Acute Lung Injury

Acute lung injury (ALI) is a significant complication of sepsis, wherein the interaction between pulmonary vascular endothelial cells and immune cells plays a pivotal role in the pathogenesis. In this study, it is demonstrated that secretion of chemokine C-C motif ligand 7 (CCL7) by endothelial cells (ECs) induces metabolic reprogramming and M1 polarization of C-C motif chemokine receptor 1-positive (CCR1⁺) macrophages. It is noteworthy that mice with specific inhibition of endothelial-derived CCL7 exhibit reduced severity of septic ALI, underscoring the critical role of CCL7 in the progression of sepsis. Mechanistically, activation of the CCL7-CCR1 axis enhances STAT1 succinylation through upregulation of KAT2A expression, leading to increased STAT1 binding to the promoter of glycolytic genes in macrophages. This epigenetic regulation modulates metabolic reprogramming and M1 polarization of macrophages, thereby driving inflammatory cascades in septic ALI. Furthermore, in sepsis models, Ccr1-knockout (Ccr1-KO) mice demonstrate attenuated lung inflammation and decreased mortality, highlighting the therapeutic potential of targeting the CCL7-CCR1 axis for the treatment of septic ALI. Collectively, findings provide novel insights into the metabolic reprogramming of macrophages and identify the CCL7-CCR1 axis as a promising therapeutic target for septic ALI.

Elevated glycolysis in lung tissue is a hallmark of sepsis-induced acute lung injury (SI-ALI), yet the role of glycolytic reprogramming and lactate-derived protein modifications in damaging epithelial cells remains poorly understood. In this study, we reveal that PDK4-driven glycolytic reprogramming promotes excessive lactate production in lung tissue during SI-ALI. Mechanistically, AARS1 in epithelial cells selectively enhances lactylation modification at the K375 site of LPCAT2, which suppresses STAT1 acetylation and facilitates STAT1 phosphorylation, nuclear translocation, and transcriptional repression of SLC7A11. This cascade ultimately triggers epithelial cells ferroptosis. Pharmacological inhibition of PDK4 attenuates lactate accumulation and LPCAT2 lactylation, thereby restoring STAT1 acetylation and SLC7A11 expression. Furthermore, AARS1 knockdown or mutation of the LPCAT2-K375 lactylation site rescues STAT1-mediated SLC7A11 suppression and mitigates ferroptosis in vitro and septic mice. Our findings revealed that elevated expression of PDK4 is a critical factor contributing to the increased lactate production in lung tissue during sepsis, and established a novel LPCAT2-K375/STAT1/SLC7A11 axis driving epithelial cells ferroptosis in SI-ALI, highlighting the crosstalk between metabolic reprogramming, post-translational modifications (PTM), and ferroptosis. Targeting the PDK4 or LPCAT2 lactylation may offer therapeutic potential for SI-ALI. In sepsis-induced acute lung injury (SI-ALI), PDK4 hyperactivation drives excessive lactate production in epithelial cells, triggering AARS1/HDAC9-mediated LPCAT2 lactylation. This modification suppresses STAT1 acetylation while enhancing phosphorylation, driving its nuclear translocation and subsequent SLC7A11 transcriptional downregulation. The resultant glutathione synthesis deficiency promotes ferroptosis, exacerbating SI-ALI progression.

BackgroundAcute lung injury (ALI) is characterized by excessive inflammation and alveolar damage, arising from pathogens or systemic insults such as sepsis, and can progress to severe acute respiratory distress syndrome (ARDS). Despite its severity, effective pharmacological treatments remain unavailable, and current clinical interventions are limited to supportive care such as mechanical ventilation. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as promising candidates for lung repair, but insufficient immunosuppressive capacity often limits their efficacy.MethodsHuman adipose-derived mesenchymal stem cells (hADMSCs) were primed with IFN-γ and TNF-α to enhance the immunomodulatory properties of their secreted EVs. We characterized unprimed control MSC-EVs (C-MEVs) and primed MSC-EVs (P-MEVs) by transmission electron microscopy, nanoparticle tracking analysis, and western blotting for EV markers. Functional assays in THP-1 and A549 cells examined anti-inflammatory potency and barrier regeneration against lipopolysaccharide (LPS)-induced damage. A preclinical mouse model of LPS-induced ALI was used to evaluate inflammatory cytokine expression, immune cell infiltration, pulmonary edema, and vascular leakage. Finally, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected Vero E6 cells were tested whether P-MEVs could mitigate the inflammatory damage characteristic of virus-triggered acute lung injury.ResultsPrimed hADMSCs exhibited elevated expression of immunosuppressive molecules (e.g., COX-2, IDO, TSG-6), without changing EV morphology or yield. P-MEVs mitigated LPS-induced inflammation more effectively than C-MEVs in THP-1 and A549 cells. In vivo, P-MEVs more robustly attenuated inflammatory cytokines, immune cell recruitment, and lung injury markers in mice challenged with LPS. In SARS-CoV-2-infected Vero E6 cells, P-MEVs suppressed cytopathic effects and inflammatory responses more potently than C-MEVs. Mechanistic analyses revealed that these enhancements were associated with elevated miRNA levels, including miR-221-3p, involved in inhibiting inflammatory pathways.ConclusionInflammatory cytokine priming substantially augments the immunomodulatory and tissue-regenerative efficacy of hADMSC-derived EVs, offering superior therapeutic effects in ALI models and promising activity against SARS-CoV-2-induced lung damage. These findings underscore the therapeutic potential of P-MEVs as an innovative, cell-free platform for treating severe pulmonary disorders, including ARDS.