Influence of gender on ethanol-induced ventricular myocyte contractile depression in transgenic mice with cardiac overexpression of alcohol dehydrogenase

Alcohol Use Disorders and Their Harmful Effects on the Contractility of Skeletal, Cardiac and Smooth Muscles

Alcohol misuse has deleterious effects on personal health, family, societal units, and global economies. Moreover, alcohol misuse usually leads to several diseases and conditions, including alcoholism, which is a chronic condition and a form of addiction. Alcohol misuse, whether as acute intoxication or alcoholism, adversely affects skeletal, cardiac and/or smooth muscle contraction. Ethanol (ethyl alcohol) is the main effector of alcohol-induced dysregulation of muscle contractility, regardless of alcoholic beverage type or the ethanol metabolite (with acetaldehyde being a notable exception). Ethanol, however, is a simple and "promiscuous" ligand that affects many targets to mediate a single biological effect. In this review, we firstly summarize the processes of excitation-contraction coupling and calcium homeostasis which are critical for the regulation of contractility in all muscle types. Secondly, we present the effects of acute and chronic alcohol exposure on the contractility of skeletal, cardiac, and vascular/ nonvascular smooth muscles. Distinctions are made between in vivo and in vitro experiments, intoxicating vs. sub-intoxicating ethanol levels, and human subjects vs. animal models. The differential effects of alcohol on biological sexes are also examined. Lastly, we show that alcohol-mediated disruption of muscle contractility, involves a wide variety of molecular players, including contractile proteins, their regulatory factors, membrane ion channels and pumps, and several signaling molecules. Clear identification of these molecular players constitutes a first step for a rationale design of pharmacotherapeutics to prevent, ameliorate and/or reverse the negative effects of alcohol on muscle contractility.

Chronic ethanol vapor exposure potentiates cardiovascular responses to acute stress in male but not in female rats

BACKGROUND

Ethanol use is related to a wide variety of negative health outcomes, including cardiovascular diseases. Stress is also involved in numerous pathologies, such as cardiovascular diseases and psychiatric disorders. Sexual dimorphism is an important factor affecting cardiovascular response and has been proposed as a potential risk factor for sex-specific health problems in humans. Here, we evaluated the effect of prolonged ethanol vapor inhalation on arterial pressure, heart rate, and tail skin temperature responses to acute restraint stress, investigating differences between male and female rats.

METHODS

We exposed male and female Long-Evans rats to ethanol vapor for 14 h, followed by ethanol withdrawal for 10 h, for 30 consecutive days, or to room air (control groups). The animals underwent surgical implantation of a cannula into the femoral artery for assessment of arterial pressure and heart rate values. The tail skin temperature was measured as an indirect measurement of sympathetic vasomotor response.

RESULTS

Chronic ethanol vapor inhalation reduced basal heart rate in both female and male rats. Sex-related difference was observed in the decrease of tail cutaneous temperature evoked by stress, but not in the pressor and tachycardiac responses. Furthermore, prolonged ethanol inhalation enhanced the blood pressure and heart rate increase caused by acute restraint stress in male, but not in female rats. However, no effect of chronic ethanol vapor was observed in the tail cutaneous temperature response to restraint in either sex.

CONCLUSION

Chronic ethanol vapor exposure increased the cardiovascular reactivity to stress in male, but not in female rats.

Minocycline reverses IL-17A/TRAF3IP2-mediated p38 MAPK/NF-κB/iNOS/NO-dependent cardiomyocyte contractile depression and death

