bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of sildenafil on coronary active and reactive hyperemia
Authors: Chen Yingjie , Du Ruisheng , Traverse Jay H. , Bache Robert J.
Published: December 2017

Sildenafil, a selective inhibitor of phosphodiesterase type 5, produces relaxation of isolated epicardial coronary artery segments by causing accumulation of cGMP. Because shear-induced nitric oxide-dependent vasodilation is mediated by cGMP, this study was performed to determine whether sildenafil would augment the coronary resistance vessel dilation that occurs during the high-flow states of exercise or reactive hyperemia. In chronically instrumented dogs, sildenafil (2 mg/kg per os) augmented the vasodilator response to acetylcholine, with a leftward shift of the dose-response curve relating coronary flow to acetylcholine dose. Sildenafil caused a 6.7 ± 2.1 mmHg decrease of mean aortic pressure, which was similar at rest and during treadmill exercise ( P < 0.05), with no change of heart rate, left ventricular (LV) systolic pressure, or LV maximal first time derivative of LV pressure. Sildenafil tended to increase myocardial blood flow at rest and during exercise (mean increase = 14 ± 3%; P < 0.05 by ANOVA), but this was associated with a significant decrease in hemoglobin, so that the relationship between myocardial oxygen consumption and oxygen delivery to the myocardium (myocardial blood flow × arterial O2 content) was unchanged. Furthermore, sildenafil did not alter coronary venous Po 2, indicating that the coupling between myocardial blood flow and myocardial oxygen demands was not altered. In addition, sildenafil did not alter the peak coronary flow rate, debt repayment, or duration of reactive hyperemia that followed a 10-s coronary occlusion. The findings suggest that cGMP-mediated resistance vessel dilation contributes little to the increase in myocardial flow that occurs during exercise or reactive hyperemia.
Late preconditioning enhances recovery of myocardial function after infarction in conscious rabbits
Authors: Takano Hitoshi , Tang Xian-Liang , Kodani Eitaro , Bolli Roberto
Published: December 2017

It is unknown whether late preconditioning (PC) enhances the recovery of left ventricular (LV) function after a myocardial infarction. Thus 25 conscious rabbits were subjected to a 30-min coronary occlusion followed by 28 days of reperfusion after PC 24 h earlier with either ischemia or nitric oxide donor administration [ S-nitroso- N-acetylpenicillamine (SNAP)]. The recovery of wall thickening (WTh) after reperfusion was significantly improved in the ischemic PC and SNAP PC groups compared with controls, both at rest and during dobutamine stress. Interestingly, neither ischemia- nor SNAP-induced late PC attenuated myocardial stunning from day 1 through day 14. Infarct size was smaller in the ischemic PC and SNAP PC groups compared with controls. In all groups, WTh at 28 days was positively and linearly related to the percentage of viable tissue in the region underlying the ultrasonic crystal ( r = 0.90), indicating that the improvement in LV function after both ischemia-induced and NO donor-induced late PC can be fully explained by the reduction in infarct size; a separate effect of late PC on LV remodeling or LV contractility need not be invoked. In conclusion, in conscious rabbits late PC, induced either by ischemia or pharmacologically, not only limits infarct size but also enhances the recovery of LV function after myocardial infarction. This finding has important clinical implications and provides triphenyltetrazolium chloride-independent evidence that late PC limits myocellular death after sustained ischemia.
Altered hemodynamics in transgenic mice harboring mutant tropomyosin linked to hypertrophic cardiomyopathy
Authors: Evans Christian C. , Pena James R. , Phillips Ronald M. , Muthuchamy Mariappan , Wieczorek David F. , Solaro R. John , Wolska Beata M.
Published: December 2017

We used transgenic (TG) mice overexpressing mutant α-tropomyosin [α-Tm(Asp175Asn)], linked to familial hypertrophic cardiomyopathy (FHC), to test the hypothesis that this mutation impairs cardiac function by altering the sensitivity of myofilaments to Ca2+. Left ventricular (LV) pressure was measured in anesthetized nontransgenic (NTG) and TG mice. In control conditions, LV relaxation was 6,970 ± 297 mmHg/s in NTG and 5,624 ± 392 mmHg/s in TG mice ( P < 0.05). During β-adrenergic stimulation, the rate of relaxation increased to 8,411 ± 323 mmHg/s in NTG and to 6,080 ± 413 mmHg/s in TG mice ( P < 0.05). We measured the pCa-force relationship (pCa = −log [Ca2+]) in skinned fiber bundles from LV papillary muscles of NTG and TG hearts. In control conditions, the Ca2+concentration producing 50% maximal force (pCa50) was 5.77 ± 0.02 in NTG and 5.84 ± 0.01 in TG myofilament bundles ( P < 0.05). After protein kinase A-dependent phosphorylation, the pCa50was 5.71 ± 0.01 in NTG and 5.77 ± 0.02 in TG myofilament bundles ( P < 0.05). Our results indicate that mutant α-Tm(Asp175Asn) increases myofilament Ca2+-sensitivity, which results in decreased relaxation rate and blunted response to β-adrenergic stimulation.
Bicarbonate exacerbates oxidative injury induced by antitumor antibiotic doxorubicin in cardiomyocytes
Authors: Konorev Eugene A. , Zhang Hao , Joseph Joy , Kennedy M. Claire , Kalyanaraman B.
Published: December 2017

