Intermittent Hypoxia Prevents Myocardial Mitochondrial Ca2+ Overload and Cell Death during Ischemia/Reperfusion: The Role of Reactive Oxygen Species

• Published in: Cells (Basel, Switzerland) Vol. 8; no. 6; p. 564
• Main Authors: Chang, Jui-Chih, Lien, Chih-Feng, Lee, Wen-Sen, Chang, Huai-Ren, Hsu, Yu-Cheng, Luo, Yu-Po, Jeng, Jing-Ren, Hsieh, Jen-Che, Yang, Kun-Ta
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 09-06-2019; MDPI
• Subjects: Annexin V; antioxidant; Antioxidants; Apoptosis; Ca2+, ROS; Calcium (mitochondrial); Calcium homeostasis; Cardiomyocytes; Caspase; Caspase-3; Catalase; Cell death; Cell viability; Coronary artery disease; Cytosol; Depolarization; Disease; Enzymes; Fura-2; Heart diseases; Homeostasis; Hydrogen peroxide; Hypoxia; intermittent hypoxia; Ischemia; Kinases; Medicine; Membrane potential; mitochondria; Neonates; Oxidative stress; Penicillin; Permeability; Physiology; Polymerase chain reaction; Proteins; Reactive oxygen species; Reperfusion; Rodents; United States > US; Taiwan
• ISSN: 2073-4409; 2073-4409
• DOI: 10.3390/cells8060564

It has been documented that reactive oxygen species (ROS) contribute to oxidative stress, leading to diseases such as ischemic heart disease. Recently, increasing evidence has indicated that short-term intermittent hypoxia (IH), similar to ischemia preconditioning, could yield cardioprotection. However, the underlying mechanism for the IH-induced cardioprotective effect remains unclear. The aim of this study was to determine whether IH exposure can enhance antioxidant capacity, which contributes to cardioprotection against oxidative stress and ischemia/reperfusion (I/R) injury in cardiomyocytes. Primary rat neonatal cardiomyocytes were cultured in IH condition with an oscillating O2 concentration between 20% and 5% every 30 min. An MTT assay was conducted to examine the cell viability. Annexin V-FITC and SYTOX green fluorescent intensity and caspase 3 activity were detected to analyze the cell death. Fluorescent images for DCFDA, Fura-2, Rhod-2, and TMRM were acquired to analyze the ROS, cytosol Ca2+, mitochondrial Ca2+, and mitochondrial membrane potential, respectively. RT-PCR, immunocytofluorescence staining, and antioxidant activity assay were conducted to detect the expression of antioxidant enzymes. Our results show that IH induced slight increases of O2−· and protected cardiomyocytes against H2O2- and I/R-induced cell death. Moreover, H2O2-induced Ca2+ imbalance and mitochondrial membrane depolarization were attenuated by IH, which also reduced the I/R-induced Ca2+ overload. Furthermore, treatment with IH increased the expression of Cu/Zn SOD and Mn SOD, the total antioxidant capacity, and the activity of catalase. Blockade of the IH-increased ROS production abolished the protective effects of IH on the Ca2+ homeostasis and antioxidant defense capacity. Taken together, our findings suggest that IH protected the cardiomyocytes against H2O2- and I/R-induced oxidative stress and cell death through maintaining Ca2+ homeostasis as well as the mitochondrial membrane potential, and upregulation of antioxidant enzymes.