bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-dose ramipril treatment improves relaxation and calcium cycling after established cardiac hypertrophy
Authors: Boateng Samuel Y. , Naqvi Ruby U. , Koban Maren U. , Yacoub Magdi H. , MacLeod Kenneth T. , Boheler Kenneth R.
Published: December 2017

Rapid cooling contractures were used in this study to test whether low-dose ramipril improves sarcoplasmic reticulum (SR) Ca2+ uptake and Na+/Ca2+ exchanger function in isolated hypertrophied rat myocytes. Compensated cardiac hypertrophy was induced by abdominal aortic constriction for 5 wk followed by administration of ramipril (50 μg · kg−1 · day−1) or vehicle for 4 wk. Myocyte cell length and cell width were significantly ( P < 0.05) increased in both hypertrophied groups (±ramipril). Myocytes were loaded with indo 1, and relaxation was investigated after rapid cooling. Hypertrophied myocyte relaxation in Na+-free/Ca2+-free solution was 63% slower ( P < 0.01) and the fall in intracellular Ca2+ was 60% slower ( P < 0.05) than the relaxation of control cells. After ramipril treatment both relaxation and the decline in intracellular Ca2+ returned to control rates through improved SR Ca2+-ATPase function. Relaxation in caffeine showed no change after hypertrophy; however, after ramipril treatment the time to 50% relaxation in caffeine decreased by 30% ( P < 0.05). The improvement in Ca2+extrusion across the sarcolemmal membrane occurred independently of changes in Na+/Ca2+ exchanger mRNA and protein abundance. These data demonstrate that ramipril improves both SR-dependent and non-SR-dependent calcium cycling after established cardiac hypertrophy. However, the improvements in function are independent of transcriptional activation and likely to involve altered intracellular ion concentrations.
Free fatty acids, but not ketone bodies, protect diabetic rat hearts during low-flow ischemia
Authors: King Linda M. , Sidell Robert J. , Wilding James R. , Radda George K. , Clarke Kieran
Published: December 2017

To determine whether the effects of fatty acids on the diabetic heart during ischemia involve altered glycolytic ATP and proton production, we measured energetics and intracellular pH (pHi) by using31P NMR spectroscopy plus [2-3H]glucose uptake in isolated rat hearts. Hearts from 7-wk streptozotocin diabetic and control rats, perfused with buffer containing 11 mM glucose, with or without 1.2 mM palmitate or the ketone bodies, 4 mM β-hydroxybutyrate plus 1 mM acetoacetate, were subjected to 32 min of low-flow (0.3 ml · g wet wt−1 · min−1) ischemia, followed by 32 min of reperfusion. In control rat hearts, neither palmitate nor ketone bodies altered the recovery of contractile function. Diabetic rat hearts perfused with glucose alone or with ketone bodies, had functional recoveries 50% lower than those of the control hearts, but palmitate restored recovery to control levels. In a parallel group with the functional recoveries, palmitate prevented the 54% faster loss of ATP in the diabetic, glucose-perfused rat hearts during ischemia, but had no effect on the rate of ATP depletion in control hearts. Palmitate decreased total glucose uptake in control rat hearts during low-flow ischemia, from 106 ± 17 to 52 ± 12 μmol/g wet wt, but did not alter the total glucose uptake in the diabetic rat hearts, which was 42 ± 5 μmol/g wet wt. Recovery of contractile function was unrelated to pHiduring ischemia; the glucose-perfused control and palmitate-perfused diabetic hearts had end-ischemic pHi values that were significantly different at 6.36 ± 0.04 and 6.60 ± 0.02, respectively, but had similar functional recoveries, whereas the glucose-perfused diabetic hearts had significantly lower functional recoveries, but their pHiwas 6.49 ± 0.04. We conclude that fatty acids, but not ketone bodies, protect the diabetic heart by decreasing ATP depletion, with neither having detrimental effects on the normal rat heart during low-flow ischemia.
Effects of tobacco smoke and benzo[a]pyrene on human endothelial cell and monocyte stress responses
Authors: Vayssier-Taussat Muriel , Camilli Tura , Aron Yolande , Meplan Catherine , Hainaut Pierre , Polla Barbara S. , Weksler Babette
Published: December 2017

Smoking is an important risk factor for atherosclerosis. We compared tobacco smoke filtrate with benzo[ a]pyrene (a prominent xenobiotic component of tobacco smoke) for the capacity to induce stress proteins and cause cell death in human monocytes and vascular endothelial cells, two cell types that are involved in the formation of atherosclerotic lesions. Exposure to freshly prepared filtrates of tobacco smoke induced in both monocytes and endothelial cells expression of the inducible heat shock protein (HSP)70 and heme oxygenase-1 (HO-1) and produced loss of mitochondrial membrane potential. Later, cell death by apoptosis or necrosis occurred depending on the concentration of tobacco smoke. These toxic effects could be prevented by the antioxidant N-acetylcysteine. In contrast, exposure of these cells to benzo[ a]pyrene alone evoked neither stress proteins nor mitochondrial damage but did induce cell death by necrosis. Thus our results indicate that tobacco smoke rapidly induces complex oxidant-mediated stress responses in both vascular endothelial cells and circulating monocytes that are independent of the benzo[ a]pyrene content of the smoke.
Essential activation of PKC-δ in opioid-initiated cardioprotection
Authors: Fryer Ryan M. , Wang Yigang , Hsu Anna K. , Gross Garrett J.
Published: December 2017

