Adhesion to fibronectin regulates interleukin-1 beta expression in microglial cells

The extracellular matrix (ECM) of the central nervous system (CNS) is rapidly degraded following acute brain injury, leading to inflammation and neuronal death. Under these conditions, the pro-inflammatory cytokine interleukin-1β (IL-1β) is primarily produced by microglial cells and is a key mediator of neuroinflammation, but whether the ECM regulates microglial IL-1 synthesis after CNS injury remains unknown. This study aimed to investigate whether cell attachment to ECM molecules modulated IL-1β production in activated microglia in vitro. We found adhesion to fibronectin, fibrillin-1 and laminin promoted microglial cell adhesion and spreading, potentiated by bacterial lipopolysaccharide (LPS) treatment. Adhesion to fibronectin (but not fibrillin-1 or laminin) regulated IL-1β expression via a cell density-dependent mechanism, whereby fibronectin-induced cell proliferation resulted in less IL-1β being produced. These data suggest an important regulatory mechanism of IL-1 production, associated with microglial migration and proliferation, driven by ECM degradation and/or synthesis in an injured brain.