Ethanol-induced HO-1 and NQO1 are differentially regulated by HIF-1alpha and Nrf2 to attenuate inflammatory cytokine expression.
Oxidative stress plays an important role in alcohol-induced inflammation and liver injury. Relatively less is known about how Kupffer cells respond to oxidative stress-induced expression of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase (NQO1) to blunt inflammation and liver injury. We showed that Kupffer cells from ethanol-fed rats and ethanol-treated rat Kupffer cells and THP-1 cells displayed increased mRNA expression of HO-1, NQO1, and hypoxia-inducible factor-1α (HIF-1α). Our studies showed that silencing with HIF-1α and JNK-1 siRNAs attenuated ethanol-mediated mRNA expression of HO-1, but not NQO1, whereas Nrf2 siRNA attenuated the mRNA expression of both HO-1 and NQO1. Additionally, JunD but not JunB formed an activator protein-1 (AP-1) oligomeric complex to augment HO-1 promoter activity. Ethanol-induced HO-1 transcription involved antioxidant response elements, hypoxia-response elements, and an AP-1 binding motif in its promoter, as demonstrated by mutation analysis of the promoter, EMSA, and ChIP. Furthermore, livers of ethanol-fed c-Jun(fl/fl) mice showed reduced levels of mRNA for HO-1 but not of NQO1 compared with ethanol-fed control rats, supporting the role of c-Jun or the AP-1 transcriptional complex in ethanol-induced HO-1 expression. Additionally, attenuation of HO-1 levels in ethanol-fed c-Jun(fl/fl) mice led to increased proinflammatory cytokine expression in the liver. These results for the first time show that ethanol regulates HO-1 and NQO1 transcription by different signaling pathways. Additionally, up-regulation of HO-1 protects the liver from excessive formation of inflammatory cytokines. These studies provide novel therapeutic targets to ameliorate alcohol induced inflammation and liver injury.
Yeligar
Samantha M
SM
Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA. syeliga@emory.edu
Machida
Keigo
K
Kalra
Vijay K
VK
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis* / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D000431:Ethanol / Q000378:metabolism / Q000494:pharmacology*; D020869:Gene Expression Profiling; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007728:Kupffer Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D016207:Cytokines; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D000431:Ethanol; D051547:Heme Oxygenase-1; D016660:NAD(P)H Dehydrogenase (Quinone); C507703:NQO1 protein, rat; D011494:Protein Kinases