Blockade by polyunsaturated n-3 fatty acids of endotoxin-induced monocytictissue factor activation is mediated by the depressed receptor expression in THP-1 cells

Background. Monocytic hypercoagulation often occurs in inflammatory conditi ons. We have previously reported that polyunsaturated n-3 fatty acids (n-3 FA) including eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) prevent the activation of monocytic tissue factor (TF) induced by bacterial endotoxin lipopolysaccharide (LPS)I in cell cultures and animals. Hypothesis. We herein explore the mode of inhibitory action of n-3 FA to de termine if LPS transmembrane signaling is blocked, exerting such antagonism . Results. Exposure of human leukemia monocytic THP-1 cells to bacterial endo toxin (Escherichia coli 0111:B04, 1.5 mu g/ml) for 6 h significantly activa ted TF activity and the production of nitric oxide (NO), tumor necrosis fac tor LY (TNF-alpha), and interleukin (IL)-1 beta in conditioned medium. Pret reatment with n-3 FA, 20:5 and 22:6 at 10 mu M, resulted in time-dependent suppression of not only TF activation but also the elicitation of NO, TNF-a lpha, and IL-1 beta, These LPS responses were substantially depressed by mo re than 50% after a 72-h pretreatment. FACScan analysis showed that n-3 FA readily prevented fluorescein isothiocyanate (FITC)conjugated LPS from bind ing to THP-1 cells by approximately 70%. The observation that anti-CD14 mAb diminished FITC-LPS binding in a dose-dependent fashion has revealed CD14 dependency in LPS recognition. LPS upregulated CD14 expression, which was s ignificantly arrested by n-3 FA, Similarly, the upregulation of the express ion of CD11b, another proposed LPS receptor, was also minimally but signifi cantly depressed by n-3 FA. Conclusion. The present study demonstrates that n-3 FA are able to block LP S transmembrane signaling via suppression of the receptor upregulation, med iating a variety of significant antagonisms against LPS action. (C) 1999 Ac ademic Press.