I. Suppression by compound 48/80 of bacterial endotoxin-inducible monocytic tissue factor activity: direct blockade of factor VII binding to THP-1 monocytes

• Published in: Biochimica et biophysica acta Vol. 1472; no. 1; pp. 385 - 394
• Main Authors: Chu, Arthur J, Walton, Melissa A, Seto, Anne, Fox, Melissa J, Prasad, Jai K, Wang, Zhen-Guo
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 18-10-1999
• Subjects: Animals; Blotting, Western; Cell Line; Compound 48/80; Endotoxin; Endotoxins - pharmacology; Factor VII; Factor VII - antagonists & inhibitors; Factor VII - metabolism; Fluorescent Antibody Technique; Haplorhini; Humans; Male; Monocyte; Monocytes - drug effects; Monocytes - metabolism; p-Methoxy-N-methylphenethylamine - pharmacology; Thromboplastin - antagonists & inhibitors; Tissue factor; Compound 48/80; Monocyte; Endotoxin; Tissue factor; Factor VII
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/S0304-4165(99)00144-0

Hypercoagulation with upregulated monocytic tissue factor (TF) activity often occurs under a variety of inflammatory conditions including endotoxemia. The antagonism to bacterial endotoxin (LPS) signaling often results in the depression in TF upregulation. We herein report that compound 48/80 (48/80) significantly depressed LPS-induced TF activity in human and cebus monkey peripheral blood monocytes. Employing a model monocyte-like cell line (THP-1), we explored the regulatory mechanism to identify the inhibitory site(s) of 48/80. We determine whether the inhibition results from the blockade of LPS signaling. 48/80 dose-dependently inhibited LPS-induced TF activity. Chase of LPS-challenged cells with 48/80 also significantly offset TF upregulation. In immunofluorescent approaches, FACScan analysis revealed that 48/80 had no effect on either LPS recognition or the expression of its receptors (CD14 and CD11b). Moreover, LPS-induced TF expression as well as synthesis remained unaffected in the presence of 48/80. Consistent with the independence of LPS action, 48/80 was also able to inhibit TF activity induced by A23187, ionomycin, or Quin-2 AM. Interestingly, 48/80 significantly decreased the FVII binding to either resting or LPS-challenged cells. In conclusion, our results elucidate that the inhibitory action of 48/80 was independent of LPS signaling including recognition, receptor expression, and the induced TF expression/synthesis. However, 48/80 was able to directly block FVII binding to monocytic TF, thereby resulting in such antagonism to LPS-induced TF-initiated extrinsic coagulation.