|
|
The role of calcium influx and calcium sensitization in contraction of isolated arteries of normotensive and hypertensive rat
Bencze, Michal ; Zicha, Josef (advisor) ; Neckář, Jan (referee) ; Chalupský, Karel (referee)
Vascular resistance is mainly determined by the contraction of vascular smooth muscle (VSM), which is regulated by the phosphorylation of myosin light chain (MLC). VSM contraction is initiated by calcium influx into the VSM cells, which is mediated by transient receptor potential (TRP) channels and L-type voltage- dependent calcium channels (L-VDCC). On the other hand, calcium sensitization is a mechanism enhancing vascular contractile response at a given level of intracellular calcium by RhoA/Rho kinase pathway-mediated inhibition of myosin light chain phosphatase. In this thesis I present the data about i) the role of TRP channels in the mechanisms of vascular smooth muscle contraction, ii) enhanced contractility of arteries from spontaneously hypertensive rats (SHR), and iii) the differences in contraction of arteries from normotensive and hypertensive rats related to the role of RhoA/Rho kinase pathway in three types of experimental hypertension (SHR, Ren-2 transgenic rats and salt-sensitive Dahl rats). In the study concerning TRP channels, I compared the effects of three commonly used non-selective TRP channels inhibitors (2-APB, SKF-96365, FFA) on isolated arteries. Among them 2-APB was the most interesting because the observed inhibitory effects of 2-APB were dependent on the type of...
|
|
|
Role of Potassium Channels in the Regulation of Vascular Smooth Muscle Tone
Bencze, Michal ; Zicha, Josef (advisor) ; Moravec, Jan (referee)
In smooth muscle cells, potassium channels play an important role in the regulation of the membrane potential of smooth muscle cells, which is closely related to vascular tone. Four different types of K+ channels have been described in vascular smooth muscle cells. Voltagegated K+ channels (KV), which can be open by depolarization. Calcium-activated potassium channels (KCa), from the same gene family, are voltage dependent, and can be activated also by elevated concentration of intracellular Ca2+. Inward rectifying channels (KIR) display negative slope conductance. These channels amplify potassium flow and function as an extracellular K+ sensor. ATP-sensitive K+ channels (KATP) channels provide a link between cell metabolism and membrane potential. Function of K+ channels is also important in endothelium, which produces many vasodilatators and vasoconstrictors. Abnormal expression profile of K+ channels is part of vascular cell membrane remodeling.
|
|
|
The role of Rho-kinase signaling pathway in the regulation of blood pressure
Brunová, Aneta ; Zicha, Josef (advisor) ; Kopkan, Libor (referee)
Calcium sensitization represents a mechanism that enables vascular smooth muscle cells to change the sensitivity of the contractile apparatus to intracellular calcium The aim of this study was to determine to what extent is calcium sensitization modulated by the renin- angiotensin system (RAS), sympathetic nervous system (SNS), nitric oxide (NO) and prostanoids produced by cyclooxygenase (COX). For this purpose we studied the effects of acute and chronic blockade of particular systems on blood pressure changes elicited in conscious normotensive rats by administration of Rho-kinase inhibitor fasudil. Adult male chronically cannulated Wistar rats were used in all experiments. Main findings of this study are as follow: 1) Decrease of blood pressure elicited by Rho-kinase inhibition was enhanced under the conditions of acute NOS inhibition. Inhibition of NOS was shown to have a bigger effect than COX inhibition (this was confirmed under the conditions of acute RAS and SNS inhibition as well). These findings are in agreement with the hypothesis that NO exerts a suppressive effect on calcium sensitization. 2) Chronic NOS inhibition caused hypertension characterized by a more pronounced blood pressure lowering after Rho-kinase inhibition in comparison with control. NO chronically suppresses the calcium...
|
|
|
Phenotypic plasticity of smooth muscle cells
Misárková, Eliška ; Zicha, Josef (advisor) ; Pácha, Jiří (referee)
Vascular smooth muscle cells display a certain level of phenotype plasticity. Under specific conditions fully differentiated cells are able to undergo dedifferentiation and to restart growth and proliferation. An organ culture method is a useful technique for the analysis of dedifferentiation of vascular smooth muscle cells, because it provides an opportunity for studying the changes in cell phenotype. The aim of this study was to investigate the basic contractile characteristics in rat femoral arteries cultured for different time periods (from one to three days). In addition, the effects of fetal bovine serum (FBS), that contains various growth factors and other biological active molecules, on contractile function were studied. We also tried to attenuate cell dedifferentiation by lowering the calcium influx, because calcium is an important second messenger participating in cell growth and proliferation. To achieve this goal we used cultivation with nifedipine, a voltage-dependent calcium channel inhibitor. The cultivation without FBS slightly decreased arterial contractility, whereas the cultivation with FBS decreased arterial contractility considerably. The major change in contractility of arteries cultivated with FBS occurred approximately within 24 hours of cultivation. The cultivation with...
|
|
|
Excitation-Contraction and Excitation-Transcription Coupling in Vascular Smooth Muscle Cells: Alterations in Experimental Hypertension and Vascular Remodeling
Misárková, Eliška ; Zicha, Josef (advisor) ; Hock, Miroslav (referee)
Vascular smooth muscle cells (VSMCs) express considerable phenotype plasticity. They are able to change their phenotype in vivo if necessary. It is important to know that during this phenotype switch the expression of transport proteins and channels is modified, which results in significant alteration of Ca2+ signaling in smooth muscle cells. In differentiated cells, which represent contractile phenotype, there are dominant rapid, transient events in intracellular Ca2+ concentration (Ca2+ i), while the resting cytosolic Ca2+ i concentration is low. In differentiated cells these Ca2+ i events are mainly caused by two components of the Ca2+ signalling pathways: 1) extracellular Ca2+ influx via L-type voltage-gated Ca2+ channels (L-type VGCC) in plasma membrane, and 2) depletion of intracellular Ca2+ stores via ryanodin receptors located on sarcoplasmic reticulum. Rapid Ca2+ i oscillations are quickly reduced by numerous Ca2+ ATPases of sarco/endoplasmic reticulum and plasma membrane. Proliferating vascular smooth muscle cells are characterized by a long-lasting Ca2+ i oscillations accompanied by sustained elevation of basal intracellular Ca2+ concentration. During phenotype switch from contractile phenotype to proliferative phenotype there is decreased Ca2+ ATPase activity, and store-operated Ca2+...
