OBJECTIVE  To investigate the regulation of acyl-CoA synthetase long-chain family member 4 （ACSL4）, a key protein involved in ferroptosis, by Sirtuin 4 （SIRT4）, and its protective effect on sepsis-associated acute kidney injury （SA-AKI）.

METHODS  Twenty-four male C57BL/6 mice were randomly divided into four groups （n=6 per group）: Sham, lipopolysaccharide （LPS）, LPS + SIRT4 inhibitor and LPS + SIRT4 inhibitor + ACSL4 inhibitor. Except for the Sham group, the other three groups were model groups. Among them, the LPS + SIRT4 inhibitor group and the LPS + SIRT4 inhibitor + ACSL4 inhibitor group were intraperitoneally injected with SIRT4-IN-1 at a dose of 10 mg/kg in physiological saline daily for 5 days. The SIRT4 inhibitor + ACSL4 inhibitor group was also intraperitoneally injected with ACSL4 inhibitor LIBX-A401 at a dose of 1 mg/kg in physiological saline. On the 6th day, all model groups were intraperitoneally injected with 10 mg/kg LPS, while the Sham group received intraperitoneal injections of equal volumes of physiological saline for 6 consecutive days as a control. After 24 hours, eyeball venous blood and kidney tissue samples were collected from each group of mice for subsequent renal function assessment, observation of renal pathological morphology, immunofluorescence staining, electron microscopy of mitochondrial ultrastructure and analysis of the expression of SIRT4 protein and proteins related to ferroptosis pathways.

RESULTS  Compared with the Sham group, mice in the LPS group exhibited significant renal tubular damage, mitochondrial morphological abnormalities, worsening renal function, increased inflammation and oxidative stress, accompanied by downregulation of SIRT4 expression, upregulation of ACSL4 expression and decreased levels of GPX4, FSP1 and FTH1 （all P＜0.05）. Compared with the LPS group, the LPS + SIRT4 inhibitor group showed no significant difference in FSP1 expression, but the aforementioned renal damage and other related protein expression changes were further exacerbated. However, the combined use of ACSL4 inhibitor reversed the additional damage caused by SIRT4 inhibition, improving renal pathological damage, mitochondrial morphology and renal function, alleviating the inflammatory cytokine storm, and partially restoring the protein levels of GPX4 and FTH1.

CONCLUSION  SIRT4 may negatively regulate the expression of ACSL4, negatively modulate the expression of GPX4 and FTH1 in SA-AKI, thereby regulating ferroptosis and alleviating sepsis-induced kidney injury.