SIRT3 mitigates osteoarthritis by suppressing ferroptosis through activating AMPK signaling pathway

Background

Osteoarthritis (OA) is characterized by cartilage degeneration and inflammatory environments that promote chondrocyte death via mechanisms including ferroptosis. SIRT3-AMPK activation inhibits inflammatory and catabolic responses in chondrocytes. However, its potential effect on chondrocyte ferroptosis remains unclear.

Objective

This study aimed to elucidate the effects of SIRT3 on ferroptosis in chondrocytes under inflammatory conditions and the underlying mechanisms involving the AMPK/mTOR signaling pathway.

Methods

Mendelian randomization was used to analyze the epidemiological relationship between SIRT3 expression and the occurrence of knee OA. ATDC5 cells were treated with IL-1β, TNF-α, or ferroptosis agonist/antagonist. SIRT3 was overexpressed in ATDC5 cells. The effects of SIRT3 on extracellular matrix metabolism, mitochondrial function, and ferroptosis were detected by Western blot, immunofluorescence, JC-1 staining, quantitative real-time PCR, and Alcian blue staining. In vivo experiments were conducted using mice subjected to destabilization of the medial meniscus to mimic OA. Then, micro-CT, histological analyses, and protein expression detections were conducted.

Results

Mendelian randomization identified SIRT3 expression as a protective factor in the development of knee OA. In vitro, IL-1β and TNF-α induced ferroptosis and oxidative stress in ATDC5 cells while down-regulating SIRT3. Treatment with the ferroptosis agonist Erastin or the antagonist Fer-1 resulted in decreased or increased protein levels of SIRT3, respectively. SIRT3 overexpression mitigated the degradation of the extracellular matrix, alleviated oxidative stress, modulated mitochondrial functions, and prevented ferroptosis in ATDC5 cells under IL-1β treatment in vitro. Furthermore, the effects of SIRT3 may be mediated by the AMPK/mTOR signaling pathway. In vivo, SIRT3 overexpression mitigated OA severity, evidenced by improved joint integrity and reduced cartilage degradation.

Conclusions

SIRT3 inhibits ferroptosis and regulates mitochondrial function via the AMPK/mTOR signaling pathway, thereby alleviating OA. Targeting the SIRT3-AMPK axis presents a promising therapeutic method for OA treatment.