Effect of nitric oxide on heme metabolism in pulmonary artery endothelial cells.
Primary intracellular targets for nitric oxide (NO) include nonheme iron-containing enzymes and protein-bound iron. Because NO is an important effector molecule in lung inflammation and endothelial cell-associated iron is critical to numerous forms of oxidant-mediated lung injury, we studied the effects of the NO donor S-nitrosoacetylpenicillamine (SNAP) on heme and iron metabolism in cultured sheep pulmonary artery endothelial cells. SNAP (300 microM) caused a transient increase in heme oxygenase-1 (HO-1) mRNA associated with a fivefold increase in HO activity that was completely blocked by the competitive HO inhibitor, tin protoporphyrin IX (SnPP). SNAP-induced activation of HO caused SnPP-sensitive reduction of activity of the hemoprotein catalase and decrease in heme iron. SNAP caused increases in iron-responsive gene products, ferritin and mitochondrial aconitase, secondary to the release of iron from heme stores via HO induction, since these changes were also sensitive to SNPP. The NO-induced increase in nonheme iron was apparent via electron paramagnetic resonance, where an enhanced SNAP-induced (300 microM for 4 h) g = 2.04 signal (e.g., dinitrosyl-iron-sulfur complex) was noted after exposure to a dose of SNAP (200 microM for 14 h) that in itself did not produce a detectable signal. These data show that exposure of pulmonary endothelial cells to NO results in profound changes in intracellular heme- and nonheme-iron homeostasis and that HO plays a central role in affecting this balance.
Department of Pharmacology, University of Pittsburgh School of Medicine, Pennsylvania 15261, USA.
E L
EL
Yee
B R
BR
Pitt
T R
TR
Billiar
Y M
YM
Kim
D000818:Animals; D002374:Catalase / Q000378:metabolism; D002478:Cells, Cultured; D004578:Electron Spin Resonance Spectroscopy; D004730:Endothelium, Vascular / Q000378:metabolism*; D005293:Ferritins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism; D006418:Heme / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics*; D007501:Iron / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D009603:Nitroso Compounds / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology; D012333:RNA, Messenger / Q000378:metabolism; D026422:S-Nitrosoglutathione; D012756:Sheep
D009603:Nitroso Compounds; D012333:RNA, Messenger; D009569:Nitric Oxide; D006418:Heme; D026422:S-Nitrosoglutathione; D005293:Ferritins; D007501:Iron; D002374:Catalase; D006419:Heme Oxygenase (Decyclizing); D005978:Glutathione