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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2006;26:2660.)
© 2006 American Heart Association, Inc.

Vascular Biology

Critical Role of Inducible Costimulator Signaling in the Development of Arteriosclerosis

Hisanori Kosuge; Jun-ichi Suzuki; Go Haraguchi; Noritaka Koga; Yasuhiro Maejima; Manabu Inobe; Mitsuaki Isobe; Toshimitsu Uede

From the Department of Cardiovascular Medicine (H.K., J.S., G.H., N.K., Y.M., M. Isobe), Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan; and the Division of Molecular Immunology (M. Inobe, T.U.), Institute for Genetic Medicine, Hokkaido University, Kita-ku, Sapporo, Japan

Correspondence to Mitsuaki Isobe, Department of Cardiovascular Medicine, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8519, Japan. E-mail isobemi.cvm{at}tmd.ac.jp

Objective— Proliferation and migration of smooth muscle cells (SMCs) and migration and accumulation of monocytes and T cells are landmark events in the development of arteriosclerosis. SMC proliferation in the intima induces interruption of blood flow and results in ischemia and graft rejection. Inducible costimulator (ICOS) is a major costimulator of T cell activation. However, the effect of costimulatory molecules on the formation of neointimal hyperplasia has not been fully elucidated. We examined the role of the ICOS pathway in SMC proliferation.

Methods and Results— ICOS ligand (ICOSL) was detected in SMCs stimulated by interleukin (IL)-1ß, and coculture of stimulated SMCs and activated T cells induced SMC proliferation. Inhibition of the ICOS pathway resulted in inhibition of SMC proliferation. In models of transplantation and vascular injury, ICOSL was induced in SMCs in the neointima. Expression of IL-1ß, a key inducer of ICOSL expression, was significantly reduced in mice treated with anti-ICOS antibody or soluble form of ICOS (ICOSIg) and in ICOS-deficient mice. Inhibition of the ICOS pathway significantly suppressed neointimal thickening.

Conclusions— These results indicate that ICOS on activated T cells contributes to neointimal formation through the regulation of SMC proliferation. These findings provide insights into new therapeutic strategies for arteriosclerosis.

The role of the ICOS pathway in SMC proliferation has not yet been evaluated. We demonstrate that blockade of the ICOS pathway significantly suppressed SMC proliferation and neointimal thickening.

Key Words: arteriosclerosis • costimulation • neointima formation • smooth muscle cells

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