title: Differential expression of toll-like receptor signaling cascades in LPS-tolerant human peripheral blood mononuclear cells.
abstract: Pre-exposure to low doses of LPS induces resistance to a lethal challenge, a phenomenon known as endotoxin tolerance. In this study, tolerance was induced in human PBMC by culturing cells with 1 ng/mL LPS for 48 h. Cells were subsequently challenged with 100 ng/mL LPS for 2, 6 and 24 h, and the expression of 84 genes encoding proteins involved in the TLR signaling pathway was evaluated at each time point by PCR array. LPS pretreatment did not modulate the expression of TLR4 and CD14 on the surface of monocytes. A gene was defined as tolerized when LPS pretreatment reversed the effect of LPS challenge on the expression of the gene or as non-tolerized when LPS pretreatment did not reverse the effects of LPS challenge. We observed impaired signal transduction through the NF-κB, JNK, ERK and TRIF pathways, whereas expression of p38 pathway-related genes was preserved in LPS-tolerant cells. These results show a distinct regulation of the TLR pathway cascades during tolerance; this may account for the differential gene expression of some inflammatory mediators, such as up-regulation of IL-10 and COX2 as well as down-regulation of TNF-α and IL-12. Depending on the effect of LPS-induced gene up-regulation or down-regulation, tolerance, as a reversion of such LPS effects, may result in repression or induction of gene expression.
authors.affiliation: Department of Medicine, Division of Infectious Diseases, Escola Paulista de Medicina, Federal University of Sao Paulo, Brazil.
authors.forename: Marialice Erdelyi
authors.initials: ME
authors.lastname: Mendes
authors.forename: Giovana Lotici
authors.initials: GL
authors.lastname: Baggio-Zappia
authors.forename: Milena Karina Coló
authors.initials: MK
authors.lastname: Brunialti
authors.forename: Maria da Luz
authors.initials: Mda L
authors.lastname: Fernandes
authors.forename: Marjorie Marini
authors.initials: MM
authors.lastname: Rapozo
authors.forename: Reinaldo
authors.initials: R
authors.lastname: Salomao
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics; D000328:Adult; D051546:Cyclooxygenase 2 / Q000235:genetics; D004731:Endotoxins / Q000276:immunology; D005786:Gene Expression Regulation; D006801:Humans; D007108:Immune Tolerance; D016753:Interleukin-10 / Q000235:genetics; D018664:Interleukin-12 / Q000235:genetics; D007963:Leukocytes, Mononuclear / Q000276:immunology* / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000235:genetics; D008070:Lipopolysaccharides / Q000276:immunology*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000235:genetics; D016133:Polymerase Chain Reaction; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000235:genetics* / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D004731:Endotoxins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D016328:NF-kappa B; C470409:TICAM1 protein, human; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D018664:Interleukin-12; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D020928:Mitogen-Activated Protein Kinases