8-Hydroxy-2-deoxyguanosine, a product of oxidative DNA degradation, is increased in the amniotic fluid of preterm births.

Abstract

8-Hydroxy-2-deoxyguanosine (8-OH-2dG) is a measurable biomarker of oxidative DNA damage. This study was designed to determine amniotic fluid 8-OH-2dG levels in healthy full-term pregnant women and preterm pregnant women. To reveal the effect of reactive oxygen species on 8-OH-2dG levels, amniotic fluid total oxidant capacity (TOS), total antioxidant capacity (TAC) and oxidative stress index (OSI) were also measured. A total of 60 patients, 35 patients with full-term pregnancy and 25 patients with preterm pregnancy, participated in the study. Labor occurring before 37 weeks of gestation was considered as spontaneous preterm birth. Amniotic fluid samples were collected from full-term patients during cesarean section or normal vaginal delivery. 8-OH-2dG concentrations in amniotic fluid samples were measured quantitatively by Enzyme-Linked Immunosorbent Assay (ELISA). Amniotic fluid total antioxidant capacity (TAC) and total oxidant capacity (TOC) was determined in amniotic samples. The amniotic fluid 8-OH-2dG levels of the preterm group were significantly higher than the full-term group (60.8±7.02 ng/mL vs. 33.6±4.11 ng/mL, p<0.01). Similarly, TOC levels of the preterm group were significantly higher than the full-term group (89.7±4.80 µmol/L vs. 54.3±6.60 µmol, p<0.02). TAC was significantly higher in the full-term group compared to the preterm group (1.87±0.10 mmol/L vs. 0.97±0.44 mmol/L, p<0.01). The OSI values of the preterm group were significantly higher than the full-term group. A negative and significant correlation was found between gestational age and amniotic fluid 8-OH-2dG levels in the full-term pregnancy group (r=-0.78, p<0.01). A negative and significant correlation was observed between TAC and amniotic fluid 8-OH-2dG levels in the full-term group (r=-0.60, p<0.02). A positive and significant correlation was also detected between TOC, OSI and amniotic fluid 8-OH-2dG levels in the full-term group. There was a negative but insignificant correlation between fetal weight and amniotic fluid 8-OH-2dG levels. The correlation analysis results of the preterm pregnancy group were similar to the full-term group. Increased reactive oxygen derivatives in preterm birth increase amniotic fluid levels of DNA degradation product 8-OH2dG and may lead to premature rupture of fetal membranes. This is the first clinical study investigating 8-OH-2dG levels in amniotic fluid of preterm birth.