Ribose Treatment Reduced the Infarct Size and Improved Heart Function after Myocardial Infarction in Rats

Objective: In this study the effect of ribose on heart function and infarct-size was analyzed 6 h after myocardial infarction (MI) in rats. Methods: Continuous i.v.-infusion of NaCl or ribose (200 mg/ kg/h) was started one day prior to induction of MI in female Sprague-Dawley rats which was done by ligation of the left coronary artery. Six hours after MI heart function was measured with 3F tip catheter, cardiac output by thermodilution method. Thereafter the ischemic area was delineated by Evans Blue infusion, and the infarct area was visualized by triphenyltetrazolium chloride staining. The mRNA expression of interleukin (IL)-1β, IL-6, matrixmetalloproteinase (MMP)-8, and -9 was measured by ribonuclease protection assay. Results: Heart function was severely depressed 6 hours after coronary artery occlusion, but recovered significantly under the influence of ribose. Left ventricular (LV) systolic pressure (LVSP) and contractility (LVdP/dtmax) were restored to the normal levels of sham-operated animals, while parameters of LV relaxation (LVdP/dtmin and time constant of relaxation τ) were impaired compared to sham-operated animals, but significantly improved by ribose treatment compared to shamtreated MI-rats. Moreover, the infarct size was significantly smaller in the ribose treated animals despite a comparable ischemic area at risk in all MI-rats. The cytokine mRNA expression after MI was significantly reduced after ribose treatment, while there were no differences regarding MMP expression. Conclusion: MI size was significantly reduced and LV function significantly improved by ribose treatment at 6 h after MI. This seemed to be based on slowing the velocity of the necrotic wave front across the LV wall after MI resulting in smaller infarcts.Fil: González, Germán Esteban. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiopatología Cardiovascular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rabald, Steffen. University of Leipzig; AlemaniaFil: Briest, Wilfried. University of Leipzig; AlemaniaFil: Gelpi, Ricardo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiopatología Cardiovascular; ArgentinaFil: Seropian, Ignacio Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiopatología Cardiovascular; ArgentinaFil: Zimmer, Heinz Gerd. University of Leipzig; AlemaniaFil: Deten, Alexander. University of Leipzig; Alemani

Specific Mechanisms underlying Right Heart Failure

AIMS: Research into right ventricular (RV) physiology and identification of pathomechanisms underlying RV failure have been neglected for many years because function of the RV is often considered to be less important for overall hemodynamics and maintenance of blood circulation. In view of this, the present study focuses on identifying specific adaptive mechanisms of the right and left ventricle (LV) during a state of chronic nitric oxide (NO) deficiency, one of the main causes of cardiac failure. NO deficiency was induced in rats by L-NAME feeding over a four weeks period. The cardiac remodeling was then characterized separately for the RV/LV using qRT-PCR, histology, and functional measurements. RESULTS: Only the RV underwent remodeling that corresponded morphologically and functionally with the pattern of dilated cardiomyopathy. Symptoms in the LV were subtle and consisted primarily of moderate hypertrophy. A massive increase in reactive oxygen species (ROS) (+4.5+/-0.8 fold, vs. control) and a higher degree of oxidized tropomyosin (+46+/-4% vs. control) and peroxynitrite (+32+/-2% vs. control) could be identified as the cause of both RV fibrosis and contractile dysfunction. The expression of superoxide dismutase-2 was specifically increased in the LV by 51+/-3% and prevented the ROS increase and the corresponding structural and functional remodeling. INNOVATION: This study identified the inability of the RV to increase its antioxidant capacity as an important risk factor for developing RV failure. CONCLUSION: Unlike the LV, the RV did not display the necessary adaptive mechanisms to cope with increased oxidative stress during a state of chronic NO deficiency