Doxorubicin, a broad-spectrum antitumor antibiotic, causes dose-dependent cardiomyopathy and heart failure. Although the exact molecular mechanisms of cardiotoxicity are not well established, oxidative mechanisms involving doxorubicin-induced superoxide anion production have been proposed. In this study, we show that bicarbonate, a physiologically relevant tissue component, greatly amplified doxorubicin-induced cardiomyocyte injury. Bicarbonate also enhanced inactivation of aconitase, a crucial tricarboxylic acid cycle enzyme, in cardiomyocytes exposed to doxorubicin. The cell-permeable superoxide dismutase mimetic, Mn(III)tetrakis (4-benzoic acid) porphyrin, reversed doxorubicin-induced cardiomyocyte injury. Bicarbonate enhanced the inactivation of purified mitochondrial aconitase in the xanthine/xanthine oxidase system, generating superoxide. The results suggest that bicarbonate amplifies the prooxidant effect of superoxide. Bicarbonate also caused an increased loading of cardiomyocytes with doxorubicin. We conclude that the bicarbonate-mediated increase in doxorubicin toxicity is due to increased intracellular loading of doxorubicin in cardiomyocytes and subsequent exacerbation of superoxide-mediated cardiomyocyte injury.
Myofilament lattice spacing as a function of sarcomere length in isolated rat myocardium
Authors: Irving Thomas C. , Konhilas John , Perry Darold , Fischetti Robert , de Tombe Pieter P.
Published: December 2017

The Frank-Starling relationship of the heart has, as its molecular basis, an increase in the activation of myofibrils by calcium as the sarcomere length increases. It has been suggested that this phenomenon may be due to myofilaments moving closer together at longer lengths, thereby enhancing the probability of favorable acto-myosin interaction, resulting in increased calcium sensitivity. Accordingly, we have developed an apparatus so as to obtain accurate measurements of myocardial interfilament spacing (by synchrotron X-ray diffraction) as a function of sarcomere length (by video microscopy) over the working range of the heart, using skinned as well as intact rat trabeculas as model systems. In both these systems, lattice spacing decreased significantly as sarcomere length was increased. Furthermore, lattice spacing in the intact muscle was significantly smaller than that in the skinned muscle at all sarcomere lengths studied. These observations are consistent with the hypothesis that lattice spacing underlies length-dependent activation in the myocardium.
Perfusion-contraction mismatch with coronary microvascular obstruction: role of inflammation
Authors: Dörge Hilmar , Neumann Till , Behrends Matthias , Skyschally Andreas , Schulz Rainer , Kasper Christoph , Erbel Raimund , Heusch Gerd
Published: December 2017

A close relationship exists between regional myocardial blood flow (RMBF) and function during acute coronary inflow restriction (perfusion-contraction matching). However, the relationship of flow and function during coronary microvascular obstruction is unknown. In 12 anesthetized dogs, the left circumflex coronary artery was perfused from an extracorporeal circuit. After control measurements, 3,000 microspheres (42 μm diameter) per milliliter per minute inflow were injected to cause a microembolism (ME, n = 6). With unchanged systemic hemodynamics and RMBF, posterior systolic wall thickening (PWT) decreased from 19.8 ± 1.9% SD at control to 13.3 ± 4.0, 10.3 ± 3.8, and 6.9 ± 4.7% ( P < 0.05 vs. control) at 1, 4, and 8 h, respectively. For comparison, inflow was progressively reduced to match PWT to that of the ME group at 1, 4, and 8 h (stenosis, STE, n = 6). RMBF in the STE group was reduced in proportion to PWT. Infarct size was not different among groups (6.5 ± 4.5 vs. 3.4 ± 3.2%). However, the number of leukocytes infiltrating the area at risk was significantly greater in the ME group than in the STE group. Coronary microembolization results in perfusion-contraction mismatch and is associated with an inflammatory response.
Tonic regulation of vascular tone by nitric oxide and chloride ions in rat isolated small coronary arteries
Authors: Graves Jonathan E. , Greenwood Iain A. , Large William A.
Published: December 2017

We have investigated the involvement of Cl− in regulating vascular tone in rat isolated coronary arteries mounted on a small vessel myograph. Mechanical removal of the endothelium or inhibition of nitric oxide (NO) synthase with N ω-nitro-l-arginine methyl ester (l-NAME, 10−4 M) led to contraction of rat coronary arteries, and these contractions were sensitive to nicardipine (10−6 M). This suggests that release of NO tonically inhibits a contractile mechanism that involves voltage-dependent Ca2+ channels. In arteries contracted withl-NAME, switching the bathing solution to physiological saline solution with a reduced Cl− concentration potentiated the contraction. DIDS (5 × 10−6–3 × 10−4 M) caused relaxation of l-NAME-induced tension (IC50 = 55 ± 10 μM), providing evidence for a role of Cl−. SITS (10−5–5 × 10−4 M) did not affectl-NAME-induced tension, suggesting that DIDS is not acting by inhibition of anion exchange. Mechanical removal of the endothelium led to contraction of arteries, which was sensitive to DIDS (IC50 = 50 ± 8 μM) and was not affected by SITS. This study suggests that, in rat coronary arteries, NO tonically suppresses a contractile mechanism that involves a Cl−conductance.
Force regulates smooth muscle actin in cardiac fibroblasts
Authors: Wang J. , Seth A. , McCulloch C. A. G.
Published: December 2017

Chronic ventricular pressure overload can regulate expression of α-smooth muscle actin (SMA) in cardiac fibroblasts, but it is unclear if force alone or the concomitant activity of angiotensin II is the principal regulatory factor. To test if SMA mRNA and protein in rat cardiac fibroblasts are regulated directly by force, we first induced SMA expression in cultured cells and then applied magnetically generated perpendicular forces through focal adhesions using collagen-coated magnetite beads. Continuous static forces (0.65 pN/μm2) selectively reduced SMA but not β-actin mRNA and protein content within 4 h (to 55 ± 9% of controls); SMA returned to baseline by 8 h. There was no change in SMA content after force application with either plasma or the cellular fibronectin IIIA domain, BSA, or poly-l-lysine beads. The early loss of SMA was apparently due to selective leakage into the cell culture medium. Treatment with angiotensin II (10 nM) abrogated the force-induced reduction of SMA and increased the levels of this protein. The stress kinase p38 was phosphorylated by force, whereas extracellular signal-regulated kinase 1/2 and c-Jun NH2-terminal kinase were unaffected. The p38 kinase inhibitor SB-203580 relieved the force-induced SMA reduction. We conclude that force-induced inhibition of SMA is mediated through the p38 kinase pathway, and this pathway antagonizes angiotensin II regulation of SMA.
Distinct roles for L- and T-type Ca2+channels in regulation of atrial ANP release
Authors: Wen Jin Fu , Cui Xun , Ahn Jin Sub , Kim Suhn Hee , Seul Kyung Hwan , Kim Sung Zoo , Park Young Kyung , Lee Ho Sub , Cho Kyung Woo
Published: December 2017

