Background: Exposure of macrophages to bacterial products such as lipopolysaccharide (LPS) results in activation of the NF-κB transcription factor, which orchestrates a gene expression programme that underpins the macrophage-dependent immune response. These changes include the induction or repression of a wide range of genes that regulate inflammation, cell proliferation, migration and cell survival. This process is tightly regulated and loss of control is associated with conditions such as septic shock, inflammatory diseases and cancer. To study this response, it is important to have in vitro model systems that reflect the behaviour of cells in vivo. In addition, it is necessary to understand the natural differences that can occur between individuals. In this report, we have investigated and compared the LPS response in macrophage derived cell lines and peripheral blood mononuclear cell (PBMC) derived macrophages.

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BackgroundNurr1 is an orphan member of the nuclear receptor superfamily; these orphan receptors are a group for which a ligand has yet to be identified. Nurr1 has been shown to regulate the expression of a small number of genes as a monomeric, constitutively active receptor. These Nurr1 regulated genes are primarily associated with dopamine cell maturation and survival. However, previous reports have shown an increased expression of Nurr1 in the synovium of patients with rheumatoid arthritis (RA) suggesting a pro-inflammatory role for Nurr1 in RA. In this study we investigate the potential pro-inflammatory role of Nurr1 by monitoring Nurr1 dependent gene expression in an immortalised synoviocyte cell line, K4IM.MethodsWe overexpressed the wild type and a dominant negative form of the orphan nuclear receptor Nurr1, in a model synoviocyte cell line. Using the Affymetrix HG-U133 Genechips we demonstrate the effects on the transcriptome by the receptor. Further evidence of gene expression change was demonstrated using quantitative RT-PCR and ELISA analysis.ResultsWe show that Nurr1 regulates transcription of a small number of genes for pro-inflammatory modulators of which the most significant is interleukin-8 (IL-8). We also demonstrate increased synthesis and secretion of IL-8 further supporting a role for Nurr1 in inflammatory signalling pathways.ConclusionUsing microarray analysis we show that elevated levels of Nurr1 leads to increased gene expression of pro-inflammatory genes: IL-8, Amphiregulin and Kit ligand in a model cell line. This data provides further evidence for an additional role for Nurr1 in inflammation and may play a role in the pathogenesis of rheumatoid arthritis.

The molecular basis to autoimmune arthritis is unclear. To identify candidate molecules that may be involved in the development and progression of collagen-induced arthritis (CIA), an animal model for human rheumatoid arthritis, we used microarray and real-time PCR assays to examine the gene expression profiles at the onset, peak and decline phase of CIA. Our results showed that, of the 514 immune-related genes assayed in microarrays, fifty-eight genes showed differential expression with thirty-one up-regulated and twenty-seven down-regulated in CIA joints, in comparison to normal joint tissue. By real-time PCR, expression of some chemokines/chemokine receptors, such as CCR1, CXCR4, CXCL13 and MCP1, showed significantly elevated in the inflamed joints. Quite a few genes were significantly up- or down-regulated at the peak time point, which indicates their roles in the progression of the disease. In addition, the expression levels of some genes remained significantly elevated at all stages of the disease. These gene expression profiles may help understand the pathogenesis of the disease.