ABSTRACT
A girl with Angelman syndrome had recurrent episodes of ventricular asystole and syncope caused by severe vagal hypertonia during outbursts of laughing. After intravenous administration of atropine, laughing no longer induced asystole or syncope. The vast majority of patients with Angelman syndrome have seizures. Since hypoxia associated with asystole can provoke convulsions, we suggest electrocardiographic evaluation of Angelman patients with symptomatic bradycardia, loss of consciousness, or convulsions related to laughing.
Subject(s)
Angelman Syndrome/physiopathology , Heart Arrest/physiopathology , Laughter/physiology , Vagus Nerve/physiopathology , Adolescent , Angelman Syndrome/therapy , Atropine/administration & dosage , Electrocardiography/drug effects , Female , Heart Arrest/prevention & control , Humans , Parasympatholytics/administration & dosage , Parasympatholytics/therapeutic use , Vagus Nerve/drug effects , Vasodilator Agents/administration & dosage , Vasodilator Agents/therapeutic useABSTRACT
The heat shock proteins (HSPs) are an important family of endogenous, protective proteins that are found in all tissues. In the heart, HSP72, the inducible form of HSP70, has been the most intensely studied. It is well established that HSP72 is induced with ischemia and is cardioprotective. Overexpression of other HSPs also is protective against cardiac injury. Recently, we observed that 17beta-estradiol increases levels of HSPs in male rat cardiac myocytes. We hypothesized that there were gender differences in HSP72 expression in the heart secondary to estrogen. To test this hypothesis, we examined cardiac levels of HSP72 by ELISA in male and female Sprague-Dawley rats. In addition, three other HSPs were assessed by Western blot (HSP27, HSP60, and HSP90). To determine whether estrogen status affected HSP72 expression in other muscles or tissues, two other muscle tissues, slow twitch muscle (soleus muscle) and fast twitch muscle (gastrocnemius muscle), were studied as well as two other organs, the kidney and liver. Because HSP72 is cardioprotective, and females are known to have less cardiovascular disease premenopause, the effects of ovariectomy were examined. We report that female Sprague-Dawley rat hearts have twice as much HSP72 as male hearts. Ovariectomy reduced the level of HSP72 in female hearts, and this could be prevented by estrogen replacement therapy. These data show that the expression of cardiac HSP72 is greater in female rats than in male rats, due to upregulation by estrogen.
Subject(s)
Estrogens/blood , Heat-Shock Proteins/biosynthesis , Myocardium/metabolism , Sex Characteristics , Animals , Chaperonin 60/biosynthesis , Estrogens/pharmacology , Female , HSP72 Heat-Shock Proteins , HSP90 Heat-Shock Proteins/biosynthesis , Kidney/metabolism , Liver/metabolism , Male , Muscle, Skeletal/metabolism , Ovariectomy , Rats , Rats, Sprague-DawleySubject(s)
Heart Injuries/enzymology , Heart Injuries/prevention & control , Heme Oxygenase (Decyclizing)/metabolism , Myocardium/enzymology , Myocardium/pathology , Animals , Apoptosis , Gene Expression Regulation, Enzymologic , Heart Injuries/metabolism , Heart Injuries/pathology , Heme Oxygenase (Decyclizing)/genetics , Heme Oxygenase-1 , Humans , Membrane Proteins , Signal Transduction , Wound HealingSubject(s)
Heat-Shock Proteins/metabolism , Heat-Shock Response/physiology , Myocardium/metabolism , Animals , Endothelium, Vascular/cytology , Endothelium, Vascular/metabolism , HSP27 Heat-Shock Proteins , HSP72 Heat-Shock Proteins , Myocardial Ischemia/metabolism , Myocardial Reperfusion , Myocardium/cytology , Neoplasm Proteins/metabolism , Rats , Research DesignABSTRACT
HSP70 is known to protect cells against stressful events. In the present study, the hypothesis was investigated that elevated HSP70 levels protect RNA polymerase I during stress, leading to decreased inhibition of ribosomal RNA (rRNA) synthesis and accelerated recovery of protein translation after stress. To this end, transcriptional and translational activity was studied in H9c2 cells during recovery after a severe heat treatment (SHT, 1 h 45 degrees C) in the presence of elevated HSP70 levels. The latter was achieved by heat pretreatment or by adenovirus-mediated hsp70 gene transfer. Rates of transcription and translation were determined by measuring cellular 3H-labelled uridine and leucine incorporation, respectively. The two types of pretreatment did not affect basal rates of transcription and translation, immediately before SHT. During SHT, both transcriptional and translational rates dropped to less than 10% of basal levels in pretreated as well as non-pretreated cells. Two and four h after SHT, both transcriptional and translational rates were significantly higher in HSP70-overexpressing cells compared to non-pretreated cells. However, immediately after SHT, transcription rates were similarly depressed in non-pretreated and pretreated cells, showing that increased levels of HSP70 did not protect RNA polymerase I activity during SHT. Thus, the HSP70-mediated acceleration of translational recovery is not preceded in time by an enhanced recovery of rRNA synthesis. Therefore, the HSP70-mediated early recovery of protein synthesis after heat stress is independent of rRNA synthesis.
