Reactive oxygen species (ROS) mediate the effects of leucine on translation regulation and type I collagen production in hepatic stellate cells.
The amino acid leucine causes an increase of collagen alpha1(I) synthesis in hepatic stellate cells through the activation of translational regulatory mechanisms and PI3K/Akt/mTOR and ERK signaling pathways. The aim of the present study was to evaluate the role played by reactive oxygen species on these effects. Intracellular reactive oxygen species levels were increased in hepatic stellate cells incubated with leucine 5 mM at early time points, and this effect was abolished by pretreatment with the antioxidant glutathione. Preincubation with glutathione also prevented 4E-BP1, eIF4E and Mnk-1 phosphorylation induced by leucine, as well as enhancement of procollagen alpha1(I) protein levels. Inhibitors for MEK-1 (PD98059), PI3K (wortmannin) or mTOR (rapamycin) did not affect leucine-induced reactive oxygen species production. However, preincubation with glutathione prevented ERK, Akt and mTOR phosphorylation caused by treatment with leucine. The mitochondrial electron chain inhibitor rotenone and the NADPH oxidase inhibitor apocynin prevented reactive oxygen species production caused by leucine. Leucine also induced an increased phosphorylation of IR/IGF-R that was abolished by pretreatment with either rotenone or apocynin. Therefore, leucine exerts on hepatic stellate cells a prooxidant action through NADPH oxidase and mitochondrial Reactive oxygen species production and these effects mediate the activation of IR/IGF-IR and signaling pathways, finally leading to changes in translational regulation of collagen synthesis.
Pérez de Obanos
María P
MP
Departamento de Bioquímica y Biología Molecular, Universidad de Navarra, 31008 Pamplona, Spain.
López-Zabalza
María J
MJ
Arriazu
Elena
E
Modol
Teresa
T
Prieto
Jesús
J
Herraiz
María T
MT
Iraburu
María J
MJ
D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D024042:Collagen Type I / Q000096:biosynthesis*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology; D047908:Intracellular Signaling Peptides and Proteins; D007930:Leucine / Q000494:pharmacology*; D008954:Models, Biological; D018384:Oxidative Stress / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects*; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000494:pharmacology*; D011972:Receptor, Insulin / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases
D000098:Acetophenones; D002352:Carrier Proteins; D024042:Collagen Type I; D048049:Extracellular Signal-Regulated MAP Kinases; D005978:Glutathione; D047908:Intracellular Signaling Peptides and Proteins; D007930:Leucine; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; D011972:Receptor, Insulin; D012402:Rotenone; D013481:Superoxides; D058570:TOR Serine-Threonine Kinases; C499526:Eif4ebp1 protein, rat; C056165:acetovanillone; C546845:mTOR protein, rat