PKM2 preconditioning protects endothelial cells from pyroptosis and BBB disruption via NRF2/TRX/TXNIP signaling in neonatal hypoxic-ischemic brain injury

BACKGROUND: Neonatal hypoxic-ischemic brain damage (HIBD) is a leading cause of neurological deficits and death in neonates. In HIBD, the death of endothelial cells and disruption of the blood-brain barrier (BBB) are closely related to the severity of brain damage and long-term clinical outcomes. There is increasing evidence that a glycolytic enzyme, pyruvate kinase M2 (PKM2), is essential for managing metabolic processes in endothelial cells, but its role (and underlying molecular mechanism) in hypoxic-ischemic (HI)-associated endothelial cell metabolism, cell survival, and BBB function remains unknown. METHODS: We established an in vivo HI-induced brain injury rat model and an in vitro model in which human cerebral microvascular endothelial cells (hCMECs) underwent oxygen-glucose deprivation (OGD). Infarct volume was measured and neurobehavioral tests were conducted to assess brain damage, and Evans blue extravasation and FITC-dextran were used to evaluate the BBB. RNA sequencing, qRT-PCR, western blotting, and immunofluorescence labeling were conducted to identify the molecular mechanisms underlying HIBD. RESULTS: PKM2 expression was upregulated in the brains of HIBD rats and in OGD-treated hCMECs. The inhibition of PKM2 greatly upregulated the expression of pyroptosis-associated proteins, including NLRP3, cleaved caspase-1, GSDMD, IL-1β, and IL-18. In contrast, the activation of PKM2 preserved junctional proteins and maintained the integrity of the BBB, which together improved functional recovery in HIBD rats. Mechanistically, preconditioning of PKM2 contributed to lactate-mediated cellular defense mechanisms, including the activation of nuclear factor erythroid 2-related factor 2 (NRF2) and thioredoxin (TRX), and to the downregulation of thioredoxin-interacting protein (TXNIP) via a modest increase in reactive oxygen species. CONCLUSIONS: Our analyses provide compelling evidence that PKM2 preconditioning attenuates endothelial cell pyroptosis and BBB disruption in neonatal HIBD by causing oxidative stress resistance and activating the NRF2/TRX/TXNIP pathway. Therefore, PKM2 represents a promising pharmacological target for treating HIBD.