Impact of chronic alcohol ingestion on cardiac muscle protein expression.

Heart disease, as well as cirrhosis, represents an important etiology of mortality in chronic alcoholics. Excessive ethanol consumption can result in a syndrome referred to as alcoholic cardiomyopathy. Alcoholic cardiomyopathy is rarely produced by short-term ethanol administration. However, it is observed in those patients who excessively consume alcohol for prolonged periods (greater than 80 g of ethanol a day for longer than 10 years). The clinical feature of this syndrome is a defect in myocardial contractility as assessed by a reduction in ejection fraction, with the degree of cardiac dysfunction proportional to the duration and severity of alcohol consumption (Urbano-Marquez, 1989). Patients diagnosed with alcoholic cardiomyopathy, who continue to drink alcohol, suffer deterioration in their condition leading to congestive heart failure and eventually death ensues. The major pathologic features revealed through biopsy or postmortem examination include dilation of both ventricles of the heart, thinning of the ventricular wall with fibrosis, and endocardial fibroelastic thickening, interstitial edema, and focal areas of necrosis within the ventricular wall (Bulloch et al., 1972; Ferrans et al., 1975; Hibbs et al., 1965). Microscopic examination of biopsy specimens obtained from humans reveals myocyte degeneration, loss of striations, and myofilament dissolution, consistent with alterations in structural and myofibrillar proteins (Alexander, 1966a,b; Bulloch et al., 1972; Ferrans et al., 1975; Hibbs et al., 1965). Addition of ethanol to the medium reduces the number and uniformity of the myofibrils of myocytes in culture (Adickes et al., 1990). The process of alterations in ethanol-induced cardiac structure and function is referred to as alcoholic heart muscle disease. The molecular basis for this disease is probably multifactorial. One explanation for reduced contractility and derangements in myofibrillar architecture is that the integrity of cellular proteins may be compromised by prolonged ethanol intake. Early work indicated that chronic ethanol consumption led to a decreased association of actin with myosin heavy chain isoform in vitro (Rubin et al., 1976), and it was suggested that persistent changes in some myofibrillar proteins may have occurred. We have provided evidence that long-term exposure of rats to a diet containing ethanol results in lower cellular content of both actin and α-myosin heavy chain isoform and an increase in the β-myosin heavy chain isoform (Vary and Deiter, 2005) (Table 1). Similarly, both Patel and colleagues (2000) and Figueredo and colleagues (1998) showed decreases in actin and α-myosin heavy chain isoform, whereas Piano et al. showed chronic ethanol consumption induces an increase in the β-myosin heavy chain isoform (Meehan et al., 1999). Table 1 provides a summary of the known changes in myocardial proteins in animals fed a diet containing ethanol. The aim of this study was to analyze cardiac muscle protein expression after chronic alcohol consumption compared with control pair-fed rats using a mass spectrometry-based proteomic approach using Cleavable ICAT™ reagents (isotope coded affinity tags). Table 1 Changes in Myocardial Proteins With Chronic Alcohol Intoxication Identified by Western Blot Techniques