ABSTRACT
Huntington's disease (HD) is an autosomal dominantly inherited neurodegenerative disorder caused by a trinucleotide repeat expansion in the Huntingtin gene. As disease-modifying therapies for HD are being developed, peripheral blood cells may be used to indicate disease progression and to monitor treatment response. In order to investigate whether gene expression changes can be found in the blood of individuals with HD that distinguish them from healthy controls, we performed transcriptome analysis by next-generation sequencing (RNA-seq). We detected a gene expression signature consistent with dysregulation of immune-related functions and inflammatory response in peripheral blood from HD cases vs. controls, including induction of the interferon response genes, IFITM3, IFI6 and IRF7. Our results suggest that it is possible to detect gene expression changes in blood samples from individuals with HD, which may reflect the immune pathology associated with the disease.
ABSTRACT
OBJECTIVE: Syndecan-4 (sdc4) is a cell-anchored proteoglycan that consists of a transmembrane core protein and glucosaminoglycan (GAG) side chains. Binding of soluble factors to the GAG chains of sdc4 may result in the dimerisation of sdc4 and the initiation of downstream signalling cascades. However, the question of how sdc4 dimerisation and signalling affects the response of cells to inflammatory stimuli is unknown. METHODS: Sdc4 immunostaining was performed on rheumatoid arthritis (RA) tissue sections. Interleukin (IL)-1 induced extracellular signal-regulated kinases (ERK) phosphorylation and matrix metalloproteinase-3 production was investigated. Il-1 binding to sdc4 was investigated using immunoprecipitation. IL-1 receptor (IL1R1) staining on wild-type, sdc4 and IL1R1 knockout fibroblasts was performed in fluorescence-activated cell sorting analyses. A blocking sdc4 antibody was used to investigate sdc4 dimerisation, IL1R1 expression and the histological paw destruction in the human tumour necrosis factor-alpha transgenic mouse. RESULTS: We show that in fibroblasts, the loss of sdc4 or the antibody-mediated inhibition of sdc4 dimerisation reduces the cell surface expression of the IL-1R and regulates the sensitivity of fibroblasts to IL-1. We demonstrate that IL-1 directly binds to sdc4 and in an IL-1R-independent manner leads to its dimerisation. IL-1-induced dimerisation of sdc4 regulates caveolin vesicle-mediated trafficking of the IL1R1, which in turn determines the responsiveness to IL-1. Administration of antibodies (Ab) against the dimerisation domain of sdc4, thus, strongly reduces the expression IL1R1 on arthritic fibroblasts both in vitro and an animal model of human RA. CONCLUSION: Collectively, our data suggest that Ab that specifically inhibit sdc4 dimerisation may support anti-IL-1 strategies in diseases such as inflammatory arthritis.
Subject(s)
Antibodies, Blocking/pharmacology , Arthritis, Rheumatoid/metabolism , Receptors, Interleukin-1 Type I/drug effects , Syndecan-4/antagonists & inhibitors , Animals , Arthritis, Rheumatoid/genetics , Arthritis, Rheumatoid/pathology , Dimerization , Disease Models, Animal , Extracellular Signal-Regulated MAP Kinases/drug effects , Extracellular Signal-Regulated MAP Kinases/metabolism , Fibroblasts/metabolism , Gene Knockout Techniques , Heparitin Sulfate , Hindlimb , Humans , Interleukin-1/metabolism , Interleukin-1beta/metabolism , MAP Kinase Signaling System , Matrix Metalloproteinase 3/metabolism , Mice , Mice, Transgenic , NIH 3T3 Cells , Osteoarthritis/genetics , Osteoarthritis/metabolism , Osteoarthritis/pathology , Phosphorylation/drug effects , Protein Transport , Receptors, Interleukin-1 Type I/metabolism , Signal Transduction , Syndecan-4/genetics , Syndecan-4/metabolism , Synovial Membrane/metabolism , Tumor Necrosis Factor-alpha/geneticsABSTRACT
