Induction of endotoxin tolerance by pathogenic Neisseria is correlated with the inflammatory potential of lipooligosaccharides and regulated by microRNA-146a.
In this article, we report that retreatment of human monocytic THP-1 cells and primary monocytes with pathogenic Neisseria or with purified lipooligosaccharides (LOS) after previous exposure to LOS induced immune tolerance, as evidenced by reduced TNF-α and IL-1β cytokine expression. LOS that we have previously shown to vary in their potential to activate TLR4 signaling, which was correlated with differences in levels of lipid A phosphorylation, had similarly variable ability to induce tolerance. Efficacy for induction of tolerance was proportional to the level of lipid A phosphorylation, as LOS from meningococcal strain 89I with the highest degree of phosphorylation was the most tolerogenic following retreatment with LOS or whole bacteria, compared with LOS from gonococcal strains 1291 and GC56 with reduced levels of phosphorylation. Hydrogen fluoride treatment of 89I LOS to remove phosphates rendered the LOS nontolerogenic. Tolerance induced by the more highly inflammatory meningococcal LOS was correlated with significantly greater downregulation of p38 activation, greater induction of the expression of A20 and of microRNA-146a, and greater reductions in IL-1R-associated kinase 1 and TRAF6 levels following LOS retreatment of cells. The role of miR-146a in regulation of induction of TNF-α was confirmed by transfecting cells with an inhibitor and a mimic of miR-146a. Our results provide a mechanistic framework for understanding the variable pathophysiology of meningococcal and gonococcal infections given that after an initial exposure, greater upregulation of microRNA-146a by more highly inflammatory LOS conversely leads to the suppression of immune responses, which would be expected to facilitate bacterial survival and dissemination.
Center for Immunochemistry, Veterans Affairs Medical Center, San Francisco, CA, 94121.
Mingfeng
M
Liu
Constance M
CM
John
Gary A
GA
Jarvis
D004268:DNA-Binding Proteins / Q000096:biosynthesis; D004731:Endotoxins / Q000276:immunology*; D004789:Enzyme Activation; D006069:Gonorrhea / Q000276:immunology; D006801:Humans; D006858:Hydrofluoric Acid / Q000494:pharmacology; D007108:Immune Tolerance / Q000187:drug effects / Q000276:immunology*; D007249:Inflammation / Q000276:immunology; D053592:Interleukin-1 Receptor-Associated Kinases / Q000378:metabolism; D053583:Interleukin-1beta / Q000096:biosynthesis; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis; D008050:Lipid A / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology*; D008585:Meningitis, Meningococcal / Q000276:immunology; D035683:MicroRNAs / Q000096:biosynthesis / Q000378:metabolism*; D009000:Monocytes / Q000276:immunology; D009344:Neisseria gonorrhoeae / Q000276:immunology; D009345:Neisseria meningitidis / Q000276:immunology*; D009687:Nuclear Proteins / Q000096:biosynthesis; D010766:Phosphorylation; D015398:Signal Transduction; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D004268:DNA-Binding Proteins; D004731:Endotoxins; C508585:IL1B protein, human; D053583:Interleukin-1beta; D047908:Intracellular Signaling Peptides and Proteins; D008050:Lipid A; D008070:Lipopolysaccharides; C542542:MIRN146 microRNA, human; D035683:MicroRNAs; D009687:Nuclear Proteins; C495345:TLR4 protein, human; D048029:TNF Receptor-Associated Factor 6; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C023023:lipid-linked oligosaccharides; C507768:IRAK1 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C076529:TNFAIP3 protein, human; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D006858:Hydrofluoric Acid