bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic coronary artery stenosis induces impaired function of remote myocardium: MRI and spectroscopy study in rat
Authors: Nahrendorf Matthias , Hiller Karl-Heinz , Greiser Andreas , Köhler Sascha , Neuberger Thomas , Hu Kai , Waller Christiane , Albrecht Matthias , Neubauer Stefan , Haase Axel , Ertl Georg , Bauer Wolfgang R.
Published: March 2015

Our purpose was to study morphological, functional, and metabolic changes induced by chronic ischemia in myocardium supplied by the stenotic vessel and in the remote area by MR techniques. A new technique of image fusion is proposed for analysis of coronary artery stenosis involving coronary MR angiography and spectroscopic imaging. Cine-MRI was performed 2 wk after induction of coronary stenosis. Global heart function and regional wall thickening were determined in 11 Wistar rats with stenosis and compared with 7 control rats. Two weeks after stenosis was induced, spin-labeling MRI for measurement of perfusion was performed in 14 isolated hearts. In eight isolated hearts with coronary stenosis, MR spectroscopy was performed, followed by angiography. 31P metabolite maps were fused with three-dimensional coronary angiograms. Induction of stenosis led to reduced segmental wall thickening (control: 75 ± 9%, ischemic region: 9 ± 3%, P < 0.05 vs. control) but also to impaired function of the remote region and lower cardiac output. Perfusion was reduced by 74.9 ± 4.0% within ischemic segments compared with a septal control region. The phosphocreatine (PCr)/ATP ratio as a marker of ischemia was reduced in the region associated with stenosis (1.09 ± 0.09) compared with remote (1.27 ± 0.08) and control hearts (1.43 ± 0.08; P < 0.05). The histological fraction of fibrosis within the ischemic region (12.8 ± 1.4%) correlated to ATP signal reduction from remote to the ischemic region ( r = 0.71, P < 0.05), but not to reduced wall thickening. Coronary narrowing caused declining function accompanied by diminished PCr/ATP, indicating impaired energy metabolism. Neither decline of function nor PCr signal decline correlated to fraction of fibrosis in histology. In contrast, reduction of ATP correlated to fibrosis and therefore to loss of viability. Impaired function within the ischemic region is associated with decreased PCr. Function of the remote region was affected as well. The fusion of PCr metabolite maps and the coronary angiogram may help to assess coronary morphology and resulting metabolic changes simultaneously.
ω-3 Fatty acids suppress monocyte adhesion to human endothelial cells: role of endothelial PAF generation
Authors: Mayer Konstantin , Merfels Martina , Muhly-Reinholz Marion , Gokorsch Stephanie , Rosseau Simone , Lohmeyer Jürgen , Schwarzer Nicole , Krüll Matthias , Suttorp Norbert , Grimminger Friedrich , Seeger Werner
Published: March 2015

Monocyte-endothelium interaction is a fundamental process in many acute and chronic inflammatory diseases. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are fish oil-derived alternative (ω-3) precursor fatty acids implicated in the suppression of inflammatory events. We investigated their influence on rolling and adhesion of monocytes to human umbilical vein endothelial cells (HUVEC) under laminar flow conditions in vitro. Exposure of HUVEC to tumor necrosis factor (TNF-α) strongly increased 1) surface expression of intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1), and E-selectin, 2) platelet-activating factor (PAF) synthesis as assessed by thrombin challenge, and 3) rate of rolling and adhesion of monocytes. Preincubation of HUVEC with EPA or DHA markedly suppressed PAF synthesis, monocyte rolling, and adherence, whereas expression of endothelial adhesion molecules was unchanged. Also, PAF receptor antagonists markedly suppressed the adhesion rate of monocytes, and EPA or DHA revealed no additional inhibitory capacity. In contrast, arachidonic acid partially reversed the effect of the antagonist. We conclude that ω-3 fatty acids suppress rolling and adherence of monocytes on activated endothelial cells in vitro by affecting endothelial PAF generation.
Probing the link between citrate and malonyl-CoA in perfused rat hearts
Authors: Poirier Myriame , Vincent Geneviève , Reszko Aneta E. , Bouchard Bertrand , Kelleher Joanne K. , Brunengraber Henri , Des Rosiers Christine
Published: March 2015

Little is known about the sources of cytosolic acetyl-CoA used for the synthesis of malonyl-CoA, a key regulator of fatty acid oxidation in the heart. We tested the hypothesis that citrate provides acetyl-CoA for malonyl-CoA synthesis after its mitochondrial efflux and cleavage by cytosolic ATP-citrate lyase. We expanded on a previous study where we characterized citrate release from perfused rat hearts (Vincent G, Comte B, Poirier M, and Des Rosiers C. Citrate release by perfused rat hearts: a window on mitochondrial cataplerosis. Am J Physiol Endocrinol Metab 278: E846–E856, 2000). In the present study, we show that citrate release rates, ranging from 6 to 22 nmol/min, can support a net increase in malonyl-CoA concentrations induced by changes in substrate supply, at most 0.7 nmol/min. In experiments with [U-13C](lactate + pyruvate) and [1-13C]oleate, we show that the acetyl moiety of malonyl-CoA is derived from both pyruvate and long-chain fatty acids. This13C-labeling of malonyl-CoA occurred without any changes in its concentration. Hydroxycitrate, an inhibitor of ATP-citrate lyase, prevents increases in malonyl-CoA concentrations and decreases its labeling from [U-13C](lactate + pyruvate). Our data support at least a partial role of citrate in the transfer from the mitochondria to cytosol of acetyl units for malonyl-CoA synthesis. In addition, they provide a dynamic picture of malonyl-CoA metabolism: even when the malonyl-CoA concentration remains constant, there appears to be a constant need to supply acetyl-CoA from various carbon sources, both carbohydrates and lipids, for malonyl-CoA synthesis.
Functional effects of novel anti-ClC-3 antibodies on native volume-sensitive osmolyte and anion channels in cardiac and smooth muscle cells
Authors: Wang Ge-Xin , Hatton William J. , Wang Grace L. , Zhong Juming , Yamboliev Ilia , Duan Dayue , Hume Joseph R.
Published: March 2015

