Abstract
Fungal gliotoxin (GTX) is known to possess several potent biological effects such as immunosuppression and apoptosis. The function of this toxin, however, remains to be established. Herein we focused on the effects of GTX on the NADPH oxidase system, which includes the production of superoxide (O2-) and the exocytosis of the oxidant-producing intracellular compartments (OPIC), in human neutrophils stimulated with phorbol myristate acetate (PMA). Biochemical analyses indicated that GTX inhibits both the extracellular release of O2- and the intracellular production of the oxidant generated upon activation of the NADPH oxidase complex, and that the toxin suppresses the up-regulation to the cell surface of alkaline phosphatase activity which is a marker enzyme of OPIC. Fluorescence as well as enzyme cytochemical studies showed that O2- is produced in intracellular compartments in PMA-stimulated cells, but not in the stimulated cells exposed to GTX. Moreover, electron microscopy revealed that GTX inhibits the association of OPIC with the plasma membrane. Taken together, the present findings confirmed that GTX inhibits the extracellular release of O2- and the intracellular production of the oxidant, and first demonstrate that the toxin suppresses the exocytosis of OPIC in human neutrophils stimulated with PMA.
