Analysis and quantitation of NF-kappaB nuclear translocation in tumor necrosis factor alpha (TNF-alpha) activated vascular endothelial cells.

Nuclear factor-kappa B (NF-kappaB) is a heterodimeric transcription factor typically composed of p50 and p65 subunits and is a pleiotropic regulator of various inflammatory and immune responses. In quiescent cells, p50/p65 dimers are sequestered in the cytoplasm bound to its inhibitors, the I-kappaBs, which prevent entry into the nucleus. Following cellular stimulation, the I-kappaBs are rapidly degraded, activating NF-kappaB. The active form of NF-kappaB rapidly translocates into the nucleus, binding to consensus sequences in the promoter/enhancer region of various genes, promoting their transcription. In human vascular endothelial cells activated with tumor necrosis factor-alpha, the activation and translocation of NF-kappaB is rapid, reaching maximal nuclear localization by 30 min. In this study, the appearance of NF-kappaB (p65 subunit, p65-NF-kappaB) in the nucleus visualized by immunofluorescence and quantified by morphometric image analysis (integrated optical density, IOD) is compared to the appearance of activated p65-NF-kappaB protein in the nucleus determined biochemically. The appearance of p65-NF-kappaB in the nucleus measured by fluorescence image analysis and biochemically express a linear correlation (R2 = 0.9477). These data suggest that localization and relative protein concentrations of NF-kappaB can be reliably determined from IOD measurements of the immunofluorescent labeled protein.