Prevention of nitrogen mustard-induced apoptosis in normal and transformedlymphocytes by ebselen

The alkylating agent, nitrogen mustard (HN2), is thought to cause apoptosis through production of free oxygen radicals. To explore the mechanism of HN 2-induced apoptosis, we utilized ebselen, a selenoorganic compound with pot ent antioxidant activity. We examined whether ebselen would inhibit apoptos is in BALB/c mouse spleen lymphocytes and human MOLT-4 leukemia cells treat ed with HN2 (2.5 muM) in vitro. Non-toxic concentrations (<50 <mu>M) of ebs elen were found to prevent HN2-induced apoptosis of murine lymphocytes in a dose-dependent manner, as measured by cell viability, hypodiploid DNA form ation, and phosphatidylserine externalization. However, ebselen was ineffec tive at preventing spontaneous apoptosis in these cells, pointing to the se lectivity of its action. Furthermore, pretreatment with ebselen at 1-10 muM for 72 hr protected MOLT-4 cells from HN2-induced apoptosis and maintained cell viability and proliferation as monitored by the above-mentioned param eters, This was accompanied by the preservation of mitochondrial transmembr ane potential and elevated glutathione levels and by a blockage of caspase- 3 and -9 activation. In vivo, ebselen also had a marked protective effect a gainst spleen weight loss associated with lymphocyte apoptosis in mice trea ted by HN2. Therefore, ebselen provides an efficient protection against HN2 -induced cell death in normal and tumoral lymphocytes and might prove usefu l as an antidote against alkylating agents. (C) 2000 Elsevier Science Inc.