Specific interaction of oxidized low-density lipoprotein with thrombospondin-1 inhibits transforming growth factor-β from its activation

Sakamoto, Yu-ichiro; Miyazaki, Akira; Tamagawa, Harumi; Wang, Guo-Ping; Horiuchi, Seikoh

doi:10.1016/j.atherosclerosis.2005.02.032

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Volume 183, Issue 1 , Pages 85-93, November 2005

Specific interaction of oxidized low-density lipoprotein with thrombospondin-1 inhibits transforming growth factor-β from its activation

Yu-ichiro Sakamoto
- Department of Medical Biochemistry, Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan
- Corresponding author. Tel.: +81 96 373 5072; fax: +81 96 364 6940.
Akira Miyazaki
- Department of Biochemistry, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
Harumi Tamagawa
- Department of Medical Biochemistry, Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan
Guo-Ping Wang
- Department of Medical Biochemistry, Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan
Seikoh Horiuchi
- Department of Medical Biochemistry, Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan

Received 5 August 2004; received in revised form 25 February 2005; accepted 25 February 2005. published online 23 May 2005.

Abstract

Oxidized LDL (Ox-LDL) plays atherogenic roles, whereas thrombospondin-1 (TSP-1) is thought to be anti-atherogenic through activation of TGF-β that contributes to plaque stabilization. Ox-LDL was prepared by incubating of human LDL with CuSO₄. Effect of Ox-LDL on TSP-1-induced TGF-β activation was examined in the present study. Incubation of Ox-LDL with mouse peritoneal macrophages for 3 days resulted in reduction in amounts of active TGF-β in the culture medium by 70–78% when compared with that of parallel incubation without Ox-LDL. TSP-1 could enhance conversion of latent TGF-β1 into active TGF-β1 in a cell-free system. This TSP-1-mediated latent TGF-β1 activation was inhibited by 30% by Ox-LDL, suggesting the possible interaction of Ox-LDL with TSP-1. Incubation of TSP-1 with [¹²⁵I]Ox-LDL or [¹²⁵I]LDL, followed by immunoprecipitation with an anti-TSP-1 antibody demonstrated that a significant amount of [¹²⁵I]Ox-LDL was co-precipitated with TSP-1 while precipitation of [¹²⁵I]LDL was negligible. Furthermore, upon TSP-1-conjugated Sepharose 4B affinity chromatography, both [¹²⁵I]Ox-LDL and [¹²⁵I]latent TGF-β1 bound to the affinity gel were eluted by unlabeled Ox-LDL. These findings indicate that Ox-LDL interacts with TSP-1 and suppresses subsequent TSP-1-dependent TGF-β activation, revealing a novel atherogenic function of Ox-LDL.

Keywords: Oxidized low-density lipoprotein, Thrombospondin-1, Transforming growth factor-β, Atherosclerosis, Inflammation