IL-1β-induced production of metalloproteinases by synovial cells depends on gap junction conductance

Synovial cells can form networks connected by gap junctions. The purpose of this study was to obtain evidence for a necessary role of gap junction intercellular communication in protein secretion by synovial cells. We developed a novel assay to measure the enzymatic activity of metalloproteinases (MMPs) produced by synovial cells in response to interleukin-1β (IL-1β) and employed the assay to explore the biological function of gap junctions. IL-1β produced a dose-dependent increase in MMP activity that was blocked by exposure to the gap junction inhibitors 18α-glycyrrhetinic acid and octanol for as few as 50 min. The inhibitors produced an immediate and marked reduction in intercellular communication, as assessed by transient current analysis using the nystatin perforated-patch method. These observations suggest that communication through gap junctions early in IL-1β signal transduction is critical to the process of cytokine-regulated secretion of MMPs by synovial cells.