Innate immune molecule surfactant protein D attenuates sepsis‐induced acute kidney injury through modulating apoptosis and NFκB‐mediated inflammation

The objective of this study is to investigate the mechanism whereby innate immune molecule surfactant protein D (SP-D) attenuates sepsis-induced acute kidney injury (AKI) through modulating apoptosis and nuclear factor kappa-B (NFkappaB)-mediated inflammation. In the present study, a mouse sepsis model was established by cecal ligation and puncture in SP-D knockout (KO) mice and wild-type (WT) mice. A sham-operated group was included as the control. The experimental materials were extracted 6 and 24 hours postoperatively. The plasma levels of tumour necrosis factor alpha (TNF-alpha) and MCP-1 were determined by enzyme-linked immunosorbent assay (ELISA). Apoptosis was measured by double staining with Annexin V/propidium iodide and flow cytometry. The levels of NFkappaB in renal tissues were measured by ELISA and Western blotting assay. Apoptosis was detected by TUNEL assays. There were no significant differences in plasma TNF-alpha levels between the WT sham group and the KO sham group at 6 and 24 hours postoperatively (P < .05), but the levels of TNF-alpha in the WT sepsis and KO sepsis groups were significantly higher than those in controls (P < .05). The levels of TNF-alpha in the KO sepsis group were significantly higher than those of the WT sepsis group (P < .05). TNF-alpha levels in the WT sepsis group and the KO sepsis group at 24 hours postoperatively were significantly higher than those at 6 hours postoperatively (P < .05). The levels of MCP-1 in the WT sepsis group and the KO sepsis group at 6 and 24 hours postoperatively were significantly higher than those in the control group (P < .05), and MCP-1 levels in the KO sepsis group were significantly higher than those in the WT sepsis group (P < .05). MCP-1 levels in the WT sepsis group and the KO sepsis group at 24 hours postoperatively were significantly higher than those at 6 hours postoperatively (P < .05). The expression of SP-D in WT kidneys was significantly lower at 6 and 24 hours postoperatively (P < .05). The number of TUNEL-positive cells in the kidneys from septic SP-D KO mice was significantly higher (P < .05). The levels of NFkappaB in septic mice were significantly increased at 6 and 24 hours after induction of sepsis compared with the sham-operated group compared with those of septic SP-D KO mice and WT mice (P < .05). Innate immune molecule SP-D significantly decreased plasma levels of inflammatory cytokines in mice and attenuated sepsis-induced AKI by inhibiting NFkappaB activity and apoptosis.