RESUMO
Hypothyroidism is commonly detected in patients with medulloblastoma (MB). However, whether thyroid hormone (TH) contributes to MB pathogenicity remains undetermined. Here, we find that TH plays a critical role in promoting tumor cell differentiation. Reduction in TH levels frees the TH receptor, TRα1, to bind to EZH2 and repress expression of NeuroD1, a transcription factor that drives tumor cell differentiation. Increased TH reverses EZH2-mediated repression of NeuroD1 by abrogating the binding of EZH2 and TRα1, thereby stimulating tumor cell differentiation and reducing MB growth. Importantly, TH-induced differentiation of tumor cells is not restricted by the molecular subgroup of MB, suggesting that TH can be used to broadly treat MB subgroups. These findings establish an unprecedented association between TH signaling and MB pathogenicity, providing solid evidence for TH as a promising modality for MB treatment.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos , Diferenciação Celular , Proteína Potenciadora do Homólogo 2 de Zeste , Meduloblastoma , Hormônios Tireóideos , Meduloblastoma/patologia , Meduloblastoma/metabolismo , Meduloblastoma/genética , Humanos , Diferenciação Celular/efeitos dos fármacos , Animais , Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Proteína Potenciadora do Homólogo 2 de Zeste/genética , Camundongos , Hormônios Tireóideos/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Neoplasias Cerebelares/patologia , Neoplasias Cerebelares/metabolismo , Neoplasias Cerebelares/genética , Neoplasias Cerebelares/tratamento farmacológico , Linhagem Celular Tumoral , Progressão da Doença , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Receptores alfa dos Hormônios Tireóideos/metabolismo , Receptores alfa dos Hormônios Tireóideos/genética , Transdução de Sinais/efeitos dos fármacosRESUMO
Thyroid hormone (TH) effects are mediated through TH receptors (TRs), TRα1, TRß1, and TRß2. The TRs bind to the DNA and regulate expression of TH target genes (canonical signaling). In addition, they mediate activation of signaling pathways (noncanonical signaling). Whether noncanonical TR action contributes to the spectrum of TH effects is largely unknown. The aim of this study was to attribute physiological effects to the TR isoforms and their canonical and noncanonical signaling. We conducted multiparameter phenotyping in male and female TR knockout mice (TRαKO, TRßKO), mice with disrupted canonical signaling due to mutations in the TR DNA binding domain (TRαGS, TRßGS), and their wild-type littermates. Perturbations in senses, especially hearing (mainly TRß with a lesser impact of TRα), visual acuity, retinal thickness (TRα and TRß), and in muscle metabolism (TRα) highlighted the role of canonical TR action. Strikingly, selective abrogation of canonical TR action often had little phenotypic consequence, suggesting that noncanonical TR action sufficed to maintain the wild-type phenotype for specific effects. For instance, macrocytic anemia, reduced retinal vascularization, or increased anxiety-related behavior were only observed in TRαKO but not TRαGS mice. Noncanonical TRα action improved energy utilization and prevented hyperphagia observed in female TRαKO mice. In summary, by examining the phenotypes of TRα and TRß knockout models alongside their DNA binding-deficient mutants and wild-type counterparts, we could establish that the noncanonical actions of TRα and TRß play a crucial role in modulating sensory, behavioral, and metabolic functions and, thus, contribute to the spectrum of physiological TH effects.
Assuntos
Camundongos Knockout , Fenótipo , Receptores alfa dos Hormônios Tireóideos , Receptores beta dos Hormônios Tireóideos , Animais , Feminino , Masculino , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Receptores beta dos Hormônios Tireóideos/genética , Receptores beta dos Hormônios Tireóideos/metabolismo , Camundongos , Transdução de Sinais/genética , Hormônios Tireóideos/metabolismo , Camundongos Endogâmicos C57BLRESUMO
Colorectal cancers (CRCs) are highly heterogeneous and show a hierarchical organization, with cancer stem cells (CSCs) responsible for tumor development, maintenance, and drug resistance. Our previous studies showed the importance of thyroid hormone-dependent signaling on intestinal tumor development and progression through action on stem cells. These results have a translational value, given that the thyroid hormone nuclear receptor TRα1 is upregulated in human CRCs, including in the molecular subtypes associated with CSC features. We used an established spheroid model generated from the human colon adenocarcinoma cell line Caco2 to study the effects of T3 and TRα1 on spheroid formation, growth, and response to conventional chemotherapies. Our results show that T3 treatment and/or increased TRα1 expression in spheroids impaired the response to FOLFIRI and conferred a survival advantage. This was achieved by stimulating drug detoxification pathways and increasing ALDH1A1-expressing cells, including CSCs, within spheroids. These results suggest that clinical evaluation of the thyroid axis and assessing TRα1 levels in CRCs could help to select optimal therapeutic regimens for patients with CRC. Proposed mechanism of action of T3/TRα1 in colon cancer spheroids. In the control condition, TRα1 participates in maintaining homeostatic cell conditions. The presence of T3 in the culture medium activates TRα1 action on target genes, including the drug efflux pumps ABCG2 and ABCB1. In the case of chemotherapy FOLFIRI, the increased expression of ABC transcripts and proteins induced by T3 treatment is responsible for the augmented efflux of 5-FU and Irinotecan from the cancer cells. Taken together, these mechanisms contribute to the decreased efficacy of the chemotherapy and allow cells to escape the treatment. Created with BioRender.com .
