Scutellarin inhibits ferroptosis by promoting cellular antioxidant capacity through regulating Nrf2 signaling

Ferroptosis is a lytic form of regulated cell death that is driven by iron-dependent lipid peroxidation and has been implicated in various diseases, including acute kidney injury (AKI). Scutellarin is a flavonoid isolated from Erigeron breviscapus (Vant.) Hand.-Mazz. and possesses various pharmacological activities, including anti-inflammatory and antioxidative properties. However, it is unclear whether scutellarin can inhibit ferroptosis and mitigate related diseases. In this study, we show that scutellarin can inhibit ferroptosis in both human HK-2 cells and mouse bone marrow-derived macrophages stimulated with RSL3 or erastin. Mitochondrial dysfunction and reactive oxygen species generation are counteracted by scutellarin treatment, suggesting the involvement of its antioxidative activity. Furthermore, scutellarin increases the nuclear levels of Nrf2 and the expressions of its target genes, including HO-1 and GPX4. Scutellarin-mediated inhibition of ferroptosis and increases in these proteins are abrogated by co-treatment with brusatol, an Nrf2 inhibitor, indicating an essential role for Nrf2 in this process. In a mouse model of folic acid-induced AKI, scutellarin mitigates acute renal damage, as revealed by histopathological analysis and serum blood urea nitrogen and creatinine assays. Folic acid-induced acute renal injury is associated with increased ferroptosis, as revealed by elevated level of 4-hydroxynonenal (4-HNE), a surrogate marker of ferroptosis, which is diminished by scutellarin co-treatment. Specifically, the elevated 4-HNE levels in macrophages (MAC-2 positive) and other renal cells are suppressed by scutellarin. Overall, scutellarin can inhibit ferroptosis both in cultured cells and in a mouse model of AKI by regulating Nrf2 signaling.