Ethanol inhibits electrically-induced calcium transients in isolated rat cardiac myocytes

Alcohol Intake Provoked Cardiomyocyte Apoptosis Via Activating Calcium-Sensing Receptor and Increasing Endoplasmic Reticulum Stress and Cytosolic [Ca2+]i

BACKGROUND

Cardiomyocyte apoptosis plays an important role in alcoholic cardiac injury. However, the association between calcium-sensing receptor (CaSR) and alcohol-induced cardiomyocyte apoptosis remain unclear. Therefore, we investigated the role and its moleculer mechanism of CaSR in rat cardiomyocyte apoptosis induced by alcohol.

METHODS

Alcohol-induced cardiomyocyte apoptosis in vivo and in vitro model of rats were applied in this study. The expression of CaSR, endoplasmic reticulum stress markers and apoptosis were tested by immunohistological staining, western blot, TUNEL and flow cytometry, respectively. [Ca2+]i were detected by confocal laser scanning microscopy.

RESULTS

Compared with the control group, alcohol intake (AI) led to abnormal arrangements of cardiomyocytes and obvious increase of myocardial apoptosis. Moreover, AI also significantly upregulated protein expression of CaSR, GRP94, caspase-12 and CHOP. Alcohol induced apoptosis of cultured cardiomyocytes of rats in a dose-dependent way. Activation of CaSR markedly enhanced cardiomyocyte apoptosis and ERS induced by alcohol, ERS inducer also significantly increased cardiomyocyte apoptosis without activating CaSR. Furthermore, GdCl3 augmented alcohol-induced increase of [Ca2+]i in cardiomyocytes, which was attenuated by NPS2390 but not 4-PBA pre-treatment.

CONCLUSIONS

Alcohol could induce cardiomyocyte apoptosis in rats in vivo and in vitro, which was mediated probably via activating CaSR, and then ERS and the increase of the cytosolic [Ca2+]i. This provides a potential target for preventing cardiomyocyte apoptosis and cardiomyopathy induced by alochol.

Alcoholic cardiomyopathy: What is known and what is not known

Excessive alcohol consumption represents one of the main causes of non-ischemic dilated cardiomyopathy. Alcoholic cardiomyopathy is characterized by dilation and impaired contraction of one or both myocardial ventricles. It represents the final effect of alcohol-induced toxicity to the heart. Several pathophysiological mechanisms have been proposed at the basis of alcohol-induced damage, most of which are still object of research. Unfortunately, symptoms of alcoholic cardiomyopathy are not specific and common to other forms of heart failure and appear when dilatation and systolic dysfunction are consolidated. Thus, early diagnosis is mandatory to prevent the development and progression to heart failure. Although physicians are aware of this disease, several pitfalls in the diagnosis, natural history, prognosis and treatment are still present. The aim of this narrative review is to describe clinical characteristics of alcoholic cardiomyopathy, highlighting the areas of uncertainty.

Myocardial Oxidative Stress and Toxicity Induced by Acute Ethanol Exposure in Mice

Alcoholic cardiomyopathy has been known for a long time, but there is little mechanistic insight into this important clinical problem. The present study was undertaken using a mouse model to test the hypothesis that alcohol exposure induces cardiac injury through induction of oxidative stress. Adult female Friend Virius B-type (FVB) mice were treated with ethanol by gavage at a dose of 5 g/kg. Six hours after the treatment, ethanol-induced myocardial injury was observed, as indicated by a significant increase in serum creatine phosphokinase activity, a common biomarker of myocardial injury, and myocardial ultrastructural alterations, predominantly mitochondrial swelling and cristae disarray and reduction in numbers. The myocardial injury was associated with a significant increase in the myocardial lipid peroxidation, determined by measuring thiobarbituric acid reactive substances (TBARS), and a significant increase in protein oxidation as measured by a protein carbonyl content assay. Acute alcohol exposure decreased glutathione (GSH) content in the heart, more so in the mitochondria than in the cytosol. These alcohol-induced myocardial injuries and oxidative stresses were all significantly inhibited by supplementation with N-acetyl-L-cysteine (NAC) prior to alcohol exposure. However, NAC did not affect the rise in blood alcohol concentrations following alcohol exposure. This study thus demonstrates that acute alcohol administration causes myocardial injury through, at least in part, the induction of oxidative stress. A rapid decrease in mitochondrial GSH content may be partially responsible for the observed mitochondrial damage.

New Treatment Strategies for Alcohol-Induced Heart Damage

High-dose alcohol misuse induces multiple noxious cardiac effects, including myocyte hypertrophy and necrosis, interstitial fibrosis, decreased ventricular contraction and ventricle enlargement. These effects produce diastolic and systolic ventricular dysfunction leading to congestive heart failure, arrhythmias and an increased death rate. There are multiple, dose-dependent, synchronic and synergistic mechanisms of alcohol-induced cardiac damage. Ethanol alters membrane permeability and composition, interferes with receptors and intracellular transients, induces oxidative, metabolic and energy damage, decreases protein synthesis, excitation-contraction coupling and increases cell apoptosis. In addition, ethanol decreases myocyte protective and repair mechanisms and their regeneration. Although there are diverse different strategies to directly target alcohol-induced heart damage, they are partially effective, and can only be used as support medication in a multidisciplinary approach. Alcohol abstinence is the preferred goal, but control drinking is useful in alcohol-addicted subjects not able to abstain. Correction of nutrition, ionic and vitamin deficiencies and control of alcohol-related systemic organ damage are compulsory. Recently, several growth factors (myostatin, IGF-1, leptin, ghrelin, miRNA, and ROCK inhibitors) and new cardiomyokines such as FGF21 have been described to regulate cardiac plasticity and decrease cardiac damage, improving cardiac repair mechanisms, and they are promising agents in this field. New potential therapeutic targets aim to control oxidative damage, myocyte hypertrophy, interstitial fibrosis and persistent apoptosis In addition, stem-cell therapy may improve myocyte regeneration. However, these strategies are not yet approved for clinical use.

