Baicalin inhibits macrophage glycolysis and succinate-driven HIF-1α signaling by targeting PKM2 to alleviate RSV-induced inflammation.

Respiratory syncytial virus (RSV) infection triggers excessive inflammation, contributing to disease severity. Baicalin exerts therapeutic effects against RSV infection by inhibiting viral replication and alleviating inflammation. However, the mechanisms underlying its immunoregulatory during RSV infection remain unclear. Here we found that baicalin alleviated RSV induced inflammation by regulating the macrophage immunometabolism. To investigate metabolic modulation, metabolomic analysis was performed, revealing an obvious reversal in the metabolic profile by baicalin administration. Further metabolic flux analysis using isotope tracers demonstrated that baicalin suppressed the accumulation of lactate and succinate induced by RSV infection. Mechanistically, baicalin inhibited glycolytic metabolism and succinate driven hypoxia-inducible factor 1α (HIF-1α) signaling during RSV infection, thereby suppressing NLR family, pyrin domain containing protein 3 (NLRP3) activation and reducing IL-1β release. The effects were validated in vitro using a glycolysis activator to confirm the suppression of glycolytic metabolism, and through co-treatment with dimethylsuccinate and RSV to verify the involvement of HIF-1α-mediated hypoxia pathway. Final targeting for baicalin at pyruvate kinase M2 (PKM2) was confirmed via molecular docking and limited proteolysis-coupled mass spectrometry. Taken together, these data elucidate a mechanism of baicalin through regulatory immunometabolism of macrophage to alleviate RSV-induced inflammation, which have critical roles in the treatment of RSV infection.