Pyruvate kinase M2 nuclear translocation regulate ferroptosis-associated acute lung injury in cytokine storm

Abstract

Abstract Background Cytokine storm (CS) is linked with macrophage dysfunction and acute lung injury (ALI), which can lead to patient mortality. Glycolysis is preferentially exploited by the pro-inflammatory macrophages, in which pyruvate kinase M2 (PKM2) is a critical enzyme. The mechanism underlying the link between CS and ALI involves cell death, with the recently discovered programmed cell death known as ferroptosis being involved. However, the relationship between the glycolysis and ferroptosis in the context of CS-related ALI remains unclear. Methods CS model was induced by sequential challenge of poly I:C (10 mg/kg, i.v) and LPS (5mg/kg, i.p) (IC: LPS) accompanied by the applications of ferrostatin-1 (ferroptosis inhibitor, 2.5mg/kg, i.p) or ML-265 (PKM2 monomer/dimer inhibitor, 50 mg/kg, i.p). Lung injury, inflammation parameters, ferroptosis parameters and cellular bioenergetics were examined. Alveolar macrophage (AM) sorting, RNA sequencing, subcellular fractionation and western blot were performed to clarify the mechanisms of PKM2 nuclear translocation in the process of ferroptosis-associated ALI in CS. In clinical cohort verification, 3 health controls and 14 patients diagnosed with lung infection were included (9 patients presented distinct characteristics indicative of CS). CD14+ monocytes from human peripheral blood were isolated and analyzed. Results CS-associated ALI induced by IC:LPS exhibit significant ferroptosis. Ferrostatin-1 treatment attenuated IC:LPS‑induced mortality and lung injury. Moreover, AM from IC:LPS model exhibited enhanced glycolysis and PKM2 translocation. The administration of ML-265 resulted in the formation of a highly active tetrameric PKM2, leading to improved survival and attenuation of ALI. Furthermore, ML-265 treatment decreased ferroptosis and restored the balance between anaerobic glycolysis and oxidative phosphorylation. Notably, in patients with lung infection, intracellular expression level of PKM2 were correlated with circulating inflammation. Enhanced ferroptosis and PKM2 nuclear translocation was noticed in CD14+ blood monocytes of lung infection patients with CS. Conclusion PKM2 is a key regulatory node integrating metabolic reprograming with intra-nuclear function for the regulation of ferroptosis. Targeting PKM2 could be explored as a potential means in the future to prevent or alleviate hyper-inflammatory state or cytokines storm syndrome with aberrant ferroptotic cell death.