Estrogens modulate RANKL-RANK/osteoprotegerin mediated interleukin-6 effect on thyrotoxicosis-related bone turnover in mice.

Interleukin-6 has been shown to cause imbalance between bone resorption and formation in thyrotoxicosis. The aim of the present study was an attempt to estimate the influence of estrogens on thyrotoxicosis-related disturbances in bone turnover in relation to RANKL-RANK/osteoprotegerin system in IL-6 deficient mice. The study was performed on 56, 12-13 weeks old, female mice: C57BL/6J (wild-type; WT) and C57BL/6J (IL6-/-Kopf) (IL-6 knock-out; IL6KO). The mice were randomly divided into 8 groups with 7 mice in each one: 1. WT controls, 2. IL6KO controls, 3. WT mice with thyrotoxicosis, 4. IL6KO mice with thyrotoxicosis, 5. WT ovariectomized, 6. IL6KO ovariectomized, 7. WT ovariectomized mice with thyrotoxicosis, and 8. IL6KO ovariectomized mice with thyrotoxicosis. Experimental model of menopause was evoked by bilateral ovariectomy carried out in 8-9 weeks old mice. Thyrotoxicosis was induced by intraperitoneal injection of levothyroxine at a dose of 1 µg/g daily over 21 days. The serum levels of TRACP5b, osteocalcin, OPG, and RANKL were determined by ELISA. RANKL serum concentrations were elevated significantly in all groups of ovariectomized mice as compared to respective controls, however, in a minor degree in IL6KO thyrotoxic mice as compared to wild-type animals. Osteoprotegerin serum levels were significantly increased in all thyrotoxic groups of mice except ovariectomized IL6KO animals. To sum up, the results of the present study suggest that IL-6 plays a key role in stimulation of RANKL-RANK/OPG system and this effect is strongly enhanced in conditions of accelerated bone turnover such as thyrotoxicosis and/or estrogen depletion.

A crucial role of interleukin-6 in the pathogenesis of thyrotoxicosis-related disturbances of bone turnover in mice.

Interleukin-6 (IL-6) has been shown to be involved in the pathogenesis of several bone diseases characterized by a negative balance between bone resorption and formation. The aim of the study was to estimate serum markers of bone turnover: osteoclast-derived tartrate-resistant acid phosphatase form 5a (TRACP 5b) reflecting resorption, and osteocalcin as a marker of bone formation in IL-6 knock-out mice to assess the role of IL-6 in the pathogenesis of thyrotoxicosis-related disturbances of bone metabolism. The study was performed on forty, 14-15 weeks old, female mice: C57BL/6J (wild-type; WT) and C57BL/6J (IL6-/-Kopf) (IL-6 knock-out; IL6KO). The mice were randomly divided into 4 groups with 10 mice in each one: 1. WT mice in thyrotoxicosis (WT-thx), 2. WT controls (WT-ctrl), 3. IL6KO mice with thyrotoxicosis (IL6KO-thx), and 4. IL6KO controls. Experimental model of hyperthyroidism was induced by intraperitoneal injection of levothyroxine at a dose of 1 microg/g, daily over 21 days. The serum levels of TRACP 5b and osteocalcin were determined by ELISA. Serum concentration of TRACP 5b (median and interquartile ranges) were significantly increased in both groups of mice with thyrotoxicosis: WT [28.2(18.8-41.6) U/l] and IL6KO [26.4(23.0-31.2) U/l] as compared to the respective controls. Osteocalcin serum levels in IL6KO-thx mice [111.9(103.1-175.6) ng/ml] were significantly elevated in comparison to WT-thx animals [46.1(32.5-58.9) ng/ml]. In summary, the results of the present study suggest that IL-6 plays a crucial role in thyrotoxicosis-related disturbances of bone turnover in mice, determining the imbalance between bone resorption and bone formation caused by excess of thyroid hormones predominantly by inhibition of bone formation.

Activity of thyroid parafollicular (C) cells in rats with hyperthyroidism--preliminary ultrastructural investigations.

In the thyroid gland of mammals, except the basic follicular (F) cells, parafollicular (C) cells are detected. They belong to disperse neuroendocrine cells of the APUD system. Co-localisation of F and C cells in the thyroid gland is not accidental. It seems possible that there is an interaction between them, mediated by the peptidergic hormones. Calcitonin (CT) is proposed as an essential indicator of C cells. The role of C cells in the function of the thyroid gland has been not clarified till now, especially in hyperthyroid state. There are only a few data which document the ultrastructure of C cells in the physiological and pathological state. In the present study, the ultrastructure of thyroid C cells in an experimental model of hyperthyroidism was evaluated. Our preliminary study may confirm the functional interaction between follicular and parafollicular cells in the thyroid gland.

Activity of thyroid parafollicular (C) cells in rats with hyperthyroidism--immunohistochemical investigations.

