bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of p38 mitogen-activated protein kinase in cardiac myocyte secretion of the inflammatory cytokine TNF-α
Authors: Ballard-Croft Cherry , White D. Jean , Maass David L. , Hybki Dixie Peters , Horton Jureta W.
Published: December 2017

This study examined the hypothesis that burn trauma promotes cardiac myocyte secretion of inflammatory cytokines such as tumor necrosis factor (TNF)-α and produces cardiac contractile dysfunction via the p38 mitogen-activated protein kinase (MAPK) pathway. Sprague-Dawley rats were divided into four groups: 1) sham burn rats given anesthesia alone, 2) sham burn rats given the p38 MAPK inhibitor SB203580 (6 mg/kg po, 15 min; 6- and 22-h postburn), 3) rats given third-degree burns over 40% total body surface area and treated with vehicle (1 ml of saline) plus lactated Ringer solution for resuscitation (4 ml · kg−1· percent burn−1), and 4) burn rats given injury and fluid resuscitation plus SB203580. Rats from each group were killed at several times postburn to examine p38 MAPK activity (by Western blot analysis or in vitro kinase assay); myocardial function and myocyte secretion of TNF-α were examined at 24-h postburn. These studies showed significant activation of p38 MAPK at 1-, 2-, and 4-h postburn compared with time-matched shams. Burn trauma impaired cardiac mechanical performance and promoted myocyte secretion of TNF-α. SB203580 inhibited p38 MAPK activity, reduced myocyte secretion of TNF-α, and prevented burn-mediated cardiac deficits. These data suggest p38 MAPK activation is one aspect of the signaling cascade that culminates in postburn secretion of TNF-α and contributes to postburn cardiac dysfunction.
Mapping action potentials and calcium transients simultaneously from the intact heart
Authors: Laurita Kenneth R. , Singal Ashish
Published: December 2017

Intracellular calcium handling plays an important role in cardiac electrophysiology. Using two fluorescent indicators, we developed an optical mapping system that is capable of measuring calcium transients and action potentials at 256 recording sites simultaneously from the intact guinea pig heart. On the basis of in vitro measurements of dye excitation and emission spectra, excitation and emission filters at 515 ± 5 and >695 nm, respectively, were used to measure action potentials with di-4-ANEPPS, and excitation and emission filters at 365 ± 25 and 485 ± 5 nm, respectively, were used to measure calcium transients with indo 1. The percent error due to spectral overlap was small when action potentials were measured (1.7 ± 1.0%, n = 3) and negligible when calcium transients were measured (0%, n = 3). Recordings of calcium transients, action potentials, and isochrone maps of depolarization time and the time of calcium transient onset indicated negligible error due to fluorescence emission overlap. These data demonstrate that the error due to spectral overlap of indo 1 and di-4-ANEPPS is sufficiently small, such that optical mapping techniques can be used to measure calcium transients and action potentials simultaneously in the intact heart.
Role of estrogen in modulating EDHF-mediated dilations in the female rat middle cerebral artery
Authors: Golding Elke M. , Kepler Tara E.
Published: December 2017

We tested the hypothesis that endothelium-derived hyperpolarizing factor (EDHF) plays a less dominant role in the female cerebrovasculature. The contribution of EDHF to the ATP-mediated dilation was determined in middle cerebral arteries (MCAs) isolated from male and female rats. Four groups of rats were tested: intact male ( n = 12), intact female ( n= 13), estrogen-treated ovariectomized female ( n = 13), and vehicle-treated ovariectomized female ( n = 20) rats. Maximal dilation to ATP was similar in all groups. However, in the presence of N ω-nitro-l-arginine methyl ester (l-NAME, 3 × 10−5 M) and indomethacin (10−5 M), the maximal dilation to ATP was significantly reduced in intact female (24 ± 9%) and estrogen-treated ovariectomized female (29 ± 9%) rats compared with intact male (95 ± 4%) and vehicle-treated ovariectomized female (96 ± 2%) rats. The ATP-mediated dilation in l-NAME- and indomethacin-treated MCAs isolated from male and ovariectomized female rats was inhibited by charybdotoxin (10−7 M), an inhibitor of large-conductance Ca2+-sensitive K+channels. We have defined EDHF as the l-NAME- and indomethacin-insensitive component of the ATP-mediated dilation. Our findings indicate that EDHF-mediated dilations are negligible in the female rat MCA; these dilations can be significantly enhanced after ovariectomy, suggesting that this effect is mediated by estrogen.
Characterization of endothelium-derived hyperpolarizing factor in the human forearm microcirculation
Authors: Halcox Julian P. J. , Narayanan Suresh , Cramer-Joyce Laura , Mincemoyer Rita , Quyyumi Arshed A.
Published: December 2017

The identity of endothelium-dependent hyperpolarizing factor (EDHF) in the human circulation remains controversial. We investigated whether EDHF contributes to endothelium-dependent vasomotion in the forearm microvasculature by studying the effect of K+and miconazole, an inhibitor of cytochrome P-450, on the response to bradykinin in healthy human subjects. Study drugs were infused intra-arterially, and forearm blood flow was measured using strain-gauge plethysmography. Infusion of KCl (0.33 mmol/min) into the brachial artery caused baseline vasodilation and inhibited the vasodilator response to bradykinin, but not to sodium nitroprusside. Thus the incremental vasodilation induced by bradykinin was reduced from 14.3 ± 2 to 7.1 ± 2 ml · min−1· 100 g−1( P < 0.001) after KCl infusion. A similar inhibition of the bradykinin ( P = 0.014), but not the sodium nitroprusside (not significant), response was observed with KCl after the study was repeated during preconstriction with phenylephrine to restore resting blood flow to basal values after KCl. Miconazole (0.125 mg/min) did not inhibit endothelium-dependent or -independent responses to ACh and sodium nitroprusside, respectively. However, after inhibition of cyclooxygenase and nitric oxide synthase with aspirin and NG-monomethyl-l-arginine, the forearm blood flow response to bradykinin ( P = 0.003), but not to sodium nitroprusside (not significant), was significantly suppressed by miconazole. Thus nitric oxide- and prostaglandin-independent, bradykinin-mediated forearm vasodilation is suppressed by high intravascular K+concentrations, indicating a contribution of EDHF. In the human forearm microvasculature, EDHF appears to be a cytochrome P-450 derivative, possibly an epoxyeicosatrienoic acid.
Cardiovascular effects of static carotid baroreceptor stimulation during water immersion in humans
Authors: Pump Bettina , Shiraishi Makoto , Gabrielsen Anders , Bie Peter , Christensen Niels Juel , Norsk Peter
Published: December 2017

