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Glycogen synthase kinase-3 negatively regulates tissue factor expression in monocytes interacting with activated platelets.

ABSTRACT: At the site of vascular injury, monocytes (MN) interacting with activated platelets (PLT) synthesize tissue factor (TF) and promote thrombus formation. Intracellular signals necessary for the expression of TF in MN, in the context of a developing thrombus, remain unknown.The study was designed to investigate the role of the glycogen synthase kinase 3 (GSK3, a serine-threonine kinase) downstream insulin receptor pathway, in PLT-induced TF expression in MN.To this purpose we used a well-characterized in vitro model of human MN-PLT interactions that allows detailed analysis of TF activity, TF protein and gene expression.The results demonstrated that, in MN interacting with activated PLT: (i) TF activity, antigen and mRNA were low until 8-10 h and dramatically increased thereafter, up to 24 h; (ii) according to the kinetics of TF expression in MN, GSK3? undergoes phosphorylation on serine 9, a process associated with down-regulation of enzyme activity; (iii) pharmacological blockade of GSK3 further increased TF expression and was accompanied by increased accumulation of NF-kB, in the nucleus; (iv) blockade of phosphoinositide-3 kinase (PI(3)K) by wortmannin inhibited PLT-induced TF expression; and (v) according to the established role of the GSK3 downstream insulin receptor, insulin increased PLT-induced TF expression in a PI(3)K-dependent manner.GSK3 acts as a molecular brake on the signaling pathway, leading to TF expression in MN interacting with activated PLT. PI(3)K, through Akt-dependent phosphorylation of GSK3, relieves this brake and allows TF gene expression. This study identifies a novel molecular link between thrombotic risk and metabolic disorders.

SUBMITTER: Di Santo A

PROVIDER: S-EPMC3091995 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Glycogen synthase kinase-3 negatively regulates tissue factor expression in monocytes interacting with activated platelets.

Di Santo A A Amore C C Dell'Elba G G Manarini S S Evangelista V V

Journal of thrombosis and haemostasis : JTH 20110501 5

<h4>Background</h4>At the site of vascular injury, monocytes (MN) interacting with activated platelets (PLT) synthesize tissue factor (TF) and promote thrombus formation. Intracellular signals necessary for the expression of TF in MN, in the context of a developing thrombus, remain unknown.<h4>Objective</h4>The study was designed to investigate the role of the glycogen synthase kinase 3 (GSK3, a serine-threonine kinase) downstream insulin receptor pathway, in PLT-induced TF expression in MN.<h4> ...[more]

PMID: 21320285

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Project description:Background & aimsGlycogen synthase kinase 3β (Gsk3β [Gsk3b]) is a ubiquitously expressed kinase with distinctive functions in different types of cells. Although its roles in regulating innate immune activation and ischaemia and reperfusion injuries (IRIs) have been well documented, the underlying mechanisms remain ambiguous, in part because of the lack of cell-specific tools in vivo.MethodsWe created a myeloid-specific Gsk3b knockout (KO) strain to study the function of Gsk3β in macrophages in a murine liver partial warm ischaemia model.ResultsCompared with controls, myeloid Gsk3b KO mice were protected from IRI, with diminished proinflammatory but enhanced anti-inflammatory immune responses in livers. In bone marrow-derived macrophages, Gsk3β deficiency resulted in an early reduction of Tnf gene transcription but sustained increase of Il10 gene transcription on Toll-like receptor 4 stimulation in vitro. These effects were associated with enhanced AMP-activated protein kinase (AMPK) activation, which led to an accelerated and higher level of induction of the novel innate immune negative regulator small heterodimer partner (SHP [Nr0b2]). The regulatory function of Gsk3β on AMPK activation and SHP induction was confirmed in wild-type bone marrow-derived macrophages with a Gsk3 inhibitor. Furthermore, we found that this immune regulatory mechanism was independent of Gsk3β Ser9 phosphorylation and the phosphoinositide 3-kinase-Akt signalling pathway. In vivo, myeloid Gsk3β deficiency facilitated SHP upregulation by ischaemia-reperfusion in liver macrophages. Treatment of Gsk3b KO mice with either AMPK inhibitor or SHP small interfering RNA before the onset of liver ischaemia restored liver proinflammatory immune activation and IRI in these otherwise protected hosts. Additionally, pharmacological activation of AMPK protected wild-type mice from liver IRI, with reduced proinflammatory immune activation. Inhibition of the AMPK-SHP pathway by liver ischaemia was demonstrated in tumour resection patients.ConclusionsGsk3β promotes innate proinflammatory immune activation by restraining AMPK activation.Lay summaryGlycogen synthase kinase 3β promotes macrophage inflammatory activation by inhibiting the immune regulatory signalling of AMP-activated protein kinase and the induction of small heterodimer partner. Therefore, therapeutic targeting of glycogen synthase kinase 3β enhances innate immune regulation and protects liver from ischaemia and reperfusion injury.

Dataset Information

Glycogen synthase kinase-3 negatively regulates tissue factor expression in monocytes interacting with activated platelets.

Publications

Glycogen synthase kinase-3 negatively regulates tissue factor expression in monocytes interacting with activated platelets.

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