The effect of caspase-inhibitors on radiation induced apoptosis in human peripheral blood lymphocytes: an electron microscopic approach.
Resting lymphocytes are sensitive to radiation damage and die by apoptosis. We investigated the effect of caspase-inhibitors on radiation induced apoptosis in human peripheral blood lymphocytes. Lymphocytes were irradiated in vitro with 5 Gy 60 Co-gamma-rays and cultured for 24 hours in the presence or absence of the caspase-inhibitors zVAD-fmk and zDEVD-fmk. Cell death was evaluated by electron microscopy. Irradiation in the absence of the inhibitors resulted in about 30% dead cells, almost all showing typical apoptotic morphologies. Addition of either one of the inhibitors could not rescue cells from death. Part of the dead lymphocytes (about 65%) still showed typical nuclear characteristics of apoptotic cells: sharply marginated, condensed chromatin, clumped into one sphere or into a crescent shaped mass. The remaining part of the dead cells had ultrastructural characteristics, aberrant from apoptotic cells: clumping of the chromatin was less pronounced and less sharply marginated. Irregular clumps were formed. Data indicate that part of the lymphocytes go in apoptosis in a caspase-independent way. The other part shows caspase-dependent apoptosis with respect to the nuclear events.
Cornelissen
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M
Department of Human Anatomy, Embryology and Histology, University of Gent, Louis Pasteurlaan 2, Belgium. ria.cornelissen@rug.ac.be
Vral
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A
Thierens
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de Ridder
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