Oxidative mitochondrial DNA damage and deletion in hepatocytes of rejecting liver allografts in rats: role of TNF-alpha.
An orthotopic liver transplant model in the rat was used to evaluate the role of tumor necrosis factor alpha (TNF-alpha) in liver transplant rejection. There were significantly increased levels of TNF-alpha mRNA and parallel increases in 8-hydroxy-2' deoxyguanosine (8-OHdG) indicative of oxidative DNA damage present 7 to 12 days after transplantation. Cells staining positively for 8-OHdG were localized to the cytoplasm of hepatocytes adjacent to the TNF-alpha expressing inflammatory cells in the portal areas or in patches surrounded by inflammatory cells in the hepatic sinusoids. Significantly more cells staining for 8-OHdG were found in the allogeneic grafts that were strongly rejected than in the syngeneic controls or in the grafts placed in species that accepted the allograft permanently after a rejection episode. TUNEL reactivity lagged 2 days behind peak reactivity for 8-OHdG. On day 12 after transplantation, many cells stained for both 8-OHdG and TUNEL, indicating that the cells suffering oxidative DNA injury were undergoing apoptosis or death. Oxidative injury resulted in mtDNA deletion consisting of 4,834 base-pairs. Studies of hepatocytes cultured from normal rats displayed dose-dependent relationships between TNF-alpha concentration and 8-OHdG and mtDNA mutation. Repetitive intraperitoneal injection of Enbrel, a TNF receptor blocker, significantly decreased hepatocyte 8-OHdG levels and the frequency of deleted mtDNA while greatly extending graft survival time. In conclusion, the data presented implicate TNF-alpha as being capable of causing oxidative DNA damage and mtDNA mutation in hepatocytes.
Nagakawa
Yuichi
Y
Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Williams
George Melville
GM
Zheng
Qizhi
Q
Tsuchida
Akihiko
A
Aoki
Tatsuya
T
Montgomery
Robert A
RA
Klein
Andrew S
AS
Sun
Zhaoli
Z
D000818:Animals; D004249:DNA Damage / Q000276:immunology*; D004272:DNA, Mitochondrial / Q000276:immunology*; D006084:Graft Rejection / Q000276:immunology*; D022781:Hepatocytes / Q000276:immunology; D016031:Liver Transplantation / Q000009:adverse effects / Q000276:immunology*; D023421:Models, Animal; D009154:Mutation; D018384:Oxidative Stress / Q000276:immunology; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology*
D004272:DNA, Mitochondrial; D014409:Tumor Necrosis Factor-alpha