STAT3/Mitophagy Axis Coordinates Macrophage NLRP3 Inflammasome Activation and Inflammatory Bone Loss

J Bone Miner Res. 2023 Feb;38(2):335-353. doi: 10.1002/jbmr.4756. Epub 2022 Dec 30.

Abstract

Signal transducer and activator of transcription 3 (STAT3), a cytokine-responsive transcription factor, is known to play a role in immunity and bone remodeling. However, whether and how STAT3 impacts macrophage NLR family pyrin domain containing 3 (NLRP3) inflammasome activation associated with inflammatory bone loss remains unknown. Here, STAT3 signaling is hyperactivated in macrophages in the context of both non-sterile and sterile inflammatory osteolysis, and this was highly correlated with the cleaved interleukin-1β (IL-1β) expression pattern. Strikingly, pharmacological inhibition of STAT3 markedly blocks macrophage NLRP3 inflammasome activation in vitro, thereby relieving inflammatory macrophage-amplified osteoclast formation and bone-resorptive activity. Mechanistically, STAT3 inhibition in macrophages triggers PTEN-induced kinase 1 (PINK1)-dependent mitophagy that eliminates dysfunctional mitochondria, reverses mitochondrial membrane potential collapse, and inhibits mitochondrial reactive oxygen species release, thus inactivating the NLRP3 inflammasome. In vivo, STAT3 inhibition effectively protects mice from both infection-induced periapical lesions and aseptic titanium particle-mediated calvarial bone erosion with potent induction of PINK1 and downregulation of inflammasome activation, macrophage infiltration, and osteoclast formation. This study reveals the regulatory role of the STAT3/mitophagy axis at the osteo-immune interface and highlights a potential therapeutic intervention to prevent inflammatory bone loss. © 2022 American Society for Bone and Mineral Research (ASBMR).

Keywords: INFLAMMATORY OSTEOLYSIS; MITOPHAGY; NLRP3 INFLAMMASOME; STAT3.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Inflammasomes* / metabolism
  • Macrophages / metabolism
  • Mice
  • Mitophagy / physiology
  • NLR Family, Pyrin Domain-Containing 3 Protein* / metabolism
  • Protein Kinases / metabolism
  • Reactive Oxygen Species / metabolism
  • STAT3 Transcription Factor / metabolism

Substances

  • Inflammasomes
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Nlrp3 protein, mouse
  • Protein Kinases
  • Reactive Oxygen Species
  • STAT3 Transcription Factor
  • Stat3 protein, mouse