Vascular endothelial growth factor-mediated induction of manganese superoxide dismutase occurs through redox-dependent regulation of forkhead and IkappaB/NF-kappaB.
The mitochondrial antioxidant manganese superoxide dismutase (Mn-SOD) plays a critical cytoprotective role against oxidative stress. Vascular endothelial growth factor (VEGF) was shown previously to induce expression of Mn-SOD in endothelial cells by a NADPH oxidase-dependent mechanism. The goal of the current study was to determine the transcriptional mechanisms underlying this phenomenon. VEGF resulted in protein kinase C-dependent phosphorylation of IkappaB and subsequent translocation of p65 NF-kappaB into the nucleus. Overexpression of constitutively active IkappaB blocked VEGF stimulation of Mn-SOD. In transient transfection assays, VEGF increased Mn-SOD promoter activity, an effect that was dependent on a second intronic NF-kappaB consensus motif. In contrast, VEGF-mediated induction of Mn-SOD was enhanced by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and by dominant negative Akt and was decreased by constitutively active Akt. Overexpression of a constitutively active (phosphorylation-resistant) form of FKHRL1 (TMFKHRL1) resulted in increased Mn-SOD expression, suggesting that the negative effect of PI3K-Akt involves attenuation of forkhead activity. In co-transfection assays, the Mn-SOD promoter was transactivated by TMFKHRL1. Flavoenzyme inhibitor, diphenyleneiodonium (DPI), and antisense oligonucleotides against p47phox (AS-p47phox) inhibited VEGF stimulation of IkappaB/NF-kappaB and forkhead phosphorylation, supporting a role for NADPH oxidase activity in both signaling pathways. Like VEGF, hepatocyte growth factor (HGF) activated the PI3K-Akt-forkhead pathway. However, HGF-PI3K-Akt-forkhead signaling was insensitive to diphenyleneiodonium and AS-p47phox. Moreover, HGF failed to induce phosphorylation of IkappaB/NF-kappaB or nuclear translocation of NF-kappaB and had no effect on Mn-SOD expression. Together, these data suggest that VEGF is uniquely coupled to Mn-SOD expression through growth factor-specific reactive oxygen species (ROS)-sensitive positive (protein kinase C-NF-kappaB) and negative (PI3K-Akt-forkhead) signaling pathways.
Abid
Md Ruhul
MR
Division of Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. rabid@bidmc.harvard.edu
Schoots
Ivo G
IG
Spokes
Katherine C
KC
Wu
Sheng-Qian
SQ
Mawhinney
Christina
C
Aird
William C
WC
D021581:Active Transport, Cell Nucleus; D002460:Cell Line; D002478:Cells, Cultured; D003331:Coronary Vessels; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D004790:Enzyme Induction / Q000187:drug effects; D051858:Forkhead Transcription Factors; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D010766:Phosphorylation; D013482:Superoxide Dismutase / Q000096:biosynthesis*; D014157:Transcription Factors / Q000378:metabolism*; D014471:Umbilical Veins
D051858:Forkhead Transcription Factors; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D014157:Transcription Factors; D013482:Superoxide Dismutase; D019255:NADPH Oxidases