Subject(s)
Acetylmuramyl-Alanyl-Isoglutamine/analogs & derivatives , Eicosanoids/biosynthesis , Kupffer Cells/drug effects , Kupffer Cells/metabolism , Lipopolysaccharides/pharmacology , Nitric Oxide/biosynthesis , Phosphatidylethanolamines/pharmacology , Tumor Necrosis Factor-alpha/biosynthesis , Acetylmuramyl-Alanyl-Isoglutamine/administration & dosage , Acetylmuramyl-Alanyl-Isoglutamine/pharmacology , Adjuvants, Immunologic/pharmacology , Animals , Cells, Cultured , Humans , Intramolecular Oxidoreductases/genetics , Intramolecular Oxidoreductases/metabolism , Lipocalins , Liposomes , Nitric Oxide Synthase/genetics , Nitric Oxide Synthase/metabolism , Phosphatidylethanolamines/administration & dosage , Phospholipases A/genetics , Phospholipases A/metabolism , Prostaglandin-Endoperoxide Synthases/genetics , Prostaglandin-Endoperoxide Synthases/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Signal Transduction/drug effects , Tumor Necrosis Factor-alpha/geneticsABSTRACT
LPS and MTP-PE (liposome-encapsulated N-acetyl-muramyl-L-alanyl-D-isoglutaminyl-L-alanine-2-:[1',2'dipalmitoyl -sni-glycero-3-(hydroxy-phosphoryl-oxyl)] etylamide) induce in liver macrophages a synthesis and release of TNF-alpha, nitric oxide and prostanoids. Both agents induce an expression of mRNA's encoding TNF-alpha, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, and of corresponding proteins. LPS and MTP-PE induce a rapid activation of the extracellular regulated kinase (ERK) isoenzymes-1 and -2. Inhibition of map kinase isoenzymes leads to a decreased release of TNF-alpha, nitric oxide and prostaglandin (PG) E2 after both agents. The transcription factors NF-kappaB and AP-1 are strongly activated by LPS within 30 minutes. MTP-PE induces a weak activation of both transcription factors only after 5 hours. Inhibition of NF-kappaB inhibits the LPS- but not the MTP-PE-induced release of TNF-alpha, nitric oxide and PGE2. PGE2 release after LPS is higher than after MTP-PE. Exogenously added PGE2 inhibits the activation of map kinase and TNF-alpha release by LPS, but not by MTP-PE. Release of nitric oxide after LPS and MTP-PE is enhanced after prior addition of PGE2. PGD2 is without any effect. MTP-PE, but not LPS, induces a cytotoxicity of Kupffer cells against P815 tumor target cells. The MTP-PE-induced cytotoxicity is reduced by TNF-alpha neutralizing antibodies, indicating the involvement of TNF-alpha. Thus our results suggest that the different potencies of LPS and MTP-PE as immunomodulators probably result from different actions on Kupffer cells, resulting in differences in the amounts and kinetics of released TNF-alpha and PGE2, and that PGE2 plays an important regulatory role in the action of LPS, but not in the actions of MTP-PE.