We hypothesized that the more-pronounced hypotensive and bradycardic effects of an antiorthostatic posture change from seated to supine than water immersion are caused by hydrostatic carotid baroreceptor stimulation. Ten seated healthy males underwent five interventions of 15-min each of 1) posture change to supine, 2) seated water immersion to the Xiphoid process (WI), 3) seated neck suction (NS), 4) WI with simultaneous neck suction (−22 mmHg) adjusted to simulate the carotid hydrostatic pressure increase during supine (WI + NS), and 5) seated control. Left atrial diameter increased similarly during supine, WI + NS, and WI and was unchanged during control and NS. Mean arterial pressure (MAP) decreased the most during supine (7 ± 1 mmHg, P < 0.05) and less during WI + NS (4 ± 1 mmHg) and NS (3 ± 1 mmHg). The decrease in heart rate (HR) by 13 ± 1 beats/min ( P < 0.05) and the increase in arterial pulse pressure (PP) by 17 ± 4 mmHg ( P< 0.05) during supine was more pronounced ( P < 0.05) than during WI + NS (10 ± 2 beats/min and 7 ± 2 mmHg, respectively) and WI (8 ± 2 beats/min and 6 ± 1 mmHg, respectively, P < 0.05). Plasma vasopressin decreased only during supine and WI, and plasma norepinephrine, in addition, decreased during WI + NS ( P < 0.05). In conclusion, WI + NS is not sufficient to decrease MAP and HR to a similar extent as a 15-min seated to supine posture change. We suggest that not only static carotid baroreceptor stimulation but also the increase in PP combined with low-pressure receptor stimulation is a possible mechanism for the more-pronounced decrease in MAP and HR during the posture change.
Effects of deletion of muscle LIM protein on myocyte function
Authors: Su Zhi , Yao Atsushi , Zubair Iram , Sugishita Kazuro , Ritter Michael , Li Fenghua , Hunter John J. , Chien Kenneth R. , Barry William H.
Published: December 2017

Muscle LIM protein (MLP) may serve as a scaffold protein on the actin-based cytoskeleton, and mice deficient in this protein (MLPKO) have been recently reported to develop dilated cardiomyopathy. To determine the causes of depressed contractility in this model, we measured intracellular Ca2+ concentration ([Ca2+]i) transients (fluo 3), cell shortening, L-type Ca2+ channel current ( I Ca,L), Na/Ca exchanger current ( I Na/Ca), and sarcoplasmic reticulum (SR) Ca content in left ventricular MLPKO myocytes. I Ca,L-voltage relationships, I Na/Ca density, and membrane capacitance did not differ between wild-type (WT) and MLPKO myocytes. The peak systolic [Ca2+]i was significantly increased in MLPKO myocytes (603 ± 54 vs. 349 ± 18 nM in WT myocytes). The decline of [Ca2+]i transients was accelerated in MLPKO myocytes, and SR Ca2+ content was increased by 21%, indicating that SR Ca2+-ATPase function is normal or enhanced in MLPKO myocytes. Confocal imaging of actin filaments stained with tetramethylrhodamine isothiocyanate-labeled phalloidin showed disorganization of myofibrils and abnormal alignment of Z bands, and fractional shortening was significantly diminished in MLPKO myocytes compared with that in WT myocytes at comparable peak [Ca2+]i. Thus a reduced [Ca2+]-induced shortening may be involved in the pathogenesis of myocardial dysfunction in this genetic model of heart failure.
Cardiomyocyte apoptosis and ventricular remodeling after myocardial infarction in rats
Authors: Palojoki Eeva , Saraste Antti , Eriksson Anders , Pulkki Kari , Kallajoki Markku , Voipio-Pulkki Liisa-Maria , Tikkanen Ilkka
Published: December 2017

We investigated the role of cardiomyocyte apoptosis in the remodeling of the left ventricle from 24 h to 12 wk after myocardial infarction in the rat. Infarct size planimetry, quantification of cardiomyocyte apoptosis, terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) methodology, and echocardiography (left ventricular diastolic diameter and ejection fraction) were performed. Sham-operated animals showed low rates of cardiomyocyte apoptosis (0.03%) and no change in diastolic diameter or ejection fraction during the study. Twenty-four hours after infarction, TUNEL positivity was high in the infarct areas (1.4%) and border zones (4.9%). It declined to 0.34% ( P < 0.01 vs. sham) at 4 wk and 0.10% at 12 wk in the border zones. In the remote myocardium, cardiomyocyte apoptosis increased to 0.07% ( P = 0.03 vs. sham) on day 1 and remained on the same level up to 4 wk. The increase in diastolic diameter 1–4 wk after infarction correlated ( r = 0.60, P < 0.01) with cardiomyocyte apoptosis in the noninfarcted myocardium, which quantitatively contributed most (>50%) to the apoptotic cell loss by 4 wk.
Limitation of heart growth in neonatal piglets by simvastatin and atorvastatin: comparison with pravastatin
Authors: Satoh Kumi , Shirota Fumiyo , Tsunajima Takahiko , Beinlich Cathy J. , Morgan Howard E. , Ichihara Kazuo
Published: December 2017

