Fig. 6: Sulfenic acid-modified SOD1 oligomers induce apoptosis of living SH-SY5Y cells

Treatment of 5 μM sulfenic acid-modified SOD1 oligomers (+) (e–h) for 3 days did induce apoptosis of living SOD1 stable cells, but no apoptosis of living SOD1 stable cells was observed when treated without SOD1 oligomers (-) (a–d). Similarly, treatment of 5 μM sulfenic acid-modified SOD1 oligomers (+) (m–p) for 3 days did induce early and late apoptosis of living TDP-43 stable cells, but no apoptosis of living TDP-43 stable cells was observed when treated without SOD1 oligomers (-) (i–l). Annexin V-FITC (green) and PI (red) were used to double stain living SOD1/TDP-43 stable cells. Confocal laser scanning microscopy was used to observe apoptotic cells. The scale bar represents 10 μm (a–p). Living SOD1 stable cells (r) or TDP-43 stable cells (t) incubated with 10 μM sulfenic acid-modified SOD1 oligomers for 3 days showed much higher rates of apoptosis than those for SOD1 stable cells (q) or TDP-43 stable cells (s) incubated with 0 μM SOD1 oligomers. The percentage of apoptotic cells was determined by flow cytometry. Four quadrants divided by annexin V-FITC/PI staining were viable cells (D3 quadrant in q–t), early apoptotic cells (D4 quadrant in q–t), late apoptotic cells (D2 quadrant in q–t), and operation damaged cells (D1 quadrant in q–t), respectively