bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of coronary artery depolarization by uridine triphosphate
Authors: Welsh Donald G. , Brayden Joseph E.
Published: December 2017

We sought to define the basic mechanisms by which pyrimidine nucleotides constrict rat coronary resistance arteries. Uridine triphosphate (UTP) caused a dose-dependent constriction in coronary arteries stripped of endothelium. UTP also depolarized and increased cytosolic Ca2+in coronary smooth muscle cells. Nisoldipine, an antagonist of voltage-operated Ca2+channels, blocked the rise in cytosolic Ca2+and reduced UTP-induced vasoconstriction by ∼75% which suggests a prominent role for depolarization in this constrictor response. The ionic basis of UTP-induced depolarization was subsequently explored in coronary smooth muscle cells using whole-cell patch-clamp electrophysiology. In the absence of K+and with CsCl in the pipette, UTP (40 μM) activated a sustained inwardly rectifying current (−0.66 ± 0.10 pA/pF at −60 mV). A 100 mM reduction in bath Na+shifted the reversal potential of this current (from −2 ± 1 to −28 ± 4 mV) and reduced the magnitude (from −2.26 ± 0.61 to −0.51 ± 0.11 pA/pF). In addition to activating a depolarizing cation current, UTP inhibited hyperpolarizing outward currents. Specifically, UTP inhibited ATP-sensitive and voltage-dependent K+currents yet had no effect on inwardly rectifying and Ca2+-activated K+channels. This study indicates that electromechanical coupling is integral to pyrimidine-induced constriction in coronary resistance arteries.
Respiratory modulation of human autonomic rhythms
Authors: Badra Leslie J. , Cooke William H. , Hoag Jeffrey B. , Crossman Alexandra A. , Kuusela Tom A. , Tahvanainen Kari U. O. , Eckberg Dwain L.
Published: December 2017

We studied the influence of three types of breathing [spontaneous, frequency controlled (0.25 Hz), and hyperventilation with 100% oxygen] and apnea on R-R interval, photoplethysmographic arterial pressure, and muscle sympathetic rhythms in nine healthy young adults. We integrated fast Fourier transform power spectra over low (0.05–0.15 Hz) and respiratory (0.15–0.3 Hz) frequencies; estimated vagal baroreceptor-cardiac reflex gain at low frequencies with cross-spectral techniques; and used partial coherence analysis to remove the influence of breathing from the R-R interval, systolic pressure, and muscle sympathetic nerve spectra. Coherence among signals varied as functions of both frequency and time. Partialization abolished the coherence among these signals at respiratory but not at low frequencies. The mode of breathing did not influence low-frequency oscillations, and they persisted during apnea. Our study documents the independence of low-frequency rhythms from respiratory activity and suggests that the close correlations that may exist among arterial pressures, R-R intervals, and muscle sympathetic nerve activity at respiratory frequencies result from the influence of respiration on these measures rather than from arterial baroreflex physiology. Most importantly, our results indicate that correlations among autonomic and hemodynamic rhythms vary over time and frequency, and, thus, are facultative rather than fixed.
Model of geometrical and smooth muscle tone adaptation of carotid artery subject to step change in pressure
Authors: Fridez P. , Rachev A. , Meister J.-J. , Hayashi K. , Stergiopulos N.
Published: December 2017

Recent experimental studies have shown significant alterations of the vascular smooth muscle (VSM) tone when an artery is subjected to an elevation in pressure. Therefore, the VSM participates in the adaptation process not only by means of its synthetic activity (fibronectins and collagen) or proliferative activity (hypertrophy and hyperplasia) but also by adjusting its contractile properties and its tone level. In previous theoretical models describing the time evolution of the arterial wall adaptation in response to induced hypertension, the contribution of VSM tone has been neglected. In this study, we propose a new biomechanical model for the wall adaptation to induced hypertension, including changes in VSM tone. On the basis of Hill's model, total circumferential stress is separated into its passive and active components, the active part being the stress developed by the VSM. Adaptation rate equations describe the geometrical adaptation (wall thickening) and the adaptation of active stress (VSM tone). The evolution curves that are derived from the theoretical model fit well the experimental data describing the adaptation of the rat common carotid subjected to a step increase in pressure. This leads to the identification of the model parameters and time constants by characterizing the rapidity of the adaptation processes. The agreement between the results of this simple theoretical model and the experimental data suggests that the theoretical approach used here may appropriately account for the biomechanics underlying the arterial wall adaptation.
NHE and ICAM-1 expression in hypoxic/reoxygenated coronary microvascular endothelial cells
Authors: Hattori Reiji , Otani Hajime , Moriguchi Yasutaka , Matsubara Hiroaki , Yamamura Tadashi , Nakao Yoshihisa , Omiya Hideyasu , Osako Motohiko , Imamura Hiroji
Published: December 2017

