Quercetin Ameliorates Sepsis-Related Acute Kidney Injury through Inhibition of Ferroptosis in Renal Tubular Epithelial Cells via the Nrf-2/GPX4 Pathway

Objectives: This study evaluates the therapeutic effect of quercetin on Sepsis-related Acute Kidney Injury (S-AKI) and explores its potential mechanisms to provide theoretical support for its use in treating S-AKI. Materials and Methods: In this study, approximately 40 mice were assigned to 4 groups: Mock, Lipopolysaccharide (LPS), and two quercetin dosage groups (low: 25 mg/kg and high: 50 mg/kg doses). All groups except Mock were administered 5 mg/kg LPS intraperitoneally to establish a model of S-AKI. Renal tissue morphological features were examined via Hematoxylin and Eosin (H&E) staining and histopathological scoring. Serum levels of the renal function markers Creatinine (Cr), Blood Urea Nitrogen (BUN), and inflammatory factors IL-1β, TNF-α, and IL-6 were measured. A septic injury model was developed in HK-2 cells using LPS stimulation, and iron content in HK-2 cells and mouse renal tissues was measured. The expressions of ferroptosis-related genes (FPN-1, COX-2, GPX4, and ACSL4) were evaluated via RT-PCR analysis. Spectrophotometry measured Malondialdehyde (MDA) and Glutathione (GSH) levels in HK-2 cells and mouse renal tissues. ELISA was used to quantify Nrf-2 and GPX4 protein levels. The effects of silencing Nrf-2 or GPX4 in HK-2 cells using shRNA were evaluated by measuring MDA and GSH levels. Results: In contrast to the LPS group, quercetin intervention (both doses) remarkably improved the morphology of mouse renal tissues, markedly reduced pathological scores of kidney injury (p < 0.05), lowered serum levels of inflammatory mediators (p < 0.05), and decreased levels of kidney function markers Cr and BUN (p < 0.05), showing a dose-dependent effect. Quercetin substantially reduced the content of ferrous ions and the expression of ferroptosis-promoting genes ACSL4 and COX-2 in HK-2 cells and mouse kidney tissues (p < 0.05), while upregulating the level of ferroptosis-inhibiting genes GPX4 and FPN-1 (p < 0.05), decreasing MDA content and increasing GSH levels (p < 0.05). The levels of Nrf-2 and GPX4 in HK-2 cells and mouse kidney tissues induced by LPS were significantly downregulated and were reversed under quercetin intervention (p < 0.001). Silencing of the Nrf-2 or GPX4 genes could antagonize the protective effects of quercetin on MDA increase and GSH reduction in HK-2 cells (p < 0.05). Conclusion: Quercetin can alleviate S-AKI by suppressing ferroptosis in renal tubular epithelial cells, with its mechanism likely involving the stimulation of the Nrf-2/GPX4 pathway.