β-Lapachone-induced reactive oxygen species (ROS) generation mediates autophagic cell death in glioma U87 MG cells

Autophagy is mainly responsible for the degradation of long-lived proteins and subcellular organelles. Autophagy is responsible for the non-apoptotic cell death, and plays a crucial role in regulating cellular functions. beta-Lapachone is a quinone-containing compound originally obtained from the lapacho tree in South America. Here, we show that beta-lapachone induces death in U87 MG cells, which is not inhibited by blockers of pan-caspase or necrosis. beta-Lapachone-induced cell death gradually increased in a time-dependent manner in U87 MG cells, which were partly prevented by pretreatment of a specific inhibitor of NQO1 (dicoumarol). These results suggested that beta-lapachone-induced cell death was mediated by NQO1-independent as well as NQO1-dependent cell death pathways. During progression of beta-lapachone-induced cell death, translocation and processing of LC3 as well as an increase in acidic vesicular organelles, as assessed by acridine orange staining, were observed. Furthermore, beta-lapachone-induced cell death was inhibited by either a knockdown of beclin-1/Atg-6 or Atg-7 gene expression or by autophagy inhibitors (3-methyl adenine or bafilomycin A1). Reactive oxygen species (ROS) were involved in beta-lapachone-induced autophagic cell death of U87 MG glioma cells, because beta-lapachone induced ROS production and antioxidant N-acetylcysteine (NAC) decreased autophagic cell death. Our results collectively demonstrate that ROS mediate beta-lapachone-induced autophagic cell death in U87 MG glioma cells. (C) 2010 Elsevier Ireland Ltd. All rights reserved.