Assuntos
Camptotecina/análogos & derivados , Neoplasias do Colo , Fluoruracila , Células-Tronco Neoplásicas , Esferoides Celulares , Receptores alfa dos Hormônios Tireóideos , Tri-Iodotironina , Humanos , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/efeitos dos fármacos , Células-Tronco Neoplásicas/patologia , Fluoruracila/farmacologia , Fluoruracila/uso terapêutico , Receptores alfa dos Hormônios Tireóideos/metabolismo , Receptores alfa dos Hormônios Tireóideos/genética , Células CACO-2 , Neoplasias do Colo/metabolismo , Neoplasias do Colo/tratamento farmacológico , Neoplasias do Colo/patologia , Neoplasias do Colo/genética , Esferoides Celulares/efeitos dos fármacos , Esferoides Celulares/metabolismo , Esferoides Celulares/patologia , Tri-Iodotironina/farmacologia , Leucovorina/farmacologia , Leucovorina/uso terapêutico , Camptotecina/farmacologia , Camptotecina/uso terapêutico , Fenótipo , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Família Aldeído Desidrogenase 1/metabolismo , Família Aldeído Desidrogenase 1/genética , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Retinal Desidrogenase/metabolismo , Retinal Desidrogenase/genética , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/genética , Subfamília B de Transportador de Cassetes de Ligação de ATP/metabolismo , Subfamília B de Transportador de Cassetes de Ligação de ATP/genéticaRESUMO
Background: Stimulation of ventricular hypertrophy and heart rate are two major cardiac effects of thyroid hormone (TH). The aim of this study was to determine in vivo which TH receptor (TR)-α or ß-and which mode of TR action-canonical gene expression or DNA-binding independent noncanonical action-mediate these effects. Methods: We compared global TRα and TRß knockout mice (TRαKO; TRßKO) with wild-type (WT) mice to determine the TR isoform responsible for T3 effects. The relevance of TR DNA binding was studied in mice with a mutation in the DNA-binding domain that selectively abrogates DNA binding and canonical TR action (TRαGS; TRßGS). Hearts were studied with echocardiography at baseline and after 7 weeks of T3 treatment. Gene expression was measured with real-time polymerase chain reaction. Heart rate was recorded with radiotelemetry transmitters for 7 weeks in untreated, hypothyroid, and T3-treated mice. Results: T3 induced ventricular hypertrophy in WT and TRßKO mice, but not in TRαKO mice. Hypertrophy was also induced in TRαGS mice. Thus, hypertrophy is mostly mediated by noncanonical TRα action. Similarly, repression of Mhy7 occurred in WT and TRαGS mice. Basal heart rate was largely dependent on canonical TRα action. But responsiveness to hypothyroidism and T3 treatment as well as expression of pacemaker gene Hcn2 were still preserved in TRαKO mice, demonstrating that TRß could compensate for absence of TRα. Conclusions: T3-induced cardiac hypertrophy could be attributed to noncanonical TRα action, whereas heart rate regulation was mediated by canonical TRα action. TRß could substitute for canonical but not noncanonical TRα action.
Assuntos
Cardiomegalia , Frequência Cardíaca , Camundongos Knockout , Receptores alfa dos Hormônios Tireóideos , Receptores beta dos Hormônios Tireóideos , Tri-Iodotironina , Animais , Masculino , Camundongos , Cardiomegalia/metabolismo , Cardiomegalia/genética , Hipotireoidismo/metabolismo , Hipotireoidismo/genética , Isoformas de Proteínas/metabolismo , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Receptores beta dos Hormônios Tireóideos/genética , Receptores beta dos Hormônios Tireóideos/metabolismoRESUMO
Thyroid hormones (TH) play critical roles during nervous system development and patients carrying coding variants of MCT8 (monocarboxylate transporter 8) or THRA (thyroid hormone receptor alpha) present a spectrum of neurological phenotypes resulting from perturbed local TH action during early brain development. Recently, human cerebral organoids (hCOs) emerged as powerful in vitro tools for disease modelling recapitulating key aspects of early human cortex development. To begin exploring prospects of this model for thyroid research, we performed a detailed characterization of the spatiotemporal expression of MCT8 and THRA in developing hCOs. Immunostaining showed MCT8 membrane expression in neuronal progenitor cell types including early neuroepithelial cells, radial glia cells (RGCs), intermediate progenitors and outer RGCs. In addition, we detected robust MCT8 protein expression in deep layer and upper layer neurons. Spatiotemporal SLC16A2 mRNA expression, detected by fluorescent in situ hybridization (FISH), was highly concordant with MCT8 protein expression across cortical cell layers. FISH detected THRA mRNA expression already in neuroepithelium before the onset of neurogenesis. THRA mRNA expression remained low in the ventricular zone, increased in the subventricular zone whereas strong THRA expression was observed in excitatory neurons. In combination with a robust up-regulation of known T3 response genes following T3 treatment, these observations show that hCOs provide a promising and experimentally tractable model to probe local TH action during human cortical neurogenesis and eventually to model the consequences of impaired TH function for early cortex development.
Assuntos
Córtex Cerebral , Transportadores de Ácidos Monocarboxílicos , Neurogênese , Organoides , RNA Mensageiro , Simportadores , Receptores alfa dos Hormônios Tireóideos , Feminino , Humanos , Gravidez , Córtex Cerebral/embriologia , Córtex Cerebral/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Transportadores de Ácidos Monocarboxílicos/genética , Transportadores de Ácidos Monocarboxílicos/metabolismo , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Neurogênese/genética , Neurônios/metabolismo , Organoides/metabolismo , Primeiro Trimestre da Gravidez/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Simportadores/genética , Simportadores/metabolismo , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos/metabolismo , Hormônios Tireóideos/genéticaRESUMO
Disrupted mitochondrial dynamics and mitophagy contribute to functional deterioration of skeletal muscle (SM) during aging, but the regulatory mechanisms are poorly understood. Our previous study demonstrated that the expression of thyroid hormone receptor α (TRα) decreased significantly in aged mice, suggesting that the alteration of thyroidal elements, especially the decreased TRα, might attenuate local THs action thus to cause the degeneration of SM with aging, while the underlying mechanism remains to be further explored. In this study, decreased expression of myogenic regulators Myf5, MyoD1, mitophagy markers Pink1, LC3II/I, p62, as well as mitochondrial dynamic factors Mfn1 and Opa1, accompanied by increased reactive oxygen species (ROS), showed concomitant changes with reduced TRα expression in aged mice. Further TRα loss- and gain-of-function studies in C2C12 revealed that silencing of TRα not only down-regulated the expression of above-mentioned myogenic regulators, mitophagy markers and mitochondrial dynamic factors, but also led to a significant decrease in mitochondrial activity and maximum respiratory capacity, as well as more mitochondrial ROS and damaged mitochondria. Notedly, overexpression of TRα could up-regulate the expression of those myogenic regulators, mitophagy markers and mitochondrial dynamic factors, meanwhile also led to an increase in mitochondrial activity and number. These results confirmed that TRα could concertedly regulate mitochondrial dynamics, autophagy, and activity, and myogenic regulators rhythmically altered with TRα expression. Summarily, these results suggested that the decline of TRα might cause the degeneration of SM with aging by regulating mitochondrial dynamics, mitophagy and myogenesis.
Assuntos
Mitocôndrias , Músculo Esquelético , Sarcopenia , Receptores alfa dos Hormônios Tireóideos , Animais , Camundongos , Envelhecimento/metabolismo , Linhagem Celular , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Mitocôndrias Musculares/metabolismo , Mitocôndrias Musculares/patologia , Dinâmica Mitocondrial , Mitofagia , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Espécies Reativas de Oxigênio/metabolismo , Sarcopenia/metabolismo , Sarcopenia/patologia , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismoRESUMO
Thyroid hormones (THs) T4 and T3 are vital for development, growth, and metabolism. Thyroid dysfunction can also cause problems in fertility, suggesting involvement of THs in reproduction. In zebrafish, there exist 2 forms of TH receptor alpha gene (thraa and thrab). Disruption of these genes by CRISPR/Cas9 showed no reproductive irregularities in the thraa mutant; however, inactivation of the thrab gene resulted in female infertility. Although young female mutants (thrabm/m) showed normal ovarian development and folliculogenesis before sexual maturation, they failed to release eggs during oviposition after sexual maturation. This spawning failure was due to oviductal blockage at the genital papilla. The obstruction of the oviduct subsequently caused an accumulation of the eggs in the ovary, resulting in severe ovarian hypertrophy, abdominal distention, and disruption of folliculogenesis. Gene expression analysis showed expression of both TH receptors and estrogen receptors in the genital papilla, suggesting a direct TH action and potential interactions between thyroid and estrogen signaling pathways in controlling genital papilla development and function. In addition to their actions in the reproductive tracts, THs may also have direct effects in the ovary, as suggested by follicle atresia and cessation of folliculogenesis in the heterozygous mutant (thrab+/m), which was normal in all aspects of female reproduction in young and sexually mature fish but exhibited premature ovarian failure in aged females. In summary, this study provides substantial evidence for roles of THs in controlling the development and functions of both reproductive tract and ovary.
