Cytokine induction of interferon regulatory factor-1 in hepatocytes.
BACKGROUND
Interferon regulatory factor-1 (IRF-1) is a transcriptional factor originally cloned from fibroblasts that activates interferons and certain interferon-responsive genes. Because IRF-1 is an "early-immediate" nuclear protein, it can function acutely after trauma or septic stimuli. We have identified IRF-1 expression in hepatocytes in vivo in sepsis. The purpose of this study was to characterize the cytokine signals that up-regulate IRF-1 messenger RNA (mRNA) in cultured hepatocytes.


METHODS
Rat hepatocytes were isolated by in situ collagenase perfusion and stimulated in vitro with cytokines. IRF-1 mRNA levels were determined by Northern blot hybridization with a DNA probe for hepatocyte IRF-1 generated with reverse transcription polymerase chain reaction with custom-designed oligonucleotide primers based on the known sequence for T-cell IRF-1.


RESULTS
Northern blot of hepatocyte RNA showed a single IRF-1 mRNA band at approximately 2.4 Kb. The mRNA levels were markedly up-regulated (vs control hepatocytes) 2 hours after in vitro stimulation with the cytokines interferon-gamma (17-fold), tumor necrosis factor-alpha (3-fold), and interleukin-1 beta (2-fold). Lipopolysaccharide had no direct effect.


CONCLUSIONS
The results showed that IRF-1 is up-regulated in hepatocytes primarily in response to interferon-gamma and to a lesser extent after tumor necrosis factor-alpha or interleukin-1 beta stimulation. This suggests that IRF-1 plays a role in regulating liver gene expression in sepsis; however, the specific genes controlled by IRF-1 remain to be determined.
Geller
D A
DA
Department of Surgery, University of Pittsburgh, PA 15261.
Nguyen
D
D
Shapiro
R A
RA
Nussler
A
A
Di Silvio
M
M
Freeswick
P
P
Wang
S C
SC
Tweardy
D J
DJ
Simmons
R L
RL
Billiar
T R
TR
D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D050856:Interferon Regulatory Factor-1; D007372:Interferons / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008297:Male; D010750:Phosphoproteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000096:biosynthesis*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D016207:Cytokines; D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D007375:Interleukin-1; C494259:Irf1 protein, rat; D010750:Phosphoproteins; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D007372:Interferons