Intermittent Hypoxia Alters Ca2+ Homeostasis in Cardiomyocytes

• Main Authors: Yu Cheng Hsu, 許育誠
• Other Authors: Kun Ta Yang
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/74747480502039162689

碩士 === 慈濟大學 === 生理暨解剖醫學研究所 === 97 === Intermittent hypoxia (IH) with repeated episodes of hypoxia-normoxia cycle has been shown to exert preconditioning-like cardio-protective effects, but the exact mechanism is still unclear. Previous studies reported that sarcoplasmic reticulum (SR) and Na+/Ca2+ exchanger (NCX) play crucial roles in regulating [Ca2+]i and cardiac dysfunction. In this work, we examined Ca2+ handling mechanisms involved in neonatal cardiomyocytes induced by intermittent hypoxia. Neonatal cardiomyocytes were subjected to intermittent (alternating 5 % O2 30 min, 21 % O2 30 min) hypoxia for 1, 2, 3 and 4 days. Intracellular Ca2+ was measured by using a live-cell fluorescence imaging system; meanwhile, the Ca2+ handing protein was analyzed by using immunocytochemistry and western blot. After cardiomyocytes were subjected to IH, the Ca2+ extrusion rate during high K+ (40 mM) and caffeine-induced Ca2+ transient increased significantly compared to room air (RA) group. We further determined the expression of Ca2+ handing protein, ryanodine receptor (RyR), sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) and sarcolemmal Na+/Ca2+ exchanger (NCX). The expression level of both RyR, SERCA and NCX was found to increase significantly after IH. Furthermore, these phenomenon was partial abolished by phenathrene (Fenton's reaction-generated OH• blocker) and chelerythrine (PKC inhibitor). We also found that PKC protein expression and activity were increased. Finally, we found that intermittent hypoxia could improve cardiomyocyte viability after subject to ischemia-reperfusion. These results suggest that intermittent hypoxia could alert cardiomyocyte Ca2+ dynamics by regulating NCX, SERCA and ryanodine receptor. Mechanistically, activation ROS and PKC could play an important role in the Ca2+ handing mechanism in IH.