P38 Mitogen-Activated Protein Kinase Inhibitor, FR167653, Inhibits Parathyroid Hormone Related Protein-Induced Osteoclastogenesis and Bone Resorption

Huiren Tao,Hideki Yoshikawa,Mina Okamoto,Akira Myoui,Masataka Nishikawa,Harish Pant

doi:10.1371/journal.pone.0023199

Huiren Tao, Hideki Yoshikawa + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0023199

Copy DOI

Journal: PloS one	Publication Date: Aug 23, 2011
Citations: 36	License type: CC BY 4.0

Affiliation: Osaka University

Abstract

p38 mitogen-activated protein kinase (MAPK) acts downstream in the signaling pathway that includes receptor activator of NF-κB (RANK), a powerful inducer of osteoclast formation and activation. We investigated the role of p38 MAPK in parathyroid hormone related protein (PTHrP)-induced osteoclastogenesis in vitro and PTHrP-induced bone resorption in vivo. The ability of FR167653 to inhibit osteoclast formation was evaluated by counting the number of tartrate-resistant acid phosphatase positive multinucleated cells (TRAP-positive MNCs) in in vitro osteoclastgenesis assays. Its mechanisms were evaluated by detecting the expression level of c-Fos and nuclear factor of activated T cells c1 (NFATc1) in bone marrow macrophages(BMMs) stimulated with sRANKL and M-CSF, and by detecting the expression level of osteoprotegerin (OPG) and RANKL in bone marrow stromal cells stimulated with PTHrP in the presence of FR167653. The function of FR167653 on bone resorption was assessed by measuring the bone resorption area radiographically and by counting osteoclast number per unit bone tissue area in calvaria in a mouse model of bone resorption by injecting PTHrP subcutaneously onto calvaria. Whole blood ionized calcium levels were also recorded. FR167653 inhibited PTHrP-induced osteoclast formation and PTHrP-induced c-Fos and NFATc1 expression in bone marrow macrophages, but not the expression levels of RANKL and OPG in primary bone marrow stromal cells treated by PTHrP. Furthermore, bone resorption area and osteoclast number in vivo were significantly decreased by the treatment of FR167653. Systemic hypercalcemia was also partially inhibited. Inhibition of p38 MAPK by FR167653 blocks PTHrP-induced osteoclastogenesis in vitro and PTHrP-induced bone resorption in vivo, suggesting that the p38 MAPK signaling pathway plays a fundamental role in PTHrP-induced osteoclastic bone resorption.

Highlights

Parathyroid hormone related protein (PTHrP), a potent stimulator of osteoclastic bone resorption, was first identified as a causative factor for humoral hypercalcemia of malignancy [1]
We previously reported that monocyte colony stimulating factor (M-CSF)-dependent sRANKL- and TNFa-induced osteoclast formation in primary bone marrow cells, and collageninduced arthritis in rats were inhibited by FR167653 [23]
To determine whether FR167653 blocks osteoclastogenesis in vitro, we investigated osteoclastogenesis in a primary bone marrow cells stimulated by PTHrP

Summary

Introduction

Parathyroid hormone related protein (PTHrP), a potent stimulator of osteoclastic bone resorption, was first identified as a causative factor for humoral hypercalcemia of malignancy [1]. A number of clinicopathological and experimental studies have shown that cancer cell-derived PTHrP promotes osteoclastic bone resorption and contributes to the development and progression of cancer metastasis to bone [2,3,4,5]. PTHrP stimulates osteoclastogenesis by acting on osteoblasts and/or bone marrow stromal cells to increase receptor activator of NF-kB ligand (RANKL) expression and reduce osteoprotegerin (OPG) expression, not by acting directly on osteoclast precursors [6]. Osteoclast precursors that express RANK, a tumor necrosis factor (TNF) receptor family member, recognize RANKL and differentiate into osteoclasts in the presence of macrophage/monocyte colony stimulating factor (M-CSF). A relative increase of RANKL versus OPG expression by PTHrP activates osteoclastic bone resorption [7,8,9,10,11,12]

Methods

Results

Conclusion