Alterations in beta-adrenergic receptor density and cyclic-AMP level in the myocardium of rats chronically treated with alcohol

Chronic alcohol consumption from adolescence-to-adulthood in mice--hypothalamic gene expression changes in the dilated cardiomyopathy signaling pathway

Background

Adolescence is a developmental stage vulnerable to alcohol drinking-related problems and the onset of alcoholism. Hypothalamus is a key brain region for food and water intake regulation, and is one of the alcohol-sensitive brain regions. However, it is not known what would be the alcohol effect on hypothalamus following adolescent alcohol intake, chronically over the adolescent development, at moderate levels.

Results

We employed a paradigm of chronic moderate alcohol intake from adolescence-to-adulthood in mice, and analyzed the alcohol effect on both behavioral and hypothalamic gene expression changes. A total of 751 genes were found and subjected to pathway analysis. The dilated cardiomyopathy (DCM) pathway was identified. The changes of ten genes under this pathway were further verified using RT-PCR. Chronic alcohol consumption during adolescence, even at moderate levels, led to a decrease of motor activity in mice, and also a concerted down regulation of signaling pathway initiating factor (SPIF) genes in the DCM signaling pathway, including β1-adrenergic receptor (Adrb1), Gs protein (Gnas), adenylyl cyclase 1 (Adcy1), and dihydropyridine receptor/L-type calcium channel (Cacna1d).

Conclusions

These findings suggest that adolescent alcohol intake may trigger gene expression changes in the CNS that parallel those found in the dilated cardiomyopathy signaling pathway. If such effects also take place in humans, our findings would serve as a warning against alcohol intake in youth, such as by teens and/or college students.

Habitual alcohol consumption is associated with lower cardiovascular stress responses--a novel explanation for the known cardiovascular benefits of alcohol?

In contrast to heavy alcohol consumption, which is harmful, light to moderate drinking has been linked to reduced cardiovascular morbidity and mortality. Effects on lipid status or clotting do not fully explain these benefits. Exaggerated cardiovascular responses to mental stress are detrimental to cardiovascular health. We hypothesized that habitual alcohol consumption might reduce these responses, with potential benefits. Advanced magnetic resonance techniques were used to accurately measure cardiovascular responses to an acute mental stressor (Montreal Imaging Stress Task) in 88 healthy adults (∼1:1 male:female). Salivary cortisol and task performance measures were used to assess endocrine and cognitive responses. Habitual alcohol consumption and confounding factors were assessed by questionnaire. Alcohol consumption was inversely related to responses of heart rate (HR) (r = -0.31, p = 0.01), cardiac output (CO) (r = -0.32, p = 0.01), vascular resistance (r = 0.25, p = 0.04) and mean blood pressure (r = -0.31, p = 0.01) provoked by stress, but not to stroke volume (SV), or arterial compliance changes. However, high alcohol consumers had greater cortisol stress responses, compared to moderate consumers (3.5 versus 0.7 nmol/L, p = 0.04). Cognitive measures did not differ. Findings were not explained by variations in age, sex, social class, ethnicity, physical activity, adrenocortical activity, adiposity, smoking, menstrual phase and chronic stress. Habitual alcohol consumption is associated with reduced cardiac responsiveness during mental stress, which has been linked to lower risk of hypertension and vascular disease. Consistent with established evidence, our findings suggest a mechanism by which moderate alcohol consumption might reduce cardiovascular disease, but not high consumption, where effects such as greater cortisol stress responses may negate any benefits.

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.

Effects of gender on the cardiac toxicity elicited by chronic ethanol intake in rats

Experiments were designed to determine if gender influences the cardiac toxicity elicited by chronic high-level ethanol intake. Male and female ethanol-preferring P-rats were allowed free access to drinking water or water containing 25% ethanol for 6 months. Left atrial preparations were then isolated, bathed in Krebs-Henseleit solution (37 degrees C), and used to examine basal contractility at 3.0 Hz stimulation, the force-frequency relationship, and the positive inotropic response to the beta-adrenoceptor agonist isoproterenol. Basal contractile function was not affected significantly by ethanol in either gender; however, atria from ethanol-treated male rats displayed diminished contractility compared to control males when measured at slow stimulation frequencies (0.1 and 0.2 Hz), during post rest potentiation (at rest intervals of 20-60 s), and in response to higher concentrations of isoproterenol (> or =3 x 10(-7) M; EC50 values were not affected). In contrast, female atria showed no effect of chronic ethanol consumption. These data suggest that ethanol consumption diminishes the cardiac reserve in male, but not female rats.