Caffeine induces endothelial tissue factor expression via phosphatidylinositol 3-kinase inhibition

Abstract

SummaryTissue factor (TF) is the key activator of coagulation and is involved in acute coronary syndromes. Caffeine is often reported to increase cardiovascular risk; however, its effect on cardiovascular morbidity and mortality is controversial. Hence, this study was designed to investigate the impact of caffeine on endothelial TF expression in vitro. Caffeine concentration-dependently enhanced TF protein expression and surface activity in human endothelial cells stimulated by tumour necrosis factor (TNF)-α or thrombin. Caffeine inhibited phosphatidylinositol 3-kinase (PI3K) activity and this effect was comparable to that of the known PI3K inhibitor LY294002. Consistently, treatment of endothelial cells with LY294002 enhanced TNF-α induced TF expression to a similar extent as caffeine, and adenoviral expression of the active PI3K mutant (p110) reversed the effect of both caffeine and LY294002 on TF expression. Caffeine and LY294002 increased DNA binding capacity of the transcription factor nuclear factor κB, whereas the activation pattern of mitogen-activated protein kinases (MAPK) remained unaltered. Luciferase reporter assay revealed a caffeine dependent activation of the TF promoter, and RT-PCR revealed a dose dependent increase in TF mRNA levels when stimulated with caffeine in the presence of TNF-α. In conclusion, caffeine enhances TNF-α-induced endothelial TF protein expression as well as surface activity by inhibition of PI3K signalling. Since the caffeine concentrations applied in the present study are within the plasma range measured in humans, our findings indicate that caffeine enhances the prothrombotic potential of endothelial cells and underscore the importance of PI3K in mediating these effects.

Inhibition of Phosphoinositol 3 Kinase Contributes to Nanoparticle-Mediated Exaggeration of Endotoxin-Induced Leukocyte Procoagulant Activity

“…Therefore, we tested whether dendrimers could inhibit PI3K, such that in the absence of negative regulation, LPS-induced inflammatory reactions including PCA expression could continue to propagate. A recent study by Gebhard et al , describing enhancement of TNF-mediated TF expression by the cationic small molecule caffeine, further fueled this hypothesis and led us to study dendrimer effects on PI3K [38]. We found that cationic PAMAM dendrimers completely abrogated kinase activity of rPI3K (Figure 7).…”

“…Some cytokines, specifically TNF and IL-1, are known to induce TF expression [38,50]. In our earlier studies, we observed an enhancement of both TNF and IL-1 by amine-terminated PAMAM dendrimers [Dobrovolskaia MA, Potter T, McNeil SE, Unpublished Data].…”

“…A recent study described the enhancement of TNF-induced TF expression by the cationic small molecule caffeine and attributed this phenomenon to the inhibition of PI3K by caffeine [38]. This prompted us to investigate the role of PI3K in the enhancement of LPS-induced TF expression by cationic dendrimers.…”

“…TF is constantly expressed on fibroblasts, smooth muscle cells and pericytes, but not on endothelial cells or monocytes. Expression and activation of TF is triggered by inflammatory stimuli (e.g., LPS, TNF and IL-1) in normal endothelial cells, normal monocytes [38,49,50], leukemia cells [51–53] and by some cytotoxic oncology drugs (e.g., daunorubicin and doxorubicin) in malignant leukocytes [54,55]. The ability of platelets to express TF is doubtful and controversial [8].…”

Intracellular receptor EPAC regulates von Willebrand factor secretion from endothelial cells in a PI3K-/eNOS-dependent manner during inflammation

“…PI3Ks have been linked to an extraordinarily diverse group of cellular functions, including inflammation and coagulation ( 95 , 96 , 97 ). An earlier study has shown that PI3K is crucial in mediating the prothrombotic potential of ECs ( 98 ). In vivo studies have shown that inhibition of PI3K strongly enhances activation of ECs, upregulates LPS-induced coagulation and inflammation, and reduces the survival time of mice ( 97 ).…”