Sirtuin 1/3 regulates p53 deacetylation to inhibit iron poisoning-induced alveolar epithelial cell death and contributes to Rapamycin-mediated protection against limb ischemia/reperfusion-induced lung injury.

Background: Acute limb ischemia is a disorder with high morbidity and mortality globally. Unfortunately, the effectiveness of limb ischemia/reperfusion (I/R)-induced acute lung injury (ALI) therapy remains limited.

Methods: I/R-induced lung injury (IRLI) rat model and LPS-stimulated cell model were established. The histological changes and collagen deposition in lungs were evaluated by H&E and Masson staining. Lung injury was assessed by pathological scoring, evaluation of arterial PaO₂ and lung water content. qRT-PCR, Western blot, immunohistochemistry, immunofluorescent staining and ELISA assay were employed to detect the expression and secretion of key molecules. The oxidative stress markers were detected using commercial kits, and CCK-8, EdU incorporation, TUNEL assays and flow cytometry were employed to detect cell proliferation and apoptosis, respectively. The interaction between U2AF2 and SIRT1/3 was examined by RIP assay, and the association between SIRT1/3 and p53, as well as the acetylation of p53, were detected by co-IP.

Results: Rapamycin induced SIRT1 and SIRT3 expression and deacetylase activities in the lung tissues of IRLI rats. Inhibition of SIRT1 or SIRT3 attenuated the protective effects of Rapamycin on I/R-induced lung injury, pyroptosis, oxidative stress and ferroptosis in vivo. In LPS-stimulated L2 cells, SIRT1 or SIRT3 was involved in Rapamycin-mediated protection in inflammation, pyroptosis, oxidative stress and ferroptosis. Mechanistically, Rapamycin enhanced the mRNA stability of SIRT1 or SIRT3 via recruiting U2AF2, and it also promoted p53 deacetylation by inducing SIRT1 and SIRT3.

Conclusion: SIRT1/3 regulated p53 deacetylation to inhibit iron poisoning-induced alveolar epithelial cell death and contributed to Rapamycin-mediated protection against limb I/R-induced ALI.