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Bacterial lipopolysaccharide rapidly inhibits expression of C-C chemokine receptors in human monocytes.

Sica A, Saccani A, Borsatti A, Power CA, Wells TN, Luini W, Polentarutti N, Sozzani S, Mantovani A - J. Exp. Med. (1997)

Bottom Line: As expected, LPS-induced inhibition of CCR2 mRNA expression was associated with a reduction of both MCP-1 binding and chemotactic responsiveness.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.

View Article: PubMed Central - PubMed

Affiliation: Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.

ABSTRACT
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-alpha). 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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Destabilization of CCR2 mRNA by LPS. (A) effect of LPS  (100 ng/ml) on the CCR2B mRNA transcript stability. Total RNA was  purified from fresh human monocytes incubated for 4 h as indicated. B  shows the ethidium bromide stained ribosomal RNA. (C) Nuclear runoff analysis of the MCP-1, CCR1, CCR2, and CCR5 genes. Fresh human monocytes were incubated with 100 ng/ml of LPS for different periods as indicated.
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Figure 2: Destabilization of CCR2 mRNA by LPS. (A) effect of LPS (100 ng/ml) on the CCR2B mRNA transcript stability. Total RNA was purified from fresh human monocytes incubated for 4 h as indicated. B shows the ethidium bromide stained ribosomal RNA. (C) Nuclear runoff analysis of the MCP-1, CCR1, CCR2, and CCR5 genes. Fresh human monocytes were incubated with 100 ng/ml of LPS for different periods as indicated.

Mentions: Having established that low concentrations of LPS cause a rapid and drastic reduction of CCR2, subsequent work was focused mainly on this receptor. To investigate the mechanism of LPS action, we estimated its effects on both mRNA stability and gene transcription (Fig. 2). ActD (1 μg/ml) was added to fresh human monocytes in the presence or absence of 100 ng/ml of LPS and total RNA was extracted at different times as indicated. In the presence of ActD the estimated half-life of the transcript was about 1.5 h (Fig. 2, lanes 2–6), while cotreatment with ActD and LPS (lanes 7–11) considerably shortened this time (∼45 min). To evaluate the effects of LPS on gene transcription, we used nuclear run-off analysis (Fig. 2 C). In agreement with published results (34), LPS was able to induce MCP-1 gene transcription. In contrast, LPS did not induce appreciable variations on the transcription rate of the CCR2, CCR1, and CCR5 genes. Taken together, these data indicate that the inhibitory action of LPS on CCR2 gene expression is posttranscriptional and suggest similarities of the mechanisms controlling gene expression of the three β chemokine receptors studied here.


Bacterial lipopolysaccharide rapidly inhibits expression of C-C chemokine receptors in human monocytes.

Sica A, Saccani A, Borsatti A, Power CA, Wells TN, Luini W, Polentarutti N, Sozzani S, Mantovani A - J. Exp. Med. (1997)

Destabilization of CCR2 mRNA by LPS. (A) effect of LPS  (100 ng/ml) on the CCR2B mRNA transcript stability. Total RNA was  purified from fresh human monocytes incubated for 4 h as indicated. B  shows the ethidium bromide stained ribosomal RNA. (C) Nuclear runoff analysis of the MCP-1, CCR1, CCR2, and CCR5 genes. Fresh human monocytes were incubated with 100 ng/ml of LPS for different periods as indicated.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196159&req=5

Figure 2: Destabilization of CCR2 mRNA by LPS. (A) effect of LPS (100 ng/ml) on the CCR2B mRNA transcript stability. Total RNA was purified from fresh human monocytes incubated for 4 h as indicated. B shows the ethidium bromide stained ribosomal RNA. (C) Nuclear runoff analysis of the MCP-1, CCR1, CCR2, and CCR5 genes. Fresh human monocytes were incubated with 100 ng/ml of LPS for different periods as indicated.
Mentions: Having established that low concentrations of LPS cause a rapid and drastic reduction of CCR2, subsequent work was focused mainly on this receptor. To investigate the mechanism of LPS action, we estimated its effects on both mRNA stability and gene transcription (Fig. 2). ActD (1 μg/ml) was added to fresh human monocytes in the presence or absence of 100 ng/ml of LPS and total RNA was extracted at different times as indicated. In the presence of ActD the estimated half-life of the transcript was about 1.5 h (Fig. 2, lanes 2–6), while cotreatment with ActD and LPS (lanes 7–11) considerably shortened this time (∼45 min). To evaluate the effects of LPS on gene transcription, we used nuclear run-off analysis (Fig. 2 C). In agreement with published results (34), LPS was able to induce MCP-1 gene transcription. In contrast, LPS did not induce appreciable variations on the transcription rate of the CCR2, CCR1, and CCR5 genes. Taken together, these data indicate that the inhibitory action of LPS on CCR2 gene expression is posttranscriptional and suggest similarities of the mechanisms controlling gene expression of the three β chemokine receptors studied here.

Bottom Line: As expected, LPS-induced inhibition of CCR2 mRNA expression was associated with a reduction of both MCP-1 binding and chemotactic responsiveness.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.

View Article: PubMed Central - PubMed

Affiliation: Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.

ABSTRACT
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-alpha). 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.

Show MeSH