Aj. Chu et Jk. Prasad, ANTAGONISM BY IL-4 AND IL-10 OF ENDOTOXIN-INDUCED TISSUE FACTOR ACTIVATION IN MONOCYTIC THP-1 CELLS - ACTIVATING ROLE OF CD14 LIGATION, The Journal of surgical research (Print), 80(1), 1998, pp. 80-87
Background. Monocytic tissue factor (TF), initiating the extrinsic blo
od coagulation pathway, is often upregulated under septic or inflammat
ory conditions. The complex activating mechanism remains largely uncle
ar and no effective strategy has been firmly established. In this stud
y, we? used a model monocytic cell line (human leukemic THP-1 promonoc
ytes) to address (1) the nature of TF activation in response to bacter
ial endotoxin and (2) the application of antiinflammatory cytokines in
relieving monocytic hypercoagulation. Results. TF in THP-1 cells was
substantially activated by exposure to bacterial endotoxin (LPS; 5 mu
g/ml) for 6 h. Human recombinant IL-4 (500 ng/ml) and IL-10 (500 ng/ml
) inhibited TF activation induced by LPS. To determine if these cytoki
nes depressed LPS recognition resulting in such inhibition, we employe
d an anti-CD14 mAb (UCHM-1; Sigma Chemical) to address the role of CD1
4 in LPS transmembrane signaling. LPS-induced TF activation was depres
sed by 35% upon inclusion of the anti-CD14 mAb (1:10 dilution). This a
ntibody alone mimicked TF activation which accounted for 35% of the LP
S-induced TF activation, suggesting the activating role of CD14 ligati
on. In addition, the anti-CD14 mAb elicited the production of nitric o
xide (NO) which was found to be independent of TF activation. NO produ
ction could serve as an independent index for monitoring LPS recogniti
on. IL-4 depressed the anti-CD14 mAb-induced TF activation as well as
NO elicitation, indicating the blockade of CD14 ligation. In contrast,
IL-10 showed differential inhibitory activities. TF activation induce
d by either LPS or anti-CD14 mAb was inhibited by IL-10 which did not
show any inhibition on NO elicitation under these conditions. In a sep
arate approach, neither IL-4 nor IL-10 inhibited phorbol ester-induced
NO elicitation, More direct evidence came from an epifluorescent demo
nstration showing that IL-4 blocked binding of FITC-conjugated LPS and
anti-CD14 mAb to THP-1 cells. Conclusions. Taken together, the result
s suggest that LPS action in relation to TF activation consists of CD1
4-independent and -dependent signaling including CD14 ligation. We als
o showed that antiinflammatory cytokines (IL-4 and -10) significantly
depressed TF activation. IL-4 antagonized CD14-dependent LPS recogniti
on leading to the depression in TF activation. (C) 1998 Academic Press
.