Atrial secretion of atrial natriuretic peptide (ANP) has been shown to be regulated by atrial workload. Although modulating factors for the secretion of ANP have been reported, the role for intracellular Ca2+on the secretion of ANP has been controversial. The purpose of the present study was to define roles for L- and T-type Ca2+channels in the regulation of ANP secretion in perfused beating rabbit atria. BAY K 8644 (BAY K) increased atrial stroke volume and pulse pressure. BAY K suppressed ANP secretion and ANP concentration in terms of extracellular fluid (ECF) translocation concomitantly with an increase in atrial dynamics. BAY K shifted the relationship between ANP secretion and ECF translocation downward and rightward. These results indicate that BAY K inhibits myocytic release of ANP. In the continuous presence of BAY K, diltiazem reversed the effects of BAY K. Diltiazem alone increased ANP secretion and ANP concentration along with a decrease in atrial dynamics. Diltiazem shifted relationships between ANP secretion and atrial stroke volume or ECF translocation leftward. The T-type Ca2+channel inhibitor mibefradil decreased atrial dynamics. Mibefradil inhibited ANP secretion and ANP concentration in contrast with the L-type Ca2+channel inhibitor. These results suggest that activation of L- and T-type Ca2+channels elicits opposite effects on atrial myocytic release of ANP.
Interaction between angiotensin II and Smad proteins in fibroblasts in failing heart and in vitro
Authors: Hao Jianming , Wang Baiqiu , Jones Stephen C. , Jassal Davinder S. , Dixon Ian M. C.
Published: December 2017

Angiotensin II (angiotensin) and transforming growth factor (TGF)-β1play an important role in cardiac fibrosis. We examined Smad proteins in 8-wk post-myocardial infarction (MI) rat hearts. AT1blockade (losartan) attenuated the activation of TGF-β1in target tissues. Losartan administration (8 wk, 15 mg · kg−1· day−1) normalized total Smad 2 overexpression in infarct scar and remnant heart tissue and normalized Smad 4 in infarct scar. Phosphorylated Smad 2 (P-Smad 2) staining decreased in cytosol from failing heart vs. the control, which was normalized by losartan, suggesting augmented P-Smad 2 movement into nuclei in untreated failing hearts. Using adult primary rat fibroblasts treated with angiotensin (10−6M), we noted rapid translocation (15 min) of P-Smad 2 into the nuclei from the cytosol. Nuclear P-Smad 2 protein level increased with angiotensin treatment, which was blocked by losartan. We conclude that angiotensin may influence total Smad 2 and 4 expression in post-MI heart failure and that angiotensin treatment is associated with rapid P-Smad 2 nuclear translocation in isolated fibroblasts. This study suggests that cross talk between angiotensin and Smad signaling is associated with fibrotic events in post-MI hearts.
Three-dimensional endocardial impedance mapping: a new approach for myocardial infarction assessment
Authors: Wolf Tamir , Gepstein Lior , Hayam Gal , Zaretzky Asaph , Shofty Rona , Kirshenbaum Dina , Uretzky Gideon , Oron Uri , Ben-Haim Shlomo A.
Published: December 2017

Precise identification of infarcted myocardial tissue is of importance in diagnostic and interventional cardiology. A three-dimensional, catheter-based endocardial electromechanical mapping technique was used to assess the ability of local endocardial impedance in delineating the exact location, size, and border of canine myocardial infarction. Electromechanical mapping of the left ventricle was performed in a control group ( n = 10) and 4 wk after left anterior descending coronary artery ligation ( n = 10). Impedance, bipolar electrogram amplitude, and endocardial local shortening (LS) were quantified. The infarcted area was compared with the corresponding regions in controls, revealing a significant reduction in impedance values [infarcted vs. controls: 168.8 ± 11.7 and 240.7 ± 22.3 Ω, respectively (means ± SE), P < 0.05] bipolar electrogram amplitude (1.8 ± 0.2 mV, 4.4 ± 0.7 mV, P < 0.05), and LS (−2.36 ± 1.6%, 11.9 ± 0.9%, P < 0.05). The accuracy of the impedance maps in delineating the location and extent of the infarcted region was demonstrated by the high correlation with the infarct area (Pearson's correlation coefficient = 0.942) and the accurate identification of the infarct borders in pathology. By accurately defining myocardial infarction and its borders, endocardial impedance mapping may become a clinically useful tool in differentiating healthy from necrotic myocardial tissue.
Effect of erythrocyte aggregation on velocity profiles in venules
Authors: Bishop Jeffrey J. , Nance Patricia R. , Popel Aleksander S. , Intaglietta Marcos , Johnson Paul C.
Published: December 2017

