bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of prostaglandin F2αon membrane currents in rabbit middle cerebral arterial smooth muscle cells
Authors: Kim Nari , Han Jin , Kim Euiyong
Published: March 2015

Although PGF2αaffects contractility of vascular smooth muscles, no studies to date have addressed the electrophysiological mechanism of this effect. The purpose of our investigation was to examine the direct effects of PGF2αon membrane potentials, Ca2+-activated K+(KCa) channels, delayed rectifier K+(KV) channels, and L-type Ca2+channels with the patch-clamp technique in single rabbit middle cerebral arterial smooth muscle cells (SMCs). PGF2αsignificantly hyperpolarized membrane potentials and increased the amplitudes of total K+currents. PGF2αincreased open-state probability but had little effect on the open and closed kinetics of KCachannels. PGF2αincreased the amplitudes of KVcurrents with a leftward shift of the activation and inactivation curves and a decrease in the activation time constant. PGF2αdecreased the amplitudes of L-type Ca2+currents without any significant change in threshold or apparent reversal potentials. This study provides the first finding that the direct effects of PGF2αon middle cerebral arterial SMCs, at least in part, could attenuate vasoconstriction.
Nutritive blood flow improves interstitial glucose and lactate exchange in perfused rat hindlimb
Authors: Newman John M. B. , Rattigan Stephen , Clark Michael G.
Published: March 2015

Microdialysis was used to assess the interstitial concentrations of glucose and lactate in the constant-flow-perfused rat hindlimb under varying levels of nutritive flow controlled by vasoconstrictors. Increased nutritive flow was achieved by norepinephrine (NE) or angiotensin II (ANG II) and decreased nutritive flow by serotonin (5-HT). NE and ANG II increased oxygen and glucose uptake as well as hindlimb lactate release by 50%. 5-HT decreased oxygen uptake by 15% but had no significant effect on glucose uptake or hindlimb lactate release. Microdialysis recovery of glucose and lactate was significantly elevated by NE and ANG II and decreased by 5-HT. The calculated interstitial concentration of glucose was increased by NE and ANG II but decreased by 5-HT. The interstitial concentration of lactate was decreased by NE and ANG II but increased by 5-HT. In all cases, nitroprusside reversed the effects of the vasoconstrictors. These data indicate that increased nutritive blood flow enhances the exchange of glucose and lactate by improving the supply of glucose to and the removal of lactate from the interstitium.
Effects of fatty acids in isolated mitochondria: implications for ischemic injury and cardioprotection
Authors: Korge Paavo , Honda Henry M. , Weiss James N.
Published: March 2015

Fatty acids accumulate during myocardial ischemia and are implicated in ischemia-reperfusion injury and mitochondrial dysfunction. Because functional recovery after ischemia-reperfusion ultimately depends on the ability of the mitochondria to recover membrane potential (ΔΨm), we studied the effects of fatty acids on ΔΨmregulation, cytochrome c release, and Ca2+handling in isolated mitochondria under conditions that mimicked aspects of ischemia-reperfusion. Long-chain but not short-chain free fatty acids caused a progressive and reversible (with BSA) increase in inner membrane leakiness (proton leak), which limited mitochondrial ability to support ΔΨm. In comparison, long-chain activated fatty acids promoted 1) a slower depolarization that was not reversible with BSA, 2) cytochrome c loss that was unrelated to permeability transition pore opening, and 3) inhibition of the adenine nucleotide translocator. Together, these results impaired both mitochondrial ATP production and Ca2+handling. Diazoxide, a selective opener of mitochondrial ATP-dependent potassium (KATP) channels, partially protected against these effects. These findings indicate that long-chain fatty acid accumulation during ischemia-reperfusion may predispose mitochondria to cytochrome c loss and irreversible injury and identify a novel cardioprotective action of diazoxide.
Cardioprotection mediated by sphingosine-1-phosphate and ganglioside GM-1 in wild-type and PKCε knockout mouse hearts
Authors: Jin Zhu-Qiu , Zhou Hui-Zhong , Zhu Peili , Honbo Norman , Mochly-Rosen Daria , Messing Robert O. , Goetzl Edward J. , Karliner Joel S. , Gray Mary O.
Published: March 2015

Sphingosine-1-phosphate (S1P) protects neonatal rat cardiac myocytes from hypoxic damage through unknown signaling pathways. We tested the hypothesis that S1P-induced cardioprotection requires activation by the ε-isoform of protein kinase C (PKCε) by subjecting hearts isolated from PKCε knockout mice and wild-type mice to 20 min of global ischemia and 30 min of reperfusion. Pretreatment with a 2-min infusion of 10 nM S1P improved recovery of left ventricular developed pressure (LVDP) in both wild-type and PKCε knockout hearts and reduced the rise in LV end-diastolic pressure (LVEDP) and creatine kinase (CK) release. Pretreatment for 2 min with 10 nM of the ganglioside GM-1 also improved recovery of LVDP and suppressed CK release in wild-type hearts but not in PKCε knockout hearts. Importantly, GM-1 but not S1P, increased the proportion of PKCε localized to particulate fractions. Our results suggest that GM-1, which enhances endogenous S1P production, reduces cardiac injury through PKCε-dependent intracellular pathways. In contrast, extracellular S1P induces equivalent cardioprotection through PKCε-independent signaling pathways.
Isoflurane activates rat mitochondrial ATP-sensitive K+channels reconstituted in lipid bilayers
Authors: Nakae Yuri , Kwok Wai-Meng , Bosnjak Zeljko J. , Jiang Ming Tao
Published: March 2015

Activation of mitochondrial ATP-sensitive K+(mitoKATP) channels is critical in myocardial protection induced by preconditioning with volatile anesthetics or brief periods of ischemia. In this study, we characterized rat mitoKATPchannels reconstituted in lipid bilayers and examined their direct regulation by isoflurane. Mitochondria and the inner membrane fraction were isolated from rat ventricles and fused into lipid bilayers. On the basis of their inhibition by 5-hydroxydecanoate (5-HD)/ATP or activation by diazoxide, mitoKATPchannels of several conductance states were observed in symmetrical (150 mM) potassium glutamate (26, 47, 66, 83, and 105 pS). Isoflurane (0.8 mM) increased the cumulative open probability from 0.09 ± 0.02 at baseline to 0.50 ± 0.09 ( P < 0.05, n = 5), which was inhibited by 5-HD. Isoflurane caused a dose-dependent rightward shift in ATP inhibition of mitoKATPchannels, which increased the IC50for ATP from 335 ± 4 to 940 ± 34 μM at 0.8 mM ( P < 0.05, n = 5∼8). We conclude that direct activation of the mitoKATPchannel by isoflurane is likely to contribute to volatile anesthetic-induced myocardial preconditioning.
Cyclic stretch induces vascular smooth muscle cell alignment via NO signaling
Authors: Standley Paul R. , Camaratta Antonino , Nolan Brian P. , Purgason Christian T. , Stanley Melinda A.
Published: March 2015

We investigated the effects of cyclic stretch on vascular smooth muscle cell (VSMC) alignment and potential overlap of signaling modalities with stretch-induced proliferation. VSMC were subjected to graded stretch (1 Hz at 100–124% of resting length) for 48 h. Graded stretch resulted in graded VSMC alignment from a minimum of completely random orientation to a maximum of ∼80–85° to the stretch vector. Alignment was reversible within 48 h of stretch cessation and independent of signaling modalities mediating stretch-induced proliferation: modulation of IGF-1, MAPK, phosphatidylinositol 3-kinase, tyrosine kinase, and stretch-activated calcium channels did not affect alignment. Nitric oxide (NO) synthase (NOS) blockade uncoupled alignment. Neither the NO donor, cytokine-induced NOS activity, nor l-citrulline affected alignment, but inhibited VSMC proliferation. Therefore, stretch-induced proliferation and alignment are differentially regulated, with NO a common signaling molecule for both. Targeting NOS in states such as restenosis and hypertension may prove to be beneficial.
Roles of L-type Ca2+ and delayed-rectifier K+ currents in sinoatrial node pacemaking: insights from stability and bifurcation analyses of a mathematical model
Authors: Kurata Yasutaka , Hisatome Ichiro , Imanishi Sunao , Shibamoto Toshishige
Published: March 2015

To elucidate the dynamical mechanisms of the sinoatrial (SA) node pacemaker activity, we investigated the roles of L-type Ca2+ ( ICa,L) and delayed-rectifier K+ ( IKr) currents in pacemaking by stability and bifurcation analyses of our rabbit SA node model (Kurata Y, Hisatome I, Imanishi S, and Shibamoto T. Am J Physiol Heart Circ Physiol 283: H2074–H2101, 2002). Equilibrium points (EPs), periodic orbits, stability of EPs, and Hopf bifurcation points were calculated as functions of conductance or gating time constants of the currents for constructing bifurcation diagrams. Structural stability (robustness) of the system was also evaluated by computing stability and dynamics during applications of constant bias currents ( Ibias). Blocking ICa,L or IKr caused stabilization of an EP and cessation of pacemaking via a Hopf bifurcation. The unstable zero-current potential region determined with Ibias applications, where spontaneous oscillations appear, shrunk and finally disappeared as ICa,L diminished, but shrunk little when IKr was eliminated. The reduced system, including no time-dependent current except ICa,L, exhibited pacemaker activity. These results suggest that ICa,L is responsible for EP instability and pacemaker generation, whereas IKr is not necessarily required for constructing a pacemaker cell system. We further explored the effects of various K+ currents with different kinetics on stability and dynamics of the model cell. The original IKr of delayed activation and inward rectification appeared to be most favorable for generating large-amplitude oscillations with stable frequency, suggesting that IKr acts as an oscillation amplifier and frequency stabilizer. IKr may also play an important role in preventing bifurcation to quiescence of the system.
Anesthetic preconditioning: triggering role of reactive oxygen and nitrogen species in isolated hearts
Authors: Novalija Enis , Varadarajan Srinivasan G. , Camara Amadou K. S. , An Jianzhong , Chen Qun , Riess Matthias L. , Hogg Neil , Stowe David F.
Published: March 2015

We postulated that anesthetic preconditioning (APC) is triggered by reactive oxygen/nitrogen species (ROS/RNS). We used the isolated guinea pig heart perfused withl-tyrosine, which reacts with ROS and RNS to form strong oxidants, principally peroxynitrite (ONOO−), and then forms fluorescent dityrosine. ROS scavengers superoxide dismutase, catalase, and glutathione (SCG) and NO· synthesis inhibitor N G-nitro-l-arginine methyl ester (l-NAME) were given 5 min before and after sevoflurane preconditioning stimuli. Drugs were washed out before 30 min of ischemia and 120 min of reperfusion. Groups were control (nontreated ischemia control), APC (two, 2-min periods of perfusion with 0.32 ± 0.02 mM of sevoflurane; separated by a 6-min period of perfusion without sevoflurane), SCG, APC + SCG,l-NAME, and APC + l-NAME. Effluent dityrosine at 1 min reperfusion was 56 ± 6 (SE)‡, 15 ± 5, 40 ± 5‡, 39 ± 4‡, 35 ± 4‡, and 33 ± 5‡ units (‡ P < 0.05 vs. APC), respectively; left ventricular pressure (%baseline) at 60 min of reperfusion was 30 ± 5‡, 60 ± 4, 35 ± 5‡, 37 ± 5‡, 44 ± 4, and 47 ± 4; and infarct size (%total heart weight) was 50 ± 5‡, 19 ± 2, 48 ± 3‡, 46 ± 4‡, 42 ± 4‡, and 45 ± 2‡. Thus APC is initiated by ROS as shown by improved function, reduced infarct size, and reduced dityrosine on reperfusion; protective and ROS/RNS-reducing effect of APC were attenuated when bracketed by ROS scavengers or NO· inhibition.
Selective contractile dysfunction of left, not right, ventricular myocardium in the SHHF rat
Authors: Janssen Paul M. L. , Stull Linda B. , Leppo Michelle K. , Altschuld Ruth A. , Marbán Eduardo
Published: March 2015

