Immunostimulatory CpG-oligodeoxynucleotides (CpG-ODN) induce early hepatic injury, but provide a late window for protection against endotoxin-mediated liver damage.
OBJECTIVE
An impaired immunologic response to infection has been recognized as a major defect in the pathogenesis of sepsis and multi-organ failure. Sepsis-associated liver dysfunction and damage are main determinants for the course of the disease. CpG-motif-containing DNA-sequences (CpG-ODN) were previously shown to confer protection in models of infection by stimulating both innate and specific immune responses. Herein, we studied the effect of CpG-ODN in lipopolysaccharide (LPS)-associated hepatotoxicity.


METHODS
Sprague Dawley rats pre-treated at day 6 with either CpG-ODN or inert DNA were challenged with E. coli LPS and subsequently studied for liver injury at 6 and 16 h using in vivo fluorescence microscopy and immunohistochemistry. Western blot protein analysis served for assessment of expression of TLR4, TNF receptor-associated factor 6 (TRAF6), NFkappaB and caspase-3. To evaluate CpG-ODN effects during non-septic conditions, additional animals were solely exposed to CpG-ODN and studied after 1 and 6 days.


RESULTS
CpG-ODN application induced marked hepatic microcirculatory deterioration and liver dysfunction at day 1, however, with almost complete recovery to normal at day 6. Interestingly, CpG-ODN pre-treatment decreased LPS-induced leukocyte-endothelial cell interaction, sinusoidal perfusion failure and caspase-3-dependent apoptotic cell death. Although Kupffer cell phagocytic activity was not affected, CpG-ODN pre-treatment in LPS-challenged animals attenuated hepatic protein expression of TRAF6 and NFkappaB and increased TLR4 by almost 100%.


CONCLUSIONS
CpG-containing DNA-sequences induce early hepatic injury, but mediate long-term protection against LPS hepatotoxicity. The mechanism of protection is based on the induction of cross-tolerance, probably via inhibition of the downstream TRAF6-NFkappaB signaling pathway and upregulation of the TLR4 surface receptor.
Slotta
Jan E
JE
Institute for Clinical and Experimental Surgery, University of Saarland, 66421 Homburg/Saar, Germany.
Scheuer
Claudia
C
Menger
Michael D
MD
Vollmar
Brigitte
B
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004195:Disease Models, Animal; D004792:Enzyme Precursors / Q000378:metabolism; D004926:Escherichia coli; D006505:Hepatitis / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control*; D008070:Lipopolysaccharides / Q000633:toxicity; D017114:Liver Failure, Acute / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008856:Microscopy, Fluorescence; D016328:NF-kappa B / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D053449:TNF Receptor-Associated Factor 4; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000378:metabolism
D000276:Adjuvants, Immunologic; C408982:CPG-oligonucleotide; D004792:Enzyme Precursors; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009838:Oligodeoxyribonucleotides; D053449:TNF Receptor-Associated Factor 4; D048029:TNF Receptor-Associated Factor 6; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases