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Open Access Highly Accessed Research article

Modulation of monosodium urate crystal-induced responses in neutrophils by the myeloid inhibitory C-type lectin-like receptor: potential therapeutic implications

Valérie Gagné1, Louis Marois1, Jean-Michel Levesque1, Hugo Galarneau1, Mireille H Lahoud2, Irina Caminschi2, Paul H Naccache1, Philippe Tessier1 and Maria JG Fernandes1*

Author Affiliations

1 Department of Microbiology, Infectious Diseases, and Immunology, Faculty of Medicine, Laval University, Centre for Research in Immunology and Rheumatology, Research Centre CHUQ-CHUL, Bloc T1-49, 2705 boulevard Laurier, Quebec, QC, G1V 4G2, Canada

2 Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3050, Australia

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Arthritis Research & Therapy 2013, 15:R73  doi:10.1186/ar4250


Please see related editorial by So, http://arthritis-research.com/content/15/5/118

Published: 9 July 2013

Abstract

Introduction

Monosodium urate crystals (MSU), the etiological agent of gout, are one of the most potent proinflammatory stimuli for neutrophils. The modulation of MSU-induced neutrophil activation by inhibitory receptors remains poorly characterized. The expression of the myeloid inhibitory C-type lectin-like receptor (MICL) in neutrophils is downregulated by several proinflammatory stimuli, suggestive of a role for this receptor in neutrophil function. We thus investigated the potential role of MICL in MSU-induced neutrophil activation.

Methods

The expression of MICL was monitored in human neutrophils by flow cytometry and Western blot analysis after stimulation with MSU. Protein tyrosine phosphorylation was also assessed by Western blot analysis and the production of IL-1 and IL-8 by enzyme-linked immunosorbent assay. Changes in the concentration of cytoplasmic free calcium were monitored with the Fura-2-acetoxymethyl ester calcium indicator. MICL expression was modulated with an anti-MICL antibody in neutrophils and siRNA in the PLB-985 neutrophil-like cell line.

Results

MSU induced the downregulation of MICL expression in neutrophils. A diminution in the expression of MICL induced by antibody cross-linking or siRNA enhanced the MSU-dependent increase in cytoplasmic calcium levels, protein tyrosine phosphorylation and IL-8 but not IL-1 production. Pretreatment of neutrophils with colchicine inhibited the MSU-induced downregulation of MICL expression.

Conclusions

Our findings strongly suggest that MICL acts as an inhibitory receptor in human neutrophils since the downregulation of MICL expression enhances MSU-induced neutrophil activation. Since MSU downregulates the expression of MICL, MICL may play a pathogenic role in gout by enhancing neutrophil effector functions. In support of this notion, colchicine counteracts the MSU-induced loss of MICL expression. Our findings thus also provide further insight into the potential molecular mechanisms behind the anti-inflammatory properties of this drug.

Keywords:
Cytokine production; out; Immunoreceptor tyrosine-based inhibitory motif; Monosodium urate crystals; Neutrophil; Signaling