During the last thirty years since the discovery of endothelin-1, the therapeutic strategy that has evolved in the clinic, mainly in the treatment of pulmonary arterial hypertension, is to block the action of the peptide either at the ETA subtype or both receptors using orally active small molecule antagonists. Recently, there has been a rapid expansion in research targeting ET receptors using chemical entities other than small molecules, particularly monoclonal antibody antagonists and selective peptide agonists and antagonists. While usually sacrificing oral bio-availability, these compounds have other therapeutic advantages with the potential to considerably expand drug targets in the endothelin pathway and extend treatment to other pathophysiological conditions. Where the small molecule approach has been retained, a novel strategy to combine two vasoconstrictor targets, the angiotensin AT1 receptor as well as the ETA receptor in the dual antagonist sparsentan has been developed. A second emerging strategy is to combine drugs that have two different targets, the ETA antagonist ambrisentan with the phosphodiesterase inhibitor tadalafil, to improve the treatment of pulmonary arterial hypertension. The solving of the crystal structure of the ETB receptor has the potential to identify allosteric binding sites for novel ligands. A further key advance is the experimental validation of a single nucleotide polymorphism that has genome wide significance in five vascular diseases and that significantly increases the amount of big endothelin-1 precursor in the plasma. This observation provides a rationale for testing this single nucleotide polymorphism to stratify patients for allocation to treatment with endothelin agents and highlights the potential to use personalized precision medicine in the endothelin field., A. P. Davenport, R. E. Kuc, C. Southan, J. J. Maguire., and Seznam literatury
Monophasic action potential (MAP) recording plays an important role in a more direct view of human myocardial electrophysiology under both physiological and pathological conditions. The procedure of MAP measuring can be simply performed using the Seldinger technique, when MAP catheter is inserted through femoral vein into the right ventricle or through femoral artery to the left ventricle. The MAP method represents a very useful tool for electrophysiological research in cardiology. Its crucial importance is based upon the fact that it enables the study of the action potential (AP) of myocardial cell in vivo and, therefore, the study of the dynamic relation of this potential with all the organism variables. This can be particularly helpful in the case of arrhythmias. There are no doubts that physiological MAP recording accuracy is almost the same as transmembrane AP as was recently confirmed by anisotropic bidomain model of the cardiac tissue. MAP recording devices provide precise information not only on the local activation time but also on the entire local repolarization time course. Although the MAP does not reflect the absolute amplitude or upstroke velocity of transmembrane APs, it delivers highly accurate information on AP duration and configuration, including early afterdepolarizations as well as relative changes in transmembrane diastolic and systolic potential changes. Based on available data, the MAP probably reflects the transmembrane voltage of cells within a few millimeters of the exploring electrode. Thus MAP recordings offer the opportunity to study a variety of electrophysiological phenomena in the in situ heart (including effects of cycle length changes and antiarrhythmic drugs on AP duration)., S.-G. Yang, O. Kittnar., and Obsahuje bibliografii a bibliografické odkazy
Although atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice, precise mechanisms that lead to the onset and persistence of AF have not completely been elucidated. Over the last decade, outstanding progress has been made in understanding the complex pathophysiology of AF. The key role of ectopic foci in pulmonary veins as a trigger of AF has been recognized. Furthermore, structural remodeling was identified as the main mechanism for AF persistence, confirming predominant role of atrial fibrosis. Systemic inflammatory state, oxidative stress injury, autonomic balance and neurohormonal activation were discerned as important modifiers that affect AF susceptibility. This new understanding of AF pathophysiology has led to the emergence of novel therapies. Ablative interventions, renin-angiotensin system blockade, modulation of oxidative stress and targeting tissue fibrosis represent new approaches in tackling AF. This review aims to provide a brief summary of novel insights into AF mechanisms and consequent therapeutic strategies., B. Aldhoon ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Bone metabolism is regulated by interaction between two skeletal cells – osteoclasts and osteoblasts. Function of these cells is controlled by a number of humoral factors, including neurohormones, which ensure equilibrium between bone resorption and bone formation. Influence of neurohormones on bone metabolism is often bimodal and depends on the tissue, in which the hormone is expressed. While hypothalamic beta-1 and beta-2-adrenergic systems stimulate bone formation, beta-2 receptors in bone tissue activate osteoclatogenesis and increases bone resorption. Chronic stimulation of peripheral beta-2 receptors is known to quicken bone loss and alter the mechanical quality of the skeleton. This is supported by the observation of a low incidence of hip fractures in patients treated with betablockers. A bimodal osteo-tropic effect has also been observed with serotonin. While serotonin synthetized in brain has osteo-anabolic effects, serotonin released from the duodenum inhibits osteoblast activity and decreases bone formation. On the other hand, both cannabinoid systems (CB1 receptors in the brain and CB2 in bone tissue) are unambiguously osteoprotective, especially with regard to the aging skeleton. Positive (protective) effects on bone have also been shown by some hypophyseal hormones, such as thyrotropin (which inhibits bone resorption) and adrenocorticotropic hormone and oxytocin, both of which stimulate bone formation. Low oxytocin levels have been shown to potentiate bone loss induced by hypoestrinism in postmenopausal women, as well as in girls with mental anorexia. In addition to reviewing neurohormones with anabolic effects, this article also reviews neurohormones with unambiguously catabolic effects on the skeleton, such as neuropeptide Y and neuromedin U. An important aim of research in this field is the synthesis of new molecules that can stimulate osteo-anabolic or inhibiting osteo-catabolic processes., I. Žofková, P. Matucha., and Obsahuje bibliografii
In this review the authors outline traditional antiresorptive pharmaceuticals, such as bisphosphonates, monoclonal antibodies against RANKL, SERMs, as well as a drug with an anabolic effect on the skeleton, parathormone. However, there is also a focus on non-traditional strategies used in therapy for osteolytic diseases. The newest antiosteoporotic pharmaceuticals increase osteoblast differentiation via BMP signaling (harmine), or stimulate osteogenic differentiation of mesenchymal stem cells through Wnt/β-catenin (icarrin, isoflavonoid caviunin, or sulfasalazine). A certain promise in the treatment of osteoporosis is shown by molecules targeting non-coding microRNAs (which are critical for osteoclastogenesis) or those stimulating osteoblast activity via epigenetic mechanisms. Vitamin D metabolites have specific antiosteoporotic potencies, modulating the skeleton not only via mineralization, but markedly also through the direct effects on the bone microstructure., I. Zofkova, J. Blahos., and Obsahuje bibliografii
The reactions of human organism to changes of internal or external environment termed as stress response have been at the center of interest during recent decades. Several theories were designed to describe the regulatory mechanisms which maintain the stability of vital physiological functions under conditions of threat or other environmental challenges. However, most of the models of stress reactivity were focused on specific aspects of the regulatory outcomes - physiological (e.g. neuroendocrine), psychological or behavioral regulation. Recently, a novel complex theory based on evolutionary and developmental biology has been introduced. The Adaptive Calibration Model of stress response employs a broad range of the findings from previous theories of stress and analyzes the responsivity to stress with respect to interindividual differences as a consequence of conditional adaptation - the ability to modify developmental trajectory to match the conditions of the social and physical environment. This review summarizes the contributions of the most important models in the field of stress response and emphasizes the importance of complex analysis of the psycho-physiological mechanisms. Moreover, it outlines the implications for nonpharmacological treatment of stress-related disorders with the application of biofeedback training as a promising tool based on voluntary modification of neurophysiological functions., I. Tonhajzerova, M. Mestanik., and Obsahuje bibliografii
Aim of the study was to test the effect of nicotine (NIC) and kainic acid (KA) co-treatment in immature rats. Male Wistar albino rats (two different age groups) were chosen for the study. Experiments started on postnatal day (PD) 8 or 21 and animals were treated twice a day for three days with nicotine, fourth day KA was administered. Animals at PD12 (PD25 respectively) were examined electrophysiologically for cortical epileptic afterdischarges (ADs). First cortical ADs in PD12 animals were longer, when compared to PD25 rats (group treated with both substances). Nor NIC or KA treatment affected the length of discharges in PD12 rats. Older experimental group exhibited the shortening of the first ADs (group treated with NIC and KA, compared with groups exposed to single treatment). Few changes were found in KA treated group – 2nd and 4th ADs were shorter when compared with first ADs. These results demonstrate that NIC treatment played minor role in seizure susceptibility of PD12 rats, sensitivity to NIC differs during ontogenesis and subconvulsive dose of KA influenced the length of discharges only in PD25 animals., V. Riljak ... [et al.]., and Obsahuje seznam literatury
