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Five-sixths nephrectomy is a widely used experimental model of chronic kidney disease (CKD) that is associated with severe mitochondrial dysfunction of the remnant tissue. In this study, we assessed the effect of CKD on mitochondrial respiration separately in the rat kidney cortex and medulla 10 weeks after induction of CKD by subtotal 5/6 nephrectomy (SNX). Mitochondrial oxygen consumption was evaluated on mechanically permeabilized samples of kidney cortex and medulla using high-resolution respirometry and expressed per mg of tissue wet weight or IU citrate synthase (CS) activity. Mitochondrial respiration in the renal cortex of SNX rats was significantly reduced in all measured respiratory states if expressed per unit wet weight and remained lower if recalculated per IU citrate synthase activity, i.e. per mitochondrial mass. In contrast, the profound decrease in the activity of CS in SNX medulla resulted in significantly elevated respiratory states expressing the OXPHOS capacity when Complexes I and II or II only are provided with electrons, LEAK respiration after oligomycin injection, and Complex IV-linked oxygen consumption per unit CS activity suggesting compensatory hypermetabolic state in remaining functional mitochondria that is not sufficient to fully compensate for respiratory deficit expressed per tissue mass. The results document that CKD induced by 5/6 nephrectomy in the rat is likely to cause not only mitochondrial respiratory dysfunction (in the kidney cortex), but also adaptive changes in the medulla that tend to at least partially compensate for mitochondria loss.

Chronic volume overload induces multiple cardiac remodeling processes that finally result in eccentric cardiac hypertrophy and heart failure. We have hypothesized that chronic angiotensin-converting enzyme (ACE) inhibition by trandolapril might affect various remodeling processes differentially, thus allowing their dissociation. Cardiac remodeling due to chronic volume overload and the effects of trandolapril were investigated in rats with an aortocaval fistula (ACF rats). The aortocaval shunt was created using a needle technique and progression of cardiac remodeling to heart failure was followed for 24 weeks. In ACF rats, pronounced eccentric cardiac hypertrophy and contractile and proarrhythmic electrical remodeling were associated with increased mortality. Trandolapril substantially reduced the electrical proarrhythmic remodeling and mortality, whereas the effect on cardiac hypertrophy was less pronounced and significant eccentric hypertrophy was preserved. Effective suppression of electrical proarrhythmic remodeling and mortality but not hypertrophy indicates that the beneficial therapeutic effects of ACE inhibitor trandolapril in volume overload heart failure might be dissociated from pure antihypertrophic effects.

Metabolic syndrome is associated with hypercholesterolemia, cardiac remodeling, and increased susceptibility to ventricular arrhythmias. Effects of diet-induced hypercholesterolemia on susceptibility to torsades de pointes arrhythmias (TdP) together with potential indicators of arrhythmic risk were investigated in three experimental groups of Carlsson’s rabbit model: (1) young rabbits (YC, young control, age 12–16 weeks), older rabbits (AC, adult control, age 20–24 weeks), and older age-matched cholesterol-fed rabbits (CH, cholesterol, age 20–24 weeks). TdP was induced by α-adrenergic stimulation by methoxamine and IKr block in 83% of YC rabbits, 18% of AC rabbits, and 21% of CH rabbits. High incidence of TdP was associated with high incidence of single (SEB) and multiple ectopic beats (MEB), but the QTc prolongation and short-term variability (STV) were similar in all three groups. In TdP-susceptible rabbits, STV was significantly higher compared with arrhythmia-free rabbits but not with rabbits with other than TdP arrhythmias (SEB, MEB). Amplitude-aware permutation entropy analysis of baseline ECG could identify arrhythmia-resistant animals with high sensitivity and specificity. The data indicate that the TdP susceptibility in methoxamine-sensitized rabbits is affected by the age of rabbits but probably not by hypercholesterolemia. Entropy analysis could potentially stratify the arrhythmic risk and identify the low-risk individuals.