Whether ClC-3 encodes volume-sensitive organic osmolyte and anion channels (VSOACs) remains controversial. We have shown previously that native VSOACs in some cardiac and vascular myocytes were blocked by a commercial anti-ClC-3 carboxy terminal antibody (Alm C592–661 antibody), although recent studies have raised questions related to the specificity of Alm C592–661 antibody. Therefore, we have developed three new anti-ClC-3 antibodies and investigated their functional effects on native VSOACs in freshly isolated canine pulmonary artery smooth muscle cells (PASMCs) and guinea pig cardiac myocytes. These new antibodies produced a common prominent immunoreactive band with an apparent molecular mass of 90–92 kDa in the guinea pig heart and PASMCs, and a similar molecular mass immunoreactive band was observed in the brain from homozgygous Clcn3+/+ mice but not from homozygous Clcn3–/– mice. VSOACs elicited by hypotonic cell swelling in PASMCs and guinea pig atrial myocytes were nearly completely abolished by intracellular dialysis with two new anti-ClC-3 antibodies specifically targeting the ClC-3 carboxy (C670–687 antibody) and amino terminus (A1–14 antibody). This inhibition of native VSOACs can be attributed to a specific interaction with endogenous ClC-3, because 1) preabsorption of the antibodies with corresponding antigens prevented the inhibitory effects, 2) extracellular application of a new antibody raised against an extracellular epitope (Ex133–148) of ClC-3 failed to inhibit native VSOACs in PASMCs, 3) intracellular dialysis with an antibody targeting Kv1.1 potassium channels failed to inhibit native VSOACs in guinea pig atrial myocytes, and 4) anti-ClC-3 C670–687 antibody had no effects on swelling-induced augmentation of the slow component of the delayed rectifying potassium current in guinea pig ventricular myocytes, although VSOACs in the same cells were inhibited by the antibody. These results confirm that endogenous ClC-3 is an essential molecular entity responsible for native VSOACs in PASMCs and guinea pig cardiac myocytes.
New insights into differential baroreflex control of heart rate in humans
Authors: Fadel P. J. , Strømstad M. , Wray D. W. , Smith S. A. , Raven P. B. , Secher N. H.
Published: March 2015

Recent data indicate that bilateral carotid sinus denervation in patients results in a chronic impairment in the rapid reflex control of blood pressure during orthostasis. These findings are inconsistent with previous human experimental investigations indicating a minimal role for the carotid baroreceptor-cardiac reflex in blood pressure control. Therefore, we reexamined arterial baroreflex [carotid (CBR) and aortic baroreflex (ABR)] control of heart rate (HR) using newly developed methodologies. In 10 healthy men, 27 ± 1 yr old, an abrupt decrease in mean arterial pressure (MAP) was induced nonpharmacologically by releasing a unilateral arterial thigh cuff (300 Torr) after 9 min of resting leg ischemia under two conditions: 1) ABR and CBR deactivation (control) and 2) ABR deactivation. Under control conditions, cuff release decreased MAP by 13 ± 1 mmHg, whereas HR increased 11 ± 2 beats/min. During ABR deactivation, neck suction was gradually applied to maintain carotid sinus transmural pressure during the initial 20 s after cuff release (suction). This attenuated the increase in HR (6 ± 1 beats/min) and caused a greater decrease in MAP (18 ± 2 mmHg, P < 0.05). Furthermore, estimated cardiac baroreflex responsiveness (ΔHR/ΔMAP) was significantly reduced during suction compared with control conditions. These findings suggest that the carotid baroreceptors contribute more importantly to the reflex control of HR than previously reported in healthy individuals.
Elasticity of passive blood vessels: a new concept
Authors: VanBavel Ed , Siersma Pier , Spaan Jos A. E.
Published: March 2015

The mechanical properties of passive blood vessels are generally thought to depend on the parallel arrangement of elastin and collagen with linear elasticity and collagen recruitment depending on vessel strain [hook-on (HO) model]. We evaluated an alternative model [serial element (SE) model] consisting of the series arrangement of an infinite number of elements, each containing elastin with a constant elastic modulus and collagen that switches stepwise from slack (zero stress) to fully rigid (infinite stiffness) on ongoing element strain. Both models were implemented with Weibull distributions for collagen recruitment strain (HO model) and collagen tightening strain (SE model). The models were tested in experiments on rat mesenteric small arteries. Strain-tension relations were obtained before and after two rounds of digestion by collagenase. Both models fitted the data prior to digestion. However, for the HO model, this required unrealistically low estimates for collagen recruitment or elastic modulus and unrealistically high estimates for distension of collagen fibers. Furthermore, the data after digestion were far better predicted by the SE model compared with the HO model. Finally, the SE model required one parameter less (collagen elastic modulus). Therefore, the SE model provides a valuable starting point for the understanding of vascular mechanics and remodeling of vessels.
Endotoxin stress-response in cardiomyocytes: NF-κB activation and tumor necrosis factor-α expression
Authors: Wright Gary , Singh Ishwar S. , Hasday Jeffery D. , Farrance Iain K. , Hall Gentzon , Cross Allan S. , Rogers Terry B.
Published: March 2015

Although tumor necrosis factor (TNF)-α is implicated in numerous cardiac pathologies, the intracellular events leading to its production by heart cells are largely unknown. The goal of the present study was to identify the role of the transcription factor nuclear factor (NF)-κB in this process. Among the many inducers of TNF-α expression in myeloid cells, only lipopolysaccharide (LPS) led to its induction in cultured neonatal myocytes. LPS also activated the NF-κB pathway, as evidenced by the degradation of the inhibitory protein IκB and the appearance of NF-κB-binding complexes in nuclear extracts. Furthermore, inhibitors of NF-κB activation, such as lactacystin, MG132, and pyrrolidine dithiocarbamate, were found to completely block the production of TNF-α in response to LPS stimulation, indicating a requirement of NF-κB for TNF-α expression. However, interleukin-1β and phorbol 12-myristate 13-acetate also activated NF-κB but did not evoke TNF-α expression, revealing that this factor is not sufficient for cytokine production. Detailed examination of the NF-κB cascade revealed that cardiac cells displayed a unique pattern of IκB degradation in response to LPS, with IκBβ but not IκBα being degraded upon stimulation. Additionally, two specific p65-containing DNA-binding complexes were observed in the nuclear extracts of neonatal cardiomyocytes: an inducible complex that is necessary for TNF-α expression and a constitutive species. Taken together, these results reveal that NF-κB is not only involved in cytokine production but also may be linked to other pathways that subserve a constitutive, protective mechanism for the heart cell.
Effects of estrogen on gender-related autonomic differences in humans
Authors: Liu C. C. , Kuo Terry B. J. , Yang Cheryl C. H.
Published: March 2015

Our previous studies demonstrated that premenopausal women have dominant vagal and subordinate sympathetic activity compared with age-matched men. This study was designed to investigate the role of estrogen in gender-related autonomic differences. We evaluated the heart rate variability of four healthy groups: agedmatched postmenopausal women without hormone replacement therapy (PM), postmenopausal women on conjugated estrogen replacement therapy (PME), men, and non-age-matched premenopausal women (PreM). Frequency-domain analysis of short-term and stationary R-R intervals was performed to evaluate low-frequency power (LF; 0.04–0.15 Hz), high-frequency power (HF; 0.15–0.40 Hz), the ratio of LF to HF (LF/HF), and LF in normalized units (LF%). No gender-related autonomic differences existed between the PM and men groups, but they did exist between the PME and men group. Compared with the PreM group, the PM group had a lower HF and higher LF% and LF/HF. Compared with the PM group, the PME group had a higher HF but lower LF% and LF/HF. These results suggest that conjugated estrogen replacement therapy may facilitate vagal and attenuate sympathetic regulation of heart rate in postmenopausal women. In addition, estrogen may play an important role in gender-related autonomic differences.
Mg2+ blocks myogenic tone but not K+-induced constriction: role for SOCs in small arteries
Authors: Zhang Jin , Wier W. Gil , Blaustein Mordecai P.
Published: March 2015

The effects of Mg2+ and nifedipine (Nif) on vasoconstriction and Ca2+ transients were studied in intact, pressurized rat mesenteric arteries with myogenic tone. Changes in cytosolic Ca2+ concentration ([Ca2+]cyt) were measured with confocal microscopy in fluo 4-AM loaded, individual myocytes. Myogenic tone was abolished by 10 mM Mg2+ or 0.3 μM Nif. Contractions induced by 75 mM K+ depolarization were blocked by 0.3 μM Nif, but not by 10 mM Mg2+. Phenylephrine (PE; 5 μM) evoked sustained [Ca2+]cyt elevation and vasoconstriction with superimposed Ca2+ oscillations and vasomotion. The subsequent addition of 10 mM Mg2+ or 0.3 μM Nif reduced [Ca2+]cyt and abolished plateau vasoconstriction. When added before PE, both Mg2+ and Nif abolished the PE-evoked Ca2+ oscillations and vasomotion. Mg2+ dilated the PE-constricted arteries after a brief (≤180–240 s) vasoconstriction, but Nif did not. Both agents also abolished the vasoconstriction attributed to Ca2+ entry through store-operated channels (SOCs) during internal Ca2+store refilling that followed store depletion. The data suggest that Ca2+ entry through SOCs helps maintain both myogenic tone and α1-adrenoceptor-induced tonic vasoconstriction.
Chronic all-transretinoic acid treatment prevents medial thickening of intramyocardial and intrarenal arteries in spontaneously hypertensive rats
Authors: Lü Lei , Yao Tai , Zhu Yi-Zhun , Huang Guo-Ying , Cao Yin-Xiang , Zhu Yi-Chun
Published: March 2015

There are in vitro data linking all- trans retinoic acid (atRA) with inhibition of hypertrophy and hyperplasia in cardiomyocytes, vascular smooth muscle cells, and fibroblasts. In the present study, we tested the hypothesis that chronic treatment with atRA may blunt the process of myocardial remodeling in spontanously hypertensive rats (SHR). Four-week-old male SHR were treated with atRA (5 or 10 mg·kg–1·day–1) given daily for 3 mo by gavage; age- and sex-matched Wistar-Kyoto rats (WKY) and placebo-treated SHR served as controls. At the end of the treatment period, cardiac geometry and function were assessed by Doppler echocardiography. Histological examination and RIA were performed to evaluate medial thickening of intramyocardial and renal arteries, perivascular and interstitial collagen content, and atrial natriuretic peptide (ANP) and IGF-I in the heart, respectively. The novel finding of the present study is that atRA prevented hypertrophy of intramyocardial and intrarenal arteries and ventricular fibrosis. However, atRA treatment did not lower blood pressure or left ventricular weight and left ventricular weight-to-body weight ratio in SHR. atRA did not change cardiac geometry and function as assessed by Doppler echocardiography. atRA showed no influence on either ANP or IGF-I levels. In conclusion, the present study suggests that chronic atRA treatment prevents medial thickening of intramyocardial and intrarenal arteries and ventricular fibrosis during the development of hypertension. Left ventricular hypertrophy and cardiac geometry and function are not changed by atRA treatment.
Improved angiogenic potency by implantation of ex vivo hypoxia prestimulated bone marrow cells in rats
Authors: Li Tao-Sheng , Hamano Kimikazu , Suzuki Kazuhiko , Ito Hiroshi , Zempo Nobuya , Matsuzaki Masunori
Published: March 2015

