Nickel(II)-induced apoptosis in murine T cell hybridoma cells is associated with increased Fas ligand expression

Nickel(II) exposure has multiple effects on the immune system, including thymic involution, decreased T cell number in the spleen, and decreased natural killer cell activity. Using a murine T cell hybridoma cell line (KMls 8.3.5.1) to model nickel-induced cell death in immune cells, we found that nickel(II) acetate treatment rapidly induced apoptosis in these cells, as signified by membrane blebbing, chromatin condensation, increased annexin V staining, and an increased proportion of cells with hypodiploid DNA. Preceding these morphological changes, nickel(II) treatment increased expression of Fas ligand (FasL) mRNA and protein levels and also increased caspase-3-like protease activity. Coincubation with caspase inhibitors markedly inhibited nickel(II)-induced apoptosis, with Z-IETD-FMK, an inhibitor of caspase-8 and granzyme B, nearly as effective as less selective caspase inhibitors. Agents that generate reactive oxygen species (ROS) cause apoptosis in a variety of cells by inducing expression of FasL. Given that nickel(II) can directly generate ROS, exposure to nickel(II) may lead to apoptosis through a similar mechanism.