RESUMEN
The variant rs26232, in the first intron of the chromosome 5 open reading frame 30 (C5orf30) locus, has recently been associated with both risk of developing rheumatoid arthritis (RA) and severity of tissue damage. The biological activities of human C5orf30 are unknown, and neither the gene nor protein show significant homology to any other characterized human sequences. The C5orf30 gene is present only in vertebrate genomes with a high degree of conservation, implying a central function in these organisms. Here, we report that C5orf30 is highly expressed in the synovium of RA patients compared with control synovial tissue, and that it is predominately expressed by synovial fibroblast (RASF) and macrophages in the lining and sublining layer of the tissue. These cells play a central role in the initiation and perpetuation of RA and are implicated in cartilage destruction. RASFs lacking C5orf30 exhibit increased cell migration and invasion in vitro, and gene profiling following C5orf30 inhibition confirmed up-regulation of genes involved in cell migration, adhesion, angiogenesis, and immune and inflammatory pathways. Importantly, loss of C5orf30 contributes to the pathology of inflammatory arthritis in vivo, because inhibition of C5orf30 in the collagen-induced arthritis model markedly accentuated joint inflammation and tissue damage. Our study reveal C5orf30 to be a previously unidentified negative regulator of tissue damage in RA, and this protein may act by modulating the autoaggressive phenotype that is characteristic of RASFs.
Asunto(s)
Artritis Reumatoide/metabolismo , Proteínas Portadoras/metabolismo , Fosfoproteínas/metabolismo , Membrana Sinovial/metabolismo , Secuencia de Aminoácidos , Animales , Proteínas Portadoras/genética , Cartílago/patología , Supervivencia Celular , Fibroblastos/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Humanos , Articulaciones/metabolismo , Leucocitos/citología , Macrófagos/metabolismo , Ratones , Ratones Endogámicos DBA , Datos de Secuencia Molecular , Invasividad Neoplásica , Análisis de Secuencia por Matrices de Oligonucleótidos , Fenotipo , Fosfoproteínas/genética , Filogenia , ARN Interferente Pequeño/metabolismo , Homología de Secuencia de Aminoácido , Distribución Tisular , Cicatrización de Heridas , Microtomografía por Rayos XRESUMEN
Emerging evidence implicates epigenetic mechanisms in the pathogenesis of rheumatoid arthritis (RA). In this study, we have investigated the role of histone deacetylase (HDAC) enzymes in RA synovial fibroblasts (RASFs), a key cellular mediator of cartilage and bone destruction and determined effects of HDAC1 inhibition on both RASF phenotype in vitro, and joint inflammation and damage in the collagen-induced arthritis (CIA) model. Expression of HDACs 1-11 messenger ribonucleic acid (mRNA) was compared between RASFs and osteoarthritic synovial fibroblast (OASFs) using quantitative polymerase chain reaction. HDAC1 expression in RASFs was inhibited using small interfering RNA (siRNA) technology to assess effects on invasiveness, migration, proliferation and apoptosis. Effects of HDAC1 knockdown (KD) on the transcriptome were assessed using gene microarrays. The effects of siRNA-mediated HDAC(KD) on clinical scores, tissue inflammation and damage were assessed on CIA up to 47 days following immunization. Expression of HDAC1 was significantly higher in RASFs than OASFs. HDAC1(KD) resulted in reduced proliferation, invasion and migration in vitro and transcriptome profiling revealed effects on expression of genes regulating proliferation migration and inflammation. Furthermore, inhibition of HDAC1 in CIA resulted in reduced joint swelling, cartilage and bone damage and lower tumor necrosis factor in joint tissue. These results implicate HDAC1 as an important mediator of tissue damage in RA and support the potential therapeutic utility of inhibitors of this enzyme.
Asunto(s)
Artritis Experimental/patología , Artritis Reumatoide/patología , Histona Desacetilasa 1/genética , Osteoartritis/patología , Animales , Apoptosis , Artritis Experimental/genética , Artritis Reumatoide/genética , Movimiento Celular , Proliferación Celular , Células Cultivadas , Fibroblastos/enzimología , Fibroblastos/patología , Perfilación de la Expresión Génica/métodos , Regulación Enzimológica de la Expresión Génica , Humanos , Masculino , Ratones , Osteoartritis/genética , Membrana Sinovial/enzimología , Membrana Sinovial/patologíaRESUMEN
RA (rheumatoid arthritis) is an inflammatory disease of synovial joints affecting approximately 1% of the population. One of the main cell types involved in damage to RA joint tissue is the FLSs (fibroblast-like synoviocytes). These have a semi-transformed, auto-aggressive phenotype typified by loss of contact inhibition, reduced apoptosis and the production of matrix-degrading enzymes. The mechanisms involved in the development of this phenotype are unclear; however, increasing evidence implicates alterations in the epigenetic regulation of gene expression. Reduced acetylation of amino acids in the tails of histone proteins is an epigenetic mark associated with transcriptional repression and is controlled by the HDAC (histone deacetylase) enzyme family. To date, evidence has implicated HDACs in the auto-aggressive phenotype of FLSs, and administration of HDAC inhibitors to both animal models of RA and individuals with juvenile arthritis has shown efficacy in attenuating inflammation and tissue damage. This highlights a role for HDACs in disease pathogenesis and, more importantly, that HDACs are potential novel therapeutic targets.