Histone lactylation exacerbates acute lung injury in septic mice by promoting ferroptosis in pulmonary microvascular endothelial cells.

BACKGROUND: Circulating lactate is associated with poor prognosis in sepsis-induced acute lung injury (S-ALI). However, it remains unclear whether microvascular dysfunction, a hallmark of S-ALI, is related to circulating lactate levels and what the underlying mechanisms are. The aim of this study was to investigate the role and mechanisms of lactate in pulmonary microvascular dysfunction in S-ALI. METHODS: The effects of lactate on pulmonary microvascular function were assessed in a septic mouse model. Primary mouse pulmonary microvascular endothelial cells (MPMVECs) were isolated to evaluate the impact of lactate on MPMVEC permeability. Transcriptomic sequencing was employed to investigate the involvement of lactate in regulating MPMVEC ferroptosis, and the results were validated by in vivo and in vitro experiments. Histone lactylation was identified as a regulator of lipid peroxidation and iron homeostasis dysregulation in lactate-induced ferroptosis in MPMVECs. Gain- and loss-of-function approaches were used to assess the role of histone lactylation in regulating ferroptosis and pulmonary microvascular dysfunction. Correlations between serum lactate and ferroptosis levels and their associations with patient prognosis were investigated in patients with sepsis-associated acute respiratory distress syndrome (S-ARDS). RESULTS: The mouse serum lactate level reached a peak at 18 h after caecal ligation and puncture surgery. Elevated lactate levels during sepsis promoted ferroptosis in PMVECs, leading to increased pulmonary vascular permeability and exacerbation of ALI. Mechanistically, lactate increased the lactylation of histone H3 at K18 (H3K18la), which promoted ACSL4 transcription in MPMVECs, resulting in excessive lipid peroxidation. Additionally, elevated H3K18la promoted LC3 transcription and indirectly upregulated NCOA4 expression through the transcription factor GATA2, facilitating ferritinophagy. Serum lactate levels were significantly correlated with ferroptosis levels in S-ARDS patients, and both were associated with poor patient prognosis. CONCLUSIONS: This study revealed a critical role for high lactate-derived histone lactylation in PMVEC ferroptosis and the progression of ALI during sepsis, providing new insights and potential therapeutic mechanisms.