Date of Award
Campus Access Dissertation
Significance: With over 15 million people in the United States alone being alcohol-dependent, alcohol is one of the most frequently abused drugs in the world. A common consequence of alcohol abuse is a form of heart disease termed alcoholic cardiomyopathy, an ailment which is responsible for over 30% of all cases of dilated cardiomyopathy. Many questions remain regarding the mechanisms whereby alcohol abuse results in alcoholic cardiomyopathy.
Methods: Male, wild-type, FVB strain mice were fed a nutritionally complete liquid diet supplemented with 4% ethanol v/v over a time course of 1, 2, 4, 8, 12, and 14 weeks. Changes in cardiac physiology were assessed at respective time points via echocardiography. Additionally, the use of histological techniques, mRNA analysis, apoptosis determination, and immunohistochemistry were employed to determine the functional and structural changes in the heart. Also, primary rat cardiac fibroblasts were cultured in the presence of 1 and 4mg/ml ethanol and assayed for fibroblast activation.
Results: Echocardiograph analysis revealed a compensatory phase that occurred early in the time course ~1-8 weeks and decompensation reverting toward heart failure at weeks 12 and 14. Throughout the study, an increase in cardiomyocyte hypertrophy,
cardiac fibrosis, apoptosis, transforming growth factor beta (TGF-β), and the presence of alpha smooth muscle actin (α-SMA)-positive cells were determined. A compensatory period in mice treated with ethanol occurred early followed by a transition to a dilated phenotype over time. A number of factors may be involved in this process including the activation of myofibroblasts and their fibrotic activities that is correlated with the presence of TGF-β.
Treatment of isolated fibroblasts with 1 and 4 mg/ml ethanol resulted in fibroblast activation and subsequent fibrogenic activity after 24 hours via an increase in contraction, α-SMA expression, migration, and expression of collagen I and TGF-β. No changes in fibroblast proliferation or apoptosis were observed. Inhibition of TGF-β by SB 431542 and RbII attenuated the ethanol-induced fibroblast activation.
Gene array analysis of ethanol-treated mice showed changes in extracellular matrix (ECM), inflammatory, oxidative stress, apoptotic, and lipid metabolism genes. Evidence of lipid accumulation and increased mast cell invasion was detected. An increase in inflammatory cytokine/chemokine mRNA (interleukin-33 (IL-33), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor-alpha (TNF-α)) was observed in cardiac fibroblasts treated with ethanol.
Law, B. A.(2012). The Role of Transforming Growth Factor-Beta In Alcohol-Induced Cardiac Fibrosis. (Doctoral dissertation). Retrieved from http://scholarcommons.sc.edu/etd/2106