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From the * Istituto di Ricerche Farmacologiche "Mario Negri", 20157 Milan, Italy; The present study was designed to investigate the effect of bacterial lipopolysaccharide (LPS)
on C-C chemokine receptors (CCR) expressed in human mononuclear phagocytes. LPS caused a rapid and drastic reduction of CCR2 mRNA levels, which binds MCP-1 and -3. CCR1 and
CCR5 mRNAs were also reduced, though to a lesser extent, whereas CXCR2 was unaffected.
The rate of nuclear transcription of CCR2 was not affected by LPS, whereas the mRNA half
life was reduced from 1.5 h to 45 min. As expected, LPS-induced inhibition of CCR2 mRNA
expression was associated with a reduction of both MCP-1 binding and chemotactic responsiveness. The capacity to inhibit CCR2 expression in monocytes was shared by other microbial agents and cytokines (inactivated Streptococci, Propionibacterium acnes, and to a lesser extent, IL-1
and TNF-
Laboratory of
Molecular Biology, Istituto G. Gaslini, 16148 Genova-Quarto, Italy; § Section of Pathology and
Immunolgy, Department of Biotechnology, University of Brescia, 25123 Italy;
Geneva Biomedical
Research Institute, Glaxo Wellcome Research and Development, 1228 Plan-les-Ouates, Geneva,
Switzerland.
). In contrast, IL-2 augmented CCR2 expression and MCP-1 itself had no effect.
These results suggest that, regulation of receptor expression in addition to agonist production is
likely a crucial point in the regulation of the chemokine system.
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