The aim of this study was an evaluation of the activity of parafollicular (C) cells in a rat experimental model of hyperthyroidism, evoked by an intraperitoneal application of L-thyroxine (40 mg/kg daily) over 15 days. For that reason, immunohistochemical investigations and evaluation of calcitonin (CT) plasma concentrations were performed. Differences in the quantity and distribution, together with enhanced CT-immunoreactivity of C cells, were observed in hyperthyroid rats, in comparison to respective values in the control group, accompanied by a significant diminution of plasma TSH and CT levels. Our preliminary study may point to a functional interaction between follicular and parafollicular cells in the thyroid gland.

Estimation of influence of high doses of cholecalciferol on thyroid parafollicular and respiratory tract neuroendocrine cells; preliminary investigations.

The aim of this study was to compare what changes are caused by high doses of cholecalciferol (100,000 UI vD3) and CaCl2 on thyroid parafollicular (C) cells and airways neuroendocrine (NE) cells in rat. Overdosage of vD3 and CaCl2 causes hypocalcaemia and strong hypercalcitoninemia in blood; C cells showed mainly signs of hypertrophy; simultaneously, the number of strong calcitoninpositive cells decreased significantly (statistically significant changes). Immunohistochemical reactions, detecting CGRP, somatostatin, synaptophysin and neuronspecific enolase did not fall under statistic analysis. Airways NE cells re-acted to hypercalcemia differently than C cells--they probably respond to different regulatory mechanisms.

Influence of cannabinoids on immunoreactivity of regulatory peptides, produced in rat thyroid C cells; preliminary investigations.

Mammalian tissues contain two types of cannabinoid receptors CB1 and CB2. The aim of our study was an evaluation of the influence of a single i.p. injection of a stable analogue of an endogenous cannabinoid anandamide--R-(+)-methanandamide (2.5 mg/kg) and CP 55,940 (0.25 mg/kg), which is an exogenous agonist of CB1 receptors, on the immunoreactivity of regulatory peptides, produced in rat thyroid C cells: calcitonin, CGRP, somatostatin and synaptophysin. This study indicates that a single injection of cannabinoids: R-(+)-methanandamide and CP 55,940 alters the immunoreactivity of regulatory peptides in thyroid parafollicular cells.

Preliminary immunohistochemical investigations of thyroid C cells in an experimental model of hyperthyroidism.

The role of the parafollicular (C) cells, the second most important cells in the thyroid gland, has not hitherto been clarified. They are considered to be disperse neuroendocrine cells of the APUD system and synthesise and release many of the regulatory peptides. Few publications are concerned with the evaluation of the structure and function of C cells in the thyroid gland or the probable relationship between these cells and the follicular cells in physiological and pathological conditions. For this reason immunohistochemical investigations were carried out into the activity of the C cells in rats in an experimental model of hyperthyroidism caused by chronic thyroxine influence. This C-cell activity was then evaluated. Differences in the quantity, distribution and calcitonin immunoreactivity of C cells were observed in hyperthyroid rats in comparison to the control group, together with a significant diminution of plasma TSH and calcitonin levels. Our preliminary study may indicate a functional interaction between follicular and parafollicular cells in the thyroid gland.

An immunohistochemical study of the thyroid parafollicular (C) cells in rats treated with cannabinoids - preliminary investigations.

The purpose of the present study was to evaluate the effect of a single intraperitoneal injection of a stable analogue of endogenous cannabinoid anandamide - R-(+)-methanandamide (2.5 mg/kg) and CP 55,940 (0.25 mg/kg), an egzogenous CB1 receptor-agonist, on the calcitonin (CT) immunoreactivity of the thyroid parafollicular (C) cells. Four hours after injection with both cannabinoids CT immunoreactivity, evaluated with an avidin-biotin peroxidase complex method by means of rabbit antibodies against CT, was seen to be enhanced in the parafollicular cells in comparison to those of the control group. In thyroids taken from cannabinoid-treated rats the majority of follicles, particularly those located peripherally were large in size, and had low epithelium. Moreover, dilatation of the blood vessels was observed. These changes were accompanied by a significant decrease in CT plasma level, without changes in calcium concentrations. This is the first evidence that a single injection of the cannabinoids R-(+)-methanandamide and CP 55,940 significantly decreases the activity of thyroid C cells.

Activity of the thyroid parafollicular (C) cells in simple and hyperactive nodular goitre treated surgically - preliminary investigations.

The aim of this study was to evaluate the significance of measuring calcitonin (CT) plasma concentrations in patients with simple and hyperthyroid goitre treated surgically. Eighty four patients who underwent operations during the years 2000-2002 were analysed. Plasma concentrations of CT were determined by commercially available radioimmunoassay on the day of hospitalisation. Elevated concentrations of CT were found in 8 patients: in 5 out of 26 (19.2%) and in 3 out of 33 (9.0%) patients with Graves' disease and with multinodular goitre, respectively. No major differences in concentrations of CT were observed in patients with simple goitre. Postoperative morphological analysis of pathologically changed hyperactive thyroids showed the presence of enlarged C cells distributed either in small groups or even singly with weakening immunohistochemical reaction for CT. These observations may point to the possibility of a relationship between the functional state of the thyroid gland and the activity of C cells.