AGER1 regulates endothelial cell NADPH oxidase-dependent oxidant stress via PKC-δ: implications for vascular disease

Abstract

Advanced glycated end-product receptor 1 (AGER1) protects against vascular disease promoted by oxidants, such as advanced glycated end products (AGEs), via inhibition of reactive oxygen species (ROS). However, the specific AGEs, sources, and pathways involved remain undefined. The mechanism of cellular NADPH oxidase (NOX)-dependent ROS generation by defined AGEs, N^ε-carboxymethyl-lysine- and methylglyoxal (MG)-modified BSA, was assessed in AGER1 overexpressing (AGER1⁺ EC) or knockdown (sh-mRNA-AGER1⁺ EC) human aortic endothelial (EC) and ECV304 cells, and aortic segments from old (18 mo) C57BL6-F₂ mice, propagated on low-AGE diet (LAGE), or LAGE supplemented with MG (LAGE+MG). Wild-type EC and sh-mRNA-AGER1⁺ EC, but not AGER1⁺ EC, had high NOX p47 ^phox and gp91 ^phox activity, superoxide anions, and NF-κB p65 nuclear translocation in response to MG and N^ε-carboxymethyl-lysine. These events involved epidermal growth factor receptor-dependent PKC-δ redox-sensitive Tyr-311 and Tyr-332 phosphorylation and were suppressed in AGER1⁺ ECs and enhanced in sh-mRNA-AGER1⁺ ECs. Aortic ROS, PKC-δ Tyr-311, and Tyr-332 phosphorylation, NOX expression, and nuclear p65 in older LAGE+MG mice were significantly increased above that in age-matched LAGE mice, which had higher levels of AGER1. In conclusion, circulating AGEs induce NADPH-dependent ROS generation in vascular aging in both in vitro and in vivo models. Furthermore, AGER1 provides protection against AGE-induced ROS generation via NADPH.