KLF2 primes the antioxidant transcription factor Nrf2 for activation in endothelial cells.
OBJECTIVE
Atheroprotective blood flow induces expression of anti-inflammatory Krüppel-like factor 2 (KLF2) and activates antioxidant transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) in vascular endothelium. Previously, we obtained KLF2-induced gene expression profiles in ECs, containing several Nrf2 target genes. Our aim was to investigate the role of KLF2 in shear stress-mediated activation of Nrf2 in human umbilical vein endothelial cells (HUVECs).


RESULTS
Expression of Nrf2 and its targets NAD(P)H dehydrogenase quinone 1 (NQO1) and heme oxygenase (HO-1) was elevated by shear and KLF2. KLF2 knockdown showed that shear-induced expression of NQO1 but not Nrf2 was dependent on KLF2. KLF2 overexpression in absence of flow resulted in more efficient activation of Nrf2 by tert-butyl hydroquinone (tBHQ) through enhanced nuclear localization, and promoted expression of a large panel of Nrf2-dependent genes resulting in superior protection against oxidative stress. Comparison of shear-, KLF2-, and Nrf2-induced transcriptomes showed that the majority of shear-modulated gene sets is influenced by KLF2 or Nrf2.


CONCLUSIONS
We report that KLF2 substantially enhances antioxidant activity of Nrf2 by increasing its nuclear localization and activation. The synergistic activity of these two transcription factors forms a major contribution to the shear stress-elicited transcriptome in endothelial cells.
Fledderus
Joost O
JO
Department of Molecular Cell Biology and Immunology, Room B244, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands.
Boon
Reinier A
RA
Volger
Oscar L
OL
Hurttila
Hanna
H
Ylä-Herttuala
Seppo
S
Pannekoek
Hans
H
Levonen
Anna-Liisa
AL
Horrevoets
Anton J G
AJ
D021581:Active Transport, Cell Nucleus; D000975:Antioxidants / Q000378:metabolism*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004790:Enzyme Induction; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks; D051547:Heme Oxygenase-1 / Q000096:biosynthesis; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000096:biosynthesis; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D011673:Pulsatile Flow; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D013314:Stress, Mechanical; D014162:Transfection; D015854:Up-Regulation; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
D000975:Antioxidants; C096161:KLF2 protein, human; D051741:Kruppel-Like Transcription Factors; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D016877:Oxidants; D034741:RNA, Small Interfering; D020122:tert-Butylhydroperoxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human