Assuntos
Infertilidade Feminina , Ovário , Peixe-Zebra , Animais , Feminino , Peixe-Zebra/genética , Infertilidade Feminina/genética , Ovário/metabolismo , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo , Mutação , Sistemas CRISPR-Cas , Reprodução/genéticaRESUMO
OBJECTIVE: Progressive hepatic fibrosis can be considered the final stage of chronic liver disease. Hepatic stellate cells (HSC) play a central role in liver fibrogenesis. Thyroid hormones (TH, e.g. thyroxine; T4 and triiodothyronine; T3) significantly affect development, growth, cell differentiation and metabolism through activation of TH receptor α and/or ß (TRα/ß). Here, we evaluated the influence of TH in hepatic fibrogenesis. DESIGN: Human liver tissue was obtained from explanted livers following transplantation. TRα-deficient (TRα-KO) and wild-type (WT) mice were fed a control or a profibrogenic methionine-choline deficient (MCD) diet. Liver tissue was assessed by qRT-PCR for fibrogenic gene expression. In vitro, HSC were treated with TGFß in the presence or absence of T3. HSC with stable TRα knockdown and TRα deficient mouse embryonic fibroblasts (MEF) were used to determine receptor-specific function. Activation of HSC and MEF was assessed using the wound healing assay, Western blotting, and qRT-PCR. RESULTS: TRα and TRß expression is downregulated in the liver during hepatic fibrogenesis in humans and mice. TRα represents the dominant isoform in HSC. In vitro, T3 blunted TGFß-induced expression of fibrogenic genes in HSC and abrogated wound healing by modulating TGFß signalling, which depended on TRα presence. In vivo, TRα-KO enhanced MCD diet-induced liver fibrogenesis. CONCLUSION: These observations indicate that TH action in non-parenchymal cells is highly relevant. The interaction of TRα with TH regulates the phenotype of HSC via the TGFß signalling pathway. Thus, the TH-TR axis may be a valuable target for future therapy of liver fibrosis.
Assuntos
Fibroblastos , Células Estreladas do Fígado , Animais , Camundongos , Humanos , Células Estreladas do Fígado/metabolismo , Hormônios Tireóideos/metabolismo , Hormônios Tireóideos/farmacologia , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Fator de Crescimento Transformador betaRESUMO
Background: The importance of thyroid hormones (THs) for peripheral body temperature regulation has been long recognized, as medical conditions such as hyper- and hypothyroidism lead to alterations in body temperature and energy metabolism. In the past decade, the brain actions of THs and their respective nuclear receptors, thyroid hormone receptor α1 (TRα1) and thyroid hormone receptor beta (TRß), coordinating body temperature regulation have moved into focus. However, the exact roles of the individual TR isoforms and their precise neuroanatomical substrates remain poorly understood. Methods: Here we used mice expressing a mutant TRα1 (TRα1+m) as well as TRß knockouts to study body temperature regulation using radiotelemetry in conscious and freely moving animals at different ambient temperatures, including their response to oral 3,3',5-triiodothyronine (T3) treatment. Subsequently, we tested the effects of a dominant-negative TRα1 on body temperature after adeno-associated virus (AAV)-mediated expression in the hypothalamus, a region known to be involved in thermoregulation. Results: While TRß seems to play a negligible role in body temperature regulation, TRα1+m mice had lower body temperature, which was surprisingly not entirely normalized at 30°C, where defects in facultative thermogenesis or tail heat loss are eliminated as confounding factors. Only oral T3 treatment fully normalized the body temperature profile of TRα1+m mice, suggesting that the mutant TRα1 confers an altered central temperature set point in these mice. When we tested this hypothesis more directly by expressing the dominant-negative TRα1 selectively in the hypothalamus via AAV transfection, we observed a similarly reduced body temperature at room temperature and 30°C. Conclusion: Our data suggest that TRα1 signaling in the hypothalamus is important for maintaining body temperature. However, further studies are needed to dissect the precise neuroanatomical substrates and the downstream pathways mediating this effect.
