Esmée Hoen1, Kim Falize2, Franka Goossens3, Sheue-yann Cheng4, Xuguang Zhu4, Anne van der Spek5, Anita Boelen6,
(1) Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam Gastroenterology, Endocrinology & Metabolism (AGEM), Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands. (2) Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam Gastroenterology, Endocrinology & Metabolism (AGEM), Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands. (3) Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam Gastroenterology, Endocrinology & Metabolism (AGEM), Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands. (4) Laboratory of Molecular Biology, National Cancer Institute, Bethesda, United States of America. (5) Department of Endocrinology and Metabolism, Amsterdam Gastroenterology Endocrinology & Metabolism (AGEM), Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands. (6) Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam Gastroenterology, Endocrinology & Metabolism (AGEM), Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.
Macrophages are immune cells with many functions, ranging from fighting infections (pro-inflammatory) to immune modulation (anti-inflammatory). It is also known that these versatile phagocytes are thyroid hormone (TH) target cells. Beside the necessary TH transporters and TH activating enzymes, macrophages possess the nuclear TH receptor alpha (TRα), through which the active TH triiodothyronine (T3) acts. We hypothesize that TH, acting via the TRα, plays a key role in macrophage function. To this end we analyzed the transcriptomic effects in macrophages of a mutation in TRα resulting in resistance to TH alpha (RTHα). In the clinical syndrome RTHα, TH is unable to bind to the TRα, resulting in hypothyroidism in tissues with TRα as the dominant receptor isoform.
We generated bone marrow derived macrophages (BMDMs) from wild type (WT) and transgenic mice with a mutation in the T3 binding domain of the TRα (TRαPV), which resembles RTHα. Naïve BMDMs (M0) were polarized into a pro-inflammatory M1 (using LPS + interferon gamma) or immunomodulatory M2 (using IL-4) phenotype. Using RNA from M0, M1 and M2 WT and TRαPV BMDMs, RNA sequencing (RNAseq) was performed.
RNAseq showed 7468 differentially expressed genes, including 2973 genes in M0, 2112 genes in M1 and 674 genes in M2 in TRαPV BMDMs. This includes both up and down regulated genes. Interestingly, 87 genes were up and 183 genes were down regulated in all three TRαPV BMDMs (M0, M1 and M2). We found genes that have already been established as TH target genes, but we also identified novel TH regulated genes. Additionally, increased anti-inflammatory associated gene expression was found in M1 and M2 TRαPV BMDMs. Pathway analysis is ongoing.
Our data show that a mutation of the TRα in the T3 binding domain, similar to RTHα, results in a profoundly altered gene expression profile in M0, M1 and M2 BMDMs. We also showed that reduced TH signaling via TRα results in increased expression of anti-inflammatory (M2) genes in M1 and M2 BMDMs, indicating that TRα-T3 action plays a role in the pro-inflammatory response of macrophages.