High insulin enhances neutrophil transendothelial migration through increasing surface expression of platelet endothelial cell adhesion molecule-1 via activation of mitogen activated protein kinase.
OBJECTIVE
There is increasing evidence that hyperinsulinaemia is linked with the development of atherosclerosis in patients with diabetes. However, the mechanisms by which hyperinsulinaemia causes accelerated atherosclerosis, especially with respect to leukocytes transendothelial migration, are poorly understood. We examined whether hyperinsulinaemia directly affects neutrophil transendothelial migration and surface expression of related endothelial adhesion molecules.


METHODS
Experiments on the transmigration of neutrophils from healthy volunteers and from patients with Type II (non-insulin-dependent) diabetes mellitus across human umbilical vein endothelial cells cultured in insulin-rich medium using cell-culture inserts were carried out. Migrated neutrophils were quantified by measuring their myeloperoxidase activities, and the surface expression of endothelial adhesion molecules was examined using an enzyme immunoassay.


RESULTS
High insulin (over 50 microU/ml for 24 h) enhanced neutrophil transendothelial migration in a dose-dependent manner. This was associated with increased expression of platelet endothelial cell adhesion molecule-1 (PECAM-1) but not of intercellular adhesion molecule-1 (ICAM-1), P-selectin or E-selectin. Both phenomena were attenuated by pretreatment with a tyrosine kinase inhibitor, especially a mitogen-activated protein kinase inhibitor, but not by inhibitors of other second messengers. In addition, a mitogen-activated protein kinase activator, anisomycin, by itself enhanced both neutrophil transendothelial migration and PECAM-1 expression within 3 h in a dose-dependent manner. Pretreatment with nitric oxide synthase inhibitors had no effect on these events.


CONCLUSIONS
These results suggest that hyperinsulinaemia could accelerate atherosclerosis by directly enhancing neutrophil transendothelial migration through increasing endothelial PECAM-1 expression via mitogen-activated protein kinase activation.
Okouchi
M
M
First Department of Internal Medicine, Nagoya City University Medical School, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan. okochi@med.nagoya-cu.ac.jp
Okayama
N
N
Imai
S
S
Omi
H
H
Shimizu
M
M
Fukutomi
T
T
Itoh
M
M
D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte / Q000187:drug effects* / Q000502:physiology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005190:Family; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D020928:Mitogen-Activated Protein Kinases / Q000097:blood*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000097:blood* / Q000187:drug effects / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012016:Reference Values; D014471:Umbilical Veins
D004791:Enzyme Inhibitors; D007328:Insulin; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases