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MicroRNA-18a enhances the interleukin-6-mediated production of the acute-phase proteins fibrinogen and haptoglobin in human hepatocytes


Brock, M; Trenkmann, M; Gay, R E; Gay, S; Speich, R; Huber, L C (2011). MicroRNA-18a enhances the interleukin-6-mediated production of the acute-phase proteins fibrinogen and haptoglobin in human hepatocytes. Journal of Biological Chemistry, 286(46):40142-40150.

Abstract

The acute-phase response is an inflammatory process triggered mainly by the cytokine IL-6. Signaling of IL-6 is transduced by activation of STAT3 (signal transducer and activator of transcription 3), which rapidly induces the production of acute-phase proteins such as haptoglobin and fibrinogen. Another target of the IL-6/STAT3 signal transduction pathway is the microRNA cluster miR-17/92. Here, we investigated the interplay of miR-17/92 and STAT3 signaling and its impact on the acute-phase response in primary human hepatocytes and hepatoma (HepG2) cells. Employing a reporter gene system consisting of STAT3-sensitive promoter sequences, we show that the miR-17/92 cluster member miR-18a enhanced the transcriptional activity of STAT3. IL-6 stimulation experiments in miR-18a-overexpressing hepatocytes and HepG2 cells revealed an augmented acute-phase response indicated by increased expression and secretion of haptoglobin and fibrinogen. This effect was due, at least in part, to repression of PIAS3 (protein inhibitor of activated STAT, 3), a repressor of STAT3 activity, which we identified as a novel direct target of miR-18a. Finally, we demonstrate that the expression of miR-17/92 in primary hepatocytes and HepG2 cells is modulated by IL-6. Our data reveal, for the first time, a microRNA-mediated positive feedback loop of IL-6 signal transduction leading to an enhanced acute-phase response in human hepatocytes.

Abstract

The acute-phase response is an inflammatory process triggered mainly by the cytokine IL-6. Signaling of IL-6 is transduced by activation of STAT3 (signal transducer and activator of transcription 3), which rapidly induces the production of acute-phase proteins such as haptoglobin and fibrinogen. Another target of the IL-6/STAT3 signal transduction pathway is the microRNA cluster miR-17/92. Here, we investigated the interplay of miR-17/92 and STAT3 signaling and its impact on the acute-phase response in primary human hepatocytes and hepatoma (HepG2) cells. Employing a reporter gene system consisting of STAT3-sensitive promoter sequences, we show that the miR-17/92 cluster member miR-18a enhanced the transcriptional activity of STAT3. IL-6 stimulation experiments in miR-18a-overexpressing hepatocytes and HepG2 cells revealed an augmented acute-phase response indicated by increased expression and secretion of haptoglobin and fibrinogen. This effect was due, at least in part, to repression of PIAS3 (protein inhibitor of activated STAT, 3), a repressor of STAT3 activity, which we identified as a novel direct target of miR-18a. Finally, we demonstrate that the expression of miR-17/92 in primary hepatocytes and HepG2 cells is modulated by IL-6. Our data reveal, for the first time, a microRNA-mediated positive feedback loop of IL-6 signal transduction leading to an enhanced acute-phase response in human hepatocytes.

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Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic and Policlinic for Internal Medicine
04 Faculty of Medicine > University Hospital Zurich > Rheumatology Clinic and Institute of Physical Medicine
04 Faculty of Medicine > Center for Integrative Human Physiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2011
Deposited On:06 Jan 2012 14:33
Last Modified:04 Aug 2017 08:02
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:0021-9258
Additional Information:This research was originally published in Journal of Biological Chemistry. Brock, M; Trenkmann, M; Gay, R E; Gay, S; Speich, R; Huber, L C (2011). MicroRNA-18a enhances the interleukin-6-mediated production of the acute-phase proteins fibrinogen and haptoglobin in human hepatocytes. Journal of Biological Chemistry, 286(46):40142-40150 © the American Society for Biochemistry and Molecular Biology.
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1074/jbc.M111.251793
PubMed ID:21953462

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