학술논문
Canonical Thyroid Hormone Receptor (3 Action Stimulates Hepatocyte Proliferation in Male Mice
Research Article
Research Article
Document Type
Academic Journal
Author
Source
Endocrinology. March 2022, Vol. 163 Issue 3, p1d, 11 p.
Subject
Language
English
ISSN
0013-7227
Abstract
A unique regenerative capacity allows the liver to maintain or regain its pivotal functions after damage (1). Understanding the underlying mechanisms is of clinical importance because stimulation of liver regeneration [...]
Context: 3,5,3'-L-triiodothyronine (T3) is a potent inducer of hepatocyte proliferation via the Wnt/[beta]-catenin signaling pathway. Previous studies suggested the involvement of rapid noncanonical thyroid hormone receptor (TR) [beta] signaling, directly activating hepatic Wnt/[beta]-catenin signaling independent from TR[beta] DNA binding. However, the mechanism by which T3 increases Wnt/[beta]-catenin signaling in hepatocytes has not yet been determined. Objective: We aimed to determine whether DNA binding of TR[beta] is required for stimulation of hepatocyte proliferation by T3. Methods: Wild-type (WT) mice, TR[beta] knockout mice (TR[[beta].sup.KO]), and TR[beta] mutant mice with either specifically abrogated DNA binding (TR[[beta].sup.GS]) or abrogated direct phosphatidylinositol 3 kinase activation (TR[[beta].sup.147F]) were treated with T3 for 6 hours or 7 days. Hepatocyte proliferation was assessed by Kiel-67 (Ki67) staining and apoptosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. Activation of [beta]-catenin signaling was measured in primary murine hepatocytes. Gene expression was analyzed by microarray, gene set enrichment analysis (GSEA), and quantitative reverse transcription polymerase chain reaction. Results: T3 induced hepatocyte proliferation with an increased number of Ki67-positive cells in WT and TR[[beta].sup.147F] mice (9.2% [+ or -] 6.5% and 10.1% [+ or -] 2.9%, respectively) compared to TR[[beta].sup.KO] and TR[[beta].sup.GS] mice (1.2% [+ or -] 1.1% and 1.5% [+ or -] 0.9%, respectively). Microarray analysis and GSEA showed that genes of the Wnt/[beta]-catenin pathway--among them, Fzd8 (frizzled receptor 8) and Ctnnb1 ([beta]-catenin)--were positively enriched only in T3-treated WT and TR[[beta].sup.147F] mice while B-cell translocation gene anti-proliferation factor 2 was repressed. Consequently, expression of Ccnd1 (CyclinD1) was induced. Conclusions: Instead of directly activating Wnt signaling, T3 and TR[beta] induce key genes of the Wnt/[beta]-catenin pathway, ultimately stimulating hepatocyte proliferation via CyclinD1. Thus, canonical transcriptional TR[beta] action is necessary for T3-mediated stimulation of hepatocyte proliferation. Keywords: liver regeneration, thyroid hormone action, [beta]-catenin signaling, gene expression, hepatocyte apoptosis Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; Btg2, B-cell translocation gene anti-proliferation factor 2; DAPI, 4',6-diamidino-2-phenylindole; Fzd8, frizzled receptor 8; IgG, immunoglobulin G; Ki67, Kiel-67; KO, knockout; MMI, 2-mercapto-1-methylimidazole; PI3K, phosphatidylinositol 3 kinase; PKA, protein kinase A; qRT-PCR, quantitative reverse transcriptase polymerase chain reaction; T3, 3,5,3'-L-triiodothyronine; T4, thyroxine; TH, thyroid hormone; TR, thyroid hormone receptor; TRE, thyroid hormone response elements; TUNEL, TdT-mediated dUTP-biotin nick end labeling; WT, wild-type.
Context: 3,5,3'-L-triiodothyronine (T3) is a potent inducer of hepatocyte proliferation via the Wnt/[beta]-catenin signaling pathway. Previous studies suggested the involvement of rapid noncanonical thyroid hormone receptor (TR) [beta] signaling, directly activating hepatic Wnt/[beta]-catenin signaling independent from TR[beta] DNA binding. However, the mechanism by which T3 increases Wnt/[beta]-catenin signaling in hepatocytes has not yet been determined. Objective: We aimed to determine whether DNA binding of TR[beta] is required for stimulation of hepatocyte proliferation by T3. Methods: Wild-type (WT) mice, TR[beta] knockout mice (TR[[beta].sup.KO]), and TR[beta] mutant mice with either specifically abrogated DNA binding (TR[[beta].sup.GS]) or abrogated direct phosphatidylinositol 3 kinase activation (TR[[beta].sup.147F]) were treated with T3 for 6 hours or 7 days. Hepatocyte proliferation was assessed by Kiel-67 (Ki67) staining and apoptosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. Activation of [beta]-catenin signaling was measured in primary murine hepatocytes. Gene expression was analyzed by microarray, gene set enrichment analysis (GSEA), and quantitative reverse transcription polymerase chain reaction. Results: T3 induced hepatocyte proliferation with an increased number of Ki67-positive cells in WT and TR[[beta].sup.147F] mice (9.2% [+ or -] 6.5% and 10.1% [+ or -] 2.9%, respectively) compared to TR[[beta].sup.KO] and TR[[beta].sup.GS] mice (1.2% [+ or -] 1.1% and 1.5% [+ or -] 0.9%, respectively). Microarray analysis and GSEA showed that genes of the Wnt/[beta]-catenin pathway--among them, Fzd8 (frizzled receptor 8) and Ctnnb1 ([beta]-catenin)--were positively enriched only in T3-treated WT and TR[[beta].sup.147F] mice while B-cell translocation gene anti-proliferation factor 2 was repressed. Consequently, expression of Ccnd1 (CyclinD1) was induced. Conclusions: Instead of directly activating Wnt signaling, T3 and TR[beta] induce key genes of the Wnt/[beta]-catenin pathway, ultimately stimulating hepatocyte proliferation via CyclinD1. Thus, canonical transcriptional TR[beta] action is necessary for T3-mediated stimulation of hepatocyte proliferation. Keywords: liver regeneration, thyroid hormone action, [beta]-catenin signaling, gene expression, hepatocyte apoptosis Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; Btg2, B-cell translocation gene anti-proliferation factor 2; DAPI, 4',6-diamidino-2-phenylindole; Fzd8, frizzled receptor 8; IgG, immunoglobulin G; Ki67, Kiel-67; KO, knockout; MMI, 2-mercapto-1-methylimidazole; PI3K, phosphatidylinositol 3 kinase; PKA, protein kinase A; qRT-PCR, quantitative reverse transcriptase polymerase chain reaction; T3, 3,5,3'-L-triiodothyronine; T4, thyroxine; TH, thyroid hormone; TR, thyroid hormone receptor; TRE, thyroid hormone response elements; TUNEL, TdT-mediated dUTP-biotin nick end labeling; WT, wild-type.