Previous Article | Next Article ![]()
Infection and Immunity, August 1999, p. 3824-3829, Vol. 67, No. 8
Eijkman-Winkler Institute for Microbiology,
Received 7 December 1998/Returned for modification 18 February
1999/Accepted 6 May 1999
During gram-negative sepsis, human monocytes are triggered to
produce large quantities of proinflammatory cytokines such as tumor
necrosis factor alpha (TNF-
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Lipopolysaccharide-Induced Tumor Necrosis Factor
Alpha Production by Human Monocytes Involves the
Raf-1/MEK1-MEK2/ERK1-ERK2 Pathway
) in response to endotoxin
(lipopolysaccharide [LPS]). Several studies have identified signal
transduction pathways that are activated by LPS, including activation
of nuclear factor-
B (NF-
B) and activation of mitogen-activated
protein kinases (MAPKs), including ERK1 and ERK2, c-Jun N-terminal
kinase, and p38. In this study, the relevance of ERK1 and ERK2
activation for LPS-induced TNF-
production by primary human
monocytes has been addressed with PD-098059, which specifically blocks
activation of MAPK kinase (MEK) by Raf-1. TNF-
levels in the
monocyte culture supernatant, induced by 10 ng of LPS/ml, were reduced
by PD-098059 (50 µM). In addition, PD-098059 also reduced TNF-
mRNA expression when cells were stimulated for 1 h with LPS. On
the other hand, LPS-induced interleukin-10 (IL-10) levels in the
monocyte supernatant were only slightly inhibited by PD-098059. Ro
09-2210, a recently identified MEK inhibitor, completely abrogated
TNF-
levels at nanomolar concentrations. IL-10 levels also were
strongly reduced. To show the efficacy of PD-098059 and Ro 09-2210, ERK1 and -2 activation was monitored by Western blotting with an
antiserum that recognizes the phosphorylated (i.e., activated) forms of
ERK1 and ERK2. Addition of LPS to human monocytes resulted in
activation of both ERK1 and ERK2 in a time- and concentration (50%
effective concentration between 1 and 10 ng of LPS/ml)-dependent
manner. Activation of ERK2 was blocked by PD-098059 (50 µM), whereas
ERK1 seemed to be less affected. Ro 09-2210 completely prevented
LPS-induced ERK1 and ERK2 activation. LPS-induced p38 activation also
was prevented by Ro 09-2210. These data further support the view that the ERK signal transduction pathway is causally involved in the synthesis of TNF-
by human monocytes stimulated with LPS.
*
Corresponding author. Mailing address: Department of
Internal Medicine, Room F02.126, University Hospital Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands. Phone: 31 30 2509111. Fax: 31 30 2523741. E-mail: B.S.vanAsbeck{at}digd.azu.nl.
Infection and Immunity, August 1999, p. 3824-3829, Vol. 67, No. 8
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|