Fig. 6

XIAP siRNA knockdown in RPE cells enhances both IL-18 and IL-1β release. a The selection of effective XIAP siRNA concentration was determined by RT-PCR assays in ARPE-19 cells, where a lower dose of XIAP siRNA (2.5 nM) achieved more than 75% inhibition on XIAP mRNA. Increasing the XIAP siRNA concentrations (5 nM or 10 nM) did not provide additional inhibition (N = 3, one-way ANOVA, p < 0.001). b Cell lysates and culture medium supernatants from non-primed ARPE-19 cells under different stimulation conditions were collected for protein analysis. Leu-Leu-OMe (LLOMe) stimulation alone triggered IL-18 secretion and XIAP reduction. Cells pre-treated with XIAP siRNA, then followed by LLOMe stimulation, exhibited more IL-18 and further decrease of XIAP, compared to LLOMe alone group. c XIAP cleavage (from a full-length 57 kDa protein to a ~ 34 kDa fragment) was present under LLOMe induced inflammasome activation but was abolished by XIAP siRNA pre-incubation. d When stimulated with a combination of IL-1α and LLOMe, a higher secreted level of IL-1β was present in the XIAP siRNA-treated primary RPE cells, compared to the control siRNA group (One-way ANOVA, *p < 0.05)