Hydrogen peroxide-induced changes of PPARγ in primary cultured cortical neurons

Abstract

To investigate whether H₂O₂treatment negatively regulates PPARγ in primary cortical neurons by increasing PPARγ phosphorylation. Primary cultured cortical neurons were treated with H₂O₂(250, 500, and 750 µmol/L) for 2 h. 30 min before the H₂O₂(500 µmol/L), the specific inhibitor of ERK1/2 activation, U0126, was added to the culture. Morphological observation, MTT assay and the trypan blue exclusion method were used to detect cell damage. Western blot was carried out to evaluate the expressions of p-PPARγ (phospho-PPARγ) and total PPARγ, as well as to investigate the nuclear translocation of PPARγ (PPARγ activity). (1) Compared with the control group, cell survival rates were decreased by H₂O₂at concentrations of 250, 500, and 750 µmol/L (74.8% ± 5.2%, 53.6% ± 6.7% and 26.5% ± 5.8%, respectively, P < 0.05), while cell death rate were increased (ctrl group 6.6% ± 1.0%, H₂O₂-injured groups: 23.1% ± 2.8%, 48.2% ± 4.1% and 75.9% ± 4.4% respectively, P < 0.05). (2) Compared with the control group, the expression of total PPARγ failed to show significant change in H₂O₂-injured group, whereas the expression of p-PPARγ increased. Neurons injured by H₂O₂(500 µmol/L) also showed a reduction of PPARγ nuclear translocation (an increase in cytosol PPARγ and a simultaneous decrease in nuclear PPARγ). (3) Compared with H₂O₂-injured group, inhibition of ERK1/2 activation decreased p-PPARγ expression, and increased PPARγ nuclear translocation, as well as improved cell survival rate (53.6% ± 6.7% vs 70.8% ± 1.3%, P < 0.05) and decreased cell death rate (48.2% ± 4.1% vs 29.8%±3.4%, P < 0.05). Phosphorylation of PPARγ may be involved in cell death induced by hydrogen peroxide in primary cultured cortical neurons.