OBJECTIVE: We analysed the role of the adaptor molecule four-and-a-half Lin11, Isl-1 & Mec-3 (LIM) domain protein 2 (FHL2) in the activation of fibroblast-like synoviocytes in human rheumatoid arthritis (RA) and tumour necrosis factor α (TNFα)-dependent animal models of the disease. METHODS: Synovial tissues of patients with RA and osteoarthritis (OA) as well as hind paw sections from arthritic human TNFα transgenic (hTNFtg) mice and synovial fibroblasts from these were analysed. The effects of cytokines on the expression of FHL2 and disease-relevant matrixmetalloproteases (MMPs) were determined. Analyses of human tissue specimens from patients treated with anti-TNFα as well as anti-TNFα treatment of hTNFtg mice were performed to substantiate the TNFα effects on FHL2 levels. FHL2(-/-) mice and hTNFtg mice (with constitutive or inducible transgene expression) were crossbred to generate TNFα overexpressing FHL2-deficient animals. Signalling pathways were analysed in cells from these mice and in human cells after knock down of FHL2 by western blot. RESULTS: FHL2 levels were higher in RA than in OA and in hTNFtg than in wild-type mice. Surprisingly, while transforming growth factor (TGF)ß-induced FHL2 expression, TNFα suppressed FHL2. In vivo, anti-TNFα treatment led to higher FHL2 levels both in RA patients and hTNFtg mice. The loss of FHL2 increased joint destruction in hTNFtg mice, which was accompanied by elevated MMP-13. In vitro, TNFα-mediated MMP-13 was significantly higher in FHL2(-/-) cells and after knock down of FHL2, which was caused by prolonged p38 MAPK activation. CONCLUSIONS: These data suggest that FHL2 serves as a protective factor and that, rather than promoting the pathology, the upregulation of FHL2 in RA occurs in frame of a regenerative attempt.
Subject(s)
DNA/genetics , Gene Expression Regulation , LIM-Homeodomain Proteins/genetics , Muscle Proteins/genetics , Osteoarthritis/genetics , Synovial Membrane/metabolism , Transcription Factors/genetics , Animals , Cells, Cultured , Chronic Disease , Humans , Immunoblotting , LIM-Homeodomain Proteins/biosynthesis , Mice , Mice, Transgenic , Muscle Proteins/biosynthesis , Osteoarthritis/metabolism , Osteoarthritis/pathology , Real-Time Polymerase Chain Reaction , Signal Transduction , Synovial Membrane/pathology , Transcription Factors/biosynthesisABSTRACT
OBJECTIVE: To elucidate the mechanisms involved in cartilage damage in an experimental model of rheumatoid arthritis (RA) by specifically addressing the time course of extracellular matrix degradation and the contribution of cell-matrix interactions for initiation and perpetuation of this process. METHODS: The human tumour necrosis factor (TNF) transgenic (hTNFtg) mouse model of RA was used to analyse the time course of pannus attachment to the cartilage and cartilage destruction, respectively, and crossed hTNFtg mice with interleukin (IL)-1(-/-) animals were used to investigate the role of IL-1 on these TNF-induced mechanisms in vivo. In addition, an in vitro attachment assay using synovial fibroblasts (SFs) from hTNFtg mice and freshly isolated articular cartilage was used to determine the role of proteoglycan loss in attachment of SFs and the role of the transmembrane heparan sulfate proteoglycan syndecan-4. RESULTS: In vivo analyses of hTNFtg mice showed that proteoglycan loss induced by IL-1 precedes and constitutes an important prerequisite for these processes as, in hTNFtg mice, IL-1 deficiency protected from the loss of cartilage proteoglycans and almost completely prevented the attachment and subsequent invasion of inflamed synovial tissue into cartilage. In vitro studies confirmed that loss of cartilage proteoglycans is required for attachment of SFs and that syndecan-4 is prominently involved in SF attachment and activation. CONCLUSIONS: The results of this study suggest that the loss of cartilage proteoglycans is an early event in the course of destructive arthritis that facilitates the attachment of the inflamed synovial membrane and also initiates matrix degradation and inflammation through cell-matrix interactions.
