NADPH oxidase gp91phox contributes to RANKL-induced osteoclast differentiation by upregulating NFATc1

Sci Rep. 2016 Nov 29:6:38014. doi: 10.1038/srep38014.

Abstract

Bone-marrow derived monocyte-macrophages (BMMs) differentiate into osteoclasts by M-CSF along subsequent RANKL stimulation possibly in collaboration with many other unknown cytokines released by pre- or mature osteoblasts. The differentiation process requires receptor activator of nuclear factor kappa-B ligand (RANKL)/RANK signaling and reactive oxygen species (ROS) such as superoxide anion (O2•-). Gp91phox, a plasma membrane subunit of NADPH oxidase (Nox), is constitutively expressed in BMMs and plays a major role in superoxide anion production. In this study, we found that mice deficient in gp91phox (gp91phox-/-) showed defects in osteoclast differentiation. Femurs of these mice produced osteoclasts at about 70% of the levels seen in femurs from wild-type mice, and accordingly exhibited excessive bone density. This abnormal bone growth in the femurs of gp91phox-/- mice resulted from impaired osteoclast differentiation. In addition, gp91phox-/- mice were defective for RANKL-induced expression of nuclear factor of activated T cells c1 (NFATc1). However, H2O2 treatment compensated for gp91phox deficiency in BMMs, almost completely rescuing osteoclast differentiation. Treating wild-type BMMs with antioxidants and superoxide inhibitors resulted in a differentiation defect resembling the phenotype of gp91phox-/- BMMs. Therefore, our results demonstrate that gp91phox-derived superoxide is important for promoting efficient osteoclast differentiation by inducing NFATc1 as a downstream signaling mediator of RANK.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bone Resorption / etiology*
  • Bone Resorption / metabolism
  • Bone Resorption / pathology
  • Cell Differentiation*
  • Cells, Cultured
  • Macrophages / cytology
  • Macrophages / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • NFATC Transcription Factors / genetics
  • NFATC Transcription Factors / metabolism*
  • Osteoclasts / cytology*
  • Osteoclasts / metabolism
  • Osteogenesis / physiology
  • RANK Ligand / genetics
  • RANK Ligand / metabolism*
  • Reactive Oxygen Species / metabolism
  • Receptors, Immunologic / physiology*
  • Signal Transduction
  • Up-Regulation

Substances

  • NFATC Transcription Factors
  • Nfatc1 protein, mouse
  • Pirb protein, mouse
  • RANK Ligand
  • Reactive Oxygen Species
  • Receptors, Immunologic
  • Tnfsf11 protein, mouse