A recent whole organ study in cat skeletal muscle showed that the increase in venous resistance seen at reduced arterial pressures is nearly abolished when the muscle is perfused with a nonaggregating red blood cell suspension. To explore a possible underlying mechanism, we tested the hypothesis that red blood cell aggregation alters flow patterns in vivo and leads to blunted red blood cell velocity profiles at reduced shear rates. With the use of fluorescently labeled red blood cells in tracer quantities and a video system equipped with a gated image intensifier, we obtained velocity profiles in venous microvessels (45–75 μm) of rat spinotrapezius muscle at centerline velocities between 0.3 and 14 mm/s (pseudoshear rates 3–120 s−1) under normal (nonaggregating) conditions and after induction of red blood cell aggregation with Dextran 500. Profiles are nearly parabolic (Poiseuille flow) over this flow rate range in the absence of aggregation. When aggregation is present, profiles are parabolic at high shear rates and become significantly blunted at pseudoshear rates of 40 s−1 and below. These results indicate a possible mechanism for increased venous resistance at reduced flows.
Glutathione attenuates coronary constriction to acetylcholine in patients with coronary spastic angina
Authors: Kugiyama Kiyotaka , Miyao Yuji , Sakamoto Tomohiro , Kawano Hiroaki , Soejima Hirofumi , Miyamoto Shinzo , Yoshimura Michihiro , Ogawa Hisao , Sugiyama Seigo , Yasue Hirofumi
Published: December 2017

This study examined the effect of reduced glutathione (GSH), an important antioxidant that restores intracellular redox imbalance and prevents inactivation of endothelial-derived nitric oxide, on the abnormal vasomotor reactivity in spastic coronary arteries. The responses of epicardial diameter of the left coronary arteries to intracoronary infusion of acetylcholine (ACh; 50 μg/min) were measured by quantitative coronary angiography before and during combined intracoronary infusion of GSH (50 mg/min for 6 min) or saline as a placebo in 24 patients with coronary spastic angina and in 28 control patients. All of the spastic coronary arteries showed constrictor response to ACh, whereas the control coronary arteries as a whole showed only minimal diameter changes to ACh. GSH infusion suppressed constrictor response of epicardial diameter to ACh in patients with coronary spastic angina, whereas it had no significant effect in control subjects. Saline infusion did not have any effects. The results indicate that GSH attenuated the constrictor response to ACh in epicardial coronary arteries of patients with coronary spastic angina. GSH may have an important role in the regulation of coronary vasomotor function in patients with coronary spastic angina.
Dynamic regulation of heart rate during acute hypotension: new insight into baroreflex function
Authors: Zhang Rong , Behbehani Khosrow , Crandall Craig G. , Zuckerman Julie H. , Levine Benjamin D.
Published: December 2017

To examine the dynamic properties of baroreflex function, we measured beat-to-beat changes in arterial blood pressure (ABP) and heart rate (HR) during acute hypotension induced by thigh cuff deflation in 10 healthy subjects under supine resting conditions and during progressive lower body negative pressure (LBNP). The quantitative, temporal relationship between ABP and HR was fitted by a second-order autoregressive (AR) model. The frequency response was evaluated by transfer function analysis. Results: HR changes during acute hypotension appear to be controlled by an ABP error signal between baseline and induced hypotension. The quantitative relationship between changes in ABP and HR is characterized by a second-order AR model with a pure time delay of 0.75 s containing low-pass filter properties. During LBNP, the change in HR/change in ABP during induced hypotension significantly decreased, as did the numerator coefficients of the AR model and transfer function gain. Conclusions: 1) Beat-to-beat HR responses to dynamic changes in ABP may be controlled by an error signal rather than directional changes in pressure, suggesting a “set point” mechanism in short-term ABP control. 2) The quantitative relationship between dynamic changes in ABP and HR can be described by a second-order AR model with a pure time delay. 3) The ability of the baroreflex to evoke a HR response to transient changes in pressure was reduced during LBNP, which was due primarily to a reduction of the static gain of the baroreflex.
VEGF increases BMEC monolayer permeability by affecting occludin expression and tight junction assembly
Authors: Wang Wen , Dentler William L. , Borchardt Ronald T.
Published: December 2017

Tight junctions between brain microvessel endothelial cells (BMECs) maintain the blood-brain barrier. Barrier breakdown is associated with brain tumors and central nervous system diseases. Tumor cell-secreted vascular endothelial growth factor (VEGF) increases microvasculature permeability in vivo and is correlated with the induction of clinically severe brain tumor edema. Here we investigated the permeability-increasing effect and tight junction formation of VEGF. By measuring [14C]sucrose flux and transendothelial electrical resistance (TER) across BMEC monolayer cultures, we found that VEGF increased sucrose permeability and decreased TER. VEGF also caused a loss of occludin and ZO-1 from the endothelial cell junctions and changed the staining pattern of the cell boundary. Western blot analysis of BMEC lysates revealed that the level of occludin but not of ZO-1 was lowered by VEGF treatment. These results suggest that VEGF increases BMEC monolayer permeability by reducing occludin expression and disrupting ZO-1 and occludin organization, which leads to tight junction disassembly. Occludin and ZO-1 appear to be downstream effectors of the VEGF signaling pathway.
Enhanced endothelin-1 response and receptor expression in small mesenteric arteries of insulin-resistant rats
Authors: Katakam Prasad V. G. , Pollock Jennifer S. , Pollock David M. , Ujhelyi Michael R. , Miller Allison W.
Published: December 2017

Hyperinsulinemia, a primary feature of insulin resistance, is associated with increased endothelin-1 (ET-1) activity. This study determined the vascular response to ET-1 and receptor binding characteristics in small mesenteric arteries of insulin-resistant (IR) rats. Rats were randomized to control (C) ( n = 32) or IR ( n = 32) groups. The response to ET-1 was assessed (in vitro) in arteries with (Endo+) and without (Endo−) endothelium. In addition, arteries (Endo+) were pretreated with the ETBantagonist A-192621 or the ETA antagonist A-127722. Finally, binding characteristics of [125I]ET-1 were determined. Results showed that in Endo+ arteries the maximal relaxation ( E max) to ET-1 was similar between C and IR groups; however, the concentration at 50% of maximum relaxation (EC50) was decreased in IR arteries. In Endo− arteries, the E max to ET-1 was enhanced in both groups. Pretreatment with A-192621 enhanced the E max and EC50 to ET-1 in both groups. In contrast, A-127722 inhibited the ET-1 response in all arteries in a concentration-dependent manner; however, a greater ET-1 response was seen at each concentration in IR arteries. Maximal binding of [125I]ET-1 was increased in IR versus C arteries although the dissociation constant values were similar. In conclusion, we found the vasoconstrictor response to ET-1 is enhanced in IR arteries due to an enhanced expression of ET receptors and underlying endothelial dysfunction.
Bioenergetic consequences of opening the ATP-sensitive K+channel of heart mitochondria
Authors: Kowaltowski Alicia J. , Seetharaman Subramaniam , Paucek Petr , Garlid Keith D.
Published: December 2017

