bluuebunny/crossref_metadata_2025 huggingface dataset:
Antioxidant pyruvate inhibits cardiac formation of reactive oxygen species through changes in redox state
Authors: Bassenge Eberhard , Sommer Olaf , Schwemmer Michael , Bünger Rolf
Published: December 2017

Myocardial ischemia-reperfusion is associated with bursts of reactive oxygen species (ROS) such as superoxide radicals (O2 −·). Membrane-associated NADH oxidase (NADHox) activity is a hypothetical source of O2 −·, implying the NADH concentration-to-NAD+ concentration ratio ([NADH]/[NAD+]) as a determinant of ROS. To test this hypothesis, cardiac NADHox and ROS formation were measured as influenced by pyruvate or l-lactate. Pre- and postischemic Langendorff guinea pig hearts were perfused at different pyruvate/l-lactate concentrations to alter cytosolic [NADH]/[NAD+]. NADHox and ROS were measured with the use of lucigenin chemiluminescence and electron spin resonance, respectively. In myocardial homogenates, pyruvate (0.05, 0.5 mM) and the NADHox blocker hydralazine markedly inhibited NADHox (16 ± 2%, 58 ± 9%). In postischemic hearts, pyruvate (0.1–5.0 mM) dose dependently inhibited ROS up to 80%. However,l-lactate (1.0–15.0 mM) stimulated both basal and postischemic ROS severalfold. Furthermore,l-lactate-induced basal ROS was dose dependently inhibited by pyruvate (0.1–5.0 mM) and not the xanthine oxidase inhibitor oxypurinol. Pyruvate did not inhibit ROS from xanthine oxidase. The data suggest a substantial influence of cytosolic NADH on cardiac O2 −· formation that can be inhibited by submillimolar pyruvate. Thus cytotoxicities due to cardiac ischemia-reperfusion ROS may be alleviated by redox reactants such as pyruvate.
Cerebral hemodynamics during arterial and CO2 pressure changes: in vivo prediction by a mathematical model
Authors: Ursino M. , Ter Minassian A. , Lodi C. A. , Beydon L.
Published: December 2017

The aim of this work was to analyze changes in cerebral hemodynamics and intracranial pressure (ICP) evoked by mean systemic arterial pressure (SAP) and arterial CO2 pressure (PaCO2 ) challenges in patients with acute brain damage. The study was performed by means of a new simple mathematical model of intracranial hemodynamics, particularly aimed at routine clinical investigation. The model was validated by comparing its results with data from transcranial Doppler velocity in the middle cerebral artery ( V MCA) and ICP measured in 44 tracings on 13 different patients during mean SAP and PaCO2 challenges. The validation consisted of individual identification of 6 parameters in all 44 tracings by means of a best fitting algorithm. The parameters chosen for the identification summarize the main aspects of intracranial dynamics, i.e., cerebrospinal fluid circulation, intracranial elastance, and cerebrovascular control. The results suggest that the model is able to reproduce the measured time patterns of V MCA and ICP in all 44 tracings by using values for the parameters that lie within the ranges reported in the pathophysiological literature. The meaning of parameter estimates is discussed, and comments on the main virtues and limitations of the present approach are offered.
BKCa channels compensate for loss of NOS-dependent coronary artery relaxation in cardiomyopathy
Authors: Clark Shawn G. , Fuchs Leslie C.
Published: December 2017

Previously, we showed that development of myocardial necrotic lesions is associated with impaired endothelium-dependent coronary artery relaxation in young cardiomyopathic hamsters. Since active necrosis declines with aging, this study was designed to determine whether coronary artery endothelium-dependent relaxation to ACh is restored and to identify the mechanisms mediating this effect. Intraluminal diameter was recorded in coronary arteries (150–250 μm) from control (C, 297 ± 5 days old) and cardiomyopathic (M, 296 ± 4 days old) hamsters. Relaxation to ACh (10−9–3 × 10−5M) was similar in vessels from C and M hamsters. However, mechanisms mediating relaxation to ACh were altered. Inhibition of nitric oxide synthase (NOS) activity with N-nitro-l-arginine (1 mM) had a greater inhibitory effect in vessels from C hamsters, indicating a reduction in NOS-dependent relaxation in vessels from M hamsters. Conversely, inhibition of large Ca2+-dependent K+ (BKCa) channels with charybdotoxin (CTX, 0.1 μM) had a greater inhibitory effect in vessels from M hamsters. In the presence of both N-nitro-l-arginine and CTX, relaxation to ACh was abolished in both groups. CTX (0.1 μM) produced a 50 ± 4 and 30 ± 3% contraction of vessels from M and C hamsters, respectively, indicating an enhanced role for BKCa channels in regulation of coronary artery tone in M hamsters. Finally, vasodilatory cyclooxygenase products contributed to ACh-induced relaxation in vessels from M, but not C, hamsters. In conclusion, NOS-dependent relaxation of coronary small arteries is reduced in the late stage of cardiomyopathy. An increase in relaxation mediated by BKCa channels and vasodilatory cyclooxygenase products compensates for this effect.
Clinical evidence for myocardial derecruitment downstream from severe stenosis: pressure-flow control interaction
Authors: Sambuceti Gianmario , Marzilli Mario , Mari Andrea , Marini Cecilia , Marzullo Paolo , Testa Roberto , Raugei Isabella , Papini Micaela , Schluter Mathis , L'Abbate Antonio
Published: December 2017

