Pre-exposure to hypoxia or septic stimuli differentially regulates endotoxin release of tumor necrosis factor, interleukin-6, interleukin-1, prostaglandin E2, nitric oxide, and superoxide by macrophages.
Shock states with resulting inadequate cellular oxygen delivery may contribute to macrophage (M phi) activation or dysregulation. In this study we compared the effects of transient anoxia and endotoxin pretreatment (LPS1) on M phi mediator release with a second endotoxin stimulus (LPS2).


METHODS
In vitro cultures of murine peritoneal exudate M phi were exposed to 2 hours of hypoxic or normoxic conditions, then incubated 22 hours under identical normoxic conditions +/- 10 ng/mL of LPS1 pretreatment. During the final 24 hours all M phis were exposed to a range of LPS2 concentrations. The M phi supernatants were assayed for tumor necrosis factor (TNF), interleukin 1 (IL-1), interleukin 6 (IL-6), prostaglandin E2 (PGE2), nitric oxide (NO), and superoxide release.


RESULTS
LPS1 markedly inhibited M phi TNF release by LPS2, but hypoxia had no effect on LPS2-triggered TNF release. Hypoxia increased M phi IL-6 production in the absence of LPS1, but inhibited the LPS1 augmentation seen under normoxic conditions. Pretreatment with LPS1 increased NO production from LPS2 under normoxic conditions, but hypoxia inhibited this effect. Superoxide production increased by LPS1 under normoxic conditions, but hypoxia significantly inhibited superoxide release.


CONCLUSIONS
The effects of transient anoxic exposure on LPS2-triggered M phi function are markedly different from the effects of pretreatment with septic stimuli (LPS1).
Department of Surgery, Hennepin County Medical Center, University of Minnesota, Minneapolis 55415.
M A
MA
West
M H
MH
Li
S C
SC
Seatter
M P
MP
Bubrick
D000704:Analysis of Variance; D000818:Animals; D015687:Cell Hypoxia / Q000502:physiology*; D016207:Cytokines / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism*; D004926:Escherichia coli; D066298:In Vitro Techniques; D007378:Interleukins / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009569:Nitric Oxide / Q000378:metabolism; D010087:Oxides / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016207:Cytokines; D007378:Interleukins; D008070:Lipopolysaccharides; D010087:Oxides; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D009569:Nitric Oxide; D015232:Dinoprostone