Antioxidant enzyme expression, lipid peroxidation, and protein oxidation in human myometrium with parturition

Oxygen levels fluctuate considerably during human labor leading to hypoxia and reoxygenation of the uteroplacental unit and in some cases may compromise the progression of labor. Our aim was to assess the possible contribution of oxidative stress to the onset of labor. Thiobarbituric acid was used as a marker of lipid peroxidation along with Western blotting using anti-dinitrophenylhydrazine (DNPH) to assess protein carbonylation in myometrial samples obtained before and after the onset of term and preterm labor. Levels of key antioxidative enzymes were also compared. Higher levels of lipid peroxidation were observed in myometrial samples obtained during term or preterm labor. Reduced levels of glutathione peroxidase (GSHPx) were also encountered in these 2 groups. Conversely, protein carbonyl content was higher in laboring term and preterm myometrial samples. Levels of catalase (CAT) and superoxide dismutase (SOD) were unaltered across all 4 groups. Lipids in the laboring myometrium are susceptible to oxidative injury possibly due to diminished protection as a result of lower GSHPx activity. The reason for enhanced protein carbonylation suggests differential mechanisms governing protein turnover in the pregnant compared with the parturient uterus. Localized, oxidant damage of human myometrium may be a causal factor in difficult deliveries.