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A structure-activity relationship for induction of meningeal inflammation by muramyl peptides
M Burroughs1, E Rozdzinski, S Geelen
1Laboratory of Molecular Infectious Diseases, Rockefeller University, New York 10021.
Abstract:
Components of bacterial peptidoglycans have potent biological activities, including adjuvant effects, cytotoxicity, and induction of sleep. Mixtures of peptidoglycan components also induce inflammation in the lung, subarachnoid space, and joint, but the structural requirements for activity are unknown. Using a rabbit model for meningitis, we determined the biological activities of 14 individual muramyl peptides constituting > 90% of the peptidoglycan of the gram-negative pediatric pathogen Haemophilus influenzae. Upon intracisternal inoculation, most of the muropeptides induced leukocytosis in cerebrospinal fluid (CSF), influx of protein into CSF, or brain edema, alone or in combination. The disaccharide-tetrapeptide, the major component of all gram-negative peptidoglycans, induced CSF leukocytosis and protein influx at doses as low as 0.4 microgram (0.42 nM). Modification of the N-acetyl muramic acid or substitution of the alanine at position four in the peptide side chain decreased leukocytosis but enhanced brain edema. As the size of the muropeptide increased, the inflammatory activity decreased. Muropeptide carrying the diaminopimelyl-diaminopimelic acid cross-link specifically induced cytotoxic brain edema. These findings significantly expand the spectrum of biological activities of natural muramyl peptides and provide the basis for a structure-activity relationship for the inflammatory properties of bacterial muropeptides.
Insights
Bacterial peptidoglycan components, like muramyl peptides from Haemophilus influenzae, trigger inflammation and brain edema. Understanding these structures helps explain their potent biological activities.
Area of Science:
- Microbiology
- Immunology
- Neuroscience
Background:
- Bacterial peptidoglycan components exhibit significant biological activities, including adjuvant effects, cytotoxicity, and sleep induction.
- Previous research indicates that peptidoglycan component mixtures can induce inflammation in various body sites, but specific structural requirements remain unclear.
Purpose of the Study:
- To investigate the biological activities of individual muramyl peptides from Haemophilus influenzae.
- To establish structure-activity relationships for the inflammatory properties of bacterial muropeptides using a rabbit meningitis model.
Main Methods:
- Intracisternal inoculation of 14 individual muramyl peptides in a rabbit meningitis model.
- Assessment of cerebrospinal fluid (CSF) leukocytosis, protein influx, and brain edema.
- Analysis of structural modifications and their impact on biological activity.
Main Results:
- Most tested muropeptides induced CSF leukocytosis, protein influx, or brain edema.
- The disaccharide-tetrapeptide, a major component of gram-negative peptidoglycans, induced CSF leukocytosis and protein influx at low doses.
- Structural modifications altered inflammatory responses; larger muropeptides showed decreased inflammatory activity, while specific cross-links induced cytotoxic brain edema.
Conclusions:
- Muramyl peptides possess a broad spectrum of biological activities, including potent inflammatory effects.
- Specific structural features of muropeptides dictate their inflammatory and cytotoxic properties.
- Findings provide a foundation for understanding the structure-activity relationship of bacterial muropeptide-induced inflammation.
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