Minocycline, an FDA-approved second-generation semisynthetic tetracycline, exerts antioxidant, anti-apoptotic and anti-inflammatory effects, independent of its antimicrobial properties. Interleukin (IL)-17A is an immune and inflammatory mediator, and its sustained induction is associated with various cardiovascular diseases. Here we investigated (i) whether IL-17A induces cardiomyocyte contractile depression and death, (ii) whether minocycline reverses IL-17A's negative inotropic effects and (iii) investigated the underlying molecular mechanisms. Indeed, treatment with recombinant mouse IL-17A impaired adult cardiomyocyte contractility as evidenced by a 34% inhibition in maximal velocity of shortening and relengthening after 4 h (P < .01). Contractile depression followed iNOS induction at 2 h (2.13-fold, P < .01) and NO generation at 3 h (3.71-fold, P <.01). Further mechanistic investigations revealed that IL-17A-dependent induction of iNOS occurred via TRAF3IP2, TRAF6, TAK1, NF-κB, and p38MAPK signaling. 1400 W, a highly specific iNOS inhibitor, suppressed IL-17A-induced NO generation and contractile depression, where as the NO donors SNAP and PAPA-NONOate both suppressed cardiomyocyte contractility. IL-17A also stimulated cardiomyocyte IL-1β and TNF-α secretion, however, their neutralization failed to modulate IL-17A-mediated contractile depression or viability. Further increases of IL-17A concentration and the duration of exposure enhanced IL-1β and TNF-α secreted levels, buthad no impact on adult cardiomyocyte viability. However, when combined with pathophysiological concentrations of IL-1β or TNF-α, IL-17A promoted adult cardiomyocyte death. Importantly, minocycline blunted IL-17A-mediated deleterious effects, indicating its therapeutic potential in inflammatory cardiac diseases.

Sex-specific cardiac phenotype and clinical outcomes in patients with hypertrophic cardiomyopathy

BACKGROUND

It is unknown whether sex-specific differences in mortality observed in HCM are due to older age of women at presentation, or whether women have greater degree of LV myopathy than men.

METHODS

We retrospectively compared clinical/imaging characteristics and outcomes between women and men in our overall cohort composed of 728 HCM patients, and in an age-matched subgroup comprised of 400 age-matched patients. We examined sex-specific differences in LV myopathy, and dissected the influence of age and sex on outcomes. LV myopathy was assessed by measuring LV mass, LVEF, global peak longitudinal systolic strain (LV-GLS), diastolic function (E/A, E/e'), late gadolinium enhancement (LV-LGE) and myocardial blood flow (MBF) at rest/stress. The primary endpoint was a composite outcome, comprising heart failure (HF), atrial fibrillation (AFib), ventricular tachycardia/fibrillation (VT/VF) and death; individual outcomes were defined as the secondary endpoint.

RESULTS

Women in the overall cohort were older by 6 years. Women were more symptomatic and more likely to have obstructive HCM. Women had smaller LV cavity size, stroke volume and LV mass, higher indexed maximum wall thickness (IMWT), more hyperdynamic LVEF and higher/similar LV-GLS. Women had similar LV-LGE and E/A, but higher E/e' and rest/stress MBF. Female sex was independently associated with the composite outcome in the overall cohort, and with HF in the overall cohort and age-matched subgroup after adjusting for obstructive HCM, LA diameter, LV-GLS.

CONCLUSIONS

Our results suggest that sex-specific differences in LV geometry, hyper-contractility and diastolic function, not greater degree of LV myopathy, contribute to a higher, age-independent risk of diastolic HF in women with HCM.

Study of Fecal and Urinary Metabolite Perturbations Induced by Chronic Ethanol Treatment in Mice by UHPLC-MS/MS Targeted Profiling

Alcoholic liver disease (ALD) as a consequence of ethanol chronic consumption could lead to hepatic cirrhosis that is linked to high morbidity and mortality. Disease diagnosis is still very challenging and usually clear findings are obtained in the later stage of ALD. The profound effect of ethanol on metabolism can be depicted using metabolomics; thus, the discovery of novel biomarkers could shed light on the initiation and the progression of the ALD, serving diagnostic purposes. In the present study, Hydrophilic Interaction Liquid Chromatography tandem Mass Spectrometry HILIC-MS/MS based metabolomics analyisis of urine and fecal samples of C57BL/6 mice of both sexes at two sampling time points was performed, monitoring the effect of eight-week ethanol consumption. The altered hepatic metabolism caused by ethanol consumption induces extensive biochemical perturbations and changes in gut microbiota population on a great scale. Fecal samples were proven to be a suitable specimen for studying ALD since it was more vulnerable to the metabolic changes in comparison to urine samples. The metabolome of male mice was affected on a greater scale than the female metabolome due to ethanol exposure. Precursor small molecules of essential pathways of energy production responded to ethanol exposure. A meaningful correlation between the two studied specimens demonstrated the impact of ethanol in endogenous and symbiome metabolism.