Subject(s)
HSP70 Heat-Shock Proteins/metabolism , Protein Biosynthesis , RNA, Ribosomal/biosynthesis , Transcription, Genetic , Adenoviridae/genetics , Adenoviridae/metabolism , Animals , Cell Line , Gene Expression Regulation , Hot Temperature , Rats , Recombinant Fusion Proteins/metabolismABSTRACT
In the eukaryotic cell an intrinsic mechanism is present providing the ability to defend itself against external stressors from various sources. This defense mechanism probably evolved from the presence of a group of chaperones, playing a crucial role in governing proper protein assembly, folding, and transport. Upregulation of the synthesis of a number of these proteins upon environmental stress establishes a unique defense system to maintain cellular protein homeostasis and to ensure survival of the cell. In the cardiovascular system this enhanced protein synthesis leads to a transient but powerful increase in tolerance to such endangering situations as ischemia, hypoxia, oxidative injury, and endotoxemia. These so-called heat shock proteins interfere with several physiological processes within several cell organelles and, for proper functioning, are translocated to different compartments following stress-induced synthesis. In this review we describe the physiological role of heat shock proteins and discuss their protective potential against various stress agents in the cardiovascular system.
Subject(s)
Cardiovascular Diseases/physiopathology , Cardiovascular Physiological Phenomena , Cardiovascular System/metabolism , Cardiovascular System/physiopathology , Heat-Shock Proteins/physiology , Animals , DNA-Binding Proteins/metabolism , Gene Expression Regulation , Heat Shock Transcription Factors , Heat-Shock Proteins/genetics , Humans , Ischemic Preconditioning, Myocardial , Signal Transduction/physiology , Transcription Factors , Transcription, Genetic/physiologyABSTRACT
Prostaglandins of the A-type (PGAs) induce heat shock protein (HSP) synthesis in a wide variety of mammalian cells resulting in protection against cellular stresses. The effect of PGAs on HSP-induction in cardiac myocytes is unknown. Therefore, we investigated the effect of PGA1 on HSP synthesis in adult rat cardiac myocytes. After 24 h of treatment, HSP72 was significantly increased 2.9-, 5.6- and 5.0-fold by PGA1 used at concentrations of 10, 20 or 40 microg/ml, respectively (P<0.05). However, the PGA1-concentration of 40 microg/ml, was found to be cytotoxic as evidenced by the release of LDH. In addition to HSP72, HSP32 was significantly increased by PGA1. The HSP32 induction was more vigorous with a marked increase with only 4 microg/ml of PGA1. No differences in the levels of HSP27, HSP60 or HSP90 were detected. When isolated cardiac myocytes were treated with PGA1, clear activation of heat shock factor (HSF) 1, one of the transcription factors for HSPs, was observed. In addition, another stress-induced transcription factor NFkappaB was also activated by PGA exposure. Despite the significant upregulation of both HSP72 and HSP32 cytoprotective properties against hypoxia and reoxygenation were absent. In conclusion, these experiments show for the first time that PGA1 induces differential expression of heat shock proteins in cardiac myocytes probably mediated through the activation of both HSF1 and NFkappaB.
