Enhancement of FGF-1 release along with cytosolic proteins from rat astrocytes by hydrogen peroxide

Abstract We previously observed that the production and release of fibroblast growth factor (FGF-1) are increased in rat astrocytes during in vitro long-term culture, that FGF-1 enhances the generation of apoE-containing high density lipoproteins (apoE/HDL), and that the wound healing of brain cryoinjury delays in apoE-deficient mouse. The detail mechanism underlying these phenomena remains unknown. In this study, we examined effects of oxidative stress on release of FGF-1 from cultured rat astrocytes. The treatment of rat astrocytes with 100 µM hydrogen peroxide (H 2 O 2 ) for 10 min enhanced FGF-1 release without inducing apoptosis. The conditioned medium prepared from the cells cultured in a fresh medium after the treatment with H 2 O 2 had the FGF-1-like activities, which enhanced cholesterol synthesis, signalings to phosphorylate Akt and ERK, and apoE secretion. The oxidative stress induced by H 2 O 2 enhanced the release of cytosolic proteins such as HSP70 and HSP90 in addition to FGF-1. Antioxidants such as ascorbic acid and ebselen suppressed the release of cytosolic proteins induced by H 2 O 2 treatment. The addition of lipoproteins such as low density lipoproteins (LDL), furthermore, canceled H 2 O 2 -induced release of FGF-1 and cytosolic proteins. Proteolysis of cytosolic proteins in the H 2 O 2 -treated rat astrocytes was enhanced in the presence of exogenous trypsin, which was attenuated by the pretreatment with LDL, suggesting that H 2 O 2 increases the permeability of the membrane of cells, which was prevented by the addition of lipoproteins. These findings suggest that oxidative stress is one of the candidates which triggers FGF-1 release from astrocytes in the brain, and that the lipid homeostasis in the cell membrane may regulate H 2 O 2 -induced release of FGF-1.