Premature senescence of human endothelial cells induced by inhibition of glutaminase

Abstract

Cellular senescence is now recognized as an important mechanism of tumor suppression, and the accumulation of senescent cells may contribute to the aging of various human tissues. Alterations of the cellular energy metabolism are considered key events in tumorigenesis and are also known to play an important role for aging processes in lower eukaryotic model systems. In this study, we addressed senescence-associated changes in the energy metabolism of human endothelial cells, using the HUVEC model of in vitro senescence. We observed a drastic reduction in cellular ATP levels in senescent endothelial cells. Although consumption of glucose and production of lactate significantly increased in senescent cells, no correlation was found between both metabolite conversion rates, neither in young endothelial cells nor in the senescent cells, which indicates that glycolysis is not the main energy source in HUVEC. On the other hand, glutamine consumption was increased in senescent HUVEC and inhibition of glutaminolysis by DON, a specific inhibitor of glutaminase, led to a significant reduction in the proliferative capacity of both early passage and late passage cells. Moreover, inhibition of glutaminase activity induced a senescent-like phenotype in young HUVEC within two passages. Together, the data indicate that glutaminolysis is an important energy source in endothelial cells and that alterations in this pathway play a role in endothelial cell senescence.

Protein expression dynamics during replicative senescence of endothelial cells studied by 2‐D difference in‐gel electrophoresis

“…Microscopic evaluation of the SA-b-Gal activity showed that about 40% of the cells in the priorsenescent passage were active. The amount of positively stained cells increased to 50% at the senescent state, and confirmed the accumulation of SA-b-Gal active cells during senescence as found by others [15,17,31,32]. A strong induction of cell cycle protein p21 was observed in the cells at the prior-senescent state and the senescent state (Fig.…”

“…These studies revealed that senescence can be triggered or accelerated by various stresses like telomere shortening, DNA damage, oxidative stress, glycation, or overexpression of certain oncogenes [12,[15][16][17][18][19][20][21]. It is known that the effect of senescence on cell function and the surrounding tissues is strongly cell-type-dependent [22,23].…”

Glutamine metabolism in advanced age

“…Thus, premature senescence of human endothelial cells is induced by the inhibition of glutaminase (demonstrated by the use of a glutaminase inhibitor as 6-diaso-5-oxo-L-norleucine). 140 Senescence and apoptosis act as parallel pathways by which severely damaged cells are eliminated from the body by the innate immune system. 141 Programmed cell death pathways are promising targets for interventions in aging and aging-related diseases.…”

Angiogenesis revisited – role and therapeutic potential of targeting endothelial metabolism

“…However, when oxidative stress impairs metabolic enzymes and glycolysis, glutamine-derived ATP production rapidly increases (Hinshaw and Burger, 1990). Blocking the conversion of glutamine into glutamate by GLS knockdown inhibits proliferation and induces a senescence-like state in endothelial cells (Unterluggauer et al, 2008). GATs also produce NH 3 from glutamine but, instead of being released, the NH 3 is transferred onto another molecule.…”