TSH beta subunit gene expression in human lymphocytes

The Human TSHβ Subunit Proteins and Their Binding Sites on the TSH Receptor Using Molecular Dynamics Simulation

To gain further insight into the binding of the normal and variant human TSHβ subunits (TSHβ and TSHβv), we modeled the 2 monomeric proteins and studied their interaction with the TSH receptor ectodomain (TSHR-ECD) using molecular dynamics simulation Furthermore, analyzed their bioactivity in vitro using recombinant proteins to confirm that such binding was physiologically relevant. Examining the interaction of TSHβ and TSHβv with the TSHR-ECD model using molecular dynamic simulation revealed strong binding of these proteins to the receptor ECD. The specificity of TSHβ and TSHβv binding to the TSHR-ECD was examined by analyzing the hydrogen-bonding residues of these subunits to the FSH receptor ECD, indicating the inability of these molecules to bind to the FSH receptors. Furthermore, the modelling suggests that TSHβ and TSHβv proteins clasped the concave surface of the leucine rich region of the TSHR ECD in a similar way to the native TSH using dynamic hydrogen bonding. These mutually exclusive stable interactions between the subunits and ECD residues included some high-affinity contact sites corresponding to binding models of native TSH. Furthermore, we cloned TSHβ and TSHβv proteins using the entire coding ORF and purified the flag-tagged proteins. The expressed TSHβ subunit proteins retained bioactivity both in a coculture system as well as with immune-purified proteins. In summary, we showed that such interactions can result in a functional outcome and may exert physiological or pathophysiological effects in immune cells.

Hormones in the immune system and their possible role. A critical review

Immune cells synthesize, store and secrete hormones, which are identical with the hormones of the endocrine glands. These are: the POMC hormones (ACTH, endorphin), the thyroid system hormones (TRH, TSH, T3), growth hormone (GH), prolactin, melatonin, histamine, serotonin, catecholamines, GnRH, LHRH, hCG, renin, VIP, ANG II. This means that the immune cells contain all of the hormones, which were searched at all and they also have receptors for these hormones. From this point of view the immune cells are similar to the unicells (Tetrahymena), so it can be supposed that these cells retained the properties characteristic at a low level of phylogeny while other cells during the evolution accumulated to form endocrine glands. In contrast to the glandular endocrine cells, immune cells are polyproducers and polyreceivers. As they are mobile cells, they are able to transport the stored hormone to different places (packed transport) or attracted by local factors, accumulate in the neighborhood of the target, synthesizing and secreting hormones locally. This is taking place, e.g. in the case of endorphin, where the accumulating immune cells calms pain caused by the inflammation. The targeted packed transport is more economical than the hormone-pouring to the blood circulation of glandular endocrines and the targeting also cares the other receptor-bearing cells timely not needed the effect. Mostly the immune-effects of immune-cell derived hormones were studied (except endorphin), however, it is not exactly cleared, while the system could have scarcely studied important roles in other cases. The evolutionary aspects and the known as well, as possible roles of immune-endocrine system and their hormones are listed and discussed.

Circulating thyroid cancer markers

PURPOSE OF REVIEW

To describe the progress in the field of circulating markers of thyroid cancer.

RECENT FINDINGS

Thyroid cancer cells in the circulation can be detected by measuring the mRNA of thyroid-specific genes. Among these, thyroglobulin, and more recently thyroid-stimulating hormone receptor mRNAs' provide high diagnostic sensitivity and specificity for thyroid cancer detection. These markers can be used in synergy with current diagnostic modalities, i.e. fine-needle aspiration and ultrasound, for preoperative diagnosis and serum thyroglobulin measurement for monitoring.

SUMMARY

For the detection of recurrent/residual thyroid cancer, serum thyroglobulin remains the sole circulating marker, but lacks sensitivity and is unreliable in the presence of antithyroglobulin antibodies. The measurement of thyroid-specific mRNA in blood may provide sensitive/specific markers, but significant variability exists among various studies for thyroglobulin mRNA in particular, questioning the validity of this marker. Recent studies have demonstrated the high sensitivity and specificity of thyroid-stimulating hormone receptor mRNA in detecting recurrent/residual disease even in the presence of thyroglobulin antibodies. Fine-needle aspiration biopsy is currently the sole method for evaluating thyroid nodules. Indeterminate fine-needle aspiration cytology is found in approximately 15-30% of specimens. Thyroid-stimulating hormone receptor mRNA measurement in patients with indeterminate fine-needle aspiration may enhance cancer detection and save unnecessary surgeries.