Assuntos
Hipotálamo , Receptores dos Hormônios Tireóideos , Animais , Camundongos , Temperatura Corporal , Hipotálamo/metabolismo , Hipotireoidismo/metabolismo , Receptores dos Hormônios Tireóideos/metabolismo , Receptores alfa dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos , Tri-Iodotironina/farmacologia , Tri-Iodotironina/metabolismoRESUMO
Thyroid hormones (TH) are important modulators of bone remodeling and thus, thyroid diseases, in particular hyperthyroidism, are able to compromise bone quality and fracture resistance. TH actions on bone are mediated by the thyroid hormone receptors (TR) TRα1 and TRß1, encoded by Thra and Thrb, respectively. Skeletal phenotypes of mice lacking Thra (Thra0/0 ) and Thrb (Thrb-/- ) are well-described and suggest that TRα1 is the predominant mediator of TH actions in bone. Considering that bone cells might be affected by systemic TH changes seen in these mutant mice, here we investigated the effects of TR knockout on osteoblasts exclusively at the cellular level. Primary osteoblasts obtained from Thra0/0 , Thrb-/- , and respective wildtype (WT) mice were analyzed regarding their differentiation potential, activity and TH responsiveness in vitro. Thra, but not Thrb knockout promoted differentiation and activity of early, mature and late osteoblasts as compared to respective WT cells. Interestingly, while mineralization capacity and expression of osteoblast marker genes and TH target gene Klf9 was increased by TH in WT and Thra-deficient osteoblasts, Thrb knockout mitigated the responsiveness of osteoblasts to short (48 h) and long term (10 d) TH treatment. Further, we found a low ratio of Rankl, a potent osteoclast stimulator, over osteoprotegerin, an osteoclast inhibitor, in Thrb-deficient osteoblasts and in line, supernatants obtained from Thrb-/- osteoblasts reduced numbers of primary osteoclasts in vitro. In accordance to the increased Rankl/Opg ratio in TH-treated WT osteoblasts only, supernatants from these cells, but not from TH-treated Thrb-/- osteoblasts increased the expression of Trap and Ctsk in osteoclasts, suggesting that osteoclasts are indirectly stimulated by TH via TRß1 in osteoblasts. In conclusion, our study shows that both Thra and Thrb differentially affect activity, differentiation and TH response of osteoblasts in vitro and emphasizes the importance of TRß1 to mediate TH actions in bone.
Assuntos
Receptores dos Hormônios Tireóideos , Receptores alfa dos Hormônios Tireóideos , Camundongos , Animais , Receptores dos Hormônios Tireóideos/genética , Receptores dos Hormônios Tireóideos/metabolismo , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos/metabolismo , Receptores beta dos Hormônios Tireóideos/genética , Receptores beta dos Hormônios Tireóideos/metabolismo , Osteoblastos/metabolismo , Osteoclastos/metabolismo , Biologia , Ligante RANK/metabolismo , Camundongos KnockoutRESUMO
Mutations in thyroid hormone receptor α1 (TRα1) cause Resistance to Thyroid Hormone α (RTHα), a disorder characterized by hypothyroidism in TRα1-expressing tissues including the heart. Surprisingly, we report that treatment of RTHα patients with thyroxine to overcome tissue hormone resistance does not elevate their heart rate. Cardiac telemetry in male, TRα1 mutant, mice indicates that such persistent bradycardia is caused by an intrinsic cardiac defect and not due to altered autonomic control. Transcriptomic analyses show preserved, thyroid hormone (T3)-dependent upregulation of pacemaker channels (Hcn2, Hcn4), but irreversibly reduced expression of several ion channel genes controlling heart rate. Exposure of TRα1 mutant male mice to higher maternal T3 concentrations in utero, restores altered expression and DNA methylation of ion channels, including Ryr2. Our findings indicate that target genes other than Hcn2 and Hcn4 mediate T3-induced tachycardia and suggest that treatment of RTHα patients with thyroxine in high dosage without concomitant tachycardia, is possible.
Assuntos
Síndrome da Resistência aos Hormônios Tireóideos , Tiroxina , Masculino , Animais , Camundongos , Tiroxina/uso terapêutico , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Síndrome da Resistência aos Hormônios Tireóideos/genética , Hormônios Tireóideos , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Mutação , Taquicardia/genéticaRESUMO
Thyroid hormone and its receptor TRα1 play an important role in brain development. Several animal models have been used to investigate this function, including mice heterozygous for the TRα1R384C mutation, which confers receptor-mediated hypothyroidism. These mice display abnormalities in several autonomic functions, which was partially attributed to a developmental defect in hypothalamic parvalbumin neurons. However, whether other cell types in the hypothalamus are similarly affected remains unknown. Here, we used single-nucleus RNA sequencing to obtain an unbiased view on the importance of TRα1 for hypothalamic development and cellular diversity. Our data show that defective TRα1 signaling has surprisingly little effect on the development of hypothalamic neuronal populations, but it heavily affects hypothalamic oligodendrocytes. Using selective reactivation of the mutant TRα1 during specific developmental periods, we find that early postnatal thyroid hormone action seems to be crucial for proper hypothalamic oligodendrocyte maturation. Taken together, our findings underline the well-known importance of postnatal thyroid health for brain development and provide an unbiased roadmap for the identification of cellular targets of TRα1 action in mouse hypothalamic development.
