The role of lipids and ROS in cardioprotective mechanism of chronic hypoxia Cardiovascular diseases, mainly ischemic heart disease is one of the most frequently cause of morbidity and mortality in developed countries. Therefore effective protection of the heart against ischemia and reperfusion injury is the crucial aim of experimental and clinical cardiology. One of the main streams of cardiovascular research is looking for possibilities of natural heart resistance augmentation. Adaptation to chronic hypoxia is one possibility how to protect the heart against ischemia-reperfusion injury. Chronic hypoxia increases resistance of the myocardium to acute deficiency of oxygen leading to vetricular arrythmias, postischemic contractile dysfunction and necrotic changes in the tissue. Recently, it has been shown that reactive oxygen species (ROS) play an important role in the cardioprotective mechanism of chronic hypoxia. It is known that oxidative stress has a harmful effect in acute ischemia-reperfusion however ROS generated during the adaptation to hypobaric intermittent chronic hypoxia play a role in the induction of cardioprotection. In this study, we demonstrated that adaptation of adult rats to chronic hypoxia increased the activity and protein abundance of manganese superoxide dismutase (MnSOD) in the...

Adaptation to chronic hypoxia increases myocardial resistance to acute ischemia/reperfusion (I/R) injury, similarly to application of exogenous erythropoietin (EPO). Nevertheless, it is not known if EPO induced by chronic hypoxia plays a role in its cardioprotective mechanism. The aim of this study was to find out if protective effect of exogenous EPO adds up to protection offered by chronic hypoxia. Adult male mice (ICR) were adapted to intermittent hypobaric hypoxia 8 hours per day, 5 days per week for 5 weeks. The degree of hypoxia corresponded to 7000 metres. Control animals were housed for the same time in normoxic environment. Resistance to I/R injury was assessed according to size of myocardial infarction induced by 45-min global ischemia and 1-h reperfusion of the heart in vitro. Animals were treated 24 h before the experiment with 200 or 5000 U/kg EPO. Treatment with 200 U/kg EPO was sufficient to significantly limit infarct size in normoxic animals (33,56 ± 2,93 % vs. 25,71 ± 2,29 %). Hypoxic adaptation decreased infarct area to 23,49 ± 2,30%, but additive effect of EPO in hypoxic group was not detected. The results indicate that exogenous EPO employs the same cardioprotective mechanisms as adaptation to chronic intermittent hypoxia. Preliminary results indicate that repeated application of EPO...

Cardiovascular diseases, particularly acute myocardial infarction, are one of the leading causes of death in developed countries. It is well known that adaptation to chronic intermittent hypobaric hypoxia (IHH) confers long-lasting cardiac protection against acute ischemia/reperfusion injury. Protein kinase C (PKC) appears to play a role in its cardioprotective mechanism since the administration of general PKC inhibitor completely abolished the improvement of ischemic tolerance in IHH hearts. However, the involvement of individual PKC isoforms remains unclear. Therefore, the primary aim of this study was to investigate the potential involvement of PKCδ and PKCε, the most prevalent PKC isoforms in rat heart, in the mechanism of IHH-induced cardioprotection. We showed that IHH up- regulated PKCδ protein in left ventricle, enhanced its phosphorylation on Ser643 and increased its co-localization with markers of mitochondrial and sarcolemmal membranes. PKCδ subcellular redistribution induced by IHH as well as the infarct size-limiting effect of IHH was reversed by acute treatment with PKCδ inhibitor rottlerin. These data support the view that PKCδ plays a significant role in IHH-induced cardioprotection. On the other hand, adaptation to IHH decreased the PKCε total protein level without affecting its...

The aim of present project was to uncover the effect of pharmacological increase in acute and chronic nitric oxide (NO) production on cardioprotective effect of chronic hypoxia. We studied the effect of NO donor molsidomine on hemodynamic conditions and ischemia - induced myocardium injury. Male Wistar rats were exposed to continual hypoxia in a normobaric chamber (10 % O2, 4 weeks). Rats received molsidomine either chronically (15 mg/kg/day) in drinking water or acutely (10 mg/kg) in saline infused 30 min before ischemia. Control rats were kept under normoxia and treated in a corresponding manner. Adaptation to chronic hypoxia resulted in development of pulmonary hypertension. Chronic treatment with molsidomine slightly reduced these consequences of chronic hypoxia but it had no effect on increased cardiac ischemic tolerance in chronically hypoxic rats. On the other hand acute treatment with molsidomine significantly reduced infarct size and increased the number of arrhythmias in both normoxic and chronically hypoxic animals. In conclusion, our data suggests that acute increase in availability of NO is cardioprotective in both normoxic and chronically hypoxic rats contrary to its chronic increase which seems to have no protective contribution.

The mortality of cardiovascular diseases remains high and it likely tends to increase in the future. Although many ways how to increase the resistance against myocardial ischemia- reperfusion damage have been described, few of them were transferred into clinical practice. Cardioprotective effect of chronic hypoxia has been described during 60s of the last century. Its detailed mechanism has not been elucidated, but a number of components has been identified. One of these components presents protein kinase C (PKC). The role of PKC was described in detail in the mechanism of ischemic preconditioning, but its involvement in the mechanism of cardioprotection induced by chronic hypoxia remains unclear. One reason is the amount of PKC isoforms, which have often contradictory effects, and the diversity of hypoxic models used. The most frequently mentioned isoforms in connection with cardioprotection are PKCδ and PKCε. The aim of my thesis was to analyze changes in these PKC isoforms at two different cardioprotective models of hypoxia - intermittent hypobaric (IHH) and continuous normobaric hypoxia (CNH). We also examined the target proteins of PKCδ and PKCε after the adaptation to IHH, which could be involved in the mechanism of cardioprotection. These included proteins associated with apoptosis and...

