Role of spleen-derived CD11b+Gr-1+ cells in sepsis-induced acute kidney injury

Abstract

Purpose: CD11b+Gr-1+ cells play a key role in inflammation and the purpose of this study was to determine whether splenic CD11b+Gr-1+ cells are mobilized to the kidney and lead to acute kidney injury during sepsis. Methods: The sepsis model was generated via cecum ligation and puncture (CLP). The mice were randomly distributed into control, sham operated, CLP and CLP+splenectomy (CLPS) groups (n=5-10/group). The percentage of CD11b+Gr-1+ cells in circulating, bone marrow and spleen were determined. Plasma concentrations of interleukin-6, interleukin-1β, creatinine (Cr) and neutrophil gelatinase-associated lipocalin were measured. CD11b+Gr-1+ cells were detected by immunofluorescence and qRT-PCR. Hematoxylin-eosin (HE) and periodic acid-Schiff (PAS) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) were performed. Expression of mammalian target of rapamycin (mTOR), hypoxia-inducible factor-1α (HIF-1α) and cleaved caspase-3 was measured. Results: The percentage of CD11b+Gr-1+ cells in blood was significantly higher in the CLP group and lower in CLPS group. CD11b+Gr-1+ cells in the spleen were significantly lower in the CLP group. In the CLP group, the plasma concentrations of interleukin-6, interleukin-1β, Cr and neutrophil gelatinaseassociated lipocalin were higher. The expression of Gr-1 and CD11b were higher in CLP. The CD11b+Gr-1+ cells were detected in the kidneys of the CLP group. HE, PAS and TUNEL showed inflammatory cell infiltration and cell apoptosis in CLP. Western blot indicated dephosphorylation of mTOR, down-expression of HIF-1α and increased expression of cleaved caspase-3 in sepsis kidney. Conclusion: Splenic CD11b+Gr-1+ cells migrated to the kidney in sepsis, which led to acute kidney injury via the inhibition of mTOR/HIF-1α.