Handbook of Vitamin C Research

Vitamin C Protects from Oxidative DNA Damage… 109Figure 13.Figure 13. Effect of vitamin C on HepG2 (A) and HL-60 (B) cell viability by LDH assay. Cells werecultured with different doses of vitamin C for 24 ( ), 48 ( ) and 72 h ( ). Asterisks indicatesignificant difference from control ** p 0.01 and * p 0.05.Cytotoxicity of vitamin C, assessed by measuring LDH release in HepG2 and HL-60cells, is shown in Figure 13. Similarly, no significant difference in LDH release was observedwhen HepG2 cells were incubated with vitamin C for 24, 48 and 72 h compared with control(Figure 13 A). However, an increase of LDH release in HL-60 cells was statisticallysignificant with 50 μM at 72 h (28%) and with 100 μM of vitamin C at 48 and 72 h (27 and36%, respectively; Figure 13 B), suggesting some membrane damage.Effect of Vitamin C on Apoptosis by the TUNEL AssayFigure 14 shows the induction of apoptosis by vitamin C on HepG2 and HL-60 cellsusing the TUNEL assay. TUNEL assay is a sensitive test to detect the DNA strand breaksthat are a hallmark of the late stages of apoptosis [72]. The baseline percentage of apoptosison untreated HepG2 and HL-60 cells was around 4% and 8%, respectively.