Objective  To evaluate the role and potential mechanism of interleukin (IL)-18/IL-18 binding protein (BP) in mediating the killing effect of natural killer (NK)-92MI cells upon endothelial cells from α-1, 3- galactosyltransferase gene-knockout (GTKO) porcine models.

  Methods  NK-92MI cells were divided into the NK, NK+IL-18, NK+GTKO, IL-18+NK+GTKO and IL-18+IL-18BP+NK+GTKO groups. The messenger ribonucleic acid (mRNA) levels of inflammation-related genes in NK-92MI cells were detected by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The killing effect of NK-92MI cells on endothelial cells from GTKO porcine models was evaluated by lactate dehydrogenase (LDH) assay. The apoptosis of endothelial cells from GTKO porcine models was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. The expression levels of proteins with killing effect and apoptosis-related proteins were determined by Western blot.

  Results  Compared with the NK, NK+IL-18 and NK+GTKO groups, the expression levels of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, IL-8, IL-3, IL-6 and granulocyte-macrophage colony stimulating factor (GM-CSF) mRNA were up-regulated in NK-92MI cells in the IL-18+NK+GTKO group, and the differences were statistically significant (all P < 0.05). Compared with the IL-18+NK+GTKO group, the expression levels of IFN-γ, TNF-α, IL-8, IL-3, IL-6 and GM-CSF mRNA were down-regulated in NK-92MI cells in the IL-18+IL-18BP+NK+GTKO group, and the differences were statistically significant (all P < 0.05). Compared with the NK+GTKO group, the expression levels of perforin, granzyme B and IFN-γ proteins in NK-92MI cells were up-regulated, the killing rate of NK-92MI cells against endothelial cells from GTKO porcine models was enhanced, the apoptosis rate of endothelial cells from GTKO porcine models was increased, and the ratios of B cell lymphoma-2 (Bcl-2)-associated X protein (Bax)/Bcl-2 and cleaved Caspase-3/Caspase-3 in endothelial cells from GTKO porcine models were elevated in the IL-18+NK+GTKO group, and the differences were statistically significant (all P < 0.05). Compared with the IL-18+NK+GTKO group, the expression levels of perforin, granzyme B and IFN-γ proteins were down-regulated, the killing rate of NK-92MI cells against endothelial cells from GTKO porcine models was decreased, the apoptosis rate of endothelial cells from GTKO porcine models was decreased, and the ratios of Bax/Bcl-2 and cleaved Caspase-3/Caspase-3 in endothelial cells from GTKO porcine models were declined in the IL-18+IL-18BP+NK+GTKO group, and the differences were statistically significant (all P < 0.05).

  Conclusions  IL-18BP may block the expression of inflammation-related genes in NK-92MI cells induced by IL-18 and the killing effect of NK-92MI cells on endothelial cells from GTKO porcine models.