Effects of doxorubicin (adriamycin) and [(+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)]propane (ICRF-187) on skeletal muscle protease activities

Adverse effects of doxorubicin (adriamycin) have been reported to be due to iron-catalyzed free radical formation, which can be prevented with the cyt oprotective chelating agent [(+)-1,2-bis(3,5-dioxopiperazinyl-1-yl)]propane (dexrazoxane; ICRF-187). Affected tissues include the heart, gastrointesti nal tract, and kidney. However, there is very little information on the eff ects of adriamycin on skeletal muscle, despite the fact that there is direc t and indirect evidence to show that both adriamycin and ICRF-187 are myoto xic. To investigate the mechanisms of cytotoxicity of these agents in skele tal muscle, we have conducted a systematic investigation of the activities of the major lysosomal (dipeptidyl aminopeptidase I and II and cathepsins B , D, H, and I,) and cytoplasmic (alanyl-, arginyl-, and leucyl aminopeptida se, dipeptidyl aminopeptidase IV, tripeptidyl aminopeptidase, and proline e ndopeptidase) muscle proteases. These enzymes play an important role in nor mal cellular function and represent potential targets for toxic and protect ive agents. Male Wistar rats (approx. 0.2 kg) were subjected to a pretreatm ent phase of 30 min followed by a treatment stage of either 2.5 or 24 h. Th e pretreatment involved injection of a single bolus of either saline (0.15 mol/l NaCl; 5 ml/kg ip) or ICRF-187 (100 mg/kg; 5 ml/kg ip). After 30 min, rats were injected again with a single bolus of either adriamycin (5 mg/kg; 10 ml/kg ip) or saline (0.15 mol/l NaCl; 10 ml/kg ip) in the treatment pha se. At either 2.5 or 24 h after the last adriamycin or saline injection, ra ts were killed for subsequent dissection of the gastrocnemius muscle for an alysis. In the 2.5-h study, there were significant reductions in cathepsin D activities of adriamycin-treated rats compared to saline injected control (p = 0.02). In both 2.5- and 24-h studies there were also significant diff erences (p = 0.05) in cathepsin H activities between rats treated with adri amycin and ICRF-187, although these differences were not significant when d ata were compared with corresponding saline-injected rats. There were no ot her overt effects for any of the other proteases at either 2.5 or 24 h. We conclude that both adriamycin and ICRF-187 have very little effect on the a ctivities of muscle proteases and that altered proteolysis is not involved in the reported pathological reactions induced by these agents. (C) 2001 Ac ademic Press.