Targeting PKM2 by (+)-homocrepidine A restrains glycolytic reprogramming and reshapes macrophage fate to alleviate acute lung injury

Alveolar Macrophages represent a critical immune population that rapidly senses excessive inflammatory stimuli and contributes substantially to the development of Acute Lung Injury (ALI). Dendrobium crepidatum is a medicinal herb traditionally used for respiratory disorders; however, its protective effects against ALI and the underlying mechanisms remain unclear. Here, we identified homocrepidine A (HCA), a high-abundance alkaloid from D. crepidatum, as an active compound that ameliorates lipopolysaccharide (LPS)-induced ALI in mice, with the natural enantiomer (+)-HCA displaying superior anti-ALI activity. (+)-HCA effectively redirected alveolar macrophage polarization away from a pro-inflammatory M1 state toward an inflammation-resolving M2 phenotype. Mechanistically, Pyruvate Kinase M2 (PKM2) was identified as the direct molecular target of (+)-HCA. Furthermore, (+)-HCA directly bound to PKM2 at His78, inhibited Tyr105 phosphorylation, promoted tetramer formation and restrained the formation of nuclear-localized dimeric PKM2. Functionally, genetic depletion of PKM2 or disruption of the His78-dependent interaction markedly weakened the ability of (+)-HCA to remodel macrophage glycolytic metabolism, suppress M1 macrophage polarization, and alleviate ALI progression. Collectively, this study identifies (+)-HCA as the bioactive enantiomer responsible for the anti-ALI activity of HCA and demonstrates that PKM2-mediated immunometabolic reprogramming underlies its protective effects. These findings establish PKM2 as a promising therapeutic target and (+)-HCA as a potential lead compound for ALI treatment.