Silvia Líšková

Nifedipine-sensitive noradrenergic vasoconstriction is enhanced in spontaneously hypertensive rats: the influence of chronic captopril treatment

Aim:  The relationship between increased sympathetic tone and enhanced activity of L‐type voltage‐dependent Ca2+ channels (L‐VDCC) in spontaneously hypertensive rats (SHR) was studied using in vivo and in vitro approaches.

Melatonin improves the restoration of endothelium-derived constricting factor signalling and inner diameter in the rat femoral artery after cessation of L-NAME treatment.

Objective Melatonin is suggested to be beneficial in several pathological conditions including arterial hypertension. One of the mechanisms proposed for its antihypertensive action is the protection against endothelial dysfunction. We investigated whether melatonin can accelerate the recovery from NG-nitro-L-arginine-methyl ester (L-NAME)-induced hypertension after the cessation of L-NAME administration. Methods Male adult Wistar rats (n=40) were randomized into 3 treated groups: 5-week L-NAME, 5-week L-NAME + 3-week vehicle, 5-week L-NAME + 3-week melatonin and into 2 age-matched control groups. The blood pressure was measured in the carotid artery. The NO-signalling was represented by NO-synthase activity and expression in the aorta and NO-mediated relaxations of femoral and mesenteric arteries. The endothelium-derived-constricting factor (EDCF)-signalling was represented by aortic cyclooxygenase-2 expression and femoral EDCF-mediated contractions. Oxidative load was determined in the aorta based on conjugated dienes concentration and inner diameter was measured in femoral arteries. Results L-NAME caused hypertension, reduced NO-signalling and arterial diameter and increased oxidative load and EDCF-signalling. While the NO-signalling was restored spontaneously 3 weeks after L-NAME cessation, the EDCF-signalling, oxidative load and arterial remodeling were completely restored only when melatonin treatment was administered during the recovery period. The blood pressure regression was comparable between spontaneous and melatonin recovery. Conclusion Although melatonin did not accelerate blood pressure reduction, it attenuated EDCF-contractions and oxidative load and enlarged arterial diameter. These effects may be beneficial for cardiovascular protection.

Ca2+ sensitization and Ca2+ entry in the control of blood pressure and adrenergic vasoconstriction in conscious Wistar-Kyoto and spontaneously hypertensive rats.

Background: Calcium entry through nifedipine-sensitive L-type voltage-dependent calcium channels (L-VDCC) is augmented in spontaneously hypertensive rats (SHR) characterized by enhanced sympathetic vasoconstriction. However, the changes of calcium sensitization mediated by RhoA/Rho kinase pathway are less understood. Methods and results: The participation of calcium entry and calcium sensitization in the control of blood pressure (BP) and vascular contraction was studied in SHR and normotensive Wistar–Kyoto (WKY) rats. The acute administration of fasudil (Rho kinase inhibitor) caused BP decrease which lasted longer in SHR. Fasudil also attenuated adrenergic contraction in femoral or mesenteric arteries of WKY and SHR. BP reduction elicited by fasudil in WKY was more pronounced than that induced by L-VDCC blocker nifedipine (−33 ± 2 vs. −15 ± 3% of baseline BP, P < 0.001), whereas both inhibitors were similarly effective in SHR (−36 ± 4 vs. −41 ± 2%). Fasudil pretreatment also attenuated BP elevation elicited by L-VDCC agonist BAY K8644 more in WKY than in SHR (−63 ± 4 vs. −42 ± 5%, P < 0.001), indicating reduced calcium sensitization in SHR. Moreover, fasudil pretreatment shifted norepinephrine dose–response curves to the right more in WKY than in SHR. The additional nifedipine pretreatment shifted these curves further to the right but this shift was more pronounced in SHR than in WKY. Thus adrenergic vasoconstriction is more dependent on L-VDCC in SHR and on RhoA/Rho kinase pathway in WKY rats. Conclusion: Ca2+ sensitization mediated by RhoA/Rho kinase pathway is attenuated in SHR compared with normotensive WKY rats. This might be a part of the compensation for enhanced Ca2+ entry through L-VDCC in genetic hypertension.

Influence of calcium-dependent potassium channel blockade and nitric oxide inhibition on norepinephrine-induced contractions in two forms of genetic hypertension

The activation of Ca(2+)-dependent K(+) channels (BK(Ca)) leads to the attenuation of vascular contraction. Our study aimed to evaluate BK(Ca) influence on norepinephrine (NE)-induced femoral artery contraction in two forms of genetic hypertension. NE dose-response curves were studied before and after BK(Ca) blockade or after combined blockade of BK(Ca) and NO synthase (NOS) in femoral arteries with intact endothelium from normotensive Wistar (WIS), hypertensive hereditary hypertriglyceridemic (HTG), or spontaneously hypertensive rats (SHR). NE-induced contractions of femoral arteries were augmented in both hypertensive strains compared with Wistar rats, but acetylcholine-induced relaxation was impaired in HTG only. The increase of basal vascular tone of isolated arteries after BK(Ca) blockade was similar in all rat strains, but subsequent NOS inhibition increased basal vascular tone more in vessels from both hypertensive rat strains. NOS inhibition increased sensitivity to NE in all strains, but BK(Ca) blockade in SHR only. Neither treatment enhanced maximal NE-induced contraction. NO-dependent attenuation of NE-induced contractions was greater in SHR than HTG or Wistar vessels, whereas large conductance Ca(2+)-dependent K(+) channels may play a greater role in modulating vascular contraction in the severe form of hypertension.

Contribution of Ca²⁺-dependent Cl⁻ channels to norepinephrine-induced contraction of femoral artery is replaced by increasing EDCF contribution during ageing.

The activation of Ca2+-dependent Cl− channels during norepinephrine-induced contraction of vascular smooth muscle was suggested to depolarize cell membrane and to increase Ca2+ entry. Hypertension and ageing are associated with altered Ca2+ handling including possible activation of Ca2+-dependent Cl− channels. Our study was aimed to determine Ca2+-dependent Cl− channels contribution to norepinephrine-induced contraction during hypertension and ageing. Norepinephrine-induced concentration-response curves of femoral arteries from 6- and 12-month-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were recorded using wire myograph. Pretreatment with Ca2+-dependent Cl- channel inhibitor indanyloxyacetic acid 94 [R(+)-IAA-94](IAA) attenuated norepinephrine-induced contraction in all groups, but relatively more in WKY than SHR arteries. The attenuation of norepinephrine-induced contraction after Ca2+-dependent Cl− channels blockade was partially reduced in 12-month-old WKY rats, but substantially diminished in 12-month-old SHR. IAA effect was enhanced after NO synthase inhibition but decreased by ageing. In 20-month-old WKY rats norepinephrine-induced contraction was not affected by IAA but was almost abolished after cyclooxygenase inhibition by indomethacin or niflumic acid. In conclusion, contribution of Ca2+-dependent Cl− channels to norepinephrine-induced contraction diminished with age, hypertension development, and/or NO synthesis inhibition. Ca2+-dependent Cl− channels are important for maintenance of normal vascular tone while their inactivation/closing might be a pathological mechanism.

The Regulatory Role of Nuclear Factor Kappa B in the Heart of Hereditary Hypertriglyceridemic Rat

Activation of nuclear factor-κB (NF-κB) by increased production of reactive oxygen species (ROS) might induce transcription and expression of different antioxidant enzymes and also of nitric oxide synthase (NOS) isoforms. Thus, we aimed at studying the effect of NF-κB inhibition, caused by JSH-23 (4-methyl-N 1-(3-phenyl-propyl)-benzene-1,2-diamine) injection, on ROS and NO generation in hereditary hypertriglyceridemic (HTG) rats. 12-week-old, male Wistar and HTG rats were treated with JSH-23 (bolus, 10 μmol, i.v.). After one week, blood pressure (BP), superoxide dismutase (SOD) activity, SOD1, endothelial NOS (eNOS), and NF-κB (p65) protein expressions were higher in the heart of HTG rats compared to control rats. On the other hand, NOS activity was decreased. In HTG rats, JSH-23 treatment increased BP and heart conjugated dienes (CD) concentration (measured as the marker of tissue oxidative damage). Concomitantly, SOD activity together with SOD1 expression was decreased, while NOS activity and eNOS protein expression were increased significantly. In conclusion, NF-κB inhibition in HTG rats led to decreased ROS degradation by SOD followed by increased oxidative damage in the heart and BP elevation. In these conditions, increased NO generation may represent rather a counterregulatory mechanism activated by ROS. Nevertheless, this mechanism was not sufficient enough to compensate BP increase in HTG rats.

Vascular reactivity of arteria femoralis in adult and aged spontaneously hypertensive and Wistar-Kyoto rats.

AIM The relationship of age and hypertension on endothelial dysfunction and increased responses to vasoconstrictor stimuli. BACKGROUND Hypertension is a disease accompanied by endothelial dysfunction and is characterized by an impaired vascular reactivity and enhanced activity of sympathetic nervous system. MATERIALS AND METHODS In our experiment, we used spontaneously hypertensive rats representing model of essential hypertension and the Wistar-Kyoto rats as normotensive strain. Femoral arteries of adult and aged rats were put into the chamber of Mulvany-Halpern isometric myograph. As the nutrient solution, the modified Krebs-Henseleit solution having temperature 37 °C and bubbled with O2 was used. After 30 minutes stabilization of blood vessels, a dose-dependent curve of norepinephrine response was recorded (concentrations 3x10-8 M, 10-7 M, 3x10-7 M, 10-6 M, 3x10-6 M, 10-5 M, 3x10-5 M, 10-4 M), followed by a dose-dependent curve of acetylcholine response (concentrations 3x10-8 M, 10-7 M, 3x10-7 M, 10-6 M, 3x10-6 M). RESULTS Our experiments recorded an increased reactivity to contraction stimuli in spontaneously hypertensive animals. Vascular reactivity to norepinephrine at 5 month and 12 month old rats from the same group was not significantly affected. Our experiments on the other hand, did not record a reduced endothelium-dependent relaxation in hypertensive compared to normotensive animals, neither in different age groups. CONCLUSIONS Increased norepinephrine-induced contraction occurs even before development of reduced acetylcholine-induced relaxation in SHR rats. We predict that in our experiment hypertension plays a bigger role in the development of endothelial dysfunction than aging (Fig. 2, Ref. 22).

Trends in vascular pharmacology research in the Department of Pharmacology and Clinical Pharmacology, Faculty of Medicine, Comenius University, Bratislava

Trends in vascular pharmacology research in the Department of Pharmacology and Clinical Pharmacology, Faculty of Medicine, Comenius University, Bratislava Research in the Department of Pharmacology started to focus intensively on fetal circulation in the 60s. Results of experiments contributed to clarification of the conversion of fetal circulation type to the adult type: the mechanism of the ductus arteriosus closure, examination of fetal and neonatal pulmonary vessel responses. In the early 80s, increased attention was dedicated to fetal vascular endothelium, later on to vascular reactivity in relation to the endothelium in adult animals. We developed original models of vascular endothelial damage using the perfusion method (repeated vasoconstrictive stimuli, deendothelization by air bubbles). We developed a new technique for in vitro endothelial loss quantification on Millipore filters. Under in vitro conditions, the protective effects of sulodexide and pentoxifylline on vascular endothelium were evaluated. In recent years were studied protective effects of selected substances in vivo in models of endothelial damage (e.g. stress, toxic tissue damage, diabetes mellitus, hypertension). The role of potassium channels in the hypertension model was studied in cooperation with the Czech Academy of Sciences. Assessment of vascular reactivity in the diabetic model was significantly improved by computer. In addition to experimental work, the department is solving problems of clinical pharmacology - especially drug risk evaluation (non-steroidal anti-inflammatory drugs). Recently, we have dealt with pharmacoepidemiological studies in geriatric patients and with cardiovascular risk of NSAIDs in relation to pharmacotherapy. The results of these studies may be an impulse for targeted problem solving in our experiments.

Erratum to “Contribution of Ca2

[This corrects the article DOI: 10.1155/2014/289361.].

IMPAIRED REGULATION OF REACTIVE OXYGEN SPECIES PRODUCTION BY NF-{KAPPA}B INHIBITION IN HEREDITARY HYPERTRIGLYCERIDEMIC RATS: PP.13.487

Objective: Activation of nuclear factor-kappa B (NF-kappa B) by increased production of reactive oxygen species (ROS) was documented by several studies. Consequently, NF-kappa B might induce increased transcription and expression of different antioxidant enzymes and nitric oxide synthase (NOS) isoforms as well. Design and Method: Thus, the goal of our study was to investigate the effect of NF-kappa B inhibition, caused by JSH-23 (4-methyl-N1-(3-phenyl-propyl)-benzene-1,2-diamine) injection, on reactive oxide species production, nitric oxide generation and blood pressure regulation in hereditary hypertriglyceridemic rats (hHTG). Adult 12-week-old male hHTG rats were treated with JSH-23 (bolus, 10 uM, i. v). After one week, systolic blood pressure was measured by tail-cuff plethysmography. Total NOS activity was determined by measuring the formation of L-[3H] citrulline from L-[3H] arginine in the heart, aorta and kidney. Protein expressions of endothelial NOS (eNOS) and NF-kappa B were determined in the heart and kidney by Western blot analysis. Reduced glutathione (GSH) levels and concentration of conjugated dienes (CD), a marker of oxidative damage, were measured in the same tissues. Results: At the end of experiment blood pressure increased significantly in hHTG rats treated with JSH-23 in comparison with age-matched untreated rats. JSH-23 treatment increased total NOS activity of hHTG rats in the heart only. Increased expression of eNOS was, however, determined also in the kidney. JSH-23 failed to affect NF-kappa B subunits expression. While increased CD concentration was seen in all tissues investigated, GSH levels were not changed by JSH-23 treatment. Conclusions: Our data clearly showed that NF-kappa B inhibition leads to increased ROS production followed by increased oxidative damage and elevated blood pressure. In these conditions, increased NO production may represent a compensatory mechanism activated due to the blood pressure elevation. Thus, the inhibition of NF-kappa B might not have allways beneficial effect, especially during the conditions with increased ROS production.