Aj. Chu et al., ANTAGONISM BY ETHANOL OF ENDOTOXIN-INDUCED TISSUE FACTOR ACTIVATION IN RELATION TO THE DEPRESSED ENDOTOXIN BINDING TO MONOCYTE-LIKE U937 CELLS, Cell biochemistry and function, 15(4), 1997, pp. 271-281
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.