Nuclear translocation of p65 NF-κB is sufficient for VCAM-1, but not ICAM-1, expression in TNF-stimulated smooth muscle cells: Differential requirement for PARP-1 expression and interaction

Abstract

Although nuclear translocation of NF-κB and subsequent binding to promoters of ICAM-1 and VCAM-1 have been shown to be decisive for their expression, a number of discrepancies in the expression patterns of these adhesion molecules have been reported in both cell culture systems and disease settings, including atherosclerosis, asthma, and autoimmune diseases. Here we show that while p65 NF-κB nuclear translocation in TNF-treated smooth muscle cells (SMCs) was sufficient for the expression of VCAM-1, expression of ICAM-1 showed a critical requirement for PARP-1. I-κBα phosphorylation and subsequent degradation were virtually identical in both TNF-treated wild-type and PARP-1 −/− SMCs. VCAM-1 expression in TNF-treated PARP-1 −/− SMCs was completely inhibited by the NF-κB inhibitor, pyrrolidine dithiocarbamate, confirming that VCAM-1 expression was indeed NF-κB-dependent. The expression of both VCAM-1 and ICAM-1 was associated with a transient interaction between PARP-1 and p65 NF-κB when examined in the fibroblastic cell line, COS-7, and in the airway epithelial cell line, A549. Such interactions were confirmed using florescence resonance energy transfer analysis. Protein acetylation activity, mediated by p300/CBP, was required for both VCAM-1 and ICAM-1 expression in TNF-treated SMCs; however, the interaction of PARP-1 with p300/CBP was dispensable for VCAM-1 expression. These findings indicate that p65 NF-κB nuclear translocation may be sufficient for certain genes (e.g., VCAM-1) while insufficient for others (e.g., ICAM-1), thus providing a novel insight into the role of NF-κB in driving target gene expression. Furthermore, the data suggest a differential requirement for PARP-1 expression in inflammatory processes.