Prolonged Exposure to Alcohol Vapor Causes Change in Cardiovascular Function in Female but not in Male Rats

BACKGROUND

Alcohol abuse is a health concern worldwide. Studies have associated alcohol abuse with cardiovascular impairments. In this study, we investigated differences in the effects of chronic alcohol vapor exposure on cardiovascular function between male and female rats by using the alcohol vapor chamber method to induce alcohol addiction-like behaviors in rats.

METHODS

We exposed male and female Long-Evans rats to alcohol vapor for 14 hours, followed by ethanol withdrawal for 10 hours, for 30 consecutive days or room air (control groups). The animals underwent preparation for the surgical implantation of cannulas into femoral vessels, for allowing the assessment of the basal arterial pressure and heart rate values, baroreflex function, and autonomic activity.

RESULTS

Female control rats showed higher basal heart rate compared to male control rats. Chronic alcohol vapor inhalation reduced basal heart rate in females, but not in males; this effect was followed by an increase in the parasympathetic tone of the heart. Further, female rats subjected to alcohol vapor showed an increase in the baroreflex activity.

CONCLUSIONS

These findings suggest that females are more sensitive to chronic alcohol vapor exposure than males because they had a reduction in basal heart rate and changes in the baroreflex activity.

Role of Alcohol Oxidative Metabolism in Its Cardiovascular and Autonomic Effects

Several review articles have been published on the neurobehavioral actions of acetaldehyde and other ethanol metabolites as well as in major alcohol-related disorders such as cancer and liver and lung disease. However, very few reviews dealt with the role of alcohol metabolism in the adverse cardiac and autonomic effects of alcohol and their potential underlying mechanisms, particularly in vulnerable populations. In this chapter, following a brief overview of the dose-related favorable and adverse cardiovascular effects of alcohol, we discuss the role of ethanol metabolism in its adverse effects in the brainstem and heart. Notably, current knowledge dismisses a major role for acetaldehyde in the adverse autonomic and cardiac effects of alcohol because of its low tissue level in vivo. Contrary to these findings in men and male rodents, women and hypertensive individuals are more sensitive to the adverse cardiac effects of similar amounts of alcohol. To understand this discrepancy, we discuss the autonomic and cardiac effects of alcohol and its metabolite acetaldehyde in a model of hypertension, the spontaneously hypertensive rat (SHR) and female rats. We present evidence that enhanced catalase activity, which contributes to cardioprotection in hypertension (compensatory) and in the presence of estrogen (inherent), becomes detrimental due to catalase catalysis of alcohol metabolism to acetaldehyde. Noteworthy, studies in SHRs and in estrogen deprived or replete normotensive rats implicate acetaldehyde in triggering oxidative stress in autonomic nuclei and the heart via (i) the Akt/extracellular signal-regulated kinases (ERK)/nitric oxide synthase (NOS) cascade and (ii) estrogen receptor-alpha (ERα) mediation of the higher catalase activity, which generates higher ethanol-derived acetaldehyde in female heart. The latter is supported by the ability of ERα blockade or catalase inhibition to attenuate alcohol-evoked myocardial oxidative stress and dysfunction. More mechanistic studies are needed to further understand the mechanisms of this public health problem.

Oxidative stress and autonomic dysregulation contribute to the acute time-dependent myocardial depressant effect of ethanol in conscious female rats

BACKGROUND

The molecular mechanisms of the acute hypotensive and indirectly assessed cardiac depressant effect of ethanol (EtOH)-evoked myocardial depression and hypotension in female rats are not known. We tested the hypothesis that a time-dependent myocardial depression caused by EtOH is initiated by its direct and indirect (cardiac vagal dominance) effects and is exacerbated by gradual development of oxidative stress.

METHODS

In conscious female rats, we directly measured left ventricular developed pressure (LVDP), the maximal rise of ventricular pressure over time (dP/dtmax ), blood pressure (BP), heart rate (HR), and sympathovagal activity following intragastric EtOH (1 g/kg) or water over 90 minutes. Catalytic activity of acetaldehyde (ACA)-generating (alcohol dehydrogenase [ADH] and catalase) and eliminating aldehyde dehydrogenase [ALDH2] enzymes along with mediators of oxidative stress were measured in myocardial tissues collected at 30, 60, or 90 minutes after EtOH or water.

