The effects of alpha-tocoferol and H2O2 on the mitochondrial membrane potential and Bax/Bcl-xL ratio in PC12 cells

Using the flow-cytometry method, we demonstrated the ability of alpha-tocopherol (alpha-T) at nano- and micromolar concentrations to recover the mitochondrial membrane potential (ΔΨm), which decreased after H₂O₂ treatment in PC12 neuronal line cells. Alterations in the ΔΨm in PC12 cells were evaluated using the fluorescent probe tetramethylrhodamine (TMRM). The higher cell-fluorescence intensity corresponded to a higher ΔΨm value. Treatment with H₂O₂ resulted in a decrease in the fluorescence intensity from 100% in the control to 43.2 ± 5.1% (p < 0.001). Long-term 18-h preincubation with 100 nM or 100 μM alpha-T increased the fluorescence intensity in PC12 cells from 43.2 ± 5.2% up to 88.4 ± 4.8 and 89.6 ± 6.5% of the control value, respectively (p < 0.01 according to the one-way analysis of variances). Alpha-T at both 100 nM and 100 μM concentrations significantly and with similar efficacy decreased the ratio of the proapoptotic protein Bax to the antiapoptotic protein Bcl-xL (Bax/Bcl-xL) in the control PC12 cells. However, we did not reveal any significant effect of H₂O₂ or preincubation with alpha-T on this ratio in PC12 lysates. Furthermore, H₂O₂ increased both the Bax and Bcl-xL levels in PC12 cells.