Objective To determine the effect of proinflammatory cytokines including interleukin-lbeta (IL-1β) and tumor necrosis factor-Alpha (TNF-α) on human serotonin transporter (SERT) in human enterocyte-like cell line Caco-2.Methods Caco2 cells were cultured for 5 days,then were divided into control group.IL-1β treated group (50 ng/ml) and TNF-α treated group (50ng/ml) for 2.24,48 and 72 hours.The expression of SERT mRNA was detected by RT-PCR at 2,24 and 48 hours and its protein expression was measured by Western blotting at 24,48 and 72 hours.Results The expression of SERT mRNA at 2,24 and 48 hours was lower both in IL-1β treated group (1.393±1.184,1.064±0.625 and 1.013±0.415,respectively) and TNF-α treated group (1.000±0.000,0.829±0.162and 0.945±0.147,respectively) in comparison with control group (2.282±1.367,1.586±0.421 and 1.86 ±O.496,respectively).There was significant difference among three groups (P<0.01).The expression of SERT protein at 24,48 and 72 hours was lower in IL-1β treated group and TNF-α treated group than in control group.Conclusions The IL-1β and TNF-α can inhibit the expressions of SERT mRNA and protein in Caco-2 cells,which indicates that IL-1β and TNF-α may change visceral sensitivity by influencing peripheral 5-hydroxytryptamine levels. Key words: Colonic neoplasms Interleukins; Tumor necrosis factor-Alpha; Serotonin transporter; Cell line,tumor