tailieunhanh - Báo cáo khoa học: Lysosomal enzymes promote mitochondrial oxidant production, cytochrome c release and apoptosis

Exposure of mammalian cells to oxidant stress causes early (iron catalysed) lysosomal rupture followed by apoptosis or necrosis. Enhanced intracellular production of reactive oxygen species (ROS), presumably of mitochondrial origin, is also observed when cells are exposed to nonoxidant pro-apoptotic agonists of cell death. We hypothesized that ROS generation in this latter case might promote the apoptotic cascade and could arise from effects of released lysosomal materials on mitochondria. | Eur. J. Biochem. 270 3778-3786 2003 FEBS 2003 doi j Lysosomal enzymes promote mitochondrial oxidant production cytochrome c release and apoptosis Ming Zhao1 Fernando Antunes1 2 John W. Eaton1 3 and Ulf T. Brunk1 - Division of Pathology II Faculty of Health Sciences Linkoping University Sweden 2Grupo de Bioquimica e Biologia Teoricas -Instituto Bento da Rocha Cabral and Department of Chemistry and Biochemistry Faculty of Sciences University of Lisbon Portugal 3 James Graham Brown Cancer Center University of Louisville Louisville KY USA Exposure of mammalian cells to oxidant stress causes early iron catalysed lysosomal rupture followed by apoptosis or necrosis. Enhanced intracellular production of reactive oxygen species ROS presumably of mitochondrial origin is also observed when cells are exposed to nonoxidant pro-apoptotic agonists of cell death. We hypothesized that ROS generation in this latter case might promote the apoptotic cascade and could arise from effects of released lysosomal materials on mitochondria. Indeed in intact cells J774 macrophages HeLa cells and AG-5-8 fibroblasts the lysosomotropic detergent O-methyl-serine dodecylamide hydrochloride MSDH causes lysosomal rupture enhanced intracellular ROS production and apoptosi j. Futthermore. in mixtures of rat liver lysosomes and mitochondria selective rupture of lysosomes by MSDH promotes mitochondrial ROS prodLiciíon and cytochrome c release whereas MSDH has no direct effect on ROSgeneration by purifed mito chondria. Intracellular lysosomal rupture is associated with the release of among other constituents cathepsins and activation of phospholipase A2 PLA2 . We find that addition of purified cathepsins B or D or of PLA2 causes substantial increases in ROSgeneration by purified mitochondria. Furthermore PLA2 - but not cathepsins B or D - causes rupture of semipurified lysosomes suggesting an amplification mechanism. Thus initiation of the apoptotic cascade by nonoxidant .