RESULTS

EtOH reduced myocardial function (LVDP and dP/dtmax ) within 5 to 10 minutes before the steady fall in BP in conscious proestrus rats. Further, EtOH shifted the sympathovagal balance, analyzed by spectral analysis of high frequency and low frequency of interbeat intervals, toward vagal dominance. Prior vagal blockade (atropine) or antioxidant (tempol) treatment attenuated EtOH-evoked myocardial depression and hypotension. Ex vivo studies revealed time-dependent: (i) enhancement of ADH, but not ALDH2 activity (indicative of elevated ACA levels), (ii) increases in phosphorylated Akt and ERK1/2, NADPH-oxidase activity, reactive oxygen species, malondialdehyde, and 4-hydroxy-2-nonenal-modified proteins. These molecular responses along with reduced myocardial catalase activity were most evident at 90 minutes post-EtOH when the reductions in cardiac function and BP reached their nadir.

CONCLUSIONS

Vagal dominance and time-dependent myocardial oxidative stress along with the accumulation of cardiotoxic aldehydes mediate EtOH-evoked myocardial dysfunction and hypotension in conscious proestrus female rats.

17-β estradiol attenuates ovariectomy-induced changes in cardiomyocyte contractile function via activation of AMP-activated protein kinase

Menopause increases the risk of cardiometabolic diseases in women. This circumstance is usually attributed to a deficiency in circulating estrogen levels although the underlying mechanism remains elusive. Given the pivotal role of AMP-activated protein kinase (AMPK) in the regulation of energy metabolism and cardiac function, this study was designed to examine the role of AMPK in estrogen deficiency and replacement-exerted cardiomyocyte responses. Adult female WT and AMPK kinase dead (KD) mice were subjected to bilateral ovariectomy (OVX) or sham operation. A cohort of ovariectomized mice received 17β-estradiol (E2) (40μg/kg/day, i.p.) for 6 weeks. Mechanical and intracellular Ca(2+) properties were evaluated including peak shortening (PS), time-to-PS (TPS), time-to-90%-relengthening (TR90), and maximal velocity of shortening/relengthening (±dL/dt). Levels of AMPK, Akt JNK, ACC, SERCA, membrane Glut4, AS160 and PGC-1α were assessed using Western blot. OVX significantly decreased PS, ±dL/dt and intracellular Ca(2+) rise in responsible to electric stimulus, prolonged TR90 and intracellular Ca(2+) decay without affecting TPS and resting intracellular Ca(2+), the effects of which were reconciled by E2 replacement. Western blot analysis depicted that OVX suppressed phosphorylation of Akt AMPK and ACC although it promoted JNK phosphorylation, the effects of which were mitigated or significantly attenuated by E2 treatment in WT but not KD mice. Moreover, OVX procedure downregulated SERCA2a and membrane Glut4 while inhibiting AS160 phosphorylation without affecting PGC-1α levels. In vitro study revealed that E2 corrected cardiomyocyte contractile dysfunction elicited by OVX in cardiomyocytes from WT but not the AMPK kinase dead mice. Taken together, these data suggest that E2 treatment ameliorates estrogen deficiency-induced changes in cardiac contractile function possibly through an AMPK-dependent mechanism.

Inhibition of CYP2E1 attenuates chronic alcohol intake-induced myocardial contractile dysfunction and apoptosis