Metabolic syndrome is associated with hypercholesterolemia, cardiac remodeling, and increased susceptibility to ventricular arrhythmias. Effects of diet-induced hypercholesterolemia on susceptibility to torsades de pointes arrhythmias (TdP) together with potential indicators of arrhythmic risk were investigated in three experimental groups of Carlsson’s rabbit model: (1) young rabbits (YC, young control, age 12–16 weeks), older rabbits (AC, adult control, age 20–24 weeks), and older age-matched cholesterol-fed rabbits (CH, cholesterol, age 20–24 weeks). TdP was induced by α-adrenergic stimulation by methoxamine and IKr block in 83% of YC rabbits, 18% of AC rabbits, and 21% of CH rabbits. High incidence of TdP was associated with high incidence of single (SEB) and multiple ectopic beats (MEB), but the QTc prolongation and short-term variability (STV) were similar in all three groups. In TdP-susceptible rabbits, STV was significantly higher compared with arrhythmia-free rabbits but not with rabbits with other than TdP arrhythmias (SEB, MEB). Amplitude-aware permutation entropy analysis of baseline ECG could identify arrhythmia-resistant animals with high sensitivity and specificity. The data indicate that the TdP susceptibility in methoxamine-sensitized rabbits is affected by the age of rabbits but probably not by hypercholesterolemia. Entropy analysis could potentially stratify the arrhythmic risk and identify the low-risk individuals.

Sepsis, newly defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection, is the most common cause of death in ICUs and one of the principal causes of death worldwide. Although substantial progress has been made in the understanding of fundamental mechanisms of sepsis, translation of these advances into clinically effective therapies has been disappointing. Given the extreme complexity of sepsis pathogenesis, the paradigm “one disease, one drug” is obviously flawed and combinations of multiple targets that involve early immunomodulation and cellular protection are needed. In this context, the immune-reprogramming properties of cell-based therapy using mesenchymal stem cells (MSC) represent an emerging therapeutic strategy in sepsis and associated organ dysfunction. This article provides an update of the current knowledge regarding MSC in preclinical models of sepsis and sepsis-induced acute kidney injury. Recommendations for further translational research in this field are discussed.

Title: Anthracycline cardiotoxicity and study of new pharmacological cardioprotectants This Ph.D. thesis is a commented collection of 3 original articles published in international journals. The first part deals with cardiotoxicity of proteasome inhibitors (PI) bortezomib and carfilzomib, which are biologically targeted drugs with a suspected risk of cardiotoxicity and heart failure (HF). As PIs are now being combined with anthracycline (ANT) anticancer drugs, which are well known for their damaging impact on the heart, a special attention was paid to this potentially risky combination. In vitro experiments with primary cardiomyocytes yielded different results depending on the employment of either neonatal or adult rat cardiomyocyte model (NVCM and AVCM, respectively). In particular, both PIs significantly increased toxicity of ANTs to NVCM, but not to AVCM, even though they inhibited proteasome activity in AVCM even more effectively. Both PIs administered in maximally tolerated doses in combination with ANT did not have a significant impact on the development of chronic ANT cardiotoxicity and HF in rabbits. Both PIs induced significant but relatively short-lived inhibition of proteasome activity in the heart, which might explain why they did not have a significant impact on a protein homeostasis...

The role of renal dysfunction in pathophysiology of congestive heart failure progression: preclinical animal studies. Abstract The thesis describes effects and pharmacological targets of eicosanoids, especially epoxyeicosatrienoic acids (EETs) that are epoxygenase metabolites of arachidonic acid (AA), in animal model of congestive heart failure (CHF) induced by volume overload via aorto- caval fistula (ACF) in hypertensive transgenic rats (TGR). Our data show that ACF TGR exhibits tissue deficiency of EETs in the left ventricle and kidney, probably mainly caused by increased EETs degradation by soluble epoxide hydrolase (sEH). Treatment by orally active EETs analogue (EET-A) improved the survival rate in ACF TGR compared to placebo. However, after adding EET-A to angiotensin-convertase enzyme inhibitor (ACEi) treatment, the survival of ACF TGR only tended to improve compared with the effects of EET-A or ACEi given alone. The protective effects of EET-A treatment were mediated by improving cardiac parameters and reducing lung congestion, not dominantly by renal mechanisms. We also found that among male (not in female) the combination of sEH inhibitor (sEHi) and ACEi treatment worsened the mortality of ACF TGR compared to ACEi monotherapy. Our data support the notion that targeting the CYP-dependent...

