Ethanol-induced modulation of hepatocellular extracellular signal-regulated kinase-1/2 activity via 4-hydroxynonenal.
Modulation of the extracellular signal-regulated kinases (ERK-1/2), a signaling pathway directly associated with cell proliferation, survival, and homeostasis, has been implicated in several pathologies, including alcoholic liver disease. However, the underlying mechanism of ethanol-induced ERK-1/2 modulation remains unknown. This investigation explored the effects of ethanol-associated oxidative stress on constitutive hepatic ERK-1/2 activity and assessed the contribution of the lipid peroxidation product 4-hydroxynonenal (4-HNE) to the observations made in vivo. Constitutive ERK-1/2 phosphorylation was suppressed in hepatocytes isolated from rats chronically consuming ethanol for 45 days. This observation was associated with an increase in 4-HNE-ERK monomer adduct concentration and a hepatic cellular and lobular redistribution of ERK-1/2 that correlated with 4-HNE-protein adduct accumulation. Chronic ethanol consumption was also associated with a decrease in hepatocyte nuclear ELK-1 phosphorylation, independent of changes in total nuclear ELK-1 protein. Primary hepatocytes treated with concentrations of 4-HNE consistent with those occurring during oxidative stress displayed a concentration-dependent decrease in constitutive ERK-1/2 phosphorylation, activity, and nuclear localization that negatively correlated with 4-HNE-ERK-1/2 monomer adduct accumulation. These data paralleled the decreased phosphorylation of the downstream kinase ELK-1. Molar ratios of purified ERK-2 to 4-HNE consistent with pathologic ratios found in vivo resulted in protein monomer-adduct formation across a range of concentrations. Collectively, these data demonstrate a novel association between ethanol-induced lipid peroxidation and the inhibition of constitutive ERK-1/2, and suggest an inhibitory mechanism mediated by the lipid peroxidation product 4-hydroxynonenal.
Sampey
Brante P
BP
Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Denver and Health Sciences Center, Denver, Colorado 80262, USA.
Stewart
Benjamin J
BJ
Petersen
Dennis R
DR
D000447:Aldehydes / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000431:Ethanol / Q000494:pharmacology*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
D000447:Aldehydes; D000431:Ethanol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C027576:4-hydroxy-2-nonenal