SULFUR MUSTARD-INDUCED INCREASE IN INTRACELLULAR FREE CALCIUM LEVEL AND ARACHIDONIC-ACID RELEASE FROM CELL-MEMBRANE

The mechanism of action of the alkylating agent bis-(2-chloroethyl)sul fide (sulfur mustard, SM) was studied using the in vitro mouse neurobl astoma-rat glioma hybrid NG108-15 clonal cell line model. Following 0. 3 mM SM exposure, cell viability remained high (>80% of untreated cont rol) up to 9 hr and then declined steadily to about 40% of control aft er 20-24 hr. During the early period of SM exposure, when there was no significant cell viability loss, the following effects were observed. The cellular glutathione level decreased 20% after 1 hr and 34% after 6 hr. Between 2 and 6 hr, there was a time-dependent increase (about 10 to 30%) in intracellular free calcium (Ca2+), which was localized t o the limiting membrane of swollen endoplasmic reticula and mitochondr ia, to euchromatin areas of the nucleus, and to areas of the cytosol a nd plasma membrane. Moreover, there was also a time-dependent increase in the release of isotopically labeled arachidonic acid ([H-3]AA) fro m cellular membranes. Increase in [H-3]AA release was 28% at 3 hr and about 60-80% between 6 and 9 hr. This increase in [H-3]AA release was inhibited by quinacrine (20 mu M), which is a phospholipase (PLA(2)) i nhibitor. At 16 hr after SM exposure, there was a large increase (abou t 200% of control) in [H-3]AA release, which was coincident with a 50% loss of cell viability. These results suggest a Ca2+-mediated toxic m echanism of SM via PLA(2) activation and arachidonate release. (C) 199 5 Academic Press, Inc.