Thyroid Follicular Cell Proliferation Research Articles

TAF1 is needed for the proliferation and maturation of thyroid follicle cells via Notch signaling.

Thyroid dysgenesis (TD) is the common pathogenic mechanism of congenital hypothyroidism (CH). In addition, known pathogenic genes are limited to those that are directly involved in thyroid development. To identify additional candidate pathogenetic genes, we performed forward genetic screening for TD in zebrafish, followed by positional cloning. The candidate gene was confirmed in vitro using the Nthy-ori 3.1 cell line and in vivo using a zebrafish model organism. We obtained a novel zebrafish line with thyroid dysgenesis and identified the candidate pathogenetic gene taf1 by positional cloning. Further molecular studies revealed that taf1 was needed for the proliferation of thyroid follicular cells by binding to the NOTCH1 promoter region. Knockdown of TAF1 impaired the proliferation and maturation of thyroid cells, thereby leading to thyroid dysplasia. This study showed that TAF1 promoted Notch signaling and that this association played a pivotal role in thyroid development.

Abstract #1400018: Genetic Alterations in NRAS, TERT, PIK3CA and SPEN Genes Leading to an Aggressive Metastatic RAI Refractory Follicular Thyroid Cancer

Follicular thyroid cancer (FTC) is a well-differentiated thyroid tumor and the second most common type after papillary thyroid cancer (PTC) with higher incidence of distant metastases, more aggressive behavior, and poorer outcome than PTC Patient is 43-year-old female with 6.2 cm TR4 left thyroid nodule on Neck US. On Exam, Cricoid is deviated to the right with left thyroid firm nodule. FNA showed Follicular neoplasm. TSH level was 1.59 (0.45-4.70 mIU/L) and Free T4 level: 1.19 (0.78-2.20 ng/dl) CT scan of neck with contrast and MRI thoracic spine: Large, solid heterogenous mass in left thyroid lobe causing lateral displacement and mild narrowing of the trachea with retrosternal extension, Osteolytic lesion of T4 vertebral body and right sided pleura-based mass at the level of T7-T8 with No enlarged cervical lymph nodes. IR biopsy of vertebra: thyroid Origin Metastatic Carcinoma, Patient underwent total thyroidectomy with central neck dissection. Follicular thyroid cancer (STAGE II pT3A,pN1B,pM1) Mutational Testing: Negative BRAF and KRAS with Positive NRAS, PIK3CA, SPEN and TERT. Patient started on TSH suppression therapy. 1 month Later: Thyroglobulin: 2443.4 ng/ml (1.3-31.8), Thyroglobulin Ab< 0.9 (0.0-4.0 IU/ml), TSH 0.02 with Free T4 2.53 FDG PET: Multifocal osseous metastatic disease, predominantly in the axial skeleton Thyrogen stimulated WBS I-123 showed No evidence of residual or metastatic disease. Patient recieved 214 mCi of iodine-131. Post treatment MN scan showed accumulation of iodine in the metastatic bone lesions with small focal activity in the thyroidectomy bed. Post RAI treatment: TG trended to 1102.7 then 1307 Patient Completed 10 fractions of external beam radiation on T4 spine Ultrasound thyroid: No residual thyroid tissue or suspicious lymph nodes Oncology started Bone directed therapy with zoledronate with consideration of PIK3CA mutation targeted therapy with Everolimus or Temsirolimus FTC is more aggressive with poorer prognosis than PTC that is more likely to hematogenously disseminate, with mortality rate of 50%. The neoplastic proliferation of thyroid follicular cells develops by altering multiple molecular pathways such as the PI3K/AKT pathway involving the RAS, RAF, RET, and NTRK1 genes. RAS is a dual activator of the mitogen activated protein kinase and PI3K/AKT pathways TERT is a catalytic subunit of the telomerase complex. Reported in 11–17% of FTC. TERT promoter mutations associated with tumor aggressiveness and mortality PIK3CA encodes p110-alpha, is a catalytic subunit of phosphatidylinositol 3-kinase (PI3K) involves in thyroid cancer tumorigenesis and progression, reported in 7.7% of FTC with sensitivity to therapies targeting PI3K49-56, AKT57-58, or mTOR59-66. In our patient, pretreatment MN scan failed to show RAI avid lesions but PET showed increase FDG uptake and since receiving RAI treatment helped in lowering TG that indicate a possibility of mixture of RAI avid and non-RAI avid lesions existing at same time so RAI treatment is still recommended despite negative Diagnostic Scan for persistent elevated TG.

