Regulation of oxidative stress on the activity of Nrf-2 factor and the expression of antioxidant enzymes in lymphoid cells of a murine model of hyperthyroidism

KLECHA A.; COSTILLA M.; CREMASCHI G.; MACRI DELBONO R.; BARREIRO ARCOS M.L,

Rosario, Santa Fé

Congreso; Reunión Anual de la Sociedad Argentina de Fisiología; 2019

Sociedad Argentina de Fisiología

Introduction: Hyperthyroidism is an endocrine disorder characterized by excessive secretion of T3 and T4 and low levels of TSH. Thyroid hormones exert pleiotropic actions on numerous tissues and induce an overall increase in metabolism, with an increase in energy demand and oxygen consumption. Objectives: Study the effect of oxidative stress on the activation of the nuclear factor Nrf-2 and the transcription of antioxidant enzymes in lymph node and spleen cells of euthyroid and hyperthyroid mice. Methodology: Hyperthyroidism was induced in Balb/c mice by treatment with 12 mg/l of T4 in drinking water for 30 days. Reactive oxygen species (ROS) were evaluated using the fluorescent probe DCFH-DA and flow cytometry. The expression of catalase (CAT), glutathione peroxidase-1 (GPx-1) and superoxide dismutase (SOD) was determined by PCR and western blot. Nrf-2 phosphorylation and its translocation to the nucleus was evaluated by western blot and confocal microscopy, respectively. Protein kinase C (PKC) activity was evaluated by measuring the incorporation of 32P into histone H1. PKC isoenzyme expression and the extracellular signal-regulated kinase (ERK) phosphorylation was evaluated by western blot. Results: We found a significant increase in the genomic and protein expression of CAT and GPx-1 in lymph node and spleen cells of hyperthyroid mice that was correlated with the increase in the ROS production. Lymphoid cells of euthyroid mice treated in vitro with H2O2 (250 μM) increased the expression of antioxidant enzymes. The hyperthyroidism increased the phosphorylation levels of Nrf-2 and ERK and the kinase activity of the classic isoenzymes of PKC (α, β and γ). Nrf-2 phosphorylation was decreased by the preincubation of lymphoid cells with staurosporine (PKC inhibitor; 5 nM) or PD 98059 (ERK inhibitor; 20 µM). Conclusions: Hyperthyroidism increases ROS and kinase activity of PKC and ERK. The activation of these transduction signals leads to phosphorylation and translocation of Nfr-2 to the nucleus where it induces the transcription of antioxidant enzymes. These results indicate the modulation of hyperthyroidism on the cellular antioxidant system.