In vivo inhibition by antioxidants of adriamycin-induced apoptosis in murine peritoneal macrophages

Adriamycin (ADM) is an oncostatic of the anthracycline family with confirme d experimental and clinical efficiency. This antitumoral drug has been repo rted to stimulate macrophage activity and is able to induce apoptosis (AP) in some tumour cells. The objective of the present work was to investigate if in vivo administration of ADM to mice induces AP in their peritoneal mac rophages (PM). AP was expressed by the apoptotic index (AI) of peritoneal m acrophages observed under fluorescence microscope after ethidium bromide an d acridine orange staining and confirmed by detection of the ladder pattern on DNA electrophoresis, indicates DNA fragmentation in 80-120 by character istic of apoptotic state. 24 hours after i.p ADM administration, AP was obs erved in PM. The effect was best visible after the injection of 5 mg/kg ADM . (AI : 76.3 +/- 8.9 vs untreated control group AI : 2.8 +/- 1.1). In the A DM heated group a DNA ladder electrophoretic pattern was observed while DNA from normal PM was genomic. Since ADM toxicity has been attributed to reac tive oxygen species generation, we investigated its possible participation in AP induction by pretreating mice with antioxidants : (+)-a-tocopherol ac id succinate (30 IU/mouse per os) for 3 days before ADM administration with E. coli lipopolysacharide (0.15 mug/mouse i.p.) 24 hours before ADM admini stration or with superoxide dismutase (10,000 IU/mouse i.p.) 1 hour before ADM administration. AI was significantly decreased, with values close to th ose of the untreated control group (AI : 15 +/- 5.7, 9.6 +/- 8.0 and 32.9 /- 6.9, respectively). Antioxidants given before ADM treatment significantl y increased the live cell index (p less than or equal to 0.001) in all the groups while inactivated antioxidants no longer protect PM against the ADM AP induction. DNA analysis confirmed the effect: in the untreated control a nd in the antioxidant protected groups DNA was genomic while in either ADM or inactivated-antioxidants + ADM treated groups, DNA presented the ladder pattern. AP can thus be induced in PM by ADM and inhibited by antioxidants. These observations may have clinical applications.