Excessive iodine induces thyroid follicular epithelial cells apoptosis by activating HIF-1α-mediated hypoxia pathway in Hashimoto thyroiditis

BackgroundHashimoto thyroiditis (HT) is considered the most common autoimmune thyroid disease. A growing body of evidence suggests that HT incidence correlates with excessive iodine intake. We should probe the effects of excessive iodine intake in HT development and its possible mechanism.Methods and resultsThe study recruited 20 patients: 10 with HT and 10 with nodular goiter. We detected the expression of an apoptosis-related protein caspase-3 by immunohistochemistry. In vitro study, we explored the proliferation and apoptosis status in thyroid follicular cells (TFCs) stimulated with different iodine concentrations by MTT and flow cytometry. Then we performed RNA sequence analysis of Nthy-ori3-1 cells treated for 48 h with KI to probe the underlying mechanism. Finally, we used RT-PCR and siRNA interference to verify the results. We identified apoptosis in thyroid tissue obtained from HT patients coincides with the increase of caspase-3 levels. In vitro study, iodine suppressed proliferation of TFCs and promoted TFCs apoptosis in a dose-dependent manner with regulating caspase-3 activation. HIF-1α-NDRG1 mediated hypoxia pathway activation promoted the transmission of essential apoptosis signals in TFCs.ConclusionOur study confirmed that excessive iodine adsorption activates the HIF-1α-mediated hypoxia pathway to promote apoptosis of TFCs, which may be an important risk factor contributing to HT development.

Abstract #1180171: A case report of acromegaly in a patient with papillary thyroid cancer

Acromegaly is a rare disorder due to hypersecretion of growth hormone (GH) with a prevalence of 4,600 per million and an incidence of 116.9 new cases per million per year. The majority of cases are caused by a somatotroph GH-secreting anterior pituitary adenoma which can have significant morbidity and mortality. Several studies indicate that excess IGF-1 can stimulate proliferation of thyroid follicular cells and increase the risk of thyroid cancer greater than five-fold.

Rabbit thyroid extracellular matrix as a 3D bioscaffold for thyroid bioengineering: a\xa0preliminary\xa0in\xa0vitro\xa0study

BackgroundAdvances in regenerative medicine technologies have been strongly proposed in the management of thyroid diseases. Mechanistically, the adoption of thyroid bioengineering requires a scaffold that shares a similar three-dimensional (3D) space structure, biomechanical properties, protein component, and cytokines to the native extracellular matrix (ECM).Methods24 male New Zealand white rabbits were used in this experimental study. The rabbit thyroid glands were decellularized by immersion/agitation decellularization protocol. The 3D thyroid decellularization scaffolds were tested with histological and immunostaining analyses, scanning electron microscopy, DNA quantification, mechanical properties test, cytokine assay and cytotoxicity assays. Meanwhile, the decellularization scaffold were seeded with human thyroid follicular cells, cell proliferation and thyroid peroxidase were determined to explore the biocompatibility in vitro.ResultsNotably, through the imaging studies, it was distinctly evident that our protocol intervention minimized cellular materials and maintained the 3D spatial structure, biomechanical properties, ECM composition, and biologic cytokine. Consequently, the decellularization scaffold was seeded with human thyroid follicular cells, thus strongly revealing its potential in reinforcing cell adhesion, proliferation, and preserve important protein expression.ConclusionsThe adoption of our protocol to generate a decellularized thyroid scaffold can potentially be utilized in transplantation to manage thyroid diseases through thyroid bioengineering.