Subject(s)
DNA-Binding Proteins/biosynthesis , Gene Expression Regulation , Heat-Shock Proteins/biosynthesis , Myocardium/metabolism , NF-kappa B/biosynthesis , Prostaglandins A/pharmacology , Animals , Blotting, Western , Cell Hypoxia/drug effects , Cells, Cultured , Dose-Response Relationship, Drug , Enzyme Activation/drug effects , Heat Shock Transcription Factors , In Vitro Techniques , L-Lactate Dehydrogenase/metabolism , Male , Myocardium/cytology , Prostaglandins A/toxicity , Rats , Rats, Sprague-Dawley , Transcription Factors , Up-RegulationABSTRACT
BACKGROUND: Previously, we have observed that the isolated, erythrocyte-perfused rabbit heart has increased levels of heat-shock protein (HSP) 72 after a mild mechanical stress. We hypothesized that stretch-activated ion channels (SACs) mediated this increase. Methods and Results-- To test this hypothesis, we subjected isolated, perfused rat hearts to mechanical stretch. Gel mobility shift assay showed that heat-shock factor (HSF) was activated in hearts with mechanical stretch, but not in controls. Supershift experiments demonstrated that HSF1 was the transcription factor. Northern blots revealed the concomitant increase in HSP72 mRNA in stretched rat hearts. In a separate set of experiments, gadolinium, an inhibitor of SACs, was added to the perfusate. Gadolinium inhibited the activation of HSF and decreased HSP72 mRNA level. Because gadolinium can inhibit both SACs and L-type calcium channels, we perfused a group of hearts with diltiazem, a specific L-type calcium channel blocker, to eliminate the involvement of L-type calcium channels. Diltiazem failed to inhibit the activation of HSF. CONCLUSIONS: Stretch in the rat heart results in activation of HSF1 and an increase in HSP72 mRNA through SACs. This represents a novel mechanism of HSF activation and may be an important cardiac signaling pathway for hemodynamic stress.
Subject(s)
DNA-Binding Proteins/metabolism , Myocardium/metabolism , Animals , Blotting, Northern , Calcium Channel Blockers/pharmacology , Calcium Channels, L-Type/metabolism , DNA-Binding Proteins/antagonists & inhibitors , Diltiazem/pharmacology , Dose-Response Relationship, Drug , Gadolinium/pharmacology , HSP72 Heat-Shock Proteins , Heat Shock Transcription Factors , Heat-Shock Proteins/genetics , Heat-Shock Proteins/metabolism , In Vitro Techniques , Male , Perfusion , RNA, Messenger/metabolism , Rats , Rats, Sprague-Dawley , Signal Transduction/drug effects , Signal Transduction/physiology , Stress, Mechanical , Transcription Factors , Ventricular Function/drug effects , Ventricular Function/physiologyABSTRACT
We investigated whether the cardioprotection induced by heat stress (HS) pretreatment is associated with mitigation of phospholipid degradation during the ischemic and/or postischemic period. The hearts, isolated from control rats and from heat-pretreated rats (42 degrees C for 15 min) either 30 min (HS0.5-h) or 24 h (HS24-h) earlier, were subjected to 45 min of no-flow ischemia, followed by 45 min of reperfusion. Unesterified arachidonic acid (AA) accumulation was taken as a measure for phospholipid degradation. Significantly improved postischemic ventricular functional recovery was only found in the HS24-h group. During ischemia, AA accumulated comparably in control and both HS groups. During reperfusion in control and HS0.5-h hearts, AA further accumulated (control hearts from 82 +/- 33 to 109 +/- 51 nmol/g dry wt, not significant; HS-0.5h hearts from 52 +/- 22 to 120 +/- 53 nmol/g dry wt; P < 0.05). In contrast, AA was lower at the end of the reperfusion phase in HS24-h hearts than at the end of the preceding ischemic period (74 +/- 18 vs. 46 +/- 23 nmol/g dry wt; P < 0.05). Thus accelerated reperfusion-induced degradation of phospholipids in control hearts is completely absent in HS24-h hearts. Furthermore, the lack of functional improvement in HS0.5-h hearts is also associated with a lack of beneficial effect on lipid homeostasis. Therefore, it is proposed that enhanced membrane stability during reperfusion is a key mediator in the heat-induced cardioprotection.