To verify the interaction between coronary pressure (CP) and blood flow (CBF) control, we studied nine candidates for angioplasty of an isolated lesion of the left anterior descending coronary artery [i.e., percutaneous transluminal coronary angioplasty (PTCA)]. CBF (i.e., flow velocity × coronary cross-sectional area at the Doppler tip) and CP were monitored during washout of 2–5 mCi of133Xe after bolus injection into the left main artery before and after PTCA. Xe mean transit time (MTT) was calculated as the area under the time-activity curve, acquired by a gamma camera, divided by the dose obtained from a model fit of the Xe curve in the anterior wall. CBF response to intracoronary adenosine (2 mg) was also assessed. PTCA increased baseline CBF (from 14.5 ± 9.4 to 20 ± 8 ml/min, P < 0.01), coronary flow reserve (from 1.52 ± 0.24 to 2.33 ± 0.8, P < 0.01), and CP (from 64 ± 9 to 100 ± 10 mmHg, P < 0.05). MTT decreased from 89 ± 32 to 70 ± 19 s ( P < 0.05) after PTCA; however, MTT and CBF changes were not correlated ( r = −0.09, not significant). Inasmuch as MTT is the ratio of distribution volume to CBF, MTT × CBF was used as an index of perfused myocardial volume. Volume increased after PTCA from 23 ± 18 to 56 ± 30 ml. A direct correlation was observed between the percent increase in distal CP and percent increase in perfused volume ( r = 0.91, P < 0.01). Thus low CP was not associated with exhaustion of flow reserve but, rather, with reduction of perfused myocardial volume. These data suggest that, in the presence of a severe coronary stenosis, derecruitment of vascular units occurs that is proportional to the decrease in driving pressure. Residual perfused units maintain a vasomotor tone, thus explaining the paradoxical persistence of coronary reserve.
Antiproliferative effect of UTP on human arterial and venous smooth muscle cells
Authors: White Pamela J. , Kumari Rajendra , Porter Karen E. , London Nicholas J. M. , Ng Leong L. , Boarder Michael R.
Published: December 2017

We have investigated the hypothesis that responses associated with proliferation are regulated by extracellular nucleotides such as ATP and UTP in cultured human vascular smooth muscle cells (VSMC) derived from internal mammary artery (IMA) and saphenous vein (SV). Platelet-derived growth factor (PDGF), ATP, and UTP each generated an increase in cytosolic free Ca2+concentration ([Ca2+]i) in both IMA- and SV-derived cells in the absence of detectable inositol 1,4,5-trisphosphate production. ATP alone had no effect on [3H]thymidine incorporation into DNA, but with a submaximal concentration of PDGF it raised [3H]thymidine incorporation in SV- but not IMA-derived cells. UTP alone also was without effect on [3H]thymidine incorporation or cell number. However, in both SV- and IMA-derived cells, UTP reduced the PDGF-stimulated [3H]thymidine response and PDGF-stimulated cell proliferation. This cannot be explained by an inhibitory effect on the p42/p44 mitogen-activated protein kinase (MAPK) cascade, since this response to PDGF was not attenuated by UTP. We conclude that, in human VSMC of both arterial and venous origin, UTP acts as an anti-proliferative regulator.
Adventitia-derived nitric oxide in rat aortas exposed to endotoxin: cell origin and functional consequences
Authors: Kleschyov Andrei L. , Muller Bernard , Keravis Thérèse , Stoeckel Marie-Elisabeth , Stoclet Jean-Claude
Published: December 2017

The role of adventitial cells in bacterial lipopolysaccharide (LPS)-induced vascular nitric oxide (NO) overproduction has been largely ignored. In rat aortas exposed to LPS in vitro or in vivo, it was found that adventitia contained the major part of NO synthase (NOS)-2 protein (Western blot and immunohistochemistry) and generated the largest amount of NO (electron paramagnetic resonance spin trapping). NOS-2 immunoreactive cells were mainly resident macrophages at an early stage (5 h, in vitro or in vivo) and fibroblasts at a later stage (20 h, in vitro). Adventitial NOS-2 activity largely accounted for 1) the relaxing effect of l-arginine in rings exposed to LPS in vivo, 2) generation of an “NO store” revealed by N-acetylcysteine-induced relaxation, and 3) formation of protein-bound dinitrosyl iron complexes in the medial layer of aortic rings exposed to LPS in vitro. In conclusion, the adventitia is a powerful source of NO triggered by LPS in the rat aorta. This novel source of NO has an important impact on smooth muscle function and might be implicated in various inflammatory diseases.
PR-39, a potent neutrophil inhibitor, attenuates myocardial ischemia-reperfusion injury in mice
Authors: Hoffmeyer Michaela R. , Scalia Rosario , Ross Chris R. , Jones Steven P. , Lefer David J.
Published: December 2017

We investigated the effects of PR-39, a recently discovered neutrophil inhibitor, in a murine model of myocardial ischemia-reperfusion injury. Mice were given an intravenous injection of vehicle ( n = 12) or PR-39 ( n = 9) and subjected to 30 min of coronary artery occlusion followed by 24 h of reperfusion. In addition, the effects of PR-39 on leukocyte rolling and adhesion were studied utilizing intravital microscopy of the rat mesentery. The area-at-risk per left ventricle was similar in vehicle- and PR-39-treated mice. However, myocardial infarct per risk area was significantly ( P < 0.01) reduced in PR-39 treated hearts (21.0 ± 3.8%) compared with vehicle (47.1 ± 4.8%). Histological analysis of ischemic reperfused myocardium demonstrated a significant ( P < 0.01) reduction in polymorphonuclear neutrophil (PMN) accumulation in PR-39-treated hearts ( n = 6, 34.3 ± 1.7 PMN/mm2) compared with vehicle-treated myocardium ( n = 6, 59.7 ± 3.1 PMN/mm2). In addition, PR-39 significantly ( P < 0.05) attenuated leukocyte rolling and adherence in rat inflamed mesentery. These results indicate that PR-39 inhibits leukocyte recruitment into inflamed tissue and attenuated myocardial reperfusion injury in a murine model of myocardial ischemia-reperfusion.
Diastolic wall stress and ANG II in cardiac hypertrophy and gene expression induced by volume overload
Authors: Yamakawa Hiroshi , Imamura Takuroh , Matsuo Takeshi , Onitsuka Hisamitsu , Tsumori Yoko , Kato Johji , Kitamura Kazuo , Koiwaya Yasushi , Eto Tanenao
Published: December 2017

