Cell adhesion molecules and insulin-like growth factor-1 in vascular disease

Recent advances in the understanding of the biologic mechanisms of vascular diseases suggest that multifactorial stimulation of the endothelial cell and its subsequent adhesion to leukocytes is a prerequisite to the formation of atherosclerotic and restenotic lesions. As leukocyte-endothelial cell interaction is coordinated by a variety of cell adhesion molecules (CAMs), we hypothesized that the expression of certain CAMs is up-regulated in the vasculature of patients who have peripheral vascular disease. In addition, we proposed that insulin-like growth factor-1 (IGF-1) increases monocyte-endothelial adhesion by means of upregulation of these CAMs.

Using immunohistochemical techniques, the expression of intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and P-selectin was examined in human vascular disease specimens. Normal aortas obtained from the organ retrieval system were studied as control specimens. Adhesion studies between human umbilical vein endothelial cells (HUVECs) incubated with IGF-1 and purified human blood monocytes labeled with 51chromium were completed. Western blotting and flow cytometry were performed to show CAM expression on IGF-1-treated HUVECs.

Of the CAMs, ICAM-1, P-selectin, and E-selectin were distinctly increased in diseased specimens when compared with control specimens (p < 0.05). Adhesion studies showed an increase in monocyte-endothelial cell adhesion of as much as 40% to 45% (p < 0.01) over baseline, with peak adherence occurring 4 hours after treatment with IGF-1. IGF-1 increased adherence in a dose- and time-dependent manner. The threshold concentration of IGF-1 that induced increased adhesion was 20 ng/ml, with a maximum effect occurring at 150 ng/ml. This increased adhesion was attenuated by pretreatment with IGF-I receptor antibody, as well as with genistein and herbimycin-A, which are potent and selective tyrosine kinase inhibitors. Increased adhesion correlated with an increase in the expression of CAMs on the surface of the HUVECs. An additive effect on adhesion was observed between IGF-1 and tumor necrosis factor-alpha (TNF-alpha) and endothelin-1 (ET-1). Finally, immunohistochemical analysis of human vascular disease specimens revealed an increased expression of IGF-1 receptors as compared with control specimens (p < 0.05).

These results suggest that IGF-1 may be important in the pathogenesis of peripheral vascular disease by increasing endothelial cell-monocyte adhesion by means of an increase in the expression of ICAM-1 and VCAM-1.