|
|
|
Myocardial cell signaling in spontaneously hypertensive rats with transgenic and congenic expression of CD36
Klevstigová, Martina ; Nováková, Olga (advisor) ; Kalous, Martin (referee) ; Zicha, Josef (referee)
Long-chain fatty acids (LCFA) are the primary energy source in the myocardium and an imbalance in the LCFA and glucose utilization could cause cardiovascular diseases. More than 50% of LCFA uptake by the heart is mediated by the fatty acid translocase CD36 and disruption of its function has been shown to impair cardiovascular functions. The spontaneously hypertensive rat (SHR) harbors a deletion variant of the Cd36 gene that results in reduced LCFA transport into myocytes. Therefore, the main aim of this thesis was to investigate the importance of a functional CD36 to sustain normal physiological functions of the heart. We used SHR and two genetic modified SHR strains, the congenic SHR-4 and the transgenic SHR-Cd36, with fully functional CD36. They differ in the CD36 expression and in the manner how they were derived from the SHR. CD36 has been proven to play a role in the pathogenesis of insulin resistance. Therefore we analyzed the effect of a functional CD36 on insulin resistance and protein kinase C (PKC) expression, which is known to be involved in the mechanism of insulin resistance, in the heart of SHR-4 and SHR. We showed that the SHR-4 had lower serum free fatty acids (FFA) and triacylglycerols (TAG) concentrations, indicating improved insulin sensitivity. Furthermore, SHR-4 had increased...
|
|
|
The role of RhoA/Rho kinase signalling pathway in the regulation of blood pressure in normotensive and hypertensive rats
Brunová, Aneta ; Zicha, Josef (advisor) ; Wasková, Petra (referee)
Evidence is accumulating that point to a major role of Rho kinase in arterial pathophysiology. Rho kinase is a key enzyme in calcium sensitization in vascular smooth muscle cells. Calcium sensitization is characterized as an increase in vascular contractility in the conditions of constant cytosolic calcium level. Inhibitors of Rho-kinase exert beneficial effects on the cardiovascular system, mainly by lowering vascular contractility. This thesis summarizes the current progress in understanding of the signaling pathways involved in the control of peripheral resistance of spontaneously hypertensive rats (SHR). It is evident that enhanced sympathetic activity and abnormal regulation of ion channel activity collectively contribute to high blood pressure maintenance in SHR.
|
|
|
L-serine induced effects on blood pressure in normotensive and hypertensive rats: the influence of anesthesia
Bencze, Michal ; Zicha, Josef (advisor) ; Husková, Zuzana (referee)
Anesthetics cause profound alterations in respiratory and cardiovascular systems. Our experiments demonstrated that different anesthetics caused different changes in blood pressure regulating components. The role of particular BP regulating systems was disclosed by their selective inhibition - sympathetic nervous system blocked by pentolinium (peripheral ganglionic blockade), renin-angiotensin system by captopril (angiotensin converting enzyme blocker) and nitric oxide production by L-NAME (nitric oxide synthase blocker). Components of blood pressure regulating mechanisms in conscious normotensive Wistar rats and spontaneously hypertensive rats were compared with four different groups of anesthetized rats by pentobarbital, ketamine-xylazine, chloralose-urethane and isoflurane. Each anesthesia caused different hemodynamic changes. If hemodynamic conditions should be similar to conscious rats, the most suitable anesthetic is pentobarbital. L-serine-induced effects represent endothelium-derived hyperpolarizing factor (EDHF)-mediated response, which is a type of endothelium-dependent regulation of vascular tone, independent of nitric oxide and prostacyclin production. Pronounced L-serine effects on blood pressure were shown in NO-deficient type of hypertension. Our study demonstrated its pronounced effects in...
|
|
|
Feeding artery of vascular accesses for hemodialysis: model of arterial adaptation to high blood flow
Tuka, Vladimír ; Malík, Jan (advisor) ; Vízek, Martin (referee) ; Zicha, Josef (referee)
Background: Arteries adapt their diameter to changing haemodynamic conditions to maintain constant wall shear stress, the force generated by flowing blood on endothelial cells. The feeding artery of haemodialysis vascular accesses is a human model of arterial adaptation to chronically high blood flow and thus to high wall shear stress. The process of arterial adaptation is endothelium dependent. Endothelial dysfunction related to End-Stage Renal Failure, diabetes mellitus, dyslipidemia may impair also the dilatation of the feeding artery of vascular accesses. First the review of the literature presents in three parts different aspects of arterial adaptation: 1) arterial adaptation with focusing on the role of haemodynamic factors, 2) the influence of end-stage renal disease on arterial adaptation, 3) feeding artery of vascular accesses as a model of arterial response to chronic increase in blood flow. Methods: We examined the feeding artery of radial and brachial polytetrafluoroethylene grafts shortly after and one and two years after access creation. We used duplex ultrasonography to obtain internal diameter and blood velocity in the feeding arteries. We calculated wall shear rate as 4 x blood velocity / internal diameter and used it as approximation of wall shear stress. Results: In the first study we...
|
|
| |
guest ::