Changes in T2 relaxation time after stroke reflect clearing processes

Background and purpose: CT and MR imaging techniques are frequently used for the diagnosis and progress monitoring of ischemic stroke in clinical practice and research. After stroke, both methods are characterized by a transient pseudo-normalized imaging signal, the so-called fogging phenomenon. This study evaluates potential pathophysiological changes associated with fogging, as well as its influence on the correct determination of the ischemic lesion in a rat stroke model. Methods: Male spontaneously hypertensive rats were subjected to permanent middle cerebral artery occlusion. Ischemic lesion volume, brain edema and gray scale value spread within the ischemic lesion were determined on T2-weighted MR sequences at days 1, 4, 8, 11 and 29 after stroke onset, and compared with immunohistochemistry for astrogliosis, microglia/macrophage infiltration and angiogenesis. Results: All animals showed MR fogging at days 4, 8 and 11 after stroke. The transient normalization of T 2 signals occurred independently from the development of infarct volumes, but coincided well with the spatio-temporal occurrence of necrosis, angiogenesis and microglia/macrophage infiltration. Conclusions: Our results suggest that the fogging effect reflects the clearance of necrotic tissue within the ischemic lesion and is thus not relevant for the determination of the lesion volume

Object-based analysis of astroglial reaction and astrocyte subtype morphology after ischemic brain injury

The astrocytic response to ischemic brain injury is characterized by specific alterations of glial cell morphology and function. Various studies described both beneficial and detrimental aspects of activated astrocytes, suggesting the existence of different subtypes. We investigated this issue using a novel object-based approach to study characteristics of astrogliosis after stroke. Spontaneously hypertensive rats received permanent middle cerebral artery occlusion. After 96 h, brain specimens were removed, fixed and stained for GFAP, glutamine synthetase (GS), S100Beta and Musashi1 (Msh1). Three regions of interest were defined (contralateral hemisphere, ipsilateral remote zone and infarct border zone), and confocal stacks were acquired (n=5 biological with each n=4 technical replicates). The stacks were background-corrected and colocalization between the selected markers and GFAP was determined using an automated thresholding algorithm. The fluorescence and colocalization channels were then converted into 3D-objects using both intensity and volume as filters to ultimately determine the final volumes of marker expression and colocalization, as well as the morphological changes of astrocyte process arborisation. We found that both S100Beta and Msh1 determined the same GFAP-positive astroglial cell population albeit the cellular compartments differed. GFAP stained most of the astrocyte processes and is hence suitable for the analysis of qualitative characteristics of astrogliosis. Due to its peri-nuclear localization, Msh1 is appropriate to estimate the total number of astrocytes even in regions with severe reactive astrogliosis. GS expression in GFAP-positive astrocytes was high in the remote zone and low at the infarct border, indicating the existence of astrocyte subclasses

Object-based analysis of astroglial reaction and astrocyte subtype morphology after ischemic brain injury

The astrocytic response to ischemic brain injury is characterized by specific alterations of glial cell morphology and function. Various studies described both beneficial and detrimental aspects of activated astrocytes, suggesting the existence of different subtypes. We investigated this issue using a novel object-based approach to study characteristics of astrogliosis after stroke. Spontaneously hypertensive rats received permanent middle cerebral artery occlusion. After 96 h, brain specimens were removed, fixed and stained for GFAP, glutamine synthetase (GS), S100Beta and Musashi1 (Msh1). Three regions of interest were defined (contralateral hemisphere, ipsilateral remote zone and infarct border zone), and confocal stacks were acquired (n=5 biological with each n=4 technical replicates). The stacks were background-corrected and colocalization between the selected markers and GFAP was determined using an automated thresholding algorithm. The fluorescence and colocalization channels were then converted into 3D-objects using both intensity and volume as filters to ultimately determine the final volumes of marker expression and colocalization, as well as the morphological changes of astrocyte process arborisation. We found that both S100Beta and Msh1 determined the same GFAP-positive astroglial cell population albeit the cellular compartments differed. GFAP stained most of the astrocyte processes and is hence suitable for the analysis of qualitative characteristics of astrogliosis. Due to its peri-nuclear localization, Msh1 is appropriate to estimate the total number of astrocytes even in regions with severe reactive astrogliosis. GS expression in GFAP-positive astrocytes was high in the remote zone and low at the infarct border, indicating the existence of astrocyte subclasses

Continuous adenosine A(2A) receptor antagonism after focal cerebral ischemia in spontaneously hypertensive rats

