Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.


A Novel Role for Monosodium Urate Monohydrate Crystals and Gouty Synovial Fluids in Monocyte Migration in Gout.

Amin1,  M. Asif, Shu1,  Qiang, Vargo1,  Jonathon W., Ruth1,  Jeffrey H., Isozaki1,  Takeo, Lee1,  Solhee, Koch2,  Alisa E.

University of Michigan Medical School, Ann Arbor, MI
Department of Veteran's Affairs and University of Michigan, Ann Arbor, MI

Background/Purpose:

Gout is characterized by intra-articular deposition of monosodium urate monohydrate (MSU) crystals. The role of neutrophil influx in acute gouty arthritis is well established, while the contribution of monocytes (MNs) and their secreted inflammatory mediators is not. Here we demonstrate the role of MSU in MN migration.

Methods:

To examine the role of MSU crystals in normal human peripheral blood (PB) MN migration, we performed MN chemotaxis in a modified Boyden chamber in vitro using either MSU crystals or gouty synovial fluids (SFs) as stimuli. To examine mechanisms of MN migration, we performed MN chemotaxis with MSU in the presence or absence of chemical signaling inhibitors. We determined the in vivo role of MSU crystals or gouty SFs in homing of dye-tagged MNs using normal human synovial tissue (ST)-severe combined immunodeficient (SCID) mouse chimeras. Gout often occurs after ingestion of rich foods, so to understand MN migration in vivo, we injected MSU crystals with fatty acid FFA C18:0 (FFA) into C57BL/6 mouse knees and examined them for MN ingress after 48 hours. To investigate the contribution of MSU to production of leukocyte chemoattractants macrophage migration inhibitory factor (MIF) and epithelial neutrophil activating factor-78 (ENA-78/CXCL5), and the signaling molecules involved in secretion of these cytokines, we stimulated MNs with MSU crystals, and performed ELISAs on conditioned medium. We also assayed for MIF in gouty SF by ELISA.

Results:

We found that there was a significant 2 fold increase in in vitro MN migration in response to MSU crystals, while gouty SFs increased MN migration 5 fold compared to negative control (n=3, p<0.05). MSU crystal induced MN migration was significantly decreased by inhibitors of p38 MAPK, Src, and NFkB, suggesting that crystal induced MN migration occurs via these pathways. To determine if MSU crystals or gouty SFs induce MN migration in vivo, we engrafted SCID mice with normal human STs. After 4 weeks, we injected dye-tagged human PB MNs via tail vein. Simultaneously, we injected MSU crystals or gouty SFs into ST grafts. After 48 hours, we harvested the STs and found an increase in MN homing to the grafts injected with MSU crystals or SFs (p<0.05), indicating that either of these stimuli could recruit MNs in vivo. Likewise, we found a marked increase in mouse MN ingress in knees when these mice were injected with MSU crystals and FFA. Human MNs stimulated with MSU for 24 hours released significantly higher quantities of the potent leukocyte chemoattractants MIF and ENA-78/CXCL5 compared to nonstimulated MNs. MIF was a mean of 6 fold higher in gouty SFs compared to osteoarthritic fluids, suggesting the importance of MIF in gouty arthritis. Next, we examined the role of signaling molecules in the production of MIF and ENA-78/CXCL5 by stimulating MNs with MSU crystals in the presence of chemical signaling inhibitors. We found that MIF or ENA-78/CXCL5 secretion depended on the p38 MAPK pathway.

Conclusion:

This data suggests an intriguing role for MSU crystals and gouty SFs in MN migration in vitro and in vivo. This data also provides evidence that MNs and their secreted products such as MIF and ENA-78/CXCL5 may be potential therapeutic targets for the treatment of diseases like gout.

To cite this abstract, please use the following information:
Amin, M. Asif, Shu, Qiang, Vargo, Jonathon W., Ruth, Jeffrey H., Isozaki, Takeo, Lee, Solhee, et al; A Novel Role for Monosodium Urate Monohydrate Crystals and Gouty Synovial Fluids in Monocyte Migration in Gout. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :1619
DOI:

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