Endotoxin-induced tissue factor messenger RNA in human monocytes is negatively regulated by a cyclic AMP-dependent mechanism

Abstract

Tissue factor (TF) is a transmembrane receptor that serves as the major cofactor for factor VIIa-catalyzed proteolytic activation of factors IX and X. In response to bacterial lipopolysaccharide (LPS), monocytes transcribe, synthesize, and express TF on their surface, thereby conveying to activated monocytes the ability to initiate the blood coagulation protease cascades. Agents that elevate cellular cyclic AMP (cAMP) inhibit the functional expression of TF by LPS-stimulated monocytes. In this study, we investigated the mechanism of this suppression. Northern blot analysis of total RNA from LPS-stimulated monocytes showed a concentration-dependent decrease in TF messenger RNA (mRNA) levels in response to dibutyryl-cAMP (dBt-cAMP). TF mRNA and procoagulant activity were inhibited as early as 1 hour after the addition of dBt-cAMP and the inhibition persisted through 4 hours. Suppression of specific mRNA abundance was also observed with agents, including forskolin and iso-butyl-methyl-xanthine (IBMX), that increase cAMP levels by independent mechanisms. Flow immunocytometric analysis confirmed that cell-surface TF protein levels declined in parallel with TF functional activity. The rate of decay of TF mRNA after the arrest of transcription by actinomycin D was not altered by the addition of dBt-cAMP, IBMX, or forskolin, thus excluding effects on TF mRNA stability. We conclude that elevated cAMP levels suppress TF mRNA by reducing the rate of TF gene transcription.

Insulin inhibits tissue factor expression in monocytes

“…The observation that LPS reduces cAMP thereby inducing optimal upregulation of TF expression implies that the LPS receptor signals to a G i a subunit, possibly G i a 2 . Previous studies [11,12] and our own data show that elevated cAMP levels inhibit TF expression in monocytes. cAMP induces the expression of several genes mediated by protein kinase A through the phosphorylation of the cAMP response element-binding protein (CREB) and the subsequent recruitment of the co-activator CREB-binding protein (CBP).…”

Inhibition of procoagulant activity of human monocytes by chenodeoxycholic acid: Involvement of protein kinase C

“…For all the experiments described below, the incubations were carried out for 4 hr, with 100 ng/ml LPS. These conditions are similar to those reported by others (8, [18][19][20]. To characterize the PCA expressed by LPS-stimulated monocytes, we assayed membranes obtained from sonicated cells for acceleration of coagulation of factor VII-or factor IX-deficient human plasmas in one-stage coagulation assays.…”

The significance of human monocyte thrombomodulin during membrane vesiculation and after stimulation by lipopolysaccharide

“…Furthermore, monocyte membrane vesiculation is enhanced after stimulation by LPS (Robinson et al, 1992;Satta et al, 1994), which results in increased expression of membrane-associated procoagulant activities. LPS stimulation results in the expression of tissue factor (Gregory et al, 1989;Ollivier et al, 1993) and enhanced exposure of phosphatidylserine, not only by cells but also in derived microparticles, the proportion of the latter being augmented (Robinson et al, 1992;Satta et al, 1994). In the present study the increase of phosphatidylserine exposure after LPS treatment is reflected by prothrombinase activity and its inhibition by annexin V, a potent procoagulant phospholipid antagonist (Funakoshi et al, 1987).…”