High blood pressure (BP) of spontaneously hypertensive rats (SHR) is maintained by enhanced activity of sympathetic nervous system (SNS), whereas that of Ren-2 transgenic rats (Ren-2 TGR) by increased activity of renin-angiotensin system (RAS). However, both types of hypertension are effectively attenuated by chronic blockade of L-type voltage-dependent calcium channel (L-VDCC). The aim of our study was to evaluate whether the magnitude of BP response elicited by acute nifedipine administration is proportional to the alterations of particular vasoactive systems (SNS, RAS, NO) known to modulate L-VDCC activity. We therefore studied thes e relationships not only in SHR, in which mean arterial pressure was modified in a wide range of 100-210 mm Hg by chronic antihypertensive treatment (captopril or hydralazine) or its withdrawal, but also in rats with augmented RAS activity such as homozygous Ren-2 TGR, pertussis toxin- treated SHR or L-NAME-treated SHR. In all studied groups the magnitude of BP response to nifedipine was proportional to actual BP level and it closely correlated with BP changes induced by acute combined blockade of RAS and SNS. BP response to nifedipine is also closely related to the degree of relative NO deficiency. This was true for both SNS- and RAS-dependent forms of genetic hypertension, suggesting common mechanisms responsible for enhanced L-VDCC opening and/or their upregulation in hypertensive animals. In conclusions, BP response to nifedipine is proportional to the vasoconstrictor activity exerted by both SNS and RAS, indicating a key importance of these two pressor systems for actual L-VDCC opening necessary for BP maintenance., J. Zicha ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Maintenance of norepinephrine (NE)-induced contraction is dependent on Ca2+ influx through L-type voltage-dependent Ca2+ channels (VDCC), which is opposed by nitric oxide. Adrenergic receptors are coupled with different G proteins, including inhibitory G proteins (Gi) that can be inactivated by pertussis toxin (PTX). Our study was aimed to investigate the effects of endothelium removal, PTX pretreatment and acute VDCC blockade by nifedipine on the contractions of femoral arteries stimulated by norepinephrine. We used 12-week-old male WKY, half of the rats being injected with PTX (10 μg/kg i.v., 48 h before the experiment), which considerably reduced their blood pressure (BP). Contractions of isolated arteries were measured using Mulvany-Halpern myograph. NE dose-response curves determined in femoral arteries from PTX-treated WKY rats were shifted to the right compared to those from control WKY. On the contrary, removal of endothelium augmented NE dose-response curves shifting them to the left. Acute VDCC blockade by nifedipine (10-7 M) abolished all differences in NE dose-response curves which were dependent on the presence of either intact endothelium or functional Gi proteins because all NE dose-response curves were identical to the curve seen in vessels with intact endothelium from PTX-treated animals. We can conclude that BP reduction after PTX injection is accompanied by the attenuation of NE-induced contraction of femoral arteries irrespective of endothelium presence. Moreover, our data indicate that both vasodilator action of endothelium and Gi-dependent vasoconstrictor effect of norepinephrine operate via the control of Ca2+ influx through VDCC., S. Líšková, J. Kuneš, J. Zicha., and Obsahuje bibliografii a bibliografické odkazy
This study investigated whether endothelin (ET)-1-induced increase in myocardial distensibility is preserved in heart failure (HF) and whether it is modulated by nitric oxide (NO) and prostaglandins. New Zealand white rabbits were treated with doxorubicin (1 mg/kg, intravenously twice a week for 8 weeks, DOX-HF group) or saline (control group). Effects of ET-1 (0.1, 1, 10 nM) were tested in papillary muscles from the DOX-HF group and a control group in the presence of: i) intact endocardial endothelium (EE); ii) damaged EE; iii) NG-nitro-L-arginine (L-NNA; NO synthase inhibitor), and iv) indomethacin (INDO; cyclooxygenase inhibitor). In the presence of an intact EE, ET-1 promoted concentration-dependent positive inotropic and lusitropic effects that were maintained after damaging the EE, in the presence of L-NNA or INDO and in the DOX-HF Group. ET-1 reduced resting tension at the end of the isometric twitch (increased diastolic distensibility) by 3.2±1.3 %, 6.0±1.6 % and 8.8±2.7 % (at 0.1, 1 and 10 nM, respectively), in muscles with intact EE, effect that was completely abolished after damaging EE, in the presence of L-NNA or INDO or in the DOX-HF Group. This study demonstrated that the increase in myocardial distensibility induced by ET-1 is absent in HF and is dependent of NO and prostaglandin release., C. Brás-Silva, D. Monteiro-Sousa, A. J. Duarte, M. Guerra, A. P. Fontes-Sousa, C. Moura, J. C. Areias, A. F. Leite-Moreira., and Obsahuje bibliografii a bibliografické odkazy