Acute effects of ethanol on action potential and intracellular Ca(2+) transient in cardiac ventricular cells: a simulation study

Alcohol consumption may result in electrocardiographic changes and arrhythmias, at least partly due to effects of ethanol on cardiac ionic currents. Contractility and intracellular Ca(2+) dynamics seem to be altered as well. In this study, we integrated the available (mostly animal) experimental data into previously published models of the rat and human ventricular myocytes to assess the share of ionic current components in ethanol-induced changes in AP configuration and cytosolic Ca(2+) transient in ventricular cardiomyocytes. The rat model reproduced well the experimentally observed changes in AP duration (APD) under ethanol (slight prolongation at 0.8 mM and shortening at ≥8 mM). These changes were almost exclusively caused by the ethanol-induced alterations of I K1. The cytosolic Ca(2+) transient decreased gradually with the increasing ethanol concentration as a result of the ethanol-induced inhibition of I Ca. In the human model, ethanol produced a dose-dependent APD lengthening, dominated by ethanol effect on I Kr, the key repolarising current in human ventricles. This effect might contribute to the clinically observed proarrhythmic effects of ethanol in predisposed individuals.

Alcoholic cardiomyopathy

Alcohol is the most frequently consumed toxic substance in the world. Low to moderate daily intake of alcohol has been shown to have beneficial effects on the cardiovascular system. In contrast, exposure to high levels of alcohol for a long period could lead to progressive cardiac dysfunction and heart failure. Cardiac dysfunction associated with chronic and excessive alcohol intake is a specific cardiac disease known as alcoholic cardiomyopathy (ACM). In spite of its clinical importance, data on ACM and how alcohol damages the heart are limited. In this review, we evaluate available evidence linking excessive alcohol consumption with heart failure and dilated cardiomyopathy. Additionally, we discuss the clinical presentation, prognosis and treatment of ACM.

Acute cor pulmonale and right heat failure complicating ethanol ablative therapy: anesthetic and radiologic considerations and management

Ethanol is an effective ablative agent used for the treatment of certain solid organ tumors and vascular malformations (VMs). The egress of ethanol beyond the target tissue can be associated with significant changes to the cardiopulmonary system that can lead to cardiac arrest. This article reviews the contemporary role of ethanol in tumor and VM treatment and discusses the physiological mechanisms of acute pulmonary hypertension and cardiovascular collapse. The importance of periprocedural recognition of the hemodynamic changes that can occur with the use of ethanol and the treatment of this condition are discussed.

Chronic alcohol intake-induced oxidative stress and apoptosis: role of CYP2E1 and calpain-1 in alcoholic cardiomyopathy

Cytochrome P-450 2E1 CYP2E1 induction has been linked to oxidative stress in a number of experimental models. The aim of this study was to investigate the relationship between CYP2E1 activity and markers of oxidative stress and cardiac cell apoptosis during the development of alcoholic cardiomyopathy (ACM). Changes in left ventricular morphology were evaluated in 4 groups of chronically instrumented dogs (control; alcohol-receiving; and alcohol-receiving plus treatment with either valsartan or carnitine) after 6 months of treatment. CYP2E1 and calpain-1 protein expression were determined by Western blotting, and apoptosis evaluated by TUNEL and immunohistochemistry. Malonyl dialdehyde levels were assessed as a marker of oxidative stress, while superoxide dismutase and glutathione peroxidase levels were evaluated as markers of antioxidant defense mechanisms. Expression of CYP2E1 was increased in the alcohol-receiving group compared with controls (P<0.05) and was associated with oxidative stress. Similarly, expression of Bad and calpain-1 protein was increased after chronic alcohol exposure, while Bcl-xL protein expression remained at a low level. Bad and calpain-1 protein expressions were significantly inhibited by treatment with valsartan or carnitine, while expression of Bcl-xL protein was increased (P<0.05). Collectively, our results indicate a possibly significant role for CYP2E1 in the oxidative stress associated with chronic alcoholism. The resulting increase in oxidative stress is accompanied by cellular apoptosis and may ultimately contribute to tissue remodeling and ACM. Importantly, these alcohol-induced effects may be abrogated by means such as angiotensin 1 receptor blockade or carnitine supplementation.

Up-Regulation of Myocardial L-Type Ca2+Channel in Chronic Alcoholic Subjects Without Cardiomyopathy

BACKGROUND

Excessive ethanol intake is one of the most frequent causes of acquired dilated cardiomyopathy in developed countries. L-type Ca(2+) channels, involved in excitation-contraction coupling, are disturbed in animal models of persistent ethanol consumption. This study was designed to evaluate the density and function of myocardial L-type Ca(2+) channel receptors in organ donors with chronic alcoholism and controls.

METHODS

The protein expression of L-type Ca(2+) channels was determined with (3)H-(+)-PN 200-110-binding experiments using a specific antibody against the alpha(1)-subunit in homogenate samples of left-ventricle apex from organ donors: healthy controls (n=11), chronic alcoholic without cardiomyopathy (n=12), and alcoholics with cardiomyopathy (n=11). Morphometric measurements of cardiomyocytes were performed.

RESULTS

Binding experiments proved an up-regulation of L-type Ca(2+) channels expression in alcoholic patients compared with controls (B(max) 2.61 +/- 1.10 vs 1.33 +/- 0.49 fmol/mg, respectively; p<0.001). This up-regulation was present in the group of alcoholic subjects without cardiomyopathy, and was not seen in those with cardiomyopathy (3.39 +/- 2.20 vs 1.77 +/- 0.53 fmol/mg, respectively; p=0.02). The cross-sectional area and perimeter of the cells were greater in alcoholic patients with cardiomyopathy compared with controls and alcoholic patients without cardiomyopathy (500 +/- 87 vs 307 +/- 74 and 255 +/- 25 microm(2), respectively; p<0.001 both) as was the perimeter (78.7 +/- 7.7 vs 61.5 +/- 7.2 and 56.5 +/- 2.8 microm, respectively; p<0.001 both). Binding results did not change after adjusting receptor measurements for cross-sectional area and cell perimeter.

CONCLUSIONS

Chronic alcoholism causes an up-regulation of myocardial L-type Ca(2+) channel receptors, which decreases when cardiomyopathy is present.

Alcohol binge before trauma/hemorrhage impairs integrity of host defense mechanisms during recovery

BACKGROUND

Alcohol abuse, both chronic and acute, is a known modulator of immune function and is associated with increased incidence of traumatic injury. Previously, we demonstrated that acute alcohol intoxication before hemorrhagic shock impairs hemodynamic and neuroendocrine counterregulation, suppresses early lung proinflammatory cytokine expression, and increases mortality from infection during recovery. In the present study, we examined the impact of a 3-day alcohol binge on host responses during trauma/hemorrhage (T x Hem) and following overnight recovery.

