290 - Optimization of selenium in cell culture media to maximize selenoenzyme activity

Abstract

Selenium plays an essential role in redox biology and redox toxicology. It is found at the active site of redox enzymes such as, glutathione peroxidases (GPx) and thioredoxin reductases (TrxR). Cell culture media is typically deficient in selenium; this deficiency could limit seleno-enzyme expression and activity, compromising the translation of data from in vitro experiments to in vivo settings. The level of selenium in cell culture media should always be a consideration. However, any supplementation must be within a range to overcome deficiency and yet not induce toxicity. The optimal level of supplementation has not been well characterized. To determine optimal levels of Se-supplementation of cell culture media we introduced varying levels of sodium selenite (Na2SeO3) or seleno-L-methionine (SLM). We established, that the window to avoid potential toxicity can be widened by using SLM instead of selenite. We assessed the expression and activity of GPx1 and GPx4 to determine the level of optimal selenium supplementation for a variety of cells. Supplementing cell culture media containing 10% FBS with 100 – 300 nM SLM, we were able to maximize GPx1 and GPx4 enzyme expression and activity. Interestingly, data from a clinical trial at The University of Iowa indicates that supplementing Se in humans does not increase GPx1 activity in blood. Subjects received ~30x the RDA (55 mg d-1) of Se as SLM daily for more than 7 mo. The level of total Se in blood increased about 50-fold. However, the activity of GPx1 in blood remained constant. Our cell culture data show the importance of supplementing cell culture media with Se to insure full activity of these enzymes. This simple maneuver will increase the rigor and reproducibility of cell culture experiments and may lead to better translation of data addressing basic redox biology.