Endothelial cells (ECs) apoptosis induced by oxidizedlow-density lipoprotein (ox-LDL) is thought to play a criticalrole in atherosclerosis. MicroRNAs (miRNAs) are a class ofnoncoding RNAs that posttranscriptionally regulate the expressionof genes involved in diverse cell functions, includingdifferentiation, growth, proliferation, and apoptosis. MiRNAlet-7 family is known to be involved in the regulation of cellapoptosis. However, the function of let-7 in ox-LDL inducedECs apoptosis and atherosclerosis is still unknown. Here, weshow that let-7c expression was markedly up-regulated inox-LDL induced apoptotic human umbilical cord veinendothelial cells (HUVECs). Let-7c over-expression enhancedapoptosis in ECs whereas inhibition of let-7c could partlyalleviate apoptotic cell death mediated by ox-LDL. Searchingfor how let-7c affected apoptosis, we discovered that antiapoptoticprotein Bcl-xl was a direct target of let-7c in ECs. Ourdata suggest that let-7c contributes to endothelial apoptosisthrough suppression of Bcl-xl.