bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of the K+-competitive H+,K+-ATPase inhibitor AZD0865 in isolated rat gastric glands
Authors: Kirchhoff P. , Andersson K. , Socrates T. , Sidani S. , Kosiek O. , Geibel J. P.
Published: June 2006

The gastric H+,K+-ATPase of the parietal cell is responsible for acid secretion in the stomach and is the main target in the pharmacological treatment of acid-related diseases. Omeprazole and other benzimidazole drugs, although having delayed efficacy if taken orally, have high success rates in the treatment of peptic ulcer disease. Potassium competitive acid blockers (P-CAB) compete with K+ for binding to the H+,K+-ATPase and thereby they inhibit acid secretion. In this study, the in vitro properties of AZD0865, a reversible H+,K+-ATPase inhibitor of gastric acid secretion, are described. We used a digital-imaging system and the pH sensitive dye BCECF to observe proton efflux from hand-dissected rat gastric glands. Glands were stimulated with histamine (100 μM) and exposed to a bicarbonate- and Na+-free perfusate to induce an acid load. H+,K+-ATPase inhibition was determined by calculating pHi recovery (dpH/dT) in the presence of omeprazole (10–200 μM) or AZD0865 (0.01–100 μM). The efficacies of both drugs were compared. Our data show that acid secretion is inhibited by both the proton pump inhibitor omeprazole and the P-CAB AZD0865. Complete inhibition of acid secretion by AZD0865 had a rapid onset of activation, was reversible, and occurred at a 100-fold lower dose than omeprazole (1 μM AZD0865 vs. 100 μM omeprazole). This study demonstrates that AZD0865 is a potent, fast-acting inhibitor of gastric acid secretion, effective at lower concentrations than drugs of the benzimidazole class. Therefore, these data strongly suggest that AZD0865 has great potential as a fast-acting, low-dose inhibitor of acid secretion.
Regulation of peroxisome proliferator-activated receptor-γ in liver fibrosis
Authors: Yang Liu , Chan Che-Chang , Kwon Oh-Sang , Liu Songling , McGhee Jason , Stimpson Stephen A. , Chen Lihong Z. , Harrington W. Wallace , Symonds William T. , Rockey Don C.
Published: June 2006

The peroxisome proliferator-activated receptors (PPARs) impart diverse cellular effects in biological systems. Because stellate cell activation during liver injury is associated with declining PPARγ expression, we hypothesized that its expression is critical in stellate cell-mediated fibrogenesis. We therefore modulated its expression during liver injury in vivo. PPARγ was depleted in rat livers by using an adenovirus-Cre recombinase system. PPARγ was overexpressed by using an additional adenoviral vector (AdPPARγ). Bile duct ligation was utilized to induce stellate cell activation and liver fibrosis in vivo; phenotypic effects (collagen I, smooth muscle α-actin, hydroxyproline content, etc.) were measured. PPARγ mRNA levels decreased fivefold and PPARγ protein was undetectable in stellate cells after culture-induced activation. During activation in vivo, collagen accumulation, assessed histomorphometrically and by hydroxyproline content, was significantly increased after PPARγ depletion compared with controls (1.28 ± 0.14 vs. 1.89 ± 0.21 mg/g liver tissue, P < 0.03). In isolated stellate cells, AdPPARγ overexpression resulted in significantly increased adiponectin mRNA expression and decreased collagen I and smooth muscle α-actin mRNA expression compared with controls. During in vivo fibrogenesis, rat livers exposed to AdPPARγ had significantly less fibrosis than controls. Collagen I and smooth muscle α-actin mRNA expression were significantly reduced in AdPPARγ-infected rats compared with controls ( P < 0.05, n = 10). PPARγ-deficient mice exhibited enhanced fibrogenesis after liver injury, whereas PPARγ receptor overexpression in vivo attenuated stellate cell activation and fibrosis. The data highlight a critical role for PPARγ during in vivo fibrogenesis and emphasize the importance of the PPARγ pathway in stellate cells during liver injury.
Proteasome inhibition attenuates hepatic injury in the bile duct-ligated mouse
Authors: Anan Akira , Baskin-Bey Edwina S. , Isomoto Hajime , Mott Justin L. , Bronk Steven F. , Albrecht Jeffrey H. , Gores Gregory J.
Published: June 2006

Proteasome inhibition has recently been demonstrated to inhibit hepatic fibrogenesis in the bile duct-ligated (BDL) mouse by blocking stellate cell NF-κB activation. The effect of proteasome inhibition on liver injury, however, is unclear. Our aims were to assess the effect of the proteasome inhibitor bortezomib on liver injury in the BDL mouse. Liver injury was assessed in 7-day BDL mice treated with a single dose of bortezomib on day 4 after bile duct ligation. Despite NF-κB inhibition by bortezomib, liver injury and hepatocyte apoptosis were reduced in treated BDL mice. The antiapoptotic effect of bortezomib was likely mediated by an increase in hepatic cellular FLICE inhibitory protein (c-FLIP) levels, a potent antiapoptotic protein. Unexpectedly, numerous mitotic hepatocytes were observed in the bortezomib-treated BDL mice liver specimens. Consistent with this observation, PCNA immunoreactivity and cyclin A protein expression were also increased with bortezomib treatment. Bortezomib therapy was also associated with a decrease in numbers and activation of Kupffer cells/macrophages. In conclusion, these data suggest that the proteasome inhibitor bortezomib reduces hepatocyte injury in the BDL mouse by mechanisms associated with a reduction in hepatocyte apoptosis, a decrease in Kupffer cell/macrophage number and activation, and increased hepatocyte proliferation.
The emerging role of PDZ adapter proteins for regulation of intestinal ion transport
Authors: Lamprecht G. , Seidler U.
Published: June 2006

