Glycine and uridine prevent D-galactosamine hepatotoxicity in the rat: role of Kupffer cells.
Extrahepatic factors, such as increased gut permeability and bacteria from the gut, have been shown to play a role in D-galactosamine toxicity in rats. Because bacterial endotoxin activates Kupffer cells, the purpose of this study was to clarify the role of Kupffer cells in the mechanism of D-galactosamine hepatotoxicity in rats and determine whether uridine, a compound that rescues animals from D-galactosamine toxicity, affects Kupffer cells. Rats were fed control or glycine (5%) containing diets to prevent Kupffer cell activation or treated with gadolinium chloride (GdCl3, 20 mg/kg) to destroy Kupffer cells selectively before injection of D-galactosamine (500 mg/kg, intraperitoneally). D-galactosamine caused panlobular focal hepatocellular necrosis, polymorphonuclear cell infiltration, and increased serum transaminases significantly at 24 hours. Dietary glycine or pretreatment with GdCl3 prevented these effects. D-galactosamine caused a transient increase in circulating endotoxin that was maximal at 1 hour and was blunted significantly by dietary glycine. Additionally, antisera to tumor necrosis factor-alpha (TNF-alpha) prevented hepatotoxicity caused by D-galactosamine. Moreover, apoptosis in hepatocytes caused by D-galactosamine occurred before necrosis (6 hours) and was prevented by glycine, GdCl3, TNF-alpha antiserum, and uridine. Thus, it was hypothesized that TNF-alpha from Kupffer cells causes apoptosis after D-galactosamine administration in the rat. Indeed, increases in TNF-alpha messenger RNA (mRNA) were detected as early as 2.5 hours after D-galactosamine treatment. Previous work proposed that uridine blocks D-galactosamine toxicity by preventing inhibition of mRNA synthesis. In view of these results, the possibility that uridine might affect Kupffer cells was investigated. Uridine significantly blunted the increase in [Ca2+]i and release of TNF-alpha caused by endotoxin in isolated Kupffer cells and prevented apoptosis caused by D-galactosamine treatment in vivo. These data support the hypothesis that uridine prevents D-galactosamine hepatotoxicity not only by rescuing the hepatocyte in the late phases of the injury but also preventing TNF-alpha release from Kupffer cells thereby blocking apoptosis that occurs early after D-galactosamine treatment. Taken together, these data strongly support the role of Kupffer cell activation by endotoxin early after D-galactosamine treatment as an important event in the mechanism of hepatotoxicity in the rat.
Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina at Chapel Hill, 27599-7365, USA.
R F
RF
Stachlewitz
V
V
Seabra
B
B
Bradford
C A
CA
Bradham
I
I
Rusyn
D
D
Germolec
R G
RG
Thurman
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002478:Cells, Cultured; D004032:Diet; D004731:Endotoxins / Q000097:blood; D005682:Gadolinium / Q000494:pharmacology; D005688:Galactosamine / Q000037:antagonists & inhibitors* / Q000506:poisoning*; D005998:Glycine / Q000008:administration & dosage / Q000494:pharmacology*; D007106:Immune Sera / Q000494:pharmacology; D007728:Kupffer Cells / Q000187:drug effects / Q000502:physiology*; D008099:Liver / Q000166:cytology / Q000187:drug effects*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D014529:Uridine / Q000494:pharmacology*
D004731:Endotoxins; D007106:Immune Sera; D014409:Tumor Necrosis Factor-alpha; D005688:Galactosamine; D005682:Gadolinium; C038958:gadolinium chloride; D005998:Glycine; D014529:Uridine