Introduction: Two major product groups originate from the arachidonic acid metabolic pathway of cytochromes P450: epoxyeicosatrienoic acid (EETs) and 19 and 20-hydroxyeicosatetraenoic acid (19- and 20-HETE). These metabolites play an important role in the regulation of blood pressure, inflammatory responses, regulation of sodium excretion and other crucial physiological processes. Hypothesis: Our studies were based on the hypothesis that abnormalities in the production and function of these cytochrome P450 metabolites significantly contribute to the pathophysiology of hypertension development, in particular in the angiotensin II-dependent models. Objective: To investigate if the increased bioavailability of the above-mentioned metabolites in the kidney tissue will result in blood pressure reduction in the ANG II - dependent rat model of hypertension. Methods: The two methods to increase the concentration of EETs was chosen. In the first part of the study, we administered a soluble epoxide hydrolase inhibitor cAUCB [cis-4- [4- (3-adamantan-1-yl- ureido) cyclohexyloxy] benzoic acid, at a dose of 26 mg.l-1 administered in drinking water], an enzyme responsible for inactivation of biologically active forms of EETs. In the second series of the experiments we applied a synthetic EET analogue, called...

This dissertation consists of three parts describing electrophysiological and contractile changes of the myocardium in sepsis, acidosis, and propofol-induced anaesthesia. The first part is focused on heart rate variability analysis in a clinically relevant porcine model of sepsis/septic shock. Heart rate variability showed fast decrease few hours after sepsis induction which preceded changes in clinical parameters commonly used for sepsis diagnosis. The same fast kinetics of heart rate variability were demonstrated in progressive septic shock and in sepsis without serious multiorgan failure. Based on these results, it seems that heart rate variability could represent an early diagnostic tool in patients threatened with sepsis. In the second part of this thesis acidosis and its effects on the cardiovascular system are analysed. Metabolic and hypercapnic acidoses were examined in domestic pigs using hemodynamic in vivo measurements and in vitro experiments focused on electrophysiology and contractility of the heart. Both types of acidosis affected circulation and reduced myocardial contractility; hence it could limit therapeutic use of hypercapnic acidosis. The thesis is completed by a study of the effect of propofol, an anaesthetic used in two above mentioned studies. In rat ventricular tissue in...

Heart rate changes mediate the embryotoxic effect of antiarrhythmic drugs in the chick embryo A significant increase in cardiovascular medication use during pregnancy has occurred in recent years but only limited evidence on its safety profile is available. We hypothesized that drug-induced bradycardia is the leading mechanism of developmental toxicity. We tested metoprolol, carvedilol, or ivabradine for embryotoxicity and their acute effect on chick embryonic model. We used video microscopy and ultrasound biomicroscopy. Significant dose-dependent mortality was achieved in embryos injected with carvedilol and ivabradine. In ED4 embryos, metoprolol, carvedilol and ivabradine reduced the heart rate by 33%, 27%, and 55%, respectively, compared to controls (6%). In ED8 embryos this effect was more pronounced with a heart rate reduction by 71%, 54%, 53%, respectively (controls 36%). Cardiac output decreased in all tested groups but only proved significant in the metoprolol group in ED8 embryos. The number of -adrenergic receptors showed a downward tendency during embryonic development but a negative chronotropic effect of tested drugs was increasingly pronounced with embryonic maturity. This effect was associated with reduced cardiac output in chick embryos, probably leading to premature death....