In the gastrointestinal tract, CFTR, in conjunction with one or several members of the SLC26 anion exchanger family, mediates electrogenic Cl−and HCO3−secretion. Na+/H+exchanger isoform NHE3, on the other hand, coupled to one or several of the SLC26 isoforms, mediates electroneutral NaCl absorption. The agonist-induced activation of anion secretion and inhibition of salt absorption causes secretory diarrhea. Current dogma sees the formation of a multiprotein complex of transport proteins, postsynaptic density-95/discs large/zonula occludens-1 (PDZ) adapter proteins, anchoring proteins, the cytoskeleton, and the involved protein kinases as one crucial step in the regulation of these transport processes. Data obtained in heterologous expression studies suggest an important role of these PDZ adapter proteins in trafficking, endocytic recycling, and membrane retention of the respective transmembrane proteins. This article reviews recent advances in our understanding of the role of the PDZ adapter proteins NHERF, E3KARP, PDZK1, IKEPP (NHERF-1 to NHERF-4), CAL, and Shank-2 that bind to CFTR, NHE3, and the intestinal SLC26 members in the regulation of intestinal fluid transport. Current concepts are mostly derived from heterologous expression studies and studies on their role in organ physiology are still in infancy. Recently, however, PDZ adapter protein-deficient mice and organ-specific cell lines have become available, and the first results suggest a more cell-type and possibly signal-specific role of these adapter proteins. This opens the potential for drug development targeted to PDZ domain interactions, which is, in theory, one of the most efficient antidiarrheal strategies.
TNF-α is crucial for the development of mast cell-dependent colitis in mice
Authors: Rijnierse Anneke , Koster Andries S. , Nijkamp Frans P. , Kraneveld Aletta D.
Published: June 2006

Inflammatory bowel disease (IBD) describes chronic inflammatory conditions of the gastrointestinal tract, and TNF-α plays a pivotal role in mediating the response. The proinflammatory cytokine TNF-α is rapidly released by mast cells after degranulation. In the present study, we hypothesized TNF-α to be an important player in our recently described mast cell-dependent murine model for IBD. The effect of neutralizing anti-TNF-α MAb was studied on colonic hypersensitivity in mice induced by a skin application of dinitrofluorobenzene (DNFB) followed by an intrarectal challenge with dintrobenzene sulfonic acid. Features of the colonic hypersensitivity response included diarrhea, mast cell infiltration and activation, infiltration of inflammatory cells in the colon, colonic patch hypertrophy, and increased mast cell-derived TNF-α levels in the colon. Anti-TNF-α MAb could effectively abrogate diarrhea in DNFB-sensitized mice 72 h after the challenge. The numbers of colonic patches and total tissue damage scores were reduced by anti-TNF-α MAb treatment in DNFB-sensitized mice 72 h after the challenge. Mast cell infiltration and activation remained unaffected by neutralizing anti-TNF-α MAb. Treatment with the corticosteroid dexamethasone, a frequently used therapeutic treatment in IBD, resulted in a reduction of diarrhea, cellular infiltration, and total tissue damage scores to the same extent as anti-TNF-α MAb. Additionally, dexamethasone treatment could also reduce total TNF-α levels in the colon, mast cell numbers, and mast cell activation in both vehicle- and DNFB-sensitized mice 72 h after the challenge. These findings suggest that TNF-α can play an instrumental role in causing inflammatory responses in the present murine model for IBD downstream from mast cell activation.
PI3-kinase activity modulates apo B available for hepatic VLDL production inapobec-1−/−mice
Authors: Chirieac Doru V. , Davidson Nicholas O. , Sparks Charles E. , Sparks Janet D.
Published: June 2006

Insulin regulates hepatic VLDL production by activation of phosphatidylinositide 3-kinase (PI3-kinase) which decreases apo B available for lipid assembly. The current study evaluated the dependence of the VLDL apolipoprotein B (apo B) pathway on PI3-kinase activity in vivo. VLDL production was examined in B100 only, apo B mRNA editing catalytic subunit 1 ( apobec-1−/−) mice, using the Triton WR 1339 method. Glucose injection suppressed VLDL triglyceride production by 28% in male and by 32% in female mice compared with saline-injected controls. When wortmannin was injected to inhibit PI3-kinase, VLDL triglyceride production was increased by 52% in males and by 89% in females, and VLDL B100 levels paralleled triglyceride changes. Pulse-chase experiments in primary mouse hepatocytes showed that wortmannin increased net freshly synthesized B100 availability by >35%. To test whether physiological insulin resistance produced equivalent effects to wortmannin, we studied male apobec-1−/−mice who became hyperlipidemic on being fed a fructose-enriched diet. Fructose-fed apobec-1−/−mice had significantly higher VLDL triglyceride and B100 production rates compared with chow-fed mice, and rates were refractile to glucose or wortmannin. Hepatic VLDL triglyceride and B100 production in wortmannin-injected chow-fed mice equaled that observed in fructose-fed mice. Together, results suggest in vivo and in vitro that wortmannin-sensitive PI3-kinases maintain a basal level of VLDL suppression that is sensitive to changes in activation and that can increase VLDL production when PI3-kinase is inhibited to levels similar to those induced by insulin resistance.
A 2D FE model of the heart demonstrates the role of the pericardium in ventricular deformation
Authors: Gibbons Kroeker Carol A. , Adeeb Samer , Tyberg John V. , Shrive Nigel G.
Published: June 2006

