Bacterial and H2O2 stress-induced apoptosis-like events in Cryptococcus neoformans

Cell death induced by adherence of Staphylococcus aureus was observed in Cryptococcus neoformans. To investigate this death mechanism, we examined three factors: actin dynamics using rhodamine-phalloidin staining, accumulation of reactive oxygen species (ROS) via conversion of 2,7'-dichlorofluorescein diacetate to 2,7'-dichlorofluorescein, and DNA fragmentation via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). In co-culture, actin visibly clumped and the percentage of ROS- and TUNEL-positive cells increased. The same cellular events were observed in C. neoformans after addition of hydrogen peroxide (H2O2), creating a bacterial cell-free system. After H,02 treatment and cell disruption, C. neoformans proteins in soluble fraction were separated by two-dimensional (2-D) electrophoresis. A voltage-dependent ion-selective channel was identified as one of the stress-enhanced proteins. Thus, the death of C. neoformans was accompanied by decreased actin turnover, enhanced ROS accumulation, and DNA fragmentation. Cell death appeared similar to apoptosis via mitochondrial pathways. (C) 2008 Elsevier Masson SAS. All rights reserved.