Cmpk2 Protects Against Acute Lung Injury in Mice.

Purpose: Acute respiratory distress syndrome (ARDS)/Acute lung injury (ALI), characterized by severe hypoxemia and pulmonary edema, involves mitochondrial dysfunction. Cytidine/uridine monophosphate kinase 2 (Cmpk2), a mitochondrial metabolic enzyme, modulates inflammation and senescence, yet its role in ARDS remains unclear. We investigated Cmpk2's function in Pseudomonas aeruginosa (P. aeruginosa)-induced ALI using Cmpk2 global knockout (KO) mice.

Methods: Cmpk2 was identified through mitochondrial gene expression analysis of ARDS datasets (GEO). Murine ALI was induced by intratracheal P. aeruginosa injection. Lung pathology (hematoxylin and eosin staining), leukocyte recruitment (flow cytometry), and cytokines (ELISA) were assessed. GO/KEGG analyses were conducted to identify Cmpk2-associated biological processes and pathways. The expression of Cmpk2 in leukocyte populations was analyzed using single-cell RNA sequencing (scRNA-seq) data from ARDS patient samples. Mouse neutrophils' phagocytosis of P. aeruginosa was quantified by flow cytometry. Zebrafish embryos were infected with P. aeruginosa and Staphylococcus aureus for bacterial burden and survival assays.

Results: Cmpk2 expression was significantly upregulated in ARDS. Cmpk2 KO exacerbated P. aeruginosa-induced ALI in mice, as evidenced by increased pathological damage and permeability, elevated proinflammatory cytokines and enhanced neutrophil infiltration. GO/KEGG analyses linked Cmpk2 to innate immunity. scRNA-seq analysis revealed an enriched expression of Cmpk2 in neutrophils. Cmpk2 deficiency impaired neutrophil phagocytosis and reduced host survival during bacterial infection, accomplished by decreased STING expression. The differences in phagocytosis between the wild-type and Cmpk2 KO mouse neutrophils/zebrafish embryos were eliminated by STING inhibitor C176.

Conclusion: Cmpk2 protects against pneumonia by attenuating neutrophil recruitment and enhancing bacterial phagocytosis via STNG-dependent mechanisms.