Abstract
Glial cells that produce and respond to various cytokines mediate inflammatory processes in the brain. Here, we show that oncostatin M (OSM) and interleukin-1 (IL-1) regulate the expression of plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA) in human astrocytes. Using the PAI-1 reporter constructs we show that the -58 to -51 proximal element mediates activation by both cytokines. This element is already bound by c-fos/c-jun heterodimers in unstimulated astrocytes, and treatment with cytokine strongly stimulates both expression of c-fos and binding of c-fos/c-jun heterodimers. In addition, IL-1 activates an inhibitory mechanism that down-regulates PAI-1 expression after longer exposure to this cytokine. Overexpression of dominant-negative signal transducer and activator of transcription-1 (STAT1), STAT3, STAT5 and inhibitor of nuclear factor-kappaB (IkappaB) suppressed OSM/IL-1-induced expression of the PAI-1 reporter construct. We conclude that OSM and IL-1 regulate the PAI-1 gene expression via up-regulating c-fos levels and subsequent binding of c-fos/c-jun heterodimers to the proximal element of the PAI-1 gene.