Tissue-specific Expression and Estrogen Receptor-mediated Regulation of Phospholipid Hydroperoxide Glutathione Peroxidase (phgpx) Gene in Mouse Embryos.

Abstract

Phospholipid hydroperoxide glutathione peroxidase (phgpx) is a membrane-associated enzyme that can reduce phospholipids, cholesterol, and thymine hydroperoxides and is detected in a variety of tissues. Recently, it has been reported that phgpx expression and enzymatic activity are up-regulated by estradiol (E2) in the female reproductive tract. We also previously demonstrated that the expression of phgpx mRNA is altered by treatment with E2 and various endocrine disrupting chemicals in male adult reproductive organs. Disruption of the phgpx in mice results in early embryonic lethality, demonstrating that phgpx is an essential material during embryogenesis. However, the expression and regulation mechanism of phgpx during embryogenesis is unclear. In this study, we demonstrated the tissue-specific expression pattern and estrogen-mediated regulation of phgpx gene in postimplantation mouse embryos. According to in situ hybridization study, phgpx mRNA was expressed in developing embryos. At embryonic days (Eds) 10.5-18.5, phgpx mRNA was highly expressed in central nervous system such as telencephalon, mesencephalon, diencephalons, and spinal cord. At Eds 17.5-18.5, phgpx mRNA was diffusely expressed in various tissues including liver, lung, kidney, stomach, and intestine. Also, pregnant ICR mice [Ed 8.5, 10.5, 12.5, and 15.5] were injected with E2 subcutaneously at dose of 10 μg/kg for 2 days and then at 24 h after final injection, real time RT-PCR analysis was carried out in the embryos. phgpx mRNA expression was significantly increased by treatment with E2, but cytosolic GPx (Gpx1) mRNA level was not significantly changed (p<0.05). Finally, to clarify the effect of E2 and an estrogen receptor (Ers)-selective ligand on the phgpx mRNA expression in developing embryos using a whole mouse embryo culture system, postimplantation mouse embryos at Ed 8.5 were exposed to various concentrations (0, 0.1, 1, 10, 100, and 1000 ng/ml) of E2, propyl pyrazole triol (PPT, an estrogen receptor alpha (Ers1)-selective ligand; 1 μg/ml), or diarylpropronitril (DPN, an estrogen receptor beta (Ers2)-selective ligand; 1 μg/ml) for 2 days and then real time RT-PCR analysis was carried out in the cultured Ed 10.5 embryos. Treatment with E2, PPT, and DPN increased both Ers1 and Ers2 mRNA levels in the cultured embryos. phgpx mRNA expression was significantly increased by treatment with E2, PPT, and DPN (p<0.05). However, Gpx1 mRNA levels by the treatment of those agents were not significantly different from the control. In addition, pre-treatment with ICI 182,780 (an Ers antagonist) completely blocked the enhancement of E2-induced phgpx mRNA expression. These results indicate that phgpx gene expression is regulated by an E2-Ers pathway in embryos. This work was supported in part by the Korea Research Foundation Grant funded by the Korean Government [MOEHRD, Basic Research Promotion Fund (KRF-2005-005-J15002 and KRF-2005-015-E00218)].