During pulmonary artery constriction (PAC), an experimental model of acute right ventricular (RV) pressure overload, the interventricular septum flattens and inverts. Finite element (FE) analysis has shown that the septum is subject to axial compression and bending when so deformed. This study examines the effects of acute PAC on the left ventricular (LV) free wall and the role the pericardium may play in these effects. In eight open-chest anesthetized dogs, LV, RV, aortic, and pericardial pressures were recorded under control conditions and with PAC. Model dimensions were derived from two-dimensional echocardiography minor-axis images of the heart. At control (pericardium closed), FE analysis showed that the septum was concave to the LV; stresses in the LV, RV, and septum were low; and the pericardium was subject to circumferential tension. With PAC, RV end-diastolic pressure exceeded LV pressure and the septum inverted. Compressive stresses developed circumferentially in the septum out to the RV insertion points, forming an arch-like pattern. Sharp bending occurred near the insertion points, accompanied by flattening of the LV free wall. With the pericardium open, the deformations and stresses were different. The RV became much larger, especially with PAC. With PAC, the arch-like circumferential stresses still developed in the septum, but their magnitudes were reduced, compared with the pericardium-closed case. There was no free wall inversion and flattening was less. From these FE results, the pericardium has a significant influence on the structural behavior of the septum and the LV and RV free walls. Furthermore, the deformation of the heart is dependent on whether the pericardium is open or closed.
Rat mesenteric arterial dilator response to 11,12-epoxyeicosatrienoic acid is mediated by activating heme oxygenase
Authors: Sacerdoti David , Bolognesi Massimo , Di Pascoli Marco , Gatta Angelo , McGiff John C. , Schwartzman Michal Laniado , Abraham Nader G.
Published: June 2006

11,12-Epoxyeicosatrienoic acid (11,12-EET), a potent vasodilator produced by the endothelium, acts on calcium-activated potassium channels and shares biological activities with the heme oxygenase/carbon monoxide (HO/CO) system. We examined whether activation of HO mediates the dilator action of 11,12-EET, and that of the other EETs, on rat mesenteric arteries. Dose-response curves (10−9to 10−6M) to 5,6-EET, 8,9-EET, 11,12-EET, 14,15-EET, and ACh (10−9to 10−4M) were evaluated in preconstricted (10−6mol/l phenylephrine) mesenteric arteries (<350 μm diameter) in the presence or absence of 1) the cyclooxygenase inhibitor indomethacin (2.8 μM), 2) the HO inhibitor chromium mesoporphyrin (CrMP) (15 μM), 3) the soluble guanylyl cyclase (GC) inhibitor ODQ (10 μM), and 4) the calcium-activated potassium channel inhibitor iberiotoxin (25 nM). The vasodilator response to 11,12-EET was abolished by CrMP and iberiotoxin, whereas indomethacin and ODQ had no effect. In contrast, the effect of ACh was attenuated by ODQ but not by CrMP. The vasodilator effect of 8,9-EET, like that of 11,12-EET, was greatly attenuated by HO inhibition. In contrast, the mesenteric vasodilator response to 5,6-EET was independent of both HO and GC, whereas that to 14,15-EET demonstrated two components, an HO and a GC, of equal magnitude. Incubation of mesenteric microvessels with 11,12-EET caused a 30% increase in CO release, an effect abolished by inhibition of HO. We conclude that the rat mesenteric vasodilator action of 11,12-EET is mediated via an increase in HO activity and an activation of calcium-activated potassium channels.
Controlled reperfusion after hypothermic heart preservation inhibits mitochondrial permeability transition-pore opening and enhances functional recovery
Authors: Bopassa J. C. , Vandroux David , Ovize M. , Ferrera R.
Published: June 2006

We investigated whether low-pressure reperfusion may attenuate postischemic contractile dysfunction, limits necrosis and apoptosis after a prolonged hypothermic ischemia, and inhibits mitochondrial permeability transition-pore (MPTP) opening. Isolated rats hearts ( n = 72) were exposed to 8 h of cold ischemia and assigned to the following groups: 1) reperfusion with low pressure (LP = 70 cmH2O) and 2) reperfusion with normal pressure (NP = 100 cmH2O). Cardiac function was assessed during reperfusion using the Langendorff model. Mitochondria were isolated, and the Ca2+resistance capacity (CRC) of the MPTP was determined. Malondialdehyde (MDA) production, caspase-3 activity, and cytochrome c were also assessed. We found that functional recovery was significantly improved in LP hearts with rate-pressure product averaging 30,380 ± 1,757 vs. 18,000 ± 1,599 mmHg/min in NP hearts ( P < 0.01). Necrosis, measured by triphenyltetrazolium chloride staining and creatine kinase leakage, was significantly reduced in LP hearts ( P < 0.01). The CRC was increased in LP heart mitochondria ( P < 0.01). Caspase-3 activity, cytochrome c release, and MDA production were reduced in LP hearts ( P < 0.001 and P < 0.01). This study demonstrated that low-pressure reperfusion after hypothermic heart ischemia improves postischemic contractile dysfunction and attenuates necrosis and apoptosis. This protection could be related to an inhibition of mitochondrial permeability transition.
Effect of pravastatin on left ventricular mass in the two-kidney, one-clip hypertensive rats
Authors: Lee Tsung-Ming , Lin Mei-Shu , Tsai Chang-Her , Chang Nen-Chung
Published: June 2006

We have demonstrated that myocardial ATP-sensitive potassium (KATP) channels are implicated in the development of cardiac hypertrophy in hyperlipidemic rabbits. We investigated the effect of pravastatin on development of ventricular hypertrophy in male normolipidemic Wistar rats with two-kidney, one-clip (2K1C) hypertension and whether the attenuated hypertrophic effect was via activation of KATPchannels. Twenty-four hours after the left renal artery was clipped, rats were treated with one of the following therapies for 8 wk: vehicle, nicorandil (an agonist of KATPchannels), pravastatin, glibenclamide (an antagonist of KATPchannels), hydralazine, nicorandil plus glibenclamide, or pravastatin plus glibenclamide. Systolic blood pressure, relative left ventricular (LV) weight, and cardiomyocyte sizes significantly increased in vehicle-treated 2K1C rats compared with those in sham-operated rats. Treatment with either nicorandil or pravastatin significantly attenuated LV hypertrophy/body weight compared with the vehicle, which was further confirmed by downregulation of LV atrial natriuretic peptide mRNA. Nicorandil-induced effects were abolished by administering glibenclamide. Similarly, pravastatin-induced beneficial effects were reversed by the addition of glibenclamide, implicating KATPchannels as the relevant target. A dissociation between the effects of blood pressure and cardiac structure was noted because pravastatin and hydralazine reduced arterial pressure similarly. These results suggest a crucial role of cardiac KATPchannel system in the development of ventricular hypertrophy in the 2K1C hypertensive rats. Pravastatin is endowed with cardiac antihypertrophic properties probably through activation of KATPchannels, independent of lipid and hemodynamic changes.
Opening mitoKATPincreases superoxide generation from complex I of the electron transport chain
Authors: Andrukhiv Anastasia , Costa Alexandre D. , West Ian C. , Garlid Keith D.
Published: June 2006

