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Effects of muramyl dipeptide and lead acetate on carbon clearance and endotoxin-induced mortality in mice
Abstract:
Muramyl dipeptide (MDP) is a nonspecific immune adjuvant thought to affect the macrophage. MDP had been used safely without immunosuppressive or toxic side effects in our laboratory and others. Endotoxin, or lipopolysaccharide (LPS), is thought to be responsible for many of the systemic toxic effects of gram-negative infection. Lead acetate potentiates the lethal effects of endotoxin, an effect attributed to increased hepatotoxicity involving both hepatocytes and Kupffer macrophages. This study was undertaken to examine putative mechanism of action of MDP relating to the reticuloendothelial system. Endotoxin was given intraperitoneally to susceptible mice that were pretreated with MDP, lead acetate, or both, and to unmodified controls. Lead acetate significantly enhanced lethality due to LPS, but pretreatment with MDP did not alter mortality. Carbon clearance was measured in mice treated with MDP, lead, or both. There was no difference in the phagocytic index of control mice and those mice treated with lead acetate at various times prior to the injection. Carbon clearance increased significantly in mice pretreated with MDP but was unaltered by the addition of lead acetate. We conclude that if hyperphagocytosis of endotoxin occurs in MDP-pretreated mice, it does not cause additional mortality. Muramyl dipeptide appeared to be a safe reticuloendothelial stimulant that did not enhance the toxicity of lead or LPS in this experimental model.
Insights
Muramyl dipeptide (MDP) is a safe immune stimulant. It did not increase mortality or toxicity when combined with lead acetate or lipopolysaccharide (LPS) in mice.
Area of Science:
- Immunology
- Toxicology
- Pharmacology
Background:
- Muramyl dipeptide (MDP) acts as a nonspecific immune adjuvant, potentially influencing macrophage activity.
- Lipopolysaccharide (LPS), an endotoxin, is associated with systemic toxicity in gram-negative infections.
- Lead acetate exacerbates endotoxin lethality by increasing hepatotoxicity.
Purpose of the Study:
- To investigate the mechanism of action of MDP on the reticuloendothelial system.
- To evaluate the combined effects of MDP, lead acetate, and LPS on mouse mortality and carbon clearance.
Main Methods:
- Mice were administered intraperitoneally with LPS, pretreated with MDP, lead acetate, or both.
- Mortality rates were recorded for all treatment groups.
- Carbon clearance assays were performed to assess reticuloendothelial system activity.
Main Results:
- Lead acetate significantly increased LPS-induced mortality.
- MDP pretreatment did not alter mortality rates, even when combined with lead acetate and LPS.
- MDP significantly enhanced carbon clearance, indicating increased phagocytic activity.
- Lead acetate did not affect carbon clearance in MDP-treated mice.
Conclusions:
- MDP is a safe reticuloendothelial stimulant.
- MDP does not enhance the toxicity of lead acetate or LPS.
- Enhanced phagocytosis of endotoxin in MDP-treated mice does not lead to increased mortality.