Stimulation of the δ1-opioid receptor confers cardioprotection to the ischemic myocardium. We examined the role of protein kinase C (PKC) after δ-opioid receptor stimulation with TAN-67 ord-Ala2-d-Leu5-enkephalin (DADLE) in a rat model of myocardial infarction induced by a 30-min coronary artery occlusion and 2-h reperfusion. Infarct size (IS) was determined by tetrazolium staining and expressed as a percentage of the area at risk (IS/AAR). Control animals, subjected to ischemia and reperfusion, had an IS/AAR of 59.9 ± 1.8. DADLE and TAN-67 administered before ischemia significantly reduced IS/AAR (36.9 ± 3.9 and 36.7 ± 4.7, respectively). The δ1-selective opioid antagonist 7-benzylidenenaltrexone (BNTX) abolished TAN-67-induced cardioprotection (54.4 ± 1.3). Treatment with the PKC antagonist chelerythrine completely abolished DADLE- (61.8 ± 3.2) and TAN-67-induced cardioprotection (55.4 ± 4.0). Similarly, the PKC antagonist GF 109203X completely abolished TAN-67-induced cardioprotection (54.6 ± 6.6). Immunofluorescent staining with antibodies directed against specific PKC isoforms was performed in myocardial biopsies obtained after 15 min of treatment with saline, chelerythrine, BNTX, or TAN-67 and chelerythrine or BNTX in the presence of TAN-67. TAN-67 induced the translocation of PKC-α to the sarcolemma, PKC-β1to the nucleus, PKC-δ to the mitochondria, and PKC-ε to the intercalated disk and mitochondria. PKC translocation was abolished by chelerythrine and BNTX in TAN-67-treated rats. To more closely examine the role of these isoforms in cardioprotection, we utilized the PKC-δ selective antagonist rottlerin. Rottlerin abolished opioid-induced cardioprotection (48.9 ± 4.8) and PKC-δ translocation without affecting the translocation of PKC-α, -β1, or -ε. These results suggest that PKC-δ is a key second messenger in the cardioprotective effects of δ1-opioid receptor stimulation in rats.
The elastin-laminin receptor functions as a mechanotransducer in vascular smooth muscle
Authors: Spofford Christina M. , Chilian William M.
Published: December 2017

Laminin and elastin, two major constituents of the extracellular matrix, bind to cells via the elastin-laminin receptor (ELR), a receptor distinct from integrins. Despite the ubiquitous nature of elastin and laminin in the matrix, the consequences of activation of the ELR are unknown. Because integrins are capable of mechanosensitive transduction, we hypothesized that the ELR would exert a similar function. Accordingly, we examined the effects of cyclical stretch on canine coronary smooth muscle gene expression and proliferation that are mediated by the ELR. Northern blot analyses showed a 31% decrease in serum-induced expression of c- fos when cells were stretched for 30 min on elastin, but no change in expression was observed on collagen. Serum-induced proliferation of stretched cells was markedly attenuated on elastin when compared with collagen. Both the molecular (decreased c- fos expression) and biological (decreased proliferation) responses on elastin were restored after blockade of the ELR with the elastin fragment hexapeptide (valine-glycine-valine-alanine-proline-glycine, VGVAPG). The inhibition was specific for this peptide, as another hydrophobic hexapeptide (valine-serine-leucine-serine-proline-glycine, VSLSPG) did not inhibit the responses. These results demonstrate that cyclic stretch inhibits c- fos expression and proliferation of coronary vascular smooth muscle cells grown on elastin matrixes, a mechanosensitive response that is transduced by the ELR.
Impact of heart failure and exercise capacity on sympathetic response to handgrip exercise
Authors: Notarius Catherine F. , Atchison Deborah J. , Floras John S.
Published: December 2017

Peak oxygen uptake (V˙o 2 peak) in patients with heart failure (HF) is inversely related to muscle sympathetic nerve activity (MSNA) at rest. We hypothesized that the MSNA response to handgrip exercise is augmented in HF patients and is greatest in those with lowV˙o 2 peak. We studied 14 HF patients and 10 age-matched normal subjects during isometric [30% of maximal voluntary contraction (MVC)] and isotonic (10%, 30%, and 50% MVC) handgrip exercise that was followed by 2 min of posthandgrip ischemia (PHGI). MSNA was significantly increased during exercise in HF but not normal subjects. Both MSNA and HF levels remained significantly elevated during PHGI after 30% isometric and 50% isotonic handgrip in HF but not normal subjects. HF patients with lower V˙o 2 peak (<56% predicted; n = 8) had significantly higher MSNA during rest and exercise than patients withV˙o 2 peak > 56% predicted ( n = 6) and normal subjects. The muscle metaboreflex contributes to the greater reflex increase in MSNA during ischemic or intense nonischemic exercise in HF. This occurs at a lower threshold than normal and is a function ofV˙o 2 peak.
Integrins and mechanotransduction of the vascular myogenic response
Authors: Davis Michael J. , Wu Xin , Nurkiewicz Timothy R. , Kawasaki Junya , Davis George E. , Hill Michael A. , Meininger Gerald A.
Published: December 2017

This review summarizes what is currently known about the role of integrins in the vascular myogenic response. The myogenic response is the rapid and maintained constriction of a blood vessel in response to pressure elevation. A role for integrins in this process has been suggested because these molecules form an important mechanical link between the extracellular matrix and the vascular smooth muscle cytoskeleton. We briefly summarize evidence for a general role of integrins in mechanotransduction. We then describe the integrin subunit combinations known to exist in smooth muscle and the vascular wall matrix proteins that may interact with these integrins. We then discuss the effects of integrin-specific peptides and antibodies on vascular tone and on calcium entry mechanisms in vascular smooth muscle. Because integrin function is linked to the cytoskeleton, we discuss evidence for the role of the cytoskeleton in determining myogenic responsiveness. Finally, we analyze evidence that integrin-linked signaling pathways, such as those involving protein tyrosine phosphorylation cascades and mitogen-activated protein kinases, are required for myogenic tone.
Use of functional proteomics to investigate PKCε-mediated cardioprotection: the signaling module hypothesis
Authors: Vondriska Thomas M. , Klein Jon B. , Ping Peipei
Published: December 2017

