Zsuzsanna Miklós

Effects of combined sex hormone replacement therapy on small artery biomechanics in pharmacologically ovariectomized rats

OBJECTIVES The purpose of this study was to determine the effects of long-term combined sexual hormone replacement therapy on the biomechanical properties of the small artery wall in castrated female rats. METHODS 30 non-pregnant mature female Sprague-Dawley rats were pharmacologically ovariectomized with 750 microg/kg triptorelin im. every 4th week. Ten of them received combined hormone replacement in form of 15 mg/kg medroxyprogesterone acetate (MPA) im. every 2 weeks and 450 microg/kg estradiol propionate im. once a week. Ten castrated animals received MPA only. Ten control, castrated animals were given the vehicles of these steroids. Ten other animals were kept parallelly, receiving the vehicles of all drugs (control animals). After 12 weeks of treatment cylindrical segments of the saphenous artery were isolated and cannulated at both ends and subjected to in vitro microarteriographic test. Pressure diameter curves, in the range of 0-200 mmHg, were recorded from segments in normal Krebs-Ringer (nKR) solution, in contraction with norepinephrine (1.6 x 10(-5) M), and then in relaxation with papaverine (2.8 x 10(-5) M). Biomechanical parameters were calculated based on the pressure diameter curves. RESULTS Combined hormone replacement therapy significantly increased the passive diameter of small arteries, as compared to those from ovariectomized animals without hormone replacement. MPA monotherapy did not alter the vessel diameter, the inner radii at 100 mmHg intraluminal pressure were, 300+/-9 microm in the control castrated, 340+/-7 microm in the estradiol + MPA replaced and 306+/-8 microm in the MPA treated groups (P < 0.05 between the control castrated and the combined treatment groups). The vascular reactivity to norepinephrine or papaverine was not changed significantly either by combined hormone replacement or by MPA monotherapy when compared with ovariectomized controls. No significant alterations were found in wall thickness and distensibility. CONCLUSIONS These results suggest that chronic medroxyprogesterone pretreatment does not influence the geometric, elastic and contractile properties of small arteries in castrated female rats. The combination of MPA + estradiol increased the morphological lumen: the morphological vasodilatation induced by estrogen, described earlier, was not affected by the addition of this progestin to the regimen.

The effects of postmenopausal hormone replacement therapy on hemostatic variables: a meta-analysis of 46 studies.

The aim of the study was to summarize and reanalyze all available data from the literature to study the overall effect of postmenopausal hormone replacement therapy (HRT) and its various forms on hemostatic variables. Studies were identified from literature searches by Medline and Index Medicus, review articles and personal communications. Reference lists of all articles were checked to find additional studies. Principal investigators were contacted and asked to provide additional data if required. Data were collected separately for each factor of the hemostatic system. Studies written in any language were included. Each collection of studies was analyzed using standard methods for meta-analysis. A total of 76 arms of 48 studies were eligible for analysis. This included 6119 women using HRT and 24 974 non-users. The age of investigated women was 40–68 years. HRT was associated with significantly decreased levels of fibrinogen, factor VIII, antithrombin III, and proteins C and S, but significantly increased plasminogen levels. HRT with estrogen alone or in combination with progestins, oral vs. transdermal regimens, different estrogen preparations and various progestins induced significantly different changes in many cases. In conclusion, HRT was associated with changes that could explain the increased rate of venous thrombotic events, and also with some changes that could account for beneficial vascular effects. Surprisingly, the addition of progestins induced favorable changes in many cases. Also, transdermal use was associated with more beneficial effects than oral regimens in some cases.

Effect of ovariectomy and hormone replacement therapy on small artery biomechanics in angiotensin-induced hypertension in rats.

Objectives To test the effects of chronic angiotensin II administration on blood pressure and small artery biomechanics in the female sex hormone-depleted state (proposed to increase cardiovascular vulnerability) and with hormone replacement. Design Biomechanical properties of saphenous artery segments from ovariectomized (n = 10), ovariectomized + chronically angiotensin II infused-(n = 10), and ovariectomized + chronically angiotensin II-infused + sex hormone-replaced (n = 10) rats were studied. Methods Surgical ovariectomy was performed. Osmotic minipumps were used for chronic angiotensin II infusion (100 ng/min per kg). For hormone replacement therapy, oestradiol-propionate, 450 μg/kg for 7 days + medroxyprogesterone-acetate, 15 mg/kg for 14 days were given, intramuscularly. After 4 weeks, cylindrical segments of the saphenous artery were prepared and subjected to in-vitro microarteriographic measurements. Pressure – diameter curves (0–200 mmHg) were recorded in Krebs–Ringer solution, with smooth muscle contracted (norepinephrine, 16 μmol/l) and with relaxed (papaverine, 28 μmol/l). Results Chronic angiotensin II infusion significantly reduced the inner radius (at 100 mmHg: 298 ± 17 μm versus 347 ± 7 μm, P < 0.001), while wall-thickness did not change. Hormone replacement restored the morphological radius (333 ± 7 μm). Angiotensin II infusion slightly increased the full contraction range of the segments (defined as the percentage difference between fully contracted and fully relaxed diameters), which was further significantly increased by hormone replacement (39 ± 4%, 46 ± 8%, 62 ± 7% at 100 mmHg, in the three groups, respectively; P < 0.05). Despite unaltered stiffness in relaxed state, elastic moduli computed for the contracted segments decreased after hormone replacement. Conclusions These observations give further experimental support to the hypothesis that sex hormone replacement might be useful in preventing the development and/or stabilization of postmenopausal hypertension, as well as in treating existing disease.

Early cardiac dysfunction is rescued by upregulation of SERCA2a pump activity in a rat model of metabolic syndrome

Various components of metabolic syndrome associate with cardiac intracellular calcium ( Cai 2+ ) mishandling, a precipitating factor in the development of heart failure. We aimed to provide a thorough description of early stage Cai 2+ ‐cycling alterations in the fructose‐fed rat, an experimental model of the disorder, where insulin resistance, hypertension and dyslipidaemia act cooperatively on the heart.

Hearts of surviving MLP-KO mice show transient changes of intracellular calcium handling

The muscle Lim protein knock-out (MLP-KO) mouse model is extensively used for studying the pathophysiology of dilated cardiomyopathy. However, explanation is lacking for the observed long survival of the diseased mice which develop until adulthood despite the gene defect, which theoretically predestines them to early death due to heart failure. We hypothesized that adaptive changes of cardiac intracellular calcium (Cai2+) handling might explain the phenomenon. In order to study the progression of changes in cardiac function and Cai2+ cycling, myocardial Cai2+-transients recorded by Indo-1 surface fluorometry were assessed with concomitant measurement of hemodynamic performance in isolated Langendorff-perfused hearts of 3- and 9-month old MLP-KO animals. Hearts were challenged with β-agonist isoproterenol and the sarcoplasmic reticular Ca2+-ATPase (SERCA2a) inhibitor cyclopiazonic acid (CPA). Cardiac mRNA content and levels of key Ca2+ handling proteins were also measured. A decline in lusitropic function was observed in 3-month old, but not in 9-month old MLP-KO mice under unchallenged conditions. β-adrenergic responses to isoproterenol were similar in all the studied groups. The CPA induced an increase in end-diastolic Cai2+-level and a decrease in Ca2+-sequestration capacity in 3-month old MLP-KO mice compared to age-matched controls. This unfavorable condition was absent at 9 months of age. SERCA2a expression was lower in 3-month old MLP-KO than in the corresponding controls and in 9-month old MLP-KO hearts. Our results show time-related recovery of hemodynamic function and an age-dependent compensatory upregulation of Cai2+ handling in hearts of MLP-KO mice, which most likely involve the normalization of the expression of SERCA2a in the affected hearts.

Depressed calcium cycling contributes to lower ischemia tolerance in hearts of estrogen-deficient rats.

