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RelA and RelB-dependent transcriptome analysis in lymphotoxin-ß receptor stimulated mouse embryonic fibroblasts

ABSTRACT: Background: Lymphotoxin signaling via the lymphotoxin-β receptor (LTβR) has been implicated in several biological processes, ranging from development of secondary lymphoid organs, maintenance of splenic tissue, host defense against pathogens, autoimmunity, and lipid homeostasis. The major transcription factor that is activated by LTβR crosslinking is NF-κB. Two signaling pathways have been described that result in the activation of classical p50-RelA and alternative p52-RelB NF-κB heterodimers. Results: Using microarray analysis, we investigated the transcriptional response downstream of the LTβR in mouse embryoni fibroblasts (MEF) and its regulation by the RelA and RelB subunits of NF-κB. We describe novel LTβR-responsive genes that are regulated by RelA and/or RelB. Interestingly, we found that the majority of LTβR-regulated genes require the presence of both RelA and RelB, suggesting significant crosstalk between the two NF-κB activation pathways. Gene Ontology (GO) analysis confirmed that LTβR-NF-κB target genes are predominantly involved in the regulation of immune responses. However, other biological processes, such as apoptosis/cell death, cell cycle, angiogenesis, and taxis were also regulated by LTβR signaling. Moreover, we show that activation of the LTβR inhibits the expression of a key adipogenic transcription factor, peroxisome proliferator activated receptor-γ (pparg), suggesting that LTβR signaling may interfere with adipogenic differentiation. Conclusions: Thus, microarray analysis of LTβR-stimulated fibroblasts revealed further insight into the transcriptional response of LTβR signaling and its regulation by the NF-κB family members RelA and RelB. Keywords: cell type comparison (wt vs relA-/- vs relB-/-) after genetic modification using a time course

ORGANISM(S): Mus musculus

PROVIDER: GSE11963 | GEO | 2008/12/18

SECONDARY ACCESSION(S): PRJNA105831

REPOSITORIES: GEO

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Project description:Mouse aorta smooth muscle cells (SMCs) express TNF receptor superfamily member 1A (TNFR1) and lymphotoxin Ã receptor (LTÃR). Circumstantial evidence has linked the SMC LTÃR to tertiary lymphoid organogenesis in diseased aortae of hyperlipidemic mice. Here, we explored potential roles of TNFR1 and LTÃR activation in cultured SMCs. TNFR1 signaling by TNF activated the classical RelA NF-ÎºB pathway, whereas LTÃR signaling by agonistic anti LTÃR antibody activated both the classical RelA and alternative RelB NF-ÎºB pathways. Addition of both agonists synergized to enhance p100 inhibitor processing to the p52 subunit of NF-ÎºB and promoted its nuclear translocation suggesting RelA-RelB cross-talk in transcription regulation. Correspondingly, microarrays showed that simultaneous TNFR1 and LTÃR activation when compared to activation of single receptors was followed by markedly elevated levels of mRNAs encoding leukocyte homeostatic chemokines CCL2, CCL5, CXCL1, and CX3CL1. Furthermore, SMCs acquired prototypical features of mesenchymal cells known as lymphoid tissue organizers (LTOs), which control tertiary lymphoid organogenesis in autoimmune diseases, through hyperinduction of CCL7, CCL9, CXCL13, CCL19, CXCL16, VCAM-1, and ICAM-1. Experiments with ltbr-/- SMCs suggested that the LTÃR-RelB activation component of NF-ÎºB signaling was obligatory to generate the LTO phenotype. TNFR1-LTÃR crosstalk also resulted in augmented synthesis and prolonged secretion of lymphorganogenic chemokine proteins into the culture medium. Thus, combined TNFR1-LTÃR signaling triggers SMC transdifferentiation into a phenotype that strikingly resembles LTOs. LTO-like SMCs may adopt a thus far unrecognized role in diseased arteries, i.e. to coordinate tertiary lymphoid organogenesis in atherosclerosis, aortic aneurysm, and transplant vasculopathy. Experiment Overall Design: Smooth muscle cells in tissue culture were stimulated with agonists and subsequently microarray, RT-PCR, and protein assays / analyses were performed

Project description:Mesenchymal stem cells (MSCs) are known to induce the conversion of activated T-cells into regulatory T-cells in vitro. The marker CD69 is a target of canonical NF-κB signaling and is transiently expressed upon activation; however, stable CD69 expression defines cells with immunoregulatory properties. Given its enormous therapeutic potential, we explored the molecular mechanisms underlying the induction of regulatory cells by MSCs. Peripheral blood CD3+ T-cells were activated and cultured in the presence or absence of MSCs. CD4+ cell mRNA expression was then characterized by microarray analysis. The drug BAY11-7082 and a siRNA against RELB were used to explore the differential roles of canonical and non-canonical NF-κB signaling, respectively. Flow cytometry and real-time PCR were used for analyses. Genes with immunoregulatory functions, CD69 and non-canonical NF-κB subunits (RELB and NFKB2) were all expressed at higher levels in lymphocytes co-cultured with MSCs. The frequency of CD69+ cells among lymphocytes cultured alone progressively decreased after activation. In contrast, the frequency of CD69+ cells increased significantly following activation in lymphocytes co-cultured with MSCs. Inhibition of canonical NF-κB signaling by BAY immediately following activation blocked the induction of CD69; however, inhibition of canonical NF-κB signaling on the 3rd day further induced the expression of CD69. Furthermore, late expression of CD69 was inhibited by RELB siRNA. These results indicate that the canonical NF-κB pathway controls the early expression of CD69 after activation; however, in an immunoregulatory context, late and sustained CD69 expression is promoted by the non-canonical pathway and is inhibited by canonical NF-κB signaling. In order to study the molecular basis by which Multipotent Mesenchymal Stromal/Stem Cells (MSC) exert their immune regulatory function, immunomagnetically purified CD3+ T-cells from the peripheral blood of 3 individuals were activated and cultured in the presence or absence of MSCs. Following 5 days, CD4+ and CD8+ T-cells were further immunomagnetically selected and their gene expression profiles were obtained by microarrays and compared. Paired samples from 3 individuals were used for this analysis.

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RelA and RelB-dependent transcriptome analysis in lymphotoxin-ß receptor stimulated mouse embryonic fibroblasts

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