AMP-activated protein kinase inhibits homocysteine-induced dysfunction and apoptosis in endothelial progenitor cells.
OBJECTIVE
Homocysteine (Hcy) has been shown to induce oxidative stress and apoptosis of endothelial progenitor cells (EPCs). AMP-activated protein kinase (AMPK) has been reported to have protective effects on endothelial function. However, effects of AMPK activation on Hcy-induced EPCs injury remain to be determined. In this study, we examined the effect of AMPK phosphorylation on Hcy-induced NO bioavailability impairment and NADPH oxidase 4 (Nox4) derived reactive oxygen species (ROS) accumulation in EPCs.


METHODS
EPCs were pre-treated with various concentrations of 5-amino-4-imidazolecarboxamide riboside-l-beta-D-ribofuranoside (AICAR), a pharmacological agonist of AMPK, and then incubated with Hcy for 24 h. Furthermore, we challenged EPCs with Hcy in the presence or absence of atorvastatin and AMPK-DN which expressed a dominant-negative mutant of AMPK. Migration, proliferation and apoptosis were assayed to evaluate EPCs function. NO production, expression of endothelial nitric oxide synthase (eNOS), intracellular ROS levels and Nox4 activation were determined to explore the potential mechanisms of Hcy-induced EPCs dysfunction.


RESULTS
We observed that AICAR attenuated the inhibition effects of Hcy on EPCs migration and proliferation. The apoptosis rates of EPCs were down-regulated by AICAR compared with the group treated with Hcy only [(0.25 mmol/L AICAR: 10.48 ± 1.6%; 0.5 mmol/L AICAR: 8.70 ± 1.0%; 1 mmol/L AICAR: 5.83 ± 1.3%) vs. (500 μmol/L Hcy only: 12.60 ± 1.9%)]. We also found that NO production and eNOS expression were up-regulated by AICAR compared with the group treated with Hcy only, while ROS accumulation and Nox4 activation were inhibited. Furthermore, atorvastatin suppressed Hcy-induced dysfunction of EPCs, increased NO production and eNOS expression, and down-regulated ROS accumulation and Nox4 activation. And these effects of atorvastatin could be blunted by AMPK-DN.


CONCLUSIONS
AMPK activation inhibits eNOS down-regulation and Nox4-derived ROS accumulation induced by Hcy in EPCs, and may contribute to the protective effects of atorvastatin on endothelial function.
Department of Cardiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, People's Republic of China.
Fang
F
Jia
Chunfang
C
Wu
Zhenyue
Z
Chen
Guoping
G
Lu
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D000069059:Atorvastatin; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D006538:Heptanoic Acids / Q000494:pharmacology; D006710:Homocysteine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006801:Humans; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011758:Pyrroles / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D012265:Ribonucleotides / Q000494:pharmacology; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
D006538:Heptanoic Acids; D011758:Pyrroles; D017382:Reactive Oxygen Species; D012265:Ribonucleotides; D006710:Homocysteine; D009569:Nitric Oxide; D000620:Aminoimidazole Carboxamide; D000069059:Atorvastatin; D052250:Nitric Oxide Synthase Type III; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide