Nonylphenol exposure is associated with oxidative and nitrative stress in pregnant women

ABSTRACT

Animal studies have shown that exposure to nonylphenol (NP) increases oxidative/nitrative stress, but whether it does so in humans is unknown. This study examines prenatal exposure to NP and its effects on oxidatively/nitratively damaged DNA, lipid peroxidation, and the activities of antioxidants. A total of 146 urine and blood specimens were collected during gestational weeks 27–38 and hospital admission for delivery, respectively. Urinary NP was analyzed by high-performance liquid chromatography (HPLC). Urinary biomarkers of oxidatively/nitratively damaged DNA and lipid peroxidation, including 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG), 8-nitroguanine (8-NO₂Gua), 8-iso-prostaglandin F_2α (8-isoPF_2α) and 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA), were simultaneously analyzed using isotope-dilution liquid-chromatography/electron spray ionization tandem mass spectrometry. The activities of maternal plasma superoxide dismutase and glutathione peroxidase were analyzed by enzyme-linked immunosorbent assay. Urinary NP level was significantly associated with 8-oxodG and 8-NO₂Gua levels in late pregnancy, suggesting that NP may enhance oxidatively and nitratively damaged DNA. The adjusted odds ratios for high 8-oxodG level exhibited a significantly dose–response relationship with NP levels, stratified into four quartiles. 8-oxodG appears to be a more sensitive and effective biomarker of NP exposure than 8-NO₂Gua. These relationships suggest NP may play a role in the pregnancy complications.

KEYWORDS:

• Lipid peroxidation
• 8-nitroguanine (8-NO2Gua)
• nonylphenol
• oxidative/nitrative stress
• 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG)

Acknowledgements

The authors would like to thank Shu-Ting Chen and Hsin-Hao Chiu for analyzing biomarkers of oxidative stress and NP; Hsiou-Chi Wu at the department of Pediatrics, Taipei City Hospital, Heping Fuyou Branch, for recruiting subjects. Ted Knoy is appreciated for his editorial assistance.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. The authors would also like to thank the National Science Council of the Republic of China, Taiwan (Contracts Nos. NSC 99-2314-B-010-018-MY3, NSC 102-2314-B-010-031-MY3) and Taipei City Government Department of Health (Contract No. 102TPECH11) for financially supporting this research.