Paulius Venalis

Activation of canonical Wnt signalling is required for TGF-β-mediated fibrosis

The transforming growth factor-β (TGF-β) signalling pathway is a key mediator of fibroblast activation that drives the aberrant synthesis of extracellular matrix in fibrotic diseases. Here we demonstrate a novel link between transforming growth factor-β and the canonical Wnt pathway. TGF-β stimulates canonical Wnt signalling in a p38-dependent manner by decreasing the expression of the Wnt antagonist Dickkopf-1. Tissue samples from human fibrotic diseases show enhanced expression of Wnt proteins and decreased expression of Dickkopf-1. Activation of the canonical Wnt pathway stimulates fibroblasts in vitro and induces fibrosis in vivo. Transgenic overexpression of Dickkopf-1 ameliorates skin fibrosis induced by constitutively active TGF-β receptor type I signalling and also prevents fibrosis in other TGF-β-dependent animal models. These findings demonstrate that canonical Wnt signalling is necessary for TGF-β-mediated fibrosis and highlight a key role for the interaction of both pathways in the pathogenesis of fibrotic diseases.

Treatment with imatinib prevents fibrosis in different preclinical models of systemic sclerosis and induces regression of established fibrosis

OBJECTIVE Imatinib is a small-molecule tyrosine kinase inhibitor capable of selective, dual inhibition of the transforming growth factor beta and platelet-derived growth factor (PDGF) pathways. Imatinib has previously been shown to prevent the development of inflammation-driven experimental fibrosis when treatment was initiated before administration of the profibrotic stimulus. The aim of this study was to confirm the efficacy of imatinib in a murine model of systemic sclerosis (SSc) that is less driven by inflammation and to investigate whether imatinib is also effective for the treatment of established fibrosis. METHODS The tight skin 1 (TSK-1) mouse model of SSc was used to evaluate the antifibrotic effects of imatinib in a genetic model of the later stages of SSc. In addition, the efficacy of imatinib for the treatment of preestablished fibrosis was analyzed in a modified model of bleomycin-induced dermal fibrosis in which the application of bleomycin was prolonged and the onset of treatment was late. RESULTS Treatment with imatinib reduced dermal and hypodermal thickening in TSK-1 mice and prevented the differentiation of resting fibroblasts into myofibroblasts. In the model of preestablished dermal fibrosis, imatinib not only stopped further progression of fibrosis but also induced regression of preexisting dermal fibrosis, with a reduction in dermal thickness below pretreatment levels. CONCLUSION These results indicate that combined inhibition of the tyrosine kinase c-Abl and PDGF receptor might be effective in the later, less inflammatory stages of SSc and for the treatment of established fibrosis. Thus, imatinib might be an interesting candidate for clinical trials in patients with longstanding disease and preexisting tissue fibrosis.

The transcription factor Fra-2 regulates the production of extracellular matrix in systemic sclerosis.

OBJECTIVE Fra-2 belongs to the activator protein 1 family of transcription factors. Mice transgenic for Fra-2 develop a systemic fibrotic disease with vascular manifestations similar to those of systemic sclerosis (SSc). The aim of the present study was to investigate whether Fra-2 plays a role in the pathogenesis of SSc and to identify the molecular mechanisms by which Fra-2 induces fibrosis. METHODS Dermal thickness and the number of myofibroblasts were determined in skin sections from Fra-2-transgenic and wild-type mice. The expression of Fra-2 in SSc patients and in animal models of SSc was analyzed by real-time polymerase chain reaction and immunohistochemistry. Fra-2, transforming growth factor beta (TGFbeta), and ERK signaling in SSc fibroblasts were inhibited using small interfering RNA, neutralizing antibodies, and small-molecule inhibitors. RESULTS Fra-2-transgenic mice developed a skin fibrosis with increases in dermal thickness and increased myofibroblast differentiation starting at age 12 weeks. The expression of Fra-2 was up-regulated in SSc patients and in different mouse models of SSc. Stimulation with TGFbeta and platelet-derived growth factor (PDGF) significantly increased the expression of Fra-2 in SSc fibroblasts and induced DNA binding of Fra-2 in an ERK-dependent manner. Knockdown of Fra-2 potently reduced the stimulatory effects of TGFbeta and PDGF and decreased the release of collagen from SSc fibroblasts. CONCLUSION We demonstrate that Fra-2 is overexpressed in SSc and acts as a novel downstream mediator of the profibrotic effects of TGFbeta and PDGF. Since transgenic overexpression of Fra-2 causes not only fibrosis but also vascular disease, Fra-2 might be an interesting novel candidate for molecular-targeted therapies for SSc.