Although Na+/H+exchange (NHE) has been implicated in myocardial reperfusion injury, participation of coronary microvascular endothelial cells (CMECs) in this pathogenesis has been poorly understood. NHE-induced intracellular Ca2+concentration ([Ca2+]i) overload in CMECs may increase the synthesis of intercellular adhesion molecules (ICAM), which is potentially involved in myocardial reperfusion injury. The present study tested the hypothesis that NHE plays a crucial role in [Ca2+]ioverload and ICAM-1 synthesis in CMECs. Primary cultures of CMECs isolated from adult rat hearts were subjected to acidic hypoxia for 30 min followed by reoxygenation. Two structurally distinct NHE inhibitors, cariporide and 5-( N- N-dimethyl)-amiloride (DMA), had no significant effect on the acidic hypoxia-induced decrease in intracellular pH (pHi) of CMECs but significantly retarded pHirecovery after reoxygenation. These NHE inhibitors abolished the hypoxia- and reoxygenation-induced increase in [Ca2+]i. Expression of ICAM-1 mRNA was markedly increased in the vehicle-treated CMECs 3 h after reoxygenation, and this was significantly inhibited by treatment with cariporide, DMA, or Ca2+-free buffer. In addition, enhanced ICAM-I protein expression on the cell surface of CMECs 8 h after reoxygenation was attenuated by treatment with cariporide, DMA, or Ca2+-free buffer. These results suggest that NHE plays a crucial role in the rise of [Ca2+]iand ICAM-1 expression during acidic hypoxia/reoxygenation in CMECs. We propose that inhibition of ICAM-1 expression in CMECs may represent a novel mechanism of action of NHE inhibitors against ischemia-reperfusion injury.
In vivo assessment of acetylcholine-releasing function at cardiac vagal nerve terminals
Authors: Kawada Toru , Yamazaki Toji , Akiyama Tsuyoshi , Shishido Toshiaki , Inagaki Masashi , Uemura Kazunori , Miyamoto Tadayoshi , Sugimachi Masaru , Takaki Hiroshi , Sunagawa Kenji
Published: December 2017

We examined whether the ACh concentration measured by cardiac microdialysis provided information on left ventricular ACh levels under a variety of vagal stimulatory and modulatory conditions in anesthetized cats. Local administration of KCl ( n = 5) and ouabain ( n = 7) significantly increased the ACh concentration in the dialysate to 4.3 ± 0.8 and 7.3 ± 1.3 nmol/l, respectively, from the baseline value of 0.6 ± 0.5 nmol/l. Intravenous administration of phenylbiguanide ( n = 5) and phenylephrine ( n = 6) significantly increased the ACh concentration to 5.4 ± 0.9 and 6.0 ± 1.5 nmol/l, respectively, suggesting that the Bezold-Jarisch and arterial baroreceptor reflexes affected myocardial ACh levels. Modulation of vagal nerve terminal function by local administration of tetrodotoxin ( n = 6), hemicholinium-3 ( n = 6), and vesamicol ( n = 5) significantly suppressed the electrical stimulation-induced ACh release from 20.4 ± 3.9 to 0.6 ± 0.1, 7.2 ± 1.9, and 2.7 ± 0.6 nmol/l, respectively. Increasing the heart rate from 120 to 200 beats/min significantly reduced the myocardial ACh levels during electrical vagal stimulation, suggesting a heart rate-dependent washout of ACh. We conclude that ACh concentration measured by cardiac microdialysis provides information regarding ACh release and disposition under a variety of pathophysiological conditions in vivo.
Calcium-independent phospholipase A2mediates CREB phosphorylation and c-fosexpression during ischemia
Authors: Williams Scott D. , Ford David A.
Published: December 2017

In isolated, perfused adult rat hearts, global ischemia increased the phosphorylation of cAMP response element-binding protein (CREB) relative to control levels, and this phosphorylation was reversed with reperfusion. CREB phosphorylation elicited by 5 min of global ischemia was sensitive to treatments with the calcium-independent phospholipase A2(iPLA2) inhibitor bromoenol lactone (BEL) and occurred in the absence of increases in myocardial cAMP content. In contrast, CREB phosphorylation elicited by 15 min of global ischemia was likely mediated by elevated cAMP levels. The expression of c- fos, in response to brief myocardial ischemia, was also sensitive to BEL treatment. The induction of iPLA2-mediated CREB phosphorylation was further substantiated by the observations that lysoplasmenylcholine increased both the phosphorylation of CREB and the induction of c- fosexpression in the absence and presence of BEL. CREB phosphorylation in both ischemic hearts and lysoplasmenylcholine-perfused hearts was inhibited by pretreatment of hearts with the specific cAMP-dependent protein kinase (PKA) inhibitor H-89. Taken together, these data demonstrate that iPLA2mediates CREB phosphorylation through a PKA-dependent pathway during brief periods of myocardial ischemia, possibly through the formation of lysophospholipids.
Regulation of tyrosine phosphorylation of PYK2 in vascular endothelial cells by lysophosphatidylcholine
Authors: Rikitake Yoshiyuki , Kawashima Seinosuke , Takahashi Tomosaburo , Ueyama Tomomi , Ishido Satoshi , Inoue Nobutaka , Hirata Ken-Ichi , Yokoyama Mitsuhiro
Published: December 2017

Lysophosphatidylcholine (LPC), a component of oxidized low-density lipoprotein, exerts various biological effects on vascular endothelial cells. However, the intracellular signaling of LPC is poorly understood. In this study, we investigated the involvement of proline-rich tyrosine kinase (PYK2) in LPC signaling in cultured bovine aortic endothelial cells by immunoprecipitation and Western blotting assays. Treatment of cells with LPC promoted a rapid increase in tyrosine phosphorylation of PYK2. LPC-stimulated PYK2 phosphorylation was inhibited by calcium chelators, 1,2-bis(2-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid-acetoxymethyl ester, EGTA, protein kinase C (PKC) inhibitor, GF-109203X, or PKC depletion by phorbol esters. PYK2 phosphorylation was inhibited by treatment with cytochalasin D but with neither botulinum C3 transferase nor overexpression of a dominant negative mutant of Rho A. LPC stimulated the association of Shc with PYK2, Shc tyrosine phosphorylation, and Grb2 binding to Shc and induced Ras activation. These results provide evidence that 1) LPC tyrosine phosphorylates PYK2 by calcium- and PKC-dependent mechanisms, 2) the intact cytoskeleton is required for LPC-stimulated PYK2 phosphorylation, and 3) LPC-activated Ras via the PYK2/Shc/Grb2 signaling.
Cardiac myocytes exposed to anoxia-reoxygenation promote neutrophil transendothelial migration
Authors: Rui Tao , Cepinskas Gediminas , Feng Qingping , Ho Ye-Shih , Kvietys Peter R.
Published: December 2017

