Objective To study the vulnerability of astrocytes bearing mutant SOD1 under the oxidative stress.Methods The cytotoxicity of the serum deprived astrocytes was measured by MTT.The level of ROS was shown by fluorescence of DCF through confocal microscopy.The expression of Nrf2,HO1 and NQO1 in the different cells was detected by Western blot.Results The level of cellular toxicity was higher in the astrocytes bearing mutant SOD1 exposed to the oxidative stress than the astrocytes hearing wild type SOD1.In the astrocytes bearing mutant SOD1,the expression of Nrf2,HO1 and NQO1 decreased.In the presence of mutant SOD1,an unexpected 44 per-cent decrease of Nrf2 was detected.This was associated with a decreases in multiple downstream phase Ⅱ detoxif-ying enzymes and antioxidant enzymes,known as NQO1 and HO1.Furthermore,our results showed that the ex-pression of NQO1 increased 1.5 and 2.5-fold by EGCG at 5 and 10 μmol/L.EGCG also elevated the expression of total Nrf2.Confocal microscopy showed that EGCG caused Nrf2 translocation from the cytoplasm to the nucleus.Conclusion Decrease in Nrf2 expression is the mechanism to explain the vulnerability of astrocytes bearing mutant SOD1 and EGCG strengthened antioxidation function by upregulating the activity of Nrf2.