METHODS

Chronically catheterized, adult male Sprague-Dawley rats were administered an intragastric bolus of alcohol (5 g/kg; 30% w/v) or isocaloric dextrose solution for 3 consecutive days, followed by a 2.5 g/kg dose on day 4 before undergoing full-thickness muscle-crush and fixed pressure (approximately 40 mmHg) hemorrhage and fluid resuscitation (2.4 x total blood volume removed).

RESULTS

Alcohol-binge produced a 16% decrease in basal mean arterial blood pressure (MABP), reduced the total blood loss required to reach and to sustain MABP of 40 mmHg, markedly blunted the increase in circulating epinephrine and norepinephrine (20-fold and 3-fold, respectively) levels, and increased immediate mortality from T x Hem. Consistent with our previous reports, significant up-regulation in lung and spleen tumor necrosis factor (TNF)-alpha and interleukin (IL)-1alpha expression was observed immediately following T x Hem and fluid resuscitation. Only the T x Hem-induced increase in lung TNF-alpha was prevented by binge alcohol administration. Following overnight recovery, significant lipopolysaccharide (LPS)-stimulated release of TNF-alpha, IL-1alpha, IL-6, and IL-10 was observed in cells isolated from blood and the alveolar and pleural compartments from all experimental groups. While T x Hem did not prevent LPS-induced release of TNF-alpha, IL-1alpha, IL-6, or IL-10 at 6 or 24 hours, alcohol binge suppressed TNF-alpha, IL-1 and IL-6 release, without altering IL-10 response in cells isolated from blood and pleural compartment. No significant modulation of alveolar macrophage response was observed following alcohol binge and T x Hem.

CONCLUSIONS

These results indicate that a 3-day alcohol binge results in hemodynamic instability associated with attenuated neuroendocrine activation and increased mortality during T x Hem as well as sustained suppression of the proinflammatory cytokine response of blood and pleural-derived cells to a "second-hit" inflammatory challenge. As a result, we speculate that the net shift toward an anti-inflammatory state may contribute to enhanced susceptibility to infection during the recovery period.

Biphasic changes in cardiac excitation-contraction coupling early in chronic alcohol exposure

Although the negative inotropic effects of both acute and chronic ethanol (EtOH) exposure are well known, little is known concerning the acute-to-chronic transition of such effects. In this study, our objective was to address this question by detailing the effects that acute EtOH exposure induces on cellular excitation-contraction (EC) coupling and, subsequently, comparing whether and how such changes translate to the early chronic EtOH condition in a rat model known to develop alcohol-induced cardiomyopathy. Acute EtOH exposure, as formerly reported, indeed induced dose-dependent negative inotropic changes in cellular EC coupling, manifest as reductions in cell shortening, Ca2+ transient amplitude, Ca2+ decay rate, and sarcoplasmic reticulum Ca2+ content of isolated rat ventricular cardiac myocytes. Supplementary to this, we found Ca2+ spark character not to be significantly affected by acute EtOH exposure. In contrast, the results obtained from cardiac myocytes isolated from rats fed a diet containing ∼9% (vol/vol) EtOH for 1 mo revealed changes in these parameters reflecting positive inotropy, whereas at 3 mo, these parameters again reflected negative inotropy similar but not identical to that induced by acute EtOH exposure. No significant changes were evident at either 1- or 3-mo chronic EtOH administration in echocardiographic parameters known to be perturbed in alcoholic cardiomyopathy (ACM), thus indicating that we were examining an asymptomatic stage in chronic EtOH administration consistent with an acute-to-chronic transition phase. Continued study of such transition-phase events should provide important insight into which molecular-cellular components of EC coupling play pivotal roles in EtOH-induced disease processes, such as ACM.

ALTERED HEMODYNAMIC COUNTER-REGULATION TO HEMORRHAGE BY ACUTE MODERATE ALCOHOL INTOXICATION

The incidence of traumatic injury, frequently associated with hemorrhagic shock, is higher in the alcohol-intoxicated individual. The outcome, as it pertains to both morbidity and mortality of this population, is partly dependent on duration of alcohol exposure and levels of blood alcohol at time of injury. In previous studies, we demonstrated that prolonged alcohol intoxication (15-h duration) produces marked hemodynamic instability and exacerbated early lung proinflammatory cytokine expression after hemorrhagic shock. The present study examines whether a shorter and more modest period of alcohol intoxication is sufficient to alter hemodynamic and proinflammatory responses to hemorrhagic shock. Chronically instrumented, conscious male Sprague-Dawley rats (250-300 g) received a single intragastric bolus of alcohol (1.75 g/kg) 30 min before the administration of fixed-volume (50%) hemorrhagic shock, followed by fluid resuscitation with Ringer lactate. Time-matched controls were administered on isocaloric dextrose bolus (3 g/kg). Alcohol (blood alcohol concentration, 152 +/- 10 mg/dL) produced a 14% decrease in basal mean arterial blood pressure and a more profound hypotensive response to equal blood loss. The 2-fold rise in circulating norepinephrine levels was similar in alcohol- and dextrose-treated hemorrhaged animals despite greater hypotension in alcohol-treated animals. Significant upregulation in lung and spleen interleukin (IL) 1, IL-6, IL-10, and tumor necrosis factor alpha expression was observed immediately after hemorrhage and fluid resuscitation, as previously reported. Only the hemorrhage-induced rise in lung IL-6 and tumor necrosis factor alpha was prevented by alcohol administration. In contrast, spleen cytokine responses to hemorrhage were not altered by alcohol administration. These results indicate that moderate acute alcohol intoxication results in significant modulation of hemodynamic and neuroendocrine responses to hemorrhagic shock.

Effects of alcohol on intracellular pH regulators and electromechanical parameters in human myocardium

BACKGROUND

Disturbances in intracellular pH (pHi) of the heart can trigger major changes in the strength and rhythm of the heartbeat. It is well known that two extruders, Na+/H+ exchange (NHE) and Na+/HCO3- symporter (NHS), and a monocarboxylic acid transporter (MCT) are involved in acid-equivalent extruding in the human heart. Drinking alcohol has been proven to affect blood pressure and heart contractility and, sometimes, causes cardiac arrhythmia. To assess the effects of alcohol on pHi regulators and electromechanical parameters, various concentrations of alcohol were superfused into human myocardium in the present study.

METHODS

Human atrial myocardium was obtained from hearts of patients undergoing corrective cardiac surgery. Institutional rules for the protection of human subjects were observed. In the whole study, pHi was measured by an epifluorescent, ratiometric microspectrofluorimetry technique with the dye BCECF, while electrophysiological experiments were performed by traditional micropipette. NHE and NHS activities were measured after pHi recovery from intracellular acidosis induced by NH4Cl prepulse, while MCT activity was measured by a lactate adding/removing technique.

RESULTS

In pHi experiments, we demonstrated that alcohol could induce a biphasic, concentration-dependent (30-1000 mM) pHi change (i.e., alkalosis after acidosis) in human atrium in HEPES-buffered Tyrode solution. To a smaller extent, similar results were found when the superfusate was replaced by HCO3- -buffered Tyrode solution. NHE activity was increased by a moderate concentration of alcohol (30 mM), while it was inhibited in a concentration-dependent manner by higher concentrations of alcohol (>100 mM). On the contrary, 30-1000 mM alcohol increased the activity of NHS in a concentration-dependent manner. Surprisingly, MCT activity was not affected by alcohol. In electromechanical experiments, we found that alcohol (30-1000 mM) had a notable concentration-dependent inhibitory effect on the contractile force, while higher concentrations of alcohol (>100 mM) decreased the action potential amplitude, upstroke velocity, duration of repolarization, and force of contractions in a concentration-dependent way. All these alcohol-induced pHi changes and electromechanical inhibitions were reversible.

CONCLUSIONS

To our knowledge, this study provides the first evidence that alcohol can affect pHi in human myocardial tissue by changing the activity of acid extruders (i.e., NHE and NHS).

Cut-off phenomenon in the protective effect of alcohols against lysophosphatidylcholine-induced calcium overload

We studied the effect of chain length on the protective effect of alcohols against lysophosphatidylcholine (LPC)-induced Ca2+ overload in neonatal rat cardiomyocytes. We previously found that ethanol retards Ca2+ elevation. Cells were loaded with the Ca2+-sensitive fluorophore fura-2, and changes in fluorescence were followed. The addition of 10 microM LPC increased Ca2+, which reached a plateau after an 8-10 min delay. The presence of 88 mM n-propanol, n-butanol, tert-butanol, or 2,2-dimethylpropanol significantly increased the delay by 94-213%. However, n-pentanol at 2 mM or 88 mM had no protective effect. Among n-alcohols, the increase in lag time was inversely proportional to the length of the carbon chain. Chain length, rather than molecular weight determines the effect, because 2,2-dimethylpropanol had a protective effect. The influence of alcohols on LPC micelle formation was estimated from the increase in octadecyl rhodamine B fluorescence; the increase by n-alcohols was directly proportional to chain length, indicating that micelle formation was not involved in the extension of lag time. The absence of the protective effect when the alcohol aliphatic chain exceeds four carbons suggests that the effect of ethanol may be mediated via a small lipophilic pocket on a protein, or to lateral pressure perturbation in the membrane.

Effect of ethanol on the electrophysiological characteristics of pulmonary vein cardiomyocytes

Ethanol consumption has been considered to contribute to the occurrences of paroxysmal atrial fibrillation. Pulmonary veins are known to initiate atrial fibrillation. This study investigated whether ethanol may induce atrial fibrillation through increasing arrhythmogenic activity of pulmonary vein cardiomyocytes. Using the whole-cell clamp technique, the action potential and ionic currents were investigated in rabbit single pulmonary vein beating cardiomyocytes with and without (control) incubation of ethanol. Compared with control cardiomyocytes, pulmonary vein cardiomyocytes receiving 0.3 mg/ml or 1 mg/ml ethanol had shorter action potential duration, but had similar beating rates (2.6+/-1.3, 2.7+/-1.2, 2.7+/-1.2 Hz) and incidences (45%, 41%, 32%) of delayed after depolarization. Pulmonary vein cardiomyocytes receiving ethanol had smaller L-type Ca(2+) currents and larger transient outward currents, but had similar transient inward, delayed rectified outward, inward rectified and pacemaker currents. These results suggest that ethanol has no direct effect on the arrhythmogenic potential of pulmonary vein cardiomyocytes.

Alcoholic cardiomyopathy: incidence, clinical characteristics, and pathophysiology

In the United States, in both sexes and all races, long-term heavy alcohol consumption (of any beverage type) is the leading cause of a nonischemic, dilated cardiomyopathy, herein referred to as alcoholic cardiomyopathy (ACM). ACM is a specific heart muscle disease of a known cause that occurs in two stages: an asymptomatic stage and a symptomatic stage. In general, alcoholic patients consuming > 90 g of alcohol a day (approximately seven to eight standard drinks per day) for > 5 years are at risk for the development of asymptomatic ACM. Those who continue to drink may become symptomatic and develop signs and symptoms of heart failure. ACM is characterized by an increase in myocardial mass, dilation of the ventricles, and wall thinning. Changes in ventricular function may depend on the stage, in that asymptomatic ACM is associated with diastolic dysfunction, whereas systolic dysfunction is a common finding in symptomatic ACM patients. The pathophysiology of ACM is complex and may involve cell death (possibly due to apoptosis) and changes in many aspects of myocyte function. ACM remains an important cause of a dilated cardiomyopathy, and in latter stages can lead to heart failure. Alcohol abstinence, as well as the use of specific heart failure pharmacotherapies, is critical in improving ventricular function and outcomes in these patients.

