|Greene, J -|
|Feugang, J -|
|Pfeiffer, K -|
|Bowers, D -|
|Ryan, P -|
Submitted to: Reproductive Biology and Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 2013
Publication Date: February 26, 2013
Citation: Greene, J.M., Feugang, J.M., Pfeiffer, K.E., Bowers, D., Ryan, P.L. 2013. L-arginine enhances cell proliferation and reduces apoptosis in human endometrial RL95-2 cells. Reproductive Biology and Endocrinology. 11:15-26. Interpretive Summary: L-arginine, a constituent of proteins, is an amino acid that has a multitude of physiological functions in mammalian systems. When fed to mice, L-arginine increases the number of offspring that are born and increases the number of sites in the uterus on to which the placenta attaches, which indicates a possible functional role for L-arginine in the uterus. This study evaluated the effect that L-arginine has on human endometrial cells, specifically monitoring its effect on cell proliferation and cell death. L-arginine increased endometrial cell proliferation; in other words, endometrial cells exposed to L-arginine multiplied faster than cells not exposed to L-arginine. In addition, the growth enhancing effect of L-arginine was inhibited when the metabolism of L-arginine was prevented, indicating that L-arginine metabolites are responsible for this effect. When evaluating cell death, L-arginine reduced the incidence of cell death in endometrial cells and the molecular mechanisms regarding this effect were elucidated. In summary, L-arginine stimulated endometrial cell growth while decreasing cell death. This data indicates a possible beneficial effect of dietary L-arginine supplementation on endometrial growth, an important aspect of the endometrium during embryo implantation.
Technical Abstract: L-arginine is considered to be one of the most versatile amino acids due to the fact that it serves as a precursor for many important molecules in cellular physiology. When supplemented in the diet, L-arginine can increase the number of implantation sites in mice and rats, suggesting an effect at the level of the endometrium. To this end, this study determined the effect that L-arginine has on apoptosis and cell proliferation in human endometrial RL95-2 cells. L-arginine at physiological (200 micromol/L) and supra-physiological (800 micromol/L) concentrations increased cell proliferation at days 2 and 4 post-treatment with a dose-dependent effect being observed on day 2. Additionally, inhibition of nitric oxide (NO) synthase and arginase, which are responsible for the conversion of L-arginine to NO and polyamines, respectively, reduced the proliferative effect of L-arginine. L-arginine also decreased the proportion of cells with TUNEL positive nuclei and increased the ratio of cells with healthy mitochondria compared to cells with a disrupted mitochondrial membrane potential, indicating that L-arginine prevents mitochondrial mediated apoptosis in endometrial RL95-2 cells. Furthermore, exposure to L-arginine did not affect total BAD protein expression; however, L-arginine increased the abundance of phosphorylated BAD protein. In summary, L-arginine added to the culture media at physiological (200 micromol/L) and supraphysiological concentrations (800 micromol/L) enhanced endometrial RL95-2 cell proliferation through mechanisms mediated by NO and polyamine biosynthesis. In addition, L-arginine reduced endometrial RL95-2 mitochondrial mediated apoptosis through increased phosphorylation of BAD protein.