The characterization of biological processes on the basis of alterations in the cellular proteins, or “proteomic” analysis, is a powerful approach that may be adopted to decipher the signaling mechanisms that underlie various pathophysiological conditions, such as ischemic heart disease. This review represents a prospectus for the implementation of proteomic analyses to delineate the myocardial intracellular signaling events that evoke cardioprotection against ischemic injury. In concert with this, the manifestation of a protective phenotype has recently been shown to involve dynamic modulation of protein kinase C-ε (PKCε) signaling complexes (Ping P, Zhang J, Pierce WM Jr, and Bolli R. Circ Res 88: 59–62, 2001). Accordingly, “the signaling module hypothesis” is formulated as a plausible mechanism by which multipurpose stress-activated proteins and signaling kinases may function collectively to facilitate the genesis of cardioprotection.
Abnormal contraction caused by expression of Gi-coupled receptor in transgenic model of dilated cardiomyopathy
Authors: Baker Anthony J. , Redfern Charles H. , Harwood Mark D. , Simpson Paul C. , Conklin Bruce R.
Published: December 2017

Although increased Gi signaling has been associated with dilated cardiomyopathy in humans, its role is not clear. Our goal was to determine the effects of chronically increased Gi signaling on myocardial function. We studied transgenic mice that expressed a Gi-coupled receptor (Ro1) that was targeted to the heart and regulated by a tetracycline-controlled expression system. Ro1 expression for 8 wk resulted in abnormal contractions of right ventricular muscle strips in vitro. Ro1 expression reduced myocardial force by >60% (from 35 ± 3 to 13 ± 2 mN/mm2, P < 0.001). Nevertheless, sensitivity to extracellular Ca2+ was enhanced. The extracellular [Ca2+] resulting in half-maximal force was lower with Ro1 expression compared with control (0.41 ± 0.05 vs. 0.88 ± 0.05 mM, P < 0.001). Ro1 expression slowed both contraction and relaxation kinetics, increasing the twitch time to peak (143 ± 6 vs. 100 ± 4 ms in control, P < 0.001) and the time to half relaxation (124 ± 6 vs. 75 ± 6 ms in control, P < 0.001). Increased pacing frequency increased contractile force threefold in control myocardium ( P < 0.001) but caused no increase of force in Ro1-expressing myocardium. When stimulation was interrupted with rests, postrest force increased in control myocardium, but there was postrest decay of force in Ro1-expressing myocardium. These results suggest that defects in contractility mediated by Gi signaling may contribute to the development of dilated cardiomyopathy.
High-affinity prorenin binding to cardiac man-6-P/IGF-II receptors precedes proteolytic activation to renin
Authors: Saris Jasper J. , Derkx Frans H. M. , De Bruin René J. A. , Dekkers Dick H. W. , Lamers Jos M. J. , Saxena Pramod R. , Schalekamp Maarten A. D. H. , Jan Danser A. H.
Published: December 2017

Mannose-6-phosphate (man-6-P)/insulin-like growth factor-II (man-6-P/IgF-II) receptors are involved in the activation of recombinant human prorenin by cardiomyocytes. To investigate the kinetics of this process, the nature of activation, the existence of other prorenin receptors, and binding of native prorenin, neonatal rat cardiomyocytes were incubated with recombinant, renal, or amniotic fluid prorenin with or without man-6-P. Intact and activated prorenin were measured in cell lysates with prosegment- and renin-specific antibodies, respectively. The dissociation constant ( Kd) and maximum number of binding sites (Bmax) for prorenin binding to man-6-P/IGF-II receptors were 0.6 ± 0.1 nM and 3,840 ± 510 receptors/myocyte, respectively. The capacity for prorenin internalization was greater than 10 times Bmax. Levels of internalized intact prorenin decreased rapidly (half-life = 5 ± 3 min) indicating proteolytic prosegment removal. Prorenin subdivision into man-6-P-free and man-6-P-containing fractions revealed that only the latter was bound. Cells also bound and activated renal but not amniotic fluid prorenin. We concluded that cardiomyocytes display high-affinity binding of renal but not extrarenal prorenin exclusively via man-6-P/IGF-II receptors. Binding precedes internalization and proteolytic activation to renin thereby supporting the concept of cardiac angiotensin formation by renal prorenin.
NGF-independent survival of postganglionic sympathetic neurons in neuronal-vascular smooth muscle cocultures
Authors: Damon Deborah H.
Published: December 2017

The present study tests the hypothesis that vascular cells promote the survival of postganglionic sympathetic neurons in the absence of nerve growth factor (NGF). To test this hypothesis, neurons isolated from superior cervical ganglia of 2- to 4-day-old rat pups were grown in the absence of NGF and in the absence and presence of vascular smooth muscle cells (VSM). Neuronal survival was assessed as a function of time in culture. At all time points studied, VSM promoted the survival of the neurons. After 5 days in the absence of NGF, 7 ± 2% of neurons survived in the absence and 28 ± 7% survived in the presence of VSM. An endothelin receptor antagonist reduced neuronal survival in cocultures grown in the absence of NGF. These data indicate that VSM produce factors other than NGF that promote the survival of cultured postganglionic sympathetic neurons. The data also indicate that endothelin contributes to this effect and suggest that endothelin as well as other VSM-derived factors may play a role in the development of sympathetic innervation to the vasculature.
Causal linear parametric model for baroreflex gain assessment in patients with recent myocardial infarction
Authors: Nollo Giandomenico , Porta Alberto , Faes Luca , Del Greco Maurizio , Disertori Marcello , Ravelli Flavia
Published: December 2017