The goal of the present study was to assess whether cardiac myocytes exposed to anoxia-reoxygenation (A/R) could generate a chemotactic gradient for polymorphonuclear neutrophil (PMN) transendothelial migration. Exposure of neonatal mouse cardiac myocytes to A/R induced an oxidant stress in the myocytes. Supernatants obtained from A/R-conditioned myocytes promoted mouse PMN migration across mouse myocardial endothelial cell monolayers. This increase in PMN transendothelial migration could be prevented if catalase or a platelet-activating factor (PAF) antagonist was added to the supernatants before assay. Supernatants from A/R-conditioned myocytes activated endothelial cells by inducing an intracellular oxidant stress. The oxidant stress and PMN transendothelial migration induced by supernatants from A/R-conditioned myocytes were substantially reduced when endothelial cells derived from manganese superoxide dismutase overexpressing mice were used in the assays. Supernatants from A/R-conditioned myocytes also increased endothelial cell surface levels of E-selectin and intercellular adhesion molecule-1. Our results indicate that cardiac myocytes exposed to A/R can generate a chemotactic gradient, presumably due to production and release of stable oxidants and PAF. The ability of supernatants from A/R-conditioned myocytes to promote PMN transendothelial migration was largely dependent on induction of an oxidant stress in endothelial cells. In addition, these supernatants also induced a proadhesive phenotype in the endothelial cells.
Cytochalasin D induces edema formation and lowering of interstitial fluid pressure in rat dermis
Authors: Berg Ansgar , Rubin Kristofer , Reed Rolf K.
Published: December 2017

The increased capillary fluid filtration required to create a rapid edema formation in acute inflammation can be generated by lowering the interstitial fluid pressure (PIF). The lowering of PIFappears to involve dynamic β1-integrin-mediated interactions between dermal cells and extracellular matrix fibers. The present study specifically investigates the role of the cell cytoskeleton, i.e., the contractile apparatus of cells, in controlling PIFin rat skin as the integrins are linked to both the cytoskeleton and the extracellular matrix. PIFwas measured using a micropuncture technique in the dorsal skin of the hind paw at a depth of 0.2–0.5 mm and following the induction of circulatory arrest with the intravenous injection of KCl in pentobarbital anesthesia. This procedure prevented the transcapillary flux of fluid and protein leading to edema formation in acute inflammation, which in turn can increase the PIFand therefore potentially mask a decrease of PIF. Control PIF( n = 42) averaged −0.8 ± 0.5 (means ± SD) mmHg. In the first group of experiments, subdermal injection of 2 μl cytochalasin D, a microfilament-disrupting drug, lowered PIFto an average of −2.8 ± 0.7 mmHg within 40 min postinjection ( P< 0.05 compared with control). Subdermal injection of vehicle (10% DMSO in PBS or PBS alone) did not change the PIF( P > 0.05). Lowering of the PIFwas not observed after the injection of colchicine or nocodazole, which specifically disrupts microtubuli in cultured cells. In the second group of experiments, 2 μl of cytochalasin D injected subdermally into rats with intact circulation increased the total tissue water (TTW) and albumin extravasation rate ( EALB) by 0.7 ± 0.2 and 0.4 ± 0.3 ml/g dry wt, respectively ( P < 0.05 compared with vehicle). Nocodazole and colchicine did not significantly alter the TTW or EALBcompared with the vehicle ( P > 0.05). Taken together, these findings strongly suggest that the connective tissue cells can participate in control of PIFvia the actin filament system. In addition, the observation that subdermal injection of cytochalasin D lowered PIFindicates that a dynamic assembly and disassembly of actin filaments also occurs in the cells of dermal tissues in vivo.
Hemorrhage-induced α-adrenergic signaling results in myocardial TNF-α expression and contractile dysfunction
Authors: Shahani Rohan , Klein Lazar V. , Marshall John G. , Nicholson Sherwin , Rubin Barry B. , Walker Paul M. , Lindsay Thomas F.
Published: December 2017

Hemorrhagic shock (HS), secondary to major blood loss, frequently precedes multiple organ dysfunction and is accompanied by a surge in circulating catecholamine levels. Expression of the cardiodepressant cytokine, tumor necrosis factor-α (TNF-α), has been observed in the heart after HS and resuscitation (HS/R) and α1-adrenergic blockade prevented translocation of the nuclear transcription factor, NF-κB, to the nucleus. We hypothesized that α1-adrenergic stimulation induces myocardial TNF-α expression, which results in depressed cardiac function after HS/R. The role of α1-adrenergic stimulation in myocardial TNF-α expression and depressed cardiac function after HS/R was assessed by treatment with the α1-adrenergic inhibitor, prazosin hydrochloride (1 mg/kg ip), for 1 h before the onset of hemorrhage. In addition, TNF-α was neutralized with a specific antibody (600 μl/kg iv) 5 min before hemorrhage. HS was induced by the withdrawal of blood to a mean blood pressure of 50 mmHg for 1 h. Contractile function was measured with the use of a Langendorff apparatus 2 h after the end of HS. HS/R led to significant decreases in left ventricular developed tension and in the maximal rate of pressure increase over time during both contraction and relaxation. Myocardial expression of TNF-α measured by enzyme-linked immunosorbent assay increased significantly after 30 min of hemorrhage and peaked after 60 min of HS and 45 min of resuscitation. Depression in cardiac function after HS/R was reversed by 85% in hearts from rats treated with a TNF-α neutralizing antibody and by 90% in hearts from rats treated with prazosin hydrochloride. We conclude that HS activates a α1-adrenergic pathway, resulting in TNF-α expression in the heart and depressed myocardial contractile function.
Activation of cardiac afferents by arachidonic acid: relative contributions of metabolic pathways
Authors: Sun Shu-Yu , Wang Wei , Schultz Harold D.
Published: December 2017

Arachidonic acid (AA) is metabolized via cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P-450 (CP450) pathways to a variety of bioactive products. The sensitivity of cardiac afferent endings to AA and its metabolites, especially those derived from LOX and CP450 pathways, is currently unclear. We examined AA-induced activation of cardiac vagal chemosensitive afferents in non- and postischemic hearts in rats and evaluated the relative contributions of the three metabolic pathways to the effects. Epicardial application of AA activated the cardiac afferents dose dependently in both nonischemic and postischemic hearts, with afferent responses greater in the latter condition. In nonischemic hearts, the afferent response to AA was abolished only after simultaneous administration of indomethacin and 17-octadecynoic acid (COX and CP450 inhibitors, respectively). Nordihydroguaiaretic acid (a LOX inhibitor) had no effect on the afferent response to AA. In postischemic hearts, abolition of the afferent response to AA required simultaneous blockade of all three pathways. None of the AA metabolic inhibitors affected resting activity of cardiac afferents in nonischemic hearts, but each suppressed afferent activity during ischemia-reperfusion. Most COX metabolites, CP450 metabolites, and 5-LOX metabolites tested were capable of activating cardiac afferents. The 12-LOX metabolites and 15-LOX metabolites had no effect on afferent activity. These data indicate that in the nonischemic heart, basal AA metabolism does not contribute to resting afferent activity, but AA is capable of activating cardiac afferents via COX and CP450 but not LOX pathways. During ischemia-reperfusion, all three metabolic pathways contribute to activation of cardiac vagal afferents with an enhanced responsiveness to AA. Our results suggest that induction of the 5-LOX pathway contributes to the enhanced sensitivity of cardiac vagal afferents to AA in the ischemic condition.
Protection of ischemic myocardium in diabetics by inhibition of electroneutral Na+-K+-2Cl−cotransporter
Authors: Ramasamy Ravichandran , Payne John A. , Whang John , Bergmann Steven R. , Schaefer Saul
Published: December 2017

Diabetes increases both the incidence of cardiovascular disease and complications of myocardial infarction and heart failure. Studies using diabetic animals have shown that changes in myocardial sodium transporters result in alterations in intracellular sodium (Nai) homeostasis. Because the changes in sodium homeostasis can be due to increased entry of Na+via the electroneutral Na+-K+-2Cl−cotransporter (NKCC), we conducted experiments in acute diabetic hearts to determine if 1) net inward cation flux via NKCC is increased, 2) this cotransporter contributes to a greater increase in Naiduring ischemia, and 3) inhibition of NKCC limits injury and improves function after ischemia-reperfusion. These issues were investigated in perfused type I diabetic and nondiabetic rat hearts subjected to ischemia and 60 min of reperfusion. A group of diabetic and nondiabetic hearts was perfused with 5 μM of bumetanide, an inhibitor of NKCC. Flux via NKCC, Nai, and ATP was measured in each group with the use of radiotracer86Rb,23Na, and31P nuclear magnetic resonance spectroscopy, respectively, whereas ischemic injury was assessed by measuring creatine kinase release on reperfusion. Cation flux via NKCC, as measured by86Rb uptake, was significantly increased in diabetic hearts. Inhibition of NKCC significantly reduced ischemic injury in diabetic hearts, improved functional recovery on reperfusion, attenuated the ischemic rise in Nai, and conserved ATP during ischemia-reperfusion. Parallel studies in nondiabetic hearts showed that NKCC inhibition was not cardioprotective. These findings demonstrate that flux via NKCC is increased in type I diabetic hearts and that inhibition with bumetanide attenuates changes in Naiand ATP during ischemia and protects against ischemic injury. The data suggest a therapeutic role for pharmacological agents that inhibit flux via NKCC in diabetic patients with myocardial ischemia.
Mitogen-activated protein kinases mediate heat shock-induced delayed protection in mouse heart
Authors: Tekin Demet , Xi Lei , Zhao Tingcun , Tejero-Taldo M. Isabel , Atluri Sumanth , Kukreja Rakesh C.
Published: December 2017

We determined the role of p38 mitogen-activated protein kinase (MAPK), 72-kDa heat shock protein (HSP72), and antioxidant enzymes in whole body heat stress (HS)-induced cardioprotection in mouse hearts. Adult male mice were treated with either HS or anesthesia only. At 0.5, 48, 72, or 120 h later, the hearts were subjected to 20 min of global ischemia and 30 min of reperfusion in Langendorff mode. A significant protection against ischemia-reperfusion injury was observed 48 h after HS as demonstrated by: 1) reduction in infarct size; 2) decrease in leakage of lactate dehydrogenase; and 3) enhanced postischemic ventricular contractile function. No such protection was observed at other post-HS time points. HS caused an ∼25% increase in phosphorylated c-Jun NH2-terminal kinase (JNK) but not p38 MAPK in the heart during the first 2-h post-HS time period. Cardioprotection was abolished by the MAPK inhibitor SB-203580, which also partially suppressed the HS-induced JNK phosphorylation. The protective effect was associated with a two- to threefold increase in HSP72 protein accumulation, but not antioxidant enzyme activities (catalase and Cu/Zn and Mn SOD) in the myocardium. Although HSP72 levels remained high 72 h after HS, the cardioprotection had already disappeared. We conclude that HS induces a transient delayed cardioprotection at 48 h after thermal stress in mice which appears to be mediated via a MAPK-signaling pathway.
Sustained high O2 use for Ca2+ handling in rat ventricular slices under decreased free shortening after ryanodine
Authors: Kohzuki Hisaharu , Misawa Hiromi , Sakata Susumu , Ohga Yoshimi , Takaki Miyako
Published: December 2017

