NF-kappaB activation, rather than TNF, mediates hepatic inflammation in a murine dietary model of steatohepatitis.
OBJECTIVE
We explored the roles of nuclear factor-kappaB (NF-kappaB) and tumor necrosis factor (TNF) alpha (TNF-alpha) as mediators of inflammation in a nutritional model of steatohepatitis.


METHODS
Wild-type (wt), TNF null -/-, and TNF receptor (R)-1-/- mice were fed a methionine- and choline-deficient (MCD) diet for up to 5 weeks. Liver injury (serum alanine aminotransferase [ALT]), hepatic inflammation, triglycerides, and lipid peroxide levels were determined. Hepatic NF-kappaB activation and expression of TNF and intercellular adhesion molecule-1 (ICAM-1) were assayed.


RESULTS
Irrespective of genotype, MCD diet-fed mice developed hepatic lipid peroxidation and serum ALT elevation; at day 10, livers from wt, TNF-/-, and TNFR-1-/- mice showed equivalent steatohepatitis. NF-kappaB/DNA binding was enhanced in hepatic nuclear fractions from MCD diet-fed wt mice compared with dietary controls; there were corresponding increases of ICAM-1 and TNF messenger RNA (mRNA). Likewise, NF-kappaB activation and ICAM-1 expression were enhanced by MCD dietary feeding in TNF-/- and TNFR-1-/- mice compared with respective controls. To establish whether NF-kappaB is a primary mediator of inflammation in experimental steatohepatitis, we over-expressed a mutant, nondegradable IkappaB (mIkappaB), delivered by adenovirus in vivo. As expected, hepatic mIkappaB expression reduced NF-kappaB/DNA binding induced by MCD dietary feeding, with resultant abrogation of ICAM-1 and TNF synthesis. Such blockade of NF-kappaB transcriptional activation substantially protected against development of steatohepatitis, with significant reductions in liver injury and hepatic inflammation.


CONCLUSIONS
In the MCD dietary model of steatohepatitis, NF-kappaB is activated early and is an important proinflammatory mediator of lesion development, but steatohepatitis occurs independently of TNF synthesis and TNFR-1 activation.
Dela Peña
Aileen
A
Storr Liver Unit, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Sydney, NSW, Australia.
Leclercq
Isabelle
I
Field
Jacqueline
J
George
Jacob
J
Jones
Brett
B
Farrell
Geoffrey
G
D000818:Animals; D002794:Choline / Q000494:pharmacology; D002796:Choline Deficiency; D004032:Diet; D004195:Disease Models, Animal; D005234:Fatty Liver / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D006505:Hepatitis / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology*; D018836:Inflammation Mediators / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D008715:Methionine / Q000172:deficiency / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
D018836:Inflammation Mediators; D016328:NF-kappa B; D012333:RNA, Messenger; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D008715:Methionine; D002794:Choline