SAT0034 Possible involvement of baff and matrixmetalloproteinase-9 in the activation of monocytes of patients with primary sjÖgren’s syndrome
Authors: K. Yoshimoto, K. Suzuki, T. Takeuchi
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> B cell activating factor belonging to TNF family (BAFF) is well known as a factor which regulates proliferation, differentiation and survival of B cells, and plays a pivotal role in the pathogenesis of primary Sjögren's syndrome (pSS). In our previous study, we found that BAFF significantly enhanced IL-6 production by pSS monocytes and the amount of IL-6 produced by BAFF-stimulated monocytes was positively and significantly correlated with the expression level of a BAFF receptor (BR3). These data collectively suggest that the BAFF signalling through BR3 is involved in activation of monocytes to promote production of inflammatory cytokines, such as IL-6. Matrix metalloproteinase-9 (MMP-9) is well known as one of the enzymes involved in degradation of extracellular matrix (ECM) and mainly produced by activated T cells and monocytes. It has been reported that the concentration of MMP-9 in saliva was significantly higher in pSS patients as compared to healthy controls (HC). Therefore, it is conceivable that MMP-9 is involved in the pathogenesis of pSS through degradation of ECM of salivary glands, which consequently results in decrease in saliva, one of the clinical manifestations of pSS. <h3>Objectives</h3> To explored the relationship between BAFF and MMP-9 in the pathogenesis of pSS. <h3>Methods</h3> Peripheral monocytes from pSS patients (n=37) and HC (n=19) were prepared by using CD14 +microbeads and cultured <i>in vitro</i> in the presence or absence of recombinant human soluble BAFF (rhsBAFF) for 96 hours. The amounts of IL-6 and MMP-9 in the culture supernatants were measured by ELISA. Signal transduction pathways were investigated by exposing rhsBAFF-stimulated pSS monocytes to several inhibitors against NF-κB (BAY11–7082 and BAY11–7085) and PI3 kinase (LY294002). FACS analysis of whole blood samples was performed to investigate the expression levels of BR3 and MMP-9 in monocytes. The expression level of MMP-9 was also analysed by quantitative RT-PCR (qPCR). Serum levels of BAFF and MMP-9 were measured by an electrochemiluminescence assay. <h3>Results</h3> Serum levels of BAFF and MMP-9 in pSS patients were significantly higher than those of HC, and the levels showed positive and significant correlation. FACS analysis of whole blood samples demonstrated that MMP-9 was mainly expressed in monocytes and that the expression level was significantly higher in pSS than in HC. ELISA and qPCR revealed that stimulation of pSS moncytes with rhsBAFF drastically enhanced the expression of MMP-9 as compared to normal monocytes. Remarkably, the amount of MMP-9 produced by the cells was positively and significantly correlated with the expression level of BR3 in pSS monocytes, suggesting that BAFF-signalling is involved in the production of MMP-9 by the cells. Moreover, the elevated production of MMP-9 was significantly suppressed by specific inhibitors against NF-κB and PI3 kinase in a dose dependent manner. <h3>Conclusions</h3> The present study suggests that BAFF stimulates monocytes through BR3 to promote MMP9 production and may contribute to ECM degradation. Our study also suggests that NF-κB and PI3 kinase are involved in the pathway. <h3>Disclosure of Interest</h3> None declared