Nitric oxide production by hepatocytes contributes to the inhibitory effect of endotoxin on insulin-like growth factor I gene expression.
We tested whether endotoxin (lipopolysaccharide, LPS) inhibits IGF-I gene expression in hepatocytes and the possible role of Kupffer cells and nitric oxide (NO) in this effect. LPS decreased IGF-I mRNA in hepatocyte cultures and increased the nitrite + nitrate levels in the culture medium. Furthermore, there was a negative correlation between the IGF-I mRNA and the nitrite+nitrate levels. When hepatocytes were cocultured with Kupffer cells, the inhibitory effect of LPS on IGF-I mRNA was higher than in hepatocyte cultures, but the stimulatory effect on nitrite+nitrate was similar in both conditions. The exogenous NO donated by S-nitroso-n-acetyl-d,l-penicillamide also decreased the IGF-I gene expression in hepatocyte cultures. In addition, two specific inducible NO synthase (iNOS) inhibitors, l-N6-(1-iminoethyl)lysine (l-NIL) and aminoguanidine, prevented the effect of LPS on nitrite+nitrate levels and on IGF-I gene expression in hepatocyte cultures. These data indicate that iNOS-derived NO may cause downregulation of IGF-I gene expression in hepatocytes. However, in cocultures, the iNOS inhibitor l-NIL prevented the effect of LPS on nitrite+nitrate levels, but only attenuated the LPS-induced decrease in IGF-I gene expression. We conclude that in hepatocytes, LPS-induced decrease in IGF-I is mainly due to induction of iNOS, whereas in the presence of Kupffer cells LPS inhibits IGF-I through NO release and through other inhibitory pathways.
Priego
Teresa
T
Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, Madrid 28040, Spain.
Granado
Miriam
M
Castillero
Estibaliz
E
Martín
Ana Isabel
AI
Villanúa
M Angeles
MA
López-Calderón
Asunción
A
D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D002478:Cells, Cultured; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D006146:Guanidines / Q000494:pharmacology; D022781:Hepatocytes / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007728:Kupffer Cells / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors; D009573:Nitrites / Q000378:metabolism; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D004731:Endotoxins; D006146:Guanidines; D008070:Lipopolysaccharides; D009566:Nitrates; D020030:Nitric Oxide Donors; D009573:Nitrites; D012333:RNA, Messenger; C110881:S-nitro-N-acetylpenicillamine; D009569:Nitric Oxide; D007334:Insulin-Like Growth Factor I; D052247:Nitric Oxide Synthase Type II; D010396:Penicillamine; C004479:pimagedine