Correlation between Endotoxin Tolerance in Human Monocyte Leukemia Cell Line THP-1 with Glucocorticoid Receptor-α

Human monoeyte leukemia cell line THP-1 was stimulated with lipopolysaccharide （LPS） to simulate the sepsis model and the expression of human glucocorticoid receptor-α （GR-α） mRNA in montocytes with endotoxin tolerance was investigated. THP-1 cells were cultured in serum-free medium, randomly divided into groups A, B, C, D and E, and stimulated with 0, 10, 10, 100, 0 ng/mL LPS for 24 h followed with 100, 100, 10, 100, 0 ng/mL LPS for another 24 h respectively. The expression of GR-α mRNA was detected by semi-quantitative reverse transcriptional polymerase chain reaction. Tumor necrosis factor-α （TNF-α） was determined by enzyme linked immunosorbent assay （ELISA）. The results showed that the A values of GR-α/β-actin in groups A, B, C, D and E was 0. 607±0. 006, 0. 368±0. 005, 0. 484±0. 008, 0. 509±0. 004 and 0. 564±0. 014 respectively with the difference being significant among the groups （P〈0. 05）. The GR-α mRNA expression was negatively correlated with the TNF-α expression （P〈0. 01）. It was concluded that the down-regulation of the expression of GR-α mRNA in endotoxin tolerance THP-1 cells might play an important role in the development of endotoxin tolerance in THP-1 cells.

Regulatory Effect of JAK2/STAT3 on the Immune Function of Endotoxin-tolerant Dendritic Cells and its Involvement in Acute Liver Failure

Background and Aims:Acute liver failure(ALF)is a potentially fatal clinical syndrome with no effective treatment.This study aimed to explore the role of Janus kinase 2/signal transducer and activator of transcription 3(JAK2/STAT3)pathway in modulating the phenotype and immune function of endotoxin-tolerant dendritic cells(ETDCs).In addition,we explored the use of EDTCs in an experimental model of ALF and investigated the associated mechanisms.Methods:In the in vitro experiment,ETDCs were transfected with adenovirus to induce SOCS1^(+/+)ETDCs and SOCS1^(−/−)ETDCs.Thereafter,costimulatory molecules and mixed lymphocyte reaction were assessed.Experimental mice were randomly divided into normal control,ALF,ALF+mock-ETDCs,ALF+SOCS1^(+/+)ETDCs,ALF+AG490,and ALF+AG490+SOCS1^(+/+)ETDCs groups.We examined the therapeutic effect of adoptive cellular immunotherapy by tail-vein injection of target ETDCs 12 h before ALF modeling.AG490,a JAK2/STAT3 inhibitor,was used in the in vivo experiment to further explore the protective mechanism of SOCS1^(+/+)ETDCs.Results:Compared with control ETDCs,SOCS1^(+/+)ETDCs had lower expression of costimulatory molecules,weaker allostimulatory ability,lower levels of IL-6 and TNF-αexpression and higher IL-10 secretion.SOCS1^(−/−)ETDCs showed the opposite results.In the in vivo experiments,the ALF+SOCS1^(+/+)ETDCs and ALF+AG490+SOCS1^(+/+)ETDCs groups showed less pathological damage and suppressed activation of JAK2/STAT3 pathway.The changes were more pronounced in the ALF+AG490+SOCS1^(+/+)ETDCs group.Infusion of SOCS1^(+/+)ETDCs had a protective effect against ALF possibly via inhibition of JAK2 and STAT3 phosphorylation.Conclusions:The SOCS1 gene had an important role in induction of endotoxin tolerance.SOCS1^(+/+)ETDCs alleviated lipopolysaccharide/D-galactosamine-induced ALF by downregulating the JAK2/STAT3 signaling pathway.

Opposite effects of miR-155 in the initial and later stages of lipopolysaccharide(LPS)-induced inflammatory response

Although microRNA-155(miR-155)is considered a pro-inflammatory mediator,cumulative evidence indicates that it also has anti-inflammatory effects in macrophages and dendritic cells.In this study,we identified the dramatic expression changes of more than half of potential miR-155-targeted genes upon lipopolysaccharide(LPS)stimulation;223 genes were down-regulated and 85 genes were up-regulated,including suppressor of cytokine signaling 1(SOCS1)and transforming growth factor-β-activated kinase 1-binding protein 2(TAB2),two well-known genes involved in miR-155-mediated regulation of the Toll-like receptor 4(TLR4)signaling pathway.We also found that miR-155 acted as an anti-inflammatory mediator in the initial stage of LPS-induced inflammatory response mainly through repressing TAB2 protein translation,and as a proinflammatory mediator by down-regulating SOCS1 in the later stage.Meanwhile,overexpression of TAB23'untranslated region(UTR)in macrophages promoted the development of endotoxin tolerance by competing for binding with miR-155,which resulted in an elevated expression level of SOCS1 protein.These findings provide new insights for understanding the regulatory mechanisms in fine-tuning of LPS-induced innate immune response.