Gene expression profiling of liver cells after copper overload in vivo and in vitro reveals new copper-regulated genes.
Copper toxicity in the liver is mediated by free-radical generation, resulting in oxidative stress. To prevent toxic accumulation of copper, liver cells adapt to high copper levels. Here, we used microarray analysis to compare the adaptive responses on global gene expression in liver cells exposed to high copper levels in vitro and in vivo. In HepG2 cells we identified two clusters of upregulated genes over time, an "early" cluster that comprised metallothionein genes and a "late" cluster, highly enriched in genes involved in proteasomal degradation and in oxidative stress response. Concomitant with the "late" cluster, we detected a significant downregulation of several copper metabolism MURR1 domain (COMMD) genes that were recently implicated in copper metabolism and inhibition of nuclear transcription factor kappaB (NF-kappaB) signaling. As metal-induced oxidative stress increases NF-kappaB activity, our data suggest a role for reduced COMMD protein levels in prolonged activation of NF-kappaB, thus inducing cell survival. Mice exposed to a copper diet that highly exceeded normal daily intake accumulated only twofold more hepatic copper than control mice. Although a moderate, but significant upregulation of a set of 22 genes involved in immunity, iron and cholesterol metabolism was detected, these cannot account for direct mechanisms involved in copper excretion. In conclusion, we identified a novel set of genes that represent a delayed response to copper overload, thus providing insight into the adaptive transcriptional response to copper-induced oxidative stress.
Muller
Patricia
P
Laboratory for Metabolic and Endocrine Diseases, University Medical Centre, Utrecht, The Netherlands.
van Bakel
Harm
H
van de Sluis
Bart
B
Holstege
Frank
F
Wijmenga
Cisca
C
Klomp
Leo W J
LW
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000145:classification / Q000235:genetics; D002460:Cell Line; D003300:Copper / Q000494:pharmacology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000235:genetics*; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D008668:Metallothionein / Q000235:genetics; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000235:genetics; D013997:Time Factors
D048868:Adaptor Proteins, Signal Transducing; C480519:COMMD1 protein, human; D002352:Carrier Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D003300:Copper; D008668:Metallothionein