In Vitro Evaluation of the Interaction of Thyroid Hormone with the Sympathetic Nervous System, via β2-Adrenergic Receptors, in Bone Tissue and in Osteoblasts

Author(s)

Bianca Neofiti Papi

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2023-03-08

Examining board members

Cecilia Helena de Azevedo Gouveia Ferreira; Marise Lazaretti Castro; Elen Haruka Miyabara; Francisco Jose Albuquerque de Paula

• Advisor: Cecilia Helena de Azevedo Gouveia Ferreira

Abstract

There is evidence that the sympathetic nervous system (SNS) negatively regulates bone mass via β2-adrenergic receptors (β2-AR) expressed in osteoblasts. Recently, we observed that mice with β2-AR receptor inactivation (β2-AR-/-) are partially resistant to the osteopenic effects of excess thyroid hormone (TH) in the skeleton, suggesting that there is an interaction between TH and SNS to regulate bone mass, involving the signaling of β2-AR receptors. The aim of this study was to investigate whether TH interacts with the β2-AR receptor signaling pathway, locally in bone tissue and in osteoblasts, to regulate bone remodeling and osteoblast biology. Therefore, we evaluated the effect of triiodothyronine (T3; 10-8- M); clenbuterol (CLE, 10--4- M), a β2-AR agonist; propranolol (PROP; 10--6- M), a β2-AR antagonist; or the combination of T3 with these drugs (T3+CLE or T3+PROP) in osteoblastic cells of the MC3T3-E1 lineage, derived from mouse calvaria. Next, we evaluated the effect of T3 (10--8- M); CLE (10--4-M), or the combination of both (T3+CLE) in primary cultures of wild-type mouse calvaria-derived osteoblasts (Selv) and β2-AR-/-. We also evaluated the effect of T3, CLE and T3+CLE in cultures of femurs and tibias (organ cultures) derived from Selv and β2-AR-/- animals. T3 and CLE alone limited cell growth in Selv cells, but not in β2-AR-/- cells. T3+CLE did not alter the negative effect of T3 on this cellular parameter. T3 also limited the growth of MC3T3-E1 cells, however, this effect was abolished when PROP was combined with T3 (T3+PROP). Treatment with T3 for 21 days induced the formation of mineralization nodules in primary osteoblast Selv cultures, which was not observed in β2-AR-/- cultures. T3 induced osteocalcin (OC) expression in primary osteoblast cultures and Selv organ cultures, but more mildly in β2-AR-/- cultures. T3 induced osteoprotegerin (OPG) expression in Selv osteoblasts (primary cultures), but not in β2-AR-/- osteoblasts. Taken together, these findings suggest that (i) the integrity of the β2-adrenergic receptor signaling pathway is necessary for T3 to promote its negative effect on cell growth and its positive effect on osteoblastic differentiation; and that (ii) there is a local interaction, in osteoblasts, between TH and the SNS, through the signaling of β2 adrenergic receptors, to regulate these processes. (AU)

• FAPESP's process: 18/02323-5 - In vitro evaluation of the interaction of thyroid hormone with the sympathetic nervous system, via beta 2 adrenergic receptors, in the bone tissue and in osteoblasts
• Grantee: Bianca Neofiti Papi
• Support Opportunities: Scholarships in Brazil - Doctorate