Effects of Glutamine Deprivation and Serum Starvation on the Growth of Human Umbilical Vein Endothelial Cells

Abstract

Glutamine and serum are essential for cell survival and proliferation in vitro, yet the signaling pathways that sense glutamine and serum levels in endothelial cells remain uninvestigated. In this study, we examined the effects of glutamine deprivation and serum starvation on the fate of endothelial cells using a human umbilical vein endothelial cell (HUVEC) model. Our data indicated that glutamine deprivation and serum starvation trigger a progressive reduction in cell viability through apoptosis induction in HUVECs as determined by DAPI staining and flow cytometry analysis. Although the apoptotic effects were more predominant in the glutamine deprivation condition, both apoptotic actions were associated with an increase in the Bax/Bcl-2 (or Bcl-xL) ratio, down-regulation of the inhibitor of apoptosis protein (IAP) family proteins, activation of caspase activities, and concomitant degradation of poly (ADP-ribose) polymerases. Moreover, down-regulation of the expression of Bid or up-regulation of truncated Bid (tBid) were observed in cells grown under the same conditions, indicating that glutamine deprivation and serum starvation induce the apoptosis of HUVECs through a signaling cascade involving death-receptor-mediated extrinsic pathways, as well as mitochondria-mediated intrinsic caspase pathways. However, apoptosis was not induced in cells grown in glutamine-and serum-free media when compared with cells exposed to glutamine deprivation or serum starvation alone. Taken together, our data indicate that glutamine deprivation and serum starvation suppress cell viability without apoptosis induction in HUVECs.Key words : HUVECs, glutamine deprivation, serum starvation, apoptosis *Corresponding author *Tel：+82-51-850-7413, Fax：+82-51-853-4036 *E-mail : choiyh@deu.ac.kr This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Linking In Vitro Models of Endothelial Dysfunction with Cell Senescence

“…For example, Jeong et al showed how glutamine deprivation and/or reduction of serum percentage induced a stress response in HUVECs denoted by increasing levels of active caspases, and a resultant decrease in cell viability as measured by metabolic parameters. However, their model did not evaluate functional capacities or senescence of HUVECs [25]. In contrast, in our model, in which cell viability was unaffected, we found that migratory and angiogenic properties of deprived HUVECs, as well as SIRT1 (an anti-aging protein) expression decreased after 96 h of starvation, and β-galactosidase activity, a marker of senescence, increased after 72 h and further by 96 h. Our results, in agreement with a previous study by Potente et al [13], suggest that the reduction in SIRT1 levels could be the main driver reducing the functional capacities of endothelial cells through modification of SIRT1-mediated transcription factors activities.…”