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

Current therapeutic targets and multifaceted physiological impacts of caffeine

Caffeine, which shares consubstantial structural similarity with purine adenosine, has been demonstrated as a nonselective adenosine receptor antagonist for eliciting most of the biological functions at physiologically relevant dosages. Accumulating evidence supports caffeine's beneficial effects against different disorders, such as total cardiovascular diseases and type 2 diabetes. Conversely, paradoxical effects are also linked to caffeine ingestion in humans including hypertension-hypotension and tachycardia-bradycardia. These observations suggest the association of caffeine action with its ingested concentration and/or concurrent interaction with preferential molecular targets to direct explicit events in the human body. Thus, a coherent analysis of the functional targets of caffeine, relevant to normal physiology, and disease pathophysiology, is required to understand the pharmacology of caffeine. This review provides a broad overview of the experimentally validated targets of caffeine, particularly those of therapeutic interest, and the impacts of caffeine on organ-specific physiology and pathophysiology. Overall, the available empirical and epidemiological evidence supports the dose-dependent functional activities of caffeine and advocates for further studies to get insights into the caffeine-induced changes under specific conditions, such as asthma, DNA repair, and cancer, in view of its therapeutic applications.

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

Coagulopathy is associated with both inflammation and infection, including infections with novel severe acute respiratory syndrome coronavirus-2, the causative agent Coagulopathy is associated with both inflammation and infection, including infection with novel severe acute respiratory syndrome coronavirus-2, the causative agent of COVID-19. Clot formation is promoted via cAMP-mediated secretion of von Willebrand factor (vWF), which fine-tunes the process of hemostasis. The exchange protein directly activated by cAMP (EPAC) is a ubiquitously expressed intracellular cAMP receptor that plays a regulatory role in suppressing inflammation. To assess whether EPAC could regulate vWF release during inflammation, we utilized our EPAC1-null mouse model and revealed increased secretion of vWF in endotoxemic mice in the absence of the EPAC1 gene. Pharmacological inhibition of EPAC1 in vitro mimicked the EPAC1-/- phenotype. In addition, EPAC1 regulated tumor necrosis factor-α-triggered vWF secretion from human umbilical vein endothelial cells in a manner dependent upon inflammatory effector molecules PI3K and endothelial nitric oxide synthase. Furthermore, EPAC1 activation reduced inflammation-triggered vWF release, both in vivo and in vitro. Our data delineate a novel regulatory role for EPAC1 in vWF secretion and shed light on the potential development of new strategies to control thrombosis during inflammation.

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

Coagulopathy is associated with both inflammation and infection, including infection with the novel SARS-CoV-2 (COVID-19). Endothelial cells (ECs) fine tune hemostasis via cAMP-mediated secretion of von Willebrand factor (vWF), which promote the process of clot formation. The e xchange p rotein directly a ctivated by c AMP (EPAC) is a ubiquitously expressed intracellular cAMP receptor that plays a key role in stabilizing ECs and suppressing inflammation. To assess whether EPAC could regulate vWF release during inflammation, we utilized our EPAC1 -null mouse model and revealed an increased secretion of vWF in endotoxemic mice in the absence of the EPAC1 gene. Pharmacological inhibition of EPAC1 in vitro mimicked the EPAC1 -/- phenotype. EPAC1 regulated TNFα-triggered vWF secretion from human umbilical vein endothelial cells (HUVECs) in a phosphoinositide 3-kinases (PI3K)/endothelial nitric oxide synthase (eNOS)-dependent manner. Furthermore, EPAC1 activation reduced inflammation-triggered vWF release, both in vivo and in vitro . Our data delineate a novel regulatory role of EPAC1 in vWF secretion and shed light on potential development of new strategies to controlling thrombosis during inflammation.

Key Point

PI3K/eNOS pathway-mediated, inflammation-triggered vWF secretion is the target of the pharmacological manipulation of the cAMP-EPAC system.

Expression of flTF and asTF splice variants in various cell strains and tissues

Tissue factor (TF) expressed at the protein level includes two isoforms: The membrane-bound full-length TF (flTF) and the soluble alternatively spliced TF (asTF). flTF is the major thrombogenic form of TF, whereas asTF is more closely associated with tumor growth, angiogenesis, metastasis and cell growth. In order to further investigate the different expression and functions of TF splice variants, the expression of these two splice variants were detected in numerous cell strains and tissues in the present study. Quantitative polymerase chain reaction was used to measure the transcript levels of the TF variants in 11 human cell lines, including cervical cancer, breast cancer, hepatoblastoma, colorectal cancer and umbilical vein cells, and five types of tissue specimen, including placenta, esophageal cancer, breast cancer, cervical cancer (alongside normal cervical tissues) and non-small cell lung cancer (alongside adjacent and normal tissues). Furthermore, the effects of chenodeoxycholic acid (CDCA) and apolipoprotein M (apoM) on the two variants were investigated. The results demonstrated that flTF was the major form of TF, and the mRNA expression levels of flTF were higher than those of asTF in all specimens tested. CDCA significantly upregulated the mRNA expression levels of the two variants. Furthermore, overexpression of apoM promoted the expression levels of asTF in Caco-2 cells. The mRNA expression levels of asTF in cervical cancer tissues were significantly higher than in the corresponding normal tissues. To the best of our knowledge, the present study is the first to compare the expression of flTF and asTF in various samples. The results demonstrated that CDCA and apoM may modulate TF isoforms in different cell lines, and suggested that asTF may serve a role in the pathophysiological mechanism underlying cervical cancer development. In conclusion, the TF isoforms serve important and distinct roles in pathophysiological processes.

