Insulin inhibits tissue factor expression in monocytes.
OBJECTIVE
Platelets from healthy subjects are inhibited by insulin but type 2 diabetes mellitus (T2DM) platelets have become insulin-resistant, which might explain their hyperactivity. In the present study we investigated whether monocytes are responsive to insulin.


RESULTS
LPS-induced tissue factor (TF) upregulation was measured in human monocytes and monocytic THP-1 cells in a factor Xa generation assay. Insulin (0.1-100 nmol L(-1)) induced a dose-dependent inhibition in both cell types and in monocytes 100 nmol L(-1) insulin inhibited cytosolic, membrane-bound and microparticle TF by 32 +/- 2, 27 +/- 3 and 52 +/- 4% (n = 3). Insulin induced Tyr phosphorylation of the insulin receptor (INS-R) and formation of an INS-R - G(i)alpha(2) complex, suggesting interference with LPS-induced cAMP control. Indeed, insulin interfered with LPS-induced cAMP decrease and TF upregulation in a manner similar to an inhibitor of G(i) (pertussis toxin) and agents that raise cAMP (iloprost, forskolin, IBMX) reduced TF upregulation. Although LPS failed to raise cytosolic Ca(2+), quenching of Ca(2+) increases (BAPTA-AM) reduced and induction of Ca(2+) entry (ionophore, P2X7 activation) enhanced upregulation of TF mRNA and procoagulant activity. Insulin interfered with MCP-1-induced Ca(2+) mobilization but not with ATP-induced Ca(2+) rises.


CONCLUSIONS
Insulin inhibits TF expression in monocytes and monocyte-derived microparticles through interference with G(i)alpha(2)-mediated cAMP suppression, which attenuates Ca(2+)-mediated TF synthesis.
Gerrits
A J
AJ
Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, The Netherlands.
Koekman
C A
CA
Yildirim
C
C
Nieuwland
R
R
Akkerman
J W N
JW
D002118:Calcium; D055252:Cell-Derived Microparticles / Q000378:metabolism; D000242:Cyclic AMP / Q000037:antagonists & inhibitors; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000378:metabolism*; D010766:Phosphorylation; D011972:Receptor, Insulin / Q000378:metabolism; D013925:Thromboplastin / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*
D007328:Insulin; D008070:Lipopolysaccharides; D013925:Thromboplastin; D000242:Cyclic AMP; D011972:Receptor, Insulin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D002118:Calcium