Impact of N-Acetylation on DNA Damage and Oxidative Stress Responses in Mammalian Cells and Human Hepatocytes Treated with Hydralazine.

Hydralazine is widely used to treat hypertension during pregnancy and has epigenetic effects in cancer therapy. Cryoplatable human hepatocytes showed concentration-dependent increase in DNA damage response (linear trend p = 0.0069) following 24 h hydralazine treatment. DNA repair-deficient UV5 Chinese hamster ovary (CHO) cell lines expressing human CYP1A2 and either NAT2*4 (reference allele) or NAT2*5 (variant allele) were treated with hydralazine for 24 h. CHO cells expressing NAT2*4 showed a higher acetylation rate than those with NAT2*5 (p < 0.001), whereas CHO cell viability did not differ significantly following hydralazine treatment (p > 0.05). Hydralazine caused a concentration-dependent increase in DNA damage response in the un-transfected UV5 CHO cell line, as well as in each of the UV5 CHO cell lines transfected with human CYP1A2 and/or NAT2 alleles. CHO cells with CYP1A2 only showed higher DNA damage response from hydralazine compared to cells with CYP1A2/NAT2*4 or CYP1A2/NAT2*5 (p < 0.05 and p < 0.0001, respectively), and higher in CYP1A2/NAT2*4 versus CYP1A2/NAT2*5 cells (p = 0.0011). Apurinic/apyrimidinic (AP) sites in CHO cells expressing only CYP1A2 were significantly higher than in the un-transfected UV5 CHO cell line (p < 0.01) and higher in CHO cells expressing CYP1A2/NAT2*4 compared to CYP1A2/NAT2*5, but the difference was not significant (p > 0.05). In contrast, ROS levels were reduced following hydralazine treatment in CHO cells with CYP1A2/NAT2*4 and CYP1A2/NAT2*5 (p < 0.001 and p < 0.05, respectively). The results of the current study document DNA damage responses associated with hydralazine in human hepatocytes and CHO cells. The DNA damage response was increased following N-hydroxylation by CYP1A2, which competes with N-acetylation by NAT2.