Cholesterol inhibits autophagy in RANKL-induced osteoclast differentiation through activating the PI3K/AKT/mTOR signaling pathway

  • Mol Biol Rep. 2022 Oct;49(10):9217-9229. doi: 10.1007/s11033-022-07747-w.
Chunyan Jiang  1  2  3  4  5 ,  Yan Wang  1  2  3  4 ,  Mengqi Zhang  1  2  3  4 ,  Jin Xu  6  7  8  9
Affiliations
  • 1. Department of Endocrinology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, China.
  • 2. Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China.
  • 3. Shandong Clinical Medical Center of Endocrinology and Metabolism, Jinan, Shandong, China.
  • 4. Institute of Endocrinology and Metabolism, Shandong Academy of Clinical Medicine, Jinan, 250021, Shandong, China.
  • 5. Department of Endocrinology, People's Hospital of Linyi, Linyi, Shandong, China.
  • 6. Department of Endocrinology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, China. [email protected].
  • 7. Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China. [email protected].
  • 8. Shandong Clinical Medical Center of Endocrinology and Metabolism, Jinan, Shandong, China. [email protected].
  • 9. Institute of Endocrinology and Metabolism, Shandong Academy of Clinical Medicine, Jinan, 250021, Shandong, China. [email protected].
PMID: 35881223 DOI: 10.1007/s11033-022-07747-w
Abstract

Background: A dysregulated balance between bone formation and bone resorption controlled by osteoblast and osteoclast will lead to osteoporosis. Cholesterol (CHO) is a crucial factor leading to osteoporosis, and Autophagy appears to involve it. Therefore, we aimed to study the molecular mechanism of Autophagy in CHO-induced osteoclasts differentiation.

Methods: Nuclear factor-κ B ligand as a receptor activator was used to induce osteoclasts differentiation of murine macrophage RAW264.7 treated with CHO, PI3-kinase inhibitor (LY294002), and Rapamycin (RAPA), respectively. Western blot assay was used to detect the expression of TRAP/ACP5 and the proteins involved in Autophagy and the PI3K/Akt/mTOR signaling pathway. In addition, TRAP staining, bone resorption assay, and F-actin immunofluorescence were performed to evaluate the ability of osteoclast formation. Transmission electron microscopy and immunofluorescence were also executed to observed the expression of LC3B, and autophagosome.

Results: When RAW264.7 was treated with 20 μg/mL CHO for 5 consecutive days, It exhibited the optimal osteoclast activity. In addition, CHO could inhibit Autophagy and activate the PI3K/Akt/mTOR signaling pathway. Moreover, the effects of CHO on osteoclast differentiation and Autophagy could partially be reversed by LY294002 and RAPA.

Conclusion: Therefore, our results demonstrated that CHO could inhibit Autophagy during osteoclast differentiation by activating the PI3K/Akt/mTOR signaling pathway. These findings provided important theoretical basis for CHO in bone resorption and formation.

Keywords
Autophagy; Cholesterol; Osteoclast differentiation; PI3K/AKT/mTOR signaling pathway.
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