Open AccessAcid‐Sensing Ion Channel 3 Deficiency Increases Inflammation but Decreases Pain Behavior in Murine Arthritis
Author(s) -
Sluka Kathleen A.,
Rasmussen Lynn A.,
Edgar Meghan M.,
O'Donnell James M.,
Walder Roxanne Y.,
Kolker Sandra J.,
Boyle David L.,
Firestein Gary S.
Publication year - 2013
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/art.37862
Subject(s) - acid sensing ion channel , inflammation , arthritis , medicine , application specific integrated circuit , matrix metalloproteinase , immunology , receptor , ion channel , computer science , embedded system
Abstract Objective Through its location on nociceptors, acid‐sensing ion channel 3 (ASIC‐3) is activated by decreases in pH and plays a significant role in musculoskeletal pain. We recently showed that decreases in pH activate ASIC‐3 located on fibroblast‐like synoviocytes (FLS), which are key cells in the inflammatory process. The purpose of this study was to test whether ASIC‐3–deficient mice with arthritis have altered inflammation and pain relative to controls. Methods Collagen antibody–induced arthritis (CAIA) was generated by injection of an anti–type II collagen antibody cocktail. Inflammation and pain parameters in ASIC‐3 −/− and ASIC‐3 +/+ mice were assessed. Disease severity was assessed by determining clinical arthritis scores, measuring joint diameters, analyzing joint histology, and assessing synovial gene expression by quantitative polymerase chain reaction analysis. Cell death was assessed with a Live/Dead assay of FLS in response to decreases in pH. Pain behaviors in the mice were measured by examining withdrawal thresholds in the joints and paws and by measuring their physical activity levels. Results Surprisingly, ASIC‐3 −/− mice with CAIA demonstrated significantly increased joint inflammation, joint destruction, and expression of interleukin‐6 (IL‐6), matrix metalloproteinase 3 (MMP‐3), and MMP‐13 in joint tissue as compared to ASIC‐3 +/+ mice. ASIC‐3 +/+ FLS showed enhanced cell death when exposed to pH 6.0 in the presence of IL‐1β, which was abolished in ASIC‐3 −/− FLS. Despite enhanced disease severity, ASIC‐3 −/− mice did not develop mechanical hypersensitivity of the paw and showed greater levels of physical activity. Conclusion Our findings are consistent with the hypothesis that ASIC‐3 plays a protective role in the inflammatory arthritides by limiting inflammation through enhanced synoviocyte cell death, which reduces disease severity, and through the production of pain, which reduces joint use.