A Jak1/2 inhibitor, baricitinib, inhibits osteoclastogenesis by suppressing RANKL expression in osteoblasts in vitro.

Kohei Murakami,Takako Suzuki,Yasuhiro Kobayashi,Teruhito Yamashita,Naoyuki Takahashi,Yukio Nakamura,Shunsuke Uehara,Nobuyuki Udagawa,Hiroyuki Kato,Midori Nakamura,Masanori Koide,Sakamuri V Reddy

doi:10.1371/journal.pone.0181126

Kohei Murakami, Takako Suzuki + Show 10 more

Open Access

https://doi.org/10.1371/journal.pone.0181126

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Journal: PloS one	Publication Date: Jul 14, 2017
Citations: 71	License type: CC BY 4.0

Affiliation: Matsumoto Dental University, Shinshu University

Abstract

The Janus kinases (Jaks) are hubs in the signaling process of more than 50 cytokine or hormone receptors. However, the function of Jak in bone metabolism remains to be elucidated. Here, we showed that the inhibition of Jak1 and/or Jak2 in osteoblast-lineage cells led to impaired osteoclastogenesis due to the reduced expression of receptor activator of nuclear factor-κB ligand (RANKL). Murine calvaria-derived osteoblasts induced differentiation of bone marrow cells into osteoclasts in the presence of 1,25-dihydroxyvitamin D3 (1,25D3) and prostaglandin E2 (PGE2) in vitro. However, treatment with the Jak1/2 inhibitor, baricitinib, markedly inhibited osteoclastogenesis in the co-culture. On the other hand, baricitinib did not inhibit RANKL-induced osteoclast differentiation of bone marrow macrophages. These results indicated that baricitinib acted on osteoblasts, but not on bone marrow macrophages. Baricitinib suppressed 1,25D3 and PGE2-induced up-regulation of RANKL in osteoblasts, but not macrophage colony-stimulating factor expression. Moreover, the addition of recombinant RANKL to co-cultures completely rescued baricitinib-induced impairment of osteoclastogenesis. shRNA-mediated knockdown of Jak1 or Jak2 also suppressed RANKL expression in osteoblasts and inhibited osteoclastogenesis. Finally, cytokine array revealed that 1,25D3 and PGE2 stimulated secretion of interleukin-6 (IL-6), IL-11, and leukemia inhibitory factor in the co-culture. Hence, Jak1 and Jak2 represent novel therapeutic targets for osteoporosis as well as inflammatory bone diseases including rheumatoid arthritis.

Highlights

Osteoclasts are bone-resorbing cells that differentiate from monocyte-macrophage lineage cells [1]
We demonstrate that a selective Jak1 and Jak2 inhibitor, baricitinib, inhibits osteoclastogenesis by suppressing RANKL expression in osteoblasts induced by 1,25D3 and prostaglandin E2 (PGE2) in vitro
To examine the effects of baricitinib on osteoclast differentiation in vitro, mouse bone marrow cells were co-cultured with calvaria-derived osteoblasts in the presence of 10−8 M 1,25D3 and 10−6 M PGE2 (Fig 1A and 1B)

Summary

Introduction

Osteoclasts are bone-resorbing cells that differentiate from monocyte-macrophage lineage cells [1]. This differentiation is tightly regulated by osteoblast lineage cells such as osteoblasts [2] and osteocytes [3, 4]. Osteoblasts express two essential cytokines for osteoclast differentiation: receptor activator of nuclear factor-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) [1]. The expression of RANKL is induced by bone resorption factors including 1,25-dihydroxyvitamin D3 (1,25D3) and prostaglandin E2 (PGE2) [1].

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