We investigated the effects of diastolic wall stress (WS) and angiotensin II (ANG II) on the left ventricular (LV) hypertrophy (LVH) induced by volume overload and on the gene expression of LV adrenomedullin (AM) and atrial natriuretic peptide (ANP) in volume overload. Diastolic WS was pharmacologically manipulated with (candesartan) or without (calcium channel blocker manidipine) inhibition of ANG II type 1 receptors in aortocaval-shunted rats over 6 wk. Diastolic WS reached a plateau at 2 wk and subsequently declined regardless of further LVH. Although diastolic WS was decreased to a similar extent by both compounds, candesartan blunted LVH over 6 wk, whereas manidipine blunted LVH at 2 wk but not after 4 wk. Levels of AM and ANP gene expression increased as LVH developed but were completely suppressed by candesartan over 6 wk. ANP expression level was also attenuated by manidipine over 6 wk, whereas AM expression level was suppressed at 2 wk but not after 4 wk by manidipine. We concluded that diastolic WS and ANG II might be potent stimuli for the LVH and LV AM and ANP gene expression in volume overload and that diastolic WS could be relatively involved in the early LVH and in the gene expression of ANP rather than of AM.
Interleukin-6 induces demargination of intravascular neutrophils and shortens their transit in marrow
Authors: Suwa Tatsushi , Hogg James C. , English Dean , Van Eeden Stephan F.
Published: December 2017

Recombinant human interleukin-6 (IL-6) causes both a thrombocytosis and leukocytosis. The thrombocytosis is caused by an accelerating thrombocytopoiesis, but the mechanism of the leukocytosis is unknown. This study was designed to determine the relative contributions of marrow stimulation and intravascular demargination to the IL-6 induced neutrophilia. IL-6 (2 μg/kg), administered intravenously to rabbits, caused a biphasic neutrophilia with an initial peak at 3 h and a second peak at 9 h. Using the thymidine analog 5′-bromo-2′-deoxyuridine (BrdU) to label dividing polymorphonuclear leukocytes (PMNs) in the bone marrow, we showed that IL-6 treatment mobilizes PMNs from the marginated pool into the circulating pool at 2–6 h with a decrease inl-selectin expression on PMNs and also accelerates the release of PMNs from the postmitotic pool in the bone marrow at 12–24 h. We have concluded that IL-6 causes a biphasic neutrophilia wherein the first peak results from the mobilization of PMNs into the circulating pool from the marginated pool and the second peak results from an accelerated bone marrow release of PMNs.
Inhibition of coronary thrombosis and local inflammation by a noncarbohydrate selectin inhibitor
Authors: Zoldhelyi Pierre , Beck Pamela J. , Bjercke Robert J. , Ober Judy C. , Hu X. , McNatt Janice M. , Akhtar Salman , Ahmed Mohammed , Clubb Fred J. , Chen Zhi-Qiang , Dixon Richard A. F. , Yeh Edward T. H. , Willerson James T.
Published: December 2017

We tested the hypothesis that selectin inhibition with blocking antibodies or a small-molecular-weight inhibitor of L-, P-, and E-selectin, methoxybenzoylpropionic acid (MBPA), prevents thrombus formation in a canine coronary Folts' model. Cyclic flow variations (CFVs) were induced by crush injury and constriction of the left anterior descending coronary artery in dogs. Systemic infusion of antibodies to P- and L-selectin abolished CFVs, respectively, in 50% and 17% of treated dogs [ P = not significant (NS)]. The combination of P- and L-selectin antibodies suppressed CFVs in 60% of treated dogs ( P = NS). In contrast, systemic selectin blockade by intravenous infusion or local adventitial application of MBPA markedly reduced CFVs and, in addition, reduced myocardial myeloperoxidase (MPO) activity. We conclude that inhibition of L-, P-, and E-selectin binding by a small-molecular-weight, noncarbohydrate compound markedly reduces arterial thrombosis, whereas systemic administration of antibodies to L- and P-selectin fail to reproduce this antithrombotic effect. These results underscore the role of selectins in the pathogenesis of arterial thrombosis under high shear stress and suggest that inhibition of P- and L- selectin may not suffice to prevent thrombus formation in this model. The role of E-selectin in thrombus formation in this model awaits further testing.
Electrical activation of endothelium evokes vasodilation and hyperpolarization along hamster feed arteries
Authors: Emerson Geoffrey G. , Segal Steven S.
Published: December 2017

Endothelial cells are considered electrically unexcitable. However, endothelium-dependent vasodilators (e.g., acetylcholine) often evoke hyperpolarization. We hypothesized that electrical stimulation of endothelial cells could evoke hyperpolarization and vasodilation. Feed artery segments (resting diameter: 63 ± 1 μm; length 3–4 mm) of the hamster retractor muscle were isolated and pressurized to 75 mmHg, and focal stimulation was performed via microelectrodes positioned across one end of the vessel. Stimulation at 16 Hz (30–50 V, 1-ms pulses, 5 s) evoked constriction (−20 ± 2 μm) that spread along the entire vessel via perivascular sympathetic nerves, as shown by inhibition with tetrodotoxin, ω-conotoxin, or phentolamine. In contrast, stimulation with direct current (30 V, 5 s) evoked vasodilation (16 ± 2 μm) and hyperpolarization (11 ± 1 mV) of endothelial and smooth muscle cells that conducted along the entire vessel. Conducted responses were insensitive to preceding treatments, atropine, or Nω-nitro-l-arginine, yet were abolished by endothelial cell damage (with air). Injection of negative current (≤1.6 nA) into a single endothelial cell reproduced vasodilator responses along the entire vessel. We conclude that, independent of ligand-receptor interactions, endothelial cell hyperpolarization evokes vasodilation that is readily conducted along the vessel wall. Moreover, electrical events originating within a single endothelial cell can drive the relaxation of smooth muscle cells throughout the entire vessel.
Cardiac vagal and sympathetic efferent discharges are differentially modified by stretch of skeletal muscle
Authors: Murata Jun , Matsukawa Kanji
Published: December 2017

