Protection of mice from lethal endotoxemia by use of an ornithine-containing lipid or a serine-containing lipid.

The effects of an ornithine-containing lipid [alpha-N-(3-acyloxyacyl)-ornithine (Orn-L)] or a serine-containing lipid [alpha-N-(3-acyloxyacyl)-serine (Ser-L)] from Flavobacterium meningosepticum on lethal endotoxemia in mice were examined. When 500 micrograms of Orn-L was intravenously administered 1 h before intravenous administration of a lethal dose of endotoxin, none of the mice died. The protective effect of Ser-L was weaker than that of Orn-L. Light and electron microscopic studies demonstrated that necrosis of hepatocytes caused by endotoxin was prevented by pretreatment with Orn-L. Furthermore, Kupffer cells were activated morphologically 1 h after the administration of Orn-L or Ser-L, and the liposomes of the lipoamino acids were incorporated into phagolysosomes in activated Kupffer cells. The activity of tumor necrosis factor in sera of endotoxin-treated mice was decreased markedly by pretreatment of mice with Orn-L. In vitro, the lipoamino acids suppressed endotoxin-induced tumor necrosis factor generation but did not suppress tumor necrosis factor generation induced by zymosan and whole cells of Staphylococcus aureus. These results suggested that Orn-L and Ser-L can be used as specific blocking agents against endotoxin. The blocking mechanism may be antagonistic, because of the structural similarities between the lipoamino acids and endotoxin lipid A.