Puerarin inhibits expression of tissue factor induced by oxidative low-density lipoprotein through activating the PI3K/Akt/eNOS pathway and inhibiting activation of ERK1/2 and NF-κB

AIMS

The present study aimed to investigate whether puerarin regulated tissue factor (TF) expression induced by oxidative low-density lipoprotein (ox-LDL), an independent risk factor for atherosclerosis, and its mechanisms.

MAIN METHODS

TF expression at the mRNA level was determined by reverse transcription-quantitative polymerase chain reaction, and its expression at the protein level, as well as other target proteins, was assessed by western blotting. Nitric oxide (NO) production was measured by a nitrate reduction method.

KEY FINDINGS

Results demonstrated that treatment with ox-LDL (50mg/l) for 24h significantly increased (P<0.01) TF expression at the mRNA and protein levels in human umbilical vein endothelial cells (HUVECs). Such an ox-LDL exposure also triggered the dephosphorylation of Akt, resulting in a reduction of NO production and activated the extracellular signal-regulated kinase (ERK)1/2 and nuclear factor (NF)-κB signaling pathways. Pre-treatment with puerarin (50-200μM) for 1h significantly attenuated the ox-LDL-induced TF expression, augmented the phosphorylation of Akt, with a resultant increase of the NO production, and inhibited the activation of ERK1/2 and NF-κB (P<0.01). However, this beneficial effect of puerarin (100μM) was abolished by LY294002 (10μM), an inhibitor of phosphoinositide 3-kinase (PI3K), or NG-nitro-L-arginine methyl ester (100μM), an inhibitor of NO synthase.

SIGNIFICANCE

These results suggested that puerarin suppressed TF expression in HUVECs through activating the PI3K/Akt/endothelial nitric oxide synthase signaling pathway and inhibiting the activation of ERK1/2 and NF-κB. These findings suggested that puerarin possessed certain anticoagulation and may be a potential novel therapeutic drug for thrombosis in coronary artery disease.

Purinergic P2Y2 Receptor Control of Tissue Factor Transcription in Human Coronary Artery Endothelial Cells: NEW AP-1 TRANSCRIPTION FACTOR SITE AND NEGATIVE REGULATOR

We recently reported that the P2Y2 receptor (P2Y2R) is the predominant nucleotide receptor expressed in human coronary artery endothelial cells (HCAEC) and that P2Y2R activation by ATP or UTP induces dramatic up-regulation of tissue factor (TF), a key initiator of the coagulation cascade. However, the molecular mechanism of this P2Y2R-TF axis remains unclear. Here, we report the role of a newly identified AP-1 consensus sequence in the TF gene promoter and its original binding components in P2Y2R regulation of TF transcription. Using bioinformatics tools, we found that a novel AP-1 site at -1363 bp of the human TF promoter region is highly conserved across multiple species. Activation of P2Y2R increased TF promoter activity and mRNA expression in HCAEC. Truncation, deletion, and mutation of this distal AP-1 site all significantly suppressed TF promoter activity in response to P2Y2R activation. EMSA and ChIP assays further confirmed that upon P2Y2R activation, c-Jun, ATF-2, and Fra-1, but not the typical c-Fos, bound to the new AP-1 site. In addition, loss-of-function studies using siRNAs confirmed a positive transactivation role of c-Jun and ATF-2 but unexpectedly revealed a strong negative role of Fra-1 in P2Y2R-induced TF up-regulation. Furthermore, we found that P2Y2R activation promoted ERK1/2 phosphorylation through Src, leading to Fra-1 activation, whereas Rho/JNK mediated P2Y2R-induced activation of c-Jun and ATF-2. These findings reveal the molecular basis for P2Y G protein-coupled receptor control of endothelial TF expression and indicate that targeting the P2Y2R-Fra-1-TF pathway may be an attractive new strategy for controlling vascular inflammation and thrombogenicity associated with endothelial dysfunction.

Inhibition of phosphoinositol 3 kinase contributes to nanoparticle-mediated exaggeration of endotoxin-induced leukocyte procoagulant activity

AIM

Disseminated intravascular coagulation is an increasing concern for certain types of engineered nanomaterials. Recent studies have shed some light on the nanoparticle physicochemical properties contributing to this toxicity; however, the mechanisms are poorly understood. Leukocyte procoagulant activity (PCA) is a key factor contributing to the initiation of this toxicity. We have previously reported on the exaggeration of endotoxin-induced PCA by cationic dendrimers. Herein, we report an effort to discern the mechanism.

MATERIALS & METHODS

Poly(amidoamine) dendrimers with various sizes and surface functionalities were studied in vitro by the recalcification test, flow cytometry and other relevant assays.

RESULTS & CONCLUSION

Cationic dendrimers exaggerated endotoxin-induced PCA, but their anionic or neutral counterparts did not; the cationic charge prompts this phenomenon, but different cationic surface chemistries do not influence it. Cationic dendrimers and endotoxin differentially affect the PCA complex. The inhibition of phosphoinositol 3 kinase by dendrimers contributes to the exaggeration of the endotoxin-induced PCA.