Assuntos
RNA , Receptores alfa dos Hormônios Tireóideos , Camundongos , Animais , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos , Glândula Tireoide , Hipotálamo/metabolismoRESUMO
Thyroid hormone (T3) is essential for normal development and metabolism, especially during postembryonic development, a period around birth in mammals when plasma T3 levels reach their peak. T3 functions through two T3 receptors, TRα and TRß. However, little is known about the tissue-specific functions of TRs during postembryonic development because of maternal influence and difficulty in manipulation of mammalian models. We have studied Xenopus tropicalis metamorphosis as a model for human postembryonic development. By using TRα knockout (Xtr·thratmshi ) tadpoles, we have previously shown that TRα is important for T3-dependent intestinal remodeling and hindlimb development but not tail resorption during metamorphosis. Here, we have identified genes bound by TR in premetamorphic wild-type and Xtr·thratmshi tails with or without T3 treatment by using chromatin immunoprecipitation-sequencing and compared them with those in the intestine and hindlimb. Compared to other organs, the tail has much fewer genes bound by TR or affected by TRα knockout. Bioinformatic analyses revealed that among the genes bound by TR in wild-type but not Xtr·thratmshi organs, fewer gene ontology (GO) terms or biological pathways related to metamorphosis were enriched in the tail compared to those in the intestine and hindlimb. This difference likely underlies the drastic effects of TRα knockout on the metamorphosis of the intestine and hindlimb but not the tail. Thus, TRα has tissue-specific roles in regulating T3-dependent anuran metamorphosis by directly targeting the pathways and GO terms important for metamorphosis.
Assuntos
Receptores alfa dos Hormônios Tireóideos , Proteínas de Xenopus , Xenopus , Animais , Humanos , Regulação da Expressão Gênica no Desenvolvimento/genética , Mamíferos/metabolismo , Metamorfose Biológica/genética , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Tri-Iodotironina/genética , Tri-Iodotironina/metabolismo , Tri-Iodotironina/farmacologia , Xenopus/genética , Xenopus/metabolismo , Proteínas de Xenopus/genética , Proteínas de Xenopus/metabolismoRESUMO
Background: Mutations of thyroid hormone receptor α (TRα1) result in resistance to thyroid hormone (RTHα), exhibiting symptoms of retarded growth, delayed bone maturation, anemia, and severe constipation. Using a mouse model of RTHα (Thra1PV/+ mouse), we aimed at understanding the molecular basis underlying the severe constipation observed in patients. Methods: The Thra1PV/+ mouse expresses a strong dominant negative mutant, PV, which has lost T3 binding and transcription activity. Thra1PV/+ mouse faithfully reproduces growth abnormalities and anemia as shown in RTHα patients and therefore is a valid model to examine causes of severe constipation in patients. We used histopathological analysis, confocal fluorescence imaging, transmission electron microscopy (TEM), and gene expression profiles to comprehensively analyze the colonic abnormalities of Thra1PV/+ mouse. Results: We found a significant increase in colonic transit time and decrease stool water content in Thra1PV/+ mouse, mimicking constipation as found in patients. Histopathological analysis showed expanded lamina propria filled with interstitium fluid between crypt columns, enlarged muscularis mucosa, and increased content of collagen in expanded submucosa. The TEM analysis revealed shorter muscle fibers with wider gap junctions between muscle cells, fewer caveolae, and hypoplastic interstitial cells of Cajal (ICC) in the rectal smooth muscles of Thra1PV/+ mice. These abnormal histological manifestations suggested defective intercellular transfer of small molecules, electrolytes, and signals for communication among muscles cells, validated by Lucifer Yellow transferring assays. Expression of key smooth muscle contractility regulators, such as calmodulin, myosin light-chain kinase, and phosphorylated myosin light chain, was markedly lower, and c-KIT signaling in ICC was attenuated, resulting in decreased contractility of the rectal smooth muscles of Thra1PV/+ mice. Collectively, these abnormal histopathological alterations and diminished contractility regulators led to the constipation exhibited in patients. Conclusions: This is the first demonstration that TRα1 mutants could act to cause abnormal rectum smooth muscle organization, defects in intercellular exchange of small molecules, and decreased expression of contractility regulators to weaken the contractility of rectal smooth muscles. These findings provide new insights into the molecular basis underlying constipation found in RTHα patients.
