Inactivation of ataxia telangiectasia mutated gene can increase intracellular reactive oxygen species levels and alter radiation-induced cell death pathways in human glioma cells

Abstract

Purpose: To investigate the effects of ataxia telangiectasia mutated (ATM)-regulated reactive oxygen species (ROS) and cell death pathways on the response of U87MG glioma cells to ionising radiation (IR) and oxidative stress.

Material and methods: ATM expression was blocked in U87MG glioma cells using a small interfering RNA (siRNA) technique. Cell survival, sub-lethal damage (SLD), and potential lethal damage (PLD) repair following IR were assessed by clonogenic assay while changes in intracellular ROS, the apoptosis, and autophagy were followed by flow cytometry and Western blotting.

Results: Blocking ATM expression in U87MG cells increased intracellular ROS levels and sensitivity to the cytotoxic effects of IR and oxygen stress; effects that could be partly counteracted by the antioxidant N-acetylcysteine (NAC). Knock down of ATM rendered cells unable to repair sub-lethal or potentially lethal damage and DNA double strand breaks (DSB) after IR exposure; something that NAC could not counteract. ATM did control the pathways a cell used to die following IR and this did seem to be ROS-dependent.

Conclusion: ATM is involved in redox control but ROS elevations following ATM knock down seem more involved in the decision as to what cell death pathway is utilised after IR than DSB repair and radiosensitivity.

Keywords:

• ATM
• radiation
• intracellular ROS
• apoptosis
• autophagy

Acknowledgments

This work is supported by NSC97-2314-B-007-003-MY2 and NHRI-EX98-9827BI from the National Science Council, and National Health Research Institute, respectively, Taiwan, to Chi-Shiun Chiang. Shu-Chi Wang is supported by NSC-096–2917-I-007-101 from the National Science Council. We thank Prof. William H. McBride, UCLA, for helpful discussions on the manuscript. The authors are grateful to the Imaging Center of National Synchrotron Radiation Research Center for allowing us to use the Laser Scanning Confocal Microscopy.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.