title: Folimycin (concanamycin A) inhibits LPS-induced nitric oxide production and reduces surface localization of TLR4 in murine macrophages.
abstract: Lipopolysaccharide (LPS) is a major cell wall component of Gram-negative bacteria and signals through a receptor complex which consists of TLR4, MD-2 and CD14. LPS signaling in macrophages induces the production of many pro-inflammatory molecules, including nitric oxide (NO). In this study, we have shown that folimycin, a macrolide antibiotic and a specific inhibitor of vacuolar ATPase (V-ATPase), inhibits LPS-induced NO production, but not TNFalpha production, in murine elicited peritoneal macrophages. However, folimycin did not affect interferon-gamma induced NO production. LPS-induced iNOS mRNA and protein expression and NF-kappaB activation were also inhibited by folimycin. Interestingly, folimycin-treated cells showed reduced surface expression of TLR4 molecules and dilated Golgi apparatus. These findings suggest that folimycin, by inhibiting V-ATPases, alters intra-Golgi pH, which in turn causes defective processing and reduced surface expression of TLR4 reducing the strength of LPS signaling in murine macrophages.
authors.affiliation: Centre for Infectious Disease Research and Biosafety Laboratories, Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors.forename: Sandeepa M
authors.initials: SM
authors.lastname: Eswarappa
authors.forename: Nirmalya
authors.initials: N
authors.lastname: Basu
authors.forename: Omana
authors.initials: O
authors.lastname: Joy
authors.forename: Dipshikha
authors.initials: D
authors.lastname: Chakravortty
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D015536:Down-Regulation; D004336:Drug Antagonism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D018942:Macrolides / Q000494:pharmacology*; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D016296:Mutagenesis; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis*
chemical_list: D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D018942:Macrolides; D051197:Toll-Like Receptor 4; D009569:Nitric Oxide; C036978:concanamycin A; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D006180:Proton-Translocating ATPases