Therapeutic angiogenesis can be induced by local implantation of bone marrow cells. We tried to enhance the angiogenic potential of this treatment by ex vivo hypoxia stimulation of bone marrow cells before implantation. Bone marrow cells were collected and cultured at 33°C under 2% O2-5% CO2-90% N2 (hypoxia) or 95% air-5% CO2 (normoxia). Cells were also injected into the ischemic hindlimb of rats after 24 h of culture. Hypoxia culture increased the mRNA expression of vascular endothelial growth factor (VEGF), vascular endothelial (VE)-cadherin, and fetal liver kinase-1 (Flk-1) from 2.5- to fivefold in bone marrow cells. The levels of VEGF protein in the ischemic hindlimb were significantly higher 1 and 3 days after implantation with hypoxia-cultured cells than with normoxia-cultured or noncultured cells. The microvessel density and blood flow rate in the ischemic hindlimbs were also significantly ( P< 0.001) higher 2 wk after implantation with hypoxia-cultured cells (89.7 ± 5.5%) than with normoxia-cultured cells (67.0 ± 9.6%) or noncultured cells (70.4 ± 7.7%). Ex vivo hypoxia stimulation increased the VEGF mRNA expression and endothelial differentiation of bone marrow cells, which together contributed to improved therapeutic angiogenesis in the ischemic hindlimb after implantation.
Microvascular reperfusion injury: rapid expansion of anatomic no reflow during reperfusion in the rabbit
Authors: Reffelmann Thorsten , Kloner Robert A.
Published: March 2015

The aim was to define the degree and time course of reperfusion-related expansion of no reflow. In five groups of anesthetized, open-chest rabbits (30-min coronary occlusion and different durations of reperfusion), anatomic no reflow was determined by injection of thioflavin S at the end of reperfusion and compared with regional myocardial blood flow (RMBF; radioactive microspheres) and infarct size (triphenyltetrazolium). The area of no reflow progressively increased from 12.2 ± 4.2% of the risk area after 2 min of reperfusion to 30.8 ± 3.1% after 2 h and 34.9 ± 3.3% after 8 h and significantly correlated with infarct size after 1 h of reperfusion ( r = 0.88–0.97). This rapid expansion of no reflow predominantly occurred during the first 2 h, finally encompassing ∼80% of the infarct size, and was accompanied by a decrease of RMBF within the risk area, being hyperemic after 2 min of reperfusion (3.78 ± 0.75 ml · min−1 · g−1) and plateauing at a level of ∼0.9 ml · min−1 · g−1 by 2 and 8 h of reperfusion (preischemic RMBF: 2.06 ± 0.01 ml · min−1 · g−1). The development of macroscopic hemorrhage lagged behind no reflow, was closely correlated with it, and may be the consequence of microvascular damage.
Adrenomedullin gene delivery attenuates myocardial infarction and apoptosis after ischemia and reperfusion
Authors: Kato Kazuo , Yin Hang , Agata Jun , Yoshida Hideaki , Chao Lee , Chao Julie
Published: March 2015

Adrenomedullin (AM) has been shown to protect against cardiac remodeling. In this study, we investigated the potential role of AM in myocardial ischemia-reperfusion (I/R) injury through adenovirus-mediated gene delivery. One week after AM gene delivery, rats were subjected to 30-min coronary occlusion, followed by 2-h reperfusion. AM gene transfer significantly reduced the ratio of infarct size to ischemic area at risk and the occurrence of sustained ventricular fibrillation compared with control rats. AM gene delivery also attenuated apoptosis, assessed by both terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and DNA laddering. The effect of AM gene transfer on infarct size, arrhythmia, and apoptosis was abolished by an AM antagonist, calcitonin gene-related peptide [CGRP(8–37)]. Expression of human AM significantly increased cardiac cGMP levels and reduced superoxide production, superoxide density, NAD(P)H oxidase activity, p38 MAPK activation, and Bax levels. Moreover, AM increased Akt and Bad phosphorylation and Bcl-2 levels, but decreased caspase-3 activation. These results indicate that AM protects against myocardial infarction, arrhythmia, and apoptosis in I/R injury via suppression of oxidative stress-induced Bax and p38 MAPK phosphorylation and activation of the Akt-Bad-Bcl-2 signaling pathway. Successful application of this technology may have a protective effect in coronary artery diseases.
Molecular mechanics of mouse cardiac myosin isoforms
Authors: Alpert Norman R. , Brosseau Christine , Federico Andrea , Krenz Maike , Robbins Jeffrey , Warshaw David M.
Published: March 2015

Two myosin isoforms are expressed in myocardium, αα-homodimers (V1) and ββ-homodimers (V3). V1exhibits higher velocities and myofibrillar ATPase activities compared with V3. We also observed this for cardiac myosin from normal (V1) and propylthiouracil-treated (V3) mice. Actin velocity in a motility assay ( Vactin) over V1myosin was twice that of V3as was the myofibrillar ATPase. Myosin's average force (Favg) was similar for V1and V3. Comparing Vactinand Favgacross species for both V1and V3, our laboratory showed previously (VanBuren P, Harris DE, Alpert NR, and Warshaw DM. Circ Res 77: 439–444, 1995) that mouse V1has greater Vactinand Favgcompared with rabbit V1. Mouse V3Vactinwas twice that of rabbit Vactin. To understand myosin's molecular structure and function, we compared α- and β-cardiac myosin sequences from rodents and rabbits. The rabbit α- and β-cardiac myosin differed by eight and four amino acids, respectively, compared with rodents. These residues are localized to both the motor domain and the rod. These differences in sequence and mechanical performance may be an evolutionary attempt to match a myosin's mechanical behavior to the heart's power requirements.
Phosphorylation of cardiac protein kinase B is regulated by palmitate
Authors: Soltys Carrie-Lynn M. , Buchholz Lori , Gandhi Manoj , Clanachan Alexander S. , Walsh Kenneth , Dyck Jason R. B.
Published: March 2015

