RasGRP2 Attenuates TAGE Modification of eNOS in Vascular Endothelial Cells

Toxic advanced glycation end-products (TAGEs) are glyceraldehyde (GA)-derived AGEs with strong cytotoxic effects. TAGEs are also involved in lifestyle-related diseases. Notably, modification of TAGEs by GA causes protein dysfunction. As endothelial nitric oxide synthase (eNOS) is constitutively expressed in vascular endothelial cells and is a source of nitric oxide (NO), we focused on it as a TAGE modification-targeting protein. Our laboratory has reported that Ras guanyl nucleotide-releasing protein 2 (RasGRP2) activates Rap1 and R-Ras, among other small GTPases, and suppresses apoptosis and TAGE-induced vascular hyperpermeability in vascular endothelial cells. Therefore, in this study, we investigated the effects of RasGRP2 on cell death, TAGE formation, and TAGE modification of eNOS in vascular endothelial cells following GA treatment using RasGRP2-overexpressing (R) cells and mock (M) immortalized human umbilical vein endothelial cells. GA treatment decreases the viability of both cell types in a concentration-dependent manner. In M cells, GA treatment increased the formation of TAGEs and TAGE modification of eNOS in a concentration-dependent manner, but this increase was suppressed in R cells. Additionally, co-treatment with aminoguanidine, an inhibitor of AGEs formation, suppressed cell death and TAGE modification of eNOS induced by GA. These results indicate that GA induces cell death, the formation of TAGEs, and TAGE modification of eNOS in vascular endothelial cells. Additionally, RasGRP2 is a protective factor that suppresses TAGE formation.