LPS increases hepatic HIF-1alpha protein and expression of the HIF-1-dependent gene aldolase A in rats.
BACKGROUND
Cellular adaptation to hypoxia is mediated in part by the transcription factor hypoxia-inducible factor 1 (HIF-1). Accumulating data suggest that pro-inflammatory mediators can up-regulate HIF-1alpha protein expression and HIF-1 DNA-binding activity in the absence of hypoxia. Accordingly, we investigated HIF-1 mediated signaling in endotoxemic rats.


METHODS
We studied three groups of male Sprague Dawley rats. Controls (N = 5) were injected i.p. with saline. Endotoxemic rats (N = 9) received a sublethal dose of lipopolysaccaride (Escherichia coli; 5 mg/kg, i.p.). A third group of rats (N = 5) received the HIF-1 stabilizing agent CoCl(2) (14 mg/kg, i.p.) at T = 0 h and T = 16 h. At T = 18 h, liver microvascular perfusion was measured using laser Doppler flowmetry and hepatic tissue samples were obtained. RNA was isolated and mRNA levels of the HIF-1 dependent genes aldolase A and vascular endothelial growth factor (VEGF) were determined using quantitative real-time RT-PCR. HIF-1alpha content was estimated by immunoprecipitation followed by Western blotting.


RESULTS
HIF-1alpha increased in hepatic tissue after treatment with LPS or CoCl(2). LPS markedly increased hepatic expression of aldolase A, but failed to alter expression of VEGF. CoCl(2) increased aldolase A and VEGF mRNA expression. Although hepatic microvascular perfusion was comparable in saline- and LPS-treated rats, hepatic microvascular blood flow and aldolase A expression were significantly inversely correlated among endotoxemic rats (r = 0.773; P = 0.003).


CONCLUSIONS
Increased expression of aldolase A in endotoxemic rats is mediated by both hypoxia-dependent and hypoxia-independent mechanisms.
Scharte
Marion
M
Department of Anesthesiology and Critical Care Medicine, University Hospital Muenster, Muenster, Germany. scharte@anit.uni-muenster.de
Han
Xianonan
X
Uchiyama
Takashi
T
Tawadrous
Zakaria
Z
Delude
Russell L
RL
Fink
Mitchell P
MP
D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D015687:Cell Hypoxia / Q000502:physiology; D017931:DNA Primers; D005634:Fructose-Bisphosphate Aldolase / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D047468:Immunoprecipitation; D017078:Laser-Doppler Flowmetry; D008070:Lipopolysaccharides / Q000633:toxicity*; D008099:Liver / Q000098:blood supply / Q000473:pathology; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D017931:DNA Primers; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D005634:Fructose-Bisphosphate Aldolase