We hypothesized that O2 wasting of Ca2+handling in the excitation-contraction coupling in ryanodine-treated failing hearts might derive from an increased external Ca2+extrusion via Na+/Ca2+ exchanger and futile Ca2+ cycling via sarcoplasmic reticulum (SR) Ca2+-ATPase. We tested this hypothesis by mechanoenergetic studies using rat left ventricular slices. After the slices were treated with ryanodine (0.1 μM), 1-Hz free shortening significantly decreased by 78–85%, whereas the observed O2consumption (V˙o 2) required for total Ca2+ handling, increased from 0.79 to 1.13 ml O2 · min−1 · 100 g LV−1 (155.6% of control). We reconfirmed that cyclopiazonic acid (10 μM), a blocker of SR Ca2+-ATPase, decreased V˙o 2 by 75–80% in normal slices. However, 100 μM of cyclopiazonic acid was needed to inhibit the V˙o 2 by 80% after ryanodine treatment. Blockade of a sarcolemmal Na+/Ca2+exchanger by KB-R7943 (10 μM) significantly decreasedV˙o 2 by 45% after ryanodine treatment without significant effects on normal slices. Our results indicated that the V˙o 2 increase following ryanodine treatment was derived from a net change of an increased external Ca2+ extrusion via Na+/Ca2+exchanger and futile Ca2+ cycling via SR Ca2+-ATPase.
Endotoxin stimulated cytokine production in rat vascular smooth muscle cells
Authors: Detmer Kristina , Wang Zhongbiao , Warejcka Debra , Leeper-Woodford Sandra K. , Newman Walter H.
Published: December 2017

Because inflammatory processes may promote the development of atherosclerosis, we examined the activation of cytokine genes in rat vascular smooth muscle cells in vitro after treatment with bacterial lipopolysaccharide (LPS). Interleukin-1 (IL-1), IL-6 and tumor necrosis factor-α (TNF-α) mRNA increased in response to LPS. Activation of nuclear factor-κB (NF-κB) presumably results in NF-κB binding to regulatory regions of target genes and activating transcription. We therefore compared the kinetics of NF-κB activation, cytokine message production, and TNF-α secretion. Maximum active NF-κB was found at 30 min after the addition of LPS and decreased thereafter. Increased IL-6 mRNA was detected at 30 min, increased TNF-α mRNA at 60 min, and increased IL-1 mRNA at 120 min. Secretion of TNF-α was dependent on LPS concentration and was first detected 120 min after LPS addition. Aspirin, which has been shown to inhibit NF-κB activation and cytokine secretion in other cell types, did not inhibit NF-κB activation or TNF-α secretion. However, aspirin reduced the amount of both TNF-α and IL-6 mRNA present 30 min after LPS addition by half ( P < 0.05).
Selective recruitment of neutrophils and lymphocytes by thrombin: a role for NF-κB
Authors: Kaur Jaswinder , Woodman Richard C. , Ostrovsky Lena , Kubes Paul
Published: December 2017

With the use of a whole blood laminar flow chamber system, we examined the types of leukocytes, adhesion molecules and the role of nuclear factor-κB (NF-κB) in thrombin-induced leukocyte recruitment. Primary human umbilical vein endothelial cells (HUVEC) stimulated with thrombin induced a significant increase in P-selectin-dependent neutrophil recruitment. Unexpectedly, brief thrombin stimulation (3 min) of endothelium also induced a significant lymphocyte recruitment 4 h later in addition to neutrophil recruitment. E-selectin antibody reduced neutrophil recruitment by >90%, whereas vascular adhesion molecule-1 (VCAM-1)/α4-integrin were primarily responsible for lymphocyte recruitment. To examine whether NF-κB contributed to leukocyte recruitment 4 h post thrombin stimulation, we treated HUVEC with the NF-κB inhibitor MG-132 for 1 h before thrombin stimulation. MG-132 significantly reduced the number of rolling (77.1%) and adherent (79.9%) leukocytes compared with thrombin stimulation alone. The inhibitor was more effective at preventing lymphocyte than neutrophil recruitment, consistent with its greater effect on VCAM-1 versus E-selectin expression. Tumor necrosis factor-α- and MG-132-treated HUVEC displayed no inhibition of leukocyte recruitment despite a decrease in NF-κB activation. In summary, thrombin causes predominant neutrophil recruitment via rapid P-selectin expression but also a delayed E-selectin- and VCAM-1-dependent neutrophil and lymphocyte recruitment via de novo protein synthesis. Although NF-κB mobilization was essential for thrombin-mediated VCAM-1-dependent recruitment, it only partially contributed to E-selectin-dependent recruitment.
Endogenous nitric oxide modulates myocardial oxygen consumption in canine right ventricle
Authors: Setty Srinath , Bian Xiaoming , Tune Johnathan D. , Downey H. Fred
Published: December 2017

The role of endogenous nitric oxide (NO) in modulating myocardial oxygen consumption (MV˙o 2) is unclear, in part because of systemic and coronary hemodynamic effects of blocking NO release. This study evaluated the effect of NO on right ventricular MV˙o 2 under controlled hemodynamic conditions. In 12 open-chest dogs, N ω-nitro-l-arginine methyl ester (l-NAME, 150 μg/min), a NO synthase (NOS) blocker, was infused into the right coronary artery. Heart rate and mean aortic pressure were constant. Right coronary blood flow and right ventricular MV˙o 2 were measured at normal and elevated right coronary perfusion pressures (RCP) before and afterl-NAME. To avoid effects of NO synthesis blockade on right coronary blood flow, which might have altered right ventricular MV˙o 2, experiments, were conducted during adenosine-induced maximal coronary vasodilation. l-NAME did not affect right coronary blood flow ( P = 0.51). However,l-NAME significantly increased right ventricular MV˙o 2 (6% at RCP 100 mmHg, and 21% at RCP 180 mmHg). Right coronary blood flow varied with perfusion pressure ( P < 0.02), and the elevation of MV˙o 2 produced by l-NAME increased at higher flows ( P < 0.04), consistent with the greater shear stress-mediated release of NO. These findings indicate that endogenous NO limits right ventricular MV˙o 2.
Adenosine A3 agonist cardioprotection in isolated rat and rabbit hearts is blocked by the A1 antagonist DPCPX
Authors: Kilpatrick Eric L. , Narayan Prakash , Mentzer Robert M. , Lasley Robert D.
Published: December 2017

