E‐Selectin Is Upregulated in Proliferating Endothelial Cells In Vitro

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Abstract
Objective: E‐selectin is an endothelial cell‐specific membrane glycoprotein that participates in leukocyte adhesion and has also been suggested to function in angiogenesis. To gain further insights into E‐selectin, we analyzed E‐selectin polypeptide in proliferating versus quiescent bovine capillary endothelial cells and its expression as a function of the cell cycle.Methods: E‐selectin polypeptide was analyzed by immunoadsorption from 35Scysteine—labeled endothelial cells, by enzyme‐linked immunosorbent assay, and by fluorescence‐activated cell sorting. The distribution of endothelial cells in G0/G1, S, and G2/M phases of the cell cycle was determined using propidium iodide staining of DNA.Results: E‐selectin was upregulated in subconfluent proliferating bovine capillars endothelial cells compared to confluent quiescent cultures. The upregulation was independent of activation in that E‐selectin was further increased by treatment with tumor necrosis factor α or lipopolysaccharide. In contrast to E‐selectin, P‐selectin and platelet‐endothelial cell adhesion molecule‐1 did not appear to be regulated by the growth state of the endothelial cells. The distribution of E‐selectin‐positive cells in G0G1, S, and G2/M phases of the cell cycle differed from E‐selectin‐negative cells in that more of the E‐selectin‐positive cells were in G2 and M.Conclusions: Increased E‐selectin expression under noninflammatory conditions is correlated with cellular proliferation and G2/M phases of the cell cycle. The expression of E‐selectin in proliferating endothelial cells in vitro is consistent with the presence of E‐selectin in proliferating endothelial cells in vivo (Kräling et al. [18]).