Inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) shift the hemostatic balance of endothelial cell surfaces in favor of prothrombotic properties by downregulating thrombomodulin (TM) and inducing tissue factor (TF) expression. We investigated the effects of retinoic acid (RA) on the prothrombotic properties of cultured umbilical vein endothelial cells exposed to TNF-alpha. The approximate 50% downregulation of TM antigen and cofactor activity induced by TNF- alpha (10 U/mL for 24 hours) was completely prevented when the cells were coincubated with both TNF-alpha and 10 mumol/L RA. In accordance with changes in cell surface TM antigen levels, the 70% decrease in TM messenger RNA (mRNA) induced by TNF-alpha was also prevented by 10 mumol/L RA. TNF-alpha induced TF activity of lysed cells (100-fold greater than untreated controls), an effect prevented when the cells were coincubated with both the TNF-alpha and 10 mumol/L RA. The 34-fold increase in TF mRNA levels induced by TNF-alpha (10 U/mL for 3 hours) was only two-fold in the presence of both TNF-alpha and RA. The effects of RA on the regulation of TM and TF expression in the cells exposed to TNF-alpha was dose-dependent from 0.01 to 10 mumol/L RA. The present results suggest that RA may affect on the mRNA level to alter TM and TF expression, effectively counteracting expression of prothrombotic properties of endothelial cells induced by inflammatory cytokines such as TNF-alpha.

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