Thyroid hormone-induced cytosol-to-nuclear translocation of rat liver Nrf2 is dependent on Kupffer cell functioning.
L-3,3',5-triiodothyronine (T(3)) administration upregulates nuclear factor-E2-related factor 2 (Nrf2) in rat liver, which is redox-sensitive transcription factor mediating cytoprotection. In this work, we studied the role of Kupffer cell respiratory burst activity, a process related to reactive oxygen species generation and liver homeostasis, in Nrf2 activation using the macrophage inactivator gadolinium chloride (GdCl(3); 10 mg/kg i.v. 72 h before T(3) [0.1 mg/kg i.p.]) or NADPH oxidase inhibitor apocynin (1.5 mmol/L added to the drinking water for 7 days before T(3)), and determinations were performed 2 h after T(3). T(3) increased nuclear/cytosolic Nrf2 content ratio and levels of heme oxygenase 1 (HO-1), catalytic subunit of glutamate cysteine ligase, and thioredoxin (Western blot) over control values, proteins whose gene transcription is induced by Nrf2. These changes were suppressed by GdCl(3) treatment prior to T(3), an agent-eliciting Kupffer-cell depletion, inhibition of colloidal carbon phagocytosis, and the associated respiratory burst activity, with enhancement in nuclear inhibitor of Nrf2 kelch-like ECH-associated protein 1 (Keap1)/Nrf2 content ratios suggesting Nrf2 degradation. Under these conditions, T(3)-induced tumor necrosis factor-α (TNF-α) response was eliminated by previous GdCl(3) administration. Similar to GdCl(3), apocynin given before T(3) significantly reduced liver Nrf2 activation and HO-1 expression, a NADPH oxidase inhibitor eliciting abolishment of colloidal carbon-induced respiratory burst activity without altering carbon phagocytosis. It is concluded that Kupffer cell functioning is essential for upregulation of liver Nrf2-signaling pathway by T(3). This contention is supported by suppression of the respiratory burst activity of Kupffer cells and the associated reactive oxygen species production by GdCl(3) or apocynin given prior to T(3), thus hindering Nrf2 activation.
Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Casilla 70000, Santiago-7, Chile. lvidela@med.uchile.cl
Luis A
LA
Videla
Pamela
P
Cornejo
Pamela
P
Romanque
Catherine
C
Santibáñez
Iván
I
Castillo
Romina
R
Vargas
D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005682:Gadolinium / Q000494:pharmacology; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis; D051547:Heme Oxygenase-1 / Q000096:biosynthesis; D007728:Kupffer Cells / Q000187:drug effects / Q000502:physiology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D010587:Phagocytosis; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D016897:Respiratory Burst / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D014284:Triiodothyronine / Q000494:pharmacology*
D000098:Acetophenones; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D014284:Triiodothyronine; D005682:Gadolinium; C056165:acetovanillone; D051547:Heme Oxygenase-1; D005721:Glutamate-Cysteine Ligase; C544143:GCLC protein, rat; C038958:gadolinium chloride