We directly measured cardiac vagal efferent nerve activity (CVNA) and cardiac sympathetic efferent nerve activity (CSNA) in cats decerebrated at the level of the precollicular-premammillary body while the hindlimb or the triceps surae muscle was passively stretched. CVNA gradually decreased during passive stretch of the hindlimb, and this decrease was sustained throughout the stretch. CSNA increased at the onset of passive stretch, but this increase was not sustained. CVNA and CSNA responded differentially to graded passive stretches of the triceps surae muscle as well as the hindlimb. The sustained decrease in CVNA but not the initial increase in CSNA became greater depending on muscle length and developed tension. The time course and direction of the cardiac autonomic responses to muscle stretch were not affected by partial sinoaortic denervation, although the magnitude of the CSNA response was augmented. We conclude that the muscle mechanoreflex contributes to differential regulation of cardiac parasympathetic and sympathetic efferent discharges during passive stretch of skeletal muscle irrespective of arterial baroreceptor input.
Role of mitochondrial and sarcolemmal KATPchannels in ischemic preconditioning of the canine heart
Authors: Sanada Shoji , Kitakaze Masafumi , Asanuma Hiroshi , Harada Kengo , Ogita Hisakazu , Node Koichi , Takashima Seiji , Sakata Yasuhiko , Asakura Masanori , Shinozaki Yoshiro , Mori Hidezo , Kuzuya Tsunehiko , Hori Masatsugu
Published: December 2017

We tested whether mitochondrial or sarcolemmal ATP-sensitive K+(KATP) channels play a key role in ischemic preconditioning (IP) in canine hearts. In open-chest beagle dogs, the left anterior descending artery was occluded four times for 5 min each with 5-min intervals of reperfusion (IP), occluded for 90 min, and reperfused for 6 h. IP as well as cromakalim and nicorandil (nonspecific KATPchannel openers) markedly limited infarct size (6.3 ± 1.2, 8.9 ± 1.9, and 7.2 ± 1.6%, respectively) compared with the control group (40.9 ± 4.1%). A selective mitochondrial KATPchannel blocker, 5-hydroxydecanoate, partially blunted the limitation of infarct size in the animals subjected to IP and those treated with cromakalim and nicorandil (21.6 ± 3.8, 25.1 ± 4.6, and 19.8 ± 5.2%, respectively). A nonspecific KATPchannel blocker, glibenclamide, completely abolished the effect of IP (38.5 ± 6.2%). Intracoronary or intravenous administration of a mitochondria-selective KATPchannel opener, diazoxide, at >100 μmol/l could only partially decrease infarct size (19.5 ± 4.3 and 20.1 ± 4.4%, respectively). In conclusion, mitochondrial and sarcolemmal KATPchannels independently play an important role in the limitation of infarct size by IP in the canine heart.
NEM and filipin increase albumin transport in lung microvessels
Authors: Rippe Bengt , Taylor Aubrey
Published: December 2017

This study was undertaken to evaluate the role of transcytosis as a bulk transfer mechanism for the passage of albumin from blood to tissue. Isolated rat lungs were continuously weighed and perfused with an albumin-serum buffer solution under strictly controlled hemodynamic conditions, which allowed measurements of microvascular pressure and of the capillary filtration coefficient ( LpS). With the use of a tissue uptake technique, it was possible to determine lung albumin clearance under isogravimetric conditions (Cliso), or at elevated filtration rates, to obtain an “apparent albumin reflection coefficient” (ςalb). Experiments were performed during control and after reducing lung temperature from 35° to 22°C and after infusions of the transcytosis inhibitors N-ethylmaleimide (NEM) or filipin. Cooling moderately increased vascular resistance and reduced LpS and Clisolargely in proportion to the induced increases in viscosity. At 35°C, NEM (0.13 mM) caused a marked increase in Lp5 and in Cl150and also caused a reduction in ςalb.Furthermore, Clisoincreased for the highest dose of filipin tested (1.8 μg/ml). The demonstrated relative cooling insensitivity of the transfer of albumin across the endothelium in rat lungs does not support the contention of transcytosis of proteins across the endothelium. Furthermore, neither NEM nor filipin inhibited lung microvascular albumin transport, but actually increased lung endothelial permeability.
Effect of extracellular Mg2+on ROS and Ca2+accumulation during reoxygenation of rat cardiomyocytes
Authors: Sharikabad Mohammad N. , Østbye Kirsten M. , Lyberg Torstein , Brørs Odd
Published: December 2017

The effects of Mg2+on reactive oxygen species (ROS) and cell Ca2+during reoxygenation of hypoxic rat cardiomyocytes were studied. Oxidation of 2′,7′-dichlorodihydrofluorescein (DCDHF) to dichlorofluorescein (DCF) and of dihydroethidium (DHE) to ethidium (ETH) within cells were used as markers for intracellular ROS levels and were determined by flow cytometry. DCDHF/DCF is sensitive to H2O2and nitric oxide (NO), and DHE/ETH is sensitive to the superoxide anion (O2−·), respectively. Rapidly exchangeable cell Ca2+was determined by45Ca2+uptake. Cells were exposed to hypoxia for 1 h and reoxygenation for 2 h. ROS levels, determined as DCF fluorescence, were increased 100–130% during reoxygenation alone and further increased 60% by increasing extracellular Mg2+concentration to 5 mM at reoxygenation. ROS levels, measured as ETH fluorescence, were increased 16–24% during reoxygenation but were not affected by Mg2+. Cell Ca2+increased three- to fourfold during reoxygenation. This increase was reduced 40% by 5 mM Mg2+, 57% by 10 μM 3,4-dichlorobenzamil (DCB) (inhibitor of Na+/Ca2+exchange), and 75% by combining Mg2+and DCB. H2O2(25 and 500 μM) reduced Ca2+accumulation by 38 and 43%, respectively, whereas the NO donor S-nitroso- N-acetyl-penicillamine (1 mM) had no effect. Mg2+reduced hypoxia/reoxygenation-induced lactate dehydrogenase (LDH) release by 90%. In conclusion, elevation of extracellular Mg2+to 5 mM increased the fluorescence of the H2O2/NO-sensitive probe DCF without increasing that of the O2−·-sensitive probe ETH, reduced Ca2+accumulation, and decreased LDH release during reoxygenation of hypoxic cardiomyocytes. The reduction in LDH release, reflecting the protective effect of Mg2+, may be linked to the effect of Mg2+on Ca2+accumulation and/or ROS levels.
Accelerated inactivation in a mutant Na+channel associated with idiopathic ventricular fibrillation
Authors: Wan Xiaoping , Chen Shenghan , Sadeghpour Azita , Wang Qing , Kirsch Glenn E.
Published: December 2017

