SIRT5 deficiency exacerbates sepsis acute renal injury by activating ACSL4/FTH1 axis dependent ferroptosis

Sepsis‑associated acute kidney injury (S‑AKI) is a major cause of morbidity and mortality in critically ill patients, yet effective targeted therapies remain lacking due to an incomplete understanding of its pathogenesis. Ferroptosis, an iron‑dependent form of regulated cell death driven by lipid peroxidation, has recently been implicated in AKI, but the upstream regulators of this process in sepsis remain undefined. Here, we identify SIRT5, a mitochondrial NAD ⁺ ‑dependent desuccinylase, as a critical endogenous suppressor of ferroptosis in S‑AKI. Using a cecal ligation and puncture (CLP) murine model and lipopolysaccharide (LPS)‑stimulated HK‑2 proximal tubular cells, we show that SIRT5 expression is significantly downregulated in septic kidney injury. Renal tubular‑specific ablation of Sirt5 exacerbated CLP‑induced renal dysfunction, structural damage, and tubular cell death, whereas AAV9‑mediated SIRT5 overexpression attenuated these pathological changes. Mechanistically, SIRT5 deficiency tipped the balance of the ACSL4/FTH1 axis toward ferroptosis: it increased ACSL4‑dependent membrane lipid remodeling and reduced FTH1‑mediated iron sequestration, accompanied by suppression of the antioxidant enzyme GPX4. Consequently, lipid peroxidation, iron overload, and mitochondrial damage were markedly amplified. Notably, knockdown of ACSL4 in SIRT5‑deficient HK‑2 cells effectively reversed lipid peroxidation, iron accumulation, and cell death, establishing ACSL4 as a key downstream effector of SIRT5‑mediated ferroptosis suppression. Our findings reveal a previously unrecognized SIRT5-ACSL4/FTH1 regulatory axis that governs ferroptotic susceptibility in renal tubular cells during sepsis, and suggest that pharmacological restoration of SIRT5 activity or blockade of ACSL4‑driven ferroptosis may offer novel therapeutic avenues for S‑AKI.