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Antimicrobial Agents and Chemotherapy, November 1998, p. 2824-2829, Vol. 42, No. 11
Eisai Co., Ltd. Tsukuba Research
Laboratories, Tsukuba, Japan,1 and
Eisai Research Institute, Andover,
Massachusetts2
Received 13 April 1998/Returned for modification 11 June
1998/Accepted 19 August 1998
As a consequence of blood-borne bacterial sepsis, endotoxin or
lipopolysaccharide (LPS) from the cell walls of gram-negative bacteria
can trigger an acute inflammatory response, leading to a series of
pathological events and often resulting in death. To block this
inflammatory response to endotoxin, a novel lipid A analogue, E5531,
was designed and synthesized as an LPS antagonist, and its biological
properties were examined in vitro and in vivo. In murine peritoneal
macrophages, E5531 inhibited the release of tumor necrosis
factor alpha (TNF-
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Suppression of Murine Endotoxin Response by E5531,
a Novel Synthetic Lipid A Antagonist
and
) by Escherichia coli LPS with a 50%
inhibitory concentration (IC50) of 2.2 nM, while E5531 elicited no significant increases in TNF-
on its own. In support of
a mechanism consistent with antagonism of binding to a cell surface
receptor for LPS, E5531 inhibited equilibrium binding of radioiodinated
LPS ([125I]2-(r-azidosalicylamido)-1,
3'-dithiopropionate-LPS) to mouse macrophages with an
IC50 of 0.50 µM. E5531 inhibited LPS-induced increases in
TNF-
in vivo when it was coinjected with LPS into C57BL/6 mice
primed with Mycobacterium bovis bacillus
Calmette-Guérin (BCG). In this model, the efficacy of E5531 was
inversely correlated to the LPS challenge dose, consistent with a
competitive antagonist-like mechanism of action. Blockade of the
inflammatory response by E5531 could further be demonstrated in other
in vivo models: E5531 protected BCG-primed mice from LPS-induced
lethality in a dose-dependent manner and suppressed LPS-induced hepatic
injury in Propionibacterium acnes-primed or
galactosamine-sensitized mice. These results argue that the novel
synthetic lipid A analogue E5531 can antagonize the action of LPS in in
vitro and suppress the pathological effects of LPS in vivo in mice.
*
Corresponding author. Mailing address: Eisai Co., Ltd,
Tsukuba Research Laboratories for Drug Discovery, Biology unit I, 1-3, Tokodai 5-chome, Tsukuba, Ibaraki 300-26, Japan. Phone: 0298-47-5719. Fax: 0298-47-2037. E-mail: s1-kobayashi{at}eisai.co.jp.
Present address: Eisai Merrimack Valley, Andover, MA 01810-1036.
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