IGFBP7 mediates oxLDL-induced human vascular endothelial cell injury by suppressing the expression of SIRT1

Endothelial cell injury plays an important role in initiating atherosclerotic lesion formation. Insulin-like growth factor binding protein 7 (IGFBP7) is known to modulate the behaviors of tumor-associated endothelial cells. This study was conducted to test whether IGFBP7 is involved in endothelial cell injury during atherosclerosis. Oxidized low-density lipoprotein (oxLDL) treatment was used to mimic atherosclerosis-related endothelial cell apoptosis and inflammation response. Small interfering RNA (siRNA) technology was employed to deplete IGFBP7 expression in human aortic endothelial cells (HAECs). HAECs were exposed to recombinant human IGFBP7 protein to evaluate the function of IGFBP7. Notably, IGFBP7 expression in HAECs was induced by oxLDL treatment. Knockdown of IGFBP7 or treatment with anti-IGFBP7 abolished oxLDL-induced apoptosis and inflammation in HAECs. Moreover, recombinant IGFBP7 (40 ng/mL but not 25 ng/ mL) promoted apoptosis and inflammation in HAECs. IGFBP7 co-localized with CD93 on the surface of HAECs. A mechanistic investigation uncovered that IGFBP7 induced endothelial cell injury through interaction with CD93 and reduction of SIRT1 expression via an autocrine manner. Overexpression of SIRT1 rescued IGFBP7-induced phenotype in HAECs. Taken together, IGFBP7 is induced by oxLDL and mediates oxLDL-induced endothelial cell apoptosis and inflammation, likely through downregulation of SIRT1. These observations support a rationale to prevent atherosclerosis by targeting IGFBP7 activity.