The pig heart grows rapidly in the first few days after birth. We examined the effects of simvastatin, atorvastatin, and pravastatin on heart growth in piglets. After vehicle, 2 mg · kg−1· day−1simvastatin, 2 mg · kg−1· day−1atorvastatin, or 4 mg · kg−1· day−1pravastatin were administered orally for 6 days, the thoracic cavity was opened, and the heart was removed under pentobarbital sodium (30 mg/kg ip) anesthesia. The heart was perfused to remove residual blood. After the heart was blotted dry, the right and left ventricular free walls were dissected. Each free wall was weighed and used for determination of DNA, RNA, and protein concentrations and mitogen-activated protein (MAP) kinase activity. Simvastatin and atorvastatin resulted in smaller increases with age in the weight, concentrations of RNA and protein, and activity of MAP kinase in the left ventricular free wall, whereas pravastatin did not. The parameters of heart growth in the right ventricular free wall were not appreciably affected by either drug. The blood pressure and heart rate were not changed by the treatments. These results suggest that simvastatin and atorvastatin interfere with heart growth in neonatal piglets after birth, especially in the left ventricular free wall.
Role of erythrocyte in regulating local O2delivery mediated by hemoglobin oxygenation
Authors: Jagger Justin E. , Bateman Ryon M. , Ellsworth Mary L. , Ellis Chris G.
Published: December 2017

The release of ATP from red blood cells (RBC) in response to low O2levels is linked to ATP production and the oxygenation state of hemoglobin. Because O2is unloaded from the RBC, the concentration of deoxygenated hemoglobin increases, displacing phosphofructokinase from the cytoplasmic domain of band 3. We hypothesize that the ATP molecules produced through this glycolytic stimulation at the membrane surface result in the release of ATP from the RBC. Rat whole blood exposed to 5 min of low Po2in vitro increased plasma [ATP] by 1.0 μM (+45%). This increase was reduced to 0.1 μM (+12%, P < 0.05) after citrate incubation and reversed after fluoride treatment (both glycolytic inhibitors) by −0.2 μM (−23%, P < 0.05). Plasma [ATP] of control RBC decreased −0.3 μM (−12%) when 8% CO ( P < 0.05) was added to the chamber. Because CO and O2bind competitively to heme, these results support our hypothesis that the release of ATP from RBC is linked to ATP production through the oxygenation state of the hemoglobin molecule.
Involvement of adenosine in vascular contractile preconditioning
Authors: Harada Nagakatsu , Sakamoto Sadaichi , Niwa Yasuharu , Nakaya Yutaka
Published: December 2017

Measurements of isometric tensions of rat aortic rings revealed the fact that when aortic rings with intact endothelium were precontracted (preconditioned) for 20 min by the α1-adrenergic agonist phenylephrine (10 μM), the tonic level of subsequent contraction by the same agonist was depressed and/or declined regardless of the presence or absence of endothelium during the second contraction. The removal of endothelium before preconditioning showed no such phenomenon. With the use of specific blockers, involvements of adenosine or of ATP-sensitive K+(KATP) channels during preconditioning or second contraction, respectively, were evaluated. Actions of nitric oxide synthase, cyclooxygenase, P2ATP purinoceptors, or KATPchannels during preconditioning appear not to be involved. Exogenous adenosine (up to 100 μM) without endothelium could mimic the preconditioning; however, contractile preconditioning by phenylephrine, mechanical stretching, or activation of protein kinase C needed to be done. The release of adenosine and adenine nucleotides from aortic rings was augmented by phenylephrine or by mechanical stretching of the rings with intact endothelium. Our results suggest that during vasocontraction, endothelium-derived adenosine acquires an ability to protect vascular tone against subsequent repeated contractions by mediating a delayed, possibly indirect, opening of KATPchannels.
Cross talk between prostacyclin and nitric oxide under shear in smooth muscle cell: role in monocyte adhesion
Authors: Osanai Tomohiro , Akutsu Noriyuki , Fujita Norio , Nakano Takao , Takahashi Koki , Guan Weiping , Okumura Ken
Published: December 2017

We tested the hypothesis that at sites of vascular damage, vessel homeostasis is maintained through the cross talk of shear-induced production of prostacyclin and nitric oxide (NO) in vascular smooth muscle cells (VSMC). Confluent A7r5 cells derived from rat aortic VSMC and mesenteric VSMC were exposed to shear stress at 15 dyn/cm2 for 90 min with the use of a cone-plate device, and productions of prostacyclin and NO were examined. Shear stress increased cumulative production of prostacyclin by 3- to 3.5-fold and that of NO by 6- to 7.5-fold. Western blot analysis showed that inducible NO synthase protein was expressed after shear stress in both types of VSMC. Inhibition of NO synthase enhanced the shear-induced production of prostacyclin from 40 to 60%. Shear-induced production of NO was suppressed by 70% after treatment with 10−4 M of indomethacin. A7r5 cells adhesiveness for monocytes was suppressed by 50% after shear stress. This suppression was abolished by pretreatment with 10−4 M of indomethacin, whereas inhibition of NO synthase only minimally inhibited it. We conclude that there is a cross talk of shear-induced production of prostacyclin and NO in VSMC. At sites of vascular damage, prostacyclin synthesis may prevent monocyte adhesiveness for VSMC through the concomitant enhancement of NO production.
Differential ANG II-induced growth activation pathways in mesenteric artery smooth muscle cells from SHR
Authors: El Mabrouk Mohammed , Touyz Rhian M. , Schiffrin Ernesto L.
Published: December 2017

