Abstract 13325: Apoptogenic Protein is Involved in Endothelial Senescence Induced by High Glucose

Abstract

Background: The Apoptogenic protein (Apop) is a novel mitochondrial protein originally identified in the atherosclerotic smooth muscle cells cultured from thoracic aortas of ApoE-deficient mice. The production of Apop using an expression vector induces death of smooth muscle cells in culture, and the inhibition of the Apop gene using siRNA prevents the reduction of cell viability induced by death inducing molecules. However, the physiological functions of Apop and its implication in diseases remain to be elucidated. Herein, we show that Apop is involved in the mechanism of high glucose-induced ROS production and senescence in endothelial cells. Methods and Results: Apop gene siRNA was introduced into human umbilical vein endothelial cells (HUVECs) using cationic lipid reagent. High glucose induced ROS production in HUVECs. Apop gene inhibition by siRNA also induced ROS production from these cells; however, HUVECs cultured in the presence of high glucose did not produce higher levels of ROS after the introduction of Apop siRNA, suggesting that high glucose and Apop inhibition may induce ROS generation in a similar way. Cells cultured in the presence of high glucose produced higher levels of ATP than in normal glucose. As expected, Apop inhibition increased ATP production of HUVECs to a similar extent as did high glucose. Morphologically, mitochondrial fragmentation, which is considered to contribute to ROS overproduction because of high glucose, was observed in HUVECs by Apop inhibition, similar to as in high glucose treated cells. As in high glucose cells, Apop gene inhibition induced senescence of HUVEC as assessed by senescence-associated b-galactosidase expression. Moreover, the expression of endothelial nitric oxide synthase of HUVECs was reduced by the inhibition of Apop. Conclusion: These results suggest that the Apop gene is implicated in mitochondrial ROS generation enhanced by glucose, and in endothelial senescence, which play important roles in the development of atherosclerosis; therefore, Apop could be a novel therapeutic target for the prevention of atherosclerosis in diabetes mellitus patients.