Assuntos
Anemia , Receptores alfa dos Hormônios Tireóideos , Humanos , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos , Mutação , Constipação Intestinal/genéticaRESUMO
Hypothyroidism has been shown to reduce infarct size in rats, but the underlying mechanisms are unclear. We used isolated pressure-constant perfused hearts of control, hypothyroid and hyperthyroid mice and measured infarct size, functional parameters and phosphorylation of key molecules in cardioprotective signaling with matched heart rate. Compared with controls, hypothyroidism was cardioprotective, while hyperthyroidism was detrimental with enlarged infarct size. Next, we asked how thyroid hormone receptor α (TRα) affects ischemia/reperfusion (IR) injury. Thus, canonical and noncanonical TRα signaling was investigated in the hearts of (i) mice lacking TRα (TRα0), (ii) with a mutation in TRα DNA-binding domain (TRαGS) and (iii) in hyperthyroid TRα0 (TRα0hyper) and TRαGS mice (TRαGShyper). TRα0 mouse hearts were protected against IR injury. Furthermore, infarct size was reduced in the hearts of TRαGS mice that lack canonical TRα signaling but maintain noncanonical TRα action. Hyperthyroidism did not increase infarct size in TRα0 and TRαGS mouse hearts. These cardioprotective effects were not associated with increased phosphorylation of key proteins of RISK, SAFE and eNOS pathways. In summary, chronic hypothyroidism and the lack of canonical TRα signaling are cardioprotective in IR injury and protection is not due to favorable changes in hemodynamics.
Assuntos
Hipertireoidismo , Hipotireoidismo , Traumatismo por Reperfusão , Ratos , Camundongos , Animais , Hipotireoidismo/metabolismo , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Hipertireoidismo/metabolismo , Hemodinâmica , Traumatismo por Reperfusão/metabolismo , Infarto , Miocárdio/metabolismoRESUMO
The THRA gene, encoding the thyroid hormone nuclear receptor TRα1, is expressed in an increasing gradient at the bottom of intestinal crypts, overlapping with high Wnt and Notch activities. Importantly, THRA is upregulated in colorectal cancers, particularly in the high-Wnt molecular subtype. The basis of this specific and/or altered expression pattern has remained unknown. To define the mechanisms controlling THRA transcription and TRα1 expression, we used multiple in vitro and ex vivo approaches. Promoter analysis demonstrated that transcription factors important for crypt homeostasis and altered in colorectal cancers, such as transcription factor 7-like 2 (TCF7L2; Wnt pathway), recombining binding protein suppressor of hairless (RBPJ; Notch pathway), and homeobox protein CDX2 (epithelial cell identity), modulate THRA activity. Specifically, although TCF7L2 and CDX2 stimulated THRA, RBPJ induced its repression. In-depth analysis of the Wnt-dependent increase showed direct regulation of the THRA promoter in cells and of TRα1 expression in murine enteroids. Given our previous results on the control of the Wnt pathway by TRα1, our new results unveil a complex regulatory loop and synergy between these endocrine and epithelial-cell-intrinsic signals. Our work describes, for the first time, the regulation of the THRA gene in specific cell and tumor contexts.
Assuntos
Neoplasias Colorretais , Genes erbA , Humanos , Camundongos , Animais , Receptores dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/genética , Receptores alfa dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos/metabolismo , Neoplasias Colorretais/genéticaRESUMO
Cadmium is a ubiquitous environmental pollutant, which can increase the risk of preeclampsia. This study was designed to determine the mechanism of cadmium exposure during pregnancy impaired placental angiogenesis that was associated with the occurrence of preeclampsia. The effects of cadmium exposure on placental thyroid hormone receptor signaling were explored. JEG3 cells were treated with CdCl2 (20 µM) and the Dio2 inhibitor, IOP (100 µM). Cadmium levels in maternal blood and placentae were increased in preeclampsia group. Placental angiogenesis of preeclampsia was decreased with decreased expression of PLGF and VEGF and increased expression of sFlt1. Meanwhile, the expression and nuclear translocation of thyroid hormone receptor α were decreased in preeclampsia placenta, as well as the expression of Dio2, but not the expression and nuclear translocation of thyroid hormone receptor ß. Furthermore, we found that cadmium exposure downregulated the expression of thyroid hormone receptor α and Dio2, but not the expression of thyroid hormone receptor ß in JEG3 cells. Also, we found that cadmium exposure decreased the expression of PLGF and VEGF and increased the expression of sFlt1 in JEG3 cells. IOP pretreatment decreased the expression of PLGF and increased the expression of sFlt1. In conclusion, our results elucidated that cadmium exposure would impair placental angiogenesis in preeclampsia through disturbing thyroid hormone receptor signaling.