Angiotensin II-induced growth signaling mechanisms were investigated in vascular smooth muscle cells (VSMCs) from mesenteric arteries of sponteneously hypertensive (SHR) and Wistar-Kyoto rats (WKY). In WKY, angiotensin II significantly increased protein synthesis ([3H]leucine incorporation) but not DNA synthesis ([3H]thymidine incorporation). In SHR, angiotensin II increased protein and DNA synthesis. VSMCs from both strains expressed angiotensin type 1 (AT1) and type 2 (AT2) receptors. Losartan (an AT1receptor antagonist) but not PD-123319 (an AT2receptor antagonist) attenuated angiotensin II-stimulated protein synthesis in WKY VSMCs. In SHR, losartan and PD-123319 partially inhibited angiotensin II-induced VSMC proliferation. The mitogen-activated protein kinase or extracellular signal-regulated protein kinase (ERK) kinase inhibitor PD-98059 blocked VSMC growth responses to angiotensin II in both strains. Angiotensin II increased ERK1/2 activation more in SHR than WKY, an effect inhibited by losartan but not PD-123319. LY-294002 [a phosphatidylinositol-3 (PI3) kinase inhibitor] blocked angiotensin II-stimulated ERK1/2 activation in SHR but not in WKY, whereas bisindolylmaleimide [a protein kinase C (PKC) inhibitor] was ineffective. In conclusion, angiotensin II stimulates VSMC proliferation via AT1and AT2receptors in SHR. In WKY, angiotensin II induces VSMC hypertrophy via AT1receptors. ERK1/2-dependent pathways regulated by intracellular Ca2+but not PKC mediate these effects. In SHR VSMCs, PI3 kinase plays a role in augmented angiotensin II-induced ERK1/2 phosphorylation. These angiotensin II-mediated signaling events could contribute to vascular remodeling in SHR.
Restoration of vasodilation and CBF autoregulation by genistein in rat pial artery after brain injury
Authors: Hong Ki Whan , Shin Hwa Kyoung , Kim Chi Dae , Lee Won Suk , Rhim Byung Yong
Published: December 2017

This study determined whether, after fluid percussion injury (FPI), tyrosine kinase activation is coupled to inhibition of K+channels and alteration in cerebral blood flow (CBF) autoregulation in the rat pial artery. Injury of moderate severity (2–2.5 atm) was produced by FPI in anesthetized rats equipped with a closed cranial window. The suppressed vasodilation of the pial arterioles to calcitonin gene-related peptide (CGRP) and levcromakalim (LMK) and altered lower limit of CBF autoregulation after FPI were restored by genistein but not by daidzein, an inactive analog. Vasodilation to S-nitroso- N-acetyl penicillamine (0.1–10 μmol/l) was, however, little influenced after FPI. The restored vasodilation was decreased by sodium orthovanadate, suggesting the reciprocal action of tyrosine phosphorylation and dephosphorylation. After FPI, CGRP-induced vasodilation restored by genistein (10 μmol/l) was strongly antagonized by iberiotoxin but not by glibenclamide, whereas LMK-induced vasodilation was, in contrast, inhibited by glibenclamide but not by iberiotoxin. Taken together, we suggest that, after FPI, activation of tyrosine kinase links the inhibition of K+channels to impaired autoregulatory vasodilation in response to acute hypotension and alteration in CBF autoregulation in the rat pial artery.
Characteristics of calcium sparks in cardiomyocytes derived from embryonic stem cells
Authors: Sauer Heinrich , Theben Tobias , Hescheler Jürgen , Lindner Michael , Brandt Mathias C. , Wartenberg Maria
Published: December 2017

In embryonic stem (ES) cell-derived cardiomyocytes, spontaneous Ca2+sparks representing Ca2+release through ryanodine receptor (RyR) channels were characterized and correlated to the expression of RyRs as well as the Ca2+load of the sarcoplasmic reticulum (SR). In very early developmental stage (VEDS) cardiac precursor cells, global intracellular Ca2+concentration ([Ca2+]i) fluctuations occurred, whereas Ca2+sparks and contractions were absent. In early developmental stages (EDS), contractions as well as Ca2+sparks were obvious. During the further differentiation to late developmental stage (LDS) cardiomyocytes, a marked increase in the frequency of global [Ca2+]itransients, the amplitude and the frequency of Ca2+sparks, as well as the expression of RyRs and the volume of RyR-positive SR, was observed. Furthermore, the caffeine-releasable SR Ca2+load was elevated in LDS compared with EDS cardiomyocytes. A high-Ca2+solution raised spark frequency as well as amplitude in EDS cardiomyocytes to the levels of LDS cardiomyocytes. The characteristics of Ca2+sparks occurring in cardiomyocytes differentiated from ES cells may be governed by the Ca2+load of the SR and/or the density of RyRs.
Muscle metaboreflex control is diminished in normotensive obese women
Authors: Negrão Carlos Eduardo , Trombetta Ivani C. , Batalha Luciana T. , Ribeiro Maurício Maltez , Rondon Maria Urbana P. Brandão , Tinucci Taís , Forjaz Cláudia L. M. , Barretto Antonio Carlos P. , Halpern Alfredo , Villares Sandra M. F.
Published: December 2017

There is no information about the muscle metaboreflex control in obese individuals. In 40 normotensive obese women (OW; body mass index 33.5 ± 0.4 kg/m2, age 32.4 ± 1.1 yr) and 15 age-matched, normotensive lean women (LW; body mass index 22.7 ± 0.8 kg/m2, age 34.4 ± 1.4 yr), we measured muscle sympathetic nerve activity (MSNA) and forearm blood flow (FBF) in the nonexercising forearm during static exercise at 10 and 30% of maximal voluntary contraction (MVC). Baseline MSNA (38 ± 2 vs. 31 ± 1 bursts/min, P = 0.001) and mean blood pressure were significantly higher in OW compared with LW. FBF was significantly lower, whereas forearm vascular resistance was significantly higher in OW. During 10% MVC, MSNA increased similarly in both groups, but during 30% MVC, MSNA was higher in LW. FBF and forearm vascular resistance responses during both 10 and 30% MVC were similar between groups. During posthandgrip circulatory arrest, MSNA remained significantly elevated compared with baseline in both groups, but this increase was significantly lower in OW (3.8 ± 0.82 vs. 9.4 ± 1.03 bursts/min, P = 0.002). In conclusion, muscle metaboreflex control of MSNA is blunted in OW. MSNA responses are not augmented during selective activation of central command/mechanoreceptors and metaboreceptors, despite increased MSNA levels in OW. Muscle vasodilatory response during graded handgrip isometric exercise is preserved in OW.
Glutathione supplementation and training increases myocardial resistance to ischemia-reperfusion in vivo
Authors: Ramires P. R. , Ji L. L.
Published: December 2017