Effect of calcium, Bay K 8644, and reduced perfusion on basic indices of myocardial function in isolated hearts from rats after prolonged exposure to ethanol

We previously reported findings consistent with a marked upregulation in functional L-type voltage-operated calcium channels (L-VOCCs) in hearts obtained from rats exposed over the long term to ethanol. These experiments were undertaken to establish whether detrimental effects on cardiac function were associated with excess calcium entry into the myocardium in these hearts. Isolated hearts from adult male Sprague-Dawley rats received intoxicating concentrations of ethanol for 6-10 days by inhalation, were perfused with Krebs-Henseleit buffer by a modified Langendorff technique, and several functional parameters were assessed continuously. In some experiments, the calcium concentration in the perfusate was first reduced from the physiologic range (1.2 mM) to 0.15 mM and then increased in a step-wise fashion to 4 mM. In other experiments, hearts were exposed to buffer containing concentrations of the L-VOCC activator, (+/-)Bay K 8644, increasing from 10(-9) to 10(-6) M. These perfusion protocols were repeated in hearts from treated animals subject to reduced coronary flow because of induction of partial left ventricular ischemia. There were some close similarities in the effects of these different stimuli. When the calcium concentration in the perfusate exceeded a physiologic level, there were signs of decreased function relative to controls in the hearts from ethanol-exposed rats. Thus R-wave amplitude and systolic pressure were lower, diastolic pressure also was reduced, but heart rate was elevated above that of controls. Similarly the presence of (+/-)Bay K 8644 in the perfusate caused a decrease in systolic and diastolic pressure and an increase in heart rate in hearts from ethanol-exposed rats. When cardiac perfusion was reduced in vitro by inflation of a balloon in the left ventricle, some of the effects of excess calcium and (+/-)Bay K 8644 were reproduced in control hearts. However, imposition of this "ischemic" stress did not appear to exacerbate the effects of prior exposure to ethanol. In general, in control hearts, indices of contractility were increased across the range of calcium concentration or by perfusing with (+/-)Bay K 8644. Hearts from ethanol-exposed rats, however, showed no further increase in these parameters once physiologic levels of calcium were exceeded, or showed inhibition of contractility in the presence of (+/-)Bay K 8644. The results are consistent with calcium entry through L-VOCCs in hearts from ethanol-exposed animals having detrimental effects on cardiac function once physiologic levels are exceeded. However, it is possible that these channels also may be involved in maintenance of cardiac function at hypocalcemic levels.

Cardiovascular effects of alcohol

The ingestion of one or two alcoholic drinks can affect heart rate, blood pressure, cardiac output, myocardial contractility, and regional blood flow. These actions generally are not clinically important. In the presence of cardiovascular disease, however, even such small quantities of alcohol might result in transient unfavorable hemodynamic changes. Moreover, alcohol abuse can produce cardiac arrhythmias, hypertension, cardiomyopathy, stroke, and even sudden death. In contrast, moderate alcohol use produces changes that have an overall favorable effect on atherosclerotic-related vascular diseases. Because cardiovascular disease due to atherosclerosis is the leading cause of death in Western society, this desirable effect of alcohol use outweighs its detrimental actions, resulting in favorable findings in population studies. Nevertheless, the body of evidence argues against encouraging alcohol use for its cardiovascular effects.

Alcohol and heart muscle disease

Ethanol consumption may induce acute and chronic effects on the myocardium. High-dose acute ethanol intake may induce a decrease in myocardial contraction and produce a variety of rhythm disturbances. These effects are more relevant in patients with underlying cardiomyopathy. Chronic ethanol intake may induce the development of a dilated cardiomyopathy, which is clinically and functionally similar to idiopathic dilated cardiomyopathy. Alcoholic cardiomyopathy is potentially reversible with abstinence. The prognosis depends on the persistence or abstinence of ethanol intake. There is a positive correlation between alcoholic cardiomyopathy and the presence of other ethanol-related diseases, such as skeletal myopathy and cirrhosis. In patients with a specific ethanol-related disease, the possible presence of other complications of alcoholism should be ruled out. Although there are several factors potentially implicated in the pathogenesis of alcohol-related myocardial damage, ethanol itself may induce direct myocardial lesions, which are dose-related and independent of nutrition, protein or ionic deficiencies. The most relevant pathogenic studies on alcoholic cardiomyopathy are based on the disruption of membrane permeability and ionic fluxes mediated by ethanol, inducing a decrease in the calcium transients through the sarcolemma and interfering with the excitation-contraction coupling of myocytes. Cell energy depletion or protein-turnover disruption may contribute to the deleterious effect of ethanol on the myocardium.

Influence of age on the inotropic response to acute ethanol exposure in spontaneously hypertensive rats

Acute ethanol exposure depresses cardiac electromechanical function, whereas chronic ethanol consumption leads to the development of a specific myopathic state. Chronic hypertension and aging have similar effects in the impairment of myocardial function. However, little is known about the effects of ethanol on cardiac mechanical function in hypertension. We studied the effect of age on baseline mechanical properties and the inotropic response to clinically relevant concentrations of ethanol (18 to 71 mmol/L) using papillary muscles from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at 10 and 25 weeks of age. Mechanical parameters measured were peak tension developed, time to peak tension, time to 90% relaxation, and maximal velocities of tension development and tension decline. SHR exhibited elevated systolic pressure and body weight as well as cardiomegaly and hepatomegaly at 10 and 25 weeks of age. Baseline mechanical properties were similar in SHR and WKY muscles at 10 weeks, whereas at 25 weeks, SHR muscles developed less tension, and both maximal velocities of tension development and tension decline were markedly depressed. Ethanol exposure produced concentration-dependent negative inotropic effects in both groups at both ages. Ethanol (> 18 nmol/L) decreased peak tension developed in both groups at 10 weeks, although higher concentrations were required at 25 weeks. The negative inotropic effect of ethanol resulted in the shortening of time to 90% relaxation in both groups at 10 weeks and was associated with a slowing of maximal velocities of both tension development and tension decline. The results suggest that aging depresses baseline mechanical properties when coupled with hypertension. In addition, the magnitude of the negative inotropic effect of ethanol was attenuated in both groups at 25 weeks of age.

