【Abstract】 Objective To observe the effect of lipopolysaccharide (LPS) on the expression of tumor necrosis factor alpha (TNF-α), high mobility group box-1 protein (HMGB-1) and transforming growth factor beta-1(TGF-β1) in rat peritoneal mesothelial cell (RPMC). Methods RPMC were isolated from rat colic omentum. The cells were incubated with LPS (1, 10 and 100 mg/L), or were under the stimulation of 10 mg/L LPS for 2, 6, 12, 18, 21, 24 and 36h. RPMC in the control group were incubated with the medium. HMGB-1 mRNA was detected by RT-PCR. TNF-α, HMGB-1 and TGF-β1 were measured by ELISA. Results Compared with the control group, the expression of HMGB-1 mRNA and HMGB-1 increased significantly in the groups stimulated by LPS in time-dependent and dose-dependent manner. TNF-α expression was found to have 2 peaks in the 36h period of LPS stimulation. TGF-β1 increased to the peak at 2h, decreased at 6h, and then increased at 12h to 36h. Conclusion HMGB-1 as a late inflammatory factor may play a role in the pathogenesis of peritonitis relating to CAPD. LPS up-regulates the expression of TNF-α, HMGB-1 and TGF-β1, leading to the continuous amplification of inflammatory processes and the aggravation of peritoneal impairment and fibrosis.