Thyroid hormone-induced oxidative stress triggers nuclear factor-kappaB activation and cytokine gene expression in rat liver

Abstract

Nuclear factor-kappaB (NF-kappaB) is a redox-sensitive factor responsible for the transcriptional activation of cytokine-encoding genes. In this study, we show that 3,3,5-triiodothyronine (T(3)) administration to rats activates hepatic NF-kappaB, as assessed by electrophoretic mobility shift assay. This response coincides with the onset of calorigenesis and enhancement in hepatic respiration, and is suppressed by the antioxidants alpha-tocopherol and N-acetylcysteine or by the Kupffer cell inactivator gadolinium chloride. Livers from hyperthyroid rats with enhanced NF-kappaB DNA-binding activity show induced mRNA expression of the NF-kappaB-responsive genes for tumor necrosis factor-alpha (TNF-alpha) and interleukin- (IL-) 10, as evidenced by reverse transcription-polymerase chain reaction assay, which is correlated with increases in the serum levels of the cytokines. T(3) also increased the hepatic levels of mRNA for IL-1alpha and those of IL-1alpha in serum, with a time profile closely related to that of TNF-alpha. It is concluded that T(3)-induced oxidative stress enhances the DNA-binding activity of NF-kappaB and the NF-kappaB-dependent expression of TNF-alpha and IL-10 genes.