Elsevier

Immunology Letters

Volume 141, Issue 2, 30 January 2012, Pages 165-168
Immunology Letters

Increased microRNA-146a/b, TRAF6 gene and decreased IRAK1 gene expressions in the peripheral mononuclear cells of patients with Sjögren's syndrome

https://doi.org/10.1016/j.imlet.2011.09.006Get rights and content

Abstract

MicroRNA-146a (miR-146a) is a microRNA supposed to regulate innate immune, inflammatory response and antiviral pathway negatively. Recently, its potential use as a biomarker for disease diagnosis, prevention and treatment has become widely investigated. In the current study, we measured the expression of miR-146a/b, and their target genes, IRAK1, IRAK4, TRAF6 in the peripheral mononuclear cells of patients with Sjögren's syndrome (n = 21) and healthy controls (n = 10) by quantitative reverse transcription polymerase chain reaction. We found that both miR-146a and miR-146b, furthermore, the gene of TRAF6 were significantly overexpressed in the Sjögren's patients, whereas the expression of IRAK1 gene was significantly decreased. The expression of IRAK4 did not differ significantly. These results suggest that in the peripheral mononuclear cells of Sjögren's patients, the transcriptional repression of IRAK1 is taking place, whereas the other NF-κB pathway regulating gene, TRAF6 is overexpressed. As IRAK1 has been regarded a crucial gene in the pathogenesis of systemic lupus erythematosus, TRAF6 can be a Sjögren's syndrome specific biomarker, confirming and partly explaining the existance of different pathogenic pathways in the two diseases. These observations, however, need still wider confirmations.

Highlights

► In Sjögren patients miRNA 146a/b, TRAF6 are overexpressed. ► IRAK 1 is repressed. ► Specific for Sjögren.

Introduction

MicroRNAs are endogenous non-coding RNAs, however, regulating gene expression, and they are important in a wide range of physiological processes [1]. MicroRNA (miR) expression profile have become widely studied as potential biomarkers of various diseases as autoimmune diseases like multiple sclerosis [2], rheumatoid arthritis (RA) [3], [4], systemic lupus erythematosus (SLE) [5], Sjögren's syndrome (SS) [6], [7], [8] or cancer [9]. However, there is still a rather great number of contradictions in the interpretation of the findings concerning the over or underexpression of the various miR groups depending on the types of cells tested in the variuos diseases. For example, microRNA-146a (miR-146a) was found to be underexpressed in the peripheral mononuclear cells of SLE patients [5] but it was overexpressed both in peripheral blood and the synovial tissue of RA subjects [3]. In the salivary glands of patients with Sjögren's syndrome representing high focus scores, the decrease in miR-17–92 was observed compared to those with low focus score [6], [7]. Furthermore, the expression analysis of miRs that are predicted to target Ro/SSA and La/SSB autoantigens revealed differential expression of certain miRs in the salivary gland tissues, salivary gland epithelial cells and peripheral blood mononuclear cells of patients with SS [8].

In the regulation of autoimmunity, myeloproliferation and cancer miR-146 is regarded as a significant brake. MiR-146a is a member of the miR-146 miRNA family, consisting of two evolutionary conserved miRNA genes; miR-146a and miR-146b. In people, these loci are located on separate chromosomes, in quite unrelated sequence contexts, but differ in their mature sequence only by 2 nt at the 3′ end [9]. Both genes respond to LPS in human monocytes, but only miR-146a is processed to a mature form, and the induction of expression of miR-146a is NF-κB dependent [10]. These authors suggest that miR-146a acts as a negative feedback regulator of the immune response by targeting two genes (adapter proteins) TRAF6 (TNF receptor-associated factor 6) and IRAK1 (IL-1 receptor-associated kinase 1), that are crucial for proinflammtory signalling [10]. In addition, miR-146 deficiency in T regs results in a defect in their suppressor function and dysregulated IFNγ responses, seemingly through an increase in signal transducer and activator 1 (Stat1) expression and activation [11], [12].

In the regulation of TLR4 signalling, MyD88 serves as one of the scaffold proteins for members of the IRAK family of kinases, including IRAK1, which then activates TRAF6 initiating, via more steps, the proteosomal degradation of IκBα and the production of free NF-κB. Free NF-κB (the p65–p50 dimer) moves into the nucleus and activates the transcription of genes encoding inflammatory molecules, like interferons and cytokines [13].