The progression of hypertension to cardiac failure involves systemic changes that may ultimately affect contractility throughout the heart. Spontaneous hypertensive heart failure (SHHF) rats have depressed left ventricular (LV) function, but right ventricular (RV) dysfunction is less well characterized. Ultrathin (87 ± 5 μm) trabeculae were isolated from end-stage failing SHHF rats and from age-matched controls. Under near-physiological conditions (1 mM Ca2+, 37°C, 4 Hz), developed force (in mN/mm2) was not significantly different in SHHF LV and RV trabeculae and those of controls. SHHF LV preparations displayed a negative force-frequency behavior (40 ± 7 vs. 23 ± 4 mN/mm2, 2 vs. 7 Hz); this relationship was positive in SHHF RV preparations (27 ± 5 vs. 40 ± 6 mN/mm2) and controls (32 ± 6 vs. 44 ± 9 mN/mm2). The response to isoproterenol (10−6M, 4 Hz) was depressed in SHHF LV preparations. The inotropic response to hypothermia was lost in SHHF LV trabeculae but preserved in SHHF RV trabeculae. Intracellular calcium measurements revealed impaired calcium handling at higher frequencies in LV preparations. We conclude that in end-stage failing SHHF rats, RV function is only marginally affected, whereas a severe contractile dysfunction of LV myocardium is present.
Abnormal cardiac function associated with sympathetic nervous system hyperactivity in mice
Authors: Brum Patricia C. , Kosek Jon , Patterson Andrew , Bernstein Daniel , Kobilka Brian
Published: March 2015

α2A-Adrenergic receptors (ARs) in the midbrain regulate sympathetic nervous system activity, and both α2A-ARs and α2C-ARs regulate catecholamine release from sympathetic nerve terminals in cardiac tissue. Disruption of both α2A- and α2C-ARs in mice leads to chronically elevated sympathetic tone and decreased cardiac function by 4 mo of age. These knockout mice have increased mortality, reduced exercise capacity, decreased peak oxygen uptake, and decreased cardiac contractility relative to wild-type controls. Moreover, we observed significant abnormalities in the ultrastructure of cardiac myocytes from α2A/α2C-AR knockout mice by electron microscopy. Our results demonstrate that chronic elevation of sympathetic tone can lead to abnormal cardiac function in the absence of prior myocardial injury or genetically induced alterations in myocardial structural or functional proteins. These mice provide a physiologically relevant animal model for investigating the role of the sympathetic nervous system in the development and progression of heart failure.
Aging alters patterns of regional nonuniformity in LV strain relaxation: a 3-D MR tissue tagging study
Authors: Fonseca Carissa G. , Oxenham Helen C. , Cowan Brett R. , Occleshaw Christopher J. , Young Alistair A.
Published: March 2015

Although age-related impairment of diastolic function is well documented, patterns of regional tissue relaxation impairment with age have not been characterized. MRI tissue tagging with a regional three-dimensional (3-D) analysis was performed in 15 younger (age 19–26 yr) and 16 older (age 60–74 yr) normal, healthy volunteers. The peak rate of relaxation of circumferential strain (RC) was decreased in the older group (on average, 105 ± 28 vs. 163 ± 18 %/s for older vs. younger, mean ± SD, P < 0.001) to a greater extent in the lateral wall than in the septum ( P = 0.016) and to a greater extent in the apex than in the base ( P < 0.001). Peak rate of relaxation of longitudinal strain (RL) was also reduced with age (94 ± 27 vs. 155 ± 18 %/s, P < 0.001) to a greater extent in the apex than in the base ( P < 0.001). Both RC and RL were greater in the apex than in the base only in the younger subjects ( P < 0.001 for each). Peak rate of torsion reversal (RT) was reduced with age (74 ± 16 vs. 91 ± 15 degrees/s, P = 0.006) to a greater extent in the base than in the apex ( P = 0.035). An increase in regional asynchrony in time to RC and time to RL ( P < 0.001 for each), but not time to RT, occurred with age. Thus patterns of regional nonuniformity of myocardial relaxation are altered in a consistent fashion with aging.
Increasing P50does not improve Do2critor systemicV˙o2in severe anemia
Authors: Eichelbrönner Otto , D'Almeida Mark , Sielenkämper Andreas , Sibbald William J. , Chin-Yee Ian H.
Published: March 2015

Reducing the hemolobin (Hb)-O2binding affinity facilitates O2unloading from Hb, potentially increasing tissue mitochondrial O2availability. We hypothesized that a reduction of Hb-O2affinity would increase O2extraction when tissues are O2supply dependent, reducing the threshold of critical O2delivery (Do2 CRIT). We investigated the effects of increased O2tension at which Hb is 50% saturated (P50) on systemic O2uptake (V˙o2 SYS), Do2 CRIT, lactate production, and acid-base balance during isovolemic hemodilution in conscious rats. After infusion of RSR13, an allosteric modifier of Hb, P50increased from 36.6 ± 0.3 to 48.3 ± 0.6 but remained unchanged at 35.4 ± 0.8 mmHg after saline (control, CON). Arterial O2saturations were equivalent between RSR13 and saline groups, but venous Po2was higher and venous O2saturation was lower after RSR13. Convective O2delivery progressively declined during hemodilution reaching the Do2 CRITat 3.4 ± 0.8 ml · min−1· 100 g−1(CON) and 3.6 ± 0.6 ml · min−1· 100 g−1(RSR13). At Hb of 8.1 g/lV˙o2 SYSstarted to decrease (CON: 1.9 ± 0.1; RSR13: 1.8 ± 0.2 ml · min−1· 100 g−1) and fell to 0.8 ± 0.2 (CON) and 0.7 ± 0.2 ml · min−1· 100 g−1(RSR13). Arterial lactate was lower in RSR13-treated than in control animals when animals were O2supply dependent. The decrease in base excess, arterial pH, and bicarbonate during O2supply dependence was significantly less after RSR13 than after saline. These findings demonstrate that during O2supply dependence caused by severe anemia, reducing Hb-O2binding affinity does not affect V˙o2 SYSor Do2 CRITbut appears to have beneficial effects on oxidative metabolism and acid base balance.
Appearance of an erythrocyte population with decreased deformability and hemoglobin content following sepsis
Authors: Condon Michael R. , Kim Jiyoun E. , Deitch Edwin A. , Machiedo George W. , Spolarics Zoltán
Published: March 2015

