Inhibition of LPL suppresses the osteoclast differentiation of bone-marrow-derived macrophages by promoting the ACSL4 ubiquitination.

BACKGROUND

The imbalance between osteoblast (OB) -led bone formation and osteoclast (OC) -induced bone resorption is a recognized reason of osteoporosis. However, further gene-related pathogenesis remains to be elucidated.

METHODS

The microarray profile GSE225974 was used to identify the differentially expressed genes (DEGs) between OC and peripheral blood mononuclear cells (PBMC). Bone-marrow-derived macrophages (BMMs) treated with 30 ng/ml macrophage-colony-stimulating factor (M-CSF) and 100 ng/ml receptor activator of NF-kappa B ligand (RANKL) was to induce osteoclastic differentiation in vitro. The expression of lipoprotein lipase (LPL) was measured by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting methods. Meanwhile, the regulatory role of LPL on osteoclastic differentiation was evaluated by monitoring cathepsin K levels and TRAP staining. Proteins related to LPL were obtained by STRING, and the interaction between proteins was verified by immunoprecipitation (IP) and ubiquitination analysis.

RESULTS

LPL was markedly up-expressed in OCs. Inhibition of LPL suppressed osteoclast differentiation of BMMs by inhibiting cathepsin K and number of TRAP-positive cells. Then the results of STRING demonstrated that proteins related to LPL including the lipid synthesis gene ACSL4. Erastin treatment prominently weakened the effects of si-LPL on cathepsin K levels and TRAP staining intensity by activating ferroptosis. Mechanically, inhibition of LPL suppressed osteoclast differentiation by promoting ubiquitination levels of ACSL4, and over-expression of USP14 reversed the effects of LPL knockdown on regulating ubiquitination of ACSL4.

CONCLUSION

Suppression of LPL inhibits the osteoclast differentiation of BMMs in vitro. The mechanism may be related to the LPL knockdown induced USP14 meidated the ACSL4 ubiquitination. Taken together, down-regulation of LPL may be a promising method to suppress osteoclast differentiation to treat osteoporosis.