Insulin enhances vascular cell adhesion molecule-1 expression in human cultured endothelial cells through a pro-atherogenic pathway mediated by p38 mitogen-activated protein-kinase.
OBJECTIVE
Although hyperinsulinaemia in Type 2 diabetes in states of insulin resistance is a risk factor for atherosclerotic vascular disease, underlying mechanisms are poorly understood. We tested the hypothesis that insulin increases monocyte-endothelial interactions, which are implicated in atherosclerosis.


METHODS
We treated human umbilical vein endothelial cells with insulin (10(-10) to 10(-7) mol/l) for 0 to 24 h. To dissect potentially implicated signal transduction pathways, we treated endothelial cells with known pharmacological inhibitors of two distinct insulin signalling pathways: the phosphatidylinositol-3'-kinase (PI3'-kinase) inhibitor wortmannin (3 x 10(-8) to 10(-6) mol/l), involved in insulin-induced endothelial nitric oxide synthase stimulation, and the p38 mitogen-activated protein (p38MAP) kinase inhibitor SB-203580 (10(-7) to 2 x 10(-6) mol/l). We measured adhesion molecule expression by cell surface enzyme immunoassays and U937 monocytoid cell adhesion in rotational adhesion assays.


RESULTS
At pathophysiological concentrations (10(-9) to 10(-7) mol/l), insulin concentration-dependently induced vascular cell adhesion molecule (VCAM)-1 (average increase: 1.8-fold) peaking at 16 h. By contrast, the expression of intercellular adhesion molecule-1 and E-selectin were unchanged. The effect on VCAM-1 was paralleled by increased U937 cell adhesion. In the absence of cytotoxicity, wortmannin significantly potentiated the effect of insulin alone on VCAM-1 surface expression and monocytoid cell adhesion, whereas SB-203580 (10(-6) mol/l) completely abolished such effects.


CONCLUSIONS
These observations indicate that insulin promotes VCAM-1 expression in endothelial cells through a p38MAP-kinase pathway, amplified by the PI3'-kinase blockage. This could contribute to explaining the increased atherosclerosis occurring in subjects with hyperinsulinaemia, or in states of insulin resistance, which feature a defective PI3'-kinase pathway.
Madonna
R
R
Center of Excellence on Aging, Chair of Cardiology, G. d'Annunzio University-Chieti, Ospedale S. Camillo de Lellis, Via Forlanini, 50, 66100, Chieti, Italy.
Pandolfi
A
A
Center of Excellence on Aging, Chair of Biology, G. d'Annunzio University, Chieti, Italy.
Massaro
M
M
CNR Institute of Clinical Physiology, Pisa and Lecce, Italy.
Consoli
A
A
Center of Excellence on Aging, Chair of Endocrinology and Metabolism, G. d'Annunzio University, Chieti, Italy.
De Caterina
R
R
Center of Excellence on Aging, Chair of Cardiology, G. d'Annunzio University-Chieti, Ospedale S. Camillo de Lellis, Via Forlanini, 50, 66100, Chieti, Italy. rdecater@unich.it.
D000730:Androstadienes / Q000494:pharmacology; D001161:Arteriosclerosis; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D014471:Umbilical Veins; D000077191:Wortmannin; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D000730:Androstadienes; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007328:Insulin; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011725:Pyridines; D018799:Intercellular Adhesion Molecule-1; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; D000077191:Wortmannin