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Differential expression of IL-1 beta, TNF-alpha, IL-6, and IL-8 in human monocytes in response to lipopolysaccharides
S Agarwal1, N P Piesco, L P Johns
1Division of Oral Biology, University of Pittsburgh School of Dental Medicine, Pennsylvania 15261-1964, USA.
Abstract:
Macrophages respond to bacterial lipopolysaccharides (LPS) and activate several host defense functions through production of mediators. However, it is not clear whether the degree of macrophage responsiveness to different sources of LPS is equivalent to or varies with the source of LPS. Therefore, in this report, we examined the extent of the human monocyte response to LPS derived from two oral pathogens, Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg). Additionally, due to its well-established ability to activate monocytes, we used LPS from Escherichia coli (Ec). Human monocytes, when activated with a specific source of LPS, exhibited rapid expression of mRNA for IL-1 beta, TNF-alpha, and IL-8, which was followed by IL-6, as measured by RNA-PCR. Moreover, the expression of mRNA for these cytokines was followed by cytokine synthesis. Monocytes from the same subject, when activated with LPS from Pg, Aa, or Ec expressed quantitatively different levels of mRNA and proteins for all four cytokines. A given LPS induced either high or low expression of the battery of cytokines tested, indicating that the expression of these pro-inflammatory cytokines may be regulated by a single or a cluster of gene(s). However, no apparent differences in the time course of mRNA expression for these cytokines were observed in response to any of the LPS tested. Furthermore, the relative ability of the different sources of LPS to induce mRNA for cytokines varied throughout a wide range of LPS concentrations. This suggests that differences exist in the sensitivity of monocytes to a specific LPS, rather than in the kinetics of the secretory process itself.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Different bacterial lipopolysaccharides (LPS) from oral pathogens and E. coli trigger varying human monocyte responses, affecting cytokine production and sensitivity.
Area of Science:
- Immunology
- Microbiology
Background:
- Macrophages are key immune cells that respond to bacterial lipopolysaccharides (LPS).
- The extent of macrophage activation varies depending on the LPS source, impacting host defense functions.
Purpose of the Study:
- To investigate and compare human monocyte responses to LPS from oral pathogens Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg).
- To evaluate monocyte responsiveness to LPS from Escherichia coli (Ec) as a control.
Main Methods:
- Human monocytes were stimulated with LPS from Aa, Pg, and Ec.
- Messenger RNA (mRNA) expression for IL-1 beta, TNF-alpha, IL-8, and IL-6 was measured using RNA-PCR.
- Cytokine protein synthesis was also assessed.
Main Results:
- Monocytes rapidly expressed mRNA for IL-1 beta, TNF-alpha, and IL-8, followed by IL-6, after LPS activation.
- LPS from different sources (Pg, Aa, Ec) induced quantitatively different levels of mRNA and protein for all tested cytokines.
- Monocyte sensitivity to LPS varied across different concentrations, suggesting source-specific differences in activation.
Conclusions:
- Human monocyte responsiveness to LPS is source-dependent, leading to varied pro-inflammatory cytokine profiles.
- Differences in monocyte activation by LPS are likely due to variations in LPS sensitivity rather than the cytokine secretion process itself.