Endogenous cardiac protection against acute ischemia/reperfusion injury can by increased by cardiac adaptation to various forms of chronic hypoxia. Chronic hypoxia induces a large variety of adaptive changes in the myocardium that could be considered as protective, but the exact mechanism of increased ischemic tolerance is unknown. Different studies suggest that catecholamine release and their effect on -adrenergic signaling after adaptation to chronic hypoxia contributes to cardioprotection. In this study we focused on characterization of -adrenergic receptors ( -ARs) in the myocardium of rats after adaptation to three different hypoxic conditions: 1. intermittent normobaric hypoxia - INH/R (23 h hypoxia, 1 h reoxygenation), 2. intermittent normobaric hypoxia - INH (8 h hypoxia, 16 h normoxia), 3. continuous normobaric hypoxia - CNH (24 h hypoxia). We compared how each hypoxic model affects the total number of -adrenergic receptors and proportion of individual subtypes ( 1-and 2-ARs) in the left and right ventricles compared control normoxic rats. The INH model had apparently no effect on -ARs in either ventricles. On the other hand, adaptation to INH/R and CNH was accompanied by a significant decrease (by about 25%) in the total number of -adrenergic receptors in the right ventricles. Our present...

Ischemic heart disease and resulting heart failure (HF) belong to the leading causes of death in developed countries. In order to prevent HF and improve clinical outcome in patients with myocardial infarction, novel therapies are required to protect the heart against the detrimental effect of ischemic injury. Due to the failure to translate numerous available experimental cardioprotective strategies into clinical practice, the need for novel protective treatments persists. We have, therefore, tried to apply a novel approach to cardiac protection against the postischemic HF induced in rats by ligation of the coronary artery. For this purpose, we have studied (i) the preventive and therapeutic effects of adaptation to continuous normobaric hypoxia (CNH; 12% O2) and exercise training (ExT; treadmill running), and (ii) the possible cardioprotective potential of epoxyeicosatrienoic acid (EET)-based therapy in order to attenuate the postischemic HF in rats. Adaptation to CNH and ExT is known for their cardioprotection in acute ischemia/reperfusion (I/R) injury manifested as reduction of infarct size. EETs exert antihypertensive effects and thus seem to be perspective for the research in clinically relevant models of cardioprotection in hypertensive animals. Our results have revealed that: - CNH prior to...

- 4 - Abstract Adaptation to hypoxia or exercise training has cardioprotective effects against acute ischemic injury, but can potentially negatively influence heart function. Possible negative changes depend on the degree of hypoxia and exercise training intensity. It is therefore necessary to evaluate the effects of the specific adaptation protocols used. The ideal technique is echocardiography, which enables non-invasive, repeated and long-term measurements of the same individual allowing to study the development of changes in the course of adaptation. The aim of this study was to determine the effects of selected protocols of adaptation to intermittent hypobaric hypoxia (corresponding to the altitude of 4,000 to 8,000 meters above sea level, for 15 weeks in total) and exercise training (running speed 30 m.min-1 for 60 min a day, 4 weeks in total) on the left ventricle geometry and systolic function in rats. We assessed basic echocardiographic parameters of the ventricle geometry and function such as fractional shortening, ejection fraction, stroke volume, cardiac output etc. The adaptation of rats to intermittent hypobaric hypoxia lead neither to the impairment of systolic function nor to the development of left ventricle hypertrophy compared to controls; signs of moderate hypertrophy were observed only...

Recently, they are examined various means for activating the endogenous signalling pathways leading to increased resistance of the myocardium from ischemic/reperfusion (I/R) injury. One of them is the adaptation to chronic hypoxia, which has been shown to reduce the incidence and severity of ventricular arrhythmias, improves the recovery of postischemic contractile function of the heart and particularly reduces the extent of myocardial infarction. Since the function of the heart depends on the maintenance of membrane integrity of cardiomyocytes there are very important phospholipase A2 (PLA2) which are involved in the repair of cellular membranes. Also they are an important component of the protective signalling pathways because they cleave membrane phospholipids to produce lipid signalling molecules. Elucidate the role of PLA2 and the precise mechanism of action of signalling pathways leading to cardioprotection could be important for the prevention and treatment of cardiovascular diseases. Therefore, in this thesis we examined the influence of continuous normobaric hypoxia (CNH) to the relative representation of cardiac PLA2 (secretory - sPLA2IIA, calcium-independent - iPLA2, cytosolic - cPLA2α and its phosphorylated form - p-cPLA2α), and proteins involved in the activation and phosphorylation of...

Ischemic heart disease is the leading cause of death and disability worldwide. The effects of ischemic heart disease are usually attributable to the detrimental effects of acute myocardial ischemia/reperfusion (I/R) injury. The aim of the thesis was to contribute to current effort to clarify the basis of mechanisms that could save the heart from I/R injury. The whole thesis is based on four studies; while the first three are published, the fourth one has been under revision. In the first study, we proved the involvement of nitric oxide (NO) in the cardioprotective mechanism of chronic hypoxia (CH). We described that exogenously increased availability of NO as well as inhibition of phosphodiesterase type 5 led to increased myocardial tolerance of normoxic and chronically hypoxic rats. The effects of both interventions were not additive, suggesting that NO is included in cardioprotective signaling of CH. Second study continued in investigating molecular mechanisms underlying cardioprotection induced by CH. We showed that infarct size-limiting effect of adaptation to CH was accompanied by increased myocardial concentration of tumor-necrosis factor alpha (TNF-α) and TNF-α receptor R2. In the third study, we examined the effect of dexrazoxane (DEX), the only clinically approved drug against...