Fibronectin modulates expression of interleukin-1 beta and its receptor antagonist in human mononuclear cells

Identification of factors that regulate production of proinflammatory cytokines may provide insight into mechanisms governing lung inflammation. One potential regulatory factor highly expressed in inflamed tissues is fibronectin (FN). To determine the potential effects of FN on interleukin (IL)-1 beta production, we exposed human peripheral blood mononuclear cells to soluble FN. This treatment resulted in the accumulation of IL-1 beta mRNA and enhancement of IL-1 beta protein synthesis and secretion. This effect was dose dependent and appeared to be mediated by the integrin alpha 5 beta 1. Treatment with FN also increased production of IL-1 receptor antagonist (IL-1ra), a naturally occurring inhibitor of IL-1 function. However, the stimulatory effect of FN on IL-1ra production was abolished by costimulation with type I collagen. We conclude that the increased deposition of FN in injured tissues may enhance the expression of IL-1 beta mRNA and augment the production and release of IL-1 beta protein by mononuclear cells. Differential expression of IL-1 beta and IL-1ra resulting in a high IL-1 beta-to-IL-1ra ratio in response to mixed matrices containing FN and type I collagen may be an important regulatory point in inflammation.