Inhibition of lysosomal enzyme release from rat leukocytes by auranofin. A new chrysotherapeutic agent

Abstract

Auranofin (SK&F D-39162), a new antiarthritic gold compound reported to be orally effective in animal (adjuvant rat) and human (rheumatoid) arthritic conditions, is a potent in vitro inhibitor of the release of lysosomal enzymes from phagocytizing rat leukocytes. Auranofin, at micromolar concentrations (1-10 microM), produced a dose-dependent reduction in extracellular levels of lysosomal enzyme markers (beta-glucuronidase and lysozyme) which are selectively released from rat leukocytes during phagocytosis of zymosan particles. The reduction in extracellular levels of lysosomal enzymes appears to be caused by inhibition of their selective cellular release, since effective concentrations of auranofin did not produce leukocyte cytotoxicity or inhibition of cell-free lysosomal enzyme activity. Morphologic and biochemical evidence indicated that auranofin also interferes with phagocytosis of zymosan particles. The potent in vitro activity of auranofin appears to result from its unique gold complex, since neither structurally related nongold compounds nor clinically used gold compounds (gold sodium thiomalate and gold thioglucose) were potent inhibitors of lysosomal enzyme release. The results of this investigation suggest that the antiarthritic activity of auranofin may be caused at least in part, by inhibition of lysosomal enzyme release and/or cellular processing of antigens.