Identification of apoptosis-inducing factor in human coronary artery endothelial cells

Apoptosis has been observed in vascular tissues in response to pro-inflammatory and pro-atherosclerotic stimuli, such as oxidized low density lipoproteins (ox-LDL), angiotensin II (Ang II), and tumor necrosis factor-alpha (TNF-alpha). Apoptosis is believed to be mediated via caspase-dependent pathway. Recently, a 57 kDa molecule, apoptosis-inducing factor (AIF), has been described as a basis for cell injury via a caspase-independent pathway. This study was designed to identify the presence of AIF and the regulation of its gene expression in human coronary artery endothelial cells (HCAECs). Reverse transcription-polymerase chain reaction (RTPCR) and Western blot were used to determine AIF mRNA and protein expression. Cultured HCAECs were treated with ox-LDL (10-40 mug/ml), angiotensin II (10(-9)-10(-6) M), or TNF-alpha (0.1-10 ng/ml). AlF was barely detectable in unstimulated HCAECs; however, treatment with ox-LDL, but not with Ang II or TNF-alpha, significantly increased the expression of AIF in a concentration- and time-dependent manner. DNA sequencing analysis substantiated the existence of AlF in the HCAECs. Treatment of cells with the caspase inhibitor with Z-VAD-finik did not change ox-LDL-mediated AlF protein expression. Ox-LDL-mediated upregulation of AIF expression was inhibited by actinomycin D, suggesting transcriptional regulation. Further, upon treatment of cells with ox-LDL AIF translocated from mitochondria to the nucleus, as determined by immunocytochemistry. These data suggest that AlF is expressed in HCAECs and is upregulated by ox-LDL. (C) 2002 Elsevier Science (USA). All rights reserved.