Nitric oxide decreases the sensitivity of pulmonary endothelial cells to LPS-induced apoptosis in a zinc-dependent fashion.
We hypothesized that: (a) S-nitrosylation of metallothionein (MT) is a component of pulmonary endothelial cell nitric oxide (NO) signaling that is associated with an increase in labile zinc; and (b) NO mediated increases in labile zinc in turn reduce the sensitivity of pulmonary endothelium to LPS-induced apoptosis. We used microspectrofluorometric techniques to show that exposing mouse lung endothelial cells (MLEC) to the NO-donor, S-nitrosocysteine, resulted in a 45% increase in fluorescence of the Zn2+-specific fluorophore, Zinquin, that was rapidly reversed by exposure to the Zn2+ chelator, NNN'N'-tetrakis-(2-pyridylmethyl)ethylenediamine; TPEN). The absence of a NO-mediated increase in labile Zn2+ in MLEC from MT-I and -II knockout mice inferred a critical role for MT in the regulation of Zn2+ homeostasis by NO. Furthermore, we found that prior exposure of cultured endothelial cells from sheep pulmonary artery (SPAEC), to the NO-donor, S-nitroso-N-acetylpenicillamine (SNAP) reduced their sensitivity to lipopolysaccharide (LPS) induced apoptosis. The anti-apoptotic effects of NO were significantly inhibited by Zn2+ chelation with low doses of TPEN (10 microM). Collectively, these data suggest that S-nitrosylation of MT is associated with an increase in labile (TPEN chelatable) zinc and NO-mediated MT dependent zinc release is associated with reduced sensitivity to LPS-induced apoptosis in pulmonary endothelium.
Tang
Zi-Lue
ZL
Department of Environmental and Occupational Health, The Graduate School of Public Health, University of Pittsburgh, PA 15260, USA.
Wasserloos
Karla J
KJ
Liu
Xianghong
X
Stitt
Molly S
MS
Reynolds
Ian J
IJ
Pitt
Bruce R
BR
St Croix
Claudette M
CM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004727:Endothelium / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung; D008668:Metallothionein / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology*; D011651:Pulmonary Artery; D012756:Sheep; D013997:Time Factors; D015032:Zinc / Q000378:metabolism*
D008070:Lipopolysaccharides; D009569:Nitric Oxide; D008668:Metallothionein; D015032:Zinc