Yonago Acta medica 2012;55:1120
Mechanisms Underlying Production and Externalization of Oxidized Phosphatidylserine in Apoptosis: Involvement of Mitochondria
Atsushi Yamashita, Hitoshi Morikawa, Naoko Tajima, Mari Teraoka, Chiaki Kusumoto, Kazuhiro Nakaso and Tatsuya Matsura
Division of Medical Biochemistry, Department of Pathophysiological and Therapeutic Science, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
The present study was performed by using selective inhibitors of caspase-8 and caspase-3 functioning upstream and downstream from mitochondria, respectively to determine whether mitochondria are involved in the mechanisms underlying production and externalization of oxidized phosphatidylserine (PSox) during Fas-mediated apoptosis. Treatment with anti-Fas antibody induced caspase-3 activation, chromatin condensation, release of cytochrome c (cyt c) from mitochondria into the cytosol as well as production of PSox and its exposure to the cell surface in Jurkat cells. Inhibition of caspase-8 by pretreatment with Z-IETD-FMK, a membrane permeable selective caspase-8 inhibitor reduced mitochondrial cyt c release, the amount of PSox not only within but also on the surface of Jurkat cells, caspase-3 activation, and apoptotic cell number after treatment with anti-Fas antibody. In contrast, Z-DEVD-FMK, a membrane permeable selective caspase-3 inhibitor was unable to inhibit cyt c release, and the amount of PSox both within and on the surface of the cells after anti-Fas antibody, although it suppressed caspase-3 activation and apoptosis. Thus, these results strongly suggest that mitochondria play an important role in production of PSox and subsequent its externalization during apoptosis.
KKey words: apoptosis; caspase inhibitor; cytochrome c; mitochondria; oxidized phosphatidylserine