Age-related decrease in proteasome expression contributes to defective nuclear factor-kappaB activation during hepatic ischemia/reperfusion.
Hepatic ischemia/reperfusion (I/R) leads to liver injury and dysfunction through the initiation of a biphasic inflammatory response that is regulated by the transcription factor nuclear factor kappaB (NF-kappaB). We have previously shown that there is an age-dependent difference in the injury response to hepatic I/R in mice that correlates with divergent activation of NF-kappaB such that young mice have greater NF-kappaB activation, but less injury than old mice. In this study, we investigated the mechanism by which age alters the activation of NF-kappaB in the liver during I/R. Young (4-5 weeks) and old (12-14 months) mice underwent partial hepatic I/R. Livers were obtained for RNA microarray analysis and protein expression assays. Using microarray analysis, we identified age-dependent differences in the expression of genes related to protein ubiquitinylation and the proteasome. In old mice, genes that are involved in the ubiquitin-proteasome pathway were significantly down-regulated during I/R. Consistent with these findings, expression of a critical proteasome subunit, non-adenosine triphosphatase 4 (PSMD4), was reduced in old mice. Expression of the NF-kappaB inhibitory protein, IkappaB alpha, was increased in old mice and was greatly phosphorylated and ubiquitinylated. The data provide strong evidence that the age-related defect in hepatic NF-kappaB signaling during I/R is a result of decreased expression of PSMD4, a proteasome subunit responsible for recognition and recruitment of ubiquitinylated substrates to the proteasome. It appears that decreased PSMD4 expression prevents recruitment of phosphorylated and ubiquitinylated IkappaB alpha to the proteasome, resulting in a defect in NF-kappaB activation.
Huber
Nadine
N
Laboratory of Trauma, Sepsis and Inflammation Research, Department of Surgery, University of Cincinnati, Cincinnati, OH 45267-0558, USA.
Sakai
Nozomu
N
Eismann
Thorsten
T
Shin
Thomas
T
Kuboki
Satoshi
S
Blanchard
John
J
Schuster
Rebecca
R
Edwards
Michael J
MJ
Wong
Hector R
HR
Lentsch
Alex B
AB
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks; D022781:Hepatocytes / Q000378:metabolism; D020672:I-kappa B Proteins / Q000378:metabolism*; D008099:Liver / Q000098:blood supply; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D016601:RNA-Binding Proteins; D015427:Reperfusion Injury / Q000378:metabolism*; D054875:Ubiquitination
D002352:Carrier Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; C490781:Psmd4 protein, mouse; D016601:RNA-Binding Proteins; D000072000:NF-KappaB Inhibitor alpha; D046988:Proteasome Endopeptidase Complex