Idiopathic ventricular fibrillation (IVF) can cause sudden death in both adults and children. One form of IVF (Brugada syndrome), characterized by S-T segment elevation (STE) in the electrocardiogram, has been linked to mutations of SCN5A, the gene encoding the voltage-gated cardiac Na+ channel. A missense mutation of SCN5A that substitutes glutamine for leucine at codon 567 (L567Q, in the cytoplasmic linker between domains I and II) is identified with sudden infant death and Brugada syndrome in one family. However, neither the functional effect of the L567Q mutation nor the molecular mechanism underlying the pathogenicity of the mutation is known. Patch-clamp analysis of L567Q channels expressed in human embryonic kidney cells revealed a marked acceleration and a negative shift in the voltage dependence of inactivation. Unlike other Brugada mutations, this phenotype was expressed independently of temperature or auxiliary β1-subunits. These results support a proposed linkage between Brugada syndrome and some instances of sudden infant death and the hypothesis that reduced Na+ conductance is the primary cause of IVF with STE.
Melatonin potentiates NE-induced vasoconstriction without augmenting cytosolic calcium concentration
Authors: Vandeputte C. , Giummelly P. , Atkinson J. , Delagrange P. , Scalbert E. , Capdeville-Atkinson C.
Published: December 2017

Because little is known of the intracellular mechanisms involved in the vasoconstrictor effect of melatonin (Mel), we examined the in vitro effects of Mel by using perfused cylindrical segments of the rat tail artery loaded with the intracellular Ca2+concentration ([Ca2+]i)-sensitive fluorescent dye, fura 2. Mel (10−14to 10−4M) had no effect on baseline perfusion pressure or [Ca2+]ibut increased, at submicromolar concentrations, the vasoconstrictor effect of norepinephrine (NE) ( P = 0.0029). Mel did not modify NE-induced [Ca2+]imobilization, and thus the [Ca2+]isensitivity of NE-induced contraction increased in the presence of Mel. Mel consistently increased KCl-induced vasoconstriction and [Ca2+]isensitivity of contraction, but differences were not statistically significant. In conclusion, Mel increases the [Ca2+]isensitivity of vasoconstriction evoked by NE suggesting that Mel may amplify endogenous vasoconstrictor responses to sympathetic outflow.
Load as an acute determinant of end-diastolic pressure-volume relation
Authors: Leite-Moreira Adelino F. , Correia-Pinto Jorge
Published: December 2017

Afterload-induced changes in myocardial relaxation are a mechanism for diastolic dysfunction when afterload is elevated beyond certain limits. The present study investigated the effects of acute afterload and preload changes on the position of the end-diastolic (ED) pressure-volume (P-V) relation. Beat-to-beat afterload elevations were induced in seven open-chest rabbits by gradually occluding the ascending aorta to increase peak left ventricular pressure (LVP) from baseline to isovolumetric level. Afterload elevations were performed at three ED LVP: 2.0 ± 0.2 (low), 5.7 ± 0.2 (mid), and 9.6 ± 0.6 (high) mmHg. Preload was altered with caval occlusions and/or intravenous dextran. Afterload elevations induced an upward shift of the diastolic P-V relation, which became more important as afterload and/or preload increased. For instance, maximal afterload elevations shifted this relation upward 2.2 ± 0.5, 5.1 ± 0.8, and 12.1 ± 1.7 mmHg at low, mid, and high preload, respectively. These effects were partially due to changes in relaxation rate and time available to relax. In conclusion, load is an acute determinant of the ED P-V relation, which, therefore, does not provide a load-independent assessment of diastolic function.
Leukocyte trafficking and myocardial reperfusion injury in ICAM-1/P-selectin-knockout mice
Authors: Briaud Stephanie A. , Ding Zhi-Ming , Michael Lloyd H. , Entman Mark L. , Daniel Sherita , Ballantyne Christie M.
Published: December 2017

P-selectin and intercellular adhesion molecule-1 (ICAM-1) mediate early interaction and adhesion of neutrophils to coronary endothelial cells and myocytes after myocardial ischemia and reperfusion. In the present study, we examined the physiological consequences of genetic deletions of ICAM-1 and P-selectin in mice. In wild-type mice, after 1 h of ischemia followed by reperfusion, neutrophil influx into the area of ischemia was increased by 3 h with a peak at 24 h and a decline by 72 h. ICAM-1/P-selectin-deficient mice showed a significant reduction in neutrophils by immunohistochemistry or by myeloperoxidase activity at 24 h but no significant difference at 3 h. Infarct size (area of necrosis/area at risk) assessed 24 h after reperfusion was not different between wild-type and deficient mice after 30 min and 1 h of occlusion. Mice with a deficiency in both ICAM-1 and P-selectin have impaired neutrophil trafficking without a difference in infarct size due to myocardial ischemia-reperfusion.
Increased inactivation of nitric oxide is involved in coronary endothelial dysfunction in heart failure
Authors: Arimura Kenichi , Egashira Kensuke , Nakamura Ryo , Ide Tomomi , Tsutsui Hiroyuki , Shimokawa Hiroaki , Takeshita Akira
Published: December 2017