Immune mechanisms in polymyositis and dermatomyositis and potential targets for therapy

PM and DM are characterized clinically by weakness and low endurance of skeletal muscle. Other organs are frequently involved, suggesting that idiopathic inflammatory myopathies (IIMs) are systemic inflammatory diseases. Involvement of immune mechanisms in IIMs is supported by the presence of T cells, macrophages and dendritic cells in muscle tissue, by the presence of autoantibodies and by HLA-DR being a strong genetic risk factor. T cells may have direct and indirect toxic effects on muscle fibres, causing muscle fibre necrosis and muscle weakness, but the target of the immune reaction is not known. A newly identified T cell subset, CD28(null) T cells, may have cytotoxic effects in the CD4(+) and CD8(+) T cell phenotype. These cells are apoptosis resistant and may contribute to treatment resistance. Several myositis-specific autoantibodies have been identified, but they are all directed against ubiquitously expressed autoantigens and the specificity of the T cell reactivity is not known. These autoantibodies are associated with distinct clinical phenotypes and some with distinct molecular pathways; e.g. sera from patients with anti-Jo-1 autoantibodies may activate the type I IFN system and these sera also contain high levels of B cell activating factor compared with other IIM subsets. The characterization of patients into subgroups based on autoantibody profiles seems to be a promising way to learn more about the specificities of the immune reactions. Careful phenotyping of infiltrating immune cells in muscle tissue before and after specific therapies and relating the molecular findings to clinical outcome measures may be another way to improve knowledge on specific immune mechanism in IIMs. Such information will be important for the development of new therapies.

Relationship between serum levels of TGF-β1 and clinical parameters in patients with rheumatoid arthritis and Sjögren's syndrome secondary to rheumatoid arthritis

TGF-β1 is a pleiotropic cytokine, which prevents inappropriate autoimmune responses and balances the requirements of proper immune cell levels during pathologic states that trigger the immune response. We assessed the serum levels of TGF-β1 and determined the relationship between TGF-β1 and clinical parameters in patients with rheumatoid arthritis (RA) and Sjögrens syndrome (SS) secondary to RA (SS + RA). Comparison of the serum levels of TGF-β1 in patients with RA, SS + RA and NHD differed significantly (51.7 ± 12.4 ng/ml (RA); 33.0 ± 3.1 ng/ml (SS + RA) and versus 31.6 ± 2.0 ng/ml (NHD)). We further found correlations between TGF-β1 levels and radiologically defined joint damage determined by the Steinbrocker scoring system, symptoms and signs of SS. We conclude that serum levels of TGF-β1 may reflect ongoing autoimmune inflammation and correlate with joint damage in RA.

CD4+ and CD8+ CD28(null) T Cells Are Cytotoxic to Autologous Muscle Cells in Patients With Polymyositis.

Inflammatory T cell infiltrates in the skeletal muscle tissue of patients with polymyositis are dominated by CD28‐negative effector (CD28null) T cells of both the CD4 and CD8 lineage. These cells are potentially cytotoxic, and the aim of the present study was to develop a fully autologous cell culture system in which to investigate the functional contribution of such CD28null T cells to myotoxicity.