Extrapituitary beta TSH and GH in early chick embryos

Somatotropes and thyrotropes are thought to be derived from the same cellular lineage and the expression of both growth hormone (GH) and thyrotropin (beta TSH) is thought to be dependent upon the same (Pit-1) transcription factor. The presence and comparative distribution of GH- and beta TSH-immunoreactivity in early chick embryos, was therefore investigated, especially as extrapituitary GH-immunoreactive cells are present in some peripheral tissues of early chick embryos prior to the ontogenic differentiation of the pituitary gland. At the end of the first trimester of incubation (embryonic day (ED) 7), GH-immunoreactivity was widespread in the head, particularly in neural tissue. Strong labeling was found in the diencephalon and mesencephalon and in neural ganglia and the trigeminal nerve. beta TSH-immunoreactivity was also present in these tissues, although restricted to the ependymal cells lining the diocoele and mesocoele and absent from mantle layers. It was also present in the cellular layer lining the otic vesicle, which was devoid of GH staining. In contrast, Rathke's pouch, the primordial pituitary gland was without GH- or beta TSH-staining. Control sections incubated with preabsorbed antisera or with pre-immune serum were completely devoid of staining. In the trunk, the epidermal cells were stained for beta TSH, but not for GH. Intense GH-immunoreactivity was present in the ventral and dorsal horns of the spinal cord and was particularly strong in the outer marginal layer. In contrast, beta TSH-immunoreactivity was again restricted to ependymal cells lining the spinal canal, which were devoid of GH-immunoreactivity. Strong GH staining was also present in the dorsal and ventral root ganglia, both of which lacked significant beta TSH staining. In non-neural tissues, both GH and beta TSH staining was present in the crop, although in topographically different cells. beta TSH-immunoreactivity was also present in the cells lining the bronchial ducts and the adluminal linings of the pleural and pericardial cavities. GH-immunoreactivity, in contrast, was absent from the lung but present in the surrounding intracostal muscles and in the Müllerian duct. Both GH- and beta TSH-immunoreactivity was present in liver hepatocytes. These results clearly show, for the first time, the presence of TSH-immunoreactivity in central and peripheral tissues of the ED7 chick embryo, prior to the differentiation of pituitary thyrotropes. They also show that beta TSH- and GH-immunoreactive cells are differentially located within embryonic tissues.

Targeting oncogenesis by introduction of a 5.2-kbp segment of the 5' regulatory region of the human thyrotropin beta-subunit gene

We produced transgenic mice carrying a fusion gene (TTP-5) consisting of a 5.2-kbp segment of the 5' flanking sequence of the human thyrotropin beta-subunit (TSH beta) gene linked to the simian virus 40 large T antigen (SVT) gene. These mice developed pituitary tumors 6 months after birth and wasted away. With the 5.2-kbp TSH beta 5' flanking region governing SVT expression, SVT mRNA was present in the pituitary and testis but not in other tissues, as detected by the reverse transcriptase-polymerase chain reaction. Histological and immunohistochemical analyses showed that the pituitary tumors of the transgenic mice were composed of moderately differentiated pituitary cells that expressed TSH, growth hormone, and prolactin. These results indicate that the 5.2-kbp segment of the human TSH beta 5' regulatory region is sufficient to drive expression of SVT and induce tumorigenesis of hormone-producing pituitary cells in transgenic mice.

Molecular diagnostic tests in the diagnosis and management of thyroid carcinoma

The application of molecular analysis of gene expression to clinical tissue samples represents one of the most exciting new areas in "translational" thyroid cancer research. Current data suggest that molecular diagnostic assays may improve the sensitivity and accuracy of fine needle aspiration of thyroid nodules, fine needle aspiration of metastases, and detection of recurrent disease in peripheral blood samples. It is likely that at least some of these tests will become useful adjuncts in the diagnostic armamentarium of clinical endocrinologists in the future.

The effect of LHRH and TRH on human interferon-gamma production in vivo and in vitro

Accumulating evidence suggests that hypothalamic luteinizing hormone-releasing hormone (LHRH) and thyrotropin-releasing hormone (TRH) are two hypophysiotropic factors which modulate the immune response. The aim of the present study was to determine the in vivo effects of an intravenous bolus of LHRH and TRH on plasma interferon (IFN)-gamma production in five normoprolactinemic women with irregular menstrual cycles. We also determined prolactin (PRL), thyrotropin (TSH), follicle stimulating hormone (FSH), and luteinizing hormone (LH) levels before and after intravenous administration of LHRH and TRH. The results demonstrate that intravenous bolus of LHRH/TRH increases plasma IFN-gamma levels, with the maximum response 45 min after in vivo administration of hypothalamic peptides and after peak levels of adenohypophyseal hormones (PRL: 15 min; TSH: 30 min; FSH: 30 min; LH: 30 min). In order to investigate a possible direct action of hypothalamic hormones on immune cells, we also evaluated, in the same subjects, the influence of LHRH and TRH on IFN-gamma production by human peripheral blood mononuclear cells (PBMCs), collected before the intravenous administration of the peptides and stimulated in vitro with bacterial superantigen staphylococcal enterotoxin A (SEA) and concanavalin A (Con A). LHRH and TRH, separately and together, significantly enhanced in vitro IFN-gamma production by SEA- and ConA-activated PBMCs. The present results suggest that hypothalamic peptides (LHRH and TRH) directly, and/or indirectly pituitary hormones (PRL, TSH, FSH, and LH) or IL-2, have stimulatory effect on IFN-gamma producing cells and are further evidence of interactions between the neuroendocrine and immune systems.

Immunoreactivity for the alpha-subunit of the pituitary glycoprotein hormones in pulmonary neuroendocrine cells of developing human lung and various perinatal diseases

Infant lung tissue, obtained at autopsy, was studied by immunohistochemistry for the presence of pituitary glycoprotein hormones (PGHs) in the lung. The infants, born at term or preterm, died of various causes. The results provide the first immunological evidence of the presence of the common a-subunit of the pituitary glycoprotein hormones (alphaPGH) in the lung. The immunoreactivity is located in the pulmonary neuroendocrine cells and neuroepithelial bodies. In addition, the cells labelled by alphaPGH antisera (alphaPGH cells) form a subpopulation of the neuroendocrine cells detected by anti-calcitonin immunohistochemistry (CT cells). Moreover, the number of alphaPGH cells appears to increase after neonatal pneumonia or when the number of CT cells is elevated following the development of disease. Also, the weak staining of one of the monoclonal antibodies against the specific b-subunit of thyrotropin (TSH) might, in combination with the increased detectability of a-subunits, indicate that TSH can be endogenously produced in the lung.