In this study isolated perfused working rat hearts were used to investigate the role of palmitate-regulated protein kinase B (PKB) phosphorylation on glucose metabolism. Rat hearts were perfused aerobically in working mode with 11 mM glucose and either 100 μU/ml insulin or 100 μU/ml insulin and 1.2 mM palmitate. PKB activity and phosphorylation state were reduced in the presence of 1.2 mM palmitate, which correlates with a decrease in glycolysis (47%), glucose oxidation (84%), and glucose uptake (43%). In contrast to skeletal muscle, neither p38 nor ERK underwent changes in their phosphorylation states in response to insulin or insulin and palmitate. Moreover, pharmacological restoration of glucose oxidation rates in hearts perfused with 1.2 mM palmitate demonstrated no increase in PKB phosphorylation state. In cultured mouse cardiac muscle HL-1 cells, insulin markedly increased PKB phosphorylation, which was blunted by pre- and cotreatment with 1.2 mM palmitate. However, neither palmitate nor C2-ceramide treatment of insulin-stimulated cells was able to accelerate PKB dephosphorylation beyond that observed following the removal of insulin alone. Taken together, these experiments show the control of PKB phosphorylation by palmitate is independent of ceramide and suggest that this signaling event may be an important regulator of myocardial glucose uptake and oxidation.
Acute protection of ischemic heart by FGF-2: involvement of FGF-2 receptors and protein kinase C
Authors: Jiang Zhi-Sheng , Padua Raymond R. , Ju Haisong , Doble Bradley W. , Jin Yan , Hao Jianming , Cattini Peter A. , Dixon Ian M. C. , Kardami Elissavet
Published: March 2015

We examined the effect of fibroblast growth factor (FGF)-2 on myocardial resistance to injury when administered after the onset of ischemia , in vivo and ex vivo, and the role of FGF-2 receptors and protein kinase C (PKC). FGF-2 was injected into the left ventricle of rats undergoing permanent surgical coronary occlusion leading to myocardial infarction (MI). After 24 h, FGF-2-treated hearts displayed significantly reduced injury, determined by histological staining and troponin T release, and improved developed pressure compared with untreated controls. An FGF-2 mutant with diminished affinity for the tyrosine kinase FGF-2 receptor 1 (FGFR1) was not cardioprotective. FGF-2-treated hearts retained improved function and decreased damage at 6 wk after MI. In the ex vivo heart, FGF-2 administration during reperfusion after 30-min ischemia improved functional recovery and increased relative levels of PKC subtypes α, ε, and ζ in the particulate fraction, in a chelerythrine-preventable mode; it also decreased loss of energy metabolites. We conclude that intramyocardial FGF-2 administration shortly after the onset of ischemia confers protection from acute and chronic cardiac dysfunction and damage; FGF-2 delivered during reperfusion protects from ischemia-reperfusion injury; and protection by FGF-2 requires intact binding to FGFR1 and is likely mediated by PKC.
Cysteinyl leukotriene-dependent [Ca2+]iresponses to angiotensin II in cardiomyocytes
Authors: Liu Pinggang , Misurski Derek A. , Gopalakrishnan Venkat
Published: March 2015

With the use of fura 2 measurements in multiple and single cells, we examined whether cysteinyl leukotrienes (CysLT) mediate angiotensin II (ANG II)-evoked increases in cytosolic free Ca2+concentration ([Ca2+]i) in neonatal rat cardiomyocytes. ANG II-evoked CysLT release peaked at 1 min. The angiotensin type 1 (AT1) antagonist losartan, but not the AT2antagonist PD-123319, attenuated the elevations in [Ca2+]iand CysLT levels evoked by ANG II. Vasopressin and endothelin-1 increased [Ca2+]ibut not CysLT levels. The 5-lipoxygenase (5-LO) inhibitor AA-861 and the CysLT1-selective antagonist MK-571 reduced the maximal [Ca2+]iresponses to ANG II but not to vasopressin and endothelin-1. While MK-571 reduced the responses to leukotriene D4(LTD4), the dual CysLT antagonist BAY-u9773 completely blocked the [Ca2+]ielevation to both LTD4and LTC4. These data confirm that ANG II-evoked increases, but not vasopressin- and endothelin-1-evoked increases, in [Ca2+]iinvolve generation of the 5-lipoxygenase metabolite CysLT. The inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] antagonist 2-aminoethoxydiphenyl borate attenuated the [Ca2+]iresponses to ANG II and LTD4. Thus AT1receptor activation by ANG II is linked to CysLT-mediated Ca2+release from Ins(1,4,5)P3-sensitive intracellular stores to augment direct ANG II-evoked Ca2+mobilization in rat cardiomyocytes.
Cardiac dysfunction in mice lacking cytochrome-coxidase subunit VIaH
Authors: Radford Nina B. , Wan Bang , Richman Angela , Szczepaniak Lidia S. , Li Jia-Ling , Li Kang , Pfeiffer Kathy , Schägger Hermann , Garry Daniel J. , Moreadith Randall W.
Published: March 2015