The present study examined the effects of oral reduced glutathione (GSH) supplementation in conjunction with endurance training on contractile function, antioxidant defense, and oxidative damage in response to ischemia-reperfusion (I/R) in rat hearts. Female Sprague-Dawley rats (age 4 mo, n = 72) were randomly assigned to a treadmill-trained (T; 25 m/min, 15% grade, for 75 min/day, 5 days/wk, for 10 wk) or untrained (U) group. Each group was further divided into rats receiving 5 g GSH/kg diet during the final 17 days of training (GSH-S) and control (C) groups. One-half of each group of rats was subjected to I/R by surgical occlusion of the main coronary artery for 45 min, followed by 30-min reperfusion or sham operation. Left ventriclar (LV) peak systolic pressure (LVSP) and contractility (+dP/d t), measured with a catheter inserted into the LV via the carotid artery, decreased with I/R in all groups ( P< 0.05). However, LVSP with I/R in the T/GSH-S group was 9.5%, 17%, and 18% higher ( P < 0.05) than that in the U/GSH-S, T/C, and U/C groups, respectively. +dP/d t with I/R was 19%, 27%, and 29% ( P < 0.05) greater in the T/GSH-S group versus the T/C, U/GSH-S, and U/C groups, respectively. I/R decreased heart GSH content by 12–17% ( P < 0.05) and increased oxidized glutathione (GSSG) by 20–27% ( P < 0.05). T/GSH-S hearts showed 15% higher GSH ( P < 0.05) and a 32% higher GSH-to-GSSG ratio ( P < 0.05) than the U/C group at the end of I/R. Myocardial superoxide dismutase, GSH peroxidase, glutathione reductase, and γ-glutamyl transpeptidase activities were increased with treadmill training in both GSH-S and C rats. I/R induced myocardial lipid peroxidation and lactate dehydrogenase release were attenuated with T/GSH-S treatment. The present data indicate that training in conjunction with dietary GSH supplementation can increase myocardial GSH content and antioxidant defense capacity, thereby protecting the intact heart against oxidative damage and functional retardation caused by I/R.
TGF-β1 modulates NOS expression and phosphorylation of Akt/PKB in rat myocytes exposed to hypoxia-reoxygenation
Authors: Chen Hongjiang , Li Dayuan , Saldeen Tom , Mehta Jawahar L.
Published: December 2017

Myocardial hypoxia-reoxygenation (H-R) is associated with upregulation of inducible nitric oxide synthase (iNOS), decrease in endothelial NOS (eNOS), and increase in protein kinase B (PKB). Previous work also shows that transforming growth factor-β1 (TGF-β1) can attenuate myocardial injury induced by H-R. We examined the modulation of NOS and PKB expression in response to H-R by TGF- β1. Myocytes from Sprague-Dawley rat hearts were cultured and exposed to hypoxia (95% N2-5% CO2, Po 2 ∼30 mmHg) for 24 h and reoxygenation (95% air-5% CO2) for 3 h. Myocytes were then examined for lactate dehydrogenase (LDH) release, iNOS activity (conversion ofl-[3H]arginine tol-[3H]citrulline), iNOS and eNOS expression, and PKB phosphorylation. H-R alone resulted in myocyte injury, upregulation of iNOS activity and expression, decrease in eNOS expression, and increase in PKB phosphorylation (all P< 0.05 vs. cells cultured in normoxic conditions). Treatment of myocytes with TGF-β1 (1 ng/ml) resulted in a reduction in LDH release, attenuation of the alterations in NOS expression (both iNOS and eNOS), and PKB phosphorylation in response to H-R (all P < 0.05 vs. H-R alone). These observations suggest that TGF-β1 decreases H-R injury and attenuates alterations in NOS and PKB phosphorylation in myocytes exposed to H-R.
Loaded shortening and power output in cardiac myocytes are dependent on myosin heavy chain isoform expression
Authors: Herron Todd J. , Korte F. Steven , McDonald Kerry S.
Published: December 2017

The purpose of this study was to examine the role of myosin heavy chain (MHC) in determining loaded shortening velocities and power output in cardiac myocytes. Cardiac myocytes were obtained from euthyroid rats that expressed α-MHC or from thyroidectomized rats that expressed β-MHC. Skinned myocytes were attached to a force transducer and a position motor, and isotonic shortening velocities were measured at several loads during steady-state maximal Ca2+ activation (PpCa4.5). MHC expression was determined after mechanical measurements using SDS-PAGE. Both α-MHC and β-MHC myocytes generated similar maximal Ca2+-activated force, but α-MHC myocytes shortened faster at all loads and generated ∼170% greater peak normalized power output. Additionally, the curvature of force-velocity relationships was less, and therefore the relative load optimal for power output (Fopt) was greater in α-MHC myocytes. Fopt was 0.31 ± 0.03 PpCa4.5 and 0.20 ± 0.06 PpCa4.5 for α-MHC and β-MHC myocytes, respectively. These results indicate that MHC expression is a primary determinant of the shape of force-velocity relationships, velocity of loaded shortening, and overall power output-generating capacity of individual cardiac myocytes.
Central volume expansion is pivotal for sustained decrease in heart rate during seated to supine posture change
Authors: Pump Bettina , Kamo Tsutomu , Gabrielsen Anders , Bie Peter , Christensen Niels Juel , Norsk Peter
Published: December 2017

