Regulation of Human C-Reactive Protein Gene Expression by Two Synergistic IL-6 Responsive Elements

Abstract

To study the mechanism of interleukin-6 (IL-6) induction of human C-reactive protein (CRP) gene expression, we have utilized a human hepatoma (PLC/PRF/5) cell culture system to analyze the trans-acting factors which bind to the 300 bp 5'-flanking region of human CRP gene. In vitro gel mobility shift analyses and methylation interference assays demonstrated that NFIL-6 alpha interacted with two IL-6 responsive elements, and HNF-1 alpha and HNF-3/Octamer-like factors interacted with the downstream IL-6 responsive element in the human CRP promoter. In vivo functional analysis by transient transfection of plasmid constructs containing site-specific mutations in one or two IL-6 responsive elements in the CRP promoter fused to a reporter gene, chloramphenicol acetyl transferase (CAT), demonstrated that the binding of NFIL-6 alpha to two IL-6 responsive elements resulted in synergistic induction of the gene. When HNF-1 alpha or HNF-3/Octamer-like factors were independently bound to their corresponding sites, they had either a positive or negative effect, respectively, on IL-6 inducible transcriptional activity.

Protective effect of the G-765C COX-2 polymorphism on subclinical atherosclerosis and inflammatory markers in asymptomatic subjects with cardiovascular risk factors

“…Whereas there are several evidences linking COX-2 expression and inflammation, the precise mechanism remains unclear [27 -29]. An association between COX-2 and IL-6 has been established in macrophages via PGE 2 [30]; furthermore, the magnitude of rise in CRP levels in cardiovascular patients was also found to be strongly dependent on the À 765G > C polymorphism [17]; since IL-6 is known to regulate CRP [31,32], it can be speculated that this polymorphism influences CRP levels via IL-6, which is also supported by our present findings. Subjects homozygous for the C allele also showed lower vWF levels, suggesting reduced endothelial damage [33] as compared with the remaining genotypes.…”

A Nuclear Receptor Corepressor–Dependent Pathway Mediates Suppression of Cytokine-Induced C-Reactive Protein Gene Expression by Liver X Receptor

“…siRNA-mediated depletion of LXR␣/␤ abolished the inhibitory effect of T0901317 on CRP gene expression, demonstrating a receptor-dependent mechanism. However, analysis of the CRP promoter did not reveal the presence of any putative LXR-responsive elements, indicating that the inhibition of cytokine-induced CRP transcription by LXR ligands is indirect through inhibition of binding of other transcription 19,[21][22][23] To localize the regions important for LXR-dependent repression, we used a series of 5Ј-deletion constructs. We identified a region in the CRP promoter between Ϫ256 and Ϫ125 that is essential for LXR ligand-mediated inhibition of cytokine-induced transcriptional activity.…”

“…19,20 In addition, hepatocyte nuclear factor-1 (HNF-1), HNF-3, and Oct-1 also play important roles in the regulation of CRP expression. [21][22][23] The liver X receptors ␣ (LXR␣) and LXR␤ (also known as NR1H3 and NR1H2, respectively) are members of the nuclear hormone receptor superfamily and have been suggested as potential targets for therapeutic intervention in human cardiovascular and metabolic disease. 24,25 LXR␣ is highly expressed in the liver and at lower levels in macrophages, intestine, adipose tissue, lung, and kidney, whereas LXR␤ is ubiquitously expressed.…”

Modulation of hepatic acute phase gene expression by epidermal growth factor and src protein tyrosine kinases in murine and human hepatic cells

“…APP gene induction, although sensitive to STATs, likely requires additional regulatory factors that may include C/EBP isoforms, 48,54,55,67,78 glucocorticoid receptor, AP-1, SP-1, and others, 56,78-81 some of which may not be similarly active in EGF-treated cells as in IL-6-treated cells. Evidently, the set of EGF-regulated factors can also yield an expression of a specific APP gene, which is higher than the expression after IL-6 treatments, as seen in the example of the CRP promoter response (Fig.…”