With the use of the cecal ligation and puncture model in mice, this study tested whether sepsis-induced decreased erythrocyte deformability is restricted to a subpopulation of cells. Erythrocyte subpopulations were isolated by centrifugal elutriation. Lineweaver-Burk conversion of deformability-response curves to shear stress was used to determine the shear stress at half-maximal cell elongation ( KEI) and maximal cell elongation (EImax). Sepsis decreased erythrocyte deformability in whole blood. KEIvalues were elevated (2.7 vs. 2.1 Pa) and EImaxvalues decreased (0.56 vs. 0.50) in sepsis compared with sham mice. KEIvalues for cells eluted at 7 ml/min (smallest and oldest cells) were similar; however, KEIvalues for cells eluted at 8 ml/min were greater in septic than sham animals (2.50 vs. 2.10). Younger and larger subpopulations of erythrocytes (eluted at 9, 10, and 11 ml/min) also showed a tendency of decreased deformability in sepsis. Mean corpuscular hemoglobin content was decreased in cells eluted at 7 and 8 ml/min in sepsis (4.5 and 10.2 pg) compared to sham (7.4 and 11.4 pg) mice. This study indicates that an erythrocyte subpopulation that represents 20% of circulating cells shows the most pronounced decrease in cell deformability during sepsis. Increased rigidity together with decreased corpuscular hemoglobin content in these cells may contribute to microcirculatory dysfunction and immune modulation during sepsis.
Mechanisms of cytokine induced NO-mediated cardiac fibroblast apoptosis
Authors: Tian Bin , Liu Jian , Bitterman Peter B. , Bache Robert J.
Published: March 2015

This study examined the role of nitric oxide (NO) in cytokine-induced apoptosis in adult cardiac fibroblasts (CFbs). In cultured adult rat CFbs, IL-1β (5 ng/ml), but not interferon-γ (10 ng/ml) or tumor necrosis factor-α (10 ng/ml), induced inducible NO synthase (iNOS) expression and NO production that was associated with an increase in caspase-3 activity and apoptotic cell death. Apoptotic frequency was reduced by the iNOS inhibitor S-methylisothiourea (3 × 10−5M). Apoptosis in response to IL-1β was attenuated by the caspase-3 inhibitor [ Z-Asp-Glu-Val-Asp-fluoromethyl ketone (Z-DVED-FMK)] but not by inhibition of guanylyl cyclase with 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). IL-1β-induced CFb apoptosis was associated with an increase in p53 and Bax protein expression with no changes in Bcl-2 or Bcl-xL. Nuclear condensation and fragmentation occurred when isolated nuclei were exposed to an NO donor { Z-1[ N-(2-aminoethyl)- N-(2-ammonoethyl)amino]diazen-1-ium-1,2-dioate (DETA-NONOate) 10−5M}, an effect that was not blocked by the peroxynitrite scavenger Mn(III)tetrakis(4-benzoic acid) porphyrin chloride. Moreover, Mn(III)tetrakis(4-benzoic acid) porphyrin chloride attenuated but did not eliminate IL-1β-induced CFb apoptosis, indicating that the proapoptotic effect of NO can occur independently of its conversion to peroxynitrite. Our results demonstrate that IL-1β-induced iNOS expression can trigger NO-dependent apoptosis in adult CFbs, which appears to result from DNA damage and may be mediated by a p53-dependent apoptotic pathway.
Pyruvate improves redox status and decreases indicators of hepatic apoptosis during hemorrhagic shock in swine
Authors: Mongan Paul D. , Capacchione John , West Shanda , Karaian John , Dubois Dawn , Keneally Ryan , Sharma Pushpa
Published: March 2015

Previous studies have shown that the liver is the first organ to display signs of injury during hemorrhagic shock. We examined the mechanism by which pyruvate can prevent liver damage during hemorrhagic shock in swine anesthetized with halothane. Thirty minutes after the induction of a 240-min controlled arterial hemorrhage targeted at 40 mmHg, hypertonic sodium pyruvate (0.5 g · kg−1 · h−1) was infused to achieve an arterial concentration of 5 mM. The volume and osmolality effects of pyruvate were matched with 10% saline (HTS) and 0.9% saline (NS). Although the peak hemorrhage volume increased significantly in both the pyruvate and HTS group, only the pyruvate treatment was effective in delaying cardiovascular decompensation. In addition, pyruvate effectively maintained the NADH/NAD redox state, as evidenced by increased microdialysate pyruvate levels and a significantly lower lactate-to-pyruvate ratio. Pyruvate also prevented the loss of intracellular antioxidants (GSH) and a reduction in the GSH-to-GSSG ratio. These beneficial effects on the redox environment decreased hepatic cellular death by apoptosis. Pyruvate significantly increased the ratio of Bcl-Xl (antiapoptotic molecule)/Bax (proapoptotic molecule), prevented the release of cytochrome c from mitochondria, and decreased the fragmentation of caspase 3 and poly(ADP ribose) polymerase (DNA repair enzyme). These beneficial findings indicate that pyruvate infused 30 min after the onset of severe hemorrhagic shock is effective in maintaining the redox environment, preventing the loss of the key antioxidant GSH, and decreasing early apoptosis indicators.
Nitric oxide synthase inhibition does not affect regulation of muscle sympathetic nerve activity during head-up tilt
Authors: Cui Jian , Zhang Rong , Wilson Thad E. , Witkowski Sarah , Crandall Craig G. , Levine Benjamin D.
Published: March 2015

