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  • Title: Activation of Erk1/2 and Akt in astrocytes under ischemia.
    Author: Jiang Z, Zhang Y, Chen X, Lam PY, Yang H, Xu Q, Yu AC.
    Journal: Biochem Biophys Res Commun; 2002 Jun 14; 294(3):726-33. PubMed ID: 12056831.
    Abstract:
    Substantial evidence has shown that extracellular signal-regulated kinases 1 and 2 (Erk1/2) and serine/threonine kinase (Akt) play important roles in regulating cell survival. We examined the activities of these kinases in astrocytes under ischemia in an anaerobic chamber. The level of phosphorylated Erk1/2 in astrocytes began to increase after 1 h ischemia, reached a maximum after 4 h ischemia, before decreasing from 5 to 6 h. Akt was activated later than Erk1/2. It was significantly increased after 4 h ischemia before declining steadily afterwards. Lactate dehydrogenase (LDH) assay and Hoechst nucleic staining indicated that U0126, which inhibits Erk1/2 phosphorylation, enhanced ischemia-induced cell death, whereas LY294002, which inhibits Akt phosphorylation, delayed cell death. These effects were dose-dependent. At 4 and 6 h ischemia, U0126-treated astrocytes expressed a lower level of Bcl-2 than controls. In contrast, LY294002-treated astrocytes expressed a higher level of Bcl-2 than controls as shown by Western blots. Bcl-x(L) expression level was not affected by either treatment. These data suggest that activation of the MAPK/Erk1/2 pathway might protect astrocytes from ischemic injury, but activation of the PI3-K/Akt pathway does not. The effect may involve Bcl-2 but not Bcl-x(L) expression.
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