The Transcriptomic Response of the Murine Thyroid Gland to Iodide Overload and the Role of the Nrf2 Antioxidant System
ANTIOXIDANTS
Authors: Chartoumpekis, Dionysios V.; Ziros, Panos G.; Georgakopoulos-Soares, Ilias; Smith, Adam A. T.; Marques, Ana Claudia; Ibberson, Mark; A. Kopp, Peter; Habeos, Ioannis; Trougakos, Ioannis P.; Khoo, Nicholas K. H.; Sykiotis, Gerasimos P.
Abstract
Background: Thyroid follicular cells have physiologically high levels of reactive oxygen species because oxidation of iodide is essential for the iodination of thyroglobulin (Tg) during thyroid hormone synthesis. Thyroid follicles (the functional units of the thyroid) also utilize incompletely understood autoregulatory mechanisms to defend against exposure to excess iodide. To date, no transcriptomic studies have investigated these phenomena in vivo. Nuclear erythroid factor 2 like 2 (Nrf2 or Nfe2l2) is a transcription factor that regulates the expression of numerous antioxidant and other cytoprotective genes. We showed previously that the Nrf2 pathway regulates the antioxidant defense of follicular cells, as well asTgtranscription and Tg iodination. We, thus, hypothesized that Nrf2 might be involved in the transcriptional response to iodide overload. Methods: C57BL6/J wild-type (WT) or Nrf2 knockout (KO) male mice were administered regular water or water supplemented with 0.05% sodium iodide for seven days. RNA from their thyroids was prepared for next-generation RNA sequencing (RNA-Seq). Gene expression changes were assessed and pathway analyses were performed on the sets of differentially expressed genes. Results: Analysis of differentially expressed messenger RNAs (mRNAs) indicated that iodide overload upregulates inflammatory-, immune-, fibrosis- and oxidative stress-related pathways, including the Nrf2 pathway. Nrf2 KO mice showed a more pronounced inflammatory-autoimmune transcriptional response to iodide than WT mice. Compared to previously published datasets, the response patterns observed in WT mice had strong similarities with the patterns typical of Graves' disease and papillary thyroid carcinoma (PTC). Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) also responded to iodide overload, with the latter targeting mRNAs that participate mainly in inflammation pathways. Conclusions: Iodide overload induces the Nrf2 cytoprotective response and upregulates inflammatory, immune, and fibrosis pathways similar to autoimmune hyperthyroidism (Graves' disease) and PTC.
The impact of partial hepatectomy on oxidative state in the liver remnant - An in vivo swine model
REDOX BIOLOGY
Authors: Florholmen-Kjaer, Ase; Goll, Rasmus; Fuskevag, Ole-Martin; Nygard, Ingvild Engdal; Paulssen, Ruth H.; Revhaug, Arthur; Mortensen, Kim Erlend
Abstract
Background: Previous studies on oxidative state after partial hepatectomy (PHx) report conflicting data on levels of glutathione (GSH) and are mainly presented in rodent models by methodology less sensitive than the present technologies. The current swine model presents GSH levels and the following genetic response post-PHx, utilizing an analytical platform more sensitive and precise than earlier available. Method: Twelve pigs were randomized to a PHx- and a control group (n=6 in each). The PHx group had a 60% hepatectomy. Serial in vivo liver biopsies during 12 h of anaesthesia post-PHx were analyzed for GSH by liquid chromatography mass spectrometry (LC-MS/MS). Transcriptional alterations of genes (GS, GCLM, GCLC, GR, HGF, NFE2L2, TGF beta 1) regulating GSH synthesis were measured by real-time PCR. Results: No difference was detected between the GSH levels in the PHx- and the control group during the experiment (P=0.247). Still, decreased gene expression of GS (P=0.026) and NFE2L2 (P=0.014) the first nine hours, and a decrease of TGF beta 1 (P=0.029) the first seven hours post-PHx was seen in the liver remnant. Conclusion: The results show that the liver has an extended capacity to maintain GSH homeostasis during major stress and parenchymal loss, even at the early onset of such trauma. This observation was not explained by increased expression of key genes in GSH pathways. Consequently, the results indicate an inherent compensatory capacity to maintain GSH homeostasis in the reduced organ. (C) 2016 The Authors. Published by Elsevier B.V.