Antiproliferative and Cytotoxic Effects of Schinus terebinthifolia Leaf Extract on Thyroid Follicular Cells

Schinus terebinthifolia Raddi, Anacardiaceae, is a Brazilian plant species, with anti-inflammatory and healing properties. This plant is popularly used for the treatment of several disorders, including thyroid dysfunctions. However, its influence on thyroid physiology is not fully understood. This study investigated the effects of a S. terebinthifolia leaf methanolic extract on the proliferation, viability, and reactive oxygen species (ROS) level of rat thyroid follicular cells. For this, PCCL3 cells were treated with different concentrations of the extract (1–100 μg/ml) and times of exposure (24, 48, and 72 h). The 30 μg/ml concentration significantly reduced cell viability. Thyrocytes treated with the extract presented altered cell morphologies and evidence of oxidative stress. The 50 μg/ml concentration of the extract elicited a pronounced increase in ROS level. The results demonstrated that S. terebinthifolia leaf is harmful to thyroid cells after exposure to high concentrations for prolonged periods. These potentially harmful effects should be considered when this medicinal plant is used in humans. This observation is particularly relevant to individuals with an increased risk of thyroid dysfunctions.

SUN-LB129 Thyroglobulin Stimulates the Secretion of Thyroxine From Thyroid Epithelial Cells in Suspension Culture via Nuclear Factor-κB Signaling Pathway

The nuclear factor (NF)-κB signaling pathway controls a variety of biological functions such as cell growth and differentiation as well as immune and inflammatory responses. Two distinct pathways of NF-κB activation are known. NF-κB signaling via non-canonical pathway plays an important role in maintaining normal thyroid function, namely, thyroid cells survival and expression of thyroid-specific proteins, such as NIS, TPO and thyroglobulin (Tg). The primary function of thyroid cells is the production of thyroid hormones, which are cleaved out by various processing enzymes from the modified tyrosine residues of the Tg molecule. Although Tg is currently recognized as no more than a scaffold protein for thyroid hormone synthesis, our group has shown that Tg stimulates the proliferation of rat thyroid follicular FRTL-5 cells via PI3K pathway. The signaling pathways underlying various functions of thyroid cells have been extensively investigated but some discrepancies still exist, depending on the experimental model systems and the types of cells used. Recently, our group discovered that Tg may directly regulate the synthesis of thyroid hormones in thyroid cells. In this study, we performed suspension culture of porcine thyroid cells and aimed to elucidate the mechanism of the effect of Tg on thyroid cells. Porcine thyroid epithelial cells were prepared from thyroid gland by enzymatic digestion and cultured in monolayer or in suspension culture. Various concentrations of Tg were added to the medium and cultured for several days. Then, the conditioned medium was collected and the amount of thyroid hormone was measured by reversed phase chromatography; the cells were harvested and mRNA levels of hormone-processing enzymes, cathepsin B, K, L and dipeptidyl peptidase I, II (DPP I, II), were measured by quantitative PCR. The amount and activation of cell signaling molecules were also evaluated by western blotting. Tg stimulated the secretion of thyroid hormone, thyroxine, from porcine thyroid cells in suspension culture, however, no stimulation by Tg was observed in monolayer culture. The expression of mRNAs of cathepsin B, K and L were reduced and that of DPP II was increased by the treatment of Tg in suspension culture. Tg increased the amount of NF-κB p52 and Rel B dose dependently. On the other hand, TSH had little effects on the amount of these proteins. Tg and TSH both activated PDK1 and MAPK p44/42 but not Akt. These results suggest that Tg regulates thyroid hormone synthesis in totally different way from TSH by altering the expression levels of hormone-processing enzymes in thyroid cells. This stimulatory effect might be mediated by NF-κB signaling pathway, whereas the proliferative effect of Tg under these conditions might be exerted via MAPK signaling pathway. The detailed mechanisms of these effects of Tg on thyroid cells are under investigation.

PD-1/PD-L1 affects Graves progression through lymphocytes on the proliferation, apoptosis and inflammatory cytokine secretion of thyroid follicular epithelial cells.

