Sympathetic nervous system activity in rat thyroid: potential role in goitrogenesis

The role of sympathetic innervation in regulation of thyroid function is incompletely understood. We, therefore, carried out studies in rats utilizing techniques of norepinephrine turnover to assess thyroid sympathetic activity in vivo. Thyroidal sympathetic activity was increased 95% by exposure to cold (4 degrees C), 42% by chronic ingestion of an iodine-deficient diet, and 32% in rats fed a goitrogenic diet (low-iodine diet supplemented with propylthiouracil). In addition, fasting for 2 days reduced sympathetic nervous system activity in thyroid by 38%. Thyroid growth and 125I uptake were also compared in intact and decentralized hemithyroids obtained from animals subjected to unilateral superior cervical ganglion decentralization. Unilateral superior cervical ganglion decentralization led to a reduction in thyroid weight, in 125I uptake by thyroid tissue, and in TSH-induced stimulation of 125I uptake in decentralized hemithyroids. These results suggest that sympathetic activity in thyroid contributes to gland enlargement and may modulate tissue responsiveness to TSH.

Nuclear localization of epidermal growth factor and epidermal growth factor receptors in human thyroid tissues

Epidermal growth factor (EGF) has widespread growth effects, and in some tissues proliferation is associated with the nuclear localization of EGF and epidermal growth factor receptor (EGFR). In the thyroid, EGF promotes growth but differs from thyrotropin (TSH) in inhibiting rather than stimulating functional parameters. We have therefore studied the occurrence and cellular distribution of EGF and EGFR in normal thyroid, in Graves' disease, where growth is mediated through the thyrotropin receptor (TSHR), and in a variety of human thyroid tumors. In the normal gland the staining was variable, but largely cytoplasmic, for both EGF and EGFR. In Graves' disease there was strong cytoplasmic staining for both EGF and EGFR, with frequent positive nuclei. Nuclear positivity for EGF and particularly for EGFR was also a feature of both follicular adenomas and follicular carcinomas. Interestingly, nuclear staining was almost absent in papillary carcinomas. These findings document for the first time the presence of nuclear EGF and EGFR in thyroid. Their predominant occurrence in tissues with increased growth (Graves' disease, follicular adenoma, and carcinoma) may indicate that nuclear EGF and EGFR play a role in growth regulation in these conditions. The absence of nuclear EGF and EGFR in papillary carcinomas would suggest that the role played by EGF in growth control differs between papillary carcinoma and follicular adenomas/carcinomas of the thyroid.

Inhibition of iodine organification and regulation of follicular size in rat thyroid tissue in vitro

The factors mediating the accumulation of thyroglobulin are of great importance to the understanding of the pathogenesis of human and experimentally induced colloid goiters. To elucidate further the underlying cellular mechanism, thyroid fragments from newborn rats were incorporated into semisolid alginate beads and were cultured as three-dimensional organoids for up to 21 d. In five parallel cultures, the medium contained either no supplements (group A), Nal (group B), thyroid-stimulating hormone (TSH) (group C), Nal plus TSH in the same concentrations as B and C (group D), or Nal and TSH (as in group D) plus methimazole (MMI, group E). The thyroid organoids maintained morphological integrity, functional activity, and ability to proliferate in vitro. Addition of iodine to the cultures significantly increased mean (+/-SEM) follicular diameters from 19.5 +/- 0.7 microm in controls to 33.9 +/- 2.2 microm (p < 0.0001) when NaI was added alone (group B), and 30.4 +/- 1.7 microm (p < 0.0001) when combined with TSH (group D). The effect of NaI on follicular size was abolished by MMI (group E, follicular diameter 23.5 +/- 1.3 microm). The results presented support the recent finding, using a rat colloid goiter model, that not only TSH but also iodine organification or its inhibition are important factors in modulating follicular morphology.

Follicle-forming cat thyroid cell lines synthesizing extracellular matrix and basal membrane components: a new tool for the study of thyroidal morphogenesis