Adenosine A3 agonists have been shown to protect ischemic rat and rabbit myocardium. However, these agonists have been reported to exert A3 independent effects, and no cardiac A3 receptor has yet been identified. We thus tested whether A3 agonist protection is due to A1receptor activation. Isolated rat and rabbit hearts were subjected to 25 and 45 min of global ischemia, respectively. Rat hearts pretreated with adenosine (100 μM), the A3 agonist 2-chloro- N 6-(3-iodobenzyl)-adenosine-5′- N-methyluronamide (Cl-IB-MECA, 50 nM), and vehicle recovered 73 ± 2%, 75 ± 4%, and 46 ± 4%, respectively, of preischemic left ventricular developed pressure (LVDP) after 30 min of reperfusion. The A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 100 nM) blocked the beneficial effects of Cl-IB-MECA (51 ± 5%) and adenosine (47 ± 6%). In rabbit hearts, the beneficial effects of the A3 agonist N 6-(3-iodobenzyl)-adenosine-5′- N-methyluronamide (50 nM) and the A1 agonist 2-chloro- N 6-cyclopentyladenosine (100 nM) on postischemic LVDP (75 ± 4 and 74 ± 5%, respectively) were blocked by DPCPX (34 ± 4 and 36 ± 3%, respectively). The reduction in infarct size with both agonists was also completely blocked by DPCPX. These results suggest that these A3 agonists protect ischemic myocardium via A1 receptor activation.
Peroxisome proliferator-activated receptor-α ligands inhibit cardiac lipoprotein lipase activity
Authors: Carroll Rogayah , Severson David L.
Published: December 2017

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that regulate gene expression of lipoprotein lipase (LPL) in liver and adipose tissue. We examined the direct effect of PPAR-α ligands on LPL catalytic activity in cultured cardiomyocytes from adult rat heart. After overnight culture (16 h), 1 μM Wy-14643 and 10 μM BM-17.0744 decreased total cellular LPL activity to ∼50% of control with no change in enzyme synthesis or mass; as a consequence, PPAR-α activation produced a significant decrease in LPL specific activity (mU/ng LPL protein). Wy-14643 and BM-17.0744 also reduced heparin-releasable LPL activity and mass in the culture medium. Inhibition of LPL activity by Wy-14643 did not reduce the ability of insulin plus dexamethasone to stimulate cellular and heparin-releasable LPL activities. A similar inhibitory effect on cellular and heparin-releasable LPL activity was observed when cardiomyocytes were cultured with 60 μM linoleic acid. In conclusion, two different PPAR-α ligands (Wy-14643 and BM-17.0744) inhibited cellular LPL activity in cultured cardiomyocytes by a posttranscriptional and posttranslational mechanism.
Mechanisms underlying delayed afterdepolarizations in hypertrophied left ventricular myocytes of rats
Authors: Mészáros János , Khananshvili Daniel , Hart George
Published: December 2017

Cardiac hypertrophy was induced in rats by daily injection of isoproterenol (5 mg/kg ip) for 7 days. Membrane voltage and currents were recorded using the whole cell patch-clamp technique in left ventricular myocytes from control and hypertrophied hearts. Ryanodine-sensitive delayed afterdepolarizations (DADs) and transient inward current ( Iti) appeared in hypertrophied cells more often and were of larger amplitude than in control cells. DADs and Itiare carried principally by Na/Ca exchange with smaller contributions from a nonselective cation channel and from a Cl−channel. The latter is expressed only in hypertrophied myocytes. In hypertrophy, the density of caffeine-induced Na/Ca exchange current ( INa/Ca) was increased by 26%, sarcoplasmic reticulum (SR) Ca2+content as assessed from the integral of INa/Cawas increased by 30%, the density of Na-pump current ( Ipump) was reduced by 40%, and the intracellular Na+content, measured by Na+-selective microelectrodes was increased by 55%. The results indicate that DADs and Itiare generated by spontaneous Ca2+release from an overloaded SR caused by a downregulated Na pump and an upregulated Na/Ca exchange. These findings may explain the propensity for arrhythmias seen in this model of hypertrophy.
Growth hormone reverses age-related cardiac myofilament dysfunction in rats
Authors: Wannenburg Thomas , Khan Amir S. , Sane David C. , Willingham Mark C. , Faucette Tony , Sonntag William E.
Published: December 2017

We tested the hypotheses that aging is associated with a reduction in overall cardiac contractility and myofilament force generation that could be reversed with growth hormone (GH) replacement. Three groups of male Brown-Norway rats were studied: young (YSAL: 8 mo old, n = 13), old (OSAL: 28 mo old, n = 13), and old GH-treated (OGH: 28 mo old, n = 12; 300 μg bovine GH, twice a day for 30 days). The left ventricular (LV) pressure-volume relation was derived in isolated hearts, after which isolated trabecular muscles from these hearts were permeabilized and maximal myofilament force generation (Fmax) was measured. LV developed pressures at a LV volume of 0.3 ml were significantly depressed with age: 84 ± 6 vs. 71 ± 6 mmHg (YSALvs. OSAL, respectively, P= 0.001) and not restored by GH (69 ± 4 mmHg). Fmaxwas reduced in the aged hearts: 47.5 ± 3.12 vs. 35.9 ± 3.03 mN/mm2(YSALvs. OSAL, respectively, P = 0.014) but was restored with GH replacement to 46.7 ± 3.12 mN/mm2(OSALvs. OGH, P = 0.021). Our results suggest that cellular myofilament contractility is reduced with aging and restored with GH replacement.
Cardiac-directed overexpression of wild-type α1B-adrenergic receptor induces dilated cardiomyopathy
Authors: Lemire Isabelle , Ducharme Anique , Tardif Jean-Claude , Poulin Francine , Jones Larry R. , Allen Bruce G. , Hébert Terence E. , Rindt Hansjörg
Published: December 2017

