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* From the Seattle Veterans Affairs Medical Center, Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Washington School of Medicine, Seattle, WA
Correspondence to Richard Goodman, MD, VA Medical Center, Pulmonary 111B, 1660 S. Columbian Way, Seattle, WA 98108
Sepsis
remains
a common risk factor for the development of ARDS. Neutrophils are
important participants in the acute lung injury process. However,
multiple CXC chemokines are present in the lung fluids of patients with
ARDS, including interleukin-8 (IL-8), epithelial neutrophil activating
protein-78, and growth-related oncogene-
, all of which are
potent and specific chemoattractants for polymorphonuclear leukocytes
(PMNs). Thus, the predominant mechanisms for PMN recruitment in ARDS
remain unclear. PMNs express two cell surface receptors for the CXC
chemokines. IL-8 binds both CXCR1 and CXCR2 with high affinity, whereas
the other CXC chemokines bind with high affinity to only CXCR2.
In vitro, stimulation of normal PMNs with IL-8 results in
internalization of both receptors. However, CXCR1 is rapidly
reexpressed, whereas CXCR2 reexpression is considerably slower. We
sought to investigate the effect of these mechanisms in
vivo, with PMNs from patients with severe sepsis. By flow
cytometry, CXCR2 expression was downregulated by 50% in patients with
sepsis (n = 14) relative to normal donors (n = 8) (p < 0.003),
while CXCR1 expression was not significantly reduced. In
vitro, the migratory response toward IL-8 was similar in PMNs from
patients with sepsis and normal donors. By contrast, the migratory
response to the other CXC chemokines, epithelial neutrophil activating
protein-78, growth-related gene-
, -ß, -
, which bind only CXCR2,
was markedly suppressed in PMNs from patients with sepsis compared with
normal PMNs (p < 0.05). Polyclonal antibody specific for CXCR1
substantially inhibited in vitro migration of PMNs from
patients with sepsis compared with normal donors (p < 0.05). As
expected, antibody inhibition of CXCR1 did not affect PMN migration to
the bacterial-derived chemoattractant,
formyl-methionyl-leucyl-phenylalanine, whose signal is mediated
by a distinct receptor. Thus, we demonstrate that CXCR2 is
downregulated to a functionally significant degree in PMNs from
patients with sepsis. We speculate that despite a redundant system of
CXC chemokines and receptors, IL-8 and CXCR1 function as the dominant
ligand/receptor pair in patients with sepsis. These observations are
relevant to therapeutic strategies aimed at attenuating host-mediated
acute inflammation, while potentially preserving host defenses mediated
by bacterial-derived peptides such as
formyl-methionyl-leucyl-phenylalanine.
This article has been cited by other articles:
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T. L. Ness, C. M. Hogaboam, R. M. Strieter, and S. L. Kunkel Immunomodulatory Role of CXCR2 During Experimental Septic Peritonitis J. Immunol., October 1, 2003; 171(7): 3775 - 3784. [Abstract] [Full Text] [PDF] |
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