Endotoxin tolerance: selective alterations in gene expression and protection against lymphocyte death.
Extensive lymphocyte apoptosis may be an important cause of immune suppression in sepsis. Here we investigated the effect of LPS tolerance on lymphocyte apoptosis in an experimental model of polymicrobial infection. Tolerance was induced by the injection of lipopolysaccharide (1.0mg/kg/subcutaneously) once a day for 5 days. Macroarray analysis of mRNA isolated from T-(CD4) lymphocytes was used to identify genes that are differentially expressed during LPS tolerance. In addition, assessment of the expression of apoptosis-associated lymphocyte gene products and apoptotic events was performed on the 8th day; 6h after the terminal challenge with polymicrobial infection or high-dose LPS administration. Survival studies with polymicrobial infection were also conducted. LPS tolerance induced a broad reprogramming of cell death pathways, including a suppression of receptor-mediated and mitochondrial apoptotic pathways, inflammatory caspases, alternate apoptotic pathways, as well as reduced expression of genes involved in necrosis. These alterations led to a marked resistance of lymphocytes against cell death during the subsequent period of sepsis. In addition, LPS tolerance produced an increased differentiation of T-lymphocytes to T(H)1 and T(H)2, with a T(H)1 differentiation predominance. Thus, in the current study we provide an evidence for a marked reprogramming of gene expression of multiple cell death pathways during LPS tolerance. These alterations may play a significant role in the observed protection of the animals from a subsequent lethal polymicrobial sepsis challenge.
Emergency Medicine Department, Medical School, University of São Paulo, São Paulo, Brazil.
Edielle S
ES
Melo
Tatiana
T
Goloubkova
Denise F
DF
Barbeiro
Renata
R
Gorjão
Dewton
D
Vasconcelos
Csaba
C
Szabo
Rui
R
Curi
Thais Martins
TM
de Lima Salgado
Irineu T
IT
Velasco
Francisco G
FG
Soriano
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000276:immunology; D007108:Immune Tolerance / Q000276:immunology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000276:immunology; D018805:Sepsis / Q000276:immunology / Q000378:metabolism / Q000517:prevention & control
D008070:Lipopolysaccharides; D012333:RNA, Messenger