High insulin exacerbates neutrophil-endothelial cell adhesion through endothelial surface expression of intercellular adhesion molecule-1 via activation of protein kinase C and mitogen-activated protein kinase

Abstract

The risk of cardiovascular diseases in diabetic patients and even in those with IGT are associated with insulin resistance, two-to threefold higher than that in control subjects [1]. The United Kingdom Prospective Diabetes Study (UKPDS) and other similar studies indicated that intensive control of blood glucose in diabetic patients prevents and slows the progression of microvascular complications, but has little effect on the prevention of macrovascular complications i. e. acute myocardial infarction (AMI) [2]. Excessive macrovascular diseases in diabetes have thus been considered to be due to insulin resistance and/or hyperinsulinaemia.A recent study has shown that vascular inflammation with atherosclerosis is responsible for the onset of AMI [3]. Adhesion of leukocytes to the endothelium, which is regulated by several endothelial adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1), E-selectin and P-selectin, is the first and crucial step in both atherosclerosis and vascular inflammation. Whereas endothelial dysfunction induced by insulin resistance and/or hyperinsulin- AbstractAims/hypothesis. The association of insulin resistance and compensatory hyperinsulinaemia with increased coronary events in diabetic patients is poorly understood. There are few publications about the direct atherogenic actions of insulin on the endothelium compared with those on vascular smooth muscle cells. The aim of this study was to elucidate whether high insulin directly affects neutrophil-endothelial cell adhesion and surface expression of endothelial adhesion molecules. We also examined what intracellular mechanisms are involved in these events. Methods. Studies of adhesion between neutrophils from healthy volunteers and human umbilical vein endothelial cells incubated in insulin-rich medium were carried out. Adhered neutrophils were quantified by measuring their myeloperoxidase activities and surface expression of endothelial adhesion molecules was examined using an enzyme immunoassay. Results. High insulin enhanced neutrophil-endothelial cell adhesion with an increase in the expression of intercellular adhesion molecule-1 but not E-selectin or P-selectin. Both phenomena were attenuated by pretreatment with protein kinase C inhibitors and a mitogen activated protein kinase inhibitor. Conclusions/interpretation. These results suggest that hyperinsulinaemia causes vascular injury by directly exacerbating neutrophil-endothelial cell adhesion through increasing endothelial expression of intercellular adhesion molecule-1 via activation of protein kinase and mitogen activated protein kinase pathways. [Diabetologia (2002) 45:556±559]

Linking Metabolism and Immunology: Diabetic Nephropathy Is an Inflammatory Disease

“…Intracellular adhesion molecule (ICAM)-1 is expressed on the surface of a number of cell types in response to PKC activation (17)(18)(19). ICAM-1 promotes inflammation by enhancing leukocyte infiltration and adherence.…”

High insulin enhances neutrophil transendothelial migration through increasing surface expression of platelet endothelial cell adhesion molecule-1 via activation of mitogen activated protein kinase

“…The involvement of endothelial PECAM-1 in insulin-enhanced PMN migration was confirmed by showing that it was inhibited by an anti-PECAM-1 Ab but not by an anti-ICAM-1, anti-Pselectin or anti-E-selectin Ab. We reported previously that high insulin increased endothelial ICAM-1 expression leading to enhanced neutrophil-endothelial cell adhesion [20]; however, it is not likely that ICAM-1 expression is correlated with PMN transendothelial migration. We found that high insulin directly enhanced endothelial PECAM-1 expression leading to increased PMN transendothelial migration, whereas many reports have indicated that surface expression of endothelial PECAM-1 is not altered by inflammatory mediators [14,28].…”

“…Neutrophil migration was stopped by removing the inserts from the wells and then the 24-well plates were centrifuged at 1500 rpm for 5 min. Migrated neutrophils in the wells were quantified with a myeloperoxidase (MPO) assay using a previously reported method [20] in which the H 2 O 2 -dependent oxidation of 3,3′,5,5′-tetramethylbenzidine (Sigma) was measured. Neutrophil migration was expressed as the ratio of MPO activity of migrated neutrophils to that of the total neutrophils (1×10 5 …”

“…Surface expression of endothelial PECAM-1 was measured using a method reported previously [20]. Briefly, after treatment of cells with or without human regular insulin in collagen I-coated 24-well plates, cells were fixed for 10 min at room temperature with 1% paraformaldehyde in PBS.…”

“…It can be either atherogenic through a mitogen-activated protein (MAP) kinase pathway or antiatherogenic through a phosphatidylinositol-3 (PI-3) kinase pathway which promotes the production of the vasodilator nitric oxide by endothelial cells [17,18,19]. We have reported previously that high insulin enhances neutrophil-endothelial cell adhesion through a protein kinase C (PKC) and MAP kinase pathways [20]. Based on these data, we evaluated the intracellular mechanisms, including the participation of nitric oxide, associated with high insulin-mediated neutrophil transendothelial migration and surface expression of endothelial PECAM-1.…”