Activation of the AMPK-FOXO3 pathway reduces fatty acid-induced increase in intracellular reactive oxygen species by upregulating thioredoxin.
OBJECTIVE
Oxidative stress induced by free fatty acids contributes to the development of cardiovascular diseases in patients with metabolic syndrome. Reducing oxidative stress may attenuate these pathogenic processes. Activation of AMP-activated protein kinase (AMPK) has been reported to reduce intracellular reactive oxygen species (ROS) levels. The thioredoxin (Trx) system is a major antioxidant system. In this study, we investigated the mechanisms involved in the AMPK-mediated regulation of Trx expression and the reduction of intracellular ROS levels.


METHODS
We observed that activation of AMPK by 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) significantly reduced ROS levels induced by palmitic acid in human aortic endothelial cells. Activation of AMPK increased expression of the antioxidant Trx, which mediated the ROS reduction. RT-PCR showed that AMPK regulated Trx at the transcriptional level.


RESULTS
Forkhead transcription factor 3 (FOXO3) was identified as the target transcription factor involved in the upregulation of Trx expression. FOXO3 bound to the Trx promoter, recruited the histone acetylase p300 to the Trx promoter, and formed a transcription activator complex, which was enhanced by AICAR treatment. AMPK activated FOXO3 by promoting its nuclear translocation. We further showed that AICAR injection increased the expression of Trx and decreased ROS production in the aortic wall of ApoE-/- mice fed a high-fat diet.


CONCLUSIONS
These results suggest that activation of the AMPK-FOXO3 pathway reduces ROS levels by inducing Trx expression. Thus, the AMPK-FOXO3-Trx axis may be an important defense mechanism against excessive ROS production induced by metabolic stress and could be a therapeutic target in treating cardiovascular diseases in metabolic syndrome.
Li
Xiao-Nan
XN
Division of Cardiothoracic Surgery, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, USA.
Song
Jun
J
Zhang
Lin
L
LeMaire
Scott A
SA
Hou
Xiaoyang
X
Zhang
Cheng
C
Coselli
Joseph S
JS
Chen
Li
L
Wang
Xing Li
XL
Zhang
Yun
Y
Shen
Ying H
YH
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D001057:Apolipoproteins E / Q000172:deficiency / Q000235:genetics; D017931:DNA Primers; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005227:Fatty Acids / Q000494:pharmacology*; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D019308:Palmitic Acid / Q000494:pharmacology*; D010957:Plasmids / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012265:Ribonucleotides / Q000494:pharmacology; D013879:Thioredoxins / Q000235:genetics*; D015854:Up-Regulation
D001057:Apolipoproteins E; D017931:DNA Primers; C499517:FOXO3 protein, human; D005227:Fatty Acids; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D012265:Ribonucleotides; D019308:Palmitic Acid; D000620:Aminoimidazole Carboxamide; D013879:Thioredoxins; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide