title: The antagonist activity of lipid IVa on the stimulation by lipid A of TNF-alpha production from canine blood mononuclear cells.
abstract: Lipid A, the active component of lipopolysaccharide (LPS), exists in the outer membrane of Gram-negative bacteria and binds to the Toll-like receptor 4 (TLR4) and MD-2 complex. On the other hand, the synthetic precursor of Escherichia coli lipid A, tetraacylated lipid IVa, is an agonist for TLR4 and MD-2 complex in murine, equine and feline cells but is an antagonist for lipid A in human cells. The aim of the study was to examine the function of canine Toll-like receptor 4 (TLR4) and MD-2 complex on canine blood mononuclear cells (BMC), by analyzing lipid A- or lipid IVa-induction of TNF-α production from these cells in order to understand canine innate immune system. After 5-h culture of canine BMC with lipid A (lipid A culture) or lipid IVa (lipid IVa culture), the TNF-α, as determined by ELISA, had increased in the supernatants of the lipid A cultures in a dose-dependent manner, whereas the TNF-α was undetectable in supernatant of lipid IVa-treated cultures. The TNF-α was statistically significantly different between the lipid A and lipid IVa cultures (100 and 1000 ng/ml). TNF-α production from canine BMC was inhibited, in a lipid IVa-dose-dependent manner, when the BMC were pre-cultured with lipid IVa for 60 min and then cultured with lipid A for 5h, while in control BMC cultures production if TNF-α was unchanged. These results indicate that the TNF-α production stimulated by lipid A was competed out by pre-exposing the BMC to lipid IVa. Thus, lipid A is an agonist for TNF-α production in canine BMC, whereas lipid IVa appears to be an antagonist against this lipid A stimulation of canine BMC.
authors.affiliation: Department of Pathobiology, Nihon University School of Veterinary Medicine, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Takasawa
authors.forename: Rui
authors.initials: R
authors.lastname: Kano
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Maruyama
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Hasegawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kamata
mesh_terms: D000818:Animals; D004285:Dogs; D006017:Glycolipids / Q000494:pharmacology*; D007113:Immunity, Innate; D066298:In Vitro Techniques; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000276:immunology*; D008050:Lipid A / Q000031:analogs & derivatives* / Q000494:pharmacology*; D051218:Lymphocyte Antigen 96 / Q000819:agonists / Q000037:antagonists & inhibitors; D008297:Male; D051197:Toll-Like Receptor 4 / Q000819:agonists / Q000037:antagonists & inhibitors; D014409:Tumor Necrosis Factor-alpha / Q000819:agonists / Q000037:antagonists & inhibitors / Q000096:biosynthesis*
chemical_list: D006017:Glycolipids; D008050:Lipid A; D051218:Lymphocyte Antigen 96; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C040142:lipid A precursors, bacterial