Objective To investigate the effect of protein inhibitor of activated signal transducer and activator of transcription 1 ( PIAS1 ) gene silencing on the inflammatory response of rat pancreatic acinar cell lines AR42J with cerulein stimulation, to study its role in the pathogenesis of acute pancreatitis.Methods The siRNA targeting PIASI was designed, synthesized, transfected into AR42J cells by lipofectmine 2000.24 h later, cerulean was added and cultured for another 24 h.Subsequent AR42J cells with cerulein stimulation were divided into 4 groups: cerulein, liposome, negative-siRNA and PIAS1-siRNA groups.In addition, a group with PBS was as control group.The activity of p38 mitogen- activated protein kinase (p38MAPK) was detected by western blotting.TNF-α, IL-1β, IL-6, matrix metalloproteinase (MMP) 9 expression were analyzed by RT-PCR and western blotting, respectively.Results The expression of p38MAPK in PIAS1-siRNA, negative-siRNA, liposome, cerulein,and control group was 1.93 ±0.11, 1.22 ±0.10, 1.30 ±0.17,1.32 ± 0.21, 0.12 ± 0.02;while the expression of phosphorylated p38MAPK was 2.10 ± 0.25, 1.36 ± 0.20,1.26 ±0.15, 1.23 ±0.25, 0.58 ±0.48, the expression in PIAS1-siRNA group was significantly increased when compared with other groups (P＜0.05).The levels of TNF-α, IL-1β, IL-6, MMP-9 mRNA were 1.66 ±0.15,1.66 ± 0.15,1.90 ±0.01, 1.56 ±0.20 in PIAS1-siRNA group, while the expression of protein was 2.06 ±0.37,2.20 ±0.34, 1.80 ±0.10, 1.17 ±0.05, which was markedly higher than those in other group (P ＜0.05).Conclusions PIAS1 gene silencing could enhance p38MAPK activity, and improve inflammatory mediator expression in pancreatic acinar cells with cerulein stimulation.