To test the hypothesis that systemic inhibition of nitric oxide (NO) synthase does not alter the regulation of sympathetic outflow during head-up tilt in humans, in eight healthy subjects NO synthase was blocked by intravenous infusion of NG-monomethyl-l-arginine (l-NMMA). Blood pressure, heart rate, cardiac output, total peripheral resistance (TPR), and muscle sympathetic nerve activity (MSNA) were recorded in the supine position and during 60° head-up tilt. In the supine position, infusion of l-NMMA increased blood pressure, via increased TPR, and inhibited MSNA. However, the increase in MSNA evoked by head-up tilt during l-NMMA infusion (change in burst rate: 24 ± 4 bursts/min; change in total activity: 209 ± 36 U/min) was similar to that during head-up tilt without l-NMMA (change in burst rate: 23 ± 4 bursts/min; change in total activity: 251 ± 52 U/min, n = 6, all P > 0.05). Moreover, changes in TPR and heart rate during head-up tilt were virtually identical between the two conditions. These results suggest that systemic inhibition of NO synthase with l-NMMA does not affect the regulation of sympathetic outflow and vascular resistance during head-up tilt in humans.
Redox factor-1 contributes to the regulation of progression from G0/G1 to S by PDGF in vascular smooth muscle cells
Authors: He Tongrong , Weintraub Neal L. , Goswami Prabhat C. , Chatterjee Papri , Flaherty Dawn M. , Domann Frederick E. , Oberley Larry W.
Published: March 2015

Redox factor-1 (Ref-1/APE), a multifunctional DNA base excision repair and redox regulation enzyme, plays an important role in oxidative signaling, transcription factor regulation, and cell cycle control. We hypothesized that Ref-1 plays a regulatory role in smooth muscle cell (SMC) proliferation induced by PDGF. Ref-1 antisense oligodeoxynucleotides (AODN), which diminished the level of Ref-1 protein in SMCs by ∼50%, inhibited PDGF-BB (composed of the homodimer of B-polypeptide chain)-induced [3H]thymidine incorporation compared with control oligodeoxynucleotides. Ref-1 AODN inhibited PDGF-BB-induced S phase entry by ∼63%, which was overcome by overexpression of Ref-1 by adenoviral-mediated gene transfer. Overexpression of Ref-1 alone without PDGF enhanced SMC entry into the S phase. Furthermore, decreasing Ref-1 protein by treatment of SMCs with Ref-1 AODN, or by immunodepletion of Ref-1 from nuclear extracts, inhibited PDGF-BB-induced activator protein-1 (AP-1) DNA binding activity. Chemical reduction restored the AP-1 DNA binding in Ref-1-depleted nuclear extracts. These results suggest that Ref-1 contributes to the regulation of PDGF-BB-stimulated cell cycle progression from G0/G1 to S in SMCs, with one of the possible steps being redox-regulation of AP-1 by Ref-1 protein.
Bezold-Jarisch reflex attenuates dynamic gain of baroreflex neural arc
Authors: Kashihara Koji , Kawada Toru , Yanagiya Yusuke , Uemura Kazunori , Inagaki Masashi , Takaki Hiroshi , Sugimachi Masaru , Sunagawa Kenji
Published: March 2015

Although acute myocardial ischemia or infarction may induce the Bezold-Jarisch (BJ) reflex through the activation of serotonin receptors on vagal afferent nerves, the mechanism by which the BJ reflex modulates the dynamic characteristics of arterial pressure (AP) regulation is unknown. The purpose of this study was to examine the effects of the BJ reflex induced by intravenous phenylbiguanide (PBG) on the dynamic characteristics of the arterial baroreflex. In seven anesthetized rabbits, we perturbed intracarotid sinus pressure (CSP) according to a white noise sequence while renal sympathetic nerve activity (RSNA), AP, and heart rate (HR) were recorded. We estimated the transfer function from CSP to RSNA (neural arc) and from RSNA to AP (peripheral arc) before and after 10 min of intravenous administration of PBG (100 μg · kg–1 · min–1). The intravenous PBG decreased mean AP from 84.5 ± 4.0 to 68.2 ± 4.7 mmHg ( P < 0.01), mean RSNA to 76.2 ± 7.0% ( P < 0.05), and mean HR from 301.6 ± 7.7 to 288.4 ± 9.0 beats/min ( P < 0.01). The intravenous PBG significantly decreased neural arc dynamic gain at 0.01 Hz (1.06 ± 0.08 vs. 0.59 ± 0.17, P < 0.05), whereas it did not affect that of the peripheral arc (1.20 ± 0.12 vs. 1.18 ± 0.41). In six different rabbits without intravenous PBG, the neural arc transfer function did not change between two experimental runs with intervening interval of 10 min, excluding the possibility that the cumulative effects of anesthetics had altered the neural arc transfer function. In conclusion, excessive activation of the BJ reflex during acute myocardial ischemia may exert an adverse effect on AP regulation, not only by sympathetic suppression, but also by attenuating baroreflex dynamic gain.
Aldosterone induces a vascular inflammatory phenotype in the rat heart
Authors: Rocha Ricardo , Rudolph Amy E. , Frierdich Gregory E. , Nachowiak Denise A. , Kekec Beverly K. , Blomme Eric A. G. , McMahon Ellen G. , Delyani John A.
Published: March 2015