We aimed to investigate the role of programmed cell death protein 1 (PD-1) and T lymphocytes in the proliferation, apoptosis and secretion of cells from patients and mice with Graves' disease (GD). The levels of serum hormones, related antibodies and inflammatory cytokines in GD patients were determined by electrochemiluminescence immunoassay and ELISA. The percentages of CD4 and CD8 T-lymphocytes and PD-1 expression were examined by flow cytometry. A GD mouse model, a thyroid follicular epithelial cell, and a CD4+PD-1+, CD4+PD-1- and CD8+PD-1+, CD8+PD-1- T lymphocyte co-culture system were constructed. The viability, apoptosis-related markers, serum hormones, related antibodies and inflammatory cytokines in thyroid follicular epithelial cells were determined by CCK-8, Western blot, qTR-PCR, electrochemiluminescence immunoassay and ELISA. Elevated free thyroid hormones (FT3, FT4), thyroid hormone antibodies (TRAb, TPOAb and TGAb), inflammatory cytokines, and inhibited TSH were observed in GD patients. The percentage of CD4+ T cells was increased, while that of CD8+ T cells was reduced in GD patients. PD-1 expression level was lifted in both CD4+ and CD8+ cells from GD patients. In mouse thyroid follicular epithelial cells co-cultured with CD4+PD-1+ and CD8+PD-1+ T lymphocytes, the cell viability, TH and TRAb levels and inflammatory cytokines level were the highest, while the TSH level and apoptosis were the lowest. PD-1 positive T lymphocytes were able to promote viability and inhibit apoptosis of thyroid follicular epithelial cells, which further caused a more accelerated development of GD.

Differential modulation by vanadium pentoxide of the secretion of CXCL8 and CXCL11 chemokines in thyroid cells

Recently it has been hypothesized that vanadium serves a carcinogenic role in the thyroid. However, to date, no invivo or invitro studies have evaluated thyroid disruption in humans and/or animals following exposure to vanadium. The present study evaluated the effect of vanadium pentoxide (V2O5) on cell viability and proliferation, and chemokine (C‑X‑C motif) ligand (CXCL)8 and CXCL11 secretion in normal thyrocytes. The results demonstrated that V2O5 had no effect on thyroid follicular cell viability and proliferation. However, V2O5 was able to induce the secretion of CXCL8 and CXCL11 chemokines from thyrocytes. Notably, V2O5 synergistically increased the effect of the interferon (IFN)‑γ on CXCL11 secretion. In addition, V2O5 synergistically increased the effect of tumor necrosis factor‑α on CXCL8 secretion, and abolished the inhibitory effect of IFN‑γ. Overall this induction of CXCL8 and CXCL11 secretion may lead to the induction and perpetuation of an inflammatory reaction in the thyroid. Further studies are now required to evaluate thyroid function and nodule development in subjects who are occupationally exposed, or living in polluted areas.

Vanadium pentoxide induces the secretion of CXCL9 and CXCL10 chemokines in thyroid cells

Vanadium is a grey metal, existing in different states of oxidation, whose most common form in commercial products is vanadium pentoxide(V2O5). All vanadium compounds have been considered toxic. A carcinogenic role of vanadium on the thyroid has recently been proposed. However no invivo or invitro studies have evaluated thyroid disruption in humans and/or animals after exposure to vanadium. In the present study we evaluate the effect of V2O5 on proliferation, and chemokine secretion in normal thyrocytes. Our study demonstrated that V2O5 has no effect on thyroid follicular cell viability or proliferation, but it is able to induce the secretion of T-helper(Th)1 chemokines into the thyroid, synergistically increasing the effect of important Th1 cytokines such as interferon (IFN)γ and tumor necrosis factor (TNF)α. Through this process, V2O5 promotes the induction and perpetuation of an inflammatory reaction in the thyroid. Further studies are necessary to evaluate thyroid function, and nodules, in subjects occupationally exposed, or living in polluted areas.

GLIS3 is indispensable for TSH/TSHR-dependent thyroid hormone biosynthesis and follicular cell proliferation.

Deficiency in Krüppel-like zinc finger transcription factor GLI-similar 3 (GLIS3) in humans is associated with the development of congenital hypothyroidism. However, the functions of GLIS3 in the thyroid gland and the mechanism by which GLIS3 dysfunction causes hypothyroidism are unknown. In the current study, we demonstrate that GLIS3 acts downstream of thyroid-stimulating hormone (TSH) and TSH receptor (TSHR) and is indispensable for TSH/TSHR-mediated proliferation of thyroid follicular cells and biosynthesis of thyroid hormone. Using ChIP-Seq and promoter analysis, we demonstrate that GLIS3 is critical for the transcriptional activation of several genes required for thyroid hormone biosynthesis, including the iodide transporters Nis and Pds, both of which showed enhanced GLIS3 binding at their promoters. The repression of cell proliferation of GLIS3-deficient thyroid follicular cells was due to the inhibition of TSH-mediated activation of the mTOR complex 1/ribosomal protein S6 (mTORC1/RPS6) pathway as well as the reduced expression of several cell division-related genes regulated directly by GLIS3. Consequently, GLIS3 deficiency in a murine model prevented the development of goiter as well as the induction of inflammatory and fibrotic genes during chronic elevation of circulating TSH. Our study identifies GLIS3 as a key regulator of TSH/TSHR-mediated thyroid hormone biosynthesis and proliferation of thyroid follicular cells and uncovers a mechanism by which GLIS3 deficiency causes neonatal hypothyroidism and prevents goiter development.

The RET/PTC-RAS-BRAF linear signaling cascade mediates the motile and mitogenic phenotype of thyroid cancer cells.

In papillary thyroid carcinomas (PTCs), rearrangements of the RET receptor (RET/PTC) and activating mutations in the BRAF or RAS oncogenes are mutually exclusive. Here we show that the 3 proteins function along a linear oncogenic signaling cascade in which RET/PTC induces RAS-dependent BRAF activation and RAS- and BRAF-dependent ERK activation. Adoptive activation of the RET/PTC-RAS-BRAF axis induced cell proliferation and Matrigel invasion of thyroid follicular cells. Gene expression profiling revealed that the 3 oncogenes activate a common transcriptional program in thyroid cells that includes upregulation of the CXCL1 and CXCL10 chemokines, which in turn stimulate proliferation and invasion. Thus, motile and mitogenic properties are intrinsic to transformed thyroid cells and are governed by an epistatic oncogenic signaling cascade.

Thyroid tumor formation in the male mouse induced by fluopyram is mediated by activation of hepatic CAR/PXR nuclear receptors

Fluopyram, a broad spectrum fungicide, caused an increased incidence of thyroid follicular cell (TFC) adenomas in males at the highest dose evaluated (750ppm equating to 105mg/kg/day) in the mouse oncogenicity study. A series of short-term mechanistic studies were conducted in the male mouse to characterize the mode of action (MOA) for the thyroid tumor formation and to determine if No Observed Effect Levels (NOELs) exist for each key event identified. The proposed MOA consists of an initial effect on the liver by activating the constitutive androstane (Car) and pregnane X (Pxr) nuclear receptors causing increased elimination of thyroid hormones followed by an increased secretion of thyroid stimulating hormone (TSH). This change in TSH secretion results in an increase of TFC proliferation which leads to hyperplasia and eventually adenomas after chronic exposure. Car/Pxr nuclear receptors were shown to be activated as indicated by increased activity of specific Phase I enzymes (PROD and BROD, respectively). Furthermore, evidence of increased T4 metabolism was provided by the induction of phase II enzymes known to preferentially use T4 as a substrate. Additional support for the proposed MOA was provided by demonstrating increased Tsh β transcripts in the pituitary gland. Finally, increased TFC proliferation was observed after 28days of treatment. In these dose–response studies, clear NOELs were established for phase 2 liver enzyme activities, TSH changes and TFC proliferation. Furthermore, compelling evidence for Car/Pxr activation being the molecular initiating event for these thyroid tumors was provided by the absence of the sequential key events responsible for the TCF tumors in Car/Pxr KO mice when exposed to fluopyram. In conclusion, fluopyram thyroid toxicity is mediated by activation of hepatic Car/Pxr receptors and shows a threshold dependent MOA.

Is prophylactic anti-resorptive therapy required in thyroid cancer patients receiving TSH-suppressive treatment with thyroxine?

