ANTAGONISM BY ETHANOL OF ENDOTOXIN-INDUCED TISSUE FACTOR ACTIVATION IN RELATION TO THE DEPRESSED ENDOTOXIN BINDING TO MONOCYTE-LIKE U937 CELLS

Our previous study has reported that ethanol (ETOH) partially inhibite d the endotoxin (LPS)-induced tissue factor (TF)-activation in monocyt es including blood peripheral monocytes as well as cultured leukemic U 937 and THP-l cells. The present study shows a strong correlation (r = 0.92; p < 0.01) between TF-activation and depression in LPS binding b locked by ETOH in U937 cells. The antagonism by ETOH of LPS binding wa s not due to a direct extracellular blockade, since ETOH did not affec t the affinity of fluorescein isothiocyanate (FITC)-LPS or -anti CD14 mAb on U937 cells. After U937 cells were treated with 2 per cent (v/v) ETOH for 3 h, LPS binding was however drastically inhibited as shown by immunostaining with FITC-LPS which was viewed on a confocal laser s canning microscope. The results imply that cellular events of the ETOH effect mediate this inhibition of LPS binding. Anti-CD14 mAb (UCHM-1) inhibited LPS binding in a dose-dependent fashion, revealing a compet itive specific binding to the LPS receptor. The results suggest that C D14 plays an important role in the recognition of LPS. FITC-UCHM-1 bin ding was significantly reduced in the cells pretreated with 2 per cent (v/v) ETOH for 3 h, indicating that ETOH modulates the ability to exp ress CD14. CD14 expression was upregulated by priming with LPS which w as offset by ETOH. Acetaldehyde, a possible metabolite of ETOH, was te sted with no effect on CD14 expression. Taken together, our results sh ow that ETOH downregulates the recognition of LPS, and suggest that th e inhibitory action is likely to be mediated by the depression in CD14 expression which was also accompanied by a significantly altered memb rane fluidity. Thus, the antagonism by ETOH of the binding of LPS resu lts in a depression in the LPS-induced TF-activation. (C) 1997 John Wi ley & Sons, Ltd.