There is an emerging consensus that pharmacological opening of the mitochondrial ATP-sensitive K+(KATP) channel protects the heart against ischemia-reperfusion damage; however, there are widely divergent views on the effects of openers on isolated heart mitochondria. We have examined the effects of diazoxide and pinacidil on the bioenergetic properties of rat heart mitochondria. As expected of hydrophobic compounds, these drugs have toxic, as well as pharmacological, effects on mitochondria. Both drugs inhibit respiration and increase membrane proton permeability as a function of concentration, causing a decrease in mitochondrial membrane potential and a consequent decrease in Ca2+uptake, but these effects are not caused by opening mitochondrial KATPchannels. In pharmacological doses (<50 μM), both drugs open mitochondrial KATPchannels, and resulting changes in membrane potential and respiration are minimal. The increased K+influx associated with mitochondrial KATPchannel opening is ∼30 nmol · min−1· mg−1, a very low rate that will depolarize by only 1–2 mV. However, this increase in K+influx causes a significant increase in matrix volume. The volume increase is sufficient to reverse matrix contraction caused by oxidative phosphorylation and can be observed even when respiration is inhibited and the membrane potential is supported by ATP hydrolysis, conditions expected during ischemia. Thus opening mitochondrial KATPchannels has little direct effect on respiration, membrane potential, or Ca2+uptake but has important effects on matrix and intermembrane space volumes.
UpregulatedTRPand enhanced capacitative Ca2+entry in human pulmonary artery myocytes during proliferation
Authors: Golovina Vera A. , Platoshyn Oleksandr , Bailey Colleen L. , Wang Jian , Limsuwan Alisa , Sweeney Michele , Rubin Lewis J. , Yuan Jason X.-J.
Published: December 2017

A rise in cytosolic Ca2+concentration ([Ca2+]cyt) due to Ca2+release from intracellular Ca2+stores and Ca2+influx through plasmalemmal Ca2+channels plays a critical role in mitogen-mediated cell growth. Depletion of intracellular Ca2+stores triggers capacitative Ca2+entry (CCE), a mechanism involved in maintaining Ca2+influx and refilling intracellular Ca2+stores. Transient receptor potential ( TRP) genes have been demonstrated to encode the store-operated Ca2+channels that are activated by Ca2+store depletion. In this study, we examined whether CCE, activity of store-operated Ca2+channels, and human TRP1 ( hTRP1) expression are essential in human pulmonary arterial smooth muscle cell (PASMC) proliferation. Chelation of extracellular Ca2+and depletion of intracellularly stored Ca2+inhibited PASMC growth in media containing serum and growth factors. Resting [Ca2+]cytas well as the increases in [Ca2+]cytdue to Ca2+release and CCE were all significantly greater in proliferating PASMC than in growth-arrested cells. Consistently, whole cell inward currents activated by depletion of intracellular Ca2+stores and the mRNA level of hTRP1 were much greater in proliferating PASMC than in growth-arrested cells. These results suggest that elevated [Ca2+]cytand intracellularly stored [Ca2+] play an important role in pulmonary vascular smooth muscle cell growth. CCE, potentially via hTRP1-encoded Ca2+-permeable channels, may be an important mechanism required to maintain the elevated [Ca2+]cytand stored [Ca2+] in human PASMC during proliferation.
Endothelial protective and antishock effects of a selective estrogen receptor modulator in rats
Authors: Ma Xin L. , Gao Feng , Chen Jun , Christopher Theodore A. , Lopez Bernard L. , Ohlstein Eliot H. , Yue Tian-Li
Published: December 2017

This study investigated whether idoxifene, a selective estrogen receptor modulator (SERM), exerted protective effects against ischemia-reperfusion-induced shock. Ovariectomized rats were treated with vehicle, idoxifene, or 17β-estradiol for 4 days. Rats were subjected to splanchnic artery occlusion (SAO) followed by reperfusion (SOA/R). In vehicle-treated rats, SAO/R resulted in hypotension, hemoconcentration, increased plasma tumor necrosis factor (TNF)-α levels, intestinal neutrophil accumulation, and endothelial dysfunction. 17β-Estradiol treatment increased plasma estradiol concentration and reduced SAO/R-induced tissue injury. Idoxifene treatment had no effect on plasma estradiol concentration but reduced SAO/R-induced hemoconcentration (+8.8 ± 1.3 vs. +14 ± 1.3% in the vehicle group, P < 0.01), TNF-α production (98 ± 3.2 vs. 214 ± 13 pg/ml, P < 0.01), and neutrophil accumulation (0.025 ± 0.005 vs. 0.047 ± 0.005 U/g protein, P < 0.01). It also improved endothelial function, prolonged survival time (172 ± 3.5 vs. 147 ± 8 min, P < 0.01), and increased survival rate (69 vs. 23%, P < 0.01). Moreover, treatment with 17β-estradiol or idoxifene in vivo reduced TNF-α-induced endothelial dysfunction in vitro. Taken together, these results demonstrated that idoxifene exerted estrogen-like, endothelial-protective, and antishock effects in ovariectomized rats, suggesting that SERMs have therapeutic potential in tissue injury resulting from ischemia-reperfusion.
Calcium preconditioning inhibits mitochondrial permeability transition and apoptosis
Authors: Xu Meifeng , Wang Yigang , Hirai Kyoji , Ayub Ahmar , Ashraf Muhammad
Published: December 2017

