Spermidine protects against acute kidney injury by modulating macrophage NLRP3 inflammasome activation and mitochondrial respiration in an eIF5A hypusination-related pathway

BACKGROUND: Acute kidney injury (AKI) is still a critical problem in clinical practice, with a heavy burden for national health system around the world. It is notable that sepsis is the predominant cause of AKI for patients in the intensive care unit and the mortality remains considerably high. The treatment for AKI relies on supportive therapies and almost no specific treatment is currently available. Spermidine is a naturally occurring polyamine with pleiotropic effects. However, the renoprotective effect of spermidine and the underlying mechanism remain elusive. METHODS: We employed mice sepsis-induced AKI model and explored the potential renoprotective effect of spermidine in vivo with different administration time and routes. Macrophage depleting was utilized to probe the role of macrophage. In vitro experiments were conducted to examine the effect of spermidine on macrophage cytokine secretion, NLRP3 inflammasome activation and mitochondrial respiration. RESULTS: We confirmed that spermidine improves AKI with different administration time and routes and that macrophages serves as an essential mediator in this protective effect. Meanwhile, spermidine downregulates NOD-like receptor protein 3 (NLRP3) inflammasome activation and IL-1 beta production in macrophages directly. Mechanically, spermidine enhances mitochondrial respiration capacity and maintains mitochondria function which contribute to the NLRP3 inhibition. Importantly, we showed that eukaryotic initiation factor 5A (eIF5A) hypusination plays an important role in regulating macrophage bioactivity. CONCLUSIONS: Spermidine administration practically protects against sepsis-induced AKI in mice and macrophages serve as an essential mediator in this protective effect. Our study identifies spermidine as a promising pharmacologic approach to prevent AKI.