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Insulin-like growth factor I retards apoptotic signaling induced by ethanol in cardiomyocytes
Abstract:
Apoptosis of cardiac muscle cells may contribute to the development of cardiomyopathy and heart failure. Alcohol (ethanol) abuse is a major cause of cardiomyopathy, but its underlying mechanism remains unknown. To determine whether ethanol causes apoptosis in cardiac muscle and whether insulin-like growth factor I (IGF 1) improves cardiac muscle survival upon ethanol exposure, we have defined the effects of ethanol and IGF I in primary cardiomyocytes. Ethanol decreased cell viability in dose-response manner from 0.2% to 1%. In contrast, ethanol (0.2-1%) did not alter viability of cardiac fibroblasts. To assess the occurrence of apoptosis, DNA fragmentation was determined with quantitation of nucleosomes. Nucleosomes were increased in ethanol-treated cells, thus confirming the apoptotic effects of ethanol. The pro-apoptotic Bax protein and Caspase 3 are important proteins of apoptotic signaling. The content of Bax and the activities of Caspase 3 were increased upon ethanol exposure. IGF I partially suppressed Bax induction, Caspase 3 activation, DNA fragmentation, and increased cardiomyocyte survival. The effects of IGF I on ethanol-induced apoptosis can be inhibited with a chemical inhibitor of PI 3 Kinase (LY-294002), suggesting that anti-apoptotic actions of IGF I involves PI 3 Kinase. These results may have important implications on further understanding the pathogenesis of alcoholic heart disease and the development of new strategies to treat alcoholic cardiomyopathy.
Insights
Alcohol abuse causes heart muscle cell death, leading to alcoholic cardiomyopathy. Insulin-like growth factor I (IGF I) shows potential in protecting heart cells from alcohol-induced apoptosis by involving PI 3 Kinase signaling.
Area of Science:
- Cardiovascular Biology
- Cell Death Mechanisms
- Molecular Cardiology
Background:
- Alcohol (ethanol) abuse is a significant cause of cardiomyopathy and heart failure.
- The precise mechanisms by which ethanol induces cardiac muscle cell death remain largely unknown.
- Apoptosis, or programmed cell death, of cardiomyocytes is a potential contributor to heart disease.
Purpose of the Study:
- To investigate the effects of ethanol on cardiomyocyte apoptosis.
- To determine if insulin-like growth factor I (IGF I) can protect cardiac muscle cells from ethanol-induced cell death.
- To elucidate the signaling pathways involved in IGF I's protective effects.
Main Methods:
- Primary cardiomyocytes were exposed to varying concentrations of ethanol (0.2-1%).
- Cell viability was assessed, and apoptosis was quantified by measuring DNA fragmentation (nucleosome release).
- Levels of pro-apoptotic proteins (Bax) and Caspase 3 activity were measured; IGF I's effects and involvement of PI 3 Kinase were examined using LY-294002.
Main Results:
- Ethanol exposure significantly decreased cardiomyocyte viability and increased DNA fragmentation, confirming apoptosis.
- Ethanol increased the expression of Bax protein and the activity of Caspase 3.
- IGF I partially inhibited ethanol-induced apoptosis by suppressing Bax induction and Caspase 3 activation, an effect dependent on PI 3 Kinase signaling.
Conclusions:
- Ethanol induces apoptosis in cardiac muscle cells through mechanisms involving Bax and Caspase 3.
- IGF I demonstrates a protective effect against ethanol-induced cardiomyocyte apoptosis, mediated via the PI 3 Kinase pathway.
- These findings offer insights into the pathogenesis of alcoholic heart disease and suggest potential therapeutic targets for alcoholic cardiomyopathy.