Reactive Oxygen Species Mediate Amplitude-Dependent Hypertrophic and Apoptotic Responses to Mechanical Stretch in Cardiac Myocytes

Abstract

Abstract-Oxidative stress stimulates both growth and apoptosis in cardiac myocytes in vitro. We investigated whether oxidative stress mediates hypertrophy and apoptosis in cyclically stretched ventricular myocytes. Neonatal rat ventricular myocytes cultured on laminin-coated silastic membranes were stretched cyclically (1 Hz) at low (nominal 5%) and high (nominal 25%) amplitudes for 24 hours. Stretch caused a graded increase in superoxide anion production as assessed by superoxide dismutase (SOD)-inhibitable cytochrome c reduction or electron paramagnetic resonance spectroscopy. The role of reactive oxygen species (ROS) was assessed using the cell-permeable SOD/catalase mimetics Mn(II/III)tetrakis(1-methyl-4-peridyl) (MnTMPyP) and EUK-8. Stretch-induced increases in protein synthesis ( 3 Hleucine incorporation) and cellular protein content were completely inhibited by MnTMPyP (0.05 mmol/L) at both low and high amplitudes of stretch. In contrast, while MnTMPyP inhibited basal atrial natriuretic factor (ANF) mRNA expression, the stretch-induced increase in ANF mRNA expression was not inhibited by MnTMPyP. In contrast to hypertrophy, only high-amplitude stretch increased myocyte apoptosis, as reflected by increased DNA fragmentation on gel electrophoresis and an Ϸ3-fold increase in the number of TUNEL-positive myocytes. Similarly, only high-amplitude stretch increased the expression of bax mRNA. Myocyte apoptosis and bax expression stimulated by high-amplitude stretch were inhibited by MnTMPyP. Both low-and high-amplitude stretch caused rapid phosphorylation of ERK1/2, while high-, but not low-, amplitude stretch caused phosphorylation of JNKs. Activation of both ERK1/2 and JNKs was ROS-dependent. Thus, cyclic strain causes an amplitude-related increase in ROS, associated with differential activation of kinases and induction of hypertrophic and apoptotic phenotypes.

Cardiac Myocyte-specific Ablation of Follistatin-like 3 Attenuates Stress-induced Myocardial Hypertrophy

“…Primary Neonatal Rat Ventricular Myocytes Culture-Primary culture of neonatal rat ventricular myocytes (NRVMs) were prepared as described previously (27). NRVMs were incubated in DMEM supplemented with 7% fetal calf serum (FCS) for 18 h after preparation and subsequently transfected with the rat small interfering RNA (siRNA) reagent, purchased from Dharmacon Inc., that represents a mixture of four different siRNAs that target Fstl3 (SMARTpool).…”

Foxo3a Inhibits Cardiomyocyte Hypertrophy through Transactivating Catalase

“…Insulin-Although insulin is able to induce cardiomyocyte hypertrophy (8,9), and ROS can mediate the hypertrophic signals (19,20,36), it remains unknown as to whether ROS participates in conveying the hypertrophic signal of insulin. We explored whether ROS is necessary for insulin to induce hypertrophy.…”

“…Endothelin-1 can directly stimulate ROS production (19) or mediate leptin-induced ROS production (22). Mechanical stretch-induced hypertrophy is mediated by ROS (20). As second messengers, ROS regulate various intracellular signal transduction cascades and the activity of * This work was supported by the National Natural Science Foundation of China (Grant 30730045), the National Basic Research Program of China (973 Program, Grant 2007CB512000), and the American Heart Association.…”

Role of mineralocorticoid receptor on atrial structural remodeling and inducibility of atrial fibrillation in hypertensive rats

“…16 ROS may act as signaling molecules for cardiac remodeling and/or injure myocardial structure directly. 17,18 There are several sources of ROS in the heart, including mitochondrial electron transport system, nitric oxide synthase, xanthine oxidase and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Rac1, one of the small G proteins, has predominant roles in NADPH oxidase activity and is critical for generating ROS.…”