C/EBPbeta is a member of the CCAAT/enhancer binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of various proinflammatory genes, including IL-6 and MCP-1. To examine the roles of the C/EBPbeta transactivation and regulatory domains in LPS-induced MCP-1 and IL-6 expression, we expressed various N-terminal truncations and deletions of C/EBPbeta in P388 murine B lymphoblasts, which lack endogenous C/EBPbeta expression and are normally unresponsive to LPS for expression of IL-6 and MCP-1. Unexpectedly, a region between amino acids 105 and 212 of C/EBPbeta that includes regulatory domains 1 and 2 facilitates C/EBPbeta activation of IL-6 expression, while having an inhibitory effect on MCP-1 expression. Thus, this region can mediate promoter-specific effects on cytokine and chemokine gene transcription. LIP, the naturally occurring truncated form of C/EBPbeta, largely retains these regulatory domains and stimulates IL-6 but not MCP-1 transcription.
"Regulatory regions for this gene include domains for inflammatory tumour necrosis factor (TNF)-inducible enhancer , for C/EBPb, a member of the CCAAT/enhancer binding protein family of transcription factors , and for C/EBPb homologous protein (CHOP) . All are implicated in CCL2 regulation and provide a link between CCL2 promoter activity and factors such as metabolic stress and visceral adipose tissue distribution     . With the rationale that the cross-talk between metabolism and inflammation could have important clinical implications, we have conducted, in a HIV-infected population, an analysis of CCL2 genetic variations and its relation to plasma levels of MCP-1, metabolic traits (i.e. "
[Show abstract][Hide abstract] ABSTRACT: Circulating CCL2 concentration has been implicated in promoting atherosclerosis in patients infected with HIV. We evaluated whether CCL2 gene variants are associated with metabolic disturbances and plasma CCL2 levels in HIV-infected patients.
CCL2 genotypes and estimated haplotypes, plasma CCL2 levels and indicators of metabolic status in HIV-infected patients were compared with a representative group of the general population. We also performed a carotid/femoral artery ultrasonography to detect sub-clinical atherosclerosis in these patients. Six haplotypes were estimated in more than the 5% of individuals, and accounted for more than 98% of the population. In HIV-infected patients, carriers of H1, H2 and H5 haplotypes had higher CCL2 concentration than carriers of H3, H4 and H6 haplotypes. However, only carriers of H1 and H5 haplotypes presented higher insulin resistance as well as higher proportion of patients affected with sub-clinical. Conversely, carriers of H2 haplotype, which also showed high plasma CCL2 concentration, were associated with less deleterious metabolic disturbances.
Our data are consistent with the hypothesis that the genetic background of the host is involved in CCL2 production and that this chemokine is implicated in promoting metabolic disturbances and sub-clinical atherosclerosis in HIV-infected patients.
[Show abstract][Hide abstract] ABSTRACT: C/EBPbeta is a member of the CCAAT/enhancer binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of various proinflammatory genes, including IL-6 and MCP-1. Serine 64 in the transactivation domain of C/EBPbeta has recently been identified as a Ras-induced phosphoacceptor site. The integrity of serine 64 along with threonine 189 is important for the Ha-ras(V12)-induced transformation of NIH3T3 cells, however no target genes dependent upon serine 64 for their expression have been reported. In order to evaluate a potential role of serine 64 in C/EBPbeta-regulated cytokine expression, we expressed a form of C/EBPbeta with an alanine substitution at serine 64 (C/EBPbeta(S64A)) in P388 murine B lymphoblasts, which lack endogenous C/EBPbeta expression and are normally unresponsive to LPS for expression of IL-6 and MCP-1. In comparison to wild type C/EBPbeta, which robustly supports the LPS-induced expression of IL-6 and MCP-1, C/EBPbeta(S64A) was severely impaired in its ability to support the LPS-induced transcription of IL-6 and MCP-1. Furthermore, LPS stimulation increased the level of phosphorylation detected at serine 64. Thus, serine 64, probably through its phosphorylation, is a critical determinant of C/EBPbeta activity in the transcription of IL-6 and MCP-1.
[Show abstract][Hide abstract] ABSTRACT: In response to inflammatory stimulation, dendritic cells (DCs) have a remarkable pattern of differentiation (maturation) that exhibits specific mechanisms to control immunity. Here, we show that in response to Lipopolysaccharides (LPS), several microRNAs (miRNAs) are regulated in human monocyte-derived dendritic cells. Among these miRNAs, miR-155 is highly up-regulated during maturation. Using LNA silencing combined to microarray technology, we have identified the Toll-like receptor/interleukin-1 (TLR/IL-1) inflammatory pathway as a general target of miR-155. We further demonstrate that miR-155 directly controls the level of TAB2, an important signal transduction molecule. Our observations suggest, therefore, that in mature human DCs, miR-155 is part of a negative feedback loop, which down-modulates inflammatory cytokine production in response to microbial stimuli.
Proceedings of the National Academy of Sciences 03/2009; 106(8):2735-40. DOI:10.1073/pnas.0811073106 · 9.67 Impact Factor
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