Objective To investigate the effect of pyrin domain 3 (NLRP3) inflammasome in the process of contrast induced human kidney cell apoptosis.Methods Human kidney 2 (HK-2) cells were cultured in DMEM-F12 medium with 5％ FBS.Cells were divided into control group,Contrast group (O group),NLRP3-siRNA+Iohexol group (si-NLRP3+O group),ASC-siRNA+Iohexol group (si-ASC+O group),and mannitol group (M group).Different concentrations of hypotonic contrast agent were added to HK-2 cell culture plates for 24,48 and 72 h.Flow cytometry was used to detect apoptosis.NLRP3 and ASC mRNA expressions were detected by RT-PCR.The expressions of NLRP3,ASC,caspase-8/cleaved caspase-8,Bcl-2/Bax,caspase-1/cleaved caspase-1,and caspase-3/cleaved caspase-3 protein were detected by Western blot.The levels of interleukin (IL) 1β and IL-18 in supernatant were detected by ELISA.Results Compared with the control group,the rate of apoptotic cells,as well as the expressions of NLRP3,ASC and cleaved caspase-1 proteins were increased in HK-2 cells of contrast group.The expressions of NLRP3 and ASC mRNA in the contrast group also increased,so did IL-1β and IL-18 levels (all P＜0.05),suggesting that NLRP3 inflammasome in HK-2 cells was activated by contrast.Compared with the control group,the expressions of cleaved caspase-8,Bax and cleaved caspase-3 protein were increased,and the expression of anti-apoptotic protein Bcl-2 was decreased (all P ＜ 0.05).Compared with the contrast group,the rate of apoptotic cells in the si-NLRP3 + contrast group and si-ASC + contrast group was significantly decreased;the expression of cleaved caspase-1 was decreased;the expressions of Bax and cleaved caspase-3 were decreased,and Bcl-2 level was increased.The expressions of IL-1β and IL-18 in the supernatant of cells were decreased (all P ＜ 0.05).Conclusion Contrast agent can activate the NLRP3 pathway in HK-2 cells and induce apoptosis,which could be reduced by blocking the NLRP3 pathway.