We tested the hypothesis whether calcium preconditioning (CPC) reduces reoxygenation injury by inhibiting mitochondrial permeability transition (MPT). Cultured myocytes were preconditioned by a brief exposure to 1.5 mM calcium (CPC) and subjected to 3 h of anoxia followed by 2 h of reoxygenation (A-R). Myocytes were also treated with 0.2 μM/l cyclosporin A (CsA), an inhibitor of MPT, before A-R. A significant increase of viable cells and reduced lactate dehydrogenase release was observed both in CPC- and CsA-treated myocytes compared with the A-R group. Cytochrome c release was predominantly observed in the cytoplasm of myocytes in the A-R group in contrast with CPC- or CsA-treated groups, where it was restricted only to mitochondria. Similarly, the cell death by apoptosis was also markedly attenuated in these groups. Electron-dense Ca2+ deposits in mitochondria were also less frequent. Atractyloside (20 μM/l), an adenine nucleotide translocase inhibitor, caused changes similar to those in the A-R group, suggesting a role of MPT in A-R injury. Protection by inhibition of MPT by CsA and CPC suggests that MPT plays an important role in reoxygenation/reperfusion injury. The data further suggest that preconditioning inhibits MPT by inhibiting Ca2+accumulation by mitochondria.
Endothelium-independent, ouabain-sensitive relaxation of bovine coronary arteries by EETs
Authors: Pratt Phillip F. , Li Pinlan , Hillard Cecilia J. , Kurian Jason , Campbell William B.
Published: December 2017

Endothelium-derived hyperpolarizing factor (EDHF) is released in response to agonists such as ACh and bradykinin and regulates vascular smooth muscle tone. Several studies have indicated that ouabain blocks agonist-induced, endothelium-dependent hyperpolarization of smooth muscle. We have demonstrated that epoxyeicosatrienoic acids (EETs), cytochrome P-450 metabolites of arachidonic acid, function as EDHFs. To further test the hypothesis that EETs represent EDHFs, we have examined the effects of ouabain on the electrical and mechanical effects of 14,15- and 11,12-EET in bovine coronary arteries. These arteries are relaxed in a concentration-dependent manner to 14,15- and 11,12-EET (EC50= 6 × 10−7M), bradykinin (EC50= 1 × 10−9M), sodium nitroprusside (SNP; EC50= 2 × 10−7M), and bimakalim (BMK; EC50= 1 × 10−7M). 11,12-EET-induced relaxations were identical in vessels with and without an endothelium. Potassium chloride (1–15 × 10−3M) inhibited [3H]ouabain binding to smooth muscle cells but failed to relax the arteries. Ouabain (10−5to 10−4M) increased basal tone and inhibited the relaxations to bradykinin, 11,12-EET, and 14,15-EET, but not to SNP or BMK. Barium (3 × 10−5M) did not alter EET-induced relaxations and ouabain plus barium was similar to ouabain alone. Resting membrane potential ( Em) of isolated smooth muscle cells was −50.2 ± 0.5 mV. Ouabain (3 × 10−5and 1 × 10−4M) decreased Em(−48.4 ± 0.2 mV), whereas 11,12-EET (10−7M) increased Em(−59.2 ± 2.2 mV). Ouabain inhibited the 11,12-EET-induced increase in Em. In cell-attached patch clamp studies, 11,12-EET significantly increased the open-state probability ( NPo) of a calcium-activated potassium channel compared with control cells (0.26 ± 0.06 vs. 0.02 ± 0.01). Ouabain did not change NPobut blocked the 14,15-EET-induced increase in NPo. These results indicate that: 1) EETs relax coronary arteries in an endothelium-independent manner, 2) unlike EETs, potassium chloride does not relax the coronary artery, and 3) ouabain inhibits bradykinin- and EET-induced relaxations as has been reported for EDHF. These findings provide further evidence that EETs are EDHFs.
Abnormal neurovascular control during exercise is linked to heart failure severity
Authors: Negrão Carlos Eduardo , Rondon Maria Urbana P. Brandão , Tinucci Taís , Alves Maria Janieire N. , Roveda Fabiana , Braga Ana Maria W. , Reis Soraya F. , Nastari Luciano , Barretto Antonio Carlos P. , Krieger Eduardo M. , Middlekauff Holly R.
Published: December 2017

The purpose of this study was to determine if abnormalities of sympathetic neural and vascular control are present in mild and/or severe heart failure (HF) and to determine the underlying afferent mechanisms. Patients with severe HF, mild HF, and age-matched controls were studied. Muscle sympathetic nerve activity (MSNA) and forearm vascular resistance (FVR) in the nonexercising arm were measured during mild and moderate static handgrip. MSNA during moderate handgrip was higher at baseline and throughout exercise in severe HF vs. mild HF (peak MSNA 67 ± 3 vs. 54 ± 3 bursts/min, P < 0.0001) and higher in mild HF vs. controls (33 ± 3 bursts/min, P < 0.0001), but the change in MSNA was not different between the groups. The change in FVR was not significantly different between the three groups during static exercise. During isolation of muscle metaboreceptors, MSNA and blood pressure remained elevated in normal controls and mild HF but not in severe HF. During mild handgrip, the increase in MSNA was exaggerated in severe HF vs. controls and mild HF, in whom MSNA did not increase. In summary, the increase in MSNA during static exercise in severe HF appears to be attributable to exaggerated central command or muscle mechanoreceptor control, not muscle metaboreceptor control.
Carotid baroreflex regulation of sympathetic nerve activity during dynamic exercise in humans
Authors: Fadel P. J. , Ogoh S. , Watenpaugh D. E. , Wasmund W. , Olivencia-Yurvati A. , Smith M. L. , Raven P. B.
Published: December 2017

We sought to determine whether carotid baroreflex (CBR) control of muscle sympathetic nerve activity (MSNA) was altered during dynamic exercise. In five men and three women, 23.8 ± 0.7 (SE) yr of age, CBR function was evaluated at rest and during 20 min of arm cycling at 50% peak O2uptake using 5-s periods of neck pressure and neck suction. From rest to steady-state arm cycling, mean arterial pressure (MAP) was significantly increased from 90.0 ± 2.7 to 118.7 ± 3.6 mmHg and MSNA burst frequency (microneurography at the peroneal nerve) was elevated by 51 ± 14% ( P < 0.01). However, despite the marked increases in MAP and MSNA during exercise, CBR-Δ%MSNA responses elicited by the application of various levels of neck pressure and neck suction ranging from +45 to −80 Torr were not significantly different from those at rest. Furthermore, estimated baroreflex sensitivity for the control of MSNA at rest was the same as during exercise ( P = 0.74) across the range of neck chamber pressures. Thus CBR control of sympathetic nerve activity appears to be preserved during moderate-intensity dynamic exercise.
Temporal effect of alcohol consumption on reactivity of pial arterioles: role of oxygen radicals
Authors: Sun Hong , Mayhan William G.
Published: December 2017

Chronic alcohol consumption reduces nitric oxide synthase-dependent responses of pial arterioles via mechanisms that remain uncertain. In addition, the temporal effects of alcohol on pial arterioles is unclear. Thus our goals were to examine the role of oxygen-derived free radicals in alcohol-induced impairment of cerebrovascular reactivity and the temporal effect of alcohol on reactivity of pial arterioles. Sprague-Dawley rats were pair-fed a liquid diet with or without alcohol for 2–3 wk, 2–3 mo, or 5–6 mo. We measured the in vivo diameter of pial arterioles in response to nitric oxide synthase-dependent dilators acetylcholine and ADP and the nitric oxide synthase-independent dilator nitroglycerin. In nonalcohol-fed rats, acetylcholine (1.0 and 10 μM) and ADP (10 and 100 μM) produced dose-related dilatation of pial arterioles. Whereas there was no difference in reactivity of arterioles to the agonists in rats fed the nonalcohol and alcohol diets for a period of 2–3 wk, there was a significant impairment in reactivity of arterioles to acetylcholine and ADP, but not nitroglycerin, in rats fed the alcohol diet for longer durations. We then found that treatment with superoxide dismutase did not alter baseline diameter of pial arterioles in nonalcohol-fed or alcohol-fed rats, but significantly improved impaired nitric oxide synthase-dependent dilatation of pial arterioles in alcohol-fed rats. Thus our findings suggest a temporal relationship in the effects of alcohol on reactivity of pial arterioles and that impaired nitric oxide synthase-dependent cerebral vasodilatation during chronic alcohol consumption may be related, in part, to enhanced release of oxygen-derived free radicals.
Targeted disruption of ICAM-1, P-selectin genes improves cardiac function and survival in TNF-α transgenic mice
Authors: Graciano Ana Lia , Bryant Debora D. , White D. Jean , Horton Jureta , Bowles Neil E. , Giroir Brett P.
Published: December 2017

We have developed a transgenic mouse model in which tumor necrosis factor (TNF)-α is overexpressed exclusively in the heart under the regulation of the α-myosin heavy chain promoter. These animals develop chronic heart failure associated with severe leukocyte infiltration in both the atria and the ventricles. The purpose of this study was to investigate the role of adhesion molecules in mediating cardiac dysfunction in the TNF-α transgenic model. TNF-α transgenic mice were bred with mice null for intercellular adhesion molecule (ICAM)-1 and P-selectin genes to obtain a lineage of ICAM-1 and P-selectin null mice with selective overexpression of TNF-α in the heart. TNF-α transgenic animals showed marked upregulation of ICAM-1 mRNA and protein; however, P-selectin mRNA and protein remained undetectable despite chronic TNF overexpression. Cardiac function was markedly improved in the ICAM-1−/−, P-selectin−/−, TNF-α transgenic group versus the ICAM+/+, P-selectin+/+, TNF-α transgenic group. Kaplan-Meier survival curves showed statistically significant prolonged survival in the ICAM-1−/−, P-selectin−/−, TNF-α transgenic animals. These data suggest that ICAM-1 mediates at least in part the cardiac dysfunction induced by TNF-α expression by cardiac myocytes.
Conduction left-to-right and right-to-left across the crista terminalis
Authors: Matsuo Kunihiro , Uno Kikuya , Khrestian Celeen M. , Waldo Albert L.
Published: December 2017

A line of block between the vena cava and the crista terminalis (CT) region is important for atrial flutter (AFL), but whether it is fixed or functional is controversial. To test the hypothesis that conduction across the CT normally occurs, but when block occurs in this region it is functional, we analyzed atrial activation during right and left atrial pacing (cycle lengths of 500–130 ms), AFL, and atrial fibrillation in 15 dogs with sterile pericarditis and 7 normal dogs. Electrograms from 396 right, left, and septal atrial sites were simultaneously recorded. Activation across the CT occurred during atrial pacing, AFL, and atrial fibrillation. Activation wave fronts from the right to the left atrium and vice versa traveled over several routes, including Bachmann's bundle and inferior to the inferior vena cava, as well as across the CT. In these models, there is no fixed conduction block across the CT, and when block in the CT region occurs, as during AFL, it is functional.
Assessment of segmental wall motion abnormalities using contrast two-dimensional echocardiography in awake mice
Authors: Suehiro Kotaro , Takuma Shin , Cardinale Carol , Hozumi Takeshi , Shimizu Juichiro , Yano Hideaki , Di Tullio Marco R. , Wang Jie , Smith Craig R. , Burkhoff Daniel , Homma Shunichi
Published: December 2017

