LDL-Proteoglycans Complex as a fatty strek site in atherosclerosis.

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09670741
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Circulatory organs internal medicine
• Research Institution: Wakayama Medical Collage
• Principal Investigator: HAMADA Masanori Wakayama Medical Collage, 医学部, 講師 (10254533)
• Project Period (FY): 1997 – 1998
• Keywords: 動脈硬化 / glycosaminoglycans / low density lipoprotein

Research Abstract

Objective : It has been reported that low density lipoprotein(LDL) produce insoluble complex with mono-sulfated glycosamino-glycans(GAGs). The complex also has a high affinity with calcium binding proteins namely osteopontin(OPN). We reported that the GAGs are increased in the aorta of experimental models of hypertension in rat. The main aim of this experiment was to investigate how the increased GAGs react with LDL to make insoluble GAGs-LDL complex at the site of atheroscleritic lesion and how the OPN is controled by angiotensin II.
Design and Methods : 96-well microtiteation plate was coated with a certain amount of LDL. A limiting quantity of biotin-conjugated proteoglycans(PrG) is allowed to bind to each coated well in competition with different kind of GAGs or lipoproteins applied during incubation period. The amount of biotin-conjugated PrG retained on well was estimated spectrophotometrically by alkaline phosphatase-avidin method. The OPN produced in the culture medium by cultur ed vascular smooth muscle cells are measured by Western blotting with monoclonal antibody to OPN.
Results : Lp(a) and very low density lipoprotein (VLDL) showed higher affinity with chondroitin-PrG than LDL and high density lipoprotein(HDL) but not significantly. Heparin showed significantly higher affinity with chondroitin-PrG than hiarulonic acid, heparan sulfate and chondroitin sulfate. Divalent cations(calcium, magnesium or manganese) were important to obtain insoluble GAGs-LDL complex in this in vitro model. Angiotensin II increased OPN protein in the medium in accordance with the concentrations between 10ィイD2-11ィエD2M to 10ィイD2-7ィエD2M. Whereas Sar-Ala angiotensin II did not. Angiotensin II receptor blockade supressed OPN increase produced by angiotensin II completely at a concentration of 10ィイD2-5ィエD2M.
Conclusions : Our results showed that GAGs and divalent cations are essential for LDL to remain in the atherosclerotic lesion. Hypertension might contribute to make the complex by enhance production of chondroitin sulfate in the aortic media. Angiotensin II might enhance hydroxyapatite formation in hypertensive atherosclerotic lesion.