ABSTRACT
Cardiac hypertrophy is a major cause of morbidity and mortality worldwide. Recent in vitro and in vivo studies have suggested that reactive oxygen species (ROS) may play an important role in cardiac hypertrophy. It was therefore thought to be of particular value to examine the effects of antioxidants on cardiac hypertrophy. Epigallocatechin-3-gallate (EGCG) is a major bioactive polyphenol present in green tea and a potent antioxidant. The current study was designed to test the hypothesis that EGCG inhibits cardiac hypertrophy in vitro and in vivo. In this study, we investigated the effects of EGCG on angiotensin II- (Ang II) and pressure-overload-induced cardiac hypertrophy. Our results showed that EGCG attenuated Ang II- and pressure-overload-mediated cardiac hypertrophy. Both reactive oxygen species generation and NADPH oxidase expressions induced by Ang II and pressure overload were suppressed by EGCG. The increased hypertension by pressure overload was almost completely blocked after EGCG treatment. Further studies showed that EGCG inhibited Ang II-induced NF-kappaB and AP-1 activation. Inhibition of the activity of NF-kappaB was through blocking ROS-dependent p38 and JNK signaling pathways, whereas inhibition of AP-1 activation was via blocking EGFR transactivation and its downstream events ERKs/PI3K/Akt/mTOR/p70(S6K). The combination of these actions resulted in repressing the reactivation of ANP and BNP, and ultimately preventing the progress of cardiac hypertrophy. These findings indicated that EGCG prevents the development of cardiac hypertrophy through ROS-dependent and -independent mechanisms involving inhibition of different intracellular signaling transductional pathways.
Subject(s)
Antioxidants/pharmacology , Cardiomegaly/prevention & control , Catechin/analogs & derivatives , Reactive Oxygen Species/metabolism , Signal Transduction/drug effects , Angiotensin II/pharmacology , Animals , Animals, Newborn , Blotting, Northern , Blotting, Western , Cardiomegaly/etiology , Catechin/pharmacology , Electrophoretic Mobility Shift Assay , Enzyme Activation/drug effects , ErbB Receptors/drug effects , ErbB Receptors/metabolism , Hypertension/chemically induced , Hypertension/complications , MAP Kinase Kinase 4/drug effects , MAP Kinase Kinase 4/metabolism , Male , NF-kappa B/drug effects , NF-kappa B/metabolism , Rats , Rats, Sprague-Dawley , Signal Transduction/physiology , Transcription Factor AP-1/drug effects , Transcription Factor AP-1/metabolism , p38 Mitogen-Activated Protein Kinases/drug effects , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
Cardiac hypertrophy is a major cause of morbidity and mortality worldwide. The hypertrophic process is mediated, in part, by oxidative stress-mediated signaling pathways. We hypothesized that isorhapontigenin (ISO), a new resveratrol analog, inhibits cardiac hypertrophy by blocking oxidative stress and oxidative stress-mediated signaling pathways. We treated cardiomyocytes with angiotensin II (Ang II) with or without ISO and found that ISO inhibited Ang II-induced cardiac hypertrophy. These effects were associated with a decrease in the levels of reactive oxygen species and H2O2 and the content of intracellular malonaldehyde and an increase in the activities of superoxide dismutase and glutathione peroxidase. Ang II induced the phosphorylation of PKC, Erk1/2, JNK, and p38 in cardiomyocytes and such phosphorylation was inhibited by ISO. ISO also blocked the PKC-dependent PI3K-Akt-GSK3beta/p70S6K pathway. These effects lead to direct or indirect inhibition of NF-kappaB and AP-1 activation. Our results revealed that pretreatment with ISO significantly inhibited Ang II-mediated NF-kappaB through affecting the degradation and phosphorylation of IkappaBalpha and the activity of IKKbeta and AP-1 activation by influencing the expression of c-Fos and c-Jun proteins. In addition, we also established the molecular link between activation of PKC and MAPKs and activation of NF-kappaB and AP-1 in cardiomyocytes. We also found that ISO treatment significantly attenuated heart weight/body weight ratio by approximately 25%, decreased posterior wall thickness and left ventricle diastolic and systolic diameters, and increased 10% fractional shortening in an aortic-banded rat model. Furthermore, treatment with ISO significantly decreased cardiac myocyte size and systolic blood pressure. These findings suggest that ISO prevents the development of cardiac hypertrophy through an antioxidant mechanism involving inhibition of different intracellular signaling transduction pathways.
