(A): Mitochondrial DNA integrity, mitochondrial DNA copy number and nuclear DNA integrity in control U937 cells (without oxidative stress) subjected to vehicle or various concentrations of (1, 3, 10, 30 or 100 μM) olaparib for 24 hours (data expressed as % of control); (B): Mitochondrial DNA integrity, mitochondrial DNA copy number and nuclear DNA integrity in control U937 cells (without oxidative stress) subjected to vehicle or various concentrations of olaparib (1, 3, 10, 30 or 100 μM), followed by treatment with H2O2 (300 μM) for 24 hours (data expressed as % of control); (C): Mitochondrial DNA integrity, mitochondrial DNA copy number and nuclear DNA integrity in control U937 cells (without oxidative stress) subjected to vehicle or various concentrations of olaparib (1, 3, 10, 30 or 100 μM), followed by treatment with H2O2 (1 mM) for 24 hours (data expressed as % of control). Results are indicated as mean ± SEM of n=3 per condition. *p<0.05 shows a significant change in response to H2O2, compared to control cells; #p<0.05 shows significant protective effect of olaparib in H2O2 challenged cells compared to vehicle-treated H2O2 challenged cells.