The Effect of Increased Selenium on Cell Health in Placental Trophoblast Cells

Abstract

Coal mining accelerates the release of selenium (Se) into the environment, where it bioaccumulates through the food chain and increases human exposure. Se is an essential trace element, but Se deficiency and Se excess have been associated with adverse pregnancy outcomes linked to placental dysfunction. Cell culture studies show that Se can increase reactive oxygen species (ROS) in placental trophoblast cells, potentially impairing cell health. This study explored the effects of Se exposure on placental trophoblast cell health and tested the hypothesis that NaSe exposure induces ROS accumulation, leading to reduced placental cell health. This thesis also investigated if ferroptosis, cellular senescence, or apoptosis are induced following exposure to Se and the mechanisms underlying these effects. HTR-8/SVneo cells, a placental trophoblast cell line, were treated with environmentally relevant sodium selenite (NaSe) concentrations (0.1, 0.2, 0.5, 1, 2 µM) for 24 hours. ROS production and mRNA expression of genes related to ferroptosis, senescence, and apoptosis were measured. I evaluated key components of ferroptosis (cellular iron content, the accumulation of malondialdehyde, and LDH release), senescence (ß-galactosidase staining), and apoptosis (TUNEL-based assay) using commercially available kits. To explore mediators underlying apoptosis, I assessed ER stress using an inhibitor experiment, followed by assessing the effect of ER stress on angiogenesis. NaSe treatment at the highest concentration (2 µM) caused a significant increase in ROS production alongside altered mRNA expression of key markers indicative of ferroptosis, senescence, and apoptosis. However, NaSe treatment did not affect functional measures of ferroptosis or cellular senescence. 2 µM of NaSe increased apoptosis, an effect which appeared to be related to increased gene expression of ER stress markers ATF4 and CHOP. To confirm NaSe could directly increase ER stress, cells were co-treated with 4-phenylbutyric acid (4PBA), an ER stress inhibitor. 4PBA blocked the NaSe-induced increase of ATF4 and CHOP. Despite the increase in ER stress, NaSe treatment did not affect angiogenesis. Given the rise in anthropogenic activities is increasing our exposure to Se, further research is needed to understand the mechanisms by which increased Se impacts mammalian reproductive function.