Abstract Acute lung injury (ALI) is marked by epithelial barrier disruption, neutrophil infiltration, and cytokine storm following exposure to endotoxin. Short Palate, Lung, and Nasal Epithelial Clone 1 (SPLUNC1, also known as BPIFA1) is a secreted protein involved in mucosal defense and epithelial homeostasis of the airways. Although SPLUNC1 has been shown to have antimicrobial properties, its role in regulating inflammation during ALI remains unclear. This study investigated how SPLUNC1 deficiency alters immune responses and tissue damage in a lipopolysaccharide (LPS)-induced murine model of ALI.Wild-type (WT) and SPLUNC1 knockout (KO) mice received an intranasal dose of 0.25 mg/kg LPS. After 24 hours, bronchoalveolar lavage fluid (BALF) and lung tissues were collected. BALF total cell counts and differential cytology were analyzed, and flow cytometry further quantified neutrophil and macrophage populations. Lung sections were stained with H 0.01). Flow cytometry showed an apparent increase in neutrophils in the BALF and lung tissue of KO mice. Histology showed more severe lung injury in SPLUNC1 KO animals, with alveolar wall thickening, small areas of collapse, scattered hemorrhage, and increased inflammatory cells concentrated around vessels and airways. The injury scores were consistently higher in KO mice than in WT (p 0.005). Cytokine and chemokine expression levels, including IL-1β, IL-6, TNF-α, CCL3, and CCL12, were elevated by about 2- to 5-fold. RNA-seq analyses revealed enrichment in cytokine-cytokine receptor interactions, TNF signaling, and NF-κB signaling, as well as genes related to neutrophil chemotaxis and apoptosis. In contrast, WT mouse lungs maintained relatively intact alveolar structure and lower cytokine induction.Loss of SPLUNC1 amplifies LPS-induced lung inflammation and tissue injury. SPLUNC1 limits neutrophil recruitment and pro-inflammatory cytokine release, acting as an intrinsic regulator of epithelial integrity. Transcriptomic findings support its role in dampening NF-κB- and TNF-mediated signaling. These data suggest that SPLUNC1 may serve as a potential therapeutic target for controlling excessive respiratory inflammation in sepsis-related or ventilator-induced lung injury. This abstract is funded by: R01-AI176537, NIH R01-AI133351
Lu et al. (Fri,) studied this question.