Morphometric and biochemical characteristics of short-term effects of ethanol on rat cardiac muscle

Assessing Drug-Induced Mitochondrial Toxicity in Cardiomyocytes: Implications for Preclinical Cardiac Safety Evaluation

Drug-induced cardiotoxicity not only leads to the attrition of drugs during development, but also contributes to the high morbidity and mortality rates of cardiovascular diseases. Comprehensive testing for proarrhythmic risks of drugs has been applied in preclinical cardiac safety assessment for over 15 years. However, other mechanisms of cardiac toxicity have not received such attention. Of them, mitochondrial impairment is a common form of cardiotoxicity and is known to account for over half of cardiovascular adverse-event-related black box warnings imposed by the U.S. Food and Drug Administration. Although it has been studied in great depth, mitochondrial toxicity assessment has not yet been incorporated into routine safety tests for cardiotoxicity at the preclinical stage. This review discusses the main characteristics of mitochondria in cardiomyocytes, drug-induced mitochondrial toxicities, and high-throughput screening strategies for cardiomyocytes, as well as their proposed integration into preclinical safety pharmacology. We emphasize the advantages of using adult human primary cardiomyocytes for the evaluation of mitochondrial morphology and function, and the need for a novel cardiac safety testing platform integrating mitochondrial toxicity and proarrhythmic risk assessments in cardiac safety evaluation.

Abstinence from alcohol consumption and exercise capacity: A pre and post intervention cohort study

The benefits or harm associated with moderate levels of alcohol consumption on cardiorespiratory fitness are unclear. We hypothesised that in moderate drinkers, four weeks of abstinence could improve cardiorespiratory fitness. This was a single centre, prospective, pre and post intervention, experimental cohort study. Participants were recruited from healthy volunteers among hospital staff, who were non-smokers, over 25 years of age and regularly consumed ≥3 units of alcohol a day, ≥4 times a week for > 1 month. Cardiopulmonary exercise test was used to provide objective, quantifiable and reproducible data. In all, 30 participated, and data were analysed for 22 participants. Mean (SD) peak oxygen consumption and oxygen consumption at anaerobic threshold were similar before and after alcohol abstinence: 37.55 (10.89) and 39.66 (11.48) (P = 0.21) and 18.52 (5.43) and 16.82 (5.19) ml/kg/min (P = 0.1), respectively. It is concluded that this preliminary study did not establish a correlation between four weeks alcohol abstinence and cardiopulmonary fitness as measured by cardiopulmonary exercise test, among healthy volunteers self-reporting moderate alcohol consumption.

Long-term consumption of energy drinks induces biochemical and ultrastructural alterations in the heart muscle

OBJECTIVE

Energy drinks (EDs) target young and active individuals and they are being marketed as enhancers of energy, concentration, and physical and cognitive performance. Their long-term consumption raises serious health concerns related to cardiovascular events. Here we investigate the effects of long-term Red Bull® consumption and its combination with alcohol on certain biochemical parameters and the ultrastructure of the myocardium.

METHODS

Male Wistar rats were categorized into four groups and given different treatments via oral administration. The Control (C) group received tap water, the Red Bull (RB) group received 1.5 ml/100 g body weight of Red Bull, the ethanol group (E) received 0.486 mg/100 g body weight of ethanol, and the Red Bull and ethanol (RBE) received a combination of the two beverages for 30 days. In the last 6 days of the experiment, the animals were tested for their physical performance by conducting a weight-loaded forced swim test. Immediately after swimming exhaustion, the animals were sacrificed under anesthesia and samples of the heart muscle were harvested for ultrastructural and biochemical analyses.

RESULTS

Our results showed a significant increase in the heart glucose and glycogen concentrations in the RB and RBE groups. Total cholesterol concentration significantly decreased in the RBE and RB groups. Total protein concentration and ALT and AST activities increased in all groups. The biochemical changes were accompanied by ultrastructural alterations.

CONCLUSION

Based on these results, we recommend that athletes and active persons should avoid the long-term consumption of the Red Bull ED and, particularly, its combination with alcohol.

