Heme oxygenase activity modulates vascular endothelial growth factor synthesis in vascular smooth muscle cells.
Hypoxia, cytokines, and nitric oxide (NO) stimulate the generation of vascular endothelial growth factor (VEGF) and induce heme oxygenase-1 (HO-1) expression in vascular tissue. HO-1 degrades heme to carbon monoxide (CO), iron, and biliverdin, the latter being reduced to bilirubin by biliverdin reductase. In the present study, we investigated the role of HO-1 in the modulation of VEGF synthesis in rat vascular smooth muscle cells (VSMC). In VSMC stimulated with cytokines, inhibition of NO production significantly, but not completely, reduced VEGF release. In contrast, inhibition of HO activity by tin protoporphyrin IX (SnPPIX) totally prevented cytokine-induced increase in VEGF, despite an augmented synthesis of intracellular NO. Stimulation of HO-1 activity by hemin enhanced VEGF production; this effect was abrogated by blockade of the HO pathway. Similarly, VEGF synthesis induced by hypoxia was down-regulated by SnPPIX, but not by inhibitors of NO synthase. To elucidate further a direct involvement of HO-1 in the observed effects, we generated transfected cells that overexpressed the HO-1 gene. Notably, these cells synthesized significantly more VEGF protein than cells transfected with a control gene. Among the products of HO-1, biliverdin and bilirubin showed no effect, whereas iron ions inhibited VEGF synthesis. Exposure of cells to 1% CO resulted in a marked accumulation of VEGF (20-fold increase) over the basal level. Our data indicate that HO-1 activity influences the generation of VEGF in VSMC in both normoxic and hypoxic conditions. As CO and iron, respectively the inducer and the inhibitor of VEGF synthesis, are concomitantly produced during the degradation of heme, these data indicate that HO by-products may differentially modulate VEGF production.
Dulak
Jozef
J
Division of Cardiology, Innsbruck University, Innsbruck, Austria. jdulak@mol.uj.edu.pl
Józkowicz
Alicja
A
Foresti
Roberta
R
Kasza
Aneta
A
Frick
Matthias
M
Huk
Ihor
I
Green
Colin J
CJ
Pachinger
Otmar
O
Weidinger
Franz
F
Motterlini
Roberto
R
D000818:Animals; D001663:Bilirubin / Q000378:metabolism; D001664:Biliverdine / Q000378:metabolism; D002478:Cells, Cultured; D003676:Deferoxamine / Q000494:pharmacology; D016228:Endothelial Growth Factors / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1; D006427:Hemin / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D007501:Iron / Q000494:pharmacology; D008222:Lymphokines / Q000235:genetics*; D008665:Metalloporphyrins / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D011524:Protoporphyrins / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D008222:Lymphokines; D008665:Metalloporphyrins; D011524:Protoporphyrins; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D006427:Hemin; C032628:tin protoporphyrin IX; D007501:Iron; D019001:Nitric Oxide Synthase; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D003676:Deferoxamine; D001664:Biliverdine; D001663:Bilirubin; D019331:NG-Nitroarginine Methyl Ester