Interactions between follicular epithelial cells and extracellular matrix (ECM) are supposed to play an important role in the development and maintenance of thyroid tissue architecture. In the present study we have therefore investigated the synthesis of ECM components by a feline thyroid cell line which is able to form follicle-like structures in vitro, and also in v-ras-transfected and control-transfected sublines. Transfections were performed by lipofection with pZSR (viral Harvey ras gene; neo) and pSV2-neo (control, neo only) plasmids. We have adapted a semisolid culture system composed exclusively of polymerized alginate and therefore devoid of ECM components. Feline cells embedded in alginate gels as single cells and cultured for up to 90 days formed cell clusters within 10 days. Follicle-like structures were formed in the original cell lines and also in the v-ras- and control-transfected cells. Differences in proliferation rates were observed, the v-ras-transfected cells growing up to two to three times faster than the non-transfected cells. Immunostaining was done using rabbit first antibodies directed against mouse collagen IV, human fibronectin, laminin (tumor Engelbreth-Holm-Swarm laminin), perlecan and other ECM components. For comparison, immunostaining was also performed on cryosections of nodular goiters of six hyperthyroid cats. The cell lines and their transfected clones stained strongly positive for collagen IV and fibronectin, and positively but less strongly for laminin and perlecan. The cat goiter tissue stained positively for collagen IV, laminin, perlecan, and fibronectin, and positive staining for S-laminin (containing the beta2-chain) was seen in blood vessel walls in this tissue. In conclusion, cat cell lines grow three-dimensionally in alginate beads over several weeks, they form follicle-like structures and express the same ECM components as the native cat goiter tissue. Transfection with v-ras does increase proliferation rate, but does not fundamentally alter formation of follicle-like structures and ECM expression. Alginate gel culture is a promising new tool for the study of follicular morphogenesis, polarity, the expression pattern of ECM components and of the interaction between thyrocytes and ECM. It avoids interference caused by gels composed of ECM components.

[Monitoring of treatment in thyroid diseases]

The effectiveness of antithyroid drug treatment of Graves' hyperthyroidism is documented by measuring initially free T4 and free T3 and later free T4, free T3 and TSH. An elevated titer of the Graves'-specific thyroid stimulating antibodies is not usually rechecked before the end of the antithyroid drug therapy. Thyroxine treatment of primary hypothyroidism is controlled by TSH measurements. In patients in whom TSH levels might be affected by drugs or nonthyroid diseases, free T4 is measured in addition to TSH. The assessment of the treatment of Hashimoto's chronic thyroiditis consists of the control of the therapy of its associated hypothyroidism. In subacute thyroiditis de Quervain control of the effectiveness of the analgesic therapy is most important. To check the effect of thyroid hormone treatment given with the intent to reduce goiter size, serial sonographies are of great value. In the follow-up of patients with thyroid carcinomas, measurements of thyroglobulin (for papillary and follicular thyroid cancers) and of calcitonin (for medullary thyroid cancers) in the serum as well as thyroid scans and other imaging procedures play an important role.

[Goiter and nodular thyroid disease: clinical guidelines for diagnosis and treatment. (Waiting? Hormone therapy? Surgery? radioiodine?)]

Nodular thyroid disease is a common problem. We present clinical guidelines for the management of patients with thyroid nodules, multinodular goiters and thyroid cysts for use by primary physicians. In the initial evaluation ultrasonography of the thyroid and fine-needle aspiration biopsy (FNAB) is recommended. FNAB has become the cornerstone in the evaluation of solitary thyroid nodules, cysts and dominant nodules within multinodular goiters. If the procedure is done properly, it should have a false-negative rate of less than 5% and a false-positive rate of not more than 1%. Thyroid radionuclide scans are less frequently used in the initial evaluation of a nodular goiter. Surgery is the primary therapy for patients with nodular thyroid disease. Other available treatment options are radioiodine and TSH-suppression with thyroxine. The main indications for surgery in euthyroid patients with thyroid nodule or with nontoxic multinodular goiter are recently documented or suspected malignancy, compression of the trachea and esophagus, significant growth of the nodule, recurrence of a cyst after aspiration, neck discomfort and cosmetic concern.

[ABC of thyroid diseases and their treatment]

Thyroid diseases are caused by a disturbance of thyroid hormone secretion, inflammations or tumors of the thyroid or combinations thereof. Most important causes for hyperthyroidism are Graves' disease and toxic nodular goiters (including toxic adenomas). Hypothyroidism is often caused by Hashimoto's chronic thyroiditis and can occur in patients after thyroidectomy. Chronic hashimoto's thyroiditis and subacute de Quervain's thyroiditis are the thyroid inflammations most frequently seen. Graves' disease and Hashimoto's thyroiditis are autoimmune thyroid diseases. Thyroid tumors encompass benign solitary nodules, diffuse and nodular goiters, papillary, follicular, medullary and anaplastic carcinomas.

