Examination of chlorpromazine and other amphipathic drugs on the activity of lipopolysaccharide antagonists, E5564 and E5531

The synthetic antagonists of lipopolysaccharide (LPS), E5531 and E5564, are analogs of the lipid A portion of LPS that not only lack agonistic activit y but also inhibit the biological effects of LPS both in vitro and in vivo. The effects of LPS and these synthetic antagonists have been localized to the recently described Toll-like receptor 4 (TLR4). A recent report indicat ed that the naturally occurring LPS antagonist Rhodobacter sphaeroides LPS loses its antagonist properties and gains proinflammatory qualities in the presence of chlorpromazine and other amphipathic drugs. To determine whethe r these reported actions occur with our chemically defined LPS antagonists, we examined the effects of chlorpromazine, fluphenazine, trifluoperazine, and lidocaine on the antagonism elicited by RsLPS and E5531 in U373 cells, which produce IL-6 in response to LPS. We also tested the effects of these amphipathic molecules on the LPS-neutralizing activity of RsLPS and E5564 o n LPS-induced TNF-alpha release in human whole blood. The results indicate that neither chlorpromazine. fluphenazine, trifluoperazine nor lidocaine al ter the activity of E5531 or E5564 in an ill vitro cell system or human who le blood. Furthermore, chlorpromazine did not affect the antagonistic activ ity of RsLPS or E5564 on IL-6 generation by peripheral blood mononuclear ce lls. Thus, based on these data, our purified synthetic LPS-antagonists do n ot appear to lose their antagonistic properties and/or become agonists in t he presence of amphipathic agents or drugs.