Pharmacological inhibition of protein S-palmitoylation suppresses osteoclastogenesis and ameliorates ovariectomy-induced bone loss

Linghui Ma; Liwei Zhang; Zirui Liao; Chunmei Xiu; Xi Luo; Na Luo; Lei Zhang; Guangxu He; Jianquan Chen

doi:10.1016/j.jot.2023.06.002

Pharmacological inhibition of protein S-palmitoylation suppresses osteoclastogenesis and ameliorates ovariectomy-induced bone loss

J Orthop Translat. 2023 Jul 17:42:1-14. doi: 10.1016/j.jot.2023.06.002. eCollection 2023 Sep.

Authors

Linghui Ma^{1

2}, Liwei Zhang³, Zirui Liao², Chunmei Xiu¹, Xi Luo², Na Luo², Lei Zhang², Guangxu He⁴, Jianquan Chen^{1

2}

Affiliations

¹ Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, Department of Clinical Medicine, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang, China.
² Orthopedic Institute, Suzhou Medical College, Soochow University, Suzhou, Jiangsu, China.
³ Department of Orthopedics, Taizhou Hospital of Zhejiang Province, Zhejiang University, Taizhou, Zhejiang, China.
⁴ Department of Orthopedics, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.

Abstract

Background: Excessive osteoclast formation disrupts bone homeostasis, thereby significantly contributing to pathological bone loss associated with a variety of diseases. Protein S-palmitoylation is a reversible post-translational lipid modification catalyzed by ZDHHC family of palmitoyl acyltransferases, which plays an important role in various physiological and pathological processes. However, the role of palmitoylation in osteoclastogenesis has never been explored. Consequently, it is unclear whether this process can be targeted to treat osteolytic bone diseases that are mainly caused by excessive osteoclast formation.

Materials and methods: In this study, we employed acyl-biotin exchange (ABE) assay to reveal protein S-palmitoylation in differentiating osteoclasts (OCs). We utilized 2-bromopalmitic acid (2-BP), a pharmacological inhibitor of protein S-palmitoylation, to inhibit protein palmitoylation in mouse bone marrow-derived macrophages (BMMs), and tested its effect on receptor activator of nuclear factor κβ ligand (RANKL)-induced osteoclast differentiation and activity by TRAP staining, phalloidin staining, qPCR analyses, and pit formation assays. We also evaluated the protective effect of 2-BP against estrogen deficiency-induced bone loss and bone resorption in ovariectomized (OVX) mice using μCT, H&E staining, TRAP staining, and ELISA assay. Furthermore, we performed western blot analyses to explore the molecular mechanism underlying the inhibitory effect of 2-BP on osteoclastogenesis.

Results: We found that many proteins were palmitoylated in differentiating OCs and that pharmacological inhibition of palmitoylation impeded RANKL-induced osteoclastogenesis, osteoclast-specific gene expression, F-actin ring formation and osteoclastic bone resorption in vitro, and to a lesser extent, osteoblast formation from MC3T3-E1 cells. Furthermore, we demonstrated that administration of 2-BP protected mice from ovariectomy-induced osteoporosis and bone resorption in vivo. Mechanistically, we showed that 2-BP treatment inhibited osteoclastogenesis partly by downregulating the expression of c-Fos and NFATc1 without overtly affecting RANKL-induced activation of osteoclastogenic AKT, MAPK, and NF-κB pathways.

Conclusion: Pharmacological inhibition of palmitoylation potently suppresses RANKL-mediated osteoclast differentiation in vitro and protects mice against OVX-induced osteoporosis in vivo. Mechanistically, palmitoylation regulates osteoclast differentiation partly by promoting the expression of c-Fos and NFATc1. Thus, palmitoylation plays a key role in promoting osteoclast differentiation and activity, and could serve as a potential therapeutic target for the treatment of osteoporosis and other osteoclast-related diseases.

The translational potential of this article: The translation potential of this article is that we first revealed palmitoylation as a key mechanism regulating osteoclast differentiation, and therefore provided a potential therapeutic target for treating osteolytic bone diseases.

Keywords: 2-bromopalmitic acid; Osteoclastogenesis; Osteoporosis; Protein S-palmitoylation.