Cytochrome -c oxidase subunit VIaH (COXVIaH) has been implicated in the modulation of COX activity. A gene-targeting strategy was undertaken to generate mice that lacked COXVIaH to determine its role in regulation of oxidative energy production and mechanical performance in cardiac muscle. Total COX activity was decreased in hearts from mutant mice, which appears to be a consequence of altered assembly of the holoenzyme COX. However, total myocardial ATP was not significantly different in wild-type and mutant mice. Myocardial performance was examined using the isolated working heart preparation. As left atrial filling pressure increased, hearts from mutant mice were unable to generate equivalent stroke work compared with hearts from wild-type mice. Direct measurement of left ventricular end-diastolic volume using magnetic resonance imaging revealed that cardiac dysfunction was a consequence of impaired ventricular filling or diastolic dysfunction. These findings suggest that a genetic deficiency of COXVIaH has a measurable impact on myocardial diastolic performance despite the presence of normal cellular ATP levels.
Respiratory variations of aortic VTI: a new index of hypovolemia and fluid responsiveness
Authors: Slama Michel , Masson Henri , Teboul Jean-Louis , Arnout Marie-Luce , Susic Dinko , Frohlich Edward , Andrejak Michel
Published: March 2015

In 12 mechanically ventilated and anesthetized rabbits, we investigated whether the magnitude of respiratory changes in the aortic velocity time integral (VTIAo), recorded by transthoracic echocardiography (TTE) during a stepwise blood withdrawal and restitution, could be used as a reliable indicator of volume depletion and responsiveness. At each step, left and right ventricular dimensions and the aortic diameter and VTIAowere recorded to calculate stroke volume (SV) and cardiac output (CO). Respiratory changes of VTIAo(maximal − minimal values divided by their respective means) were calculated. The amount of blood withdrawal correlated negatively with left and right ventricular diastolic diameters, VTIAo, SV, and CO and correlated directly with respiratory changes of VTIAo. Respiratory VTIAovariations (but not other parameters) at the last blood withdrawal step was also correlated with changes in SV after blood restitution ( r = 0.83, P < 0.001). In conclusion, respiratory variations in VTIAousing TTE appear to be a sensitive index of blood volume depletion and restitution. This dynamic parameter predicted fluid responsiveness more reliably than static markers of cardiac preload.
Role of protein phosphatases in hypoxic preconditioning
Authors: Ladilov Yury , Maxeiner Hagen , Wolf Christopher , Schäfer Claudia , Meuter Karsten , Piper H. Michael
Published: March 2015

To find a protein kinase C (PKC)-independent preconditioning mechanism, hypoxic preconditioning (HP; i.e., 10-min anoxia and 10-min reoxygenation) was applied to isolated rat hearts before 60-min global ischemia. HP led to improved recovery of developed pressure and reduced end-diastolic pressure in the left ventricle during reperfusion. Protection was unaffected by the PKC inhibitor bisindolylmaleimide (BIM; 1 μmol/l). It was abolished by the inhibitor of protein phosphatases 1 and 2A cantharidin (20 or 5 μmol/l) and partially enhanced by the inhibitor of protein phosphatase 2A okadaic acid (5 nmol/l). In adult rat cardiomyocytes treated with BIM and exposed to 60-min simulated ischemia (anoxia, extracellular pH 6.4), HP led to attenuation of anoxic Na+/Ca2+overload and of hypercontracture, which developed on reoxygenation. This protection was prevented by treatment with cantharidin but not with okadaic acid. In conclusion, HP exerts PKC-independent protection on ischemic-reperfused rat hearts and cardiomyocytes. Protein phosphatase 1 seems a mediator of this protective mechanism.
Reactive oxygen species are critical mediators of coronary collateral development in a canine model
Authors: Gu Weidong , Weihrauch Dorothee , Tanaka Katsuya , Tessmer John P. , Pagel Paul S. , Kersten Judy R. , Chilian William M. , Warltier David C.
Published: March 2015

Recent evidence suggests that reactive oxygen species (ROS) promote proliferation and migration of vascular smooth muscle (VSMC) and endothelial cells (EC). We tested the hypothesis that ROS serve as crucial messengers during coronary collateral development. Dogs were subjected to brief (2 min), repetitive coronary artery occlusions (1/h, 8/day, 21 day duration) in the absence (occlusion, n = 8) or presence of N-acetylcysteine (NAC) (occlusion + NAC, n = 8). A sham group ( n = 8) was instrumented identically but received no occlusions. In separate experiments, ROS generation after a single 2-min coronary artery occlusion was assessed with dihydroethidium fluorescence. Coronary collateral blood flow (expressed as a percentage of normal zone flow) was significantly increased (71 ± 7%) in occlusion dogs after 21 days but remained unchanged (13 ± 3%) in sham dogs. Treatment with NAC attenuated increases in collateral blood flow (28 ± 8%). Brief coronary artery occlusion and reperfusion caused ROS production (256 ± 33% of baseline values), which was abolished with NAC (104 ± 12%). Myocardial interstitial fluid produced tube formation and proliferation of VSMC and EC in occlusion but not in NAC-treated or sham dogs. The results indicate that ROS are critical for the development of the coronary collateral circulation.
Loss of cardiac sympathetic neurotransmitters in heart failure and NE infusion is associated with reduced NGF
Authors: Qin Fuzhong , Vulapalli Raju S. , Stevens Suzanne Y. , Liang Chang-Seng
Published: March 2015

