Regulation of Human Thrombin-Activable Fibrinolysis Inhibitor Gene Expression in Megakaryocyte-Like (Dami) and Monocyte/Macrphage- Like (THP-1) Cell Lines
Notice bibliographique
Résumé
Abstract Thrombin-activable fibrinolysis inhibitor (TAFI) is a carboxypeptidase zymogen defining a pathway that functions as a molecular link between coagulation and fibrinolysis. Activation by thrombin, the thrombin-thrombomodulin complex, or plasmin, the resultant enzyme (TAFIa) affects the balance between these two cascades by attenuating positive feedback in the fibrinolytic cascade, thereby inhibiting fibrin clot lysis. Plasma TAFI antigen levels vary significantly between individuals, which has implicated TAFI as a risk factor for thrombotic diseases. TAFIa can also inactivate pro-inflammatory peptides such as the anaphylatoxins and bradykinin, suggesting a role for the TAFI pathway as a link between coagulation and inflammation. TAFI expression in cultured hepatic cells is decreased by interleukins −1 and −6, and plasma TAFI levels in human are decreased in experimental endotoxemia. Although the liver is the main source of plasma TAFI, TAFI has also been identified in platelets, and TAFI mRNA has been detected in the Dami (megakaryoblastic) cell line (but not the MEG-01 cell line). TAFI mRNA has also been detected in adipocytes of patients with type 2 diabetes; however, TAFI mRNA expression in human umbilical vein endothelial cells is still a point of controversy. It has been hypothesized that platelet TAFI arises from TAFI gene expression in megakaryocytes (MK). Using RT-PCR and real-time RT-PCR, we not only confirmed the presence of TAFI mRNA in Dami cells, but also found that TAFI mRNA abundance was increased throughout Dami cell differentiation along the megakaryocytes/platelet lineage (up to 8 fold increase after 48 hours) stimulated by phorbol myristate acetate (PMA) treatment. The quantitative real-time RT-PCR experiments revealed that TAFI mRNA is present in differentiated Dami cells at a level that is only one-hundredth of that observed in HepG2 (hepatoma) cells. Using transfection experiments with luciferase reporter plasmids containing progressive deletions of the human TAFI 5′-flanking region, we identified the sequence between −438 and −257 (relative to the initiator methionine codon) to be responsible for the enhanced TAFI gene transcription as Dami cells differentiate into more mature MK-like cells. Moreover, using western blot analysis, we detected TAFI protein expression in the medium of differentiated Dami cells, but not untreated Dami cells. Together, these data provide further evidence supporting the idea that platelet TAFI is generated from TAFI gene expression in megakaryocytes rather than by uptake from the plasma. To study TAFI gene regulation in monocytes and macrophages, RT-PCR and realtime RT-PCR were used to detected and quantify, respectively, TAFI mRNA expression in both THP-1 and THP-1 cells that have been differentiated into macrophage-like cells (THP-1ma) by PMA treatment. TAFI mRNA abundance was similar in THP-1 cells as what was observed in differentiated Dami cells. In addition, we found a progressive decrease in TAFI mRNA abundance throughout the THP-1 differentiation with an 85% decrease after 24 hours of PMA treatment. Transfection experiments using luciferase reporter plasmids representing progressive deletions of the human TAFI 5′-flanking region identified sequences between −151 and −121 as harboring key promoter elements for the differentiation-associated decrease in TAFI gene expression as THP-1 differentiate into macrophage-like cells. However, no TAFI protein was detected in either THP-1 or THP-1ma conditioned medium using western blot analyses. Nonetheless, extra-hepatic expression of TAFI, such as platelet, monocytes and macrophages, suggests novel roles for TAFI pathway beyond regulation of fibrin clot breakdown.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».