OBJECTIVES: Notch ligands and receptors have recently been shown to be differentially expressed in osteoarthritis (OA). We aim to further elucidate the functional role of Notch signalling in OA using Notch1 antisense transgenic (Notch1 AS) mice. METHODS: Notch and hedgehog signalling were analysed by real-time PCR and immunohistochemistry. Notch-1 AS mice were employed as a model of impaired Notch signalling in vivo. Experimental OA was induced by destabilisation of the medial meniscus (DMM). The extent of cartilage destruction and osteophyte formation was analysed by safranin-O staining with subsequent assessment of the Osteoarthritis Research Society International (OARSI) and Mankin scores and µCT scanning. Collagen X staining was used as a marker of chondrocyte hypertrophy. The role of hairy/enhancer of split 1 (Hes-1) was investigated with knockdown and overexpression experiments. RESULTS: Notch signalling was activated in human and murine OA with increased expression of Jagged1, Notch-1, accumulation of the Notch intracellular domain 1 and increased transcription of Hes-1. Notch1 AS mice showed exacerbated OA with increases in OARSI scores, osteophyte formation, increased subchondral bone plate density, collagen X and osteocalcin expression and elevated levels of Epas1 and ADAM-TS5 mRNA. Inhibition of the Notch pathway induced activation of hedgehog signalling with induction of Gli-1 and Gli-2 and increased transcription of hedgehog target genes. The regulatory effects of Notch signalling on Gli-expression were mimicked by Hes-1. CONCLUSIONS: Inhibition of Notch signalling activates hedgehog signalling, enhances chondrocyte hypertrophy and exacerbates experimental OA including osteophyte formation. These data suggest that the activation of the Notch pathway may limit aberrant hedgehog signalling in OA.

• MeSH
• artritida experimentální metabolismus   MeSH
• chondrocyty metabolismus   MeSH
• kloubní chrupavka metabolismus   MeSH
• kvantitativní polymerázová řetězová reakce MeSH
• membránové glykoproteiny metabolismus   MeSH
• myši transgenní MeSH
• myši MeSH
• osteoartróza metabolismus   MeSH
• osteofyt metabolismus   MeSH
• receptor Notch1 metabolismus   MeSH
• signální transdukce MeSH
• stupeň závažnosti nemoci MeSH
• transkripční faktor HES1 metabolismus   MeSH
• transportní proteiny metabolismus   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Mesenchymal responses are an essential aspect of tissue repair. Failure to terminate this repair process correctly, however, results in fibrosis and organ dysfunction. Therapies that block fibrosis and restore tissue homeostasis are not yet available for clinical use. Here we characterize the nuclear receptor NR4A1 as an endogenous inhibitor of transforming growth factor-β (TGF-β) signaling and as a potential target for anti-fibrotic therapies. NR4A1 recruits a repressor complex comprising SP1, SIN3A, CoREST, LSD1, and HDAC1 to TGF-β target genes, thereby limiting pro-fibrotic TGF-β effects. Even though temporary upregulation of TGF-β in physiologic wound healing induces NR4A1 expression and thereby creates a negative feedback loop, the persistent activation of TGF-β signaling in fibrotic diseases uses AKT- and HDAC-dependent mechanisms to inhibit NR4A1 expression and activation. Small-molecule NR4A1 agonists can overcome this lack of active NR4A1 and inhibit experimentally-induced skin, lung, liver, and kidney fibrosis in mice. Our data demonstrate a regulatory role of NR4A1 in TGF-β signaling and fibrosis, providing the first proof of concept for targeting NR4A1 in fibrotic diseases.