Sympathetic neurotransmitters are diminished in cardiac efferent nerve endings in congestive heart failure (CHF). Similar changes occur after exogenous norepinephrine (NE) infusion. Since NE reduces nerve growth factor (NGF) in cultured cardiomyocytes, we proposed to determine whether the loss of noradrenergic transmitters in the failing heart is caused by the NE-mediated reduction of NGF or its neurotrophic receptor tyrosine kinase A (TrKA). Dogs were assigned to receive either rapid ventricular pacing (225 beats/min) or NE infusion (0.5 μg/kg/min) for 8 wk. Control animals received either cardiac pacing of 100 beats/min or saline infusion. We measured NGF and TrKA proteins by Western blot and immunocytochemistry and measured NGF and TrKA mRNAs by reverse transcription polymerase chain reaction, neuronal catecholaminergic histofluorescence, tyrosine hydroxylase-immunostained profiles, and plasma NE. Rapid ventricular pacing produced CHF with increased plasma NE, decreased myocardial NGF protein (0.61 ± 0.07 vs. 1.04 ± 0.04, P < 0.05), TrKA protein (0.75 ± 0.08 vs. 0.98 ± 0.06, P < 0.05), NGF and TrKA mRNAs and reduced catecholaminergic histofluorescence (197 ± 23 vs. 485 ± 43, P < 0.05), and tyrosine hydroxylase profiles (360 ± 51 vs. 773 ± 36, P < 0.05). Decreases in tissue NGF and TrKA protein were also noted by immunocytochemistry. Similar changes occurred in NE-treated animals. Tissue NGF and TrKA levels correlated closely with the noradrenergic transmitter profiles. We conclude that cardiac NGF and TrKA are reduced by rapid ventricular pacing and NE infusion, and that these changes correlate with decreases of cardiac catecholaminergic and tyrosine hydroxylase profiles. Findings indicate that decrease of cardiac sympathetic transmitters in heart failure is associated with NE-mediated reduction of NGF and TrKA.
Input-size dependence of the baroreflex neural arc transfer characteristics
Authors: Kawada Toru , Yanagiya Yusuke , Uemura Kazunori , Miyamoto Tadayoshi , Zheng Can , Li Meihua , Sugimachi Masaru , Sunagawa Kenji
Published: March 2015

Static characteristics of the baroreflex neural arc from pressure input to sympathetic nerve activity (SNA) show sigmoidal nonlinearity, whereas its dynamic characteristics approximate a derivative filter where the magnitude of SNA response becomes greater as the input frequency increases. To reconcile the static nonlinear and dynamic linear components, we examined the effects of input amplitude on the apparent linear transfer function of the neural arc. In nine anesthetized rabbits, we perturbed isolated carotid sinus pressure by using binary white noise while varying the input amplitude among 5, 10, 20, and 40 mmHg. With increasing input amplitude, the transfer gain at 0.01 Hz decreased from 1.21 ± 0.27 to 0.49 ± 0.28 arbitrary units/mmHg ( P < 0.01). Moreover, the slope of the transfer gain between 0.03 and 0.3 Hz decreased from 14.3 ± 3.7 to 6.5 ± 2.5 dB/decade ( P < 0.01). We conclude that the model consisting of a sigmoidal component following rather than preceding a derivative component explains the observed results and thus can be used as a first approximation of the overall neural arc transfer characteristics.
VEGF increases endothelial permeability by separate signaling pathways involving ERK-1/2 and nitric oxide
Authors: Breslin Jerome W. , Pappas Peter J. , Cerveira Joaquim J. , Hobson Robert W. , Durán Walter N.
Published: March 2015

We tested the hypothesis that VEGF regulates endothelial hyperpermeability to macromolecules by activating the ERK-1/2 MAPK pathway. We also tested whether PKC and nitric oxide (NO) mediate VEGF-induced increases in permeability via the ERK-1/2 pathway. FITC-Dextran 70 flux across human umbilical vein endothelial cell monolayers served as an index of permeability, whereas Western blots assessed the phosphorylation of ERK-1/2. VEGF-induced hyperpermeability was inhibited by antisense DNA oligonucleotides directed against ERK-1/2 and by blockade of MEK and Raf-1 activities (20 μM PD-98059 and 5 μM GW-5074). These blocking agents also reduced ERK-1/2 phosphorylation. The PKC inhibitor bisindolylmaleimide I (10 μM) blocked both VEGF-induced ERK-1/2 activation and hyperpermeability. The NO synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (200 μM) and the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidiazoline-1-oxyl-3-oxide (100 μM) abolished VEGF-induced hyperpermeability but did not block ERK-1/2 phosphorylation. These observations demonstrate VEGF-induced hyperpermeability involves activation of PKC and NOS as well as Raf-1, MEK, and ERK-1/2. Furthermore, our data suggest that ERK-1/2 and NOS are elements of different signaling pathways in VEGF-induced hyperpermeability.
β-Hydroxybutyrate inhibits myocardial fatty acid oxidation in vivo independent of changes in malonyl-CoA content
Authors: Stanley William C. , Meadows Steven R. , Kivilo Krista M. , Roth Bridgette A. , Lopaschuk Gary D.
Published: March 2015

This study tested the hypothesis that an acute infusion of β-hydroxybutyrate inhibits myocardial fatty acid uptake and oxidation in vivo. Anesthetized pigs were untreated ( n = 6) or treated with an intravenous infusion of fat emulsion ( n = 7) to elevate plasma free fatty acid levels. A third group received fat emulsion plus an intravenous infusion of β-hydroxybutyrate (25 μmol·kg–1·min–1; n = 7) for 60 min. All animals received a continuous infusion of [3H]palmitate, and myocardial fatty acid oxidation was measured from the cardiac production of3H2O. Plasma free fatty acid concentrations were elevated in the fat emulsion group (0.77 ± 0.11 mM) compared with the untreated group (0.15 ± 0.03 mM), which resulted in greater myocardial free fatty acid oxidation. In contrast, the group receiving β-hydroxybutyrate in addition to fat emulsion had elevated β-hydroxybutyrate concentration (0.87 ± 0.11 vs. 0.04 ± 0.01 mM), but suppressed fatty acid oxidation (0.053 ± 0.013 μmol·g–1·min–1) ( P < 0.05) compared with the fat emulsion group (0.116 ± 0.029 μmol·g–1·min–1). There were no differences among the three groups in the tissue content for malonyl-CoA, acetyl-CoA, or free CoA or the activity of acetyl-CoA carboxylase; thus the inhibition of fatty acid oxidation by elevated β-hydroxybutyrate did not appear to be due to malonyl-CoA inhibition of carnitine palmitoyl transferase-I or to an increase in the acetyl-CoA-to-free CoA ratio. In conclusion, fatty acid uptake and oxidation is blocked by an infusion of β-hydroxybutyrate; this effect was not due to elevated myocardial malonyl-CoA content.
Failing atrial myocardium: energetic deficits accompany structural remodeling and electrical instability
Authors: Cha Yong-Mei , Dzeja Petras P. , Shen Win K. , Jahangir Arshad , Hart Chari Y. T. , Terzic Andre , Redfield Margaret M.
Published: March 2015