Using transgenesis as a paradigm, we show here that α1-adrenergic receptors (α1AR) play an important role in cardiac homeostasis. Cardiomyocyte-specific overexpression of the α1BAR subtype resulted in the development of dilated cardiomyopathy and death at ∼9 mo of age with typical signs of heart failure. Histological analyses showed the enlargement of all four cardiac chambers and cardiomyocyte disarray in the failing hearts. Transgenic animals showed increased left ventricular areas, as assessed by echocardiography. In addition, a progressive decrease in left ventricular systolic function was revealed. The abundance and activity of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2) were reduced, and the ratio of phospholamban to SERCA2 was increased. α-Myosin heavy chain (MHC) mRNA was less abundant in older transgenic ventricles, whereas β-MHC was induced in the failing hearts. Titin mRNA abundance was decreased at 9 mo, whereas atrial natriuretic factor mRNA was elevated at all times. This model mimics structural and functional features of idiopathic dilated cardiomyopathy. The results of this study suggest that chronic α1AR activity is deleterious for cardiac function.
Hemorrhagic shock primes the hepatic portal circulation for the vasoconstrictive effects of endothelin-1
Authors: Pannen Benedikt H. J. , Schroll Stephan , Loop Torsten , Bauer Michael , Hoetzel Alexander , Geiger Klaus K.
Published: December 2017

To test whether hemorrhagic shock and resuscitation (HSR) alters the vascular responsiveness of the portohepatic circulation to endothelins (ETs), we studied the macro- and microcirculatory effects of the preferential ETAreceptor agonist ET-1 and of the selective ETBreceptor agonist sarafotoxin 6c (S6c) after 1 h of hemorrhagic hypotension and 5 h of volume resuscitation in the isolated perfused rat liver ex vivo using portal pressure-flow relationships and epifluorescence microscopy. Although HSR did not cause major disturbances of hepatic perfusion per se, the response to ET-1 (0.5 × 10−9M) was enhanced, leading to greater increases in portal driving pressure, total portal resistance, and zero-flow pressures and more pronounced decreases in portal flow, sinusoidal diameters, and hepatic oxygen delivery compared with time-matched sham shock controls. In sharp contrast, the constrictive response to S6c (0.25 × 10−9M) remained unchanged. Thus HSR primes the portohepatic circulation for the vasoconstrictive effects of ET-1 but does not alter the effects of the ETBreceptor agonist S6c. The enhanced sinusoidal response may contribute to the subsequent development of hepatic microcirculatory failure after secondary insults that are associated with increased generation of ET-1.
Relationship between interstitial fluid volume and pressure (compliance) in hypothyroid rats
Authors: Wiig Helge , Lund Tjøstolv
Published: December 2017

There is clinical and experimental evidence that lack of thyroid hormones may affect the composition and structure of the interstitium. This can influence the relationship between volume and pressure during changes in hydration. Hypothyrosis was induced in rats by thyroidectomy 8 wk before the experiments. Overhydration was induced by infusion of acetated Ringer, 5, 10, and 20% of the body weight, while fluid was withdrawn by peritoneal dialysis with hypertonic glucose. Interstitial fluid pressure (Pi) in euvolemia (euvolemic control situation) and experimental situation was measured with micropipettes connected to a servocontrolled counterpressure system. The corresponding interstitial fluid volume (Vi) was found as the difference between extracellular fluid volume measured as the distribution volume of51Cr-labeled EDTA and plasma volume measured using125I-labeled human serum albumin. In euvolemia, Viwas similar or lower in the skin and higher in skeletal muscle of hypothyroid than in euthyroid control rats, whereas the corresponding Piwas higher in all tissues. During overhydration, Pirose to the same absolute level in both types of rats, whereas during peritoneal dialysis there was a linear relationship between volume and pressure in all tissues and types of rats. Interstitial compliance (Ci), calculated as the inverse value of the slope of the curve relating changes in volume and pressure in dehydration, did not differ significantly in the hindlimb skin of hypothyroid and euthyroid rats. However, in skeletal muscle, Ciwas 1.3 and 2.0 ml · 100 g−1· mmHg−1in hypothyroid and euthyroid rats ( P < 0.01), with corresponding numbers for the back skin of 2.7 and 5.0 ml · 100 g−1· mmHg−1( P < 0.01). These experiments suggest that lack of thyroid hormones in rats changes the interstitial matrix, again leading to reduced Ciand reduced ability to mobilize fluid from the interstitium.
Effects of autonomic blockers on linear and nonlinear indexes of blood pressure and heart rate in SHR
Authors: Mestivier Denis , Dabiré Hubert , Chau Nguyen Phong
Published: December 2017

