Oxidative stress and inflammation in retained placenta: a pilot study of protein and gene expression of GPX1 and NFκB

BACKGROUND: Retained placenta is associated with severe postpartum hemorrhage. Its etiology is unknown and its biochemistry has not been studied. We aimed to assess whether levels of the antioxidative enzyme Glutathione Peroxidase 1 (GPX1) and the transcription factor Nuclear Factor κβ (NFκβ), as markers of oxidative stress and inflammation, were affected in retained placentas compared to spontaneously released placentas from otherwise normal full term pregnancies. METHODS: In a pilot study we assessed concentrations of GPX1 by ELISA and gene (mRNA) expression of GPX1, NFκβ and its inhibitor Iκβα, by quantitative real-time-PCR in periumbilical and peripheral samples from retained (n = 29) and non-retained (n = 31) placental tissue. RESULTS: Median periumbilical GPX1 concentrations were 13.32 ng/ml in retained placentas and 17.96 ng/ml in non-retained placentas (p = 0.22), peripheral concentrations were 13.27 ng/ml and 19.09 ng/ml (p = 0.08). Retained placental tissue was more likely to have a low GPX1 protein concentration (OR 3.82, p = 0.02 for periumbilical and OR 3.95, p = 0.02 for peripheral samples). Median periumbilical GPX1 gene expressions were 1.13 for retained placentas and 0.88 for non-retained placentas (p = 0.08), peripheral expression was 1.32 and 1.18 (p = 0.46). Gene expressions of NFκβ and Iκβα were not significantly different between retained and non-retained placental tissue. CONCLUSIONS: Women with retained placenta were more likely to have a low level of GPX1 protein concentration in placental tissue compared to women without retained placenta and retained placental tissue showed a tendency of lower median concentrations of GPX1 protein expression. This may indicate decreased antioxidative capacity as a component in this disorder but requires a larger sample to corroborate results.