Subject(s)
Arachidonic Acid/metabolism , Fatty Acids, Nonesterified/metabolism , Myocardial Ischemia/metabolism , Myocardial Reperfusion Injury/metabolism , Myocardial Reperfusion Injury/prevention & control , Myocardium/metabolism , Animals , Biomarkers/analysis , Creatine Kinase/blood , HSP70 Heat-Shock Proteins/metabolism , Heat Stress Disorders , In Vitro Techniques , Male , Myocardial Ischemia/physiopathology , Myocardial Reperfusion , Myocardial Reperfusion Injury/physiopathology , Rats , Rats, Inbred Lew , Reference Values , Ventricular Function, LeftABSTRACT
Heat stress pretreatment of the heart is known to protect this organ against an ischemic/reperfusion insult 24 h later. Degradation of membrane phospholipids resulting in tissue accumulation of polyunsaturated fatty acids, such as arachidonic acid, is thought to play an important role in the multifactorial process of ischemia/reperfusion-induced damage. The present study was conducted to test the hypothesis that heat stress mitigates the postischemic accumulation of arachidonic acid in myocardial tissue, as a sign of enhanced membrane phospholipid degradation. The experiments were performed on hearts isolated from rats either 24 h after total body heat treatment (42 degrees C for 15 min) or 24 h after sham treatment (control). Hearts were made ischemic for 45 min and reperfused for another 45 min. Heat pretreatment resulted in a significant improvement of postischemic hemodynamic performance of the isolated rat hearts. The release of creatine kinase was reduced from 30 +/- 14 (control group) to 17 +/- 5 units/g wet wt per 45 min (heat-pretreated group) (p < or = 0.05). Moreover, the tissue content of the inducible heat stress protein HSP70 was found to be increased 3-fold 24 h after heat treatment. Preischemic tissue levels of arachidonic acid did not differ between heat-pretreated and control hearts. The postischemic ventricular content of arachidonic acid was found to be significantly reduced in heat-pretreated hearts compared to sham-treated controls (6.6 +/- 3.3. vs. 17.8 +/- 12.0 nmol/g wet wt). The findings suggest that mitigation of membrane phospholipid degradation is a potential mechanism of heat stress-mediated protection against the deleterious effects of ischemia and reperfusion on cardiac cells.
Subject(s)
Arachidonic Acid/analysis , Hot Temperature/therapeutic use , Myocardial Ischemia/prevention & control , Myocardial Reperfusion Injury/prevention & control , Stress, Physiological/metabolism , Animals , Creatine Kinase/analysis , Cytoplasm/enzymology , Fatty Acids/analysis , Male , Membrane Lipids/analysis , Myocardium/chemistry , Myocardium/cytology , Myocardium/enzymology , Phospholipids/analysis , Rats , Rats, Inbred LewABSTRACT
Improvement of post-ischemic cardiac function 24 h after heat stress has been attributed to the increased cardiac tissue content of the inducible heat stress protein hsp70. Previous studies indicated that hsp70 is already significantly upregulated a few hours after heat stress. To delineate the relationship between hsp70 tissue content and heat stress-induced cardioprotection in the early time frame after heat stress, if any, post-ischemic functional recovery of isolated, ejecting rat hearts and the actual cardiac hsp70 content were investigated 0.5, 3, 6 and 24 h after heat stress (42 degrees C for 15 min). Recovery (% of pre-ischemic value) of cardiac output, left ventricular developed pressure, and positive and negative left ventricular dP/dtmax was studied during reperfusion after 45 min of global ischemia. Anesthetized non heat-stressed rats served as controls. The recovery of all hemodynamic variables was significantly worse in hearts isolated 30 min after heat stress than in control hearts. When the time interval between heat treatment and the ischemic episode was prolonged, a gradual improvement of post-ischemic functional recovery was observed. Only 24 h after heat treatment functional recovery was significantly better in the heat-stressed than in the control group. Compared to control hearts (0.27+/-0.10 mg/g total protein) cardiac hsp70 content was already significantly increased 0.5 h after heat stress (0.51+/-0.03 mg/g total protein). The cardiac hsp70 content further increased to 0. 70+/-0.11, 0.89+/-0.35 and 1.01+/-0.25 mg/g total protein, at 3, 6 and 24 h after heat stress, respectively. The present findings clearly show that heat stress is associated with a fast rise in the myocardial hsp70 content which, however, is not uniquely correlated with improved ischemia tolerance of the treated hearts, which only occurs 24 h later.
