TFAP2B governs the regulation of SIRT1 to inhibit osteoclast-induced bone destruction

Background: Cholesteatoma is a benign epithelial lesion that affects the middle ear or mastoid process, causing otorrhea and hearing impairment. Currently, the pathogenesis of temporal bone injury in middle ear cholesteatoma remains elusive, hindering the development of effective treatment strategies.

Methods and results: We examined the expression of transcription factor AP-2-beta (TFAP2B) and its downstream factor silent mating type information regulation 2 homolog 1 (SIRT1) in clinical samples from patients with middle ear cholesteatoma and analyzed the potential correlation between TFAP2B expression and clinical conditions. The findings revealed a significant down-regulation of TFAP2B and SIRT1 in patients diagnosed with middle ear cholesteatoma (p < 0.01), and TFAP2B expression was negatively correlated with the clinical manifestations of hearing impairment and bone destruction. We further explored the role of TFAP2B in the differentiation of RAW 264.7 cells into osteoclasts induced by receptor activator of nuclear factor kappa B ligand (RANKL) in vitro. TFAP2B overexpression significantly inhibited, while TFAP2B knockdown promoted osteoclast differentiation of RAW264.7 cells. Further investigation suggested that TFAP2B positively regulated SIRT1 (p < 0.01) and negatively regulated NF-κB activation. Finally, we demonstrated that TFAP2B transcriptionally regulated SIRT, which inhibited the activation of the NF-κB signaling pathway by reducing the acetylation level of the p65 subunit, thereby suppressing osteoclast differentiation.

Conclusions: TFAP2B/SIRT1 plays a crucial role in regulating osteoclast differentiation in middle ear cholesteatoma. The downregulation of TFAP2B/SIRT1 triggers enhanced osteoclast differentiation, which may contribute to one of the mechanisms underlying bone destruction in middle ear cholesteatoma.

Middle ear cholesteatoma; NF-κB p65; Osteoclast differentiation; SIRT1; TFAP2B.