Alcohol intake is associated with myocardial contractile dysfunction and apoptosis although the precise mechanism is unclear. This study was designed to examine the effect of the cytochrome P450 enzyme CYP2E1 inhibition on ethanol-induced cardiac dysfunction. Adult male mice were fed a 4% ethanol liquid or pair-fed control diet for 6weeks. Following 2weeks of diet feeding, a cohort of mice started to receive the CYP2E1 inhibitor diallyl sulfide (100mg/kg/d, i.p.) for the remaining feeding duration. Cardiac function was assessed using echocardiographic and IonOptix systems. Western blot analysis was used to evaluate CYP2E1, heme oxygenase-1 (HO-1), iNOS, the intracellular Ca(2+) regulatory proteins sarco(endo)plasmic reticulum Ca(2+)-ATPase, Na(+)Ca(2+) exchanger and phospholamban, pro-apoptotic protein cleaved caspase-3, Bax, c-Jun-NH(2)-terminal kinase (JNK) and apoptosis signal-regulating kinase (ASK-1). Ethanol led to elevated levels of CYP2E1, iNOS and phospholamban, decreased levels of HO-1 and Na(+)Ca(2+) exchanger, cardiac contractile and intracellular Ca(2+) defects, cardiac fibrosis, overt O(2)(-) production, and apoptosis accompanied with increased phosphorylation of JNK and ASK-1, the effects were significantly attenuated or ablated by diallyl sulfide. Inhibitors of JNK and ASK-1 but not HO-1 inducer or iNOS inhibitor obliterated ethanol-induced cardiomyocyte contractile dysfunction, substantiating a role for JNK and ASK-1 signaling in ethanol-induced myocardial injury. Taken together, these findings suggest that ethanol metabolism through CYP2E1 may contribute to the pathogenesis of alcoholic cardiomyopathy including myocardial contractile dysfunction, oxidative stress and apoptosis, possibly through activation of JNK and ASK-1 signaling.

Insulin-like growth factor I (IGF-1) deficiency ameliorates sex difference in cardiac contractile function and intracellular Ca(2+) homeostasis

Sex difference in cardiac contractile function exists which may contribute to the different prevalence in cardiovascular diseases between genders. However, the precise mechanisms of action behind sex difference in cardiac function are still elusive. Given that sex difference exists in insulin-like growth factor I (IGF-1) cascade, this study is designed to evaluate the impact of severe liver IGF-1 deficiency (LID) on sex difference in cardiac function. Echocardiographic, cardiomyocyte contractile and intracellular Ca(2+) properties were evaluated including ventricular geometry, fractional shortening, peak shortening, maximal velocity of shortening/relengthening (±dL/dt), time-to-peak shortening (TPS), time-to-90% relengthening (TR(90)), fura-fluorescence intensity (FFI) and intracellular Ca(2+) clearance. Female C57 mice exhibited significantly higher plasma IGF-1 levels than their male counterpart. LID mice possessed comparably low IGF-1 levels in both sexes. Female C57 and LID mice displayed lower body, heart and liver weights compared to male counterparts. Echocardiographic analysis revealed larger LV mass in female C57 but not LID mice without sex difference in other cardiac geometric indices. Myocytes from female C57 mice exhibited reduced peak shortening, ±dL/dt, longer TPS, TR(90) and intracellular Ca(2+) clearance compared with males. Interestingly, this sex difference was greatly attenuated or abolished by IGF-1 deficiency. Female C57 mice displayed significantly decreased mRNA and protein levels of Na(+)-Ca(2+) exchanger, SERCA2a and phosphorylated phospholamban as well as SERCA activity compared with male C57 mice. These sex differences in Ca(2+) regulatory proteins were abolished or overtly attenuated by IGF-1 deficiency. In summary, our data suggested that IGF-1 deficiency may significantly attenuated or mitigate the sex difference in cardiomyocyte contractile function associated with intracellular Ca(2+) regulation.

ALDH2 in alcoholic heart diseases: molecular mechanism and clinical implications

Alcoholic cardiomyopathy is manifested as cardiac hypertrophy, disrupted contractile function and myofibrillary architecture. An ample amount of clinical and experimental evidence has depicted a pivotal role for alcohol metabolism especially the main alcohol metabolic product acetaldehyde, in the pathogenesis of this myopathic state. Findings from our group and others have revealed that the mitochondrial isoform of aldehyde dehydrogenase (ALDH2), which metabolizes acetaldehyde, governs the detoxification of acetaldehyde formed following alcohol consumption and the ultimate elimination of alcohol from the body. The ALDH2 enzymatic cascade may evolve as a unique detoxification mechanism for environmental alcohols and aldehydes to alleviate the undesired cardiac anomalies in ischemia-reperfusion and alcoholism. Polymorphic variants of the ALDH2 gene encode enzymes with altered pharmacokinetic properties and a significantly higher prevalence of cardiovascular diseases associated with alcoholism. The pathophysiological effects of ALDH2 polymorphism may be mediated by accumulation of acetaldehyde and other reactive aldehydes. Inheritance of the inactive ALDH2*2 gene product is associated with a decreased risk of alcoholism but an increased risk of alcoholic complications. This association is influenced by gene-environment interactions such as those associated with religion and national origin. The purpose of this review is to recapitulate the pathogenesis of alcoholic cardiomyopathy with a special focus on ALDH2 enzymatic metabolism. It will be important to dissect the links between ALDH2 polymorphism and prevalence of alcoholic cardiomyopathy, in order to determine the mechanisms underlying such associations. The therapeutic value of ALDH2 as both target and tool in the management of alcoholic tissue damage will be discussed.

