Jürgen Beer

Universitätsklinikum Erlangen, Erlangen, Bavaria, Germany

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Publications (3)25.91 Total impact

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    ABSTRACT: To investigate the role of liver X receptors (LXRs) in experimental skin fibrosis and evaluate their potential as novel antifibrotic targets. We studied the role of LXRs in bleomycin-induced skin fibrosis, in the model of sclerodermatous graft-versus-host disease (sclGvHD) and in tight skin-1 (Tsk-1) mice, reflecting different subtypes of fibrotic disease. We examined both LXR isoforms using LXRα-, LXRβ- and LXR-α/β-double-knockout mice. Finally, we investigated the effects of LXRs on fibroblasts and macrophages to establish the antifibrotic mode of action of LXRs. LXR activation by the agonist T0901317 had antifibrotic effects in bleomycin-induced skin fibrosis, in the sclGvHD model and in Tsk-1 mice. The antifibrotic activity of LXRs was particularly prominent in the inflammation-driven bleomycin and sclGvHD models. LXRα-, LXRβ- and LXRα/β-double-knockout mice showed a similar response to bleomycin as wildtype animals. Low levels of the LXR target gene ABCA-1 in the skin of bleomycin-challenged and control mice suggested a low baseline activation of the antifibrotic LXR signalling, which, however, could be specifically activated by T0901317. Fibroblasts were not the direct target cells of LXRs agonists, but LXR activation inhibited fibrosis by interfering with infiltration of macrophages and their release of the pro-fibrotic interleukin-6. We identified LXRs as novel targets for antifibrotic therapies, a yet unknown aspect of these nuclear receptors. Our data suggest that LXR activation might be particularly effective in patients with inflammatory disease subtypes. Activation of LXRs interfered with the release of interleukin-6 from macrophages and, thus, inhibited fibroblast activation and collagen release.
    No preview · Article · Mar 2014 · Annals of the rheumatic diseases
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    ABSTRACT: Systemic sclerosis (SSc) is a connective tissue disease that is characterized by microvascular disease and tissue fibrosis. Progressive loss and irregular architecture of the small blood vessels are well characterized, but the potential involvement of the lymphatic vessel system has not been analyzed directly in SSc. This study was undertaken to assess whether the lymphatic vascular system is affected in SSc, and whether changes to the lymphatic vessels are associated with dystrophic changes and tissue damage in patients with SSc. Lymphatic endothelial cells in skin biopsy samples from patients with SSc and age- and sex-matched healthy volunteers were identified by staining for podoplanin and prox-1, both of which are specifically expressed in lymphatic endothelial cells but not in blood vascular endothelial cells. CD31 was used as a pan-endothelial cell marker. Statistical analyses were performed using Kruskal-Wallis, Mann-Whitney U, and Spearman's rank correlation tests. The numbers of podoplanin- and prox-1-positive lymphatic vessels were significantly reduced in patients with SSc as compared with healthy individuals. The number of podoplanin-positive lymphatic precollector vessels was significantly lower in SSc patients with fingertip ulcers than in SSc patients without ulcers. Moreover, the number of lymphatic vessels correlated inversely with the number of fingertip ulcers at the time of biopsy and with the number of fingertip ulcers per year. The inverse correlation between lymphatic precollector vessel counts and fingertip ulcers remained significant after statistical adjustment for the blood vessel count, age, and modified Rodnan skin thickness score. These results demonstrate a severe reduction in the number of lymphatic capillaries and lymphatic precollector vessels in patients with SSc. Patients with decreased lymphatic vessel counts may be at particularly high risk of developing fingertip ulcers.
    Full-text · Article · May 2010 · Arthritis & Rheumatology
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    ABSTRACT: The cannabinoid receptor CB2 is predominantly expressed in non-neuronal tissue and exerts potent immunomodulatory effects. This study was undertaken to evaluate the role of CB2 in the pathogenesis of dermal fibrosis. Mice deficient in CB2 (CB2(-/-) mice) and their wild-type littermates (CB2(+/+) mice) were injected with bleomycin to induce experimental fibrosis. Mice were treated with selective agonists and antagonists of CB2. Lesional skin was evaluated for dermal thickness and numbers of infiltrating leukocytes. Bone marrow transplantation experiments were performed. CB2(-/-) mice were more sensitive to bleomycin-induced dermal fibrosis than were CB2(+/+) mice, and showed increased dermal thickness. Leukocyte counts were significantly higher in the lesional skin of CB2(+/+) mice. Increased dermal fibrosis was also observed upon treatment with the CB2 antagonist AM-630. In contrast, the selective CB2 agonist JWH-133 reduced leukocyte infiltration and dermal thickening. The phenotype of CB2(-/-) mice was mimicked by transplantation of CB2(-/-) bone marrow into CB2(+/+) mice, whereas CB2(-/-) mice transplanted with bone marrow from CB2(+/+) mice did not display an increased sensitivity to bleomycin-induced fibrosis, indicating that leukocyte expression of CB2 critically influences experimental fibrosis. Our findings indicate that CB2 limits leukocyte infiltration and tissue fibrosis in experimental dermal fibrosis. Since selective CB2 agonists are available and well tolerated, CB2 might be an interesting molecular target for the treatment of early inflammatory stages of systemic sclerosis.
    Preview · Article · Apr 2009 · Arthritis & Rheumatology