SPLUNC1 knockout enhances LPS-induced lung injury by increasing recruitment of CD11b+Gr-1+ cells to the spleen of mice.

Short palate, lung and nasal epithelium clone 1 (SPLUNC1) is a tissue-specific gene of nasopharyngeal tissue, and has been recognized as a potential tumor-suppressor gene in nasopharyngeal carcinoma. As a secreted protein, SPLUNC1 plays an important role in innate immunity including antimicrobial and host defense. However, the related immune cells which are regulated by SPLUNC1 remain elusive. In the present study, an acute lung injury (ALI) mouse model was established by administration of lipopolysaccharide (LPS) intraperitoneal injections to wild-type and SPLUNC1-/- mice (5 mg/kg). Pathologic results showed that the SPLUNC1-/- group appeared to have more severe pulmonary damage and infiltrated inflammatory cells compared with the WT group after LPS treatment for 24, 48, 72 and 96 h. The mRNA expression levels of interleukin-6 (IL-6), chemokine (C-C motif) ligand-2 (CCL-2), chemokine (C-C motif) ligand-3 (CCL-3) and chemokine (C-X-C motif) ligand-1 (CXCL-1) in lungs of the SPLUNC1-/- group were higher than these levels in lungs of the WT group at different time points after LPS injection. The percentage of splenic CD11b+Gr-1+ myeloid-derived suppressor cells (MDSCs) in the SPLUNC1-/- mice was higher than this percentage in the WT mice at the time points of 72 and 96 h post LPS injection (P<0.05). These findings demonstrated that SPLUNC1 had a certain protective effect on the LPS-induced ALI mouse model as well as it was found to inhibit the recruitment of MDSCs to the spleen in this model.