Bcl-2 prevents hypoxia/reoxygenation-induced cell death through suppressed generation of reactive oxygen species and upregulation of Bcl-2 proteins

✍ Scribed by Yasukazu Saitoh; Rika Ouchida; Nobuhiko Miwa

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 251 KB
• Volume: 90
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.10723

✦ Synopsis

Abstract

The function of bcl‐2 in preventing cell death is well known, but the mechanisms whereby bcl‐2 functions are not well characterized. One mechanism whereby bcl‐2 is thought to function is by alleviating the effects of oxidative stress upon the cell. To examine whether Bcl‐2 can protect cells against oxidative injury resulting from post‐hypoxic reoxygenation (H/R), we subjected rat fibroblasts Rat‐1 and their bcl‐2 transfectants b5 to hypoxia (5% CO~2~, 95% N~2~) followed by reoxygenation (5% CO~2~, 95% air). The bcl‐2 transfectants exhibited the cell viability superior to that of their parent non‐transfectants upon treatment with reoxygenation after 24‐, 48‐, or 72‐h hypoxia, but not upon normoxic serum‐deprivation or upon serum‐supplied hypoxic treatment alone. Thus bcl‐2 transfection can prevent cell death of some types, which occurred during H/R but yet not appreciably until termination of hypoxia. The time‐sequential events of H/R‐induced cell death were shown to be executed via (1) reactive oxygen species (ROS) production at 1–12 h after H/R, (2) activation of caspases‐1 and ‐3, at 1–3 h and 3–6 h after H/R, respectively, and (3) loss of mitochondrial membrane potential (ΔΨ) at 3–12 h after H/R. These cell death‐associated events were prevented entirely except caspase‐1 activation by bcl‐2 transfection, and were preceded by Bcl‐2 upregulation which was executed as early as at 0–1 h after H/R for the bcl‐2 transfectants but not their non‐transfected counterpart cells. Thus upregulation of Bcl‐2 proteins may play a role in prevention of H/R‐induced diminishment of cell viability, but may be executed not yet during hypoxia itself and be actually operated as promptly as ready to go immediately after beginning of H/R, resulting in cytoproteciton through blockage of either ROS generation, caspase‐3 activation, or ΔΨ decline. © 2003 Wiley‐Liss, Inc.