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Infection and Immunity, May 2001, p. 3143-3149, Vol. 69, No. 5
Departments of
Pediatrics,1 Microbiology and
Immunology,3 and Biochemisty and
Molecular Biology,2 Dalhousie University and
IWK Grace Health Centre, Halifax, Nova Scotia, Canada
Received 5 October 2000/Returned for modification 20 December
2000/Accepted 21 February 2001
Neutrophils exposed to low concentrations of gram-negative
lipopolysaccharide (LPS) become primed and have an increased oxidative response to a second stimulus (e.g.,
formyl-methionyl-leucyl-phenylalanine [fMLP]). In studies aimed at
understanding newborn sepsis, we have shown that neutrophils of
newborns are not primed in response to LPS. To further understand the
processes involved in LPS-mediated priming of neutrophils, we explored
the role of extracellular signal-related protein kinases (ERK 1 and 2)
of the mitogen-activated protein kinase family. We found that LPS
activated ERK 1 and 2 in cells of both adults and newborns and that
activation was plasma dependent (maximal at
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.5.3143-3149.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Activation of Extracellular Signal-Related Protein Kinases 1 and
2 of the Mitogen-Activated Protein Kinase Family by
Lipopolysaccharide Requires Plasma in Neutrophils from Adults and
Newborns
5%) through LPS-binding
protein. Although fibronectin in plasma is required for
LPS-mediated priming of neutrophils of adults assessed by
fMLP-triggered oxidative burst, it was not required for LPS-mediated
activation of ERK 1 and 2. LPS-mediated activation was dose and time
dependent; maximal activation occurred with approximately 5 ng of LPS
per ml and at 10 to 40 min. We used the inhibitor PD 98059 to study the
role of ERK 1 and 2 in the LPS-primed fMLP-triggered oxidative burst.
While Western blotting showed that 100 µM PD 98059 completely
inhibited LPS-mediated ERK activation, oxidative response to fMLP by a
chemiluminescence assay revealed that the same concentration inhibited
the LPS-primed oxidative burst by only 40%. We conclude that in
neutrophils, LPS-mediated activation of ERK 1 and 2 requires plasma and
that this activation is not dependent on fibronectin. In addition, we
found that the ERK pathway is not responsible for the lack of LPS
priming in neutrophils of newborns but may be required for 40% of the
LPS-primed fMLP-triggered oxidative burst in cells of adults.
*
Corresponding author. Mailing address: 8th Floor East
Research Laboratories, IWK Heath Centre, 5850 University Ave., Halifax, Nova Scotia B3J 3G9, Canada. Phone: (902) 428-8498. Fax: (902) 428-3217. E-mail: Robert.Bortolussi{at}DAL.ca.
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