The Interaction between Tumor Necrosis Factor-Like Weak Inducer of Apoptosis and its Receptor Fibroblast Growth Factor-Inducible 14 Promotes the Recruitment of Neutrophils into the Ischemic Brain

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor-inducible 14 (Fn14) are expressed in endothelial cells and perivascular astrocytes. Here, we show that TWEAK induces a dose-dependent increase in the expression of the chemokine monocyte chemoattractant protein-1 (MCP-1) in astrocytes, and that this effect is mediated by its interaction with Fn14 via nuclear factor-kappaB pathway activation. Exposure to oxygen-glucose deprivation (OGD) conditions increases TWEAK and Fn14 mRNA expression in wild-type (Wt) astrocytic cultures. Likewise, incubation under OGD conditions induces the expression of MCP-1 in Wt astrocytes but not in astrocytes deficient on either TWEAK (TWEAK(-/-)) or Fn14 (Fn14(-/-)). We also found that TWEAK induces the passage of neutrophils to the abluminal side of an in vitro model of the blood-brain barrier. Our earlier studies indicate that cerebral ischemia increases the expression of TWEAK and Fn14 in the endothelial cell-basement membrane-astrocyte interface. Here, we report that middle cerebral artery occlusion increases the expression of MCP-1 and the recruitment of neutrophils into the ischemic tissue in Wt but not in TWEAK(-/-) or Fn14(-/-) mice. These novel results indicate that during cerebral ischemia, the interaction between TWEAK and Fn14 leads to the recruitment of leukocytes into the ischemic tissue.