title: Electronegative LDL circulating in smokers impairs endothelial progenitor cell differentiation by inhibiting Akt phosphorylation via LOX-1.
abstract: Endothelial progenitor cells (EPCs), important for endothelial regeneration and vasculogenesis, are reduced by cigarette smoking. To elucidate the mechanisms, we examined the effects of electronegative LDL, circulating in chronic smokers, on EPC differentiation. Using ion-exchange chromatography, we purified smoker LDL into five subfractions, L1-L5. In matched, nonsmoking healthy subjects, L5, the most electronegative subfraction, was either absent or scanty. Sustained L5 treatment inhibited CD31 and KDR expression and EPC differentiation, whereas L1-L4 had no effect. L5 also inhibited telomerase activity to accelerate EPC senescence in correlation with reduced Akt phosphorylation. Transfection of day 3 EPCs with dominant negative Akt constructs inhibited CD31 and KDR expression, stalled EPC differentiation, and promoted early senescence. In contrast, transfection with constitutively active Akt rendered the EPCs resistant to L5, allowing normal maturation. L5 upregulated the lectin-like oxidized low density lipoprotein receptor 1 (LOX-1), and pretreatment of EPCs with TS20, a LOX-1-neutralizing antibody, blocked internalization of L5 by EPCs and prevented L5-mediated inhibition of EPC differentiation. Mixing L5 with L1 to physiological L5/L1 ratios did not attenuate L5's effects. These findings suggest that cigarette smoking is associated with the formation of L5, which inhibits EPC differentiation by impairing Akt phosphorylation via the LOX-1 receptor.
authors.affiliation: Department of Medicine, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Daming
authors.initials: D
authors.lastname: Tang
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lu
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Walterscheid
authors.forename: Hsin-Hung
authors.initials: HH
authors.lastname: Chen
authors.forename: David A
authors.initials: DA
authors.lastname: Engler
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sawamura
authors.forename: Po-Yuan
authors.initials: PY
authors.lastname: Chang
authors.forename: Hazim J
authors.initials: HJ
authors.lastname: Safi
authors.forename: Chao-Yuh
authors.initials: CY
authors.lastname: Yang
authors.forename: Chu-Huang
authors.initials: CH
authors.lastname: Chen
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000502:physiology; D002454:Cell Differentiation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism; D005260:Female; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051127:Scavenger Receptors, Class E / Q000378:metabolism*; D012907:Smoking / Q000009:adverse effects*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D001616:beta-Galactosidase / Q000032:analysis
chemical_list: D008077:Lipoproteins, LDL; D051127:Scavenger Receptors, Class E; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D051057:Proto-Oncogene Proteins c-akt; D001616:beta-Galactosidase