E-SELECTIN GENE-EXPRESSION IN VASCULAR SMOOTH-MUSCLE CELLS - EVIDENCEFOR A TISSUE-SPECIFIC REPRESSOR

E-Selectin is an inducible, endothelium-specific, cell surface adhesio n molecule that mediates inflammatory responses in the vasculature. No nendothelial cell types such as cultured human aortic smooth muscle ce lls (HASMCs) lack the ability to express E-selectin. We tested the hyp othesis that HASMCs express a negative regulatory factor that inhibits E-selectin gene expression. E-Selectin mRNA and gene transcription we re not detected in HASMCs after treatment with tumor necrosis factor-c u (TNF-alpha) by Northern and nuclear runoff analyses, respectively. H owever, both E-selectin mRNA and gene transcription were dramatically induced by TNF-a in the same cells pretreated with the protein synthes is inhibitor cycloheximide. Lipopolysaccharide demonstrated similar ef fects. Furthermore, E-selectin was detected on the cell surface of HAS MCs after washing out of cycloheximide. Cycloheximide pretreatment ena bled immortalized human dermal microvascular endothelial cells that ha ve lost the ability to express E-selectin to induce both E-selectin mR NA and gene transcription in response to TNF-alpha. Induction of E-sel ectin mRNA by lipopolysaccharide or TNF-alpha in cycloheximide-treated HASMCs was inhibited by the antioxidant pyrrolidinedithiocarbamate an d the serine protease inhibitor N-n-L-tosyl-L-phenylalanine chlorometh yl ketone, suggesting that a nuclear factor-kappa B-like mechanism may play an important role in E-selectin gene expression in HASMCs. These data strongly suggest that a labile repressor protein(s) plays an imp ortant role in inhibiting E-selectin gene expression in HASMCs likely at the level of gene transcription. Except for this repressor, HASMCs and endothelial cells may share similar regulatory mechanisms for cont rolling E-selectin expression.