Recent results in normotensive Wistar-Kyoto (WKY) rats show that nonlinear method may be more specific to quantify sympathetic and parasympathetic activities than the low (LF) and high frequencies (HF) spectral powers of blood pressure (BP) and R-R interval (RR). The present study extends this conclusion to spontaneously hypertensive rats (SHR). Blood pressure was recorded for 30 min before and after intravenous injection of saline, hexamethonium, atropine, atenolol, or prazosin. Mean level, standard deviation (SD), spectral LF and HF components, and three nonlinear indexes (percentage of recurrence, percentage of determinism, and length index of the recurrence plot method) were used to analyze the BP and RR signals. In conscious SHR, sympathetic but not parasympathetic blockade reduced BP level and LF-BP, and increased nonlinear indexes of BP. RR increased after β-sympathetic and ganglionic blockade, decreased after parasympathetic blockade, and remained unchanged after α1-sympathetic blockade. SD-RR decreased after ganglionic and α1 blockade, whereas HF-RR increased after β-sympathetic blockade. The effects on nonlinear indexes of RR are clear and consistent: only α1-blockade increased the indexes. Our nonlinear indexes may be useful to investigate cardiovascular functions in normotension and hypertension.
MR imaging measurement of compartmental water diffusion in perfused heart slices
Authors: Forder John R. , Bui Jonathan D. , Buckley David L. , Blackband Stephen J.
Published: December 2017

Myocardial tissue slices were isolated from the left ventricular free wall (7 slices) and left ventricular papillary muscle (3 slices) of New Zealand White male rabbits ( n= 4) and were subsequently superfused with a modified St. Thomas' Hospital cardioplegic solution at 19°C. The diffusion-weighted images were obtained with a 600-MHz nuclear magnetic resonance spectrometer using diffusion gradient b-values that ranged from 166 to 6,408 s/mm2; the apparent diffusion coefficient of water in the tissues were subsequently calculated. All of the tissue samples that were studied exhibited nonmonoexponential diffusion. Data from seven slices were mathematically fitted by a biexponential expression with a fast diffusion component of 0.72 ± 0.07 × 10−3 mm2/s, and a slow diffusion component of 0.060 ± 0.033 × 10−3 mm2/s. The fast component dominated the calculated apparent diffusion coefficient of the tissue, composed of 82 ± 3% of the overall diffusion-dependent signal decay. Thus myocardial tissue exhibits characteristics consistent with multiple compartments of diffusion. This work has important implications for myocardial diffusion tensor imaging, as well as the changes in diffusion that have been reported following myocardial ischemia.
Lipopolysaccharide reduces intercellular coupling in vitro and arteriolar conducted response in vivo
Authors: Tyml Karel , Wang Xiaowei , Lidington Darcy , Ouellette Yves
Published: December 2017

Our recent in vitro study (Lidington et al. J Cell Physiol 185: 117–125, 2000) suggested that lipopolysaccharide (LPS) reduces communication along blood vessels. The present investigation extended this study to determine whether any effect of LPS and/or inflammatory cytokines [tumor necrosis factor-α, interleukin (IL)-1β, and IL-6] on endothelial cell coupling in vitro could also be demonstrated for an arteriolar conducted response in vivo. Using an electrophysiological approach in monolayers of microvascular endothelial cells, we found that LPS (10 μg/ml) but not these cytokines reduced intercellular conductance ( c i) (an index of cell communication) and that LPS together with these cytokines did not further reduce c i. Also, c i was restored after LPS washout, and the LPS-induced reduction was prevented by protein tyrosine kinase (PTK) inhibitors (1.5 μM Tyr A9 and 10 nM PP-2). In our in vivo experiments in arterioles of the mouse cremaster muscle, local electrical stimulation evoked vasoconstriction that conducted along arterioles. LPS in the muscle superfusate did not alter local vasoconstriction but reduced the conducted response. Washout of LPS restored the conducted response, whereas PTK inhibitors prevented the effect of LPS. On the basis of a newly developed mathematical model, the LPS-induced reduction in conducted response was predicted to reduce the arteriolar ability to increase resistance to blood flow. We conclude that LPS can reduce communication in in vitro and in vivo systems comparably in a reversible and tyrosine kinase-dependent manner. Based on literature and present results, we suggest that LPS may compromise microvascular hemodynamics at both the arteriolar responsiveness and the conduction levels.
Na+/H+exchange subtype 1 inhibition reduces endothelial dysfunction in vessels from stunned myocardium
Authors: Symons J. David , Schaefer Saul
Published: December 2017

Myocardial ischemia and reperfusion cause myocyte and vascular dysfunction, frequently termed “stunning.” We hypothesized that inhibiting the Na+/H+exchanger subtype 1 isoform (NHE1) during ischemia and reperfusion limits myocardial and coronary microvascular stunning. Anesthetized rats completed 2 × 10-min coronary artery occlusions separated by 5-min of reperfusion, followed by 15 or 60 min of reperfusion. Vehicle (saline) or the NHE1inhibitor cariporide (HOE-642) was administered 15 min before ischemia and was continued throughout each protocol. After reperfusion, hearts were excised, and the reactivity of resistance arteries (internal diameter, ∼120 μm) was assessed. The first derivative of left ventricular (LV) pressure, LV developed pressure, and LV systolic wall thickening were depressed ( P < 0.05) similarly in vehicle- and cariporide-treated rats during ischemia and after 15 or 60 min of reperfusion compared with sham-operated animals that were not exposed to ischemia (i.e., controls). In vessels obtained after 15 min of reperfusion, the maximal response to acetylcholine-induced relaxation (10−8–10−4M) was blunted ( P < 0.05) in vessels from vehicle- (∼35%) and cariporide-treated rats (∼55%) compared with controls (∼85%). However, the percent relaxation to acetylcholine was greater ( P < 0.05) in cariporide-treated rats compared with vehicle-treated rats. Maximal contractile responses to endothelin-1 (10−11–10−7M) were increased ( P < 0.05) similarly in vehicle- and cariporide-treated rats compared with controls. Relaxation to sodium nitroprusside (10−4M) was not different among groups. Results were similar in vessels obtained from animals after 60 min of reperfusion. These findings suggest that NHE1inhibition before coronary occlusion lessens ischemia-induced microvascular dysfunction for 15–60 min after reperfusion but does not alter myocardial contractile function in the area at risk.