Sex difference in alcoholism: who is at a greater risk for development of alcoholic complication?

AIMS

Alcohol abuse and alcoholism are among the major medical problems afflicting both men and women. While men display a higher prevalence for alcoholism, it is women who suffer a much greater risk for alcoholism-associated bodily damage. Although women generally consume less alcohol compared to men, females usually suffer more severe brain and other organ damage following binge or chronic alcohol abuse.

MAIN METHODS AND KEY FINDINGS

Although many biological (i.e., genetic risk and neurological abnormalities) and psychosocial (i.e., impact of positive drinking expectancies, personality characteristics and deviance proneness) factors appear to impact men and women equally. These factors especially social and environmental, physiological, genetic and neurobiological ones have been demonstrated to contribute to the sex difference in response to alcohol intake, as well as the development of alcoholic complications. A number of neurotransmitters and growth factors may be partially involved in these differences between men and women. The mesolimbic dopamine system is implicated in the development of addictive behaviors. Differences in dopamine receptor density are found between sexes where gonadal steroid hormones may play a role. Inhibitory GABAergic and stimulatory glutamatergic systems also act as neuromodulators in the brain and differences in their specific receptors have been identified between men and women (particularly GABA(A) receptors and NMDA receptors).

SIGNIFICANCE

Given the variety of factors contributing to the sex difference in response to alcohol intake, alcoholism treatment should take sex dimorphism into consideration. Furthermore, future research needs to be directed towards a better understanding of the mechanism of action of alcohol in both men and women.

Alcohol and acetaldehyde in public health: from marvel to menace

Alcohol abuse is a serious medical and social problem. Although light to moderate alcohol consumption is beneficial to cardiovascular health, heavy drinking often results in organ damage and social problems. In addition, genetic susceptibility to the effect of alcohol on cancer and coronary heart disease differs across the population. A number of mechanisms including direct the toxicity of ethanol, its metabolites [e.g., acetaldehyde and fatty acid ethyl esters (FAEEs)] and oxidative stress may mediate alcoholic complications. Acetaldehyde, the primary metabolic product of ethanol, is an important candidate toxin in developing alcoholic diseases. Meanwhile, free radicals produced during ethanol metabolism and FAEEs are also important triggers for alcoholic damages.

Mechanisms of alcoholic heart disease

Compromised heart function is regularly seen in patients with chronic alcohol ingestion and is often manifested as cardiomegaly, reduced myocardial contractility (with concomitant reductions in ejection fraction and stroke volume), myocardial fibrosis, enhanced risk of stroke and hypertension, and disruptions in the myofibrillary structure. A number of mechanisms including oxidative damage, deposition of triglycerides, altered fatty acid extraction, decreased myofilament Ca(2+) sensitivity, and impaired protein synthesis have been proposed for the development of alcoholic cardiomyopathy. Nonetheless, the underlying mechanism(s) has not been delineated. Several alcohol metabolites have been identified as specific toxins of myocardial tissue, including ethanol, its first and major metabolic product--acetaldehyde--and fatty acid ethyl esters. Acetaldehyde directly impairs cardiac contractile function, disrupts cardiac excitation-contraction coupling and promotes oxidative damage and lipid peroxidation. Unfortunately, the most direct approach to studying this (direct administration of acetaldehyde) is impossible, since direct intake of acetaldehyde is highly toxic and unsuitable for chronic studies. In order to overcome this obstacle, transgenic mice have recently been produced to artificially alter ethanol/acetaldehyde metabolism, resulting in elevated acetaldehyde levels after ethanol ingestion. This review will summarize some of the postulated mechanisms for alcoholic cardiomyopathy, with special emphasis on animal models.