Opening the mitochondrial ATP-sensitive K+channel (mitoKATP) increases levels of reactive oxygen species (ROS) in cardiomyocytes. This increase in ROS is necessary for cardioprotection against ischemia-reperfusion injury; however, the mechanism of mitoKATP-dependent stimulation of ROS production is unknown. We examined ROS production in suspensions of isolated rat heart and liver mitochondria, using fluorescent probes that are sensitive to hydrogen peroxide. When mitochondria were treated with the KATPchannel openers diazoxide or cromakalim, their ROS production increased by 40–50%, and this effect was blocked by 5-hydroxydecanoate. ROS production exhibited a biphasic dependence on valinomycin concentration, with peak production occurring at valinomycin concentrations that catalyze about the same K+influx as KATPchannel openers. ROS production decreased with higher concentrations of valinomycin and with all concentrations of a classical protonophoretic uncoupler. Our studies show that the increase in ROS is due specifically to K+influx into the matrix and is mediated by the attendant matrix alkalinization. Myxothiazol stimulated mitoKATP-dependent ROS production, whereas rotenone had no effect. This indicates that the superoxide originates in complex I (NADH:ubiquinone oxidoreductase) of the electron transport chain.
High-fat diet-induced reduction in nitric oxide-dependent arteriolar dilation in rats: role of xanthine oxidase-derived superoxide anion
Authors: Erdei Nóra , Tóth Attila , Pásztor Enikő T. , Papp Zoltán , Édes István , Koller Akos , Bagi Zsolt
Published: June 2006

Obesity frequently leads to the development of hypertension. We hypothesized that high-fat diet (HFD)-induced obesity impairs the endothelium-dependent dilation of arterioles. Male Wistar rats were fed with normal (control) or HFD (60% of saturated fat, for 10 wk). In rats with HFD, body weight, mean arterial blood pressure, and serum insulin, cholesterol, and glucose were elevated. In isolated gracilis muscle arterioles (diameter: ∼160 μm) of HFD, rat dilations to ACh (at 1 μM, maximum: 83 ± 3%) and histamine (at 10 μM, maximum: 16 ± 4%) were significantly ( P < 0.05) decreased compared with those of control responses (maximum: 90 ± 2 and 46 ± 4%, respectively). Dilations to the NO donor sodium nitroprusside were similar in the two groups. Inhibition of NO synthesis by Nω-nitro-l-arginine methyl ester reduced ACh- and histamine-induced dilations in control arterioles but had no effect on microvessels of HFD rats. The superoxide dismutase mimetic Tiron or xanthine oxidase inhibitor allopurinol enhanced ACh (maximum: 90 ± 2 and 93 ± 2%, respectively)- and histamine (maximum: 30 ± 7 and 37 ± 8%, respectively)-induced dilations in HFD arterioles, whereas the NAD(P)H oxidase inhibitor apocynin had no significant effect. Correspondingly, in carotid arteries of HFD rats, an enhanced superoxide production was shown by lucigenin-enhanced chemiluminescence, in association with an increased xanthine oxidase, but not NAD(P)H oxidase activity. In addition, a marked xanthine oxidase immunostaining was detected in the endothelial layer of the gracilis arterioles of HFD, but not in control rats. These findings suggest that, in obese rats, NO mediation of endothelium-dependent dilation of skeletal muscle arterioles is reduced because of an enhanced xanthine oxidase-derived superoxide production. These alterations demonstrate substantial dysregulation of arteriolar tone by the endothelium in HFD-induced obesity, which may contribute to disturbed tissue blood flow and development of increased peripheral resistance.
Enhanced α1-adrenergic trophic activity in pulmonary artery of hypoxic pulmonary hypertensive rats
Authors: Faber James E. , Szymeczek Caroline L. , Salvi Sundeep S. , Zhang Hua
Published: June 2006

Mechanisms that induce the excessive proliferation of vascular wall cells in hypoxic pulmonary hypertension (PH) are not fully understood. Alveolar hypoxia causes sympathoexcitation, and norepinephrine can stimulate α1-adrenoceptor (α1-AR)-dependent hypertrophy/hyperplasia of smooth muscle cells and adventitial fibroblasts. Adrenergic trophic activity is augmented in systemic arteries by injury and altered shear stress, which are key pathogenic stimuli in hypoxic PH, and contributes to neointimal formation and flow-mediated hypertrophic remodeling. Here we examined whether norepinephrine stimulates growth of the pulmonary artery (PA) and whether this is augmented in PH. PA from normoxic and hypoxic rats [9 days of 0.1 fraction of inspired O2(FiO2)] was studied in organ culture, where wall tension, Po2, and Pco2were maintained at values present in normal and hypoxic PH rats. Norepinephrine treatment for 72 h increased DNA and protein content modestly in normoxic PA (+10%, P < 0.05). In hypoxic PA, these effects were augmented threefold ( P < 0.05), and protein synthesis was increased 34-fold ( P < 0.05). Inferior thoracic vena cava from normoxic or hypoxic rats was unaffected. Norepinephrine-induced growth in hypoxic PA was dose dependent, had efficacy greater than or equal to endothelin-1, required the presence of wall tension, and was inhibited by α1A-AR antagonist. In hypoxic pulmonary vasculature, α1A-AR was downregulated the least among α1-AR subtypes. These data demonstrate that norepinephrine has trophic activity in the PA that is augmented by PH. If evident in vivo in the pulmonary vasculature, adrenergic-induced growth may contribute to the vascular hyperplasia that participates in hypoxic PH.
Nitrite as a vascular endocrine nitric oxide reservoir that contributes to hypoxic signaling, cytoprotection, and vasodilation
Authors: Gladwin Mark T. , Raat Nicolaas J. H. , Shiva Sruti , Dezfulian Cameron , Hogg Neil , Kim-Shapiro Daniel B. , Patel Rakesh P.
Published: June 2006

Accumulating evidence suggests that the simple and ubiquitous anion salt, nitrite (NO2−), is a physiological signaling molecule with potential roles in intravascular endocrine nitric oxide (NO) transport, hypoxic vasodilation, signaling, and cytoprotection after ischemia-reperfusion. Human and animal studies of nitrite treatment and NO gas inhalation provide evidence that nitrite mediates many of the systemic therapeutic effects of NO gas inhalation, including peripheral vasodilation and prevention of ischemia-reperfusion-mediated tissue infarction. With regard to nitrite-dependent hypoxic signaling, biochemical and physiological studies suggest that hemoglobin possesses an allosterically regulated nitrite reductase activity that reduces nitrite to NO along the physiological oxygen gradient, potentially contributing to hypoxic vasodilation. An expanded consideration of nitrite as a hypoxia-dependent intrinsic signaling molecule has opened up a new field of research and therapeutic opportunities for diseases associated with regional hypoxia and vasoconstriction.
Comparison of Ca2+-handling properties of canine pulmonary vein and left atrial cardiomyocytes
Authors: Coutu Pierre , Chartier Denis , Nattel Stanley
Published: June 2006

Cardiac tissue in the pulmonary vein sleeves plays an important role in clinical atrial fibrillation. Mechanisms leading to pulmonary vein activity in atrial fibrillation remain unclear. Indirect experimental evidence points to pulmonary vein Ca2+handling as a potential culprit, but there are no direct studies of pulmonary vein cardiomyocyte Ca2+handling in the literature. We used the Ca2+-sensitive dye indo-1 AM to study Ca2+handling in isolated canine pulmonary vein and left atrial myocytes. Results were obtained at 35°C and room temperature in cells from control dogs and in cardiomyocytes from dogs subjected to 7-day rapid atrial pacing. We found that basic Ca2+-transient properties (amplitude: 186 ± 28 vs. 216 ± 25 nM; stimulus to half-decay time: 192 ± 9 vs. 192 ± 9 ms; atria vs. pulmonary vein, respectively, at 1 Hz), beat-to-beat regularity, propensity to alternans, β-adrenergic response (amplitude increase at 0.4 Hz: 96 ± 52 vs. 129 ± 61%), number of spontaneous Ca2+-transient events after Ca2+loading (in normal Tyrode: 0.9 ± 0.2 vs. 1.3 ± 0.2; with 1 μM isoproterenol: 7.6 ± 0.3 vs. 5.1 ± 1.8 events/min), and caffeine-induced Ca2+-transient amplitudes were not significantly different between atrial and pulmonary vein cardiomyocytes. In an arrhythmia-promoting model (dogs subjected to 7-day atrial tachypacing), Ca2+-transient amplitude and kinetics were the same in cells from both pulmonary veins and atrium. In conclusion, the similar Ca2+-handling properties of canine pulmonary vein and left atrial cardiomyocytes that we observed do not support the hypothesis that intrinsic Ca2+-handling differences account for the role of pulmonary veins in atrial fibrillation.
Coronary vasoconstrictor influence of angiotensin II is reduced in remodeled myocardium after myocardial infarction
Authors: Merkus Daphne , Haitsma David B. , Sorop Oana , Boomsma Frans , de Beer Vincent J. , Lamers Jos M. J. , Verdouw Pieter D. , Duncker Dirk J.
Published: June 2006

The renin-angiotensin system plays an important role in cardiovascular homeostasis by contributing to the regulation of blood volume, blood pressure, and vascular tone. Because AT1receptors have been described in the coronary microcirculation, we investigated whether ANG II contributes to the regulation of coronary vascular tone and whether its contribution is altered during exercise. Since the renin-angiotensin system is activated after myocardial infarction, resulting in an increase in circulating ANG II, we also investigated whether the contribution of ANG II to the regulation of vasomotor tone is altered after infarction. Twenty-six chronically instrumented swine were studied at rest and while running on a treadmill at 1–4 km/h. In 13 swine, myocardial infarction was induced by ligation of the left circumflex coronary artery. Blockade of AT1receptors (irbesartan, 1 mg/kg iv) had no effect on myocardial O2consumption but resulted in an increase in coronary venous O2tension and saturation both at rest and during exercise, reflecting coronary vasodilation. Despite increased plasma levels of ANG II after infarction and maintained coronary arteriolar AT1receptor levels, the vasodilation evoked by irbesartan was significantly reduced both at rest and during exercise. In conclusion, despite elevated plasma levels, the vasoconstrictor influence of ANG II on the coronary circulation in vivo is reduced after myocardial infarction. This reduction in ANG II-induced coronary vasoconstriction may serve to maintain perfusion of the remodeled myocardium.
In SHR aorta, calcium ionophore A-23187 releases prostacyclin and thromboxane A2 as endothelium-derived contracting factors
Authors: Gluais Pascale , Paysant Jerôme , Badier-Commander Cécile , Verbeuren Tony , Vanhoutte Paul M. , Félétou Michel
Published: June 2006

In mature spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), acetylcholine and the calcium ionophore A-23187 release endothelium-derived contracting factors (EDCFs), cyclooxygenase derivatives that activate thromboxane-endoperoxide (TP) receptors on vascular smooth muscle. The EDCFs released by acetylcholine are most likely prostacyclin and prostaglandin (PG)H2, whereas those released by A-23187 remain to be identified. Isometric tension and the release of PGs were measured in rings of isolated aortas of WKY and SHR. A-23187 evoked the endothelium-dependent release of prostacyclin, thromboxane A2, PGF2α, PGE2, and possibly PGH2 (PGI2 ≫ thromboxane A2 = PGF2α = PGE2). In SHR aortas, the release of prostacyclin and thromboxane A2 was significantly larger in response to A-23187 than to acetylcholine. In response to the calcium ionophore, the release of thromboxane A2 was significantly larger in aortas of SHR than in those of WKY. In both strains of rat, the inhibition of cyclooxygenase-1 prevented the release of PGs and the occurrence of endothelium-dependent contractions. Dazoxiben, the thromboxane synthase inhibitor, abolished the A-23187-dependent production of thromboxane A2 and inhibited by approximately one-half the endothelium-dependent contractions. U-51605, an inhibitor of PGI synthase, reduced the release of prostacyclin elicited by A-23187 but induced a parallel increase in the production of PGE2 and PGF2α, suggestive of a PGH2 spillover, which was associated with the enhancement of the endothelium-dependent contractions. These results indicate that in the aorta of SHR and WKY, the endothelium-dependent contractions elicited by A-23187 involve the release of thromboxane A2 and prostacyclin with a most likely concomitant contribution of PGH2.
Passive pericardial constraint protects against stretch-induced vulnerability to atrial fibrillation in rabbits
Authors: Ninio Daniel M. , Saint David A.
Published: June 2006

Atrial fibrillation is more common in conditions with elevated atrial pressure and can be induced experimentally with acute increases in atrial pressure. We examined the effect of increased atrial pressure with and without pericardial constraint to better separate the effects of increased pressure and atrial stretch. In Langendorff-perfused rabbit hearts with intact pericardium, after ligating the pulmonary and caval veins, intra-atrial pressures were increased in a stepwise manner by adjusting the pulmonary outflow cannula. Rapid burst pacing was applied to induce atrial fibrillation at increasing intra-atrial pressures from 0 to 24 cmH2O. The atrial refractory period was recorded at each pressure using a single extra stimulus. The protocol was repeated after the pericardium was removed. When the pericardium was intact, atrial stretch was limited by passive constraint, and sustained atrial fibrillation could not be induced despite atrial pressures in excess of 20 cmH2O. In contrast, when the pericardium was removed, atrial fibrillation could be reliably induced when atrial pressure exceeded 15 cmH2O. This suggests that the electrophysiological effects of acute atrial volume loading rely on atrial stretch rather than increased atrial pressure alone.
Upregulation of intermediate-conductance Ca2+-activated K+channel (IKCa1) mediates phenotypic modulation of coronary smooth muscle
Authors: Tharp D. L. , Wamhoff B. R. , Turk J. R. , Bowles D. K.
Published: June 2006

A hallmark of smooth muscle cell (SMC) phenotypic modulation in atherosclerosis and restenosis is suppression of SMC differentiation marker genes, proliferation, and migration. Blockade of intermediate-conductance Ca2+-activated K+channels (IKCa1) has been shown to inhibit restenosis after carotid balloon injury in the rat; however, whether IKCa1 plays a role in SMC phenotypic modulation is unknown. Our objective was to determine the role of IKCa1 channels in regulating coronary SMC phenotypic modulation and migration. In cultured porcine coronary SMCs, platelet-derived growth factor-BB (PDGF-BB) increased TRAM-34 (a specific IKCa1 inhibitor)-sensitive K+current 20-fold; increased IKCa1 promoter histone acetylation and c- jun binding; increased IKCa1 mRNA ∼4-fold; and potently decreased expression of the smooth muscle differentiation marker genes smooth muscle myosin heavy chain (SMMHC), smooth muscle α-actin (SMαA), and smoothelin-B, as well as myocardin. Importantly, TRAM-34 completely blocked PDGF-BB-induced suppression of SMMHC, SMαA, smoothelin-B, and myocardin and inhibited PDGF-BB-stimulated migration by ∼50%. Similar to TRAM-34, knockdown of endogenous IKCa1 with siRNA also prevented the PDGF-BB-induced increase in IKCa1 and decrease in SMMHC mRNA. In coronary arteries from high fat/high cholesterol-fed swine demonstrating signs of early atherosclerosis, IKCa1 expression was 22-fold higher and SMMHC, smoothelin-B, and myocardin expression significantly reduced in proliferating vs. nonproliferating medial cells. Our findings demonstrate that functional upregulation of IKCa1 is required for PDGF-BB-induced coronary SMC phenotypic modulation and migration and support a similar role for IKCa1 in coronary SMC during early coronary atherosclerosis.
SERCA overexpression reduces hydroxyl radical injury in murine myocardium
Authors: Hiranandani Nitisha , Bupha-Intr Tepmanas , Janssen Paul M. L.
Published: June 2006

