maintaining the homeostasis of sodium in the organism. Spontaneous hypertension by itself enhanced the activity of Na,K-ATPase probably as a consequence of a higher number of active enzyme molecules, as suggested by the 15% increase of V(max), along with improved affinity to ATP, as indicated by the 30% decrease in the value of Michaelis-Menten constant K(m) in untreated SHR vs. untreated normotensive rats. Quercetin induced a decrease of Na,K-ATPase activity in the presence of all ATP and Na(+) concentrations investigated. Evaluation of kinetic parameters resulted in a constant V(max) value. The ATP-binding properties of the enzyme were not influenced by quercetin, as suggested by statistically insignificant changes in the value of K(m) both in controls and in SHR. On the other hand, the affinity to sodium decreased, as suggested by an increase in the K(Na) value by 22% and 31% in normotensive and hypertensive groups, respectively. This impairment in the affinity of the Na(+)-binding site of Na,K-ATPase molecules was probably responsible for the deteriorated enzyme function in the kidneys of quercetin treated animals.

Simvastatin alleviates myocardial contractile dysfunction and lethal ischemic injury in rat heart independent of cholesterol-lowering effects

Statins, the inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are most frequently used drugs in the prevention of coronary artery disease due to their cholesterol-lowering activity. However, it is not exactly known whether these effects of statins or those independent of cholesterol decrease account for the protection against myocardial ischemia-reperfusion (I/R) injury. In this study, we investigated the effect of 5-day treatment with simvastatin (10 mg/kg) in Langendorff-perfused hearts of healthy control (C) and diabetic-hypercholesterolemic (D-H; streptozotocin + high fat-cholesterol diet, 5 days) rats subjected to 30-min global ischemia followed by 40-min reperfusion for the examination of postischemic contractile dysfunction and reperfusion-induced ventricular arrhythmias or to 30-min (left anterior descending) coronary artery occlusion and 2-h reperfusion for the infarct size determination (IS; tetrazolium staining). Postischemic recovery of left ventricular developed pressure (LVDP) in animals with D-H was improved by simvastatin therapy (62.7+/-18.2 % of preischemic values vs. 30.3+/-5.7 % in the untreated D-H; P<0.05), similar to the values in the simvastatin-treated C group, which were 2.5-fold higher than those in the untreated C group. No ventricular fibrillation occurred in the simvastatin-treated C and D-H animals during reperfusion. Likewise, simvastatin shortened the duration of ventricular tachycardia (10.2+/-8.1 s and 57.8+/-29.3 s in C and D-H vs. 143.6+/-28.6 s and 159.3+/-44.3 s in untreated C and D-H, respectively, both P<0.05). The decreased arrhythmogenesis in the simvastatin-treated groups correlated with the limitation of IS (in % of risk area) by 66 % and 62 % in C and D-H groups, respectively. However, simvastatin treatment decreased plasma cholesterol levels neither in the D-H animals nor in C. The results indicate that other effects of statins (independent of cholesterol lowering) are involved in the improvement of contractile recovery and attenuation of lethal I/R injury in both, healthy and diseased individuals.