Expression of Plasmodium falciparum 3D7 STEVOR proteins for evaluation of antibody responses following malaria infections in naïve infants

Clinical immunity to Plasmodium falciparum malaria develops after repeated exposure to the parasite. At least 2 P. falciparum variant antigens encoded by multicopy gene families (var and rif) are targets of this adaptive antibody-mediated immunity. A third multigene family of variant antigens comprises the stevor genes. Here, 4 different stevor sequences were selected for cloning and expression in Escherichia coli and His6-tagged fusion proteins were used for assessing the development of immunity. In a cross-sectional analysis of clinically immune adults living in a malaria endemic area in Ghana, high levels of anti-STEVOR IgG antibody titres were determined in ELISA. A cross-sectional study of 90 nine-month-old Ghanaian infants using 1 recombinant STEVOR showed that the antibody responses correlated positively with the number of parasitaemia episodes. In a longitudinal investigation of 17 immunologically naïve 9-month-old infants, 3 different patterns of anti-STEVOR antibody responses could be distinguished (high, transient and low). Children with high anti-STEVOR-antibody levels exhibited an elevated risk for developing parasitaemia episodes. Overall, a protective effect could not be attributed to antibodies against the STEVOR proteins chosen for the study presented here.

Natural antibodies target virus-antibody complexes to organized lymphoid tissue

Natural antibodies (NA) specific for infectious pathogens are found at low titer (usually <1:40) in the serum of healthy, non-immunized, individuals. Therefore, NA are part of the first line of defence against blood borne microorganisms. They directly neutralize viral infections or lyse pathogens by activating the complement cascade. In addition, recent studies highlighted their role in the pooling of infectious pathogens and other antigens to the spleen. This prevents infection of vital target organs and enhances the induction of adaptive immune responses. Specific T and B-cell responses are exclusively induced in highly organized secondary lymphoid organs including lymph nodes and the spleen. As a consequence, mice with disrupted microorganisation of lymphoid organs have defective adaptive immunity. In addition, some pathogens including lymphocytic choriomeningitis virus (LCMV), Leishmania and HIV developed strategies to destroy the splenic architecture in order to induce an acquired immunosuppression and to establish persistent infection. NA antibodies enhance early neutralizing antibodies in the absence of T help mainly by targeting antigen to the splenic marginal zone. In addition, by activating the complement cascade, NA enhance T cell and T-cell dependent B-cell responses. Therefore, natural antibodies are an important link between innate and adaptive immunity.

Post-translational tyrosine nitration of eosinophil granule toxins mediated by eosinophil peroxidase

Nitration of tyrosine residues has been observed during various acute and chronic inflammatory diseases. However, the mechanism of tyrosine nitration and the nature of the proteins that become tyrosine nitrated during inflammation remain unclear. Here we show that eosinophils but not other cell types including neutrophils contain nitrotyrosine-positive proteins in specific granules. Furthermore, we demonstrate that the human eosinophil toxins, eosinophil peroxidase (EPO), major basic protein, eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP), and the respective murine toxins, are post-translationally modified by nitration at tyrosine residues during cell maturation. High resolution affinity-mass spectrometry identified specific single nitration sites at Tyr349 in EPO and Tyr33 in both ECP and EDN. ECP and EDN crystal structures revealed and EPO structure modeling suggested that the nitrated tyrosine residues in the toxins are surface exposed. Studies in EPO(-/-), gp91phox(-/-), and NOS(-/-) mice revealed that tyrosine nitration of these toxins is mediated by EPO in the presence of hydrogen peroxide and minute amounts of NOx. Tyrosine nitration of eosinophil granule toxins occurs during maturation of eosinophils, independent of inflammation. These results provide evidence that post-translational tyrosine nitration is unique to eosinophils.

Monomerization of dimeric IgG of intravenous immunoglobulin (IVIg) increases the antibody reactivity against intracellular antigens

Intravenous immunoglobulin (IVIg) preparations are derived from pooled plasma from up to 60,000 healthy human donors and reflect the immunologic experience of the donor population. IVIg contains monomeric and dimeric IgG populations which are in a dynamic equilibrium depending on concentration, pH, temperature, donor pool size, time and stabilizers added in order to keep the portion of dimeric IgG below a certain level. In the present study, monomeric and dimeric fractions were isolated by size exclusion chromatography. The dimeric fractions, however, showed a dynamic instability and tended to dissociate. Both dimeric and monomeric IgG fractions were acid treated (pH 4) in order to dissociate the dimeric IgG. Western-blot analysis identified a sub-population of SDS resistant IgG dimers. Furthermore, the reactivities of the fractions were tested against a panel of self- and exo-antigens. There was a marked increase in activity of the dimeric compared to the monomeric IgG fraction against various intracellular self-antigens. Our data indicates that the increased reactivities of pH 4-treated fractions can mainly be attributed to dimer dissociation, as pH 4-treated monomers do not show significantly increased activities against a range of antigens.