ObjectiveEstrogens enhance ischemia tolerance (IT) in the myocardium, the mechanism of which remains unclear. We investigated the effects of long-term estrogen deprivation on the intracellular calcium (Ca2+i) transient of the heart and its possible influence on IT. MethodsHearts of ovariectomized (OVX) and sham-operated (control) adult female rats (some receiving estrogen therapy) were studied 10 weeks after surgical operation: control (n = 8), OVX (n = 10), sham-operated estrogen-substituted (n = 7), and ovariectomized estrogen-substituted (n = 9). In vivo heart function was assessed by echocardiography, whereas Ca2+i transients were recorded, concomitantly with left ventricular pressure and coronary flow, by Indo-1 surface fluorometry in isolated Langendorff-perfused hearts. Isolated hearts were subjected to a 30-minute global ischemia–30-minute reperfusion protocol. Left ventricular expression of myocardial sarcoendoplasmic reticulum Ca2+-ATPase (SERCA2a), phospholamban (PLB), and Ser16-phosphorylated PLB was measured. ResultsOvariectomy did not influence resting cardiac function in vivo or ex vivo. However, Ca2+ removal was slower. During ischemia, Ca2+i elevation and ischemic contracture were more pronounced after ovariectomy. Postischemic restitution of inotropic function (developed pressure; +dP/dtmax) and lusitropic function (−dP/dtmax) and Ca2+i transient recovery (amplitude; ±dCa2+i/dtmax) were decreased in OVX hearts. Sarcoendoplasmic reticulum Ca2+-ATPase expression was unaltered, whereas PLB and Ser16-phosphorylated PLB levels were higher after ovariectomy. All effects of ovariectomy were restored by estrogen therapy. ConclusionsOvariectomy impairs myocardial Ca2+ removal by increasing the expression of the SERCA2a inhibitor PLB. Defective Ca2+ transport causes ischemic Ca2+i overload and insufficient postischemic recovery of Ca2+i transients, which entail depressed hemodynamic restitution. Protection of intact Ca2+ cycling in the myocardium by estrogens plays a major role in enhancing IT.

Mathematical modelling of the calcium-left ventricular pressure relationship in the intact diabetic rat heart

Aim:  The objective was to characterize cross‐bridge kinetics from the cytoplasmic calcium ion concentration ([Ca2+]i) and the left ventricular pressure (LVP) in the early‐stage diabetic rat heart under baseline conditions and upon β‐adrenergic stimulation.

LPA1 receptor-mediated thromboxane A2 release is responsible for lysophosphatidic acid-induced vascular smooth muscle contraction

Lysophosphatidic acid (LPA) has been recognized recently as an endothelium‐dependent vasodilator, but several lines of evidence indicate that it may also stimulate vascular smooth muscle cells (VSMCs), thereby contributing to vasoregulation and remodeling. In the present study, mRNA expression of all 6 LPA receptor genes was detected in murine aortic VSMCs, with the highest levels of LPA1, LPA2, LPA4, and LPA6. In endothelium‐denuded thoracic aorta (TA) and abdominal aorta (AA) segments, 1‐oleoyl‐LPA and the LPA1–3 agonist VPC31143 induced dose‐dependent vasoconstriction. VPC31143‐induced AA contraction was sensitive to pertussis toxin (PTX), the LPA1&3 antagonist Ki16425, and genetic deletion of LPA1 but not that of LPA2 or inhibition of LPA3, by diacylglycerol pyro‐phosphate. Surprisingly, vasoconstriction was also diminished in vessels lacking cyclooxygenase‐1 [COX1 knockout (KO)] or the thromboxane prostanoid (TP) receptor (TP KO). VPC31143 increased thromboxane A2 (TXA2) release from TA of wild‐type, TP‐KO, and LPA2‐KO mice but not from LPA1‐KO or COX1‐KO mice, and PTX blocked this effect. Our findings indicate that LPA causes vasoconstriction in VSMCs, mediated by LPA1‐, Gi‐, and COX1‐dependent autocrine/paracrine TXA2 release and consequent TP activation. We propose that this new‐found interaction between the LPA/LPA1 and TXA2/TP pathways plays significant roles in vasoregulation, hemostasis, thrombosis, and vascular remodeling. —Dancs, P. T., Ruisanchez, E., Balogh, A., Panta, C. R., Miklós, Z., Nüsing, R. M., Aoki, J., Chun, J., Offermanns, S., Tigyi, G., Benyó, Z. LPA1 receptor‐mediated thromboxane A2 release is responsible for lysophos‐phatidic acid‐induced vascular smooth muscle contraction. FASEB J. 31, 1547–1555 (2017) www.fasebj.org