Hydroxyl radicals (·OH) are involved in the pathogenesis of ischemia-reperfusion injury and are observed in clinical situations, including acute heart failure, stroke, and myocardial infarction. Acute transient exposure to ·OH causes an intracellular Ca2+overload and leads to impaired contractility. We investigated whether upregulation of sarcoplasmic reticulum Ca2+-ATPase function (SERCA) can attenuate ·OH-induced dysfunction. Small, contracting right ventricular papillary muscles from wild-type (WT) SERCA1a-overexpressing (transgenic, TG) and SERCA2a heterogeneous knockout (HET) mice were directly exposed to ·OH. This brief 2-min exposure led to a transient elevation of diastolic force (Fdia) and depression of developed force (Fdev). In WT mice, Fdiaincreased to 485 ± 49% and Fdevdecreased to 11 ± 3%. In sharp contrast, in TG mice Fdiaincreased only to 241 ± 17%, whereas Fdevdecreased only to 51 ± 5% ( P < 0.05 vs. WT). In HET mice, Fdiarose more than WT (to 597 ± 20%, P < 0.05), whereas Fdevwas reduced in a similar amount. After ∼45 min after ·OH exposure, a new steady state was reached: Fdevreturned to 37 ± 6% and 32 ± 6%, whereas Fdiacame back to 238 ± 28% and 292 ± 17% in WT and HET mice, respectively. In contrast, the sustained dysfunction was significantly less in TG mice: Fdiaand Fdevreturned to 144 ± 20% and 67 ± 6%, respectively. Before exposure to ·OH, there is decrease in phospholamban (PLB) phosphorylation at Ser16 (pPLBSer16) and PLB phosphorylation at Thr17 (pPLBThr17) in TG mice and an increase in pPLBSer16 and pPLBThr17 in HET mice versus WT. After exposure to ·OH there is decrease in pPLBSer16 in WT, TG, and HET mice but no significant change in the level of pPLBThr17 in any group. The results indicate that SERCA overexpression can reduce the ·OH-induced contractile dysfunction in murine myocardium, whereas a reduced SR Ca2+-ATPase activity aggravates this injury. Loss of pPLB levels at Ser16 likely amplifies the differences observed in injury response.
Exercise training improves aortic depressor nerve sensitivity in rats with ischemia-induced heart failure
Authors: Rondon Eduardo , Brasileiro-Santos Maria S. , Moreira Edson D. , Rondon Maria U. P. B. , Mattos Katt C. , Coelho Marcele A. , Silva Gustavo J. J. , Brum Patricia C. , Fiorino Patricia , Irigoyen Maria C. , Krieger Eduardo M. , Middlekauff Holly R. , Negrão Carlos E.
Published: June 2006

Exercise training improves arterial baroreflex control in heart failure (HF) rabbits. However, the mechanisms involved in the amelioration of baroreflex control are unknown. We tested the hypothesis that exercise training would increase the afferent aortic depressor nerve activity (AODN) sensitivity in ischemic-induced HF rats. Twenty ischemic-induced HF rats were divided into trained ( n = 11) and untrained ( n = 9) groups. Nine normal control rats were also studied. Power spectral analysis of pulse interval, systolic blood pressure, renal sympathetic nerve activity (RSNA), and AODN were analyzed by means of autoregressive parametric spectral and cross-spectral algorithms. Spontaneous baroreflex sensitivity of heart rate (HR) and RSNA were analyzed during spontaneous variation of systolic blood pressure. Left ventricular end-diastolic pressure was higher in HF rats compared with that in the normal control group ( P = 0.0001). Trained HF rats had a peak oxygen uptake higher than untrained rats and similar to normal controls ( P = 0.01). Trained HF rats had lower low-frequency [1.8 ± 0.2 vs. 14.6 ± 3 normalized units (nu), P = 0.0003] and higher high-frequency (97.9 ± 0.2 vs. 85.0 ± 3 nu, P = 0.0005) components of pulse interval than untrained rats. Trained HF rats had higher spontaneous baroreceptor sensitivity of HR (1.19 ± 0.2 vs. 0.51 ± 0.1 ms/mmHg, P = 0.003) and RSNA [2.69 ± 0.4 vs. 1.29 ± 0.3 arbitrary units (au)/mmHg, P = 0.04] than untrained rats. In HF rats, exercise training increased spontaneous AODN sensitivity toward normal levels (trained HF rats, 1,791 ± 215; untrained HF rats, 1,150 ± 158; and normal control rats, 2,064 ± 327 au/mmHg, P = 0.05). In conclusion, exercise training improves AODN sensitivity in HF rats.
Hypoxia results in an HIF-1-dependent induction of brain-specific aldolase C in lung epithelial cells
Authors: Jean Jyh-Chang , Rich Celeste B. , Joyce-Brady Martin
Published: June 2006

Aldolase C (EC 4.1.2.13 ) is a brain-specific aldolase isoform and a putative target of the transcription factor hypoxia-inducible factor (HIF)-1. We identified aldolase C as a candidate hypoxia-regulated gene in mouse lung epithelial (MLE) cells using differential display. We show that the message accumulates in a robust fashion when MLE cells are exposed to 1% oxygen and is inversely related to oxygen content. Induction in hypoxia is dependent on protein synthesis. We localized a hypoxia-responsive element (HRE) in the aldolase C promoter using a series of deletion and heterologous expression studies. The HRE overlaps with a region of the proximal aldolase C promoter that is also related to its brain-specific expression. The HRE contains an Arnt (HIF-1β) and an HIF-1α site. We show that induction in hypoxia is dependent on the HIF-1 site and that HIF-1α protein is present, by gel-shift assay, within nuclear complexes of MLE cells in hypoxia. Aldolase C mRNA expression is developmentally regulated in the fetal lung, rapidly downregulated in the newborn lung at birth, and inducible in the adult lung when exposed to hypoxia. This pattern of regulation is not seen in the brain. This preservation of this HRE in the promoters of four other species suggests that aldolase C may function as a stress-response gene.
Gene expression profiling identifies regulatory pathways involved in the late stage of rat fetal lung development
Authors: Weng Tingting , Chen Zhongming , Jin Nili , Gao Li , Liu Lin
Published: June 2006

