Propranolol Promotes Bone Formation and Limits Resorption Through Novel Mechanisms During Anabolic Parathyroid Hormone Treatment in Female C57BL/6J Mice

Annika Treyball, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Audrey C. Bergeron, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Daniel J. Brooks, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA.
Audrie L. Langlais, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Hina Hashmi, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Kenichi Nagano, Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA.
Deborah Barlow, Department of Biomedical Sciences, University of New England, Biddeford, ME, USA.
Ryan J. Neilson, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Tyler A. Roy, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Kathleen T. Nevola, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Karen L. Houseknecht, Department of Biomedical Sciences, University of New England, Biddeford, ME, USA.
Roland Baron, Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA.
Mary L. Bouxsein, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA.
Anyonya R. Guntur, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.
Katherine J. Motyl, Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, ME, USA.

Abstract

Although the nonselective β-blocker, propranolol, improves bone density with parathyroid hormone (PTH) treatment in mice, the mechanism of this effect is unclear. To address this, we used a combination of in vitro and in vivo approaches to address how propranolol influences bone remodeling in the context of PTH treatment. In female C57BL/6J mice, intermittent PTH and propranolol administration had complementary effects in the trabecular bone of the distal femur and fifth lumbar vertebra (L ), with combination treatment achieving microarchitectural parameters beyond that of PTH alone. Combined treatment improved the serum bone formation marker, procollagen type 1 N propeptide (P1NP), but did not impact other histomorphometric parameters relating to osteoblast function at the L . In vitro, propranolol amplified the acute, PTH-induced, intracellular calcium signal in osteoblast-like cells. The most striking finding, however, was suppression of PTH-induced bone resorption. Despite this, PTH-induced receptor activator of nuclear factor κ-B ligand (RANKL) mRNA and protein levels were unaltered by propranolol, which led us to hypothesize that propranolol could act directly on osteoclasts. Using in situ methods, we found Adrb2 expression in osteoclasts in vivo, suggesting β-blockers may directly impact osteoclasts. Consistent with this, we found propranolol directly suppresses osteoclast differentiation in vitro. Taken together, this work suggests a strong anti-osteoclastic effect of nonselective β-blockers in vivo, indicating that combining propranolol with PTH could be beneficial to patients with extremely low bone density. © 2022 American Society for Bone and Mineral Research (ASBMR).