Release of β-glucuronidase from peritoneal macrophages of normal and endotoxin-tolerant mice

Abstract

Lysosomal enzyme release from cells involved in inflammatory response could play a central role in the pathogenesis of endotoxin shock. Therefore we have studied the release of the lysosomal enzyme, β-glucuronidase, from peritoneal macrophages obtained from normal and endotoxin-tolerant B6CBF1 mice both before and after challenge with lethal doses of endotoxin. Unstimulated cells from tolerant mice spontaneously released a smaller percentage of their total β-glucuronidase content in culture than cells from normal mice during a 5-h incubation period. In support of the lysosomal enzyme release hypothesis, it was found that the in vitro release of β-glucuronidase was accelerated when cells were collected from the mouse peritoneum 3 h after i.v. challenge with a lethal dose (1.0 mg) of endotoxin. The increased in vitro "leakiness" of peritoneal macrophages following endotoxin challenge was less marked when tolerance was induced in mice by prior repeated injections of endotoxin. Furthermore, measurements of the total enzyme activities of peritoneal cells revealed a significant reduction in the β-glucuronidase content of cells from normal mice 3 h after endotoxin challenge but no such decrease for cells from tolerant mice. These results suggest that macrophages in endotoxin-sensitive mice release their lysosomal enzymes in vivo during endotoxemia, whereas cells found in tolerant mice do not.In related experiments, the phagocytosis of latex particles and inhibition of bacterial growth by macrophages from normal and tolerant mice were compared. These studies suggest that cells from tolerant mice may also release a smaller percentage of their lysosomal enzymes during phagocytosis.