[Effect of melatonin on the proliferation, apoptosis, and expression of bcl-2 in oxidized low-density lipoprotein-induced endothelial progenitor cells].
OBJECTIVE
To explore the effect of melatonin(Mel) on the proliferation, apoptosis and expression of bcl-2 in oxidized low-density lipoprotein(ox-LDL)-induced endothelial progenitor cells (EPC) from human umbilical cord blood in vitro.


METHODS
Total mononuclear cells were isolated from human umbilical cord blood in vitro by Ficoll density gradient centrifugation, and the cells were plated on fibronectin-coated culture dishes. After 7 days, the attached cells were divided into 7 groups: a control group (normal cells), 3 ox-LDL groups[the attached cells were incubated with different concentrations of ox-LDL(5,10,and 20mg/L) for 24 hours], and 3 Mel groups[the attached cells were incubated with different concentrations of Mel (0.5,1.0, and 2.0 mmol/L) respectively for 24 hours before incubation with 10 mg/L ox-LDL]. EPC was identified by examining the expression of CD34, vascular endothelial growth factor receptor-2(VEGFR-2) and CD133 under a laser scanning confocal microscope. We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to detect the effect of Mel and ox-LDL on the multiplication ability of EPC. Flow cytometry was used to detect the apoptosis. The expressions of Bcl-2 mRNA and protein were detected respectively by RT-PCR and immunohistochemistry technology.


RESULTS
After being exposed to the ox-LDL, the proliferation of EPC in the 3 ox-LDL groups was lower, and the apoptosis rate was higher than that in the control group in a dose-dependent manner (P<0.01); Mel was added at different concentrations before the ox-LDL incubation, and the cells in the 3 Mel groups showed higher proliferation and lower apoptosis rate than those of the 3 ox-LDL groups (P<0.01). Expression of Bcl-2 mRNA and protein of EPC in the 3 Mel groups was higher than that in the 3 ox-LDL groups (P<0.01).


CONCLUSIONS
Ox-LDL can inhibit the proliferation of EPC and promote the apoptosis of the cells by down-regulating the bcl-2 expression. Mel can inhibit these effects of ox-LDL.
Li
Xiu-li
XL
Department of Cardiology, Xiangya Hospital, Central South University, Changsha 410008, China. lixiuli791@sina.com
Xie
Xiu-mei
XM
Chen
Xiao-bin
XB
He
Jin
J
Fang
Ye-qing
YQ
D017209:Apoptosis / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D008077:Lipoproteins, LDL / Q000009:adverse effects; D008550:Melatonin / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects*
D008077:Lipoproteins, LDL; D019253:Proto-Oncogene Proteins c-bcl-2; C099252:oxidized low density lipoprotein; D008550:Melatonin