Expression of adhesion molecules in endothelial cells-implication of diabetic vascular dysfunction

WS3-J-5-06 EXPRESSION OF ADHESION MOLECULES IN ENDOTHELIAL CELLS-IMPLICATION OF DIABETIC VASCULAR DYSFUNCTION A. Kashiwagi, Y. Tanaka, N. Takahara, H. Takil), H. Maegawa, K. Horiikel), Y. Shigeta Third Department of Medicine, First Dep. Biochemistry 1), Shiga University of Medical Science, Otsu, Japan Accelerated atherogenesis is one of characteristics of patients with diabetes mellitus. In the most early event of atherogenesis, monocyte adhesion to endothelial cells and its migration into subendothelial space is thought to be critical. The process can be mediated by interaction between adhesion molecules on endothelial cell (EC) surface and those counterparts on monocytes. Therefore, increased expression of these adhesion molecules on EC surface may potentiate atherogenesis. Several lines of evidence have indicated that various cytokines and hemodynamic factors can induce those expression on ECs. Thus, in the present study, we studied changes in expression of adhesion molecules in ECs by either high glucose or oxidized LDL in culture medium. 1) ICAM-1 expression on human umbilical vein ECs exposed to 33 mM high glucose (HG) increased by 32% (p<0.01) vs 5.5 mM glucose (NG). The effect was D-glucose concentration- and time-dependently induced. However, both expression of E-selectin and VCAM- 1 were not affected by HG condition. In consistent with that, adhesion of THP-1 cells to ECs increased by 30% (p<0.01) in ECs exposed to HG for 48h. Furthermore, TNF-ct-induced increase in ICAM-1 expression was potentiated by HG condition. Furthermore, hyperosmolar condition also induced ICAM-I expression on EC surface. 2) This high glucose effect could be modified in cells exposed to radical scavengers or iron cheletors. 3) Oxidized LDL is the key component in endothelial cell injury. Increased oxidative stress in diabetes may accelerate LDL oxidation. Interestingly, oxidized LDL and its component lysophosphatidylcholine (LysoPC) could stimulate ICAM-1 expression in the ECs. Kume et al have also reported that both VCAM-I and ICAM-I express in cultured rabbit aortic ECs exposed to LysoPC resulting in increased mococyte adhesion to the ECs. These results indicate that hyperglycemia, hyperosmolarity, and increased oxidized LDL (especially LysoPC) found in diabetes can modulate adhesion molecule expression on endothelial cell surface and can initiate monocyte recruitment in the early course of atherogenesis in diabetes. WS4-A-1-01 LEUKOCYTE INDUCED VASCULAR ENDOTHELIAL CELL INJURY---INVOLVEMENT OF CELL ADHESION MOLECULES Sei-itsu Murota Department of Physiological Chemistry, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan Treatment of leukocytes with phorbol myristate acetate (PMA) caused significant increases in the expression of adhesion molecules, CD1 la, CD1 lb, CD1 lc and CD18. The addition of the PMA-stimulated leukocytes to an endothelial cell monolayer caused a signigicant increase m the intracellular peroxide level of the endothelial cells after 15 minutes and endothelial cell injury after 5 hours. Both the early increase in the peroxide production and the late cell lysis were abolished in the presence of specific antibodies against CDlla, CDllb, CD18 and ICAM-1, but not CDllc. These antibodies affected neither the production of active oxygen species by the leukocytes nor the rate of adhesion of leukocytes to endothelial cells. These data indicate that the adhesion through CD11/CD18-ICAM-1 is necessary for the leukocytes to induce endothelial cell injury as well as peroxide production in endothelial cells. Both the early and late events were only partially blocked by catalase but almost completely abolished by deferoxamine, a chelator of ferrous ions, suggesting that hydroxyl radicals produced by endothelial cells by xanthine oxidase may injure themselves. Pretreatment of endothelial cells with allopurinol, a specific inhibitor of xanthine oxidase, caused significant inhibition of both the early and the late events, suggesting that the binding of adhesion molecules such as ICAM-1 and CD11/CD18, but not CD1 lc, may trigger the activation of xanthine oxidase of endothelial cells and have the cells to produce more hydrogen peroxide and ferrous ions, followed by producing more hydrogen peroxide. The hydrogen peroxide produced by endothelial cells themselves and by leukocytes may be converted to hydroxyl radicals by ferrous ions, which may cause lethal cell damage. Examination of xanthine oxidase activity in endothelial cells showed that the enzyme activity increased double within 15 minutes after the addition of PMA activated leukocytes.

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