(1368) Metabolic Crosstalk Between Alveolar Macrophages and Epithelium in Acute Lung Injury

Introduction: Dysregulated inflammation is a key feature of acute lung injury (ALI). Upregulation of glycolysis via PFKFB 3 in alveolar type 2 (AT2) cells can function as an innate protective mechanism during ALI. Lactate has been shown to shift macrophages to an anti-inflammatory phenotype, but relevance is unknown in ALI.We hypothesized that increased glycolysis in AT2 cells will result in increased lactate production which will shift alveolar macrophages (AM) towards a pro-resolving phenotype.

Methods: ALI was induced by either intratracheal (i.t.) LPS or acid aspiration. Mice received lactate i.t after induction of ALI . A549 cells were co-cultured with primary human AMs, isolated from rejected donor lungs. Histone-lactylation was determined by Western Blot. Raw 264.7 cells stimulated with LPS were used to perform transposase-accessible chromatin using sequencing (ATAC-seq) with Transcription Factor Enrichment Analysis (TFEA) as a downstream analysis pipeline.

Results: Lactate improved ALI in WT mice. Lactate shifted cytokine expression in AMs towards increased IL-10 and Arg-1 but decreased IL-1 and IL-6 production.SPC-ER Pfkfb3 loxp/loxp animals display exacerbated injury and inflammation following ALI. i.t lactate significantly attenuated ALI phenotype in SPC-ER Pfkfb3 loxp/loxp with increased IL-10 and Arg1 mRNA expression in AM. Human primary AM co-cultured with A549 cells had reduced inflammatory responses. Histone lactylation, a newly described histone modification, was increased in ALI and further augmented by administration of lactate. ATAC-seq revealed that CTCF and CEBP family members, which are important regulators of macrophage chromatin organization and function, were highly active with LPS+L-lactate versus LPS alone.

Conclusions: Modifying the AM phenotype is critical to regulating airway inflammation in ALI. PFKFB3 drives lactate production in AT2 cells, which is able to shift AMs towards an anti-inflammatory phenotype. Preliminary experiments point towards histone-lactylation as a potential mechanism relevant in several murine ALI models and primary human AMs. Modifying the AM phenotype via metabolic crosstalk with the alveolar epithelium metabolism acts as an innate protective mechanism to dampen excessive airway inflammation in ALI.