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      Propylthiouracil prevents cutaneous and pulmonary fibrosis in the reactive oxygen species murine model of systemic sclerosis

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          Abstract

          Introduction

          Recent advances suggest that the cellular redox state may play a significant role in the progression of fibrosis in systemic sclerosis (SSc). Another, and as yet poorly accounted for, feature of SSc is its overlap with thyroid abnormalities. Previous reports demonstrate that hypothyroidism reduces oxidant stress. The aim of this study was therefore to evaluate the effect of propylthiouracil (PTU), and of the hypothyroidism induced by it, on the development of cutaneous and pulmonary fibrosis in the oxidant stress murine model of SSc.

          Methods

          Chronic oxidant stress SSc was induced in BALB/c mice by daily subcutaneous injections of hypochlorous acid (HOCl) for 6 weeks. Mice ( n = 25) were randomized into three arms: HOCl ( n = 10), HOCl plus PTU ( n = 10) or vehicle alone ( n = 5). PTU administration was initiated 30 minutes after HOCl subcutaneous injection and continued daily for 6 weeks. Skin and lung fibrosis were evaluated by histologic methods. Immunohistochemical staining for alpha-smooth muscle actin (α-SMA) in cutaneous and pulmonary tissues was performed to evaluate myofibroblast differentiation. Lung and skin concentrations of vascular endothelial growth factor (VEGF), extracellular signal-related kinase (ERK), rat sarcoma protein (Ras), Ras homolog gene family (Rho), and transforming growth factor (TGF) β were analyzed by Western blot.

          Results

          Injections of HOCl induced cutaneous and lung fibrosis in BALB/c mice. PTU treatment prevented both dermal and pulmonary fibrosis. Myofibroblast differentiation was also inhibited by PTU in the skin and lung. The increase in cutaneous and pulmonary expression of VEGF, ERK, Ras, and Rho in mice treated with HOCl was significantly prevented in mice co-administered ////with PTU.

          Conclusions

          PTU, probably through its direct effect on reactive oxygen species or indirectly through thyroid function inhibition, prevents the development of cutaneous and pulmonary fibrosis by blocking the activation of the Ras-ERK pathway in the oxidant-stress animal model of SSc.

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          Most cited references 53

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          Simple method of estimating severity of pulmonary fibrosis on a numerical scale.

          A continuous numerical scale for determining the degree of fibrosis in lung specimens was devised for correlation with other pulmonary variables such as lung function tests or mineral burden. Grading was scored on a scale from 0 to 8, using the average of microscope field scores. The system allows fibrosis to be measured in small samples of tissue (1 cm) which can provide a detailed description of the changes in a lung, currently not possible with most existing methods.
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            Sex affects immunity.

            Sex based differences in immune responses, affecting both the innate and adaptive immune responses, contribute to differences in the pathogenesis of infectious diseases in males and females, the response to viral vaccines and the prevalence of autoimmune diseases. Indeed, females have a lower burden of bacterial, viral and parasitic infections, most evident during their reproductive years. Conversely, females have a higher prevalence of a number of autoimmune diseases, including Sjogren's syndrome, systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritis (RA) and multiple sclerosis (MS). These observations suggest that gonadal hormones may have a role in this sex differential. The fundamental differences in the immune systems of males and females are attributed not only to differences in sex hormones, but are related to X chromosome gene contributions and the effects of environmental factors. A comprehensive understanding of the role that sex plays in the immune response is required for therapeutic intervention strategies against infections and the development of appropriate and effective therapies for autoimmune diseases for both males and females. This review will focus on the differences between male and female immune responses in terms of innate and adaptive immunity, and the effects of sex hormones in SLE, MS and RA. Copyright © 2011 Elsevier Ltd. All rights reserved.
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              Uncontrolled expression of vascular endothelial growth factor and its receptors leads to insufficient skin angiogenesis in patients with systemic sclerosis.

              Systemic sclerosis (SSc) skin lesions are characterized by disturbed vessel morphology with enlarged capillaries and an overall reduction in capillary density, suggesting a deregulated, insufficient angiogenic response. It has been postulated that this phenomenon is due to reduced expression of the potent angiogenic factor vascular endothelial growth factor (VEGF). In contrast to this hypothesis, we demonstrate that the expression of both VEGF and its receptors VEGFR-1 and VEGFR-2 is dramatically upregulated in skin specimens of SSc patients throughout different disease stages. Interestingly, upregulation of VEGF was not mediated by hypoxia-inducible transcription factor-1 (HIF-1) as indicated by only a weak expression of the oxygen-sensitive alpha-subunit of HIF-1 in the skin of SSc patients. This was unexpected on measuring low Po2 values in the SSc skin by using a polarographic oxygen microelectrode system. Considering our observation that PDGF and IL-1beta costimulated VEGF expression, we propose that chronic and uncontrolled VEGF upregulation that is mediated by an orchestrated expression of cytokines rather than VEGF downregulation is the cause of the disturbed vessel morphology in the skin of SSc patients. Consequently, for therapeutic approaches aiming to improve tissue perfusion in these patients, a controlled expression and timely termination of VEGF signaling appears to be crucial for success of proangiogenic therapies.
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                Author and article information

                Contributors
                Journal
                Arthritis Res Ther
                Arthritis Res. Ther
                Arthritis Research & Therapy
                BioMed Central
                1478-6354
                1478-6362
                2013
                16 September 2013
                : 15
                : 5
                : R120
                Affiliations
                [1 ]Department of Clinical and Experimental Medicine, Division of Internal Medicine, University of Messina, Via Consolare Valeria n°1, 98100, Messina, Italy
                [2 ]Department of Clinical and Experimental Medicine, Division of Pharmacology, University of Messina, Via Consolare Valeria n°1, 98100, Messina, Italy
                [3 ]Department of Clinical and Experimental Medicine, Division of Rheumatology, University of Messina, Via Consolare Valeria n°1, 98100, Messina, Italy
                [4 ]Department of Internal Medicine, Division of Rheumatology, University of Louisville, Louisville, KY 40292, Kentucky, USA
                Article
                ar4300
                10.1186/ar4300
                3978728
                24286160
                Copyright © 2013 Bagnato et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Categories
                Research Article

                Orthopedics

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