Recent evidence suggests the possibility that enhanced inactivation of endothelium-derived nitric oxide (NO) by oxygen free radical (OFR) may cause endothelial dysfunction in heart failure (HF). To test this hypothesis, we examined the effect of antioxidant therapy on endothelium-dependent vasodilation of the coronary circulation in a canine model of tachycardia-induced HF. Endothelium-dependent vasodilation was less than that in controls, and OFR formation in coronary arterial and myocardial tissues was greater in HF dogs than those in controls. The immunohistochemical staining of 4-hydroxy-2-nonenal, OFR-induced lipid peroxides was detected in coronary microvessels of HF dogs. Intracoronary infusion of the cell-permeable OFR scavenger Tiron inhibited OFR formation and improved endothelium-dependent vasodilation in HF dogs but not in controls. The NO synthesis inhibitor N G-monomethyl-l-arginine (l-NMMA) diminished the beneficial effect of Tiron in HF dogs. Endothelium-independent vasodilation was similar between control and HF dogs, and no change in its response was noted by Tiron or Tiron plus l-NMMA in either group. In summary, antioxidant treatment with Tiron improved coronary vascular endothelium-dependent vasodilation by increasing NO activity in tachycardia-induced HF. Thus coronary endothelial dysfunction in HF may be, at least in part, due to increased inactivation of NO by OFR.
Effect of ascorbic acid treatment on conduit vessel endothelial dysfunction in patients with hypertension
Authors: Duffy Stephen J. , Gokce Noyan , Holbrook Monika , Hunter Liza M. , Biegelsen Elizabeth S. , Huang Annong , Keaney John F. , Vita Joseph A.
Published: December 2017

Hypertension is associated with low plasma ascorbic acid levels and impaired endothelial function. Recent evidence suggests that increased vascular oxidative stress contributes to the pathophysiology of endothelial dysfunction and hypertension. We recently showed that chronic oral ascorbic acid therapy lowers blood pressure in hypertensive patients. We hypothesized that it would also improve endothelial vasomotor function. In a randomized, double-blind, placebo-controlled study, we examined the effect of acute (2 g po) and chronic (500 mg/day for 1 mo) ascorbic acid treatment on brachial artery flow-mediated dilation in 39 patients with hypertension. Compared with 82 age- and gender-matched normotensive controls, these patients had impaired endothelium-dependent, flow-mediated dilation of the brachial artery [8.9 ± 6.1 vs. 11.2 ± 5.7% (SD), P < 0.04]. After therapy, plasma ascorbic acid concentrations increased acutely from 50 ± 12 to 149 ± 51 μmol/l and were maintained at 99 ± 33 μmol/l with chronic treatment (both P < 0.001). As previously reported, chronic ascorbic acid therapy reduced systolic and mean blood pressure in these patients. However, acute or chronic ascorbic acid treatment had no effect on brachial artery endothelium-dependent, flow-mediated dilation or on endothelium-independent, nitroglycerin-mediated dilation. These results demonstrate that conduit vessel endothelial dysfunction secondary to hypertension is not reversed by acute or chronic treatment with oral ascorbic acid. The effects of this treatment on resistance vessel vasomotor function warrant further investigation.
Estimation of left ventricular operating stiffness from Doppler early filling deceleration time in humans
Authors: Garcia Mario J. , Firstenberg Michael S. , Greenberg Neil L. , Smedira Nicholas , Rodriguez Leonardo , Prior David , Thomas James D.
Published: December 2017

Shortened early transmitral deceleration times ( E DT) have been qualitatively associated with increased filling pressure and reduced survival in patients with cardiac disease and increased left ventricular operating stiffness ( K LV). An equation relating K LV quantitatively to E DT has previously been described in a canine model but not in humans. During several varying hemodynamic conditions, we studied 18 patients undergoing open-heart surgery. Transesophageal echocardiographic two-dimensional volumes and Doppler flows were combined with high-fidelity left atrial (LA) and left ventricular (LV) pressures to determine K LV. From digitized Doppler recordings, E DT was measured and compared against changes in LV and LA diastolic volumes and pressures. E DT(180 ± 39 ms) was inversely associated with LV end-diastolic pressures ( r = −0.56, P = 0.004) and net atrioventricular stiffness ( r = −0.55, P = 0.006) but had its strongest association with K LV ( r = −0.81, P < 0.001). K LV was predicted assuming a nonrestrictive orifice ( K nonrest) from E DT as K nonrest= (0.07/ E DT)2 with K LV = 1.01 K nonrest − 0.02; r = 0.86, P < 0.001, Δ K( K nonrest − K LV) = 0.02 ± 0.06 mmHg/ml. In adults with cardiac disease, E DT provides an accurate estimate of LV operating stiffness and supports its application as a practical noninvasive index in the evaluation of diastolic function.
Volume expansion potentiates cardiac sympathetic afferent reflex in dogs
Authors: Wang Wei , Schultz Harold D. , Ma Rong
Published: December 2017

Our previous study (27) showed that the cardiac sympathetic afferent reflex (CSAR) was enhanced in dogs with congestive heart failure. The aim of this study was to test whether blood volume expansion, which is one characteristic of congestive heart failure, potentiates the CSAR in normal dogs. Ten dogs were studied with sino-aortic denervation and bilateral cervical vagotomy. Arterial pressure, left ventricular pressure, left ventricular epicardial diameter, heart rate, and renal sympathetic nerve activity were measured. Coronary blood flow was also measured and, depending on the experimental procedure, controlled. Blood volume expansion was carried out by infusion of isosmotic dextran into a femoral vein at 40 ml/kg at a rate of 50 ml/min. CSAR was elicited by application of bradykinin (5 and 50 μg) and capsaicin (10 and 100 μg) to the epicardial surface of the left ventricle. Volume expansion increased arterial pressure, left ventricular pressure, left ventricular diameter, and coronary blood flow. Volume expansion without controlled coronary blood flow only enhanced the RSNA response to the high dose (50 μg) of epicardial bradykinin (17. 3 ± 1.9 vs. 10.6 ± 4.8%, P < 0.05). However, volume expansion significantly enhanced the RSNA responses to all doses of bradykinin and capsaicin when coronary blood flow was held at the prevolume expansion level. The RSNA responses to bradykinin (16. 9 ± 4.1 vs. 5.0 ± 1.3% for 5 μg, P < 0.05, and 28.9 ± 3.7 vs. 10.6 ± 4.8% for 50 μg, P < 0.05) and capsaicin (29.8 ± 6.0 vs. 9.3 ± 3.1% for 10 μg, P < 0.05, and 34.2 ± 2.7 vs. 15.1 ± 2.7% for 100 μg, P < 0.05) were significantly augmented. These results indicate that acute volume expansion potentiated the CSAR. These data suggest that enhancement of the CSAR in congestive heart failure may be mediated by the concomitant cardiac dilation, which accompanies this disease state.
Conducted vasoconstriction in rat mesenteric arterioles: role for dihydropyridine-insensitive Ca2+channels
Authors: Gustafsson Finn , Andreasen Ditte , Salomonsson Max , Jensen Boye L. , Holstein-Rathlou Niels-Henrik
Published: December 2017

