Over the past 15 years, there have been intense efforts focused on determining the structures and biological activities of muramyl peptides (MPs). This interest in MPs is based , in a large part, on the assumption that MPs are tailored from bacterial cell wall peptidoglycan; once thus produced, they then can elicit their central nervous and immune system activities which are involved in host defense as well as physiological responses. However, this assumption has never been experimentally verified. The broad objective of this proposal is to investigate the hypothesis that mammalian macrophages produce and release biologically active MPs during the digestion of bacterial cell walls. This hypothesis is proposed because: a) MPs are present in mammalian tissue, including the brain, and have profound effects on the central nervous and immune systems, yet there are no known mammalian synthetic pathways for MPs; and b) our preliminary data and previously published data suggest that macrophages do, in fact, release biologically active substances of low molecular weight whose effects mimic those of synthetic MPs. However, chemical characterization of substances released by macrophages during peptidoglycan digestion has not been done, nor have the biological activities of such released substances been characterized except in our preliminary experiments. Therefore, to test our hypothesis: Viable bacteria, radioactively marked in their cell walls, will be fed to murine macrophages. The substances released by the macrophages will be fractionated using various chromatographic techniques (e.g., reversed phase C18-HPLC). 2)Fractions thus obtained will be tested for their ability to enhance rabbit sleep and body temperature in vivo.3) Fractions containing biological activity will be purified and retested, and substances will be identified by amino acid analysis and mass spectrometry. The proposed studies will help to evaluate the role MPs may play in the regulation of central nervous system and immune system involvement in host defense and physiological responses.
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