LAUSR

Background Deposition of monosodium urate (MSU) crystals in the joints or other tissues is a hallmark in the pathogenesis of gout. The urate crystal-induced inflammation is known to be mediated mainly by neutrophils besides monocytes and macrophages. Although MSU crystal-mediated signal transduction is in the focus of recent investigations, the molecular mechanism is only partially characterised. Objectives In this study, we investigated the role of Src family kinases in MSU crystal-induced in vitro activation of primary murine and human neutrophils and their in vivo significance in experimental model of gout. Methods Bone marrow isolated neutrophils from wild type and triple Src family kinases-deficient (Hck–/–Fgr–/–Lyn–/–) mice or vehicle and Src-inhibitor treated human neutrophils were stimulated with different concentration of MSU crystals. The superoxide production of the cells was measured by a luminometric assay, while the supernatants of MSU crystal activated cells were analysed by using various enzyme-linked immunosorbent assay (ELISA) kits. The phagocytosis of the urate crystals by neutrophils was followed by videomicroscopy and flow cytometry. Gouty arthritis was induced by injection of MSU crystals into the hind paws of the experimental mice and was assessed by ankle thickness measurements and detection of the synovial cytokine levels by ELISA. Results The MSU crystal-induced superoxide release, cytokine production and the crystal-phagocytosis were abrogated in Src family kinases-deficient murine or in Src-inhibitor treated human neutrophils. In contrast to wild type animals, Src family kinases-deficient mice showed significantly decreased paw swelling and neutrophil accumulation at the site of inflammation. In line with this, the synovial levels of interleukin-1β and CXCL2 were also strongly reduced in Src family kinases-deficient mice compared to wild type animals. Conclusions Src family kinases play an indispensable role in MSU crystal-induced superoxide and cytokine production as well as crystal-phagocytosis of neutrophils. The fact, that Src family kinases-deficient mice are partially protected from crystal-induced inflammatory reactions indicate the important role of these kinases in in vivo gouty arthritis These kinases are also play important role in the development of in vivo gouty arthritis as the. Identification of these key players in urate crystal-induced intracellular signalling pathways in neutrophils leads to a better understanding of the pathogenesis of gout and may help to develop novel therapeutic strategies in MSU crystal-associated inflammatory diseases. Acknowledgements MTA-SE “Lendulet” Inflammation Physiology Research Group of the Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary and F.K. was a recipient of János Bolyai Research Scholarship of the Hungarian Academy of Sciences. Disclosure of Interest None declared