Cardiomyopathy in Murine Models of Systemic Sclerosis

Cardiomyopathy has emerged as a leading cause of death in patients with systemic sclerosis (SSc). However, the pathogenesis of SSc‐related cardiomyopathy is poorly understood, and new therapies as well as platforms for testing are needed. The aim of this study was to characterize the histopathologic features of cardiomyopathy in patients with SSc and in common mouse models of SSc.

CD4+ and CD8+ CD28null T cells are Cytotoxic to Autologous Muscle Cells in Polymyositis Patients

Inflammatory T cell infiltrates in the skeletal muscle tissue of patients with polymyositis are dominated by CD28‐negative effector (CD28null) T cells of both the CD4 and CD8 lineage. These cells are potentially cytotoxic, and the aim of the present study was to develop a fully autologous cell culture system in which to investigate the functional contribution of such CD28null T cells to myotoxicity.

Prevalence of paraneoplastic rheumatic syndromes and their antibody profile among patients with solid tumours

The aims of this study were to assess the prevalence of paraneoplastic rheumatic syndromes in a cohort of patients with newly diagnosed solid tumours and to describe their autoimmune profile, comparing it to the controls. Screening questionnaires (3,770) were distributed, and during a three-step study, 94 patients were confirmed to have both paraneoplastic syndrome and oncology diagnoses. Three control groups–patients with undifferentiated arthritis, Raynauds phenomenon for non-malignant causes and solid tumours only–were designed to compare with the paraneoplastic cases and their immunology profile. The prevalence of paraneoplastic rheumatic syndromes was 2.65% (95% CI 0.21–3.20). The group of patients with arthritis and the group of patients with Raynauds syndrome were found to prevail among other clinical presentations of paraneoplastic rheumatic syndromes. Both paraneoplastic syndromes were linked to malignancies of the urogenital system. Antinuclear antibodies were found to be similarly frequent in the paraneoplastic arthritis, paraneoplastic Raynauds phenomenon and the solid tumour groups. No differences were observed when comparing paraneoplastic arthritis and undifferentiated arthritis, except that the patients with paraneoplastic arthritis were older. Comparing paraneoplastic Raynauds to Raynauds phenomenon, male preponderance in the paraneoplastic Raynauds phenomenon group was observed, and the patients were obviously older. Paraneoplastic rheumatic syndromes are rare and more often occur in older patients. Among them, paraneoplastic arthritis and Raynauds syndrome were the most frequent. The immunology profile does not help in discriminating between arthritis and paraneoplastic arthritis patients and is of limited use in Raynauds differential diagnosis.

Lack of inhibitory effects of the anti-fibrotic drug imatinib on endothelial cell functions in vitro and in vivo.

Systemic sclerosis (SSc) is a systemic autoimmune disease that is characterized by microangiopathy with progressive loss of capillaries and tissue fibrosis. Imatinib exerts potent anti‐fibrotic effects and is currently evaluated in clinical trials. The aim of the present study was to exclude that the anti‐fibrotic effects of imatinib are complicated by inhibitory effects on endothelial cell functions, which might augment vascular disease in SSc. Endothelial cells and mice were treated with pharmacologically relevant concentrations of imatinib. The expression of markers of vascular activation was assessed with real‐time PCR. Proliferation was analysed with the cell counting experiments and the MTT assay. Apoptosis was quantified with caspase 3 assays, annexin V in vitro and with TUNEL staining in vivo. Migration was studied with scratch and transwell assays. Tube forming was investigated with the matrigel assay. Imatinib did not alter the expression of markers of vascular activation. Imatinib did not increase the percentage of annexin V positive cells or the activity of caspase 3. No reduction in proliferation or metabolic activity of endothelial cells was observed. Imatinib did not affect migration of endothelial cells and did not reduce the formation of capillary tubes. Consistent with the in vitro data, no difference in the number of apoptotic endothelial cells was observed in vivo in mice treated with imatinib. Imatinib does not inhibit activation, viability, proliferation, migration or tube forming of endothelial cells in vitro and in vivo. Thus, treatment with imatinib might not augment further endothelial cell damage in SSc.