Redox regulation of thyroid hormone-induced Kupffer cell-dependent IkappaB-alpha phosphorylation in relation to inducible nitric oxide synthase expression.
Thyroid hormone-induced calorigenesis promotes oxidative stress in the liver with higher respiratory burst activity in Kupffer cells, which could increase the expression of redox-sensitive genes. Our aim was to test the hypothesis that L-3,3',5-triiodothyronine (T3) triggers inducible nitric oxide synthase (iNOS) expression in rat liver by upstream mechanisms involving the inhibitor of kappa (Ikappa) kinase activation. T3 administration (daily doses of 0.1 mg/kg for three consecutive days) induced a calorigenic response, with maximal increases in the content of hepatic thiobarbituric acid reactants or protein carbonyls and NOS activity at 48-72 h after treatment, compared to control values. In this time interval, the serum levels of tumor necrosis factor-alpha (TNF-alpha; ELISA) are enhanced, concomitantly with higher liver IkappaB-alpha phaphosphorylation (Western blot analysis), NF-kappaB DNA binding (electrophoretic mobility shift assay), and iNOS mRNA expression (reverse transcription-polymerase chain reaction). These changes and the increase in hepatic NOS activity are abolished by the administration of either alpha-tocopherol (100 mg/kg) or the Kupffer cell inactivator gadolinium chloride (10 mg/kg) prior to T3. It is concluded that T3-induced oxidative stress triggers the redox upregulation of liver iNOS expression through a cascade initiated by TNF-a produced by Kupffer cells and involving Ikappa-alpha phosphorylation and NF-kappaB activation, a response that may represent a defense mechanism by protecting the liver from cytokine-mediated lethality and ROS toxicity.
Fernández
Virginia
V
Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile.
Tapia
Gladys
G
Varela
Patricia
P
Videla
Luis A
LA
D000818:Animals; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D020672:I-kappa B Proteins / Q000187:drug effects / Q000378:metabolism*; D007728:Kupffer Cells / Q000187:drug effects / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D013997:Time Factors; D014284:Triiodothyronine / Q000378:metabolism / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D020672:I-kappa B Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D017392:Thiobarbituric Acid Reactive Substances; D014409:Tumor Necrosis Factor-alpha; D014284:Triiodothyronine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat