Ascorbate and α-Tocopherol Prevent Apoptosis Induced by Serum Removal Independent of Bcl-2

Abstract

Cells require serum to maintain growthin vitro.Serum provides growth and survival factors and its removal causes an oxidative stress that induces peroxidations in membrane lipids and development of programmed cell death (apoptosis) in some cells. Cells containing Bcl-2 are partially protected against both lipid peroxidation and apoptosis and some cell lines, such as Daudi, which lack this protein, are very sensitive to serum removal. Thus, cells are grown for 48 h in the absence of fetal calf serum and apoptotic cells are scored. HL-60 cells containing a moderate amount of Bcl-2 show 30% apoptosis, while 55% cells are apoptotic of the Bcl-2-negative Daudi cell population. Apoptosis is reduced to 15% in the transiently transfected Daudi/Bcl-2 cells. Ascorbate (Asc) and α-tocopherol (αTOH) can prevent lipid peroxidation and apoptosis caused by serum withdrawal, when added to culture media, even in the absence of Bcl-2. Also, these two antioxidants increase survival of cells grown in the absence of serum independent of their Bcl-2 content. Immunostaining and quantification of Bcl-2 show that HL-60 cell line is a heterogeneous population relative to the expression of Bcl-2. When these cells are grown in the presence of serum, cells lacking Bcl-2 survive, but no Bcl-2-negative cells survive without serum. Part of this population of Bcl-2-negative cells is rescued by Asc and αTOH. Antioxidants effective at the plasma membrane such as Asc and αTOH can protect cells from oxidative damage and prevent apoptosis independent of Bcl-2 content.