The aim of this study was to evaluate the role of voltage-operated Ca2+ channels in the initiation and conduction of vasoconstrictor responses to local micropipette electrical stimulation of rat mesenteric arterioles (28 ± 1 μm, n = 79) in vivo. Local and conducted (600 μm upstream from the pipette) vasoconstriction was not blocked by TTX (1 μmol/l, n= 5), nifedipine, or nimodipine (10 μmol/l, n = 9). Increasing the K+ concentration of the superfusate to 75 mmol/l did not evoke vasoconstriction, but this depolarizing stimulus reversibly abolished vasoconstrictor responses to current stimulation ( n = 7). Addition of the T-type Ca2+antagonist mibefradil (10 μmol/l, n = 6) to the superfusate reversibly blocked local and conducted vasoconstriction to current stimulation. With the use of RT-PCR techniques, it was demonstrated that rat mesenteric arterioles <40 μm do not express mRNA for L-type Ca2+ channels (α1C-subunit), whereas mRNA coding for T-type subunits was found (α1G- and α1H-subunits). The data indicate that L-type Ca2+ channels are absent from rat mesenteric arterioles (<40 μm). Rather, the vasoconstrictor responses appear to rely on other types of voltage-gated, dihydropyridine-insensitive Ca2+ channels, possibly of the T-type.
Ischemic dysfunction in transgenic mice expressing troponin I lacking protein kinase C phosphorylation sites
Authors: MacGowan Guy A. , Du Congwu , Cowan Douglas B. , Stamm Christof , McGowan Francis X. , Solaro R. John , Koretsky Alan P. , Del Nido Pedro J.
Published: December 2017

To determine the in vivo functional significance of troponin I (TnI) protein kinase C (PKC) phosphorylation sites, we created a transgenic mouse expressing mutant TnI, in which PKC phosphorylation sites at serines-43 and -45 were replaced by alanine. When we used high-perfusate calcium as a PKC activator, developed pressures in transgenic (TG) perfused hearts were similar to wild-type (WT) hearts ( P = not significant, NS), though there was a 35% and 32% decrease in peak-systolic intracellular calcium ( P < 0.01) and diastolic calcium ( P < 0.005), respectively. The calcium transient duration was prolonged in the TG mice also (12–27%, ANOVA, P < 0.01). During global ischemia, TG hearts developed ischemic contracture to a greater extent than WT hearts (41 ± 18 vs. 69 ± 10 mmHg, perfusate calcium 3.5 mM, P < 0.01). In conclusion, expression of mutant TnI lacking PKC phosphorylation sites results in a marked alteration in the calcium-pressure relationship, and thus susceptibility to ischemic contracture. The reduced intracellular calcium and prolonged calcium transients suggests that a potent feedback mechanism exists between the myofilament and the processes controlling calcium homeostasis.
Upregulation of angiotensin-converting enzyme by vascular endothelial growth factor
Authors: Saijonmaa Outi , Nyman Tuulikki , Kosonen Riikka , Fyhrquist Frej
Published: December 2017

The role of vascular endothelial growth factor (VEGF), a potent endothelium-specific angiogenic factor, in the regulation of angiotensin-converting enzyme (ACE) in cultured human umbilical vein endothelial cells (HUVECs) was studied. VEGF (0.07–1.2 × 10−6mmol/l) caused a dose-dependent increase in ACE measured in intact endothelial cells and increased the expression of ACE mRNA. The stimulatory effect of VEGF was inhibited by pretreatment of endothelial cells with the tyrosine kinase inhibitor herbimycin (4.35 × 10−5mmol/l). The stimulatory effect of VEGF was potentiated by the selective cGMP phosphodiesterase inhibitor zaprinast (0.1 mmol/l). The nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester (l-NAME; 5.4 mmol/l) suppressed the stimulatory effect of VEGF. The nonselective cyclooxygenase (COX) inhibitor indomethacin (5 μM) and the selective COX-2 inhibitor NS-398 (5 μM) potentiated the stimulatory effect of VEGF, whereas the selective COX-1 inhibitor resveratrol (5 μM) was without effect. ACE induction by VEGF was inhibited by the selective protein kinase C (PKC) inhibitor GF109203X (2.5 × 10−3mmol/l) and by downregulating PKC with phorbol 12-myristate 13-acetate. In summary, VEGF induced ACE in cultured HUVECs. Intracellular events such as tyrosine kinase activation, PKC activation, and increase of cGMP were probably involved in ACE induction by VEGF. Nitric oxide may partially contribute to ACE induction by VEGF. The powerful capacity of VEGF to increase ACE in endothelial cells shown here suggests a synergistic relation between VEGF and the renin-angiotensin system in vascular biology and pathophysiology.
Simultaneous arterial calcium dynamics and diameter measurements: application to myoendothelial communication
Authors: Schuster Alexander , Oishi Hirotaka , Bény Jean-Louis , Stergiopulos Nikolaos , Meister Jean-Jacques
Published: December 2017

The goal of the present study was to analyze the intercellular calcium communication between smooth muscle cells (SMCs) and endothelial cells (ECs) by simultaneously monitoring artery diameter and intracellular calcium concentration in a rat mesenteric arterial segment in vitro under physiological pressure (50 mmHg) and flow (50 μl/min) in a specially developed system. Intracellular calcium was expressed as the fura 2 ratio. The diameter was measured using a digital image acquisition system. Stimulation of SMCs with the α1-agonist phenylephrine (PE) caused not only an increase in the free intracellular calcium concentration of the SMCs as expected but also in the ECs, suggesting a calcium flux from the SMCs to the ECs. The gap junction uncoupler palmitoleic acid greatly reduced this increase in calcium in the ECs on stimulation of the SMCs with PE. This indicates that the signaling pathway passes through the gap junctions. Similarly, although vasomotion originates in the SMCs, calcium oscillates in both SMCs and ECs during vasomotion, suggesting again a calcium flux from the SMCs to the ECs.
VEGF121- and bFGF-induced increase in collateral blood flow requires normal nitric oxide production
Authors: Yang H. T. , Yan Z. , Abraham Judith A. , Terjung Ronald L.
Published: December 2017

