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Granzyme B of cytotoxic T cells induces extramitochondrial reactive oxygen species production via caspase-dependent NADPH oxidase activation

By J. Aguiló, A. Anel, E. Catalán, A. Sebastián, R. Acín-Pérez, J. Naval, R. Wallich, M. Simon and J. Pardo


Induction of reactive oxygen species (ROS) is a hallmark of granzyme B (gzmB)-mediated pro-apoptotic processes and target cell death. However, it is unclear to what extent the generated ROS derive from mitochondrial and/or extra-mitochondrial sources. To clarify this point, we have produced a mutant EL4 cell line, termed EL4-ρ<sup>0</sup>, which lacks mitochondrial DNA, associated with a decreased mitochondrial membrane potential and a defective ROS production through the electron transport chain of oxidative phosphorylation. When incubated with either recombinant gzmB plus streptolysin or ex vivo gzmB<sup>+</sup> cytotoxic T cells, EL4-ρ<sup>0</sup> cells showed phosphatydylserine translocation, caspase 3 activation, Bak conformational change, cytochrome c release and apoptotic morphology comparable to EL4 cells. Moreover, EL4-ρ<sup>0</sup> cells produced ROS at levels similar to EL4 under these conditions. GzmB-mediated ROS production was almost totally abolished in both cell lines by the pan-caspase inhibitor, Z-VAD-fmk. However, addition of apocynin, a specific inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, led to a significant reduction of ROS production and cell death only in EL4-ρ<sup>0</sup> but not EL4 cells. These data suggest that gzmB-induced cell death is accompanied by a caspase-dependent pathway of extra-mitochondrial ROS production, most probably through activation of NADPH oxidase

Year: 2010
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Provided by: MPG.PuRe
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