OBJECTIVE: Glucagon-like peptide 1 (GLP-1), one of the incretin hormones, has been reported to increase positive inotropic activity in cardiac myocytes and protect against myocardial injury. However, the effects upon endothelial cells and the mechanisms involved are not fully understood. We assessed the hypothesis that GLP-1 has protective effects against inflammation and oxidative stress on human endothelial cells. METHODS AND RESULTS: The effects of the GLP-1 analog liraglutide upon TNF-α-induced injury of the human umbilical vein endothelial cells (HUVECs) were evaluated. First, ROS induced by TNF-α was measured by staining with CM-H(2)DCFDA. Intracellular ROS production of HUVECs was significantly decreased in a dose-dependent manner until 30 nM while liraglutide inhibited the induction of gp91(phox) and p22(phox), subunit of NADPH oxidase, by TNF-α. In addition, protein levels of SOD-2, catalase and GPx were significantly increased by liraglutide. Second, rapid translocation of PKC-α into the membrane following TNF-α was evident. Liraglutide significantly inhibited this very rapid TNF-α-induced translocation of PKC-α into membrane at 2.5 min. Third, liraglutide significantly inhibited NF-κB activation and upregulated I-κB family while phosphorylation of IKK-α/β, which is upstream of NF-κB signaling, was also downregulated after 15 min of TNF-α treatment. Finally, liraglutide inhibited apoptosis of HUVEC and expression of Pentraxin-3 induced by TNF-α. CONCLUSION: Liraglutide exerts marked anti-oxidative and anti-inflammatory effects on endothelial cells with inhibition of PKC-α, NADPH oxidase, NF-κB signaling and upregulation of protective anti-oxidative enzymes.
OBJECTIVE:Glucagon-like peptide 1 (GLP-1), one of the incretin hormones, has been reported to increase positive inotropic activity in cardiac myocytes and protect against myocardial injury. However, the effects upon endothelial cells and the mechanisms involved are not fully understood. We assessed the hypothesis that GLP-1 has protective effects against inflammation and oxidative stress on human endothelial cells. METHODS AND RESULTS: The effects of the GLP-1 analog liraglutide upon TNF-α-induced injury of the human umbilical vein endothelial cells (HUVECs) were evaluated. First, ROS induced by TNF-α was measured by staining with CM-H(2)DCFDA. Intracellular ROS production of HUVECs was significantly decreased in a dose-dependent manner until 30 nM while liraglutide inhibited the induction of gp91(phox) and p22(phox), subunit of NADPH oxidase, by TNF-α. In addition, protein levels of SOD-2, catalase and GPx were significantly increased by liraglutide. Second, rapid translocation of PKC-α into the membrane following TNF-α was evident. Liraglutide significantly inhibited this very rapid TNF-α-induced translocation of PKC-α into membrane at 2.5 min. Third, liraglutide significantly inhibited NF-κB activation and upregulated I-κB family while phosphorylation of IKK-α/β, which is upstream of NF-κB signaling, was also downregulated after 15 min of TNF-α treatment. Finally, liraglutide inhibited apoptosis of HUVEC and expression of Pentraxin-3 induced by TNF-α. CONCLUSION: Liraglutide exerts marked anti-oxidative and anti-inflammatory effects on endothelial cells with inhibition of PKC-α, NADPH oxidase, NF-κB signaling and upregulation of protective anti-oxidative enzymes.