Spectral and cross-spectral analysis of R-R interval and systolic arterial pressure (SAP) spontaneous fluctuations have been proposed for noninvasive evaluation of baroreflex sensitivity (BRS). However, results are not in good agreement with clinical measurements. In this study, a bivariate parametric autoregressive model with exogenous input (ARXAR model), able to divide the R-R variability into SAP-related and -unrelated parts, was used to quantify the gain (αARXAR) of the baroreflex regulatory mechanism. For performance assessing, two traditional noninvasive methods based on frequency domain analysis [spectral, baroreflex gain by autogressive model (αAR); cross-spectral, baroreflex gain by bivariate autoregressive model (α2AR)] and one based on the time domain [baroreflex gain by sequence analysis (αSEQ)] were considered and compared with the baroreflex gain by phenylephrine test (αPHE). The BRS evaluation was performed on 30 patients (61 ± 10 yr) with recent (10 ± 3 days) myocardial infarction. The ARXAR model allowed dividing the R-R variability (950 ± 1,099 ms2) into SAP-related (256 ± 418 ms2) and SAP-unrelated (694 ± 728 ms2) parts. αAR (12.2 ± 6.1 ms/mmHg) and α2AR (8.9 ± 5.6 ms/mmHg) as well as αSEQ (12.6 ± 7.1 ms/mmHg) overestimated BRS assessed by αPHE (6.4 ± 4.7 ms/mmHg), whereas the ARXAR index gave a comparable value (αARXAR = 5.4 ± 3.3 ms/mmHg). All noninvasive methods were significantly correlated to αPHE (αARXAR and αSEQ were more correlated than the other indexes). Thus the baroreflex gain obtained describing the causal dependence of R-R interval on SAP showed a good agreement with αPHE and may provide additional information regarding the gain estimation in the frequency domain.
Mechanism of reversible 99mTc-sestamibi perfusion defects during pharmacologically induced vasodilatation
Authors: Wei Kevin , Le Elizabeth , Bin Jian-Ping , Coggins Matthew , Jayawera Ananda R. , Kaul Sanjiv
Published: December 2017

Reversible perfusion defects on 99mTc-sestamibi imaging during hyperemia are thought to occur due to myocardial blood flow (MBF) “mismatch” between regions with and without stenosis. We have recently shown that myocardial blood volume (MBV) distal to a stenosis decreases during hyperemia, resulting in a reversible perfusion defect on myocardial contrast echocardiography (MCE). In this study, we hypothesized that a reversible perfusion defect on99mTc-sestamibi imaging during hyperemia results from the same mechanism. We tested our hypothesis under the following conditions: 1) increases in MBF in the absence of changes in MBV by using direct intracoronary infusion of adenosine ( group I, n = 10 dogs); 2) decrease in MBV despite an increase in MBF by left main infusion of adenosine proximal to a noncritical coronary stenosis placed on either coronary artery ( group II, n = 13 dogs); and 3) reduction in both resting MBF and MBV by placement of a severe stenosis ( group III, n = 7 dogs). In group I dogs, no difference in MBV or 99mTc-sestamibi uptake was found between the two coronary beds despite an up to fourfold increase in MBF in one bed with adenosine. In group II dogs, MBV distal to the stenosis decreased during hyperemia despite a twofold increase in mean MBF. A good correlation was found between99mTc-sestamibi uptake and MBV ratios from the stenosed versus normal bed ( r = 0.91, P < 0.001). In group III dogs, both MBF and MBV were decreased in the stenosed bed at rest with a good correlation noted between99mTc-sestamibi uptake and MBV ratios from the stenosed versus normal bed ( r = 0.92, P = 0.004). We conclude that reversible defects on99mTc-sestamibi during vasodilator stress imaging are related to decreases in MBV distal to a stenosis and not to “flow mismatch” between beds. The decrease in MBV results in reduced99mTc-sestamibi uptake during hyperemia.
AT1 receptor block does not affect arterial baroreflex during pregnancy in rabbits
Authors: O'Hagan Kathleen P. , Skogg Kara A. , Stevenson Jennifer B.
Published: December 2017

The role of ANG II in the arterial baroreflex control of renal sympathetic nerve activity (RSNA) in eight term-pregnant (P) and eight nonpregnant (NP) conscious rabbits was assessed using sequential intracerebroventricular and intravenous infusions of losartan, an AT1 receptor antagonist. The blood pressure (BP)-RSNA relationship was generated by sequential inflations of aortic and vena caval perivascular occluders. Pregnant rabbits exhibited a lower maximal RSNA reflex gain (−44%) that was primarily due to a reduction in the maximal sympathetic response to hypotension (P, 248 ± 20% vs. NP, 357 ± 41% of rest RSNA, P < 0.05). Intracerebroventricular losartan decreased resting BP in P (by 9 ± 3 mmHg, P < 0.05) but not NP rabbits, and had no effect on the RSNA baroreflex in either group. Subsequent intravenous losartan decreased resting BP in NP and further decreased BP in P rabbits, but had no significant effect on the maximal RSNA reflex gain. ANG II may have an enhanced role in the tonic support of BP in pregnancy, but does not mediate the gestational depression in the arterial baroreflex control of RSNA in rabbits.
COX-2-dependent delayed dilatation of cerebral arterioles in response to bradykinin
Authors: Brian Johnny E. , Faraci Frank M. , Moore Steven A. ,   (With the Technical Assistance of Paula Ludwig)
Published: December 2017

