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Selective modulation of lipopolysaccharide-induced death and cytokine production by various muramyl peptides
M A Parant1, P Pouillart, C Le Contel
1Centre National de la Recherche Scientifique and University Paris 6, France.
Abstract:
Pretreatment of animals with the adjuvant muramyl dipeptide enhances both the production of circulating tumor necrosis factor and the sensitivity to the lethal effect of a lipopolysaccharide (LPS) challenge. The present study examined the capacity of various adjuvant muramyl dipeptide derivatives to potentiate responsiveness to LPS administration. Cytokine levels in serum were determined at various time intervals after LPS administration by bioassays and immunoassays; the cytokines examined were tumor necrosis factor, interleukin-1, interleukin-6, and gamma interferon. The time course of cytokine response was not modified by the pretreatment, but most of the levels were strongly enhanced. However, of the four compounds which were found to be potent priming agents, only two caused an increased sensitivity to LPS lethality, showing that elevated titers of cytokines in serum were not correlated with host sensitization. Interestingly, previous studies have shown that these two compounds also display neurobiological properties, implying a possible role of the central nervous system in LPS lethality. However, two hydrophilic derivatives with low activity as priming agents were capable of decreasing the toxicity of LPS when given after the challenge in galactosamine-sensitized mice. These results illustrate the diversity of responses elicited by immunological priming. They raise unanswered questions on the importance of endogenous mediators in the pathophysiological alterations during toxic shock.
Insights
Muramyl dipeptide derivatives can enhance cytokine production but do not always increase sensitivity to lipopolysaccharide (LPS) lethality. Some derivatives, however, can reduce LPS toxicity in specific models, highlighting diverse immune responses.
Area of Science:
- Immunology
- Toxicology
- Pharmacology
Background:
- Adjuvant muramyl dipeptide primes animals, increasing tumor necrosis factor and sensitivity to lipopolysaccharide (LPS) lethality.
- Understanding how muramyl dipeptide derivatives modulate LPS responsiveness is crucial for immune modulation and sepsis research.
Purpose of the Study:
- To investigate the capacity of various muramyl dipeptide derivatives to potentiate responsiveness to LPS administration.
- To determine the correlation between cytokine levels and host sensitization to LPS lethality.
- To explore the potential role of the central nervous system and the protective effects of certain derivatives.
Main Methods:
- Administration of muramyl dipeptide derivatives followed by LPS challenge in animal models.
- Quantification of serum cytokines (tumor necrosis factor, interleukin-1, interleukin-6, gamma interferon) using bioassays and immunoassays.
- Assessment of host sensitivity to LPS lethality and LPS toxicity in galactosamine-sensitized mice.
Main Results:
- Pretreatment with muramyl dipeptide derivatives enhanced serum cytokine levels post-LPS challenge, but not the time course of the response.
- Only two of four potent priming agents increased sensitivity to LPS lethality, indicating cytokine levels are not directly correlated with sensitization.
- Two hydrophilic derivatives reduced LPS toxicity when administered post-challenge in galactosamine-sensitized mice.
Conclusions:
- Muramyl dipeptide derivatives exhibit diverse effects on immune responses and LPS toxicity.
- Elevated cytokine titers do not necessarily correlate with increased host sensitization to LPS lethality.
- The findings suggest a complex interplay of factors, potentially involving the central nervous system, in LPS-induced pathophysiology and toxic shock.