Murine models of cardiac disease are becoming an important tool for studying pathophysiological processes. Development of methods to accurately assess ventricular function are therefore important. The purpose of this study was to evaluate the feasibility of echocardiographic assessment of segmental wall motion abnormalities in a murine model of myocardial infarction. Two-dimensional contrast (C+) and noncontrast (C−) echocardiography were performed in 76 awake mice 2 days before and 2 days after left coronary ligation. The short-axis images obtained with two-dimensional echocardiography and corresponding postmortem cross-sectional histological samples stained with Evans blue dye were each divided into 16 segments, and all matched segments were examined for correlation between wall motion abnormalities and myocardial hypoperfusion. With the use of contrast enhancement, the number of visualized segments was significantly increased (base: C− 86%, C+ 98%; midpapillary: C− 57%, C+ 89%; apex: C− 30%, C+ 74%). Agreement between echocardiographically assessed regional wall motion abnormalities and pathologically determined hypoperfusion in basal, midpapillary, and apical levels were 90%, 93%, and 93%, respectively. Agreement between echocardiographically normal wall motion and pathologically normal findings in basal, midpapillary, and apical levels were 99%, 88%, and 71%, respectively. Thus echocardiographic assessment of segmental wall motion in awake mice was feasible and the accuracy was improved with the use of a contrast agent.
ATP consumption by uncoupled mitochondria activates sarcolemmal KATP channels in cardiac myocytes
Authors: Sasaki Norihito , Sato Toshiaki , Marbán Eduardo , O'Rourke Brian
Published: December 2017

We tested whether close coupling exists between mitochondria and sarcolemma by monitoring whole cell ATP-sensitive K+ (KATP) current ( I K,ATP) as an index of subsarcolemmal energy state during mitochondrial perturbation. In rabbit ventricular myocytes, either pinacidil or the mitochondrial uncoupler dinitrophenol (DNP), which rapidly switches mitochondria from net ATP synthesis to net ATP hydrolysis, had little immediate effect on I K,ATP. In contrast, in the presence of pinacidil, exposure to 100 μM DNP rapidly activated I K,ATP with complex kinetics consisting of a quick rise [time constant of I K,ATP increase (τ) = 0.13 ± 0.01 min], an early partial recovery (τ = 0.43 ± 0.04 min), and then a more gradual increase. This DNP-induced activation of I K,ATP was reversible and accompanied by mitochondrial flavoprotein oxidation. The F1F0-ATPase inhibitor oligomycin abolished the DNP-induced activation of I K,ATP. The initial rapid rise in I K,ATP was blunted by atractyloside (an adenine nucleotide translocator inhibitor), leaving only a slow increase (τ = 0.66 ± 0.17 min, P < 0.01). 2,4-Dinitrofluorobenzene (a creatine kinase inhibitor) slowed both the rapid rise (τ = 0.20 ± 0.01 min, P < 0.05) and the subsequent declining phase (τ = 0.88 ± 0.19 min, P < 0.05). From single KATP channel recordings, we excluded a direct effect of DNP on KATP channels. Taken together, these results indicate that rapid changes in F1F0-ATPase function dramatically alter subsarcolemmal energy charge, as reported by pinacidil-primed KATP channel activity, revealing cross-talk between mitochondria and sarcolemma. The effects of mitochondrial ATP hydrolysis on sarcolemmal KATP channels can be rationalized by reversal of F1F0-ATPase and the facilitation of coupling by the creatine kinase system.
Optical mapping of activation patterns in an animal model of congenital heart block
Authors: Restivo Mark , Kozhevnikov Dmitry O. , Boutjdir Mohamed
Published: December 2017

Congenital heart block (CHB) is associated with high mortality and affects children of mothers with autoantibodies (IgG) to ribonucleoproteins SSB/La and SSA/Ro. IgG from mothers of children with CHB (positive IgG) was used to assess activation patterns in both the right atrium (RA) and right ventricle (RV) of Langendorff-perfused young rabbit hearts. Optical action potentials (AP) were obtained by using a 124-site photodiode array with 4-[-[2-(di- n-butylamino)-6-naphthyl]vinyl]pyridinium. Optical APs were recorded to simultaneously image activation patterns from the RA and RV. Perfusion of positive IgG (800–1,200 μg/ml) resulted in sinus bradycardia and varying degrees of heart block. Activation maps revealed marked conduction delay at the sinoatrial junction but only minor changes in overall atrial and ventricular activation patterns. No conduction disturbances were seen in the presence of IgG from mothers with healthy children. In conclusion, besides atrioventricular (AV) block, positive IgG induces sinus bradycardia. These results establish that the sequelae of CHB are associated with impaired intrasinus and/or sinoatrial conduction. The findings raise the possibility that sinus bradycardia in the developing heart may indicate the potential for AV conduction disturbances.
Accuracy of echocardiographic estimates of left ventricular mass in mice
Authors: Collins Keith A. , Korcarz Claudia E. , Shroff Sanjeev G. , Bednarz James E. , Fentzke Richard C. , Lin Hua , Leiden Jeffrey M. , Lang Roberto M.
Published: December 2017

Genetically modified mice have created the need for accurate noninvasive left ventricular mass (LVM) measurements. Recent technical advances provide two-dimensional images adequate for LVM calculation using the area-length method, which in humans is more accurate than M-mode methods. We compared the standard M-mode and area-length methods in mice over a wide range of LV sizes and weights (62–210 mg). Ninety-one CD-1 mice (38 normal, 44 aortic banded, and 9 inherited dilated cardiomyopathy) were imaged transthoracically (15 MHz linear transducer, 120 Hz). Compared with necropsy weights, area-length measurements showed higher correlation than the M-mode method ( r = 0.92 vs. 0.81), increased accuracy (bias ± SD: 1.4 ± 27.1% vs. 36.7 ± 51.6%), and improved reproducibility. There was no significant difference between end-systolic and end-diastolic estimates. The truncated ellipsoid estimation produced results similar in accuracy to the area-length method. Whereas current echocardiographic technology can accurately and reproducibly estimate LVM with the two-dimensional, area-length formula in a variety of mouse models, additional technological improvements, rather than refinement of geometric models, will likely improve the accuracy of this methodology.