Prolonged shear stress and KLF2 suppress constitutive proinflammatory transcription through inhibition of ATF2.
Absence of shear stress due to disturbed blood flow at arterial bifurcations and curvatures leads to endothelial dysfunction and proinflammatory gene expression, ultimately resulting in atherogenesis. KLF2 has recently been implicated as a transcription factor involved in mediating the anti-inflammatory effects of flow. We investigated the effect of shear on basal and TNF-alpha-induced genomewide expression profiles of human umbilical vein endothelial cells (HUVECs). Cluster analysis confirmed that shear stress induces expression of protective genes including KLF2, eNOS, and thrombomodulin, whereas basal expression of TNF-alpha-responsive genes was moderately decreased. Promoter analysis of these genes showed enrichment of binding sites for ATF transcription factors, whereas TNF-alpha-induced gene expression was mostly NF-kappaB dependent. Furthermore, human endothelial cells overlying atherosclerotic plaques had increased amounts of phosphorylated nuclear ATF2 compared with endothelium at unaffected sites. In HUVECs, a dramatic reduction of nuclear binding activity of ATF2 was observed under shear and appeared to be KLF2 dependent. Reduction of ATF2 with siRNA potently suppressed basal proinflammatory gene expression under no-flow conditions. In conclusion, we demonstrate that shear stress and KLF2 inhibit nuclear activity of ATF2, providing a potential mechanism by which endothelial cells exposed to laminar flow are protected from basal proinflammatory, atherogenic gene expression.
Fledderus
Joost O
JO
Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
van Thienen
Johannes V
JV
Boon
Reinier A
RA
Dekker
Rob J
RJ
Rohlena
Jakub
J
Volger
Oscar L
OL
Bijnens
Ann-Pascale J J
AP
Daemen
Mat J A P
MJ
Kuiper
Johan
J
van Berkel
Theo J C
TJ
Pannekoek
Hans
H
Horrevoets
Anton J G
AJ
D051698:Activating Transcription Factor 2 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D050197:Atherosclerosis / Q000235:genetics*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D016000:Cluster Analysis; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000235:genetics*; D051741:Kruppel-Like Transcription Factors / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D013314:Stress, Mechanical; D013997:Time Factors; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; C096161:KLF2 protein, human; D051741:Kruppel-Like Transcription Factors; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D011494:Protein Kinases