During prolonged, static carotid baroreceptor stimulation by neck suction (NS) in seated humans, heart rate (HR) decreases acutely and thereafter gradually increases. This increase has been explained by carotid baroreceptor adaptation and/or buffering by aortic reflexes. During a posture change from seated to supine (Sup) with similar carotid stimulation, however, the decrease in HR is sustained. To investigate whether this discrepancy is caused by changes in central blood volume, we compared ( n = 10 subjects) the effects of 10 min of seated NS (adjusted to simulate carotid stimulation of a posture change), a posture change from seated to Sup, and the same posture change with left atrial (LA) diameter maintained unchanged by lower body negative pressure (Sup + LBNP). During Sup, the prompt decreases in HR and mean arterial pressure (MAP) were sustained. HR decreased similarly within 30 s of NS (65 ± 2 to 59 ± 2 beats/min) and Sup + LBNP (65 ± 2 to 58 ± 2 beats/min) and thereafter gradually increased to values of seated. MAP decreased similarly within 5 min during Sup + LBNP and NS (by 7 ± 1 to 9 ± 1 mmHg) and thereafter tended to increase toward values of seated subjects. Arterial pulse pressure was increased the most by Sup, less so by Sup + LBNP, and was unchanged by NS. LA diameter was only increased by Sup. In conclusion, static carotid baroreceptor stimulation per se causes the acute (<30 s) decrease in HR during a posture change from seated to Sup, whereas the central volume expansion (increased LA diameter and/or arterial pulse pressure) is pivotal to sustain this decrease. Thus the effects of central volume expansion override adaptation of the carotid baroreceptors and/or buffering of aortic reflexes.
Impaired NO-dependent dilation of skeletal muscle arterioles in hypertensive diabetic obese Zucker rats
Authors: Frisbee Jefferson C. , Stepp David W.
Published: December 2017

This study determined alterations to nitric oxide (NO)-dependent dilation of skeletal muscle arterioles from obese (OZR) versus lean Zucker rats (LZR). In situ cremaster muscle arterioles from both groups were viewed via television microscopy, and vessel dilation was measured with a video micrometer. Arteriolar dilation to acetylcholine and sodium nitroprusside was reduced in OZR versus LZR, although dilation to aprikalim was unaltered. NO-dependent flow-induced arteriolar dilation (via parallel microvessel occlusion) was attenuated in OZR, impairing arteriolar ability to regulate wall shear rate. Vascular superoxide levels, as assessed by dihydroethidine fluorescence, were elevated in OZR versus LZR. Treatment of cremaster muscles of OZR with the superoxide scavengers polyethylene glycol-superoxide dismutase and catalase improved arteriolar dilation to acetylcholine and sodium nitroprusside and restored flow-induced dilation and microvascular ability to regulate wall shear rate. These results suggest that NO-dependent dilation of skeletal muscle microvessels in OZR is impaired due to increased levels of superoxide. Taken together, these data suggest that the development of diabetes and hypertension in OZR may be associated with an impaired skeletal muscle perfusion via an elevated vascular oxidant stress.
Bradykinin elicits “second window” myocardial protection in rat heart through an NO-dependent mechanism
Authors: Ebrahim Zaileen , Yellon Derek M , Baxter Gary F
Published: December 2017

Bradykinin is an important endogenous mediator exerting acute protective effects in the ischemic myocardium. The aims of this study were to investigate whether exogenously administered bradykinin could evoke delayed myocardial protection and to determine whether any protection observed might be dependent on nitric oxide (NO) generation. Conscious rats received bradykinin (40 μg/kg iv) or saline, preceded 15–20 min earlier by the NO synthase inhibitor N ω-nitro-l-arginine methyl ester (l-NAME, 10 mg/kg ip) or saline. Twenty-four hours later, hearts were Langendorff perfused and subjected to 35 min of regional ischemia and 120 min of reperfusion. Infarct size was assessed using tetrazolium staining and expressed as a percentage of the risk zone. Bradykinin pretreatment reduced the infarct-to-risk ratio from 53.5 ± 3.2% to 29.1 ± 4.7% ( P< 0.01). The administration of l-NAME before bradykinin abrogated the delayed protection (infarct size 52.3 ± 5.0%) but alone did not influence infarct size (53.5 ± 4.8%). These results are the first to demonstrate that bradykinin can evoke a delayed (“second window”) enhancement of myocardial tolerance to ischemia, an action that is dependent on the early generation of NO.
Epoxyeicosatrienoic acid-induced relaxation is impaired in insulin resistance
Authors: Miller Allison W. , Dimitropoulou Christiana , Han Guichun , White Richard E. , Busija David W. , Carrier Gerald O.
Published: December 2017

We assessed the effect of epoxyeicosatrienoic acids (EETs) in intact mesenteric arteries and Ca2+-activated K+ (BKCa) channels of isolated vascular smooth muscle cells from control and insulin-resistant (IR) rats. The response to 11,12-EET and 14,15-EET was assessed in small mesenteric arteries from control and IR rats in vitro. Mechanistic studies were performed in endothelium intact or denuded arteries and in the presence of pharmacological inhibitors. Moreover, EET-induced activation of the BKCa channel was assessed in myocytes in both the cell-attached and the inside-out (I/O) patch-clamp configurations. In control arteries, both EET isomers induced relaxation. Relaxation was impaired by endothelium denudation, N ω-nitro-l-arginine, or iberiotoxin (IBTX), whereas it was abolished by IBTX + apamin or charybdotoxin + apamin. In contrast, the EETs did not relax IR arteries. In control myocytes, the EETs increased BKCa activity in both configurations. Conversely, in the cell-attached mode, EETs had no effect on BKCachannel activity in IR myocytes, whereas in the I/O configuration, BKCa channel activity was enhanced. EETs induce relaxation in small mesenteric arteries from control rats through KCa channels. In contrast, arteries from IR rats do not relax to the EETs. Patch-clamp studies suggest impaired relaxation is due to altered regulatory mechanisms of the BKCachannel.
Gap junction channels formed by coexpressed connexin40 and connexin43
Authors: Valiunas Virginijus , Gemel Joanna , Brink Peter R. , Beyer Eric C.
Published: December 2017

Many cardiovascular cells coexpress multiple connexins (Cx), leading to the potential formation of mixed (heteromeric) gap junction hemichannels whose biophysical properties may differ from homomeric channels containing only one connexin type. We examined the potential interaction of connexin Cx43 and Cx40 in HeLa cells sequentially stably transfected with these two connexins. Immunoblots verified the production of comparable amounts of both connexins, cross-linking showed that both connexins formed oligomers, and immunofluorescence showed extensive colocalization. Moreover, Cx40 copurified with (His)6-tagged Cx43 by affinity chromatography of detergent-solubilized connexons, demonstrating the presence of both connexins in some hemichannels. The dual whole cell patch-clamp method was used to compare the gating properties of gap junctions in HeLa Cx43/Cx40 cells with homotypic (Cx40-Cx40 and Cx43-Cx43) and heterotypic (Cx40-Cx43) gap junctions. Many of the observed single channel conductances resembled those of homotypic or heterotypic channels. The steady-state junctional conductance ( gj,ss) in coexpressing cell pairs showed a reduced sensitivity to the voltage between cells ( Vj) compared with homotypic gap junctions and/or an asymmetrical Vjdependence reminiscent of heterotypic gap junctions. These gating properties could be fit using a combination of homotypic and heterotypic channel properties. Thus, whereas our biochemical evidence suggests that Cx40 and Cx43 form heteromeric connexons, we conclude that they are functionally insignificant with regard to voltage-dependent gating.
Mechanisms of endothelial P2Y1- and P2Y2-mediated vasodilatation involve differential [Ca2+]iresponses
Authors: Marrelli Sean P.
Published: December 2017

The present study was designed to evaluate the role of endothelial intracellular Ca2+concentration ([Ca2+]i) in the difference between P2Y1- and P2Y2-mediated vasodilatations in cerebral arteries. Rat middle cerebral arteries were cannulated, pressurized, and luminally perfused. The endothelium was selectively loaded with fura 2, a fluorescent Ca2+indicator, for simultaneous measurement of endothelial [Ca2+]iand diameter. Luminal administration of 2-methylthioadenosine 5′-triphosphate (2-MeS-ATP), an endothelial P2Y1agonist, resulted in purely nitric oxide (NO)-dependent dilation and [Ca2+]iincreases up to ∼300 nM (resting [Ca2+]i= 145 nM). UTP, an endothelial P2Y2agonist, resulted in dilations that were both endothelium-derived hyperpolarizing factor (EDHF)- and NO-dependent with [Ca2+]iincreases to >400 nM. In the presence of NG-nitro-l-arginine-indomethacin to inhibit NO synthase and cyclooxygenase, UTP resulted in an EDHF-dependent dilation alone. The [Ca2+]ithreshold for NO-dependent dilation was 220 vs. 340 nM for EDHF. In summary, the differences in the mechanism of vasodilatation resulting from stimulation of endothelial P2Y1and P2Y2purinoceptors result in part from differential [Ca2+]iresponses. Consistent with this finding, these studies also demonstrate a higher [Ca2+]ithreshold for EDHF-dependent responses compared with NO.
Oxidative stress contributes to vascular endothelial dysfunction in heart failure
Authors: Indik Julia H. , Goldman Steven , Gaballa Mohamed A.
Published: December 2017

Congestive heart failure (HF) is characterized by inadequate nitric oxide (NO) production in the vasculature. Because NO is degraded by oxygen radicals, we hypothesized that NO is degraded faster in HF from inadequate peripheral arterial antioxidant reserves. HF was induced in male Sprague-Dawley rats by left coronary artery ligation. Vascular endothelial function was evaluated by measuring the NO-mediated vasorelaxation response to acetylcholine (ACh; 10−9–10−4M) in excised aortas. This was repeated with the free radical generator pyrogallol (20 μM) and again with pyrogallol and superoxide dismutase (SOD; 60 U/ml). Aortic and myocardial SOD activity was also determined. ACh-induced vasorelaxation was reduced in HF ( n = 9) compared with normal control rats ( n = 11; P < 0.001). Pyrogallol further reduced vasorelaxation in HF: 74 ± 11% at 10−4M ACh versus 58 ± 10% in normal control rats ( P < 0.004). There was a trend ( P = 0.06) toward reduced SOD activity in HF aortas. In conclusion, altered NO-dependent vasorelaxation in HF is in part due to excessive degradation of NO and is likely related to reduced vascular SOD activity.
High-salt diet impairs hypoxia-induced cAMP production and hyperpolarization in rat skeletal muscle arteries
Authors: Frisbee Jefferson C. , Sylvester Francis A. , Lombard Julian H.
Published: December 2017

This study determined the effects of hypoxia on diameter, vascular smooth muscle (VSM) transmembrane potential ( E m), and vascular cAMP levels for in vitro cannulated skeletal muscle resistance arteries (gracilis arteries) from Sprague-Dawley rats fed a low-salt (LS) or a high-salt (HS) diet. Arterial diameter and VSM E m were measured in response to hypoxia, iloprost, cholera toxin, forskolin, and aprikalim. In HS rats, arterial dilation and VSM hyperpolarization after hypoxia, iloprost, and cholera toxin were impaired versus responses in LS rats, whereas responses to forskolin and aprikalim were unaltered. Blockade of prostaglandin H2 and thromboxane A2 receptors had no effect on responses to hypoxia or iloprost in vessels from both rat groups, suggesting that inappropriate activation of these receptors does not contribute to the impaired hypoxic dilation with HS. Hypoxia, cholera toxin, and iloprost increased vascular cAMP levels in vessels of LS rats only, whereas forskolin increased cAMP levels in all vessels. These data suggest that reduced hypoxic dilation of skeletal muscle microvessels in rats on a HS diet may reflect an impaired ability of VSM to produce cAMP after exposure to prostacyclin.
Role of heme oxygenase-1 in hypoxia-reoxygenation: requirement of substrate heme to promote cardioprotection
Authors: Foresti Roberta , Goatly Helen , Green Colin J. , Motterlini Roberto
Published: December 2017