The angiogenic proteins basic fibroblast growth factor (bFGF; FGF-2) and vascular endothelial growth factor 121 (VEGF121) are each able to enhance the collateral-dependent blood flow after bilateral femoral artery ligation in rats. To study the effect of nitric oxide (NO) synthase (NOS) inhibition on bFGF- or VEGF121-induced blood flow expansion, the femoral arteries of male Sprague-Dawley rats were ligated bilaterally, and the animals were given tap water [non- NG-nitro-l-arginine methyl ester (l-NAME) group; n = 36] or water that contained l-NAME (l-NAME group; 2 mg/ml, n = 36). Animals from each group were further divided into three subgroups: vehicle ( n = 12), bFGF (5 μg · kg−1· day−1, n = 12), or VEGF121(10 μg · kg−1· day−1, n = 12). Growth factors were delivered via intra-arterial infusion with osmotic pumps over days 1–14. On day 16, after a 2-day delay to permit clearance of bFGF and VEGF from the circulation, maximal collateral blood flow was determined by85Sr- and141Ce-labeled microspheres during treadmill running.l-NAME (∼137 mg · kg−1· day−1) for 18 days increased systemic blood pressure (∼26%, P < 0.001). In the absence of l-NAME, collateral-dependent blood flows to the calf muscles were greater in the VEGF121- and bFGF-treated subgroups (85 ± 4.5 and 80 ± 2.9 ml · min−1· 100 g−1, respectively) than in the vehicle subgroup (49 ± 3.0 ml · min−1· 100 g−1, P < 0.001). In the presence of NOS inhibition byl-NAME, blood flows to the calf muscles were essentially equivalent among the three subgroups (54 ± 3.0, 56 ± 5.1, and 47 ± 2.0 ml · min−1· 100 g−1in the bFGF-, VEGF121-, and vehicle-treated subgroups, respectively) and were not different from the blood flow in the non-l-NAME vehicle subgroup. Our results therefore indicate that normal NO production is essential for the enhanced vascular remodeling induced by exogenous bFGF or VEGF121in this rat model of experimental peripheral arterial insufficiency. These results imply that a blunted endothelial NO production could temper vascular remodeling in response to these angiogenic growth factors.
Prevention of ischemic ventricular tachycardia of Purkinje origin: role for α2-adrenoceptors in Purkinje?
Authors: Arnar David O. , Xing Dezhi , Lee Hon-Chi , Martins James B.
Published: December 2017

Recent studies have shown the presence of postjunctional α2-adrenergic receptors on canine Purkinje fibers but not muscle cells. Stimulation of these receptors results in prolongation of the action potential duration and the Purkinje relative refractory period. We studied the effect of α2-adrenergic agonists on inducible ischemic ventricular tachycardia (VT) of both Purkinje fiber and myocardial origin. Open-chest dogs in whom VT was induced with extrastimuli after occlusion of the anterior descending coronary artery were studied. A mapping system, incorporating Purkinje signals, characterized the mechanisms of VT. The α2-adrenergic agonists clonidine (0.5–4.0 μg/kg) or UK 14,304 (4–5 μg/kg) versus saline were given intravenously after reproducibility of inducible sustained monomorphic VT had been demonstrated. Eighteen dogs were given clonidine, eleven of which had focal Purkinje VT. Of these 11 dogs, clonidine blocked VT induction in 9 (81.9%) and rendered VT nonsustained in 1 (9.1%), and VT remained inducible in 1 dog (9.1%), although this was focal midmyocardial VT only. In the seven dogs with VT of myocardial origin, six (85.6%) remained inducible with clonidine, whereas one dog (14.4%) had only nonsustained VT after clonidine. Of the six dogs, UK 14,304 blocked VT induction in four (66.6%) and rendered VT nonsustained in one (16.7%), and VT remained inducible in one dog (16.7%). In four dogs with VT of myocardial origin, VT remained inducible. In the eight control dogs that were given saline, focal Purkinje VT was repeatedly inducible. Pharmacological stimulation of postjunctional α2-adrenoceptors on Purkinje fibers may selectively prevent induction of VT of Purkinje fiber origin in the ischemic canine ventricle.
Cardioprotection is strain dependent in rat in response to whole body hyperthermia
Authors: Patel Hemal H. , Hsu Anna , Gross Garrett J.
Published: December 2017

Previous results showed a genetic component to cardioprotection. Therefore, we investigated the heat shock response in Wistar and Sprague-Dawley (SD) rats at 24 and 48 h. Rats were subjected to whole body hyperthermia achieving colonic temperatures of 40 or 42°C for 20 min. After recovery hearts were excised for protein measurements or were subjected to 30 min of ischemia and then 2 h of reperfusion. Heat shock protein (HSP) expression was determined by Western blotting and infarct size was determined by triphenyltetrazolium staining. All groups of SD and Wistar rats demonstrated HSP72 and HSP90 induction at both time points in response to a heat stress of 42°C. At 24 h there was only a significant reduction in infarct size seen in control vs. small SD (60.0 ± 4.8 vs. 26.5 ± 2.3) rats. However, at 48 h control versus small SD (60.0 ± 4.8 vs. 17.6 ± 3.8) and Wistar (59.4 ± 4.3 vs. 29.8 ± 6.0) and control versus large SD (53.7 ± 2.6 vs. 19.8 ± 4.7) and Wistar (57.3 ± 1.6 vs. 34.5 ± 2.8) rats demonstrated a significant reduction in infarct size with a greater reduction observed in SD rats. We conclude that heat shock-induced cardioprotection in rats is dependent on strain, temperature, time after stress, and size.