The Sp1 transcription factor is essential for the expression of gliostatin/thymidine phosphorylase in rheumatoid fibroblast-like synoviocytes

Abstract

IntroductionGliostatin/thymidine phosphorylase (GLS/TP) has angiogenic and arthritogenic activities, and aberrant GLS production has been observed in the active synovial membranes of rheumatoid arthritis (RA) patients. The human GLS gene promoter contains at least seven consensus binding sites for the DNA binding protein Sp1. Here we examined whether Sp1 is necessary for GLS production in RA. We also studied the effects of the Sp1 inhibitor mithramycin on GLS production in RA fibroblast-like synoviocytes (FLSs).MethodsFLSs from RA patients were treated with specific inhibitors. The gene and protein expression of GLS were studied using the quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and an enzyme immunoassay. Intracellular signalling pathway activation was determined by western blotting analysis, a luciferase assay, a chromatin immunoprecipitation (ChIP) assay and a small interfering RNA (siRNA) transfection.ResultsThe luciferase and ChIP assays showed that Sp1 binding sites in the GLS promoter were essential for GLS messenger RNA (mRNA) expression. GLS production was suppressed in FLSs by siRNA against Sp1 transfection. Mithramycin decreased GLS promoter activity, mRNA and protein expression in FLSs. Tumour necrosis factor-α (TNF-α) significantly increased GLS expression in RA FLSs; this effect was reduced by pre-treatment with cycloheximide and mithramycin.ConclusionsPretreatment of mithramycin and Sp1 silencing resulted in a significant suppression of GLS production in TNF-α-stimulated FLSs compared to controls. GLS gene expression enhanced by TNF-α was partly mediated through Sp1. As physiological concentrations of mithramycin can regulate GLS production in RA, mithramycin is a promising candidate for anti-rheumatic therapy.

Thymidine Phosphorylase in Cancer; Enemy or Friend?

“…The fact that TP levels are elevated in non-malignant cells in the tumour microenvironment (TME) suggests that raised TP expression is influenced by local inflammation and stress conditions like hypoxia in the TME rather than genetic changes. This is supported by the observation of increased TP levels in non-malignant chronic inflammatory conditions like arthritis and psoriasis [27].…”

“…TNFα activates SP1 which in turn binds to the promoter region of the TP gene leading to expression of the TP protein. Activation of NFκB is another mechanism by which TNFα leads to TP overexpression in cancer [25,27]. Interferon (IFN) α, β and γ activate the IFN-stimulated response element (ISRE) and the signal transduction and activator of transcription 1 (STAT1) causing expression of TP [25,28].…”

Molecular mechanism of monoamine oxidase A gene regulation under inflammation and ischemia‐like conditions: key roles of the transcription factors GATA2, Sp1 and TBP

“…; Ikuta et al . ). The regulatory role of Sp1 in MAOA gene regulation is interesting because Sp1 expression/transcriptional activity is altered in neurological disorders, including Alzheimer's and early Huntington's disease.…”

MicroRNA-124 inhibits the progression of adjuvant-induced arthritis in rats

“…Gliostatin/thymidine phosphorylase (GLS/TP) has angiogenic and arthritogenic activities, and aberrant GLS production has been observed in the active synovial membranes of patients with RA 35. Sp1 knockdown significantly decreases the GLS production in TNF-α-stimulated RA fibroblast-like synoviocytes.…”