Radioprotective properties of detoxified lipid A

Endotoxic lipopolysaccharide (LPS) has long been known to possess radioprotective properties. Nevertheless, the toxicity of LPS, or its principal bioactive component, Lipid A, has detracted from its potential use as a radioprotectant. Recently, a relatively non-toxic monophosphoryl Lipid A that retains many of the immunobiological properties of native LPS has been prepared from a polyaccharide-deficient and heptoseless Re mutant strain of S. minnesota. The authors conducted experiments that evaluated and compared the radioprotective efficiency of native endotoxin, as well as the mono (detoxified) and diphosphoryl (toxic) forms of Lipid A, in both responder (CD2F1 and C3H/HeN) and non-responder (C3H/HeJ) mice. It has been found that the optimal dose for the mono- and diphosphoryl Lipid A are approximately the same (800 μg/kg in CD2F1 mice), and that both compounds provide maximum protection when administered 24 h before exposure to an LD100 dose of cobalt - 60 gamma radiation. Possible mechanisms for the radioprotective action of detoxified Lipid A are suggested