Regulatory Effects of Cytokines on Spontaneous Pyroptosis in Neutrophils

Objective To explore the regulatory effects of cytokines interleukin(IL)-1β,IL-6,tumor necrosis factor alpha(TNF-ɑ),gamma interferon(IFN-γ),granulocyte colony-stimulating factor(G-CSF),and granulocyte-macrophage colony-stimulating factor(GM-CSF)on spontaneous pyroptosis in neutrophils.Methods Neutrophils isolated from mouse bone marrow by density-gradient centrifugation were cultured in vitro for 20 h with or without 10,50 or 100 ng/mL IL-1β,IL-6,IFN-γ,G-CSF or GM-CSF,or for 12 h with or without 1,10 or 50 ng/mL TNF-α.After incubation,cells were stained with annexin Ⅴ(AV)/propidium iodide(PI),and the proportions and absolute number of neutrophils undergoing different forms of cell death were determined by fluorescence microscopy combined with manual counting.Pyroptotic neutrophils were identified by cell morphology in conjunction with AV/PI staining.Flow cytometry with counting beads was employed to measure the proportions and number of AV/PI-stained Ly6g⁺neutrophils in different forms of cell death.Western blotting was employed to assess the cleavage and activation levels of cysteinyl aspartate-specific proteinase-3(caspase-3)and gasdermin E(GSDME).Results Treatment with IL-1β or IL-6 had no significant effect on the proportion or number of neutrophils undergoing spontaneous pyroptosis.After 12 h of treatment with TNF-α at 1,10,and 50 ng/mL,the proportions of pyroptotic neutrophils were(14.79±0.45)%,(19.99±3.02)%,and(20.66±1.99)%,respectively,higher than that[(10.22±1.12)%]in the untreated control(P=0.024,P<0.001,and P<0.001,respectively).Treatment with 10,50,and 100 ng/mL IFN-γ for 20 h reduced the proportion of pyroptotic neutrophils from(17.43±1.88)%to 12.00%(all P<0.001).G-CSF at 10,50,and 100 ng/mL reduced the proportion of pyroptotic cells to around 6.00%and greatly inhibited the cleavage of both caspase-3 and GSDME.After 20 h of treatment with 10,50,and 100 ng/mL GM-CSF,the proportions of pyroptotic neutrophils decreased to(7.52±0.53)%,(5.27±2.30)%,and(0.64±1.11)%,respectively.Conclusions Neither IL-1β nor IL-6 affects GSDME-mediated spontaneous pyroptosis in neutrophils.TNF-ɑ induces spontaneous pyroptosis in neutrophils,whereas IFN-γ,G-CSF,and GM-CSF demonstrate inhibitory effects.