Bradykinin (BK) is released in the brain during injury and inflammation. Activation of endothelial BK receptors produces acute dilatation of cerebral arterioles that is mediated by reactive oxygen species (ROS). ROS can also modulate gene expression, including expression of the inducible isoform of cyclooxygenase (COX-2). We hypothesized that exposure of the brain to BK would produce acute dilatation, which would be followed by a delayed dilatation mediated by COX-2. To test this hypothesis in anesthetized rats, BK was placed twice in cranial windows for 7 min, after which the windows were flushed to remove residual BK. The two BK exposures were separated by 30 min. Each BK exposure produced acute dilatation of cerebral arterioles, after which diameter rapidly returned to baseline. Over the subsequent 4.5 h after the second BK exposure, arterioles dilated 48 ± 8%. Treatment of the cranial window with NS-398, a selective COX-2 inhibitor, or dexamethasone, significantly attenuated the delayed dilatation. Aminoguanidine, a selective inhibitor of inducible nitric oxide synthase, did not alter the delayed dilatation. Cotreatment of cranial windows with BK, superoxide dismutase, and catalase also prevented the delayed dilatation. In separate experiments, exposure of the cortical surface to BK upregulated leptomeningeal expression of COX-2 mRNA. Our results suggest that acute, time-limited exposure of the brain to BK produces delayed dilatation of cerebral arterioles dependent on expression and activity of COX-2.
Impaired sarcoplasmic reticulum function leads to contractile dysfunction and cardiac hypertrophy
Authors: Meyer Markus , Trost Susanne U. , Bluhm Wolfgang F. , Knot Harm J. , Swanson Eric , Dillmann Wolfgang H.
Published: December 2017

Sarcoplasmic reticulum (SR)-mediated Ca2+sequestration and release are important determinants of cardiac contractility. In end-stage heart failure SR dysfunction has been proposed to contribute to the impaired cardiac performance. In this study we tested the hypothesis that a targeted interference with SR function can be a primary cause of contractile impairment that in turn might alter cardiac gene expression and induce cardiac hypertrophy. To study this we developed a novel animal model in which ryanodine, a substance that alters SR Ca2+release, was added to the drinking water of mice. After 1 wk of treatment, in vivo hemodynamic measurements showed a 28% reduction in the maximum speed of contraction (+dP/d tmax) and a 24% reduction in the maximum speed of relaxation (−dP/d tmax). The slowing of cardiac relaxation was confirmed in isolated papillary muscles. The late phase of relaxation expressed as the time from 50% to 90% relaxation was prolonged by 22%. After 4 wk of ryanodine administration the animals had developed a significant cardiac hypertrophy that was most prominent in both atria (right artrium +115%, left atrium +100%, right ventricle +23%, and left ventricle +13%). This was accompanied by molecular changes including a threefold increase in atrial natriuretic factor mRNA and a sixfold increase in β-myosin heavy chain mRNA. Sarcoplasmic endoplasmic reticulum Ca2+mRNA was reduced by 18%. These data suggest that selective impairment of SR function in vivo can induce changes in cardiac gene expression and promote cardiac growth.
In vivo chemotactic properties and spatial expression of PDGF in developing mesenteric microvascular networks
Authors: Zeller Peter J. , Skalak Thomas C. , Ponce Ana M. , Price Richard J.
Published: December 2017

The recruitment of perivascular cells to developing microvessels is a key component of microvessel assembly. Whereas platelet-derived growth factor (PDGF) signaling is critical for this process during embryonic development, its role from the postnatal stages through adulthood remains unclear. We investigated the potential role of PDGF signaling during microvessel assembly by measuring in vivo the migration of labeled fibroblasts to PDGF in mesenteric connective tissue and by examining PDGF-B and PDGF receptor-β (PGDFR-β) expression in microvascular networks during normal maturation. PDGF-B homodimer (PDGF-BB; 30 ng/ml) application elicited a significant ( P < 0.05) increase (7.8 ± 4.1 cells) in labeled fibroblasts within 100 μm of the source micropipette after 2 h. PDGF-A homodimer (30 ng/ml) application and control solution did not elicit directed migration. PDGF-B was expressed in microvessel endothelium and smooth muscle, whereas PDGFR-β was expressed in endothelium, smooth muscle, and interstitial fibroblasts. Given that PDGF-BB elicits fibroblast migration in the mesentery and that PDGF-B and PDGFR-β are expressed in a pattern that indicates paracrine signaling from microvessels to the interstitium, the results are consistent with a role for PDGF-B in perivascular cell recruitment to microvessels.
Pathways of bradykinin degradation in blood and plasma of normotensive and hypertensive rats
Authors: Dendorfer Andreas , Wolfrum Sebastian , Wagemann Marc , Qadri Fatimunnisa , Dominiak Peter
Published: December 2017

Kinins are vasoactive peptide hormones that can confer protection against the development of hypertension. Because their efficacy is greatly influenced by the rate of enzymatic degradation, the activities of various kininases in plasma and blood of spontaneously hypertensive rats (SHR) were compared with those in normotensive Wistar-Kyoto rats (WKY) to identify pathogenic alterations. Either plasma or whole blood was incubated with bradykinin (10 μM). Bradykinin and kinin metabolites were measured by high-performance liquid chromatography. Kininase activities were determined by cumulative inhibition of angiotensin I-converting enzyme (ACE), carboxypeptidase N (CPN), and aminopeptidase P (APP), using selective inhibitors. Plasma of WKY rats degraded bradykinin at a rate of 13.3 ± 0.94 μmol · min−1· l−1. The enzymes ACE, APP, and CPN represented 92% of this kininase activity, with relative contributions of 52, 25, and 16%, respectively. Inclusion of blood cells at physiological concentrations did not extend the activities of these plasma kininases further. No differences of kinin degradation were found between WKY and SHR. The identical conditions of kinin degradation in WKY and SHR suggest no pathogenic role of kininases in the SHR model of genetic hypertension.
Age-related changes in adenosine-mediated relaxation of coronary and aortic smooth muscle
Authors: Hinschen Andrea K. , Rose'Meyer Roselyn B. , Headrick John P.
Published: December 2017

