Inhibition of LPS-induced systemic and local TNF production by a synthetic anti-endotoxin peptide (SAEP-2)

Abstract

Lipopolysaccharide (LPS) exerts its biological activity through the lipid A moiety. We tested the efficiency in inhibiting TNF production in sera and in tissues of mice and in the derma of rabbits challenged with LPS, of a synthetic anti-LPS peptide (SAEP-2) previously shown to specifically detoxify the lipid A region of LPS on the basis of structural similarities with the antibiotic polymyxin B (PMXB). In mice, SAEP-2 (100 μg/mouse, i.v.) injected with various schedules ('-30 to +10 min from LPS at 50 ng/mouse, i.v.) significantly inhibited serum TNF as well as liver, spleen and lung-associated TNF. In rabbits, SAEP-2 significantly inhibited TNF produced in dermal tissue and the resulting local hemorrhagic necrosis. The amount of tissue-associated TNF released by LPS challenge in the mouse was up to 6 times that present in the serum and inhibition by SAEP-2 or PMXB accounted for 75% of the total. Direct measurement of the binding kinetics by surface plasmon resonance and molecular filtration at equilibrium revealed that SAEP-2 and PMXB bind to LPS only in the presence of a significant amount of water but that they are unable to bind LPS in undiluted serum. Altogether these findings strongly suggest that inhibition of LPS-induced TNF by SAEP-2 and PMXB may occur in tissues.