Keywords TSH suppression Osteoporosis Thyroxine Bisphosphonate Atrial fibrillation FRAX QFractureIntroductionThyroid stimulating hormone (TSH) acts via its G-proteincoupled receptor (TSHR) to stimulate proliferation ofthyroid follicular cells, iodine uptake, and the synthesis andsecretion of thyroglobulin, thyroxine (T4) and 3,5,3

High Iodine Blocks a Notch/miR-19 Loop Activated by the BRAFV600E Oncoprotein and Restores the Response to TGFβ in Thyroid Follicular Cells

Excess iodine inhibits thyroid follicular cell proliferation associated with TGFβ pathway activation, although thyroid cancers are frequently refractory to TGFβ signaling. The TGFβ pathway is predicted to be regulated by miR-17-92 cluster microRNAs. MicroRNAs are small noncoding RNAs that inhibit target mRNA translation and have emerged as potent modulators of tumorigenesis. Although the BRAF(V600E) mutation is the most prevalent alteration in thyroid cancer, the impact of iodine intake on BRAF-mediated oncogenesis remains unclear. Therefore, the aim of this study was to investigate the influence of high iodine on miR-17-92 transcriptional regulation and expression in thyroid cells expressing activated BRAF. Rat thyroid follicular cells that conditionally express BRAF(V600E) under doxycycline stimulation (PC-BRAF(V600E)-6) were derived from the PCCl3 line. These cells were treated with doxycycline for two days, in the absence or presence of 10 μM sodium iodide. The thyroid cancer cell lines BCPAP and KTC2 were also analyzed. Expression of the miR-17-92 cluster and Notch1 was analyzed by quantitative polymerase chain reaction, and expression of these genes was modulated by anti-miR or anti-Notch1 siRNAs transfection. Protein expression was assessed by Western blot. Luciferase assays were used to quantify Smad4 3'-UTR/miR-19 interaction and Notch signaling activation. TGFβ responsiveness was evaluated by cell cycle analysis of TGFβ-treated cells. High iodine blocked BRAF(V600E)-induced upregulation of miR-17-92, including miR-19a/b. miR-17-92 promoter region analysis revealed a putative binding site for Hes1, a transcription factor responsive to Notch signaling. Notch-1 overexpression resulted in miR-19 upregulation in normal thyroid cells, while Notch-1 knockdown blocked BRAF-induced miR-19 expression. Moreover, in anaplastic thyroid cancer cells, Notch-1 knockdown reduced miR-19. Expression of BRAF(V600E) decreased Smad4 protein in normal thyroid cells. Smad4 was validated as a miR-19 target by luciferase assays, which revealed reduced luminescence associated with miR-19 interaction in Smad4 3'-UTR. Iodine treatment restored Smad4 levels in BRAF-activated cells, resulting in enhanced G1-cell cycle arrest in response to TGFβ. Moreover, this effect was mimicked in papillary thyroid cancer cells treated with anti-miR-19. High iodine abrogates BRAF(V600E)-induced activation of miR-19, a newly identified Smad4 regulator, through Notch pathway inhibition and restores responsiveness to TGFβ signaling. Our results indicate that iodine exerts protective effects in thyroid cells, attenuating acute BRAF oncogene-mediated microRNA deregulation.

Thyrotropin Regulates Thyroid Cell Proliferation by Up-Regulating miR-23b and miR-29b that Target SMAD3

MicroRNA (miRNA or miR) have emerged as an important class of short endogenous RNA that act as post-transcriptional regulators of gene expression and have a critical role in cell proliferation and differentiation. The aim of this study was to elucidate the role of miRNA in the proliferation of differentiated thyroid cells that require TSH for their growth. To elucidate the role of miRNA in thyroid cell proliferation, we have analyzed the miRNA expression profile of PC Cl 3 cells before and after the stimulation by TSH. We report the identification of two specific miRNA (miR-23b and miR-29b) whose up-regulation by TSH is required for thyroid cell growth. We identified mothers against decapentaplegic homolog 3 (Smad3), a member of the TGF-β pathway that has an inhibitor role in thyroid follicular cell proliferation as a target of miR-23b and miR-29b. Functional studies demonstrated that the overexpression of miR-23b and miR-29b promotes thyroid cell growth. Interestingly, an increased expression of both these miRNA was also detected in experimental and human goiters. These findings support the idea that the regulation of miRNA expression synergizes with the traditional proliferation pathways in promoting cell growth.