We tested whether adenosine mediates nitric oxide (NO)-dependent and NO-independent dilation in coronary and aortic smooth muscle and whether age selectively impairs NO-dependent adenosine relaxation. Responses to adenosine and the relatively nonselective analog 5 ′-N-ethylcarboxamidoadenosine (NECA) were studied in coronary vessels and aortas from immature (1–2 mo), mature (3–4 mo), and moderately aged (12–18 mo) Wistar and Sprague-Dawley rats. Adenosine and NECA induced biphasic concentration-dependent coronary vasodilation, with data supporting high-sensitivity (pEC50 = 5.2–5.8) and low-sensitivity (pEC50 = 2.3–2.4) adenosine sites. Although sensitivity to adenosine and NECA was unaltered by age, response magnitude declined significantly. Treatment with 50 μM N G-nitro-l-arginine methyl ester (l-NAME) markedly inhibited the high-sensitivity site, although response magnitude still declined with age. Aortic sensitivity to adenosine declined with age (pEC50 = 4.7 ± 0.2, 3.5 ± 0.2, and 2.9 ± 0.1 in immature, mature, and moderately aged aortas, respectively), and the adenosine receptor transduction maximum also decreased (16.1 ± 0.8, 12.9 ± 0.7, and 9.6 ± 0.7 mN/mm2 in immature, mature, and moderately aged aortas, respectively). l-NAME decreased aortic sensitivity to adenosine in immature and mature tissues but was ineffective in the moderately aged aorta. Data collectively indicate that 1) adenosine mediates NO-dependent and NO-independent coronary and aortic relaxation, 2) maturation and aging reduce NO-independent and NO-dependent adenosine responses, and 3) the age-related decline in aortic response also involves a reduction in the adenosine receptor transduction maximum.
Ischemic-reperfused isolated working mouse hearts: membrane damage and type IIA phospholipase A2
Authors: De Windt Leon J. , Willems Jodil , Roemen Theo H. M. , Coumans Will A. , Reneman Robert S. , Van Der Vusse Ger J. , Van Bilsen Marc
Published: December 2017

For the murine heart the relationships between ischemia-reperfusion-induced loss of cardiac function, enzyme release, high-energy phosphate (HEP), and membrane phospholipid metabolism are ill-defined. Accordingly, isolated ejecting murine hearts were subjected to varying periods of ischemia, whether or not followed by reperfusion. On reperfusion, hemodynamic function was almost completely restored after 10 min of ischemia [83 ± 14% recovery of cardiac output (CO)], but was severely depressed after 15 and 20 min of ischemia (40 ± 24 and 31 ± 24% recovery of CO, respectively). Reperfusion was associated with partial recovery of HEP stores and enhanced degradation of phospholipids as indicated by the accumulation of fatty acids (FA). Myocardial FA content and enzyme release during reperfusion were correlated ( r = 0.70), suggesting that membrane phospholipid degradation and cellular damage are closely related phenomena. To investigate the role of type IIA secretory phospholipase A2(sPLA2) in this process, hearts from wild-type and sPLA2-deficient mice were subjected to ischemia-reperfusion. Postischemic functional recovery, ATP depletion, enzyme release, and FA accumulation were not significantly different between wild-type and sPLA2- deficient hearts. These findings argue against a prominent role of type IIA sPLA2in the development of irreversible cell damage in the ischemic-reperfused murine myocardium.
Coronary and myocardial effects of acetaminophen: protection during ischemia-reperfusion
Authors: Merrill G. , McConnell P. , Vandyke K. , Powell S.
Published: December 2017

Acetaminophen is a phenol with antioxidant properties, but little is known about its actions on the mammalian myocardium and coronary circulation. We studied isolated, perfused guinea pig hearts, and tested the hypothesis that acetaminophen-treated hearts would be protected during ischemia-reperfusion. Acetaminophen concentrations in the range of 0.3–0.6 mmol/l caused modest but significant ( P< 0.05) coronary vasoconstriction and positive inotropy. The effects were more brisk during constant pressure perfusion than during constant flow. During 20 min of low-flow, global myocardial ischemia and 40 min of reperfusion, hearts treated with acetaminophen retained or recovered a greater percentage of left ventricular function than hearts treated with vehicle. Myofibrillar ultrastructure appeared to be preserved in the reperfused myocardium with acetaminophen. By using chemiluminescence and spin-trap methodologies, we investigated acetaminophen-mediated antioxidant mechanisms to help explain the cardioprotection. The burst of hydroxyl radicals seen between 0 and 10 min of reperfusion was significantly attenuated ( P < 0.05) by acetaminophen but not by vehicle. The 3-morpholinosydnominine (SIN-1) generation of peroxynitrite and its oxidative interaction with luminol to produce blue light during ischemia-reperfusion was also blocked by acetaminophen. Our results show that acetaminophen provides significant functional and structural protection to the ischemic-reperfused myocardium, and the mechanism of cardioprotection seems to involve attenuation of the production of both hydroxyl radicals and peroxynitrite.
A novel technique for measurement of pericardial pressure
Authors: deVries Gwyneth , Hamilton Douglas R. , Ter Keurs Henk E. D. J. , Beyar Rafael , Tyberg John V.
Published: December 2017

To determine whether pericardial liquid pressure accurately measures pericardial constraint, we developed a technique in which a catheter was positioned perpendicular to the epicardial surface. This device, which occupies little or no pericardial space, couples the thin film of liquid to a transducer. In six open-chest dogs, we also measured left ventricular (LV) end-diastolic pressure (LVEDP) and anteroposterior and septum-to-free wall diameters. LVEDP was raised incrementally to ∼25 mmHg by saline infusion. With the use of the product of the two diameters as an index of area ( A LV), LVEDP- A LV relationships were obtained with the pericardium closed and again after the pericardium had been widely opened to obtain the isovolumic difference in LVEDP (ΔLVEDP). In all dogs, the technique yielded values of pericardial pressure equal to ΔLVEDP as well as equal to that measured using a previously placed balloon transducer in the same location and at the same A LV. We conclude that, when the pressure of the pericardial liquid is appropriately measured, it (in addition to the balloon-measured contact stress) defines the diastolic constraining effect of the pericardium. Furthermore, we suggest that earlier measurements of pericardial “liquid pressure” were low, due to an artifact of measurement.
Angiotensin II regulates phosphorylation of translation elongation factor-2 in cardiac myocytes
Authors: Everett Allen D. , Stoops Tamara D. , Nairn Angus C. , Brautigan David
Published: December 2017