Subject(s)
Hot Temperature/adverse effects , Myocardial Ischemia/physiopathology , Stress, Physiological/physiology , Animals , Coronary Circulation , HSP70 Heat-Shock Proteins/metabolism , Hemodynamics , In Vitro Techniques , Male , Myocardial Ischemia/metabolism , Myocardial Reperfusion Injury/metabolism , Myocardial Reperfusion Injury/physiopathology , Myocardial Reperfusion Injury/prevention & control , Myocardium/metabolism , Rats , Rats, Inbred LewABSTRACT
To explore the effects of heat stress (HS) in aged hypertrophied and nonhypertrophied rat hearts, postischemic recovery was investigated 15 mo after aortic constriction (AoB) or sham operation (Sham). Twenty-four hours after HS (42 degrees C; 15 min) or control treatment (normothermia), global ischemia was induced for 20 min in isolated AoB hearts and for 20 or 30 min in Sham hearts. After HS, postischemic recovery after 20-min ischemia in AoB hearts and 30-min ischemia in Sham hearts, respectively, was significantly better than in corresponding controls. In AoB hearts, cardiac output (CO), left ventricular developed pressure (LVDP), and the positive maximal first derivative of left ventricular pressure (+dP/dtmax) recovered to 33 +/- 26 (means +/- SD), 87 +/- 5, and 72 +/- 12%, respectively, after HS and to 5 +/- 8, 22 +/- 39, and 17 +/- 29% of preischemic values, respectively, in controls. Postischemic arrhythmias were significantly reduced in HS hypertrophied hearts, but creatine kinase (CK) loss was not reduced. In Sham hearts subjected to 30 min ischemia, CO, LVDP, and +dP/dtmax recovered to 20 +/- 20, 75 +/- 8, and 59 +/- 15%, respectively, after HS and to 3 +/- 8, 21 +/- 32, and 16 +/- 32% of preischemic values, respectively, in controls. Duration of arrhythmias and CK loss were not reduced in the heated hearts. When Sham hearts were subjected to only 20-min ischemia, functional recovery was not different in HS and control hearts, indicating that HS pretreatment extends the ischemic interval before irreversible injury occurs in the heart. In all HS Sham hearts, the myocardial 72-kDa HS protein (HSP 70) content was significantly increased. However, in HS AoB hearts, HSP 70 levels were not significantly different from the values in the control hearts. These results indicate that HS pretreatment induces cardioprotection in aged hypertrophied and nonhypertrophied rat hearts, which, however, cannot be unequivocally related to increased HSP 70 tissue contents.
Subject(s)
Cardiomegaly/physiopathology , Coronary Circulation , HSP70 Heat-Shock Proteins/biosynthesis , Heart/physiopathology , Hemodynamics , Hyperthermia, Induced , Myocardial Ischemia/prevention & control , Myocardium/metabolism , Animals , Aorta, Abdominal/physiology , Blood Pressure , Body Weight , Cardiac Output , DNA Primers , Diastole , HSP70 Heat-Shock Proteins/analysis , Heart/physiology , In Vitro Techniques , Male , Myocardial Ischemia/physiopathology , Myocardial Reperfusion , Organ Size , Polymerase Chain Reaction , Rats , Rats, Inbred Lew , Ventricular Function, LeftABSTRACT
The cellular mechanism of heat shock-mediated cardioprotection is still under debate. Because heat pretreatment negatively affects the normoxic left ventricular contractile performance in vitro when the extracellular Ca2+ concentration ([Ca2+]o) is relatively low (0.65-1.25 mM), the intracellular Ca2+ homeostasis was studied in more detail in cardiomyocytes isolated from adult rats 24 h after heat stress (42 degrees C for 15 min) or anesthesia (control). Sensitivity to Ca2+ overload was assessed by exposure to veratridine (quiescent cells) or to [Ca2+]o ranging from 0.125 to 20 mM in quiescent and paced cardiomyocytes. The fraction of irreversibly hypercontracted cells was not different between groups. The fura-2 fluorescence ratio (I340/I380), which was used as a measure for cytoplasmic Ca2+ concentration ([Ca2+]i) in quiescent cells after exposure to [Ca2+]o (0.5-10 mM), was also not different between groups. Myofilament Ca2+ sensitivity was assessed in paced (0.5 Hz) cells by simultaneous measurement of [Ca2+]i transients and cell shortening. At stepwise increases of [Ca2+]o from 1 to 10 mM, these parameters were comparable between groups. The diastolic cell length shortened progressively and equally in both groups after increasing [Ca2+]o. However, within 2 min of return from 10 to 1 mM [Ca2+]o, cells from heat-shocked rats retained the same length, whereas cells from control rats contracted further (P = 0.05). These data suggest that heat stress improves relaxation after challenge with high [Ca2+]o.