Antagonism of the adenosine A(2A) receptor (A(2A)R) has been shown to elicit substantial neuroprotective properties when given immediately after cerebral ischemia. We asked whether the continuous application of a selective A(2A)R antagonist within a clinically relevant time window will be a feasible and effective approach to treat focal cerebral ischemia. To answer this question, we subjected 20 male spontaneously hypertensive rats to permanent middle cerebral artery occlusion and randomized them equally to a verum and a control group. Two hours after stroke onset, the animals received a subcutaneous implantation of an osmotic minipump filled with 5 mg kg(-1) day(-1) 8-(3-chlorostyryl) caffeine (CSC) or vehicle solution. The serum level of CSC was measured twice a day for three consecutive days. The infarct volume was determined at days 1 and 3 using magnetic resonance imaging. We found the serum level of CSC showing a bell-shaped curve with its maximum at 36 h. The infarct volume was not affected by continuous CSC treatment. These results suggest that delayed and continuous CSC application was not sufficient to treat acute ischemic stroke, potentially due to unfavorable hepatic elimination and metabolization of the pharmaceutical

Astrocytic mitochondrial membrane hyperpolarization following extended oxygen and glucose deprivation

Astrocytes can tolerate longer periods of oxygen and glucose deprivation (OGD) as compared to neurons. The reasons for this reduced vulnerability are not well understood. Particularly, changes in mitochondrial membrane potential (Δψm) in astrocytes, an indicator of the cellular redox state, have not been investigated during reperfusion after extended OGD exposure. Here, we subjected primary mouse astrocytes to glucose deprivation (GD), OGD and combinations of both conditions varying in duration and sequence. Changes in Δψm, visualized by change in the fluorescence of JC-1, were investigated within one hour after reconstitution of oxygen and glucose supply, intended to model in vivo reperfusion. In all experiments, astrocytes showed resilience to extended periods of OGD, which had little effect on Δψm during reperfusion, whereas GD caused a robust Δψm negativation. In case no Δψm negativation was observed after OGD, subsequent chemical oxygen deprivation (OD) induced by sodium azide caused depolarization, which, however, was significantly delayed as compared to normoxic group. When GD preceded OD for 12 h, Δψm hyperpolarization was induced by both GD and subsequent OD, but significant interaction between these conditions was not detected. However, when GD was extended to 48 h preceding OGD, hyperpolarization enhanced during reperfusion. This implicates synergistic effects of both conditions in that sequence. These findings provide novel information regarding the role of the two main substrates of electron transport chain (glucose and oxygen) and their hyperpolarizing effect on Δψm during substrate deprivation, thus shedding new light on mechanisms of astrocyte resilience to prolonged ischemic injury

Crucial role of interleukin-6 in the development of norepinephrine-induced left ventricular remodeling in mice

BACKGROUND: Elevated serum concentration of interleukin (IL)-6 is a predictor for poor prognosis in congestive heart failure. It was shown previously in rats, that IL-6 expression in the left ventricle (LV) was followed by LV hypertrophy. METHODS: Using IL-6 deficient mice (IL-6(-/-)), we studied the role of IL-6 in a model of norepinephrine (NE)-induced LV hypertrophy. RESULTS: In wild type (WT) mice, IL-6 mRNA expression and its concentration in the serum were elevated after 4 h of NE-treatment (s.c. 0.25 mg.h)./kg Further, NE-induced LV hypertrophy was detected: LV weight/body weight (LVW/BW) ratio (+12.3+/-3%, p < 0.05) and mRNA expression of atrial natriuretic peptide (ANP) in WT mice (+120+/-25%, p < 0.05) after 3 days were increased. In contrast, NE did not induce elevation of LVW/BW ratio and ANP expression in IL-6(-/-) mice. Replacement with recombinant IL-6 restored the hypertrophy-inducing effect of NE in IL-6(-/-) mice. As to the extracellular matrix (ECM) proteins, NE increased collagen type I and III expression only in WT mice and not in IL-6(-/-) mice. The addition of recombinant IL-6 elevated the expression of the ECM proteins to the WT level. CONCLUSION: IL-6 is a major player in the development of NE-induced LV hypertrophy in mice