FSTL1 silencing protects against lipopolysaccharide-induced ferroptosis in renal tubular cells by regulating the PI3K/Akt pathway

Sepsis-associated acute kidney injury (AKI) is a major cause of morbidity and mortality, and lipopolysaccharide (LPS)-induced ferroptosis is a critical mechanism of renal tubular cell injury. Follistatin-like 1 (FSTL1) is a matricellular protein implicated in inflammation and oxidative stress; however, its role in LPS-induced ferroptosis in renal tubular cells remains unknown. Human renal proximal tubular epithelial (HK-2) cells were exposed to increasing concentrations of LPS to evaluate FSTL1 expression levels. FSTL1 silencing was achieved by siRNA transfection, and its effects on PI3K/Akt signaling, apoptosis, oxidative stress, and ferroptosis were assessed using western blotting, RT-qPCR, flow cytometry, and fluorescent probes. The PI3K/Akt inhibitor LY294002 was used to validate the involvement of this pathway. FSTL1 expression was significantly upregulated by LPS in a dose-dependent manner at both the mRNA and protein levels. Silencing FSTL1 markedly increased the phosphorylation of PI3K and Akt and significantly attenuated LPS-induced apoptosis, as evidenced by increased cell viability and decreased number of Annexin V-positive cells. FSTL1 silencing also decreased reactive oxygen species and malondialdehyde levels, while enhancing superoxide dismutase activity and glutathione content. Moreover, FSTL1 silencing reduced mitochondrial ferrous iron accumulation and restored Nrf2, SLC7A11, GPX4, and FTH1, alongside decreased ACSL4 expression. These protective effects were reversed by LY294002, indicating a dependence on PI3K/Akt signaling. FSTL1 mediates LPS-induced apoptosis, oxidative stress, and ferroptosis in renal tubular cells via the PI3K/Akt pathway. Targeting FSTL1-PI3K/Akt signaling may represent a novel approach to mitigate ferroptotic injury in endotoxin-stimulated renal tubular cells, providing mechanistic insights relevant to LPS-induced tubular injury model.