Vascular inflammation was examined as a potential mechanism of aldosterone-mediated myocardial injury in uninephrectomized rats receiving 1% NaCl-0.3% KCl to drink for 1, 2, or 4 wk and 1) vehicle, 2) aldosterone infusion (0.75 μg/h), or 3) aldosterone infusion (0.75 μg/h) plus the selective aldosterone blocker eplerenone (100 mg · kg−1· day−1). Aldosterone induced severe hypertension at 4 wk [systolic blood pressure (SBP), 210 ± 3 mmHg vs. vehicle, 131 ± 2 mmHg, P < 0.001], which was partially attenuated by eplerenone (SBP, 180 ± 7 mmHg; P < 0.001 vs. aldosterone alone and vehicle). No significant increases in myocardial interstitial collagen fraction or hydroxyproline concentration were detected throughout the study. However, histopathological analysis of the heart revealed severe coronary inflammatory lesions, which were characterized by monocyte/macrophage infiltration and resulted in focal ischemic and necrotic changes. The histological evidence of coronary lesions was preceded by and associated with the elevation of cyclooxygenase-2 (up to ∼4-fold), macrophage chemoattractant protein-1 (up to ∼4-fold), and osteopontin (up to ∼13-fold) mRNA expression. Eplerenone attenuated proinflammatory molecule expression in the rat heart and subsequent vascular and myocardial damage. Thus aldosterone and salt treatment in uninephrectomized rats led to severe hypertension and the development of a vascular inflammatory phenotype in the heart, which may represent one mechanism by which aldosterone contributes to myocardial disease.
Positive inotropic effect of ceramide in adult ventricular myocytes: mechanisms dissociated from its reduction in Ca2+influx
Authors: Liu Shi J. , Kennedy Richard H.
Published: March 2015

Ceramide, a sphingolipid metabolite produced by activation of sphingomyelinase, has been previously shown to reduce L-type Ca2+channel current ( ICa,L) in adult rat ventricular myocytes; however, its effect on contractile function is unknown. In this study, we investigated the effects of ceramide on excitation-contraction coupling in adult ventricular myocytes and on left ventricular (LV) function in isolated hearts. Surprisingly, in patch-clamped myocytes, ceramide increased contraction concomitant with reductions in ICa,L. In intact myocytes, ceramide increased cell shortening (CS) concurrently with enhancing maximum rates of shortening and relaxation and the duration of contraction. Ceramide also increased the amplitudes of postrest potentiated (PRP) contraction. In fura-PE3-loaded myocytes, ceramide increased systolic Ca2+and the magnitude and maximum rates of the rising and declining phases of Ca2+transients. Ceramide-elicited decreases in magnitudes of PRP relative to steady-state contraction and the Ca2+transient suggest an increased fractional Ca2+release from the sarcoplasmic reticulum (SR). However, ceramide slightly reduced the caffeine-induced Ca2+transient and had no significant effect on the amplitude of the PRP-elicited Ca2+transient. Additionally, the ceramide-induced upward shift in the relationship of contraction and the Ca2+transient and increase in the Ca2+responsiveness of CS suggest an increase in myofilament Ca2+sensitivity. In isolated hearts, ceramide increased LV developed pressure and maximum rates of contraction and relaxation at balloon volumes of 30–50 μl. In summary, regardless of decreasing ICa,L, ceramide elicits distinct positive inotropic and lusitropic effects, resulting probably from enhanced SR Ca2+release and uptake, and increased Ca2+sensitivity of ventricular myocytes.
Acute and chronic NOS inhibition enhances α2- adrenoreceptor-stimulated RhoA and Rho kinase in rat aorta
Authors: Carter Rebecca W. , Begaye McKenzie , Kanagy Nancy L.
Published: March 2015

We demonstrated that arteries from rats made hypertensive with chronic nitric oxide (NO) synthase (NOS) inhibition ( Nω-nitro-l-arginine in drinking water, LHR) have enhanced contractile sensitivity to α2-adrenergic receptors (α2-AR) agonist UK-14304 compared with arteries from normotensive rats (NR). NO may regulate vascular tone in part through suppression of RhoA and Rho kinase (ROK). We hypothesized that enhanced RhoA and ROK activity augments α2-AR contraction in LHR aortic rings. Y-27632 eliminated UK-14304 contraction in LHR and NR aortic rings. The order of increasing sensitivity to Y-27632 was the following: endothelium-intact NR, LHR, and endothelium-denuded NR. UK-14304 stimulated RhoA translocation to the membrane fraction in LHR and denuded NR but not in intact NR aorta. Basally, more RhoA was present in the membrane fraction in denuded NR than in intact NR or LHR aorta. Relaxation to S-nitroso- N-acetyl-penicillamine and Y-27632 in denuded ionomycin-permeabilized rings was greater in NR than in LHR. Together these studies indicate α2-AR contraction depends on ROK activity more in NR than LHR aorta. Additionally, endogenous NO may regulate RhoA activation, whereas chronic NOS inhibition appears to cause RhoA desensitization.
Characterization of fibrillatory rhythms by ensemble vector directional analysis
Authors: Kadish Alan , Johnson David , Choe Willie , Goldberger Jeffrey , Horvath George
Published: March 2015

Recent studies have demonstrated that fibrillatory rhythms are not random phenomena but have definable patterns. However, standard mapping techniques may have limitations in their ability to identify the organization of fibrillation. The purpose of this study was to develop and apply a method, “ensemble vector mapping,” for characterizing the spatiotemporal organization of fibrillation. Ventricular fibrillation was induced by burst pacing in normal mongrel dogs. In a separate protocol, atrial fibrillation was induced by epicardial aconitine application. Epicardial electrograms were recorded from a 112-electrode plaque array using a computerized mapping system. Vectors were created by summing orthogonal bipolar electrograms. The magnitude of the vectors was transformed using a logarithmic function, integrated over time, and normalized for local electrogram amplitude to produce an “ensemble vector” index whose magnitude is high when beat-to-beat activation direction is consistent and low when activation direction is variable. The mean index was 137 ± 36 mV/s during ventricular pacing at a cycle length of 300 ms but only 39 ± 23 mV/s during ventricular fibrillation ( P < 0.001). The ensemble vector index was also lower during atrial fibrillation (60 ± 54 mV/s) than during atrial pacing (115 ± 27 mV/s, P < 0.01 vs. atrial fibrillation) but not as low as during ventricular fibrillation ( P < 0.05, atrial vs. ventricular fibrillation). The index was also capable of distinguishing atrial tachycardia from atrial fibrillation. Ensemble vector mapping produces an objective assessment of the consistency of myocardial activation during fibrillation. The consistency of activation direction differs in different models of fibrillation and is higher during atrial than ventricular fibrillation. This technique has the potential to rapidly characterize repetitive activation patterns in fibrillatory rhythms and may help distinguish among different characteristics of fibrillatory rhythms.
Determinants of left ventricular preload-adjusted maximal power
Authors: Segers Patrick , Tchana-Sato Vincent , Leather H. Alex , Lambermont Bernard , Ghuysen Alexandre , Dogne Jean-Michel , Benoit Patricia , Morimont Philippe , Wouters Patrick F. , Verdonck Pascal , Kolh Philippe
Published: March 2015

