Fibronectin-adherent monocytes express tissue factor and tissue factor pathway inhibitor whereas endotoxin-stimulated monocytes primarily express tissue factor: physiologic and pathologic implications.
BACKGROUND
Monocytes are critical cells in initiating physiologic and/or pathologic tissue factor (TF)-induced intravascular and extravascular coagulation. Monocytes constitutively express small amounts of TF and tissue factor pathway inhibitor (TFPI). Non-adherent lipopolysaccharide (LPS)-stimulated monocytes express significant amounts of TF; however, increased expression of TFPI by these cells is controversial. Further, whether fibronectin-adherent monocytes (mimicking conditions in the extravascular space) express sufficient TFPI to inhibit TF-procoagulant activity (PCA) is unknown.


OBJECTIVE
To compare TF and TFPI expression by fibronectin-adherent and LPS-stimulated non-adherent monocytes.


METHODS
Monocytes were isolated from normal peripheral blood, adhered to fibronectin or stimulated with lipopolysaccharide (LPS) under non-adherent conditions and examined for expression of TF and TFPI using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), ELISA and factor X (FX) activation.


RESULTS
Under LPS-free conditions, the fibronectin-adherent monocyte TF mRNA, antigen and activity were markedly upregulated. Notably, cell and microparticle (MP)-associated TF and alternatively spliced TF (asTF) were all upregulated. TFPI mRNA and antigen were also upregulated in the fibronectin-adherent monocytes, which significantly inhibited TF-PCA. TFPI mRNAs for both alpha and beta forms were detected. The peak in TFPI activity occurred in tandem with the peak in TF-PCA. In contrast, LPS-stimulated monocytes, which expressed cell and MP-associated TF and asTF, demonstrated only minimal expression of TFPI as determined by mRNA, antigen or inhibition of TF activity.


CONCLUSIONS
Both LPS-stimulated and fibronectin-adherent monocytes demonstrate a procoagulant phenotype by expressing TF but only fibronectin-adherent monocytes express significant amounts of TFPI to control thrombin generation and fibrin formation in the context of extravascular space.
Bajaj
M S
MS
Department of Medicine, David Geffen School of Medicine, and UCLA/Orthopedic Hospital, Los Angeles, CA 90095-1690, USA. mbajaj@mednet.ucla.edu
Ghosh
M
M
Bajaj
S P
SP
D001483:Base Sequence; D002448:Cell Adhesion; D017931:DNA Primers / Q000235:genetics; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000633:toxicity; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013925:Thromboplastin / Q000235:genetics / Q000378:metabolism*
D017931:DNA Primers; D005353:Fibronectins; D008070:Lipopolysaccharides; D008074:Lipoproteins; D012333:RNA, Messenger; C051928:lipoprotein-associated coagulation inhibitor; D013925:Thromboplastin