Health & Environmental Research Online (HERO)


Print Feedback Export to File
975872 
Journal Article 
Abstract 
Hypoxia decreases nitric oxide production by lipopolysaccharide stimulated macrophages 
Barson, R; Cui, HM; Jin, Y; Liu, YS; Nelin, LD 
2008 
Yes 
Free Radical Biology and Medicine
ISSN: 0891-5849
EISSN: 1873-4596 
45 
Suppl. 
S132-S132 
English 
WOS:000260867900372 
is part of a larger document 3452652 SFRBM's 15th Annual Meeting: Program and Abstracts
Oxygen is a co-factor in nitric oxide (NO) production from NO synthases (NOS). We hypothesized that hypoxia may limit NO production by inducible NOS (iNOS) in macrophages. to test this hypothesis we studied RAW 264.7 cells grown in either 21% O2/5% CO2 (normoxia) or 1% O2/5% CO2 (hypoxia). After stimulation with lipopolysaccharide (LPS) production of NO after 24 h was lower in the cells incubated in hypoxia than in the cells incubated in normoxia (309 ± 28 vs 106 ± 4 nmol/mg protein, p<0.005). the levels of NO production after 24 h in non-LPS stimulated cells was very low in both hypoxia and normoxia and did not differ between the groups (5 ± 1 vs 3 ± 1, p = 0.23). Despite the lower NO production seen in hypoxia, the LPS-stimulated iNOS protein levels by Western blot were actually greater in the cells incubated in hypoxia than in normoxia (densitometry values normalized to β-actin, 3.1 ± 0.2 normoxia vs 5.0 ± 0.4 hypoxia, p<0.05). LPS stimulated RAW 264.7 cells were then incubated for 24 h in either normoxia or hypoxia, washed, given fresh media, and then incubated for an additional 24 h in either the other condition or continued in the same condition. The LPS-stimulated cells that were incubated for 48 h in hypoxia had significantly lower levels of NO production than did those cells incubated for 48 h in normoxia (84 ± 5 versus 446 ± 77 nmol/mg protein, p<0.01). LPS-stimulated cells that were incubated in normoxia for 24 h followed by hypoxia for 24 h had lower (p<0.05) levels of NO production (105 ± 33 nmol/mg protein), while cells that were incubated for 24 hours in hypoxia followed by 24 h in normoxia had similar levels of NO production (612 ± 50 nmol/mg protein), compared to those cells that were incubated in normoxia for 48 h. the levels of iNOS protein were greatest (p<0.001 compared to the other 3 groups) in the cells incubated for 48 h in hypoxia, and the cells incubated for 24 h of hypoxia followed by 24 h of normoxia had higher (p<0.05) levels of iNOS protein than did cells incubated for 48 h in normoxia. These results suggest that hypoxia decreases NO production in a macrophage cell line stimulated with LPS, but that iNOS protein expression is actually increased by hypoxia. These data may have important implications for host defense when hypoxia is super-imposed on infection. 
Society for Free Radical Biology and Medicine 15th Annual Meeting 
Indianapolis, IN 
November 19-23, 2008