Interaction between high-fat diet and alcohol dehydrogenase on ethanol-elicited cardiac depression in murine myocytes

OBJECTIVE

Consumption of high-fat diet and alcohol is associated with obesity, leading to enhanced morbidity and mortality. This study was designed to examine the interaction between high-fat diet and the alcohol metabolizing enzyme alcohol dehydrogenase (ADH) on ethanol-induced cardiac depression.

RESEARCH METHODS AND PROCEDURES

Mechanical and intracellular Ca2+ properties were measured in cardiomyocytes from ADH transgenic and Friend Virus-B type (FVB) mice fed a low- or high-fat diet for 16 weeks. Expression of protein kinase B (Akt) and Foxo3a, two proteins essential for cardiac survival, was evaluated by Western blot. Cardiac damage was determined by carbonyl formation.

RESULTS

High fat but not ADH induced obesity without hyperglycemia or hypertension, prolonged time-to-90% relengthening (TR90), and depressed peak shortening (PS) and maximal velocity of shortening/relengthening (+/- dL/dt) without affecting intracellular Ca2+ properties. Ethanol suppressed PS and intracellular Ca2+ rise in low-fat-fed FVB mouse cardiomyocytes. ADH but not high-fat diet shifted the threshold of ethanol-induced inhibition of PS and +/- dL/dt to lower levels. The amplitude of ethanol-induced cardiac depression was greater in the high-fat but not the ADH group without additive effects. Ethanol down- and up-regulated Akt and Foxo3a expression, respectively, and depressed intracellular Ca2+ rise, the effects of which were exaggerated by ADH, high-fat, or both. High-fat diet, but not ADH, enhanced Foxo3a expression and carbonyl content in non-ethanol-treated mice. Ethanol challenge significantly enhanced protein carbonyl formation, with the response being augmented by ADH, high-fat, or both.

DISCUSSION

Our data suggest that high-fat diet and ADH transgene may exaggerate ethanol-induced cardiac depression and protein damage in response to ethanol.

Sex dimorphism in cardiac pathophysiology: experimental findings, hormonal mechanisms, and molecular mechanisms

The higher cardiovascular risk in men and post-menopausal women implies a protective action of estrogen. A large number of experimental studies have provided strong support to this concept. However, the recent clinical trials with negative outcomes regarding hormone replacement therapy call for "post hoc" reassessment of existing information, models, and research strategies as well as a summary of recent findings. Sex steroid hormones, in particular estrogen, regulate numerous processes that are related to the development and progression of cardiovascular disease through a variety of signaling pathways. Use of genetically modified models has resulted in interesting information on diverse actions mediated by steroid receptors. By focusing on experimental findings, we have reviewed hormonal, cellular, and signaling mechanisms responsible for sex dimorphism and actions of hormone replacement therapy and addressed current limitations and future directions of experimental research.

Cardiac overexpression of catalase antagonizes ADH-associated contractile depression and stress signaling after acute ethanol exposure in murine myocytes

Alcohol dehydrogenase (ADH), which oxidizes ethanol into acetaldehyde, exacerbates ethanol-induced cardiac depression, although the mechanism of action remains unclear. This study was designed to examine the impact of antioxidant catalase (CAT) on cardiac contractile response to ethanol and activation of stress signaling. ADH-CAT double transgenic mice were generated by crossing CAT and ADH lines. Mechanical, intracellular Ca(2+) properties and reactive oxygen species generation were measured in ventricular myocytes. ADH-CAT, ADH, CAT and wild-type FVB myocytes exhibited similar mechanical and intracellular Ca(2+) properties. ADH or ADH-CAT myocytes had higher acetaldehyde-producing ability. Ethanol (80-640 mg/dl) suppressed FVB cell shortening and intracellular Ca(2+) transients with maximal inhibitions of 43.5 and 45.2%, respectively. Ethanol-induced depression on cell shortening and intracellular Ca(2+) was augmented in ADH group with maximal inhibitions of 66.8 and 69.6%, respectively. Interestingly, myocytes from CAT-ADH mice displayed normal ethanol response with maximal inhibitions of 46.0 and 47.2% for cell shortening and intracellular Ca(2+), respectively. CAT transgene lessened ethanol-induced inhibition on cell shortening (maximal inhibition of 30.3%) but not intracellular Ca(2+). ADH amplified ethanol-induced reactive oxygen species generation, which was nullified by the CAT transgene. Western blot analysis showed that ethanol reduced ERK phosphorylation and enhanced JNK phosphorylation without affecting p38 phosphorylation. The ethanol-induced changes in phosphorylation of ERK and JNK were amplified by ADH. CAT transgene itself did not affect ethanol-induced response in ERK and JNK phosphorylation, but it cancelled ADH-induced effects. These data suggest that antioxidant CAT may effectively antagonize ADH-induced enhanced cardiac depression in response to ethanol.

