Reduced expression of flice-inhibitory protein (FLIP) and NFκB is associated with death receptor-induced cell death in human aortic endothelial cells (HAECs)

We investigated the effects of TNF receptor 1 (TNFR1) and 2 (TNFR2) modulation on the death of human aortic endothelial cells (HAECs) resistant to TNF-alpha -induced cell death. Alteration of the transcription of anti-apoptotic proteins, including inhibitor of apoptosis protein 1, 2 (cIAP1, 2), TNF receptor-associated factor 1 (TRAF1), nuclear factor kappa BI protein (NF kappa B1), and FLICE-inhibitory protein (FLIP) was assessed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). TNF-ct (200 ng/ml) or actinomycin D (ActD) (5 ng/ml) did not kill cells, while 5 ng/ml of TNF-alpha and 5 ng/ml of ActD increased expression of Fas (CD95) and FasL (CD95L), and 45% of cells died. TNFR2 blockade suppressed NF kappa B1 and FLIP expression and increased cell death. TNFR1 blockade enhanced FLIP expression and decreased cell death. Cells insensitive to TNF-alpha may respond to TNF-alpha through TNFR that induces transcription of NF kappa B1 and FLIP. Down-regulation of these proteins may facilitate death of cells insensitive to TNF-alpha -induced cell death. (C) 2001 Academic Press.