Hepatocellular hypertrophy and cell proliferation in Sprague–Dawley rats from dietary exposure to potassium perfluorooctanesulfonate results from increased expression of xenosensor nuclear receptors PPARα and CAR/PXR

The present study investigated the potential role for activation of PPARα and CAR/PXR by potassium PFOS (K+PFOS) with respect to the etiology of hepatic hypertrophy and hepatocellular adenoma in rats. Male Sprague–Dawley rats were fed K+PFOS (20 or 100ppm) for either 1, 7, or 28 days. Wyeth 14,643 (Wy 14,643, 50ppm) and phenobarbital (PB, 500ppm) were the controls for PPARα and CAR/PXR activation, respectively. Measurements included: plasma ALT, AST, cholesterol, triglycerides, and glucose; liver protein and DNA content; liver activities of palmitoyl CoA oxidase (ACOX), Cyp4A, CYP2B, and CYP3A; induction of liver CYP4A1, CYP2E1, CYP2B1/2, and CYP3A1 proteins (SDS-PAGE and Western blots); liver and thyroid microscopic histopathology, apoptotic index, and cell proliferation index. Terminal body weight was decreased by K+PFOS (100ppm) and Wy 14,643. All test-compound treatments increased liver weight. Plasma lipids were decreased by both PFOS and Wy 14,643. After treatment for 1 day, K+PFOS (100ppm), PB, and Wy 14,643 increased mean hepatic DNA concentration and total hepatic DNA, and total DNA remained elevated after treatment for 7 days and 28 days (PB and Wy 14,643 only). Hepatic P450 concentration was elevated after 7 and 28 days by K+PFOS and by PB. K+PFOS and Wy 14,643 increased liver activities of ACOX and CYP4A as well as increased liver CYP4A1 protein. By 28 days of treatment, K+PFOS and PB increased liver activities of CYP2B and CYP3A as well as increased liver CYP2B1/2 and CYP3A1 proteins, and Wy 14,643 increased CYP2B enzyme activity to a slight extent. All test compounds increased the liver cell proliferative index and decreased the liver apoptotic index. No histological changes of the thyroid were noted; however, PB and WY increased thyroid follicular cell proliferation index (seven-day treatment only), while K+PFOS did not. The thyroid follicular cell apoptotic index did not differ between groups. The hepatomegaly and hepatocellular adenoma observed after dietary exposure of Sprague–Dawley rats to K+PFOS likely are due to the increased expression of xenosensor nuclear receptors PPARα and CAR/PXR. Given the markedly lower or absent response of human hepatocytes to the proliferative stimulus from activation of PPARα and CAR/PXR, the hepatocellular proliferative response from activation of these receptors by PFOS observed in rats is not expected to be of human relevance.

Expressions of estrogen receptor β1 and β2 in human thyroid neoplasms and its clinical implication

The expressions of estrogen receptor (ER) α,ERβ1,and ERβ2 in thyroid carcinoma,thyroid adenoma,and adjacent normal thyroid tissue were determined by RT-PCR and immunohistochemistry,and the relationship of expression levels of three ERs and the main clinical pathologic parameters were evaluated.The result showed that ERα mRNA expression in papillary thyroid carcinoma(PTC) tissues was significantly higher than adjacent normal tissue,while,ERβ2 mRNA expression in PTC tissues was significantly lower than normal tissue ( P＜0.05 ).The positive expression of ERβ1 and ERβ2 in the thyroid carcinoma was related with the histological variant of carcinomas; the ERβ2 expressions were related with the lymph node metastasis and TNM staging of the carcinomas.These results suggest that the decreased ERβ2 expression may induce proliferation and carcinogenesis of thyroid follicular epithelial cells as well as progression of the carcinoma,and is a powerful prognostic indicator. Key words: Thyroid neoplasms; Estrogen receptor

