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) and osteocalcin in IL-6 knock-out mice to assess the role of IL-6 in the pathogenesis of thyrotoxicosis-related disturbances of bone metabolism.
Material and methods: C57BL/6J (wild-type; WT) and C57BL/6JIL6−/−Kopf (IL-6 knock-out; IL6KO) mice randomly divided into 4 groups with 10 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. The serum levels of TRACP 5b and osteocalcin were determined by ELISA.
Results: Serum concentration of TRACP 5b (median and interquartile ranges) were significantly increased in both groups of mice with thyrotoxicosis: WT (28.2 (18.841.6) U/l) and IL6KO (26.4 (23.031.2) U/l) as compared to the respective controls. Osteocalcin serum levels in IL6KO-thx mice (111.9 (103.1175.6) ng/ml) were significantly elevated in comparison to WT-thx animals (46.1 (32.558.9) ng/ml).
Conclusions: 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.
Acknowledgements: This work was supported by AMB Grant 3-50693L (to JM) and KBN Grant 2P05B01826 (to KK).