Beneficial vs. detrimental actions of ethanol on heart and coronary vascular muscle: roles of Mg2+ and Ca2+

Epidemiologic studies suggest that daily ingestion of small amounts of alcohol may protect the heart, whereas higher intake may be detrimental. We studied: 1) cardiac performance, bioenergetics, and [Mg2+]i of isolated working rat hearts during perfusion with Krebs-Henseleit medium containing different concentrations of ethanol (EtOH), 2) mechanical responses. Ca2+ metabolism and Mg content of isolated coronary arteries obtained from dogs, sheep, and piglets subjected to varying concentrations of EtOH and [Mg2+]o and 3) intracellular free Ca2+ of isolated rat cardiac myocytes. In intact hearts, EtOH produced a biphasic hemodynamic change, depending upon concentration; 15 mM EtOH (0.07 g/dl) and 45 mM EtOH (0.21 g/dl) were stimulatory: 90 (0.42 g/dl), 135 (0.63 g/dl), and 170 mM (0.79 g/dl) EtOH were depressive. EtOH 15 and 45 mM increased coronary flow up to 150%, cardiac output up to 130%, stroke volume up to 135%, and oxygen consumption (VO2) up to 130%. However, 90 mM and higher EtOH depressed most hemodynamic parameters (except for heart rate) dose dependently. Lactic acid, lactic acid dehydrogenase, and creatine phosphokinase levels in the perfusate tended to be elevated progressively with increasing duration of EtOH perfusion and pH tended to be reduced (p < 0.05). [31P]NMR spectroscopy on hearts revealed that EtOH > or = 90 mM resulted in rises in Pi/ATP concentration ratio with no significant change in PCr/ATP ratio; [Mg2+]i levels fell and cytosolic pH tended to become slightly acidotic [19F]NMR spectroscopy of isolated myocytes revealed that [Ca2+]i rises at high concentrations of EtOH. With respect to coronary vascular muscle (CVM), low concentrations of EtOH resulted in a concentration-dependent reduction in contractions induced by K+, angiotensin II, and 5-HT; concentration-effect curves were shifted rightward to higher concentrations. Low [Mg2+]o potentiated contractions of CVM induced by EtOH. Low EtOH also resulted in reductions in exchangeable and membrane-bound 45Ca in CVM; medium to high concentrations of EtOH reduced Mg content in CVM and increased 45Ca. In the absence of [Ca2+]o, caffeine and EtOH induced similar, transient contractions followed by relaxation in K(+)-depolarized coronary arterial tissues. EtOH-induced contractions were completely abolished by pretreatment of tissues with caffeine. These results on isolated coronary vessels suggest that in addition to a need for [Ca2+]o, an intracellular release of Ca2+ is needed for EtOH to induce contractions. Overall, the data indicate that low concentrations of EtOH (15, 45 mM) are beneficial on cardiac performance, at least in the intact rat heart and coronary arteries: higher concentrations of EtOH (90, 135 mM) are detrimental. High concentrations of EtOH decrease coronary flow, lead to loss of cellular Mg2+, hypoxia, metabolic acidosis of the myocardium, cell membrane damage, and Ca2+ overload, which could result in cardiac failure. Cellular loss of Mg2+ appears to be causative in the detrimental actions of EtOH on the heart.

Ethanol and cocaine cause additive inhibitory effects on the calcium transients and contraction in single cardiomyocytes

The heart is a major locus for the toxic actions of cocaine and ethanol, each of which has been shown to interfere with excitation-contraction coupling in cardiac muscle cells. Because these drugs are frequently used in combination, the present study was designed to investigate how they interact to modify the Ca2+ transient and associated contraction in fura2-loaded cardiomyocytes. A high-speed imaging technique using a charge-coupled device as detector and short-term image store was used to measure cytosolic Ca2+ and contraction simultaneously from fluorescence images obtained during the contractile cycle. Ethanol (100 mM) and cocaine (50 microM) caused reversible reductions in Ca2+ transient amplitude of 24.3 +/- 3.0% and 25.1 +/- 3.6%, respectively. Neither agent modified basal Ca2+. Ethanol treatment decreased peak shortening by 44.3 +/- 3.5%, whereas the contractile depression by cocaine was 31.4 +/- 5.3%. The relatively greater effect of ethanol on contraction resulted from a Ca2+-independent component of ethanol action on contractility. When cardiomyocytes were exposed simultaneously to ethanol and cocaine, Ca2+ transient amplitude was reduced by 38.7 +/- 3.0%, and peak contraction was decreased by 55.1 +/- 3.5%. These values represent a significantly greater inhibition than observed with either drug alone (p < 0.02) and are compatible with additive effects of the two drugs acting at distinct loci within the excitation-contraction coupling pathway. Thus, simultaneous use of cocaine and ethanol leads to an enhanced depression of myocardial contractility, which is likely to contribute to the cardiotoxic actions of the combination of these two drugs.

Acute and chronic effects of ethanol on papillary muscles from spontaneously hypertensive rats

The effects of chronic ethanol ingestion (12 weeks) on the mechanical properties of hypertrophied papillary muscle and the in vitro effects of ethanol (80-640 mg/dl) was studied. Papillary muscles from spontaneously hypertensive rats (SHRs) and their normotensive controls, the Wistar-Kyoto rat (WKY), were used in this study. Peak-developed tension was significantly less in muscles obtained from SHR compared with WKY even when normalized for muscle cross-sectional area. Chronic ethanol ingestion resulted in a significant shortening of both contraction and relaxation duration in muscles from SHR and WKY. In muscles from SHR and WKY, acute in vitro ethanol exposure produced concentration-dependent negative inotropic effects that were associated with a reduction in the duration of contraction and relaxation and marked slowing in the maximum velocities of tension development and decay. These findings suggest that the contractile response to ethanol exposure, in vitro, is not modified by either chronic ethanol ingestion or hypertension.

Ethanol at pharmacologically relevant concentrations inhibits contractility of isolated smooth muscle cells of cat esophagus

Acute ethanol, in both man and cats, decreases contractility of both lower esophageal sphincter (LES) and smooth muscle portion of the lower esophageal (LE) body. Because these inhibitory effects were not abolished, in cats, by cervical vagotomy or intravenous tetrodotoxin, we surmised a direct inhibitory effect of ethanol on muscle cells. Accordingly, to test this possibility, we exposed isolated, esophageal smooth muscle cells (LES and LE) to ethanol (0-150 mM) for 0 to 40 min, and then a contractile agent, carbachol, or its vehicle was added. Thirty seconds later, cells were fixed and cell shortening was measured as an index of contractility. In the absence of ethanol, carbachol dose-dependently induced shortening of muscle cells from both LE and LES. Ethanol significantly attenuated carbachol-induced maximal shortening of cells from both LE and LES. Potency for carbachol in LES (but not LE) was also decreased by ethanol. Isolated muscle cells remained viable after incubation with ethanol. Thus inhibition by ethanol: can occur directly on esophageal muscle; occurs at pharmacologically relevant ethanol concentrations; and is not simply caused by cytotoxicity of ethanol.

Ethanol inhibits contractility of esophageal smooth muscle strips

Acute ethanol (EtOH) in vivo decreases both the pressure of the lower esophageal sphincter (LES) and the amplitude of contractions of the smooth muscle of the lower esophageal body (LEB) in both man and cat. However, the mechanism of this inhibitory effect of EtOH is unclear. This inhibitory effect could be caused by a direct effect of EtOH on the esophagus or be secondary to known inhibitory effects of EtOH on the central nervous system. To this end, we evaluated the in vitro effect of EtOH on contractility of smooth muscle strips from both LES and LEB. Circular muscle strips from LES and LEB were isolated from cats. Changes in resting tension of LES strips and changes in stimulant-induced tension of LES or LEB strips were measured in the presence of up to five concentrations of EtOH (12.5- 100 mM). Stimulants included electric field stimulation (EFS) and carbachol. EtOH at 75 mM significantly decreased resting LES tension. EtOH also decreased maximal contractile responses to carbachol in both LES and LEB and increased the EC50 of carbachol for LES, but not LEB. EtOH also modulated EFS-induced esophageal contractility; EtOH potentiated EFS-induced "on-response relaxation" in LES and decreased EFS-induced "off-response contractions" In LEB. EtOH-induced inhibition of esophageal contractility seemed to be reversible. EtOH did not result in muscle fatigue. Thus, EtOH can directly inhibit contractility of the esophagus, and does so reversibly and at pharmacologically relevant concentrations.

A new model for the research into rhythmic contraction activity of cardiomyocytes in vitro

Heart cells continue to contract rhythmically after isolation and in culture in vitro. We describe a model of heart preparation in vitro that permits quantitative research on the frequency of contractions of cardiomyocytes. The chick embryo heart explants placed on a network of elastic glass fibers continued beating for months, recorded and analyzed with the methods of computer-assisted image analysis. The efficacy of this experimental model for the screening of effects of various agents on the frequency of contractions was examined by following the effects of nifedipine, caffeine, ethanol, and benzamide. The reversibility of the effects and the reproducibility of results were demonstrated quantitatively. The significance of a mechanical elastic load provided by glass fibers for the preservation of long-lasting contractile activity of cardiomyocytes is discussed and the common occurrence of oscillatory contraction processes in various eucaryotic cells is noted.

Effect of ethanol on function of the rat heart and skeletal muscles

The present study was undertaken to evaluate the acute effects of ethanol on responses of the rat heart and skeletal muscles both in vivo and in vitro. In the anesthetized rat, intravenous infusion of ethanol at 0.1-0.5 g/kg body weight (33-167 mM) decreased the breathing rate by 8-83%, heart rate by 4-52%, and QRS amplitude by 5-27%, and increased the P-R interval by 1-49%. In the anterior tibialis muscle subjected to repetitive nerve stimulation at 100 Hz for 0.5 sec, ethanol at 0.1 g/kg increased the amplitude of the muscle action potential (AP) by 7%, whereas at 0.5 g/kg it decreased the muscle AP by 32%. The nerve-evoked tetanic tension was reduced by 7-34% at 0.1-0.5 g/kg ethanol. In the isolated rat heart, perfusion of ethanol at 0.1-3.0% (22-651 mM) decreased the heart rate by 8-48% and QRS amplitude by 10-39%, and increased the P-R interval by 5-61%. Left ventricular pressure was increased by 10% at 0.1% ethanol, and decreased by 80% at 3.0% ethanol. In the isolated rat phrenic nerve-diaphragm muscle preparation subjected to repetitive nerve stimulation at 100 Hz for 0.5 sec, 0.1-3.0% ethanol decreased the amplitude of the nerve AP by 5-89%, nerve-evoked muscle AP by 2-96%, and peak tetanic tension by 1-87%. On repetitive direct muscle stimulation at 100 Hz for 0.5 sec, 0.1-3.0% ethanol decreased the amplitude of the muscle-evoked muscle AP by 8-65%, and muscle-evoked tetanic tension by 2-65%. These studies indicate that ethanol causes smaller reduction in responses of the heart and skeletal muscles at clinical concentrations, but marked reduction in these responses at higher concentrations due to direct action on excitability of these tissues. At higher concentrations, ethanol causes greater reduction in excitability of the skeletal muscle than of the heart.

Ethanol inhibition of Ca2+ and Na+ currents in the guinea-pig heart

The effects of ethanol on L-type Ca2+ and fast Na+ currents (ICa and INa, respectively) were examined using the whole-cell patch-clamp experiments on guinea-pig ventricular cells. At a clinically relevant concentration of 24 mM, ethanol slightly but significantly shortened the action potential duration, and reduced the ICa by 7 +/- 4% (mean +/- S.D.). This concentration of ethanol did not affect INa, but a lethal concentration of ethanol (80 mM) significantly inhibited INa by 13 +/- 5%. The voltage dependence of INa activation was not affected by ethanol, whereas the inhibitions of ICa by 80 mM ethanol and INa by 240 mM were both accompanied by a several mV shift in the channel availability curve toward more negative potentials, suggesting that the channels in the inactivated state are more susceptible to ethanol. The ICa inhibition by ethanol at clinically relevant concentrations could contribute to a negative inotropic effect, action potential shortening and development of arrhythmias, while the pathophysiological significance of ethanol inhibition of INa seems less important.

Effects of ethanol on the contractile function of the heart: a review

Chronic ethanol consumption leads to a number of alterations in the contractile function of the heart and is a leading cause of cardiomyopathy. Ethanol also has an acute negative inotropic effect mediated by direct interaction with cardiac muscle cells, although this action is often masked by indirect actions resulting from enhanced release of catecholamines in vivo. This article reviews the effects of ethanol on the contractile function of the heart. The specific targets affected by ethanol in cardiac muscle cells are discussed in terms of potential mechanisms underlying the depressions of contractility resulting from both acute and chronic actions of ethanol.