Ethanol and acetaldehyde in alcoholic cardiomyopathy: from bad to ugly en route to oxidative stress

Alcoholic cardiomyopathy is characterized by cardiomegaly, disruptions of myofibrillary architecture, reduced myocardial contractility, decreased ejection fraction, and enhanced risk of stroke and hypertension. Although several mechanisms have been postulated for alcoholic cardiomyopathy, including oxidative damage, accumulation of triglycerides, altered fatty acid extraction, decreased myofilament Ca(2+) sensitivity, and impaired protein synthesis, neither the mechanism nor the ultimate toxin has been unveiled. Primary candidates acting as specific toxins of myocardial tissue are ethanol; its first and major metabolic product, acetaldehyde; and fatty acid ethyl esters. Acetaldehyde has been demonstrated to impair directly cardiac contractile function, disrupt cardiac excitation-contractile coupling, and contribute to oxidative damage and lipid peroxidation. Acetaldehyde-elicited cardiac dysfunction may be mediated through cytochrome P450 oxidase, xanthine oxidase, and the stress-signaling cascade. Unfortunately, the most direct approach that can be used to examine toxicity is hampered by the fact that direct intake of acetaldehyde is highly toxic and unsuitable for long-term study. To overcome this obstacle, transgenic mice have been used to alter artificially ethanol/acetaldehyde metabolism, resulting in elevated acetaldehyde concentrations after ethanol ingestion. In this review, we summarize results obtained with the use of transgenic animal models to elucidate the role of acetaldehyde in the mechanism of action in alcoholic cardiomyopathy.

Cardiac overexpression of alcohol dehydrogenase exacerbates cardiac contractile dysfunction, lipid peroxidation, and protein damage after chronic ethanol ingestion

BACKGROUND

Alcoholic cardiomyopathy is manifested as ventricular dysfunction, although its specific toxic mechanism remains obscure. This study was designed to examine the impact of enhanced acetaldehyde exposure on cardiac function via cardiac-specific overexpression of alcohol dehydrogenase (ADH) after alcohol intake.

METHODS

ADH transgenic and wild-type FVB mice were placed on a 4% alcohol or control diet for 8 weeks. Mechanical and intracellular Ca2+ properties were evaluated in cardiac myocytes. Levels of acetaldehyde, lipid peroxidation, and protein carbonyl formation were determined.

RESULTS

FVB and ADH mice consuming ethanol exhibited elevated blood ethanol/acetaldehyde, cardiac acetaldehyde, and cardiac hypertrophy compared with non-ethanol-consuming mice. However, the levels of cardiac acetaldehyde and hypertrophy were significantly greater in ADH ethanol-fed mice than FVB ethanol-fed mice. ADH transgene itself did not affect mechanical and intracellular Ca2+ properties with the exception of reduced resting intracellular Ca2+ and Ca2+ re-sequestration at low pace frequency. Myocytes from ethanol-fed mice showed significantly depressed peak shortening, velocity of shortening/relengthening, rise of intracellular Ca2+ transients, and sarco(endo)plasmic reticulum Ca2+ load associated with similar duration of shortening/relengthening compared with myocytes from control mice. Strikingly, the ethanol-induced mechanical and intracellular Ca2+ defects were exacerbated in ADH myocytes compared with the FVB group except velocity of shortening/relengthening. The lipid peroxidation end products malondialdehyde and protein carbonyl formation were significantly elevated in both livers and hearts after chronic ethanol consumption, with the cardiac lipid and protein damage being exaggerated by ADH transgene.

CONCLUSION

These data suggest that increased cardiac acetaldehyde exposure due to ADH transgene may play an important role in cardiac contractile dysfunctions associated with lipid and protein damage after alcohol intake.