HDL-Mediated Efflux of Intracellular Cholesterol Is Impaired in Fibroblasts From Tangier Disease Patients

Author:

Rogler Gerhard1,Trümbach Barbara1,Klima Birgit1,Lackner Karl J.1,Schmitz Gerd1

Affiliation:

1. From the Institute for Clinical Chemistry and Laboratory Medicine, University of Regensburg, Federal Republic of Germany.

Abstract

Abstract To further elucidate the cellular mechanisms leading to HDL deficiency in Tangier disease, HDL-mediated cholesterol efflux was studied in cultured skin fibroblasts from Tangier patients. Both Tangier and control fibroblasts show specific saturable binding of HDL 3 to the cell membrane (B max = 70 and 52 ng/mg protein, respectively; K d =8.8 and 10.6 μg/mL, respectively). There was no appreciable uptake of HDL 3 by Tangier and control fibroblasts, indicating that cholesterol efflux from fibroblasts occurs at the cell membrane. When cellular cholesterol was labeled to equilibrium by [ 14 C]cholesterol incubation for 48 hours at 37°C, HDL 3 -mediated cholesterol efflux from Tangier fibroblasts was only 50% of control fibroblasts. To define this abnormality in HDL 3 -mediated cholesterol efflux more precisely, several additional experiments were performed. First, membrane desorption of cholesterol was determined after cell membranes were labeled with [ 14 C]cholesterol for 3 hours at 15°C. With this labeling protocol, there was no difference in HDL 3 -mediated cholesterol efflux between control and Tangier fibroblasts. Second, efflux of newly synthesized sterols was determined after incorporation of the precursor [ 14 C]mevalonolactone. Under these conditions, specific HDL 3 -mediated efflux of sterols was almost absent in Tangier fibroblasts. Third, cells were labeled by incubation with reconstituted [ 3 H]cholesteryl-linoleate-LDL. Efflux of LDL-derived cholesterol was only slightly reduced for the first 4 hours of incubation. After 12 hours, there was no difference between control and Tangier cells. The combined data indicate that the reduced efflux of cholesterol from Tangier fibroblasts observed after homogeneous labeling is due to severely reduced efflux of newly synthesized sterol. Since it has been shown previously that efflux of newly synthesized cholesterol depends on HDL-mediated activation of protein kinase C (PKC), the effect of pharmacological activation of PKC was analyzed. Incubation of Tangier fibroblasts in the presence of 1,2-dioctanoylglycerol (10 −5 mol/L), a membrane-permeable activator of PKC, led to normalization of HDL 3 -mediated efflux of newly synthesized cholesterol. These data were interpreted to indicate that impaired activation of PKC rather than a defect in the transport mechanism of cellular cholesterol leads to reduced HDL-mediated efflux of cholesterol from Tangier fibroblasts.

Publisher

Ovid Technologies (Wolters Kluwer Health)

Subject

Cardiology and Cardiovascular Medicine

Reference33 articles.

1. Tangier Disease

2. The Inheritance of High Density Lipoprotein Deficiency (Tangier Disease)*

3. Assmann G Schmitz G Brewer HB Jr. Familial HDL deficiency: Tangier disease. In: Scriver CR Beaudet AS Sly WS Valle D eds. The Metabolic Basis of Inherited Disease . 6th ed. New York NY: McGraw-Hill; 1989:1267-1282.

4. Homozygous Tangier disease and cardiovascular disease

Cited by 121 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3