Etiology of alcoholic cardiomyopathy: Mitochondria, oxidative stress and apoptosis

Putative mechanisms leading to the development of alcoholic cardiomyopathy (ACM) include the interrelated cellular processes of mitochondria metabolism, oxidative stress and apoptosis. As mitochondria fuel the constant energy demands of this continually contracting tissue, it is not surprising that alcohol-induced molecular changes in this organelle contribute to cardiac dysfunction and ACM. As the causal relationship of these processes with ACM has already been established, the primary objective of this review is to provide an update of the experimental findings to more completely understand the aforementioned mechanisms. Accordingly, recent data indicate that alcohol impairs mitochondria function assessed by membrane potential and respiratory chain activity. Indictors of oxidative stress including superoxide dismutase, glutathione metabolites and malondialdehyde are also adversely affected by alcohol oftentimes in a sex-dependent manner. Additionally, myocardial apoptosis is increased based on assessment of TUNEL staining and caspase activity. Recent work has also emerged linking alcohol-induced oxidative stress with apoptosis providing new insight on the codependence of these interrelated mechanisms in ACM. Attention is also given to methodological differences including the dose of alcohol, experimental model system and the use of males versus females to highlight inconsistencies and areas that would benefit from establishment of a consistent model.

Chronic plus binge ethanol feeding induces myocardial oxidative stress, mitochondrial and cardiovascular dysfunction, and steatosis

Alcoholic cardiomyopathy in humans develops in response to chronic excessive alcohol consumption; however, good models of alcohol-induced cardiomyopathy in mice are lacking. Herein we describe mouse models of alcoholic cardiomyopathies induced by chronic and binge ethanol (EtOH) feeding and characterize detailed hemodynamic alterations, mitochondrial function, and redox signaling in these models. Mice were fed a liquid diet containing 5% EtOH for 10, 20, and 40 days (d) combined with single or multiple EtOH binges (5 g/kg body wt). Isocalorically pair-fed mice served as controls. Left ventricular (LV) function and morphology were assessed by invasive pressure-volume conductance approach and by echocardiography. Mitochondrial complex (I, II, IV) activities, 3-nitrotyrosine (3-NT) levels, gene expression of markers of oxidative stress (gp91phox, p47phox), mitochondrial biogenesis (PGC1α, peroxisome proliferator-activated receptor α), and fibrosis were examined. Cardiac steatosis and fibrosis were investigated by histological/immunohistochemical methods. Chronic and binge EtOH feeding (already in 10 days EtOH plus single binge group) was characterized by contractile dysfunction (decreased slope of end-systolic pressure-volume relationship and preload recruitable stroke work), impaired relaxation (decreased time constant of LV pressure decay and maximal slope of systolic pressure decrement), and vascular dysfunction (impaired arterial elastance and lower total peripheral resistance). This was accompanied by enhanced myocardial oxidative/nitrative stress (3-NT; gp91phox; p47phox; angiotensin II receptor, type 1a) and deterioration of mitochondrial complex I, II, IV activities and mitochondrial biogenesis, excessive cardiac steatosis, and higher mortality. Collectively, chronic plus binge EtOH feeding in mice leads to alcohol-induced cardiomyopathies (National Institute on Alcohol Abuse and Alcoholism models) characterized by increased myocardial oxidative/nitrative stress, impaired mitochondrial function and biogenesis, and enhanced cardiac steatosis.

Drug-induced mitochondrial dysfunction and cardiotoxicity

Mitochondria has an essential role in myocardial tissue homeostasis; thus deterioration in mitochondrial function eventually leads to cardiomyocyte and endothelial cell death and consequent cardiovascular dysfunction. Several chemical compounds and drugs have been known to directly or indirectly modulate cardiac mitochondrial function, which can account both for the toxicological and pharmacological properties of these substances. In many cases, toxicity problems appear only in the presence of additional cardiovascular disease conditions or develop months/years following the exposure, making the diagnosis difficult. Cardiotoxic agents affecting mitochondria include several widely used anticancer drugs [anthracyclines (Doxorubicin/Adriamycin), cisplatin, trastuzumab (Herceptin), arsenic trioxide (Trisenox), mitoxantrone (Novantrone), imatinib (Gleevec), bevacizumab (Avastin), sunitinib (Sutent), and sorafenib (Nevaxar)], antiviral compound azidothymidine (AZT, Zidovudine) and several oral antidiabetics [e.g., rosiglitazone (Avandia)]. Illicit drugs such as alcohol, cocaine, methamphetamine, ecstasy, and synthetic cannabinoids (spice, K2) may also induce mitochondria-related cardiotoxicity. Mitochondrial toxicity develops due to various mechanisms involving interference with the mitochondrial respiratory chain (e.g., uncoupling) or inhibition of the important mitochondrial enzymes (oxidative phosphorylation, Szent-Györgyi-Krebs cycle, mitochondrial DNA replication, ADP/ATP translocator). The final phase of mitochondrial dysfunction induces loss of mitochondrial membrane potential and an increase in mitochondrial oxidative/nitrative stress, eventually culminating into cell death. This review aims to discuss the mechanisms of mitochondrion-mediated cardiotoxicity of commonly used drugs and some potential cardioprotective strategies to prevent these toxicities.