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      Effect of Alpha-Melanocyte-Stimulating Hormone on Interleukin 8 and Monocyte Chemotactic Protein 1 Expression in a Human Retinal Pigment Epithelial Cell Line

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          Abstract

          Purpose: To examine melanocortin receptor (from MC-1 to MC-5) mRNA and the effect of α-melanocyte-stimulating hormone (α-MSH) on interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) expression in a human retinal pigment epithelial cell line (ARPE-19) stimulated with IL-1β or tumor necrosis factor α (TNF-α). Methods: Expressions of MC-1 to MC-5 mRNA were examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). α-MSH and IL-1β or TNF-α were added to serum-free medium. IL-8 and MCP-1 mRNA were measured by real-time PCR. IL-8 and MCP-1 protein concentrations were measured using enzyme-linked immunosorbent assay. Nuclear factor ĸB (NF-ĸB) translocation was examined by immunofluorescent staining/microscopy. Results: MC-1 to MC-5 receptor mRNA was expressed in unstimulated cells. IL-1β stimulated IL-8 and MCP-1 mRNA at 6 h. TNF-α stimulated IL-8 and MCP-1 mRNA expression at 1.5 and 3 h. α-MSH (10<sup>–14</sup> to 10<sup>–10</sup> M) inhibited IL-8 and MCP-1 mRNA expression in the cells stimulated with IL-1β or TNF-α. α-MSH inhibited IL-1β or TNF-α-stimulated IL-8 and MCP-1 protein levels in the media. Immunofluorescent staining/microscopy of NF-ĸB in the nucleus was dense 30 min after stimulation with IL-1β or TNF-α and was decreased by α-MSH. Conclusions: ARPE-19 cells had MC-1 mRNA. α-MSH inhibited IL-8 and MCP-1 expression and protein secretion. Possibly, the effect on chemotactic factors may be via suppression of NF-ĸB translocation.

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          The cloning of a family of genes that encode the melanocortin receptors.

          Melanocyte-stimulating hormone (MSH) and adrenocorticotropic hormone (ACTH) regulate pigmentation and adrenal cortical function, respectively. These peptides also have a variety of biological activities in other areas, including the brain, the pituitary, and the immune system. A complete understanding of the biological activities of these hormones requires the isolation and characterization of their corresponding receptors. The murine and human MSH receptors (MSH-Rs) and a human ACTH receptor (ACTH-R) were cloned. These receptors define a subfamily of receptors coupled to guanine nucleotide-binding proteins that may include the cannabinoid receptor.
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            lnterleukin-8 and Related Chemotactic Cytokines—CXC and CC Chemokines

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              Evidence of autocrine modulation of macrophage nitric oxide synthase by alpha-melanocyte-stimulating hormone.

              alpha-Melanocyte-stimulating hormone (alpha-MSH) is a potent inhibitory agent in all major forms of inflammation. To identify a potential mechanism of antiinflammatory action of alpha-MSH, we tested its effects on production of nitric oxide (NO), believed to be a mediator common to all forms of inflammation. We measured NO and alpha-MSH production in RAW 264.7 cultured murine macrophages stimulated with bacterial lipopolysaccharide and interferon gamma. alpha-MSH inhibited production of NO, as estimated from nitrite production and nitration of endogenous macrophage proteins. This occurred through inhibition of production of NO synthase II protein; steady-state NO synthase II mRNA abundance was also reduced. alpha-MSH increased cAMP accumulation in RAW cells, characteristic of alpha-MSH receptors in other cell types. RAW cells also expressed mRNA for the primary alpha-MSH receptor (melanocortin 1). mRNA for proopiomelanocortin, the precursor molecular of alpha-MSH, was expressed in RAW cells, and tumor necrosis factor alpha increased production and release of alpha-MSH. These results suggest that the proinflammatory cytokine tumor necrosis factor alpha can induce macrophages to increase production of alpha-MSH, which then becomes available to act upon melanocortin receptors on the same cells. Such stimulation of melanocortin receptors could modulate inflammation by inhibiting the production of NO. The results suggest that alpha-MSH is an autocrine factor in macrophages which modulates inflammation by counteracting the effects of proinflammatory cytokines.
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                Author and article information

                Journal
                ORE
                Ophthalmic Res
                10.1159/issn.0030-3747
                Ophthalmic Research
                S. Karger AG
                0030-3747
                1423-0259
                2005
                October 2005
                15 September 2005
                : 37
                : 5
                : 279-288
                Affiliations
                Department of Ophthalmology, Toyama Medical and Pharmaceutical University, Toyama, Japan
                Article
                87699 Ophthalmic Res 2005;37:279–288
                10.1159/000087699
                16118510
                0e3a0fa9-d8a4-4c5a-acf1-edfe9fbaca7a
                © 2005 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                History
                : 17 November 2004
                : 24 February 2005
                Page count
                Figures: 6, References: 27, Pages: 10
                Categories
                Original Paper

                Vision sciences,Ophthalmology & Optometry,Pathology
                Chemokine,Interleukin 1β,ARPE-19 cells,α-Melanocyte-stimulating hormone,Tumor necrosis factor α

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