Fetal lung development is a complex biological process that involves temporal and spatial regulations of many genes. To understand the molecular mechanisms of this process, we investigated gene expression profiles of fetal lungs on gestational days 18, 19, 20, and 21, as well as newborn and adult rat lungs. For this analysis, we used an in-house rat DNA microarray containing 6,000 known genes and 4,000 expressed sequence tags (ESTs). Of these, 1,512 genes passed the statistical significance analysis of microarray (SAM) test; an at least twofold change was shown for 583 genes (402 known genes and 181 ESTs) between at least two time points. K-means cluster analysis revealed seven major expression patterns. In one of the clusters, gene expression increased from day 18 to day 20 and then decreased. In this cluster, which contained 10 known genes and 5 ESTs, 8 genes are associated with development. These genes can be integrated into regulatory pathways, including growth factors, plasma membrane receptors, adhesion molecules, intracellular signaling molecules, and transcription factors. Real-time PCR analysis of these 10 genes showed an 88% consistency with the microarray data. The mRNA of LIM homeodomain protein 3a (Lhx3), a transcription factor, was enriched in fetal type II cells. In contrast, pleiotrophin, a growth factor, had a much higher expression in fetal lung tissues than in fetal type II cells. Immunohistochemistry revealed that Lhx3 was localized in fetal lung epithelial cells and pleiotrophin in the mesenchymal cells adjacent to the developing epithelium and blood vessel. Using GenMAPP, we identified four regulatory pathways: transforming growth factor-β signaling, inflammatory response, cell cycle, and G protein signaling. We also identified two metabolic pathways: glycolysis-gluconeogenesis and proteasome degradation. Our results may provide new insights into the complex regulatory pathways that control fetal lung development.
Fetal Haematocrit Is a Determinant of Placental Size in Term Pregnancies
Authors: Chan Karen K.L. , Lao Terence T.
Published: June 2006

Placental size may be influenced by maternal factors, placental function as well as the fetal condition. So far, no studies have examined how the fetal oxygen-carrying capacity or haemoglobin/haematocrit levels would affect placental growth in normal human pregnancies. The aim of this study was to investigate the relationships between placental size and fetal arterial cord blood haemoglobin and haematocrit levels at the time of caesarean delivery. Umbilical arterial cord blood was taken for arterial haemoglobin and haematocrit levels immediately after delivery. The relative placental size (defined by the ratio of placental weight to fetal weight) was inversely correlated with both arterial haemoglobin (r = –0.455, p = 0.001) and haematocrit levels (r = –0.425, p = 0.003) in women who had undergone elective caesarean sections. No significant correlation was found between the relative placental size with other maternal and fetal factors.
Frequency of Hypoferritinemia, Iron Deficiency and Iron Deficiency Anemia in Outpatients
Authors: Akarsu Saadet , Kilic Mehmet , Yilmaz Erdal , Aydin Mustafa , Taskin Erdal , Aygun A. Denizmen
Published: June 2006

The prevalence rates of hypoferritinemia (IDec/one abnormal indicator), iron deficiency (IDef/two abnormal indicators) and iron deficiency anemia (IDA) in children who were referred to the outpatient clinics of the Department of Pediatrics for the first time within 1 month were investigated. Exclusion criteria were iron therapy before and during the study period and a history of chronic illness. Acute-phase reactants, such as erythrocyte sedimentation rate and C-reactive protein levels, were measured in all cases indicative of infectious diseases. Blood samples were obtained from each study patient admitted to the outpatient clinics during the study period. The hospital charts were later further evaluated, and samples of patients with any current illness known to interact with the iron status of the patient were discarded, and patients were contacted to supply new samples about 1 month after treatment of the infection. Thus, in patients with indications of an infection, samples obtained 1 month after treatment were assessed.The children (n = 557) were divided into four age groups: those aged 4 months to 2 years (group I), 2–6 years (group II), 7–12 years (group III) and 12–18 years (group IV). Children with a decrease in serum ferritin levels without anemia (IDec), and those with lower ferritin, transferrin saturation (TS) and serum iron (SI) concentration (IDef) were evaluated. IDA was diagnosed if hemoglobin (Hb) concentrations were lower than those adjusted for age, ferritin <12 ng/ml and TS ≤16% and if SI was decreased. IDec, IDef and IDA were detected in 26, 11.1 and 12.7% of the patients, respectively. Only 50.1% of the patients visiting the outpatient clinics were found to be normal. The rates of IDec (28.9%), IDef (21.9%) and IDA (26.2%) were highest in group I. IDec had the highest percentages in all groups. In group I, the rates of IDec, IDef, and IDA were 37.2, 66.1 and 69%, respectively. SI concentration was abnormal in 77.1% of the cases in group I (4 months to 2 years of age). Half of the patients referred to the outpatient clinics were suffering from abnormalities related to lower SI concentrations. Close monitoring and treatment of iron deficiency is advised especially in early childhood.
Treatment of Iron Deficiency Anemia with Intravenous Iron Preparations
Authors: Akarsu Saadet , Taskin Erdal , Yilmaz Erdal , Yilmaz Huseyin , Kilic Mehmet , Aygun A. Denizmen
Published: June 2006

Objective: We aimed to determine the effects of intravenous iron therapy on blood parameters in pediatric patients who do not tolerate oral iron therapy for any reason. Patients and Methods: The patient group consisted of candidates for elective operations requiring blood transfusions in order to raise hemoglobin (Hb) concentrations rapidly and for whom oral iron administration is useless and compliance with long-term treatment is definitely impossible due to sociocultural factors. Sixty-two children were included in the study. Venous blood samples were taken at diagnosis, and after 1 week and 1, 2 and 3 months. Hb, hematocrit, erythrocyte indices (mean erythrocyte volume, mean erythrocyte Hb and mean erythrocyte Hb concentration), serum iron (SI) levels, iron binding capacity, transferrin receptor (CD71) and serum ferritin levels were measured. Iron sucrose was used as an intravenous iron preparation. Results: All children showed improvements in iron deficiency anemia. A statistically significant elevation occurred between the time of diagnosis and week 1 (p<0.05) in nearly all parameters. SI was raised until at least 1 month of therapy. There was no significant difference between transferrin receptors measured before and after the intravenous iron therapy. Ferritin did not exceed the values achieved in the 1st month. Mild side effects were encountered in only 8 (12.9%) patients. Treatment was not discontinued because of side effects in any case. The patients in the control group were given an oral form containing ferroglycine sulfate. Conclusion: Intravenous iron therapy can replace oral therapy in patients whose blood parameters must be raised rapidly and in situations where oral iron administration would not be appropriate for any reason. However, reinforcement with oral iron therapy or additional intravenous doses would be appropriate.