Different responses to homocysteine in primary endothelial cells and an immortalized endothelial cell line

Endothelial cells play a key role in maintaining vascular homeostasis, and disruption of their function contributes to endothelial dysfunction. The underlying mechanisms have been studied using primary endothelial cells (HUVEC) and hybrid endothelial cell line EA.hy926, and their responses to disrupting agents should be similar. In this study, we investigated the effects of elevated homocysteine (HCY) concentrations, a risk factor for endothelial dysfunction development, in both cell types. Using multiple approaches, the inhibitory effect of HCY was consistently observed in HUVEC. In contrast, EA.hy926 cells exhibited increased proliferation and viability at lower doses, whereas the highest dose (10 mM) was inhibitory to both cell types. The bimodal and stimulatory effect of HCY in EA.hy926 cells was abolished by aminooxyacetic acid, a dominant inhibitor of cystathionine beta-synthase suggesting that decreased HCY levels and the formation of glutathione and hydrogen sulfide protected these cells. No such effect was found in HUVEC. The PI3K/Akt and MAPK/ERK signaling pathways were differentially activated in both models, suggesting their differing contributions to the HCY response. These findings reveal the cell-specific mechanisms of HCY-induced endothelial disruption, contributing to a better understanding of the mechanisms underlying endothelial dysfunction.