Increased protein synthesis is the cardinal feature of cardiac hypertrophy. We have studied angiotensin II (ANG II)-dependent regulation of eukaryotic elongation factor-2 (eEF-2), an essential component of protein translation required for polypeptide elongation, in rat neonatal cardiac myocytes. eEF2 is fully active in its dephosphorylated state and is inhibited following phosphorylation by eEF2 kinase. ANG II treatment (10−10–10−7M) for 30 min produced an AT1receptor-specific and concentration- and time-dependent reduction in the phosphorylation of eEF-2. Protein phosphatase 2A (PP2A) inhibitors okadaic acid and fostriecin, but not the PP2B inhibitor FK506, attenuated ANG II-dependent dephosphorylation of eEF-2. ANG II activated mitogen-activated protein kinase, (MAPK) within 10 min of treatment, and blockade of MAPK activation with PD-98059 (1–20 nM) inhibited eEF-2 dephosphorylation. The effect of ANG II on eEF-2 dephosphorylation was also blocked by LY-29004 (1–20 nM), suggesting a role for phosphoinositide 3-kinase, but the mammalian target rapamycin inhibitor rapamycin (10–100 nM) had no effect. Together these results suggest that the ANG II-dependent increase in protein synthesis includes activation of eEF-2 via dephosphorylation by PP2A by a process that involves both PI3K and MAPK.
Role of nitric oxide and protein kinase C in ACh-induced cardioprotection
Authors: Liu Huiping , McPherson Bradley C. , Zhu Xiangdong , Da Costa Mark L. A. , Jeevanandam Valluvan , Yao Zhenhai
Published: December 2017

We examined the roles of nitric oxide and protein kinase C (PKC) in ACh-produced protection of cultured cardiomyocytes during simulated ischemia and reoxygenation. Cell viability was quantified using propidium iodide in chick embryonic ventricular myocytes. O2radicals were quantified using 2′,7′-dichlorofluorescin diacetate. After a 10-min infusion of ACh (0.5 or 1 mM) and a 10-min drug-free period, we simulated ischemia for 1 h and reoxygenation for 3 h. ACh reduced cardiocyte death [32 ± 4%; n = 6 and 23 ± 4%; n = 7 ( P < 0.05)] and attenuated oxidant stress during ischemia and reoxygenation in a concentration-dependent manner compared with controls (47 ± 4%; n = 8; P < 0.05). The increase in O2radicals before simulated ischemia [357 ± 49; n = 4 and 528 ± 52; n = 8 vs. 211 ± 34; n = 8; P < 0.05 (arbitrary units)] was abolished by the specific nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME) and was markedly attenuated by NG-monomethyl-l-arginine (l-NMMA). l-NAME or l-NMMA blocked the protective effects of ACh, which selectively increased PKC-ε isoform activity in the particulate fraction. The PKC inhibitor Gö-6976 had no effect on O2radical production before simulated ischemia but it abolished the protection; therefore nitric oxide is a large component of ACh-generated O2radicals. Nitric oxide and O2radicals activate the PKC-ε isoform by which ACh protects against injury.
Comparison of effects of diabetes mellitus on an EDHF-dependent and an EDHF-independent artery
Authors: Wigg Susan J. , Tare Marianne , Tonta Mary A. , O'Brien Richard C. , Meredith Ian T. , Parkington Helena C.
Published: December 2017

The hypothesis tested in this study is that diabetes has a different impact on an artery in which endothelium-dependent responses derive from both nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) compared with responses in which NO predominates and EDHF is absent. The streptozotocin-treated rat model of diabetes was used, and the arteries were mounted on a wire myograph. In mesenteric arteries depolarized and constricted with phenylephrine, acetylcholine evoked hyperpolarization (31 ± 2 mV) and complete relaxation; these responses were attributed to EDHF and NO. In femoral arteries, acetylcholine evoked a small, NO-mediated hyperpolarization (5 ± 1 mV) and incomplete relaxation. Bradykinin evoked NO-dependent responses in mesenteric arteries. Whereas diabetes significantly impaired the EDHF-dependent hyperpolarization and relaxation in mesenteric arteries, NO-dependent responses in femoral and mesenteric arteries were preserved. 1-Ethyl-2-benzimidazolinone evoked hyperpolarization and relaxation in mesenteric arteries, and this was impaired in diabetes. In conclusion, NO-dependent responses are preserved in diabetes, whereas endothelial responses-dependent upon EDHF appear to be impaired. The putative channels responsible for mediating the EDHF response may be altered in diabetes.
Protection of ischemic hearts by high glucose is mediated, in part, by GLUT-4
Authors: Ramasamy Ravichandran , Hwang Yuying C. , Whang John , Bergmann Steven R.
Published: December 2017

Metabolic interventions that promote glucose use during ischemia have been shown to protect ischemic myocardium and improve functional recovery on reperfusion. We evaluated whether the cardioprotection afforded by high glucose during low-flow ischemia is associated with changes in the sarcolemmal content of glucose transporters, specifically GLUT-4. Isolated rat hearts were paced at 300 beats/min and perfused under normal glucose (5 mM) or high glucose (10 mM) conditions in buffer containing 0.4 mM albumin, 0.4 mM palmitate, and 70 mU/l insulin and subjected to 50 min of low-flow ischemia and 60 min of reperfusion. To determine the importance of insulin-sensitive glucose transporters in mediating cardioprotection, a separate group of hearts were perfused in the presence of cytochalasin B (10 μM), a preferential inhibitor of insulin-sensitive glucose transporters. Ischemic contracture during low-flow ischemia and creatine kinase release on reperfusion was decreased, and the percent recovery of left ventricular function with reperfusion was enhanced in hearts perfused with high glucose ( P < 0.03). Hearts perfused with high glucose exhibited increased GLUT-4 protein expression in the sarcolemmal membrane compared with control hearts under baseline conditions, and these changes were additive with low-flow ischemia. In addition, high glucose did not affect the baseline distribution of sarcolemmal GLUT-1 and blunted any changes with low-flow ischemia. These salutary effects were abolished when glucose transporters are blocked with cytochalasin B. These data demonstrate that protection of ischemic myocardium by high glucose is associated with increased sarcolemmal content of the insulin-sensitive GLUT-4 and suggest a target for the protection of jeopardized myocardium.
Correlation of HO-1 expression with onset and reversal of hypoxia-induced vasoconstrictor hyporeactivity
Authors: Jernigan Nikki L. , O'Donaughy Theresa L. , Walker Benjimen R.
Published: December 2017

Rats exposed to chronic hypoxia (CH; 4 wk at 0.5 atm) exhibit attenuated renal vasoconstrictor reactivity to phenylephrine (PE). Preliminary studies from our laboratory suggest that this response is mediated by hypoxic induction of heme oxygenase (HO) and subsequent release of the endogenous vasodilator carbon monoxide. Because vascular HO mRNA is increased within hours of hypoxic exposure, we hypothesized that the onset of reduced reactivity may occur fairly rapidly and correlate with HO expression. Therefore, we examined the onset of attenuated vasoconstriction on CH exposure as well as the duration of hyporeactivity on return to a normoxic environment. Renal vascular resistance (RVR) responses to graded intravenous infusion of PE were measured in conscious rats under control conditions and after 24 h, 48 h, and 4 wk of CH exposure. Vasoreactivity responses were also determined in 4-wk CH rats 1, 5, 24, and 96 h after return to normoxia. We found that RVR responses to PE were significantly blunted after 48 h and 4 wk but not after 24 h of hypoxic exposure. Inhibition of HO with zinc protoporphyrin IX increased RVR and decreased renal blood flow in 48-h CH rats but not controls. Although reactivity to PE was gradually restored after 4 wk of CH, responsiveness was still slightly blunted at 96 h after return to normoxia. Western blot analysis demonstrated a correlation between HO-1 protein levels and attenuated vasoconstrictor response in CH and posthypoxic rats. These data suggest that the onset and offset of physiologically relevant vascular HO expression occur within 2–3 days.
Nitric oxide generation by isolated descending vasa recta
Authors: Rhinehart Krisitie L. , Pallone Thomas L.
Published: December 2017

Nitric oxide (NO) generation by the outer medullary descending vasa recta (OMDVR) was measured with the fluorescent dye 4,5-diaminofluoroscein (DAF-2) during 30-min incubations. Addition of 0.1 or 1.0 mM l-arginine to the incubation buffer increased the DAF-2 signal by 8.7 and 13.6% ( P = 0.08 and P < 0.05), respectively. Compared withl-arginine alone (0.1 mM), bradykinin (BK; 1 × 10−7 M) enhanced the DAF-2 signal by 11.1% ( P < 0.05). The NO synthase inhibitor N ω-nitro-l-arginine methyl ester (0.1 mM) reversed the BK-stimulated NO generation as measured with either DAF-2 or by the oxidation of Fe2+ hemoglobin. Using 1 mM 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol), a cell-permeant superoxide dismutase mimetic, we tested whether reduction of superoxide anion increases intracellular NO. Tempol increased DAF-2 fluorescence by 12 and 23.3%, respectively, over BK-stimulated or control vessels. Tempol also vasodilated ANG II (1 × 10−8 M)-preconstricted OMDVR ( P < 0.05). We conclude that NO generation by isolated OMDVR can be increased by l-arginine, that the endothelium-dependent vasodilator BK enhances NO production, and that NO consumption by superoxide plays a role in the determination of cellular NO concentrations.
Differential effects of protein kinase C on human vascular smooth muscle cell proliferation and migration
Authors: Itoh Hiroyuki , Yamamura Shinji , Ware J. Anthony , Zhuang Shaobin , Mii Shinsuke , Liu Bo , Kent K. Craig
Published: December 2017

Vascular smooth muscle cell (SMC) migration and proliferation contribute to intimal hyperplasia, and protein kinase C (PKC) may be required for both events. In this report, we investigated the role of PKC in proliferation and migration of SMC derived from the human saphenous vein. Activation of PKC by phorbol-12,13-dibutyrate (PDBu) or (−)-indolactam [(−)-ILV] increases SMC proliferation. Downregulation of PKC activity by prolonged incubation with phorbol ester or inhibition of PKC with chelerythrine in SMC diminished agonist-stimulated proliferation. In contrast, stimulation of PKC with PDBu or (−)-ILV inhibited basal and agonist-induced SMC chemotaxis. Moreover, downregulation of PKC or inhibition with chelerythrine accentuated migration. We postulated that the inhibitory effect of PKC on SMC chemotaxis was mediated through cAMP-dependent protein kinase (protein kinase A, PKA). In support of this hypothesis, we found that activation of PKC in SMC stimulated PKA activity. The cAMP agonist forskolin significantly inhibited SMC chemotaxis. Furthermore, the inhibitory effect of PKC on SMC chemotaxis was completely reversed by cAMP or PKA inhibitors. In search of the PKC isotype(s) underlying these differential effects of PKC in SMC, we identified eight isotypes expressed in human SMC. Only PKC-α, -βI, -δ, and -ε were eliminated by downregulation, suggesting that one or more of these four enzymes facilitate the observed phorbol ester-dependent effects of PKC in SMC. In summary, we found that PKC activation enhances proliferation but inhibits migration of human vascular SMC. These differential effect of PKC on vascular cells appears to be mediated through PKC-α, -βI, -δ, and/or -ε.