Interleukin-21 promotes osteoclastogenesis in RAW264.7 cells through the PI3K/AKT signaling pathway independently of RANKL

Xing,Rui; Zhang,Yingjian; Li,Changhong; Sun,Lin; Yang,Lin; Zhao,Jinxia; Liu,Xiangyuan

doi:10.3892/ijmm.2016.2722

Interleukin-21 promotes osteoclastogenesis in RAW264.7 cells through the PI3K/AKT signaling pathway independently of RANKL

Authors:
- Rui Xing
- Yingjian Zhang
- Changhong Li
- Lin Sun
- Lin Yang
- Jinxia Zhao
- Xiangyuan Liu
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Affiliations: Department of Rheumatology and Immunology, Peking University Third Hospital, Beijing 100191, P.R. China
Published online on: August 30, 2016 https://doi.org/10.3892/ijmm.2016.2722
Pages: 1125-1134
Copyright: © Xing et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

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Abstract

Cytokines play a key role in the bone destruction of rheumatoid arthritis (RA). Interleukin-21 (IL-21) promotes osteoclastogenesis in RA in a receptor activator of nuclear factor-κB ligand (RANKL)-dependent way. Whether IL-21 is capable of promoting osteoclastogenesis directly in the absence of RANKL remains unknown. In the present study, we examined the osteoclastogenic activity of IL-21 in RAW264.7 cells in the absence of RANKL. We found that IL-21 enhanced osteoclastogenesis and this was demonstrated by increased numbers of tartrate-resistant acid phosphatase (TRAP)-positive stained, multinucleated cells compared with the negative control. Western blot analysis and immunocytochemistry showed the positive expression of calcitonin receptor (CTR) in the IL-21 group. RT-PCR and RT-qPCR also verified the increased mRNA expression of CTR and cathepsin K in the IL-21 group compared with the negative control. The scanning electronic microscope images showed a few resorption pits on the bone slices cultured with IL-21. The phosphoinositide 3-kinase (PI3K)/AKT pathway inhibitor LY294002 significantly suppressed IL-21-induced osteoclastogenesis. Taken together, these findings suggest that IL-21 has direct osteoclastogenic potential independently of RANKL. IL-21 may promote osteoclastogenesis through the PI3K/AKT signaling pathway. Therapy targeting IL-21 may be of value in preventing bone erosions in patients with RA.

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