Maximal left ventricular (LV) hydraulic power output (PWRmax), corrected for preload as PWRmax/(Ved)β (where Ved is the end-diastolic volume and β is a constant coefficient), is an index of LV contractility. Whereas preload-adjusted maximal power (PAMP) is usually calculated with β = 2, there is uncertainty about the optimal value of β (β = 1 for the normal LV and 2 for the dilated LV). The aim of this work is to study the determining factors of β. The data set consisted of 245 recordings (steady state and vena cava occlusion) in 10 animals in an ischemic heart pig model. The occlusion data yielded the slope ( E es; 2.01 ± 0.77 mmHg/ml, range 0.71–4.16 mmHg/ml) and intercept (V0; −11.9 ± 22.6 ml; range −76 to 39 ml) of the end-systolic pressure-volume relation, and the optimal β-factor (assessed by fitting an exponential curve through the Ved-PWRmax relation) was 1.94 ± 0.88 (range 0.29–4.73). The relation of β with Ved was weak [β = 0.60 + 0.02(Ved); r 2 = 0.20]. In contrast, we found an excellent exponential relation between V0 and β [β = 2.16[Formula: see text] r 2 = 0.70]. PAMP, calculated from the steady-state data, was 0.64 ± 0.40 mW/ml2 (range 0.14–2.83 mW/ml2) with a poor correlation with E es ( r = 0.30, P< 0.001). An alternative formulation of PAMP as PWRmax/(Ved − V0)2, incorporating V0, yielded 0.47 ± 0.26 mW/ml2 (range 0.09–1.42 mW/ml2) and was highly correlated with E es ( r = 0.89, P< 0.001). In conclusion, correct preload adjustment of maximal LV power requires incorporation of V0 and thus of data measured under altered loading conditions.
Isoflurane-induced preconditioning is attenuated by diabetes
Authors: Tanaka Katsuya , Kehl Franz , Gu Weidong , Krolikowski John G. , Pagel Paul S. , Warltier David C. , Kersten Judy R.
Published: March 2015

Volatile anesthetics stimulate, but hyperglycemia attenuates, the activity of mitochondrial ATP-regulated K+ channels. We tested the hypothesis that diabetes mellitus interferes with isoflurane-induced preconditioning. Acutely instrumented, barbiturate-anesthetized dogs were randomly assigned to receive 0, 0.32, or 0.64% end-tidal concentrations of isoflurane in the absence or presence of diabetes (3 wk after administration of alloxan and streptozotocin) in six experimental groups. All dogs were subjected to a 60-min left anterior descending coronary artery occlusion followed by 3 h of reperfusion. Myocardial infarct size (triphenyltetrazolium staining) was 29 ± 3% ( n = 8) of the left ventricular area at risk in control experiments. Isoflurane reduced infarct size (15 ± 2 and 13 ± 1% during 0.32 and 0.64% concentrations; n = 8 and 7 dogs, respectively). Diabetes alone did not alter infarct size (30 ± 3%; n = 8) but blocked the protective effects of 0.32% (27 ± 2%; n = 7) and not 0.64% isoflurane (18 ± 3%; n = 7). Infarct size was directly related to blood glucose concentrations in diabetic dogs, but this relationship was abolished by higher concentrations of isoflurane. The results indicate that blood glucose and end-tidal isoflurane concentrations are important determinants of infarct size during anesthetic-induced preconditioning.
CD117+ stem cells play a key role in therapeutic angiogenesis induced by bone marrow cell implantation
Authors: Li Tao-Sheng , Hamano Kimikazu , Nishida Masahiko , Hayashi Masanori , Ito Hiroshi , Mikamo Akihito , Matsuzaki Masunori
Published: March 2015

Therapeutic angiogenesis can be induced by the implantation of bone marrow mononuclear cells. We investigated the roles of mature mononuclear cell and stem cell fractions in bone marrow in this treatment. Although CD34 is the most popular marker for stem cell selection for inducing therapeutic angiogenesis, we separated CD117-positive cells (CD117+) from mature bone marrow mononuclear cells [CD117-negative cells (CD117–)] from mice using the antibody to the stem cell receptor, because some of the bone marrow stem cells that express CD117+ and CD34– might generate angiogenic cytokines and differentiate into endothelial cells. The angiogenic potency of CD117+ and CD117– cells was investigated in vitro and in vivo. Significantly higher levels of VEGF were secreted from the CD117+ cells than from the CD117– cells ( P < 0.001). Most of the CD117– cells died, but the CD117+ cells grew well and differentiated into endothelial cells within 14 days of culture. The CD117+ cells survived and were incorporated in microvessels within 14 days of being implanted into the ischemic hindlimbs of mice, but the CD117– cells did not. The microvessel density and blood perfusion of the ischemic hindlimbs were significantly higher in the CD117+ cell-implanted mice than in the CD117– cell-implanted mice ( P < 0.01). The microvessel density in ischemic hindlimbs was also significantly higher in the CD117+ cell-implanted mice than in the total bone marrow cell-implanted mice ( P < 0.05). Thus CD117+ stem cells play a key role in the therapeutic angiogenesis induced by bone marrow cell implantation.
Endogenously released ATP mediates shear stress-induced Ca2+influx into pulmonary artery endothelial cells
Authors: Yamamoto Kimiko , Sokabe Takaaki , Ohura Norihiko , Nakatsuka Hideki , Kamiya Akira , Ando Joji
Published: March 2015

The mechanisms by which flow-imposed shear stress elevates intracellular Ca2+in cultured endothelial cells (ECs) are not fully understood. Here we report finding that endogenously released ATP contributes to shear stress-induced Ca2+responses. Application of flow of Hanks' balanced solution to human pulmonary artery ECs (HPAECs) elicited shear stress-dependent increases in Ca2+concentrations. Chelation of extracellular Ca2+with EGTA completely abolished the Ca2+responses, whereas the phospholipase C inhibitor U-73122 or the Ca2+-ATPase inhibitor thapsigargin had no effect, which thereby indicates that the response was due to the influx of extracellular Ca2+. The Ca2+influx was significantly suppressed by apyrase, which degrades ATP, or antisense oligonucleotide targeted to P2X4purinoceptors. A luciferase luminometric assay showed that shear stress induced dose-dependent release of ATP. When the ATP release was inhibited by the ATP synthase inhibitors angiostatin or oligomycin, the Ca2+influx was markedly suppressed but was restored by removal of these inhibitors or addition of extracellular ATP. These results suggest that shear stress stimulates HPAECs to release ATP, which activates Ca2+influx via P2X4receptors.
IRAK1 deletion disrupts cardiac Toll/IL-1 signaling and protects against contractile dysfunction
Authors: Thomas James A. , Haudek Sandra B. , Koroglu Tolga , Tsen May F. , Bryant Debora D. , White D. Jean , Kusewitt Donna F. , Horton Jureta W. , Giroir Brett P.
Published: March 2015

Myocardial contractile dysfunction accompanies both systemic and cardiac insults. Septic shock and burn trauma can lead to reversible contractile deficits, whereas ischemia and direct inflammation of the heart can precipitate transient or permanent impairments in contractility. Many of the insults that trigger contractile dysfunction also activate the innate immune system. Activation of the innate immune response to infection is coordinated by the conserved Toll/interleukin-1 (IL-1) signal transduction pathway. Interestingly, components of this pathway are also expressed in normal and failing hearts, although their function is unknown. The hypotheses that Toll/IL-1 signaling occurs in the heart and that intact pathway function is required for contractile dysfunction after different insults were tested. Results from these experiments demonstrate that lipopolysaccharides (LPS) activate Toll/IL-1 signaling and IL-1 receptor-associated kinase-1 (IRAK1), a critical pathway intermediate in the heart, indicating that the function of this pathway is not limited to immune system tissues. Moreover, hearts lacking IRAK1 exhibit impaired LPS-triggered downstream signal transduction. Hearts from IRAK1-deficient mice also resist acute LPS-induced contractile dysfunction. Finally, IRAK1 inactivation enhances survival of transgenic mice that develop severe myocarditis and lethal heart failure. Thus the Toll/IL-1 pathway is active in myocardial tissue and interference with pathway function, through IRAK1 inactivation, may represent a novel strategy to protect against cardiac contractile dysfunction.
The novel serine protease PreR-Co promotes endothelium-independent vasorelaxation in rabbit aortic rings
Authors: Peral de Bruno María , Vincent Paula A. , Romano Liliana , Guardia D. Cecilia , Coviello Alfredo , De Vito Eduardo
Published: March 2015

The effect of a novel enzyme (PreR-Co) that activates renal prorenin was studied on rabbit aortas with and without endothelium. It was tested 1) in the basal tone of nonstimulated or ANG II-sensitized rings or rings precontracted with norepinephrine (NE), PGF2α, high KCl concentration, and 2) in rings pretreated with enalaprilat, losartan, PD-123319, N ω-nitro-l-arginine methyl ester, HOE-140, indomethacin, or serine protease inhibitors (PMSF, aprotinin, or soybean trypsin inhibitor); kallilkrein and bradykinin were also tested in ANG II-sensitized rings. PreR-Co produced a vasorelaxant effect in the basal tone and in the precontracted rabbit aorta. The effect was endothelium independent, potentiated by endothelium removal or nitric oxide (NO) synthase inhibition, and abolished by boiling the enzyme. In addition, the effect improved when basal tone was increased in ANG II-sensitized aortic rings or in precontracted vessels. No activation of the ANG II, bradykinin, prostaglandin, or NO pathway mediating the PreR-Co response could be obtained, suggesting a direct action of the enzyme. This action seems to be dependent on esterasic activity because serine protease inhibitors like PMSF and aprotinin were able to block the vasorelaxant effect of PreR-Co.
Immunomodulatory effects of sensory nerves during respiratory syncytial virus infection in rats
Authors: Auais Alexander , Adkins Becky , Napchan Galia , Piedimonte Giovanni
Published: March 2015

Respiratory syncytial virus (RSV) infection is associated with exaggerated neurogenic inflammation in the airways. This study sought to determine whether irritation of the mucosal sensory fibers affects the recruitment of lymphocytes and monocytes to RSV-infected airways. Pathogen-free rats were inoculated with RSV or with virus-free medium and were injected 5 days later with capsaicin to stimulate airway sensory nerves. Bronchoalveolar lavage was performed 1, 5, or 10 days after nerve stimulation, and samples were analyzed by differential cell count and flow cytometry. Without nerve stimulation, RSV caused a minimal increase in the number of lymphocytes and monocytes above pathogen-free control levels. After nerve stimulation, numerous lymphocytes, predominantly CD4+ T cells, and monocytes were recruited in the airways of infected rats, whereas no difference was found in pathogen-free controls. RSV induced overexpression of the neurokinin 1 (NK1) receptor for substance P on discrete lymphocyte subpopulations within the bronchial-associated lymphoid tissue (BALT), and treatment with a specific NK1receptor antagonist abolished the recruitment of both lymphocytes and monocytes to infected airways. Our data suggest that airborne irritants stimulating mucosal sensory fibers during RSV infection exert important immunomodulatory effects by attracting to the infected airways selected lymphocyte subpopulations from the local BALT as well as monocytes.