SIRT3 deficiency is resistant to erastin-induced autophagy-dependent ferroptosis by inhibiting the AMPK/mTOR pathway and promoting glutathione peroxidase 4 levels

Abstract Background: Ferroptosis, an autophagy-dependent cell death, is characterized by lipid peroxidation and iron accumulation, closely associated with pathogenesis of gestational diabetes mellitus (GDM). Sirtuin 3 (SIRT3) has positive regulation on phosphorylation of AMPK, related to maintainance of cellular redox homeostasis. However, whether SIRT3 can confer autophagy by activating the AMPK-mTOR pathway and consequently promote induction of ferroptosis is unknown. Methods: We used human trophoblastic cell line HTR-8/SVneo and porcine trophoblastic cell line pTr2 to deterimine the mechanism of SIRT3 on autophagy and ferroptosis. Results: The expression of SIRT3 protein was significantly elevated in trophoblastic cells exposed to high concentrations of glucose and ferroptosis-inducing compounds. Increased SIRT3 expression contributed to classical ferroptotic events and autophagy activation, whereas SIRT3 silencing led to resistance against both ferroptosis and autophagy. In addition, autophagy inhibition impaired SIRT3-enhanced ferroptosis. On the contrary, autophagy induction had a synergistic effect with SIRT3. Based on mechanistic investigations, SIRT3 depletion inhibited activation of the AMPK-mTOR pathway and enhanced glutathione peroxidase 4 (GPX4) level, thereby suppressing autophagy and ferroptosis. Furthermore, depletion of AMPK blocked induction of ferroptosis in trophoblasts. Conclusions: We concluded that upregulated SIRT3 enhanced autophagy activation by promoting AMPK-mTOR pathway and decreasing GPX4 level to induce ferroptosis in trophoblastic cells. SIRT3 deficiency was resistant to high glucose- and erastin-induced autophagy-dependent ferroptosis and is therefore a potential therapeutic approach for treating GDM.