The effect of a range of alcohols on the contraction of guinea-pig ventricular myocytes

Previous results have shown that ethanol and some anaesthetics have a negative inotropic effect on the heart. This study was undertaken to investigate the influence of a range on n-alcohols (with chain lengths from 2 to 8) on contractility in guinea-pig ventricular myocytes. The results demonstrate that the negative inotropic action of alcohols increases dramatically as the chain length increases. The concentration required to reduce the magnitude of contraction to 50% of control (IC50) was 274 mM, 26 mM, 1.4 mM and 235 microM for ethanol, butanol, hexanol and octanol, respectively. The relationship between the logarithm of IC50 and chain length was linear for all the alcohols tested (up to a chain length of 8).

Cardiac inotropic effects of ethanol and calcium-channel modulators

Our objective was to analyze the influence of ethanol ingestion on the in vitro inotropic effects of dihydropyridines alone, or in combination with ethanol, on atrial muscle from rats offered a liquid diet with ethanol ("ethanol rats," ER) or without ethanol ("normal rats," NR). Left atria from NR or ER were superfused with Tyrode's solution (36 degrees C) and driven at 1.5 Hz while recording tension. Bay K 8644 (BAYK) increased, while nimodipine or ethanol decreased, the tension developed and the velocity of development of tension. The preparations recovered rapidly from the effects of ethanol, but not from those of the dihydropyridines. The effects of ethanol and dihydropyridines in combination were the result of the additive or counteractive actions of the drugs. The effects of ethanol and nimodipine on ER preparations were not different from those observed in NR. The action of BAYK was significantly smaller in ER than in NR. In other words, chronic ingestion of ethanol reduced the positive inotropic effect of BAYK, but it did not modify the negative inotropic action of nimodipine or ethanol.

Ethanol decreases cytosolic-free calcium ions in vascular smooth muscle cells as assessed by digital image analysis

Effects of ethanol on intracellular-free Ca2+ concentration in cultured rat aortic smooth muscle cells were examined by digital imaging fluorescence microscopy using the Ca2+ fluorescence indicator, fura-2. Ethanol induced dose-dependent decrements in cytosolic-free Ca2+ concentration at 45 mM and 90 mM, which was consistent with previously reported observations of relaxation in intact rat aortic tissues. However, ethanol at high pharmacological concentrations (e.g., 450 mM) failed to induce any further inhibition in cytosolic-free Ca2+ concentration. Our results suggest that the vasodilator effects of ethanol, observed on intact blood vessels, may result in part from an interference with the availability of Ca2+ for excitation-contraction coupling in vascular smooth muscle cells.

Increased ventricular vulnerability in a chronic ethanol model despite reduced electrophysiologic responses to catecholamines

An increased incidence of sudden death has been reported in chronic alcoholism. To assess electrical vulnerability of the heart, action potential responses, and the role of the sympathetic system, a well-nourished canine model has been studied intact under chloralose anesthesia after 1 year of ethanol consumption at 36% of caloric intake. Two alcoholic groups were compared with controls (Group 1). In Group 2 myocardial vulnerability was assessed after chronic EtOH and superimposed acute administration. In Group 3 basal vulnerability was related to circulating norepinephrine and release of neurohormone from the myocardium. Subsequently the responsiveness to catecholamine infusion was determined. To assess vulnerability an electrode catheter was placed in the right ventricular apex. The basal ventricular fibrillation threshold (VFT) was reduced to 27 +/- 3 ma in Group 2 versus 43 +/- 1.0 in Group 1. Acute infusion of ethanol in Group 2 further reduced the threshold. Group 3 had a reduced basal VFT. Baseline arterial plasma levels of norepinephrine were 8-fold higher and coronary venous levels 13 times higher in the alcoholic group than in Group 1. However, VFT was not responsive to infused epinephrine, compared with Group 1 controls. In vitro study of superfused ventricular tissue from Group 3 revealed that basal action potential amplitude, overshoot, and resting potential were comparable with normals. Basal repolarization time (90%) was 198 +/- 12 msec in Group 3 versus 215 +/- 6 msec in Group 1 (p less than 0.05). After acute EtOH, repolarization time was shortened to 170 +/- 8.6 in Group 1 at 90 mg% ethanol (p less than 0.002), with minimal further change up to 280 mg%.(ABSTRACT TRUNCATED AT 250 WORDS)

Contractile, metabolic and electrophysiologic effects of ethanol in the isolated rat heart

The metabolic, functional and electrical effects of ethanol were studied in the isolated isovolumic rat heart retrogradely perfused at constant flow using phosphorus-31 nuclear magnetic resonance spectroscopy and surface electrogram recordings. Ethanol (0.75 to 6.0 vol%; 128 to 1024 mM) caused a concentration-dependent decline in developed pressure without a change in adenosine triphosphate, phosphocreatine, inorganic phosphate or pH. Ethanol (6%) caused abolition of electrical activity. The functional decline could be rapidly and completely reversed by perfusing with ethanol-free solution and, significantly although not completely, reversed by increasing perfusate calcium to 4 mM. Furthermore, ethanol shifted the perfusate calcium-tetanic pressure relationship in the presence of ryanodine (1 microM) downwards and to the right. The results suggest ethanol's acute effects in this model are not mediated by changes in energy metabolism or cellular pH, but rather by sarcolemmal effects and by a decrease in both myofilament calcium sensitivity and maximal force generating ability.

Inotropic effects of ethanol and dihydropyridines on the guinea pig heart atrial muscle

The effects of ethanol and/or dihydropyridines (DHPs) on force of contraction of atrial muscle were studied. Guinea pig atrial strips superfused with Tyrode's solution (36 degrees C) were driven (1.5 Hz) while recording muscle tension. Bay K 8644 (BAYK) increased, while nimodipine or ethanol reduced, the peak tension developed and the maximum velocity of development of tension. The effects of ethanol were readily reversible, but those of the DHPs were not. The combined actions of ethanol and DHPs were the result of the synergism or antagonism of the drugs tested. The shorter duration of the action of ethanol resulted in the effect of DHPs being still evident well after the exposure to the drugs ended. In summary, ethanol and nimodipine exerted depressant actions on atrial contractile force, while BAYK had opposite effects. The different mechanisms of action may explain the different duration of the effects of ethanol (physical agent) and DHPs (receptor-binding chemicals).