Oxidative Stress Inhibits Apoptosis in Human Lymphoma Cells

Yang-Ja Lee,Emily Shacter

doi:10.1074/jbc.274.28.19792

Abstract

Apoptosis and necrosis are two forms of cell death that are induced under different conditions and that differ in morphological and biochemical features. In this report, we show that, in the presence of oxidative stress, human B lymphoma cells are unable to undergo apoptosis and die instead by a form of necrosis. This was established using the chemotherapy drug VP-16 or the calcium ionophore A23187 to induce apoptosis in Burkitt's lymphoma cell lines and by measuring classical markers of apoptotic death, including cell morphology, annexin V binding, DNA ladder formation, and caspase activation. In the presence of relatively low levels of H2O2 (75-100 microM), VP-16 and A23187 were unable to induce apoptosis in these cells. Instead, the cells underwent non-apoptotic cell death with mild cytoplasmic swelling and nuclear shrinkage, similar to the death observed when they were treated with H2O2 alone. We found that H2O2 inhibits apoptosis by depleting the cells of ATP. The effects of H2O2 can be overcome by inhibitors of poly(ADP)-ribosylation, which also preserve cellular ATP levels, and can be mimicked by agents such as oligomycin, which inhibit ATP synthesis. The results show that oxidants can manipulate cell death pathways, diverting the cell away from apoptosis. The potential physiological ramifications of this finding will be discussed.

Highlights

From the Division of Hematologic Products, Food and Drug Administration, Center for Biologics Evaluation and Research, Bethesda, Maryland 20892-4555
Modes of Cell Death Induced in Burkitt’s Lymphoma Cells by VP-16 and H2O2—VP-16 is a topoisomerase II inhibitor, which is widely used for cancer chemotherapy [21] and is known to kill a variety of different tumor cells by inducing apoptosis
The results show that H2O2 inhibits the ability of agents such as the chemotherapy drug VP-16 or the calcium ionophore A23187 to induce apoptosis in Burkitt’s lymphoma cells

Summary

Introduction

From the Division of Hematologic Products, Food and Drug Administration, Center for Biologics Evaluation and Research, Bethesda, Maryland 20892-4555. We show that, in the presence of oxidative stress, human B lymphoma cells are unable to undergo apoptosis and die instead by a form of necrosis. This was established using the chemotherapy drug VP-16 or the calcium ionophore A23187 to induce apoptosis in Burkitt’s lymphoma cell lines and by measuring classical markers of apoptotic death, including cell morphology, annexin V binding, DNA ladder formation, and caspase activation. Apoptosis is regarded as an active and progressive response to physiologic and pathologic stimuli [2, 3] It is characterized by early and prominent condensation of nuclear chromatin, loss of plasma membrane phospholipid asymmetry, activation of proteases and endonucleases, enzymatic cleavage of the DNA into oligonucleosomal fragments, and segmentation of the cells into membrane-bound “apoptotic bodies.”. Oxidative stress can manipulate the mechanism of cell death, diverting it away from apoptosis to necrosis

Methods

Results

Conclusion