• MeSH
• alkoholická cirhóza jater metabolismus   patologie   MeSH
• dospělí MeSH
• fibroblasty metabolismus   MeSH
• fibróza MeSH
• histondeacetylasa 1 metabolismus   MeSH
• histondemethylasy metabolismus   MeSH
• hojení ran MeSH
• idiopatická plicní fibróza metabolismus   patologie   MeSH
• jaderné receptory - podrodina 4, skupina A, člen 1 genetika   metabolismus   fyziologie   MeSH
• játra metabolismus   patologie   MeSH
• korepresorové proteiny metabolismus   MeSH
• kultivované buňky MeSH
• kůže cytologie   metabolismus   patologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• myši knockoutované MeSH
• myši MeSH
• plíce metabolismus   patologie   MeSH
• represorové proteiny metabolismus   MeSH
• senioři MeSH
• signální transdukce MeSH
• studie případů a kontrol MeSH
• systémová sklerodermie metabolismus   patologie   MeSH
• transformující růstový faktor beta metabolismus   MeSH
• transkripční faktor Sp1 metabolismus   MeSH
• zvířata MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• myši MeSH
• senioři MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: Vitamin D receptor (VDR) is a member of the nuclear receptor superfamily. Its ligand, 1,25-(OH)2D, is a metabolically active hormone derived from vitamin D3. The levels of vitamin D3 are decreased in patients with systemic sclerosis (SSc). Here, we aimed to analyse the role of VDR signalling in fibrosis. METHODS: VDR expression was analysed in SSc skin, experimental fibrosis and human fibroblasts. VDR signalling was modulated by siRNA and with the selective agonist paricalcitol. The effects of VDR on Smad signalling were analysed by reporter assays, target gene analyses and coimmunoprecipitation. The effects of paricalcitol were evaluated in the models of bleomycin-induced fibrosis and fibrosis induced by overexpression of a constitutively active transforming growth factor-β (TGF-β) receptor I (TBRI(CA)). RESULTS: VDR expression was decreased in fibroblasts of SSc patients and murine models of SSc in a TGF-β-dependent manner. Knockdown of VDR enhanced the sensitivity of fibroblasts towards TGF-β. In contrast, activation of VDR by paricalcitol reduced the stimulatory effects of TGF-β on fibroblasts and inhibited collagen release and myofibroblast differentiation. Paricalcitol stimulated the formation of complexes between VDR and phosphorylated Smad3 in fibroblasts to inhibit Smad-dependent transcription. Preventive and therapeutic treatment with paricalcitol exerted potent antifibrotic effects and ameliorated bleomycin- as well as TBRI(CA)-induced fibrosis. CONCLUSIONS: We characterise VDR as a negative regulator of TGF-β/Smad signalling. Impaired VDR signalling with reduced expression of VDR and decreased levels of its ligand may thus contribute to hyperactive TGF-β signalling and aberrant fibroblast activation in SSc.

• MeSH
• bleomycin toxicita   MeSH
• dospělí MeSH
• ergokalciferoly farmakologie   MeSH
• fibroblasty účinky léků   metabolismus   MeSH
• fibróza chemicky indukované   metabolismus   MeSH
• kůže účinky léků   metabolismus   patologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• malá interferující RNA metabolismus   MeSH
• mladý dospělý MeSH
• modely nemocí na zvířatech MeSH
• myši MeSH
• proteiny Smad účinky léků   metabolismus   MeSH
• receptory kalcitriolu agonisté   metabolismus   MeSH
• senioři MeSH
• signální transdukce účinky léků   fyziologie   MeSH
• systémová sklerodermie metabolismus   MeSH
• transformující růstový faktor beta účinky léků   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• myši MeSH
• senioři MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

OBJECTIVES: S100A4 is a calcium binding protein with regulatory functions in cell homeostasis, proliferation and differentiation that has been shown to promote cancer progression and metastasis. In the present study, we evaluated the role of S100A4 in fibroblast activation in systemic sclerosis (SSc). METHODS: The expression of S100A4 was analysed in human samples, murine models of SSc and in cultured fibroblasts by real-time PCR, immunohistochemistry and western blot. The functional role of S100A4 was evaluated using siRNA, overexpression, recombinant protein and S100A4 knockout (S100A4(-/-)) mice. Transforming growth factor β (TGF-β) signalling was assessed by reporter assays, staining for phosphorylated Smad2/3 and analyses of target genes. RESULTS: The expression of S100A4 was increased in SSc skin and in experimental fibrosis in a TGF-β/Smad-dependent manner. Overexpression of S100A4 or stimulation with recombinant S100A4 induced an activated phenotype in resting normal fibroblasts. In contrast, knockdown of S100A4 reduced the pro-fibrotic effects of TGF-β and decreased the release of collagen. S100A4(-/-) mice were protected from bleomycin-induced skin fibrosis with reduced dermal thickening, decreased hydroxyproline content and lower myofibroblast counts. Deficiency of S100A4 also ameliorated fibrosis in the tight-skin-1 (Tsk-1) mouse model. CONCLUSIONS: We characterised S100A4 as a downstream mediator of the stimulatory effects of TGF-β on fibroblasts in SSc. TGF-β induces the expression of S100A4 to stimulate the release of collagen in SSc fibroblasts and induce fibrosis. Since S100A4 is essentially required for the pro-fibrotic effects of TGF-β and neutralising antibodies against S100A4 are currently evaluated, S100A4 might be a candidate for novel antifibrotic therapies.

• MeSH
• dospělí MeSH
• fibroblasty metabolismus   MeSH
• kůže metabolismus   MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• modely nemocí na zvířatech MeSH
• myši knockoutované MeSH
• myši MeSH
• protein Smad2 metabolismus   MeSH
• protein Smad3 metabolismus   MeSH
• proteiny S100 metabolismus   MeSH
• senioři MeSH
• systémová sklerodermie metabolismus   MeSH
• transformující růstový faktor beta metabolismus   MeSH
• zvířata MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• myši MeSH
• senioři MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH