title: mTOR complex 2 activation by reconstituted high-density lipoprotein prevents senescence in circulating angiogenic cells.
abstract: 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.
  
  
  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.
  
  
  CONCLUSIONS
  rHDL stimulates sustained mTOR phosphorylation and mTOR-rictor complex formation and inhibits senescence onset in CACs through mTOR complex 2 pathway activation.
authors.affiliation: Department of Pathology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, People's Republic of China.
authors.forename: Xianrong
authors.initials: X
authors.lastname: Guo
authors.forename: Miao
authors.initials: M
authors.lastname: Yu
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Kang
authors.forename: Hongchao
authors.initials: H
authors.lastname: Yin
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D002478:Cells, Cultured; D016922:Cellular Senescence; D006801:Humans; D008075:Lipoproteins, HDL / Q000494:pharmacology*; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D008810:Mice, Inbred C57BL; D046912:Multiprotein Complexes; D018919:Neovascularization, Physiologic; D010766:Phosphorylation; D011506:Proteins / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism
chemical_list: D008075:Lipoproteins, HDL; D046912:Multiprotein Complexes; D011506:Proteins; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C509186:TERT protein, human; D019098:Telomerase; D020123:Sirolimus