mTOR Complex 2 Activation by Reconstituted High-Density Lipoprotein Prevents Senescence in Circulating Angiogenic Cells

• Published in: Arteriosclerosis, thrombosis, and vascular biology Vol. 31; no. 6; pp. 1421 - 1429
• Main Authors: Guo, Xianrong, Yu, Miao, Kang, Xiaomin, Yin, Hongchao
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01.06.2011; Lippincott Williams & Wilkins
• Subjects: Active Transport, Cell Nucleus; Animals; Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Blood vessels and receptors; Cardiology. Vascular system; Cells, Cultured; Cellular Senescence; Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous; Fundamental and applied biological sciences. Psychology; Humans; Lipoproteins, HDL - pharmacology; Male; Mechanistic Target of Rapamycin Complex 1; Medical sciences; Mice; Mice, Inbred C57BL; Multiprotein Complexes; Neovascularization, Physiologic; Phosphorylation; Proteins - physiology; Proto-Oncogene Proteins c-akt - metabolism; Signal Transduction; Sirolimus - pharmacology; Telomerase - metabolism; TOR Serine-Threonine Kinases - metabolism; Vertebrates: cardiovascular system; Vascular disease; Prevention; endothelial function; Signal transduction; Senescence; Atherosclerosis; Cardiovascular disease; vascular biology; Lipoprotein; cardiovascular disease prevention
• ISSN: 1079-5642; 1524-4636
• DOI: 10.1161/ATVBAHA.111.224089

OBJECTIVE—Circulating angiogenic cells (CACs) participate in neovascularization and arterial repair. Although high-density lipoprotein (HDL) is known to enhance the functional activity of CACs, the mechanisms underlying this regulation are poorly understood. Here, we examined the mechanism(s) by which reconstituted HDL (rHDL) affects CAC senescence. METHODS AND RESULTS—CACs isolated from human peripheral blood and treated with rHDL displayed reduced senescence, as measured by acidic β-galactosidase staining. This protective effect was blocked by the mammalian target of rapamycin (mTOR) inhibitor (rapamycin). According to Western blot analysis and immunoprecipitation results, rHDL promoted mTOR phosphorylation, mTOR-rictor complex formation, and mTOR-rictor–dependent Akt activation, which were accompanied by increased nuclear translocation of human telomerase reverse transcriptase and enhanced nuclear telomerase activity. Suppression of rictor gene expression with a small interfering RNA blocked mTOR-rictor complex formation and Akt activation. The suppression also abolished the rHDL-induced inhibition of CAC senescence and promotion of nuclear telomerase activity. Treatment of aged mice with rHDL attenuated spleen-derived CAC senescence. In CACs isolated from rHDL-treated aged mice, the phosphorylated mTOR and Akt levels were significantly enhanced. CONCLUSION—rHDL stimulates sustained mTOR phosphorylation and mTOR-rictor complex formation and inhibits senescence onset in CACs through mTOR complex 2 pathway activation.