Differential activation of NF-κB in human aortic endothelial cells conditioned to specific flow environments

Endothelial cell-monocyte interaction plays an important role in atherogenesis. The expressions of some endothelial cell adhesion molecules involved in endothelial cell-monocyte interactions are regulated by transcription factor NF-κB. Because low shear stress has been known to influence endotheliaI monocyte adhesion, the differential activation of NF- κB under different flow regimens across time (0.5-24 h) was investigated. Nuclear proteins from flow-conditioned human aortic endothelial cells (HAEC) were analyzed by electrophoretic mobility shift assay using [γ-³²P]dATP- labeled NF-κB-specific oligonucleotide. Our results demonstrated that NF- κB activation was significantly elevated in HAEC exposed to prolonged (>2 h) steady low shear (2 dyn/cm²) and pulsatile low shear (2 ± 2 dyn/cm²) compared with HAEC exposed to high shear (16 dyn/cm²). In contrast, at 30 min, high shear-exposed HAEC exhibited an early, transient increase in NF-KB activity, relative to low shear-exposed cells, which reversed on continued exposure to high shear. Maximum activity in both low shear- and pulsatile low shear-conditioned HAEC was observed at 16 h compared with HAEC exposed to prolonged high shear. These results indicate that exposure of HAEC to prolonged low shear conditions is associated with significantly increased and prolonged NF-κB activity. This observation might provide a mechanism to explain the increased monocyte adhesion in atherosclerosisprone arterial sites exposed to chronic low-shear flow patterns.