Effects of the inflammatory mediator IL-1β on acid-induced changes in wild-type (WT) fibroblast-like synoviocytes (FLS). (A) Real-time PCR of WT FLS determined the expression of acid-sensing ion channel (ASIC)1 and ASIC3 after incubation with or without IL-1β at pH 7.4. There was a significant increase in expression of ASIC3 mRNA and a decrease in expression of ASIC1 mRNA in the group treated with IL-1β when compared to WT FLS not treated with IL-1β (P <0.05). (B) Ca2+ imaging determined (Ca2+)i in WT FLS treated with IL-1β followed by exposure to pH 6.0 and normalized to responses at pH 7.4. WT FLS incubated with IL-1β showed greater increases in (Ca2+)i intensity when compared to WT FLS not treated with IL-1β (P <0.05). (C) Western blot analysis determined the acid-induced responses of extracellular signal-regulated kinase (ERK) and p-ERK in WT FLS treated with IL-1β. After exposure to pH 6.0, p-ERK expression was significantly higher in WT FLS with IL-1β when compared to that in WT FLS without IL-1β (P <0.05).