Disruption of thyroid hormone homeostasis in Ugt1a-deficient Gunn rats by microsomal enzyme inducers is not due to enhanced thyroxine glucuronidation

Microsomal enzyme inducers (MEI) that increase UDP-glucuronosyltransferases (UGTs) are thought to increase glucuronidation of thyroxine (T 4), thus reducing serum T 4, and subsequently increasing thyroid stimulating hormone (TSH). Ugt1a1 and Ugt1a6 mediate T 4 glucuronidation. Therefore, this experiment determined the involvement of Ugt1a enzymes in increased T 4 glucuronidation, decreased serum T 4, and increased TSH after MEI treatment. Male Wistar and Ugt1a-deficient Wistar (Gunn) rats were fed a control diet or diet containing pregnenolone-16α-carbonitrile (PCN; 800 ppm), 3-methylcholanthrene (3-MC; 200 ppm), or Aroclor 1254 (PCB; 100 ppm) for 7 days. Serum T 4, triiodothyronine (T 3), and TSH concentrations, hepatic T 4/T 3 glucuronidation, and thyroid histology and follicular cell proliferation were investigated. PCN, 3-MC, and PCB treatments decreased serum T 4, whereas serum T 3 was maintained in both Gunn and Wistar rats (except for PCB treatment). TSH was increased in Wistar and Gunn rats after PCN (130 and 277%) or PCB treatment (72 and 60%). T 4 glucuronidation in Wistar rats was increased after PCN (298%), 3-MC (85%), and PCB (450%), but was extremely low in Gunn rats, and unchanged after MEI. T 3 glucuronidation was increased after PCN (121%) or PCB (58%) in Wistar rats, but only PCN increased T 3 glucuronidation in Gunn rats (43%). PCN treatment induced thyroid morphological changes and increased follicular cell proliferation in both strains. These data demonstrate that T 4 glucuronidation cannot be increased in Ugt1a-deficient Gunn rats. Thus, the decrease in serum T 4, increase in TSH, and increase in thyroid cell proliferation after MEI are not dependent on increased T 4 glucuronidation, and cannot be attributed to Ugt1a enzymes.

Role of UDP-Glucuronosyltransferase (UGT) 2B2 in Metabolism of Triiodothyronine: Effect of Microsomal Enzyme Inducers in Sprague Dawley and UGT2B2-Deficient Fischer 344 Rats

Microsomal enzyme inducers (MEI) that increase UDP-glucuronosyltransferases (UGTs) can impact thyroid hormone homeostasis in rodents. Increased glucuronidation can result in reduction of serum thyroid hormone and a concomitant increase in thyroid-stimulating hormone (TSH). UGT2B2 is thought to glucuronidate triiodothyronine (T(3)). The purposes of this study were to determine the role of UGT2B2 in T(3) glucuronidation and whether increased T(3) glucuronidation mediates the increased TSH observed after MEI treatment. Sprague Dawley (SD) and UGT2B2-deficient Fischer 344 (F344) rats were fed a control diet or diet containing pregnenolone-16alpha-carbonitrile (PCN; 800 ppm), 3-methylcholanthrene (3-MC; 200 ppm), or Aroclor 1254 (PCB; 100 ppm) for 7 days. Serum thyroxine (T(4)), T(3), and TSH concentrations, hepatic androsterone/T(4)/T(3) glucuronidation, and thyroid follicular cell proliferation were determined. In both SD and F344 rats, MEI treatments decreased serum T(4), whereas serum T(3) was maintained (except with PCB treatment). Hepatic T(4) glucuronidation increased significantly after MEI in both rat strains. Compared with the other MEI, only PCN treatment significantly increased T(3) glucuronidation (281 and 497%) in both SD and UGT2B2-deficient F344 rats, respectively, and increased both serum TSH and thyroid follicular cell proliferation. These data demonstrate an association among increases in T(3) glucuronidation, TSH, and follicular cell proliferation after PCN treatment, suggesting that T(3) is glucuronidated by other PCN-inducible UGTs in addition to UGT2B2. These data also suggest that PCN (rather than 3-MC or PCB) promotes thyroid tumors through excessive TSH stimulation of the thyroid gland.