Therefore, in the current study, we investigated the expression of miR-146a and miR-146b in the peripheral mononuclear cells of patients with Sjögren's syndrome compared to the cells of healthy controls. Concurrently, we also measured the expression of the IRAK1, IRAK4, and TRAF6 genes which are supposed to be under the control of miR-146a [10], [13], [14], [15].

Section snippets

Patients

Twenty-one patients with primer Sjögren's syndrome (pSS) (1 male, 20 female; mean age 60.5 ± 12.4 years) were enrolled in the present study, recruited from the Autoimmune Outpatient Clinic of the Division of Clinical Immunology, 3rd Department of Medicine, Medical and Health Science Center, University of Debrecen. The diagnosis of pSS (primer Sjögren) was established according to the European–American consensus criteria [16]. These patients did not receive any immunosuppressive or

Overexpression of microRNA-146a and microRNA-146b in patients with Sjögren's syndrome as compared with normal controls

The relative expression of miR-146a and miR-146b was sigificantly higher in the mononuclear cells of patients with Sjögren's syndrome than in those of the normal controls (miR-146a: Sjögren patents: 2.91 ± 2.53 versus 1.0, p < 0.001; miR-146b: Sjögren's patients: 2.13 ± 2.10 versus 1.0, p < 0.001). The values of controls are not documented. These data are shown in Fig. 1. (In consequence of the relatively high number of cases, the data are presented in box-plot and not in dot-plot diagrams.)

Underexpression of IRAK1 and overexpression of TRAF6 genes in patients with Sjögren's syndrome as compared with normal controls

The

Discussion

IL-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6) are two key adaptor molecules downstream of Toll-like and IL-1 receptors (TIRs) signalling pathway [17], [18]. Evidence has shown that miR-146a can inhibit the expression of IRAK1 and TRAF6 [9], [19], [20], impairs NF-κB activity [19], and suppresses the expression of NF-κB target genes such as IL-6, IL-8, IL-1β and TNFα [4]. It has to be stressed that the expression rate and suppressive effects of miR-146a,

Conflict of interest

No disclosure to report.

Acknowledgments

We thank Professor Dr. Gyula Szegedi for the important scientific discussions, furthermore, Katalin Deák, Ildikó Kovács and Andrea Nagy for the excellent technical help. This work was supported by the grants of the Hungarian Research Fund (OTKA 71883) and the TÁMOP 4.2.1./B-09/1/KONV-2010-0007 project, which was co-financed by the European Union and the European Social Fund.

References (29)

  • Y. Tang et al.

    MicroRNA-146A contributes to abnormal activation of the type I interferon pathway in human lupus by targeting the key signaling proteins

    Arthritis Rheum

    (2009)
  • I. Alevizos et al.

    MicroRNA profiling of minor salivary glands identifies disease and inflammation biomarkers in Sjögren's syndrome patients

    Arthitis Rheum

    (2009)
  • E.K. Kapsogeorgou et al.

    Cellular microRNAs (miRNAs) and Sjögren's syndrome: candidate regulators of autoimmune response and autoantigen expression

    J Autoimmun

    (2011)
  • M.P. Boldin et al.

    miR-146 is a significant brake on autoimmunity, myeloproliferation and cancer in mice

    J Exp Med

    (2011)
  • Cited by (120)

    • MicroRNA regulation in autoimmune diseases

      2022, Post-transcriptional Gene Regulation in Human Disease: Volume 32
    • A comprehensive review on miR-146a molecular mechanisms in a wide spectrum of immune and non-immune inflammatory diseases

      2020, Immunology Letters
      Citation Excerpt :

      Several factors can underlie this irregularity [52,55–76]. Evidence has shown that genetic polymorphisms in miRNAs genes and also their target molecules influence the effects of miRNAs on their targets and can even alter the target molecules response pattern to the miRNAs-induced effects [52,55]. Competing endogenous RNAs (ceRNAs) or miRNA sponges can also interfere in binding of target molecules to miRNAs [62–65].

    View all citing articles on Scopus
    1

    Joint last authors contributing equally to this paper.

    View full text