Assuntos
Poluentes Ambientais , Pré-Eclâmpsia , Cádmio/metabolismo , Linhagem Celular Tumoral , Poluentes Ambientais/metabolismo , Feminino , Humanos , Neovascularização Patológica , Placenta/metabolismo , Fator de Crescimento Placentário/metabolismo , Fator de Crescimento Placentário/farmacologia , Pré-Eclâmpsia/induzido quimicamente , Pré-Eclâmpsia/metabolismo , Gravidez , Receptores dos Hormônios Tireóideos/metabolismo , Receptores alfa dos Hormônios Tireóideos/metabolismo , Receptores beta dos Hormônios Tireóideos/metabolismo , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/metabolismo , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/farmacologiaRESUMO
Long-term exposure of exogenous compounds to thyroid hormone receptors (TRs) may lead to thyroid dysfunction. Quantitative structure-activity relationship (QSAR) is expected to predicting the binding affinity of compounds to TR. In this work, two comprehensive and large datasets for TRα and TRß were collected and investigated. Five machine learning models were established to predict the pIC50 of compounds. Meanwhile, the reliability of the models was ensured by a variety of evaluation parameters. The results showed that the support vector regression model exhibited the best robustness and external prediction ability (r2train = 0.77, r2test = 0.78 for TRα, r2train = 0.78, r2test = 0.80 for TRß). We have proposed an appropriate mechanism for explaining the TR binding affinity of a compound. The molecular volume, mass, and aromaticity affected the activity of TRα. Molecular weight, electrical properties and molecular hydrophilicity played a significant role in the binding affinity of compounds to TRß. We also characterized the application domain of the model. Finally, the obtained models were utilized to predict the TR binding affinities of 109 compounds from the list of endocrine disruptors. Therefore, this model is expected to be an effective tool for alerting the effects of exogenous compounds on the thyroid system.
Assuntos
Receptores dos Hormônios Tireóideos , Receptores alfa dos Hormônios Tireóideos , Algoritmos , Aprendizado de Máquina , Relação Quantitativa Estrutura-Atividade , Receptores dos Hormônios Tireóideos/química , Receptores dos Hormônios Tireóideos/metabolismo , Reprodutibilidade dos Testes , Receptores alfa dos Hormônios Tireóideos/química , Receptores alfa dos Hormônios Tireóideos/metabolismo , Receptores beta dos Hormônios Tireóideos/química , Receptores beta dos Hormônios Tireóideos/metabolismoRESUMO
Thyroid hormone (T3 ) acts on the testis via thyroid hormone receptor alpha 1 (TRα1), though the cellular localization of TRα1 in testis remains controversial. Studies on the presence of TRα1 in the epididymis are also lacking. The present study, therefore, examined the cellular localization and expression pattern of TRα1 in testis and epididymis of Parkes mice during postnatal development. Immunohistochemical results showed localization of TRα1 in interstitial and tubular compartments of the testis all through the development. On postnatal day (PND) 14, only leptotene spermatocytes showed TRα1-immunoreactivity in the testis, while at PND 28, 42, and 90, a diverse staining pattern for TRα1 was seen in almost all the seminiferous tubules mainly in leptotene spermatocytes, round and elongating spermatids, and in Leydig cells. Further, qRT-PCR and immunoblot analyses showed that TRα1 was expressed in the testis at the transcript as well as protein level throughout the postnatal development. TRα1 was also seen in principal cells of the epididymis, with maximal expression at PND 90. TRα1 was also present in cauda epididymidal spermatozoa of adult mice at PND 90. The results suggest that TRα1 is expressed in the testis and epididymis and that it may help to regulate the spermatogenic process and male fertility.
Assuntos
Epididimo , Testículo , Receptores alfa dos Hormônios Tireóideos/genética , Animais , Epididimo/crescimento & desenvolvimento , Epididimo/metabolismo , Imuno-Histoquímica , Masculino , Camundongos , Espermátides/metabolismo , Testículo/metabolismo , Receptores alfa dos Hormônios Tireóideos/metabolismoRESUMO
Thyroid hormone is critical during the development of vertebrates and affects the function of many organs and tissues, especially the intestine. Triiodothyronine (T3) is the active form and can bind to thyroid hormone nuclear receptors (TRs) to play a vital role in the development of vertebrates. The resistance to thyroid hormone α, as seen in patients, has been mimicked by the ThraE403X mutation. To investigate the mechanisms underlying the effect of TRα1 on intestinal development, the present study employed proteomic analysis to identify differentially expressed proteins (DEPs) in the distal ileum between homozygous ThraE403X/E403X and wild-type Thra+/+ mice. A total of 1,189 DEPs were identified, including 603 upregulated and 586 downregulated proteins. Proteomic analysis revealed that the DEPs were highly enriched in the metabolic process, the developmental process, the transporter of the nutrients, and the intestinal immune system-related pathway. Of these DEPs, 20 proteins were validated by parallel reaction monitoring analysis. Our intestinal proteomic results provide promising candidates for future studies, as they suggest novel mechanisms by which TRα1 may influence intestinal development, such as the transport of intestinal nutrients and the establishment of innate and adaptive immune barriers of the intestine.