The failing ventricular myocardium is characterized by reduction of high-energy phosphates and reduced activity of the phosphotransfer enzymes creatine kinase (CK) and adenylate kinase (AK), which are responsible for transfer of high-energy phosphoryls from sites of production to sites of utilization, thereby compromising excitation-contraction coupling. In humans with chronic atrial fibrillation (AF) unassociated with congestive heart failure (CHF), impairment of atrial myofibrillar energetics linked to oxidative modification of myofibrillar CK has been observed. However, the bioenergetic status of the failing atrial myocardium and its potential contribution to atrial electrical instability in CHF have not been determined. Dogs with ( n = 6) and without ( n = 6) rapid pacing-induced CHF underwent echocardiography (conscious) and electrophysiological (under anesthesia) studies. CHF dogs had more pronounced mitral regurgitation, higher atrial pressure, larger atrial area, and increased atrial fibrosis. An enhanced propensity to sustain AF was observed in CHF, despite significant increases in atrial effective refractory period and wavelength. Profound deficits in atrial bioenergetics were present with reduced activities of the phosphotransfer enzymes CK and AK, depletion of high-energy phosphates (ATP and creatine phosphate), and reduction of cellular energetic potential (ATP-to-ADP and creatine phosphate-to-Cr ratios). AF duration correlated with left atrial area ( r = 0.73, P = 0.01) and inversely with atrial ATP concentration ( r = −0.75, P = 0.005), CK activity ( r = −0.57, P = 0.054), and AK activity ( r = −0.64, P = 0.02). Atrial levels of malondialdehyde, a marker of oxidative stress, were significantly increased in CHF. Myocardial bioenergetic deficits are a conserved feature of dysfunctional atrial and ventricular myocardium in CHF and may constitute a component of the substrate for AF in CHF.
Influence of gender on the response to hemodynamic overload after myocardial infarction
Authors: Jain Mohit , Liao Ronglih , Podesser Bruno K. , Ngoy Soeun , Apstein Carl S. , Eberli Franz R.
Published: March 2015

After myocardial infarction (MI), the left ventricle (LV) undergoes ventricular remodeling characterized by progressive global dilation, infarct expansion, and compensatory hypertrophy of the noninfarcted myocardium. Little attention has been given to the response of remodeling myocardium to additional hemodynamic overload. Studies have indicated that gender may influence remodeling and the response to both MI and hemodynamic overload. We therefore determined 1) structural and function consequences of superimposing hemodynamic overload (systemic hypertension) on remodeling myocardium after a MI and 2) the potential influence of gender on this remodeling response. Male and female Dahl salt-sensitive and salt-resistant rats underwent coronary ligation, resulting in similar degrees of MI. One week post-MI, all rats were placed on a high-salt diet. Four groups were then studied 4 wk after initiation of high-salt feeding: MI female, MI female + hypertension, MI male, and MI male + hypertension. Hypertension-induced pressure overload resulted in additional comparable degrees of myocardial hypertrophy in both females and males. In females, hypertension post-MI resulted in concentric hypertrophy with no additional cavity dilation and no measurable scar thinning. In contrast, in males, hypertension post-MI resulted in eccentric hypertrophy, further LV cavity dilation, and scar thinning. Physiologically, concentric hypertrophy in post-MI hypertensive females resulted in elevated contractile function, whereas eccentrically hypertrophied males had no such increase. Female gender influences favorably the remodeling and physiological response to hemodynamic overload after large MI.
Tropomyosin 3 expression leads to hypercontractility and attenuates myofilament length-dependent Ca2+activation
Authors: Pieples Kathy , Arteaga Grace , Solaro R. John , Grupp Ingrid , Lorenz John N. , Boivin Greg P. , Jagatheesan Ganapathy , Labitzke Erin , deTombe Pieter P. , Konhilas John P. , Irving Thomas C. , Wieczorek David F.
Published: March 2015

Tropomyosin (TM), an integral component of the thin filament, is encoded by three striated muscle isoforms: α-TM, β-TM, and TPM 3. Although the α-TM and β-TM isoforms are well characterized, less is known about the function of the TPM 3 isoform, which is predominantly found in the slow-twitch musculature of mammals. To determine its functional significance, we ectopically expressed this isoform in the hearts of transgenic mice. We generated six transgenic mouse lines that produce varying levels of TPM 3 message with ectopic TPM 3 protein accounting for 40–60% of the total striated muscle tropomyosin. The transgenic mice have normal life spans and exhibit no morphological abnormalities in their sarcomeres or hearts. However, there are significant functional alterations in cardiac performance. Physiological assessment of these mice by using closed-chest analyses and a work-performing model reveals a hyperdynamic effect on systolic and diastolic function. Analysis of detergent-extracted fiber bundles demonstrates a decreased sensitivity to Ca2+in force generation and a decrease in length-dependent Ca2+activation with no detectable change in interfilament spacing as determined by using X-ray diffraction. Our data are the first to demonstrate that TM isoforms can affect sarcomeric performance by decreasing sensitivity to Ca2+and influencing the length-dependent Ca2+activation.