Heme oxygenase-1 (HO-1) catalyzes the enzymatic degradation of heme to carbon monoxide, bilirubin, and iron. All three products possess biological functions; bilirubin, in particular, is a potent free radical scavenger of which its antioxidant property is enhanced at low oxygen tension. Here, we investigated the effect of severe hypoxia and reoxygenation on HO-1 expression in cardiomyocytes and determined whether HO-1 and its product, bilirubin, have a protective role against reoxygenation damage. Hypoxia caused a time-dependent increase in both HO-1 expression and heme oxygenase activity, which gradually declined during reoxygenation. Reoxygenation of hypoxic cardiomyocytes produced marked injury; however, incubation with hemin or bilirubin during hypoxia considerably reduced the damage at reoxygenation. The protective effect of hemin is attributable to increased availability of substrate for heme oxygenase activity, because hypoxic cardiomyocytes generated very little bilirubin when incubated with medium alone but produced substantial bile pigment in the presence of hemin. Interestingly, incubation with hemin also maintained high heme oxygenase activity levels during the reoxygenation period. Reactive oxygen species generation was enhanced after hypoxia, and hemin and bilirubin were capable once again to attenuate this effect. These results indicate that the HO-1-bilirubin pathway can effectively defend hypoxic cardiomyocytes against reoxygenation injury and highlight the issue of heme availability in the cytoprotective action afforded by HO-1.
MRI assessment of LV relaxation by untwisting rate: a new isovolumic phase measure of τ
Authors: Dong Sheng-Jing , Hees Paul S. , Siu Cynthia O. , Weiss James L. , Shapiro Edward P.
Published: December 2017

Most noninvasive measures of diastolic function are made during left ventricular (LV) filling and are therefore subject to “pseudonormalization,” because variation in left atrial (LA) pressure may confound the estimation of relaxation rate. Counterclockwise twist of the LV develops during ejection, but untwisting occurs rapidly during isovolumic relaxation, before mitral opening. We hypothesized that the rate of untwisting might reflect the process of relaxation independent of LA pressure. Recoil rate (RR), the velocity of LV untwisting, was measured by tagged magnetic resonance imaging and regressed against the relaxation time constant (τ), recorded by catheterization, in 10 dogs at baseline and after dobutamine, saline, esmolol, and methoxamine treatment. RR correlated closely (average r = −0.86) with τ and was unaffected by elevated LA pressure. Multiple regression showed that τ, but not LA or aortic pressure, was an independent predictor of RR ( P < 0.0001, P = 0.99, and P = 0.18, respectively). The rate of recoil of torsion, determined wholly noninvasively, provides an isovolumic phase, preload-independent assessment of LV relaxation. Use of this novel parameter should allow the detailed study of diastolic function in states known to affect filling rates, such as aging, hypertension, and congestive heart failure.
Protein kinase C isoform expression and activity in the mouse heart
Authors: Schreiber Kathy L. , Paquet Louise , Allen Bruce G. , Rindt Hansjörg
Published: December 2017

The expression of protein kinase C (PKC) isoforms in the developing murine ventricle was studied using Western blotting, assays of PKC activity, and immunoprecipitations. The abundance of two Ca2+-dependent isoforms, PKCα and PKCβII, as well as two Ca2+-independent isoforms, PKCδ and PKCε, decreased during postnatal development to <15% of the levels detected at embryonic day 18. The analysis of the subcellular distribution of the four isoforms showed that PKCδ and PKCε were associated preferentially with the particulate fraction in fetal ventricles, indicating a high intrinsic activation state of these isoforms at this developmental time point. The expression of PKCα in cardiomyocytes underwent a developmental change. Although preferentially expressed in neonatal cardiomyocytes, this isoform was downregulated in adult cardiomyocytes. In fast-performance liquid chromatography-purified ventricular extracts, the majority of PKC activity was Ca2+-independent in both fetal and adult ventricles. Immunoprecipitation assays indicated that PKCδ and PKCε were responsible for the majority of the Ca2+-independent activity. These studies indicate a prominent role for Ca2+-independent PKC isoforms in the mouse heart.
Modulation of liver mitochondrial NOS is implicated in thyroid-dependent regulation of O2 uptake
Authors: Carreras María Cecilia , Peralta Jorge G. , Converso Daniela P. , Finocchietto Paola V. , Rebagliati Inés , Zaninovich Angel A. , Poderoso Juan José
Published: December 2017

Changes in O2 uptake at different thyroid status have been explained on the basis of the modulation of mitochondrial enzymes and membrane biophysical properties. Regarding the nitric oxide (NO) effects, we tested whether liver mitochondrial nitric oxide synthase (mtNOS) participates in the modulation of O2 uptake in thyroid disorders. Wistar rats were inoculated with 400 μCi131I (hypothyroid group), 20 μg thyroxine (T4)/100 g body wt administered daily for 2 wk (hyperthyroid group) or vehicle (control). Basal metabolic rate, mitochondrial function, and mtNOS activity were analyzed. Systemic and liver mitochondrial O2 uptake and cytochrome oxidase activity were lower in hypothyroid rats with respect to controls; mitochondrial parameters were further decreased byl-arginine (−42 and −34%, P < 0.05), consistent with 5- to 10-fold increases in matrix NO concentration. Accordingly, mtNOS expression (75%) and activity (260%) were selectively increased in hypothyroidism and reverted by hormone replacement without changes in other nitric oxide isoforms. Moreover, mtNOS activity correlated with serum 3,5,3′-triiodothyronine (T3) and O2 uptake. Increased mtNOS activity was also observed in skeletal muscle mitochondria from hypothyroid rats. Therefore, we suggest that modulation of mtNOS is a substantial part of thyroid effects on mitochondrial O2 uptake.