Acute hypoxia increases alveolar macrophage tumor necrosis factor activity and alters NF-kappaB expression.
Alterations in alveolar macrophage (AM) function during sepsis-induced hypoxia may influence tumor necrosis factor (TNF) secretion and the progression of acute lung injury. Nuclear factor (NF)-kappaB is thought to regulate the expression of endotoxin [lipopolysaccharide (LPS)]-induced inflammatory cytokines such as TNF, and NF-kappaB may also be influenced by changes in O2 tension. It is thus proposed that acute changes in O2 tension surrounding AMs alter NF-kappaB activation and TNF secretion in these lung cells. AM-derived TNF secretion and NF-kappaB expression were determined after acute hypoxic exposure of isolated Sprague-Dawley rat AMs. Adhered AMs (10(6)/ml) were incubated (37 degrees C at 5% CO2) for 2 h with LPS (Pseudomonas aeruginosa, 1 microgram/ml) in normoxia (21% O2-5% CO2) or hypoxia (1.8% O2-5% CO2). AM-derived TNF activity was measured with a TNF-specific cytotoxicity assay. Electrophoretic mobility shift and supershift assays were used to determine NF-kappaB activation and to identify NF-kappaB isoforms in AM extracts. In addition, mRNAs for selected AM proteins were determined with RNase protection assays. LPS-exposed AMs in hypoxia had higher levels of TNF (P < 0.05) and enhanced expression of NF-kappaB (P < 0.05); the predominant isoforms were p65 and c-Rel. Increased mRNA bands for TNF-alpha, interleukin-1alpha, and interleukin-1beta were also observed in the hypoxic AMs. These results suggest that acute hypoxia in the lung may induce enhanced NF-kappaB activation in AMs, which may result in increased production and release of inflammatory cytokines such as TNF.
Leeper-Woodford
S K
SK
Department of Physiology, Mercer University School of Medicine, Macon, Georgia 31207, USA. leeper.sk@gain.mercer.edu
Detmer
K
K
D000208:Acute Disease; D000818:Animals; D016207:Cytokines / Q000235:genetics; D004247:DNA / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D016676:Macrophages, Alveolar / Q000378:metabolism*; D008297:Male; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016207:Cytokines; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D004247:DNA